Ab Initio Study of Phase Stability in Doped TiO2

Ab-initio density functional theory (DFT) calculations of the relative stability of anatase and rutile polymorphs of TiO2 were carried using all-electron atomic orbitals methods with local density approximation (LDA). The rutile phase exhibited a moderate margin of stability of ~ 3 meV relative to the anatase phase in pristine material. From computational analysis of the formation energies of Si, Al, Fe and F dopants of various charge states across different Fermi level energies in anatase and in rutile, it was found that the cationic dopants are most stable in Ti substitutional lattice positions while formation energy is minimised for F- doping in interstitial positions. All dopants were found to considerably stabilise anatase relative to the rutile phase, suggesting the anatase to rutile phase transformation is inhibited in such systems with the dopants ranked F>Si>Fe>Al in order of anatase stabilisation strength. Al and Fe dopants were found to act as shallow acceptors with charge compensation achieved through the formation of mobile carriers rather than the formation of anion vacancies

Les effets du dopage au cuivre sur l'activité photocatalytique sur les plans (101) d'anatase TiO2: une étude théorique

International audienceCopper dopants are varyingly reported to enhance photocatalytic activity at titanium dioxide surfaces through uncertain mechanisms. In order to interpret how copper doping might alter the performance of titanium dioxide photocatalysts in aqueous media we applied density functional theory methods to simulate surface units of doped anatase (101) planes. By including van der Waals interactions, we consider the energetics of adsorbed water at anatase surfaces in pristine and copper doped systems. Simulation results indicate that copper dopant at anatase (101) surfaces is most stable in a 2+ oxidation state and a disperse configuration, suggesting the formation of secondary CuO phases is energetically unfavourable. In agreement with previous reports, water at the studied surface is predicted to exhibit molecular adsorption with this tendency slightly enhanced by copper. Results imply that the enhancement of photoactivity at anatase surfaces through Cu doping is more likely to arise from electronic interactions mediated by charge transfer and inter-bandgap states increasing photoexcitation and extending surface-hole lifetimes rather than through the increased density of adsorbed hydroxyl groups.https://doi.org/10.1016/j.apsusc.2016.06.178Il a été rapporté que les dopants au cuivre amélioraient l'activité photocatalytique à la surface du dioxyde de titane par le biais de mécanismes incertains. Afin d’interpréter la façon dont le dopage au cuivre pourrait altérer les performances des photocatalyseurs en dioxyde de titane en milieu aqueux, nous avons appliqué des méthodes de théorie de la densité fonctionnelle pour simuler des unités de surface de plans anatase (101) dopés. En incluant les interactions de van der Waals, nous considérons l’énergétique de l’eau adsorbée aux surfaces anatases dans les systèmes vierges et dopés au cuivre. Les résultats de la simulation indiquent que le dopant au cuivre à la surface de l'anatase (101) est le plus stable dans un état d'oxydation 2+ et dans une configuration dispersée, ce qui suggère que la formation de phases secondaires de CuO est énergétiquement défavorable. En accord avec les rapports précédents, il est prévu que l'eau présente à la surface étudiée présente une adsorption moléculaire avec cette tendance légèrement renforcée par le cuivre. Les résultats impliquent que l'amélioration de la photoactivité sur les surfaces de l'anatase par le dopage au Cu est plus susceptible de résulter d'interactions électroniques induites par le transfert de charge et les états inter-bandes interdites augmentant la photoexcitation et allongeant la durée de vie des trous de surface plutôt que par la densité accrue de groupes hydroxyles adsorbés.https://doi.org/10.1016/j.apsusc.2016.06.17

Theoretical insights into the hydrophobicity of low index CeO2 surfaces

The hydrophobicity of CeO2 surfaces is examined here. Since wettability measurements are extremely sensitive to experimental conditions, we propose a general approach to obtain contact angles between water and ceria surfaces of specified orientations based on density functional calculations. In particular, we analysed the low index surfaces of this oxide to establish their interactions with water. According to our calculations, the CeO2 (111) surface was the most hydrophobic with a contact angle of {\Theta} = 112.53{\deg} followed by (100) with {\Theta} = 93.91{\deg}. The CeO2 (110) surface was, on the other hand, mildly hydrophilic with {\Theta} = 64.09{\deg}. By combining our calculations with an atomistic thermodynamic approach, we found that the O terminated (100) surface was unstable unless fully covered by molecularly adsorbed water. We also identified a strong attractive interaction between the hydrogen atoms in water molecules and surface oxygen, which gives rise to the hydrophilic behaviour of (110) surfaces. Interestingly, the adsorption of water molecules on the lower-energy (111) surface stabilises oxygen vacancies, which are expected to enhance the catalytic activity of this plane. The findings here shed light on the origin of the intrinsic wettability of rare earth oxides in general and CeO2 surfaces in particular and also explain why CeO2 (100) surface properties are so critically dependant on applied synthesis methods

Electro‐Olefination—A Catalyst Free Stereoconvergent Strategy for the Functionalization of Alkenes

Conventional methods carrying out C(sp2)−C(sp2) bond formations are typically mediated by transition‐metal‐based catalysts. Herein, we conceptualize a complementary avenue to access such bonds by exploiting the potential of electrochemistry in combination with organoboron chemistry. We demonstrate a transition metal catalyst‐free electrocoupling between (hetero)aryls and alkenes through readily available alkenyl‐tri(hetero)aryl borate salts (ATBs) in a stereoconvergent fashion. This unprecedented transformation was investigated theoretically and experimentally and led to a library of functionalized alkenes. The concept was then carried further and applied to the synthesis of the natural product pinosylvin and the derivatization of the steroidal dehydroepiandrosterone (DHEA) scaffold

Using different Facebook advertisements to recruit men for an online mental health study: Engagement and selection bias.

A growing number of researchers are using Facebook to recruit for a range of online health, medical, and psychosocial studies. There is limited research on the representativeness of participants recruited from Facebook, and the content is rarely mentioned in the methods, despite some suggestion that the advertisement content affects recruitment success. This study explores the impact of different Facebook advertisement content for the same study on recruitment rate, engagement, and participant characteristics. Five Facebook advertisement sets ("resilience", "happiness", "strength", "mental fitness", and "mental health") were used to recruit male participants to an online mental health study which allowed them to find out about their mental health and wellbeing through completing six measures. The Facebook advertisements recruited 372 men to the study over a one month period. The cost per participant from the advertisement sets ranged from $0.55 to$3.85 Australian dollars. The "strength" advertisements resulted in the highest recruitment rate, but participants from this group were least engaged in the study website. The "strength" and "happiness" advertisements recruited more younger men. Participants recruited from the "mental health" advertisements had worse outcomes on the clinical measures of distress, wellbeing, strength, and stress. This study confirmed that different Facebook advertisement content leads to different recruitment rates and engagement with a study. Different advertisement also leads to selection bias in terms of demographic and mental health characteristics. Researchers should carefully consider the content of social media advertisements to be in accordance with their target population and consider reporting this to enable better assessment of generalisability

Dairy product production and lactose demand in New Zealand and Ireland under different simulated milk product-processing portfolios

peer-reviewedMaximising dairy industry profitability involves maximising product returns for a specific set of costs or minimising costs for a certain level of output. A strategy currently utilised by the New Zealand dairy industry to optimise the value of exports is to incorporate imported lactose along with local milk to maximise the production of whole milk powder (WMP) while complying with the Codex Alimentarius (Codex) standards, in addition to increasing the exported product for every litre of milk. This study investigated the impact of different product portfolio strategies on lactose requirements for the Irish and New Zealand dairy industries for current and predicted 2020 milk output projections. A mass balance processing sector model that accounts for all inputs, outputs and losses involved in dairy processing was used to simulate the processing of milk into WMP, skim milk powder (SMP), cheese, butter and fluid milk of different proportions. All scenarios investigated projected an increase in production and revenue from 2012 to 2020. Higher cheese production reduced industry lactose demand through whey processing, while scenarios reliant on an increase in the proportion of WMP were associated with increased lactose deficits.Livestock Improvement Corporation Pat Shannon Scholarshi

Química ambiental e dialógica de Paulo Freire no ensino médio técnico: Breve Relato de experiência / Paulo Freire's environmental and dialogical chemistry in technical high school: Brief Experience report

1 INTRODUÇÃODebates profundos sobre poluição, aquecimento global e buraco na camada de ozônio tornaram-se necessários,especialmente em contextos escolares, devido os impactos da influência antrópica sobre o meio ambiente. Portanto, a problemática: “é possível discutir conceitos de Química Ambiental através da perspectiva dialógica de Paulo Freire para alunos de Ensino Médio (EM) de uma escola técnica em Manaus-AM?” nasceu permeada pela perspectiva dialógica do educador brasileiro Paulo Freire, cuja premissa era de que o aluno é sujeito com capacidade crítica. A Química Ambiental é uma ciência responsável por explicar as reações, destinos, movimentos e fontes das substâncias químicas nas três interfaces: ar, água e solo (BAIRD; CANN, 2011), portanto, a atuação do homem influencia fortemente nas reações químicas no ambiente em seu entorno. 2 METODOLOGIAA pesquisa teve natureza qualitativa, onde os resultados foram coletados mediante questionário aplicado aos alunos, com quatro perguntas dissertativas e questionário aplicado para professora-orientadora durante estágio curricular supervisionado no 2º semestre de 2014. Os sujeitos participantes da pesquisa foram alunos do 2º ano do Ensino médio integrado ao Técnico em Química do IFAM Campus Manaus Centro. O recurso pedagógico diferencial é a utilização de textos e imagens de cunho crítico, tais como charges, dentre outros, aliados a problematizações das temáticas apresentadas, estimulando o diálogo em todo o processo. A proposta metodológica ocorreu em 4 etapas: 1) proposta temática permeando-se na perspectiva dialógica de Paulo Freire, 2) problematização dos temas propostos mediante uso de imagens conforme Bizo (2009), 3) sugestão de atividades: quatro textos relacionados às temáticas abordadas foram sorteados para as quatro equipes de oito alunos defenderem dentro de 10 minutos, com o intuito de aprofundar os conteúdos 4) Avaliação das atividades implementadas através das respostas dos questionários aplicados aos alunos e a professora. 3 RESULTADOS E DISCUSSÃOApós as análises de ambos os questionários aplicados, o  questionário  respondido  pela  professora  indicou  que a metodologia aplicada (uso de imagens para o ensino de química ambiental) propicia o diálogo, apontando como fator a postura dialógica da estagiária durante o processo. No item “o que você sugere de melhorias?” presente no questionário, 12 alunos apontaram como melhorias mais objetividade e interação com os alunos, sugerindo durante o processo metodológico, tais alunos não se sentiram ouvidos adequadamente, enquanto 5 alunos não apontaram melhorias na metodologia proposta. No último item do questionário, os alunos felicitaram o esforço conjunto com a professora, a relevância dos conteúdos abordados para a sociedade e como isso os fizeram repensar suas atitudes sobre o ambiente que os cercam, atingindo um dos pontos focais da pedagogia de Paulo Freire: questionar situações problemáticas com o objetivo de pensar, refletir sobre as situações do contexto social abordado, como a problemática ambiental discutida, que se queiram mudar, mediante conscientização-ação (BARBOSA, 2006). A docente responsável comentou com a estagiária que os alunos a procuraram depois agradecendo por terem estudado e debatido sobre aqueles conteúdos, pois lhes trouxeram um novo olhar e permitiram aplicar esses conhecimentos para o vestibular. 4 CONSIDERAÇÕES FINAISConsiderando o processo formativo da estagiária, é compreensível que alguns alunos não se sentiram confortáveis com a abordagem realizada. No entanto, após a análise dos questionários da professora e dos alunos, entende-se que a proposta metodológica possibilitou o diálogo entre a professora estagiária e os alunos, mesmo sob supervisão da docente responsável pela turma, bem como a conscientização dos alunos para a relevância da Química Ambiental. AGRADECIMENTOSAgradeço ao Instituto Federal de Educação, Ciência e Tecnologia do Amazonas, Campus Manaus Centro, por oportunizar a relação da Química com o Ensino no estágio-pesquisa durante a graduação em Licenciatura em Química durante 2014