7,221 research outputs found
New Solutions to the Strong CP Problem
We exhibit a solution to the strong CP problem in which ultraviolet physics
renders the QCD theta angle physically unobservable. Our models involve new
strong interactions beyond QCD and particles charged under both the new
interactions and ordinary color.Comment: RevTex, 2-columns, 5 pages, 1 fig. Revised version, including
additional discussion of the UV theory and the low-energy effective theory,
to appear in Physics Letters
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Targeting RyR Activity Boosts Antisense Exon 44 and 45 Skipping in Human DMD Skeletal or Cardiac Muscle Culture Models.
Systemic delivery of antisense oligonucleotides (AO) for DMD exon skipping has proven effective for reframing DMD mRNA, rescuing dystrophin expression, and slowing disease progression in animal models. In humans with Duchenne muscular dystrophy treated with AOs, low levels of dystrophin have been induced, and modest slowing of disease progression has been observed, highlighting the need for improved efficiency of human skipping drugs. Here, we demonstrate that dantrolene and Rycals S107 and ARM210 potentiate AO-mediated exon skipping of exon 44 or exon 45 in patient-derived myotube cultures with appropriate mutations. Further, dantrolene is shown to boost AO-mediated exon skipping in patient-derived, induced cardiomyocyte cultures. Our findings further validate the ryanodine receptors (RyR) as the likely target responsible for exon skip boosting and demonstrate potential applicability beyond exon 51 skipping. These data provide preclinical support of dantrolene trial as an adjuvant to AO-mediated exon-skipping therapy in humans and identify a novel Rycal, ARM210, for development as a potential exon-skipping booster. Further, they highlight the value of mutation-specific DMD culture models for basic discovery, preclinical drug screening and translation of personalized genetic medicines
Observation of Bulk Fermi Arc and Polarization Half Charge from Paired Exceptional Points
The ideas of topology have found tremendous success in Hermitian physical
systems, but even richer properties exist in the more general non-Hermitian
framework. Here, we theoretically propose and experimentally demonstrate a new
topologically-protected bulk Fermi arc which---unlike the well-known surface
Fermi arcs arising from Weyl points in Hermitian systems---develops from
non-Hermitian radiative losses in photonic crystal slabs. Moreover, we discover
half-integer topological charges in the polarization of far-field radiation
around the Fermi arc. We show that both phenomena are direct consequences of
the non-Hermitian topological properties of exceptional points, where
resonances coincide in their frequencies and linewidths. Our work connects the
fields of topological photonics, non-Hermitian physics and singular optics, and
paves the way for future exploration of non-Hermitian topological systems.Comment: 7 pages, 4 figure
Approach to Acoustic Emission Signal Analysis - Theory and Experiment
Acoustic Emission (AE) signals are notorious for their complexity and irreproducibility. Because AE source characteristics are virtually unknown and because the detected AE signals are colored by the propagation media, the sensor response and the instrumentation set tings, interpretations of test results such as spectral analysis or correlation studies are mostly qualitative and sometimes controversial; theories either are empirically derived or cannot be verified by experiments . In this paper, we sketch an approach to the AE signal analysis problem. We first report the development of a theory which allows the computation of the displacement as a function of time at an arbitrary ·point on an infinite plate due to an arbitrary point source force function . The theory is based on a new Fourier inversion technique which yields exact formulas similar to those developed for seismological ray theories. We then report experimental results obtained on a 2. 52 em thick aluminum plate using a reproducible step function stress release pulse as a simulated AE signal and a wide band displacement capacitive transducer as a sensor. The measurements are in quantitative agreement with the predictions of theory. We also discuss applications wherein the simulated signal, capacitive transducer and plate theory are used for AE source signature analysis, and sensor calibration problems
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Phase Coexistence of Ferroelectric Vortices and Classical a1/a2 Domains in PbTiO3/SrTiO3 Superlattices.
The invariant manifold approach applied to nonlinear dynamics of a rotor-bearing system
The invariant manifold approach is used to explore the dynamics of a
nonlinear rotor, by determining the nonlinear normal modes, constructing a
reduced order model and evaluating its performance in the case of response to
an initial condition. The procedure to determine the approximation of the
invariant manifolds is discussed and a strategy to retain the speed dependent
effects on the manifolds without solving the eigenvalue problem for each spin
speed is presented. The performance of the reduced system is analysed in
function of the spin speed
Grain Boundary Scars and Spherical Crystallography
We describe experimental investigations of the structure of two-dimensional
spherical crystals. The crystals, formed by beads self-assembled on water
droplets in oil, serve as model systems for exploring very general theories
about the minimum energy configurations of particles with arbitrary repulsive
interactions on curved surfaces. Above a critical system size we find that
crystals develop distinctive high-angle grain boundaries, or scars, not found
in planar crystals. The number of excess defects in a scar is shown to grow
linearly with the dimensionless system size. The observed slope is expected to
be universal, independent of the microscopic potential.Comment: 4 pages, 3 eps figs (high quality images available from Mark Bowick
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