The Usutu virus is an arbovirus transmitted by mosquitoes and causing disease in birds. The virus was detected in Austria
for the first time in 2001, while a major outbreak occurred in 2003. Rubel et al. (2008) developed a nine-compartment deterministic SEIR model to explain the spread of the disease. We extended this to a hierarchical
Bayes model assuming random variation in temperature data, in reproduction data of birds, and in the number of birds found
to be infected. The model was implemented in R, combined with the FORTRAN subroutine for the original deterministic model.
Analysis was made by MCMC using a random walk Metropolis scheme. Posterior means, medians, and credible intervals were calculated
for the parameters. The hierarchical Bayes approach proved to be fruitful in extending the deterministic model into a stochastic
one. It allowed for Bayesian point and interval estimation and quantification of uncertainty of predictions. The analysis
revealed that some model parameters were not identifiable; therefore we kept constant some of them and analyzed others conditional
on them. Identifiability problems are common in models aiming to mirror the mechanism of the process, since parameters with
natural interpretation are likely to exhibit interrelationships. This study illustrated that Bayesian modeling combined with
conditional analysis may help in those cases. Its application to the Usutu model improved model fit and revealed the structure
of interdependencies between model parameters: it demonstrated that determining some of them experimentally would enable estimation
of the others, except one of them, from available data. 相似文献
The site of Bonneval (France) exhibits a 6 m thick stratigraphical sequence in which Middle and Lower Palaeolithic artefacts were discovered. The stratigraphy of the site consists of an alternation of loess-like silt layers deposited along glacial stages, and paleosoil horizons corresponding to the vegetal stabilization of the area during interglacials. These layers hence provide past environmental informations and can be used as stratigraphical markers and compared with well dated sequences of Northern France. Eight sediment samples from this Middle and Upper Pleistocene sequence were dated using the recuperated optically stimulated luminescence (Re-OSL) signal of quartz grains. The middle-size fraction (40–63 μm) shows a good reproducibility of the OSL signals which allows the application of a multiple-aliquot additive-dose approach for De determination. For all samples, the growth curves are linear up to an accumulated dose of 3000 Gy. The Re-OSL ages range from ~100 to ~450 ka and are in good agreement with the independent chronological information; they establish when handaxe industries have been made during the Middle and Upper Pleistocene in the Paris Basin. 相似文献
The present study focuses on the nutrient sources and gradients in Paranaguá Bay (Southern Brazil), where nutrient inputs are related to losses from fertilizer loading in Paranaguá harbour and the discharge of untreated waste water. The input of dissolved inorganic nutrients to the bay from the harbour and city, as well as from river and atmospheric deposition, amounted to 642?t?year?1 DIN-N and 92?t?year?1 PO4-P. Harbour losses accounted for 6?% of total DIN-N and 39?% of total PO4-P loads to the bay, whereas sewage inputs from the city were responsible for 21?% and 22?%, respectively. River inputs made up 68?% of DIN-N, mainly in the form of nitrate, and 35?% of PO4-P loads, while atmospheric wet deposition was estimated to be in the order of 5?% of DIN-N and 4?% of PO4-P loads. Local maxima in nutrient levels deriving from highly concentrated sewage discharge were observed in front of the harbour and city of Paranaguá, but the plumes are diluted rapidly due to short residence times. DIN concentrations are negatively correlated with salinity, indicating the importance of freshwater input as a main factor controlling nitrogen distribution. Elevated phosphate levels in the stratified middle section of the bay may result both from harbour emissions and phosphate remobilization from sediments. Generally lower DIN and PO4 concentrations during the warmer rainy season are supposed to be due to intensified assimilation rates especially in the middle section of the bay where dense phytoplankton blooms are observed. The bay as a whole cannot be classified as being seriously eutrophic, albeit eutrophication symptoms prevail in some restricted locations in front of Paranaguá harbour. 相似文献
The present study focuses on the nutrient sources and gradients in Paranaguá Bay (Southern Brazil), where nutrient inputs are related to losses from fertilizer loading in Paranaguá harbour and the discharge of untreated waste water. The input of dissolved inorganic nutrients to the bay from the harbour and city, as well as from river and atmospheric deposition, amounted to 642 t year−1 DIN-N and 92 t year−1 PO4-P. Harbour losses accounted for 6 % of total DIN-N and 39 % of total PO4-P loads to the bay, whereas sewage inputs from the city were responsible for 21 % and 22 %, respectively. River inputs made up 68 % of DIN-N, mainly in the form of nitrate, and 35 % of PO4-P loads, while atmospheric wet deposition was estimated to be in the order of 5 % of DIN-N and 4 % of PO4-P loads. Local maxima in nutrient levels deriving from highly concentrated sewage discharge were observed in front of the harbour and city of Paranaguá, but the plumes are diluted rapidly due to short residence times. DIN concentrations are negatively correlated with salinity, indicating the importance of freshwater input as a main factor controlling nitrogen distribution. Elevated phosphate levels in the stratified middle section of the bay may result both from harbour emissions and phosphate remobilization from sediments. Generally lower DIN and PO4 concentrations during the warmer rainy season are supposed to be due to intensified assimilation rates especially in the middle section of the bay where dense phytoplankton blooms are observed. The bay as a whole cannot be classified as being seriously eutrophic, albeit eutrophication symptoms prevail in some restricted locations in front of Paranaguá harbour.
In this work we evaluate the implications of climate change for future fluvial flood risk in Europe, considering climate developments
under the SRES A2 (high emission) and B2 (low emission) scenario. We define flood risk as the product of flood probability
(or hazard), exposure of capital and population, and vulnerability to the effect of flooding. From the European flood hazard
simulations of Dankers and Feyen (J Geophys Res 114:D16108. doi:, 2009) discharges with return periods of 2, 5, 10, 20, 50, 100, 250 and 500 years were extracted and converted into flood inundation
extents and depths using a planar approximation approach. Flood inundation extents and depths were transformed into direct
monetary damage using country specific flood depth-damage functions and land use information. Population exposure was assessed
by overlaying the flood inundation information with data on population density. By linearly interpolating damages and population
exposed between the different return periods, we constructed damage and population exposure probability functions under present
and future climate. From the latter expected annual damages (EAD) and expected annual population exposed (EAP) were calculated.
To account for flood protection the damage and population exposure probability functions were truncated at design return periods
based on the country GDP/capita. Results indicate that flood damages are projected to rise across much of Western Europe.
Decreases in flood damage are consistently projected for north-eastern parts of Europe. For EU27 as a whole, current EAD of
approximately €6.4 billion is projected to amount to €14–21.5 billion (in constant prices of 2006) by the end of this century,
depending on the scenario. The number of people affected by flooding is projected to rise by approximately 250,000 to 400,000.
Notwithstanding these numbers are subject to uncertainty, they provide an indication of potential future developments in flood
risk in a changing climate. 相似文献
The Sharm El-Sheikh/Ras-Nasrani area is one of the most attractive tourist resorts in Egypt particularly and in the world
in general. The area has been rapidly growing during the last few years. Many construction projects including villages, hotels,
beaches, and roads have recently been undertaken. The following study demonstrates the use of high-resolution satellite images,
QuickBird imagery, acquired on June 2nd, 2007 (0.61 m spatial resolution), for detailed mapping of the recent developments
and the slope instability hazard zones. The results were confirmed by field reconnaissance. Our findings indicate that there
are many development areas threatened by unstable zones. The hazard areas have been delineated and classified, and a final
slope instability hazard map has been established. Different factors were found to have a crucial impact on the slope instability,
some natural and others man-made. These unstable localities need to be remediated and/or monitored to avoid any loss in property
and/or lives. 相似文献
Knowing how many samples to test to adequately characterize soil and rock units is always challenging. A large number of tests decrease the uncertainty and increase the confidence in the resulting values of design parameters. Unfortunately, this large value also adds to project costs. This paper presents a method to determine the number of samples as a function of the coefficient of variation. If, as in the case of a reliability-based design, the resistance factors are a function of the coefficient of variation of the measurements, then lowering the coefficient of variation (COV) can result in lowering of the resistance factor resulting in a less conservative design. In this study, laboratory samples were isolated by specific unified soil classification system soil type and general site location. A distribution was fitted for each of the geotechnical parameters measured. For each scenario, groups of 2, 3, 4, 5, 10, 15, 20, 30, 50, and 100 random samples were generated by using Monte Carlo simulations from the fitted distributions. For each group, the variability was calculated in terms of the COV. In all cases, the COV decreased as the sample size increased. However, the rate of decrease for the COV was the greatest at a low number of samples; it becomes increasingly smaller at a higher number of samples. 相似文献
The paper presents a synthesis of the approach recently developed to constrain the nature and the age of recent element mobility in weathering profiles. The approach relies on a comparison of variations of trace elements and U-series disequilibria in weathering profiles. It is exemplified in the case of old lateritic profiles from the Kaya toposequence, Burkina Faso. Trace elements and 238U---234U---230Th disequilibria have been analysed in whole rock samples from two pits located in very contrasted topographical positions. Trace element data show that the whole toposequence is marked by an intense chemical remobilization, including uranium, from the cap to the lower part of the profiles. 238U---234U---230Th disequilibrium data outline that all the levels of the profiles are affected by recent U---Th fractionations, and that each level of the toposequence is marked by U gains and losses. The chronological approach developed in this paper leads to an age of about 400 kyr for the dismantling of the iron cap, and ages ranging from 0 to 400 kyr for U accumulation in the pink clay horizon of the profiles. The depth repartition of U accumulation in the profile implies that the remobilisation processes in this toposequence varied through time, on time constants similar to those of climatic variations. To cite this article: F. Chabaux et al., C. R. Geoscience 335 (2003).相似文献