Preliminary report on the hydrography and oyster growing conditions in Choctawhatchee Bay, July 11-13, 1961

The hydrographic conditions in an estuary such as Choctavhatchee Bay, are complex and dynamic. Temperature and salinity measurements taken at any estuarine sampling station are subject to wide fluctuation depending on local tide and weather conditions. In this respect, the following report is only a preliminary indication of the hydrographic conditions existing in Choctawhatchee Bay while this data is being collected. Choctawhatchee Bay is approximately 32 miles long and from three and a half to six miles wide. Large portions of the western half of Choctawhatchee Bay are militarily restricted. The unrestricted area from Valpariso south to Buccaroo Point receives large volumes of treated sewage from Eglin Air Force Base and associated housing developments. The Florida State Board of Health considers the oysters in this area to be polluted.Since the primary purpose of this survey was to ascertain the optimum oyster growing and harvesting areas, only the eastern half of the bay was surveyed. Conclusions of that survey are reported. (10pp.

Changes in extracellular pH during electrical stimulation of isolated rat vagus nerve

Double-barrelled pH-sensitive micro-electrodes were used to record changes of extracellular pH during repetitive stimulation of isolated rat vagus nerves. It was found that a small initial alkaline shift was followed by a prolonged acidification. The acidification was correlated in time with the poststimulus undershoot of the extracellular K+ activity and with the recovery phase of the nerve conduction velocity. In the presence of ouabain, the acid component of the pH change was completely abolished (indicating a metabolic origin), whereas the alkaline component remained unaltered. These pH changes were too small to make a significant contribution to the activity-related changes in conduction velocity of the vagal C-fibres

The limitations of speech control: perceptions of provision of speech-driven environmental controls

This study set out to collect data from assistive technology professionals about their provision of speech-driven environmental control systems. This study is part of a larger study looking at developing a new speech-driven environmental control system

Y coupled terahertz quantum cascade lasers

Here we demonstrate a Y coupled terahertz (THz) quantum cascade laser (QCL) system. The two THz QCLs working around 2.85 THz are driven by independent electrical pulsers. Total peak THz output power of the Y system, with both arms being driven synchronously, is found to be more than the linear sum of the peak powers from the individual arms; 10.4 mW compared with 9.6 mW (4.7 mW + 4.9 mW). Furthermore, we demonstrate that the emission spectra of this coupled system are significantly different to that of either arm alone, or to the linear combination of their individual spectra.Comment: 9 pages, 3 figure

Reversible Mode Switching in Y coupled Terahertz Lasers

Electrically independent terahertz (THz) quantum cascade lasers (QCLs) are optically coupled in a Y configuration. Dual frequency, electronically switchable emission is achieved in one QCL using an aperiodic grating, designed using computer-generated hologram techniques, incorporated directly into the QCL waveguide by focussed ion beam milling. Multi-moded emission around 2.9 THz is inhibited, lasing instead occurring at switchable grating-selected frequencies of 2.88 and 2.92 THz. This photonic control and switching behaviour is selectively and reversibly transferred to the second, unmodified QCL via evanescent mode coupling, without the transfer of the inherent grating losses

Early-warning indicators for rate-induced tipping

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.A dynamical system is said to undergo rate-induced tipping when it fails to track its quasi-equilibrium state due to an above-critical-rate change of system parameters. We study a prototypical model for rate-induced tipping, the saddle-node normal form subject to time-varying equilibrium drift and noise. We find that both most commonly used early-warning indicators, increase in variance and increase in autocorrelation, occur not when the equilibrium drift is fastest but with a delay. We explain this delay by demonstrating that the most likely trajectory for tipping also crosses the tipping threshold with a delay, and therefore, the tipping itself is delayed. We find solutions of the variational problem determining the most likely tipping path using numerical continuation techniques. The result is a systematic study of the most likely tipping time in the plane of two parameters, distance from tipping threshold and noise intensity