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Biomedical subjects

H E Stone

Publications and source records attributed to H E Stone.

7 recordsLinked to original sources
PubMed1999

Does over-accomodation occur when using aircraft head-up displays?

BACKGROUND: Whether over-accommodation is caused by the use of head-up displays is still under debate. Most prior experimentation has involved cognitively demanding tasks, which are known to affect the accommodation response. The simulations have often been unrealistic and involved short working distances. HYPOTHESIS: Over-accommodation is caused not by the presence of a head-up display per se, but rather by the cognitive demand of the task. METHODS: The effect of increasing the task cognitive load and the use of forward looking infra-red imagery (FLIR) on the ocular accommodative response and task performance was assessed with a realistic head-up display assisted flying task. FLIR increases cognitive load due to its poor resolution and the need for interpretation of the images. RESULTS: Over-accommodation was found to be small in magnitude (0.17+/-0.03D; range -0.02-0.45D) occurring only with cognitively demanding tasks and with forward looking infrared imagery. Response times to detect tanks in the outside world scene were slower with increased cognitive load and forward looking infra-red imagery, along with a reduced detection rate, decreased accuracy of tracking tanks in the outside world and poorer control of the head-up display pitch ladder. When discrimination was added to detection in an outside world task, decisions were delayed until they could be accurately made, rather than performance degraded. CONCLUSION: The use of a virtual head-up display in a simulated aircraft environment did not adversely affect ocular accommodation. However, increased cognitive demand or FLIR imagery caused significant inward shifts of accommodation.

Accommodation, Ocular↗
PubMed1993

A comparison of peripheral nerve repair using an absorbable tubulization device and conventional suture in primates.

Median nerve regeneration was studied in 30 adult primates after repair by microsurgical suture or tubulization with a nonwoven, bioabsorbable, polyglycolic acid device. The two methods were compared electrophysiologically and histologically 6 and 12 months after repair. The electrophysiology included recording of electrically evoked compound action potentials and subsequent determination of threshold, conduction velocity, amplitude, and area above the baseline for each component. Measurements were obtained before nerve transection and at the time of biopsy by stimulating both proximal and distal to the transection site. Analysis of all electrophysiological parameters revealed no statistically significant differences (p less than 0.05) between the two repair techniques. Histopathology included examination of cross sections proximal and distal to the repair sites and longitudinal sections through the coaptation site. End organs (Meissner's and Pacinian corpuscles and muscle) were sectioned to determine the degree of reinnervation. No significant differences between the repair techniques were observed by histological analysis of these sections. These evaluations indicated that the tubulization repair technique produced results comparable to that of the suture technique.

Electrophysiology↗
PubMed1989

Muscle plasticity: comparison of a 30-Hz burst with 10-Hz continuous stimulation.

The changes in the contractile properties induced by a 30-Hz phasic stimulation paradigm were measured and compared with the changes induced by a 10-Hz continuous stimulation paradigm. The study was performed on the tibialis anterior muscles of cats with one paradigm applied to one hindlimb muscle and the other to the contralateral limb. Both hindlimb muscles received the same number of stimuli in a day, making the average stimulation frequency 10 Hz. Two periods of daily stimulation were studied, 8 and 24 h/day. Muscles stimulated at 30 Hz produced greater overall tetanic tension and, during a prolonged stimulation test, exerted a greater mean tension than muscles stimulated at 10 Hz (50 and 32% increase for animals stimulated for 8 and 24 h/day, respectively). Muscle mass was least reduced and fewer pathological abnormalities were observed in the muscles stimulated at 30 Hz. There were no apparent differences in the histochemistry or biochemistry between muscles stimulated at 10 and 30 Hz, which could account for these differences in muscle properties. These results indicate the 30-Hz paradigm may be better suited than 10 Hz continuous stimulation for applications requiring sustained muscle tension such as correction of scoliosis or muscle conditioning for motor prostheses.

Animals↗
PubMed1978

Arterial ligation in epistaxis.

Unremitting severe nose bleeds may require arterial ligation. One or more of the four vascular systems supplying the nose may need such surgical interference. Dye injection of 14 cadavers was performed to demonstrate the vascular supply of the nose and the effects of various arterial ligations. Depending upon the site of haemorrhage within the nose, up to three vascular systems may need occlusion. These are the ipsilateral and contralateral external carotid arterial systems and the ipsilateral ethmoidal arteries.

Aged↗
PubMed1975

Primary adenocarcinoma of the middle ear.

Primary adenocarcinoma of the middle ear is rare. It may or may not be associated with chronic suppurative otitis media. After the exclusion of a primary site elsewhere, the tumor should be managed by surgery and postoperative radiotherapy, especially if tumor excision is incomplete. We report a case in which primary papillary adenocarcinoma developed in the middle ear, possibly due to aberrant ceruminous gland elements. The findings prior to histologic examination were unusual in that they were consistent with a tumor of the glomus tympanicum or glomus jugulare.

Adenocarcinoma↗