Entanglement of orbital angular momentum for the signal and idler beams in parametric down-conversion

We calculate the anticipated correlation between measurements of the orbital angular momentum of the signal and idler beams for parametric down-conversion. These calculations apply to the experiments where the orbital angular momentum state is measured by the use of computer-generated holograms. Displacement of these holograms with respect to the beam axis allows the measurement of superpositions of Laguerre—Gaussian modes. The correlations between such superposition modes of the signal and idler beams show their entanglement and could be used for Bell-type tests of nonlocality.     

Comparison of numerical methods for solving Liapunov matrix equations†

A numerical comparison is made of most published methods for solving the linear matrix equations which arise when a quadratic form Liapunov function is applied to a constant linear system (continuous or discrete, real or complex). Generally, for the real equations direct methods are satisfactory for systems of order ten or less, whereas for larger order systems iterative methods (based upon expressing the solution in terms of an infinite series) are to be preferred. For the complex equations the most convenient numerical method uses an explicit representation for the solution in terms of the eigenvalues and vectors of the system matrix. If the system matrix is in companion form then algorithms taking account of this structure offer minor improvements.     

Retrodiction as a tool for micromaser field measurements

We use retrodictive quantum theory to describe cavity field measurements by successive atomic detections in the micromaser. We calculate the state of the micromaser cavity field prior to detection of sequences of atoms in either the excited or ground state, for atoms that are initially prepared in the excited state. This provides the POM elements, which describe such sequences of measurements.     

Adaptive forecasting techniques

The class of exponential smoothing models which vary the values of their parameters to adapt to changing conditions in a time series are referred to as adaptive forecasting techniques. In this article criteria for evaluating forecasting models are presented and the features of a simple exponential smoothing model that are exploited by the adaptive techniques are discussed. Several adaptive forecasting schemes are described and classified, and examples of the performance of these techniques are presented.     

A low magnetic field gyrotron—gyro-magnetron

A gyrotron device operating at a substantially reduced magnetic field is proposed. The operating beam voltage is moderately low and the waveguide circuit resembles the anode block of a conventional magnetron. The dispersion relationship is given. A proof of principle experiment is suggested.     

Fluctuations in light intensity modulate ion fluxes from grape berry mesocarp: direct evidence from microelectrode ion flux estimations

Canopy architecture and light spectral composition have long been considered as important factors determining grape juice acidity and K+concentrations. In this study, we provide direct evidence that fluctuations in intensity of light incident on berry tissue may significantly modulate net ion fluxes from and into the berry mesocarp. The MIFE technique was used to quantify fluxes of K+, H+, and Ca²⁺in Pinot Noir and Emperor grape berries. Transition from dark to light induced complex multiphase kinetics of K+flux resulting in significant shift towards net K+uptake by the peripheral mesocarp tissue. When light intensity was modulated in a square-wave manner with a period of 5 to 15 min (mimicking periodicity of natural variations during a typical autumn day in Hobart), K+flux oscillated with the same frequency and a magnitude of about 100 nmol/m²s. Changes in H+and Ca²⁺fluxes showed high positive (R = 0.8) and negative (R = 0.9) correlation, respectively, with those in K+. To the best of our knowledge, these data from excised fruit provide the first reported evidence that light directly incident on bunches may modulate apoplasmic pH and K+concentration in grape. Possible underlying mechanisms are discussed.     

Shoot growth on de-fruited grapevines: a physiological indicator for irrigation scheduling

A simple and inexpensive but biologically meaningful way of gauging grapevine water status that can guide irrigation scheduling is described. The growth rate of shoots on grapevines from which all fruit has been removed (de-fruited shoot growth) is presented as a sensitive indicator of vine and soil water status and we propose a procedure for irrigation scheduling based on monitoring de-fruited shoot growth and soil moisture. These guidelines were derived from corresponding measurements of de-fruited shoot growth and soil moisture potential that were undertaken at frequent intervals (generally 1 to 2 days). De-fruited shoot growth rate between 48 and 71 days after anthesis was linearly correlated with the mean moisture potential of the soil at depths of 60 cm and 90 cm in the centre of the drip-irrigated zone (r = 0.94). De-fruited shoot growth effectively ceased when soil moisture potential at these points had decreased to -70 kPa, although much of the root zone would have been even drier. De-fruited shoot growth thus shows an integrated and dynamic response to vine-available soil water that could aid irrigation scheduling.     

Cognitive Set and Food Acceptance

A consumer panel was randomly divided into two groups. Each group was asked to rate the acceptance of an almond nut dairy bar on five consecutive days and to complete a 30-item questionnaire about their current physical state. For the positive group, all the statements were positive (e.g., “I feel great”), while for the negative group all the statements were negative (e.g., “I feel tired”). Acceptance ratings of the dairy bars were significantly higher for the positive group than for the negative group but questionnaire responses did not change over the five days of the experiment.