420 research outputs found
Probability density function of turbulent velocity fluctuations in rough-wall boundary layer
The probability density function of single-point velocity fluctuations in
turbulence is studied systematically using Fourier coefficients in the
energy-containing range. In ideal turbulence where energy-containing motions
are random and independent, the Fourier coefficients tend to Gaussian and
independent of each other. Velocity fluctuations accordingly tend to Gaussian.
However, if energy-containing motions are intermittent or contaminated with
bounded-amplitude motions such as wavy wakes, the Fourier coefficients tend to
non-Gaussian and dependent of each other. Velocity fluctuations accordingly
tend to non-Gaussian. These situations are found in our experiment of a
rough-wall boundary layer.Comment: 6 pages, to appear in Physical Review
Microstructure and phase stability of suspension high velocity oxy-fuel sprayed yttria stabilised zirconia coatings from aqueous and ethanol based suspensions
Two commercial 7-8 wt.% Yttria Stabilised Zirconia (YSZ) suspensions were sprayed by Suspension High Velocity Oxy Fuel (SHVOF) thermal spraying for advanced high temperature coatings. Heat treatments of the free-standing coatings were conducted at 800 °C and 1000 °C for 72 h. The SHVOF coatings using two liquid carriers: water and ethanol, behaved differently in terms of micro-structure and phase stability. The ethanol coatings retained a fully tetragonal composition after heat treatments; while the aqueous coatings, however, underwent the undesirable tetragonal to monoclinic phase transformation at 1000 °C, which is lower than previously reported temperatures (>1200 °C) in thermal sprayed YSZ coatings. The heat treatments not only resulted in densification of both coatings, but also caused excessive crystallite growth in aqueous coatings promoting the undesirable phase transformation. On the contrary, the ethanol suspension improved the phase stability by favouring the homogenization of yttrium during spraying
Stacking disorder in 뱉RuCl_{3} investigated via x-ray three-dimensional difference pair distribution function analysis
The van der Waals layered magnet α â RuCl_{3} offers tantalizing prospects for the realization of Majorana quasiparticles. Efforts to understand this are, however, hampered by inconsistent magnetic and thermal transport properties likely coming from the formation of structural disorder during crystal growth, postgrowth processing, or upon cooling through the first order structural transition. Here, we investigate structural disorder in α â RuCl_{3} using x-ray diffuse scattering and three-dimensional difference pair distribution function analysis. We develop a quantitative model that describes disorder in α â RuCl_{3} in terms of rotational twinning and intermixing of the high- and low-temperature structural layer stacking. This disorder may be important to consider when investigating the detailed magnetic and electronic properties of this widely studied material
Numerical investigation of the wake interaction between two model wind turbines with span-wise offset
Structure of Charge Density Waves in LaBaCuO
Although charge-density wave (CDW) correlations exist in several families of
cuprate supercon-ductors, they exhibit substantial variation in CDW wavevector
and correlation length, indicating a key role for CDW-lattice interactions. We
investigated this interaction in LaBaCuO using single
crystal x-ray diffraction to collect a large number of CDW peak intensities,
and determined the Cu and La/Ba atomic distortions induced by the formation of
CDW order. Within the CuO planes, the distortions involve a periodic
modulation of the Cu-Cu spacing along the direction of the ordering wave
vector. The charge ordering within the copper-oxygen layer induces an
out-of-plane breathing modulation of the surrounding lanthanum layers, which
leads to a related distortion on the adjacent copper-oxygen layer. Our result
implies that the CDW-related structural distortions do not remain confined to a
single layer but rather propagate an appreciable distance through the crystal.
This leads to overlapping structural modulations, in which CuO planes
exhibit distortions arising from the orthogonal CDWs in adjacent layers as well
as distortions from the CDW within the layer itself. We attribute this striking
effect to the weak c-axis charge screening in cuprates and suggest this effect
could help couple the CDW between adjacent planes in the crystal.Comment: 9 pages; Accepted in Phys. Rev.
Randomized Dose-Ranging Controlled Trial of AQ-13, a Candidate Antimalarial, and Chloroquine in Healthy Volunteers
OBJECTIVES: To determine: (1) the pharmacokinetics and safety of an investigational aminoquinoline active against multidrugâresistant malaria parasites (AQ-13), including its effects on the QT interval, and (2) whether it has pharmacokinetic and safety profiles similar to chloroquine (CQ) in humans. DESIGN: Phase I double-blind, randomized controlled trials to compare AQ-13 and CQ in healthy volunteers. Randomizations were performed at each step after completion of the previous dose. SETTING: TulaneâLouisiana State UniversityâCharity Hospital General Clinical Research Center in New Orleans. PARTICIPANTS: 126 healthy adults 21â45 years of age. INTERVENTIONS: 10, 100, 300, 600, and 1,500 mg oral doses of CQ base in comparison with equivalent doses of AQ-13. OUTCOME MEASURES: Clinical and laboratory adverse events (AEs), pharmacokinetic parameters, and QT prolongation. RESULTS: No hematologic, hepatic, renal, or other organ toxicity was observed with AQ-13 or CQ at any dose tested. Headache, lightheadedness/dizziness, and gastrointestinal (GI) tractârelated symptoms were the most common AEs. Although symptoms were more frequent with AQ-13, the numbers of volunteers who experienced symptoms with AQ-13 and CQ were similar (for AQ-13 and CQ, respectively: headache, 17/63 and 10/63, p = 0.2; lightheadedness/dizziness, 11/63 and 8/63, p = 0.6; GI symptoms, 14/63 and 13/63; p = 0.9). Both AQ-13 and CQ exhibited linear pharmacokinetics. However, AQ-13 was cleared more rapidly than CQ (respectively, median oral clearance 14.0â14.7 l/h versus 9.5â11.3 l/h; p †0.03). QTc prolongation was greater with CQ than AQ-13 (CQ: mean increase of 28 ms; 95% confidence interval [CI], 18 to 38 ms, versus AQ-13: mean increase of 10 ms; 95% CI, 2 to 17 ms; p = 0.01). There were no arrhythmias or other cardiac AEs with either AQ-13 or CQ. CONCLUSIONS: These studies revealed minimal differences in toxicity between AQ-13 and CQ, and similar linear pharmacokinetics
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