23,075 research outputs found
Unified model of loop quantum gravity and matter
We reconsider the unified model of gravitation and Yang--Mills interactions
proposed by Chakraborty and Peld\'an, in the light of recent formal
developments in loop quantum gravity. In particular, we show that one can
promote the Hamiltonian constraint of the unified model to a well defined
anomaly-free quantum operator using the techniques introduced by Thiemann, at
least for the Euclidean theory. The Lorentzian version of the model can be
consistently constructed, but at the moment appears to yield a correct weak
field theory only under restrictive assumptions, and its quantization appears
problematic.Comment: 4 pages, dedicated to Michael P. Ryan on the occasion of his sixtieth
birthda
Emissivity coatings for low-temperature space radiators Quarterly progress report no. 1, 1 Jul. - 30 Sep. 1965
Emissivity coatings for low temperature spacecraft radiator
CELSS Transportation Analysis
Regenerative life support systems based on the use of biological material was considered for inclusion in manned spacecraft. Biological life support systems are developed in the controlled ecological life support system (CELSS) program. Because of the progress achieved in the CELSS program, it is determined which space missions may profit from use of the developing technology. Potential transportation cost savings by using CELSS technology for selected future manned space missions was evaluated. Six representative missions were selected which ranged from a low Earth orbit mission to those associated with asteroids and a Mars sortie. The crew sizes considered varied from four persons to five thousand. Other study parameters included mission duration and life support closure percentages, with the latter ranging from complete resupply of consumable life support materials to 97% closure of the life support system. The analytical study approach and the missions and systems considered, together with the benefits derived from CELSS when applicable are described
The Synthesis of Prilocaine from Toluene
Prilocaine hydrochloride is a local anesthetic from the amide family. Commonly used in dental work as an injected topical anesthetic, prilocaine temporarily numbs and inhibits nerve endings in soft tissue for up to two hours, leading to a decrease in pain. The synthesis of prilocaine is a four step process which starts with a mono-nitration of toluene. The nitrated product is then reduced by catalytic hydrogenation to produce toluidine. O-toluidine hydrochloride is isolated by treating toluidine with acetic anhydride followed by an extraction for purification. The acetylated product was then mixed with 2-choloropropionyl chloride to produce the final prilocaine product. In an effort to make the reaction more environmentally friendly, diethyl ether was replaced by methoxycyclopentane in the mono-nitration of toluene
The development of an advanced system to cool a man in a pressure suit
Conductive cooling system for cooling man in pressurized space sui
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