Fourier Transform Domain Analysis of High <Emphasis Type="Italic">T</Emphasis><Subscript><Emphasis Type="Italic">c</Emphasis></Subscript> Superconducting Rectangular Microstrip Patch over Ground Plane with Rectangular Aperture

A rigorous full-wave analysis in the Fourier transform domain is carried out in order to obtain the resonant frequencies and half-power bandwidths of the high T _c superconducting rectangular microstrip patches over ground planes with rectangular apertures. To include the effect of the superconductivity of the microstrip patch in the full-wave analysis, a complex surface impedance is considered. This impedance is determined by using London’s equation and the two-fluid model of Gorter and Casimir. The validity of the solution is tested by comparison of the computed results with previously published data. Variations of the resonant frequency with the high T _c superconducting film thickness are presented. Results showing the effect of the temperature on the resonant frequency and half-power bandwidth of the superconducting microstrip antenna with a rectangular aperture in the ground plane are also given. Finally, a comparison between the efficiency of two antennas is presented. For the first antenna, YBCO patch with YBCO ground plane are considered. For the second antenna, the patch and the ground plane are with copper.     

Seebeck coefficients of half-metallic ferromagnets

In this article the Co₂ based Heusler compounds are discussed as potential materials for spin voltage generation. The compounds were synthesized by arc melting and consequent annealing. Band structure calculations were performed which revealed the compounds to be half-metallic ferromagnets. Magnetometry was performed on the samples and the Curie temperatures and the magnetic moments were determined. The Seebeck coefficients were measured from low to ambient temperatures for all compounds. For selected compounds high temperature measurements up to 900 K were performed.     

Ultrasound-accelerated aromatisation of trans- and cis-pyrazolines under heterogeneous conditions using claycop

A simple, efficient and eco-friendly procedure has been developed for the aromatisation of various pyrazolines in heterogeneous media using clay-supported copper(II) nitrate (claycop) under ultrasound activation. The reaction rate enhancement and the sonication effect are discussed.     

Covering the vertices of a graph with cycles of bounded length

Let c_k(G) be the minimum number of elementary cycles of length at most k necessary to cover the vertices of a given graph G. In this work, we bound c_k(G) by a function of the order of G and its independence number.     

Resolution Enhancement of Plasmonic Sensors by Metal‐Insulator‐Metal Structures

Optical sensors based on surface plasmons have attracted much attention over the past decades owing to the wealth of applications in bio‐ and chemical and gas sensing. In surface plasmon resonance sensors, a single metal layer is commonly used, but its resolution is limited because of broad resonances. In this context, we have developed a sensor chip based on a stack of metals and a dielectric, e.g. a metal‐insulator‐metal structure, consisting of a thick insulator layer sandwiched by metal layers, that exhibits a sharp resonance due to the excitation of surface plasmon polaritons hybrid modes. We have performed both experiments and theoretical simulations to estimate the enhancement of the sensitivity of such a structure. By changing the refractive index of an aqueous solution of glucose on top of the sensor chip, we found that the use of a metal‐insulator‐metal structure improves the figure of merit of the sensor 7.5 times compared to that of a conventional surface plasmon resonance sensor chip.