1,124 research outputs found
Preparation of highly fluorinated diols containing ether linkages.
Hydroxy-terminated perfluoroethers and polyurethane resins derived from ethers have outstanding chemical resistance and good thermal properties. They can be used as potting compounds, coatings, and seals. The hydroxy-terminated ethers serve as intermediates in the synthesis of highly fluorinated elastomers and adhesives
Preparation of highly fluorinated polyurethanes
New polyurethanes, formed from a reaction of a prepolymer diol and a perfluorinated diisocyanate, are nonflammable and possess high corrosion resistance and good low temperature flexibility. Polymer hardness increases rapidly with increasing ratio of diisocaynate to diol, but its glass transition temperature is not adversely affected
Hydroxy terminated perfluoro ethers Patent
Chemical synthesis of hydroxy terminated perfluoro ethers as intermediates for highly fluorinated polyurethane resin
Highly fluorinated polyurethanes
The reaction perfluorinated hydroxyl terminated polyether with diisocyanate to form polyurethane is discussed. Data are given on the resin's oxidation stability, chemical resistance, and low temperature flexibility
Preparation of perfluoropolyether prepolymers
Fluorinated prepolymers are used to generate highly fluorinated polymers which possess most of the desirable properties of polytetrafluoroethylene, such as nonflammability and high corrosion resistance, while retaining good low temperature flexibility
Film advance indicator
A film advancement indicator which includes an optical sensor that detects the rotational movement of a disc that rotates only when the film advance is described. When the film does not advance, an indicator light is activated. A counter is included in the electronic circuit to determine the number of film frames advanced
Getting DNA twist rigidity from single molecule experiments
We use an elastic rod model with contact to study the extension versus
rotation diagrams of single supercoiled DNA molecules. We reproduce
quantitatively the supercoiling response of overtwisted DNA and, using
experimental data, we get an estimation of the effective supercoiling radius
and of the twist rigidity of B-DNA. We find that unlike the bending rigidity,
the twist rigidity of DNA seems to vary widely with the nature and
concentration of the salt buffer in which it is immerged
Carbon Dioxide Sequestration to form Calcium Carbonate Nanoparticles
The emission of carbon dioxide caused by burning fossil fuels is one of the leading sources of global warming. Reducing the amount of CO2 released into the atmosphere through carbon sequestration can mitigate this problem. One method of carbon sequestration is the use of a carbon dioxide scrubber. Once captured, CO2 can be used to create a valuable chemical commodity such as calcium carbonate nanoparticles. To create CaCO3 particles in the 50-100 nanometer range, a chemical additive is necessary to limit particle size. The study used a laboratory scale carbon dioxide scrubber to react CO2 with calcium chloride and OH- ions to form calcium carbonate nanoparticles. Varying CaCl2 concentrations were tested as well as two chemical additives (AOT and PEG) in varying amounts. The resulting CaCO3 nanoparticles were analyzed to determine average particle size using dynamic light scattering. The study confirmed that the scrubber process effectively reduced CO2 released from the system. In general, larger quantities of additive led to smaller particles, but while AOT and PEG both limit CaCO3 particle size, AOT was the most effective. Unexpected results showed that larger concentrations of CaCl2 reduce the formation of bubble build-up in the reactor. Future work can be done to explore this effect of CaCl2 on sud formation by monitoring and recording bubble levels during the reaction
Termination Casts: A Flexible Approach to Termination with General Recursion
This paper proposes a type-and-effect system called Teqt, which distinguishes
terminating terms and total functions from possibly diverging terms and partial
functions, for a lambda calculus with general recursion and equality types. The
central idea is to include a primitive type-form "Terminates t", expressing
that term t is terminating; and then allow terms t to be coerced from possibly
diverging to total, using a proof of Terminates t. We call such coercions
termination casts, and show how to implement terminating recursion using them.
For the meta-theory of the system, we describe a translation from Teqt to a
logical theory of termination for general recursive, simply typed functions.
Every typing judgment of Teqt is translated to a theorem expressing the
appropriate termination property of the computational part of the Teqt term.Comment: In Proceedings PAR 2010, arXiv:1012.455
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