Thesis (doctoral)--Uppsala University, 1995. / Includes bibliographical references (p. 66-72).

The investigation was carried out in order to determine the seasonal variation in some of the properties of agar from British Columbia Gracilaria confervoldes. Optimum conditions for the preparation of agar were determined. The methods employed in the preparation of the seaweed for extraction were found to affect the properties of the agar. A very marked seasonal variation in the gelation property of the agar was obtained and the maximum gel strength values were found to vary with the source of the seaweed. Maximum gel strength values obtained during the investigation were found to be 100% and more higher than that of commercial Difco Bacto agar. The other significant physical properties of the agar prepared in this investigation were found to be comparable to those reported by other investigators working with Graollaria confervoldes in other parts of the world. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate

Thesis (M.S.)--University of Wisconsin--Madison, 1970. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Conventional and molecular methods for the improved detection of B. anthracis in environmental material were studied. A system was developed which combines a selective enrichment broth with two-phase concentration using polyethylene glycol and potassium phosphate to form the two immiscible phases. The enrichment broth alone, based on polymyxin B sulphate, lysozyme, EDTA and thallous acetate, which comprise PLET agar (PLETA), allowed the selective recovery of B. anthracis from a mixture of B. anihracis and closely related B. cereus. When soil was added to the broth, however, B. anthracis was rapidly overgrown by other naturally occurring Bacillus species. Recovery of B. anlhracis was improved by using semi-solid PLET broth or by adding chelating agents or the monobactam antibiotic aztreonam to the broth. The combination of chemicals required for optimal recovery of B. anthracis varied according to the composition of the soil. Use of the two-phase concentration system showed that in soil B. anthracis spores are generally attached to soil particles and need to be separated before they can be concentrated. Separation was achieved by pre-soaking the soil in water. The sensitivity of standard PLETA is approximately 5- 50 spores per gram of soil depending on the sample composition. The system finally recommended for the most reliable and sensitive detection of spores in soil achieved an average 25 fold greater sensitivity than PLETA. Further enrichment of the B. anthrcicis concentrate obtained using the optimised enrichment method allowed the PCR detection of B. cinthracis DNA. The sensitivity of the PCR was affected by the composition of the soil. In the absence of inhibition the PCR detection limit was approximately 10 - 100 spores per gram. A multiplex PCR was developed which targets DNA from pXO1, pX02 and the B. anthracis chromosome. The PCR allowed the rapid identification of colonies suspected of being B. anthracis. In addition to being essential for the definitive identification of B. anthracis, the ability to determine the presence of virulence plasmids in B. anthracis has reduced the need to use animals for virulence tests. Attenuated pX01⁺/pX02^- or pX01^-/pX02^- strains of B. anthracis are occasionally found in the environment. Naturally occurring pX01^-/pX02^- derivatives have not been isolated. No other plasmid DNA has been identified in B. anthracis. To examine the nature of the stability of pX01 and pX02 in B. anthracis, the effect of selective pressure for non-indigenous plasmid DNA that had been introduced into B. nnthracis was studied. A plasmid based on the minimal replicon of pAMß 1 (pAEX-5E, 5.8. kb) was found to be stable in pX01⁺/pX02^- and pX01^-/pX02⁺ derivatives of B. anthracis for more than 100 generations of growth. In the pX01⁺/pX02^- and pX01⁺/pX02^- derivatives of B. anthracis, pAEX-5E was expelled within 105 culture generations. Loss of pAEX-5E was most rapid in the pX01⁺/pX02^- derivative. Plasmids pXOI and pX02 both remained stable under selection pressure for pAEX-5E, and in the pX01⁺/pX02^- derivative retention of pX01 led to a reduction in growth rate. This indicates that, in the absence of pX02, B. anlhracis will endure a significant metabolic compromise in order to retain pX01. This study has provided extensive new information about the selective recovery of B. anthracis. in environmental material and novel'data about the stability of identity plasmids pXO1 and pX02 under selective pressure for non-indigenous plasmid DNA.

Magnetic particles offer attractive features, so its development in a wide range of disciplines, including medical applications, has been very fruitful. As a result of the special physical properties of magnetic nanoparticles, many potential applications are made available in biomedicine. The most important feature of these particles is its magnetic forces, and it has been utilized in applications such as magnetic separation, drug delivery, hyperthermia and magnetic resonance imaging contrast agent. The important properties of magnetic particles for biomedical applications are nontoxicity, biocompatiblilty, injectability, and high-level accumulation in the target tissue or organ to two most important property among those mentioned above are nontoxicity and biocompatiblilty for available clinical trials. Some researchers have used polymers or polysaccharides coating on these surface of the magnetic material to improve the material's nontoxicity and biocompatiblilty. Common materials are dextran, polyethylene glycol, polyvinyl alcohol, starch and chitin and so on. We embedd Fe3O4 magnetic nanoparticles into agar hydrogels in the experiment, then made into powder by drying and grinding, using XRD, FTIR, TEM, SQUID, TGA and zeta potential identification of material properties. We examined its toxicity and the possibility for large scale production. This method can make use of simple and inexpensive way to mass-produce synthetic these biocompatible magnetic materials.

A need exists for developing a drying technique for heat-sensitive materials as the conventional heat-based drying methods often produce changes in their physico-chemical properties. This thesis presents a non-thermal electrohydrodynamic (EHD) drying technique that may be used to dry both heat-sensitive and viscous materials. A single point-to-plate EHD system was used in de-watering sugar solutions and glycerin-water mixtures having viscosity between 2 and 22 mPa s. The EHD and forced air (2.5 m s-1) each produced 3 to 5 times higher evaporation rate than the control, which was at ambient temperature and relative humidity. The vapor flux decreased considerably and quadratically compared with the control as viscosity increased, and the dehydration kinetics was linear regardless of viscosity. Agar gels showed a linear relationship between vapor flux and time, and EHD was effective in drying at sub-zero temperatures. The agar temperature during drying was significantly below the ambient, indicating evaporative and entropic cooling.

Proefschrift--Ghent. / Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 83-92).

Proefschrift--Ghent. / Includes bibliography.

No description available.