850 research outputs found
The impact of diffusion on confined oscillated bubbly fluid
We consider the dynamics of monodisperse bubbly fluid confined by two plane
solid walls and subjected to small-amplitude high-frequency transversal
oscillations. The frequency these oscillations is assumed to be high in
comparison with typical relaxation times for a single bubble, but comparable
with the eigenfrequency of volume oscillations. A time-averaged description
accounting for mutual coupling of the phases and the diffusivity of bubbles is
applied. We find nonuniform steady states with the liquid quiescent on average.
At relatively low frequencies accumulation of bubbles either at the walls or in
planes oriented parallel to the walls is detected. These one-dimensional states
are shown to be unstable. At relatively high frequencies the bubbles accumulate
at the central plane and the solution is stable.Comment: 12 pages, 9 figures, submitted to Phys. Fluid
Effects of non-invasive vagus nerve stimulation on attack frequency over time and response rates in patients with chronic cluster headache
Analysing delays between time course gene expression data and biomarkers
Associating time course gene expression data to biomarkers can help to understand disease progression or response to therapy. However, detecting associations between these expression profiles is not a trivial task. Often expression changes occur not simultaneously but delayed in time and common used methods to detect correlation will fail to identify these associations. We have developed an efficient approach, DynOmics, based on Fast Fourier Transform to identify coordinated response dynamics between time course 'omics' experiments and specific biomarkers of interest while taking time shift into account. We applied DynOmics to a rat study investigating molecular response dynamics to different dosages of acetaminophen ('paracetamol'). We show how DynOmics can extract relevant molecule expression profiles that enables a better understanding of the molecular pathways related to acetaminophen toxic dosage and renal damage
Stochastic dynamics of resistive switching: fluctuations lead to optimal particle number
Resistive switching (RS) is one of the foremost candidates for building novel
types of non-volatile random access memories. Any practical implementation of
such a memory cell calls for a strong miniaturization, at which point
fluctuations start playing a role that cannot be neglected. A detailed
understanding of switching mechanisms and reliability is essential. For this
reason, we formulate a particle model based on the stochastic motion of oxygen
vacancies. It allows us to investigate fluctuations in the resistance states
of a switch with two active zones. The vacancies' dynamics are governed by a
master equation. Upon the application of a voltage pulse, the vacancies travel
collectively through the switch. By deriving a generalized Burgers equation we
can interpret this collective motion as nonlinear traveling waves, and
numerically verify this result. Further, we define binary logical states by
means of the underlying vacancy distributions, and establish a framework of
writing and reading such memory element with voltage pulses. Considerations
about the discriminability of these operations under fluctuations together
with the markedness of the RS effect itself lead to the conclusion, that an
intermediate vacancy number is optimal for performance
A Randomized ShamâControlled CrossâOver Study on the ShortâTerm Effect of NonâInvasive Cervical Vagus Nerve Stimulation on Spinal and Supraspinal Nociception in Healthy Subjects
Objective
The aim of the present study was to test the effects of vagus nerve stimulation (VNS) on the descending pain inhibition, quantified by the nociceptive flexor (RIII) reflex and the conditioned pain modulation (CPM) paradigm, and on supraspinal nociceptive responses, assessed by pain intensity and unpleasantness ratings and late somatosensory evoked potentials (SEPs), in healthy subjects.
Background
Nonâinvasive vagus nerve stimulation (nVNS) showed promising effects on headache and pain treatment. Underlying mechanisms are only incompletely understood but may include the activation of the descending pain inhibitory system and/or the modification of emotional responses to pain.
Methods
Twentyâseven adult, healthy, and painâfree subjects participated in this doubleâblind crossâover study conducted at a university research center. They received 4 minutes of cervical nVNS or sham stimulation in randomized order. RIII reflexes, pain ratings, and SEPs were assessed before, during, and 5, 15, 30, and 60 minutes after nVNS/sham stimulation, followed by CPM testing. The primary outcome was the nVNS effect on the RIII reflex size. Three subjects were excluded after the preparatory session (before randomization), 1 subject was excluded after outlier analysis, leaving 23 for analysis.
Results
RIII reflex areas were 917.1 ± 563.8 ”V Ă ms (mean ± SD) before, 952.4 ± 467.4 ”V Ă ms during and 929.2 ± 484.0 ”V Ă ms immediately after nVNS and 858.4 ± 489.2 ”V Ă ms before, 913.9 ± 539.7 ”V Ă ms during and 862.4 ± 476.0 ”V Ă ms after sham stimulation, revealing no differences between the immediate effects of nVNS and sham stimulation (F [3,66] = 0.67, P = .574). There also were no effects of nVNS over sham on RIII reflex areas up to 60 minutes after nVNS (F [1.7,37.4] = 1.29, P = .283). Similarly, there was no statistically significant effect of nVNS on pain intensity ratings and thresholds, RIII reflex thresholds, late SEP amplitudes, and the CPM effect, compared to sham. Pain unpleasantness ratings statistically significantly decreased from 4.4 ± 2.4 (NRS 0â10) to 4.1 ± 2.5 during nVNS compared to sham stimulation (F [1,22] = 8.74, P = .007), but there were no longer lasting effects (5â60 minutes after stimulation).
Conclusions
The present study does not support an acute effect of nVNS on descending pain inhibition, pain intensity perception or supraspinal nociception in healthy adults. However, there was a small effect on pain unpleasantness during nVNS, suggesting that nVNS may preferentially act on affective, not somatosensory pain components
Case-control risk factor study of methicillin-resistant Staphylococcus pseudintermedius (MRSP) infection in dogs and cats in Germany
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