• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 125
  • 52
  • 44
  • 32
  • 32
  • 32
  • 32
  • 32
  • 32
  • 24
  • 6
  • 5
  • 3
  • 2
  • 2
  • Tagged with
  • 346
  • 346
  • 57
  • 43
  • 40
  • 38
  • 38
  • 33
  • 29
  • 29
  • 29
  • 27
  • 26
  • 26
  • 25
  • 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.
281

Australian Quaternary studies : a compilation of papers and documents submitted for the degree of Doctor of Science in the Faculty of Science, University of Adelaide / by Patrick De Deckker.

De Deckker, P. (Patrick) January 2002 (has links)
"April 2002" / Includes bibliographical references and list of the publications and papers submitted. / 2 v. (various pagings) : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Contains the majority of the author's scientific publications. Aims at reconstructing Quaternary paleoenvironments, mostly from the Australian region, using the fossil remains of organisms as well as new geochemical techniques. / Thesis (D.Sc.)--University of Adelaide, Dept. of Geology and Geophysics, 2002
282

Studies on the marine algae of southern Australia / by H.B.S. Womersley / The marine algae of Kangaroo Island. 1-4 / Marine coastal zonation in southern Australia in relation to a general scheme of classification / A general account of the intertidal ecology of South Australian coasts / Protochara, a new genus of characeae from Western Australia / The archipelago of the recherche. 3b, Marine algae / The species of macrocystis with special reference to those on southern Australian coasts / Australian species of Sargassum subgenus Phyllotrichia / A new marine Vaucheria from Australia / New marine Chlorophyta from southern Australia / A critical survey of the marine algae of southern Australia. 1, Chlorophyta / The genus Codium (Chlorophyta) in southern Australia / Marine algae from Arnhem Land, North Australia / The structure and reproduction of Gulsonia annulata Harvey (Rhodophyta) / Studies on the Sarcomenia group of the Rhodophyta / The marine algae of Australia / A free floating marine red algae / Sympodophyllum, a new genus of Delesseriaceae (Rhodophyta) from South Australia / The structure and systematic position of the Australiasian brown alga, Notheia anomala / The structure and systematic position of the Australiasian brown alga, Notheia anomala / Australian species of Sargassum subgenus Anthropycus

Womersley, H. B. S. (Hugh Bryan Spencer), 1922-, University of Adelaide. Dept. of Botany January 1959 (has links)
"Adelaide, Dec. 1959." / Includes bibliographical references. / 1 v. (various pagings) : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The studies included in this thesis have been carried out since 1946 in the Department of Botany, University of Adelaide. The 25 papers, reprints from various journals, have been grouped in two sections; firstly those on intertidal ecology; secondly taxonomic studies (in order of publication). One paper on a freshwater Charophyte is also included. / Thesis (D.Sc.)--University of Adelaide, Dept. of Botany, 1959
283

Lokala organ i Norden 1968-1986 : från idé till verklighet / Neighbourhood councils in the Nordic countries 1968-1986 : from idea to reality

Kolam, Kerstin January 1987 (has links)
Neighbourhood councils are sub-municipal committees which operate within a geographically delimited area of a municipality or a municipal department. Their activities cover a single established policy area such as social services (single functioned committee) or several areas such as education, leisure, and social issues (multi-functioned committee). The thesis includes a comparative analysis of the origin, occurance, and performance of multi-functioned neighbourhood councils in Finland, Norway, and Sweden during the period 1968-1986. In the case of Denmark, the debate is analyzed and the question posed as to why neighbourhood councils were not introduced during this period.It is the interplay between a number of factors which determines how and why neighbourhood councils occur and in some cases endure and are developed further. The countries' traditions and characteristics - such as the size of the public sector and local government's share of it, size of municipalities, and political culture - are important in this context. Increased democracy and greater effectivity were the main aims of the reform and these have been achieved to some extent. The occurance of neighbourhood councils also means that participation, recruitment, articulation of demands, and communication between elector and elected are changed and somewhat improved. Where neighbourhood councils exist, greater consideration is given to geographical (rather than departmental) principles in the distribution and redistribution of services and welfare. Neighbourhood councils are clearly a source of further variation between and within the Nordic countries. It is, however, too early to judge whether the variation within countries will develop into inappropriate deviations from the principal of equal services for all or if they, on the contrary, are indications of greater future responsiveness. / digitalisering@umu
284

Assessing landscape complexity using remotely sensed and field based measurements : does landscape complexity drive leafroller parasitism rates on Oregon caneberry farms?

Winfield, Tammy L. 08 March 2013 (has links)
Landscape heterogeneity is thought to differ among farm management types (i.e. organic and conventional), and this difference is hypothesized to result in variations in pest control by natural enemies. However, it is unclear if these variations in pest control are driven by landscape structure or by farm management practices themselves. Remotely sensed datasets were used to describe the landscape structure surrounding a group of organic and conventional caneberry farms in Oregon and Washington that have different leafroller parasitism rates attributed to farm management type. A finer scale survey was done at one of the farms using the remotely sensed data as well as field surveys. Landscape metrics of diversity, richness and percent non-crop were used to describe the landscapes surrounding the farm fields at scales ranging from 0.05 km to 5.00 km for the large scale study, and 0.05 km to 0.20 km for the fine scale study. In the fine scale study, data on parasitoid species assemblages, diversity, and parasitism rate were collected and analyzed against the calculated landscape metrics spatially and seasonally. The purpose of this study was to quantify effects of farm management type on habitat structure, effect of habitat structure on leafroller parasitism rate, and to access correlations between landscape metrics calculated at the landscape and field scale. Overall, the farms were embedded in a landscape that was broadly similar, with very few differences in landscape structure occurring between organic and conventional farms. Organic farms had higher vegetation height class diversity at the largest scale compared to conventional farms, while conventional farms had significantly higher percent non-crop area compared to organic farms. There was no significant effect of any of the calculated landscape metrics on parasitism rates. In the field scale study, no correlations were found between habitat metrics and parasitism rates, or between field based metrics and those calculated at the landscape scale. The results of this study suggest that conventional and organic caneberry farms in the Willamette Valley are broadly similar in the habitat conditions they provide parasitoids. This suggests that management changes to pesticide use alone could increase levels of leafroller biological control on conventional farms to levels that are comparable to those seen on organic farms. Our comparisons of the landscape scale and field scale landscape metrics showed no connection, this suggests that direct comparisons cannot be made with these particular metrics at these very different scales. Rather than comparing these types of data, it may be more useful to combine them in order to increase the resolution and predictive power of remotely sensed data for describing landscapes at broad scales. / Graduation date: 2013
285

Humpback whales (Megaptera novaeangliae) in the South Pacific breeding grounds : an allocation from feeding areas and an abundance estimate of whales specific to French Polynesia waters

Gibb, Giselle Renee 09 July 2009 (has links)
South Pacific humpback whales were devastated by commercial whaling in their Antarctic feeding areas during the 20th century. Understanding migratory connections and current abundance of these isolated breeding stocks is crucial for the allocation of historical Antarctic catches in population dynamic models used to assess current recovery. However, only a small number of migratory connections have been documented between Oceania breeding stocks within the South Pacific and feeding areas in the Antarctic. In addition, little is known about abundance of these stocks which encompass a vast oceanic region. For this thesis I first used mixed-stock analysis (MSA) to allocate migratory connections from four Antarctic feeding areas (n=142) to seven South Pacific breeding stocks (n=1,373), including four in Oceania, based on genetic marker frequencies. The use of this method was justified by the breeding stocks showing genetic differentiation at the haplotype level with an F[subscript ST] value of 0.027 (p-value <0.001). The results showed a relatively strong connection of Western Australia to Antarctic Area IV, Tonga to the border of Antarctic Area VI/I, Colombia to the Antarctic Peninsula, and a split allocation of Eastern Australia and New Caledonia to Antarctic Area V. This study provides the first population-level information supporting previous individual-based studies that humpback whale migration may not necessarily be direct north south. Next, utilizing capture-recapture methodology of unique humpback whale fluke photographs, I estimated abundance of one of the least studied Oceania breeding stocks, French Polynesia, a stock which also showed no significant migratory allocation using MSA. Taking into consideration the possible advantages of using Quality Control (QC) photographs to minimize bias in matching, estimates were generated using the complete photo catalogue and also using only photographs adhering to QC criteria. I found that the choice of using QC has an effect on the abundance generated and discuss the implications of this finding. Despite the photo catalogue used, the French Polynesia stock is estimated to number less than 1,900 individuals. Lastly, to provide additional information on the French Polynesia stock I used photo-identification to compare French Polynesia whales to whales in the Antarctic Peninsula and Strait of Magellan (Antarctic Area I), a possible migratory connection suggested by previous microsatellite genotyping. No conclusive matches were found. Although this does not discount the possibility of a few migrants traveling between these regions it does indicate the Antarctic Peninsula and the Strait of Magellan are not primary feeding areas of French Polynesia. This new information regarding abundance and migration of French Polynesia whales is important for the Comprehensive Assessment of Southern Hemisphere humpback whales. This document is currently being completed as the International Whaling Commission considers the next critical steps in recovery for Oceania humpback whales stocks. / Graduation date: 2010
286

Kriminalitetens geografi : vardagsbrottslighetens spatiala fördelning i Borlänge

Axelsson, Henrik January 2008 (has links)
The aim of this thesis is to describe and analyze the geographical distribution of everyday criminality in the town of Borlänge during the year 2002 and to analyze which measures to be taken in the physical social planning to decrease this everyday criminality there. The term everyday criminality is here to be understood as those categories of crime that appear most frequently in the records of reports to the police every year. Here two kinds of crime have been in focus, thefts from cars and office burglary.In fulfilling this aim two main questions have been answered. The first one is how the everyday criminality was distributed geographically in the town of Borlänge during the year 2002. The second one is which measures to be taken in the physical social planning to decrease this everyday criminality in the town of Borlänge.In order to answer the first question a spatial autocorrelation analysis, Local Moran LISA has been used. This method is based on the measurement Moran´s I and shows the spatial autocorrelation for every single location. To answer the second question three different theories of crime prevention through environmental design have been studied and applied in the analysis. These are Jane Jacobs’ ideas about ”the living city”, Oscar Newman´s ideas about ”defensible space” and Ronald V. Clarke´s theories about crime prevention.The major conclusions that can be drawn from this thesis are that the risk of being exposed to thefts from cars, during the analyzed time period, was highest in Centrum and Hagalund and their surroundings. The lowest risk of being exposed to this type of crime was found in Domnarvet and Islingby, during the year 2002. The highest risk of being a victim of the crime office burglary was found in Hagalund and its surroundings and in the single area of Kvarnsveden. The corresponding lowest risk was found in Lergärdet and its surroundings and in Norra Backa and Kupolen. The measures that should be taken in order to decrease these types of criminality can be divided into overall changes and place-specific changes. When it comes to the crime thefts from cars a more attractive central business district, a better view of parking lots from nearby buildings, dividing of larger parking lot zones into smaller ones, migration of hidden parking lots and stronger access control to parking lots where problems with this kind of crime have occurred have been suggested as overall changes. The corresponding place-specific changes are to remove vegetation that is blocking the view, better lighting and to put up signs with information about increased risk of exposure to crime at parking lots with the most problems. To decrease the amount of office burglaries overall changes as to create a better view of the area from nearby surroundings, move bigger office compartments or divide them into smaller units, rebuild characteristic buildings and increase security by strengthening the access control to offices with these kinds of problems could be useful. Finally there are possibilities to decrease office burglary by using place-specific measures as surveillance cameras combined with signs containing information about these, high fences and better lighting around the buildings where a higher risk of being exposed to this kind of criminality is present.
287

Dinoflagellate cyst assemblages and environmental factors controlling their distribution in New England (USA) estuaries

Pospelova, Vera January 2003 (has links)
Extensive data sets of water quality and sediment chemistry as well as detailed historical records were used to analyze environmental factors controlling dinoflagellate cyst distribution in shallow estuaries (lagoons and embayments) of southern New England. Cyst abundance, species richness, the proportion of cysts produced by heterotrophic and autotrophic dinoflagellates, and the composition of cyst assemblages reflect spatial and temporal variation in environmental conditions. The cyst record in sediment cores from two embayments, New Bedford Harbor and Apponagansett Bay, Massachusetts demonstrates cyst sensitivity to environmental change caused by anthropogenic activity in the watersheds. Intensive industrialization and urbanization occurred during the 20th century in New Bedford Harbor resulted in extreme eutrophication and toxic pollution (heavy metals and PCBs). These conditions are reflected in declining cyst diversity and wide fluctuation in total cyst production. At the same time, the proportion of certain heterotrophic taxa increases. As impacts of extreme eutrophication and toxic pollution cannot be separated, the cyst response must be interpreted as a cumulative «pollution signal». The spatial distribution of modern dinoflagellate cysts in the area supports this signal. Cysts vary along gradients of nutrient enrichment, corresponding to distance from sewage outfalls. Dinoflagellate cysts in surface sediments from New England lagoons also were studied. A comparison of assemblages to water quality parameters, that are affected greatly by the degree of water exchange between lagoon and ocean, indicates that temperature and salinity are the main abiotic factors controlling cyst distribution in these estuaries. A new species of dinoflagellate cyst, Islandinium brevispinosum, has been identified and described. This species was found within a narrow range of water temperature and salinity, and at elevated nutrient levels. Dinoflagellate cysts reflect environmental conditions at the small spatial scales necessary to characterize variability within estuaries. However, the relative importance of abiotic factors controlling the spatial and temporal distribution of dinoflagellate cysts is likely to vary with the hydrological differences between lagoons and embayments. Therefore, dinoflagellate cysts can be useful indicators of environmental conditions in and human impacts on shallow estuaries.
288

Ecological separation among fern species in an old-growth forest

Karst, Justine. January 2001 (has links)
The validity of niche-assembly rules in explaining community structure is revisited by testing for ecological separation among ferns. An intensive, fine-scale survey of fern abundance and environmental variation was done in 1-ha of old-growth forest. Three methods of detecting niche segregation (canonical correspondence analysis, detrended correspondence analysis and GIS mapping) suggested that most fern species at the site are distributed according to distinct environmental preferences. The most important gradients separating fern species are first, the amount of soil moisture and second, soil nitrate concentration. Contrary to other findings, pH had little influence on controlling fern distribution. Spatial autocorrelation, detected by partialled ordinations, obscured the presence of niche partitioning. As well, sampling grain changed the apparent location of some species on environmental gradients and their ecological similarity to other species. Finer-scaled environmental heterogeneity or dispersal-mediated processes may account for the unexplained variation in fern species abundance of this site.
289

Farmland birds in semi-natural pastures : conservation and management /

Söderström, Bo, January 1900 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.
290

Distribuição de bivalve invasor Limnoperna fortunei (Dunker, 1857) na Bacia do Rio Prata após vinte anos (1991-2014) de sua introdução na America do Sul /

Pessotto, Marco Aurélio. January 2015 (has links)
Orientador: Marcos Gomes Nogueira / Banca: Antonio Leão Castilho / Banca: Eliana Aparecida Passareli / Resumo: O mexilhão-dourado (Limnoperna fortunei) é um bivalve de água doce pertencente à família Mytilidae. Originário de rios e arroios da China e do sudeste asiático, a espécie foi introduzida acidentalmente na América do Sul em 1991, no estuário do rio da Prata, provavelmente através de água de lastro. A partir disso, dispersou-se para os rios Paraguai, Uruguai e Paraná, principais canais de drenagem da bacia do Prata. Devido ao seu grande potencial reprodutivo, crescimento rápido e capacidade de formar aglomerados populacionais em curto espaço de tempo, L. fortunei causa grandes alterações ecológicas e econômicas, como a obstrução nas canalizações e entradas de água de usinas hidrelétricas e redes de tratamento de água. O presente estudo teve como objetivo avaliar a distribuição de L. fortunei nos principais corpos d'água formadores da Bacia do rio da Prata, bem como a possível influência das condições ambientais sobre as densidades populacionais. Os dados foram obtidos a partir de amostragens realizadas em janeiro/fevereiro e junho/julho de 2010, com coletas complementares em junho de 2013 e fevereiro de 2014. Foram empregados arrastos verticais com rede cônica de 68 μm de abertura de malha para coleta das larvas e simultaneamente determinadas as variáveis limnológicas (temperatura, transparência, turbidez, pH, condutividade e oxigênio dissolvido). Conclui-se que o processo de dispersão da espécie se deu de uma forma muita rápida, uma vez que a sua chegada ao continente ocorreu há apenas duas décadas e atualmente encontra-se amplamente distribuída por toda a bacia (aproximadamente 15 graus de latitude e extensão linear de 1700 km). Isto se explica devido a elevada capacidade de dispersão intrínseca da espécie (larvas planctônicas livre-natantes), incrustação em embarcações e ampla tolerância aos fatores ambientais. Picos máximos de densidade, cerca de 60.000 ind.m-3, foram encontrados nos... / Abstract: The golden mussel (Limnoperna fortunei) is a freshwater bivalve belonging to Mytilidae family. Originally from rivers and streams of China and Southeast Asia, the species was accidentally introduced in South America in 1991, in the River the la Plata estuary, probably through ballast water. From there, it dispersed to the rivers Paraguay, Uruguay and Paraná, major drainage channels of the basin. Due to its great reproductive potential, rapid growth and ability to form settlements in short time, L. fortunei cause major ecological and economic changes, such as blockage of the drainage system and water intakes of power plants and water treatment networks. This study aimed to evaluate the distribution of L. fortunei in the main water bodies of the River de la Plata Basin, as well as the possible influence of environmental conditions on the population densities. Data were obtained from samples taken in January/February and June/July 2010, with additional sampling in June 2013 and February 2014. Vertical hauls were employed with conical network of 68 μm mesh size to collect the larvae and the limnological variables (temperature, transparency, turbidity, pH, conductivity and dissolved oxygen) were simultaneously determined. It is concluded that the species dispersion process was very fast, since their arrival in the continent occurred just two decades ago and presently it is widely distributed throughout the basin (approximately 15 degrees latitude and a linear extension of 1700 km). This is explained by the high intrinsic dispersal ability of the species (free planktonic larvae), boat incrustation and broad tolerance to environmental factors. Maximum density peaks, about 60,000 ind. m-3, were found in the lower reaches of the basin, the River de la Plata ((URU/ARG), where the species was introduced. However, we refutes the hypothesis that there is a decreasing gradient of abundance in the south-north direction. Correlation analyzes indicate ... / Mestre

Page generated in 0.1158 seconds