Accurate first-derivative nonadiabatic couplings for the H3 system

A conical intersection exists between the ground (1 2 A[prime]) and the first-excited (2 2A[prime]) electronic potential energy surfaces (PESs) of the H3 system for C3v geometries. This intersection induces a geometric phase effect, an important factor in accurate quantum mechanical reactive scattering calculations, which at low energies can be performed using the ground PES only, together with appropriate nuclear motion boundary conditions. At higher energies, however, such calculations require the inclusion of both the 1 2A[prime] and 2 2A[prime] electronic PESs and the corresponding nuclear derivative couplings. Here we present ab initio first-derivative couplings for these states obtained by analytic gradient techniques and a fit to these results. We also present a fit to the corresponding 1 2A[prime] and 2 2A[prime] adiabatic electronic PESs, obtained from the ab initio electronic energies. The first-derivative couplings are compared with their approximate analytical counterparts obtained by Varandas et al. [J. Chem. Phys. 86, 6258 (1987)] using the double many-body expansion method. As expected, the latter are accurate close to conical intersection configurations but not elsewhere. We also present the contour integrals of the ab initio couplings along closed loops around the above-mentioned conical intersection, which contain information about possible interactions between the 2 2A[prime] and 3 2A[prime] states

Surf zone currents and influence on surfability

Surfing headlands are shallow and exposed coastal features that provide a specific form of breaking wave allowing a board-rider to ride on the unbroken wave face. The seabed shape and refraction of the waves in relation to depth contours provide the greatest influence on the quality of the surf break. The large scale and orientation of the Raglan headland allows only the low frequency swells to refract around the headland to create seven different surfing breaks. Each represents a compartmentalization of the shoreline along the headland. This creates variability in wave and current characteristics depending on the orientation and bathymetry at different locations. This provides not only potential access points through the surf-zone (ie: smaller currents), but greater surfability in a range of conditions that is not possible on small scale headlands. Headlands with surfing waves can be classified as mis-aligned sections of the coast, where the higher oblique angle of the breaking surf generates strong wave-driven currents. These currents are far greater than that found on coastlines in equilibrium with the dominant swell direction, where comparatively insignificant longshore drift is found. The strength and direction of wave-driven currents in the surf zone can influence the surfability of a break. At a surfing headland strong currents flowing downdrift along the shoreline make it difficult for a paddling surfer to get to the "take-off" location of the break, or maintain position in the line-up. In comparison currents flowing updrift along headlands makes getting "out the back" relatively easy, although surfers can be taken out to sea past the "take-off" point by a fast flowing current. Field experiments at Raglan, on the west coast of New Zealand have been conducted to measure current speed and direction during a large swell event. Observations of surfers attempting to paddle through the breaking-wave zone, confirms the strength of the wave-driven currents with surfers being swept rapidly down the headland. Results from the experiments at Raglan, have shown strong currents in the inshore breaking wave zone with burst-averaged velocities attaining 0.8 ms-1, and maximum bed orbital velocities of up to 2.0 ms-1. Interestingly, further offshore the currents have been found to flow in a re-circulating gyre back up the headland. Comparisons are made from observations of waves and currents found at other surfing headlands around the world. The effect that strong currents may have on the surfability of artificial surfing reefs needs to be considered in the design process, if the surfing amenity is to be maximised for large surf conditions

Changing the Paradigm for Pesticide Resistance Management

Collaborative action on the part of all stakeholders in pest management is essential to effectively address the challenges of pesticide resistance. The US Environmental Protection Agency, through its Pesticide Program Dialogue Committee, recently posted a report on pesticide resistance management and the role the Agency can play in these efforts. In this perspectives piece, we commend the Agency for acknowledging these needs, and encourage implementation of the recommendations. We urge all stakeholders to follow the example set by EPA to engage openly, listen to other stakeholders, and determine their role as part of the broader community that is needed to address the challenges of resistance. Our contention is that pesticide resistance will continue to escalate until all stakeholders evaluate their roles in resistance management and work together as a community to influence effective management

Braconid and ichneumonid (Hymenoptera) parasitoid wasps of Lepidoptera from the Maltese Islands

Fourteen species of Ichneumonidae are here recorded from the Maltese Islands. Of these, all were reared from Lepidoptera hosts with the exception of Netelia (Paropheltes) inedita (Kokujev) which was collected from a malaise trap. Of these, the following species (or genera) are here reported for the first time from the Maltese Islands: Chirotica meridionalis Horstmann, Gelis carbonarius (de Stefani), G. exareolatus (Fӧrster), G. seyrigi Ceballos, Glypta sp., Meloboris sp., Netelia (Paropheltes) inedita (Kokujev), Ophion obscuratus Fabricius and Orthizema sp. Twenty-five species of Braconidae are also here reported from Lepidoptera hosts with the exception of Homolobus (Phylacter) meridionalis van Achterberg which was collected from a malaise trap. Of these, the following species (or genera) represent new records for the Maltese Islands: Apanteles metacarpalis (Thomson), Ascogaster sp., Clinocentrus excubitor (Haliday) [previously misidentified as C. exsertor (Nees) by Papp (2015)], Cotesia vestalis (Haliday) [previously misidentified as C. ruficrus (Haliday) by Papp (2015)], Dolichogenidea britannica (Wilkinson), Homolobus (Phylacter) meridionalis van Achterberg, Iconella ? meruloides (Nixon), Lysitermus tritoma (Bouček), Lysitermus suecius (Hedqvist), Microgaster messoria Haliday, Meteorus pulchricornis (Wesmael), Pholetesor circumscriptus (Nees) [previously misidentified as P. bicolor (Nees) by Papp (2015)] and Spathius pedestris Wesmael. Thus previous records of Clinocentrus exsertor and Pholetesor bicolor from Malta were found to be based on misidentifications and are here excluded from the braconid fauna of Malta. Maltese records of Cotesia abjecta (Marshall) and Cotesia jucunda (Marshall) by Papp (2015) were found to be misidentifications and should both refer to C. glomerata (Linnaeus). Thus, both Cotesia abjecta and Cotesia jucunda are also here removed from the braconid fauna of Malta. The record of Cotesia tibialis (Curtis) by Papp (2015) was also based on a misidentification and should be attributed to C. ruficrus (Haliday). Thus, C. tibialis is also removed from the braconid fauna of Malta.peer-reviewe

Synthesis and characterisation of an N-heterocyclic carbene with spatially-defined steric impact

The synthesis and co-ordination chemistry of a new ‘bulky yet flexible’ N-heterocyclic carbene (“IPaul”) is reported. This carbene has spatially-defined steric impact; steric maps show that two quadrants are very bulky while the other two are quite open. The electronic properties of this carbene are very similar to those of other 1,3-diarylimidazol-2-ylidenes. Copper, silver, iridium, and nickel complexes of the new ligand have been prepared. In solution, the ligand adopts two different conformations, while X-ray crystallographic analyses of the transition metal complexes suggest that the syn-conformer is preferred in the solid state due to intermolecular interactions. The copper complex of this new ligand has been shown to be highly-active in the hydrosilylation of carbonyl compounds, when compared to the analogous IPr, IMes, IPr* and IPr*OMe complexes

SIMD Tree Algorithms for Image Correlation

This paper examines the applicability of fine-grained tree-structured SIMD machines, which are amenable to highly efficient VLSI implementation to image correlation which is a representative of image window-based operations. Several algorithms are presented for image shifting and correlation operations. A particular massively parallel machine called NON-VON is used for purposes of explication and performance evaluation. Although the most recent version of the NON-VON architecture also supports other interconnection topologies and execution modes, only its tree-structured communication capabilities and its SIMD mode of execution are considered in this paper. Novel algorithmic techniques are described, such as vertical pipelining, subproblem partitioning, associative matching, and data duplication that effectively exploit the massive parallelism available in fine-grained SIMD tree machines while avoiding communication bottlenecks. Simulation results are presented and compared with results obtained or forecast for other highly parallel machines. The relative advantages and limitations of the class of machines under consideration are then outlined

Finding qualitative research: an evaluation of search strategies

BACKGROUND: Qualitative research makes an important contribution to our understanding of health and healthcare. However, qualitative evidence can be difficult to search for and identify, and the effectiveness of different types of search strategies is unknown. METHODS: Three search strategies for qualitative research in the example area of support for breast-feeding were evaluated using six electronic bibliographic databases. The strategies were based on using thesaurus terms, free-text terms and broad-based terms. These strategies were combined with recognised search terms for support for breast-feeding previously used in a Cochrane review. For each strategy, we evaluated the recall (potentially relevant records found) and precision (actually relevant records found). RESULTS: A total yield of 7420 potentially relevant records was retrieved by the three strategies combined. Of these, 262 were judged relevant. Using one strategy alone would miss relevant records. The broad-based strategy had the highest recall and the thesaurus strategy the highest precision. Precision was generally poor: 96% of records initially identified as potentially relevant were deemed irrelevant. Searching for qualitative research involves trade-offs between recall and precision. CONCLUSIONS: These findings confirm that strategies that attempt to maximise the number of potentially relevant records found are likely to result in a large number of false positives. The findings also suggest that a range of search terms is required to optimise searching for qualitative evidence. This underlines the problems of current methods for indexing qualitative research in bibliographic databases and indicates where improvements need to be made

Identification of the [FeFe]-Hydrogenase Responsible for Hydrogen Generation in Thermoanaerobacterium saccharolyticum and Demonstration of Increased Ethanol Yield via Hydrogenase Knockout

Three putative hydrogenase enzyme systems in Thermoanaerobacterium saccharolyticum were investigated at the genetic, mRNA, enzymatic, and phenotypic levels. A four-gene operon containing two [FeFe]-hydrogenase genes, provisionally termed hfs (hydrogenase-Fe-S), was found to be the main enzymatic catalyst of hydrogen production. hfsB, perhaps the most interesting gene of the operon, contains an [FeFe]-hydrogenase and a PAS sensory domain and has several conserved homologues among clostridial saccharolytic, cellulolytic, and pathogenic bacteria. A second hydrogenase gene cluster, hyd, exhibited methyl viologen-linked hydrogenase enzymatic activity, but hyd gene knockouts did not influence the hydrogen yield of cultures grown in closed-system batch fermentations. This result, combined with the observation that hydB contains NAD(P)+ and FMN binding sites, suggests that the hyd genes are specific to the transfer of electrons from NAD(P)H to hydrogen ions. A third gene cluster, a putative [NiFe]-hydrogenase with homology to the ech genes, did not exhibit hydrogenase activity under any of the conditions tested. Deletion of the hfs and hydA genes resulted in a loss of detectable methyl viologen-linked hydrogenase activity. Strains with a deletion of the hfs genes exhibited a 95% reduction in hydrogen and acetic acid production. A strain with hfs and ldh deletions exhibited an increased ethanol yield from consumed carbohydrates and represents a new strategy for engineering increased ethanol yields in T. saccharolyticum

Natural Competence in Thermoanaerobacter and Thermoanaerobacterium Species

Low-G+C thermophilic obligate anaerobes in the class Clostridia are considered among the bacteria most resistant to genetic engineering due to the difficulty of introducing foreign DNA, thus limiting the ability to study and exploit their native hydrolytic and fermentative capabilities. Here, we report evidence of natural genetic competence in 13 Thermoanaerobacter and Thermoanaerobacterium strains previously believed to be difficult to transform or genetically recalcitrant. In Thermoanaerobacterium saccharolyticum JW/SL-YS485, natural competence- mediated DNA incorporation occurs during the exponential growth phase with both replicating plasmid and homologous recombination-based integration, and circular or linear DNA. In T. saccharolyticum, disruptions of genes similar to comEA, comEC, and a type IV pilus (T4P) gene operon result in strains unable to incorporate further DNA, suggesting that natural competence occurs via a conserved Gram-positive mechanism. The relative ease of employing natural competence for gene transfer should foster genetic engineering in these industrially relevant organisms, and understanding the mechanisms underlying natural competence may be useful in increasing the applicability of genetic tools to difficult-to-transform organisms