487 research outputs found
Effect of blockage ratio on drag and pressure distributions for bodies of revolution at transonic speeds
Experimental data were obtained in two wind tunnels for 13 models over a Mach number range from 0.70 to 1.02. Effects of increasing test-section blockage ratio in the transonic region near a Mach number of 1.0 included change in the shape of the drag curves, premature drag creep, delayed drag divergence, and a positive increment of pressures on the model afterbodies. Effects of wall interference were apparent in the data even for a change in blockage ratio from a very low 0.000343 to an even lower 0.000170. Therefore, models having values of blockage ratio of 0.0003 - an order of magnitude below the previously considered safe value of 0.0050 - had significant errors in the drag-coefficient values obtained at speeds near a Mach number of 1.0. Furthermore, the flow relief afforded by slots or perforations in test-section walls - designed according to previously accepted criteria for interference-free subsonic flow - does not appear to be sufficient to avoid significant interference of the walls with the model flow field for Mach numbers very close to 1.0
HST Observations of Giant Arcs: High Resolution Imaging Of Distant Field Galaxies.
We present HST imaging of eight spectroscopically-confirmed giant arcs, pairs
and arclets. These objects have all been extensively studied from the ground
and we demonstrate the unique advantages of HST imaging in the study of such
features by a critical comparison of our data with the previous observations.
In particular we present new estimates of the core radii of two clusters
(Cl0024+16, A370) determined from lensed features which are identifiable in our
HST images. Although our HST observations include both pre- and
post-refurbishment images, the depth of the exposures guarantees that the
majority of the arcs are detected with diffraction-limited resolution. A number
of the objects in our sample are multiply-imaged and we illustrate the ease of
identification of such features when working at high resolution. We discuss the
morphological and scale information on these distant field galaxies in the
light of HST studies of lower redshift samples. We conclude that the dominant
population of star-forming galaxies at z=1 is a factor of 1.5-2 times smaller
than the similar group in the local field. This implies either a considerable
evolution in the sizes of star-forming galaxies within the last 10 Gyrs
or a shift in the relative space densities of massive and dwarf star-forming
systems over the same timescale.Comment: 9 pages (no figures), uuencoded, compressed Postscript. Postscript
text, tables and figures (803 Kb) available via anonymous ftp in at
ftp://ociw.edu//pub/irs/pub/hstarcs.tar.
An investigation of the existence of a surface water layer on aircraft radomes during simulated flight in heavy precipitation
An experiment to investigate the electromagnetic attenuation effects of an impacting water spray on an aircraft weather radome was conducted in Langley's 4 X 7 m. wind tunnel equipped with a water spray system. Results indicate no significant liquid water film formed at the stagnation point of the radome under the test conditions. However, a water sheath was observed standing away from the radome surface, which could possibly have significant attenuation properties of its own. Due to the lack of fidelity in modeling both the natural environment with the tunnel apparatus and the water sheath, it is recommended that further studies be undertaken to better define the water distribution in the vicinity of the radome and measure its effect on weather radar performance
Evolution since z = 0.5 of the Morphology-Density relation for Clusters of Galaxies
Using traditional morphological classifications of galaxies in 10
intermediate-redshift (z~0.5) clusters observed with WFPC-2 on the Hubble Space
Telescope, we derive relations between morphology and local galaxy density
similar to that found by Dressler for low-redshift clusters. Taken
collectively, the `morphology-density' relationship, M-D, for these more
distant, presumably younger clusters is qualitatively similar to that found for
the local sample, but a detailed comparison shows two substantial differences:
(1) For the clusters in our sample, the M-D relation is strong in centrally
concentrated ``regular'' clusters, those with a strong correlation of radius
and surface density, but nearly absent for clusters that are less concentrated
and irregular, in contrast to the situation for low redshift clusters where a
strong relation has been found for both. (2) In every cluster the fraction of
elliptical galaxies is as large or larger than in low-redshift clusters, but
the S0 fraction is 2-3 times smaller, with a proportional increase of the
spiral fraction. Straightforward, though probably not unique, interpretations
of these observations are (1) morphological segregation proceeds
hierarchically, affecting richer, denser groups of galaxies earlier, and (2)
the formation of elliptical galaxies predates the formation of rich clusters,
and occurs instead in the loose-group phase or even earlier, but S0's are
generated in large numbers only after cluster virialization.Comment: 35 pages, 19 figures, uses psfig. Accepted for publication in Ap
Lopsided Galaxies, Weak Interactions and Boosting the Star Formation Rate
To investigate the link between weak tidal interactions in disk galaxies and
the boosting of their recent star formation, we obtain images and spatially
integrated spectra (3615A < lambda < 5315A) for 40 late-type spiral galaxies
(Sab-Sbc) with varying degrees of lopsidedness (a dynamical indicator of weak
interactions). We quantify lopsidedness as the amplitude of the m=1
Fourier component of the azimuthal surface brightness distribution, averaged
over a range of radii. We compare the young stellar content, quantified by
EW(H\delta_abs) and the strength of the 4000 Angstrom break (D_4000), with
lopsidedness and find a 3-4 sigma correlation between the two. We also find a
3.2 sigma correlation between EW(H\beta_emission) and lopsidedness. Using the
evolutionary population synthesis code of Bruzual & Charlot we model the
spectra as an ``underlying population'' and a superimposed ``boost population''
with the aim of constraining the fractional boost in the SFR averaged over the
past 0.5 Gyr (the characteristic lifetime of lopsidedness). From the difference
in both EW(H\delta_abs) and D_4000 between the most and least symmetric thirds
of our sample, we infer that ~ 1x10^9 M_solar of stars are formed over the
duration of a lopsided event in addition to the ``underlying'' SFH (assuming a
final galactic stellar mass of 10^10 M_solar). This corresponds to a factor of
8 increase in the SFR over the past 5x10^8 years. For the nuclear spectra, all
of the above correlations except D_4000 vs. are weaker than for the disk,
indicating that in lopsided galaxies, the SF boost is not dominated by the
nucleus.Comment: 35 pages, including 10 figures, to appear in the Astrophysical
Journal, abridged abstrac
Optical Star-Formation Rate Indicators
Using integrated optical spectrophotometry for 412 star-forming galaxies at
z~0, and fiber-aperture spectrophotometry for 120,846 SDSS galaxies at z~0.1,
we investigate the H-alpha, H-beta, [O II] 3727, and [O III] 5007 nebular
emission lines and the U-band luminosity as quantitative star-formation rate
(SFR) indicators. We demonstrate that the extinction-corrected H-alpha
luminosity is a reliable SFR tracer even in highly obscured star-forming
galaxies. We find that variations in dust reddening dominate the systematic
uncertainty in SFRs derived from the observed H-beta, [O II], and U-band
luminosities, producing a factor of ~1.7, ~2.5, and ~2.1 scatter in the mean
transformations, respectively. We show that [O II] depends weakly on variations
in oxygen abundance over a wide range in metallicity, 12+log(O/H)=8.15-8.7 dex
(Z/Z_sun=0.28-1.0), and that in this metallicity interval galaxies occupy a
narrow range in ionization parameter (-3.8<log U<-2.9 dex). We show that the
scatter in [O III] 5007 as a SFR indicator is a factor of 3-4 due to its
sensitivity to metal abundance and ionization. We develop empirical SFR
calibrations for H-beta and [O II] parameterized in terms of the B-band
luminosity, which remove the systematic effects of reddening and metallicity,
and reduce the SFR scatter to +/-40% and +/-90%, respectively, although
individual galaxies may deviate substantially from the median relations.
Finally, we compare the z~0 relations between blue luminosity and reddening,
ionization, and [O II]/H-alpha ratio against measurements at z~1 and find broad
agreement. (Abridged.)Comment: ApJ, accepted; no changes from previously posted version; emulateapj
style; 41 pages, 23 figures, 2 table
Development and Validation of the Behavioral Tendencies Questionnaire
At a fundamental level, taxonomy of behavior and behavioral tendencies can be described
in terms of approach, avoid, or equivocate (i.e., neither approach nor avoid). While there are
numerous theories of personality, temperament, and character, few seem to take advantage
of parsimonious taxonomy. The present study sought to implement this taxonomy by
creating a questionnaire based on a categorization of behavioral temperaments/tendencies
first identified in Buddhist accounts over fifteen hundred years ago. Items were developed
using historical and contemporary texts of the behavioral temperaments, described as
βGreedy/Faithfulβ, βAversive/Discerningβ, and βDeluded/Speculativeβ. To both maintain
this categorical typology and benefit from the advantageous properties of forced-choice
response format (e.g., reduction of response biases), binary pairwise preferences for items
were modeled using Latent Class Analysis (LCA). One sample (n1 = 394) was used to estimate
the item parameters, and the second sample (n2 = 504) was used to classify the participants
using the established parameters and cross-validate the classification against
multiple other measures. The cross-validated measure exhibited good nomothetic span
(construct-consistent relationships with related measures) that seemed to corroborate the
ideas present in the original Buddhist source documents. The final 13-block questionnaire
created from the best performing items (the Behavioral Tendencies Questionnaire or BTQ)
is a psychometrically valid questionnaire that is historically consistent, based in behavioral
tendencies, and promises practical and clinical utility particularly in settings that teach and
study meditation practices such as Mindfulness Based Stress Reduction (MBSR)
Overexpression of P70 S6 kinase protein is associated with increased risk of locoregional recurrence in node-negative premenopausal early breast cancer patients
The RPS6KB1 gene is amplified and overexpressed in approximately 10% of breast carcinomas and has been found associated with poor prognosis. We studied the prognostic significance of P70 S6 kinase protein (PS6K) overexpression in a series of 452 node-negative premenopausal early-stage breast cancer patients (median follow-up: 10.8 years). Immunohistochemistry was used to assess PS6K expression in the primary tumour, which had previously been analysed for a panel of established prognostic factors in breast cancer. In a univariate analysis, PS6K overexpression was associated with worse distant disease-free survival as well as impaired locoregional control (HR 1.80, P 0.025 and HR 2.50, P 0.006, respectively). In a multivariate analysis including other prognostic factors, PS6K overexpression remained an independent predictor for poor locoregional control (RR 2.67, P 0.003). To our knowledge, P70 S6 kinase protein is the first oncogenic marker that has prognostic impact on locoregional control and therefore may have clinical implications in determining the local treatment strategy in early-stage breast cancer patients
Development of a Halotolerant Community in the St. Lucia Estuary (South Africa) during a Hypersaline Phase
Background: The St. Lucia Estuary, Africaβs largest estuarine lake, is currently experiencing unprecedented freshwater deprivation which has resulted in a northward gradient of drought effects, with hypersaline conditions in its northern lakes. Methodology/Principal Findings: This study documents the changes that occurred in the biotic communities at False Bay from May 2010 to June 2011, in order to better understand ecosystem functioning in hypersaline habitats. Few zooplankton taxa were able to withstand the harsh environmental conditions during 2010. These were the flatworm Macrostomum sp., the harpacticoid copepod Cletocamptus confluens, the cyclopoid copepod Apocyclops cf. dengizicus and the ciliate Fabrea cf. salina. In addition to their exceptional salinity tolerance, they were involved in a remarkably simple food web. In June 2009, a bloom of an orange-pigmented cyanobacterium (Cyanothece sp.) was recorded in False Bay and persisted uninterruptedly for 18 months. Stable isotope analysis suggests that this cyanobacterium was the main prey item of F. cf. salina. This ciliate was then consumed by A. cf. dengizicus, which in turn was presumably consumed by flamingos as they flocked in the area when the copepods attained swarming densities. On the shore, cyanobacteria mats contributed to a population explosion of the staphylinid beetle Bledius pilicollis. Although zooplankton disappeared once salinities exceeded 130, many taxa are capable of producing spores or resting cysts to bridge harsh periods. The hypersaline community was disrupted by heavy summer rains in 2011, which alleviated drought conditions and resulted in a sharp increase in zooplankton stock an
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1974
History of Golf (1) The Nine Toughest Holes in the World (2) Stockie Madness (3) Bartender, One More Round for Pythium (3) Panel: 1973 Turf Problems in Review - 1974 Possible Remedies (A1-A12) Movement of Water to a Holding Pond (A13) Maintenance of Low Budget, Short Season Golf Courses (A16) Turfgrass Fertilization (A18) Determining Turfgrass Fertilizer Needs (A25) Shortage of Plant Food and How to Adjust to Supply and Cost (A29) Panel: Tricalcium Arsenate - Use and Abuse (A33-A46) Operating and Maintaining Municipal Golf Courses (A48) Maintenance of a High Budget Golf Course (A51) Trends in Agricultural Education and Where Are the Emphases (A58) Maintenance of Municipal Parks and Recreation Areas (A60) Maintenance of Grass Tennis Courts (A63) Transition from Natural to Artificial Turf (A67) Plant materials for Outlying Areas (A71) Care of University Grounds (A76) Maintenance of Industrial Sites (A79) Turfgrass Diseases and Systemic Fungicides (A81) A Look at the Future (A 84) Watering of Golf Course Turf (A92
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