Charged-Surface Instability Development in Liquid Helium; Exact Solutions

The nonlinear dynamics of charged-surface instability development was investigated for liquid helium far above the critical point. It is found that, if the surface charge completely screens the field above the surface, the equations of three-dimensional (3D) potential motion of a fluid are reduced to the well-known equations describing the 3D Laplacian growth process. The integrability of these equations in 2D geometry allows the analytic description of the free-surface evolution up to the formation of cuspidal singularities at the surface.Comment: latex, 5 pages, no figure

Anderson localization of a weakly interacting one dimensional Bose gas

We consider the phase coherent transport of a quasi one-dimensional beam of Bose-Einstein condensed particles through a disordered potential of length L. Among the possible different types of flow identified in [T. Paul et al., Phys. Rev. Lett. 98, 210602 (2007)], we focus here on the supersonic stationary regime where Anderson localization exists. We generalize the diffusion formalism of Dorokhov-Mello-Pereyra-Kumar to include interaction effects. It is shown that interactions modify the localization length and also introduce a length scale L* for the disordered region, above which most of the realizations of the random potential lead to time dependent flows. A Fokker-Planck equation for the probability density of the transmission coefficient that takes this new effect into account is introduced and solved. The theoretical predictions are verified numerically for different types of disordered potentials. Experimental scenarios for observing our predictions are discussed.Comment: 20 pages, 13 figure

Loss of Andreev Backscattering in Superconducting Quantum Point Contacts

We study effects of magnetic field on the energy spectrum in a superconducting quantum point contact. The supercurrent induced by the magnetic field leads to intermode transitions between the electron waves that pass and do not pass through the constriction. The latter experience normal reflections which couple the states with opposite momenta inside the quantum channel and create a minigap in the energy spectrum that depends on the magnetic field

Re-entrant localization of single particle transport in disordered Andreev wires

We study effects of disorder on the low energy single particle transport in a normal wire surrounded by a superconductor. We show that the heat conductance includes the Andreev diffusion decreasing with increase in the mean free path $\ell$ and the diffusive drift produced by a small particle-hole asymmetry, which increases with increasing $\ell$. The conductance thus has a minimum as a function of $\ell$ which leads to a peculiar re-entrant localization as a function of the mean free path.Comment: 4 pages, 2 figure

Binding of molecules to DNA and other semiflexible polymers

A theory is presented for the binding of small molecules such as surfactants to semiflexible polymers. The persistence length is assumed to be large compared to the monomer size but much smaller than the total chain length. Such polymers (e.g. DNA) represent an intermediate case between flexible polymers and stiff, rod-like ones, whose association with small molecules was previously studied. The chains are not flexible enough to actively participate in the self-assembly, yet their fluctuations induce long-range attractive interactions between bound molecules. In cases where the binding significantly affects the local chain stiffness, those interactions lead to a very sharp, cooperative association. This scenario is of relevance to the association of DNA with surfactants and compact proteins such as RecA. External tension exerted on the chain is found to significantly modify the binding by suppressing the fluctuation-induced interaction.Comment: 15 pages, 7 figures, RevTex, the published versio

Optical properties of new indotricarbocyanine dye as a limiter of laser radiation power

We present results of experimental and theoretical studies of the optical characteristics of a new indotricarbocyanine dye that is capable of effectively limiting the power of laser radiation in the visible spectral range. The spectral-luminescent and energy characteristics of the dye molecules and their absorption spectra from the excited state with nanosecond resolution are investigated experimentally. Quantum-chemical methods are used to calculate electronic absorption spectra from the ground (S0 → Sn) and excited (S1 → Sn) states and to determine the nature of electronic states of the molecule and the rate constants of intramolecular photo-physical processes. The results of the theoretical research agree with experimental data. It is shown that the investigated dye has singlet-singlet absorption at 400–600 nm. Nonlinear absorption of the dye upon excitation by radiation of the second harmonic of a Nd:YAG laser is studied by z-scanning with an open diaphragm. The ratio of dye absorption cross sections from the excited and ground states at 532 nm is determined in the framework of a three-level model. The results are compared with those for previously studied compounds

Transanal surgery in the treatment of rectal tumors

In last two decades, transanal endoscopic microsurgery (TEM) in treatment of both benign and malignant tumor of rectum is actively developing. The aim of this review was to describe the current status of transanal interventions. Due to the low level of recurrens (mean about 6 %) TEM has become the method of choice for removal of rectal adenomas. Several studies have demonstrated the benefits of treatment TEM in cases of early T1 cancer compared to conventional resection. However, for more invasive adenocarcinomas performing TEM remains controversial, but it’s very promising method for the complex treatment. Just as transanal mesorectal exision in treatment of mid- and low rectal cancer as a new strategy – natural orifice transluminal surgery. However, it lack of evidence base and international experience in small series presented, so large randomized trials is needed

Diffusion controlled initial recombination

This work addresses nucleation rates in systems with strong initial recombination. Initial (or `geminate') recombination is a process where a dissociated structure (anion, vortex, kink etc.) recombines with its twin brother (cation, anti-vortex, anti-kink) generated in the same nucleation event. Initial recombination is important if there is an asymptotically vanishing interaction force instead of a generic saddle-type activation barrier. At low temperatures, initial recombination strongly dominates homogeneous recombination. In a first part, we discuss the effect in one-, two-, and three-dimensional diffusion controlled systems with spherical symmetry. Since there is no well-defined saddle, we introduce a threshold which is to some extent arbitrary but which is restricted by physically reasonable conditions. We show that the dependence of the nucleation rate on the specific choice of this threshold is strongest for one-dimensional systems and decreases in higher dimensions. We discuss also the influence of a weak driving force and show that the transport current is directly determined by the imbalance of the activation rate in the direction of the field and the rate against this direction. In a second part, we apply the results to the overdamped sine-Gordon system at equilibrium. It turns out that diffusive initial recombination is the essential mechanism which governs the equilibrium kink nucleation rate. We emphasize analogies between the single particle problem with initial recombination and the multi-dimensional kink-antikink nucleation problem.Comment: LaTeX, 11 pages, 1 ps-figures Extended versio

Localization in a random phase-conjugating medium

We theoretically study reflection and transmission of light in a one-dimensional disordered phase-conjugating medium. Using an invariant imbedding approach a Fokker-Planck equation for the distribution of the probe light reflectance and expressions for the average probabilities of reflection and transmission are derived. A new crossover length scale for localization of light is found, which depends on the competition between phase conjugation and disorder. For weak disorder, our analytical results are in good agreement with numerical simulations.Comment: RevTex, 4 pages, 4 figure

Beyond Anderson localization in 1D: Anomalous localizacion of microwaves in random waveguides

Experimental evidence demonstrating that anomalous localization of waves can be induced in a controllable manner is reported. A microwave waveguide with dielectric slabs randomly placed is used to confirm the presence of anomalous localization. If the random spacing between slabs follows a distribution with a power-law tail (Lévy-type distribution), unconventional properties in the microwave-transmission fluctuations take place revealing the presence of anomalous localization. We study both theoretically and experimentally the complete distribution of the transmission through random waveguides characterized by α ¼ 1=2 (“Lévy waveguides”) and α ¼ 3=4, α being the exponent of the power-law tail of the Lévy-type distribution. As we show, the transmission distributions are determined by only two parameters, both of them experimentally accessible. Effects of anomalous localization on the transmission are compared with those from the standard Anderson localization.J. C., F. C., J. S.-D., and V. A. G. acknowledge financial support from MINECO (Spain) under the Projects No. FIS2012-35719-C02-02, No. TEC2010-19751, and No. CSD2008-00066 (CONSOLIDER Program). A. A. F.-M. and J. A. M.-B. thank Fondo Institucional PIFCA through Grant No. BUAP-CA-169 for partial support.Fernandez Marin, AA.; Mendez Bermudez, J.; Carbonell Olivares, J.; Cervera Moreno, FS.; Sánchez-Dehesa Moreno-Cid, J.; Gopar, VA. (2014). Beyond Anderson localization in 1D: Anomalous localizacion of microwaves in random waveguides. PHYSICAL REVIEW LETTERS. 113(23):233901-1-233901-5. doi:10.1103/PhysRevLett.113.233901S233901-1233901-511323Anderson, P. W. (1958). Absence of Diffusion in Certain Random Lattices. Physical Review, 109(5), 1492-1505. doi:10.1103/physrev.109.1492Lagendijk, A., Tiggelen, B. van, & Wiersma, D. S. (2009). Fifty years of Anderson localization. Physics Today, 62(8), 24-29. doi:10.1063/1.3206091Wiersma, D. S., Bartolini, P., Lagendijk, A., & Righini, R. (1997). 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A Lévy flight for light. Nature, 453(7194), 495-498. doi:10.1038/nature06948Karbasi, S., Frazier, R. J., Koch, K. W., Hawkins, T., Ballato, J., & Mafi, A. (2014). Image transport through a disordered optical fibre mediated by transverse Anderson localization. Nature Communications, 5(1). doi:10.1038/ncomms4362Riboli, F., Caselli, N., Vignolini, S., Intonti, F., Vynck, K., Barthelemy, P., … Wiersma, D. S. (2014). Engineering of light confinement in strongly scattering disordered media. Nature Materials, 13(7), 720-725. doi:10.1038/nmat3966Falceto, F., & Gopar, V. A. (2010). Conductance through quantum wires with Lévy-type disorder: Universal statistics in anomalous quantum transport. EPL (Europhysics Letters), 92(5), 57014. doi:10.1209/0295-5075/92/57014Boosé, D., & Luck, J. M. (2007). Statistics of quantum transmission in one dimension with broad disorder. Journal of Physics A: Mathematical and Theoretical, 40(47), 14045-14067. doi:10.1088/1751-8113/40/47/002Beenakker, C. W. J., Groth, C. W., & Akhmerov, A. R. (2009). Nonalgebraic length dependence of transmission through a chain of barriers with a Lévy spacing distribution. Physical Review B, 79(2). doi:10.1103/physrevb.79.024204Burioni, R., Caniparoli, L., & Vezzani, A. (2010). Lévy walks and scaling in quenched disordered media. Physical Review E, 81(6). doi:10.1103/physreve.81.060101Uchaikin, V. V., & Zolotarev, V. M. (1999). Chance and Stability. doi:10.1515/9783110935974Abrikosov, A. A. (1981). The paradox with the static conductivity of a one-dimensional metal. Solid State Communications, 37(12), 997-1000. doi:10.1016/0038-1098(81)91203-5Mello, P. A. (1986). Central‐limit theorems on groups. Journal of Mathematical Physics, 27(12), 2876-2891. doi:10.1063/1.527265Markos, P., & Soukoulis, C. M. (2008). Wave Propagation. doi:10.1515/9781400835676Kuhl, U., Izrailev, F. M., & Krokhin, A. A. (2008). Enhancement of Localization in One-Dimensional Random Potentials with Long-Range Correlations. 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