2,522 research outputs found

    Anisotropic electronic structure in quasi-one-dimensional K0.3MoO3: An angle-dependent x-ray absorption study

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    100學年度杜昭宏升等參考著作[[abstract]]The electronic structure of quasi-one-dimensional (quasi-1D) blue bronze, K0.3MoO3, was investigated by angle-dependent x-ray absorption near-edge structure (XANES) spectroscopy at O and K K and Mo L3 edges along the quasi-1D MoO6 octahedron-chain direction, i.e., the b axis, and the octahedron-in-plane direction, i.e., the d axis, well below its Peierls phase transition temperature (180 K). The O K-edge XANES spectra indicate that the angle dependence of O 2p–Mo 4d hybridization, especially those with the π* character, is more significant along the b axis than along the d axis. Similar trend is also observed in the Mo L3-edge XANES spectra. The K K-edge XANES spectra reveal anisotropic effect of hybridization of K 4p states with O 2p states on the MoO6 octahedron.[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]SCI[[booktype]]紙本[[countrycodes]]US

    Cutting Edge : Failure of Antigen-Specific CD4+ T Cell Recruitment to the Kidney during Systemic Candidiasis

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    Copyright © 2014 The Authors. Acknowledgments We thank E. Bolton and H. Bagavant for reagents and advice. We also acknowledge the staff of the Medical Research Facility at the University of Aberdeen for care of the animals used in this study. This work was supported by the Medical Research Council and the Wellcome Trust.Peer reviewedPublisher PD

    Defining the latent phase of labour: is it important?

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    Background and rationale: The latent phase of labour is recognised as a period of uncertainty for both women and midwives. There is evidence from the literature of considerable variation in labour definitions and practice. Stimulated by discussion at an international maternity research conference, we set out to explore opinions regarding the need for labour stage definitions. Aim: to identify health professionals’ views regarding the need for a definition of the onset and the end of the latent phase of labour. Methods: This was an opportunistic, semi-structured, online survey of attendees at a maternity care research conference, which included midwives, other clinicians, academics, advocates and user representatives. Attendees (approximately 100) were invited to participate through a single email invitation sent by the conference committee and containing a link to the survey. Consent was sought on the landing page. Ethical approval was obtained from Bournemouth University’s research ethics committee. Quantitative questions were analysed using simple descriptive statistics using IBM SPSS Statistics Version 24. Open questions were analysed using content analysis and where participants gave a more detailed answer, these were analysed using a thematic approach. Findings: Participants in the survey (n = 21) came from twelve countries. Most of the participants thought that there was a need to define the onset of the latent phase (n = 15, 71%). Common characteristics were cited, but the main theme in the open comments referred to the importance of women’s perceptions of labour onset. Most participants (n = 18, 86%) thought that there was a need to define the end of the latent phase. This was felt necessary because current practice within facilities is usually dictated by a definition. The characteristics suggested were also not unexpected and there was some consensus; but the degree of cervical dilatation that signified the end of the latent phase varied among participants. There was significant debate about whether a prolonged latent phase was important; for example, was it associated with adverse consequences. Most participants thought it was important (n = 15, 71%), but comments indicated that the reasons for this were complex. Themes included the value that women attached to knowing the duration of labour and the need to support women in the latent phase. Implications for practice: The findings from this small, opportunistic survey reflect the current debate within the maternal health community regarding the latent phase of labour. There is a need for more clarity around latent phase labour (in terms of both the definition and the support offered) if midwives are to provide care that is both woman centred and evidence-based. The findings will inform the development of a larger survey to explore attitudes towards labour definitions

    Redshifts in the Southern Abell Redshift Survey Clusters. I. The Data

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    The Southern Abell Redshift Survey contains 39 clusters of galaxies with redshifts in the range 0.0 < z < 0.31 and a median redshift depth of z = 0.0845. SARS covers the region 0 21h (while avoiding the LMC and SMC) with b > 40. Cluster locations were chosen from the Abell and Abell-Corwin-Olowin catalogs while galaxy positions were selected from the Automatic Plate Measuring Facility galaxy catalog with extinction-corrected magnitudes in the range 15 <= b_j < 19. SARS utilized the Las Campanas 2.5 m duPont telescope, observing either 65 or 128 objects concurrently over a 1.5 sq deg field. New redshifts for 3440 galaxies are reported in the fields of these 39 clusters of galaxies.Comment: 20 pages, 5 figures, accepted for publication in the Astronomical Journal, Table 2 can be downloaded in its entirety from http://trotsky.arc.nasa.gov/~mway/SARS1/sars1-table2.cs

    X-ray Over-Luminous Elliptical Galaxies: A New Class of Mass Concentrations in the Universe?

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    We detect four isolated, X-ray over-luminous (Lx>2e43 [h/0.5]**-2 erg/s) elliptical galaxies (OLEGs) in our 160 square degree ROSAT PSPC survey. The extent of their X-ray emission, total X-ray luminosity, total mass, and mass of the hot gas in these systems correspond to poor clusters, and the optical luminosity of the central galaxies (M_R<-22.5 + 5 lg h) is comparable to that of cluster cDs. However, there are no detectable fainter galaxy concentrations around the central elliptical. The mass-to-light ratio within the radius of detectable X-ray emission is in the range 250-450 Msun/Lsun, which is 2-3 times higher than typically found in clusters or groups. These objects can be the result of galaxy merging within a group. However, their high M/L values are difficult to explain in this scenario. OLEGs must have been undisturbed for a very long time, which makes them the ultimate examples of systmes in hydrostatic equilibrium. The number density of OLEGs is n=2.4(+3.1-1.2}x10**-7 (h/0.5)**-3 Mpc**-3 at the 90% confidence. They comprise 20% of all clusters and groups of comparable X-ray luminosity, and nearly all galaxies brighter than M_R=-22.5. The estimated contirubution of OLEGs to the total mass density in the Universe is close to that of T>7 keV clusters.Comment: 4 pages, 2 figures, uses emulateapj.sty, submitted to ApJ Letter

    Insulation of a synthetic hydrogen metabolism circuit in bacteria

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    <p>Abstract</p> <p>Background</p> <p>The engineering of metabolism holds tremendous promise for the production of desirable metabolites, particularly alternative fuels and other highly reduced molecules. Engineering approaches must redirect the transfer of chemical reducing equivalents, preventing these electrons from being lost to general cellular metabolism. This is especially the case for high energy electrons stored in iron-sulfur clusters within proteins, which are readily transferred when two such clusters are brought in close proximity. Iron sulfur proteins therefore require mechanisms to ensure interaction between proper partners, analogous to many signal transduction proteins. While there has been progress in the isolation of engineered metabolic pathways in recent years, the design of insulated electron metabolism circuits <it>in vivo </it>has not been pursued.</p> <p>Results</p> <p>Here we show that a synthetic hydrogen-producing electron transfer circuit in <it>Escherichia coli </it>can be insulated from existing cellular metabolism via multiple approaches, in many cases improving the function of the pathway. Our circuit is composed of heterologously expressed [Fe-Fe]-hydrogenase, ferredoxin, and pyruvate-ferredoxin oxidoreductase (PFOR), allowing the production of hydrogen gas to be coupled to the breakdown of glucose. We show that this synthetic pathway can be insulated through the deletion of competing reactions, rational engineering of protein interaction surfaces, direct protein fusion of interacting partners, and co-localization of pathway components on heterologous protein scaffolds.</p> <p>Conclusions</p> <p>Through the construction and characterization of a synthetic metabolic circuit <it>in vivo</it>, we demonstrate a novel system that allows for predictable engineering of an insulated electron transfer pathway. The development of this system demonstrates working principles for the optimization of engineered pathways for alternative energy production, as well as for understanding how electron transfer between proteins is controlled.</p

    Mg-induced increase of band gap in Zn1-xMgxO nanorods revealed by x-ray absorption and emission spectroscopy

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    [[abstract]]X-rayabsorption near-edge structure (XANES) and x-ray emission spectroscopy (XES) measurements were used to investigate the effect of Mgdoping in ZnOnanorods. The intensities of the features in the O K-edge XANES spectra of Zn1−xMgxOnanorods are lower than those of pure ZnOnanorods, suggesting that Mgdoping increases the negative effective charge of O ions. XES and XANES spectra of O 2p states indicate that Mgdoping raises (lowers) the conduction-band-minimum (valence-band-maximum) and increases the band gap. The band gap is found to increase linearly with the Mg content, as revealed by photoluminescence and combined XANES and XES measurements.[[booktype]]紙本[[booktype]]電子版[[countrycodes]]US
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