27 research outputs found
Manipulation of laser-generated energetic proton spectra in near critical density plasma
No full textWe present simulations that demonstrate the production of quasi-monoenergetic proton bunches from the interaction of a CO2 laser pulse train with a near-critical density hydrogen plasma. The multi-pulse structure of the laser leads to a steepening of the plasma density gradient, which the simulations show is necessary for the formation of narrow-energy spread proton bunches. Laser interactions with a long, front surface, scale-length (p ) plasma, with linear density gradient, were observed to generate proton beams with a higher maximum energy, but a much broader spectrum compared to step-like density profiles. In the step-like cases, a peak in the proton energy spectra was formed and seen to scale linearly with the ratio of laser intensity to plasma density
A Bayesian framework to investigate radiation reaction in strong fields
Get PDFRecent experiments aiming to measure phenomena predicted by strong-field quantum electrodynamics (SFQED) have done so by colliding relativistic electron beams and high-power lasers. In such experiments, measurements of collision parameters are not always feasible. However, precise knowledge of these parameters is required to accurately test SFQED. Here, we present a novel Bayesian inference procedure that infers collision parameters that could not be measured on-shot. This procedure is applicable to all-optical non-linear Compton scattering experiments investigating radiation reaction. The framework allows multiple diagnostics to be combined self-consistently and facilitates the inclusion of known information pertaining to the collision parameters. Using this Bayesian analysis, the relative validity of the classical, quantum-continuous and quantum-stochastic models of radiation reaction was compared for several test cases, which demonstrates the accuracy and model selection capability of the framework and highlight its robustness if the experimental values of fixed parameters differ from their values in the models.</p
The ascension, pleroma and ecclesia concepts in Ephesians
No full textThe basic aim of the study is to investigate
the relationship between a number of christological
and ecclesiological themes. The first section of the
essay is concerned with the identification of the
traditions employed by the author in his presentation
of an ascension theology in 1:20-23 and 4:8-10.
Having once established these traditions, an attempt
is made to trace a Traditiongeschichte for them.
The second part of the essay is concerned with the
relationship between the ascension theology and the
kephale and pleroma motifs which are present in both
pericopes. This investigation necessitates an
examination of the Pauline theology. At the same
time within this section an attempt is made to trace
the source of the pleroma terminology as used by the
author of the epistle. In the third section of the
essay the interest is more general; an attempt is
made to discover how the "component parts" of the
author's ascension theology are used elsewhere in the
epistle. In the fourth and last section of the essay
the interest is again with traditions, specifically
the use made of the traditions inherent in the
ascension pericopes in the epistle in the writings
of both the Church Fathers and of authors outside
the main stream of Christian thought
Control Systems and Data Management for High-Power Laser Facilities
Get PDFInternational audienceThe next generation of high-power lasers enables repetition of experiments at orders of magnitude higher frequency than was possible using the prior generation. Facilities requiring human intervention between laser repetitions need to adapt in order to keep pace with the new laser technology. A distributed networked control system can enable laboratory-wide automation and feedback control loops. These higher-repetition-rate experiments will create enormous quantities of data. A consistent approach to managing data can increase data accessibility, reduce repetitive data-software development, and mitigate poorly organized metadata. An opportunity arises to share knowledge of improvements to control and data infrastructure currently being undertaken. We compare platforms and approaches to state-of-the-art control systems and data management at high-power laser facilities, and we illustrate these topics with case studies from our community
Neurons with Complex Karyotypes Are Rare in Aged Human Neocortex
No full textFunding Information: We thank J. Lannigan and M. Solga (University of Virginia [UVA] fluorescence-activated cell sorting [FACS] core), Y. Bao (UVA genome analysis and technology core), and A. Koeppel (UVA bioinformatics core) for their contributed expertise. We thank P. Lansdorp (University of British Columbia) for prompt sharing of unpublished metadata, and F.H. Gage (Salk Institute) and J.V. Moran (University of Michigan) for critical feedback. Human tissue was obtained from the National Institute for Child Health and Human Development (NIH) Brain and Tissue Bank for Developmental Disorders at the University of Maryland, Baltimore (contract HHSN2752009000011C, ref. no. N01-HD-9-011). Data are documented through the Brain Somatic Mosaicism Network Knowledge Portal ( synapse.org/BSMN ) and made available at the National Institute of Mental Health (NIMH) Data Archive. NIH funding to M.J.M. ( U01 MH106882 ), to D.R.W. ( U01 MH106893 ), and to M.J.M. and S.B. ( U01 MH106882-03S1 ) supported this work. I.E.B. received support from the McDonnell Foundation , and W.D.C. received support from NIH T32 GM008136-30 . Funding Information: We thank J. Lannigan and M. Solga (University of Virginia [UVA] fluorescence-activated cell sorting [FACS] core), Y. Bao (UVA genome analysis and technology core), and A. Koeppel (UVA bioinformatics core) for their contributed expertise. We thank P. Lansdorp (University of British Columbia) for prompt sharing of unpublished metadata, and F.H. Gage (Salk Institute) and J.V. Moran (University of Michigan) for critical feedback. Human tissue was obtained from the National Institute for Child Health and Human Development (NIH) Brain and Tissue Bank for Developmental Disorders at the University of Maryland, Baltimore (contract HHSN2752009000011C, ref. no. N01-HD-9-011). Data are documented through the Brain Somatic Mosaicism Network Knowledge Portal (synapse.org/BSMN) and made available at the National Institute of Mental Health (NIMH) Data Archive. NIH funding to M.J.M. (U01 MH106882), to D.R.W. (U01 MH106893), and to M.J.M. and S.B. (U01 MH106882-03S1) supported this work. I.E.B. received support from the McDonnell Foundation, and W.D.C. received support from NIH T32 GM008136-30. Publisher Copyright: © 2019 The Author(s)A subset of human neocortical neurons harbors complex karyotypes wherein megabase-scale copy-number variants (CNVs) alter allelic diversity. Divergent levels of neurons with complex karyotypes (CNV neurons) are reported in different individuals, yet genome-wide and familial studies implicitly assume a single brain genome when assessing the genetic risk architecture of neurological disease. We assembled a brain CNV atlas using a robust computational approach applied to a new dataset (>800 neurons from 5 neurotypical individuals) and to published data from 10 additional neurotypical individuals. The atlas reveals that the frequency of neocortical neurons with complex karyotypes varies widely among individuals, but this variability is not readily accounted for by tissue quality or CNV detection approach. Rather, the age of the individual is anti-correlated with CNV neuron frequency. Fewer CNV neurons are observed in aged individuals than in young individuals
Bayesian Optimization Algorithms for Accelerator Physics
No full textAccelerator physics relies on numerical algorithms to solve optimization problems in online accelerator control and tasks such as experimental design and model calibration in simulations. The effectiveness of optimization algorithms in discovering ideal solutions for complex challenges with limited resources often determines the problem complexity these methods can address. The accelerator physics community has recognized the advantages of Bayesian optimization algorithms, which leverage statistical surrogate models of objective functions to effectively address complex optimization challenges, especially in the presence of noise during accelerator operation and in resource-intensive physics simulations. In this review article, we offer a conceptual overview of applying Bayesian optimization techniques toward solving optimization problems in accelerator physics. We begin by providing a straightforward explanation of the essential components that make up Bayesian optimization techniques. We then give an overview of current and previous work applying and modifying these techniques to solve accelerator physics challenges. Finally, we explore practical implementation strategies for Bayesian optimization algorithms to maximize their performance, enabling users to effectively address complex optimization challenges in real-time beam control and accelerator design.Accelerator physics relies on numerical algorithms to solve optimization problems in online accelerator control and tasks such as experimental design and model calibration in simulations. The effectiveness of optimization algorithms in discovering ideal solutions for complex challenges with limited resources often determines the problem complexity these methods can address. The accelerator physics community has recognized the advantages of Bayesian optimization algorithms, which leverage statistical surrogate models of objective functions to effectively address complex optimization challenges, especially in the presence of noise during accelerator operation and in resource-intensive physics simulations. In this review article, we offer a conceptual overview of applying Bayesian optimization techniques towards solving optimization problems in accelerator physics. We begin by providing a straightforward explanation of the essential components that make up Bayesian optimization techniques. We then give an overview of current and previous work applying and modifying these techniques to solve accelerator physics challenges. Finally, we explore practical implementation strategies for Bayesian optimization algorithms to maximize their performance, enabling users to effectively address complex optimization challenges in real-time beam control and accelerator design
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An exploration and critique of Katz and Mair's Cartel Party theory
No full textThere have been a variety of attempts in recent years to categorise party systems. This work examines one such attempt at a new party type, Katz and Mair's cartel party theory, which was first proposed in 1995. It will initially approach the cartel party theory from a theoretical angle looking at the internal tensions and inconsistencies within the theory. The German party system will then be looked at to see what it reveals about the theory so a new critique can be drawn up and modifications to the theory suggested. Katz and Mair argue that faced with declining electoral support and falling membership levels, political parties have turned towards the state in order to secure much needed resources. These resources can take the form of control over electoral rules, state funding and access to the media. At the same time parties attempt to use their position of dominance to control the entrance of new parties into the cartel. This in turn leads to organisational and ideological change within the parties, creating cartel parties. These issues will be explored by looking at the German party system and using this example to critique and modify the theory. When Katz and Mair first put forward their theory they admitted it was very vague in some areas. This work addresses some of these issues, fleshing out the theory and providing modifications where it is unsatisfactory
Development and worldwide use of non-lethal, and minimal population-level impact, protocols for the isolation of amphibian chytrid fungi
Get PDF© The Author(s) 2018.Parasitic chytrid fungi have emerged as a significant threat to amphibian species worldwide, necessitating the development of techniques to isolate these pathogens into culture for research purposes. However, early methods of isolating chytrids from their hosts relied on killing amphibians. We modified a pre-existing protocol for isolating chytrids from infected animals to use toe clips and biopsies from toe webbing rather than euthanizing hosts, and distributed the protocol to researchers as part of the BiodivERsA project RACE; here called the RML protocol. In tandem, we developed a lethal procedure for isolating chytrids from tadpole mouthparts. Reviewing a database of use a decade after their inception, we find that these methods have been applied across 5 continents, 23 countries and in 62 amphibian species. Isolation of chytrids by the non-lethal RML protocol occured in 18% of attempts with 207 fungal isolates and three species of chytrid being recovered. Isolation of chytrids from tadpoles occured in 43% of attempts with 334 fungal isolates of one species (Batrachochytrium dendrobatidis) being recovered. Together, these methods have resulted in a significant reduction and refinement of our use of threatened amphibian species and have improved our ability to work with this group of emerging pathogens.T.W.J.G., M.C.F., D.S.S., A.L., E.C., F.C.C., J.B., A.A.C., C.M., F.S., B.R.S., S.O., were supported through the Biodiversa project RACE: Risk Assessment of Chytridiomycosis to European Amphibian Biodiversity (NERC standard grant NE/K014455/1 and NE/E006701/1; ANR-08-BDVA-002-03). M.C.F., J.S., C.W., P.G. were supported by the Leverhulme Trust (RPG-2014-273), M.C.F., A.C., C.W. were supported by the Morris Animal Foundation. J.V. was supported by the Bolyai János Research Grant of the Hunagrian Academy of Sciences (BO/00597/14). F.G. and D.G. were supported by the Conservation Leadership Programme Future Conservationist Award. C.S.A. was supported by Fondecyt (No. 1181758). M.C.F. and A.C. were supported by. Mohamed bin Zayed Species Conservation Fund Project (152510704). GMR held a doctoral scholarship (SFRH/ BD/69194/2010) from Fundação para a Ciência e a Tecnologia. L.F.T., C.L., L.P.R. K.R.Z., T.Y.J., T.S.J. were supported by São Paulo Research Foundation (FAPESP #2016/25358-3), the National Counsel of Technological and Scientifc Development (CNPq #300896/2016–6) and a Catalyzing New International Collaborations grant from the United States NSF (OISE-1159513). C.S.A. was supported by Fondecyt (No. 1181758). T.M.D. was supported by the Royal Geographical Society and the Royal Zoological Society of Scotland. B.W. was supported by the National Research Foundation of Korea (2015R1D1A1A01057282).Peer Reviewe
Extended X-ray absorption spectroscopy using an ultrashort pulse laboratory-scale laser-plasma accelerator
Get PDFLaser-driven compact particle accelerators can provide ultrashort pulses of broadband X-rays, well suited for undertaking X-ray absorption spectroscopy measurements on a femtosecond timescale. Here the Extended X-ray Absorption Fine Structure (EXAFS) features of the K-edge of a copper sample have been observed over a 250 eV window in a single shot using a laser wakefield accelerator, providing information on both the electronic and ionic structure simultaneously. This capability will allow the investigation of ultrafast processes, and in particular, probing high-energy-density matter and physics far-from-equilibrium where the sample refresh rate is slow and shot number is limited. For example, states that replicate the tremendous pressures and temperatures of planetary bodies or the conditions inside nuclear fusion reactions. Using high-power lasers to pump these samples also has the advantage of being inherently synchronised to the laser-driven X-ray probe. A perspective on the additional strengths of a laboratory-based ultrafast X-ray absorption source is presented
