519 research outputs found
The provision of solar energy to rural households through a fee-for-service system
This baseline report is part of an evaluation commissioned by the Policy
and Operations Evaluation Department (IOB) of the Netherlands
Ministry of Foreign Affairs. It belongs to a series of impact evaluations
of renewable energy and development programmes supported by the
Netherlands, with a focus on the medium and long term effects of these
programmes on end-users or final beneficiaries. A characteristic of
these studies is the use of mixed methods, being quantitative research
techniques, in combination with qualitative techniques, to get insight in
the magnitude of effects. The purpose of the impact evaluations is to
account for assistance provided and to draw lessons from the findings
for improvement of policy and policy implementation. The results of
these impact evaluations will be input to a policy evaluation of the
“Promoting Renewable Energy Programme” (PREP) to be concluded in
2014
Space Complexity of Stack Automata Models
This paper examines several measures of space complexity on variants of stack automata: non-erasing stack automata and checking stack automata. These measures capture the minimum stack size required to accept any word in a language (weak measure), the maximum stack size used in any accepting computation on any accepted word (accept measure), and the maximum stack size used in any computation (strong measure). We give a detailed characterization of the accept and strong space complexity measures for checking stack automata. Exactly one of three cases can occur: the complexity is either bounded by a constant, behaves (up to small technicalities explained in the paper) like a linear function, or it grows arbitrarily larger than the length of the input word. However, this result does not hold for non-erasing stack automata; we provide an example when the space complexity grows with the square root of the input length. Furthermore, an investigation is done regarding the best complexity of any machine accepting a given language, and on decidability of space complexity properties
First Principles Calculations of Fe on GaAs (100)
We have calculated from first principles the electronic structure of 0.5
monolayer upto 5 monolayer thick Fe layers on top of a GaAs (100) surface. We
find the Fe magnetic moment to be determined by the Fe-As distance. As
segregates to the top of the Fe film, whereas Ga most likely is found within
the Fe film. Moreover, we find an asymmetric in-plane contraction of our
unit-cell along with an expansion perpendicular to the surface. We predict the
number of Fe 3d-holes to increase with increasing Fe thickness on -doped
GaAs.Comment: 9 pages, 14 figures, submitted to PR
Postglacial Colonisation Patterns and the Role of Isolation and Expansion in Driving Diversification in a Passerine Bird
Pleistocene glacial cycles play a major role in diversification and speciation, although the relative importance of isolation and expansion in driving diversification remains debated. We analysed mitochondrial DNA sequence data from 15 great reed warbler (Acrocephalus arundinaceus) populations distributed over the vast Eurasian breeding range of the species, and revealed unexpected postglacial expansion patterns from two glacial refugia. There were 58 different haplotypes forming two major clades, A and B. Clade A dominated in Western Europe with declining frequencies towards Eastern Europe and the Middle East, but showed a surprising increase in frequency in Western and Central Asia. Clade B dominated in the Middle East, with declining frequencies towards north in Central and Eastern Europe and was absent from Western Europe and Central Asia. A parsimonious explanation for these patterns is independent postglacial expansions from two isolated refugia, and mismatch distribution analyses confirmed this suggestion. Gene flow analyses showed that clade A colonised both Europe and Asia from a refugium in Europe, and that clade B expanded much later and colonised parts of Europe from a refugium in the Middle East. Great reed warblers in the eastern parts of the range have slightly paler plumage than western birds (sometimes treated as separate subspecies; A. a. zarudnyi and A. a. arundinaceus, respectively) and our results suggest that the plumage diversification took place during the easterly expansion of clade A. This supports the postglacial expansion hypothesis proposing that postglacial expansions drive diversification in comparatively short time periods. However, there is no indication of any (strong) reproductive isolation between clades and our data show that the refugia populations became separated during the last glaciation. This is in line with the Pleistocene speciation hypothesis invoking that much longer periods of time in isolation are needed for speciation to occur
Within-Host Speciation of Malaria Parasites
BACKGROUND: Sympatric speciation—the divergence of populations into new species in absence of geographic barriers to hybridization—is the most debated mode of diversification of life forms. Parasitic organisms are prominent models for sympatric speciation, because they may colonise new hosts within the same geographic area and diverge through host specialization. However, it has been argued that this mode of parasite divergence is not strict sympatric speciation, because host shifts likely cause the sudden effective isolation of parasites, particularly if these are transmitted by vectors and therefore cannot select their hosts. Strict sympatric speciation would involve parasite lineages diverging within a single host species, without any population subdivision. METHODOLOGY/PRINCIPAL FINDINGS: Here we report a case of extraordinary divergence of sympatric, ecologically distinct, and reproductively isolated malaria parasites within a single avian host species, which apparently occurred without historical or extant subdivision of parasite or host populations. CONCLUSIONS/SIGNIFICANCE: This discovery of within-host speciation changes our current view on the diversification potential of malaria parasites, because neither geographic isolation of host populations nor colonization of new host species are any longer necessary conditions to the formation of new parasite species
Malaria parasites (Plasmodium spp.) infecting introduced, native and endemic New Zealand birds
Avian malaria is caused by intracellular mosquito-transmitted protist parasites in the order Haemosporida, genus Plasmodium. Although Plasmodium species have been diagnosed as causing death in several threatened species in New Zealand, little is known about their ecology and epidemiology. In this study, we examined the presence, microscopic characterization and sequence homology of Plasmodium spp. isolates collected from a small number of New Zealand introduced, native and endemic bird species. We identified 14 Plasmodium spp. isolates from 90 blood or tissue samples. The host range included four species of passerines (two endemic, one native, one introduced), one species of endemic pigeon and two species of endemic kiwi. The isolates were associated into at least four distinct clusters including Plasmodium (Huffia) elongatum, a subgroup of Plasmodium elongatum, Plasmodium relictum and Plasmodium (Noyvella) spp. The infected birds presented a low level of peripheral parasitemia consistent with chronic infection (11/15 blood smears examined). In addition, we report death due to overwhelming parasitemia in a blackbird, a great spotted kiwi and a hihi. These deaths were attributed to infections with either Plasmodium spp. lineage LINN1 or P. relictum lineage GRW4. To the authors’ knowledge, this is the first published report of Plasmodium spp. infection in great spotted and brown kiwi, kereru and kokako. Currently, we are only able to speculate on the origin of these 14 isolates but consideration must be made as to the impact they may have on threatened endemic species, particularly due to the examples of mortality
Имитация распределенной обработки информации в вычислительных системах и локальных вычислительных сетях
Предложено использовать для анализа вариантов организации распределенной обработки информации в вычислительных системах и локальных вычислительных сетях вероятностный граф реализации вычислительного процесса с явными связями типа вероятностных сетевых графиков.Запропоновано використовувати для аналізу варіантів організації розподіленої обробки інформації в обчислювальних системах і в локальних обчислювальних мережах імовірнісний граф реалізації обчислювального процесу з явними зв’язками типу імовірнісних сіткових графіків.It іs оffered to use for analyzing variants of organization of distributed information processing in computing systems and local computing networks a probabilistic graph for realizing a computing process with evident relationships of the type probabilistic network diagrams
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