1,721,463 research outputs found
Simulating design rainfall extremes in locations with limited observational records
No full textThe prospect of climatic change and its impacts have brought spatial statistics of extreme events into sharper focus. The so-called "water bombs" or "explosive cyclones" are predicted to become more frequent in the extra-tropical regions, and, actually, they raise serious concerns in some regions of the Mediterranean area. However, quantitative statistical methods to properly account for the probability of occurrence of these super-extreme events in formerly untouched areas are still lacking. This is due to their rare occurrence and to the limited spatial scale at which these events occur. In order to overcome the lack of data, different studies concerning flood frequency analysis underline the importance of combining local flood data with additional types of information, to improve the quality of the estimation of the exceedance probability for a given discharge. We propose to apply such a kind of approach in extreme rainfall frequency analysis, with the adoption of a Bayesian framework, aimed at combining local gauge information, discontinuous in space and time, with climatic regional information. The identification of this type of hierarchic relationship can complement local information, conditioning the exceedance probability to the large and meso-scale characteristics of the system, allowing the simulation of design rainfall extremes in sites where historical evidence of that hazard is lacking. The Bayesian approach allows us also to keep track of all the uncertainties involved in the prediction process, producing a measure of uncertainty associated to the estimates. The case study refers to a database of daily rainfall measurements extracted from the NOAA GHCN-Daily dataset, recorded during the 20th century by 700 rain gauges distributed in the Mediterranean basin. First, to identify the conditional variables, we analyse the large-scale environment associated with the different intense precipitation systems in the Mediterranean area, exploiting the reanalysis of the European Centre for Medium-Range Weather Forecasts (ERA-20). With the aim to define the hierarchical relationships between the events and their type, we relate the daily precipitation with different parameters both atmospherical and local. Despite the high variability, different climatic configurations that combined with the local morphology and the seasonal condition of the Mediterranean Sea can trigger very intense precipitation events are identified. Once defined the hierarchical relationships, the parameters are calibrated and the methodology is tested on a subset of daily series provided by local authorities, evenly distributed on the whole domain. The results, compared with those obtained with the classic techniques of frequency analysis and spatial interpolation, demonstrate an increased knowledge coming from climate and local factors, ensuring more reliable and accurate spatial assessment of extreme thunderstorm probabilit
A global assessment of the timing of extreme rainfall from TRMM and GPM for improving hydrologic design
Full text linkThe tropical rainfall measuring mission (TRMM) has revolutionized the measurement of precipitation worldwide. However, TRMM significantly underestimates rainfall in deep convection systems, being therefore of little help for the analysis of extreme precipitation depths. This work evaluates the ability of both TRMM and the recently launched global precipitation measurement (GPM) mission to help in the identification of the timing of severe rainfall events. We compare the date of occurrence of the most severe daily rainfall recorded each year by a global rain gauge network with the ones estimated by TRMM. The match rate between the two is found to approach 50%, indicating significant consistency between the two data sources. This figure rises to 60% for GPM, indicating the potential for this new mission to improve the accuracy associated with TRMM. Further efforts are needed in improving the GPM conversion algorithms in order to reduce the bias affecting the estimation of intense depths. The results however show that the timing estimated from GPM can provide a solid basis for an extensive characterization of the spatio-temporal distribution of extreme rainfall in poorly gauged regions of the world
Supplemental nutrition for retinal health: Evidence based analysis of commercial preparations in India
Full text linkPURPOSE: Antioxidants have been lately postulated as supportive and prophylactic supplements for various retinal disorders, especially age-related macular degeneration (AMD). Forty-eight brands of such supplements containing lutein and zeaxanthin are available in India. The aim of the study was to assess the market leaders in supplements for ophthalmology in view of AREDS recommendations. METHODS: Descriptive review of top-selling supplements for eye health were compared to the contents of the AREDS-recommended levels. RESULTS: None of the top 10 selling brands had exact or near similar composition as recommended in the AREDS-2 study, which is the most widely accepted level-1 evidence in AMD prevention. CONCLUSION: Physicians prescribing these antioxidants, especially for the prevention of advanced AMD, should be vigilant and aware of the contents of the prescribed brands
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
σ<sup>n</sup> LBDR: generic congestion handling routing implementation for two-dimensional mesh network-on-chip
No full textThe number of cores on a chip is increasing from a few cores to thousands. However, the communication mechanisms for these systems do not scale at the same pace, leading to certain challenges. One of them is on-chip congestion. There are many table-based approaches for congestion handling and avoidance, but these are not acceptable as they impose high area and power overheads. In this study, the authors propose two congestion handling strategies aiming to capture the congestion in few bits to avoid congested routes. The first approach called σnLBDR (logic based distributed routing) captures congestion present at nodes n-hop away from the current node, reducing area, power and overall packet latency. However, all nodes in the network do not experience same congestion level. For this, their second approach, weighted σnLBDR, uses a different set of bits for each node and results in the further improvement in area and power. This study shows a comparison of both approaches with each other and also with other similar approaches. From their experimental results, they show that σnLBDR and weighted σnLBDR improve latency by 20 and 30%, respectively, and have less area and power overhead as compared with baseline table-based approach
Faricimab phase 3 DME trial significance of personalized treatment intervals (PTI) regime for future DME trials
No full textA simple and robust approach for adapting design storms to assess climate-induced changes in flash flood hazard
Full text linkISSN:0309-1708ISSN:1872-9657ISSN:1872-965
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