Mechanical stability and thermodynamic properties of OsC from first-principles calculations

The elastic and thermodynamic characteristics of OsC crystal have been predicted through a method of density functional theory within the generalized gradient approximation (GGA). Compared with WC-type OsC, NaCl-type OsC is not only energy unfavorable but also mechanics unstable. The five independent elastic constants (C_ij), bulk modulus (B₀), the dependence of bulk modulus on temperature and pressure as well as the thermal expansion coefficient (α_V) at various temperatures for WC-type OsC are discussed. According to our calculations, WC-type OsC should be an ultra-incompressible material with high bulk modulus about 381 GPa. In addition, the bulk modulus will increase with increasing pressure while decrease with increasing temperature. The researches on the thermal expansion coefficient indicate that there will be a knee point during the process of thermal expansion coefficient variation versus increasing temperature. Our results may provide useful information for theoretical and experimental investigation of OsC.     

Two Dimensional 1HNMR Studies on 2′5′-Dideoxyadenosylcobalamin

The ¹HNMR spectrum of 2′,5′-dideoxyadenosylcobalamin, a Coenzyme B₁₂(5′-deoxyadenosylcobalamin) analogue, has been assigned by 2D COSY. Its proton coupling constants have also been measured by J-resolved experiment. The comparison between the analogue and Coenzyme B¹² was made.     

Assignments of Nonexchangeable Proton Resonances and the Solution Structures of d–TGGGT

In this paper, we report the studies of the solution structures of synthetic pentadeoxyribonucleotide d-TGGGT(NH₄ ⁺ salt) using 2D–NMR. The 1H–NMR experiments with different temperatures and concentrations reveal an equilibrium between single strand and aggregation. In the experimental condition(22°C, 13mmol/ L), the cross peaks in the COSY spectrum are mainly from single strand, and the spin systems of sugar resonances of this component can be assigned. In contrast, the cross peaks in the NOESY spectrum mainly come from aggregation and the sequential assignments of bases, sugar 1′, 2′ and 2″ protons can be carried out. From NOE connectivities, it is obvious that the aggregation adopts a right–handed helix conformation. It is suggested that the aggregation in our experiment corresponds to the tetramolecular complex.     

Conformational Analysis of Baclofen Analogues by 1H and 13C NMR: Phaclofen,Saclofen, and Hydroxy-Saclofen. Influence of the Anionic Moiety

The conformations of three analogues of baclofen 1: phaclofen, saclofen, and hydroxy-saclofen 2–4, potent GABA_B antagonists, in solution (D₂O) are estimated from high-resolution (300 MHz) H NMR coupling data. Conformations and populations of conformers are calculated by means of a modified Karplus-like relationship for the vicinal coupling constants. H NMR spectral analysis evidences how 1–3 keep in solution the preferred a conformation around C3-C4 bond. A partial rotation is set up around C2–C3 bond (the conformations about C2–C3 are all highly populated in solution) particularly for 2 and 3 while 1 shows a relative preferred a conformation. This evidences the influence of the anionic moiety.     

Calcium isotope fractionation in liquid chromatography with crown ether resin in methanol medium

Breakthrough mode liquid chromatography was employed to investigate calcium (Ca) isotope fractionation in methanol medium. Highly porous silica beads, the inner pores of which were embedded with a benzo-18-crown-6 ether resin, were used as column packing material. Enrichment of heavier isotopes of Ca was observed in the frontal part of the respective Ca chromatograms. The values of the isotope fractionation coefficient (?) were in the order of 10^?3 at 25 °C. Use of methanol as solvent has little advantage over the aqueous system as far as the values of ? are concerned. However, a substantial improvement was observed concerning the adsorption capacity of the crown ether resin for Ca ions. Molecular orbital calculations supported the present isotopic results in a qualitative fashion.     

Dynamics of nuclei with antikaons

Self-consistent calculations of single -nuclear states and multi -nuclear states are briefly reviewed. Dynamical effects for deeply bound nuclear states are studied within the relativistic mean-field (RMF) approach. By varying the strength of -nucleus interaction, we cover a wide range of binding energies . Our calculations provide a lower limit on the widths of nuclear bound states for binding energy in the range . Substantial polarization is found in light nuclei for deeply bound nuclear states, with central nuclear densities about twice higher than for the corresponding nuclei without . Multi- nuclear calculations indicate that the binding energy per meson saturates upon increasing the number of mesons embedded in the nuclear medium. The nuclear and densities increase only moderately and are close to saturation, with no indication of any kaon-condensation precursor phenomena.     

超快速COSY类2D NMR实验弛豫假峰的抑制

在脉冲梯度场基础上研究了进一步缩短COSY类2D NMR实验数据采集时间的新方法.利用主动屏蔽梯度场线圈的梯度场恢复时间仅为100μs数量级这一特点,提出一类基于脉冲梯度场消除弛豫假峰的脉冲序列.并以DQF-COSY脉冲序列为例加以验证.实验结果表明:采用文中的方法,取序列重复时间远小于T₁和T₂是切实可行的;梯度场技术能很好地抑制弛豫假蜂以达到2D NMK数据的快速采集.     

Benchmark full configuration interaction calculations on N2

Summary Valence Full Configuration Interaction (FCI) calculations are reported for the N₂ molecule with a 4s3p triple-zeta basis set at different distances. The size of the FCI space is more than 225 000 000 symmetry-adapted Slater determinants. The computation requires about 1400 s of c.p.u. time per iteration on a CRAY C90, and is one of the largest FCI calculations ever converged. Our results, as is in general the case for FCI computations, can be used to test the performance of approximated methods used to study electronic correlation in molecules. The authors of this paper have agreed to not receive the proofs for correction.     

Electron capture into few-electron heavy ions: Independent particle model

We apply the density matrix theory to re-investigate the radiative electron capture into heavy ions with one valence electron. Attention has been paid particularly to the magnetic sublevel population of the residual ions, as described in terms of alignment parameters. Simple method, based on an independent particle model, which takes into account the Pauli principle, is proposed for evaluating the alignment of the excited ionic states. By making use of this method, detailed calculations are performed for electron capture into (initially) hydrogen-like and lithium-like europium, gold and uranium ions, and are compared with the results of the multiconfiguration Dirac-Fock approach.As seen from the calculations and from the comparison with available experimental results, the independent particle model provides a good estimate for the alignment parameters of few-electron heavy ions. Therefore, our simple model may help to understand the basic properties of the X-ray emission from heavy, few-electron ions without the need for invoking sophisticated MCDF calculations.     

Zero-point momentum in complex media

In this work we apply field regularization techniques to formulate a number of new phenomena related to momentum induced by electromagnetic zero-point fluctuations. We discuss the zero-point momentum associated with magneto-electric media, with moving media, and with magneto-chiral media.