2,215 research outputs found
Simple atmospheric perturbation models for sonic-boom-signature distortion studies
Sonic-boom propagation from flight level to ground is influenced by wind and speed-of-sound variations resulting from temperature changes in both the mean atmospheric structure and small-scale perturbations. Meteorological behavior generally produces complex combinations of atmospheric perturbations in the form of turbulence, wind shears, up- and down-drafts and various wave behaviors. Differences between the speed of sound at the ground and at flight level will influence the threshold flight Mach number for which the sonic boom first reaches the ground as well as the width of the resulting sonic-boom carpet. Mean atmospheric temperature and wind structure as a function of altitude vary with location and time of year. These average properties of the atmosphere are well-documented and have been used in many sonic-boom propagation assessments. In contrast, smaller scale atmospheric perturbations are also known to modulate the shape and amplitude of sonic-boom signatures reaching the ground, but specific perturbation models have not been established for evaluating their effects on sonic-boom propagation. The purpose of this paper is to present simple examples of atmospheric vertical temperature gradients, wind shears, and wave motions that can guide preliminary assessments of nonturbulent atmospheric perturbation effects on sonic-boom propagation to the ground. The use of simple discrete atmospheric perturbation structures can facilitate the interpretation of the resulting sonic-boom propagation anomalies as well as intercomparisons among varied flight conditions and propagation models
Mechanical Design Analysis of Several Noncritical Air-cooled Turbine Disks and a Corrugated-insert Air-cooled Turbine Rotor Blade
Ariel - Volume 5 Number 5
Editors
Mark Dembert
J. D. Kanofsky
Entertainment
Robert Breckenridge
Joe Conti
Gary Kaskey
Photographer
Scot Kastner
Overseas Editor
Mike Sinason
Circulation
Jay Amsterdam
Humorist
Jim McCann
Staff
Ken Jaffe
Bob Sklaroff
Janet Welsh
Dave Jacoby
Phil Nimoityn
Frank Chervane
Statics and dynamics of single DNA molecules confined in nanochannels
The successful design of nanofluidic devices for the manipulation of biopolymers requires an understanding of how the predictions of soft condensed matter physics scale with device dimensions. Here we present measurements of DNA extended in nanochannels and show that below a critical width roughly twice the persistence length there is a crossover in the polymer physics
PGC‑1α alternative promoter (Exon 1b) controls augmentation of total PGC‑1α gene expression in response to cold water immersion and low glycogen availability
This investigation sought to determine whether post-exercise cold water immersion and low glycogen availability, separately
and in combination, would preferentially activate either the Exon 1a or Exon 1b Peroxisome proliferator-activated
receptor gamma coactivator 1-alpha (PGC-1α) promoter. Through a reanalysis of sample design, we identified that the
systemic cold-induced augmentation of total PGC-1α gene expression observed previously (Allan et al. in J Appl Physiol
123(2):451–459, 2017) was largely a result of increased expression from the alternative promoter (Exon 1b), rather than
canonical promoter (Exon 1a). Low glycogen availability in combination with local cooling of the muscle (Allan et al. in
Physiol Rep 7(11):e14082, 2019) demonstrated that PGC-1α alternative promoter (Exon 1b) expression continued to rise at
3 h post-exercise in all conditions; whilst, expression from the canonical promoter (Exon 1a) decreased between the same
time points (post-exercise–3 h post-exercise). Importantly, this increase in PGC-1α Exon 1b expression was reduced compared
to the response of low glycogen or cold water immersion alone, suggesting that the combination of prior low glycogen and
CWI post-exercise impaired the response in gene expression versus these conditions individually. Data herein emphasise the
influence of post-exercise cooling and low glycogen availability on Exon-specific contro
Ariel - Volume 6 Number 4
Editors
Mark Dembert
J.D. Kanofsky
Frank Chervenak
John Lammie
Curt Cummings
Entertainment
Robert Breckenridge
Joe Conti
Gary Kaskey
Photographer
Larry Glazerman
Overseas Editor
Mike Sinason
Humorist
Jim McCann
Staff
Ken Jaffe
Bob Sklaroff
Halley Faust
Jim Burk
Ariel - Volume 6 Number 4 (Alternate Version)
Editors
Mark Dembert
J.D. Kanofsky
Frank Chervenak
John Lammie
Curt Cummings
Entertainment
Robert Breckenridge
Joe Conti
Gary Kaskey
Photographer
Larry Glazerman
Overseas Editor
Mike Sinason
Humorist
Jim McCann
Staff
Kenn Jaffe
Bob Sklaroff
Halley Faust
Jim Burke
Jay Amsterdam
Morton A. Klein
Nancy Redfer
Thorium isotopes tracing the iron cycle at the Hawaii Ocean Time-series Station ALOHA
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 169 (2015): 1-16, doi:10.1016/j.gca.2015.07.019.The role of iron as a limiting micronutrient motivates an effort to understand the supply and
removal of lithogenic trace metals in the ocean. The long-lived thorium isotopes (232 Th and
230 Th) in seawater can be used to quantify the input of lithogenic metals attributable to the partial
dissolution of aerosol dust. Thus, Th can help in disentangling the Fe cycle by providing an
estimate of its ultimate supply and turnover rate. Here we present time-series (1994-2014) data
on thorium isotopes and iron concentrations in seawater from the Hawaii Ocean Time-series
Station ALOHA. By comparing Th-based dissolved Fe fluxes with measured dissolved Fe
inventories, we derive Fe residence times of 6-12 months for the surface ocean. Therefore, Fe
inventories in the surface ocean are sensitive to seasonal changes in dust input. Ultrafiltration
results further reveal that Th has a much lower colloidal content than Fe does, despite a common
source. On this basis, we suggest Fe colloids may be predominantly organic in composition, at
least at Station ALOHA. In the deep ocean (>2 km), Fe approaches a solubility limit while Th,
surprisingly, is continually leached from lithogenic particles. This distinction has implications
for the relevance of Fe ligand availability in the deep ocean, but also suggests Th is not a good
tracer for Fe in deep waters. While uncovering divergent behavior of these elements in the water
column, this study finds that dissolved Th flux is a suitable proxy for the supply of Fe from dust
in the remote surface ocean.We acknowledge funding from the W.O. Crosby Postdoctoral Fellowship to CTH and the
National Science Foundation through C-MORE, NSF-OIA EF-0424599 to EAB, and NSF-DMR
Author Posting
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