470 research outputs found
Resolutions of National Parliaments in EU affairs: The Crucial Role of Issue Entrepreneurs
This paper analyses the activity of national parliaments in EU affairs in the form of resolutions. Covering the time period from the late 1990s until the present, the paper examines parliamentary motions and resolutions on EU affairs in six West European countries: Austria, France, Germany, Ireland, Spain and the United Kingdom. Differences in the frequency of resolutions between countries as well as between party groups with regard to motions are examined. Moreover, all motions and resolutions were hand coded to establish the valence of the texts, i.e. the extent to which they are supportive or critical of the government. Formal scrutiny powers in EU affairs do not seem to have an impact on the frequency with which resolutions are issued. The activity of national parliaments in the form of resolutions is mostly driven by âissue entrepreneursâ, parties which are critical of the European Union and which see it as a salient issue. Motions initiated by issue entrepreneurs are very critical of the governmentâs policy and of the European Union. Moreover, Motions by issue entrepreneurs tend to have a longer preamble and a shorter operational part compared to motions by mainstream opposition and government parties. The reason for this is most likely that issue entrepreneurs use motions to express their opinion on the EU in general instead of formulating a targeted criticism of the governmentâs policy. The parliamentary activity brought about by issue entrepreneurs might thus not lead to an increase in actual democratic control and accountability in EU affairs
Out-Of-Focus Holography at the Green Bank Telescope
We describe phase-retrieval holography measurements of the 100-m diameter
Green Bank Telescope using astronomical sources and an astronomical receiver
operating at a wavelength of 7 mm. We use the technique with parameterization
of the aperture in terms of Zernike polynomials and employing a large defocus,
as described by Nikolic, Hills & Richer (2006). Individual measurements take
around 25 minutes and from the resulting beam maps (which have peak signal to
noise ratios of 200:1) we show that it is possible to produce low-resolution
maps of the wavefront errors with accuracy around a hundredth of a wavelength.
Using such measurements over a wide range of elevations, we have calculated a
model for the wavefront-errors due to the uncompensated gravitational
deformation of the telescope. This model produces a significant improvement at
low elevations, where these errors are expected to be the largest; after
applying the model, the aperture efficiency is largely independent of
elevation. We have also demonstrated that the technique can be used to measure
and largely correct for thermal deformations of the antenna, which often exceed
the uncompensated gravitational deformations during daytime observing.
We conclude that the aberrations induced by gravity and thermal effects are
large-scale and the technique used here is particularly suitable for measuring
such deformations in large millimetre wave radio telescopes.Comment: 10 pages, 7 figures (accepted by Astronomy & Astrophysics
Modification of Projected Velocity Power Spectra by Density Inhomogeneities in Compressible Supersonic Turbulence
(Modified) The scaling of velocity fluctuation, dv, as a function of spatial
scale L in molecular clouds can be measured from size-linewidth relations,
principal component analysis, or line centroid variation. Differing values of
the power law index of the scaling relation dv = L^(g3D) in 3D are given by
these different methods: the first two give g3D=0.5, while line centroid
analysis gives g3D=0. This discrepancy has previously not been fully
appreciated, as the variation of projected velocity line centroid fluctuations
(dv_{lc} = L^(g2D)) is indeed described, in 2D, by g2D=0.5. However, if
projection smoothing is accounted for, this implies that g3D=0. We suggest that
a resolution of this discrepancy can be achieved by accounting for the effect
of density inhomogeneity on the observed g2D obtained from velocity line
centroid analysis. Numerical simulations of compressible turbulence are used to
show that the effect of density inhomogeneity statistically reverses the effect
of projection smoothing in the case of driven turbulence so that velocity line
centroid analysis does indeed predict that g2D=g3D=0.5. Using our numerical
results we can restore consistency between line centroid analysis, principal
component analysis and size-linewidth relations, and we derive g3D=0.5,
corresponding to shock-dominated (Burgers) turbulence. We find that this
consistency requires that molecular clouds are continually driven on large
scales or are only recently formed.Comment: 28 pages total, 20 figures, accepted for publication in Ap
A modified parallel tree code for N-body simulation of the Large Scale Structure of the Universe
N-body codes to perform simulations of the origin and evolution of the Large
Scale Structure of the Universe have improved significantly over the past
decade both in terms of the resolution achieved and of reduction of the CPU
time. However, state-of-the-art N-body codes hardly allow one to deal with
particle numbers larger than a few 10^7, even on the largest parallel systems.
In order to allow simulations with larger resolution, we have first
re-considered the grouping strategy as described in Barnes (1990) (hereafter
B90) and applied it with some modifications to our WDSH-PT (Work and Data
SHaring - Parallel Tree) code. In the first part of this paper we will give a
short description of the code adopting the Barnes and Hut algorithm
\cite{barh86} (hereafter BH), and in particular of the memory and work
distribution strategy applied to describe the {\it data distribution} on a
CC-NUMA machine like the CRAY-T3E system. In the second part of the paper we
describe the modification to the Barnes grouping strategy we have devised to
improve the performance of the WDSH-PT code. We will use the property that
nearby particles have similar interaction list. This idea has been checked in
B90, where an interaction list is builded which applies everywhere within a
cell C_{group} containing a little number of particles N_{crit}. B90 reuses
this interaction list for each particle in the cell in turn.
We will assume each particle p to have the same interaction list.
Thus it has been possible to reduce the CPU time increasing the performances.
This leads us to run simulations with a large number of particles (N ~
10^7/10^9) in non-prohibitive times.Comment: 13 pages and 7 Figure
On the use of fractional Brownian motion simulations to determine the 3D statistical properties of interstellar gas
Based on fractional Brownian motion (fBm) simulations of 3D gas density and
velocity fields, we present a study of the statistical properties of
spectro-imagery observations (channel maps, integrated emission, and line
centroid velocity) in the case of an optically thin medium at various
temperatures. The power spectral index gamma_W of the integrated emission is
identified with that of the 3D density field (gamma_n) provided the medium's
depth is at least of the order of the largest transverse scale in the image,
and the power spectrum of the centroid velocity map is found to have the same
index gamma_C as that of the velocity field (gamma_v). Further tests with
non-fBm density and velocity fields show that this last result holds, and is
not modified either by the effects of density-velocity correlations. A
comparison is made with the theoretical predictions of Lazarian & Pogosyan
(2000).Comment: 28 pages, 14 figures, accepted for publication in ApJ. For preprint
with higher-resolution figures, see
http://www.cita.utoronto.ca/~mamd/miville_fbm2003.pd
Habitable Zones and UV Habitable Zones around Host Stars
Ultraviolet radiation is a double-edged sword to life. If it is too strong,
the terrestrial biological systems will be damaged. And if it is too weak, the
synthesis of many biochemical compounds can not go along. We try to obtain the
continuous ultraviolet habitable zones, and compare the ultraviolet habitable
zones with the habitable zones of host stars. Using the boundary ultraviolet
radiation of ultraviolet habitable zone, we calculate the ultraviolet habitable
zones of host stars with masses from 0.08 to 4.00 \mo. For the host stars with
effective temperatures lower than 4,600 K, the ultraviolet habitable zones are
closer than the habitable zones. For the host stars with effective temperatures
higher than 7,137 K, the ultraviolet habitable zones are farther than the
habitable zones. For hot subdwarf as a host star, the distance of the
ultraviolet habitable zone is about ten times more than that of the habitable
zone, which is not suitable for life existence.Comment: 5 pages, 3 figure
Utilising Nonlinear Air Damping as a Soft Mechanical Stopper for MEMS Vibration Energy Harvesting
This paper reports on the theory and experimental verification of utilising air damping as a soft stopper mechanism for piezoelectric vibration energy harvesting to enhance shock resistance. Experiments to characterise device responsiveness under various vibration conditions were performed at different air pressure levels, and a dimensionless model was constructed with nonlinear damping terms included to model PVEH response. The relationship between the quadratic damping coefficient ζ n and air pressure is empirically established, and an optimal pressure level is calculated to trade off harvestable energy and device robustness for specific environmental conditions
Star Clusters
This review concentrates almost entirely on globular star clusters. It
emphasises the increasing realisation that few of the traditional problems of
star cluster astronomy can be studied in isolation: the influence of the Galaxy
affects dynamical evolution deep in the core, and the spectrum of stellar
masses; in turn the evolution of the core determines the highest stellar
densities, and the rate of encounters. In this way external tidal effects
indirectly influence the formation and evolution of blue stragglers, binary
pulsars, X-ray sources, etc. More controversially, the stellar density appears
to influence the relative distribution of normal stars. In the opposite sense,
the evolution of individual stars governs much of the early dynamics of a
globular cluster, and the existence of large numbers of primordial binary stars
has changed important details of our picture of the dynamical evolution. New
computational tools which will become available in the next few years will help
dynamical theorists to address these questions.Comment: 10 pages, 3 figures, Te
A thin layer of phytoplankton observed in the Philippine Sea with a synthetic moored array of autonomous gliders
Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 114 (2009): C10020, doi:10.1029/2009JC005317.A synthetic moored array composed of five buoyancy-propelled autonomous underwater gliders was used to characterize mesoscale variability and phytoplankton distribution in a 100 km à 100 km domain in the Philippine Sea east of Luzon Strait for 10 days in May 2004. The study area, located east of the Kuroshio near the subtropical front, is dominated by strong internal tides, by energetic westward-propagating mesoscale eddies with azimuthal velocities exceeding 50 cm/s, and by a deep (130 m) maximum in chlorophyll fluorescence. Each glider in the array was instructed to maintain geographic position while repeatedly profiling to 200-m depth. Good station-keeping performance enabled the resulting series of vertical profiles to be interpreted in the same manner as a physically moored chain of instruments. Although organized primarily as a demonstration of glider capabilities, this field exercise provides a unique data set for examining biological-physical interactions in the open ocean. Here we report on the evolution of a thin layer of phytoplankton observed near the deep chlorophyll maximum. Coincident observations of fine structure in temperature and salinity suggest that the thinning process of this layer was driven primarily by physical forcing, most probably vertical shear associated with energetic diurnal internal waves, as opposed to a biological mechanism, such as convergent swimming, grazing, or spatial variation in growth rate.The Office of Naval Research provided
support for fieldwork and analysis through grants N-00014-00-1-0256 and
N-00014-05-1-0367
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