Use of photoacoustic excitation and laser vibrometry to remotely detect trace explosives.

In this paper, we examine a laser-based approach to remotely initiate, measure, and differentiate acoustic and vibrational emissions from trace quantities of explosive materials against their environment. Using a pulsed ultraviolet laser (266 nm), we induce a significant (>100 Pa) photoacoustic response from small quantities of military-grade explosives. The photoacoustic signal, with frequencies predominantly between 100 and 500 kHz, is detected remotely via a wideband laser Doppler vibrometer. This two-laser system can be used to rapidly detect and discriminate explosives from ordinary background materials, which have significantly weaker photoacoustic response. A 100 ng/cm2 limit of detection is estimated. Photoablation is proposed as the dominant mechanism for the large photoacoustic signals generated by explosives.

Intertrochanteric fractures of the hip treated with the hip compression screw: analysis of problems.

Seventy-five patients were treated for intertrochanteric hip fractures with the hip compression screw. There were 4 cases in which the lag screw was inserted twice into the femoral head. Three of these patients had a poor result due to superolateral migration and extrusion of the lag screw. The fact that the lag screw is large in comparison to the femoral head makes double placement dangerous. Satisfactory guide wire placement is essential for a one time, precise insertion of the lag screw into the femoral head. The use of a threaded tip guide wire minimizes the chance of it falling out when withdrawing the reamer or tap. If the position of a lag screw is unacceptable, it seems better to insert a flanged nail rather than a second screw in a second track.

Tuberculosis in a rheumatoid patient. A case report.

A 72-year-old white woman with seropositive rheumatoid arthritis subsequently developed polyarticular tuberculosis. Clinical and radiographic evidence of deterioration of the right knee and left elbow was erroneously attributed to progressive rheumatoid arthritis. The diagnosis of a tuberculous infection was unduly delayed. Failure to recognize this infection might have been disastrous if a total knee arthroplasty had been performed as planned. This case illustrates the importance of awareness of other possible origins of joint destruction and infection in rheumatoid patients with rapid deterioration of joint function.