Thesis (Ph. D.)--Joint Program in Marine Geology and Geophysics (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), September 2003. / Includes bibliographical references.

LD2668 .T4 1954 S31 / Master of Science

No description available.

Alpha-melanotropin (alpha-melanocyte stimulating hormone, α-MSH) exerts its biological action by binding to specific receptors on the outer cell membranes of its target tissues with a high degree of affinity and specificity. Current evidence suggests that this takes place both in vitro and in vivo in both normal and malignant melanocytes. Thus, if it were possible to attach a radioisotope (e.g., ¹²⁵I) to α-MSH, or a suitable analogue, without interfering with the receptor affinity of the hormone, then a radioreceptor assay could be developed which would allow hormone-receptor interaction to be studied in detail. In addition, this radio-labeled melanotropin might be expected to accumulate in melanoma tumors in vivo thus facilitating tumor localization by nuclear imaging methods as has been successfully accomplished for thyroid tumors. The present studies were initiated to develop a radioactive melanotropin with full, or nearly full, biological activity. This labeled melanotropin must be of sufficient specific radioactivity to be suitable as a tracer in a radioreceptor assay and ultimately as a marker for in vivo tumor localization. The studies described herein provide information concerning: chloramine T induced iodination, lactoperoxidase catelyzed iodination, and iodogen induced iodination of α-MSH and certain structural analogues. Radio-labeled derivatives of various melanotropins were prepared using a variety of iodination techniques. Under conditions commonly used for the iodination of other peptides a substantial loss of biological activity of the native hormone (α-MSH) was observed. This loss of hormonal activity was primarily a consequence of oxidation of methinonine and occurred regardless of the oxidant used (chloramine T, lactoperoxidase-hydrogen perioxide, or iodogen). Under similar iodination conditions using 4-norleucine-alpha-melanotropin ([Nle⁴]-α-MSH), satisfactory incorporation of label into the peptide was accomplished without significant loss of biological activity. Data are presented suggesting that this peptide is far superior to α-MSH for use in the preparation of a radioactive melanotropin. Although some success was achieved using [Nle⁴]-α-MSH with all three iodination methods, the simplest and most consistent method involved the use of iodogen followed by purification of the labeled product using high performance liquid chromatography (HPLC). This importance of these studies in the development of a tracer for a radio-receptor assay and for in vivo localization of melanoma tumors is discussed.

Recent years have seen increasing use of atmospheric radionuclides for dating and tracing hydrogeologic processes. Hydrologists often assume that meteoric sources of these nuclides are dominant in ground water and that age-dating methods are limited primarily by analytical detection capability. However, in some cases, subsurface production may also limit the usefulness of these nuclides for dating. Equilibrium radionuclide concentrations are calculated as a function of depth for a variety of rock types. Production mechanisms include fissioning of heavy radionuclides; spallation by cosmic-ray nucleons; capture of neutrons, a-particles, muons and protons; and photonuclear reactions. Calculations indicate that deep subsurface production of ³H, ¹⁴c, ⁸⁵Kr and ⁹⁹Tc is generally below detection but that deep production of ³⁶C1, ³⁹Ar, ⁸¹Kr and ¹²⁹I establishes limits to age-dating of water in most rocks. Parameters for estimating production of ¹⁰Be, ²²Na, ²⁶Al, ³⁷Ar, ³²Si, ⁴¹Ca and ⁷⁹Se are included in appendices. Evidence for in-situ production of ³⁶C1 and ¹²⁹I is presented for two field studies. Concentrations in ground water from the Stripa granite, Sweden, were determined by accelerator mass spectrometry. ¹²⁹I values range from 1,000 to 200,000 atoms/ml, compared to an estimated background concentration in pre-1945 water of 20 atoms/ml. The high levels are attributed to production by spontaneous fission of ²³⁸U in the granite (44 ppm U). ³⁶C1/C1 ratios range from 50-200 x 10 -15 compared to about 40 x 10⁻¹⁵ in meteoric recharge. An increase in ratios with depth has been attributed to production of ³⁶C1 by neutron- capture on ³⁵C1 and is used to set upper limits on the residence time of water in the granite. The validity of using ³⁶C1/C1 ratios as a monitor of deep lithospheric neutron fluxes was tested by measuring the ratios in Cl extracted from Stripa granite. The average ratio, 190 x 10⁻¹⁵, agrees with ratios calculated based on rock chemistry, 190 x 10⁻¹⁵, and on the measured neutron flux, 220 x 10⁻¹⁵. ¹²⁹I and ³⁸C1 were also measured in uranium ores from the Koongarra and Ranger deposits, N.T., Australia. Samples from the oxidized ore zone contain only 6-23% of the ¹²⁹I contents predicted for equilibrium, suggesting preferential loss of ¹²⁹I relative to U during weathering. ³⁶C1 is produced as a result of high neutron fluxes in the ore. Measured ³⁶C1/C1 ratios range from 3 x 10 -12 to 1 x 10⁻¹⁰, corresponding to apparent neutron fluxes of 2 x 10⁵ to 1 x 10⁷/cm²/yr.

MSc., Faculty of Science, University of the Witwatersrand, 2011 / ABSTRACT This study was an investigation of the impact of recharge water with respect to quality and quantity into the Rehabilitated Block I opencast operation, a former opencast coal mine in Mpumalanga, Witbank Coalfields western complex. The rehabilitated areas consisted of three mined mini-pit areas known as Block I, Block I Extension A and B. The area has been rehabilitated by backfilling and leveling of spoil material, subsoil material, placement of approximately 400-mm topsoil layer and grassing. As part of the vegetation maintenance lime is added per annum, in an effort to neutralize the soil cover and further assist in neutralizing the potential acid mine drainage. Additional monitoring boreholes were drilled to increase the monitoring of the water quantity and qualities. Ground and surface water samples were taken, analysed for pH, conductivity, redox potential, sulphates, carbonates and trace metals. The pH of the ground and surface water ranged from moderately acidic to alkaline. One of the monitoring boreholes located on the lowest elevation of the Block I area was observed to be filled up to the collar level of the borehole with water samples showing elevated Fe and Mn concentrations of 216 and 46.2 mg l-1 respectively. The water classification revealed the following facies: Ca-Mg sulphate type for the borehole water and Ca-Mg sulphate-bicarbonate type for the surface waters. Acid base accounting studies on the soil samples showed a negative net neutralising potential of up to -9.8 kg t-1 CaCO3 which indicated the potential of acid mine drainage in the area. The total metal analyses showed that the area was contaminated with heavy metals such as Fe, Cr, Mn, Ni and Zn and the metalloid As was also detected. The highest recorded concentrations of total metals were 78 252; 2 402; 1 959; 1 360 and 15 109 mg kg-1 respectively. The highest concentration of Arsenic was detected at 824 mg kg-1 respectively. The transmissivity of the boreholes in the spoil material was highly variable and ranges from 100 to 5 000 m2 day-1. Pump testing suggests that borehole yields of between 23 and 4 l s-1 can be expected in the spoil areas. The specific yield or the drainage porosity of the spoil material was in the range of 25 to 30 %.

No description available.

Novel glass tracers, organic and inorganic polymers based on narrow band atomic fluorescence, have been developed for deployment as environmental tracers. The use of discrete fluorescent species in an environmentally stable host has been investigated to replace existing toxic, broad band molecular dye tracers. The narrow band emission signals offer the potential for the tracing of a large numbers of signals in the same environment; this has been investigated by examining multiple doped tracers which have the potential for coding to specific effluent sources or particulates. The concept of using lanthanide doped glasses as environmental tracers has been demonstrated. The spectral characterisation and concentration studies of the lanthanide doped tracer allow the selection of parameters to produce future tracers and detection systems for particular applications. Therefore by altering the chosen lanthanide dopant, number of dopants, dopant concentration and using selective excitation and emission wavelengths there are a huge number of possible unique tracer combinations. The significantly narrower bandwidth emission peaks of the lanthanide based tracers achieve more selective detection of multiple tracers without overlap interference and gives the potential to selectively and simultaneously monitor many different tracers in the same location. The spectral lifetime characteristics of the lanthanide tracers are very different from the lifetime of background fluorescence which is typically molecular in origin. This is an extra discrimination against background interference and is an important additional advantage of using lanthanide based tracers. Overall this work shows that a very large number of unique environmental tracers can be obtained by varying the concentration, the number of lanthanide ions in a glass and also the possibility of using organic and inorganic lanthanide chelate doped tracers.

No description available.

Thesis (M.S.)--Baylor University, 2005. / Includes bibliographical references (p. 48-50).