No description available.

No description available.

No description available.

No description available.

The intent of this study was to compare the rate of gastric emptying of three commercially available athletic drinks (GA, BT, and BP) against water, and in doing so to assess the exchange of water, carbohydrate and electrolytes 15 minutes after ingestion. Nine men and three women reported to the laboratory after having fasted for 12 hours.' A No. 20 French Levine Tube was inserted through the nasal passage and into the stomach. The subjects drank down 400 ml of the test solution containing 25 mg of phenol red which was used as a volume indicator. Fifteen minutes after ingestion, the gastric contents were aspirated via the tube by means of a 50 ml syringe. The 4 conditions were tested in one morning, with the order of feedings rotated between subjects. The recovered gastric contents were measured for total volume, volume of original drink, carbohydrate content and gastric electrolyte exchange. Student t values were used to test the difference between means set at the P < .05 level of confidence. BT and BP were found to empty statistically the same volume of fluid in 15 minutes as did water, while GA emptied 39% less volume than did water. BT, BP, and GA contributed 1.9, 4.5 and 6.8 gm of carbohydrate respectively in 15 minutes. These data are in agreement with previous findings that high glucose concentrations (GA - 4.5 gam) cause a slowing of gastric emptying.

The transdermal delivery of drugs has a lot of advantages above other routes of delivery, such as the avoidance of first-pass hepatic and intestinal metabolism, the non-invasive infusion of drugs, etc. However, the transdermal delivery of drugs, especially hydrophilic drugs, is limited due to the lipophilic nature of the stratum corneum. Methotrexate is a folic acid antagonist with antineoplastic activity and is used for the treatment of psoriasis and Kaposi's sarcoma. The permeation of methotrexate through the skin for systemic use is however limited due to its high molecular weight, the fact that it is mainty dissociated at physiological pH and its hydrophilic nature (Alvarez-Figueroa et al.. 2001). Thus the aim of my study was to enhance the permeation of methotrexate with the use of terpene. Terpenes are lipophilic in nature and have Log P values of around 2-4 (Godwin & Michniak, 1999). These characteristics make them excellent candidates as penetration enhancers. Terpenes are not only used for penetration enhancers, but in a huge number of other products, such as aromatherapeutic oils. For this reason the permeation of the terpenes through human skin and the effect of methotrexate on this permeation were also determined. The following enhancers were used in this study: menthol, menthone. isomenthol, limonene, B-myrcene, a-pinene and 1,8-cineole Five different sets of experiments were done in this study: a) a control experiment with methotrexate in the absence of the terpenes without ethanol; b) a control experiment with methotrexate in the absence of the terpenes with ethanol: c) experiments with methotrexate in the presence of the terpenes; d) control experiments with the terpenes in the absence of methotrexate and e) experiments with tile terpenes in the presence of methotrexate. For this study only human female abdominal skin was used. A saturated solution of methotrexate in water:propylene glycol (50:50) with a pH between 4 and 5 (Vaidyanathan et al., 1985) was used as the model drug and the receptor phase was PBS-buffer (pH=74) and water:ethanol (50:50) for HPLC and GC analysis respectively. The dilfusion apparatus used consisted of Vertical Franz diffusion cells with a capacity of 2 ml and a diffusion area of 1.075 cm2. The cells were placed in a water bath (+- 37 "C) on magnetic stirrers for the duration of the experiment. After the receptor phase was placed in the receptor compartment the cells were equilibrated for an hour before putting 25 ul of a 5% terpene solution in absolute ethanol on the skin in the donor compartment. This was left for half and hour to allow evaporation of the ethanol. The saturated solution of the methotrexate was now placed on the skin in the donor compartment. The experiments for methotrexate stretched over a period of 12 hours and samples were collected every 2 hours. The terpene experiments were performed over a 24-hour period and samples were taken at 2,4,6,12 and 24 hours. The concentration methotrexate permeated was determined by using HPLC-analysis and terpenes by using GC-analysis. The flux (ug/cm2/h), kp(cm/h), lag time (h) and enhancement ratio were calculated to compare the methotrexate permeation in the control and actual experiments. The results showed that a-pinene, B-myrcene and isomenthol enhanced the permeation of methotrexate most, although all the terpenes had an enhancing effect. They produced a 4- fold increase in the flux values of methotrexate. Due to the fact that the terpene experiments were only a semi-quantitative evaluation only the percentage terpenes that permeated was calculated. The experiments were done on all the terpenes except apinene. All the terpenes permeated the skin with menthol having the highest permeation. The results also showed that methotrexate did have an effect on the terpene permeation. Menthone and menthol's permeation was higher in the presence of methotrexate, while the other terpenes had a higher permeation in the absence of methotrexate. The reason for this is not clear. In conclusion, the study revealed that the enhancers used did have an enhancing effect on methotrexate permeation. This could be due to the extraction or disruption of lipids by the terpenes (Zhoa & Singh, 2000) or an increase in diffusivity and partitioning. The terpene experiments also showed that the terpenes do permeate the skin and that methotrexate does have an effect on this permeation. / Thesis (M.Sc.)--North-West University, Potchefstroom Campus, 2004.

No description available.

The technology of supercritical fluid extraction (SFE) offers the opportunity to efficiently extract both relatively non-polar analytes as well as ionic materials (such as metal ions) that can be mobilized with the addition of complexing reagents. The nebulizer of a conventional flame atomic absorption spectrometer (FAAS) was modified to extend the range of metals amenable to on-line detection. The flow injection thermospray-FAAS (FI-TE-FAAS) interface provided efficient detection for a variety of less volatile elements (Co, Cr(III), Cr(VI), Fe, Ni, Mn and Al) present as ions in aqueous media or as complexes in the supercritical fluid (SC-CO2) carrier phase. The range of possible metal analytes that can be monitored has been increased over the nine elements (Ag, As, Cd, Cu, Hg, Mn, Pb, Se and Zn) that could be detected with an all-silica interface. The acetylacetonate complexes offered considerable potential for metal detection in an SC-CO2 carrier phase. Limits of detection (LODs) were used to compare the instrument responses to different metals. (Abstract shortened by UMI.)

No description available.

The hydroxyl (OH) radical is a common intermediate species in any hydrogen- or hydrocarbon-based flame. Investigating OH at elevated temperatures and pressures is not a trivial task, and many considerations must be made to fully study the molecule. Shock tubes can provide the experimenter with a wide range of temperatures and pressures to investigate a variety of combustion characteristics including, but not limited to, OH kinetic profiles. Described in this dissertation is the diagnostic used to measure OH within a shock tube using UV absorption spectroscopy from an enhanced UV Xenon lamp passed through a spectrometer. OH absorption was made over a narrow range of wavelengths around 309.551 nm within the widely studied OH X→A ground vibrational transition region. Experiments have been performed in the shock-tube facility at Texas A&M University using this OH absorption diagnostic. A calibration mixture of stoichiometric H2/O2 diluted in 98% argon by volume was tested initially and compared with a well-known hydrogen-based kinetics mechanism to generate an absorption coefficient correlation. This correlation is valid over the range of conditions observed in the experiments at two pressures near 2 and 13 atm and temperatures from 1182 to 2017 K. Tests were completed using the absorption coefficient correlation on stoichiometric mixtures of methane, methane and water, ethane, ethylene, and acetylene to compare against a comprehensive, detailed chemical kinetics mechanism which considers up through C5 hydrocarbons. Measurements of methane show good agreement in peak OH formation and ignition delay time when compared with the mechanism. Improvements can be made in the shape of the methane-oxygen OH profile, and sensitivity and rate of production analyses were performed with the mechanism to identify key reactions for tuning. Similar results were found for methane-water-oxygen mixtures with no difference in profile shape or ignition delay time noted. There is room for improvement between the mechanism and measured values of OH for ethane-, ethylene-, and acetylene-based mixtures, although interesting pre-ignition features are nonetheless captured relatively well by the mechanism. Uncertainty in the measurement comes from the inherent noise in the photomultiplier tube signal and is ±25-150 ppm for the 2-atm experiments and ±6-25 ppm for the 13-atm experiments.