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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.

The Gatun Structure a geological assessment of a newly recognized impact structure near Lake Gatun in the Republic of Panama /

Tornabene, Livio Leonardo. January 2001 (has links)
Thesis (M.S.)--University of South Florida, 2001. / Title from PDF of title page. Includes bibliographical references.

Probability of meteorite immpact in Sweden since year 2000

Wrige, Cecilia January 2015 (has links)
This Thesis investigates the number of possible meteorite impacts in Sweden since the year 2000. Sweden did not until recently have any photographic monitoring of incoming meteorites, thus a search through media reporting observations from the public has been performed. A theoretical approximation, based on an established extra-terrestrial mass ux, gives the number of 210 possible meteorite impacts for this time period. All of these could have been reballs, but by subtracting the daylight hours and bad weather conditions, only 47 reballs could have been seen during the 15 years. All of the 210 events could also have dropped meteorites on the ground, but when subtracting areas where it is very unlikely to recover a meteorite, like large forest areas and lakes, the number of possible meteorites is 73. The newspaper articles published since 2000 regarding reball observations gives 37 plausible meteorites. The theoretical value and the number of observations are similar enough that the theoretical approximation is probable to be correct.

Lead in the early solar system

Arden, John Walter January 1989 (has links)
No description available.

A combined experimental and computational study of nanopaleomagnetic recorders in meteoritic metal

Blukis, Roberts January 2019 (has links)
A nanoscale intergrowth of fine tetrataenite particles in an iron rich matrix, known as the `cloudy zone' has recently been recognised as a stable paleomagnetic recorder. It is found in meteorites containing iron-nickel alloy that have developed the characteristic Widmanst\"atten pattern. However, the close particle proximity and high magnetocrystalline anisotropy of the cloudy zone make it a highly unconventional material to use in paleomagnetic studies. Open questions about the formation of the cloudy zone, its exact composition and structure, and how it acquires a remanence remain unanswered. To use the cloudy zone as a reliable and accurate paleomagnetic recorder, its properties have to be well understood. The particle size in the cloudy zone has been measured to be between $\sim$500 nm and $\sim$10 nm, however, it is rarely higher than $\sim$150 nm. This fine lengthscale makes it difficult to study the cloudy zone with conventional methods. No known single method can provided the solution to all current problems concerning the use of the cloudy zone as a paleomagnetic recorder. Therefore, to explore the properties of the cloudy zone a multi-method approach using advanced nanoscale investigation techniques and theoretical calculations was adopted. The formation of the cloudy zone within the context of the Fe-Ni phase diagram was studied using Monte Carlo simulations. These simulations were supplemented by Density Functional Theory (DFT) calculations. DFT was also used to explore the preferred chemical ordering schemes of the matrix as well as its ground magnetic state. The 3D structure of the cloudy zone was imaged with sub-nanometer resolution using Atom Probe Tomography (APT). This was one of the first applications of APT to image meteoritic metal. Accurate composition measurements of the matrix and tetrataenite as well as kamacite were made. Synchrotron M\"ossbauer spectroscopy was used to provide high spatial resolution information of the magnetic state of the matrix and tetrataenite in the cloudy zone as well as the surrounding metal. The matrix was conclusively demonstrated to be paramagnetic at room temperature as a bulk material. X-Ray holography was used for the first time to directly image magnetisation of individual paleomagnetic remanence carriers under high applied fields. In-field hysteresis behaviour of individual particles in the cloudy zone was measured by directly imaging the sample magnetisation with a resolution of $\sim$25 nm. The cloudy zone was found to consist of strongly interacting single domain particles. The experimental observations were supported by modelling. The combined approach of multiple methods was capable of providing answers to some of the important questions about the cloudy zone. The cloudy zone was found to be highly stable against remagnetisation by applied external fields. If the particle size is below $\sim$80-50 nm the cloudy zone was found to consist of isolated single-domain tetrataenite particles sitting in a paramagnetic matrix. The matrix might become ferrimagnetic at very low temperatures. Depending on how the magnetisation is measured, the measurement might be affected by the matrix changing its magnetic state to ferromagnetic at surfaces. This phenomena should not affect the overall stability of the cloudy zone as a paleomagnetic recorder. Due to the close proximity of the tetrataenite particles, there are strong magnetostatic interactions between them. This finding demands that new methods be developed for correct interpretation of the remanence recorded in the cloudy zone.

An investigation of the Whitecourt meteorite impact crater (Alberta, Canada)

Kofman, Randolf Unknown Date
No description available.

An investigation of the Whitecourt meteorite impact crater (Alberta, Canada)

Kofman, Randolf 06 1900 (has links)
The <1,130 year old Whitecourt Meteorite Impact Crater, located several kilometres south of Whitecourt, Alberta (Canada), is a well-preserved bowl-shaped structure having a depth and diameter of ~6 m and 36 m. There are less than a dozen known terrestrial sites of similar size and age. Unlike most of these sites, the Whitecourt Crater contains nearly all the features associated with small impact craters including meteorites, an ejecta blanket, an observable transient crater boundary, a raised rim, and a number of associated shock indicators. The results of this study indicate that the crater formed from the impact of a type IIIAB iron meteorite travelling east-northeast at <10 km/s, striking the surface at an angle between 40 and 55 to horizontal. At present, it appears that the main mass survived atmospheric transit relatively intact to fragment and partially melt during impact, ejecting meteoritic shrapnel, most of which landed downrange.

The geophysical signatures and exploration potential of Australia's meteorite impact structures /

Hawke, Philip James. January 2004 (has links)
Thesis (Ph.D.)--University of Western Australia, 2004.

Impact crater particulates : microscopic meteoritic material surrounding meteorite craters /

Smith, Toby Russell. January 1995 (has links)
Thesis (Ph. D.)--University of Washington, 1995. / Vita. Includes bibliographical references (leaves [233]-240).

Topics in lunar evolution using sample analysis and remotely sensed information

Joy, Katherine H. January 2007 (has links)
No description available.

Representing science in the UK news media : 'life on Mars?' : cell nucleus replacement and Gulf War syndrome

Holliman, Richard January 2000 (has links)
This thesis addresses contemporary debates in the sociology of science, the sociology of media and the public understanding of science by examining the UK television and print media coverage of three substantive scientific issues. The first case study follows the debate as to whether a Martian meteorite (ALH 84001) provided evidence of ancient bacterial life-forms that could prove primitive life had once existed on Mars. The second case study tracks the use of cell nucleus replacement to “clone” mammals. The third case study examines the scientific and political controversy over the existence, symptoms, causes and response to “Gulf War syndrome”. The empirical research employed methodologies developed at the Glasgow Media Group, providing a comparative analysis of the production, content and reception of news media coverage of the case studies. The methods included interviews with scientists, journalists, media professionals and interest groups, a two-year content analysis of press and television news and focus group interviews. The content analysis discovered that media coverage of the case studies was extensive, unevenly distributed over time and emphasised scientific and science-based controversy as news values. The production analysis highlighted the importance of the interaction between scientific institutions and the media. For example, science journalists regularly draw on scientific journals as credible source material. The scientific community actively maintained this situation through information subsidies as a way of generating science news. The reception analysis demonstrated that news media, especially television news, provided an important source of information for audience members. Audience members were active consumers of science news, based on their education, gender, age and personal experience of science. Motivation to consume science news was also a key factor for audience members, varying according to the scientific issue being covered by the media. Overall, this thesis has highlighted the contested interactions that construct and interpret news media coverage of science. By analysing these complex interactions, this thesis contributes to contemporary concerns about the public presentation of science.

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