17 research outputs found

    Date 2014-03-31

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    Title Interfaces the tandem protein identification algorithm in

    Functional characterization of infiltrating T lymphocytes in human hepatic allografts

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    We have employed recently developed techniques in T-cell culturing to study the nature and function of infiltrating hepatic allograft T cells. Using the rationale that intragraft T cells are activated during cell mediated damage to the allograft, we were able to show that these cells would propagate and remain functionally active in the presence of the T-cell growth factor, IL-2. In several instances, phenotyiic analysis of cells grown in this manner was very similar to that found within the graft. Both proliferative and cytotoxic responses could be detected from the cultured cell lines. The majority of the proliferative responses were donor-directed and immunogenetic analysis could define donor-directed HLA reactivity, to either class I or class II antigens, or both. Monoclonal anti-HLA antibodies inhibition profiles verified the apparent HLA reactivity. In a smaller percentage of cases, only IL-2 responsiveness could be detected, and no HLA reactivity could be determined. Cytotoxicity could be detected against both class I and class II antigens, however, those cells which demonstrated a greater magnitude of donor-directed cytotoxicity appeared to be directed against class I antigens. A significant correlation between donor-directed proliferation of biopsy cultured lymphocytes and cellular rejection was found. This model appears to be useful in delineating functions of the intragraft T-cell population during rejection. © 1986

    Obliterative bronchiolitis after lung and heart-lung transplantation An analysis of risk factors and management

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    With a prevalence of 34% (55/162 at-risk recipients) and a mortality of 25% (14/55 affected recipients), obliterative bronchiolitis is the most significant long-term complication after pulmonary transplantation. Because of its importance, we examined donor-recipient characteristics and antecedent clinical events to identify factors associated with development of obliterative bronchiolitis, which might be eliminated or modified to decrease its prevalence. We also compared treatment outcome between recipients whose diagnosis was made early by surveillance transbronchial lung biopsy before symptoms or decline in pulmonary function were present versus recipients whose diagnosis was made later when symptoms or declines in pulmonary function were present. Postoperative airway ischemia, an episode of moderate or severe acute rejection (grade III/IV), three or more episodes of histologic grade II (or greater) acute rejection, and cytomegalovirus disease were risk factors for development of obliterative bronchiolitis. Recipients with obliterative bronchiolitis detected in the preclinical stage were significantly more likely to be in remission than recipients who had clinical disease at the time of diagnosis: 81% (13/15) versus 33% (13/40); p<0.05. These results indicate that acute rejection is the most significant risk factor for development of obliterative bronchiolitis and that obliterative bronchiolitis responds to treatment with augmented immunosuppression when it is detected early by surveillance transbronchial biopsy

    Sensory Perception of Food and Insulin-Like Signals Influence Seizure Susceptibility

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    Food deprivation is known to affect physiology and behavior. Changes that occur could be the result of the organism's monitoring of internal and external nutrient availability. In C. elegans, male mating is dependent on food availability; food-deprived males mate with lower efficiency compared to their well-fed counterparts, suggesting that the mating circuit is repressed in low-food environments. This behavioral response could be mediated by sensory neurons exposed to the environment or by internal metabolic cues. We demonstrated that food-deprivation negatively regulates sex-muscle excitability through the activity of chemosensory neurons and insulin-like signaling. Specifically, we found that the repressive effects of food deprivation on the mating circuit can be partially blocked by placing males on inedible food, E. coli that can be sensed but not eaten. We determined that the olfactory AWC neurons actively suppress sex-muscle excitability in response to food deprivation. In addition, we demonstrated that loss of insulin-like receptor (DAF-2) signaling in the sex muscles blocks the ability of food deprivation to suppress the mating circuit. During low-food conditions, we propose that increased activity by specific olfactory neurons (AWCs) leads to the release of neuroendocrine signals, including insulin-like ligands. Insulin-like receptor signaling in the sex muscles then reduces cell excitability via activation of downstream molecules, including PLC-Îł and CaMKII

    Impact of topographic resolution on simulated regional groundwater flow and residence time.

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    International audienceLarge regional numerical models are often used for the prediction of groundwater fluxes to surface water or to assess the impacts of changes in either climate, land use or groundwater exploitation. Such models typically use a large grid size and a low-resolution land surface topography. The objective of our study was to assess if such large models can provide accurate predictions of fluxes to rivers based on representative recharge and hydraulic properties. For this purpose, a simplified 95 km-long 2D cross-section hydrogeological model was developed using the topography of an area from the Appalachian Highlands to the St. Lawrence Lowlands in southwestern Quebec (Canada). Numerical simulations were completed with a fixed numerical grid but with four levels of topographic resolution using data points at intervals of 30, 90, 500 and 1000 m. The regional rock aquifer models all used the same depth-decreasing hydraulic conductivity (K) profile based on field conditions. Steady-state groundwater flow and age simulations were done by imposing heads corresponding to the topography in order to obtain flowpaths and surface fluxes (inflow and outflow). Simulated inflows were compared to recharge values independently estimated with the HELP infiltration model calibrated with total flow and baseflow in gauged watersheds. Results show that topographic resolution has a major impact on surface fluxes, both entering and exiting the aquifer. In order for smooth-topography models to represent fluxes to streams, it is necessary to use “equivalent” K values that are significantly higher than estimates based on thousands of specific capacity tests. For simulations using large regional groundwater flow models with smoothed topography, a choice has to be made between the proper representation of surface fluxes using unrealistic K values and the underestimation of surface fluxes using representative K profiles

    Multi-scale integrated characterization of heterogeneous hydraulic and thermal properties of a deltaic aquifer

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    International audienceHistorically, heat and temperature observations have been occasionally used to help understand aquifer systems or constrain numerical flow models. However, the development of fiber optics (FO) as part of the Distributed Temperature Sensing (DTS) technology has spun a renewed interest in the use of heat as a groundwater tracer. Recent studies have shown the possibility to carry out an active heat tracer test using fiber optics and heating cables installed by direct push and to invert the resulting thermal responses to estimate a vertical profile of groundwater fluxes. However, a better understanding of how FO-DTS results compare to other aquifer characterization methods is needed to guide its future application and integration into a practical workflow. The objective of this study was thus to compare the information provided by FO-DTS with other direct and indirect measurements used to characterize the heterogeneity of granular aquifers at multiple scales. The multiscale integrated characterization was carried out at a heterogeneous deltaic aquifer located north of Quebec City, Canada. This aquifer has been the object of a complete hydrogeological characterization and thus provides a wide range of existing data against which the acquired data can be compared. This communication will focus on the multiscale methodology for the granular aquifer characterization including FO-DTS measurements. Based on an existing numerical hydrogeological model, three sites with a range of horizontal groundwater fluxes were selected for active FO-DTS heat tracer experiments. At one of the sites, direct push monitoring wells were also installed downstream to measure the hydraulic conductivity of the hydrofacies and the arrival of the thermal front from the heat tracer test. A previous study established a relationship between the hydrofacies of the deltaic aquifer to cone penetration test (CPT) response. As such, each FO cable and monitoring well direct-push installation was preceded by a co-located CPT. Soil cores were also taken for laboratory measurements of hydraulic and thermal properties. The vertical profiles of groundwater fluxes from FO-DTS were found to correlate well with the relative magnitude of permeability of the hydrofacies identified with CPT profiles. FO-DTS could thus provide a qualitative or quantitative proxy for hydraulic conductivity and allow the recognition of hydrofacies at a fine scale. At the aquifer scale, the total flux measured by FO-DTS can also be compared to fluxes obtained from numerical models and thus provide a constraint to validate models. Overall, this study shows that not only does FO-DTS provide coherent results with other characterization methods, but it also adds the key measurement of groundwater flux that cannot be easily obtained by other means. FO-DTS thus has the potential to become a significant addition to existing characterization methods for granular aquifers

    Inferring high-resolution aquifer hydraulic conductivity and groundwater fluxes by active heat tracer using direct push fiber optics

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    International audienceCharacterizing aquifer heterogeneity for contaminant transport prediction remains a challenge in subsurface hydrology. In recent years, fiber optics (FO) Distributed Temperature Sensing (DTS) has enabled the study of transient hydrogeological processes with high spatial and temporal resolutions. Recent studies have shown that vertical profiles of groundwater fluxes can be quantified in granular aquifers through inversion of the thermal responses from active heat tracer tests using FO cables installed by direct push. Here, we further investigate the potential of active FO-DTS methods for granular aquifer characterization by performing a multiscale characterization and active heat tracer experiment in a well-characterized heterogeneous deltaic aquifer located north of Quebec City, Canada. This aquifer has been the object of detailed hydrogeological characterization and thus provides a wide range of existing data. In particular, we will test whether the vertical distribution of groundwater fluxes in the sub-surface determined by these inversions can be used to estimate hydraulic properties at a spatial scale that can be used to assess the impact of aquifer heterogeneity on mass transport and dispersion. This communication focuses on a site where two FO cables were installed 10 m apart by direct push. An active heat tracer experiment was carried out with the two FO cables, and the resulting thermal responses were inverted to obtain high-resolution vertical profiles of the groundwater fluxes at each FO cable. Heating was carried out in the saturated zone, between depths of 12 to 40 m with a 25-cm vertical sampling. Using data from a piezometric survey, the groundwater fluxes from the FO-DTS were used to estimate a range of hydraulic conductivities (K). A previous study at the field site has shown that cone penetration test (CPT) profiles can be used to recognize the different hydrofacies with distinct ranges of hydraulic conductivity present in the deltaic aquifer. As the two FO cables were co-located with a previously done CPT profile, the measured fluxes and estimated K values could be compared to known ranges of K. Results show quite varying temperature profiles and accordingly distinct groundwater fluxes. These varying fluxes are coherently correlated to the different hydrofacies identified with the co-located CPT responses at a similar vertical scale. The two FO-DTS temperature profiles are also quite similar when considering the small variations in hydrofacies found along their length. These results show that FO-DTS heat tracer tests provide consistent and representative measurements of groundwater fluxes in agreement with the heterogeneous distribution of K as indicated by CPT. Thus, compared with existing hydraulic methods, FO-DTS heat tracer tests provide new and complementary data that have a great potential for characterizing solute transport in granular aquifers with a high spatial resolution

    On the use of the ground water fluxes for hydraulic tomography: Theoretical and field-based assessments

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    International audienceHydraulic tomography is known for imaging hydraulic conductivity of aquifers. In hydraulic tomography, the aquifer is stressed sequentially at several locations with pumping or slug tests while hydraulic heads are observed in different points. These hydraulic head data along with a numerical model are then used to reconstruct the hydraulic conductivity distribution of the aquifer through inversion process. The reconstructed distribution usually represents smooth-low resolution model of hydraulic conductivity which may be suitable for representation of groundwater flow with limited applicability to transport problems. Here, we investigate the added value of using groundwater fluxes measurement for the reconstruction of hydraulic conductivity in tomographic experiment. Vertical profile of groundwater flux may be estimated using active fiber optic distributed temperature sensor (FO-DTS) methods with FO cables installed by direct push so as it is in direct contact with formation. In active FO-DTS, FO cable is heated and heat is transported by conduction and convection. So different water fluxes result in different temperature behavior. This study is carried out in two parts. First, we conducted a synthetic analyze where we used a sequence of synthetic multivariate Gaussian aquifers with different tomographic configurations and datasets. This analysis showed that joint inversion of groundwater fluxes and hydraulic heads leads to better hydraulic conductivity resolution than using hydraulic heads solely. Inversion of groundwater fluxes alone is also superior than using only hydraulic heads. Then, insights gained from the synthetic study were used to guide the implementation of a field study at the Saint-Lambert experimental site located 40 km south of Quebec City, Canada. The tomography experiment was performed between 3 wells closely spaced (between 5 and 9 m) and two active FO-DTS cables. FO cables were installed vertically by a direct push drilling technique at mid-point between the central pumping well and two observation wells. Discrete intervals along the observation wells were also isolated with packers to monitor temperature and hydraulic heads at different depths in these two screened observational wells. First, the aquifer was constrained to pumping continuously for 24 hours at a constant rate of 10 LPM with simultaneously recording temperature (passive mode) and hydraulic heads in 8 discrete well intervals and in the pumping well itself as well as along the 2 FO-DTS with approximate resolution of 25 cm. Then, by analyzing the piezo-metric heads and making sure that steady-state conditions were achieved, the pumping was held at the same rate but heat was injected to fiber optic cables (active mode) for another 64-hour period. After this period, heating and pumping were stopped. Preliminary results show the feasibility of the active FO-DTS in capturing varying groundwater fluxes with depth, as reflected in the different temporal temperature trend. These temperature trends will be used to estimate the vertical groundwater flux profile from these temperature temporal trends at a vertical resolution of approximately 25 cm. Then estimated fluxes will be used for hydraulic tomography. Those experimental results along with the synthetic analyze are shown to be promising in improving characterization of hydraulic conductivity of aquifers

    CHARACTERIZATION OF HETEROGENEOUS PROPERTIES AND GROUNDWATER FLUXES IN A GRANULAR AQUIFER USING DIRECT PUSH ACTIVE FIBER OPTIC DTS

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    International audienceThe development of fiber optic (FO) Distributed Temperature Sensing (DTS) as a tool for hydrogeological measurements with high spatial and temporal resolution has shown potential for characterizing aquifer heterogeneity, which remains a challenge and is needed to predict contaminant transport. Recent studies have shown that groundwater fluxes can be quantified along a vertical profile in granular aquifers by inverting the thermal responses from active heat tracer tests using FO cables. Here, we further investigate the use of active FO-DTS methods and the resulting high resolution profiles for granular aquifer characterization by comparing results with cone penetration tests (CPT), which provide indications of hydrofacies. A multiscale characterization and active heat tracer experiments were performed in a well-studied heterogeneous deltaic aquifer located north of Quebec City, Canada.Four active FO-DTS heat tracer experiments were conducted by deploying fiber optic cables by direct push at locations with a previous CPT. Interpretation of thermal responses from the active FO-DTS experiments was done with analytical solutions for heat transport, providing independent and accurate estimates of thermal properties and fluxes every 25 centimeters. The resulting profiles of fluxes from DTS measurements correlate well with the response obtained with CPT. Furthermore, as a previous study established a relationship between CPT response and different aquifer materials and their hydraulic properties, the resulting flux profiles from active FO-DTS can be used to obtain a stratigraphy of the different hydrofacies.Active FO-DTS experiments can thus provide a qualitative or quantitative proxy for hydraulic conductivity and allow the recognition of hydrofacies at a sub-metric vertical scale. At the aquifer scale, the total flux estimated from FO-DTS measurements can also be compared and used as constraints for fluxes obtained from a numerical model. Overall, this study shows that not only does FO-DTS provide coherent results with other characterization methods, but it also adds the key measurement of groundwater flux with great accuracy that cannot be easily obtained by other means. FO-DTS has thus the potential to become a significant addition to existing characterization methods for granular aquifers
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