bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparing effects of attractive interactions in crowded systems: nonspecific, hydrophobic, and hydrogen bond interactions
Authors: Bazmi Saman , Wallin Stefan
Published: January 2024

The equilibrium stability of a protein is determined by its amino acid sequence and the solution conditions, such as temperature, pH and presence of chemical denaturant. The stability of a single protein in two identical solutions can nonetheless differ if other macromolecules, termed cosolutes or crowders, are present in one of the solutions at concentrations high enough to occupy a substantial fraction of the solution volume. This effect, due to the presence of the crowders, decreases or increases the stability depending on the interactions between the protein and crowders. Hard-core steric repulsions, which are responsible for the reduction in free volume, are expected to entropically stabilize the protein while attractive interactions can be destabilizing. Here we use a coarse-grained protein model to assess the impact of different types of crowder-protein interactions on the stability of a 35-amino acid model sequence folding into a helical bundle. We find that, for the same interaction strength and concentration, spherical crowders with a hydrophobic character are more destabilizing than crowders interacting nonspecifically with the protein. However, the two types of interactions differ in the degree of association between crowders and protein. At an interaction strength for which the attractive interactions roughly counteracts the stabilizing hard-core repulsions, the nonspecific interactions lead to much stronger crowder-protein association than the hydrophobic interactions. Additionally, we study crowders in the form of polypeptide chains, which are capable of hydrogen bonding with the protein. These peptide crowders have a destabilizing effect even at relatively low crowder concentrations, especially if the sequence of the peptide crowders includes hydrophobic amino acids. Our findings emphasize the importance of the interplay between different types of attractive crowder-protein interactions and entropic effects in determining the net effect on protein stability.
Association between lactic acidosis and multiple organ dysfunction syndrome after cardiopulmonary bypass
Authors: Zheng Dan , Yu Guo-Liang , Zhou Yi-Ping , Zhang Qiao-Min , Wang Chun-Guo , Zhang Sheng
Published: January 2024

Background

The relationship between hyperlactatemia and prognosis after cardiopulmonary bypass (CPB) is controversial, and some studies ignore the presence of lactic acidosis in patients with severe hyperlactacemia. This study explored the association between lactic acidosis (LA) and the occurrence of multiple organ dysfunction syndrome (MODS) after cardiopulmonary bypass.

Methods

This study was a post hoc analysis of patients who underwent cardiac surgery between February 2017 and August 2018 and participated in a prospective study at Taizhou Hospital. The data were collected at: ICU admission (H0), and 4, 8, 12, 24, and 48 h after admission. Blood lactate levels gradually increased after CPB, peaking at H8 and then gradually decreasing. The patients were grouped as LA, hyperlactatemia (HL), and normal control (NC) based on blood test results 8 h after ICU admission. Basic preoperative, perioperative, and postoperative conditions were compared between the three groups, as well as postoperative perfusion and oxygen metabolism indexes.

Results

There were 22 (19%), 73 (64%), and 19 (17%) patients in the LA, HL, and NC groups, respectively. APACHE II (24h) and SOFA (24h) scores were the highest in the LA group (P < 0.05). ICU stay duration was the longest for the LA group (48.5 (42.5, 50) h), compared with the HL (27 (22, 48) h) and NC (27 (25, 46) h) groups (P = 0.012). The LA group had the highest incidence of MODS (36%), compared with the HL (14%) and NC (5%) groups (P = 0.015). In the LA group, the oxygen extraction ratio (O2ER) was lower (21.5 (17.05, 32.8)%) than in the HL (31.3 (24.8, 37.6)%) and the NC group (31.3 (29.0, 35.4) %) (P = 0.018). In the univariable analyses, patient age (OR = 1.054, 95% CI [1.003–1.109], P = 0.038), the LA group (vs. the NC group, (OR = 10.286, 95% CI [1.148–92.185], P = 0.037), and ΔPCO2 at H8 (OR = 1.197, 95% CI [1.022–1.401], P = 0.025) were risk factor of MODS after CPB.

Conclusions

We speculated that there was correlation between lactic acidosis and MODS after CPB. In addition, LA should be monitored intensively after CPB.
Static versus dynamic muscle modelling in extinct species: a biomechanical case study of the Australopithecus afarensis pelvis and lower extremity
Authors: Wiseman Ashleigh L.A. , Charles James P. , Hutchinson John R.
Published: January 2024

The force a muscle generates is dependent on muscle structure, in which fibre length, pennation angle and tendon slack length all influence force production. Muscles are not preserved in the fossil record and these parameters must be estimated when constructing a musculoskeletal model. Here, we test the capability of digitally reconstructed muscles of the Australopithecus afarensis model (specimen AL 288-1) to maintain an upright, single-support limb posture. Our aim was to ascertain the influence that different architectural estimation methods have on muscle specialisation and on the subsequent inferences that can be extrapolated about limb function. Parameters were estimated for 36 muscles in the pelvis and lower limb and seven different musculoskeletal models of AL 288-1 were produced. These parameters represented either a ‘static’ Hill-type muscle model (n = 4 variants) which only incorporated force, or instead a ‘dynamic’ Hill-type muscle model with an elastic tendon and fibres that could vary force-length-velocity properties (n = 3 variants). Each muscle’s fibre length, pennation angle, tendon slack length and maximal isometric force were calculated based upon different input variables. Static (inverse) simulations were computed in which the vertical and mediolateral ground reaction forces (GRF) were incrementally increased until limb collapse (simulation failure). All AL 288-1 variants produced somewhat similar simulated muscle activation patterns, but the maximum vertical GRF that could be exerted on a single limb was not consistent between models. Three of the four static-muscle models were unable to support >1.8 times body weight and produced models that under-performed. The dynamic-muscle models were stronger. Comparative results with a human model imply that similar muscle group activations between species are needed to sustain single-limb support at maximally applied GRFs in terms of the simplified static simulations (e.g., same walking pose) used here. This approach demonstrated the range of outputs that can be generated for a model of an extinct individual. Despite mostly comparable outputs, the models diverged mostly in terms of strength.
Electrical stimulation promoting the angiogenesis in diabetic rat perforator flap through attenuating oxidative stress-mediated inflammation and apoptosis
Authors: Chen Cong , Li Xiaolu , Hu Yong , Chen Yuan , Wang Hongrui , Li Xian , Li Xiucun
Published: January 2024

Background

Skin flap transplantation is one of the effective methods to treat the diabetes-related foot ulceration, but the intrinsic damage to vessels in diabetes mellitus (DM) leads to the necrosis of skin flaps. Therefore, the discovery of a non-invasive and effective approach for promoting the survival of flaps is of the utmost importance. Electrical stimulation (ES) promotes angiogenesis and increases the proliferation, migration, and elongation of endothelial cells, thus being a potential effective method to improve flap survival.

Objective

The purpose of this study was to elucidate the mechanism used by ES to effectively restore the impaired function of endothelial cells caused by diabetes.

Methods

A total of 79 adult male Sprague-Dawley rats were used in this study. Gene and protein expression was assessed by PCR and western blotting, respectively. Immunohistochemistry and hematoxylin-eosin staining were performed to evaluate the morphology and density of the microvessels in the flap.

Results

The optimal duration for preconditioning the flap with ES was 7 days. The flap survival area percentage and microvessels density in the DMES group were markedly increased compared to the DM group. VEGF, MMP2, and MMP9 protein expression was significantly upregulated. ROS intensity was significantly decreased and GSH concentration was increased. The expression of IL-1β, MCP‑1, cleaved caspase-3, and Bax were downregulated in the DMES group, while TGF-β expression was upregulated.

Conclusions

ES improves the angiogenesis in diabetic ischemic skin flaps by attenuating oxidative stress–mediated inflammation and apoptosis, eventually increasing their viability.
Extending beyond individual caves: a graph theory approach broadening conservation priorities in Amazon iron ore caves
Authors: Oliveira Marcus P. A. , Ferreira Rodrigo L.
Published: January 2024

The Amazon is renowned worldwide for its biological significance, but it also harbors substantial mineral reserves. Among these, the ferruginous geosystems of the region are critical for iron ore extraction, accounting for 10% of Brazil’s export revenue. Additionally, this region holds a significant speleological heritage with more than 1,000 caves. However, cave conservation efforts are often in conflict with land use, necessitating mediation through environmental regulations. While conservation decisions typically consider only the caves’ characteristics, such an approach fails to account for the interactions among cave communities and their surrounding landscape. This poses a challenge to reserve design for cave conservation purposes. To address this issue, we assessed the predictors that influence the similarity among cave communities, suggesting the use of this parameter as a proxy for subterranean connectivity. Applying graph theory, we proposed a tool to aid in the selection of priority caves for conservation purposes. Our study involved the sampling of invertebrates in 69 iron ore caves and analyzing 28 environmental variables related to these subterranean habitats and adjacent landscape. Our analysis revealed that landscape and habitat characteristics are more important than geographical distance in determining patterns of similarity among caves. Our graph approach highlighted densely interconnected clusters based on similarity. However, specific caves stood out for harboring exclusive fauna and/or exhibiting habitat specificity, making them unique in the study area. Thus, we recommend prioritizing cave clusters for conservation, assembling both singular caves and others that influence them. It is crucial to note that protocols for the protection of subterranean biodiversity must consider measures that encompass both the caves and the surrounding landscape. Our methodology provides insights into the connectivity among caves, identifies existing groups, highlights singular (or unique) cavities that require preservation, and recognizes those influencing these unique habitats. This methodological advancement is crucial for the development of better conservation policies for the speleological heritage in areas under constant economic pressure.
Transformational Leadership: A Comparative Exploration of the Leadership Prowess of Jeff Bezos and Steve Jobs
Authors: Adigwe Chinasa Susan
Published: January 2024

This exploratory study delves into the intricacies of transformational leadership within the technology sector, drawing insights from the leadership styles of Steve Jobs of Apple and Jeff Bezos of Amazon. The research aimed to understand how transformational leadership traits influence organizational outcomes like innovation, employee motivation, engagement, and overall performance. To achieve this, the study employed a mixed-method approach, incorporating both quantitative and qualitative data collection techniques. Primary data was gathered using a structured questionnaire, which was administered to a purposively sampled group of 567 respondents, all holding leadership or managerial roles in various industries. The questionnaire design integrated both closed-ended and open-ended questions to facilitate a comprehensive analysis. The data analysis involved rigorous regression analysis to quantitatively assess the relationships between specific transformational leadership traits and organizational outcomes. Key findings revealed a strong positive correlation between the level of inspirational motivation demonstrated by leaders and the degree of organizational innovation. Additionally, significant relationships were observed between the extent of individualized consideration by leaders and employee motivation and engagement, as well as between strategic vision and risk-taking by leaders and key organizational performance metrics. Drawing from these insights, the study recommends cultivating a leadership style that emphasizes inspirational motivation, individualized consideration, and strategic risk-taking. This approach is crucial for fostering innovation, enhancing employee motivation and engagement, and improving overall organizational performance in the rapidly evolving technology sector.
Organic Farming at Eastern Ghat Hill: A Boon to Tribal Farmers
Authors: Bharathi C. Sharmila
Published: January 2024

Kollihills is a small mountain range located at the tail end of the Eastern Ghats in Namakkal District of Tamil Nadu. Krishi Vigyan Kendra, Namakkal is being implemented Paramparaghat Krishi Vikas Yojana (PKVY) scheme at Elangiyampatti and Ariyur Nadu villages of Kollihills, Namakkal District, Tamil Nadu since 2019. Local group formed in the name of KVK Masila PKVY Farmers group with 21 tribal farmers covering in an area of 20 ha. The crops covered under organic farming are Black pepper, Cardamom, Hill banana, Coffee, Vegetables, Tapioca and Millets. Initially 12 capacity building programmes were conducted to the tribal farmers on organic farm management, organic input production for soil fertility management, adoption of PGS standards in field practices and PGS certification. The tribal farmers started organic cultivation by using vermicompost, panchakavya, IISR Tricho capsules, bio fertilizers and waste decomposer application produced by their own. They did primary processing of organic spices and plantation crops by using primary processing unit established by KVK under TSP scheme and maintained by these farmers group. After completion of 3 years organic farming practices, all the tribal farmers got organic certification. They harvested 1370 kg of black pepper, 145 kg of Cardamom, 1700 kg of coffee beans, 625 bunches of hill banana, 9.1 tonnes of vegetables and 1.4 tonnes of millets per 0.4 ha area and sold the organic produce with brand name to nearby markets in Namakkal, Salem, Karur and Erode. They realized a net income of Rs.301500 from black pepper, Rs.317050 from caradamom, Rs.93700 from coffee, Rs.155400 from hill banana, Rs.112580 and Rs.23930 from Millets each in an area of 0.4 ha.
Influence of Nitrogen Levels and Zinc Application on Morphological and Physiological Attributes of Rice Varieties
Authors: BV Nagesha , Thatikunta Ramesh , Reddy S Narender , Krishna L , Supriya K
Published: January 2024

A field experiment was conducted during Kharif and Rabi, 2018 at the College of Agriculture, Rajendranagar, Hyderabad to study the effect of different nitrogen levels and zinc application on growth and development in paddy. The experiment was laid out in split plot design with three varieties as main plots, and six nutrient levels as sub plots and replicated thrice. Among the varieties Kunaram Sannalu has recorded lowest Plant height and Telangana Sona has recorded highest Plant height (63.3, 98.8 and 103.3 cm at vegetative, flowering and grain filling stages respectively), with maximum stem thickness 5.37, 6.09 and 6.17 mm at vegetative, flowering and grain filling stage respectively), Crop growth rate (13.451 25.77 and 8.86 g m-2 day-1 at vegetative, flowering and grain filling stage respectively), Total dry matter (2959, 7585 and 8909 kg ha-1 at vegetative, flowering and grain filling stages respectively) and had taken more number of days to panicle initiation (67), flowering (86) and maturity (122). Tella Hamsa has recorded less stem thickness, Crop growth rate, total dry matter and has taken less number of days to panicle initiation (64), flowering (83) and maturity (118). Application of 25% higher than RDN + 0.5% ZnSO4 foliar spray resulted in maximum plant height, stem thickness, crop growth rate, and total dry matter.
Entomotoxic Effect of Five Varieties of Bambara Groundnut (Vigna subterranea) and a Variety of Red Bean (Phaseolus vulgaris) against Old Larvae and Adults of Tribolium castaneum Herbst (Coleoptera, Tenebrionidae)
Authors: Mamoudou Salma , Habiba Kouninki
Published: January 2024

The entomotoxic effect of five varieties of Bambara groundnut (McFoSc, BlRSc, BlRAcV, MnRSc, and BnRaSc) and one variety of common bean flours (GGR) is evaluated on old larvae and adults of Tribolium castaneum (Coleoptera, Tenebrionidae) under laboratory conditions with ambient temperatures ranging from 32°C to 36°C. This study aims to mitigate the damage caused by Tribolium castaneum to stored grains and legumes. The flour from each variety was obtained by grinding and sieving. A total of 150g of each flour sample was infested with either 20 old larvae or 20 newly emerged Tribolium castaneum. The variables observed included mortality rates of old larvae and adults, the number of F1 progeny, and the number of larvae, nymphs, and adults in the first generation. The flour of red millet (MR) which is a cereal was considered as control. After introducing the adults into the flours of different varieties, no mortality was observed for the ML, MCFOSC, MNRSC, BNRASC, and GGR varieties within 24 hours. The mortality rates were 1.25 ± 0.96 and 5 ± 0.72 for the BIRSC and BIRACV varieties, respectively. After four weeks of treatment, the cumulative mortality rates for the larvae were 93.75% for the GGR variety, 66.25% for the BIRACV variety, 56.25% for the MCFOSC variety, 55% for the BIRSC variety, 37.5% for the MNRSC variety, 31.25% for the BNRASC variety, and only 5% for the control (MR). The flours of these leguminous crops have a negative impact on the development of Tribolium castaneum by prolonging the duration of larval development. It suggests that these different leguminous seed varieties can be effective in controlling insects during storage.
Rheological characterization of schizophyllan aqueous solutions after denaturation–renaturation treatment
Authors: Fang Yapeng , Takahashi Rheo , Nishinari Katsuyoshi
Published: April 2004

Schizophyllan (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

CD4–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

Antigen‐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

Fire 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

This 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

On 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

To 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

An 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

There 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

The 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

A 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

Human 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

Individuals 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

N‐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

Oligodendrocytes 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.
Astrocyte‐induced regulatory T cells mitigate CNS autoimmunity
Authors: Trajkovic Vladimir , Vuckovic Olivera , Stosic‐Grujicic Stanislava , Miljkovic Djordje , Popadic Dusan , Markovic Milos , Bumbasirevic Vladimir , Backovic Aleksandar , Cvetkovic Ivana , Harhaji Ljubica , Ramic Zorica , Mostarica Stojkovic Marija
Published: April 2004

Although astrocytes presumably participate in maintaining the immune privilege of the central nervous system (CNS), the mechanisms behind their immunoregulatory properties are still largely undefined. In this study, we describe the development of regulatory T cells upon contact with astrocytes. Rat T cells pre‐incubated with astrocytes completely lost the ability to proliferate in response to mitogenic stimuli. The cells were blocked in G0/G1 phase of the cell cycle, expressed less IL‐2R, and produced significantly lower amounts of interferon‐γ (IFN‐γ), but not interleukin‐2 (IL‐2), IL‐10, or tumor necrosis factor (TNF). These anergic cells completely prevented mitogen‐induced growth of normal T lymphocytes, as well as CNS antigen‐driven proliferation of autoreactive T cells. The suppressive activity resided in both CD4+ and CD8+ T‐cell compartments. Heat‐sensitive soluble T‐cell factors, not including transforming growth factor‐β (TGF‐β) or IL‐10, were solely responsible for the observed suppression, as well as for the transfer of suppressive activity to normal T cells. The administration of astrocyte‐induced regulatory T cells markedly alleviated CNS inflammation and clinical symptoms of CNS autoimmunity in rats with experimental allergic encephalomyelitis. Finally, the cells with suppressive properties were readily generated from human lymphocytes after contact with astrocytes. Taken together, these data indicate that astrocyte‐induced regulatory T cells might represent an important mechanism for self‐limitation of excessive inflammation in the brain. © 2004 Wiley‐Liss, Inc.
Nestin expression in hippocampal astrocytes after injury depends on the age of the hippocampus
Authors: Abdel‐Rahman Ali , Rao Muddanna S. , Shetty Ashok K.
Published: April 2004

Analysis of the expression of nestin in reactive astrocytes facilitates quantification of the extent of activation of astrocytes after injury in the mature CNS. We hypothesize that the capability of astrocytes for re‐expressing nestin in response to CNS injury diminishes as a function of age. We quantified astrocytes positive for S‐100β protein, glial fibrillary acidic protein (GFAP) and nestin in the hippocampus of young adult, middle‐aged, and aged Fischer 344 rats after an intracerebroventricular kainic acid (KA) administration. In all age groups, KA administration induced degeneration of CA3 pyramidal neurons, which led to a significant deafferentation in the CA1 region. The KA‐induced neurodegeneration and deafferentation resulted in an increased population of astrocytes positive for S‐100β and glial fibrillary acidic protein (GFAP) in all age groups. Interestingly, these increases were highly comparable across the three age groups. However, in areas of both neurodegeneration and deafferentation, the overall numerical density of nestin‐positive reactive astrocytes varied depending on the age at the time of injury with noticeably decreased numerical density in the injured middle‐aged and aged hippocampus. In contrast, nestin‐immunoreactive radial glia framework after lesion is not impaired with aging in the ependymal lining of the CA3 region. © 2004 Wiley‐Liss, Inc.
Comparative study of the in vitro apatite‐forming ability of poly(ε‐caprolactone)–silica sol–gels using three osteoconductivity tests (static, dynamic, and alternate soaking process)
Authors: Eglin David , Ali Saad A. M. , Perry Carole C.
Published: April 2004

The in vitro apatite‐forming ability of poly(ε‐caprolactone) (70 wt %)–silica sol–gels, with hydroxyl and triethoxysilane end‐groups with potential use in bone repair have been assessed using static and dynamic osteoconductivity tests. Diffuse reflectance infrared spectroscopy, scanning electron microscopy, and microanalysis techniques were used to observe and characterize precipitates formed on the material's surface. An apatite layer was observed to form on both of the composites' surface. However, variations were observed according to the test method used, in accordance with other studies on bioactive ceramics. A third method, the “alternate soaking process” (ASP) was developed to provide rapid results and quantify the amount of calcium‐containing precipitates formed on the surface of potentially “bioactive” materials. The results presented here show that for a material to be bioactive and have the ability to form a precipitate containing calcium and phosphate ions, levels of calcium ions measured by a complexometric assay should be significantly higher than the level of 5 μg/cm2. This level of calcium ions was obtained after 20 ASP cycles for the hydroxyl and triethoxysilane end‐capped poly(ε‐caprolactone) samples that did not form precipitates on their surfaces even after >50 ASP cycles. For the two sol–gel silica composites containing approximately 70% hydroxyl and triethoxysilane poly(ε‐caprolactone), there was no significant difference in the amount of calcium‐containing precipitate as observed using the in vitro apatite‐forming ability tests suggesting that polymer end‐group modification is not detrimental to the apatite‐forming ability of such composites. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 718–727, 2004