361 research outputs found
Studies of distant clusters of galaxies
No full textA technique of constructing crude, low-resolution Spectral Energy Distributions (SEDs) for galaxies in distant clusters, using a set of intermediate bandwidth filters and a CCD detector, is developed which is capable of redressing many of the problems which have previously beset work in this field. The technique has been used to study galaxies in the distant clusters 0016+16 (z = 0.54) and Abell 370 (z = 0.37).These SEDs are then used to individually classify each object in the CCD field, ascribing both an estimated redshift and a galaxy type. The SEDs have been extended into the rest-frame ultraviolet (~ 270 nm) by imaging high redshift galaxies in blue passbands. Monitoring the behaviour of the Colour-Magnitude effect in the optical and -ultraviolet (uv) regions, indicates the presence of a new class of object which exhibits excess emission in the uv whilst having optical colours similar to nearby E/SO galaxies. The significance of this uv-excess is addressed by examining the available uv spectroscopy of nearby early-type galaxies obtained from observations carried out on the International Ul traviolet Explorer satellite. This study, in conjunction with a series of crude evolutionary models, leads to the conclusion that the uv-excess is most likely a manifestation of evolutionary differences in the spectral properties of galaxies at high redshifts, resulting from increased levels of star formation. Having developed such methods for using distant clusters of galaxies as evolutionary probes, a catalogue of candidate distant clusters is constructed from high contrast copies of deep 4m photographic plates. Finally, a series of possible future observations bcised on such a resource, combining a wide range of techniques, is outlined
Research Priorities for the Conservation and Sustainable Governance of Andean Forest Landscapes
No full textThe long-term survival of Andean forest landscapes (AFL) and of their capacity to contribute to sustainable development in a context of global change requires integrated adaptation and mitigation responses informed by a thorough understanding of the dynamic and complex interactions between their ecological and social components. This article proposes a research agenda that can help guide AFL research efforts for the next 15 years. The agenda was developed between July 2015 and June 2016 through a series of workshops in Ecuador, Peru, and Switzerland and involved 48 researchers and development experts working on AFL from different disciplinary perspectives. Based on our review of current research and identification of pressing challenges for the conservation and sustainable governance of AFL, we propose a conceptual framework that draws on sustainability sciences and social–ecological systems research, and we identify a set of high-priority research goals and objectives organized into 3 broad categories: systems knowledge, target knowledge, and transformation knowledge. This paper is intended to be a reference for a broad array of actors engaged in policy, research, and implementation in the Andean region. We hope it will trigger collaborative research initiatives for the continued conservation and sustainable governance of AFL
Dynamics and modulation of human immunodeficiency virus type 1 transcripts in vitro and in vivo
No full textReductions in viral load and increases in T lymphocyte numbers in treatment-naive patients with advanced HIV-1 infection treated with ritonavir, zidovudine and zalcitabine triple therapy.
No full textDynamics and modulation of human immunodeficiency virus type 1 transcripts in vitro and in vivo
No full textThe dynamics of human immunodeficiency virus type 1 (HIV-1) transcription was analyzed in vitro and in vivo by using a specific molecular approach which allows accurate quantitation of the different classes of viral mRNAs. Unspliced (US) and multiply spliced (MS) HIV-1 transcripts were assayed by competitive reverse transcription (cRT)-PCR, using a single competitor RNA bearing in tandem internally deleted sequences of both template species. Acute HIV-1 infection of primary peripheral blood mononuclear cells (PBMCs), monocytes/macrophages cells, and the A3.01 T-lymphocyte-derived cell line was studied; both classes of HIV-1 mRNAs increased exponentially (tau(2) > 0.98) at days 1 to 3 and 1 to 4 postinfection in HIVIIIB-infected A3.01 cells and PBMCs, respectively, whereas monocytes/macrophages infected with monocytotropic HIVBaL exhibited a linear (tau(2) = 0.81 to 0.94) accumulation of US and MS transcripts. Following induction of chronically infected ACH-2 cells, MS transcripts increased 2 h postinduction and peaked at 5 h (doubling time, 58 min), while at 24 h, US mRNAs increased 3,053-fold compared with basal time (doubling time, 137 min). To address the biopathological significance of HIV-1 expression pattern during infection progression, pilot cross-sectional and longitudinal analyses were carried out with samples from untreated and treated HIV-1-infected patients. In almost all untreated (recently infected, long-term nonprogressor, and progressor) patients, MS transcript levels followed the general trend of systemic HIV-1 activity. In patients under treatment with powerful antiretroviral compounds, viral MS transcripts rapidly fell to undetectable levels, indicating that in vivo, levels of RIS mRNAs in PBMCs are closely associated with the number of newly infected cells and suggesting a new role for the quantitative analysis of HIV-1 transcription in infected patients
L\u27Epithète et la Connivence. Ecriture concertée chez les Evangéliques français (1523-1534)
No full textMaximum power point tracking under realistic operating conditions
No full textThe process of tracking the Maximum Power Point (MPP), known as MPPT, becomes problematic under realistic operating conditions due to the potential for there to be more than one local maxima. A very detailed physics based model has been developed for a PV module (in this application a PV roof tile) using the Orcad platform for PSpice. This model is unusual in that it properly represents partial module shading and cell temperature variation. The PV roof tile, based on polycrystalline silicon cells, comprises 18 series-connected cells. In the model, each cell is represented by a standard two-diode sub-model, for which different levels of radiation and cell temperature can be simulated to obtain a realistic overall I-V characteristic for the module. The model can be extended to model any reasonable number of PV roof tiles wired in series and parallel to form a roof array. The IV characteristics calculated in this way using PSpice will be validated using an outdoor PV roof test system located at the University of Strathclyde, Glasgow
Experimental study of high-Ti and low-Ti basalts: liquid lines of descent and silicate liquid immiscibility in large igneous provinces
No full textsponsorship: We thank J. Berndt and T. D. van Gerve for assistance with microprobe analyses. R. Dennen is thanked for his help in editing the manuscript. We thank Othmar Muentener for editorial handling, Felix Marxer and Edmond Mathez for constructive reviews. The figures in this publication were produced using the Matplotlib python library and Adobe Illustrator. YZ was supported by an ERC Runner-up FWO grant to ON. ON acknowledges support from the KU Leuven through a KU Leuven Starting Grant and a FWO Odysseus project. BC is a Research Associate of the Belgian Fund for Scientific Research-FNRS. (ERC Runner-up FWO, KU Leuven, FWO Odysseus project)status: Published onlin
A review of the literature on the relationships between trees, land use, and hydrological processes in the Andes
No full textIn the Andean region, interest is growing in the use of trees to restore degraded areas through afforestation, reforestation or agroforestry. In addition to the economic benefits that these interventions can generate, particularly in the case of commercial plantations with exotic trees, one of the main arguments used to support these actions has been their purportedly positive effects on the recovery of the water provision and regulation functions of ecosystems. However, the relationship between tree cover and water is complex and may have positive or negative effects on the ecological functions of watersheds, depending on diverse factors. In this study, we compiled and synthetized the literature on the relationships between woody plants, land use and hydrologic processes in the Andes. The results showed that there is very limited and fragmented knowledge, with significant gaps in specific areas. While most studies focus on native forests and on agricultural land uses, there is very little research on paramos (Andean moorlands) or on agroforestry, the latter limited to coffee agroforestry. Furthermore, the results from different studies are often not comparable and are sometimes contradictory because of varying research design and methods.
Our qualitative review highlighted the importance of montane cloud forests in water provision, in particular through the interception of horizontal precipitation. In addition, native forests play an important role in water regulation in comparison with crop and pasture lands, as they reduce runoff and store more water. Our results also showed that paramos provide higher water regulation than forested areas with exotic species and other land covers by maintaining base flows. Plantations with exotic taxa, such as pines and eucalypts, provide overall lower water provision than other land uses. However, their effect on water regulation defies simple comparisons with other uses: they have lower base flow and higher peak flow than other uses, and lower infiltration and water storage than forests and paramos, but perform better in these respects than natural pastures. The reviewed studies indicated that water provisioning from coffee agroforestry systems is lower than in coffee systems without shade, but that these levels vary according to the tree species. The tree species, and in particular the management practices, influence the water regulatory role of coffee agroforestry systems with shade as compared to systems without shade: while run-off is higher in systems with exotic taxa (e.g. pine, eucalypts), the level of infiltration varies according to management and leaf characteristics. Even though there remain important knowledge gaps on the role of forests and trees in the hydrology of Andean watersheds, especially regarding the combined impacts of land use and land cover change, our review results can help inform degraded land restoration practices and policies in the Andean region
Perfectionnement de la méthode de détection de la Fumonisine B1 dans le plasma chez le canard
No full textLa Fumonisine B1 est une mycotoxine potentiellement carcinogène pour l homme. Le but de cet essai est de déterminer la plus petite quantité de FB1 détectable dans le plasma de canard après administration orale. 25 canetons mulards ont reçu par voie orale des doses de FB1 de 0 à 80 mg par kg de poids vif. Leur sang a été collecté 90 minutes après administration. La FB1 a été déterminée par HPLC et fluorométrie, après purification sur colonnes échangeuses d ions. Cette méthode de purification a été sélectionnée parmi plusieurs méthodes. Les résultats obtenus révèlent une limite de détection de 0,11mg/l. Ces concentrations sont atteintes pour une administration orale de 5mg/kg. Néanmoins, la comparaison statistique (ANOVA, p<0,05) des animaux exposés aux témoins révèle une différence significative dès la dose de 0,3 mg/kg.TOULOUSE3-BU Santé-Centrale (315552105) / SudocTOULOUSE-EN Vétérinaire (315552301) / SudocSudocFranceF
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