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Biomedical subjects

P Lucas

Publications and source records attributed to P Lucas.

101 records · Page 6Linked to original sources
PubMed1980

Stationary convection in dilute solutions of He in superfluid He.

Two symmetric, convecting steady states have been observed in a novel cell of unity aspect ratio and studied over a range of temperature for two concentrations of (3)He in superfluid (4)He. An existing theory due to Parshin has been related to the conditions necessary for convection in this system, defining a Rayleigh number closely analogous to that of a classical one-component Bénard system. Values of this Rayleigh number at the onset of convection calculated from experimental data are found to have little temperature dependence, with an average value near that for a classical one-component fluid in this geometry. The Prandtl number is small and temperature dependent, with a smallest calculated value of 0.05.

Journal Article↗
PubMed1978

[Experimental study of intensifying screens used in diagnostic radiography (author's transl)].

A physical experimental study of intensifying screens for diagnostic radiography was set up. Experimental conditions were identical with those of medical practice. Spectra speeds of several films and spectral emission of intensifying screens were built up. Speeds of screen-film combinations, as well as definitions, were measured. Results are available to range the different screens-film systems after their speed factor, at 40, 70 and 120 kV, with mention of definition of these systems. It so objectively appears that rare-earth intensifying screens make possible a decrease of X-ray exposure for patient under a factor 2 to 2,5 and a less early wearing of apparatus, namely of X-ray tubes.

Evaluation Studies as Topic↗
PubMedDate not supplied

MRI of the foot and ankle.

The foot and ankle are among the hardest of all areas to image because of the complex three-dimensional anatomy. Magnetic resonance imaging (MRI), with its multiplanar capabilities, excellent soft-tissue contrast, ability to image bone marrow, noninvasiveness, and lack of ionizing radiation, has become a valuable tool in evaluating patients with foot and ankle problems. MRI is more specific than bone scintigraphy and provides more information than ultrasound and computed tomography. Arthroscopy of the ankle is limited to the articular surface and joint space. MRI allows a global evaluation of the bones, tendons, ligaments, and other structures with a single examination that exceeds the capabilities of all other available techniques. This monograph was written to provide a useful guide to basic technique, indications, positioning, anatomy, and interpretation of foot and ankle MRI. The first part describes the performance of the MRI examination with reference to the positioning of the foot, types of coils, and advantages and disadvantages of the different sequences and imaging planes. The next section was written by an experienced foot and ankle orthopedic surgeon and outlines the indications for MRI for the common foot and ankle symptom complexes and the information that the surgeon hopes to obtain from the study. This is followed by a review of pertinent anatomy, as it applies to imaging, with emphasis on osseous structures, ligaments, tendons, and muscles. The final section is a comprehensive review of the common pathologic conditions encountered in the foot and ankle. We hope that radiologists and radiologists-in-training find this article a useful reference tool and gain a better understanding of this complex area of musculoskeletal imaging.

Animals↗
PubMedDate not supplied

[Recurrent familial neuropathy due to compression (author's transl)].

The authors describe a family, of which 13 members had peripheral neuropathy manifesting as episodes of paralysies usually provoked by minor compression of nerve trunks. Nerve and muscle biopsies in two patients, demonstrated many thickenings of the myelin sheath ("tomacula"). Electron microscopy investigations are used as a basis for discussing the origin and place of this affection among other hereditary neuropathies.

Adolescent↗