2,605 research outputs found
Helioseismic tests of diffusion theory
We present a quantitative estimate of the accuracy of the calculated
diffusion coefficients, by comparing predictions of solar models with
observational data provided by helioseismology. By taking into account the
major uncertainties in building solar models we conclude that helioseismology
confirms the diffusion efficiency adopted in SSM calculations, to the 10%
level.Comment: 5 pages with 1 ps figure included, LaTeX file with l-aa.sty,
submitted to Astronomy and Astrophysic
Is G a conversion factor or a fundamental unit?
By using fundamental units c, h, G as conversion factors one can easily
transform the dimensions of all observables. In particular one can make them
all ``geometrical'', or dimensionless. However this has no impact on the fact
that there are three fundamental units, G being one of them. Only experiment
can tell us whether G is basically fundamental.Comment: 2 page
Connection between charge transfer and alloying core-level shifts based on density-functional calculations
The measurement of alloying core-level binding energy (CLBE) shifts has been
used to give a precise meaning to the fundamental concept of charge transfer.
Here, ab-initio density-functional calculations for the intermetallic compound
MgAu are used to investigate models which try to make a connection between the
core levels shifts and charge transfer. The calculated CLBE shifts agree well
with experiment, and permit an unambiguous separation into initial-state and
screening contributions. Interestingly, the screening contribution is large and
cannot be neglected in any reasonable description. Comparison of the calculated
results with the predictions of simple models show that these models are not
adequate to describe the realistic situation. On the positive side, the
accuracy of the density-functional calculations indicates that the combination
of experiments with such calculations is a powerful tool to investigate unknown
systems.Comment: RevTeX 10 pages incl 8 figure
Structure and gap of low- (GaIn)O alloys
We study the electronic and local structural properties of pure and
In-substituted -GaO using density functional theory (DFT). Our
main result is that the structural energetics of In in GaO causes most
sites to be essentially inaccessible to In substitution, thus reducing the
maximum In content in thi to somewhere between 12 and 25 \% in this phase. We
also find that the gap variation with doping is essentially due to "chemical
pressure", i.e. volume variations with doping.Comment: 4 pages, 3 figure
Stability of Ge-related point defects and complexes in Ge-doped SiO_2
We analyze Ge-related defects in Ge-doped SiO_2 using first-principles
density functional techniques. Ge is incorporated at the level of ~ 1 mol % and
above. The growth conditions of Ge:SiO_2 naturally set up oxygen deficiency,
with vacancy concentration increasing by a factor 10^5 over undoped SiO_2, and
O vacancies binding strongly to Ge impurities. All the centers considered
exhibit potentially EPR-active states, candidates for the identification of the
Ge(n) centers. Substitutional Ge produces an apparent gap shrinking via its
extrinsic levels.Comment: RevTeX 4 pages, 2 ps figure
Beauveria bassiana strain ATCC 74040 (Naturalis®), a valuable tool for the control of the cherry fruit fly (Rhagoletis cerasi)
Naturalis® is a bioinsecticide based on living conidiospores of the naturally occuring
Beauveria bassiana strain ATCC 74040. The entomopathogenic fungus acts primarily by
contact: once attached to the insect’s cuticle, the conidiospores germinate producing
penetration hyphae, which enter and proliferate inside the insect’s body. The fungus
invades and feeds on its host, causing its death due to dehydration and/or depletion of
nutrients. Several years of laboratory, semi-field and field studies showed that also Tephritid
flies (Ceratitis capitata, Rhagoletis cerasi, Bactrocera oleae) are susceptible to infection by
B. bassiana strain ATCC 74040. The results of efficacy trials conducted in 2004-05 are
reported. Naturalis was tested both alone and in an integrated pest management strategy.
The product showed high efficacy in controlling R. cerasi, comparable to or higher than
that of the chemical reference treatment. The B. bassiana-based product Naturalis can thus
be considered an efficient tool for the control of the cherry fruit fly
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