22,564 research outputs found
Analytical solution of Stokes flow inside an evaporating sessile drop: Spherical and cylindrical cap shapes
Exact analytical solutions are derived for the Stokes flows within
evaporating sessile drops of spherical and cylindrical cap shapes. The results
are valid for arbitrary contact angle. Solutions are obtained for arbitrary
evaporative flux distributions along the free surface as long as the flux is
bounded at the contact line. The field equations, E^4(Psi)=0 and Del^4(Phi)=0,
are solved for the spherical and cylindrical cap cases, respectively. Specific
results and computations are presented for evaporation corresponding to uniform
flux and to purely diffusive gas phase transport into an infinite ambient.
Wetting and non-wetting contact angles are considered with the flow patterns in
each case being illustrated. For the spherical cap with evaporation controlled
by vapor phase diffusion, when the contact angle lies in the range
0<theta_c<pi, the mass flux of vapor becomes singular at the contact line. This
condition required modification when solving for the liquid phase transport.
Droplets in all of the above categories are considered for the following two
cases: the contact lines are either pinned or free to move during evaporation.
The present viscous flow behavior is compared to the inviscid flow behavior
previously reported. It is seen that the streamlines for viscous flow lie
farther from the substrate than the corresponding inviscid ones.Comment: Revised version; in review in Physics of Fluid
MEASURING THE IMPACT OF ETHIOPIA'S NEW EXTENSION PROGRAM ON THE PRODUCTIVE EFFICIENCY OF FARMERS
This paper employed a robust stochastic efficiency decomposition technique that accounts for scale effects to derive the technical, allocative, and overall productive efficiency of two samples of farmers, participants and non-participants in the New Extension Program (NEP), in two agro-climatic zones in eastern Ethiopia. Using data for the 2001/2002 agricultural year, we find that both groups of farmers in the two zones have considerable overall productive inefficiencies. In the wet highlands, although the participants in NEP used a superior technology and have higher technical efficiencies, their allocative efficiencies turned out to be lower than the non-participant farmers, relative to their respective technologies. However, both groups exhibit similar productive efficiencies. In the dry lands, apart from using homogeneous production technologies, the two groups do not have significantly different technical and allocative efficiencies and that they have similar productive efficiencies. Therefore, we find no empirical evidence of a positive impact of NEP on overall productive efficiency in both agro-climatic zones. An investigation of the influence of several socio-economic and institutional factors revealed that education, credit, previous participation in extension programs, off-farm income and the share of the leading cropping system have a positive impact on efficiency.Teaching/Communication/Extension/Profession,
Why Northern Ghana Lags Behind in Ghana's Growth and Poverty Reduction Success
Ghana's post adjustment growth and poverty reduction performance has been hailed as impressive, albeit with spatial disparities in the distribution of welfare, especially between the north and south of the country. Researchers generally agree that economic growth does not always reduce poverty. Indeed, the effectiveness of growth in reducing poverty depends on the level of inequality in the population. Growth that increases inequality may not reduce poverty; growth that does not change inequality (distribution-neutral growth) and growth that reduces inequality (pro-poor growth) result in poverty reduction. Policy makers can promote pro-poor growth by empowering the poor to participate in growth directly. Policy makers can focus on interventions that improve productivity in smallholder agriculture, particularly export crops, increasing employment of semi-skilled or unskilled labour, promoting technology adoption, increasing access to production assets, as well as effective participation in input and product markets. Also, increasing public spending on social services and infrastructure made possible by redistribution of the benefits of growth benefits the poor, indirectly
Unleashing the Power of Distributed CPU/GPU Architectures: Massive Astronomical Data Analysis and Visualization case study
Upcoming and future astronomy research facilities will systematically
generate terabyte-sized data sets moving astronomy into the Petascale data era.
While such facilities will provide astronomers with unprecedented levels of
accuracy and coverage, the increases in dataset size and dimensionality will
pose serious computational challenges for many current astronomy data analysis
and visualization tools. With such data sizes, even simple data analysis tasks
(e.g. calculating a histogram or computing data minimum/maximum) may not be
achievable without access to a supercomputing facility.
To effectively handle such dataset sizes, which exceed today's single machine
memory and processing limits, we present a framework that exploits the
distributed power of GPUs and many-core CPUs, with a goal of providing data
analysis and visualizing tasks as a service for astronomers. By mixing shared
and distributed memory architectures, our framework effectively utilizes the
underlying hardware infrastructure handling both batched and real-time data
analysis and visualization tasks. Offering such functionality as a service in a
"software as a service" manner will reduce the total cost of ownership, provide
an easy to use tool to the wider astronomical community, and enable a more
optimized utilization of the underlying hardware infrastructure.Comment: 4 Pages, 1 figures, To appear in the proceedings of ADASS XXI, ed.
P.Ballester and D.Egret, ASP Conf. Serie
Characterization of Freshwater Natural Dissolved Organic Matter (DOM): Mechanistic Explanations for Protective Effects Against Metaltoxicity and Direct Effects on Organisms
Dissolved organic matter (DOM) exerts direct and indirect influences on aquatic organisms. In order to better understand how DOM causes these effects, potentiometric titration was carried out for a wide range of autochthonous and terrigenous freshwater DOM isolates. The isolates were previously characterized by absorbance and fluorescence spectroscopy. Proton binding constants (pKa) were grouped into three classes:acidic (pKa †5), intermediate (5 \u3c pKa †8.5) and basic (pKa \u3e 8.5). Generally, the proton site densities (LT) showed maximum peaks at the acidic and basic ends around pKa values of 3.5 and 10, respectively. More variably positioned peaks occurred in the intermediate pKa range. The acidâbase titrations revealed the dominance of carboxylic and phenolic ligands with a trend for more autochthonous sources to have higher total LT. A summary parameter, referred to as the Proton Binding Index (PBI), was introduced to summarize chemical reactivity of DOMs based on the data of pKa and LT. Then, the already published spectroscopic data were explored and the specific absorbance coefficient at 340 nm (i.e. SAC340), an index of DOM aromaticity,was found to exhibit a strong correlation with PBI. Thus, the tendencies observed in the literature that darker organic matter is more protective against metal toxicity and more effective in altering physiological processes in aquatic organisms can now be rationalized on a basis of chemical reactivity to protons
Intending to be ethical: An examination of consumer choice in sweatshop avoidance
While much research in ethical consumption has focused on contexts such as food, this research explores ethical consumer decision-making in the context of intention to avoid sweatshop apparel. This research seeks to deepen the Theory of Planned Behavior with respect to the motivation and volitional stages underlying behavior. The findings of the research, based on 794 consumers, are novel and support an enriched framework which reveals that the role of attitude, subjective norm and perceived behavioral control are mediated by desire, intention and plan. The findings have implications for research seeking to address the âintention-behaviorâ gap
The Influence of Dissolved Organic Matter (DOM) on Sodium Regulation and Nitrogenous Waste Excretion in the Zebrafish (Danio rerio)
Dissolved organic matter (DOM) is both ubiquitous and diverse in composition in natural waters, but its effects on the branchial physiology of aquatic organisms have received little attention relative to other variables (e.g. pH, hardness, salinity, alkalinity). Here, we investigated the effects of four chemically distinct DOM isolates (three natural, one commercial, ranging from autochthonous to highly allochthonous, all at âŒ6 mg C lâ1) on the physiology of gill ionoregulation and nitrogenous waste excretion in zebrafish acclimated to either circumneutral (7.0â8.0) or acidic pH (5.0). Overall, lower pH tended to increase net branchial ammonia excretion, net K+ loss and [3H]PEG-4000 clearance rates (indicators of transcellular and paracellular permeability, respectively). However, unidirectional Na+ efflux, urea excretion and drinking rates were unaffected. DOM sources tended to stimulate unidirectional Na+ influx rate and exerted subtle effects on the concentration-dependent kinetics of Na+ uptake, increasing maximum transport capacity. All DOM sources reduced passive Na+ efflux rates regardless of pH, but exerted negligible effects on nitrogenous waste excretion, drinking rate, net K+ loss or [3H]PEG4000 clearance, so the mechanism of Na+ loss reduction remains unclear. Overall, these actions appear beneficial to ionoregulatory homeostasis in zebrafish, and some may be related to physicochemical properties of the DOM sources. They are very different from those seen in a recent parallel study on Daphnia magna using the same DOM isolates, indicating that DOM actions may be both species and DOM specific
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