990 resultados para electrostatic potential
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In Central California, and elsewhere around the world, a great deal of discussion is occurring about the use of marine protected areas (MPAs) as a tool to help manage marine resources. This discussion is taking place because there is growing evidence that humans have depleted marine resources in many parts of the world, often despite strong regulatory efforts. Moreover, there is also mounting evidence that the degradation of marine resources began long ago, and we do not fully realize how much humans have altered “natural” environments. This uncertainty has led people to discuss the use of MPAs as a precautionary tool to prevent depletion or extinction of marine resources, and as a means of redressing past damages. The discussion about the use of marine reserves is increasing in intensity in California because several resource management agencies are considering reserves as they create or revise management plans. Often, the discussions surrounding this important public policy debate lead to questions about the biological or ecological value of existing marine protected areas. More than 100 MPAs exist along the coast of California. Many of these were established arbitrarily and lack specific purposes. Some California marine protected areas also have co-occurring or overlapping boundaries, have conflicting designations for use, and have conflicting rules and regulations. Because few of the existing marine protected areas have clearly articulated goals or objectives, however, it is difficult or impossible to evaluate their ecological effectiveness. (PDF contains 18 pages.)
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This report seeks to discuss a variety of approaches to poverty in order to illustrate the diversity of poor people, and the range of ways in which people are poor, facilitating a broader understanding of poverty and the significance of aquatic resources in poor people’s livelihoods. This is intended to provide a balance to the general neglect of the poor in the pursuit of aquaculture development within the Fisheries sector. It is also intended that this approach to poverty will assist in the planning and targeting of aquatic resource interventions that aim to promote poverty alleviation. In its many different forms, poverty remains a persistent problem with a great number of people facing deprivation and vulnerable livelihoods. Rates of poverty alleviation also differ; whereas the Red River Delta has achieved the greatest reductions in poverty, the Mekong Delta has achieved the smallest improvements, with possible indications that inequality has increased (see 2.4). Inequality between regions persists despite progress in all regions. (PDF has 37 pages.)
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The use of reproductive and genetic technologies can increase the efficiency of selective breeding programs for aquaculture species. Four technologies are considered, namely: marker-assisted selection, DNA fingerprinting, in-vitro fertilization, and cryopreservation. Marker-assisted selection can result in greater genetic gain, particularly for traits difficult or expensive to measure, than conventional selection methods, but its application is currently limited by lack of high density linkage maps and by the high cost of genotyping. DNA fingerprinting is most useful for genetic tagging and parentage verification. Both in-vitro fertilization and cryopreservation techniques can increase the accuracy of selection while controlling accumulation of inbreeding in long-term selection programs. Currently, the cost associated with the utilization of reproductive and genetic techniques is possibly the most important factor limiting their use in genetic improvement programs for aquatic species.
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This is a copy of an article published in the Human gene therapy © 2012 copyright Mary Ann Liebert, Inc.; Human gene therapy is available online at: http://online.liebertpub.com.
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The United States and Japanese counterpart panels on aquaculture were formed in 1969 under the United States-Japan Cooperative Program in Natural Resources (UJNR). The panels currently include specialists drawn from the federal departments most concerned with aquaculture. Charged with exploring and developing bilateral cooperation, the panels have focused their efforts on exchanging information related to aquaculture which could be of benefit to both countries. The UJNR was begun during the Third Cabinet-Level Meeting of the Joint United States-Japan Committee on Trade and Economic Affairs in January 1964. In addition to aquaculture, current subjects in the program include desalination of seawater, toxic microorganisms, air pollution, energy, forage crops, national park management, mycoplasmosis, wind and seismic effects, protein resources, forestry, and several joint panels and committees in marine resources research, development, and utilization. Accomplishments include: Increased communication and cooperation among technical specialists; exchanges of information, data, and research findings; annual meetings of the panels, a policy-coordinative body; administrative staff meetings; exchanges of equipment, materials, and samples; several major technical conferences; and beneficial effects on international relations. (PDF file contains 76 pages.)
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The commercial development of ocean thermal energy conversion (OTEC) operations will involve some environmental perturbations for which there is no precedent experience. The pumping of very large volumes of warm surface water and cold deep water and its subsequent discharge will result in the impingement, entrainment, and redistribution of biota. Additional stresses to biota will be caused by biocide usage and temperature depressions. However, the artificial upwelling of nutrients associated with the pumping of cold deep water, and the artificial reef created by an OTEC plant may have positive effects on the local environment. Although more detailed information is needed to assess the net effect of an OTEC operation on fisheries, certain assumptions and calculations are made supporting the conclusion that the potential risk to fisheries is not significant enough to deter the early development of IDEe. It will be necessary to monitor a commercial-scale plant in order to remove many of the remaining uncertainties. (PDF file contains 39 pages.)
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RRAs were carried out in two Small Tank Cascade systems (STCs) of North West Province, Sri Lanka (less than 1000 ha total watershed area). A total of 21 tanks and 7 villages were investigated with primary emphasis on two upper watershed communities. The two systems differ primarily in their resource base; namely rainfall, natural forests and proximity to large scale perennial irrigation resources. [PDF contains 86 pages]
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The visit highlighted the vital contribution of the inland fisheries sector to provision of basic food security within the uncleared area (farmers report very low consumption frequencies for all other fish or meat protein substitutes). A 30-mile system of Brackish water lagoons which demarcates the cleared and uncleared areas is the main source of retailed fish in the uncleared area. Second in importance is the inland tank fishery, where the bulk of production emanates from 17 major irrigation reservoirs. [PDF contains 29 pages]
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Phosphorus removal by wetlands and basins in Lake Tahoe may be improved through designing these systems to filter storm water through media having higher phosphorus removal capabilities than local parent material. Substrates rich in iron, aluminum and calcium oftentimes have enhanced phosphorus removal. These substrates can be naturally occurring, byproducts of industrial or water treatment processes, or engineered. Phosphorus removal fundamentally occurs through chemical adsorption and/or precipitation and much of the phosphorus can be irreversibly bound. In addition to these standard media, other engineered substrates are available to enhance P removal. One such substrate is locally available in Reno and uses lanthanum coated diatomaceous earth for arsenate removal. This material, which has a high positive surface charge, can also irreversibly remove phosphorus. Physical factors also affect P removal. Specifically, specific surface area and particle shape affect filtration capacity, contact area between water and the surface area, and likelihood of clogging and blinding. A number of substrates have been shown to effectively remove P in case studies. Based upon these studies, promising substrates include WTRs, blast furnace slag, steel furnace slag, OPC, calcite, marble Utelite and other LWAs, zeolite and shale. However, other nonperformance factors such as environmental considerations, application logistics, costs, and potential for cementification narrow the list of possible media for application at Tahoe. Industrial byproducts such as slags risk possible leaching of heavy metals and this potential cannot be easily predicted. Fly ash and other fine particle substrates would be more difficult to apply because they would need to be blended, making them less desirable and more costly to apply than larger diameter media. High transportation costs rule out non-local products. Finally, amorphous calcium products will eventually cementify reducing their effectiveness in filtration systems. Based upon these considerations, bauxite, LWAs and expanded shales/clays, iron-rich sands, activated alumina, marble and dolomite, and natural and lanthanum activated diatomaceous earth are the products most likely to be tested for application at Tahoe. These materials are typically iron, calcium or aluminum based; many have a high specific surface area; and all have low transportation costs. (PDF contains 21 pages)
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Carbon nanotubes have unprecedented mechanical properties as defect-free nanoscale building blocks, but their potential has not been fully realized in composite materials due to weakness at the interfaces. Here we demonstrate that through load-transfer-favored three-dimensional architecture and molecular level couplings with polymer chains, true potential of CNTs can be realized in composites as Initially envisioned. Composite fibers with reticulate nanotube architectures show order of magnitude improvement in strength compared to randomly dispersed short CNT reinforced composites reported before. The molecular level couplings between nanotubes and polymer chains results in drastic differences in the properties of thermoset and thermoplastic composite fibers, which indicate that conventional macroscopic composite theory falls to explain the overall hybrid behavior at nanoscale.
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Abstract. The atomic motion is coupled by the fast and slow components due to the high frequency vibration of atoms and the low frequency deformation of atomic lattice, respectively. A two-step approximate method was presented to determine the atomic slow motion. The first step is based on the change of the location of the cold potential well bottom and the second step is based on the average of the appropriate slow velocities of the surrounding atoms. The simple tensions of one-dimensional atoms and two-dimensional atoms were performed with the full molecular dynamics simulations. The conjugate gradient method was employed to determine the corresponding location of cold potential well bottom. Results show that our two-step approximate method is appropriate to determine the atomic slow motion under the low strain rate loading. This splitting method may be helpful to develop more efficient molecular modeling methods and simulations pertinent to realistic loading conditions of materials.
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Trace metals constitute a major form of water pollutant that can adversely affect fish production. The potentially toxic metals have been identified as lead, zinc, copper, arsenic, antimony, mercury beryllium, barium, cadmium, chromium, nickel, selenium among others. Preliminary laboratory studies have been directed to the determination of traces of lead in the aquatic biota and its toxicity. There are indications that the levels reported in effluents from some of the industries may be above the tolerant limits of local fish species and organisms that make up their food. Metal pollution could become a serious problem to freshwater fisheries in the future as a result of increasing urbanization and industrialization, unless efforts are made to prevent it
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Niger River Basin Development Authority Minna (NRBDA) is one of the eleven river basins in Nigeria now undergoing transition towards partial commercialisation. In the light of this the need to be self-sustaining through exploration and exploitation of every possible areas along their operation to yield revenue cannot be over-emphasized. Therefore it is most pertinent to consider fisheries activities along their water bodies as one of the major sources of revenue by organising the local fishermen operating along the water into cooperative bodies and made to pay for fishing rights. Strategies to accomplish this objective is highlighted. The need to embark on aquaculture projects by construction of fish ponds at suitable sites along the reservoirs and developing the recreational potentials of their water bodies as sources of revenue is also stressed