259 research outputs found
An Analytical Survey of Population and Development in Bangladesh
This paper is titled an Analytical Survey. As a survey it sets out to collect and pull together what is know from the many studies and detailed aspects of population and development in Bangladesh. And as an analysis it sets out to make sense of a complex situation, to pick out the various economic, social, demographic and environmental forces that shape Bangladesh's present predicament and set the bounds for its future possibilities.
Two particular problems call for special attention in an analysis of Bangladesh. Agriculture measured relative to other Asian countries, has achieved little in the last decades that could be called dynamic progress. And human fertility, a generation after mortality has declined, remains high with little sign of falling. The source of both problems we seek in the social structure of rural Bangladesh, in the particular incentives this structure gives to those who control it, in the legacy of underadministration and underinvestment left by the country's colonial past, and in the extreme lack of security faced by a population that lives in a crowded and uncertain environment
Who pollutes in Scotland? A prelude to an analysis of sustainability policies in a devolved context
The notion of sustainable development has begun to figure prominently in the regional, as well as the national, policy concerns of many industrialized countries. Indicators have typically been used to monitor changes in economic, environmental and social variables to show whether economic development is on a sustainable path. This paper focuses on pollution in Scotland and analyses the sustainability policies in a devolved political context
Eta-photoproduction in a gauge-invariant chiral unitary framework
We analyse photoproduction of eta mesons off the proton in a gauge-invariant
chiral unitary framework. The interaction kernel for meson-baryon scattering is
derived from the leading order chiral effective Lagrangian and iterated in a
Bethe-Salpeter equation. The recent precise threshold data from the Crystal
Ball at MAMI can be described rather well and the complex pole corresponding to
the S11(1535) is extracted. An extension of the kernel is also discussed.Comment: Updated version to be published in Physics Letters
Upgrade of the Glasgow photon tagging spectrometer for Mainz MAMI-C
The Glasgow photon tagging spectrometer at Mainz has been upgraded so that it
can be used with the 1500 MeV electron beam now available from the Mainz
microtron MAMI-C. The changes made and the resulting properties of the
spectrometer are discussed.Comment: 20 pages, 12 figure
Toward control of gold cluster aggregation on TiO(2) via surface treatments
Published: October 1, 2015Well-defined Au–TiO₂ materials were synthesized by deposition of triphenylphosphine-protected Au₉ clusters on TiO₂ (Aeroxide P-25), pre-treated in eight different ways and subsequently exposed to two post-treatments. X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectroscopy studies showed that in most cases the PPh₃ ligand shell was removed upon deposition even before post-treatment, coinciding with some cluster aggregation. However, clusters deposited on TiO₂ treated using H₂SO₄ and H2O₂ showed remarkable resistance to aggregation, even after high-temperature calcination, while clusters on H₂-treated TiO₂ showed the greatest resistance to aggregation under ozonolysis.Jan-Yves Ruzicka, Faridah Abu Bakar, Christoffer Hoeck, Rohul Adnan, Campbell McNicoll, Tim Kemmitt, Bruce C. Cowie, Gregory F. Metha, Gunther G. Andersson, and Vladimir B. Golovk
Measurement of the transverse target and beam-target asymmetries in meson photoproduction at MAMI
We present new data for the transverse target asymmetry T and the very first
data for the beam-target asymmetry F in the
reaction up to a center-of-mass energy of W=1.9 GeV. The data were obtained
with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility
of the Mainz Microtron MAMI. All existing model predictions fail to reproduce
the new data indicating a significant impact on our understanding of the
underlying dynamics of meson photoproduction. The peculiar nodal
structure observed in existing T data close to threshold is not confirmed.Comment: 5 pages, 3 figures, accepted for publication in PR
Measurement of the beam-helicity asymmetry in the photoproduction of -pairs off protons and off neutrons
Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz
for the photoproduction of mixed-charge pion pairs in the reactions
off free protons and
and
off quasi-free nucleons bound
in the deuteron for incident photon energies up to 1.4 GeV. Circularly
polarized photons were produced from bremsstrahlung of longitudinally polarized
electrons and tagged with the Glasgow-Mainz magnetic spectrometer. The charged
pions, recoil protons, recoil neutrons, and decay photons from mesons
were detected in the 4 electromagnetic calorimeter composed of the Crystal
Ball and TAPS detectors. Using a complete kinematic reconstruction of the final
state, excellent agreement was found between the results for free and
quasi-free protons, suggesting that the quasi-free neutron results are also a
close approximation of the free-neutron asymmetries. A comparison of the
results to the predictions of the Two-Pion-MAID reaction model shows that the
reaction mechanisms are still not well understood, in particular at low
incident photon energies in the second nucleon-resonance region.Comment: accepted for publication in Eur. phys. J.
Photoproduction of pi0-mesons off neutrons in the nucleon resonance region
Precise angular distributions have been measured for the first time for the
photoproduction of -mesons off neutrons bound in the deuteron. The
effects from nuclear Fermi motion have been eliminated by a complete kinematic
reconstruction of the final state. The influence of final-state-interaction
effects has been estimated by a comparison of the reaction cross section for
quasi-free protons bound in the deuteron to the results for free protons and
then applied as a correction to the quasi-free neutron data. The experiment was
performed at the tagged photon facility of the Mainz Microtron MAMI with the
Crystal Ball and TAPS detector setup for incident photon energies between
~GeV and ~GeV. The results are compared to the predictions from
reaction models and partial-wave analyses based on data from other isospin
channels. The model predictions show large discrepancies among each other and
the present data will provide much tighter constraints. This is demonstrated by
the results of a new analysis in the framework of the Bonn-Gatchina
coupled-channel analysis which included the present data.Comment: accepted for publication in Phys; Rev. Let
The isospin structure of photoproduction of pi-eta pairs from the nucleon in the threshold region
Photoproduction of -pairs from nucleons has been investigated from
threshold up to incident photon energies of ~1.4~GeV. The quasi-free
reactions , ,
, and were for
the first time measured from nucleons bound in the deuteron. The corresponding
reactions from a free-proton target were also studied to investigate
final-state interaction effects (for neutral pions the free-proton results
could be compared to previous measurements; the reaction was measured for the first time). For the
final state coherent production via the
reaction was also investigated. The experiments were performed at the tagged
photon beam of the Mainz MAMI accelerator using an almost coverage
electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors.
The total cross sections for the four different final states obey the relation
as expected for a
dominant contribution from a
reaction chain,
which is also supported by the shapes of the invariant-mass distributions of
nucleon-meson and - pairs. The experimental results are compared to
the predictions from an isobar reaction model.Comment: accepted for publication in Phys. Lett.
Quasi-free photoproduction of η-mesons off 3He nuclei
Quasi-free photoproduction of η-mesons has been measured off nucleons bound in 3He nuclei for incident photon energies from the threshold region up to 1.4 GeV. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with an almost 4π covering electromagnetic calorimeter, combining the TAPS and Crystal Ball detectors. The η-mesons were detected in coincidence with the recoil nucleons. This allowed a comparison of the production cross section off quasi-free protons and quasi-free neutrons and a full kinematic reconstruction of the final state, eliminating effects from nuclear Fermi motion. In the S11(1535) resonance peak, the data agree with the neutron/proton cross section ratio extracted from measurements with deuteron targets. More importantly, the prominent structure observed in photoproduction off quasi-free neutrons bound in the deuteron is also clearly observed. Its parameters (width, strength) are consistent with the expectations from the deuteron results. On an absolute scale the cross sections for both quasi-free protons and neutrons are suppressed with respect to the deuteron target pointing to significant nuclear final-state interaction effects
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