442 research outputs found
"Single-cycle" ionization effects in laser-matter interaction
We investigate numerically effects related to ``single-cycle'' ionization of
dense matter by an ultra-short laser pulse. The strongly non-adiabatic response
of electrons leads to generation of a megagauss steady magnetic field in
laser-solid interaction. By using two-beam interference, it is possible to
create periodic density structures able to trap light and to generate
relativistic ionization frontsComment: 12 pages, 6 figures, to be published in Laser and Particle Beam
Long-term management of chronic immune thrombocytopenic purpura in adults
Chronic immune thrombocytopenic purpura (ITP) is generally a more benign disease than previously thought. Currently it is recommended that only those patients with severe and/or symptomatic thrombocytopenia definitely require treatment. Additional factors, such as age, lifestyle, and uremia can also influence the hemorrhagic risk and should be carefully assessed before decision-making on the appropriate management of patients with less severe forms of ITP. The recent introduction of new classes of therapeutic agents such as rituximab and the thrombopoietic growth factors has had a major impact on the management of ITP. Updated treatment guidelines have recently been made available but they are based largely on expert opinion rather than on high-quality clinical trial evidence. This structured review is focused on the management of adults with chronic ITP, including the use of new classes of agents
Sierpi\'{n}ski curve Julia sets for quadratic rational maps
We investigate under which dynamical conditions the Julia set of a quadratic
rational map is a Sierpi\'{n}ski curveComment: 19 pages, 10 Figures, Substancial modification of previous version,
Accepted for publication in Ann. Acad. Sci. Fenn. Mat
Nonlinear resonance reflection from and transmission through a dense glassy system built up of oriented linear Frenkel chains: two-level models
A theoretical study of the resonance optical response of assemblies of
oriented short (as compared to an optical wavelength) linear Frenkel chains is
carried out using a two-level model. We show that both transmittivity and
reflectivity of the film may behave in a bistable fashion and analyze how the
effects found depend on the film thickness and on the inhomogeneous width of
the exciton optical transition.Comment: 26 pages, 9 figure
A method of detecting radio transients
Radio transients are sporadic signals and their detection requires that the
backends of radio telescopes be equipped with the appropriate hardware and
software to undertake this. Observational programs to detect transients can be
dedicated or they can piggy-back on observations made by other programs. It is
the single-dish single-transient (non-periodical) mode which is considered in
this paper. Because neither the width of a transient nor the time of its
arrival is known, a sequential analysis in the form of a cumulative sum (cusum)
algorithm is proposed here. Computer simulations and real observation data
processing are included to demonstrate the performance of the cusum. The use of
the Hough transform is here proposed for the purpose of non-coherent
de-dispersion. It is possible that the detected transients could be radio
frequency interferences (RFI) and a procedure is proposed here which can
distinguish between celestial signals and man-made RFI. This procedure is based
on an analysis of the statistical properties of the signals
UK Housing Market: Time Series Processes with Independent and Identically Distributed Residuals
The paper examines whether a univariate data generating process can be identified which explains the data by having residuals that are independent and identically distributed, as verified by the BDS test. The stationary first differenced natural log quarterly house price index is regressed, initially with a constant variance and then with a conditional variance. The only regression function that produces independent and identically distributed standardised residuals is a mean process based on a pure random walk format with Exponential GARCH in mean for the conditional variance. There is an indication of an asymmetric volatility feedback effect but higher frequency data is required to confirm this. There could be scope for forecasting the index but this is tempered by the reduction in the power of the BDS test if there is a non-linear conditional variance process
Cost-effectiveness of posaconazole versus fluconazole or itraconazole in the prevention of invasive fungal infections among high-risk neutropenic patients in Spain
Multidisciplinary approach to the treatment of invasive fungal infections in adult patients. Prophylaxis, empirical, preemptive or targeted therapy, which is the best in the different hosts?
Generation of ultra-short light pulses by a rapidly ionizing thin foil
A thin and dense plasma layer is created when a sufficiently strong laser
pulse impinges on a solid target. The nonlinearity introduced by the
time-dependent electron density leads to the generation of harmonics. The pulse
duration of the harmonic radiation is related to the risetime of the electron
density and thus can be affected by the shape of the incident pulse and its
peak field strength. Results are presented from numerical
particle-in-cell-simulations of an intense laser pulse interacting with a thin
foil target. An analytical model which shows how the harmonics are created is
introduced. The proposed scheme might be a promising way towards the generation
of attosecond pulses.
PACS number(s): 52.40.Nk, 52.50.Jm, 52.65.RrComment: Second Revised Version, 13 pages (REVTeX), 3 figures in ps-format,
submitted for publication to Physical Review E, WWW:
http://www.physik.tu-darmstadt.de/tqe
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