The collisional stabilization of excited β-naphthylamine molecules by the paraffin hydrocarbons in the gas phase

The transfer of vibrational energy from molecules of β-naphthylamine excited by the mercury lines at 2804 Å and 2652 Å to the homologous series of paraffin hydrocarbons up to n-hexane has been investigated in the gas phase at 180°C. Although the average amount of energy transferred collisionally increases with the complexity of the added gas by a factor of 5, the transfer efficiency expressed as an accommodation coefficient remains virtually unchanged.

A transfer mechanism based on the internal redistribution of vibrational energy within the collision complex is examined, in terms of which it is unnecessary to invoke vibration-vibration transfer except for pentane and hexane. The collision duration estimated on the basis of this model is well within an order of magnitude of that expected from collision diameters and relative velocities of the molecules concerned.     

H-atom abstraction dynamics of reactions between Cl atoms and heterocyclic organic molecules

The HCl(v' = 0, J') rotational state distributions produced in the photoinitiated reactions of ground spin-orbit state Cl(2P3/2) atoms with the organic heterocycles oxirane (c-C2H4O), thiirane (c-C2H4S) and oxetane (c-C3H6O) have been measured using the technique of 2 + 1 resonance-enhanced multiphoton ionization in a time-of-flight mass spectrometer. In contrast to previous studies of H-atom abstraction dynamics by Cl atoms with linear functionalized molecules, the nascent HCl(v' = 0, J') products of the reactions of the three-membered heterocycles oxirane and thiirane are formed rotationally cold, with mean rotational energies <Erot> of (0.28 ± 0.02) kcal mol-1 and (0.31 ± 0.02) kcal mol-1, respectively. The reaction of Cl atoms with the four-membered heterocycle oxetane, however, results in more rotationally excited HCl(v' = 0, J') products for which <Erot> = (0.78 ± 0.03) kcal mol-1. Ab initio calculations were performed at the G2//MP2/6-311G(d,p) level to characterize molecular complexes and transition states on the reactive pathways. In all cases, the reactions were calculated to be barrierless, and weakly bound pre- and post-reaction complexes were located on the potential energy surfaces. The observed distributions and calculated reaction profiles are compared with previous studies of the reactions of Cl atoms with linear functionalized organic molecules and the consequences of the constrained molecular geometry on the HCl(v' = 0, J') rotational distribution discussed in terms of the dipole-dipole interaction model proposed previously.     

A study of the polymerization of styrene by Rayleigh-Brillouin spectroscopy

The Rayleigh-Brillouin spectrum has been used to probe the kinetics of the thermal polymerization of styrene. The behaviour of the velocity and attenuation of hypersound in the medium is consistent with frequency-dependent bulk and shear viscosities. The characteristic relaxation times are dependent on the degree of polymerization.

The relaxation times continuously increase as the polymerization proceeds. In the initial stages of the experiment the measured sound velocity and absorption coefficients correspond to the zero frequency values, and as the polymerization proceeds these quantities go over to the infinite frequency values.     

Semisimple strata for p-adic classical groups

Let F₀ be a non-archimedean local field, of residual characteristic different from 2, and let G be a unitary, symplectic or orthogonal group defined over F₀. In this paper, we prove some fundamental results towards the classification of the representations of G via types [8]. In particular, we show that any positive level supercuspidal representation of G contains a semisimple skew stratum, that is, a special character of a certain compact open subgroup of G. The intertwining of such a stratum has been calculated in [19].     

Immunochemical detection of metabolites of parent and nitro polycyclic aromatic hydrocarbons in urine samples from persons occupationally exposed to diesel exhaust

An immunochemical assay was developed for the detection of metabolites excreted in urine as a result of occupational exposure to PAHs and nitro-PAHs. These metabolites were analyzed in a competitive ELISA, using an existing antibody (4D5) that has been developed against 6-aminobenzo[a]pyrene coupled to bovine serum albumine (B[a]P-BSA). A solid phase extraction (SPE) work-up procedure was optimized by dilution of pooled urine samples from rats exposed to 1-NP, in human urine. The application was validated by comparison of test results with urinary excreted 1-hydroxypyrene (1-OH-P) levels in a study among 28 railroad workers. Excretion of urinary metabolites was determined over two consecutive workdays. The 24 h average excretion of metabolites as determined in the immunoassay was not related to levels of particulate matter in the breathing zones of workers, not to 1-OH-P excretion levels of the day of urine collection. However, it was significantly associated with the personal dust exposure of the day before (P<0.0001), suggesting slow excretion of urinary metabolites. Smoking habits caused minor interference (P<0.1).     

Synthesis of cross-conjugated polyketones by the crossed-aldol condensation of cyclic ketones with aromatic dialdehydes

Insoluble cross-conjugated polyketones were prepared from terephthalaldehyde and a variety of cycloaliphatic ketones by the crossed-aldol condensation. Elemental analyses and infrared spectra suggest that the polymeric aldol intermediates were not completely dehydrated. Evidence is also presented that suggests conjugate addition of the base to the α,β-unsaturated ketone may occur. Soluble cross-conjugated polyketones were prepared from terephthalaldehyde and 2-indanone, which contains no beta hydrogens, and from cycloaliphatic ketones and 1,2-bis(4-formylphenoxy)ethane, a dialdehyde containing isolated aldehyde groups. It is proposed, therefore, that the lack of solubility in the terephthalaldehyde-based polyketones arises from crosslinking via enolate anions formed at the beta position of the cyclic ketones, which are delocalized through the carbonyl groups of neighboring backbone repeating units. © 1995 John Wiley & Sons, Inc.