Quantifying intermittency in the open drivebelt billiard

A "drivebelt" stadium billiard with boundary consisting of circular arcs of differing radius connected by their common tangents shares many properties with the conventional "straight" stadium, including hyperbolicity and mixing, as well as intermittency due to marginally unstable periodic orbits (MUPOs). Interestingly, the roles of the straight and curved sides are reversed. Here, we discuss intermittent properties of the chaotic trajectories from the point of view of escape through a hole in the billiard, giving the exact leading order coefficient lim(t→∞)tP(t) of the survival probability P(t) which is algebraic for fixed hole size. However, in the natural scaling limit of small hole size inversely proportional to time, the decay remains exponential. The big distinction between the straight and drivebelt stadia is that in the drivebelt case, there are multiple families of MUPOs leading to qualitatively new effects. A further difference is that most marginal periodic orbits in this system are oblique to the boundary, thus permitting applications that utilise total internal reflection such as microlasers.     

Diamond nanoparticles as photoluminescent nanoprobes for biology and near-field optics

We present results showing the potential of diamond nanoparticles with size <50 nm as photoluminescent nanoprobes for serving as stable point-like emitters attached at the tip apex of a near-field optical microscope to achieve enhanced spatial resolution.     

Dependence of chaotic diffusion on the size and position of holes

A particle driven by deterministic chaos and moving in a spatially extended environment can exhibit normal diffusion, with its mean square displacement growing proportional to the time. Here, we consider the dependence of the diffusion coefficient on the size and the position of areas of phase space linking spatial regions ('holes') in a class of simple one-dimensional, periodically lifted maps. The parameter dependent diffusion coefficient can be obtained analytically via a Taylor-Green-Kubo formula in terms of a functional recursion relation. We find that the diffusion coefficient varies non-monotonically with the size of a hole and its position, which implies that a diffusion coefficient can increase by making the hole smaller. We derive analytic formulas for small holes in terms of periodic orbits covered by the holes. The asymptotic regimes that we observe show deviations from the standard stochastic random walk approximation. The escape rate of the corresponding open system is also calculated. The resulting parameter dependencies are compared with the ones for the diffusion coefficient and explained in terms of periodic orbits.     

Impedance spectroscopy study on the ionic conductivity processes of the novel LiFeVO<Subscript>4</Subscript> phase

The recently discovered compound LiFeVO₄ was prepared by solid-state reaction at 570 °C during a 7-h period. The X-ray diffraction pattern revealed an orthorhombic crystal structure. Thermogravimetric measurements revealed a reversible mechanism which was attributed to absorption–desorption of humidity. Impedance spectroscopy measurements were carried out at 25 °C steps in the temperature range from 25 to 500 °C and equivalent circuits were drawn to fit the impedance measurement results at each temperature level. The elements of the equivalent circuits were assigned to bulk, grain boundary, and along grain boundary conductivity. All three conduction mechanisms were found to be humidity sensitive. Arrhenius plots were plotted for the bulk and grain boundary conductivity processes. The activation energy for the bulk conductivity process was calculated to be 0.25 eV over the temperature range from 175 to 500 °C and the activation energy for the grain boundary conductivity process was calculated to be 0.41 eV from 300 to 500 °C and 0.20 eV from 175 to 275 °C. An explanation for the existence of these two grain boundary activation energies is attempted. The dependence of the material conductivity mechanisms on humidity suggests that LiFeVO4 could be used as a humidity sensor.     

(MS)SM‐like models on smooth Calabi‐Yau manifolds from all three heterotic string theories

We perform model searches on smooth Calabi‐Yau compactifications for both the supersymmetric E₈ × E₈ and SO(32) as well as for the non‐supersymmetric SO(16) × SO(16) heterotic strings simultaneously. We consider line bundle backgrounds on both favorable CICYs with relatively small h₁₁ and the Schoen manifold. Using Gram matrices we systematically analyze the combined consequences of the Bianchi identities and the tree‐level Donaldson‐Uhlenbeck‐Yau equations inside the Kähler cone. In order to evaluate the model building potential of the three heterotic theories on the various geometries, we perform computer‐aided scans. We have generated a large number of GUT‐like models (up to over a few hundred thousand on the various geometries for the three heterotic theories) which become (MS)SM‐like upon using a freely acting Wilson line. For all three heterotic theories we present tables and figures summarizing the potentially phenomenologically interesting models which were obtained during our model scans.     

Composition and morphological characteristics of sialoliths

Sialolithiasis refers to pathological minerilazation in the salivary glands and ducts. Aiming to a better understanding of the formation phenomena, structural and morphological analysis of a relatively large ensemble of sialoliths extracted from 22 patients via sielendoscopy was performed. Characterization methods, including Fourier Transform Infrared (FTIR) Spectroscopy, X‐Ray Diffraction, Raman spectroscopy and Scanning Electron Microscopy (SEM), showed that the large majority of 90% of sialoliths were composed of carbonate apatite as the inorganic phase, while SEM imaging revealed the presence of bacteria in 13 cases. Furthermore, carbonate apatite crystals in the form of parallel or randomly oriented sheets were observed and in some cases rhombohedral calcite‐type nanocrystals were detected. The present findings may contribute to a better understanding of the formation mechanisms in vivo and and contribute to the treatment of sialolithiasis.