29,831 research outputs found
Fracturing Jazz, Freeing Fusion: Miles Davis’s Role in Counterculture Rock
The paper details Miles Davis\u27s influence in the counterculture rock and roll movement through his development of jazz fusion and his personal connections with rock musicians of the period, as well the overlap in musical ideology that occurred when both rock and jazz began to incorporate elements of each others\u27 styles
Terahertz Spectroscopy in the Lab and at Telescopes
The section of the electromagnetic spectrum extending roughly from wavelengths of 3 mm to 30 μm is commonly known as the far-infrared or TeraHertz (THz) region. It contains the great majority of the photons emitted by the universe, and THz observations of molecules and dust are able penetrate deeply into molecular clouds, thus revealing the full history of star and planet formation. Accordingly, the upcoming deployments of the Herschel, ALMA, and SOFIA observatories promise to revolutionize our understanding of THz astrophysics. To fully realize this promise, however, it is essential that we achieve a quantitative experimental understanding of the dust, ice, and gas which make up the ISM. After outlining the tremendous impact that Tom Phillips has had on astronomical applications of THz radiation, this contribution will describe how emerging technologies in ultrafast lasers are enabling the development of integrated frequency- and time-domain THz facilities that can acquire high dynamic range optical constants of the major components that comprise astrophysical dust, ice and organics across the full wavelength region accessible to Herschel and other THz observatories
Chemistry in Dense Molecular Clouds: Theory and Observational Constraints
For the most part, gas phase models of the chemistry of dense molecular clouds
predict the abundances of simple species rather well. However, for larger molecules and even for
small systems rich in carbon these models often fail spectacularly. We present a brief review of the
basic assumptions and results of large scale modeling of the chemistry in dense molecular clouds.
Particular attention will be paid to the influence of the gas phase ratios of the major elements
in molecular clouds, and the likely role grains play in maintaining these ratios as clouds evolve
from initially diffuse objects to denser cores with associated stellar and planetary formation.
Recent spectral line surveys at centimeter and millimeter wavelengths along with selected
observations in the submillimeter have now produced an accurate "inventory" of the gas phase
elemental budgets in different types of molecular clouds, though gaps in our knowledge clearly
remain. The constraints these observations place on theoretical models of interstellar chemistry
can be used to gain insights into why the models fail, and show also which neglected processes
must be included in more complete analyses. Looking toward the future, truly protostellar regions
are only now becoming available for both experimental and theoretical study, and some of the
expected modifications of molecular cloud chemistry in these sources are therefore outlined
Carbon Chemistry in Dense Molecular Clouds: Theory and Observational Constraints
For the most part, gas phase models of the chemistry of dense molecular clouds
predict the abundances of simple species rather well. However, for larger molecules and even
for small systems rich in carbon these models often fail spectacularly. We present a brief review
of the basic assumptions and results of large scale modeling of the carbon chemistry in dense
molecular clouds. Particular attention will be paid to the influence of the gas phase C/O ratio in
molecular clouds, and the likely role grains play in maintaining this ratio as clouds evolve from
initially diffuse objects to denser cores with associated stellar and planetary formation.
Recent spectral line surveys at centimeter and millimeter wavelengths along with selected
observations in the submillimeter have now produced an accurate "inventory" of the gas phase
carbon budget in several different types of molecular clouds, though gaps in our knowledge clearly
remain. The constraints these observations place on theoretical models of interstellar chemistry
can be used to gain insights into why the models fail, and show also which neglected processes
must be included in more complete analyses. Looking toward the future, larger molecules are
especially difficult to study both experimentally and theoretically in such dense, cold regions, and
some new methods are therefore outlined which may ultimately push the detectability of small
carbon chains and rings to much heavier species
ZEKE-PFI spectroscopy of 1:1 complexes of sodium with water and ammonia
ZEKE-PFI (zero kinetic energy pulsed field ionization) photoelectron spectra of the Na(H_2O), Na(D_2O), Na(NH_3), and Na(ND_3) complexes are reported. Spectra of all four complexes were obtained by single-photon ionization, and, for the Na(NH_3) and Na(ND_3) complexes, by two-color (1 + 1′) photoionization as well, with the Ã^2E state serving as the intermediate resonance. Improved values for the ionization energies (IE) and intermolecular vibrational frequencies of the complexes were determined. The single-photon ZEKE-PFI spectra show transitions only between states of the same vibrational symmetry, in accord with the selection rule for allowed electronic transitions. Some of the two-color ZEKE-PFI spectra, however, show strong transitions between states of different vibrational symmetry which we attribute to vibronic coupling in the intermediate state
High-Resolution 4.7 Micron Keck/NIRSPEC Spectroscopy of the CO Emission from the Disks Surrounding Herbig Ae Stars
We explore the high-resolution (λ/Δλ = 25,000; Δv = 12 km s^(-1)) M-band (4.7-5.1 μm) spectra of several disk-dominated Herbig Ae (HAe) systems: AB Aur, MWC 758, MWC 480, HD 163296, and VV Ser. All five objects show ^(12)CO v = 1-0 emission lines up to J = 42, but there is little or no evidence of moderate-J, v = 2-1 transitions despite their similar excitation energies. AB Aur shows ^(13)CO emission as well. The line/continuum ratios and intensity profiles are well correlated with inclination, and they trace collisionally driven emission from the inner disk (R_(th) ≾ 0.5-1 AU) as well as resonance fluorescence to much larger radii (R_(hν) ≾ 50-100 AU for J ≾ 10). The temperature, density, and radiation field profiles required to fit the CO emission are in good agreement with models of HAe disks derived from their spectral energy distributions. High-resolution and high dynamic range infrared spectroscopy of CO, and future observations of less abundant species, thus provide direct access to the physicochemical properties and surface structure of disks in regions where planet formation likely occurs
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Identifiability in Age/Period/Cohort Mortality Models
The addition of a set of cohort parameters to a mortality model can generate complex identifiability issues due to the collinearity between the dimensions of age, period and cohort. These issues can lead to robustness problems and difficulties making projections of future mortality rates. Since many modern mortality models incorporate cohort parameters, we believe that a comprehensive analysis of the identifiability issues in age/period/cohort mortality models is needed. In this paper, we discuss the origin of identifiability issues in general models before applying these insights to simple but commonly used mortality models. We then discuss how to project mortality models so that our forecasts of the future are independent of any arbitrary choices we make when fitting a model to data in order to identify the historical parameters
Solar performance evaluation test program of the 9.5-ft-diam. electroformed nickel concentrator S/N 1 at Table Mountain, California
Optical and calorimetric tests of nickel mirrors for use as power source for thermionic generator
FARM LEVEL EFFECTS AN INCREASE IN FEDERAL CIGARETTE TAXES UNDER TWO SCENARIOS: KEEP VS ELIMINATE THE TOBACCO PROGRAM
Agricultural and Food Policy,
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