Time-dependent analysis of a fiber-optic passive-loop resonator

A time-dependent analysis of an all-single-mode fiber-optic resonator is presented in which the input field is allowed to exhibit an arbitrary dependence on time. In particular, the transmissivity of the resonator is evaluated for an input field possessing an arbitrary temporal coherence, which allows one to consider the role of the source coherence time as compared with the fiber time delay

Propagation and stability of optical pulses in a diffractive dispersive non-linear medium

Propagation and stability of light pulses under the combined influence of the optical Kerr effect, dispersion and diffraction are investigated by adopting a variational procedure. In particular, it is found that 'light bullets', i.e. radially symmetric pulses propagating without distortion, are not necessarily unstable under perturbations which do not maintain radial symmetry

Optical Maser Emission from Trivalent Praseodymium in Calcium Tungstate

Coherent emission at 1.047 µ from trivalent praseodymium in calcium tungstate was observed. This emission coincides with strong infrared fluorescence at the same wavelength and was found to be stimulated mostly by absorption of blue light by the 3P0, 3P1, and 3P2 bands. The emission corresponds to a 1G4-->3H4 transition with the terminal level 377 cm^–1 from the ground state. The oscillation threshold was the same at 4.2°, 20°, and 78°K. No stimulated emission was observed at room temperature. The lifetime of the metastable state 1G4 is 50×10^–3 sec. A new technique used to measure the lifetime is described

Calcium Niobate Ca(NbO3)2—A New Laser Host Crystal

Large single crystals of calcium niobate Ca(NbO3)2, grown by the zochralski technique, are transparent and can be doped with rare earth or transition metal ions. Laser action has been observed in calcium niobate doped with trivalent neodymium, holmium, praseodymium, erbium, and thulium

Built-in reduction of statistical fluctuations of partitioning objects

Our theoretical and numerical investigation of the movement of an object that partitions a microtubule filled with small particles indicates that vibrations warranted by thermal equilibrium are reached only after a time that increases exponentially with the number of particles involved. This points to a basic mechanical process capable of breaching, on accessible time scales, the ultimate ergodic constraints that force randomness on bound microscale and nanoscale systems

Seismic vulnerability assessment on a territorial scale based on a Bayesian approach

Italian historical centres are mostly characterized by aggregate buildings. As defined by the Italian codes (Norme Tecniche per le Costruzioni 2008 and Circolare n. 617), the analysis of the most representative local mechanisms of collapse must be performed in order to assess their vulnerability. In this article, the out-of-plane local mechanisms of collapse analysis is implemented by applying a new method of analysis based on a probabilistic approach. Usually information which are necessary for the implementation of the local mechanisms analyses are affected by uncertainty or are missing, therefore in lots of cases it is only possible to hypothesize them on the basis of the other buildings information collected during the on-site survey. In this context, the implementation of a Bayesian approach allows to deduce buildings lacking information (i.e. wall thickness and interstorey height) starting from certain collected data (i.e. facades height). The historical centre of Timisoara (Romania) is selected as the case study for the implementation of this new method of analysis, given the extension of the on-site survey already carried out in the area (information about more than 200 structural units have been collected) and the seismic vulnerability assessment on an urban scale already performed by applying a traditional method. Results obtained by adopting the two approaches are then compared and a validation and a calibration of the new one is carried out

Pair Connectedness and Shortest Path Scaling in Critical Percolation

We present high statistics data on the distribution of shortest path lengths between two near-by points on the same cluster at the percolation threshold. Our data are based on a new and very efficient algorithm. For $d=2$ they clearly disprove a recent conjecture by M. Porto et al., Phys. Rev. {\bf E 58}, R5205 (1998). Our data also provide upper bounds on the probability that two near-by points are on different infinite clusters.Comment: 7 pages, including 4 postscript figure