Degassing

Measurements of the concentration of rare gases and trace elements in oceanic basalts provided a new information concerning the structure if the Earth mantle and its evolution. The results set important constraints that need to be incorporated into any comprehensive understanding of the early history of the planets. Some of the highlights of these results are described and an indication is given how they are derived

How life affects the geochemical cycle of carbon

Developing a quantitative understanding of the biogeochemical cycles of carbon as they have worked throughout Earth history on various time scales, how they have been affected by biological evolution, and how changes in the carbon content of ocean and atmosphere may have affected climate and the evolution of life are the goals of the research. Theoretical simulations were developed that can be tuned to reproduce such data as exist and, once tuned, can be used to predict properties that have not yet been observed. This is an ongoing process, in which models and results are refined as new data and interpretations become available and as understanding of the global system improves. Results of the research are described in several papers which were published or submitted for publication. These papers are summarized. Future research plans are presented

The Design and Implementation of Surface Acoustic Wave Devices for Linear FM and Nonlinear FM Pulse Compression Technique for Radar Applications

The purpose of this work is to design, fabricate, and compare dispersive SAW devices using both linear FM and a new non-linear FM scheme. This new non-linear FM scheme uses the Blackman function as the modulating signal of the FM waveform. Up-chirped and V-chirped devices for both linear and the new non-linear FM scheme and their corresponding matched filters are compared. Design considerations are discussed in detail. An efficient sampling algorithm (which can also be applied to other non-linearly modulated FM waveforms) developed to facilitate the design of the SAW devices is presented

From Scouts to Soldiers: The Evolution of Indian Roles in the U.S. Military, 1860-1945

The eighty-six years from 1860-1945 was a momentous one in American Indian history. During this period, the United States fully settled the western portion of the continent. As time went on, the United States ceased its wars against Indian tribes and began to deal with them as potential parts of American society. Within the military, this can be seen in the gradual change in Indian roles from mostly ad hoc forces of scouts and home guards to regular soldiers whose recruitment was as much a part of the United States’ war plans as that of any other group. The gradual granting of citizenship to Indians, culminating in the Indian Citizenship Act of 1924, played a vital role in resolving the issue of whether Indians were even able to volunteer or enlist for regular service. Being primarily concerned with finding ways to win on the battlefield, the military proved more willing to accept aspects of Indian culture that the U.S. did not generally permit in civilian life, provided it did not interfere with the individual Indian’s abilities or duties as a soldier. However, the military was nevertheless a product of the same society that held various prejudices toward Indians, even if such prejudices were mollified by the desire to win battles. This thesis tells of the gradual acceptance of Indians into military and American life, a process that is still continuing today

Some Perspectives of the Major Biogeochemical Cycles

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94582/1/eost3946.pd

Carbon Cycle Modelling

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94608/1/eost3991.pd

Comments requested

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95017/1/eost3321.pd

The geochemical carbon cycle and the uptake of fossil fuel CO2

Atmospheric carbon dioxide levels are controlled over long time scales by the transfer of carbon between the atmosphere, oceans, and sedimentary rocks— a process referred to as the CO2 geochemical cycle. Carbon dioxide is injected into the atmosphere‐ocean system by volcanism; it is removed by the weathering of silicate rocks on the continents followed by the deposition of carbonate minerals on the sea floor. Humans are currently perturbing the natural carbon cycle by burning fossil fuels and deforesting the tropics, both of which add CO2 to the atmosphere. The effects of human activities on future atmospheric CO2 levels can be estimated by including anthropogenic emissions in a model of the long‐term carbon cycle. The model predicts that CO2 concentrtions could increase by a factor of six or more during the next few centuries if we consume all of the available fossil fuels. Preserving existing forests and/or reforesting parts of the planet could mitigate the CO2 increase to some extent, but cannot be depended on to make a significant difference. Because the removal processes for atomspheric CO2 are slow, the maximum CO2 level reached is relatively insensitive to the fossil fuel burning rate unless the burning rate is many times smaller than its present value. The model also predicts that hundreds of thousand of years could pass before atmospheric CO2 returns to its original preindustral level. Implications of these results for future energy and land use policies are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87506/2/175_1.pd

Why the oxygen isotopic composition of sea water changes with time

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94773/1/grl4282.pd