An ecophysiological approach to crop losses exemplified in the system wheat, leaf rust, and glume blotch

The motive of the author to embark upon the research reported here was the need to develop new concepts to approach the problem of crop losses, and eventually the problem of their prevention by means of disease control and plant breeding. The introduction of ecophysiology as an approach, explained above, was the first result. An ecophysiological treatment of processes like growth and development of plants in health and disease necessitates adjustments of current thoughts on experimental techniques and on organization in research (Van der Wal and Cowan, 1974).In order to measure plant or aegricorpus responses concurrently with environmental factors in climate chamber and field experiments during periods Of months, a great variety of instruments had to be bought, modified, or devised. The climate chamber had to be adjusted to allow for high light intensities with a view to growing wheat under conditions approximating those of early summer in the Netherlands; the yield of the spring wheat 'Kolibri' was c. 0.5 kg.m -2, which is nearly equivalent to the average field production of the country. Regulations for the prevention and control of contamination by aphids and mildew without any use of chemicals were issued after detailed experimentation (Van der Wal, unpubl.). Several instruments have been developed, usually with the help of others; this has led to two publications (Schurer and Van der Wal, 1972; Tegelaar and Van der Wal, 1974). These efforts resulted in the experimental designs described in the appendix. Field experiments, conducted in the same period as the climate chamber experiments reported here, will be published later. It is felt that the techniques to record growth of pathogens are still inadequate.The results reported in the appendix show that the 'state' of the plant at the time of infection is a major determinant of the plant's future behaviour, which plant breeders and pathologists can express in terms of resistance and tolerance. The conceptual framework presented above may contribute to a future revision of crop husbandry and crop protection practices

Energy consumption and constant current operation in membrane capacitive deionization

Membrane capacitive deionization (MCDI) is a water desalination technology based on applying a cell voltage between two oppositely placed porous electrodes sandwiching a spacer channel that transports the water to be desalinated. In the salt removal step, ions are adsorbed at the carbon–water interface within the micropores inside the porous electrodes. After the electrodes reach a certain adsorption capacity, the cell voltage is reduced or even reversed, which leads to ion release from the electrodes and a concentrated salt solution in the spacer channel, which is flushed out, after which the cycle can start over again. Ion-exchange membranes are positioned in front of each porous electrode, which has the advantage of preventing the co-ions from leaving the electrode region during ion adsorption, while also allowing for ion desorption at reversed voltage. Both effects significantly increase the salt removal capacity of the system per cycle. The classical operational mode of MCDI at a constant cell voltage results in an effluent stream of desalinated water of which the salt concentration varies with time. In this paper, we propose a different operational mode for MCDI, whereby desalination is driven by a constant electrical current, which leads to a constant salt concentration in the desalinated stream over long periods of time. Furthermore, we show how the salt concentration of the desalinated stream can be accurately adjusted to a certain setpoint, by either varying the electrical current level and/or the water flow rate. Finally, we present an extensive dataset for the energy requirements of MCDI, both for operation at constant voltage and at constant current, and in both cases also for the related technology in which membranes are not included (CDI). We find consistently that in MCDI the energy consumption per mole of salt removed is lower than that in CDI. Within the range 10–200 mM ionic strength of the water to be treated, we find for MCDI a constant energy consumption of 22 kT per ion removed. Results in this work are an essential tool to evaluate the economic viability of MCDI for the treatment of saltwater

Effect of electrode thickness variation on operation of capacitive deionization

In capacitive deionization (CDI) water is desalinated by applying an electrical field between two porous electrodes placed on either side of a spacer channel that transports the aqueous solution. In this work we investigate the equilibrium salt adsorption and the dynamic development of the effluent salt concentration in time, both as function of spacer and electrode thicknesses. The electrode thickness will be varied in a symmetric manner (doubling both electrodes) and in an asymmetric manner, by doubling and tripling one electrode but not the other. To describe the structure of the electrostatic double layer (EDL) which determines the salt adsorption in the micropores of activated carbons, a modified Donnan-model is set up which successfully describes the data, also for situations of very significant electrode thickness ratios. We develop a generalized CDI transport model accounting for thickness variations, which compares favorably with experimental data for the change of the effluent salt concentration in time. These experiments are aimed at further testing our equilibrium and transport models, specifically the assumption therein that in first approximation, for electrodes made of chemically unmodified activated carbon particles, the EDL structure is independent of the sign of the electronic charge. To investigate the relevance of chemical surface charge we also varied pH of the salt solution flowing into the cell

Time-dependent ion selectivity in capacitive charging of porous electrodes

In a combined experimental and theoretical study, we show that capacitive charging of porous electrodes in multicomponent electrolytes may lead to the phenomenon of time-dependent ion selectivity of the electrical double layers (EDLs) in the electrodes. This effect is found in experiments on capacitive deionization of water containing NaCl/CaCl2 mixtures, when the concentration of Na+ ions in the water is five times the Ca2+-ion concentration. In this experiment, after applying a voltage difference between two porous carbon electrodes, first the majority monovalent Na+ cations are preferentially adsorbed in the EDLs, and later, they are gradually replaced by the minority, divalent Ca2+ cations. In a process where this ion adsorption step is followed by washing the electrode with freshwater under open-circuit conditions, and subsequent release of the ions while the cell is short-circuited, a product stream is obtained which is significantly enriched in divalent ions. Repeating this process three times by taking the product concentrations of one run as the feed concentrations for the next, a final increase in the Ca2+/Na+-ratio of a factor of 300 is achieved. The phenomenon of time-dependent ion selectivity of EDLs cannot be explained by linear response theory. Therefore, a nonlinear time-dependent analysis of capacitive charging is performed for both porous and flat electrodes. Both models attribute time-dependent ion selectivity to the interplay between the transport resistance for the ions in the aqueous solution outside the EDL, and the voltage-dependent ion adsorption capacity of the EDLs. Exact analytical expressions are presented for the excess ion adsorption in planar EDLs (Gouy-Chapman theory) for mixtures containing both monovalent and divalent cations

A change in inflammatory foot print precedes plaque instability: A systematic evaluation of cellular aspects of the adaptive immune response in human atherosclerosis

Transplant surger

Generation of entangled states of two atoms inside a leaky cavity

An in-depth theoretical study is carried out to examine the quasi-deterministic entanglement of two atoms inside a leaky cavity. Two $\Lambda$-type three-level atoms, initially in their ground states, may become maximally entangled through the interaction with a single photon. By working out an exact analytic solution, we show that the probability of success depends crucially on the spectral function of the injected photon. With a cavity photon, one can generate a maximally entangled state with a certain probability that is always less than 50%. However, for an injected photon with a narrower spectral width, this probability can be significantly increased. In particular, we discover situations in which entanglement can be achieved in a single trial with an almost unit probability