Chris Martin

We introduce and study a natural extension of Marcus external contextual grammars. This mathematically simple mechanism which generates a proper subclass of simple matrix languages, known to be mildly context-sensitive ones, is still mildly context-sensitive. Furthermore, we get an infinite hierarchy of mildly context-sensitive families of languages. Then we attempt to fill a gap regarding the linguistic relevance of these mechanisms which consists in defining a tree structure on the strings generated by many-dimensional external contextual grammars, and investigate some related issues. Several open problems are finally discussed

Introduction: Endotracheal intubation in the prehospital setting poses unique challengeswhere multiple ETI attempts are associated with adverse patient outcomes. Early identificationof difficult ETI cases will allow providers to tailor airway-man agement efforts to minimizecomplications associated with ETI. We sought to derive and validate a prehospital difficult airwayidentification tool based on predictors of difficult ETI in other settings. Methods: We prospectively collected patient and airway data on all airway attempts from 16Advanced Life Support ground emergency medical services agencies from January2011 to October 2014. Cases that required more than two ETI attempts and cases where analternative airway strategy was employed after one unsuccessful ETIattempt were categorized as “difficult.” We used a random allocation sequence to split the datainto derivation and validation subsets. Using backward elimination, factors with a p 3, limited neckmovement, trismus/jaw clenched, inability to palpate thelandmarks of the neck, and fluid in the airwa y such as blood or emesis. This was the most parsimonious model and exhibited good fit with an AUC of 0.68. When applied to the validatio n set,the model had an AUC of 0.63 with high specificity for identifying di fficult ETI if >2factors were present ). Conclusion: We have developed a simple tool using five factors that may aid p rehospitalproviders in the identification of difficult ETI.

Nowadays, the high-temperature plasticity of yttria-stabilized tetragonal zirconia polycrystals is successfully explained in terms of a threshold stress. Despite the fact that its existence is very well proved experimentally, the origin and nature of the threshold stress are still unexplained. This work develops a possible explanation for the threshold stress in YTZPs. The model developed in this paper is able to explain quantitatively the dependence of this threshold stress with temperature and grain size. The model is able to predict the influence of a glassy phase present at grain boundaries and the values of the threshold stress in YTZP nanocrystals. The theoretical results are discussed and compared with the available data in the literature