Aquarium fisheries as a non-timber forest product: experiences from conservation through community development in North Rupununi District, Guyana

Deforestation is one of the major global conservation issues. Solutions are being sought to tackle this ongoing forest loss, including establishment of initiatives to provide new sources of income for local communities that promote the sustainable use of forests in the interest of biodiversity conservation. One such project ‘Iwokrama’, demonstrates how tropical forests and associated habitats can be sustainably used. In the central Guyana wetlands of the Rupununi, illegal fishing of arapaima Arapaima gigas, had led to a huge reduction in its numbers. Iwokrama responded by initiating the Arapaima Management Plan in 2002. This highlighted the need for another source of local income from fisheries, and a business that undertakes sustainable harvest of fish for the aquarium trade was developed. Harvesting of a few selected fish species is carried-out by members of the local community who are paid a daily wage. Fishing methods target individual species to avoid incidental by-catch. Four species are primarily caught as they are numerous in the Rupununi and are of high trade value. To ensure ecological and economical sustainability, catch per unit effort is monitored; where this begins to drop for any given species, harvesting is suspended and the population is allowed to recover before harvesting resumes. The project has developed into a self-sustaining business, managed by the community themselves. During 2005, the project reached financial sustainability with current profits of over US$3,000 feeding back into local community initiatives

Nonlocal vertices and analyticity: Landau equations and general Cutkosky rule

We study the analyticity properties of amplitudes in theories with nonlocal vertices of the type occurring in string field theory and a wide class of nonlocal field theory models. Such vertices are given in momentum space by entire functions of rapid decay in certain (including Euclidean) directions ensuring UV finiteness but are necessarily of rapid increase in others. A parametric representation is obtained by integrating out the loop (Euclidean) momenta after the introduction of generalized Schwinger parameters. Either in the original or parametric representation, the well-defined resulting amplitudes are then continued in the complex space of the external momenta invariants. We obtain the alternative forms of the Landau equations determining the singularity surfaces showing that the nonlocal vertices serve as UV regulators but do not affect the local singularity structure. As a result the full set of singularities known to occur in local field theory also occurs here: normal and anomalous thresholds as well as acnodes, crunodes, and cusps that may under certain circumstances appear even on the physical sheet. Singularities of the second type also appear as shown from the parametric representation. We obtain the general Cutkosky discontinuity rule for encircling a singularity by employing contour deformations only in the finite plane. The unitarity condition (optical theorem) is then discussed as a special application of the rule across normal thresholds and the hermitian analyticity property of amplitudes.Comment: 31 pages, 5 figures. Typos corrected, some additional clarifying comments, one added referenc

Traffic, urban growth and suburban sprawl

Cities are still getting bigger in the western world. Even though urbanpopulations are barely reproducing themselves and migration from thecountryside to the town has slowed to a trickle, the demand for more livingspace shows no sign of abating as cities continue to expand their bordersthrough suburban sprawl. The automobile, of course, makes this possiblebut we show no signs of moving to other forms of transport that mightenable our cities to become a little more compact. The problems of sprawlare pervasive. Besides congestion, time wasted, and the long term costs ofusing non-renewable energy, the lack of good social infrastructure inrapidly growing suburban areas together with the erosion of agriculturalland, often of high environmental quality, has focused the debate onwhether or not such forms of development are sustainable. In this paper,we begin by noting that suburban sprawl is an age-old phenomenon whichrepresents a fine balance between the forces that are pushing peopletogether in cities and those that are forcing them out. These lead todifferent types of sprawl in different places and at different times butwhatever the variety, there are costs to be borne. We briefly review these,noting how these affect suburban sprawl in Europe, and the efforts of theEuropean Commission to understand the problem. We conclude not with aplea that cities should be compacted and all automobile traffic removedbut that we should engage in policies for ?smart growth? such as thosebeing adopted in North America

Fourth Order Algorithms for Solving the Multivariable Langevin Equation and the Kramers Equation

We develop a fourth order simulation algorithm for solving the stochastic Langevin equation. The method consists of identifying solvable operators in the Fokker-Planck equation, factorizing the evolution operator for small time steps to fourth order and implementing the factorization process numerically. A key contribution of this work is to show how certain double commutators in the factorization process can be simulated in practice. The method is general, applicable to the multivariable case, and systematic, with known procedures for doing fourth order factorizations. The fourth order convergence of the resulting algorithm allowed very large time steps to be used. In simulating the Brownian dynamics of 121 Yukawa particles in two dimensions, the converged result of a first order algorithm can be obtained by using time steps 50 times as large. To further demostrate the versatility of our method, we derive two new classes of fourth order algorithms for solving the simpler Kramers equation without requiring the derivative of the force. The convergence of many fourth order algorithms for solving this equation are compared.Comment: 19 pages, 2 figure

Distance learning of engineering based subjects: A case study.

YesWith the advancement of technology, significant changes have been introduced into the learning and teaching environment. The importance of enhancing the interest of learners is an on-going challenge for educators of all levels. In this respect, teaching and learning practices are adapting to students¿ exposure to technological and social trends. In this presentation, a case study of using technology to enhance the learners¿ environment for engineering-based subjects in higher education is presented. The approach consists of delivering interactive materials through a Virtual Learning Environment and integrating web application technologies to enhance the learners¿ experience. Due to the vast subject areas in engineering and the variety of content of each subject, a general methodology is first identified and adopted. This consists of stages that show the progress from initial development to deployment of the materials, followed by evaluation of the module and further improvements carried out on the module based on qualitative evaluation. The evaluation process consists of the application of electronic surveys for feedback on the distance learning module. In addition, monitoring of the students¿ usage of the materials is also carried out. The presentation concludes with the presentation of the initial results from a current e-learning module

Any order imaginary time propagation method for solving the Schrodinger equation

The eigenvalue-function pair of the 3D Schr\"odinger equation can be efficiently computed by use of high order, imaginary time propagators. Due to the diffusion character of the kinetic energy operator in imaginary time, algorithms developed so far are at most fourth-order. In this work, we show that for a grid based algorithm, imaginary time propagation of any even order can be devised on the basis of multi-product splitting. The effectiveness of these algorithms, up to the 12$^{\rm th}$ order, is demonstrated by computing all 120 eigenstates of a model C$_{60}$ molecule to very high precisions. The algorithms are particularly useful when implemented on parallel computer architectures.Comment: 8 pages, 3 figure

Enhancement of variation of fundamental constants in ultracold atom and molecule systems near Feshbach resonances

Scattering length, which can be measured in Bose-Einstein condensate and Feshbach molecule experiments, is extremely sensitive to the variation of fundamental constants, in particular, the electron-to-proton mass ratio (m_e/m_p or m_e/Lambda_{QCD}, where Lambda_{QCD} is the QCD scale). Based on single- and two-channel scattering model, we show how the variation of the mass ratio propagates to the scattering length. Our results suggest that variation of m_e/m_p on the level of 10^{-11}~10^{-14} can be detected near a narrow magnetic or an optical Feshbach resonance by monitoring the scattering length on the 1% level. Derived formulae may also be used to estimate the isotopic shift of the scattering length

The Temporal Doppler Effect: When The Future Feels Closer Than The Past

People routinely remember events that have passed and imagine those that are yet to come. The past and the future are sometimes psychologically close ( just around the corner ) and other times psychologically distant ( ages away ). Four studies demonstrate a systematic asymmetry whereby future events are psychologically closer than past events of equivalent objective distance. When considering specific times (e.g., 1 year) or events (e.g., Valentine\u27s Day), people consistently reported that the future was closer than the past. We suggest that this asymmetry arises because the subjective experience of movement through time (whereby future events approach and past events recede) is analogous to the physical experience of movement through space. Consistent with this hypothesis, experimentally reversing the metaphorical arrow of time (by having participants move backward through virtual space) completely eliminated the past-future asymmetry. We discuss how reducing psychological distance to the future may function to prepare people for upcoming action