Study of the ground-state correlations and continuum model calculations for photonuclear reactions

Using the effective operator formalism, the importance of ground-state correlations on photonuclear cross sections is studied. For purposes of orientation, a bound-state calculation is first performed to take into account the mixing of 2p-2h and 3p-3h configurations into the 1p-1h dipole states. Inclusion of these configurations is found to affect the energies of the 1p-1h states in opposite directions and the combined effect, including that on the transition strengths, is negligible. Most of the reduction in the absorption comes from the ground-state correlations of which the A-dependence is examined with a model interaction. We then proceed to calculate the excitation function for the reactions using effective dipole matrix elements obtained from the continuum wave functions of the coupled-channels calculation. Application to the case of ¹⁶O leads to a reduction of about 25 % in the cross sections.     

Theoretical Studies of O(1D)+HD (v=0, j=0, 1, 2, 3)→OD(H)+H(D) Reaction

利用准经典轨线计算方法在DK势能面上对O+HD进行了计算,获得了产物的反应截面和分支比OD/OH. 计算结果表明,当碰撞能由4.6 kJ/mol增加到46.0 kJ/mol时,产物的反应截面随着碰撞能的增加明显减小;产物的平均分支比随着转动量子数的增加逐渐减小.     

A new effect of ultrasonication on the formation of BaTiO3 nanoparticles

A new effect of ultrasonic irradiation on the formation of BaTiO₃ particles was identified. Ultrasonication caused the aggregation of the original 5–10 nm BaTiO₃ particles in the same crystal axis and accelerated the formation of BaTiO₃ particles significantly. Furthermore, narrow size distribution was obtained for the aggregated particles under ultrasonic irradiation.     

Solution structures by NMR of a novel antifungal drug: Petriellin A

Petriellin A is a novel cyclic depsipeptide antifungal compound consisting of nine l-configured residues, one d-phenyllactic acid (PhLac) and three unknown chiral centres: two N-methyl-threonines (MeThr1 & MeThr2) and one N-methyl-isoleucine (MeIle). NMR experiments including 2D ROESY, NOESY along with structural and energy calculations predicted that the unknown chiral centres were all l-configured, which was later verified chemically. Simulated annealing, dynamics calculations and minimisation processes showed Petriellin A to have a folded "C-shaped" structure.     

Design and synthesis of a tetracyclic pyrimidine-fused benzodiazepine library

Method development for a heterocyclic library which entails novel scaffolds of benzodiazepines fused with various heterocycles, such as pyrimidines, indolines, and tetrahydroquinolines, was accomplished. The new synthetic strategy is based on an electrophilic cyclization reaction involving an iminium intermediate formed by the corresponding aminopyrimidine with a carbonyl compound to give the desired heterocycles in high yields. Subsequent replacement of the chloro group in the resulted structures with a nucleophile, such as boronic acids, amines, alcohols and thiols, led to a library of privileged compounds with up to eight accessible diversity points.     

An efficient and regiospecific strategy to N7-substituted purines and its application to a library of trisubstituted purines

A regiospecific strategy for the preparation of N(7)-substituted purines in an efficient manner was devised. This approach to 6,7,8-trisubstituted purines relies on the cyclization reactions of suitably substituted pyrimidines (1) with either a carboxylic acid or an aldehyde. The method development for the five-step synthetic strategy outlined here was completed using 5-amino-4,6-dichloropyrimidine (4) as the starting material. The utility of this methodology was demonstrated through the preparation of a 40-membered library of 6,7,8-trisubstituted purines (3) in good yields and high purity.     

Distribution, structure, and dynamics of cesium and iodide ions at the H2O-CCl4 and H2O-vapor interfaces

Molecular dynamics simulations utilizing many-body potentials of H2O-CCl4 and H2O-vapor interfaces were carried out at different cesium and iodide ion concentrations to compare ion distribution, interfacial orientational and structural properties, and dynamics. It was found that cesium was repelled by both interfaces, and iodide was active at both interfaces, but to a much greater degree at the H2O-vapor interface. At the interface, the iodide dipole was strongly induced, orienting perpendicular to the interface for both systems, leading to stronger hydrogen bonds with water. For the H2O-CCl4 interface, though, there was a compensation between these strong hydrogen bonds and short to moderate ranged repulsion between iodide and CCl4. Hydrogen bond distance and angular distributions showed weaker water-water hydrogen bonds at both interfaces, but generally stronger water-iodide hydrogen bonds. Both translational and rotational dynamics of water were faster at the interface, while for CCl4, its translational dynamics was slower, but rotational dynamics faster at the interface. For many of the studied systems and species, translational diffusion was found to be anisotropic at both interfacial and bulk regions.     

Surface segregation of dissolved salt ions

Surface segregation of iodide, but not of fluoride or cesium ions, is observed by a combination of metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS(HeI)) of amorphous solid water exposed to CsI or CsF vapor. The same surface ionic behavior is also derived from molecular dynamics (MD) simulations of the corresponding aqueous salt solutions. The MIES results show the propensity of iodide, but not fluoride, for the surface of the amorphous solid water film, providing thus strong evidence for the suggested presence of heavier halides (iodide, bromide, and to a lesser extent chloride) at the topmost layer of aqueous surfaces. In contrast, no appreciable surface segregation of ions is observed in methanol, neither in the experiment nor in the simulation. Furthermore, the present results indicate that, as far as the thermodynamic aspects of solvation of alkali halides are concerned, amorphous solid water and methanol surfaces behave similarly as surfaces of the corresponding liquids.     

ZnS thin film deposited with chemical bath deposition process directed by different stirring speeds

In this combined film thickness, scanning electron microscopy (SEM), X-ray diffraction and optical properties study, we explore the effects of different stirring speeds on the growth and optical properties of ZnS film deposited by CBD method. From the disclosed changes of thickness of ZnS film, we conclude that film thickness is independent of the stirring speeds in the heterogeneous process (deposition time less than 40 min), but increases with the stirring speeds and/or deposition time increasing in the homogeneous process. Grazing incident X-ray diffraction (GIXRD) and the study of optical properties disclosed that the ZnS films grown with different stirring speeds show partially crystallized film and exhibit good transmittance (70-88% in the visible region), but the stirring speeds cannot give much effects on the structure and optical properties in the homogeneous process.     

Modified subgradient extragradient algorithms for variational inequality problems and fixed point problems

The subgradient extragradient method can be considered as an improvement of the extragradient method for variational inequality problems for the class of monotone and Lipschitz continuous mappings. In this paper, we propose two new algorithms as combination between the subgradient extragradient method and Mann-like method for finding a common element of the solution set of a variational inequality and the fixed point set of a demicontractive mapping.