Metabolic-heat relation for aerobic yeast respiration and fermentation

A specially developed temperature control system on a laboratory scale fermenter enabled continuous measurement of the rate of heat production during undisturbed growth of microbial cultures. Apart from being correlated with oxygen uptake rate, the heat of fermentation was established as an additional indicator of metabolic activity. The ‘aerobic respiration’ energetic activity of Candida utilis, Candida lipolytica and Saccharomyces cerevisiae on different carbon substrates was investigated with cultures of the latter species being also studied under the ‘aerobic fermentation’ conditions induced by glucose catabolite repression.     

Reaction of zirconium fluoride glass with water: kinetics of dissolution

When liquid water contacts a zirconium-barium-lanthanum fluoride glass, at least three different processes occur. Barium and zirconium fluoride dissolve into the water, water penetrates into the glass, and zirconium fluoride crystals grow on the glass surface, in static solution. The rate of dissolution, as measured by solution analysis, is possibly controlled by diffusion in the solid surface; surface blockage and surface reactions are other possible kinetic steps involved. Diffusion in solution is not the controlling mechanism. Hydrogen profiles in the glass surface suggest that the penetration rate of water into the glass is controlled by diffusion and a surface reaction.     

Fiber-optic devices for local area network application

Recent developments on fiber-optic devices are reviewed from the local area network (LAN) application viewpoint. Future technical trends are also discussed, along with current research activities. In local area network systems, low device cost and easy maintenance or maintenance-free devices are especially required. Light sources and photodetectors suitable for the systems are described. InGaAsP/InP light emitting diodes can cover a broad application field, up to a gigabits per second super high-speed network region. Optical passive devices, which include branching couplers, switches and connectors, are mentioned as essential components. Compact transmitter/receiver module technology is a key factor in realizing optical-fiber local area network systems. An example of 200-Mbit/s transmitter/receiver module is reported.     

ON THE IMPACT FATIGUE CRACK GROWTH BEHAVIOUR OF METALLIC MATERIALS

The impact fatigue crack growth characteristics of a low carbon steel and an aluminium alloy were studied. An impact fatigue testing machine of the Hopkinson bar type was used in these experiments to conduct a series of crack growth tests under simple impact stresses. The following characteristics of impact fatigue crack growth behaviour were revealed: (1) crack growth rate is higher in impact fatigue than in non-impact fatigue; (2) crack opening ratio in impact fatigue takes a higher value than in non-impact fatigue; (3) crack tip plastic zone size is smaller in impact fatigue than in non-impact fatigue.     

The geometric nature of plasticity laws

This paper concerns the plasticity constitutive laws in small strain. In the thermodynamic approach developed here, the key concept is that of internal variables. The differential nature of plasticity law has been pointed out for a long time. If we unite the invariance condition of these laws in a state variable transformation, this involves, ultimately, that the natural mathematic frame of plasticity theory is Differential Geometry. The system state is defined as a point of a differentiable manifold. The state variable are the local coordinates of this point in a chart. The internal stresses are the components of a covariant vector of the cotangent bundle to internal state manifold and the elastic domain is a convex part of cotangent vector space. The plastic yield criteria such as von Mises condition define a Riemannian structure over the manifold. The metric element is identified with the internal dissipation element. Constitutive laws link the covariant derivatives of the thermodynamic stress with the state variable. Hardening modulus splits up in two parts, kinematic hardening and metric hardening. This last is defined by Christoffel connection coefficients. Applied to von Mises isotropic yield condition, the metric hardening is identified with isotropic hardening. The Baltov-Sawczuk model is also analysed. The use of appropriate polar coordinates simplifies significantly the computations. Generalization to a significant category of non-differentiable yield criteria, such as Tresca condition, is considered by introducting a metric tensor family. The adaptation of Drucker's postulate to the proposed model requires the introduction of parallel transport of the internal stress covector. Generally, this transport is different over distinctive paths joining two points. This fact expresses internal state manifold curvature. The Riemann-Christoffel tensor is computed for von Mises, Baltov-Sawczuk and Tresca models.     

The radiation crosslinking and scission of ethylene-propylene copolymers studied by solid-state nuclear magnetic resonance

Methyl groups from chain scission and H-crosslinks have been identified by solid-state nuclear magnetic resonance in amorphous ethylene-propylene copolymers containing 23 and 36 mole % propylene after γ-irradiation to 10 MGy at 30°C. G (scission) and G (crosslink) values determined from the n.m.r. spectra and by extraction are in agreement, which suggests that the crosslinks are not clustered. This may differ from the situation in polyethylene where there is a substantial crystalline content. G(S). G(X) and the ratio G(S)/G(X) increase with increasing propylene content of the copolymers.     

Functionalization of soluble polymers

Summary The synthesis of di-(4-formylphenyloxyethyl) poly(oxyethylene) and the corresponding oxime derivative are described. Kinetic aspects of the reaction of the dichloro telechelic with 4-hydroxy benzaldehyde are investigated and discussed.     

Dicyanate semi IPNs—A new class of high performance,high temperature plastics

Dicyanate Semi-Interpenetrating Polymer Networks (semi IPNs) are made by dissolving a thermoplastic in crosslinking dicyanates and then curing the resulting mixture. The semi IPNs produced are strong, with tensile strengths of 10,000 to 12,000 psi, and flexible, with elongations to break of 10 to 17 percent. Dicyanate semi IPNs also have good thermal stability and the softening temperatures of the IPNs are significantly, higher than those of the corresponding thermoplastics.     

Die zweiten krümmungsradien bei ebenen zwangläufenThe second curvature radii in plane kinematics

In plane Euclidean kinematics for every path the curvature radius of the evolute can be used to describe the third order properties. We investigate this second curvature radius of envelopes including the case of point-paths. For example there is a simple relation between the 2nd curvature radii of an envelope and of the path of its momentary 1st curvature center in the point of contact. In particular the derived formulas enable us to discuss the envelope c_o,if instantaneously the pole P is the 1st curvature center of the moved curve. Generally in such contact points on the pole tangent there is a self-osculation of c_o. Further we get the surprisingresult that all points ≠ P on the pole tangent have a common second curvature center, but in general distinct from that of the pole P. At last there is shown how the second curvature centers can be constructed by usual graphical methods of acceleration analysis.     

Simulation and optimization of tool-life in manufacturing centers

This paper presents the development of an optimization and a computer-simulation model to evaluate the process plans of a manufacturing center by analyzing the effect of tool failure on system performance. The GPSS/PC simulation program that is used in this study has been built with variables, functions and matrices so that many experiments could be conducted with the model. Sensitivity analysis is presented and the developed model has proven to be useful in determining optimum sequencing of parts for various operating policies.