1,175 research outputs found
Abnormal infant islet morphology precedes insulin resistance in PCOS-like monkeys.
Polycystic ovary syndrome (PCOS) is prevalent in reproductive-aged women and confounded by metabolic morbidities, including insulin resistance and type 2 diabetes. Although the etiology of PCOS is undefined, contribution of prenatal androgen (PA) exposure has been proposed in a rhesus monkey model as premenopausal PA female adults have PCOS-like phenotypes in addition to insulin resistance and decreased glucose tolerance. PA female infants exhibit relative hyperinsulinemia, suggesting prenatal sequelae of androgen excess on glucose metabolism and an antecedent to future metabolic disease. We assessed consequences of PA exposure on pancreatic islet morphology to identify evidence of programming on islet development. Islet counts and size were quantified and correlated with data from intravenous glucose tolerance tests (ivGTT) obtained from dams and their offspring. Average islet size was decreased in PA female infants along with corresponding increases in islet number, while islet fractional area was preserved. Infants also demonstrated an increase in both the proliferation marker Ki67 within islets and the beta to alpha cell ratio suggestive of enhanced beta cell expansion. PA adult females have reduced proportion of small islets without changes in proliferative or apoptotic markers, or in beta to alpha cell ratios. Together, these data suggest in utero androgen excess combined with mild maternal glucose intolerance alter infant and adult islet morphology, implicating deviant islet development. Marked infant, but subtle adult, morphological differences provide evidence of islet post-natal plasticity in adapting to changing physiologic demands: from insulin sensitivity and relative hypersecretion to insulin resistance and diminished insulin response to glucose in the mature PCOS-like phenotype
The Neighborhoodâs Catalogue: Lower East Side Planning and Design File
This catalogue was designed to support the process of slow redevelopment over time, combined with conservation of diverse social and historical continuity and the exploration of new land and building uses. The catalogue shows how to involve neighborhoods in participation, supportive design, incremental planning and phased development. This project was made possible by a grant from the National Endowment for the Arts. Reprinted in 1987.https://dc.uwm.edu/caupr_mono/1047/thumbnail.jp
Gauge invariance and background field formalism in the exact renormalisation group
We discuss gauge symmetry and Ward-Takahashi identities for Wilsonian flows
in pure Yang-Mills theories. The background field formalism is used for the
construction of a gauge invariant effective action. The symmetries of the
effective action under gauge transformations for both the gauge field and the
auxiliary background field are separately evaluated. We examine how the
symmetry properties of the full theory are restored in the limit where the
cut-off is removed.Comment: version to be published in PL
Equilibrium Properties of Temporally Asymmetric Hebbian Plasticity
A theory of temporally asymmetric Hebb (TAH) rules which depress or
potentiate synapses depending upon whether the postsynaptic cell fires before
or after the presynaptic one is presented. Using the Fokker-Planck formalism,
we show that the equilibrium synaptic distribution induced by such rules is
highly sensitive to the manner in which bounds on the allowed range of synaptic
values are imposed. In a biologically plausible multiplicative model, we find
that the synapses in asynchronous networks reach a distribution that is
invariant to the firing rates of either the pre- or post-synaptic cells. When
these cells are temporally correlated, the synaptic strength varies smoothly
with the degree and phase of synchrony between the cells.Comment: 3 figures, minor corrections of equations and tex
Modulating Carrier Kinetics in BiVO4 Photoanodes through Molecular Co4O4 Cubane Layers
Understanding the role and immobilization of molecular catalysts on photoelectrodes is essential to use their full potential for efficient solar fuel generation. Here, a CoII4O4 cubane with proven catalytic performance and an active H2OâCo2(OR)2âOH2 edge-site moiety is immobilized on BiVO4 photoanodes through a versatile layer-by-layer assembly strategy. This delivers a photocurrent of 3.3 mA cmâ2 at 1.23 VRHE and prolonged stability. Tuning the thickness of the Co4O4 layer has remarkable effects on photocurrents, dynamic open circuit potentials, and charge carrier behavior. Comprehensive-time and frequency-dependent perturbation techniques are employed to investigate carrier kinetics in transient and pseudo-steady-state operando conditions. It is revealed that the Co4O4 layer can prolong carrier lifetime, unblock kinetic limitations at the interface by suppressing recombination, and enhance charge transfer. Additionally, its flexible roles are identified as passivation/hole trapping/catalytic layer at respective lower/moderate/higher potentials. These competing functions are under dynamic equilibrium, which fundamentally defines the observed photocurrent trends
Copper(II) defect-cubane water oxidation electrocatalysts: from molecular tetramers to oxidic nanostructures
We report on the synthesis and spectroscopic evidence for a sequence of structural transformations of a new defect-cubane type copper complex, [Cu4(pyalk)4(OAc)4](ClO4)(HNEt3), which acts as a pre-catalyst for water oxidation. In situ and post-catalytic studies showed that the tetrameric complex undergoes a structural transformation into dimeric and monomeric species, induced by water molecules and carbonate anions, respectively. Further, the observed electrocatalytic water oxidation activity has been confirmed to arise from in situ-generated Cu(II) oxidic nanostructures at the electrode interface
Mean Field Dynamics in Non-Abelian Plasmas from Classical Transport Theory
Based on classical transport theory, we present a general set of covariant
equations describing the dynamics of mean fields and their statistical
fluctuations in a non-Abelian plasma in or out-of-equilibrium. A procedure to
obtain the collision integrals for the Boltzmann equation from the microscopic
theory is described. As an application, we study a hot non-Abelian plasma close
to equilibrium, where the fluctuations are integrated out explicitly. For soft
fields, and at logarithmic accuracy, we obtain B\"odeker's effective theory.Comment: 4 pages, revtex, no figures. Typo removed, a reference updated,
version as to appear in Phys. Rev. Let
Improved Analysis of GW150914 Using a Fully Spin-Precessing Waveform Model
This paper presents updated estimates of source parameters for GW150914, a binary black-hole coalescence event detected by the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015 [Abbott et al. Phys. Rev. Lett. 116, 061102 (2016).]. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] presented parameter estimation of the source using a 13-dimensional, phenomenological precessing-spin model (precessing IMRPhenom) and an 11-dimensional nonprecessing effective-one-body (EOB) model calibrated to numerical-relativity simulations, which forces spin alignment (nonprecessing EOBNR). Here, we present new results that include a 15-dimensional precessing-spin waveform model (precessing EOBNR) developed within the EOB formalism. We find good agreement with the parameters estimated previously [Abbott et al. Phys. Rev. Lett. 116, 241102 (2016).], and we quote updated component masses of 35+5â3Mâ and 30+3â4M â (where errors correspond to 90% symmetric credible intervals). We also present slightly tighter constraints on the dimensionless spin magnitudes of the two black holes, with a primary spin estimate < 0.65 and a secondary spin estimate < 0.75 at 90% probability. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] estimated the systematic parameter-extraction errors due to waveform-model uncertainty by combining the posterior probability densities of precessing IMRPhenom and nonprecessing EOBNR. Here, we find that the two precessing-spin models are in closer agreement, suggesting that these systematic errors are smaller than previously quoted
Probing the extragalactic fast transient sky at minute timescales with DECam
Searches for optical transients are usually performed with a cadence of days
to weeks, optimised for supernova discovery. The optical fast transient sky is
still largely unexplored, with only a few surveys to date having placed
meaningful constraints on the detection of extragalactic transients evolving at
sub-hour timescales. Here, we present the results of deep searches for dim,
minute-timescale extragalactic fast transients using the Dark Energy Camera, a
core facility of our all-wavelength and all-messenger Deeper, Wider, Faster
programme. We used continuous 20s exposures to systematically probe timescales
down to 1.17 minutes at magnitude limits (AB), detecting hundreds of
transient and variable sources. Nine candidates passed our strict criteria on
duration and non-stellarity, all of which could be classified as flare stars
based on deep multi-band imaging. Searches for fast radio burst and gamma-ray
counterparts during simultaneous multi-facility observations yielded no
counterparts to the optical transients. Also, no long-term variability was
detected with pre-imaging and follow-up observations using the SkyMapper
optical telescope. We place upper limits for minute-timescale fast optical
transient rates for a range of depths and timescales. Finally, we demonstrate
that optical -band light curve behaviour alone cannot discriminate between
confirmed extragalactic fast transients such as prompt GRB flashes and Galactic
stellar flares.Comment: Published in MNRA
Dynamics of coupled bosonic systems with applications to preheating
Coupled, multi-field models of inflation can provide several attractive
features unavailable in the case of a single inflaton field. These models have
a rich dynamical structure resulting from the interaction of the fields and
their associated fluctuations. We present a formalism to study the
nonequilibrium dynamics of coupled scalar fields. This formalism solves the
problem of renormalizing interacting models in a transparent way using
dimensional regularization. The evolution is generated by a renormalized
effective Lagrangian which incorporates the dynamics of the mean fields and
their associated fluctuations at one-loop order. We apply our method to two
problems of physical interest: (i) a simple two-field model which exemplifies
applications to reheating in inflation, and (ii) a supersymmetric hybrid
inflation model. This second case is interesting because inflation terminates
via a smooth phase transition which gives rise to a spinodal instability in one
of the fields. We study the evolution of the zero mode of the fields and the
energy density transfer to the fluctuations from the mean fields. We conclude
that back reaction effects can be significant over a wide parameter range. In
particular for the supersymmetric hybrid model we find that particle production
can be suppressed due to these effects.Comment: 23 pages, 16 eps-figures, minor changes in the text, references
added, accepted for publication in PR
- âŠ