bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheological characterization of schizophyllan aqueous solutions after denaturation–renaturation treatment
Authors: Fang Yapeng , Takahashi Rheo , Nishinari Katsuyoshi 
Published: April 2004

AbstractSchizophyllan (SPG) with a molecular weight of 2.6×106, designated SPG‐1, is denatured and then renatured at a concentration of 1.8 wt % by alkalization–neutralization. The prepared denatured–renatured samples (DRSPG‐1) are diluted to various concentrations and equilibrated for 10 days before rheological and intrinsic viscosity measurements. When concentration (Cp) is above 0.75 wt %, DRSPG‐1 aqueous systems have weak gel‐type rheological properties. However, for 0.28 wt % ≤ Cp ≤ 0.65 wt % and Cp ≤ 0.19 wt %, DRSPG‐1 aqueous systems behave as power law fluids and Newtonian fluids, respectively, which are attributed to the moderate isotropy degree of DRSPG‐1 chains. Furthermore, a critical overlap parameter of c*[η] = 1.2 is determined for DRSPG‐1 in aqueous solutions, which is close to that of 1 for intact SPG in water while far smaller than that of 4.3 for SPG in DMSO. This is considered to be due to the strong interactions of DRSPG‐1 chains in water, further confirmed by the intrinsic viscosity measurements in which the DRSPG‐1 aqueous solution shows an abnormally large value of Huggins constant. Regarding the structure of DRSPG‐1 weak gels, multiruns of dynamic strain sweep measurements suggest that the dominant structures are aggregates formed by hydrogen‐bonding associations of DRSPG‐1 chains rather than the permanent three‐dimensional network. In addition, the step‐shear rate tests are performed to study the thixotropic properties of DRSPG‐1 aqueous systems. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Impact of early expression of TCR α  chain on thymocyte development
Authors: Huang Ching‐Yu , Kanagawa Osami 
Published: April 2004

AbstractCD4–CD8– thymocytes expressing a transgenic T cell receptor (TCR) α  chain have decreased capacity to give rise to CD4+CD8+ thymocytes when compared with wild‐type thymocytes. This inefficient CD4–CD8– to CD4+CD8+ maturation is mediated by the transgenic TCR α  chain pairing with endogenous TCR β  chain but not with endogenous TCR γ  chain. Comparison between TCR α  chain‐transgenic mice with or without a functional pre‐TCR α  (pTα ) chain reveals that the formation of transgenic α /endogenous β  TCR on CD4–CD8– thymocytes inhibits the formation of pre‐TCR, but at the same time mediates CD4–CD8– to CD4+CD8+ maturation in the absence of pre‐TCR, albeit inefficiently. These results indicate that α β  TCR and pre‐TCR provide different signals for thymocyte development. They also suggest that the precise regulation of the sequential rearrangements of TCR β  and α  loci and the cellular expansion induced by the pre‐TCR may both be evolved to ensure the efficient generation of mature α β  T cells.
Synthesis of several chemokines but few cytokines by primed uncommitted precursor CD4 T cells suggests that these cells recruit other immune cells without exerting direct effector functions
Authors: Yang Li , Mosmann Tim 
Published: April 2004

AbstractAntigen‐stimulated naive CD4 T cells may differentiate into effector T cells such as Th1 and Th2 cells, or may remain as proliferating but uncommitted, primed, precursor cells (Thpp cells) that can subsequently differentiate into Th1 or Th2 cells in appropriate cytokine environments. To examine potential Thpp effector functions, we compared the genes expressed by mouse Thpp, naive, Th1 and Th2 cells, using Affymetrix GeneChip and RNase Protection assays. Similar to naive CD4 T cells, Thpp cells expressed IL‐2 but not the cytokines characteristic of differentiated Th1 or Th2 cells, such as IFN‐γ, IL‐4, or IL‐5. However, Thpp, Th1 and Th2 cells, but not naive cells, expressed several CC chemokines including CCL1/TCA3, CCL5/RANTES, CCL3/MIP‐1α, CCL4/MIP‐1β, and CCL9/MIP‐1γ. Secretion of the corresponding proteins was confirmed by ELISA and Elispot. Consistent with this chemokine expression, supernatants of activated Thpp, Th1 and Th2 cells but not naive CD4T cells induced pertussis toxin‐sensitive chemotaxis of B and T cells. Supernatants of Thpp cells did not bias differentiation of naive CD4 T cells towards either Th1 or Th2 cells. The secretion of several chemokines, but few cytokines, by primed uncommitted Thpp cells suggests that their activation during an immune response may recruit effector cells without directly polarizing effector functions.
Heat transfer by radiation and convection in fire testing
Authors: Wickström Ulf 
Published: April 2004

AbstractFire safety engineers, especially those experts writing fire test standards, often have different understandings of the concepts of heat transfer from a fire to a surface by radiation and convection. The concepts are therefore often not very well defined, in e.g. ISO and CEN standards, leading in many cases to confusions, misunderstandings and considerable errors. This paper is an effort, in a very simple way, to make the issue a little clearer, particularly for use in international standardization work. ISO/TC92 and the International FORUM of Fire Research Directors are currently endorsing very important work on procedures to calibrate heat flux meters.The two entities, heat transfer by radiation and convection, may be treated independently. The presentation below is deliberately very short and basic avoiding many phenomena that are not immediately needed in most fire standardization work. Recommendations are reached on how to define and measure heat transfer in fire testing. Copyright © 2004 John Wiley & Sons, Ltd.
Experimental and analytical studies of steel joint components at elevated temperatures
Authors: Spyrou Spyros , Davison Buick , Burgess Ian , Plank Roger 
Published: April 2004

AbstractThis paper reports on experimental furnace testing and development of simple analytical models intended to initiate the development of a Component Method for modelling of steel beam‐to‐column connections in fire conditions. The basic theme of the Component Method is to consider any joint as an assembly of individual simple components. Each of these components is simply a non‐linear spring, possessing its own level of strength and stiffness in tension, compression or shear, and these will degrade as its temperature rises.The main objective of this study was to investigate experimentally and analytically the behaviour of tension and compression zones of end‐plate connections at elevated temperatures. A series of experiments has been carried out, and these are described in the paper. Simplified analytical models of the component behaviour have been developed, and these have been validated against the tests and against detailed finite element simulations. The simplified models have been shown to be very reliable for this very common type of joint, although similar equations will need to be developed for other configurations. The component models developed have been shown to produce moment‐rotation curves which correlate well with the results of previous furnace tests on complete connection behaviour in fire. The principles of the Component Method can be used directly in either simplified or finite element modelling, without attempting to predict of the overall joint behaviour in fire. This will enable semi‐rigid behaviour to be taken into account in the analytical fire engineering design of steel‐framed buildings, for which it is inadequate simply to consider the degradation of the ambient‐temperature moment‐rotation characteristics of a joint without taking account of the high axial forces which also occur. Copyright © 2004 John Wiley & Sons, Ltd.
Comparison of BRE simple design method for composite floor slabs in fire with non‐linear FE modelling
Authors: Huang Zhaohui , Burgess Ian , Plank Roger , Bailey Colin 
Published: April 2004

AbstractOn the basis of test evidence a new design method has been developed recently by one of the authors, for calculating the performance of composite flooring systems subject to fire. The method models simply the influence of tensile membrane action in the composite floor slabs. The objective of this paper is to show some detailed comparisons between the simple design method and finite element modelling using the computer program Vulcan, which has been developed at the University of Sheffield, in order to check the applicability and inherent conservatism of the method. Initially a 9 m × 9 m square ribbed concrete slab, for which all four edges are vertically supported, is analysed. Different temperature distribution patterns across the thickness of the slab are used to investigate the influence of thermal curvature on the structural behaviour. The effect of changing the edge support conditions is also analysed.As part of this study a large generic composite flooring system with a footprint of 36 m × 36 m has been designed. The frame is based on a regular 9 m × 9 m column grid. A series of analyses has been performed, based on different patterns of fire protection to the downstand steel beams. The influence of the proportion of steel reinforcement on the structural behaviour has been investigated, and it is evident that the presence or absence of tensile membrane action in the concrete slabs is a major influence on the ultimate integrity of the flooring system at high distortions. The ability of the slab reinforcement to sustain the tensile stresses caused at high temperatures and deflections is clearly a key factor in ensuring that fracture of slabs does not occur. From both the Vulcan modelling and the simplified design method it is shown that tensile membrane action can be important in carrying the loads applied to the slabs at high temperatures and deflections. However, it is apparent that the simple design method predicts a greater contribution to load‐carrying capacity due to tensile membrane action than does the Vulcan modelling, especially for high reinforcement ratios, and that further work needs to be done to resolve this discrepancy. Copyright © 2004 John Wiley & Sons, Ltd.
Modeling of the thermal degradation of structural wood members exposed to fire
Authors: Janssens Marc L. 
Published: April 2004

AbstractTo accurately predict the structural performance of a wood member, knowledge is required of the rate at which it chars and the temperature distribution in the residual load‐bearing section. The charring rate and temperature distribution can be calculated with a model that predicts the thermal degradation or pyrolysis of wood exposed to a high‐temperature environment. More than 50 wood pyrolysis models have been developed since World War II. They range from simple analytical expressions to complex systems of coupled partial differential equations that describe the heat and mass transfer through wood and char.This paper presents a brief overview of the aforementioned models and provides a more detailed description of a new model. This model is referred to by the acronym CROW (Charring Rate Of Wood). Although the intent was to keep CROW as simple as possible, the model accounts for the four major factors that affect the thermal degradation of wood: dry density of the wood; moisture content of the wood; lignin content of the wood; char contraction.The predictive capability of CROW was evaluated on the basis of ASTM E 119 furnace data obtained for a Douglas fir glulam beam tested under different loads. CROW predictions, with some adjustment for moisture effects, are in reasonable agreement with the measurements. The model will be most useful to predict performance of wood members exposed under thermal conditions that deviate from the standard fire (natural or parametric fires) and/or members that are protected by a membrane. Copyright © 2004 John Wiley & Sons, Ltd.
Mechanical properties of structural steel at elevated temperatures and after cooling down
Authors: Outinen Jyri , Mäkeläinen Pentti 
Published: April 2004

AbstractAn experimental research programme was carried out during the years 1994–2001 in the Laboratory of Steel Structures at Helsinki University of Technology in order to investigate the mechanical properties of several structural steels at elevated temperatures by using mainly the transient state tensile test method. The aim was to produce accurate material data for use in different structural analyses. The main test results are public and they are available for other researchers.In this paper the experimental test results for the mechanical properties of the studied steel grades S350GD+Z, S355 and S460M at fire temperatures are presented with a short description of the testing facilities. A test series was also carried out for cold‐formed material taken from rectangular hollow sections of structural steel S355J2H and these test results are also given in this report.The mechanical properties of structural steel after cooling down have also been examined briefly and these test results are given in this report.The test results were used to determine the temperature dependencies of the mechanical properties, i.e. yield strength, modulus of elasticity and thermal elongation, of the studied steel material at temperatures up to 950°C. The test results are compared with the material model for steel according to Eurocode 3: Part 1.2. Copyright © 2004 John Wiley & Sons, Ltd.
Compression properties of wood as functions of moisture, stress and temperature
Authors: Jong Francisco , Clancy Paul 
Published: April 2004

AbstractThere has been considerable research in recent times on light‐timber framed structures in fires. These structures have included horizontal (floor‐like) panels in bending, and walls under eccentric and approximately concentric vertical loading. It has been assumed that these structures behave elastically and hence the elastic modulus of wood in compression is the dominant mechanical property. It has also been assumed that the elastic modulus is a function of temperature alone. It has always been expected that compression properties would be significantly affected by moisture and stress. However, these variables have been largely ignored to simplify the complex problem of predicting the response of light‐timber framed structures in fire. Full‐scale experiments on both the panels and walls have demonstrated the high level of significance of moisture and stress on the time‐to‐failure for a limited range of conditions. Described in this paper is an overview of these conditions and experiments undertaken to obtain compression properties as a functions of the variables—moisture, stress and temperature. Creep models for incorporating these variables are proposed. The significance of creep behaviour in comparison with elastic behaviour is evaluated. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling of the Cardington LBTF steel frame building fire tests
Authors: Moss Peter J. , Charles Clifton G. 
Published: April 2004

AbstractThe design of multi‐storey steel framed office and other commercial buildings for fire resistance has traditionally been undertaken on the premise that the building will suffer partial or total collapse unless the beams and columns are insulated from temperature rise under fully developed fire conditions. Since 1990, a growing body of evidence has shown that there is a substantial inelastic reserve of strength available from a typical composite steel beam/concrete floor slab system with uninsulated beams. An intensive research effort is underway in a number of countries to determine the extent of this reserve of strength and the mechanisms involved in its delivery. The research discussed in this paper involves experimental testing and advanced finite element (FE) modelling. It is leading on to design procedure development to take account of the inelastic reserve of strength available from this type of building system.This paper describes advanced finite element analyses undertaken on the complete building system of an eight‐storey steel framed building subject to severe fire conditions. This building is located at the Cardington Large Building Test Facility in the UK and was subjected to a number of large‐scale fire burnout tests in 1995 and 1996. The test programme included a number of large‐scale fire tests using wood cribs and office furniture as the fuel.Three of the large scale fire tests were modelled, covering different enclosure characteristics and fire conditions. The paper gives an overview of the model used and compares the analytical results with those obtained experimentally. Differences between the results are noted and some explanations given for these. Copyright © 2004 John Wiley & Sons, Ltd.
Nonlinear Model Reduction of a Two‐Dimensional MCFC Model with Internal Reforming
Authors: Mangold M. , Sheng M. 
Published: April 2004

AbstractA reduced nonlinear model of a planar molten carbonate fuel cell is presented. The model is derived from a spatially distributed dynamic model of the cell by applying the Karhunen Loève Galerkin procedure. The reduced model is of considerably lower order than the original one and requires much less computation time. The comparison between the two models shows that the reduced model can describe the dynamics of the temperature field with sufficient accuracy and has good extrapolation qualities with respect to changes in the model parameters.
Differential generation of oligodendrocytes from human and rodent embryonic spinal cord neural precursors
Authors: Chandran Siddharthan , Compston Alastair , Jauniaux Eric , Gilson Jennifer , Blakemore William , Svendsen Clive 
Published: April 2004

AbstractHuman neural precursors are considered to have widespread therapeutic possibilities on account of their ability to provide large numbers of cells whilst retaining multipotentiality. Application to human demyelinating diseases requires improved understanding of the signalling requirements underlying the generation of human oligodendrocytes from immature cell populations. In this study, we compare and contrast the capacity of neural precursors derived from the developing human and rodent spinal cord to generate oligodendrocytes. We show that the developing human spinal cord (6–12 weeks of gestation) displays a comparable ventrodorsal gradient of oligodendrocyte differentiation potential to the embryonic rodent spinal cord. In contrast, fibroblast growth factor 2 (FGF‐2) expanded human neural precursors derived from both isolated ventral or dorsal cultures show a reduced capacity to generate oligodendrocytes, whereas comparable rodent cultures demonstrate a marked increase in oligodendrocyte formation following FGF‐2 treatment. In addition, we provide evidence that candidate growth factors suggested from rodent studies, including FGF‐2 and platelet‐derived growth factor (PDGF) do not stimulate proliferation of human oligodendrocyte lineage cells. Finally, we show that the in vivo environment of the acutely demyelinating adult rat spinal cord is insufficient to stimulate the differentiation of immature human spinal cord cells to oligodendrocytes. These results provide further evidence for inter‐species difference in the capacity of neural precursors to generate oligodendrocytes. © 2004 Wiley‐Liss, Inc.
Loss of tuberous sclerosis complex 1 (Tsc1) expression results in increased Rheb/S6K pathway signaling important for astrocyte cell size regulation
Authors: Uhlmann Erik J. , Li Wen , Scheidenhelm Danielle K. , Gau Chia‐Ling , Tamanoi Fuyuhiko , Gutmann David H. 
Published: April 2004

AbstractIndividuals with tuberous sclerosis complex (TSC) develop central nervous system abnormalities that may reflect astrocyte dysfunction. In an effort to model astrocyte dysfunction in TSC, we generated mice lacking Tsc1 (hamartin) expression in astrocytes and demonstrated that Tsc1‐null astrocytes exhibit abnormalities in contact inhibition growth arrest. In this study, we demonstrate that hamartin‐deficient astrocytes are also defective in cell size regulation. We show that the increase in Tsc1‐null astrocyte size is associated with increased activation of the S6‐kinase pathway. In keeping with recent reports that the hamartin/tuberin complex may regulate Rheb and downstream S6K activation, we demonstrate that expression of either Rheb or S6K in primary astrocytes results in increased S6 pathway activation, and that inhibition of Rheb activity in Tsc1‐deficient astrocytes using either pharmacologic or genetic strategies markedly reduces S6 activation. Collectively, these observations suggest that TSC inactivation in astrocytes results in defective cell size regulation associated with dysregulated Rheb/mTOR/S6K pathway activity. © 2004 Wiley‐Liss, Inc.
N‐myc downstream‐regulated gene 1 expression in injured sciatic nerves
Authors: Hirata Kazuho , Masuda Katsuaki , Morikawa Wataru , He Jian‐Wen , Kuraoka Akio , Kuwano Michihiko , Kawabuchi Masaru 
Published: April 2004

AbstractN‐myc downstream‐regulated gene 1 (NDRG1)/RTP/Drg1/Cap43/rit42/TDD5/Ndr1 is expressed ubiquitously and has been proposed to play a role in growth arrest and cell differentiation. A recent study showed that mutation of this gene is responsible for hereditary motor and sensory neuropathy‐Lom. However, the role of this gene in the peripheral nervous system is not fully understood. In our study, rabbit polyclonal antibodies were raised against this gene product and were used to examine changes in its expression over the time course of Wallerian degeneration and ensuing regeneration after crush injury of mouse sciatic nerves. Fluorescent immunohistochemistry showed that NDRG1 was expressed over the intact nerve fibers. Double labeling with a Schwann cell (SC) marker, S‐100 protein (S‐100), revealed that NDRG1 was localized in the cytoplasm of S‐100‐positive Schwann cells (SCs). NDRG1 expression was maintained in the early stage of myelin degradation but was then markedly depleted at the end stage of myelin degradation when frequent occurrence of BrdU‐labeled SCs was observed (at 7–9 days). The depletion of NDRG1 at this time point was also confirmed by Western blotting analysis. NDRG1 expression finally recovered at the stage of remyelination, with immunoreactivity stronger than that in intact nerves. These findings suggest that NDRG1 may play an important role in the terminal differentiation of SCs during nerve regeneration. © 2004 Wiley‐Liss, Inc.
Unique distributions of the gap junction proteins connexin29, connexin32, and connexin47 in oligodendrocytes
Authors: Kleopa Kleopas A. , Orthmann Jennifer L. , Enriquez Alan , Paul David L. , Scherer Steven S. 
Published: April 2004

AbstractOligodendrocytes of adult rodents express three different connexins: connexin29 (Cx29), Cx32, and Cx47. In this study, we show that Cx29 is localized to the inner membrane of small myelin sheaths, whereas Cx32 is localized on the outer membrane of large myelin sheaths; Cx29 does not colocalize with Cx32 in gap junction plaques. All oligodendrocytes appear to express Cx47, which is largely restricted to their perikarya. Cx32 and Cx47 are colocalized in many gap junction plaques on oligodendrocyte somata, particularly in gray matter. Cx45 is detected in the cerebral vasculature, but not in oligodendrocytes or myelin sheaths. This diversity of connexins in oligodendrocytes (in different populations of cells and in different subcellular compartments) likely reflects functional differences between these connexins and perhaps the oligodendrocytes themselves. © 2004 Wiley‐Liss, Inc.