The first INTEGRAL-OMC catalogue of optically variable sources

The Optical Monitoring Camera (OMC) onboard INTEGRAL provides photometry in the Johnson V-band. With an aperture of 50 mm and a field of view of 5deg x 5deg, OMC is able to detect optical sources brighter than V~18, from a previously selected list of potential targets of interest. After more than nine years of observations, the OMC database contains light curves for more than 70000 sources (with more than 50 photometric points each). The objectives of this work have been to characterize the potential variability of the objects monitored by OMC, to identify periodic sources and to compute their periods, taking advantage of the stability and long monitoring time of the OMC. To detect potential variability, we have performed a chi-squared test, finding 5263 variable sources out of an initial sample of 6071 objects with good photometric quality and more than 300 data points each. We have studied the periodicity of these sources using a method based on the phase dispersion minimization technique, optimized to handle light curves with very different shapes.In this first catalogue of variable sources observed by OMC, we provide for each object the median of the visual magnitude, the magnitude at maximum and minimum brightness in the light curve during the window of observations, the period, when found, as well as the complete intrinsic and period-folded light curves, together with some additional ancillary data.Comment: Accepted by Astronomy & Astrophysics; 13 pages, 16 figures. Figures' resolution has been degraded to fit astro-ph constraint

Chirality in Bare and Passivated Gold Nanoclusters

Chiral structures have been found as the lowest-energy isomers of bare (Au$_{28}$ and Au$_{55}) and thiol-passivated (Au$_{28}(SCH$_{3})$_{16}$and Au$_{38}(SCH_{3})_{24}) gold nanoclusters. The degree of chirality existing in the chiral clusters was calculated using the Hausdorff chirality measure. We found that the index of chirality is higher in the passivated clusters and decreases with the cluster size. These results are consistent with the observed chiroptical activity recently reported for glutahione-passivated gold nanoclusters, and provide theoretical support for the existence of chirality in these novel compounds.Comment: 5 pages, 1 figure. Submitted to PR

Predictive modelling of magnesium concentration in grapevine petioles as a basis for liming recommendations in vineyard acid soils

Soil acidification is a natural process which can either be accelerated by the activity of plants, animals and humans, but can be controlled through appropriate soil management. The main aim of this work was to develop a predictive modelling of magnesium concentration in grapevine petioles for liming amendment recommendation in vineyard acid soils. One liming material, dolomite, has been added to the soil at three doses: 0.9, 1.8 and 2.7 t CaCO3 ha-1. Magnesium exchangeable content in soil surface and concentrations of this nutrient in petioles of leaf samples were investigated during three years. Exchangeable magnesium in soil tended to increase with increasing dolomite application rate. These increases were significant among all the doses and the control, except for the dose of 0.9. However, only between the highest dose and the control significant differences in magnesium concentration in petioles could be detected. In addition, one linear model has been proposed to make liming recommendations in vineyard acid soils based on petiole magnesium concentrations.

Identification of novel bioactive peptides

Motivation: Targeting agents are the most commonly used strategies in therapeutics and diagnostic treatment.They can be classified in two main classes: chemicals and biologicals. Chemicals (farmaceutics and related) have been used for years, but nowadays biologicals experience an increasing demand because of their potentially higher specificity and affinity. Bioactive peptides from rational design can act as targeting agents that specifically interact with, and mostly inhibit, a biomolecule of interest (Seignauric et al., 2011).Methods: We have built a large library of peptides, and are screening for those that have biological activity, specially related to cell proliferation inhibition. The initial inconvenience is that small peptides cannot be expressed from single transcription unit as larger proteins, as they will be destroyed by cell proteases system. It is necessary to include the peptide library into a protein scaffold. We have designed a novel structure that includes the variable peptide sequence from the library between two mini-domains "EFLIVIKS" (one letter aminoacid code) able to form a noncovalent loop (Gururaja et al., 2010). In one of our constructs we have included a T7 promoter to allow conditional expression in bacteria. For its expression, we have designed two large nucleotide sequences (79 and 124 nucleotides, the large one includes the variable peptide sequence) that assemble by 20 complementary nucleotides in their 3' ends. By polymerization, both oligos strings are filled and form a two-chain structure, that will be inserted in a expression vector to obtain our peptide library. We transform bacteria (E. coli) and yeast (Schizosaccharomyces pombe) in order to identify those colonies excpressing the bioactive peptides that kill the cells or interrupt cell cycle

Cloning and expression of a Saccharomyces cerevisiae RNA-dependent RNA polymerase

RNA-dependent RNA polymerases (RdRp) are ubiquous enzimes  first described in RNA viruses and virus-like elements. In Saccharomyces cerevisiae this enzyme can be found, fused with capsid proteins, encoded by the L-A helper virus-like particle. Replication cycle of L-A is coupled to that of M satellite particle, which confers a killer phenotype to the yeast (Schmitt & Breinig, 2002). RdRp recognizes and replicates ssRNA from both L-A and M virus. RdRp recognizes a 3'-Terminal Recognition Element (3'TRE), a small stem-loop 5 bases from the 3' end (Ribas, Fujimuras, & Wickner, 1994), which can be used as an effective tool for primerless replication of RNA molecules. To gain further insight on the virus-like particle replication mechanism and to evaluate its possible biotechnological application, the present project is focused on cloning the RdRp coding sequence in several different expression vectors and expressing the protein using different Escherichia coli strains as hosts. Once RdRp is efficiently expressed, we will proceed to purify it by affinity chromatography and test the protein activity by replicating full length viral RNA´s and other RNA sequences with or without the 3'TRE sequence. In our communication we will present our advances in cloning, expression, purification and activity of the yeast polymeras

Secondary homotopy groups

Secondary homotopy groups supplement the structure of classical homotopy groups. They yield a track functor on the track category of pointed spaces compatible with fiber sequences, suspensions and loop spaces. They also yield algebraic models of homotopy types with homotopy groups concentrated in two consecutive dimensions.Comment: We added further commets and references to make the paper more easily readabl

The Second INTEGRAL AGN Catalogue

The INTEGRAL mission provides a large data set for studying the hard X-ray properties of AGN and allows testing of the unified scheme for AGN. We present analysis of INTEGRAL IBIS/ISGRI, JEM-X, and OMC data for 199 AGN supposedly detected by INTEGRAL above 20 keV. The data analysed here allow a significant spectral extraction on 148 objects and an optical variability study of 57 AGN. The slopes of the hard X-ray spectra of Seyfert 1 and Seyfert~2 galaxies are found to be consistent within the uncertainties, whereas higher cut-off energies and lower luminosities are measured for the more absorbed / type 2 AGN. The intermediate Seyfert 1.5 objects exhibit hard X-ray spectra consistent with those of Seyfert 1. When applying a Compton reflection model, the underlying continua appear the same in Seyfert 1 and 2 with photon index 2, and the reflection strength is about R = 1, when assuming different inclination angles. A significant correlation is found between the hard X-ray and optical luminosity and the mass of the central black hole in the sense that the more luminous objects appear to be more massive. There is also a general trend toward the absorbed sources and type 2 AGN having lower Eddington ratios. The black holemass appears to form a fundamental plane together with the optical and X-ray luminosity of the form Lv being proportional to Lx^0.6 M^0.2, similar to that found between radio luminosity Lr, Lx, and M. The unified model for Seyfert galaxies seems to hold, showing in hard X-rays that the central engine is the same in Seyfert 1 and 2, but seen under different inclination angles and absorption. (Abridged)Comment: 26 pages, 16 figures, accepted for publication in A&A. Corrections by language editor included in version

COMBUSTION MODEL FOR SPARK IGNITION ENGINES OPERATING ON GASOLINE-ETHANOL BLENDS

This article presents a phenomenological combustion model using turbulent flame propagation theory developed by Keck and coworkers, 1974. The model was adapted to work with gasoline-ethanol blends, following correlations presented by Bayraktar,2005. New sub-models were introduced for intake valve velocity and combustion efficiency. These allow simulating the effect of compression ratio, spark timing and fuel change. Results show good agreement with the ones in the original work as well as with experimental results in a Cooperative Fuels Research (CFR) engine