THE INTERFERENCE FREE DETERMINATION OF SELENIUM IN ENVIRONMENTAL AND CLINICAL SAMPLES BY ICP-MS

The determination of selenium in environmental and clinical samples by ICP-MS is complicated by both poor sensitivity and severe interferences resulting from both the sample matrix and the argon plasma. The purpose of this study was to investigate ways of overcoming these problems thus enabling Se to be determined both accurately and precisely. A novel procedure for the accurate determination of selenium in serum using electrothermal vaporisation inductively coupled plasma mass spectrometry (ETV-ICP-MS) has been developed. A simple 1:20 dilution of the serum with 1% nitric acid negates the need for a lengthy sample digestion procedure. Several of the interferences normally associated with the analysis of selenium by ICP-MS are successfully eliminated. Analytical method characteristics include; detection limits of approximately 0.l ng gˉ¹ for 77Se and 82Se, short and long term reproducibility between 4.7% and 4.9%, and 3.2% and 3.8% (RSD) for 77Se and 82Se respectively, and accuracy of ±1.81% (77Se) and± 1.10% (82Se) for the certified reference material NIST SRM 1598. Further development of the procedure involved the application of isotope dilution analysis with the measurement of the 82Se/77Se isotope ratio, following spiking with selenium enriched in 77Se. Accuracy (±0-2%) and precision (±1-3%) of the method is demonstrated with the analysis of several certified reference materials (TMRAIN-95, LGC 6010, TMDA-54.2 and NIST 1598) where all results fell within the certified limits. A comparison of the new ETV procedures with established ICP-MS methods involving hydride generation and the use of organic solvents with pneumatic nebulisation was performed. Full uncertainty estimates for each of the procedures investigated were calculated. The uncertainty estimates calculated highlight the improvements in accuracy and precision achievable with isotope dilution analysis, demonstrated by a 2.5 fold improvement in the uncertainty compared with the non-IDMS ETV procedure. The addition of nitrogen and helium to the different Ar gas streams of the ETV-ICP-MS system was performed. The introduction of both nitrogen and helium to the argon nebuliser and outer gas streams, resulted in a reduction in the interference from argon polyatomic species. Careful optimisation of plasma parameters such as RF power and gas flow rates using a plasma containing 50% helium in the argon outer gas stream, successfully gave rise to a 2-fold improvement in the detection limits for 76Se and 78Se compared with an argon only plasma. This study has resulted in the successful development of a high accuracy procedure to determine selenium in both environmental and clinical samples. This is of great importance considering the high level of interest regarding selenium and human health matters and the significance of accurate analytical data.LGC, Teddington, Middlesex, TWll OL

Non-linear exchange rate pass through in industrial economies

This paper presents theoretical arguments for a non-linear pass-through relationship for import and export prices and investigates the relationship empirically. The theoretical argument is based on the menu-cost approach in which small absolute changes in exchange rates may not prompt price changes because the costs of doing so exceed the extra profits generated for firms involved in international trade. This relationship is investigated empirically using quarterly data for the period 1979q1 to 2015q1 for a sample of seventeen countries. In the case of import prices, evidence is found of non-linear adjustment consistent with the theoretical model in four out of seventeen cases. In the case of export prices, such a relationship is only evident for two economies in the sample. However, for both the import and export price cases, a significant positive non-linear relationship is found for the two largest economies in the sample i.e. the United States and Japan

Teaching the multiplier: the value of a quantitative approach

To create an engaging and motivating learning environment, we have developed software which is based on estimated parameters for the UK economy. The program allows students to both simulate the effects of economic policy on national income and its components as well as the flexibility to vary key parameters of interest in order to assess the impact on economic performance. In this paper we present the main features of the software and the model on which it is based. We discuss the potential uses of the software within a class-room context and consider two simulations. The first of these is a fiscal expansion designed to bring down unemployment and the second is an exogenous shock to consumption affecting the parameters of the consumption-income relationship. This paper advocates that students' understanding of theoretical models can be greatly enhanced by the addition of practical examples that can be used in lectures and tutorials as well as for independent study

The subjective world of home care workers in dementia: an “order of worth” analysis

The perspective of domiciliary workers is needed to recruit a high-quality workforce and meet growing demand. An English ethnographic study yielded extensive insights. To structure analysis of the study data, we apply a method developed by political theorists Boltanski and Thévenot that identifies key variables in different values systems. This “orders of worth” framework is used to map out the distinctive features of the subjective world of home carers. The results can be drawn on to formulate recruitment and retention policies, to design reward strategies or to ensure that training and education opportunities engage effectively with the workforce

A Canadian Study toward Changing Local Practice in the Diagnosis of Pediatric Celiac Disease

Background. The European Society for Pediatric Gastroenterology, Hepatology and Nutrition endorses serological diagnosis (SD) for pediatric celiac disease (CD). The objective of this study was to pilot SD and to prospectively evaluate gastrointestinal permeability and mucosal inflammation at diagnosis and after one year on the gluten-free diet (GFD). We hypothesized that SD would be associated with similar short term outcomes as ED. Method. Children, 3-17 years of age, referred for possible CD were eligible for SD given aTTG level ≥200 U/mL, confirmed by repeat aTTG and HLA haplotypes. Gastrointestinal permeability, assessed using sugar probes, and inflammation, assessed using fecal calprotectin (FC), at baseline and after one year on a GFD were compared to patients who had ED. Results. Enrolled SD ( = 40) and ED ( = 48) patients had similar demographics. ED and SD groups were not different in baseline lactulose: mannitol ratio (L : M) (0.049 versus 0.034; = 0.07), fractional excretion of sucrose (%FES; 0.086 versus 0.092; = 0.44), or fecal calprotectin (FC; 89.6 versus 51.4; = 0.05). At follow-up, urine permeability improved and was similar between groups, L : M (0.022 versus 0.025; = 0.55) and %FES (0.040 versus 0.047; = 0.87) ( > 0.05). FC improved but remained higher in the SD group (37.1 versus 15.9; = 0.04). Conclusion. Patients on the GFD showed improved intestinal permeability and mucosal inflammation regardless of diagnostic strategy. This prospective study supports that children diagnosed by SD have resolving mucosal disease early after commencing a GFD

'Going the extra mile' for older people with dementia: Exploring the voluntary labour of homecare workers.

Homecare workers provide essential physical, social and emotional support to growing numbers of older people with dementia in the UK. Although it is acknowledged that the work can sometimes be demanding, some homecare workers regularly 'go the extra mile' for service users, working above and beyond the usual remit of the job. This form of voluntarism has been interpreted as an expression of an essentially caring nature, but also as the product of a work environment structured to tacitly endorse the provision of unpaid labour. This paper draws on a qualitative study of what constitutes 'good' homecare for older people with dementia. Using homecare workers' reflexive diaries ( n = 11) and interviews with homecare workers ( n = 14) and managers ( n = 6), we explore manifestations of, and motivations for, homecare workers going the extra mile in their everyday work. We describe three modes of voluntary labour based on these accounts which we characterise as affective, performative and pragmatic. Our study highlights the complex relationships between job satisfaction, social benefit and commercial gain in the homecare work sector. Further research is needed to define the full range of affective and technical skills necessary to deliver good homecare, and to ensure that homecare work is appropriately credited

2018 Scholars at Work Conference Program

Program for the 2018 Scholars at Work Conference at Minnesota State University, Mankato on March 30, 2018

Network Structure of Vertebrate Scavenger Assemblages at the Global Scale: Drivers and Ecosystem Functioning Implications

The organization of ecological assemblages has important implications for ecosystem functioning, but little is known about how scavenger communities organize at the global scale. Here, we test four hypotheses on the factors affecting the network structure of terrestrial vertebrate scavenger assemblages and its implications on ecosystem functioning. We expect scavenger assemblages to be more nested (i.e. structured): 1) in species‐rich and productive regions, as nestedness has been linked to high competition for carrion resources, and 2) regions with low human impact, because the most efficient carrion consumers that promote nestedness are large vertebrate scavengers, which are especially sensitive to human persecution. 3) We also expect climatic conditions to affect assemblage structure, because some scavenger assemblages have been shown to be more nested in colder months. Finally, 4) we expect more organized assemblages to be more efficient in the consumption of the resource. We first analyzed the relationship between the nestedness of the scavenger assemblages and climatic variables (i.e. temperature, precipitation, temperature variability and precipitation variability), ecosystem productivity and biomass (i.e. NDVI) and degree of human impact (i.e. human footprint) using 53 study sites in 22 countries across five continents. Then, we related structure (i.e. nestedness) with its function (i.e. carrion consumption rate). We found a more nested structure for scavenger assemblages in regions with higher NDVI values and lower human footprint. Moreover, more organized assemblages were more efficient in the consumption of carrion. However, our results did not support the prediction that the structure of the scavenger assemblages is directly related to climate. Our findings suggest that the nested structure of vertebrate scavenger assemblages affects its functionality and is driven by anthropogenic disturbance and ecosystem productivity worldwide. Disarray of scavenger assemblage structure by anthropogenic disturbance may lead to decreases in functionality of the terrestrial ecosystems via loss of key species and trophic facilitation processes

Scavenging in the Anthropocene: Human impact drives vertebrate scavenger species richness at a global scale

Understanding the distribution of biodiversity across the Earth is one of the most challenging questions in biology. Much research has been directed at explaining the species latitudinal pattern showing that communities are richer in tropical areas; however, despite decades of research, a general consensus has not yet emerged. In addition, global biodiversity patterns are being rapidly altered by human activities. Here, we aim to describe large‐scale patterns of species richness and diversity in terrestrial vertebrate scavenger (carrion‐consuming) assemblages, which provide key ecosystem functions and services. We used a worldwide dataset comprising 43 sites, where vertebrate scavenger assemblages were identified using 2,485 carcasses monitored between 1991 and 2018. First, we evaluated how scavenger richness (number of species) and diversity (Shannon diversity index) varied among seasons (cold vs. warm, wet vs. dry). Then, we studied the potential effects of human impact and a set of macroecological variables related to climatic conditions on the scavenger assemblages. Vertebrate scavenger richness ranged from species‐poor to species rich assemblages (4–30 species). Both scavenger richness and diversity also showed some seasonal variation. However, in general, climatic variables did not drive latitudinal patterns, as scavenger richness and diversity were not affected by temperature or rainfall. Rainfall seasonality slightly increased the number of species in the community, but its effect was weak. Instead, the human impact index included in our study was the main predictor of scavenger richness. Scavenger assemblages in highly human‐impacted areas sustained the smallest number of scavenger species, suggesting human activity may be overriding other macroecological processes in shaping scavenger communities. Our results highlight the effect of human impact at a global scale. As speciesrich assemblages tend to be more functional, we warn about possible reductions in ecosystem functions and the services provided by scavengers in human‐dominated landscapes in the Anthropocene