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1.
Glênisson de Oliveira Jan M. L. Martin Indira K. C. Silwal Joel F. Liebman 《Journal of computational chemistry》2001,22(13):1297-1305
A long‐standing controversy concerning the heat of formation of methylenimine has been addressed by means of the W2 (Weizmann‐2) thermochemical approach. Our best calculated values, ΔH°f,298(CH2NH) = 21.1±0.5 kcal/mol and ΔH°f,298(CH2NH2+) = 179.4±0.5 kcal/mol, are in good agreement with the most recent measurements but carry a much smaller uncertainty. As a byproduct, we obtain the first‐ever accurate anharmonic force field for methylenimine: upon consideration of the appropriate resonances, the experimental gas‐phase band origins are all reproduced to better than 10 cm?1. Consideration of the difference between a fully anharmonic zero‐point vibrational energy and B3LYP/cc‐pVTZ harmonic frequencies scaled by 0.985 suggests that the calculation of anharmonic zero‐point vibrational energies can generally be dispensed with, even in benchmark work, for rigid molecules. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1297–1305, 2001 相似文献
2.
Johra Khan Prashanta Kumar Deb Somi Priya Karla Damin Medina Rajlakshmi Devi Sanjay G. Walode Mithun Rudrapal 《Molecules (Basel, Switzerland)》2021,26(13)
Flavonoids comprise a large group of structurally diverse polyphenolic compounds of plant origin and are abundantly found in human diet such as fruits, vegetables, grains, tea, dairy products, red wine, etc. Major classes of flavonoids include flavonols, flavones, flavanones, flavanols, anthocyanidins, isoflavones, and chalcones. Owing to their potential health benefits and medicinal significance, flavonoids are now considered as an indispensable component in a variety of medicinal, pharmaceutical, nutraceutical, and cosmetic preparations. Moreover, flavonoids play a significant role in preventing cardiovascular diseases (CVDs), which could be mainly due to their antioxidant, antiatherogenic, and antithrombotic effects. Epidemiological and in vitro/in vivo evidence of antioxidant effects supports the cardioprotective function of dietary flavonoids. Further, the inhibition of LDL oxidation and platelet aggregation following regular consumption of food containing flavonoids and moderate consumption of red wine might protect against atherosclerosis and thrombosis. One study suggests that daily intake of 100 mg of flavonoids through the diet may reduce the risk of developing morbidity and mortality due to coronary heart disease (CHD) by approximately 10%. This review summarizes dietary flavonoids with their sources and potential health implications in CVDs including various redox-active cardioprotective (molecular) mechanisms with antioxidant effects. Pharmacokinetic (oral bioavailability, drug metabolism), toxicological, and therapeutic aspects of dietary flavonoids are also addressed herein with future directions for the discovery and development of useful drug candidates/therapeutic molecules. 相似文献
3.
Electrokinetic transport of an uncharged nonconducting microsized liquid droplet in a charged hydrogel medium is studied. Dielectric polarization of the liquid drop under the action of an externally imposed electric field induces a non-homogeneous charge density at the droplet surface. The interactions of the induced surface charge of the droplet with the immobile charges of the hydrogel medium generates an electric force to the droplet, which actuates the drop through the charged hydrogel medium. A numerical study based on the first principle of electrokinetics is adopted. Dependence of the droplet velocity on its dielectric permittivity, bulk ionic concentration, and immobile charge density of the gel is analyzed. The surface conduction is significant in presence of charged gel, which creates a concentration polarization. The impact of the counterion saturation in the Debye layer due to the dielectric decrement of the medium is addressed. The modified Nernst–Planck equation for ion transport and the Poisson equation for the electric field is considered to take into account the dielectric polarization. A quadrupolar vortex around the uncharged droplet is observed when the gel medium is considered to be uncharged, which is similar to the induced charge electroosmosis around an uncharged dielectric colloid in free-solution. We find that the induced charge electrokinetic mechanism creates a strong recirculation of liquid within the droplet and the translational velocity of the droplet strongly depends on its size for the dielectric droplet embedded in a charged gel medium. 相似文献
4.
Sarifuddin Santabrata Chakravarty Prashanta Kumar Mandal Helge I. Andersson 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2009,56(Z2):299-323
The present investigation deals with a mathematical model representing the mass transfer to blood streaming through the arteries
under stenotic condition. The mass transport refers to the movement of atherogenic molecules, that is, blood-borne components,
such as oxygen and low-density lipoproteins from flowing blood into the arterial walls or vice versa. The blood flowing through
the artery is treated to be Newtonian and the arterial wall is considered to be rigid having differently shaped stenoses in
its lumen arising from various types of abnormal growth or plaque formation. The nonlinear unsteady pulsatile flow phenomenon
unaffected by concentration-field of the macromolecules is governed by the Navier–Stokes equations together with the equation
of continuity while that of mass transfer is controlled by the convection-diffusion equation. The governing equations of motion
accompanied by appropriate choice of the boundary conditions are solved numerically by MAC(Marker and Cell) method and checked
numerical stability with desired degree of accuracy. The quantitative analysis carried out finally includes the respective
profiles of the flow-field and concentration along with their distributions over the entire arterial segment as well. The
key factors like the wall shear stress and Sherwood number are also examined for further qualitative insight into the flow
and mass transport phenomena through arterial stenosis. The present results show quite consistency with several existing results
in the literature which substantiate sufficiently to validate the applicability of the model under consideration. 相似文献
5.
Mandal Prashanta Kumar Seth Gauri Shanker Sarkar Subharthi Chamkha Ali 《Journal of Thermal Analysis and Calorimetry》2021,143(3):1901-1916
Journal of Thermal Analysis and Calorimetry - Numerical simulation of a non-linear mathematical model governing an arbitrarily oblique slip flow of a nanofluid, with suspended carbon nanotubes in... 相似文献
6.
This paper deals with an iterative algorithm with the help of averaged mappings for the common solution of a fixed point problem of a finite collection of k-strictly pseudocontractive non-self mappings and a system of variational inequality problems in the setting of a real Hilbert space. Under some suitable conditions, the sequence generated by the proposed algorithm converges strongly to the common solution of the above said problems. Also, a numerical example is given to establish the superiority of the proposed algorithm over some existing methods. 相似文献
7.
A 2-D finite-volume model is developed to simulate nonlinear IEF in complex microgeometries. This mathematical model is formulated based on the mass conservation and ionic dissociation relations of amphoteric macromolecules, charge conservation, and the electroneutrality condition. Based on the 2-D model, three different separation cases are studied: an IPG in a planar channel, an ampholyte-based pH gradient in a planar channel, and an ampholyte-based pH gradient in a contraction-expansion channel. In the IPG case, cacodylic acid (pK(1) = 6.21) and Tris (pK(1) = 8.3) are used as the acid and base, respectively, to validate the 2-D IEF model. In the ampholyte-based pH gradient cases, IEF is performed in the pH range, 6.21-8.3 using 10 ampholytes in the planar channel and 20 ampholytes in the contraction-expansion channel. The numerical results reveal different focusing efficiencies and resolution in the narrow and wide sections of the contraction-expansion channel. To explain this, the expressions for separation resolution and peak concentrations of separands in the contraction-expansion channel are presented in terms of the channel shape factor. In a 2-D planar channel, a focused band remains straight all the time. However, in a contraction-expansion channel, initially straight bands take on a crescent profile as they pass through the trapezoidal sections joining the contraction and expansion sections. 相似文献
8.
Prashanta K. Mishra Vivekananda Chakravortty Kailash C. Dash 《Transition Metal Chemistry》1991,16(1):73-75
Summary Zr(acac)4 undergoes ligand exchanges with various tri- and tetradentate Schiff base ligands, forming compounds of the Zr(L)2 type (H2L=tetradentate H2Sal2en, H2Sal2pn, H2Sal2
o-phen and the tridentate H2SAP) and Zr(acac)2L (H2L=H2SAN. H2SAE). Upon reaction with a combination of tri- and tetradentate ligands, Zr(acac)4 yields Zr(L)(L) complexes (H2L=H2Sal2en or H2Sal2
o-phen; H2L=H2SAN, H2SAE, or H2SAP), which have been characterised by analytical data, m.ps, electrical conductivities, i.r. and n.m.r (1H and13C) spectra, they have a coordination number of 6, 7 or 8. 相似文献
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10.
Armin Darvish Jung Soo Lee Bin Peng Jugal Saharia Ramalingam VenkatKalyana Sundaram Gaurav Goyal Nuwan Bandara Chi Won Ahn Jungsuk Kim Prashanta Dutta Irwin Chaiken Min Jun Kim 《Electrophoresis》2019,40(5):776-783
Enveloped viruses fuse with cells to transfer their genetic materials and infect the host cell. Fusion requires deformation of both viral and cellular membranes. Since the rigidity of viral membrane is a key factor in their infectivity, studying the rigidity of viral particles is of great significance in understating viral infection. In this paper, a nanopore is used as a single molecule sensor to characterize the deformation of pseudo‐type human immunodeficiency virus type 1 at sub‐micron scale. Non‐infective immature viruses were found to be more rigid than infective mature viruses. In addition, the effects of cholesterol and membrane proteins on the mechanical properties of mature viruses were investigated by chemically modifying the membranes. Furthermore, the deformability of single virus particles was analyzed through a recapturing technique, where the same virus was analyzed twice. The findings demonstrate the ability of nanopore resistive pulse sensing to characterize the deformation of a single virus as opposed to average ensemble measurements. 相似文献