32 research outputs found
Setting Africa’s rainfall straight: A warping approach to position and timing errors in rainfall estimates
No full textThere is an increasing number of rainfall products available over Africa and globally. Rainfall has considerable socio-economic impacts in sub-Saharan Africa, and the sparse gauge and radar networks make such estimates particularly valuable. They are used in many important applications such as drought/flood forecasting, water management or climate monitoring. The choice of which one to use has a significant influence on the output and performance of such applications. The large number of available rainfall products makes it difficult to select the “best” one for one’s need. Among the rainfall products, there is an increasing number of satellite-based estimates with ever finer resolution. They are particularly valuable in Africa where the gauge network is not dense enough to represent the high variability of the rainfall during the monsoon season. However, there are substantial differences between them. Rainfall events are moving systems which can be described by their positions and timings beside of their intensity. A position or timing error will also lead to mismatches in the rainfall occurrence or intensity. This is especially true for localized rainfall events such as the convective rainstorms occurring during the rainy season in sub-Saharan Africa. However, rainfall is mainly evaluated with respect to its intensity or occurrence, while position and timing errors are rarely studied.Mathematical PhysicsWater Resource
Treatment Techniques for Combined Sewer Overflows
No full textDuring storm events, the flow in a combined sewer system can exceed the capacity and, as a result, a combined sewer overflow (CSO) will occur. During a CSO raw wastewater is discharged to surface water. This wastewater is a mixture of raw sanitary wastewater, raw industrial wastewater and rainwater. The receiving water will get polluted by dissolved as well as undissolved pollutants. Therefore a CSO can cause damage to the ecological and biological state of the receiving water and besides it can cause public health risks. Until now the problem, with respect to CSOs in the Netherlands, is dominated by a quantitative approach. CSO flow rates and frequencies were in the past decades the main subject of research. These frequencies were translated into the Wet Verontreiniging Oppervlaktewater (1970). In the year 1998 the Ministry of Transport and Water Management came with a renewed policy, the fourth Memorandum on Water Management, dealing with groundwater, dehydration and water quality, for the protection and the recovery of nature. At the end of 2000 the European Water Framework Directive (WFD) came into force, which charges the European members of the EU to report obligatory. The aim of the WFD is to have an ecological and biological balance for all surface waters and groundwater in Europe effectively working in 2015. Measures are required to push back the pollution by defined dangerous substances. Measures with regard to the reduction of CSO frequencies alone is not enough to fulfil the legislation. When a CSO occurs an amount of pollutants will enter the surface water. CSO water needs to be treated to prevent pollution and odour annoyances to the surroundings. The goal of this research is to find a suitable treatment technique or a combination of treatment techniques. Primary and secondary techniques, adsorption and disinfection techniques are described. Primary techniques remove suspended solids and a fraction of the organic material, secondary techniques remove suspended solids and biological degradable material. Adsorption techniques are used to remove for example endocrine disrupting substances and disinfection techniques are used to minimize health risks for the population. In the Netherlands CSOs occur five to ten times a year per location. Therefore a treatment technique needs to be able to start up in a few minutes even after a long period without feedwater and should be able to handle wide and quick variations in flow without causing any inconveniences to the surroundings. Primary techniques like sieving, the Netting TrashTrapTM system and sedimentation basins and secondary techniques like membrane filtration, sand filtration and synthetic medium filtration are described. Adsoprtion techniques like activated carbon filtration and ion exchange and disinfection techniques like ozone dosage, chlorine dosage and UV treatment are described.Sanitary EngineeringWatermanagementCivil Engineering and Geoscience
Spin pump turnstile: Parametric pumping of a spin-polarized current through a nearly closed quantum dot
No full textComparison of Rainfall Products over Sub-Saharan Africa
No full textAn ever-increasing number of rainfall estimates is available. They are used in many important applications such as flood/drought monitoring, water management, or climate monitoring. Such data are especially valuable in sub-Saharan Africa, where rainfall has considerable socioeconomic impacts and the gauge and radar networks are sparse. The choice of a rainfall product can significantly influence the performance of such applications. This study reviews previous works, evaluating or comparing rainfall products over different parts of sub-Saharan Africa. Three types of rainfall products are considered: The gauge-only, the satellite-based, and the reanalysis ones. In addition to the global rainfall products, we included three regional ones specifically developed for Africa: The African Rainfall Climatology version 2 (ARC2), the Rainfall Estimate version 2 (RFE2), and the Tropical Applications ofMeteorology Using Satellite Data and Ground-Based Observations (TAMSAT) AfricanRainfall Climatology and Time Series (TARCAT). The gauge density, the orography, and the rainfall regime, which vary with the climate and the season, influence the performance of the rainfall products. This review does not focus on comparing results, as many other publications doing so are already available. Instead, we propose this review as a guide through the different rainfall products available over Africa, and the factors influencing their performances. With this review, the reader can make informed decisions about which products serve their specific purpose best.Water Resource
INFRARED OBSERVATION OF THE STRETCHING MODE OF LINEAR GeC
No full textAuthor Institution: Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129GeCGe was first produced by dual laser ablationof germanium and carbon rods, and the stretching fundamental was assigned at 1920.7 cm. Later work enhanced the production of the molecule via laser ablation of a single, sintered germanium-carbon rod, thus enabling the identification of two additional infrared active vibrational fundamentals =735.6 cm and =580.1 cm. In the present work using the same technique, GeC trapped in solid Ar at 10 K has been observed by FTIR spectroscopy . Comparison of C isotopic shift measurements with the predictions of density functional theory (DFT) calculations at the B3LYP/cc-pV(D,T)Z level confirm the identification of the stretching fundamental at 1279.6 cm. \newline\newline D.L. Robbins, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. \textbf{114}, 3570 (2001).\newline E. Gonzalez, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. in press
FTIR AND DFT STUDIES OF NOVEL GERMANIUM-CARBON AND MIXED GERMANIUM-SILICON-CARBON CLUSTERS
No full textD.L. Robbins, C.M.L. Rittby, and W.R.M. Graham J. Chem. Phys. 114, 3570 (2001).Author Institution: Department of Physics and Astronomy, TCUThe vibrational fundamentals and structures of novel germanium-carbon and mixed germanium-silicon-carbon clusters, formed by laser ablation and trapped in solid Ar, are currently under Vibrational fundamentals and ground state geometries are characterized by comparison of Fourier transform infrared measurements of vibrational frequencies and isotopic shifts for the matrix isolated clusters with the predictions of density functional theory (DFT). Linear has been detected, the first species to be observed optically, and its fundamental identified at . The results are in excellent agreement with DFT predictions. Additional results and assignments for clusters will be reported
Can a European Monetary Fund address the weaknesses of the Eurozone?
No full textThis dissertation examines measures in response to the European sovereign debt crisis aimed at achieving closer fiscal union. The first is the European Financial Stability Facility (EFSF) which provides financial assistance to Euro area member states beset by budgetary difficulties. The second is the establishment of a Euroepan Monetary Fund as a permanent Euro area support fund to be based in the EFSF. The author analyses the suitability of the establishment of a European Monetary Fund as a measure to avoid future crises. Special attention is paid to the legal basis and feasibility of the measures in question
Multimodal histopathologic models stratify hormone receptor-positive early breast cancer
No full textAbstract The Oncotype DX® Recurrence Score (RS) is an assay for hormone receptor-positive early breast cancer with extensively validated predictive and prognostic value. However, its cost and lag time have limited global adoption, and previous attempts to estimate it using clinicopathologic variables have had limited success. To address this, we assembled 6172 cases across three institutions and developed Orpheus, a multimodal deep learning tool to infer the RS from H&E whole-slide images. Our model identifies TAILORx high-risk cases (RS > 25) with an area under the curve (AUC) of 0.89, compared to a leading clinicopathologic nomogram with 0.73. Furthermore, in patients with RS ≤ 25, Orpheus ascertains risk of metastatic recurrence more accurately than the RS itself (0.75 vs 0.49 mean time-dependent AUC). These findings have the potential to guide adjuvant therapy for high-risk cases and tailor surveillance for patients at elevated metastatic recurrence risk
Gauge-adjustment of satellite-based rainfall estimates using morphing
No full textWater ResourcesMathematical Physic
Spatial and Time Warping for Gauge Adjustment of Rainfall Estimates
No full textMany satellite-based estimates use gauge information for bias correction. In general, bias-correction methods are focused on the intensity error and do not explicitly correct possible position or timing errors. However, position and timing errors in rainfall estimates can also lead to errors in the rainfall occurrence or the intensity. This is especially true for localized rainfall events such as the convective rainstorms occurring during the rainy season in sub-Saharan Africa. We investigated the use of warping to correct such errors. The goal was to gauge-adjust satellite-based estimates with respect to the position and the timing of the rain event, instead of its intensity. Warping is a field-deformation method that transforms an image into another one. We compared two methods, spatial warping focusing on the position errors and time warping for the timing errors. They were evaluated on two case studies: a synthetic rainfall event represented by an ellipse and a rain event in southern Ghana during the monsoon season. In both cases, the two warping methods reduced significantly the respective targeted (position or timing) errors. In the southern Ghana case, the average position error was decreased by about 45 km by the spatial warping and the average timing error was decreased from more than 1 h to 0.2 h by the time warping. Both warping methods also improved the continuous statistics on the intensity: the correlation went from 0.18 to at least 0.62 after warping in the southern Ghana case. The spatial warping seems more interesting because of its positive impact on both position and timing errors.Water ResourcesMathematical Physic
