Path Integral Approach to the Non-Relativistic Electron Charge Transfer

A path integral approach has been generalized for the non-relativistic electron charge transfer processes. The charge transfer - the capture of an electron by an ion passing another atom or more generally the problem of rearrangement collisions is formulated in terms of influence functionals. It has been shown that the electron charge transfer process can be treated either as electron transition problem or as elastic scattering of ion and atom in the some effective potential field. The first-order Born approximation for the electron charge transfer cross section has been reproduced to prove the adequacy of the path integral approach for this problem.Comment: 19 pages, 1 figure, to appear in Journal of Physics B: Atomic, Molecular & Optical, vol.34, 200

First Results from KamLAND: Evidence for Reactor Anti-Neutrino Disappearance

KamLAND has been used to measure the flux of $\bar{\nu}_e$'s from distant nuclear reactors. In an exposure of 162 ton$\cdot$yr (145.1 days) the ratio of the number of observed inverse $\beta$-decay events to the expected number of events without disappearance is $0.611\pm 0.085 {\rm (stat)} \pm 0.041 {\rm (syst)}$ for $\bar{\nu}_e$ energies $>$ 3.4 MeV. The deficit of events is inconsistent with the expected rate for standard $\bar{\nu}_e$ propagation at the 99.95% confidence level. In the context of two-flavor neutrino oscillations with CPT invariance, these results exclude all oscillation solutions but the `Large Mixing Angle' solution to the solar neutrino problem using reactor $\bar{\nu}_e$ sources.Comment: 6 pages, 6 figure

Microstructural and high-temperature impedance spectroscopy study of Ba6MNb9O30 (M=Ga, Sc, In) relaxor dielectric ceramics with tetragonal tungsten bronze structure

The authors would like to thank to the following funding organisations: the Royal Society for providing a research fellowship (F.D.M.), EPSRC for providing the PhD student grant (A.R.) and Roberto Rocca Education Program for providing an additional fellowship (A.R.).This work reports on the microstructural and high-temperature impedance spectroscopy study of a family of dielectric ceramics Ba6MNb9O30 (M=Ga, Sc, In) of tetragonal tungsten bronze (TTB) structure with relaxor properties. For Ba6GaNb9O30 and Ba6InNb9O30 pellets, the SEM images have revealed good, dense internal microstructures, with well-bonded grains and only discrete porosity; in contrast Ba6ScNb9O30 pellets had a poorer microstructure, with many small and poorly-bonded grains gathered in agglomerates, resulting in significant continuous porosity and poorly defined grain boundary regions. The electroactive regions were characterised by the bulk and grain boundaries capacitances and resistances, while their contribution to the electrical conduction process was estimated by determining activation energies from the temperature (Arrhenius) dependence of both electric conductivities and time constants. For Ga and In analogues the electronic conductivity are dominated by the bulk response, while for Sc analogue, the poorly defined grain boundaries give a bulk-like response, mixing with the main bulk contribution.PostprintPeer reviewe

Methane exchange in a boreal forest estimated by gradient method

Forests are generally considered to be net sinks of atmospheric methane (CH4) because of oxidation by methanotrophic bacteria in well-aerated forests soils. However, emissions from wet forest soils, and sometimes canopy fluxes, are often neglected when quantifying the CH4 budget of a forest. We used a modified Bowen ratio method and combined eddy covariance and gradient methods to estimate net CH4 exchange at a boreal forest site in central Sweden. Results indicate that the site is a net source of CH4. This is in contrast to soil, branch and leaf chamber measurements of uptake of CH4. Wetter soils within the footprint of the canopy are thought to be responsible for the discrepancy. We found no evidence for canopy emissions per se. However, the diel pattern of the CH4 exchange with minimum emissions at daytime correlated well with gross primary production, which supports an uptake in the canopy. More distant source areas could also contribute to the diel pattern; their contribution might be greater at night during stable boundary layer conditions

A mutant O-GlcNAcase enriches Drosophila developmental regulators

YesProtein O-GlcNAcylation is a reversible post-translational modification of serines/threonines on nucleocytoplasmic proteins. It is cycled by the enzymes O-GlcNAc transferase (OGT) and O-GlcNAc hydrolase (O-GlcNAcase or OGA). Genetic approaches in model organisms have revealed that protein O-GlcNAcylation is essential for early embryogenesis. Drosophila melanogaster OGT/supersex combs (sxc) is a polycomb gene, null mutants of which display homeotic transformations and die at the pharate adult stage. However, the identities of the O-GlcNAcylated proteins involved, and the underlying mechanisms linking these phenotypes to embryonic development, are poorly understood. Identification of O-GlcNAcylated proteins from biological samples is hampered by the low stoichiometry of this modification and limited enrichment tools. Using a catalytically inactive bacterial O-GlcNAcase mutant as a substrate trap, we have enriched the O-GlcNAc proteome of the developing Drosophila embryo, identifying, amongst others, known regulators of Hox genes as candidate conveyors of OGT function during embryonic development.Wellcome Trust Investigator Award (110061); MRC grant (MC_UU_12016/5); and Royal Society Research Grant

Integrating Diverse Datasets Improves Developmental Enhancer Prediction

Gene-regulatory enhancers have been identified using various approaches, including evolutionary conservation, regulatory protein binding, chromatin modifications, and DNA sequence motifs. To integrate these different approaches, we developed EnhancerFinder, a two-step method for distinguishing developmental enhancers from the genomic background and then predicting their tissue specificity. EnhancerFinder uses a multiple kernel learning approach to integrate DNA sequence motifs, evolutionary patterns, and diverse functional genomics datasets from a variety of cell types. In contrast with prediction approaches that define enhancers based on histone marks or p300 sites from a single cell line, we trained EnhancerFinder on hundreds of experimentally verified human developmental enhancers from the VISTA Enhancer Browser. We comprehensively evaluated EnhancerFinder using cross validation and found that our integrative method improves the identification of enhancers over approaches that consider a single type of data, such as sequence motifs, evolutionary conservation, or the binding of enhancer-associated proteins. We find that VISTA enhancers active in embryonic heart are easier to identify than enhancers active in several other embryonic tissues, likely due to their uniquely high GC content. We applied EnhancerFinder to the entire human genome and predicted 84,301 developmental enhancers and their tissue specificity. These predictions provide specific functional annotations for large amounts of human non-coding DNA, and are significantly enriched near genes with annotated roles in their predicted tissues and lead SNPs from genome-wide association studies. We demonstrate the utility of EnhancerFinder predictions through in vivo validation of novel embryonic gene regulatory enhancers from three developmental transcription factor loci. Our genome-wide developmental enhancer predictions are freely available as a UCSC Genome Browser track, which we hope will enable researchers to further investigate questions in developmental biology. © 2014 Erwin et al

The importance of parameter choice in modelling dynamics of the eye lens

The lens provides refractive power to the eye and is capable of altering ocular focus in response to visual demand. This capacity diminishes with age. Current biomedical technologies, which seek to design an implant lens capable of replicating the function of the biological lens, are unable as yet to provide such an implant with the requisite optical quality or ability to change the focussing power of the eye. This is because the mechanism of altering focus, termed accommodation, is not fully understood and seemingly conflicting theories require experimental support which is difficult to obtain from the living eye. This investigation presents finite element models of the eye lens based on data from human lenses aged 16 and 35 years that consider the influence of various modelling parameters, including material properties, a wide range of angles of force application and capsular thickness. Results from axisymmetric models show that the anterior and posterior zonules may have a greater impact on shape change than the equatorial zonule and that choice of capsular thickness values can influence the results from modelled simulations

A gross anatomical study of the styloid process of the temporal bone in Japanese cadavers

Background: The incidence of an elongated styloid process (SP) and average length and diameter of SP have not been reported using Japanese cadavers. Data on the female-to-male ratio of an elongated SP vary. We calculated the average length and diameter of SP in Japanese cadavers and compared SP lengths between sexes. Materials and methods: Twenty-seven sides (right and left of bodies) in males and 51 sides in females were analyzed. Measurements were obtained from the inferior external acoustic meatus to the distal tip of the SP. SP diameters at the proximal base, midpoint, and distal tip were measured. SP >30 mm was considered elongated. We used Welch’s t-test for the statistical analysis. Fisher’s exact two-tailed test was also performed to analyze the female-to-male elongation ratio. A p-value <0.05 was considered statistically significant. Results: SP elongation prevalence was 29.5% in our sample. The average full length was 27.04±7.88 mm overall; the average diameters were 5.41±1.77 mm at the proximal base and 2.21±1.22 mm at the distal tip. The average SP measurement was 26.81±5.92 mm in males and 27.16±8.79 mm in females (p=0.74). The female-to-male ratio of SP elongation was 1:2 (p=0.041). Females had longer full lengths of non-elongated SPs than males (p=0.004). Males had wider diameters at the proximal base of elongated SPs than females (p=0.017). Conclusions: The average length of SP was 27.04 mm in the Japanese population and about 30% of the Japanese presented SP≥30 mm. Male had significantly higher rate than female among the SP≥30 mm, and female had significantly longer SPs than male among the SP<30 mm. Anatomically, the SP gets narrow as distally goes. Our anatomical findings would be beneficial to creating treatment plans, diagnosis, and surgery

High Affinity for Farnesyltransferase and Alternative Prenylation Contribute Individually to K-Ras4B Resistance to Farnesyltransferase Inhibitors

Farnesyltransferase inhibitors (FTIs) block Ras farnesylation, subcellular localization and activity, and inhibit the growth of Ras-transformed cells. Although FTIs are ineffective against K-Ras4B, the Ras isoform most commonly mutated in human cancers, they can inhibit the growth of tumors containing oncogenic K-Ras4B, implicating other farnesylated proteins or suggesting distinct functions for farnesylated and for geranylgeranylated K-Ras, which is generated when farnesyltransferase is inhibited. In addition to bypassing FTI blockade through geranylgeranylation, K-Ras4B resistance to FTIs may also result from its higher affinity for farnesyltransferase. Using chimeric Ras proteins containing all combinations of Ras background, CAAX motif, and K-Ras polybasic domain, we show that either a polybasic domain or an alternatively prenylated CAAX renders Ras prenylation, Ras-induced Elk-1 activation, and anchorage-independent cell growth FTI-resistant. The polybasic domain alone increases the affinity of Ras for farnesyltransferase, implying independent roles for each K-Ras4B sequence element in FTI resistance. Using microarray analysis and colony formation assays, we confirm that K-Ras function is independent of the identity of the prenyl group and, therefore, that FTI inhibition of K-Ras transformed cells is likely to be independent of K-Ras inhibition. Our results imply that relevant FTI targets will lack both polybasic and potentially geranylgeranylated methionine-CAAX motifs