Clifford G. Y. Lau

Visual‐vestibular interaction and cerebellar atrophy

The vestibular and optokinetic ocular control systems were studied in 10 patients with cerebellar atrophy and in 10 normal subjects using (1) constant velocity optokinetic stimulation, (2) sinusoidal rotation in the dark, and (3) sinusoidal rotation in the light with a surrounding fixed optokinetic drum. The gain (maximum slow component velocity/maximum head or drum velocity) of induced nystagmus was calculated from electro-oculographic recordings. Optokinetic nystagmus was abnormal in seven patients and the average optokinetic gain in the patients was significantly (p < 0.01) less than that of the normal group. Three patients with “clinically pure” cerebellar atrophy had increased vestibular responses, and one patient with clinical signs of peripheral neuropathy had decreased responses, probably due to associated vestibular nerve disease. The average vestibulo-ocular reflex gain in patients did not differ significantly from controls (p > 0.05). Three patients had normal vestibular and optokinetic responses when tested independently, but had abnormal visual-vestibular interaction. These patients probably had selective disorders of the midline cerebellar pathways that mediate visual-vestibular interaction. By studying each system, both independently and during interaction, all patients were identified as abnormal, and a more precise anatomic localization of the atrophy was obtained.

Global nanotechnology research metrics

Text mining was used to extract technical intelligence from the open source global nanotechnology and nanoscience research literature. An extensive nanotechnology/nanoscience-focused query was applied to the Science Citation Index/Social Science Citation Index (SCI/SSCI) databases. The nanotechnology/nanoscience research literature infrastructure (prolific authors, key journals/institutions/countries, most cited authors/journals/documents) was obtained using bibliometrics. A novel addition was the use of institution and country auto-correlation maps to show co-publishing networks among institutions and among countries, and the use of institution-phrase and country-phrase cross-correlation maps to show institution networks and country networks based on use of common terminology (proxy for common interests). The use of factor matrices quantified further the strength of the linkages among institutions and among countries, and validated the co-publishing networks shown graphically on the maps.

Ewald’s Second Law of Labyrinthine Function and the Vestibuloocular Reflex

There is general agreement that the functioning of the vestibuloocular reflex (VOR) arc is primarily determined by the characteristics of the nerve responses to labyrinthine organ stimulation. Throughout the years, physiologists and clinicians have endeavored to abstract significant features from the VOR response which would indicate whether or not the inner ear is functioning normally. One such characteristic of labyrinthine function, known for almost 100 years, which applies when there is only one normal labyrinth, is embodied in Ewald’s second law. This law predicts that when the normal horizontal semicircular canal is stimulated by angular acceleration which causes endolymph displacement toward the ampulla [ampullopetal (AP) displacement], greater VOR responses will be produced than by acceleration which causes ampullofugal (AF) displacement. Changes in first order neuron firing rates in primates in response to constant angular acceleration which produces AP fluid displacement were recently shown to be approximately 1.5 times greater than those induced by accelerations in the opposite direction, thus providing physiologic support for Ewald’s law (3,4). Furthermore, whereas firing rates could be considerably increased by large AP stimuli, AF stimuli soon silenced the spontaneous firing, thus creating a significant directional difference in the vestibular neuron response.

Relation of seminal nanotechnology document production to total nanotechnology document production - South Korea

This study evaluates trends in quality of nanotechnology and nanoscience papers produced by South Korean authors. The metric used to gauge quality is ratio of highly cited nanotechnology papers to total nanotechnology papers produced in sequential time frames. In the first part of this paper, citations (and publications) for nanotechnology documents published by major producing nations and major producing global institutions in four uneven time frames are examined. All nanotechnology documents in the Science Citation Index [SCI, 2006] for 1998, 1999–2000, 2001–2002, 2003 were retrieved and analyzed in March 2007.In the second part of this paper, all the nanotechnology documents produced by South Korean institutions were retrieved and examined. All nanotechnology documents produced in South Korea (each document had at least one author with a South Korea address) in each of the above time frames were retrieved and analyzed. The South Korean institutions were extracted, and their fraction of total highly cited documents was compared to their fraction of total published documents. Non-Korean institutions that co-authored papers were included as well, to offer some perspective on the value of collaboration.

Implications of Ewald's Second Law for Diagnois of Unilateral Labyrinthine Paralysis

The feasibility of replacement of the caloric test with sinusoidal rotatory stimulations of differing frequencies was investigated in ten normal subjects and seven patients with unilateral labyrinthine paralysis. Testing was performed at frequencies ranging from 0.0125 to 0.2 Hz at 60°/sec and at 0.05 Hz at peak velocities of 30°/sec to 180°/sec. Gain, phase, and asymmetry of the nystagmic responses were measured in these groups. Results indicated that the rotatory test was not reliable enough to be used as the sole measure for identifying patients with unilateral labyrinthine lesions.

Implications of Ewald's Second Law for the Evaluation of Vestibular Function

The significance of Ewalds second law in the evaluation of the vestibulo-ocular reflex (VOR) was Investigated using the transfer characteristics of the vestibular and VOR systems in normal rabbits and rabbits in which one horizontal semicircular canal had been blocked. The transfer characteristics of the vestibular system were derived from the experimental results reported by Goldberg and Fernandez in 1971. A comparison was made of the properties of the bilateral and monolateral VOR systems with the predictions of a piecewise linear model of the vestibular system. The data received quantitatively collaborate the prediction of Ewalds second law as ft applies to the VOR responses.

A Model for Visual-Vestibular Interaction

During head movement in the light, clear vision is maintained by the combined responses of several systems including the fixation smooth pursuit system, the optokinetic system, and the vestibuloocular reflex (VOR). The pursuit tracking system has been known to have low-pass characteristics. On the other hand, the vestibuloocular reflex has been known to have a decreased response at low frequencies. During simultaneous stimulation of the visual and vestibular systems, the gain is almost 1 for a wide range of frequencies.

Modified Health Effects of Non-ionizing Electromagnetic Radiation Combined with Other Agents Reported in the Biomedical Literature

Ionizing and non-ionizing electromagnetic field (EMF) radiation, either stand-alone or in combination with other agents, exert health effects on biological systems. The present chapter examines the scope of non-ionizing EMF radiation combined effects; i.e., identifies effects on biological systems from combined exposure to non-ionizing electromagnetic fields/radiation and at least one other agent. Only articles in which the presence of non-ionizing EMF radiation had some effect (beneficial or adverse) on the biological system were selected. A comprehensive and novel query was developed using an iterative hybrid approach, whereby articles related by common text and by citation linkages were retrieved. This retrieved literature was: (1) clustered algorithmically into 32 biomedical sub-themes (assigned by the authors); (2) grouped through factor analysis into 32 factors; and (3) subsequently grouped manually (by the authors) into an effects-based taxonomy. The common principles within each thematic cluster/group that accounted for the combined effects were identified.