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Theoretical Treatment (theoretical + treatment)
Selected AbstractsBiodoped Ceramics: Synthesis, Properties, and ApplicationsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2006Smita Y. Gadre This feature article focuses on biodoped ceramics. These are inorganic materials in which biological materials are incorporated, thus adding new functionality to them. A brief overview of the prominent synthesis techniques for biodoped ceramics, with emphasis on modified sol,gel processes for metal oxide matrices, is given first. Theoretical treatments of the encapsulation of biologicals within a porous ceramic matrix are reviewed. Experimental studies of the stability and dynamics of protein entrapment in silica and other ceramic matrices are also discussed. Finally, key applications of biodoped ceramics in biochemical species detection, bio-catalysis, and drug delivery are presented. [source] Electromigration diffusivity spectrometry: A way for simultaneous determination of diffusion coefficients from mixed samplesELECTROPHORESIS, Issue 17 2010Suhua Yang Abstract A novel method was proposed for simultaneous measurement of diffusion coefficients, (D), from mixed samples by electrophoresis and termed electromigration-based diffusivity spectrometry. After theoretical treatment, D- equation for practical use has been deduced. With a modified CE system built in laboratory, electromigration-based diffusivity spectrometry has been realized and validated to suit for fast and accurate determination of diffusivities of mixed aromatic amino acids, phenols and aromatic organic acid, giving diffusivity spectra by peak area versus D, much similar to mass spectra. The precision of the measurement was found to critically depend on pH value of running buffer, which should be so selected that the analytes and internal standards could be charged at above 0.5e. The standards have to be selected at an electric flux far from each other and from analytes. In these cases, sample and running buffer concentrations, voltage and system temperature were found to have only negligible impact on the determination. In our test, the obtained measuring precision was generally kept within 1% for five runs, and the measured values of D agreed well with those from literature, with a deviation of less than 2.2% after the right use of calibration standards. [source] A solid-state 23Na NMR study of monovalent cation binding to double-stranded DNA at low relative humidityMAGNETIC RESONANCE IN CHEMISTRY, Issue 4 2008Alan Wong Abstract We report a solid-state 23Na NMR study of monovalent cation (Li+, Na+, K+, Rb+, Cs+ and NH4+) binding to double-stranded calf thymus DNA (CT DNA) at low relative humidity, ca 0,10%. Results from 23Na31P rotational echo double resonance (REDOR) NMR experiments firmly establish that, at low relative humidity, monovalent cations are directly bound to the phosphate group of CT DNA and are partially dehydrated. On the basis of solid-state 23Na NMR titration experiments, we obtain quantitative thermodynamic parameters concerning the cation-binding affinity for the phosphate group of CT DNA. The free energy difference (,G° ) between M+ and Na+ ions is as follows: Li+ (,1.0 kcal mol,1), K+ (7.2 kcal mol,1), NH4+ (1.0 kcal mol,1), Rb+ (4.5 kcal mol,1) and Cs+ (1.5 kcal mol,1). These results suggest that, at low relative humidity, the binding affinity of monovalent cations for the phosphate group of CT DNA follows the order: Li+ > Na+ > NH4+ > Cs+ > Rb+ > K+. This sequence is drastically different from that observed for CT DNA in solution. This discrepancy is attributed to the different modes of cation binding in dry and wet states of DNA. In the wet state of DNA, cations are fully hydrated. Our results suggest that the free energy balance between direct cation,phosphate contact and dehydration interactions is important. The reported experimental results on relative ion-binding affinity for the DNA backbone may be used for testing theoretical treatment of cation-phosphate interactions in DNA. Copyright © 2008 John Wiley & Sons, Ltd. [source] A comparison of DA white dwarf temperatures and gravities from Lyman and Balmer line studiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2001M.A. Barstow We present measurements of the effective temperatures and surface gravities for a sample of hot DA white dwarfs, using the Lyman line data available from the HUT, ORFEUS and FUSE FUV space missions. Comparing the results with those from the standard Balmer line technique, we find that there is a general good overall agreement between the two methods. However, significant differences are found for a number of stars, but not always of a consistent nature in that sometimes the Balmer temperature exceeds that derived from the Lyman lines and in other instances it is lower. We conclude that, with the latest model atmosphere calculations, these discrepancies probably do not arise from an inadequate theoretical treatment of the Lyman lines but rather from systematic effects in the observation and data reduction processes, which dominate the statistical errors in these spectra. If these systematic data reduction effects can be adequately controlled, the Lyman line temperature and gravity measurements are consistent with those obtained from the Balmer lines when allowance is made for reasonable observational uncertainties. [source] Light,matter interaction in photonic crystal slabsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2007Lucio Claudio Andreani Abstract A theoretical treatment of waveguide-embedded photonic crystals based on a guided-mode expansion method is reviewed. The following issues are discussed: (i) a formulation of the method for calculating photonic-mode dispersion and intrinsic losses due to out-of-plane diffraction, (ii) modelling of disorder-induced losses due to fabrication imperfections, and (iii) a quantum-mechanical treatment of radiation-matter interaction, with application to exciton-polaritons in photonic crystal slabs. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Resonant X-ray scattering in the presence of several anisotropic factorsACTA CRYSTALLOGRAPHICA SECTION A, Issue 1 2000E. N. Ovchinnikova The general form of the X-ray susceptibility tensor near absorption edges is found when several anisotropic factors, such as the anisotropy of local atomic environment, magnetic ordering and orbital ordering, simultaneously exist in a crystal. Different phenomenological approaches are used to obtain the explicit form of the susceptibility tensor and to find the contributions from each anisotropic factor separately as well as `combined' terms owing to their simultaneous existence. The results of the theoretical treatment are applied to the resonant diffraction by La0.5Sr1.5MnO4 below the Néel temperature, where charge and orbital ordering coexist with anisotropy of local atomic environment and magnetic ordering. [source] Kinetics and Efficacy of an Organophosphorus Hydrolase in a Rodent Model of Methyl-parathion PoisoningACADEMIC EMERGENCY MEDICINE, Issue 7 2010Chip Gresham MD ACADEMIC EMERGENCY MEDICINE 2010; 17:736,740 © 2010 by the Society for Academic Emergency Medicine Abstract Objectives:, Organophosphorus (OP) pesticides exert a tremendous health burden, particularly in the developing world. Limited resources, the severity of intentional OP ingestions, and a paucity of beneficial therapies all contribute to the morbidity and mortality of this broad class of chemicals. A novel theoretical treatment for OP poisoning is the use of an enzyme to degrade the parent OP in the circulation after poisoning. The aims of this study were to determine the pharmacokinetics and efficacy of an OP hydrolase (OpdA) in a rodent model of severe methyl-parathion poisoning. Methods:, Two animal models were used. First, Wistar rats were administered two different doses of the hydrolase (0.15 and 1.5 mg/kg), and the ex vivo hydrolytic activity of plasma was determined by a fluorometric method. Second, an oral methyl-parathion animal poisoning model was developed to mimic severe human poisoning, and the efficacy of postpoisoning OpdA (as measured by survival to 4 and 24 hours) was determined. Results:, The half-life of OpdA in the Wistar rat was dependent on the dose administered and ranged between 45.0 and 57.9 minutes. The poisoning model of three times the lethal dose to 50% of the population (3 × LD50) of methyl-parathion resulted in 88% lethality at 4 and 24 hours. Using a single dose of 0.15 mg/kg OpdA 10 minutes after poisoning resulted in 100% survival at 4 hours (p = 0.001 vs. placebo), but 0% at 24 hours postpoisoning (p = NS vs. placebo). Conclusions:, The OP hydrolase OpdA exhibits pharmacokinetics suitable for repeated dosing and increases short-term survival after severe methyl-parathion poisoning. [source] Reliability of self-reported willingness-to-pay and annual income in patients treated for toenail onychomycosisBRITISH JOURNAL OF DERMATOLOGY, Issue 5 2007P.M.H. Cham Summary Background, Willingness-to-pay (WTP) is a health economics measure that has recently been used for skin diseases to evaluate patients' quality of life. However, the reliability of this measure has not been investigated in the dermatology literature and is essential in validating its use in health services research. Objectives, This study evaluated the test-retest reliability of self-reported annual income and WTP, a health economics measure of disease impact, in patients with toenail onychomycosis. Methods, Forty-six patients enrolled in a randomized clinical trial comparing two different dosing regimens of terbinafine completed a self-administered questionnaire at baseline and 1 month later. The questionnaire asked: (i) how much patients would be willing to pay for a theoretical treatment with a cure rate of 85% for their current onychomycosis (10 categories: $0,50, $51,100, to > $800); and (ii) annual income (10 categories: $0,10 000 to > $200 000). Results, Forty-four patients reported WTP at both visits, and 55% reported the same WTP. The quadratic-weighted (Fleiss,Cohen) , statistic indicated moderate agreement (, = 0·50, 95% confidence interval, CI 0·24,0·75, P < 0·01) as did the Spearman rank-order correlation coefficient (rs = 0·57, P < 0·01; median difference = 0, P = 0·50). Strong agreement was shown among the 42 patients who reported income at both visits; 71% reported the same annual income category (, = 0·72, 95% CI 0·47,0·96, P < 0·01; rs = 0·68, P < 0·01; median difference = 0, P = 0·77). Age, disease severity and duration, previous therapy, self-reported annual income, and medication side-effects were not statistically associated with the reliability of WTP. Conclusions, WTP and annual income demonstrated moderate and strong test-retest reliability, respectively. Self-reported WTP can serve as a reliable measure for future health economics research on onychomycosis. [source] Enantioselective Proteins: Selection, Binding Studies and Molecular Modeling of Antibodies with Affinity towards Hydrophobic BINOL DerivativesCHEMBIOCHEM, Issue 16 2007Brian Schou Rasmussen Dr. Abstract In this paper, the initial steps towards the design of novel artificial metalloenzymes that exploit proteins as a second coordination sphere for traditional metal,ligand catalysis are described. Phage display was employed to select and study antibody fragments capable of recognizing hydrophobic BINOL derivatives designed to mimic BINAP, a widely used ligand in asymmetric metal-catalyzed reactions. The binding affinities of the selected antibodies towards a series of haptens were evaluated by using ELISA assays. A homology model of one of the most selective antibodies was constructed, and a computer-assisted ligand-docking study was carried out to elucidate the binding of the hapten. It was shown that, due to the hydrophobic nature of the haptens, a higher level of theoretical treatment was required to identify the correct binding modes. A small selection of the antibodies was found to discriminate between enantiomers and small structural modifications of the BINOL derivatives. The selectivities arise from hydrophobic interactions, and we propose that the identified set of antibodies provides a foundation for a novel route to artificial metalloenzymes. [source] Dynamic models allowing for flexibility in complex life histories accurately predict timing of metamorphosis and antipredator strategies of preyFUNCTIONAL ECOLOGY, Issue 6 2009Andrew D. Higginson Summary 1.,The development of antipredator defences in the larval stage of animals with complex life cycles is likely to be affected by costs associated with creating and maintaining such defences because of their impact on the timing of maturation or metamorphosis. 2.,Various theoretical treatments have suggested that investment in defence should both increase or decrease with increasing resource availability, but a recent model predicts investment in defences should be highest at intermediate resource level and predator density. 3.,Previous models of investment in defence and timing of metamorphosis provide a poor match to empirical data. Here we develop a dynamic state-dependent model of investment in behavioural and morphological defences that enables us to allow flexibility in investment in defences over development, the timing of metamorphosis and the size of the organism at metamorphosis that were absent from previous theory. 4.,We show that the inclusion of this flexibility results in different predictions to those of the fixed investment approach used previously, especially when we allow metamorphosis to occur at the optimal time and state for the organism. 5.,Under these more flexible conditions, we predict that morphological defences should be insensitive to resource level whilst behavioural defences should either increase or decrease with increasing resources depending on the predation risk and the magnitude of the fitness benefits of large size at metamorphosis. 6.,Our work provides a formal framework in which we might progress in the study of how the use of antipredator defences is affected by their costs. Most of the predictions of our model in are in good accord with empirical results, and can be understood in terms of the underlying biological assumptions. The reasons why simpler models failed to match empirical observations can be explained, and our predictions that are a poor match help to target the circumstances which warrant future study. [source] Studies of electron transfer dynamics in particle-surface interactionsISRAEL JOURNAL OF CHEMISTRY, Issue 1-2 2005Vladimir A. EsaulovArticle first published online: 10 MAR 2010 A review of recent work on electron transfer processes leading to neutralization of positive ions and formation of negative ions is presented. Experiments were performed on simple jellium-like metal surfaces, transition metals, and specific characteristics of electronic band structure were investigated for some cases, revealing differences in electron transfer processes between surfaces of the same element. It was shown that electronegative adsorbates like oxygen and chlorine provoke strong changes in electron transfer rates, which are akin to promotion and poisoning of reactions at surfaces. The results of experiments on Auger neutralization of He+ ions on Ag surfaces and H, and F, formation on Ag and Pd surfaces are presented and compared with recent theoretical treatments of these processes. The effect of adsorbates is illustrated by the example of chlorine adsorption on silver. Directions where further theoretical effort would considerably advance the understanding of these phenomena are delineated. [source] Electrosprayed polymer particles: Effect of the solvent propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009Chul Ho Park Abstract Electrospraying technology has been studied in many fields to produce particles of various substances from nanoscale to microscale sizes. Unlike pure liquids, droplets formed by electrospraying that are comprised of polymer solutions undergo additional solidification processes involving solvent evaporation, which primarily determine the particle size and morphology. Herein, the effects of the solvent properties on the morphology and dimensions of solidified particles were systematically studied. In general, the size of the solidified spherical particles with smooth surfaces reflected that of the initially formed liquid droplets, which could partially be estimated by theoretical equations developed for pure liquids. Particle sizes increased with an increase in polymer content and a decrease in the boiling point of the volatile solvent. Inhomogeneous drying processes related to phase separation or skin formation resulted in hollow, cuplike, and porous particle structures, with particle sizes and morphologies that were outside of the scope of the theoretical treatments. The selection of a proper solvent or solvent mixture seemed to be a convenient way to control the particle morphologies, such as hollow, cuplike, or porous structures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Condition-dependent mutation rates and sexual selectionJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2009S. COTTON Abstract ,Good genes' models of sexual selection show that females can gain indirect benefits for their offspring if male ornaments are condition-dependent signals of genetic quality. Recurrent deleterious mutation is viewed as a major contributor to variance in genetic quality, and previous theoretical treatments of ,good genes' processes have assumed that the influx of new mutations is constant. I propose that this assumption is too simplistic, and that mutation rates vary in ways that are important for sexual selection. Recent data have shown that individuals in poor condition can have higher mutation rates, and I argue that if both male sexual ornaments and mutation rates are condition-dependent, then females can use male ornamentation to evaluate their mate's mutation rate. As most mutations are deleterious, females benefit from choosing well-ornamented mates, as they are less likely to contribute germline-derived mutations to offspring. I discuss some of the evolutionary ramifications of condition-dependent mutation rates and sexual selection. [source] | ||||||||||||||||||||||