37 research outputs found
Optical spectroscopy of thin film semiconductor structures
No full textThis thesis consists of a study of several thin film semiconductor structures of practical technological use either presently or in the near future. The first system studied is an ultra thin film single crystal gallium arsenide layer. The absorption spectra of these layers are measured and transitions at both the F- point and L-point of the Brillouin Zone are observed, the latter are not normally measurable in thicker layers. The observed shift in the F-point absorption edge is attributed to contributions from the Franz-Keldysh Effect and the Moss-Burstein Effect. The temperature dependence of the L-point energy gap is measured and compared with previous data. The next system investigated is an n-type porous silicon layer coated with p-type polyaniline. Both photoluminescence and electroluminescence spectra and the electrical characteristics have been measured for this system. The interface between the two layers is found to be a rectifying junction consistent with a potential barrier formed at the interface. In forward bias, it is possible to generate electroluminescence in the visible and near infra red regions. The final structure studied is a thin film cadmium sulphide-cadmium telluride solar cell structure. The cells are found to have a low efficiency of around 1% as grown, but a process of treatment with cadmium chloride and annealing in air improves this by a factor of approximately ten. Photoluminescence measurements on the back surface of the cadmium telluride revealed three major emission bands at 1.59 eV, 1.55 eV and 1.45 eV. By varying temperature and incident laser power, attempts at assigning the bands to specific impurity centres in the cadmium telluride is made Using a novel bevelling etch technique to prepare samples, depth dependent measurement of the photoluminescence is possible. This reveals that the major changes associated with the improvement in efficiencies occurs at the interface between the CdS and the CdTe
Altered Expression of the Dna Mismatch Repair Proteins Hmlh1 and Hmsh2 in Cutaneous Dysplastic Nevi and Malignant Melanoma
No full text Molecular alterations in the mismatch repair system suggest that this mechanism may be important in the evolution of cutaneous melanoma. Our current study evaluated the expression of two mismatch repair proteins, hMLH1 and hMSH2, in dysplastic nevi (DN) and cutaneous melanoma (CM). Immunohistochemical staining of these proteins was performed on 55 CM and 30 DN specimens. The staining results were divided into three groups: negative, partially positive and strongly positive. Normal adjacent skin cells served as an internal control for positive immunostaining. Altered immunoreactivity of one of the proteins was found in four (13.4%) DN and seven (12.7%) CM. Lack of staining for hMLH1 was observed in two (6.7%) cases of DN and five (9.1%) cases of CM; staining for hMSH2 was absent in two (6.7%) of the DN and two (3.6%) of the CM specimens. Partially positive staining was found in 33.3% and 53.3% for hMLH1 and hMSH2, respectively, in DN, and in 54.5% and 69.1%, respectively, in CMM. Our study shows that complete or partial loss of MMR protein expression occurs in a subset of both DN and CM and may represent a distinct pathway in the development of some DN and CM. </jats:p
Evaluation of putative molecular biomarkers in abdominal and retroperitoneal leiomyosarcomas
No full textAltered expression of the DNA mismatch repair proteins hMLH1 and hMSH2 in cutaneous dysplastic nevi and malignant melanoma
No full textPreparation and characterisation of thin film CdS/CdTe solar cells produced by close space sublimation.
No full textInherited mutations impair responses to environmental carcinogens: Cancer prevention in mutation carriers
No full textSome environmental carcinogens may be responsible for a modest increase in the numbers of cancers after years of exposure. Economic or political factors weigh against widespread bans of carcinogens. However, lists of chemicals and agents that cause cancer assume that everyone is equally susceptible to their carcinogenic effects. 
Hereditary cancer gene mutations can target specific tissues if they are exposed to a carcinogen and the hereditary deficit impairs normal protective responses. Mutation carriers should then have higher risks for specific cancers caused by specific carcinogens.
 
For example, it can be predicted that BRCA1 or BRCA2 mutation carriers should be highly susceptible to the carcinogen formaldehyde. High formaldehyde levels can overwhelm normal enzyme detoxification systems or detoxification genes may be inadequate or missing. Formaldehyde that is not detoxified causes strands of DNA to cross-link to each other and to nearby proteins. Carriers of mutations in BRCA1/2 dependent pathways are deficient in the ability to undo these cross-links. 

Human myeloid leukemias are linked to formaldehyde. Inherited biallelic BRCA2 gene defects and other defects in BRCA1/2 mediated pathways dramatically increase risks for myeloid leukemia, even among infants. In 12 of 15 studies, heterozygous BRCA1 or BRCA2 mutations increase risks for myeloid leukemias. Moreover, chromosome arms lost in hereditary breast cancers encode enzymes essential for formaldehyde metabolism. BRCA1/2 mutation carriers may reduce their very high cancer risks by lowering their exposure to formaldehyde.
 
Cancers associated with many other hereditary gene deficits can also be stimulated by distinct environmental hazards. Widespread education could prevent or delay some cancers in mutation carriers
An investigation of domestic workers' perceptions into the effects of employer involvement on parenting and parental autonomy
No full textBibliography: leaves 77-81.Domestic workers (DWs) have been described in sociological literature as "trapped" workers. They have been portrayed as workers coerced into powerlessness and unassertiveness by virtue of their economic dependence on employers. Observations of DWs in clinical settings have confirmed these assertions. This study examines how eight DWs negotiate their parental authority f autonomy while having their own children living with them on their employers' premises and also having employers involved in parenting DWs' children. The results are based on semi-structured interviews with DWs. Interviews were taped, transcribed and the data analysed qualitatively. Results were discussed according to the following themes: 1. the nature of employer involvement 2. areas of employer involvement 3. areas of employer non-involvement in parenting and its relationship to the issues of power, culture and difference. Emergent themes were identified and discussed. Overall the expected finding that DWs would experience difficulties with parental autonomy was not supported. Recommendations regarding implications for treatment and research are made
Vapour sorption, wavelength tracking and thermo-optic properties of dual slab waveguide interferometers
No full textThe dual slab waveguide interferometer is introduced as a device which has many applications in various research areas. Reported is its ability to provide details on the mechanism for the vapour sorption of thin polymer films, the development of the interferometer as a wavelength tracking device for the telecommunications industry and a method to characterise the thermo-optic properties of III-V semiconductor alloys. The vapour sorption mechanisms of thin films of polymers Polyisobutylene (PIB) and Polyvinylpyrrolidone (PVP) on exposure to several solvents are investigated. Coating interferometer chips with a thin layer of polymer and monitoring the interference fringe pattern for changes due to the exposure to a solvent vapour provides information on the mechanism for vapour sorption as one of swelling rather than void-filling. Interferometer sensitivities to vapour concentrations are linear and depend on refractive index differences between polymer and condensed vapour. An interferometer manufactured from III-V semiconductor compounds is developed to produce a device which can operate as a wavelength tracker. Sensitivities of over 6 mrad / pm and 7 mrad / pm for single and dual quaternary systems respectively indicate that a device of length around 5 mm would be capable of detecting picometer input wavelength changes including thermal background noise. The sensitivity to thermal changes provides a simple method for determining the thermo-optic coefficient of two Indium Gallium Arsenide Phosphide (InGaAsP) alloy compositions as (3.15±0.08)x 10(^-4)K(^-1) and (2.60±0.017)x10(^-4)k(6-1) forInGaAsP compounds with bandgap wavelengths around 1.3 μm and 1.15 μm respectively
Evaluación de los niveles de N-aciletanolaminas (NAEs) en aquenios secos de cuatro cultivares de cannabis sativa L.
No full textWe utilized high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS), on dry achenes from four cultivars of Cannabis Sativa L.; CA, Cannabis Sativa L. Cultivar Amnesia; CB, Cannabis Sativa L. Cultivar Beldia; CM, Cannabis Sativa L. Cultivar Mexicana; CK, Cannabis Sativa L. Cultivar Khardala, to detect and quantify N-acylethanolamines (NAEs), which are bioactive compounds involved in lipid and energy metabolism. These plants were grown in Chefchaouen, northern Morocco. All four varieties displayed identical NAE lipid profiles, dominated by those derived from 16C and 18C fatty acids. In general, the NAE species presented the following concentration order: [LEA] > [OEA > POEA] > [SEA] > [PEA]. NAE-MUFA was the most abundant type, followed by NAE-PUFA and NAE-SFA, comprising 44, 37, and 19% of all NAEs, respectively, across the varieties. This research provides first-time quantification of NAEs in Cannabis achenes, thus enriching our understanding of these plants’ pharmaceutical and nutritional potential.Empleamos cromatografía líquida de alta resolución-espectrometría de masas (HPLC-MS/MS), en aquenios secos de cuatro cultivares de Cannabis Sativa L: CA, Cultivar Amnesia; CB, Cultivar Beldia; CM, Cultivar Mexicana; CK Cultivar Khardala, para detectar y cuantificar N-aciletanolaminas (NAE), compuestos bioactivos implicados en el metabolismo lipídico y energético. Estas plantas se cultivaron en Chefchaouen, al norte de Marruecos. Las cuatro variedades mostraron perfiles lipídicos de NAE idénticos, predominando los derivados de los ácidos grasos 16C y 18C. En general, las especies de NAE presentaron el siguiente orden de concentración: [LEA] > [OEA > POEA] > [SEA] > [PEA]. NAE-MUFA son los más abundante, seguido de NAE-PUFA y NAE-SFA, que presentan el 44%, el 37% y el 19% de todos los NAE respectivamente, en todas las variedades. Esta investigación proporciona por primera vez una cuantificación de las NAE en los aquenios del cannabis, enriqueciendo nuestra comprensión del potencial farmacéutico y nutricional de la plant
