Mouthparts of Megaselia scalaris (Loew) (Diptera: Phoridae)

Mouthparts of adult Megaselia scalaris (Loew), a fly species of medical importance, were examined using scanning electron microscopy. Sexual dimorphism of the labellum was observed in the mouthpart structures of this species. The labella of males were clothed with a dense covering of microtrichia, but these were found to be entirely absent from the labella of females. Aside from this difference, trichoid and conical sensilla that are most likely used as taste or contact chemoreceptors appear on the labellum and labrum of both sexes. In addition, five pairs of sharply pointed teeth at the ventral surface of the labellum is another feature that is shared by the two sexes. A plausible feeding mechanism for this fly is also advanced.     

Lag and anticipatory synchronization based parameter estimation scheme in modulated time-delayed systems

In this article, we have shown that using delay dynamical systems as base, one can use the modulation of the various parameters, to transmit multiple signals through a single chaotic time series. It is shown that under certain conditions the original signals and parameters of the driving signals can be recovered with the help of an adaptive demodulator. An important aspect of the present method is that the communication is possible between two time-delayed systems with parameter mismatch using lag and anticipatory synchronization. The whole idea is presented on the basis of Mackey–Glass system, with variable time delay.     

Unification of generalized open sets on topological spaces

A new kind of sets called generalized μ-closed (briefly g μ-closed) sets are introduced and studied in a topological space by using the concept of generalized open sets introduced by á. Császár. The class of all g μ-closed sets is strictly larger than the class of all μ-closed sets. Furthermore, g-closed sets (in the sense of N. Levine [17]) is a special type of g μ-closed sets in a topological space. Some of their properties are investigated. Finally, some characterizations of μ _g -regular and μ _g -normal spaces have been given.     

Two-warehouse production model for deteriorating inventory items with stock-dependent demand under inflation over a random planning horizon

This paper develops a production-inventory model for a deteriorating item with stock-dependent demand under two storage facilities over a random planning horizon, which is assumed to follow exponential distribution with known parameter. The effects of learning in set-up, production, selling and reduced selling is incorporated. Different inflation rates for various inventory costs and time value of money are also considered. A hybrid genetic algorithm is designed to solve the optimization problem which is hard to solve with existing algorithms due to the complexity of the decision variable. To illustrate the model and to show the effectiveness of the proposed approach a numerical example is provided. A sensitivity analysis of the optimal solution with respect to the parameters of the system is carried out.     

Spectral analytic comparisons for data augmentation

The sandwich algorithm (SA) is an alternative to the data augmentation (DA) algorithm that uses an extra simulation step at each iteration. In this paper, we show that the sandwich algorithm always converges at least as fast as the DA algorithm, in the Markov operator norm sense. We also establish conditions under which the spectrum of SA dominates that of DA. An example illustrates the results.     

Caractérisation spectrale de la forme de Jordan

Soit , où désigne l'ensemble des matrices n×n à coefficients complexes. Nous montrons qu'on peut complètement caractériser la forme de Jordan de A en examinant le polynôme caractéristique de tA+X pour tous les tC et tous les . Ceci nous permet de donner une démonstration plus élémentaire d'un théorème de Baribeau et Ransford sur les transformations holomorphes de qui préservent le spectre.

Denote by the set of complex n×n matrices, and let . We give a variational, purely spectral characterization of the Jordan form of A by examining the characteristic polynomial of the perturbed matrices tA+X for tC and . This allows us to give a more elementary proof of a theorem of Baribeau and Ransford on spectrum-preserving holomorphic maps on .     

A Born scatterer in an acoustical waveguide

Scattering from a Born inhomogeneity in a homogeneous, acoustical waveguide is considered and results compared to the corresponding scattering in a homogeneous, unbounded medium. It is found that the Ewald sphere in the unbounded medium case is replaced by a Ewald "strip" in a waveguide, the strip consisting of many individual Ewald spheres embedded in a ball the radius of which is twice that of an individual sphere. The physics behind the Ewald strip is discussed along with the implications of waveguide Born data.     

An ellipsometric investigation of Ag/SiO$\mathsf{_2}$ nanocomposite thin films

Dielectric properties of silver/SiO₂ nanocomposite thin films grown by high-pressure d.c. sputtering technique were studied by spectroscopic ellipsometry (300-800 nm). The dielectric behavior of the nanocomposite thin films largely depended on the particle size, its number density and the surrounding environments. The films showed semiconductor-like behavior up to a critical particle size and concentration, beyond which the films exhibited the typical surface plasmon resonance characteristics in their optical properties. The refractive index was also found to have a strong dependence on the particle size and its dispersion in the matrix. The results were found to be consistent with those obtained from UV-VIS optical absorbance data. Bruggeman effective medium theory was used to explain the experimental results.Received: 3 April 2002, Published online: 23 July 2003PACS:   78.67.-n Optical properties of nanoscale materials and structures - 78.67.Bf Nanocrystals and nanoparticles     

Synthesis,structural and electrical properties of Ti modified Bi2Sn2O7 pyrochlore

Polycrystalline ceramic samples of Bi₂Sn_2−xTi_xO₇ (x=0.00, 0.2, 0.4, 0.6 and 0.8) have been synthesized by standard high temperature solid state reaction method. The effect of homovalent cation (titanium) substitution on the Sn-site on the structural and electrical properties of the pure Bi₂Sn₂O₇ ceramic have been studied by X-ray diffraction followed by SEM, dielectric and dc conductivity studies. The structural analysis indicates that the increase of titanium contents do not lead to any secondary phase. The frequency and temperature dependent dielectric studies have been carried out. It is found that the Ti doping reduces the material particle size. The size of the particles are strongly influenced by the addition of titanium to the system. The substitution of Ti for Sn ions affected the degree of disorder and modified the dielectric properties leading to more resistive ceramic compounds. The activation energies of all the compounds were calculated using the relation σ=σ₀exp(−Ea/kT).