THE REACTION OF DIMETHYL SULFOXIDE AND SYM-DICHLORO-BIS(2,4,6-TRICHLOROPHENYL) UREA

Abstract

Sym-dichloro-bis(2,4,6-trichlorophenyl) urea reacts explosively with dimethyl sulfoxide to yield phosgene, formaldehyde, methane, sulfur dioxide, ethylene chloride, methylene dichloride, chlorinated disulfides, and insoluble bis(2,4,6-trichlorophenyl) urea. The products, other than bis(2,4,6-trichlorophenyl) urea, are separated and characterized by means of gas chromatography and mass spectrometry. A homolytic mechanism is proposed for the reaction.     

Effect of reflection type on detonation initiation at shock-wave focusing

Abstract. From practical and theoretical standpoints, the initiation of combustion in gaseous media due to the shock waves focusing process at various reflectors is a subject of much current interest. The complex gas flowfield coupled with chemical kinetics provides a wide spectrum of possible regimes of combustion, such as fast flames, deflagration, detonation etc. Shock wave reflection at concave surfaces or wedges causes converging of the flow and produces local zones with extremely high pressures and temperatures. The present work deals with the initiation of detonation due to shock waves focusing at parabolic and wedge reflectors. Particular attention has been given to the determination of the critical values of the incident shock wave (ISW) Mach number, parameters of the combustible mixture, and geometrical sizes of reflector at which different combustion regimes could be generated. Received 30 August 1999 / Accepted 23 February 2000     

Modeling Variability Order: A Semiparametric Bayesian Approach

In comparing two populations, sometimes a model incorporating a certain probability order is desired. In this setting, Bayesian modeling is attractive since a probability order restriction imposed a priori on the population distributions is retained a posteriori. Extending the work in Gelfand and Kottas (2001) for stochastic order specifications, we formulate modeling for distributions ordered in variability. We work with Dirichlet process mixtures resulting in a fully Bayesian semiparametric approach. The details for simulation-based model fitting and prior specification are provided. An example, based on two small subsets of time intervals between eruptions of the Old Faithful geyser, illustrates the methodology.     

Consonant recognition in quiet as a function of aging among normal hearing subjects

Consonant recognition in quiet using the Nonsense Syllable Test (NST) [Resnick et al., J. Acoust. Soc. Am. Suppl. 1 58, S114 (1975)] was investigated in 62 normal hearing subjects 20 to 65 years of age at their most comfortable listening levels (MCLs) and at 8 dB above and below MCL. Although overall consonant recognition performance was high (as expected for normal listeners), the effects of age decade, relative presentation level, and NST subsets were all significant, as was the interaction of age X level. The interactions of age X NST subset, and age X subset X level were nonsignificant. These findings suggest that consonant recognition decreases with normal aging, particularly below MCL. However, the relative perceptual difficulty of the seven subtests is the same across age groups. Confusion matrices were similar across levels and age groups. Percent information transmitted for several consonant features was calculated from the confusion matrices. Older subjects showed decrements in performance primarily for the features recognized relatively less accurately by the younger subjects. The results suggest that normal hearing older individuals listening in quiet have decreased consonant recognition ability, but that their confusions are similar to those of younger persons.     

Quantitative laser photoacoustic detector spectroscopy: HD 5-0 transitions

Intracavity photoacoustic spectroscopy of HD in the 5-0 R(0), R(1), and R(2) transitions demonstrates the use of a transition of known strength to calibrate the response of a photoacoustic detector by simultaneous in situ measurements. Excellent agreement in line strengths for the HD 5-0 transitions is found with the earlier determination due to McKellar et al. Our experiments, however, were conducted with a pressure-pathlength product only 10^-6 of that used by McKellar et al.     

Surfaces on Lie groups,on Lie algebras,and their integrability

We study the cohomology of the Schwinger term arising in second quantization of the class of observables belonging to the restricted general linear algebra. We prove that, for all pseudodifferential operators in 3+1 dimensions of this type, the Schwinger term is equivalent to the twisted Radul cocycle, a modified version of the Radul cocycle arising in non-commutative differential geometry. In the process we also show how the ordinary Radul cocycle for any pair of pseudodifferential operators in any dimension can be written as the phase space integral of the star commutator of their symbols projected to the appropriate asymptotic component.     

H/D exchange under mild conditions in arenes and unactivated alkanes with C6D6 and D2O using rigid,electron-rich iridium PCP pincer complexes

The synthesis and characterization of an iridium polyhydride complex (Ir-H4) supported by an electron-rich PCP framework is described. This complex readily loses molecular hydrogen allowing for rapid room temperature hydrogen isotope exchange (HIE) at the hydridic positions and the α-C–H site of the ligand with deuterated solvents such as benzene-d₆, toluene-d₈ and THF-d₈. The removal of 1–2 equivalents of molecular H₂ forms unsaturated iridium carbene trihydride (Ir-H3) or monohydride (Ir-H) compounds that are able to create further unsaturation by reversibly transferring a hydride to the ligand carbene carbon. These species are highly active hydrogen isotope exchange (HIE) catalysts using C₆D₆ or D₂O as deuterium sources for the deuteration of a variety of substrates. By modifying conditions to influence the Ir-Hn speciation, deuteration levels can range from near exhaustive to selective only for sterically accessible sites. Preparative level deuterations of select substrates were performed allowing for procurement of >95% deuterated compounds in excellent isolated yields; the catalyst can be regenerated by treatment of residues with H₂ and is still active for further reactions.

The synthesis and characterization of an iridium polyhydride complex (Ir-H4) supported by an electron-rich PCP framework and capable of mild hydrogen/deuterium exchange catalysis is described.