Etude des variations saisonnières des crues par le modèle de dépassement

Cet article présente les résultats d'une étude traitant de deux aspects importants de l'application du modèle de dépassement en hydrologie. Ce modèle a été utilisé pour l'étude des variations saisonnieres des débits des rivières du Québec et du Nouveau-Brunswick. Ces variations ont généralement un effet important sur l'homogénéité des débits dans différentes périodes de l'année. Les modèles de dépassement sont capables de prendre ces variations saisonnières en considération en tenant compte des dépassements qui ne sont pas identiquement distribués lorsqu'ils proviennent de différentes saisons. L'étude traite spécialement le problème du choix de saisons à entrer dans le modèle. Particulièrement, on souligne l'importance de déterminer les saisons en se basant sur les données disponibles au lieu de se limiter aux quatre saisons habituelles: hiver, printemps, été et automne. On propose une procédure graphique qui, associée au modèle de dépassement, permet de délimiter les saisons dans les stations hydrologiques étudiées. La procédure est appliquée, sous deux formes différentes, à des stations de jaugeage dans les provinces du Québec et du Nouveau-Brunswick. Ceci nous a permis de diviser l'année convenablement en saisons dans différentes parties des deux provinces. Cette partition a été basée uniquement sur les débits de crues dans chaque station, et sans donner aucune considération à la location géographique de ces stations, mais il s'est avéré ultérieurement que cette subdivision des deux provinces représente en fait une partition géographique des stations hydrologiques.L'évaluation du débit de base représente un point d'une importance majeure dans l'application du modèle de dépassement. Une estimation du débit de base est proposée dans ce travail en utilisant l'analyse de régression multiple. Une approche basée sur l'ajustement du nombre de dépassements à une loi de Poisson a été suivie pour la détermination de ce niveau de base dans chaque station de jaugeage. Une forte corrélation est détectée entre le débit de base et la surface drainée, impliquant qu'il est possible de calculer le débit de base dans une station qui ne contient pas d'enregistrements.Les résultats de la régionalisation géographique de la saisonnalité sont analysés pour détecter et interpréter les liens entre les régions déterminées et les caractéristiques physiques et climatologiques des zones étudiées dans les deux provinces. Une association est démontrée entre ces deux paramètres qui semble être justifiable du point de vu hydrologique et climatologique. En conclusion, les résultats de cet article montrent la faisabilité technique et l'efficacité du modèle proposé pour l'étude des variations saisonnières des crues.The partial duration series (pds) method for flood frequency estimation analyzes ail flood peaks above a certain base level, or truncation level, QB, along with the times of occurrence of these flood « exceedances ». It has been shown that seasonal trends in river-flow processes have a significant effect on the distribution of flood exceedances. Two pds models have been presented in the literature for studying these seasonal variations in flood magnitude. The first, which can be called the « discrete seasonal pds mode) », divides the year into n seasons and determines n different distribution functions to fit the exceedances in each of these n seasons. The second, which can be called the « continuous seasonal pds model », accounts for seasonal flood variations by modeling flood magnitude as a continuous time-dependent random variable. The discrete seasonal model makes a few assumptions concerning flood characteristics, but the statistical estimation of its parameters is considerably less complex than in the case of the continuous seasonal model. Results of a study using the discrete seasonal pds modal are presented in this paper, along with two important applications of this modal in hydrology.The model is applied to 34 gaging stations in the province of Quebec and 28 stations in the province of New-Brunswick, Canada. Knowing the base level, QB, is essential for applying this model, but there is no universal technique for determining this truncation level. In this study, a technique is proposed that uses multiple regression for estimating QB. Regression equations, using one or more transformed or untransformed independent variables, are derived. Results for the province of Quebec show that the two-year flood estimate QDA explains 92.5 % of the variability of the base flow QB, and the drainage basin area SD explains 83 % of QB variability. The existence of a strong correlation between QB and SD suggests that it is possible to determine the base flow at sites where no historical record is available, by using the physical characteristics of the basin.A graphical procedure associated with the partial duration series model is proposed to study the seasonal trends in flood data at the selected gaging stations. The study deals specifically with the choice of seasons to be entered into the pds model. It is particularly emphasized that the seasons should be determined on the basis of the data on band, instead of taking the four usual seasons (winter, spring, summer, and fall). Two different forms of the graphical procedure are applied to the gaging stations in the provinces of Quebec and New Brunswick. The first, applied to the province of Quebec, consists of plotting the mean number of exceedances A (t) in a lime interval (0, 1•] equal 1a one year, against the lime t, for each station, and for a number of increasing base levels. The behavior of these A (1) plots (change at slope, piecewise linearity, etc.) indicates the significant seasons for each station. The second form of the graphical procedure, applied to stations in the province of New-Brunswick, is slightly different front the procedure mentioned above. For each station of the province, a relatively high base level is selected, corresponding to a mean number of exceedances per year in the order of 0.3 to 1.0. The Limes of occurrence of these exceedances are used to define the significant hydrological seasons in the year, which are then presented in graphical form. Varying the base level gives a fine seasonal partitioning of the year for each station, and allows grouping the stations into geographical regions that are homogeneous In seasonal flood distribution. Both versions of the graphical procedure are based on the same idea, and call far careful graphical examination of the seasonal behavior of floods at different gaging stations.An appropriate partitioning of the year into seasons is obtained for different parts of the two provinces. For bath provinces, and for al' the stations that were investigated, no more than two significant seasons were found necessary for modeling seasonal flood variations. Based on the seasons determined for each station, and the geographical distribution of these stations, a geographical regionalization of seasonality Is obtained for the provinces of Quebec and New-Brunswick. Each province is divided into tour homogeneous regions, and appropriate seasons for each region are proposed.The discrete seasonal model was found adequate and sufficient for the study of the seasonal behavior of floods in the provinces of Quebec and New-Brunswick. However, more detailed studios would be necessary to determine with more certitude if the continuous seasonal model is more appropriate in some cases. In all cases, a graphical examination of the empirical distribution function of flood magnitudes occurring in various periods of the year may help either in identifying homogeneous periods within which flood magnitudes may be considered as identically distributed, or In indicating a need for modeling flood magnitude as a random variable whose distribution varies continuously with time

Estimation de la température de l'eau de rivière en utilisant les réseaux de neurones et la régression linéaire multiple

La température de l'eau en rivière est un paramètre ayant une importance majeure pour la vie aquatique. Les séries temporelles décrivant ce paramètre thermique existent, mais elles sont moins nombreuses et souvent courtes, ou comptent parfois des valeurs manquantes. Cette étude présente la modélisation de la température de l'eau en utilisant des réseaux de neurones et la régression linéaire multiple pour relier la température de l'eau à celle de l'air et le débit du ruisseau Catamaran, situé au Nouveau-Brunswick, Canada. Une recherche multidisciplinaire à long terme se déroule présentement sur ce site. Les données utilisées sont de 1991 à 2000 et comprennent la température de l'air de la journée en cours, de la veille et de l'avant-veille, le débit ainsi que le temps transformé en série trigonométrique. Les données de 1991 à 1995 ont été utilisées pour l'entraînement ou la calibration du modèle tandis que les données de 1996 à 2000 ont été utilisées pour la validation du modèle. Les coefficients de détermination obtenus pour l'entraînement sont de 94,2 % pour les réseaux de neurones et de 92,6 % pour la régression linéaire multiple, ce qui donne un écart-type des erreurs de 1,01 C pour les réseaux de neurones et de 1,05 C pour la régression linéaire multiple. Pour la validation, les coefficients de détermination sont de 92,2 % pour les réseaux de neurones et de 91,6 % pour la régression linéaire multiple, ce qui se traduit en un écart-type des erreurs de 1,10 C pour les réseaux de neurones et de 1,25 C pour la régression linéaire multiple. Durant la période d'étude (1991-2000), le biais a été calculé à +0,11 C pour le modèle de réseaux de neurones et à -0,26 °C pour le modèle de régression. Ces résultats permettent de conclure qu'il est possible de prévoir la température de l'eau de petits cours d'eau en utilisant la température de l'air et le débit, aussi bien avec les réseaux de neurones qu'avec la régression linéaire multiple. Les réseaux de neurones semblent donner un ajustement aux données légèrement meilleur que celui offert par la régression linéaire multiple, toutefois ces deux approches de modélisation démontrent une bonne performance pour la prédiction de la température de l'eau en rivière.Water temperature is a parameter of great importance for water resources. For instance, modifications of the thermal regime of a river can have a significant impact on fish habitat. Therefore, understanding and predicting water temperatures is essential in order to help prevent or forecast high temperature problems. In order to predict water temperatures, data series are necessary. Many data series exist for air temperatures, but water temperature series are relatively scarce and those available are often short or have missing values. This study presents the modelling of water temperature using neural networks and multiple linear regression to relate water temperature to air temperature and discharge in Catamaran Brook, New Brunswick, Canada.Catamaran Brook is a small stream (51 km2) where long-term multidisciplinary habitat research is being carried out. Many variables can impact water temperatures in a river, such as air temperature, solar radiation, wind speed, discharge, groundwater flow, etc. For this study, only air temperature and discharge were used. These were judged to be the most often available parameters for modelling temperatures in rivers, and to have the greatest impact on water temperature. More precisely, input variables included current air temperature (°C), air temperature of the previous day (°C), air temperature two days earlier (°C), discharge (m3 /s) and a trigonometric function of time (days). Data used for the analysis were from 1991 to 2000. Data from 1991 to 1995 were used to calibrate the model while data from 1996 to 2000 were used for validation purposes. Observed and predicted water temperatures for each model were presented for the calibration data and the validation data. The coefficient of determination, R2, was used to compare the efficiency of both models as well as the residual standard deviation and the bias. This is equivalent to basing the comparison on the standard deviation (or variance) of the residuals. Coefficients of determination for calibration were 94.2% for the neural networks and 92.6% for the multiple linear regression, which correspond to a residual standard deviation of 1.01°C for the neural networks and of 1.05°C for the multiple linear regression. For validation, coefficients of determination were 92.2% for the neural networks and 91.6% for the multiple linear regression, which correspond to a residual standard deviation of 1.10°C for the neural networks, and of 1.25°C for the multiple regression. The overall bias during the study period (1991-2000) was calculated at +0.11°C for the neural network model and at -0.26°C for the regression model. Results indicated that it was possible to predict water temperature for a small stream using air temperature, flow and time, as input variables, with neural networks and multiple linear regression. The residual series obtained by both models were very similar. Of the two models, neural networks gave slightly better results in terms of fit, but the small difference in results lets us believe that both approaches are equally good in predicting stream water temperatures

Inflammatory monocytes require type I interferon receptor signaling to activate NK cells via IL-18 during a mucosal viral infection

The requirement of type I interferon (IFN) for natural killer (NK) cell activation in response to viral infection is known, but the underlying mechanism remains unclear. Here, we demonstrate that type I IFN signaling in inflammatory monocytes, but not in dendritic cells (DCs) or NK cells, is essential for NK cell function in response to a mucosal herpes simplex virus type 2 (HSV-2) infection. Mice deficient in type I IFN signaling, Ifnar(-/-) and Irf9(-/-) mice, had significantly lower levels of inflammatory monocytes, were deficient in IL-18 production, and lacked NK cell-derived IFN-gamma. Depletion of inflammatory monocytes, but not DCs or other myeloid cells, resulted in lower levels of IL-18 and a complete abrogation of NK cell function in HSV-2 infection. Moreover, this resulted in higher susceptibility to HSV-2 infection. Although Il18(-/-) mice had normal levels of inflammatory monocytes, their NK cells were unresponsive to HSV-2 challenge. This study highlights the importance of type I IFN signaling in inflammatory monocytes and the induction of the early innate antiviral response

Variation of the mastoid segment of the facial canal and of the stylomastoid foramen

Universitatea de Stat de Medicină şi Farmacie „Nicolae Testemiţanu”, Chişinău, Republica MoldovaIntroduction. Taking into consideration that the ratio of the facial nerve iatrogenic injuries in primary mastoidectomy is 0.6%-3.7%, and a twice higher ratio of 4%-10% is reported for the revision surgery, the knowledge about variability of the mastoid segment of the facial canal and its exit orifice is of high clinical significance for the head and neck surgery. Aim of study. The purpose of our study was to determine the variability and specific features of the mastoid segment of the facial canal and of the stylomastoid foramen. Methods and materials. Our research was carried out at the Department of anatomy and clinical anatomy of Nicolae Testemitanu State University of Medicine and Pharmacy of the Republic of Moldova. Out of 82 temporal bones, 41 were from the right side and 41 were from the left one. The length of the mastoid segment of the facial canal, its exit angle, the transverse and longitudinal diameters of the stylomastoid foramen were taken. For the database storage an Excel 2019 sheath was used. For the statistical analysis of the obtained morphometric parameters the descriptive and inferential statistics methods were applied. Results. Three variants of the mastoid segment exit angle were determined: sharp, right and obtuse angles. The exit angle of the mastoid segment on the right temporal bones had a mean value of 112.9±23.61° and on the left side it was 113.1±19.76°, p=0.971. The mean length of the mastoid segment on the right temporal bones was 15.7±3.66 mm and on the left bones it was 14.5±3.84 mm, p=0.153. The transverse diameter of the stylomastoid foramen on the right specimens was 2.9±0.80 mm, and on the left ones it was 2.4±0.60 mm, with a statistically significant difference, p=0.012. The longitudinal diameter of the right stylomastoid foramens had a mean value of 3.3±0.96 mm, and of the left orifices it was 2.7±0.81 mm, with a statistically significant difference, p=0.007. Variable shapes of the stylomastoid foramen were established: oval, round, triangular, quadrangular, semilunar and irregular shapes. Conclusion. Both the mastoid segment of the facial canal and the stylomastoid foramen are subjected to individual variability. Three variants were characteristic of the mastoid segment exit angle: sharp, right and obtuse ones. The exit angle of the mastoid segment of the facial canal was higher on the left side, but the length of the mastoid segment was higher on the right side. Both the transverse and the longitudinal diameters of the stylomastoid foramen were higher on the right side. The transverse diameter of the stylomastoid foramen, on both sides, had lower mean values compared to the mean values of its longitudinal diameter. primary mastoidectomy is 0.6%-3.7%, and a twice higher ratio of 4%-10% is reported for the revision surgery, the knowledge about variability of the mast oid segment of the facial canal and its exit orifice is of high clinical significance for t he head and neck surgery. Aim of study. The purpose of our study was to determine the variability and s pecific features of the mastoid segment of the facial canal and of the st ylomastoid foramen. Methods and materials. Our research was carried out at the Department of anatomy and clinical anatomy of Nicolae Testemitanu State University of Medicine and Pharmacy of the Republic of Moldova. Out of 82 temporal bones, 41 were from the right side and 41 were from the left one. The length of the mastoid segment of the facial canal, its exit angle, the transverse and longitudinal diameters of the stylomastoid foramen were taken. For the database storage an Excel 2019 sheath was used. For the statistical analysis of the obtained m orphometric parameters the descriptive and inferential statistics methods were applied. Results. Three variants of the mastoid segment exit angle were determined: sharp, right and obtuse angles. The exit angle of the mastoid segment on the right temporal bones had a mean value of 112.9±23.61° and on the left side it was 113.1±19.76°, p=0.971. The mean l ength of the mastoid segment on the right temporal bones was 15.7±3.66 mm and on the left bones it was 14.5±3.84 mm, p=0.153. The transverse diameter of the stylomastoid for amen on the right specimens was 2.9±0.80 mm, and on the left ones it was 2.4±0.60 mm, with a st atistically significant difference, p=0.012. The longitudinal diameter of the right stylomasto id foramens had a mean value of 3.3±0.96 mm, and of the left orifices it was 2.7±0.81 mm, with a statistically significant difference, p=0.007. Variable shapes of the stylomastoid foramen were es tablished: oval, round, triangular, quadrangular, semilunar and irregular shapes. Conclusion. Both the mastoid segment of the facial canal and the stylomastoid foramen are subjected to individual variability. Three variants were chara cteristic of the mastoid segment exit angle: sharp, right and obtuse ones. The exit angle of th e mastoid segment of the facial canal was higher on the left side, but the length of the mastoid se gment was higher on the right side. Both the transverse and the longitudinal diameters of the st ylomastoid foramen were higher on the right side. The transverse diameter of the stylomastoid for amen, on both sides, had lower mean values compared to the mean values of its longitudinal diameter

Paleoecological Successions from Shallow-marine Depositional Environments in Upper Silurian Carbonate Rocks of Blair County, Pennsylvania

Studies of paleoenvironment and paleoecology are important for investigating relationships between the different environmental and biological variables that influenced biodiversification patterns during the Silurian Period. The mixed carbonate and siliciclastic rocks of the Bloomsburg and Mifflintown Formations in central Pennsylvania represent transitions between carbonate ramp and deltaic settings. The goal of this study was to assess changes in depositional environment and paleoecology of an undescribed Bloomsburg/Mifflintown locality in Bellwood, Pennsylvania. In central Pennsylvania, the interfingered relationship of mixed carbonate and siliciclastic mudstones of the Mifflintown Formation with red fine-grained sandstones and shales of the Bloomsburg Formation presented challenges for deciphering the formations. Five stratigraphic sections were measured and described, in addition to identification of fossils and petrographic analysis of rock samples. A relatively diverse range of marine invertebrate fossils was observed, including ostracods, brachiopods, mollusks, crinoids, tentaculitids, bryozoa. orthocerid nautiloids, sponges, tabulate corals, and a rare eurypterid tergite. Nine lithologies were identified, including: (1) bioclastic wackestone-packstone, (2) siliciclastic mudstone, (3) mottled nodular-bedded packstone (4) fossiliferous mudstone-wackestone, (5) laminated peloidal grainstone, (6) recrystallized skeletal packstone, (7) intraclastic conglomerate and detrital carbonates, (8) massive microcrystalline carbonate, and (9) laminated brown calcareous mudstone. The observed fossil taxa were identified to study patterns in paleoecological and faunal community composition across different depositional environments. Based on lithological associations, four lithofacies were identified: (1) distal slope, (2) open lagoon and subtidal channels, (3) intertidal channels, and (4) tidal flat and channels. Most paleoenvironmental shifts were gradual. Paleoecology patterns assessed at the community-level illustrated variation in fauna based on substrate consistency and energy levels. The majority of paleoecommunities consisted of open marine fauna, with one community dominated by semi-restricted, brackish fauna. Faunal communities showed more variation in open marine environments such as ramp, open lagoon, and reef shoals. The undifferentiated Bloomsburg and Mifflintown Formations at Bellwood, Pennsylvania illustrate a general coarsening-upward sequence that reflects a shallowing of depositional environments likely relating to fluxes in siliciclastic sediment input, relating to lateral migration of a coastal delta, relative sea level change, or potentially both. Deposition was dominated by storm-driven processes, with lesser influence of tidal energy during periods of fair weather. The stratigraphy exposed at the Bellwood outcrop represents the evolution of a semi-protected, muddy, low-gradient carbonate ramp system, as it became influenced by siliciclastic influx associated with coastal delta progradation