A technique is presented that utilizes an on-axis intensity measurement to detect the reflected light from a multiple CD-ROM surface. The thesis includes a computer simulation of the detected signal for scans of various structures and discusses finite size detector effects. A suitably sized detector passes 77% of the total light flux at the detector plane without affecting the depth discrimination property of the technique. Experimentally, a breadboard Height Readout System (HRS) could detect height differences on test relief structures. A signal to noise ratio was obtained that corresponds to a noise equivalent height sensitivity of 30 Angstroms. Therefore, the HRS could discriminate between five levels on the test structure. An addition to the new technique uses a phase plate to determine if the focused beam is going into or out of a pit. Thus, the storage capability per unit area on the disk surface can be increased.

published_or_final_version / Botany / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Different concentrations of various browning inhibitors and a firming agent were evaluated to prevent browning and softening of Bartlett, Bosc and Anjou pear slices during cold storage at 2-4°C. Browning inhibition effect of Semperfresh, Snow Fresh and cysteine were compared with that of 4-hexylresorcinol (4-HR). The effect of ripeness on color and texture changes as well as the influence of storage temperature on texture and color retention was investigated. 4-HR residual content under different treatment conditions and its sensory properties were analyzed. 4-HR was an effective browning inhibitor at concentration as low as 0.005% when combined with 0.5% ascorbic acid (AA). Cysteine (0.5%) with 0.5% ascorbic acid (AA) effectively inhibited Anjou and Bosc pear slice browning for 25 days and its sensory properties merit further study. A combination of 1.0% AA and 1.0% calcium lactate prevented Anjou pear slices from discoloration, but also caused tissue leaking and softening. Semperfresh and Snow Fresh did not maintain flesh color effectively. 1.0% calcium lactate maintained slice firmness at an acceptable level for 30 days when the average firmness of whole pears at slicing was 49, 38 and 43 Newton (N) for Bartlett, Bosc and Anjou respectively. A storage temperature of 0°C significantly retained better texture than the control of 2-4°C. Slices with acceptable texture and color were achieved by treatment with a solution of 0.01% 4-HR, 0.5% AA, and 1.0% calcium lactate for 2 min, vacuum packaging, and storage at 2-4°C for 30 days for Bartlett and Bosc, and 15 days for Anjou. 4-HR residual content increased with increasing dipping times and concentrations, with the latter being the major factor. The 4-HR residual decreased with storage time for all the treatments. Sensory tests indicated that panelists detected the overall differences between 0.01% 4-HR treated samples and the controls for both Bartlett and Anjou pears (P<0.01). There were no significant differences in preference between treated sample and control for Anjou pears. / Graduation date: 1999

Processing and storage of berry fruits is accompanied by various changes, the important ones being the changes in the soluble solids content, titratable acidity, pH, pigments, and texture. A study was made of these changes in processed strawberries, raspberries, blackberries and blueberries, still cooked and stored at 78°F for one and six months in No. 10 cans. Three samples of the above four berries were analyzed before processing, immediately after processing and after one and six months of storage at 78°F. Five samples of syrups were collected from both center and side of the cans by means of 50 ml pipettes. These five samples were from top, 1 3/4", 3 l/2", and 5 1/4" from the top and from the bottom and a mean sample was taken from the drained syrup. The cans were then drained on an 8 mesh 10" screen. 100 gram samples of the drained solids from top, middle and bottom were collected for texture measurements. The results indicated the following: 1. There is a decrease in soluble solids of the syrup and drained weight of the fruit immediately after processing. Softening of berries progresses with storage. 2. There is an increase in titratable acidity, pH and pigments of the syrup immediately after processing. Titratable acidity and pigments increase with storage and pH values were lower. 3. There is a tendency to reach an equilibrium in the can with regards to soluble solids in all berries and pigments in case of strawberries with a lower tendency for raspberries. In the case of titratable acidity equilibrium was almost realized in strawberries and blueberries. All berry packs showed no equilibrium in the pH value after six months. 4. No noticeable differences between samples collected from centers and side of the can. / Graduation date: 1963

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