The Patterns of High-Level Magnetic Activity Occurring on the Surface of V1285 Aql: The OPEA Model of Flares and DFT Models of Stellar Spots

Statistically analyzing Johnson UBVR observations of V1285 Aql during the three observing seasons, both activity level and behavior of the star are discussed in respect to obtained results. We also discuss the out-of-flare variation due to rotational modulation. Eighty-three flares were detected in the U-band observations of season 2006 . First, depending on statistical analyses using the independent samples t-test, the flares were divided into two classes as the fast and the slow flares. According to the results of the test, there is a difference of about 73 s between the flare-equivalent durations of slow and fast flares. The difference should be the difference mentioned in the theoretical models. Second, using the one-phase exponential association function, the distribution of the flare-equivalent durations versus the flare total durations was modeled. Analyzing the model, some parameters such as plateau, half-life values, mean average of the flare-equivalent durations, maximum flare rise, and total duration times are derived. The plateau value, which is an indicator of the saturation level of white-light flares, was derived as 2.421{\pm}0.058 s in this model, while half-life is computed as 201 s. Analyses showed that observed maximum value of flare total duration is 4641 s, while observed maximum flare rise time is 1817 s. According to these results, although computed energies of the flares occurring on the surface of V1285 Aql are generally lower than those of other stars, the length of its flaring loop can be higher than those of more active stars.Comment: 44 pages, 10 figures, 5 tables, 2011PASP..123..659

Persistent and context-dependent effects of the larval feeding environment on post-metamorphic performance through the adult stage

One of the central issues in ecology is the identification of processes affecting the population structure and dynamics of species with complex life cycles. In such species, variation in both the number of larvae that enter a population and their phenotype are important drivers of survival and growth after metamorphosis. Larval experience can have strong effects on key post-metamorphic traits, but the temporal scale of such ‘trait-mediated effects’ may be short, and their magnitude may depend on the environment experienced after metamorphosis. We used an intertidal barnacle to study the long-term consequences of trait-mediated effects under different post-metamorphic conditions by manipulating larval food concentration and monitoring patterns of survival and growth in juveniles at 2 intertidal levels over a 5 mo period. In 2 replicated experiments, higher food levels resulted in increased body size, mass and reserves (measured from elemental composition) in the settling larval stage and increased body size of newly metamorphosed juveniles. In Expt 1, high food concentration reduced juvenile mortality at low intertidal levels, while on the upper intertidal, mortality was high for all larval food concentrations. By contrast, in Expt 2, low larval food concentration decreased juvenile survival at both shore levels. When present, effects were established early (Weeks 1 or 2) and persisted for over 10 wk in Expt 1 and 22 wk in Expt 2. Interactive effects of the larval and juvenile environments can have important implications for population size: trait-mediated effects may persist for long periods, helping to explain patterns of adult abundance

Metabolic switching of human skeletal muscle cells in vitro

In this review we will focus on external factors that may modify energy metabolism in human skeletal muscle cells (myotubes) and the ability of the myotubes to switch between lipid and glucose oxidation. We describe the metabolic parameters suppressibility, adaptability and substrate-regulated flexibility, and show the influence of nutrients such as fatty acids and glucose (chronic hyperglycemia), and some pharmacological agents modifying nuclear receptors (PPAR and LXR), on these parameters in human myotubes. Possible cellular mechanisms for changes in these parameters will also be highlighted.The present work was funded by University of Oslo, The European Nutrigenomics Organisation (NuGO), The Norwegian Diabetes Foundation, AstraZeneca, Freia Chocolade Fabriks Medical Foundation, and The Anders Jahre’s Foundatio

DeepPrecip: A deep neural network for precipitation retrievals

Remotely-sensed precipitation retrievals are critical for advancing our understanding of global energy and hydrologic cycles in remote regions. Radar reflectivity profiles of the lower atmosphere are commonly linked to precipitation through empirical power laws, but these relationships are tightly coupled to particle microphysical assumptions that do not generalize well to different regional climates. Here, we develop a robust, highly generalized precipitation retrieval from a deep convolutional neural network (DeepPrecip) to estimate 20-minute average surface precipitation accumulation using near-surface radar data inputs. DeepPrecip displays high retrieval skill and can accurately model total precipitation accumulation, with a mean square error (MSE) 99 % lower, on average, than current methods. DeepPrecip also outperforms a less complex machine learning retrieval algorithm, demonstrating the value of deep learning when applied to precipitation retrievals. Predictor importance analyses suggest that a combination of both near-surface (below 1 km) and higher-altitude (1.5 &ndash; 2 km) radar measurements are the primary features contributing to retrieval accuracy. Further, DeepPrecip closely captures total precipitation accumulation magnitudes and variability across nine distinct locations without requiring any explicit descriptions of particle microphysics or geospatial covariates. This research reveals the important role for deep learning in extracting relevant information about precipitation from atmospheric radar retrievals.</p

Photometric Variability in the Ultracool Dwarf BRI 0021-0214: Possible Evidence for Dust Clouds

We report CCD photometric monitoring of the nonemission ultracool dwarf BRI 0021-0214 (M9.5) obtained during 10 nights in 1995 November and 4 nights in 1996 August, with CCD cameras at 1 m class telescopes on the observatories of the Canary Islands. We present differential photometry of BRI 0021-0214, and we report significant variability in the I-band light curve obtained in 1995. A periodogram analysis finds a strong peak at a period of 0.84 day. This modulation appears to be transient because it is present in the 1995 data but not in the 1996 data. We also find a possible period of 0.20 day, which appears to be present in both the 1995 and 1996 datasets. However, we do not find any periodicity close to the rotation period expected from the spectroscopic rotational broadening (< 0.14 day). BRI 0021-0214 is a very inactive object, with extremely low levels of Halpha and X-ray emission. Thus, it is unlikely that magnetically induced cool spots can account for the photometric variability. The photometric variability of BRI 0021-0214 could be explained by the presence of an active meteorology that leads to inhomogeneous clouds on the surface. The lack of photometric modulation at the expected rotational period suggests that the pattern of surface features may be more complicated than previously anticipated.Comment: Accepted for publication in ApJ. 26 pages, 13 figures include

GRAPE: GRaphical Abstracted Protein Explorer

The region surrounding a protein, known as the surface of interaction or molecular surface, can provide valuable insight into its function. Unfortunately, due to the complexity of both their geometry and their surface fields, study of these surfaces can be slow and difficult and important features may be hard to identify. Here, we describe our GRaphical Abstracted Protein Explorer, or GRAPE, a web server that allows users to explore abstracted representations of proteins. These abstracted surfaces effectively reduce the level of detail of the surface of a macromolecule, using a specialized algorithm that removes small bumps and pockets, while preserving large-scale structural features. Scalar fields, such as electrostatic potential and hydropathy, are smoothed to further reduce visual complexity. This entirely new way of looking at proteins complements more traditional views of the molecular surface. GRAPE includes a thin 3D viewer that allows users to quickly flip back and forth between both views. Abstracted views provide a fast way to assess both a molecule's shape and its different surface field distributions. GRAPE is freely available at http://grape.uwbacter.org

A detailed study of the rise phase of a long duration X-ray flare in the young star TWA 11B

We analyzed a long duration flare observed in a serendipitous XMM-Newton detection of the M star CD-39 7717B (TWA 11B), member of the young stellar association TW Hya (~ 8 Myr). Only the rise phase (with a duration of ~ 35 ks) and possibly the flare peak were observed. We took advantage of the high count-rate of the X-ray source to carry out a detailed analysis of its spectrum during the whole exposure. After a careful analysis, we interpreted the rise phase as resulting from the ignition of a first group of loops (event A) which triggered a subsequent two-ribbon flare (event B). Event A was analyzed using a single-loop model, while a two-ribbon model was applied for event B. Loop semi-lengths of ~ 4 R* were obtained. Such large structures had been previously observed in very young stellar objects (~ 1 - 4 Myr). This is the first time that they have been inferred in a slightly more evolved star. The fluorescent iron emission line at 6.4 keV was detected during event B. Since TWA 11B seems to have no disk, the most plausible explanation found for its presence in the X-ray spectrum of this star is collisional - or photo- ionization. As far as we are concerned, this is only the third clear detection of Fe photospheric fluorescence in stars other than the Sun.Comment: Accepted for publication in ApJ. 15 pages, 9 figure

The Density of Coronal Plasma in Active Stellar Coronae

We have analyzed high-resolution X-ray spectra of a sample of 22 active stars observed with the High Energy Transmission Grating Spectrometer on {\em Chandra} in order to investigate their coronal plasma density. Densities where investigated using the lines of the He-like ions O VII, Mg XI, and Si XIII. While Si XIII lines in all stars of the sample are compatible with the low-density limit, Mg XI lines betray the presence of high plasma densities ($> 10^{12}$ cm$^{-3}$) for most of the sources with higher X-ray luminosity ($> 10^{30}$ erg/s); stars with higher $L_X$ and $L_X/L_{bol}$ tend to have higher densities at high temperatures. Ratios of O VII lines yield much lower densities of a few $10^{10}$ cm$^{-3}$, indicating that the ``hot'' and ``cool'' plasma resides in physically different structures. Our findings imply remarkably compact coronal structures, especially for the hotter plasma emitting the Mg XI lines characterized by coronal surface filling factor, $f_{MgXI}$, ranging from $10^{-4}$ to $10^{-1}$, while we find $f_{OVII}$ values from a few $10^{-3}$ up to $\sim 1$ for the cooler plasma emitting the O VII lines. We find that $f_{OVII}$ approaches unity at the same stellar surface X-ray flux level as solar active regions, suggesting that these stars become completely covered by active regions. At the same surface flux level, $f_{MgXI}$ is seen to increase more sharply with increasing surface flux. These results appear to support earlier suggestions that hot $10^7$ K plasma in active coronae arises from flaring activity, and that this flaring activity increases markedly once the stellar surface becomes covered with active regions.Comment: 53 pages, 19 figures, accepted for publication in Astrophysical Journal. A version of the paper with higher quality figures is available from http://www.astropa.unipa.it/Library/preprint.htm