Similarities in drinking behavior of twin's friends: moderation of heritability of alcohol use

Previous research has indicated that friends' drinking may influence alcohol use in adolescents and young adults. We explored whether similarities in the drinking behavior of friends of twins influence the genetic architecture of alcohol use in adolescence and young adulthood. Survey data from The Netherlands Twin Register were available for 1,526 twin pairs aged 16-25 years. We categorized the twin pairs as concordant (both report similar alcohol use in their friends) or discordant for the alcohol use of their friends. Genetic moderator models were tested by carrying out multi-group analyzes in Mplus. Findings showed a significant moderation effect. Genetic factors were more and common environment less important in the explanation of variation in alcohol use in twins discordant for alcohol use of friends than in twins concordant for alcohol use of friend

Copolar and cross-polar radiation of Vivaldi antenna on dielectric substrate

The copolar and cross-polar radiation patterns of the Vivaldi antenna on a dielectric substrate are calculated anal validated by measurements. The method involves a two-step procedure, The electric field distribution across the antenna slot aperture is calculated first. The radiated fields are then calculated, using Green's functions. The continuous exponential tapered shape is approximated by annular linearly tapered sections, The conical transmission-line theory and a variational method yield the electric field in each section. The radiation calculation is based on closed-form expressions for the dyadic Green's function of an elementary electric field source in a conducting half sheet. Both copolar and cross-polar radiation patterns of the Vivaldi antenna are calculated by integrating the Green's functions weighted by the electric field distribution over the antenna aperture. The effect of lateral truncation is taken into account by defining weighting patterns. The method is validated by original measurements and limitations of the model are discussed, Antenna directivity and sensitivity are calculated

A New Variational Formulation, Applicable To Shielded and Open Multilayered Transmission-lines With Gyrotropic Non-hermitian Lossy Media and Lossless Conductors

A new variational expression is derived for the propagation constant of inhomogeneous shielded and open planar lines with gyrotropic lossy substrates, It yields rapidly convergent results even when higher order modes are considered. Results obtained on open and shielded lines and structures agree very well with experimental results. The efficiency of the formulation is such that calculations are made on-line on a regular PC

Theoretical evaluation of dielectric absorption of microwave energy at the scale of nucleic acids

A theoretical model is proposed for the evaluation of dielectric properties of the cell nucleus between 0.3 and 3 GHz, as a function of its nucleic acids (NA) concentration (C-NA). It is based on literature data on dielectric properties of DNA solutions and nucleoplasm. In skeletal muscle cells, the specific absorption rate (SAR) ratio between nucleoplasm and cytoplasm is found to be larger than one for CNA above 30 mg/ml. A nearly linear relationship is found between CNA and this nucleocytoplasmic SAR ratio. Considering the nanoscale of the layer of condensed counterions and bound water molecules at the NA-solution interface, the power absorption per unit volume is evaluated at this precise location. It is found to be between one and two orders of magnitude above that in muscle tissue as a whole. Under realistic microwave (MW) exposure conditions, however, these SAR inhomogeneities do not generate any significant thermal gradient at the scale considered here. Nevertheless, the question arises of a possible biological relevance of nonnegligible and preferential heat production at the location of the cell nucleus and of the NA molecules. (C) 2004 Wiley-Liss, Inc

Modeling Resonance in Wave-guide-to-microstrip Junctions By Unilateral Fin Line Resonators

A method for the rigorous calculation of the resonant frequencies observed in waveguide-to-microstrip transitions is developed. The method is general and includes all types of waveguide-to-microstrip junctions. The resonant parts are modeled as unilateral fin line resonators with similar shapes. The resonance frequencies are determined by using the Spectral Domain Approach with appropriate basis functions. Measurements were made. They are in good agreement with the data computed from the model

Electromagnetic modes in conical transmission lines with application to the linearly tapered slot antenna

A transmission line analysis of bow-tie antenna and linearly tapered slot antenna (LTSA) is presented. These structures belong to the class of conical transmission lines defined here in terms of conical coordinates. A complete set of solutions of Helmholtz equation is obtained exhibiting TE and TM modes. Modal fields are expressed by Lame and Bessel-Schelkunoff functions. TE and TM eigenmode analysis is particularized to the bow-tie structure. Bow-tie antenna and LTSA are shown to be dual conical transmission lines by the image method and Babinet's principle, The modes of LTSA are calculated on the basis of the results obtained for the bow-tie structure. The radiation pattern of LTSA is computed as the integral of a closed-form expression of the dyadic Green's function weighted by the modal electric field distribution over the slot aperture. The obtained dominant mode radiation patterns are validated by measurements from the literature. The radiation patterns of the first two-order modes are calculated and compared

Theoretical and Experimental-evidence of Nonreciprocal Effects On Magnetostatic Forward Volume Wave Resonators

An unexpected nonreciprocal behavior is observed on Magnetostatic Forward Volume Waves (MSFVW) Straight Edge Resonators (SER's) using YIG films. The nonreciprocal effect is theoretically predicted by taking into account the demagnetizing effect of the de biasing magnetic field when calculating the forward and reverse propagation constants of MSFVW inside the MG film, Hence, a nonreciprocal scattering matrix of the MSFVW-YIG-SER coupled to its transducers is calculated. The measured values of the transmission coefficients agree extremely well with the predicted ones. They both present an important nonreciprocal phase behavior

Spectral-domain Form of New Variational Expression for Very Fast Calculation of Multilayered Lossy Planar Line Parameters

A new spectral domain formulation of the propagation characteristics for planar and coplanar lines is presented. It is based on a newly established variational principle, valid for a spatial as well as for a spectral formulation. In combination with conformal mapping, it drastically reduces the complexity of the numerical computation and leads to rapidly convergent results even when higher order modes are considered. Mathieu functions are shown to be very efficient expressions for trial fields of the dominant and the higher order modes in slots. Calculation is fast: it is made on-line on a regular PC. Results obtained on open and shielded lines have been successfully checked with new experimental data and with previously published data. The method is general enough to accommodate gyrotropic substrates. The paper however is limited to isotropic media