1,186 research outputs found
High genetic diversity and clonal growth in relict populations of Olea europaea subsp. laperrinei (Oleaceae) from Hoggar, Algeria.
The Laperrine's olive (Olea europaea subsp. laperrinei) is an endemic tree from Saharan massifs. Its populations have substantially regressed since the Pleistocene and are presently distributed in a fragmented habitat. Long-term persistence of this taxon is uncertain and programmes of preservation have to be urgently implemented. To define a conservation strategy, the genetic diversity and breeding system of this tree have to be investigated.
One hundred and eleven ramets were prospected in the laperrinei populations from the Tamanrasset region, southern Algeria. Genetic polymorphism was revealed at nuclear and chloroplast DNA (cpDNA) microsatellite loci allowing a comparative assessment of the genetic diversity of laperrinei and Mediterranean populations based on bi-parental and maternal markers. Additionally, nuclear microsatellite markers enabled the genotypes to be identified unambiguously.
Based on nuclear microsatellite data, the total diversity was high (Ht=0.61) in laperrinei populations and similar to that observed in western Mediterranean populations. A substantial cpDNA diversity (Ht=0.19) was also observed. Genetically identical ramets originated from the same stump (which can cover >80 m2) were identified in each population. Sixteen per cent of genets exhibited more than one ramet. In addition, several cases of somatic mutations were unambiguously revealed in distinct ramets stemming from the same stump.
These data show that highly isolated and small laperrinei populations are able to maintain a high genetic diversity. This supports the existence of relict trees persisting for a very long time (probably since the last humid transition, 3000 years ago). It is proposed that the very long persistence associated with an asexual multiplication of highly adapted trees could be a strategy of survival in extreme conditions avoiding a mutational meltdown due to reproduction in reduced populations
Ultra-narrow (sub-MHz) linewidth emission from discrete mode laser diodes
A class of laser which exhibits ultra-narrow sub MHz linewidth emission necessary for numerous applications in optical communications and sensors is described. The spectral performance of commercial discrete mode (DM) and distributed feedback (DFB) lasers is compared. The devices used in this work are asymmetrically coated ridge waveguide Fabry Perot lasers which incorporated etched slot features and emitting around lambda = 1.55 mum. The active region of the devices consisted of a strained compensated InAlGaAs MQW structure
Mol-CycleGAN - a generative model for molecular optimization
Designing a molecule with desired properties is one of the biggest challenges
in drug development, as it requires optimization of chemical compound
structures with respect to many complex properties. To augment the compound
design process we introduce Mol-CycleGAN - a CycleGAN-based model that
generates optimized compounds with high structural similarity to the original
ones. Namely, given a molecule our model generates a structurally similar one
with an optimized value of the considered property. We evaluate the performance
of the model on selected optimization objectives related to structural
properties (presence of halogen groups, number of aromatic rings) and to a
physicochemical property (penalized logP). In the task of optimization of
penalized logP of drug-like molecules our model significantly outperforms
previous results
Les phĂ©nomĂšnes de dĂ©pendance Ă lâenvironnement: rĂ©flexions sur lâautonomie humaine Ă partir de la clinique neurologique
Dans cet article, nous proposons dâanalyser la perte dâautonomie caractĂ©risĂ©e par les phĂ©nomĂšnes de dĂ©pendance Ă lâenvironnement observĂ©s chez certains patients neurologiques prĂ©sentant des lĂ©sions des lobes frontaux. Des propositions thĂ©oriques issues de la neuropsychologie cognitive et de la thĂ©orie de la mĂ©diation sont dĂ©veloppĂ©es et confrontĂ©es. La dĂ©marche offre lâoccasion, au plan thĂ©orique, de questionner la dĂ©tĂ©rioration possible du systĂšme de la personne suite Ă des lĂ©sions cĂ©rĂ©brales et, au plan mĂ©thodologique, dâinterroger notre maniĂšre dâexaminer ces patients en confrontant les modĂšles thĂ©oriques aux observations clinique
Utilisation de la Réalité Virtuelle en neuropsychologie clinique
Dans cet article, les principales applications des techniques de RĂ©alitĂ© Virtuelle en clinique neuropsychologique sont examinĂ©es. Il s\u27agit, d\u27une part, de l\u27aide Ă l\u27Ă©valuation des troubles cognitifs et comportementaux secondaires aux lĂ©sions du systĂšme nerveux central et, d\u27autre part, des perspectives ouvertes dans le champ de la prise en charge rĂ©Ă©ducative de ces dĂ©ficits. Ces donnĂ©es cliniques et expĂ©rimentales permettent de discuter l\u27intĂ©rĂȘt et les limites de l\u27utilisation de ces techniques
The Joint European Compound Library:boosting precompetitive research
The Joint European Compound Library (JECL) is a new high-throughput screening collection aimed at driving precompetitive drug discovery and target validation. The JECL has been established with a core of over 321000 compounds from the proprietary collections of seven pharmaceutical companies and will expand to around 500000 compounds. Here, we analyse the physicochemical profile and chemical diversity of the core collection, showing that the collection is diverse and has a broad spectrum of predicted biological activity. We also describe a model for sharing compound information from multiple proprietary collections, enabling diversity and quality analysis without disclosing structures. The JECL is available for screening at no cost to European academic laboratories and SMEs through the IMI European Lead Factory (http://www.europeanleadfactory.eu/)
Phylogenomics indicates the âliving fossilâ Isoetes diversified in the Cenozoic
The fossil record provides an invaluable insight into the temporal origins of extant lineages of organisms. However, establishing the relationships between fossils and extant lineages can be difficult in groups with low rates of morphological change over time. Molecular dating can potentially circumvent this issue by allowing distant fossils to act as calibration points, but rate variation across large evolutionary scales can bias such analyses. In this study, we apply multiple dating methods to genome-wide datasets to infer the origin of extant species of Isoetes, a group of mostly aquatic and semi-aquatic isoetalean lycopsids, which closely resemble fossil forms dating back to the Triassic. Rate variation observed in chloroplast genomes hampers accurate dating, but genome-wide nuclear markers place the origin of extant diversity within this group in the mid-Paleogene, 45â60 million years ago. Our genomic analyses coupled with a careful evaluation of the fossil record indicate that despite resembling forms from the Triassic, extant Isoetes species do not represent the remnants of an ancient and widespread group, but instead have spread around the globe in the relatively recent past
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