Phenyl-triazine oligomers for light-driven hydrogen evolution

The design of stable, yet highly tunable organic photocatalysts which orchestrate multi-step electron transfer reactions is at the heart of the newly emerging field of polymer photocatalysis. Covalent triazine frameworks such as the archetypal CTF-1 have been theorized to constitute a new class of photocatalytically active polymers for light-driven water splitting. Here, we revisit the ionothermal synthesis of CTF-1 by trimerization of 1,4-dicyanobenzene catalyzed by the Lewis acid zinc chloride and demonstrate that the microporous black polymer CTF-1 is essentially inactive for hydrogen evolution. Instead, highly photoactive phenyl-triazine oligomers (PTOs) with higher crystallinity as compared to CTF-1 are obtained by lowering the reaction temperature to 300 °C and prolonging the reaction time to >150 hours. The low reaction temperature of the PTOs largely prevents incipient carbonization and thus results in a carbon-to-nitrogen weight ratio close to the theoretical value of 3.43. The oligomers were characterized by MALDI-TOF and quantitative solid-state NMR spectroscopy, revealing variations in size, connectivity and thus nitrile-to-triazine ratios depending on the initial precursor dilution. The most active PTO samples efficiently and stably reduce water to hydrogen with an average rate of 1076 (±278) μmol h−1 g−1 under simulated sunlight illumination, which is competitive with the best carbon nitride-based and purely organic photocatalysts. The photocatalytic activity of the PTOs is found to sensitively depend on the polymerization degree, thus suggesting a prominent role of the unreacted nitrile moieties in the photocatalytic process. Notably, PTOs even show moderate hydrogen production without the addition of any co-catalyst

Rational design of carbon nitride photocatalysts by identification of cyanamide defects as catalytically relevant sites

The heptazine-based polymer melon (also known as graphitic carbon nitride, g-C3N4) is a promising photocatalyst for hydrogen evolution. Nonetheless, attempts to improve its inherently low activity are rarely based on rational approaches because of a lack of fundamental understanding of its mechanistic operation. Here we employ molecular heptazine-based model catalysts to identify the cyanamide moiety as a photocatalytically relevant 'defect'. We exploit this knowledge for the rational design of a carbon nitride polymer populated with cyanamide groups, yielding a material with 12 and 16 times the hydrogen evolution rate and apparent quantum efficiency (400 nm), respectively, compared with the unmodified melon. Computational modelling and material characterization suggest that this moiety improves coordination (and, in turn, charge transfer kinetics) to the platinum co-catalyst and enhances the separation of the photogenerated charge carriers. The demonstrated knowledge transfer for rational catalyst design presented here provides the conceptual framework for engineering high-performance heptazine-based photocatalysts

Development of Trust in an Online Breast Cancer Forum: A Qualitative Study

Background: Online health forums provide peer support for a range of medical conditions, including life-threatening and terminal illnesses. Trust is an important component of peer-to-peer support, although relatively little is known about how trust forms within online health forums. Objective: The aim of this paper is to examine how trust develops and influences sharing among users of an online breast cancer forum. Methods: An interpretive qualitative approach was adopted. Data were collected from forum posts from 135 threads on nine boards on the UK charity, Breast Cancer Care (BCC). Semi-structured interviews were conducted with 14 BCC forum users. Both datasets were analysed thematically using Braun and Clarke’s [2006] approach and combined to triangulate analysis. Results: Trust operates in three dimensions, structural, relational and temporal, which intersect with each other and do not operate in isolation. The structural dimension relates to how the affordances and formal rules of the site affected trust. The relational dimension refers to how trust was necessarily experienced in interactions with other forum users: it emerged within relationships and was a social phenomenon. The temporal dimension relates to how trust changed over time and was influenced by the length of time users spent on the forum. Conclusions: Trust is a process that changes over time, and which is influenced by structural features of the forum and informal but collectively understood relational interactions among forum users. The study provides a better understanding of how the intersecting structural, relational and temporal aspects that support the development of trust facilitate sharing in online environments. These findings will help organisations developing online health forums

Perpetrators, victims, bystanders and up standers: cyber bullying in a special school context.

This study offers a multi-dimensional analysis of ‘real world’ cyberbullying between members of a special school community. The purpose of this article is to analyse the social and educational contexts within which interactions of this nature are embedded.The interview both illuminated a number of themes pertinent to the current literature and extended those related to the call for further analysis of the contextual determinants of cyberbullying.The influence of the conditions experienced by the children involved (Attention Deficit Hyperactivity Disorder (ADHD) and Autistic Spectrum Condition (ASC)) is discussed and demonstrated. This use of natural observation provides a current and ‘real world’ illustration of teacher perceptions of the complex behaviours and interactions occurring in cyberspace, which hold potential for grave consequences. A hopeful tone is maintained as the potential for selfless upstander behaviour and resolution via the involvement of supportive and knowledgeable pastoral staff is realised in the article’s conclusion.<br/

The Use of Sexually Explicit Internet Material and Its Antecedents: A Longitudinal Comparison of Adolescents and Adults

An implicit assumption in research on adolescents’ use of sexually explicit internet material (SEIM) is that they may feel more attracted to such material than adults, given the “forbidden” character of SEIM for minors. However, systematic comparisons between adolescents’ and adults’ SEIM use and of its antecedents are missing. We conducted a two-wave panel survey among a nationally representative sample of 1,445 Dutch adolescents and a nationally representative sample of 833 Dutch adults. Adolescents’ and adults’ SEIM use was similar. When significant differences in the SEIM use occurred, they indicated that adults used SEIM more often than adolescents. Male adults were the most frequent users of SEIM. No difference in the antecedent structure of SEIM use emerged between adolescents and adults. In both groups, males, sensation seekers, as well as people with a not exclusively heterosexual orientation used SEIM more often. Among adolescents and adults, lower life satisfaction increased SEIM use. Our findings suggest that the frequency of SEIM use and its antecedents are largely the same among adolescents and adults

Inequitable walking conditions among older people: examining the interrelationship of neighbourhood socio-economic status and urban form using a comparative case study

<p>Abstract</p> <p>Background</p> <p>Supportive neighbourhood walking conditions are particularly important for older people as they age and who, as a group, prefer walking as a form of physical activity. Urban form and socio-economic status (SES) can influence neighbourhood walking behaviour. The objectives of this study were: a) to examine how urban form and neighbourhood SES inter-relate to affect the experiences of older people who walk in their neighbourhoods; b) to examine differences among neighbourhood stakeholder key informant perspectives on socio-political processes that shape the walkability of neighbourhood environments.</p> <p>Methods</p> <p>An embedded comparative case study examined differences among four Ottawa neighbourhoods that were purposefully selected to provide contrasts on urban form (inner-urban versus suburban) and SES (higher versus lower). Qualitative data collected from 75 older walkers and 19 neighbourhood key informants, as well as quantitative indicators were compared on the two axes of urban form and SES among the four neighbourhoods.</p> <p>Results and discussion</p> <p>Examining the inter-relationship of neighbourhood SES and urban form characteristics on older people's walking experiences indicated that urban form differences were accentuated positively in higher SES neighbourhoods and negatively in lower SES neighbourhoods. Older people in lower SES neighbourhoods were more affected by traffic hazards and more reliant on public transit compared to their higher SES counterparts. In higher SES neighbourhoods the disadvantages of traffic in the inner-urban neighbourhood and lack of commercial destinations in the suburban neighbourhood were partially offset by other factors including neighbourhood aesthetics. Key informant descriptions of the socio-political process highlighted how lower SES neighbourhoods may face greater challenges in creating walkable places. These differences pertained to the size of neighbourhood associations, relationships with political representatives, accessing information and salient neighbourhood association issues. Findings provide evidence of inequitable walking environments.</p> <p>Conclusion</p> <p>Future research on walking must consider urban form-SES inter-relationships and further examine the equitable distribution of walking conditions as well as the socio-political processes driving these conditions. There is a need for municipal governments to monitor differences in walking conditions among higher and lower SES neighbourhoods, to be receptive to the needs of lower SES neighbourhood and to ensure that policy decisions are taken to address inequitable walking conditions.</p

Phatic systems in digital society

In our contemporary society, phatic technologies routinely establish, develop and maintain personal and emotional relationships across time and space. This phenomenon is reminiscent of Giddens’ 1990 concept of abstract systems made of symbolic tokens and expert systems that dis-embed and re-embed public and professional life. In this paper, we develop social theory that aims to provide a better understanding of the prominent role of phatic technologies in society. We proceed in three stages: first, we critique and revise Giddens’ vague concept of symbolic tokens and its implications for time space distanciation by introducing novel concepts from measurement science. This focuses on forms of information that are relatively precise and communal. Secondly, building on our new formulation of abstract systems, we propose new sociological concepts, phatic systems and symbolic indicators, to enable social theory to explore and analyse the rise of phatic technologies. The concepts focus on the personal and emotional. Thirdly, reflecting on the fact that our digital society is held together by software, we introduce concepts from theoretical computer science to relate the abstract sociological idea of phatic systems and symbolic indicators to the concrete nature of digital data