141 research outputs found
Catchment travel time distributions and water flow in soils
No full textMany details about the flow of water in soils in a hillslope are unknowable given current technologies. One way of learning about the bulk effects of water velocity distributions on hillslopes is through the use of tracers. However, this paper will demonstrate that the interpretation of tracer information needs to become more sophisticated. The paper reviews, and complements with mathematical arguments and specific examples, theory and practice of the distribution(s) of the times water particles injected through rainfall spend traveling through a catchment up to a control section (i.e., “catchment” travel times). The relevance of the work is perceived to lie in the importance of the characterization of travel time distributions as fundamental descriptors of catchment water storage, flow pathway heterogeneity, sources of water in a catchment, and the chemistry of water flows through the control section. The paper aims to correct some common misconceptions used in analyses of travel time distributions. In particular, it stresses the conceptual and practical differences between the travel time distribution conditional on a given injection time (needed for rainfall‐runoff transformations) and that conditional on a given sampling time at the outlet (as provided by isotopic dating techniques or tracer measurements), jointly with the differences of both with the residence time distributions of water particles in storage within the catchment at any time. These differences are defined precisely here, either through the results of different models or theoretically by using an extension of a classic theorem of dynamic controls. Specifically, we address different model results to highlight the features of travel times seen from different assumptions, in this case, exact solutions to a lumped model and numerical solutions of the 3‐D flow and transport equations in variably saturated, physically heterogeneous catchment domains. Our results stress the individual characters of the relevant distributions and their general nonstationarity yielding their legitimate interchange only in very particular conditions rarely achieved in the field. We also briefly discuss the impact of oversimple assumptions commonly used in analyses of tracer data
On the probability of extinction of the Haiti cholera epidemic
No full textMore than three years after its appearance in Haiti, cholera has already caused more than 8,500 deaths and 695,000 infections and it is feared to become endemic. However, no clear evidence of a stable environmental reservoir of pathogenic Vibrio cholerae, the infective agent of the disease, has emerged so far, suggesting the possibility that the transmission cycle of the disease is being maintained by bacteria freshly shed by infected individuals. Should this be the case, cholera could in principle be eradicated from Haiti. Here, we develop a framework for the estimation of the probability of extinction of the epidemic based on current information on epidemiological dynamics and health-care practice. Cholera spreading is modeled by an individual-based spatially-explicit stochastic model that accounts for the dynamics of susceptible, infected and recovered individuals hosted in different local communities connected through hydrologic and human mobility networks. Our results indicate that the probability that the epidemic goes extinct before the end of 2016 is of the order of 1 %. This low probability of extinction highlights the need for more targeted and effective interventions to possibly stop cholera in Haiti. © 2014 The Author(s)
Abdominal wall defect repair with biological prosthesis in transplanted patients: single center retrospective analysis and review of the literature
No full textThe risk of fascial dehiscence, wound infection and incisional hernias in organ recipients is higher. Retrospective analysis of our departments database, checking the last 12 years (2000-2012), and of the literature (1966-2012) were conducted. In our database we found seven patients: five liver (71.4 %), one kidney (14.3 %), one multivisceral (14.3 %); five males (71.4 %), two females (28.6 %). Five (71.4 %) were operated in urgency setting and two in ordinary setting (28.6 %). The mean/median number of laparotomies before the incisional hernia is of 2.1/1 (range 1-5). In five patients swine intestinal submucosa (71.4 %) have been used and in two porcine dermal collagen (28.6 %). The mean/median age was 48.3/52 years (range 18-61). The mean/median body mass index was 26.7/27 (range 19-34). The mean/median for follow-up after intervention was 40.1/33 months (range 50-21). Recurrence rate was 14.3 %. Complication rate was 28.6 %. Adding the present report, the literature reports 70 cases. 20 % of prosthesis have been implanted inlay, 25.7 % underlay, in 5.7 % intraperitoneal and in 48.6 % were not specified. The mean age ranges from 0.7 to 48.3 years. Kidney, liver, pancreas, bowel and multivisceral transplant are reported. Porcine dermal collagen has been implanted in 24.3 %, human dermal collagen in 51.4 % and swine intestinal submucosa in 24.3 %. The immunosuppression regimens comprehend variable associations of tacrolimus, steroids, mycophenolate mofetil, sirolimus, thymoglobulin, azathioprine/basiliximab and daclizumab. The mean follow-up is 16.2 months. The mean complication rate is 9.4 %. Biological prosthesis seems to be useful and safe in abdominal wall repair surgery in transplanted patients
Detection of Vibrio cholerae O1 and O139 in environmental waters of rural Bangladesh: A flow-cytometry-based field trial
No full textPresence of Vibrio cholerae serogroups O1 and O139 in the waters of the rural area of Matlab, Bangladesh, was investigated with quantitative measurements performed with a portable flow cytometer. The relevance of this work relates to the testing of a field-adapted measurement protocol that might prove useful for cholera epidemic surveillance and for validation of mathematical models. Water samples were collected from different water bodies that constitute the hydrological system of the region, a well-known endemic area for cholera. Water was retrieved from ponds, river waters, and irrigation canals during an inter-epidemic time period. Each sample was filtered and analysed with a flow cytometer for a fast determination of V. cholerae cells contained in those environments. More specifically, samples were treated with O1- and O139-specific antibodies, which allowed precise flow-cytometry-based concentration measurements. Both serogroups were present in the environmental waters with a consistent dominance of V. cholerae O1. These results extend earlier studies where V. cholerae O1 and O139 were mostly detected during times of cholera epidemics using standard culturing techniques. Furthermore, our results confirm that an important fraction of the ponds' host populations of V. cholerae are able to self-sustain even when cholera cases are scarce. Those contaminated ponds may constitute a natural reservoir for cholera endemicity in the Matlab region. Correlations of V. cholerae concentrations with environmental factors and the spatial distribution of V. cholerae populations are also discussed
Can the dropout risk of candidates with hepatocellular carcinoma predict survival after liver transplantation?
No full textIn the last US national conference on liver transplantation for hepatocellular carcinoma (HCC), a continuous priority score, that incorporates model for end-stage liver disease (MELD), alpha-fetoprotein and tumor size, was recommended to ensure a more equitable liver allocation. However, prioritizing highest alpha-fetoprotein levels or largest tumors may select lesions at a higher risk for recurrence; similarly, patients with higher degree of liver failure could have lower postoperative survival. Data from 300 adult HCC recipients were reviewed and the proposed HCC-MELD equation was applied to verify if it can predict post-transplantation survival. The 5-year survival and recurrence rates after transplantation were 72.8 and 13.5%, respectively. Cox regression analysis confirmed HCC-MELD as predictive of both postoperative survival and recurrence (p < 0.001). The 5-year predicted survival and recurrence rates were plotted against the HCC-MELD-based dropout probability: the higher the dropout probability while on waiting list, the lower the predicted survival after transplantation, that is worsened by hepatitis C positivity; similarly, the higher the predicted HCC recurrence rate after transplantation. The HCC priority score could predict the postoperative survival of HCC recipients and could be useful in selecting patients with greater possibilities of survival, resulting in higher post-transplantation survival rates of HCC populations
UN PECULIARE CASO DI “UNEXPECTED DONOR-DERIVED INFECTION” DA E.COLI ESBL MANIFESTATASI COME ARTERITE CON UGUALE EVOLUZIONE NEI RENI GEMELLI
No full textCOLONIZZAZIONE ED INFEZIONE DA KLEBSIELLA PNEUOMONIAE PRODUTTRICE DI CARBAPENEMASI (KPC) NEL PAZIENTE SOTTOPOSTO A TRAPIANTO DI RENE
No full textLa colonizzazione da KPC nei pazienti sottoposti a trapianto di rene non si associa ad un peggiore
outcome del graft e della sopravvivenza del paziente. Le infezioni da KPC sono un evento più raro ma con
impatto negativo sull’outcome del trapiant
Geomorphic signatures on Brutsaert base flow recession analysis
No full textThis paper addresses the signatures of catchment geomorphology on base flow recession curves. Its relevance relates to the implied predictability of base flow features, which are central to catchment-scale transport processes and to ecohydrological function. Moving from the classical recession curve analysis method, originally applied in the Finger Lakes Region of New York, a large set of recession curves has been analyzed from Swiss streamflow data. For these catchments, digital elevation models have been precisely analyzed and a method aimed at the geomorphic origins of recession curves has been applied to the Swiss data set. The method links river network morphology, epitomized by time-varying distribution of contributing channel sites, with the classic parameterization of recession events. This is done by assimilating two scaling exponents, β and bG, with |dQ/dt| â̂ Q β where Q is at-a-station gauged flow rate and N(l) â̂ N(l)â̂G(l)bG where l is the downstream distance from the channel heads receding in time, N(l) is the number of draining channel reaches located at distance l from their heads, and G(l) is the total drainage network length at a distance greater or equal to l, the active drainage network. We find that the method provides good results in catchments where drainage density can be regarded as spatially constant. A correction to the method is proposed which accounts for arbitrary local drainage densities affecting the local drainage inflow per unit channel length. Such corrections properly vanish when the drainage density become spatially constant. Overall, definite geomorphic signatures are recognizable for recession curves, with notable theoretical and practical implications. Key Points signatures of catchment geomorphology on base flow recession curves Analysis of streamflow data and DEM for 27 catchments in Switzerland New conceptual model accounting for uneven drainage densit
Aplicação complementar de enxofre em diferentes doses na cultura do alho.
No full textO objetivo deste trabalho foi avaliar o efeito da adubação complementar com enxofre elementar sobre a produtividade de bulbos em três cultivares de alho, bem como seu efeito em diversas caracteristicas ligadas à morfologia e crescimento do bulbo e da planta
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