THE USE OF CHEMICAL MARKERS AND MODEL STUDIES TO ASSESS THE IN VITRO PRO- AND ANTIOXIDATIVE PROPERTIES OF METHYLXANTHINE-RICH BEVERAGES

Chemical markers and model studies are useful in predicting the stability and shelf life of foods and beverages in food technology and chemistry. Chemical modification induced by food processing has an impact on the reactivity and chemical properties of the food constituents, frequently giving rise to new molecules with enhanced antioxidative activity and potential health benefit. In the case of coffee, tea, and cocoa, these positive characteristics are often associated with dietary polyphenols. In particular, the often referred to “paradox” behavior of endogenous polyphenols to act as anti- and/or prooxidants is demonstrated with the aid of in vitro model studies. Furthermore, in-situ chemical markers such as 8-oxocaffeine are described in methylxanthine-rich beverages that reflect oxidative reactions. Such chemicals can be employed to help assess the impact of processing conditions on food quality as well as to predict the stability of the final product.     

Firm Partial Modularity and Performance in the Electronic Manufacturing Services Industry

Firms continue to develop new ways to decentralize non-core activities to outside parties. Scholars have approached this issue with modularity theory, suggesting a continuum of arrangements ranging from hierarchy to market. Hierarchy relies on fiat, while partially modular forms, those forms between hierarchy and market, require greater coordination, communication and relationships between firms than do fully modular (or market) forms. While modularity theory identifies this continuum, the associated empirical literature tends to dichotomize modularity: firms are either modular or they are not. Nor does the empirical literature examine the performance outcomes of modular arrangements within this continuum. By examining firms that vary between full integration and partial modularity with a continuous modularity measure, this paper empirically examines the performance outcomes associated with a range of modularity levels. We derive this measure from a peculiar inventory option available within the electronic manufacturing services (EMS) industry. Our data include observations on 260 firms over five years. We find that more firms rely on partially modular arrangements, the lower their performance. We suggest explanations for this result, and areas of future research meant to pursue it.     

Wave interactions and wave-structure scattering in nonlinear patterned waveguides

The nonlinear interactions between discrete optical solitons that propagate in different regimes of diffraction, and the nonlinear scattering of dispersive waves by local optical potentials, were studied experimentally. It is well known in electromagnetism that when linear coherent waves meet they interfere without interactions. Linear waves also scatter through local optical structures without exchanging any power with guided and anti-guided modes of these structures. When a focusing Kerr nonlinearity is present, linearly inhibited phenomena, which break these rules, are shown to exist. Our studies were performed with Silica glass and semiconductor AlGaAs nonlinear planar modulated waveguides, excited by ultra-short pulses in the near infrared spectral regime.     

Considerations for the Systematic Design of Machine Self-Diagnosis

An approach is suggested for the cost-effective systematic design of product on-board diagnostics that allow simple and complex appliances to diagnose or predict failures within themselves. This methodology differs from other current less formal approaches in that it encourages a wholly integrated design philosophy. Trends indicate that on-board diagnostic capabilities will become much more important in both the eyes of the consumer and the manufacturer in years to come. As such, the lack of a formal approach could represent a significant design bottleneck. The approach offered represents a meaningful first step in avoiding such a bottleneck. Furthermore, the technique can be used for evaluation and retrofit of diagnostics on existing products. Relevant background regarding machine self-diagnostics is presented, and future research needs are identified.     

Electrohydrodynamic Augmentation of Forced Convection Heat Transfer

Augmentation of heat transfer due to injection of an ion flux through a thermal boundary layer is measured in a forced convection heat transfer apparatus. A nickel mesh injection grid is used to minimize the effect of the ``corona wind' associated with point discharges and thus to isolate an electrohydrodynamic (EHD) instability mechanism. The EHD instability is shown to be a viable mechanism in augmenting forced convection heat transfer. Change in the Nusselt number is documented as a function of an EHD instability interaction parameter, Reynolds number, and temperature gradient.     

30-kVA Transistor Inverter Auxiliary Power Supply for People Mover, Part I-Power Circuit

The design and performance of a people mover?a 30- kVA 400-Hz transistor inverter which furnishes all loads, except propulsion power, on a small advanced urban transit vehicle?is described in this first installment of a two part sequence of papers. With a nominal 750-V dc input, the inverter supplies 30 kVA at 0.8-lagging power factor, 200-V line-to-line root mean square (rms), and three- phase 400-Hz output. The design and performance of the power circuit is described in Part I, and the design and performance of the control is covered in Part II.     

The Interpretation of Train Rolling Resistance from Fundamental Mechanics

Past efforts in railway improvement have focused on increased train stability and ride quality for safe and smooth operations at higher speed. The question of energy consumption has rarely been considered. In view of projections of higher fuel costs and increased rail traffic volume, energy effects caused by improved train resistance should be considered. First-order expressions for the rolling resistance of freight trains on level tangent track were derived from the basic principles of physics and engineering. The average power dissipated by the suspension system was obtained from a linear model of the track train system. Hysteresis in the soil is computed using basic principles of soil mechanics. Losses due to wheel rolling friction, imposed wheel sliding, and bearings were estimated from simple engineering and considerations. Rolling resistance as would be measured in coast down or drawbar pull tests on level tangent track is found to depend strongly on the quality of the track as well as weight and speed. On good track, most of the rolling resistance is due to bearing resistance, while on poor track, suspension losses predominate. Empirical expressions such as the Davis formula, which have been used in the past by the railroad industry, are unable to describe train rolling resistance adequately because of the way in which they are parameterized. Some of the parameter values obtained from fits to experimental data do not carry the physical meaning with which they were traditionally associated.