A question-answering system using argumentation

This paper presents a novel approach to question answering: the use of argumentation techniques. Our question answering system deals with argumentation in student essays: it sees an essay as an answer to a question and gauges its quality on the basis of the argumentation found in it. Thus, the system looks for expected types of argumentation in essays (i.e. the expectation is that the kind of argumentation in an essay is correlated to the type of question). Another key feature of our work is our proposed categorisation for argumentation in student essays, as opposed to categorisation of argumentation in research papers, where - unlike the case of student essays - it is relatively well-known which kind of argumentation can be found in specific sections

On-shelf transport of slope water lenses within the seasonal pycnocline

We show that discrete lenses of anomalously high-salinity water, originating from the shelf edge and trapped within the seasonal pycnocline, are advected 100 km or more onto the Celtic Sea continental shelf. We propose that the lenses are created by increased diapycnal mixing at the shelf edge associated with breaking high-frequency internal wave packets. Quasi-synoptic hydrography sections show the lenses to be 3–5 km wide, their temporal persistence confirmed by moored instrumentation and a series of CTD casts. Estimates of the propagation speed of these features (∼0.020 m s−1) compare favorably with the magnitude of observed residual currents. Residual current variability within the pycnocline is dominated by vertical structures most consistent with the second baroclinic mode. The residual flow is therefore thought to be predominantly driven by non-linear second mode internal tidal waves. These are observations of a shelf edge exchange process not previously identified

Climate change effects on snow conditions in mainland Australia and adaptation at ski resorts through snowmaking

We examined the effects of past and future climate change on natural snow cover in southeastern mainland Australia and assessed the role of snowmaking in adapting to projected changes in snow conditions. Snow-depth data from 4 alpine sites from 1957 to 2002 indicated a weak decline in maximum snow depths at 3 sites and a moderate decline in mid- to late-season snow depths (August to September). Low-impact and high-impact climate change scenarios were prepared for 2020 and 2050 and used as input for a climate-driven snow model. The total area with an average of at least 1 d of snow cover per year was projected to decrease by 10 to 39% by 2020, and by 22 to 85 % by 2050. By 2020, the length of the ski season was projected to have decreased by 10 to 60%, while by 2050 the decrease was 15 to 99%. Based on target snow-depth profiles from May to September nominated by snowmaking managers at various ski resorts, the snow model simulated the amount of snow that is needed to be made each day, taking into account natural snowfall, snow-melt and the pre-existing natural snow depth. By the year 2020, an increase of 11 to 27 % in the number of snow guns would be required for the low impact scenario, and 71 to 200% for the high impact scenario. This corresponds to changes in total snow volume of 5 to 17% for the low impact scenario to 23 to 62% for the high impact scenario. Therefore, with sufficient investment in snow guns, the Australian ski industry may be able to manage the effect of projected climate change on snow cover until at least 2020

Changes in turbulent mixing shift competition for light between phytoplankton species

The intriguing impact of physical mixing processes on species interactions has always fascinated ecologists. Here, we exploit recent advances in plankton models to develop competition theory that predicts how changes in turbulent mixing affect competition for light between buoyant and sinking phytoplankton species. We compared the model predictions with a lake experiment, in which the turbulence structure of the entire lake was manipulated using artificial mixing. Vertical eddy diffusivities were calculated from the measured temperature microstructure in the lake. Changes in turbulent mixing of the lake caused a dramatic shift in phytoplankton species composition, consistent with the predictions of the competition model. The buoyant and potentially toxic cyanobacterium Microcystis dominated at low turbulent diffusivity, whereas sinking diatoms and green algae dominated at high turbulent diffusivity. These findings warn that changes in the turbulence structure of natural waters, for instance driven by climate change, may induce major shifts in the species composition of phytoplankton communities

The C-terminus of the phage λ Orf recombinase is involved in DNA binding

Phage λ Orf substitutes for the activities of the Escherichia coli RecFOR proteins in vivo and is therefore implicated as a recombination mediator, encouraging the assembly of bacterial RecA onto single-stranded DNA (ssDNA) coated with SSB. Orf exists as a dimer in solution, associates with E. coli SSB and binds preferentially to ssDNA. To help identify interacting domains we analysed Orf and SSB proteins carrying mutations or truncations in the C-terminal region. A cluster of acidic residues at the carboxy-terminus of SSB is known to attract multiple protein partners to assist in DNA replication and repair. In this case an alternative domain must be utilized since Orf association with SSB was unaffected by an SSB113 point mutant (P176S) or removal of the last ten residues (ΔC10). Structurally the Orf C-terminus consists of a helix with a flexible tail that protrudes from each side of the dimer and could serve as a binding site for either SSB or DNA. Eliminating the six residue flexible tail (ΔC6) or the entire helix (ΔC19) had no significant impact on the Orf–SSB interaction. However, the OrfΔC6 protein exhibited reduced DNA binding, a feature shared by single amino acid substitutions within (W141F) or adjacent (R140A) to this region. The OrfΔC19 mutant bound poorly to DNA and secondary structure analysis in solution revealed that this truncation induces protein misfolding and aggregation. The results show that the carboxy-terminus of Orf is involved in nucleic acid recognition and also plays an unexpected role in maintaining structural integrity