Notes on The Feynman Checkerboard Problem

The Feynman checkerboard problem is an interesting path integral approach to the Dirac equation in `1+1' dimensions. I compare two approaches reported in the literature and show how they may be reconciled. Some physical insights may be gleaned from this approach.Comment: 9 page

Intimacy, pleasure and the men who pay for sex

About the repository: This book brings together chapters by academics, researchers and practitioners to analyse how crimes such as sex work, domestic violence and rape and sexual assault have risen up the Government agenda in recent years. For example, the 'Paying the Price' consultation exercise on sex work in 2004, and recent legislation around sex crimes, including the Sex Offences Act (2003). This is a multi-disciplinary, social scientific, pro-feminist collection, which draws upon practice, empirical research, documentary analysis and overviews of research in the areas of sex work and sexual violence. Within Sex as Crime there are two distinct sub-sections: 'Sex for Sale' and 'Sex as Violence', but the broader and overriding link of sex as crime remains a paramount theme that spans the collection. Chapters include discussions of the impact of new regulations on street sex workers, and of street sex work on community residents, the use of the internet by men who pay for sex and men who sell it, sexual violence and identity, sex crimes against children and protecting children online and working with sex offenders. Other chapters explore reasons for such offending behaviour

Sex on the net: online relations between the men who pay for sex

[About the Book] How do people have relationships when they are apart, or develop them when they've never even met? From MySpace and weblogs to romance and sexuality, this book draws together a range of studies on remote relationships, investigating the intricate, intimate ways that people forge connections online. The term 'remote' refers to the technologies that facilitate forms of communication, and also underlines the lack of physicality involved in these relationships, developed at a distance. Using empirical data, these collected essays explore a wide variety of relationships, examining the methodological and ethical issues that researchers face. Remote Relationships in a Small World, part of a new generation of online studies, responds to the need for research that focuses on social relationships

Combining internal- and external-training-load measures in professional rugby league

Purpose: This study investigated the effect of training mode on the relationships between measures of training load in professional rugby league players. Methods: Five measures of training load (internal: individualized training impulse, session rating of perceived exertion; external—body load, high-speed distance, total impacts) were collected from 17 professional male rugby league players over the course of two 12-week pre-season periods. Training was categorized by mode (small-sided games, conditioning, skills, speed, strongman, and wrestle) and subsequently subjected to a principal component analysis. Extraction criteria were set at an eigenvalue of greater than one. Modes that extracted more than one principal component were subjected to a varimax rotation. Results: Small-sided games and conditioning extracted one principal component, explaining 68% and 52% of the variance, respectively. Skills, wrestle, strongman, and speed extracted two principal components explaining 68%, 71%, 72%, and 67% of the variance respectively. Conclusions: In certain training modes the inclusion of both internal and external training load measures explained a greater proportion of the variance than any one individual measure. This would suggest that in those training modes where two principal components were identified, the use of only a single internal or external training load measure could potentially lead to an underestimation of the training dose. Consequently, a combination of internal and external load measures is required during certain training modes

Parameter Estimation as a Problem in Statistical Thermodynamics

Abstract. In this work, we explore the connections between parameter fitting and statistical thermodynamics using the maxent principle of Jaynes as a starting point. In particular, we show how signal averaging may be described by a suitable one particle partition function, modified for the case of a variable number of particles. These modifications lead to an entropy that is extensive in the number of measurements in the average. Systematic error may be interpreted as a departure from ideal gas behavior. In addition, we show how to combine measurements from different experiments in an unbiased way in order to maximize the entropy of simultaneous parameter fitting. We suggest that fit parameters may be interpreted as generalized coordinates and the forces conjugate to them may be derived from the system partition function. From this perspective, the parameter fitting problem may be interpreted as a process where the system (spectrum) does work against internal stresses (non-optimum model parameters) to achieve a state of minimum free energy/maximum entropy. Finally, we show how the distribution function allows us to define a geometry on parameter space, building on previous wor

Feminism, Abortion and Disability: irreconcilable differences?

There has been considerable discussion of the political allegiance between the feminist and disability movements, but the question of abortion remains a thorny one. Disability rights advocates have been keen to demonstrate that it is possible to believe in a woman's right to sovereignty over the body and, yet, be opposed to the selective abortion of an impaired foetus – describing the latter as a form of 'weak' eugenics. The aim of this paper is to show that whilst there may be some points of agreement between the feminist and disability movements on the question of abortion, there exist fundamental and irreconcilable differences

Exercise tolerance during VO2max testing is a multifactorial psychobiological phenomenon

Fifty-nine men completed a VO2max test and a questionnaire to establish reasons for test termination, perceived exercise reserve (difference between actual test duration and the duration the individual perceived could have been achieved if continued until physical limitation), and perception of verbal encouragement. Participants gave between 1 and 11 factors as reasons for test termination, including leg fatigue, various perceptions of physical discomfort, safety concerns, and achievement of spontaneously set goals. The two most common main reasons were leg fatigue and breathing discomfort, which were predicted by pre-to-post test changes in pulmonary function (p = 0.038) and explosive leg strength (p = 0.042; R2 = 0.40). Median (interquartile range) perceived exercise reserve, was 45 (50) s. Two-thirds of participants viewed verbal encouragement positively, whereas one-third had a neutral or negative perception. This study highlights the complexity of exercise tolerance during VO2max testing and more research should explore these novel findings

Plasmodium falciparum Parasites Are Killed by a Transition State Analogue of Purine Nucleoside Phosphorylase in a Primate Animal Model

Plasmodium falciparum causes most of the one million annual deaths from malaria. Drug resistance is widespread and novel agents against new targets are needed to support combination-therapy approaches promoted by the World Health Organization. Plasmodium species are purine auxotrophs. Blocking purine nucleoside phosphorylase (PNP) kills cultured parasites by purine starvation. DADMe-Immucillin-G (BCX4945) is a transition state analogue of human and Plasmodium PNPs, binding with picomolar affinity. Here, we test BCX4945 in Aotus primates, an animal model for Plasmodium falciparum infections. Oral administration of BCX4945 for seven days results in parasite clearance and recrudescence in otherwise lethal infections of P. falciparum in Aotus monkeys. The molecular action of BCX4945 is demonstrated in crystal structures of human and P. falciparum PNPs. Metabolite analysis demonstrates that PNP blockade inhibits purine salvage and polyamine synthesis in the parasites. The efficacy, oral availability, chemical stability, unique mechanism of action and low toxicity of BCX4945 demonstrate potential for combination therapies with this novel antimalarial agent

Sterile Protection against Plasmodium knowlesi in Rhesus Monkeys from a Malaria Vaccine: Comparison of Heterologous Prime Boost Strategies

Using newer vaccine platforms which have been effective against malaria in rodent models, we tested five immunization regimens against Plasmodium knowlesi in rhesus monkeys. All vaccines included the same four P. knowlesi antigens: the pre-erythrocytic antigens CSP, SSP2, and erythrocytic antigens AMA1, MSP1. We used four vaccine platforms for prime or boost vaccinations: plasmids (DNA), alphavirus replicons (VRP), attenuated adenovirus serotype 5 (Ad), or attenuated poxvirus (Pox). These four platforms combined to produce five different prime/boost vaccine regimens: Pox alone, VRP/Pox, VRP/Ad, Ad/Pox, and DNA/Pox. Five rhesus monkeys were immunized with each regimen, and five Control monkeys received a mock vaccination. The time to complete vaccinations was 420 days. All monkeys were challenged twice with 100 P. knowlesi sporozoites given IV. The first challenge was given 12 days after the last vaccination, and the monkeys receiving the DNA/Pox vaccine were the best protected, with 3/5 monkeys sterilely protected and 1/5 monkeys that self-cured its parasitemia. There was no protection in monkeys that received Pox malaria vaccine alone without previous priming. The second sporozoite challenge was given 4 months after the first. All 4 monkeys that were protected in the first challenge developed malaria in the second challenge. DNA, VRP and Ad5 vaccines all primed monkeys for strong immune responses after the Pox boost. We discuss the high level but short duration of protection in this experiment and the possible benefits of the long interval between prime and boost