Foreword

No abstract available

Direitos humanos, orientação sexual e identidade de gênero na commonwealth: da História e do Direito ao desenvolvimento de diálogos ativistas e internacionais

As temáticas de orientação sexual e identidade de gênero estão chegando ao centro dos debates mundiais sobre direitos humanos e mudança social. Tais debates são particularmente vigorosos em muitos países-membros da Commonwealth, uma vez que a criminalização das práticas sexuais consentidas entre pessoas do mesmo sexo persiste na maioria de seus Estados Membros. O presente artigo busca analisar as causas dessa criminalização e as lutas organizadas pela descriminalização da homossexualidade em diversos desses estados da Commonwealth. O artigo está organizado em cinco partes: na primeira parte, apresentar-se-á resumo da criminalização contemporânea da homossexualidade na Commonwealth, incluindo alguns exemplos atuais de injustiça enfrentada por pessoas em vários estados e abordando as temáticas de direitos humanos, orientação sexual e identidade de gênero. A segunda parte é uma contribuição original para os debates acadêmicos internacionais sobre sexualidade e gênero; com ampla cobertura de exemplos de estados no Sul global. A terceira parte apresenta uma visão histórica da criminalização do comportamento homossexual no Reino Unido, uma vez que é de relevância contextual para todos os países da Commonwealth. A quarta parte fornece a primeira análise sistemática de dados sobre leis relacionadas à orientação sexual e identidade de gênero em cada um dos 54 estados da Commonwealth. Finalmente, a quinta parte examina a própria Commonwealth, com foco nas tentativas existentes de ativistas, especialistas e políticos de endereçar os direitos humanos de maneira generalista e a orientação sexual e a identidade de gênero de maneira específica na agenda da Commonwealth

Foreword

No abstract available

Understanding the kinetic and thermodynamic origins of xylene separation in UiO-66(Zr) via molecular simulation

Xylene isomers are precursors in many important chemical processes, yet their separation via crystallization or distillation is energy intensive. Adsorption presents an attractive, lower-energy alternative and the discovery of adsorbents which outperform the current state-of-the-art zeolitic materials represents one of the key challenges in materials design, with metal-organic frameworks receiving particular attention. One of the most well-studied systems in this context is UiO-66(Zr), which selectively adsorbs ortho-xylene over the other C8 alkylaromatics. The mechanism behind this separation has remained unclear, however. In this work, we employ a wide range of computational techniques to explore both the equilibrium and dynamic behavior of the xylene isomers in UiO-66(Zr). In addition to correctly predicting the experimentally-observed ortho-selectivity, we demonstrate that the equilibrium selectivity is based upon the complete encapsulation of ortho-xylene within the pores of the framework. Furthermore the flexible nature of the adsorbent is crucial in facilitating xylene diffusion and our simulations reveal for the first time significant differences between the intracrystalline diffusion mechanisms of the three isomers resulting in a kinetic contribution to the selectivity. Consequently it is important to include both equilibrium and kinetic effects when screening MOFs for xylene separations

Industrially challenging separations via adsorption in metal-organic frameworks : a computational exploration

In recent years, metal-organic frameworks (MOFs) have been identified as promising adsorbents in a number of industrially relevant, yet challenging, separations, including the removal of propane from propane/propylene mixtures and the separation of mixtures of xylene isomers. The highly tuneable nature of MOFs - wherein structures may be constructed from a variety of diverse building blocks – has resulted in the publication of a staggering number of frameworks incorporating a wide range of network topologies, pore shapes and pore diameters. As a result, there are a huge number of candidate adsorbents to consider for a given separation. Molecular simulation techniques allow the identification of those structural features and characteristics of a MOF which exert the greatest influence on the adsorption and separation of the compounds of interest, providing insights which can both guide the selection and accelerate the development of adsorbents for a specific application. The separation of propane/propylene mixtures via adsorption has typically focused on selective adsorption of the olefin, propylene, via specific olefin-adsorbent interactions. These propylene-selective MOFs result in processes which selectively remove the most abundant species in the process stream and are typically characterised by high heats of adsorption, resulting in large adsorption units and adsorbents which are difficult to regenerate. In this work, the capability of MOFs to selectively adsorb propane over propylene is explored, potentially allowing for the design of smaller and more energy-efficient adsorption units. By studying a range of different MOFs as well as carbon-based model pores, it was found that the low-pressure selectivity of the structure is determined by the strength of the electrostatic interaction between propylene and the framework, while the adsorptive preference at industrially-relevant pressures is dominated by the enhanced packing efficiency of propylene over propane. The confinement of C3 molecules, however, may be employed to negate this entropic advantage and guide the development of materials which selectively adsorb propane over propylene. It has recently been reported that the adsorptive preference of a MOF for one xylene isomer over another may be predicted based solely on the pore size distribution of the structure. In this work, the impact of pore size on selectivity was studied systematically in both one-dimensional model pore systems of varying geometries and analogous published MOF structures. The ability of the framework to discriminate between xylene molecules in these systems was found to be determined primarily by the different packing arrangements available to the different isomers – while small pores were found to favour the slimmest of the isomers, larger pores were found to favour the more compact ortho- isomer. Finally, the adsorption and diffusion of xylene isomers in a more complex MOF, UiO-66(Zr), was studied in depth. Simulations were able to correctly predict the previously-reported preference of the MOF for ortho-xylene (oX). The smaller volume of the oX molecule compared to the other isomers was found to be responsible both for an enhanced entropic contribution and higher guest-host interaction energies. The importance of framework flexibility in the diffusion of xylene isomers in UiO-66(Zr) was also explored, with distortion of the structure in response to interaction with adsorbed molecules found to be essential in allowing xylenes to diffuse through the pore space

Bullying victimization and psychosis : the inter-dependence and independence of risk trajectories

In the last several years a number of studies have noted an association between bullying and psychotic symptoms. Our aim here is to offer an overview on the topic, focusing especially on a developmental perspective. First, we highlight the latest studies to date regarding psychosis across the continuum and its relationship with bullying. In the second section, we summarize the three main explanatory models investigated: developmental, biological and cognitive models. In the discussion section we affirm that the sharing of numerous risk factors put people at risk of both psychosis and of being bullied, and bullying itself may further enhance the development of psychosis. Moreover, bullying is a risk factor for several mental disorders and is non-specific for psychosis, but there is some particularity in the trajectory involved between victimization and the onset of psychosis. In conclusion we recommend that the study of bullying in psychosis requires careful study of the developmental trajectories involved and research should now focus on how personal, social and biological factors interact between them

Computational evaluation of the impact of incorporated nitrogen and oxygen heteroatoms on the affinity of polyaromatic ligands for carbon dioxide and methane in metal–organic frameworks

Density functional theory is employed to explore the binding of carbon dioxide and methane in a series of isoreticular metal–organic frameworks, with particular emphasis on understanding the impact of directly incorporated nitrogen and oxygen heteroatoms on the affinity of the ligand for CO2 and CH4. While the strongest binding sites for both CO2 and CH4 were found to be directly above the aromatic rings of the core of the ligand, the introduction of heteroatoms to the core systems was shown to significantly alter both the binding strength and preferred binding locations of CH4 and CO2. The presence of pyrazine rings within the ligand was observed to create new binding sites for both CO2 and CH4 and, in the case of CO2, severely reduce the binding strength or entirely eliminate binding sites that were prominent in the analogous carbocyclic ligands. These results suggest that while the presence of framework nitrogen and oxygen heteroatoms provides a route to ligands with enhanced affinity for methane, a similar increase in affinity for CO2 is not guaranteed

Computational evaluation of the impact of incorporated nitrogen and oxygen heteroatoms on the affinity of polyaromatic ligands for carbon dioxide and methane in metal–organic frameworks

Density functional theory is employed to explore the binding of carbon dioxide and methane in a series of isoreticular metal–organic frameworks, with particular emphasis on understanding the impact of directly incorporated nitrogen and oxygen heteroatoms on the affinity of the ligand for CO2 and CH4. While the strongest binding sites for both CO2 and CH4 were found to be directly above the aromatic rings of the core of the ligand, the introduction of heteroatoms to the core systems was shown to significantly alter both the binding strength and preferred binding locations of CH4 and CO2. The presence of pyrazine rings within the ligand was observed to create new binding sites for both CO2 and CH4 and, in the case of CO2, severely reduce the binding strength or entirely eliminate binding sites that were prominent in the analogous carbocyclic ligands. These results suggest that while the presence of framework nitrogen and oxygen heteroatoms provides a route to ligands with enhanced affinity for methane, a similar increase in affinity for CO2 is not guaranteed

The right isotherms for the right reasons?: validation of generic force fields for prediction of methane adsorption in metal-organic frameworks

In recent years, the use of computational tools to aid in the evaluation, understanding and design of advanced porous materials for gas storage and separation processes has become ever-more widespread. High-performance computing facilities have become more powerful and more accessible and molecular simulation of gas adsorption has become routine, often involving the use of a number of default and commonly-used parameters as a result. In this work, we consider the application of molecular simulation in one particular field of adsorption – the prediction of methane adsorption in metal-organic frameworks in the low-loading regime – and employ a range of computational techniques to evaluate the appropriateness of many commonly chosen simulation parameters to these systems. In addition to confirming the power of relatively simple generic force fields to quickly and accurately predict methane adsorption isotherms in a range of MOFs, we demonstrate that these force fields are capable of providing detailed molecular-level information which is in very good agreement with quantum chemical predictions. We highlight a number of chemical systems in which molecular-level insight from generic force fields should be approached with a degree of caution and provide some general recommendations for best-practice in simulations of CH4 adsorption in MOFs