• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 285
  • 203
  • 58
  • 12
  • 11
  • 9
  • 5
  • 4
  • 4
  • 3
  • 3
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 715
  • 257
  • 230
  • 137
  • 125
  • 100
  • 71
  • 55
  • 51
  • 46
  • 41
  • 41
  • 38
  • 38
  • 37
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
261

Linkages between environmental conditions and recreational king mackerel catch off west-central FLorida

Wall, Carrie C 01 June 2006 (has links)
The objective of this study was to determine if fronts sustained up to three days will result in an aggregation of kingfish due to the anticipated accumulation of forage, increasing fishing success at these locations. Automated algorithms to detect frontal features in satellite-derived sea surface temperature, chlorophyll concentration, water clarity, and fluorescence images were successfully adapted for the coastal waters off west-central Florida. The surface ocean fronts were used to study the linkages between environmental conditions and recreational catch statistics of king mackerel (Scomberomorus cavalla) during 19 seasonal tournaments held in April to May and October to November of 2004 and 2005. The local winds estimated from a USF Coastal Ocean Monitoring and Prediction System observing station were analyzed with the frontal data to examine factors that influence oceanic frontal formation and stability. The front detection algorithms were also applied to high-r esolution bathymetry data which serves as a new technique for analyzing bottom topography. The spatial relationships between catch data collected through 415 angler interviews, frontal boundaries and stability, bathymetric gradients, bottom structure, and baitfish presence were identified using ESRI ArcGIS.Fishing success and fishing effort were highly variable regarding the distance of fishing activity to the nearest front. This was attributed to non-persistent winds. Intermediate water clarity (0.7 to 1.0 mW cm-2 microm-1 sr-1), the presence of baitfish, and the side of the front with relatively less chlorophyll showed the greatest influence on the king mackerel catch rates. Fishing success was found to be significantly higher at fishing locations where baitfish were reported present compared to where they were not reported. Concurrent with the 2005 harmful algal bloom event, a significant decrease in king mackerel catch occurred in the fall of 2005 (208 fish) compared to fall 20 04 (818) and spring 2005 (538). Additionally, fishing locations with baitfish present were observed about 15% less often during the fall of 2005 than the preceding seasons. From this, a model can be developed to diagnose the environmental conditions that can be used by resource managers to better understand variations in catch, which result from naturally occurring phenomena or man-induced overfishing.
262

Micronekton and Macrozooplankton of the Western Antarctic Peninsula and the Eastern Ross Sea: Contrast Between Two Different Thermal Regimes

Parker, Melanie Leigh 01 January 2012 (has links)
ABSTRACT Micronekton and macrozooplankton were sampled from the Western Antarctic Peninsula (WAP) and eastern Ross Sea regions. Samples were collected over the course of six research cruises to the Southern Ocean. Four of those cruises were conducted in the Marguerite Bay region of the WAP during the austral fall and winter of 2001 and 2002. A fifth cruise sampled faunal assemblages at nine sites, ranging from Joinville Island at the northern tip of the WAP to Charcot Island near the southern extent of the WAP, during austral fall 2010. A sixth cruise was conducted in the pack ice within the offshore, continental slope, and continental shelf zones of the Eastern Ross Sea during austral summer 1999/2000. The purpose of this dissertation was to describe the macrozooplanktonic/ micronektonic faunal assemblages present in each of those regions and relate differences in species composition and distribution patterns to local bathymetry, hydrography, and physical conditions. A variety of multivariate techniques were used to identify unique multispecies assemblages and to quantify the contributions of both oceanic and neritic species to the assemblages within each study region. The invertebrate micronekton/macrozooplankton communities found in the Marguerite Bay region of the WAP during the 2001/2002 cruises were a mixture of oceanic and neritic fauna: a direct result of local hydrographic conditions. Near the shelf break and in the outer reaches of the Marguerite Trough, a deep canyon transecting the shelf in a south-southeast direction, the communities were more diverse, dominated by oceanic species such as the euphausiid, Euphausia triacantha, the salp, Salpa thompsoni, and, an amphipod, Themisto gaudichaudii. The assemblages present in the nearshore fjords exhibited lower diversity and were dominated by neritic species such as the euphausiid, E. crystallorophias, and the mysid, Antarctomysis ohlinii. At the mid-shelf and mid-trough locations, the assemblages were composed of a variable mixture of oceanic and neritic fauna. The faunal mixing and overall species composition in those areas is the result of episodic Circumpolar Deep Water (CDW) intrusions onto the shelf via deep bathymetric features such as the Marguerite Trough. Distinct multispecies assemblages were identified at Joinville, Croker Passage, Marguerite Bay, Charcot Island, and from a region that included samples from sites near Anvers Island, Renaud Island and the Marguerite Trough. Assemblages at Joinville and Croker Passage were both dominated by E. superba and S. thompsoni, but hydrographic conditions at Joinville favored a neritic assemblage, underscored by the substantial numbers of the nototheniid fish, Pleuragramma antarcticum. The assemblage at Croker Passage was more oceanic in nature with major inputs from the myctophid fish, Electrona antarctica and the amphipod, T. gaudichaudii. Marguerite Bay and Charcot Island were well-mixed assemblages with strong representation by both neritic and oceanic fauna. The mid-peninsula assemblage was also oceanic in character, being overwhelmingly dominated by the euphausiid, Thysanoessa macrura, and T. gaudichaudii. Pleuragramma antarcticum were captured at five sites: Joinville, Croker Passage, Marguerite Bay, and the two sites near Charcot Island. They were completely absent at the two sites near Anvers Island, at Renaud Island, and in the Marguerite Trough. In the eastern Ross Sea, cluster analyses identified three primary groups, which were characterized as oceanic, mixed, and neritic assemblages due partly to their geographical location, but mostly to their faunal composition. The oceanic assemblage contained the highest number of taxa and was dominated by oceanic fauna, such as the hydrozoans Diphyes antarctica and Calycopsis borchgrevinki, and the scyphozoan Atolla wyvillei. Top contributors in the mixed assemblage included those species that dominated in the oceanic assemblage as well as substantial contributions from E. superba and the tunicate, Ihlea racovitzai. The neritic assemblage was overwhelmingly dominated by E. crystallorophias and E. superba. The physical environment strongly impacted micronektonic/ macrozooplanktonic distributions and densities in the eastern Ross Sea. Changes in faunal composition were directly related to temperature differences encountered at the shelf break and the subsequent filtering out of oceanic fauna from cold, shelf waters where endemic fauna were most prevalent.
263

Sand distribution along shelf-edge deltaic systems : a case study from eastern offshore Trinidad

Davila-Chacon, Anmar Carolina 15 February 2011 (has links)
The study area is situated along the obliquely converging boundary of the Caribbean and South American plates offshore eastern offshore Trinidad. Major structural elements in the shelf break and deep-water slope regions include normal and counter-normal faults to the south and large transpressional fault zones to the north. Well logs and biostratigraphic information were analyzed for twenty-four wells in the study area to refine previous depositional environment interpretations. For purposes of this net sand distribution analysis it was decided to consider the deltaic portion of the shelf transit cycle, against the marine portion of the shelf transit cycle and were named T and R cycles, respectively. T and R cycles were interpreted based on well log patterns and depositional facies shifts. Six T/R cycles were interpreted within the Pliocene to recent stratigraphic succession and shelf edge trajectories were also mapped for each of these cycles based on earlier stratigraphic correlations. Net-to-gross (NTG) ratios were calculated for each component of the T/R cycles and plotted against total thicknesses and net sand values. In addition, NTG trends were mapped for each interval and analyzed based on their proximity to the corresponding shelf edge. Mapping of the shelf edge trajectories (SET) revealed that (1) SET migrate northeasterly across the Columbus Basin through time and (2) shelf edge orientations are parallel to the strike of growth faults in the south but deflect to the northeast near the Darien Ridge indicating a strong underlying structural control. The NTG plots and maps also revealed that (1) For T cycles, NTG values never exceed 60% and are inversely proportional to total thickness, (2) For R cycles, NTG values are highly variably ranging from 35% to 90%, (3) NTG values increase as the shelf break is approached and (4) The distribution of NTG ratios is also controlled by accommodation space created by local structures. The Guiana current is believed to play an important role in the redistribution and reworking of sand in the Columbus Basin. Aggradation and progradation distances were computed for each interval and the results suggest that the younger Sequences C2 (T-R cycle E) and C3 (T-R cycle F) show a stronger progradational trend than the older C4, C5 and C6. This strong progradational trend might indicate delivery of sand basinwards, while for the older intervals; the aggradational trend suggests an increase in sediment storage. In long-term scale (1-2 m.y.) the Orinoco Delta seems to behave as an aggradational delta that increases sediment storage due to growth fault and high subsidence rates. However, in the short-term scale, the Orinoco delta seems to behave as a rapid progradational delta, for the younger sequences C2 and C3, where sediment bypass is more likely to occur; and as a rapid aggradational (slow prograding) margin for the older intervals C4, C5 and C6. / text
264

Seismic wave propagation through flood basalts and stratigraphic correlation on the Faroes shelf

Schuler, Juerg January 2013 (has links)
No description available.
265

Impacts of Bubbles on Optical Estimates of Calcium Carbonate in the Great Calcite Belt

Brown, Michael Scott 20 March 2014 (has links)
In this MSc thesis I determine if wind-generated bubbles elevated measurements of above-water normalized water-leaving radiance (nLw) and subsequent remote sensing estimates of particulate inorganic carbon (PIC) in a coccolithophore bloom on the Patagonian Shelf. Although no measurements were made of bubbles, shipboard wind speed was used as a proxy for bubble backscattering. An empirical orthogonal function (EOF) analysis was performed on nLw. The first EOF accounted for 95% of the variance, and was attributed to changes in spectral amplitude. Scores of the first EOF were positively correlated with flow-through PIC backscattering (bb′) > 5x10-4 m-1, indicating that above this threshold PIC was an optically active seawater constituent. There was only evidence for a bubble elevation of nLw at values of bb′ < 5x10-4 m-1 and wind speeds > 12.5 m s-1. There was no evidence for a bubble elevation of PIC estimated using the two-band PIC algorithm.
266

Consumers' attitudes regarding the link between frozen and fresh vegetables and health / Emdri Maria van der Walt

Van der Walt, Emdri Maria January 2003 (has links)
Vegetables and fruit appear to confer protection against various diseases, but most adults in South Africa eat substantially less than the recommended amounts. Many barriers and factors that influence vegetable consumption have been identified in the literature. One major barrier is the perishability of vegetables. Frozen vegetables can be a useful way in encouraging greater intakes. Some consumers are, however, of the opinion that processing destroy nutrients to a large extent. There is, therefore, a lack of understanding of the freezing process. Research on the attitudes of consumers towards frozen vegetables in South Africa is limited. Objective: The purpose of this study was to determine the attitudes of consumers regarding the link between frozen and fresh vegetables and health and the attributes of frozen vegetables. Subjects/Setting: One thousand nine hundred and ninety seven South African respondents, representative of the four major race groups of South Africa (whites, blacks, coloureds and Indians) were randomly chosen from metropolitan areas from the nine provinces in South Africa. Questionnaires, existing of 17 food-related sections, including subsections on vegetables and health, were designed by researchers in co-operation with business partners. MARKINOR, a market research company, was contracted to collect the data. Respondents were questioned regarding their attitudes towards the link between frozen and fresh vegetables and health. Statistical analysis performed: The quantitative data produced by the survey was analysed by using the StatisticaⓇ-programme in order to generate the relevant tabulations, descriptive statistics and statistical tests. Results: Overall, the attitudes of consumers towards frozen vegetables were found to be negative. Practical and statistically significant attitude differences towards frozen vegetables were found between most variables. Results from this study revealed that different levels of education, age and gender do not have a big influence on consumer's attitudes towards frozen vegetables. However, practical and statistically significant differences were found between the various LSM (Living Standards Measure) groups, especially with regard to the convenience of frozen vegetables. Results also indicated that Indians, the age group 61+ and males were the most negative towards frozen vegetables. Almost 75% of all consumers indicated that they never eat frozen vegetables. Only 1% of consumers in the LSM group 2 own a fridge/freezer. An alarmingly 26% of all consumers indicated that they are not convinced that vegetables are healthy. Application/Conclusions: Nutrition professionals should use these findings to target messages in health-promotion programmes to increase the overall consumption of vegetables. The use of frozen vegetables by consumers with frozen storage facilities should be promoted aggressively. Consumers also need practical advice on how to overcome the barriers to dietary change. Nutrition counseling efforts should also be aimed specifically at increasing frozen vegetable consumption among targeted subgroups, particularly Indians, males and the age group 61+. It is strongly recommended that suitable measuring instruments be developed for assessing the knowledge and attitude of South Africans towards vegetable and fruit consumption and the ability of individuals to improve their health. The results of this study may prove to be very useful in this regard. / Thesis (M.Sc. (Dietetics))--North-West University, Potchefstroom Campus, 2004.
267

ECONOMIC AND EXPLORATORY REVIEW OF GAS HYDRATES AND OTHER GAS MANIFESTATIONS OF THE URUGUAYAN CONTINENTAL SHELF

de Santa Ana, Hector, Latrónica, Luis, Tomasini, Juan, Morales, Ethel, Ferro, Santiago, Gristo, Pablo, Machado, Larisa, Veroslavsky, Gerardo, Ucha, Nelson 07 1900 (has links)
This contribution aims to publicize the efforts made in the identification of gas hydrates in the Uruguayan continental shelf, analyze the most outstanding aspects related to its energy potential, as well as include this topic in other areas of knowledge for a comprehensive understanding of the subject. The hydrates, crystalline solid formed mainly by water and natural gas, are reservoirs of carbon that occur naturally in the continents in permafrost areas, and at sea, in the offshore basins of continental margins. They contain more than twice the total carbon in the world, surpassing the conventional hydrocarbon reserves. Principal energy programs foresee its commercial exploitation by 2015. International research programs include not only the energy aspect, but studying such systems considering their participation in the global carbon cycle, climate change and benthic communities associated with them. In our country, several seismic surveys showed evidence of the presence of gas hydrates in continental shelf and the surrounding area. The first survey was carried out by Brazil in the south of the Brazilian continental shelf, ANCAP then showed the continuity of the hydrate layer on the Uruguayan continental shelf and estimated the gas potential of the mineralized layer (87 TCF). Finally, the BGR survey verified the existence of seismic evidence of gas hydrates layer and the presence of free gas below these. The typical seismic response of gas hydrate and free gas is the BSR (Bottom Simulating Reflector) and is interpreted as a positive intensity reflection, followed by a negative intensity, showing the wave passage from a high acoustic impedance zone to a low acoustic impedance zone.
268

Provenance and Depositional History of Late Pleistocene New Jersey Shelf Sediments

Turner, Roxie Jessica 12 May 2005 (has links)
Pleistocene New Jersey shelf sedimentology is strongly influenced by glacially driven sea level changes. A combination of regressive shoreline processes, subaerial exposure, fluvial downcutting, and deposition and reworking during transgression has influenced the NJ shelf sediment composition. Sediment provenance and transport history may be determined on a shelf environment through analysis of grain size distribution, heavy mineral content, magnetic mineral concentrations, and isotopic dating methods. A combination of surface grab and stratigraphic samples were analyzed within the study area. Relatively high percentages of heavy minerals were found in the 2 phi and 3 phi size fractions and hornblende grains provided K-Ar age values indicating two groups of sediment sources. The first source is Grenville with apparent ages above 900 Ma deposited during marine OIS 1. The second source is a mixed assemblage of Grenvillian and Paleozoic sources deposited during marine OIS 3, with apparent ages of approximately 850 ± 20 Ma.
269

Ascophyllm nodosum Extracts Improve Shelf Life and Nutritional Quality of Spinach (Spinacia oleracea L.)

Fan, Di 29 September 2010 (has links)
In order to develop an environmentally friendly seaweed extract treatment which will benefit both pre- and post-harvest qualities of vegetables, the effects of pre-harvest application of the brown algae Ascophyllum nodosum extracts on the nutritional quality and post-harvest storability of spinach (Spinacia oleracea L.) was investigated. Plants treated with A. nodosum extracts accumulated higher concentrations of iron, potassium, total soluble protein, and total phenolics as compared to untreated controls. 1H NMR and LC-MS analysis revealed a roughly 50% enhanced accumulation of the 9 flavonoids identified, which is partially confirmed by the elevated chalcone isomerase activity. A. nodosum extract treatment caused an increase in transcription of the genes related to plant growth, osmolyte accumulation, and antioxidative activities. Post-harvest analysis revealed that A. nodosum extract treatment caused an enhanced storability of spinach leaves in terms of visual quality, weight loss, and senescence. Lipid peroxidation and ascorbate content were correlated with visual quality during storage. Animal experiments using the Caenorhabditis elegans nematode model revealed that spinach extracts prolonged the life span of C. elegans, and A. nodosum extract-enhanced polyphenols exerted improved beneficial effects in C. elegans against oxidative and heat stresses. Taken together, the results suggest that A. nodosum extracts enhance both pre- and post-harvest quality of spinach through stimulation of flavonoid pathways, thus leading to accumulation of flavonoids and promotion of anti-radical capacity in spinach leaves, which may protect the plant tissue against reactive oxygen species and subsequent decay. Furthermore, the increased flavonoid content in spinach exerted beneficial effects in C. elegans against oxidative and heat stresses via different mechanisms.
270

D-6 naftos telkinio eksploatacija tarptautinės jūrų teisės požiūriu / D-6 oil fields exploitation in the background of the international maritime law

Milvydas, Ričardas 05 February 2013 (has links)
Magistro baigiamajame darbe “D-6 naftos telkinio eksploatacija tarptautinės jūrų teisės požiūriu” analizuojami tarptautinės teisės šaltiniai, reglamentuojantys jūrinių naftos platformų statybą, eksploataciją bei atsakomybę už jų sukeltą žalą kitai valstybei. Nagrinėjama kurios tarptautinės sutartys, kiti teisės aktai yra privalomi Rusijos Federacijai ir turi būti taikomi eksploatuojant naftos telkinius Baltijos jūros kontinentiniame šelfe Rusijos jurisdikcijos zonoje. Taip pat darbe yra nurodomi atvejai, kuriais Rusija nesilaikė jai privalomų tarptautinės teisės normų projektuodama, statydama ir eksploatuodama naftos platformą D-6. Analizuojama, ar Rusijos Federacija būtų atsakinga prieš Lietuvos Respubliką už žalą, kuri gali kilti eksploatuojant D-6 naftos platformą. Tuo tikslu nagrinėjami du atsakomybės taikymo pagrindai: atsakomybė už tarptautinės teisės normų pažeidimus ir atsakomybė už kitos valstybės interesams padarytą žalą veiksmais, kurių nedraudžia tarptautinė teisė. Vertinant “griežtos” atsakomybės taikymo principą analizuojamas JT Tarptautinės teisės komisijos darbas šioje srityje. Siekiama nustatyti, ar yra susiformavęs tarptautinis paprotys, numatantis tokią valstybės atsakomybę už sukeltą žalą. Darbo pabaigoje pateikiamos išvados. Remiantis atlikto tyrimo rezultatais konstatuojama, kad projektuojant ir statant D-6 naftos platformą buvo pažeistos tarptautinės teisės normos, tačiau šiuo metu eksploatuojant platformą Rusija laikosi tarptautinės teisės reikalavimų... [toliau žr. visą tekstą] / The Master’s thesis “D-6 oil fields exploitation in the background of the international maritime law” analyzes sources of the international law governing construction and exploitation of offshore platforms as well as responsibility for the damages to other countries caused by such platforms. The thesis also analyzes which international treaties and other legislation are mandatory to the Russian Federation and must be followed in exploiting oil fields continental shelf in the Baltic Sea in the area of the Russian jurisdiction. Besides, the thesis provides for the cases where Russia violated mandatory legislation in planning, erecting and exploiting oil platform D-6. Furthermore, the thesis analyzes whether the Russian Federation would be liable against the Republic of Lithuania for the damages which may arise from exploitation of D-6 oil platform. To that end, the thesis analyzes two principles of liability: liability for violations of the international legislation and liability for the damages to the interests of the other country resulting from the actions not prohibited by the international law. For assessment of the principle of application of “strict” liability, the work done by the UN International Law Commission is analyzed. Attempts are made to find out whether there is an international custom providing for the country’s liability for the caused damages. The thesis is finalized by the findings. Taking into consideration the research results it is stated that planning... [to full text]

Page generated in 0.068 seconds