The X-ray Structural Study of Some Organic Crystals

Isoclovene, C15H24, is a liquid sesquiterpene of hitherto virtually unknown constitution. It forms two isomorphous hydrohalide derivatives, isoclovene hydrochloride and isoclovene hydrobromide, which crystallise in the monoclinic space group, P2, with two molecules per unit cell. An attempt was made initially to carry through a structural analysis of the hydrohromide derivative using the heavy atom technique and two dimensional Fourier methods. Only the (010) electron-density projection, when calculated on the basis of the heavy atom phases, gave an unambiguous representation of the molecule, hut the prohibitive length of projection (13.8 A) prevented any significant resolution being achieved. The (001) electron-density projection provided a representation of the molecule and its superimposed mirror image due to the existence of the well known false symmetry centre which exists between two phase-determining atoms in the non-centric projections of space group P2 . Further spurious symmetry was present in the (100) electron-density projection because the heavy atom phases could only be coupled with about one half of the observed terms, those satisfying the condition k + l = 2n. Attempts to correlate these three projections of the molecule on the basis of tentative trial structures were not successful. The solution of the structure resulted from the application of superposition methods to a three dimensional sharpened Patterson function computed with data derived from the hydrochloride derivative. A three dimensional representation of the molecule and its superimposed mirror image was thereby obtained. This map was compared with the essentially analogous distribution given by a triple Fourier synthesis phased solely on the chlorine atom phases. The corresponding prominent peaks on both maps were assumed to indicate the most likely atomic sites. Thereafter, there existed the interpretationsl problem of selecting ''true peaks" from their ''mirror image" counterparts. Seven carbon atoms were located and included with chlorine in the initial phasing calculations. Four successive triple Fourier syntheses sufficed to reveal the structure. Two further Fo syntheses and twelve successive least squares cycles reduced the discrepancy over 976 observed terms to 12.5%. This analysis has led to a determination of the molecular structure and relative configuration of isoclovene hydrochloride. From these results the structure of the parent compound, isoclovene, has been deduced. Photo-irradiated acridizinium bromide, C26N2H20Br2, has been obtained in a crystalline form belonging to the monoclinic space group P2 1/m with two molecules per unit cell. The projections of the Patterson function on the three main zones have been examined but it has not yet proved possible to derive an entirely satisfactory trial structure for the most favourable (100), projection

Indirect short-selling constraints

In this thesis, I use two strategies of inquiry to further our understanding of indirect short-selling constraints. First, I interview a series of experienced market practitioners to identify their attitudes towards indirect constraints. I find little support for D’Avolio’s (2002) suggestions that short-selling is inhibited by managers’ fear of tracking error and by the cultural pressures of a society that can vilify short-sellers. However, I am able to introduce a new, social, indirect constraint to the literature – the perception that short-selling is a form of ‘trading’ as distinct from ‘investment’, and the consequent lack of acceptance amongst stakeholders that this engenders. This constraint reveals a divide between the attitudes of the academic community and parts of the institutional practitioner community on the subject of short-selling. However, interviewees argue that this indirect constraint is diminishing over time. This raises the prospect of markets in practice converging in behaviour towards the markets assumed in classical asset pricing models, and has implications for market efficiency. My second strategy of inquiry is to use a large, new stock lending database to explore three risk-related indirect constraints to short-selling. I examine ‘crowded exits’, a general class of liquidity problem, and find that these are associated with statistically and economically significant losses for short-sellers. I also examine ‘manipulative short squeezes’, a liquidity problem arising from predatory trading. Consistent with theory and the literature on the subject, I find that these are rare for larger, more liquid stocks. However, when they do occur, these events generate statistically significant losses for short-sellers. Finally, I build upon the work of Gamboa-Cavazos and Savor (2007) and investigate the response of short-sellers to losses. I find that short-sellers close their positions in response to accounting losses and not simply in response to rising share prices. This is consistent with short-sellers’ use of risk management tools that are designed to crystallize small losses. These serve to limit the risk of potentially unlimited losses and to reduce short positions at times of heightened synchronization risk. Stocks subject to shortcovering in this manner do not subsequently under-perform the market. My findings demonstrate that a sophisticated group of traders, strongly associated with price setting, does not suffer from the bias known as loss realization aversion

Developing short-selling on the mainland Chinese equity markets

We review the theory and evidence on liquidity, price discovery and market efficiency associated with securities lending and short-selling. We also study the efforts by the Hong Kong and Taiwan stock exchanges to develop short-selling. We build on this to generate ideas for the development of securities lending and short-selling in mainland China. We argue that a phased program of reform, well-implemented, can help build confidence in the mainland Chinese equity markets, by aiding price discovery and improving market liquidity. JEL classification: G15; G1

Risk Assessment Techniques for Split Capital Investment Trusts

The split capital investment trust crisis has brought into focus the need for more reliable risk assessment techniques for shares in the sector. We discuss the strengths and weaknesses of traditional pricing and risk description measures for split capital investment trusts (eg gross redemption yield, cover, hurdle rates) and ways of making these more useful. We then examine alternative pricing and risk assessment techniques (eg option pricing, sensitivity measures). In particular, some of the problems with the application of traditional option pricing techniques are discussed and methods for dealing with them suggested. We propose the use of stochastic modelling for both pricing shares and understanding their risks

Hidden Risks In The CDO - Squared Market

We show that there are risks (default location risk and overlap risk) unique to CDO-squared structures. These risks may not be well-understood by investors and credit rating agencies. As a result, the tranche of a CDO-squared having the same name and similar rating to the tranche of a CDO may have a very different risk profile, and the returns offered to CDO-squared investors may be unattractive on a risk-adjusted basis. We believe that the hidden risks in CDO-squared structures will be clearly exposed in a distressed credit environment

Effect of anti-TNF and conventional synthetic disease-modifying anti-rheumatic drug treatment on work disability and clinical outcome in a multicentre observational cohort study of psoriatic arthritis

OBJECTIVE: To determine the effect of medical treatment on work disability in patients with active PsA in a real-world setting.METHODS: Four hundred patients with active PsA commencing or switching to anti-TNF or conventional synthetic DMARD (csDMARD) were recruited to a multicentre UK prospective observational cohort study. Work disability was measured using the work productivity and activity-specific health problem instrument and peripheral joint activity was measured with the disease activity in PsA composite measure.RESULTS: Four hundred patients were recruited, of whom 229 (57.25%) were working (of any age). Sixty-two patients of working age (24%) were unemployed. At 6 months there was a 10% improvement in presenteeism (P = 0.007) and a 15% improvement in work productivity (P = 0.001) among working patients commenced on csDMARDs (n = 164) vs a larger and more rapid 30% improvement in presenteeism (P &lt; 0.001) and 40% improvement in work productivity (P &lt; 0.001) among those commenced on anti-TNF therapy (n = 65). Clinical response was poor among patients commenced on a csDMARD (n = 272), with an 8.4 point improvement in disease activity in PsA (P &lt; 0.001) vs those commenced on anti-TNF therapy (n = 121), who had a 36.8 point improvement (P &lt; 0.001).CONCLUSION: We report significant and clinically meaningful improvements in both work disability and clinical outcomes after commencement of anti-TNF therapy in a real-world setting. Improvements in all outcomes among those commencing csDMARDs were slower and of a smaller magnitude.</p

Lockdown labs : pivoting to remote learning in forensic science higher education

Forensic Science training and education is reliant on the application of knowledge to casework scenarios and the development of key practical skills that provide a platform for career development in the field. The COVID-19 pandemic introduced a number of challenges to effectively deliver practical content online and remotely, whilst still meeting intended learning outcomes, accreditation requirements, and attaining a high level of student engagement and experience. The MSc Forensic Science programme featured in this study is a one-year degree programme with a strong emphasis on the practical elements of forensic science, and a diverse international student cohort. Therefore, the restrictions associated with the pandemic made it very difficult not only to plan the delivery of material but also to adapt the content itself for effective online and remote learning. By focusing on the intended learning outcomes, a number of innovative teaching practices were developed to successfully transition from face-to-face teaching to online and remote delivery. A range of online and practical resources were developed, including a laboratory home kit, demonstration videos, online practical technique simulations (produced by Learning Science), data analysis tasks, and interactive workshops and activities, all designed to consolidate student learning and build confidence, in preparation for such a time that on campus practical teaching could resume. The initial feedback received from these activities from both staff and students was extremely positive and the transition from classroom to online teaching was a success, as reflected in student attainment and later student feedback. Students reported that they had a better understanding of what was expected of them, including knowledge of protocols and techniques, and felt much more confident moving into the next stage of their learning development. Even though the practical laboratory sessions were the most significantly affected by the restrictions associated with the pandemic, and resulted in reduced interaction for the students, this was counteracted by virtual sessions and workshops, which gave students the opportunity to engage with each other and communicate their thoughts and opinions, ultimately building key presentation and group working skills. This case study will detail the pivot to remote learning, as well as critically evaluating the feedback from students and discussing the changes that are likely to be retained as longer-term teaching practices, versus those that were a necessary temporary addition or adjustment in response to the pandemic