17,548 research outputs found
Effects of flanges on pressure distribution on a flat plate and on a corrugated surface at Mach numbers from 0.60 to 1.97
An 8 by 6 foot supersonic wind tunnel was used to obtain the static pressure distribution on a plate in the region of a flange placed normal to the airstream. Tests were conducted on both a flat plate surface and a corrugated surface using flange heights ranging from 10 to 125 percent of the boundary layer height. Data were obtained at a zero degree angle-of-attack and at Mach numbers from 0.60 to 1.97
Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
We present theoretical atmosphere, spectral, and light-curve models for
extrasolar giant planets (EGPs) undergoing strong irradiation for which {\it
Spitzer} planet/star contrast ratios or light curves have been published (circa
June 2007). These include HD 209458b, HD 189733b, TrES-1, HD 149026b, HD
179949b, and And b. By comparing models with data, we find that a
number of EGP atmospheres experience thermal inversions and have stratospheres.
This is particularly true for HD 209458b, HD 149026b, and And b.
This finding translates into qualitative changes in the planet/star contrast
ratios at secondary eclipse and in close-in EGP orbital light curves. Moreover,
the presence of atmospheric water in abundance is fully consistent with all the
{\it Spitzer} data for the measured planets. For planets with stratospheres,
water absorption features invert into emission features and mid-infrared fluxes
can be enhanced by a factor of two. In addition, the character of near-infrared
planetary spectra can be radically altered. We derive a correlation between the
importance of such stratospheres and the stellar flux on the planet, suggesting
that close-in EGPs bifurcate into two groups: those with and without
stratospheres. From the finding that TrES-1 shows no signs of a stratosphere,
while HD 209458b does, we estimate the magnitude of this stellar flux
breakpoint. We find that the heat redistribution parameter, P, for the
family of close-in EGPs assumes values from 0.1 to 0.4. This paper
provides a broad theoretical context for the future direct characterization of
EGPs in tight orbits around their illuminating stars.Comment: Accepted to Ap. J., provided here in emulateapj format: 28 pages, 8
figures, many with multiple panel
Non-detection of the OH Meinel system in comet P/Swift-Tuttle
We report a search for emissions from the OH Meinel system in high-resolution near-infrared spectra of comet P/Swift-Tuttle. Because of the large cometary heliocentric velocity and high resolution of the spectrograph, the cometary lines should be well separated from the bright OH sky lines. Contrary to the findings of Tozzi et al. (1994) - who report seeing cometary OH at intensities comparable to the sky emissions in their low-resolution spectra - we find no OH in these spectra with an upper limit of 5% the value of the night sky lines. The non-detection of these cometary lines is consistent with theoretical calculations of expected emission strengths from prompt and fluorescent emission from cometary OH
A high-Resolution Catalog of Cometary Emission Lines
Using high-resolution spectra obtained with the Hamilton echelle spectrograph at Lick Observatory, we have constructed a catalog of emission lines observed in comets Swift-Tuttle and Brorsen-Metcalf. The spectra cover the range between 3800 Ă
and 9900 Ă
with a spectral resolution of λ/Îλ~42000. In the spectra, we catalog 2997 emission lines of which we identify 2438. We find cometary lines due to H, O, C_2, CN, NH_2, C_3, H_2O^+, CH, and CH^+. We list 559 unidentified lines compiled from the two spectra and comment on possibilities for their origins
Eddy Impacts on the Florida Current
The Gulf Stream in the Atlantic carries warm water northwards and forms both the return closure of the subtropical gyre as well as the upper limb of the meridional overturning circulation. Recent time series recorded east of the Bahamas at 26°N indicate that from May 2009 to April 2011, in contrast with past observations, the northward flowing Antilles Current covaried with the Gulf Stream in the Florida Straitsâthe Florida Currentâeven though the Florida and Antilles Currents are separated by banks and islands spanning 150?km. The peak-to-trough amplitude of transport variations during this period was 15?Ă?106?m3?s?1 for the Florida Current and 12?Ă?106?m3?s?1 for the Antilles Current, at time scales of 50?days to a year. From satellite observations, we show that the fluctuations in both the Florida and Antilles Currents between May 2009 and April 2011 are driven by eddy activity east of the Bahamas. Since the Florida Current time series is a critical time series for the state of the oceans, and often compared to climate models, this newly identified source of variability needs careful consideration when attributing the variability of the Florida Current to changes in the larger-scale circulations (e.g., gyre and overturning) or wind forcing.<br/
"More than a game": the impact of sport-based youth mentoring schemes on developing resilience toward violent extremism
This paper draws upon the findings of an evaluation of âMore than a Gameâ, a sport-focused youth mentoring program in Melbourne, Australia that aimed to develop a community-based resilience model using team-based sports to address issues of identity, belonging, and cultural isolation amongst young Muslim men in order to counter forms of violent extremism. In this essay we focus specifically on whether the intense embodied encounters and emotions experienced in team sports can help break down barriers of cultural and religious difference between young people and facilitate experiences of resilience, mutual respect, trust, social inclusion and belonging. Whilst the project findings are directly relevant to the domain of countering violent extremism, they also contribute to a growing body of literature which considers the relationship between team-based sport, cross-cultural engagement and the development of social resilience, inclusion and belonging in other domains of youth engagement and community-building
Pregnancy diagnosis using ultrasound
Few Western Australian ewe flocks are diagnosed for pregnancy despite the precence of high numbers of barren ewes. Surveys of farm flocks in the early 1970s recorded that between 14 and 29 per cent of ewes failed to lamb each year.
Techniques for diagnosing pregnant ewes have been available for many years, but ultrasonic devices and computer technology have made it possible for skilled operators to determine whether ewes are pregnant and more importantly, whether they have one, two or more foetuses.
Once the number of pregnant ewes is known farmers can use labour more efficiently. They can minimise the cost of supplementary feeding, particularily if the use of diagnostic techniques identifies ewes bearing twin lambs. Failure to carefully manage a flock with multiple lambs could lead to reduced wool production per head, reduced lamb growth and morre ewe and lamb deaths
The Far-Ultraviolet Spectra of TW Hya. II. Models of H2 Fluorescence in a Disk
We measure the temperature of warm gas at planet-forming radii in the disk
around the classical T Tauri star (CTTS) TW Hya by modelling the H2
fluorescence observed in HST/STIS and FUSE spectra. Strong Ly-alpha emission
irradiates a warm disk surface within 2 AU of the central star and pumps
certain excited levels of H2. We simulate a 1D plane-parallel atmosphere to
estimate fluxes for the 140 observed H2 emission lines and to reconstruct the
Ly-alpha emission profile incident upon the warm H2. The excitation of H2 can
be determined from relative line strengths by measuring self-absorption in
lines with low-energy lower levels, or by reconstructing the Ly-alpha profile
incident upon the warm H2 using the total flux from a single upper level and
the opacity in the pumping transition. Based on those diagnostics, we estimate
that the warm disk surface has a column density of log
N(H2)=18.5^{+1.2}_{-0.8}, a temperature T=2500^{+700}_{-500} K, and a filling
factor of H2, as seen by the source of Ly-alpha emission, of 0.25\pm0.08 (all
2-sigma error bars). TW Hya produces approximately 10^{-3} L_\odot in the FUV,
about 85% of which is in the Ly-alpha emission line. From the H I absorption
observed in the Ly-alpha emission, we infer that dust extinction in our line of
sight to TW Hya is negligible.Comment: Accepted by ApJ. 26 pages, 17 figures, 6 table
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