INTEGRATED WEED CONTROL IN MAIZE.

Integrated pest management has been implemented as a general practice by EU legislation. As weed control actually is the most important crop protection measure in maize for Western Europe, the new legislation will have its impact. The question is of course which systems can be successfully implemented in practice with respect to labour efficiency and economical parameters. During 3 successive growing seasons (2007, 2008, 2009) weed control in maize was evaluated, the main focus was put on different techniques of integrated weed control and was compared with chemical weed control. Additionally, during 4 successive growing seasons (2011, 2012, 2013 and 2014) two objects based on integrated weed control and two objects based on mechanical weed control were compared to about twenty different objects of conventional chemical weed control. One of the objects based on mechanical weed control consisted of treatment with the flex-tine harrow before and after emergence in combination with chemical weed control at a reduced rate in 3-4 leave stage. The second one consisted of broadcast mechanical treatments before and after emergence followed by a final in-row application of herbicides and an inter-row cultivation at 6-7(8) leave stage. All trials were conducted on the Experimental farm of Bottelare HoGent-UGent on a sandy loam soil. Maize was growing in 1/3 crop rotation. The effect on weed growth as well as the economic impact of the different applications was evaluated. Combining chemical and mechanical weed control is a possible option in conventional farming but the disadvantages must be taken into account. A better planned weed control based on the real present weed-population in combination with a carefully thought-out choice of herbicides should also be considered as an IPM--approach.

WEED POPULATION IN RELATION TO CROP ROTATION AND NITROGEN FERTILISATION.

In order to assess the impact of crop rotation and nitrogen fertilisation in an agro system, a long-term field experiment has been established in 2006 at the experimental farm of Ghent University and University College Ghent (Bottelare-Belgium). The trial comprises 11 different crop rotations in combination with four nitrogen fertilizer regimes. The different crop rotations are monoculture of grain- and silage maize, whether or not followed by Italian ryegrass, permanent and temporary grass-clover and six other rotations of maize in combination with potatoes, wheat, fodder beet and peas. Normal crop husbandry measures were taken for each crop. The experiment was set up on a sandy loam soil, according to a strip plot design with 3 replicates. In the course of the experiment, crop rotation was the horizontal factor and fertilizer nitrogen (N) the vertical factor. The effect of crop rotation on yield, disease pressure, soil structure and earthworm abundance were evaluated yearly. In autumn 2013 the weed seed bank was analysed for each plot using the seedling emergence method. The obtained results indicated differences between the different crop rotations.

Chemical weed control in triticale (x Triticosecale Wittmack): review of five years of field experiments.

During five subsequent growing seasons field experiments were carried out at the experimental farm of the University College Ghent (Belgium) to evaluate the selectivity and efficacy of herbicides for chemical weed control in triticale (x Triticosecale Wittmack). The experiments were set up on a sandy loam soil, according to a completely randomised block design with four replicates. Several herbicides and combinations of herbicides were applied pre- and post-emergence, at different rates. The influence of the different treatments on weed diversity, weed density, growth inhibition and chlorosis of the crop and grain yield was studied. Results obtained from these field trials indicated differences between the different treatments.

SWNT array resonant gate MOS transistor.

We show that thin horizontal arrays of single wall carbon nanotubes (SWNTs) suspended above the channel of silicon MOSFETs can be used as vibrating gate electrodes. This new class of nano-electromechanical system (NEMS) combines the unique mechanical and electronic properties of SWNTs with an integrated silicon-based motion detection. Its electrical response exhibits a clear signature of the mechanical resonance of SWNT arrays (120-150 MHz) showing that these thin horizontal arrays behave as a cohesive, rigid and elastic body membrane with a Young's modulus in the order of 1-10 GPa and ultra-low mass. The resonant frequency can be tuned by the gate voltage and its dependence is well understood within the continuum mechanics framework.

Nanotube devices based crossbar architecture: toward neuromorphic computing.

Nanoscale devices such as carbon nanotube and nanowires based transistors, memristors and molecular devices are expected to play an important role in the development of new computing architectures. While their size represents a decisive advantage in terms of integration density, it also raises the critical question of how to efficiently address large numbers of densely integrated nanodevices without the need for complex multi-layer interconnection topologies similar to those used in CMOS technology. Two-terminal programmable devices in crossbar geometry seem particularly attractive, but suffer from severe addressing difficulties due to cross-talk, which implies complex programming procedures. Three-terminal devices can be easily addressed individually, but with limited gain in terms of interconnect integration. We show how optically gated carbon nanotube devices enable efficient individual addressing when arranged in a crossbar geometry with shared gate electrodes. This topology is particularly well suited for parallel programming or learning in the context of neuromorphic computing architectures.

Scaling law in carbon nanotube electromechanical devices.

We report a method for probing electromechanical properties of multiwalled carbon nanotubes (CNTs). This method is based on atomic force microscopy measurements on a doubly clamped suspended CNT electrostatically deflected by a gate electrode. We measure the maximum deflection as a function of the applied gate voltage. Data from different CNTs scale into an universal curve within the experimental accuracy, in agreement with a continuum model prediction. This method and the general validity of the scaling law constitute a very useful tool for designing actuators and in general conducting nanowire-based nanoelectromechanical systems.

Room-temperature ferromagnetic nanotubes controlled by electron or hole doping.

Nanotubes and nanowires with both elemental (carbon or silicon) and multi-element compositions (such as compound semiconductors or oxides), and exhibiting electronic properties ranging from metallic to semiconducting, are being extensively investigated for use in device structures designed to control electron charge. However, another important degree of freedom--electron spin, the control of which underlies the operation of 'spintronic' devices--has been much less explored. This is probably due to the relative paucity of nanometre-scale ferromagnetic building blocks (in which electron spins are naturally aligned) from which spin-polarized electrons can be injected. Here we describe nanotubes of vanadium oxide (VO(x)), formed by controllable self-assembly, that are ferromagnetic at room temperature. The as-formed nanotubes are transformed from spin-frustrated semiconductors to ferromagnets by doping with either electrons or holes, potentially offering a route to spin control in nanotube-based heterostructures.

Effect of different chemical and mechanical defolation methods on the skin quality of potatoes.

Without foliage destruction an efficient harvest is impossible. Potatoes for the fresh market are often harvested when the foliage is still heavy green due to tuber size and starch content that must be limited. Tubers from immature vines are typically very susceptible to skinning and mechanical injury during harvest. Young tubers from immature vines need more time after foliage destruction to set periderm than tubers from senescent vines where the formation of periderm is already started. Spray schemes based on metoxuron, carfentrazone-ethyl and diquat at a dose of 300 g/ha caused slower leaf and stem desiccation. Over the 3 growing seasons it could be concluded that mechanical foliage destruction in combination with carfentrazone-ethyl + mineral oil promoted periderm formation better than the other desiccation schemes tested. A split treatment with diquat at 300 g/ha or carfentrazone-ehtyl + mineral oil followed by a second application of diquat or carfentrazone-ethyl can led to a slower periderm formation and even give secondary growth. A double treatment of diquat (300 g/ha) or carfentrazone-ethyl + mineral oil followed by diquat (600 g/ha) after 3 days gave satisfactory results. Rhizoctonia tuber infection increased with a longer field period after treatment. In general the increase was more pronounced for the spray schemes where skin set of the tubers was less fast.

Field-modulated carrier transport in carbon nanotube transistors.

We have investigated the electrical transport properties of carbon nanotube field-effect transistors as a function of channel length, gate dielectric film thickness, and dielectric material. Our experiments show that the bulk properties of the semiconducting carbon nanotubes do not limit the current flow through the metal/nanotube/metal system. Instead, our results can be understood in the framework of gate and source-drain field induced modulation of the nanotube band structure at the source contact. The existence of one-dimensional Schottky barriers at the metal/nanotube interface determines the device performance and results in an unexpected scaling behavior.

Carbon nanotubes as schottky barrier transistors.

We show that carbon nanotube transistors operate as unconventional "Schottky barrier transistors," in which transistor action occurs primarily by varying the contact resistance rather than the channel conductance. Transistor characteristics are calculated for both idealized and realistic geometries, and scaling behavior is demonstrated. Our results explain a variety of experimental observations, including the quite different effects of doping and adsorbed gases. The electrode geometry is shown to be crucial for good device performance.

Ambipolar electrical transport in semiconducting single-wall carbon nanotubes.

Ambipolar electrical transport is reported in single-wall carbon nanotube (SWNT) field-effect transistors. In particular, the properties of SWNT junctions to TiC are discussed in detail. The carbide-nanotube junctions are abrupt and robust. In contrast to planar junctions, these contacts present low resistance for the injection of both p- and n-type carriers--the apparent barrier height of the junction is modified by the gate field. Thus SWNTs offer the novel possibility of ambipolar Ohmic contacts.

Improvement of malt modification by use of Rhizopus VII as starter culture.

The development of a selected starter culture on malting barley and its effects on malt quality aspects were studied. Application of Rhizopus sporangiospores in a malting process resulted in increased beta-glucanase and xylanase contents of the malting barley and improved starchy endosperm cell-wall degradation. Activation of the sporangiospores and optimization of the inoculation procedure led to a further increase in enzyme levels and to larger and more consistent impacts on cell-wall modification. Whereas the main effect of the starter culture on beta-glucan degradation was observed during malting, a further decrease in beta-glucan during mashing suggests that the microbial enzymes that survived the kilning step were active during mashing. Other quality aspects that were influenced by the starter culture activity were protein modification, wort color, and wort pH. The level of microbial enzymes produced was related to the amount of barley kernels infected with the starter culture.

Degradation of starchy endosperm cell walls in nongerminating sterilized barley by fungi.

Strains of fungi from different origins, including isolates of the natural microflora of barley, were screened for their ability to modify barley starchy endosperm cell walls in situ. In an initial step, fungi were selected that degrade the major component of the cell walls, that is, (1-->3),(1-->4)-beta-D-glucan, in vitro on artificial media. Nongerminating, sterilized barley, obtained by gamma-irradiation, was inoculated with such fungi and subjected to solid state fermentation under conditions resembling those of a traditional malting process. For some strains of fungi, a clear correlation between the production of endo-beta-glucanase and the friability of the treated kernels was found. Image analysis of Calcofluor stained longitudinal sections of barley kernels fermented with the endo-beta-glucanase producing strains showed that starchy endosperm cell walls were modified. As malt quality is inversely related to its (1-->3),(1-->4)-beta-D-glucan content, the selected strains have high potential to be used as starter cultures during malt production, contributing to the processing quality of the final product.

Purification, characterization and structural analysis of an abundant beta-1,3-glucanase from banana fruit.

An abundant, catalytically active beta-1,3-endoglucanase (EC 3.2.1. 39) has been isolated from the pulp of ripe bananas. Biochemical analysis of the purified protein, molecular modelling, and molecular cloning of the corresponding gene indicate that this banana enzyme closely resembles previously characterized plant beta-glucanases with respect to its amino-acid sequence, structure and biological activity. The results described in this paper demonstrate both the occurrence of an abundant active beta-1,3-endoglucanases in fruits and also readdress the question of the possible involvement of these enzymes in the ripening and/or softening process.