5,639 research outputs found
Who Should be Interviewed in Surveys of Household Income?
This study tests the null hypothesis that it is sufficient to interview only the household head to obtain accurate information on household income. Results show that using a husband’s estimate of his wife’s income does not produce statistically reliable results for poverty analysis. Estimates of the wife’s income provided by the husband and wife are in agreement in only six percent of households. While limiting interviews to one person has the advantage of reducing the time and expense of household surveys, this appears detrimental in terms of accuracy, and may lead to incorrect conclusions on the determinants of poverty.Africa, gender, household dynamics, household surveys, Malawi, poverty, Agricultural Finance,
The Monoceros very-high-energy gamma-ray source
The H.E.S.S. telescope array has observed the complex Monoceros Loop
SNR/Rosette Nebula region which contains unidentified high energy EGRET sources
and potential very-high-energy (VHE) gamma-ray source. We announce the
discovery of a new point-like VHE gamma-ray sources, HESS J0632+057. It is
located close to the rim of the Monoceros SNR and has no clear counterpart at
other wavelengths. Data from the NANTEN telescope have been used to investigate
hadronic interactions with nearby molecular clouds. We found no evidence for a
clear association. The VHE gamma-ray emission is possibly associated with the
lower energy gamma-ray source 3EG J0634+0521, a weak X-ray source 1RXS
J063258.3+054857 and the Be-star MWC 148.Comment: 4 pages, 4 figures, Contribution to the 30th ICRC, Merida Mexico,
July 200
Electron-beam-induced shift in the apparent position of a pinned vortex in a thin superconducting film
When an electron beam strikes a superconducting thin film near a pinned
vortex, it locally increases the temperature-dependent London penetration depth
and perturbs the circulating supercurrent, thereby distorting the vortex's
magnetic field toward the heated spot. This phenomenon has been used to
visualize vortices pinned in SQUIDs using low-temperature scanning electron
microscopy. In this paper I develop a quantitative theory to calculate the
displacement of the vortex-generated magnetic-flux distribution as a function
of the distance of the beam spot from the vortex core. The results are
calculated using four different models for the spatial distribution of the
thermal power deposited by the electron beam.Comment: 9 pages, 6 figures, resubmitted to PRB with referee-suggested
revisions, includes new paragraph on numerical evaluatio
SHCal13 Southern Hemisphere calibration, 0–50,000 years cal BP
The Southern Hemisphere SHCal04 radiocarbon calibration curve has been updated with the addition of new data sets extending measurements to 2145 cal BP and including the ANSTO Younger Dryas Huon pine data set. Outside the range of measured data, the curve is based upon the Northern Hemisphere data sets as presented in IntCal13, with an interhemispheric offset averaging 43 ± 23 yr modeled by an autoregressive process to represent the short-term correlations in the offset
SHCal04 Southern Hemisphere Calibration, 0–11.0 cal kyr BP
Recent measurements on dendrochronologically-dated wood from the Southern Hemisphere have shown that there are differences between the structural form of the radiocarbon calibration curves from each hemisphere. Thus, it is desirable, when possible, to use calibration data obtained from secure dendrochronologically-dated wood from the corresponding hemisphere. In this paper, we outline the recent work and point the reader to the internationally recommended data set that should be used for future calibration of Southern Hemisphere ¹⁴C dates
Chasing the second gamma-ray bright isolated neutron star: 3EG J1835+5918/RX J1836.2+5925
The EGRET telescope aboard NASAs Compton GRO has repeatedly detected 3EG
J1835+5918, a bright and steady source of high-energy gamma-ray emission with
no identification suggested until recently. The long absence of any likely
counterpart for a bright gamma-ray source located 25 degrees off the Galactic
plane initiated several attempts of deep observations at other wavelengths. We
report on counterparts in X-rays on a basis of a 60 ksec ROSAT HRI image. In
order to conclude on the plausibility of the X-ray counterparts, we reanalyzed
data from EGRET at energies above 100 MeV and above 1 GeV, including data up to
CGRO observation cycle 7. The gamma-ray source location represents the latest
and probably the final positional assessment based on EGRET data. The X-ray
counterparts were studied during follow-up optical identification campaigns,
leaving only one object to be likely associated with the gamma-ray source 3EG
J1835+5918. This object, RX J1836.2+5925, has the characteristics of an
isolated neutron star and possibly of a radio-quiet pulsar.Comment: 5 pages, 3 figures. To appear in the Proceedings of the 270.
WE-Heraeus Seminar on Neutron Stars, Pulsars and Supernova Remnants, Jan.
21-25, 2002, Physikzentrum Bad Honnef, eds W. Becker, H. Lesch & J. Truemper.
Proceedings are available as MPE-Report 27
Tuning the exciton g-factor in single InAs/InP quantum dots
Photoluminescence data from single, self-assembled InAs/InP quantum dots in
magnetic fields up to 7 T are presented. Exciton g-factors are obtained for
dots of varying height, corresponding to ground state emission energies ranging
from 780 meV to 1100 meV. A monotonic increase of the g-factor from -2 to +1.2
is observed as the dot height decreases. The trend is well reproduced by sp3
tight binding calculations, which show that the hole g-factor is sensitive to
confinement effects through orbital angular momentum mixing between the
light-hole and heavy-hole valence bands. We demonstrate tunability of the
exciton g-factor by manipulating the quantum dot dimensions using pyramidal InP
nanotemplates
XMM-Newton observations of HESS J1813-178 reveal a composite Supernova remnant
We present X-ray and 12CO(J=1-0) observations of the very-high-energy (VHE)
gamma-ray source HESS J1813-178 with the aim of understanding the origin of the
gamma-ray emission. Using this dataset we are able to undertake spectral and
morphological studies of the X-ray emission from this object with greater
precision than previous studies. NANTEN 12CO(J=1-0) data are used to search for
correlations of the gamma-ray emission with molecular clouds which could act as
target material for gamma-ray production in a hadronic scenario. The NANTEN
12CO(J=1-0) observations show a giant molecular cloud of mass 2.5 10^5
M_{\sun} at a distance of 4 kpc in the vicinity of HESS J1813-178. Even
though there is no direct positional coincidence, this giant cloud might have
influenced the evolution of the gamma-ray source and its surroundings. The
X-ray data show a highly absorbed non-thermal X-ray emitting object coincident
with the previously known ASCA source AX J1813-178 showing a compact core and
an extended tail towards the north-east, located in the centre of the radio
shell-type Supernova remnant (SNR) G12.82-0.2. This central object shows
morphological and spectral resemblance to a Pulsar Wind Nebula (PWN) and we
therefore consider that the object is very likely to be a composite SNR. We
discuss the scenario in which the gamma-rays originate in the shell of the SNR
and the one in which they originate in the central object. We demonstrate, that
in order to connect the core X-ray emission to the VHE gamma-ray emission
electrons have to be accelerated to energies of at least 1 PeV.Comment: Submitted to A&
Equidistribution of the Fekete points on the sphere
The Fekete points are the points that maximize a Vandermonde-type determinant
that appears in the polynomial Lagrange interpolation formula. They are well
suited points for interpolation formulas and numerical integration. We prove
the asymptotic equidistribution of the Fekete points in the sphere. The way we
proceed is by showing their connection with other array of points, the
Marcinkiewicz-Zygmund arrays and the interpolating arrays, that have been
studied recently
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