A buoyant tornado-probe concept incorporating an inverted lifting device

Addition of an inverted lifting device to a simple balloon probe is shown to make possible low-altitude entry to tornado cores with easier launch conditions than for the simple balloon probe. Balloon-lifter combinations are particularly suitable for penetration of tornadoes with average to strong circulation, but tornadoes of less than average circulation which are inaccessible to simple balloon probes become accessible. The increased launch radius which is needed for access to tornadoes over a wide range of circulation results in entry times of about 3 minutes. For a simple balloon probe the uninflated balloon must be first dropped on, or near, the track of the tornado from a safe distance. The increase in typical launch radius from about 0.75 kilometer to slightly over 1.0 kilometer with a balloon-lifter combination suggests that a direct air launch may be feasible

Phase Field Crystals as a Coarse-Graining in Time of Molecular Dynamics

Phase field crystals (PFC) are a tool for simulating materials at the atomic level. They combine the small length-scale resolution of molecular dynamics (MD) with the ability to simulate dynamics on mesoscopic time scales. We show how PFC can be interpreted as the result of applying coarse-graining in time to the microscopic density field of molecular dynamics simulations. We take the form of the free energy for the phase field from the classical density functional theory of inhomogeneous liquids and then choose coefficients to match the structure factor of the time coarse-grained microscopic density field. As an example, we show how to construct a PFC free energy for Weber and Stillinger's two-dimensional square crystal potential which models a system of proteins suspended in a membrane.Comment: 5 pages, 4 figures, typos corrected, more explanation in parts, equilib vs non-equilib clarifie

Improved method of producing oxide-dispersion-strengthened alloys

Dispersion strengthened alloys having the required properties are produced by a process in which the refractory particles are less than 100 to 500 A thick. These are fine enough to ensure the strength characteristics without appreciable degradation of other characteristics. The alloy consists of a matrix metal and a dispersoid metal

Tree size and herbivory determine below-canopy grass quality and species composition in savannahs

Large single-standing trees are rapidly declining in savannahs, ecosystems supporting a high diversity of large herbivorous mammals. Savannah trees are important as they support both a unique flora and fauna. The herbaceous layer in particular responds to the structural and functional properties of a tree. As shrubland expands stem thickening occurs and large trees are replaced by smaller trees. Here we examine whether small trees are as effective in providing advantages for grasses growing beneath their crowns as large trees are. The role of herbivory in this positive tree-grass interaction is also investigated. We assessed soil and grass nutrient content, structural properties, and herbaceous species composition beneath trees of three size classes and under two grazing regimes in a South African savannah. We found that grass leaf content (N and P) beneath the crowns of particularly large (ca. 3. 5 m) and very large trees (ca. 9 m) was as much as 40% greater than the same grass species not growing under a tree canopy, whereas nutrient contents of grasses did not differ beneath small trees

Understanding the local livelihood system in reosurce management: the pelagic longline fishery in Gouyaye, Grenada

ABSTRACT There is a need to include social objectives in fisheries management, and this paper focuses on one set of social considerations, those regarding livelihood. We pay particular attention to sustainable livelihood strategies, the importance of commercial pelagic longline fishing for the entire community livelihood system, and implications for management. Field data were obtained between December 2002 and March 2004 in Gouyave, Grenada, using participant observation, semi-structured interviews, and a quantitative survey. The economic base (fishing and agriculture) of the community is both unpredictable and seasonal, therefore individuals and households engage in diverse strategies to secure their livelihood. Three livelihood strategies were deemed important: 1) livelihood diversification, developing additional sources of income from agriculture, wage labor, and trade work, 2) fishing diversification, learning to switch to alternative gear and species, and 3) the availability of an informal "social security net" involving cash and in-kind assistance. These strategies help to spread the flow of income and food during lean times and across seasons. A major management implication is that fishery managers need to pay attention to the multi-species nature of fisheries and to the importance of livelihood diversification, including reliance on other economic sectors. RESUMEN Existe la necesidad de incluir objetivos sociales en el manejo de la industria pesquera y este artículo se focaliza en un grupo de consideraciones sociales, las que se refieren al sustento. Prestanos particular atención a las estrategias de los sustento sostenibles, la importancia de la pesca pelágica comercial para el sustento de toda la comunida y las implicaciones para su manejo. Los datos de campo fueron obtenidos entre Diciembre del 2002 y Marzo del 2004 de Gouyave, Grenada a través del estudio de los participantes, entrevistas semi-estructuradas y un examen cuantitativo. La base económica (pesca y agricultura) de la comunidad es tanto impredecible como variable, por lo tanto individuos y hogares adoptan estrategias diversificadas para logar la seguridad del sustento. Tres estrategias de sustento fueron consideradas importantes: 1) diversificación de las actividades para sustento desarrollando fuentes de ingresos adicionales en agricultura, labor pagada y trabajo de obrero, 2) la diversificación de la pesca aprendiendo a utilizar hacia equipos y especies alternativas, y 3) la disponibilidad de una red de seguridad social que incluye asistencia monetaria y en especie. Estas estrategias diversificadas ayudan a distribuir el flujo de ingresos y alimentos a través de las estaciones. Un mayor involvcramiento en el manejo implica que los gerentes pesqueros presten mayor cuidado a la naturaleza multi-especies de la pesca y a la importancia de la diversificacion del sustento, incluyendo la confianza en otros sectores económicos

HAS THE WORLD TRADE ORGANIZATION PROMOTED SUCCESSFUL REGIONAL TRADE AGREEMENTS?

This study uses econometric gravity equations to test whether the WTO has promoted successful regional trade agreements (RTA). Two important findings emerge. First, we find that two countries that are members of the GATT/WTO and enter into a regional trade agreement stimulate trade. However, the effect on trade is not nearly as large as that between two RTA members that belong to the GATT/WTO. Contrary to the findings in Rose (2004), this result tends to support the fact that the GATT/WTO has liberalized multilateral trade, outside of RTAs. In other words, the effect of an RTA on countries’ trade who are not party to the GATT/WTO should generate a large RTA trade response due to relatively large pre-existing trade distortions. Second, we show that the GATT/WTO has not promoted successful RTAs using explicit RTA variables that controls for the notification status (to the GATT/WTO) of an RTA. Interestingly, non-notified RTAs trade significantly more than their notified counterparts.International Relations/Trade,