Extrinsic parameter extraction and RF modelling of CMOS

An analytical approach for CMOS parameter extraction which includes the effect of parasitic resistance is presented. The method is based on small-signal equivalent circuit valid in all region of operation to uniquely extract extrinsic resistances, which can be used to extend the industry standard BSIM3v3 MOSFET model for radio frequency applications. The verification of the model was carried out through frequency domain measurements of S-parameters and direct time domain measurement at 2.4 GHz in a large signal non-linear mode of operation. (C) 2003 Elsevier Ltd. All rights reserved.

Range expansion in an invasive small mammal: influence of life-history and habitat quality.

Invasive species pose a major threat to biodiversity but provide an opportunity to describe the processes that lead to changes in a species’ range. The bank vole (Myodes glareolus) is an invasive rodent that was introduced to Ireland in the early twentieth century. Given its continuing range expansion, the substantial empirical data on its spread thus far, and the absence of any eradication program, the bank vole in Ireland represents a unique model system for studying the mechanisms influencing the rate of range expansion in invasive small mammals. We described the invasion using a reaction–diffusion model informed by empirical data on life history traits and demographic parameters. We subsequently modelled the processes involved in its range expansion using a rule-based spatially explicit simulation. Habitat suitability interacted with density-dependent parameters to influence dispersal, most notably the density at which local populations started to donate emigrating individuals, the number of dispersing individuals and the direction of dispersal. Whilst local habitat variability influenced the rate of spread, on a larger scale the invasion resembled a simple reaction–diffusion process. Our results suggest a Type 1 range expansion where the rate of expansion is generally constant over time, but with some evidence for a lag period following introduction. We demonstrate that a two-parameter empirical model and a rule-based spatially explicit simulation are sufficient to accurately describe the invasion history of a species that exhibits a complex, density-dependent pattern of dispersal.

The white dwarf's carbon fraction as a secondary parameter of Type Ia supernovae

Context. Binary stellar evolution calculations predict thatChandrasekhar-mass carbon/oxygen white dwarfs (WDs) show a radiallyvarying profile for the composition with a carbon depleted core. Manyrecent multi-dimensional simulations of Type Ia supernovae (SNe Ia),however, assume the progenitor WD has a homogeneous chemicalcomposition.
Aims: In this work, we explore the impact ofdifferent initial carbon profiles of the progenitor WD on the explosionphase and on synthetic observables in the Chandrasekhar-mass delayeddetonation model. Spectra and light curves are compared to observationsto judge the validity of the model.
Methods: The explosion phaseis simulated using the finite volume supernova code Leafs, which isextended to treat different compositions of the progenitor WD. Thesynthetic observables are computed with the Monte Carlo radiativetransfer code Artis. Results: Differences in binding energies ofcarbon and oxygen lead to a lower nuclear energy release for carbondepleted material; thus, the burning fronts that develop are weaker andthe total nuclear energy release is smaller. For otherwise identicalconditions, carbon depleted models produce less 56Ni.Comparing different models with similar 56Ni yields showslower kinetic energies in the ejecta for carbon depleted models, butonly small differences in velocity distributions and line velocities inspectra. The light curve width-luminosity relation (WLR) obtained formodels with differing carbon depletion is roughly perpendicular to theobserved WLR, hence the carbon mass fraction is probably only asecondary parameter in the family of SNe Ia.
Tables 3 and 4 are available in electronic form at http://www.aanda.org