1,243 research outputs found
PROCESS SPECIFICATIONS FOR CHEMICAL HAZARD CONTROL-PUREX PLANT
Purex process specifications related to chemical hazards control are presented. These specifications are a part of the basis for the flowsheets or are to be used in situations not covered by other instructions. (J.R.D.
Shock absorbing support and restraint means Patent
Shock absorbing couch for body support under high acceleration or deceleration force
Developmental neurotoxicants and the vulnerable male brain: a systematic review of suspected neurotoxicants that disproportionally affect males
The prevalence of neurodevelopmental disorders (NDs), including autism spectrum disorder, attention‑deficit/hyperactivity disorder, tic disorder, obsessive‑compulsive disorder, and emotional disturbances, has increased notably in the past few decades. To date, debate continues as to the origins of NDs. Increases in widespread exposure to and bioaccumulation of chemical neurotoxicants have paralleled the upsurge in NDs, and are suggested to be causal agents for NDs. One consistent aspect of NDs is the male preponderance. This review considers the issue of male preponderance by reviewing the gender‑specific neurotoxic effects of recognized neurotoxicant chemicals to assess their possible etiology in NDs. This investigation consisted of a systematic literature review of original studies published from 1970-2016 on suspected neurotoxicants, to examine whether they have a disproportionate adverse effect based on gender. Based on that review, the neurotoxicants exhibiting consistent gender‑specific effects, with exposed males being more affected (than similarly exposed females), were: lead, Thimerosal/ethylmercury, some organochlorine pesticides (e.g., dieldrin, endosulfan, and heptachlor), and air pollution. The next group identified were neurotoxicants exhibiting gender‑specific neurotoxic effects, with males being somewhat (but not consistently) more affected than females: mercury vapor, polychlorinated biphenyls (PCBs), and organophosphate pesticides. Finally, there was a group of studies in which the neurotoxicants exhibited apparent gender‑related neurotoxic effects but failed to show whether exposed males were consistently more affected than females: inorganic mercury salts, methylmercury species, and certain endocrine disruptors (e.g., phthalates and BPA). The overall conclusion from the studies reviewed was that the brain in males is more vulnerable to many toxic exposures than it is in females. Evidence suggests that the reasons for the male brain being more vulnerable include: (1) greater glutathione availability in females; (2) greater sulfate‑based detoxification capacity in females; (3) potentiating effects of co‑exposure to neurotoxicants and testosterone; (4) greater neuroinflammatory response in males; (5) reduced vulnerability to oxidative stress in females; and (6) neuroprotective effects of female hormones (estrogen and progesterone), especially in the reduction of inflammation and oxidative stress
Entropic particle transport: higher order corrections to the Fick-Jacobs diffusion equation
Transport of point-size Brownian particles under the influence of a constant
and uniform force field through a three-dimensional channel with smoothly
varying periodic cross-section is investigated. Here, we employ an asymptotic
analysis in the ratio between the difference of the widest and the most narrow
constriction divided through the period length of the channel geometry. We
demonstrate that the leading order term is equivalent to the Fick-Jacobs
approximation. By use of the higher order corrections to the probability
density we derive an expression for the spatially dependent diffusion
coefficient D(x) which substitutes the constant diffusion coefficient present
in the common Fick-Jacobs equation. In addition, we show that in the diffusion
dominated regime the average transport velocity is obtained as the product of
the zeroth-order Fick-Jacobs result and the expectation value of the spatially
dependent diffusion coefficient . The analytic findings are corroborated
with the precise numerical results of a finite element calculation of the
Smoluchowski diffusive particle dynamics occurring in a reflection symmetric
sinusoidal-shaped channel.Comment: 9 pages, 3 figure
Phase resolved spectroscopy and Kepler photometry of the ultracompact AM CVn binary SDSS J190817.07+394036.4
{\it Kepler} satellite photometry and phase-resolved spectroscopy of the
ultracompact AM CVn type binary SDSS J190817.07+394036.4 are presented. The
average spectra reveal a variety of weak metal lines of different species,
including silicon, sulphur and magnesium as well as many lines of nitrogen,
beside the strong absorption lines of neutral helium. The phase-folded spectra
and the Doppler tomograms reveal an S-wave in emission in the core of the He I
4471 \AA\,absorption line at a period of \,sec
identifying this as the orbital period of the system. The Si II, Mg II and the
core of some He I lines show an S-wave in absorption with a phase offset of
compared to the S-wave in emission. The N II, Si III and some
helium lines do not show any phase variability at all. The spectroscopic
orbital period is in excellent agreement with a period at \,sec detected in the three year {\it Kepler} lightcurve. A
Fourier analysis of the Q6 to Q17 short cadence data obtained by {\it Kepler}
revealed a large number of frequencies above the noise level where the majority
shows a large variability in frequency and amplitude. In an O-C analysis we
measured a xs\,s for some of
the strongest variations and set a limit for the orbital period to be
s\,s. The shape of the phase folded
lightcurve on the orbital period indicates the motion of the bright spot.
Models of the system were constructed to see whether the phases of the radial
velocity curves and the lightcurve variation can be combined to a coherent
picture. However, from the measured phases neither the absorption nor the
emission can be explained to originate in the bright spot.Comment: Accepted for publication in MNRAS, 15 pages, 14 figures, 5 table
A longitudinal cohort study of the relationship between Thimerosal-containing hepatitis B vaccination and specific delays in development in the United States: Assessment of attributable risk and lifetime care costs
AbstractEpidemiological evidence suggests a link between mercury (Hg) exposure from Thimerosal-containing vaccines and specific delays in development. A hypothesis-testing longitudinal cohort study (n=49,835) using medical records in the Vaccine Safety Datalink (VSD) was undertaken to evaluate the relationship between exposure to Hg from Thimerosal-containing hepatitis B vaccines (T-HBVs) administered at specific intervals in the first 6months of life and specific delays in development [International Classification of Disease, 9th revision (ICD-9): 315.xx] among children born between 1991 and 1994 and continuously enrolled from birth for at least 5.81years. Infants receiving increased Hg doses from T-HBVs administered within the first month, the first 2months, and the first 6months of life were significantly more likely to be diagnosed with specific delays in development than infants receiving no Hg doses from T-HBVs. During the decade in which T-HBVs were routinely recommended and administered to US infants (1991–2001), an estimated 0.5–1million additional US children were diagnosed with specific delays in development as a consequence of 25μg or 37.5μg organic Hg from T-HBVs administered within the first 6months of life. The resulting lifetime costs to the United States may exceed $1 trillion
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In silico modeling of oxygen-enhanced MRI of specific ventilation.
Specific ventilation imaging (SVI) proposes that using oxygen-enhanced 1H MRI to capture signal change as subjects alternatively breathe room air and 100% O2 provides an estimate of specific ventilation distribution in the lung. How well this technique measures SV and the effect of currently adopted approaches of the technique on resulting SV measurement is open for further exploration. We investigated (1) How well does imaging a single sagittal lung slice represent whole lung SV? (2) What is the influence of pulmonary venous blood on the measured MRI signal and resultant SVI measure? and (3) How does inclusion of misaligned images affect SVI measurement? In this study, we utilized two patient-based in silico models of ventilation, perfusion, and gas exchange to address these questions for normal healthy lungs. Simulation results from the two healthy young subjects show that imaging a single slice is generally representative of whole lung SV distribution, with a calculated SV gradient within 90% of that calculated for whole lung distributions. Contribution of O2 from the venous circulation results in overestimation of SV at a regional level where major pulmonary veins cross the imaging plane, resulting in a 10% increase in SV gradient for the imaging slice. A worst-case scenario simulation of image misalignment increased the SV gradient by 11.4% for the imaged slice
Modeling rhythmic patterns in the hippocampus
We investigate different dynamical regimes of neuronal network in the CA3
area of the hippocampus. The proposed neuronal circuit includes two fast- and
two slowly-spiking cells which are interconnected by means of dynamical
synapses. On the individual level, each neuron is modeled by FitzHugh-Nagumo
equations. Three basic rhythmic patterns are observed: gamma-rhythm in which
the fast neurons are uniformly spiking, theta-rhythm in which the individual
spikes are separated by quiet epochs, and theta/gamma rhythm with repeated
patches of spikes. We analyze the influence of asymmetry of synaptic strengths
on the synchronization in the network and demonstrate that strong asymmetry
reduces the variety of available dynamical states. The model network exhibits
multistability; this results in occurrence of hysteresis in dependence on the
conductances of individual connections. We show that switching between
different rhythmic patterns in the network depends on the degree of
synchronization between the slow cells.Comment: 10 pages, 9 figure
Biased Brownian motion in extreme corrugated tubes
Biased Brownian motion of point-size particles in a three-dimensional tube
with smoothly varying cross-section is investigated. In the fashion of our
recent work [Martens et al., PRE 83,051135] we employ an asymptotic analysis to
the stationary probability density in a geometric parameter of the tube
geometry. We demonstrate that the leading order term is equivalent to the
Fick-Jacobs approximation. Expression for the higher order corrections to the
probability density are derived. Using this expansion orders we obtain that in
the diffusion dominated regime the average particle current equals the
zeroth-order Fick-Jacobs result corrected by a factor including the corrugation
of the tube geometry. In particular we demonstrate that this estimate is more
accurate for extreme corrugated geometries compared to the common applied
method using the spatially dependent diffusion coefficient D(x,f). The analytic
findings are corroborated with the finite element calculation of a
sinusoidal-shaped tube.Comment: 10 pages, 4 figure
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