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Les parasporines sont des toxines Cry du bacille de Thuringe actives contre des cellules tumorales. Ce travail montre que la parasporine PS1Aa2 (Cry31Aa2) forme des pores dans des membranes artificielles, comme de nombreuses toxines Cry. Ceux-ci ont plusieurs niveaux de conductance dont les plus fréquents étaient de 11, 16 et 21 pS dans une solution de 150 mM KCl. Nos résultats de microspectrofluorométrie avec la sonde Fura-2 montrent que la présence de la PS1Aa2 peut produire des augmentations du calcium intracellulaire, la plupart du temps sous la forme d’oscillations calciques et parfois des augmentations soutenues. Ces réponses ont été observées en présence et en absence de calcium extracellulaire, dans les lignées tumorales HeLa et HepG2 et dans la lignée non tumorale HEK 293. Bien que quelques études aient montré que le calcium semble intervenir dans leur mode d’action, de telles oscillations calciques n’ont jamais été décrites auparavant pour des toxines Cry. Les expériences ont dû être faites à des concentrations beaucoup plus élevées de toxine que prévues sur la base des résultats publiés de cytotoxicité. Malgré la présence des fragments identifiés auparavant comme actifs, sa faible efficacité semble liée à la présence d’ADN dans les préparations qui entraîne la précipitation de la protéine. Les travaux futurs sur cette toxine seraient donc grandement facilités par une amélioration de sa méthode de préparation. / Parasporins are Cry toxins from Bacillus thuringiensis that are active against tumor cells. This work shows that parasporin PS1Aa2 (Cry31Aa2) forms pores in artificial membranes like many Cry toxins. These pores have several levels of conductance; the most frequently seen in 150 mM KCl solutions were of 11, 16 and 21 pS. Our microspectrofluorometric results with the Fura-2 probe showed that the presence of PS1Aa2 can induce changes in intracellular calcium levels, most often in the form of calcium oscillations and sometimes as sustained increases. Such responses were observed in the presence and absence of extracellular calcium, with the tumor cell lines HeLa and HepG2, and with the non-tumorous cell line HEK 293. Calcium oscillations have not been described previously for Cry toxins even though some studies have shown that calcium appears to be involved in their mode of action. Our experiments required the use of much higher concentrations of toxin than suggested from the published cytotoxicity results. Despite the presence of fragments previously identified as active, its low efficacy appears to be related to the presence of DNA in the preparations causing the protein to precipitate. Future work on this toxin would therefore be greatly facilitated by an improvement in its method of preparation.

La production de radicaux libres oxygénés (ROS), la surcharge calcique cytosolique et l’ouverture des pores de transition membranaires mitochondriales (mPTP) consécutives à l’ischémie myocardique (IM) sont aggravées lors de la reperfusion. Dans cette thèse, nous nous sommes intéressés : 1) à l’évaluation des effets de la trimétazidine sur le seuil électrique de fibrillation ventriculaire (VFT) et sur les lésions structurales et fonctionnelles des mitochondries lors de l’IM (étude 1, N=26 porcs); 2) à la détermination de la cinétique d’évolution des lésions d’ischémie/reperfusion (I/R) (étude 2a, N=30 porcs) ;3) à l’étude de l’impact de la ranolazine, du propranolol et de leur association dans la préventions des lésions d’I/R (étude 2b, N=30 porcs). Ces études qui ont été réalisées sur le cœur de porcs anesthésiés, ont permis de suivre l’évolution des paramètres électrophysiologiques et hémodynamiques cardiaques et, à l’échelle cellulaire, l’évolution de la structure et de la fonction des mitochondries. Les résultats montrent : 1) dans l’étude 1 : que la TMZ prévient la chute du VFT et l’ensemble des altérations structurales et fonctionnelles mitochondriales observées lors de l’IM ; 2) dans l’étude 2a : que les lésions observées durant l’IM sont significativement aggravées dans les premières dizaines de secondes de la reperfusion alors qu’une certaine amélioration est observée après 10 et surtout 45 min de reperfusion; 3) dans l’étude 2b : qu’un prétraitement par de la ranolazine, du propranolol et par leur association réduit la sévérité de ces lésions d’I/R. Les mécanismes moléculaires et cellulaires d’action des produits utilisés dans cette étude seraient en rapport avec l’amélioration des lésions de l’I/R / The generation of reactive oxygen species (ROS), the cytosolic calcium overload and the opening of mitochondrial permeability transition pores (mPTP) resulting from myocardial ischemia (MI) are aggravated during reperfusion. In the present work, the following points have been addressed: 1) the evaluation of trimetazidine effects on the electrical threshold of ventricular fibrillation (VFT) and both structural and functional alterations of mitochondria during MI (study 1, N=26 pigs); 2) the determination of the kinetics of ischemia/reperfusion (I/R) lesions (study 2a, N=30 pigs); 3) the protective effects of ranolazine and propranolol, alone or combined on I/R lesions (study 2b, N=30 pigs). All studies were performed in anesthetized pigs. They allowed to follow changes in cardiac electrophysiological and hemodynamic parameters and, at the cellular level, changes in the structure and function of mitochondria. The obtained results show: 1) in study 1, that TMZ can prevent the drop in VFT and all structural and functional alterations of mitochondria noticed during MI; 2) in study 2a, that the lesions seen during MI are significantly aggravated within the first seconds of reperfusion whereas some improvement is observed after 10 minutes and more markedly after 45 minutes of reperfusion; 3) in study 2b, that pretreatment with ranolazine or propranolol, alone or combined can reduce the severity of I/R lesions. The molecular and cellular mechanisms of action of both agents are thought to be involved in this improvement of I/R lesions

Le dioxyde d’uranium (UO2) est utilisé en tant que combustible, sous forme de pastilles élaborées par métallurgie des poudres, dans les réacteurs nucléaires à eau pressurisée. Lors de transitoires de puissance, le centre des pastilles est le siège de mécanismes de déformation visco-plastique qui peuvent être partiellement reproduits, hors irradiation, par des essais de compression uniaxiale à haute température (typiquement 1500°C). Les conditions de sollicitation et la microstructure initiale des pastilles d’UO2 ont une influence sur leur comportement mécanique macroscopique. A l’échelle des grains, des mécanismes de sous-structuration interviennent mais, à ce jour, la sous-structure n’est pas quantifiée et le rôle des pores sur ces mécanismes n’est pas connu. Afin d’apporter des réponses sur ces points, deux lots de pastilles (L1 et L2) de taille de grains similaires, de même fraction volumique de pores, mais ceux-ci étant distribués différemment (2,5 fois plus de pores intra-granulaires dans L1 que dans L2), ont été fabriqués. Ils ont ensuite été soumis à des essais mécaniques dans différentes conditions. Le résultat montre que le lot L2 présente une vitesse de fluage plus élevée que le lot L1. Les techniques Electron BackScatter Diffraction (EBSD) et Electron Channeling Contrast Imaging (ECCI) ont été mises en œuvre et optimisées pour suivre l’évolution de la microstructure après déformation. En EBSD, le développement d’une procédure adaptée aux matériaux poreux a permis de détecter des sous-joints de grains (S-JG) de très faible désorientation (jusqu’à 0,1°), de mener une étude statistique de l'évolution de la sous-structuration des grains et d'évaluer la densité de dislocations géométriquement nécessaires générées. Différents types d’arrangements de dislocations formant les S-JG ont été révélés et analysés par ECCI. Grâce à la complémentarité de l’EBSD et de l’ECCI, la répartition des pores dans les grains et la localisation des S-JG ont pu être mises en regard. Les résultats montrent que le nombre ainsi que la fraction linéaire des S-JG et leur désorientation augmente avec le taux et la vitesse de déformation. Aux forts taux de déformation, cela conduit à la formation de nouveaux grains par un mécanisme de restauration/recristallisation dynamique par rotation de sous-grains. Pour des conditions de sollicitation identiques, les échantillons du lot L1 présentent un nombre et une fraction linéaire de S-JG nettement supérieurs à ceux du lot L2. De plus, dans le lot L1, les S-JG se localisent essentiellement à proximité des joints de grains alors qu’ils sont répartis dans l’ensemble du grain pour le lot L2. Ces différences seraient liées à une réduction du libre parcours moyen des dislocations du fait de la présence des pores intra-granulaires / Uranium dioxide (UO2) is used as a fuel, in pressurized water nuclear reactors, in the form of pellets produced by powder metallurgy. During power transients, the center part of pellets undergoes visco-plastic deformation by creep mechanisms. These mechanisms can be partially reproduced, out of irradiation, by uniaxial compression tests at high temperature (typically 1500°C). Testing conditions and initial microstructure of the UO2 pellets influence their macroscopic mechanical behavior. At the grain scale, sub-structuring mechanisms are involved, but, up to now, the sub-structure is not quantified and the role of pores on these mechanisms is unknown. In order to provide answers to these points, two batches of pellets (L1 and L2), characterized by a similar grain size, a same volume fraction of pores, but different pores distribution (2.5 times more intra-granular pores in L1 than in L2), were elaborated. They were submitted to mechanical tests under different conditions. The result shows that L1 has as a lower creep rate than L2. Electron Backscatter Diffraction (EBSD) and Electron Channeling Contrast Imaging (ECCI) techniques were used and optimized for porous materials to analyze the evolution of the microstructure after deformation. An original EBSD methodology was implemented to detect Sub-Grain Boundaries (S-GB) with very low disorientation angles (down to 0.1°), study statistically the grain fragmentation into sub-grains and evaluate the average density of the geometrically necessary dislocations. Thanks to ECCI, the arrangement of dislocations in some S-GB was evidenced and analyzed. EBSD and ECCI complementarity allowed relating the distribution of pores within the grains and the S-GB location. The results obtained on the two batches show that the number and the linear fraction of S-GB increases with the deformation level and rate. At high deformation rates, new grains appear by a mechanism of dynamic recovery/recrystallization by rotation of sub-grains. For identical loading conditions and strain rates, the samples of batch L1 have a number and a linear fraction of S-GB that are significantly higher than those of batch L2. Furthermore, in batch L1, S-GB are located essentially in the vicinity of the grain boundaries while they are distributed throughout the grain for batch L2. These microstructural differences seem to be related to a dislocation's mean free path reduction due to the presence of intra-granular pores

Le séchage et l’imbibition sont des phénomènes physiques indispensables, de nos jours, à la formulation de nombreux matériaux en milieu industriel. Ces phénomènes, comme on peut l’observer avec l’apparition de fissures lors du séchage d’une peinture fraichement appliquée, peuvent affecter de manière irréversible l’aspect, l’intégrité ou la durabilité du matériau concerné. De plus, dans l’industrie, la connaissance des mécanismes physiques mis en jeu lors de ces étapes de séchage ou d’imbibition reste fréquemment empirique, conduisant à de fortes consommations d’énergie. La compréhension fondamentale de ces phénomènes représente donc un enjeu industriel majeur.En utilisant des techniques de mesure telles que l’Imagerie à Résonnance Magnétique (IRM) ou la microscopie électronique, nous nous sommes intéressés à la physique des écoulements fluides dans des milieux poreux modèles, déformables ou non-déformables, dont la taille caractéristique des pores varie de l’échelle du millimètre à celle de quelques nanomètres.Le résultat essentiel de ces travaux de thèse est la démonstration que l’évolution de la distribution de liquide dans ces milieux modèles, lors du séchage, provient de la compétition entre deux phénomènes physiques, quelle que soit la taille des pores, et que le matériau fissure ou subisse du retrait. Ces phénomènes physiques sont : le ré-équilibrage capillaire, ayant lieu lors de la substitution de l’eau par l’air dans le milieu poreux, provoquant un écoulement fluide selon la direction du gradient des pressions de Laplace imposé au liquide par l’évaporation, et le développement d’une région sèche apparente depuis la surface libre de l’échantillon.Plus précisément, nous montrons que le phénomène de ré-équilibrage capillaire est permanent lors du séchage et permet de maintenir une saturation homogène dans les régions humides de l’échantillon quel que soit le régime de séchage rencontré ou la taille des pores de cet échantillon. Pour des pores de dimension supérieure à quelques nanomètres, nous montrons que le séchage s’opère en deux étapes : une première période à fort taux de séchage dont la durée décroit avec la réduction de la taille des pores, cette étape est suivie d’une seconde période présentant le développement d’une région sèche depuis la surface de l’échantillon provoquant une chute du taux de séchage. Nous démontrons aussi que les phénomènes de fracturation et de retrait peuvent influer de façon significative sur la durée de cette première période.Quand la taille des pores devient inferieure à quelques nanomètres, nous montrons que l’infime rayon de courbure de l’interface eau-air développant dans les pores du milieu poreux tend à limiter le taux d’évaporation de l’échantillon et entraine sa décroissance progressive au cours du séchage. De manière surprenante, dans ce cas particulier, la distribution d’eau à travers l’échantillon reste homogène tout au long du séchage. Cette dernière observation nous renseigne sur le fonctionnement du mécanisme de ré-équilibrage capillaire dans les nano-pores et montre que les propriétés d’écoulement liquides en milieux confinés diffèrent grandement de celles rencontrées dans des milieux plus grossiers / Drying and imbibition are widely used in industry to formulate and process materials. Familiar to anyone who ever filled a sponge with water and left it to dry, or spread a coat of paint, fluid to solid transitions may affect the aspect, the integrity and the durability of the material processing. Moreover, in industry this transitional steps frequently relies on empirical techniques for the control of both of these phenomena, resulting in an overconsumption of energy. The understanding of the mechanisms behind drying and imbibition are therefore of crucial industrial stakes.Using measurement techniques such as MRI imaging or electron microscopy, we studied the physics of fluid flow within model deformable and non-deformable porous media with pore sizes ranging from a couple of millimiters to a few nanometers, during imbibition or drying.A fundamental discovery our work features is the demonstration that during convective drying, in any case, namely even down to a nanometric pore size, and even if the material shrinks or fracture during the process, the liquid distribution within a sample evolves from the competition between two phenomena. Particularly, capillary re-equilibration caused by capillary effects inducing liquid flow to equilibrate Laplace pressure throughout the partially saturated regions of the samples, and, the inward development of an apparent dry region from the surface of the sample exposed to the airflow.In details, this manuscript shows that at all time capillary-equilibration enables to maintain a homogeneous saturation within the wet region of the porous sample and two regimes may be distinguished from considerations on the drying rate and the pore size of the material. Namely, for pore sizes superior to a couple of nano meters, a first regime exhibits a high drying rate down to lower saturation with increasing pore size, followed by a second regime where a dry region develops from the sample free surface, resulting in a falling rate period. Note that deformation such as shrinkage and crack may convey the extension of the period of high rate. However, in smaller pores the small curvature of the air-water interface limits the evaporation rate from the very beginning of the process and gives rise to a progressively decreasing drying rate while a homogeneous distribution of water is maintained throughout the sample. This last piece of information emphasizes that in nano-pores capillary equilibration still occurs in a series of instantaneous scattered rearrangements of liquid throughout the sample and finally that the flowing properties of the liquid strongly differ from standard unidirectional liquid flow

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Ce travail concerne principalement la détermination des propriétés acoustiques de mousses. Il s’agit d’un projet mené dans le cadre d’une collaboration entre une équipe de physico-chimie des mousses chargée de l’élaboration de matériaux modèles (laboratoire Navier UMR 8205 CNRS) et une équipe d’acousticiens chargée de l’étude de leurs propriétés acoustiques (laboratoire MSME UMR 8208 CNRS). Cette thèse s’articule essentiellement autour de trois parties principales, dont le contenu est résumé ci-dessous. 1) La première partie porte sur la génération de surfaces de réponse par des approximations polynomiales, dans le but de disposer d'un modèle intermédiaire entre le modèle éléments finis micro-macro et la réponse macroscopique. Au lieu d'appeler le modèle éléments finis systématiquement dans un travail d'optimisation, on a recourt à la surface de réponse qui contient l'information associée aux points de calcul éléments finis ainsi que les interpolations correspondantes. Ce manuscrit a été publié dans le journal AAA sous forme de communication rapide. 2) La deuxième partie porte sur la mise au point d'un modèle semi-analytique définit à partir d'une formule disponible pour prédire la perméabilité d'une plaque infinie percée par un trou de surface connue. Ce modèle, utilisé de manière appropriée, permet de calculer la perméabilité de mousses dont la taille de bulles est constante et le taux de fermeture de membranes variable. Des validations numériques par éléments finis et expérimentales sont proposées. L'article a été accepté pour publication dans la revue Physical Review E. 3) La troisième partie, porte sur un calcul éléments finis dans lequel un grand nombre de réalisations sont menées de manière à prendre en compte l'ensemble des combinaisons possibles lorsque on dispose de caractérisation expérimentales fines à l'échelle de la microstructure et que l'on souhaite connaitre la réponse de la mousse avec précision. Le manuscrit est en préparation et la revue visée pour ce dernier manuscrit est le journal Materials and Design. Une introduction et une conclusion générale complètent ces trois parties, et permettent de mettre en perspectives ces contributions par rapport à la littérature existante sur le sujet / This work mainly concerns the determination of the acoustic properties of foams. This is a project carried out as part of a collaboration between a team of physico-chemistry of foams in charge of the development of model materials (Navier laboratory UMR 8205 CNRS) and a team of acousticians responsible for the study of their acoustic properties (MSME laboratory UMR 8208 CNRS). This thesis is structured around three main parts, the content of which is summarized below. 1) The first part deals with the generation of response surfaces by polynomial approximations, in order to have an intermediate model between the micro-macro finite element model and the macroscopic response. Instead of calling the finite element model systematically in an optimization work, we use the response surface that contains the information associated with finite element calculation points and the corresponding interpolations. This manuscript was published in the AAA journal as a fast track publication. 2) The second part focuses on the development of a semi-analytical model defined from an available formula to predict the permeability of a circular orifice in a thin plate. This model, used in an appropriate way, makes it possible to calculate the permeability of foams with a constant bubble size but a tuned membrane content. Numerical validations by finite element computations are proposed. The article has been accepted for publication in the journal Physical Review E. 3) The third part deals with a finite element calculation in which a large number of realizations are carried out in order to take into account all the possible combinations when one has fine experimental characterization at the microstructure scale and that one seek to determine the properties of the foam with precision. The manuscript is in preparation and a possible journal for the publication of this manuscript is the journal Materials and Design. An introduction and a general conclusion complete these three parts, and make it possible to discuss these contributions

Submitted by LUMA CASTRO DE SOUZA null (lumasouza30@hotmail.com) on 2017-03-22T13:39:12Z No. of bitstreams: 1 Luma_Castro_de_Souza.pdf: 1962132 bytes, checksum: d9f166261796c44cf5d9fa2c419999e6 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-03-22T19:35:40Z (GMT) No. of bitstreams: 1 souza_lc_dr_jabo.pdf: 1962132 bytes, checksum: d9f166261796c44cf5d9fa2c419999e6 (MD5) / Made available in DSpace on 2017-03-22T19:35:40Z (GMT). No. of bitstreams: 1 souza_lc_dr_jabo.pdf: 1962132 bytes, checksum: d9f166261796c44cf5d9fa2c419999e6 (MD5) Previous issue date: 2017-03-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A operação de escarificação altera a estrutura do solo, afetando a dinâmica da emissão de CO2 do solo em curto período de tempo. Assim, com este estudo, objetivou-se: i - investigar a variação temporal da emissão de CO2 do solo após escarificação para o plantio da cana-de-açúcar em Latossolo e em Argissolo; ii - caracterizar a emissão de CO2, associada à distribuição de poros, em Latossolo e em Argissolo, submetidos à escarificação na linha de plantio e escarificação em área total para o plantio da cana-de-açúcar. O delineamento experimental utilizado foi em parcelas grandes pareadas. Os tratamentos utilizados consistiram na escarificação na linha de plantio (ELP) e escarificação em área total (EAT), em Latossolo e em Argissolo, localizados nos municipios de Guariba e Monte Alto, respectivamente. Para atender ao primeiro objetivo, avaliaram-se a emissão de CO2, a temperatura do solo (Tsolo) e a umidade do solo (Usolo) ao longo de 12 dias no Latossolo e em 11 dias no Argissolo, na camada de 0-0,10 m de profundidade. No Latossolo, não foi observado correlação entre a emissão de CO2, tanto com a Usolo como para Tsolo. No Argissolo, a emissão de CO2 foi correlacionada à Usolo, tanto no solo sob ELP (R2 = 0,86) quanto no solo sob EAT (R2 = 0,58). As emissões totais de CO2 no período de estudo foram maiores no Latossolo, no solo sob escarificação em linha de plantio e em área total (ELP = 1,042.6 kg CO2 ha-1 e EAT = 1,336.3 kg ha-1 de CO2), e menores no Argissolo (ELP = 659,1 kg CO2 ha-1 e EAT = 702,8 kg CO2 ha-1). No Latossolo, a emissão de CO2 foi menor no solo sob preparo com escarificação somente na linha de plantio do que no solo sob preparo com escarificação em área total. No Argissolo, a emissão de CO2 não diferiu em função do preparo. Para atender ao segundo objetivo, além de avaliar a emissão de CO2, temperatura e umidade do solo, avaliaram-se também a distribuição do tamanho de poros, o carbono orgânico associado aos minerais (COAM) e o carbono orgânico particulado (COP) na camada de 0-0,10 m de profundidade. No Latossolo, somente as propriedades: emissão de CO2, COP e classe de poro C4 (ɸ ≤ 0,04 mm) diferiram em função da escarificação. O modelo de regressão múltipla explicou 72% da variabilidade da emissão de CO2 no solo submetido a ELP para o COAM e C2 (0,05 < ɸ ≤ 0,1 mm). No Argissolo, a emissão de CO2, temperatura, umidade do solo, COAM, COP e as classes de tamanho de poros não diferiram em função das escarificações. Na regressão múltipla, a umidade do solo, C1 (ɸ ≥ 0,1 mm) e o COAM explicaram, juntas, 82% da variabilidade da emissão de CO2 no solo sob ELP. No Latossolo, a escarificação em linha de plantio e em área total afetaram diretamente a estrutura do solo, causando mudanças na porosidade e alterações na emissão de CO2 do solo. No Argissolo, a escarificação em linha de plantio e em área total não afetaram a emissão de CO2. / The chiseling operations alters the soil structure and affects the dynamics of the soil CO2 emission in a short period of time. Thus, the aim of this study was to: i- Investigate the temporal variation of CO2 emission after chiseling for the planting of sugarcane in Latossolo and Argissolo, ii – Characterize and correlation the soil CO2 emission and pore distribution in Latossolo and Argissolo with chiseling at line and total area to sugarcane planting. The experimental design used was in paired large plots. The treatments consisted of chiseling at the planting line (ELP) and chiseling at total area (EAT) in Latossolo and Argissolo, located in the municipalities of Guariba and Monte Alto, respectively. In order to attend the first aim, the CO2 emission, temperature and soil moisture were observed for 11 and 12 days, respectively at Argissolo and Latossolo, in the 0-0.10 m depth layer. The Latossolo did not show relationship among CO2 emission, Usoil and Tsoil to both chiseling. However, the Argissolo showed a significant relationship between the CO2 emission and Usoil to both chiseling, ELP (R2 = 0.86) and EAT (R2 = 0.58). The total CO2 emission was higher at Latossolo in both chiseling (ELP = 1,042.6 kg CO2 ha-1 and EAT = 1,336.3 kg ha-1 CO2) when compared with the Argissolo (ELP = 659.1 kg CO2 ha-1 and EAT = 702.8 kg CO2 ha-1). In the Latossolo, CO2 emission was lower in the soil under preparation with chiseling only in the planting line than in the soil under preparation with chiseling in the total area. In the Argissolo, the CO2 emission did not differ according to the preparation. In order to attend the second aim, the CO2 emission, temperature and soil moisture were also observed. Moreover, the distribution of pores size, organic carbon associated with minerals (COAM) and particulate organic carbon (COP) were also evaluated, in the 0-0.10 m depth layer. To Latossolo, the CO2 emission, COP and the distribution of pores size (C4; ɸ ≤ 0.04 mm) had significate difference between the chiseling. The multiple regression model was able to explain 72% of the CO2 emission variability to COAM and C2 (0.05 <ɸ ≤ 0.1 mm) at soil under ELP. To Argissolo, the CO2 emission, temperature, soil moisture, COAM, COP and distribution of pores size were not different between the chiseling. The soil moisture, C1 (ɸ ≥ 0,1 mm) and COAM were able to explain 82% of CO2 emission variability at soil under ELP. Therefore, the chiseling affected the soil porosity and soil CO2 emission directly at Latossolo. However, the chiseling did not affect the soil CO2 emission at Argissolo.

Improving agricultural water management is important for conserving water during dry seasons, using limited water resources in the most efficient way, and minimizing environmental risks (e.g., leaching, surface runoff). The understanding of water movement in different zones of agricultural production fields is crucial to developing an effective irrigation strategy. This work centered on optimizing field water management by characterizing the spatial patterns of soil hydraulic properties. Soil hydraulic conductivity was measured across different zones in a farmer’s field, and its spatial variability was investigated by using geostatistical techniques. Since direct measurement of hydraulic conductivity is time-consuming and arduous, pedo-transfer functions (PTFs) have been developed to estimate hydraulic conductivity indirectly through more easily measurable soil properties. Due to ignoring soil structural information and spatial covariance between soil variables, PTFs often perform unsatisfactorily when field-scale estimations of hydraulic conductivity are needed. The performance of PTFs in estimating hydraulic conductivity in the field was therefore critically evaluated. Due to the presence of structural macro-pores, saturated hydraulic conductivity (Ks) showed high spatial heterogeneity, and this variability was not captured by texture-dominated PTF estimates. However, the general spatial pattern of near-saturated hydraulic conductivity can still be reasonably generated by PTF estimates. Therefore, the hydraulic conductivity maps based on PTF estimates should be evaluated carefully and handled with caution. Recognizing the significant contribution of macro-pores to saturated water flow, PTFs were further improved by including soil macro-porosity and were proven to perform much better in estimating Ks compared with established PTFs tested in this study. Additionally, the spatial relationship between hydraulic conductivity and its potential influencing factors were further quantified by the state-space approach. State-space models outperformed current PTFs and effectively described the spatial characteristics of hydraulic conductivity in the studied field. These findings provided a basis for modeling water/solute transport in the vadose zone, and sitespecific water management.

Ostracodes, bi-valved crustaceans, are potentially excellent proxies for salinity.They are abundant, react to changes in salinity, and secrete low-magnesium calcite shells that preserve information about their host water chemistry. Changes in valve trace element concentration, stable isotope composition, and sieve pore shape values have been linked to changes in salinity. This study analyzed the response of the euryhaline ostracode, Cyprideis americana, to salinity in six lakes from two Bahamian islands across two seasons. The purpose of this work was to determine which compositional and morphological variables in C. americana are the most useful for paleosalinity reconstructions.Ostracode and water samples were collected from lakes of varying water chemistry on San Salvador Island (winter and summer seasons), and Exuma (winter season). Dissolved oxygen, pH, salinity, and temperature measurements were taken for each lake. The best-preserved valves from each lake were analyzed for sieve pore circularity, Mg and Ca concentrations, and δ18 O isotopic composition. Mg/Ca ratios and Kd[Mg] values were calculated for each lake. Each parameter was plotted against salinity for all of the lakes and for lakes from each season and island. Only the samples collected during the summer followed expected trends: with increases in lake water salinity, Mg/Ca ratio decreased, δ18 O composition increased, and sieve pore circularity decreased. Samples collected from the winter field sessions did not follow expected trends, potentially due to the breeding and moulting habits of C. americana. Temperature was more correlative with valve composition than a previous study of C. americana suggests, but is supportive of similar correlations of Cyprideis species in continental and other island settings. The valve Mg/Ca ratio and mean sieve pore circularity showed the best correlation with salinity and are the variables that will be most useful in paleosalinity studies from sediment cores. Future work should further investigate the relationship between mean sieve pore circularity and lake salinity as well as the breeding and moulting habits of C. americana. Such work may allow for past salinity ranges to be reconstructed from fossil C. americana samples.