1,101 research outputs found
From quantum to classical instability in relativistic stars
It has been shown that gravitational fields produced by realistic
classical-matter distributions can force quantum vacuum fluctuations of some
nonminimally coupled free scalar fields to undergo a phase of exponential
growth. The consequences of this unstable phase to the background spacetime
have not been addressed so far due to known difficulties concerning
backreaction in semiclassical gravity. It seems reasonable to believe, however,
that the quantum fluctuations will "classicalize" when they become large
enough, after which backreaction can be treated in the general-relativistic
context. Here we investigate the emergence of a classical regime out of the
quantum field evolution during the unstable phase. By studying the appearance
of classical correlations and loss of quantum coherence, we show that by the
time backreaction becomes important the system already behaves classically.
Consequently, the gravity-induced instability leads naturally to initial
conditions for the eventual classical description of the backreaction. Our
results give support to previous analyses which treat classically the
instability of scalar fields in the spacetime of relativistic stars, regardless
whether the instability is triggered by classical or quantum perturbations.Comment: 16 pages. Minor changes to match the published versio
Trace metals and over-expression of metallothioneins in bladder tumoral lesions: a case-control study
<p>Abstract</p> <p>Background</p> <p>Previous studies have provided some evidence of a possible association between cancer and metallothioneins. Whether this relates to an exposure to carcinogenic metals remains unclear.</p> <p>Methods</p> <p>In order to examine the association between the expression of metallothioneins and bladder tumors, and to compare the levels of arsenic, cadmium, chromium, lead and nickel in animals with bladder tumors and animals without bladder tumors, 37 cases of bovine bladder tumors and 17 controls were collected. The detection and quantification of metallothioneins in bladder tissue of both cases and controls was performed by immunohistochemistry. And the quantification of metals in tissue and hair was assessed by inductively coupled plasma – mass spectrometry.</p> <p>Results</p> <p>Increased expression of metallothioneins was associated with bladder tumors when compared with non-tumoral bladder tissue (OR = 9.3, 95% CI: 1.0 – 480). The concentrations of cadmium, chromium, lead and nickel in hair of cases were significantly higher than those of controls. However, as for the concentration of metals in bladder tissue, the differences were not significant.</p> <p>Conclusion</p> <p>Though the sample size was small, the present study shows an association between bladder tumors and metallothioneins. Moreover, it shows that concentrations of metals such as cadmium, chromium, lead and nickel in hair may be used as a biomarker of exposure.</p
Observation of Replica Symmetry Breaking in the 1D Anderson Localization Regime in an Erbium-Doped Random Fiber Laser
The analogue of the paramagnetic to spin-glass phase transition in disordered
magnetic systems, leading to the phenomenon of replica symmetry breaking, has
been recently demonstrated in a two-dimensional random laser consisting of an
organic-based amorphous solid-state thin film. We report here the first
demonstration of replica symmetry breaking in a one-dimensional photonic system
consisting of an erbium-doped random fiber laser operating in the
continuous-wave regime based on a unique random fiber grating system, which
plays the role of the random scatterers and operates in the Anderson
localization regime. The clear transition from a photonic paramagnetic to a
photonic spin glass phase, characterized by the probability distribution
function of the Parisi overlap, was verified and characterized. In this unique
system, the radiation field interacts only with the gain medium, and the fiber
grating, which provides the disordered feedback mechanism, does not interfere
with the pump
Morfometria das lâminas epidérmicas primárias e secundárias do casco de equinos
Foi estudado o comprimento das lâminas epidérmicas primárias e secundárias da pinça e dos quartos lateral e medial, distribuÃdas nos terços proximal, médio e distal dos cascos de equinos. Utilizaram-se os membros de oitos cavalos adultos utilizados para tração de carroças, que não apresentavam afecções podais, sendo quatro fêmeas e quatro machos, sem raça definida. Fragmentos foram retirados das diferentes regiões dos cascos e submetidos à técnica histológica convencional. As amostras foram coradas com H&E e analisadas em microscópio óptico. As lâminas epidérmicas primárias apresentaram-se maiores nos cascos dos membros torácicos em relação aos membros pélvicos nos terços proximal e médio e nas regiões do quarto medial e na pinça. As lâminas secundárias foram maiores também no membro torácico no terço médio e no quarto medial. Comparando-se o comprimento das lâminas epidérmicas entre as regiões do casco, observou-se que as lâminas primárias são menores no terço proximal e maiores na pinça, enquanto as menores lâminas secundárias estão no terço proximal e no quarto medial. Os resultados sugerem que a morfologia das lâminas nas diversas regiões do casco sofra influência do trabalho realizado pelo animal, assim como, das diferentes distribuições de força existentes no mesmo.We studied the length of primary and secondary epidermal laminae of the toe and the lateral and medial quarters of horses, distributed into proximal, middle and distal thirds of the hooves. Eight limbs from adult crossbred horses, four females and four males, used to pull carts without pedal conditions. Fragments were taken from different regions of the hooves and subjected
to conventional histological techniques. The samples were stained with hematoxylin-eosin and analyzed by light microscopy. The primary epidermal laminae were higher in the hooves of forelimbs compared to hindlimbs in the proximal and middle thirds and the regions of the medial quarter and toe. The secondary laminae were higher in forelimb of the middle third and medial quarter. Comparing the length of the epidermal laminae between hoof parts, it was seen that the primary laminae are lower in the proximal third and higher in the toe, while the secondary laminae are lower in the proximal third and medial quarter. The results suggested that the morphology of the laminae in the different regions of the hooves is influenced through the work performed by the animal, as well as through the different distribution of forces
Nonequilibrium Zaklan model on Apollonian Networks
The Zaklan model had been proposed and studied recently using the equilibrium
Ising model on Square Lattices (SL) by Zaklan et al (2008), near the critica
temperature of the Ising model presenting a well-defined phase transition; but
on normal and modified Apollonian networks (ANs), Andrade et al. (2005, 2009)
studied the equilibrium Ising model. They showed the equilibrium Ising model
not to present on ANs a phase transition of the type for the 2D Ising model.
Here, using agent-based Monte-Carlo simulations, we study the Zaklan model with
the well-known majority-vote model (MVM) with noise and apply it to tax evasion
on ANs, to show that differently from the Ising model the MVM on ANs presents a
well defined phase transition. To control the tax evasion in the economics
model proposed by Zaklan et al, MVM is applied in the neighborhood of the
critical noise to the Zaklan model. Here we show that the Zaklan model
is robust because this can be studied besides using equilibrium dynamics of
Ising model also through the nonequilibrium MVM and on various topologies
giving the same behavior regardless of dynamic or topology used here.Comment: 11 pages, 6 figures. arXiv admin note: substantial text overlap with
arXiv:1204.0386 and arXiv:0910.196
Densidade das lâminas epidérmicas primárias e secundárias nos cascos de equinos
Diferenças na morfologia microscópica dos cascos dos membros pélvicos e torácicos dos equinos têm sido pouco relatadas na literatura, principalmente no tocante a distribuição de lâminas epidérmicas primárias e secundárias nas diversas regiões. O propósito deste estudo foi quantificar a densidade de lâminas epidérmicas primárias e secundárias no casco de equinos. Foram utilizados membros torácicos e pélvicos de oito equinos adultos e sem raça definida. Em uma secção transversal de aproximadamente 0,5cm de altura da sola dos cascos foi quantificada a densidade das lâminas epidérmicas primárias tanto na região da pinça quanto dos quartos lateral e medial. Fragmentos com aproximadamente 1cm³ foram retirados dos terços proximal, médio e distal do casco, nas diferentes regiões e submetidos a técnica histológica convencional, a densidade de lâminas epidérmicas secundárias foi quantificada com auxilio de microscópio óptico. Os dados foram analisados estatisticamente em relação aos membros torácicos e pélvicos e entre suas diversas regiões. A densidade de lâminas epidérmicas primárias varia ao redor da circunferência do casco, sendo maior na região da pinça do casco e diminui gradualmente em direção ao bulbo do casco, não existindo diferença entre membros pélvicos e torácicos. A densidade média de lâminas epidérmicas secundárias por lâmina epidérmica primária não varia em torno da circunferência dos cascos, assim como, quando comparada entre os membros torácicos e pélvicos. A variação da densidade das lâminas epidérmicas primárias em torno do casco parece fazer parte de uma resposta adaptativa às diferentes tensões existentes em cada região. O melhor entendimento da morfologia das estruturas do casco contribui na melhor compreensão do diagnóstico, fisiopatologia e tratamento das afecções que as acometem.Differences in the microscopic morphology of the hoof in forelimbs and hindlimbs of horses have been scarcely reported in the literature, especially concerning the distribution of primary and secondary epidermal laminae in the different regions. This study aimed to determine the density of primary and secondary epidermal laminae in the hoof of horses. For this, it was used fore and hindlimbs of 16 adult mixed breed horses. With a cross section 0.5 cm above the sole, it was quantified the primary epidermal laminae in the regions of the toe, and of lateral and medial quarters. Fragments with about 1cm ³ were taken from the proximal, middle and distal thirds of the hooves, in the different regions, subjected to conventional histological techniques and examined with an optical microscope. Data were statistically analyzed in relation to the fore and hindlimbs and between their various regions. The density of primary epidermal laminae varied around the hoof circumference, with greater values in the hoof toe, which gradually decreased towards the bulb of the hoof, without difference between thoracic and pelvic limbs. The average density of the secondary epidermal laminae per primary epidermal lamina does not change around the circumference of the hoof. Our findings indicated that the density of epidermal laminae is not different between fore and hindlimbs. The variation in the density of primary epidermal laminae around the hoof seems to be part of an adaptive response to different stresses in each region. A better understanding of the structural morphology contributes to a better understanding of the diagnosis, pathophysiology, and treatment of disorders that affect the hoof
Global patterns for the spatial distribution of floating microfibers: Arctic Ocean as a potential accumulation zone
Despite their representativeness, most studies to date have underestimated the amount of microfibers (MFs) in
the marine environment. Therefore, further research is still necessary to identify key processes governing MF
distribution. Here, the interaction among surface water temperature, salinity, currents and winds explained the
patterns of MF accumulation. The estimated density of floating MFs is ~5900 ± 6800 items m 3 in the global
ocean; and three patterns of accumulation were predicted by the proposed model: (i) intermediate densities in
ocean gyres, Seas of Japan and of Okhotsk, Mediterranean and around the Antarctic Ocean; (ii) high densities in
the Arctic Ocean; and (iii) point zones of highest densities inside the Arctic Seas. Coastal areas and upwelling
systems have low accumulation potential. At the same time, zones of divergences between westerlies and trade
winds, located above the tropical oceanic gyres, are predicted to accumulate MFs. In addition, it is likely that the
warm branch of the thermohaline circulation has an important role in the transport of MFs towards the Arctic
Ocean, emphasizing that surface water masses are important predictors. This study highlights that the Arctic
Ocean is a dead end for floating MFs.FEDER; Fundação para a Ciência e Tecnologia- FCTinfo:eu-repo/semantics/publishedVersio
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