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141.
We have modeled the transformation of cellulose Iβ to a high temperature (550 K) structure, which is considered to be the first step in cellulose pyrolysis. We have performed molecular dynamics simulations at constant pressure using the GROMOS 45a4 united atom forcefield. To test the forcefield, we computed the density, thermal expansion coefficient, total dipole moment, and dielectric constant of cellulose Iβ, finding broad agreement with experimental results. We computed infrared (IR) spectra of cellulose Iβ over the range 300-550 K as a probe of hydrogen bonding. Computed IR spectra were found to agree semi-quantitatively with experiment, especially in the O-H stretching region. We assigned O-H stretches using a novel synthesis of normal mode analysis and power spectrum methods. Simulated IR spectra at elevated temperatures suggest a structural transformation above 450 K, a result in agreement with experimental IR results. The low-temperature (300-400 K) structure of cellulose Iβ is dominated by intrachain hydrogen bonds, whereas in the high-temperature structure (450-550 K), many of these transform to longer, weaker interchain hydrogen bonds. A three-dimensional hydrogen bonding network emerges at high temperatures due to formation of new interchain hydrogen bonds, which may explain the stability of the cellulose structure at such high temperatures. 相似文献
142.
Sanghera N Correia BE Correia JR Ludwig C Agarwal S Nakamura HK Kuwata K Samain E Gill AC Bonev BB Pinheiro TJ 《Chemistry & biology》2011,18(11):1422-1431
The prion protein (PrP) resides in lipid rafts in?vivo, and lipids modulate misfolding of the protein to infectious isoforms. Here we demonstrate that binding of recombinant PrP to model raft membranes requires the presence of ganglioside GM1. A combination of liquid- and solid-state NMR revealed the binding sites of PrP to the saccharide head group of GM1. The binding epitope for GM1 was mapped to the folded C-terminal domain of PrP, and docking simulations identified key residues in the C-terminal region of helix C and the loop between strand S2 and helix B. Crucially, this region of PrP is linked to prion resistance in?vivo, and structural changes caused by lipid binding in this region may explain the requirement for lipids in the generation of infectious prions in?vitro. 相似文献
143.
The paper deals with the classical Caristi fixed point theorem in vector valued metric spaces. The results obtained seem to be new in this setting. 相似文献
144.
Nadjet Abada Ravi P. Agarwal Mouffak Benchohra Hadda Hammouche 《Applications of Mathematics》2011,56(2):227-250
In this paper we establish sufficient conditions for the existence of mild solutions and extremal mild solutions for some
densely defined impulsive semilinear neutral functional differential inclusions in separable Banach spaces. We rely on a fixed
point theorem for the sum of completely continuous and contraction operators. 相似文献
145.
In this work, we establish a strong duality theorem for Mond–Weir type multiobjective higher-order nondifferentiable symmetric dual programs. This fills some gaps in the work of Chen [X. Chen, Higher-order symmetric duality in nondifferentiable multiobjective programming problems, J. Math. Anal. Appl. 290 (2004) 423–435]. 相似文献
146.
In this work, strongly continuous semigroups of pseudocontractions are studied based on an implicit iterative algorithm. Strong convergence theorems of fixed points are obtained in an arbitrary Banach space. 相似文献
147.
Tricarbonyl rhenium(I) complexes, such as Re(bpy)(CO)(3)Cl where bpy = 2,2'-bipyridyl, have demonstrated superior activity in catalyzing CO(2) reduction in the presence of sacrificial electron donors. We have utilized density functional theory (DFT) to investigate a potential pathway for formate production via a rhenium-hydride insertion mechanism in the presence of triethylamine (TEA). On the basis of prior studies, we re-examined the role of TEA and studied a catalytic cycle for CO(2) reduction in which TEA functions as both the hydrogen atom and the electron donor for reducing CO(2) into formate. The catalytic cycle is found to be exothermic with inclusion of solvation and may be viewed as a two-electron reduction of CO(2) because the net result is a transfer of hydride from TEA to CO(2). In addition, we have identified structures of key intermediates in the CO(2)-reduction process and found that the insertion step has a very modest barrier in acetonitrile. These findings provide a molecular-level understanding to formate production via CO(2) reduction mediated by transition-metal complexes. A theoretical investigation is underway to elucidate the formation of carbon monoxide, another common product in Re-catalyzed CO(2) reduction. 相似文献
148.
Ritu Agarwal Sunil D. Purohit Kritika 《Mathematical Methods in the Applied Sciences》2019,42(18):7160-7171
In calcium signalling, activation of receptor is a very significant aspect. To understand the mechanism of calcium signalling, receptors are the important components. The mobilization of intracellular calcium from intracellular stores depends upon binding of agonist to cell surface receptor. Thrombin is chosen as model ligand. In order to understand thrombin receptor activation, we analyze fractional model incorporating derivative of arbitrary order and nonsingular kernel which can precisely describe the effect of memory and can explain the model in better and more efficient manner as compared with fractional operators with singular kernels. The problem has been solved by perturbation iterative method. Using fixed‐point theorem, it is proved that solution of the system will exist and also it will be unique. 相似文献
149.
R. K. Sinha A. Dhal P. Agarwal S. Kumar Monika B. B. Singh R. Kumar P. Bringel A. Neusser R. Kumar K. S. Golda R. P. Singh S. Muralithar N. Madhavan J. J. Das K. S. Thind A. K. Sinha I. M. Govil R. K. Bhowmik J. B. Gupta P. K. Joshi A. K. Jain S. C. Pancholi L. Chaturvedi 《The European Physical Journal A - Hadrons and Nuclei》2006,29(2):253-253
150.
Bao Qiang YAN Donal O'REGAN Ravi P. AGARWAL 《数学学报(英文版)》2007,23(8):1447-1456
This paper presents a lower and upper solution technique for singular second order boundary value problems on the half line. 相似文献