4,785 research outputs found
Effect of tip planform on blade loading characteristics for a two-bladed rotor in hover
A laser velocimeter was used to study the flow surrounding a 2.13 m diam. two-bladed, teetering model-scale helicopter rotor operating in the hover condition. The rotor system employed interchangeable blade tips over the outer 25% radius. A conventional rectangular planform and an experimental ogee tip shape were studied. The radial distribution of the blade circulation was obtained by measuring the velocity tangent to a closed rectangular contour around the airfoil section at a number of radial locations. A relationship between local circulation and bound vorticity was invoked to obtain the radial variations in the sectional lifting properties of the blade. The tip vortex-induced velocity was also measured immediately behind the generating blade and immediately before the encounter with the following blade. The mutual influence between blade loading, shed vorticity, and the structure of the encountered vortex are quantified by the results presented and are discussed comparatively for the rectangular and ogee planforms. The experimental loading for the rectangular tip is also compared with predictions of existing rotor analysis
Role of Geoinformatics for Ghana oil and gas industry
The Geoinformatics Engineer (GE), who uses mathematical theory and precise measurements for the collection and distribution of geospatial data, plays a significant role in the oil and gas industry. The paper reviews the role the HE would play in t he recent oil and gas discovery in Ghana. This is because the GE is required in the planning and execution of nearly every form of activities at the upstream, midstream and downstream; for example offshore and onshore construction, exploration and engineering for the production and dissemination of oil and gas. Ghana is at the initial stages in the commercial production of oil and gas; and thus needs research institutions with excellent practical and research skills, such as the Department of Geomat ic Engineering (DGE), Kwame Nkrumah University of Science and Technology (KNUST), Ghana and School of Earth Sciences and Engineering (SESE), Hohai University, China, in employing Geoinformatics theories, applications and principles for geospatial decision making for sustainable production of oil and gas for Ghana and the Sub - Saharan Africa. SESE expertise in 3S Technology would greatly assist in the construction and monitoring of oil and gas infrastructures at the upstream, midstream and downstr eam. The pap er recommends useful suggestions for smooth management of the oil and gas industry focusing on GEs and research institutions
Surfactant status and respiratory outcome in premature infants receiving late surfactant treatment.
BACKGROUND:Many premature infants with respiratory failure are deficient in surfactant, but the relationship to occurrence of bronchopulmonary dysplasia (BPD) is uncertain. METHODS:Tracheal aspirates were collected from 209 treated and control infants enrolled at 7-14 days in the Trial of Late Surfactant. The content of phospholipid, surfactant protein B, and total protein were determined in large aggregate (active) surfactant. RESULTS:At 24 h, surfactant treatment transiently increased surfactant protein B content (70%, p < 0.01), but did not affect recovered airway surfactant or total protein/phospholipid. The level of recovered surfactant during dosing was directly associated with content of surfactant protein B (r = 0.50, p < 0.00001) and inversely related to total protein (r = 0.39, p < 0.0001). For all infants, occurrence of BPD was associated with lower levels of recovered large aggregate surfactant, higher protein content, and lower SP-B levels. Tracheal aspirates with lower amounts of recovered surfactant had an increased proportion of small vesicle (inactive) surfactant. CONCLUSIONS:We conclude that many intubated premature infants are deficient in active surfactant, in part due to increased intra-alveolar metabolism, low SP-B content, and protein inhibition, and that the severity of this deficit is predictive of BPD. Late surfactant treatment at the frequency used did not provide a sustained increase in airway surfactant
Differential impact of two risk communications on antipsychotic prescribing to people with dementia in Scotland: segmented regression time series analysis 2001-2011
The two risk communications were associated with reductions in antipsychotic use, in ways which were compatible with marked differences in their content and dissemination. Further research is needed to ensure that the content and dissemination of regulatory risk communications is optimal, and to track their impact on intended and unintended outcomes. Although rates are falling, antipsychotic prescribing in dementia in Scotland remains unacceptably hig
Analytical Study of Diffusive Relativistic Shock Acceleration
Particle acceleration in relativistic shocks is studied analytically in the
test-particle, small-angle scattering limit, for an arbitrary velocity-angle
diffusion function D. Accurate analytic expressions for the spectral index s
are derived using few (2-6) low-order moments of the shock-frame angular
distribution. For isotropic diffusion, previous results are reproduced and
justified. For anisotropic diffusion, s is shown to be sensitive to D,
particularly downstream and at certain angles, and a wide range of s values is
attainable. The analysis, confirmed numerically, can be used to test
collisionless shock models and to observationally constrain D. For example,
strongly forward- or backward-enhanced diffusion downstream is ruled out by GRB
afterglow observations.Comment: 4 pages, 2 figures, PRL accepted, minor change
Development of a physical map of the soybean pathogen Fusarium virguliforme based on synteny with Fusarium graminearum genomic DNA
<p>Abstract</p> <p>Background</p> <p>Reference genome sequences within the major taxa can be used to assist the development of genomic tools for related organisms. A major constraint in the use of these sequenced and annotated genomes is divergent evolution. Divergence of organisms from a common ancestor may have occurred millions of years ago, leading to apparently un-related and un-syntenic genomes when sequence alignment is attempted.</p> <p>Results</p> <p>A series of programs were written to prepare 36 Mbp of <it>Fusarium graminearum </it>sequence in 19 scaffolds as a reference genome. Exactly 4,152 Bacterial artificial chromosome (BAC) end sequences from 2,178 large-insert <it>Fusarium virguliforme </it>clones were tested against this sequence. A total of 94 maps of <it>F. graminearum </it>sequence scaffolds, annotated exonic fragments and associated <it>F. virguliforme </it>sequences resulted.</p> <p>Conclusion</p> <p>Developed here was a technique that allowed the comparison of genomes based on small, 15 bp regions of shared identity. The main power of this method lay in its ability to align <it>diverged </it>sequences. This work is unique in that discontinuous sequences were used for the analysis and information not readily apparent, such as match direction, are presented. The 94 maps and JAVA programs are freely available on the Web and by request.</p
Monitoring wolf populations using howling points combined with sign survey transects
Wolves respond to simulated howling, especially during the mating and breeding seasons. Simulated howling points are, therefore, commonly used by many wolf researchers around the world to estimate pack numbers in a given area. A large amount of information is available on various pack breeding
areas in Asturias, the only region in north-western Spain where the Iberian wolf (Canis lupus signatus, Cabrera 1907) is not classed as a game species. Wolf research began there in the early 1980s. We present the results of the latest study on population status, conducted between July and November, 2001. Using sampling transects to detect wolf scat and scratch marks and designated howling and observation points, twenty one (21) wolf packs were
definitely located, with two others considered “likely”. Nineteen (19) packs were detected using howling points (n=314). The results of this study show that simulated howling points and sampling transects are reliable and
inexpensive way of detecting wolf packs
A Search for a Sub-Earth Sized Companion to GJ 436 and a Novel Method to Calibrate Warm Spitzer IRAC Observations
We discovered evidence for a possible additional 0.75 R_Earth transiting
planet in the NASA EPOXI observations of the known M dwarf exoplanetary system
GJ 436. Based on an ephemeris determined from the EPOXI data, we predicted a
transit event in an extant Spitzer Space Telescope 8 micron data set of this
star. Our subsequent analysis of those Spitzer data confirmed the signal of the
predicted depth and at the predicted time, but we found that the transit depth
was dependent on the aperture used to perform the photometry. Based on these
suggestive findings, we gathered new Warm Spitzer Observations of GJ 436 at 4.5
microns spanning a time of transit predicted from the EPOXI and Spitzer 8
micron candidate events. The 4.5 micron data permit us to rule out a transit at
high confidence, and we conclude that the earlier candidate transit signals
resulted from correlated noise in the EPOXI and Spitzer 8 micron observations.
In the course of this investigation, we developed a novel method for correcting
the intrapixel sensitivity variations of the 3.6 and 4.5 micron channels of the
Infrared Array Camera (IRAC) instrument. We demonstrate the sensitivity of Warm
Spitzer observations of M dwarfs to confirm sub-Earth sized planets. Our
analysis will inform similar work that will be undertaken to use Warm Spitzer
observations to confirm rocky planets discovered by the Kepler mission.Comment: 22 pages, 8 figures, accepted for publication in PAS
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