The Ultraviolet Imaging Telescope: Instrument and Data Characteristics

The Ultraviolet Imaging Telescope (UIT) was flown as part of the Astro observatory on the Space Shuttle Columbia in December 1990 and again on the Space Shuttle Endeavor in March 1995. Ultraviolet (1200-3300 Angstroms) images of a variety of astronomical objects, with a 40 arcmin field of view and a resolution of about 3 arcsec, were recorded on photographic film. The data recorded during the first flight are available to the astronomical community through the National Space Science Data Center (NSSDC); the data recorded during the second flight will soon be available as well. This paper discusses in detail the design, operation, data reduction, and calibration of UIT, providing the user of the data with information for understanding and using the data. It also provides guidelines for analyzing other astronomical imagery made with image intensifiers and photographic film.Comment: 44 pages, LaTeX, AAS preprint style and EPSF macros, accepted by PAS

UV Colors and Extinctions of HII Regions in the Whirlpool Galaxy (M51)

Far-UV (1520 ang.), U, H-alpha, and R images of the interacting Sbc spiral galaxy M51 were obtained by the Ultraviolet Imaging Telescope (UIT) and at Mt. Laguna Observatory. The mu(152)-mu(U) radial gradient of >1 mag, becoming bluer with increasing radius, is attributed primarily to a corresponding radial extinction gradient. Magnitudes in both UV bands and H-alpha fluxes are reported for 28 HII regions. Optical extinctions for the 28 corresponding UV sources are computed from the measured m(152)-U colors by fitting to the optical extinctions of Nakai and Kuno (1995). The normalized far-UV extinction A(152)/E(B-V) increases with radius or decreasing metallicity, from 5.99 to 6.54, compared with the Galactic value 8.33. The best-fit m(152)-U color for no extinction, -3.07, is the color of a model solar metallicity starburst of age ~2.5 Myr with IMF slope -1.0. HII regions show decreasing observed H-alpha fluxes with decreasing radius, relative to the H-alpha fluxes predicted from the observed f(152) for age 2.5 Myr, after correction for extinction. We attribute the increasing fraction of ``missing'' H-alpha flux with decreasing radius to increasing extinction in the Lyman continuum. Increasing extinction-corrected far-UV flux of the HII regions with decreasing radius is probably a result of the corresponding increasing column density of the interstellar gas resulting in larger mass OB associations. The estimated dust-absorbed Lyman continuum flux is ~0.6 times the far-infrared energy flux of M51 observed by IRAS.Comment: 21 pages, 6 figures, latex, uses AASMS4 and EPS

Ultraviolet Signatures of Tidal Interaction in the Giant Spiral Galaxy, M101

We present new evidence for tidal interactions having occurred in the disk of M101 in the last 10^8 - 10^9 years. Recent imaging of the far-ultraviolet emission from M101 by the Shuttle-borne Ultraviolet Imaging Telescope (UIT) reveals with unprecedented clarity a disk-wide pattern of multiple linear arm segments (``crooked arms''). The deep FUV image also shows a faint outer spiral arm with a (``curly tail'') feature that appears to loop around the supergiant HII region NGC 5471 - linking this outlying starburst with the rest of the galaxy. These FUV-bright features most likely trace hot O & B-type stars along with scattered light from associated nebular dust. Counterparts of the outermost ``crooked arms'' are evident in maps at visible wavelengths and in the 21-cm line of HI. The inner-disk FUV arms are most closely associated with H$\alpha$ knots and the outer (downstream) sides of CO arms. Comparisons of the ``crooked arm'' and ``curly tail'' morphologies with dynamical simulations yield the greatest similitude, when the non- axisymmetric forcing comes from a combination of ``external interactions'' with one or more companion galaxies and ``internal perturbations'' from massive objects orbiting within the disk. We speculate that NGC 5471 represents one of these ``massive disturbers'' within the disk, whose formation followed from a tidal interaction between M101 and a smaller galaxy.Comment: Paper format (latex); length of paper (8); 4 gif figure files; uses aas2pp4.sty AASTeX macro file; to be published in Part I of the Astrophysical Journa

The Atacama Cosmology Telescope: Two-Season ACTPol Spectra and Parameters

We present the temperature and polarization angular power spectra measured by the Atacama Cosmology Telescope Polarimeter (ACTPol). We analyze night-time data collected during 2013-14 using two detector arrays at 149 GHz, from 548 deg$^2$ of sky on the celestial equator. We use these spectra, and the spectra measured with the MBAC camera on ACT from 2008-10, in combination with Planck and WMAP data to estimate cosmological parameters from the temperature, polarization, and temperature-polarization cross-correlations. We find the new ACTPol data to be consistent with the LCDM model. The ACTPol temperature-polarization cross-spectrum now provides stronger constraints on multiple parameters than the ACTPol temperature spectrum, including the baryon density, the acoustic peak angular scale, and the derived Hubble constant. Adding the new data to planck temperature data tightens the limits on damping tail parameters, for example reducing the joint uncertainty on the number of neutrino species and the primordial helium fraction by 20%.Comment: 23 pages, 25 figure

US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report

This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in Dark Matter" held at University of Maryland on March 23-25, 2017.Comment: 102 pages + reference

H. N. Werkman

A piece commissioned for COLDFRONT – Singular Vispo :: First Encounters. Artists were asked to talk about their introduction to Visual Poetry and the piece of work that changed the way they saw language

Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli

Cytochrome bd is a tri-heme (b558, b595, d) respiratory oxygen reductase that is found in many bacteria including pathogenic species. It couples the electron transfer from quinol to O2 with generation of an electrochemical proton gradient. We examined photolysis and subsequent recombination of CO with isolated cytochrome bd from Escherichia coli in oneelectron reduced (MV) and fully reduced (R) states by microsecond time-resolved absorption spectroscopy at 532-nm excitation. Both Soret and visible band regions were examined. CO photodissociation from MV enzyme possibly causes fast (t,1.5 ms) electron transfer from heme d to heme b595 in a small fraction of the protein, not reported earlier. Then the electron migrates to heme b558 (t,16 ms). It returns from the b-hemes to heme d with t,180 ms. Unlike cytochrome bd in the R state, in MV enzyme the apparent contribution of absorbance changes associated with CO dissociation from heme d is small, if any. Photodissociation of CO from heme d in MV enzyme is suggested to be accompanied by the binding of an internal ligand (L) at the opposite side of the heme. CO recombines with heme d (t,16 ms) yielding a transient hexacoordinate state (CO-Fe2+ -L). Then the ligand slowly (t,30 ms) dissociates from heme d. Recombination of CO with a reduced heme b in a fraction of the MV sample may also contribute to the 30-ms phase. In R enzyme, CO recombines to heme d (t,20 ms), some heme b558 (t,0.2–3 ms), and finally migrates from heme d to heme b595 (t,24 ms) in ,5% of the enzyme population. Data are consistent with the recent nanosecond study of Rappaport et al. conducted on the membranes at 640-nm excitation but limited to the Soret band. The additional phases were revealed due to differences in excitation and other experimental conditions

Is vaccine the magic bullet for malaria elimination? A reality check

Malaria remains a major health burden especially for the developing countries. Despite concerted efforts at using the current control tools, such as bed nets, anti malarial drugs and vector control measures, the disease is accountable for close to a million deaths annually. Vaccines have been proposed as a necessary addition to the armamentarium that could work towards elimination and eventual eradication of malaria in view of their historical significance in combating infectious diseases. However, because malaria vaccines would work differently depending on the targeted parasite stage, this review addresses the potential impact various malaria vaccine types could have on transmission. Further, because of the wide variation in the epidemiology of malaria across the endemic regions, this paper proposes that the ideal approach to malaria control ought to be tailor-made depending on the specific context. Finally, it suggests that although it is highly desirable to anticipate and aim for malaria elimination and eventual eradication, many affected regions should prioritize reduction of mortality and morbidity before aspiring for elimination

Has the DOTS Strategy Improved Case Finding or Treatment Success? An Empirical Assessment

Background: Nearly fifteen years after the start of WHO's DOTS strategy, tuberculosis remains a major global health problem. Given the lack of empirical evidence that DOTS reduces tuberculosis burden, considerable debate has arisen about its place in the future of global tuberculosis control efforts. An independent evaluation of DOTS, one of the most widely-implemented and longest-running interventions in global health, is a prerequisite for meaningful improvements to tuberculosis control efforts, including WHO's new Stop TB Strategy. We investigate the impact of the expansion of the DOTS strategy on tuberculosis case finding and treatment success, using only empirical data. Methods and Findings: We study the effect of DOTS using time-series cross-sectional methods. We first estimate the impact of DOTS expansion on case detection, using reported case notification data and controlling for other determinants of change in notifications, including HIV prevalence, GDP, and country-specific effects. We then estimate the effect of DOTS expansion on treatment success. DOTS programme variables had no statistically significant impact on case detection in a wide range of models and specifications. DOTS population coverage had a significant effect on overall treatment success rates, such that countries with full DOTS coverage benefit from at least an 18% increase in treatment success (95% CI: 5–31%). Conclusions: The DOTS technical package improved overall treatment success. By contrast, DOTS expansion had no effect on case detection. This finding is less optimistic than previous analyses. Better epidemiological and programme data would facilitate future monitoring and evaluation efforts