Genetic engineering of microorganisms: free release into the environment

Genetic engineering now makes possible the insertion of DNA from many organisms into other prokaryotic, eukaryotic and viral hosts. This technology has been used to construct a variety of such genetically engineered microorganisms (GEMs). The possibility of accidental or deliberate release of GEMs into the natural environment has recently raised much public concern. The prospect of deliberate release of these microorganisms has prompted an increased need to understand the processes of survival, expression, transfer and rearrangement of recombinant DNA molecules in microbial communities. The methodology which is being developed to investigate these processes will greatly enhance our ability to study microbial population ecology

Collagen degradation and neutrophilic infiltration: a vicious circle in inflammatory bowel disease

Cellular mechanisms in basic and clinical gastroenterology and hepatolog

Recrystallization behaviour of high-flux hydrogen plasma exposed tungsten

Knowledge of a material’s thermal stability under extreme synergistic particle and heat loads is crucial for developing high performance reactor materials. In this work, the recrystallization behaviour of tungsten under the influence of hydrogen is investigated by low energy high flux hydrogen plasma exposure for various lengths of time. The microstructural changes following exposure are probed by micro-indentation, electron back-scatter diffraction measurements and the characteristic time for recrystallization is assessed using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model. A recrystallization activation energy in the range of 425 to 440 kJ.mol-1_ is determined, identical to that of oven annealed samples, thereby indicating an insignificant influence of hydrogen plasma on the recrystallization kinetics of tungsten

Recrystallization behaviour of high-flux hydrogen plasma exposed tungsten

Knowledge of a material’s thermal stability under extreme synergistic particle and heat loads is crucial for developing high performance reactor materials. In this work, the recrystallization behaviour of tungsten under the influence of hydrogen is investigated by low energy high flux hydrogen plasma exposure for various lengths of time. The microstructural changes following exposure are probed by micro-indentation, electron back-scatter diffraction measurements and the characteristic time for recrystallization is assessed using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model. A recrystallization activation energy in the range of 425 to 440 kJ.mol-1 is determined, identical to that of oven annealed samples, thereby indicating an insignificant influence of hydrogen plasma on the recrystallization kinetics of tungsten

Amorphous and anisotropic surface relief formation in tungsten under repeated high-flux hydrogen plasma loads

Facing extreme plasma loads, the structural integrity of the tungsten divertor is crucial for ITER, an engineering marvel in nuclear fusion reactors, to achieve its fusion performance targets. Induced by repeated transient heating from plasmas, the thermal fatigue damage of tungsten–typically accompanied by the formation of surface relief–has been identified as a critical issue but an in-depth understanding is still lacking. Here, we report the formation of amorphous and anisotropic surface relief on ITER-grade tungsten surfaces under ITER-relevant hydrogen plasma loads. Measured by both electron backscatter diffraction over large fields of view and transmission Kikuchi diffraction of site-specific lamellae, such surface relief preferentially forms on grains with {1 1 0} planes parallel to the surface. This cannot be explained by the orientation-dependent resolved shear stress according to the Schmid law, threshold displacement energy anisotropy, or oxidation anisotropy. Furthermore, surface relief amorphization is revealed by high-resolution transmission electron microscopy imaging and selected area electron diffraction analysis, and is explained by a novel vacancy-induced amorphization mechanism. The results provide new insights into the thermal fatigue behavior of tungsten for fusion applications

Carbon fractions in the rhizosphere of pea inoculated with 2,4 diacetylphloroglucinol producing and non-producing Pseudomonas fluorescens F113

The definitive version is available at www.blackwell-synergy.com. Copyright Blackwell Publishing DOI : 10.1046/j.1365-2672.1999.00809.xThe aim of this work was to determine the effect of wild type and functionally modified Pseudomonas fluorescens strains on C fractions in the rhizosphere of pea. The lacZY marked F113 strain produces the antibiotic 2,4 diacetylphloroglucinol (DAPG) useful in plant disease control. The modified strain of F113 was repressed in production of DAPG, creating the DAPG negative strain F113 G22. The F113 treatment resulted in a significantly lower shoot/root ratio. The F113 G22 treatment had a significantly greater indigenous and total fluorescent Pseudomonas population than the control and F113 (DAPG+) treatment. Both strains significantly increased the water soluble carbohydrates and the total water soluble carbon in the pea rhizosphere soil. Strain F113 significantly increased the soil protein content relative to the control but not in relation to the F113 G22 treatment. The F113 treatment had a significantly greater organic acid content than the control and F113 G22 treatments, whilst the F113 G22 treatment was also significantly greater than the control. Both inocula resulted in significantly lower phosphate contents than the control. The F113 inocula significantly increased alkaline phosphatase, sulphatase and urease activities, and reduced glucosidase activities indicating increased carbon availability. Both inocula increased C availability, however, antibiotic production by strain F113 reduced the utilisation of organic acids released from the plant resulting in differing effects of the two strains on nutrient availability, plant growth, soil enzyme activities and Pseudomonas populations.Peer reviewe

Power deposition behavior of high-density transient hydrogen plasma on tungsten in Magnum-PSI

The lifetime of plasma-facing components (PFCs) will have a strong influence on the efficiency and viability of future fusion power plants. However, the PFCs suffer from thermal stresses and physical sputtering induced by edge-localized modes (ELMs). ELMs in future fusion devices are expected to occur with a high plasma density compared to current day devices such that coupling of recycling neutrals and plasma ions will be strong. Because of the scale hierarchy of future fusion devices compared to the present ones, the influence of this coupling is difficult to predict. Here, we investigate the ELM-like hydrogen plasma induced heat loads on tungsten in the linear device Magnum-PSI, producing similar to 1 ms plasma pulses with electron densities up to 3.5 x 10(21) m(-3). A combination of time-resolved Thomson scattering and coherent Thomson scattering was used to acquire plasma parameters in front of the target. Moreover, a fast infrared camera coupled to finite element thermal analyses allowed to determine the deposited heat loads on the target. We found a significant inconsistency between the plasma power calculated with a conventional collisionless sheath model and the absorbed power by the target. Moreover, plasma stagnation upstream and plasma cooling downstream were observed during the pulses. The observations are explained based on ionization and elastic collisions between the recycling neutrals and plasma ions. The results highlight the impact of plasma-neutral interaction on the power deposition behavior of ELM-like hydrogen plasma on tungsten