1,959 research outputs found
PSD-95 Is Associated with the Postsynaptic Density and Not with the Presynaptic Membrane at Forebrain Synapses
PSD-95, a prominent protein component of the postsynaptic density (PSD) fraction from rat forebrain, has been localized by light microscopy to dendrites of hippocampal neurons (Cho et al., 1992) and to the presynaptic plexus of cerebellar basket cells (Kistner et al., 1993). Here we extend these studies to show that an affinity-purified antibody to PSD-95 labels the dendrites of most neurons in the forebrain and of a subset of neurons in the cerebellum. To confirm that PSD-95 is associated with the PSD at forebrain synapses and to clarify whether it is also associated with the presynaptic membrane, we employed immunogold electron microscopy of forebrain synaptosomes. Gold-labeled antibodies to PSD-95 labeled postsynaptic densities in both intact and lysed forebrain synaptosomes but did not label presynaptic terminals or the presynaptic membrane. The asymmetric distribution of PSD-95 at synapses contrasts with that of its homologs, disks-large and ZO-1, which are arranged symmetrically at septate and tight junctions, respectively
Complications of circumcision in male neonates, infants and children: a systematic review.
BACKGROUND: Approximately one in three men are circumcised globally, but there are relatively few data on the safety of the procedure. The aim of this paper is to summarize the literature on frequency of adverse events following pediatric circumcision, with a focus on developing countries. METHODS: PubMed and other databasess were searched with keywords and MeSH terms including infant/newborn/pediatric/child, circumcision, complications and adverse events. Searches included all available years and were conducted on November 6th 2007 and updated on February 14th 2009. Additional searches of the Arabic literature included searches of relevant databases and University libraries for research theses on male circumcision.Studies were included if they contained data to estimate frequency of adverse events following neonatal, infant and child circumcision. There was no language restriction. A total of 1349 published papers were identified, of which 52 studies from 21 countries met the inclusion criteria. The Arabic literature searches identified 46 potentially relevant papers, of which six were included. RESULTS: Sixteen prospective studies evaluated complications following neonatal and infant circumcision. Most studies reported no severe adverse events (SAE), but two studies reported SAE frequency of 2%. The median frequency of any complication was 1.5% (range 0-16%). Child circumcision by medical providers tended to be associated with more complications (median frequency 6%; range 2-14%) than for neonates and infants. Traditional circumcision as a rite of passage is associated with substantially greater risks, more severe complications than medical circumcision or traditional circumcision among neonates. CONCLUSIONS: Studies report few severe complications following circumcision. However, mild or moderate complications are seen, especially when circumcision is undertaken at older ages, by inexperienced providers or in non-sterile conditions. Pediatric circumcision will continue to be practiced for cultural, medical and as a long-term HIV/STI prevention strategy. Risk-reduction strategies including improved training of providers, and provision of appropriate sterile equipment, are urgently needed
Spectral Theory of Time Dispersive and Dissipative Systems
We study linear time dispersive and dissipative systems. Very often such
systems are not conservative and the standard spectral theory can not be
applied. We develop a mathematically consistent framework allowing (i) to
constructively determine if a given time dispersive system can be extended to a
conservative one; (ii) to construct that very conservative system -- which we
show is essentially unique. We illustrate the method by applying it to the
spectral analysis of time dispersive dielectrics and the damped oscillator with
retarded friction. In particular, we obtain a conservative extension of the
Maxwell equations which is equivalent to the original Maxwell equations for a
dispersive and lossy dielectric medium.Comment: LaTeX, 57 Pages, incorporated revisions corresponding with published
versio
Blunting the Spike: the CV Minimum Period
The standard picture of CV secular evolution predicts a spike in the CV
distribution near the observed short-period cutoff P_0 ~ 78 min, which is not
observed. We show that an intrinsic spread in minimum (`bounce') periods P_b
resulting from a genuine difference in some parameter controlling the evolution
can remove the spike without smearing the sharpness of the cutoff. The most
probable second parameter is different admixtures of magnetic stellar wind
braking (at up to 5 times the GR rate) in a small tail of systems, perhaps
implying that the donor magnetic field strength at formation is a second
parameter specifying CV evolution. We suggest that magnetic braking resumes
below the gap with a wide range, being well below the GR rate in most CVs, but
significantly above it in a small tail.Comment: 5 pages, 4 figures; accepted for publication in MNRA
Line Emitting Galaxies Beyond a Redshift of 7: An Improved Method for Estimating the Evolving Neutrality of the Intergalactic Medium
The redshift-dependent fraction of color-selected galaxies revealing Lyman
alpha emission has become the most valuable constraint on the evolving
neutrality of the early intergalactic medium. However, in addition to resonant
scattering by neutral gas, the visibility of Lyman alpha is also dependent on
the intrinsic properties of the host galaxy, including its stellar population,
dust content and the nature of outflowing gas. Taking advantage of significant
progress we have made in determining the line emitting properties of galaxies, we propose an improved method, based on using the measured
slopes of the rest-frame ultraviolet continua of galaxies, to interpret the
growing body of near-infrared spectra of galaxies in order to take into
account these host galaxy dependencies. In a first application of our new
method, we demonstrate its potential via a new spectroscopic survey of
galaxies undertaken with the Keck MOSFIRE spectrograph. Together with earlier
published data our data provides improved estimates of the evolving visibility
of Lyman alpha, particularly at redshift . As a byproduct, we also
present a new line emitting galaxy at a redshift which supersedes an
earlier redshift record. We discuss the improving constraints on the evolving
neutral fraction over and the implications for cosmic reionization.Comment: To be submitted to Ap
The Influence of the Degree of Heterogeneity on the Elastic Properties of Random Sphere Packings
The macroscopic mechanical properties of colloidal particle gels strongly
depend on the local arrangement of the powder particles. Experiments have shown
that more heterogeneous microstructures exhibit up to one order of magnitude
higher elastic properties than their more homogeneous counterparts at equal
volume fraction. In this paper, packings of spherical particles are used as
model structures to computationally investigate the elastic properties of
coagulated particle gels as a function of their degree of heterogeneity. The
discrete element model comprises a linear elastic contact law, particle bonding
and damping. The simulation parameters were calibrated using a homogeneous and
a heterogeneous microstructure originating from earlier Brownian dynamics
simulations. A systematic study of the elastic properties as a function of the
degree of heterogeneity was performed using two sets of microstructures
obtained from Brownian dynamics simulation and from the void expansion method.
Both sets cover a broad and to a large extent overlapping range of degrees of
heterogeneity. The simulations have shown that the elastic properties as a
function of the degree of heterogeneity are independent of the structure
generation algorithm and that the relation between the shear modulus and the
degree of heterogeneity can be well described by a power law. This suggests the
presence of a critical degree of heterogeneity and, therefore, a phase
transition between a phase with finite and one with zero elastic properties.Comment: 8 pages, 6 figures; Granular Matter (published online: 11. February
2012
H\"older equicontinuity of the integrated density of states at weak disorder
H\"older continuity, , with
a constant independent of the disorder strength is proved for the
integrated density of states associated to a discrete random
operator consisting of a translation invariant hopping
matrix and i.i.d. single site potentials with an absolutely
continuous distribution, under a regularity assumption for the hopping term.Comment: 15 Pages, typos corrected, comments and ref. [1] added, theorems 3,4
combine
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