16,882 research outputs found
3.8-Micron Photometry During the Secondary Eclipse of the Extrasolar Planet HD 209458b
We report infrared photometry of the extrasolar planet HD 209458b during the
time of secondary eclipse (planet passing behind the star). Observations were
acquired during two secondary eclipses at the NASA Infrared Telescope Facility
(IRTF) in September 2003. We used a circular variable filter (1.5-percent
bandpass) centered at 3.8 microns to isolate the predicted flux peak of the
planet at this wavelength. Residual telluric absorption and instrument
variations were removed by offsetting the telescope to nearby bright comparison
stars at a high temporal cadence. Our results give a secondary eclipse depth of
0.0013 +/- 0.0011, not yet sufficient precision to detect the eclipse, whose
expected depth is approximately 0.002 - 0.003. We here elucidate the current
observational limitations to this technique, and discuss the approach needed to
achieve detections of hot Jupiter secondary eclipses at 3.8 microns from the
ground.Comment: 5 pages, 5 figures, in press for MNRA
Structures in granitic bathyliths and associated foldbelts in relation to mineral resources
There are no author-identified significant results in this report
Contributions to workload of rotational optical transformations
An investigation of visuomotor adaptation to optical rotation and optical inversion was conducted. Experiment 1 examined the visuomotor adaptability of subjects to an optically rotating visual world with a univariate repeated measures design. Experiment 1A tested one major prediction of a model of adaptation put forth by Welch who predicted that the aversive drive state that triggers adaptation would be habituated to fairly rapidly. Experiment 2 was conducted to investigate the role of motor activity in adaptation to optical rotation. Specifically, this experiment contrasted the reafference hypothesis and the proprioceptive change hypothesis. Experiment 3 examined the role of cognition, error-corrective feedback, and proprioceptive and/or reafferent feedback in visuomotor adaptation to optical inversion. Implications for research and implications for practice were suggested for all experiments
Radiometer requirements for Earth-observation systems using large space antennas
Requirements are defined for Earth observation microwave radiometry for the decade of the 1990's by using large space antenna (LSA) systems with apertures in the range from 50 to 200 m. General Earth observation needs, specific measurement requirements, orbit mission guidelines and constraints, and general radiometer requirements are defined. General Earth observation needs are derived from NASA's basic space science program. Specific measurands include soil moisture, sea surface temperature, salinity, water roughness, ice boundaries, and water pollutants. Measurements are required with spatial resolution from 10 to 1 km and with temporal resolution from 3 days to 1 day. The primary orbit altitude and inclination ranges are 450 to 2200 km and 60 to 98 deg, respectively. Contiguous large scale coverage of several land and ocean areas over the globe dictates large (several hundred kilometers) swaths. Radiometer measurements are made in the bandwidth range from 1 to 37 GHz, preferably with dual polarization radiometers with a minimum of 90 percent beam efficiency. Reflector surface, root mean square deviation tolerances are in the wavelength range from 1/30 to 1/100
Triple-Pomeron Matrix Model for Dispersive Corrections to Nucleon-Nucleus Total Cross Section
Dispersive corrections to the total cross section for high-energy scattering
from a heavy nucleus are calculated using a matrix model, based on the
triple-Pomeron behavior of diffractive scattering from a single nucleon, for
the cross section operator connecting different states of the projectile
nucleon . Energy-dependent effects due to the decrease in longitudinal momentum
transfers and the opening of more channels with increasing energy are included.
The three leading terms in an expansion in the number of inelastic transitions
are evaluated and compared to exact results for the model in the uniform
nuclear density approximation for the the scattering of nucleons from Pb^{208}
for laboratory momenta ranging from 50 to 200 GeV/c.Comment: 16 pages, 2 figures, RevTex
Deciphering the Atmospheric Composition of WASP-12b: A Comprehensive Analysis of its Dayside Emission
WASP-12b was the first planet reported to have a carbon-to-oxygen ratio (C/O)
greater than one in its dayside atmosphere. However, recent work to further
characterize its atmosphere and confirm its composition has led to incompatible
measurements and divergent conclusions. Additionally, the recent discovery of
stellar binary companions ~1" from WASP-12 further complicates the analyses and
subsequent interpretations. We present a uniform analysis of all available
Hubble and Spitzer Space Telescope secondary-eclipse data, including
previously-unpublished Spitzer measurements at 3.6 and 4.5 microns. The primary
controversy in the literature has centered on the value and interpretation of
the eclipse depth at 4.5 microns. Our new measurements and analyses confirm the
shallow eclipse depth in this channel, as first reported by Campo and
collaborators and used by Madhusudhan and collaborators to infer a carbon-rich
composition. To explain WASP-12b's observed dayside emission spectrum, we
implemented several recent retrieval approaches. We find that when we exclude
absorption due to C2H2 and HCN, which are not universally considered in the
literature, our models require implausibly large atmospheric CO2 abundances,
regardless of the C/O. By including C2H2 and HCN in our models, we find that a
physically-plausible carbon-rich solution achieves the best fit to the
available photometric and spectroscopic data. In comparison, the best-fit
oxygen-rich models have abundances that are inconsistent with the chemical
equilibrium expectations for hydrogen-dominated atmospheres and are 670 times
less probable. Our best-fit solution is also 7.3*10^{6} times more probable
than an isothermal blackbody model.Comment: 8 pages, 7 figures, accepted for publication in Ap
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Structural MRI Correlates of Episodic Memory Processes in Parkinson's Disease Without Mild Cognitive Impairment.
BackgroundChanges in episodic memory are common early in Parkinson's disease (PD) and may be a risk factor for future cognitive decline. Although medial temporal lobe (MTL) memory and frontostriatal (FS) executive systems are thought to play different roles in distinct components of episodic memory impairment in PD, no study has investigated whether different aspects of memory functioning are differentially associated with MTL and FS volumes in nondemented patients without mild cognitive impairment (PD-woMCI).ObjectivesThe present study investigated MRI markers of different facets of memory functioning in 48 PD-woMCI patients and 42 controls.MethodsRegional volumes were measured in structures comprising the MTL and FS systems and then correlated with key indices of memory from the California Verbal Learning Test.ResultsIn PD-woMCI patients, memory was impaired only for verbal learning, which was not associated with executive, attention/working memory, or visuospatial functioning. Despite an absence of cortical atrophy, smaller right MTL volumes in patients were associated with poorer verbal learning, long delayed free recall, long delayed cued recall, and recognition memory hits and false positives. Smaller right pars triangularis (inferior frontal) volumes were also associated with poorer long delayed cued recall and recognition memory hits. These relationships were not found in controls.ConclusionsThe findings indicate that MTL volumes are sensitive to subtle changes in almost all facets of memory in PD-woMCI, whereas FS volumes are sensitive only to memory performances in cued-testing formats
The Capabilities Approach as a Solution to the Need for a More Encompassing Definition of Poverty
This Comment addresses the historical and present manifestations that result from the lack of values reflected in the federal poverty line. An alternative to this measure may be based on the capabilities approach. This approach looks further than simply the means to equality, and instead focuses on the ends--that is achieving well-being, and the freedom to pursue well-being. The capabilities approach is further described through an example of an effort to operationalize the theory by the United National Development Programme. Ultimately, this Comment proposes that renewed attention be focused on reforming the federal poverty line in light of the philosophical groundwork laid by the capabilities approach
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