The initial step in odor recognition by the nose is the binding of odorant molecules to receptor sites embedded in the dendritic membranes of olfactory receptor cells. Despite considerable interest and experimentation into the nature of these receptor sites, little is known of their specificity to different types of odorant molecules. This lack of knowledge partially stems from the fact that the nature of receptor proteins is most effectively studied when specific and irreversible inhibitors are available for use as chemical probes, yet no such agents have been discovered for use in the olfactory system. A series of alkylating agents and other chemically active odorants were tested to determine whether they might react with specific odorant receptors and modify olfactory responses. Electroolfactogram (EOG) recordings were obtained before, during, and after treatment of the olfactory mucosae of grass frogs (Rana pipiens) with a chemically active odorant.

Drug abuse is a very common problem these days; and this problem is especially rampant among the young people of South Africa. Early problems in family management, the antisocial behaviour of the child, and peer pressure and rejection ignite the early onset of substance abuse. Treatment programmes and therapeutic methods to treat chemical dependency are available and utilised, but the high relapse rate and lack of support from family members and dysfunctional families, as well as the fears and challenges expressed by in-patient youth about being reintegrated with their families and a lack of supporting literature in this regard remain a cause for concern and need to be considered by the social work profession in order to plan effective intervention strategies. In response to this situation a research project was undertaken with the purpose of exploring and describing the perceptions, expectations, fears and needs of chemically dependent youth in a rehabilitation centre about being integrated into their family systems in an attempt to forward recommendations to assist social workers in rendering effective therapeutic services to service users in rehabilitation centres who have a substance abuse problem. A qualitative approach was utilised following an explorative, descriptive and contextual research design. The study was conducted at an in-patient rehabilitation centre called the Dr Fabian and Florence Ribeiro Treatment Centre in Cullinan, Gauteng Province in South Africa. Data were collected by means of semi-structured interviews. A sample of participants was selected by using purposive sampling from a population of service users in the Dr Fabian and Florence Ribeiro Centre who are chemically dependent. Data were analysed according to the framework provided by Tesch (cited in Creswell, 2003). Guba‘s model (cited in Krefting, 1991) was employed for data verification. The research findings point to the fact that participants had both negative and positive perceptions about going back to their respective families. On the one hand, there were negative perceptions shared. These were founded on a feeling of worry about the fact that their families criticised them a lot or that their families would not accept that they had changed, would still treat them like addicts, and not trust them. Furthermore, they feared relapse, triggers in their environment and family members who were abusing a substance. On the other hand, some participants perceived the reintegration with their families, following treatment, in a positive light as they were looking forward to joining them again after being in v treatment for three months.They were excited about the fact that they had been granted an opportunity where they could show their families that they have changed and have the chance of starting a new life. Moreover, part of the research findings point to the fact that some of the participants‘ families had already organised employment, a place for them to stay and financial assistance. From the research findings it became clear that the participants harboured the following expectations towards the families with whom they were reuniting: They need the family‘s love and support; to trust them again: to mend severed relationships and spend quality time together; to provide practical and material help, and for the family to be educated on addiction and for the family to accompany them to aftercare. In terms of research findings directed at the site (i.e., the rehabilitation centre) where the research was conducted the participants indicated that they needed more activities, they would like their families to be part of their recovery process, and expressed the need for individual sessions apart from group sessions and aftercare services. In terms of recommendations it was apparent that community members, community organisations and the government sector need to develop and launch chemical substance abuse prevention and awareness programmes through various media, (i.e. articles in newspapers, magazines, talks and documentaries on radio and television, community gatherings and meetings in all communities). Moreover, it is recommended that parents should take responsibility for monitoring and countering substance abuse in their children. Families need to be empowered through talks, attending parenting skills training, workshops and group meetings. South Africa needs to develop a policy focusing on families. Furthermore, it is recommended that treatment centres need to provide individual sessions, family therapy, aftercare services and more extramural activities, if these are not included in their treatment regime. / Social Work / M.A. (Social Science)

Membrane desalination has become one of the most important desalination technologies used in the world. It provides high water quality for numerous applications and it demonstrates excellent desalination efficiency. One of the most troubling drawbacks of membrane desalination is membrane fouling. It decreases the performance of the membranes and increases the energy requirement. Two of the most important causes of fouling are microbes and organic matter. Hence, to maintain an optimized desalination performance, routine inspection of microbial and organic contents of water is crucial for desalination plants. In this study, water samples were obtained from different treatment points in an ultrafiltration (UF)/nanofiltration (NF) seawater desalination pilot plant. This was performed to better understand how the water quality changes along the desalination scheme. The effect of fouling control techniques, including Chemically Enhanced Backwash (CEB), Cleaning in Place (CIP), and the addition of a biocide (DBNPA) was studied. Different analytical tools were applied, including Bactiquant, Total Organic Carbon (TOC), Assimilable Organic Carbon (AOC), and Liquid Chromatography for Organic Carbon Detection (LC-OCD). Out results showed that UF did not decrease TOC but it was sufficient in removing up to 99.7% of bacteria. Nanofiltration, removed up to 95% of TOC. However, NF permeate had a high increase in AOC as compared to the raw seawater sample. The LC-OCD results suggested that this might be due to the increased low molecular weight neutrals which were the most common organic species in the NF permeate. The fouling control techniques showed various effects on the desalination efficiency. Daily CEB did not cause a reduction in TOC or bacteria but decreased AOC in the UF filtrate. The biocide addition resulted in an adequate membranes protection from fouling and it did not affect the investigated water parameters. When the dosing of biocide was stopped, the water quality parameters did not change, but the NF pressure drop increased rapidly, indicating fouling of this membrane. CIP did not show an impact on the organic and microbial contents of water, but it was efficient in restoring the operations back to acceptable pressure levels. These results indicated that the applied fouling protection techniques were beneficial in fouling control.

No description available.

Chemically Induced Dynamic Nuclear Polarization (CIDNP) is an efficient method of creating non-equilibrium polarization of nuclear spins by using chemical reactions, which have radical pairs as intermediates. The CIDNP effect originates from (i) electron spin-selective recombination of radical pairs and (ii) the dependence of the inter-system crossing rate in radical pairs on the state of magnetic nuclei. The CIDNP effect can be investigated by using Nuclear Magnetic Resonance (NMR) methods. The gain from CIDNP is then two-fold: it allows one to obtain considerable amplification of NMR signals; in addition, it provides a very useful tool for investigating elusive radicals and radical pairs. While the mechanisms of the CIDNP effect in liquids are well established and understood, detailed analysis of solid-state CIDNP mechanisms still remains challenging; likewise a common theoretical frame for the description of CIDNP in both solids and liquids is missing. Difficulties in understanding the spin dynamics that lead to the CIDNP effect in the solid-state case are caused by the anisotropy of spin interactions, which increase the complexity of spin evolution. In this work, we propose to analyze CIDNP in terms of level crossing phenomena, namely, to attribute features in the CIDNP magnetic field dependence to Level Crossings (LCs) and Level Anti-Crossings (LACs) in a radical pair. This approach allows one to describe liquid-state CIDNP; the same holds for the solid-state case where anisotropic interactions play a significant role in CIDNP formation. In solids, features arise predominantly from LACs, since in most cases anisotropic couplings result in perturbations, which turn LCs into LACs. We have interpreted the CIDNP mechanisms in terms of the LC/LAC concept. This consideration allows one to find analytical expressions for a wide magnetic field range, where several different mechanisms are operative; furthermore, the LAC description gives a way to determine CIDNP sign rules. Thus, LCs/LACs provide a consistent description of CIDNP in both liquids and solids with the prospect of exploiting it for the analysis of short-lived radicals and for optimizing the polarization level.

Indiana University-Purdue University Indianapolis (IUPUI) / Fluoridation of community water supplies for the purpose of preventing dental caries remains one of the top 10 public health interventions of the last century. However, exposure (ingestion) of greater than optimal amounts of fluoride from a variety of sources has led to an increase in the prevalence of dental fluorosis. We propose that dental fluorosis represents a complex condition caused by environmental and genetic factors. Purpose: To assess the role of genetics in the pathogenesis of dental fluorosis using genetically separate inbred strains of mice. Methods: Twelve genealogically disparate strains of mice were treated with 0 ppm, 25 ppm, and 50 ppm of fluoride in their drinking water. Each mouse was given weekly dental fluorosis evaluations. After 60 days of treatment, femurs were collected for fluoride analysis. Mandibular incisors were isolated for quantitative light induced fluorescence (QLF) studies and fluoride analysis. Digital and 35 mm images were taken of all mouse incisors in order to apply and compare the Dean's Index and the modified Thylstrup and Fejerskov Index (TFI), both indices of dental fluorosis. Skeletal radiographs were taken on the euthanized mice and later examined for extra skeletal calcifications and other gross bony deformities. Results: Differences in dental fluorosis susceptibility/resistance were identified between the strains, ranging from mild, moderate, to severe dental fluorosis. Furthermore, we found clustering of strains into distinct phenotypic groups. The A/J mouse strain was highly susceptible, with a rapid onset and severe development of dental fluorosis compared with the other strains tested. The 129P3/J mouse strain was least affected with negligible dental fluorosis. From the skeletal radiographs, no gross skeletal lesions or evidence of bone dysplasia were noted. Similar body burden of fluoride, as judged from analysis of mineralized tissues, was seen in all strains despite differences in their predispositions to develop dental fluorosis. Both the Dean's and TF indices are useful for classifying the stage or severity of fluorosis in mice, and there are advantages to the use of digital images over conventional 35 mm slide images. Both indices correlate well with the amount of fluoride exposure during amelogenesis; however, these indices are not promising indicators of fluoride burden during amelogenesis. Conclusions: QLF proved to be an innovative and useful tool for the quantification of dental fluorosis. Furthermore, these observations support the role of a genetic component in the pathogenesis of fluorosis.

No description available.

This project aims to obtain and interpret the measurements of the mean longitudinal magnetic field of the chemically peculiar star V1148 Ori. To achieve this aim 12 spectropolarimetric observations obtained by the CFHT using the spectropolarimeter ESPaDOnS were used. The method used to extract the magnetic field signatures from the spectra is called least-squares deconvolution. This method yields line-averaged profiles with a high signal-to-noise ratio. These mean line profiles are necessary to compute the mean longitudinal field. Results of the mean longitudinal field measurements were plotted as a function of the rotational phase, and to this, a sinusoidal function describing a dipolar field was fitted. The dipolar field parameters were computed for two different stellar radii. Inconsistent values for the stellar radii were obtained from the literature, and therefore we calculated two values for each of the parameters. For the surface polar field strength, we found BR1 = 17.38±0.30 kG and BR2 = 12.81±0.22 kG. The calculations involving one of the stellar radii gave results more consistent with previous findings. However, the discrepancy in parameter values could not be accounted for by the small uncertainties. So no definite conclusions can be drawn about the dipolar field parameters. Our fit aligns well with our longitudinal field measurements, no clear indication of any significant deviation from our model assumption, which suggests that the mean longitudinal field is consistent with a large-scale dipolar-like structure.

Magnetic fields play a crucial roll in the stellar activity and evolutionof stars. Despite much research there is much that we do notunderstand. Among Ap stars, empirical evidence has suggested a minimumthreshold for the dipolar magnetic field strength of Bp ≈ 300G.This thesis studies the magnetic field of the Ap star EP UMa usingthe oblique rotator model, which is modeling the star’s magnetic fieldas a dipole. The magnetic field was calculated through the StokesV- and I-spectrum emitted by the star. In total 16 observations ofthe Stokes V and I spectrum were used, collected from the spectropolarimeterNARVAL. These spectra were then analysed using the leastsquares deconvolution method, creating average Stokes V and I profiles,through which the magnetic field were calculated. The result ofthis study indicates a magnetic field of EP UMa with polar strengthof 74G ≤ Bp ≤ 196G, which is well below the suggested minimumthreshold.

Hydrogen evolution via proton reduction occurs at a high rate at the surface of Pt than at Au electrodes. Using cyclic voltammetry, chemically modified nanometer-sized Au electrodes, prepared by the Laser-Assisted Puller Method, were employed to examine current amplification by electrocalysis at Pt nanoparticles adsorbed on the modified Au electrode surfaces. The electrodes were modified with Self-Assembled Monolayers (SAMs) of cysteamine and soaked in Pt colloid solutions overnight. Monitoring the decrements of the characteristic steady-state catalytic current for proton reduction indicated that aggregates of Pt nanoparticles are adsorbed on the cysteamine monolayers and desorb from them particle by particle. The results also indicate that some particles are strongly attached to the modified electrode surface and do not deplete even after thorough rinsing.