Direct Recording System Research Articles

The relationship between ST segment deviation projected to the front of the chest during exercise and simultaneous Holter monitoring.

Simultaneous two-channel Holter monitoring, with a direct recording system, and maximal exercise testing with a 12-lead precordial electrocardiographic mapping system were performed in 50 patients with chest pain (41 with documented coronary artery disease, 9 without). The exploring Holter leads were placed to correspond to CM5 and an aVF-like lead. In 36 patients, ST segment changes were found with both Holter and the 12-lead precordial electrocardiogram, while in 12 patients no ischaemic changes were detected by either method. Thus the results of the two methods concurred in 48 of 50 patient (96%). The magnitude of the ischaemic change was similar in 24 of 36 patients (67%), while the Holter system underestimated the ischaemic change by 0.5-2.0 mm in 12 patients. When the maximal ST segment deviation in V5 was compared with CM5, the deviations with both systems were identical in all but one patient in whom a difference of 0.5 mm was found. The use of a Holter lead resembling a VF identified maximal ST segment change on only one occasion, and in only four patients was an ST segment change of 1 mm noted. In conclusion, ambulatory monitoring utilizing only CM5 seems to detect most episodes with ST segment changes, but the use of a 12-lead precordial mapping system during exercise testing may expand the possibility of defining the optimal sites for the exploring Holter leads to detect maximal ST segment change.

Objective Speckle Method Using Stick-On Foil And Its Applications

Objective speckle from a stick-on foil is a new approach to applying the objective white light speckle method to in-plane displacement measurements. By a relatively easy technique a thin aluminum foil is mounted onto the specimen surface and a random grating is scratched onto it, yielding high reflectance and fine optical details. After double exposure by a direct recording system without using a lens, the resulting holographic film possesses a broad spatial spectrum and displacement information. Full-field contour maps of equal displacement can be obtained that are of good contrast and high sensitivity and that have a large adjustable measurement range. The method can be applied to practical engineering problems for both plane and developable curved surfaces.

Practical Aspects of Ambulatory St Segment Monitoring: Comparison of Frequency - Modulated and Direct Recording Systems

Practical Aspects of Ambulatory St Segment Monitoring: Comparison of Frequency - Modulated and Direct Recording Systems

A Television System for the Direct Analysis of X-Ray Diffraction Patterns

Further progress has been made with a direct recording system of X-ray diffraction patterns from single crystals. In this system the pattern is formed on a phosphor screen and viewed by a T.V. camera tube whose video output is digitised and presented to a computer. Earlier work had shown that with a sufficiently high degree of light amplification between the phosphor and and the T.V. camera, individual 8keV quantum scintillations could be detected and moderately weak patterns could be displayed on a T.V. monitor. However, for quantitative work on weak patterns the limit is set by the quantum noise due to the low X-ray flux; consequently, in the present system the camera tube, which is now an Image Isocon, is operated in an integrating mode. After each 'exposure', during which the reading beam is switched off, the integrated charge pattern on the target of the Isocon is read out in a strobing fashion: the target is scanned at normal speeds but the beam is switched on only at those points where diffraction spots are known to be situated. The charge image of a diffraction spot is neutralised when the spot has been scanned, i.e. the read-out from the camera is destructive. It has been found that, owing to slight crystal misorientation and to aberrations in the light-and electron-optical systems, the positions of the diffraction spots can only be predicted approximately from the lattice spacings and initial orientation of the crystal: a computer-controlled search for the spots is, therefore, necessary.

Wideband Direct Recording with High-Frequency Bias

Most present day wideband magnetic tape recorders utilize a FM system for encoding and decoding the information applied to the tape. In the past FM has been employed for reasons of linearity and to avoid the amplitude modulation which occurs due to varying head-to-tape contact. Recent developments in heads, tapes, and transports, however, have removed many of the constraints which originally forced the use of a FM system. Consideration of a high-frequency bias system for video and wideband instrumentation recorders, therefore, is again made possible. As a direct recording system holds so much promise in the areas of linearity and distortion properties, it becomes necessary to establish the transfer function for tape when it is acted upon by a high-frequency bias. The purpose of this paper is to develop a method that may be used to establish the feasibility of such a system and to set down its physical and magnetic parameters. A three-dimensional magnetic moment distribution function J(H+, H−) is used to describe the magnetic properties of the tape. Then the actual transfer characteristics of the headtape system are developed by applying the magnetic field about the record head to the three-dimensional distribution function J(H+, H−).

Continuous rapid infrared CO2 analysis; fractional sampling and accuracy in determining alveolar CO2.

Abstract Detailed techniques are presented for a method of alveolar CO 2 determination which utilizes a fractional to-and-fro continuous sampling method and a rapid infrared absorption gas analyzer with a direct recording system. The validity of the method was established by comparing the alveolar CO 2 values with arterial CO 2 tensions of blood drawn simultaneously. Twenty-two such comparisons reveal a mean deviation of −0.9 mm. Hg with a standard deviation of the mean of ± 1.8 mm. Hg. The limitations of the method are discussed. The method is compared with other methods for determining alveolar CO 2 concentration. The practical value of the infrared method as a clinical guide to proper administration of artificial ventilation is demonstrated.