Lowest enthalpy polymorph of cold-compressed graphite phase

Based on an ab initio evolutionary algorithm, a novel carbon polymorph with an orthorhombic Cmcm symmetry is predicted, named as C carbon, which has the lowest enthalpy among the previously proposed cold-compressed graphite phases.     

Effects of pinhole diameters on beam characteristics for silicon thin film optical inspection

Peak power density stability and beam-wander precision of probe laser are important factors affecting the inspection results in the precision thin film optical measurements. Pinhole is frequently used as a spatial filter in the optical inspection system. In this work, four different diameters of pinhole are investigated experimentally. It is found that pinhole diameter of 0.3 mm is considered to be a promising candidate for mounting in front of probe laser for silicon thin film optical inspection due to better peak power density stability and better beam-wander precision.     

Enantioselectivity of basic analytes in CZE enantioseparation under reversed-polarity mode using sulfated beta-cyclodextrins as chiral selectors: An unusual temperature effect

Temperature effects on the enantioselectivity of basic analytes in CZE enantioseparation were studied under reversed-polarity mode using randomly sulfate-substituted beta-CDs (MI-S-beta-CD) as chiral seletors. Two catecholamines (epinephrine and isoproterenol) and two structurally related compounds (octopamine and norephedrine) were selected as test compounds in an electrophoretic system at low pH. The mobility differences between the (+)-enantiomers and the (-)-enantiomers of the two catecholamines and dopamine at 40 degrees C are greater than those at 25 degrees C with MI-S-beta-CD, even at a concentration as low as 0.3% w/v. Thus the enantioselectivity of these three basic analytes increases with increasing temperature. This phenomenon results from the inequality of the temperature effect on the mobility of the two enantiomers. In contrast, norephedrine behaves differently. The (+)-enantiomers of these basic analytes were found to migrate faster than the (-)-enantiomers. Consequently, the unusual temperature effect on the enantioselectivity can be observed when the mobility difference of the (+)-enantiomer between 40 and 25 degrees C is greater than that of the (-)-enantiomer using MI-S-beta-CD at a concentration greater than about 0.7% w/v for enantioseparation of isoproterenol, 0.4% w/v for epinephrine, and 0.3% w/v for octopamine. This unusual temperature effect offers the advantages to enhance enantioselectivity, to improve enantioseparation, and to reduce migration times.     

New constituents from the heartwood of Picea morrisonicola HAYATA

Three new constituents, including a p-menthane type monoterpene, trans-p-menthane-7,8,9-triol (1), an aromatic, 2,6-dihydroxy-3,4-dimethylbenzoic acid methyl ester (2), and a lignan, (+)-morrisonicolanin (3), were isolated from the low polar layer of heartwood extracts of Picea morrisonicola, and their structures were elucidated on the basis of spectroscopic analysis. Of these compounds identified, 1 was obtained as its diacetylated derivative 1a, and 2 was the chemical entity first isolated from a natural source.     

Electrophoretic mobility, zeta potential, and fixed charge density of bovine knee chondrocytes, methyl methacrylate-sulfopropyl methacrylate, polybutylcyanoacrylate, and solid lipid nanoparticles

The electrophoretic mobility and zeta potential of bovine knee chondrocytes (BKCs), methyl methacrylate-sulfopropyl methacrylate (MMA-SPM) nanoparticles (NPs), polybutylcyanoacrylate (PBCA) NPs, and solid lipid nanoparticles (SLNs) were investigated under the influences of Na+, K+, and Ca2+ with various ionic strengths. The fixed charge density in the surface layers of the four biocolloidal particles was estimated from the experimental mobility of capillary electrophoresis with a theory of soft charged colloids. The results revealed that, for a specific cationic species, the absolute values of the electrophoretic mobility, the zeta potential, and the fixed charge density decreased with an increase in ionic strength. For a constant ionic strength, the effect of ionic species on the reduction in the absolute values of the electrophoretic mobility, the zeta potential, and the fixed charge density followed the order Na+>K+>Ca2+ for the negatively charged BKCs, MMA-SPM NPs, and SLNs. The reverse order is true for the positively charged PBCA NPs.     

Physanolide A, a novel skeleton steroid, and other cytotoxic principles from Physalis angulata

[reaction: see text] A novel withasteroid, physanolide A (1), with an unprecedented skeleton containing a seven-membered ring, and two new physalins, physalins U (2) and V (3), were isolated from Physalis angulata. The structures were elucidated from spectroscopic analysis, and plausible biosynthetic pathways were postulated. Physalins B (4), D (5), and F (6) showed strong cytotoxicity against multiple tumor cell lines, including KB, A431, HCT-8, PC-3, and ZR751, with EC(50) values less than 4 microg/mL.     

Possible room temperature ferromagnetism of Li-doped anatase TiO2: A first-principles study

The electronic structures and magnetic properties in substitutionally lithium-doped anatase TiO₂ (Li-TiO₂) have been investigated by density functional calculations. We found that while Li itself is nonmagnetic, it generates holes residing in O 2pπ orbitals that lead to magnetic moments in TiO₂. The magnetic moments are delocalized but inhomogeneous distributed in the lattice with long rang ferromagnetic interactions among them. The inhomogeneous distribution of the magnetic moments and the specific crystal symmetry results in distance as well as directional dependence of the ferromagnetism stability of the Li-TiO₂ system. Our calculations suggest Li-TiO₂ to be potential spintronics material.     

A mechanism for radon decline prior to the 1978 Izu-Oshima-Kinkai earthquake in Japan

Precursory changes in the radon concentration of groundwater were observed by Wakita et al. (1980) prior to the 1978 Izu-Oshima-Kinkai earthquake of magnitude 7.0. Mechanisms for interpreting the anomalous radon decrease are examined in this paper. The SKE-1 well is situated in a volcanic-rock fractured aquifer of limited recharge. Given these geological conditions, the dilation of brittle rock mass occurred at a rate faster than the recharge of groundwater and gas saturation developed in newly created cracks preceding the earthquake. Radon volatilization into the gas phase can explain the anomalous decrease of radon precursory to the 1978 earthquake. To support the hypothesis, vapor–liquid two-phase radon-partitioning experiments were conducted at formation temperature (14 °C) using formation water from the SKE-1 well. Experimental data indicated that the decrease in radon concentration from 483 ± 3 count/min to 439 ± 7 count/min required a gas saturation of 2.35% developed in rock cracks through the dilatancy process.     

Quantum spins in Mackay icosahedral gold nanoparticles

We report on the direct observation of the intrinsic magnetization behavior of Mackay icosahedral Au nanoparticles. The spin arrangements in 3.5-nm icosahedral Au particles are found to be ferrimagnetic-like, where the core and surface moments point in opposite directions, with a net spontaneous magnetic moment of 16 μ_B per particle. The unpaired spins behave as J = 1/2 quantum spins. The average level separation is found to be a factor of ~1.53 larger than that estimated according to the Kubo formula for spherical Au particles. This reflects the fact that there are considerably fewer atoms packed in a particle with an icosahedral geometry than with a spherical one.