687 research outputs found
Uniform shrinking and expansion under isotropic Brownian flows
We study some finite time transport properties of isotropic Brownian flows.
Under a certain nondegeneracy condition on the potential spectral measure, we
prove that uniform shrinking or expansion of balls under the flow over some
bounded time interval can happen with positive probability. We also provide a
control theorem for isotropic Brownian flows with drift. Finally, we apply the
above results to show that under the nondegeneracy condition the length of a
rectifiable curve evolving in an isotropic Brownian flow with strictly negative
top Lyapunov exponent converges to zero as with positive
probability
Thermal Requirements for Emergence of Overwintered Sorghum Midge (Diptera: Cecidomyiidae)
Emergence of overwintered sorghum midges, Contarinia sorghicola (Coquillett), was monitored during 1979, 1980, and 1981. Differences in emergence times and distributions among years was a function of soil temperature and rainfall. A heat unit accumulation model incorporating a rainfall adjustment factor was developed which described adult emergence in the spring. Adult midges initiated emergence after accumulating 431 centigrade heat units (based on mean daily to-cm soil temperatures starting 1 April) above a threshold temperature of 14.8°C, whereas, 679 and 977 heat units were required for 50 and 95% emergence, respectively. Sorghum midges that overwintered in johnsongrass spikelets emerged after similar heat unit accumulations as midges that overwintered in sorghum spikelets. The time that midges initiated diapause one year had little effect on the timing or distribution of emergence the following spring. No midges terminated diapause and emerged as adults during the same season that diapause was initiated. Of the diapausing midges, 23% failed to emerge until the second spring and 2.6% emerged the third spring, but times and distributions of emergence were similar for all years
Caustics in turbulent aerosols
Networks of caustics can occur in the distribution of particles suspended in
a randomly moving gas. These can facilitate coagulation of particles by
bringing them into close proximity, even in cases where the trajectories do not
coalesce. We show that the long-time morphology of these caustic patterns is
determined by the Lyapunov exponents lambda_1, lambda_2 of the suspended
particles, as well as the rate J at which particles encounter caustics. We
develop a theory determining the quantities J, lambda_1, lambda_2 from the
statistical properties of the gas flow, in the limit of short correlation
times.Comment: 4 pages, 3 figure
Fabrication of cm scale buckypapers of horizontally aligned multiwalled carbon nanotubes highly filled with Fe3C: the key roles of Cl and Ar-flow rates
A key challenge in the fabrication of ferromagnetically filled carbon-nanotube buckypapers in the presence of Cl-radicals is the achievement of a preferential horizontal nanotube-alignment.</p
CLTs and asymptotic variance of time-sampled Markov chains
For a Markov transition kernel P and a probability distribution
Ό on nonnegative integers, a time-sampled Markov chain evolves according
to the transition kernel PÎŒ = ÎŁkÎŒ(k)Pk. In this note we obtain CLT
conditions for time-sampled Markov chains and derive a spectral formula
for the asymptotic variance. Using these results we compare efficiency of
Barker's and Metropolis algorithms in terms of asymptotic variance
Field emission properties of nano-composite carbon nitride films
A modified cathodic arc technique has been used to deposit carbon nitride
thin films directly on n+ Si substrates. Transmission Electron Microscopy
showed that clusters of fullerene-like nanoparticles are embedded in the
deposited material. Field emission in vacuum from as-grown films starts at an
electric field strength of 3.8 V/micron. When the films were etched in an
HF:NH4F solution for ten minutes, the threshold field decreased to 2.6
V/micron. The role of the carbon nanoparticles in the field emission process
and the influence of the chemical etching treatment are discussed.Comment: 22 pages, 8 figures, submitted to J. Vac. Sc. Techn.
Electron-electron interaction in carbon nanostructures
The electron-electron interaction in carbon nanostructures was studied. A new
method which allows to determine the electron-electron interaction constant
from the analysis of quantum correction to the magnetic
susceptibility and the magnetoresistance was developed. Three types of carbon
materials: arc-produced multiwalled carbon nanotubes (arc-MWNTs), CVD-produced
catalytic multiwalled carbon nanotubes (c-MWNTs) and pyrolytic carbon were used
for investigation. We found that =0.2 for arc-MWNTs (before and
after bromination treatment); = 0.1 for pyrolytic graphite;
0 for c-MWNTs. We conclude that the curvature of graphene layers
in carbon nanostructures leads to the increase of the electron-electron
interaction constant .Comment: 12 pages, 18 figures, to be published in the Proceedings of the NATO
Advanced Research Workshop on Electron Correlation in New Materials and
Nanosystems, NATO Science Series II, Springer, 200
Detection of Giardia and helminths in Western Europe at local K9 (canine) sites (DOGWALKS Study)
Background
Intestinal parasite contamination from infected dogs can place other dogs and humans at risk. A study was initiated to estimate the prevalence of canine intestinal parasitism by collecting fecal samples in cities across Western Europe.
Methods
Fresh fecal samples were collected from 2469 dogs visiting 164 parks in 33 cities across 12 countries. Each owner responded to a questionnaire focusing on their dogâs signalment and recent anthelmintic treatment history. The collected samples were examined for hookworms, whipworms, ascarids and Giardia using a coproantigen diagnostic immunoassay and microscopy following centrifugal flotation.
Results
Nematodes or Giardia were detected in at least one sample from 100% of cities and in 93.3% of parks. Nematodes were detected in 57% of parks. Overall, 22.8% of dogs tested positive for an intestinal parasite, with Giardia being the most commonly identified parasites (17.3% of dogs, 83.5% of parks). For nematode infection, 7.6% of all dogs tested positive, with 9.9% of dogs agedââ1 month had passed since the previous dose.
Conclusions
The prevalence estimates of intestinal parasite infections in dogs reported here highlight the need for owner education concerning guidelines for regular testing and treatment, even in older dogs. Failure to adhere to guidelines can result in ongoing transmission of these infections, including those with zoonotic potential. Combining coproantigen immunoassay with centrifugal flotation for diagnostic testing and regular anthelmintic treatment are important measures for ensuring optimal intestinal parasite control
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Economic Cost of Functional Neurologic Disorders: A Systematic Review.
BACKGROUND AND OBJECTIVES: Functional neurologic disorder (FND) represents genuine involuntary neurologic symptoms and signs including seizures, weakness, and sensory disturbance, which have characteristic clinical features, and represent a problem of voluntary control and perception despite normal basic structure of the nervous system. The historical view of FND as a diagnosis of exclusion can lead to unnecessary health care resource utilization and high direct and indirect economic costs. A systematic review was performed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to assess these economic costs and to assess for any cost-effective treatments. METHODS: We searched electronic databases (PubMed, PsycInfo, MEDLINE, EMBASE, and the National Health Service Economic Evaluations Database of the University of York) for original, primary research publications between inception of the databases and April 8, 2022. A hand search of conference abstracts was also conducted. Key search terms included "functional neurologic disorder," "conversion disorder," and "functional seizures." Reviews, case reports, case series, and qualitative studies were excluded. We performed a descriptive and qualitative thematic analysis of the resulting studies. RESULTS: The search resulted in a total of 3,244 studies. Sixteen studies were included after screening and exclusion of duplicates. These included the following: cost-of-illness (COI) studies that were conducted alongside cohort studies without intervention and those that included a comparator group, for example, another neurologic disorder (n = 4); COI studies that were conducted alongside cohort studies without intervention and those that did not include a comparator group (n = 4); economic evaluations of interventions that were either pre-post cohort studies (n = 6) or randomized controlled trials (n = 2). Of these, 5 studies assessed active interventions, and 3 studies assessed costs before and after a definitive diagnosis of FND. Studies showed an excess annual cost associated with FND (range 86,722 2021 US dollars), which consisted of both direct and large indirect costs. Studies showed promise that interventions, including provision of a definitive diagnosis, could reduce this cost (range 9%-90.7%). No cost-effective treatments were identified. Study comparison was limited by study design and location heterogeneity. DISCUSSION: FND is associated with a significant use of health care resources, resulting in economic costs to both the patient and the taxpayer and intangible losses. Interventions, including accurate diagnosis, seem to offer an avenue toward reducing these costs
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