25,747 research outputs found
An analytic Approach to Turaev's Shadow Invariant
In the present paper we extend the "torus gauge fixing approach" by Blau and
Thompson (Nucl. Phys. B408(1):345--390, 1993) for Chern-Simons models with base
manifolds M of the form M= \Sigma x S^1 in a suitable way. We arrive at a
heuristic path integral formula for the Wilson loop observables associated to
general links in M. We then show that the right-hand side of this formula can
be evaluated explicitly in a non-perturbative way and that this evaluation
naturally leads to the face models in terms of which Turaev's shadow invariant
is defined.Comment: 44 pages, 2 figures. Changes have been made in Sec. 2.3, Sec 2.4,
Sec. 3.4, and Sec. 3.5. Appendix C is ne
Predicting success in weaning from mechanical ventilation in patients with and without cardiac disease
Multi-excitonic complexes in single InGaN quantum dots
Cathodoluminescence spectra employing a shadow mask technique of InGaN layers
grown by metal organic chemical vapor deposition on Si(111) substrates are
reported. Sharp lines originating from InGaN quantum dots are observed.
Temperature dependent measurements reveal thermally induced carrier
redistribution between the quantum dots. Spectral diffusion is observed and was
used as a tool to correlate up to three lines that originate from the same
quantum dot. Variation of excitation density leads to identification of exciton
and biexciton. Binding and anti-binding complexes are discovered.Comment: 3 pages, 4 figure
The local atomic quasicrystal structure of the icosahedral Mg25Y11Zn64 alloy
A local and medium range atomic structure model for the face centred
icosahedral (fci) Mg25Y11Zn64 alloy has been established in a sphere of r = 27
A. The model was refined by least squares techniques using the atomic pair
distribution (PDF) function obtained from synchrotron powder diffraction. Three
hierarchies of the atomic arrangement can be found: (i) five types of local
coordination polyhedra for the single atoms, four of which are of Frank-Kasper
type. In turn, they (ii) form a three-shell (Bergman) cluster containing 104
atoms, which is condensed sharing its outer shell with its neighbouring
clusters and (iii) a cluster connecting scheme corresponding to a
three-dimensional tiling leaving space for few glue atoms. Inside adjacent
clusters, Y8-cubes are tilted with respect to each other and thus allow for
overall icosahedral symmetry. It is shown that the title compound is
essentially isomorphic to its holmium analogue. Therefore fci-Mg-Y-Zn can be
seen as the representative structure type for the other rare earth analogues
fci-Mg-Zn-RE (RE = Dy, Er, Ho, Tb) reported in the literature.Comment: 12 pages, 8 figures, 2 table
On the (Mis)Specification of Seasonality and Its Consequences: an Empirical Investigation with U.S. Data
Higgs Phenomenology in Warped Extra-Dimensions with a 4th Generation
We study a warped extra-dimension scenario where the Standard Model fields
lie in the bulk, with the addition of a fourth family of fermions. We
concentrate on the flavor structure of the Higgs couplings with fermions in the
flavor anarchy ansatz. Even without a fourth family, these couplings will be
generically misaligned with respect to the SM fermion mass matrices. The
presence of the fourth family typically enhances the misalignment effects and
we show that one should expect them to be highly non-symmetrical in the
inter-generational mixing. The radiative corrections from the new
fermions and their flavor violating couplings to the Higgs affect negligibly
known experimental precision measurements such as the oblique parameters and
or . On the other hand,
processes, mediated by tree-level Higgs exchange, as well as radiative
corrections to and put some generic pressure
on the allowed size of the flavor violating couplings. But more importantly,
these couplings will alter the Higgs decay patterns as well as those of the new
fermions, and produce very interesting new signals associated to Higgs
phenomenology in high energy colliders. These might become very important
indirect signals for these type of models as they would be present even when
the KK mass scale is high and no heavy KK particle is discovered.Comment: 39 pages, 6 figure
Secondary Outcomes of a Pilot Randomized Trial of Azithromycin Treatment for Asthma
OBJECTIVES: The respiratory pathogen Chlamydia pneumoniae (C. pneumoniae) produces acute and chronic lung infections and is associated with asthma. Evidence for effectiveness of antichlamydial antibiotics in asthma is limited. The primary objective of this pilot study was to investigate the feasibility of performing an asthma clinical trial in practice settings where most asthma is encountered and managed. The secondary objectives were to investigate (1) whether azithromycin treatment would affect any asthma outcomes and (2) whether C. pneumoniae serology would be related to outcomes. This report presents the secondary results. DESIGN: Randomized, placebo-controlled, blinded (participants, physicians, study personnel, data analysts), allocation-concealed parallel group clinical trial. SETTING: Community-based health-care settings located in four states and one Canadian province. PARTICIPANTS: Adults with stable, persistent asthma. INTERVENTIONS: Azithromycin (six weekly doses) or identical matching placebo, plus usual community care. OUTCOME MEASURES: Juniper Asthma Quality of Life Questionnaire (Juniper AQLQ), symptom, and medication changes from baseline (pretreatment) to 3 mo posttreatment (follow-up); C. pneumoniae IgG and IgA antibodies at baseline and follow-up. RESULTS: Juniper AQLQ improved by 0.25 (95% confidence interval; −0.3, 0.8) units, overall asthma symptoms improved by 0.68 (0.1, 1.3) units, and rescue inhaler use decreased by 0.59 (−0.5, 1.6) daily administrations in azithromycin-treated compared to placebo-treated participants. Baseline IgA antibodies were positively associated with worsening overall asthma symptoms at follow-up (p = 0.04), but IgG was not (p = 0.63). Overall asthma symptom improvement attributable to azithromycin was 28% in high IgA participants versus 12% in low IgA participants (p for interaction = 0.27). CONCLUSIONS: Azithromycin did not improve Juniper AQLQ but appeared to improve overall asthma symptoms. Larger community-based trials of antichlamydial antibiotics for asthma are warranted
Plasma Oscillations and Expansion of an Ultracold Neutral Plasma
We report the observation of plasma oscillations in an ultracold neutral
plasma. With this collective mode we probe the electron density distribution
and study the expansion of the plasma as a function of time. For classical
plasma conditions, i.e. weak Coulomb coupling, the expansion is dominated by
the pressure of the electron gas and is described by a hydrodynamic model.
Discrepancies between the model and observations at low temperature and high
density may be due to strong coupling of the electrons.Comment: 4 pages, 4 figures. Accepted Phys. Rev. Let
Non-thermal leptogenesis via direct inflaton decay without SU(2)(L) triplets
We present a non-thermal leptogenesis scenario following standard
supersymmetric hybrid inflation, in the case where light neutrinos acquire mass
via the usual seesaw mechanism and inflaton decay to heavy right-handed
neutrino superfields is kinematically disallowed, or the right-handed neutrinos
which can be decay products of the inflaton are unable to generate sufficient
baryon asymmetry via their subsequent decay. The primordial lepton asymmetry is
generated through the decay of the inflaton into light particles by the
interference of one-loop diagrams with exchange of different right-handed
neutrinos. The mechanism requires superpotential couplings explicitly violating
a U(1) R-symmetry and R-parity. We take into account the constraints from
neutrino masses and mixing and the preservation of the primordial asymmetry. We
consider two models, one without and one with SU(2)(R) gauge symmetry. We show
that the former is viable, whereas the latter is ruled out. Although the broken
R-parity need not have currently observable low-energy signatures, some
R-parity-violating slepton decays may be detectable in the future colliders.Comment: 22 pages including 9 figures, uses Revtex, version to appear in PR
Experimental and theoretical analysis of the upper critical field in FSF trilayers
The upper critical magnetic field H_{c2} in thin-film FSF trilayer spin-valve
cores is studied experimentally and theoretically in geometries perpendicular
and parallel to the heterostructure surface. The series of samples with
variable thicknesses of the bottom and of the top Cu_{41}Ni_{59} F-layers are
prepared in a single run, utilizing a wedge deposition technique. The critical
field H_{c2} is measured in the temperature range K and for magnetic
fields up to 9 Tesla. A transition from oscillatory to reentrant behavior of
the superconducting transition temperature versus F-layers thickness, induced
by an external magnetic field, has been observed for the first time. In order
to properly interpret the experimental data, we develop a quasiclassical
theory, enabling one to evaluate the temperature dependence of the critical
field and the superconducting transition temperature for an arbitrary set of
the system parameters. A fairly good agreement between our experimental data
and theoretical predictions is demonstrated for all samples, using a single set
of fit parameters. This confirms adequacy of the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) physics in determining the unusual
superconducting properties of the studied Cu_{41}Ni_{59}/Nb/Cu_{41}Ni_{59}
spin-valve core trilayers.Comment: 16 pages, 7 figures; published versio
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