bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental sandstone weathering using different wetting and drying moisture amplitudes
Authors: Sumner P. D. , Loubser M. J. 
Published: September 2007

AbstractWetting and drying is an acknowledged yet still poorly understood rock weathering process. Previous experiments documented in the literature measure physical changes or mass loss in relation to moisture oscillations but only one study directly compares different moisture amplitudes by using different modes of moisture application. In this experimental study, four sets of sandstone tablets are subjected to 48 h wetting and drying cycles at set moisture content fluctuations of 29, 42, 56 and 63% respectively. A common moisture application, full immersion, is used for all four sets. Mass loss after 52 cycles averaged 0·27%, some three times more than that of the control samples. Average porosity of the samples increased, while water absorption capacities and the saturation coefficients of the samples decreased. No discernable difference in mass loss or change in physical properties was found between the different sample sets. When compared with previous studies, results suggest that the effect of moisture application type may be more of a controlling factor on the weathering effect than actual moisture content achieved. A need to move towards a more standardized approach in wetting and drying experimental studies is emphasized. Copyright © 2007 John Wiley & Sons, Ltd.
Molecular dynamics study of the interaction of a shock wave with a biological membrane
Authors: Lechuga Javier , Drikakis Dimitris , Pal Sandip 
Published: September 2007

AbstractThis paper presents a computational study of the interaction of a shock wave with a biological membrane. The membrane model comprises 21 555 atoms which build 66 dalmitoyloleoylphosphatidylcholine (POPC) lipids forming the bilayer, and 4237 water molecules, with the distance between the layers being set to fit around the actual membrane thickness (54 Å), and the lattice period being set to fit the actual surface density of lipid molecules. We have employed a molecular dynamics method for solving the Newton equations of motion numerically thereby providing a strategy to understand the basic physics of the biological structure at atomistic level. A shock wave has been modelled as an impulse of 40 Pa s, and simulations for the interaction of the shock wave with the membrane have been performed for 200 ps to investigate the different effects of the shock wave on different membrane properties including thickness, area, volume, order parameter and lateral diffusion. Copyright © 2007 John Wiley & Sons, Ltd.
Numerical solution of the oxygen diffusion problem in cylindrically shaped sections of tissue
Authors: Boureghda Abdellatif 
Published: September 2007

AbstractA mathematical model is presented which describes the diffusion of oxygen in absorbing tissue, and numerical solution of its partial differential equation is obtained by the finite difference equations. The diffusion with absorption model is associated with the process of a moving boundary which marks the furthest penetration of oxygen in the absorbing cylindrically shaped sections of tissue and also allows for an initial distribution of oxygen through the absorbing tissue. Copyright © 2007 John Wiley & Sons, Ltd.
Finite volume methods and the equations of finite scale: A mimetic approach
Authors: Margolin L. G. , Shashkov M. 
Published: September 2007

AbstractAfter introducing the general concept of mimetic differencing, we focus on two specific methodologies, nonoscillatory methods and finite volume approximations. We provide a brief historical account of the development of these two mimetic strategies. We then describe the extension of these strategies to new techniques, a discrete operator calculus and implicit large eddy simulation. In each case, we provide illustrative examples. Further abstraction of these ideas leads to the concept of equations of finite scale, which we advocate as a more appropriate PDE model for constructing numerical algorithms. Published in 2007 by John Wiley & Sons, Ltd.
Efficient computation of steady water flow with waves
Authors: Wackers Jeroen , Koren Barry 
Published: September 2007

AbstractA surface‐capturing model for steady water flow is presented. This volume‐of‐fluid model without reconstruction consists only of conservation laws, hence, it can be solved very efficiently. The model contains a high‐accuracy compressive water surface discretization and turbulence; it is solved with a linear multigrid technique and defect correction. Results show that the model is accurate and the solver gives fast convergence. Copyright © 2007 John Wiley & Sons, Ltd.
Price discovery in the treasury futures market
Authors: Brandt Michael W. , Kavajecz Kenneth A. , Underwood Shane E. 
Published: September 2007

AbstractThe paper conducts a regression analysis utilizing both futures and cash market prices and net orderflow to determine where price discovery takes place as well as the forces at play that influence the location. Specifically, given the strong theoretical linkage between the U.S. Treasury cash and futures markets, they compare how orderflow contributes to price discovery and analyze how and when information flows from one market to the other. How a number of environmental variables (trader type, financing rates, and liquidity) impact the information flows between these two markets is also considered. Their findings provide new evidence on the extent to which price discovery happens away from a primary market. © 2007 Wiley Periodicals, Inc. Jrl Fut Mark 27: 1021–1051, 2007
Serum and forskolin cooperate to promote G1 progression in Schwann cells by differentially regulating cyclin D1, cyclin E1, and p27Kip expression
Authors: Iacovelli Jared , Lopera Jorge , Bott Marga , Baldwin Elizabeth , Khaled Annette , Uddin Nizam , Fernandez‐Valle Cristina 
Published: September 2007

AbstractProliferation of Schwann cells in vitro, unlike most mammalian cells, is not induced by serum alone but additionally requires cAMP elevation and mitogenic stimulation. How these agents cooperate to promote progression through the G1 phase of the cell cycle is unclear. We studied the integrative effects of these compounds on receptor‐mediated signaling pathways and regulators of G1 progression. We show that serum alone induces strong cyclical expression of cyclin D1 and E1, 6 and 12 h after addition, respectively. Serum also promotes strong but transient erbB2, ERK, and Akt phosphorylation, but Schwann cells remain arrested in G1 due to high levels of the inhibitor, p27Kip. Forskolin with serum promotes G1 progression in 22% of Schwann cells between 18 and 24 h by inducing a steady decline in p27Kip levels that reaches a nadir at 12 h coinciding with peak cyclin E1 expression. Forskolin also delays neuregulin‐induced loss of erbB2 receptors allowing strong acute activation of PI3K, sustained erbB2 phosphorylation and G1 progression in 31% of Schwann cells. We find that the ability of forskolin to decrease p27Kip is associated with its ability to decrease Krox‐20 expression that is induced by serum and further increased by neuregulin. Our results explain why serum is required but insufficient to stimulate proliferation and identify two routes by which forskolin promotes proliferation in the presence of serum and neuregulin. These findings provide insights into how G1 progression and, cell cycle arrest leading to myelination are regulated in Schwann cells. © 2007 Wiley‐Liss, Inc.
Lack of P2X receptor mediated currents in astrocytes and GluR type glial cells of the hippocampal CA1 region
Authors: Jabs Ronald , Matthias Katja , Grote Alexander , Grauer Michael , Seifert Gerald , Steinhäuser Christian 
Published: September 2007

AbstractPurinergic signalling plays a major role in intercellular communication between neurons and glial cells. Glial cells express metabotropic receptors for ATP and adenosine, the latter being activated after ATP cleavage through extracellular ecto‐ATPase activity. Ionotropic receptors for extracellular ATP, so called P2X receptors, might contribute to neuron–glia signalling. However, experimental evidence for the presence of these receptors in glial cells is less convincing so far. In a previous study, immunohistochemistry was used to identify P2X1–4,6,7 receptor protein in S100β‐positive hippocampal glial cells. Applying patch clamp and fast application techniques, here we challenged the question of the functional expression of these receptors. Time correlated membrane currents served as test criterion for receptor function, since P2X receptor activation leads to the opening of unspecific cation channels in a millisecond time scale. Agonists were applied via short pressure puffs, with a fast concentration clamp method and through UV flash triggered photolysis of caged ATP. Two types of murine hippocampal macroglial cells, both labelled by the expression of green fluorescence protein driven by the human glial fibrillary acid protein promoter, were analysed in acute brain slices and in freshly dissociated cell suspensions. Surprisingly, ATP or related agonists completely failed to activate currents. Additionally, changes in spontaneously occurring glial postsynaptic currents were never observed. These results have been verified using rat and human hippocampal tissue as well as investigating cells from P2X7 knock out mice. It is concluded that in acute preparations, astroglial cells of the hippocampal CA1 subfield do not express functional P2X receptors. © 2007 Wiley‐Liss, Inc.
The term structure of credit spreads in project finance
Authors: Sorge Marco , Gadanecz Blaise 
Published: September 2007

AbstractThis paper finds that the term structure of credit spreads in project finance is hump‐shaped. This contrasts with other types of debt, where credit risk is shown instead to increase monotonically with maturity ceteris paribus. We emphasize a number of peculiar features of project finance structures that might underlie this finding, such as high leverage decreasing over time, long‐term political risk guarantees and the sequential resolution of uncertainty along project advancement stages. Our result is particularly relevant given the importance of project finance as a source of long‐term capital for infrastructure especially in developing countries and has implications for risk management in the framework of Basel II. Copyright © 2007 John Wiley & Sons, Ltd.
Foreign direct investment and exchange rate uncertainty in South‐East Asia
Authors: Gottschalk Sylvia , Hall Stephen 
Published: September 2007

AbstractWe investigate the relationship between exchange rate volatility, exchange rate risk diversification and the location of foreign direct investment in the manufacturing industries of Indonesia, Malaysia, Philippines and Thailand. We found a strong role for the yen/dollar exchange rate in location decisions of the US and Japanese investors. There is evidence in the literature that Japanese firms invest in Asia to circumvent the appreciation of the yen. Our results show that the volatility of the yen and the correlation between local exchange rates and the yen are significant determinants of the US and Japanese investments in the region. Copyright © 2007 John Wiley & Sons, Ltd.
Preliminary tribological evaluation of nanostructured diamond coatings against ultra‐high molecular weight polyethylene
Authors: Hill Michael R. , Catledge Shane A. , Konovalov Valeriy , Clem William C. , Chowdhury Shafiul A. , Etheridge Brandon S. , Stanishevsky Andrei , Lemons Jack E. , Vohra Yogesh K. , Eberhardt Alan W. 
Published: September 2007

AbstractBackground: Some loss of joint prostheses has been attributed to osteolytic loosening associated with debris from wear of polyethylene articulating against metal alloys. Reduced polyethylene wear has been reported with ceramics serving as an alternative counterface. Methods: Nanostructured Diamond (NSD) coatings were deposited onto Ti6Al4V by microwave plasma‐assisted chemical vapor deposition, with both hydrogen‐rich (H‐NSD) and helium‐rich (He‐NSD) feedgas mixtures. Pin‐on‐disk wear tests of polyethylene against NSD and CoCr were performed in serum lubrication at body temperature. Scanning electron microscopy was used to examine surface morphology, and nanoindentation was used to determine hardness and modulus of the polyethylene wear surfaces. Raman spectroscopy, surface roughness, and wettability analyses of the NSD coatings were performed. Results: Raman spectroscopy confirmed sp2 and sp3 bonded carbon in the NSD coatings. No significant differences in wear factors were found between polyethylene on H‐NSD, He‐NSD, and CoCr, despite higher roughness and friction coefficients for the He‐NSD and H‐NSD coatings, compared with CoCr. Contact angles for the diamond coatings were reduced following the wear tests, indicating that these surfaces became more hydrophilic. Numerous small protuberances were observed on pins articulated against CoCr, and a single, large protuberance was observed in polyethylene‐on‐NSD. These features were conjectured to be reconsolidated polyethylene particles. Nanoindentation modulus and hardness of the worn polyethylene surfaces were lower for polyethylene‐on‐diamond than for polyethylene‐on‐CoCr. Conclusions: As a counterface to polyethylene, NSD‐coated Ti6Al4V produced wear factors comparable to CoCr in the present pin‐on‐disk tests, a promising step towards its use in joint replacement bearing applications. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008
Comparison of the release behaviors of cupric ions from metallic copper and a novel composite in simulated body fluid
Authors: Li Juan , Suo Jinping , Huang Xunbin , Ye Chang , Wu Xiwang 
Published: September 2007

AbstractThe copper‐containing intrauterine devices (Cu‐IUDs) are being increasingly used worldwide as an effective contraceptive for family planning. To avoid abnormal bleeding, pain, and partial and complete expulsion which are associated with the burst release of copper during the first few days, a novel crosslinked composite based on poly(vinyl alcohol) that contained cupric ions, but not metallic copper, was synthesized. It is hypothesized that the burst release of cupric ions could be avoided and the utility of the cupric ions could be improved by this novel composite. To evaluate these effects of the composite, the corrosion products and the release rate of cupric ions after soaking in simulated body fluid (SBF) for different time spans were studied by environmental scanning electron microscopy, X‐ray energy dispersive spectroscopy, X‐ray diffraction, and atomic absorption spectrophotometer. In the first week, the release amount of cupric ions in the composite was 0.486 μg/mm2. In the fifth week, it decreased to 0.0278 μg/mm2. But for metallic copper, these were 5.93 μg/mm2 and 0.041 μg/mm2, respectively. No significant change on time‐dependence was found for the release rates of cupric ions in the composite compared with that of metallic copper. Moreover, no other new elements, such as P, Cl, and Ca, appeared on the surface of the composite, and no Cu2O was formed after immersing in SBF for 90 days. All of these results suggested that burst release of cupric ions could be avoided and the effective utility of copper could be improved in this composite. In view of the earlier results, this novel copper‐containing composite might serve as a potential substitute for conventional materials of IUDs in the future. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008
Development of acellular dermis from porcine skin using periodic pressurized technique
Authors: Prasertsung Isarawut , Kanokpanont Sorada , Bunaprasert Tanom , Thanakit Voranuch , Damrongsakkul Siriporn 
Published: September 2007

AbstractIn this work, a new method for producing acellular dermis (ADM), a natural scaffold used for dermal replacement, from porcine skin was developed. Fresh porcine skin from local slaughterhouse was dehaired by sodium sulphide following by epidermis removal using glycerol. After fat removal by chloroform/methanol (2/1 v/v) solvent, cellular components were removed using enzymatic treatment incorporated with a periodic pressurized technique. The effects of enzyme type (trypsin and dispase II) and periodic pressurized conditions on the efficiency of cell removal were investigated. When periodic pressure was applied, enzymatic treatment time could be shorten since the enzyme solution was able to penetrate into tight dermis. As a result, cells could be easily removed from porcine skin as noticed quantitatively by DNA assay and qualitatively by H&E staining. When enzyme refreshment was introduced into the decellularized process, the percentage of cell removal was further enhanced. This ensured that no inhibitions effect from the removed cells on enzyme‐substrate interaction. Moreover, short‐time enzymatic treatment with periodic pressurized technique could prevent the disruption of dermal structure, as observed by SEM. Dispase II can be used to remove cell better than trypsin in the periodic pressurized technique. However, in vivo study indicated that numerous fibroblast from the host tissue infiltrated into ADM prepared using both enzymes. Neo‐collagen and neo‐capillaries were produced in both implanted ADMs. The result elucidated that the use of periodic pressurized technique with enzymatic treatment has a high potential to be a new method to produce ADM for skin tissue engineering. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008
Expression of serum amyloid A transcripts in human bone tissues, differentiated osteoblast‐like stem cells and human osteosarcoma cell lines
Authors: Kovacevic Alenka , Hammer Astrid , Stadelmeyer Elke , Windischhofer Werner , Sundl Monika , Ray Alpana , Schweighofer Natascha , Friedl Gerald , Windhager Reinhard , Sattler Wolfgang , Malle Ernst 
Published: September 2007

AbstractAlthough the liver is the primary site of cytokine‐mediated expression of acute‐phase serum amyloid A (SAA) protein, extrahepatic production has also been reported. Besides its role in amyloidosis and lipid homeostasis during the acute‐phase, SAA has recently been assumed to contribute to bone and cartilage destruction. However, expression of SAA in human osteogenic tissue has not been studied. Therefore, we first show that SAA1 (coding for the major SAA isoform) but not SAA2 transcripts are expressed in human trabecular and cortical bone fractions and bone marrow. Next, we show expression of (i) IL‐1, IL‐6, and TNF receptor transcripts; (ii) the human homolog of SAA‐activating factor‐1 (SAF‐1, a transcription factor involved in cytokine‐mediated induction of SAA genes); and (iii) SAA1/2 transcripts in non‐differentiated and, to a higher extent, in osteoblast‐like differentiated human mesenchymal stem cells. Third, we provide evidence that human osteoblast‐like cells of tumor origin (MG‐63 and SAOS‐2) express SAF‐1 under basal conditions. SAA1/2 transcripts are expressed under basal conditions (SAOS‐2) and cytokine‐mediated conditions (MG‐63 and SAOS‐2). RT‐PCR, Western blot analysis, and immunofluorescence technique confirmed cytokine‐mediated expression of SAA on RNA and protein level in osteosarcoma cell lines while SAA4, a protein of unknown function, is constitutively expressed in all osteogenic tissues investigated. J. Cell. Biochem. 103: 994–1004, 2008. © 2007 Wiley‐Liss, Inc.
Corticosterone induces steroidogenic lesion in cultured adult rat leydig cells by reducing the expression of star protein and steroidogenic enzymes
Authors: Rengarajan Srinivasan , Balasubramanian Karundevi 
Published: September 2007

AbstractThe present study was designed to investigate the dose‐dependent direct effect of corticosterone on adult rat Leydig cell steroidogenesis in vitro. Leydig cells were isolated from the testis of normal adult male albino rats, purified on discontinuous Percoll gradient and plated in culture plates/flasks overnight at 34°C in a CO2 incubator under 95% air and 5% CO2 using DME/F12 medium containing 1% fetal bovine serum. After the attachment of cells, serum‐containing medium was removed and cells were exposed to different doses (0, 50, 100, 200, 400, and 800 nM) of corticosterone using serum‐free fresh medium for 24 h at 34°C. At the end of exposure period, cells were utilized for assessment of the activities and mRNA expression of steroidogenic enzymes (cytochrome P450 side chain cleavage enzyme, 3β‐hydroxysteroid dehydrogenase, 17β‐hydroxysteroid dehydrogenase, and cytochrome P450 aromatase) and steroidogenic acute regulatory protein gene expression. Testosterone and estradiol production were also quantified. Activities of cytochrome P450 side chain cleavage enzyme, 3β‐ and 17β‐hydroxysteroid dehydrogenases were declined significantly in a dose‐dependent manner after corticosterone exposure, while their mRNA expression were significantly reduced at higher doses of corticosterone exposure. The activity and mRNA expression of cytochrome P450 aromatase registered a significant increase at 100 nM dose of corticosterone whereas at 200–800 nM doses both the activity as well as the mRNA levels was significantly reduced below the basal level. StAR protein gene expression was significantly inhibited by higher doses of corticosterone employed. At all doses employed, corticosterone significantly reduced the production of testosterone by Leydig cells, while estradiol level registered a significant increase at 50 and 100 nM doses but at higher doses, it registered a significant decrease when compared to basal level. It is concluded from the present in vitro study that the molecular mechanism by which corticosterone reduces the production of Leydig cell testosterone is by reducing the activities and mRNA expression of steroidogenic enzymes and steroidogenic acute regulatory protein. J. Cell. Biochem. 103: 1472–1487, 2008. © 2007 Wiley‐Liss, Inc.
GLYCAM06: A generalizable biomolecular force field. Carbohydrates
Authors: Kirschner Karl N. , Yongye Austin B. , Tschampel Sarah M. , González‐Outeiriño Jorge , Daniels Charlisa R. , Foley B. Lachele , Woods Robert J. 
Published: September 2007

AbstractA new derivation of the GLYCAM06 force field, which removes its previous specificity for carbohydrates, and its dependency on the AMBER force field and parameters, is presented. All pertinent force field terms have been explicitly specified and so no default or generic parameters are employed. The new GLYCAM is no longer limited to any particular class of biomolecules, but is extendible to all molecular classes in the spirit of a small‐molecule force field. The torsion terms in the present work were all derived from quantum mechanical data from a collection of minimal molecular fragments and related small molecules. For carbohydrates, there is now a single parameter set applicable to both α‐ and β‐anomers and to all monosaccharide ring sizes and conformations. We demonstrate that deriving dihedral parameters by fitting to QM data for internal rotational energy curves for representative small molecules generally leads to correct rotamer populations in molecular dynamics simulations, and that this approach removes the need for phase corrections in the dihedral terms. However, we note that there are cases where this approach is inadequate. Reported here are the basic components of the new force field as well as an illustration of its extension to carbohydrates. In addition to reproducing the gas‐phase properties of an array of small test molecules, condensed‐phase simulations employing GLYCAM06 are shown to reproduce rotamer populations for key small molecules and representative biopolymer building blocks in explicit water, as well as crystalline lattice properties, such as unit cell dimensions, and vibrational frequencies. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008