1,593 research outputs found
Stochastic Development Regression on Non-Linear Manifolds
We introduce a regression model for data on non-linear manifolds. The model
describes the relation between a set of manifold valued observations, such as
shapes of anatomical objects, and Euclidean explanatory variables. The approach
is based on stochastic development of Euclidean diffusion processes to the
manifold. Defining the data distribution as the transition distribution of the
mapped stochastic process, parameters of the model, the non-linear analogue of
design matrix and intercept, are found via maximum likelihood. The model is
intrinsically related to the geometry encoded in the connection of the
manifold. We propose an estimation procedure which applies the Laplace
approximation of the likelihood function. A simulation study of the performance
of the model is performed and the model is applied to a real dataset of Corpus
Callosum shapes
Ătude de l'impact des activitĂ©s touristiques sur la qualitĂ© de l'eau et l'organisation des peuplements macrobenthiques au sein des cours d'eau de la PrincipautĂ© d'Andorre
Le dĂ©veloppement considĂ©rable de l'activitĂ© touristique hivernale et estivale entraĂźne des perturbations au niveau des principaux cours d'eau andorrans. Il est intĂ©ressant d'Ă©tudier l'impact de ces perturbations sur des rĂ©seaux hydrographiques de haute altitude caractĂ©risĂ©s par des conditions du milieu particuliĂšres (basse tempĂ©rature-forte pente). Les donnĂ©es disponibles concernant la physicochimie et la faune des eaux andorranes sont rĂ©duites (PUIG, 1979 ; PEĂA, 1983).Treize stations ont Ă©tĂ© Ă©tudiĂ©es dans le cadre de ces travaux.Au cours d'un cycle annuel (automne 1998 Ă automne 1999), huit prĂ©lĂšvements d'invertĂ©brĂ©s benthiques ont Ă©tĂ© rĂ©alisĂ©s Ă chaque station Ă l'aide d'un filet Surber (vide de maille : 200 ”m-surface Ă©chantillonnĂ©e : 1/ 20e m2).Neuf paramĂštres physicochimiques (tempĂ©rature, pH, conductivitĂ©, DCO, DBO5, nitrates, nitrites, ammoniaque, phosphates) ont Ă©tĂ© mesurĂ©s de façon hebdomadaire Ă chaque station.Le traitement des donnĂ©es physicochimiques par analyses discriminantes rĂ©vĂšle l'existence d'un gradient amont-aval de dĂ©gradation de la qualitĂ© de l'eau. ParallĂšlement, la qualitĂ© de l'eau suit un cycle saisonnier mis en Ă©vidence par l'opposition entre campagnes d'Ă©tĂ© et d'hiver-printemps 1999, d'une part, et campagnes d'automne 1998-1999, d'autre part.L'analyse de la rĂ©partition spatiotemporelle de la faune benthique, basĂ©e Ă©galement sur des analyses discriminantes, met en Ă©vidence la disparition des taxons polluosensibles dans les stations intermĂ©diaires et aval comme les filtreurs (Simuliidae), les prĂ©dateurs (Perlodae, Perlididae, Rhyacophilidae) et les fragmenteurs (Nemouridae, Leuctridae) et l'apparition de nouveaux taxons polluotolĂ©rants en aval (Chironomidae, OligochĂštes). Ce genre de phĂ©nomĂšne a dĂ©jĂ Ă©tĂ© observĂ© dans d'autres cours d'eau de montagne soumis Ă des perturbations entraĂźnant l'augmentation de la charge organique (DECAMPS et PUJOL, 1977).Ces taxons polluotolĂ©rants comme par exemple, les OligochĂštes qui prolifĂšrent dans la zone aval du cours d'eau principal (Gran Valira) et en aval de l'unique station d'Ă©puration situĂ©e sur l'AriĂšge remplacent dans la structure trophique d'autres taxons polluosensibles. Ce phĂ©nomĂšne s'observe Ă©galement au sein d'un mĂȘme groupe trophique, c'est le cas des prĂ©dateurs composĂ©s des Perlidae, des Perlodidae et des Rhyacophilidae prĂ©sents dans les stations de haute altitude et qui disparaissent en aval oĂč ils sont remplacĂ©s par les AchĂštes (Glossiphoniidae).Le calcul de plusieurs indices biologiques d'Ă©valuation de la qualitĂ© des eaux (IBGN - BMWP), de richesse et de diversitĂ© spĂ©cifiques (indices de Shannon et de Margalef), de structure des peuplements (CUMMINS, 1979, 1985) met en Ă©vidence la diminution de la richesse et de la diversitĂ© spĂ©cifiques des stations amont vers les stations aval.L'impact du dĂ©veloppement touristique se manifeste Ă partir des stations de moyenne altitude. Dans ces stations, la pollution est partiellement Ă©vacuĂ©e, chaque automne, par l'eau de bonne qualitĂ© en provenance des zones amont des cours d'eau. Ce phĂ©nomĂšne se traduit par une grande variabilitĂ© des conditions physicochimiques et de la composition des communautĂ©s benthiques. Dans les stations aval, la pollution prend plutĂŽt un caractĂšre chronique suite Ă la concentration des pollutions en provenance des diffĂ©rentes zones perturbĂ©es. La variabilitĂ© des conditions du milieu et des assemblages faunistiques est donc moindre.Les rĂ©sultats obtenus Ă partir du traitement des donnĂ©es physicochimiques et faunistiques mettent en Ă©vidence une dĂ©gradation de l'intĂ©gritĂ© Ă©cologique des cours d'eau (modifications physicochimiques, modifications du peuplement, diminution de la diversitĂ©). L'impact des perturbations d'origine anthropique suit un cycle dĂ©pendant de la frĂ©quentation touristique. Au cours de ce cycle, alternent deux pĂ©riodes " critiques " caractĂ©risĂ©es par des perturbations hivernales (ski) et estivales (tourisme, randonnĂ©es) et une pĂ©riode de " rĂ©cupĂ©ration " durant l'automne.Ces travaux ont permis de tester l'hypothĂšse des perturbations intermĂ©diaires du milieu (CONNELL, 1978 ; RESH, 1988 ; TOWNSEND et al., 1997) et de rechercher les seuils d'intensitĂ© des perturbations et/ou l'amplitude de ces perturbations ainsi que leur impact nĂ©gatif sur la composition faunistique (EDWARD et RYKIEL, 1985 ; PICKETT et al., 1989 ; REICE et al., 1990).The important development of tourism during winter and summer disturb the main Andorran streams. The impact of these disturbances were studied in high altitude streams characterised by particular environmental conditions (e.g. low temperature - steep slope) as little is known about water quality and associated benthic fauna in Andorran streams (PUIG, 1979; PEĂA, 1983).Thirteen sites were seasonally studied during one year, from autumn 1998 to autumn 1999, in each site, eight macroinverbrates samples were coffected using a Surber sampling net (mesh size 200 ”m - sampling area : 1/20e m2). In addition, nine physicochemical parameters (temperature - pH - conductivity - DCO - DBO5 - nitrate- nitrite - ammonia - phosphate) were weekly measured in each site during the entire sampfing period.A discriminant analysis performed on the physicochemical data reaveled and upstreamdownstream gradient of the water quality, with highest disturbance in the downstream sites. From a temporal point of view, the water quality follows a seasonal cycle highlighted by the opposition between on the one hand winter-spring and summer 1999, and on the other hand autumn 1998-1999.The spatio-temporal distribution of the benthic fauna, based on the discriminant analysis, highlighted the disappearance of polluo-sensitive taxa in intermediate and downstream sites such as filtering collectors (Simuliidae), predators (Perfidae - Perlodidae - Rhyacophilidae) and shredders (Nemouridae - Leuctridae). In these areas, sensitive taxa were replaced by polluo-tolerant ones such as Chironomidae and Oligocheta. These patterns were already observed in other mountain streams subjected to high organic disturbances (DECANTS et PUJOL, 1977).As a consequence, polluo-tolerant taxa replace polluo-sensitives taxa with similar functionnal status. For example Oligocheta, proliferate in the downstream (Gran Valira), whereas upstream, they were only abundant on a point source pollution site located on the Ariege river. The same phenomenon was also observed for predators: high unpolluted altitude sites were characterised by stoneflies and caddisflies (Perlidae, Perlodidae, Rhyacophilidae) which were replaced downstream by leeches (Glossiphoniidae). As a consequence, the calculation of the several biological indices of water quality (I.B.G.N - B.M.W.Y'), and diversity descriptors (taxa richness - Shannon index - Margalef index), indicate a drastic reduction of the taxa diversity, evenness and water quality from. upstream to downstrearn sites.Disturbances associated with tourism developinent appeared in the medium altitude sites. In these sites, the water quality benefits from the good water quality from the upstream sites during high discharge periods (i.e. in autumn). This phenomena explained the observed temporal variabihty of both physicochemical conditions and benthic fauna structure. In the down-stream sites, the pollution can be considered as chronic and hence, low envirorimental variability was observed. These results show that Andorran stream ecological integrity is low fonn both physicochemical diversity and population assemblages point of views. Moreover, the impact of anthropic disturbances followed an annual cycle according to tourisin. activities with pollution peaks in winter and suminer corresponding respectively to ski resort and hiking tourisin. The only partial recovery period is represented by the autumn high drainage period.From a theoretical point of view, these results allowed to test the intermediate disturbance hypothesis (CONNELL, 1978; RESH, 1988; TOWNSFND et al., 1997) and to search the threshold of resistence/resilience characteristics of a stream ecosystern considering stream. benthic assemblages (EDWARD et RYKIEL, 1985; REICE et al., 1990; PICKETT et al., 1989)
Les récepteurs 5-HT4b adoptent différentes conformations ligand-spécifique ayant des propriétés de signalisation et de régulation distinctes
Les antidĂ©presseurs actuels sont trĂšs similaires au niveau de leur mĂ©canisme dâaction et sont plus ou moins efficaces. Un des problĂšmes majeurs est leur long temps de latence Ă fournir une action thĂ©rapeutique dĂ» aux adaptations des sites prĂ© et post synaptiques. Dans un modĂšle animal, nous avons rĂ©cemment dĂ©couvert que lâagoniste RS67333 des rĂ©cepteurs 5-HT4 Ă©tait en mesure de produire en trois jours les mĂȘmes effets antidĂ©presseurs qui normalement prennent de deux Ă trois semaines Ă apparaĂźtre avec les antidĂ©presseurs actuellement disponibles. De plus, nous avons constatĂ© que les effets antidĂ©presseurs de cet agoniste possĂ©daient une rĂ©sistance Ă la tolĂ©rance. Il y a dâautres agonistes du mĂȘme rĂ©cepteur, tel que le prucalopride qui ne produit pas dâeffets antidĂ©presseurs comme RS67333. Ătant donnĂ© que lâefficacitĂ© du Prucalopride Ă stimuler les 5-HT4Rs est similaire sinon plus grande que celle de RS67333, nous avons Ă©noncĂ© lâhypothĂšse que le rĂ©cepteur 5-HT4 pourrait adopter diffĂ©rentes conformations actives suite Ă son activation par diffĂ©rents agonistes. Nous avons ainsi dĂ©cidĂ© dâexplorer les principales rĂ©ponses fonctionnelles des rĂ©cepteurs 5-HT4B en observant leurs propriĂ©tĂ©s de rĂ©gulation et de signalisation.
Nous avons montrĂ© que lâisoforme B du rĂ©cepteur 5-HT4, Ă©tant hautement exprimĂ© dans le systĂšme limbique, dĂ©tient une signalisation et une rĂ©gulation diffĂ©rentes dĂ©pendant du ligand activateur. Nos rĂ©sultats indiquent que chacun des agonistes testĂ©s (5-HT, RS67333, ML10302, Zacopride, Prucalopride) modulent distinctivement la production dâAMPc et lâinternalisation du rĂ©cepteur. Les rĂ©sultats nous ont clairement permis de dĂ©terminer que les agonistes possĂšdent une efficacitĂ© et ou puissance diffĂ©rentes les uns par rapport aux autres. De plus, lâordre dâefficacitĂ© des agonistes Ă moduler la voie de lâAMPc Ă©tait (Prucalopride > Zacopride = ML10302 = 5-HT > RS67333) et est diffĂ©rente de leur ordre dâefficacitĂ© Ă induire la rĂ©gulation du rĂ©cepteur par internalisation (5-HT > Zacopride > Prucalopride > ML10302 = RS67333). Ainsi, nous avons montrĂ© que les 5-HT4Rs adoptent des conformations qui sont ligand-spĂ©cifiques.
Cela implique que la sĂ©lectivitĂ© fonctionnelle serait un facteur important Ă considĂ©rer dans les mĂ©canismes dâaction antidĂ©presseur des agonistes de ce rĂ©cepteur.Antidepressants currently available are very similar toward their mechanism of action and are more or less effective. One major problem is their long latency to provide a therapeutic effect due to adaptations of pre and post synaptic locations. In an animal model, we recently discovered that the agonist RS67333 of the 5-HT4 receptors was able to produce in three days the same antidepressant effects that normally take two to three weeks to appear with the currently available antidepressants. In addition, we found that the antidepressant effects of this agonist had a resistance to tolerance. There are others agonists of the same receptor such as prucalopride, which does not produce antidepressant effects as RS67333. Since the effectiveness of prucalopride to stimulate 5-HT4Rs is similar if not greater than RS67333, we stated the hypothesis that the 5-HT4 receptor could adopt different active conformations following its activation by various agonists. We decided to explore the major functional responses of 5-HT4B by observing their regulatory and signaling properties.
We showed that the B isoform of the 5-HT4, being highly expressed in the limbic system, has a different signaling and regulation depending on the ligand. Our results indicate that each of the agonists tested (5-HT, RS67333, ML10302, Zacopride, Prucalopride) distinctively modulate cAMP production and receptor internalization. The results have clearly identified that agonists differed in potency and efficacy. Moreover, the order of effectiveness of agonists to modulate the cAMP pathway was (prucalopride> zacopride = 5-HT = ML10302> RS67333) different from their order of effectiveness in inducing receptor regulation by internalization (5-HT> Zacopride> Prucalopride> RS67333 = ML10302). Thus, we have shown that 5-HT4Rs adopt conformations that are ligand-specific. This implies that functional selectivity is an important factor in the mechanisms of antidepressant action of this receptor agonists
The Candida albicans Dse1 Protein Is Essential and Plays a Role in Cell Wall Rigidity, Biofilm Formation, and Virulence
The fungal pathogen Candida albicans is one of the leading causative agents of death in immunocompromised individuals. It harbors an arsenal of cell wall anchored factors that are implicated in virulence such as filamentation inducing factors, adhesins, lipases, proteases, and superoxide dismutases. Dse1 is a cell wall protein involved in cell wall metabolism. The purpose of this study is to characterize the role Dse1 plays in virulence. Dse1 appears to be an essential gene as no homozygous null mutant was possible. The heterozygote mutant exhibited increased susceptibility to calcofluor white, a cell wall disrupting agent, with a subsequent reduction in cell wall chitin content, decreased oxidative stress tolerance, a 30% reduction in biofilm formation, and a delay in adhesion that was mirrored by a reduction in virulence in a mouse model of infection. Dse1 thus appears to be an important protein involved in cell wall integrity and rigidity
Should We Learn Probabilistic Models for Model Checking? A New Approach and An Empirical Study
Many automated system analysis techniques (e.g., model checking, model-based
testing) rely on first obtaining a model of the system under analysis. System
modeling is often done manually, which is often considered as a hindrance to
adopt model-based system analysis and development techniques. To overcome this
problem, researchers have proposed to automatically "learn" models based on
sample system executions and shown that the learned models can be useful
sometimes. There are however many questions to be answered. For instance, how
much shall we generalize from the observed samples and how fast would learning
converge? Or, would the analysis result based on the learned model be more
accurate than the estimation we could have obtained by sampling many system
executions within the same amount of time? In this work, we investigate
existing algorithms for learning probabilistic models for model checking,
propose an evolution-based approach for better controlling the degree of
generalization and conduct an empirical study in order to answer the questions.
One of our findings is that the effectiveness of learning may sometimes be
limited.Comment: 15 pages, plus 2 reference pages, accepted by FASE 2017 in ETAP
1,3-Diallyl-5-chloro-1H-benzimidazol-2(3H)-one
The benzimidazolone part of the title molÂecule, C13H13ClN2O, is almost planar (r.m.s. deviation = 0.006â
Ă
) and its mean plane is aligned at dihedral angles of 62.5â
(1) and 78.0â
(1)° with respect to the mean planes of the allyl substituents
Anatomie du nerf laryngé externe et ses applications chirurgicales
Objectif : La lĂ©sion de la branche externe du nerf laryngĂ© supĂ©rieur (BeNLS) , non rare lors de la chirurgie thyroĂŻdienne, est responsable de modifications de la voix et de troubles de la dĂ©glutition. Mais ses diffĂ©rentes variantes anatomiques ainsi que les faibles taux de son identification ont dĂ©couragĂ© les chirurgiens de son repĂ©rage systĂ©matique.Le but de notre travail est de faire une description anatomique des variantes de la BeNLS , dâestimer la frĂ©quence des nerfs Ă risque et de dĂ©crire les techniques chirurgicales de son identification pour proposer une approche systĂ©matique de sa prĂ©servation.MatĂ©riel et mĂ©thodes: Il sâagit dâune Ă©tude prospective portant sur 10 patients ayant eu une chirurgie thyroĂŻdienne et chez qui on a procĂ©dĂ© Ă un repĂ©rage systĂ©matique de la BeNLS dans lâespace avasculaire de Reeve. On a utilisĂ© la classification de Cernea pour regrouper les variations anatomiques rencontrĂ©es.RĂ©sultats : On a procĂ©dĂ© Ă la dissection de 13 nerfs. Le taux dâidentification de la BeNLS Ă©tait de 84% , 38% sont de Type 2a , 46% sont de Type 2b. Des complications ont Ă©tĂ© notĂ©es chez 3 patients dont 2 qui prĂ©sentent une BeNLS de Type Ni.Conclusion : On pense que la variante anatomique de la BeNLS de type 2 prĂ©sente un risque de blessure car le chirurgien manipule le pĂ©dicule supĂ©rieur au niveau du centimĂštre critique situĂ© au-dessus du pĂŽle supĂ©rieur de la thyroĂŻde. Le sous-type 2b , le plus frĂ©quent dans notre sĂ©rie , est une variante Ă haut risque. Lâidentification du nerf lors de la chirurgie thyroĂŻdienne est la solution de choix.Mots-clĂ©s : Branche externe du nerf laryngĂ© supĂ©rieur, anatomie, muscle crico-thyroĂŻdien, chirurgie thyroĂŻdienne, voix
Hernie obturatrice étranglée: à propos de deux cas
La hernie obturatrice (HO) est rare. Elle est Ă l'origine de 0,2 Ă 1,6% des occlusions mĂ©caniques de l'intestin grĂȘle avec un taux de mortalitĂ© etmorbiditĂ© aprĂšs chirurgie est respectivement de 35 et 18%. Nous rapportons le cas de deux patientes chez qui le diagnostic de HO Ă©tranglĂ©e est Ă©tablie dans le cadre du bilan d'une occlusion. La HO est une entitĂ© dont le diagnostic prĂ©opĂ©ratoire est difficile en raison de la faible spĂ©cificitĂ© clinique. L'examen tomodensitomĂ©trique semble ĂȘtre une aide majeure au diagnostic étiologique. Mais une fois le diagnostic d'occlusion posĂ©, une intervention en urgence permettra d'en prĂ©ciser l'Ă©tiologie et d'en rĂ©aliser le traitement. Tout retard thĂ©rapeutique majore la mortalitĂ© et la morbiditĂ©
COVID-19 Detection on Chest x-ray Images by Combining Histogram-oriented Gradient and Convolutional Neural Network Features
The COVID-19 coronavirus epidemic has spread rapidly worldwide after a person became infected with a severe health problem. The World Health Organization has declared the coronavirus a global threat (WHO). Early detection of COVID 19, particularly in cases with no apparent symptoms, may reduce the patients mortality rate. COVID 19 detection using machine learning techniques will aid healthcare systems around the world in recovering patients more rapidly. This disease is diagnosed using x-ray images of the chest; therefore, this study proposed a machine vision method for detecting COVID-19 in x-ray images of the chest. The histogram-oriented gradient (HOG) and convolutional neural network (CNN) features extracted from x-ray images were fused and classified using support vector machine (SVM) and softmax. The proposed feature fusion technique (99.36 percent) outperformed individual feature extraction methods such as HOG (87.34 percent) and CNN (93.64 percent)
Assessing the consequences of gestational diabetes mellitus on offspring's cardiovascular health: MySweetHeart Cohort study protocol, Switzerland.
Gestational diabetes mellitus (GDM) is a state of glucose intolerance with onset during pregnancy. GDM carries prenatal and perinatal risks as well as long-term risks for the mother and her child. GDM may be involved in the foetal programming of long-term cardiovascular health. However, evidence is sparse and the effect of GDM on cardiovascular health is unknown. To address these issues, we will conduct MySweetHeart Cohort study. The objectives are to assess the effect of GDM on offspring's cardiovascular health early in life by using surrogate markers of cardiovascular disease and atherosclerosis.
This is a cohort study of 100 offspring of women with GDM and 100 offspring of women without GDM. At inclusion, a baseline assessment of the mothers will be conducted through means of self-report questionnaires, a researcher-administrated interview, blood pressure and anthropometric measurements, and a maternal blood sampling. Between the 30th and 34th weeks of gestation, a foetal echography will be performed to assess the foetal cardiac structure and function, the fetomaternal circulation and the hepatic volume. At birth, maternal and neonatal characteristics will be assessed. An echocardiography will be performed to assess cardiac structure and function 2-7 days after birth; carotid intima-media thickness will be also measured to assess vascular structure. MySweetHeart Cohort is linked to MySweetHeart Trial (clinicaltrials.gov/ct2/show/NCT02890693), a randomised controlled trial assessing the effect of a multidimensional interdisciplinary lifestyle and psychosocial intervention to improve the cardiometabolic and mental health of women with GDM and their offspring. A long-term follow-up of children is planned.
Ethical approval has been obtained through the state Human Research Ethics Committee of the Canton de Vaud (study number 2016-00745). We aim to disseminate the findings through regional, national and international conferences and through peer-reviewed journals.
ClinicalTrials.gov (clinicaltrials.gov/ct2/show/NCT02872974)
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