Word-level Symbolic Trajectory Evaluation

Symbolic trajectory evaluation (STE) is a model checking technique that has been successfully used to verify industrial designs. Existing implementations of STE, however, reason at the level of bits, allowing signals to take values in {0, 1, X}. This limits the amount of abstraction that can be achieved, and presents inherent limitations to scaling. The main contribution of this paper is to show how much more abstract lattices can be derived automatically from RTL descriptions, and how a model checker for the general theory of STE instantiated with such abstract lattices can be implemented in practice. This gives us the first practical word-level STE engine, called STEWord. Experiments on a set of designs similar to those used in industry show that STEWord scales better than word-level BMC and also bit-level STE.Comment: 19 pages, 3 figures, 2 tables, full version of paper in International Conference on Computer-Aided Verification (CAV) 201

Determination of complex dielectric functions of ion implanted and implanted‐annealed amorphous silicon by spectroscopic ellipsometry

Measuring with a spectroscopic ellipsometer (SE) in the 1.8–4.5 eV photon energy region we determined the complex dielectric function (ϵ = ϵ1 + iϵ2) of different kinds of amorphous silicon prepared by self‐implantation and thermal relaxation (500 °C, 3 h). These measurements show that the complex dielectric function (and thus the complex refractive index) of implanted a‐Si (i‐a‐Si) differs from that of relaxed (annealed) a‐Si (r‐a‐Si). Moreover, its ϵ differs from the ϵ of evaporated a‐Si (e‐a‐Si) found in the handbooks as ϵ for a‐Si. If we use this ϵ to evaluate SE measurements of ion implanted silicon then the fit is very poor. We deduced the optical band gap of these materials using the Davis–Mott plot based on the relation: (ϵ2E2)1/3 ∼ (E− Eg). The results are: 0.85 eV (i‐a‐Si), 1.12 eV (e‐a‐Si), 1.30 eV (r‐a‐Si). We attribute the optical change to annihilation of point defects

Review of a major epidemic of methicillin-resistant Staphylococcus aureus: The costs of screening and consequences of outbreak management

Background: A major outbreak of methicillin-resistant Staphylococcus aureus (MRSA) occurred in locations C and Z of our hospital and lasted for several years. It affected 1,230 patients and 153 personnel. Methods: Outbreak management was installed according to the Dutch "search and destroy" policy. A rapid, high-throughput method for molecular screening of potential MRSA carriers was implemented. Outbreak isolates were retrospectively genotyped by pulsed field gel electrophoresis. Costs of molecular screening were compared with screening by culture. Results: Genotyping results revealed 4 distinct epidemic MRSA clones. Three were present in hospital C. Because of a merger of hospitals, these clones spread to hospital Z. Another clone of MRSA affected other health care-related institutions in the region. Because of the implementation of strict containment measures of the "search and destroy" policy, the annual number of tests decreased from 100,000 to 18,000. The disposables and reagents used in polymerase chain reaction technology are more expensive than those of conventional methods. However, the clinical and economic benefits of fast results in regard to expenses of the hospital clearly outweigh the higher costs of screening. Conclusion: The implementation of a rapid, high-throughput molecular screening system greatly contributed to the effectiveness of strict containment measures of the "search and destroy" policy. The major epidemic clones of MRSA in the outbreak were eradicated by this strategy

Direct simulation of ion beam induced stressing and amorphization of silicon

Using molecular dynamics (MD) simulation, we investigate the mechanical response of silicon to high dose ion-irradiation. We employ a realistic and efficient model to directly simulate ion beam induced amorphization. Structural properties of the amorphized sample are compared with experimental data and results of other simulation studies. We find the behavior of the irradiated material is related to the rate at which it can relax. Depending upon the ability to deform, we observe either the generation of a high compressive stress and subsequent expansion of the material, or generation of tensile stress and densification. We note that statistical material properties, such as radial distribution functions are not sufficient to differentiate between different densities of amorphous samples. For any reasonable deformation rate, we observe an expansion of the target upon amorphization in agreement with experimental observations. This is in contrast to simulations of quenching which usually result in denser structures relative to crystalline Si. We conclude that although there is substantial agreement between experimental measurements and most simulation results, the amorphous structures being investigated may have fundamental differences; the difference in density can be attributed to local defects within the amorphous network. Finally we show that annealing simulations of our amorphized samples can lead to a reduction of high energy local defects without a large scale rearrangement of the amorphous network. This supports the proposal that defects in amorphous silicon are analogous to those in crystalline silicon.Comment: 13 pages, 12 figure

The Amplitude of Non-Equilibrium Quantum Interference in Metallic Mesoscopic Systems

We study the influence of a DC bias voltage V on quantum interference corrections to the measured differential conductance in metallic mesoscopic wires and rings. The amplitude of both universal conductance fluctuations (UCF) and Aharonov-Bohm effect (ABE) is enhanced several times for voltages larger than the Thouless energy. The enhancement persists even in the presence of inelastic electron-electron scattering up to V ~ 1 mV. For larger voltages electron-phonon collisions lead to the amplitude decaying as a power law for the UCF and exponentially for the ABE. We obtain good agreement of the experimental data with a model which takes into account the decrease of the electron phase-coherence length due to electron-electron and electron-phonon scattering.Comment: New title, refined analysis. 7 pages, 3 figures, to be published in Europhysics Letter

Proprioception mediates the association between systemic inflammation and muscle weakness in patients with knee osteoarthritis: Results from the Amsterdam Osteoarthritis cohort

Objectives: To determine whether systemic inflammation is associated with poor proprioception; to confirm that systemic inflammation is associated with muscle weakness; and to determine whether poor proprioception mediates the association between systemic inflammation and muscle weakness in knee osteoarthritis. Design: Cross-sectional study. Subjects: A total of 689 participants with knee osteoarthritis from the Amsterdam Osteoarthritis (AMS-OA) cohort. Methods: Systemic inflammation was assessed by erythrocyte sedimentation rate, knee proprioception by determining the joint motion detection threshold, and muscle strength with an isokinetic dynamometer. Linear regression models were used to estimate direct associations between systemic inflammation, proprioception and muscle strength, and the indirect association (mediation) between systemic inflammation and muscle strength via proprioception adjusted for potential confounders. Results: Higher erythrocyte sedimentation rates were associated with poor proprioception (p = 0.022). Poor proprioception (p < 0.001) and higher erythrocyte sedimentation rates (p < 0.001) were associated with muscle weakness. Poor proprioception mediated the association between systemic inflammation and muscle weakness (p = 0.035). Conclusion: Results suggest that systemic inflammation is associated with poor proprioception in knee osteoarthritis. Poor proprioception may be a pathway through which systemic inflammation is associated with muscle weakness in patients with knee osteoarthritis