Increase in community-acquired methicillin-resistant Staphylococcus aureus at a Naval Medical Center.

A retrospective review of methicillin-resistant Staphylococcus aureus isolates from the Naval Medical Center, San Diego, for the years 1994 through 1997, found that the annual number of community-acquired MRSA isolates increased during the period. These outpatient isolates were more likely than inpatient isolates to be sensitive to a greater number of antibiotics.

Measurement of ultrashort pulse durations by interferometric autocorrelation: influence of various parameters.

The interferometric autocorrelation technique for the measurement of ultrashort pulse durations is studied in detail. Effects of group velocity mismatch, group velocity dispersion, fundamental depletion, and pulse shape are carefully examined. A simple semianalytical calculation is developed that takes group velocity mismatch into account that can be used to predict the validity of this technique with real experimental parameters. A more complete calculation is also presented to analyze the effects of fundamental depletion or phase mismatch. Finally, the influence of the pulse shape is considered and a simple experimental procedure is proposed to determine whether a pulse is transform limited.

Sub-20-fs tunable pulses in the visible from an 82-MHz optical parametric oscillator.

We have produced pulses tunable in the 590-666-nm range, with durations down to 13 fs, using an 82-MHz Ti:sapphire second-harmonic-pumped, high-bandwidth, beta-barium borate optical parametric oscillator in a fused-silica prism group-delay-dispersion-compensated, six-mirror folded ring cavity.

UV enhancement and erasure of second-harmonic generation in germanosilicate fibers.

Exposure of germanosilicate fibers to cw UV light at 351.1 nm from an argon-ion laser is shown to have dramatic effects on the seeded preparation of the material for second-harmonic generation. We show that 100 microW of 351.1-nm radiation for periods as short as 20 s leads to large, permanent enhancements of the second-harmonic conversion efficiency. The UV exposure provides an increase of 7 orders of magnitude in final conversion efficiency in one regime of IR preparation intensity and allows preparation with cw IR and second-harmonic wavelengths. In addition, the 351.1-nm wavelength was shown to erase the chi((2)) grating much more efficiently than did 514.5-nm radiation.

Explaining the optical fuse.

Experiments show that the characteristic periodic damage pattern that results from the optical fuse can be produced by purely thermal means by heating the fiber to temperatures in the 700-1000 degrees C range in the absence of light. The nature of the damage region bubbles suggests local temperatures high enough to soften the fiber core. The additional energy required may be supplied by an exothermic mechanism. Consideration of activated interstitial diffusion of various potential oxidants: unoxidized sites with O(2) could be responsible.