21,610 research outputs found
Downsizing a Great Observatory: Reinventing Spitzer in the Warm Mission
The Spitzer Space Telescope transitioned from the cryogen mission to the IRAC warm mission during 2009. This transition involved changing several areas of operations in order to cut the mission annual operating costs to 1/3 of the cryogen mission amount. In spite of this substantial cut back, Spitzer continues to have one of the highest science return per dollar ratio of any of NASA's extended missions. This paper will describe the major operational changes made for the warm mission and how they affect the science return. The paper will give several measures showing that warm Spitzer continues as one of the most scientifically productive mission in NASA's portfolio. This work was performed at the California Institute of Technology under contract to the National Aeronautics and Space Administration
Intermedia Substitutability and Market Demand by National Advertisers
We assess substitutable and complementary relationships among eight national advertising media classes, as well as the magnitude of their own-price elasticities. We use a translog demand model, whose parameters we estimate by three-stage least squares, based on 1960-94 annual U.S. data.We find aggregate demand by national advertisers for each of the eight media is own-price inelastic, and that cross-price elasticities suggest slightly more substitute than complementary relationships, although both are rather weak. These patterns are consistent with long prevailing institutional arrangements and media selection practices.
Understanding Hope: A Review of Measurement and Construct Validity Research
Hope has been discussed by philosophers, theologians, educators, and scientists, to name but a few groups of people, over the preceding two millennia. During the last 15 years, C. R. Snyder and his colleagues at the University of Kansas have developed a theory and associated measures of the hope construct that have received extensive, detailed attention both within and outside the field of psychology. In this chapter, we describe Snyder\u27s hope model and some of the research findings that have supported the validity of this construct. Beginning with a conceptual definition of hope, we move to relevant findings about the usefulness of hope in the lives of individuals in various life arenas. We describe measures developed for assessing hope in children and adults, as well as current issues associated with the validity of hope measurement. Finally, we discuss future directions for further investigation of hope
No Indications of Axion-Like Particles From Fermi
As very high energy (~100 GeV) gamma rays travel over cosmological distances,
their flux is attenuated through interactions with the extragalactic background
light. Observations of distant gamma ray sources at energies between ~200 GeV
and a few TeV by ground-based gamma ray telescopes such as HESS, however,
suggest that the universe is more transparent to very high energy photons than
had been anticipated. One possible explanation for this is the existence of
axion-like-particles (ALPs) which gamma rays can efficiently oscillate into,
enabling them to travel cosmological distances without attenuation. In this
article, we use data from the Fermi Gamma Ray Space Telescope to calculate the
spectra at 1-100 GeV of two gamma ray sources, 1ES1101-232 at redshift z=0.186
and H2356-309 at z=0.165, and use this in conjunction with the measurements of
ground-based telescopes to test the ALP hypothesis. We find that the
observations can be well-fit by an intrinsic power-law source spectrum with
indices of -1.72 and -2.1 for 1ES1101-232 and H2356-309, respectively, and that
no ALPs or other exotic physics is necessary to explain the observed degree of
attenuation.Comment: 7 pages, 4 figures. v3: Matches published version, the analysis of
H2356-309 is revised, no change in conclusion
Quantifying the effects of spatial resolution and noise on galaxy metallicity gradients
Metallicity gradients are important diagnostics of galaxy evolution, because
they record the history of events such as mergers, gas inflow and
star-formation. However, the accuracy with which gradients can be measured is
limited by spatial resolution and noise, and hence measurements need to be
corrected for such effects. We use high resolution (~20 pc) simulation of a
face-on Milky Way mass galaxy, coupled with photoionisation models, to produce
a suite of synthetic high resolution integral field spectroscopy (IFS)
datacubes. We then degrade the datacubes, with a range of realistic models for
spatial resolution (2 to 16 beams per galaxy scale length) and noise, to
investigate and quantify how well the input metallicity gradient can be
recovered as a function of resolution and signal-to-noise ratio (SNR) with the
intention to compare with modern IFS surveys like MaNGA and SAMI. Given
appropriate propagation of uncertainties and pruning of low SNR pixels, we show
that a resolution of 3-4 telescope beams per galaxy scale length is sufficient
to recover the gradient to ~10-20% uncertainty. The uncertainty escalates to
~60% for lower resolution. Inclusion of the low SNR pixels causes the
uncertainty in the inferred gradient to deteriorate. Our results can
potentially inform future IFS surveys regarding the resolution and SNR required
to achieve a desired accuracy in metallicity gradient measurements.Comment: 21 pages, 11 figures, 20 pages Supplementary Online Material provided
with 10 additional figures, accepted for publication in MNRA
Global Gene Expression Profiling of Individual Human Oocytes and Embryos Demonstrates Heterogeneity in Early Development
Early development in humans is characterised by low and variable embryonic viability, reflected in low fecundity and high rates of miscarriage, relative to other mammals. Data from assisted reproduction programmes provides additional evidence that this is largely mediated at the level of embryonic competence and is highly heterogeneous among embryos. Understanding the basis of this heterogeneity has important implications in a number of areas including: the regulation of early human development, disorders of pregnancy, assisted reproduction programmes, the long term health of children which may be programmed in early development, and the molecular basis of pluripotency in human stem cell populations. We have therefore investigated global gene expression profiles using polyAPCR amplification and microarray technology applied to individual human oocytes and 4-cell and blastocyst stage embryos. In order to explore the basis of any variability in detail, each developmental stage is replicated in triplicate. Our data show that although transcript profiles are highly stage-specific, within each stage they are relatively variable. We describe expression of a number of gene families and pathways including apoptosis, cell cycle and amino acid metabolism, which are variably expressed and may be reflective of embryonic developmental competence. Overall, our data suggest that heterogeneity in human embryo developmental competence is reflected in global transcript profiles, and that the vast majority of existing human embryo gene expression data based on pooled oocytes and embryos need to be reinterpreted
Massive Lyman Break Galaxies at z~3 in the Spitzer Extragalactic First Look Survey
We investigate the properties of 1088 Lyman Break Galaxies (LBGs) at z~3
selected from a ~2.63M/L$ in
rest-frame near-infrared. Most infrared-luminous LBGs (S_{24um} > 100 uJy) are
dusty star-forming galaxies with star formation rates of 100--1000 Msun/yr,
total infrared luminosity of > 10^12 Lsun. By constructing the UV luminosity
function of massive LBGs, we estimate that the lower limit for the star
formation rate density from LBGs more massive than 10^11 Msun at z~3 is > 3.3 x
10^-3 Msun/yr/Mpc^3, showing for the first time that the UV-bright population
of massive galaxies alone contributes significantly to the global star
formation rate density at z~3. When combined with the star formation rate
densities at z < 2, our result reveals a steady increase in the contribution of
massive galaxies to the global star formation from z=0 to z=3, providing strong
support to the downsizing of galaxy formation.Comment: 15 pages, 13 figures. Accepted for publication in Ap
Effects of intervention upon precompetition state anxiety in elite junior tennis players: The relevance of the matching hypothesis
Reproduced with permission of publisher from:
Terry, P., Coakley, L., & Karageorghis, C. Effects of intervention upon precompetition state anxiety in elite junior tennis players: the relevance of the matching hypothesis. Perceptual and Motor Skills, 1995, 81, 287-296. © Perceptual and Motor Skills 1995The matching hypothesis proposes that interventions for anxiety should be matched to the modality in which anxiety is experienced. This study investigated the relevance of the matching hypothesis for anxiety interventions in tennis. Elite junior tennis players (N = 100; Age: M = 13.9 yr., SD = 1.8 yr.) completed the Competitive State Anxiety Inventory-2 before and after one of four randomly assigned intervention strategies approximately one hour prior to competition at a National Junior Championship. A two-factor multivariate analysis of variance (group x time) with repeated measures on the time factor gave no significant main effect by group but indicated significant reductions in somatic anxiety and cognitive anxiety and a significant increase in self-confidence following intervention. A significant group by time interaction emerged for self-confidence. The results question the need to match intervention strategy to the mode of anxiety experienced
Two Cultures Collide: Bridging the Generation Gap in a Non - traditional Mentorship
Cross - cultural mentoring relationships between younger mentors and older mentees are increasing in frequency across all levels of post - secondary education. Generational cultural differences can result in conflict and misunderstanding and therefore should be considered in non - traditional inter - generational mentoring relationships. Through auto - ethnographic inquiry, we, a younger faculty member and older graduate student, explored our mentoring relationship. We identified communication, respect, and ambiguous roles as issues that significantly impacted our mentorship. The manifestation of power was also highlighted in the study.
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