No description available.

As electronics reach nanometer size scales, new avenues of integrating biology and electronics become available. For example, nanoscale field-effect transistors have been integrated with single neurons to detect neural activity. Researchers have also used nanoscale materials to build electronic ears and noses. Another exciting development is the use of nanoscale biosensors for the point-of-care detection of disease biomarkers. This thesis addresses many issues that are relevant for electrical sensing applications in biological environments. As an experimental platform we have used carbon nanotube field-effect transistors for the detection of biological proteins. Using this experimental platform we have probed many of properties that control sensor function, such as surface potentials, the response of field effect transistors to absorbed material, and the mass transport of proteins. Field effect transistor biosensors are a topic of active research, and were first demonstrated in 1962. Despite decades of research, the mass transport of proteins onto a sensor surface has not been quantified experimentally, and theoretical modeling has not been reconciled with some notable experiments. Protein transport is an important issue because signals from low analyte concentrations can take hours to develop. Guided by mass transport modeling we modified our sensors to demonstrate a 2.5 fold improvement in sensor response time. It is easy to imagine a 25 fold improvement in sensor response time using more advanced existing fabrication techniques. This improvement would allow for the detection of low concentrations of analyte on the order of minutes instead of hours, and will open the door point-of-care biosensors. / Graduation date: 2011

The effect of frozen storage time on the composition of the cell wall polysaccharide (CWP) of muskmelon (Cucumis melo) cultivars at different stages of maturity was investigated. Changes in composition, firmness, drip loss, and color of Cantaloupe and Honey Dew melon flesh were determined at three stages of maturity and for three periods of storage at -23°C. Relationships between firmness, drip loss, and other composition measurements, as well as the total CWP sugar composition, were also determined. Cell wall polyssacharides were isolated and purified, and fractionations were performed using cyclohexane trans- 1,2-diamine tetraacetate (CDTA), Na₂C0₃, guanidinium thiocyanate (GTC), and KOH. All fractions and residues were dialysed and then freeze-dried. Following hydrolysis of CWP fractions with trifluoroacetate (TFA), the alditol acetate derivatives of neutral sugars from each CWP fraction were prepared and analyzed by gas chromatography, using myo-inositol as the internal standard. TFA insoluble fractions were analyzed colorimetrically using phenol-sulphuric acid reagent. Uronic acid was determined using 0.15% m-hydroxybiphenyl for absorbance at 520 nm with galacturonic acid as the standard. It was determined that CDTA and Na₂C0₃ fractions were composed of typical pectic materials, containing mostly galacturonic acid with the neutral sugars arabinose, galactose, rhamnose, and a smaller amount of xylose. As maturity increased, CDTA fraction yields increased, though total neutral sugar CWP compositions decreased. GTC and KOH fractions were typical of hemicellulose, and contained principally xylose, glucose, galactose, mannose, and fucose, with very small amounts of uronic acid, arabinose, and rhamnose. Residue fractions contained principally glucose and galactose, with smaller amounts of mannose, xylose, arabinose, and fucose. With the exception of xylose and glucose, all neutral sugars decreased significantly (p < 0.01) as maturity increased in both the Cantaloupe and Honey Dew melons. Total uronic acid did not change as maturity increased, except for Cantaloupe, where total uronic acid decreased from the ripe to overripe stages. The CDTA fraction yield increased and all neutral sugars decreased significantly (p < 0.05) as storage time was increased. Only the CDTA fraction yield was negatively correlated with the firmness of both melons, and was positively correlated with drip loss as maturity and frozen storage time were increased. Firmness was positively correlated with Na₂C0₃ and GTC fraction yield in Cantaloupe, whereas for Honey Dew there was no correlation between firmness and Na₂C0₃ or GTC fraction yield as maturity increased. The KOH fraction was negatively correlated with firmness in Cantaloupe, whereas there was no correlation between firmness and KOH fractions in Honey Dew existed as maturity increased. The residue fractions increased in both melons only from the underripe to the ripe stages, and did not change from ripe to overripe. Firmness was positively correlated with total rhamnose, arabinose, mannose, and galactose as maturity increased, and the drip loss was negatively correlated with all total neutral sugars as storage time was increased. During frozen storage, there was a significant decreases (p < 0.05) in total CWP sugars in relation to increased storage time. The decrease in total sugars was more dramatic during the 0 to 5 month period than the 5 to 10 month period of frozen storage. Galactose did not change in the Cantaloupe, whereas in Honey Dew it decreased 34.3% from 0 to 5 months then decreased only 13% from 5 to 10 months of storage. / Graduation date: 1994

Pregnant and weanling rats were fed liquid diets with or without 30 percent of total kcal from ethanol and varying levels of copper in order to determine if ethanol ingestion would exaggerate a marginal copper status to an obvious copper deficiency. Pregnant albino rats were fed either 0.75 or 3.75 mg Cu/L throughout gestation and the first 15 days of lactation while female weanling rats received 0.5 or 2.5 mg Cu/L for 5 weeks. Ethanol consumption exaggerated a marginal copper status during reproduction as evidenced by significant reductions in maternal liver copper concentration and enzymatic activity of the copper metalloprotein Copper-Zinc superoxide dismutase in offspring liver. Ethanol had little or no effect upon copper status in weanling rats. In addition, serum copper failed to reflect a developing depletion of liver copper when ethanol was being consumed. Since it is known that the average American diet is just adequate in copper content, and that copper balance is difficult to achieve during times of increased metabolic demand, pregnant subjects may be at a great risk to develop a copper deficiency when ethanol is being consumed. This ethanol and copper interaction, however, will likely go undetected if only serum copper is used as an indicator of copper status. / Graduation date: 1989

Pasteurization radiation offers a new means of extending the refrigerated storage life of foods. This procedure avoids many of the undesirable changes which result when sterilization radiation is used and still eliminates most of the spoilage organisms. Shrimp was treated with 5 ppm chlortetracycline and subjected to pasteurization levels of gamma radiation and stored at 38°F. The levels of irradiation used were 0.5 and 0.75 megarad. These levels were based on the flavor threshold of irradiation intensity. The quality of the stored irradiated shrimp was determined by subjective evaluation, chemical analyses and microbiological examinations. The storage life of the shrimp irradiated at 0.5 megarad was extended to 5 weeks, compared with 1 week for the unirradiated samples held at the same temperature. Throughout the ten week storage period, the samples which received doses of 0.5 megarad and CTC and those which received 0.75 megarad with and without CTC remained in good condition. / Graduation date: 1963

Once historically widespread throughout the Willamette and Umpqua River drainages, the Willamette Oregon chub is now restricted to scattered populations along 15 miles of the Middle Fork of the Willamette River whereas the Umpqua Oregon chub is still widely distributed. The decline in the Willamette drainage was more severe because changes in the physical and biological habitat were more severe when compared to the Umpqua drainage. The Willamette Oregon chub may be more sensitive to environmental degradations than the Umpqua Oregon chub. The difference in sensitivity to degradation is a result of ecological differences between Willamette and Umpqua Oregon chub. Willamette Oregon chub inhabited areas with primarily very little if any current, fed in the water column, and spawned in aquatic vegetation. Umpqua Oregon chub inhabited areas with primarily slow water velocities, fed on benthic prey, and spawned over gravel substrate. Because Willamette Oregon chub inhabit slackwater habitats they may be more sensitive to water velocity increases and exotic species, whereas Umpqua Oregon chub have a habitat refuge in relatively faster water velocity habitats. Willamette Oregon chub larval stages are described and illustrated. The following combination of characters distinguish Willamette Oregon chub larvae from other cyprinid larvae found in the Willamette drainage: 33-37 myomeres, preanal length of 52-61%, and absence of snout pigment. Willamette Oregon chub larvae generally congregated in nearshore areas, in the upper layers of the water column, in shallow water. They fed primarily in the water column, and ate primarily rotifers and cladocerans. / Graduation date: 1989

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No description available.

No description available.

Female golden Syrian hamsters are seasonally breeding animals, capable of maintaining continuous estrous cycles when the daylength is 12.5 hrs. or longer. In shorter photoperiod (SP) the ovaries of anovulatory animals are characterized by few small growing follicles, an absence of corpora lutea and extensive hypertrophied interstitium. Steroid-histochemical studies revealed that enzymes related to steroidogenesis show intense activity in the interstitial tissue of SP-exposed animals. The major objectives of these studies were to examine SP-induced hormonal and ovarian changes which occur prior to onset of the acyclic condition in inbred LSH/SsLak hamsters. Other experiments explored hormonal changes in the absence of ovarian hormones and the interaction of SP and steroids. Initial results revealed that the LSH/SsLak hamster ceased estrous cyclicity between 14 and 31 days of SP exposure, a response far more uniform than generally seen in outbred hamsters. Experiments carried out in SP-exposed cyclic animals indicated that the secondary FSH surge and follicular recruitment were not affected by SP treatment, follicular recruitment were not affected by SP treatment, and that no major changes in gonadotropin levels and ovarian steroids were present on individual days of the estrous cycle. Once the animals were anestrous, daily gonadotropin surges were present and pituitary gonadotropin contents increases. Serum PRL levels showed a slight, yet significant, decrease in SP cycling animals followed by a further reduction in pituitary and serum levels after animals ceased cycling. Medial basal hypothalamic LHRH contents did change in SP, yet there was a significant increase in the preoptic area, and LHRH became significantly elevated in both areas after the animals became anestrous. Ovarian histology revealed fewer corpora lutea and a slight shift from healthy to atretic antral follicles. Experiments carried out in ovariectomized SP-treated animals showed that serum gonadotropin levels were significantly reduced, and that estrogen treatment was either equally or less effective in reducing levels in SP animals. In contrast, PRL levels did not change and responded in a dose dependent way to estrogen treatment. Although the studies yielded no definite proof, the result suggest that SP impairs the maintenance of follicular growth leading eventually to the acyclic state.