3,619 research outputs found
Shortage of vaccines during a yellow fever outbreak in Guinea.
A yellow fever epidemic erupted in Guinea in September, 2000. From Sept 4, 2000, to Jan 7, 2001, 688 instances of the disease and 225 deaths were reported. The diagnosis was laboratory confirmed by IgM detection in more than 40 patients. A mass vaccination campaign was limited by insufficient international stocks. After the epidemic in Guinea, the International Coordinating Group on Vaccine Provision for Epidemic Meningitis Control decided that 2 million doses of 17D yellow fever vaccine, being stored as part of a UNICEF stockpile, should be used only in response to outbreaks
Modelling Interregional Trade of Energy Crops in Eastern Germany
Renewable resources gain in importance in our modern society. The line of reasoning is based on their positive effects on agriculture, the environment and the economy. To support renewable energy from biomass the EU promotes the cultivation of energy crops. A spatial equilibrium model is applied based on the concept of maximizing net welfare, to provide information whether energy crop production competes with food production for land area. The Model of Interregional Trade of Energy Crops (ITEC) refers to Eastern Germany and adjacent areas of Poland. First results show that the regions have enough feedstocks to meet the required demand for food and biofuel production. In many cases both food crops and biofuels are either traded on interregional basis or exported to "Rest of Europe" indicating that there is no competition between food and energy crops. Only green maize for biogas production strongly competes in areas where the crop is required as feed for cattle.Energy crops, spatial equilibrium analysis, interregional trade, International Relations/Trade,
A relativistic model for neutrino pion production from nuclei in the resonance region
We present a relativistic model for electroweak pion production from nuclei,
focusing on the and the second resonance region. Bound states are
derived in the Hartree approximation to the Walecka model.
Final-state interactions of the outgoing pion and nucleon are described in a
factorized way by means of a relativistic extension of the Glauber model. Our
formalism allows a detailed study of neutrino pion production through ,
, energy, angle and out-of-plane distributions.Comment: 3 pages, 1 figure, poster presented at the NuInt07 conference on
few-GeV neutrino physic
Differential Immune Recognition of LCMV Nucleoprotein and Glycoprotein in Transgenic Mice Expressing LCMV cDNA Genes
AbstractWe have generated doubly transgenic (DT) mice that independently express cDNA genes for the nucleocapsid protein (NP) and the surface glycoproteins (GP) of lymphocytic choriomeningitis virus (LCMV). By RT-PCR, transcription of both transgenes was detected at low levels in brain and kidney but was not observed in the thymus. Additionally, transcription of the GP transgene was observed in the spleen. Following challenge with exogenous LCMV, an anti-NP CTL response was induced in LCMV-infected DT mice, suggesting that nonresponsiveness to NP had not been established. In contrast, LCMV-infected DT mice were nonresponsive to GP and failed to mount any CTL response against GP, either at Day 7 or Day 30 postinfection or following expansion of splenocyte populationsin vitro.A significant number (33%) of adult DT mice survived intracerebral infection with LCMV, suggesting that virus-induced immunopathology in the central nervous system can be diminished by combined expression of the transgenes whereas no protective effect was conferred on singly transgenic mice, expressing NP or GP alone. The DT mice therefore create a novel host genetic background for comparative studies of the anti-LCMV immune responses relative to parental C57Bl/6 mice
Cd-vacancy and Cd-interstitial complexes in Si and Ge
The electrical field gradient (EFG), measured e.g. in perturbed angular
correlation (PAC) experiments, gives particularly useful information about the
interaction of probe atoms like 111In / 111Cd with other defects. The
interpretation of the EFG is, however, a difficult task. This paper aims at
understanding the interaction of Cd impurities with vacancies and interstitials
in Si and Ge, which represents a controversial issue. We apply two
complementary ab initio methods in the framework of density functional theory
(DFT), (i) the all electron Korringa-Kohn-Rostoker (KKR) Greenfunction method
and (ii) the Pseudopotential-Plane-Wave (PPW) method, to search for the correct
local geometry. Surprisingly we find that both in Si and Ge the substitutional
Cd-vacancy complex is unstable and relaxes to a split-vacancy complex with the
Cd on the bond-center site. This complex has a very small EFG, allowing a
unique assignment of the small measured EFGs of 54MHz in Ge and 28MHz in Si.
Also, for the Cd-selfinterstitial complex we obtain a highly symmetrical split
configuration with large EFGs, being in reasonable agreement with experiments
Real space first-principles derived semiempirical pseudopotentials applied to tunneling magnetoresistance
In this letter we present a real space density functional theory (DFT)
localized basis set semi-empirical pseudopotential (SEP) approach. The method
is applied to iron and magnesium oxide, where bulk SEP and local spin density
approximation (LSDA) band structure calculations are shown to agree within
approximately 0.1 eV. Subsequently we investigate the qualitative
transferability of bulk derived SEPs to Fe/MgO/Fe tunnel junctions. We find
that the SEP method is particularly well suited to address the tight binding
transferability problem because the transferability error at the interface can
be characterized not only in orbital space (via the interface local density of
states) but also in real space (via the system potential). To achieve a
quantitative parameterization, we introduce the notion of ghost semi-empirical
pseudopotentials extracted from the first-principles calculated Fe/MgO bonding
interface. Such interface corrections are shown to be particularly necessary
for barrier widths in the range of 1 nm, where interface states on opposite
sides of the barrier couple effectively and play a important role in the
transmission characteristics. In general the results underscore the need for
separate tight binding interface and bulk parameter sets when modeling
conduction through thin heterojunctions on the nanoscale.Comment: Submitted to Journal of Applied Physic
On the Origin of Metallicity and Stability of the Metastable Phase in Chemically Exfoliated MoS
Chemical exfoliation of MoS via Li-intercalation route has led to many
desirable properties and spectacular applications due to the presence of a
metastable state in addition to the stable H phase. However, the nature of the
specific metastable phase formed, and its basic charge conduction properties
have remained controversial. Using spatially resolved Raman spectroscopy (~1
micrometer resolution) and photoelectron spectroscopy (~120 nm resolution), we
probe such chemically exfoliated MoS samples in comparison to a
mechanically exfoliated H phase sample and confirm that the dominant metastable
state formed by this approach is a distorted T' state with a small
semiconducting gap. Investigating two such samples with different extents of Li
residues present, we establish that Li+ ions, not only help to exfoliate
MoS into few layer samples, but also contribute to enhancing the relative
stability of the metastable state as well as dope the system with electrons,
giving rise to a lightly doped small bandgap system with the T' structure,
responsible for its spectacular properties.Comment: 34 pages, Main manuscript + Supplementary Materia
Accurate evaluation of the interstitial KKR-Green function
It is shown that the Brillouin zone integral for the interstitial KKR-Green
function can be evaluated accurately by taking proper care of the free-electron
singularities in the integrand. The proposed method combines two recently
developed methods, a supermatrix method and a subtraction method. This
combination appears to provide a major improvement compared with an earlier
proposal based on the subtraction method only. By this the barrier preventing
the study of important interstitial-like defects, such as an electromigrating
atom halfway along its jump path, can be considered as being razed.Comment: 23 pages, RevTe
Building the case for biofortification: measuring and maximizing impact in the HarvestPlus program
This paper describes the research and related activities that HarvestPlus undertook at each stage of the research process—discovery, proof of concept, delivery at scale—to establish and continuously strengthen the evidence base for program impact. Structured around the program’s theory of change, the evidence base includes estimates of the magnitude of potential impacts on key development outcomes as well as support for key assumptions that underlie outcomes along the impact pathway from release of biofortified varieties through adoption by farmers, consumption by consumers, and ultimately, to improved nutritional status. The HarvestPlus experience has important lessons for research for development (R4D) programs, many of which struggle to demonstrate progress towards outcomes and impacts throughout the research process.Keywords: Research for Development (R4D), Impact Assessment, Theory of Change, Micronutrient Deficiencies, Crop Varietal Improvemen
Vacancy complexes with oversized impurities in Si and Ge
In this paper we examine the electronic and geometrical structure of
impurity-vacancy complexes in Si and Ge. Already Watkins suggested that in Si
the pairing of Sn with the vacancy produces a complex with the Sn-atom at the
bond center and the vacancy split into two half vacancies on the neighboring
sites. Within the framework of density-functional theory we use two
complementary ab initio methods, the pseudopotential plane wave (PPW) method
and the all-electron Kohn-Korringa-Rostoker (KKR) method, to investigate the
structure of vacancy complexes with 11 different sp-impurities. For the case of
Sn in Si, we confirm the split configuration and obtain good agreement with EPR
data of Watkins. In general we find that all impurities of the 5sp and 6sp
series in Si and Ge prefer the split-vacancy configuration, with an energy gain
of 0.5 to 1 eV compared to the substitutional complex. On the other hand,
impurities of the 3sp and 4sp series form a (slightly distorted) substitutional
complex. Al impurities show an exception from this rule, forming a split
complex in Si and a strongly distorted substitutional complex in Ge. We find a
strong correlation of these data with the size of the isolated impurities,
being defined via the lattice relaxations of the nearest neighbors.Comment: 8 pages, 4 bw figure
- …