Phase Equilibria in the Systems NiO-Cr2,O3,-O2, MgO-Cr2O3−O2, and CdO-Cr2,O3,-O2, at High Oxygen Pressures

Phase equilibria were determined for the systems NiO-Cr₂O₃−O₂, MgO-Cr₂O₃,-O₂, and CdO-Cr₂O₃−O₂ from 450° to above 850° C and at oxygen pressures of from 2 to 3500 atm. Only two intermediate phases were found in the nickel system: NiCrO., (CrVO₄ structure) and the spinel NiCr₂O₄. The magnesium and cadmium systems are similar in that they have three analogous phases: the low-temperature α-MgCrO₄ and α-CdCrO₄ (both with the CrVO₄ structure), the high-temperature β-MgCrO₄ and β-CdCrO₄ (both with the α-MnMoO₄ structure), and the spinels MgCr₂O₄ and CdCr₂O₄. The cadmium system contains an additional phase, Cd₂CrO₅, which is primitive monoclinic.     

Electrical Properties of ZnO-Bi2O3 Ceramics

The nonlinear volt-ampere characteristics and small-signal ac capacitance and resistance of sintered ZnO containing 0.5 mol% Bi₂O₃ were measured. Many of the electrical properties are related directly to the microstructure, which consists of conductive ZnO grains separated by a continuous amorphous Bl₂O₃, phase. The origin of the nonlinear conduction in the intergranular phase was confirmed by experiments with evaporated thin films. The proposed conduction mechanism in varistors containing ZnO and Bi₂O₃ is a combination of hopping and tunneling in the amorphous phase.     

SUBCHRONIC TOXICITY STUDY OF EASTERN BLACK NIGHTSHADE (SOLANUM PTYCANTHUM) BERRIES IN SPRAGUE-DAWLEY RATS

Species of the Solanum nigrum complex, including eastern black nightshade (S. ptycanthum Dun.), are common nuisance plants, and their berries often contaminate agricultural commodities. Black nightshade plants and their fruits contain solanaceous glycoalkaloids, but little information is available regarding their toxicity in vivo. Male and female rats were fed diets containing 0, 1, 5 or 25% (w/w) eastern black nightshade berries (BNB) for 13 weeks. BNB had no effect upon clinical appearance and behavior, body weight, food and water consumption, serum chemical profiles or organ weights. Gross or microscopic lesions related to BNB were not found. Anemia was present in high-dose males after six weeks and in mid-dose males, high-dose males and high-dose females after 13 weeks. Erythrocyte counts, hemoglobin concentrations and hematocrits of these groups were significantly decreased and averaged 81–93% of their respective control values. Erythrocyte counts, hemoglobin concentration and hematocrits of males fed 1% BNB, females fed 1% BNB and females fed 5% BNB averaged 94–97% of the control values after 13 weeks. These findings indicate that ingestion of low to moderate amounts of S. ptycanthum berries does not pose a significant health risk, although anemia may be a potential consequence of prolonged exposure to highly contaminated foodstuffs .     

FROM THE DEPTHS TO THE HEIGHTS: BOOK REVIEWS

The Enigma cipher machine had the confidence of German forces who depended upon its security. This misplaced confidence was due in part to the large key space the machine provided. This paper derives for the first time the exact number of theoretical cryptographic key settings and machine configurations for the Enigma cipher machine. It also calculates the number of practical key settings Allied cryptanalysts were faced with on a daily basis throughout World War II. Finally, it shows the relative contribution each component of the Enigma added to the overall strength of the machine.     

VOLATILES IN A FAT-BASED FAT SUBSTITUTE MODEL COMPOUND, ESTERIFIED PROPOXYLATED GLYCEROL SOYATE

Static headspace and GC/IR-MS (capillary gas-liquid chromatography, with an infrared detector and a mass spectrometer), were used to collect, separate, identify, and quantitate the volatile products in the EPG-08 soyate sample, (esterified propoxylated glycerol, which is a model fat substitute compound with 8 moles of propylene oxide per mole of glycerol), EPG-00 soyate (essentially trans-esterified soybean oil with no added propylene oxide), and a 50:50 (v:v) mixture of the two oil samples. Each sample was heated at £192C for 12 h/day until the oil contained £20% triacylglycerol polymer. The EPG-08 soyate samples were heated for 36 h, whereas the EPG-00 soyate and the 50:50 mix samples were heated for 48 h. The major volatile decomposition products found included hexanal     

On the stability problem for distributed parameter energy systems†

In this paper asymptotic stability of the non-trivial or operating equilibrium state of a distributed parameter energy system is considered. Sufficient conditions are obtained by the method of comparison functions. This enables one to obtain bounds on the maximum value of the state variables. The criteria derived depend on the eigenvalues of the linearized system as well as on a bound for the feedback control law.     

Multi-stage Monte Carlo optimization applied to a large travelling salesman problem

Multi-stage Monte Carlo optimization (MSMCO) and its attendant limit theory are applied to the problem of finding the shortest routes to connect 249 points. Comparisons of the MSMCO technique's performance are made with other methods. The limit theory idea of averaging errors or pinning down frequently occurring sub-routes is used extensively. Multi-stage is a series of consecutive regular Monte Carlo optimizations run over an ever changing and narrowing feasible solution region following the best answer so far. The preliminary sampling in the early stages, points the way to the optimal solution region of the sampling distribution of feasible solutions. Then the n-dimensional rectangles (for a function of n variables) focus in and find the oplimals. Multi-stage is of course an approximation technique. However the approximations can outperform many other algorithms if the sampling and limit theory are carefully applied. It also allows one to make use of simplifying transformations (like the ranking transformation used here) to reduce the number of variables in the simulation.     

On the Stability of Equilibrium of a Distributed Parameter Feedback Control System

In this paper the stability problem for n general class of non-linear feedback control systems governed by parabolic partial differential equations is considered. Sufficient conditions for asymptotic stability are derived by the method of comparison functions. Two classes of feedback control systems are considered. The basic tool in the analysis is the Westphal-Priodi theorem and an extension originally suggested by Szarski. The main results are applied to an illustrative example.     

Production scheduling decision rules in changing and non-linear environments

Holt at al. (1960) modollod the production scheduling problem with quadratic costs and derived an optimal set of scheduling rules. Our experiment found those rules may not be effective if costs are non-quadratic. This may explain the relative lack of use of these rules in industry.     

Sensitivity Problems in Distributive Systems

The effects of parameter variations on the external characteristics of distributive systems are considered. It is shown that this class of problems can be brought within the framework of modern system sensitivity analysis. The interaction between feedback and system sensitivity is analysed.