Dynamic diamond anvil cell (dDAC): a novel device for studying the dynamic-pressure properties of materials

We have developed a unique device, a dynamic diamond anvil cell (dDAC), which repetitively applies a time-dependent load/pressure profile to a sample. This capability allows studies of the kinetics of phase transitions and metastable phases at compression (strain) rates of up to 500 GPa/s (approximately 0.16 s(-1) for a metal). Our approach adapts electromechanical piezoelectric actuators to a conventional diamond anvil cell design, which enables precise specification and control of a time-dependent applied load/pressure. Existing DAC instrumentation and experimental techniques are easily adapted to the dDAC to measure the properties of a sample under the varying load/pressure conditions. This capability addresses the sparsely studied regime of dynamic phenomena between static research (diamond anvil cells and large volume presses) and dynamic shock-driven experiments (gas guns, explosive, and laser shock). We present an overview of a variety of experimental measurements that can be made with this device.     

Simultaneous nonlinear absorption and index effects in the propagation of intense TEA CO2 laser pulses through CDF3

Changes in the beam profile of the CO2 laser 10R(26) line, caused by transmission through, and absorption by, CDF3 were studied using an array of pyroelectric detectors. During the propagation of the laser beam through CDF3, nonlinear absorption and self-defocusing of the beam have both been determined from measurements of the effect on the exit beam of fluence, radiant energy, CDF3 pressure, transmission cell length, and distance from the exit of the cell to the detector array.     

Creep of CaO/MgO refractories

The creep properties of a standard doloma brick (containing 40% MgO) and a magnesia-enriched doloma product (containing 60% MgO) have been compared with the behaviour of CaO-MgO samples having compositions and microstructures similar to those of the pellet raw materials used for manufacture of the fired doloma refractories. The creep strength is shown to be improved not only by magnesia enrichment but also by reducing the impurity levels, particularly the Fe₂O₃ content.     

Thermal shock of ß-alumina with zirconia additions

Sodium-alumina electrolyte tubes were prepared from spray dried precursor powders with additions of 2, 5, 10 and 15 wt % ZrO₂ made by the sodium zirconate route. The thermal shock behaviour of ring segments cut from the tubes was examined by quenching into water at 0° C. At the 2% ZrO₂ level the dispersed ZrO₂ particle size was low, <0.5m, and the tetragonal phase was retained. For higher weight fractions, particle coarsening during the-alumina sintering schedule was extensive and the large particles transformed to monoclinic on cooling. At the 15% ZrO₂ level the-alumina had a slightly reduced strength and high resistance to thermal shock and to thermal shock damage, quenching into water from 800° C effecting only a 43% reduction in strength. These observations are consistent with the effects of microcracking in the vicinity of second phase ZrO₂ particles.     

Mode matching for a passive resonant ring laser gyroscope

An analytical method of matching the mode of an input laser to the lowest-order mode of a passive resonant ring laser gyro is described, as are the steps in determining the location and focal length of cylindrical mode matching lenses. Results were obtained with no mode matching, with a compromise spherical lens, with horizontal mode matching only, and with the proper cylindrical mode matching lenses. Compared with no mode matching, the latter case shows that the amplitude of the lowest-order mode is increased approximately 2.5 times. In addition, the number and intensity of higher-order modes are reduced to near zero, and the relative intensity of the lowest-order mode to the higher-order mode increased from approximately 5 to approximately 60 times greater.     

Fibrous myopathy. A rheumatic complication of drug abuse

A progressive fibrous myopathy may result from chronic intramuscular drug abuse. This complication may mimic other rheumatic disorders and early recognition may prevent disability. The patient described here presented with fixed flexion and extension contracture of hips and knees, respectively, after abusing meperidine and other agents for 3 years. Soft tissues of thighs and buttocks were "wood hard," EMG showed absence of action potentials in affected muscles, and biopsy revealed extensive replacement of muscle with dense, acellular fibrous tissue. Possible mechanisms are discussed.