Microstrip resonator for microwaves with controllable polarization

In this work the authors implemented a resonator based upon microstrip cavities that permits the generation of microwaves with arbitrary polarization. Design, simulation, and implementation of the resonators were performed using standard printed circuit boards. The electric field distribution was mapped using a scanning probe cavity perturbation technique. Electron spin resonance using a standard marker was carried out in order to verify the polarization control from linear to circular.Comment: 3 pages, 3 figures, submitted to Appl. Phys. Let

Analysis of the temperature influence on Langmuir probe measurements on the basis of gyrofluid simulations

The influence of the temperature and its fluctuations on the ion saturation current and the floating potential, which are typical quantities measured by Langmuir probes in the turbulent edge region of fusion plasmas, is analysed by global nonlinear gyrofluid simulations for two exemplary parameter regimes. The numerical simulation facilitates a direct access to densities, temperatures and the plasma potential at different radial positions around the separatrix. This allows a comparison between raw data and the calculated ion saturation current and floating potential within the simulation. Calculations of the fluctuation-induced radial particle flux and its statistical properties reveal significant differences to the actual values at all radial positions of the simulation domain, if the floating potential and the temperature averaged density inferred from the ion saturation current is used.Comment: Submitted to Plasma Physics and Controlled Fusio

Magnon Heat Conductivity and Mean Free Paths in Two-Leg Spin Ladders: A Model-Independent Determination

The magnon thermal conductivity $\kappa_{\mathrm{mag}}$ of the spin ladders in $\rm Sr_{14}Cu_{24-x}Zn_xO_{41}$ has been investigated at low doping levels $x=0$, 0.125, 0.25, 0.5 and 0.75. The Zn-impurities generate nonmagnetic defects which define an upper limit for $l_{\mathrm{mag}}$ and therefore allow a clear-cut relation between $l_{\mathrm{mag}}$ and $\kappa_{\mathrm{mag}}$ to be established independently of any model. Over a large temperature range we observe a progressive suppression of $\kappa_{\mathrm{mag}}$ with increasing Zn-content and find in particular that with respect to pure $\rm Sr_{14}Cu_{24}O_{41}$ $\kappa_{\mathrm{mag}}$ is strongly suppressed even in the case of tiny impurity densities where $l_{\mathrm{mag}}\lesssim 374$~{\AA}. This shows unambiguously that large $l_{\mathrm{mag}}\approx 3000$~{\AA} which have been reported for $\rm Sr_{14}Cu_{24}O_{41}$ and $\rm La_{5}Ca_9Cu_{24}O_{41}$ on basis of a kinetic model are in the correct order of magnitude

Irrigação do cajueiro-anão-precoce na região de Teresina.

bitstream/CPAMN-2009-09/20953/1/CT186.pd

The motion of two masses coupled to a massive spring

We discuss the classical motion of a spring of arbitrary mass coupled to two arbitrary massive blocks attached at its ends. A general approach to the problem is presented and some general results are obtained. Examples for which a simple elastic function can be inferred are discussed and the normal modes and normal frequencies obtained. An approximation procedure to the evaluation of the normel frequencies in the case of uniform elastic function and mass density is also discussed.Comment: Standard Latex file plus three eps figure