An analysis of the shapes of interstellar extinction curves. VII Milky Way spectrophotometric optical-through-ultraviolet extinction and its R-dependence

We produce a set of 72 NIR-through-UV extinction curves by combining new Hubble Space Telescope/STIS optical spectrophotometry with existing International Ultraviolet Explorer spectrophotometry (yielding gapless coverage from 1150 to 10000 ?) and NIR photometry. These curves are used to determine a new, internally consistent NIR-through-UV Milky Way mean curve and to characterize how the shapes of the extinction curves depend on R(V). We emphasize that while this dependence captures much of the curve variability, considerable variation remains that is independent of R(V). We use the optical spectrophotometry to verify the presence of structure at intermediate wavelength scales in the curves. The fact that the optical-through-UV portions of the curves are sampled at relatively high resolution makes them very useful for determining how extinction affects different broadband systems, and we provide several examples. Finally, we compare our results to previous investigations

Some Useful Sources

We have provided here an annotated list of resources, key organisations and programmes that support young fathers and details of data sources for secondary use. The information complements the citations within the individual articles in this themed section

Effect of substrate misorientation on ordering in Ga0.5In0.5P

Journal ArticleOrdering produced in Gao.5Ino.5P epitaxial layers grown by OMVPE can be controlled by variations in the substrate misorientation as well as the growth temperature and the growth rate. The ordering produced at a growth temperature of 620°C and a relatively low growth rate of 0.5 /μm/hr is found to depend strongly on both the direction and angle of substrate misorientation

New Ultraviolet Extinction Curves for Interstellar Dust in M31

New low-resolution UV spectra of a sample of reddened OB stars in M31 were obtained with HST/STIS to study the wavelength dependence of interstellar extinction and the nature of the underlying dust grain populations. Extinction curves were constructed for four reddened sightlines in M31 paired with closely matching stellar atmosphere models. The new curves have a much higher S/N than previous studies. Direct measurements of N(H I) were made using the Ly$\alpha$ absorption lines enabling gas-to-dust ratios to be calculated. The sightlines have a range in galactocentric distance of 5 to 14 kpc and represent dust from regions of different metallicities and gas-to-dust ratios. The metallicities sampled range from Solar to 1.5 Solar. The measured curves show similarity to those seen in the Milky Way and the Large Magellanic Cloud. The Maximum Entropy Method was used to investigate the dust composition and size distribution for the sightlines observed in this program finding that the extinction curves can be produced with the available carbon and silicon abundances if the metallicity is super-Solar.Comment: ApJ, in press, 9 pages, 5 figure

Electron tunneling detected by electrostatic force

Journal ArticleA method is introduced for measuring the tunneling of electrons between a specially fabricated scanning probe microscope tip and a surface. The technique is based upon electrostatic force detection of charge as it is transferred to and from a small (10217 F) electrically isolated metallic dot on the scanning probe tip. The methods for dot fabrication, charging, and discharging are described and electron tunneling to a sample surface is demonstrated

Single electron tunneling to insulator surfaces detected by electrostatic force

Journal ArticleThe detection of single-electron tunneling events between a metallic scanning probe tip and an insulating surface is demonstrated by an electrostatic force method. When a voltage-biased oscillating atomic force microscopy tip is placed within tunneling range of the surface of an insulator, single-electron tunneling events are observed between the tip and electronic states at the surface. The events cause an abrupt reduction in cantilever oscillation amplitude, due to the instantaneous reduction of the force gradient at the tip. In most cases, only a single electron tunnels to or from the surface. Experimental data show that no physical contact is made during the tunneling events

Book Usage Is Rollin’ Down: Multifaceted Assessment of Monograph Collection Performance to Optimize Purchase Decisions

Georgia State University’s print circulation has declined over 50% since 2010. Collection development librarians made several small-scale adjustments to address this trend, yet the drop off in use continued unabated. We had to totally rethink the book budget. To make changes strategically and responsibly, we needed answers to a variety of questions: Are there disciplines that do not need firm order allocations or even monographs? Does format matter? Does it matter how the titles are acquired with regard to approval versus firm order versus demand-driven acquisition (DDA)? This paper discusses the multifaceted data-driven analysis we developed in order to provide a detailed and holistic picture of monograph collection performance and buying patterns. We share how we developed our analysis, what our data revealed, and the action items generated by our activities. This paper details how to combine large data sets from multiple sources for assessment, and how combining use and acquisitions data of print and electronic monographs helped us make improved purchasing decisions at Georgia State University

Instability induced tunneling and repeatable charge injection to SiO2 surfaces by electrostatic force microscopy

Journal ArticleThe dynamic response and stability of a voltage biased oscillating cantilever in the proximity of an insulating sample surface is investigated. As the tip approaches the sample surface, the cantilever can jump between two different oscillation modes. The jump is detected as an abrupt increase in the amplitude. This abrupt increase in amplitude can bring the tip into tunneling range of the sample surface and electrons can tunnel between the metallic tip and insulator surface. The electron tunneling decreases the electrostatic force and force gradient sensed by the cantilever. These changes reduce the oscillation amplitude, causing the cantilever to return to the original oscillation mode. The tunneling of tens of electrons from a metallic tip to a SiO2 surface is detected by measuring the electrostatic force between the tip and the sample. Manipulation of a small number of electrons can be achieved by changing the polarity of the voltage applied, allowing the injection and extraction of electrons to and from an insulator surface