Shannon entropies of atomic structure factors,off-diagonal order and radial correlation

Shannon entropies of one- and two-electron atomic structure factors in the position and momentum representations are used to examine the behaviour of the off-diagonal elements of density matrices with respect to the uncertainty principle and to analyse the effects of radial correlation on off-diagonal order. We show that radial correlation induces off-diagonal order in position space which is characterized by larger entropic values. Radial correlation in momentum space is characterized by smaller entropic values as information is forced into regions closer to the diagonal. Related off-diagonal correlation functions are also discussed.     

Synthesis and characterisation of new ditopic receptors for guanosine

Novel ditopic receptors for guanosine have been prepared and characterised. Their association constants with a lipophilic guanosine derivative are somewhat smaller than the expected values for a guanosine-cytidine base pair, but remain in a useful range for building supramolecular structures.     

Self-consistent mean-field model based on molecular dynamics: application to lipid-cholesterol bilayers

We have developed a dynamic self-consistent mean-field model, based on molecular-dynamics simulations, to study lipid-cholesterol bilayers. In this model the lipid bilayer is represented as a two-dimensional lattice field in the lipid chain order parameters, while cholesterol molecules are represented by hard rods. The motion of rods in the system is continuous and is not confined to lattice cells. The statistical mechanics of chain ordering is described by a mean field derived from an extension of a model due to Marcelja. The time evolution of the system is governed by stochastic equations. The ensemble of chain configurations required in partition sums, and the energies of interaction, are taken from atomistic level molecular-dynamics simulations of lipid bilayers. The model allows us to simulate systems 500 nm in lateral size for 20 micros time scales, or greater. We have applied the model to dipalmitoyl-phosphatidylcholine-cholesterol (Chol) bilayers at 50 degrees C for Chol concentrations between 2% and 33%. At low concentrations of Chol (2%-4%), the model predicts the formation of isolated clusters of Chol surrounded by relatively ordered lipid chains, randomly dispersed in the disordered bilayer. With increasing Chol composition, regions of Chol-induced order begin to overlap. Starting from about 11% Chol this ordering effect becomes system wide and regions unaffected by Chol are no longer detectable. From the analysis of properties of the model we conclude that the change in lipid chain order with increasing Chol concentration is continuous over the 20-mus scale of the simulations. We also conclude that at 50 degrees C no large-scale Chol-rich and Chol-depleted coexisting phase-separated regions form at any concentration. At no point in any of the simulations do we observe a higher degree of lateral organization, such as Chol-based superlattice structures.     

Photoelectric photometry of the open cluster NGC 1778

PhotoelectricU, B, V magnitudes and colours for 48 stars in the open cluster NGC 1778 have been determined. The colour excess is \(0_ \cdot ^m 34\) , distance to the cluster 1062 pc, and apparent diameter of the cluster 4.5 minutes of arc. The age is estimated at 1.6×10⁸ years.     

Synthesis and characterization of novel chiral imidazolium and pyridinium ionic liquids derived from tartaric acid and 2-oxazolidinone

Abstract

Novel chiral imidazolium and pyridinium ionic liquids based on tartaric acid and 2-oxazolidinone were designed. Symmetrical dicationic ionic liquids based on tartaric acid have been synthesized and characterized. These chiral ionic liquids were designed by employing very short and simple methods. Incorporation of alkyl halide over tartaric acid and 2-oxazolidinone is an important step. N-methyl imidazole and pyridine were used for preparation of quaternary salts. These ionic liquids have been evaluated for the asymmetric sulfide oxidation. Chiral ionic liquids based on tartaric acid showed superior chiral inducing property as compare to 2-oxazolidinone based chiral ionic liquids.     

On the calculation of Rys polynomials and quadratures

A discretized Stieltjes procedure is used to generate Rys polynomials from a three-term recurrence relationship. We show that this process is numerically stable in contrast to the evaluation from the moments of the system and polynomial coefficients, i.e., the Stieltjes procedure, where numerical instabilities arise. Rys quadratures may thus be calculated in an accurate manner from the Rys polynomials generated via this discretized Stieltjes procedure.     

Standardization of the ayurvedic formulation Haridra Khanda using high-performance thin-layer chromatography-densitometry

The present study aimed to standardize the Ayurvedic preparation Haridra Khanda containing Curcuma longa as a major ingredient. Various physicochemical parameters such as alcohol-soluble extractive, water-soluble extractive, total ash, and acid-insoluble ash were determined according to the Ayurvedic Pharmacopoeia of India. Microscopic evaluation of the formulation revealed the presence of various diagnostic cell structures of C. longa. Trace metal analysis indicated the absence of toxic metals such as As, Cd, Hg, and Pb. High-performance thin-layer chromatographic (HPTLC) fingerprint patterns at multiple wavelengths (254, 366, and 430 nm) identified the number of components present at each wavelength. The bioactive markers curcumin (C1), demethoxycurcumin (C2), and bisdemethoxycurcumin (C3) were quantified by using a simple, rapid, and efficient HPTLC method using plates precoated with silica gel 60F254 stationary phase. The instrumental precision [coefficient of variation (CV)] was 0.51, 0.64, and 0.79% and the repeatability of the method (CV) was 0.89, 1.11, and 0.95%, respectively, for C1 to C3. Limits of detection and quantitation for compounds C1 to C3 were 20, 20, and 15 ng and 50, 40, and 50 ng, respectively. Response was a linear function in the ranges of 50-350, 40-240, and 50-300 ng with correlation coefficient (r) = 0.9998, 0.9995, and 0.9992, respectively, for C1 to C3. The mean recovery values of 99.63 (C1), 98.65 (C2), and 98.97% (C3) indicated the excellent accuracy of the method. It is shown that HPTLC can be applied successfully for the marker evaluation of the formulation containing C. longa.     

Anisotropic charge transport properties of chrysene derivatives as organic semiconductor: A computational study

We used density functional theory to calculate the angular resolution anisotropic charge mobility of the substituted chrysene molecules, viz, 4,10‐diphenoxychrysene (DPC), 4,10‐bis(phenylsulfanyl)chrysene (BPSC), and ethyl 8,9,12‐trimethoxychrysene‐6‐carboxylate (ETCC). The highest occupied molecular orbital–lowest unoccupied molecular orbital gap for DPC, BPSC, and ETCC was calculated to be 3.92, 3.83, and 3.81 eV, respectively, which inferred the compounds to be wide‐band‐gap semiconductors indicating that the compounds should have high stability in atmospheric conditions. The fact is also supported by electronic band‐structure calculation. In addition, higher electron affinity of studied compounds as compared with the bare chrysene molecule imparts enhancement of n‐type character in the compounds. The maximum hole ( ) and electron mobilities ( ) for DPC compound were found to be 0.739 cm²V^?1s^?1 and 0.319 cm²V^?1s^?1, respectively, at Φ = 0°. On the other hand, in the case of BPSC crystal, comparatively larger anisotropic electron mobility (0.709 cm²V^?1s^?1 at Φ = 0° and Φ = 179.90°) than the hole mobility (0.208 cm²V^?1s^?1 at Φ = 127.19° and Φ = 307.10°) was noted. Similarly, in ETCC, the parallel dimers were found to contribute maximum and of 0.052 and 0.102 cm²V^?1s^?1, respectively, at Φ = 0°. The substitution of ‐SPh in BPSC and ‐OCH₃ and ‐CO₂CH₂CH₃ in ETCC have relatively more impact on band reduction than ‐OPh in DPC, thus facilitating electron transport in BPSC and ETCC.     

Effect of Cation Proportion on the Structural and Magnetic Properties of Ni-Zn Ferrites Nano-Size Particles Prepared By Co-Precipitation Technique

用共沉淀法制备了结构式为Ni1-xZnxFe2O4 (x=0.0,0.1,0.2,0.3,0.4,0.5,0.6,0.7)的铁酸盐纳米颗粒,并对这些纳米颗粒进行了X射线衍射,磁化和交流易感性的测量．X射线衍射的分析结果确认了样品中形成的单相结构．从X射线衍射谱获得的晶格参数随锌的配比x的增大而增大．通过X射线衍射强度比的计算获得了阳离子分布．磁化研究的结果表明在x<0.4时亚铁磁结构与磁性有共线性关系,而x>0.4时没有共线性关系．交流易感性测量获得的居里温度TC被发现随x的升高而降低．     

Reduction and Elimination of Humic Acid Fouling in Air Sparged Membrane Distillation Using Nanocarbon Immobilized Membrane

In this paper, we present the treatment of humic acid solution via carbon nanotube immobilized membrane (CNIM) distillation assisted by air sparging (AS). Carbon nanotubes offer excellent hydrophobicity to the modified membrane surface and actively transport water vapor molecules through the membrane to generate higher vapor flux and better rejection of humic acid. The introduction of air sparging in the membrane distillation (MD) system has changed the humic substance fouling by changing the colloidal behavior of the deposits. This modified MD system can sustain a higher run time of separation and has enhanced the evaporation efficiency by 20% more than the regular membrane distillation. The air sparging has reduced the deposition by 30% in weight and offered lesser fouling of membrane surface even after a longer operating cycle. The water vapor flux increased with temperature and decreased as the volumetric concentrating factor (VCF) increased. The mass transfer coefficient was found to be the highest for the air sparged—carbon nanotube immobilized membrane (AS-CNIM) integrated membrane distillation. While the highest change in mass transfer coefficient (MTC) was found for polytetrafluoroethylene (PTFE) membrane with air sparging at 70 °C.