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Biomedical subjects

D Krell

Publications and source records attributed to D Krell.

At least 37 records · Page 2Linked to original sources
PubMed1985

Stiffness changes in thermodynamic Nitinol with increasing temperature.

The purpose of this study was to measure and describe the physical properties of a recently-developed thermodynamic Nitinol alloy, type A-138, at intervals of temperature between room and body temperatures. The properties of stiffness, flexure yield strength and permanent deformation were measured, demonstrating that the working range of Nitinol A-138 is directly related to increases in temperature between 75 degrees F and 100 degrees F. As stiffness of the .017'' round A-138 Nitinol wire increases, the yield point decreases. In the loading cycle, yield points dropped from 36 degrees angular deflection at 75 degrees F to 25 degrees at 100 degrees F. In the unloading cycle, the yield point at 75 degrees F was 41 degrees of deflection, with force dropping to zero at 35 degrees; at 100 degrees F, yield point was only 12 degrees and force did not drop to zero until unloaded to 3 degrees angular deflection.

Alloys↗
PubMed1984

Effects of auditory stimulus timing in the respiratory cycle on the evoked cardiac response in man at rest.

The present experiments were carried out in 21 healthy adults to study the effects of auditory stimulus timing within the respiratory cycle on evoked cardiac response. The stimulus (80 dB white noise) was started by the first and finished by the second R-wave after change in respiratory phase, and presented in different series in either early inspiration or early expiration. The spirogram and eight sequential interbeat intervals (IBI) after respiratory phase change were recorded. The mean of IBI and standard deviation (SD) were calculated separately for each IBI of 20 trials for each subject, during both the prestimulus and poststimulus phases. The stimulus effects were expressed as changes from prestimulus conditions, in terms of delta IBI and delta SD. The mean of each of the eight IBI and its SD were found to vary consistently in the same direction, i.e., SD increased with increasing mean IBI. Stimulation during early inspiration did not produce any effect during this respiratory phase. It was not before the beginning of the following expiration that a significant deceleration was evoked, which was associated with an enhanced delta SD, whereas stimulation during early expiration promptly evoked a biphasic cardiac response of the deceleration - acceleration pattern and an increase and decrease in delta SD, respectively. While SD was found to be a function of age, no such finding was obtained for delta IBI and delta SD. These results are discussed in terms of the "vagal gating" hypothesis.

Acoustic Stimulation↗
PubMed1983

[Clinical, electroneurographic and neuroautonomic findings in patients with chronic renal insufficiency and following kidney transplantation].

Orientation onsigns of sensomotor polyneuritis seems appropriate for monitoring the status of patients with chronic uremia. The maximum speed of motor and F-wave transmission by the N. fibularis and the mean instantaneous arrhythmia are parameters which, before clinical symptoms appear, permit the accurate assessment of motor and vegetative lesions and may be useful as a basis on which treatment can be corrected.

Adult↗
PubMed1982

An investigation of linear dimensional changes as a function of temperature in an 0.010 inch 55cobalt-substituted annealed nitinol alloy wire.

There are two frequently used methods of aligning malposed teeth by means of an arch wire. The first method is to deflect and tie the arch wire, which has a low modulus of elasticity, into the deepest part of the bracket slot. This low-modulus arch wire is not permanently deformed, and the elastic forces in it return the arch wire (which is tied to the bracket on the tooth) to its preformed shape. The second method is to stretch an elastic material (for example, Unitek ligature threads, Unitek Alastik modules, Ormco power threads, or Ormolast ligature modules) from the bracket tie wings to a preformed stiff arch wire which has a high modulus of elasticity and the teeth move from their malposed position to the stiff arch wire form. The objective of this investigation was to stretch a thermodynamic nitinol wire from 8 percent to 12 percent of its original length and measure the shrinkage of the wire in length. If the quantity of shrinkage of a 0.010-inch nitinol ligature type of wire were great enough, the second method of moving teeth to a stiff preformed arch wire by employing the thermodynamic nitinol stretched wire as a "wire rubber band" could be used to move teeth. This could serve as a possible alternative to Alastik and elastic modules in which there is a great deal of inherent force decay and permanent deformation. When the thermodynamic nitinol wire was heated through its transition temperature range, three different magnitudes of shrinkage occurred. The first was less than 1.0 percent of the original stretched length of the wire, the second was between 6 percent and 7 percent of the original stretched length of the wire, and the third was approximately 1.0 percent.

Alloys↗
PubMed1981

[Clinical tachistoscopy: physical-technical requirements and diagnostic use in brain damaged patients].

The importance of physical marginal conditions in tachistoscopic measurements with statements about the arrangement of the content of the picture, light-technical parameters, optimum viewing distance and time of exposure is emphasized. Historic and topical technological solutions in tachistoscopy are discussed. A projection tachistoscope of own design is presented. The fields of tachistoscopic applications as well as results obtained in psycho-diagnostic examinations of patients with cerebral lesions are reported. For a picture series offering the possibility of differentiation age-dependent standard values are given. At advanced age and in cerebro-organic processes significant losses of performances are found.

Adolescent↗
PubMed1980

[SI nomenclature in psychiatry and neurology].

The present study is intended to discuss some problems of introduction of the International System of Units (SI) in neuropsychiatry. Tabular surveys with important measuring points in the clinical field were demonstrated and connected with helps for calculation between traditional values and the SI.

Humans↗
PubMed1978

[Possibility of research specific utilization of clinical television setups].

The present study is intended to discuss use of video tape technics in psychiatric research in reference to method, engineering and clinical investigation. A self created variant of a clinical television system is debated. With the support of video tape methods will be realize improvements in quality of psychiatric investigation in view of procedure and determination of the results as well as reliability, objectiveness and exactitude in connection with a postgraduate continued professional training. Reconsiderations of psychiatric documentation systems with regard to reliability represent an other important field of employment.

Audiovisual Aids↗
PubMed1976

[Correlation between reflex behavior and EEG in a brain-stem tumor].

In a female patient with a tumour of the brain stem the e.e.g. showed signs of increasing general functional disorders and additional transient high voltage monographic waves with bilateral frontal and central accentuation, which we regarded as brain stem disturbances. At the same time the authors observed a characteristic inhibition of the amplitude of brain reflexes as well as high phases of a polyphasic stimulation--response potential with stimulation of the tibial nerve. Beside these inhibition phenomena, signs of disinhibition were verified (nociceptive, trigemino-trigeminal reflex, polyphasic disinhibited brain reflex?). The photostimulation was without influence on the sensitivity of motoneurons.

Adolescent↗
PubMed1975

[On the problems of psychophysiological data determination].

Together with the description of difficulties of registration specific individual, stimulus, and motivation reactions are dealt with. Possibilities are shown of changes of the signalto-noise ratio in the example of a superimposition related to an event. Particularly the problems of the design of psychological complementary diagnostics for the recognition of habitual factors and factor related to specific reactions to trauma are discussed.

Computers↗