4,796 research outputs found
Estimation of the gravitational wave polarizations from a non template search
Gravitational wave astronomy is just beginning, after the recent success of
the four direct detections of binary black hole (BBH) mergers, the first
observation from a binary neutron star inspiral and with the expectation of
many more events to come. Given the possibility to detect waves from not
perfectly modeled astrophysical processes, it is fundamental to be ready to
calculate the polarization waveforms in the case of searches using non-template
algorithms. In such case, the waveform polarizations are the only quantities
that contain direct information about the generating process. We present the
performance of a new valuable tool to estimate the inverse solution of
gravitational wave transient signals, starting from the analysis of the signal
properties of a non-template algorithm that is open to a wider class of
gravitational signals not covered by template algorithms. We highlight the
contributions to the wave polarization associated with the detector response,
the sky localization and the polarization angle of the source. In this paper we
present the performances of such method and its implications by using two main
classes of transient signals, resembling the limiting case for most simple and
complicated morphologies. Performances are encouraging, for the tested
waveforms: the correlation between the original and the reconstructed waveforms
spans from better than 80% for simple morphologies to better than 50% for
complicated ones. For a not-template search this results can be considered
satisfactory to reconstruct the astrophysical progenitor
Non-Standard Time Reversal for Particle Multiplets and the Spin-Flavor Structure of Hadrons
We show that a system of quarks interacting with chiral fields provides a
physical representation of a ``non-standard'' time reversal for particle
multiplets proposed by Weinberg. As an application, we argue that, if the
internal structure of hadrons is described by a chiral lagrangian, the
so-called time-reversal-odd quark distribution functions might not be forbidden
by time-reversal invariance.Comment: 2 pages, proceedings of "The Spin Structure of the Proton", ECT -
Trento, July 2001. Eds. S Bass, A De Roeck and A Deshpand
Losing the Best and the Brightest: The Disappearing Wage Premium for H-1B Visa Recipients
The pressure for immigration reform in the technology industry revolves heavily around the use of the H-1B visa, which allows companies to temporarily hire highly skilled workers. This Note provides an empirical analysis of the historical wages of H-1B workers and domestic workers in the technology industry to determine whether H-1B workers earn more or less than domestic workers in the same industry. In the technology industry, H-1B workers\u27 wage premium has eroded in recent years relative to domestic workers, leading to stagnant wages that may deter the best and the brightest from choosing to enter into the H-1B process. To enhance the H-1B program, Congress should adopt immigration reform that sets aside a certain number of visas specifically for the technology industry. Additionally, this reform should mimic Canada\u27s hybrid system by adopting a points-based system that gives preference to immigrants with arranged employment opportunities. Finally, as seen in the success of Canada\u27s Provincial Nominee Program, the reform should allot these visas to each state to determine the most effective and efficient allocation of H-1B visas in the state and allow immigrants to apply directly to each state
Inside Dropbox: Understanding Personal Cloud Storage Services
Personal cloud storage services are gaining popularity. With a rush of providers to enter the market and an increasing of- fer of cheap storage space, it is to be expected that cloud storage will soon generate a high amount of Internet traffic. Very little is known about the architecture and the perfor- mance of such systems, and the workload they have to face. This understanding is essential for designing efficient cloud storage systems and predicting their impact on the network. This paper presents a characterization of Dropbox, the leading solution in personal cloud storage in our datasets. By means of passive measurements, we analyze data from four vantage points in Europe, collected during 42 consecu- tive days. Our contributions are threefold: Firstly, we are the first to study Dropbox, which we show to be the most widely-used cloud storage system, already accounting for a volume equivalent to around one third of the YouTube traffic at campus networks on some days. Secondly, we characterize the workload typical users in different environments gener- ate to the system, highlighting how this reflects on network traffic. Lastly, our results show possible performance bot- tlenecks caused by both the current system architecture and the storage protocol. This is exacerbated for users connected far from control and storage data-center
Dynamics of Phase Transitions in Asymmetric Nuclear Matter
We present several possibilities offered by the reaction dynamics of
dissipative heavy ion collisions to study in detail the symmetry term of the
nuclear equation of state, . In particular we discuss isospin effects on
the nuclear liquid-gas phase transition, {\it Isospin Distillation}, and on
collective flows. We stress the importance of a microscopic relativistic
structure of the effective interaction in the isovector channel. The
possibility of an {\it early} transition to deconfined matter in high isospin
density regions is also suggested. We finally select {\it Eleven} observables,
in different beam energy regions, that appear rather sensitive to the isovector
part of the nuclear , in particular in more exclusive experiments.Comment: 8 pages, 7 figures, ISPUN02 Conference, Halong-Vietnam, Nov.20-25
2002, to appear in Nucl.Phys.A. Elsevier Proceedings Styl
The impact of significant input of fine sediment on benthic fauna at tributary junctions: a case study of the Bermejo-Paraguay River confluence, Argentina
This study examines the morphological features, suspended sediment inputs and hydraulic conditions within a large river in association with ecological patterns before and after a tributary confluence. In order to examine these effects, the macroinvertebrate distributions from three reaches of the Paraguay and Bermejo Rivers (Paraguay-Argentina) are investigated. The Bermejo River is a tributary that supplies significant quantities of fine sediment to the Paraguay River, primarily in suspension. Two reaches were examined on the Paraguay River, upstream and downstream of the Bermejo River junction, with the third study reach located on the Bermejo River, upstream of the confluence with the Paraguay River. The results provide clear evidence that a significantly increased loading of fine sediment at a river confluence has effects on the distribution and potential movement of benthic invertebrates in the lotic environment by representing physical barriers at affected sites. These effects may be important at both local and regional scales, and such increases in suspended sediment (especially associated with anthropogenic change) may thus pose a major threat to ecosystem integrity that has been historically underestimated
Testing Deconfinement at High Isospin Density
We study the transition from hadronic matter to a mixed phase of quarks and
hadrons at high baryon and isospin densities reached in heavy ion collisions.
We focus our attention on the role played by the nucleon symmetry energy at
high density.In this respect the inclusion of a scalar isovector meson, the
\delta-coupling, in the Hadron Lagrangian appears rather important. We study in
detail the formation of a drop of quark matter in the mixed phase, and we
discuss the effects on the quark drop nucleation probability of the finite size
and finite time duration of the high density region. We find that, if the
parameters of quark models are fixed so that the existence of quark stars is
allowed, then the density at which a mixed phase starts forming drops
dramatically in the range Z/A \sim 0.3--0.4. This opens the possibility to
verify the Witten-Bodmer hypothesis on absolute stability of quark matter using
ground-based experiments in which neutron-rich nuclei are employed. These
experiments can also provide rather stringent constraints on the Equation of
State (EoS) to be used for describing the pre-Supernova gravitational collapse.
Consistent simulations of neutron rich heavy ion collisions are performed in
order to show that even at relatively low energies, in the few AGeV range, the
system can enter such unstable mixed phase. Some precursor observables are
suggested, in particular a ``neutron trapping'' effect.Comment: 32 pages, 14 figures, elsart late
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