Matter wave soliton bouncer

Dynamics of a matter wave soliton bouncing on the reflecting surface (atomic mirror) under the effect of gravity has been studied by analytical and numerical means. The analytical description is based on the variational approach. Resonant oscillations of the soliton's center of mass and width, induced by appropriate modulation of the atomic scattering length and the slope of the linear potential are analyzed. In numerical experiments we observe the Fermi type acceleration of the soliton when the vertical position of the reflecting surface is periodically varied in time. Analytical predictions are compared with the results of numerical simulations of the Gross-Pitaevskii equation and qualitative agreement between them is found.Comment: 8 pages, 5 figure

Signes + et - : perception du circuit électrique

Les représentations symboliques utilisées en physique (schémas, signes, etc.) font rarement l'objet d'un enseignement explicite. Il est plausible que les étudiants suppléent à cette carence en formant leur propre sémantique. Ainsi les signes + et - employés en électrocinétique semblent renvoyer pour une proportion significative d'étudiants à la désignation électrostatique. Ce comportement va de pair avec une analyse du circuit électrique privilégiant certains points de celui-ci, notamment les pôles de générateurs, perçus comme chargés.Symbolic representations used in physics (Schemas, signs, etc.), are rarely explicitly taught. It is plausible that students supply this failure, by elaborating their own semantic. Thus, for significant number of students the + and - signs employed in electro kinetics, seem to have the same indication as in electrostatics. This behaviour keeps up with a specific approach of electric circuit, which privileges certain points, especially generator poles, perceived as charged

Variational analysis of flat-top solitons in Bose-Einstein condensates

Static and dynamic properties of matter-wave solitons in dense Bose-Einstein condensates, where three-body interactions play a significant role, have been studied by a variational approximation (VA) and numerical simulations. For experimentally relevant parameters, matter-wave solitons may acquire a flat-top shape, which suggests employing a super-Gaussian trial function for VA. Comparison of the soliton profiles, predicted by VA and those found from numerical solution of the governing Gross-Pitaevskii equation shows good agreement, thereby validating the proposed approach.Comment: 14 pages, 5 figure

Développement d’une nouvelle méthode de régionalisation basée sur le concept de « régime des débits naturels » : la méthode éco-géographique

Nous proposons une nouvelle méthode de régionalisation des débits fondée sur le concept de « régime des débits naturels » introduit en écologie aquatique : l’approche éco-géographique. Elle se distingue de deux approches de régionalisation existantes (approches hydrologique et écologique) sur les trois points suivants : le choix des variables hydrologiques, l’échelle d’analyse et la finalité de la régionalisation. En ce qui concerne le choix des variables hydrologiques, la nouvelle méthode est fondée sur le choix des caractéristiques des débits et non sur les variables hydrologiques. Ces caractéristiques des débits sont définies au moyen de l’analyse en composantes principales appliquée sur les variables hydrologiques. Contrairement aux autres approches, l’approche éco-géographique tient compte de toutes les caractéristiques des débits dans la régionalisation conformément au concept de « régime des débits naturels ». Quant à l’échelle d’analyse, à l’instar de l’approche écologique, la nouvelle méthode s’applique aussi à toutes les échelles d’analyse (annuelle, mensuelle et journalière) mais en les considérant séparément afin de tenir compte de toutes les caractéristiques de débits dans la régionalisation. Enfin, la finalité de la nouvelle méthode est de pouvoir déterminer les facteurs de variabilité spatiale des caractéristiques de débits (et non des variables hydrologiques) au moyen de l’analyse canonique des corrélations, notamment afin d’assurer une gestion durable des ressources hydriques dans un contexte de changement de l’environnement. Nous avons appliqué cette nouvelle méthode aux débits moyens annuels au Québec.Flow regionalization has been the subject of numerous hydrologic studies. However, despite the development of regionalization methods, there are still differences in the approaches used amongst hydrologists on the one hand, and between hydrologists and experts in other fields (aquatic ecology and physical geography) on the other hand. Those differences relate to five aspects of the regionalization process: the choice of hydrologic variables, station grouping methods to produce homogeneous hydrologic regions, the choice of appropriate statistical laws to estimate quantiles for non-gauged or partially-gauged sites, the scale of flow analysis, and the ultimate purpose of the regionalization exercise. Depending on the choice of hydrologic variables, the scale of analysis and their ultimate purpose, regionalization studies may thus be divided according to two distinct approaches: the hydrologic approach and the ecologic approach.The ultimate purpose of the hydrologic approach is to estimate flows at non-gauged or partially-gauged sites. For this reason, it has been primarily concerned with methods that allow the grouping of stations into homogeneous hydrologic regions and with the choice of statistical laws to estimate quantiles for non-gauged or partially-gauged sites. However, despite its undeniable interest from a practical point of view, this approach does not address the concerns of ecologists and geographers for three reasons: 1) the choice of hydrologic variables used for regionalization is not based on a scientific concept (this choice is arbitrary, and the variables selected do not constrain all the flow characteristics); 2) the ultimate purpose of the regionalization exercise is limited to estimating flows and is of limited interest to geographers and ecologists; 3) regionalization is performed at a daily scale, without taking into account other scales.To make up for these limitations, ecologists have recently proposed regionalization based on the “natural flow regime” concept (the ecologic approach), which allows all fundamental flow characteristics (magnitude, frequency, duration, timing of occurrence and variability) to be taken into account. The rationale for considering all flow characteristics is that each characteristic has an effect on the behaviour of river ecosystems. Hence, regionalization based on the ecologic approach relies on a large number of hydrologic variables that define the fundamental flow characteristics. Rather than being arbitrary, the choice of variable is based on this new paradigm. Regionalization using the ecologic approach considers all time scales, and its ultimate purpose is to account for differences in the structure and biological composition of aquatic ecosystems.However, one of the limitations of studies based on this approach is that, no matter how numerous they are, the variables used for regionalization do not constrain all flow characteristics, as required by the natural flow regime concept, so that application of this concept is incomplete. In addition, simultaneous analysis of all time scales does not allow consideration of all flow characteristics. To overcome these limitations, we propose a new regionalization approach based on the natural flow regime concept, an “ecogeographic” approach that differs from the ecologic approach in three ways. First, the proposed method is based on the use of flow characteristics rather than hydrologic variables. The reason for this is that there are an infinite number of hydrologic variables to define the five fundamental characteristics, making it impossible to account for all of them in the regionalization process. In contrast, since the number of fundamental flow characteristics is limited, they can all be taken into account, consistent with the “natural flow regime” requirements. Second, the ultimate purpose of the proposed regionalization method is to identify the physiographic and climatic factors that explain the spatial variability of these fundamental characteristics. To achieve this goal, it is necessary to analyze the different time scales (daily, monthly, annual) separately given the fact that it is impossible to constrain the effect of these various physiographic and climatic factors at all time scales. Indeed, some factors may show an effect at some time scales and not at others. This ultimate purpose addresses the concerns of geographers interested in explaining the spatial variability of such phenomena, among other things. Finally, separate analysis of the various time scales makes it possible to define all flow characteristics linked to a given time scale. As such, application of the “natural flow regime” concept to regionalization is complete.Application of the ecogeographical method involves four separate steps: 1) the definition of the flow characteristics for the hydrologic series of interest; 2) the determination of minor and major characteristics using principal component analysis, where a “major” flow characteristic is defined as one which meets the following criterion: TVE ≥ (100% / N), where N is the total number of characteristics that define the analyzed hydrologic series and TVE is the total variance explained; 3) the grouping of stations in homogeneous hydrologic regions based on factorial scores. Homogeneous hydrologic regions are divided in two types based on the presence or absence of stations: effective homogeneous regions contain stations whereas fictive homogenous regions do not; 4) the determination of the factors that affect the spatial variability of flow characteristics. This is achieved using canonical correlation analysis, an approach that we have applied to average annual flows in Quebec watersheds

Modes de variabilité temporelle des débits moyens annuels et leurs liens avec les indices climatiques au québec (canada)

La variabilité interannuelle des débits moyens annuels (1970-1995) de 70 stations hydrologiques réparties dans les trois grands bassins versants du Québec a été étudiée au moyen d’une analyse en composantes principales et d’un lissage par une moyenne mobile simple. Cinq modes de variabilité ont été ainsi identifiés selon la succession des phases de baisse et de hausse des débits. Les trois premiers modes caractérisent les rivières du bassin du fleuve Saint-Laurent. Le premier mode, qui regroupe le plus grand nombre de stations situées sur les deux rives du fleuve, montre une période de baisse des débits (avant 1980), suivie d’une longue phase de hausse modérée des débits. Ce mode est positivement corrélé à l’oscillation australe. Le second mode, qui regroupe les rivières situées au nord de la rive sud du Saint-Laurent, est caractérisé par des débits qui diminuent entre 1975 et 1985, puis augmentent. Il n’est corrélé à aucun indice climatique. Les stations qui forment le troisième mode sont principalement localisées en rive nord. Ce mode est caractérisé par deux phases de hausse séparées par une phase de baisse des débits. Certaines stations de ce mode sont corrélées aux oscillations arctique, australe et nord atlantique. Les deux derniers modes caractérisent les rivières situées au nord du 55e parallèle, dans les bassins de la Baie d’Ungava et de la Baie d’Hudson. Ces modes montrent une phase de diminution continue depuis la seconde période des années 1970 ou une phase de diminution précédée d’une longue phase normale des débits. Ils sont négativement corrélés à l’oscillation arctique et nord atlantique. Il se dégage de cette étude que la variabilité interannuelle des débits n’est pas synchrone à l’intérieur du bassin du fleuve Saint-Laurent.The temporal variability of the annual average discharges (1970-1995) of 70 hydrological stations distributed among Québec three main watersheds was studied by principal component analysis and smoothing by a simple moving average. Five temporal variability modes were thus identified according to the succession of decreasing and increasing discharge phases. The first three modes characterize rivers of the St. Lawrence watershed. The first mode, which includes the greatest number of stations located on both shores of the river, shows a period of decreasing discharges (before 1980), followed by a long phase of moderately increasing discharges. This mode is positively correlated with the Southern Oscillation. The second mode, which includes rivers located in the northern part of the south shore of the St. Lawrence, is characterized by discharges decreasing between 1975 and 1985 and then increasing. It is not correlated with any climate index. The stations forming the third mode are mainly located on the north shore. This mode is characterized by two increasing phases separated by a decreasing discharge phase. Some stations of this mode are correlated with the Arctic, Southern and North Atlantic Oscillations. The last two modes characterize rivers located north of the 55th parallel, in the Ungava Bay and Hudson Bay watersheds. These modes show a continuously decreasing phase since the second period of the 1970s or a decreasing phase preceded by a long normal discharge phase. They are negatively correlated with the Arctic and North Atlantic Oscillations. This study shows that the interannual discharge variability is not synchronous within the St. Lawrence River watershed

Seroprevalence of and associated risk factors for Leptospira interrogans serovar Hardjo infection of cattle in Setif, Algeria

Background: Leptospirosis is a cosmopolitan zoonosis caused by Leptospira interrogans responsible for heavy loss both economically and in health, in humans and animals. This study was conducted to determine the seroprevalence and risk factors associated with Leptospira interrogans serovar Hardjo infection in cattle in the state of Setif, northeastern Algeria.Methodology: Between the period 2015 and 2019, a total of 48 randomly selected herds of cattle were investigated, and 406 sera from apparently healthy cattle were analyzed using an indirect enzyme-linked immuno-sorbent assay (ELISA). In order to determine possible risk factors related to leptospirosis, a pre-validated questionnaire was administered to herd owners.Results: The herd prevalence of Leptospira interrogans serovar Hardjo was 31.25% (15/48, 95% CI 19.95–45.33) while the cattle prevalence was 5.42% (22/406, 95% CI 3.61–8.07). Multivariable logistic regression analysis showed that the age of cattle between 3 and 6 years (OR = 9.25; p< 0.03), breeding herd size > 20 cows (OR = 13.65; p< 0.01), and semi-intensive management system (OR = 0.21; p< 0,02) were significantly associated with seropositivity to Leptospira interrogans serovar Hardjo.Conclusion: We concluded from this study that Leptospira interrogans serovar Hardjo is circulating among cattle farms in the state of Setif, Algeria. Furthermore, we recommend more studies to be carried out to prove the infectivity and implementation good hygienic practices among cattle farms and people at risk. Keywords: ELISA, herds, questionnaire, leptospirosis, prevalence, Algeri

Existence and Uniqueness of the Solution for the Stochastic Equation of Motion of a Viscous Gas in a Discretized One-Dimensional Domain

A stochastic equation system corresponding to the description of the motion of a barotropic viscous gas in a discretized one-dimensional domain with a weight regularizing the density is considered. In [3], [4], the existence and uniqueness of the solution of this discretized problem in the stationary case was established. In this paper, by applying the technics used in [3], we generalize this result in the periodic case. 2010 Mathematics Subject Classification: 39A50, 34C25, 37N10, 34A45