6,217 research outputs found
WMAP Constraints on a Quintessence Model
We use the results from the Wilkinson Microwave Anisotropy Probe (WMAP) for
the locations of peaks and troughs of the Cosmic Microwave Background (CMB)
power spectrum, together with constraints from large-scale structure, to study
a quintessence model in which the pure exponential potential is modified by a
polynomial factor. Our analysis, in the cosmological
parameters space shows that this quintessence model is favoured compared to
CDM for and relatively high values of early
quintessence; for , quintessence and CDM give similar results,
except for high values of early quintessence, in which case CDM is
favoured.Comment: 3 pages. Talk presented by N. M. C. Santos at the Tenth Marcel
Grossmann Meeting on General Relativity, Rio de Janeiro, July 200
Quantum Process Estimation via Generic Two-Body Correlations
Performance of quantum process estimation is naturally limited to
fundamental, random, and systematic imperfections in preparations and
measurements. These imperfections may lead to considerable errors in the
process reconstruction due to the fact that standard data analysis techniques
presume ideal devices. Here, by utilizing generic auxiliary quantum or
classical correlations, we provide a framework for estimation of quantum
dynamics via a single measurement apparatus. By construction, this approach can
be applied to quantum tomography schemes with calibrated faulty state
generators and analyzers. Specifically, we present a generalization of "Direct
Characterization of Quantum Dynamics" [M. Mohseni and D. A. Lidar, Phys. Rev.
Lett. 97, 170501 (2006)] with an imperfect Bell-state analyzer. We demonstrate
that, for several physically relevant noisy preparations and measurements, only
classical correlations and small data processing overhead are sufficient to
accomplish the full system identification. Furthermore, we provide the optimal
input states for which the error amplification due to inversion on the
measurement data is minimal.Comment: 7 pages, 2 figure
Prospects for the rapid detection of mealiness in apples by nondestructive NMR relaxometry
The potential of nuclear magnetic resonance (NMR) relaxometry for quantitative evaluation of apple mealiness has been investigated. The degree of "mealiness" was defined by several mechanical techniques, including penetration, compression and shear rupture as well as by the BRIX (soluble solids) and juiciness levels. These data were correlated with both magnetic resonance imaging (MRI) and NMR water proton transverse relaxation time measurements on a fruit-by-fruit basis. It was found that increasing mealiness caused a systematic increase in the transverse relaxation rate. The potential for rapid, on-line NMR/MRI detection of apple mealiness is discussed
Microencapsulación de compuestos de actividad biologica
La microencapsulación de compuestos de actividad biológica (ADN, fármacos, proteÃnas, probióticos, enzimas, etc.), desde el punto de vista tecnológico podrÃa definirse como el proceso de recubrimiento de dichos compuestos, bajo la forma de moléculas, partÃculas sólidas o glóbulos lÃquidos, con materiales de distinta naturaleza, para dar lugar a partÃculas de tamaño micrométrico. Uno de los polÃmeros naturales más utilizados para la producción de microesferas es el quitosano. Diversos métodos han sido propuestos para la producción de microcápsulas divididos en tres grupos: procesos fÃsicos, procesos quÃmicos y procesos fÃsico-quÃmicos.
En el presente trabajo se ensayaron distintas metodologÃas para la producción de microesferas y micropartÃculas de quitosano. Según la metodologÃa empleada se obtuvieron distintos tipos de esferas en lo que respecta a tamaño y densidad. Las micropartÃculas obtenidas se evaluaron mediante microscopÃa óptica, electrónica de barrido, asà como se realizó la evaluación de su estabilidad y liberación del agente encapsulado
Can be sensitive to new physics beyond the Standard Model ?
We investigate the impact of new physics beyond the Standard Model to the process, which is responsible for the short-distance
contribution to the radiative decay \Otogamma. We study three representative
extensions of the Standard Model, namely a one-family technicolor model, a two
Higgs doublet model and a model containing scalar leptoquarks. When constraints
arising from the observed transition and the upper limit on
mixing are taken into account, we find no significant
contributions of new physics to the process.Comment: 9 pages, RevTex, no figure
Propriedades tecnológicas de bactérias ácido lácticas e staphilococcaceae isoladas da microbiota de embutidos cárneos artesanais na região Sul/Brasil.
Projeto/Plano de Ação: 03.08.06.009
Visao retrospectiva do melhoramento genetico do algodoeiro moco (Gossypium hirsutum r. marie galante Hutch) no nordeste do Brasil.
bitstream/item/33387/1/VISAO-RETROSPECTIVA.pd
A low CMB variance in the WMAP data
We have estimated the CMB variance from the three-year WMAP data, finding a
value which is significantly lower than the one expected from Gaussian
simulations using the WMAP best-fit cosmological model, at a significance level
of 98.7 per cent. This result is even more prominent if we consider only the
north ecliptic hemisphere (99.8 per cent). Different analyses have been
performed in order to identify a possible origin for this anomaly. In
particular we have studied the behaviour of single radiometers and single year
data as well as the effect of residual foregrounds and 1/f noise, finding that
none of these possibilities can explain the low value of the variance. We have
also tested the effect of varying the cosmological parameters, finding that the
estimated CMB variance tends to favour higher values of than the one of
the WMAP best-fit model. In addition, we have also tested the consistency
between the estimated CMB variance and the actual measured CMB power spectrum
of the WMAP data, finding a strong discrepancy. A possible interpretation of
this result could be a deviation from Gaussianity and/or isotropy of the CMB.Comment: 13 pages, 5 figures. Some new tests added. Section 5 largely
modified. Accepted for publication in MNRA
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