Chemical studies of the degree of decomposition and dissolution in microwave digests

Most methods for the determination of trace elements in organic matter require the sample to be brought into solution, which may be achieved by heating with strong oxidising agents such as concentrated mineral acids, to decompose the organic matrix sufficiently to render the sample soluble, whilst not necessarily achieving complete decomposition. The use of microwave heating for this purpose, using sealed vessels under pressure, was investigated for a variety of food samples. One drawback of this otherwise rapid method is the time taken to cool the vessels before opening. The use of liquid nitrogen to cool the vessel walls - before, during and after the heating cycle - was investigated, and its effect on the progress of the digestion was assessed. Another problem is the control of internal pressure, which can rise very rapidly when digesting samples of high organic content, and ways of controlling excess pressure when digesting larger samples were devised. These included the use of an open pre-digestion under reflux using a microwavetransparent coolant liquid, and the use of vessels capable of withstanding higher pressures. The latter proved more convenient as they enabled complete dissolution to be achieved in a single stage without pre-digestion, although cooling of these vessels was much slower than for the low pressure vessels, so overall sample preparation time was similar. Various methods were developed for the complete dissolution of the samples using nitric acid and hydrogen peroxide. The degree of decomposition achieved for the different methods and sample types was monitored by measurement of residual carbon in the digests. A few samples were virtually completely decomposed with nitric acid alone, while the use of hydrogen peroxide, following a nitric acid digestion, was found to reduce residual carbon substantially in the others. The undecomposed material was analysed by various methods including ultraviolet/visible spectrometry, infrared spectrometry and thin layer chromatography. Decomposition products were found to include carboxylic acids, oxalates, phosphates, nitrates and nitro-aromatics. Complete decomposition of milk powder, which proved most resistant to oxidation, was achieved by further treatment with perchloric acid. This was found necessary for anodic stripping voltammetric analysis, which required the destruction of interfering organic species for accurate determination of trace elements, unlike other techniques such as inductively coupled plasma-mass spectrometry, where complete decomposition was not required

Content and discontent: a qualitative exploration of obstacles to elearning engagement in medical students

BACKGROUND: Elearning is ubiquitous in healthcare professions education. Its equivalence to ‘traditional’ educational delivery methods is well established. There is a research imperative to clarify when and how to use elearning most effectively to mitigate the potential of it becoming merely a ‘disruptive technology.’ Research has begun to broadly identify challenges encountered by elearning users. In this study, we explore in depth the perceived obstacles to elearning engagement amongst medical students. Sensitising concepts of achievement emotions and the cognitive demands of multi-tasking highlight why students’ deeply emotional responses to elearning may be so important in their learning. METHODS: This study used focus groups as a data collection tool. A purposeful sample of 31 participated. Iterative data gathering and analysis phases employed a constant comparative approach to generate themes firmly grounded in participant experience. RESULTS: Key themes that emerged from the data included a sense of injustice, passivity and a feeling of being ‘lost at sea’. The actual content of the elearning resource provided important context. CONCLUSIONS: The identified themes have strong emotional foundations. These responses, interpreted through the lens of achievement emotions, have not previously been described. Appreciation of their importance is of benefit to educators involved in curriculum development or delivery. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12909-016-0710-5) contains supplementary material, which is available to authorized users

Seasonal Variation in 25(OH)D at Aberdeen (57°N) and Bone Health Indicators- Could Holidays in the Sun and Cod Liver Oil Supplements Alleviate Deficiency?

Vitamin D has been linked with many health outcomes. The aim of this longitudinal study, was to assess predictors of seasonal variation of 25-hydroxy-vitamin D (25(OH)D) (including use of supplements and holidays in sunny destinations) at a northerly latitude in the UK (57°N) in relation to bone health indicators. 365 healthy postmenopausal women (mean age 62.0 y (SD 1.4)) had 25(OH)D measurements by immunoassay, serum C-telopeptide (CTX), estimates of sunlight exposure (badges of polysulphone film), information regarding holidays in sunny destinations, and diet (from food diaries, including use of supplements such as cod liver oil (CLO)) at fixed 3-monthly intervals over 15 months (subject retention 88%) with an additional 25(OH)D assessment in spring 2008. Bone mineral density (BMD) at the lumbar spine (LS) and dual hip was measured in autumn 2006 and spring 2007 (Lunar I-DXA). Deficiency prevalence (25(OH)

Changes in vitamin biomarkers during a 2-year intervention trial involving increased fruit and vegetable consumption by free-living volunteers

Peer reviewedPublisher PD

Comparing trends in BMI and waist circumference

The nature of excess body weight may be changing over time to one of greater central adiposity. The aim of this study is to determine whether BMI and waist circumference (WC) are increasing proportionately among population subgroups and the range of bodyweight, and to examine the public health implications of the findings. Our data are from two cross-sectional surveys (the US National Health and Nutrition Examination Studies (NHANES) in 1988-1994 (NHANES III) and 2005-2006), from which we have used samples of 15,349 and 4,176 participants aged ≥20 years. Between 1988-1994 and 2005-2006 BMI increased by an average of 1.8kg/m2 and WC by 4.7cm (adjusted for sex, age, race-ethnicity, and education). The increase in WC was more than could be attributed simply to increases in BMI. This independent increase in WC (of on average, 0.9cm) was consistent across the different BMI categories, sexes, education levels, and race-ethnicity groups. It occurred in younger but not older age groups. Overall in each BMI category, the prevalence of low-risk WC decreased and the prevalence of increased-risk or substantially increased-risk WC increased. These results suggest that the adverse health consequences associated with obesity may be increasingly underestimated by trends in BMI alone. Since WC is closely linked to adverse cardiovascular outcomes, it is important to know the prevailing trends in both of these parameters

Modifiable lifestyle factors associated with risk of sessile serrated polyps, conventional adenomas, and hyperplastic polyps

ObjectiveTo identify modifiable factors associated with sessile serrated polyps (SSPs) and compare the association of these factors with conventional adenomas (ADs) and hyperplastic polyps (HPs).DesignWe used data from the Tennessee Colorectal Polyp Study, a colonoscopy-based case–control study. Included were 214 SSP cases, 1779 AD cases, 560 HP cases and 3851 polyp-free controls.ResultsCigarette smoking was associated with increased risk for all polyps and was stronger for SSPs than for ADs (OR 1.74, 95% CI 1.16 to 2.62, for current vs never, ptrend=0.008). Current regular use of non-steroidal anti-inflammatory drugs was associated with a 40% reduction in SSP risk in comparison with never users (OR 0.68, 95% CI 0.48 to 0.96, ptrend=0.03), similar to the association with AD. Red meat intake was strongly associated with SSP risk (OR 2.59, 95% CI 1.41 to 4.74 for highest vs lowest intake, ptrend&lt;0.001) and the association with SSP was stronger than with AD (ptrend=0.003). Obesity, folate intake, fibre intake and fat intake were not associated with SSP risk after adjustment for other factors. Exercise, alcohol use and calcium intake were not associated with risk for SSPs.ConclusionsSSPs share some modifiable risk factors for ADs, some of which are more strongly associated with SSPs than ADs. Thus, preventive efforts to reduce risk for ADs may also be applicable to SSPs. Additionally, SSPs have some distinctive risk factors. Future studies should evaluate the preventive strategies for these factors. The findings from this study also contribute to an understanding of the aetiology and biology of SSPs.</jats:sec

‘Blind time’ – current limitations on laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) for ultra-transient signal isotope ratio analysis and application to individual sub-micron sized uranium particles

The application of laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) to the isotope ratio analysis of UOx particles has the potential to improve the isotopic determination of these particles when compared to currently utilised ICP-MS techniques. To investigate this a high-speed, integrated ablation cell and dual concentric injector design was tested in the expectation that the resulting increase in signal to noise ratio and sample ion yield would improve the determination of 234U/238U, 235U/238U and 236U/238U for such materials. However, when compared to a slower washout, more established low-volume cell design, the highly transient signals of the new design proved challenging for the mixed detector array of the multi-collector mass spectrometer, introducing a new bias. We describe a major component of this bias, referred to as ‘blind time’, and model its impact on UOx particle analysis. After accounting for blind time, average precisions for the uranium isotopic composition of sub-micron sized UOx particles using LA-MC-ICP-MS were 3% 1RSD for 235U/238U and 8% 1RSD for 234U/238U. When ablating a glass rather than a UOx particle, uncertainties of 1.3% 1RSD for 235U/238U were achieved for 150 nm equivalent particle sizes using LA-MC-ICP-MS

A high anticholinergic burden is associated with a history of falls in the previous year in middle-aged women:findings from the Aberdeen Prospective Osteoporosis Screening Study

APOSS was funded by the Grampian Osteoporosis Trust. A.D.A. received an Aberdeen Summer Research Scholarship supported by the funding from the Grampian Osteoporosis Trust Charity. The funder has no role in design, analysis, interpretation and reporting of the work presented. We gratefully acknowledge the Steering Committee of APOSS for permission to conduct this research.Peer reviewedPostprin