1,205 research outputs found
Sustainability for all? a North-South-East-West model
This paper examines whether it is possible for all countries to simultaneously achieve efficient and
sustainable allocations of resources even if they do not cooperate in a world with inter-generational
and intra-generational externalities. Using a simple model with two governments one for the north-
and one for the south- we show that one hemisphere cannot always achieve efficiency and
sustainability independently of the other, that is, whatever allocation is chosen by the other
hemisphere. However, the north and the south can simultaneously achieve efficiency and
sustainability if each government aims separately at these two goals in its own hemisphere
X-ray Raman compression via two-stream instability in dense plasmas
A Raman compression scheme suitable for x-rays, where the Langmuir wave is
created by an intense beam rather than the pondermotive potential between the
seed and pump pulses, is proposed.
The required intensity of the seed and pump pulses enabling the compression
could be mitigated by more than a factor of 100, compared to conventionally
available other Raman compression schemes. The relevant wavelength of x-rays
ranges from 1 to 10 nm
Application of novel techniques for interferogram analysis to laser-plasma femtosecond probing
Recently, two novel techniques for the extraction of the phase-shift map
(Tomassini {\it et.~al.}, Applied Optics {\bf 40} 35 (2001)) and the electronic
density map estimation (Tomassini P. and Giulietti A., Optics Communication
{\bf 199}, pp 143-148 (2001)) have been proposed. In this paper we apply both
methods to a sample laser-plasma interferogram obtained with femtoseconds probe
pulse, in an experimental setup devoted to laser particle acceleration studies.Comment: Submitted to Laser and Particle Beam
Shocks in unmagnetized plasma with a shear flow: Stability and magnetic field generation
A pair of curved shocks in a collisionless plasma is examined with a
two-dimensional particle-in-cell (PIC) simulation. The shocks are created by
the collision of two electron-ion clouds at a speed that exceeds everywhere the
threshold speed for shock formation. A variation of the collision speed along
the initially planar collision boundary, which is comparable to the ion
acoustic speed, yields a curvature of the shock that increases with time. The
spatially varying Mach number of the shocks results in a variation of the
downstream density in the direction along the shock boundary. This variation is
eventually equilibrated by the thermal diffusion of ions. The pair of shocks is
stable for tens of inverse ion plasma frequencies. The angle between the mean
flow velocity vector of the inflowing upstream plasma and the shock's
electrostatic field increases steadily during this time. The disalignment of
both vectors gives rise to a rotational electron flow, which yields the growth
of magnetic field patches that are coherent over tens of electron skin depths.Comment: 10 pages, 10 figures accepted for publication in Physics of Plasma
Introducing CatOracle: Corpus-based concatenative improvisation with the Audio Oracle algorithm
CATORACLE responds to the need to join high-level control of audio timbre with the organization of musical form in time. It is inspired by two powerful existing tools: CataRT for corpus-based concatenative synthesis based on the MUBU for MAX library, and PYORACLE for computer improvisation, combining for the first time audio descriptor analysis and learning and generation of musical structures. Harnessing a user-defined list of audio fea- tures, live or prerecorded audio is analyzed to construct an “Audio Oracle” as a basis for improvisation. CatOracle also extends features of classic concatenative synthesis to include live interactive audio mosaicking and score-based transcription using the BACH library for MAX. The project suggests applications not only to live performance of written and improvised electroacoustic music, but also computer-assisted composition and musical analysis
Dynamic Control of Laser Produced Proton Beams
The emission characteristics of intense laser driven protons are controlled
using ultra-strong (of the order of 10^9 V/m) electrostatic fields varying on a
few ps timescale. The field structures are achieved by exploiting the high
potential of the target (reaching multi-MV during the laser interaction).
Suitably shaped targets result in a reduction in the proton beam divergence,
and hence an increase in proton flux while preserving the high beam quality.
The peak focusing power and its temporal variation are shown to depend on the
target characteristics, allowing for the collimation of the inherently highly
divergent beam and the design of achromatic electrostatic lenses.Comment: 9 Pages, 5 figure
Spatial distribution of emission in Unidentified Infrared Bands from Midcourse Space Experiment Survey
Recently the Midcourse Space Experiment (MSX) has surveyed the Galactic plane
in mainly four infrared bands between 6 and 25 micron. Two of these bands cover
several Unidentified Infrared emission Bands (UIBs). With the aim of extracting
the spatial distribution of the UIB emission on a large scale, a scheme has
been developed to model the MSX data with emission in the UIBs alongwith the
underlying thermal continuum from the interstellar dust. In order to test this
scheme, a sample of five Galactic compact H II regions (Sh-61, Sh-138, Sh-152,
Sh-156, Sh-186; Zavagno & Ducci 2001) for which imaging study in some
individual UIBs is available from ISOCAM measurements, has been studied. The
results of this comparative study on small angular scale are as follows : (i)
the morphological details extracted from our scheme agree very well with those
from the superior ISOCAM measurements; (ii) the integrated strength of UIBs
extracted from the MSX database correlates extremely well with the sum of the
strengths of individual UIBs measured from ISOCAM. This tight correlation is
very encouraging and promises the potential of MSX database for study of large
scale spatial distribution of UIB emission (and the carriers of UIBs) in the
entire Galactic plane.Comment: to be published in Astronomy & Astrophysics; (9 pages including 2
tables & 11 figures
Characterisation of deuterium spectra from laser driven multi-species sources by employing differentially filtered image plate detectors in Thomson spectrometers
A novel method for characterising the full spectrum of deuteron ions emitted
by laser driven multi-species ion sources is discussed. The procedure is based
on using differential filtering over the detector of a Thompson parabola ion
spectrometer, which enables discrimination of deuterium ions from heavier ion
species with the same charge-to-mass ratio (such as C6+, O8+, etc.). Commonly
used Fuji Image plates were used as detectors in the spectrometer, whose
absolute response to deuterium ions over a wide range of energies was
calibrated by using slotted CR-39 nuclear track detectors. A typical deuterium
ion spectrum diagnosed in a recent experimental campaign is presented.Comment: 7 pages, 7 figure
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