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| 2. |
- Hiller, D., et al.
(författare)
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Absence of quantum confinement effects in the photoluminescence of Si3N4-embedded Si nanocrystals
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:20, s. 204301-
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Tidskriftsartikel (refereegranskat)abstract
- Superlattices of Si-rich silicon nitride and Si3N4 are prepared by plasma-enhanced chemical vapor deposition and, subsequently, annealed at 1150 degrees C to form size-controlled Si nanocrystals (Si NCs) embedded in amorphous Si3N4. Despite well defined structural properties, photoluminescence spectroscopy (PL) reveals inconsistencies with the typically applied model of quantum confined excitons in nitride-embedded Si NCs. Time-resolved PL measurements demonstrate 10(5) times faster time-constants than typical for the indirect band structure of Si NCs. Furthermore, a pure Si3N4 reference sample exhibits a similar PL peak as the Si NC samples. The origin of this luminescence is discussed in detail on the basis of radiative defects and Si3N4 band tail states in combination with optical absorption measurements. The apparent absence of PL from the Si NCs is explained conclusively using electron spin resonance data from the Si/Si3N4 interface defect literature. In addition, the role of Si3N4 valence band tail states as potential hole traps is discussed. Most strikingly, the PL peak blueshift with decreasing NC size, which is often observed in literature and typically attributed to quantum confinement (QC), is identified as optical artifact by transfer matrix method simulations of the PL spectra. Finally, criteria for a critical examination of a potential QC-related origin of the PL from Si3N4-embedded Si NCs are suggested.
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| 3. |
- Spirkoska, D., et al.
(författare)
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Structural and optical properties of high quality zinc-blende/wurtzite GaAs nanowire heterostructures
- 2009
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 80:24
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Tidskriftsartikel (refereegranskat)abstract
- The structural and optical properties of three different kinds of GaAs nanowires with 100% zinc-blende structure and with an average of 30% and 70% wurtzite are presented. A variety of shorter and longer segments of zinc-blende or wurtzite crystal phases are observed by transmission electron microscopy in the nanowires. Sharp photoluminescence lines are observed with emission energies tuned from 1.515 eV down to 1.43 eV when the percentage of wurtzite is increased. The downward shift of the emission peaks can be understood by carrier confinement at the interfaces, in quantum wells and in random short period superlattices existent in these nanowires, assuming a staggered band offset between wurtzite and zinc-blende GaAs. The latter is confirmed also by time-resolved measurements. The extremely local nature of these optical transitions is evidenced also by cathodoluminescence measurements. Raman spectroscopy on single wires shows different strain conditions, depending on the wurtzite content which affects also the band alignments. Finally, the occurrence of the two crystallographic phases is discussed in thermodynamic terms.
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| 4. |
- Estradé, S., et al.
(författare)
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Distinguishing the core from the shell in MnOx/MnOy and FeOx/MnOx core/shell nanoparticles through quantitative electron energy loss spectroscopy (EELS) analysis
- 2012
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Ingår i: Micron. - : Elsevier BV. - 0968-4328 .- 1878-4291. ; 43:1, s. 30-36
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Forskningsöversikt (refereegranskat)abstract
- The structural and chemical characterization of inverted bi-magnetic MnOx(antiferromagnetic)/MnOy(ferrimagnetic) and FeOx(soft-ferrimagnetic)/MnOx(hard-ferrimagnetic) core/shell nanoparticles has been carried out by means of scanning transmission electron microscopy with electron energy loss spectroscopy analysis, (S)TEM-EELS. Quantitative EELS was applied to assess the local composition of the nanoparticles by evaluating the local Mn oxidation state based on the Mn L-3/L-2 peak intensity ratio and the Mn L-3 peak onset. The analysis allows to unambiguously distinguish the core from the shell and to determine the nature of the involved manganese oxides in both cases. The results evidence that the structure of the nanoparticles is, in fact, more complex than the one designed by the synthesis parameters.
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| 5. |
- Estrader, M., et al.
(författare)
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Robust antiferromagnetic coupling in hard-soft bi-magnetic core/shell nanoparticles
- 2013
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- The growing miniaturization demand of magnetic devices is fuelling the recent interest in bi-magnetic nanoparticles as ultimate small components. One of the main goals has been to reproduce practical magnetic properties observed so far in layered systems. In this context, although useful effects such as exchange bias or spring magnets have been demonstrated in core/shell nanoparticles, other interesting key properties for devices remain elusive. Here we show a robust antiferromagnetic (AFM) coupling in core/shell nanoparticles which, in turn, leads to the foremost elucidation of positive exchange bias in bi-magnetic hard-soft systems and the remarkable regulation of the resonance field and amplitude. The AFM coupling in iron oxide-manganese oxide based, soft/hard and hard/soft, core/shell nanoparticles is demonstrated by magnetometry, ferromagnetic resonance and X-ray magnetic circular dichroism. Monte Carlo simulations prove the consistency of the AFM coupling. This unique coupling could give rise to more advanced applications of bi-magnetic core/shell nanoparticles.
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| 6. |
- Ferrando, Carlos, et al.
(författare)
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Effects of oxygen on post-surgical infections during an individualised perioperative open-lung ventilatory strategy : a randomised controlled trial
- 2020
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Ingår i: British Journal of Anaesthesia. - : ELSEVIER SCI LTD. - 0007-0912 .- 1471-6771. ; 124:1, s. 110-120
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Tidskriftsartikel (refereegranskat)abstract
- Background: We aimed to examine whether using a high fraction of inspired oxygen (FIO2) in the context of an individualised intra- and postoperative open-lung ventilation approach could decrease surgical site infection (SSI) in patients scheduled for abdominal surgery. Methods: We performed a multicentre, randomised controlled clinical trial in a network of 21 university hospitals from June 6, 2017 to July 19, 2018. Patients undergoing abdominal surgery were randomly assigned to receive a high (0.80) or conventional (0.3) FIO2 during the intraoperative period and during the first 3 postoperative hours. All patients were mechanically ventilated with an open-lung strategy, which included recruitment manoeuvres and individualised positive end-expiratory pressure for the best respiratory-system compliance, and individualised continuous postoperative airway pressure for adequate peripheral oxyhaemoglobin saturation. The primary outcome was the prevalence of SSI within the first 7 postoperative days. The secondary outcomes were composites of systemic complications, length of intensive care and hospital stay, and 6-month mortality. Results: We enrolled 740 subjects: 371 in the high FIO2 group and 369 in the low FIO2 group. Data from 717 subjects were available for final analysis. The rate of SSI during the first postoperative week did not differ between high (8.9%) and low (9.4%) FIO2 groups (relative risk [RR]: 0.94; 95% confidence interval [CI]: 0.59-1.50; P=0.90]). Secondary outcomes, such as atelectasis (7.7% vs 9.8%; RR: 0.77; 95% CI: 0.48-1.25; P=0.38) and myocardial ischaemia (0.6% [n=2] vs 0% [n=0]; P=0.47) did not differ between groups. Conclusions: An oxygenation strategy using high FIO2 compared with conventional FIO2 did not reduce postoperative SSIs in abdominal surgery. No differences in secondary outcomes or adverse events were found.
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| 7. |
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| 8. |
- Isaksson, Kerstin, et al.
(författare)
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Mutuality and Reciprocity in the Psychological Contracts of Temporary and Permanent Workers
- 2010
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Ingår i: Employment Contracts, Psychological Contracts, and Employee Well-Being: An International Study. - : Oxford University Press. - 9780191715389 - 9780199542697
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- One of the distinctive features of this study is the opportunity to compare the responses of employers and employees. The aim of this chapter is to determine the level of agreement about the content and fulfilment of the psychological contract. A second aim is to determine whether higher levels of agreement are associated with more positive outcomes. The results reveal relatively modest levels of agreement about promises made, agreement being somewhat higher with respect to permanent rather than temporary workers. With respect to fulfilment of promises, there is a fair degree of reciprocity with both parties tending to report moderate fulfilment. Higher levels of agreement about promises made and fulfilled are not strongly associated with more positive outcomes; rather it is the measure of fairness that is more important in determining outcomes. This raises questions about the role of mutuality in the exchange at the heart of the psychological contract.
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| 9. |
- Leipold, Sina, et al.
(författare)
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Lessons, narratives, and research directions for a sustainable circular economy
- 2023
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Ingår i: Journal of Industrial Ecology. - : Wiley. - 1088-1980 .- 1530-9290. ; 27:1, s. 6-18
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Tidskriftsartikel (refereegranskat)abstract
- The current enthusiasm for the circular economy (CE) offers a unique opportunity to advance the impact of research on sustainability transitions. Diverse interpretations of CE by scholars, however, produce partly opposing assessments of its potential benefits, which can hinder progress. Here, we synthesize policy-relevant lessons and research directions for a sustainable CE and identify three narratives—optimist, reformist, and skeptical—that underpin the ambiguity in CE assessments. Based on 54 key CE scholars’ insights, we identify three research needs: the articulation and discussion of ontologically distinct CE narratives; bridging of technical, managerial, socio-economic, environmental, and political CE perspectives; and critical assessment of opportunities and limits of CE science–policy interactions. Our findings offer practical guidance for scholars to engage reflexively with the rapid expansion of CE knowledge, identify and pursue high-impact research directions, and communicate more effectively with practitioners and policymakers.
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| 10. |
- Lopez-Ortega, A., et al.
(författare)
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Strongly exchange coupled inverse ferrimagnetic soft/hard, MnxFe3-xO4/FexMn3-xO4, core/shell heterostructured nanoparticles
- 2012
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 4:16, s. 5138-5147
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Tidskriftsartikel (refereegranskat)abstract
- Inverted soft/hard, in contrast to conventional hard/soft, bi-magnetic core/shell nanoparticles of MnxFe3-xO4/FexMn3-xO4 with two different core sizes (7.5 and 11.5 nm) and fixed shell thickness (similar to 0.6 nm) have been synthesized. The structural characterization suggests that the particles have an interface with a graded composition. The magnetic characterization confirms the inverted soft/hard structure and evidences a strong exchange coupling between the core and the shell. Moreover, larger soft core sizes exhibit smaller coercivities and loop shifts, but larger blocking temperatures, as expected from spring-magnet or graded anisotropy structures. The results indicate that, similar to thin film systems, the magnetic properties of soft/hard core/shell nanoparticles can be fine tuned to match specific applications.
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