Cent Of Amplitude Research Articles

ASCA observations of the Crab-like pulsar/nebula system PSR B0540-69

The ASCA satellite has observed the 50-ms pulsar PSR B0540–69 and its associated supernova remnant SNR 0540–693 in the Large Magellanic Cloud 15 times in total, at least once a year, between 1993 June and 1999 November, including six observations with the pulsar as the main target. In all the observations, a point-like X-ray source was clearly detected at the position of PSR B0540–69 and the X-ray pulsations were detected at large significance. Folded light curves are identical throughout the observations, showing one broad pulse with a small notch at the top. Pulse frequency history during the 6.4 yr of the ASCA observations is well characterized by a second-order polynomial with a breaking index of 2.10±0.05, assuming no glitches occurred during the period. The frequency history smoothly follows the Ginga and ROSAT results and connects to the RXTE results without a measurable discontinuity. The X-ray spectrum of the whole source is well represented by a single power-law model of photon index, α=2.00±0.02, and a small photoelectric absorption, NH=(4.3±0.2)×1021 cm-2. The X-ray spectrum can also be represented by a pulsed power-law spectrum with photon index of 1.80±0.05 with 24 per cent in amplitude at 1 keV, embedded in a constant power-law component with photon index of 2.17±0.02 ascribed to a nebular component. Spectral properties of the X-ray emission from the pulsar and the nebula remain unchanged over the six years and are quite similar to those of the Crab pulsar and nebula.

Superposition of the diffraction fields of apertures: an experimental test

In Kirchhoff diffraction theory it is assumed that the effects of separate apertures in a screen are superposable. Thus, for example, a two-slit pattern is the (complex) superposition of the two individual single-slit patterns. The validity of the assumption has been tested with 10 GHz microwaves (λ = 30 mm) incident at 45° on two parallel slits, of width ½λ, in a conducting screen, their spacing being λ. The diffraction pattern immediately behind the screen was measured by using the optically modulated scatterer technique. With the electric field in the incident wave parallel to the slits there was, on average, a 7 per cent discrepancy in amplitude from what would be predicted by superposition of the effects of the two separate apertures. With the electric field perpendicular to the slits the discrepancy increased to 25 per cent in amplitude. The results may be interpreted by saying that the two–slit pattern is indeed the result of interference between two separate single–slit patterns, but their phases and amplitudes are different from what would be expected from simple theory. It is as if the wave emitted from each slit is affected (by 10 or 30 per cent) by whether the other slit is open or closed. The difference between the results for the two polarizations is explained by the boundary condition on the surface of the screen, which tends to suppress communication between the slits when the polarization of the incident wave is parallel to the slits.

Observations of geomagnetic pulsations and variations with a new borehole magnetometer down to depths of 3000 m

b A triaxial magnetometer has been developed for investigating the in situ skin effect of horizontal geomagnetic pulsations and variations in deep boreholes. The observations were carried out in the pilot borehole of the Continental Deep Drilling Program of Germany (KTB) down to depths of 3000 m and up to temperature of 90 dC. A weak skin effect, due to the known very low conductivity of the penetrated crystalline rocks, of 90 to 95 per cent in amplitude and -5d to -10d rotation in phase has been observed at periods of 10 s and magnetometer depth of 2400 m. An essential prerequisite for all calculations is the accurate determination of the orientation of the downhole magnetometer. It is demonstrated how oriented record samples of temporal variations at depth correlate precisely with those from the surface. Results from surface magnetotelluric (MT) investigations show strong local distortions of the telluric field. The distortion of the MT tensor response has been determined by means of newly introduced skin-effect transfer functions, which are assumed to be undistorted.

Seismic calibration using the simplex algorithm

AbstractWe have modified the software of Sauter and Dorman (1986) to produce a robust and flexible calibration program that works in the frequency domain for longer and noisy calibration signals, as well as in the time domain when shorter, high signal-to-noise calibration signals may be used. The most important improvement was to replace the least squares fitting of the complex polynomial representation of the response function with the simplex fitting of the pole-zero representation of the response function. The simplex algorithm always converges to a minimum, regardless of starting model, and by fitting the poles and zeroes directly, we minimize the degrees of freedom of the solution. Typical VAX 11/750 CPU requirements are on the order of 2 to 3 minutes for both codes, with average errors less than 1 per cent in amplitude and 1° in phase.

Seismic system calibration: 2. Cross-spectral calibration using random binary signals

abstractWe present a rapid and accurate method of calibrating seismic systems using a random binary calibration signal and cross-spectral techniques. The complex transfer function obtained from the cross spectrum is least-squares fit to the ratio of two polynomials in s(s = iω) whose degrees are determined by a linear systems analysis. This provides a compact representation of the system frequency response. We demonstrate its application to two seismic systems, the IDA and SRO seismomenters. This method yields calibrations to an accuracy of better than 1 per cent in amplitude and 1° in phase.

Pressure Waves from a Geyser

Abstract It seemed probable that as a geyser builds up toward eruption, it should send out detectable pressure waves, which might make it possible to predict the time of eruption. Waves produced by Old Faithful Geyser in Yellowstone National Park were detected by a sensitive microbarograph at various surface locations within a few hundred feet of the geyser vent. The waves occur in bursts, and tend to increase about 50 per cent in amplitude within five minutes prior to an eruption, and to decrease about 20 per cent in period within two minutes before an eruption. However, changes in amplitude and period within bursts of waves are great enough to obscure the longer-time variations, and to make it impossible to predict eruptions in the field by this method.

The diagnosis of angina pectoris

The diagnosis of angina pectoris is dependent upon the history and electrocardiographic changes. It should be emphasized that electrocardiographic changes must be interpreted with a knowledge of the clinical history, so that the significance of suggestive changes is more apparent. The difficulty experienced by the patient with angina is characterized as a distress or discomfort, and not a pain. The discomfort is provoked by exertion, digestion, excitement, and emotion, and is classically located in the retrosternal area, with radiation to the inner aspect of the left arm, the hypothenar eminence, and the fourth and fifth fingers. The distress may radiate to the neck, the right arm, and the jaw, and may occur in only a segment of the distribution. It develops gradually over a period of 10 seconds to 2 minutes and is relieved promptly by rest or nitroglycerin. It may also be relieved by carotid sinus massage. It is usually wise to perform a double two-step Master's test, with the test discontinued if the patient develops discomfort. Positive electrocardiographic changes after exercise include: (1) right-angle S-T segment depression of 0.5 mm. or more, (2) S-T segment elevation, (3) bundle branch block, (4) inverted T waves becoming upright, and (5) T waves increasing 5 mm. or 300 per cent in amplitude, or inverted U waves. These changes are also significant if they occur spontaneously during the period of anginal distress. Suggestive electrocardiographic changes after exercise are: (1) arrhythmias, (2) inverted T waves with or without exercise, especially if the inversion is more than 2 mm., (3) postextrasystolic T-wave change with or without exercise, and (4) junctional S-T segment depression greater than 2 mm. Negative and false-positive changes after exercise include: (1) junctional S-T segment depression of less than 2 mm., (2) T of P depression, (3) inverted T waves less than 2 mm. with or without exercise, (4) autonomic changes, and (5) falsepositive results in patients with hypertrophy, bundle branch block, Wolff-Parkinson-White syndrome, after digitalization, or pericarditis. A double Master's exercise test was analyzed in 350 patients with normal resting electrocardiograms. One hundred and ninety had a definite history of angina, with positive changes in 57.9 per cent, suggestive changes in 14.2 per cent, and negative changes in 27.9 per cent. One hundred and sixty had a negative history, with positive changes in only 4.4 per cent, suggestive in 1.2 per cent, and negative in 94.4 per cent. Of 14 patients with coronary disease and inverted T waves in the control tracing, 2 had right-angle S-T depression, in 9 the T waves became upright, and in 3 there was no change. With improving methods of therapy, correct and early diagnosis is essential in the proper management of the patient with angina pectoris.

Contour of the toe pulse, reactive hyperemia, and pulse transmission velocity: Group and repeat variability, effect of age, exercise, and disease

1. 1. In 170 normal young men, 270 normal middle-aged men, 57 patients with arterial hypertension, and 36 patients with peripheral vascular disease, the toe pulse was photoelectrically recorded before and for vive minutes after arterial occlusion (reactive hyperemia). The following items were measured: absolute and relative crest time (per cent of cycle length); relative amplitude (per cent of peak amplitude) at one-fourth and one-half of the diastolic phase; amplitude changes during reactive hyperemia (in per cent of amplitude before arterial occlusion). 2. 2. There was an initial drop of the amplitude ten seconds after release of arterial occlusion in the normal groups and in the patients with peripheral vascular disease, but not in the hypertensive patients. 3. 3. The reactive hyperemia was not significantly different in the normal younger and older age groups but was much weaker and delayed in patients with peripheral vascular disease; in the more advanced cases it was entirely absent. The maximum increase of the amplitude during reactive hyperemia was moderately decreased also in the hypertensive patients. 4. 4. There was a statistically highly significant increase of the absolute and relative crest time, and slowing of the decline in the diastolic phase with age. 5. 5. The hypertensive patients showed no significant differences in the crest time, but a significantly slower diastolic decline as compared to normals. 6. 6. The rise as well as the decline of the pulse was significantly slower in patients with peripheral vascular disease. 7. 7. The separation of the patients with peripheral vascular disease from normals, investigated by distribution analysis, was excellent for all items of the contours analysis, particularly for the relative crest time and relative amplitude at one-fourth of the diastolic phase, and superior to the separation by means of reactive hyperemia. 8. 8. In about 10 per cent of hyperentsive patients the crest time and the diastolic decline were significantly delayed, even in the absence of clinical peripheral arteriosclerosis. 9. 9. The deviation of pulse contour and reactive hyperemia in patients with peripheral vascular disease depends on the degree of impairment rather than on the type of disease. 10. 10. The highly significant separation between the groups with all items of contour analysis is contrasted by a relatively poor consistency in repeat experiments in twenty-six normal young men. 11. 11. The pulse transmission velocity was determined in meters per second from the interval first heart sound to footpoint of the pulse, a correction for the isometric phase of contraction, and the distance from heart to toe. The values are in general agreement with earlier observations. The increase of the pulse transmission velocity with age and in hypertension, and the decrease in perpheral vascular disease were statistically highly significant. 12. 12. There was no interindividual correlation between blood pressure and pulse transmission time in the normal groups, but there was a significant correlation between intraindividual variations of blood pressure and pulse wave transmission time. In hypertensive patients, there was a significant inter-individual correlation. 13. 13. The effect of exercise on pulse transmission velocity, contour of the toe pulse, and reactive hyperemia was studied in seven normal young men. 14. 14. The results substantiate the diagnostic value of analysis of the digital pulse for early recognition of vascular degeneration with age or in disease, and normal limits for separation of normal and abnormal are suggested.