Part I Electrochemically induced reactions of some halogenated organic compounds Part II novel rearrangements of pyridazine derivatives

The reduction of pentafluoropyridine gave, as the major products, octafluoro-4,4'-bipyridyl in aprotic systems and 4-H-tetrafluoropyridine with added proton donor. Garbanionic intermediates were not trapped by carbon dioxide to give acids. Voltammetric results for a series of polyfluoropyridines suggest that the negative charge in the radical anion is mainly in the 4-position. Reduotion of pentaohloropyridine in dime thylformamide gave 4-H-tetrachloropyridine, with some 4,4'-bistetraohloropyridylmeroury when using a mercury cathode. Intermediate carbanions were trapped by carbon dioxide, giving an acid mixture, which yielded 4-H-tetrachloropyridine and heptachlorobipyridyl on decarboxylation. Hexaohlorobenzene behaved similarly. Simple perfluoro-olefins eliminated fluoride ion on reduction and were subsequently oligomerised by it. Intermediate carbanions were trapped by water. The electrochemical products were high-boiling oils, resulting from reaction with the solvent. Oxidation of polyfluoroanisoles containing para hydrogen gave coupling to the corresponding 4,4'-dimethoxybiphenyl derivative. No coupling occurred when this position was blocked by fluorine. Trapping of intermediate radical cations with acetic acid was unproductive. PART II The photochemical and thermal rearrangements of a number of perfluoroalkylpyridazines in static systems was investigated. As had previously been reported, photolysis of perfluoro-4,5-dialkyl- pyridazines gave mainly perf1uoro-2,6-dialkylpyrazines, although in some cases perfluoro-2,6-dlal]sylpyrazines were also formed. The pyrolysis of perfluoro-4,5-clialkylpyridazines gave mainly perfluoro-4,5-dialkylpyrimidines and in some cases a small amount of the -2,5-pyrazine. Perfluoro-4-alkylpyridazines gave mixtures of perfluoro- 4-alkyl- and -5-alkylpyrimidines. These results can be explained by a mechanism involving diazabenzvalene Intermediates. The photolysis and pyrolysis of mixtures gave no exchange of substituent groups indicative of a bimolecular process. In the pyrolyses, the conversios of the less reactive pyridazlne was catalysed and that of the more reactive pyrldazlne Inhibited. The relative amounts rearranged ruled out a 1 : 1 Intermediate and a Slels-Alder mechanism, which would involve exchange of nitrogen, was further ruled out by (^15)N-labelling. The catalytic mechanism proposed Involves a transfer of vibrational excitation

An experimental effort to improve the Nimbus high resolution infrared radiometer Final report, 1 May 1964 - 15 Feb. 1965

Electronics modifications and improved detector cooling for Nimbus high resolution infrared radiomete

High resolution nighttime cloud-cover radiometer Quarterly report XVII, 1 Oct. 1965 - 1 Jan. 1966

Electronic, optical, mechanical, and electron packaging component and system design reviews for high resolution cloud cover infrared radiomete

II Zwicky 23 and Family

II Zwicky 23 (UGC 3179) is a luminous, nearby compact narrow emission line starburst galaxy with blue optical colors and strong emission lines. We present a photometric and morphological study of II Zw 23 and its interacting companions using data obtained with the WIYN 3.5-m telescope in Kitt Peak, Arizona. II Zwicky 23 has a highly disturbed outer structure with long trails of debris that may be feeding tidal dwarfs. Its central regions appear disky, a structure that is consistent with the overall rotation pattern observed in the H-alpha velocity field measured from Densepak observations obtained with WIYN. We discuss the structure of II Zwicky 23 and its set of companions and possible scenarios of debris formation in this system.Comment: 5 pages, 2 figures. To appear in the proceedings of ESO Astrophysics Symposia: "Groups of Galaxies in the Nearby Universe", eds. I. Saviane, V. Ivanov, J. Burissova (Springer

Lasing and cooling in a hot cavity

We present a microscopic laser model for many atoms coupled to a single cavity mode, including the light forces resulting from atom-field momentum exchange. Within a semiclassical description, we solve the equations for atomic motion and internal dynamics to obtain analytic expressions for the optical potential and friction force seen by each atom. When optical gain is maximum at frequencies where the light field extracts kinetic energy from the atomic motion, the dynamics combines optical lasing and motional cooling. From the corresponding momentum diffusion coefficient we predict sub-Doppler temperatures in the stationary state. This generalizes the theory of cavity enhanced laser cooling to active cavity systems. We identify the gain induced reduction of the effective resonator linewidth as key origin for the faster cooling and lower temperatures, which implys that a bad cavity with a gain medium can replace a high-Q cavity. In addition, this shows the importance of light forces for gas lasers in the low-temperature limit, where atoms can arrange in a periodic pattern maximizing gain and counteracting spatial hole burning. Ultimately, in the low temperature limit, such a setup should allow to combine optical lasing and atom lasing in single device.Comment: 11 pages, 6 figure

A Search for Ultraviolet Emission from LINERs

We have obtained Hubble Space Telescope WFPC2 2200 A and optical V-band images of 20 low-luminosity active galactic nuclei, most of which are spectroscopically classified as LINERs, in order to search for a possible photoionizing continuum. Six (30%) of the galaxies are detected in the UV. Two of the detected galaxies (NGC 3642 and NGC 4203) have compact, unresolved nuclear UV sources, while the remaining four UV sources (in NGC 4569, NGC 5005, NGC 6500, and NGC 7743) are spatially extended. Combining our sample with that of Maoz et al. (1995), we find that the probability of detection of a nuclear UV source is greatest for galaxies having low internal reddening and low inclination, and we conclude that dust obscuration is the dominant factor determining whether or not a UV source is detected. Large emission-line equivalent widths and the presence of broad-line emission also increase the likelihood of detection of nuclear UV emission. Our results suggest that the majority of LINERs harbor obscured nuclear UV sources, which may be either accretion-powered active nuclei or young star clusters. Under the assumption that the compact UV sources in NGC 3642 and NGC 4203 have nonstellar power-law spectra extending into the extreme ultraviolet, the extrapolated ionizing fluxes are sufficiently strong to photoionize the narrow-line regions of these objects. The V-band images of many galaxies in our sample reveal remarkably strong dust lanes which may be responsible for obscuring some UV sources.Comment: 25 pages, 4 figures, 3 tables, LaTeX, AASTeX v4.0 style file, accepted for publication in The Astrophysical Journal, additional figures available at http://astro.berkeley.edu/~barth/papers/u