High-energy picosecond pulses from a 2850 nm fiber amplifier.

We report the demonstration of a 2850 nm diode-pumped Ho3+, Pr3+ co-doped fluoride fiber amplifier that delivers pulses with an average power of 2.45 W, 122 µJ energy, and 500 ps duration at a repetition rate of 20 kHz. To the best of our knowledge, the average power and pulse energy are the highest to be obtained from a sub-nanosecond fiber source operating in the 3 µm spectral region. The amplifier is seeded by an optical parametric generation source and is pumped around 915 nm using widely available InGaAs laser diodes.

Polarization-switchable Q-switched DFB fiber laser.

A polarization switchable Q-switched distributed feedback (DFB) fiber laser is presented. This what we believe to be a new Q-switching method allows one to obtain linearly polarized laser emission in either x or y direction. The principle of this method is based on a variable birefringent phase shift induced by a lateral stress applied at a precise location along a fiber Bragg grating by a specially designed hyper-elastic device. A piezoelectric actuator controls the amount of stress delivered to the fiber, thus allowing a precise and rapid tuning of the cavity Q-factor.

High power handling shape memory alloy optical fiber connector.

We present a novel shape memory alloy-based optical fiber splicing device that can provide robust, low loss, and high power handling splices between single-mode fibers of identical or entirely different glass compositions. The achieved splice loss was as low as 0.12 dB between two SMF-28 fibers with an average value of 0.23 dB. To the best of our knowledge, this is the first demonstration of a purely mechanical splicing device that can withstand optical powers in excess of 10 W with various combinations of silica and fluoride fibers. The device can be used in moderate to high power all-fiber components, especially those involving junctions unsuitable to fusion splicing, such as fiber lasers and amplifiers based on fluoride, chalcogenide, or microstructured fibers.

Caffeine as an adjuvant to ibuprofen in treating childhood headaches.

In adults, caffeine has been shown to enhance the effectiveness of most analgesics, including ibuprofen. This double-blind cross-over pilot study evaluated the effect of ibuprofen and caffeine compared with ibuprofen and placebo in 12 children with headaches. Patients completed diaries for both headaches. Outcome measures included a five-faces severity scale, a measure of clinical disability, and a scale of pain severity. Comparison of the cumulative response scores revealed a trend toward a greater response to ibuprofen-caffeine treatment of headaches (P = 0.14, P = 0.09, and P = 0.07 for the three measures, respectively). Further larger studies are needed to confirm this effect and to identify potential responders.

The economics of escape behaviour in the pea aphid, Acyrthosiphon pisum.

Pea aphids have several alternative responses to the detection of alarm pheromone produced by conspecifics. One of these, dropping from the feeding site to the ground, is potentially costly owing to the risk of desiccation-induced mortality on the ground before another host plant can be reached. Both dropping and walking from the feeding site incur a cost due to lost feeding opportunity. The aphids' decision as to which anti-predator tactic to use should be sensitive to the costs of their behaviour. Consequently, aphids should be less likely to drop when the risk of desiccation is higher, and less likely to drop or walk when the lost opportunity cost is higher. We tested these predictions by manipulating climatic severity (temperature and humidity) and host quality, respectively. As predicted, aphids are less likely to drop or walk in response to pheromone when feeding on high quality than on low quality hosts, and less likely to drop when the environment is hot and dry than when it is more benign. The latter is true whether the aphids are feeding on real or simulated leaves. Since all aphids were of the same clone, these results show that individual aphid genotypes possess the ability to adaptively modify their escape behaviour with changes in prevailing conditions. A number of other behavioural observations in the aphid literature may be interpreted in an economic or cost-benefit framework. The approach holds considerable promise for understanding many aspects of the anti-predator behaviour of aphids and other animals.

Intraoperative femoral nerve stimulation in evaluation of patellar tracking: tourniquet effects and catheter placement.

BACKGROUND: Dynamic intraoperative assessment of patella tracking utilizes femoral nerve stimulation to contract the quadriceps muscles in assessing the proper distance to transfer the tibial tubercle during distal realignment procedures for patellofemoral instability. PURPOSE: We describe the effects of tourniquet inflation and catheter placement on intraoperative femoral nerve stimulation for assessment of patellar tracking. METHODS: Percutaneous electromyographic (EMG) needles were placed into the quadriceps and sartorius muscles to monitor muscle activity and changes in amplitude threshold (mA) required for femoral nerve stimulation with increasing tourniquet inflation times. Eleven patients used ultrasound for catheter placement and ten were manually placed based upon body landmarks. RESULTS: Tourniquet application time correlated positively with the change in amplitude threshold required to generate muscle contraction. Patients had an average four-fold increase in required stimulus amplitude from the baseline thresholds (pre-tourniquet inflation) to final thresholds (tourniquet inflated) with a two-hour tourniquet inflation time. The use of ultrasound for catheter placement significantly decreased the baseline amplitude required in comparison with catheters placed without ultrasound, (p = 0.0330). CONCLUSIONS: Increased tourniquet inflation times require greater stimulus amplitude to generate quadriceps muscle contraction. Ultrasound guidance for catheter placement can provide femoral nerve stimulation at low amplitudes.