11,361 research outputs found
Poverty Measures and Anti-Poverty Policy
[Excerpt] Amartya Sen has made fundamental contributions to the study of distributional aspects of economic growth and decline. Among his pathbreaking works are his lectures on the economics of inequality (Sen, 1973), his article on the axiomatics of poverty measurement (Sen, 1976), and his book on anti-poverty policy in the context of famines (Sen, 1981).
This paper is concerned with one of these areas, namely, the measurement of poverty and the implications for anti-poverty policy. In the 1960\u27s and 1970\u27s those who were working in the poverty field held a number of somewhat incompletely articulated views as to the extent of poverty in an economy. One was the judgment that a country is poorer the larger is the number or fraction of its people below an agreed-upon poverty standard. Second, the severity of poverty depends on how poor the poor are. As formulated then, the larger is the average income shortfall among the poor, the more severe is poverty. Thirdly, it was recognized that some of the poor are poorer than others, and the extent of poverty should also depend on the distribution of income among the poor
Transient photon production in a QGP
We discuss the shortcomings of a formula that has been used in the literature
to compute the number of photons emitted by a hot or dense system during a
finite time, and show that the transient effects it predicts for the photon
rate are unphysical.Comment: 4 pages, to appear in the proceedings of Hadron Physics - RANP 2004,
Angra dos Reis, Brazi
Single-inclusive production of large-pT charged particles in hadronic collisions at TeV energies and perturbative QCD predictions
The single inclusive spectrum of charged particles with transverse momenta
pT=3-150 GeV/c measured at midrapidity by the CDF experiment in
proton-antiproton (p-pbar) collisions at sqrt(s)=1.96 TeV is compared to
next-to-leading order (NLO) perturbative QCD calculations using the most recent
parametrizations of the parton distributions and parton-to-hadron fragmentation
functions. Above pT~20 GeV/c, there is a very sizeable disagreement of the
Tevatron data compared to the NLO predictions and to xT-scaling expectations,
suggesting a problem in the experimental data. We also present the predictions
for the pT-differential charged hadron spectra and the associated theoretical
uncertainties for proton-proton (p-p) collisions at LHC energies
(sqrt(s)=0.9-14 TeV). Two procedures to estimate the charged hadron spectra at
LHC heavy-ion collision energies (sqrt(s)=2.76,5.5 TeV) from p-p measurements
are suggested.Comment: 23 pages, 9 figures. A few text additions. Accepted for publication
in JHE
870 micron Imaging of a Transitional Disk in Upper Scorpius: Holdover from the Era of Giant Planet Formation?
We present 880 micron images of the transition disk around the star [PZ99]
J160421.7-213028, a solar-mass star in the nearby Upper Scorpius association.
With a resolution down to 0.34 arcsec, we resolve the inner hole in this disk,
and via model fitting to the visibilities and spectral energy distribution we
determine both the structure of the outer region and the presence of sparse
dust within the cavity. The disk contains about 0.1 Jupiter masses of
mm-emitting grains, with an inner disk edge of about 70 AU. The inner cavity
contains a small amount of dust with a depleted surface density in a region
extending from about 20-70 AU. Taking into account prior observations
indicating little to no stellar accretion, the lack of a binary companion, and
the presence of dust near 0.1 AU, we determine that the most likely mechanism
for the formation of this inner hole is the presence of one or more giant
planets.Comment: 12 pages, 7 figures. To appear in the Astrophysical Journa
Three-dimensional fluid motion in Faraday waves: creation of vorticity and generation of two-dimensional turbulence
We study the generation of 2D turbulence in Faraday waves by investigating
the creation of spatially periodic vortices in this system. Measurements which
couple a diffusing light imaging technique and particle tracking algorithms
allow the simultaneous observation of the three-dimensional fluid motion and of
the temporal changes in the wave field topography. Quasi-standing waves are
found to coexist with a spatially extended fluid transport. More specifically,
the destruction of regular patterns of oscillons coincides with the emergence
of a complex fluid motion whose statistics are similar to that of
two-dimensional turbulence. We reveal that a lattice of oscillons generates
vorticity at the oscillon scale in the horizontal flow. The interaction of
these vortices explain how 2D turbulence is fueled by almost standing waves.
Remarkably, the curvature of Lagrangian trajectories reveals a "footprint" of
the forcing scale vortices in fully developed turbulence. 2D Navier-Stokes
turbulence should be considered a source of disorder in Faraday waves. These
findings also provide a new paradigm for vorticity creation in 2D flows
Cosmic Neutron Star Merger Rate and Gravitational Waves constrained by the R Process Nucleosynthesis
The cosmic evolution of the neutron star merger (NSM) rate can be deduced
from the observed cosmic star formation rate. This allows to estimate the rate
expected in the horizon of the gravitational wave detectors advanced Virgo and
ad LIGO and to compare those rates with independent predictions. In this
context, the rapid neutron capture process, or r process, can be used as a
constraint assuming NSM is the main astrophysical site for this nucleosynthetic
process. We compute the early cosmic evolution of a typical r process element,
Europium. Eu yields from NSM are taken from recent nucleosynthesis
calculations. The same approach allows to compute the cosmic rate of Core
Collapse SuperNovae (CCSN) and the associated evolution of Eu. We find that the
bulk of Eu observations at high iron abundance can be rather well fitted by
either CCSN or NSM scenarios. However, at lower metallicity, the early Eu
cosmic evolution favors NSM as the main astrophysical site for the r process. A
comparison between our calculations and spectroscopic observations at very low
metallicities allows to constrain the coalescence timescale in the NSM scenario
to about 0.1 to 0.2 Gyr. These values are in agreement with the coalescence
timescales of some observed binary pulsars. Finally, the cosmic evolution of Eu
is used to put constraints on the NSM rate, the merger rate in the horizon of
the gravitational wave detectors advanced Virgo/ad LIGO, as well as the
expected rate of electromagnetic counterparts to mergers (kilonovae) in large
near-infrared surveys.Comment: accepted in MNRAS, 19 page
The existence of a critical length scale in regularised friction
We study a regularisation of Coulomb's friction law on the propagation of
local slip at an interface between a deformable and a rigid solid. This
regularisation, which was proposed based on experimental observations, smooths
the effect of a sudden jump in the contact pressure over a characteristic
length scale. We apply it in numerical simulations in order to analyse its
influence on the behaviour of local slip. We first show that mesh convergence
in dynamic simulations is achieved without any numerical damping in the bulk
and draw a convergence map with respect to the characteristic length of the
friction regularisation. By varying this length scale on the example of a given
slip event, we observe that there is a critical length below which the friction
regularisation does not affect anymore the propagation of the interface
rupture. A spectral analysis of the regularisation on a periodic variation of
Coulomb's friction is conducted to confirm the existence of this critical
length. The results indicate that if the characteristic length of the friction
regularisation is smaller than the critical length, a slip event behaves as if
it was governed by Coulomb's law. We therefore propose that there is a domain
of influence of the friction regularisation depending on its characteristic
length and on the frequency content of the local slip event. A byproduct of the
analysis is related to the existence of a physical length scale characterising
a given frictional interface. We establish that the experimental determination
of this interface property may be achieved by experimentally monitoring slip
pulses whose frequency content is rich enough.Comment: 21 pages, 7 figure
Synthetic considerations in the self-assembly of coordination polymers of pyridine-functionalised hybrid Mn-Anderson polyoxometalates
The incorporation of polyoxometalates (POMs) as structural units into ordered porous constructs such as metal-organic frameworks (MOFs) is desirable for a range of applications where intrinsic properties inherited from both the MOF and POM are utilised, including catalysis and magnetic data storage. The controlled self-assembly of targeted MOF topologies containing POM units is hampered by the wide range of oxo and hydroxo units on the peripheries of POMs that can act as coordinating groups towards linking metal cations leading to a diverse range of structures, but incorporation of organic donor units into hybrid POMs offers an alternative methodology to programmably synthesise POM/MOF conjugates. Herein, we report six coordination polymers obtained serendipitously wherein Zn2+ and Cu2+ link pyridine-appended Mn-Anderson clusters into two- and three-dimensional network solids with complex connectivities and topologies. Careful inspection of their solid-state structures has allowed us to identify common structure-directing features across these coordination polymers, including a square motif where two Zn2+ cations bridge two POMs. By correlating certain structural motifs with synthetic conditions we have formulated a series of design considerations for the self-assembly of coordination polymers of hybrid POMs, encompassing the selection of reaction conditions, co-ligands and linking metal cations. We anticipate that these synthetic guidelines will inform the future assembly of hybrid POMs into functional MOF materials
An efficient multi-core implementation of a novel HSS-structured multifrontal solver using randomized sampling
We present a sparse linear system solver that is based on a multifrontal
variant of Gaussian elimination, and exploits low-rank approximation of the
resulting dense frontal matrices. We use hierarchically semiseparable (HSS)
matrices, which have low-rank off-diagonal blocks, to approximate the frontal
matrices. For HSS matrix construction, a randomized sampling algorithm is used
together with interpolative decompositions. The combination of the randomized
compression with a fast ULV HSS factorization leads to a solver with lower
computational complexity than the standard multifrontal method for many
applications, resulting in speedups up to 7 fold for problems in our test
suite. The implementation targets many-core systems by using task parallelism
with dynamic runtime scheduling. Numerical experiments show performance
improvements over state-of-the-art sparse direct solvers. The implementation
achieves high performance and good scalability on a range of modern shared
memory parallel systems, including the Intel Xeon Phi (MIC). The code is part
of a software package called STRUMPACK -- STRUctured Matrices PACKage, which
also has a distributed memory component for dense rank-structured matrices
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