Acoustical Imaging and Holography Seventh International Symposium

I am going to report briefly on the Acoustical Imaging and Holography Conference that was concluded yesterday in Chicago. These conferences were started in 1967, and are concerned primarily with ultrasonics and visualization techniques as applied to medicine, nondestructive evaluation, sonar, seismic analysis and acoustic microscopy

Flaw Detection and Characterization in Ceramics with the Scanning Laser Acoustic Microscope (SLAM)

The high resolving power coupled with the real time capability of the SLAM make it a useful technique for characterization of materials including ceramics. The elastic structure of·ceramics is often dependent upon the details of the fabrication process, e.g., sintering, hot pressing, amount of. binder, etc .. Accordingly, acoustic micrographs and acoustic interferograms which reveal characteristic sonic transmission patterns and sonic velocity variations, respectively, can be used to nondestructively evaluate ceramics to ensure material uniformity. In addition, the ability to nondestructively detect flaws and inclusions is important in fracture toughness studies and in the evaluation of finished components

High Resolutional Real Time Acoustic Microscopy

A commercially available scanning-laser-acoustic-microscope {SLAM) has been developed which provides new and unique analytical capabilities for materials science and non-destructive testing. By employing 100 MHz acoustic waves to create images, the elastic microstructure of complex materials is visualized directly. The acoustic micrographs which contain 2 x 104 image points, are displayed on a real time TV monitor. The sample remains accessible to the investigator during the procedure and stressing fixtures can be employed. Dynamic activities can be recorded either on movie film or video tape. There are two acoustic imaging modes which appear to be essential for flaw and defect characterization. The first mode displays the acoustic transmission level through the sample (normal mode) and the second mode displays fringes related to the acoustic phase (interference mode). The presence of a defect within a sample may be evidenced by a change in transmission level or a change in phase or both. The nature of the defect (e.g. high density inclusion or void) can be determined through the combined analysis of the interference and normal mode micrographs. The SLAM technique has been applied to a wide variety of materials including ceramics, metals, glasses, polymers, etc. Defect localization down to 25 μm has been achieved. Samples can be systematically searched, area by area, by simply repositioning the part on the stage of the microscope and observing the acoustic image on the TV monitor

Lunar surface dynamics: Some general conclusions and new results from Apollo 16 and 17

Exposure ages of Apollo 17 rocks as measured by tracks and the Kr-Kr rare gas method are reported. Concordant ages of 22 - or + 1 million year (my) are obtained for the station 6 boulder sample 76315. This value is interpreted as the time when the station 6 boulder was emplaced in its present position. Reasonable agreement is also obtained by the two methods for another station 6 boulder, sample 76015. Discordant ages (respectively 5 and 28 my by the track and rare gas methods) are obtained for the station 7 boulder sample, 77135, indicating that the boulder was emplaced at least 5 my ago. The 72 my exposure age of 75035, in general agreement with previous measurements of approximately 85 my for another Camelot boulder, may well date the formation of Camelot. Rock 76015 was split and one surface exposed to the sky through a very small solid angle

Acoustic Microscopy of Ceramics

The scanning laser acoustic microscope (SLAM) is applied to the problem of nondestructive testing of ceramic materials. The employment of a very high resolution ultrasonic imaging instrument provides capabilities which supplement ultrasonic pulse-echo testing. In addition, by means of showing a picture of the flaw, the SLAM technique provides its own capabilities which alleviate some of the limitations of other techniques. Flaws of various types are documented in this paper

Scanning Laser Acoustic Microscope Visualization of Solid Inclusions in Silicon Nitride

The Scanning Laser Acoustic Microscope (SLAM) operating at a frequency of 100 MHz is used to characterize solid inclusions in silicon nitride. Ten, seven millimeter thick discs, with 100 and 400 micron implanted inclusions are analyzed. We find that the images of a solid inclusion are characterized by a bright high transmission central zone, a well defined dark boundary and a characteristic diffraction ring pattern. These image features differentiate solid inclusions from pores and voids which may also be encountered in the samples. The images of the implanted flaws were generally found to be larger than anticipated. This can be understood in terms of the divergence of the sound due to diffraction and due to lens action of the curved boundary of the flaw. Our initial observations suggest that accurate estimates of defect size may be obtaiRable from a more complete analysis of SLAM micrographs

Differentiation of Various Flaw Types in Ceramics Using the Scanning Laser Acoustic Microscope

High frequency acoustic imaging represents a powerful technique for the nondestructive evaluation of optically opaque materials. In this report the Scanning Laser Acoustic Microscope (SLAM) is used to detect and characterize flaws in ceramics. SLAM micrographs showing typical examples of cracks, laminar flaws, porosity and solid inclusions. are presented. The various flaw types are easily differentiated on the basis of their characteristic acoustic signatures. The importance of an imaging approach to the nondestructive evaluation of ceramics is demonstrated

Nanowire-based All Oxide Solar Cells

We present an all-oxide solar cell fabricated from vertically oriented zinc oxide nanowires and cuprous oxide nanoparticles. Our solar cell consists of vertically oriented n-type zinc oxide nanowires, surrounded by a film constructed from p-type cuprous oxide nanoparticles. Our solution-based synthesis of inexpensive and environmentally benign oxide materials in a solar cell would allow for the facile production of large-scale photovoltaic devices. We found that the solar cell performance is enhanced with the addition of an intermediate oxide insulating layer between the nanowires and the nanoparticles. This observation of the important dependence of the shunt resistance on the photovoltaic performance is widely applicable to any nanowire solar cell constructed with the nanowire array in direct contact with one electrode

A pilot open label, single dose trial of fenobam in adults with fragile X syndrome

ObjectiveA pilot open label, single dose trial of fenobam, an mGluR5 antagonist, was conducted to provide an initial evaluation of safety and pharmacokinetics in adult males and females with fragile X syndrome (FXS).MethodsTwelve subjects, recruited from two fragile X clinics, received a single oral dose of 50-150 mg of fenobam. Blood for pharmacokinetic testing, vital signs and side effect screening was obtained at baseline and numerous time points for 6 h after dosing. Outcome measures included prepulse inhibition (PPI) and a continuous performance test (CPT) obtained before and after dosing to explore the effects of fenobam on core phenotypic measures of sensory gating, attention and inhibition.ResultsThere were no significant adverse reactions to fenobam administration. Pharmacokinetic analysis showed that fenobam concentrations were dose dependent but variable, with mean (SEM) peak values of 39.7 (18.4) ng/ml at 180 min after the 150 mg dose. PPI met a response criterion of an improvement of at least 20% over baseline in 6 of 12 individuals (4/6 males and 2/6 females). The CPT did not display improvement with treatment due to ceiling effects.ConclusionsClinically significant adverse effects were not identified in this study of single dose fenobam across the range of dosages utilised. The positive effects seen in animal models of FXS treated with fenobam or other mGluR5 antagonists, the apparent lack of clinically significant adverse effects, and the potential beneficial clinical effects seen in this pilot trial support further study of the compound in adults with FXS