2,383 research outputs found
Resonantly Forced Inhomogeneous Reaction-Diffusion Systems
The dynamics of spatiotemporal patterns in oscillatory reaction-diffusion
systems subject to periodic forcing with a spatially random forcing amplitude
field are investigated. Quenched disorder is studied using the resonantly
forced complex Ginzburg-Landau equation in the 3:1 resonance regime. Front
roughening and spontaneous nucleation of target patterns are observed and
characterized. Time dependent spatially varying forcing fields are studied in
the 3:1 forced FitzHugh-Nagumo system. The periodic variation of the spatially
random forcing amplitude breaks the symmetry among the three quasi-homogeneous
states of the system, making the three types of fronts separating phases
inequivalent. The resulting inequality in the front velocities leads to the
formation of ``compound fronts'' with velocities lying between those of the
individual component fronts, and ``pulses'' which are analogous structures
arising from the combination of three fronts. Spiral wave dynamics is studied
in systems with compound fronts.Comment: 14 pages, 19 figures, to be published in CHAOS. This replacement has
some minor changes in layout for purposes of neatnes
Three-State Feshbach Resonances Mediated By Second-Order Couplings
We present an analytical study of three-state Feshbach resonances induced by
second-order couplings. Such resonances arise when the scattering amplitude is
modified by the interaction with a bound state that is not directly coupled to
the scattering state containing incoming flux. Coupling occurs indirectly
through an intermediate state. We consider two problems: (i) the intermediate
state is a scattering state in a distinct open channel; (ii) the intermediate
state is an off-resonant bound state in a distinct closed channel. The first
problem is a model of electric-field-induced resonances in ultracold collisions
of alkali metal atoms [Phys. Rev. A 75, 032709 (2007)] and the second problem
is relevant for ultracold collisions of complex polyatomic molecules, chemical
reaction dynamics, photoassociation of ultracold atoms, and electron - molecule
scattering. Our analysis yields general expressions for the energy dependence
of the T-matrix elements modified by three-state resonances and the dependence
of the resonance positions and widths on coupling amplitudes for the
weak-coupling limit. We show that the second problem can be generalized to
describe resonances induced by indirect coupling through an arbitrary number of
sequentially coupled off-resonant bound states and analyze the dependence of
the resonance width on the number of the intermediate states.Comment: 27 pages, 4 figures; added a reference; journal reference/DOI refer
to final published version, which is a shortened and modified version of this
preprin
Analysis of Antarctic glacigenic sediment provenance through geochemical and petrologic applications
The number of provenance studies of glacigenic sediments in Antarctica has increased dramatically over the past decade, providing an enhanced understanding of ice sheet history and dynamics, along with the broader geologic history. Such data have been used to assess glacial erosion patterns at the catchment scale, flow path reconstructions over a wide range of scales, and ice sheet fluctuations indicated by iceberg rafted debris in circumantarctic glacial marine sediments. It is notable that even though most of the bedrock of the continent is ice covered and inaccessible, provenance data can provide such valuable information about Antarctic ice and can even be used to infer buried rock types along with their geo- and thermochronologic history. Glacigenic sediments provide a broader array of provenance analysis opportunities than any other sediment type because of their wide range of grain sizes, and in this paper we review methods and examples from all size fractions that have been applied to the Antarctic glacigenic sedimentary record. Interpretations of these records must take careful consideration of the choice of analytical methods, uneven patterns of erosion, and spatial variability in sediment transport and rock types, which all may lead to a preferential identification of different elements of sources in the provenance analyses. Because of this, we advocate a multi-proxy approach and highlight studies that demonstrate the value of selecting complementary provenance methods
Polypill for prevention of cardiovascular disease in an Urban Iranian population with special focus on nonalcoholic steatohepatitis: A pragmatic randomized controlled trial within a cohort (PolyIran - Liver) â Study protocol
Background: Cardiovascular disease (CVD) is among the most common causes of mortality in all populations. Nonalcoholic steatohepatitis is a common finding in patients with CVD. Prevention of CVD in individual patients typically requires periodic clinical evaluation, as well as diagnosis and management of risk factors such as hypertension and hyperlipidemia. However, this is resource consuming and hard to implement, especially in developing countries. We designed a study to investigate the effects of a simpler strategy: a fixed-dose combination pill consisting of aspirin, valsartan, atorvastatin and hydrochlorthiazide (PolyPill) in an unselected group of persons aged over 50 years. Design: The PolyIran-Liver study was performed in Gonbad city as an open label pragmatic randomized controlled trial nested within the Golestan Cohort Study. We randomly selected 2,400 cohort study participants aged above 50 years, randomly assigned them to intervention or usual care and invited them to participate in an additional measurement study (if they met the eligibility criteria) to measure liver related outcomes. Those agreeing and randomized to the intervention arm were offered a daily single dose of PolyPill. We will follow participants for 5 years. The primary outcome is major cardiovascular events, secondary outcomes include all-cause mortality and liver related outcomes: liver stiffness and liver enzyme levels. Cardiovascular outcomes and mortality will be determined from the cohort study and liver-related outcomes in those consenting to follow up. Analysis will be by allocated group. Trial Status: Between October and December 2011, 1,320 intervention and 1,080 control participants were invited to participate in the additional measurement study. For all these participants, the major cardiovascular events will be determined using blind assessment of outcomes through the cohort study. In the intervention and control arms, 875 (66%) and 721 (67%) respectively, met the eligibility criteria and agreed to participate in the additional measurement study. Liver related outcomes will be measured in these participants. Of the 1,320 participants randomized to the intervention, 787 (60%) accepted the PolyPill. Conclusion: The PolyIran-liver urban study will provide us with important information on the effectiveness of PolyPill on major cardiovascular events, all-cause mortality and liver related outcomes. (ClinicalTrials.gov ID: NCT01245608). © 2015, Academy of Medical Sciences of I.R. Iran. All rights reserved
Novel technique for the CO<sub>2</sub> laser fabrication of optical devices with sub-micrometer ablation depth precision
We present novel techniques for the processing of fibre end face and cladding surfaces using a 9.6 ”m CO2 laser. We investigate the effects of pulse duration on process parameters
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Laschamp Excursion at Mono Lake?
The Laschamp Geomagnetic Excursion (ca. 41 ka) and a related increase of cosmogenic nuclides provides a global tie point among sedimentary and ice core records. In the Wilson Creek Formation, Mono Lake, California, the Laschamp Excursion has not been recognized although the so-called Mono Lake excursion was found in the section with an estimated age of about 28 14C ka. However, our reevaluation of the age of the Mono Lake excursion at its type locality using new 14C dates on carbonates and 40Ar/39Ar sanidine dates on ash layers yields an estimate of 38-41 ka. This chronology and the absence of a second excursion in the Wilson Creek Formation suggest that the distinct paleomagnetic feature with negative inclinations at Mono Lake is correlative with the Laschamp Excursion
Accommodating quality and service improvement research within existing ethical principles
Funds were provided by a Canadian Institute of Health Research grant (Nominated PI: Monica Taljaard, PJT â 153045). Funds were also generously provided by Charles Weijer, who is funded by a Tier 1 Canadian Research Chair.Peer reviewedPublisher PD
Prevention of serious respiratory syncytial virus-related illness. I: Disease pathogenesis and early attempts at prevention
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