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At least 91 records · Page 5Linked to original sources
PubMed2003

Anisotropic ultrafast dissociation probed by the Doppler effect in resonant photoemission from CF4.

The resonant Auger spectrum from the decay of F 1s-excited CF4 is measured. Several lines exhibit a nondispersive kinetic energy as the exciting photon energy is tuned through the resonance region. The F 1s(-1) atomiclike Auger line is split into two components due to the emission of Auger electrons by a fragment in motion, when electron emission is observed along the polarization vector of the light. This Doppler splitting is direct evidence that the core excitation leads to T(d)-->C(3v) symmetry lowering, by elongation of a specific C-F bond preferentially aligned along the polarization vector of the incident photon.

Journal Article↗
PubMedDate not supplied

[Use of the Doppler effect in the prevention of accidental intraarterial injection of a sclerosing agent].

A high degree of safety has been reached in sclerotherapy. The accidental intra-arterial injection of a sclerosant is considered to be a rare but serious complication. After mentioning the importance of clinical examination the author considers the import of the ultra-sound method to diagnostics and the prevention of some complications in sclerotherapy. He recalls the dangerous zones and situations, and clearly demonstrates the precision of the Doppler which indicates arterial vessels. It is important to interpret correctly the language of the ultra-sound investigation, and to evaluate the spontaneous signals from the arteries by exploring the sounds produced by venous circulation with the various available techniques. The discussion involves 76 patients examined by the Doppler before sclerosis. No complications were observed, although in 17 cases there were arterioles close to the varices or microvaries to be injected. This proves the importance of the Doppler in the daily practice of all angiologists.

Humans↗
PubMedDate not supplied

[Measurement of carotid diastolic flow by ultrasonography using the Doppler effect, and its value in diagnosis (authors transl)].

Blood supply to the brain is related to carotid diastolic flow, which is a function of cardiac output and distal arterial resistance. It is used to calculate the resistance index (Ir) of Planiol and Pourcelot which enables quantitative measurement of distal circulatory resistance. The Ir is of no value in young subjects with satisfactory arterial compliance and in atheromatous subjects with flattened curves from loss of elasticity of the arterial walls. More precise information can be obtained by calculating the ratio of the areas under the curves. Diastolic flow may be reduced (Ir tending towards 1) or increased (Ir lower than normal) either uni- or bilaterally, with very different diagnostic significance. Unilateral flow reduction results from partial obstruction while bilateral reduction occurs during the course of general affections. Angiomas cause a unilateral increase in flow. Variations in the results of repeated examinations can also supply useful information.

Adolescent↗
PubMed2004

Charge-state distribution and Doppler effect in an expanding photoionized plasma.

The charge state distributions of Fe, Na, and F are determined in a photoionized laboratory plasma using high resolution x-ray spectroscopy. Independent measurements of the density and radiation flux indicate unprecedented values for the ionization parameter xi=20-25 erg cm s(-1) under near steady-state conditions. Line opacities are well fitted by a curve-of-growth analysis which includes the effects of velocity gradients in a one-dimensional expanding plasma. First comparisons of the measured charge state distributions with x-ray photoionization models show reasonable agreement.

Journal Article↗
PubMedDate not supplied

Determination of human sperm count and sperm motility using a laser beam and the Doppler effect (LAZYMOT machine).

For 25 consecutive human semen samples, a comparison was made of sperm count and sperm motility values obtained by routine manual methods and by using a machine that measures these functions by analysing the deflection of an impinging laser beam (Lazymot machine). Sperm counts in undiluted semen were approximately 5 times higher with the laser machine. As sperm counts increased to about 300 million/ml the counts obtained by the two methods converged as the chance of the beam hitting a spermatozoon and not another type of particle increased. In semen diluted 1 + 4 with Baker's solution, the uncorrected laser count agreed well with the sperm count obtained using a haemocytometer. Multiplication of the laser count by 5 did not reach the same count as that measured in the undiluted sample, showing that the dilution had dissolved some of the smaller particles. It was recommended to measure laser percentage motility in undiluted semen but the values obtained bore no relationship to those obtained using a haemocytometer and neither did the values obtained for laser percentage sperm with progressive motility. The mean laser velocity of the total motility was 23-64 micron/sec and for the progressive particles was 48-84 micron/sec, values which were much faster that the acceptably normal values of 8-30 micron/sec found for selected progressively motile spermatozoa timed with a stopwatch. The laser machine detected an increase in counts and the presence of residual motility after cytoplasm had been stripped away from the spermatozoa with a saponin reagent. The laser machine was unable to detect any increase in speed on increasing the temperature to 37 degrees C. It was concluded that the Lazymot machine as presently designed is not useful in the andrological laboratory for routine counting and motility determinations, mainly due to the absence of a size discriminator against the multitude of small particles that are present in human semen.

Humans↗