2,453 research outputs found
Earthshine as an Illumination Source at the Moon
Earthshine is the dominant source of natural illumination on the surface of
the Moon during lunar night, and at locations within permanently shadowed
regions that never receive direct sunlight. As such, earthshine may enable the
exploration of areas of the Moon that are hidden from solar illumination. The
heat flux from earthshine may also influence the transport and cold trapping of
volatiles present in the very coldest areas. In this study, Earth's spectral
radiance at the Moon is examined using a suite of Earth spectral models created
using the Virtual Planetary Laboratory (VPL) three dimensional modeling
capability. At the Moon, the broadband, hemispherical irradiance from Earth
near 0 phase is approximately 0.15 watts per square meter, with comparable
contributions from solar reflectance and thermal emission. Over the simulation
timeframe, spanning two lunations, Earth's thermal irradiance changes less than
a few mW per square meter as a result of cloud variability and the
south-to-north motion of sub-observer position. In solar band, Earth's
diurnally averaged light curve at phase angles < 60 degrees is well fit using a
Henyey Greenstein integral phase function. At wavelengths > 0.7 microns, near
the well known vegetation "red edge", Earth's reflected solar radiance shows
significant diurnal modulation as a result of the longitudinal asymmetry in
projected landmass, as well as from the distribution of clouds. A simple
formulation with adjustable coefficients is presented for estimating Earth's
hemispherical irradiance at the Moon as a function of wavelength, phase angle
and sub-observer coordinates. It is demonstrated that earthshine is
sufficiently bright to serve as a natural illumination source for optical
measurements from the lunar surface.Comment: 27 pages, 15 figures, 1 tabl
River Restoration Effects on Steelhead Populations in the Manistee River, Michigan: Analysis Using an Individual‐Based Model
The Manistee River, Michigan, watershed includes two dams as well as residential and agricultural development, and the river itself contains a sizeable population of steelhead Oncorhynchus mykiss that supports a valuable recreational fishery. Restoration of the Manistee River and its flow regime may improve steelhead habitat and the fishery. We developed an individual‐based model of steelhead in the Manistee River to assess the population effects of changes in the number of spawners, water discharge from Tippy Dam, and water temperature. The model follows steelhead from spring spawning to the end of the growing season in early fall and depicts the river environment as a series of cells that vary in dimension, water velocity, and substrate. Simulated water discharge, temperature, and prey availability changed daily based on observations from Tippy Dam. Empirically based models describe individual steelhead fry and parr foraging and growth. In the model, steelhead select habitats and maximize individual fitness while accounting for dominance and the availability of feeding territories. We calibrated the model to replicate fish growth, mortality, and population size. Simulation experiments manipulated the number of spawning females, water discharge, and water temperature. The results suggest that Manistee River steelhead incur density limitations in the fry and parr stages and that water discharge and temperature changes affect the number and biomass of parr. Increasing river discharge negatively affected parr numbers and weight. Decreasing maximum midsummer temperature increased parr numbers and weight when the change was large, but otherwise had little effect. These results indicate that restoration of the natural flow regime in the Manistee River will probably increase the quality of the habitat for steelhead but that density limitations in the fry and parr stages may ultimately limit population growth.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141355/1/tafs1654.pd
Examination of Post-Service Health-Related Quality of Life Among Rural and Urban Military Members of the Millennium Cohort Study
Little information exists on the health-related quality of life (HRQL) of U.S. veterans based on rural (versus urban) status, especially those in younger age groups, and whether deployment influences this outcome. We addressed these questions in the Millennium Cohort Study, a prospective investigation of U.S. military personnel assessed first in 2001 and then subsequently every three years via self-administered questionnaires. Participants separated from the military at the time of the most recent survey were eligible (n = 10,738). HRQL was assessed using the SF-36V Physical Component Summary (PCS) and Mental Component Summary (MCS) scores. Rural status was assigned from zip codes using the Rural-Urban Commuting Area classification. The mean age of participants was 35 years (SD = 8.98). Compared with urban dwellers, rural residents reported significantly lower unadjusted mean PCS (49.80 vs. 50.42) and MCS (49.97 vs. 50.81) scores, but differences became nonsignificant after covariate adjustment. No interaction was seen between deployment and rural status. Rural status is not independently associated with HRQL among recent U.S. veterans
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The bicycle wheel analogy for linear closures of small suborbital cheek defects
Primary closure of suborbital skin defects can cause tension along the closure resulting in ectropion. The bicycle wheel analogy is a simple yet effective guide to aid in reducing tension vectors resulting in ectropion
Correlates of Christian Religious Identification and Deidentification Among Sexual and Gender Minorities: A U.S. Probability Sample
Using a U.S. nationally representative sample of 1,529 sexual and gender minorities (SGMs), we examined the demographic and developmental correlates of Christian religious deidentification. We found that SGMs who were older, Black, cisgender men, and/or lived in the American South were more likely to identify as Christian in adulthood, relative to other SGMs. Those who were never Christian reported being more out to family and friends at earlier ages than those who were raised Christian. SGMs who were raised Christian, but did not identify as Christian in adulthood reported, more adverse childhood experiences and bullying than other SGMs. Sexual minorities who identified as Christian in adulthood reported more internalized homophobia in adulthood than other sexual minorities. Finally, sexual minorities who were raised Christian, regardless of their adulthood religious identification, reported experiencing more stigma than sexual minorities who were not raised Christian. No differences were noted in measures of adulthood resilience or health. Taken together, results indicate that identifying as Christian—in childhood and/or adulthood—is associated with greater experiences of stigma and stress than not identifying as Christian in adulthood
Physical Characterization of Active Asteroid (6478) Gault
Main belt asteroid (6478) Gault has been dynamically linked with two
overlapping asteroid families: Phocaea, dominated by S-type asteroids, and
Tamara, dominated by low-albedo C-types. This object has recently become an
interesting case for study, after images obtained in late 2018 revealed that it
was active and displaying a comet-like tail. Previous authors have proposed
that the most likely scenarios to explain the observed activity on Gault were
rotational excitation or merger of near-contact binaries. Here we use new
photometric and spectroscopic data of Gault to determine its physical and
compositional properties. Lightcurves derived from the photometric data showed
little variation over three nights of observations, which prevented us from
determining the rotation period of the asteroid. Using WISE observations of
Gault and the near-Earth Asteroid Thermal Model (NEATM) we determined that this
asteroid has a diameter 6 km. NIR spectroscopic data obtained with the
Infrared Telescope Facility (IRTF) showed a spectrum similar to that of
S-complex asteroids, and a surface composition consistent with H chondrite
meteorites. These results favor a compositional affinity between Gault and
asteroid (25) Phocaea, and rules out a compositional link with the Tamara
family. From the spectroscopic data we found no evidence of fresh material that
could have been exposed during the outburst episodes.Comment: 9 pages, 4 figures, accepted for publication in ApJ
A foundation for provitamin A biofortification of maize: genome-wide association and genomic prediction models of carotenoid levels.
Efforts are underway for development of crops with improved levels of provitamin A carotenoids to help combat dietary vitamin A deficiency. As a global staple crop with considerable variation in kernel carotenoid composition, maize (Zea mays L.) could have a widespread impact. We performed a genome-wide association study (GWAS) of quantified seed carotenoids across a panel of maize inbreds ranging from light yellow to dark orange in grain color to identify some of the key genes controlling maize grain carotenoid composition. Significant associations at the genome-wide level were detected within the coding regions of zep1 and lut1, carotenoid biosynthetic genes not previously shown to impact grain carotenoid composition in association studies, as well as within previously associated lcyE and crtRB1 genes. We leveraged existing biochemical and genomic information to identify 58 a priori candidate genes relevant to the biosynthesis and retention of carotenoids in maize to test in a pathway-level analysis. This revealed dxs2 and lut5, genes not previously associated with kernel carotenoids. In genomic prediction models, use of markers that targeted a small set of quantitative trait loci associated with carotenoid levels in prior linkage studies were as effective as genome-wide markers for predicting carotenoid traits. Based on GWAS, pathway-level analysis, and genomic prediction studies, we outline a flexible strategy involving use of a small number of genes that can be selected for rapid conversion of elite white grain germplasm, with minimal amounts of carotenoids, to orange grain versions containing high levels of provitamin A
Thorium isotopes tracing the iron cycle at the Hawaii Ocean Time-series Station ALOHA
The role of iron as a limiting micronutrient motivates an effort to understand the supply and removal of lithogenic trace metals in the ocean. The long-lived thorium isotopes (²³²Th and ²³⁰Th) in seawater can be used to quantify the input of lithogenic metals attributable to the partial dissolution of aerosol dust. Thus, Th can help in disentangling the Fe cycle by providing an estimate of its ultimate supply and turnover rate. Here we present time-series (1994–2014) data on thorium isotopes and iron concentrations in seawater from the Hawaii Ocean Time-series Station ALOHA. By comparing Th-based dissolved Fe fluxes with measured dissolved Fe inventories, we derive Fe residence times of 6–12 months for the surface ocean. Therefore, Fe inventories in the surface ocean are sensitive to seasonal changes in dust input. Ultrafiltration results further reveal that Th has a much lower colloidal content than Fe does, despite a common source. On this basis, we suggest Fe colloids may be predominantly organic in composition, at least at Station ALOHA. In the deep ocean (>2 km), Fe approaches a solubility limit while Th, surprisingly, is continually leached from lithogenic particles. This distinction has implications for the relevance of Fe ligand availability in the deep ocean, but also suggests Th is not a good tracer for Fe in deep waters. While uncovering divergent behavior of these elements in the water column, this study finds that dissolved Th flux is a suitable proxy for the supply of Fe from dust in the remote surface ocean.National Science Foundation (U.S.) (Grant NS-OIA E-0424599
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