Structure and electronic properties of the quasi-one-dimensional Ba₂Co₁₋ₓZnₓS₃ series

This work focuses on the structure and physical properties of the solid solution Ba₂Co₁₋ₓZnₓS₃ (0 ≤ x ≤ 1), a family of quasi-one-dimensional sulfides with end members Ba₂CoS₃ and Ba₂ZnS₃. The structure of selected compounds with increasing Zn²⁺ content has been analysed using, neutron diffraction, TEM and EXAFS and the physical properties via magnetic susceptibility and resistivity measurements. The progressive substitution of the non-magnetic Zn²⁺ cation for Co²⁺ rapidly destroys the antiferromagnetic transition present at 46 K in the quasi one-dimensional Ba₂CoS₃, leading to paramagnetic behaviour down to the lowest investigated temperature (5K) for compounds with x > 0.25. For compounds with x ≥ 0.4, a pure CW regime is recovered around 300 K, yielding effective moments consistent with the g factor of the tetrahedrally coordinated Co²⁺ previously determined for Ba₂CoS₃. The Zn²⁺/Co²⁺ substitution also removes the metallic-like behaviour of Ba₂CoS₃ causing an increase in the value of the resistivity with all the Ba₂Co₁₋ₓZnₓS₃ compounds showing semiconducting behaviour. The negative magnetoresistance of Ba₂CoS₃ is improved by the Zn²⁺/Co²⁺ substitution, with values of – 6% for Ba₂Co₀.₇₅Zn₀.₂₅S₃, – 9% for Ba₂Co₀.₅Zn₀.₅S₃ and – 8% for Ba₂Co₀.₂₅Zn₀.₇₅S₃. However, there does not seem to be a correlation between the values of the resistivity and the magnetoresistance and the content of Zn²⁺, leading to the hypothesis that transport properties may be linked more closely to extrinsic properties

Methods in Plant Foliar Volatile Organic Compounds Research

Plants are a major atmospheric source of volatile organic compounds (VOCs). These secondary metabolic products protect plants from high-temperature stress, mediate in plant–plant and plant–insect communication, and affect our climate globally. The main challenges in plant foliar VOC research are accurate sampling, the inherent reactivity of some VOC compounds that makes them hard to detect directly, and their low concentrations. Plant VOC research relies on analytical techniques for trace gas analysis, usually based on gas chromatography and soft chemical ionization mass spectrometry. Until now, these techniques (especially the latter one) have been developed and used primarily by physicists and analytical scientists, who have used them in a wide range of scientific research areas (e.g., aroma, disease biomarkers, hazardous compound detection, atmospheric chemistry). The interdisciplinary nature of plant foliar VOC research has recently attracted the attention of biologists, bringing them into the field of applied environmental analytical sciences. In this paper, we review the sampling methods and available analytical techniques used in plant foliar VOC research to provide a comprehensive resource that will allow biologists moving into the field to choose the most appropriate approach for their studies

Epigenetic stability of repressed states involving the histone variant macroH2A revealed by nuclear transfer to Xenopus oocytes

How various epigenetic mechanisms restrict chromatin plasticity to determine the stability of repressed genes is poorly understood. Nuclear transfer to Xenopus oocytes induces the transcriptional reactivation of previously silenced genes. Recent work suggests that it can be used to analyze the epigenetic stability of repressed states. The notion that the epigenetic state of genes is an important determinant of the efficiency of nuclear reprogramming is supported by the differential reprogramming of given genes from different starting epigenetic configurations. After nuclear transfer, transcription from the inactive X chromosome of post-implantation-derived epiblast stem cells is reactivated. However, the same chromosome is resistant to reactivation when embryonic fibroblasts are used. Here, we discuss different kinds of evidence that link the histone variant macroH2A to the increased stability of repressed states. We focus on developmentally regulated X chromosome inactivation and repression of autosomal pluripotency genes, where macroH2A may help maintain the long-term stability of the differentiated state of somatic cells

A comparative study of the evolution of prestige formations and of speakers' attitudes in Occitan and Catalan

This thesis explores the nature and the mechanism of change of language prestige and language attitudes in two neighbouring languages: Occitan and Catalan. These two Romance minority languages show great similarities in their early external history and striking differences in their more recent past. The concepts of language attitudes and prestige call for a multidisciplinary approach which incorporates aspects from social psychology, ethnography, historical sociolinguistics and sociology to enable the author to depict in a comprehensive manner the interaction between the formation of the perception of language prestige and the declaration of language attitudes.An important rationale in this thesis is the search for an understanding of the patterns of change in prestige descriptions. Prestige and attitudes are generally interpreted as static entities but a diachronic overview of the values attached to Catalan and Occitan displays signs of disparity and evolution which are scrutinised through the analysis of selected Occitan and Catalan grammars from different periods. The data collected through semi-structured interviews with Occitan and Catalan speakers and processed with the method of Critical Discourse Analysis provides an enlightening synchronic perspective on the language situations. The combination of diachronic and present-day approaches to language representations fosters an original apparatus to investigate the gradually developing contrasts between the symbolisation of the two languages. A second point of focus for the comparison of the Occitan and Catalan linguistic situations resides in the transnational position of their linguistic communities. Since Occitan and Catalan are both spoken in France and Spain, the fascinating mismatch between the linguistic borders and the political territories provide an original and supplementary instrument of analysis of the influences of the national policies on individual attitudes. The bi-national division of Catalan and Occitan offers an examination of the inter-relation between macro-level representations and micro-level perceptions and a clarification of the dynamicity of the power relations between minority and majority groups.The objective of the study is primarily to contribute to a theorisation of language prestige through its conceptualisation as a process, and not an inherent quality, influencing, renewing or destroying, positive language attitudes which, in turn, can reinforce or challenge the preconceived and established form of prestige. The dynamic and malleable forms of prestige and attitudes need the explanatory help of the concept of language ideologies which, taken as beliefs about a language, embodies the modern and growing differentiation in the attribution of language values to Catalan and Occitan. Language ideologies as well as constituting a link between the macro and micro-domains reflect the emblematic discrepancies between a growingly powerful and confrontational Catalan prestige and a compartmentalised and disunited Occitan prestige.EThOS - Electronic Theses Online ServiceAHRCGBUnited Kingdo

A comparative study of the evolution of prestige formations and of speakers' attitudes in Occitan and Catalan

This thesis explores the nature and the mechanism of change of language prestige and language attitudes in two neighbouring languages: Occitan and Catalan. These two Romance minority languages show great similarities in their early external history and striking differences in their more recent past. The concepts of language attitudes and prestige call for a multidisciplinary approach which incorporates aspects from social psychology, ethnography, historical sociolinguistics and sociology to enable the author to depict in a comprehensive manner the interaction between the formation of the perception of language prestige and the declaration of language attitudes.An important rationale in this thesis is the search for an understanding of the patterns of change in prestige descriptions. Prestige and attitudes are generally interpreted as static entities but a diachronic overview of the values attached to Catalan and Occitan displays signs of disparity and evolution which are scrutinised through the analysis of selected Occitan and Catalan grammars from different periods. The data collected through semi-structured interviews with Occitan and Catalan speakers and processed with the method of Critical Discourse Analysis provides an enlightening synchronic perspective on the language situations. The combination of diachronic and present-day approaches to language representations fosters an original apparatus to investigate the gradually developing contrasts between the symbolisation of the two languages. A second point of focus for the comparison of the Occitan and Catalan linguistic situations resides in the transnational position of their linguistic communities. Since Occitan and Catalan are both spoken in France and Spain, the fascinating mismatch between the linguistic borders and the political territories provide an original and supplementary instrument of analysis of the influences of the national policies on individual attitudes. The bi-national division of Catalan and Occitan offers an examination of the inter-relation between macro-level representations and micro-level perceptions and a clarification of the dynamicity of the power relations between minority and majority groups.The objective of the study is primarily to contribute to a theorisation of language prestige through its conceptualisation as a process, and not an inherent quality, influencing, renewing or destroying, positive language attitudes which, in turn, can reinforce or challenge the preconceived and established form of prestige. The dynamic and malleable forms of prestige and attitudes need the explanatory help of the concept of language ideologies which, taken as beliefs about a language, embodies the modern and growing differentiation in the attribution of language values to Catalan and Occitan. Language ideologies as well as constituting a link between the macro and micro-domains reflect the emblematic discrepancies between a growingly powerful and confrontational Catalan prestige and a compartmentalised and disunited Occitan prestige.EThOS - Electronic Theses Online ServiceAHRCGBUnited Kingdo

Room HVAC Influences on the Removal of Airborne ParticulateMatter: Implications for School Reopening during theCOVID-19 Pandemic

(1) Background: Many schools and higher education settings have confronted the issue of reopening their facilities after the COVID-19 pandemic. In response, several airflow strategies spanning from adding portable air purifiers to major mechanical overhauls have been suggested to equip classrooms with what is necessary to provide a safe and reliable environment. Yet, there are many unknowns about specific contributions of the building system and its design and performance on indoor air quality (IAQ) improvements. (2) Methods: this study examined the combined effect of ventilation type, airflow rates, and filtration on IAQ in five different classrooms. Experiments were conducted by releasing inert surrogate particles into the classrooms and measuring the concentrations in various locations of the room. (3) Results: we showed that while the distribution of particles in the space is a complex function of space geometry and air distribution configurations, the average decay rate of contaminants is proportional to the number of air changes per hour in the room. (4) Conclusions: rooms with a central HVAC system responded quicker to an internal source of contamination than rooms with only fan coil units. Furthermore, increasing the ventilation rate without improved filtration is an inefficient use of energy

Stability, fatty acid composition and sensory properties of the <i>M. Longissimus </i>muscle from beef steers grazing either chicory / ryegrass or ryegrass

Research has shown both production and health benefits for the use of chicory (Cichorium intybus) within ruminant diets. Despite this, little was known about the the effects of this forage, containing differing fatty acid profiles and secondary plant compounds compared to ryegrass, on beef stability, fatty acid composition or sensory properties. An experiment was conducted to investigate whether the inclusion of chicory in the diet of grazing beef steers would alter the meat stability, fatty acid composition and sensory properties of the M. Longissimus muscle compared to beef steers grazing perennial ryegrass (Lolium perenne). Triplicate 2 ha plots were established with a chicory (cv. Puna II) / perennial ryegrass (cv. Premium) mix or a perennial ryegrass (cv. Premium) control. A core group of 36 Belgian Blue - cross steers were used within a two-year beef finishing experiment (n=6 per replicate plot). In the second grazing year, steers were slaughtered as they reached a target fat class of 3. After dressing, half carcass sides were hung for 48 h and then then quartered between the junction of the 10th and 11th rib. Muscle pH was checked at 2 and 48 h post-slaughter. A 250 mm-long section of the hindloin joint containing the M. Longissimus lumborum muscle was removed from the left side of the carcass, posterior to the 10th rib. A 20 mm-thick steak was cut and a muscle sample was vacuum packed and frozen at -20? C for subsequent analysis of vitamin E, a further steak being retained for fatty acid analysis. The remaining section of the loin was vacuum-packed in modified atmosphere packs and subjected to simulated retail display. The remaining section of the conditioned loin was used for sensory analysis. Data on pH, vitamin E concentration and colour stability in a simulated retail display showed there were no effects of including chicory in the diet of grazing beef steers on meat stability. There were also no differences found in the fatty acid composition or the overall eating quality of the steaks from the two treatments. In conclusion, there were no substantive effects of including chicory in the swards of grazing beef cattle on meat stability, fatty acid composition or sensory properties when compared with beef steers grazing ryegrass-only swards.publishersversionPeer reviewe