Hydrodynamics of Ebrié lagoon as revealed by a chemical and isotopic study

To determine the origin and the circulation of waters in the different areas of the Ebrié lagoon (Ivory Coast), ionic concentrations (K+, Cl-) and isotopic ... measurements were performed. Sixty stations were sampled. Chemical and isotopic analyses were made thrice during a hydrological cycle : in may 1986, at the end of the great dry season; in October 1986, during the maximum of rainfall, in december 1987, after the Comoe river peak flow. From a hydrodynamical point of view, the results reported in this work indicate that the lagoon comprises four distinctive areas. The first is filled with freshwater all the year round and is characterized by an weak isotopic enrichment (these waters are of continental origin and annually renewed); the second corresponds to oligohaline waters ... (waters essentially of continental origin and poorly renewed); the third area is constituted of a mixure of waters of continental and oceanic origins. The latter group can be separated into two subgroups : a group completely renewed by oceanic water during the dry season and another group totally renewed by freshwater during the rainy and flood seasons. (D'après résumé d'auteur

Multi-class Image Segmentation in Fluorescence Microscopy Using Polytrees

Multi-class segmentation is a crucial step in cell image analysis. This process becomes challenging when little information is available for recognising cells from the background, due to their poor discriminative features. To alleviate this, directed acyclic graphs such as trees have been proposed to model top-down statistical dependencies as a prior for improved image segmentation. However, using trees, modelling the relations between labels of multiple classes becomes difficult. To overcome this limitation, we propose a polytree graphical model that captures label proximity relations more naturally compared to tree based approaches. A novel recursive mechanism based on two-pass message passing is developed to efficiently calculate closed form posteriors of graph nodes on the polytree. The algorithm is evaluated using simulated data, synthetic images and real fluorescence microscopy images. Our method achieves Dice scores of 94.5% and 98% on macrophage and seed classes, respectively, outperforming GMM based classifiers

Fossil evidence for a pharyngeal origin of the vertebrate pectoral girdle

The origin of vertebrate paired appendages is one of the most investigated and debated examples of evolutionary novelty. Paired appendages are widely considered key innovations that allowed new opportunities for controlled swimming and gill ventilation and were prerequisites for the eventual transition from water to land. The last 150 years of debate has been shaped by two contentious theories: the ventrolateral fin-fold hypothesis and the archipterygium hypothesis. The latter proposes that fins and girdles evolved from an ancestral gill arch. Although tantalizing developmental evidence has revived interest in this idea, it is apparently unsupported by fossil evidence. Here we present fossil evidence of a pharyngeal basis for the vertebrate shoulder girdle. We use CT scanning to reveal details of the braincase of Kolymaspis sibirica, a placoderm fish from the Early Devonian of Siberia that suggests a pharyngeal component of the shoulder. We combine these findings with refreshed comparative anatomy of placoderms and jawless outgroups to place the origin of the shoulder girdle on the sixth branchial arch. These findings provide a novel framework for understanding the origin of the pectoral girdle. Our new evidence clarifies the location of the presumptive head-trunk interface in jawless fishes and explains the constraint on branchial arch number in gnathostomes. The results revive a key aspect of the archipterygium hypothesis, but also reconciles it with the ventrolateral fin fold model

Homogénéisation des signaux isotopiques, 18O et 3H, dans un système hydrologique de haute montagne : la Vallée d'Aoste (Italie)

L'analyse de l'origine et de la dynamique des écoulements souterrains dans l'aquifère du milieu alluvial de la plaine d'Aoste (Italie) a été menée en étudiant les teneurs isotopiques (18O et 3H) des eaux sur l'ensemble du système hydrologique. La démarche a consisté en un suivi isotopique des précipitations pluvio-neigeuses, des sources de versants, du réseau de surface et de l'aquifère alluvial, complété par des analyses ponctuelles concernant l'horizon superficiel des glaciers et les sous-écoulements glaciaires. Le signal d'entrée en 18O porté par les précipitations présente une grande variabilité liée au contexte orographique (effet d'écran) et climatique (pluie ou neige). Celle-ci est mise en évidence par les changements saisonniers du gradient 18O/altitude. En moyenne annuelle (1994), ce gradient établi en Vallée d'Aoste à partir de mesures sur les précipitations récoltées entre 300 et 3500 m d'altitude (sur huit stations) est de - 0.18 ± 0.02 ‰ pour 100 m, avec un écart-type (s) des valeurs de ± 4,8 ‰. L'ensemble des résultats en 18O montre au cours du cycle hydrologique, un amortissement à la fois important et progressif du signal d'entrée fourni par les précipitations. Cet amortissement, de l'ordre de 30 fois dans l'aquifère alluvial (sigma=± 0.15 ‰), est particulièrement sensible au niveau de la glace et des sous-écoulements glaciaires. En ce qui concerne les résultats en 3H, les teneurs mesurées dans les précipitations se révèlent être étroitement liées avec l'origine et la trajectoire des masses d'air humide. Par ailleurs, on note une bonne concordance entre les temps de séjour des eaux dans l'aquifère alluvial calculés à partir des valeurs en 18O et ceux fournis par le 3H.The hydrogeological study of the alluvial aquifer of the Aosta plain (Italy) is chosen as one of the most appropriate examples representative of the Italian-French-Swiss Alps. This study has been carried out using two environmental isotopes (18O and 3H) for groundwater samples taken from this aquifer in order to shed light on the origin of water and the hydrodynamic characteristics of the aquifer.The surface area of this aquifer is 70 km_ and mean elevation ranges between 400 and 700 m (asl). This surface area constitutes a part of the watershed area that amounts 2400 km_ with a mean elevation of 2200 m (asl). The watershed possesses several mountain peaks, Mt. Blanc, Mt. Cervin, Mt. Grand Paradis, the elevation of which rise to over 4000 m.The input signal, quantitative and qualitative as well, provided by the precipitation shows a wide variability linked to both orographic (screen effect) and climatic (rain or snow) influences. This variability is marked by differences in the 18O/altitude gradient, which is seasonally dependent. A unique and linear relation is observed during spring and summer ; in autumn and winter results show an important gradient up to 2000 m but a less important one for higher altitudes.The mean annual (1994) gradient of - 0.18 ± 0.02 ‰ for 100 m is determined in Aosta valley for altitudes between 300 and 3500 m, and the standard deviation (sigma) of the mean volume-weighted value for precipitation is ± 4.8 ‰. Furthermore, the 18O values measured in the alluvial aquifer have shown a very low dispersion (sigma=± 0.15 ‰), which corresponds to a buffering effect of a factor 30. These results evidenced, thus, an homogenization process within the different water bodies.To analyze this homogenization process, the different components of the hydrologic system have been studied, i.e. the monitoring of the springs and runoff waters, with complementary local measurements of the upper part of ice cores and the glacier underflows. Using standard deviations (sigma) as criteria for the homogenization process, one can see a large and progressive decrease along the hydrological cycle, with a special amplitude in ice cores and glacier underflows : precipitation (± 4.8 ‰), ice core (± 0.8 ‰), glacier underflow (± 0.10 ‰), spring (± 0.15 ‰), surface runoff network (± 0.3 ‰), alluvial aquifer (± 0.15 ‰).In ice cores, the different process : freezing and thawing, compression, and vapor / liquid / solid exchanges have caused the 18O homogenization. Dealing with the springs on the slopes of the valley, the preferential flow paths linked to the fracturation lead to a mixing of waters and hence to a very buffered outflow signal. The combined effect of all these explains the stability and the uniformity of the data found in the alluvial water body.As far as the 3H concentrations are concerned, the values measured are tightly linked with the origin and the transport of humid air masses. For closely spaced stations, a significant difference in the input signal has been correlated to various climatic influences. Using 3H data from the Thonon-les-Bains station (included in the WMO-IAEA observation network) as input, the calculated transit times of 2.5 to 7.5 years are very close to those calculated with 18O, i.e. 4 to 7 years

Effect of Pores on Mechanical Behavior. Application to the Composite Material

The effects of microscopic pores, during the historical deformation on the behavior of ductile material are experimentally and numerically investigated. The material used in this study is constituted from the glass beads which are incorporated in the polyester resin. During moulding of these constituents, the pores remain in the material because of the resin viscosity. The experimental technique used for the characterization of the effect of pores is the tensile test. The constitutive equations of poroelastoplasticity are developed according to the micromechanical consideration. The material model developed by Gurson is extended to this composite material. The numerical results are obtained and compared with the experimental ones.Выполнены экспериментальное исследование и численное моделирование влияния микроскопических пор на поведение вязкого материала при деформировании с учетом истории нагружения. Объектом исследования служил композитный материал на основе полиэстер- ной резины с включениями из бисера. В процессе формовки указанных компонентов в материале образуются поры из-за вязкости резины. Для оценки эффекта пор использовали экспериментальную технологию испытаний на растяжение. В рамках микромеханического подхода получены основные уравнения пороупругопластичности. Проведено обобщение модели материала Гурсона на исследуемый композитный материал. Результаты расчетов сопоставлены с экспериментальными данными.Виконано експериментальні дослідження і числове моделювання впливу мікроскопічних пор на поведінку в ’язкого матеріалу при деформуванні з урахуванням історії навантаження. Об’єктом дослідження служив композитний матеріал на основі поліестерної гуми з вкрапленнями з бісеру. У процесі формовки указаних компонентів у матеріалі з ’являються пори внаслідок в ’язкості гуми. Для оцінки ефекту пор використовували експериментальну технологію випробувань на розтяг. У рамках мікромеханічного підходу отримано основні рівняння поропружнопластичності. Проведено узагальнення моделі матеріалу Гурсона на композитний матеріал, що досліджується. Розрахункові результати зіставляються з експериментальними

Bayesian Polytrees With Learned Deep Features for Multi-Class Cell Segmentation.

The recognition of different cell compartments, the types of cells, and their interactions is a critical aspect of quantitative cell biology. However, automating this problem has proven to be non-trivial and requires solving multi-class image segmentation tasks that are challenging owing to the high similarity of objects from different classes and irregularly shaped structures. To alleviate this, graphical models are useful due to their ability to make use of prior knowledge and model inter-class dependences. Directed acyclic graphs, such as trees, have been widely used to model top-down statistical dependences as a prior for improved image segmentation. However, using trees, a few inter-class constraints can be captured. To overcome this limitation, we propose polytree graphical models that capture label proximity relations more naturally compared to tree-based approaches. A novel recursive mechanism based on two-pass message passing was developed to efficiently calculate closed-form posteriors of graph nodes on polytrees. The algorithm is evaluated on simulated data and on two publicly available fluorescence microscopy datasets, outperforming directed trees and three state-of-the-art convolutional neural networks, namely, SegNet, DeepLab, and PSPNet. Polytrees are shown to outperform directed trees in predicting segmentation error by highlighting areas in the segmented image that do not comply with prior knowledge. This paves the way to uncertainty measures on the resulting segmentation and guide subsequent segmentation refinement

Interacting polytropic gas model of phantom dark energy in non-flat universe

By introducing the polytropic gas model of interacting dark energy, we obtain the equation of state for the polytropic gas energy density in a non-flat universe. We show that for even polytropic index by choosing $K>Ba^{\frac{3}{n}}$, one can obtain $\omega^{\rm eff}_{\Lambda}<-1$, which corresponds to a universe dominated by phantom dark energy.Comment: 7 page

Holographic dark energy in a non-flat universe with Granda-Oliveros cut-off

Motivated by Granda and Oliveros (GO) model, we generalize their work to the non-flat case. We obtain the evolution of the dark energy density, the deceleration and the equation of state parameters for the holographic dark energy model in a non-flat universe with GO cut-off. In the limiting case of a flat universe, i.e. $k = 0$, all results given in GO model are obtained.Comment: 11 pages, 5 figure

A cross dialectal view of the Arabic dative alternation

This paper is concerned with the syntax of ditransitive verbs in Arabic.We concentrate on the vernaculars, focussing in particular on three geographically spread dialects: Egyptian Cairene Arabic, the dominant vernacular in Egypt, Hijazi Arabic, spoken in Western Saudi Arabia and Maltese, a mixed language with a Magrebi/Siculo-Arabic stratum. We show that all three exhibit an alternation (the dative alternation) between a ditransitive ('double object') construction and a corresponding prepositional dative construction, and outline a number of differences between these constructions in the different varieties of Arabic. We consider the distribution of verbs exhibiting the dative alternation in the light of Ryding's (2011) observations concerning Modern Standard Arabic