| 1. |
- Behm, K. T., et al.
(författare)
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A spectrometer for ultrashort gamma-ray pulses with photon energies greater than 10 MeV
- 2018
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 89:11
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Author(s). We present a design for a pixelated scintillator based gamma-ray spectrometer for non-linear inverse Compton scattering experiments. By colliding a laser wakefield accelerated electron beam with a tightly focused, intense laser pulse, gamma-ray photons up to 100 MeV energies and with few femtosecond duration may be produced. To measure the energy spectrum and angular distribution, a 33 × 47 array of cesium-iodide crystals was oriented such that the 47 crystal length axis was parallel to the gamma-ray beam and the 33 crystal length axis was oriented in the vertical direction. Using an iterative deconvolution method similar to the YOGI code, modeling of the scintillator response using GEANT4 and fitting to a quantum Monte Carlo calculated photon spectrum, we are able to extract the gamma ray spectra generated by the inverse Compton interaction.
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| 2. |
- Cole, J. M., et al.
(författare)
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Experimental Evidence of Radiation Reaction in the Collision of a High-Intensity Laser Pulse with a Laser-Wakefield Accelerated Electron Beam
- 2018
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Ingår i: Physical Review X. - 2160-3308. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of energetic particles in strong electromagnetic fields can be heavily influenced by the energy loss arising from the emission of radiation during acceleration, known as radiation reaction. When interacting with a high-energy electron beam, today's lasers are sufficiently intense to explore the transition between the classical and quantum radiation reaction regimes. We present evidence of radiation reaction in the collision of an ultrarelativistic electron beam generated by laser-wakefield acceleration (μ 500 MeV) with an intense laser pulse (a0 > 10). We measure an energy loss in the postcollision electron spectrum that is correlated with the detected signal of hard photons (γ rays), consistent with a quantum description of radiation reaction. The generated γ rays have the highest energies yet reported from an all-optical inverse Compton scattering scheme, with critical energy > 30 MeV.
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| 3. |
- Behm, M, et al.
(författare)
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Accumulation of nuclear ADAR2 regulates adenosine-to-inosine RNA editing during neuronal development
- 2017
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Ingår i: Journal of cell science. - : The Company of Biologists. - 1477-9137 .- 0021-9533. ; 130:4, s. 745-753
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Tidskriftsartikel (refereegranskat)abstract
- Adenosine to inosine (A-to-I) RNA editing is important for a functional brain and most known sites of selective RNA editing has been found to diversify the number of protein isoforms involved in neurotransmission. In absence of the active editing enzymes, ADAR1 or ADAR2, mice fail to survive until adulthood. Nuclear A-to-I editing of neuronal transcripts is regulated during brain development with low levels in the embryo and a dramatic increase after birth. Yet, little is known about the mechanisms that regulate editing during development. Here we demonstrate lower levels of ADAR2 in the nucleus of immature neurons than in mature neurons. We show that importin-α4, which increases during neuronal maturation, interacts with ADAR2 and contributes to the editing efficiency by bringing it into the nucleus. Moreover, we detect an increased number of interactions between ADAR2 and the nuclear isomerase Pin1 as neurons mature, which contribute to ADAR2 protein stability. Together, these findings explain how nuclear editing of substrates important for neuronal function can increase as the brain develops.
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| 4. |
- Das, B, et al.
(författare)
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High performance metal nitrides, MN (M = Cr, Co) nanoparticles for non-aqueous hybrid supercapacitors
- 2015
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Ingår i: Advanced Powder Technology. - : Elsevier BV. - 0921-8831 .- 1568-5527. ; 26:3, s. 783-788
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Tidskriftsartikel (refereegranskat)abstract
- In this study, metal nitrides MN (M = Cr, Co) nanoparticles of particle size similar to 20-30 nm have been prepared under NH3 + N-2 atmosphere at relatively low temperature. The Cr-urea complex was directly converted to CrN with an intermediate formation of Cr2O3, whereas CoN was prepared from Co3O4. These compounds were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM) techniques. The electrochemical properties were evaluated by galvanostatic cycling, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical performance of the resultant MN nanoparticles showed that they can be used as potential electrode materials for non-aqueous hybrid electrochemical supercapacitors (HESCs). The MN/AC showed high specific capacitance of 75 and 37 F g (1) for M = Cr, Co, respectively when cycled at 30 mA g (1) in non-aqueous electrolyte.
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| 5. |
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| 6. |
- Lu, Huiran, et al.
(författare)
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Flexible Paper Electrodes for Li-Ion Batteries Using Low Amount of TEMPO-Oxidized Cellulose Nanofibrils as Binder
- 2016
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society. - 1944-8244 .- 1944-8252. ; 8:28, s. 18097-18106
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Tidskriftsartikel (refereegranskat)abstract
- Flexible Li-ion batteries attract increasing interest for applications in bendable and wearable electronic devices. TEMPO-oxidized cellulose nanofibrils (TOCNF), a renewable material, is a promising candidate as binder for flexible Li-ion batteries with good mechanical properties. Paper batteries can be produced using a water-based paper making process, avoiding the use of toxic solvents. In this work, finely dispersed TOCNF was used and showed good binding properties at concentrations as low as 4 wt %. The TOCNF was characterized using atomic force microscopy and found to be well dispersed with fibrils of average widths of about 2.7 nm and lengths of approximately 0.1-1 μm. Traces of moisture, trapped in the hygroscopic cellulose, is a concern when the material is used in Li-ion batteries. The low amount of binder reduces possible moisture and also increases the capacity of the electrodes, based on total weight. Effects of moisture on electrochemical battery performance were studied on electrodes dried at 110 °C in a vacuum for varying periods. It was found that increased drying time slightly increased the specific capacities of the LiFePO4 electrodes, whereas the capacities of the graphite electrodes decreased. The Coulombic efficiencies of the electrodes were not much affected by the varying drying times. Drying the electrodes for 1 h was enough to achieve good electrochemical performance. Addition of vinylene carbonate to the electrolyte had a positive effect on cycling for both graphite and LiFePO4. A failure mechanism observed at high TOCNF concentrations is the formation of compact films in the electrodes.
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| 7. |
- Nylén, Linda, et al.
(författare)
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Investigation of the oxygen evolving electrode in pH-neutral electrolytes : Modelling and experiments of the RDE-cell
- 2007
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 52:13, s. 4513-4524
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Tidskriftsartikel (refereegranskat)abstract
- A model has been developed to illustrate the complex interplay between the acidifying electrode reactions for oxygen evolution, mass transport and homogeneous reactions in pH-neutral electrolytes. Modelled polarisation curves of the oxygen evolution reaction were verified by polarisation curves experimentally measured in 5 M NaClO4 on a RDE of DSA material. The conditions in the simulations and in the experiments were similar to those in the chlorate process (high ionic strength, 70 degrees C, chromate-containing electrolyte, DSA electrode), in which the oxygen evolution reaction is one of the possible side reactions. The model predicted the concentration gradients of H+, OH-, CrO42- and HCrO4- during oxygen evolution on the RDE. It was found that an important part of the chromate buffering effect at high current densities occurs in a thin (in the order of nanometers) reaction layer at the anode. From comparisons between the model and experiments, a buffering reaction has been proposed. The most likely reaction for the chromate buffering in the investigated system is CrO42- reacting with water to HCrO4- and OH-. In the chlorate process, where chromate is a buffer and oxygen evolution is a side reaction, it is likely that chromate promotes oxygen evolution from OH-.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Seidel, Y. E., et al.
(författare)
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Stability of nanostructured Pt/glassy carbon electrodes prepared by colloidal lithography
- 2008
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 155:3, s. K50-K58
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Tidskriftsartikel (refereegranskat)abstract
- The stability of nanostructured Pt/glassy carbon (GC) model electrodes upon exposure to a realistic electrochemical/electrocatalytic reaction environment (continuous reaction, continuous electrolyte flow) was studied by microscopic techniques, X-ray photoelectron spectroscopy, and electrochemical measurements. The model electrodes consist of Pt nanostructures with well-defined sizes and regular spacing on planar GC substrates, and were fabricated using colloidal lithography techniques. Additional plasma treatments of the GC substrates prior to Pt deposition were tested to improve the stability of the resulting Pt/GC model electrodes. Both evaporation and sputter deposition were used for Pt-film fabrication. The model catalysts prepared by Pt evaporation were found to be rather unstable. The stability was significantly improved for sputter-deposited Pt films, and Pt sputter deposition on a GC substrate, pretreated first in oxygen plasma and then in Ar plasma, resulted in stable model electrodes with a fully intact layer of Pt nanostructures after the electrocatalytic experiments.
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| 12. |
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| 13. |
- Witman, Nevin M., 1982-, et al.
(författare)
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ADAR-Related Activation of Adenosine-to-Inosine RNA Editing During Regeneration
- 2013
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Ingår i: Stem Cells and Development. - : Mary Ann Liebert Inc. - 1547-3287 .- 1557-8534. ; 22:16, s. 2254-2267
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Tidskriftsartikel (refereegranskat)abstract
- Urodele amphibians possess an amazing regenerative capacity that requires the activation of cellular plasticity in differentiated cells and progenitor/stem cells. Many aspects of regeneration in Urodele amphibians recapitulate development, making it unlikely that gene regulatory pathways which are essential for development are mutually exclusive from those necessary for regeneration. One such post-transcriptional gene regulatory pathway, which has been previously shown to be essential for functional metazoan development, is RNA editing. RNA editing catalyses discrete nucleotide changes in RNA transcripts, creating a molecular diversity that could create an enticing connection to the activated cellular plasticity found in newts during regeneration. To assess whether RNA editing occurs during regeneration, we demonstrated that GABRA3 and ADAR2 mRNA transcripts are edited in uninjured and regenerating tissues. Full open-reading frame sequences for ADAR1 and ADAR2, two enzymes responsible for adenosine-to-inosine RNA editing, were cloned from newt brain cDNA and exhibited a strong resemblance to ADAR (adenosine deaminase, RNA-specific) enzymes discovered in mammals. We demonstrated that ADAR1 and ADAR2 mRNA expression levels are differentially expressed during different phases of regeneration in multiple tissues, whereas protein expression levels remain unaltered. In addition, we have characterized a fascinating nucleocytoplasmic shuttling of ADAR1 in a variety of different cell types during regeneration, which could provide a mechanism for controlling RNA editing, without altering translational output of the editing enzyme. The link between RNA editing and regeneration provides further insights into how lower organisms, such as the newt, can activate essential molecular pathways via the discrete alteration of RNA sequences.
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| 14. |
- Wreland Lindström, Rakel, et al.
(författare)
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Electrocatalysis and transport effects on nanostructured Pt/GC electrodes
- 2010
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Ingår i: J ELECTROANAL CHEM. - : Elsevier BV. - 1572-6657 .- 0022-0728. ; 644:2, s. 90-102
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Tidskriftsartikel (refereegranskat)abstract
- The role and contribution of transport processes in electrocatalytic reactions was investigated in model studies of the oxidation of CO (single-product reaction) and formaldehyde (dual-product reaction), using nanostructured Pt/glassy carbon electrodes with variable Pt loading and defined reactant transport conditions. Nanostructured electrodes with monodispersed, uniformly distributed Pt nanostructures (100-140 nm diameter) supported on planar glassy carbon (GC) electrodes with different densities were prepared by Colloidal Lithography (CL) or Hole-Mask Colloidal Lithography (HCL). Transport effects were evaluated by varying the density of the nanostructures and the electrolyte flow. The resulting changes in the transport limited reaction current (CO oxidation - transition from planar to spherical diffusion with decreasing Pt nanostructure density) and in the distribution of the reaction products HCOOH and CO2 (HCHO oxidation), which is probed by differential electrochemical mass spectrometry (DEMS), are discussed focusing on transport effects. The increasing amount of CO2 with decreasing space velocity (higher nanostructure density, lower electrolyte flow) is explained by increasing re-adsorption and further reaction of desorbing reaction intermediates. (C) 2009 Elsevier B.V. All rights reserved.
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