4,955 research outputs found

    Ion backflow studies with a triple-GEM stack with increasing hole pitch

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    Gas Electron Multipliers have undergone a very consistent development since their invention in 1997. Their production procedures have been tuned in such a way that nowadays it is possible to produce foils with areas of the order of the square meter that can operate at a reasonable gain, uniform over large areas and with a good stability in what concerns electrical discharges. For the third run of LHC, they will be included in the CMS and ALICE experiments after significant upgrades of the detectors, confirming that these structures are suitable for very large experiments. In the special case of Time Projection Chambers, the ion backflow and the energy resolution are sensitive issues that must be addressed and the GEM has shown to be able to deal with both of them. In this work, a stack of three GEMs with different pitches has been studied as a possible future approach for ion-backflow suppression to be used in TPCs and other detection concepts. With this approach, an ion backflow of 1 % with an energy resolution of 12 % at 5.9 keV has been achieved with the detector operating in an Ar/CO2 (90/10) mixture at a gain of ~ 2000.Comment: 15 pages, 11 figure

    Matter-wave 2D solitons in crossed linear and nonlinear optical lattices

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    It is demonstrated the existence of multidimensional matter-wave solitons in a crossed optical lattice (OL) with linear OL in the xx-direction and nonlinear OL (NOL) in the yy-direction, where the NOL can be generated by a periodic spatial modulation of the scattering length using an optically induced Feshbach resonance. In particular, we show that such crossed linear and nonlinear OL allows to stabilize two-dimensional (2D) solitons against decay or collapse for both attractive and repulsive interactions. The solutions for the soliton stability are investigated analytically, by using a multi-Gaussian variational approach (VA), with the Vakhitov-Kolokolov (VK) necessary criterion for stability; and numerically, by using the relaxation method and direct numerical time integrations of the Gross-Pitaevskii equation (GPE). Very good agreement of the results corresponding to both treatments is observed.Comment: 8 pages (two-column format), with 16 eps-files of 4 figure

    The Relation between the Radial Temperature Profile in the Chromosphere and the Solar Spectrum at Centimeter, Millimeter, Sub-millimeter, and Infrared Wavelengths

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    Solar observations from millimeter to ultraviolet wavelengths show that there is a temperature minimum between photosphere and chromosphere. Analysis based on semi-empirical models locate this point at about 500 km over the photosphere. The consistency of these models has been tested by means of millimeter to infrared observations. In the present work, we show that variations of the theoretical radial temperature profile near the temperature minimum impacts the brightness temperature at centimeter, submillimeter, and infrared wavelengths, but the millimeter wavelength emission remains unchanged. We found a region between 500 and 1000 km over the photosphere that remains hidden to observations at the frequencies under study in this work.Comment: Accepted in Solar Physic

    Women cotton farmers: Their perceptions and experiences with transgenic varieties: A case study for Colombia

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    This paper explores gender differences in cotton cultivation and looks into the perceptions and experiences of women and men with transgenic varieties. With few exceptions, researchers in the area of impact evaluation of crop biotechnology have only marginally included gender considerations in their work. This exploratory pilot study was developed in order to incorporate gender into our quantitative evaluation work. This study used a participatory and descriptive approach that allowed us to listen to women and men farmers' perceptions and insights. The project was conducted in the main cotton-producing regions of Colombia where a handful of transgenic varieties have been in the market for the past six years.crop biotechnology, Genetically modified crops, Genetic engineering, Cotton, Gender,

    Human case of West Nile neuroinvasive disease in Portugal, summer 2015

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    A case of West Nile virus (WNV) infection was reported in the Algarve region, Portugal, in the first week of September 2015. WNV is known to circulate in Portugal, with occasional reports in horses and birds (2004 to 2011) and very sporadically human cases (in 2004 and in 2010). Here we present the clinical and laboratory aspects related to the first human case of West Nile neuroinvasive disease reported in Portugal

    Impaired regeneration of dystrophin-deficient muscle fibers is caused by exhaustion of myogenic cells

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    Duchenne muscular dystrophy is one of the most devastating myopathies. Muscle fibers undergo necrosis and lose their ability to regenerate, and this may be related to increased interstitial fibrosis or the exhaustion of satellite cells. In this study, we used mdx mice, an animal model of Duchenne muscular dystrophy, to assess whether muscle fibers lose their ability to regenerate after repeated cycles of degeneration-regeneration and to establish the role of interstitial fibrosis or exhaustion of satellite cells in this process. Repeated degenerative-regenerative cycles were induced by the injection of bupivacaine (33 mg/kg), a myotoxic agent. Bupivacaine was injected weekly into the right tibialis anterior muscle of male, 8-week-old mdx (N = 20) and C57Bl/10 (control, N = 10) mice for 20 and 50 weeks. Three weeks after the last injection, the mice were killed and the proportion of regenerated fibers was counted and reported as a fibrosis index. Twenty weekly bupivacaine injections did not change the ability of mdx muscle to regenerate. However, after 50 weekly bupivacaine injections, there was a significant decrease in the regenerative response. There was no correlation between the inability to regenerate and the increase in interstitial fibrosis. These results show that after prolonged repeated cycles of degeneration-regeneration, mdx muscle loses its ability to regenerate because of the exhaustion of satellite cells, rather than because of an increase in interstitial fibrosis. This finding may be relevant to cell and gene therapy in the treatment of Duchenne muscular dystrophy.69169

    The CGM and IGM at z\sim5: metal budget and physical connection

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    We present further results of a survey for absorption line systems in the spectra of four high redshift quasars (5.79 \le zem_{\textrm{em}} \le 6.13) obtained with the ESO Very Large Telescope X-Shooter. We identify 36 CIV\textrm{CIV} and 7 SiIV\textrm{SiIV} systems with a \ge 5σ\sigma significance. The highest redshift CIV\textrm{CIV} and SiIV\textrm{SiIV} absorbers identified in this work are at z = 5.80738 ±\pm 0.00017 and z = 5.77495 ±\pm 0.00038, respectively. We compute the comoving mass density of SiIV\textrm{SiIV} (ΩSiIV\Omega_{\textrm{SiIV}}) and find that it evolves from ΩSiIV\Omega_{\textrm{SiIV}} = 4.32.1+2.1^{+2.1}_{-2.1} ×\times109^{-9} at = 5.05 to ΩSiIV\Omega_{\textrm{SiIV}} = 1.40.4+0.6^{+0.6}_{-0.4} ×\times109^{-9} at = 5.66. We also measure ΩCIV\Omega_{\textrm{CIV}} = 1.60.1+0.4^{+0.4}_{-0.1} ×\times108^{-8} at = 4.77 and ΩCIV\Omega_{\textrm{CIV}} = 3.41.1+1.6^{+1.6}_{-1.1} ×\times109^{-9} at = 5.66. We classify our CIV\textrm{CIV} absorber population by the presence of associated low\textit{low} and/or high ionisation\textit{high ionisation} systems and compute their velocity width (Δ\Deltav90_{90}). We find that all CIV\textrm{CIV} systems with Δ\Deltav90_{90} > 200 kms1^{-1} have associated low ionisation\textit{low ionisation} systems. We investigate two such systems, separated by 550 physical kpc along a line of sight, and find it likely that they are both tracing a multi-phase medium where hot and cold gas is mixing at the interface between the CGM and IGM. We further discuss the \textrm{MgII} systems presented in a previous work and we identify 5 SiII\textrm{SiII}, 10 AlII\textrm{AlII}, 12 FeII\textrm{FeII}, 1 CII\textrm{CII}, 7 MgI\textrm{MgI} and 1 CaII\textrm{CaII} associated transitions. We compute the respective comoving mass densities in the redshift range 2 to 6, as allowed by the wavelength coverage.Comment: Accepted for publication in MNRAS 22 pages, 19 figures, 6 table

    CORG: a database for COmparative Regulatory Genomics

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    Sequence conservation in non-coding, upstream regions of orthologous genes from man and mouse is likely to reflect common regulatory DNA sites. Motivated by this assumption we have delineated a catalogue of conserved non-coding sequence blocks and provide the CORG-'COmparative Regulatory Genomics'-database. The data were computed based on statistically significant local suboptimal alignments of 15 kb regions upstream of the translation start sites of, currently, 10 793 pairs of orthologous genes. The resulting conserved non-coding blocks were annotated with EST matches for easier detection of non-coding mRNA and with hits to known transcription factor binding sites. CORG data are accessible from the ENSEMBL web site via a DAS service as well as a specially developed web service (http://corg.molgen.mpg.de) for query and interactive visualization of the conserved blocks and their annotation
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