13,867 research outputs found
The Critical Finite Size Scaling Relation of the Order-Parameter Probability Distribution for the Three-Dimensional Ising Model on the Creutz Cellular Automaton
We study the order parameter probability distribution at the critical point
for the three-dimensional spin-1/2 and spin-1 Ising models on the simple cubic
lattice with periodic boundary conditions. The finite size scaling relation for
the order parameter probability distribution is tested and verified numerically
by microcanonical Creutz cellular automata simulations. The state critical
exponent \delta, which characteries the far tail regime of the scaling order
parameter probability distribution, is estimated for 3-d Ising models using the
cellular automaton simulations at the critical temperature. The results are in
good agreement with the monte carlo calculations.Comment: 8 pages 5 figure
Cosmic String Network Evolution in arbitrary Friedmann-Lemaitre models
We use the velocity-dependent one-scale model by Martins & Shellard to
investigate the evolution of a GUT long cosmic string network in arbitrary
Friedmann-Lemaitre models. Four representative models are used to show that in
general there is no scaling solution. The implications for structure formation
are briefly discussed.Comment: 8 pages, 4 postscript figures included, submitted to Phys. Rev.
Characterization of k-carrageenan/Locust bean gumbased films with b-carotene emulsion
New bio-based materials have been exploited to develop biodegradable and edible
films as an effort to extend shelf life and improve quality of food while reducing packaging waste. The objective of this study was to investigate physicochemical properties of k-carrageenan/locust bean gum (k-car/LBG) films with different bcarotene emulsion concentrations.
To prepare oil-in-water emulsions, b-carotene (0.03% v/v) was dissolved in mediumchain triglycerides (MCTs), and the solution was mixed (1:9 v/v) with a pectin solution (3% w/v) as emulsifier. Film forming solutions were prepared by adding b-carotene emulsion (0-3% w/w) into the k-car/LBG solution (40/60% w/w) with 0.3% (w/v) of glycerol. Films with different b-carotene concentrations were characterized in terms of optical, mechanical and barrier properties and compared with control films without bcarotene.
The results suggested that mechanical, physical and barrier properties of k-car/LBG films were influenced by the presence of b-carotene. Results showed that addition of b-carotene to the k-car/LBG films studied resulted in significant decrease (p<0.05) in water vapour transmission rate values. Film opacity values (ranging from 4.9 to 12.5 %) increased when b-carotene was incorporated to the film.
Therefore, b-carotene emulsions have potential to be used as a natural additive on kcar/LBG films, particularly in the food packaging industry
Atmospheric characterization of Proxima b by coupling the Sphere high-contrast imager to the Espresso spectrograph
Context. The temperate Earth-mass planet Proxima b is the closest exoplanet
to Earth and represents what may be our best ever opportunity to search for
life outside the Solar System. Aims. We aim at directly detecting Proxima b and
characterizing its atmosphere by spatially resolving the planet and obtaining
high-resolution reflected-light spectra. Methods. We propose to develop a
coupling interface between the SPHERE high-contrast imager and the new ESPRESSO
spectrograph, both installed at ESO VLT. The angular separation of 37 mas
between Proxima b and its host star requires the use of visible wavelengths to
spatially resolve the planet on a 8.2-m telescope. At an estimated
planet-to-star contrast of ~10^-7 in reflected light, Proxima b is extremely
challenging to detect with SPHERE alone. However, the combination of a
~10^3-10^4 contrast enhancement from SPHERE to the high spectral resolution of
ESPRESSO can reveal the planetary spectral features and disentangle them from
the stellar ones. Results. We find that significant but realistic upgrades to
SPHERE and ESPRESSO would enable a 5-sigma detection of the planet and yield a
measurement of its true mass and albedo in 20-40 nights of telescope time,
assuming an Earth-like atmospheric composition. Moreover, it will be possible
to probe the O2 bands at 627, 686 and 760 nm, the water vapour band at 717 nm,
and the methane band at 715 nm. In particular, a 3.6-sigma detection of O2
could be made in about 60 nights of telescope time. Those would need to be
spread over 3 years considering optimal observability conditions for the
planet. Conclusions. The very existence of Proxima b and the SPHERE-ESPRESSO
synergy represent a unique opportunity to detect biosignatures on an exoplanet
in the near future. It is also a crucial pathfinder experiment for the
development of Extremely Large Telescopes and their instruments (abridged).Comment: 16 pages, 7 figures, revised version accepted to A&
Ground state and low excitations of an integrable chain with alternating spins
An anisotropic integrable spin chain, consisting of spins and
, is investigated \cite{devega}. It is characterized by two real
parameters and , the coupling constants of the spin
interactions. For the case and the ground state
configuration is obtained by means of thermodynamic Bethe ansatz. Furthermore
the low excitations are calculated. It turns out, that apart from free magnon
states being the holes in the ground state rapidity distribution, there exist
bound states given by special string solutions of Bethe ansatz equations (BAE)
in analogy to \cite{babelon}. The dispersion law of these excitations is
calculated numerically.Comment: 16 pages, LaTeX, uses ioplppt.sty and PicTeX macro
Leptospira interrogans outer membrane protein-based nanohybrid sensor for the diagnosis of leptospirosis
Leptospirosis is an underestimated tropical disease caused by the pathogenic Leptospira species and responsible for several serious health problems. Here, we aimed to develop an ultrasen-sitive DNA biosensor for the rapid and on-site detection of the Loa22 gene of Leptospira interrogans using a gold nanoparticle–carbon nanofiber composite (AuN/CNF)-based screen-printed electrode. Cyclic voltammetry and electrochemical impedance were performed for electrochemical analysis. The sensitivity of the sensor was 5431.74 µA/cm2 /ng with a LOD (detection limit) of 0.0077 ng/µL using cyclic voltammetry. The developed DNA biosensor was found highly specific to the Loa22 gene of L. interrogans, with a storage stability at 4¿ C for 180 days and a 6% loss of the initial response. This DNA-based sensor only takes 30 min for rapid detection of the pathogen, with a higher specificity and sensitivity. The promising results obtained suggest the application of the developed sensor as a point of care device for the diagnosis of leptospirosis.This research was funded by the Indian Council of Medical Research (ICMR), grant Leptos/27/2013-ECD-1. N.C.-M. acknowledges the Portuguese Foundation for Science and Technology under the Horizon 2020 Program (PTDC/PSI-GER/28076/2017), Supported by Excellence project FIM UHK (K.K.)
Critical Behaviour of integrable mixed spins chains
We construct a mixed spin 1/2 and integrable model and investigate its
finite size properties. For a certain conformal invariant mixed spin system the
central charge can be decomposed in terms of the conformal anomaly of two
single integrable models of spin 1/2 and spin . We also compute the
ground state energy and the sound velocity in the thermodynamic limit.Comment: This was the first correct calculation of the central charge in mixed
integrable spin chains. For effects of a magnetic field see
J.Phys.A:Math.Gen. 26 (1993) 730
Evidence for a spectroscopic direct detection of reflected light from 51 Peg b
The detection of reflected light from an exoplanet is a difficult technical
challenge at optical wavelengths. Even though this signal is expected to
replicate the stellar signal, not only is it several orders of magnitude
fainter, but it is also hidden among the stellar noise. We apply a variant of
the cross-correlation technique to HARPS observations of 51 Peg to detect the
reflected signal from planet 51 Peg b. Our method makes use of the
cross-correlation function of a binary mask with high-resolution spectra to
amplify the minute planetary signal that is present in the spectra by a factor
proportional to the number of spectral lines when performing the cross
correlation. The resulting cross-correlation functions are then normalized by a
stellar template to remove the stellar signal. Carefully selected sections of
the resulting normalized CCFs are stacked to increase the planetary signal
further. The recovered signal allows probing several of the planetary
properties, including its real mass and albedo. We detect evidence for the
reflected signal from planet 51 Peg b at a significance of 3\sigma_noise. The
detection of the signal permits us to infer a real mass of 0.46^+0.06_-0.01
M_Jup (assuming a stellar mass of 1.04\;M_Sun) for the planet and an orbital
inclination of 80^+10_-19 degrees. The analysis of the data also allows us to
infer a tentative value for the (radius-dependent) geometric albedo of the
planet. The results suggest that 51Peg b may be an inflated hot Jupiter with a
high albedo (e.g., an albedo of 0.5 yields a radius of 1.9 \pm 0.3 R_Jup for a
signal amplitude of 6.0\pm0.4 x 10^-5). We confirm that the method we perfected
can be used to retrieve an exoplanet's reflected signal, even with current
observing facilities. The advent of next generation of observing facilities
will yield new opportunities for this type of technique to probe deeper into
exoplanets.Comment: 9 pages, 6 figure
Os media participativos e o poder da identidade na oncologia: O cidadão e a instituição enquanto marcas interactivas
Neste artigo procuramos averiguar a relevância que as marcas e identidades têm nas
plataformas participativas no contexto da saúde, em particular na oncologia. Apesar de estas
plataformas disponibilizarem aos cidadãos e instituições as mesmas ferramentas, a sua capacidade de
mobilização não é a mesma. As instituições parecem ter maior facilidade, mas nem sempre tal
acontece. Discutir o conceito de marca e de identidade contribuirá para responder a esta questão, bem
como compreender porque é que as diferenças entre os cidadãos e as instituições se podem atenuar
nos novos media. Baseamos a nossa análise na observação de páginas do Facebook, de instituições
oncológicas e de grupos de apoio de cidadãos; num conjunto de entrevistas a doentes e familiares
oncológicos; e em diferentes estudos na saúde. No fim, procura-se esclarecer a importância do estudo
das marcas e da identidade, como possÃvel directriz de novas soluções nos media participativos, que
contribuam para atenuar o problema individual do cidadão que se relaciona com o cancro.info:eu-repo/semantics/publishedVersio
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