26,074 research outputs found
Poverty in Metropolitan Areas of the U.S.: Causes and Consequences
This paper re-examines the determinants of poverty using a pooled data set of 331 U.S. Metropolitan Statistical Areas (MSAs) measured over four decennial censuses from 1970 to 2000. Our principal conclusions are that the determinants of poverty that we have identified are relatively stable predictors of poverty levels, but that results for first differences are sensitive to the time period of estimation. We also examine whether poverty as an initial condition has an effect on future growth in incomes and/or employment, and our tentative conclusion is that a higher level of existing poverty is indeed a detriment to future growth.
The intrinsic strangeness and charm of the nucleon using improved staggered fermions
We calculate the intrinsic strangeness of the nucleon, - ,
using the MILC library of improved staggered gauge configurations using the
Asqtad and HISQ actions. Additionally, we present a preliminary calculation of
the intrinsic charm of the nucleon using the HISQ action with dynamical charm.
The calculation is done with a method which incorporates features of both
commonly-used methods, the direct evaluation of the three-point function and
the application of the Feynman- Hellman theorem. We present an improvement on
this method that further reduces the statistical error, and check the result
from this hybrid method against the other two methods and find that they are
consistent. The values for and found here, together with
perturbative results for heavy quarks, show that dark matter scattering through
Higgs-like exchange receives roughly equal contributions from all heavy quark
flavors.Comment: 17 pages, 14 figure
Thin Films of 3He -- Implications on the Identification of 3 He -A
Recently the identification of 3He-A with the axial state has been
questioned. It is suggested that the A-phase can actually be in the axiplanar
state. We point out in the present paper that experiments in a film geometry
may be useful to distinguish the above two possibilities. In particular a
second order phase transition between an axial and an axiplanar state would
occur as a function of thickness or temperature.Comment: 3 pages, no figures latex- revtex aps accepted by J. of Low
Temperature Physic
Development of the Magnetic Excitations of Charge-Stripe Ordered La(2-x)Sr(x)NiO(4) on Doping Towards Checkerboard Charge Order
The magnetic excitation spectrums of charge stripe ordered La(2-x)Sr(x)NiO(4)
x = 0.45 and x = 0.4 were studied by inelastic neutron scattering. We found the
magnetic excitation spectrum of x = 0.45 from the ordered Ni^2+ S = 1 spins to
match that of checkerboard charge ordered La(1.5)Sr(0.5)NiO(4). The distinctive
asymmetry in the magnetic excitations above 40 meV was observed for both doping
levels, but an additional ferromagnetic mode was observed in x = 0.45 and not
in the x = 0.4. We discuss the origin of crossover in the excitation spectrum
between x = 0.45 and x = 0.4 with respect to discommensurations in the charge
stripe structure.Comment: 4 Figures. To be appear in the J. Kor. Phys. Soc. as a proceedings
paper from the ICM 2012 conferenc
More pieces of the puzzle: Chemistry and substructures in the Galactic thick disk
We present a study of the chemical abundances of Solar neighbourhood stars
associated to dynamical structures in the Milky Way's (thick) disk. These stars
were identified as overdensity in the eccentricity range 0.3< ecc < 0.5 in the
Copenhagen-Geneva Survey by Helmi et al. (2006). We find that the stars with
these dynamical characteristics do not constitute a homogeneous population. A
relatively sharp transition in dynamical and chemical properties appears to
occur at a metallicity of [Fe/H] ~ -0.4. Stars with [Fe/H] > -0.4 have mostly
lower eccentricities, smaller vertical velocity dispersions, are alpha-enhanced
and define a rather narrow sequence in [alpha/Fe] vs [Fe/H], clearly distinct
from that of the thin disk. Stars with [Fe/H] < -0.4 have a range of
eccentricities, are hotter vertically, and depict a larger spread in
[alpha/Fe]. We have also found tentative evidence of substructure possibly
associated to the disruption of a metal-rich star cluster. The differences
between these populations of stars is also present in e.g. [Zn/Fe], [Ni/Fe] and
[SmII/Fe], suggesting a real physical distinction.Comment: Astrophysical Journal in press. 5 pages, 4 figure
New Candidates for Topological Insulators : Pb-based chalcogenide series
Here, we theoretically predict that the series of Pb-based layered
chalcogenides, PbBiSe and PbSbTe, are possible
new candidates for topological insulators. As increases, the phase
transition from a topological insulator to a band insulator is found to occur
between and 3 for both series. Significantly, among the new topological
insulators, we found a bulk band gap of 0.40eV in PbBiSe which is one
of the largest gap topological insulators, and that PbSbTe is
located in the immediate vicinity of the topological phase boundary, making its
topological phase easily tunable by changing external parameters such as
lattice constants. Due to the three-dimensional Dirac cone at the phase
boundary, massless Dirac fermions also may be easily accessible in
PbSbTe
Enhancing Bremsstrahlung Production From Ultraintense Laser-Solid Interactions With Front Surface Structures
We report the results of a combined study of particle-in-cell and Monte Carlo
modeling that investigates the production of Bremsstrahlung radiation produced
when an ultraintense laser interacts with a tower-structured target. These
targets are found to significantly narrow the electron angular distribution as
well as produce significantly higher energies. These features combine to create
a significant enhancement in directionality and energy of the Bremstrahlung
radiation produced by a high-Z converter target. These studies employ
short-pulse, high intensity laser pulses, and indicate that novel target design
has potential to greatly enhance the yield and narrow the directionality of
high energy electrons and -rays. We find that the peak -ray
brightness for this source is 6.010 at 10MeV and 1.410 at 100MeV (0.1 bandwidth).Comment: arXiv admin note: text overlap with arXiv:1310.328
An HI census of Loose Groups of Galaxies
We present results from our Parkes Multibeam HI survey of 3 loose groups of
galaxies that are analogous to the Local Group. This is a survey of groups
containing only spiral galaxies with mean separations of a few hundred kpc, and
total areas of approximately 1 sq. Mpc; groups similar to our own Local Group.
We present a census of the HI-rich objects in these groups down to an M(HI),
1-sigma sensitivity ~7x10^5 M(sun), as well as the detailed properties of these
detections from follow-up Compact Array observations. We found 7 new HI-rich
members in the 3 groups, all of which have stellar counterparts and are,
therefore, typical dwarf galaxies. The ratio of low-mass to high-mass gas-rich
galaxies in these groups is less than in the Local Group meaning that the
``missing satellite'' problem is not unique. No high-velocity cloud analogs
were found in any of the groups. If HVCs in these groups are the same as in the
Local Group, this implies that HVCs must be located within ~300-400 kpc of the
Milky Way.Comment: 6 pages, to appear in the ASP proceedings of IAU Symposium 217,
"Recycling intergalactic and interstellar matter", eds. Pierre-Alain Duc,
Jonathan Braine, Elias Brink
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