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The ITER Divertor’s 316L stainless steel cooling water pipe connections are to be remotely maintained by the first-of-a-kind Divertor Remote Handling System (DRHS) and its suite of cutting, welding and inspection tools. The requirement for welding of the highest quality in a radioactive, magnetic and high temperature environment, places significant technical risks on the technologies selected for use. This paper reports the R&D activities undertaken to mitigate these risks and concludes with the key findings and recommendations for the ongoing design. Gas Tungsten Arc Welding (GTAW) trials demonstrated that a code compliant, autogenous butt weld of 3 mm wall thickness is possible, but requires precise process control, novel techniques, and tight tolerances on material composition. The most significant findings were that vertically-offset filler-rings could be employed to positive effect, and a controlled Sulphur content of 100–150 ppm for the stainless-steel pipework was found to be necessary. The galvanic cell technology selected for the welding back-purge oxygen sensor was tested and verified for use in operating environments of 300 Gy/h gamma dose rate, 3mT magnetic field, and 60 °C ambient temperature. Cutting trials developed optimum parameters for lathe-based orbital cutting with regards to the required tool longevity, the vacuum-clean environment and the need to re-weld the joint. Finally, Volumetric Inspection trials investigated the effectiveness of Electro Magnetic Transducer (EMAT) and Phased Array Ultrasonic Testing (PAUT) methods at detecting a range of manufactured surface and volumetric defects in the weld. EMAT was found better suited to the application, but the work highlighted the need for a deeper understanding of the detection needs and their relationship to potential failure modes.

The Oryza sativa constitutive disease resistance 1 (OsCDR1) gene product is an aspartic proteinase that has been implicated in disease resistance signaling. This apoplastic enzyme is a member of the group of 'atypical' plant aspartic proteinases. Recombinant OsCDR1 expressed in Escherichia coli exhibited protease activity against succinylated-casein substrate. Inactivating the enzyme through modification of an aspartate residue present in the deduced active site completely abolished its proteinase activity. Infiltration of the OsCDR1 fusion protein into leaves of Arabidopsis plants induced PR2 transcripts in both the infiltrated leaf (primary) and in non-treated secondary leaves while the inactive recombinant protein failed to induce either local or systemic PR2. These findings demonstrate that OsCDR1 is capable of inducing systemic defense responses in plants.

Tobacco plants over-expressing L-phenylalanine ammonia-lyase (PAL(+)) produce high levels of chlorogenic acid (CGA) and exhibit markedly reduced susceptibility to infection with the fungal pathogen Cercospora nicotianae, although their resistance to tobacco mosaic virus (TMV) is unchanged. Levels of the signal molecule salicylic acid (SA) were similar in uninfected PAL(+) and control plants and also following TMV infection. In crosses of PAL(+) tobacco with tobacco harboring the bacterial NahG salicylate hydroxylase gene, progeny harboring both transgenes lost resistance to TMV, indicating that SA is critical for resistance to TMV and that increased production of phenylpropanoid compounds such as CGA cannot substitute for the reduction in SA levels. In contrast, PAL(+)/NahG plants showed strongly reduced susceptibility to Cercospora nicotianae compared to the NahG parent line. These results are consistent with a recent report questioning the role of PAL in SA biosynthesis in Arabidopsis, and highlight the importance of phenylpropanoid compounds such as CGA in plant disease resistance.

The mechanisms involved in plant defense show several similar characteristics with the innate immune systems of vertebrates and invertebrates. In animals, nitric oxide (NO) cooperates with reactive oxygen intermediates (ROI) to kill tumor cells and is also required for macrophage killing of bacteria. Such cytotoxic events occur because unregulated levels of NO determine its diffusion-limited reaction with O2 – generating peroxynitrite (ONOO – ), a mediator of cellular injury in many biological systems. In soybean suspension cells, unregulated NO production during the onset of a pathogen-induced hypersensitive response (HR) is not sufficient to activate the hypersensitive cell death, which is triggered only by fine tuning the NO/ROI ratio. Furthermore, that hypersensitive cell death is activated following interaction of NO with H2O2, rather than O2 – . Increasing O2 – levels reduces NO-derived toxicity, and the addition of ONOO – to soybean suspensions does not affect cell viability. Consistently with the fact that ONOO – is not an essential mediator of NO/RO-induced cell death, during the HR superoxide dismutase (SOD) accelerates O2 – dismutation to H2O2 and therefore minimizes the loss of NO by reaction with O2 – and triggers hypersensitive cell death through the NO/H2O2 synergism. Consequently, the rates of production and dismutation of O2 – generated during the oxidative burst play a crucial role in modulating NO signaling through the cell death pathway, which proceeds through mechanisms different from those commonly observed in animals. © 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

Pre-inoculation of plants with a pathogen that induces necrosis leads to the development of systemic acquired resistance (SAR) to subsequent pathogen attack [1]. The phenylpropanoid-derived compound salicylic acid (SA) is necessary for the full expression of both local resistance and SAR [2] [3]. A separate signaling pathway involving jasmonic acid (JA) is involved in systemic responses to wounding and insect herbivory [4] [5]. There is evidence both supporting and opposing the idea of cross-protection against microbial pathogens and insect herbivores [6] [7]. This is a controversial area because pharmacological experiments point to negative cross-talk between responses to systemic pathogens and responses to wounding [8] [9] [10], although this has not been demonstrated functionally in vivo. Here, we report that reducing phenylpropanoid biosynthesis by silencing the expression of phenylalanine ammonialyase (PAL) reduces SAR to tobacco mosaic virus (TMV), whereas overexpression of PAL enhances SAR. Tobacco plants with reduced SAR exhibited more effective grazing-induced systemic resistance to larvae of Heliothis virescens, but larval resistance was reduced in plants with elevated phenylpropanoid levels. Furthermore, genetic modification of components involved in phenylpropanoid synthesis revealed an inverse relationship between SA and JA levels. These results demonstrate phenylpropanoid-mediated cross-talk in vivo between microbially induced and herbivore-induced pathways of systemic resistance.

This Comment examines the issue of telecommunications accounting rates in order to gain an understanding of the current relationship between the USA and the Caribbean nations. The initiative taken by the Federal Communications Commission on this issue will either increase the region's dependency status or protect US telecommunications carriers that handle Caribbean traffic. The present status of FCC accounting rate policy is restrained. This works in favor of Caribbean nations. If the USA and the nations of the Caribbean work together a more reasonable accounting rate will result for both.

The photocontrol of l -phenylalanine ammonia-lyase (EC 4.3.1.5) activity in discs of potato (Solanum tuberosum) tuber parenchyme has been investigated by density labelling with 2H from 2H2O. Labelling of enzyme was measured by analysis of the equilibrium distribution of enzyme activity in CsCl density gradients as a function of buoyant density corrected with respect to the distribution of the external marker enzyme β-galctosidase (β- d -galactoside galactohydrolase, EC 3.2.1.23). It is demonstrated that the white-light mediated stimulation of phenylalanine ammonia-lyase activity involves stimulation of the rate of de novo production of active enzyme.

1. (1) The synthesis and removal of phenylalanine ammonia-lyase (EC 4.3.1.5) in illuminated discs of potato (Solanum tuberosum cv King Edward) tuber tissue has been investigated by density labelling with deuterium (2H) from deuterium oxide (2H2O) followed by centrifugation to equilibrium in a CsCl density gradient. 2. (2) Temporal changes in enzyme level have been described in terms of the equation (dE/dt) = ks − kdE where (dE/dt) is the rate of change of enzyme level per unit of tissue (E) with respect to time (t), ks is the rate constant for synthesis of the enzyme and kd is the rate constant for the removal of active enzyme. 3. (3) The optimal concentration of 2H2O was determined by analysis of the relationship between 2H2O concentration, development of enzyme activity and the magnitude of the increase in buoyant density of phenylalanine ammonialyase. A concentration of 2H2O of about 40% (v/v) was found to be optimal, allowing achievement of maximal or near maximal increases in the buoyant density of the enzyme without inhibition of the development of enzyme activity, thereby circumventing the major drawback of 2H2O as a source of density label. 4. (4) The overlapping distribution profiles of enzyme activity after density gradient centrifugation were resolved by an iterative method of best fit which allows estimation of the proportions of pre-existing, unlabelled enzyme and newly synthesised, labelled enzyme at the end of the labelling period. This technique has been developed to obtain the rate constants for enzyme synthesis and for removal of active enzyme throughout the period of rapid change in enzyme level. 5. (5) It is demonstrated that the initial rapid increase in phenylalanine ammonia-lyase activity in illuminated discs reflects an increase in the rate constant for enzyme synthesis in the absence of activation of pre-existing enzyme and in the absence of removal of active enzyme. The abrupt transition to a phase of decline in enzyme activity is caused by (a) a reduction in the rate constant for enzyme synthesis and (b) a dramatic increase in the rate constant for removal of active enzyme. The subsequent stabilisation of the enzyme level is caused by decay of both rate constants to relatively low levels. 6. (6) The results are consistent with the hypothesis that rapid modulation of enzyme levels during tissue differentiation is achieved by simultaneous changes in the rate constants for both enzyme synthesis and for removal of active enzyme.