HT Cas - eclipsing dwarf nova during its superoutburst in 2010

We present results of a world-wide observing campaign of the eclipsing dwarf nova - HT Cas during its superoutburst in November 2010. Using collected data we were able to conduct analysis of the light curves and we calculated $O-C$ diagrams. The CCD photometric observations enabled us to derive the superhump period and with the timings of eclipses the orbital period was calculated. Based on superhump and orbital period estimations the period excess and mass ratio of the system were obtained

IX Draconis - a curious ER UMa-type dwarf nova

We report results of an extensive world-wide observing campaign devoted to a very active dwarf nova star - IX Draconis. We investigated photometric behaviour of the system to derive its basic outburst properties and understand peculiarities of IX Dra as well as other active cataclysmic variables, in particular dwarf novae of the ER Uma-type. In order to measure fundamental parameters of the system, we carried out analyses of the light curve, O-C diagram, and power spectra. During over two months of observations we detected two superoutbursts and several normal outbursts. The V magnitude of the star varied in the range 14.6 - 18.2 mag. Superoutbursts occur regularly with the supercycle length of 58.5+/-0.5 d. When analysing data over the past 20 years, we found that the supercycle length is increasing at a rate of P_dot = 1.8 * 10^{-3}. Normal outbursts appear to be irregular, with typical occurrence times in the range 3.1 - 4.1 d. We detected a double-peaked structure of superhumps during superoutburst, with the secondary maximum becoming dominant near the end of the superoutburst. The mean superhump period observed during superoutbursts equals 0.066982(36) d, which is constant over the last two decades of observations. Based on the power spectrum analysis, the evaluation of the orbital period was problematic. We found two possible values: the first one, 0.06641(3) d, which is in agreement with previous studies and our O-C analysis (0.06646(2) d), and the second one, 0.06482(3) d, which is less likely. The evolutionary status of the object depends dramatically on the choice between these two values. A spectroscopic determination of the orbital period is needed. We updated available information on ER UMa-type stars and present a new set of their basic statistics. Thereby, we provide evidence that this class of stars is not uniform.Comment: Accepted for publication in MNRAS; 15 pages, 15 figures, 6 tables; typo correcte

Transcriptome of the deep-sea black scabbardfish, Aphanopus carbo (Perciformes: Trichiuridae) : tissue-specific expression patterns and candidate genes associated to depth adaptation

Deep-sea fishes provide a unique opportunity to study the physiology and evolutionary adaptation to extreme environments. We carried out a high throughput sequencing analysis on a 454 GS-FLX titanium plate using unnormalized cDNA libraries from six tissues of A. carbo. Assemblage and annotations were performed by Newbler and InterPro/Pfam analyses, respectively. The assembly of 544,491 high quality reads provided 8,319 contigs, 55.6% of which retrieved blast hits against the NCBI nonredundant database or were annotated with ESTscan. Comparison of functional genes at both the protein sequences and protein stability levels, associated with adaptations to depth, revealed similarities between A. carbo and other bathypelagic fishes. A selection of putative genes was standardized to evaluate the correlation between number of contigs and their normalized expression, as determined by qPCR amplification. The screening of the libraries contributed to the identification of new EST simple-sequence repeats (SSRs) and to the design of primer pairs suitable for population genetic studies as well as for tagging and mapping of genes. The characterization of the deep-sea fish A. carbo first transcriptome is expected to provide abundant resources for genetic, evolutionary, and ecological studies of this species and the basis for further investigation of depth-related adaptation processes in fishes.Publisher PDFPeer reviewe

Novel Microscopic Mechanism of Intermixing during Growth on Soft Metallic Substrates

Generic computer simulations using empiric interatomic potentials suggest a new, collective mechanism that could be responsible for mixing at heteroepitaxial interfaces. Even if single adsorbate atoms diffuse by hopping on the substrate surface and do not mix at the terraces, two-dimensional islands formed by nucleation may become unstable above a certain critical size and explode upwards forming clusters of several atomic layers. This process is accompanied by strong distortions of the underlying atomic layers, and on soft materials it can result in surface etching and incorporation of substrate atoms into the islands.Fil: Gomez, Liliana Maria. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, Ingeniería y Agrimensura; ArgentinaFil: Slutzky, Claudia Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Ferron, Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: de la Figuera, J.. Sandia National Laboratories; Estados UnidosFil: Camarero, J.. Universidad Autónoma de Madrid; EspañaFil: Vazquez de Parga, A.. Universidad Autónoma de Madrid; EspañaFil: de Miguel, J.J.. Universidad Autónoma de Madrid; EspañaFil: Miranda, R.. Universidad Autónoma de Madrid; Españ

Mixing Time Scales in a Supernova-Driven Interstellar Medium

We study the mixing of chemical species in the interstellar medium (ISM). Recent observations suggest that the distribution of species such as deuterium in the ISM may be far from homogeneous. This raises the question of how long it takes for inhomogeneities to be erased in the ISM, and how this depends on the length scale of the inhomogeneities. We added a tracer field to the three-dimensional, supernova-driven ISM model of Avillez (2000) to study mixing and dispersal in kiloparsec-scale simulations of the ISM with different supernova (SN) rates and different inhomogeneity length scales. We find several surprising results. Classical mixing length theory fails to predict the very weak dependence of mixing time on length scale that we find on scales of 25--500 pc. Derived diffusion coefficients increase exponentially with time, rather than remaining constant. The variance of composition declines exponentially, with a time constant of tens of Myr, so that large differences fade faster than small ones. The time constant depends on the inverse square root of the supernova rate. One major reason for these results is that even with numerical diffusion exceeding physical values, gas does not mix quickly between hot and cold regions.Comment: 23 pages, 14 figures that include 7 simulation images and 19 plots, accepted for publication at Ap

Discretization-related issues in the KPZ equation: Consistency, Galilean-invariance violation, and fluctuation--dissipation relation

In order to perform numerical simulations of the KPZ equation, in any dimensionality, a spatial discretization scheme must be prescribed. The known fact that the KPZ equation can be obtained as a result of a Hopf--Cole transformation applied to a diffusion equation (with \emph{multiplicative} noise) is shown here to strongly restrict the arbitrariness in the choice of spatial discretization schemes. On one hand, the discretization prescriptions for the Laplacian and the nonlinear (KPZ) term cannot be independently chosen. On the other hand, since the discretization is an operation performed on \emph{space} and the Hopf--Cole transformation is \emph{local} both in space and time, the former should be the same regardless of the field to which it is applied. It is shown that whereas some discretization schemes pass both consistency tests, known examples in the literature do not. The requirement of consistency for the discretization of Lyapunov functionals is argued to be a natural and safe starting point in choosing spatial discretization schemes. We also analyze the relation between real-space and pseudo-spectral discrete representations. In addition we discuss the relevance of the Galilean invariance violation in these consistent discretization schemes, and the alleged conflict of standard discretization with the fluctuation--dissipation theorem, peculiar of 1D.Comment: RevTex, 23pgs, 2 figures, submitted to Phys. Rev.

Micotoxinas em produtos derivados de milho comercializados em Minas Gerais.

O objetivo deste trabalho foi avaliar a incidência de aflatoxinas e de fumonisinas totais em canjiquinha, fubá e farinha de milho comercializados no município de Sete Lagoas, Estado de Minas Gerais.bitstream/item/145127/1/circ-204-1.pd

Incidência de aflatoxinas e fumonisinas em produtos de milho consumidos no estado de Minas Gerais.

As aflatoxinas e as fumonisinas são micotoxinas usualmente encontradas em milho e, quando ingeridas, são capazes de provocar malefícios à saúde humana e animal. Assim, objetivou-se avaliar a incidência de aflatoxinas e de fumonisinas em seis marcas de canjiquinha, cinco de fubá e cinco de farinha de milho comercializadas em quatro supermercados do município de Sete Lagoas, MG. As análises foram realizadas por fluorimetria, utilizando-se colunas de imunoafinidade AflaTest e FumoniTest para as análises de aflatoxinas e fumonisinas, respectivamente. Dentre os produtos analisados, o fubá apresentou contaminação com ambas micotoxinas em todas as marcas, com valores que variaram entre 0,04 ?g kg-1 e 1,6 ?g kg-1 e entre 55 e 985 ?g kg-1 para aflatoxinas e fumonisinas, respectivamente. A farinha de milho apresentou pequena contaminação com aflatoxinas (0,36 - 0,49 e 0,181 ?g kg-1) em três marcas e de fumonisinas (20 ?g kg-1 e 37 ?g kg-1) em duas marcas. Foi detectada presença de aflatoxina em três marcas de canjiquinha, variando entre 0,008 e 0,21 ?g kg-1, e de fumonisina em apenas uma com 60 ?g kg-1. Os produtos analisados apresentaram concentrações abaixo dos limites máximos tolerados no Brasil para ambas as micotoxinas, não oferecendo riscos para a saúde dos consumidores