Mlh2 is an accessory factor for DNA mismatch repair in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, the essential mismatch repair (MMR) endonuclease Mlh1-Pms1 forms foci promoted by Msh2-Msh6 or Msh2-Msh3 in response to mispaired bases. Here we analyzed the Mlh1-Mlh2 complex, whose role in MMR has been unclear. Mlh1-Mlh2 formed foci that often colocalized with and had a longer lifetime than Mlh1-Pms1 foci. Mlh1-Mlh2 foci were similar to Mlh1-Pms1 foci: they required mispair recognition by Msh2-Msh6, increased in response to increased mispairs or downstream defects in MMR, and formed after induction of DNA damage by phleomycin but not double-stranded breaks by I-SceI. Mlh1-Mlh2 could be recruited to mispair-containing DNA in vitro by either Msh2-Msh6 or Msh2-Msh3. Deletion of MLH2 caused a synergistic increase in mutation rate in combination with deletion of MSH6 or reduced expression of Pms1. Phylogenetic analysis demonstrated that the S. cerevisiae Mlh2 protein and the mammalian PMS1 protein are homologs. These results support a hypothesis that Mlh1-Mlh2 is a non-essential accessory factor that acts to enhance the activity of Mlh1-Pms1

Using domain-independent problems for introducing formal methods

The key to the integration of formal methods into engineering practice is education. In teaching, domain-independent problems i.e., not requiring prior engineering background-offer many advantages. Such problems are widely available, but this paper adds two dimensions that are lacking in typical solutions yet are crucial to formal methods: (i) the translation of informal statements into formal expressions; (ii) the role of formal calculation (including proofs) in exposing risks or misunderstandings and in discovering pathways to solutions. A few example problems illustrate this: (a) a small logical one showing the importance of fully capturing informal statements; (b) a combinatorial one showing how, in going from "real-world" formulations to mathematical ones, formal methods can cover more aspects than classical mathematics, and a half-page formal program semantics suitable for beginners is presented as a support; (c) a larger one showing how a single problem can contain enough elements to serve as a Leitmotiv for all notational and reasoning issues in a complete introductory course. An important final observation is that, in teaching formal methods, no approach can be a substitute for an open mind, as extreme mathphobia appears resistant to any motivation

Random and exhaustive generation of permutations and cycles

In 1986 S. Sattolo introduced a simple algorithm for uniform random generation of cyclic permutations on a fixed number of symbols. This algorithm is very similar to the standard method for generating a random permutation, but is less well known. We consider both methods in a unified way, and discuss their relation with exhaustive generation methods. We analyse several random variables associated with the algorithms and find their grand probability generating functions, which gives easy access to moments and limit laws.Comment: 9 page

Which mathematics for the Information Society?

MathIS is a new project that aims to reinvigorate secondary- school mathematics by exploiting insights of the dynamics of algorithmic problem solving. This paper describes the main ideas that underpin the project. In summary, we propose a central role for formal logic, the development of a calculational style of reasoning, the emphasis on the algorithmic nature of mathematics, and the promotion of self-discovery by the students. These ideas are discussed and the case is made, through a number of examples that show the teaching style that we want to introduce, for their relevance in shaping mathematics training for the years to come. In our opinion, the education of software engineers that work effectively with formal methods and mathematical abstractions should start before university and would benefit from the ideas discussed here.Long-term collaboration with J. N. Oliveira on calculational approaches to mathematics is deeply acknowledged. We are also grateful to the anonymous referees for their valuable comments. This research was supported by FCT (the Portuguese Foundation for Science and Technology), in the context of the MATHIS Project under contract PTDC/EIA/73252/2006. The work of Joao F. Ferreira and AlexandraMendeswas further supported by FCT grants SFRH/BD/24269/2005 and SFRH/BD/29553/2006, respectively

Plasma afterglow-assisted oxidation of iron–copper bilayers

International audienceIron layers with variable thicknesses, deposited onto copper thin films, are oxidized by a plasma afterglow at atmospheric pressure. Such a bilayer arrangement enables the growth of caterpillar-like patterns covered by CuO and Fe2O3 nanostructures. Two main mechanisms are at stake: either copper comes up to the surface through cracks or boundaries between the columns of the coating, or it diffuses through parts of the Fe2O3 layer made permeable by tensile stress. Structures grown by the former mechanisms are characterized by a central channel, whereas those grown by the latter exhibit a plane interface above which stands an equiaxed grain heap. This result was used to localize the growth of nanowires in cracks formed priory to the afterglow-assisted treatment. By resorting to XPS microscopy experiments carried out with the scanning photoelectron microscope at the ESCAMicroscopy beamline of the Elettra synchrotron facility in Trieste, we could gain access to the surface composition of a single isolated pattern

Synthesis of RuO 2 nanowires from Ru thin films by atmospheric pressure micro-post-discharge

International audienceOxidation by a micro-post-discharge at atmospheric pressure of thin films of ruthenium deposited on fused silica by pressure-modulated magnetron sputtering is studied. Single-crystalline RuO 2 nanowires are obtained for the first time with a diffusion process over large areas. Nanowires grow typically at temperatures below 550-600 K, provided the level of stress is high enough to fragment grains in sub-grains with sizes between 30 and 50 nm. Because of the alternation of dense and porous layers forming the coating, inward diffusion of vacancies leads to no patent Kirkendall's effect, pores being distributed over the whole coating thickness and not mainly at the interface with the substrate. The centre of the treatment being heated at temperatures higher than 900 K, gaseous RuO 4 is formed, leading to an evaporated area. At its edge, a ring of microcrystals is formed, likely by a CVD mechanism

Nanostructures design by plasma afterglow-assisted oxidation of iron–copper thin films

International audienceOxidizing thin films made of Fe-Cu alloy with an Ar-O 2 micro-afterglow operated at atmospheric pressure shows remarkable growth processes. The presence of iron in copper up to about 50% leads to the synthesis of CuO nanostructures (nanowalls, nanotowers and nanowires). Nanotowers show the presence of an amorphous phase trapped between crystalline domains. Beyond 50%, Fe 2 O 3 iron nano-blades are also found. CuO nanowires as small as 5 nm in diameter can be synthesized. Thanks to the presence of patterned domains induced by buckling, it was possible to show that the stress level decreases when the iron content in the alloy increases. Iron blades grow from the inner Fe 2 O 3 layer through the overlying CuO if it is thin enough

Divergence in Dialogue

Copyright: 2014 Healey et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.This work was supported by the Economic and Social Research Council (ESRC; http://www.esrc.ac.uk/) through the DynDial project (Dynamics of Conversational Dialogue, RES-062-23-0962) and the Engineering and Physical Sciences Research Council (EPSRC; http://www.epsrc.ac.uk/) through the RISER project (Robust Incremental Semantic Resources for Dialogue, EP/J010383/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript