published_or_final_version / Botany / Doctoral / Doctor of Philosophy

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No description available.

It was the purpose of this investigation to isolate and characterize the pigments of Mycobacterium rhodochrous by partition behavior, chromatographic data, and absorption spectra. In addition, it was the purpose to determine whether or not the type of pigments found in M. rhodochrous is typical of those found in other mycobacteria.

LD2668 .T4 1949 P35 / Master of Science

Call number: LD2668 .T4 1959 P65

Thesis (M.Sc.(Physiological Chemistry)--University of the Witwatersrand, Faculty of Science, 1954.

Thesis (MTech(Chemistry))--Cape Technikon, Cape Town,1995 / The naphtho[2,3-c]pyran occurs frequently in nature as derivatives of the 5,10 quinones. The most common examples include the eleutherins and protoaphins. These naturally occurring compounds have been found to possess antibiotic activity through the process of bioactivation. The possibility of appropriately substituted compounds functioning as bioreductive alkylating agents provides a logical model that has a great deal of predictive power. The thesis deals with the synthesis of some naphtho[2,3-c]pyrans to be tested biologically; the challenge being to design compounds in a biologically inactive form which become activated only subsequent to an in-vivo transformation. Chapter One describes and compares a high yielding synthesis of a naphtho[2,3c] pyran, hongconin, to a previous route.,a Racemic hongconin (29) has been synthesised from adduct (43) formed by reaction between 1-methoxycyclohexa1,4- diene (41) and 1,4-benzoquinone (42). The key steps includes Fries and Claisen rearrangements, base and cerium(lVj initiated pyran ring formation, C-4 pyran ring hydroxylation and silver(ll) mediated oxidation. The target compound (29) was tested in vitro for antimicrobial activity and compared to the results obtained for isoeleutherin (2) and its 9-demethoxy analoque (30). The spectral data, melting points and yields of the individual compounds is as described in Chapter Two.

Color is a visual characteristic which imparts the ability to categorize different objects. When light strikes an object, there are three possibilities as to what can happen. The light may be reflected, refracted or scattered. Human perception of color is due to a combination of these. Plastics are polymeric materials. Polymers are generally colorless and need colorants in order to have some color. One or more pigments in certain ratios can be used to give a specific color to plastics. Slight variations in the proportions of either of the used pigments, or their dispersion, may result in a color that is different from the desired one. There can also be many other reasons for color mismatch such as processing or degradation effects. This study utilized the historical data records of SABIC IP to look at effects of changing Grade on color (i.e. when the same color is produced from resin blends which may have different amounts of resins, pigments or additives). These records were also used to study effects of change in screw diameter and configuration on color (i.e. when the same grade of a color is produced on two different production lines, different screw diameters and configurations). The effects of the processing parameters on the colors were also investigated by carrying out experiments using a twin screw extruder at SABIC IP’s plant in Cobourg. Resins, pigments and additives were dry blended and extruded while being subjected to different processing conditions. Three processing parameters, namely temperature, rpm and feed-rate, were chosen for the study. A three level factorial design of experiments was used. An analysis of variance (ANOVA) has been utilized to find the effects of individual parameters on color and the interaction between two parameters and their cumulative effect on color. / UOIT