Effects of rodent poisoning on Powelliphanta traversi

Rat predation is a threat to lowland Powelliphanta traversi (giant predatory land snail), and we have shown that ‘press’ poisoning of rodents (rats and mice) using brodifacoum baits significantly reduces rat abundance relative to non-poisoned areas. The effect on P. t. traversi was evident by the increase in population size, mainly due to adult migration, and a decrease in rat-damaged shells, for areas where rat predation occurs. A longer-term study is required to determine whether prolonged rat control benefits P. t. traversi recruitment. Mouse control was inadequate with use of brodifacoum baits. We document a concomitant rise in bird predation of P. traversi when rat abundance was reduced, suggesting that control of both is necessary to make real conservation gains. However, mortality related to other factors was more common than that caused by predators, possibly due to the habitat drying out periodically. We suggest that low recruitment rates, predator targeting of juveniles (i.e. blackbirds, song thrush and possibly mice and hedgehogs) and poor habitat conditions are the main threats to survival of lowland P. traversi

Habitat use of Tradescantia fluminensis by Powelliphanta traversi

This study was initiated owing to concern that removal of the invasive ground cover, Tradescantia fluminensis, might adversely effect the rare, giant predatory land snail, Powelliphanta traversi. Of 18 sites surveyed in the Horowhenua District, seven sites provide habitat for P. traversi and do not contain Tradescantia. Five colonies of P. traversi are affected by Tradescantia, these are: Waiopehu Scenic Reserve, Prouse’s Bush, Kimberley Scenic Reserve, Ohau River Bush, and Hillas Covenant. Tradescantia infestation at these sites varies from heavy (Prouse’s Bush) to forest edge only (Hillas Covenant). Overall, Tradescantia affects a small proportion of snail habitat in the Horowhenua District. Our study of P. traversi at Prouse’s Bush, using harmonic radar to follow long-term movements and cotton tracks for short-term movements, indicates that this snail commonly occurs under Tradescantia, sometimes exclusively, and that many of the snails move regularly between leaf litter and this weed. Moreover, Tradescantia provides an important refuge for juvenile snails at Prouse’s Bush. Hence, removing Tradescantia from this site would have a detrimental impact on P. traversi. Graduated control of Tradescantia and concomitant replacement with native ground cover could be of mutual benefit to P. traversi and other ground-dwelling invertebrates

``Plug and play'' systems for quantum cryptography

We present a time-multiplexed interferometer based on Faraday mirrors, and apply it to quantum key distribution. The interfering pulses follow exactly the same spatial path, ensuring very high stability and self balancing. Use of Faraday mirrors compensates automatically any birefringence effects and polarization dependent losses in the transmitting fiber. First experimental results show a fringe visibility of 0.9984 for a 23km-long interferometer, based on installed telecom fibers.Comment: LaTex, 6 pages, with 2 Postscript figures, Submitted to Applied Physics Letter

A dynamic simulation model for possum and gorse control on a farm woodlot

Managers of farm woodlots in New Zealand are confronted by two major problems: possums and gorse. If these remain uncontrolled then they have a severe impact on the returns from farm woodlots. This paper presents a system dynamics model which has been developed to assist in the analysis of control measures for managing gorse and possums on a farm woodlot in the Makara Valley, Wellington. The model has four main sectors: a tree growth module for radiata pine; a growth module for gorse; a module for the stock of possums present in the habitat; and a module of financial indicators. A number of control experiments are presented which indicate the long term financial and physical consequences of different gorse and possum control measures. The model clearly demonstrates the complex nature of the dynamic behaviour of a system involving biological and environmental factors (ie possums, gorse and trees) and human intervention (in terms of silviculture, and possum and gorse control)

Low Timing Jitter Detector for Gigahertz Quantum Key Distribution

A superconducting single-photon detector based on a niobium nitride nanowire is demonstrated in an optical-fibre-based quantum key distribution test bed operating at a clock rate of 3.3 GHz and a transmission wavelength of 850 nm. The low jitter of the detector leads to significant reduction in the estimated quantum bit error rate and a resultant improvement in the secrecy efficiency compared to previous estimates made by use of silicon single-photon avalanche detectors.Comment: 11 pages, including 2 figure

Phenomena exposure from the large scale gas injection test (Lasgit) dataset using a bespoke data analysis toolkit

The Large Scale Gas Injection Test (Lasgit) is a field-scale experiment designed to study the impact of gas buildup and subsequent migration through an engineered barrier system. Lasgit has a substantial experimental dataset containing in excess of 21 million datum points. The dataset is anticipated to contain a wealth of information, ranging from long-term trends and system behaviours to small-scale or ‘second-order’ features. In order to interrogate the Lasgit dataset, a bespoke computational toolkit, designed to expose difficult to observe phenomena, has been developed and applied to the dataset. The preliminary application of the toolkit, presented here, has resulted in a large number of phenomena being indicated/quantified, including highlighting of second-order events (small gas flows, perturbations in stress/pore-water sensors, etc.) and quantification of temperature record frequency content. Localized system behaviour has been shown to occur along with systematic aberrant behaviours that remain unexplained

A novel quantum key distribution scheme with orthogonal product states

The general conditions for the orthogonal product states of the multi-state systems to be used in quantum key distribution (QKD) are proposed, and a novel QKD scheme with orthogonal product states in the 3x3 Hilbert space is presented. We show that this protocol has many distinct features such as great capacity, high efficiency. The generalization to nxn systems is also discussed and a fancy limitation for the eavesdropper's success probability is reached.Comment: 4 Pages, 3 Figure

Precise calculation of parity nonconservation in cesium and test of the standard model

We have calculated the 6s-7s parity nonconserving (PNC) E1 transition amplitude, E_{PNC}, in cesium. We have used an improved all-order technique in the calculation of the correlations and have included all significant contributions to E_{PNC}. Our final value E_{PNC} = 0.904 (1 +/- 0.5 %) \times 10^{-11}iea_{B}(-Q_{W}/N) has half the uncertainty claimed in old calculations used for the interpretation of Cs PNC experiments. The resulting nuclear weak charge Q_{W} for Cs deviates by about 2 standard deviations from the value predicted by the standard model.Comment: 24 pages, 8 figure

Ten years of pulling: Ecosystem recovery after long‐term weed management in Garry oak savanna

Ecosystem restoration is the practice of assisting recovery in degraded ecological communities. The aims of restoration are typically broad, involving the reinstatement of composition, structure, function, and resilience to disturbances. One common restoration tactic in degraded urban systems is to control invasive species, relying on passive restoration for further ecosystem‐level recovery. Here, we test whether this is an effective restoration strategy in Garry oak savanna, a highly threatened and ecologically important community in the North American Pacific Northwest. In urban savanna patches surrounding Victoria, British Columbia, community members have been actively removing aggressive invasive exotic species for over a decade. Based on vegetation surveys from 2007, we tested ecosystem changes in structure, composition, and resilience (i.e., functional redundancy and response diversity) across 10 years of varied management levels. We expected higher levels of invasive species management would correspond with improvements to these ecosystem metrics. However, management explained little of the patterns found over the 10‐year‐period. Woody encroachment was a complicated process of native and exotic invasion, while resilience and compositional changes were most closely tied with landscape connectivity. Thus, though invasive species management may prevent further degradation, active restoration strategies after removal are likely required for recovery of the ecosystem

Measurement of the 6s - 7p transition probabilities in atomic cesium and a revised value for the weak charge Q_W

We have measured the 6s - 7p_{1/2,3/2} transition probabilities in atomic cesium using a direct absorption technique. We use our result plus other previously measured transition rates to derive an accurate value of the vector transition polarizability \beta and, consequently, re-evaluate the weak charge Q_W. Our derived value Q_W=-72.65(49) agrees with the prediction of the standard model to within one standard deviation.Comment: 4 pages, 2 figure