Unlike interactions in simulated methane clathrate hydrates.

Ph. D. University of KwaZulu-Natal, Durban 2014.Clathrate hydrates are an ice-like substance consisting of networks of water molecules, held together by hydrogen bonds, enclosing trapped gas molecules. Natural gas clathrate hydrates (in which the trapped gas species is chiefly methane) are of interest in the field of offshore gas exploitation, where they frequently form blockages in natural gas pipelines. Knowledge of the phase equilibria of methane clathrate hydrate can thus reduce the overall monetary cost of natural gas extraction. Computer simulation of molecular systems is useful to understand fundamental mechanisms, and serves as a complementary method to laboratory experiments in the study of chemical systems. The Lennard-Jones potential is frequently used to describe intermolecular interactions in molecular simulations. Correction factors are often applied to the Lennard-Jones potential, although the effect of these correction factors on the behaviour of simulated molecular systems is not fully understood. This thesis examines the effect of Lennard-Jones correction factors on simulated methane clathrate hydrates using three different computational approaches: lattice distortion theory, grand canonical Monte Carlo simulations (which emulate gas adsorption into the clathrate lattice), and direct estimation of the heat of dissociation coupled with the Clausius-Clapeyron equation. In addition, the use of the results of grand canonical Monte Carlo simulations to infer phase equilibria was demonstrated in this thesis. The application of Lennard-Jones correction factors in lattice distortion calculations was found to not be viable, due to the extreme sensitivity of the perturbation potential (the quantity of interest in this theory) to changes in the values of the correction factors. Unlike interactions were found to weakly influence methane adsorption into the clathrate hydrate crystal, and so the application of correction factors in grand canonical Monte Carlo simulations is demonstrated to be ineffectual. The direct estimation of the heat of dissociation was shown to be viable when matching to calorimetric data, and the inference of phase equilibria by coupling the Clausius-Clapeyron equation with this approach was shown to yield agreeable results

Monte Carlo simulations of systems of light alcohols + water + n-dodecane and water solubility and structures in polytetrafluoroethylene.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.Polytetrafluoroethylene (Teflon®) is encountered in many environments – frying pans, clothing, osmotic distillation membranes, to name a few – yet the solubility and clustering behaviour of water with this material was not found in the open literature. This information may be useful in applications where an absence of water is desired, such as in clothing and textiles. Previous work on polyethylene + water has shown that small water clusters form in the amorphous portion of the polymer. This work investigated this phenomenon for the case of polytetrafluoroethylene + water. Initially, a test system of light alcohols + water + n-dodecane was investigated using Gibbs Ensemble Monte Carlo simulations and compared to previous laboratory experiments. This test system was investigated in order to gain expertise in the methodologies and theory behind Monte Carlo simulation, as well as to gain experience with using the necessary software. For this test system, it was found that the TraPPE parameters representing the interactions between the alcohols and the n-dodecane were not adequate and lead to increasing deviations with increasing carbon number in the alcohol. To replicate the conditions of the amorphous polymer matrix, liquid-liquid equilibrium between water and the polymer was investigated. Gibbs Ensemble Monte Carlo simulations have been performed for systems of perfluoroalkanes and water to determine the influence of temperature and carbon number on the solubility and clustering behaviour of water within the perfluoroalkanes. The temperature range in this study was from 450 K to 600 K, and the perfluoroalkane carbon number range was from 8 to 300 carbon atoms. With increasing carbon number, it was found that there was an asymptotic value of 98.0 mole percent water in the polymer phase. With increasing temperatures it was found that there were exponential increases in solubility of water into the polymer matrix. Previous work on clustering and supramolecular structure of perfluoroalkanes described the rigidity of the perfluoroalkane chains in comparison to alkane chains, thus explaining the large increases in free volume with increasing temperature in the polymer matrix observed in this work. A discontinuity with regard to both solubility and clustering behavior was observed for a polymer carbon number of 10 to 12 carbon atoms. Prior work on the energy contributions towards the helical structure of perfluoroalkanes showed a shift in the energy contribution regime for carbon numbers larger than ~10 carbon atoms, which may explain this discontinuity. It was found that linear water clusters accounted for up to ~90 percent of the water clusters, concurring with previous work on water clustering in polyethylene

A survey of the prevalence of diabetes type 2 amongst schizophrenics in a chronic care treatment facility

Objective: The determination of the prevalence of type 2 diabetes in a group of patients suffering from schizophrenia who have been hospitalized in a chronic care facility and to consider the role of factors which may contribute to the increased risk of developing diabetes.Method: The hospital files of patients suffering from diabetes type 2 were reviewed and assessments were made in terms of age, gender and body mass index (BMI) duration of stay and co-existing medical conditions. Fasting blood glucose estimations were done on all schizophrenic patients not receiving treatment for diabetes. Medications of patients were recorded. A protocol was prepared and approval to conduct the study was obtained from the hospital authorities. Results: Of 494 schizophrenic patients 19 (3.85%) were found to suffer from diabetes. 68% of patients in the diabetic group were found to be overweight in terms of BMI rating. Only one patient had a medical condition. Proportionately the number of women was relatively high. Conclusion: The prevalence if diabetes type 2 in a group of chronically ill hospitalised patients with schizophrenia is significantly lower than in outpatient populations. Residing in a facility long term may serve as a protective factor. The exclusion of psychological stressors such as isolation, poverty and abandonment may account for the finding. Keywords: Diabetes type 2; Schizophrenia; Antipsychotic drugs; Risk factors; Hospitalisation African Journal of Psychiatry Vol. 10 (3) 2007: pp. 143-14

Evaluation of Lorazepam as an Anxiolytic Agent in Psychiatric Practice

The efficacy of lorazepam, one of the newer benzodiazepines, as an anxiolytic agent is assessed in a study involving 35 non-hospitalised patients. No serious sideeffects were encountered and the drug, administered orally, was well tolerated. The patients exhibited anxiety as a primary symptom or in association with other disease entities. The drug appeared to be most effective against insomnia, tension and anxiety.S. Afr. Med. J., 48, 681 (1974)

Sorption of natural gas in cement hydrate by Monte Carlo simulation

Concrete, a combination of cement, water, sand, and aggregates, is a ubiquitous engineering and construction material. This composite material is exposed to a wide variety of environmental conditions that can cause degradation, such as extremes of temperature, and exposure to corrosive substances. This study is concerned with the sorption of natural gas constituents and their mixtures in cement hydrate using atomistic Monte Carlo simulation in the grand canonical ensemble. Pure species sorption isotherms were generated at 273, 298, and 323 K for gas fugacities up to 103 kPa. Comparison of gas uptake and the isosteric heat of adsorption in cement was undertaken for all of the species in the study, and the influences of both temperature and gas fugacity on sorption characteristics were considered. The selectivity of adsorption of hydrogen sulphide in a natural gas blend was also considered, as it is typically responsible for the degradation of concrete infrastructure

and they lived

Black and white summer wedding photograph, of a happy couple dancing.https://digitalcommons.cedarville.edu/library_photo_contest_fall_2018/1070/thumbnail.jp

Isolating and Identifying Fungal Endophytes from Roots of Rare Orchid Cypripedium arietinum in Grand Sable Dunes, Michigan

Recently the population of Cypripedium arietinum in Grand Sable Dunes, Michigan was estimated at more than 3.5 million plants, greater than 90% of the world’s known population. There is little research on this species’ root associated fungal endophytes. This new population estimate allows the ethical, destructive sampling required to shed light on root associated symbionts and further successful preservation and restoration of the species. Samples were collected of current year’s roots from 75 C. arietinum orchids at 75 locations within 4 jack pine forests in the Grand Sable Dunes, Pictured Rocks National Lakeshore, Michigan. Fungal endophyte cultures were obtained from roots and subcultured for DNA extraction. DNA was PCR amplified with primers that isolate the highly conserved 5.8s rDNA and the highly variable internal transcribed spacer (ITS) regions on either side of it. DNA was sequenced and sequences were identified using NCBI BLAST. Of the 36 DNA samples 27 were positively identified. Phialocephala fortinii and Leptodontidium orchidicola were the most prevalent identifications. These fungi both have saprotrophic abilities and may play an important role in C. arietinum’s lifecycle