7,559 research outputs found
Computer programs for prediction of structural vibrations due to fluctuating pressure environments. Volume 1 - Theoretical analyses Final report
Theoretical analyses for computer program to calculate random vibrations of reinforced rectangular cylindrical panels in fluctuating pressure environmen
Associated Charmonium Production in p-pbar Annihilation
In this paper we summarize our recent results for low energy associated
charmonium production cross sections, using 1) crossing symmetry, and 2) an
explicit hadronic model. These predictions are of relevance to the planned
charmonium and charmonium hybrid production experiment PANDA at GSI.Comment: 5 pages, 5 figures. Contribution to the Second Meeting of the APS
Topical Group on Hadron Physics GHP2006. (Nashville, TN, 22-24 Oct. 2006
Hadron Loops: General Theorems and Application to Charmonium
In this paper we develop a formalism for incorporating hadron loops in the
quark model. We derive expressions for mass shifts, continuum components and
mixing amplitudes of "quenched" quark model states due to hadron loops, as
perturbation series in the valence-continuum coupling Hamiltonian. We prove
three general theorems regarding the effects of hadron loops, which show that
given certain constraints on the external "bare" quark model states, the
valence-continuum coupling, and the hadrons summed in the loops, the following
results hold: (1) The loop mass shifts are identical for all states within a
given N,L multiplet. (2) These states have the same total open-flavor decay
widths. (3) Loop-induced valence configuration mixing vanishes provided that
{\L}_i \neq \L_f or . The charmonium system is used as a
numerical case study, with the decay model providing the
valence-continuum coupling. We evaluate the mass shifts and continuum mixing
numerically for all 1S, 1P and 2S charmonium valence states due to loops of D,
D, D and D meson pairs. We find that the mass shifts are quite
large, but are numerically similar for all the low-lying charmonium states, as
suggested by the first theorem. Thus, loop mass shifts may have been "hidden"
in the valence quark model by a change of parameters. The two-meson continuum
components of the physical charmonium states are also found to be large,
creating challenges for the interpretation of the constituent quark model.Comment: 10 pages, 1 ps figure. Typos corrected; discussion of psi-eta_c mass
splitting added, published versio
Inflation Targeting and the Anchoring of Inflation Expectations in The Western Hemisphere
We investigate the extent to which long-run inflation expectations are well anchored in three western hemisphere countries—Canada, Chile, and the United States—using a high-frequency event-study analysis. Specifically, we use daily data on far-ahead forward inflation compensation—the difference between forward rates on nominal and inflation-indexed bonds—as an indicator of financial market perceptions of inflation risk and the expected level of inflation at long horizons. For the United States, we find that far-ahead forward inflation compensation reacts significantly to macroeconomic data releases, suggesting that long-run inflation expectations are not completely anchored. In contrast, the Canadian inflation compensation data do not exhibit significant sensitivity to either Canadian or U.S. macroeconomic news, consistent with the view that inflation targeting in Canada has been successful in anchoring long-run inflation expectations. Finally, while the requisite data for Chile is only available for a limited sample period (2002-2005), our results are consistent with the hypothesis that inflation targeting in Chile has also succeeded in anchoring long-run inflation expectations.
Charmonium-Nucleon Dissociation Cross Sections in the Quark Model
Charmonium dissociation cross sections due to flavor-exchange
charmonium-baryon scattering are computed in the constituent quark model. We
present results for inelastic and scattering amplitudes
and cross sections into 46 final channels, including final states composed of
various combinations of , , , and . These results
are relevant to experimental searches for the deconfined phase of quark matter,
and may be useful in identifying the contribution of initial
production to the open-charm final states observed at RHIC through the
characteristic flavor ratios of certain channels. These results are also of
interest to possible charmonium-nucleon bound states.Comment: 10 pages, 5 eps figures, revte
A search for 183-GHz emission from water in late-type stars
A search was made for 183 GHz line emission from water vapor in the direction of twelve Mira and two semiregular variables. Upper limits to the emission are in the range of 2000 to 5000 Jy. It is estimated that thermal emission from the inner regions of late type stellar envelopes will be on the order of ten Jy. Maser emission, according to one model, would be an order of magnitude stronger. From the limited set sampled, the possibility of very strong maser emission at 183 GHz cannot yet be ruled out
Unquenching the Quark Model and Screened Potentials
The low-lying spectrum of the quark model is shown to be robust under the
effects of `unquenching'. In contrast, the use of screened potentials is shown
to be of limited use in models of hadrons. Applications to unquenching the
lattice Wilson loop potential and to glueball mixing in the adiabatic hybrid
spectrum are also presented.Comment: 6 pages, 3 ps figures, revtex. Version to appear in J. Phys.
Interaction between Faraday rotation and Cotton-Mouton effects in polarimetry modeling for NSTX
The evolution of electromagnetic wave polarization is modeled for propagation
in the major radial direction in the National Spherical Torus Experiment (NSTX)
with retroreflection from the center stack of the vacuum vessel. This modeling
illustrates that the Cotton-Mouton effect-elliptization due to the magnetic
field perpendicular to the propagation direction-is shown to be strongly
weighted to the high-field region of the plasma. An interaction between the
Faraday rotation and Cotton-Mouton effects is also clearly identified.
Elliptization occurs when the wave polarization direction is neither parallel
nor perpendicular to the local transverse magnetic field. Since Faraday
rotation modifies the polarization direction during propagation, it must also
affect the resultant elliptization. The Cotton-Mouton effect also intrinsically
results in rotation of the polarization direction, but this effect is less
significant in the plasma conditions modeled. The interaction increases at
longer wavelength, and complicates interpretation of polarimetry measurements.Comment: Contributed paper published as part of the Proceedings of the 18th
Topical Conference on High-Temperature Plasma Diagnostics, Wildwood, New
Jersey, May, 201
183 GHz water line variation: An energetic outburst in orion KL
Observations of the 3(13)-2(20) transition of water vapor in the direction of Ori MC1 in 1980 February show a 50% flux increase and an apparent additional red shift of approximately 2 km/s relative to the line observed in 1977 December. From a detailed examination of the amplitude and frequency calibration, it appears unlikely that the effect is due to systematic error. The increase is attributed to the appearance of a new component at a velocity of 12 km/s with respect to the local standard of rest. The new component also has broad wings. Increased emission from a region in the high-velocity core of Ori MC1 can be due either to additional far-IR radiation to pump the 1983 GHz transition or to a change in the physical conditions in the gas. Statistical equilibrium calculations using the large-velocity-gradient formalism were carried out to develop a model for the emission. The calculations support a model in which the gas in the region of enhanced emission is hotter than the dust. The temporal coincidence between the 183 GHZ increase and the 22 GH1 water maser outburst suggests a common, impulsive cause, which has heated the gas in a part of the HV source, enhancing the emission in both transitions
Cytosolic recognition of flagellin by mouse macrophages restricts Legionella pneumophila infection.
To restrict infection by Legionella pneumophila, mouse macrophages require Naip5, a member of the nucleotide-binding oligomerization domain leucine-rich repeat family of pattern recognition receptors, which detect cytoplasmic microbial products. We report that mouse macrophages restricted L. pneumophila replication and initiated a proinflammatory program of cell death when flagellin contaminated their cytosol. Nuclear condensation, membrane permeability, and interleukin-1beta secretion were triggered by type IV secretion-competent bacteria that encode flagellin. The macrophage response to L. pneumophila was independent of Toll-like receptor signaling but correlated with Naip5 function and required caspase 1 activity. The L. pneumophila type IV secretion system provided only pore-forming activity because listeriolysin O of Listeria monocytogenes could substitute for its contribution. Flagellin monomers appeared to trigger the macrophage response from perforated phagosomes: once heated to disassemble filaments, flagellin triggered cell death but native flagellar preparations did not. Flagellin made L. pneumophila vulnerable to innate immune mechanisms because Naip5+ macrophages restricted the growth of virulent microbes, but flagellin mutants replicated freely. Likewise, after intratracheal inoculation of Naip5+ mice, the yield of L. pneumophila in the lungs declined, whereas the burden of flagellin mutants increased. Accordingly, macrophages respond to cytosolic flagellin by a mechanism that requires Naip5 and caspase 1 to restrict bacterial replication and release proinflammatory cytokines that control L. pneumophila infection
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