911 research outputs found
Couplings of the Rho Meson in a Holographic dual of QCD with Regge Trajectories
The couplings of the meson with any hadron H are
calculated in a holographic dual of QCD where the Regge trajectories for mesons
are manifest. The resulting couplings grow linearly with the exciting number of
H, thus are far from universal. A simple argument has been given for this
behavior based on quasi-classical picture of excited hadrons. It seems that in
holographic duals with exact Regge trajectories the universality
should be violated. The -dominance for the electromagnetic form factors
of H are also strongly violated, except for the lowest state, the pion. Quite
unexpected, the form factor of the pion is completely saturated by the
contribution of the . The asymptotic behavior of the form factors are
also calculated, and are found to be perfectly accordant with the prediction of
conformal symmetry and pertubative QCD.Comment: 9 page
Twist-3 Distribute Amplitude of the Pion in QCD Sum Rules
We apply the background field method to calculate the moments of the pion
two-particles twist-3 distribution amplitude (DA) in QCD sum
rules. In this paper,we do not use the equation of motion for the quarks inside
the pion since they are not on shell and introduce a new parameter to
be determined. We get the parameter in this approach. If
assuming the expansion of in the series in Gegenbauer polynomials
, one can obtain its approximate expression which can be
determined by its first few moments.Comment: 12 pages, 3 figure
Subconjunctivally implantable hydrogels with degradable and thermoresponsive properties for sustained release of insulin to the retina.
The objective of this work is to develop subconjunctivally implantable, biodegradable hydrogels for sustained release of intact insulin to the retina to prevent and treat retinal neurovascular degeneration such as diabetic retinopathy. The hydrogels are synthesized by UV photopolymerization of N-isopropylacrylamide (NIPAAm) monomer and a dextran macromer containing multiple hydrolytically degradable oligolactate-(2-hydroxyetheyl methacrylate) units (Dex-lactateHEMA) in 25:75 (v:v) ethanol:water mixture solvent. Insulin is loaded into the hydrogels during the synthesis process with loading efficiency up to 98%. The hydrogels can release biologically active insulin in vitro for at least one week and the release kinetics can be modulated by varying the ratio between NIPAAm and Dex-lactateHEMA and altering the physical size of the hydrogels. The hydrogels are not toxic to R28 retinal neuron cells in culture medium with 100% cell viability. The hydrogels can be implanted under the conjunctiva without causing adverse effects to the retina based on hematoxylin and eosin stain, immunostaining for microglial cell activation, and electroretinography. These subconjunctivally implantable hydrogels have potential for long-term periocular delivery of insulin or other drugs to treat diabetic retinopathy and other retinal diseases
Spectral control of high-harmonic generation via drive laser pulse shaping in a wide-diameter capillary
We experimentally investigate spectral control of high-harmonic generation in a wide-diameter (508 μm) capillary that allows using significantly lower gas pressures coupled with elevated drive laser energies to achieve higher harmonic energies. Using phase shaping to change the linear chirp of the drive laser pulses, we observe wavelength tuning of the high-harmonic output to both larger and smaller values. Comparing tuning via the gas pressure with the amount of blue shift in the transmitted drive laser spectrum, we conclude that both adiabatic and non-adiabatic effects cause pulse-shaping induced tuning of high harmonics. We obtain a fractional wavelength tuning, Δλ/λ, in the range from −0.007 to + 0.01, which is comparable to what is achieved with standard capillaries of smaller diameter and higher pressures
Asymptotic stability, concentration, and oscillation in harmonic map heat-flow, Landau-Lifshitz, and Schroedinger maps on R^2
We consider the Landau-Lifshitz equations of ferromagnetism (including the
harmonic map heat-flow and Schroedinger flow as special cases) for degree m
equivariant maps from R^2 to S^2. If m \geq 3, we prove that near-minimal
energy solutions converge to a harmonic map as t goes to infinity (asymptotic
stability), extending previous work down to degree m = 3. Due to slow spatial
decay of the harmonic map components, a new approach is needed for m=3,
involving (among other tools) a "normal form" for the parameter dynamics, and
the 2D radial double-endpoint Strichartz estimate for Schroedinger operators
with sufficiently repulsive potentials (which may be of some independent
interest). When m=2 this asymptotic stability may fail: in the case of
heat-flow with a further symmetry restriction, we show that more exotic
asymptotics are possible, including infinite-time concentration (blow-up), and
even "eternal oscillation".Comment: 34 page
Dynamics of a deformable self-propelled particle under external forcing
We investigate dynamics of a self-propelled deformable particle under
external field in two dimensions based on the model equations for the center of
mass and a tensor variable characterizing deformations. We consider two kinds
of external force. One is a gravitational-like force which enters additively in
the time-evolution equation for the center of mass. The other is an
electric-like force supposing that a dipole moment is induced in the particle.
This force is added to the equation for the deformation tensor. It is shown
that a rich variety of dynamics appears by changing the strength of the forces
and the migration velocity of self-propelled particle
Coherent control of high harmonic generation in a large-volume capillary for seeding of free-electron lasers
FEL-1 at FERMI@Elettra is a seeded free-electron laser using sub-harmonic seeding to generate soft x-rays down to 10 nm. The current seed laser, a standard solid-state laser followed by frequency quadrupling in nonlinear crystals, has a minimum wavelength of 200 nm. Injecting much shorter seed-laser wavelengths, for which high-harmonic generation (HHG) is of high promise, can shorten the laser output wavelength significantly. However, the minimum seed pulse energy required is not readily available with standard approaches to HHG. To increase the energy available in a particular harmonic for seeding, we use a gas-filled capillary with a large diameter (500 μm), pumped by an 8 mJ, 35 fs Ti:Sapphire laser. A wide capillary allows a large gas volume for HHG, thereby increasing the output energy. We also investigate the coherent control of HHG by shaping the spectral phase of the drive laser using an acousto-optic programmable dispersive filter. Here, we use a learning algorithm with the objective to simultaneously tune and selectively enhance an individual harmonic order. We present first results including pressure dependent harmonic output energy, spectrum and beam stability, as these are important for seeding of FELs. Further, we discuss initial experiments with coherent control that has shown selective enhancement up to a factor of 10
Blow up criterion for compressible nematic liquid crystal flows in dimension three
In this paper, we consider the short time strong solution to a simplified
hydrodynamic flow modeling the compressible, nematic liquid crystal materials
in dimension three. We establish a criterion for possible breakdown of such
solutions at finite time in terms of the temporal integral of both the maximum
norm of the deformation tensor of velocity gradient and the square of maximum
norm of gradient of liquid crystal director field.Comment: 22 page
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