717 research outputs found
Travel mode substitution in Sao Paulo : estimates and implications for air pollution control
How would travel demand in Sao Paulo respond to demand management instruments? Could higher gasoline prices or lower metro fares (or changes in travel time) help reduce congestion or pollution? The authors use cross-sectional variation from an urban travel survey to study the substitutability in demand between travel modes. The method assumes that the set of trips is given (that is, origin-destination pairs do not change). Choice of mode was found to be quite insensitive to changes; all elasticities were lower than 0.5 in absolute value, and most were close to zero. While the sensitivity of mode choice to relative travel times (that is, speeds) was somewhat greater than that to costs, the general finding is that mode choice is quite inflexible. So, subsidies to less polluting (less congesting) travel modes would not help much in attracting travelers from more polluting (more congesting) modes. (The same holds for subsidized means of making them run faster.) But there are important limitations in the scope of the study. First, the study does not discuss optimal pricing. It merely examines the likely sign and magnitude of the links between pollution and policy parameters such as prices and travel speeds. Second, aggregate demand by mode could also depend on the city's shape and its travel intensity (the number, direction, and length of trips). For example, if a"city"stretches along a constructed metro line, the study would not capture such a phenomenon, since sensitive trip generation is excluded. These issues are not examined in the study.Roads&Highways,Consumption,Economic Theory&Research,Environmental Economics&Policies,Transport Economics Policy&Planning,Roads&Highways,Economic Theory&Research,Urban Transport,Environmental Economics&Policies,Transport and Environment
Aquaculture for the poor in Cambodia
This lesson learned reviewed the current status of aquaculture in Cambodia. It primarily covers inland fish farming development and coastal aquaculture projects targeted at poverty alleviation and food security. It focuses on approaches aimed at developing low cost systems, and less on high input aquaculture systems that are usually inaccessible to poor families.
Institutional histories, seasonal floodplains (mares), and livelihood impacts of fish stocking in the Inner Niger River Delta of Mali
The Community-based Fish Culture in Seasonal Floodplains and Irrigation Systems (CBFC) project is a five year research project supported by the Challenge Program on Water and Food (CPWF), with the aim of increasing productivity of seasonally occurring water bodies through aquaculture. The project has been implemented in Bangladesh, Cambodia, China, Mali and Vietnam, where technical and institutional options for community based aquaculture have been tested. The project began in 2005 and was completed in March 2010. The seasonally flooded depressions in the Inner Niger Delta (known as mares) represent a critical fishery resource for the inhabitants of the village of Komio, and at present, access is open to all residents. A proposal to build stocked fish enclosures in the main village mare presents potential benefits and risks. On one hand, overall productivity in the mare could be significantly increased, providing important sources of protein and cash during the annual drought period, when few livelihood activities can be performed and when village livelihoods are at their most vulnerable. Enhanced productivity in mares may also decrease local household pressures for seasonal labor migration. On the other hand, a resulting increase in the value of these mares may encourage elite capture of project benefits or rentseeking by certain village leaders of the landowning Marka ethnic group. Using qualitative interviews and focus group discussions, the study provides evidence of how local institutional and leadership capacity for equitable common property resource management have evolved since the introduction of irrigated farming systems (known as PΘrimΦtres IrriguΘs Villageois or PIVs) in the 1990s.Fishing rights, River fisheries, Livelihoods
Mixing height determination by ceilometer
International audienceA novel method for estimating the mixing height based on ceilometer measurements is described and tested against commonly used methods for determining mixing height. In this method an idealised backscatter profile is fitted to the observed backscatter profile. The mixing height is one of the idealised backscatter profile parameters. An extensive amount of ceilometer data and vertical soundings data from the Helsinki area in 2002 is utilized to test the applicability of the ceilometer for mixing height determination. The results, including 71 convective and 38 stable cases, show that in clear sky conditions the mixing heights determined from ceilometer based aerosol profiles and BL-height estimates based on sounding data are in a good agreement. Rejected outlier cases corresponded to very low aerosol concentrations in the mixed layer leading to a very weak aerosol backscatter signal in the lowest layer
El método de Liapunov-Schmidt.
En esta investigación se estudiaran las soluciones de la Ecuación Diferencial Parcial Elíptica. Una de las técnicas de gran utilidad en el estudio de las soluciones de las ecuaciones diferenciales, es el método de Liapunov-Schmidt.
Se presenta la relación existente entre las soluciones de la Ecuación Diferencial y los puntos críticos de un funcional, definido sobre un espacio de Hilbert real
On the parameterisation of the urban atmospheric sublayer in meteorological models
International audienceThe increased resolution of numerical weather prediction models allows nowadays addressing more specifically urban meteorology and air pollution processes and forecasts. This has triggered new interest in modelling and describing experimentally the specific features and processes of urban areas. Recent developments and results performed within the EU-funded project FUMAPEX on integrated systems for forecasting urban meteorology and air pollution are reported here. Issues of optimum resolution, parameterising urban roughness and surface exchange fluxes and the role of the urban soil layers are addressed with advanced meso- or sub-meso meteorological models. Recommendations, especially with respect to advanced urban air quality forecasting and information systems, are given together with an assessment of the needed further research and data
Towards improving the simulation of meteorological fields in urban areas through updated/advanced surface fluxes description
International audienceThe increased resolution of numerical weather prediction models allows nowadays addressing more realistically urban meteorology and air pollution processes. This has triggered new interest in modelling and describing experimentally the specific features and processes of urban areas. Recent developments and results performed within the EU-funded project FUMAPEX on integrated systems for forecasting urban meteorology and air pollution are reported here. Sensitivity studies with respect to optimum resolution, parametrisation of urban roughness and surface exchange fluxes and the role of urban soil layers are carried out with advanced meso- or sub-meso meteorological models. They show that sensible improvements can be achieved by higher model resolution that is accompanied with better description of urban surface features. Recommendations, especially with respect to advanced urban air quality forecasting and information systems, are given together with an assessment of the needed further research and data
Physiological Experimentation with the Crayfish Hindgut: A Student Laboratory Exercise
The purpose of the report is to describe dissection techniques for preparing the crayfish hindgut and to demonstrate how to make physiological recordings with a force transducer to monitor the strength of contraction. In addition, we demonstrate how to visually monitor peristaltic activity, which can be used as a bioassay for various peptides, biogenic amines and neurotransmitters. This preparation is amenable to student laboratories in physiology and for demonstrating pharmacological concepts to students. This preparation has been in use for over 100 years, and it still offers much as a model for investigating the generation and regulation of peristaltic rhythms and for describing the mechanisms underlying their modulation. The pharmacological assays and receptor sub-typing that were started over 50 years ago on the hindgut still contribute to research today. This robust preparation is well suited to training students in physiology and pharmacology
European framework for online integrated air quality and meteorology modelling - EuMetChem COST action ES1004 (03.2011 - 02.2015)
Localized thinning for strain concentration in suspended germanium membranes and optical method for precise thickness measurement
We deposited Ge layers on (001) Si substrates by molecular beam epitaxy and used them to fabricate suspended membranes with high uniaxial tensile strain. We demonstrate a CMOS-compatible fabrication strategy to increase strain concentration and to eliminate the Ge buffer layer near the Ge/Si hetero-interface deposited at low temperature. This is achieved by a two-steps patterning and selective etching process. First, a bridge and neck shape is patterned in the Ge membrane, then the neck is thinned from both top and bottom sides. Uniaxial tensile strain values higher than 3% were measured by Raman scattering in a Ge membrane of 76 nm thickness. For the challenging thickness measurement on micrometer-size membranes suspended far away from the substrate a characterization method based on pump-and-probe reflectivity measurements was applied, using an asynchronous optical sampling technique.EC/FP7/628197/EU/Heat Propagation and Thermal Conductivity in Nanomaterials for Nanoscale Energy Management/HEATPRONAN
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