Use of Empirical Correlations to Determine Solvent Effects in the Solvolysis of S-Methyl Chlorothioformate

The specific rates of solvolysis of S-methyl chlorothioformate (MeSCOCl) are analyzed in 20 solvents of widely varying nucleophilicity and ionizing power at 25.0 °C using the extended Grunwald-Winstein Equation. A stepwise SN1 (DN + AN) mechanism is proposed in the more ionizing solvents including six aqueous fluoroalcohols. In these solvents, a large sensitivity value of 0.79 towards changes in solvent nucleophilicity (l) is indicative of profound rearside nucleophilic solvation of the developing carbocation. In twelve of the more nucleophilic pure alchohols and aqueous solutions, the sensitivities obtained for solvent nucleophilicity (l) and solvent ionizing power (m) are similar to those found in acyl chlorides where an association-dissociation (AN + DN) mechanism is believed to be operative

Analysis of the Nucleophilic Solvation Effects in Isopropyl Chlorothioformate Solvolysis

Correlation of the solvent effects through application of the extended Grunwald-Winstein equation to the solvolysis of isopropyl chlorothioformate results in a sensitivity value of 0.38 towards changes in solvent nucleophilicity (l) and a sensitivity value of 0.72 towards changes in solvent ionizing power (m). This tangible l value coupled with the negative entropies of activation observed indicates a favorable predisposition towards a modest rear-side nucleophilic solvation of a developing carbocation. Only in 100% ethanol was the bimolecular pathway dominant. These observations are very different from those obtained for the solvolysis of isopropyl chloroformate, where dual reaction channels were proposed, with the addition-elimination reaction favored in the more nucleophilic solvents and a unimolecular fragmentation-ionization mechanism favored in the highly ionizing solvents

The role of resistance to varroa destructor and deformed wing virus in the European honey bee (apis mellifera)

The European honey bee (Apis mellifera) is of global importance as a pollinator. Over the past 30 years an increase in colonies lost during winter has occurred, particularly in the northern hemisphere. These losses are attributed to the ectoparasitic mite Varroa destructor that acts as a vector of RNA viruses, most notably Deformed wing virus (DWV). Three master variants of the DWV have been discovered; Type-A, B, and C. The increase in overwinter colony losses are closely linked to DWV. At the same time DWV may also offer protection to colonies via superinfection exclusion (SIE), which may be linked to Varroa-tolerant colonies. However, the role of each DWV variant in colony survivorship and mite-tolerance is limited, so the main thrust of the thesis is to address this issue. Firstly, the detection of all three DWV master variants was only possible via Next Generation Sequencing (NGS), therefore I developed a reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR) assay that enabled the detection of all three DWV master variants. This allowed me to re-analyse historic samples, and revealed that type-A and C were involved in the untimely demise of treated colonies. Secondly, I used the new assay to survey the three DWV master variants in English and Welsh honey bee colonies. DWV type-B was found to dominate colonies regardless of season, whilst overwinter losses remained low. English and Welsh Varroa tolerant colonies were also shown to have DWV viral loads similar to colonies which receive Varroa treatment throughout the year. Thirdly, I conducted a similar study as Chapter two except in the USA. Here DWV type-A was dominant and linked to overwinter colony losses. Varroa tolerant bees also had DWV loads similar to Varroa treated colonies, a result which suggests mite-tolerant traits evolve over time. Fourthly, DWV populations were assessed in Varroa-tolerant colonies from the Arnot forest, USA. This study disproved that avirulent DWV infections were present and supports the importance of other life history traits being involved in the survival of these colonies. Finally, the role of DWV viral recombinants were investigated on a landscape scale using samples from England and Wales, and the USA. This provided further evidence that viral recombinants are not as fit as parent genomes. Together these results deepen our understanding of DWV variants and their impact on colony survivorship

Use of Linear Free Energy Relationships (LFERs) to Elucidate the Mechanisms of Reaction of a γ-Methyl-β-alkynyl and an ortho-Substituted Aryl Chloroformate Ester

The specific rates of solvolysis of 2-butyn-1-yl-chloroformate (1) and 2-methoxyphenyl chloroformate (2) are studied at 25.0 °C in a series of binary aqueousorganic mixtures. The rates of reaction obtained are then analyzed using the extended Grunwald-Winstein (G-W) equation and the results are compared to previously published G-W analyses for phenyl chloroformate (3), propargyl chloroformate (4), p-methoxyphenyl choroformate (5), and p-nitrophenyl chloroformate (6). For 1, the results indicate that dual side-by-side addition-elimination and ionization pathways are occurring in some highly ionizing solvents due to the presence of the electron-donating γ-methyl group. For 2, the analyses indicate that the dominant mechanism is a bimolecular one where the formation of a tetrahedral intermediate is rate-determining

Perceiving ‘capability’ within dynamic capabilities: the role of owner-manager self-efficacy

This article combines two popular, yet separate concepts, dynamic capabilities and self-efficacy. Both are concerned with ability / capability and offer potentially valuable synergies. As such, our in-depth qualitative study based in three micro-enterprises in the United Kingdom (UK), investigated, ‘what role(s) may owner-manager perceived self-efficacy play as a micro-foundation of dynamic capabilities in micro-enterprises?’ Our findings show that perceived self-efficacy can influence dynamic capability enactment in multifaceted ways and even suggest that in some cases, perceived self-efficacy is a crucial component of dynamic capabilities, without which there may be no such capability. These insights help open up the black box of dynamic capabilities by contributing important knowledge to the growing body of research into the micro-foundations of such capabilities. Furthermore, our study illuminates the importance of idiosyncratic micro-foundations of dynamic capabilities in micro-enterprises and expands extant knowledge of the potential effects of self-efficacy in the small business and entrepreneurship domain

DWV-A lethal to honey bees (Apis mellifera): a colony level survey of DWV variants (A, B, and C) in England, Wales, and 32 states across the US

The strong association between Varroa destructor, deformed wing virus (DWV), and high overwintering colony losses (OCL) of honey bees is well established. Three DWV master variants (DWV-A, -B, and -C) have been described, and their role in colony mortality remains an open question. Therefore, the aim of this study is to investigate the seasonal prevalence, viral load, and changing distribution of the three DWV master variants within honey bee colonies from England, Wales, and 32 states across the United States. Here, we report that in 2016, DWV-B was prevalent (100%, n = 249) and dominant (95%) in England and Wales, compared to the US. (56%, n = 217 and 23%, respectively), where DWV-A was prevalent (83%, n = 217) and dominant (63%). DWV-C was regularly detected in low viral loads (1 × 1010) in surviving colonies from all sample locations, providing further supporting evidence of DWV-A exhibiting increased virulence over DWV-B at the colony level

Correlation of the Rates of Solvolysis of Two Arenesulfonyl Chlorides and of trans-β-Styrenesulfonyl Chloride – Precursors in the Development of New Pharmaceuticals

Additional specific rates of solvolysis have been determined, mainly in fluoroalcohol containing solvents, for benzenesulfonyl chloride (1) and p-nitrobenzene-sulfonyl chloride (2). For trans-β-styrenesulfonyl chloride (3), a study has been carried out in 43 pure and binary solvents, covering a wide range of hyroxylic solvent systems. For the specific rates of solvolyses of each of the three substrates, a good correlation was obtained over the full range of solvents when the extended Grunwald-Winstein equation was applied. The sensitivities to changes in solvent nucleophilicity and solvent ionizing power are similar to values determined earlier and an SN2 process is proposed. For 3, kinetic solvent isotope effects of 1.46 for kH2O/kD2O and 1.76 for kMeOH/kMeOD were determined. These are also compared to literature values for other sulfonyl chlorides

Suitability of aircraft wastewater for pathogen detection and public health surveillance

International air travel is now widely recognised as one of the primary mechanisms responsible for the transnational movement and global spread of SARS-CoV-2. Monitoring the viral load and novel lineages within human-derived wastewater collected from aircraft and at air transport hubs has been proposed as an effective way to monitor the importation frequency of viral pathogens. The success of this approach, however, is highly dependent on the bathroom and defecation habits of air passengers during their journey. In this study of UK adults (n = 2103), we quantified the likelihood of defecation prior to departure, on the aircraft and upon arrival on both short- and long-haul flights. The results were then used to assess the likelihood of capturing the signal from infected individuals at UK travel hubs. To obtain a representative cross-section of the population, the survey was stratified by geographical region, gender, age, parenting status, and social class. We found that an individual's likelihood to defecate on short-haul flights ( 6 h in duration). This behaviour pattern was higher among males and younger age groups. The maximum likelihood of defecation was prior to departure (< 39 %). Based on known SARS-CoV-2 faecal shedding rates (30–60 %) and an equal probability of infected individuals being on short- (71 % of inbound flights) and long-haul flights (29 %), we estimate that aircraft wastewater is likely to capture ca. 8–14 % of SARS-CoV-2 cases entering the UK. Monte Carlo simulations predicted that SARS-CoV-2 would be present in wastewater on 14 % of short-haul flights and 62 % of long-haul flights under current pandemic conditions. We conclude that aircraft wastewater alone is insufficient to effectively monitor all the transboundary entries of faecal-borne pathogens but can form part of a wider strategy for public heath surveillance at national borders

Suitability of aircraft wastewater for pathogen detection and public health surveillance

International air travel is now widely recognised as one of the primary mechanisms responsible for the transnational movement and global spread of SARS-CoV-2. Monitoring the viral load and novel lineages within human-derived wastewater collected from aircraft and at air transport hubs has been proposed as an effective way to monitor the importation frequency of viral pathogens. The success of this approach, however, is highly dependent on the bathroom and defecation habits of air passengers during their journey. In this study of UK adults (n = 2103), we quantified the likelihood of defecation prior to departure, on the aircraft and upon arrival on both short- and long-haul flights. The results were then used to assess the likelihood of capturing the signal from infected individuals at UK travel hubs. To obtain a representative cross-section of the population, the survey was stratified by geographical region, gender, age, parenting status, and social class. We found that an individual's likelihood to defecate on short-haul flights ( 6 h in duration). This behaviour pattern was higher among males and younger age groups. The maximum likelihood of defecation was prior to departure (< 39 %). Based on known SARS-CoV-2 faecal shedding rates (30–60 %) and an equal probability of infected individuals being on short- (71 % of inbound flights) and long-haul flights (29 %), we estimate that aircraft wastewater is likely to capture ca. 8–14 % of SARS-CoV-2 cases entering the UK. Monte Carlo simulations predicted that SARS-CoV-2 would be present in wastewater on 14 % of short-haul flights and 62 % of long-haul flights under current pandemic conditions. We conclude that aircraft wastewater alone is insufficient to effectively monitor all the transboundary entries of faecal-borne pathogens but can form part of a wider strategy for public heath surveillance at national borders