2,620 research outputs found

    First observation of electric-quadrupole infrared transitions in water vapour

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    Molecular absorption of infrared radiation is generally due to ro-vibrational electric-dipole transitions. Electric-quadrupole transitions may still occur, but they are typically a million times weaker than electric-dipole transitions, rendering their observation extremely challenging. In polyatomic or polar diatomic molecules, ro-vibrational quadrupole transitions have never been observed. Here, we report the first direct detection of quadrupole transitions in water vapor. The detected quadrupole lines have intensity largely above the standard dipole intensity cut-off of spectroscopic databases and thus are important for accurate atmospheric and astronomical remote sensing

    High sensitivity Cavity Ring Down spectroscopy of 18O enriched carbon dioxide between 5850 and 7000 cm-1: Part III-Analysis and theoretical modeling of the 12C17O2, 16O12C17O, 17O12C18O, 16O13C17O and 17O13C18O spectra

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    More than 19,700 transitions belonging to 11 isotopologues of carbon dioxide have been assigned in the room temperature absorption spectrum of highly 18O enriched carbon dioxide recorded by very high sensitivity CW-Cavity Ring Down spectroscopy between 5851 and 6990 cm-1 (1.71-1.43 \mum). This third and last report is devoted to the analysis of the bands of five 17O containing isotopologues present at very low concentration in the studied spectra: 16O12C17O, 17O12C18O, 16O13C17O, 17O13C18O and 12C17O2 (627, 728, 637, 738 and 727 in short hand notation). On the basis of the predictions of effective Hamiltonian models, a total of 1759, 1786, 335, 273 and 551 transitions belonging to 24, 24, 5, 4 and 7 bands were rovibrationally assigned for 627, 728, 637, 738 and 727, respectively. For comparison, only five bands were previously measured in the region for the 728 species. All the identified bands belong to the \deltaP=8 and 9 series of transitions, where P=2V1+V2+3V3 is the polyad number (Vi are vibrational quantum numbers). The band-by-band analysis has allowed deriving accurate spectroscopic parameters of 61 bands from a fit of the measured line positions. Two interpolyad resonance perturbations were identified

    Orexin-A exerts equivocal role in atherosclerosis process depending on the duration of exposure : in vitro study

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    Orexin-A is a peptide hormone that plays a crucial role in feeding regulation and energy homeostasis. Diurnal intermittent fasting (DIF) has been found to increase orexin-A plasma levels during fasting hours, while Ramadan fasting which resembles DIF, has led to beneficial effects on endothelial function. Herein, we aimed to investigate the effects of orexin-A on the expression of molecules involved in the atherogenesis process: Monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) and tissue inhibitor of metalloproteinase-1 and 2 (TIMP-1 and TIMP-2), in human aortic endothelial cells (HAECs). HAECs were incubated with orexin-A at concentrations of 40 ng/mL, 200 ng/mL and 400 ng/mL for 6, 12 and 24 h. The mRNA levels of MCP-1, MMP-2, MMP-9, TIMP-1, and TIMP-2 and orexin-1 receptor were measured by real-time qPCR. We also evaluated the MMP-2, p38, phospho-p38, NF-κΒ/p65 as well as TIMP-1 protein levels by Western blot and ELISA, respectively. MMP-2 activity was measured by gelatin zymography. Short-term 6-h incubation of HAECs with orexin-A at a high concentration (400 ng/mL) decreased MCP-1, MMP-2 expression, MMP-2/TIMP-1 ratio (p < 0.05), and MMP-2 activity, while incubation for 24 h increased MCP-1, MMP-2 expression (p < 0.05), MMP-2/TIMP-1 and MMP-2/TIMP-2 ratio (p < 0.01 and p < 0.05, respectively) as well as MMP-2 activity. The dual effects of orexin-A are mediated, at least in part, via regulation of p38 and NF-κΒ pathway. Orexin-A may have an equivocal role in atherosclerosis process with its effects depending on the duration of exposure

    Pluto's lower atmosphere structure and methane abundance from high-resolution spectroscopy and stellar occultations

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    Context: Pluto possesses a thin atmosphere, primarily composed of nitrogen, in which the detection of methane has been reported. Aims: The goal is to constrain essential but so far unknown parameters of Pluto's atmosphere such as the surface pressure, lower atmosphere thermal stucture, and methane mixing ratio. Methods: We use high-resolution spectroscopic observations of gaseous methane, and a novel analysis of occultation light-curves. Results: We show that (i) Pluto's surface pressure is currently in the 6.5-24 microbar range (ii) the methane mixing ratio is 0.5+/-0.1 %, adequate to explain Pluto's inverted thermal structure and ~100 K upper atmosphere temperature (iii) a troposphere is not required by our data, but if present, it has a depth of at most 17 km, i.e. less than one pressure scale height; in this case methane is supersaturated in most of it. The atmospheric and bulk surface abundance of methane are strikingly similar, a possible consequence of the presence of a CH4-rich top surface layer.Comment: AA vers. 6.1, LaTeX class for Astronomy & Astrophysics, 9 pages with 5 figures Astronomy and Astrophysics Letters, in pres

    L'infection par le VIH chez les femmes en âge de procréer à Sassandra (Côte d'Ivoire)

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    Le travail, réalisé en 1988-1989, a consisté à comparer les caractéristiques socio-démographiques des femmes en âge de procréer (15-49 ans) d'une sous-préfecture rurale de Côte d'Ivoire (Sassandra) avec leur statut sérologique VIH afin de dégager des variables explicatives de cette séropositivité. Il n'a pas été possible de tester que 521 femmes sur les 1084 qui constituaient la population de départ, mais les deux sous-populations ne diffèrent que par les lieux de naissance et de résidence. La séropositivité tréponémique est élevée, de façon homogène. Pour la séropositivité du VIH, le taux global de séropositivité est de 6,1 plus ou moins 0,02 %, soit un taux intermédiaire (différences non significatives) entre ceux trouvés lors de l'enquête nationale en zone rurale (4,9 %) et en zone urbaine (7,3 %). Ce taux de séropositivité est lié au lieu de naissance (même après ajustement sur le taux de présentation); les femmes nées dans la région sont plus souvent positives que les autres et les femmes nées dans les villages plus souvent que celles nées en ville (p = 0,005 et 0,02). En revanche, les femmes mariées sont moins souvent positives que les femmes non mariées et que celles vivant en union libre (p = 0,02 et 0,0005); la polygamie semble apporter une certaine protection envers le VIH par rapport à la monogamie. Enfin les femmes séropositives ont eu plus souvent des enfants mort-nés et moins souvent des enfants décédés que les femmes séronégatives (p = 0,02 et 0,03). Il est proposé de renforcer les activités de surveillance prénatale et de les renforcer surtout en zone rurale pour prévenir de nouvelles infections par le VIH. (Résumé d'auteur
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