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Sökning: WFRF:(Kettle B.)

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1.
  • Jacobsson, Jesper, 1984-, et al. (författare)
  • An open-access database and analysis tool for perovskite solar cells based on the FAIR data principles
  • 2022
  • Ingår i: Nature Energy. - : Springer Nature. - 2058-7546. ; 7:1, s. 107-115
  • Tidskriftsartikel (refereegranskat)abstract
    • Large datasets are now ubiquitous as technology enables higher-throughput experiments, but rarely can a research field truly benefit from the research data generated due to inconsistent formatting, undocumented storage or improper dissemination. Here we extract all the meaningful device data from peer-reviewed papers on metal-halide perovskite solar cells published so far and make them available in a database. We collect data from over 42,400 photovoltaic devices with up to 100 parameters per device. We then develop open-source and accessible procedures to analyse the data, providing examples of insights that can be gleaned from the analysis of a large dataset. The database, graphics and analysis tools are made available to the community and will continue to evolve as an open-source initiative. This approach of extensively capturing the progress of an entire field, including sorting, interactive exploration and graphical representation of the data, will be applicable to many fields in materials science, engineering and biosciences. 
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2.
  • Maitrallain, A., et al. (författare)
  • Parametric study of high-energy ring-shaped electron beams from a laser wakefield accelerator
  • 2022
  • Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 24:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Laser wakefield accelerators commonly produce on-axis, low-divergence, high-energy electron beams. However, a high charge, annular shaped beam can be trapped outside the bubble and accelerated to high energies. Here we present a parametric study on the production of low-energy-spread, ultra-relativistic electron ring beams in a two-stage gas cell. Ring-shaped beams with energies higher than 750 MeV are observed simultaneously with on axis, continuously injected electrons. Often multiple ring shaped beams with different energies are produced and parametric studies to control the generation and properties of these structures were conducted. Particle tracking and particle-in-cell simulations are used to determine properties of these beams and investigate how they are formed and trapped outside the bubble by the wake produced by on-axis injected electrons. These unusual femtosecond duration, high-charge, high-energy, ring electron beams may find use in beam driven plasma wakefield accelerators and radiation sources.
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3.
  • Spesyvtsev, R., et al. (författare)
  • Generation of electron high energy beams with a ring-like structure by a dual stage laser wakefield accelerator
  • 2019
  • Ingår i: Relativistic Plasma Waves and Particle Beams as Coherent and Incoherent Radiation Sources III. - : SPIE. - 9781510627383 ; 11036
  • Konferensbidrag (refereegranskat)abstract
    • The laser wake-field accelerator (LWFA) traditionally produces high brightness, quasi-monoenergetic electron beams with Gaussian-like spatial and angular distributions. In the present work we investigate the generation of ultra-relativistic beams with ring-like structures in the blowout regime of the LWFA using a dual stage accelerator. A density down-ramp triggers injection after the first stage and is used to produce ring-like electron spectra in the 300 - 600 MeV energy range. These well defined, annular beams are observed simultaneously with the on-axis, high energy electron beams, with a divergence of a few milliradians. The rings have quasi-monoenergetic energy spectra with an RMS spread estimated to be less than 5%. Particle-in-cell simulations confirm that off-axis injection provides the electrons with the initial transverse momentum necessary to undertake distinct betatron oscillations within the plasma bubble during their acceleration process.
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4.
  • Double, K L, et al. (författare)
  • The comparative biology of neuromelanin and lipofuscin in the human brain
  • 2008
  • Ingår i: Cellular and Molecular Life Sciences (CMLS). - : Springer Science and Business Media LLC. - 1420-682X .- 1420-9071. ; 65:11, s. 1669-1682
  • Tidskriftsartikel (refereegranskat)abstract
    • Neuromelanin and lipofuscin are two pigments produced within the human brain that, until recently, were considered inert cellular waste products of little interest to neuroscience. Recent research has increased our understanding of the nature and interactions of these pigments with their cellular environment and suggests that these pigments may, indeed, influence cellular function. The physical appearance and distribution of the pigments within the human brain differ, but both accumulate in the aging brain and the pigments share some structural features. Lipofuscin accumulation has been implicated in postmitotic cell aging, while neuromelanin is suggested to function as an iron-regulatory molecule with possible protective functions within the cells which produce this pigment. This review presents comparative aspects of the biology of neuromelanin and lipofuscin, as well as a discussion of their hypothesized functions in brain and their possible roles in aging and neurodegenerative disease. © 2008 Birkhaueser.
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5.
  • Hussein, A. E., et al. (författare)
  • Laser-wakefield accelerators for high-resolution X-ray imaging of complex microstructures
  • 2019
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Laser-wakefield accelerators (LWFAs) are high acceleration-gradient plasma-based particle accelerators capable of producing ultra-relativistic electron beams. Within the strong focusing fields of the wakefield, accelerated electrons undergo betatron oscillations, emitting a bright pulse of X-rays with a micrometer-scale source size that may be used for imaging applications. Non-destructive X-ray phase contrast imaging and tomography of heterogeneous materials can provide insight into their processing, structure, and performance. To demonstrate the imaging capability of X-rays from an LWFA we have examined an irregular eutectic in the aluminum-silicon (Al-Si) system. The lamellar spacing of the Al-Si eutectic microstructure is on the order of a few micrometers, thus requiring high spatial resolution. We present comparisons between the sharpness and spatial resolution in phase contrast images of this eutectic alloy obtained via X-ray phase contrast imaging at the Swiss Light Source (SLS) synchrotron and X-ray projection microscopy via an LWFA source. An upper bound on the resolving power of 2.7 ± 0.3 μm of the LWFA source in this experiment was measured. These results indicate that betatron X-rays from laser wakefield acceleration can provide an alternative to conventional synchrotron sources for high resolution imaging of eutectics and, more broadly, complex microstructures.
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6.
  • Kettle, B., et al. (författare)
  • Single-Shot Multi-keV X-Ray Absorption Spectroscopy Using an Ultrashort Laser-Wakefield Accelerator Source
  • 2019
  • Ingår i: Physical Review Letters. - 0031-9007. ; 123:25
  • Tidskriftsartikel (refereegranskat)abstract
    • Single-shot absorption measurements have been performed using the multi-keV x rays generated by a laser-wakefield accelerator. A 200 TW laser was used to drive a laser-wakefield accelerator in a mode which produced broadband electron beams with a maximum energy above 1 GeV and a broad divergence of ≈15 mrad FWHM. Betatron oscillations of these electrons generated 1.2±0.2×106 photons/eV in the 5 keV region, with a signal-to-noise ratio of approximately 300 1. This was sufficient to allow high-resolution x-ray absorption near-edge structure measurements at the K edge of a titanium sample in a single shot. We demonstrate that this source is capable of single-shot, simultaneous measurements of both the electron and ion distributions in matter heated to eV temperatures by comparison with density functional theory simulations. The unique combination of a high-flux, large bandwidth, few femtosecond duration x-ray pulse synchronized to a high-power laser will enable key advances in the study of ultrafast energetic processes such as electron-ion equilibration.
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7.
  • Settele, Josef, et al. (författare)
  • Rice ecosystem services in South-east Asia
  • 2018
  • Ingår i: Paddy and Water Environment. - : Springer. - 1611-2490 .- 1611-2504. ; 16:2, s. 211-224
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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8.
  • Shefferson, Richard P., et al. (författare)
  • Drivers of vegetative dormancy across herbaceous perennial plant species
  • 2018
  • Ingår i: Ecology Letters. - : WILEY. - 1461-023X .- 1461-0248. ; 21:5, s. 724-733
  • Tidskriftsartikel (refereegranskat)abstract
    • Vegetative dormancy, that is the temporary absence of aboveground growth for 1year, is paradoxical, because plants cannot photosynthesise or flower during dormant periods. We test ecological and evolutionary hypotheses for its widespread persistence. We show that dormancy has evolved numerous times. Most species displaying dormancy exhibit life-history costs of sprouting, and of dormancy. Short-lived and mycoheterotrophic species have higher proportions of dormant plants than long-lived species and species with other nutritional modes. Foliage loss is associated with higher future dormancy levels, suggesting that carbon limitation promotes dormancy. Maximum dormancy duration is shorter under higher precipitation and at higher latitudes, the latter suggesting an important role for competition or herbivory. Study length affects estimates of some demographic parameters. Our results identify life historical and environmental drivers of dormancy. We also highlight the evolutionary importance of the little understood costs of sprouting and growth, latitudinal stress gradients and mixed nutritional modes.
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9.
  • Soliman, S.M., et al. (författare)
  • Towards the chemical control of molecular packing: syntheses and crystal structures of three trans-[NiL4(NCS)2] complexes
  • 2014
  • Ingår i: Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials. - 2052-5206 .- 2052-5192. ; 70:1, s. 115-125
  • Tidskriftsartikel (refereegranskat)abstract
    • Three nickel(II) isothiocyanato complexes of the formulatrans-[NiL4(NCS)2] (L = ethylisonicotinate, methylisonicotinateand 4-benzoylpyridine) have been prepared: [Ni(ethylisonicotinate)4(NCS)2] (I), [Ni(methylisonicotinate)4(NCS)2](II) and [Ni(4-benzoylpyridine)4(NCS)2] (III). All threecomplexes are monomeric and have a distorted octahedralgeometry around NiII. Despite their apparent molecularsimilarity, the crystal density of (III) (1.454 g cm 3) issignificantly higher than that of (I) and (II) (both1.408 g cm 3), suggesting that the molecular packing is mostefficient in (III). A study of the molecular Hirshfeld surfaces,together with density functional theory (DFT) calculations,provide insights into the origin of the molecular packingfeatures, and it is suggested that the greater crystal density of(III) results from smaller intermolecular electrostatic repulsions.
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10.
  • Streeter, M. J.V., et al. (författare)
  • Characterization of laser wakefield acceleration efficiency with octave spanning near-IR spectrum measurements
  • 2022
  • Ingår i: Physical Review Accelerators and Beams. - 2469-9888. ; 25:10
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on experimental measurements of energy transfer efficiencies in a GeV-class laser wakefield accelerator. Both the transfer of energy from the laser to the plasma wakefield and from the plasma to the accelerated electron beam was diagnosed by simultaneous measurement of the deceleration of laser photons and the acceleration of electrons as a function of plasma length. The extraction efficiency, which we define as the ratio of the energy gained by the electron beam to the energy lost by the self-guided laser mode, was maximized at 19±3% by tuning the plasma density and length. The additional information provided by the octave-spanning laser spectrum measurement allows for independent optimization of the plasma efficiency terms, which is required for the key goal of improving the overall efficiency of laser wakefield accelerators.
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