To determine whether the increasing use of percutaneous fine-needle biopsy of abdominal lesions is associated with an increase in serious complications, the author updated a literature search and evaluated a questionnaire (distributed among selected hospitals in the United States in 1986 and 1987) that followed up a questionnaire distributed in 1983. The updated literature review revealed a total of 24 deaths and 20 needle tract seedings. The updated questionnaire revealed five deaths after 16,381 biopsies (0.031%), whereas the previous questionnaire had shown four deaths after 63,108 biopsies (0.006%). Two similar European questionnaires revealed mortality rates of 0.008% and 0.018%, respectively. Of the total of 33 deaths, 21 involved biopsies of liver lesions; six involved pancreatic biopsies. Seventeen of the 21 deaths after liver biopsies were secondary to hemorrhage; five of the six deaths after pancreatic biopsies were due to pancreatitis. Of the 23 instances of needle tract seeding, 10 occurred after biopsies of pancreatic malignancies. The frequencies of needle tract seeding in the four questionnaires were 0.005%, 0.006%, 0.003%, and 0.009%, respectively. Although infrequent, serious complications may be associated with this procedure. The author makes suggestions that may help minimize them.

Propofol is the most important intravenous general anesthetic in current clinical use. It acts by potentiating GABAA receptors, but where it binds to this receptor is not known and has been a matter of some controversy. We have synthesized a novel propofol analogue photolabeling reagent that has a biological activity very similar to that of propofol. We confirmed that this reagent labeled known propofol binding sites in human serum albumin which have been identified using X-ray crystallography. Using a combination of the protiated label and a deuterated version, and mammalian receptors labeled in intact membranes, we have identified a novel binding site for propofol in GABAA receptors consisting of both β3 homopentamers and α1β3 heteropentamers. The binding site is located within the β subunit, at the interface between the transmembrane domains and the extracellular domain, and lies close to known determinants of anesthetic sensitivity in transmembrane segments TM1 and TM2.

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Adsorption is a fundamental process for separating inorganic and organic contaminants from waters and waste waters. The most common environmental applications of this process are embodied in ion-exchange and activatedsarbon systems. Although such processes are generally capable of highly effective separations, the design and operation of specific systems is frequently complicated by the composition of waters and wastes and by the intricate matrix of interactions commonly associated with heterogeneous systems. These complications are particularly severe in applications involving the removal of specifically targeted organic compounds from complex mixtures, a circumstance encountered with increasing frequency as water decontamination requirements become more stringent.Adsorption system design traditionally has been based on information gained from pilot-plant test programs. The pilot-plant design approach acknowledges the system specificity of particular applications, but it does not lend itself easily to prediction of system responses to variables other than those specifically tested, nor to elucidation of design principles that can be e x t r a p lated to other applications.Mathematical process models can facilitate the design of full-scale systems simply by reducing the number of pilotscale tests required to evaluate various operating conditions and design parameters. Such models can generally be calibrated from simple and well-controlled bench-scale experiments, thus 1040 Environ. Sci. Technal.. Vai. 21. No. 11, 1987 U Q positioning pilot test programs principally for verification of design bases rather than for primary data development.Once verified, a process model can be used to examine conditions other than those directly measured. Such a model can also project adsorber response and sensitivity to a variety of circumstances that may be anticipated but not easily reproduced or experimentally simulated in the pilot program. The logistics, time, and expense normally associated with pilot-scale test equipment and programs make these important considerations.This paper provides an overview and analysis of certain contemporary elements and applications of adsorption process modeling. Included is a discussion that expands upon considerations initiated in a recent ES&T feature article that described processes for removing dissolved organic contaminants from water ( I ) . In addition, this paper lays a foundation for more detailed descriptions of research developments in adsorber modeling (2-4).The work is not exhaustive in that it makes no attempt to present and critique all models and approaches available. Rather, it focuses on the Freundlich and Ideal Adsorbed Solution Theory equilibrium models and a two-resistance, homogeneous-surface-diffusion dynamic model as examples that seem particularly suited for simulating adsorption processes and predicting their behavior in water and waste treatment applications. A discussion of modeling approaches and parameter estimation techniques that address environmental complexit...

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The study of the tribological performance of piston rings plays an important role in piston assembly design. In this study, a comprehensive analysis of piston-ring pack lubrication has been developed. The model employs a flow-continuity algorithm and considers relative ring locations in the piston-ring pack as well as oil accumulation in front of the ring in determining the oil availability. The computer model is able to predict the effect that bore distortion and ring conformability have on piston-ring performance. (This influence is discussed in Part 2 of the paper). In this part of the paper (Part 1), the theoretical formulation of the model is briefly described. The model is verified through comparison of the calculated ring±liner film thicknesses with those measured experimentally by Hamilton and Moore on a diesel engine. Then some results, obtained under situations where film thicknesses are circumferentially uniform, are presented to simulate a piston-ring pack in a modern petrol engine as an example to demonstrate the capabilities of the model and to show the effects of some important factors on the performance characteristics of the ring pack. The authors have found that the model developed is a robust one which can be used to analyse the tribological performance of ring packs effectively in both circular and distorted cylinder bores of internal combustion (IC) engines.

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