Statistical analysis of low level atmospheric turbulence

The statistical properties of low-level wind-turbulence data were obtained with the model 1080 total vector anemometer and the model 1296 dual split-film anemometer, both manufactured by Thermo Systems Incorporated. The data obtained from the above fast-response probes were compared with the results obtained from a pair of Gill propeller anemometers. The digitized time series representing the three velocity components and the temperature were each divided into a number of blocks, the length of which depended on the lowest frequency of interest and also on the storage capacity of the available computer. A moving-average and differencing high-pass filter was used to remove the trend and the low frequency components in the time series. The calculated results for each of the anemometers used are represented in graphical or tabulated form

Two stochastic models for simulation of correlated random processes

Mathematical models for simulation of correlated stochastic processes with stationary Gaussian propertie

A method for the measurement and the statistical analysis of atmospheric turbulence

The instantaneous values of output voltages representing the wind velocity vector and the temperature at different elevations of the 250-foot meteorological tower located at NASA Wallops Flight Center are provided with the three dimensional split-film TSI Model 1080 anemometer system. The output voltages are sampled at a rate of one every 5 milliseconds, digitized and stored on digital magnetic tapes for a time period of approximately 40 minutes, with the use of a specially designed data acqusition system. A new calibration procedure permits the conversion of the digital voltages to the respective values of the temperature and the velocity components in a Cartesian coordinate system connected with the TSI probe with considerable accuracy. Power, cross, coincidence and quadrature spectra of the wind components and the temperature are obtained with the use of the fast Fourier transform. The cosine taper data window and ensemble and frequency smoothing techniques are used to provide smooth estimates of the spectral functions

An experimental study of the atmospheric boundary layer modified by a change in surface roughness and surface temperature

Turbulent flow, resembling an on-shore flow from the ocean crossing the beach at an oblique angle, is investigated. Measurements of this flow have been taken at high sample rates and include measurements at various heights, high enough to describe the portion of the mean wind and temperature profiles and fluxes that are of interest for the solution of practical engineering problems. These problems could include air pollution (fumigation and plume trapping), operation of low flying aircraft, crop-spraying and crop-dusting operations

An evlauation of the three-dimensional split-film anemometer for measurements of atmospheric turbulence

A three-dimensional split-film anemometer was tested in turbulent, as well as in nonturbulent flow downstream from a wind tunnel turbulence grid. The data obtained with this probe in the turbulence behind the grid, indicated that the measured turbulence intensities were somewhat lower than the intensity measured with the conventional hot-wire anemometry; a result of the finite dimensions of the sensor arrays. The probe yaw angle was determined to be accurate within three degrees. Statistical averages, determined by mean-wind direction and vertical and lateral directions were computed on the basis of the probe yaw angle

Three-dimensional single roughness element in a turbulent boundary layer, A

CER65-HT-VAS-73.October 1965.Includes bibliographical references (page 8).Prepared for U.S. Army Research Grant.Under grant DA-AMC-28-043-64-G-9

Intermittent permeation of cylindrical nanopores by water

Molecular Dynamics simulations of water molecules in nanometre sized cylindrical channels connecting two reservoirs show that the permeation of water is very sensitive to the channel radius and to electric polarization of the embedding material. At threshold, the permeation is {\emph{intermittent}} on a nanosecond timescale, and strongly enhanced by the presence of an ion inside the channel, providing a possible mechanism for gating. Confined water remains surprisingly fluid and bulk-like. Its behaviour differs strikingly from that of a reference Lennard-Jones fluid, which tends to contract into a highly layered structure inside the channel.Comment: 4 pages, 4 figure

Yield of screening for atrial fibrillation in primary care with a hand-held, single-lead electrocardiogram device during influenza vaccination

Aims To assess the yield of screening for atrial fibrillation (AF) with a hand-held single-lead electrocardiogram (ECG) device during influenza vaccination in primary care in the Netherlands. Methods and results We used the MyDiagnostick to screen for AF in persons who participated in influenza vaccination sessions of ten Dutch primary care practices. In case of suspected AF detection by the stick, the recorded 1-min ECG registrations were analysed by a cardiologist. We scrutinized electronic medical files of the general practitioners to obtain information about the cases screened. Multivariable logistic regression analysis was performed to predict the relation between patient characteristics and a new screen-detected diagnosis of AF. In total, 3269 persons were screened for AF during the influenza vaccination sessions of 10 general practitioner practices. As a result, 37 (1.1%) new cases of AF were detected. Prior transient ischeamic attack or stroke (OR 6.05; 95%CI 1.93-19.0), and age (OR 1.09 per year; 95% CI 1.05-1.14) were independent predictors for such newly screen-detected AF. Of the 37 screen-detected AF cases, 2.7% had a CHA2DS2-VASc of 0, 18.9% a score of 1, and 78.4% a score of 2 or more. The majority needed oral anticoagulant therapy. Conclusions Screening seems feasible with an easy to use single-lead, hand-held ECG device with automatic AF detection during influenza vaccination in primary care and results in a '1-day' yield of 1.1% new cases of AF. Trial registration clinicaltrials.gov NCT02006524

Simulations of a single membrane between two walls using a Monte Carlo method

Quantitative theory of interbilayer interactions is essential to interpret x-ray scattering data and to elucidate these interactions for biologically relevant systems. For this purpose Monte Carlo simulations have been performed to obtain pressure P and positional fluctuations sigma. A new method, called Fourier Monte-Carlo (FMC), that is based on a Fourier representation of the displacement field, is developed and its superiority over the standard method is demonstrated. The FMC method is applied to simulating a single membrane between two hard walls, which models a stack of lipid bilayer membranes with non-harmonic interactions. Finite size scaling is demonstrated and used to obtain accurate values for P and sigma in the limit of a large continuous membrane. The results are compared with perturbation theory approximations, and numerical differences are found in the non-harmonic case. Therefore, the FMC method, rather than the approximations, should be used for establishing the connection between model potentials and observable quantities, as well as for pure modeling purposes.Comment: 10 pages, 10 figure

Opportunistic screening versus usual care for diagnosing atrial fibrillation in general practice:a cluster randomised controlled trial

BackgroundAtrial fibrillation [AF] increases the risk of stroke, heart failure, and all-cause mortality. AF may be asymptomatic and therefore remain undiagnosed. Devices such as single-lead electrocardiographs [ECGs] may help GPs to diagnose AF.AimTo investigate the yield of opportunistic screening for AF in usual primary care using a single-lead ECG device.Design and settingA clustered, randomised controlled trial among patients aged &gt;= 65 years with no recorded AF status in the Netherlands from October 2014 to March 2016.MethodFifteen intervention general practices used a single-lead ECG device at their discretion and 16 control practices offered usual care. The follow-up period was 1 year, and the primary outcome was the proportion of newly diagnosed cases of AF.ResultsIn total. 17 107 older people with no recorded AF status were eligible to participate in the study. In the intervention arm. 10.7% of eligible patients [n = 919] were screened over the duration of the study year. The rate of newly diagnosed AF was similar in the intervention and control practices [1.43% versus 1.37%, P= 0.73]. Screened patients were more likely to have comorbidities, such as hypertension [60.0% versus 48.7%], type 2 diabetes [24.3% versus 18.6%], and chronic obstructive pulmonary disease [11.3% versus 7.4%], than eligible patients not screened in the intervention arm. Among patients with newly diagnosed AF in intervention practices. 27% were detected by screening, 23% by usual primary care. and 50% by a medical specialist or after stroke/transient ischaemic attack.ConclusionOpportunistic screening with a single-lead ECG at the discretion of the GP did not result in a higher yield of newly detected cases of AF in patients aged &gt;= 65 years in the community than usual care. For higher participation rates in future studies, more rigorous screening methods are needed.</p