92 research outputs found
Magnetism in reduced dimensions
We propose a short overview of a few selected issues of magnetism in reduced
dimensions, which are the most relevant to set the background for more
specialized contributions to the present Special Issue. Magnetic anisotropy in
reduced dimensions is discussed, on a theoretical basis, then with experimental
reports and views from surface to single-atom anisotropy. Then conventional
magnetization states are reviewed, including macrospins, single domains,
multidomains, and domain walls in stripes. Dipolar coupling is examined for
lateral interactions in arrays, and for interlayer interactions in films and
dots. Finally thermally-assisted magnetization reversal and superparamagnetism
are presented. For each topic we sought a balance between well established
knowledge and recent developments.Comment: 13 pages. Part of a Special Issue of the C. R. Physique devoted to
spinelectronics (2005
The Origin and Evolutionary History of HIV-1 Subtype C in Senegal
Background: The classification of HIV-1 strains in subtypes and Circulating Recombinant Forms (CRFs) has helped in tracking the course of the HIV pandemic. In Senegal, which is located at the tip of West Africa, CRF02_AG predominates in the general population and Female Sex Workers (FSWs). In contrast, 40% of Men having Sex with Men (MSM) in Senegal are infected with subtype C. In this study we analyzed the geographical origins and introduction dates of HIV-1 C in Senegal in order to better understand the evolutionary history of this subtype, which predominates today in the MSM population Methodology/Principal Findings: We used a combination of phylogenetic analyses and a Bayesian coalescent-based approach, to study the phylogenetic relationships in pol of 56 subtype C isolates from Senegal with 3,025 subtype C strains that were sampled worldwide. Our analysis shows a significantly well supported cluster which contains all subtype C strains that circulate among MSM in Senegal. The MSM cluster and other strains from Senegal are widely dispersed among the different subclusters of African HIV-1 C strains, suggesting multiple introductions of subtype C in Senegal from many different southern and east African countries. More detailed analyses show that HIV-1 C strains from MSM are more closely related to those from southern Africa. The estimated date of the MRCA of subtype C in the MSM population in Senegal is estimated to be in the early 80's. Conclusions/Significance: Our evolutionary reconstructions suggest that multiple subtype C viruses with a common ancestor originating in the early 1970s entered Senegal. There was only one efficient spread in the MSM population, which most likely resulted from a single introduction, underlining the importance of high-risk behavior in spread of viruses
Genome-enabled insights into the biology of thrips as crop pests
Background
The western flower thrips, Frankliniella occidentalis (Pergande), is a globally invasive pest and plant virus vector on a wide array of food, fiber, and ornamental crops. The underlying genetic mechanisms of the processes governing thrips pest and vector biology, feeding behaviors, ecology, and insecticide resistance are largely unknown. To address this gap, we present the F. occidentalis draft genome assembly and official gene set.
Results
We report on the first genome sequence for any member of the insect order Thysanoptera. Benchmarking Universal Single-Copy Ortholog (BUSCO) assessments of the genome assembly (size = 415.8 Mb, scaffold N50 = 948.9 kb) revealed a relatively complete and well-annotated assembly in comparison to other insect genomes. The genome is unusually GC-rich (50%) compared to other insect genomes to date. The official gene set (OGS v1.0) contains 16,859 genes, of which ~ 10% were manually verified and corrected by our consortium. We focused on manual annotation, phylogenetic, and expression evidence analyses for gene sets centered on primary themes in the life histories and activities of plant-colonizing insects. Highlights include the following: (1) divergent clades and large expansions in genes associated with environmental sensing (chemosensory receptors) and detoxification (CYP4, CYP6, and CCE enzymes) of substances encountered in agricultural environments; (2) a comprehensive set of salivary gland genes supported by enriched expression; (3) apparent absence of members of the IMD innate immune defense pathway; and (4) developmental- and sex-specific expression analyses of genes associated with progression from larvae to adulthood through neometaboly, a distinct form of maturation differing from either incomplete or complete metamorphosis in the Insecta.
Conclusions
Analysis of the F. occidentalis genome offers insights into the polyphagous behavior of this insect pest that finds, colonizes, and survives on a widely diverse array of plants. The genomic resources presented here enable a more complete analysis of insect evolution and biology, providing a missing taxon for contemporary insect genomics-based analyses. Our study also offers a genomic benchmark for molecular and evolutionary investigations of other Thysanoptera species
The Intensity of IUGR-Induced Transcriptome Deregulations Is Inversely Correlated with the Onset of Organ Function in a Rat Model
A low-protein diet applied during pregnancy in the rat results in intrauterine growth restricted (IUGR) fetuses. In humans, IUGR is associated with increased perinatal morbidity, higher incidence of neuro-developmental defects and increased risk of adult metabolic anomalies, such as diabetes and cardiovascular disease. Development and function of many organs are affected by environmental conditions such as those inducing fetal and early postnatal growth restriction. This phenomenon, termed âfetal programmingâ has been studied unconnectedly in some organs, but very few studies (if any) have investigated at the same time several organs, on a more comparative basis. However, it is quite probable that IUGR affects differentially most organ systems, with possible persistent changes in gene expression. In this study we address transcriptional alterations induced by IUGR in a multi-organ perspective, by systematic analysis of 20-days rat fetuses. We show that (1) expressional alterations are apparently stronger in organs functioning late in foetal or postnatal life than in organs that are functioning early (2) hierarchical classification of the deregulations put together kidney and placenta in one cluster, liver, lungs and heart in another; (3) the epigenetic machinery is set up especially in the placenta, while its alterations are rather mild in other organs; (4) the genes appear deregulated in chromosome clusters; (5) the altered expression cascades varies from organ to organ, with noticeably a very significant modification of the complement and coagulation cascades in the kidney; (6) we found a significant increase in TF binding site for HNF4 proteins specifically for liver genes that are down-regulated in IUGR, suggesting that this decrease is achieved through the action of HNF transcription factors, that are themselves transcriptionnally induced in the liver by IUGR (x 1.84 fold). Altogether, our study suggests that a combination of tissue-specific mechanisms contributes to bring about tissue-driven modifications of gene cascades. The question of these cascades being activated to adapt the organ to harsh environmental condition, or as an endpoint consequence is still raised
Newcastle Disease Virus in Madagascar: Identification of an Original Genotype Possibly Deriving from a Died Out Ancestor of Genotype IV
In Madagascar, Newcastle disease (ND) has become enzootic after the first documented epizootics in 1946, with recurrent annual outbreaks causing mortality up to 40%. Four ND viruses recently isolated in Madagascar were genotypically and pathotypically characterised. By phylogenetic inference based on the F and HN genes, and also full-genome sequence analyses, the NDV Malagasy isolates form a cluster distant enough to constitute a new genotype hereby proposed as genotype XI. This new genotype is presumably deriving from an ancestor close to genotype IV introduced in the island probably more than 50 years ago. Our data show also that all the previously described neutralising epitopes are conserved between Malagasy and vaccine strains. However, the potential implication in vaccination failures of specific amino acid substitutions predominantly found on surface-exposed epitopes of F and HN proteins is discussed
Contribution à l'étude in-vitro de la voie de transmission de force myofasciale: anatomie, biomécanique et implications cliniques
RĂ©sumĂ©Ce travail de thĂšse contribue Ă dĂ©terminer chez lâhumain, le rĂŽle de diffĂ©rentes structures fasciales (expansions aponĂ©vrotiques, tissu conjonctif arĂ©olaire, fascia profond et paratendon) disposĂ©es en parallĂšle ou en sĂ©rie avec leur tendon respectif. La premiĂšre partie de ce travail est consacrĂ©e Ă lâĂ©tude de lâexpansion aponĂ©vrotique du biceps brachial. Deux protocoles ont Ă©tĂ© dĂ©veloppĂ©s sur spĂ©cimens cadavĂ©riques frais. Un premier, anatomique, a permis de mettre en Ă©vidence des caractĂ©ristiques individuelles telles que la longueur et la largeur sans lien avec le sexe et la latĂ©ralitĂ©. Dâautre part, une partie profonde de lâexpansion aponĂ©vrotique du biceps brachial a Ă©tĂ© observĂ©e de façon constante. Le second, biomĂ©canique, nous a permis dâĂ©tudier les mouvements de flexion du coude et de supination de lâavant-bras ainsi que les bras de leviers instantanĂ©s du muscle biceps brachial avec et sans la prĂ©sence de son expansion aponĂ©vrotique. Les rĂ©sultats nous indiquent que cette structure limite la flexion du coude ainsi que la supination de lâavant-bras, tout en maintenant une rythmicitĂ© entre la flexion et la supination. Dâautre part, elle permet dâaugmenter le bras de levier musculaire du muscle biceps brachial en flexion et en supination.Dans la seconde partie de ce travail, notre Ă©tude in-vitro sâest intĂ©ressĂ©e Ă la contribution relative des structures tendineuses et fasciales sur l'avantage mĂ©canique musculaire lors dâune plastie du ligament croisĂ© antĂ©rieur aux tendons des muscles droit interne et demi-tendineux. Les rĂ©sultats suggĂšrent que la voie myofasciale des muscles droit interne et du demi-tendineux semble cruciale pour la transmission de force permettant le dĂ©placement du segment jambier. MalgrĂ© les limitations inhĂ©rentes aux Ă©tudes sur prĂ©parations anatomiques, ce travail contribue Ă une meilleure connaissance de certaines structures fasciales, dont les implications cliniques devraient ĂȘtre prises en considĂ©ration.Doctorat en Sciences biomĂ©dicales et pharmaceutiquesinfo:eu-repo/semantics/nonPublishe
Rh-gene frequencies in pygmies (Batswa) of the Belgian Congo [23]
SCOPUS: le.jinfo:eu-repo/semantics/publishe
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