The practice of acidifying the tomato (Lycopersicum esculentum) by additives in canning was investigated from the standpoint of adjusting and maintaining a pH desirable to prevent microbial growth without adversely effecting quality. Approximately one-third or more of tomato acids were in their salt form and, consequently, the most effective acid groups are neutral. In 75°F storage for 52 weeks the pH of non-acidified tomatoes packed in #303x406 cans rose 0.1 units. This rise was believed to be due to corrosion points through pinholes in the enamel films of all the cans by the reaction: H⁺ + Sn⁰ → H⁰ + Sn⁺. Ten tomato varieties from four geographical regions were canned and evaluated for effects of additives on pH and composition. No distinguishing characteristics were noted in packs from the different regions. Salts with citric and malic acids added at less than 1.0 meq/100 g tomato equally depressed the pH by about 0.2 units. Fumaric and phosphoric acids were more effective. None of the acids used as acidulants showed any significant effects on drained weight, refractive index, can vacuum, can corrosion, or chemical composition. The effects of neutral salts for adjusting canned tomato pH were evaluated. Calcium and magnesium chloride depressed the pH by 0.06 units for each meq added up to two meq/100 g tomato. These salts were approximately seven times more effective than sodium chloride for depressing pH. Calcium chloride was more effective than magnesium, sodium, or potassium chlorides in preventing drained weight loss when up to 2.0 meq of each of these salts were added per 100 g tomato (2 meq CaCl₂ = 0.11% CaCl₂). Evidence shown by alcohol soluble acidity indicates that sodium ions were removed from added sodium chloride into the alcohol insoluble fraction. Processing times of 15 and 45 minutes at 210℉ were compared as to their effect on tomato compositional changes. Heat penetration curves 0 showed that internal fruit temperature reached 150℉ in the 15 minute 0 heat process, while over 190℉ was reached inside tomatoes processed 45 minutes. Five tomato varieties showed no significant pH change related to length of heat process. Titratable acidity was slightly higher by 0.1 meq/100 g in tomato samples processed 45 minutes. Other variables for the sample sets of the two processing times were compared by Duncan's multiple range tests and by partial correlations among them. Variables also included alcohol soluble and insoluble acidities, water insoluble solids, reducing sugars, amino nitrogen, phosphoric acid, refractive index, and lactic, oxalic, fumaric, succinic, malic, citric and pyrrolidone carboxylic (PCA) acid determined by gas chromatography. Although differences between the two processes were small, correlations among variables were higher in the sample set processed for 45 minutes. These relationships imply that thermal, non-enzymatic effects were slightly more pronounced in the set processed for 45 minutes. The rate of formation of PCA appears to be higher during the early stages of heat processing. Small within-can variations were found to exist. Centrifuged tomato solids were 0.028 pH lower than that of the serum. / Ph. D.

This dissertation presents a generalized analytical study of the whirl instability of a rotating propeller or rotor system. The mathematical model consists of rigid members with three degrees-of-freedom at the wing root and the wing-drive-shaft joints. In addition, each blade has lagging and flapping freedom. Two dimensional aerodynamics, including compressibility and stall effects, are included. Whirl stability boundaries and characteristics are presented. The parameters investigated include both mechanical and operating variations such as shaft stiffness, number of blades and air density. It was found that decreasing forward speed can result in a whirl instability when blade stall is taken into account. No condition was found in which the rotor went into a forward precessional mode of motion. / Ph. D.

M.S.

M.S.

The benevolence ethic, a moral formula for successful living which began in the 1660's with a group of low church divines, gained in popularity until it reached its peak of influence in the first half of the eighteenth century. That Henry Fielding, one of the century's most successful novelists, adhered to the ethic and incorporated it in his works is clear from an examination of his journals and his fiction. In his three major novels, Joseph Andrews, Tom Jones and Amelia, Fielding's incorporation of the ethic is evident, and it is his varying use of the ethic in these three novels which contributes heavily to the relative success or failure of each. Fielding's primary vehicle for incorporating the ethic in the novels is a central triangle of characters which reappears in each novel and consists of an older benevolent gentleman, a good-natured young man and a beautiful, innocent and virtuous young woman. His vehicle varies, however, in that each novel focuses on a different member of the triangle, in each the triangle members are interrelated differently and they develop individually in different degrees. In his most successful novel, Tom Jones, Fielding used the ethic as a basic part of the plot. In Joseph Andrews, his first novel, the ethic is blurred by satire, and in his last novel, Amelia, it is distorted with· sentimentalism. / M.A.

M.Arch.

Ph. D.

New concepts in linear, time invariant model realization using sensitivity functions are presented. These concepts involve approaching the device modeling problem from an error gradient minimization viewpoint. This leads to the attainment of a minimal index of performance function (IP) and, consequently, emulates a desired device model response either in the frequency or time domain. In the frequency domain the problem of characterizing the AC error gradients for a small signal transistor model is considered. The integral of the weighted squared-error is the IP functional incorporated. It is found that the error gradients all contain a similar expression whose values, when chosen properly, create zero valued gradients and a zero valued (globally minimal) IP functional. Hence a graphical analysis routine based on the similarity expression is developed to provide the advantages listed below: (i) Simplicity. This technique requires no optimization scheme and completely eliminates computer computation costs. (ii) Insensitive model. A design scheme is affixed to the graphical analysis scheme so as to yield insensitive voltage and/or current transfer functions; with respect to drifts in hᵢₑ and hₒₑ transistor parameters. (iii) Basic building block. The small signal model design technique offers a basic building block upon which high frequency model realization techniques, the hybrid pi model for example, can be implemented. In the time domain a variable structure cascaded building block technique was designed and provides among its main features: (i) Simplicity. Although an optimization procedure is required in this technique the circuit analysis program incorporated in the negative gradient algorithm is fixed in terms of the topological structure it must analyse. That is, it need not be updated to calculate new gradient terms for a topologically changing structure as is required by previous variable structure modeling techniques. (ii) Capable of fitting high order responses within a relaxed block by block IP functional. No individual block in the structure may be required to achieve a certain strict IP functional, while the structure in its entirety may achieve the strict functional. (iii) Direct approach. This device modeling technique offers a concise approach to the modeling problem. The design engineer need only know a device characteristic response in order to approach the problem. Further research possibilities include characterization of the AC error gradients for the hybrid pi transistor model and possibly a series, parallel, series-parallel, or parallel-series connection would prove even more beneficial than the cascaded block time domain approach. / Ph. D.

The mycotoxin, aflatoxin B₁, elaborated by the fungus Aspergillus flavus is a coumarin-type compound. This compound has previously been reported in the literature to have an effect on rat liver mitochondria, although the reports are inconsistent. The effect of this compound on oxygen consumption by rat liver mitochondria was examined potentiometrically. All experiments were carried out below the critical micelle concentration of aflatoxin B₁ which was determined in the oxygen electrode solution of Estabrook to be 0.48 mM. Mitochondria were isolated from 80-150 g male Sprague-Dawley derived rats. Aflatoxin B₁ at a concentration of 0. 48 mM was found to inhibit oxygen consumption by 43% in the presence of ADP and by 63% in the presence of DNP. The inhibition brought about by 0.48 mM aflatoxin B₁ occurs when either succinate or β-hydroxybutyrate is used as a substrate. When electrons were fed into the electron transport chain at cytochrome c₁ (or c) using TMPD and ascorbate no inhibition was observed. TMPD, however, released the inhibition brought about by 0.48 mM aflatoxin B₁ in the presence of succinate or β-hydroxybutyrate as substrates. No relief of the inhibition was obtained with menadione. The site of inhibition appears to be between cytochrome b and cytochrome c₁ (or c). The ADP:0 ratio was also depressed by 35% in the presence of 0.48 mM aflatoxin B₁ when NAD-dependent substrates were employed. Mitochondria from protein deficient animals were found to be 42% less sensitive to inhibition by aflatoxin B₁ than mitochondria from protein sufficient animals. The ADP:0 ratio with NAD-dependent substrates was found to be 37% less sensitive in mitochondria from protein deficient animals than in protein sufficient animals. Gregg particles were prepared from mitochondria isolated from protein deficient as well as protein sufficient animals. Both types of submitochondrial particles were found to be more sensitive to aflatoxin B₁ than the whole mitochondria. It was concluded that the inhibition was limited in whole mitochondria by the inner mitochondrial membrane; and in protein deficient mitochondria there is an alteration in the inner mitochondrial membrane which makes aflatoxin B₁ a less potent inhibitor of electron flow. The fact that the inhibition occurs in the presence of DNP as well as ADP indicates that the inhibition is in the electron transport chain and not in the phosphorylating functions ancillary to the chain. DNPstimulated ATPase activity was only slightly affected by aflatoxin B₁ in the absence of reducing substrates. DNP-stimulated ATPase activity was however markedly reduced in the presence of reducing substrate and aflatoxin B₁. This supports the contention that aflatoxin B₁ effects electron transport in the chain and not in the phosphorylating functions ancillary to the chain though some effect is seen there also. / Ph. D.

Sodium borohydride in aqueous dimethylsulfoxide has been shown to be a good reducing agent for converting certain activated aromatic halo-compounds to their corresponding dehalogenated products. The order for ease of removal of the halogen is I>Br>Cl. The activating groups are those that are strongly electron-withdrawing. The reactivity for activating aryl halides substituted with groups such as -NO₂, -CF₃, -F, -Cl, -Br, and -I is in the order ortho > meta > para, thus indicating that the activating effect has its origins in inductive rather than resonance effects. The removal of halogen appears to be occurring via a displacement on-halogen. This has been demonstrated in certain cases by using deuterium oxide instead of water in the reaction. When this is done, the halogen is replaced by deuterium instead of hydrogen. This indicates that the halogen leaves without its bonding electrons, thus leaving a carbanionic site on the aromatic ring. The carbanion is subsequently quenched by a proton from the water. This reaction has also been shown to be applicable to aromatic systems other than benzene. On-halogen type displacement by the hydride ion also occurs on certain polyhalogenated alkanes with the formation of a guasi-carbanionic intermediate which can be quenched by a proton from water, undergo alpha elimination, or undergo beta elimination. The alpha elimination occurs when a good leaving group is not present on the beta carbon. Attempts at trapping the carbene type intermediate from alpha eliminations were unsuccessful, evidently because of the presence of the water in the reaction medium. In two cases eliminations have occurred through a benzene system to generate para-xylylenes. Diazonium salts were also shown to undergo direct reduction with sodium borohydride, thus providing a new route for the deamination of aromatic amines. / Ph. D.