151 research outputs found
Parity Doubling and the S Parameter Below the Conformal Window
We describe a lattice simulation of the masses and decay constants of the
lowest-lying vector and axial resonances, and the electroweak S parameter, in
an SU(3) gauge theory with and 6 fermions in the fundamental
representation. The spectrum becomes more parity doubled and the S parameter
per electroweak doublet decreases when is increased from 2 to 6,
motivating study of these trends as is increased further, toward the
critical value for transition from confinement to infrared conformality.Comment: 4 pages, 5 figures; to be submitted to PR
Molecular Gas in the Host Galaxy of a Quasar at Redshift z=6.42
Observations of the molecular gas phase in quasar host galaxies provide
fundamental constraints on galaxy evolution at the highest redshifts. Molecular
gas is the material out of which stars form; it can be traced by spectral line
emission of carbon--monoxide (CO). To date, CO emission has been detected in
more than a dozen quasar host galaxies with redshifts (z) larger 2, the record
holder being at z=4.69. At these distances the CO lines are shifted to longer
wavelengths, enabling their observation with sensitive radio and millimetre
interferometers. Here we present the discovery of CO emission toward the quasar
SDSS J114816.64+525150.3 (hereafter J1148+5251) at a redshift of z=6.42, when
the universe was only 1/16 of its present age. This is the first detection of
molecular gas at the end of cosmic reionization. The presence of large amounts
of molecular gas (M(H_2)=2.2e10 M_sun) in an object at this time demonstrates
that heavy element enriched molecular gas can be generated rapidly in the
earliest galaxies.Comment: 12 pages, 2 figures. To appear in Nature, July, 200
Composite bosonic baryon dark matter on the lattice: SU(4) baryon spectrum and the effective Higgs interaction
First assessment of the comparative toxicity of ivermectin and moxidectin in adult dung beetles: Sub-lethal symptoms and pre-lethal consequences
Among macrocyclic lactones (ML), ivermectin (IVM) and moxidectin (MOX) potentially affect all
Ecdysozoan species, with dung beetles being particularly sensitive. The comparative effects of IVM
and MOX on adult dung beetles were assessed for the first time to determine both the physiological
sub-lethal symptoms and pre-lethal consequences. Inhibition of antennal response and ataxia
were tested as two intuitive and ecologically relevant parameters by obtaining the lowest observed
effect concentration (LOEC) values and interpolating other relevant toxicity thresholds derived from
concentration-response curves (IC50, as the concentration of each ML where the antennal response is
inhibited by half; and pLC50, as the quantity of ingested ML where partial paralysis was observed by half
of treated individuals) from concentration-response curves. Both sub-lethal and pre-lethal symptoms
obtained in this study coincided in that IVM was six times more toxic than MOX for adult dung beetles.
Values of LOEC, IC50 and pLC50 obtained for IVM and MOX evaluated in an environmental context
indicate that MOX, despite needing more time for its elimination in the faeces, would be half as harmful
to dung beetles as IVM. This approach will be valuable to clarify the real impact of MLs on dung beetle
health and to avoid the subsequent environmental consequences
Strongly interacting dynamics and the search for new physics at the LHC
We present results for the spectrum of a strongly interacting SU(3) gauge
theory with light fermions in the fundamental representation.
Carrying out non-perturbative lattice calculations at the lightest masses and
largest volumes considered to date, we confirm the existence of a remarkably
light singlet scalar particle. We explore the rich resonance spectrum of the
8-flavor theory in the context of the search for new physics beyond the
standard model at the Large Hadron Collider (LHC). Connecting our results to
models of dynamical electroweak symmetry breaking, we estimate the vector
resonance mass to be about 2 TeV with a width of roughly 450 GeV, and predict
additional resonances with masses below ~3 TeV.Comment: 6 pages, 6 figures. Added report number. Version submitted to journa
Linear sigma EFT for nearly conformal gauge theories
We construct a generalized linear sigma model as an effective field theory (EFT) to describe nearly conformal gauge theories at low energies. The work is motivated by recent lattice studies of gauge theories near the conformal window, which have shown that the lightest flavor-singlet scalar state in the spectrum (Ï) can be much lighter than the vector state (Ï) and nearly degenerate with the PNGBs (Ï) over a large range of quark masses. The EFT incorporates this feature. We highlight the crucial role played by the terms in the potential that explicitly break chiral symmetry. The explicit breaking can be large enough so that a limited set of additional terms in the potential can no longer be neglected, with the EFT still weakly coupled in this new range. The additional terms contribute importantly to the scalar and pion masses. In particular, they relax the inequality M2Ï â„ 3M2Ï, allowing for consistency with current lattice data
Attenuated allergic airway hyperresponsiveness in C57BL/6 mice is associated with enhanced surfactant protein (SP)-D production following allergic sensitization
BACKGROUND: C57BL/6 mice have attenuated allergic airway hyperresponsiveness (AHR) when compared with Balb/c mice but the underlying mechanisms remain unclear. SP-D, an innate immune molecule with potent immunosuppressive activities may have an important modulatory role in the allergic airway response and the consequent physiological changes. We hypothesized that an elevated SP-D production is associated with the impaired ability of C57BL/6 mice to develop allergic AHR. METHODS: SP-D mRNA and protein expression was investigated during development of allergic airway changes in a model of Aspergillus fumigatus (Af)-induced allergic inflammation. To study whether strain dependency of allergic AHR is associated with different levels of SP-D in the lung, Balb/c and C57BL/6 mice were compared. RESULTS: Sensitization and exposure to Af induced significant airway inflammation in both mouse strains in comparison with naïve controls. AHR to acetylcholine however was significantly attenuated in C57BL/6 mice in spite of increased eosinophilia and serum IgE when compared with Balb/c mice (p < 0.05). Af challenge of sensitized C57BL/6 mice induced a markedly increased SP-D protein expression in the SA surfactant fraction (1,894 ± 170% of naïve controls) that was 1.5 fold greater than the increase in Balb/c mice (1,234 ± 121% p < 0.01). These changes were selective since levels of the hydrophobic SP-B and SP-C and the hydrophilic SP-A were significantly decreased following sensitization and challenge with Af in both strains. Further, sensitized and exposed C57BL/6 mice had significantly lower IL-4 and IL-5 in the BAL fluid than that of Balb/c mice (p < 0.05). CONCLUSIONS: These results suggest that enhanced SP-D production in the lung of C57BL/6 mice may contribute to an attenuated AHR in response to allergic airway sensitization. SP-D may act by inhibiting synthesis of Th2 cytokines
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