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Thesis (M.S.W.)--Smith College School for Social Work, Northampton, Mass., 2009. / Includes bibliographical references (p. 38-39).

Thesis (Ph.D.) - University of St Andrews, August 2009. / Restricted until 18th August 2011.

The purpose of the descriptive research was to investigate the relationship between an adherence to the Black community's belief and value system about Black skin tones and Black school-age children's skin tone preferences and perceptions of occupational life opportunities. Six Black skin tones were scaled via Thurstone's method of paired comparisons and the law of comparative judgment. The result was an interval level Skin Tone Scale on which the skin tones were positioned from most to least preferred by the children. The most preferred skin tones ranged from medium to honey brown. The least preferred were the extreme tones of very light yellow and very dark brown. Data collection was accomplished with the Porter Skin Tone Connotation Scale (PSTCS). The instrument was constructed from the forced choice preference paradigm. Data were obtained from a volunteer sample of 98 Black school-age children who resided in a city in Arizona. Data collection and analyses were constructed to test two hypotheses: (1) Black school-age children's skin tone classifications for differential status occupations will be related to gender, age, and perception of own skin tone as indexed by the skin tone values of the Skin Tone Scale, and (2) with increasing age, Black school-age children's skin tone preferences will be more systematically related to the skin tone values of the Skin Tone Scale. Testing of the first hypothesis with multiple regression indicated that the independent variables did not account for enough variance to support the hypothesis. Analysis of the second hypothesis with coefficient gamma suggested a trend toward more systematic agreement with the Skin Tone Scale with increasing age. Results of the first hypothesis were discussed in relation to composition of the sample, gender differences, the achievement value of the Black sociocultural system, and these Black children's lived experience. Results of the second hypothesis reflected those from similar investigations conducted in the 1940s. The results suggested Black children still most prefer brown skin tones and least prefer extreme light and dark skin tones. Black children's preferences for Black skin tones have not altered in approximately forty years.

Probiotic bacteria have been investigated in the prevention and treatment of various diseases and allergies. The current study was undertaken to determine the effect of eight probiotic Lactobacillus species against bacterial human skin pathogens using several techniques. Antimicrobial activity of lactobacilli against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Propionibacterium acnes was evaluated using lactobacilli broth cultures (BCB) and cell free supernatant (CFS). Antimicrobial activity was significantly greater with BCB compared with CFS especially for Lactobacillus plantarum and Lactobacillus acidophilus. Lactobacilli and pathogen aggregation, biofilm formation and adhesion to keratin were assessed. L. casei and L. plantarum were selected for further study as they showed the greatest co-aggregation (18.02 ± 1.34% with L. casei and 14.92 ± 1.45% with L. plantarum) with the pathogens (16.63 ± 1.65% with S. aureus 3761 and 14.58 ± 1.68% with P. aeruginosa) and prevention of biofilm formation by the pathogens. The antimicrobial activity of human beta defensin-2 (hBD-2) alone or with L. plantarum against pathogens was assessed. The results with hBD-2 showed that hBD-2 (10 μg / ml for 5 h) and L. plantarum together were significantly more inhibitory against S. aureus than hBD-2 alone. The presence of NaCl reduced the effectiveness of hBD-2 alone and with L. plantarum. In the presence of L. plantarum, inactivation of mprF and dlt genes led to increased binding of hBD-2 by the bacterial cell wall, and then inhibition growth of bacterial cell wall. Studies investigated the effect of exposure of methicillin resistant Staphylococcus aureus (MRSA) to the supernatant of L. plantarum the susceptibility of MRSA to β-lactams. MRSA became sensitive to β-lactams when treated with culture supernatant of L. plantarum. Gene expression studies demonstrated that the mecR1-mecI-mecA-PBP2 signalling pathway was impeded by exposure to culture supernatant of L. plantarum and β-lactams. The studies reported here demonstrate a possible alternative approach to dealing with skin pathogens, which may have clinical implications especially with regard to MRSA infections, and continued research is advised.

For understanding the mechanisms of low level laser/light therapy (LLLT), accurate knowledge of light interaction with tissue is necessary. In order to have a successful therapy, laser energy needs to be delivered effectively to the target location which depending on the application can be within various layers of skin or deeper. The energy deposition is controlled by input parameters such as wavelength, beam profile and laser power, which should be selected appropriately. This thesis reports a numerical study that investigates the laser penetration through the human skin and also provides a scale for selection of wavelength, beam profile and laser power for therapeutic applications. First, human skin is modeled as a three-layer participating medium, namely epidermis, dermis, and subcutaneous, where its geometrical and optical properties were obtained from the literature. Both refraction and reflection are taken into account at the boundaries according to Snell’s law and Fresnel relations. Then, a three dimensional multi-layer reduced-variance Monte Carlo tool was implemented to simulate the laser penetration and absorption through the skin. Local profiles of light penetration and volumetric absorption densities were simulated for uniform as well as Gaussian profile beams with different spreads at 155 mW average power over the spectral range from 1000 nm to 1900 nm. The results showed that lasers within this wavelength range could be used to effectively and safely deliver energy to specific skin layers as well as to achieve large penetration depths for treating deep tissues, without causing any skin damage. In addition, by changing the beam profile from uniform to Gaussian, the local volumetric dosage could be increased as much as three times for otherwise similar lasers. In the second part of this thesis, a three-dimensional single-layer reduced-variance inverse Monte Carlo method was developed to find the optical properties of the skin using the experimental values of transmittance and reflectance. The results showed that both transmittance and reflectance scale well with transport optical thickness. Moreover, it was also shown that penetration depth is highly sensitive to the laser wavelength and varied within the range from 1.7 mm to 4.5 mm. / text

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