[Doppler effect in isolated syndromes of central retinal artery occlusion].
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Adult↗
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Results for “Doppler Effect”
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Spectroscopic observation of the rotational Doppler effect.
We report on the first spectroscopic observation of the rotational Doppler shift associated with light beams carrying orbital angular momentum. The effect is evidenced as the broadening of a Hanle electromagnetically induced transparency coherence resonance on Rb vapor when the two incident Laguerre-Gaussian laser beams have opposite topological charges. The observations closely agree with theoretical predictions.
Journal Article↗
[Comparative study of the vertebrobasilar circulation using the Doppler effect, cineangiogammagraphy (time-limit carotido-basilar) and angiography. Apropos of 38 cases].
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Adult↗
[Uses in vascular symptomatology of the ultrasonic flowmeter with Doppler effect in patients revascularized for peripheral obliterating arteritis].
The Authors present 38 cases of surgical revascularization for arteriosclerosis obliterans of the lower extremities, operated in Clinica Chirurgica of Ancona during the space of three Years, from 1974-1977. The morphological profile of the sphygmic wave and pressures of occlusion or Travis Winsor's index were studied pre and postoperatively with Doppler ultrasonic flowmeter. The patency of vascular grafts and after thromboendarterectomy was shown by T.W.'s index. With this method, besides establishing a program for postoperative arteriography, a lesser use of the latter was shown.
Arteriosclerosis Obliterans↗
Doppler effects in heterogeneous media with applications to ocean acoustic modeling.
Doppler shift corrections to ocean acoustic signals are complicated by the multi-spatial-scale structure of the ocean medium, resulting in a multi-time-scale structure of the acoustic Green function. Repeated reflections and refractions lead in general to an infinite number of acoustic paths or modes, with different times of flight, connecting source and receiver. The rate of change of these flight times with source or receiver motion gives rise to Doppler shift corrections, and each acoustic path or mode has a different correction. A clean Doppler correction (in the sense of an observable coherent motion-induced frequency shift for each path or mode) is shown to emerge only when the medium is homogeneous along the direction of source or receiver motion, even when it is highly inhomogeneous in directions orthogonal to the motion. A very general quantitative theory for this correction is developed, encompassing earlier results in the literature, and presented in a form amenable to efficient numerical implementation in data processing.
Journal Article↗
The Doppler effect is not what you think it is: dramatic pitch change due to dynamic intensity change.
Historically, auditory pitch has been considered to be a function of acoustic frequency, with only a small effect being due to absolute intensity. Yet we found that when tones are Doppler shifted so that frequency drops, the pitch dramatically rises and falls, closely following the pattern of dynamic intensity change. We show that continuous intensity change can produce pitch variation comparable to a frequency change approaching an octave. This effect opposes and is an order of magnitude larger than the well-known effect of discrete intensity change in the frequency range employed. We propose that the perceptual interaction of continuous changes in pitch and loudness reflects a natural correlation between changes in frequency and intensity that is neurally encoded to facilitate the parsing and processing of meaningful acoustic patterns.
Adolescent↗
Doppler effect for sound emitted by a moving airborne source and received by acoustic sensors located above and below the sea surface.
The acoustic emissions from a propeller-driven aircraft are received by a microphone mounted just above ground level and then by a hydrophone located below the sea surface. The dominant feature in the output spectrum of each acoustic sensor is the spectral line corresponding to the propeller blade rate. A frequency estimation technique is applied to the acoustic data from each sensor so that the Doppler shift in the blade rate can be observed at short time intervals during the aircraft's transit overhead. For each acoustic sensor, the observed variation with time of the Doppler-shifted blade rate is compared with the variation predicted by a simple ray-theory model that assumes the atmosphere and the sea are distinct isospeed sound propagation media separated by a plane boundary. The results of the comparison are shown for an aircraft flying with a speed of about 250 kn at altitudes of 500, 700, and 1000 ft.
Acoustics↗
[Classification of changes in circulatory rate in the arteries of the lower limbs. Transcutaneous measurement by Doppler effect].
Ultra-sonic recording using a directional flowmeter in the peripheral arteries is an essential part of vascular studies. An attempt at systematisation of changes in the patterns of circulatory speed is proposed, which may be used not only by the clinician but also the statistician.
Blood Flow Velocity↗
[Recording of fetal respiratory movements based on studying the shifting of the amniotic fluid in the trachea by the Doppler effect].
Examination of 80 women in their third trimester with chronic fetal abnormalities has shown that movement of the amniotic fluid in the fetal trachea can be detected during fetal respirations. The pattern of amniotic fluid velocity is significantly affected by chronic fetal stress. Evaluation of pneumodopplerographic findings enables identification of 90% of satisfactory and 80% of poor fetal conditions.
Amniotic Fluid↗
[The doppler effect applied to the study of the vertebral arteries (author's transl)].
Results and correlation with arteriographic findings in 25 cases. The methodological criteria essential to the reliability of this examination are described, as well as the special conditions of recording which may influence interpretation. The respective values for systolic and diastolic circulatory rates obtained on ultrasound curves led the authors to classify the results into five groups. There was satisfactory correlation between the latter and the anatomical data provided by arteriography of the vertebral arteries. Such a quantitative approach provides an assessment of the functionally normal or pathological state of the vertebral arteries and of circulatory assymetry.
Angiography↗
[Doppler effect and the Swan-Ganz catheter. Advantage in diagnosis and treatment of gaseous embolism by neurosurgical procedure (author's transl)].
During the neurosurgical procedure in the sitting position a prospective study was performed with a Swan-Ganz catheter on 99 subjects. Gaseous embolism occured in 11 subjects (11%). The frequency increased twofold in the surgery of pontocerebellar angle tumors. Haemodynamic study of 10 gaseous embolisms showed a rise in pulmonary arterial pressure (15.3 +/- 5.2 to 32.4 +/- 32.4 +/- 7.7 mm Hg; p < 0.005) with a rise in pulmonary resistances (22 +/- 1.2 to 9.0 +/- 3.1 units; p < 0.005) and in right ventricular systolic work index (7.8 +/- 1.3 to 14.4 +/- 6.3 gm/m2; p < 0.02). The fall in mean arterial blood pressure was inconstant and moderate (89 +/- 19 to 78 +/- 23 mm Hg; p < 0.05) as was the fall in cardiac output (5.6 +/- 0.9 to 5.0 +/- 0.8 l/min; p < 0.01). Increasing FIO2 hid hypoxemia but, in five subjects, the intrapulmonary shunt rose from 7 to 31%. The therapeutic aspects are reviewed.
Anesthesia↗
Anomalous Doppler-effect and polariton-mediated cooling of two-level atoms.
We consider an atom moving in a near resonant laser field with its dipole strongly coupled to a resonator field mode. As compared to the standard Doppler shift, we find a substantially different and counterintuitive linear velocity dependence of the light scattering properties. The mechanical force of the laser field exhibits strong velocity selectivity at a polariton resonance, which gives rise to an enhanced friction force and Doppler cooling even in the directions perpendicular to the resonator axis. This effect allows for sub-Doppler cooling of atoms even with a nondegenerate ground state.
Journal Article↗
[Diagnosis of varicocele by Doppler effect].
Varicoceles, which may produce oligo-astherospermia are a curable cause of subfertility in the male. Doppler velocimetry of the anterior spermatic venous plexus or pampiniform plexus allows the diagnosis of clinical and infraclinical varicoceles to be confirmed. It can also assess and quantify the spontaneous increase in flow due to venous distension and Valsalva reflux related to valvular incompetence. 50 patients investigated for conjugal infertility and suffering of oligo-astherospermia were included in this study. All underwent clinical examination by an andrologist, spermatic venography and Doppler examination before and after embolization. Doppler examination was performed with patients in the dorsal decubitus position using an 8 MHz transducer. Varicocele was confirmed in 84% of patients suffering of oligo-astherospermia. --Comparison with the results on clinical examination demonstrated a specificity of 100% but a sensitivity of only 66%. --Compared with venography taken as a reference, Doppler had a sensitivity and specificity of 94% and 100% for the examinations carried out after embolization. In the hands of a suitably trained doctor, Doppler examination is today the most rapid, simplest, least costly and most reliable non invasive method for diagnosis of varicoceles. In recent months Doppler hemodynamic data have been complemented by ultrasonographic images obtained using a high resolution apparatus emitting at 7.5 MHz. In the presence of varicocele, the pampiniform plexus has an alveolar appearance and the diameter of the principal draining vein is greater than 3 mm. These dates should be compared with those obtained on venography.
Embolization, Therapeutic↗
[Physiologic mechanisms of use of the Doppler effect in echolocation by Rhinolophus ferrumequinum bats].
During the flight, the greater horse-shoe bat R. ferrumequinum decreases the frequency in the medial part of the emmited signal in proportion to the relative target--bat velocity. The value of the decrease is approximately equal to the Doppler shift; as a result, the animal picks up the echo at its species specific frequency irrespectively of the flight velocity. Threshold curve of bat's auditory system plotted in terms of N4, exhibits a sharp turning peak with a slope of about 83 dB/kHz towards low frequencies. The species specific frequency lies between the frequencies corresponding to the highest and the lowest thresholds. The described peculiarities of emission and perception of signals allow to consider the orientation system in the bat as a Doppler compensating system which provides the effective detection and discrimination of moving targets (e.g., a prey), improves spatial characteristics of hearing and enables the animal to evaluate the velocity during approaching the target.
Animals↗
[Considerations on the role of the so-called non-invasive investigations: Doppler effect, rheography and labeled fibrinogen testi in acute arterial and venous leg].
The author outlines the first results obtained with Doppler investigation in arterial and venous emergencies. He analyzed thereafter the Kakkar test, through which he can detect acute venous more easily than with Doppler. He insists on the difficulty of detecting through either one of these methods, some cases of thrombosis located in the abdominal veins.
Acute Disease↗
Is transcranial Doppler effective in avoiding the hazards of carotid surgery?
The middle cerebral artery flow velocities were measured to test the hypothesis that transcranial Doppler is a useful technique for intraoperative monitoring in 50 consecutive carotid endarterectomies which were performed under local anaesthesia. The patients' neurological status was continuously monitored. The peak middle cerebral artery velocities were measured before clamping, during clamping and after restoration of flow, and again 24 h and 4 weeks later. Clamping produced a decrease in the velocity of the middle cerebral artery, from 97 to 45 cm/s (P < 0.001). Neurological manifestations occurred in eight patients; one patient lost consciousness, and seven experienced transient focal deficits during the procedure. Another three (6%) developed minor strokes postoperatively. The velocity changes were similar in those who developed complications to those who did not. These results do not support the view that transcranial Doppler monitoring is helpful in deciding whether to use a shunt during carotid endarterectomy. Further data are needed to evaluate the importance of transcranial Doppler monitoring during carotid surgery.
Adult↗
[Aortic flow measurement by transesophageal Doppler effect].
Continuous measurement of cardiac output by thermodilution is invasive, impractical and unpleasant for the patient. We propose to measure descending aortic blood flow with a specially designed intra-oesophageal Doppler echo probe. The apparatus is composed of two main parts. First an A scan system makes possible the measurement of the diameter of the vessel, second a continuous wave velocimeter is used to measure the spatial mean velocity of the blood. An output calculator determines the descending aortic blood flow. The oesophageal catheter contains three ultrasonic transducers at its tip mounted on an epoxy resin bracket produced by moulding. They are connected to a flexible hose placed inside a flexible polyvinyl sheath whose outer diameter is 6.8 mm and length is 50 cm. A cylindrical latex balloon is mounted on this sheath which is water inflated to minimum pressure, ensuring a good ultrasonic coupling between the transducers and the oesophageal wall. Connection between the probe and the apparatus is made by three coaxial cables. Three isolator-transformers are built into the connector cable to ensure a safe electrical circuit. After having bled the probe of any air, the balloon is deflated. The probe is gently introduced into the oesophagus by nasal or oral route until the transducers are situated between the 5th and 6th vertebra. The balloon is then inflated to minimum pressure with 10 ml of distilled water contained in a syringe. To find the aorta, the velocimeter is first used like a Doppler stethoscope. The probe is rotated into a position corresponding to the maximum level of Doppler signal.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
[Pre-occlusive stenosis of the internal carotid artery. Haemodynamic study by Doppler effect, phonoangiography-oculoplethysmography and arteriography (author's transl)].
The diagnosis of near total occlusion of the internal carotid artery was made on a group of 122 patients (90 symptomatic - 32 asymptomatic) by Doppler examination on one hand and carotid phonoangiography and oculoplethysmography, used together, on the other hand. The angiographic examination, including the study of the extra cranial arteries and the intra cerebral vessels, was performed. It has shown that a stenosis (greater than or equal to 90% of an internal carotid artery was the only lesion on 65 patients (53.3%) and that in 57 cases (46.7%) there were multiple lesions. 96 patients (76 symptomatic - 20 asymptomatic) were operated on. 4 patients (4.2%) died but the mortality was none in the group of 20 asymptomatic patients. 19 patients refused the operation and we have noted 7 occlusions of the internal carotid artery and 2 patients died (10.2%). On 7 patients with a surgical contra indication we have noted 1 secondary occlusion. We have to consider a near total occlusion of the internal carotid artery as an emergency. Its diagnosis by non invasive techniques must be followed by heparin therapy and angiographic examination. The carotid endarterectomy will respect the external carotid artery patency.
Angiography↗