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- Hansen, Steffen Foss, et al.
(författare)
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To be or not to be a nanomaterial
- 2022
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Ingår i: Journal of Nanoparticle Research. - : Springer Science and Business Media LLC. - 1388-0764 .- 1572-896X. ; 24:12
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Tidskriftsartikel (refereegranskat)abstract
- In early 2021, the new definition of the term “nanomaterial” proposed by the European Commission (EC) was subject to a stakeholder consultation and in June 2022, the EC published its updated definition. Based on an independent analysis of the different versions of the definition and the results of the stakeholder consultation, the aim of this paper is to identify key aspects to be considered when deciding whether a material should be regarded as a nanomaterial. More than 130 comments submitted during the stakeholder consultation by various organizations, companies, citizens, and authorities were analyzed. We find that the introduction of new terms such as “solid particles” has added clarity to terms used in the former definition. Our analysis shows that stakeholders seemed inclined to maintain the default number-based 50% threshold value, but were opposed to (1) the possible flexibility of varying the threshold in specific sectorial legislation, (2) the default inclusion of carbonaceous materials < 1 nm, and (3) the use of volume specific surface area (VSSA) other than for excluding materials from being defined as nanomaterials. Overall, we find that the updated definition addresses many of the limitations of the former definition. However, the updated definition also creates new challenges that will have to be addressed via development of new regulatory guidance. Apart from the relatively minor change of the VSSA threshold from 5 to 6 m2/cm3, it generally seems that no arguments from the stakeholder consultation made the EC reconsider its position. Graphical Abstract: [Figure not available: see fulltext.].
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| 2. |
- Kumar Maroju, Praveen, et al.
(författare)
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Attosecond pulse shaping using a seeded free-electron laser
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 578, s. 386-391
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Tidskriftsartikel (refereegranskat)abstract
- Attosecond pulses are central to the investigation of valence- and core-electron dynamics on their natural timescales. The reproducible generation and characterization of attosecond waveforms has been demonstrated so far only through the process of high-order harmonic generation. Several methods for shaping attosecond waveforms have been proposed, including the use of metallic filters, multilayer mirrors and manipulation of the driving field. However, none of these approaches allows the flexible manipulation of the temporal characteristics of the attosecond waveforms, and they suffer from the low conversion efficiency of the high-order harmonic generation process. Free-electron lasers, by contrast, deliver femtosecond, extreme-ultraviolet and X-ray pulses with energies ranging from tens of microjoules to a few millijoules. Recent experiments have shown that they can generate subfemtosecond spikes, but with temporal characteristics that change shot-to-shot. Here we report reproducible generation of high-energy (microjoule level) attosecond waveforms using a seeded free-electron laser. We demonstrate amplitude and phase manipulation of the harmonic components of an attosecond pulse train in combination with an approach for its temporal reconstruction. The results presented here open the way to performing attosecond time-resolved experiments with free-electron lasers.
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| 3. |
- Maroju, Praveen K., et al.
(författare)
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A Novel Attosecond Timing Tool for Free-Electron Laser Experiment
- 2020
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Ingår i: High Intensity Lasers and High Field Phenomena 2020. - 9781943580736
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Konferensbidrag (refereegranskat)abstract
- We demonstrate a novel timing tool for Free-Electron Lasers to determine the delay between an attosecond pulse train and infrared pulse with sub-optical-cycle resolu-. tion.
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