bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability of a Stratified Layer of a Gravitating Partially Ionized Plasma
Authors: Bhatia P. K. , Sankhla V. D. 
Published: July 2007

AbstractThe instability in a stratified layer of a self‐gravitating partially ionized plasma has been studied in the presence of effects of Hall currents. For a plasma permeated by a uniform vertical magnetic field, the dispersion relation has been obtained through variational method. It is found that the Hall currents have a destabilizing effect while the neutral gas frictional effects have a stabilizing influence.
Central Structure of Dβ Line in Low Pressure T‐Tube Deuterium Plasmas
Authors: Pavlov M. , Mijatović Z. 
Published: July 2007

AbstractThe perturbing ion motion effect on the relative central dip of the Hβ (Dβ) has been firmly established for numerous values of the reduced mass of the radiating atom – perturbing ion. In this paper the ion motion effect is confirmed for the cases in which the reduced mass and electron densities are constant, while the temperature of plasma is changing. Also a dependence of the dip values on electron density Ne is checked following theoretical results of Demura, Lisitza and Sholin. It is shown that the dip value is a linear function of N, where α is a number close to 1.
The Arc Cathode Regime: An Approach from Basic Laws
Authors: Hantzsche E. 
Published: July 2007

AbstractThe question is examined whether or not the existence of a cathode mechanism with high power density may be predicted from general physical laws, as well as the order of magnitude of the main cathode parameters of such a discharge. The answer is yes, though – because of many feedbacks and simplifications – the numerical values calculated in this way are not more than crude estimations.Essentially two conditions have to be fulfilled: The first is the dominance of collective electron emission processes, the second is the dominance of Joule heating combined with the limit of stationarity. Both conditions result in similar values of the cathode parameters.In this low‐current region (about 10…100 A) the existence of a high‐current density cathode mechanism (order of magnitude: 108 A/cm2) is proved, with consequences for all the other parameters, in rough agreement with the results of measurements in arc cathode spots. Thus the typical arc spot regime may be founded theoretically by these argumentations.
General Formulation for the Ponderomotive Force in a Warm Two Fluid Magnetized Plasma
Authors: Tyagi S. S. , Srivastava M. P. 
Published: July 2007

AbstractA general expression for the ponderomotive force in a warm, inhomogeneous, nonstationary, magnetized and collisionless two fluid plasma in the presence of electromagnetic field is obtained. We start with two fluid equations viz. continuity, momentum equations and Maxwell's equation. Expanding the physical quantities in terms of a high frequency part and a slowly varying part and averaging the quantities over one period of the high frequency, we have obtained the expression for the ponderomotive force. The results are compared with the results of earlier workers under different approximations.
Ternary Complexes of Zinc(II), Cyclen and Pyridinecarboxylic Acids
Authors: Vargová Zuzana , Kotek Jan , Rudovský Jakub , Plutnar Jan , Gyepes Robert , Hermann Petr , Györyová Katarina , Lukeš Ivan 
Published: July 2007

AbstractBinary and ternary systems containing Zn2+, cyclen and/or pyridinecarboxylic acids and amides [picolinic (HL1), nicotinic (HL2) and dipicolinic (H2L3) acids and nicotinamide (L4)] have been investigated in solution and in the solid state. Dissociation and stability constants for the ligands and binary systems, respectively, are in accordance with literature results. Both picolinic and dipicolinic acids form stable ternary complexes with the [Zn(cyclen)]2+species; a weak interaction is observed for nicotinic acid and nicotinamide. The formation of ternary complexes stabilizes the products of protonation at the cyclen nitrogen atom, and these protonated complexes are found even up to pH = 7. The structures of the complexes in solution correlate well with those found in the solid state and by molecular modelling calculations. The solid‐state structures of several complexes are determined. The zinc atom in the [Zn(cyclen)(NO3)]+complex is bound in an N4O tetragonal‐pyramidal environment. The nicotinic acid anion forms a bridge in the [{Zn(cyclen)}2(μ‐L2‐N,O)]3+cation, and both [Zn(cyclen)]2+units exhibit tetragonal‐pyramidal arrangements. An unusual coordination mode is found in the [{Zn(cyclen)}2(μ‐L1‐O:N,O′)]3+cation, where the picolinic acid anion also bridges two [Zn(cyclen)]2+units but is coordinated monodentately through one oxygen atom to one unit (N4O tetragonal pyramid) and chelates through the other pyridine nitrogen and carboxylate oxygen atoms. Nicotinamide in the [Zn(cyclen)(L4‐N)]2+cation is bound to the [Zn(cyclen)]2+unit through the pyridine nitrogen atom in the axial position of the tetragonal pyramid. This is the first fully quantitative assessment of Zn2+‐cyclen‐ligand ternary systems, and the results, namely the presence of protonated cyclen in the ternary species even at high pH, are relevant for evaluation of the [Zn(cyclen)]2+unit as a model complex for zinc‐containing enzymes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Silicon–Phosphorus and Silicon–Arsenic Cage Compounds with Bicyclo[2.2.1]heptane, Bicyclo[3.2.1]octane and Tricyclo[3.3.3.1.03,7]nonane Backbones
Authors: Tekautz Günter , Baumgartner Judith , Dransfeld Alk , Hassler Karl 
Published: July 2007

AbstractThe reaction of tris(chlorodimethylsilyl)methylsilane (1) and 1,1,2,2‐tetrakis(chlorodimethylsilyl)‐1,2‐dimethyldisilane (2) with sodium/potassium arsenide Na3As/K3As afforded decamethyl‐2,3,5,6,7‐pentasila‐1,4‐diarsabicyclo[2.2.1]heptane (3)and dodecamethyl‐2,3,4,6,7,8,9‐heptasila‐1,5‐diarsatricyclo[3.3.1.03,7]nonane (4). Compounds 3 and 4 were isolated from the reaction mixture by fractional crystallization and structurally characterized by single‐crystal X‐ray crystallography. The reaction of 1 with an excess amount of sodium/potassium phosphide (Na3P/K3P) afforded the cage‐shaped anionsodium hexamethyl‐2,4,6,7‐tetrasila‐1‐phosphanido‐3,5‐diphosphabicyclo[3.2.1]octane (5), which reacts with chlorotrimethylsilane to form trimethylsilyl‐substituted derivative 6. The molecular structures of 5 and 6 were established by X‐ray crystallography. Cages 3–6 were also characterized by 29Si‐ and 31P NMR spectroscopy. Owing to indirect spin–spin coupling between the 29Si and 31P nuclei, the resonances of the 29Si nuclei in the spectra of 5 and 6 are only of first order approximately. To account for the observed preferences of the cage structures in these reactions, extensive B3LYP/6‐31G* quantum chemical calculations of relative energies of bicyclo[2.2.2] and bicyclo[3.2.1] isomers of Si8H14, PSi7H13, P2Si6H12 and P3Si5H11 were conducted. On the basis of the computed charge distributions, the concept of topological charge stabilization was used to predict the relative stabilities. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Activated Aryl Chlorides: Useful Partners for the Coupling with 2‐Substituted Thiazoles in the Palladium‐Catalysed C‐H Activation/Functionalisation Reaction
Authors: Gottumukkala Aditya L. , Doucet Henri 
Published: July 2007

AbstractAryl chlorides are noticeably uncommon partners in coupling reactions with heteroaromatics through C‐H activation. We report herein that as little as 1 mol‐% of the air‐stable PdCl(dppb)(C3H5) complex catalyses the direct coupling of electron‐deficient aryl chlorides with 2‐substituted thiazole derivatives. A range of functionalities on the aryl chloride such as acetyl, formyl, ester, nitro, nitrile or trifluoromethyl is tolerated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Shearing‐Like Distortion in Binuclear End‐to‐End CuII Azido Compounds: An Ab Initio Study of the Magnetic Interactions
Authors: Angels Carvajal Maria , Aronica Christophe , Luneau Dominique , Robert Vincent 
Published: July 2007

AbstractThe direct control of magnetic interactions in CuII azido‐bridged binuclear complexes is investigated by means of explicitly correlated ab initio calculations. It is shown that in the end‐to‐end series, the shearing‐like asymmetry parameter δ = dlong(Cu–N) – dshort(Cu–N) should be considered as an important parameter in the control of the coupling constant. A practical route that could be used to enhance the ferromagnetism of the compound is suggested in light of our calculations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Oxidation of Inorganic Sulfur Compounds in Acidophilic Prokaryotes
Authors: Rohwerder T. , Sand W. 
Published: July 2007

AbstractThe oxidation of reduced inorganic sulfur compounds to sulfuric acid is of great importance for biohydrometallurgical technologies as well as the formation of acidic (below pH 3) and often heavy metal‐contaminated environments. The use of elemental sulfur as an electron donor is the predominant energy‐yielding process in acidic natural sulfur‐rich biotopes but also at mining sites containing sulfidic ores. Contrary to its significant role in the global sulfur cycle and its biotechnological importance, the microbial fundamentals of acidophilic sulfur oxidation are only incompletely understood. Besides giving an overview of sulfur‐oxidizing acidophiles, this review describes the so far known enzymatic reactions related to elemental sulfur oxidation in acidophilic bacteria and archaea. Although generally similar reactions are employed in both prokaryotic groups, the stoichiometry of the key enzymes is different. Bacteria oxidize elemental sulfur by a sulfur dioxygenase to sulfite whereas in archaea, a sulfur oxygenase reductase is used forming equal amounts of sulfide and sulfite. In both cases, the activation mechanism of elemental sulfur is not known but highly reactive linear sulfur forms are assumed to be the actual substrate. Inhibition as well as promotion of these biochemical steps is highly relevant in bioleaching operations. An efficient oxidation can prevent the formation of passivating sulfur layers. In other cases, a specific inhibition of sulfur biooxidation may be beneficial for reducing cooling and neutralization costs. In conclusion, the demand for a better knowledge of the biochemistry of sulfur‐oxidizing acidophiles is underlined.
Heterogeneity of gene expression profiles in head and neck cancer
Authors: Pramana Jimmy , Pimentel Nuno , Hofland Ingrid , Wessels Lodewijk F. A. , van Velthuysen Marie‐Louise F. , Atsma Douwe , Rasch Coen R. N. , van den Brekel Michiel W. M. , Begg Adrian C. 
Published: July 2007

AbstractBackground.Results of gene expression profiling studies from different institutes often lack consistency. This could be due to the use of different microarray platforms and protocols, or to intratumoral heterogeneity in mRNA expression. The aim of our study was to quantify intratumoral heterogeneity in head and neck cancer.Methods.Forty‐four fresh frozen biopsies were taken from 22 patients, 2 per tumor. RNA was extracted, tested for quality, amplified, labeled, and hybridized to a 35k oligoarray.Results.Unsupervised clustering analyses using all genes, the most variable genes, or random gene sets showed that 80% to 90% of biopsy pairs clustered together. A within‐pair‐between‐pair scatter ratio analysis showed that the similarity between matching pairs was significantly greater than that between random pairs (p <.00001).Conclusions.Two biopsies from the same tumor show far greater similarity in gene expression than biopsies from different tumors, supporting the use of 1 biopsy for expression profiling. © 2007 Wiley Periodicals, Inc. Head Neck 2007
Integration of the sensory inputs to place cells: What, where, why, and how?
Authors: Jeffery Kathryn J. 
Published: July 2007

AbstractThe hippocampal place cells are a highly multimodal class of neurons, receiving information from many different sensory sources to correctly localize their firing to restricted regions of an environment. Evidence suggests that the sensory information is processed upstream of the hippocampus, to extract both angular and linear metric information, and also contextual information. These various kinds of information need to be integrated for coherent firing fields to be generated, and the present article reviews recent evidence concerning how this occurs. It is concluded that there is a functional dissociation of the cortical inputs, with one class of incoming information comprising purely metric information concerning distance and orientation, probably routed via the grid cells and head direction cells. The other class of information is much more heterogeneous and serves, at least in part, to contextualize the spatial inputs so as to provide a unique representation of the place the animal is in. Evidence from remapping studies suggests that the metric and contextual inputs interact upstream of the place cells, perhaps in entorhinal cortex. A full understanding of the generation of the hippocampal place representation will require elucidation of the representational functions of the afferent cortical areas. © 2007 Wiley‐Liss, Inc.
Regional variability, processing methods, and biophysical properties of human fascia lata extracellular matrix
Authors: Derwin Kathleen A. , Baker Andrew R. , Spragg Rebecca K. , Leigh Diane R. , Farhat Walid , Iannotti Joseph P. 
Published: July 2007

AbstractThis study aims to assess the regional variability, processing methods, mechanical, biochemical, and cellular properties of human fascia lata as a scaffold for soft tissue repair and tissue engineering applications. Ten pairs of fascia lata (donor age 18–55) were used. One fascia patch from each pair was used to assess the geometric and biomechanical variability of fresh fascia. The other from each pair was subjected to 1 of 2 allograft processing methods: antibiotic soak alone or acellularization plus antibiotic soak. Stiffness, modulus, hydroxyproline, chondroitin/dermatan sulfate glycosaminoglycan (CSDS GAG), and DNA content were quantified in fascia from fresh and treated groups. The effect of location was not significant for thickness or stiffness within a 6 × 12 cm2 region of the iliotibial tract of fresh human fascia lata. Processing did not significantly change the stiffness, modulus, or CSDS GAG content of fascia ECM. However, hydroxyproline (collagen) content is significantly reduced in acellularized fascia, probably reflecting a removal of soluble collagen during the treatment (p < 0.02). Processing reduced the DNA content of fresh fascia approximately 10‐fold (p < 0.001). The mechanical, chemical and ultrastructural similarities between fascia lata and tendon may make fresh or processed fascia an attractive ECM scaffold for soft tissue, particularly tendon, repair. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Three‐dimensional nanocomposite scaffolds with ordered cylindrical orthogonal pores
Authors: Rodríguez Hernández José Carlos , Serrano Aroca Ángel , Gómez Ribelles José Luis , Pradas Manuel Monleón 
Published: July 2007

AbstractA silica reinforcement can improve the mechanical properties of hydrogels in the rubbery state. A method to prepare a scaffold with a well‐ordered array of cylindrical pores is presented in this work, which yields a scaffold with a biphasic matrix of a hybrid nanocomposite: the hydrogel poly(2‐hydroxyethyl acrylate) (PHEA) and a silica network obtained by an acid catalyzed sol–gel process of tetraethoxysilane (TEOS). As porogenic template of the scaffold stacked layers of commercial polyamide 6 fabrics were used, which were compressed and sintered. Porosity and dynamic mechanical response of the resulting scaffolds were measured and compared with the bulk properties. Removal of the organic polymer phase of the scaffold by pyrolysis revealed the overall continuity of the silica network; the residue maintained the original cylindrical pore structure of the scaffolds, though slightly shrunk. Atomic force microscopy topography measurements of these pyrolysed residues revealed a silica structure with particle aggregates having sizes around tens of nanometers. The silica distribution was assessed by X‐ray microanalysis mapping, showing homogeneity at a micrometer scale. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008
Identification of osteopontin phosphorylation sites involved in bone remodeling and inhibition of pathological calcification
Authors: Saad Fawzy A. , Salih Erdjan , Glimcher Melvin J. 
Published: July 2007

AbstractOsteopontin is a noncollagenous, phosphorylated extracellular glycoprotein, expressed in mineralized and nonmineralized tissues, organs and body fluids. The protein contains an RGD tripeptide cell‐binding motif, and is subjected to a variety of posttranslational modifications that play important roles in its multiple biological functions, such as bone remodeling and inhibition of pathological calcification. In this study, we have expressed bovine osteopontin in a prokaryotic system and identified the seven amino acid residues phosphorylated in vitro by CKII. J. Cell. Biochem. 103: 852–856, 2008. © 2007 Wiley‐Liss, Inc.
Kinetic study of ytterbium(III) extraction from sulfate medium with Cyanex 923
Authors: Wang Weiwei , Liu Jianjun , He Wenwei , Li Deqian 
Published: July 2007

AbstractThe kinetics of ytterbium(III) extraction from sulfate medium with Cyanex 923 in heptane has been investigated with a constant interfacial cell with laminar flow, which aimed to identify the extraction regime, reaction zone and rate equations. It was found that the extraction rate of ytterbium(III) increased linearly with stirring speed and specific interfacial area. The activation energy Ea (9.56 kJ mol−1), activation enthalpy ΔH± (7.05 kJ mol−1), activation entropy ΔS±298 (−0.31 kJ mol−1) and Gibbs free energy of activation ΔG±298 (98.3 kJ mol−1) were calculated from the dependence of extraction rate on temperature. The experiential rate equations were obtained by investigating the influence of the concentration of various species on the extraction rate. A diffusion regime has been deduced from evidence of the linear dependence of extraction rate on stirring speed and the low value of the activation energy. The liquid–liquid interface is most probably the reaction zone in view of the linear dependence of extraction rate on specific interfacial area, the high interfacial activity and low water‐solubility of extractant. Thus the mass transfer rate is controlled by interfacial film diffusion of species. Copyright © 2007 Society of Chemical Industry
Optimization of media constituents through response surface methodology for improved production of alkaline proteases by Serratia rubidaea
Authors: Doddapaneni Kiran Kumar , Tatineni Radhika , Potumarthi Ravichandra , Mangamoori Lakshmi Narasu 
Published: July 2007

AbstractBACKGROUND: Response surface methodology is used to build a predictive model of the combined effects of independent variables (pH, salt concentration starch and casein). The model was validated in a laboratory‐scale bioreactor for extracellular protease production from a newly isolated Serratia rubidaea.RESULTS: Optimum medium conditions obtained from the optimization experiments after 48 h incubation were starch, 8 g L−1; casein, 4 g L−1; salt concentration 6.25 g L−1; and initial pH, 8. A coefficient of determination (R2) value of 0.9305 shows the fitness of the second‐order model for the present studies. Results of model coefficients estimated by multiple linear regressions indicate that linear effects of casein concentration (P < 0.001308) and initial pH (P < 7.91 E‐07) are more significant than similarly interactive effects of starch and casein (P < 0.019153), casein and salt concentration (P < 0.016294), casein and pH (P < 0.039904) and salt concentration and pH (p < 0.017845). The P‐values of quadratic effects of casein, x2 × x2 (P < 0.000171); SC, x3 × x3 (P < 0.009134); initial pH, x4 × x4 (P < 0.000114) are more significant for maximal production. After optimization, protease production was enhanced experimentally by almost 65% in a shake flask and by almost 115% in a bioreactor.CONCLUSION: The alkaline proteases secreted by S. rubidaea were significant from an industrial perspective because of their stability against surfactants, oxidants and solvents. The statistical design is useful in economic protease production in a cost‐effective medium for potential use on an industrial scale. Copyright © 2007 Society of Chemical Industry
Alternative technologies for biotechnological fuel ethanol manufacturing
Authors: Vertès Alain A , Inui Masayuki , Yukawa Hideaki 
Published: July 2007

AbstractThe challenges of implementing biorefineries on a global scale include socioeconomic, financial, and technological constraints. In particular, the development of biorefineries is tightly linked to the continued availability of fermentation raw materials. These constraints can be relaxed by the use of diverse raw materials, while advances that confer higher flexibility would enable biotechnological plant managers to swiftly react to volatile markets. In conventional processes,Saccharomyces cerevisiaegrows on a relatively limited range of substrates, and produces only a single product—ethanol. Given the observed maturity of theS. cerevisiaefermentation technology, alternatives to baker's yeast may be needed to tip the economic balance in favour of biotechnological ethanol. These alternative fermentation technologies may allow a greater diversity of substrates to be used to produce an individually tailored mix of ethanol and other chemicals. Copyright © 2007 Society of Chemical Industry
Horseradish peroxidase‐catalysed oxidation of aqueous natural and synthetic oestrogens
Authors: Khan Usman , Nicell James A 
Published: July 2007

AbstractThe horseradish peroxidase (HRP)‐catalysed oxidation of selected potent oestrogens, including the natural oestrogens 17β‐oestradiol and oestriol and the synthetic oestrogen ethinyloestradiol, was studied and compared with that of phenol. HRP catalysed the oxidation of these oestrogens and phenol over a wide range of pH values, with optimal performance around neutral pH, which is in the range of typical urban wastewaters. In comparison with that of phenol, the oxidation of oestrogens consistently required less hydrogen peroxide. In addition, the rate of oxidation of oestradiol was equivalent, twofold faster and fivefold faster compared with that of ethinyloestradiol, oestriol and phenol respectively. For all substrates studied, similar kinetics of removal were observed provided that sufficient enzyme was added to reactions to compensate for differences in substrate affinity. In contrast with earlier studies with phenols in which HRP was observed to be susceptible to significant inactivation due to interactions with hydrogen peroxide and reaction products, minimal inactivation of HRP was observed during the present study, probably owing to the very low concentration of target substrates used here (i.e. 10 µmol dm−3) relative to earlier studies with other phenolic substrates. These observations suggest that this enzymatic approach has strong potential to be used to target the treatment of oestrogenic compounds. Copyright © 2007 Society of Chemical Industry