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Computation using a coherent system of units demonstrates simply that no significant specific biological and pharmacological effects can be expected from very highly diluted solutions.
In addition to the inherent qualities of a digital image, the qualities of the monitor and graphics control card as well as the viewing conditions will affect the perceived quality of an image that is displayed on a soft copy display (SD) system. With the implementation of picture archiving and communication systems (PACS), many diagnoses are being made based on images displayed on SD devices, and consequently SD quality may affect the accuracy of diagnosis. Unlike the traditional film-on-lightbox display, optimal SD system parameters are not well defined, and many issues remain unsettled. In this article, the human observer performance, as measured by contrast sensitivity, for several SD devices including an active matrix liquid crystal flat panel monitor is reported. Contrast sensitivities were measured with various display system configurations. Experimental results showed that contrast sensitivity depends on many factors such as the type of monitor, the monitor brightness, and the gamma settings of the graphics card in a complex manner. However, there is a clear correlation between the measured contrast thresholds and the gradient of the display device's luminance response curve. Based on this correlation, it is proposed to use the gradient of luminance response curve as a quality-index or metric for SD devices.
Wave-front distortion compensation using direct system performance metric optimization is studied both theoretically and experimentally. It is shown how different requirements for wave-front control can be incorporated, and how information from different wave-front sensor types can be fused, within a generalized gradient descent optimization paradigm. In our experiments a very-large-scale integration (VLSI) system implementing a simultaneous perturbation stochastic approximation optimization algorithm was applied for real-time adaptive control of multielement wave-front correctors. The custom-chip controller is used in two adaptive laser beam focusing systems, one with a 127-element liquid-crystal phase modulator and the other with beam steering and 37-control channel micromachined deformable mirrors. The submillisecond response time of the micromachined deformable mirror and the parallel nature of the analog VLSI control architecture provide for high-speed adaptive compensation of dynamical phase aberrations of a laser beam under conditions of strong intensity scintillations. Experimental results demonstrate improvement of laser beam quality at the receiver plane in the spectral band up to 60 Hz.
A brief historical review of customary measurements, the resultant chaos and the desirability for a simplified unified measurement system is discussed. The basic units of the International System of Units are described and defined, along with their application in Medicine.
The German "Law for Units of Measure" have restricted the number of units of measure acceptable for business and official dealings. As of January 1, 1978, many common units are no longer to be used. They have been replaced by less familiar units.
BACKGROUND: Stimulation of the subthalamic nucleus is proposed for the treatment of patients presenting with severe Parkinson disease. The effect on gait is not clearly established. OBJECTIVES: To evaluate objectively the influence of bilateral subthalamic nucleus stimulation on gait in Parkinson disease and to compare it with the effects of levodopa treatment. METHODS: Ten patients underwent bilateral subthalamic nucleus stimulation. The preoperative and postoperative (3 months after surgery) clinical gait disturbances, as well as spatial and temporal gait parameters, were analyzed in off and on-drug conditions. The gait analysis was performed using a video motion analysis system (optoelectronic VICON system; Oxford Metrics, Oxford, England). RESULTS: In the off condition, there was an improvement after surgery for the total motor score and the gait subscore. In the on-drug condition, there was an improvement in levodopa-induced dyskinesias and the motor score, whereas the gait subscore was unchanged. For the gait parameters measured by the video motion analysis system system, there was also an improvement in the off condition and to a lesser extent in the on-drug condition. CONCLUSIONS: Our method allowed exact quantification of the benefit of surgery on gait parameters. Compared with the levodopa treatment, the effect of stimulation on gait kinematic parameters seems to be qualitatively similar but quantitatively different with a lower benefit on gait velocity and stride length. Concerning the pathophysiology of gait troubles in Parkinson disease, the deficit in control of stride length would be the fundamental deficit. The study underlines the possible role of the subthalamic nucleus on the stride length regulation.
The abilities of the human visual system to perform metrical judgements (comparison of lengths, estimation of angles...) involve the existence of some geometrical structure in the visual perceptual space. The question arises whether this geometrical structure is rigidly determined or is subject to adaptive changes. We have tried to answer the question by using a paradigm in which subjects are exposed to a vertically lengthened visual world and then asked to compare simultaneously presented lengths and to evaluate angles between two lines. Their perceptual responses clearly indicate a plastic adaptation to the deformed environment, though the adaptation was never complete after several days of continuous exposure to strong (25%) lengthening. For a maximum time of exposure of 7 days the rate of adaptation was found to be roughly independent of the initial degree of optical distortion. Visuomanual coordination was also investigated in these subjects, but the responses were less conclusive in this case, because of the high inter-subject variability.
The authors suggest a unified system of designation of type--sizes of surgical suture materials of various nature and structure, which removes the existing discrepancy between the numbering of foreign and Soviet threads as well as of Soviet threads produced by different enterprises of the country. Introduction of the new system of metric sizes of the suture threads will allow surgeons to be properly orientated in the choice of the necessary suture material and make easier the work of services engaged in the development and realization of surgical suture materials.
This paper gives a survey of urodynamic data that may be used for evaluating functional aspects of the bladder and its excretory tract. The different parameters are physically defined. Units of the International System are used in the dimensional formulae, which facilitates the establishment of relations between these parameters. The so-called urethral drag can be derived from the pressure law of Blasius. The calculation is as follows: urethral drag = vesical pressure/(maximum urethral discharge). This value is proportional to the true vesical resistance in a physical sense.
A quantitative taxonomy of primate striatal neurons was elaborated on the basis of the morphology of Golgi-impregnated neurons. Dendritic arborizations were reconstructed from serial sections and digitized in three dimensions by means of a video computer system. Topological, metrical, and geometrical parameters were measured for each neuron. Groups of neurons were isolated by using uni- and multidimensional statistical tests. A neuronal species was defined as a group of neurons characterized quantitatively by a series of nonredundant parameters, differing statistically from other groups, and appearing as a separate cluster in principal component analysis. Four neuronal species were isolated: (1) the spiny neuronal species (96% of striatal neurons) characterized by spine-free proximal dendrites (up to 31 microns) and spine-laden distal dendrites, which are more numerous, shorter, and less spiny in the human than in the monkey, (2) the leptodendritic neuronal species (2%) characterized by a small number of long, thick, smooth, and sparsely ramified dendrites, (3) the spidery neuronal species (1%) characterized by very thick dendritic stems and a large number of varicose recurrent distal processes, and (4) the microneuronal species (1%) characterized by numerous short, thin, and beaded axonlike processes. All striatal neurons give off a local axonal arborization. The size and shape of cell bodies were analyzed quantitatively in Golgi material and in materials treated for Nissl-staining, immunohistochemical demonstration of parvalbumin and histochemical demonstration of acetylcholinesterase. Only three types were distinguishable: small, round cell bodies corresponding to either spiny neurons or microneurons, medium-size elongated cell bodies, which were parvalbumin-immunoreactive and corresponded to leptodendritic neurons, and large round cell bodies, which were acetylcholinesterase-positive and corresponded to spidery neurons. Thorough analysis of previously elaborated classifications revealed that spidery neurons do not exist in rats and cats and that large cholinergic neurons in these species correspond to leptodendritic neurons. From this, it can be assumed that the dendritic domain of striatal cholinergic neurons is considerably smaller in primates than in other species. Computer simulations based on both the frequency of each neuronal species and their three-dimensional dendritic morphology revealed that the striatum consists of two intertwined dendritic lattices: a fine-grain lattice (300-600 microns) formed by the dendritic arborizations of spiny, spidery, and microneurons, and a large-grain lattice (1,200 microns) formed by the dendritic arborizations of leptodendritic neurons. This suggests that cortical information can be processed in the striatum through two different systems: a fine-grain system that would conserve the precision of the cortical input, and a large-grain system that would blur it.
A major international movement is in progress to extend metrication using the International System of Units. Significantly involved is the field of medicine. Extensive changes adopted abroad now appear in foreign medical literature, and physicians in the United States commonly are unprepared to interpret medical information from abroad because the data are reported in unfamiliar terms. The system has broad immediate and future implications to American physicians.
Saccadic as well as smooth pursuit movements were studied by means of electro-oculograms in a group of 14 patients affected by cerebellar diseases. Ten patients had cerebellar atrophies, and four had undergone surgery for cerebellar tumors. Loss of gain of the pursuit system and metric alteration of saccades were the most striking abnormalities observed. Dysmetria was shown to be related to the amplitude of the movement and to the sector of the perimeter within which the movement occurs (movements occurring in the more eccentric sector were more disturbed). A tendency to produce saccades slower than normal was noted in patients affected by olivopontocerebellar atrophy. The clinical and pathophysiological significance of this finding is discussed with particular reference to Wadia-Swaami hereditary ataxia.
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