Importance of storm events in controlling ecosystem structure and function in a Florida gulf coast estuary

From 8/95 to 2/01, we investigated the ecological effects of intra- and inter-annual variability in freshwater flow through Taylor Creek in southeastern Everglades National Park. Continuous monitoring and intensive sampling studies overlapped with an array of pulsed weather events that impacted physical, chemical, and biological attributes of this region. We quantified the effects of three events representing a range of characteristics (duration, amount of precipitation, storm intensity, wind direction) on the hydraulic connectivity, nutrient and sediment dynamics, and vegetation structure of the SE Everglades estuarine ecotone. These events included a strong winter storm in November 1996, Tropical Storm Harvey in September 1999, and Hurricane Irene in October 1999. Continuous hydrologic and daily water sample data were used to examine the effects of these events on the physical forcing and quality of water in Taylor Creek. A high resolution, flow-through sampling and mapping approach was used to characterize water quality in the adjacent bay. To understand the effects of these events on vegetation communities, we measured mangrove litter production and estimated seagrass cover in the bay at monthly intervals. We also quantified sediment deposition associated with Hurricane Irene's flood surge along the Buttonwood Ridge. These three events resulted in dramatic changes in surface water movement and chemistry in Taylor Creek and adjacent regions of Florida Bay as well as increased mangrove litterfall and flood surge scouring of seagrass beds. Up to 5 cm of bay-derived mud was deposited along the ridge adjacent to the creek in this single pulsed event. These short-term events can account for a substantial proportion of the annual flux of freshwater and materials between the mangrove zone and Florida Bay. Our findings shed light on the capacity of these storm events, especially when in succession, to have far reaching and long lasting effects on coastal ecosystems such as the estuarine ecotone of the SE Everglades.

Segregation of Palaemonid Shrimp Along an Everglades Estuarine Gradient: Do Multiple Species Have Similar Trophic Function?

Variation in physical gradients and production along estuaries can alter species compositions. Spatiotemporal variation in abundance and distribution of palaemonid shrimp species was investigated in relation to seasonal freshwater inputs and salinity in the Shark River Estuary, Everglades National Park, Florida, USA. Using trapping techniques, multiple sites were sampled repeatedly extending from the headwaters to the Gulf of Mexico. Stable isotope analyses were also performed on a subset of samples. Five palaemonid species occurred in the samples: Palaemonetes paludosus (Gibbes, 1850), Palaemonetes pugio (Holthuis, 1949), Palaemonetes intermedius (Holthuis, 1949), Palaemon floridanus (Chace, 1942), and Leander paulensis(Ortmann, 1897). Overall, shrimp catches in traps doubled in the dry season. Catches in the upper estuary were dominated by P.paludosus, particularly in the wet season, while catch per unit effort at the most downstream and highest salinity sites were dominated by P. floridanus. At mid-estuary, several species co-occurred. δ15n analyses revealed that most species filled similar roles in the community, with the exception of P. paludosus, which shifted from enrichment in the dry season to depletion in the wet season as it expanded downstream in the estuary. Palaemonid δ13C values varied between sites and seasons, with shrimp in upstream sites being more depleted. These data suggest that changes in salinity regimes resulting from Everglades restoration efforts may result in species replacement, with potential implications for trophic dynamics.

Stochastic descriptors to study the fate and potential of naive T cell clonotypes in the periphery

The population of naive T cells in the periphery is best described by determining both its T cell receptor diversity, or number of clonotypes, and the sizes of its clonal subsets. In this paper, we make use of a previously introduced mathematical model of naive T cell homeostasis, to study the fate and potential of naive T cell clonotypes in the periphery. This is achieved by the introduction of several new stochastic descriptors for a given naive T cell clonotype, such as its maximum clonal size, the time to reach this maximum, the number of proliferation events required to reach this maximum, the rate of contraction of the clonotype during its way to extinction, as well as the time to a given number of proliferation events. Our results show that two fates can be identified for the dynamics of the clonotype: extinction in the short-term if the clonotype experiences too hostile a peripheral environment, or establishment in the periphery in the long-term. In this second case the probability mass function for the maximum clonal size is bimodal, with one mode near one and the other mode far away from it. Our model also indicates that the fate of a recent thymic emigrant (RTE) during its journey in the periphery has a clear stochastic component, where the probability of extinction cannot be neglected, even in a friendly but competitive environment. On the other hand, a greater deterministic behaviour can be expected in the potential size of the clonotype seeded by the RTE in the long-term, once it escapes extinction.

Realized Matrix-Exponential Stochastic Volatility with Asymmetry, Long Memory and Spillovers

The paper develops a novel realized matrix-exponential stochastic volatility model of multivariate returns and realized covariances that incorporates asymmetry and long memory (hereafter the RMESV-ALM model). The matrix exponential transformation guarantees the positivedefiniteness of the dynamic covariance matrix. The contribution of the paper ties in with Robert Basmann’s seminal work in terms of the estimation of highly non-linear model specifications (“Causality tests and observationally equivalent representations of econometric models”, Journal of Econometrics, 1988, 39(1-2), 69–104), especially for developing tests for leverage and spillover effects in the covariance dynamics. Efficient importance sampling is used to maximize the likelihood function of RMESV-ALM, and the finite sample properties of the quasi-maximum likelihood estimator of the parameters are analysed. Using high frequency data for three US financial assets, the new model is estimated and evaluated. The forecasting performance of the new model is compared with a novel dynamic realized matrix-exponential conditional covariance model. The volatility and co-volatility spillovers are examined via the news impact curves and the impulse response functions from returns to volatility and co-volatility.

Linking gene expression in the intestine to production of gametes through the phosphate transporter PITR-1 in Caenorhabditis elegans

Inorganic phosphate is an essential mineral for both prokaryotic and eukaryotic cell metabolism and structure. Its uptake into the cell is mediated by membrane bound transporters and coupled to Na+ transport. Mammalian sodium-dependent Pi co-transporters have been grouped into three families NaPi-I, NaPi-II, and NaPi-III. Despite being discovered more than 2 decades ago, very little is known about requirements for NaPi-III transporters in vivo, in the context of intact animal models. Here we find that impaired function of the C. elegans NaPi-III transporter, pitr-1, results in decreased brood size and dramatically increased expression of vitellogenin by the worm intestine. Unexpectedly, we found that the effects of pitr-1 mutation on vitellogenin expression in the intestine could only be rescued by expression of pitr-1 in the germline, and not by expression of pitr-1 in the intestine itself. Our results indicate the existence of a signal from the germline that regulates gene expression in the intestine, perhaps linking nutrient export from the intestine to production of gametes by the germline.

Dynamics of spatial heterogeneity in a landfill with interacting phase densities:a stochastic analysis

A landfill represents a complex and dynamically evolving structure that can be stochastically perturbed by exogenous factors. Both thermodynamic (equilibrium) and time varying (non-steady state) properties of a landfill are affected by spatially heterogenous and nonlinear subprocesses that combine with constraining initial and boundary conditions arising from the associated surroundings. While multiple approaches have been made to model landfill statistics by incorporating spatially dependent parameters on the one hand (data based approach) and continuum dynamical mass-balance equations on the other (equation based modelling), practically no attempt has been made to amalgamate these two approaches while also incorporating inherent stochastically induced fluctuations affecting the process overall. In this article, we will implement a minimalist scheme of modelling the time evolution of a realistic three dimensional landfill through a reaction-diffusion based approach, focusing on the coupled interactions of four key variables - solid mass density, hydrolysed mass density, acetogenic mass density and methanogenic mass density, that themselves are stochastically affected by fluctuations, coupled with diffusive relaxation of the individual densities, in ambient surroundings. Our results indicate that close to the linearly stable limit, the large time steady state properties, arising out of a series of complex coupled interactions between the stochastically driven variables, are scarcely affected by the biochemical growth-decay statistics. Our results clearly show that an equilibrium landfill structure is primarily determined by the solid and hydrolysed mass densities only rendering the other variables as statistically "irrelevant" in this (large time) asymptotic limit. The other major implication of incorporation of stochasticity in the landfill evolution dynamics is in the hugely reduced production times of the plants that are now approximately 20-30 years instead of the previous deterministic model predictions of 50 years and above. The predictions from this stochastic model are in conformity with available experimental observations.

The impact of maternal inflammation and maternal stress in the regulation of neurodevelopment and physiological function

The mechanisms governing fetal development follow a tightly regulated pattern of progression such that interference at any one particular stage is likely to have consequences for all other stages of development in the physiological system that has been affected thereafter. These disturbances can take the form of many different events but two of the most common and widely implicated in causing detrimental effects to the developing fetus are maternal immune activation (MIA) and maternal stress. MIA has been shown to cause an increase in circulating proinflammatory cytokines in both the maternal and fetal circulation. This increase in proinflammatory mediators in the fetus is thought to occur by fetal production rather than through exchange between the maternal-fetal interface. In the case of maternal stress it is increased levels of stress related hormones such as cortisol/corticosterone which is thought to elicit the detrimental effects on fetal development. In the case of both maternal infection and stress the timing and nature of the insult generally dictates the severity and type of effects seen in affected offspring. We investigated the effect of a proinflammatory environment on neural precursor cells of which exposure resulted in a significant decrease in the normal rate of proliferation of NPCs in culture but did not have any effect on cell survival. These effects were seen to be age dependent. Using a restraint stress model we investigated the effects of prenatal stress on the development of a number of different physiological systems in the same cohort of animals. PNS animals exhibited a number of aberrant changes in cardiovascular function with altered responses to stress and hypertension, modifications in respiratory responses to hypercapnic and hypoxic challenges and discrepancies in gastrointestinal innervation. Taken together these findings suggest that both maternal infection and maternal stress are detrimental to the normal development of the fetus.

Antigen Drives Regulatory B10 Cell Development and Function

B cells mediate immune responses via the secretion of antibody and interactions with other immune cell populations through antigen presentation, costimulation, and cytokine secretion. Although B cells are primarily believed to promote immune responses using the mechanisms described above, some unique regulatory B cell populations that negatively influence inflammation have also been described. Among these is a rare interleukin (IL)-10-producing B lymphocyte subset termed “B10 cells.” B cell-derived IL-10 can inhibit various arms of the immune system, including polarization of Th1/Th2 cell subsets, antigen presentation and cytokine production by monocytes and macrophages, and activation of regulatory T cells. Further studies in numerous autoimmune and inflammatory models of disease have confirmed the ability of B10 cells to negatively regulate inflammation in an IL-10-dependent manner. Although IL-10 is indispensable to the effector functions of B10 cells, how this specialized B cell population is selected in vivo to produce IL-10 is unknown. Some studies have demonstrated a link between B cell receptor (BCR)-derived signals and the acquisition of IL-10 competence. Additionally, whether antigen-BCR interactions are required for B cell IL-10 production during homeostasis as well as active immune responses is a matter of debate. Therefore, the goal of this thesis is to determine the importance of antigen-driven signals during B10 cell development in vivo and during B10 cell-mediated immunosuppression.

Chapter 3 of the dissertation explored the BCR repertoire of spleen and peritoneal cavity B10 cells using single-cell sequencing to lay the foundation for studies to understand the full range of antigens that may be involved in B10 cell selection. In both the spleen and peritoneal cavity B10 cells studied, BCR gene utilization was diverse, and the expressed BCR transcripts were largely unmutated. Thus, B10 cells are likely capable of responding to a wide range of foreign and self-antigens in vivo.

Studies in Chapter 4 determined the predominant antigens that drive B cell IL-10 secretion during homeostasis. A novel in vitro B cell expansion system was used to isolate B cells actively expressing IL-10 in vivo and probe the reactivities of their secreted monoclonal antibodies. B10 cells were found to produce polyreactive antibodies that bound multiple self-antigens. Therefore, in the absence of overarching active immune responses, B cell IL-10 is secreted following interactions with self-antigens.

Chapter 5 of this dissertation investigated whether foreign antigens are capable of driving B10 cell expansion and effector activity during an active immune response. In a model of contact-induced hypersensitivity, in vitro B cell expansion was again used to isolate antigen-specific B10 clones, which were required for optimal immunosuppression.

The studies described in this dissertation shed light on the relative contributions of BCR-derived signals during B10 cell development and effector function. Furthermore, these investigations demonstrate that B10 cells respond to both foreign and self-antigens, which has important implications for the potential manipulation of B10 cells for human therapy. Therefore, B10 cells represent a polyreactive B cell population that provides antigen-specific regulation of immune responses via the production of IL-10.

Study of insulin-like growth factor signaling in mitochondrial function

Insulin-like Growth Factor-1 (IGF-1) signalling promotes cell growth and is associated with cancer progression, including metastasis, epithelial-mesenchymal transition (EMT), and resistance to therapy. Mitochondria play an essential role in cancer cell metabolism and accumulating evidence demonstrates that dysfunctional mitochondria associated with release of mitochondrial reactive oxygen species (ROS) can influence cancer cell phenotype and invasive potential. We previously isolated a mitochondrial UTP carrier (PNC1/SLC25A33) whose expression is regulated by IGF-1, and which is essential for mitochondrial maintenance. PNC1 suppression in cancer cells results in mitochondrial dysfunction and acquisition of a profound ROS-dependent invasive (EMT) phenotype. Moreover, over-expression of PNC1 in cancer cells that exhibit an EMT phenotype is sufficient to suppress mitochondrial ROS production and reverse the invasive phenotype. This led us to investigate the IGF-1-mitochondrial signalling axis in cancer cells. We found that IGF-1 signalling supports increased mitochondrial mass and Oxphos potential through a PI3K dependant pathway. Acute inhibition of IGF-1R activity with a tyrosine kinase inhibitor results in dysfunctional mitochondria and cell death. We also observed an adaptive response to IGF-1R inhibition upon prolonged exposure to the kinase inhibitor, where increased expression of the EGF receptor can compensate for loss of mitochondrial mass through activation of PI3K/mTOR signalling. However, these cells exhibit impaired mitochondrial biogenesis and mitophagy. We conclude that the IGF-1 is required for mitochondrial maintenance and biogenesis in cancer cells, and that pharmacological inhibition of this pathway may induce mitochondrial dysfunction and may render the cells more sensitive to glycolysis-targeted drugs.

Parallel nonconvex generalized Benders decomposition for natural gas production network planning under uncertainty

A scenario-based two-stage stochastic programming model for gas production network planning under uncertainty is usually a large-scale nonconvex mixed-integer nonlinear programme (MINLP), which can be efficiently solved to global optimality with nonconvex generalized Benders decomposition (NGBD). This paper is concerned with the parallelization of NGBD to exploit multiple available computing resources. Three parallelization strategies are proposed, namely, naive scenario parallelization, adaptive scenario parallelization, and adaptive scenario and bounding parallelization. Case study of two industrial natural gas production network planning problems shows that, while the NGBD without parallelization is already faster than a state-of-the-art global optimization solver by an order of magnitude, the parallelization can improve the efficiency by several times on computers with multicore processors. The adaptive scenario and bounding parallelization achieves the best overall performance among the three proposed parallelization strategies.

The technical and artistic branches and ways of organizing production in Argentine soap operas

Production processes and work organization in the cultural industries have been little discussed. For this reason, the study focuses on the production phases and the division of labor in technical and artistic branches in Argentine soap operas. There are six branches: production, direction, photography, art, sound and edition. We explain the branches, the workers involved and their function and activities. This research is based on a communicational perspective, the Political Economy of Communication and recovers contributions of the Sociology of Labour. From this combination, we attempt to provide elements of analysis to understand the functioning and organisation of daily television series. In the same way, we examine the creative work, the types of work redundant or random, the division of labour and the economies of time. The methodological approach is qualitative. In this way, the examination is based on the production of interviews with key actors of the sector and the documentary and bibliographical survey so as to systematize the data for the research.

Who is in charge? An L2 Discourse Intonation Study on Four Prosodic Parameters to Exert the Pragmatic Function of Dominance and Control in the Context of L2 Non-specialist Public Speaking

This paper reports the findings from a study of the learning of English intonation by Spanish speakers within the discourse mode of L2 oral presentation. The purpose of this experiment is, firstly, to compare four prosodic parameters before and after an L2 discourse intonation training programme and, secondly, to confirm whether subjects, after the aforementioned L2 discourse intonation training, are able to match the form of these four prosodic parameters to the discourse-pragmatic function of dominance and control. The study designed the instructions and tasks to create the oral and written corpora and Brazil’s Pronunciation for Advanced Learners of English was adapted for the pedagogical aims of the present study. The learners’ pre- and post-tasks were acoustically analysed and a pre / post- questionnaire design was applied to interpret the acoustic analysis. Results indicate most of the subjects acquired a wider choice of the four prosodic parameters partly due to the prosodically-annotated transcripts that were developed throughout the L2 discourse intonation course. Conversely, qualitative and quantitative data reveal most subjects failed to match the forms to their appropriate pragmatic functions to express dominance and control in an L2 oral presentation.

Obestatin as a key regulator of metabolism and cardiovascular function with emerging therapeutic potential for diabetes

Obestatin is a 23-amino acid C-terminally amidated gastrointestinal peptide derived from preproghrelin and which forms an alpha helix. Although obestatin has a short biological half-life and is rapidly degraded, it is proposed to exert wide-ranging pathophysiological actions. Whilst the precise nature of many of its effects is unclear, accumulating evidence supports positive actions on both metabolism and cardiovascular function. For example, obestatin has been reported to inhibit food and water intake, body weight gain, and gastrointestinal motility, and to also mediate promotion of cell survival and prevention of apoptosis. Obestatin-induced increases in β-cell mass, enhanced adipogenesis and improved lipid metabolism have been noted along with upregulation of genes associated with β-cell regeneration, insulin production and adipogenesis. Furthermore, human circulating obestatin levels generally demonstrate an inverse association with obesity and diabetes, whilst the peptide has been shown to confer protective metabolic effects in experimental diabetes, suggesting that it may hold therapeutic potential in this setting. Obestatin also appears to be involved in blood pressure regulation and to exert beneficial effects on endothelial function, with experimental studies indicating that it may also promote cardioprotective actions against, for example, ischaemia-reperfusion injury. This review will present a critical appraisal of the expanding obestatin research area and discuss the emerging therapeutic potential of this peptide for both metabolic and cardiovascular complications of diabetes. 

Risque de prix et décisions de production et d'exportation : le cas de l'agriculture au Québec

Cette thèse porte sur l’effet du risque de prix sur la décision des agriculteurs et les transformateurs québécois. Elle se divise en trois chapitres. Le premier chapitre revient sur la littérature. Le deuxième chapitre examine l’effet du risque de prix sur la production de trois produits, à savoir le maïs grain, la viande de porc et la viande d’agneau dans la province Québec. Le dernier chapitre est centré sur l’analyse de changement des préférences du transformateur québécois de porc pour ce qui est du choix de marché. Le premier chapitre vise à montrer l’importance de l’effet du risque du prix sur la quantité produite par les agriculteurs, tel que mis en évidence par la littérature. En effet, la littérature révèle l’importance du risque de prix à l’exportation sur le commerce international. Le deuxième chapitre est consacré à l’étude des facteurs du risque (les anticipations des prix et la volatilité des prix) dans la fonction de l’offre. Un modèle d’hétéroscédasticité conditionnelle autorégressive généralisée (GARCH) est utilisé afin de modéliser ces facteurs du risque. Les paramètres du modèle sont estimés par la méthode de l’Information Complète Maximum Vraisemblance (FIML). Les résultats empiriques montrent l’effet négatif de la volatilité du prix sur la production alors que la prévisibilité des prix a un effet positif sur la quantité produite. Comme attendu, nous constatons que l’application du programme d’assurance-stabilisation des revenus agricoles (ASRA) au Québec induit une plus importante sensibilité de l’offre par rapport au prix effectif (le prix incluant la compensation de l’ASRA) que par rapport au prix du marché. Par ailleurs, l’offre est moins sensible au prix des intrants qu’au prix de l’output. La diminution de l’aversion au risque de producteur est une autre conséquence de l’application de ce programme. En outre, l’estimation de la prime marginale relative au risque révèle que le producteur du maïs est le producteur le moins averse au risque (comparativement à celui de porc ou d’agneau). Le troisième chapitre consiste en l’analyse du changement de préférence du transformateur québécois du porc pour ce qui est du choix de marché. Nous supposons que le transformateur a la possibilité de fournir les produits sur deux marchés : étranger et local. Le modèle théorique explique l’offre relative comme étant une fonction à la fois d’anticipation relative et de volatilité relative des prix. Ainsi, ce modèle révèle que la sensibilité de l’offre relative par rapport à la volatilité relative de prix dépend de deux facteurs : d’une part, la part de l’exportation dans la production totale et d’autre part, l’élasticité de substitution entre les deux marchés. Un modèle à correction d’erreurs est utilisé lors d’estimation des paramètres du modèle. Les résultats montrent l’effet positif et significatif de l’anticipation relative du prix sur l’offre relative à court terme. Ces résultats montrent donc qu’une hausse de la volatilité du prix sur le marché étranger par rapport à celle sur le marché local entraine une baisse de l’offre relative sur le marché étranger à long terme. De plus, selon les résultats, les marchés étranger et local sont plus substituables à long terme qu’à court terme.

Occupational exposure to Aspergillus spp. in poultry and swine feed production

Workers from feed production often develop allergic respiratory symptoms and fungi are likely to be a significant contributing factor to these symptoms. This study intended to characterize fungal contamination in two feed production units, one for poultry and other for swine consumption. We aimed at identifying which unit presented the highest risk of occupational exposure to Aspergillus spp.