2,470 research outputs found
L'agriculture d'oasis. Bibliographie
La compréhension de l'agriculture oasienne, forme d'occupation et d'exploitation des zones arides, nécessite une approche globale. Cette bibliographie présente 312 références concernant : les déserts et les zones arides qui permettent de restituer l'oasis dans son environnnement; les thèmes tels que micro-climat, salinité, érosion, eau, pastoralisme, marché de la datte; les aspects non agricoles tels qu'histoire, faune, artisanat; les cultures oasiennes, le palmier dattier, mais aussi son environnement et les cultures qui l'accompagnen
Decreased MCM2-6 in Drosophila S2 cells does not generate significant DNA damage or cause a marked increase in sensitivity to replication interference.
A reduction in the level of some MCM proteins in human cancer cells (MCM5 in U20S cells or MCM3 in Hela cells) causes a rapid increase in the level of DNA damage under normal conditions of cell proliferation and a loss of viability when the cells are subjected to replication interference. Here we show that Drosophila S2 cells do not appear to show the same degree of sensitivity to MCM2-6 reduction. Under normal cell growth conditions a reduction of >95% in the levels of MCM3, 5, and 6 causes no significant short term alteration in the parameters of DNA replication or increase in DNA damage. MCM depleted cells challenged with HU do show a decrease in the density of replication forks compared to cells with normal levels of MCM proteins, but this produces no consistent change in the levels of DNA damage observed. In contrast a comparable reduction of MCM7 levels has marked effects on viability, replication parameters and DNA damage in the absence of HU treatment
Magnetic states and spin-glass properties in Bi0.67Ca0.33MnO3: macroscopic ac measurements and neutron scattering
We report on the magnetic properties of the manganite Bi_{1-x}Ca_{x}MnO_3
(x=0.33) at low temperature. The analysis of the field expansion of the ac
susceptibility and the observation of aging properties make clear that a spin
glass phase appears below T = 39K, in the presence of magnetic order. Neutron
scattering shows both magnetic Bragg scattering and magnetic diffusion at small
angles, and confirms this coexistence. In contrast to Pr_{1-x}Ca_{x}MnO_3
(x=0.3-0.33) which exhibits a mesoscopic phase separation responsible for a
field driven percolation, the glassy and short range ferromagnetic order
observed here does not cause colossal magnetoresistance (CMR).Comment: accepted in Phys Rev
Compounds binding to the bacterial beta ring
The present invention relates to compounds which bind to the hydrophobic pocket of the B clamp, i.e., to the surface of the
Bring with which said protein interacts with other proteins of the bacterial replication complex during DNA replication.
These compounds are derived from the acetylated peptide AcOLDLF (P6) to improve their affinity to their target
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High-resolution quantitative imaging of mammalian and bacterial cells using stable isotope mass spectrometry
Background: Secondary-ion mass spectrometry (SIMS) is an important tool for investigating isotopic composition in the chemical and materials sciences, but its use in biology has been limited by technical considerations. Multi-isotope imaging mass spectrometry (MIMS), which combines a new generation of SIMS instrument with sophisticated ion optics, labeling with stable isotopes, and quantitative image-analysis software, was developed to study biological materials. Results: The new instrument allows the production of mass images of high lateral resolution (down to 33 nm), as well as the counting or imaging of several isotopes simultaneously. As MIMS can distinguish between ions of very similar mass, such as ^{12}C^{15}N^{-} and ^{13}C^{14}N^{-}, it enables the precise and reproducible measurement of isotope ratios, and thus of the levels of enrichment in specific isotopic labels, within volumes of less than a cubic micrometer. The sensitivity of MIMS is at least 1,000 times that of ^{14}C autoradiography. The depth resolution can be smaller than 1 nm because only a few atomic layers are needed to create an atomic mass image. We illustrate the use of MIMS to image unlabeled mammalian cultured cells and tissue sections; to analyze fatty-acid transport in adipocyte lipid droplets using ^{13}C-oleic acid; to examine nitrogen fixation in bacteria using ^{15}N gaseous nitrogen; to measure levels of protein renewal in the cochlea and in post-ischemic kidney cells using ^{15}N-leucine; to study DNA and RNA co-distribution and uridine incorporation in the nucleolus using ^{15}N-uridine and ^{81}Br of bromodeoxyuridine or ^{14}C-thymidine; to reveal domains in cultured endothelial cells using the native isotopes ^{12}C, ^{16}O, ^{14}N and ^{31}P; and to track a few ^{15}N-labeled donor spleen cells in the lymph nodes of the host mouse. Conclusion: MIMS makes it possible for the first time to both image and quantify molecules labeled with stable or radioactive isotopes within subcellular compartments
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
Characterization and Expression of Glutamate Dehydrogenase in Response to Acute Salinity Stress in the Chinese Mitten Crab, Eriocheir sinensis
Glutamate dehydrogenase (GDH) is a key enzyme for the synthesis and catabolism of glutamic acid, proline and alanine, which are important osmolytes in aquatic animals. However, the response of GDH gene expression to salinity alterations has not yet been determined in macro-crustacean species.GDH cDNA was isolated from Eriocheir sinensis. Then, GDH gene expression was analyzed in different tissues from normal crabs and the muscle of crabs following transfer from freshwater (control) directly to water with salinities of 16‰ and 30‰, respectively. Full-length GDH cDNA is 2,349 bp, consisting of a 76 bp 5'- untranslated region, a 1,695 bp open reading frame encoding 564 amino acids and a 578 bp 3'- untranslated region. E. sinensis GDH showed 64-90% identity with protein sequences of mammalian and crustacean species. Muscle was the dominant expression source among all tissues tested. Compared with the control, GDH expression significantly increased at 6 h in crabs transferred to 16‰ and 30‰ salinity, and GDH expression peaked at 48 h and 12 h, respectively, with levels approximately 7.9 and 8.5 fold higher than the control. The free amino acid (FAA) changes in muscle, under acute salinity stress (16‰ and 30‰ salinities), correlated with GDH expression levels. Total FAA content in the muscle, which was based on specific changes in arginine, proline, glycine, alanine, taurine, serine and glutamic acid, tended to increase in crabs following transfer to salt water. Among these, arginine, proline and alanine increased significantly during salinity acclimation and accounted for the highest proportion of total FAA.E. sinensis GDH is a conserved protein that serves important functions in controlling osmoregulation. We observed that higher GDH expression after ambient salinity increase led to higher FAA metabolism, especially the synthesis of glutamic acid, which increased the synthesis of proline and alanine to meet the demand of osmoregulation at hyperosmotic conditions
Predicting survival after pulmonary metastasectomy for colorectal cancer: previous liver metastases matter
BACKGROUND: Few patients with lung metastases from colorectal cancer (CRC) are candidates for surgical therapy with a curative intent, and it is currently impossible to identify those who may benefit the most from thoracotomy. The aim of this study was to determine the impact of various parameters on survival after pulmonary metastasectomy for CRC. METHODS: We performed a retrospective analysis of 40 consecutive patients (median age 63.5 [range 33-82] years) who underwent resection of pulmonary metastases from CRC in our institution from 1996 to 2009. RESULTS: Median follow-up was 33 (range 4-139) months. Twenty-four (60%) patients did not have previous liver metastases before undergoing lung surgery. Median disease-free interval between primary colorectal tumor and development of lung metastases was 32.5 months. 3- and 5-year overall survival after thoracotomy was 70.1% and 43.4%, respectively. In multivariate analysis, the following parameters were correlated with tumor recurrence after thoracotomy; a history of previous liver metastases (HR = 3.8, 95%CI 1.4-9.8); and lung surgery other than wedge resection (HR = 3.0, 95%CI 1.1-7.8). Prior resection of liver metastases was also correlated with an increased risk of death (HR = 5.1, 95% CI 1.1-24.8, p = 0.04). Median survival after thoracotomy was 87 (range 34-139) months in the group of patients without liver metastases versus 40 (range 28-51) months in patients who had undergone prior hepatectomy (p = 0.09). CONCLUSION: The main parameter associated with poor outcome after lung resection of CRC metastases is a history of liver metastases
From Late Miocene to Holocene: Processes of Differentiation within the Telestes Genus (Actinopterygii: Cyprinidae)
Investigating processes and timing of differentiation of organisms is critical in the understanding of the evolutionary mechanisms involved in microevolution, speciation, and macroevolution that generated the extant biodiversity. From this perspective, the Telestes genus is of special interest: the Telestes species have a wide distribution range across Europe (from the Danubian district to Mediterranean districts) and have not been prone to translocation. Molecular data (mtDNA: 1,232 bp including the entire Cyt b gene; nuclear genome: 11 microsatellites) were gathered from 34 populations of the Telestes genus, almost encompassing the entire geographic range. Using several phylogenetic and molecular dating methods interpreted in conjunction with paleoclimatic and geomorphologic evidence, we investigated the processes and timing of differentiation of the Telestes lineages. The observed genetic structure and diversity were largely congruent between mtDNA and microsatellites. The Messinian Salinity Crisis (Late Miocene) seems to have played a major role in the speciation processes of the genus. Focusing on T. souffia, a species occurring in the Danube and Rhone drainages, we were able to point out several specific events from the Pleistocene to the Holocene that have likely driven the differentiation and the historical demography of this taxon. This study provides support for an evolutionary history of dispersal and vicariance with unprecedented resolution for any freshwater fish in this region
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