An Experimental Method of Determining the Shape of Millimicrosecond Radiation Pulses

The problem with which this investigation is concerned was to construct suitable apparatus to measure accurately the shape and the duration of a pulse of δ-radiation of approximately 10 Mev energy and 20 mμ sec duration. In particular, the shape of the tail of the pulse had to be determined as accurately as possible, so that millimicrosecond half lives can be measured accurately with the betatron

UPPER GREAT LAKES TRANSPORTATION IMPACT FORECASTING SYSTEM

Community/Rural/Urban Development,

Microscopic measurement of the linear compressibilities of two-dimensional fatty acid mesophases

The linear compressibility of two-dimensional fatty acid mesophases has determined by grazing incidence x-ray diffraction. Surface pressure vs molecular area isotherms were reconstructed from these measurements, and the linear compressibility (relative distortion along a given direction for isotropic applied stress) was determined both in the sample plane and in a plane normal to the aliphatic chain director (transverse plane). The linear compressibilities range over two orders of magnitude from 0.1 to 10 m/N and are distributed depending on their magnitude in 4 different sets which we are able to associate with different molecular mechanisms. The largest compressibilities (10m/N) are observed in the tilted phases. They are apparently independent of the chain length and could be related to the reorganization of the headgroup hydrogen-bounded network, whose role should be revalued. Intermediate compressibilities are observed in phases with quasi long-range order (directions normal to the molecular tilt in L_2 or L_2' phases, S phase), and could be related to the ordering of these phases. The lowest compressibilities are observed in the solid untilted CS phase and for 1 direction of the S and L_2'' phases. They are similar to the compressibility of crystalline polymers and correspond to the interactions between methyl groups in the crystal. Finally, negative compressibilities are observed in the transverse plane for L_2' and L_2'' phases and can be traced to subtle reorganizations upon untilting.Comment: 24 pages, 17 figure

Reversible crosslinking of polymers bearing pendant or terminal thiol groups prepared by nitroxide-mediated radical polymerization

Monomers or N-alkoxyamine initiators containing protected thiol groups are utilized to prepare polymers via nitroxide-mediated radical polymerization. Following thiol deprotection, the macromolecular properties of these polymers are manipulated, by adjusting the redox conditions to either form or cleave disulfide bonds, or irreversibly cap free thiols by the rapid addition to a maleimide Michael acceptor. Formation of disulfide bonds under dilute conditions results in intramolecular disulfide formation, resulting in internal polymer collapse. Alternatively, disulfide formation under high concentration results in intermolecular crosslinking of polymers to form networked macromolecular assemblies.© 2013 Elsevier Ltd. All rights reserved

Reactivity of TEMPO anion as a nucleophile and its applications for selective transformations of haloalkanes or acyl halides to aldehydes

Sodium 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO&#8722;Na+), generated by reduction of TEMPO· with sodium naphthalenide in THF, reacted with alkyl halides or acyl halides to produce O-alkylated or acylated TEMPOs, which were in turn oxidized with mCPBA or reduced with DIBAL-H to afford the corresponding aldehydes, thus accomplishing a new protocol for the halides-carbonyls conversion.</p

Urushiol Detection using a Profluorescent Nitroxide

A method to visually detect minute amounts of urushiol, the toxic catechol from poison oak, poison ivy, and poison sumac, has been developed utilizing the reaction of a profluorescent nitroxide with the B-n-butylcatecholboronate ester formed in situ from urushiol and B-n-butylboronic acid. The resulting N-alkoxyamine is strongly fluorescent upon illumination with a fluorescent lamp, allowing the location of the toxic urushiol contamination to be visualized. This methodology constitutes the groundwork for the future development of a spray to detect urushiol to avoid contact dermatitis, as well as to detect catecholamines for biomedical applications