903 resultados para dead-zone


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During the 18th Annual 2008 SAIL meeting at the Smithsonian Tropical Research Institute in Panama, a suggestion was made for the need to digitize and make available through the Aquatic Commons some of the early documents related to the U.S. biological survey of Panama from 1910 to 1912. With SAIL’s endeavor, a new digital project was born and this presentation describes its process, beginning to final product. The main source consulted for determining copyright clear publications was: Heckadon-Moreno. 2004. Naturalists on the Isthmus of Panama: A hundred years of natural history on the biological bridge of the Americas. 1st English ed. Smithsonian Tropical Research Institute, Panama City, Republic of Panama. (Document contains 26 slides)

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During the 18th Annual 2008 SAIL meeting at the Smithsonian Tropical Research Institute in Panama, Vielka Chang-Yau, librarian, mentioned the need to digitize and make available through the Aquatic Commons some of the early documents related to the U.S. biological survey of Panama from 1910 to 1912. With the assistance of SAIL, a regional marine librarian’s group, a digital project developed and this select bibliography represents the sources used for the project. It will assist researchers and librarians in finding online open access documents written during the construction of the Panama Canal, specifically between 1910-1912. As the project progressed, other items covering the region and its biological diversity were discovered and included. The project team expects that the coverage will continue to expand over time. (PDF contains 9 pages)

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Executive Summary: Information found in this report covers the years 1986 through 2005. Mussel Watch began monitoring a suite of trace metals and organic contaminants such as DDT, PCBs and PAHs. Through time additional chemicals were added, and today approximately 140 analytes are monitored. The Mussel Watch Program is the longest running estuarine and coastal pollutant monitoring effort conducted in the United States that is national in scope each year. Hundreds of scientific journal articles and technical reports based on Mussel Watch data have been written; however, this report is the first that presents local, regional and national findings across all years in a Quick Reference format, suitable for use by policy makers, scientists, resource managers and the general public. Pollution often starts at the local scale where high concentrations point to a specific source of contamination, yet some contaminants such as PCBs are atmospherically transported across regional and national scales, resulting in contamination far from their origin. Findings presented here showed few national trends for trace metals and decreasing trends for most organic contaminants; however, a wide variety of trends, both increasing and decreasing, emerge at regional and local levels. For most organic contaminants, trends have resulted from state and federal regulation. The highest concentrations for both metal and organic contaminants are found near urban and industrial areas. In addition to monitoring throughout the nation’s coastal shores and Great Lakes, Mussel Watch samples are stored in a specimen bank so that trends can be determined retrospectively for new and emerging contaminants of concern. For example, there is heightened awareness of a group of flame retardants that are finding their way into the marine environment. These compounds, known as polybrominated diphenyl ethers (PBDEs), are now being studied using historic samples from the specimen bank and current samples to determine their spatial distribution. We will continue to use this kind of investigation to assess new contaminant threats. We hope you find this document to be valuable, and that you continue to look towards the Mussel Watch Program for information on the condition of your coastal waters. (PDF contains 118 pages)

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Eterio Pajares, Raquel Merino y José Miguel Santamaría (eds.)

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The microgravity research, as a branch of the advanced sciences and a spe- cialized field of high technology, has been made in China since the late 1980's. The research group investigating microgravity fluid physics consisted of our col- leagues and the authors in the Institute of Mechanics of the Chinese Academy of Sciences (CAS), and we pay special attention to the floating zone convection as our first research priority. Now, the research group has expanded and is a part of the National Microgravity Laboratory of the CAS, and the research fields have been extended to include more subjects related to microgravity science. Howev- er, the floating zone convection is still an important topic that greatly holds our research interests.

目录

1. models of floating zone convection
1.1 floating-zone crystal growth
1.2 physical model
1.3 hydrodynamic model
1.4 mathematical model
references
2. basic features of floating zone convection
2.1 equations and boundary conditions
2.2 simple solutions of fz convection
2.3 solution for two-layers flow
2.4 numerical simulation
2.5 onset of oscillation
references
3. experimental method of fz convection
3.1 ground-based simulation experiments for pr≥1
3.2 temperature and velocity oscillations
3.3 optical diagnostics of free surface oscillation
3.4 critical parameters
3.5 microgravity experiments
3.6 ground-based simulation experiment for pr《1
.references
4. mechanism on the onset of oscillatory convection
4.1 order of magnitude analysis
4.2 mechanism of hydrothermal instability
4.3 linear stability analysis
4.4 energy instability of thermocapillary convection
4.5 unsteady numerical simulation of 2d and 3d
4.6 two bifurcation transitions in the case of small pr number fluid
4.7 two bifurcation transitions in the case of large pr number fluid
4.8 transition to turbulence
references
5. liquid bridge volume as a critical geometrical parameter
5.1 critical geometrical parameters
5.2 ground-based and mierogravity experiments
5.3 instability analyses of a large prandtl number (pr≥1)fluid
5.4 instability analyses of a small prandtl number (pr《1)fluid
5.5 numerical simulation on two bifurcation process
references
6. theoretical model of crystal growth by the floating zone method
6.1 concentration distribution in a pure diffusion process
6.2 solutal capillary convection and diffusion
6.3 coupling with phase change convection
6.4 engineering model of floating zone technique
references
7. influence of applied magnetic field on the fz convection
7.1 striation due to the time-dependent convection
7.2 applied steady magnetic field and rotational magnetic field
7.3 magnetic field design for floating half zone
7.4 influence of magnetic field on segregation
references
8. influence of residual acceleration and g-jitter
8.1 residual acceleration in microgravity experiments
8.2 order of magnitude analyses (oma)
8.3 rayleigh instability due to residual acceleration
8.4 ground-based experiment affected by a vibration field
8.5 numerical simulation of a low frequency g-jitter
8.6 numerical simulation of a high frequency g-jitter
references

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In the past few years, large-scale, high-seas driftnet fishing has sparked intense debate and political conflict in many oceanic regions. In the Pacific Ocean the driftnet controversy first emerged in the North Pacific transition zone and subarctic frontal zone, where driftnet vessels from Japan, the Republic of Korea, and Taiwan pursue their target species of neon flying squid. Other North Pacific driftnet fleets from Japan and Taiwan target stocks of tunas and billfishes. Both types of driftnet fishing incidentally kill valued non-target species of marine life, including fish, mammals, birds, and turtles. In response to public concerns about driftnet fishing, government scientists began early on to assemble available information and consider what new data were required to assess impacts on North Pacific marine resources and the broader pelagic ecosystem. Accordingly, a workshop was convened at the NMFS Honolulu Laboratory in May 1988 to review current information on the biology, oceanography, and fisheries of the North Pacific transition zone and subarctic frontal zone. The workshop participants, from the United States and Canada, also developed a strategic plan to guide NMFS in developing a program of driftnet fishery research and impact assessment. This volume contains a selection of scientific review papers presented at the 1988 Honolulu workshop. The papers represent part of the small kernel of information available then, prior to the expansion of cooperative international scientific programs. Subsequent driftnet fishery monitoring and research by the United States, Canada, Japan, Korea, and Taiwan have added much new data. Nevertheless, this collection of papers provides a historical perspective and contains useful information not readily available elsewhere. (PDF file contains 118 pages.)

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The aims of this paper are twofold. Firstly to characterise rural poverty and to give a broad overview of the agro-ecological, climatic and socio-economic conditions in Sri Lanka which shape poverty. Secondly to present the methodology employed to screen suitable field research areas and the techniques subsequently used to carry out Rapid Rural Appraisal in two upper-watersheds villages. Also presented are details of a concurrent stakeholder analysis that aimed to investigate the capacity of secondary stakeholders to promote sustainable aquatic resource development and to invite their participation in the formulation of a participatory research agenda.[PDF contains 58 pages]

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Village tanks are put to a wide range of uses by the rural communities that depend on them for their survival. As the primacy of irrigation has decreased under these tanks due to a variety of climatic and economic reasons there is a need to reevaluate their use for other productive functions. The research presented in this paper is part of a programme investigating the potential to improve the management of living aquatic resources in order to bring benefits to the most marginal groups identified in upper watershed areas. Based on an improved typology of seasonal tanks, the seasonal changes and dynamics of various water quality parameters indicative of nutrient status and fisheries carrying capacity are compared over a period of one year. Indicators of Net (Primary) Productivity (NP): Rates of Dissolved Oxygen (DO) change, Total Suspended Solids (TSS): Total Suspended Volatile solids (TVSS) ratios are the parameters of principle interest. Based on these results a comparative analysis is made on two classes of ‘seasonal’ and ‘semi-seasonal’ tanks. Results indicate a broad correlation in each of these parameters with seasonal trends in tank hydrology. Highest productivity levels are associated with periods of declining water storage, whilst the lowest levels are associated with the periods of maximum water storage shortly after the NW monsoon. This variation is primarily attributed to dilution effects associated with depth and storage area. During the yala period, encroachment of the surface layer by several species of aquatic macrophyte also has progressively negative impacts on productivity. The most seasonal tanks show wider extremes in seasonal nutrient dynamics, overall, with less favourable conditions than the ‘semi-seasonal’ tanks. Never the less all the tanks can be considered as being highly productive with NP levels comparable to fertilised pond systems for much of the year. This indicates that nutrient status is not likely to be amongst the most important constraints to enhancing fish production. Other potential management improvements based on these results are discussed. [PDF contains 19 pages]

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Approximately 100,000 cubic yards of sand was transported to the ocean beach to renourish the eroded beach front during the period December 1985 through May 1986. The ocean beach at Sebastian Inlet SRA was previously studied in a project examining the benthic macrofauna and the fishes of the nearshore zone during 1981-1982 (Allenbaugh, 1984; Peters, 1984; Nelson, unpublished). In view of the existing data, the US Army Corps of Engineers provided funding to study the effects of the beach renourishment activities at Sebastian Inlet SRA on the benthic macrofauna and the fishes of the nearshore zone. This is the report on the results of this study.

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Samples of zooplankton and fish were collected from six sampling points in Nyanza Gulf, Lake Victoria in Kenya from June to December 1998, using 76 mu m memo-filament mesh size strainer and an 80 mu m mesh size plankton net. Identification and enumeration were done in the laboratory. Occurrence, numerical and points methods were used in stomach anlaysis of fish. Copepoda, Rotifera and Cladocera were the major zooplankton groups identified, zooplankton such as Moina, Daphnia and Caridina nilotica were important prey items for Lates niloticus, Oreochromis niloticus and Rastrineobola argentea

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Questionnaires containing 39 questions were prepared and administered to 50 women in ten fishing villages in the Southern Kainji Lake Basin to assess the level of women participation in fisheries activities. Results showed that 100% of the women interviewed were involved in fisheries activities and the following factors were considered. Age group between 20-30 years was 18%; 31-40 years; 30%; and above 40 years had the highest percentage of 40%. Also 98% of the women involve in fisheries activities were married while only 2% were not married. Muslin women constituted 82% while 18% were Christians. About 70% of Hausas were involved: no Igbos and Yorubas, while 30% were other tribes, which included Ijaws, Isokos and Urohobos. The percentage of women without education amounted to 62%, those women with Koranic education accounted for 22%, 14% had primary education while only 2% had secondary education. Few women were directly involved in fishing and statistical analysis showed that there was insignificant difference from village to village. All the women (100%) were involved in fish processing and storage (preservation) before sale. Only 26% of the women were not involved in fish marketing. Also 26% of the women made profits ranging from N500 to N1,000 per week, 24% make N1,000 to N1,500 per week, 12% made N1,500 to N2,000 and 38% made profit above N2,000. Statistical analysis showed that there was a significant difference in the profit made by the women (P<0.05) from the foregoing, women were actively involved in all fisheries activities

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This thesis consists of two separate parts. Part I (Chapter 1) is concerned with seismotectonics of the Middle America subduction zone. In this chapter, stress distribution and Benioff zone geometry are investigated along almost 2000 km of this subduction zone, from the Rivera Fracture Zone in the north to Guatemala in the south. Particular emphasis is placed on the effects on stress distribution of two aseismic ridges, the Tehuantepec Ridge and the Orozco Fracture Zone, which subduct at seismic gaps. Stress distribution is determined by studying seismicity distribution, and by analysis of 190 focal mechanisms, both new and previously published, which are collected here. In addition, two recent large earthquakes that have occurred near the Tehuantepec Ridge and the Orozco Fracture Zone are discussed in more detail. A consistent stress release pattern is found along most of the Middle America subduction zone: thrust events at shallow depths, followed down-dip by an area of low seismic activity, followed by a zone of normal events at over 175 km from the trench and 60 km depth. The zone of low activity is interpreted as showing decoupling of the plates, and the zone of normal activity as showing the breakup of the descending plate. The portion of subducted lithosphere containing the Orozco Fracture Zone does not differ significantly, in Benioff zone geometry or in stress distribution, from adjoining segments. The Playa Azul earthquake of October 25, 1981, Ms=7.3, occurred in this area. Body and surface wave analysis of this event shows a simple source with a shallow thrust mechanism and gives Mo=1.3x1027 dyne-cm. A stress drop of about 45 bars is calculated; this is slightly higher than that of other thrust events in this subduction zone. In the Tehuantepec Ridge area, only minor differences in stress distribution are seen relative to adjoining segments. For both ridges, the only major difference from adjoining areas is the infrequency or lack of occurrence of large interplate thrust events.

Part II involves upper mantle P wave structure studies, for the Canadian shield and eastern North America. In Chapter 2, the P wave structure of the Canadian shield is determined through forward waveform modeling of the phases Pnl, P, and PP. Effects of lateral heterogeneity are kept to a minimum by using earthquakes just outside the shield as sources, with propagation paths largely within the shield. Previous mantle structure studies have used recordings of P waves in the upper mantle triplication range of 15-30°; however, the lack of large earthquakes in the shield region makes compilation of a complete P wave dataset difficult. By using the phase PP, which undergoes triplications at 30-60°, much more information becomes available. The WKBJ technique is used to calculate synthetic seismograms for PP, and these records are modeled almost as well as the P. A new velocity model, designated S25, is proposed for the Canadian shield. This model contains a thick, high-Q, high-velocity lid to 165 km and a deep low-velocity zone. These features combine to produce seismograms that are markedly different from those generated by other shield structure models. The upper mantle discontinuities in S25 are placed at 405 and 660 km, with a simple linear gradient in velocity between them. Details of the shape of the discontinuities are not well constrained. Below 405 km, this model is not very different from many proposed P wave models for both shield and tectonic regions.

Chapter 3 looks in more detail at recordings of Pnl in eastern North America. First, seismograms from four eastern North American earthquakes are analyzed, and seismic moments for the events are calculated. These earthquakes are important in that they are among the largest to have occurred in eastern North America in the last thirty years, yet in some cases were not large enough to produce many good long-period teleseismic records. A simple layer-over-a-halfspace model is used for the initial modeling, and is found to provide an excellent fit for many features of the observed waveforms. The effects on Pnl of varying lid structure are then investigated. A thick lid with a positive gradient in velocity, such as that proposed for the Canadian shield in Chapter 2, will have a pronounced effect on the waveforms, beginning at distances of 800 or 900 km. Pnl records from the same eastern North American events are recalculated for several lid structure models, to survey what kinds of variations might be seen. For several records it is possible to see likely effects of lid structure in the data. However, the dataset is too sparse to make any general observations about variations in lid structure. This type of modeling is expected to be important in the future, as the analysis is extended to more recent eastern North American events, and as broadband instruments make more high-quality regional recordings available.