14,442 research outputs found

    Plasma igniter for internal combustion engine

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    An igniter for the air/fuel mixture used in the cylinders of an internal combustion engine is described. A conventional spark is used to initiate the discharge of a large amount of energy stored in a capacitor. A high current discharge of the energy in the capacitor switched on by a spark discharge produces a plasma and a magnetic field. The resultant combined electromagnetic current and magnetic field force accelerates the plasma deep into the combustion chamber thereby providing an improved ignition of the air/fuel mixture in the chamber

    Museum DNA reveals the demographic history of the endangered Seychelles warbler

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    The importance of evolutionary conservation ā€“ how understanding evolutionary forces can help guide conservation decisions ā€“ is widely recognized. However, the historical demography of many endangered species is unknown, despite the fact that this can have important implications for contemporary ecological processes and for extinction risk. Here, we reconstruct the population history of the Seychelles warbler (Acrocephalus sechellensis) ā€“ an ecological model species. By the 1960s, this species was on the brink of extinction, but its previous history is unknown. We used DNA samples from contemporary and museum specimens spanning 140 years to reconstruct bottleneck history. We found a 25% reduction in genetic diversity between museum and contemporary populations, and strong genetic structure. Simulations indicate that the Seychelles warbler was bottlenecked from a large population, with an ancestral Ne of several thousands falling to <50 within the last century. Such a rapid decline, due to anthropogenic factors, has important implications for extinction risk in the Seychelles warbler, and our results will inform conservation practices. Reconstructing the population history of this species also allows us to better understand patterns of genetic diversity, inbreeding and promiscuity in the contemporary populations. Our approaches can be applied across species to test ecological hypotheses and inform conservation

    Braids and factorizable inverse monoids

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    What is the untangling effect on a braid if one is allowed to snip a string, or if two specified strings are allowed to pass through each other, or even allowed to merge and part as newly reconstituted strings? To calculate the effects, one works in an appropriate factorizable inverse monoid, some aspects of a general theory of which are discussed in this paper. The coset monoid of a group arises, and turns out to have a universal property within a certain class of factorizable inverse monoids. This theory is dual to the classical construction of fundamental inverse semigroups from semilattices. In our braid examples, we will focus mainly on the ``merge and part'' alternative, and introduce a monoid which is a natural preimage of the largest factorizable inverse submonoid of the dual symmetric inverse monoid on a finite set, and prove that it embeds in the coset monoid of the braid group

    Presentations of factorizable inverse monoids

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    It is well-known that an inverse monoid is factorizable if and only if it is a homomorphic image of a semidirect product of a semilattice (with identity) by a group. We use this structure to describe a presentation of an arbitrary factorizable inverse monoid in terms of presentations of its group of units and semilattice of idempotents, together with some other data. We apply this theory to quickly deduce a well known presentation of the symmetric inverse monoid on a nite set

    An atomic scale comparison of the reaction of BioglassĀ® in two types of simulated body fluid

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    A class of melt quenched silicate glasses, containing calcium, phosphorus and alkali metals, and having the ability to promote bone regeneration and to fuse to living bone, is produced commercially as Bioglass. The changes in structure associated with reacting the bioglass with a body fluid simulant (a buffered Tris(hydroxymethyl)aminomethane growth medium solution or a blood plasma-like salt simulated body fluid) at 37Ā°C have been studied using both high energy and grazing incidence x-ray diffraction. This has corroborated the generic conclusions of earlier studies based on the use of calciaā€“silica sol-gel glasses whilst highlighting the important differences associated with glass composition; the results also reveal the more subtle effects on reaction rates of the choice of body fluid simulant. The results also indicate the presence of tricalcium phosphate crystallites deposited onto the surface of the glass as a precursor to the growth of hydroxyapatite, and indicates that there is some preferred orientation to their growth

    Clinical communication skills learning outcomes among first year medical students are consistent irrespective of participation in an interview for admission to medical school

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    Background: Although contentious most medical schools interview potential students to assess personal abilities such as communication. Aims: To investigate any differences in clinical communication skills (CCS) between first year students admitted to UQ medical school with or without an admissions interview. Methods: A retrospective analysis of 1495 student assessment scores obtained after structured communication skills training (CCS) between 2007 and 2010. Results: The average assessment score was 3.76 ([95% CI, 3.73-3.78]) and adjusting for student characteristics, showed no main effect for interview (p=0.89). The strongest predictor of scores was gender with females achieving significantly higher scores (3.91 [95% CI, 3.54-4.28] vs. 3.76 [95% CI, 3.39-4.13]; pā‰¤0.001). Conclusions: Data show no differences in post-training assessment measures between students who were interviewed during selection or not. Further research about the quality and retention of communications skills after training is warranted
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