A two-dimensional finite element algorithm for the simultaneous solution of the semiconductor device equations with automatic convergence

The proposed algorithm solves equations governing the behaviour of semiconductor devices using a finite element technique. Electrostatic potential and the hole and electron quasi-Fermi potentials are chosen as the solution variables. The equation set is written in a steady-state form using these three variables and this gives rise to a system of three nonlinear partial differential equations. The equations, which are intimately coupled, are solved simultaneously using a weighted residual formulation. Convergence of the nonlinear solution procedure using any initial guess is guaranteed by employing ‘incremental loading’ coupled to a test for divergence that is applied at each iterative step. The triangular elements used in the program are automatically generated from a mesh of eight-node isoparametric elements that is itself an automatically generated subdivision of a small number of eight-node (super) elements. A novel method of generating an initialisation state using the boundary element method is also described.     

Segregation analysis of complex phenotypes: an application to schizophrenia and auditory P300 latency

Traditional models of the genetic transmission of human diseases have often assumed that the phenotype is a simple dichotomous trait, which is unrealistic for many psychiatric conditions, and may result in loss of valuable information. We describe a new model for complex phenotypes, implemented in the program COMDS, which subclassifies normal and affected individuals into polychotomies correlated with the underlying genetic liability to the disorder. The model is applied to 18 Scottish pedigrees ascertained for schizophrenia, in which auditory P300 latency had been measured as a possible correlate of the genetic predisposition to schizophrenia. The results suggest that there may be a major locus for schizophrenia, but that there are also other familial determinants, possibly a second modifier locus. In addition, the results indicate that auditory P300 latency may be a useful measure of the genetic predisposition to schizophrenia among asymptomatic relatives, although the relationship between P300 latency and the degree of genetic predisposition in clinical cases was not significant, presumably because other factors are operating on P300 latency. Because of the possible selection biases in this sample, there is a need to replicate these findings in systematically ascertained pedigrees.     

Impact of modern technique on long-term results of total condylar knee arthroplasty

This study reports the 14-year survivorship for 106 consecutive total condylar knee arthroplasties implanted using modern technique. All were performed by a single surgeon and have been observed prospectively since 1979. Failure was defined as revision for any reason, or radiographic evidence of loosening of the components. Life-table analysis reveals a 95.6% clinical survival rate at 14 years, with no radiographically loose components. Confidence interval is +/- 4.2%. There were 4 revisions, but none for aseptic loosening, and there are no impending revisions. Thirty-seven patients (49 knees) were known to be deceased as of April 1993, and 8 other patients are lost to followup. Clinical results for patients with pre- and postoperative Hospital For Special Surgery knee scores show 72 knees rated excellent and 11 good (mean score, 90 points). The 4 failures were rated poor. Mean flexion was 100 degrees. Radiographs of 93 knees were evaluated using the criteria of the Knee Society. Average overall alignment was 5 degrees valgus. Radiolucencies were present in 29 of 78 femoral components with adequate radiographs, and averaged 1 mm in 1 zone. Tibial radiolucency was present in 42 of 93 tibiae, again averaging 1 mm in 1 zone, with no loose pegs. In comparison with the first series of total condylar prostheses, this series showed comparable clinical results, with improved radiographic results, and no radiographic failures.     

Factors to be considered in the evaluation of bioavailability and bioequivalence of topical formulations

In this paper, an attempt is made to find functional definitions of bioavailability and bioequivalence for topical products and to examine critical factors that influence topical bioavailability and bioequivalence. A physical model approach for quantifying the problem and increasing our understanding is presented here. The key assumptions are (1) that the target site is in the lower epidermis (basal layer) or in the dermis, and (2) that it is the thermodynamic activity (i.e., the free drug concentration, C*, of the active drug species) at the target site that is the true correlate of drug effectiveness. Studies initiated to implement the physical model approach involved first validating a 'three-tiered' model for finite dose drug uptake/transport in skin with experimentally determined input parameters (partition coefficient, K, and steady-state permeability coefficients, P, for the stratum corneum, viable epidermis, and dermis). Hydrocortisone was used as the model drug with hairless guinea pig skin as the model membrane. The physical model is used to show, via the C* concept, how formulation factors may influence bioavailability and bioequivalence. Finally, a method is presented for predicting the efficacy of topical formulations employing appropriate in vitro data and physical model calculations.     

Comparison of body composition measured by total body potassium and infrared interactance

OBJECTIVE: The purpose of this study was to find how closely a near infrared instrument (IRI), Futrex 5000, would compare to whole body counting (WBC) of potassium-40 (40K) in assessing body composition. DESIGN: We measured lean body mass (LBM) and percent total body fat (PCF) in 177 males and 27 females by total body potassium (TBK) and by infrared interactance (IRI). TBK was assessed by 2 pi whole body counter (WBC) and IRI by Futrex (F) instrument. These subjects were measured for TBK and for IRI within 1 week of each other. RESULT: A large mean difference (p < or = 0.001) was found between the results using the two instruments: IRI data for LBM were higher and PCF lower compared to TBK. CONCLUSION: As shown by repeated TBK measurements over a 22-year period in these same volunteers, this technique is reliable. The IRI assessments did not come to a close fit with TBK.