1,355 research outputs found
Extracting W Boson Couplings from the Production of Four Leptons
We consider the processes , including all possible charged lepton combinations, with
regard to measuring parameters characterizing the boson. We calculate at
what level these processes can be used to measure anamolous triple-boson
vertice coupling parameters for the cases of colliders at 500
and 1 center of mass energies.Comment: 13 pages,OCIP/C-93-
Globular Clusters in the dE,N galaxy NGC 3115 DW1: New Insights from Spectroscopy and HST Photometry
The properties of globular clusters in dwarf galaxies are key to
understanding the formation of globular cluster systems, and in particular in
verifying scenarios in which globular cluster systems of larger galaxies formed
(at least partly) from the accretion of dwarf galaxies. Here, we revisit the
globular cluster system of the dE,N galaxy NGC 3115 DW1 - a companion of the
nearby S0 galaxy NGC 3115 - adding Keck/LRIS spectroscopy and HST/WFPC2 imaging
to previous ground-based photometry. Spectra for seven globular clusters reveal
normal abundance ratios with respect to the Milky Way and M31 clusters, as well
as a relatively high mean metallicity ([Fe/H] = -1.0+/-0.1 dex). Crude
kinematics indicate a high velocity dispersion within 10 kpc which could either
be caused by dark matter dominated outer regions, or by the stripping of outer
globular clusters by the nearby giant galaxy NGC 3115. The total galaxy mass
out to 3 and 10 kpc lies between 10^10 and 10^11 solar masses and 2*10^10 and
4*10^11 solar masses, respectively, depending on the mass estimator used and
the assumptions on cluster orbits and systemic velocity. The HST imaging allows
measurement of sizes for two clusters, returning core radii around 2.0 pc,
similar to the sizes observed in other galaxies. Spectroscopy allows an
estimate of the degree of contamination by foreground stars or background
galaxies for the previous ground-based photometry, but does not require a
revision of previous results: NGC 3115 DW1 hosts around 60+/-20 clusters which
corresponds to a specific frequency of 4.9+/-1.9, on the high end for massive
dEs. Given its absolute magnitude (M_V=-17.7 mag) and the properties of its
cluster system, NGC 3115 DW1 appears to be a transition between a luminous dE
and low-luminosity E galaxy.Comment: 25 pages, 8 figures, accepted for publication in The Astronomical
Journal, August 2000 issu
Antisymmetric tensor unparticle and the radiative lepton flavor violating decays
We study the contribution of the tensor unparticle mediation to the branching
ratios of the radiative lepton flavor violating decays and predict a
restriction region for free parameters of the scenario by using experimental
upper limits. We observe that the branching ratios of the radiative lepton
flavor violating decays are sensitive to the fundamental mass scales of the
scenario and to the scale dimension of antisymmetric tensor unparticle. We
obtain a more restricted set for the free parameters in the case of the
\mu\rightarrow e \gamma decayComment: 15 pages, 10 figure
Reversible catastrophic oxidation of a 38Fe-34Ni-25Cr alloy induced by sodium sulphate at low oxygen potential atmospheres
International audienceThe chromia-forming nickel-based alloy Haynes (R) HR-120 was oxidised with and without Na2SO4 deposit in a CO/H-2/CO2 (45/45/10%vol.) simulated process atmosphere at 900 degrees C for 96 h. During the first hours of oxidation, samples covered by sodium sulphate exhibit higher oxidation rate than non-covered ones. However, after 24 h both sulphate-covered and uncovered specimens follow the same linear kinetics. In this very low oxygen partial pressure environment (10(-18) atm), the presence of Na2SO4 promotes the growth of localized iron-rich oxide nodules leading to the observed accelerated oxidation. The development of these nodules is discussed to be the result of the chromia dissolution induced by a basic fluxing mechanism. As soon as the salt is evaporated, slower kinetics are observed and the nodules disappear. In these specific conditions, the oxidation could be considered as a self-healing process
The Yang-Baxter equation for PT invariant nineteen vertex models
We study the solutions of the Yang-Baxter equation associated to nineteen
vertex models invariant by the parity-time symmetry from the perspective of
algebraic geometry. We determine the form of the algebraic curves constraining
the respective Boltzmann weights and found that they possess a universal
structure. This allows us to classify the integrable manifolds in four
different families reproducing three known models besides uncovering a novel
nineteen vertex model in a unified way. The introduction of the spectral
parameter on the weights is made via the parameterization of the fundamental
algebraic curve which is a conic. The diagonalization of the transfer matrix of
the new vertex model and its thermodynamic limit properties are discussed. We
point out a connection between the form of the main curve and the nature of the
excitations of the corresponding spin-1 chains.Comment: 43 pages, 6 figures and 5 table
Unraveling the Nature of Charge Excitations in LaCuO with Momentum-Resolved Cu -edge Resonant Inelastic X-ray Scattering
Results of model calculations using exact diagonalization reveal the orbital
character of states associated with different Raman loss peaks in Cu -edge
resonant inelastic X-ray scattering (RIXS) from LaCuO. The model
includes electronic orbitals necessary to highlight non-local Zhang-Rice
singlet, charge transfer and - excitations, as well as states with apical
oxygen 2 character. The dispersion of these excitations is discussed with
prospects for resonant final state wave-function mapping. A good agreement with
experiments emphasizes the substantial multi-orbital character of RIXS profiles
in the energy transfer range 1-6 eV.Comment: Original: 4.5 pages. Replaced: 4 pages and 4 figures with updated
content and reference
Genomic evidence for sulfur intermediates as new biogeochemical hubs in a model aquatic microbial ecosystem
Background: The sulfur cycle encompasses a series of complex aerobic and anaerobic transformations of S-containing
molecules and plays a fundamental role in cellular and ecosystem-level processes, influencing biological carbon transfers and
other biogeochemical cycles. Despite their importance, the microbial communities and metabolic pathways involved in
these transformations remain poorly understood, especially for inorganic sulfur compounds of intermediate oxidation states
(thiosulfate, tetrathionate, sulfite, polysulfides). Isolated and highly stratified, the extreme geochemical and environmental
features of meromictic ice-capped Lake A, in the Canadian High Arctic, provided an ideal model ecosystem to resolve the
distribution and metabolism of aquatic sulfur cycling microorganisms along redox and salinity gradients.
Results: Applying complementary molecular approaches, we identified sharply contrasting microbial communities and
metabolic potentials among the markedly distinct water layers of Lake A, with similarities to diverse fresh, brackish and saline
water microbiomes. Sulfur cycling genes were abundant at all depths and covaried with bacterial abundance. Genes for
oxidative processes occurred in samples from the oxic freshwater layers, reductive reactions in the anoxic and sulfidic
bottom waters and genes for both transformations at the chemocline. Up to 154 different genomic bins with potential for
sulfur transformation were recovered, revealing a panoply of taxonomically diverse microorganisms with complex metabolic
pathways for biogeochemical sulfur reactions. Genes for the utilization of sulfur cycle intermediates were widespread
throughout the water column, co-occurring with sulfate reduction or sulfide oxidation pathways. The genomic bin
composition suggested that in addition to chemical oxidation, these intermediate sulfur compounds were likely produced
by the predominant sulfur chemo- and photo-oxidisers at the chemocline and by diverse microbial degraders of organic
sulfur molecules.
Conclusions: The Lake A microbial ecosystem provided an ideal opportunity to identify new features of the biogeochemical
sulfur cycle. Our detailed metagenomic analyses across the broad physico-chemical gradients of this permanently stratified
lake extend the known diversity of microorganisms involved in sulfur transformations over a wide range of environmental
conditions. The results indicate that sulfur cycle intermediates and organic sulfur molecules are major sources of electron
donors and acceptors for aquatic and sedimentary microbial communities in association with the classical sulfur cycl
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