6,820 research outputs found
Design and assembly sequence analysis of option 3 for CETF reference space station
A design and assembly sequence was conducted on one option of the Dual Keel Space Station examined by a NASA Critical Evaluation Task Force to establish viability of several variations of that option. A goal of the study was to produce and analyze technical data to support Task Force decisions to either examine particular Option 3 variations in more depth or eliminate them from further consideration. An analysis of the phasing assembly showed that use of an Expendable Launch Vehicle in conjunction with the Space Transportation System (STS) can accelerate the buildup of the Station and ease the STS launch rate constraints. The study also showed that use of an Orbital Maneuvering Vehicle on the first flight can significantly benefit Station assembly and, by performing Station subsystem functions, can alleviate the need for operational control and reboost systems during the early flights. In addition to launch and assembly sequencing, the study assessed stability and control, and analyzed node-packaging options and the effects of keel removal on the structural dynamics of the Station. Results of these analyses are presented and discussed
A computational investigation of cardiovascular haemodynamic abnormalities in turner syndrome patients
Girls with Turner syndrome (TS), a chromosomal condition in which a female has complete or partial absence of the second sex chromosome, present a unique group of patients, with an increased risk of cardiovascular disease. Congenital heart abnormalities occur in up to 50% of TS individuals and mortality rates are three times higher compared with the general population, with the most common cause of death being from cardiovascular disease [1-2]. We hypothesise that patients with TS present a greater variance in aortic arch morphology and haemodynamics than their healthy counterparts, because each TS patient is regarded as a unique anatomical and physiological case study. In this investigation, we present the first ever computational fluid dynamic analysis of TS children, with patient-specific physiologically realistic haemodynamic conditions. Computational models were used to analyse the arterial blood flow in TS children, who are known to present an increased risk of cardiovascular disease. Three-dimensional patient geometries of the aortic arch were reconstructed while numerical simulations were performed within a finite-volume method framework, using patient-specific phase-contrast MRI obtained boundary conditions. Velocity streamlines and time-dependent metrics, such as the timeaveraged wall shear stress (TAWSS) and oscillatory shear index (OSI), were computed for all models. Particular attention was paid to regions of low mean and oscillatory haemodynamic wall shear stresses as our current understanding of subclinical atherosclerosis links these blood flow-induced biomechanical stimuli with damage to the arterial vascular endothelium. Preliminary results have found morphological aortic differences between patients to have a strong effect on the haemodynamic environment and may be a marker for increased cardiovascular risk
Native Aggregates for Skid Resistance
The objectives of the study were 1) to identify sources of native aggregates with varying histories of skid resistance performance; 2) to evaluate and correlate native aggregate characteristics, processing techniques, and other factors with skid resistance and surface mixture performance; and 3) to provide guidelines for implementation of research findings. Limestone, sandstone, river gravel, and control aggregates (granite, traprock, and slags) were subjected to a battery of tests to determine physical relationships between aggregate type and skid resistance.
Laboratory results were analyzed for correlations among themselves and for correlations with skid number data obtained from pavements containing aggregates involved in the study. No significant correlation could be found between any of the laboratory results and field skid numbers. This was particularly disturbing with reference to the KTRP test. It was thought that it could be used to adequately predict field skid performance. However, preliminary findings have shown no such relationship. It is recommended that the KTRP test be amended to provide a more defined weight loss over time to attempt to explain the behavior of an aggregate\u27s skid resistance over time
Evaluation of Asphalt Additive -- Chemkrete
Construction, performance, and cost-effectiveness evaluations of an AC-10 treated with Chemkrete (CTI-101) and an untreated AC-20 are presented. Laboratory tests, and field tests which include marshall stability, density test, repeated load test, road-ratter deflection data, and visual observation are summarized.
Because of the apparent failure of Chemkrete to significantly enhance the performance of the pavement, and the additional cost for the use of Chemkrete, it would not be recommended for further use in the state of Kentucky
Feminist phenomenology and the woman in the running body
Modern phenomenology, with its roots in Husserlian philosophy, has been taken up and utilised in a myriad of ways within different disciplines, but until recently has remained relatively under-used within sports studies. A corpus of sociological-phenomenological work is now beginning to develop in this domain, alongside a longer standing literature in feminist phenomenology. These specific social-phenomenological forms explore the situatedness of lived-body experience within a particular social structure. After providing a brief overview of key strands of phenomenology, this article considers some of the ways in which sociological, and particularly feminist phenomenology, might be used to analyse female sporting embodiment. For illustrative purposes, data from an autophenomenographic project on female distance running are also included, in order briefly to demonstrate the application of phenomenology within sociology, as both theoretical framework and methodological approach
Intercomparison of Satellite-Derived Snow-Cover Maps
In anticipation of the launch of the Earth Observing System (EOS) Terra, and the PM-1 spacecraft in 1999 and 2000, respectively, efforts are ongoing to determine errors of satellite-derived snow-cover maps. EOS Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Microwave Scanning Radiometer-E (AMSR-E) snow-cover products will be produced. For this study we compare snow maps covering the same study area acquired from different sensors using different snow- mapping algorithms. Four locations are studied: 1) southern Saskatchewan; 2) a part of New England (New Hampshire, Vermont and Massachusetts) and eastern New York; 3) central Idaho and western Montana; and 4) parts of North and South Dakota. Snow maps were produced using a prototype MODIS snow-mapping algorithm used on Landsat Thematic Mapper (TM) scenes of each study area at 30-m and when the TM data were degraded to 1 -km resolution. National Operational Hydrologic Remote Sensing Center (NOHRSC) 1 -km resolution snow maps were also used, as were snow maps derived from 1/2 deg. x 1/2 deg. resolution Special Sensor Microwave Imager (SSM/1) data. A land-cover map derived from the International Geosphere-Biosphere Program (IGBP) land-cover map of North America was also registered to the scenes. The TM, NOHRSC and SSM/I snow maps, and land-cover maps were compared digitally. In most cases, TM-derived maps show less snow cover than the NOHRSC and SSM/I maps because areas of incomplete snow cover in forests (e.g., tree canopies, branches and trunks) are seen in the TM data, but not in the coarser-resolution maps. The snow maps generally agree with respect to the spatial variability of the snow cover. The 30-m resolution TM data provide the most accurate snow maps, and are thus used as the baseline for comparison with the other maps. Comparisons show that the percent change in amount of snow cover relative to the 3 0-m resolution TM maps is lowest using the TM I -km resolution maps, ranging from 0 to 40%. The highest percent change (less than 100%) is found in the New England study area, probably due to the presence of patchy snow cover. A scene with patchy snow cover is more difficult to map accurately than is a scene with a well-defined snowline such as is found on the North and South Dakota scene where the percent change ranged from 0 to 40%. There are also some important differences in the amount of snow mapped using the two different SSM/I algorithms because they utilize different channels
Measuring the Stellar Masses of z~7 Galaxies with Spitzer Ultrafaint Survey Program (SURFS UP)
We present Spitzer/IRAC observations of nine -band dropouts highly
magnified (2<mu<12) by the Bullet Cluster. We combine archival imaging with our
Exploratory program (SURFS UP), which results in a total integration time of
~30 hr per IRAC band. We detect (>3sigma) in both IRAC bands the brightest of
these high-redshift galaxies, with [3.6]=23.80+-0.28 mag, [4.5]=23.78+-0.25
mag, and (H-[3.6])=1.17+-0.32 mag. The remaining eight galaxies are undetected
to [3.6]~26.4 mag and [4.5]~26.0 mag with stellar masses of ~5x10^7 M_sol. The
detected galaxy has an estimated magnification of mu=12+-4, which implies this
galaxy has an ultraviolet luminosity of L_1500~0.3 L*_{z=7} --- the lowest
luminosity individual source detected in IRAC at z>7. By modeling the broadband
photometry, we estimate the galaxy has an intrinsic star-formation rate of
SFR~1.3 M_sol/yr and stellar mass of M~2x10^9 M_sol, which gives a specific
star-formation rate of sSFR~0.7 Gyr^-1. If this galaxy had sustained this
star-formation rate since z~20, it could have formed the observed stellar mass
(to within a factor of ~2), we also discuss alternate star-formation histories
and argue the exponentially-increasing model is unlikely. Finally, based on the
intrinsic star-formation rate, we estimate this galaxy has a likely [C II] flux
of = 10^{-17} erg/s/cm2.Comment: Accepted to ApJL. 6 pages, 3 figures, 2 table
Key Ne states identified affecting -ray emission from F in novae
Detection of nuclear-decay rays provides a sensitive thermometer of
nova nucleosynthesis. The most intense -ray flux is thought to be
annihilation radiation from the decay of F, which is destroyed
prior to decay by the F(,)O reaction. Estimates of
F production had been uncertain, however, because key near-threshold
levels in the compound nucleus, Ne, had yet to be identified. This
Letter reports the first measurement of the
F(He,)Ne reaction, in which the placement of two
long-sought 3/2 levels is suggested via triton--
coincidences. The precise determination of their resonance energies reduces the
upper limit of the rate by a factor of at nova temperatures and
reduces the average uncertainty on the nova detection probability by a factor
of 2.1.Comment: 6 pages, 4 figure
New -ray Transitions Observed in Ne with Implications for the O(,)Ne Reaction Rate
The O(,)Ne reaction is responsible for breakout
from the hot CNO cycle in Type I x-ray bursts. Understanding the properties of
resonances between and 5 MeV in Ne is crucial in the
calculation of this reaction rate. The spins and parities of these states are
well known, with the exception of the 4.14- and 4.20-MeV states, which have
adopted spin-parities of 9/2 and 7/2, respectively. Gamma-ray
transitions from these states were studied using triton--
coincidences from the F(He,)Ne reaction measured
with GODDESS (Gammasphere ORRUBA Dual Detectors for Experimental Structure
Studies) at Argonne National Laboratory. The observed transitions from the
4.14- and 4.20-MeV states provide strong evidence that the values are
actually 7/2 and 9/2, respectively. These assignments are consistent
with the values in the F mirror nucleus and in contrast to previously
accepted assignments
Early Economic Evaluation of Diagnostic Technologies: Experiences of the NIHR Diagnostic Evidence Co-operatives
Diagnostic tests are expensive and time-consuming to develop. Early economic evaluation using decision modeling can reduce commercial risk by providing early evidence on cost-effectiveness. The National Institute for Health Research Diagnostic Evidence Co-operatives (DECs) was established to catalyze evidence generation for diagnostic tests by collaborating with commercial developers; DEC researchers have consequently made extensive use of early modeling. The aim of this article is to summarize the experiences of the DECs using early modeling for diagnostics. We draw on 8 case studies to illustrate the methods, highlight methodological strengths and weaknesses particular to diagnostics, and provide advice. The case studies covered diagnosis, screening, and treatment stratification. Treatment effectiveness was a crucial determinant of cost-effectiveness in all cases, but robust evidence to inform this parameter was sparse. This risked limiting the usability of the results, although characterization of this uncertainty in turn highlighted the value of further evidence generation. Researchers evaluating early models must be aware of the importance of treatment effect evidence when reviewing the cost-effectiveness of diagnostics. Researchers planning to develop an early model of a test should also 1) consult widely with clinicians to ensure the model reflects real-world patient care; 2) develop comprehensive models that can be updated as the technology develops, rather than taking a âquick and dirtyâ approach that may risk producing misleading results; and 3) use flexible methods of reviewing evidence and evaluating model results, to fit the needs of multiple decision makers. Decision models can provide vital information for developers at an early stage, although limited evidence mean researchers should proceed with caution
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