151 research outputs found
Intervention and the politics of information: US attention to foreign civil conflict
To improve scholarly understanding of the domestic drivers of third-party intervention in civil conflicts, this dissertation borrows a theoretical framework from the policy process literature. Specifically, I explain intervention through the lens of punctuated equilibrium theory (PET), a view which holds that the attention of government policymakers to most issues is persistently low but can be suddenly and dramatically mobilized. To apply this theory to the study of intervention, I collect data on US congressional speeches and US news coverage of foreign civil conflicts, 1946-1999. I then use the data to investigate the correlates of senior policymaker attention and its effects on intervention decisions. With respect to correlates, I find clear evidence that PET mechanisms motivate US congressional attention to civil conflict: I find that the distribution of change in attention to civil conflicts is leptokurtic, that civil conflicts are more likely to reach the attention of US senior policymakers if they have already reached the attention of actors lower in the policy process, and that congressional attention is subject to crowding effects. With respect to effects on policy, my findings are mixed. Congressional attention increases the likelihood of intervention when I look at all interventions but, when looking at only major interventions and controlling for prior US intervention, I find congressional attention has no statistically significant effect.Includes bibliographical references
Victoria\u27s Little Secret: Addressing Child Labor
This mini-case outlines a series of articles that ran in Bloomberg outlining the use of child slave labor in the fair trade cotton fields of Burkina Faso that had been used exclusively in Victoriaâs Secret products. Giving students and opportunity to develop strategies and tactics that respond to a real-world public relations issue, this case also lets students explore the CSR issues inherent in a firmâs supply chain. Although trying to do the âright thingâ Victoriaâs Secret got caught up in the certification dilemma that many firms face.
Part II of vide
Reduced Electron Model with Accurate Trapping Effects for Non-Linear Ion Accoustic Waves
Ion Accoustic Wave (IAW) dynamics are usually simulated assuming an isothermal Boltzmann ïŹuid response of the electrons. It has been shown that results from the Boltzmann model may signiïŹcantly diïŹer from cor- responding ones obtained considering the fully kinetic electron dynamics, in particular wrt. the non-linear instability mechanisms of ïŹnite amplitude IAWs [1]. For ZTe /Ti 10 (Z the ionization degree and Te/i the electron/ion temperature), the positive contribution from trapped electrons to the non- linear kinetic frequency shift of IAWs in fact dominates over the negative one from trapped ions [2]. But carrying out simulations over IAW time scales while evolving fully kinetic electrons is a multi-scale computation and thus numerically very costly. For a spatially one-dimensional system, we shall present the implementation of an improved reduced electron model, the so- called adiabatic model, based on the adiabatic invariance of the phase space action u dx, [(x, u) the electron (position, velocity) in the wave frame, the integral being taken over a transit/bounce period for passing/trapped parti- cles] [3]. Simulations obtained with this adiabatic model, which only need to resolve the slow IAW time scale, are successfully compared to fully kinetic ones, in particular for computing non-linear frequency shifts of IAWs over diïŹerent ZTe /Ti regimes resulting from both electron and ion trapping. [1] C. Riconda, A. Heron, D. Pesme, S. Hšller, V. T. Tikhonchuk, and F. Detering, Phys. Rev. Lett. 94, 055003 (2005). [2] R. Berger, S. Brunner, T. Chapmann, L. Divol, C. H. Still, and E. J. Valeo, Phys. Plasmas 20, 032107 (2013). [3] R. L. Dewar, Phys. Fluids 15, 712 (1972)
Detector Description and Performance for the First Coincidence Observations between LIGO and GEO
For 17 days in August and September 2002, the LIGO and GEO interferometer
gravitational wave detectors were operated in coincidence to produce their
first data for scientific analysis. Although the detectors were still far from
their design sensitivity levels, the data can be used to place better upper
limits on the flux of gravitational waves incident on the earth than previous
direct measurements. This paper describes the instruments and the data in some
detail, as a companion to analysis papers based on the first data.Comment: 41 pages, 9 figures 17 Sept 03: author list amended, minor editorial
change
Upper limits on the strength of periodic gravitational waves from PSR J1939+2134
The first science run of the LIGO and GEO gravitational wave detectors
presented the opportunity to test methods of searching for gravitational waves
from known pulsars. Here we present new direct upper limits on the strength of
waves from the pulsar PSR J1939+2134 using two independent analysis methods,
one in the frequency domain using frequentist statistics and one in the time
domain using Bayesian inference. Both methods show that the strain amplitude at
Earth from this pulsar is less than a few times .Comment: 7 pages, 1 figure, to appear in the Proceedings of the 5th Edoardo
Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July
200
Searching for gravitational waves from known pulsars
We present upper limits on the amplitude of gravitational waves from 28
isolated pulsars using data from the second science run of LIGO. The results
are also expressed as a constraint on the pulsars' equatorial ellipticities. We
discuss a new way of presenting such ellipticity upper limits that takes
account of the uncertainties of the pulsar moment of inertia. We also extend
our previous method to search for known pulsars in binary systems, of which
there are about 80 in the sensitive frequency range of LIGO and GEO 600.Comment: Accepted by CQG for the proceeding of GWDAW9, 7 pages, 2 figure
Search for Gravitational Waves from Primordial Black Hole Binary Coalescences in the Galactic Halo
We use data from the second science run of the LIGO gravitational-wave
detectors to search for the gravitational waves from primordial black hole
(PBH) binary coalescence with component masses in the range 0.2--.
The analysis requires a signal to be found in the data from both LIGO
observatories, according to a set of coincidence criteria. No inspiral signals
were found. Assuming a spherical halo with core radius 5 kpc extending to 50
kpc containing non-spinning black holes with masses in the range 0.2--, we place an observational upper limit on the rate of PBH coalescence
of 63 per year per Milky Way halo (MWH) with 90% confidence.Comment: 7 pages, 4 figures, to be submitted to Phys. Rev.
Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers
We study frequency dependent (FD) input-output schemes for signal-recycling
interferometers, the baseline design of Advanced LIGO and the current
configuration of GEO 600. Complementary to a recent proposal by Harms et al. to
use FD input squeezing and ordinary homodyne detection, we explore a scheme
which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are
sub-optimal among all possible input-output schemes, provide a global noise
suppression by the power squeeze factor, while being realizable by using
detuned Fabry-Perot cavities as input/output filters. At high frequencies, the
two schemes are shown to be equivalent, while at low frequencies our scheme
gives better performance than that of Harms et al., and is nearly fully
optimal. We then study the sensitivity improvement achievable by these schemes
in Advanced LIGO era (with 30-m filter cavities and current estimates of
filter-mirror losses and thermal noise), for neutron star binary inspirals, and
for narrowband GW sources such as low-mass X-ray binaries and known radio
pulsars. Optical losses are shown to be a major obstacle for the actual
implementation of these techniques in Advanced LIGO. On time scales of
third-generation interferometers, like EURO/LIGO-III (~2012), with
kilometer-scale filter cavities, a signal-recycling interferometer with the FD
readout scheme explored in this paper can have performances comparable to
existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi
Analysis of LIGO data for gravitational waves from binary neutron stars
We report on a search for gravitational waves from coalescing compact binary
systems in the Milky Way and the Magellanic Clouds. The analysis uses data
taken by two of the three LIGO interferometers during the first LIGO science
run and illustrates a method of setting upper limits on inspiral event rates
using interferometer data. The analysis pipeline is described with particular
attention to data selection and coincidence between the two interferometers. We
establish an observational upper limit of 1.7 \times 10^{2}M_\odot$.Comment: 17 pages, 9 figure
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