Photon statistics anomalies in adiabatic transfer between two cavity modes

Adiabatic transfer between two degenerate cavity modes is investigated theoretically using a counter-intuitive pulse sequence. Several measures of successful state transfer are shown to correlate strongly with anomalous values of the photon statistics of the initial mode. The detailed behaviour of theses anomalies originate from the way the state approaches vacuum and their features are found to give a good indication of the effciency and robustness of the state transfer.     

Reduced irrigation and rootstock effects on vegetative growth,yield and its components,and leaf physiological responses of Shiraz

Background and Aims: The study investigated whether rootstocks can modify grapevine responses to reduced irrigation. Methods and Results: Drip-irrigated Shiraz vines on eight rootstocks were subjected to industry standard and 30% reduced irrigation regimes over four seasons. Reducing irrigation decreased pruning weights and yield, but did not consistently affect irrigation water use index (IWUI). It increased leaf Δ¹³C. Reduced irrigation and elevated vapour pressure deficit (VPD) were associated with decreases in leaf water potential (ψ_l), leaf stomatal conductance and assimilation rate. Reducing irrigation raised leaf transpiration efficiency, whereas elevated VPD lowered it. These effects of reduced irrigation were independent of rootstock. Vines grafted to 101-14 had a higher ψ_l and achieved the highest yield and IWUI. The yields of vines grafted to Ramsey, Schwarzmann and 140 Ruggeri were also high. Vines grafted to 101-14, Ramsey and 1103 Paulsen had the higher rates of leaf assimilation. Rootstock did not affect Δ¹³C. Conclusion: The gain in leaf transpiration efficiency caused by reducing irrigation was not associated with a gain in IWUI. Rootstocks 101-14, Ramsey, Schwarzmann and 140 Ruggeri achieved higher yields and IWUI under both standard and reduced irrigation regimes. Significance of the Study: Among grafted vines growing on saline soil but receiving non-saline irrigation water and subject to a 30% reduction in irrigation, the yield responses of vines grafted on rootstocks rated as having good drought tolerance were the same as those of vines grafted on rootstocks rated as having poor drought tolerance.     

The Use of SI Units

It is intended that, generally, the SI system of units shall be used in the Society's publications, in accordance with accepted rules. It is important to appreciate that SI units have evolved, that further additions and amendments may be made, and, particularly, that there is still lack of uniformity in interpretation and application of the system. It may be argued that the Society, through its Publications Committee, should take a lead in proposing and adopting one well-considered procedure. On the other hand, it can be maintained that what is required is a clear exposition of the “state of the art”, and that it is this that the Society can and should provide to guide readers of its publications and contributors to them. This paper, sponsored by the Publications Committee, is designed to serve as a guide to SI units and the use of the SI system. It owes its inception to MrR. Murphy of the Department of Industrial Chemistry, The Queen's University, Belfast. It was his “Notes on the Use of SI Units”, submitted to the Committee, which led to the decision that a more general paper on SI units should be produced. A large part of the information regarding SI equivalents for cgs (centimetre-gram-second) and ft-lb-sec (foot-pound-second) units is taken from his paper. The Committee is much indebted to him for this. It is also much obliged to him for the many helpful and instructive comments he made following very thorough reading of the paper in draft.     

Soil water depletion rates under large grapevines

Over two consecutive seasons, daily rates of change in the water content of the top 120 cm of soil were calculated for sample sites located at 50 cm from the butts of 12 Colombard vines on Ramsey rootstock which were part of a controlled deficit irrigation experiment. Records were selected where the rate represented a change due solely to depletion of soil water by grapevine evapotranspiration (ΔS_ET). Soil water availability was quantified as a logarithmic transformation of the absolute value of the root-weighted measure of soil matric potential. ΔS_ET was negatively correlated with soil water availability and positively correlated with reference crop evapotranspiration (ETo). At very high values of soil water availability, i.e. soil matric potential between -8 and -16 kPa, and after the canopy was fully developed, ΔS_ET had a 1:1 relationship with ETo. When root-weighted soil matric potential was greater than -16 kPa, the mean values of the ratio of soil water depletion rate to reference crop evapotranspiration (ΔS_ET/ETo), varied from 0.1 to 1.2 for 30-day periods between bud burst and leaf fall. Considering the full set of measurements, ΔS_ET/ETo was highly negatively correlated with soil water availability for all 30-day periods except those less than 60 days from bud burst. In the period 150 to 179 days after bud burst, 70% of the variance in ΔS_ET/ETo was accounted for by regression on soil water availability for values of root-weighted soil matric potential between -8 and -100 kPa. During this period a fall in root-weighted soil matric potential from -10 to -42 kPa was associated with a decline in the value of ΔS_ET/ETo from 1.3 to 0.6. At both high and low values of ETo, the ratio of ΔS_ET/ETo fell linearly with declining soil water availability. The changes in values of midafternoon stem water potential and stomatal conductance associated with this decline in ΔS_ET/ETo are discussed.     

Digital tracker with output feedback: application to aircraft controls

A linear-quadratic output-feedback approach is given for designing digital servo-control systems of specified structure. The result is digital controllers that have a sensible structure based on classical control theory, in contrast to standard LQR design using state feedback plus an observer. The correct initial conditions for determining the LQ tracker output-feedback gains are not uniformly distributed as is traditionally assumed, but are shown to be explicitly given in terms of the step command magnitude. Both pole and zero placement are used to optimize the performance index. Arbitrary systems are treated, not only those with integrators in the forward paths, by adding a term to the performance index that weights the steady-state error. The approach works even if the system is non-minimum-phase. Necessary conditions are derived that may be used in a gradient-based routine to determine the optimal digital control gains. The approach does not rely on redesign of a continuous control system using techniques like the bilinear transformation, but uses direct discrete-time design. An aircraft digital command augmentation system is included as a sample design.