| 1. |
- Belmonte, J.C., et al.
(författare)
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Micromachined twin gas sensor for CO and O2 quantification based on catalytically modified nano-SnO2
- 2006
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 114:2, s. 881-892
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present a micromachined twin sensor that can distinguish between carbon monoxide (CO) and O2 gas taking advantage of the high sensitivity of SnO2 to these gases. The SnO2 nanoparticles of both sensors are catalytically modified with different Pd loadings that act as active filters. In this way, one sensor response is turned to present a higher sensitivity to CO than to O2, whereas the other sensor is mainly turned for detecting O2 variations. The twin sensor has two membranes in the same die of micromachined silicon. Each membrane works independently from the other without any cross talk of temperature. The resistance data obtained from this twin sensor as a function of CO and O 2 concentrations is parametrized. Then, two functions are calculated for the quantification of CO/O2 gas mixtures. A comparison with commercial gas sensors is shown. © 2005 Elsevier B.V. All rights reserved.
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| 2. |
- Heiss, M., et al.
(författare)
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Self-assembled quantum dots in a nanowire system for quantum photonics
- 2013
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Ingår i: Nature Materials. - 1476-4660. ; 12:5, s. 439-444
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Tidskriftsartikel (refereegranskat)abstract
- Quantum dots embedded within nanowires represent one of the most promising technologies for applications in quantum photonics. Whereas the top-down fabrication of such structures remains a technological challenge, their bottom-up fabrication through self-assembly is a potentially more powerful strategy. However, present approaches often yield quantum dots with large optical linewidths, making reproducibility of their physical properties difficult. We present a versatile quantum-dot-innanowire system that reproducibly self-assembles in core-shell GaAs/AlGaAs nanowires. The quantum dots form at the apex of a GaAs/AlGaAs interface, are highly stable, and can be positioned with nanometre precision relative to the nanowire centre. Unusually, their emission is blue-shifted relative to the lowest energy continuum states of the GaAs core. Large-scale electronic structure calculations show that the origin of the optical transitions lies in quantum confinement due to Al-rich barriers. By emitting in the red and self-assembling on silicon substrates, these quantum dots could therefore become building blocks for solid-state lighting devices and third-generation solar cells.
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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. |
- He, Jia, et al.
(författare)
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Socially Desirable Responding : Enhancement and Denial in 20 Countries
- 2015
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Ingår i: Cross-cultural research. - : SAGE Publications. - 1069-3971 .- 1552-3578. ; 49:3, s. 227-249
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Tidskriftsartikel (refereegranskat)abstract
- This article investigated the dimensionality, measurement invariance, and cross-cultural variations of social desirability. A total of 3,471 university students from 20 countries completed an adapted version of the Marlowe-Crowne scale. A two-dimensional structure was revealed in the pooled sample, distinguishing enhancement (endorsement of positive self-description) and denial (rejection of negative self-description). The factor structure was supported in most countries; medium-sized item bias was found in two denial items. In a multilevel analysis, we found that (a) there was more cross-cultural variation in denial than enhancement; (b) females tended to score higher on enhancement whereas males tended to score higher on denial; (c) the Human Development Index, an indicator of country socioeconomic development, was the best (negative) predictor of denial; and (d) both enhancement and denial seemed to be associated with country-level values and personality pertinent to fitting in. We conclude that social desirability has a positive and a negative impression management dimension that are meaningfully associated with country-level characteristics, and we argue that social desirability is better interpreted as culturally regulated response amplification.
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| 5. |
- He, Jia, et al.
(författare)
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On Enhancing the Cross-Cultural Comparability of Likert-Scale Personality and Value Measures : A Comparison of Common Procedures
- 2017
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Ingår i: European Journal of Personality. - : John Wiley & Sons. - 0890-2070 .- 1099-0984. ; 31:6, s. 642-657
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to evaluate a number of procedures that have been proposed to enhance cross-cultural comparability of personality and value data. A priori procedures (anchoring vignettes and direct measures of response styles (i.e. acquiescence, extremity, midpoint responding, and social desirability), a posteriori procedures focusing on data transformations prior to analysis (ipsatization and item parcelling), and two data modelling procedures (treating data as continuous vs as ordered categories) were compared using data collected from university students in 16 countries. We found that (i) anchoring vignettes showed lack of invariance, so they were not bias-free; (ii) anchoring vignettes showed higher internal consistencies than raw scores where all other correction procedures, notably ipsatization, showed lower internal consistencies; (iii) in measurement invariance testing, no procedure yielded scalar invariance; anchoring vignettes and item parcelling slightly improved comparability, response style correction did not affect it, and ipsatization resulted in lower comparability; (iv) treating Likert-scale data as categorical resulted in higher levels of comparability; (v) factor scores of scales extracted from different procedures showed similar correlational patterning; and (vi) response style correction was the only procedure that suggested improvement in external validity of country-level conscientiousness. We conclude that, although no procedure resolves all comparability issues, anchoring vignettes, parcelling, and treating data as ordered categories seem promising to alleviate incomparability. We advise caution in uncritically applying any of these procedures.
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