Approach to modelling of microstrip-microslot applicator

Microstrip-slot applicators are used for biomedical applications, but their modelling is not easy. We present an approach which considers this type of structure on a lossy medium as a succession of microstrip lines with tuning septums of different sizes. Using a classical spectral-domain approach (SDA) model, calculations of the resonant frequency have been performed and compared with experimental measurements for different simple structures of microstrip-slot applicators.     

Comparison of education versus behavioral skills training interventions in lowering sexual HIV-risk behavior of substance-dependent adolescents.

Substance-dependent adolescents (N?=?34) in a residential drug treatment facility received either a 6-session behavior skills training HIV-risk reduction intervention or standard HIV education. After the intervention, adolescents who received behavior skills training exhibited increased knowledge about HIV-AIDS, more favorable attitudes toward prevention and condom use, more internal locus of control, increased self-efficacy, increased recognition of HIV risk and decreases in high-risk sexual activity. Self-report data were corroborated by records for the treatment of sexually transmitted diseases. The results from this pilot demonstration effort suggest that skills training based on cognitive–behavioral principles may be effective in lowering high-risk adolescents' vulnerability to HIV infection and warrant evaluation in a controlled comparison with a larger sample. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental determination of propagation parameters of a microstrip line with tuning septums

The letter refers to the experimental determination of the propagation characteristics of a microstrip line with tuning septums. The purpose of this study is to measure with accuracy the (?, ?) diagram for the two fundamental modes of this line using a crossratio technique.     

Formation of a long-lived P+BA- state in plant pheophytin-exchanged reaction centers of Rhodobacter sphaeroides R26 at low temperature

Femtosecond transient absorption spectroscopy in the range of 500-1040 nm was used to study electron transfer at 5 K in reaction centers of Rhodobacter sphaeroides R26 in which the bacteriopheophytins (BPhe) were replaced by plant pheophytin a (Phe). Primary charge separation took place with a time constant of 1.6 ps, similar to that found in native RCs. Spectral changes around 1020 nm indicated the formation of reduced bacteriochlorophyll (BChl) with the same time constant, and its subsequent decay in 620 ps. This observation identifies the accessory BChl as the primary electron acceptor. No evidence was found for electron transfer to Phe, indicating that electron transfer from BA- occurs directly to the quinone (QA) through superexchange. The results are explained by a model in which the free energy level of P+Phe- lies above that of P+BA-, which itself is below P*. Assuming that the pigment exchange does not affect the energy levels of P* and P+BA-, our results strongly support a two-step model for primary electron transfer in the native bacterial RC, with no, or very little, admixture of superexchange.     

Time-domain response of MIS coplanar waveguides for MMICs

An MIS coplanar waveguide propagating a slow-wave mode has been characterised in the time domain. The theoretical analysis proposed to obtain the time-domain response of the line gives results in good agreement with measurements. The circuit analysis used is suitable for the determination of spurious propagation effects, inherent to the use of miniature waveguides encountered in MMICs, such as Schottky contact coplanar lines and coupled microstrip lines laid on MIS substrates.     

Rigorous analysis of planar MIS transmission lines

The realisation of distributed microwave integrated circuits can be expected by using very low phase velocity propagation modes on MIS and Schottky planar transmission lines. Up to now, the frequency behaviour of such lines has been obtained by using analytical models. We present a rigorous analysis of a MIS microstrip line, the validity of which is testified by comparison to experimental values.     

Systematic determination of the propagation characteristics ofcoplanar lines on semiconductor substrate

A method allowing the systematic determination of the propagation characteristics of micron-size waveguides and overcoming the influence of feeding access discontinuities is presented. The complex propagation constant and characteristic impedance of a slow-wave Schottky contact coplanar line are determined in the 1 to 26 GHz frequency range under different DC bias conditions. This method is successfully used to characterize the Schottky contact coplanar line of micron size under drastic conditions, that is, high value of slow-wave factor, significant attenuation, dispersive transmission line, and strong mismatches between feeding line and device under test. Comparisons with transmission line model theoretical results show very good agreement, despite the large slow-wave factor, attenuation, and dispersion of the waveguide. The electric schemes of the feeding access discontinuities are also presented     

Factor structure and validation of an adolescent version of the Condom Attitude Scale: An instrument for measuring adolescents' attitudes toward condoms.

The Condom Attitude Scale (W. P. Sacco, B. Levine, D. L. Reed, & K. Thompson, 1991) was modified for use with adolescents. In Study 1, a modified 35-item version, pilot tested with 195 African American adolescents, achieved a Cronbach's alpha of .88. In Study 2, convergent validity was assessed with a sample of 312 African American adolescents. Psychometric properties were evaluated with item analysis, factor analysis, and reliability estimation. The scale was refined to 23 items with a full scale Cronbach's alpha of .80. In Study 3, temporal stability was assessed with 88 African American adolescents. In Study 4, a cross-validation sample of predominantly White adolescents (N?=?2) assessed whether the measure's psychometric properties and factor structure replicated in a more heterogeneous adolescent sample. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of full wave approaches for determination of microstrip conductor losses for MMIC applications

Losses due to ohmic conductors in planar lines are evaluated by two full wave analyses, the first one using impedance surface concept associated with the modified spectral domain approach (SDA) and the second a more accurate mode matching technique. To state the respective validity domain of the two numerical simulations, results are compared to experimental data.<>