Higher order linearization in non-linear random vibration

In this paper a higher order linearization method for analyzing non-linear random vibration problems is presented. The non-linear terms of the given equation are replaced by unknown linear terms. These are in turn described by extra non-linear differential equations. The combined system of equations is then linearized to arrive at a higher degree-of-freedom equation for the original system. The method is illustrated by considering the Duffing oscillator under white noise input. The equivalent two d.o.f linear system is derived by the present method. Numerical results on steady state variance and PSD functions are obtained. These are found to be better than the simple linearization results.     

Revisiting the Hinsberg Reaction: Facile and Expeditious Synthesis of 3‐Substituted Quinoxalin‐2(1H)‐ones under Catalyst‐Free Conditions in Water

Substituted benzene‐1,2‐diamine reacted with various α‐keto esters at 50° under mild conditions for 15 min using H₂O as reaction medium, providing a variety of 3‐substituted quinoxalinone derivatives in excellent yields. The reaction was instantaneous, and products were isolated by simple filtration.     

A stainless steel multi‐well plate (SS‐MWP) for high‐throughput Raman analysis of dilute solutions

The use of Raman spectroscopy for the qualitative and quantitative analysis of dilute aqueous solutions is of interest to the biopharmaceutical manufacturing sector. However, the inherent weakness of the Raman effect, coupled with spectral variability due to spurious signals from sample holders, can produce significant problems for chemometric‐based high‐throughput assays. Therefore, there is a need for a multi‐well sample holder that ensures robust and repeatable measurements, in particular from dilute aqueous solutions such as cell culture media. Here we demonstrate the efficacy of a novel, electropolished, stainless steel multi‐well plate (SS‐MWP) sample holder with 96 wells for dilute aqueous solution analysis. A comprehensive study of the spectroscopic behaviour was carried out and comparisons made with multi‐well plates fabricated from polystyrene, polypropylene, and aluminium. A key factor in the validation studies is the use of intrinsically weak Raman scattering systems, e.g. water and dilute glucose solutions. The data collected show that the SS‐MWPs are much superior in terms of robustness, resistance to chemical attack, and measurement reproducibility and as such are the ideal sample holders for Raman analysis of dilute solutions. Copyright © 2010 John Wiley & Sons, Ltd.     

Intermediate statistics as a consequence of deformed algebra

We present a formulation of deformed oscillator algebra which leads to intermediate statistics as a continuous interpolation between Bose-Einstein and Fermi-Dirac statistics. It is deduced that a generalized permutation or exchange symmetry leads to the introduction of the basic number and it is then established that this in turn leads to the deformed algebra of oscillators. We obtain the mean occupation number describing the particles obeying intermediate statistics which thus establishes the interpolating statistics and describe boson-like and fermion-like particles obeying intermediate statistics. We also obtain an expression for the mean occupation number in terms of an infinite continued fraction, thus clarifying successive approximations.     

Synthesis, biological evaluation and in silico metabolic and toxicity prediction of some flavanone derivatives

Flavones chemically are anthoxanthins, occur either in the free state or as glycosides associated with tannins (flavanoids). Flavanoids (derivatives of flavone) possess various pharmacological activities and due to its xanthine-oxidase enzyme inhibitory effect it also has superoxide-scavenging activities. A series of 2-phenyl-2,3-dihydrochromon-4-one derivatives (flavanone derivatives) were synthesized from chalcones by cyclization method and their activities were evaluated against some gram positive and gram-negative bacteria. IR, NMR and CHN analysis confirmed the structure of the synthesized compounds. The results of the antibacterial studies shows that compounds 2b, 2e, 2f and 2h possess activity against many bacterial strains. Among that the compound (2h) has remarkable activity against all strains viz. 25 microg/ml inhibitory concentration against S. aureus, S. sonnei, E. coli, S. typhimurium and V. cholerae. Compound 2f possess minimum inhibitory concentration of 200 microg/ml against E. coli and S. typhimurium and 25 microg/ml against S. sonnei, S. dysenteriae and V. cholerae. In silico metabolic and toxicity study of the synthesized compounds were performed and the predicted result showed that the compound having hydroxyl functional group undergo sulfate and O-glucuronide conjugation reaction and methoxy derivatives undergo demethylation reaction. The biologically active compounds are free of toxicity in oncogene, teratogen, sensitivity and immunotoxicity.     

Sc(OTf)3-catalyzed one-pot ene-Prins cyclization: a novel synthesis of octahydro-2H-chromen-4-ols

(R)-Citronellal undergoes initial ene reaction followed by Prins cyclization with aldehydes in the presence of 5 mol % of scandium triflate at ambient temperature to furnish octahydro-2H-chromen-4-ols in good yields and with high cis-selectivity. The use of scandium triflate makes this procedure simple, more convenient, and practical.     

Raman scattering studies on n-heptane under high pressure

High-pressure Raman scattering studies at ambient temperature are performed on n-heptane. We observe a liquid-solid transition around 1.5 GPa from the changes in the Raman spectra. This has been reported in earlier works. With increasing pressure, we observe large changes in the Raman modes and the spectra show a distinct change around 7.5 GPa. This marks the solid-solid transition at 7.5 GPa observed in n-heptane for the first time. As predicted in theoretical work, we observe dampening of methyl rotation in n-heptane below 7.5 GPa. With increase in pressure above 7.5 GPa we observe a definitive conversion of gauche to trans conformation in the solid phase. Upon release of pressure we do not observe any hysteresis, which suggests that the solid-solid transition takes place with no volume change or is a second-order transition. In this paper we propose this transition to be an orientational order-disorder transition driven by the dampening of the rotation of the methyl group.