Contribution of time of day and the circadian clock to the heat stress responsive transcriptome in Arabidopsis.

In Arabidopsis, a large subset of heat responsive genes exhibits diurnal or circadian oscillations. However, to what extent the dimension of time and/or the circadian clock contribute to heat stress responses remains largely unknown. To determine the direct contribution of time of day and/or the clock to differential heat stress responses, we probed wild-type and mutants of the circadian clock genes CCA1, LHY, PRR7, and PRR9 following exposure to heat (37 °C) and moderate cold (10 °C) in the early morning (ZT1) and afternoon (ZT6). Thousands of genes were differentially expressed in response to temperature, time of day, and/or the clock mutation. Approximately 30% more genes were differentially expressed in the afternoon compared to the morning, and heat stress significantly perturbed the transcriptome. Of the DEGs (~3000) specifically responsive to heat stress, ~70% showed time of day (ZT1 or ZT6) occurrence of the transcriptional response. For the DEGs (~1400) that are shared between ZT1 and ZT6, we observed changes to the magnitude of the transcriptional response. In addition, ~2% of all DEGs showed differential responses to temperature stress in the clock mutants. The findings in this study highlight a significant role for time of day in the heat stress responsive transcriptome, and the clock through CCA1 and LHY, appears to have a more profound role than PRR7 and PRR9 in modulating heat stress responses during the day. Our results emphasize the importance of considering the dimension of time in studies on abiotic stress responses in Arabidopsis

Molecular Dynamics Simulation of Solvent-Polymer Interdiffusion. I. Fickian diffusion

The interdiffusion of a solvent into a polymer melt has been studied using large scale molecular dynamics and Monte Carlo simulation techniques. The solvent concentration profile and weight gain by the polymer have been measured as a function of time. The weight gain is found to scale as t^{1/2}, which is expected for Fickian type of diffusion. The concentration profiles are fit very well assuming Fick's second law with a constant diffusivity. The diffusivity found from fitting Fick's second law is found to be independent of time and equal to the self diffusion constant in the dilute solvent limit. We separately calculated the diffusivity as a function of concentration using the Darken equation and found that the diffusivity is essentially constant for the concentration range relevant for interdiffusion.Comment: 17 pages and 7 figure

Electrocatalytic degradation of phenol on Pt- and Ru-doped Ti-SnO2-Sb anodes in an alkaline medium

[EN] In this work, the electrocatalytic performance of Ti/SnO2-Sb(13-x)-Pt-Ru(x) anodes (x = 0.0, 3.25 and 9.75 at.%) towards phenolate elimination has been analyzed and compared to those of conventional Ti/RuO2 and Ti/Co3O4 anodes, to evaluate their application for decontamination of concentrated alkaline phenolic wastewaters. The effects of the applied current density and the nature of the anode on the activity, kinetics and current efficiency for phenolate elimination, COD removal and benzoquinone by-product formation/degradation have been thoroughly examined. The Ti/SnO2-Sb-Pt anode exhibits the best electroactivity, fastest kinetics and highest current efficiency among the studied anodes, but poor electrochemical stability. The introduction of small amounts of Ru (3.25–9.75 at.%) brings about a slight loss of the electrocatalytic performance, but it causes a remarkable increase in the stability of the electrode. In terms of energy consumption and stability, the Ti/SnO2-Sb(9.75)-Pt-Ru(3.25) electrode seems to be the most promising anode material for the electrochemical treatment of alkaline phenolic wastewaters. The increase in current density generally leads to significantly faster phenolate, benzoquinone and COD degradations, but with lower efficiency because of an increasing selectivity to water oxidation. A correction of the ideal kinetic model has been proposed to predict the oxidation of organics on non-active metal oxide anodes. ©2016 Elsevier B.V. All rights reserved.Financial support from the Spanish Ministerio de Economia y Competitividad and FEDER funds (MAT2013-42007-P, IJCI-2014-20012) and from the Generalitat Valenciana (PROMETEO2013/038) is gratefully acknowledged.Berenguer Betrián, R.; Sieben, JM.; Quijada Tomás, C.; Morallón, E. (2016). Electrocatalytic degradation of phenol on Pt- and Ru-doped Ti-SnO2-Sb anodes in an alkaline medium. Applied Catalysis B: Environmental. 199:394-404. https://doi.org/10.1016/j.apcatb.2016.06.038S39440419

Determination of pulsation periods and other parameters of 2875 stars classified as MIRA in the All Sky Automated Survey (ASAS)

We have developed an interactive PYTHON code and derived crucial ephemeris data of 99.4% of all stars classified as 'Mira' in the ASAS data base, referring to pulsation periods, mean maximum magnitudes and, whenever possible, the amplitudes among others. We present a statistical comparison between our results and those given by the AAVSO International Variable Star Index (VSX), as well as those determined with the machine learning automatic procedure of Richards et al. 2012. Our periods are in good agreement with those of the VSX in more than 95% of the stars. However, when comparing our periods with those of Richards et al, the coincidence rate is only 76% and most of the remaining cases refer to aliases. We conclude that automatic codes require still more refinements in order to provide reliable period values. Period distributions of the target stars show three local maxima around 215, 275 and 330 d, apparently of universal validity, their relative strength seems to depend on galactic longitude. Our visual amplitude distribution turns out to be bimodal, however 1/3 of the targets have rather small amplitudes (A $<$ 2.5$^{m}$) and could refer to semi-regular variables (SR). We estimate that about 20% of our targets belong to the SR class. We also provide a list of 63 candidates for period variations and a sample of 35 multiperiodic stars which seem to confirm the universal validity of typical sequences in the double period and in the Petersen diagramsComment: 14 pages, 14 figures, and 8 tables. Accepted to The Astrophysical Journal Supplement Series, September 201

Temperature Dependence of Low-Lying Electronic Excitations of LaMnO_3

We report on the optical properties of undoped single crystal LaMnO_3, the parent compound of the colossal magneto-resistive manganites. Near-Normal incidence reflectance measurements are reported in the frequency range of 20-50,000 cm-1 and in the temperature range 10-300 K. The optical conductivity, s_1(w), is derived by performing a Kramers-Kronig analysis of the reflectance data. The far-infrared spectrum of s_1(w) displays the infrared active optical phonons. We observe a shift of several of the phonon to high frequencies as the temperature is lowered through the Neel temperature of the sample (T_N = 137 K). The high-frequency s_1(w) is characterized by the onset of absorption near 1.5 eV. This energy has been identified as the threshold for optical transitions across the Jahn-Teller split e_g levels. The spectral weight of this feature increases in the low-temperature state. This implies a transfer of spectral weight from the UV to the visible associated with the paramagnetic to antiferromagnetic state. We discuss the results in terms of the double exchange processes that affect the optical processes in this magnetic material.Comment: 7 pages, 5 figure

Lifetime of electronic excitations in metal nanoparticles

9 páginas, 4 figuras.-- Trabajo presentado al "6th International Meeting on Photodynamics" celebrado en La Habana (Cuba) del 1 al 5 de febrero de 2010.Electronic excitations in metal particles with sizes up to a few nanometers are shown to have a one-electron character when a laser pulse is applied off the plasmon resonance. The calculated lifetimes of these excitations are in the femtosecond timescale but their values are substantially different from those in bulk. This deviation can be explained from the large weight of the excitation wave function in the nanoparticle surface region, where dynamic screening is significantly reduced. The well-known quadratic dependence of the lifetime with the excitation energy in bulk breaks down in these finite-size systems.We acknowledge the partial support of the Basque Government, the University of the Basque Country UPV/EHU (grant no. 9/UPV 00206.215-13639/2001) and the Spanish MEC (grants FIS2007-66711-C02-02 and MAT2008-06843-C03-01). JAA acknowledges the financial support of Ikerbasque.Peer reviewe

Optical conductivity in doped manganites with planar x2^2-y2^2 orbital order

We investigate a planar model for the ferromagnetic (FM) phase of manganites, which develops orbital order of $e_g$ electrons with x$^2$-y$^2$-symmetry at low temperature. The dynamic structure factor of orbital excitations and the optical conductivity $\sigma(\omega)$ are studied with help of a finite-temperature diagonalization method. Our calculations provide a theoretical prediction for $\sigma(\omega)$ for the 2D FM state and are of possible relevance for the recently found A-type phase of manganites at high doping which consists of FM layers coupled antiferromagnetically. In the x$^2$-y$^2$ ordered regime $\sigma(\omega)$ shows both a Drude peak and a gapped incoherent absorption due to a gap in the orbital excitations.Comment: 5 pages, 5 figures, to appear in Phys. Rev. Let