1,678 research outputs found
Differential rotation of nonlinear r-modes
Differential rotation of r-modes is investigated within the nonlinear theory
up to second order in the mode amplitude in the case of a slowly-rotating,
Newtonian, barotropic, perfect-fluid star. We find a nonlinear extension of the
linear r-mode, which represents differential rotation that produces large scale
drifts of fluid elements along stellar latitudes. This solution includes a
piece induced by first-order quantities and another one which is a pure
second-order effect. Since the latter is stratified on cylinders, it cannot
cancel differential rotation induced by first-order quantities, which is not
stratified on cylinders. It is shown that, unlikely the situation in the
linearized theory, r-modes do not preserve vorticity of fluid elements at
second-order. It is also shown that the physical angular momentum and energy of
the perturbation are, in general, different from the corresponding canonical
quantities.Comment: 9 pages, revtex4; section III revised, comments added in Introduction
and Conclusions, references updated; to appear in Phys. Rev.
On-chip quantum interference between silicon photon-pair sources
Large-scale integrated quantum photonic technologies1, 2 will require on-chip integration of identical photon sources with reconfigurable waveguide circuits. Relatively complex quantum circuits have been demonstrated already1, 2, 3, 4, 5, 6, 7, but few studies acknowledge the pressing need to integrate photon sources and waveguide circuits together on-chip8, 9. A key step towards such large-scale quantum technologies is the integration of just two individual photon sources within a waveguide circuit, and the demonstration of high-visibility quantum interference between them. Here, we report a silicon-on-insulator device that combines two four-wave mixing sources in an interferometer with a reconfigurable phase shifter. We configured the device to create and manipulate two-colour (non-degenerate) or same-colour (degenerate) path-entangled or path-unentangled photon pairs. We observed up to 100.0 ± 0.4% visibility quantum interference on-chip, and up to 95 ± 4% off-chip. Our device removes the need for external photon sources, provides a path to increasing the complexity of quantum photonic circuits and is a first step towards fully integrated quantum technologies
On possibility of measurement of the electron beam energy using absorption of radiation by electrons in a magnetic field
The possibility of the precise measurement of the electron beam energy using
absorption of radiation by electrons in a static and homogeneous magnetic field
in a range up to a few hundred GeV energies, was considered in [1]. With the
purpose of experimental checking of this method in a range of several tens MeV
energies, the possibility of measurement of absolute energy of the electron
beam energy with relative accuracy up to 10^{-4} is examined in details.Comment: 14 pages, 10 figure
Host-microbe interaction in the gastrointestinal tract
The gastrointestinal tract is a highly complex organ in which multiple dynamic physiological processes are tightly coordinated while interacting with a dense and extremely diverse microbial population. From establishment in early life, through to host-microbe symbiosis in adulthood, the gut microbiota plays a vital role in our development and health. The effect of the microbiota on gut development and physiology is highlighted by anatomical and functional changes in germ-free mice, affecting the gut epithelium, immune system, and enteric nervous system. Microbial colonisation promotes competent innate and acquired mucosal immune systems, epithelial renewal, barrier integrity, and mucosal vascularisation and innervation. Interacting or shared signalling pathways across different physiological systems of the gut could explain how all these changes are coordinated during postnatal colonisation, or after the introduction of microbiota into germ-free models. The application of cell-based in vitro experimental systems and mathematical modelling can shed light on the molecular and signalling pathways which regulate the development and maintenance of homeostasis in the gut and beyond. This article is protected by copyright. All rights reserved
X-Ray Scattering Measurements of the Transient Structure of a Driven Charge-Density-Wave
We report time-resolved x-ray scattering measurements of the transient
structural response of the sliding {\bf Q} charge-density-wave (CDW) in
NbSe to a reversal of the driving electric field. The observed time scale
characterizing this response at 70K varies from 15 msec for driving
fields near threshold to 2 msec for fields well above threshold. The
position and time-dependent strain of the CDW is analyzed in terms of a
phenomenological equation of motion for the phase of the CDW order parameter.
The value of the damping constant, eV
seconds \AA, is in excellent agreement with the value
determined from transport measurements. As the driving field approaches
threshold from above, the line shape becomes bimodal, suggesting that the CDW
does not depin throughout the entire sample at one well-defined voltage.Comment: revtex 3.0, 7 figure
Cost of Outpatient Arthroscopic Anterior Cruciate Ligament Reconstruction Among Commercially Insured Patients in the United States, 2005-2013
Background: Despite the significance of anterior cruciate ligament (ACL) injuries, these conditions have been under-researched from a population-level perspective. It is important to determine the economic effect of these injuries in order to document the public health burden in the United States. Purpose: To describe the cost of outpatient arthroscopic ACL reconstruction and health care utilization among commercially insured beneficiaries in the United States. Study Design: Economic and decision analysis; Level of evidence, 3. Methods: The study used the Truven Health Analytics MarketScan Commercial Claims and Encounters database, an administrative claims database that contains a large sample (approximately 148 million) of privately insured individuals aged <65 years and enrolled in employer-sponsored plans. All claims with Current Procedural Terminology (CPT) code 29888 (arthroscopically aided ACL reconstruction or augmentation) from 2005 to 2013 were included. “Immediate procedure” cost was computed assuming a 3-day window of care centered on date of surgery. “Total health care utilization” cost was computed using a 9-month window of care (3 months preoperative and 6 months postoperative). Results: There were 229,446 outpatient arthroscopic ACL reconstructions performed over the 9-year study period. Median immediate procedure cost was 13,403.38. Patients who underwent concomitant collateral ligament (medial [MCL], lateral [LCL]) repair or reconstruction had the highest costs for both immediate procedure (17,006.34). For patients who had more than 1 reconstruction captured in the database, total health care utilization costs were higher for the second procedure than the first procedure (15,000.36), despite the fact that immediate procedure costs were lower for second procedures (9445.26). Conclusion: These results provide a foundation for understanding the public health burden of ACL injuries in the United States. Our findings suggest that further research on the prevention and treatment of ACL injuries is necessary to reduce this burden
Novel Collective Effects in Integrated Photonics
Superradiance, the enhanced collective emission of energy from a coherent
ensemble of quantum systems, has been typically studied in atomic ensembles. In
this work we study theoretically the enhanced emission of energy from coherent
ensembles of harmonic oscillators. We show that it should be possible to
observe harmonic oscillator superradiance for the first time in waveguide
arrays in integrated photonics. Furthermore, we describe how pairwise
correlations within the ensemble can be measured with this architecture. These
pairwise correlations are an integral part of the phenomenon of superradiance
and have never been observed in experiments to date.Comment: 7 pages, 3 figure
Ctcf haploinsufficiency mediates intron retention in a tissue-specific manner
CTCF is a master regulator of gene transcription and chromatin organisation with occupancy at thousands of DNA target sites genome-wide. While CTCF is essential for cell survival, CTCF haploinsufficiency is associated with tumour development and hypermethylation. Increasing evidence demonstrates CTCF as a key player in several mechanisms regulating alternative splicing (AS), however, the genome-wide impact of Ctcf dosage on AS has not been investigated.
We examined the effect of Ctcf haploinsufficiency on gene expression and AS in five tissues from Ctcf hemizygous (Ctcf+/-) mice. Reduced Ctcf levels caused distinct tissue-specific differences in gene expression and AS in all tissues. An increase in intron retention (IR) was observed in Ctcf+/- liver and kidney. In liver, this specifically impacted genes associated with cytoskeletal organisation, splicing and metabolism. Strikingly, most differentially retained introns were short, with a high GC content and enriched in Ctcf binding sites in their proximal upstream genomic region. This study provides new insights into the effects of CTCF haploinsufficiency on organ transcriptomes and the role of CTCF in AS regulation
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