Portfolio return autocorrelation and non-synchronous trading in UK equities

Although infrequent trading in equity stocks is more prevalent in the United Kingdom (and other non-United States countries), we find that it is proportionally more important in explaining the degree of serial correlation in stock returns in the US than in the UK, in contrast to much of the existing literature.We show that infrequent trading cannot explain more than a small proportion of the serial correlation observed in monthly UK stock returns and hence, other explanations for return predictability must be sought. Many studies have shown that stock market returns in the UK and other international markets are substantially and significantly serially correlated. The success of an investment strategy that is based on the apparent predictability of returns depends on whether the serial correlation is truly random and period specific or due to time varying risk premia or to market microstructure effects. A frequently noted explanation for this serial correlation is market thinness or, more precisely, the infrequency with which a substantial number of UK stocks are traded. Non-synchronous trading results in a measurement error in the observed data for returns on individual stocks, portfolios and market indices. This measurement error generates serial correlation in the observed returns. Here, we assess the extent to which the observed serial correlation in returns can be explained by equity non-trading behaviour. This will reveal whether there is any residual serial correlation left to be explained by alternative sources. We find that, whilst a proportion of the serial correlation in the returns of portfolios of low value stocks can be explained by non-trading, much of it still remains unexplained.

Real-world Quantum Sensors: Evaluating Resources for Precision Measurement

Quantum physics holds the promise of enabling certain tasks with better performance than possible when only classical resources are employed. The quantum phenomena present in many experiments signify nonclassical behavior, but do not always imply superior performance. Quantifying the enhancement achieved from quantum behavior requires careful analysis of the resources involved. We analyze the specific case of parameter estimation using an optical interferometer, where increased precision can be achieved using quantum probe states. Common performance measures are examined and it is shown that some overestimate the improvement. For the simplest experimental case we compare the different measures and show this overestimate explicitly. We give the preferred analysis of real-world experiments and calculate benchmark values for experimental parameters necessary to realize a precision enhancement.Comment: 8 pages, 3 figure

'If I cannot access services then there is no reason for me to test': the impact of health service charges on HIV testing and treatment amongst migrants in England

Policy governing entitlement to access government health care for foreign nationals in England is a subject of debate, controversy and confusion. Of particular concern to health providers has been the impact of National Health Service charges on delaying HIV testing and anti-retroviral treatment uptake and adherence amongst certain migrant groups. Data obtained through focus groups with 70 migrants from southern Africa, suggest that confusion over health care entitlements exists amongst those seeking health care and is reported amongst health service providers. This confusion, as well as financial difficulties and fears over deportation facing some migrants, can in turn be a factor influencing their decisions to avoid formal health services, resort to alternative and often ineffective or potentially adverse forms of therapy, and delay HIV testing and treatment uptake

PU(2) monopoles and a conjecture of Marino, Moore, and Peradze

In this article we show that some of the recent results of Marino, Moore, and Peradze (math.DG/9812042, hep-th/9812055) -- in particular their conjecture that all closed, smooth four-manifolds with b_2^+ > 1 (and Seiberg-Witten simple type) are of `superconformal simple type' -- can be understood using a simple mathematical argument via the PU(2)-monopole cobordism of Pidstrigach and Tyurin (dg-ga/9507004) and results of the first and third authors (dg-ga/9712005, dg-ga/9709022).Comment: 13 pages, 1 figure. Improved exposition, typographical slips corrected, figure and references added. Minor correction on page 2. To appear in Mathematical Research Letter

Effect of Single Window System Procedures on Cargo Clearance Efficiency in Kenya: A Case for Mombasa Port

A Single Window Concept is a one-stop facility that allows exchange of information between all parties involved in trade across borders. It is aimed at reducing the complexity, time and costs of clearing goods at the ports. The Concept has been successfully implemented in Kenya in areas such as the Mombasa port, Jomo Kenyatta International airport, Moi International airport and Kenyan borders. The study sought to identify the Effect of Single Window System on cargo clearance efficiency at the port of Mombasa. In particular, to determine its effect on shipping procedures, Pre-clearance permits and Customs goods declaration procedures at the port of Mombasa. The study adopted a quantitative approach targeting a population of 155 respondents. Stratified sampling technique was used to get a sample size of 112 respondents. Data was collected using a structured questionnaire with Likert scale measurement. Data was collected and analyzed using descriptive as well as inferential statistics. The study found that Single Window concept has positive effect on Shipping procedures (p-value 0.952), Pre-clearance permits (p-value 0.861), Customs goods declaration procedures (p-value 0.950) and hence improved cargo clearance efficiency at the port of Mombasa. The study recommends more studies to be done on variables that affect cargo clearance efficiency at the port of Mombasa which were not covered under this study. Keywords: Concept, One-stop facility, Cargo clearance, Pre-clearance permits, Customs goods declarations, Regulatory agencies, Electronic cargo authentication.DOI: 10.7176/EJBM/11-24-11Publication date: August 31st 2019

Frustrated spin order and stripe fluctuations in FeSe

The charge and spin dynamics of the structurally simplest iron-based superconductor, FeSe, may hold the key to understanding the physics of high temperature superconductors in general. Unlike the iron pnictides, FeSe lacks long range magnetic order in spite of a similar structural transition around 90\,K. Here, we report results of Raman scattering experiments as a function of temperature and polarization and simulations based on exact diagonalization of a frustrated spin model. Both experiment and theory find a persistent low energy peak close to 500cm$^{-1}$ in $B_{1g}$ symmetry, which softens slightly around 100\,K, that we assign to spin excitations. By comparing with results from neutron scattering, this study provides evidence for nearly frustrated stripe order in FeSe.Comment: 12 pages, 12 figure