Motion of a spherical particle in a cylindrical channel using arbitrary Lagrangian-Eulerian method

A finite element particle transport model, consisting of Navier-Stokes and continuity equations defined in arbitrary Lagrangian-Eulerian (ALE) kinematics, is employed to describe the motion of a rigid uncharged spherical particle in a cylindrical channel of uniform cross-section. The wall correction factors for the spherical particle moving with a fluid confined in an infinitely long cylindrical channel, as well as in finite length channels are presented. Two finite channel effects are considered, namely, motion of the particle at the entrance and exit of an open channel, and the motion of a particle toward the capped end of the channel. The numerical model demonstrates good agreement with many existing analytical results for infinite channels in the Stokes flow regime. Simple correlations for the hindrance factors are presented.     

Unique Bora[1]ferrocenophanes with Sterically Protected Boron: A Potential Gateway to Helical Polyferrocenes

Silicon‐bridged [1]ferrocenophanes are a versatile class of monomers to obtain well‐defined metallopolymers, however, their boron‐bridged analogues are far less utilized despite being significantly higher strained. We assumed that the reactivity of known bora[1]ferrocenophanes towards ring‐opening polymerization is hampered by π‐donating R₂N groups at the bridging boron atom and therefore prepared the first bora[1]ferrocenophanes lacking such electronic stabilization. The new, isolated ferrocenophane with a 2,4,6‐triisopropylphenyl group attached to the bridging boron atom exhibits the most tilted Cp rings among all isolated strained sandwich compounds [α(DFT)=33.3°] with a measured record value of the bathochromic shift (λ_max=516 nm). Attempts to purify the mesityl analogue by vacuum sublimation transformed this monomer to a purple‐colored polymer that resulted in Cotton effects in circular dichroism spectroscopy. DFT calculations revealed a left‐handed helical structure for this polymer. This is the first evidence for a polyferrocene with a chiral secondary structure.     

Experimental and DFT generated Raman study of two bent-core monomeric liquid crystalline compounds

The temperature dependence Raman spectra of two liquid crystalline compounds defined by the chemical formula of 3,5-difluoro-4?-(4-pentylcyclohexyl)-(1,1?-biphenyl)-4-carbonitrile and 3,4,5-trifluoro-4?-(4-pentylcyclohexyl)-1,1?-biphenyl is being first reported in this study. These compounds are bent-core monomers and their bent nature has been verified by the Density Functional Theory (DFT). The temperature-dependent Raman spectroscopy has been widely used in understanding the effects of temperature-based phase transitions on the molecular vibrations. The same spectroscopic technique; helps to understand various phase transitions temperature in the liquid crystalline compounds (LC) and also their molecular arrangements during the phase transitions. This study has successfully revealed the nature of intermolecular interactions between the investigated compounds during the phase transitions and the correlation between the observed Raman spectra and the measurement temperature. The contributions of different types of chemical bonds in the investigated LC compounds to their recorded Raman spectra have also been discussed in detail. In predicting the observed Raman spectra, the theoretical Raman spectra obtained from the DFT calculation was used as a reliable tool. In the light of the calculated data, the peak position, line width, and integral intensity data for each band in the observed Raman spectra were reported.     

Hypolipidemic effect of steroid compound from Cestrum diurnum (Solanaceae: Solanales) in normocholesterolemic albino rat

The present study was carried out to establish the hypolipidemic effect of a phyto-steroid compound isolated from the chloroform: methanol extract of fresh mature leaves of the plant Cestrum diurnum (Solanaceae: Solanales). Change in the haematological parameters was studied in normocholesterolemic albino rats after oral administration of single dose of isolated phytosteroid (2 mg/ day) up to 15 days and compared with control rats. Application of phytosteroid fraction resulted in a significant reduction in total plasma cholesterol and free cholesterol levels. The plasma triglyceride levels also decreased significantly. A sharp increase in the HDL cholesterol level and a significant decrease in the LDL and VLDL amount were also documented. Free fatty acid level was significantly low in treated rats.     

[8+3]‐Cycloaddition of Tropones with Azaoxyallyl Cations

Although azaoxyallyl cations are widely used as 1,3‐dipoles for various cycloaddition reactions leading to nitrogen‐containing heterocycles, their application in higher‐order cycloaddition reaction remains scarce. Herein, we present the [8+3]‐cycloaddition reaction of tropones with in situ generated azaoxyallyl cations allowing the one‐step construction of cycloheptatriene‐fused 1,4‐oxazinones in moderate to good yields. This base‐promoted new carbon‐oxygen and carbon‐nitrogen bond‐forming reaction takes place under mild conditions in the absence of transition metal catalysts.     

Role of initial conditions in the dynamics of a double pendulum at low energies

We consider the low energy dynamics of the double pendulum. Low energy implies energies close to the critical value required to make the outer pendulum rotate. All the known interesting results for the double pendulum are at high energies, that is, energies higher than that required to make both pendulums rotate. We show that interesting behavior can occur at low energies as well by which we mean energies just sufficient to make the outer pendulum rotate. A harmonic balance and the Lindstedt–Poincare analysis at the low energies establish that at small, but finite amplitude; the two normal modes behave differently. While the frequency of the “in-phase” mode is almost unchanged with increasing amplitude, the frequency of the “out-of-phase” mode drops sharply. Numerical analysis verifies this analytic result and since the perturbation theory indicates a mode softening for the out-of-phase mode at a critical amplitude, we did a careful numerical analysis of the low energy region just above the threshold for onset of rotation for the outlying pendulum. We find chaotic behavior, but the chaos is a strong function of the initial condition.     

Photophysical characterization of layer-by-layer self-assembled films of deoxyribonucleic acid

This communication reports the photophysical characterization of self-assembled layer-by-layer (LbL) films of DNA (deoxyribonucleic acid) fabricated at different temperatures by electrostatic interaction with a polycation, poly(allylamine hydrochloride). It was observed that there was a successful incorporation of DNA molecules in DNA-PAH LbL films at room temperature as well as after melting temperature. An abrupt increase in intensity was observed in the absorption spectra of the films fabricated at high temperature which is an indication of the immobilization of unzipped DNA after melting of DNA. The films were observed to remain unaffected even after 250 h of film fabrication. The total electrostatic interaction time between DNA and PAH is about 15 min, that is, no PAH binding site is free.      

发展中国家化学实验教学的现代化——挑战与机会

在多数发展中国家,中学及大专院校的化学实验教学呈现一幅沉闷景象。近30年来实验课在很多国家一直不太景气,尽管科研和生产实验室中使用计算机化数据处理支持的复杂的高科技仪器已是很平常的事情,但学生实验室却穷得连pH计、比色计这样最简单的仪器也没有。     

High spin spectroscopy of 139Pr

The high spin states in N=80 ¹³⁹Pr have been investigated by in-beam γ-spectroscopic techniques following the reaction ¹³⁰Te (¹⁴N, 5n) reaction at E=75 MeV, using a gamma detector array, consisting of seven 23% compton-suppressed high purity germanium detectors and a multiplicity ball of fourteen bismuth germanate elements. Based on γ-γ coincidence data, the level scheme of ¹³⁹Pr has been considerably extended up to 7.2 MeV excitation. Tentative spin-parity assignments are done for the newly proposed levels on the basis of the DCO ratios corresponding to strong gates and the available information from the earlier light ion experiments.     

Do ‘Quark-Stars’ Exist?

Possible existence of quark-matter in dense neutron-stars is discussed using Quantum Chromodynamical equation of state for cold degenerate quark-matter.