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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.
21

Molecular fungal diversity and its ecological function in sand-dune soils

Gonzalez Gonzalez, Irma January 2015 (has links)
There are about 100,000 described fungal species, however, the diversity could be higher because conventional techniques do not allow identification of all groups of fungi and there are still unexplored geographical areas. High-throughput DNA sequencing methods provide the opportunity to resolve the diversity and distribution of mycelia in soil. Soils are the largest pool of terrestrial carbon and macromolecular materials, such as lignin and cellulose, form an important part of this soil carbon. Saprotrophs (decomposers) fungi degrade lignin and cellulose that is important to the global carbon cycle, although lignin is highly resistant to degradation if compared with cellulose. In this work, we investigated the diversity of fungi in sand-dune soils and their involvement in the decomposition of lignin and cellulose. The key findings of this work were:•A comparison of sand-dune ecosystems from two reserves in the UK showed differences in the ion concentrations, pH and total organic carbon in soils, suggesting that there were different environmental conditions that could potentially affect the distribution/presence of microbial communities in soils, e.g. fungal communities.•Fungi from field samples were identified using 454 pyrosequencing. The identified fungal species belong to groups with different ecologies, among which are wood-rotting fungi that are the main agents responsible for the lignin breakdown. The fungal communities were distributed differently across the different sand-dune ecosystems, sampling times and type of bait materials.•Lignin and cellulose can be degraded in field samples over time. Lignin degradation was shown by the shifts in the [Ac/Al]S, [Ac/Al]G and [S/G] relative lignin decomposition state proxies, and cellulose degradation by the shifts in the [cellulose:cellulose+lignin] ratio. Cellulose degradation was faster than lignin, thus confirming previous studies.•The degradation of both lignin and cellulose was different depending on the type of plant material, ecosystem/soil characteristics where the material was buried and fungal communities present on the bait materials.•Lignin breakdown was most likely to be by white-rot fungi that were identified colonising the bait materials.
22

Source of sand for An Nafud sand sea, Kingdom of Saudi Arabia

Faulkender, DeWayne J. January 2011 (has links)
Typescript (photocopy). / Digitized by Kansas State University Libraries / Department: Geology.
23

The morphology and genesis of lunettes in southern South Australia

Campbell, Elizabeth M. (Elizabeth Mary) January 1967 (has links) (PDF)
[Typescript]
24

CHARACTERIZATION OF SULFUR-ASPHALT-DUNE SAND PAVING MIXTURES

Aboaziza, Abdelaziz Hassan January 1981 (has links)
The primary objective of this study is to investigate the suitability of utilizing dune sand as a paving construction material in hot desert-like areas of the world, where regions of sand dunes exist. The high availability, low cost, and excellent physical properties of the current surplus of elemental sulfur and the benefits given to asphaltic binders by sulfur raises the possibility of using sulfur in asphalt mixes to produce stable mixtures with locally obtainable dune sand. Characterization of various sulfur-asphalt-dune sand mixtures for highway construction were made. The materials used in this investigation were elemental sulfur, AR-4000 (60-70 pen.) asphalt, and dune sand from Yuma, Arizona. The main variables include (a)proportion of sulfur and asphalt in the binder, (b)amount of binder in the mixture, (c)curing temperature, (d)test temperature, and (e)mixing techniques. The various mixtures were prepared by the one-wet mixing cycle technique. Similar dune sand mixtures with asphalt only were evaluated for comparison purposes. The different mixes were evaluated by the Marshall method, tensile strength tests (double punch), compression tests (standard and immersion), flexural tests (standard), dynamic modulus tests (double punch), and microscopic examinations of sulfur-asphalt binders and sulfur-asphalt-dune sand mixtures (thin sections). Preliminary characterizations of the various mixes were made on the basis of their Marshall stability, flow, density, and air void contents. Other engineering properties such as tensile strength, compressive strength, modulus of rupture, dynamic modulus, and microscopic studies were determined for selected mixes. The results consistently indicated that the sulfur-asphalt-dune sand mixes exhibited superior engineering characteristics and performance as compared to similar mixes without sulfur. The overall conclusion drawn from this study is that the dune sand which is not normally accepted for use as aggregate in asphaltic mixtures, can be used with the utilization of sulfur-asphalt binder systems to produce paving mixtures with compatible or better engineering properties in comparison to conventional asphaltic concretes.
25

Beaches and sand dunes in Grand Beach Provincial Park, Manitoba: development of management guidelines to ensure long-term ecological sustainability

Demski, Allyson 04 January 2012 (has links)
The purpose of this study was to develop management guidelines to ensure the long term ecological sustainability of the beach and sand dune area of Grand Beach Provincial Park. A qualitative approach was taken including interviews of individuals who use Grand Beach. A literature review was completed describing the history of use at Grand Beach Provincial Park, ecological processes specific to the park, and management guidelines in other jurisdictions in Canada with similar natural features. Aerial imagery provided a temporal look at intensely used areas in the park. Recommendations include: 1) completion of a biophysical study of the park including an inventory of flora and fauna species 2) development of a monitoring plan incorporating the natural environment with the human dimension of the park 3) engagement of park visitors through signage, education and awareness, and 4) engage the scientific community to form partnerships for further research studies in the park.
26

Beaches and sand dunes in Grand Beach Provincial Park, Manitoba: development of management guidelines to ensure long-term ecological sustainability

Demski, Allyson 04 January 2012 (has links)
The purpose of this study was to develop management guidelines to ensure the long term ecological sustainability of the beach and sand dune area of Grand Beach Provincial Park. A qualitative approach was taken including interviews of individuals who use Grand Beach. A literature review was completed describing the history of use at Grand Beach Provincial Park, ecological processes specific to the park, and management guidelines in other jurisdictions in Canada with similar natural features. Aerial imagery provided a temporal look at intensely used areas in the park. Recommendations include: 1) completion of a biophysical study of the park including an inventory of flora and fauna species 2) development of a monitoring plan incorporating the natural environment with the human dimension of the park 3) engagement of park visitors through signage, education and awareness, and 4) engage the scientific community to form partnerships for further research studies in the park.
27

Microwave remote sensing of Saharan ergs and Amazon vegetation /

Stephen, Haroon, January 2006 (has links) (PDF)
Thesis (Ph. D.)--Brigham Young University. Dept of Electrical and Computer Engineering, 2006. / Includes bibliographical references (p. 115-121).
28

Micrometeorological studies in the coastal desert of southern Peru

Stearns, Charles Richard, January 1967 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 173-176).
29

Beach and dune erosion during severe storms

Hughes, Steven Allen, January 1981 (has links)
Thesis (Ph. D.)--University of Florida, 1981. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 285-290).
30

Chemistry, mineralogy, and grain properties at Namib and High dunes, Bagnold dune field, Gale crater, Mars: A synthesis of Curiosity rover observations

Ehlmann, B. L., Edgett, K. S., Sutter, B., Achilles, C. N., Litvak, M. L., Lapotre, M. G. A., Sullivan, R., Fraeman, A. A., Arvidson, R. E., Blake, D. F., Bridges, N. T., Conrad, P. G., Cousin, A., Downs, R. T., Gabriel, T. S. J., Gellert, R., Hamilton, V. E., Hardgrove, C., Johnson, J. R., Kuhn, S., Mahaffy, P. R., Maurice, S., McHenry, M., Meslin, P.-Y., Ming, D. W., Minitti, M. E., Morookian, J. M., Morris, R. V., O'Connell-Cooper, C. D., Pinet, P. C., Rowland, S. K., Schröder, S., Siebach, K. L., Stein, N. T., Thompson, L. M., Vaniman, D. T., Vasavada, A. R., Wellington, D. F., Wiens, R. C., Yen, A. S. 12 1900 (has links)
The Mars Science Laboratory Curiosity rover performed coordinated measurements to examine the textures and compositions of aeolian sands in the active Bagnold dune field. The Bagnold sands are rounded to subrounded, very fine to medium sized (similar to 45-500m) with 6 distinct grain colors. In contrast to sands examined by Curiosity in a dust-covered, inactive bedform called Rocknest and soils at other landing sites, Bagnold sands are darker, less red, better sorted, have fewer silt-sized or smaller grains, and show no evidence for cohesion. Nevertheless, Bagnold mineralogy and Rocknest mineralogy are similar with plagioclase, olivine, and pyroxenes in similar proportions comprising >90% of crystalline phases, along with a substantial amorphous component (35%15%). Yet Bagnold and Rocknest bulk chemistry differ. Bagnold sands are Si enriched relative to other soils at Gale crater, and H2O, S, and Cl are lower relative to all previously measured Martian soils and most Gale crater rocks. Mg, Ni, Fe, and Mn are enriched in the coarse-sieved fraction of Bagnold sands, corroborated by visible/near-infrared spectra that suggest enrichment of olivine. Collectively, patterns in major element chemistry and volatile release data indicate two distinctive volatile reservoirs in Martian soils: (1) amorphous components in the sand-sized fraction (represented by Bagnold) that are Si-enriched, hydroxylated alteration products and/or H2O- or OH-bearing impact or volcanic glasses and (2) amorphous components in the fine fraction (<40m; represented by Rocknest and other bright soils) that are Fe, S, and Cl enriched with low Si and adsorbed and structural H2O. Plain Language Summary The Bagnold dune field is an active sand field with moving dunes and sits between the landing site of the Curiosity rover and rocks of interest higher up on Mount Sharp. When passing through the dune field, we used all of Curiosity's instruments to measure the chemistry, mineralogy, and grain size of sands in the Bagnold dune field in order to figure out where they came from, how the sands are transported, and what volatile materials (like water) lie within Martian soils. We found that the Bagnold sand dunes are very well sorted; no dusty materials are found within them, in stark contrast to soils seen previously with Curiosity and with rovers at other landing sites. We found that the coarser sand grains are enriched in the volcanic minerals olivine and pyroxene, confirming a prediction from orbit that wind-related activity seems to concentrate these phases. We also found that the dunes were much lower in water and other volatile elements like sulfur and chlorine versus all previous Mars soils. Using a combination of the rover's sieving system and chemical measurement tools, we figured out that two types of materials host water. In the first type of material, common in these sands, water is low in abundance (similar to 1%), very tightly bound to the grains, and is not released until temperatures >200 degrees C. In the second type of material, water is higher in abundance (2%) and more easily released by heating. Sieved water-bearing fine materials may be a useful resource for human explorers.

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