438 research outputs found
A Gaia DR 2 and VLT/FLAMES search for new satellites of the LMC
A wealth of tiny galaxies populates the surroundings of the Milky Way. Some
of these objects might have their origin as former satellites of the Large
Magellanic Cloud. Examples of the importance of understanding how many systems
are genuine satellites of the MW or the LMC are the implications that the
number and mass function of satellites have for dark matter theories and the
treatment of baryonic physics in simulations of structure formation. Here we
aim at deriving the bulk motions and estimates of the internal velocity
dispersion and metallicity properties in four recently discovered distant
southern dwarf galaxy candidates, Columba I, Reticulum III, Phoenix II and
Horologium II. We combine Gaia DR2 astrometric measurements, photometry and new
FLAMES spectroscopic data in the region of the CaII triplet lines; such
combination is essential for finding potential member stars in these low
luminosity systems. We find very likely member stars in all four satellites and
are able to determine (or place limits on) the systems bulk motions and average
internal properties. The systems are found to be very metal-poor, in agreement
with dwarf galaxies and dwarf galaxy candidates of similar luminosity. The only
system that we can place firmly in the category of dwarf galaxies is Phx II,
given its resolved large velocity dispersion ( km/s) and
intrinsic metallicity spread (0.33 dex). Also for Col I we measure a clear
metallicity spread. The orbital pole of Phx II is well constrained and close to
that of the LMC, suggesting a prior association. The uncertainty on the orbital
poles of the other systems are presently very large, so that an association
cannot be excluded, apart from Col I. Using the numbers of potential former
satellites of the LMC identified here and in the literature, we obtain for the
LMC a dark matter mass of M M.Comment: 16 pages, 11 figures, 4 tables, accepted for publication in A&
Drought effects on buds growth and dynamic of Tunisian cork oak populations
Forest species have adapted to their local climate by changing some of their phenological characteristics. Differential phenological responses may modify tree chance of survival by altering the competitive balance between them. The study of key phenological stages (budding, budburst, flowering, falling leaves ...) knew a renewed interest these last years for climate changes consequences researches. Characterizing the phenological variability response, of five Tunisian cork oak populations from contrasting climatic situations, in front to water deficit, has been the subject of this study. Large differences between populations from highest and coldest sites as well as those of lowest and warm sites were detected and adaptative responses specific to some populations were founded
Study of seasonal sexual activity variations in Algerian rams: Sexual behaviour, testosterone concentration control and environmental factors
This study focuses on the determination of seasonal effect on two main andrological sexual activity parameters within young and adults rams of Rembi breed from Algeria for a period of one year. The experiment involved a weekly evaluation of malesâ sexual behaviour and a monthly measurement of serum testosterone concentration in order to know the main testicular endocrine activity. The purpose of this experiment was to assess better the characteristics of the reproductive activity between two categories of rams age-wise and to define the variations and interactions between the two parameters during each season. Data shows no statistically significant effect of age on the testosterone concentration but showed a highly significant difference between age groups in terms of sexual behaviour. Seasonal variations of the studied parameters were statistically significant in both ram ages with higher values during spring and autumn and lower values during summer and winter.Keywords: Rembi, ram, testosterone, sexual activity, season, age.African Journal of Biotechnology Vol. 12(41), pp. 6042-604
Development of a Conditional Mesd (Mesoderm Development) Allele for Functional Analysis of the Low-Density Lipoprotein Receptor-Related Family in Defined Tissues
The Low-density lipoprotein receptor-Related Protein (LRP) family members are essential for diverse processes ranging from the regulation of gastrulation to the modulation of lipid homeostasis. Receptors in this family bind and internalize a diverse array of ligands in the extracellular matrix (ECM). As a consequence, LRPs regulate a wide variety of cellular functions including, but not limited to lipid metabolism, membrane composition, cell motility, and cell signaling. Not surprisingly, mutations in single human LRPs are associated with defects in cholesterol metabolism and development of atherosclerosis, abnormalities in bone density, or aberrant eye vasculature, and may be a contributing factor in development of Alzheimerâs disease. Often, members of this diverse family of receptors perform overlapping roles in the same tissues, complicating the analysis of their function through conventional targeted mutagenesis. Here, we describe development of a mouse Mesd (Mesoderm Development) conditional knockout allele, and demonstrate that ubiquitous deletion of Mesdusing Cre-recombinase blocks gastrulation, as observed in the traditional knockout and albino-deletion phenotypes. This conditional allele will serve as an excellent tool for future characterization of the cumulative contribution of LRP members in defined tissues
Virulence of Moroccan f. Revealed by International Differential Barley Genotypes
Pyrenophora teres f. teres (Ptt), causing net blotch in barley, is an important and frequently isolated leaf pathogen across the globe. The virulence spectrum of Ptt from North Africa including Morocco is poorly understood. Sixteen barley genotypes were challenged, at seedling stage, with 15 Ptt isolates that were collected from different agroecological zones of Morocco. The experiment was conducted in a factorial arrangement of treatments in a randomized complete block design with three replicates. The ANOVA revealed highly significant (P < 0.001) effects of genotype (G), isolate (I) and GĂI interaction explaining 23.2, 62.5, and 13.9% of the variation, respectively. Therefore, the current study revealed highly diverse virulence pattern of Moroccan isolates. Furthermore, the results indicated that minor virulence of Ptt isolates dominated over virulence interaction. In addition, Taffa (6-rowed) and Aglou (2 rowed), had the highest level of resistance to Ptt, while Coast and Rabat071 were the most susceptible genotypes. Pt2, Pt7, Pt8 and Pt4 were being the most virulent isolates, while Pt10 and Pt11 were the least virulent isolates. The emergence of the new Ptt pathotypes, which were highly virulent to durable resistance in Rabat071 posed a risk of breaking down the currently deployed resistance to net blotch in Morocco. A careful evaluation and selection of Ptt isolates based on minor virulence pattern to barley genotypes is essential for successful barley breeding program for resistance to net blotch in Morocco
Size Matters: Microservices Research and Applications
In this chapter we offer an overview of microservices providing the
introductory information that a reader should know before continuing reading
this book. We introduce the idea of microservices and we discuss some of the
current research challenges and real-life software applications where the
microservice paradigm play a key role. We have identified a set of areas where
both researcher and developer can propose new ideas and technical solutions.Comment: arXiv admin note: text overlap with arXiv:1706.0735
Ăcoulements pulsĂ©s Ă deux phases en conduites dĂ©formables et poreuses Ă parois Ă©lastiques et anisotropes: Application Ă la microcirculation sanguine
Lâobjet du prĂ©sent travail consiste en la modĂ©lisation numĂ©rique dâĂ©coulements du sang considĂ©rĂ© comme un fluide Ă deux phases (fluide newtonien-fluide de Casson gĂ©nĂ©ralisĂ©) en rĂ©gime pulsĂ©, dans une conduite dĂ©formable. Une telle modĂ©lisation tient compte, en plus du caractĂšre non newtonien du fluide, du dĂ©placement axial et radial de la paroi, de sa porositĂ© et de lâanisotropie. En utilisant une mĂ©thode numĂ©rique aux diffĂ©rences finies implicites pour rĂ©soudre les systĂšmes des Ă©quations locales, intĂ©grales et le systĂšme des Ă©quations de la paroi, les quantitĂ©s locales et globales de lâĂ©coulement ont Ă©tĂ© dĂ©terminĂ©es
Image quality comparison between a phase-contrast synchrotron radiation breast CT and a clinical breast CT: a phantom based study
In this study we compared the image quality of a synchrotron radiation (SR) breast computed tomography (BCT) system with a clinical BCT in terms of contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), noise power spectrum (NPS), spatial resolution and detail visibility. A breast phantom consisting of several slabs of breast-adipose equivalent material with different embedded targets (i.e., masses, fibers and calcifications) was used. Phantom images were acquired using a dedicated BCT system installed at the Radboud University Medical Center (Nijmegen, The Netherlands) and the SR BCT system at the SYRMEP beamline of Elettra SR facility (Trieste, Italy) based on a photon-counting detector. Images with the SR setup were acquired mimicking the clinical BCT conditions (i.e., energy of 30 keV and radiation dose of 6.5 mGy). Images were reconstructed with an isotropic cubic voxel of 273 ”m for the clinical BCT, while for the SR setup two phase-retrieval (PhR) kernels (referred to as âsmoothâ and âsharpâ) were alternatively applied to each projection before tomographic reconstruction, with voxel size of 57 Ă 57 Ă 50 ”m3. The CNR for the clinical BCT system can be up to 2-times higher than SR system, while the SNR can be 3-times lower than SR system, when the smooth PhR is used. The peak frequency of the NPS for the SR BCT is 2 to 4-times higher (0.9 mmâ1 and 1.4 mmâ1 with smooth and sharp PhR, respectively) than the clinical BCT (0.4 mmâ1). The spatial resolution (MTF10%) was estimated to be 1.3 lp/mm for the clinical BCT, and 5.0 lp/mm and 6.7 lp/mm for the SR BCT with the smooth and sharp PhR, respectively. The smallest fiber visible in the SR BCT has a diameter of 0.15 mm, while for the clinical BCT is 0.41 mm. Calcification clusters with diameter of 0.13 mm are visible in the SR BCT, while the smallest diameter for the clinical BCT is 0.29 mm. As expected, the image quality of the SR BCT outperforms the clinical BCT system, providing images with higher spatial resolution and SNR, and with finer granularity. Nevertheless, this study assesses the image quality gap quantitatively, giving indications on the benefits associated with SR BCT and providing a benchmarking basis for its clinical implementation. In addition, SR-based studies can provide a gold-standard in terms of achievable image quality, constituting an upper-limit to the potential clinical development of a given technique
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