10,556 research outputs found
Considerations of electron beam propagation from space vehicles
Theoretical analysis of electron beam array propagation from spacecraf
On the chemical composition of L-chondrites
Radiochemical neutron activation analysis of Ag, As, Au, Bi, Co, Cs, Ga, In, Rb, Sb, Te, Tl, and Zn and major element data in 14 L4-6 and 3 LL5 chondrites indicates that the L group is unusually variable and may represent at least 2 subgroups differing in formation history. Chemical trends in the S/Fe rich subgroup support textural evidence indicating late loss of a shock formed Fe-Ni-S melt; the S/Fe poor subgroup seemingly reflects nebular fractionation only. Highly mobile In and Zn apparently reflect shock induced loss from L chondrites. However, contrasting chemical trends in several L chondrite sample sets indicate that these meteorites constitute a more irregular sampling of, or more heterogeneous parent material than do carbonaceous or enstatite chondrites. Data for 15 chondrites suggest higher formation temperatures and/or degrees of shock than for LL5 chondrites
Lunette: A Two-Lander Discovery-Class Geophysics Mission to the Moon
The document “The Scientific Context for the Exploration of the Moon” [1] designated understanding the structure and composition of the lunar interior (to provide fundamental information on the evolution of a differentiated planetary body) as the second highest priority lunar science concept that needed to be addressed. To this end, the Science Mission Directorate formulated the International Lunar Network (ILN) mission concept (web site) that enlisted international partners to enable the establishment of a geophysical network on the lunar surface. NASA would establish the first four “anchor nodes” in the 2018 time frame. These nodes are envisioned to use radioisotope power systems to allow operation of each node for at least 6 years. Each anchor node will contain a seismometer, magnetometer, laser retroreflector, and a heat flow probe [2] and will be distributed across the lunar surface to form a much more widespread network that the Apollo passive seismic, magnetometer, heat flow, and the Apollo and Luna laser retroreflector networks. (Fig. 1). It is planned that the four anchor nodes will be launched on an Atlas 5 launch vehicle and the cost is estimated to exceed that for a New Frontiers mission. What we present here is an alternative to the ILN architecture that will still return the data required to understand the nature of the lunar interior and determine how the Moon evolved
ULAS J234311.93-005034.0: A gravitational lens system selected from UKIDSS and SDSS
We report the discovery of a new gravitational lens system. This object, ULAS
J234311.93-005034.0, is the first to be selected by using the new UKIRT
Infrared Deep Sky Survey (UKIDSS), together with the Sloan Digital Sky Survey
(SDSS). The ULAS J234311.93-005034.0 system contains a quasar at redshift 0.788
which is doubly imaged, with separation 1.4". The two quasar images have the
same redshift and similar, though not identical, spectra. The lensing galaxy is
detected by subtracting point-spread functions from R-band images taken with
the Keck telescope. The lensing galaxy can also be detected by subtracting the
spectra of the A and B images, since more of the galaxy light is likely to be
present in the latter. No redshift is determined from the galaxy, although the
shape of its spectrum suggests a redshift of about 0.3. The object's lens
status is secure, due to the identification of two objects with the same
redshift together with a lensing galaxy. Our imaging suggests that the lens is
found in a cluster environment, in which candidate arc-like structures, that
require confirmation, are visible in the vicinity. Further discoveries of
lenses from the UKIDSS survey are likely as part of this programme, due to the
depth of UKIDSS and its generally good seeing conditions.Comment: Accepted by MNRA
Bringing closure to microlensing mass measurement
Interferometers offer multiple methods for studying microlensing events and
determining the properties of the lenses. We investigate the study of
microlensing events with optical interferometers, focusing on narrow-angle
astrometry, visibility, and closure phase. After introducing the basics of
microlensing and interferometry, we derive expressions for the signals in each
of these three channels. For various forecasts of the instrumental performance,
we discuss which method provides the best means of measuring the lens angular
Einstein radius theta_E, a prerequisite for determining the lens mass. If the
upcoming generation of large-aperture, AO-corrected long baseline
interferometers (e.g. VLTI, Keck, OHANA) perform as well as expected, theta_E
may be determined with signal-to-noise greater than 10 for all bright events.
We estimate that roughly a dozen events per year will be sufficiciently bright
and have long enough durations to allow the measurement of the lens mass and
distance from the ground. We also consider the prospects for a VLTI survey of
all bright lensing events using a Fisher matrix analysis, and find that even
without individual masses, interesting constraints may be placed on the bulge
mass function, although large numbers of events would be required.Comment: 23 pages, aastex, submitted to Ap
Comorbidity and Quality of Life in Adults with Hair Pulling Disorder
Hair pulling disorder (HPD; trichotillomania) is thought to be associated with significant psychiatric comorbidity and functional impairment. However, few methodologically rigorous studies of HPD have been conducted, rendering such conclusions tenuous. The following study examined comorbidity and psychosocial functioning in a well-characterized sample of adults with HPD (N=85) who met DSM-IV criteria, had at least moderate hair pulling severity, and participated in a clinical trial. Results revealed that 38.8% of individuals with HPD had another current psychiatric diagnosis and 78.8% had another lifetime (present and/or past) psychiatric diagnosis. Specifically, HPD showed substantial overlap with depressive, anxiety, addictive, and other body-focused repetitive behavior disorders. The relationships between certain comorbidity patterns, hair pulling severity, current mood and anxiety symptoms, and quality of life were also examined. Results showed that current depressive symptoms were the only predictor of quality of life deficits. Implications of these findings for the conceptualization and treatment of HPD are discussed
Factor Analysis of the Milwaukee Inventory for Subtypes of Trichotillomania-Adult Version
The Milwaukee Inventory for Subtypes of Trichotillomania-Adult Version (MIST-A; Flessner et al., 2008) measures the degree to which hair pulling in Trichotillomania (TTM) can be described as “automatic” (i.e., done without awareness and unrelated to affective states) and/or “focused” (i.e., done with awareness and to regulate affective states). Despite preliminary evidence in support of the psychometric properties of the MIST-A, emerging research suggests the original factor structure may not optimally capture TTM phenomenology. Using data from a treatment-seeking TTM sample, the current study examined the factor structure of the MIST-A via exploratory factor analysis. The resulting two factor solution suggested the MIST-A consists of a 5-item “awareness of pulling” factor that measures the degree to which pulling is done with awareness and an 8-item “internal-regulated pulling” factor that measures the degree to which pulling is done to regulate internal stimuli (e.g., emotions, cognitions, and urges). Correlational analyses provided preliminary evidence for the validity of these derived factors. Findings from this study challenge the notions of “automatic” and “focused” pulling styles and suggest that researchers should continue to explore TTM subtypes
Clarifying the Relationship Between Trichotillomania and Anxiety
Although research has consistently linked unidimensional anxiety with Trichotillomania (TTM) severity, the relationships between TTM severity and anxiety dimensions (e.g., cognitive and somatic anxiety) are unknown. This knowledge gap limits current TTM conceptualization and treatment. The present study examined these relationships with data collected from ninety-one adults who participated in a randomized clinical trial for TTM treatment. Based on prior research, it was hypothesized that TTM severity would be related to the cognitive anxiety dimension and that psychological inflexibility would mediate the association. Hypotheses were not made regarding the relationship between TTM severity and somatic anxiety. Regression analyses indicated that only cognitive dimensions of anxiety predicted TTM severity and that psychological inflexibility mediated this relationship. Implications for the conceptualization and treatment of TTM are discussed
Photographic Assessment of Change in Trichotillomania: Psychometric Properties and Variables Influencing Interpretation
Although photographic assessment has been found to be reliable in assessing hair loss in Trichotillomania, the validity of this method is unclear, particularly for gauging progress in treatment. The current study evaluated the psychometric properties of photographic assessment of change in Trichotillomania. Photographs showing hair loss of adults with Trichotillomania were taken before and after participating in a clinical trial for the condition. Undergraduate college students (N = 211) rated treatment response according to the photos, and additional archival data on hair pulling severity and psychosocial health were retrieved from the clinical trial. Photographic assessment of change was found to possess fair reliability (ICC = 0.53), acceptable criterion validity (r = 0.51), good concurrent validity (r = 0.30–0.36), and excellent incremental validity (ΔR2 = 8.67, p \u3c 0.01). In addition, photographic measures were significantly correlated with change in quality of life (r = 0.42), and thus could be considered an index of the social validity of Trichotillomania treatment. Gender of the photo rater and pulling topography affected the criterion validity of photographic assessment (partial η2 = 0.05–0.11). Recommendations for improving photographic assessment and future directions for hair pulling research are discussed
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