Optical diagnosis of dense plasma evolution during irradiation by ultra-intense laser pulses

Intense laser-solid interactions have been the focus of much research for a number of decades, and many attractive properties have been demonstrated, such as the ability to produce beams of highly energetic particles, as well as intense X-ray, γ-ray, and THz radiation. This thesis reports on investigations into ultra-intense (10¹⁹ - 10²¹ Wcm⁻²) laser-solid interactions, using optical diagnostic techniques applied at state-of-the-art high power laser facilities. Experiments and numerical modelling are undertaken to introduce new methods of optically probing the properties of dense plasmas and their evolution during irradiation by intense laser light. The results reported provide new insight into the physical processes occurring, and the methods that are developed and demonstrated in this thesis have the potential to be employed on future experiments to characterise laser-plasma interactions. The new results introduced in this thesis are presented in three parts. In the first, experimental measurements of the specularly reflected light from the front surface of microstructured targets are reported. Based on these measurements and ray-tracing modelling, an analytical model is developed that utilises microstructured targets, and measurements of the spacing between the intensity maxima in the reflected light, to determine the laser focal spot size and the electron temperature within the region of the laser focal spot. These properties are difficult to measure by other means, and so the method proposed could be employed on future experiments to provide an enhancement to the research being undertaken. The second study is an investigation of stripe patterns measured in the profile of the laser light transmitted through expanding ultrathin foil targets, as they undergo relativistic self-induced transparency. Analysis of these results, along with numerical modelling, demonstrate that the size, ellipticity, and angular orientation of the plasma aperture directly influences the spatial-intensity distribution of these stripes. Previous studies have shown the potential for directly controlling the distribution of the electron beams produced during laser-plasma interactions by altering the spatial properties of the relativistic plasma aperture. The results presented here form part of an important study into how relativistic self-induced transparency can be utilised to enhance laserdriven ion acceleration. In the final study, measurements of the spectra of laser light back-reflected from thin foil targets are analysed. Observed shifting and broadening of the spectra, relative to the input laser spectrum, is discussed. It is found that the interaction between the outwards expansion due to thermal pressure and the inwards laser hole-boring radiation pressure can be probed by spectral measurements. The force which is dominant over the timescale of the interaction can be determined. From this, a diagnostic technique is presented that could be employed on future experiments to probe the direction of motion of the plasma critical surface during irradiation. In addition, this technique provides a method of estimating the reflectivity of the plasma, through measuring the degree of self-phase modulation occurring in the spectra. These three studies provide new insight into the complex dynamics of relativistically intense laser-plasma interactions, and demonstrate optical techniques that can be utilised in future experimental investigations to diagnose various properties of the motion and evolution of the dense plasma.Intense laser-solid interactions have been the focus of much research for a number of decades, and many attractive properties have been demonstrated, such as the ability to produce beams of highly energetic particles, as well as intense X-ray, γ-ray, and THz radiation. This thesis reports on investigations into ultra-intense (10¹⁹ - 10²¹ Wcm⁻²) laser-solid interactions, using optical diagnostic techniques applied at state-of-the-art high power laser facilities. Experiments and numerical modelling are undertaken to introduce new methods of optically probing the properties of dense plasmas and their evolution during irradiation by intense laser light. The results reported provide new insight into the physical processes occurring, and the methods that are developed and demonstrated in this thesis have the potential to be employed on future experiments to characterise laser-plasma interactions. The new results introduced in this thesis are presented in three parts. In the first, experimental measurements of the specularly reflected light from the front surface of microstructured targets are reported. Based on these measurements and ray-tracing modelling, an analytical model is developed that utilises microstructured targets, and measurements of the spacing between the intensity maxima in the reflected light, to determine the laser focal spot size and the electron temperature within the region of the laser focal spot. These properties are difficult to measure by other means, and so the method proposed could be employed on future experiments to provide an enhancement to the research being undertaken. The second study is an investigation of stripe patterns measured in the profile of the laser light transmitted through expanding ultrathin foil targets, as they undergo relativistic self-induced transparency. Analysis of these results, along with numerical modelling, demonstrate that the size, ellipticity, and angular orientation of the plasma aperture directly influences the spatial-intensity distribution of these stripes. Previous studies have shown the potential for directly controlling the distribution of the electron beams produced during laser-plasma interactions by altering the spatial properties of the relativistic plasma aperture. The results presented here form part of an important study into how relativistic self-induced transparency can be utilised to enhance laserdriven ion acceleration. In the final study, measurements of the spectra of laser light back-reflected from thin foil targets are analysed. Observed shifting and broadening of the spectra, relative to the input laser spectrum, is discussed. It is found that the interaction between the outwards expansion due to thermal pressure and the inwards laser hole-boring radiation pressure can be probed by spectral measurements. The force which is dominant over the timescale of the interaction can be determined. From this, a diagnostic technique is presented that could be employed on future experiments to probe the direction of motion of the plasma critical surface during irradiation. In addition, this technique provides a method of estimating the reflectivity of the plasma, through measuring the degree of self-phase modulation occurring in the spectra. These three studies provide new insight into the complex dynamics of relativistically intense laser-plasma interactions, and demonstrate optical techniques that can be utilised in future experimental investigations to diagnose various properties of the motion and evolution of the dense plasma

ULTRAVIOLET ROLL-TO-ROLL NANOIMPRINT LITHOGRAPHIC FABRICATION OF FLEXIBLE POLYMER MOULDS

Ph.DDOCTOR OF PHILOSOPH

Protocol for a systematic review: understanding the motivations and barriers to uptake and use of female-initiated, primary biomedical HIV prevention technologies in sub-Saharan Africa.

BACKGROUND: Women in sub-Saharan Africa are disproportionately affected by high rates of HIV, yet relatively few products exist for female-initiated HIV prevention. New antiretroviral (ARV)-based prevention options could present opportunities for women to expand their HIV prevention choices; however, acceptability and adherence play a key role in the effectiveness of these products and implementation is still in early stages. To better understand which HIV prevention options might best serve women in sub-Saharan Africa, how and why, this review will explore qualitative evidence from clinical trials and implementation studies alike using a meta-ethnographic approach to synthesise data and interpret results. METHODS/DESIGN: This systematic review will use a meta-ethnographic approach to analyse qualitative data extracted from multiple studies featuring actual use of female-initiated technologies for HIV prevention. The search strategy will be applied in seven databases and papers will be selected using strict inclusion and exclusion criteria. The review will closely follow the guidance set forth by preferred reporting items for systematic reviews and meta-analyses (PRISMA) and Centre for Reviews Dissemination (CRD) where the guidance applies to qualitative data. Two reviewers will review all papers during the paper selection phase, with consultation from a third reviewer to confirm consensus. All papers included in the review will be read and analysed by two reviewers. The final analysis will be conducted by three primary reviewers with additional input from all other authors. DISCUSSION: With new HIV prevention technologies currently in early implementation phases and still more on the horizon, there is much to learn about how best these products may be delivered. A review such as this could help to inform the real-world implementation of the next wave of new HIV prevention technologies such as ARV-based oral pre-exposure prophylaxis (PrEP)

Changes in dietary patterns and body composition within 12 months of liver transplantation

Background: Cardiometabolic risk factors are increasing in liver transplant recipients (LTR). Influencing dietary factors have not been assessed. The aim of this observational study was to assess changes in weight, metabolic function, dietary intake and eating behaviours in the first year after orthotopic liver transplantation (OLT). Methods: Consecutive recruitment of 17 patients (14 males) awaiting OLT at a single tertiary hospital. Dietary intake, food behaviours and anthropometry were recorded at baseline, and 6 and 12 months posttransplant. Results: By 12 months, patients had gained on average 7.3% of body weight. The prevalence of overweight or obesity increased from baseline 53% to 77% (P=0.001). By 6 months, 65% (n=11/17) of patients had altered glucose metabolism. Dietary intake was consistent with a Western-style dietary pattern with high saturated fat. Over half of the patients (69%, n=11/16) reported low to no depressive feelings and rated their self-esteem as good (53%, n=9/16). The Power of Food Scale increased between pre and post-transplant, indicating a stronger appetitive drive. Conclusions: Weight gain occurs early post-transplant, with significant metabolic dysfunction present within 6 months, however is not associated with significant psychological distress. Early dietary intervention designed to limit weight gain and target cardiometabolic health is recommended for this unique patient population

H-Diplo Roundtable Review

Cambridge:Harvard University Press. 2014. ISBN: 9780674729711 (hardcover, $45.00/£29.95/€35.00) Modern European history was under the anniversary spotlight in 2014-2015. The centenary of the beginning of the First World War brought forth a steady stream of commemorations and publications. Standing out was Christopher Clark’s The Sleepwalkers, a global bestseller, whose controversial reinterpretation of the crisis of July 1914 and of the responsibility for its violent outcome ignited a widespread academic and public debate.1 Overshadowed by the anniversary of the Great War’s outbreak was the bicentenary of another great war’s conclusion, two hundred years after the end of the Napoleonic wars. In this relatively subdued realm, most of the attention was devoted to the final instance of armed conflict, with official commemorations of, books about, large-scale reenactments of, and multimedia exhibitions displaying the Battle of Waterloo

A Near-Infrared and X-ray Study of W49B: A Wind Cavity Explosion

We present near-infrared narrow-band images of the supernova remnant W49B, taken with the WIRC instrument on the Hale 200 inch telescope on Mt. Palomar. The 1.64 micron [Fe II] image reveals a barrel-shaped structure with coaxial rings, which is suggestive of bipolar wind structures surrounding massive stars. The 2.12 micron shocked molecular hydrogen image extends 1.9 pc outside of the [Fe II] emission to the southeast. We also present archival Chandra data, which show an X-ray jet-like structure along the axis of the [Fe II] barrel, and flaring at each end. Fitting single temperature X-ray emission models reveals: an enhancement of heavy elements, with particularly high abundances of hot Fe and Ni, and relatively metal-rich core and jet regions. We interpret these findings as evidence that W49B originated inside a wind-blown bubble (R ~ 5 pc) interior to a dense molecular cloud. This suggests that W49B's progenitor was a supermassive star, that could significantly shape its surrounding environment. We also suggest two interpretations for the jet morphology, abundance variations and molecular hydrogen emission: (1) the explosion may have been jet-driven and interacting with the molecular cavity (i.e. a Gamma-ray burst); or (2) the explosion could have been a traditional supernova, with the jet structure being the result of interactions between the shock and an enriched interstellar cloud.Comment: 9 pages with embedded figures Accepted by the Astrophysical Journa

Vervet monkey development in a life historical perspective

Juvenile primates have rarely been the focus of primate life history research. I followed two cohorts of vervet monkeys from birth to the end of the juvenile period. This presented us with data to study the physical and behavioural development during early life, including an assessment of inter-individual variation in both social behaviour and growth rates. Overall, my data show that—as both theory predicts and other empirical studies have demonstrated- that juveniles develop in a social and ecological context that is dynamic and not fixed. Early life experiences may therefore influence the degree to which adult vervets are able to cope with variation in their social and ecological environments, and may also help explain the inter-individual variation we see within and across populations

Biodiversity enhances ecosystem multifunctionality across trophic levels and habitats

The importance of biodiversity for the integrated functioning of ecosystems remains unclear because most evidence comes from analyses of biodiversity\u27s effect on individual functions. Here we show that the effects of biodiversity on ecosystem function become more important as more functions are considered. We present the first systematic investigation of biodiversity\u27s effect on ecosystem multifunctionality across multiple taxa, trophic levels and habitats using a comprehensive database of 94 manipulations of species richness. We show that species-rich communities maintained multiple functions at higher levels than depauperate ones. These effects were stronger for herbivore biodiversity than for plant biodiversity, and were remarkably consistent across aquatic and terrestrial habitats. Despite observed tradeoffs, the overall effect of biodiversity on multifunctionality grew stronger as more functions were considered. These results indicate that prior research has underestimated the importance of biodiversity for ecosystem functioning by focusing on individual functions and taxonomic groups

The Grizzly, February 27, 2014

Second Ricochet Production Revisits the CIE Questions • New Program Mandates Additional Community Involvement on Campus • Reception to Take Place on Final Week of Brian H. Peterson Exhibit • Woodstock to Present her Research in News Consumption Lecture • Reputation of Bomberger\u27s Heefner Pipe Organ Growing • Jewish Studies Lectures Continue • Ursinus Alumnus Takes on the NFL • Opinion: Great Progress, But We\u27re Not There Yet!; Straight Wealthy White Guys Deserve a Say Too • Winter Olympic Games Come to a Close • Wrestling, Women\u27s Swimming Best in Conferencehttps://digitalcommons.ursinus.edu/grizzlynews/1899/thumbnail.jp