On chains in HH-closed topological pospaces

We study chains in an $H$-closed topological partially ordered space. We give sufficient conditions for a maximal chain $L$ in an $H$-closed topological partially ordered space such that $L$ contains a maximal (minimal) element. Also we give sufficient conditions for a linearly ordered topological partially ordered space to be $H$-closed. We prove that any $H$-closed topological semilattice contains a zero. We show that a linearly ordered $H$-closed topological semilattice is an $H$-closed topological pospace and show that in the general case this is not true. We construct an example an $H$-closed topological pospace with a non-$H$-closed maximal chain and give sufficient conditions that a maximal chain of an $H$-closed topological pospace is an $H$-closed topological pospace.Comment: We have rewritten and substantially expanded the manuscrip

Normally preordered spaces and utilities

In applications it is useful to know whether a topological preordered space is normally preordered. It is proved that every $k_\omega$-space equipped with a closed preorder is a normally preordered space. Furthermore, it is proved that second countable regularly preordered spaces are perfectly normally preordered and admit a countable utility representation.Comment: 17 pages, 1 figure. v2 contains a second proof to the main theorem with respect to the published version. The last section of v1 is not present in v2. It will be included in a different wor

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

Tobacco smoking prevalence among a cross-section of dentists in Queensland, Australia

The purpose of this study was to investigate the epidemiology of tobacco smoking among dentists in Queensland, Australia. We utilized an anonymous, self-reporting questionnaire which was posted to 400 dentists during 2004. The overall response rate was 72.1%, among whom the prevalence of current smoking was estimated to be 3.9% (95%CI: 2.2-6.9), with a further 11.0% being ex-smokers (95%CI: 7.9-15.2). Smoking rates varied by age, with 6.1% of dentists aged younger than 30 years who were smokers. The lowest smoking prevalence was seen among dentists aged between 30 and 40 years (1.4%), and the highest among those aged over 60 years (7.1%). Regarding weekly work hours, the highest smoking prevalence was seen among dentists who worked between 25 and 35 hrs per week (6.8%). Ex-smokers were more likely to work less than 25 hrs per week (21.7%). Smoking rates also varied by career length, with the lowest prevalence among dentists who had worked 10 to 20 years (1.3%) and the highest rate among those who had worked over 40 years (6.7%). A similar trend was revealed for ex-smokers, with prevalence rates of 1.7% and 33.3%, respectively. Overall, our study suggests that the prevalence of smoking is rather low among Queensland dentists. As the distribution of smoking was not uniform however, future preventive measures will need to consider the individual situation of dentists who smoke, particularly those in the older age groups