268 research outputs found
Reactions of Tetracyclone Molybdenum Complexes with Electrophilic Alkynes: Cyclopentadienone-Alkyne Coupling and Alkyne Coordination
The reactions of the complexes [Mo(CO)2(η4-C4Ph4CO)2] and [Mo(CO)3(NCMe)(η4-C4Ph4CO)] with the alkynes dimethyl acetylenedicarboxylate (DMAD; RCâĄCR where R = CO2Me) and methyl propiolate (RCâĄCH) have been studied. In the case of DMAD, the initial product is the green carbonyl complex [Mo(CO)(RCâĄCR)(η5,Ï-C4Ph4COCRâCR)] (3), in which two alkyne molecules have been incorporated: one is linked to the carbonyl group of the tetracyclone ligand, whereas the other is Ï-bound to the metal as a four-electron donor. Oxidation of this compound affords yellow [Mo(O)(RCâĄCR)(η5,Ï-C4Ph4COCRâCR)] (8). When the Ï-acceptor carbonyl ligand is replaced by the Ï-donor oxo group, the alkyne ligand changes orientation: it lies parallel to the MoâCO bond in 3 but perpendicular to the MoâO group in 8. Analogous complexes (9, 10) were isolated in the case of methyl propiolate; each exists as a mixture of two isomers depending on the orientation of the unsymmetrical alkyne ligand
Reactions of Tetracyclone Molybdenum Complexes with Electrophilic Alkynes: Cyclopentadienone-Alkyne Coupling and Alkyne Coordination
The reactions of the complexes [Mo(CO)2(η4-C4Ph4CO)2] and [Mo(CO)3(NCMe)(η4-C4Ph4CO)] with the alkynes dimethyl acetylenedicarboxylate (DMAD; RCâĄCR where R = CO2Me) and methyl propiolate (RCâĄCH) have been studied. In the case of DMAD, the initial product is the green carbonyl complex [Mo(CO)(RCâĄCR)(η5,Ï-C4Ph4COCRâCR)] (3), in which two alkyne molecules have been incorporated: one is linked to the carbonyl group of the tetracyclone ligand, whereas the other is Ï-bound to the metal as a four-electron donor. Oxidation of this compound affords yellow [Mo(O)(RCâĄCR)(η5,Ï-C4Ph4COCRâCR)] (8). When the Ï-acceptor carbonyl ligand is replaced by the Ï-donor oxo group, the alkyne ligand changes orientation: it lies parallel to the MoâCO bond in 3 but perpendicular to the MoâO group in 8. Analogous complexes (9, 10) were isolated in the case of methyl propiolate; each exists as a mixture of two isomers depending on the orientation of the unsymmetrical alkyne ligand
Gravitational waves from inspiralling compact binaries: Parameter estimation using second-post-Newtonian waveforms
The parameters of inspiralling compact binaries can be estimated using
matched filtering of gravitational-waveform templates against the output of
laser-interferometric gravitational-wave detectors. Using a recently calculated
formula, accurate to second post-Newtonian (2PN) order [order , where
is the orbital velocity], for the frequency sweep () induced by
gravitational radiation damping, we study the statistical errors in the
determination of such source parameters as the ``chirp mass'' , reduced
mass , and spin parameters and (related to spin-orbit and
spin-spin effects, respectively). We find that previous results using template
phasing accurate to 1.5PN order actually underestimated the errors in ,
, and . For two inspiralling neutron stars, the measurement errors
increase by less than 16 percent.Comment: 14 pages, ReVTe
Post-Newtonian SPH calculations of binary neutron star coalescence. I. Method and first results
We present the first results from our Post-Newtonian (PN) Smoothed Particle
Hydrodynamics (SPH) code, which has been used to study the coalescence of
binary neutron star (NS) systems. The Lagrangian particle-based code
incorporates consistently all lowest-order (1PN) relativistic effects, as well
as gravitational radiation reaction, the lowest-order dissipative term in
general relativity. We test our code on sequences of single NS models of
varying compactness, and we discuss ways to make PN simulations more relevant
to realistic NS models. We also present a PN SPH relaxation procedure for
constructing equilibrium models of synchronized binaries, and we use these
equilibrium models as initial conditions for our dynamical calculations of
binary coalescence. Though unphysical, since tidal synchronization is not
expected in NS binaries, these initial conditions allow us to compare our PN
work with previous Newtonian results.
We compare calculations with and without 1PN effects, for NS with stiff
equations of state, modeled as polytropes with . We find that 1PN
effects can play a major role in the coalescence, accelerating the final
inspiral and causing a significant misalignment in the binary just prior to
final merging. In addition, the character of the gravitational wave signal is
altered dramatically, showing strong modulation of the exponentially decaying
waveform near the end of the merger. We also discuss briefly the implications
of our results for models of gamma-ray bursts at cosmological distances.Comment: RevTeX, 37 pages, 17 figures, to appear in Phys. Rev. D, minor
corrections onl
Analysis of LIGO data for gravitational waves from binary neutron stars
We report on a search for gravitational waves from coalescing compact binary
systems in the Milky Way and the Magellanic Clouds. The analysis uses data
taken by two of the three LIGO interferometers during the first LIGO science
run and illustrates a method of setting upper limits on inspiral event rates
using interferometer data. The analysis pipeline is described with particular
attention to data selection and coincidence between the two interferometers. We
establish an observational upper limit of 1.7 \times 10^{2}M_\odot$.Comment: 17 pages, 9 figure
Meta-analysis of data from animal studies:A practical guide
AbstractMeta-analyses of data from human studies are invaluable resources in the life sciences and the methods to conduct these are well documented. Similarly there are a number of benefits in conducting meta-analyses on data from animal studies; they can be used to inform clinical trial design, or to try and explain discrepancies between preclinical and clinical trial results. However there are inherit differences between animal and human studies and so applying the same techniques for the meta-analysis of preclinical data is not straightforward. For example preclinical studies are frequently small and there is often substantial heterogeneity between studies. This may have an impact on both the method of calculating an effect size and the method of pooling data. Here we describe a practical guide for the meta-analysis of data from animal studies including methods used to explore sources of heterogeneity
Psychosocial Treatment of Children in Foster Care: A Review
A substantial number of children in foster care exhibit psychiatric difficulties. Recent epidemiologi-cal and historical trends in foster care, clinical findings about the adjustment of children in foster care, and adult outcomes are reviewed, followed by a description of current approaches to treatment and extant empirical support. Available interventions for these children can be categorized as either symptom-focused or systemic, with empirical support for specific methods ranging from scant to substantial. Even with treatment, behavioral and emotional problems often persist into adulthood, resulting in poor functional outcomes. We suggest that self-regulation may be an important mediat-ing factor in the appearance of emotional and behavioral disturbance in these children
Longitudinal retinal changes in MOGAD
OBJECTIVE: Patients with myelin oligodendrocyte glycoprotein antibody (MOG-IgG) associated disease (MOGAD) suffer from severe optic neuritis (ON) leading to retinal neuro-axonal loss, which can be quantified by optical coherence tomography (OCT). We assessed whether ON-independent retinal atrophy can be detected in MOGAD. METHODS: Eighty MOGAD patients and 139 healthy controls (HC) were included. OCT data was acquired with 1) Spectralis spectral domain OCT (MOGAD (N=66) and HC (N=103)) and 2) Cirrus HD-OCT (MOGAD (N=14) and HC (N=36)). Macular combined ganglion cell and inner plexiform layer (GCIPL) and peripapillary retinal nerve fibre layer (pRNFL) were quantified. RESULTS: At baseline, GCIPL and pRNFL were lower in MOGAD eyes with a history of ON (MOGAD-ON) compared with MOGAD eyes without a history of ON (MOGAD-NON) and HC (p12 months ago (p<0.001). The overall MOGAD cohort did not exhibit faster GCIPL thinning compared with HC. INTERPRETATION: Our study suggests the absence of attack-independent retinal damage in MOGAD. Yet, ongoing neuroaxonal damage or oedema resolution seems to occur for up to 12 months after ON, which is longer than what has been reported with other ON forms. These findings support that the pathomechanisms underlying optic nerve involvement and the evolution of OCT retinal changes after ON is distinct in MOGAD. This article is protected by copyright. All rights reserved
AnĂĄlise histolĂłgica e histoquĂmica de cistos intra-epiteliais de tubas uterinas de novilhas mestiças
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