Surface characterization of fluorinated polymers (PTFE, PVDF, PFA) for use in ultratrace analysis

Surface characterization of new unused PTFE, PFA and PVDF labware has been carried out by light microscopy, scanning electron microscopy, profilometry and atomic force microscopy. It has been found that in spite of higher micro-roughness, PFA exhibits the lowest nano-roughness and hence seems best suited as vessel material for relatively mild pressureless chemical operations for sample preparation of ultrapure substances, as container material for storage of ultrapure liquids, and for transport of such liquids, e.g., from the producer in the chemical to the end user in the microelectronics industry. This suitability refers only to the surface quality of the investigated materials. PTFE-surfaces, due to the sintering process of production, exhibit the most unfavourable surface quality of the investigated fluorinated polymers.     

Radioanalytical monitoring of the formation of barium sulfate in aqueous solutions

The formation of barium sulfate in aqueous media causes problems of insoluble scale formation. On the other hand, the coprecipitation of uranium and transuranium elements with barium sulfate has been suggested for the determination of these elements in environmental monitoring processes. Therefore, the study of barium sulfate crystal growth is required. The investigations done so far suffer from the low sensitivity of the analytical methods used. In the present work we have overcome this problem by using¹³¹Ba for the preparation of supersaturated solutions. Thus kinetics parameters such as induction time and precipitation rates were measured. The polynuclear mechanism was found to be operative at high and the spiral growth at low supersaturations.     

Measurements: developments in the USA

Summary Sales and use of analytical instruments have expanded in the United States over the past two years, despite the recessionary nature of the economy. Interest in increasing the quality of analytical measurements seems to be undiminished, if not growing. Trends in several measurement areas, including health, environment, manufacturing, and commerce, are described as they bear on this growth of interest in reliably accurate measurements. The paper also considers trends in the development of reference materials and accreditation of laboratories in the USA. United States of America participation in efforts of the International Organization for Standardization, and a study by the International Bureau of Weights and Measures of how to provide for international traceability for analytical chemical measurements are mentioned.     

Improving the testability of switched-capacitor filters

A design-for-test methodology for SC filters is presented, based on an architecture using some additional circuitry and providing extra capabilities for both off- and on-line tests. The approach uses a comparison (voting) mechanism to indicate whether or not two copies of a filter element (a biquad, for instance) have a similar response during their actual operation. The design and implementation of a few filter examples are included to assess the potential usefulness of this new approach.     

Putting reader roles to the test: an ethnomethodological approach

That readers read within roles has long been argued by literary theorists and more recently by technical communication theorists. Yet few scholars have attempted to put their theories to a test. The study reported in this paper attempts to do by using a conversation analysis tool called ethnomethodology. In an experimental setting, subjects were videotaped reading and responding to a set of instructions. Their responses indicate that: readers will often choose to play a role different from the one embedded in a text, especially if the text role offends them in some way; readers with similar education and interest may display different reader roles, making these roles difficult to predict; and within a single reading, a reader may change roles frequently. The paper concludes by discussing the implications of the findings and the appropriateness of ethnomethodology for reader-role research     

Improvement of power supply EMC by chaos

The authors demonstrate the feasibility of using chaos to depress the spectral peaks of the interference from a switched mode power supply. A boost converter is used to show experimentally that the spectrum of the input current is spread, its peaks are reduced and EMC is improved, compared to the case when the circuit is operating periodically     

MOSFET modeling for circuit simulation

An overview of MOSFET modeling for circuit simulation is presented. After discussing some of the implications of analog and low-power applications, the history of the MOS models commonly used in SPICE-like circuit simulators is presented, followed by a discussion of the evolution of strategies for modeling the geometry dependence of MOSFET characteristics. The growth of complexity and requirements for future MOS models are also considered     

Micron-image transfer system with brightness amplifier in gold-vapor laser

A gas-discharge gold-vapor laser on self-terminating transitions with operating wavelength λ=312.2 nm has been used to develop a highly efficient system for image transfer. An optical scheme and all its parameters have been chosen optimal for image quality. It has been found both theoretically and experimentally that the best results on micron-structure image transfer are obtained with 2–5-times image reduction. Various types of masks have been used. A 1-µm structure has been resolved due to the choice of optimal exposure time of 10 ms under a period of pulse repetition (0.6 – 0.8) ms; in this case, the minimal fringe dimension was ≈2 µm with an image dimension of 2 mm for a laser tube 1.8 cm in diameter.