The Effect of Planarization on Width

We study the effects of planarization (the construction of a planar diagram $D$ from a non-planar graph $G$ by replacing each crossing by a new vertex) on graph width parameters. We show that for treewidth, pathwidth, branchwidth, clique-width, and tree-depth there exists a family of $n$-vertex graphs with bounded parameter value, all of whose planarizations have parameter value $\Omega(n)$. However, for bandwidth, cutwidth, and carving width, every graph with bounded parameter value has a planarization of linear size whose parameter value remains bounded. The same is true for the treewidth, pathwidth, and branchwidth of graphs of bounded degree.Comment: 15 pages, 6 figures. To appear at the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

Algorithms for outerplanar graph roots and graph roots of pathwidth at most 2

Deciding whether a given graph has a square root is a classical problem that has been studied extensively both from graph theoretic and from algorithmic perspectives. The problem is NP-complete in general, and consequently substantial effort has been dedicated to deciding whether a given graph has a square root that belongs to a particular graph class. There are both polynomial-time solvable and NP-complete cases, depending on the graph class. We contribute with new results in this direction. Given an arbitrary input graph G, we give polynomial-time algorithms to decide whether G has an outerplanar square root, and whether G has a square root that is of pathwidth at most 2

The association between survey timing and patient-reported experiences with hospitals: results of a national postal survey

<p>Abstract</p> <p>Background</p> <p>Research on the effect of survey timing on patient-reported experiences and patient satisfaction with health services has produced contradictory results. The objective of this study was thus to assess the association between survey timing and patient-reported experiences with hospitals.</p> <p>Methods</p> <p>Secondary analyses of a national inpatient experience survey including 63 hospitals in the 5 health regions in Norway during the autumn of 2006. 10,912 (45%) patients answered a postal questionnaire after their discharge from hospital. Non-respondents were sent a reminder after 4 weeks. Multilevel linear regression analysis was used to assess the association between survey timing and patient-reported experiences, both bivariate analysis and multivariate analysis controlling for other predictors of patient experiences.</p> <p>Results</p> <p>Multivariate multilevel regression analysis revealed that survey time was significantly and negatively related to three of six patient-reported experience scales: doctor services (Beta = -0.424, <it>p</it>< 0.05), information about examinations (Beta = -0.566, <it>p </it>< 0.05) and organization (Beta = -0.528, <it>p </it>< 0.05). Patient age, self-perceived health and type of admission were significantly related to all patient-reported experience scales (better experiences with higher age, better health and routine admission), and all other predictors had at least one significant association with patient-reported experiences.</p> <p>Conclusions</p> <p>Survey time was significantly and negatively related to three of the six scales for patient-reported experiences with hospitals. Large differences in survey time across hospitals could be problematic for between-hospital comparisons, implying that survey time should be considered as a potential adjustment factor. More research is needed on this topic, including studies with other population groups, other data collection modes and a longer time span.</p

(Homo)glutathione Deficiency Impairs Root-knot Nematode Development in Medicago truncatula

Root-knot nematodes (RKN) are obligatory plant parasitic worms that establish and maintain an intimate relationship with their host plants. During a compatible interaction, RKN induce the redifferentiation of root cells into multinucleate and hypertrophied giant cells essential for nematode growth and reproduction. These metabolically active feeding cells constitute the exclusive source of nutrients for the nematode. Detailed analysis of glutathione (GSH) and homoglutathione (hGSH) metabolism demonstrated the importance of these compounds for the success of nematode infection in Medicago truncatula. We reported quantification of GSH and hGSH and gene expression analysis showing that (h)GSH metabolism in neoformed gall organs differs from that in uninfected roots. Depletion of (h)GSH content impaired nematode egg mass formation and modified the sex ratio. In addition, gene expression and metabolomic analyses showed a substantial modification of starch and γ-aminobutyrate metabolism and of malate and glucose content in (h)GSH-depleted galls. Interestingly, these modifications did not occur in (h)GSH-depleted roots. These various results suggest that (h)GSH have a key role in the regulation of giant cell metabolism. The discovery of these specific plant regulatory elements could lead to the development of new pest management strategies against nematodes

Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

Simulated consultations: a sociolinguistic perspective

Background: Assessment of consulting skills using simulated patients is widespread in medical education. Most research into such assessment is sited in a statistical paradigm that focuses on psychometric properties or replicability of such tests. Equally important, but less researched, is the question of how far consultations with simulated patients reflect real clinical encounters – for which sociolinguistics, defined as the study of language in its socio-cultural context, provides a helpful analytic lens. Discussion: In this debate article, we draw on a detailed empirical study of assessed role-plays, involving sociolinguistic analysis of talk in OSCE interactions. We consider critically the evidence for the simulated consultation (a) as a proxy for the real; (b) as performance; (c) as a context for assessing talk; and (d) as potentially disadvantaging candidates trained overseas. Talk is always a performance in context, especially in professional situations (such as the consultation) and institutional ones (the assessment of professional skills and competence). Candidates who can handle the social and linguistic complexities of the artificial context of assessed role-plays score highly – yet what is being assessed is not real professional communication, but the ability to voice a credible appearance of such communication. Summary: Fidelity may not be the primary objective of simulation for medical training, where it enables the practising of skills. However the linguistic problems and differences that arise from interacting in artificial settings are of considerable importance in assessment, where we must be sure that the exam construct adequately embodies the skills expected for real-life practice. The reproducibility of assessed simulations should not be confused with their validity. Sociolinguistic analysis of simulations in various professional contexts has identified evidence for the gap between real interactions and assessed role-plays. The contextual conditions of the simulated consultation both expect and reward a particular interactional style. Whilst simulation undoubtedly has a place in formative learning for professional communication, the simulated consultation may distort assessment of professional communication These sociolinguistic findings contribute to the on-going critique of simulations in high-stakes assessments and indicate that further research, which steps outside psychometric approaches, is necessary

Modelling and experimental studies on the transfer of radionuclides to fruit

Although fruit is an important component of the diet, the extent to which it contributes to radiological exposure remains unclear, partially as a consequence of uncertainties in models and data used to assess transfer of radionuclides in the food chain. A Fruits Working Group operated as part of the IAEA BIOMASS (BIOsphere Modelling and ASSessment) programme from 1997 to 2000, with the aim of improving the robustness of the models that are used for radiological assessment. The Group completed a number of modelling and experimental activities including: (i) a review of experimental, field and modelling information on the transfer of radionuclides to fruit; (ii) discussion of recently completed or ongoing experimental studies; (iii) development of a database on the transfer of radionuclides to fruit; (iv) development of a conceptual model for fruit and (v) two model intercomparison studies and a model validation study. The Group achieved significant advances in understanding the processes involved in transfer of radionuclides to fruit. The work demonstrated that further experimental and modelling studies are required to ensure that the current generation of models can be applied to a wide range of scenarios