Theoretical study of the mechanism of dry oxidation of 4H-SiC

Possible defect structures, arising from the interaction of O-2 molecules with an ideal portion of the SiC/SiO2 interface, have been investigated systematically using density functional theory. Based on the calculated total energies and assuming thermal quasiequilibrium during oxidation, the most likely routes leading to complete oxidation have been determined. The defect structures produced along these routes will remain at the interface in significant concentration when stopping the oxidation process. The results obtained for their properties are well supported by experimental findings about the SiC/SiO2 interface. It is found that carbon-carbon bonds can explain most of the observed interface states but not the high density near the conduction band of 4H-SiC

Mechanochemical synthesis of crystalline and amorphous digold(i) helicates exhibiting anion- and phase-switchable luminescence properties

For the first time, mechanochemical synthesis has been used for the preparation of crystalline and amorphous dinuclear gold(i) helicates, [Au2L2](X)2 (L = xantphos; X = CF3SO3, SCN, BF4 and PF6), that show anion- and phase-switchable luminescence properties. This solid-state approach provides strategies for developing switchable luminescent materials

mini spindles: A Gene Encoding a Conserved Microtubule-Associated Protein Required for the Integrity of the Mitotic Spindle in Drosophila

We describe a new Drosophila gene, mini spindles (msps) identified in a cytological screen for mitotic mutant. Mutation in msps disrupts the structural integrity of the mitotic spindle, resulting in the formation of one or more small additional spindles in diploid cells. Nucleation of microtubules from centrosomes, metaphase alignment of chromosomes, or the focusing of spindle poles appears much less affected. The msps gene encodes a 227-kD protein with high similarity to the vertebrate microtubule-associated proteins (MAPs), human TOGp and Xenopus XMAP215, and with limited similarity to the Dis1 and STU2 proteins from fission yeast and budding yeast. Consistent with their sequence similarity, Msps protein also associates with microtubules in vitro. In the embryonic division cycles, Msps protein localizes to centrosomal regions at all mitotic stages, and spreads over the spindles during metaphase and anaphase. The absence of centrosomal staining in interphase of the cellularized embryos suggests that the interactions between Msps protein and microtubules or centrosomes may be regulated during the cell cycle

Role of oxygen vacancy defect states in the n-type conduction of β-Ga[sub 2]O[sub 3]

Based on semiempirical quantum-chemical calculations, the electronic band structure of β-Ga2O3 is presented and the formation and properties of oxygen vacancies are analyzed. The equilibrium geometries and formation energies of neutral and doubly ionized vacancies were calculated. Using the calculated donor level positions of the vacancies, the high temperature n-type conduction is explained. The vacancy concentration is obtained by fitting to the experimental resistivity and electron mobility

The A-kinase anchoring protein GSKIP regulates GSK3β activity and controls palatal shelf fusion in mice

A-kinase anchoring proteins (AKAPs) represent a family of structurally diverse proteins, all of which bind protein kinase A (PKA). A member of this family is Glycogen synthase kinase 3{beta} (GSK3{beta}) interaction protein (GSKIP). GSKIP interacts with PKA and also directly with GSK3{beta}. The physiological function of the GSKIP protein in vivo is unknown. We developed and characterized a conditional knockout mouse model and found that GSKIP deficiency caused lethality at birth. Embryos obtained through Caesarean section at embryonic day E18.5 were cyanotic, suffered from respiratory distress, and failed to initiate breathing properly. Additionally, all GSKIP-deficient embryos showed an incomplete closure of the palatal shelves accompanied by a delay in ossification along the fusion area of secondary palatal bones. On the molecular level, GSKIP deficiency resulted in decreased phosphorylation of GSK3{beta} at Ser9 starting early in development (E 10.5), leading to enhanced GSK3{beta} activity. At embryonic day 18.5 GSK3{beta} activity decreased to levels close to that of wild type. Our findings reveal a novel, crucial role for GSKIP in the coordination of GSK3{beta} signaling in palatal shelf fusion

Meat production and maintaining biodiversity: Grazing by traditional breeds and crossbred beef cattle in marshes and grasslands

Questions: Sustainable rangeland utilization considering traditions and economic reasons is compulsory for harmonising the needs of the agricultural and nature conservation sectors. For proper rangeland management it is crucial to compare the grazing effects of traditional breeds and crossbred animals of the same species that might have different effects on the rangelands. To fill this knowledge gap, in a grazing experiment, we investigated the effect of cattle breeds on the vegetation to test the effects on nature conservation value and agricultural production value. We hypothesized that the effects of cattle grazing on habitat conservation values and forage quality depend on the grazing breed, because breeds differ in selectivity, body size and trampling effect. Location: Marshes and alkaline wet grasslands in Hortobágy National Park, Hungary. Methods: We recorded the percentage cover of vascular plants in three consecutive years in a total of 60 plots in 12 areas grazed by traditional (0.61 AU/ha) and largesized crossbred beef cattle (0.68 AU/ha). Results: We found that the effect of cattle breed on the habitat conservation values and forage quality is dependent on the habitat type. The traditional breed maintained a significantly higher species number and Shannon diversity in marshes than the crossbred beef cattle. Grazing of crossbred cattle led to decreasing moisture indicator values in marsh habitats. Conclusions: Our findings revealed that traditional breeds should be prioritized in the management of wet alkaline grasslands and marshes. Crossbred beef cattle might be a substitute but only in case traditional breeds are not available for the management of alkaline wet grasslands. In marshes, however, we recommend prioritizing the traditional breeds as they maintain higher diversity compared to crossbred beef cattle

Defects in SiO2 as the possible origin of near interface traps in the SiC∕SiO2 system: A systematic theoretical study

A systematic study of the level positions of intrinsic and carbon defects in SiO2 is presented, based on density functional calculations with a hybrid functional in an alpha-quartz supercell. The results are analyzed from the point of view of the near interface traps (NIT), observed in both SiC/SiO2 and Si/SiO2 systems, and assumed to have their origins in the oxide. It is shown that the vacancies and the oxygen interstitial can be excluded as the origin of such NIT, while the silicon interstitial and carbon dimers give rise to gap levels in the energy range inferred from experiments. The properties of these defects are discussed in light of the knowledge about the SiC/SiO2 interface

Physics and chemistry of hydrogen in the vacancies of semiconductors

Hydrogen is well known to cause electrical passivation of lattice vacancies in semiconductors. This effect follows from the chemical passivation of the dangling bonds. Recently it was found that H in the carbon vacancy of SiC forms a three-center bond with two silicon neighbors in the vacancy, and gives rise to a new electrically active state. In this paper we examine hydrogen in the anion vacancies of BN, AlN, and GaN. We find that three-center bonding of H is quite common and follows clear trends in terms of the second-neighbor distance in the lattice, the typical (two-center) hydrogen-host-atom bond length, the electronegativity difference between host atoms and hydrogen, as well as the charge state of the vacancy. Three-center bonding limits the number of H atoms a nitrogen vacancy can capture to two, and prevents electric passivation in GaAs as well

Conceptions of the Catastrophe. Discourses on the Past before the Rise of Holocaust Memory

Analysis of early-ypost war institutinonal discourses on the recent past