• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 984
  • 815
  • 62
  • 54
  • 39
  • 39
  • 39
  • 39
  • 39
  • 37
  • 15
  • 13
  • 13
  • 8
  • 5
  • Tagged with
  • 2375
  • 742
  • 690
  • 650
  • 398
  • 237
  • 195
  • 188
  • 168
  • 167
  • 153
  • 149
  • 146
  • 144
  • 137
  • 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.
181

The water balance in Graminha Basin

Aulin, Beatrice, Linnea, Henriksson January 2014 (has links)
Today, only 7 % of the Atlantic Rainforest, that once covered Brazil, remains scattered across the southern parts of the country. As the forest is rapidly disappearing, the government of Brazil has emerging interest of preservation. Thus more and more areas are turned into national parks and reserves. At the outskirts of one of these reserves, the Iracambi research station is situated. The center makes an effort to carry out applied research to find methods of preserving and learning about the forest. It is within that context the project described in this report has been performed. The project aimed to establish a water balance over Graminha Basin, the main river in the Iracambi research area. By doing this the understanding of the fluctuations of the amount of water in the ecosystem could increase. An important part of the objective was also to assess which methods can be used practically at Iracambi.The project was carried out during the rainy season from February 13th to April 12, 2012. During this time the water flow was measured at five stations along the river, using a current meter and instant slug-injection. Between six and fifteen flow measurements were made at each station. Slug- injection was generally the most suitable gauging method to use in the area. Precipitation was measured at two points. Evaporation was measured using an evaporation pan, and also calculated using the Penman-Monteith equation. Even though, the parameterization of the Penman-Monteith needs to be improved it was deemed to be the more suitable method for the area.The results give a rough estimate of the water balance during the period. It was concluded that the storage decreased during the project period. Based on the flow measurements and observations it was concluded that the areas covered by forest were less affected by the floods that occurred during heavy rainfalls than the areas covered by grass. Further on, the result of this report indicates that the Iracambi research station can continue to carry out assessments for changes in water flow, rainfall and evaporation with the simple equipment used in this project. However, more expensive and advanced equipment would be beneficial to establish a more accurate water balance. / Idag återstår endast 7% av den atlantiska regnskogen som en gång täckte Brasilien södra kust. Regnskogen försvinner snabbt vilket har lett till att Brasiliens regering de senaste åren visat ett ökat intresse att bevara regnskogen. Fler och fler områden har förvandlats till nationalparker och reservat. I utkanten till ett av dessa reservat ligger forskningsstationen Iracambi. Iracambi bedriver forskning i och runt området för att hitta metoder för att bevara regnskogen och öka kunskapen om området. Detta projekt är ett litet bidrag till detta arbete. Det övergripande syftet med projektet var att upprätta en vattenbalans över floden Graminhas avrinningsområde. Detta är huvudfloden i området och genom upprätta en vattenbalans kan förståelsen för förändringarna av vattentillgången i ekosystemet öka. Ett viktigt mål med projektet var också att finna verktyg som forskningsstationen Iracambi kan använda för kontinuerliga mätningar av de parametrar som ingår i vattenbalansen.Projektets genomfördes under regnperioden mellan den 13 februari och den 12 april, 2012. Flödesmätningarna utfördes vid fem mätstationer längs floden Graminha. Två typer av utrustning användes: flygel och konduktivitetsmätare. Rekommendationen för Iracambi var att fortsätta mätningarna med framförallt konduktivitetsmätaren. Uppskattningarna av avdunstningen genomfördes på två sätt: dels genom upprättandet av en evaporationspanna, dels genom beräkningar. Beräkningarna genomfördes med Penman-Monteith ekvationen och det kunde konstateras att även om de ingående parametrarna innehåller en del osäkerheter, så var detta den mest passande metoden för att beräkna avdunstningen. Nederbörd mättes på två platser med hjälp av enkla regnmätare konstruerade av pet-flaskor.Slutligen upprättades en vattenbalans för området. Utifrån denna kunde det konstateras att vattenmagasinet för hela orådet minskade under mätperioden. Utifrån flödesmätningar samt observationer kunde slutsatsen dras att skogsområdena drabbades mindre än de gräsbevuxna områdena av de kraftiga översvämningarna som uppstod under intensiva regn. Vidare visar resultaten att forskningsstationen Iracambi kan få en bra uppskattning av flödesförändringar, nederbörd och avdunstning med hjälp av den enkla utrustning som användes i detta projekt. / Minor Field Study
182

In vitro modelling of the immunological interactions between the salmon louse, Lepeophtheirus salmonis (Kroyer, 1837), and the Atlantic salmon, Salmo salar (L., 1758)

Butler, Ricky January 2001 (has links)
Atlantic salmon, SaI1M salar. L., have been shown to be more susceptible to infections by the caligid copepod Lepeophtheirus salmonis (Kreyer, 1837) than other salmonid species. Atlantic salmon exhibit a reduced cellular immune response to the attached parasite which has led to the hypothesis of the presence of sea louse associated compounds that depressed the fish's normally efficient inflammatory mechanisms. The aim of the current study was to test this hypothesis. A biochemically defmed in vitro culture system was developed that would allow collection of the secreted/excreted products of the copepodid larvae of L. salmonis, and avoid their contamination by metabolites of the host from their collection, in vivo. Available tissue culture methods proved inadequate in supporting copepodid culture because of the louse requirement for a seawater maintenance medium that was osmotically unsuitable for cultured cells. Tissue engineering technologies developed in the construction of human living skin equivalents were successful in the development of an Atlantic Salmon Skin Equivalent (ASSE). ASSE is a novel organotypic tissue culture substrate that was constructed from Atlantic salmon fibroblasts (AS-6) and primary cultures of Atlantic salmon epithelial cells. Cells were supported in a matrix of collagen fibres, acid extracted from the tails of rats, and combined using a layering technique to create a substitute salmon skin. ASSE has a fibroblastic dermal equivalent overlaid by an epidermis-like layer and a layer of collagen, and was maintainable in a seawater media. During its development, the cells within ASSE showed signs of differentiation that included stratification, increased fibronectin production by cultured fibroblasts, and the formation of a basement membrane-like layer at the junction of the dermis and epidermis. In this environment, ASSE allowed the survival of copepodid larvae for an average of 12 days, a period approximately 5 days longer than that of their free-swimming counterparts. Furthermore, cultured copepodids were observed feeding, exhibiting the normal range of settlement behaviours, and also showed increases in their length. However, metamorphosis to the chalimus I stage did not occur and was not stimulated by the supplementation of ASSE with salmon mucus, salmon peptone or DL methionine. Nevertheless, copepodid maintenance on ASSE allowed the collection of the compounds they released into the culture media. These were assayed for their effects on the immunological functioning of salmon macrophages. These assays demonstrated that the chemotaxic ability of macrophages was significantly reduced following treatment with louse culture supernatants . (LCS), as was their phagocytic ability. In both assays, the activity of each function was approximately 50% lower than that recorded in untreated cells. Intracellular respiratory burst and the phagocytic index of active phagocytes, however, was not affected. The biological activity of LCS was inhibited following heating, dilution, and treatment with proteinase K, indicating that the active immunosuppressive compounds were either themselves proteins, or required protein to be effective. The active substance was designated Louse Immunomodulatory Factor (LIF). The enzyme profiles of culture supernatants were investigated using API ZYM test strips. The profiles of LCS supernatants were significantly different to those of control supernatants from the early stages of louse incubation with ASSE. LCS supernatants showed elevated levels of leucine aminopeptidase, C4 and C8 esterases, alkaline phosphatase, P-glucuronidase, and Nacetyl- j-glucosaminidase. The involvement of these enzymes in the digestive processes of arthropods is well documented. However, the presence of the chitin hydrolysing enzyme Nacetyl- Beglucosaminidase, may also be suggestive of the preparation of copepodids for moulting. This, and the involvement of these enzymes in digestion in copepodids, and as possible immunomodulatory compounds is discussed. Gel filtration chromatography identified 14 proteins in the LCS that were not present in the control supernatants. These proteins were in the molecular weight range <1 kOa to 2665 kOa. No biological activity was attributed to these proteins when isolated by chromatography and assayed for their effects on macrophage chemotaxis. This lack of activity may be associated with their dilution during the chromatography process in which the supernatants were diluted approximately 5000 times. Experimental evidence showed that the activity of LIF was absent when supernatants were diluted to 1:1000, and so methods of concentration may be required in order to establish the immunological activity of these proteins. This study has developed an Atlantic salmon skin substitute that could have a great number of applications in the study of salmonid metabolism, cellular communication, immunology, and drug and chemical testing. Here, it supported the extended maintenance of sea lice larvae in vitro and allowed the collection of the products of their culture. The findings have shown that the copepodid stage of L. salmonis produces substances, LIF, that depress the chemotaxic and phagocytic activity of salmon macrophages, in vitro. These active substances may also be responsible for the depression of the inflammatory responses of sea lice infected Atlantic salmon, in vivo.
183

Analysis of meteorological observations from an array of buoys during JASIN

Ishida, Hiroshi 14 December 1979 (has links)
Observations of wind speed and direction, air and sea temperature, and solar radiation were obtained from an array of buoys in JASIN. The observations were analyzed to show spatial and temporal variability. Spectra of wind speed and air and sea temperature were computed to illustrate the distribution of variance over periods ranging from 3.5 minutes to 40 days. When plotted on log-log graphs the spectral estimates generally decrease with increasing frequency with slopes between -3/2 and -2. Spectra of air and sea temperature have a peak at the diurnal frequency. When plotted in variance-preserving form, the spectrum of wind speed is consistent with a spectral gap and is qualitatively similar to other observations of low frequency spectra. On the basis of a cross-correlation analysis, it appears that mesoscale eddies propagated with the mean wind speed except during frontal passages. Based on the cross-correlation between wind speed and air temperature, there is evidence of horizontal roll vortices or organized convection. / Graduation date: 1980
184

Field studies of the oxidation of dimethyl sulphide in the atmosphere

Robertson, Leonie January 2000 (has links)
No description available.
185

Palaeobiogeography of Early Cretaceous calcareous nannoplankton

Street, Christianne January 1999 (has links)
No description available.
186

Effects of climatic variability on spatial characteristics of European river flows

Shorthouse, Caroline January 1999 (has links)
No description available.
187

Geophysical studies in the Hebrides Terrace seamount area

Omran, Mohamed Ahmed January 1990 (has links)
No description available.
188

Magnetic properties of quaternary deep-sea sediments : use as proxies for dust inputs?

Mutch, Thomas J. January 2000 (has links)
No description available.
189

End of the Scottish Enlightenment in its transatlantic context : moral education in the thought of Dugald Stewart and Samuel Stanhope Smith, 1790-1812

Bow, Charles Bradford January 2012 (has links)
The thesis explores the history of the Scottish Enlightenment in its transatlantic context and, in particular, the diffusion of Scottish Enlightenment moral philosophy in late eighteenth and early nineteenth-century Scotland and the United States. This project is the first full-scale attempt to examine the tensions between late eighteenth-century Scottish Enlightenment intellectual culture and counter-Enlightenment interests in the Atlantic World. My comparative study focuses on two of the most influential university educators in Scotland and the newly-founded United States. These are Dugald Stewart at the University of Edinburgh and Samuel Stanhope Smith at the College of New Jersey (which later became Princeton University). Stewart and Smith are ideal for a transatlantic comparative project of this kind, because of their close parallels as moral philosophy professors at the University of Edinburgh (1785-1810) and the College of New Jersey (1779-1812) respectively; their conflicts with ecclesiastical factions and counter-Enlightenment policies in the first decade of the nineteenth century; and finally their uses and adaptations of Scottish Enlightenment moral philosophy. The broader question I address is how the diffusion and fate of Scottish Enlightenment moral thought was affected by the different institutional and, above all, religious contexts in which it was taught. Dugald Stewart’s and Stanhope Smith’s interpretations of central philosophical themes reflected their desire to improve the state of society by educating enlightened and virtuous young men who would later enter careers in public life. In doing so, their teaching of natural religion and metaphysics brought them into conflict with religious factions, namely American religious revivalists on Princeton’s Board of Trustees and members of the Scottish ecclesiastical Moderate party, who believed that revealed religion should provide the foundation of education. The controversies that emerged from these tensions did not develop in an intellectual vacuum. My research illustrates how the American and Scottish reception of the French Revolution; the 1793-1802 Scottish Sedition Trials; Scottish and American ‘polite’ culture; Scottish secular and ecclesiastical politics; American Federalist and Republican political debates; American student riots between 1800 and 1807; and American religious revivalism affected Smith’s and Stewart’s programmes of moral education. While I identify this project as an example of cultural and intellectual history, it also advances interests in the history of education, ecclesiastical history, transnational history, and comparative history. The thesis has two main parts. The first consists of three chapters on Dugald Stewart’s system of moral education: the circumstances in which Stewart developed his moral education as a modern version of Thomas Reid’s so-called Common Sense philosophy, Stewart’s applied ethics, and finally, his defence of the Scottish Enlightenment in the context of the 1805 John Leslie case. Complementing the chronology and themes in part one, the second part consists of three chapters on Smith’s programme of moral education: the circumstances that gave rise to Smith’s creation of the Princeton Enlightenment, Smith’s applied ethics, and finally, Smith’s defence of his system of moral education in the contexts of what he saw as two converging counter- Enlightenment factions (religious revivalists and rebellious students) at Princeton. In examining these areas, I argue that Dugald Stewart and Samuel Stanhope Smith attempted to systematically sustain Scottish Enlightenment ideas (namely Scottish philosophy) and values (‘Moderatism’) against counter-Enlightenment movements in higher education.
190

The behavioural, chemical and host ecology of two species of copepods (Copepoda: Caligidae) parasitic on Atlantic salmon (Salmo salar L.)

Smallman, Duncan Robert January 2009 (has links)
<i>Caligus elongatus </i>and <i>Lepeophtheirus salmonis </i>are ectoparasites of Atlantic salmon and sea trout (<i>S. trutta).</i> Solid phase extraction (SPE) and stir bar sorptive extraction (SBSE) were used to investigate and compare the odour profiles of Atlantic salmon, sea trout, haddock and turbot. The behavioural responses of <i>L. salmonis </i>copepodids towards the different extracts of the four species were tested on Y-tube bioassays. Copepodids showed significant increases in swimming activity in the presence of SPE and SBSE extracts of salmon and sea trout. The copepodids showed a significant preference for SPE extracts of salmon and sea trout only. Haddock SPE extracts elicited a significant increase in activity but no significant odour preference. <i>L. salmonis</i> copepodid behaviour when presented with sea trout and haddock odours was tested in a Y-tube bioassay. Significant increases in activity in the presence of both species odours was found. Copepodids showed a significant preference for sea trout conditioned water over blank artificial seawater and for artificial seawater over haddock odour. <i>C. elongates</i> copepodids showed no significant chemotactic responses in Y-tube experiments. Analysis of video tracked three-way olfactometer experiments found significant increases in the swimming activity and larger turning angles by <i>C. elongates </i>in the presence of salmon odour. When compared to <i>L. salmonis, </i>significant differences in swimming behaviour were found. A weak but significant correlation was found between the ecology of the hosts and the presence or absence of Caligid copepods. This is discussed in the context of the ecological traits and the influence these have on potential co-occurrence. In addition the reproductive strategies of <i>C. elongatus</i> and <i>L. salmonis</i> were investigated and the differences found are discussed in the context of co-existence.

Page generated in 0.0809 seconds