Materials processing in space: Early experiments

The characteristics of the space environment were reviewed. Potential applications of space processing are discussed and include metallurgical processing, and processing of semiconductor materials. The behavior of fluid in low gravity is described. The evolution of apparatus for materials processing in space was reviewed

Preliminary assessment of the vacuum environment in the wake of large space vehicles

The vacuum environment in the wake region of presently planned large space vehicles is calculated using simplified models of the particle fluxes from the various sources. The fluxes which are calculated come directly from the ambient, are due to ambient particles backscattered from spacecraft emissions, and are due to self scattering of spacecraft emissions. Using nominal values for the surface emissions, the flux density environment behind a large unmanned craft at 550 km altitude is calculated. Calculations indicate that the flux density on a wake vacuum experiment conducted in the vicinity of the shuttle is substantially greater than that behind unmanned craft

Calculations of K+, K- and phi Production in Near-Threshold Proton-Nucleus Collisions

K+, K- and \phi meson production in proton-nucleus (pA) collisions has been calculated within a BUU transport model. It is shown that the nucleon-hyperon strangeness transfer channel is essential. The role of three-body reactions has been investigated within the medium. The targetmass dependence of $\phi$ production is predicted to give important information on the in-medium properties of all three mesons.Comment: Talk presented by H.W.B. at the Budapest 2004 workshop on 'Hot and Dense Matter in Relativistic Heavy Ion Collisions', March 24-27, 2004, Budapest, Hungar

Postflight analysis of the single-axis acoustic system on SPAR VI and recommendations for future flights

The single axis acoustic levitator that was flown on SPAR VI malfunctioned. The results of a series of tests, analyses, and investigation of hypotheses that were undertaken to determine the probable cause of failure are presented, together with recommendations for future flights of the apparatus. The most probable causes of the SPAR VI failure were lower than expected sound intensity due to mechanical degradation of the sound source, and an unexpected external force that caused the experiment sample to move radially and eventually be lost from the acoustic energy well

Highly polarized alkenes as organocatalysts for the polymerization of lactones and trimethylene carbonate

In this work, the activity of N-heterocyclic olefins (NHOs), a newly emerging class of organopolymerization catalyst, is investigated to affect the metal-free polymerization of lactones and trimethylene carbonate (TMC). A decisive structure−activity relationship is revealed. While catalysts of the simplest type bearing an exocyclic CH2 moiety polymerize L-lactide (L-LA) and δ-valerolactone (δ-VL) in a non-living and non-quantitative manner, the introduction of methyl substituents on the exocyclic carbon radically changes this behavior. 2-Isopropylidene-1,3,4,5-tetramethylimidazoline is found to be highly active for a range of monomers such as L-LA, δ-VL, ε-caprolactone (ε-CL), and TMC, with quantitative conversion occurring within seconds with catalyst loadings of just 0.2 mol %. The high activity of this NHO further enables the ring-opening polymerization (ROP) of the macrolactone ω-pentadecalactone (PDL). However, this broad applicability is offset by a lack of control over the polymerizations, including side reactions as a consequence of its strong basicity. To overcome this, a saturated, imidazolinium-derived analogue was synthesized and subsequently demonstrated to possess a harnessed reactivity which enables it to polymerize both L-LA and TMC in a controlled manner (ĐM < 1.2). NMR spectroscopic and MALDI-ToF MS experiments highlight the differences in polymerization pathways for 2-methylene-1,3,4,5-tetramethylimidazoline, in which the exocyclic carbon is not substituted, in contrast to 2-isopropylidene-1,3,4,5-tetramethylimidazoline, with the former operating via its nucleophilicity and the latter acting as a base with enolizable δ-VL

Molecular ruby: exploring the excited state landscape

The discovery of the highly NIR-luminescent molecular ruby [Cr(ddpd)2]3+ (ddpd = N,N′-dimethyl-N,N′-dipyridin-2-ylpyridine-2,6-diamine) has been a milestone in the development of earth-abundant luminophors and has led to important new impulses in the field of spin-flip emitters. Its favourable optical properties such as a high photoluminescence quantum yield and long excited state lifetime are traced back to a remarkable excited state landscape which has been investigated in great detail. This article summarises the results of these studies with the aim to create a coherent picture of the excited state ordering and the ultrafast as well as long-timescale dynamics. Additional experimental data is provided to fill in gaps left by previous reports

Deer--from field to table

"One of the problems facing a deer hunter is what to do with the deer after it is killed. Most hunters want a trophy as well as the meat. Deer meat, or venison, is nutritious and as versatile as beef; however, the eating quality or acceptability is greatly influenced by the hunter's actions immediately after the deer is killed. The hunter needs a sharp hunting knife with at least a four-inch blade, some strong twine or string, and a nylon or other strong rope for hanging or transporting the carcass."--First page.W.C. Stringer, Viola Smith, H.D. Naumann (Department of Food Science and Nutrition, College of Agriculture)Reviewed and reprinted 8/87/10