On a class of pseudo‐logarithmic amplifiers suitable for use with digitally switched resistors

This paper describes three circuits that implement pseudo‐logarithmic functions, which are simple and easy to implement. The circuits can be realized using operational amplifiers or current feedback amplifiers. Tuning can be achieved using switched resistors, or active resistors, or tunable transconductors, but are best suited for use with digitally switched resistors. Frequency response and stability considerations for two of the circuits are thoroughly discussed and PSPICE results confirming the theoretical results are presented alongside measured results. Copyright © 2007 John Wiley & Sons, Ltd.     

An enhanced current-mode instrumentation amplifier

An enhanced current-mode instrumentation amplifier is presented. The circuit is based on a current conveyor-operational amplifier combined configuration that offers significant improvement in accuracy as compared with the basic current-mode instrumentation amplifier based on current conveyors only     

Relationships among life events, self-derogation, and psychological impairment in psychiatric outpatients.

Investigated relationships among stressful life events, self-derogation, and psychological impairment in 97 community mental health center outpatients to test predicted associations among the 3 variables and a path hypothesis linking life events to impairment via a self-derogatory reaction to life experiences. Results suggest that life events and self-derogation are each associated with impairment but that life events do not affect health–sickness via self-derogation. The possibility of inferring an etiological role for life events and self-derogation in psychopathology is briefly discussed. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Life events and two-year outcome in schizophrenia.

Tested the hypothesis that higher aggregate levels of objective life-events stress before a 1st-time psychiatric admission for schizophrenia will relate to better outcome. Ss were 15–55 yr old schizophrenics classified by any 1 of 3 methods from a larger investigation of 1st-admission inpatients. Hospitalization and 2-yr follow-up assessments were made with structured, standardized interview schedules. 31 Schneiderian, 39 New Haven Index, and 41 DSM-II schizophrenics were then bifurcated into high- and low-event groups. The test for different group outcomes was made with a MANOVA of 5 measures of outcome functioning. Where the MANOVAs were significant, t tests were employed to determine group differences in specific outcome areas. Findings support the hypothesis for Schneiderian and New Haven diagnostic criteria. Further analyses suggested that results were not attributable to demographic factors, premorbid status, severity of pathology at admission, or interim stress levels and probably were not exclusively the effect of precipitating life events shortly before hospitalization. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A note on an extension of matrix grammars generating two-dimensional languages

An extended version of the parallel/sequential table matrix models called extended table matrix grammars (Ex-TMG), generating arrays of symbols, is proposed. The effect of imposing different types of control on the sequence of application of the tables is studied. The notion of assigning “terminal weights” to matrix grammars for describing parquet deformations is extended to Ex-TMGs.     

Enhancing the improved Howland circuit

In this paper, an enhanced version of the improved Howland circuit is proposed. An improvement in output impedance to a maximum factor of two is obtained. The theoretical derivation is presented, including analysis from a two-port network perspective, and both simulation and experimental results using a general purpose opamp confirm the expected result.     

Micro X-ray visualisation of the interaction of geosynthetic clay liner components after partial hydration

High-resolution X-ray tomography was used to observe a partially hydrated geosynthetic clay liner (GCL) specimen to gain a better understanding of the interaction of its compnents (i.e., geotextiles, fibres and bentonite) on partial hydration when deployed as part of a composite liner system. Detailed in-situ studies of hydration processes in GCLs has proven difficult despite more than two decades of effort. X-ray tomographs were collected at spatial resolutions of 12 and 7?μm to identify the different components within a GCL, as well as to examine in finer detail their interaction within the GCL after initial partial hydration. Tomograph projections provided an excellent aspect of the interaction of these components and some concepts, such as the presence of shearing features within the bentonite component, may require re-consideration based on evidence from X-ray tomography.