8,230 research outputs found
Genetically modified rice adoption : implications for welfare and poverty alleviation
The first generation of genetically modified (GM) crop varieties sought to increase producer profitability through cost reductions or higher yields, while the next generation of GM food research is focusing on breeding for attributes of interest to consumers. Golden Rice, for example, has been genetically engineered to contain a higher level of vitamin A and thereby boost the health of poor people in developing countries. This paper analyzes the potential economic effects of adopting both types of innovation in Asia, including its impact on rice producers and consumers. It does so using the global economy-wide computable general equilibrium model known as GTAP. The results suggest the farm productivity gains could be dwarfed by the welfare gains resulting from the potential health-enhancing attributes of golden rice, which would boost the productivity of unskilled workers among Asia's poor.Agricultural Research,Environmental Economics&Policies,Labor Policies,Crops&Crop Management Systems,Economic Theory&Research,Crops&Crop Management Systems,Environmental Economics&Policies,Agricultural Research,Economic Theory&Research,Drylands&Desertification
Products of Random Matrices
We derive analytic expressions for infinite products of random 2x2 matrices.
The determinant of the target matrix is log-normally distributed, whereas the
remainder is a surprisingly complicated function of a parameter characterizing
the norm of the matrix and a parameter characterizing its skewness. The
distribution may have importance as an uncommitted prior in statistical image
analysis.Comment: 9 pages, 1 figur
Ethane steam reforming over a platinum/alumina catalyst: effect of sulphur poisoning
In this study we have examined the adsorption of hydrogen sulfide and methanethiol over platinum catalysts and examined the effect of these poisons on the steam reforming of ethane. Adsorption of hydrogen sulfide was measured at 293 and 873 K. At 873 K the adsorbed state of hydrogen sulfide in the presence of hydrogen was SH rather than S, even though the Pt:S ratio was unity. The effect of 11.2 ppm hydrogen sulfide or methanethiol on the steam reforming of ethane was studied at 873 K and 20 barg. Both poisons deactivated the catalyst over a number of hours, but methanethiol was found to be more deleterious, reducing the conversion by almost an order of magnitude, possibly due to the co-deposition of sulfur and carbon. Changes in the selectivity revealed that the effect of sulfur was not uniform on the reactions occurring, with the production of methane reduced proportionally more than the other products, due to the surface sensitivity of the hydrogenolysis and methanation reactions. The water-gas shift reaction was affected to a lesser extent. No regeneration was observed when hydrogen sulfide was removed from the feedstream in agreement with adsorption studies. A slight regeneration was observed when methanethiol was removed from the feed, but this was believed to be due to the removal of carbon rather than sulfur. The overall effect of sulfur poisoning was to reduce activity and enhance hydrogen selectivity
Heat Transfer from a Hemisphere-cylinder Equipped with Flow-separation Spikes
Average heat-transfer, temperature-recovery, and pressure-distribution measurements were obtained over the hemispherical nose of a body of revolution both with and without flow-separation spikes. The tests, conducted in a range of Reynolds numbers from 1.55 to 9.85 x 10(5) and from Mach number 0.12 to 5.04, indicated that in supersonic flow the addition of spikes approximately doubles the rate of heat transfer, regardless of spike length
Creation of Entanglement by Interaction with a Common Heat Bath
I show that entanglement between two qubits can be generated if the two
qubits interact with a common heat bath in thermal equilibrium, but do not
interact directly with each other. In most situations the entanglement is
created for a very short time after the interaction with the heat bath is
switched on, but depending on system, coupling, and heat bath, the entanglement
may persist for arbitrarily long times. This mechanism sheds new light on the
creation of entanglement. A particular example of two quantum dots in a closed
cavity is discussed, where the heat bath is given by the blackbody radiation.Comment: 4 revtex pages, 1 eps figure; replaced with published version; short
discussion on entanglement distillation adde
Loss of Spin Entanglement For Accelerated Electrons in Electric and Magnetic Fields
Using an open quantum system we calculate the time dependence of the
concurrence between two maximally entangled electron spins with one accelerated
uniformly in the presence of a constant magnetic field and the other at rest
and isolated from fields. We find at high Rindler temperature the proper time
for the entanglement to be extinguished is proportional to the inverse of the
acceleration cubed.Comment: 10 pages, 4 figures, appendix and other discussion added, fixed some
typographical errors and some references were correcte
The Refractive Index of Silicon at Gamma Ray Energies
The index of refraction n(E_{\gamma})=1+\delta(E_{\gamma})+i\beta(E_{\gamma})
is split into a real part \delta and an absorptive part \beta. The absorptive
part has the three well-known contributions to the cross section \sigma_{abs}:
the photo effect, the Compton effect and the pair creation, but there is also
the inelastic Delbr\"uck scattering. Second-order elastic scattering cross
sections \sigma_{sca} with Rayleigh scattering (virtual photo effect), virtual
Compton effect and Delbr\"uck scattering (virtual pair creation) can be
calculated by integrals of the Kramers-Kronig dispersion relations from the
cross section \sigma_{abs}. The real elastic scattering amplitudes are
proportional to the refractive indices \delta_{photo}, \delta_{Compton} and
\delta_{pair}. While for X-rays the negative \delta_{photo} dominates, we show
for the first time experimentally and theoretically that the positive
\delta_{pair} dominates for \gamma rays, opening a new era of \gamma optics
applications, i.e. of nuclear photonics.Comment: 4 pages, 3 figure
The Controversies and Difficulties of Diagnosing Primary Ciliary Dyskinesia
We welcome the correspondence from Lavie and Amirav (1), highlighting the difficulties diagnosing primary ciliary dyskinesia (PCD) and the role of high-speed video analysis (HSVA). As members of the European Respiratory Society (ERS) PCD Diagnostic Task Force (2) and/or large PCD Centres, we agree that HSVA has an important role that is not recognized by the American Thoracic Society (ATS) PCD Diagnostic Guideline (3). This risks a large proportion of false-negative âmissedâ diagnoses and a sizable number of false-positive cases; we make additional important observations.</div
Dialogue Concerning Two Views on Quantum Coherence: Factist and Fictionist
A controversy that has arisen many times over in disparate contexts is
whether quantum coherences between eigenstates of certain quantities are fact
or fiction. We present a pedagogical introduction to the debate in the form of
a hypothetical dialogue between proponents from each of the two camps: a
factist and a fictionist. A resolution of the debate can be achieved, we argue,
by recognizing that quantum states do not only contain information about the
intrinsic properties of a system but about its extrinsic properties as well,
that is, about its relation to other systems external to it. Specifically, the
coherent quantum state of the factist is the appropriate description of the
relation of the system to one reference frame, while the incoherent quantum
state of the fictionist is the appropriate description of the relation of the
system to another, uncorrelated, reference frame. The two views, we conclude,
are alternative but equally valid paradigms of description.Comment: 14 pages, Contribution to the Int. J. of Quant. Info. issue dedicated
to the memory of Asher Peres; v2 updated summary and critique of prior
literatur
The context, influences and challenges for undergraduate nurse clinical education: Continuing the dialogue
Introduction â Approaches to clinical education are highly diverse and becoming increasingly complex to sustain in complex milieu
Objective â To identify the influences and challenges of providing nurse clinical education in the undergraduate setting and to illustrate emerging solutions.
Method: A discursive exploration into the broad and varied body of evidence including peer reviewed and grey literature.
Discussion - Internationally, enabling undergraduate clinical learning opportunities faces a range of challenges. These can be illustrated under two broad themes: (1) Legacies from the past and the inherent features of nurse education and (2) Challenges of the present, including, population changes, workforce changes, and the disconnection between the health and education sectors. Responses to these challenges are triggering the emergence of novel approaches, such as collaborative models.
Conclusion(s) â Ongoing challenges in providing accessible, effective and quality clinical learning experiences are apparent
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