A multiple wavelength, portable, solar spectroradiometer designed to measure atmospheric optical depth at several discrete wavelengths between 1 mum and 4 mum has been developed. The instrument employs a manually operated filter wheel to select wavelength bands with minimal gaseous absorption, and a thermoelectrically cooled PbSe photoconductor is used as the detector. Mechanically chopped solar radiation is converted by the photoconductor into a modulated electrical signal which is then processed by a miniaturized lock-in amplifier to produce a DC voltage proportional to solar irradiance. Example optical depth measurements are presented and discussed.

A versatile solar spectroradiometer has been designed which is capable of measuring direct solar radiation, the solar aureole, and sky radiance far from the sun. An active tracker consisting of a quadrant detector, telescope and stepper-motor driven alt-azimuth mount is used to position the spectroradiometer by computer control for solar tracking and almucantur scans. An internally baffled telescope designed to suppress stray light is employed as the optical receiver, and a photodiode serves to convert the collected flux to an electrical signal. A digitally controlled gain-switching transimpedance amplifier is used to scale the photodiode output to accommodate the large signal range encountered between measuring direct solar radiation and sky radiance well away from the sun. Example measurements are presented which demonstrate the system's capabilities.

Thesis (M.Sc). / Title from title page of PDF (viewed 2008/01/28). Written for the Dept. of Physics. Includes bibliographical references.

A solar spectroradiometer is an instrument used for measuring the transmitted solar radiation on a quasi-continuous basis. An existing computer controlled solar spectroradiometer system has been modified and made operable. Test measurements have shown that the signal to noise ratio (which is time of day and wavelength dependent) is at an acceptable level. The chief use of the spectroradiometer will be for atmospheric transmittance studies, which will require calibration of the instrument. Strategies for calibrating the instrument have been discussed.

Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on Feb. 6, 2009). Includes bibliographical references (p. 60-65).

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 83-85). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 64-65). Also available on the World Wide Web.

No description available.

Ultraviolet (UV) radiation is a potent DNA-damaging agent and a known inducer of mutations and skin cancer. The increasing incidence of skin cancer has emphasised the importance of understanding the mechanistic processes involved in the interaction of UV radiation with DNA. One of the most significant photoproducts, induced by UV light, in the DNA molecule is the cis-syn cyclobutane pyrimidine dimer. These dimers, particularly the cytosinecontaining dimers, have been implicated in the mutagenic and carcinogenic effects of sunlight. Dimerisation of contiguous pyrimidine residues in DNA can result from direct irradiation (A = 295-310 nm) or photosensitised irradiation (A > 300 nm) by endogenous photosensitisers. Direct irradiation of DNA produces a wide range of photoproducts, whereas triplet photosensitisation of DNA by acetone produces only thymine, cytosine and cytosinethymine dimers. Thus, acetone photosensitisation of DNA can be used in the elucidation of the mechanistic processes involved in the formation of photoproducts from the direct irradiation of DNA. Calf thymus DNA was irradiated in the presence of acetone at wavelengths greater than 300 nm, using a high pressure mercury lamp. Experimental conditions investigated were irradiation time, acetone concentration and DNA concentration. Irradiated DNA samples were degraded by hot acid hydrolysis to excise the dimers. The yields of thymine and cytosine-thymine dimers were able to be quantitated by reverse phase high performance liquid chromatography with DV detection.Independent kinetic mechanisms were proposed for thymine and cytosine-thymine dimerisation in calf thymus DNA. Rate constants were assigned from experimentally determined values, values cited in literature and values calculated from Stern-Volmer steady state analysis of the proposed mechanisms. Verification of the proposed kinetic mechanisms was achieved by the comparison of experimental dimer yields with those calculated from the computer simulation of the proposed kinetic mechanism. The computer program CAKE (Computer Analysis of Kinetic Equations) was used to obtain the simulated data. Good agreement between the experimental and simulated data was taken as corroboration of the proposed kinetic mechanism. A section of this work was concerned with the application of spectroradiometry to determine the amount of light intensity absorbed by irradiated solutions. The modification, calibration and operation of a Macam SR 9010 spectroradiometer to achieve this aim is discussed. / Thesis (M.Sc.)-University of Natal, Durban, 1992.

Thesis (M.Sc.). / Written for the Dept. of Geography. Title from title page of PDF (viewed 2008/05/28). Includes bibliographical references.