4,693 research outputs found
Fluctuation dynamo amplified by intermittent shear bursts in convectively driven magnetohydrodynamic turbulence
Intermittent large-scale high-shear flows are found to occur frequently and
spontaneously in direct numerical simulations of statistically stationary
turbulent Boussinesq magnetohydrodynamic (MHD) convection. The energetic
steady-state of the system is sustained by convective driving of the velocity
field and small-scale dynamo action. The intermittent emergence of flow
structures with strong velocity and magnetic shearing generates magnetic energy
at an elevated rate over time-scales longer than the characteristic time of the
large-scale convective motion. The resilience of magnetic energy amplification
suggests that intermittent shear-bursts are a significant driver of dynamo
action in turbulent magnetoconvection
The Older Population and the Aged Patient
Modern medical practice requires that the physician and other members of the health team have full appreciation of the impact of disease and disability upon identifiable groups of patients and recognize how nonmedical factors affect treatment and prognosis. It is important for the physician to have some idea of the patient\u27s socioeconomic status and the actual and potential number of patients with not only a common diagnosis, but also similarities in their living conditions. With such knowledge, the physician can be much more realistic and efficient in his therapeutic efforts. Persons 65 years of age and over are commonly referred to as the older population. Brotman (1968) recently identified the special characteristics of those 75 years of age and over, referring to these people as the aged. This subdividing of the older population is of considerable value, as the important health and socioeconomic facts common to a specific group can be lost in the mass of the older population
Lagrangian Statistics of Navier-Stokes- and MHD-Turbulence
We report on a comparison of high-resolution numerical simulations of
Lagrangian particles advected by incompressible turbulent hydro- and
magnetohydrodynamic (MHD) flows. Numerical simulations were performed with up
to collocation points and 10 million particles in the Navier-Stokes
case and collocation points and 1 million particles in the MHD case. In
the hydrodynamics case our findings compare with recent experiments from
Mordant et al. [1] and Xu et al. [2]. They differ from the simulations of
Biferale et al. [3] due to differences of the ranges choosen for evaluating the
structure functions. In Navier-Stokes turbulence intermittency is stronger than
predicted by a multifractal approach of [3] whereas in MHD turbulence the
predictions from the multifractal approach are more intermittent than observed
in our simulations. In addition, our simulations reveal that Lagrangian
Navier-Stokes turbulence is more intermittent than MHD turbulence, whereas the
situation is reversed in the Eulerian case. Those findings can not consistently
be described by the multifractal modeling. The crucial point is that the
geometry of the dissipative structures have different implications for
Lagrangian and Eulerian intermittency. Application of the multifractal approach
for the modeling of the acceleration PDFs works well for the Navier-Stokes case
but in the MHD case just the tails are well described.Comment: to appear in J. Plasma Phy
Extreme-value statistics from Lagrangian convex hull analysis for homogeneous turbulent Boussinesq convection and MHD convection
We investigate the utility of the convex hull of many Lagrangian tracers to
analyze transport properties of turbulent flows with different anisotropy. In
direct numerical simulations of statistically homogeneous and stationary
Navier-Stokes turbulence, neutral fluid Boussinesq convection, and MHD
Boussinesq convection a comparison with Lagrangian pair dispersion shows that
convex hull statistics capture the asymptotic dispersive behavior of a large
group of passive tracer particles. Moreover, convex hull analysis provides
additional information on the sub-ensemble of tracers that on average disperse
most efficiently in the form of extreme value statistics and flow anisotropy
via the geometric properties of the convex hulls. We use the convex hull
surface geometry to examine the anisotropy that occurs in turbulent convection.
Applying extreme value theory, we show that the maximal square extensions of
convex hull vertices are well described by a classic extreme value
distribution, the Gumbel distribution. During turbulent convection,
intermittent convective plumes grow and accelerate the dispersion of Lagrangian
tracers. Convex hull analysis yields information that supplements standard
Lagrangian analysis of coherent turbulent structures and their influence on the
global statistics of the flow.Comment: 18 pages, 10 figures, preprin
A Comparison of Four Approaches to Discretization Based on Entropy †
We compare four discretization methods, all based on entropy: the original C4.5 approach to discretization, two globalized methods, known as equal interval width and equal frequency per interval, and a relatively new method for discretization called multiple scanning using the C4.5 decision tree generation system. The main objective of our research is to compare the quality of these four methods using two criteria: an error rate evaluated by ten-fold cross-validation and the size of the decision tree generated by C4.5. Our results show that multiple scanning is the best discretization method in terms of the error rate and that decision trees generated from datasets discretized by multiple scanning are simpler than decision trees generated directly by C4.5 or generated from datasets discretized by both globalized discretization methods
l. suis medication of piglets with Baycoxo 5% against coccidiose and for stabilisation of the microflora against intestinal infections and reducing the application of antibiotica and vaccines against diarrhoea with E.coli and Clostridia
After the oral treatment of all p1glets 3 - 5 days after birth with Baycox 5% we found a better intestine health in the suckling and in the flatdeck period. ln this study there was a reduced diarrhoea dunng suckling and in the flatdeck.With the Baycox• therapeutic the vaccination program against E. coli and Clostridium perfringens Typ C and the application of antibiotica to the weaners could be decreased for nearly 40 % during the breeding period. AII pigs got better health status with higher weight gain and uniformity
Haemoglobin and size dependent constraints on swimbladder inflation in fish larvae
In developmental studies of fish species (especially physostomians) it could be demonstrated,
that the lack of haemoglobin during larval and juvenile stages is a relatively common phenomenon.
Generally it is linked with body translucency. In representatives of the families Galaxiidae,
Osmeridae and Clupeidae, partly reared, partly observed immediately after being caught in the wild, it
turned out, that this condition coincides with a considerable delay in swimbladder inflation. To determine
the moment of its first inflation, larvae placed in a hermetic chamber were observed under a
dissecting microscope. While lowering the pressure, the expanding swimbladder showed whether or
not its content is really gaseous. The reason postulated to be responsible for the delayed inflation is
that larvae lacking haemoglobin do not have the possibility of oxygen transport to their buoyancy
organ by means of the blood. Apart of this, capillarity force calculations and body force estimations
show that with decreasing size the constraints linked with surface tension increase overproportionally.
While in larger sized larvae like trout we could demonstrate inflation by swallowing air, in species with
small larvae this was not the case. Below a certain size, even in physostomians, the ductus pneumaticus
is no alternative to the blood pathway for swimbladder inflation
DPP-4 inhibitor dose selection according to manufacturer specifications:A Contemporary Experience From UK General Practice
Recently, 2 dipeptidyl peptidase-4 (DPP-4) inhibitors, sitagliptin and saxagliptin, adjusted dosing specification from creatinine clearance to glomerular filtration rate, more typically reported in routine laboratory tests. This cross-sectional study examines all DPP-4 inhibitor initiations that require dose adjustment and the dose selection using data from UK general practice. Results indicate that 34% of patients taking a nonlinagliptin DPP-4 inhibitor were given a higher dose and 11% a lower dose than specified in the Summary of Product Characteristics. This reinforces the deviation from Summary of Product Characteristics prescription of DPP-4 inhibitors identified in earlier studies despite improvement in compatibility with routine reporting. (C) 2019 The Authors. Published by Elsevier Inc
The Spatio-Temporal Structure of Spiral-Defect Chaos
We present a study of the recently discovered spatially-extended chaotic
state known as spiral-defect chaos, which occurs in low-Prandtl-number,
large-aspect-ratio Rayleigh-Benard convection. We employ the modulus squared of
the space-time Fourier transform of time series of two-dimensional shadowgraph
images to construct the structure factor .
This analysis is used to characterize the average spatial and temporal scales
of the chaotic state. We find that the correlation length and time can be
described by power-law dependences on the reduced Rayleigh number .
These power laws have as yet no theoretical explanation.Comment: RevTex 38 pages with 13 figures. Due to their large size, some
figures are stored as separate gif images. The paper with included hi-res eps
figures (981kb compressed, 3.5Mb uncompressed) is available at
ftp://mobydick.physics.utoronto.ca/pub/MBCA96.tar.gz An mpeg movie and
samples of data are also available at
ftp://mobydick.physics.utoronto.ca/pub/. Paper submitted to Physica
- …