50,685 research outputs found
Analytical Appendix 2: The Challenges of Managing Small Scale Fisheries in West Africa
This is the Final Technical Report to the DFID regarding The Management of Conflict in Tropical Fisheries project R7334. Ghana's small-scale marine fisheries face considerably less problems and challenges than its neighbours. There is no foreign industrial fleet competing with canoes for resources and the economy, although weakened, is comparatively stronger than other West African fishing nations. However, like many other coastal fishing nations, Ghana is still trying to find a successful means of marrying two different systems. The traditional management system, which, for generations has sustained small-scale fishing communities along the coast, is under threat from the modern management system that sees fish as a commodity for trading by entrepreneurs, rather than the basis for an entire way of life. Economic difficulties that stem from Ghana's commitment to neo-liberal economic reforms have further complicated the situation. State priorities and policies with regard to poverty alleviation in coastal communities are dictated largely by outside interests rather than internal needs. As the economy and economic policy has focused on the individual and the market, so the role of community, and indeed traditional systems has come under threat. This battle between the two systems is being played out in the arena of small-scale fisheries management. Increased competition, decreased enforcement and a failure to support traditional systems is putting increasing pressure of small-scale fishing communities. Although recent initiatives by the World Bank to reverse this trend are having some impact, the future for traditional fisheries management of small-scale fisheries in Ghana looks bleak
Four pi-recoil proportional counter used as neutron spectrometer
Study considers problems encountered in using 4 pi-recoil counters for neutron spectra measurement. Emphasis is placed on calibration, shape discrimination, variation of W, the average energy loss per ion pair, and the effects of differentiation on the intrinsic counter resolution
Review of river fisheries valuation in Central and South America
Unlike Africa and Asia, where a large part of the population are heavily dependent upon fishing for their livelihoods, fishing for a living in the interior of Central and South America (CSA) remains a marginal occupation for all but the most isolated of families. As such, the economics and management of fisheries on the continent have received little attention from within the continent and the rest of the world. This study shows that while a number of studies have been carried out on fishing in the region, they tend to be limited in their geographical focus and time scale. Although fishing of freshwater species may appear to be comparatively insignificant in the region, the rivers of CSA are very important. This report attempts to analyze the literature available on CSA river fisheries and attempts to draw out an economic value of these fisheries. It is divided into a number of sections. First, the authors describe the major river basins on the continent, characterize their fisheries, and place freshwater fisheries in CSA into a global context. Second, the authors provide a review of valuation techniques for fisheries and use this analytical framework to review the principal literature on freshwater fisheries in the region. Then they turn their attention to the economic impact of dams and water abstraction schemes, reviewing the available literature to ascertain how/if economic values are computed for the impact on fisheries. Finally, they offer some conclusions and recommendations on the direction for future studies of freshwater fisheries in CSA
A Foundation of Programming a Multi-Tape Quantum Turing machine
The notion of quantum Turing machines is a basis of quantum complexity
theory. We discuss a general model of multi-tape, multi-head Quantum Turing
machines with multi final states that also allow tape heads to stay still.Comment: A twelve page version is to appear in the Proceedings of the 24th
International Symposium on Mathematical Foundations of Computer Science in
September, 1999. LNC
COMMUNITY DEVELOPMENT--MID-COAST MAINE
Community/Rural/Urban Development,
Quantum cryptography protocols robust against photon number splitting attacks for weak laser pulses implementations
We introduce a new class of quantum quantum key distribution protocols,
tailored to be robust against photon number splitting (PNS) attacks. We study
one of these protocols, which differs from the BB84 only in the classical
sifting procedure. This protocol is provably better than BB84 against PNS
attacks at zero error.Comment: 4 pages, 2 figure
On the origin of noisy states whose teleportation fidelity can be enhanced through dissipation
Recently Badziag \emph{et al.} \cite{badziag} obtained a class of noisy
states whose teleportation fidelity can be enhanced by subjecting one of the
qubits to dissipative interaction with the environment via amplitude damping
channel (ADC). We show that such noisy states result while sharing the states
(| \Phi ^{\pm}> =\frac{1}{\sqrt{2}}(| 00> \pm | 11>)) across ADC. We also show
that under similar dissipative interactions different Bell states give rise to
noisy entangled states that are qualitatively very different from each other in
the sense, only the noisy entangled states constructed from the Bell states (|
\Phi ^{\pm}>) can \emph{}be made better sometimes by subjecting the unaffected
qubit to a dissipative interaction with the environment. Importantly if the
noisy state is non teleporting then it can always be made teleporting with this
prescription. We derive the most general restrictions on improvement of such
noisy states assuming that the damping parameters being different for both the
qubits. However this curious prescription does not work for the noisy entangled
states generated from (| \Psi ^{\pm}> =\frac{1}{\sqrt{2}}(| 01> \pm | 10>)).
This shows that an apriori knowledge of the noisy channel might be helpful to
decide which Bell state needs to be shared between Alice and Bob. \emph{}Comment: Latex, 18 pages: Revised version with a new result. Submitted to PR
Quantum electrodynamics of a free particle near dispersive dielectric or conducting boundaries
Quantum electrodynamics near a boundary is investigated by considering the
inertial mass shift of an electron near a dielectric or conducting surface. We
show that in all tractable cases the shift can be written in terms of integrals
over the TE and TM reflection coefficients associated with the surface, in
analogy to the Lifshitz formula for the Casimir effect. We discuss the
applications and potential limitations of this formula, and provide exact
results for several models of the surface
Detecting Electronic Coherence by Multidimensional Broadband Stimulated X-Ray Raman Signals
Nonstationary molecular states which contain electronic coherences can be
impulsively created and manipulated by using recently-developed ultrashort
optical and X-ray pulses via photoexcitation, photoionization and Auger
processes. We propose several stimulated-Raman detection schemes that can
monitor the phase-sensitive electronic and nuclear dynamics. Three detection
protocols of an X-ray broadband probe are compared - frequency dispersed
transmission, integrated photon number change, and total pulse energy change.
In addition each can be either linear or quadratic in the X-ray probe
intensity. These various signals offer different gating windows into the
molecular response which is described by correlation functions of electronic
polarizabilities. Off-resonant and resonant signals are compared
Supercatalysis
We show that entanglement-assisted transformations of bipartite entangled
states can be more efficient than catalysis [D. Jonathan and M. B. Plenio,
Phys. Rev. Lett. 83, 3566 (1999)}, i.e., given two incomparable bipartite
states not only can the transformation be enabled by performing collective
operations with an auxiliary entangled state, but the entanglement of the
auxiliary state itself can be enhanced. We refer to this phenomenon as
supercatalysis. We provide results on the properties of supercatalysis and its
relationship with catalysis. In particular, we obtain a useful necessary and
sufficient condition for catalysis, provide several sufficient conditions for
supercatalysis and study the extent to which entanglement of the auxiliary
state can be enhanced via supercatalysis.Comment: Latex, 5 page
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