The importance of the classical channel in the impurity transport of optimized stellarators

In toroidal magnetic confinement devices, such as tokamaks and stellarators, neoclassical transport is usually an order of magnitude larger than its classical counterpart. However, when a high-collisionality species is present in a stellarator optimized for low Pfirsch-Schl\"uter current, its classical transport can be comparable to the neoclassical transport. In this letter, we compare neoclassical and classical fluxes and transport coefficients calculated for Wendelstein 7-X (W7-X) and Large Helical Device (LHD) cases. In W7-X, we find that the classical transport of a collisional impurity is comparable to the neoclassical transport for all radii, while it is negligible in the LHD cases, except in the vicinity of radii where the neoclassical transport changes sign. In the LHD case, electrostatic potential variations on the flux-surface significantly enhance the neoclassical impurity transport, while the classical transport is largely insensitive to this effect in the cases studied.Comment: 10 pages, 2 figure

Eating Biodiversity: Investigating the Links Between Grassland Biodiversity and Quality Food Production

Modern food production systems are generally detrimental to biodiversity, and the widespread loss of species-diverse grassland as a consequence of intensive farming methods is well documented. Since the 1980s, a range of policy measures and financial incentives for farmers have been introduced in Europe to halt (and in some cases, reverse) this trend, primarily to meet environmental objectives of species and habitat conservation and landscape protection. Biodiversity, where associated with agricultural production, has largely been regarded as a positive \u27externality\u27 to the process of food production; a ‘product’ which benefits wider society without necessarily conferring an agricultural benefit to the producer. However, with increasing emphasis on food quality, and the marketing of food products by geographical origin, method of production, gastronomic value and nutritional and health properties, there is potential to improve financial returns for farmers and the wider rural economy. Production in which grassland biodiversity is an ‘input’ to the livestock production food chain are embedded in some speciality systems, notably in mountain areas of Europe (Peeters and Frame, 2002). In the context of conserving grassland biodiversity there is a need to improve our understanding of the links between food products and animal diets, including pasture composition. This paper outlines a 3-year project funded by the UK RELU programme (RELU, 2005) which commenced in 2005. Results are not yet available so this summary focuses on the strategy being followed and the wider implications of linking enhanced food-product value to biodiversity

Structural Adaptability Facilitates Histidine Heme Ligation in a Cytochrome P450

Almost all known members of the cytochrome P450 (CYP) superfamily conserve a key cysteine residue that coordinates the heme iron. Although mutation of this residue abolishes monooxygenase activity, recent work has shown that mutation to either serine or histidine unlocks non-natural carbene- and nitrene-transfer activities. Here we present the first crystal structure of a histidine-ligated P450. The T213A/C317H variant of the thermostable CYP119 from Sulfolobus acidocaldarius maintains heme iron coordination through the introduced ligand, an interaction that is accompanied by large changes in the overall protein structure. We also find that the axial cysteine C317 may be substituted with any other amino acid without abrogating folding and heme cofactor incorporation. Several of the axial mutants display unusual spectral features, suggesting that they have active sites with unique steric and electronic properties. These novel, highly stable enzyme active sites will be fruitful starting points for investigations of non-natural P450 catalysis and mechanisms

Flexural Strength of Reinforced Concrete RAC Beams Exposed to 6-hour Fire – Part 2: Rich Mix

In this research work, experimental investigation on flexural strength of reinforced concrete beams exposed to fire for 6-hours at the temperature of 1000˚C is presented. The beams are made with 50% replacement of natural coarse aggregates with recyclable concrete aggregates. A total of 12 reinforced concrete beams using 1:1.5:3 mix (rich mix) and 0.54 water-cement ratio were cast. The beams were prepared in two groups. Group 1 beams were prepared with 50% recyclable aggregates, whereas group 2 beams were cast with all-natural aggregates (control specimens). All beams were exposed to fire at the above-mentioned temperature followed by testing in universal load testing machine under central point load. Comparison of the results reveals that proposed beams show comparable resistance even after exposed to 6-hours fire at 1000°C

Duplex strand joining reactions catalyzed by vaccinia virus DNA polymerase

Vaccinia virus DNA polymerase catalyzes duplex-by-duplex DNA joining reactions in vitro and many features of these recombination reactions are reprised in vivo. This can explain the intimate linkage between virus replication and genetic recombination. However, it is unclear why these apparently ordinary polymerases exhibit this unusual catalytic capacity. In this study, we have used different substrates to perform a detailed investigation of the mechanism of duplex-by-duplex recombination catalyzed by vaccinia DNA polymerase. When homologous, blunt-ended linear duplex substrates are incubated with vaccinia polymerase, in the presence of Mg(2+) and dNTPs, the appearance of joint molecules is preceded by the exposure of complementary single-stranded sequences by the proofreading exonuclease. These intermediates anneal to form a population of joint molecules containing hybrid regions flanked by nicks, 1–5 nt gaps, and/or short overhangs. The products are relatively resistant to exonuclease (and polymerase) activity and thus accumulate in joining reactions. Surface plasmon resonance (SPR) measurements showed the enzyme has a relative binding affinity favoring blunt-ended duplexes over molecules bearing 3′-recessed gaps. Recombinant duplexes are the least favored ligands. These data suggest that a particular combination of otherwise ordinary enzymatic and DNA-binding properties, enable poxvirus DNA polymerases to promote duplex joining reactions

Analysis of detector performance in a gigahertz clock rate quantum key distribution system

We present a detailed analysis of a gigahertz clock rate environmentally robust phase-encoded quantum key distribution (QKD) system utilizing several different single-photon detectors, including the first implementation of an experimental resonant cavity thin-junction silicon single-photon avalanche diode. The system operates at a wavelength of 850 nm using standard telecommunications optical fibre. A general-purpose theoretical model for the performance of QKD systems is presented with reference to these experimental results before predictions are made about realistic detector developments in this system. We discuss, with reference to the theoretical model, how detector operating parameters can be further optimized to maximize key exchange rates

Impact of Long-Term Loading on Reinforced Concrete Beams Made with Partial Replacement of Coarse Aggregates with Recycled Aggregates from Old Concrete

This research work presents an experimental evaluation of the effect of sustained loading on reinforced concrete beams made with 50% replacement of natural coarse aggregates with aggregates from old concrete. A total of 9 RC beams were cast, 6 with natural coarse aggregates and 3 with recycled concrete aggregates. All beams were cured for 28 days in standard fashion. Among the first batch, 3 beams were used to test under short term loading till failure. An application of 50% of short-term loading followed on all beams assembled on purpose made frames. All beams were monitored for deflection, strain, and cracking. Both deflection and strain remained within limits. Crack monitoring revealed maximum crack width 0.5 mm. After six months of sustained load, beams were removed from the frames and tested in universal load testing machine with central point load till failure. The load-deflection pattern of all beams was observed to be almost similar and 22.12% higher in recycled concrete beams than all-natural aggregate beams. The results show promising use of recycled concrete aggregates in new concrete subjected to sustained loading

Flexural Stress-Strain Behavior of RC Beams Made with Partial Replacement of Coarse Aggregates with Coarse Aggregates from Old Concrete: Part-1: 1:2:4 Ratio

Occupancy, particularly in urban areas, requires more space than ever. Space constraints need erection of high rise buildings in place of short height buildings. This need demolishing of old structures which creates huge quantities of demolished concrete. One of its best disposals is its use in new concrete. Therefore, this research work uses 50% replacement of natural coarse aggregates with coarse aggregates from old concrete to study the flexural stress-strain behavior of reinforced concrete beams. Total of 12 reinforced concrete beams (900x150x150 mm) were cast with 2#4 bars in tension and 2#4 bars in compression zones. Ordinary Portland cement with hill sand and crush aggregate was used in 1:2:4 proportions. Water cement ratio used is 0.54. The beams were cast in two batches, one with 100% natural aggregates and another with 50% natural coarse aggregates replaced with coarse aggregates from old concrete. In each batch 3 beams were cured for 7 and 28 days respectively. After curing all beams were tested with central point load. The beams were monitored at regular intervals for load, displacement, strain and load until first crack. The beams under study were compared with the controlled specimen. The results were in good agreement with the normal concrete specimen. Maximum reduction in flexural stress is recorded as 8.8% for 7-day cured beams and 5.52% for 28-day cured specimen. Thus, the use of coarse aggregates from demolished concrete in new concrete is proved to be promising partial replacement of coarse aggregate in terms of flexural stress-strain relationship

Being with donkeys: insights into the valuing and wellbeing of donkeys in central Ethiopia

This paper explores the interwoven lives of donkeys and the people who depend on them for their livelihoods in central Ethiopia. Drawing on data from twelve participatory workshops, insights are elicited into the ways donkey guardians’ value and treat their donkeys. Methodologically, Participatory Rural Appraisal (PRA) and Appreciative Inquiry (AI) techniques were merged to explore the complex and multi-dimensional contributions donkeys make to participants’ lives. Findings reveal the keeping of donkeys can make the difference between destitution and modest survival, but societal perception of donkeys as low-status animals has an impact on their owners’ lives and donkey wellbeing. This research contributes empirical insights on the valuing of donkeys and enables a deepened understanding of human-donkey relations. The combination of PRA and AI in the methodology demonstrates how to formulate a compassionate and empathetic approach for exploring donkey value and wellbeing with marginalised groups