The effect of parallel static and microwave electric fields on excited hydrogen atoms

Motivated by recent experiments we analyse the classical dynamics of a hydrogen atom in parallel static and microwave electric fields. Using an appropriate representation and averaging approximations we show that resonant ionisation is controlled by a separatrix, and provide necessary conditions for a dynamical resonance to affect the ionisation probability. The position of the dynamical resonance is computed using a high-order perturbation series, and estimate its radius of convergence. We show that the position of the dynamical resonance does not coincide precisely with the ionisation maxima, and that the field switch-on time can dramatically affect the ionisation signal which, for long switch times, reflects the shape of an incipient homoclinic. Similarly, the resonance ionisation time can reflect the time-scale of the separatrix motion, which is therefore longer than conventional static field Stark ionisation. We explain why these effects should be observed in the quantum dynamics. PACs: 32.80.Rm, 33.40.+f, 34.10.+x, 05.45.Ac, 05.45.MtComment: 47 pages, 20 figure

Principal-Agent Relationships in Agricultural Cooperatives: An Empirical Analysis from Rural Alberta

Cooperatives throughout North America are consolidating at an increasing rate and for a variety of reasons. While many cooperatives merge with others or are acquired to achieve greater economies of scale, several fail due to changes in the external economy, which make them redundant. Often, such redundancy is reflected in a heightened sense of member dissatisfaction. Many argue that such dissatisfaction is likely to arise in cooperatives as a result of principal-agent problems. In order to determine whether or not cooperative managers maintain the same goals as their owners, this study uses data from a member-survey to compare Alberta cooperative members' objectives with those they believe to be held by their cooperatives' managers. An econometric model of the difference between members' expectations and perceptions shows how various socioeconomic variables affect the extent to which these objectives are aligned. The results of this analysis can help cooperative boards design managerial incentive programs to better align their goals with those of the cooperative membership.Agribusiness,

Charmonium excited state spectrum in lattice QCD

Working with a large basis of covariant derivative-based meson interpolating fields we demonstrate the feasibility of reliably extracting multiple excited states using a variational method. The study is performed on quenched anisotropic lattices with clover quarks at the charm mass. We demonstrate how a knowledge of the continuum limit of a lattice interpolating field can give additional spin-assignment information, even at a single lattice spacing, via the overlap factors of interpolating field and state. Excited state masses are systematically high with respect to quark potential model predictions and, where they exist, experimental states. We conclude that this is most likely a result of the quenched approximation.Comment: Fixed typos: normalisation of chi-squared, some operator projections in appendix, missing lattice irrep tabl

Reproducibilty of partial weight bearing

Objectives: To find out whether partial weight bearing can be reproduced and retained. Design: In vivo experiment in normal subjects. Intervention: Training for partial weight bearing (25% of body weight) using bathroom scales. Main outcome measurement: Reproducibility on force platform immediately after training and after 60 min. Results: Twelve subjects were asked to reproduce 25% of their body weight through either the dominant or non-dominant limb on force platform after three practice attempts on bathroom scales with concurrent visual feedback. No feedback was provided after the measurements on force plate. The process was repeated after 1 h without any practice sessions in the interim period to find out if the weight practised could be retained. The mean 0-min reading was found to be 25.9% of body weight while the mean 60-min reading was found to be 24.4%. The p-value for the difference between the two means was found to be 0.3841. Conclusions: This study indicates that partial weight bearing instructions can be quantified and graded. Simple bathroom scales are sufficient to educate the patients and this can be practised at home after an initial period of supervision

Polarization morphology of SiO masers in the circumstellar envelope of the AGB star R Cassiopeiae

Silicon monoxide maser emission has been detected in the circumstellar envelopes of many evolved stars in various vibrationally-excited rotational transitions. It is considered a good tracer of the wind dynamics close to the photosphere of the star. We have investigated the polarization morphology in the circumstellar envelope of an AGB star, R Cas. We mapped the linear and circular polarization of SiO masers in the v=1, J=1-0 transition. The linear polarization is typically a few tens of percent while the circular polarization is a few percent. The fractional polarization tends to be higher for emission of lower total intensity. We found that, in some isolated features the fractional linear polarization appears to exceed 100%. We found the Faraday rotation is not negligible but is ~15 deg., which could produce small scale structure in polarized emission whilst total intensity is smoother and partly resolved out. The polarization angles vary considerably from feature to feature but there is a tendency to favour the directions parallel or perpendicular to the radial direction with respect to the star. In some features, the polarization angle abruptly flips 90 deg. We found that our data are in the regime where the model of Goldreich et al (1973) can be applied and the polarization angle flip is caused when the magnetic field is at close to 55 deg. to the line of sight. The polarization angle configuration is consistent with a radial magnetic field although other configurations are not excluded.Comment: 14 pages, 15 figures. Accepted for publication in MNRA

The behavior of the electron density and temperatue at Millstone Hill during the equinox transition study September 1984

The ionospheric electron density and temperature variations is simulated during the equinox transition study in September 1984 and the results are compared with measurements made at Millstone Hill. The agreement between the modeled and measured electron density and temperature for the quiet day (18 September) is very good but there are large differences on the day of the storm (19 September). On the storm day, the measured electron density decreases by a factor of 1.7 over the previous day, while the model density actually increases slightly. The model failure is attributed to an inadequate increase in the ratio of atomic oxygen to molecular neutral densities in the MSIS neutral atmosphere model, for this particular storm. A factor of 3 to 5 increase in the molecular to atomic oxygen density ratio at 300 km is needed to explain the observed decrease in electron density. The effect of vibrationally excited N sub 2 on the electron density were studied and found to be small

The effect of cattle slurry in combination with nitrate and the nitrification inhibitor dicyandiamide on in situ nitrous oxide and dinitrogen emissions

peer-reviewedA field study was conducted to determine the effect of the nitrification inhibitor dicyandiamide (DCD) on N2O and N2 emissions after cattle slurry (CS) application in the presence of nitrate (NO3) fertiliser on seven different occasions (between March 2009 and March 2011). N2O emissions from CS in the presence of NO3 fertiliser were very high (0.4–8.7% of applied N) over a 20-day period, under mild moist conditions. Emissions were significantly larger from the CS treatment compared to an NH4+-N source, supplying the same rate of N as in the slurry. This study supports the view that organic fertilisers should not be applied at the same time as nitrate-based fertilisers, as significant increases in N2O emissions occur. The average N2O mole fraction (N2O/(N2O + N2)) over all seven application dates was 0.34 for CSNO3 compared to 0.24 for the NH4ClNO3 treatment, indicating the dominance of N2 emissions. The rate of nitrification in CSNO3 was slower than in NH4ClNO3, and DCD was found to be an effective nitrification inhibitor in both treatments. However, as N2O emissions were found to be predominantly associated with the NO3 pool, the effect of DCD in lowering N2O emissions is limited in the presence of a NO3 fertiliser. To obtain the maximum cost-benefit of DCD in lowering N2O emissions, under mild moist conditions, it should not be applied to a nitrate containing fertiliser (e.g. ammonium nitrate or calcium ammonium nitrate), and therefore the application of DCD should be restricted to ammonium-based organic or synthetic fertilisers.This research was funded by the Irish National Development Plan, through the Research Stimulus Fund (RSF 07 519), administered by the Irish Department of Agriculture, Food and the Marine

Using functional near infrared spectroscopy to assess cognitive performance of UAV sensor operators during route scanning

The composition of UAV (Unmanned Aerial Vehicle) crew will sometimes define roles specific to tasks associated with the Ground Control Station (GCS). The sensor operator task is specific to both the type of platform and GCS they are operating, but in many instances the role of this operator is critical in determining mission success. In order to assess mission effectiveness we applied human performance measures that focussed on neurological brain imaging techniques and other physiological biomarkers in conjunction with behavioral data acquired from the sensor operator task. In the execution of the experiment, this included such tasks as route scanning, target detection and positive identification, and the tracking of identified targets. Within the scope of this paper, we reported the preliminary results for the route scanning task. Over the duration of three trials brain activity measures from the prefrontal cortex region were acquired via functional near infrared spectroscopy (fNIRS) in this research study. As the trials progressed, there was a significant difference between low and high performers on the route scanning task as determined by specific biomarkers, namely oxygenated haemoglobin. These findings support previous studies and indicates the benefits of applying neurophysiological measures in order to gain further objective insight into human cognitive performance. The use of fNIRS in this context is also discussed in terms of providing a key benefit in dynamically evaluating human performance in parallel with personalized training for UAV operators

Nonlinear double-diffusive intrusions at the equator

Previous, linear analysis has suggested that observations of interleaving, quasi-horizontal layers in the equatorial oceans may be explained by double-diffusive or inertial instability. Here we describe an idealized, two-dimensional, numerical investigation of the nonlinear development of these instabilities, focusing almost exclusively on the double-diffusive case. We consider the mechanisms for equilibration and maintenance of the interleaving intrusions and perform a thorough sensitivity analysis. Nonlinearity arising from changes in diffusive regime is found to be more important than advective nonlinearity in promoting global equilibration. When variations in effective flux ratio are weak, local constraints prevent equilibration until large amplitudes are reached. When variations in flux ratio with density ratio are allowed, small-scale staircase and mesoscale intrusive instabilities coexist, leading to staircase-like intrusions with sharp, steppy interfaces. Solutions are found to equilibrate at between 3 and 13 times the amplitude where mean salinity gradients overturn. Cross-equatorial diffusivities between 20 and 400 m2 s-1 are found in realistic cases with intrusion lengths of up to 40 km. A modified estimate of the effective cross-equatorial diffusivity based on a balance of lateral advection and vertical diffusion tends to overestimate the sensitivity to the mean horizontal and vertical gradients of salinity and underestimates the sensitivity to the vertical diffusivity but does give values within an order of magnitude of those derived from numerical experiments. For comparison, we give a single example of inertially driven interleaving layers which reach 190 km in length giving cross-equatorial heat fluxes four times larger than realistic doublediffusively driven cases. Although the inertial case is not considered in detail, we speculate that observed interleaving is more likely to be created by inertial than double-diffusive instability