Introduction: During vocal fold vibration, the medial surface of both folds forms a convergent shape during opening and a divergent shape during closing. A greater maximum divergence angle is associated with greater closing forces which will increase the closing speed of the glottis. An increased closing speed results in a greater acoustic intensity and greater vocal efficiency. Indentation testing showed that as the strain increases, the inferior aspect of the folds becomes stiffer than the superior aspect, resulting in the vertical stiffness gradient (VSG). We hypothesize that a reduction of the vertical stiffness gradient will reduce the maximum divergence angle.Methods: Four excised canine larynges were tested. Stress-strain curves of the superior and inferior aspects of the fold in the mid membranous plane of the baseline larynges were taken using the indentation method. Calcium hydroxylapatite (CaHA) crystals were then injected into the superior aspect of the fold. The stress-strain tests were repeated. Particle imaging velocimetry (PIV) of the intraglottal velocity fields was performed in three larynges at different subglottal pressures in the mid coronal plane for the baseline and CaHA-injected larynges.Results: CaHA injection reduced the inferior-superior stiffness gradient in all larynges. The maximal divergence angle was markedly reduced. In some cases, there was not a divergent angle.Discussion: Marked reduction of the vertical stiffness gradient significantly reduces the maximum divergence angle. Clinical implications will be discussed.

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718HUSS, HICKS, AND ALLEN J. SPACECRAFT which are used in real time by the flight crew and by the ground-control team to further enhance flight safety. From the standpoint of mission design, it never has been necessary to sacrifice mission objectives for crew safety or to sacrifice crew safety to achieve mission objectives. The general concepts that were established during Project Mercury for abort procedures and for flight-control limits have proven applicable in subsequent manned space-flight programs. Through the proper definition of mission-design-related constraints and through the establishment of trajectory-control limits and operational procedures, sufficient flight safety has been achieved for manned earth-orbital missions. JUNE 1968A model has been devised for computing loads and heat-transfer coefficients due to impingement of greatly underexpanded plumes on adjacent surfaces. Newtonian concepts are used for the load distribution, and an analogy is drawn between the impingement region arid a blunt body with locally similar conditions in order to obtain the heat transfer. Empirical data are not required. Experimental data have been critically examined, and the Newtonian concepts appear to describe the problem if the plume total-to-ambient pressure ratio is sufficiently high and the surface is sufficiently close to the nozzle. These conditions are generally satisfied in spacecraft control systems. Above the minimum pressure ratio, loads and much of the heat transfer are shown to be insensitive to changes in the ambient conditions. Peak heating, however, appears to reach a maximum value before leveling out at some lower value. Effects of scale are noted in the heat transfer. Nomenclature a-a constant, Eq. (7) A = area s, c = sine and cosine, respective!}' c p = exhaust gas specific heat h = heat-transfer coefficient K = radius of curvature L -y distance from plume centerline to body surface at plume origin p, p, T = pressure, density, and temperature generally at some local point in the plume [0] = order of magnitude Rb = body radius s = streamline path length 5 = arc length on body surface V = velocity in the plume x, y, z = right-hand coordinate system originating at the nozzle exit with x axis aligned with plume axis and y axis pointing away from impingement surface a.= cone half-angle y -cone half-angle for conical segments, 0 for other surfaces 6 = angle between velocity vector and plume axis ON -angle between velocity vector and a normal to the body surface M = exhaust gas viscosity £ = body axis 0 = angle from x, y plane measured about body axis, positive counterclockwise 01 = angle body axis makes with nozzle axis, positive counterclockwise 0 2 = angle in y, z plane between y axis and radial to body surface, positive clockwise Subscripts B = base region of the body c = rocket chamber condition cf = centrifugal force correction N = local normal component o = point where pF 2 cos 2 0# is a maximum s = properties along a streamline t = stagnation conditions w = wall conditions 1 = conditions ahead of...

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The various techniques for introducing color into a schlieren system were explored, and all of them were found to have drawbacks such that the added dimension of color in a schlieren has never been utilized for extensive quantitative measurements. An entirely new technique using a diffraction grating to produce the color has been introduced as a modification of the conventional schlieren system. It provides solutions to the problems of sensitivity, range of measurement deflection and undesirable effects of diffraction which have limited the usefulness of color systems in the past. Methods for analyzing a conventional schlieren have been modified for the analysis of a color schlieren result. Surface pressures and flow field analysis for some simple two-dimensional airfoil shapes have been obtained by these color techniques developed here, and the results compare very well with theoretical pressure calculations.