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DNA microarrays is a technology that can be used to diagnose cancer and other diseases. To automate the analysis of such data, pattern recognition and machine learning algorithms can be applied. However, the curse of dimensionality is unavoidable: very few samples to train, and many attributes in each sample. As the predictive accuracy of supervised classifiers decays with irrelevant and redundant features, the necessity of a dimensionality reduction process is essential. The main idea is to retain only the genes that are the most influential in the classification of the disease. In this paper, a new methodology based on Principal Component Analysis and Logistics Regression is proposed. Our method enables the selection of particular genes that are relevant for classification. Experiments were run using eight different classifiers on two benchmark datasets: Leukemia and Lymphoma. The results show that our method not only reduces the number of required attributes, but also increase the classification accuracy in more than 10% in all the cases we tested.

We present the current status of the White Dwarf Photosphere Experiment at the Z Pulsed Power Facility at Sandia National Laboratories. This experiment has evolved into a unique platform for simultaneously measuring emission, absorption, and back-lighter continua spectra of plasmas with white dwarf (WD) photospheric compositions and conditions (Te∼1 eV, ne∼1016–1018e/cm3); our current experiments involve line profile measurements of hydrogen—corresponding to the most common surface composition in white dwarf stars, with future experiments planned for helium, carbon, and oxygen. These profiles will test line broadening theories used in white dwarf model atmospheres to infer the fundamental parameters (e.g., effective temperature and mass) of thousands of WDs. This experiment uses the large amount of x-rays generated from a z-pinch dynamic hohlraum to radiatively drive plasma formation in a gas cell. We reach significantly higher densities than the landmark study of Wiese et al. (1972), thereby putting competing line broadening theories to the test in a regime where their predictions strongly diverge. The simultaneous measurement of emission, absorption, and back-lighter continua in macroscopic plasmas represents a significant advance relative to hydrogen line profile experiments of the past.

Retinal images can be used to detect and follow up several important chronic diseases. The classification of retinal images requires an experienced ophthalmologist. This has been a bottleneck to implement routine screenings performed by general physicians. It has been proposed to create automated systems that can perform such task with little intervention from humans, with partial success. In this work, we report advances in such endeavor, by using a Lattice Neural Network with Dendritic Processing (LNNDP). We report results using several metrics, and compare against well known methods such as Support Vector Machines (SVM) and Multilayer Perceptrons (MLP). Our proposal shows better performance than other approaches reported in the literature. An additional advantage is that unlike those other tools, LNNDP requires no parameters, and it automatically constructs its structure to solve a particular problem. The proposed methodology requires four steps: (1) Pre-processing, (2) Feature computation, (3) Classification and (4) Post-processing. The Hotelling T2 control chart was used to reduce the dimensionality of the feature vector, from 7 that were used before to 5 in this work. The experiments were run on images of DRIVE and STARE databases. The results show that on average, F1-Score is better in LNNDP, compared with SVM and MLP implementations. Same improvement is observed for MCC and the accuracy. HighlightsFirst implementation of a Lattice Neural Network with Dendritic Processing to solve classify retinal images.The performance is competitive compared with common approaches like Support Vector Machines and Multilayer Perceptrons.The Lattice Neural Network with Dendritic Processing does not require the adjustment of parameters by the user.

We present an experimental platform for measuring hydrogen Balmer emission and absorption line profiles for plasmas with white dwarf (WD) photospheric conditions (T_e ~ 1 eV, n_e ~ 10^17 cm^-3). These profiles will be used to benchmark WD atmosphere models, which, used with the spectroscopic method, are responsible for determining fundamental parameters (e.g., effective temperature, mass) for tens of thousands of WDs. Our experiment, performed at the Z Pulsed Power Facility at Sandia National Laboratories, uses the large amount of x-rays generated from a z-pinch dynamic hohlraum to drive plasma formation in a gas cell. The platform is unique compared to past hydrogen line profile experiments in that the plasma is radiation-driven. This decouples the heating source from the plasma to be studied in the sense that the radiation temperature causing the photoionization is independent of the initial conditions of the gas. For the first time we measure hydrogen Balmer lines in absorption at these conditions in the laboratory for the purpose of benchmarking Stark-broadened line shapes. The platform can be used to study other plasma species and to explore non-LTE, time-dependent collisional-radiative atomic kinetics., Comment: Accepted to High Energy Density Physics, 10 pages (double-column), 9 figures

Radial-Basis Function Neural Networks (RBFN) are a well known formulation to solve classification problems. In this approach, a feedforward neural network is built, with one input layer, one hidden layer and one output layer. The processing is performed in the hidden and output layers. To adjust the network for any given problem, certain parameters have to be set. The parameters are: the centers of the radial functions associated to the hidden layer and the weights of the connections to the output layer. Most of the methods either require a lot of experimentation or may demand a lot of computational time. In this paper we present a novel method based on a partition algorithm to automatically compute the amount and location of the centers of the radial-basis functions. Our results, obtained by running it in seven public databases, are comparable and even better than some other approaches.

We present a comprehensive survey of CII* absorption detections toward stars within 100 pc in order to measure the distribution of electron densities present in the local interstellar medium (LISM). Using high spectral resolution observations of nearby stars obtained by GHRS and STIS onboard the Hubble Space Telescope, we identify 13 sight lines with 23 individual CII* absorption components, which provide electron density measurements, the vast majority of which are new. We employ several strategies to determine more accurate CII column densities from the saturated CII resonance line, including, constraints of the line width from the optically thin CII* line, constraints from independent temperature measurements of the LISM gas based on line widths of other ions, and third, using measured SII column densities as a proxy for CII column densities. The sample of electron densities appears consistent with a log-normal distribution and an unweighted mean value of n_e(CII_SII) = 0.11^+0.10_-0.05 cm^-3. Seven individual sight lines probe the Local Interstellar Cloud (LIC), and all present a similar value for the electron density, with a weighted mean of n_e(LIC) = 0.12 +/- 0.04 cm^-3. The Hyades Cloud, a decelerated cloud at the leading edge of the platoon of LISM clouds, has a significantly higher electron density than the LIC. Observed toward G191-B2B, the high electron density may be caused by the lack of shielding from such a strong radiation source. Given some simple assumptions, the range of observed electron densities translates into a range of thermal pressures, P/k = 3300^+5500_-1900 K cm^-3. This work greatly expands the number of electron density measurements and provides important constraints on the ionization, abundance, and evolutionary models of the local interstellar medium. (abridged)

We spectroscopically measure multiple hydrogen Balmer line profiles from laboratory plasmas to investigate the theoretical line profiles used in white dwarf atmosphere models. X-ray radiation produced at the Z Pulsed Power Facility at Sandia National Laboratories initiates plasma formation in a hydrogen-filled gas cell, replicating white dwarf photospheric conditions. Here we present time-resolved measurements of H$\beta$ and fit this line using different theoretical line profiles to diagnose electron density, $n_{\rm e}$, and $n=2$ level population, $n_2$. Aided by synthetic tests, we characterize the validity of our diagnostic method for this experimental platform. During a single experiment, we infer a continuous range of electron densities increasing from $n_{\rm e}\sim4$ to $\sim30\times10^{16}\,$cm$^{-3}$ throughout a 120-ns evolution of our plasma. Also, we observe $n_2$ to be initially elevated with respect to local thermodynamic equilibrium (LTE); it then equilibrates within $\sim55\,$ns to become consistent with LTE. This supports our electron-temperature determination of $T_{\rm e}\sim1.3\,$eV ($\sim15,000\,$K) after this time. At $n_{\rm e}\gtrsim10^{17}\,$cm$^{-3}$, we find that computer-simulation-based line-profile calculations provide better fits (lower reduced $\chi^2$) than the line profiles currently used in the white dwarf astronomy community. The inferred conditions, however, are in good quantitative agreement. This work establishes an experimental foundation for the future investigation of relative shapes and strengths between different hydrogen Balmer lines., Comment: 11 double-column pages, 15 figures, Accepted for publication in ApJ

Barriers to retention in HIV care are detrimental to patients' progress along the HIV continuum of care. Previous literature has focused on individual, client-level barriers, and interventions to address them. In contrast, less work has examined the role of system-level barriers on HIV care outcomes. This study seeks to understand how individual and systemic barriers individually are associated with clinic appointment attendance and virologic suppression in HIV-infected patients attending the largest HIV clinic in Miami-Dade, FL. In addition, we examined the synergistic effects of these barriers as potential syndemic factors on these health outcomes. Barriers to clinic attendance were determined in a face-to-face study interview with 444 HIV-infected outpatients (187 regular attenders, 191 irregular attenders, and 66 nonattenders) identified from electronic medical records. Compared with the other attendance groups, nonattenders had higher viral loads, were less likely to be virologically suppressed, had lower CD4 counts, had higher depressive symptoms, life chaos, lower quality of life, and higher rates of food insecurity, and recent drug use. Additionally, nonattenders compared with regular attenders had lower physician relationship ratings, had lower medical information clarity and more often reported transportation as a barrier to clinic attendance. When viewed as a syndemic, compared with patients not reporting any barriers, patients with 3 or more individual-level barriers were more likely to have a detectable viral load (odds ratio = 3.60, 95% CI: 1.71 to 7.61). Our findings suggest that patients presenting to the clinic with multiple barriers should be prioritized for assistance and future interventions to improve retention in care. Interventions should address multiple individual and system-level barriers simultaneously with particular attention to addressing depressive symptoms, organizational skills, relationship with the physician, and HIV-related health education.

DNA microarrays are being used to characterize the genetic expression of several illnesses, such as cancer. There has been interest in developing automated methods to classify the data generated by those microarrays. The problem is complex due to the availability of just a few samples to train the classifiers, and the fact that each sample may contain several thousands of features. One possibility is to select a reduced set of features genes. In this work we propose a wrapper method that is a modified version of the Inertial Geometric Particle Swarm Optimization.We name it MIGPSO. We compare MIGPSO with other approaches. The results are promising. MIGPSO obtained an increase in accuracy of about 4i¾?%. The number of genes selected is also competitive.

Numerous high-resolution spectra of the δ Scuti star 4 CVn were gathered at McDonald Observatory in Texas, USA. They were prepared for interpretation using standard IRAF routines for a subsequent frequency analysis and mode identification with the software FAMIAS. After the reduction process a clear trend in the first moment of the line profile (radial velocity) remained, indicating the signature of binary motion. This was corrected for by fitting a Keplerian orbit, followed by a detailed analysis of the data in the reference frame of the primary. The results of the frequency analysis are in good agreement with previous photometric studies. This paper presents thirteen pulsation modes that were detected in the data sets for the years 2010 and/or 2011. Future work involves spectroscopic mode identification and subsequent seismic modeling (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Experimental tests are in progress to evaluate the accuracy of the modeled iron opacity at solar interior conditions [J.E. Bailey et al., Phys. Plasmas 16, 058101 (2009)]. The iron sample is placed on top of the Sandia National Laboratories z-pinch dynamic hohlraum (ZPDH) radiation source. The samples are heated to 150 - 200 eV electron temperatures and 7e21 - 4e22 e/cc electron densities by the ZPDH radiation and backlit at its stagnation [T. Nagayama et al., Phys. Plasmas 21, 056502 (2014)]. The backlighter attenuated by the heated sample plasma is measured by four spectrometers along +/- 9 degree with respect to the z-pinch axis to infer the sample iron opacity. Here we describe measurements of the source-to-sample distance that exploit the parallax of spectrometers that view the half-moon-shaped sample from +/-9 degree. The measured sample temperature decreases with increased source-to-sample distance. This distance must be taken into account for understanding the sample heating., Comment: Published online 17 July 2014 (http://scitation.aip.org/content/aip/journal/rsi/85/11/10.1063/1.4889776)

We carry out high-speed photometry on 20 of the shortest-period, detached white dwarf binaries known and discover systems with eclipses, ellipsoidal variations (due to tidal deformations of the visible white dwarf), and Doppler beaming. All of the binaries contain low-mass white dwarfs with orbital periods less than 4 hr. Our observations identify the first eight tidally distorted white dwarfs, four of which are reported for the first time here, which we use to put empirical constraints on the mass-radius relationship for extremely low-mass (, 14 pages, 5 figures, accepted for publication in The Astrophysical Journal

Electro-mechanical meters are commonly employed to measure the consumption of utilities. Basically there exist two types of analog meters: the ones that use rotary dials (like an odometer) and the ones with pointer dials (like a speedometer). Former approaches to automated meter reading have dealt with the first kind of meters. Considering that automated reading of the latter ones can be confusing, in this work we introduce a methodology based on image processing and segmentation to enable the image acquisition and processing of pointer dials to obtain efficiently and accurately readings. This methodology uses an image acquired with a smart phone and by applying a sequence of image processing functions it finds and extracts the dial images of such meter images. Then the methodology identifies the position of the pointers followed by a clever implementation that enables the reading. The database is composed with more than a hundred images taken under different light conditions, perspectives and angles. The method is able to extract the reading in an average of 3 seconds, with a 92 % accuracy with images taken in-field. Our method, enables the use of a common smart phone to acquire and automatically extract the reading of a pointer-type dial meter. This allows interesting applications that could help people to monitor their energy consumption and learn patterns to save energy. This could be one step ahead of energy saving policies that can be discovered through massive data analysis.

Hubble Space Telescope spectra obtained in 2010 and 2011, three and four years after the large amplitude dwarf nova outburst of V455 And, were combined with optical photometry and spectra to study the cooling of the white dwarf, its spin, and possible pulsation periods after the outburst. The modeling of the ultraviolet (UV) spectra show that the white dwarf temperature remains ~600 K hotter than its quiescent value at three years post outburst, and still a few hundred degrees hotter at four years post outburst. The white dwarf spin at 67.6 s and its second harmonic at 33.8 s are visible in the optical within a month of outburst and are obvious in the later UV observations in the shortest wavelength continuum and the UV emission lines, indicating an origin in high temperature regions near the accretion curtains. The UV light curves folded on the spin period show a double-humped modulation consistent with two-pole accretion. The optical photometry two years after outburst shows a group of frequencies present at shorter periods (250-263 s) than the periods ascribed to pulsation at quiescence, and these gradually shift toward the quiescent frequencies (300-360 s) as time progresses past outburst. The most surprising result is that the frequencies near this period in the UV data are only prominent in the emission lines, not the UV continuum, implying an origin away from the white dwarf photosphere. Thus, the connection of this group of periods with non-radial pulsations of the white dwarf remains elusive., 18 pages, 14 figs; accepted for ApJ

We present the discovery of photometric variability in the DQ white dwarf SDSS J103655.39+652252.2 (SDSS J1036+6522). Time-series photometry reveals a coherent monoperiodic modulation at a period of 1115.64751(67) s with an amplitude of 0.442% +/- 0.024%; no other periodic modulations are observed with amplitudes >~0.13%. The period, amplitude, and phase of this modulation are constant within errors over 16 months. The spectrum of SDSS J1036+6522 shows magnetic splitting of carbon lines, and we use Paschen-Back formalism to develop a grid of model atmospheres for mixed carbon and helium atmospheres. Our models, while reliant on several simplistic assumptions, nevertheless match the major spectral and photometric properties of the star with a self-consistent set of parameters: Teff~15,500 K, log g ~9, log(C/He)=-1.0, and a mean magnetic field strength of 3.0 +/- 0.2 MG. The temperature and abundances strongly suggest that SDSS J1036+6522 is a transition object between the hot, carbon-dominated DQs and the cool, He-dominated DQs. The variability of SDSS J1036+6522 has characteristics similar to those of the variable hot carbon-atmosphere white dwarfs (DQVs), however, its temperature is significantly cooler. The pulse profile of SDSS J1036+6522 is nearly sinusoidal, in contrast with the significantly asymmetric pulse shapes of the known magnetic DQVs. If the variability in SDSS J1036+6522 is due to the same mechanism as other DQVs, then the pulse shape is not a definitive diagnostic on the absence of a strong magnetic field in DQVs. It remains unclear whether the root cause of the variability in SDSS J1036+6522 and the other hot DQVs is the same., Accepted for publication in ApJ. 12 pages, 9 figures

One of the most intriguing questions confronting the bone morphogenetic protein family is the mechanism of ligand recognition, because there are more ligands than receptors. Crystal structures of two type II receptors, ActR-II and BMPR-II, are essentially identical, and a loop structure (A-loop) has been suggested to play a role in determining ligand specificity. A solution biophysical study showed mutations of several A-loop residues in these two receptors exert different ligand binding effects. Thus, the issues of mechanism of ligand recognition and specificity remain unresolved. We examined effects of mutations of residues Y40, G47, and S107 in BMPR-II. These residues are not identified as being in contact with the ligand in the BMP-7-BMPR-II complex but are found mutated in genetic diseases. They are likely to be useful in identifying their roles in differentiating the various BMP ligands. Spectroscopic probing revealed little mutation-induced structural change in BMPR-II. Ligand binding studies revealed that Y40 plays a significant role in differentiating three distinct ligands; G47 and S107 affect ligand binding to a lesser extent. The role of the A-loop in ActR-II or BMPR-II is dependent on the host sequence of the receptor extracellular domain (ECD) in which it is embedded, suggesting a host-guest relationship between the A-loop and the rest of the ECD. Computational analysis demonstrated a long-range connectivity between Y40, G47, and S107 and other locations in BMPR-II. An integration of these results on functional energetics and protein structures clearly demonstrates, for the first time, an intradomain communication network within BMPR-II.

We measure apparent velocities (v_app) of absorption lines for 36 white dwarfs (WDs) with helium-dominated atmospheres -- 16 DBAs and 20 DBs -- using optical spectra taken for the European Southern Observatory SN Ia progenitor survey (SPY). We find a difference of 6.9+/-6.9 km/s in the average apparent velocity of the H-alpha lines versus that of the HeI 5876AA for our DBAs. This is a measure of the blueshift of this He line due to pressure effects. By using this as a correction, we extend the gravitational redshift method employed by Falcon et al. (2010) to use the apparent velocity of the HeI 5876AA line and conduct the first gravitational redshift investigation of a group of WDs without visible hydrogen lines. We use biweight estimators to find an average apparent velocity, _BI, (and hence average gravitational redshift, _BI) for our WDs; from that we derive an average mass, _BI. For the DBAs, we find _BI = 40.8+/-4.7 km/s and derive _BI = 0.71 +0.04 -0.05 Msun. Though different from of DAs (32.57 km/s) at the 91% confidence level and suggestive of a larger DBA mean mass than that for normal DAs derived using the same method (0.647 +0.013 -0.014 Msun; Falcon et al. 2010), we do not claim this as a stringent detection. Rather, we emphasize that the difference between _BI of the DBAs and of normal DAs is no larger than 9.2 km/s, at the 95% confidence level; this corresponds to roughly 0.10 Msun. For the DBs, we find ^He_BI = 42.9+/-8.49 km/s after applying the blueshift correction and determine _BI = 0.74 +0.08 -0.09 Msun. The difference between ^He_BI of the DBs and of DAs is less than or equal to 11.5 km/s (~0.12 Msun), at the 95% confidence level. The gravitational redshift method indicates much larger mean masses than the spectroscopic determinations of the same sample by Voss et al. (2007)..., Comment: Accepted to the Astrophysical Journal, 10 pages double-column, 3 figures, 5 tables

We measure apparent velocities (v_app) of the Halpha and Hbeta Balmer line cores for 449 non-binary thin disk normal DA white dwarfs (WDs) using optical spectra taken for the ESO SN Ia Progenitor surveY (SPY; Napiwotzki et al. 2001). Assuming these WDs are nearby and co-moving, we correct our velocities to the Local Standard of Rest so that the remaining stellar motions are random. By averaging over the sample, we are left with the mean gravitational redshift, : we find = = 32.57 +/- 1.17 km/s. Using the mass-radius relation from evolutionary models, this translates to a mean mass of 0.647 +0.013 -0.014 Msun. We interpret this as the mean mass for all DAs. Our results are in agreement with previous gravitational redshift studies but are significantly higher than all previous spectroscopic determinations except the recent findings of Tremblay & Bergeron (2009). Since the gravitational redshift method is independent of surface gravity from atmosphere models, we investigate the mean mass of DAs with spectroscopic Teff both above and below 12000 K; fits to line profiles give a rapid increase in the mean mass with decreasing Teff. Our results are consistent with no significant change in mean mass: ^hot = 0.640 +/- 0.014 Msun and ^cool = 0.686 +0.035 -0.039 Msun., Comment: Accepted for publication in ApJ, 14 pages, 12 figures

In the past decades, large scale surveys have discovered a large number of white dwarfs. For example, the Sloan Digital Sky Survey (SDSS) Data Release 7 [5] lists about 20 000 spectroscopically confirmed new white dwarfs. More than just a number, the new discoveries revealed different flavors of white dwarfs, including a new class of pulsators [7] and a larger percentage of stars with a magnetic field [4]. The HET Dark Energy Experiment (HETDEX) will use the 9.2 m Hobby‐Eberly Telescope at McDonald Observatory and a set of 150 spectrographs to map the three‐dimensional positions of one million galaxies. The main goal of the survey is to probe dark energy by observing the recent universe (2⩽z⩽4). However, this unique, magnitude‐limited survey (V⩽22) will also provide a variety of by‐products. We expect to obtain spectra for about 10 000 white dwarfs in the next 3 to 4 years.

We present a preliminary report from the laboratory astrophysics experiments to create macroscopic (∼19 cm3) hydrogen‐plasmas with white dwarf (WD) photospheric conditions (i.e., temperature, electron density). These experiments, performed at the Z Pulsed Power Facility at Sandia National Laboratories, will serve as benchmarks for fundamental atomic line profile measurements in emission and absorption; they are targeted to address the discrepancy between theory and observation of WD photospheres—cooler photospheres in particular.

We measure apparent velocities (νapp) of the Hα and Hβ Balmer line cores for 16 helium‐dominated white dwarfs (WDs) using optical spectra taken for the European Southern Observatory SN Ia progenitor survey (SPY). Following the gravitational redshift method employed by Falcon et al. [1], we find a mean apparent velocity of 〈νapp〉 = 39.58±4.41 km s−1 and use it to derive a mean mass of 〈M〉 = 0.701−0.046+0.042M⊙. Though the sample is small, the mean mass appears to be larger than the mean mass of DAs derived using the same method [0.647−0.014+0.013M⊙,1].

We measured the electrical resistance of a copper powder sample under uniaxial compression. The resistance is controlled by the oxide layer on grains. It follows a power law versus the pressure, with an exponent which is different from that expected either with Hertz or plastic contact between grains. A theoretical explanation based on a description of two grains in contact is proposed. We show that the strong dependence of the macroscopic resistance with the pressure applied to the powder is a consequence of large variabilities and heterogeneities present at the contact surface between two grains.

We present a comprehensive survey of CII* absorption detections toward stars within 100 pc in order to measure the distribution of electron densities present in the local interstellar medium (LISM). Using high spectral resolution observations of nearby stars obtained by GHRS and STIS onboard the Hubble Space Telescope, we identify 13 sight lines with 23 individual CII* absorption components, which provide electron density measurements, the vast majority of which are new. We employ several strategies to determine more accurate CII column densities from the saturated CII resonance line, including, constraints of the line width from the optically thin CII* line, constraints from independent temperature measurements of the LISM gas based on line widths of other ions, and third, using measured SII column densities as a proxy for CII column densities. The sample of electron densities appears consistent with a log-normal distribution and an unweighted mean value of n_e(CII_SII) = 0.11^+0.10_-0.05 cm^-3. Seven individual sight lines probe the Local Interstellar Cloud (LIC), and all present a similar value for the electron density, with a weighted mean of n_e(LIC) = 0.12 +/- 0.04 cm^-3. The Hyades Cloud, a decelerated cloud at the leading edge of the platoon of LISM clouds, has a significantly higher electron density than the LIC. Observed toward G191-B2B, the high electron density may be caused by the lack of shielding from such a strong radiation source. Given some simple assumptions, the range of observed electron densities translates into a range of thermal pressures, P/k = 3300^+5500_-1900 K cm^-3. This work greatly expands the number of electron density measurements and provides important constraints on the ionization, abundance, and evolutionary models of the local interstellar medium. (abridged), Comment: 41 pages, 9 figures; Accepted for publication in ApJ

The Z Facility at Sandia National Laboratories [Matzen et al., Phys. Plasmas 12, 055503 (2005)] provides MJ-class x-ray sources that can emit powers >0.3 PW. This capability enables benchmark experiments of fundamental material properties in radiation-heated matter at conditions previously unattainable in the laboratory. Experiments on Z can produce uniform, long-lived, and large plasmas with volumes up to 20 cc, temperatures from 1–200 eV, and electron densities from 1017–23 cc−1. These unique characteristics and the ability to radiatively heat multiple experiments in a single shot have led to a new effort called the Z Astrophysical Plasma Properties (ZAPP) collaboration. The focus of the ZAPP collaboration is to reproduce the radiation and material characteristics of astrophysical plasmas as closely as possible in the laboratory and use detailed spectral measurements to strengthen models for atoms in plasmas. Specific issues under investigation include the LTE opacity of iron at stellar-interior conditi...

We have finally measured the evolutionary rate of cooling of the pulsating hydrogen atmosphere (DA) white dwarf ZZ Ceti (Ross 548), as reflected by the drift rate of the 213.13260694 s period. Using 41 yr of time-series photometry from 1970 November to 2012 January, we determine the rate of change of this period with time to be dP/dt = (5.2 ± 1.4) × 10-15 s s-1 employing the O-C method and (5.45 ± 0.79) × 10-15 s s-1 using a direct nonlinear least squares fit to the entire lightcurve. We adopt the dP/dt obtained from the nonlinear least squares program as our final determination, but augment the corresponding uncertainty to a more realistic value, ultimately arriving at the measurement of dP/dt = (5.5 ± 1.0) × 10-15 s s-1. After correcting for proper motion, the evolutionary rate of cooling of ZZ Ceti is computed to be (3.3 ± 1.1) × 10-15 s s-1. This value is consistent within uncertainties with the measurement of (4.19 ± 0.73) × 10-15 s s-1 for another similar pulsating DA white dwarf, G 117-B15A. Measuring the cooling rate of ZZ Ceti helps us refine our stellar structure and evolutionary models, as cooling depends mainly on the core composition and stellar mass. Calibrating white dwarf cooling curves with this measurement will reduce the theoretical uncertainties involved in white dwarf cosmochronometry. Should the 213.13 s period be trapped in the hydrogen envelope, then our determination of its drift rate compared to the expected evolutionary rate suggests an additional source of stellar cooling. Attributing the excess cooling to the emission of axions imposes a constraint on the mass of the hypothetical axion particle., La lista completa de autores que integran el documento puede consultarse en el archivo., Facultad de Ciencias Astronómicas y Geofísicas

Hot white dwarfs with carbon-dominated atmospheres (hot DQs) are a cryptic class of white dwarfs. In addition to their deficiency of hydrogen and helium, most of these stars are highly magnetic, and a large fraction vary in luminosity. This variability has been ascribed to nonradial pulsations, but increasing data call this explanation into question. We present studies of short-term variability in seven hot DQ white dwarfs. Three (SDSS J1426+5752, SDSS J2200-0741, and SDSS J2348-0942) were known to be variable. Their photometric modulations are coherent over at least two years, and we find no evidence for variability at frequencies that are not harmonics. We present the first time-series photometry for three additional hot DQs (SDSS J0236-0734, SDSS J1402+3818, and SDSS J1615+4543); none are observed to vary, but the signal-to-noise is low. Finally, we present high speed photometry for SDSS J0005-1002, known to exhibit a 2.1 d photometric variation; we do not observe any short-term variability. Monoperiodicity is rare among pulsating white dwarfs, so we contemplate whether the photometric variability is due to rotation rather than pulsations; similar hypotheses have been raised by other researchers. If the variability is due to rotation, then hot DQ white dwarfs as a class contain many rapid rotators. Given the lack of companions to these stars, the origin of any fast rotation is unclear -- both massive progenitor stars and double degenerate merger remnants are possibilities. We end with suggestions on future work that would best clarify the nature of these rare, intriguing objects., Comment: 9 pages, 7 figures; accepted for publication in the Astrophysical Journal

DNA microarrays is a technology that can be used to diagnose cancer and other diseases. To automate the analysis of such data, pattern recognition and machine learning algorithms can be applied. However, the curse of dimensionality is unavoidable: very few samples to train, and many attributes in each sample. As the predictive accuracy of supervised classifiers decays with irrelevant and redundant features, the necessity of a dimensionality reduction process is essential. In this paper, we propose a new methodology that is based on the application of Principal Component Analysis and other statistical tools to gain insight in the identification of relevant genes. We run the approaches using two benchmark datasets: Leukemia and Lymphoma. The results show that it is possible to reduce considerably the number of genes while increasing the performance of well known classifiers.

Gas injection at the bottom of an immersed granular layer made of particles slightly heavier than the surrounding fluid leads, in the stationary regime, to the formation of a dense suspension resulting from the competition between particle entrainment by bubbles and sedimentation. The statistical study of bubbles characteristics shows that above a critical gas flow-rate, the bubble population splits in two, with small bubbles appearing in the suspension. The bubble main orientation axis displays two bifurcations, with a coexistence zone. Contrary to the intuition, the horizontal extent of the region explored by bubbles depends not on the flow-rate, but only on the effective gravity., L'injection de gaz à la base d'un lit granulaire immergé formé de particules légèrement plus lourdes que le liquide environnant conduit à la formation, en régime stationnaire, d'une suspension dense résultant d'une compétition entre l'entraînement des particules par les bulles et leur sédimentation. L'étude statistique des propriétés des bulles dans ce régime montre qu'au-delà d'un débit critique d'injection de gaz, la population de bulles se scinde en deux avec l'apparition de petites bulles dans la suspension. L'orientation de l'axe principal des bulles montre deux bifurcations, avec une zone de coexistence. De manière non-intuitive, l'extension horizontale de la région explorée par les bulles ne dépend pas du débit, mais uniquement de la gravité effective.

National audience; Dans cette communication, nous rappelons tout d’abord les différents régimes de fonctionnement dumodèle de Pernarowski. Ce dernier permet de décrire l’activité électrique des céllules béta du pancréas. Par la suite,nous définissons le modèle à dérivées fractionnaires. En particulier, le schéma d’intégration numérique choisipour résoudre le système d’équations à dérivée fractionnaire est intégralement présenté. Notre analyse montrequ’avec ce modèle fractionnaire, l’activité électrique peut être contrôlée par l’ordre des dérivées fractionnaires ;ce qui pourraît rendre compte de certains dysfonctionnement dans la sécrétion de l’insuline par les céllules béta dupancréas.

National audience; Nous présentons une ligne électrique dont la tension obéit aux équations de Klein-Gordon d’ordre 5afin d’en étudier les propriétés de transmission. Nous focalisons sur la transmission d’énergie en bande interdite,c’est à dire lorsque le système est excité en dehors de sa bande passante. Nous avons pu expérimentallement mettreen évidence que lorsque l’amplitude de l’excitation excède un seuil, le système génére des modes non linéaires deforte amplitude via le phénomène de supratransmission.

National audience; Cette Communication porte sur une étude numérique visant à montrer les conditions d'existence du phénomène de supratransmission dans un milieu gouverné par l'équation de sine-gordon à couplage mixte: le couplage linéaire pur étant associé à un couplage non linéaire. Nous montrons également l'effet de la variation du coefficient du couplage non linéaire sur l'amplitude de seuil du signal excitateur nécessaire pour déclencher le phénomène de supratransmission dans le milieu, en maintenant constant le coefficient du couplage linéaire pur.

National audience; Cette communication est consacrée à l’étude expérimentale du comportement d’un circuit électronique non linéaire du type FitzHugh-Nagumo soumis exclusivement à du bruit. En l’absence de bruit, le circuit est paramétré en mode excitable près de la bifurcation d’Andronov-Hopf. Cette dernière se manifeste par un changement du fonctionnement du circuit qui devient oscillant. Nous montrons que le circuit peut utiliser le bruit pour déclencher des ondes du type potentiels d’action. Ce déclenchement atteint une régularité qui peut être maximisée pour une quantité appropriée de bruit via le phénomène de Résonance Cohérente.

National audience; Nous étudions le phénomène de supratransmission dans un milieu non linéaire discret, soumis, à une excitation périodique dont la fréquence appartient à la bande interdite. Nous montrons l’existence d’un seuil de tension au dessus duquel l’instabilité modulationnelle (IM) va se développer dans la ligne, valeur de seuil dépendant de la fréquence d’excitation. Si elle n’empêche pas l’apparition de l’IM par supratransmission, la dissipation présente dans la ligne est un obstacle à la génération des solitons de cut-off, obstacle que nous sommes parvenus à contourner par un choix approprié de l’amplitude de l’excitation.

National audience; Dans cette communication, nous menons conjointement une étude en simulation numérique ainsi qu’une étude expérimentale de la réponse du système de FitzHugh-Nagumo soumis à une excitation bi-chromatique. Cette excitation est constituée d’un signal basse fréquence perturbé par une composante haute fréquence additive. Selon l’amplitude B de la perturbation haute fréquence, la réponse du système peut être optimisée à la basse fréquence. Un choix approprié du rapport des fréquences d’excitations peut conduire à une meilleure optimisation de la réponse du système.

National audience; Cette communication porte sur une étude numérique visant à montrer que le bruit peut permettre le déclenchement de modes Breather dans le système de sine-Gordon. Dans un premier temps, en l’absence de bruit, le phénomène de supratransmission introduit et quantifié par Geniet et Léon est vérifié : il existe une amplitude critique de l’excitation sinusoıdale au delà de laquelle le milieu transmet de l’énergie bien qu’excité en dehors de sa bande passante. Nous montrons que sous certaines conditions, le bruit peut faciliter l’apparition de ce phénomène de supratransmission et déclencher des modes Breather.

International audience; A joint gas-liquid flow through a quasi-2D porous medium leads to three hydrodynamic regimes depending on the imposed gas and liquid flow rates. The image analysis highlights the difficulty of a classical morphological algorithm in accurately detecting the bubbles contour and structure. We introduce two more sophisticated methods leading to more realistic contours, and compare quantitatively these three methods. The statistical properties of the bubbles make it possible to determine the typical bubble sizes in the different flow regimes and the global perimeter, characteristic of the interfaces. This latter seems to exhibit a minimum for the transition regime, due to bubble coalescence in the system.; Un écoulement conjoint gaz-liquide dans un milieu poreux quasi-2D conduit à trois régimes hydrodynamiques suivant la valeur des débits imposés. L'analyse des images met en évidence la difficulté d'un algorithme morphologique classique à détecter précisément le contour et la structure des bulles. Nous introduisons deux méthodes plus sophistiquées permettant d'obtenir des contours plus réalistes, et comparons quantitativement ces trois méthodes. L'étude statistique des propriétés des bulles permet de déterminer les tailles typiques des bulles dans les différents régimes d'écoulement, ainsi que le périmètre global, caractéristique des interfaces. Ce dernier semble atteindre un minimum pour le régime de transition, dûà la coalescence de bulles dans le système.