Surendranath College

About: Surendranath College is a based out in . It is known for research contribution in the topics: Multiplier (Fourier analysis) & Graded-index fiber. The organization has 87 authors who have published 181 publications receiving 1316 citations. The organization is also known as: Ripon College.

On the Jacobi Last Multiplier, integrating factors and the Lagrangian formulation of differential equations of the Painlevé–Gambier classification

Abstract: We use a formula derived almost seventy years ago by Madhav Rao connecting the Jacobi Last Multiplier of a second-order ordinary differential equation and its Lagrangian and determine the Lagrangians of the Painleve equations. Indeed this method yields the Lagrangians of many of the equations of the Painleve–Gambier classification. Using the standard Legendre transformation we deduce the corresponding Hamiltonian functions. While such Hamiltonians are generally of non-standard form, they are found to be constants of motion. On the other hand for second-order equations of the Lienard class we employ a novel transformation to deduce their corresponding Lagrangians. We illustrate some particular cases and determine the conserved quantity (first integral) resulting from the associated Noetherian symmetry. Finally we consider a few systems of second-order ordinary differential equations and deduce their Lagrangians by exploiting again the relation between the Jacobi Last Multiplier and the Lagrangian.

Constraining the contribution of active galactic nuclei to reionization

Abstract: Recent results have suggested that active galactic nuclei (AGN) could provide enough photons to reionise the Universe We assess the viability of this scenario using a semi-numerical framework for modeling reionisation, to which we add a quasar contribution by constructing a Quasar Halo Occupation Distribution (QHOD) based on Giallongo et al observations Assuming a constant QHOD, we find that an AGN-only model cannot simultaneously match observations of the optical depth $\tau_e$, neutral fraction, and ionising emissivity Such a model predicts $\tau_e$ too low by $\sim 2\sigma$ relative to Planck constraints, and reionises the Universe at $z\lesssim 5$ Arbitrarily increasing the AGN emissivity to match these results yields a strong mismatch with the observed ionising emissivity at $z\sim 5$ If we instead assume a redshift-independent AGN luminosity function yielding an emissivity evolution like that assumed in Madau & Haardt model, then we can match $\tau_e$ albeit with late reionisation, however such evolution is inconsistent with observations at $z\sim 4-6$ and poorly motivated physically These results arise because AGN are more biased towards massive halos than typical reionising galaxies, resulting in stronger clustering and later formation times AGN-dominated models produce larger ionising bubbles that are reflected in $\sim\times 2$ more 21cm power on all scales A model with equal parts galaxies and AGN contribution is still (barely) consistent with observations, but could be distinguished using next-generation 21cm experiments HERA and SKA-low We conclude that, even with recent claims of more faint AGN than previously thought, AGN are highly unlikely to dominate the ionising photon budget for reionisation

Effects of thermal radiation and Ohmic dissipation on MHD Casson nanofluid flow over a vertical non-linear stretching surface using scaling group transformation

Abstract: The problem of steady magnetohydrodynamic boundary layer flow of a Casson nanofluid over a vertical stretching surface with non-linear stretching velocity and suction has been investigated numerically. We have incorporated the combined effects of thermal radiation and the Ohmic dissipation with thermophoresis and Brownian motion on heat and mass transfer in Casson nanofluid. The governing equations are reduced to a system of nonlinear ordinary differential equations with associated boundary conditions by applying scaling group transformations. The reduced nonlinear ordinary differential equations are then solved numerically by Runge–Kutta–Fehlberg fifth-order method with shooting technique. The effects of magnetic field, Prandtl number, Ohmic dissipation, Brownian motion parameter, thermophoresis parameter and Lewis number on the local Nusselt and local Sherwood numbers are analyzed. It is found that the velocity decreases with increase in the buoyancy parameter whereas it decreases with Rayleigh number. Further, temperature decreases with increase in the radiation parameter whereas opposite effect is seen with increase in the magnetic parameter. Further, the local Nusselt number decreases with increase in the Brownian motion parameter and thermophoresis parameter, whereas opposite trend of these parameters is seen on the local Sherwood number.

Possible Link Between Stress-related Factors and Altered Body Composition in Women with Polycystic Ovarian Syndrome

Abstract: Background: Stress is an invisible factor affecting modern day living and is strongly associated with many disease pathogenesis including polycystic ovarian syndrome (PCOS) in women. PCOS is the most frequent endocrinological disorder that affects women of reproductive age, leading to metabolic dysfunction and body composition alterations. Salivary amylase and cortisol are major stress mediators that have been implicated in PCOS. However, their role in altering body composition in PCOS is yet to be deciphered. Aim: The present study aimed at understanding the relation between stress-associated factors and alterations in body composition among PCOS patients. Design: This study enrolled a total of 100 patients (PCOS) and 60 age-matched controls. The female patients were of ages between 13 and 30 years. Materials and Methods: Standard assay kits were used to evaluate the α-amylase activity and cortisol level in saliva. The participants were chosen on the basis of the Rotterdam American Society for Reproductive Medicine/European Society of Human Reproduction criteria. Saliva was collected from each participant as per the protocol of Salimetrics, USA. Statistical Analysis: Statistical analysis was performed using SPSS version 20 for Windows. The quantitative variables are described as mean ± standard deviation. P

Desert actinobacteria as a source of bioactive compounds production with a special emphases on Pyridine-2,5-diacetamide a new pyridine alkaloid produced by Streptomyces sp. DA3-7.

Abstract: In the present study, 134 morphologically distinct actinobacteria isolates were obtained from soil samples from 10 different localities in the Saudi Arabian desert. The preliminary screening revealed that 16 of these isolates possessed antimicrobial activity. One isolate, which was identified as Streptomyces sp. DA3-7, possessed broad-spectrum antimicrobial activity against both gram-positive and gram-negative bacteria, as well as against fungi, and modified nutrient glucose medium was suitable for Streptomyces sp. DA3-7 to produce extracellular metabolites. The ethyl acetate extract of Streptomyces sp. DA3-7 exhibited antimicrobial activity against Enterococcus faecalis and Salmonella typhimurium, with minimum inhibitory concentrations of 78 and 156μg/mL, respectively, as well as strong cytotoxicity (24h IC50 85μg/mL) against MCF-7 human breast adenocarcinoma cells. The active compound was separated, purified, and identified as Pyridine-2,5-diacetamide (C9H11N3O2+H+, 194.21), which possessed a lowest minimum inhibitory concentration (31.25μg/mL) against both Escherichia coli and Cryptococcus neoformans. The antimicrobial activities of this novel compound are reported here for the first time.