U.S. East Coast Trough Indices at 500 hPa and New England Winter Climate Variability

Using monthly gridded 500-hPa data, two synoptic indices are defined to better understand the principle mechanisms controlling intraseasonal to multiannual winter climate variability in NewEngland (NE). The “trough axis index” (TAI) is created to quantify the mean longitudinal position of the common East Coast pressure trough, and the “trough intensity index” (TII) is calculated to estimate the relative amplitude of this trough at 42.5°N. The TAI and TII are then compared with records for NE regional winter precipitation, temperature, and snowfall with the goal of understanding physical mechanisms linking NE winter climate with regional sea surface temperatures (SST), the North Atlantic Oscillation (NAO), and the Pacific–North American (PNA) teleconnection pattern. The TAI correlates most significantly with winter precipitation at inland sites, such that a western (eastern)trough axis position is associated with greater (lower) average monthly precipitation. Also, significant correlations between the TAI and both NE regional SSTs and the NAO suggest that longitudinal shifting of the trough is one possible mechanism linking the North Atlantic with NE regional winterclimate variability. The NE winter temperature is significantly correlated with the TII, regional SSTs, and the NAO. While the PNA also correlates with the TII, NE winter climate variables are apparently unrelated to the PNA index

Coherent control of microwave pulse storage in superconducting circuits

Coherent pulse control for quantum memory is viable in the optical domain but nascent in microwave quantum circuits. We show how to realize coherent storage and on-demand pulse retrieval entirely within a superconducting circuit by exploiting and extending existing electromagnetically induced transparency technology in superconducting quantum circuits. Our scheme employs a linear array of superconducting artificial atoms coupled to a microwave transmission line.Comment: 13 pages, 4 figures and some supplementary materia

Nonlinear optical thresholding in a 4-Channel OCDMA system via two-photon absorption

We demonstrate the use of a Two-Photon Absorption based detector in an OCDMA system. This detector provides a significant performance improvement over standard linear detection

Pulse pedestal suppression using four-wave mixing in an SOA

Experimental results are presented demonstrating how four-wave mixing in a semiconductor optical amplifier can be used to remove pulse pedestals introduced due to nonlinearities which occur upon pulse propagation in an optical system. Such pedestals would degrade the performance of an optical time-division-multiplexed system due to coherent interaction between channels. An improvement of the temporal pulse suppression ratio to greater than 30 dB is achieved regardless of the level of the pulse pedestal on the input signal. This improvement takes place simultaneously with wavelength conversion and compression of the optical pulse

Development of design criteria for an electrochemical water reclamation system

Electrochemical system design to recover water from human urin

Numerical analysis of four-wave mixing between 2 ps mode-locked laser pulses in a tensile-strained bulk SOA

A numerical model of four-wave mixing between 2-ps pulses in a tensile-strained bulk semiconductor optical amplifier is presented. The model utilizes a modified Schrodinger equation to model the pulse propagation. The Schrodinger equation parameters such as the material gain first and second order dispersion, linewidth enhancement factors and optical loss coefficient are obtained using a previously developed steady-state model. The predicted four-wave mixing pulse characteristics show reasonably good agreement with experimental pulse characteristics obtained using frequency resolved optical gating

The relationship of marine stratus to synoptic conditions

The marine stratus which persistently covered most of the eastern Pacific Ocean, had large clear areas during the FIRE Intensive Field Operations (IFO) in 1987. Clear zones formed inside the large oceanic cloud mass on almost every day during the IFO. The location and size of the clear zones varied from day to day implying that they were related to dynamic weather conditions and not to oceanic conditions. Forecasting of cloud cover for aircraft operations during the IFO was directed towards predicting when and where the clear and broken zones would form inside the large marine stratus cloud mass. The clear zones often formed to the northwest of the operations area and moved towards it. However, on some days the clear zones appeared to form during the day in the operations area as part of the diurnal cloud burn off. The movement of the clear zones from day to day were hard to follow because of the large diurnal changes in cloud cover. Clear and broken cloud zones formed during the day only to distort in shape and fill during the following night. The field forecasters exhibited some skill in predicting when the clear and broken cloud patterns would form in the operations area. They based their predictions on the analysis and simulations of the models run by NOAA's Numeric Meteorological Center. How the atmospheric conditions analyzed by one NOAA/NMC model related to the cloud cover is discussed

Experimental investigation of the impact of optical injection on vital parameters of a gain-switched pulse source

An analysis of optical injection on a gain-switched distributed feedback (DFB) laser and its impact on pulse parameters that influence the performance of the pulse source in high-speed optical communication systems is presented in this paper. A range of 10 GHz in detuning and 5 dB in injected power has been experimentally identified to attain pulses, from an optically injected gain-switched DFB laser, with durations below 10 ps and pedestal suppression higher than 35 dB. These pulse features are associated with a side mode suppression ratio of about 30 dB and a timing jitter of less than 1 ps. This demonstrates the feasibility of using optical injection in conjunction with appropriate pulse compression schemes for developing an optimized and cost-efficient pulse source, based on a gain-switched DFB laser, for high-speed photonic systems

Analysis and design of a modular multilevel converter with trapezoidal modulation for medium and high voltage DC-DC transformers

Conventional dual active bridge topologies provide galvanic isolation and soft-switching over a reasonable operating range without dedicated resonant circuits. However, scaling the two-level dual active bridge to higher dc voltage levels is impeded by several challenges among which the high dv/dt stress on the coupling transformer insulation. Gating and thermal characteristics of series switch arrays add to the limitations. To avoid the use of standard bulky modular multilevel bridges, this paper analyzes an alternative modulation technique where staircase approximated trapezoidal voltage waveforms are produced; thus alleviating developed dv/dt stresses. Modular design is realized by the utilization of half-bridge chopper cells. Therefore, the analyzed converter is a modular multi-level converter operated in a new mode with no common-mode dc arm currents as well as reduced capacitor size, hence reduced cell footprint. Suitable switching patterns are developed and various design and operation aspects are studied. Soft switching characteristics will be shown to be comparable to those of the two-level dual active bridge. Experimental results from a scaled test rig validate the presented concept

Exploring the anthelmintic properties of Australian native shrubs with respect to their potential role in livestock grazing systems

We measured in vitro anthelmintic activity in extracts from 85 species of Australian native shrub, with a view to identifying species able to provide a degree of worm control in grazing systems. Approximately 40% of the species showed significant activity in inhibiting development of Haemonchus contortus larvae. The most active extracts showed IC50 values of 60–300 mg/ml. Pre-incubation with polyvinylpolypyrrolidine removed the activity from some extracts, implicating tannins as the bioactive agent, while in other cases the pre-incubation had no effect, indicating the presence of other anthelmintic compounds. Plant reproductive maturity (onset of flowering or fruiting) was associated with increasing anthelmintic activity in some species. Variability was observed between plants of the same species growing in different environments, while variation between individual plants of the same species within a single field suggests the existence of distinct chemotypes. Significant activity against adult H. contortus worms in vitro was also demonstrated in a limited number of extracts tested against this life stage. Our study indicates that there is potential for Australian native shrubs to play an anthelmintic role in grazing systems, and highlights some plant biology factors which will need to be considered in order to maximize any anthelmintic effects.A. C. Kotze, J. O’Grady, J. Emms, A. F. Toovey, S. Hughes, P. Jessop, M. Bennell P. E. Vercoe and D. K. Revel