[1] We present a methodology to obtain frequencydependent relative site amplification factors using ambient seismic noise. We treat a seismic network or array as a forced damped harmonic oscillator system where each station responds to a forcing function obtained from frequencywavenumber beams of the ambient noise field. A network or array beam is necessary to estimate the forcing function. Tak...

TO THE EDITOR—I read with interest the article by Farrin Manian regarding the role of postoperative factors in surgical site infections (SSIs) [1]. I agree with Dr Manian that, although the majority of SSIs are almost certainly determined during surgery, there are definitely factors after the patient leaves the operating room that can lead to infection. Dr Manian cites several references regard...