An application of fragment interaction analysis based on local MP2

We have developed a method named ‘fragment interaction analysis based on local MP2’ (abbreviated as FILM). This method enables us to decompose the interaction energy associated with dispersion interactions into contributions of localized occupied orbitals. In this study, the basis set dependence of the results derived from FILM was examined. The results suggested that the individual ratio of pair correlation energies of selected orbital pairs to the total dispersion interaction was almost independent of the basis set size. As an illustrative example, detailed analysis was performed on the human immunodeficiency virus type 1 protease complexed with lopinavir molecule.     

Effect of chemical crosslinking on mechanical and electrical properties of ultrahigh-molecular-weight polyethylene-carbon fiber blends prepared by gelation/crystallization from solutions

In an attempt to improve the mechanical property of polyethylene composite at high temperature, crosslinking of ultrahigh-molecular-weight polyethylene (UHMWPE) and carbon fiber (CF) blends was carried out by using dicumyl peroxide (DCP). The specimens were prepared by gelation/crystallization from solutions. The effect of chemical crosslinking on mechanical and electrical properties of UHMWPE/CF blends with composition of 1/0, 1/0.25, and 1/1 (w/w) were investigated in detail. Electrical conductivity and thermal mechanical properties of the blends with the 1/1 composition were greatly improved by incorporation of enough content of CF and adequate crosslinking network formation. Surprisingly, the Young’s modulus of the 1/1 blend reached 20 GPa at room temperature (20 °C). On the other hand, heat treatment at 135 °C played an important role for obtaining a high PTC effect for the UHMWPE-CF blend in which the PTC intensity reached 10⁷.     

Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)2] (M=Co,Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study

The different thermally induced intermolecular electron transfer (IET) processes that can take place in the series of complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)₂], for which M=Co ( 2 ), Fe ( 3 ) and Ni( 4 ), and Cat‐N‐BQ and Cat‐N‐SQ denote the mononegative (Cat‐N‐BQ^?) or dinegative (Cat‐N‐SQ^2?) radical forms of the tridentate Schiff‐base ligand 3,5‐di‐tert‐butyl‐1,2‐quinone‐1‐(2‐hydroxy‐3,5‐di‐tert‐butylphenyl)imine, have been studied by variable‐temperature UV/Vis and NMR spectroscopies. Depending on the metal ion, rather different behaviors are observed. Complex 2 has been found to be one of the few examples so far reported to exhibit the coexistence of two thermally induced electron transfer processes, ligand‐to‐metal (IET^LM) and ligand‐to‐ligand (IET^LL). IET^LL was only found to take place in complex 3 , and no IET was observed for complex 4 . Such experimental studies have been combined with ab initio wavefunction‐based CASSCF/CASPT2 calculations. Such a strategy allows one to solicit selectively the speculated orbitals and to access the ground states and excited‐spin states, as well as charge‐transfer states giving additional information on the different IET processes.     

Observation of transverse polarization asymmetries of charged pion pairs in e+e- annihilation near √s = 10.58 GeV

The interference fragmentation function translates the fragmentation of a quark with a transverse projection of the spin into an azimuthal asymmetry of two final-state hadrons. In e(+)e(-) annihilation the product of two interference fragmentation functions is measured. We report nonzero asymmetries for pairs of charge-ordered π(+)π(-) pairs, which indicate a significant interference fragmentation function in this channel. The results are obtained from a 672 fb(-1) data sample that contains 711 × 10(6) π(+)π(-) pairs and was collected at and near the Υ(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider.     

Large-scale atomistic simulations of nanostructured materials based on divide-and-conquer density functional theory

A linear-scaling algorithm based on a divide-and-conquer (DC) scheme is designed to perform large-scale molecular-dynamics simulations, in which interatomic forces are computed quantum mechanically in the framework of the density functional theory (DFT). This scheme is applied to the thermite reaction at an Al/Fe₂O₃ interface. It is found that mass diffusion and reaction rate at the interface are enhanced by a concerted metal-oxygen flip mechanism. Preliminary simulations are carried out for an aluminum particle in water based on the conventional DFT, as a target system for large-scale DC-DFT simulations. A pair of Lewis acid and base sites on the aluminum surface preferentially catalyzes hydrogen production in a low activation-barrier mechanism found in the simulations.     

Procyanidins are potent inhibitors of LOX-1: a new player in the French Paradox

Lectin-like oxidized LDL receptor-1 (LOX-1) is an endothelial receptor for oxidized LDL (oxLDL) and plays multiple roles in the development of cardiovascular diseases. We screened more than 400 foodstuff extracts for identifying materials that inhibit oxLDL binding to LOX-1. Results showed that 52 extracts inhibited LOX-1 by more than 70% in cell-free assays. Subsequent cell-based assays revealed that a variety of foodstuffs known to be rich in procyanidins such as grape seed extracts and apple polyphenols, potently inhibited oxLDL uptake in Chinese hamster ovary (CHO) cells expressing LOX-1. Indeed, purified procyanidins significantly inhibited oxLDL binding to LOX-1 while other ingredients of apple polyphenols did not. Moreover, chronic administration of oligomeric procyanidins suppressed lipid accumulation in vascular wall in hypertensive rats fed with high fat diet. These results suggest that procyanidins are LOX-1 inhibitors and LOX-1 inhibition might be a possible underlying mechanism of the well-known vascular protective effects of red wine, the French Paradox.     

Three-dimensional global analysis of thermal stress and dislocations in a silicon ingot during a unidirectional solidification process with a square crucible

A three-dimensional global model was used to obtain the solution of a thermal field within the entire furnace during a unidirectional solidification process of multicrystalline silicon with a square crucible. Then the thermal stress distribution in the silicon ingot was solved. Based on the solution of thermal stress, relaxation of stress and multiplication of dislocations were performed by using the Haasen–Alexander–Sumino model (HAS model). The influence of crucible constraint on stress levels and dislocations was investigated. It was found that the crucible constraint had significant influence on the thermal stresses and dislocations in the ingot. The results indicated that it is important to reduce the crucible constraint in order to relax thermal stresses and reduce dislocations in a silicon ingot during the solidification process.     

Photo‐capacitance spectroscopy investigation of deep‐level defects in AlGaN/GaN hetero‐structures with different current collapses

We have investigated electronic deep levels in two AlGaN/GaN hetero‐structures with different current collapses grown at 1150 and 1100 °C by a photo‐capacitance spectroscopy technique, using Schottky barrier diodes. Three specific deep levels located at ～2.07, ～2.80, and ～3.23 eV below the conduction band were found to be significantly enhanced for severe current collapse, being in reasonable agreement with photoluminescence and capacitance–voltage characteristics. These levels probably originate in Ga vacancies and residual C impurities and are probably responsible for the current collapse phenomena of the AlGaN/GaN hetero‐structures. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of the rate constants of the reactions of NO3 radical with CF3I and I(2P3/2)

The rate constant of the reaction of NO₃ radical with CF₃I was determined by a relative rate method using a Fourier transform infrared (FTIR) spectrometer smog chamber with a long path length gas cell. As a result, the upper limit of the rate constant was determined to be <2.2 × 10^?18 cm³ molecule^?1 s^?1 in 100 Torr of total pressure at 298 K, which suggests that CF₃I emitted into the atmosphere accumulates during night. The rate constant of the reaction of NO₃ with I(²P_3/2) was also measured using time‐resolved cavity ring‐down spectroscopy. The rate constant showed no pressure dependence in the range of 100–500 Torr of total pressure at 298 K and was determined to be (3.9 ± 1.0) × 10^?11 cm³ molecule^?1 s^?1. The present result is different from the previous ones and is about half of that reported most recently. From this rate constant, it is likely that the reaction of NO₃ radical with I(²P_3/2) does not have a much influence on the loss of I(²P_3/2) and the formation cycle of IO radical in the atmosphere. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 649–660, 2012