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  • 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.
71

Energieffektivisering i Stigbygeln : En förstudie

Häggkvist, Ylva January 2016 (has links)
Diös fastigheter is Northern Sweden's largest private real estate company. The bulk of the company's holdings constists of centrally located retail, industrial and office buildings, 23 of which are located in Umeå. Diös fastigheter works continuosly to decrease energy consumption in their building stock. One part of this work is to pursue the Greenbuildning environmental certification for buildings. This paper examines a building named Stigbygeln 2, situated on Dragonfältet i Umeå, currently rented by the logistics company PostNord. The energy consumption last year was approximately 290 kWh per square meter. This paper examines the reasons for the high energy consumption and which measures to increase energy-efficiency yield the largest energy-savings at the lowest cost.   At the present time Stigbygeln 2 is connected to the municipal district heating network, and distric heating is utilized as heating source to warm the inlet air of the ventilation system, which in turn warms a significant portion of the facilities found in the building. Heating of supply air constitutes 85% of the total heat load, and there is no system for heat recovery.   Stigbygeln has been constructed in the simulation tool IDA ICE in accordance with known conditions, and different measures to increase efficiency have been investigated, individually as well as combined. Through LCC analysis, savings resulting from decreased energy consumption have been weighed against the initial investment cost and the operational cost.   The result shows that a switch to FXT ventilation would yield the largest energy savings, 57%, and that this is also the financially most advantageous route. Conversion to geothermal heating reduces energy consumption by 37%, but is not economically viable. A swith to LED lighting is a measure that yields a good return on the investment cost and lowers energy consumption by 7%. The savings are greatest when a change of ventilation system is combined with a change to LED lighting.
72

Interannual variability and future changes of the Southern Ocean sea ice cover

Lefebvre, Wouter 16 November 2007 (has links)
The interannual variability of the sea ice in the Southern Ocean and its evolution projected for the end of the 21st century are investigated using observations and different types of models. First of all, none of the known atmospheric modes of variability are able to explain much of the total sea ice extent variability in the Southern Ocean. However, they have large influences on the local and regional scales. In particular, the response of the sea ice to the Southern Annular Mode is characterized by a dipole between the Ross Sea and the region around the Antarctic Peninsula caused by a low pressure anomaly in the Amundsen Sea in high SAM-index years. Secondly, the sea ice extent in the different regions seems to be mostly uncorrelated, showing that the total sea ice cover cannot be seen as a single entity, but merely as a combination of regional covers. Finally, it is shown why the projected distribution of sea ice is not a simple extrapolation of the current sea ice trends. The mechanisms responsible for the regional variability of the future sea-ice extents are discussed.
73

Physical processes in Antarctic landfast sea ice

Crocker, Gregory Bruce January 1988 (has links)
No description available.
74

Geophysical and numerical modelling investigations of the ice caps in Severnaya Zemlya

Bassford, Robin Paul January 2002 (has links)
No description available.
75

Molecular biology of salt tolerance in the facultative halophyte Mesembryanthemum crystallinum: Identification and regulation of stress-responsive mRNAs.

Vernon, Daniel Marc. January 1992 (has links)
As sessile organisms, plants are subject to numerous environmental insults. Of these, salinity is one of the most widespread and important in terms of limiting plant distribution and productivity. Molecular studies have established that plants challenged by high salinity respond by increasing expression of specific genes. A functional role for the products of such genes in stress tolerance has not been established, however, and little is known about the biochemical mechanisms that allow plants to tolerate osmotic stress. Mesembryanthemum crystallinum is a facultative halophyte capable of adjusting to and surviving in highly saline conditions. I have generated and screened a subtracted cDNA library to identify mRNAs that accumulate during this plant's adaptation to salt stress. Three mRNAs were identified that increased in abundance in leaf tissue of salt stressed plants. Patterns of induction for these mRNAs differed. The most dramatically-induced mRNA, Imt1, was characterized in depth. Imt1 expression was induced in leaves and, transiently, in roots. Nuclear run-on assays indicated that the gene is transcriptionally regulated. In several respects, the expression of Imt1 differed from that of other salinity-responsive genes involved in photosynthetic metabolism in M. crystallinum: The mRNA was induced by salinity and low temperature, but not by drought, and its induction by stress was not influenced by plant age. Imt1 encoded a predicted polypeptide of Mr 40,250 which exhibited sequence similarity to several hydroxymethyl transferases. The IMT1 protein was expressed in E. coli and identified by functional assay as a myo-inositol methyl transferase that catalyzes the first step in the biosynthesis of the cyclic sugar alcohol pinitol. The presence of high levels of sugar alcohols has been correlated with osmotolerance in a wide range of organisms, and the stress-initiated transcriptional induction of IMT1 expression in a facultative halophyte provides the strongest support to date for the importance of sugar alcohols in establishing tolerance to osmotic stress in higher plants. The ability of this methyl transferase to generate a putative osmoprotectant from a ubiquitous plant substrate makes it an attractive candidate enzyme for the creation of stress-resistant transgenic plants.
76

Late Devensian glaciation of the north of Ireland

McCarron, Stephen Gerard January 2000 (has links)
No description available.
77

A study of the mechanisms of climate change at the Last Glacial Maximum

Hewitt, Christopher D. January 2000 (has links)
No description available.
78

The iridocorneal-endothelial syndrome : a study of cell and basement membrane pathology

Levy, Somin Gabriel January 1996 (has links)
No description available.
79

A geographical information system-based synthesis of the Labrador Sector of the Laurentide Ice Sheet

Knight, Jane January 1996 (has links)
No description available.
80

Analysis of Spatial and Temporal Variations in Strain Rates Near Swiss Camp, Greenland

Rumrill, Julie 13 February 2009 (has links)
In this thesis, I present results from a two-year study of strain-rate variations along a flow line on the western margin of the Greenland ice sheet. I used baseline network solutions to investigate variations in longitudinal strain rates over the 2006 and 2007 melt seasons. Analyses revealed high-magnitude, short-duration events of increased longitudinal strain early in the melt season coincident with a high melt year, suggesting a link between melt production and its effects on seasonal ice flow. Results from 2006 data show that longitudinal strain rates became variable shortly after the onset of melt (day 186) changing up to ~ 15 x 10-4 a-1 within 24 hours. The onset of melting occurred earlier in 2007 (day 153) and was also followed closely by strain-rate deviation from background rates calculated prior to melting. The data revealed rapid (hours to days), high-magnitude (two to ten times greater than background rates) changes in longitudinal strain rates (hereafter referred to as ‘high-strain’ events) that occurred both on the small-scale (affecting 1-4 baselines) and on the large-scale (affecting 5 or more baselines). Large-scale high-strain events were infrequent, on the order of two events per season. Events were likely caused by drainage of supraglacial meltwater that penetrated to the bed of the glacier raising the basal water pressure. The increase in pressure reduced the basal resistive stress, and allowed rapid local acceleration. The basal stress reduction was transmitted to areas of higher stress which resulted in longitudinal compression of the ice down glacier and longitudinal extension up glacier. The evolution of high-strain events altered longitudinal strain rates more than 15 km along flow from the site of initiation. I estimated the origin and spatial extent of highstrain events by assessing the magnitude of the strain-rate variations in various baselines, and observing whether the altered strain regime was extensive or compressive. Magnitude and timing of changes in strain suggest that high-strain events originated in the ablation zone, the equilibrium zone, and inland of the equilibrium zone, and indicate that short-term altered stress conditions are not confined to the ablation zone. The background strain-rate for 2007 (~ -7 x 10-4 a-1 for a 37 km longitudinal baseline) was similar to the 2006 longitudinal background rate. When extrapolating the 2006 background rate over the melt season, the expected change in baseline length (~ 11 m) was similar to the observed change (~ 9 m). In contrast, when extrapolating the 2007 background rate over the melt season, the expected shortening was ~ 6 m, but the observed shortening was less than 1 m. This result suggests that seasonal high-strain events have the ability to alter longitudinal baseline length, allowing a greater ice flux to lower elevations where melting occurs for a larger portion of the year. However, the cumulative seasonal effects of both large-scale and small-scale strain events are modest, and indicate that seasonal changes in strain rates have a minor effect on the overall stability of the ice sheet. Nevertheless, it is possible that over much longer timescales these seasonal changes may become more important with increasing temperatures and available melt. Results from this study may also be useful in making broader inferences regarding the response of grounded portions of the ice sheet to seasonal changes in basal resistive stress.

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