Effective vehicle width in self-paced tracking.

In self-paced tracking tasks, such as driving, the speed is related to the lateral tolerance. This lateral tolerance has been varied in two ways in previous studies by changing the track width for constant vehicle width and vice versa. The current study used both an automobile driving task and a computer/mouse task to show that these two ways of varying lateral tolerance did not produce equivalent results. Subjects behaved as if vehicle width were less important than track width. Speeds and errors both increased as vehicle width increased for a constant lateral tolerance. This could have safety consequences when driving in confined spaces.

Adaptive optics for array telescopes using piston-and-tilt wave-front sensing.

A near-infrared adaptive optics system operating at approximately 50 Hz has been used to control phase errors adaptively between two mirrors of the Multiple Mirror Telescope by stabilizing the position of the interference fringe in the combined unresolved far-field image. The resultant integrated images have angular resolutions of better than 0.1 arcsec and fringe contrasts of >0.6. Measurements of wave-front tilt have confirmed the wavelength independence of image motion. These results show that interferometric sensing of phase errors, when combined with a system for sensing the wave-front tilt of the individual telescopes, will provide a means of achieving a stable diffraction-limited focus with segmented telescopes or arrays of telescopes.

Pseudomembranous colitis: how useful is endoscopy?

Clostridium difficile colitis may be diagnosed either by endoscopy or by laboratory tests. To determine the role of endoscopy, we reviewed 59 cases of confirmed C. difficile colitis. In all patients, the etiology was confirmed by stool tests. Twenty-nine underwent lower gastrointestinal endoscopy. In 16 (55%) there was endoscopic confirmation of pseudomembranes while 4 (14%) had only nonspecific colitis. There was no apparent difference in the rate of detection of pseudomembranes between rigid sigmoidoscopy (57%), flexible sigmoidoscopy (50%), and colonoscopy (50%). Vancomycin and metronidazole were equally effective therapy but treatment with vancomycin cost more than 250 times that for metronidazole. There were no patients in whom the diagnosis was made by endoscopy alone. Endoscopy was costly and insensitive, while noninvasive stool tests were cheap and accurate. We conclude that endoscopy should be relegated to a secondary role in the workup of antibiotic-associated diarrhea.

Penetration of eight beta-lactam antibiotics into the peritoneal fluid. A pharmacokinetic investigation.

Serial serum and peritoneal fluid samples were taken after intravenous injection of cefuroxime sodium, cefoxitin sodium, cefotaxime sodium, cefoperazone sodium, ceftazidime, moxalactam disodium, mezlocillin sodium, and piperacillin sodium. Time-concentration curves were obtained for both pharmacokinetic compartments. The geometric mean of peritoneal fluid concentrations from eight to ten patients was used to define the time-concentrations curve for each substance. Serum pharmacokinetic values were calculated using an open two-compartment model. The concentrations (Cps) were calculated from peritoneal fluid concentrations by quadratic interpolation. The time for which one fourth of the Cp (Cp1/4) is maintained within the peritoneal cavity varied according to the substance and can be used to estimate dosage intervals. The Cp1/4 was compared with the minimal inhibitory concentrations for 1,344 pathogens encountered in 415 intra-abdominal infections from 31 studies.

Ticarcillin therapy of risk patients with infections due to Pseudomonas aeruginosa.

The implication of nosocomial infection due to Pseudomonas aeruginosa is demonstrated by comparing the bacteriological findings with the clinical picture of ten patients in a surgical intensive care unit. The occurrence of this organism and its resistance to beta-lactam-antibiotics and aminoglycosides is demonstrated. Ticarcillin was administered to ten patients following bacteriological and clinical evidence of infections due to P. aeruginosa. The pathogenicity of P. aeruginosa as an organism complicating the course of severely injured patients is discussed. Therapeutic consequences in regard to possible combination with other antibiotics are suggested.

The politics of medical inflation.

This paper discusses the politics of anti-inflationary policy in the medical care sector. We first clarify the issue by distinguishing between four different conceptions commonly used when discussing medical inflation. We then present some of the standard solutions to these problems suggested by economists. In the main part of the paper, we analyze the response of the government. We show that the underlying causes for failure in the economic market are likely to exist in the political market as well. In particular, the public good aspect of anti-inflationary policy fails to provide a strong incentive for the consumers of medical care. In contrast, the providers have very powerful incentives in the political market because the benefits of governmental action in this sector greatly affect them. Providers exert great pressure to prevent government policies aimed at reducing medical care expenditures. We present evidence and theory to explicate which sets of circumstances are most conducive to governmental action. We show that the most effective anti-inflationary programs in medical financing are least likely to be implemented and that a dispersed, pluralistic financing structure reduces the government's incentive to curb inflation.