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PubMedDate not supplied

[Pregnancy in women working on video terminal units].

Only a small proportion of pregnancy failures could be explained by simple genetic or clear--cut environmental/occupational factors. Adverse reproductive outcomes (spontaneous abortion, preterm delivery, low birth weight and congenital malformations), have been reported in a certain number of retrospective studies which were designed to examine the possible role of occupation and working or living conditions and pregnancy outcome. Future prospective projects should assess the (non)existence of the relationship between radiological risks and job stress with pregnancy outcome. Future prospective projects should assess the (non)existence of the relationship between radiological risks and job stress with pregnancy outcome among female video terminal operators.

Abortion, Spontaneous↗
PubMedDate not supplied

Construction of parametric model of operator and workstation.

The purpose of development of a parametric model and the construction and formulation of the parametric model are described. To validate the parametric model, the distribution of the difference between the preferred and theoretical seat height settings of a number of office workers was evaluated from the standpoint of the static posture that does not change with time. The results of precise measurements made for an engineering workstation and an operator were also evaluated. Finally, the theoretical seat height settings with dynamic posture were evaluated. The validity of the parametric model was verified under the experimental conditions.

Algorithms↗
PubMed1992

Obstacles encountered in the development of the low vision enhancement system.

The Johns Hopkins Wilmer Eye Institute and the NASA Stennis Space Center are collaborating on the development of a new high technology low vision aid called the Low Vision Enhancement System (LVES). The LVES consists of a binocular head-mounted video display system, video cameras mounted on the head-mounted display, and real-time video image processing in a system package that is battery powered and portable. Through a phased development approach, several generations of the LVES can be made available to the patient in a timely fashion. This paper describes the LVES project with major emphasis on technical problems encountered or anticipated during the development process.

Audiovisual Aids↗
PubMed1976

On-line computer processing of pressure data from cardiac catheterizations.

A flexible program system for on-line analysis of pressure data from cardiac catheterizations is described. The programs are implemented on an IBM 1800 computer, equipped with remote oscilloscope/keyboard terminals. The current computer system can handle any combination of up to 4 pressure signals. During catheterization, measurement specifications (i.e. calibration levels or sites of pressure recordings) are entered via the keyboard immediately before each recording. As an option the whole expected measurement sequence may be stored on disk before the catheterization starts. This method will minimize the necessary interaction with the computer when the same catheterization procedure is used on several occasions. Changes from the predetermined scheme may, however, be undertaken before each recording to meet with unexpected events that may arise during the catheterization. After computer detection of calibration levels, the recorded signals are digitized during 20 seconds and analysed beat-by-beat. Calculated values are averaged and presented on the terminal oscilloscope in tabular and/or graphic form. The waveform analysis performed by the program system is validated in a statistical comparison between manually and automatically computed values.

Cardiac Catheterization↗
PubMed1977

Catalog card production with a programmable terminal.

Application of a programmable terminal and printer to the cataloging task of a small medical library is described. The application is independent of a computer; the terminal is used in "local" mode only. Full sets of catalog cards are produced, following a single typing of descriptive cataloging data and tracings. Books can be cataloged the same day they are received. Actual cost per book is just over a dollar, for equipment rental, card stock, and the cataloger's time at the console, after call number, tracings, and main entry for the book have been determined.

Catalogs, Library↗
PubMed1987

Conformational analysis of the cholecystokinin C-terminal octapeptide: a nuclear magnetic resonance and computer-simulation approach.

The C-terminal octapeptide portion of cholecystokinin (CCK8) has well-defined biological properties which include action as a neurotransmitter and induction of gall-bladder contraction and pancreatic enzyme secretion. Many analogues of CCK8 have been prepared and tested for potency, making this an ideal model system in which to initiate evaluation of structure-function relationships. The present study uses high-resolution proton nuclear magnetic resonance (NMR) spectroscopy and energy minimization techniques to evaluate the solution (DMSO) and in vacuo conformation(s) of CCK8. The NMR results provide amide and C alpha H alpha chemical shift temperature dependencies and all phi dihedral angles and chi 1 rotamer populations. The energy minimization data located deep potential energy wells, for which all torsion angles are reported. Collectively, the data support models for CCK8 where the structures are characterized by a high degree of folding. These conformations are characterized by sharp turns, possibly stabilized by hydrogen-bonds. Taken together with pharmacologic data and somewhat similar folded structures implied from fragments of CCK8, it is suggested that both electrostatic and steric effects are needed for full biological potency.

Computer Simulation↗
PubMed1983

Energy and nutrient calculations using an Optical Character Reader system.

A new application of the Optical Character Reader (OCR) system for dietary data tabulation has been presented. Comparison of the reproducibility of energy and nutrient values, when hand calculation, on-line computer, and OCR methods of calculation are used, revealed no significant differences. The OCR system increased turn-around time for obtaining results, but use of a clinician's time was greatly reduced in comparison to either the hand calculation or the on-line computer method. Once the initial investment for an OCR system had been made, a significant reduction was realized in the cost of a clinician's time used for energy and nutrient calculations. When the factors of reproducibility, time, and cost were considered, this study found the OCR method for dietary calculations as acceptable as either hand calculation or on-line computer methods. Clinicans using the OCR or hand calculation method did not need computer facilities, but computer keyboard terminals were required for the on-line method.

Computers↗
PubMed1990

Computer study of presynaptic inhibition controlling the spread of action potentials into axonal terminals.

1. The effect of presynaptic, axoaxonal inhibition, that exerts its action by producing a local conductance increase, on the behavior of action potentials at postsynaptic axon terminals is analyzed computationally. The significance of the location and strength of the presynaptic inhibition, as well as the morphology and membrane properties of the axonal terminals, are considered. 2. Keeping the specific properties of terminal membrane and axoplasm constant, the critical "silent" steady-state conductance change (gcrit) that blocks propagation is linearly scaled with the terminal diameter raised to the 3/2 power. At the midpoint of a 5 lambda long, 1 micron diameter axon that has the standard Hodgkin and Huxley (1952) kinetics at 18 degrees C (and an input conductance of 8.7 nS), gcrit is 72 nS. At 0 degrees C, gcrit = 200 nS, whereas at 30 degrees C gcrit = 30 nS. 3. The critical conductance change that blocks propagation depends steeply on the density of excitable channels (gNa) at the terminal. For a geometrically uniform terminal at 18 degrees C, the action potential can not be blocked by a local shunt when gNa greater than 600 mS/cm2. 4. An axoaxonal synapse in the proximity of the postsynaptic release site has graded control over the spike amplitude (and, therefore, over the postsynaptic output) at that site. Presynaptic inhibition located remotely from the release site has an all-or-none effect at the release site. 5. Inhibition is more effective in attenuating the spike at the terminal when it impinges onto a passive terminal rather than on an excitable one. 6. The detectability of the conductance increase as well as the change in action potential amplitude associated with the presynaptic inhibition is poor at only a short distance from the axoaxonal synapse. The presence of bottlenecks and varicosities at some axonal terminals enhances this decoupling effect even more. Thus presynaptic inhibition may reduce the potential near the output site of the affected axon significantly, without producing any noticeable conductance or voltage change at a distance of only several tens of micrometers (a few tenths of a space constant) away from it. 7. Varicosities and bottlenecks typically found along axonal terminals are the optimal loci for presynaptic inhibition to be most effective in attenuating the action potential at the terminal. Even with high density of excitable channels, propagation with such terminal geometry is insecure, and one, or few, quanta of inhibitory transmitter (a conductance change of several nanosiemens) can block propagation there.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1992

Visual increment and decrement threshold curves as a function of luminance range and noise in simulated computed tomographic scans.

OBJECTIVES: The effect of luminance range compression on the visual threshold of a target in a computed tomographic (CT) scan was investigated in eight experiments. METHODS: Both visual increment thresholds of a hot target and visual decrement thresholds of a cold target were obtained. Realistic noisy CT images simulating a scan reconstruction and partial volume blurring were tested as representative of complex medical images. Negative versions, high luminance versions, and noise-free versions of these CT images also were tested. RESULTS AND CONCLUSIONS: In all the noisy images, as the luminance range of the image was compressed, proportionately smaller physical luminance differences between the target and its local background were needed to reach visual threshold. However, the thresholds were the same in terms of the difference in CT numbers between target and background. Noise in terms of CT numbers sets the threshold for a wide range of display conditions. In the noise-free CTs, as the luminance range was compressed, the luminance differences between the target and background needed to reach threshold also decreased, but only marginally. However, in terms of CT numbers, the thresholds were increased.

Analysis of Variance↗
PubMed1992

A universal system for interactive image-directed neurosurgery.

Stereotactic methods confer great accuracy to intracranial target localization, but require strict adherence to a complex program of mechanical and computational maneuvers. A computerized, articulated, localizing 'arm' has been developed that frees the neurosurgeon of these constraints and provides a completely intuitive, 'user-friendly' interface. This universal system is independent of whatever localizing fiducial system is selected. The arm may be sterilized for intracranial use. A variety of intraoperative end effectors may be selected. The patient's CT/MR/PET scans are loaded into computer memory and a three-dimensional shaded surface wireframe diagram of the patient's head is displayed simultaneously with up to 3 independent sets of cross-referenced CT/MR/PET scan images on the intraoperative video screen. The arm's endpoint location and the directional vector are shown as cursors on the relevant scan slices, and change continuously as the surgeon moves the arm. Because the information is continuously updated, an unlimited number of targets and trajectories may be displayed throughout the operation. The arm has an ultimate design accuracy for end-point localization to within 0.1 mm throughout a target volume of 40 x 40 x 40 cm. The tested application accuracy of the first prototype model is 0.31 mm. In clinical use during 30 surgeries, its real-world application accuracy is 0.9 mm. This system provides stereotactic accuracy and universally compatible, intuitive, interactive operation.

Biopsy↗
PubMed1986

How to keep up with the medical literature: V. Access by personal computer to the medical literature.

Access to the medical literature through personal computers is now readily available and can greatly reduce logistical barriers to using recently published journal articles to support clinical decisions. In this article, we describe many of the options available to clinicians who wish to do their own computer searching of MEDLINE, the largest of the electronic services for the biomedical literature. The "bare bones" computer equipment needed includes a terminal or personal computer, a modern and telephone line, and a printer. Access to MEDLINE is then gained through subscribing to any of a burgeoning number of database vendors. A comparison of 17 permutations and combinations of software and vendors shows that the software and vendors vary substantially in efficiency, cost, and ease of use. Direct subscription to MEDLINE is least expensive, PaperChase is the simplest service to use, and Colleague and Medis provide both MEDLINE access plus full-text journals online. Basic search techniques are illustrated for three clinical problems.

Computers↗
PubMed1991

[Eyeglass frame for detection of eye, head movements and pupillary diameter].

Up till now, the simultaneous recording of the movements of the eyes, the movements of the head and the diameter of the pupil required the combined use of several apparatus. In this paper we present a new apparatus developed for the simultaneous recording of the movements of the eyes and of the head, and the diameter of the pupil. The apparatus consists of a portable frame (weight 215 g) a 19" rack containing electronics, and a PC for storing and analyzing the recorded data. In comparison with other systems providing similar measuring possibilities the present apparatus has the advantage of smaller dimensions and lower weight.

Computer Terminals↗