Second LDEF Post-Retrieval Symposium interim results of experiment A0034

Thermal control coatings and contaminant collector mirrors were exposed on the leading and trailing edge modules of Long Duration Exposure Facility (LDEF) experiment A0034 to provide a basis of comparison for investigating the role of atomic oxygen in the stimulation of volatile outgassing products. The exposure of identical thermal coatings on both the leading and trailing edges of the LDEF and the additional modified exposure of identical coatings under glass windows and metallic covers in each of the flight modules provided multiple combinations of space environmental exposure to the coatings and the contaminant collector mirrors. Investigations were made to evaluate the effects of the natural space and the induced environments on the thermal coatings and the collector mirrors to differentiate the sources of observed material degradation. Two identical flight units were fabricated for the LDEF mission, each of which included twenty-five thermal control coatings mounted in isolated compartments, each with an adjacent contaminant collector mirror mounted on the wall. The covers of the flight units included apertures for each compartment, exposing the thermal coatings directly to the space environment. Six of these compartments were sealed with ultraviolet-grade transmitting quartz windows and four other compartments were sealed with aluminum covers. One module of this passive LDEF experiment, occupying one-sixth of a full tray, was mounted in Tray C9 (leading edge), while the other identical module was mounted in Tray C3 (trailing edge)

The radio emission from the Galaxy at 22 MHz

We present maps of the 22MHz radio emission between declinations -28d and +80d, covering ~73% of the sky, derived from observations with the 22MHz radiotelescope at the Dominion Radio Astrophysical Observatory (DRAO). The resolution of the telescopt (EWxNS) is 1.1d x 1.7d secant(zenith angle). The maps show the large scale features of the emission from the Galaxy including the thick non-thermal disk, the North Polar Spur (NPS) and absorption due to discrete HII regions and to an extended band of thermal electrons within 40d of the Galactic centre. We give the flux densities of nine extended supernova remnants shown on the maps

The most massive galaxies in clusters are already fully grown at z∼0.5z \sim 0.5

By constructing scaling relations for galaxies in the massive cluster MACSJ0717.5 at $z=0.545$ and comparing with those of Coma, we model the luminosity evolution of the stellar populations and the structural evolution of the galaxies. We calculate magnitudes, surface brightnesses and effective radii using HST/ACS images and velocity dispersions using Gemini/GMOS spectra, and present a catalogue of our measurements for 17 galaxies. We also generate photometric catalogues for $\sim 3000$ galaxies from the HST imaging. With these, we construct the colour-magnitude relation, the fundamental plane, the mass-to-light versus mass relation, the mass-size relation and the mass-velocity dispersion relation for both clusters. We present a new, coherent way of modelling these scaling relations simultaneously using a simple physical model in order to infer the evolution in luminosity, size and velocity dispersion as a function of redshift, and show that the data can be fully accounted for with this model. We find that (a) the evolution in size and velocity dispersion undergone by these galaxies between $z \sim 0.5$ and $z \sim 0$ is mild, with $R_e(z) \sim (1+z)^{-0.40\pm0.32}$ and $\sigma(z) \sim (1+z)^{0.09 \pm 0.27}$, and (b) the stellar populations are old, $\sim 10$ Gyr, with a $\sim 3$ Gyr dispersion in age, and are consistent with evolving purely passively since $z \sim 0.5$ with $\Delta \log M/L_B = -0.55_{-0.07}^{+0.15} z$. The implication is that these galaxies formed their stars early and subsequently grew dissipationlessly so as to have their mass already in place by $z \sim 0.5$, and suggests a dominant role for dry mergers, which may have accelerated the growth in these high-density cluster environments.Comment: 20 pages; accepted for publication in MNRA

X-ray astronomy in the new Millenium. A Summary

Recent X-ray observations have had a major impact on topics ranging from protostars to cosmology. They have also drawn attention to important and general physical processes that currently limit our understanding of thermal and nonthermal X-ray sources. These include unmeasured atomic astrophysics data (wavelengths, oscillator strengths etc.), basic hydromagnetic processes (e.g. shock structure, reconnection), plasma processes (such as electron-ion equipartition and heat conduction) and radiative transfer (in disks and accretion columns). Progress on these problems will probably come from integrative studies that draw upon observations, throughout the electromagnetic spectrum, of different classes of source. X-ray observations are also giving a new perspective on astronomical subjects, like the nature of galactic nuclei and the evolution of stellar populations. They are contributing to answering central cosmological questions including the measurement of the matter content of the universe, understanding its overall luminosity density, describing its chemical evolution and locating the first luminous objects. X-ray astronomy has a healthy future with several international space missions under construction and in development.Comment: 12 page

Committee Decisions under Alternative Procedural Rules: An Experimental Study Applying a New Nonmonetary Method of Preference Inducement

Committees operating with simple majority rule procedures and with closed rule procedures are studied. A new method (the duplicate method) was used to induce preferences. The results of the control experiments compare favorably to those for which monetary incentives have been used. In all cases the core is a relatively accurate model of committee choices

Phase Diagram for Anderson Disorder: beyond Single-Parameter Scaling

The Anderson model for independent electrons in a disordered potential is transformed analytically and exactly to a basis of random extended states leading to a variant of augmented space. In addition to the widely-accepted phase diagrams in all physical dimensions, a plethora of additional, weaker Anderson transitions are found, characterized by the long-distance behavior of states. Critical disorders are found for Anderson transitions at which the asymptotically dominant sector of augmented space changes for all states at the same disorder. At fixed disorder, critical energies are also found at which the localization properties of states are singular. Under the approximation of single-parameter scaling, this phase diagram reduces to the widely-accepted one in 1, 2 and 3 dimensions. In two dimensions, in addition to the Anderson transition at infinitesimal disorder, there is a transition between two localized states, characterized by a change in the nature of wave function decay.Comment: 51 pages including 4 figures, revised 30 November 200

Human embryos from overweight and obese women display phenotypic and metabolic abnormalities

STUDY QUESTION Is the developmental timing and metabolic regulation disrupted in embryos from overweight or obese women? SUMMARY ANSWER Oocytes from overweight or obese women are smaller than those from women of healthy weight, yet post-fertilization they reach the morula stage faster and, as blastocysts, show reduced glucose consumption and elevated endogenous triglyceride levels. WHAT IS KNOWN ALREADY Female overweight and obesity is associated with infertility. Moreover, being overweight or obese around conception may have significant consequences for the unborn child, since there are widely acknowledged links between events occurring during early development and the incidence of a number of adult disorders. STUDY DESIGN, SIZE, DURATION We have performed a retrospective, observational analysis of oocyte size and the subsequent developmental kinetics of 218 oocytes from 29 consecutive women attending for ICSI treatment and have related time to reach key developmental stages to maternal bodyweight. In addition, we have measured non-invasively the metabolic activity of 150 IVF/ICSI embryos from a further 29 consecutive women who donated their surplus embryos to research, and have related the data retrospectively to their body mass index (BMI). PARTICIPANTS/MATERIALS, SETTING, METHODS In a clinical IVF setting, we compared oocyte morphology and developmental kinetics of supernumerary embryos collected from overweight and obese women, with a BMI in excess of 25 kg/m2 to those from women of healthy weight. A Primovision Time-Lapse system was used to measure developmental kinetics and the non-invasive COnsumption/RElese of glucose, pyruvate, amino acids and lactate were measured on spent droplets of culture medium. Total triglyceride levels within individual embryos were also determined. MAIN RESULTS AND THE ROLE OF CHANCE Human oocytes from women presenting for fertility treatment with a BMI exceeding 25 kg/m2 are smaller (R2 = −0.45; P = 0.001) and therefore less likely to complete development post-fertilization (P < 0.001). Those embryos that do develop reach the morula stage faster than embryos from women of a BMI < 25 kg/m2

Electric Birefringence and Electrophoretic Light Scattering for Colloid Stability Characterisation

The effect of an electric field on a dilute suspension of asymmetric colloidal particles is to impose rotational order which can be detected as an induced birefringence in the sol. Furthermore,· if the particles are charged, such rotation is followed by electrophoretic translation. In a single apparatus, pulsed electric fields have been applied to sols of the rod-like clay mineral attapulgite, and both the transient induced birefringence and the variation in the fluctuations of the scattered light have been measured. Experiments involving the addition of CTAB surfactant, resulted in the measurement of the electrical polarisability anisotropy, electrophoretic mobility, translatory and rotary diffusion coefficients as the inherent negative surface charge of the mineral particles was swept through the zero point of charge and into a positive condition. The accompanying changes in sol stability and flocculation were monitored in terms of these parameters

Recent X-Ray Observations of SN1986J with ASCA and ROSAT

We present ASCA and ROSAT observations of SN 1986J covering the period 1991 August to 1996 January. From observations with the ROSAT HRI and PSPC, we find that the 0.5-2.5 keV flux decreased proportional to $t^{-2}$ during this period; the ASCA data are consistent with this result and extend it to the 2-10 keV band. ASCA spectra from 1994 January and 1996 January are consistent with thermal emission from a solar metallicity plasma at an equilibrium temperature kT = 5-7.5 keV, somewhat hotter than that observed from other X-ray supernovae. These spectra also show a clear Fe K emission line at 6.7 keV with FWHM < 20,000 km/s (90% confidence). This limit on the line width is consistent with the reverse shock model of Chevalier & Fransson (1994), but does not rule out the clumpy wind model of Chugai (1993).Comment: 20 pages, 9 postscript figures, latex, uses aastex4.0, submitted to The Astrophysical Journa