216 research outputs found
Developing Prospective Interim and Future Academic Library Leaders: Reflections for Leadership Practice
This chapter offers a reflective perspective about the author's experience as interim leader in an academic library, grounded in relevant discussion from the literature to present the case for the intentional practice of preparing future interim and ongoing leaders through support for developmental programs, leader modeling, mentorship, and operationalizing the role of leadership in organizational life.Ye
The Orbit, Mass, and Albedo of Transneptunian Binary 1999 RZ253
We have observed 1999 RZ253 with the Hubble Space Telescope at seven separate
epochs and have fit an orbit to the observed relative positions of this binary.
Two orbital solutions have been identified that differ primarily in the
inclination of the orbit plane. The best fit corresponds to an orbital period,
P=46.263 +0.006/-0.074 days, semimajor axis a=4,660 +/-170 km and orbital
eccentricity e=0.460 +/-0.013 corresponding to a system mass m=3.7 +/-0.4
x10^18 kg. For a density of rho = 1000 kg m^-3 the albedo at 477 nm is p = 0.12
+/-0.01, significantly higher than has been commonly assumed for objects in the
Kuiper Belt. Multicolor, multiepoch photometry shows this pair to have colors
typical for the Kuiper belt with a spectral gradient of 0.35 per 100 nm in the
range between 475 and 775 nm. Photometric variations at the four epochs we
observed were as large as 12 +/-3% but the sampling is insufficient to confirm
the existence of a lightcurve
Natural heritage assessment of wetlands and riparian areas in the Uncompahgre River Basin, A: eastern Montrose and Ouray counties, Volume 2
Includes bibliographical references.May 1999.Prepared for: Colorado Dept. of Natural Resources, by Thomas Stephens ... [et al.]
REALISTIC DETECTABILITY OF CLOSE INTERSTELLAR COMETS
During the planet formation process, billions of comets are created and ejected into interstellar space. The detection and characterization of such interstellar comets (ICs) (also known as extra-solar planetesimals or extra-solar comets) would give us in situ information about the efficiency and properties of planet formation throughout the galaxy. However, no ICs have ever been detected, despite the fact that their hyperbolic orbits would make them readily identifiable as unrelated to the solar system. Moro-Martin et al. have made a detailed and reasonable estimate of the properties of the IC population. We extend their estimates of detectability with a numerical model that allows us to consider "close" ICs, e.g., those that come within the orbit of Jupiter. We include several constraints on a "detectable" object that allow for realistic estimates of the frequency of detections expected from the Large Synoptic Survey Telescope (LSST) and other surveys. The influence of several of the assumed model parameters on the frequency of detections is explored in detail. Based on the expectation from Moro-Martin et al., we expect that LSST will detect 0.001-10 ICs during its nominal 10 year lifetime, with most of the uncertainty from the unknown number density of small (nuclei of similar to 0.1-1 km) ICs. Both asteroid and comet cases are considered, where the latter includes various empirical prescriptions of brightening. Using simulated LSST-like astrometric data, we study the problem of orbit determination for these bodies, finding that LSST could identify their orbits as hyperbolic and determine an ephemeris sufficiently accurate for follow-up in about 4-7 days. We give the hyperbolic orbital parameters of the most detectable ICs. Taking the results into consideration, we give recommendations to future searches for ICs.Peer reviewe
Evidence of Orbital Motion in the Binary Brown Dwarf Kelu-1AB
We have resolved Kelu-1 into a binary system with a separation of ~290 mas
using the Laser Guide Star Adaptive Optics system on the Keck II telescope. We
have also re-analyzed a 1998 HST observation of Kelu-1 and find that the
observed PSF is best fit by a binary object separated by 45 mas. Observations
on multiple epochs confirm the two objects share a common proper motion and
clearly demonstrate the first evidence of orbital motion. Kelu-1B is fainter
than Kelu-1A by 0.39+/-0.01 magnitudes in the K' filter and 0.50+/-0.01
magnitudes in the H filter. We derive spectral types of L2+/-1 and L3.5+/-1 for
Kelu-1A and B, respectively. The separation of flux into the two components
rectifies Kelu-1's over-luminosity problem that has been known for quite some
time. Given the available data we are able to constrain the inclination of the
system to >81 degrees and the orbital period to >~40 years.Comment: 15 pages, 3 figures, Accepted to PASP. Changes include: title, author
list, new data, more analysis, and new journa
Searching for Exosatellites Orbiting L and T Dwarfs: Connecting Planet Formation to Moon Formation and Finding New Temperate Worlds
L-type and T-type dwarfs span the boundaries between main-sequence stars,
brown dwarfs, and planetary-mass objects. For these reasons, L and T dwarfs are
the perfect laboratories for exploring the relationship between planet
formation and moon formation, and evidence suggests they may be swarming with
close-in rocky satellites, though none have been found to date. The discovery
of satellites orbiting L or T dwarfs will have transformative implications for
the nature of planets, moons and even life in the Universe. These transiting
satellites will be prime targets for characterization with NASA's James Webb
Space Telescope. In this white paper, we discuss the scientific motivations
behind searching for transiting satellites orbiting L and T dwarfs and argue
that robotizing current 1-to-2-meter US optical/infrared (O/IR) facilities and
equipping them with recently developed low-cost infrared imagers will enable
these discoveries in the next decade. Furthermore, robotizing the 1-to-2-meter
O/IR fleet is highly synergistic with rapid follow-up of transient and
multi-messenger events.Comment: Science white paper submitted to the Astro 2020 Decadal Survey on
Astronomy and Astrophysic
The check-up: in-person, computerized, and telephone adaptations of motivational enhancement treatment to elicit voluntary participation by the contemplator
Countless barriers come between people who are struggling with substance abuse and those charged with providing substance abuse treatment. The check-up, a form of motivational enhancement therapy, is a harm reduction intervention that offers a manner of supporting individuals by lowering specific barriers to reaching those who are untreated. The check-up was originally developed to reach problem drinkers who were neither seeking treatment nor self-initiating change. The intervention, marketed as an opportunity to take stock of one's experiences, involves an assessment and personalized feedback delivered with a counseling style termed motivational interviewing. Check-ups can be offered in care settings to individuals who, as a result of screening, manifest risk factors for specific disorders such as alcoholism. They can also be free-standing and publicized widely to the general public. This paper will discuss illustrations of in-person, computerized, in-school, and telephone applications of the free-standing type of check-up with reference to alcohol consumers, adult and adolescent marijuana smokers, and gay/bisexual males at risk for sexual transmission of HIV. The paper's major focus is to highlight how unique features of each application have the potential of reducing barriers to reaching specific at-risk populations. Also considered are key policy issues such as how check-up services can be funded, which venues are appropriate for the delivery of check-up interventions, pertinent competency criteria in evaluating staff who deliver this intervention, how marketing can be designed to reach contemplators in untreated at-risk populations, and how a check-up's success ought to be defined
Impact of age and race on outcomes of a program to prevent excess weight gain and disordered eating in adolescent girls
Interpersonal psychotherapy (IPT) prevents weight gain and reduces loss-of-control (LOC)-eating in adults. However, IPT was not superior to health-education (HE) for preventing excess weight gain and reducing LOC-eating over 1-year in adolescent girls at risk for excess weight gain and eating disorders. Limited data suggest that older and non-White youth may be especially responsive to IPT. In secondary analyses, we examined if age or race moderated weight and LOC-eating outcomes. The 113 participants (12–17 years; 56.6% White) from the original trial were re-contacted 3 years later for assessment. At baseline and follow-up visits through 3 years, we assessed BMI, adiposity by dual energy X-ray absorptiometry, and LOC-eating presence. In linear mixed models, baseline age moderated 3-year BMI outcome; older girls in IPT had the lowest 3-year BMI gain compared to younger girls in IPT and all girls in HE, p = 0.04. A similar pattern was observed for adiposity. Race moderated 3-year LOC-eating; non-White girls in IPT were most likely to abstain from LOC-eating at 3 years compared to all other girls, p = 0.04. This hypothesis-generating analysis suggests future studies should determine if IPT is especially efficacious at reducing LOC-eating in older, non-White adolescents
Reflected Spectra and Albedos of Extrasolar Giant Planets I: Clear and Cloudy Atmospheres
The reflected spectra of extrasolar giant planets are primarily influenced by
Rayleigh scattering, molecular absorption, and atmospheric condensates. We
present model geometric albedo and phase integral spectra and Bond albedos for
planets and brown dwarfs with masses between 0.8 and 70 Jupiter masses.
Rayleigh scattering predominates in the blue while molecular absorption removes
most red and infrared photons. Thus cloud-free atmospheres, found on giant
planets with effective temperatures exceeding about 400 K, are quite dark in
reflected light beyond 0.6 microns. In cooler atmospheres first water clouds
and then other condensates provide a bright reflecting layer. Only planets with
cloudy atmospheres will be detectable in reflected light beyond 1 micron.
Thermal emission dominates the near-infrared for warm objects with clear
atmospheres. However the presence of other condensates, not considered here,
may brighten some planets in reflected near-infrared light and darken them in
the blue and UV. Bond albedos, the ratio of the total reflected to incident
power, are sensitive to the spectral type of the primary. Most incident photons
from early type stars will be Rayleigh scattered, while most incident photons
from late type stars will be absorbed. The Bond albedo of a given planet thus
may range from 0.4 to 0.05, depending on the primary type. Condensation of a
water cloud increases the Bond albedo of a given planet by up to a factor of
two. The spectra of cloudy planets are strongly influenced by poorly
constrained cloud microphysical properties, particularly particle size and
supersaturation. Both Bond and geometric albedos are comparatively less
sensitive to variations in planet mass and effective temperature.Comment: AASTeX; 23 pages, 2 tables, 18 figures; ApJ in press; typo fixe
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