GaAs single-mode rib waveguides with reactive ion-etched totally reflecting corner mirrors

The fabrication and optical properties of reactive ion-etched, totally reflecting mirrors for single-mode GaAs rib waveguides are described. Low loss and orientation independance make the device useful in integrated optics, in order to increase packing density and to facilitate waveguide to fiber coupling. Results of displacement sensitivity calculations are also shown.     

Implementation of sustainable sanitation in existing urban areas: long-term strategies for an optimised solution.

If technologies for decentralised sanitation and reuse (DESAR) and for natural stormwater management should at least partially replace existing systems, then intensive reconstruction work becomes essential. A conversion can only be realised successively over a long period due to high construction and financial expenses and requires new strategies. This paper presents the development and practical implementation of a mathematical tool to find an optimised strategy for the realisation of alternative and more decentralised drainage and sanitation concepts in existing urban areas. The succession of construction measures (e.g. the implementation of decentralised greywater recycling) for the whole period of consideration is determined based upon a mathematical optimisation model on the condition that the favoured future state is known. The model describes the complex interdependencies of the urban water and nutrient cycle and enables the minimisation of both financial efforts and ecological impacts on the way toward the future state. The results of the implementation for a rural area in Germany show that the mathematical optimisation is an adequate instrument to support decision-making processes in finding strategies for the realisation of sustainable urban water management.     

The effect of short- vs. long-term platelet-activating factor exposure on mouse preimplantation embryo development

Preimplantation mouse embryos (n = 1540) were cultured in the presence of platelet-activating factor (PAF) (10(-7)- 10(-14) mol/l) to the hatched blastocyst stage. A dose-dependent negative correlation (-0.75783) relationship between blastocysts and the concentration of PAF was statistically significantly different (p < 0.001). Long-term but not short-term PAF exposure is detrimental to preimplantation Swiss Webster mouse embryos. Short-term PAF (10(-9) mol/l) exposure was found significantly (p < 0.05) to reduce blastocoel diameter. The effect of PAF during preimplantation development may be genotype dependent and be affected by the culture conditions.     

Das Verhalten organischer Pigmente in Polymeren

The importance of colouring matter is of prime importance in the plastics industry. The individual behaviour of organic pigments in the various polymer materials necessitates, however, on the part of the plastics manufacturer a precise knowledge of ?which pigment for which plastic”?. For example, a well known Thioindigo pigment behaves very differently in various polymer materials : In polystyrene, depending on the concentration used, it is monomolecularly dissolved, in associated solution or present as undissolved particles. In PVC, however, the good migration fastness is indicative of the insolubility of the pigment in this medium and so it is not surprising that PVC is the ideal plastic medium for this pigment. The behaviour of organic pigments in polymers is largely a function of molecular structure, e. g. intermolecular H-bonds can cause a decrease in solubility of a pigment in a polymer material, which in turn results in improved migration fastness. This is demonstrated by the improved migration fastness of variously substituted β-hydroxy naphthoic acid arylamide derivatives. Many phenomena exist however, which as yet can only be explained on the basis of the crystal structure of the pigment particles, i. e. the presence of aggregates or agglomerates. Such a phenomenon is, for example, the dispersibility of pigments in polymers. Here pigment surface, wettability by polymer and intermolecular forces are all of importance. In general, the dispersibility is better the smaller the specific surface area, as is shown for a typical quinacridone pigment. The influence of the rate of wetting on dispersibility is demonstrated using polyethylene wax. A further effect, which demonstrates the intermolecular forces between pigment and polymer, is the way in which certain pigments influence the rate of crystallization of partly crystalline polymers. This itself is connected with the shape and size of the pigment particles embedded in the polymer material. Such effects are demonstrated by measurements on various polyethylene objects. The pigment in this case was a naphthalene tetra carbonic acid derivative in both cis and trans form with widely varying specific surface areas.     

Pro- und Antioxydantien auf dem Fettgebiet XVII: Fette und Fettstoffwechsel der Winterschläfer, 1. Mitteilung: Der Siebenschläfer (Glis glis L.)

Pro- and Antioxidants in the Field of Fats XVII: Fats and Fat-metabolism of Hibernating Animals I. The Seven Sleepers. (Glis glis L.) After a short review of the literature about hibernation, the analysis of the lipids of the seven sleepers (Glis glis L.) is given. The problem, whether the yellow lipochrome results from the autoxidation of polyenoic fatty acids because of the decrease in biological antioxidants, especially vitamin E, could not be completely explained. The brown tissue, the socalled “sleep gland” contains substances which are insoluble in fat solvents and probably formed by the reaction of polyenes with proteins or by the autoxidation of lipoproteins which contain them.     

Routing on Meshes with Buses

We consider the problem of routing packets on an MIMD mesh-connected array of processors augmented with row and column buses. We give lower bounds and randomized algorithms for the problem of routing k-permutations (where each processor is the source and destination of exactly k packets) on a d-dimensional mesh with buses, which we call the (k,d)-routing problem. We give a general class of ``hard' permutations which we use to prove lower bounds for the (k,d)-routing problem, for all k,d≥ 1. For the (1,1)- and (1,2)-routing problems the worst-case permutations from this class are identical to ones published by other authors, as are the resulting lower bounds. However, we further show that the (1,d)-routing problem requires 0.72 ... n steps for d=3, 0.76 ... n steps for d=4, and slightly more than steps for all d≥ 5. We also obtain new lower bounds for the (k,d)-routing problem for k,d > 1, which improve on the bisection lower bound in some cases. These lower bounds hold for off-line routing as well. We develop efficient algorithms for the (k,1)-routing problem and for the problem of routing k-randomizations (where each processor has k packets initially and each packet is routed to a random destination) on the one-dimensional mesh and use them in a general (k,d)-routing algorithm which improves considerably on previous results. In particular, the routing time for the (1,d)-routing problem is bounded by steps with high probability (whp), whenever for some constant ε > 0, and the routing time for the (k,d)-routing problem is steps whp whenever for some constant ε > 0 and k≥ 3.6 ... d, matching the bisection lower bound. We then present a simple algorithm for the (2,2)-routing problem running in 1.39 ... n+o(n) steps whp. Finally, for the important special case of routing permutations on two-dimensional meshes with buses, the (1,2)-routing problem, we give a more sophisticated algorithm that runs in 0.78 ... n+o(n) steps whp. Received May 18, 1994; revised June 23, 1995.