1,642 research outputs found
A Comparative Estimation of Financial Frictions in Japan and Korea
We apply the Business Cycle Accounting method a la Chari, Kehoe, and McGrattan (2007) to the Japanese and the Korean economy and quantitatively analyze the effects of financial frictions during the recent recessions. First, we compute exogenous distor- tions in the financial, government purchases, labor, and production markets. The preliminary results show that the sudden drop in production efficiency (TFP) was the main reason of the Korean recession while the increase in labor market distortions was the main reason of the Japanese slump. Next, we orthogonalize the innovations to the distortions and quantify the maximum spill-over effects of financial frictions on output fluctuations in both countries following Christiano and Davis (2006). Our results imply that financial frictions may have been important in explaining the recessions in both countries through their effects on TFP and labor market distortions
An interoceptive predictive coding model of conscious presence
We describe a theoretical model of the neurocognitive mechanisms underlying conscious presence and its disturbances. The model is based on interoceptive prediction error and is informed by predictive models of agency, general models of hierarchical predictive coding and dopaminergic signaling in cortex, the role of the anterior insular cortex (AIC) in interoception and emotion, and cognitive neuroscience evidence from studies of virtual reality and of psychiatric disorders of presence, specifically depersonalization/derealization disorder. The model associates presence with successful suppression by top-down predictions of informative interoceptive signals evoked by autonomic control signals and, indirectly, by visceral responses to afferent sensory signals. The model connects presence to agency by allowing that predicted interoceptive signals will depend on whether afferent sensory signals are determined, by a parallel predictive-coding mechanism, to be self-generated or externally caused. Anatomically, we identify the AIC as the likely locus of key neural comparator mechanisms. Our model integrates a broad range of previously disparate evidence, makes predictions for conjoint manipulations of agency and presence, offers a new view of emotion as interoceptive inference, and represents a step toward a mechanistic account of a fundamental phenomenological property of consciousness
Monopole-vortex complex in a theta vacuum
We discuss aspects of the monopole-vortex complex soliton arising in a
hierarchically broken gauge system, G to H to 1, in a theta vacuum of the
underlying G theory. Here we focus our attention mainly on the simplest such
system with G=SU(2) and H=U(1). A consistent picture of the effect of the theta
parameter is found both in a macroscopic, dual picture and in a microscopic
description of the monopole-vortex complex soliton.Comment: 18 pages 3 figure
Amplified Dispersive Fourier-Transform Imaging for Ultrafast Displacement Sensing and Barcode Reading
Dispersive Fourier transformation is a powerful technique in which the
spectrum of an optical pulse is mapped into a time-domain waveform using
chromatic dispersion. It replaces a diffraction grating and detector array with
a dispersive fiber and single photodetector. This simplifies the system and,
more importantly, enables fast real-time measurements. Here we describe a novel
ultrafast barcode reader and displacement sensor that employs
internally-amplified dispersive Fourier transformation. This technique
amplifies and simultaneously maps the spectrally encoded barcode into a
temporal waveform. It achieves a record acquisition speed of 25 MHz -- four
orders of magnitude faster than the current state-of-the-art.Comment: Submitted to a journa
Gravitational waves from black hole-neutron star binaries I: Classification of waveforms
Using our new numerical-relativity code SACRA, long-term simulations for
inspiral and merger of black hole (BH)-neutron star (NS) binaries are
performed, focusing particularly on gravitational waveforms. As the initial
conditions, BH-NS binaries in a quasiequilibrium state are prepared in a
modified version of the moving-puncture approach. The BH is modeled by a
nonspinning moving puncture and for the NS, a polytropic equation of state with
and the irrotational velocity field are employed. The mass ratio of
the BH to the NS, , is chosen in the range between 1.5
and 5. The compactness of the NS, defined by , is chosen to be between 0.145 and 0.178. For a large value of for
which the NS is not tidally disrupted and is simply swallowed by the BH,
gravitational waves are characterized by inspiral, merger, and ringdown
waveforms. In this case, the waveforms are qualitatively the same as that from
BH-BH binaries. For a sufficiently small value of Q \alt 2, the NS may be
tidally disrupted before it is swallowed by the BH. In this case, the amplitude
of the merger and ringdown waveforms is very low, and thus, gravitational waves
are characterized by the inspiral waveform and subsequent quick damping. The
difference in the merger and ringdown waveforms is clearly reflected in the
spectrum shape and in the "cut-off" frequency above which the spectrum
amplitude steeply decreases. When an NS is not tidally disrupted (e.g., for
Q=5), kick velocity, induced by asymmetric gravitational wave emission, agrees
approximately with that derived for the merger of BH-BH binaries, whereas for
the case that the tidal disruption occurs, the kick velocity is significantly
suppressed.Comment: 25 pages, 3 jpg figures, accepted for publication in PRD; erratum is
added on Jul 23. 201
Prediction of risk of fracture in the tibia due to altered bone mineral density distribution resulting from disuse : a finite element study
The disuse-related bone loss that results from immobilisation following injury shares characteristics with osteoporosis in postmenopausal women and the aged, with decreases in bone mineral density (BMD) leading to weakening of the bone and increased risk of fracture. The aim of the study was to use the finite element method to: (i) calculate the mechanical response of the tibia under mechanical load and (ii) estimate the risk of fracture; comparing between two groups, an able bodied (AB) group and spinal cord injury (SCI) patients group suffering from varying degree of bone loss. The tibiae of eight male subjects with chronic SCI and those of four able-bodied (AB) age-matched controls were scanned using multi-slice peripheral Quantitative Computed Tomography. Images were used to develop full three-dimensional models of the tibiae in Mimics (Materialise) and exported into Abaqus (Simulia) for calculation of stress distribution and fracture risk in response to specified loading conditions – compression, bending and torsion. The percentage of elements that exceeded a calculated value of the ultimate stress provided an estimate of the risk of fracture for each subject, which differed between SCI subjects and their controls. The differences in BMD distribution along the tibia in different subjects resulted in different regions of the bone being at high risk of fracture under set loading conditions, illustrating the benefit of creating individual material distribution models. A predictive tool can be developed based on these models, to enable clinicians to estimate the amount of loading that can be safely allowed onto the skeletal frame of individual patients who suffer from extensive musculoskeletal degeneration (including SCI, multiple sclerosis and the ageing population). The ultimate aim would be to reduce fracture occurrence in these vulnerable groups
Extended Quantum Dimer Model and novel valence-bond phases
We extend the quantum dimer model (QDM) introduced by Rokhsar and Kivelson so
as to construct a concrete example of the model which exhibits the first-order
phase transition between different valence-bond solids suggested recently by
Batista and Trugman and look for the possibility of other exotic dimer states.
We show that our model contains three exotic valence-bond phases (herringbone,
checkerboard and dimer smectic) in the ground-state phase diagram and that it
realizes the phase transition from the staggered valence-bond solid to the
herringbone one. The checkerboard phase has four-fold rotational symmetry,
while the dimer smectic, in the absence of quantum fluctuations, has massive
degeneracy originating from partial ordering only in one of the two spatial
directions. A resonance process involving three dimers resolves this massive
degeneracy and dimer smectic gets ordered (order from disorder).Comment: 20 pages, 13 figures, accepted for publication in J. Stat. Mec
Deficiency in clonogenic endometrial mesenchymal stem cells in obese women with reproductive failure – a pilot study
The mechanisms of obesity associated reproductive complications remain poorly understood. Endometrial mesenchymal stem-cells are critical for cyclic renewal and uterine function. Recently, W5C5+ cells, with high clonogenicity, capable of producing endometrial stroma in vivo, have been described. We sought to investigate the abundance and cloning efficiency of W5C5+ and W5C5− endometrial cells in relation to Body Mass Index, age and reproductive outcome.
Design
W5C5+ and W5C5− cells were purified from mid-luteal endometrial biopsies (n = 54) by magnetic bead separation and subjected to in vitro colony-forming assays.
Results
First trimester pregnancy losses were significantly higher in obese subjects (n = 12) compared to overweight (n = 20) and subjects with normal Body Mass Index (n = 22) (P0.05).
Conclusions
Our observations suggest that the regenerative capacity and plasticity of the endometrium of obese women is suboptimal, which in turn may account for the increased risk of reproductive complications associated with obesity
Phase transitions of a tethered surface model with a deficit angle term
Nambu-Goto model is investigated by using the canonical Monte Carlo
simulations on fixed connectivity surfaces of spherical topology. Three
distinct phases are found: crumpled, tubular, and smooth. The crumpled and the
tubular phases are smoothly connected, and the tubular and the smooth phases
are connected by a discontinuous transition. The surface in the tubular phase
forms an oblong and one-dimensional object similar to a one-dimensional linear
subspace in the Euclidean three-dimensional space R^3. This indicates that the
rotational symmetry inherent in the model is spontaneously broken in the
tubular phase, and it is restored in the smooth and the crumpled phases.Comment: 6 pages with 6 figure
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