Analysis of large oxygenated and nitrated polycyclic aromatic hydrocarbons formed under simulated diesel engine exhaust conditions (by compound fingerprints with SPE/LC-API-MS)

The analysis of organic compounds in combustion exhaust particles and the chemical transformation of soot by nitrogen oxides are key aspects of assessment and mitigation of the climate and health effects of aerosol emissions from fossil fuel combustion and biomass burning. In this study we present experimental and analytical techniques for efficient investigation of oxygenated and nitrated derivatives of large polycyclic aromatic hydrocarbons (PAHs), which can be regarded as well-defined soot model substances. For coronene and hexabenzocoronene exposed to nitrogen dioxide under simulated diesel exhaust conditions, several reaction products with high molecular mass could be characterized by liquid chromatography-atmospheric pressure chemical (and photo) ionization-mass spectrometry (LC-APCI-MS and LC-APPI-MS). The main products of coronene contained odd numbers of nitrogen atoms (m/z 282, 256, 338), whereas one of the main products of hexabenzocoronene exhibited an even number of nitrogen atoms (m/z 391). Various reaction products containing carbonyl and nitro groups could be tentatively identified by combining chromatographic and mass spectrometric information, and changes of their relative abundance were observed to depend on the reaction conditions. This analytical strategy should highlight a relatively young technique for the characterization of various soot-contained, semi-volatile, and semi-polar reaction products of large PAHs

Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy

Background A reliable system for grading operative difficulty of laparoscopic cholecystectomy would standardise description of findings and reporting of outcomes. The aim of this study was to validate a difficulty grading system (Nassar scale), testing its applicability and consistency in two large prospective datasets. Methods Patient and disease-related variables and 30-day outcomes were identified in two prospective cholecystectomy databases: the multi-centre prospective cohort of 8820 patients from the recent CholeS Study and the single-surgeon series containing 4089 patients. Operative data and patient outcomes were correlated with Nassar operative difficultly scale, using Kendall’s tau for dichotomous variables, or Jonckheere–Terpstra tests for continuous variables. A ROC curve analysis was performed, to quantify the predictive accuracy of the scale for each outcome, with continuous outcomes dichotomised, prior to analysis. Results A higher operative difficulty grade was consistently associated with worse outcomes for the patients in both the reference and CholeS cohorts. The median length of stay increased from 0 to 4 days, and the 30-day complication rate from 7.6 to 24.4% as the difficulty grade increased from 1 to 4/5 (both p < 0.001). In the CholeS cohort, a higher difficulty grade was found to be most strongly associated with conversion to open and 30-day mortality (AUROC = 0.903, 0.822, respectively). On multivariable analysis, the Nassar operative difficultly scale was found to be a significant independent predictor of operative duration, conversion to open surgery, 30-day complications and 30-day reintervention (all p < 0.001). Conclusion We have shown that an operative difficulty scale can standardise the description of operative findings by multiple grades of surgeons to facilitate audit, training assessment and research. It provides a tool for reporting operative findings, disease severity and technical difficulty and can be utilised in future research to reliably compare outcomes according to case mix and intra-operative difficulty

Population‐based cohort study of outcomes following cholecystectomy for benign gallbladder diseases

Background The aim was to describe the management of benign gallbladder disease and identify characteristics associated with all‐cause 30‐day readmissions and complications in a prospective population‐based cohort. Methods Data were collected on consecutive patients undergoing cholecystectomy in acute UK and Irish hospitals between 1 March and 1 May 2014. Potential explanatory variables influencing all‐cause 30‐day readmissions and complications were analysed by means of multilevel, multivariable logistic regression modelling using a two‐level hierarchical structure with patients (level 1) nested within hospitals (level 2). Results Data were collected on 8909 patients undergoing cholecystectomy from 167 hospitals. Some 1451 cholecystectomies (16·3 per cent) were performed as an emergency, 4165 (46·8 per cent) as elective operations, and 3293 patients (37·0 per cent) had had at least one previous emergency admission, but had surgery on a delayed basis. The readmission and complication rates at 30 days were 7·1 per cent (633 of 8909) and 10·8 per cent (962 of 8909) respectively. Both readmissions and complications were independently associated with increasing ASA fitness grade, duration of surgery, and increasing numbers of emergency admissions with gallbladder disease before cholecystectomy. No identifiable hospital characteristics were linked to readmissions and complications. Conclusion Readmissions and complications following cholecystectomy are common and associated with patient and disease characteristics

Analysis of fatty acids and fatty alcohols reveals seasonal and sex-specific changes in the diets of seabirds

A key challenge in ecology is to find ways to obtain complete and accurate information about the diets of animals. Traditional methods of collecting such information from seabirds (usually stomach content analysis or observations of prey at nests) are hampered by biases and only give information from the immediate time of sampling. Furthermore, the period of investigation using traditional methods is often restricted to the few short months of breeding. Here, we use an analysis of fatty acids and fatty alcohols from blood, adipose tissue and stomach oil to investigate how the diets of male and female common guillemots (Uria aalge), black-legged kittiwakes (Rissa tridactyla), and northern fulmars (Fulmarus glacialis) differed through the sampling period (prelaying and breeding season) and by sex. Diets of both sexes of all three species generally varied across the season, but sex differences were apparent only in fulmars during prelaying. Our study shows that FA analysis can provide significant insights into diets of seabirds, in particular periods of the annual cycle which are not readily studied using traditional methods