Systematic virtual screening in search of SARS CoV-2 inhibitors against spike glycoprotein: pharmacophore screening,molecular docking,ADMET analysis and MD simulations

Molecular Diversity - In the absence of efficient anti-viral medications, the coronavirus disease 2019 (COVID-19), stemming from severe acute respiratory syndrome coronavirus-2 (SARS CoV-2), has...     

Absolute and Convective Instabilities in the Compressible Boundary Layer on a Rotating Disk

A numerical study has been undertaken to investigate the nature of inviscid instability of the three-dimensional compressible boundary layer flow due to a rotating disk. The compressible Rayleigh equation is integrated using a spectral Chebyshev-collocation method together with a fourth-order Runge–Kutta integrator. In the context of spatio-temporal stability analysis, the singularities of the resulting dispersion relation are determined and the ones that satisfy the Briggs–Bers pinching criterion have been selected. In certain finite parameter regions of eigenvalues (wave numbers and wave angles, for instance) it is found that by varying the Mach number, absolute instability occurs in the compressible boundary layer on a rotating disk. The range corresponding to the incompressible flow case given in Lingwood (1995) (ε between 14.615° and 38.114°) is verified. The results of Cole (1995) are also verified. The overall effect of compressibility is to reduce the extent of absolute instability at higher Mach numbers. The effect of heating the wall is to enhance the absolute instability properties, however, cooling the wall is found to decrease greatly the region of absolute instability regime for the range of Mach numbers studied. It is also shown in this study that for non-insulated walls a direct spatial resonance of the eigenmodes is possible and this raises the possibility of large local algebraic growth of perturbations being important in some instances. Received 15 October 1999 and accepted 10 December 1999     

Structure of Some 4f Rare Earth Liquid Metals — A Charged Hard Sphere Approach

A well-established pseodopotential is used to study the structure of some 4f rare earth liquid metals (Ce, Pr, Eu, Gd, Tb, and Yb). The structure factor S(q), pair distribution function g(r), interatomic distance r₁, and coordination number n₁ are calculated using Charged Hard Sphere (CHS) reference system. To introduce the exchange and correlation effects, the local field correction due to Sarkar et al. (S) is applied. The present investigation is successful in generating the structural information of Ce, Pr, Eu, Gd, Tb, and Yb 4f rare earth liquid metals.     

Recent advances in upper rim functionalization of resorcin[4]arene derivatives: Synthesis and applications

Abstract

During the last decades, resorcin[4]arenes have drawn much attention in the field of supramolecular chemistry because of their practical applicability in different areas. Therefore, many scientists have investigated this class of derivatives in recent years. In this article, we comprehensively reviewed a brief literature survey on the chemistry of upper rim functionalization of calix[4]resorcinarene derivatives and their applications concerning optical chemosensors, liquid crystal materials, host-guest systems, catalysis, drug delivery, biological activities, and analytical applications. This short review describes the survey of literature synthesis and upper rim functionalization of resorcin[4]arenes and their different application published in the last six years (2015–2020).     

The hydrodynamic stability of channel flow with compliant boundaries

An asymptotic theory is developed for the hydrodynamic stability of an incompressible fluid flowing in a channel in which one wall is rigid and the other is compliant. We exploit the multideck structure of the flow to investigate theoretically the development of disturbances to the flow in the limit of large Reynolds numbers. A simple spring-plate model is used to describe the motion of the compliant wall, and this study considers the effect of the various wall parameters, such as tension, inertia, and damping, on the stability properties. An amplitude equation for a modulated wavetrain is derived and the properties of this equation are studied for a number of cases including linear and nonlinear theory. It is shown that in general the effect of viscoelastic damping is destabilizing. In particular, for large damping, the analysis points to a fast travelling wave, short-scale instability, which may be related to a flutter instability observed in some experiments. This work also demonstrates that the conclusions obtained by previous investigators in which the effect of tension, inertia, and other parameters is neglected, may be misleading. Finally it is shown that a set of compliant-wall parameters exists for which the Haberman type of critical layer analysis leads to stable equilibrium amplitudes, in contrast to many other stability problems where such equilibrium amplitudes are unstable.P.S. is grateful to the University of Zimbabwe for financial support. J.S.B.G. is grateful to the E.P.S.R.C. for the computing resources acquired under Grants GR/H58568-C88 and GR/H 83683 used in this research.     

Interface thermal resistance and thermal conductivity in composites – an abrupt junction thermal diode model

An abrupt junction diode model is proposed to study the interface thermal resistance and thermal conductivity of composite. We have demonstrated that the structure of thermal diode greatly influences the heat flow and hence it is possible to regulate the heat flow via the geometry of the diode. The composite materials can significantly reduce the thermal conductivity compared to an equivalent single material. By tuning the mass ratio of oscillator of right segment to that of oscillator of left segment of the composite, _MR/_ML$M_{\mathrm{R}}/M_{\mathrm{L}}$, crossover between negative differential thermal resistance and positive differential thermal resistance as well as figure of merit for composite material can be tuned. It is also seen that the composite will work as a better thermal insulating material than its pure constituent materials.     

Enzymic activity of whole cells entrapped in reversed micelles

Studies have been conducted on the enzymic activity of Baker’s yeast and also of Brewer’s yeast entrapped into the reversed micelles formed by cetyl pyridinium chloride (CPC1) in n-hexane. The activities of α-amylase and invertase enzymes in the entrapped cells have been estimated and compared with those in the control experiments where there was no entrapment. The following significant observations have been made: 1. except for invertase, enzymes in Brewer’s yeast, the entrapped yeast cells showed enhanced enzymic activities; 2. when the yeast cells were entrapped inside the reversed micelles along with substrates of the two enzymes, α-amylase, and invertase, the activity of each of these enzymes showed a further enhancement in comparison to that showed in the experiments in which substrates of the individual enzymes alone were entrapped-the phenomenon of synergism; 3. when the yeast cells and the respective substrates were entrapped inside separate reversed micelles and the solutions containing entrapped cells and entrapped substrates were mixed, the activities of the individual enzymes, α-amylase and invertase, showed further enhancement in comparison to the case in which the cells and the substrates were entrapped inside the same reversed micelle (in this case also the phenomenon of synergism was observed); and (4) In the case of experiments in which there was no entrapment, it was observed that the presence of substrates induced more release of enzymes from the yeast cells. These observations on yeast cells, which to the best of our knowledge have not been reported before, should be biotechnologically relevant.     

Robustness to nonnormality of some transformations of the sample correlation coefficient

In this paper, some of the familiar transformations of r are examined for their robustness to nonnormality. General results are given for any parent population f(x, y) and any general transformation g(r) of r. Two types of parent populations are considered for exemplification: The bivariate Edgeworth series distribution and the truncated bivariate normal distribution. The effects of nonnormality are assessed through the parameters μ′₁, μ₂, γ₁, γ₂. Tables are provided comparing these quantities against their bivariate normal counterparts.     

Simultaneous quantification of brexpiprazole and sertraline HCl in synthetic mixture by thin-layer chromatography method

According to the International Council for Harmonisation (ICH) Q2 (R1) guideline, a sensitive, precise, accurate and robust high-performance thin-layer chromatographic (HPTLC) method was developed and validated for the simultaneous quantification of a newer combination of brexpiprazole (BREX) and sertraline HCl (SERT) in bulk and synthetic mixture. Stationary phase selected was pre-coated silica gel aluminum plate 60 F_254, and n-propanol‒hexane‒toluene‒triethylamine (7:2:1:0.1, V/V) was used as developing mobile phase. An appreciable absorbance shows at 254 nm, therefore the common detection wavelength was selected for the simultaneous quantification of BREX and SERT. The method was validated for different parameters: linearity, precision, accuracy, robustness, limit of detection and limit of quantification as per ICH guideline. The correlation coefficients (r²) for BREX and SERT were found to be 0.9940 and 0.9911, respectively. The mean of percentage recoveries for BREX and SERT were found to be 99.40–102.10% and 99.52–101.05%, respectively. The proposed HPTLC method has potential application for the quantification of BREX and SERT simultaneously in bulk and synthetic mixture both qualitatively and quantitatively.

     

Phonon dispersion relation of liquid metals

The phonon dispersion curves of some liquid metals, viz. Na (Z = 1), Mg (Z = 2), Al (Z = 3) and Pb (Z = 4), have been computed using our model potential. The charged hard sphere (CHS) reference system is applied to describe the structural information. Our model potential along with CHS reference system is capable of explaining the phonon dispersion relation for monovalent, divalent, trivalent and tetravalent liquid metals.