6,589 research outputs found
Strong-Coupling Theory of Rattling-Induced Superconductivity
In order to clarify the mechanism of the enhancement of superconducting
transition temperature due to anharmonic local oscillation of a
guest ion in a cage composed of host atoms, i.e., {\it rattling}, we analyze
the anharmonic Holstein model by applying the Migdal-Eliashberg theory. From
the evaluation of the normal-state electron-phonon coupling constant, it is
found that the strong coupling state is developed, when the bottom of a
potential for the guest ion becomes wide and flat. Then, is
enhanced with the increase of the anharmonicity in the potential, although
is rather decreased when the potential becomes a double-well type
due to very strong anharmonicity. From these results, we propose a scenario of
anharmonicity-controlled strong-coupling tendency for superconductivity induced
by rattling. We briefly discuss possible relevance of the present scenario with
superconductivity in -pyrochlore oxides.Comment: 8 pages, 6 figure
Derivation of genetic interaction networks from quantitative phenotype data
We have generalized the derivation of genetic-interaction networks from quantitative phenotype data. Familiar and unfamiliar modes of genetic interaction were identified and defined. A network was derived from agar-invasion phenotypes of mutant yeast. Mutations showed specific modes of genetic interaction with specific biological processes. Mutations formed cliques of significant mutual information in their large-scale patterns of genetic interaction. These local and global interaction patterns reflect the effects of gene perturbations on biological processes and pathways
Peso relativo de órgãos de frangos de corte alimentados com diferentes dietas.
No Brasil, para atender as exigências nutricionais, as dietas para monogástricos são formuladas principalmente a base de milho e farelo de soja, entretanto estas matérias-primas apresentam alto valor no mercado, com isso, tem-se buscado alternativas para substitui-las nas dietas. Por outro lado, alimentos alternativos podem conter fatores antinutricionais, como por exemplo os fitatos que podem formar complexos insolúveis com proteínas e minerais ? reduzindo a disponibilidade destes nutrientes. O uso de enzimas exógenas nas dietas de frangos pode trazer alguns benefícios, tais como: redução na viscosidade da digesta, melhora da digestão e absorção de nutrientes, aumento no consumo alimentar, melhora ganho de peso e na conversão alimentar, diminuição do tamanho do trato gastrointestinal, alteração na população de microrganismos do trato gastrointestinal, redução do consumo de água e do conteúdo de água nas excretas e reduz a excreção de nutrientes (2). Objetivou-se com este trabalho avaliar o efeito das dietas experimentais sobre o peso relativo da moela, fígado e ceco de frangos de corte, quando alimentados com com dietas contendo diferentes matérias primas na presença e ausência de fitase
Time-resolved spectral correlations of long-duration Gamma-Ray Bursts
For a sample of long GRBs with known redshift, we study the distribution of
the evolutionary tracks on the rest-frame luminosity-peak energy Liso-Ep'
diagram. We are interested in exploring the extension of the `Yonetoku'
correlation to any phase of the prompt light curve, and in verifying how the
high-signal prompt duration time, Tf, in the rest frame correlates with the
residuals of such correlation (Firmani et al. 2006). For our purpose, we
analyse separately two samples of time-resolved spectra corresponding to 32
GRBs with peak fluxes >1.8 phot cm^-2 s^-1 from the Swift-BAT detector, and 7
bright GRBs from the CGRO-BATSE detector previously processed by Kaneko et al.
(2006). After constructing the Liso-Ep' diagram, we discuss the relevance of
selection effects, finding that they could affect significantly the
correlation. However, we find that these effects are much less significant in
the Liso x Tf-Ep' diagram, where the intrinsic scatter reduces significantly.
We apply further corrections for reducing the intrinsic scatter even more. For
the sub-samples of GRBs (7 from Swift and 5 from CGRO) with measured jet break
time, we analyse the effects of correcting Liso by jet collimation. We find
that (i) the scatter around the correlation is reduced, and (ii) this scatter
is dominated by the internal scatter of the individual evolutionary tracks.
These results suggest that the time, integrated `Amati' and `Ghirlanda'
correlations are consequences of the time resolved features, not of selection
effects, and therefore call for a physical origin. We finally remark the
relevance of looking inside the nature of the evolutionary tracks.Comment: 11 pages, 6 figures, 4 tables. Submitted to MNRAS (Sept 8th), after
referee comment
On the future of Gamma-Ray Burst Cosmology
With the understanding that the enigmatic Gamma-Ray Burts (GRBs) are beamed
explosions, and with the recently discovered ``Ghirlanda-relation'', the dream
of using GRBs as cosmological yardsticks may have come a few steps closer to
reality. Assuming the Ghirlanda-relation is real, we have investigated possible
constraints on cosmological parameters using a simulated future sample of a
large number of GRBs inspired by the ongoing SWIFT mission. Comparing with
constraints from a future sample of Type Ia supernovae, we find that GRBs are
not efficient in constraining the amount of dark energy or its equation of
state. The main reason for this is that very few bursts are available at low
redshifts.Comment: 5 pages, 2 figures, matches version accepted for publication in JCA
High Incidence of Osteoporosis in a Natural History Cohort of Patients with Moderate to Severe Chronic Graft-Versus-Host Disease and Risk Factor Analysis
Avaliação do efeito de pesticidas no crescimento micelial de Cercospora caricis.
bitstream/CENARGEN/24080/1/cot094.pd
Clustering in non-self-conjugate nuclei \u3csup\u3e10\u3c/sup\u3eBe and \u3csup\u3e18\u3c/sup\u3eO
Clustering phenomena in 10Be and 18O were studied by means of resonance elastic scattering of α-particles on 6He and 14C. Excitation functions for α+6He and α+14C were measured and detailed R-matrix analyses of the excitation functions was performed. We compare the experimental results with the predictions of modern theoretical approaches and discuss properties of cluster rotational bands
Study of the Mg waiting point relevant for x-ray burst nucleosynthesis via the Mg(,)Al reaction
The Mg(,)Al reaction rate has been identified as a
major source of uncertainty for understanding the nucleosynthesis flow in
Type-I x-ray bursts (XRBs). We report a direct measurement of the energy- and
angle-integrated cross sections of this reaction in a 3.3-6.9 MeV
center-of-mass energy range using the MUlti-Sampling Ionization Chamber
(MUSIC). The new Mg(,)Al reaction rate is a factor of
4 higher than the previous direct measurement of this reaction within
temperatures relevant for XRBs, resulting in the Mg waiting point of
x-ray burst nucleosynthesis flow to be significantly bypassed via the
() reactionComment: 6 pages, 3 figures, 1 tabl
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