3,329 research outputs found
Combinaison de prĂ©visions hydrologiques globales et locales Ă lâaide de mĂ©thodes simples
Lâaugmentation exponentielle de la capacitĂ© de calcul, jumelĂ©e Ă la forte croissance de la
disponibilité de données satellites des derniÚres décennies et à la collaboration des données
scientifiques ont menĂ© au rĂ©cent dĂ©veloppement dâun bon nombre de systĂšmes de prĂ©visions
hydrologiques large-échelle. Les prévisions produites par ces systÚmes chevauchent souvent des
régions déjà couvertes par des systÚmes de prévisions hydrologiques locaux plus spécialisés.
Cette recherche porte la possibilitĂ© dâobtenir de lâinformation des prĂ©visions de ces systĂšmes
large-Ă©chelle afin dâamĂ©liorer les prĂ©visions locales. Plus prĂ©cisĂ©ment, les prĂ©visions large-Ă©chelle
du National Surface and River Prediction System (NSRPS) sont combinées aux prévisions
hydrologiques locales du SystÚme de Prévision Hydrologique (SPH) opéré par le MinistÚre de
lâEnvironnement et de la Lutte aux changements climatiques (MELCCFP) Ă lâaide de mĂ©thodes
simples dans le but dâoptimiser les prĂ©visions locales. La combinaison est effectuĂ©e Ă lâaide
de plusieurs méthodes. PremiÚrement, une moyenne simple est utilisée en guise de référence
de performance. Ensuite plusieurs variantes de moyennes pondérées sont utilisées, soit une
premiĂšre variante oĂč les poids sont calculĂ©s analytiquement selon les rĂ©sidus des modĂšles et trois
autres variantes oĂč les poids sont optimisĂ©s en utilisant comme fonction coĂ»t le KlingâGupta
Efficiency (KGE), le Reduced Continuous Ranked Probability Score (RCRPS) et le Ignorance
Score (IGN). Le Bayesian Model Averaging est aussi utilisé afin de combiner les prévisions
probabilistes des deux systĂšmes. Il sâagit dâune mĂ©thode plus Ă©laborĂ©e qui utilisent comme poids
les probabilitĂ©s Ă posteriori dâun modĂšle Ă avoir gĂ©nĂ©rĂ© les observations. Les rĂ©sultats montrent
clairement quâune amĂ©lioration des prĂ©visions hydrologiques locales est possible en utilisant des
mĂ©thodes de combinaisons simples, et ce mĂȘme si la performance du systĂšme de prĂ©vision local
est drastiquement meilleure. LâĂ©valuation de la performance des prĂ©visions est effectuĂ©e selon
de multiples critĂšres afin de sâassurer que les rĂ©sultats prĂ©sentent un portrait juste et gĂ©nĂ©ral de
lâimpact de la combinaison. Pour ce faire, les critĂšres de Nash-Sutcliffe Efficiency (NSE), KGE,
RCRPS et IGN sont utilisés. Les résultats sont moyennés sur 40 emplacements jaugés et analysées
pour des horizons de prévision allant de 3 à 120 h. Pour toutes les méthodes autres que la moyenne
simple, des gains en performance sont observés pour tous les critÚres pour des horizons de 60
h et plus et aucun critĂšre ne rĂ©vĂšle une perte de performance, peu importe lâhorizon analysĂ©.
Enfin, lâeffet de la combinaison des prĂ©visions sur les bassins non-jaugĂ©s est analysĂ© selon une
simulation leave-one-out sur 29 bassins de validation. Des comportements trĂšs similaires aux
bassins jaugés sont observés, suggérant que ces méthodes de combinaisons pourraient améliorer
les prĂ©visions hydrologiques des bassins des territoires plus Ă©loignĂ©s et isolĂ©s, oĂč aucune station
de mesure nâest prĂ©sente
Diagnosis and management of a full thickness macular hole
Background: First stage macular holes are not always easily identified without the use of medical imagery. Differential diagnosis from other macular conditions is possible with a keen eye and the use of a binocular fundus lens. However, the advent of optical coherence tomography facilitates accurate diagnosis.
Case Report: This report demonstrates a classical case of a full thickness macular hole. The clinical signs are not pathognomonic at first, but typical signs develop in the following weeks. The different stages of the disease are described, as well as current state of surgical treatment and possible outcomes.
Conclusions: Early diagnosis allows quick visual recovery. Nevertheless, this condition can be treated up to one year after occurrence with significant improvement of visual function
Wavefront Aberrations in Subjects Wearing Soft Aspheric Contact Lenses and Those Wearing Spherical Ones
Purpose: To measure the level of higher order aberrations (HOA) when wearing a soft aspheric contact lens (CL), compared to a spherical CL, in myopic subjects.
Method: Fifteen myopic subjects aged 20-30 years were tested for the presence of dry eye. Aberrometry measurements were done without a contact lens as well as with a spherical CL and an aspheric CL. Root mean square error (RMS) of HOA, spherical aberration (SA) and coma were measured five times in an interval of 15 seconds without blinking for each of the 3 conditions.
Results: Wearing a spherical CL produced a significant increase of SA and horizontal coma compared to an eye without a contact lens. When wearing an aspheric CL, there was a trend towards a smaller increase of these aberrations. However, the difference between both types of lens was not statistically significant. In terms of total HOA, these were higher when wearing the spherical CL, while they tended to be less with the aspheric CL. As for the variations between blinks, there was a similar increase in total HOA and individual modes with time for the three conditions.
Conclusion : Wearers of aspheric CL seem to show a tendency towards smaller amounts of SA, horizontal coma and HOA in general in comparison with wearers of SCL. However, total HOA increases during a long interval between blinks, no matter the condition
Full-Field, Carrier-Less, Polarization-Diversity, Direct Detection Receiver based on Phase Retrieval
We realize dual-polarization full-field recovery using intensity only
measurements and phase retrieval techniques based on dispersive elements.
30-Gbaud QPSK waveforms are transmitted over 520-km standard single-mode fiber
and equalized from the receiver outputs using 2X2 MIMO
Identification du marqueur de cellules souches cancéreuses CD133 comme nouvelle cible de la MT1-MMP dans les cellules tumorales du cerveau
L'implication de la Membrane Type-Matrix Metalloproteinase (MT1-MMP) dans la progression du cancer a Ă©tĂ© grandement Ă©tudiĂ©e dans la derniĂšre dĂ©cennie. Elle possĂšde une vaste variĂ©tĂ© de substrats, incluant des composants de la matrice extracellulaire, des cytokines et des rĂ©cepteurs membranaires. Nos rĂ©sultats identifient le marqueur de cellules souches (CSC) CD133 comme une nouvelle cible de l'activitĂ© protĂ©olytique de la MT1-MMP. Des essais d'immunoprĂ©cipitation et de clivage in vitro effectuĂ©s Ă l'aide de protĂ©ines recombinantes ont dĂ©montrĂ© que la MT1-MMP interagit physiquement avec CD133 et clive son domaine N-terminal Ă la position 30KAWNâY34. De plus, cette interaction semble commencer au niveau intracellulaire, dans le rĂ©ticulum endoplasmique, avant l'activation de la proMT1-MMP et avant la maturation complĂšte de CD133; toutefois, seulement la forme mature de CD133 peut ĂȘtre clivĂ©e. Ces rĂ©sultats reprĂ©sentent la premiĂšre interaction protĂ©ine-protĂ©ine connue de CD133, dont la fonction cellulaire demeure incomprise. Des expĂ©riences supplĂ©mentaires pourraient mener Ă une meilleure comprĂ©hension de cette protĂ©ine et de son rĂŽle dans la biologie des CSCs. \ud
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MOTS-CLĂS DE LâAUTEUR : MT1-MMP, CSC, N-terminal, rĂ©ticulum endoplasmiqu
Acting as a molecular tailor : dye structural modifications for improved sensitivity towards lysophosphatidic acids sensing
Lysophosphatidic acids (LPA) are key biomarkers for several physiological processes, the monitoring of which can provide insights into the hostâs health. Common lab-based techniques for their detection are cumbersome, expensive and necessitate specialized personnel to operate. LPA-sensitive fluorescent probes have been described, albeit for non-aqueous conditions, which impedes their use in biological matrices. In this paper, we explore in detail the influence of structure on the extent of aggregation-induced fluorescence quenching using specially synthesized styrylpyridinium dyes bearing structural adaptations to bestow them enhanced affinity towards LPA in aqueous media. Spectroscopic investigations supported by time-resolved fluorimetry revealed the contribution of excimer formation to the fluorescence quenching mechanism displayed by the fluorescent probes. Experimental observations of the influence of structure on detection sensitivity were supported by DFT calculations
Disruptive mixed in vitro-in silico approach for protein engineering and screening
We present a strategy that combines wet-lab experimentation and computational protein design for engineering polypeptide chains. The protein sequences were numerically coded and then processed using Fourier Transform (FT). Fourier coefficients were used to calculate the energy spectra called protein spectrum . We use the protein spectrum to model the biological activity/fitness of protein from sequence data. We assume that the protein fitness (catalytic efficacy, thermostabilty, binding affinity, aggregation, stabilityâŠ) is not purely local, but globally distributed over the linear sequence of the protein. Our patented method does not require any protein 3D structure information and find patterns that correlate with changes in protein activity (or fitness) upon amino acids residue substitutions. A minimal wet lab data sampled from mutation libraries (single or multiple points mutations) were used as learning data sets in heuristic approaches that were applied to build predictive models. We show the performance of the approach on designed libraries for 3 examples (enantioselectivity, thermostability and binding affinity) and discuss how our approach can tackle epistatic phenomena. We can screen up to 1 billion (109) protein variants in a very short time
Substantiating the influence of pore surface functionalities on the stability of grubbs catalyst in mesoporous SBA-15 silica
The influence of pore surface functionalities in mesoporous SBAâ15 silica on the stability of a model olefin metathesis catalyst, namely Grubbsâ
I, is substantiated. In particular, it is demonstrated that the nature of the interaction between the ruthenium complex and the surface is strongly depending on the presence of surface silanols. For this study, differently functionalized mesoporous SBAâ15 silica materials were synthesized according to standard procedures and, subsequently, the Grubbsâ
I catalyst was incorporated into these different host materials. All of the materials were thoroughly characterized by elemental analyses, nitrogen physisorption at â196â°C, thermogravimetric analyses, solidâstate NMR spectroscopy, and infrared spectroscopy (ATRâIR). By such inâdepth characterization of the materials, it became possible to achieve models for the surface/catalyst interactions as a function of surface functionalities in SBAâ15; for example, in the case of purely siliceous silanolârich SBAâ15, octenylâsilane modified SBAâ15, and silylated equivalents. It was evidenced that large portions of the chemisorbed species that are detected spectroscopically arise from interactions between the tricyclohexylphosphine and the surface silanols. A catalytic study using diethyldiallylmalonate in presence of the various functionalized silicas shows that the presence of surface silanols significantly decreases the longevity of the ringâclosing metathesis catalyst, whereas the passivation of the surface by trimethylsilyl groups slows down the catalysis rate, but does not affect significantly the lifetime of the catalyst. This contribution thus provides new insights into the functionalization of SBAâ15 materials and the role of surface interactions for the grafting of organometallic complexes
InnovâSAR: A new approach for protein engineering and screening
We present a strategy that combines wet-lab experimentation and computational protein design for engineering polypeptide chains. The protein sequences were numerically coded and then processed using Fourier Transform (FT). Fourier coefficients were used to calculate the energy spectra called protein spectrum . We use the protein spectrum to model the biological activity/fitness of protein from sequence data. We assume that the protein fitness (catalytic efficacy, thermostabilty, binding affinity, aggregation, stabilityâŠ) is not purely local, but globally distributed over the linear sequence of the protein. Our patented method does not require protein 3D structure information and find patterns that correlate with changes in protein activity (or fitness) upon amino acids residue substitutions. A minimal wet lab data set sampled from mutation libraries (single or multiple points mutations) were used as learning data sets in heuristic approaches that were applied to build predictive models. We show the performance of the approach on designed libraries for different examples1 and discuss how our approach can tackle epistatic phenomena2. We can screen up to 1 billion (109) protein variants in a very short time. F. Cadet, N. Fontaine, I. Vetrivel, M. Ng Fuk Chong, O. Savriama, X. Cadet, P. Charton (2018), Application of Fourier transform and proteochemometrics principles to protein engineering, BMC Bioinformatics (2018) 19:382, doi.org/10.1186/s12859-018-2407-8, https://rdcu.be/9qjp F. Cadet, N. Fontaine, G. Li, J. Sanchis, M. Ng Fuk Chong, R .Pandjaitan, I. Vetrivel 1, B. Offmann & M. T. Reetz (2018), A machine learning approach for reliable prediction of amino acid interactions and its application in the directed evolution of enantioselective enzymes, Scientific Reports 8(1), 16757, doi: 10.1038/s41598-018-35033-y. www.nature.com/articles/s41598-018-35033-
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