Polarization-mode dispersion measurement by an optical time-domain reflectometer with polarimetry assuming backscattering by randomly oriented nonspherical particles

In previous work on polarization-mode dispersion (PMD) measurement with an optical time-domain reflectometer with polarimetry (p-OTDR), scatterers were assumed to be a cloud of small spherical particles in a fiber. We have found that the p-OTDR waveforms were fitted well by modified Mueller matrices, assuming scattering by a cloud of nonspherical particles. We realized a PMD measurement based on the p-OTDR Jones matrix eigenanalysis (JME) method. The measured PMD was consistent with that of JME standard measurement with transmission-type polarimetry.     

Dynamics of large semiflexible chains probed by fluorescence correlation spectroscopy

Fluorescence correlation spectroscopy was used to probe the dynamics of lambda-phage DNA in aqueous solution labeled with the randomly intercalating dye TOTO. The linear macromolecules (i). carry more than one chromophore and (ii). are larger than the waist of the focal volume. The correlation function decays significantly faster than expected for a stiff globule of corresponding size but is in good agreement with the dynamic model of semiflexible chains including hydrodynamic interactions. As the chromophore density is lowered the correlation time decreases in accordance with this model.     

Fractionalized fermi liquids

In spatial dimensions d>or=2, Kondo lattice models of conduction and local moment electrons can exhibit a fractionalized, nonmagnetic state (FL(*)) with a Fermi surface of sharp electronlike quasiparticles, enclosing a volume quantized by (rho(a)-1)(mod 2), with rho(a) the mean number of all electrons per unit cell of the ground state. Such states have fractionalized excitations linked to the deconfined phase of a gauge theory. Confinement leads to a conventional Fermi liquid state, with a Fermi volume quantized by rho(a)(mod 2), and an intermediate superconducting state for the Z2 gauge case. The FL(*) state permits a second order metamagnetic transition in an applied magnetic field.     

Microstructure and dynamics near an attractive colloidal glass transition

The microstructure and dynamics of a colloidal system interacting via short-ranged interparticle potential is studied by ultra-small-angle x-ray scattering and x-ray photon correlation spectroscopy. A colloidal gas-liquid type transition is induced when the short-ranged attractive interactions attain sufficient magnitude. The development of liquidlike structure is preceded by a systematic transition in the particle dynamics from diffusive to constrained motion and then completely frozen behavior. This demonstrates the existence of a jamming transition induced by strong short-ranged attractive interactions even at low packing fractions.     

Wavelength beam combining of ytterbium fiber lasers

Wavelength beam combining of five ytterbium fiber lasers is demonstrated in a master-oscillator power-amplifier configuration at combined powers up to 6 W. The combined beam profile has an M2 value of 1.14, which is equal to that of an individual fiber. Beam steering in one dimension over 140 resolvable spots is also demonstrated.     

Effect of fast neutron irradiation on magnetic properties of fullerene superconductor Rb3C60

Effects of fast neutron irradiation and post-annealing on magnetic properties of Rb₃C₆₀ were studied through the dc magnetization measurement. Rb₃C₆₀ powder samples were prepared in an evacuated quartz glass tube, and the temperature and the magnetic field dependences of dc magnetization were measured before and after irradiation and after post-annealing. The neutron fluences were 1.0, 1.8 and 3.3 × 10¹⁶ n/cm², and the post-annealing was made at a temperature of 473 K for 3 h. Magnetic hysteresis of the samples irradiated at the fluence of 1.8 and 3.3 × 10¹⁶ n/cm² disappeared, and the hysteresis curves hardly changed at the fluence of 1.0 × 10¹⁶ n/cm². As for the post-annealing effect, the hysteresis curves of the sample irradiated at the fluence of 1.8 × 10¹⁶ n/cm² were completely recovered after annealing, while those of the other samples, which had a magnetic background before irradiation, were not recovered. In this study, it was found that the loss of superconductivity in Rb₃C₆₀ powder is observed when the neutron irradiation fluence exceeds 1.0 × 10¹⁶ n/cm², and the lost superconductivity is completely recovered by the post-annealing at 473 K for 3 h.     

The dynamics of a one-dimensional disordered morse attice: Cooling caused by adiabatic stretching

The dynamics of a disordered one-dimensional lattice of a finite length consisting of N particles interacting according to the Morse potential was studied. Disordering was caused by random interaction potential values between neighboring particles. The dynamics of adiabatic stretching of the Morse lattice was considered in detail. An equation relating temperature to the geometric mean normal vibration frequency, that is, $ T \propto \sqrt[N]{{\omega ^1 \omega ^2 \ldots \omega ^N }} The dynamics of a disordered one-dimensional lattice of a finite length consisting of N particles interacting according to the Morse potential was studied. Disordering was caused by random interaction potential values between neighboring particles. The dynamics of adiabatic stretching of the Morse lattice was considered in detail. An equation relating temperature to the geometric mean normal vibration frequency, that is, , was obtained in the quasi-harmonic limit. At low temperatures and certain deformation values, strong interaction between modes was observed which resulted in intense energy exchange between them. The reason for this was pair resonances of the nω ⁱ = ω ^j type. In addition, there were triple resonances ω ⁱ + ω ^j = ω ^k . Close agreement between analytic results and numerical simulation was obtained. At low specific energy € values, the dynamics of the Morse lattice closely resembled the dynamics of the Fermi-Pasta-Ulam lattice. Original Russian Text ? V.N. Likhachev, T.Yu. Astakhova, G.A. Vinogradov, 2009, published in Khimicheskaya Fizika, 2009, Vol. 28, No. 1, pp. 71–82.     

Nucleon internal structure: a new set of quark, gluon momentum, angular momentum operators and parton distribution functions

It is unavoidable to deal with the quark and gluon momentum and angular momentum contributions to the nucleon momentum and spin in the study of nucleon internal structure. However we never have the quark and gluon momentum, orbital angular momentum and gluon spin operators which satisfy both the gauge invariance and the canonical momentum and angular momentum commutation relation. The conflicts between the gauge invariance and canonical quantization requirement of these operators are discussed. A new set of quark and gluon momentum, orbital angular momentum and spin operators, which satisfy both the gauge invariance and canonical momentum and angular momentum commutation relation, are proposed. The key point to achieve such a proper decomposition is to separate the gauge field into the pure gauge and the gauge covariant parts. The same conflicts also exist in QED and quantum mechanics and have been solved in the same manner. The impacts of this new decomposition to the nucleon internal structure are discussed.     

D abstraction by H at a D-saturated Ru(0 0 1) surface

D abstraction (ABS) by H at Ru(0 0 1) surfaces initially saturated with D adatoms has been investigated using in situ mass spectrometry. HD and D₂ desorption rates are measured at various surface temperatures T as a function of H exposure time. Yield of D₂ desorption increases with T, while that of HD is little affected. Analyzing the measured rate curves, HD and D₂ desorption orders are evaluated to be 1.7 ± 0.1 and 2.5 ± 0.1, respectively, with respect to D coverage θ_D. To pursue the origin of the derived non-integral reaction orders the rate curves are further analyzed with the rate equations constructed to involve several ABS channels. Consequently, we find that the HD desorption is mainly governed by a second-order rate law in θ_D rather than the conventional hot atom-mediated ABS reaction even when it is corrected to include an isotope effect on ABS. We argue that such second-order ABS kinetics becomes important when the H atoms in excited state of chemisorption have energetically relaxed to some extent, and thereby tend to reside at, e.g. hexagonal closed packed hollow sites, interacting with nearby adatoms. On the other hand, the D₂ rate curves can be fit with third-order kinetics, consistent with the Langmuir-Hinshelwood mechanism in a super-saturation state. The isotope effect plays an essential role in the ABS reaction of D abstraction by H which competes with H abstraction by H as D adatoms are replaced by H atoms.     

Effects of acid and alkaline based surface preparations on spray deposited cerium based conversion coatings on Al 2024-T3

Cerium based conversion coatings were spray deposited on Al 2024-T3 and characterized to determine the effect of surface preparation on the deposition rate and surface morphology. It was found that activation of the panel using a 1-wt.% sulfuric acid solution increased the coating deposition rate compared to alkaline cleaning alone. Analysis of the surface morphology of the coatings showed that the coatings deposited on the acid treated panels exhibited fewer visible cracks compared to coatings on alkaline cleaned panels. Auger electron spectroscopy depth profiling showed that the acid activation decreased the thickness of the aluminum oxide layer and the concentration of magnesium on the surface of the panels compared to the alkaline treatment. Additionally, acid activation increased the copper concentration at the surface of the aluminum substrate. Based on the results, the acid based surface treatment appeared to expose copper rich intermetallics, thus increasing the number of cathodic sites on the surface, which led to an overall increase in the deposition rate.