| 1. |
- Ahdida, C., et al.
(författare)
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The experimental facility for the Search for Hidden Particles at the CERN SPS
- 2019
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Ingår i: Journal of Instrumentation. - : Institute of Physics Publishing (IOPP). - 1748-0221. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- The Search for Hidden Particles (SHiP) Collaboration has shown that the CERN SPS accelerator with its 400 GeV/c proton beam offers a unique opportunity to explore the Hidden Sector [1-3]. The proposed experiment is an intensity frontier experiment which is capable of searching for hidden particles through both visible decays and through scattering signatures from recoil of electrons or nuclei. The high-intensity experimental facility developed by the SHiP Collaboration is based on a number of key features and developments which provide the possibility of probing a large part of the parameter space for a wide range of models with light long-lived super-weakly interacting particles with masses up to O(10) GeV/c(2) in an environment of extremely clean background conditions. This paper describes the proposal for the experimental facility together with the most important feasibility studies. The paper focuses on the challenging new ideas behind the beam extraction and beam delivery, the proton beam dump, and the suppression of beam-induced background.
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| 2. |
- Milstead, David A., et al.
(författare)
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The active muon shield in the SHiP experiment
- 2017
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- The SHiP experiment is designed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. An essential task for the experiment is to keep the Standard Model background level to less than 0.1 event after 2 x 10(20) protons on target. In the beam dump, around 10(11) muons will be produced per second. The muon rate in the spectrometer has to be reduced by at least four orders of magnitude to avoid muon-induced combinatorial background. A novel active muon shield is used to magnetically deflect the muons out of the acceptance of the spectrometer. This paper describes the basic principle of such a shield, its optimization and its performance.
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| 3. |
- Tapia-Ruiz, Nuria, et al.
(författare)
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2021 roadmap for sodium-ion batteries
- 2021
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 2515-7655. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- Increasing concerns regarding the sustainability of lithium sources, due to their limited availability and consequent expected price increase, have raised awareness of the importance of developing alternative energy-storage candidates that can sustain the ever-growing energy demand. Furthermore, limitations on the availability of the transition metals used in the manufacturing of cathode materials, together with questionable mining practices, are driving development towards more sustainable elements. Given the uniformly high abundance and cost-effectiveness of sodium, as well as its very suitable redox potential (close to that of lithium), sodium-ion battery technology offers tremendous potential to be a counterpart to lithium-ion batteries (LIBs) in different application scenarios, such as stationary energy storage and low-cost vehicles. This potential is reflected by the major investments that are being made by industry in a wide variety of markets and in diverse material combinations. Despite the associated advantages of being a drop-in replacement for LIBs, there are remarkable differences in the physicochemical properties between sodium and lithium that give rise to different behaviours, for example, different coordination preferences in compounds, desolvation energies, or solubility of the solid-electrolyte interphase inorganic salt components. This demands a more detailed study of the underlying physical and chemical processes occurring in sodium-ion batteries and allows great scope for groundbreaking advances in the field, from lab-scale to scale-up. This roadmap provides an extensive review by experts in academia and industry of the current state of the art in 2021 and the different research directions and strategies currently underway to improve the performance of sodium-ion batteries. The aim is to provide an opinion with respect to the current challenges and opportunities, from the fundamental properties to the practical applications of this technology.
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| 4. |
- Rakov, Vladimir A., et al.
(författare)
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Mechanism of the lightning M component
- 1995
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 100:D12, s. 25701-25710
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of simultaneous measurements of the channel-base current and the vertical electric field 30 m from triggered lightning reveals that the fields associated with M components, although essentially electrostatic, appear to be proportional to the time derivatives of the associated M currents. Based on this finding, coupled with other observations and modeling, a mechanism for the lightning M component is proposed. According to this mechanism an M component involves a downward progressing incident wave (the analog of a leader) followed by an upward progressing reflected wave (the analog of a return stroke). However, as opposed to a leader-return stroke sequence in which the latter removes the charge deposited by the former, both the upward and the downward processes contribute about equally to the total charge flowing from the bottom of the channel at any instant of time. Such a mode of charge transfer to ground, distinctly different from a leader-return stroke sequence, is possible because of the presence of a path capable of supporting the propagation of a traveling wave (facilitated by a continuing current flowing to ground) and the fact that the ground is essentially a short circuit for the downward incident wave, so that the magnitude of the current reflection coefficient at ground is virtually equal to unity. We show that some observed properties of M components can be explained if the lightning channel traversed by an M-current wave is represented as a linear R-C transmission line. In this view, the preferential attenuation of the higher-frequency components on an R-C line is responsible for the lack of frequencies above several kilohertz in both the M-current pulses measured at the channel base and the M-light pulses observed in the bottom 1 km or so of the channel. Further, the relatively high characteristic impedance of the channel, of the order of tens to hundreds of kilohms for frequencies below some kilohertz, inferred from the linear R-C line approximation, is consistent with the observation that even a relatively poor ground is sensed by an incident M wave as essentially a short circuit. However, on a linear R-C transmission line the higher-frequency components travel faster than lower-frequency components (this velocity dispersion implying that the original pulse would spread while propagating along the line), whereas the shape of the M-light pulses does not change much within the bottom 1 km or so, as if the channel were a distortionless transmission line. We speculate, on physical grounds, that the front of the traveling M-current pulse heats the channel so that the pulse tail encounters a lowered resistance and, as a result, accelerates. By virtue of these two opposing effects, velocity dispersion and channel nonlinearity, an M pulse is formed whose more-or-less symmetrical shape is preserved over a relatively large distance, as in the case of a soliton.
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| 5. |
- Hill-Pearce, R. E., et al.
(författare)
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The effect of bilayer regions on the response of epitaxial graphene devices to environmental gating
- 2015
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Ingår i: Carbon. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0008-6223 .- 1873-3891. ; 93, s. 896-902
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Tidskriftsartikel (refereegranskat)abstract
- The effect of a bilayer area on the electronic response to environmental gating of a monolayer graphene Hall bar device is investigated using room temperature magnetotransport and scanning Kelvin probe microscopy measurements in a controlled environment. The device is tuned through the charge neutrality point with n-p-n-junctions formed. Scanning Kelvin probe measurements show that the work function of the monolayer graphene decreases more than that of the bilayer area however magnetotransport measurements show a larger change in carrier concentration for bilayer graphene with environmental gating. Interface scattering at the boundary between the monolayer and bilayer regions also affects device response with field-dependent suppression of the conductivity observed near the charge neutrality point. Simultaneous electronic and environmental scanning Kelvin probe measurements are used to build nano-scale maps of the work function of the device surface revealing the areas of greatest work function change with environmental gating. Crown Copyright (C) 2015 Published by Elsevier Ltd. All rights reserved.
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| 6. |
- Bulcha, Berhanu, et al.
(författare)
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Phase Locking of a 2.5 THz Quantum Cascade Laser to a Microwave Reference using THz Schottky Mixer
- 2015
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Ingår i: 40th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2015, Hong Kong, China, 23-28 August. - 2162-2027. - 9781479982721
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Konferensbidrag (refereegranskat)abstract
- The frequency of a 2.5 THz QCL are stabilized to sub-hertz accuracy by phase-locking to a stable 100 MHz microwave reference, using a 2.3–3.2 THz room temperature Schottky diode based harmonic mixer. The down-converted phase locked beat note is stable over a long term test.
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| 7. |
- Kajtez, Janko, et al.
(författare)
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3D-Printed Soft Lithography for Complex Compartmentalized Microfluidic Neural Devices
- 2020
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Ingår i: Advanced Science. - : Wiley. - 2198-3844. ; 7:16
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Tidskriftsartikel (refereegranskat)abstract
- Compartmentalized microfluidic platforms are an invaluable tool in neuroscience research. However, harnessing the full potential of this technology remains hindered by the lack of a simple fabrication approach for the creation of intricate device architectures with high-aspect ratio features. Here, a hybrid additive manufacturing approach is presented for the fabrication of open-well compartmentalized neural devices that provides larger freedom of device design, removes the need for manual postprocessing, and allows an increase in the biocompatibility of the system. Suitability of the method for multimaterial integration allows to tailor the device architecture for the long-term maintenance of healthy human stem-cell derived neurons and astrocytes, spanning at least 40 days. Leveraging fast-prototyping capabilities at both micro and macroscale, a proof-of-principle human in vitro model of the nigrostriatal pathway is created. By presenting a route for novel materials and unique architectures in microfluidic systems, the method provides new possibilities in biological research beyond neuroscience applications.
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| 8. |
- Weng, Ming-Hung, et al.
(författare)
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Study of the interface properties of TiO 2/SiO 2/SiC by photocapacitance
- 2011
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Ingår i: 8th European Conference on Silicon Carbide and Related Materials, ECSCRM 2010. - 9783037850794 ; , s. 350-353
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Konferensbidrag (refereegranskat)abstract
- We have investigated the annealing of fixed oxide charge and interfacial traps in MISiC strucures by means of the photo capacitance voltage technique at temperatures up to 500°C. Elevated temperature measurements show reduced hysteresis and reduced fixed oxide charge at the interface. The photo capacitance technique shows a real-time measurement at elevated temperatures, in which electrons are populated by photo energy, in a 4H-SiC MIS structure. We also confirm the reduction of fixed oxide charge at the interface by means of high temperature post deposition annealing, which occurs during the high temperature measurements.
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| 9. |
- Westin, E. M., et al.
(författare)
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New weldable 316L stainless flux-cored wires with reduced Cr(VI) fume emissions : part 1—health aspects of particle composition and release of metals
- 2021
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Ingår i: Welding in the World. - : Springer Nature. - 0043-2288 .- 1878-6669. ; 65:12, s. 2319-2337
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Tidskriftsartikel (refereegranskat)abstract
- Welding fumes have been found to be carcinogenic and stainless steel welders may be at higher risk due to increased formation of hexavalent chromium (Cr(VI)). The slag-shielded methods, identified to generate most airborne particles and Cr(VI), would potentially be most harmful. With ever-stricter limits set to protect workers, measures to minimize human exposure become crucial. Austenitic stainless steel flux-cored wires of 316L type have been developed with the aim to reduce the toxicity of the welding fume without compromised usability. Collected particles were compared with fumes formed using solid, metal-cored, and standard flux-cored wires. The size, morphology, and composition were characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Total metal concentrations and released amounts of metals (Cr, Cr(VI), Ni, Mn, Fe) were investigated after complete digestion in aqua regia and after incubation in phosphate buffered saline (PBS) by means of flame furnace atomic absorption spectroscopy (AAS), inductively coupled plasma mass spectroscopy (ICP-MS), and UV–vis spectroscopy. The cytotoxicity of the particles was assessed with the Alamar blue assay for cell viability using cultured human bronchial epithelial cells (HBEC-3kt). The findings correlate well with previous in vitro toxicity studies for standard and experimental wires. The new optimized 316L-type flux-cored wires showed improved weldability and generated less Cr(VI) in wt.-% than with solid wire. The respirable particles were confirmed to be less acute toxic in HBEC-3kt cells as compared to standard flux-cored wires. The highest cell viability (survival rate) was observed for the metal-cored wire.
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