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El Rastreo de los Cielos de Catalina (Catalina Sky Survey) en la Universidad de Arizona opera tres telescopios a tiempo completo en la b´usqueda de objetos cercanos a la Tierra (NEOs). CSS ha descubierto el 47% de todos los NEOs conocidos, reportado 46 millones de posiciones de asteroides, y nuestra fotometr´ıa se ha utilizado para generar curvas de luz para 500 mil millones de estrellas. Nuestros telescopios son capaces de adquirir datos de forma altamente automatizada y estamos trabajando para que uno de ellos sea autónomo desde la selección del objetivo hasta la elaboración de informes de datos de alta confianza. Se cubren varios aspectos de la automatización de alto nivel en CSS, con énfasis en el software gestor de colas, dando una breve descripción de CSS y exponiendo los resultados obtenidos

In 2018, Solar Cycle 24 entered a deep solar minimum. During this period, we collected night sky brightness data at Cosmic Campground International Dark Sky Sanctuary (CCIDSS) in the USA (2018 September 4–2019 January 4) and at Aotea/Great Barrier Island International Dark Sky Sanctuary (AGBIIDSS) in New Zealand (2018 March 26–August 31. These sites have artificial-light-pollution-free natural night skies. The equipment employed are identical Unihedron SQM-LU-DL meters, used as single-channel differential photometers, to scan the sky as Earth rotates on its axis. We have developed new analysis techniques which select those data points which are uninfluenced by Sun, Moon, or clouds to follow brightness changes at selected points on the celestial sphere and to measure the brightness of the airglow above its quiescent level. The 2018 natural night sky was measured to change in brightness by approximately 0.9 mag arcsec−2 at both locations. Preliminary results indicate the modulations of the light curves (brightness versus R.A.) we observed are related in complex ways to elements of space weather conditions in the near-Earth environment. In particular, episodes of increased night sky brightness are observed to be contemporaneous with geomagnetic activity, increases in mean solar wind speed, and some solar proton/electron fluence events. Charged particles in the solar wind take days to reach near-Earth environment after a coronal hole is observed to be facing in our direction. Use of this information could make it possible to predict increases in Earth's natural night sky brightness several days in advance. What we have learned during this solar minimum leads us to search for other solar driven changes in night sky brightness as the Sun begins to move into solar maximum conditions.

The design and synthesis of catalysts, especially for the production of solar fuels, is a major challenge in developing sources of renewable energy. Catalyst development requires an understanding of the mechanism(s) involved and the nature of the active site. While platinum group metals have unrivalled activity for both hydrogen and oxygen evolution, they are scarce and expensive. Photocatalytic systems relying on earth-abundant materials are therefore desirable for large scale energy production. Herein, we examine the structure and electronic properties of an amorphous molybdenum sulfide species and its possible use for photocatalytic hydrogen evolution. The catalyst was grown on a seeded quantum-rod sensitizer, a model system for investigating the photophysics of solar fuel generation. This catalyst s activity is shown experimentally to be associated with under-coordinated molybdenum centers, and we document that a reduced form of MoS3 is an active species for hydrogen generation. Molybdenum sulfides are prevalent in both biological enzymes and industrial catalysts. Mo metalloenzymes are involved in carbon, nitrogen, and sulfur metabolism, while synthetic molybdenum sulfides serve as industrial hydrotreating catalysts and are proven electrocatalysts for the hydrogen evolution reaction (HER). MoS2, [13,14] incomplete cubane [Mo3S4] 4+ clusters, molecular molybdenum catalysts, and amorphous MoS2 made by a reduction of MoS3 [19] have been shown to be active HER catalysts. Highly active HER catalysts, including Pt, have a Gibbs free energy of H adsorption (DGH) close to zero. [14] Density functional theory calculations show that the equatorial sulfur atoms in Fe–Mo cofactors in nitrogenase enzymes as well as the bridging S atom on the edge sites of MoS2 bind H atoms with DGH 0. These calculations, coupled with scanning tunneling microscopy (STM) studies, have indicated that molybdenum sulfide based hydrodesulfurization and HER catalysts derive their activities from under-coordinated atoms. Recent investigations of MoS2 nanoparticles using STM combined with electrochemical measurements have revealed that HER activity scales with the number of edge sites, rather than nanoparticle area, adding substantial evidence that undercoordination is critical to activity. There is also substantial current interest in molecularly thick and structurally disordered metal oxide and sulfide layers supported on electrodes, surfaces, and nanoparticles as potential catalysts for the HER and oxygen evolution reaction (OER). Such ultrathin films can support a variety of unusual and possibly favorable bonding geometries and may retain flexibility in healing and recovering. Despite their potential, such systems remain very difficult to characterize, impeding reproducibility and the communication of results between groups. Mechanisms are difficult to pin down when structural and electronic characterization is lacking. In this work, we use X-ray absorption techniques to obtain structural information on a catalytically active disordered molybdenum chalcogenide species that was grown on a wellcontrolled seeded quantum rod photosensitizer system with very high surface area. The high surface area of the colloidal system enables us to employ a variety of X-ray characterization techniques. Yet the system is also well-defined: Amorphous layers of MoS3 are deposited on quantumcontrolled photosensitizers. We take advantage of recent work showing that cadmium chalcogenide nanocrystals can be engineered to systematically control the separation of photogenerated holes and electrons, thus allowing us to modulate the photochemical yield of hydrogen. Nanorods of CdS grown on CdSe seeds with varying diameters and pure CdS nanorods of differing length were synthesized by a seeded-growth method previously reported. These particles have been of interest as a model system for investigating photochemical HER because their [*] Dr. M. L. Tang, D. C. Grauer, Dr. L. Amirav, Prof. J. R. Long, Prof. A. P. Alivisatos Department of Chemistry, University of California, Berkeley Material Sciences, Lawrence Berkeley National Laboratory (LBNL) Berkeley, CA 94720 (USA) E-mail: alivis@berkeley.edu jyano@lbl.gov

The thermoelectric properties of the tetradymite-type Bi2−xSbxTe2S solid solution (0 ≤ x ≤ 2) are reported for the temperature range 5–300 K. The properties of non-stoichiometric, Cl and Sn doped n- and p-type variants are reported as well. The Seebeck coefficients for these materials range from −170 to +270 μV K−1 while the resistivities range from those of semimetals, 2 mΩ cm, to semiconductors, >1000 mΩ cm. Thermal conductivities were low for most compositions, typically 1.5 W m−1 K−1. Nominally undoped Bi2Te2S shows the highest thermoelectric efficiency amongst the tested materials with a ZT = 0.26 at 300 K that decreased to 0.04 at 100 K. The crystal structure of Sb2Te2S, a novel tetradymite-type material, is also reported.

Helical Dirac fermions—charge carriers that behave as massless relativistic particles with an intrinsic angular momentum (spin) locked to its translational momentum—are proposed to be the key to realizing fundamentally new phenomena in condensed matter physics. Prominent examples include the anomalous quantization of magneto-electric coupling, half-fermion states that are their own antiparticle, and charge fractionalization in a Bose– Einstein condensate, all of which are not possible with conventional Dirac fermions of the graphene variety. Helical Dirac fermions have so far remained elusive owing to the lack of necessary spin-sensitive measurements and because such fermions are forbidden to exist in conventional materials harbouring relativistic electrons, such as graphene or bismuth. It has recently been proposed that helical Dirac fermions may exist at the edges of certain types of topologically ordered insulators—materials with a bulk insulating gap of spin–orbit origin and surface states protected against scattering by time-reversal symmetry—and that their peculiar properties may be accessed provided the insulator is tuned into the so-called topological transport regime. However, helical Dirac fermions have not been observed in existing topological insulators. Here we report the realization and characterization of a tunable topological insulator in a bismuthbased class of material by combining spin-imaging and momentum-resolved spectroscopies, bulk charge compensation, Hall transport measurements and surface quantum control. Our results reveal a spin-momentum locked Dirac cone carrying a nontrivial Berry’s phase that is nearly 100 per cent spin-polarized, which exhibits a tunable topological fermion density in the vicinity of the Kramers point and can be driven to the long-sought topological spin transport regime. The observed topological nodal state is shown to be protected even up to 300 K. Our demonstration of room-temperature topological order and non-trivial spintexture in stoichiometric Bi_2Se_3.M_x (M_x indicates surface doping or gating control) paves the way for future graphene-like studies of topological insulators, and applications of the observed spinpolarized edge channels in spintronic and computing technologies possibly at room temperature.

The NFO WebScope is a Web-based observatory which has been in use since 2004 December. The telescope is an 0.6 m Group 128 Cassegrain reflector with a new drive and control system. By optical modifications and appropriate image treatment, we have been able to reach a differential photometric accuracy of about 0.005 mag per observation in work on eclipsing binary stars. In addition, middle school, high school, college, graduate students, and public school teachers use this telescope to conduct their astronomical research projects under a NASA IDEAS grant.

International audience; We report on the analysis of multisite time-series photometry of the pulsating pre-white dwarf (GW Vir star) PG 1707+427, obtained by the Whole Earth Telescope collaboration. This is the last of the known GW Vir stars without surrounding nebulae to be resolved by multisite data. Successful resolution of the pulsation spectrum resulted from the combination of high signal-to-noise observations with a large telescope and wide coverage in longitude with smaller telescopes. We find a series of 8 pulsation frequencies (along with two nonlinear combination frequencies), and identify 7 of them as part of a sequence of l=1 modes, with a common period spacing of 23.0 s. This spacing implies that the mass of PG 1707+427 is 0.57 M&sun;. Preliminary model fits suggest that the mass determined via asteroseismology is consistent with the mass determined from spectroscopy combined with evolutionary tracks.

This paper presents empirical results from a deep imaging survey of galaxies in the local universe at the J and Ks wavelengths. Three hundred ninety-one images have been obtained and calibrated using the same camera and filter set with the Steward Observatory 1.6 m Kuiper Telescope on Mount Bigelow and the 2.3 m Bok Telescope on Kitt Peak. The limiting magnitude is typically 22 mag arcsec-1 at J and 21 mag arcsec-1 at Ks. The central surface brightness, apparent magnitudes, sizes, scale lengths, and inclinations are tabulated from measurements made using these data. The purpose of this paper is to provide basic near-infrared data on a variety of galaxy types.

We report the identification of cyclical changes in the orbital period of the eclipsing dwarf novae V2051 Ophiuchi and V4140 Sagitarii. We used sets of white dwarf mid-eclipse timings to construct observed-minus-calculated diagrams covering, respectively, 25 and 16 years of observations. The V2051 Oph data present cyclical variations that can be fitted by a linear plus sinusoidal function with period 22 +/- 2 yr and amplitude 17 +/- 3 s. The statistical significance of this period by an F-test is larger than 99.9 per cent. The V4140 Sgr data present cyclical variations of similar amplitude and period 6.9 +/- 0.3 yr which are statistically significant at the 99.7 per cent level. We derive upper limits for secular period changes of |dP/dt| < 3x10^{-12} and |dP/dt| < 1.8x10^{-11}, respectively for V2051 Oph and V4140 Sgr. We combined our results with those in the literature to construct a diagram of the amplitude versus period of the modulation for a sample of 11 eclipsing cataclysmic variables (CVs). If the cyclical period changes are the consequence of a solar-type magnetic activity cycle in the secondary star, then magnetic activity is a widespread phenomenon in CVs, being equally common among long- and short-period systems. This gives independent evidence that the magnetic field (and activity) of the secondary stars of CVs do not disappear when they become fully convective. We also find that the fractional cycle period changes of the short-period CVs are systematically smaller than those of the long-period CVs., 9 pages, 4 postscript figures, coded with MNRAS latex style file. To appear in Monthly Notices of the Royal Astronomical Society

The SIRTF Nearby Galaxy Survey is a comprehensive infrared imaging and spectroscopic survey of 75 nearby galaxies. Its primary goal is to characterize the infrared emission of galaxies and their principal infrared-emitting components, across a broad range of galaxy properties and star formation environments. SINGS will provide new insights into the physical processes connecting star formation to the interstellar medium properties of galaxies, and provide a vital foundation for understanding infrared observations of the distant universe and ultraluminous and active galaxies. The galaxy sample and observing strategy have been designed to maximize the scientific and archival value of the data set for the SIRTF user community at large. The SIRTF images and spectra will be supplemented by a comprehensive multi-wavelength library of ancillary and complementary observations, including radio continuum, HI, CO, submillimeter, BVRIJHK, H-alpha, Paschen-alpha, ultraviolet, and X-ray data. This paper describes the main astrophysical issues to be addressed by SINGS, the galaxy sample and the observing strategy, and the SIRTF and other ancillary data products., 26 pages, 9 figures, PASP, in press

This paper introduces a continuing survey of galaxies in the local universe. Consistent deep images are being acquired for a representative sample of 321 galaxies in the Uppsala General Catalogue down to 21.7 mag arcsec-2 at Ks (2.16 μm) and 22.4 mag arcsec-2 at J (1.25 μm) using a NICMOS camera with a 38 × 38 field of view attached to the 61 inch (1.5 m) telescope on Mount Bigelow. We provide some examples of the results being obtained by employing 64 deep images of a subset of 44 galaxies. Bulge-to-disk ratios are tabulated for 30 galaxies. The brightness of the central region of 44 galaxies declines approximately 5 mag from Hubble type S0 to Sm. An exponential vertical scale height at Ks is found to be 500 pc for the disk of UGC 5173. Arm amplitudes of four nearly face-on spiral galaxies are found to range between 11% and 88% compared to the interarm region. There is some evidence that the arm amplitude is larger at Ks than it is at J. Color gradients are measured for 15 galaxies with only one showing a significant nonzero result. A measurement of galactic symmetry applied to 64 deep images reveals an average asymmetry of 7.6% (σ = 4.6%) for these galaxies.

The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and compositions, critical to understanding post-main-sequence evolution, along with their cooling rates, which will allow us to calibrate their ages directly. The most important set of white dwarf variables to measure are the oldest of the pulsators, the cool DA variables (DAVs), which have not been explored previously through asteroseismology due to their complexity and instability. Through a time-series photometry data set spanning 10 yr, we explore the pulsation spectrum of the cool DAV, G29-38 and find an underlying structure of 19 (not including multiplet components) normal-mode, probably l=1 pulsations amidst an abundance of time variability and linear combination modes. Modeling results are incomplete, but we suggest possible starting directions and discuss probable values for the stellar mass and hydrogen layer size. For the first time, we have made sense out of the complicated power spectra of a large-amplitude DA pulsator. We have shown that its seemingly erratic set of observed frequencies can be understood in terms of a recurring set of normal-mode pulsations and their linear combinations. With this result, we have opened the interior secrets of the DAVs to future asteroseismological modeling, thereby joining the rest of the known white dwarf pulsators.

A sensitive spectropolarimetric search for magnetic fields has been carried out on a selection of pulsating white dwarfs of both DAV and DBV spectral types. Despite multiple epochs and uncertainties as low as σBe=1 kG, the observations succeed only in setting upper limits for the fields present on G22629, GD 385, ZZ Ceti, and GD 358. The results are inconsistent with a global magnetic field of the strength suggested by the pulsation spectrum of ZZ Ceti, and they approach in sensitivity the field inferred as existing on GD 358. However, if, as has been proposed, magnetic fields can be generated in many white dwarfs by dynamo action, they could be so tangled in structure as to go undetected by direct observational means.

We present our analysis of 240 hr of white-light, high-speed photometry of the dwarf nova-like helium variable PG 1346+082 (CR Boo). We identify two frequencies in the low-state power spectrum, at 679.670 ± 0.004 μHz and 669.887 ± 0.008 μHz. The 679.670 μHz variation is coherent over at least a 2 week time span, the first demonstration of a phase-coherent photometric variation in any dwarf nova-like interacting binary white dwarf system. The high-state power spectrum contains a complex fundamental with a frequency similar, but not identical, to the low-state spectrum, and a series of harmonics not detected in low state. We also uncover an unexpected dependence of the high-frequency power's amplitude and frequency structure on overall system magnitude. We discuss these findings in light of the general AM CVn system model, particularly the implications of the high-order harmonics on future studies of disk structure, mass transfer, and disk viscosity.

A cobalt-sulfide (Co-S) film prepared via electrochemical deposition on conductive substrates is shown to behave as an efficient and robust catalyst for electrochemical and photoelectrochemical hydrogen generation from neutral pH water. Electrochemical experiments demonstrate that the film exhibits a low catalytic onset overpotential (η) of 43 mV, a Tafel slope of 93 mV/dec, and near 100% Faradaic efficiency in pH 7 phosphate buffer. Catalytic current densities can approach 50 mA/cm2 and activity is maintained for at least 40 h. The catalyst can also be electrochemically coated on silicon, rendering a water-compatible photoelectrochemical system for hydrogen production under simulated 1 sun illumination. The facile preparation of this Co-S film, along with its low overpotential, high activity, and long-term aqueous stability, offer promising features for potential use in solar energy applications. © 2013 American Chemical Society.

This paper presents the results of high speed photo­ metric observations of the cool variable DA white dwarf (DAV) GD 154 obtained with the Whole Earth Telescope. GD 154 is one of the c;oolest pulsating DA white dwarfs and its study is important for understanding the red edge of the ZZ Ceti insta­ bility strip. Its power spectrum is dominated by three indepen­ dent modes (P 1 = 1186.5s, Pz = 1088.6s and P3 = 402.6s), and their harmonics and linear combinations. None of the half-integer harmonics reported in previous observations were present during the WET campaign. We propose that the ob­ served modes are trapped in the thin outer hydrogen layers. From the resulting identification of the pulsation modes, one derives an estimate of the rotation period (2.3 days) and of the mass ofthe outer hydrogen layer (2 X w-IO M *).

A new technique is described for arthroscopic reduction and internal fixation (ARIF) of avulsion fractures involving the insertion of the anterior cruciate ligament (ACL). Conventional methods of treatment of ACL avulsion in adults may lead to suboptimal results owing to stiffness from either prolonged immobilization or the morbidity of arthrotomy. Contemporary techniques of arthroscopic reduction and percutaneous pinning do not achieve rigid fixation and thus still require cast immobilization. The placement of cannulated screws through the anteromedial arthroscopic portal provides rigid fixation while avoiding arthrotomy, allowing early mobilization and return to activity. The possibility of interstitial damage to the ACL and implications regarding tensioning of the ligament are considered A typical case illustrates ARIF of ACL avulsion. The technique minimizes morbidity and optimizes function.

The ZZ Ceti stars form a class of variable white dwarfs: the hydrogen dominated atmosphere ones, which do pulsate in an instability strip in the effective temperature range 13000K-11500K. We know 22 such ZZ Ceti white dwarfs. Their variations are caused by nonradial g-mode pulsations with periods are in the range 100-1000 seconds.A subsample of the ZZ Ceti stars shows amplitude variations on time scales of the order of one month. These variations could be driven by nonlinear phenomena.

We show that the strongly spin-orbit coupled materials Bi_2Te_3 and Sb_2Te_3 and their derivatives belong to the Z_2 topological-insulator class. Using a combination of first-principles theoretical calculations and photoemission spectroscopy, we directly show that Bi_2Te_3 is a large spin-orbit-induced indirect bulk band gap (δ∼150 meV) semiconductor whose surface is characterized by a single topological spin-Dirac cone. The electronic structure of self-doped Sb_2Te_3 exhibits similar Z_2 topological properties. We demonstrate that the dynamics of spin-Dirac fermions can be controlled through systematic Mn doping, making these materials classes potentially suitable for topological device applications.

We show that the strongly spin-orbit coupled materials Bi2Te3 and Sb2Te3 and their derivatives belong to the Z2 topological-insulator class. Using a combination of first-principles theoretical calculations and photoemission spectroscopy, we directly show that Bi2Te3 is a large spin-orbit-induced indirect bulk band gap (delta approximately 150 meV) semiconductor whose surface is characterized by a single topological spin-Dirac cone. The electronic structure of self-doped Sb2Te3 exhibits similar Z2 topological properties. We demonstrate that the dynamics of spin-Dirac fermions can be controlled through systematic Mn doping, making these materials classes potentially suitable for topological device applications.

Recent experiments and theories have suggested that strong spin–orbit coupling effects in certain band insulators can give rise to a new phase of quantum matter, the so-called topological insulator, which can show macroscopic quantum-entanglement effects. Such systems feature two-dimensional surface states whose electrodynamic properties are described not by the conventional Maxwell equations but rather by an attached axion field, originally proposed to describe interacting quarks. It has been proposed that a topological insulator with a single Dirac cone interfaced with a superconductor can form the most elementary unit for performing fault-tolerant quantum computation. Here we present an angle-resolved photoemission spectroscopy study that reveals the first observation of such a topological state of matter featuring a single surface Dirac cone realized in the naturally occurring Bi_2Se_3 class of materials. Our results, supported by our theoretical calculations, demonstrate that undoped Bi_2Se_3 can serve as the parent matrix compound for the long-sought topological device where in-plane carrier transport would have a purely quantum topological origin. Our study further suggests that the undoped compound reached via n-to-p doping should show topological transport phenomena even at room temperature.

To generate monoclonal antibodies, immunogen fractions were purified from embryonic chick retinae by temperature-induced detergent-phase separation employing Triton X-114. Under reducing conditions, the monoclonal antibody (mAb) 2M6 identifies a protein doublet at 40 and 46×103Mr, which appears to form disulfide-coupled multimers. The 2M6 antigen is regulated developmentally during retinal histogenesis and its expression correlates with Müller glial cell differentiation. Isolated glial endfeet and retinal glial cells in vitro were found to be 2M6-positive, identified with the aid of the general glia marker mAb R5. mAb 2M6 does not bind to any other glial cell type in the CNS as judged from immunohistochemical data. Cell-type specificity was further substantiated by employing retinal explant and single cell cultures on laminin in conjunction with two novel neuron-specific monoclonal antibodies. MAb 2M6 does not bind either to neurites or to neuronal cell bodies. Incubation of retinal cells in vitro with bromodeoxyuridine (BrdU) and subsequent immunodouble labeling with mAb 2M6 and anti-BrdU reveal that mitotic Müller cells can also express the 2M6 antigen. To investigate whether Müller cell differentiation depends on interactions with earlier differentiating ganglion cells, transections of early embryonic optic nerves in vivo were performed. This operation eliminates ganglion cells. Müller cell development and 2M6 antigen expression were not affected, suggesting a ganglion-cell-independent differentiation process. If, however, the optic nerve of juvenile chicken was crushed to induce a transient degeneration/regeneration process in the retina, a significant increase of 2M6 immunoreactivity became evident. These data are in line with the hypothesis that Müller glial cells, in contrast to other distinct glial cell types, might facilitate neural regeneration.

The control of innate immune responses through activation of the nuclear transcription factor NF-κB is essential for the elimination of invading microbial pathogens. We showed that the bacterialN-(3-oxo-dodecanoyl) homoserine lactone (C12) selectively impairs the regulation of NF-κB functions in activated mammalian cells. The consequence is specific repression of stimulus-mediated induction of NF-κB–responsive genes encoding inflammatory cytokines and other immune regulators. These findings uncover a strategy by which C12-producing opportunistic pathogens, such asPseudomonas aeruginosa, attenuate the innate immune system to establish and maintain local persistent infection in humans, for example, in cystic fibrosis patients.

As first pointed out by Warner (1985), the overall properties of CP Pup and V1500 Cyg are very similar: both were very fast, very large amplitude novae with ~ 0.3 mag photometric humps at roughly the orbital period. Neither variation is strictly periodic (Patterson 1979; Warner 1985). Variable circular polarization (with period slightly different from the orbital period) has been found in V1500 Cyg showing that its white dwarf is strongly magnetic and has broken synchronism with the secondary star (Stockman, Schmidt & Lamb 1988). In contrast, no circular polarization has been found in CP Pup. Nonetheless, does the slight difference between the photometric and spectroscopic periods indicate it is also a magnetic system (Warner 1985; Bianchini et al. 1985a)? New photometric and spectroscopic data for CP Pup are reported which resolve the aliases and confusion in the periods found by Bianchini et al. (1985a,b), Warner (1985) and Duerbeck et al. (1987) and allow an examination of the evidence for its magnetic nature.

The four known pulsators lie at 80, 000 K < Teff < 160, 000 K and 6 < log g < 8, or about 1.5 < log L/L < 3, in the HR diagram. Our non-pulsating DO white dwarfs may be outside the temperature range of the instability strip, being slightly cooler than the GW Vir pulsators (or slightly hotter in the case of H 1504+65).The non-pulsating planetary nuclei have high temperatures and show helium and carbon features in their spectra, but are more luminous than the pulsators, since they have decidedly lower surface gravities.

On the basis of our preliminary analysis of the harmonic structure, we suggest that the 1493 s oscillation is either the orbital period of the system or the rotation period of a magnetized, accreting white dwarf. The 1471 s is most probably a nonradial oscillation of the primary white dwarf since its character mimics that of oscillations seen in single DB variables.

Context. PG 1159-035, a pre-white dwarf with Teff ≃ 140000 K, is the prototype of both two classes: the PG 1159 spectroscopic class and the DOV pulsating class. Previous studies of PG 1159-035 photometric data obtained with the Whole Earth Telescope (WET) showed a rich frequency spectrum allowing the identification of 122 pulsation modes. Analyzing the periods of pulsation, it is possible to measure the stellar mass, the rotational period and the inclination of the rotation axis, to estimate an upper limit for the magnetic field, and even to obtain information about the inner stratification of the star. Aims. We have three principal aims: to increase the number of detected and identified pulsation modes in PG 1159-035, study trapping of the star's pulsation modes, and to improve or constrain the determination of stellar parameters. Methods. We used all available WET photometric data from 1983, 1985, 1989. 1993 and 2002 to identify the pulsation periods. Results. We identified 76 additional pulsation modes, increasing to 198 the number of known pulsation modes in PG 1159-035, the largest number of modes detected in any star besides the Sun. From the period spacing we estimated a mass M/M⊙= 0.59 ±0.02 for PG 1159-035, with the uncertainty dominated by the models, not the observation. Deviations in the regular period spacing suggest that some of the pulsation modes are trapped, even though the star is a pre-white dwarf and the gravitational settling is ongoing. The position of the transition zone that causes the mode trapping was calculated at rc/R* = 0.83 ± 0.05. From the multiplet splitting, we calculated the rotational period Prot = 1.3920 ± 0.0008 days and an upper limit for the magnetic field, B < 2000 G. The total power of the pulsation modes at the stellar surface changed less than 30% for ℓ = 1 modes and less than 50% for ℓ = 2 modes. We find no evidence of linear combinations between the 198 pulsation mode frequencies. PG 1159-035 models have not significative convection zones, supporting the hypothesis that nonlinearity arises in the convection zones in cooler pulsating white dwarf stars., La lista completa de autores que integran el documento puede consultarse en el archivo., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata

WOS: 000182039700036, We have acquired new time series photometry of the two pulsating DB white dwarf stars KUV 05134+2605 and PG 1654+160 with the Whole Earth Telescope. Additional single-site photometry is also presented. We use all these data plus all available archival measurements to study the temporal behaviour of the pulsational amplitudes and frequencies of these stars for the first time. We demonstrate that both KUV 05134+2605 and PG 1654+160 pulsate in many modes, the amplitudes of which are variable in time; some frequency variability of PG 1654+160 is also indicated. Beating of multiple pulsation modes cannot explain our observations; the amplitude variability must therefore be intrinsic. We cannot find stable modes to be used for determinations of the evolutionary period changes of the stars. Some of the modes of PG 1654+160 appear at the same periods whenever detected. The mean spacing of these periods (approximate to40 s) suggests that they are probably caused by non-radial gravity-mode pulsations of spherical degree l = 1. If so, PG 1654+160 has a mass around 0.6 M.. The time-scales of the amplitude variability of both stars (down to two weeks) are consistent with theoretical predictions of resonant mode coupling, a conclusion which might however be affected by the temporal distribution of our data.

The pulsating DAV white dwarf G185-32 was observed with the Whole Earth Telescope in 1992, during XCov8. We briefly report on the weighted Fourier transform of the data obtained.

The pulsating PG 1159 planetary nebula central star RXJ 2117+3412 has been observed over three successive seasons of a multisite photometric campaign. The asteroseismological analysis of the data, based on the 37 identified l = 1 modes among the 48 independent pulsation frequencies detected in the power spectrum, leads to the derivation of the rotational splitting, the period spacing and the mode trapping cycle and amplitude, from which a number of fundamental parameters can be deduced. The average rotation period is 1.16 ± 0.05 days. The trend for the rotational splitting to decrease with increasing periods is incompatible with a solid body rotation. The total mass is 0.56⁺⁰˙⁰²₋₀.₀₄ Mѳ and the He-rich envelope mass fraction is in the range 0.013–0.078 M*. The luminosity derived from asteroseismology is log(L/Lѳ) = 4.05⁺⁰˙²³₋₀.₃₂ and the distance 760⁺²³⁰₋₂₃₅ pc. At such a distance, the linear size of the planetary nebulae is 2.9 ± 0.9 pc. The role of mass loss on the excitation mechanism and its consequence on the amplitude variations is discussed.

We report the analysis of 154 hours of nearly continuous high-speed photometric data on the pulsating DB white dwarf (DBV) GD 358 obtained during the Whole Earth Telescope (WET) run of May 1990. The Fourier transform (FT) of the light curve is dominated by power in the range from 1200 – 1700μHz with more than 180 significant peaks in the total transform. We also see significant power at the sums and differences of the dominant frequencies, indicating the importance of nonlinear behavior. We can use this data to obtain an accurate total stellar mass, and surface He layer mass. The implied surface He layer mass, if correct, provides a significant and surprising challenge to stellar evolution theory, as well as the theory of chemical mixing.

Pharmaceutical prices in the United States are under evaluation as policy makers decide how to reduce health care expenditures and public subsidy of the pharmaceutical industry. Furthermore, evidence of higher drug prices in the United States, compared with those in other countries, fuels the prescription drug price debate. These issues are not new to the public forum and much can be learned from prior debates and policies. This paper begins by reviewing the pricing debate with the Kefauver hearings on monopolies held during the late 1950s and early 1960s and continues with the current price debate. Government reports and academic studies are discussed, addressing the methodological differences and their implications to policy makers. Finally, the literature review includes foreign government prescription drug programs with their respective prescription drug expenditures. Evidence provided by academics about the pricing practices of the drug manufacturers indicates product quality and price information would force firms to compete on the price level, thus reducing pharmaceutical product pricing to the "true" market price.

PG2303+243 is a pulsating DA white dwarf (or ZZ Ceti), located on the cool side of the instability strip. Due to the potential interest of that star for asteroseismologic analysis, we reobserved PG2303+243. The improved time resolution (4 µHz) of this new set of data allows the detection of as many as 22 periods. A preliminary analysis, using the most recently available studies of linear adiabatic non radial pulsations in stratified white dwarfs, is presented. We suggest that 18 of the 22 modes observed, may be identified as g-modes of 1 = 1, 2, 3 and 4, trapped, or partially-trapped in the outer hydrogen envelope. From the data presented in this paper we derive a preliminary value — 8.7 ≤ logQ H ≤— 7.6 for the hydrogen envelope mass.

Twenty-two patients sustained injury to the biceps tendon, rotator cuff interval, or superior labrum. Seven patients with "interval lesions" underwent biceps tenodesis, one biceps repair, and three subscapularis repairs. All were satisfied, although one tenodesis failed with distal biceps retraction. Key arthroscopic findings included biceps or subscapularis fraying. Thirteen patients with "S.L.A.P. (superior labrum anterior to posterior) lesions" underwent labral debridement. All but one obtained pain relief. Eight cadaveric shoulders exhibited extreme anatomic variability of the bicipital origin/superior labral attachment. Biomechanical study showed anterior-superior and posterior-superior labral strain with simulated biceps contraction to be greatest in shoulder abduction (p < 0.01). Biceps tendon strain was greatest in shoulder adduction (p < 0.05). A continuum of injuries to the biceps tendon exist, from the rotator cuff interval to the labral attachment. Key arthroscopic findings may assist in the difficult diagnosis of interval lesions. Individual anatomy and mechanism of injury may determine the site of the lesion.

We have measured the cooling rate of the 13,000K DA white dwarf G117-B15A by measuring the rate of period change with time for the main pulsation of this ZZ Ceti star, using the Whole Earth Telescope. The observed rate of period change is larger than the predictions of g-mode pulsation theory applied to C/O core white dwarf models.

We report the first results of the Whole Earth Telescope observations of AM CVn in March/April 1990. The Fourier Spectrum of the light curve shows harmonically related peaks. High frequency sidebands with the fine-splitting of 21 µHz are observed for the fundamental period of 1051 s and its 4 lowest harmonics. These have not been observed before. The fundamental period itself is not detected.

The unusual variable star AM CVn has puzzled astronomers for over 40 years. This object, both a photometric and spectroscopic variable, is believed to contain a pair of hydrogen-deficient white dwarfs of extreme mass ratio, transferring material via an accretion disk. We examine the photometric properties of AM CVn, analyzing 289 hours of high-speed photometric data spanning 1976 to 1992. The power spectrum displays significant peaks at 988.7, 1248.8, 1902.5, 2853.8, 3805.2, 4756.5, and 5707.8 microHz (1011.4, 800.8, 525.6, 350.4, 262.8, 210.2, and 175.2 s). We find no detectable power at 951.3 microHz (1051 s), the previously reported main frequency. The 1902.5, 2853.9, and 3805.2 microHz peaks are multiplets, with frequency splitting in each case of 20.77 +/- 0.05 microHz. The 1902.5 microHz seasonal pulse shapes are identical, within measurement noise, and maintain the same amplitude and phase as a function of color. We have determined the dominant frequency to be 1902.50902 +/- 0.00001 microHz with dot P = +1.71 (+/- 0.04) x 10(exp -11) s/s. We discuss the implications of these findings on a model for AM CVn.

We report on the analysis of 154 hours of early continuous high-speed photometry on the pulsating DB white dwarf (DBV) GD 358, obtained during the Whole Earth Telescope (WET) run of 1990 May. The power spectrum of the light curve is dominated by power in the range from 1000 to 2400 microHz with more than 180 significant peaks in the total spectrum. We identify all of the triplet frequencies as degree l = 1, and from the details of their spacings we derive the total stellar mass as 0.61 + or - 0.03 solar mass, the mass of the outer helium envelope as 2.0 + or - 1.0 x 10(exp -6) M(sub *), the absolute luminosity as 0.050 + or - 0.012 solar luminosity and the distance as 42 + or - 3 pc. We find strong evidence for differential rotation in the radial direction -- the outer envelope is rotating at least 1.8 times faster than the core -- and we detect the presence of a weak magnetic field with a strength of 1300 + or - 300 G. We also find a significant power at the sums and differences of the dominant frequencies, indicating nonlinear processes are significant, but they have a richness and complexity that rules out resonant mode coupling as a major cause.

Photometric observations and analysis of the optical, UV, EUV, and X-ray spectra are presented for the EUV/X-ray source RE 1016-53. Multiwavelength observations of RE 1016-53 point out that it is a precataclysmic binary. Optical spectra exhibit the steep blue continuum and Balmer absorption typical of a hot white dwarf, but there are bright, narrow emission lines of H I, He I, and Ca II superimposed on this. The white dwarf component, with T (eff) = 55,800 +/- 1000 K and log g = 7.81 +/- 0.007, dominates the spectrum from the optical to the EUV/X-ray. An He II 4686 A absorption line suggests that the white dwarf is a hydrogen-helium (DAO) hybrid star. Four of the five precataclysmic binaries with white dwarfs with T(eff) greater than 40,000 K appear to be DAOs. A mass of 0.57 +/- 0.003 solar mass has been derived.

For many years VY Aquarii has been regarded as a charter member of the class fo recurrent novae, because it erupted several times, with outburst amplitudes of ~8 mag, exceeding those normally attributed to dwarf novae. We present observations obtained both in quiescence and eruption that emphasize the great similarity of the star to well-credentialed dwarf novae like WZ Sagittae. Long-term visual and photographic coverage shows two types of eruptions, differing in brightness and timescale by a factor of ~5. A transient wave in the quiescent light curve suggests a period in the range 80-120 minutes, which could be the orbital period of the underlying binary. Photometry during a long eruption in 1986 showed a large-amplitude modulation ("superhump") with a period of 92.7 (or possibly 99.1) minutes, which slowly decreased during the eruption. These are normal signatures of SU Ursae Majoris stars, a subclass of dwarf novae. The superhumps observed in SU UMa stars appear to show a similar degree of period instability, such that P ~ -(3-10)X10-5. Perhaps a more physically significant expression of this is a period-magnitude law: the periods decrease by 0.64±0.10% per magnitude of decline,_ at least during the early decline. This is a plausible decrease to expect from the precessing-disk model for the origin of superhumps, assuming the disk to be largest near maximum light.

The pulsating pre-white dwarf star PG 1707+427 has been observed with time-series photometry for more than 291 hr spanning four observing seasons (1987-1990). The principal pulsational band of periods near 448 s, found in earlier data, was observed to vary regularly in amplitude, suggesting that it was unresolved. By dividing the data into separate blocks of time, we were able to resolve this peak into two components (A and B) with periods near 447.16 and 448.95 s. Both modes appeared to be relatively constant in amplitude to the accuracy of our measurements over the observed span of time