4,180 research outputs found

    Application of a Two-Parameter Quantum Algebra to Rotational Spectroscopy of Nuclei

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    A two-parameter quantum algebra Uqp(u2)U_{qp}({\rm u}_2) is briefly investigated in this paper. The basic ingredients of a model based on the Uqp(u2)U_{qp}({\rm u}_2) symmetry, the qpqp-rotator model, are presented in detail. Some general tendencies arising from the application of this model to the description of rotational bands of various atomic nuclei are summarized.Comment: 8 pages, Latex File, to be published in Reports on Mathematical Physic

    An Uqp(u2)U_{qp}(u_2) Rotor Model for Rotational Bands of Superdeformed Nuclei

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    A nonrigid rotor model is developed from the two-parameter quantum algebra Uqp(u2)U_{qp}({\rm u}_2). [This model presents the Uqp(u2)U_{qp}({\rm u}_2) symmetry and shall be referred to as the qp-rotor model.] A rotational energy formula as well as a qp-deformation of E2 reduced transition probabilities are derived. The qp-rotor model is applied (through fitting procedures) to twenty rotational bands of superdeformed nuclei in the A∌130A \sim 130, 150 and 190 mass regions. Systematic comparisons between the qp-rotor model and the q-rotor model of Raychev, Roussev and Smirnov, on one hand, and a basic three-parameter model, on the other hand, are performed on energy spectra, on dynamical moments of inertia and on B(E2) values. The physical signification of the deformation parameters q and p is discussed.Comment: 24 pages, Latex File, to appear in IJMP

    A System of Interest in Spectroscopy: The qp-Rotor System

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    A rotor system, having the symmetry afforded by the two-parameter quantum algebra Uqp(u(2)), is investigated in this communication. This system is useful in rotational spectroscopy of molecules and nuclei. In particular, it is shown to lead to a model (viz., the qp-rotor model) for describing (via an energy formula and a qp-deformation of E2 reduced transition probabilities) rotational bands of deformed and superdeformed nuclei

    The importance of habitat quality for marine reserve fishery linkages

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    We model marine reserve - fishery linkages to evaluate the potential contribution of habitat-quality improvements inside a marine reserve to fish productivity and fishery catches. Data from Mombasa Marine National Park, Kenya, and the adjacent fishery are used. Marine reserves increase total fish biomass directly by providing refuge from exploitation and indirectly by improving fish habitat in the reserve. As natural mortality of the fish stock decreases in response to habitat enhancement in the reserve, catches increase by up to 2.6 tonnes (t).km(-2).year(-1) and total fish biomass by up to 36 t.km(-2). However, if habitat-quality improvement reduces the propensity of fish to move out of the reserve, catches may fall by up to 0.9 t.km(-2).year(-1). Our results indicate that habitat protection in reserves can underpin fish productivity and, depending on its effects on fish movements, augment catches


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    In Honduras, traditional coffee processing is the cause of two major problems: poor coffee quality and contaminated water. In this paper we present a method that determines the trade-off between economic efficiency and contamination in a Honduran sub-watershed. The method is a bioeconomic model based on mathematical programming that stimulates the functioning of the interlinked economic and ecological processes in the sub-watershed. We compare various scenarii where the model is given the possibility of replacing traditional coffee processing plants with a network of improved ecological plants. For different levels of contamination the model determines the optimal location and size of new coffee processing plants along river streams by minimizing transport, variable and fixed costs. The restrictions of the system are the volume of wet coffee to be processed, the available stream water, and in the alternative scenarii, investment capital and contaminant concentration in the river. We apply the method to a typical sub-watershed in the hillsides of western Honduras and show that coffee quality can be improved and contamination can be reduced substantially at a relatively low cost.coffee, environment, water quality, mathematical programming, transport cost, spatial analysis, watershed, Honduras., Environmental Economics and Policy,

    Circumstellar environment of RX Puppis

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    The symbiotic Mira, RX Pup, shows long-term variations in its mean light level due to variable obscuration by circumstellar dust. The last increase in extinction towards the Mira, between 1995 and 2000, has been accompanied by large changes in the degree of polarization in the optical and red spectral range. The lack of any obvious associated changes in the position angle may indicate the polarization variations are driven by changes in the properties of the dust grains (e.g. variable quantity of dust and variable particle size distribution, due to dust grain formation and growth) rather than changes in the viewing geometry of the scattering region(s), e.g. due to the binary rotation.Comment: Paper presented at Torun 2000 conference on Post-AGB objects as a phase of stellar evolution; 8 pages, 3 figure