8,417 research outputs found
Single-Photon Observables and Preparation Uncertainty Relations
We propose a procedure for defining all single-photon observables in terms of
Positive-Operator Valued Measures (POVMs), in particular spin and position. We
identify the suppression of -helicity photon states as a projection from an
extended Hilbert space onto the photon Hilbert space. We show that all
single-photon observables are in general described by POVMs, obtained by
applying this projection to opportune Projection-Valued Measures (PVMs),
defined on the extended Hilbert space. The POVMs associated to momentum and
helicity reduce to PVMs, unlike those associated to position and spin, this
fact reflecting the intrinsic unsharpness of these observables. We finally
extensively study the preparation uncertainty relations for position and
momentum and the probability distribution of spin, exploring single photon
Gaussian states for several choices of spin and polarization.Comment: 25 pages (7 Figures); revised and extended version; in submissio
Discovery of a 6.4 h black hole binary in NGC 4490
We report on the discovery with Chandra of a strong modulation (~90% pulsed
fraction) at ~6.4 h from the source CXOU J123030.3+413853 in the star-forming,
low-metallicity spiral galaxy NGC 4490, which is interacting with the irregular
companion NGC 4485. This modulation, confirmed also by XMM-Newton observations,
is interpreted as the orbital period of a binary system. The spectra from the
Chandra and XMM-Newton observations can be described by a power-law model with
photon index ~1.5. During these observations, which span from 2000 November to
2008 May, the source showed a long-term luminosity variability by a factor of
~5, between ~2E+38 and 1.1E+39 erg/s (for a distance of 8 Mpc). The maximum
X-ray luminosity, exceeding by far the Eddington limit of a neutron star,
indicates that the accretor is a black hole. Given the high X-ray luminosity,
the short orbital period and the morphology of the orbital light curve, we
favour an interpretation of CXOU J123030.3+413853 as a rare high-mass X-ray
binary system with a Wolf-Rayet star as a donor, similar to Cyg X-3. This would
be the fourth system of this kind known in the local Universe. CXOU
J123030.3+413853 can also be considered as a transitional object between high
mass X-ray binaries and ultraluminous X-ray sources (ULXs), the study of which
may reveal how the properties of persistent black-hole binaries evolve entering
the ULX regime.Comment: Fig. 1 in reduced quality; minor changes to match the MNRAS versio
Spectral variability in Swift and Chandra observations of the Ultraluminous source NGC 55 ULX1
NGC 55 ULX1 is a bright Ultraluminous X-ray source located 1.78 Mpc away. We
analysed a sample of 20 Swift observations, taken between 2013 April and
August, and two Chandra observations taken in 2001 September and 2004 June. We
found only marginal hints of a limited number of dips in the light curve,
previously reported to occur in this source, although the uncertainties due to
the low counting statistics of the data are large. The Chandra and Swift
spectra showed clearly spectral variability which resembles those observed in
other ULXs. We can account for this spectral variability in terms of changes in
both the normalization and intrinsic column density of a two-components model
consisting of a blackbody (for the soft component) and a multicolour accretion
disc (for the hard component). We discuss the possibility that strong outflows
ejected by the disc are in part responsible for such spectral changes.Comment: 9 pages, 6 figure; accepted to be published on MNRA
Contribuição ao estudo da epidemiologia da citomegalovirose em crianças portadoras da sÃndrome de Down
Inovação no desenvolvimento de embalagens para frutas e vegetais in natura
A maioria das pessoas não se dá conta que as embalagens para
hortifruticolas acondicionam seres vivos. Estas embalagens possuem
significados e usos tão especÃficos que mereceriam estar catalogadas
numa categoria particular e não na categoria genérica de embalagens
para alimentos.
Os seres vivos que acondicionam pertencem a diversos tipos, espécies e
categorias, e possuem qualidades essenciais e caracterÃsticas
organolépticas, sensoriais únicas. Por isto, as embalagens para
hortofruticolas, e o seu processo de desenvolvimento, devem que
respeitar o caráter único de cada produto. O desrespeito a este caráter
único tem contribuÃdo fortemente para que as embalagens reduzam o
tempo de vida útil das frutas, legumes e verduras e aumentem as perdas
pós-colheita. As embalagens não devem ser genéricas. Contudo, esta não
tem sido a visão dos projetistas e dos produtores industriais das
embalagens para hortifruticolas.
A Divisão de Desenho Industrial do Instituto Nacional de Tecnologia criou
um processo – e método – inovador de design para o projeto de
embalagens para frutas, legumes e verduras, que respeita as
singularidades de cada tipo de produto. Apresentamos este processo e
método neste artigo. Submetemos a avaliações - sob o ponto de vista de
redução das perdas -, estas novas embalagens em comparação com todas
as outras existentes no Brasil. Escolhemos as embalagens para caquis
(Diospyros kaki) para demonstrar estas avaliações porque no Brasil perde-se,
nos processos de pós-colheita, cerca de 80 % de todo o caqui plantado.ABSTRACT: Most people do not realize that the packaging for
horticultural
contained living beings. These packages have specific meanings and uses
that deserve to be cataloged in a particular category and not in the
general category of food packaging.
Living beings contained therein belong to various types, species and
categories, and have unique essential qualities, organolep_c properties
and sensory characteristics. Therefore, the packaging for horticultural,
and its development process, must respect the unique character of each
product. Failure to comply with this unique character have contributed
strongly to the packaging reduce the useful life of fruits and vegetables
and increase post-harvest losses. Packaging must not be generic.
However, this has not been the vision of designers and industrial
producers of packaging for horticultural.
We present this process and method in this paper. We submit to
assessments these new packages compared with all other existing in
Brazil, from the point of view reducing losses. We chose the packaging for
persimmons (Diospyros kaki) to demonstrate these assessments because
in Brazil in the post-harvest processes about 80% of all planted
persimmon are lost.info:eu-repo/semantics/publishedVersio
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