Infrared absorption and emission characteristics of interstellar PAHs

The mid-infrared interstellar emission spectrum with features at 3.28, 6.2, 7.7, 8.7 and 11.3 microns is discussed in terms of the Polycyclic Aromatic Hydrocarbon (PAH) hypothesis, which is based on the suggestive, but inconclusive comparison between the interstellar emission spectrum with the infrared absorption and Raman spectra of a few PAHs. The fundamental vibrations of PAHs and PAH-like species which determine the IR and Raman properties are discussed. Interstellar IR band emission is due to relaxation from highly vibrationally excited PAHs excited by ultraviolet photons. The excitation/emission process is described and the IR fluorescence from one PAH, chrysene, is traced. Generally, there is sufficient energy to populate several vibrational levels in each mode. Molecular vibrational potentials are anharmonic and emission from these higher levels will fall at lower frequencies and produce weak features to the red of the stronger fundamentals. This process is also described and can account for some spectroscopic details of the interstellar emission spectra previously unexplained. Analysis of the interstellar spectrum shows that PAHs contain between 20 and 30 carbon atoms are responsible for the emission

Parametric study of manned life support systems. Volume 1 - Summary Final report, Jul. 1967 - Aug. 1968

Summary data on methodology, mission and vehicle criteria for parametric study of manned life support system

Geology of the Northern Llano Uplift, Junction to Llano, Texas

This year\u27s Texas Academy of Science Geology Field Trip will visit nine interesting locations in two different areas in the Texas Hill Country (Figure 1). In the first area we will look at the Cretaceous stratigraphy around Junction, Texas (Figures 1, 2, 3, and 4). The expedition will then travel to the northern part of the Llano uplift and study Cambrian and Precambrian stratigraphy and structure of the northern Llano Uplift (Figures 4 and 5). Stop 9 will be at Cooper’s BBQ for lunch

The hydrogen coverage of interstellar PAHs

The rate at which the CH bond in interstellar Polycyclic Aromatic Hydrocarbons (PAHs) rupture due to the absorption of a UV photon has been calculated. The results show that small PAHs (less than or equal to 25 carbon atoms) are expected to be partially dehydrogenated in regions with intense UV fields, while large PAHs (greater than or equal to 25 atoms) are expected to be completely hydrogenated in those regions. Because estimate of the carbon content of interstellar PAHs lie in the range of 20 to 25 carbon atoms, dehydrogenation is probably not very important. Because of the absence of other emission features besides the 11.3 micrometer feature in ground-based 8 to 13 micrometer spectra, it has been suggested that interstellar PAHs are partially dehydrogenated. However, IRAS 8 to 22 micrometer spectra of most sources that show strong 7.7 and 11.2 micrometer emission features also show a plateau of emission extending from about 11.3 to 14 micrometer. Like the 11.3 micrometer feature, this new feature is attributed to the CH out of plane bending mode in PAHs. This new feature shows that interstellar PAHs are not as dehydrogenated as estimated from ground-based 8 to 13 micrometer spectra. It also constrains the molecular structure of interstellar PAHs. In particular, it seems that very condensed PAHs, such as coronene and circumcoronene, dominate the interstellar PAH mixture as expected from stability arguments

A study of the applicability of nucleation theory to quasi-thermodynamic transitions of second and higher Ehrenfest-order, supplement 3

The work includes an investigation of the applicability of the nucleation theory to second and higher order thermodynamic transitions in the Ehrenfest sense, and a number of significant conclusions relevant to first order transitions, as well. The underlying theoretical method consisted of expanding the Gibbs' free energy in a Maclarin or Taylor series and then using fundamental thermodynamic determinable quantities, and interpreting the results. Work was performed on the existence and interpretation of an interfacial energy between phases in a second order transition in addition to an investigation of the solid-liquid interfacial energy for various polymers. Extensive considerations were devoted to various aspects of a particular polymer, polyvinylidene fluoride (PVDF or PVF2), including an experimetal investigation of the effects of an applied electric field on the morphology of melt crystallization and on the nucleation and growth of polarized domains

Full Open Population Capture-Recapture Models with Individual Covariates

Traditional analyses of capture-recapture data are based on likelihood functions that explicitly integrate out all missing data. We use a complete data likelihood (CDL) to show how a wide range of capture-recapture models can be easily fitted using readily available software JAGS/BUGS even when there are individual-specific time-varying covariates. The models we describe extend those that condition on first capture to include abundance parameters, or parameters related to abundance, such as population size, birth rates or lifetime. The use of a CDL means that any missing data, including uncertain individual covariates, can be included in models without the need for customized likelihood functions. This approach also facilitates modeling processes of demographic interest rather than the complexities caused by non-ignorable missing data. We illustrate using two examples, (i) open population modeling in the presence of a censored time-varying individual covariate in a full robust-design, and (ii) full open population multi-state modeling in the presence of a partially observed categorical variable

A study of the applicability of nucleation theory to quasi-thermodynamic transformations of second and higher Ehrenfest-order

Transient and steady-state phenomena in temperature, stress, and electric, field intensity in ferroelectric polymers were investigated. The application and extension of the theory in the primary stage to the polarization domain nucleation and growth in ferroelectric polymers were developed. The kinetics of this growth were investigated. Expressions describing nucleation under the influence of an electric field were found through the expansion of the Gibbs' free energy in a Maclaurin series. The series was expanded in the electric field strength rather than the degree of undercooling. The resulting expressions were manipulated and applied to the case of nucleation of polarized domains in ferroelectric polymers. The kinetics of the nucleation and growth of polarized domains are also investigated. This was accomplished through the modification of the Johnson-Mehl-Avrami treatment of crystallization kinetics to be applicable to the growth of polarization domains in ferroelectric materials

Infrared fluorescence from PAHs in the laboratory

Several celestial objects, including UV rich regions of planetary and reflection nebulae, stars, H II regions, and extragalactic sources, are characterized by the unidentified infrared emission bands (UIR bands). A few years ago, it was proposed that polycyclic aromatic hydrocarbon species (PAHs) are responsible for most of the UIR bands. This hypothesis is based on a spectrum analysis of the observed features. Comparisons of observed IR spectra with lab absorption spectra of PAHs support the PAH hypothesis. An example spectrum is represented, where the Orion Bar 3.3 micron spectrum is compared with the absorption frequencies of the PAHs Chrysene, Pyrene, and Coronene. The laser excited 3.3 micron emission spectrum is presented from a gas phase PAH (azulen). The infrared fluorescence theory (IRF) is briefly explained, followed by a description of the experimental apparatus, a report of the results, and discussion

Is There a Significant Difference Between the Results of the Coulomb Dissociation of 8B and the Direct Capture 7Be(p,g)8B Reaction?

Recent claims of the Seattle group of evidence of "slope difference between CD [Coulomb Dissociation] and direct [capture] results" are based on wrong and selective data. When the RIKEN2 data are included correctly, and previously published Direct Capture (DC) data are also included, we observe only a 1.9 sigma difference in the extracted so called "scale independent slope (b)", considerably smaller than claimed by the Seattle group. The very parameterization used by the Seattle group to extract the so called b-slope parameter has no physical foundation. Considering the physical slope (S' = dS/dE), we observe a 1.0 sigma agreement between slopes (S') measured in CD and DC, refuting the need for new theoretical investigation. The claim that S17(0) values extracted from CD data are approximately 10% lower than DC results, is based on misunderstanding of the CD method. Considering all of the published CD S17(0) results, with adding back an unconfirmed E2 correction of the MSU data, yields very consistent S17(0) results that agree with recent DC measurements of the Seattle and Weizmann groups. The recent correction of the b-slope parameter (0.25 1/MeV) suggested by Esbensen, Bertsch and Snover was applied to the wrong b-slope parameter calculated by the Seattle group. When considering the correct slope of the RIKEN2 data, this correction in fact leads to a very small b-slope parameter (0.14 1/MeV), less than half the central value observed for DC data, refuting the need to correct the RIKEN2 data. In particular it confirms that the E2 contribution in the RIKEN2 data is negligible. The dispersion of measured S17(0) is mostly due to disagreement among individual DC experiments and not due to either experimental or theoretical aspects of CD.Comment: Reference 12 amended with an important communication from Dr. Bertsc