Effect of thermal gradient on frequencies of an orthotropic rectangular plate whose thickness varies in two directions

A simple model is presented for the use of research workers in space technology, mechanical sciences and nuclear energy where certain components of the structures have to operate under elevated temperatures. The effect of a constant thermal gradient on the free vibrations of an orthotropic rectangular plate whose thickness varies linearly in two directions is considered. An approximate but quite convenient frequency equation is derived by using Rayleigh-Ritz techniques with a two-term deflection function. The upper bound on the frequency corresponding to the first mode of vibrations is obtained for various boundary conditions, and for various values of the length to width ratio, two paper constants and the temperature gradient.     

Odd-even effect in fragment angular momentum in low-energy fission of actinides

Quantitative explanation for the odd-even effect on fragment angular momenta in the low-energy fission of actinides have been provided by taking into account the single particle spin of the odd proton at the fragment’s scission point deformation in the case of odd-Z fragments along with the contribution from the population of angular momentum bearing collective vibrations of the fissioning nucleus at scission point. The calculated fragment angular momenta have been found to be in very good agreement with the experimental data for fragments in the mass number region of 130–140. The odd-even effect observed in the fragment angular momenta in the low-energy fission of actinides has been explained quantitatively for the first time.      

An In Silico investigation for acyclovir and its derivatives to fight the COVID-19: Molecular docking,DFT calculations,ADME and td-Molecular dynamics simulations

In the present work, we have designed three molecules, acyclovir (A), ganciclovir (G) and derivative of hydroxymethyl derivative of ganciclovir (CH₂OH of G, that is D) and investigated their biological potential against the Mpro of nCoV via in silico studies. Further, density functional theory (DFT) calculations of A, G and D were performed using Gaussian 16 on applying B3LYP under default condition to collect the information for the delocalization of electron density in their optimized geometry. Authors have also calculated various energies including free energy of A, G and D in Hartree per particle. It can be seen that D has the least free energy. As mentioned, the molecular docking of the A, G and D against the Mpro of nCoV was performed using iGemdock, an acceptable computational tool and the interaction has been studied in the form of physical data, that is, binding energy for A, G and D were calculated in kcal/mol. It can be seen the D showed effective binding, that is, maximum inhibition that A and G. For a better understanding for the inhibition of the Mpro of nCoV by A, G and D, temperature dependent molecular dynamics simulations were performed. Different trajectories like RMSD, RMSF, Rg and hydrogen bond were extracted and analyzed. The results of molecular docking of A, G and D corroborate with the td-MD simulations and hypothesized that D could be a promising candidate to inhibit the activity of Mpro of nCoV.     

Natural frequencies of a non homogeneous isotropic elastic infinite plate of variable thickness resting on elastic foundation

Summary The dynamic free response of a nonhomogeneous isotropic elastic infinite plate of parabolically varying thickness resting on an elastic foundation has been studied. The frequencies, deflections and moments corresponding to the first five modes of vibration have been computed for the two combinations of boundary conditions, clamped-clamped (C-C) and clamped-simply supported (C-SS) and various values of taper constant, nonhomogeneity parameter and foundation modulus by applying the method of Frobenius for the solution of the governing differential equation of motion.

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Sommario Si sono studiate le oscillazioni libere di una piastra elastica infinita, non omogenea, isotropa, di spessore parabolicamente variabile, poggiata su un suolo elastico. Applicando il metodo di Frobenius per la soluzione della equazione differenziale del moto si sono calcolate le frequenze, le deformate ed i momenti corrispondenti ai primi cinque modi di vibrazione per due combinazioni di condizioni al contorno, incastro-incastro ed incastro-appoggio e diversi valori della rastremazione, del parametro di non omogeneità e del modulo del suolo.

     

Analyses of tensile deformation of nanocrystalline α-Fe2O3+fcc-Al composites using molecular dynamics simulations

The tensile deformation of nanocrystalline α-Fe₂O₃+fcc-Al composites at room temperature is analyzed using molecular dynamics (MD) simulations. The analyses focus on the effects of variations in grain size and phase volume fraction on strength. For comparison purposes, nanostructures of different phase volume fractions at each grain size are given the same grain morphologies and the same grain orientation distribution. Calculations show that the effects of the fraction of grain boundary (GB) atoms and the electrostatic forces between atoms on deformation are strongly correlated with the volume fractions of the Al and Fe₂O₃ phases. In the case of nanocrystalline Al where electrostatic forces are absent, dislocation emission initiates primarily from high-angle GBs. For the composites, dislocations emits from both low-angle and high-angle GBs due to the electrostatic effect of Al-Fe₂O₃ interfaces. The effect of the interfaces is stronger in structures with smaller average grain sizes primarily because of the higher fractions of atoms in interfaces at smaller grain sizes. At all grain sizes, the strength of the composite lies between those of the corresponding nanocrystalline Al and Fe₂O₃ structures. Inverse Hall-Petch (H-P) relations are observed for all structures analyzed due to the fact that GB sliding is the dominant deformation mechanism. The slopes of the inverse H-P relations are strongly influenced by the fraction of GB atoms, atoms associated with defects, and the volume fractions of the Al and Fe₂O₃ phases.     

Free vibrations of an isotropic nonhomogeneous infinite plate of linearly varying thickness

Summary The free transverse vibrations of an isotropic nonhomogeneous infinite plate of variable thickness have been studied on the basis of classical plate theory. The governing differential equation of motion has been solved by Frobenius method by expressing the transverse displacement as an infinite series. The frequencies corresponding to the first two modes of vibration are computed for different values of thickness variation constant, nonhomogeneity parameter, and different combinations of boundary conditions.

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Sommario Viene considerato il problema delle vibrazioni flessionali libere di una lastra infinita, isotropa, non omogenea, di spessore variabile. L'equazione del moto è stata risolta col metodo di Frobenius, esprimendo lo spostamento mediante sviluppo in serie. Sono state calcolate le prime due au to frequenze per varie combinazioni delle condizioni ai limiti e per differenti valori dei parametri caratteristici della variazione di spessore e della disomogeneità.

     

Probing electronic environment in gamma irradiated sodium borosilicate glass and simulated waste glass: a perturbed angular correlation spectroscopy study

Journal of Radioanalytical and Nuclear Chemistry - Time Differential Perturbed Angular Correlation (TDPAC) has been used to investigate the local structural changes (if any) in Sodium borosilicate...     

Microwave-Mediated Modification of Selected Limonoids with DMAB Reagent and Antibacterial Studies

N,N-Dimethylaniline.borane (DMAB) is a stable, multifaceted electrophilic boron agent that displays hydroboration of C = C as well as selective reduction of functional groups under reflux, microwave, and ultrasound conditions. Natural products contain a plethora of functional groups that govern the specific bioactivity. It will be interesting to correlate the change in a functional group with the concern for change in bioactivity. Current research emphasizes the influence of microwave irradiation on moderately reactive DMAB reagent towards the functional group modification of selected limonoid-phytochemicals of Meliaceae family viz. cedrelone, azadirone, nimbin, and azadiradione. DMAB conveniently reduces the ketone, epoxide group into alcohol, and does a hydroboration reaction on the C = C bond. It does not show interest to reduce the ester group irrespective of 30 min of MW irradiation. Except for these reducing properties, the reagent DMAB unveils chemo-selective nature in respect of different functional groups and utilizes in an asymmetric synthesis. The coalescence of amine.borane with microwave irradiation brings forth a commodious and prompt method for the selective reduction of functional groups. The bioactive efficacy of modified phytochemicals is further taken for the antimicrobial studies.     

Shock waves in reactive hydrodynamics

Using the weakly non-linear geometrical acoustics theory, we obtain the small amplitude high frequency asymptotic solution to the basic equations in Eulerian coordinates governing one dimensional unsteady planar, spherically and cylindrically symmetric flow in a reactive hydrodynamic medium. We derive the transport equations for the amplitudes of resonantly interacting waves. The evolutionary behavior of non-resonant wave modes culminating into shock waves is also studied.