This thesis discusses the problem of decomposing rectilinear regions, with or without holes, into a minimum number of rectangles. There are two different types of decomposition considered here : decomposing a figure into non-overlapping parts, called partitioning, and decomposing a figure into possibly overlapping parts, called covering. A method is outlined and proved for solving the above two problems, and algorithms for the solutions of these problems are presented. The partitioning problem can be solved in time O(n⁵ ²), where n is the number of vertices of the figure, whereas the covering problem is exponential in its time complexity. / M.S.

Stress can have a significant effect on the stability of pillars. To get an accurate picture of pillar stability, information is needed not only on the initial stress magnitude and distribution but also on all subsequent stress changes. Sonic methods have the potential to be among the fastest, most economical and least destructive means of stress measurement. Wave propagation velocity has long been applied to the investigation of the upper mantle and crust stress. Recently, it has also been applied to rock burst prediction and mine site investigations. Another parameter for investigating stress in rocks is the attenuation coefficient. Attenuation has been observed to be more sensitive to stress changes than wave velocity; however, the measurement of attenuation is more difficult than that of wave velocity. In this study, the mechanism of sonic attenuation in rock is reviewed. Both the velocity and the attenuation of sound waves in five different rock types under various stress levels were examined in the laboratory. It was found that the relationship between the velocity ratio and stress and that between the attenuation ratio and stress, for a specific rock type, can be expressed by simplified second order polynomial equations. / Master of Science

Experiments were conducted on the effectiveness of exposure to simultaneous temperature shock with chlorination, monochloramine, and ammonia as control agents of the Asiatic clam, Corbicula sp. Control procedures were evaluated based on lethal and sublethal responses (e.g., glycogen, tissue water, dry weight index, and siphoning activity) of clams during 30-day laboratory artificial stream studies. Studies also were conducted comparing sublethal responses (e.g., glycogen, tissue water, soluble protein, and siphoning activity) of clams to copper, a component of power plant effluents, during 30-day laboratory, site-specific, and in-situ copper exposures. This was done to evaluate the use of the Asiatic clam as a biomonitoring organism of copper contamination. Regarding temperature and chlorine interactions, it was demonstrated that an increase of 10° C was needed to increase significantly adult and juvenile mortality in the presence of chlorine (0.30 mg/l TRC) during winter and summer. Naturally high temperatures also increased adult mortality during in-plant chlorination procedures, with the highest mortality occurring during the spring. Significant decreases in the dry weight condition index were observed for adults chlorinated at 5° increases during winter and at 10° C increases for control (non-chlorinated) clams during both winter and summer. Similarly, glycogen content responded with a temperature-dependent decrease in both control and chlorinated clams during the summer. In addition, exposure to increased temperatures significantly increased the siphoning activity of control adults during summer and juveniles during winter. Chlorinated clams experienced near total inhibition of siphoning activity at all temperatures tested, except for adults exposed at 33° C. Increased dsiphoning activity, decreased glycogen content, and possibly ammonia accumulation in the mantle cavity were believed to be responsible for the increased mortality of clams chlorinated at higher temperatures. Total residual chlorine, with < 90% as monochloramine, was found to be equally toxic to adults and more toxic to juveniles compared to total residual chlorine containing higher amounts of free residual chlorine. Since free residual chlorine is considered to be more toxic than combined residual chlorine (e.g., monochloramine), questions were raised as to which form of chlorine was actually exposed to the tissues of adducted Asiatic clams. Ammonia was considerably less toxic to adults but more toxic to juveniles compared to chlorine. Both monochloramine and ammonia caused significant reductions in clam glycogen content and siphoning activity. The siphoning activity of clams exposed to ammonia, although significantly reduced, was considerably higher than siphoning activities observed for monochlorinated and chlorinated clams. Clam tissue water content decreased in the presence of ammonia but remained unaffected in the presence of monochloramine. Ammonia toxicity to adult clams was highly pH dependent but may be useful in controlling larval stages of Asiatic clams. More definitive research is needed to evaluate fully the potential of monochlorination as a biofouling control agent. Clams were more sensitive to copper exposures, with respect to glycogen content, in field-located (i.e. site-specific) artificial streams than in laboratory artificial streams. Specifically, the "no observable effect concentration" was between 5.5 and 8.4 μg Cu/1 during the 30-day site-specific studies compared to 17.2-32.1 μg Cu/1 in the laboratory. Copper significantly increased clam tissue water content during the Clinch River and June site-specific studies. However, clam soluble protein content demonstrated no consistent dose-dependent response during the laboratory or site-specific studies. Glycogen and tissue water content, although subject to some seasonal influences, are recommended for use in Corbicula for future site-specific and in-situ long-term toxicity experiments. / Master of Science

Using 'Redchief' (Junebearer) and 'Tribute' (dayneutral) cultivars, greenhouse and field studies were conducted to determine the effects of defoliation on photosynthesis, growth and yield of the strawberry. From preliminary photosynthesis experiments it was found that both 'Redchief' and 'Tribute' strawberry leaves reached maximum net photosynthesis (Pn) concurrently with full leaf expansion at approximately 8 to l0 days and 4 to 5 days, respectively, after unfolding. By exposing the plants to increasing irradiance it was determined that these cultivars were light saturated at 600 to 700)Ï molâ ¢m⁻²s⁻¹. Neither cultivar showed a consistent diurnal pattern when Pn was monitored hourly over two consecutive days. / Master of Science

The mechanism responsible for the killing of tumor cells after injection of mice with a mixture of tumor cells and Propionibacterium acnes were investigated. Tumor cells were injected intramuscularly into Balb/c mice either alone or together with P. acnes vaccine. The tumor cells were then removed from the injection site 12 hours after injection, and transferred into fresh mice. Tumor cells from control animals given tumor cells only caused tumors when transferred into fresh mice 12 hours after injection whereas tumor cells from animals given both tumor cells and vaccine did not develop tumors in the fresh nice. ELISA tests were done to estimate the number of tumor cells in the lesions. In control animals given 10⁵ tumor cells the estimated numbers dropped to 10³ cells at 24 hours, but thereafter rose steadily. Palpable tumors were present 7-10 days later. In animals given 10⁵ tumor cells + 500 ug of P. acnes vaccine, estimated tumor cell numbers fell steadily, and could not be detected after 2 days. Palpable tumors never developed in these animals. These results indicate that tumor cells are killed, or rendered nontumorigenic, during the first 12 hours after co-injection into mice with P. acnes Histological studies showed that injection of P. acnes vaccine, with or without tumor cells, induced large numbers of polymorphonuclear leukocytes (PMNs) at 12 hours. To determine the role of PMNs in the killing of tumor cells, tumor cells were incubated with supernatant obtained from the phagocytosis mixture of PHNs and P. genes. After a 2- hr. incubation, the tumor cells were washed and injected into fresh mice. No tumors developed, indicating that a product of the phagocytosis of P. acnes by PMNs played a role in the killing of tumor cells. Bacterial vaccines such as P. freudenreichii, which are poorly protective against tuner cells, produced phagocytosis supernatants which were unable to kill tumor cells. Various oxygen radical scavengers/inhibitors were used to test their effect on the toxicity of the supernatant on tumor cells and chinese hamster ovary cells. Both azide and catalase rendered the supernatant nontoxigenic, suggesting that H₂O₂, produced by PHNs during phagocytosis of P. acnes, is responsible for the killing of tumor cells. However, the addition of catalase 30 minutes after the start of phagocytosis had no effect on the toxicity of the supernatant, suggesting that H₂O₂ is converted to other toxic radicals during the course of phagocytosis of P. acnes by PMNs. The oxygen consumption levels of PHNs during phagocytosis of P. acnes or other bacterial vaccines was measured and found to be similar regardless of the antitumor ability of the vaccine used. This suggests that the difference in the ability of various vaccines to protect mice against tumors may be in the production of a particular oxygen radical by PMNs during phagocytosis, and not in the production of different quantities of the same radicals. / Master of Science / incomplete_metadata

Overtaking and passing maneuvers on two-lane rural roads is still one of the most complex situations drivers are faced with in everyday driving. In passing, drivers must judge the speed, acceleration and deceleration capabilities of their own vehicle, that of the impeding vehicle and the speed and rate of closure of the oncoming vehicle. They also have to make decisions on the adequacy of an acceptable gap and sight distance. This report presents an investigation of the adequacy of the current "Manual on Uniform Traffic Control Devices" (MUTCD) for marking on two-lane, two-way roads. It examines the existing criteria, problems associated with it and its reasonableness. Passing sight distances which incorporates both the option of aborting or completing the passing maneuver is presented. A model describing the kinematics of vehicle trajectories during the passing maneuver on two-lane roads is utilized for this purpose. The model is based on the presence of a delima zone during the passing maneuver. At this point, the decision to complete or abort the passing maneuver provides the same factor of safety. This critical position is located using the model. The parameters that strongly influence the required sight distance are investigated. Thus passing sight distances that will provide reasonable margin of safety throughout the passing maneuver will be achieved. It is realized from the results that the current MUTCD passing sight distance is inadequate from a safety standpoint, except for high accelerations and high decelerations. / Master of Science

An analytical model was developed to simulate the stress state of notched tensile specimens. Actual experiments are being carried out by other investigators to study the relaxation of residual stresses in specimens containing stress raisers. In the present work, the stress state developed in notched tensile specimens was assessed by determining the response of the stress state in the form of x-ray line profiles; this is useful in the understanding and measurement of effects due to such stress states obtained in actual experiments. The theoretical relationship between the stress gradient and the depth of penetration of the x-ray beam at the edge of a notch tensile specimen was also studied. In addition, the effect of changes in the radius of curvature of the notch-tip on errors in measured stress values is also considered. Furthermore, a description of the state-of-the-art x-ray system being used in the experimental work is also included. / Master of Science

The generality of the [4+1] cyclopentene annulation was demonstrated by the total synthesis of (±)-pentalenene and its C-9 epimer which were prepared in a stereocontrolled manner in analogy with the synthesis of (±)-isocomene, (±)-hirsutene and (±)-pentalenic acid. The key features of this synthesis involved preparation of acid 161, its conversion to diazoketone 148, intramolecular cyclopropanation of this substance to vinylcyclopropane 163 and the vinylcyclopropane-cyclo pentene rearrangement of several derivatives of 195 to triquinanes 147, 146, 197, and 204. A detailed study of temperature, conformation, and electronic effects on the diradical scission of vinylcyclopropanes of type 195 was carried out under pyrolytic conditions. Conclusive results regarding conformational stability at C-9 were also attained and exploited in the context of stereocontrol at this center. As a result of this synthesis, several new methods of functional transformations emerged, such as the selective reduction of conjugated esters and a new method of preparation of enolethers from carboxylic acids. / Master of Science / incomplete_metadata

Cakes were prepared with high fructose corn syrup as the total sweetening agent in a moisture adjusted formulation which allowed for the moisture content of the syrup. Three treatments were produced by adding glucose-delta-lactone and cream of tartar (high acid), cream of tartar (medium acid), or no addition (low acid). Cakes were baked and.immediately tested under controlled conditions. The pH and specific gravity were determined for cake batters. Baked cakes were evaluated for pH, standing height as an index to volume, moisture, deformation, crust color, and crust and crumb browning. Volume, color and browning were all significantly affected by pH adjustment. As acidity increased, cakes had less volume and a gummy, pudding-like texture. Color decreased and browning decreased at higher levels of acidity. Thus, it was concluded that increasing acidity decreased the over-development of color and browning, but altered the texture. The high fructose corn syrup sweetened cakes that were moderately acidified by the addition of cream of tartar alone were less brown but lighter in texture than the other treatments. / Master of Science

A test fixture for combined tension-compression cyclic testing of unidirectional composites was designed and characterized using 606l-O aluminum specimens. The elastoplastic response of graphite/aluminum l5° off-axis and 90° specimens under tension-compression cyclic loading was subsequently investigated at three temperatures, -l50°F, room temperature and 250°F. The test results showed that the tensile response was predominantly elastoplastic, whereas the compressive response could not be characterized exclusively on the basis of the classical plasticity theory. Secondary dissipative mechanisms caused by inherent voids in the material's microstmcture had an apparent influence on the elastoplastic behavior in compression. At different test temperatures, the initial yield stress in tension and compression were translated in the tension direction with increasing temperature. This is believed to be caused by residual stresses induced in each phase of the composite. The micromechanics model proposed by Aboudi was subsequently employed to correlate the experimental and analytical results at room temperature. A semi-inverse methodology was incorporated to determine the in-situ properties of the constituents. Comparison between the analytical and experimental results showed good agreement for monotonic tensile response. For tension-compression cyclic loading, fairly good correlation was obtained for l5° specimens, but poor for 90° specimens. The major cause of the discrepancy is suggested to be caused by the secondary dissipative mechanisms. / Master of Science