3,718 research outputs found
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Di-μ-oxido-bis-[(1,4,8,11-tetra-aza-cyclo-tetra-decane-κN,N',N'',N''')dimangan-ese(III,IV)] bis-(tetra-phenyl-borate) chloride acetonitrile disolvate.
The title compound, [Mn(2)O(2)(C(10)H(24)N(4))(2)](C(24)H(20)B)(2)Cl·2CH(3)CN, is a mixed-valent Mn(III)/Mn(IV) oxide-bridged mangan-ese dimer with one chloride and two tetra-phenyl-borate counter-anions. There are two non-coordinated mol-ecules of acetonitrile in the formula unit. A center of inversion is present between the two metal atoms, and, consequently, there is no distinction between Mn(III) and Mn(IV) metal centers. In the Mn(2)O(2) core, the Mn-O distances are 1.817 (3) and 1.821 (3) Å. The cyclam ligand is in the cis configuration. The chloride counter-anion resides on a center of symmetry, whereas the tetra-phenyl-borate counter-anion is in a general position. The cyclam ligand is hydrogen bonded to the acetonitrile as well as to the chloride anion. One of the phenyl rings of the anion and the acetonitrile solvent molecule are each disordered over two sets of sites
Perturbative Analysis of Spectral Singularities and Their Optical Realizations
We develop a perturbative method of computing spectral singularities of a
Schreodinger operator defined by a general complex potential that vanishes
outside a closed interval. These can be realized as zero-width resonances in
optical gain media and correspond to a lasing effect that occurs at the
threshold gain. Their time-reversed copies yield coherent perfect absorption of
light that is also known as an antilaser. We use our general results to
establish the exactness of the n-th order perturbation theory for an arbitrary
complex potential consisting of n delta-functions, obtain an exact expression
for the transfer matrix of these potentials, and examine spectral singularities
of complex barrier potentials of arbitrary shape. In the context of optical
spectral singularities, these correspond to inhomogeneous gain media.Comment: 13 pages, 2 figures, one table, a reference added, typos correcte
Atom-molecule conversion with particle losses
Based on the mean-field approximation and the phase space analysis, we study
the dynamics of an atom-molecule conversion system subject to particle loss.
Starting from the many-body dynamics described by a master equation, an
effective nonlinear Schr\"odinger equation is introduced. The classical phase
space is then specified and classified by fixed points. The boundary, which
separate different dynamical regimes have been calculated and discussed. The
effect of particle loss on the conversion efficiency and the self-trapping is
explored.Comment: 6 pages, 5 figure
J0316+4328: a Probable "Asymmetric Double" Lens
We report a probable gravitational lens J0316+4328, one of 19 candidate
asymmetric double lenses (2 images at a high flux density ratio) from CLASS.
Observations with the Very Large Array (VLA), MERLIN and the Very Long Baseline
Array (VLBA) imply that J0316+4328 is a lens with high confidence. It has 2
images separated by 0.40", with 6 GHz flux densities of 62 mJy and 3.2 mJy. The
flux density ratio of ~19 (constant over the frequency range 6-22 GHz) is the
largest for any 2 image gravitational lens. High resolution optical imaging and
deeper VLBI maps should confirm the lensing interpretation and provide inputs
to detailed lens models. The unique configuration will give strong constraints
on the lens galaxy's mass profile.Comment: Accepted to MNRAS Letters. 5 pages, 6 figures, 3 table
Gravitational waves from extreme mass-ratio inspirals in Dynamical Chern-Simons gravity
Dynamical Chern-Simons gravity is an interesting extension of General
Relativity, which finds its way in many different contexts, including string
theory, cosmological settings and loop quantum gravity. In this theory, the
gravitational field is coupled to a scalar field by a parity-violating term,
which gives rise to characteristic signatures. Here we investigate how
Chern-Simons gravity would affect the quasi-circular inspiralling of a small,
stellar-mass object into a large non-rotating supermassive black hole, and the
accompanying emission of gravitational and scalar waves. We find the relevant
equations describing the perturbation induced by the small object, and we solve
them through the use of Green's function techniques. Our results show that for
a wide range of coupling parameters, the Chern-Simons coupling gives rise to an
increase in total energy flux, which translates into a fewer number of
gravitational-wave cycles over a certain bandwidth. For space-based
gravitational-wave detectors such as LISA, this effect can be used to constrain
the coupling parameter effectively.Comment: RevTex4, 18 pages, 7 figures, 1 tabl
A Complete Sample of Megaparsec Size Double Radio Sources from SUMSS
We present a complete sample of megaparsec-size double radio sources compiled
from the Sydney University Molonglo Sky Survey (SUMSS). Almost complete
redshift information has been obtained for the sample. The sample has the
following defining criteria: Galactic latitude |b| > 12.5 deg, declination <
-50 deg and angular size > 5 arcmin. All the sources have projected linear size
larger than 0.7 Mpc (assuming H_o = 71 km/s/Mpc). The sample is chosen from a
region of the sky covering 2100 square degrees. In this paper, we present
843-MHz radio images of the extended radio morphologies made using the Molonglo
Observatory Synthesis Telescope (MOST), higher resolution radio observations of
any compact radio structures using the Australia Telescope Compact Array
(ATCA), and low resolution optical spectra of the host galaxies from the 2.3-m
Australian National University (ANU) telescope at Siding Spring Observatory.
The sample presented here is the first in the southern hemisphere and
significantly enhances the database of known giant radio sources. The giant
radio sources with linear size exceeding 0.7 Mpc have an abundance of (215
Mpc)^(-3) at the sensitivity of the survey. In the low redshift universe, the
survey may be suggesting the possibility that giant radio sources with relict
lobes are more numerous than giant sources in which beams from the centre
currently energize the lobes.Comment: 67 pages, 29 figures, for full resolution figures see
http://www.astrop.physics.usyd.edu.au/SUMSS/PAPERS/Submit-May11-ms.pd
Derivation of the formyl-group oxygen of chlorophyll b from molecular oxygen in greening leaves of a higher plant (Zea mays)
Using mass spectroscopy, we demonstrate as much as 93% enrichment of the 7-formyl group oxygen of chlorophyll b when dark-grown, etiolated maize leaves are greened under white light in the presence of 18O2. This suggests that a mono-oxygenase is involved in the oxidation of its methyl group precursor. The concomitant enrichment of about 75% of the 131-oxygen confirms the well-documented finding that this oxo group, in both chlorophyll a and b, also arises from O2. High 18O enrichment into the 7-formyl oxygen relative to the substrate 18O2 was achieved by optimization of the greening conditions in combination with a reductive extraction procedure. It indicates not only a single pathway for Chl b formyl group formation, but also unequivocally demonstrates that molecular oxygen is the sole precursor of the 7-formyl oxygen
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The biological embedding of early-life socioeconomic status and family adversity in children's genome-wide DNA methylation.
AimTo examine variation in child DNA methylation to assess its potential as a pathway for effects of childhood social adversity on health across the life course.Materials & methodsIn a diverse, prospective community sample of 178 kindergarten children, associations between three types of social experience and DNA methylation within buccal epithelial cells later in childhood were examined.ResultsFamily income, parental education and family psychosocial adversity each associated with increased or decreased DNA methylation (488, 354 and 102 sites, respectively) within a unique set of genomic CpG sites. Gene ontology analyses pointed to genes serving immune and developmental regulation functions.ConclusionFindings provided support for DNA methylation as a biomarker linking early-life social experiences with later life health in humans
The geometry of thermodynamic control
A deeper understanding of nonequilibrium phenomena is needed to reveal the
principles governing natural and synthetic molecular machines. Recent work has
shown that when a thermodynamic system is driven from equilibrium then, in the
linear response regime, the space of controllable parameters has a Riemannian
geometry induced by a generalized friction tensor. We exploit this geometric
insight to construct closed-form expressions for minimal-dissipation protocols
for a particle diffusing in a one dimensional harmonic potential, where the
spring constant, inverse temperature, and trap location are adjusted
simultaneously. These optimal protocols are geodesics on the Riemannian
manifold, and reveal that this simple model has a surprisingly rich geometry.
We test these optimal protocols via a numerical implementation of the
Fokker-Planck equation and demonstrate that the friction tensor arises
naturally from a first order expansion in temporal derivatives of the control
parameters, without appealing directly to linear response theory
Synchronization in small-world systems
We quantify the dynamical implications of the small-world phenomenon. We
consider the generic synchronization of oscillator networks of arbitrary
topology, and link the linear stability of the synchronous state to an
algebraic condition of the Laplacian of the graph. We show numerically that the
addition of random shortcuts produces improved network synchronizability.
Further, we use a perturbation analysis to place the synchronization threshold
in relation to the boundaries of the small-world region. Our results also show
that small-worlds synchronize as efficiently as random graphs and hypercubes,
and more so than standard constructive graphs
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