A study of some non-covalent functional group π interactions

The present thesis is concerned with the quantification of weak non-covalent interactions between a simple π system and functional groups through dynamic NMR studies of conformational equilibria of specifically designed molecular balance systems. The work begins with an introduction which provides a formal review of the current literature on various aspects of non-covalent π-interactions, starting with an examination of the physical properties of non-covalent arene interactions, including arene-arene interactions, the behaviour of aromatic rings as hydrogen bond acceptors and the interactions between aromatic rings and cationic species. The use of molecular balance systems for studying these weak interactions will then be discussed together with some other important methods used. The introduction concludes with an account of olefinic !-interactions and methods for their study as described in the current chemical literature. The second section presents and discusses the results obtained in the present study and begins with the description of the synthetic routes employed to prepare two series of molecular balance systems, both of which feature a common bicyclo[3.2.2]nona-6,8-diene framework and a flexible three carbon atom bridge, whose central carbon atom can possess two different functional groups. The relative abundance of each of the two possible conformers in solution provides a measure of the relative interaction energies. Dynamic NMR studies in a range of solvents were employed to study each derivative. The results from these studies were then compared in order to gain insight into the relative strengths of both olefinic and aromatic π-interactions. The thesis concludes with a formal description of the experimental procedures used in this study and appendices detailing the data obtained from dynamic NMR studies and crystal structure data

Critical Metals in the Path towards the Decarbonisation of the EU Energy Sector: Assessing Rare Metals as Supply-Chain Bottlenecks in Low-Carbon Energy Technologies

In order to tackle climate change, to increase energy supply security and to foster the sustainability and competitiveness of the European economy, the EU has made the transition to a low-carbon economy a central policy priority. This report builds on the first study conducted in 2011 (Critical Metals in Strategic Energy Technologies), where critical metals were identified which could become a bottleneck to the supply-chain of various low-carbon energy technologies. The first study concentrated on the six SET-Plan technologies, namely: wind, solar (both PV and CSP), CCS, nuclear fission, bioenergy and the electricity grid. Fourteen metals were identified to be a cause for concern. After taking into account market and geopolitical parameters, five metals were labelled ‘critical’, namely: tellurium, indium, gallium, neodymium and dysprosium. The potential supply chain constraints for these materials were most applicable to the deployment of wind and solar energy technologies. In the follow-up study reported here, other energy and low-carbon technologies are investigated that not only play an important role in the EU's path towards decarbonisation but also may compete for the same metals as identified in the six SET-Plan technologies. Eleven technologies are analysed including fuel cells, electricity storage, electric vehicles and lighting. As in the first report, sixty metals, i.e. metallic elements, metallic minerals and metalloids are considered; only iron, aluminium and radioactive elements were specifically excluded. Graphite was also included, reflecting its status as a critical raw material. Where possible, the study models the implications for materials demand as a result of the scenarios described in the EU Energy Roadmap 2050. Consequently, the results obtained in the first study are updated to reflect the data that has become available in the roadmap. This second study found that eight metals have a high criticality rating and are therefore classified as ‘critical’. These are the six rare earth elements (dysprosium, europium, terbium, yttrium, praseodymium and neodymium), and the two metals gallium and tellurium. Four metals (graphite, rhenium, indium and platinum) are found to have a medium-to-high rating and are classified as ‘near critical’, suggesting that the market conditions for these metals should be monitored in case the markets for these metals deteriorate thereby increasing the risk of supply chain bottlenecks. Metals demand in the electric vehicle, wind, solar and lighting sectors were identified to be of particular concern. As in the first report, ways of mitigating the supply-chain risks for the critical metals are considered. These fall into three categories; increasing primary supply, reuse/recycling and substitution In addition, a number of topics were identified as possibly meriting further research, but could not be considered within the immediate scope of this study. These include conducting further studies to look at raw materials requirements for hybrid and electric vehicles for a wider range of technology uptake and penetration scenarios; developing new and more detailed scenarios for the uptake and technology mix of options for stationary energy storage; undertaking similar studies in defence and aerospace; improving statistics on the contribution of recycling to world production for a number of metals; and investigating the contribution of greater traceability and transparency to reducing raw materials supply risk. Finally, it is important not to overstate the bottlenecks due to the risks of raw material shortages for key decarbonisation technologies. This is because there are still many years before the large uptake of some technologies and in the coming years, there are numerous options that will become available to mitigate the risks identified.JRC.F.6-Energy systems evaluatio

Revision of the European Ecolabel Criteria for: Hand dishwashing detergents Preliminary Report

The EU Ecolabel criteria for hand dishwashing detergents are under revision. This revision process will take into account the current market conditions and the EU Ecolabel criteria will aim at addressing the most important environmental impacts of the hand dishwashing detergents in a life cycle perspective. The identification of the main hotspots is carried out in this study by means of an initial extensive literature review and subsequent LCA studies. LCA studies showed that the largest contribution to the environmental impact profile of hand dishwashing detergents is - by far - the use phase, particularly the energy needed to heat the water. For some impact categories, the sourcing of raw materials and the end of life are also important. Based on the normalisation assessment, by far the most important impact categories for hand dishwashing detergents in Europe are natural land transformation and fossil depletion. The study reveals that there are several improvement opportunities such reduction in the wash temperature or used of concentrated detergents. Changes in the detergent formulation can also reduce the impacts in different categories.JRC.J.5-Sustainable Production and Consumptio

Surfing the π-clouds for Non-covalent Interactions: A comparative Study of Arenes versus Alkenes

A comparative study by NMR spectroscopy using molecular balances indicates that non-covalent functional group interactions with an arene dominate over those with an alkene and a p-facial intramolecular hydrogen bond from a hydroxyl group to an arene is favoured by ~1.2 kJ mol-1. The strongest interaction observed in this study is with the cyano group and analysis of the series of Et, CH=CH2, C≡CH and C≡N groups is indicative of a weak long range electrostatic interaction and a correlation with the electrophilicity of the Ca atom of the Y substituent. Changes in the free energy differences of conformers show a linear dependence on the solvent hydrogen bond acceptor parameter β

Noncovalent Interactions of pi Systems with Sulfur: The Atomic Chameleon of Molecular Recognition

The relative strength of noncovalent interactions between a thioether sulfur atom and various π systems in designed top pan molecular balances was determined by NMR spectroscopy. Compared to its oxygen counterpart, the sulfur atom displays a remarkable ability to interact with almost equal facility over the entire range of π systems studied, with the simple alkene emerging as the most powerful partner. With the exception of the O⋅⋅⋅heteroarene interaction, all noncovalent interactions of sulfur with π systems are favoured over oxygen

Principles of Periodontology

Periodontal diseases are among the most common diseases affecting humans. Dental biofilm is a contributor to the etiology of most periodontal diseases. It is also widely accepted that immunological and inflammatory responses to biofilm components are manifested by signs and symptoms of periodontal disease. The outcome of such interaction is modulated by risk factors (modifiers), either inherent (genetic) or acquired (environmental), significantly affecting the initiation and progression of different periodontal disease phenotypes. While definitive genetic determinants responsible for either susceptibility or resistance to periodontal disease have yet to be identified, many factors affecting the pathogenesis have been described, including smoking, diabetes, obesity, medications, and nutrition. Currently, periodontal diseases are classified based upon clinical disease traits using radiographs and clinical examination. Advances in genomics, molecular biology, and personalized medicine may result in new guidelines for unambiguous disease definition and diagnosis in the future. Recent studies have implied relationships between periodontal diseases and systemic conditions. Answering critical questions regarding host‐parasite interactions in periodontal diseases may provide new insight in the pathogenesis of other biomedical disorders. Therapeutic efforts have focused on the microbial nature of the infection, as active treatment centers on biofilm disruption by non‐surgical mechanical debridement with antimicrobial and sometimes anti‐inflammatory adjuncts. The surgical treatment aims at gaining access to periodontal lesions and correcting unfavorable gingival/osseous contours to achieve a periodontal architecture that will provide for more effective oral hygiene and periodontal maintenance. In addition, advances in tissue engineering have provided innovative means to regenerate/repair periodontal defects, based upon principles of guided tissue regeneration and utilization of growth factors/biologic mediators. To maintain periodontal stability, these treatments need to be supplemented with long‐term maintenance (supportive periodontal therapy) programs

Acute periodontal lesions

This is a review and update on acute conditions affecting the gingival tissues, including abscesses in the periodontium, necrotizing periodontal diseases, and other acute conditions that cause gingival lesions with acute presentation, such as infectious process not associated with oral bacterial biofilms, muco-cutanenous disorders, and traumatic and allergic lesions. A periodontal abscess is clinically important since it is a relatively frequent dental emergency, it can compromise the periodontal prognosis of the affected tooth, and because bacteria within the abscess have been identified, mainly by the type of etiology, and there are clear diffrences between those affecting a previously existing periodontal pocket ahd those affecting healthy sites. Therapy for this acute condition consists of drainage and tissue debridement, with individual evaluation of the need for systemic antimicrobial therapy. the definitive treatment of the pre-existing condition should be accomplished after the acute phase is controlled. Necrotizing periodontal disease (NPD) present three typical clinical features : papilla necrosis, gingival bleeding, and pain. Although the prevalence of these diseases is not high, their importance is clear, since they represent the most severe conditions associated with dental biofilm, with very rapid tissue destruction. In adittion to bacteria, the etiology of NPD includes numerous factors that alter the host response and predispose to these diseases, including HIV infection, malnutrition, stress, and tobacco smoking. The treatment consists of superficial debridement, careful mechanical oral hygiene, rinsing with chlorhexidine, and daily re-evaluation. Systemic antimicrobials may be used adjunctively in severe cases or in non-responding conditions and the best option is metronidazole.Once the acute disease is under control, definitive treatment should be provided, including the adequate therapy for the pre-existing gingivitis or periodontitis. Among other acute conditions affecting the periodontal tissues, but not caused by the microorganisms present in oral biofilms , are infectious diseases, muco-cutaneous diseases and traumatic or allergic lesions. In most cases, the gingival envolvement is not severe, though they are common and may prompt a dental emergency visit. These conditions may the direct result of a trauma or the consequence of the breaking of vesicles and bullae. A proper differential diagnosis is important for an adequate management of the case