89,992 research outputs found
Blood pressure and indices of glomerular filtration area in hypertensive and normotensive Prague rats
The involvement of the kidney in the pathogenesis of hypertension has long been recognised, although the specific renal mechanisms underlying this phenomenon are still unknown. A current hypothesis attributes hyper tension to a reduction in glomerular filtration area by glomerular loss, The present study analyses the relationship between glomerular number and volume and conscious systolic blood pressure (SBP) in 4- to 53-week-old hypertensive (PHR) and normotensive (PNR) rats of the Prague strain. Adult PHRs had higher SEP, were larger and had larger kidneys than PNRs, but 20% fewer glomeruli, A significant negative correlation between SEP and glomerular number was found in PHR males, but not in PHR females or PNRs. There was no correlation at all between glomerular volume and SEP and, in young animals, both SEP and glomerular number were higher in PHRs than in PNRs. In addition, in adult PHRs, glomerular volume and SEP were higher in males than in females. In summary, a generally valid, causal relation-ship linking raised blood pressure to decreased glomerular number or volume could not be demonstrated in the Prague rat model of genetically determined hypertension. The nature of the renal mechanism(s) determining the hypertension in this model remains unknown. Copyright (C) 2000 S. Karger AG, Basel
Neonatal abstinence syndrome: Pharmacologic strategies for the mother and infant.
Opioid use in pregnancy has increased dramatically over the past decade. Since prenatal opioid use is associated with numerous obstetrical and neonatal complications, this now has become a major public health problem. In particular, in utero opioid exposure can result in neonatal abstinence syndrome (NAS) which is a serious condition characterized by central nervous system hyperirritability and autonomic nervous system dysfunction. The present review seeks to define current practices regarding the approach to the pregnant mother and neonate with prenatal opiate exposure. Although the cornerstone of prenatal management of opioid dependence is opioid maintenance therapy, the ideal agent has yet to be definitively established. Pharmacologic management of NAS is also highly variable and may include an opioid, barbiturate, and/or α-agonist. Genetic factors appear to be associated with the incidence and severity of NAS. Establishing pharmacogenetic risk factors for the development of NAS has the potential for creating opportunities for personalized genomic medicine and novel, individualized therapeutic interventions
Pairing mean-field theory for the dynamics of dissociation of molecular Bose-Einstein condensates
We develop a pairing mean-field theory to describe the quantum dynamics of
the dissociation of molecular Bose-Einstein condensates into their constituent
bosonic or fermionic atoms. We apply the theory to one, two, and
three-dimensional geometries and analyze the role of dimensionality on the atom
production rate as a function of the dissociation energy. As well as
determining the populations and coherences of the atoms, we calculate the
correlations that exist between atoms of opposite momenta, including the column
density correlations in 3D systems. We compare the results with those of the
undepleted molecular field approximation and argue that the latter is most
reliable in fermionic systems and in lower dimensions. In the bosonic case we
compare the pairing mean-field results with exact calculations using the
positive- stochastic method and estimate the range of validity of the
pairing mean-field theory. Comparisons with similar first-principle simulations
in the fermionic case are currently not available, however, we argue that the
range of validity of the present approach should be broader for fermions than
for bosons in the regime where Pauli blocking prevents complete depletion of
the molecular condensate.Comment: 16 pages, 10 figure
High-precision elements of double-lined spectroscopic binaries from combined interferometry and spectroscopy. Application to the beta Cephei star beta Centauri
We present methodology to derive high-precision estimates of the fundamental
parameters of double-lined spectroscopic binaries. We apply the methods to the
case study of the double-lined beta Cephei star beta Centauri. We also present
a detailed analysis of beta Centauri's line-profile variations caused by its
oscillations. We point out that a systematic error in the orbital amplitudes,
and any quantities derived from them, occurs if the radial velocities of
blended component lines are computed without spectral disentangling. This
technique is an essential ingredient in the derivation of the physical
parameters if the goal is to obtain a precision of only a few percent. We have
devised iteration schemes to obtain the orbital elements for systems whose
lines are blended throughout the orbital cycle. We find the following
parameters for beta Cen: and , an age of years. We deduce two oscillation
frequencies for the broad-lined primary of beta Centauri with degrees higher
than 2. We propose that our iteration schemes be used in any future derivations
of the spectroscopic orbital parameters of double-lined binaries with blended
component lines to which disentangling can be successfully applied.Comment: 12 pages, 13 figures, accepted for publication in A&
High Redshift Standard Candles: Predicted Cosmological Constraints
We investigate whether future measurements of high redshift standard candles
(HzSCs) will be a powerful probe of dark energy, when compared to other types
of planned dark energy measurements. Active galactic nuclei and gamma ray
bursts have both been proposed as potential HzSC candidates. Due to their high
luminosity, they can be used to probe unexplored regions in the expansion
history of the universe. Information from these regions can help constrain the
properties of dark energy, and in particular, whether it varies over time.
We consider both linear and piecewise parameterizations of the dark energy
equation of state, , and assess the optimal redshift distribution a
high-redshift standard-candle survey could take to constrain these models.
The more general the form of the dark energy equation of state being
tested, the more useful high-redshift standard candles become. For a linear
parameterization of , HzSCs give only small improvements over planned
supernova and baryon acoustic oscillation measurements; a wide redshift range
with many low redshift points is optimal to constrain this linear model.
However to constrain a general, and thus potentially more informative, form of
, having many HzSCs can significantly improve limits on the nature of
dark energy.Comment: Accepted MNRAS, 27 Pages, 15 figures, matches published versio
Probing the classical field approximation - thermodynamics and decaying vortices
We review our version of the classical field approximation to the dynamics of
a finite temperature Bose gas. In the case of a periodic box potential, we
investigate the role of the high momentum cut-off, essential in the method. In
particular, we show that the cut-off going to infinity limit decribes the
particle number going to infinity with the scattering length going to zero. In
this weak interaction limit, the relative population of the condensate tends to
unity. We also show that the cross-over energy, at which the probability
distribution of the condensate occupation changes its character, grows with a
growing scattering length. In the more physical case of the condensate in the
harmonic trap we investigate the dissipative dynamics of a vortex. We compare
the decay time and the velocities of the vortex with the available analytic
estimates.Comment: 7 pages, 8 eps figures, submitted to J. Optics B for the proceedings
of the "Atom Optics and Interferometry" Lunteren 2002 worksho
Differential regulation of bladder pain and voiding function by sensory afferent populations revealed by selective optogenetic activation
Bladder-innervating primary sensory neurons mediate reflex-driven bladder function under normal conditions, and contribute to debilitating bladder pain and/or overactivity in pathological states. The goal of this study was to examine the respective roles of defined subtypes of afferent neurons in bladder sensation and function in vivo via direct optogenetic activation. To accomplish this goal, we generated transgenic lines that express a Channelrhodopsin-2-eYFP fusion protein (ChR2-eYFP) in two distinct populations of sensory neurons: TRPV1-lineage neurons (Trpv1Cre;Ai32, the majority of nociceptors) and Nav1.8+ neurons (Scn10aCre;Ai32, nociceptors and some mechanosensitive fibers). In spinal cord, eYFP+ fibers in Trpv1Cre;Ai32 mice were observed predominantly in dorsal horn (DH) laminae I-II, while in Scn10aCre;Ai32 mice they extended throughout the DH, including a dense projection to lamina X. Fiber density correlated with number of retrogradely-labeled eYFP+ dorsal root ganglion neurons (82.2% Scn10aCre;Ai32 vs. 62% Trpv1Cre;Ai32) and degree of DH excitatory synaptic transmission. Photostimulation of peripheral afferent terminals significantly increased visceromotor responses to noxious bladder distension (30–50 mmHg) in both transgenic lines, and to non-noxious distension (20 mmHg) in Scn10aCre;Ai32 mice. Depolarization of ChR2+ afferents in Scn10aCre;Ai32 mice produced low- and high-amplitude bladder contractions respectively in 53% and 27% of stimulation trials, and frequency of high-amplitude contractions increased to 60% after engagement of low threshold (LT) mechanoreceptors by bladder filling. In Trpv1Cre;Ai32 mice, low-amplitude contractions occurred in 27% of trials before bladder filling, which was pre-requisite for light-evoked high-amplitude contractions (observed in 53.3% of trials). Potential explanations for these observations include physiological differences in the thresholds of stimulated fibers and their connectivity to spinal circuits
Entanglement properties of degenerate four-wave mixing of matter-waves in a periodic potential
In a recent experiment Campbell et al. [Phys. Rev. Lett. 96, 020406 (2006)]
observed degenerate four-wave mixing of matter-waves in a one-dimensional
optical lattice, a process with potential for generating entanglement among
atoms. We analyse the essential quantum features of the experiment to show that
entanglement is created between the quadratures of the two scattered atomic
clouds and is a true many-body (rather than two-body) effect. We demonstrate a
significant violation of entanglement inequalities that is robust to a moderate
level of coherent seeding. The system is thus a promising candididate for
generating macroscopically entangled atomic samples.Comment: 4 pages, 3 figure
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