Low-temperature combustion chemistry of biofuels: pathways in the initial low-temperature (550 K-750 K) oxidation chemistry of isopentanol

The branched C(5) alcohol isopentanol (3-methylbutan-1-ol) has shown promise as a potential biofuel both because of new advanced biochemical routes for its production and because of its combustion characteristics, in particular as a fuel for homogeneous-charge compression ignition (HCCI) or related strategies. In the present work, the fundamental autoignition chemistry of isopentanol is investigated by using the technique of pulsed-photolytic Cl-initiated oxidation and by analyzing the reacting mixture by time-resolved tunable synchrotron photoionization mass spectrometry in low-pressure (8 Torr) experiments in the 550-750 K temperature range. The mass-spectrometric experiments reveal a rich chemistry for the initial steps of isopentanol oxidation and give new insight into the low-temperature oxidation mechanism of medium-chain alcohols. Formation of isopentanal (3-methylbutanal) and unsaturated alcohols (including enols) associated with HO(2) production was observed. Cyclic ether channels are not observed, although such channels dominate OH formation in alkane oxidation. Rather, products are observed that correspond to formation of OH viaβ-C-C bond fission pathways of QOOH species derived from β- and γ-hydroxyisopentylperoxy (RO(2)) radicals. In these pathways, internal hydrogen abstraction in the RO(2)? QOOH isomerization reaction takes place from either the -OH group or the C-H bond in α-position to the -OH group. These pathways should be broadly characteristic for longer-chain alcohol oxidation. Isomer-resolved branching ratios are deduced, showing evolution of the main products from 550 to 750 K, which can be qualitatively explained by the dominance of RO(2) chemistry at lower temperature and hydroxyisopentyl decomposition at higher temperature.     

Genetic association of the EGR2 gene with bipolar disorder in Korea

The early growth response gene 2 (EGR2) is located at chromosome 10q21, one of the susceptibility loci in bipolar disorder (BD). EGR2 is involved in cognitive function, myelination, and signal transduction related to neuregulin-ErbB receptor, Bcl-2 family proteins, and brain-derived neurotrophic factor. This study investigated the genetic association of the EGR2 gene with BD and schizophrenia (SPR) in Korea. In 946 subjects (350 healthy controls, 352 patients with BD, and 244 with SPR), nine single nucleotide polymorphisms (SNPs) in the EGR2 gene region were genotyped. Five SNPs showed nominally significant allelic associations with BD (rs2295814, rs61865882, rs10995315, rs2297488, and rs2297489), and the positive associations of all except rs2297488 remained significant after multiple testing correction. Linkage disequilibrium structure analysis revealed two haplotype blocks. Among the common identified haplotypes (frequency > 5%), 'T-G-A-C-T (block 1)' and 'A-A-G-C (block 2)' haplotypes were over-represented, while 'C-G-G-T-T (block 1)' haplotype was under-represented in BD. In contrast, no significant associations were found with SPR. Although an extended analysis with a larger sample size or independent replication is required, these findings suggest a genetic association of EGR2 with BD. Combined with a plausible biological function of EGR2, the EGR2 gene is a possible susceptibility gene in BD.     

Spectroscopic identification of benzyl-type radicals generated by corona discharge of 2-chloro-4-fluorotoluene

By means of a technique of corona excited supersonic expansion coupled with a pinhole-type glass nozzle, we generated vibronically excited but jet-cooled benzyl-type radicals from precursor 2-chloro-4-fluorotoluene seeded in a large amount of inert carrier gas He. From an analysis of the visible vibronic emission spectrum, we found evidence of the formation of the 2-chloro-4-fluorobenzyl and 4-fluorobenzyl radicals. A possible pathway for the formation of these benzyl-type radicals is herein proposed. Also, the electronic energy in the D(1) → D(0) transition and the vibrational mode frequencies of the 2-chloro-4-fluorobenzyl radical in the ground electronic state were accurately determined, for the first time, by comparison with ab initio calculations and the known vibrational data of the precursor.     

4,17,25,26‐Tetraaza‐6,9,12,15‐tetra­oxa‐2,19,21,24‐tetrathiatricyclo[18.4.11,4.117,20]hexacosa‐1(25),20(26)‐diene‐3,5,16,18‐tetraone

The title compound, C₁₄H₁₆N₄O₈S₄, has crystallographic C₂ symmetry with half a molecule in the asymmetric unit and a dihedral angle of 58.7 (1)° between the two planar 1,3,4‐thiadiazole five‐membered rings of the macrocyclic, giving the molecule a twisted conformation.     

Unique geometric and electronic structure of CO adsorbed on Ge(100): A DFT study

CO adsorption on the Ge(100) surface has been investigated using a slab model with density functional theory implemented in SIESTA. CO was found to be exclusively adsorbed on the asymmetric dimer with C attaching on the lower Ge dimer atom. The adsorption process is barrierless. The calculated adsorption energy and vibration frequencies are comparable to previous experimental results. The crystal orbital Hamilton analysis showed that the bonding between Ge and CO is mainly attributable to the Ge 4p_z orbital overlapping with C 2 s, or with CO molecular orbitals 3σ and 4σ. The repulsive energy between adsorbed CO molecules is less than 1 kcal/mol. The diffusion barrier of CO on the Ge(100) surface is about 14 kcal/mol.     

Analysis of High Power Millimeter Wave Waveguide Mode Converters with Input Mode Mixture

Based on the coupled mode theory, this paper presents the study on the influence of input mode mixture in circular oversized waveguide mode converters. Three kinds of commonly used waveguide mode converters, including the waveguide mode converters with varying wall radius or small axis perturbations, and the waveguide mode converters with bent structures, are taken as the examples. The results show that the spurious input modes do not simply superimpose onto the output modes, and in some cases they may deteriorate the conversion efficiency for the main output mode. Methods for transforming such spurious input mode mixture simultaneously into the main output mode are also presented in this paper.     

Irregular elliptical plasmonic rings for engineering near-field and phase

Metallic glasses find wide applications in nanotechnology and micro electro-mechanical systems because of their unique physical properties due to their amorphous structures. The material removal mechanism in nanometric cutting of Cu₅₀Zr₅₀, a typical metallic glass, is studied using molecular dynamics method. The chip formation, workpiece deformation and scratching forces under various scratching depths, scratching velocities and temperatures are investigated. The effect of void defect on the cutting behaviors of metallic glass is also explored. The results show that the material removal in nanometric cutting process is based on extrusion instead of shearing, achieving a good understanding of material removal at the nanoscale.