WILBERT

Wildauer Bücher+E-Medien Recherche-Tool

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
• Springer  (2,354,543)
Collection
Keywords
Publisher
Language
Years
• 1
Springer
Publication Date: 2018-03-05
Description: An uncertainty comparison method is proposed to assess the homogeneity of reference materials. The method compares “standard uncertainty associated with between-unit variability” ( u bb ) with “target standard uncertainty” ( u trg ) or “measurement uncertainty” ( u meas ) to solve the problems in assessing homogeneity of reference materials. Methods for the calculation of u bb , u trg and u meas as well as criterion for the quantitative judgment of sample homogeneity are introduced. When u bb  ≤ 0.3 u trg , it shows the sample is considered to be homogeneous; when 0.3 u trg  〈  u bb  ≤ 0.7 u trg , the sample is considered to be sufficiently homogeneous for the intended use; and when u bb  〉 0.7 u trg , the sample is considered to be inhomogeneous. The uncertainty comparison method is compared with the F test method and shown to be more objective for the assessment of the homogeneity of certified reference materials for the chemical testing of toys.
Print ISSN: 0949-1775
Electronic ISSN: 1432-0517
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 2
Springer
Publication Date: 2018-03-05
Print ISSN: 0949-1775
Electronic ISSN: 1432-0517
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 3
Springer
Publication Date: 2018-03-05
Print ISSN: 0949-1775
Electronic ISSN: 1432-0517
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 4
Springer
Publication Date: 2018-03-05
Description: Uncertainty in measurement is very important in the process of conformity assessment. As it is generally declared, based on the measured value of a property of an item, there is always the risk of incorrect decisions, which are of two types: an item accepted as “conforming” may actually be “non-conforming”, and an item rejected as “non-conforming” may actually be “conforming”. In order to reduce the risks associated with decision-making, it is required to reduce the measurement uncertainty to an acceptable level termed as “target uncertainty”. In order to reduce the uncertainty of a particular measurement, it would be necessary to focus on decreasing the uncertainties arising from the relevant components. There are always different solutions to reduce the uncertainties arising from each inclusive component. Each of these solutions imposes a different cost on the measurement system. Therefore, a solution should be selected, among several possible alternatives, to reduce the uncertainties arising from each relevant component and to impose the lowest cost to the measurement system to “target uncertainty”. Accordingly, in this paper through a case study, a model is presented that can reduce uncertainty with the lowest possible cost to the optimally needed level using a mathematical optimization technique. The mathematical model presented in this paper can be used in measurement uncertainty optimization in many laboratories, which require a reduction in uncertainty and the risks associated with decision-making based on measurement results. Furthermore, the use of the proposed model will help to reduce the unnecessary costs of analysis in different laboratory centers.
Print ISSN: 0949-1775
Electronic ISSN: 1432-0517
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 5
Springer
Publication Date: 2018-03-05
Description: This article discusses the accuracy of the gravimetric measurement method of total particulate matter concentration in waste gases where the basic assumption is that sample collection of dust-laden gas is done in a grid with a finite number of points in the conduit’s measurement plane. In this standard approach, the sample is assumed to be representative for dust-laden gas in the conduit, and consequently, the total particulate matter concentration measured for the sample is considered the mean concentration in the conduit. The article investigates this assumption against the standard-imposed number of sampling points and in view of spatial distributions of particulate matter concentration in industrial plants which—being continuous—are not identified in measuring practice. Possible distributions were simulated both for particulate matter concentration and for gas velocity in rectangular conduits, and the following were calculated: (a) an accurate mean particulate matter concentration in the measurement plane, based on its definition employing continuous distributions of particulate matter concentration and gas velocity and (b) the concentration in a sample, i.e. measured concentration. Measurement deviation between those concentrations was determined, which is specific for cumulative gas sampling. Using the obtained set of possible deviations, an estimation method was suggested for the relevant uncertainty component of the gravimetric method, which so far has not been taken into account in the industrial measurement accuracy analyses. It turns out that the level of this uncertainty component for measuring the mean particulate matter concentration in the conduit (resulting from “measurement discretization”) is not to be ignored.
Print ISSN: 0949-1775
Electronic ISSN: 1432-0517
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 6
Springer
Publication Date: 2018-03-05
Print ISSN: 0949-1775
Electronic ISSN: 1432-0517
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 7
Springer
Publication Date: 2018-03-05
Description: Sum parameters (otherwise known as composite parameters) describe similar chemical, physicochemical or biological characteristics of different substances, substance groups or mixtures of substances. These might contain the same chemical element. Such parameters are total organic carbon or total bound nitrogen. Chemical oxygen demand is a shared chemical characteristic—the oxidizability of constituents by dichromate. The focus of the paper is on the uncertainty estimation of the determination of chemical sum parameters in water samples from method validation derived data—total organic carbon, chemical oxygen demand, biochemical oxygen demand, total bound nitrogen and total suspended solids. The results for the measurement uncertainty estimations according to ISO 21748 and ISO 11352, as only applicable to the field of water analysis, are presented and compared. Based on the results obtained and the experimental design, the use of ISO 11352 for the measurement uncertainty estimation is recommended. This international standard employs fewer determinations (a minimum number of eight measurements are required, compared to fifteen), fewer working days (one compared to five) and easier measurement uncertainty components’ calculations and even gives opportunity for routine laboratories to use standard solutions over the more expensive certified reference materials for the measurement uncertainty estimation during the method validation in water analysis.
Print ISSN: 0949-1775
Electronic ISSN: 1432-0517
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 8
Springer
Publication Date: 2018-03-05
Electronic ISSN: 1432-0509
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 9
Springer
Publication Date: 2018-03-05
Electronic ISSN: 1432-0509
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 10
Springer
Publication Date: 2018-03-05
Electronic ISSN: 1432-0509
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 11
Springer
Publication Date: 2018-03-05
Description: Purpose The purpose of this study is to assess the heterogeneity of tumor enhancement using fractal analysis on contrast-enhanced computed tomography (CE-CT) for predicting malignant potential of gastrointestinal stromal tumor (GIST). Methods We retrospectively identified 64 patients (36 M/28 W; median age: 65) with GISTs who received CE-CT and 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) followed by curative surgery. Fractal analysis was applied to CE-CT image, and fractal dimension (FD) was measured. Diagnostic value of FD for malignant potential of GIST was compared with that of FDG-PET using the risk classification and Ki67 index. Results 14 patients were categorized as the high risk, and 50 patients were as the very low, low or intermediate risk. FD of high-risk group was significantly higher than that of the other-risk group ( p  〈 0.05). The areas under the ROC curves of FD and SUV max for prediction of high-risk group were 0.82 and 0.93 (accuracy: 84.4% and 98.5%). FD showed a significant positive correlation with Ki67 index ( p  = 0.01). Conclusion Diagnostic value of CT fractal analysis for prediction of high-risk GIST is comparable with FDG-PET. In terms of cost and availability, fractal analysis has a potential to be an optimal preoperative biomarker.
Electronic ISSN: 1432-0509
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 12
Springer
Publication Date: 2018-03-05
Description: Vascular complications are a significant source of morbidity and mortality among renal transplant recipients. Imaging using ultrasound, CT, and MRI plays a key role in diagnosing such complications. This review focuses on the major vascular complications of renal grafts, which include transplant renal arterial and venous stenoses, arterial and venous thromboses, arteriovenous fistulas, and pseudoaneurysms. Etiology, diagnostic modalities useful for diagnosis, and imaging appearance will be presented.
Electronic ISSN: 1432-0509
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 13
Springer
Publication Date: 2018-03-05
Description: Acute pathology in the abdominal aorta is associated with significant morbidity and mortality. The most feared complication of abdominal aortic disease is acute rupture in the setting of atherosclerotic abdominal aortic aneurysm. Although frank rupture often is easily diagnosed on CT, other findings such as a hyperattenuating crescent, discontinuous intimal calcium, and draping of the aorta are subtle signs of aneurysm instability. A true aneurysm should be distinguished from a rapidly growing, saccular pseudoaneurysm in the setting of infectious aortitis, as treatment strategy differs. Acute aortic syndrome involving the abdominal aorta, such as dissection and intramural hematoma, often is an extension of thoracic aortic disease, whereas penetrating atherosclerotic ulcers occasionally involve only the abdominal aorta. The goal of treating acute aortic pathology is to repair and prevent rupture, as well as restore and maintain perfusion of the lower extremities, kidneys, and mesentery. However, both open and endovascular repair of the abdominal aorta may become acutely complicated, resulting in compromise of these goals. Examples include aortoenteric fistula, endoleak, anastomotic pseudoaneurysm, graft infection, and thrombosis or kinking of a stent graft resulting in ischemia of the limbs and mesentery.
Electronic ISSN: 1432-0509
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 14
Springer
Publication Date: 2018-03-05
Description: In the published article, the author B. Babbitt was cited as affiliation 9, but should have been cited as affiliation 2. In addition, there are 2 errors in the affiliations. The correct affiliations are shown in this erratum.
Electronic ISSN: 1550-7416
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 15
Springer
Publication Date: 2018-03-05
Description: The rapidly increasing number of therapeutic biologics in development has led to a growing recognition of the need for improvements in immunogenicity assessment. Published data are often inadequate to assess the impact of an antidrug antibody (ADA) on pharmacokinetics, safety, and efficacy, and enable a fully informed decision about patient management in the event of ADA development. The recent introduction of detailed regulatory guidance for industry should help address many past inadequacies in immunogenicity assessment. Nonetheless, careful analysis of gathered data and clear reporting of results are critical to a full understanding of the clinical relevance of ADAs, but have not been widely considered in published literature to date. Here, we review visualization and modeling of immunogenicity data. We present several relatively simple visualization techniques that can provide preliminary information about the kinetics and magnitude of ADA responses, and their impact on pharmacokinetics and clinical endpoints for a given therapeutic protein. We focus on individual sample- and patient-level data, which can be used to build a picture of any trends, thereby guiding analysis of the overall study population. We also discuss methods for modeling ADA data to investigate the impact of immunogenicity on pharmacokinetics, efficacy, and safety.
Electronic ISSN: 1550-7416
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 16
Springer
Publication Date: 2018-03-05
Description: The original version of the published article contains errors throughout the text, which were introduced by the typesetter when performing the author’s proof corrections.
Electronic ISSN: 1550-7416
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 17
Springer
Publication Date: 2018-03-05
Description: The citation of the author name “Ah-Ng Tony Kong” in PubMed is not the author’s preference. Instead of “Kong AT”, the author prefers “Kong AN”.
Electronic ISSN: 1550-7416
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 18
Springer
Publication Date: 2018-03-05
Description: There are several drug products that bind phosphate or bile acid in the gastrointestinal (GI) tract to exert their therapeutic efficacy. In vitro binding studies are used to assess bioequivalence (BE) of these products. The objective of this study is to identify the common deficiencies in Abbreviated New Drug Applications (ANDAs) for these products. Deficiencies were compiled from ANDAs containing in vitro binding BE studies. The deficiencies were classified into eight categories: Pre-Study Method Validation, During-Study Sample Analysis, Study Design, Study Procedure, Dissolution/Disintegration, Analytical Site Inspection, Data Submission, and Formulations. Within each category, additional subcategories were defined to characterize the deficiencies. A total of 712 deficiencies from 95 ANDAs for 11 drug products were identified and included in the analysis. The four categories with the most deficiencies were During-Study Sample Analysis (27.8%), Pre-Study Method Validation (17.3%), Data Submission (16.7%), and Study Design (15.7%). For the During-Study Sample Analysis category, failure to submit complete raw data or analytical runs ranked as the top deficiency (32.8%). For the Study Design category, using an unacceptable alternate study design (26.8%) was the most common deficiency. Within this category, other commonly occurring deficiencies included incorrect/insufficient number of absorbent concentrations, failure to pre-treat drug product with acid, insufficient number of replicates in study, incorrect calculation of k1 and k2 values, incorrect dosage form or pooled samples used in the study, and incorrect pH of study medium. The review and approval of these products may be accelerated if these common deficiencies are addressed in the original ANDA submissions.
Electronic ISSN: 1550-7416
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 19
Springer
Publication Date: 2018-03-05
Description: The American Association of Pharmaceutical Scientists (AAPS) biosimilar focus group on nonclinical and clinical assays has developed this manuscript to guide the industry on best practices and testing strategies when developing neutralizing antibody (NAb) assays for biosimilar programs. The immunogenicity assessment to biosimilar and originator drug products is one of the key aspects of clinical programs for biosimilars to demonstrate biosimilarity. Establishing that there are no clinically meaningful differences in immune response between a proposed product and the originator product is a key element in the demonstration of biosimilarity. It is critical to collect, evaluate, and compare the safety and immunogenicity data from the clinical pharmacology, safety, and/or efficacy studies especially when the originator drug product is known to have potential for immune-mediated toxicity. This manuscript aims to provide a comprehensive review and recommendations on assay formats, critical reagents, approaches to method development, and validation of the neutralizing antibody assays in extrapolation within the scope of biosimilar drug development programs. Even if there are multiple options on the development and validation of NAb assays for biosimilar programs, the type of drug and its MoA will help determine the assay format and technical platform for NAb assessment (e.g., cell-based or non-cell-based assay). We recommend to always perform a one-assay approach as it is better to confirm the biosimilarity using one-assay for NAb. If a one-assay approach is not feasible, then a two-assay format may be used. This manuscript will provide all the details necessary to develop NAb assays for biosimilars.
Electronic ISSN: 1550-7416
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 20
Springer
Publication Date: 2018-03-05
Description: According to the National Center of Health Statistics, cancer was the culprit of nearly 600,000 deaths in 2016 in the USA. It is by far one of the most heterogeneous diseases to treat. Treatment for metastasized cancers remains a challenge despite modern diagnostics and treatment regimens. For this reason, alternative approaches are needed. Chemoprevention using dietary phytochemicals such as triterpenoids, isothiocyanates, and curcumin in the prevention of initiation and/or progression of cancer poses a promising alternative strategy. However, significant challenges exist in the extrapolation of in vitro cell culture data to in vivo efficacy in animal models and to humans. In this review, the dose at which these phytochemicals elicit a response in vitro and in vivo of a multitude of cellular signaling pathways will be reviewed highlighting Nrf2-mediated antioxidative stress, anti-inflammation, epigenetics, cytoprotection, differentiation, and growth inhibition. The in vitro - in vivo dose response of phytochemicals can vary due, in part, to the cell line/animal model used, the assay system of the biomarker used for the readout, chemical structure of the functional analog of the phytochemical, and the source of compounds used for the treatment study. While the dose response varies across different experimental designs, the chemopreventive efficacy appears to remain and demonstrate the therapeutic potential of triterpenoids, isothiocyanates, and curcumin in cancer prevention and in health in general.
Electronic ISSN: 1550-7416
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 21
Springer
Publication Date: 2018-03-05
Description: For accurately measuring the volume change of a soil specimen under monotonic and cyclic loading, a new double-cell system is described in this paper. This newly designed double-cell system is equipped with local linear variable differential transformers (LVDTs) and can also accommodate large specimens. Careful calibrations, including the effect of cell pressure change, “creep” of inner cell volume, the effect of temperature fluctuation, and loading ram movement, are presented and discussed by comparing the possible errors with those of other existing apparatuses. This system exhibits superior performances in volume change due to cell pressure, temperature sensitivity, and accuracy of loading ram movement. Three monotonic compression tests under saturated and unsaturated conditions were conducted to evaluate the performance of volume change measurement and local LVDTs. Moreover, six different frequencies were used to verify the workability and accuracy of this system in conducting cyclic testing. The results indicate that the maximum frequency this system can achieve, with a satisfactory precision, is 0.2 Hz, which is four times higher than what the previous systems could achieve. Finally, several suggestions are made on how to improve the system’s performance even better.
Print ISSN: 1861-1125
Electronic ISSN: 1861-1133
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 22
Springer
Publication Date: 2018-03-05
Description: The presence of underground voids has an adverse influence on the performance of shallow foundations. In this study, the bearing capacity and failure mechanism of footings placed on cohesive-frictional soils with voids are evaluated using discontinuity layout optimization. By introducing a reduction coefficient, a set of design charts that can be directly applied to the classical bearing capacity formulation is presented. The results indicate that the undrained bearing capacity with voids is sensitive to soil weight and cohesion, as both the bearing capacity and stability issues exist in the problem. The failure mechanism is directly related to a variety of soil properties, the locations of single voids, and the horizontal distance between two voids. The presence of voids has a more dominant effect on c – φ soils compared to that on undrained soil. An interpretation of the critical and adverse locations for single-void and dual-void cases with various soil strengths is presented.
Print ISSN: 1861-1125
Electronic ISSN: 1861-1133
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 23
Springer
Publication Date: 2018-03-05
Description: It is a well-known fact that addressing hydromechanical problems in saturated soils with the finite element method and equal-order interpolation formulations in displacements and pore pressures produces unstable results. Classically, stabilization has been achieved by increasing the interpolation degree of displacement with respect to pore pressure, hence fulfilling the Babuska–Brezzi condition. However, the use of quadratic elements involves high computational costs. From that point of view, the use of stabilized low-order elements is a more desirable option. Much research has been carried out in different directions in the stabilization of low-order formulations for saturated soils in quasistatic conditions, among others with the technique based on strain field enhancement through internal degrees of freedom. This article presents an alternative displacement–pore pressure formulation for saturated soil dynamics based on the enhancement of the displacement field through incompatible modes.
Print ISSN: 1861-1125
Electronic ISSN: 1861-1133
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 24
Springer
Publication Date: 2018-03-05
Description: Simvastatin (Sim), a lipid-lowering drug has been studied in chronic neuroinflammation associated with degenerative brain disorders due to its potential protective properties against inflammatory reaction, oxidative damage, neuronal dysfunction, and death. Meanwhile, potential application of Sim in neuroinflammation will require a suitable delivery system that can overcome notable challenges pertaining to poor blood–brain barrier (BBB) permeability and side/off-target effects. Herein, we engineered and characterized nano-sized polymersomes loaded with Sim (Sim-Ps) using PEG-PdLLA (methoxy polyethylene glycol-poly( d , l ) lactic acid) diblock co-polymers. Studies in BV2 microglia indicated that Sim-Ps was superior to Sim alone in suppressing nitric oxide (NO) and proinflammatory cytokines (interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) secretion against LPS activation. The effectiveness of Sim-Ps as compared with Sim alone, in attenuating NO and cytokine production by activated BV2 cells can be attributed to (a) colloidal stability of the delivery platform, (b) protracted release of biologically active Sim, and (c) particulate internalization coupled with enhanced Sim exposure to BV2 cells. Intranasal delivery in BALB/c mice demonstrated enhanced brain distribution with increasing time after administration. Overall data demonstrated suitability of PEG-PdLLA polymersomes in Sim delivery for potential application in treating neuroinflammation.
Electronic ISSN: 1550-7416
Topics: Chemistry and Pharmacology
Location Call Number Limitation Availability
Others were also interested in ...
• 25
Springer
Publication Date: 2018-03-05
Description: An axisymmetric lower bound limit analysis technique in combination with the finite elements has been used to investigate the effect of considering a non-associated flow rule on the stability number ( γH / c ) for a vertical circular unsupported excavation in a general cohesive–frictional soil medium, where (1) H is the excavation height, (2) γ defines the unit weight of the soil mass, and (3) c indicates the cohesion of the soil mass. The results are derived for different magnitudes of dilative coefficient ( η ), friction angle ( ϕ ), and normalized excavation height ( H / b ), where b  = the radius of the excavation. The results clearly indicate the increase in γH / c with an increase in η value. It is expected that the charts provided in this note will be quite helpful for the practicing engineers.
Print ISSN: 1861-1125
Electronic ISSN: 1861-1133
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 26
Springer
Publication Date: 2018-03-05
Description: This paper introduces X-ray tomography as an experimental method that allows grain-scale measurements for both porosity and degree of saturation. A whole configuration and set-up were developed specifically for the study of unsaturated Hostun sand and its water retention behaviour, using X-ray CT. A “step-by-step” protocol to obtain reconstructed volumes of sufficient quality where the three phases of the specimen can be clearly distinguished (i.e., grain, water and air) was also presented. A post-processing of the images helped the visualization and the characterization of the three phases within the specimen. A region growing separation tool was used to obtain trinarized volumes, allowing a qualitative/quantitative analysis to be performed. A qualitative interpretation of the resulting images has been done focusing on the water retention domains, where images of each different domain were retrieved for different suction values. Later, local measurements of relevant soil variables were conducted for a chosen subvolume of ≈ 3 ×  D 50 . This helped to build a map of measurement that covers the entire specimen field. Finally, water retention curve of Hostun sand was plotted and compared to a reference one. An investigation about the relation between the state variables: porosity and degree of saturation, for a constant suction, was performed. A noteworthy trend between porosity and degree of saturation was identified and discussed. The analysis presented in this study could be adapted for other granular materials, combined with pore size distribution and pore shape description, in order to understand the local relation between water retention behaviour characteristics and build a model that covers the whole retention behaviour of unsaturated granular materials.
Print ISSN: 1861-1125
Electronic ISSN: 1861-1133
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 27
Springer
Publication Date: 2018-03-05
Description: The focus of this paper is on quantitative evaluation of four different methods that use closed-form equations to calculate the nominal load in steel grid-reinforced soil walls under operational (end of construction) conditions. The four methods are the Coherent Gravity Method used in the UK, the AASHTO Simplified Method (USA), the PWRC Method used in Japan and the Simplified Stiffness Method. The accuracy of the methods is quantified based on analysis of bias statistics where bias is the ratio of measured to predicted (nominal) load. A large database of 113 measured reinforcement loads collected from 11 instrumented field walls is used in the study. For walls constructed with frictional soils, the Coherent Gravity Method and PWRC Method were the least accurate. The AASHTO Simplified Method demonstrated better accuracy and the Simplified Stiffness Method was the most accurate of all methods examined. The Coherent Gravity Method and the updated Simplified Stiffness Method for steel grid walls in the current study have the advantage that they can be used with soils that have a dependable soil cohesive strength component. However, the accuracy of the Simplified Stiffness Method was much better for all soil types based on bias analyses.
Print ISSN: 1861-1125
Electronic ISSN: 1861-1133
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 28
Springer
Publication Date: 2018-03-05
Description: Based on the Brazilian test results of 23 kinds of transversely isotropic rocks, five trends are obtained for the variation of normalized failure strength (NFS) as a function of the weak plane-loading angles. For each angle, three kinds of fracture patterns are obtained. Furthermore, a new numerical approach based on the particle discrete element method is put forward to systematically investigate the influence of the micro-structure of rock matrix and strength of weak plane on NFS and fracture patterns. The results reveal that the trend of NFS and fracture patterns are slightly influenced by coordination number of rock particles and tensile strength of weak plane, but greatly influenced by percentage of pre-existing cracks and shear strength of weak plane. Micro-parameters of the numerical approach are calibrated to reproduce behaviours of transversely isotropic rocks with different trends, and the simulation results are well matched with experimental results in terms of NFS and fracture patterns. Finally, the numerical approach is applied to study the failure process of layered surrounding rock after tunnel excavation. The simulation results also agree well with observation results of engineering projects.
Print ISSN: 1861-1125
Electronic ISSN: 1861-1133
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 29
Springer
Publication Date: 2018-03-05
Description: The reduction in volume for unsaturated soils wetted at constant total stress is indicated as capillary collapse. Several studies conducted on standard laboratory specimens (macro-scale) outlined the role of initial void ratio, confining pressure and matric suction on collapse onset. Conversely, few observations were made at grain scale, although an important influence of soil structure has been supposed since years. This paper investigated the collapse of coarse and fine sands derived from a pyroclastic soil of Southern Italy. The X-ray computed tomography was used to identify the mechanisms acting at grain scale and to measure the local variations of soil structure. The experimental procedure consisted in preparing remoulded unsaturated specimens and reducing the matric suction until the collapse occurred under self-weight. At different stages of the process, the sample was imaged by X-ray tomography. The experimental results provided original insight into: (1) transformation of soil structure during the wetting tests; (2) variation of porosity, water content and degree of saturation for the whole specimen; and (3) local variations of those variables in several representative sub-volumes. It is worth noting that collapse of coarse sand specimen occurred before saturation. This was also emphasized by the presence of macro-voids at collapse.
Print ISSN: 1861-1125
Electronic ISSN: 1861-1133
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 30
Springer
Publication Date: 2018-03-05
Description: Advances in multi-material 3D printing technologies have opened a new horizon for design and fabrication of architected multi-materials in multiple length scales from nano-/microscale to meso-/macroscales. In this study, we apply modified couple stress and first-order shear deformation theories for a size-dependent structural analysis of 3D printable functionally graded (FG) doubly-curved panels where their microarchitecture can be engineered to improve their structural performance. This non-classical model incorporates the microstructure-dependent size effects for the structural performance through the introduction of a length scale in the kinematics of deformation. The volume fraction of matrix in the dual-phase (inclusion and matrix) FG size-dependent panels varies continuously through the thickness. The microarchitecture of inclusion and matrix in FG panels is engineered to show its effect on the structural responses. We implement the standard mechanics homogenization technique via finite element simulation to accurately predict the effective mechanical properties of FG materials for different topologies of engineered microarchitecture to show the significance of selecting appropriate micromechanical modeling for analyzing FG structures. Governing equations derived by variational Hamilton’s principle are solved by applying the Galerkin method for different sets of boundary conditions. We investigate the effects of material length scale, material composition, heterogeneous material distribution, particulate topology, length-to-thickness ratio, and panel curvature on the structural performance. It is found that the fundamental frequencies of size-dependent two-phase FG doubly-curved panels with square-shape inclusions are higher than for those with other topologies, which sheds lights on the engineering of the inclusion shape in advanced architected materials to optimize their structural performance.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 31
Springer
Publication Date: 2018-03-05
Description: This paper concerns a new and fast meshfree method for the linear coupled thermoelasticity problem. The resulting algorithm provides an attractive alternative to existing mesh-based and meshfree methods. Compared with mesh-based methods, the proposed technique inherits the advantages of meshfree methods allowing the use of scattered points instead of a predefined mesh. Compared with the existing meshfree methods, the proposed technique is truly meshless, requiring no background mesh for both trial and test spaces and, more importantly, numerical integrations are done over low-degree polynomials rather than complicated shape functions. In fact, this method mimics the known advantages of both meshless and finite element methods, where in the former triangulation is not required for approximation and in the latter the stiffness and mass matrices are set up by integration against simple polynomials. The numerical results of the present work concern the thermal and mechanical shocks in a finite domain considering classical coupled theory of thermoelasticity.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 32
Springer
Publication Date: 2018-03-05
Description: According to classical gas dynamic theory, if a steady supersonic parallel flow encounters a sudden change in the wall slope, two very different phenomena may occur. If the flow expands around a sharp corner, the well-known isentropic Prandtl–Meyer fan is observed. Conversely, a shock wave occurs if the flow is compressed: for wedge angles smaller than the detachment value, which depends on the uniform upstream state, an oblique shock originates at the corner; at larger deviation angles, a detached shock is formed. A unified description of these flows is presented here to extend the validity of the common $$\beta$$ – $$\vartheta$$ (shock angle–deflection angle) diagram for shocked non-isentropic flows into the realm of isentropic expansions. The new graph allows for a straightforward identification of the wave angles for self-similar flow fields around compressive and rarefactive corners. Besides, it clarifies the relation between shock waves and rarefaction fans in the neighbourhood of the $${\vartheta =0}$$ axis, where shock waves are weak enough to be fairly well approximated by isentropic compressions. At $${\vartheta =0}$$ , indeed, shock and rarefaction curves are demonstrated to be first order continuous. This result is interpreted in view of the bisector rule for oblique shock waves. Exemplary diagrams are reported for both ideal-gas flows, dilute-gas flows and non-ideal flows of dense vapours in the close proximity of the liquid–vapour saturation curve and critical point. The application of the new diagram is illustrated for the textbook case of the supersonic flow past a diamond-shaped airfoil.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 33
Springer
Publication Date: 2018-03-05
Description: Molecular dynamics simulations with Adaptive Intermolecular Reactive Empirical Bond Order force fields were conducted to determine the transversely isotropic elastic properties of carbon nanotubes (CNTs) containing vacancies. This is achieved by imposing axial extension, twist, in-plane biaxial tension, and in-plane shear to the defective CNTs. The effects of vacancy concentrations, their position, and the diameter of armchair CNTs were taken into consideration. Current results reveal that vacancy defects affect (i) the axial Young’s and shear moduli of smaller-diameter CNTs more than the larger ones and decrease by 8 and 16% for 1 and 2% vacancy concentrations, respectively; (ii) the plane strain bulk and the in-plane shear moduli of the larger-diameter CNTs more profoundly, reduced by 33 and 45% for 1 and 2% vacancy concentrations, respectively; and (iii) the plane strain bulk and in-plane shear moduli among all the elastic coefficients. It is also revealed that the position of vacancies along the length of CNTs is the main influencing factor which governs the change in the properties of CNTs, especially for vacancy concentration of 1%. The current fundamental study highlights the important role played by vacancy defected CNTs in determining their mechanical behaviors as reinforcements in multifunctional nanocomposites.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 34
Springer
Publication Date: 2018-03-05
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 35
Springer
Publication Date: 2018-03-05
Description: A depth-averaged two-velocity grain–fluid mixture model is proposed to describe flows of grain–fluid mixtures. Motivated by the experimental observations, the proposed model considers that the granular and the fluid phases are moving with different velocities, and the velocity difference between the granular phase and the fluid phase is coupled with the granular dilatancy that is described by a granular dilatancy law. The characteristics of flows allow to formulate a simpler depth-averaged PDE system. To scrutinize the proposed equations, an analysis for steady flows in rectangular channels is performed, which reproduces the cross-stream velocity profiles commonly observed in fields. Additionally, a uniform flow is investigated to illustrate the effects of the granular dilatancy on the velocities, flow depth, and volume fractions.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 36
Springer
Publication Date: 2018-03-05
Description: This paper deals with the coupled bending–torsional vibrations of beams carrying an arbitrary number of viscoelastic dampers and attached masses. Exact closed analytical expressions are derived for the frequency response under harmonically varying, arbitrarily placed polynomial loads, making use of coupled bending–torsion theory including warping effects and taking advantage of generalized functions to model response discontinuities at the application points of dampers/masses. In this context, the exact dynamic Green’s functions of the beam are also obtained. The frequency response solutions are the basis to derive the exact dynamic stiffness matrix and load vector of a two-node coupled bending–torsional beam finite element with warping effects, which may include any number of dampers/masses. Remarkably, the size of the dynamic stiffness matrix and load vector is $$8\times 8$$ and $$8\times 1$$ , respectively, regardless of the number of dampers/masses and loads along the beam finite element.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 37
Springer
Publication Date: 2018-03-05
Description: In this paper, we study buckling of radially FGM circular plates. In a previous study, a fourth-order polynomial expressing the exact solution of a linear elastic problem was used as buckling mode shape. To generalise such investigation, in this contribution the buckling mode is postulated to take the shape of a fifth-order polynomial function of the radial coordinate. The flexural rigidity is consequently sought as a polynomial of suitable order, expressing the functional grading. New solutions in closed form are then obtained by a semi-inverse method. It is found that suitable choices of functional grading may increase the buckling load up to 246% with respect to the homogeneous and uniform cases.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 38
Springer
Publication Date: 2018-03-05
Description: Molecular mechanics/molecular dynamics (MM/MD) methods are widely used in computer simulations of deformation (including buckling, vibration, and fracture) of low-dimensional carbon nanostructures (single-layer graphene sheets (SLGSs), single-walled nanotubes, fullerenes, etc). In MM/MD simulations, the interactions between carbon atoms in these nanostructures are modeled using force fields (e.g., AIREBO, DREIDING, MM3/MM4). The objective of the present study is to fit the DREIDING force field parameters (see Mayo et al. J Phys Chem 94:8897–8909, 1990 ) to most closely reproduce the mechanical parameters of graphene (Young’s modulus, Poisson’s ratio, bending rigidity modulus, and intrinsic strength) known from experimental studies and quantum mechanics simulations since the standard set of the DREIDING force field parameters (see Mayo et al. 1990 ) leads to unsatisfactory values of the mechanical parameters of graphene. The values of these parameters are fitted using primitive unit cells of graphene acted upon by forces that reproduce the homogeneous deformation of this material in tension/compression, bending, and fracture. (Different sets of primitive unit cells are used for different types of deformation, taking into account the anisotropic properties of graphene in states close to failure.) The MM method is used to determine the dependence of the mechanical moduli of graphene (Young’s modulus, Poisson’s ratio, and bending rigidity modulus) on the scale factor. Computer simulation has shown that for large linear dimensions of SLGSs, the mechanical parameters of these sheets are close to those of graphene. In addition, computer simulation has shown that accounting for in-layer van der Waals forces has a small effect on the value of the mechanical moduli of graphene.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 39
Springer
Publication Date: 2018-03-05
Description: The sensitivity of tropical cyclone (TC) intensification to the ambient rotation effect under vertical shear is investigated. The results show that the vortices develop more rapidly with intermediate planetary vorticity, which suggests an optimal latitude for the TC development in the presence of vertical shear. This is different from the previous studies in which no mean flow is considered. It is found that the ambient rotation has two main effects. On the one hand, the boundary layer imbalance is largely controlled by the Coriolis parameter. For TCs at lower latitudes, due to the weaker inertial instability, the boundary inflow is promptly established, which results in a stronger moisture convergence and thus greater diabatic heating in the inner core region. On the other hand, the Coriolis parameter modulates the vertical realignment of the vortex with a higher Coriolis parameter, favoring a quicker vertical realignment and thus a greater potential for TC development. The combination of these two effects results in an optimal latitude for TC intensification in the presence of a vertical shear investigated.
Print ISSN: 0894-0525
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 40
Springer
Publication Date: 2018-03-05
Description: By using idealized numerical simulations, the impact of tropical cyclone size on secondary eyewall formation (SEF) is examined. Both unbalanced boundary layer and balanced processes are examined to reveal the underlying mechanism. The results show that a tropical cyclone (TC) with a larger initial size favors a quicker SEF and a larger outer eyewall. For a TC with a larger initial size, it will lead to a stronger surface entropy flux, and thus more active outer convection. Meanwhile, a greater inertial stability helps the conversion from diabatic heating to kinetic energy. Furthermore, the progressively broadening of the tangential wind field will induce significant boundary layer imbalances. This unbalanced boundary layer process results in a supergradient wind zone that acts as an important mechanism for triggering and maintaining deep convection. In short, different behaviors of balanced and unbalanced processes associated with the initial wind profile lead to different development rates of the secondary eyewall.
Print ISSN: 0894-0525
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 41
Springer
Publication Date: 2018-03-05
Description: Statistical methods for category (yes/no) forecasts, such as the Threat Score, are typically used in the verification of precipitation forecasts. However, these standard methods are affected by the so-called “double-penalty” problem caused by slight displacements in either space or time with respect to the observations. Spatial techniques have recently been developed to help solve this problem. The fractions skill score (FSS), a neighborhood spatial verification method, directly compares the fractional coverage of events in windows surrounding the observations and forecasts. We applied the FSS to hourly precipitation verification by taking hourly forecast products from the GRAPES (Global/Regional Assimilation Prediction System) regional model and quantitative precipitation estimation products from the National Meteorological Information Center of China during July and August 2016, and investigated the difference between these results and those obtained with the traditional category score. We found that the model spin-up period affected the assessment of stability. Systematic errors had an insignificant role in the fraction Brier score and could be ignored. The dispersion of observations followed a diurnal cycle and the standard deviation of the forecast had a similar pattern to the reference maximum of the fraction Brier score. The coefficient of the forecasts and the observations is similar to the FSS; that is, the FSS may be a useful index that can be used to indicate correlation. Compared with the traditional skill score, the FSS has obvious advantages in distinguishing differences in precipitation time series, especially in the assessment of heavy rainfall.
Print ISSN: 0894-0525
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 42
Springer
Publication Date: 2018-03-05
Description: We compared the regional synoptic patterns and local meteorological conditions during persistent and non-persistent pollution events in Beijing using US NCEP–Department of Energy reanalysis outputs and observations from meteorological stations. The analysis focused on the impacts of high-frequency (period 〈 90 days) variations in meteorological conditions on persistent pollution events (those lasting for at least 3 days). Persistent pollution events tended to occur in association with slow-moving weather systems producing stagnant weather conditions, whereas rapidly moving weather systems caused a dramatic change in the local weather conditions so that the pollution event was short-lived. Although Beijing was under the influence of anomalous southerly winds in all four seasons during pollution events, notable differences were identified in the regional patterns of sea-level pressure and local anomalies in relative humidity among persistent pollution events in different seasons. A region of lower pressure was present to the north of Beijing in spring, fall, and winter, whereas regions of lower and higher pressures were observed northwest and southeast of Beijing, respectively, in summer. The relative humidity near Beijing was higher in fall and winter, but lower in spring and summer. These differences may explain the seasonal dependence of the relationship between air pollution and the local meteorological variables. Our analysis showed that the temperature inversion in the lower troposphere played an important part in the occurrence of air pollution under stagnant weather conditions. Some results from this study are based on a limited number of events and thus require validation using more data.
Print ISSN: 0894-0525
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 43
Springer
Publication Date: 2018-03-05
Description: A humidification system was deployed to measure aerosol hygroscopicity at a rural site of the North China Plain during the haze red-alert period 17–22 December 2016. The aerosol scattering coefficients under dry [relative humidity (RH) 〈 30%] and wet (RH in the range of 40%–85%) conditions were simultaneously measured at wavelengths of 450, 550, and 700 nm. It is found that the aerosol scattering coefficient and backscattering coefficient increased by only 29% and 10%, respectively when RH went up from 40% to 80%, while the hemispheric backscatter fraction went down by 14%, implying that the aerosol hygroscopicity represented by the aerosol scattering enhancement factor f (RH) is relatively low and RH exerted little effects on the aerosol light scattering in this case. The scattering enhancement factors do not show significant differences at the three wavelengths, only with an approximate 2% variation, suggesting that the aerosol hygroscopicity is independent of the wavelength. Aerosol hygroscopicity is highly dependent on the aerosol chemical composition. When there is a large mass fraction of inorganics and a small mass fraction of organic matter, f(RH) reaches a high value. The fraction of NO 3 – was strongly correlated with the aerosol scattering coefficient at RH = 80%, which suggests that NO 3 – played an important role in aerosol hygroscopic growth during the heavy pollution period.
Print ISSN: 0894-0525
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 44
Springer
Publication Date: 2018-03-05
Description: We present mobile vehicle lidar observations in Tianjin, China during the spring, summer, and winter of 2016. Mobile observations were carried out along the city border road of Tianjin to obtain the vertical distribution characteristics of PM 2.5 . Hygroscopic growth was not considered since relative humidity was less than 60% during the observation experiments. PM 2.5 profile was obtained with the linear regression equation between the particle extinction coefficient and PM 2.5 mass concentration. In spring, the vertical distribution of PM 2.5 exhibited a hierarchical structure. In addition to a layer of particles that gathered near the ground, a portion of particles floated at 0.6–2.5-km height. In summer and winter, the fine particles basically gathered below 1 km near the ground. In spring and summer, the concentration of fine particles in the south was higher than that in the north because of the influence of south wind. In winter, the distribution of fine particles was opposite to that measured during spring and summer. High concentrations of PM 2.5 were observed in the rural areas of North Tianjin with a maximum of 350 μg m –3 on 13 December 2016. It is shown that industrial and ship emissions in spring and summer and coal combustion in winter were the major sources of fine particles that polluted Tianjin. The results provide insights into the mechanisms of haze formation and the effects of meteorological conditions during haze–fog pollution episodes in the Tianjin area.
Print ISSN: 0894-0525
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 45
Springer
Publication Date: 2018-03-05
Description: The optical and radiative properties of aerosols during a severe haze episode from 15 to 22 December 2016 over Beijing, Shijiazhuang, and Jiaozuo in the North China Plain were analyzed based on the ground-based and satellite data, meteorological observations, and atmospheric environmental monitoring data. The aerosol optical depth at 500 nm was 〈 0.30 and increased to 〉 1.4 as the haze pollution developed. The Ångström exponent was 〉 0.80 for most of the study period. The daily single-scattering albedo was 〉 0.85 over all of the North China Plain on the most polluted days and was 〉 0.97 on some particular days. The volumes of fine and coarse mode particles during the haze event were approximately 0.05–0.21 and 0.01–0.43 μm 3 , respectively—that is, larger than those in the time without haze. The daily absorption aerosol optical depth was about 0.01–0.11 in Beijing, 0.01–0.13 in Shijiazhuang, and 0.01–0.04 in Jiaozuo, and the average absorption Ångström exponent varied between 0.6 and 2.0. The aerosol radiative forcing at the bottom of the atmosphere varied from –23 to –227,–34 to –199, and –29 to –191 W m –2 for the whole haze period, while the aerosol radiative forcing at the top of the atmosphere varied from –4 to –98, –10 to –51, and –21 to –143 W m –2 in Beijing, Shijiazhuang, and Jiaozuo, respectively. Satellite observations showed that smoke, polluted dust, and polluted continental components of aerosols may aggravate air pollution during haze episodes. The analysis of the potential source contribution function and concentration-weighted trajectory showed that the contribution from local emissions and pollutants transport from upstream areas were 190–450 and 100–410 μg m –3 , respectively.
Print ISSN: 0894-0525
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 46
Springer
Publication Date: 2018-03-05
Description: This study aims to detect the primary precursors and impact mechanisms for January surface temperature anomaly (JSTA) events in China against the background of global warming, by comparing the causes of two extreme JSTA events occurring in 2008 and 2011 with the common mechanisms inferred from all typical episodes during 1979–2008. The results show that these two extreme events exhibit atmospheric circulation patterns in the mid–high latitudes of Eurasia, with a positive anomaly center over the Ural Mountains and a negative one to the south of Lake Baikal (UMLB), which is a pattern quite similar to that for all the typical events. However, the Eurasian teleconnection patterns in the 2011 event, which are accompanied by a negative phase of the North Atlantic Oscillation, are different to those of the typical events and the 2008 event. We further find that a common anomalous signal appearing in early summer over the tropical Indian Ocean may be responsible for the following late-winter Eurasian teleconnections and the associated JSTA events in China. We show that sea surface temperature anomalies (SSTAs) in the preceding summer over the western Indian Ocean (WIO) are intimately related to the UMLB-like circulation pattern in the following January. Positive WIOSSTAs in early summer tend to induce strong UMLB-like circulation anomalies in January, which may result in anomalously or extremely cold events in China, which can also be successfully reproduced in model experiments. Our results suggest that the WIOSSTAs may be a useful precursor for predicting JSTA events in China.
Print ISSN: 0894-0525
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 47
Springer
Publication Date: 2018-03-05
Description: The western North Pacific anomalous anticyclone (WNPAC) is an important atmospheric circulation system that conveys El Niño impact on East Asian climate. In this review paper, various theories on the formation and maintenance of the WNPAC, including warm pool atmosphere–ocean interaction, Indian Ocean capacitor, a combination mode that emphasizes nonlinear interaction between ENSO and annual cycle, moist enthalpy advection/Rossby wave modulation, and central Pacific SST forcing, are discussed. It is concluded that local atmosphere–ocean interaction and moist enthalpy advection/Rossby wave modulation mechanisms are essential for the initial development and maintenance of the WNPAC during El Niño mature winter and subsequent spring. The Indian Ocean capacitor mechanism does not contribute to the earlier development but helps maintain the WNPAC in El Niño decaying summer. The cold SST anomaly in the western North Pacific, although damped in the summer, also plays a role. An interbasin atmosphere–ocean interaction across the Indo-Pacific warm pool emerges as a new mechanism in summer. In addition, the central Pacific cold SST anomaly may induce the WNPAC during rapid El Niño decaying/La Niña developing or La Niña persisting summer. The near-annual periods predicted by the combination mode theory are hardly detected from observations and thus do not contribute to the formation of the WNPAC. The tropical Atlantic may have a capacitor effect similar to the tropical Indian Ocean.
Print ISSN: 0894-0525
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 48
Springer
Publication Date: 2018-03-05
Description: Urban microclimate peculiarities in two Arctic cities in northwestern Russia—Kirovsk (67.62°N, 33.67°E) and Apatity (67.57°N, 33.38°E)—were investigated by using mobile temperature records. The experiment was carried out in and around Apatity and Kirovsk in February 2014 and December 2016. The DS18B20 digital thermometer was installed on the roof of a car (height: approximately 1.2 m) to measure and record temperature variations automatically. In addition to the digital thermometer, the car was also equipped with an onboard global positioning system, allowing every temperature measurement to be referenced with an altitude and a latitude/longitude position. The possibility of urban heat island formation in these polar cities, above the Arctic Circle, was studied. Our analysis indicated that on 11 February 2014, the temperature varied in accordance with the background environmental lapse rate (–0.0045°C m –1 ), and nearly corresponded to it (–0.0165°C m –1 ) on 12 February 2014. On 6 December 2016, a strong local temperature inversion with a positive value of 0.032°C m –1 was detected, seemingly caused by the formation of a cold air pool in the valley near Kirovsk. It was found that the temperature variations within and outside these cities are strongly influenced by local topographic effects and the physical conditions of the atmospheric boundary layer.
Print ISSN: 0894-0525
Topics: Geosciences
Location Call Number Limitation Availability
Others were also interested in ...
• 49
Springer
Publication Date: 2018-03-05
Print ISSN: 0001-6268
Electronic ISSN: 0942-0940
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 50
Springer
Publication Date: 2018-03-05
Description: Background Brain metastases from hepatocellular carcinoma (HCC) are rare, but their incidence is increasing because of developments in recent therapeutic advances. The purpose of this study was to investigate the characteristics of brain metastases from HCC, to evaluate the predictive factors, and to assess the efficacy of gamma knife surgery (GKS). Method A retrospective study was performed on patients with brain metastases from HCC who were treated at Tokyo Gamma Unit Center from 2005 to 2014. Results Nineteen patients were identified. The median age at diagnosis of brain metastases was 67.0 years. Fifteen patients were male and four patients were female. Six patients were infected with hepatitis B virus (HBV). Two patients were infected with hepatitis C virus (HCV). Eleven patients were not infected with HBV or HCV. The median interval from the diagnosis of HCC to brain metastases was 32.0 months. The median number of brain metastases was two. The median Karnofsky performance score at first GKS was 70. The median survival time following brain metastases was 21.0 weeks. Six-month and 1-year survival rates were 41.2 and 0%, respectively. One month after GKS, no tumor showed progressive disease. The HBV infection (positive vs. negative) was significantly associated with survival according to univariate analysis ( p  = 0.002). Conclusions The patients having brain metastases from HCC had poor prognosis and low performance state. Therefore, GKS is an acceptable option for controlling brain metastases from HCC because GKS is noninvasive remedy and local control is reasonable.
Print ISSN: 0001-6268
Electronic ISSN: 0942-0940
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 51
Springer
Publication Date: 2018-03-05
Print ISSN: 0001-6268
Electronic ISSN: 0942-0940
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 52
Springer
Publication Date: 2018-03-05
Description: Background Full recovery is unlikely for severe cubital tunnel syndrome, and prognostic factors remain uncertain. We aimed to identify predictors of surgical outcome for these patients. Methods One hundred forty-six patients with McGowan grade III cubital tunnel syndrome were evaluated retrospectively with a minimum follow-up of 2 years. All patients underwent either in situ decompression or subcutaneous transposition. The primary outcome measure was postoperative McGowan grade. Predictors included age, sex, dominant hand, disease duration, diabetes mellitus, smoking, alcohol, surgical procedure, follow-up time and preoperative electrophysiological data. Spearman’s rank correlation and ordinal logistic regression model were used to assess the effect of independent variables on the postoperative McGowan grade. Results At the last follow-up, improvement by at least one McGowan grade was reached in 118 cases (80.8%), and complete recovery was achieved in 40 hands (27.4%), while 28 extremities (19.2%) remained at grade III. Older age [per 10-year increase, odds ratio (OR) 2.10; 95% confidence interval (95% CI) 1.55–2.84, p  〈 0.001], longer disease duration (per 1-year increase, OR 1.31; 95% CI 1.16–1.49, p  〈 0.001), absent sensory nerve conduction (OR 2.55; 95% CI 1.25–5.21, p  = 0.010) and shorter postoperative follow-up (per 1-year increase, OR 0.76; 95% CI 0.65–0.90, p  = 0.001) were associated with a higher postoperative McGowan grade. Conclusion Significant improvement but not complete recovery could be expected following in situ decompression or subcutaneous transposition for severe cubital tunnel syndrome. Older age, longer disease duration, absent sensory nerve conduction and shorter postoperative follow-up are independent predictors of worse outcomes.
Print ISSN: 0001-6268
Electronic ISSN: 0942-0940
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 53
Springer
Publication Date: 2018-03-05
Description: Background Perineural spread (PNS) of pelvic cancer along the lumbosacral plexus is an emerging explanation for neoplastic lumbosacral plexopathy (nLSP) and an underestimated source of patient morbidity and mortality. Despite the increased incidence of PNS, these patients are often times a clinical conundrum—to diagnose and to treat. Building on previous results in modeling glioblastoma multiforme (GBM), we present a mathematical model for predicting the course and extent of the PNS of recurrent tumors. Methods We created three-dimensional models of perineurally spreading tumor along the lumbosacral plexus from consecutive magnetic resonance imaging scans of two patients (one each with prostate cancer and cervical cancer). We adapted and applied a previously reported mathematical model of GBM to progression of tumor growth along the nerves on an anatomical model obtained from a healthy subject. Results We were able to successfully model and visualize perineurally spreading pelvic cancer in two patients; average growth rates were 60.7 mm/year for subject 1 and 129 mm/year for subject 2. The model correlated well with extent of PNS on MRI scans at given time points. Conclusions This is the first attempt to model perineural tumor spread and we believe that it provides a glimpse into the future of disease progression monitoring. Every tumor and every patient are different, and the possibility to report treatment response using a unified scale—as “days gained”—will be a necessity in the era of individualized medicine. We hope our work will serve as a springboard for future connections between mathematics and medicine.
Print ISSN: 0001-6268
Electronic ISSN: 0942-0940
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 54
Springer
Publication Date: 2018-03-05
Description: Background Overall (OS) and progression-free survival (PFS) of patients undergoing spinal ependymoma resection has been frequently reported. Contrarily, OS and PFS of purely intramedullary ependymomas have not been clearly determined yet. Methods The data of 37 patients undergoing resection of an intramedullary ependymoma (IE) from January 2000 to December 2016 were analysed retrospectively. Results The mean age was 46 years. The male:female ratio was 24:13. The median duration of symptoms was 12 months. Sixty-two per cent of ependymomas were in the cervical, 24% in the thoracic, and 14% in the conus region in our series. The median volume was 1.3 ml. A syrinx was found in 49% and a cyst in 32%. GTR was achieved in 89%, STR in three (8%), and PR in one patient (3%). Median follow-up was 114 months. PFS was 87%, 82%, and 82% at 5, 10, and 15 years, respectively. OS was 97%, 88%, and 63% at 5, 10, and 15 years, respectively. There was a significant difference in PFS depending on the extent of resection and in OS depending on the pre-operative clinical status. There was no significant difference in OS and PFS regarding the other examined influencing factors. Conclusion GTR resection was the most important factor influencing PFS. According to our results OS of IEs is much worse than that of spinal ependymomas. Our analysis confirms that patients with good pre-operative (McCormick grade 1 and 2) clinical status have significantly better OS than patients with McCormick grade 3 and higher.
Print ISSN: 0001-6268
Electronic ISSN: 0942-0940
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 55
Springer
Publication Date: 2018-03-05
Description: Background Mycotic aneurysms, although well recognized, are relatively rare intracranial vascular pathology. These aneurysms are typically located in distal cortical vessels. When these aneurysms are located in eloquent cerebral territories, they may become challenging to treat. Eloquent location may necessitate intraoperative angiographic evaluation to verify complete aneurysmal occlusion/obliteration and preservation of normal adjacent vasculture. Recently, ICG videoangiography has become a widely used intra-operative adjunct and is an important tool used to assess complete occlusion and vessel patency at the conclusion of clip reconstruction. In this report, we outline the comprehensive and concurrent utilization of both vascular imaging modalities to ensure safe and complete occlusion of a mycotic aneurysm. Methods We describe our experience with a patient with left M4, Rolandic, enlarging mycotic aneurysm that was treated in a comprehensive fashion with microsurgery and intra-operative angiography (IA). Conclusions ICG videoangiography, in combination with concurrent intraoperative angiography in the setting of complex vascular lesions, may support intraoperative decision-making and provide demonstration of complete occlusion in an immediate fashion. A hybrid operative suite allows for high-quality imaging confirming complete resection.
Print ISSN: 0001-6268
Electronic ISSN: 0942-0940
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 56
Springer
Publication Date: 2018-03-05
Description: Background Ayub Ommaya proposed a surgical technique for subcutaneous reservoir and pump placement in 1963 to allow access to intraventricular cerebrospinal fluid (CSF). Currently, the most common indication for Ommaya reservoir insertion (ORI) in adults is for patients with hematologic or leptomeningeal disorders requiring repeated injection of chemotherapy into the CSF space. Historically, the intraventricular catheter has been inserted blindly based on anatomical landmarks. The purpose of this study was to examine short-term complication rates with ORI with image guidance (IG) and without image guidance (non-IG). Methods We retrospectively evaluated all operative cases of ORI from 2000 to 2014 by the senior author. Patient demographic data, surgical outcomes, and peri-operative complications were collected. Accurate placement and early (30-day) morbidity or mortality were considered primary outcomes. Results Fifty-five consecutive patients underwent ORI by the senior author over the study period (43.5 ± 16.6 years; 40.0% female). Indications for placement included acute lymphoblastic leukemia, diffuse large B-cell lymphoma, and leptomeningeal carcinomatosis. There were seven (12.7%) total complications: three (37.5%) with no-IG versus four (8.5%) with IG. Catheter malpositions were significantly higher in the non-IG group at 37.5% compared to 2.1%. Catheters were also more likely to require multiple passes with non-IG at 25% compare to 0% with IG. There were no early infections in either group. Conclusions We demonstrate improved accuracy and decreased complications using an image-guided approach compared with a traditional approach. Our results support routine use of intra-operative image guidance for proximal catheter insertion in elective ORI for intraventricular chemotherapy.
Print ISSN: 0001-6268
Electronic ISSN: 0942-0940
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 57
Springer
Publication Date: 2018-03-05
Description: Background Intraperitoneal pressure (IPP) counteracts the diversion of cerebrospinal fluid (CSF) from the cranial to the peritoneal compartment during ventriculoperitoneal shunting. Animal studies suggest that the intrinsic IPP exceeds the intraperitoneal hydrostatic pressure. The intrinsic IPP in mobile patients is relevant for shunt therapy, but data about it is not available. Methods The IPP was measured indirectly in 25 mobile subjects (13 female) by applying a standard intravesical pressure measurement technique. Measurements were carried out in reference to the navel (supine position) and the xiphoid (upright position). Results were adjusted for the intraperitoneal hydrostatic pressure and correlated afterward with general body measures. Results The corrected mean (SD) IPP measured in the supine position was 4.4 (4.5) cm H 2 O, and the mean (SD) upright IPP was 1.6 (7.8) cm H 2 O ( p  = 0.02). A positive correlation was found between the body mass index (BMI) and the IPP in the upright ( r  = 0.51) and supine ( r  = 0.65) body positions, and between the abdominal circumference and the IPP in the supine position ( r  = 0.63). Conclusions The intrinsic IPP in mobile subjects exceeds the intraperitoneal hydrostatic pressure. Thus, the intrinsic IPP counteracts the diversion of CSF into the peritoneal compartment. The intrinsic IPP is correlated with mobile patients’ general body measures.
Print ISSN: 0001-6268
Electronic ISSN: 0942-0940
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 58
Springer
Publication Date: 2018-03-05
Description: Background The aim of this retrospective study was to investigate the long-term seizure control and antiepileptic drug (AED) prescriptions, as well as identifying predictors of seizure(s) before and after surgery in a population-based cohort of operated intracranial meningioma patients. Methods A total of 113 consecutive adult (〉 18 years old) patients with newly diagnosed meningioma operated at the Karolinska University Hospital between 2006 and 2008 were included and followed up until the end of 2015. Data on seizure activity and AED prescriptions were obtained through chart review and telephone interview. Logistic regression and survival analysis were applied to identify risk factors for pre- and postoperative seizures. Results A total of 21/113 (18.6%) patients experienced seizures before surgery of which 8/21 (38.1%) went on to become seizure-free after surgery. Thirteen (14%) patients experienced new-onset seizures after surgery. The regression analysis revealed tumor diameter ≥ 3.5 cm as a risk factor for preoperative seizures (OR 3.83, 95% CI 1.14–12.87). Presence of headache (OR 0.19, 95% CI 0.05–0.76) and skull base tumor location (OR 0.14, 95% CI 0.04–0.44) decreased the risk of preoperative seizures. Postoperative seizures were associated with tumor diameter ≥ 3.5 cm (OR 2.65, 95% CI 1.06–6.62) and history of preoperative seizures (OR 3.50, 95% CI 1.55–7.90). Conclusion Seizures are common before and after intracranial meningioma surgery. Approximately one third of patients with preoperative seizures become seizure-free on long-term follow-up after surgery, while 14% experienced new-onset seizures after surgery. Larger tumor size, absence of headache, and non-skull base location were associated with preoperative seizures, while tumor size and preoperative seizures were associated with postoperative seizures.
Print ISSN: 0001-6268
Electronic ISSN: 0942-0940
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 59
Springer
In: 4OR
Publication Date: 2018-03-05
Print ISSN: 1619-4500
Electronic ISSN: 1614-2411
Topics: Mathematics
Location Call Number Limitation Availability
Others were also interested in ...
• 60
Springer
In: 4OR
Publication Date: 2018-03-05
Print ISSN: 1619-4500
Electronic ISSN: 1614-2411
Topics: Mathematics
Location Call Number Limitation Availability
Others were also interested in ...
• 61
Springer
Publication Date: 2018-03-05
Print ISSN: 0001-6322
Electronic ISSN: 1432-0533
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 62
Springer
Publication Date: 2018-03-05
Print ISSN: 0001-6322
Electronic ISSN: 1432-0533
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 63
Springer
Publication Date: 2018-03-05
Description: Mitochondrial complex I deficiency occurs in the substantia nigra of individuals with Parkinson’s disease. It is generally believed that this phenomenon is caused by accumulating mitochondrial DNA damage in neurons and that it contributes to the process of neurodegeneration. We hypothesized that if these theories are correct, complex I deficiency should extend beyond the substantia nigra to other affected brain regions in Parkinson’s disease and correlate tightly with neuronal mitochondrial DNA damage. To test our hypothesis, we employed a combination of semiquantitative immunohistochemical analyses, Western blot and activity measurements, to assess complex I quantity and function in multiple brain regions from an extensively characterized population-based cohort of idiopathic Parkinson’s disease ( n  = 18) and gender and age matched healthy controls ( n  = 11). Mitochondrial DNA was assessed in single neurons from the same areas by real-time PCR. Immunohistochemistry showed that neuronal complex I deficiency occurs throughout the Parkinson’s disease brain, including areas spared by the neurodegenerative process such as the cerebellum. Activity measurements in brain homogenate confirmed a moderate decrease of complex I function, whereas Western blot was less sensitive, detecting only a mild reduction, which did not reach statistical significance at the group level. With the exception of the substantia nigra, neuronal complex I loss showed no correlation with the load of somatic mitochondrial DNA damage. Interestingly, α-synuclein aggregation was less common in complex I deficient neurons in the substantia nigra. We show that neuronal complex I deficiency is a widespread phenomenon in the Parkinson’s disease brain which, contrary to mainstream theory, does not follow the anatomical distribution of neurodegeneration and is not associated with the neuronal load of mitochondrial DNA mutation. Our findings suggest that complex I deficiency in Parkinson’s disease can occur independently of mitochondrial DNA damage and may not have a pathogenic role in the neurodegenerative process.
Print ISSN: 0001-6322
Electronic ISSN: 1432-0533
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 64
Springer
Publication Date: 2018-03-05
Description: A GGGGCC hexanucleotide repeat expansion in the C9orf72 gene is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia. Neurodegeneration may occur via transcription of the repeats into inherently toxic repetitive sense and antisense RNA species, or via repeat-associated non-ATG initiated translation (RANT) of sense and antisense RNA into toxic dipeptide repeat proteins. We have previously demonstrated that regular interspersion of repeat RNA with stop codons prevents RANT (RNA-only models), allowing us to study the role of repeat RNA in isolation. Here we have created novel RNA-only Drosophila models, including the first models of antisense repeat toxicity, and flies expressing extremely large repeats, within the range observed in patients. We generated flies expressing ~ 100 repeat sense or antisense RNA either as part of a processed polyadenylated transcript or intronic sequence. We additionally created Drosophila expressing 〉 1000 RNA-only repeats in the sense direction. When expressed in adult Drosophila neurons polyadenylated repeat RNA is largely cytoplasmic in localisation, whilst intronic repeat RNA forms intranuclear RNA foci, as does 〉 1000 repeat RNA, thus allowing us to investigate both nuclear and cytoplasmic RNA toxicity. We confirmed that these RNA foci are capable of sequestering endogenous Drosophila RNA-binding proteins, and that the production of dipeptide proteins (poly-glycine–proline, and poly-glycine–arginine) is suppressed in our models. We find that neither cytoplasmic nor nuclear sense or antisense RNA are toxic when expressed in adult Drosophila neurons, suggesting they have a limited role in disease pathogenesis.
Print ISSN: 0001-6322
Electronic ISSN: 1432-0533
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 65
Springer
Publication Date: 2018-03-05
Description: Meninges that surround the CNS consist of an outer fibrous sheet of dura mater (pachymeninx) that is also the inner periosteum of the skull. Underlying the dura are the arachnoid and pia mater (leptomeninges) that form the boundaries of the subarachnoid space. In this review we (1) examine the development of leptomeninges and their role as barriers and facilitators in the foetal CNS. There are two separate CSF systems during early foetal life, inner CSF in the ventricles and outer CSF in the subarachnoid space. As the foramina of Magendi and Luschka develop, one continuous CSF system evolves. Due to the lack of arachnoid granulations during foetal life, it is most likely that CSF is eliminated by lymphatic drainage pathways passing through the cribriform plate and nasal submucosa. (2) We then review the fine structure of the adult human and rodent leptomeninges to establish their roles as barriers and facilitators for the movement of fluid, cells and pathogens. Leptomeningeal cells line CSF spaces, including arachnoid granulations and lymphatic drainage pathways, and separate elements of extracellular matrix from the CSF. The leptomeningeal lining facilitates the traffic of inflammatory cells within CSF but also allows attachment of bacteria such as Neisseria meningitidis and of tumour cells as CSF metastases. Single layers of leptomeningeal cells extend into the brain closely associated with the walls of arteries so that there are no perivascular spaces around arteries in the cerebral cortex. Perivascular spaces surrounding arteries in the white matter and basal ganglia relate to their two encompassing layers of leptomeninges. (3) Finally we examine the roles of ligands expressed by leptomeningeal cells for the attachment of inflammatory cells, bacteria and tumour cells as understanding these roles may aid the design of therapeutic strategies to manage developmental, autoimmune, infectious and neoplastic diseases relating to the CSF, the leptomeninges and the associated CNS.
Print ISSN: 0001-6322
Electronic ISSN: 1432-0533
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 66
Springer
Publication Date: 2018-03-05
Description: The barrier between the blood and the ventricular cerebrospinal fluid (CSF) is located at the choroid plexuses. At the interface between two circulating fluids, these richly vascularized veil-like structures display a peculiar morphology explained by their developmental origin, and fulfill several functions essential for CNS homeostasis. They form a neuroprotective barrier preventing the accumulation of noxious compounds into the CSF and brain, and secrete CSF, which participates in the maintenance of a stable CNS internal environment. The CSF circulation plays an important role in volume transmission within the developing and adult brain, and CSF compartments are key to the immune surveillance of the CNS. In these contexts, the choroid plexuses are an important source of biologically active molecules involved in brain development, stem cell proliferation and differentiation, and brain repair. By sensing both physiological changes in brain homeostasis and peripheral or central insults such as inflammation, they also act as sentinels for the CNS. Finally, their role in the control of immune cell traffic between the blood and the CSF confers on the choroid plexuses a function in neuroimmune regulation and implicates them in neuroinflammation. The choroid plexuses, therefore, deserve more attention while investigating the pathophysiology of CNS diseases and related comorbidities.
Print ISSN: 0001-6322
Electronic ISSN: 1432-0533
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 67
Springer
Publication Date: 2018-03-05
Description: Amyloid-β (Aβ) is a peptide deposited in the brain parenchyma in Alzheimer’s disease and in cerebral blood vessels, causing cerebral amyloid angiopathy (CAA). Aβ pathology is transmissible experimentally in animals and through medical procedures in humans, such as contaminated growth hormone or dura mater transplantation in the context of iatrogenic prion disease. Here, we present four patients who underwent neurosurgical procedures during childhood or teenage years and presented with intracerebral haemorrhage approximately three decades later, caused by severe CAA. None of these patients carried pathogenic mutations associated with early Aβ pathology development. In addition, we identified in the literature four patients with a history of neurosurgical intervention and subsequent development of CAA. These findings raise the possibility that Aβ pathology may be transmissible, as prion disease is, through neurosurgical procedures.
Print ISSN: 0001-6322
Electronic ISSN: 1432-0533
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 68
Springer
Publication Date: 2018-03-05
Description: Multiple sclerosis (MS) is a highly heterogeneous disease with large inter-individual differences in disease course. MS lesion pathology shows considerable heterogeneity in localization, cellular content and degree of demyelination between patients. In this study, we investigated pathological correlates of disease course in MS using the autopsy cohort of the Netherlands Brain Bank (NBB), containing 182 MS brain donors. Using a standardized autopsy procedure including systematic dissection from standard locations, 3188 tissue blocks containing 7562 MS lesions were dissected. Unbiased measurements of lesion load were made using the tissue from standard locations. Lesion demyelinating and innate inflammatory activity were visualized by immunohistochemistry for proteolipid protein and human leukocyte antigen. Lesions were classified into active, mixed active/inactive (also known as chronic active), inactive or remyelinated, while microglia/macrophage morphology was classified as ramified, amoeboid or foamy. The severity score was calculated from the time from first symptoms to EDSS-6. Lesion type prevalence and microglia/macrophage morphology were analyzed in relation to clinical course, disease severity, lesion load and sex, and in relation to each other. This analysis shows for the first time that (1) in progressive MS, with a mean disease duration of 28.6 ± 13.3 years (mean ± SD), there is substantial inflammatory lesion activity at time to death. 57% of all lesions were either active or mixed active/inactive and 78% of all patients had a mixed active/inactive lesion present; (2) patients that had a more severe disease course show a higher proportion of mixed active/inactive lesions ( p  = 6e−06) and a higher lesion load ( p  = 2e−04) at the time of death, (3) patients with a progressive disease course show a higher lesion load ( p  = 0.001), and a lower proportion of remyelinated lesions ( p  = 0.03) compared to patients with a relapsing disease course, (4) males have a higher incidence of cortical grey matter lesions ( p  = 0.027) and a higher proportion of mixed active/inactive lesions compared to females across the whole cohort ( p  = 0.007). We confirm that there is a higher proportion of mixed active/inactive lesions ( p  = 0.006) in progressive MS compared to relapsing disease. Identification of mixed active/inactive lesions on MRI is necessary to determine whether they can be used as a prognostic tool in living MS patients.
Print ISSN: 0001-6322
Electronic ISSN: 1432-0533
Topics: Medicine
Location Call Number Limitation Availability
Others were also interested in ...
• 69
Springer
Publication Date: 2018-03-05
Description: Sediment resuspension is commonly assumed to be eroded from the seabed surface by an excess bottom shear stress and evolves in layers from the top down. Although considerable investigations have argued the importance of wave-induced seabed fluidization in affecting the sediment resuspension, few studies have been able to reliably evaluate its quantitative contribution till now. Attempt is made to preliminarily quantify the contribution of fluidization to resuspension using a series of large-scale wave flume experiments. The experimental results indicated that fluidization of the sandy silts of the Huanghe Delta account for 52.5% and 66.8% of the total resuspension under model scales of 4/20 and 6/20 (i.e., relative water depth: the ratio of wave height to water depth), respectively. Some previously reported results obtained using the same flume and sediments are also summarized for a contrastive analysis, through which not only the positive correlation is confirmed, but also a parametric equation for depicting the relationship between the contribution of fluidization and the model scale is established. Finally, the contribution of fluidization is attributed to two physical mechanisms: (1) an attenuation of the erosion resistance of fluidized sediments in surface layers due to the disappearing of original cohesion and the uplifting effect resulting from upward seepage flows, and (2) seepage pumping of fines from the interior to the surface of fluidized seabed.
Print ISSN: 0253-505X
Electronic ISSN: 1869-1099
Topics: Geosciences , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 70
Springer
Publication Date: 2018-03-05
Description: The southern Patagonian stock (SPS) of Argentinian shortfin squid, Illex argentinus , is an economically important squid fishery in the Southwest Atlantic. Environmental conditions in the region play an important role in regulating the population dynamics of the I. argentinus population. This study develops an environmentally dependent surplus production (EDSP) model to evaluate the stock abundance of I. argentines during the period of 2000 to 2010. The environmental factors (favorable spawning habitat areas with sea surface temperature of 16–18°C) were assumed to be closely associated with carrying capacity (K) in the EDSP model. Deviance Information Criterion (DIC) values suggest that the estimated EDSP model with environmental factors fits the data better than a Schaefer surplus model without environmental factors under uniform and normal scenarios. The EDSP model estimated a maximum sustainable yield (MSY) from 351 600 t to 685 100 t and a biomass from 1 322 400 t to 1 803 000 t. The fishing mortality coefficient of I. argentinus from 2000 to 2010 was smaller than the values of F0.1 and F MSY . Furthermore, the time series biomass plot of I. argentinus from 2000 to 2010 shows that the biomass of I. argentinus and this fishery were in a good state and not presently experiencing overfishing. This study suggests that the environmental conditions of the habitat should be considered within squid stock assessment and management.
Print ISSN: 0253-505X
Electronic ISSN: 1869-1099
Topics: Geosciences , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 71
Springer
Publication Date: 2018-03-05
Description: The southern uplift of the Qiongdongnan Basin is a deepwater area in which no wells have beens drilled. The Miocene-Quaternary strata in the Xisha Islands, which are located 40–100 km to the south, are composed of carbonate reef formations. Paleotectonic and paleogeographic analyses of the basin suggest that the southern uplift experienced favorable geological conditions for the development of carbonate reefs during the Miocene. The high-impedance carbonates have high amplitudes and low frequencies on seismic profiles. The reefs are distributed on paleotectonic highs and are thicker than the contemporaneous formations. A forward model of the variation in carbonate thickness based on lithological and velocity information from wells in nearby regions can simulate the seismic response of carbonates with different thicknesses. We identified several important controlling points for determining the thickness of carbonates from seismic profiles, including the pinchout point, the λ /4 thickness point, and the λ /2 thickness point. We depict a carbonate thickness map in the deepwater area of the southern Qiongdongnan Basin based on this model. The carbonate thickness map, the paleotectonic and paleogeographic background, and the seismic response characteristics of reefs suggest that the carbonates that developed on the southern uplift of the Qiongdongnan Basin during the Miocene were mainly an isolated carbonate platform peninsula and ramp deposits. It consisted of gentle ramp platform, steep slope platform, platform depression, gravity flow, and reef bank facies.
Print ISSN: 0253-505X
Electronic ISSN: 1869-1099
Topics: Geosciences , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 72
Springer
Publication Date: 2018-03-05
Description: BMP2 plays crucial roles in vertebrate developmental process and acts as a bone inducer during osteogenesis. We present here the molecular cloning of bmp2 cDNA from the marine flatfish Cynoglossus semilaevis , and the analysis of bmp2 expression profiling and promoter function. The full length of bmp2 cDNA sequence is 2 048 bp, which encodes a protein of 422 amino acids. Tissue expression distribution of bmp2 was examined in 14 tissues of mature individuals by quantitative real time PCR (qRT-PCR). The results revealed that bmp2 was expressed ubiquitously, and the highest expression level was detected in the spinal cord. Moreover, bmp2 expression levels were detected at 15 sampling time points of early developmental stages (egg, larva, juvenile and fingerling stages). The highest expression level of bmp2 was observed at the gastrula stage, which was about ten times higher than those at the other three embryo stages. Whole-mount in situ hybridization showed that the bmp2 signal was strongly detected at the location of the crown-like larval fin, heart and liver, and slightly expressed in the notochord at one day post hatch (dph); then the expression of bmp2 started to be concentrated in notochord at three dph. Subsequently, we characterized the 5′-flanking region of bmp2 by testing the promoter activity by Luciferase reporter assays. Positive regulatory region was detected at the location of–179 to +109. The predicted transcription factor binding sites (E-box binding factors, zinc finger transcription factor, etc.) in this region might participate in the transcriptional regulation of the bmp2 gene.
Print ISSN: 0253-505X
Electronic ISSN: 1869-1099
Topics: Geosciences , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 73
Springer
Publication Date: 2018-03-05
Description: The Oligocene Huagang Formation is the main sandstone reservoir in the Xihu Sag, situated in the east of the East China Sea Shelf Basin. With an integrated approach of thin-section petrography, ultra-violet fluorescence microscopy, scanning electron microscopy, and isotope geochemistry, the different diagenetic features were identified, the typical diagenetic parasequences were established, and the diagenetic fluids evolution history were reconstructed for the Oligocene Huagang Formation sandstone reservoir in the south of Xihu Sag. The Huagang Formation sandstone reservoir is now in Period B of the mesodiagenesis, which has undergone significant diagenetic alterations such as mechanical compaction, Pore-lining chlorite cement, feldspar dissolution, quartz cementation and dissolution, and carbonate cementation. Three types of carbonate cements (early siderite, medium ferrocalcite and late ankerite) were identified in the Huagang Formation sandstone reservoir. The carbon and oxygen isotopic compositions of carbonate cements show that the early calcite precipitate from alkaline lacustrine environment whereas the late carbonate cements were closely related to the organic acids. To the Huagang Formation sandstone reservoir, it has experienced two main episodes of dissolution during diagenesis. The early dissolution is that unstable components such as feldspar, lithic fragments, and carbonate cement were dissolved by acidic water. The second dissolution is that quartz and other silicate minerals were dissolved under the alkaline condition. Two main phases of hydrocarbon charging occurred in this study area. The first hydrocarbon emplacement was prior to the medium carbonate cementation but posterior to feldspar dissolution and the onset of quartz cementation at the end of the Miocene. The second hydrocarbon charging occurred in the Quaternary period after the late carbonate precipitation.
Print ISSN: 0253-505X
Electronic ISSN: 1869-1099
Topics: Geosciences , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 74
Springer
Publication Date: 2018-03-05
Description: The Okinawa Trough (OT) is a back-arc basin at an initial spreading stage that is under the influence of subduction of the Philippine Sea Plate. In this study, we analyzed the geochemical compositions of basaltic glass in the OT and discussed the effects of different magmatic sources, evolution, and subducted components in basalts. Our results showed that the middle and southern regions of the OT exhibit characteristics consistent with an iron-rich tholeiite series. Trace element proportions conform to the typical spider diagram pattern characteristic of back-arc basin basalts, rich in large ion lithophile elements (LILEs) including Rb, Ba, Pb, U, and Th, while depleted in high field-strength elements (HFSEs) including Nb, Ta, Zr, Hf, and Ti. The distribution of rare earth elements (REEs) is also consistent with enrichment by right-leaning light rare earth elements (LREEs). The addition of enriched mantle type I (EMI) materials as well as mantle heterogeneity may have led to variable degrees of enrichment in different regions. The magma source of the middle trough has undergone crystallization towards pyroxene, while development of plagioclase was restricted partly, and the crystallization of spinel and olivine ceased altogether. At the same time, crystallization of the southern OT magma source was dominated by olivine and including the formation of plagioclase, pyroxene, and magnetite (or titanomagnetite). Finally, the results of this study showed that 90% Th, 95% Ba in the southern basalt, 50%–70% Th and 70%–90% Ba in the middle basalt originated from subducted component. Different subducted component influence may be due to different subduction zone structural feature.
Print ISSN: 0253-505X
Electronic ISSN: 1869-1099
Topics: Geosciences , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 75
Springer
Publication Date: 2018-03-05
Description: Agarases are hydrolytic enzymes that act on the hydrolysis of agar and have a broad range of applications in food, cosmetics and pharmaceutical industries. In this study, a glycerol feeding strategy based on induction mode optimization for high cell density and β-agarase production was established, which could effectively control acetate yield. First, exponential feeding strategy of glycerol with different overall specific growth rates ( μ ) was applied in the pre-induction phase. The results showed that the low μ ( μ =0.2) was suggested to be the optimal for cell growth and β-agarase production. Second, the effects of induction temperature and the inducer concentration on cell growth and β-agarase production were investigated in the post-induction phase. When induced by isopropyl-β-d-thiogalactoside (IPTG), the strategy of 0.8 mmol/L IPTG induction at 20°C was found to be optimal for β-agarase production. When cultivation was induced by continuous lactose feeding strategy of 1.0 g/(L·h), the β-agarase activity reached 112.5 U/mL, which represented the highest β-agarase production to date. Furthermore, the β-agarase was capable of degrading G. lemaneiformis powder directly to produce neoagarooligosaccharide, and the hydrolysates were neoagarotetraose (NA4) and neoagarohexaose (NA6). The overall research may be useful for the industrial production and application of β-agarase.
Print ISSN: 0253-505X
Electronic ISSN: 1869-1099
Topics: Geosciences , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 76
Springer
Publication Date: 2018-03-05
Description: The Liwan Sag, with an area of 4 000 km 2 , is one of the deepwater sags in the Zhujiang River (Pearl River) Mouth Basin, northern South China Sea. Inspired by the exploration success in oil and gas resources in the deepwater sags worldwide, we conducted the thermal modeling to investigate the tectono-thermal history of the Liwan Sag, which has been widely thought to be important to understand tectonic activities as well as hydrocarbon potential of a basin. Using the multi-stage finite stretching model, the tectonic subsidence history and the thermal history have been obtained for 12 artificial wells, which were constructed on basis of one seismic profile newly acquired in the study area. Two stages of rifting during the time periods of 49–33.9 Ma and 33.9–23 Ma can be recognized from the tectonic subsidence pattern, and there are two phases of heating processes corresponding to the rifting. The reconstructed average basal paleo-heat flow values at the end of the rifting events are ~70.5 and ~94.2 mW/m 2 respectively. Following the heating periods, the study area has undergone a persistent thermal attenuation phase since 23 Ma and the basal heat flow cooled down to ~71.8–82.5 mW/m 2 at present.
Print ISSN: 0253-505X
Electronic ISSN: 1869-1099
Topics: Geosciences , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 77
Springer
Publication Date: 2018-03-05
Description: The chromosomes of spinyhead croaker Collichthys lucidus (Richardson, 1844) were characterized for the first time by fluorescence staining, self genomic in situ hybridization (self-GISH), and multicolor fluorescence in situ hybridization (FISH) with 18S rDNA, 5S rDNA and telomeric sequence probes. The female karyotype has exclusively 24 pairs of acrocentric chromosomes (2n=48a, NF=48), while the male one consists of 22 pairs of acrocentric chromosomes, 2 monosomic acrocentric chromosomes and a metacentric chromosome (2n=1m+46a, NF=48). The difference between female and male karyotypes indicates the presence of a sex chromosome of X 1 X 1 X 2 X 2 /X 1 X 2 Y type, where Y is the unique metacentric chromosome in the male karyotype. As revealed by FISH, 5S rDNA and 18S rDNA sites were mapped at syntenic position of the largest acrocentric chromosome (X 1 ), and the short arms of the Y chromosome as well. An X 1 -chromosome specific interstitial telomeric signal (ITS) was detected overlapping the 5S rDNA sites. In addition, self-GISH revealed that the repetitive DNAs accumulated on all the putative sex chromosome. Chromosome fusion accompanied by a partial deletion in the ancestral karyotype (2n=48a) is hypothesized for the origin of such multiple sex chromosome system. The present study, as the first description of differentiated sex chromosome in family Sciaenidae, will give clues to the studies on the sex chromosome of other Sciaenids.
Print ISSN: 0253-505X
Electronic ISSN: 1869-1099
Topics: Geosciences , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 78
Springer
Publication Date: 2018-03-05
Description: Three comprehensive surveys were performed in the Changjiang (Yangtze River) Estuary (CJE) to understand the biogenic silica (BSi) composition, behavior and budget. It is indicated that the BSi is composed of phytoliths, phytoplankton and sponges; phytolith BSi has 16 forms and account for 23% to 83% of the bulk BSi in the maximum turbidity zone. The budget shows that the major exogenous BSi source in the water column of the CJE is the riverine input, accounting for 95% of the total BSi input. Dominant processes that maintain BSi levels in the water column are the primary production (55 Gmol/a) and the subsequent BSi sedimentation (46 Gmol/a); and the BSi pool produced by the primary production represents two point three times the BSi loading of the Changjiang River and 63% of the BSi output, respectively. The net export (26 Gmol/a) of BSi from the CJE to the East China Sea and Yellow Sea roughly equals the riverine BSi loading. The observed total accumulation of BSi is one point seven times larger than the loading of total BSi output, with 53% to 88% of phytolith BSi and their assemblage, indicating that there has already been a “filter” of terrestrial BSi. The reverse weathering in sediments is an important process for the reactive silica removal in the CJE due to authigenic alterations. It is indicated that the phytolith fluxes in the suspended load represent a significant BSi source in the estuary, and the CJE would act as a net BSi sink.
Print ISSN: 0253-505X
Electronic ISSN: 1869-1099
Topics: Geosciences , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 79
Springer
Publication Date: 2018-03-05
Description: In this paper, we present the elastic solutions for the problem of an internal pressurized functionally graded thick-walled tube based on the Voigt method in Xin et al. (Int J Mech Sci 89:344–349, 2014 ); a transversely isotropic functionally graded thick-walled tube subjected to internal pressure is studied. It is assumed that the functionally graded tube is made up of two linear isotropic elastic materials; the matrix is reinforced by fibers with circular cross section all aligned in the circumferential direction. The volume fraction of the reinforced material is identical with our previous work (i.e., Xin et al. in Int J Mech Sci 89:344–349, 2014 ). By using the Mori–Tanaka method, this paper obtains the differential equation of the radial displacement and then the numerical results of the radial displacement and the stresses are deduced. The approximate analytical solutions are also derived which agree well with the numerical results on the basis of the Mori–Tanaka method. Further, both based on the Mori–Tanaka method, the results received by the present model are compared with those by a particle model for solving an isotropic inner-pressurized FGM tube problem. Finally, in the numerical part the influences of the volume fraction and the elastic moduli’s ratio on radial displacement and the stresses are discussed.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 80
Springer
Publication Date: 2018-03-05
Description: In this paper, an elastic metamaterial is proposed by integrating a two-dimensionally periodic honeycomb lattice and tetrachiral metamaterial inclusions for low-frequency wave applications. Plane wave propagation in infinite periodic cells is investigated through using Floquet–Bloch principles and the finite element method. Two separate negative pass bands induced by different mechanisms appear in the band structures of wave propagation in the proposed elastic metamaterial. The working mechanisms of those two negative pass bands are revealed though analyzing the eigenmodes of the unit cell and the dynamic effective material properties. Numerical examples validate the proposed model and show that negative refraction of elastic waves in the elastic metamaterial has been obtained. The design concept of this type of elastic may be of use for the design of broadband flat lenses for elastic wave focusing.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 81
Springer
Publication Date: 2018-03-05
Description: This paper presents a smoothed FE-Meshfree (SFE-Meshfree) method for solving solid mechanics problems. The system stiffness matrix is calculated via a strain-smoothing technique with the composite shape function, which is based on the partition of unity-based method, combing the classical isoparametric quadrilateral function and radial-polynomial basis function. The corresponding Gauss integration in the element is replaced by line integration along the edges of the smoothing cells, so no derivatives of the composite shape functions are needed during the field gradient estimation process. Several numerical examples including an automobile mechanical component are employed to examine the presented method. Calculation results indicate that SFE-Meshfree can obtain a high convergence rate and accuracy without introducing additional degrees of freedom to the system. In addition, it is also more tolerant with respect to mesh distortion. The volumetric locking problem is also explored in this paper under a selective smoothing integration scheme.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 82
Springer
Publication Date: 2018-03-05
Description: Under consideration is the finite-size scaling of the elastic properties in two-phase random polycrystals with individual grains belonging to any arbitrary crystal class. These polycrystals are generated by Voronoi Tessellations with varying grain sizes and volume fractions. Any given realization of such a microstructure sampled randomly is highly anisotropic and heterogeneous. Using extremum principles in elasticity, we introduce the notion of a ‘Heterogeneous Anisotropy Index $$\left( A^U_H\right)$$ ’ and examine its role in the scaling of elastic properties at finite mesoscales ( $$\delta$$ ). The relationship between $$A^U_H$$ and the Universal Anisotropy Index $$A^U$$ by Ranganathan and Ostoja-Starzewski (Phys Rev Lett 101(5):055504, 2008 ) is established for special cases. The index $$A^U_H$$ turns out to be a function of 43 variables—21 independent components for each phase and the volume fraction of either phase. The scale-dependent bounds are then obtained by setting up and solving 9250 Dirichlet and Neumann type boundary value problems consistent with the Hill–Mandel homogenization condition. Subsequently, the concept of an elastic scaling function is introduced that takes a power-law form in terms of $$A^U_H$$ and ( $$\delta$$ ). Finally, a material scaling diagram is constructed by employing the elastic scaling function which captures the convergence to the effective properties for any two-phase elastic microstructure.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 83
Springer
Publication Date: 2018-03-05
Description: In this paper, we propose and study a single-phase elastic metamaterial with periodic chiral local resonator, which is composed of cylindrical central core surrounded by evenly distributed ligaments and embedded in the matrix in a square lattice. Based on the analytical and numerical analysis, we prove that the translational resonance of the unit cell can lead to negative effective mass density, and the rotational resonance of it can produce negative effective modulus. They can also work together to generate double-negative effective material properties. The wave attenuation of elastic waves in this elastic metamaterial is also demonstrated, which is owing to the negative effective mass density. In addition, the damping of the base material is also considered in the simulation. We finally examine the existence of negative band, and this leads to the physics of negative refraction, which is induced by simultaneous translational and rotational resonance of the unit cell. Our work can serve as the theoretical foundation for the design of single-phase elastic metamaterials.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 84
Springer
Publication Date: 2018-03-05
Description: The problem of structural design of polymeric and composite viscoelastic materials is currently of great interest. The development of new methods of calculation of the stress–strain state of viscoelastic solids is also a current mathematical problem, because when solving boundary value problems one needs to consider the full history of exposure to loads and temperature on the structure. The article seeks to build an iterative algorithm for calculating the stress–strain state of viscoelastic structures, enabling a complete separation of time and space variables, thereby making it possible to determine the stresses and displacements at any time without regard to the loading history. It presents a modified theoretical basis of the iterative algorithm and provides analytical solutions of variational problems based on which the measure of the rate of convergence of the iterative process is determined. It also presents the conditions for the separation of space and time variables. The formulation of the iterative algorithm, convergence rate estimates, numerical computation results, and comparisons with exact solutions are provided in the tension plate problem example.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
Location Call Number Limitation Availability
Others were also interested in ...
• 85
Springer
Publication Date: 2018-03-05
Description: This manuscript investigates the thermal stresses and temperatures in a porous plate hydrated with a liquid. The upper surface is taken to be impermeable, traction free and subjected to a thermal shock. The lower surface is laid on a rigid foundation. The effect of the porosity is analyzed through graphs. It is noticed that all functions for the two phases increase with the increasing porosity except for the stress and the displacement. The effect of time is analyzed through graphs. It is observed that the heat and elastic effects propagate with finite speeds. Comparison is made with a problem with the same configuration in the absence of fluid when the medium is not porous. It was found that the existence of the fluid decreases the temperature and the displacement, whereas opposite behavior is observed for the stress.
Print ISSN: 0001-5970
Electronic ISSN: 1619-6937
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics