Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Oregon Graduate Center, 1986.

Thesis (Ph. D.)--Oregon Graduate Center, 1985.

Substance use disorders (SUDs) such as opioid addiction account for a large portion of the total global burden of disease. Nearly 5% of all disability-adjusted life years and 4% of overall mortality appear to be attributed to SUDs. An SUD, such as opioid use is often characterized by its addictiveness and frequent relapse among those who attempt quitting. Despite traditional methods of treatment, 5-year relapse rates are as high as 97% for opioid dependence. Alternative or novel forms of treating opioid addiction should be investigated and adopted, especially in countries which face an “epidemic” of opioid use and dependence, such as the United States. Ibogaine is a naturally occurring indole alkaloid that may be an effective alternative form of treatment for individuals struggling with opiate addiction and/or withdrawal. Preliminary research has found that iboga alkaloids such as ibogaine are effective at reducing morphine self-administration in rats. An elaborate history of human case reports has found ibogaine to be successful at reducing drug self-administration, withdrawal symptoms, and ceasing opioid cravings. The complex pharmacological profile of ibogaine is mediated by several classes of neurological receptors and transporters, including the sigma-2, kappa- and mu-opioid, 5HT2 and 5HT3 receptors, 34 nicotinic receptors, and the N-methyl-d-aspartic acid ion channel. Ibogaine’s combined interaction with all of these receptors has been suggested to reset or normalize neuroadaptation related to drug sensitization and tolerance. The resulting anti-addictive physiological and psychological properties appear to persist beyond pharmacokinetic elimination from serum or brain tissue, but may also cause unwanted side effects such as cardiovascular and neurologic toxicity. Developing a safe and effective standard dosing regimen has proven to be difficult in humans. The controversial therapeutic use of ibogaine in medical and nonmedical settings has been called a “vast uncontrolled experiment” or “medical subculture”, and ibogaine remains unscheduled in much of the world. However, ibogaine does not appear to have potential for recreational or other forms of abuse. During the 1995 Ibogaine Review Meeting, none of the consultants to NIDA were concerned about the abuse of ibogaine. Opiate users struggling with addiction and also interested in ibogaine therapy prompted the formation of “informal” treatment networks. Ibogaine therapy clinics catering to foreigners have also become more common in the Caribbean and Latin America. In order to clarify ibogaine’s clinical safety and therapeutic use against opiate dependence, the following thesis will investigate and analyze the ibogaine literature. Areas of focus for future ibogaine research will be identified, such as the invention of ibogaine congeners that retain efficacy against opioid dependence, but minimize unwanted toxic or psychological effects.

The -effects of water repellent solution concentration, distribution of various components and wood-w9ter repellent bond type were studied using Corsican pine'(Pinus, nigra) and European beech'(Falas*sylvatica) wood. The -resin component protects treated wood by forming an impermeable coating on cell lumina., whilst the wax gives protection by hydrophobic action. Increased concentration and treatment severity cause deeper penetration and increased loading and provide better protection. Water repellents are distributed in highest concentration at the treate; end and in gradually decreasing amounts inwards. Weathering rapidly reduces the effectiveness of the coating action, because in the absence of hydrophobes water is able to gain rapid access to all treated capillaries. However, hydrophobic treatments continue to provide protection to inner wood even after end grain degradation, because water is able to penetrate treated cells only to the depth of the degraded zone. Loss of water repellent effectiveness in the surface zone due to weathering occurs even though hydrophobic substances remain. This is almost certainly associated wi. th degrade of wood structure and wooddeposit bond. Pine specimens were treated with alkylchlorosilanes and alkylene oxides and double treated with an epoxide and a resin-wax water repellent to study the performance of chemically bonded treatments. Both silane and epoxide treatments proved to be resistant to exposure. Silanes provide initial water repellency similar to that provided by resin-wax and are far more resistant to weathering. Loss of effectiveness of silane treatments is attributed to wood degrade enhanced by the effect of HC1 produced in the reaction. Stabilization obtained by epoxides is extremely resistant to exposure. Reduced water absorption, due to OH-group blocking and cell-wall bulking, but no water repellency is shown by epoxy-treated wood. The full potential of water repellents applied to stabilized wood was not realized due to problems encountered in applying resinous solutions to epoxy treated wood.

Corsican pine (Pinus nigra) and beech (Fagus sylvatica) wood specimens were modified with n-butyl isocyanate (n-Bu-NCO), phenyl isocyanate (Ph-NCO), 1,6-diisocyanatohexane (HDI) and tolylene 2,4-diisocyanate (TDI), using pyndine as the swelling agent and catalyst. Several levels of weight gain were achieved by varying the reaction time. For each species the approximate general reaction rate order based on hydroxyl substitution was Ph-NCO > n-BuNCO > HDI > TDI for Corsican pine, and HDI > Ph-NCO > n-Bu-NCO > TDI for beech. The effect of chemical modification in the sorption properties and in the associated dimensional stability of wood was investigated by determining sorption isotherms and measuring the respective volumetric swelling at each relative humidity (RH) level. The treatment depressed the isotherms evenly over the entire range of RH for all levels of reaction, however, the difunctionally modified wood tended to show lower reduction in sorption at low RH's. The reduction in sorption was closely accompanied by a reduction in swelling indicating that within the accuracy of the experiment no voids were formed within the cell walls due to the treatment. The TDI treated specimens showed higher reduction in swelling under RH conditions than at saturation in liquid water. This was interpreted as to be caused by the formation of rigid TDI crosslinkages. The mechanisms of reduction in wood hydroscopicity were investigated by fitting data to the Hailwood-Horrobin sorption model. It was shown that the chemical modification treatment affects both monomolecular and polymolecular sorption. The accessibility of bonding sites was also reduced. Regression analysis revealed that the reduction in monomolecular sorption is chiefly governed by the decrease in site accessibility and that the reduction in polymolecular sorption is governed by the increase in the adduct volume in the cell wall. Investigation of the causes of the reduction in site accessibility by analyzing the sorption isotherms for wood modified with n-Bu-NCO and with a bulkier monofunctional isocyanate (octadecyl isocyanate) suggest that the accessibility of the internal wood surfaces is related to the weight gain and not to the fraction of hydroxyl groups (OH) reacted. This suggests that the reduction in accessibility is caused by a 'shielding effect' where the adducts physically cover some of the adjacent unreacted sorption sites. With difunctionally modified wood no evidence of crosslinking effectiveness was indicated at saturation in liquid water. However, when the samples were soaked in pyridine, the crosslinkages seemed to influence superswelling in comparison to that shown by mono functionally reacted wood. Finally, tensile strength tests carried out on modified and unmodified wood strips revealed that with the exception of n-Bu-NCO treated samples, the wood strength is slightly but significantly reduced by the treatments.

M.Ing. / Timber is an organic, orthotropic material of which the strength is currently not fully utilised in structural designs. Most design codes treat timber as an isotropic material with special clauses to compensate for the weaker strength across the grain. Several safety factors are used to accommodate the large variations in the strength of timber. In the orthotropic approach presented here, the unidirectional properties of timber are assumed as constant. It is also assumed that the large strength variation which is observed between samples of the same group, can mostly be attributed to the grain slope variation in a sample. The finite element method is employed to model grain slopes around a predetermined defect in a sample. The sample is then forced to fail at this defect, and the finite element model is then analyzed at the failure load to determine which stress combination led to the failure. Initial unidirectional material strengths are used in a failure criterion to evaluate the critical stress combination. The method of least squares is used to fit the predicted strength against the experimental strength. In this process new values are found for the unidirectional material strengths. The process is then repeated to determine whether another stress combination is not more critical than the original choice. As soon as the numerically acquired material strengths stabilise, it is compared with known values. The results indicate that the strength of a timber section can be predicted on the grounds of the observed fibre directions if the unidirectional material strengths are known.

No description available.

No description available.

Creep and recovery tests in compression parallel to the grain were conducted on 2 in. by 2 in. Douglas-fir specimens 4 in. long at four different levels of moisture. Specimens were loaded in stages up to a predetermined load. Instantaneous axial and lateral deformation as well as creep measurements were taken at each stage. Creep was observed over periods ranging from five minutes to twenty-five hours. Similarly, recovery was observed during unloading at successively lower stress levels. There are indications that creep as well as negative creep and negative recovery were mainly due to moisture present in the cell walls. Creep, In general, appeared to be more marked in the green specimens than in the intermediate and air-dry conditions. The only oven-dry specimen showed less creep than the air-dry specimens. Results also show that the values of the coefficient of lateral deformation(formula omitted) (both radial and tangential), during the load rise were entirely different from those during the period of creep, indicating that the corresponding deformations were entirely different. The µ’s for the change In load were always higher than those for the periods of creep. All specimens tested showed a recovery of more than 50% of the longitudinal creep. This indicates that creep in wood is made up of two parts, recoverable and permanent creep. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate