Tunable Laser-Plasma Acceleration with Ionization Injection

Accelerating electrons to relativistic energies by an intense laser field interacting with a plasma is a widely considered concept to drive future applications such as compact light sources. The strong requirements on the electron beam quality imposed by these applications requires to precisely control the injection and acceleration dynamics and hence the parameters of the laser-plasma accelerated electrons. This thesis studies electron beam generation with ionization injection in a nitrogen doped hydrogen plasma, focused on tunability and improvement of electron beam parameters. A capillary type plasma target was developed and characterized with Computational Fluid Dynamic (CFD) simulations allowing extensive parameter scans. It is demon- strated that electron beam parameters can be tuned in a wide range with peak energies between 200MeV and 350MeV, bunch charges between 100pC and 350pC at percent- level shot-to-shot stability, by varying the laser focus position, laser pulse energy, plasma density and the nitrogen concentration. The accelerator performance could be optimized by controlling beam loading effects with a combination of the nitrogen concentration and the laser pulse energy, resulting in electron beams with reduced energy spread at simultaneously increased peak charge density. The laser pulse energy showed the strongest influence on the transverse beam parameters, allowing to fine-tune beam divergence and beam emittance, a crucial prerequisite to optimize electron beams for the transport with electron beam optics. The broad parameter scans could be reproduced with Particle-In-Cell (PIC) simulations, providing an in-depth understanding of the injection and acceleration dynamics in the ionization injection scheme. The presented results and the identified scalings can give a guideline for the operation regime for future experiments and to develop improved plasma targets to further enhance the electron beam quality

Learning masculinities in a Japanese high school rugby club

This paper draws on research conducted on a Tokyo high school rugby club to explore diversity in the masculinities formed through membership in the club. Based on the premise that particular forms of masculinity are expressed and learnt through ways of playing (game style) and the attendant regimes of training, it examines the expression and learning of masculinities at three analytic levels. It identifies a hegemonic, culture-specific form of masculinity operating in Japanese high school rugby, a class-influenced variation of it at the institutional level of the school and, by further tightening its analytic focus, further variation at an individual level. In doing so this paper highlights the ways in which diversity in the masculinities constructed through contact sports can be obfuscated by a reductionist view of there being only one, universal hegemonic patterns of masculinity

Nonlinear elasticity of stiff biopolymers connected by flexible linkers

Networks of the biopolymer actin, cross-linked by the compliant protein filamin, form soft gels. They can, however, withstand large shear stresses due to their pronounced nonlinear elastic behavior. The nonlinear elasticity can be controlled by varying the number of cross-links per actin filament. We propose and test a model of rigid filaments decorated by multiple flexible linkers that is in quantitative agreement with experiment. This allows us to estimate loads on individual cross-links, which we find to be less than 10 pN. © 2009 The American Physical Society

'Dressage Is Full of Queens!' Masculinity, Sexuality and Equestrian Sport

Attitudes towards sexuality are changing and levels of cultural homophobia decreasing, yet there remain very few openly gay men within sport. As a proving ground for heteromasculinity, sport has traditionally been a hostile environment for gay men. This article is based on an ethnographic study within a sporting subworld in which gay men do appear to be accepted: equestrian sport. Drawing on inclusive masculinity theory, equestrian sport is shown to offer an unusually tolerant environment for gay men in which heterosexual men of all ages demonstrate low levels of homophobia. Inclusive masculinity theory is a useful framework for exploring the changing nature of masculinities and this study demonstrates that gay men are becoming increasingly visible and accepted within once unreceptive locales, such as sport and rural communities. However, this more tolerant attitude is purchased at the expense of a subordinated feminine Other, perpetuating the dominance of men within competitive sport. © The Author(s) 2012

LUX -- A Laser-Plasma Driven Undulator Beamline

The LUX beamline is a novel type of laser-plasma accelerator. Building on the joint expertise of the University of Hamburg and DESY the beamline was carefully designed to combine state-of-the-art expertise in laser-plasma acceleration with the latest advances in accelerator technology and beam diagnostics. LUX introduces a paradigm change moving from single-shot demonstration experiments towards available, stable and controllable accelerator operation. Here, we discuss the general design concepts of LUX and present first critical milestones that have recently been achieved, including the generation of electron beams at the repetition rate of up to 5 Hz with energies above 600 MeV and the generation of spontaneous undulator radiation at a wavelength well below 9 nm.Comment: submitte

Polycyclic aromatic hydrocarbons (PAHs) degradation by laccase from a tropical white rot fungus Ganoderma lucidum

Laccase enzyme was produced from an isolate of the white rot fungus, Ganoderma lucidum Chaaim-001 BCU. The enzyme was subsequently evaluated for its degradative ability towards sixteen types of polycyclic aromatic hydrocarbons (PAHs). The G. lucidum laccase degraded antracene completely with or without a redox mediator (2 mM 1-hydroxybenzotriazole) and also degraded benzo[a]pyrene, fluorine, acenapthene, acenaphthylene and benzo[a]anthracene up to 100.0, 98.6, 95.4, 90.1 and 85.3 %,respectively, when the mediator was present. In the absence of the mediator, the ability to degrade these compounds dropped to 71.71, 62.9, 80.49, 85.85 and 9.14% respectively. Compared to the laccase enzyme from Trametes vesicolor, G. lucidum laccase appeared to retain more of its capability todegrade these PAHs when the mediator was absent

'It's a Form of Freedom': The experiences of people with disabilities within equestrian sport

This paper explores the embodied, gendered experiences of disabled horse‐riders. Drawing on data from five in‐depth interviews with paradressage riders, the ways in which their involvement in elite disability sport impacts upon their sense of identity and confidence are explored, as well as the considerable health and social benefits that this involvement brings. Social models of disability are employed and the shortcomings of such models, when applied to disability sport, are highlighted. The data presented here demonstrates the necessity of seeing disability sport as an embodied experience and acknowledging the importance of impairment to the experiences of disabled athletes. Living within an impaired body is also a gendered experience and the implications of this when applied to elite disability sport are considered

Prevalence of sexual harassment among Norwegian female elite athletes in relation to sport type

Although it is often assumed that the prevalence of sexual harassment is different in different sports, this assumption has not been empirically tested. This study considers whether the experience of sexual harassment varies by sport. The female elite athletes (N = 553) in the study participated in 56 different sport disciplines. These were grouped as follows :1) team or individual sports; 2) extent to which clothing required for competition is revealing ; 3) gender structure (male-or female dominated membership statistics); and 4) gender culture (masculine, gender-neutral, or feminine). The data show that sexual harassment occurs in every sport group. Female elite athletes who participated in ‘masculine’ sports appear to experience more harassment than women in the other groups. We conclude that, when it comes to female athletes’ experiences of sexual harassment, sport type matters far less than sport participation per se