2,255 research outputs found
Analytical study of coherence in seeded modulation instability
We derive analytical expressions for the coherence in the onset of modulation
instability, in excellent agreement with thorough numerical simulations. As
usual, we start by a linear perturbation analysis, where broadband noise is
added to a continuous wave (CW) pump; then, we investigate the effect of adding
a deterministic seed to the CW pump, a case of singular interest as it is
commonly encountered in parametric amplification schemes. Results for the
dependence of coherence on parameters such as fiber type, pump power,
propagated distance, seed signal-to-noise ratio are presented. Finally, we show
the importance of including higher-order linear and nonlinear dispersion when
dealing with generation in longer wavelength regions (mid IR). We believe these
results to be of relevance when applied to the analysis of the coherence
properties of supercontinua generated from CW pumps.Comment: 6 pages, 8 figure
Recommended from our members
Developing and evaluating interventions to reduce inappropriate prescribing by general practitioners of antibiotics for upper respiratory tract infections: a randomised controlled trial to compare paper-based and web-based modelling experiments
Background: Much implementation research is focused on full-scale trials with little evidence of preceding modelling work. The Medical Research Council Framework for developing and evaluating complex interventions has argued for more and better theoretical and exploratory work prior to a trial as a means of improving intervention development. Intervention modelling experiments (IMEs) are a way of exploring and refining an intervention before moving to a full-scale trial. They do this by delivering key elements of the intervention in a simulation that approximates clinical practice by, for example, presenting general practitioners (GPs) with a clinical scenario about making a treatment decision.
Methods: The current proposal will run a full, web-based IME involving 250 GPs that will advance the methodology of IMEs by directly comparing results with an earlier paper-based IME. Moreover, the web-based IME will evaluate an intervention that can be put into a full-scale trial that aims to reduce antibiotic prescribing for upper respiratory tract infections in primary care. The study will also include a trial of email versus postal invitations to participate.
Discussion: More effective behaviour change interventions are needed and this study will develop one such intervention and a system to model and test future interventions. This system will be applicable to any situation in the National Health Service where behaviour needs to be modified, including interventions aimed directly at the public.
Trial registration: ClinicalTrials (NCT): NCT0120673
Relativistic models for quasi-elastic neutrino scattering
We present quasi-elastic neutrino-nucleus cross sections in the energy range
from 150 MeV up to 5 GeV for the target nuclei 12C and 56Fe. A relativistic
description of the nuclear dynamics and the neutrino-nucleus coupling is
adopted. For the treatment of final-state interactions (FSI) we rely on two
frameworks succesfully applied to exclusive electron-nucleus scattering: a
relativistic optical potential and a relativistic multiple-scattering Glauber
approximation. At lower energies, the optical-potential approach is considered
to be the optimum choice, whereas at high energies a Glauber approach is more
natural. Comparing the results of both calculations, it is found that the
Glauber approach yields valid results down to the remarkably small nucleon
kinetic energies of 200 MeV. We argue that the nuclear transparencies extracted
from A(e,e'p) measurements can be used to obtain realistic estimates of the
effect of FSI mechanisms on quasi-elastic neutrino-nucleus cross sections. We
present two independent relativistic plane-wave impulse approximation (RPWIA)
calculations of quasi-elastic neutrino-nucleus cross sections. They agree at
the percent level, showing the reliability of the numerical techniques adopted
and providing benchmark RPWIA results.Comment: revised version,28 pages, 7 figures, accepted in Phys.Rev.
Universal decay law in charged-particle emission and exotic cluster radioactivity
A linear universal decay formula is presented starting from the microscopic
mechanism of the charged-particle emission. It relates the half-lives of
monopole radioactive decays with the -values of the outgoing particles as
well as the masses and charges of the nuclei involved in the decay. This
relation is found to be a generalization of the Geiger-Nuttall law in
radioactivity and explains well all known cluster decays. Predictions on the
most likely emissions of various clusters are presented.Comment: 2 figure
Huge Seebeck coefficients in non-aqueous electrolytes
The Seeebeck coefficients of the non-aqueous electrolytes tetrabutylammonium
nitrate, tetraoctylphosphonium bromide and tetradodecylammonium nitrate in
1-octanol, 1-dodecanol and ethylene-glycol are measured in a temperature range
from T=30 to T=45 C. The Seebeck coefficient is generally of the order of a few
hundreds of microvolts per Kelvin for aqueous solution of inorganic ions. Here
we report huge values of 7 mV/K at 0.1M concentration for tetrabutylammonium
nitrate in 1-dodecanol. These striking results open the question of
unexpectedly large kosmotrope or "structure making" effects of
tetraalkylammonium ions on the structure of alcohols.Comment: Submitted to J. Chem. Phy
Thermoelectric energy recovery at ionic-liquid/electrode interface
A Thermally Chargeable Capacitor containing a binary solution of
1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide (EMIMTFSI) in
acetonitrile is electrically charged by applying a tempera- ture gradient to
two ideally polarisable electrodes. The corresponding thermoelectric
coefficient is -1.7 mV/K for platinum foil electrodes and -0.3 mV/K for
nanoporous carbon electrodes. Stored electrical energy is extracted by
discharging the capacitor through a resistor. The measured capacitance of the
electrode/ionic- liquid interface is 5 micro F for each platinum electrode
while it becomes four orders of magnitude larger mF for a single
nanoporous carbon electrode. Reproducibility of the effect through repeated
charging-discharging cycles under a steady-state temperature gradient
demonstrates the robustness of the electrical charging pro- cess at the
liquid/electrode interface. The acceleration of the charging by convective
flows is also observed. This offers the possibility to convert waste-heat into
electric energy without exchanging electrons between ions and electrodes, in
contrast to what occurs in most thermogalvanic cells.Comment: 8 pages, 11 figure
- …