bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intrinsic Differences in the Initiation of B Cell Receptor Signaling Favor Responses of Human IgG+ Memory B Cells over IgM+ Naive B Cells
Authors: Davey Angel M. , Pierce Susan K. 
Published: March 2012

Abstract
The acquisition of long-lived memory B cells (MBCs) is critical for the defense against many infectious diseases. Despite their importance, little is known about how Ags trigger human MBCs, even though our understanding of the molecular basis of Ag activation of B cells in model systems has advanced considerably. In this study, we use quantitative, high-resolution, live-cell imaging at the single-cell and single-molecule levels to describe the earliest Ag-driven events in human isotype-switched, IgG-expressing MBCs and compare them with those in IgM-expressing naive B cells. We show that human MBCs are more robust than naive B cells at each step in the initiation of BCR signaling, including interrogation of Ag-containing membranes, formation of submicroscopic BCR oligomers, and recruitment and activation of signaling-associated kinases. Despite their robust response to Ag, MBCs remain highly sensitive to FcγRIIB-mediated inhibition. We also demonstrate that in the absence of Ag, a portion of MBC receptors spontaneously oligomerized, and phosphorylated kinases accumulated at the membrane and speculate that heightened constitutive signaling may play a role in maintaining MBC longevity. Using high-resolution imaging, we have provided a description of the earliest events in the Ag activation of MBCs and evidence for acquired cell-intrinsic differences in the initiation of BCR signaling in human naive and MBCs.
Regulating Mammalian Target of Rapamycin To Tune Vaccination-Induced CD8+ T Cell Responses for Tumor Immunity
Authors: Li Qingsheng , Rao Rajesh , Vazzana Joseph , Goedegebuure Peter , Odunsi Kunle , Gillanders William , Shrikant Protul A. 
Published: March 2012

Abstract
Vaccine strategies aimed at generating CD8+ T cell memory responses are likely to show augmented efficacy against chronic challenges like tumor. The abundance in variety of memory CD8+ T cells behooves development of vaccine strategies that generate distinct memory responses and evaluate them for tumor efficacy. In this study, we demonstrate the ability of a variety of rapamycin treatment regimens to regulate virus vaccination-induced CD8+ T cell memory responses and tumor efficacy. Strikingly, a short course of high-dose, but not low-dose, rapamycin treatment transiently blocks viral vaccination-induced mammalian target of rapamycin activity in CD8+ T cells favoring persistence and Ag-recall responses over type 1 effector maturation; however, prolonged high-dose rapamycin administration abrogated memory responses. Furthermore, a short course of high-dose rapamycin treatment generated CD8+ T cell memory responses that were independent of IL-15 and IL-7 and were programmed early for sustenance and greater tumor efficacy. These results demonstrate the impact a regimen of rapamycin treatment has on vaccine-induced CD8+ T cell responses and indicates that judicious application of rapamycin can augment vaccine efficacy for chronic challenges.
Pretransfusion Testing Practices in North America, 2005–2010: An Analysis of the College of American Pathologists Interlaboratory Comparison Program J-Survey Data, 2005–2010
Authors: Downes Katharine A , Shulman Ira A 
Published: February 2012

Context.—Data collection and analysis of the College of American Pathologists (CAP) Interlaboratory Comparison Program (Proficiency Testing) J-Survey results provide insights into North American pretransfusion compatibility testing practices and trends.Objectives.—To assess current North American manual testing practices for ABO grouping, rhesus (Rh) typing, antibody screening, and crossmatching using CAP proficiency testing data.Design.—Analysis of the CAP Interlaboratory Comparison Program J-Survey data (2005–2010) to identify laboratory methods used for ABO grouping, Rh typing, antibody screening, and crossmatching. Data were analyzed by test method using Microsoft (Redmond, Washington) Excel software.Results.—The method used most often in ABO grouping and Rh typing was tube testing. Many laboratories also used tube testing for antibody detection and crossmatching, but during the study period, the proportion of laboratories using gel-based methodologies increased considerably.Conclusions.—Most North American CAP laboratories continue to use tube methods for ABO/Rh testing. Use of gel-based methodologies increased during the past 5 years for antibody screening and crossmatching.
Measurement of Cell Death in Mammalian Cells
Authors: Cummings Brian S. , Wills Lauren P. , Schnellmann Rick G. 
Published: March 2012

AbstractMethods for assessing mammalian cell death are presented in this unit. The unit is divided into six sections: (1) a brief overview of cytotoxicity and pathways of cell death, (2) a method to measure cell death using lactate dehydrogenase (LDH) release as a marker of membrane integrity, (3) a flow cytometry method that simultaneously measures two types of cell death, necrosis, and apoptosis, (4) use of fluorescence microscopy and nuclear morphology to assess apoptosis and necrosis, (5) the use of multi‐well plates and high‐content analysis imaging systems to assess nuclear morphology, and (6) a discussion of the use of cytotoxicity assays to determine the mechanisms of cell death. Curr. Protoc. Pharmacol. 56:12.8.1‐12.8.24. © 2012 by John Wiley & Sons, Inc.
Die Diaryl(oxy)methyl‐Gruppe: mehr als ein unbeteiligter Zuschauer in chiralen Auxiliaren, Katalysatoren und Dotierstoffen
Authors: Braun Manfred 
Published: March 2012

AbstractSowohl als freier Alkohol wie auch in deprotonierter Form erscheint ein Carbinolrest mit zwei identischen geminalen Arylsubstituenten auf den ersten Blick als eine achirale Struktureinheit. Ist sie jedoch in ein chirales Molekül eingebunden, so werden beide Arylgruppen diastereotop. Somit können sie zu einer Erhöhung der Stereoselektivität beitragen, was sie auch in einer Vielzahl von Reaktionen tun. Dieser Kurzaufsatz stellt Entwicklungen in der Stereochemie vor, an denen die Diaryl(oxy)methyl‐Gruppe beteiligt ist, und unterstreicht die nutzbringenden Effekte dieser Gruppe. Im Blickpunkt dieser Übersicht stehen Auxiliare und stöchiometrisch eingesetzte Metallkomplexe, ferner Metall‐ und Organokatalysatoren sowie schließlich chirale Dotierstoffen für Flüssigkristalle, die alle das Diaryl(oxy)methyl‐Motiv aufweisen.
Effect of the molecular structure of semicrystalline polyethylene on mechanical properties studied by molecular dynamics
Authors: Queyroy Séverine , Monasse Bernard 
Published: March 2012

AbstractWe present results from molecular dynamics simulations for an all‐atoms model of a semicrystalline polyethylene under uniaxial tensile test. Our model has a realistic semicrystalline organization of two high molecular chains which are involved in two crystalline and two amorphous phases. The tie‐molecules link these phases. A high content of tie‐molecules is compatible with the stability of the semicrystalline organizations in the initial state. The main objective of the study is to check the effect of some molecular parameters, poorly known from experiments, on the mechanical properties under uniaxial tensile test. It is a way to have an insight on the value of the probable molecular parameters. We show that the number of tie‐molecules mainly acts on the elastic modulus and the lamellar thickness acts on the yield stress. A nearly constant stress, a plateau, results from the narrow length‐distribution of tie‐molecules. This plateau is not observed during mechanical experiments. This plateau is the direct result of isomolecular tie‐molecules. The only way to predict the progressive increase of the stress up to the yields stress observed experimentally is to consider a large length‐distribution of tie‐molecules. This progressive increase of stress implies a progressive deformation of the crystalline phase. The basic mechanism of plastic deformation is the pull‐out of crystalline chain segments by the tie‐molecules in extended conformation. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Shear‐strain step response in linear regime of dilute suspensions of naturally bent carbon nanotubes
Authors: Cruz C. , Illoul L. , Chinesta F. , Régnier G. 
Published: March 2012

AbstractImpressive enhancements of the storage modulus have been documented when low volume fractions of single wall carbon nanotubes (SWNTs) are added to a Newtonian solvent for obtaining dilute suspensions. The intrinsic bending dynamics of carbon nanotubes (CNTs) has been proposed to explain such elasticity. CNTs contain topological defects inducing naturally bent structures in absence of external forces and, hence, a semiflexible filament with a bent configuration at minimal internal‐bending‐energy is used for mimicking the structure of SWNTs in suspension. Previous continuous model is discretized as a nonfreely jointed bead‐rod chain with a naturally bent configuration for simulating the rheological behavior after a shear‐strain step in linear regime of SWNT dilute suspensions by using a Brownian dynamics (BD) approach. In general, bead‐rod chains exhibit an instantaneous relaxation after a high shear‐strain step. Bending rigidity and number of constitutive rods are found to be determinant parameters in the internal‐energy relaxation behavior of nonfreely jointed bead‐rod chains in dilute solution. Proper comparisons between the BD simulation results and the experimental data for treated SWNT dilute suspensions confirm the consistency of the physical model mimicking the structure of a SWNT. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Modeling of pneumatic melt spinning processes
Authors: Jarecki Leszek , Blonski Slawomir , Blim Anna , Zachara Andrzej 
Published: March 2012

AbstractComputer simulation of the pneumatic processes of fiber formation from the polymer melts is discussed. The dynamics of air‐drawing of thin polymer streams in supersonic air jets formed in the Laval nozzle is presented versus the melt blowing process. In the Laval nozzle process, the air flow takes place with high Reynolds number and the k–ω model is used which considers kinetic energy of the air flow and the specific dissipation rate of the kinetic energy. For melt blowing, the air fields are simulated with the use of the k–ε turbulent model. The air velocity, temperature, and pressure distributions along the centerline of the air jets are considered in the modeling of both pneumatic processes. The air fields are predetermined at the absence of the polymer streams for several air compression values in the Laval nozzle inlet and several initial air velocities in the melt blowing process. Each polymer stream in a usual configuration of a single row of the filaments in the process is considered as non‐interacting aerodynamically with other streams, and the air jet is assumed to be undisturbed by the polymer streams. Air‐drawing of the polymer filaments is simulated as controlled by the distribution of air velocity, temperature, and pressure on the air jet centerline with the use of a stationary model of melt spinning in a single‐, thin‐filament approximation. Effects of non‐linear viscoelasticity of the polymer melt subjected to fast uniaxial elongation are accounted for in the modeling. Strong influence of the air jet velocity, the melt viscosity which controls response of the polymer melt on the air‐drawing forces, and the die‐to‐collector distance has been predicted. Influence of initial air temperature, geometry of the air die, initial velocity and temperature of the melt, extrusion orifice diameter can be also predicted from the model. The example computations concern air‐drawing of isotactic polypropylene with the use of the Laval nozzle are compared with the predictions for the melt blowing process. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Modeling stiffness of nanolayered silicate‐modified polyamide 6 via FEM micromechanical modeling and analytical composite models
Authors: Huang Jing , Geier Simon , Schmauder Siegfried , Weber Ulrich 
Published: March 2012

AbstractIn this work, numerical and analytical models are chosen to study reinforcement effect of nanolayered silicate modified polyamide 6 (PA 6) composites at ambient temperature. A numerical self‐consistent unit cell model in conjunction with finite element method is applied to predict the stiffness of this polymer nanocomposite, which has been successfully applied for simulating mechanical behavior of metal matrix composites. In this work, a rectangular inclusion (layered silicate) is surrounded by PA 6 polymer matrix, which is again embedded in the PA 6/layered silicate nanocomposite. The stiffness of the composite is determined iteratively in a self‐consistent manner. For comparison, two analytical composite models (Halpin–Tsai model and Tangdon–Weng model) are implemented to evaluate the stiffness of this nanocomposite via calculations performed within MATLAB. In the modeling volume fraction, aspect ratio, exfoliation and orientation of the nanolayered silicate are taken into account. It is demonstrated that the numerical approach using the self‐consistent embedded cell model coincides well with experimental results of the stiffness of the composite. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Nucleated crystallization of isotactic polypropylene in multilayered sandwich nanocomposites with gold particles
Authors: Slouf Miroslav , Sikora Antonin , Pavlova Ewa , Vlkova Helena , Baldrian Josef , Base Tomas , Piorkowska Ewa 
Published: March 2012

AbstractNucleation of isotactic polypropylene (PP) crystallization by gold particles with various sizes and shapes was studied. The morphology of gold particles ranged from microcrystals with well‐developed crystal facets (AuMC) to vacuum‐sputtered 5 nm gold nanoparticles (AuNP), 30 nm gold nanoislands (AuNI), and compact gold nanolayer (AuNL). To minimize agglomeration of Au particles in molten PP, the nucleated crystallization was studied by means of the improved sandwich method, which consisted in the controlled deposition of a homogeneous nucleant layer between ∼ 100 μm PP films, followed by the careful thermal treatment and the evaluation of the nucleation activity by three independent methods: polarized‐light microscopy, two‐dimensional wide‐angle X‐ray scattering, and differential scanning calorimetry. It was demonstrated that the nucleating activity of gold strongly depended on its morphology: The nucleation effect of microcrystalline AuMC resulted in a transcrystallization comparable to that caused by a strong commercial α‐nucleant (Hyperform HPN‐68), whereas the effect of vacuum‐sputtered layers of nanocrystalline AuNL, AuNI, and AuNP was extremely weak. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Synthesis, Characterization, and Energetic Properties of Salts of the 1‐Cyanomethyl‐1,1‐dimethylhydrazinium Cation
Authors: Miró Sabaté Carles , Delalu Henri , Jeanneau Erwann 
Published: March 2012

Abstract1,1‐Dimethylhydrazine can be readily alkylated with bromoacetonitrile to form 1‐cyanomethyl‐1,1‐dimethylhydrazinium bromide ([(CH3)2N(CH2CN)NH2]Br, 1). The metathesis reaction of compound 1 led to the formation of a new family of energetic salts based on the [(CH3)2N(CH2CN)NH2]+ cation and nitrate (2), perchlorate (3), azide (4), 5‐aminotetrazolate ([H2N‐CN4]−, 5), 5,5′‐azobistetrazolate ([N4C‐NN‐CN4]2−, 7), and picrate (8) anions. The new materials were characterized by elemental analysis, mass spectrometry, and (multinuclear) NMR and vibrational (infrared and Raman) spectroscopies. Additionally, the molecular structure of the [(CH3)2N(CH2CN)NH2]+ cation in compounds 1, 3, and 8 and that of sodium 5,5′‐azobistetrazolate octahydrate (NaZT⋅8 H2O) were solved by X‐ray diffraction techniques. The hydrogen‐bonding networks found in the structure of salts 1, 3, 8, and NaZT⋅8 H2O are described using graph‐set analysis. The melting and decomposition points of the new compounds were determined by differential scanning calorimetry, and insight into their sensitivity towards impact, friction, and electrostatics was gained by submitting the materials to standard tests. Furthermore, we estimated some performance parameters of interest and predicted the decomposition gases formed upon decomposition of salts 2, 3, 4, 5, 6, 7, 8 and of mixtures with an oxidizer. The interesting thermal, sensitivity, and performance properties of some of the compounds described in this work make them attractive towards a prospective energetic application.
Tragverhalten von hohen Stahlbetontürmen für Aufwindkraftwerke
Authors: Goldack Arndt 
Published: March 2012

AbstractAufwindkraftwerke sind solarthermische Kraftwerke zur Gewinnung erneuerbarer Energie aus der direkten und indirekten Sonneneinstrahlung. Für diese Kraftwerke sind Türme mit Höhen bis zu 1000 m und mehr erforderlich, die als freistehende Stahlbetonröhren geplant sind. Diese Stahlbetonröhren werden mit mehreren Aussteifungen wie z. B. Speichenrädern, die über die Höhe verteilt angeordnet sind, ausgesteift, um die Membranschnittgrößen aus Wind möglichst gering zu halten. Das Tragverhalten dieser mehrfach ausgesteiften Türme besteht aus einem stabartigen über die gesamte Turmröhre und einem schalenartigen Tragverhalten in den Segmenten zwischen den Aussteifungen. Die Traglasten verschiedener 1000 m hoher Türme wurden mit geometrisch und physikalisch nichtlinearen FEM‐Berechnungen ermittelt. Dabei zeigt sich, dass die Rissbildung das Tragverhalten maßgeblich beeinflusst. In Verbindung mit dem Flankensog führt diese zu einer typischen sichelförmigen Ovalisierung der Segmente zwischen den Aussteifungen, die auf das schalenartige Tragverhalten zurückzuführen ist. Es zeigte sich, dass das schalenartige Tragverhalten im Bereich der sichelförmigen Ovalisierung infolge Biegung mit Längsdruck maßgebend ist. Vergleichsrechnungen am obersten Turmsegment zeigen wiederum dieses typische Tragverhalten.Load bearing of high rise tubes for solar updraft towersSolar updraft power plants are solar thermal power plants for producing renewable electric energy from direct and indirect solar radiation. These power plants demand for high rise tower tubes with heights up to 1000 m and more, which are planned as cantilevering tubes out of structural concrete. These tower tubes are provided with several stiffeners such as spoke wheels distributed over the height to keep the membrane forces due to wind at a minimum. The load bearing of these multi‐stiffened towers consists of a cantilever‐like and a shell‐like in the segments between two stiffeners. The ultimate loads of several 1000 m high tower tubes were investigated by geometrical and physical non‐linear FEM calculations. Cracking of the concrete has a reasonable impact on the ultimate limit state and results together with the flank suction in a typical sickle‐like ovalling between the luv and the flank suction. The ultimate limit state of these towers is governed by the shell‐like behavior in the sickle‐like deformation with bending and longitudinal force. Additional non‐linear FEM calculations of the topmost segment of the tower show the same deformation and failure mechanism.
Solare Aufwindkraftwerke: Ein Beitrag der Bautechnik zur nachhaltigen und wirtschaftlichen Energieerzeugung
Authors: Harte Reinhard , Höffer Rüdiger , Krätzig Wilfried B. , Mark Peter , Niemann Hans‐Jürgen 
Published: March 2012

AbstractSolare Aufwindkraftwerke stellen eine Technologie zur Erzeugung solar‐basierter elektrischer Energie in den Wüsten unserer Erde dar, die verschiedene Defizite bisheriger Konzepte überwindet. Weltweit sind derartige Kraftwerksprojekte in der Vorplanung. Der vorliegende Beitrag beginnt mit der Skizzierung des Arbeitsprinzips solarer Aufwindkraftwerke. Es folgen klimatologische und wind‐technologische Planungsvoraussetzungen, wobei die Windlastermittlung im Grenzschicht‐Windkanal näher begründet wird. Sodann wird der zentrale Solarkamin behandelt, eine dünne, ringversteifte Stahlbetonschale extremer Höhe, die größte bautechnische Herausforderung dieses Kraftwerkstyps. Weiter folgt die Erläuterung grundlegender bautechnischer Anforderungen an den Solarkollektor, der die größte jemals überglaste Fläche darstellt, sowie der Windeinwirkungen auf die Verglasung und die Tragkonstruktion. Einen wichtigen Aspekt bilden Anforderungen an die Dauerhaftigkeit der eingesetzten Baustoffe für eine mindestens 100‐jährige Nutzung des Turms in einem extremen Wüstenklima. Der Artikel endet mit Kostenschätzungen für den produzierten Strom und einem Technologieausblick.Solar updraft power plants: A structural engineering contribution for sustainable and economic power generationSolar updraft power technology serves to generate electricity in the world‐wide deserts, overcoming several deficits of present renewable energy technologies. In several suited countries such power plant projects are in preparation. The present contribution starts with an explanation of the working principle of solar updraft power plants, followed by their climatic and wind‐technologic design assumptions, terminated by the wind‐load determination in boundary layer wind‐tunnels. Then the central solar chimney – the power tower – will be treated, a thin ring‐stiffened RC shell of extreme height forming the utmost structural challenge of such power plants. This part is followed by an explanation of technical requirements for the collector construction, which represents by far the largest glass‐covered area ever built, and of the wind loading at the glazing and the supporting structure. Further important aspects are formed by the durability requirements of the applied construction materials for at least 100 years of service‐duration of the tower in extreme desert climates. The paper closes with cost estimates for the generated electric power and with a technology outlook.
Kollektorentwicklung für solare Parabolrinnenkraftwerke
Authors: Schiel Wolfgang 
Published: March 2012

AbstractIn den letzten Jahren wurden mehrere große solarthermische Kraftwerke in Spanien und Nordafrika gebaut und in Betrieb genommen. Bis Ende 2013 werden allein in Spanien solarthermische Kraftwerke mit einer Leistung von insgesamt ca. 2,5 GW am Netz angeschlossen sein. Die meisten dieser Anlagen sind sogenannte Parabolrinnenkraftwerke, die zurzeit am weitesten fortgeschrittene solarthermische Technologie. Diese Kraftwerke bestehen aus großen Kollektorfeldern mit hunderttausenden Quadratmetern Kollektorflächen, die die erforderliche Wärme für den Betrieb eines konventionellen Kraftwerksblocks bereitstellen. Die Kosten dieser solarthermischen Technologie werden im Wesentlichen durch die Kosten des Kollektorfeldes bestimmt. Um in Zukunft mit fossilen Kraftwerken vergleichbare Stromerzeugungskosten zu erzielen, sind weitere Entwicklungsarbeiten der solarspezifischen Komponenten im Hinblick auf Kostensenkung und Effizienzsteigerung erforderlich, insbesondere beim Solarkollektor.Collector dvelopment for solar parabolic trough power plantsIn the last years several solar thermal power plants were constructed and successfully put into operation in Spain and North Africa. By the end of 2013, a total of 2, 5 GW solar thermal power plants will be in operation in Spain alone. Most of these plants are parabolic trough power plants, which is currently the most highly developed solar thermal technology. These power plants consist of a large solar collector field with hundreds of thousands of m2 collector areas, which generate the required warmth for the operation of a conventional power block. The costs of this technology are primarily determined by the costs of the collector field. In order to achieve electricity generation costs that are competitive to fossil power plants, further developments of the solar components with regard to cost reduction and increased efficiency are necessary, especially for the solar collector.