Illuminance and luminance distributions of a prototype ambient illumination system for Space Station Freedom

Preliminary results of research conducted in the late 1970's indicate that perceptual qualities of an enclosure can be influenced by the distribution of illumination within the enclosure. Subjective impressions such as spaciousness, perceptual clarity, and relaxation or tenseness, among others, appear to be related to different combinations of surface luminance. A prototype indirect ambient illumination system was developed which will allow crew members to alter surface luminance distributions within an enclosed module, thus modifying perceptual cues to match crew preferences. A traditional lensed direct lighting system was compared to the prototype utilizing the full-scale mockup of Space Station Freedom developed by Marshall Space Flight Center. The direct lensed system was installed in the habitation module with the indirect prototype deployed in the U.S. laboratory module. Analysis centered on the illuminance and luminance distributions resultant from these systems and the implications of various luminaire spacing options. All test configurations were evaluated for compliance with NASA Standard 3000, Man-System Integration Standards

Travelling Salesman Problem with a Center

We study a travelling salesman problem where the path is optimized with a cost function that includes its length $L$ as well as a certain measure $C$ of its distance from the geometrical center of the graph. Using simulated annealing (SA) we show that such a problem has a transition point that separates two phases differing in the scaling behaviour of $L$ and $C$, in efficiency of SA, and in the shape of minimal paths.Comment: 4 pages, minor changes, accepted in Phys.Rev.

Relativistic quantum plasma dispersion functions

Relativistic quantum plasma dispersion functions are defined and the longitudinal and transverse response functions for an electron (plus positron) gas are written in terms of them. The dispersion is separated into Landau-damping, pair-creation and dissipationless regimes. Explicit forms are given for the RQPDFs in the cases of a completely degenerate distribution and a nondegenerate thermal (J\"uttner) distribution. Particular emphasis is placed on the relation between dissipation and dispersion, with the dissipation treated in terms of the imaginary parts of RQPDFs. Comparing the dissipation calculated in this way with the existing treatments leads to the identification of errors in the literature, which we correct. We also comment on a controversy as to whether the dispersion curves in a superdense plasma pass through the region where pair creation is allowed.Comment: 16 pages, 1 figur

Phase Transition in the Number Partitioning Problem

Number partitioning is an NP-complete problem of combinatorial optimization. A statistical mechanics analysis reveals the existence of a phase transition that separates the easy from the hard to solve instances and that reflects the pseudo-polynomiality of number partitioning. The phase diagram and the value of the typical ground state energy are calculated.Comment: minor changes (references, typos and discussion of results

Evidence for a functional role of the pineal in bovines

Dat die epifise moontlik n regulerende invloed op die gonadotrofiese funksie van die adenohipofise ultoefen, is m.b.v. in vitro tegnieke ondersoek. Bykomstig, is n aaneenlopende stelsel ontwerp om die meganisme van die werking van die antionadotrofiese beginsel van die epifise te bestudeer, aangesien daar n direkte negatiewe terugvoer van hiposifiele LH op die hipothalamus voorgekom het toe adenohipofisiale en hipothalamiese weefsel gesamentlik gekweek is. Resultate het aangetoon dat die hormone van die epifise die vrystelling van die tersake hipothalamiese vrystellingsfaktore inhibeer, waardeur die afskeiding van LH deur die adenohipofise verminder word. Laastens toon die resultate aan dat die epifise die produksie van LH-inhiberende faktore geproduseer deur die hipothalamus, stimuleer. SUMMARY:The possibility that the pineal exerts a regulatory influence on the gonadotrophic function of the adenohypophysis was investigated using in vitro techniques. Additionally, since a direct negative feedback of pituitary LH onto the hypothalamus occured when adenohypophysical and hypothalamic tiisisues were incubated together, a continuous-flow system was devised to study the mechanisms of action of the pineal anti-gonadotrophic principles. Results demonstrated that the bovine pineal has marked anti-gonadotrophic properties in vitro. Data showed that the pineal hormones inhibited the release of the relevant hypothalamic release factor, thereby reducing secretion of LH from the adenohypophysis. Finally, results indicated that the pineal also stimulated the production by the hypothalamus of an LH-inhibitory factor