Editorial: Thank You, Gordon Hodgson!

... after four years of dedicated and extremely creative service, Dr. Gordon Hodgson steps down as academic editor of Arctic and Information North. His tenure in this position has been notable in many ways and caps a career in government service and academic life that has touched hundreds of graduate students and aspiring Arctic authors. ... In the trenchant editorials appearing over his by-line, Gordon Hodgson has written his thoughts on arctic sovereignty, the need for a Nobel prize for arctic socio-economic studies, the desirability of creating a circumpolar university and a comprehensive northern on-line library system capable of text retrieval and delivery. ... Whatever the response, Arctic's reader's have come to expect the editorial airing of complex northern issues, and the editorial page will continue under the leadership of our new editor Dr. Karen McCullough. ..

A simple model of EMI-induced timing jitter in digital circuits, its statistical distribution and its effect on circuit performance

A simple model has been developed to characterize electromagnetic interference induced timing variations (jitter) in digital circuits. The model is based on measurable switching parameters of logic gates, and requires no knowledge of the internal workings of a device. It correctly predicts not only the dependence of jitter on the amplitude, modulation depth and frequency of the interfering signal, but also its statistical distribution. The model has been used to calculate the immunity level and bit error rate of a synchronous digital circuit subjected to radio frequency interference, and to compare the electromagnetic compatibility performance of fast and slow logic devices in such a circuit

Treatment of input uncertainty in hydrologic modeling: Doing hydrology backward with Markov chain Monte Carlo simulation

There is increasing consensus in the hydrologic literature that an appropriate framework for streamflow forecasting and simulation should include explicit recognition of forcing and parameter and model structural error. This paper presents a novel Markov chain Monte Carlo (MCMC) sampler, entitled differential evolution adaptive Metropolis (DREAM), that is especially designed to efficiently estimate the posterior probability density function of hydrologic model parameters in complex, high-dimensional sampling problems. This MCMC scheme adaptively updates the scale and orientation of the proposal distribution during sampling and maintains detailed balance and ergodicity. It is then demonstrated how DREAM can be used to analyze forcing data error during watershed model calibration using a five-parameter rainfall-runoff model with streamflow data from two different catchments. Explicit treatment of precipitation error during hydrologic model calibration not only results in prediction uncertainty bounds that are more appropriate but also significantly alters the posterior distribution of the watershed model parameters. This has significant implications for regionalization studies. The approach also provides important new ways to estimate areal average watershed precipitation, information that is of utmost importance for testing hydrologic theory, diagnosing structural errors in models, and appropriately benchmarking rainfall measurement devices

Characterization of resistance breaking Meloidogyne incognita - like populations using lectins, monoclonal antibodies and spores of Pasteuria penetrans

Six clones de #Meloidogyne, provenant de populations récoltées en Côte d'Ivoire et qui possèdent un phénotype estérasique particulier (codé pVI) ainsi que la faculté de briser la résistance conférée par le gène #Mi, ont été comparés à #M. incognita à l'aide de différentes sondes. Le marquage à l'aide de lectines des exsudats amphidiaux de juvéniles de second stade ne permet pas de distinguer ces lignées de #M. incognita. Des souches de #Pasteuria penetrans permettent de les distinguer et mettent aussi en évidence une certaine variabilité au sein de ce groupe. Deux anticorps monoclonaux, spécifiques de #M. incognita indiquent que les clones de phénotype pVI partagent certains caractères avec #M. incognita$ mais aussi qu'ils s'en distinguent. (Résumé d'auteur

Effect of logic family on radiated emissions from digital circuits

Radiated emissions were measured for simple digital circuits designed to operate with various logic families. Emissions in the near and far field were found to depend both on the circuit layout and the choice of logic family. However, the difference in peak emissions between any two logic families was found to be independent of circuit layout. The greatest difference in peak emissions was between high-speed 74ACT logic and low-speed 4000 CMOS logic devices, with a mean value of approximately 20 dB. Emissions from a more complex circuit were compared with the measurements on simple loop circuits. Test circuits were used to measure the propagation delay, the rise and fall times, the maximum operating frequency and the transient switching currents between two successive logic gates for each logic family. Empirical formulas have been derived that relate relative peak emissions to these switching parameters. It is hoped that these will assist designers to assess the effect of choice of logic family on electromagnetic compatibility

Plasma formation from ultracold Rydberg gases

Recent experiments have demonstrated the spontaneous evolution of a gas of ultracold Rydberg atoms into an expanding ultracold plasma, as well as the reverse process of plasma recombination into highly excited atomic states. Treating the evolution of the plasma on the basis of kinetic equations, while ionization/excitation and recombination are incorporated using rate equations, we have investigated theoretically the Rydberg-to-plasma transition. Including the influence of spatial correlations on the plasma dynamics in an approximate way we find that ionic correlations change the results only quantitatively but not qualitatively

Neutral Plasma Oscillations at Zero Temperature

We use cold plasma theory to calculate the response of an ultracold neutral plasma to an applied rf field. The free oscillation of the system has a continuous spectrum and an associated damped quasimode. We show that this quasimode dominates the driven response. We use this model to simulate plasma oscillations in an expanding ultracold neutral plasma, providing insights into the assumptions used to interpret experimental data [Phys. Rev. Lett. 85, 318 (2000)].Comment: 4.3 pages, including 3 figure