611 research outputs found

    Modeling, synthesis, and characterization of thin film copper oxide for solar cells

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    The modeling, growth, and characterization of Copper Oxide thin films for solar cell applications are reported. Cu_2O has several attractive properties which include its direct band gap (Eg=2.17 eV) for use in photoelectrolysis of water and use in tandem multi-junction cells. Detailed balance calculations predict efficiencies on the order of 20% while Cu_2O cells have yet to even pass 2% efficiency. The device physics model reveals that defects, particularly at the heterojunction interface, are the main reason for lowered efficiencies. Epitaxial Cu_2O (100) thin films on MgO are fabricated using RF Oxygen plasma MBE. The films are quite smooth and showed mobilites in the range of 10-100 cm^2/V*sec and carrier concentrations in the range of 10^(14)-10^(17). Finally, the epitaxial growth of Cu_2O on a MgO template is demonstrated

    Some results on singular value inequalities of compact operators in Hilbert space

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    We prove several singular value inequalities for sum and product of compact operators in Hilbert space. Some of our results generalize the previous inequalities for operators. Also, applications of some inequalities are given.Comment: 1

    Core promoter short tandem repeats as evolutionary switch codes for primate speciation

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    Alteration in gene expression levels underlies many of the phenotypic differences across species. Because of their highly mutable nature, proximity to the +1 transcription start site (TSS), and the emerging evidence of functional impact on gene expression, core promoter short tandem repeats (STRs) may be considered an ideal source of variation across species. In a genome-scale analysis of the entire Homo sapiens protein-coding genes, we have previously identified core promoters with at least one STR of ≥6-repeats, with possible selective advantage in this species. In the current study, we performed reverse analysis of the entire Homo sapiens orthologous genes in mouse in the Ensembl database, in order to identify conserved STRs that have shrunk as an evolutionary advantage to humans. Two protocols were used to minimize ascertainment bias. Firstly, two species sharing a more recent ancestor with Homo sapiens (i.e. Pan troglodytes and Gorilla gorilla gorilla) were also included in the study. Secondly, four non-primate species encompassing the major orders across Mammals, including Scandentia, Laurasiatheria, Afrotheria, and Xenarthra were analyzed as out-groups. We introduce STR evolutionary events specifically identical in primates (i.e. Homo sapiens, Pan troglodytes, and Gorilla gorilla gorilla) vs. non-primate out-groups. The average frequency of the identically shared STR motifs across those primates ranged between 0.00005 and 0.06. The identified genes are involved in important evolutionary and developmental processes, such as normal craniofacial development (TFAP2B), regulation of cell shape (PALMD), learning and long-term memory (RGS14), nervous system development (GFRA2), embryonic limb morphogenesis (PBX2), and forebrain development (APAF1). We provide evidence of core promoter STRs as evolutionary switch codes for primate speciation, and the first instance of identity-by-descent for those motifs at the interspecies level. © 2014 Wiley Periodicals, Inc

    Evaluation of metallothionein protein as a biomarker of Mercury pollution in Scat (Scatophagus argus)

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    Total Metallothionein (MT) biosynthesis and Mercury bioaccumulation under control & acute Mercury exposure were investigated in Scat (Scatophagus argus). Tissues from liver and gill of samples Scats were exposed to different Mercury concentrations (10, 20, 30μ g/l) for 24, 48, 72 hours. Mercury contents were determined through Cold Vapour Atomic Absorption Spectrometry (CVAAS). Total MT levels were determined by Enzyme-linked Immunosorbent Assay (ELISA) method. Induction of MT during exposure was tissue specific, displaying different response patterns in gill and liver. Mercury accumulated in liver much stronger than gill and the latter also showed lower MT level. Although after exposure to different mercury concentration during different periods, MT biosynthesis in liver showed a significant increase (P<0.05) but in gill did not significantly modify total MT except for 72h exposure at 30 g/l. Nonetheless, the relationship between MT biosynthesis and Mercury bioaccumulation in both tissues was significant. The results suggest that this form of MT presence in S. argus was Hg-inducible and could be extended as a biomarker of Mercury pollution in marine ecosystems and especially in Persian Gulf

    The incidence of prostate cancer in Iran: Results of a population-based cancer registry

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    Background: Little is known about the epidemiology of prostate cancer in Iranian men. We carried out an active prostate cancer surveillance program in five provinces of Iran. Methods: Data used in this study were obtained from population-based cancer registries between 1996 and 2000. Results: The age-standardized incidence rate of prostate carcinoma in the five provinces was 5.1 per 100,000 person-years. No significant difference was seen in the age-standardized incidence rate of prostate cancer within the provinces studied. The mean±SD age of patients with prostate cancer was 67±13.5 years. Conclusion: The incidence of prostate cancer in Iran is very low as compared to the Western countries. This can partly be explained by lack of nationwide screening program, younger age structure and quality of cancer registration system in Iran

    The Molecular Gas Reservoirs of z2z\sim 2 Galaxies: A comparison of CO(1-0) and dust-based molecular gas masses

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    We test the use of long-wavelength dust continuum emission as a molecular gas tracer at high redshift, via a unique sample of 12, z~2 galaxies with observations of both the dust continuum and CO(1-0) line emission (obtained with the Atacama Large Millimeter Array and Karl G. Jansky Very Large Array, respectively). Our work is motivated by recent, high redshift studies that measure molecular gas masses (\ensuremath{\rm{M}_{\rm{mol}}}) via a calibration of the rest-frame 850μ850\mum luminosity (L850μm,restL_\mathrm{850\mu m,rest}) against the CO(1-0)-derived \ensuremath{\rm{M}_{\rm{mol}}}\ of star-forming galaxies. We hereby test whether this method is valid for the types of high-redshift, star-forming galaxies to which it has been applied. We recover a clear correlation between the rest-frame 850μ850\mum luminosity, inferred from the single-band, long-wavelength flux, and the CO(1-0) line luminosity, consistent with the samples used to perform the 850μ850\mum calibration. The molecular gas masses, derived from L850μm,restL_\mathrm{850\mu m,rest}, agree to within a factor of two with those derived from CO(1-0). We show that this factor of two uncertainty can arise from the values of the dust emissivity index and temperature that need to be assumed in order to extrapolate from the observed frequency to the rest-frame at 850μm\mathrm{\mu m}. The extrapolation to 850μm\mathrm{\mu m} therefore has a smaller effect on the accuracy of \Mmol\ derived via single-band dust-continuum observations than the assumed CO(1-0)-to-\ensuremath{\rm{M}_{\rm{mol}}}\ conversion factor. We therefore conclude that single-band observations of long-wavelength dust emission can be used to reliably constrain the molecular gas masses of massive, star-forming galaxies at z2z\gtrsim2

    Eurasian house mouse (Mus musculus L.) differentiation at microsatellite loci identifies the Iranian plateau as a phylogeographic hotspot

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    Background: The phylogeography of the house mouse (Mus musculus L.), an emblematic species for genetic and biomedical studies, is only partly understood, essentially because of a sampling bias towards its most peripheral populations in Europe, Asia and the Americas. Moreover, the present-day phylogeographic hypotheses stem mostly from the study of mitochondrial lineages. In this article, we complement the mtDNA studies with a comprehensive survey of nuclear markers (19 microsatellite loci) typed in 963 individuals from 47 population samples, with an emphasis on the putative Middle-Eastern centre of dispersal of the species. Results: Based on correspondence analysis, distance and allele-sharing trees, we find a good coherence between geographical origin and genetic make-up of the populations. We thus confirm the clear distinction of the three best described peripheral subspecies, M. m. musculus, M. m. domesticus and M. m. castaneus. A large diversity was found in the Iranian populations, which have had an unclear taxonomic status to date. In addition to samples with clear affiliation to M. m. musculus and M. m. domesticus, we find two genetic groups in Central and South East Iran, which are as distinct from each other as they are from the south-east Asian M. m. castaneus. These groups were previously also found to harbor distinct mitochondrial haplotypes. Conclusion: We propose that the Iranian plateau is home to two more taxonomic units displaying complex primary and secondary relationships with their long recognized neighbours. This central region emerges as the area with the highest known diversity of mouse lineages within a restricted geographical area, designating it as the focal place to study the mechanisms of speciation and diversification of this species

    The Bright and Dark Sides of High-Redshift starburst galaxies from {\it Herschel} and {\it Subaru} observations

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    We present rest-frame optical spectra from the FMOS-COSMOS survey of twelve z1.6z \sim 1.6 \textit{Herschel} starburst galaxies, with Star Formation Rate (SFR) elevated by ×\times8, on average, above the star-forming Main Sequence (MS). Comparing the Hα\alpha to IR luminosity ratio and the Balmer Decrement we find that the optically-thin regions of the sources contain on average only 10\sim 10 percent of the total SFR whereas 90\sim90 percent comes from an extremely obscured component which is revealed only by far-IR observations and is optically-thick even in Hα\alpha. We measure the [NII]6583_{6583}/Hα\alpha ratio, suggesting that the less obscured regions have a metal content similar to that of the MS population at the same stellar masses and redshifts. However, our objects appear to be metal-rich outliers from the metallicity-SFR anticorrelation observed at fixed stellar mass for the MS population. The [SII]6732_{6732}/[SII]6717_{6717} ratio from the average spectrum indicates an electron density ne1,100 cm3n_{\rm e} \sim 1,100\ \mathrm{cm}^{-3}, larger than what estimated for MS galaxies but only at the 1.5σ\sigma level. Our results provide supporting evidence that high-zz MS outliers are the analogous of local ULIRGs, and are consistent with a major merger origin for the starburst event.Comment: 6 pages, 4 figures, Accepted for publication in ApJ Letter

    Evidence for Pop III-like stellar populations in the most luminous Lyman-α emitters at the epoch of re-ionisation:spectroscopic confirmation

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    Faint Lyman-α\alpha (Lyα\alpha) emitters become increasingly rarer towards the re-ionisation epoch (z~6-7). However, observations from a very large (~5deg2^2) Lyα\alpha survey at z=6.6 (Matthee et al. 2015) show that this is not the case for the most luminous emitters. Here we present follow-up observations of the two most luminous z~6.6 Lyα\alpha candidates in the COSMOS field: `MASOSA' and `CR7'. We used X-SHOOTER, SINFONI and FORS2 (VLT), and DEIMOS (Keck), to confirm both candidates beyond any doubt. We find redshifts of z=6.541 and z=6.604 for MASOSA and CR7, respectively. MASOSA has a strong detection in Lyα\alpha with a line width of 386±30386\pm30 km/s (FWHM) and with high EW0_0 (>200 \AA), but it is undetected in the continuum. CR7, with an observed Lyα\alpha luminosity of 1043.93±0.0510^{43.93\pm0.05}erg/s is the most luminous Lyα\alpha emitter ever found at z>6. CR7 reveals a narrow Lyα\alpha line with 266±15266\pm15 km/s FWHM, being detected in the NIR (rest-frame UV, with β=2.3±0.1\beta=-2.3\pm0.1) with an excess in JJ, and also strongly detected in IRAC/Spitzer. We detect a narrow HeII1640A˚\AA emission line (6σ6\sigma) which explains the excess seen in the JJ band photometry (EW0_0~80 \AA). We find no other emission lines from the UV to the NIR in our X-SHOOTER spectra, nor any signatures of Wolf-Rayet (WR) stars. We find that CR7 is best explained by a combination of a PopIII-like population which dominates the rest-frame UV and the nebular emission, and a more normal stellar population which dominates the mass. HST/WFC3 observations show that the light is indeed spatially separated between a very blue component, coincident with Lyα\alpha and HeII emission, and two red components (~5 kpc away), which dominate the mass. Our findings are consistent with theoretical predictions of a PopIII wave, with PopIII star formation migrating away from the original sites of star formation
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