580 research outputs found
Deep spectroscopy of the low-metallicity blue compact dwarf galaxy SBS 0335-052
The results of deep long-slit spectroscopy of the extremely low-metallicity
blue compact dwarf (BCD) galaxy SBS 0335-052 are presented. Down to intensity
levels of 10^{-3 ... -4} of Hbeta, unprecedented for spectroscopy of
extra-galactic giant H II regions, we detect numerous weak permitted and
forbidden nebular lines in the brightest part of the galaxy. With varying
degrees of confidence, the detections include lines of high-ionization ions
like Fe^{4+} -Fe^{6+}, implying very hard ionizing radiation. Two broad
emission features, possibly from Wolf-Rayet stars, and stellar He II 4200
absorption are seen in the same region. The large spatial extent of He II 4686
emission (implying the presence of sufficient ionizing photons with energies
above 54 eV) and the spatial distribution of the electron temperature suggest
that at least some part of the hard radiation is associated with shocks.
Extended Halpha emission is detected over ~ 6 - 8 kpc, a much larger area than
in previous studies, suggesting that hot ionized gas is spread out far away
from the central ionizing clusters. This shows that nebular line and continuous
emission can significantly modify the colours of these extended regions and
must be taken into account in studies of the underlying stellar population.Comment: 5 pages, 3 Postscript figures, accepted for publication in the
Astronomy and Astrophysic
Physico-Chemical-Managed Killing of Penicillin-Resistant Static and Growing Gram-Positive and Gram-Negative Vegetative Bacteria
Systems and methods for the use of compounds from the Hofmeister series coupled with specific pH and temperature to provide rapid physico-chemical-managed killing of penicillin-resistant static and growing Gram-positive and Gram-negative vegetative bacteria. The systems and methods represent the more general physico-chemical enhancement of susceptibility for a wide range of pathological macromolecular targets to clinical management by establishing the reactivity of those targets to topically applied drugs or anti-toxins
The He abundance in the metal-deficient blue compact dwarf galaxies Tol 1214-277 and Tol 65
We present high-quality Keck telescope spectroscopic observations of the two
metal-deficient blue compact dwarf (BCD) galaxies Tol 1214-277 and Tol 65.
These data are used to derive the heavy-element and helium abundances. We find
that the oxygen abundances in Tol 1214-277 and Tol 65 are the same,
12+logO/H=7.54+/-0.01, or Zsun/24, despite the different ionization conditions
in these galaxies. The nitrogen-to-oxygen abundance ratio in both galaxies is
logN/O=-1.64+/-0.02 and lies in the narrow range found for the other most
metal-deficient BCDs. We use the five strongest HeI emission lines 3889, 4471,
5876, 6678 and 7065, to correct self-consistently their intensities for
collisional and fluorescent enhancement mechanisms and to derive the He
abundance. Underlying stellar absorption is found to be important for the HeI
4471 emission line in both galaxies, being larger in Tol 65. The weighted He
mass fractions in Tol 1214-277 and Tol 65 are respectively Y=0.2458+/-0.0039
and 0.2410+/-0.0050 when the three HeI emission lines, 4471, 5876 and 6678, are
used, and are, respectively, 0.2466+/-0.0043 and 0.2463+/-0.0057 when the HeI
4471 emission line is excluded. These values are in very good agreement with
recent measurements of the He mass fraction in others of the most
metal-deficient BCDs by Izotov and coworkers. We find that the combined effect
of the systematic uncertainties due to the underlying HeI stellar absorption
lines, ionization and temperature structure of the HII region and collisional
excitation of the hydrogen emission lines is likely small, not exceeding ~2%
(the error is 2sigma). Our results support the validity of the standard big
bang model of nucleosynthesis.Comment: 22 pages, 3 Postscript figures, accepted for publication in the
Astrophysical Journa
Friction and Wear Management Using Solvent Partitioning of Hydrophilic-Surface-Interactive Chemicals Contained in Boundary Layer-Targeted Emulsions
Lubrication additives of the current invention require formation of emulsions in base lubricants, created with an aqueous salt solution plus a single-phase compound such that partitioning within the resulting emulsion provides thermodynamically targeted compounds for boundary layer organization thus establishing anti-friction and/or anti-wear. The single-phase compound is termed "boundary layer organizer", abbreviated BLO. These emulsion-contained compounds energetically favor association with tribologic surfaces in accord with the Second Law of Thermodynamics, and will organize boundary layers on those surfaces in ways specific to the chemistry of the salt and BLO additives. In this way friction modifications may be provided by BLOs targeted to boundary layers via emulsions within lubricating fluids, wherein those lubricating fluids may be water-based or oil-based
Friction and Wear Modifiers Using Solvent Partitioning of Hydrophilic Surface-Interactive Chemicals Contained in Boundary Layer-Targeted Emulsions
A wear and/or friction reducing additive for a lubricating fluid in which the additive is a combination of a moderately hydrophilic single-phase compound and an anti-wear and/or anti-friction aqueous salt solution. The aqueous salt solution produces a coating on boundary layer surfaces. The lubricating fluid can be an emulsion-free hydrophobic oil, hydraulic fluid, antifreeze, or water. Preferably, the moderately hydrophilic single-phase compound is sulfonated castor oil and the aqueous salt solution additionally contains boric acid and zinc oxide. The emulsions produced by the aqueous salt solutions, the moderately hydrophilic single-phase compounds, or the combination thereof provide targeted boundary layer organizers that significantly enhance the anti-wear and/or anti-friction properties of the base lubricant by decreasing wear and/or friction of sliding and/or rolling surfaces at boundary layers
The afterglows of gamma-ray bursts
Gamma-ray burst astronomy has undergone a revolution in the last three years, spurred by the discovery of fading long-wavelength counterparts. We now know that at least the long duration GRBs lie at cosmological distances with estimated electromagnetic energy release of 10^51–10^53 erg, making these the brightest explosions in the Universe. In this article we review the current observational state, beginning with the statistics of X-ray, optical, and radio afterglow detections. We then discuss the insights these observations have given to the progenitor population, the energetics of the GRB events, and the physics of the afterglow emission. We focus particular attention on the evidence linking GRBs to the explosion of massive stars. Throughout, we identify remaining puzzles and uncertainties, and emphasize promising observational tools for addressing them. The imminent launch of HETE-2 and the increasingly sophisticated and coordinated ground-based and space-based observations have primed this field for fantastic growth
The afterglows of gamma-ray bursts
Gamma-ray burst astronomy has undergone a revolution in the last three years, spurred by the discovery of fading long-wavelength counterparts. We now know that at least the long duration GRBs lie at cosmological distances with estimated electromagnetic energy release of 10^51–10^53 erg, making these the brightest explosions in the Universe. In this article we review the current observational state, beginning with the statistics of X-ray, optical, and radio afterglow detections. We then discuss the insights these observations have given to the progenitor population, the energetics of the GRB events, and the physics of the afterglow emission. We focus particular attention on the evidence linking GRBs to the explosion of massive stars. Throughout, we identify remaining puzzles and uncertainties, and emphasize promising observational tools for addressing them. The imminent launch of HETE-2 and the increasingly sophisticated and coordinated ground-based and space-based observations have primed this field for fantastic growth. This overview is a combined write-up of talks given at this conference and in NASA's Goddard Space Flight Center
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