Gegenbauer-solvable quantum chain model

In an innovative inverse-problem construction the measured, experimental energies $E_1$, $E_2$, ...$E_N$ of a quantum bound-state system are assumed fitted by an N-plet of zeros of a classical orthogonal polynomial $f_N(E)$. We reconstruct the underlying Hamiltonian $H$ (in the most elementary nearest-neighbor-interaction form) and the underlying Hilbert space ${\cal H}$ of states (the rich menu of non-equivalent inner products is offered). The Gegenbauer's ultraspherical polynomials $f_n(x)=C_n^\alpha(x)$ are chosen for the detailed illustration of technicalities.Comment: 29 pp., 1 fi

Anomalous double peak structure in Nb/Ni superconductor/ferromagnet tunneling DOS

We have experimentally investigated the density of states (DOS) in Nb/Ni (S/F) bilayers as a function of Ni thickness, $d_F$. Our thinnest samples show the usual DOS peak at $\pm\Delta_0$, whereas intermediate-thickness samples have an anomalous ``double-peak'' structure. For thicker samples ($d_F \geq 3.5$ nm), we see an ``inverted'' DOS which has previously only been reported in superconductor/weak-ferromagnet structures. We analyze the data using the self-consistent non-linear Usadel equation and find that we are able to quantitatively fit the features at $\pm\Delta_0$ if we include a large amount of spin-orbit scattering in the model. Interestingly, we are unable to reproduce the sub-gap structure through the addition of any parameter(s). Therefore, the observed anomalous sub-gap structure represents new physics beyond that contained in the present Usadel theory.Comment: 4 pages, 3 figure

Effect of fertilization and stimulation of Hevea brasiliensis trees on mineral compositions and properties of produced latex and rubber

This publication reports the mineral composition and the properties of latex and rubber obtained from a fertilizer agronomical trial conducted in Kasetsart University Sitthiporn Kritsadakon Research Station, south Thai l and. This trial was designed to study the effect of 4 fertilizer levels on RRIM 600 clone trees tapped with the recommended tapping system (S/ 2 d2) with or without stimulation (ET2.5% 4/y). Latex and rubber characterization was conducted on biannual sampling campaigns from 2014 to 2017. Nitrogen (N) and mineral (P, K, Mg, Ca, Ashes) contents were measured on latex and USS rubber made from this latex. Dry Rubber Content (DRC) and Mechanical Stability (MST) of latex as well as Wallace plasticity (P 0), plasticity retention index (PRI) of USS rubber were measured. After 3 agronomical years, latex yield was found to be increased by both fertilization level and stimulation. Concerning N and mineral compositions of latex and USS rubber, no significant effect of fertilization was observed. However, stimulation application was found to be associated with the increase of P content of latex and N, P and Mg contents of USS rubber. Concerning physical properties of late x (DRC,MST) and USS rubber (Po,PRI), none of these indicators was found to be influenced by either fertilization levels, or stimulant application or their interaction Finally, comparison between latex and USS rubber mineral contents showed that most of P (60%), Mg (82%), and K (89%) was leached in the waste water during the USS making process while the majority of N (34% leached) and the totality of Ca stayed within rubber. The mineral content of the USS process waste water was found to be in the same order of magnitude as the amount brought by fertilizer. Hence, USS process water recycling could be an option to consider. (Résumé d'auteur

X-ray diffraction measurements of the c-axis Debye-Waller factors of YBa2Cu3O7 and HgBa2CaCu2O6

We report the first application of x-rays to the measurement of the temperature dependent Bragg peak intensities to obtain Debye-Waller factors on high-temperature superconductors. Intensities of (0,0,l) peaks of YBa2Cu3O7 and HgBa2CaCu2O6 thin films are measured to obtain the c-axis Debye-Waller factors. While lattice constant and some Debye-Waller factor measurements on high Tc superconductors show anomalies at the transition temperature, our measurements by x-ray diffraction show a smooth transition of the c-axis Debye-Waller factors through T$_c$. This suggests that the dynamic displacements of the heavy elements along the c-axis direction in these compounds do not have anomalies at Tc. This method in combination with measurements by other techniques will give more details concerning dynamics of the lattice.Comment: 4 pages, 2 figures. To be published in Physical Review B (Brief Report

Localization transition of random copolymers at interfaces

We consider adsorption of random copolymer chains onto an interface within the model of Garel et al. Europhysics Letters 8, 9 (1989). By using the replica method the adsorption of the copolymer at the interface is mapped onto the problem of finding the ground state of a quantum mechanical Hamiltonian. To study this ground state we introduce a novel variational principle for the Green's function, which generalizes the well-known Rayleigh-Ritz method of Quantum Mechanics to nonstationary states. Minimization with an appropriate trial Green's function enables us to find the phase diagram for the localization-delocalization transition for an ideal random copolymer at the interface.Comment: 5 page

Grain boundary effects on magnetotransport in bi-epitaxial films of La0.7_{0.7}Sr0.3_{0.3}MnO3_3

The low field magnetotransport of La$_{0.7}$Sr$_{0.3}$MnO$_3$ (LSMO) films grown on SrTiO$_3$ substrates has been investigated. A high qualtity LSMO film exhibits anisotropic magnetoresistance (AMR) and a peak in the magnetoresistance close to the Curie temperature of LSMO. Bi-epitaxial films prepared using a seed layer of MgO and a buffer layer of CeO$_2$ display a resistance dominated by grain boundaries. One film was prepared with seed and buffer layers intact, while a second sample was prepared as a 2D square array of grain boundaries. These films exhibit i) a low temperature tail in the low field magnetoresistance; ii) a magnetoconductance with a constant high field slope; and iii) a comparably large AMR effect. A model based on a two-step tunneling process, including spin-flip tunneling, is discussed and shown to be consistent with the experimental findings of the bi-epitaxial films.Comment: REVTeX style; 14 pages, 9 figures. Figure 1 included in jpeg format (zdf1.jpg); the eps was huge. Accepted to Phys. Rev.

Observational Limits on Machos in the Galactic Halo

We present final results from the first phase of the EROS search for gravitational microlensing of stars in the Magellanic Clouds by unseen deflectors (machos: MAssive Compact Halo Objects). The search is sensitive to events with time scales between 15 minutes and 200 days corresponding to deflector masses in the range 1.e-7 to a few solar masses. Two events were observed that are compatible with microlensing by objects of mass of about 0.1 Mo. By comparing the results with the expected number of events for various models of the Galaxy, we conclude that machos in the mass range [1.e-7, 0.02] Mo make up less than 20% (95% C.L.) of the Halo dark matter.Comment: 4 pages, 3 Postscript figures, to be published in Astronomy & Astrophysic

Non-Hermitian matrix description of the PT symmetric anharmonic oscillators

Schroedinger equation H \psi=E \psi with PT - symmetric differential operator H=H(x) = p^2 + a x^4 + i \beta x^3 +c x^2+i \delta x = H^*(-x) on L_2(-\infty,\infty) is re-arranged as a linear algebraic diagonalization at a>0. The proof of this non-variational construction is given. Our Taylor series form of \psi complements and completes the recent terminating solutions as obtained for certain couplings \delta at the less common negative a.Comment: 18 pages, latex, no figures, thoroughly revised (incl. title), J. Phys. A: Math. Gen., to appea