5,690 research outputs found
The Off-forward Quark-Quark Correlation Function
The properties of the non-forward quark-quark correlation function are
examined. We derive constraints on the correlation function from the
transformation properties of the fundamental fields of QCD occurring in its
definition. We further develop a method to construct an ansatz for this
correlator. We present the complete leading order set of generalized parton
distributions in terms of the amplitudes of the ansatz. Finally we conclude
that the number of independent generalized parton helicity changing
distributions is four.Comment: Accepted for publication in Physical Review
Acceleration of cosmic rays and gamma-ray emission from supernova remnants in the Galaxy
Galactic cosmic rays are believed to be accelerated at supernova remnant
shocks. Though very popular and robust, this conjecture still needs a
conclusive proof. The strongest support to this idea is probably the fact that
supernova remnants are observed in gamma-rays, which are indeed expected as the
result of the hadronic interactions between the cosmic rays accelerated at the
shock and the ambient gas. However, also leptonic processes can, in most cases,
explain the observed gamma-ray emission. This implies that the detections in
gamma rays do not necessarily mean that supernova remnants accelerate cosmic
ray protons. To overcome this degeneracy, the multi-wavelength emission (from
radio to gamma rays) from individual supernova remnants has been studied and in
a few cases it has been possible to ascribe the gamma-ray emission to one of
the two processes (hadronic or leptonic). Here we adopt a different approach
and, instead of a case-by-case study we aim for a population study and we
compute the number of supernova remnants which are expected to be seen in TeV
gamma rays above a given flux under the assumption that these objects indeed
are the sources of cosmic rays. The predictions found here match well with
current observational results, thus providing a novel consistency check for the
supernova remnant paradigm for the origin of galactic cosmic rays. Moreover,
hints are presented for the fact that particle spectra significantly steeper
than E^-2 are produced at supernova remnants. Finally, we expect that several
of the supernova remnants detected by H.E.S.S. in the survey of the galactic
plane should exhibit a gamma-ray emission dominated by hadronic processes (i.e.
neutral pion decay). The fraction of the detected remnants for which the
leptonic emission dominates over the hadronic one depends on the assumed values
of the physical parameters and can be as high as roughly a half.Comment: 14 pages, 4 figures, 4 tables, submitted to MNRA
Variación no alométrica en el cráneo del perezoso bayo Bradypus variegatus (Schinz, 1825) (Mammalia, Pilosa, Bradypodidae)
Brown-throated sloth Bradypus variegatus (Schinz, 1825) is a monomorphic mammal, and its skull ontogeny is poorly known. Here, we present a study of the ontogenetic allometric relationship between skull size and shape in 21 specimens of different sizes, for which size and shape were determined by means of geometric morphometric methods. Results indicate that skull shape variation can hardly be explained by skull size. Several studies have shown unique morphological traits of sloths from mammalian norms, affecting varied phenotypic traits from skeletal parts to soft tissues. This non-allometric scaling of skull form in sloth can be seen as another uniqueness of this taxonomic group.El perezoso bayo Bradypus variegatus (Schinz, 1825) es un mamÃfero monomórfico, de ontogenia craneal poco conocida. En este estudio analizamos la alometrÃa estática entre tamaño y forma, utilizando 21 especÃmenes diferentes de edades diversas. El tamaño y la forma fueron determinados mediante técnicas de morfometrÃa geométrica. De los resultados obtenidos se desprende que la variación en la forma craneal queda muy poco explicada por la variación en el tamaño. Muchos estudios han señalado caracterÃsticas morfológicas únicas en los perezosos en relación al resto de mamÃferos, caracterÃsticas fenotÃpicas que van de la estructura esquelética a tejidos blandos. En este caso, el escalado no alométrico del cráneo deberÃa ser visto como otra caracterÃstica única de este grupo taxonómico
Very high energy emission from the hard spectrum sources HESS J1641-463, HESS J1741-302 and HESS J1826-130
A recent study of the diffuse -ray emission in the Central Molecular
Zone using very high energy (VHE, E 0.1 TeV) H.E.S.S. data suggests that
the Galactic Center (GC) is the most plausible supplier of Galactic
ultra-relativistic cosmic-rays (CRs) up to the knee at about 10 eV
(PeV). However, the GC might not be the only source capable to accelerate CRs
up to PeV energies in the Galaxy. Here we present H.E.S.S. data analysis
results and interpretation of three H.E.S.S. sources, with spectra extending
beyond 10 TeV and relatively hard spectral indices compared with the average
spectral index of H.E.S.S. sources, namely HESS J1641-463, HESS J1741-302 and
HESS J1826-130. Although the nature of these VHE -ray sources is still
open, their spectra suggest that the astrophysical objects producing such
emission must be capable of accelerating the parental particle population up to
energies of at least several hundreds of TeV. Assuming a hadronic scenario,
dense gas regions can provide rich target material for accelerated particles to
produce VHE -ray emission via proton-proton interactions followed by a
subsequent decay. Thus, detailed investigations of the interstellar
medium along the line of sight to all of these sources have been performed by
using data from available atomic and molecular hydrogen surveys. The results
point out the existence of dense interstellar gas structures coincident with
the best fit positions of these sources. One can find possible hadronic models
with CRs being accelerated close to the PeV energies to explain the
-ray emission from all of these sources, which opens up the possibility
that a population of PeV CR accelerators might be active in the Galaxy.Comment: 8 pages, 2 figures, in Proceedings of 35th ICRC, Busan (Korea) 201
Zeno physics in ultrastrong circuit QED
We study the Zeno and anti-Zeno effects in a superconducting qubit
interacting strongly and ultrastrongly with a microwave resonator. Using a
model of a frequently measured two-level system interacting with a quantized
mode, we show different behaviors and total control of the Zeno times depending
on whether the rotating-wave approximation can be applied in the
Jaynes-Cummings model, or not. We exemplify showing the strong dependence of
our results with the properties of the initial field states and suggest
applications for quantum tomography.Comment: 5 pages, 3 figure
HESS J1826130: A Very Hard -Ray Spectrum Source in the Galactic Plane
HESS J1826130 is an unidentified hard spectrum source discovered by
H.E.S.S. along the Galactic plane, the spectral index being = 1.6 with
an exponential cut-off at about 12 TeV. While the source does not have a clear
counterpart at longer wavelengths, the very hard spectrum emission at TeV
energies implies that electrons or protons accelerated up to several hundreds
of TeV are responsible for the emission. In the hadronic case, the VHE emission
can be produced by runaway cosmic-rays colliding with the dense molecular
clouds spatially coincident with the H.E.S.S. source.Comment: 6 pages, 3 figures, Proceedings of the 6th International Symposium on
High Energy Gamma-Ray Astronomy (Gamma2016), Heidelberg, German
Biological activity of glucosinolate derived compounds isolated from seed meal of Brassica crops and evaluated as plant and food protection agents
Glucosinolates are amino acid derived allelochemicals characteristic of plants of the order Capparales. These compounds are present in seeds of agriculturally common Brassica crops in varying quantities depending on the species (ref). The use of the remaining seed cake after oil extraction has traditionally been limited by the concentration of these compounds. However, the extraction of glucosinolates from seed meal is nowadays possible and it further contributes to an increased quality of the seed meal for feed (Sørensen et al., this conference). Glucosinolates are hydrolysed by endogenous enzymes (myrosinases; EC 3.2.1.147) and a number of compounds are produced depending on the parent glucosinolate and the environmental conditions.1 Among these compounds, oxazolidine-2-thiones are known for their antinutritional effects on monogastric animals, whereas isothiocyanates are fungicidal, nematocidal and herbicidal.2,3 The possibility for using glucosinolates as precursors for environmental friendly biocides therefore exists, which could contribute to increase the value of the Brassica seed meal
EPOC en la mujer
The prevalence of chronic obstructive pulmonary disease (COPD) is increasing
worldwide, mainly due to the increase in women. In developed countries, COPD in
women is mainly a result of exposure to tobacco smoke and in developing countries
to inhalation of biomass combustion products. Underdiagnosis of COPD is more
common in women since this disease has classically been associated with men.
Moreover, COPD in women shows certain differential features, such as a greater
expression of aspects related to perception (dyspnea and health-related quality
of life), a high prevalence of malnutrition, anxiety and depression, and a
distinct distribution of emphysema from that in men. Better phenotypical
characterization of COPD in women would allow its impact on the health system to
be more accurately evaluated and more individualized therapeutic strategies to be
designe
Measuring Entanglement in a Photonic Embedding Quantum Simulator
Measuring entanglement is a demanding task that usually requires full
tomography of a quantum system, involving a number of observables that grows
exponentially with the number of parties. Recently, it was suggested that
adding a single ancillary qubit would allow for the efficient measurement of
concurrence, and indeed any entanglement monotone associated to antilinear
operations. Here, we report on the experimental implementation of such a
device---an embedding quantum simulator---in photonics, encoding the entangling
dynamics of a bipartite system into a tripartite one. We show that bipartite
concurrence can be efficiently extracted from the measurement of merely two
observables, instead of fifteen, without full tomographic information.Comment: Updated versio
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