Phase-coherence threshold and vortex-glass state in diluted Josephson-junction arrays in a magnetic field

We study numerically the interplay of phase coherence and vortex-glass state in two-dimensional Josephson-junction arrays with average rational values of flux quantum per plaquette $f$ and random dilution of junctions. For $f=1/2$, we find evidence of a phase coherence threshold value $x_s$, below the percolation concentration of diluted junctions $x_p$, where the superconducting transition vanishes. For $x_s < x < x_p$ the array behaves as a zero-temperature vortex glass with nonzero linear resistance at finite temperatures. The zero-temperature critical currents are insensitive to variations in $f$ in the vortex glass region while they are strongly $f$ dependent in the phase coherent region.Comment: 6 pages, 4 figures, to appear in Phys. Rev.

Resistivity scaling and critical dynamics of fully frustrated Josephson-junction arrays with on-site dissipation

We study the scaling behavior and critical dynamics of the resistive transition in Josephson-junction arrays, at f=1/2 flux quantum per plaquette, by numerical simulation of an on-site dissipation model for the dynamics. The results are compared with recent simulations using the resistively-shunted-junction model. For both models, we find that the resistivity scaling and critical dynamics of the phases are well described by the same critical temperature as for the chiral (vortex-lattice) transition, with a power-law divergent correlation length. The behavior is consistent with the single transition scenario, where phase and chiral variables order at the same temperature, but with different dynamic exponents z for phase coherence and chiral order.Comment: 17 pages, 13 figures, to appear in Phys. Rev.

Vortex dynamics in disordered Josephson junction arrays: from plastic flow to flux flow

We study the dynamics of Josephson junction arrays with positional disorder and driven by an external current. We consider weak magnetic fields, corresponding to a frustration $f=n+1/25$ with $n$ integer. We find that above the critical current $i_c$ there is a plastic flow of vortices, where most of the vortices are pinned and only a few vortices flow through channels. This dynamical regime is characterized by strong fluctuations of the total vorticity. The number of the flow channels grow with increasing bias current. At larger currents there is a dynamical regime characterized by the homogeneous motion of all the vortices, i.e. a flux flow regime. We find a dynamical phase transition between the plastic flow and the flux flow regimes when analyzing voltage-voltage correlation functions.Comment: 9 pages. 3 Figures available upon request. Presented in the Workshop on Josephson Junction Arrays, ICTP (August 1995). To appear in Physica B (1996

Accumulation of Phenolic Acids during Storage over Differently Handled Fresh Carrots

Carrots contain a significant content of phenolic compounds, mainly phenolic acids. Technological processing of carrots inflicts wounding stress and induces accumulation of these compounds, especially caffeic acid derivatives, in the periderm tissue. In this study, the effect of minimal processing (polishing, washing, peeling, and grating) on the retention of soluble phenolic acids in carrots was monitored during cold storage. Storage for up to 4 weeks and 24 h was used for whole and grated carrot samples, respectively. Total phenolic acid levels found in differently processed carrots varied greatly at the beginning of the storage period and on dry weight basis they ranged from 228 ± 67.9 mg/kg (grated carrot) to 996 ± 177 mg/kg (machine washed). In each case, processing followed by storage induced phenolic acid accumulation in the carrots. At the end of the experiment (4 weeks at +8 °C), untreated and machine-washed carrots contained ca. 4-fold more phenolic acids than at day 0. Similarly, polished carrots contained 9-fold and peeled carrots 31-fold more phenolic acids than at day 0. The phenolic acid content in grated carrot doubled after 24 h storage at +4 °C. Individual phenolic acids were characterized by high resolution mass spectrometry. MS data strongly suggest the presence of daucic acid conjugates of phenolic acids in carrot. Storage time did not have statistically similar effect on all compounds and generally in a way that dicaffeoyldaucic acid had the highest increase. This research provides important information for primary production, packaging, catering, the fresh-cut industry and consumers regarding the selection of healthier minimally processed carrots.202

Application of chemometrics to assess the influence of ultrasound frequency, Lactobacillus sakei culture and drying on beef jerky manufacture: Impact on amino acid profile, organic acids, texture and colour

The effects of ultrasound (US) frequency, addition of Lactobacillus sakei culture and drying time on key nutritional (protein, amino acids, and organic acids) and physicochemical properties (texture and colour) of cultured and uncultured beef jerky were evaluated. Cultured and uncultured jerky samples were subjected to US frequencies of 25 kHz, 33 kHz and 45 kHz for 30 min prior to marination and drying. Principal component analysis demonstrated a significant effect of beef jerky processing conditions on physicochemical properties. Taurine content of jerky samples was found to increase with an increase in ultrasonic frequencies for cultured samples. No significant changes in colour values were observed for ultrasound pre-treated and control samples. Interactive effects of culture treatment, drying and ultrasonic frequency were observed. This study demonstrates that the nutritional profile of beef jerky can be improved through the incorporation of L. sakei

The impact of TP-AGB stars on hierarchical galaxy formation models

The spectro-photometric properties of galaxies in galaxy formation models are obtained by combining the predicted history of star formation and mass accretion with the physics of stellar evolution through stellar population models. In the recent literature, significant differences have emerged regarding the implementation of the Thermally-Pulsing Asymptotic Giant Branch phase of stellar evolution. The emission in the TP-AGB phase dominates the bolometric and near-IR spectrum of intermediate-age (~1 Gyr) stellar populations, hence it is crucial for the correct modeling of the galaxy luminosities and colours. In this paper for the first time, we incorporate a full prescription of the TP-AGB phase in a semi-analytic model of galaxy formation. We find that the inclusion of the TP-AGB in the model spectra dramatically alters the predicted colour-magnitude relation and its evolution with redshift. When the TP-AGB phase is active, the rest-frame V-K galaxy colours are redder by almost 2 magnitudes in the redshift range z~2-3 and by 1 magnitude at z~1. Very red colours are produced in disk galaxies, so that the V-K colour distributions of disk and spheroids are virtually undistinguishable at low redshifts. We also find that the galaxy K-band emission is more than 1 magnitude higher in the range z~1-3. This may alleviate the difficulties met by the hierarchical clustering scenario in predicting the red galaxy population at high redshifts. The comparison between simulations and observations have to be revisited in the light of our results.Comment: 6 pages, 4 figures. Accepted for publication on MNRAS Letter

Influence of production on the presence of patulin and ochratoxin A in fruit juices and wines of Argentina

In this study, the relative frequency and concentration of patulin (PAT) and ochratoxin A (OTA) in fruit juices and wines collected in Argentina between 2005 and 2013 were determined by high performance liquid chromatography. PAT was detected in 1997 of 5958 samples (ranging from 3.0 to 19,622 μg/L), and 510 samples presented PAT levels above 50 μg/L. The highest incidence of PAT was observed in 2005 (243 of 419 samples) while the lowest was quantified in 2009 (104 of 482 samples). OTA was detected in only 22 of 1401 samples at concentrations ranging from 0.15 to 3.6 μg/L, and the highest incidence was observed in 2007 (8 of 153 samples). The concentration of PAT and OTA in the beverages analyzed was found to be affected by the type of fruit product, fruit commodity and production year. A great amount of data on the incidence of these mycotoxins in these matrixes can be further used in the development and reinforcement of measures to reduce the burden of their presence in juices and wines. This is important since PAT levels above the limit set by regulations were high and fruit juices are quite consumed by children. Although OTA contamination was low, effective ways to safeguard consumer exposure to PAT and OTA and consequently to protect public health are essential and indispensable.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Criotecnología de Alimento

Current-voltage characteristics of diluted Josephson-junction arrays: scaling behavior at current and percolation threshold

Dynamical simulations and scaling arguments are used to study the current-voltage (IV) characteristics of a two-dimensional model of resistively shunted Josephson-junction arrays in presence of percolative disorder, at zero external field. Two different limits of the Josephson-coupling concentration $p$ are considered, where $p_c$ is the percolation threshold. For $p$ $>$ $p_c$ and zero temperature, the IV curves show power-law behavior above a disorder dependent critical current. The power-law behavior and critical exponents are consistent with a simple scaling analysis. At $p_c$ and finite temperature $T$, the results show the scaling behavior of a T=0 superconducting transition. The resistance is linear but vanishes for decreasing $T$ with an apparent exponential behavior. Crossover to non-linearity appears at currents proportional to $$, with a thermal-correlation length exponent $\nu_T$ consistent with the corresponding value for the diluted XY model at $p_c$.Comment: Revtex, 9 postscript pages, to appear in Phys. Rev.

3-D Radiative Transfer Calculations of Radiation Feedback from Massive Black Holes: Outflow of Mass from the Dusty "Torus"

Observational and theoretical arguments suggest that the momentum carried in mass outflows from AGN can reach several times L / c, corresponding to outflow rates of hundreds of solar masses per year. Radiation pressure on lines alone may not be sufficient to provide this momentum deposition, and the transfer of reprocessed IR radiation in dusty nuclear gas has been postulated to provide the extra enhancement. The efficacy of this mechanism, however, will be sensitive to multi-dimensional effects such as the tendency for the reprocessed radiation to preferentially escape along sight-lines of lower column density. We use Monte Carlo radiative transfer calculations to determine the radiation force on dusty gas residing within approximately 10 parsecs from an accreting super-massive black hole. We calculate the net rate of momentum deposition in the surrounding gas and estimate the mass-loss rate in the resulting outflow as a function of solid angle for different black hole luminosities, sightline-averaged column densities, clumping parameters, and opening angles of the dusty gas. We find that these dust-driven winds carry momentum fluxes of 1-5 times L / c and correspond to mass-loss rates of 10-100 solar masses per year for a 10^8 solar mass black hole radiating at or near its Eddington limit. These results help to explain the origin of high velocity molecular and atomic outflows in local ULIRGs, and can inform numerical simulations of galaxy evolution including AGN feedback.Comment: 15 pages, 14 figures. Submitted to ApJ; v2 Corrected spelling and other small typos; v3 Included additional details and references to match accepted versio