The Twittering Presidents An analysis of tweets from @BarackObama and @realDonaldTrump

This paper uses a Systemic Functional Multimodal Discourse Analysis (SF-MDA) approach to analyse tweets from the Twitter accounts of Presidents Barack Obama (@Barack Obama) and Donald Trump (@realDonaldTrump). The tweets were posted during the last nine months of President Obama’s effective presidency and the first nine months of President Trump’s presidency. The tweets are analysed using automated text analysis which is interpreted through an SF-MDA lens, supplemented by manual analysis. The analysis examines ideational and interpersonal emphasis in the tweets with the aim of showing how the composition and content construct a view of how each president and his presidency are presented to the public. The findings suggest marked contrasts in presidential style with President Trump foregrounding the interpersonal while President Obama foregrounds the ideational. Where President Trump presents as self-promoting, autocratic, opinionated and igniting discord in his tweets, President Obama presents as democratic, moderate, restrained and seeking social harmony

Mass spectrometry of B. subtilis CopZ: Cu(I)-binding and interactions with bacillithiol

CopZ from Bacillus subtilis is a well-studied member of the highly conserved family of Atx1-like copper chaperones. It was previously shown via solution and crystallographic studies to undergo Cu(I)-mediated dimerisation, where the CopZ dimer can bind between one and four Cu(I) ions. However, these studies could not provide information about the changing distribution of species at increasing Cu(I) levels. To address this, electrospray ionisation mass spectrometry using soft ionisation was applied to CopZ under native conditions. Data revealed folded, monomeric CopZ in apo- and Cu(I)-bound forms, along with Cu(I)-bound dimeric forms of CopZ at higher Cu(I) loading. Cu4(CopZ)2 was the major dimeric species at loadings >1 Cu(I)/CopZ, indicating the cooperative formation of the tetranuclear Cu(I)-bound species. As the principal low molecular weight thiol in B. subtilis, bacillithiol (BSH) may play a role in copper homeostasis. Mass spectrometry showed that increasing BSH led to a reduction in Cu(I)-bound dimeric forms, and the formation of S-bacillithiolated apo-CopZ and BSH adducts of Cu(I)-bound forms of CopZ, where BSH likely acts as a Cu(I) ligand. These data, along with the high affinity of BSH for Cu(I), determined here to be β2(BSH) = ∼4 × 1017 M−2, are consistent with a role for BSH alongside CopZ in buffering cellular Cu(I) levels. Here, mass spectrometry provides a high resolution overview of CopZ–Cu(I) speciation that cannot be obtained from less discriminating solution-phase methods, thus illustrating the potential for the wider application of this technique to studies of metal–protein interactions

Plant species' origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands

Exotic species dominate many communities; however the functional significance of species’ biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands

Chlorhexidine versus povidone–iodine skin antisepsis before upper limb surgery (CIPHUR) : an international multicentre prospective cohort study

Introduction Surgical site infection (SSI) is the most common and costly complication of surgery. International guidelines recommend topical alcoholic chlorhexidine (CHX) before surgery. However, upper limb surgeons continue to use other antiseptics, citing a lack of applicable evidence, and concerns related to open wounds and tourniquets. This study aimed to evaluate the safety and effectiveness of different topical antiseptics before upper limb surgery. Methods This international multicentre prospective cohort study recruited consecutive adults and children who underwent surgery distal to the shoulder joint. The intervention was use of CHX or povidone–iodine (PVI) antiseptics in either aqueous or alcoholic form. The primary outcome was SSI within 90 days. Mixed-effects time-to-event models were used to estimate the risk (hazard ratio (HR)) of SSI for patients undergoing elective and emergency upper limb surgery. Results A total of 2454 patients were included. The overall risk of SSI was 3.5 per cent. For elective upper limb surgery (1018 patients), alcoholic CHX appeared to be the most effective antiseptic, reducing the risk of SSI by 70 per cent (adjusted HR 0.30, 95 per cent c.i. 0.11 to 0.84), when compared with aqueous PVI. Concerning emergency upper limb surgery (1436 patients), aqueous PVI appeared to be the least effective antiseptic for preventing SSI; however, there was uncertainty in the estimates. No adverse events were reported. Conclusion The findings align with the global evidence base and international guidance, suggesting that alcoholic CHX should be used for skin antisepsis before clean (elective upper limb) surgery. For emergency (contaminated or dirty) upper limb surgery, the findings of this study were unclear and contradict the available evidence, concluding that further research is necessary

Predicting invasion in grassland ecosystems: is exotic dominance the real embarrassment of richness?

Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance by a single exotic species. Here, we used a globally replicated study to quantify relationships between exotic richness and abundance in grass-dominated ecosystems in 13 countries on six continents, ranging from salt marshes to alpine tundra. We tested effects of human land use, native community diversity, herbivore pressure, and nutrient limitation on exotic plant dominance. Despite its widespread use, exotic richness was a poor proxy for exotic dominance at low exotic richness, because sites that contained few exotic species ranged from relatively pristine (low exotic richness and cover) to almost completely exotic-dominated ones (low exotic richness but high exotic cover). Both exotic cover and richness were predicted by native plant diversity (native grass richness) and land use (distance to cultivation). Although climate was important for predicting both exotic cover and richness, climatic factors predicting cover (precipitation variability) differed from those predicting richness (maximum temperature and mean temperature in the wettest quarter). Herbivory and nutrient limitation did not predict exotic richness or cover. Exotic dominance was greatest in areas with low native grass richness at the site- or regional-scale. Although this could reflect native grass displacement, a lack of biotic resistance is a more likely explanation, given that grasses comprise the most aggressive invaders. These findings underscore the need to move beyond richness as a surrogate for the extent of invasion, because this metric confounds monodominance with invasion resistance. Monitoring species’ relative abundance will more rapidly advance our understanding of invasions.This is the publisher’s final pdf. The published article is copyrighted by John Wiley & Sons Ltd and can be found at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2486

The discourses of secondary school mathematics

A systemic functional analysis of the oral pedagogical discourse and board texts of secondary school mathematics lessons differentiated on the basis of school sector, gender and social class is completed through the development of a computer program to handle the linguistic analysis and the construction of a Hallidayan systemic framework for mathematical symbolism and visual depiction. The new frameworks allow for investigation of the unique contributions of language, mathematical symbolism and visual display in the construction of meaning in mathematical texts and the process of semiotic metaphor which occurs in movements between these codes. The systemic analysis of the classroom discourse is situated within a Foucauldian perspective of power, knowledge and truth in mathematics, mathematics education and wider discursive practices involving the private and state school sectors. The analysis of linguistic patterns, register selections and genres of four Year Ten secondary school mathematics lessons reveals that in private elite single sex schools the male students demonstrate the greatest participation and access to the discourse of mathematics while the female students participate in interpersonal patterns of deference which do not resonate with the tenor dimensions of mathematics. The monofunctional tendency orientated towards interpersonal meaning in the lesson of the working class students at a government school indicates that the social goal of the lesson is primarily directed towards maintaining tenor relations through covert manipulation as opposed to learning mathematics. The limited functionality of practical lessons in mathematics is also demonstrated as a shift from everyday discourse to mathematical discourse does not occur. Mathematical pedagogical discourse is characterised by a dense texture which arises in part from the strategies by which meaning is encoded in mathematical symbolism. As opposed to the lexical density and grammatical intricacy of written and spoken language respectively, mathematical symbolism realises grammatical density whereby multiple levels of clausal rankshift preserve the nuclear configurations of Operative processes and participants which describe relations of parts to the whole and continuous patterns of variation. In addition, inherent difficulties in mathematical pedagogical discourse arise from long implication chains of reasoning and dependence on multiple semiotic resources with the latter resulting in referential complexity and iii multisemiotic intertwining of lexical and participant chains and strings. The results of the analysis, interpreted through Bernstein's theory of pedagogical practices and coding orientations and Halliday's formulations of spoken and written language, reveal that the semantic orientation of working class students does not accord with that realised in mathematics