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We present results from a molecular dynamics study of the dissociation behavior of carbon dioxide (CO(2)) hydrates. We explore the effects of hydrate occupancy and temperature on the rate of hydrate dissociation. We quantify the rate of dissociation by tracking CO(2) release into the liquid water phase as well as the velocity of the hydrate-liquid water interface. Our results show that the rate of dissociation is dependent on the fractional occupancy of each cage type and cannot be described simply in terms of overall hydrate occupancy. Specifically, we find that hydrates with similar overall occupancy differ in their dissociation behavior depending on whether the small or large cages are empty. In addition, individual cages behave differently depending on their surrounding environment. For the same overall occupancy, filled small and large cages dissociate faster in the presence of empty large cages than when empty small cages are present. Therefore, hydrate dissociation is a collective phenomenon that cannot be described by focusing solely on individual cage behavior. 相似文献
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Sapna Jain 《Linear algebra and its applications》2006,418(1):130-141
Fire [P. Fire, A class of multiple-error-correcting binary codes for non-independent errors, Sylvania Reports RSL-E-2, Sylvania Reconnaissance Systems, Mountain View, California, 1959] introduced the concept of bursts for classical codes where codes are subsets/subspaces of the space , the space of all n-tuples with entries from a finite field Fq. In this paper, we introduce the notion of bursts for m-metric array codes where m-metric array codes are subsets/subspaces of the space Matm×s(Fq), the linear space of all m × s matrices with entries from a finite field Fq, endowed with a non-Hamming metric. We also obtain some bounds (analogous to Fire’s bound [P. Fire, A class of multiple-error-correcting binary codes for non-independent errors, Sylvania Reports RSL-E-2, Sylvania Reconnaissance Systems, Mountain View, California, 1959], Rieger’s bound [S.H. Reiger, Codes for the correction of clustered errors, IRE-Trans., IT-6 (1960), 16-21] etc. in classical codes) on the parameters of m-metric array codes for the detection and correction of burst errors. 相似文献
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Investigations on the phase diagrams of two bi-component mixtures of liquid crystals are presented. Whereas in one of the bi-component systems, smectic A (SmA) phase is seen to be induced, in the other case the so-called nematic “island” has been observed. The dielectric properties of magnetically oriented sample forming nematic phase and induced smectic phase in one of the mixtures, and a nematic “island” and SmA phase in the other mixture, were measured in the frequency range from 1?Hz to 10?MHz at different temperatures. The transition temperatures obtained from the polarizing microscope and differential scanning calorimeter measurements agree well with the dielectric relaxation data. 相似文献
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Oberstrass FC Allain FH Ravindranathan S 《Journal of the American Chemical Society》2008,130(36):12007-12020
RNA recognition by proteins is often accompanied by significant changes in RNA dynamics in addition to conformational changes. However, there are very few studies which characterize the changes in molecular motions in RNA on protein binding. We present a quantitative (13)C NMR relaxation study of the changes in RNA dynamics in the pico-nanosecond time scale and micro-millisecond time scale resulting from interaction of the stem-loop SRE-RNA with the VTS1p-SAM domain. (13)C relaxation rates of the protonated carbons of the nucleotide base and anomeric carbons have been analyzed by employing the model-free formalism, for a fully (13)C/(15)N-labeled sample of the SRE-RNA in the free and protein-bound forms. In the free RNA, the nature of molecular motions are found to be distinctly different in the stem and the loop region. On binding to the protein, the nature of motions becomes more homogeneous throughout the RNA, with many residues showing increased flexibility at the aromatic carbon sites, while the anomeric carbon sites become more rigid. Surprisingly, we also observe indications of a slow collective motion of the RNA in the binding pocket of the protein. The observation of increased motions on binding is interesting in the context of growing evidence that binding does not always lead to motional restrictions and the resulting entropy gain could favor the free energy of association. 相似文献
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Anuj Kumar Sapna Pathak Mahendra Singh Poonam Tandon V. D. Gupta 《Macromolecular Symposia》2009,277(1):51-61
Poly(4-methyl-2-pentyne) (PMP) is an amorphous glassy disubstituted acetylene based polymer. The excellent gas-separation and mechanical properties of these polymers have stipulated their use as membrane material for vapor and gas separation. PMP is among the hydrocarbon disubstituted polyacetylenes which have been synthesized to date. This polymer combines excellent gas and vapor permeability with good resistance to organic solvents. As was shown recently, PMP offers promise in the manufacture of nanocomposite membranes for the separation of various hydrocarbon mixtures. It is also of importance as its monomer, 4-methyl- 2-pentyne, can be easily derived from commercial compounds, 4-methyl-2-pentene or methyl isobutyl ketone, produced on a large scale. It is known that PMP exists in cis and trans configurations. Synthetic conditions, e.g., the used catalyst, temperature, solvent etc., of substituted polyacetylenes decide percentage of different configurations (cis or trans). Different geometries of macromolecules can influence the supramolecular structure of the polymer, which primarily defines its properties, such as solubility, permeability, sorption, etc. Qualitative assignments of few bands of IR spectra are reported earlier. We present here, complete normal mode analysis and dispersion curves for PMP using Wilson GF matrix method modified by Higgs using Urey-Bradley force field. Dispersion curves for PMP are drawn and salient features are discussed. Predicted values of specific heat via density-of-states are also reported. 相似文献
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Trends in microRNA detection 总被引:1,自引:0,他引:1
MicroRNAs (miRNAs) are short, ~22 nucleotide length RNAs that perform gene regulation. Recently, miRNA has been shown to be
linked with the onset of cancer and other diseases based on miRNA expression levels. It is important, therefore, to understand
miRNA function as it pertains to disease onset; however, in order to fully understand miRNA’s role in a disease, it is necessary
to detect the expression levels of these small molecules. The most widely used miRNA detection method is Northern blotting,
which is considered as the standard of miRNA detection methods. This method, however, is time-consuming and has low sensitivity.
This has led to an increase in the amount of detection methods available. These detection methods are either solid phase,
occurring on a solid support, or solution phase, occurring in solution. While the solid-phase methods are adaptable to high-throughput
screening and possess higher sensitivity than Northern blotting, they lack the ability for in vivo use and are often time-consuming.
The solution-phase methods are advantageous in that they can be performed in vivo, are very sensitive, and are rapid; however,
they cannot be applied in high-throughput settings. Although there are multiple detection methods available, including microarray
technology, luminescence-based assays, electrochemical assays, etc., there is still much work to be done regarding miRNA detection.
The current gaps of miRNA detection include the ability to perform multiplex, sensitive detection of miRNA with single-nucleotide
specificity along with the standardization of these new methods. Current miRNA detection methods, gaps in these methods, miRNA
therapeutic options, and the future outlook of miRNA detection are presented here. 相似文献