Effects of electrical charging on the mechanical Q of a fused silica disk

We report on the effects of an electrical charge on mechanical loss of a fused silica disk. A degradation of Q was seen that correlated with charge on the surface of the sample. We examine a number of models for charge damping, including eddy current damping and loss due to polarization. We conclude that rubbing friction between the sample and a piece of dust attracted by the charged sample is the most likely explanation for the observed loss.Comment: submitted to Review of Scientific Instrument

Compact cavity-dumped Q-switched Er: YAG laser

Published 13 September 2016Abstract not availableLachlan Harris, Myles Clark, Peter Veitch, and David Ottawa

Power scalable TEM(oo) CW Nd: YAG laser with thermal lens compensation

We present finite-element analyzes and experimental results to validate our approach for building high-power single-mode Nd:YAG lasers. We show that the thermooptical and thermomechanical properties of a slab laser can be controlled. This is essential for the use of the proposed unstable resonator. We include demonstration of an efficient subscale laser operating at 20 W TEM00.D. Mudge, M. Ostermeyer, P. J. Veitch, J. Munch, B. Middlemiss, D. J. Ottaway and M. W. Hamilto

The Melanocortin-4 Receptor Integrates Circadian Light Cues and Metabolism

The melanocortin system directs diverse physiological functions from coat color to body weight homoeostasis. A commonality among melanocortin-mediated processes is that many animals modulate similar processes on a circannual basis in response to longer, summer days, suggesting an underlying link between circadian biology and the melanocortin system. Despite key neuroanatomical substrates shared by both circadian and melanocortin-signaling pathways, little is known about the relationship between the two. Here we identify a link between circadian disruption and the control of glucose homeostasis mediated through the melanocortin-4 receptor (Mc4r). Mc4r-deficient mice exhibit exaggerated circadian fluctuations in baseline blood glucose and glucose tolerance. Interestingly, exposure to lighting conditions that disrupt circadian rhythms improve their glucose tolerance. This improvement occurs through an increase in glucose clearance by skeletal muscle and is food intake and body weight independent. Restoring Mc4r expression to the paraventricular nucleus prevents the improvement in glucose tolerance, supporting a role for the paraventricular nucleus in the integration of circadian light cues and metabolism. Altogether these data suggest that Mc4r signaling plays a protective role in minimizing glucose fluctuations due to circadian rhythms and environmental light cues and demonstrate a previously undiscovered connection between circadian biology and glucose metabolism mediated through the melanocortin system

Stabilization of injection-locked lasers using spatial mode interference

We report the use of spatial-mode-interference, or tilt-locking, for the active stabilization of injection-locking of a Nd:YAG laser. We show that this control scheme is robust and adds negligible frequency noise to the injection-locked laserOttaway, D.J.; Gray, M.B.; Shaddock, D.A.; Hollitt, C.; Veitch, P.J.; Munch, J.; McClelland, David Ernes

Observation on a bloom of Gyrodinium aureolum Hulbert on the south coast of Ireland, summer 1976, associated with mortalities of littoral and sub-littoral organisms

In late July and early August 1976, kills of lugworm (Arenicola marina (L.)) and other marine life were reported from several areas of the south coast of Ireland. These reports were investigated and further field observations were made. The mortalities were associated with a bloom of the naked dinoflagellate Gyrodinium aureolum Hulbert. The possible origins of the bloom and its movement along the coast are discussed

Sea anemones may thrive in a high CO2 world

Increased seawater pCO 2, and in turn 'ocean acidification' (OA), is predicted to profoundly impact marine ecosystem diversity and function this century. Much research has already focussed on calcifying reef-forming corals (Class: Anthozoa) that appear particularly susceptible to OA via reduced net calcification. However, here we show that OA-like conditions can simultaneously enhance the ecological success of non-calcifying anthozoans, which not only play key ecological and biogeochemical roles in present day benthic ecosystems but also represent a model organism should calcifying anthozoans exist as less calcified (soft-bodied) forms in future oceans. Increased growth (abundance and size) of the sea anemone (Anemonia viridis) population was observed along a natural CO 2 gradient at Vulcano, Italy. Both gross photosynthesis (P G) and respiration (R) increased with pCO 2 indicating that the increased growth was, at least in part, fuelled by bottom up (CO 2 stimulation) of metabolism. The increase of P G outweighed that of R and the genetic identity of the symbiotic microalgae (Symbiodinium spp.) remained unchanged (type A19) suggesting proximity to the vent site relieved CO 2 limitation of the anemones' symbiotic microalgal population. Our observations of enhanced productivity with pCO 2, which are consistent with previous reports for some calcifying corals, convey an increase in fitness that may enable non-calcifying anthozoans to thrive in future environments, i.e. higher seawater pCO 2. Understanding how CO 2-enhanced productivity of non- (and less-) calcifying anthozoans applies more widely to tropical ecosystems is a priority where such organisms can dominate benthic ecosystems, in particular following localized anthropogenic stress. © 2012 Blackwell Publishing Ltd

Cryogenic, conduction cooled, end pumped, zigzag slab laser, suitable for power scaling

Thermo mechanical and thermo optical properties of Yb:YAG improve significantly at cryogenic temperatures. We present the first end pumped, zigzag slab Yb:YAG geometry, which is cryogenically conduction cooled, robust, and power scalable. © OSA 2012.M. Ganija, D. Ottaway, P. Veitch, and J. Munc