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Advanced high temperature structural materials for the National Aero-Space Plane (NASP) program are subjected to high level thermomechanical loadings during laboratory testing. This paper describes the technical performance of a laser speckle image correlation instrument for obtaining optical strain measurements at elevated temperatures of 1100°C and above. The technical approach to this project involved the development of an optical strain sensor incorporating laser speckle imaging and digital cross-correlation techniques for uni-axial strain and deformation measurements. This PC-based instrumentation system consists of three main modules: three high-resolution, line-scan, charge-coupled device (CCD) cameras with special optics; three electromechanical shutters for triple-beam sequential illuminations by a continuous wave probing laser; two digital signal processing (DSP) system boards and DSP analysis software using Hypersignal-Windows Block Diagram programming modules. Surface strain and deformation measurements along the central axis were performed for nickel-based alloy and silicon-carbide coated carbon-carbon composite samples in a cantilever fixture under thermomechanical loading. The comparative simulation study was performed using analytical/graphical computation of thermomechanically loaded test samples. The experimental test results showed that the acquired speckle images used for the cross-correlation calculations suffered insignificant degradation or drift due to the presence of extreme thermal conditions. This optical strain gage sensor requires no surface preparation or application of micro-indentation marks or targets. The multi-level operating software consists of several modules, each performing a different task such as hardware initiation, image acquisition, digital signal processing, strain/deformation analysis data storage, and graphical presentation. Application of the digital laser speckle cross-correlation method has been extended for in situ monitoring and characterization of laser-processed refractory ceramic coating film formation.

To the Editor. — Subcutaneous heparin injections causing hematomas of the rectus abdominis muscle have been recognized since the institution of low-dose heparin in the 1970s. The article by Tsapatsaris 1 documents this complication. The technique of " subcutaneous" injections is quite variable and deserves some attention in assessing the possible cause of inadvertent intramuscular injection. While I was a member of the US Army Medical Corps from 1973 through 1975, an epidemic of hematomas of the rectus abdominis muscle occurred in patients with recent myocardial infarctions. There was a great deal of concern initially that these patients had acute abdomens until further evaluation elucidated the cause for their abdominal pain. After the recognition of this complication, appropriate injections were carefully made to avoid these complications and no further significant hematomas occurred. There are other possibilities that could explain a hematoma of the rectus abdominis muscle. The technique of injection should

Renal tubular necrosis was observed following intramuscular injections of cephalothin into rats. Lesions were consistently produced with 5.0g/kg and were maximal in severity at the 2nd and 3rd days following injection. Renal tubular necrosis following cephalothin was similar in morphology to that produced by nephrotoxic doses (2.0 g/kg) of cephaloridine. The nephrotoxic potential of cephalothin has been demonstrated in the rat model and caution is urged in using large doses of cephalothin.

The pharmacokinetics of cefaclor and cephalexin were characterized in patients with creatinine clearances ranging from 0 to 147 ml/min. Each of 24 fasted subjects received a single 500-mg oral dose of cefaclor, and 13 of these subjects later received 500 mg of cephalexin. Serum and urine levels of the antibiotics were measured by bioassay. The serum half-lives were highly correlated with corrected creatinine clearance (cefaclor r = 0.92, cephalexin r = 0.94). Linear regression estimates of the half-life of cefaclor were 2.3 h in the anephric patient and 40 min in the patient with a corrected creatinine clearance of 100 ml/min. For cephalexin, corresponding half-lives were 15.4 h and 58 min. We present a dosage nomogram for calculating the appropriate adjustments to the loading dose based on patient weight and maintenence dose based on corrected creatinine clearance.

To the Editor.— The article by Vickery et al in the May 1975 issue of theArchives(135:720-725, 1975) that described the success of the Automated Military Outpatient System (AMOS) project was very comprehensive regarding current practices and effects of the army corpsmen who act as physician's assistants (ie, (AMOSISTS), but it does not focus on the potential medicolegal problems that may evolve. I had the opportunity to implement the AMOS program at Kirk Army Hospital in April 1974, and served as chief of this project until June 1975. Our triage system processed more than 22,000 patients, and the AMOSISTs provided primary care to 9,000 patients during this period. The designers of the program did an excellent job in providing a functional system that provides a high quality of medical care to patients with acute and minor illnesses, while adeptly avoiding areas of maximal malpractice liability. Patient acceptance in our