| 1. |
- Anckarsäter, Henrik, 1966, et al.
(författare)
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Persistent regional frontotemporal hypoactivity in violent offenders at follow-up.
- 2007
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Ingår i: Psychiatry research. - : Elsevier BV. - 0165-1781 .- 0925-4927 .- 1872-7123. ; 156:1, s. 87-90
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Tidskriftsartikel (refereegranskat)abstract
- Since cross-sectional brain-imaging studies demonstrating frontotemporal cerebral hypoactivity in violent offenders have generally been carried out around the time of trial and sentencing, the findings might be influenced by the stressful situation of the subjects. It seems that no group of offenders with this finding has yet been followed longitudinally. We have re-examined nine offenders convicted of lethal or near-lethal violence in whom single photon emission tomography (SPECT) previously had demonstrated frontotemporal hypoperfusion. The mean interval between the initial and the follow-up examination was 4 years. The initially observed hypoactivity was found to have remained virtually unchanged at follow-up: no mean change in the group exceeded 5% in 12 assessed regions of interest. Although preliminary due to the small sample size, this study suggests that frontotemporal brain hypoactivity is a trait rather than a state in perpetrators of severe violent crimes.
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| 2. |
- Chen, Weimin, 1959-, et al.
(författare)
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Magneto-optical spectroscopy of defects in wide bandgap semiconductors : GaN and SiC
- 2000
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Ingår i: Proceedings Conference on Optoelectronic and Microelectronic Materials and Devices. - : IEEE. - 0780366980 ; , s. 497-502
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Konferensbidrag (refereegranskat)abstract
- We review recent progress in our understanding of intrinsic defects in GaN and SiC, gained from magneto-optical studies by Zeeman measurements and optically detected magnetic resonance. The two best-known intrinsic defects in these two wide bandgap semiconductors, i.e. the Ga interstitial in GaN and the silicon vacancy in SiC, are discussed in detail. The Ga interstitial is the first and only intrinsic defect in GaN that has so far been unambiguously identified, either in the presumably isolated form or in a family of up to three complexes. The silicon vacancy is among the most studied intrinsic defect in SiC, at least in two charge states, and yet still remains controversial.
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| 3. |
- Elbe, Pia, et al.
(författare)
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Effects of auditory and tactile distraction in adults with low and high ADHD symptoms
- 2024
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Ingår i: Journal of Cognitive Psychology. - : Taylor & Francis. - 2044-5911 .- 2044-592X. ; 36:5, s. 645-656
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate whether symptoms of attention deficit hyperactivity disorder (ADHD) impact distraction by unexpected deviant sounds and vibrations. The hypothesis was that there would be a difference between individuals with low and high ADHD symptom severity in deviance distraction. In a cross-modal oddball task, we measured the impact of to-be-ignored deviating auditory and vibro-tactile stimuli in 45 adults who were 18 years or older, and self-reported ADHD symptoms using the screening tool of the adult ADHD self-report scale (ASRS). Results did not show a difference between groups with low and high symptoms of ADHD in their propensity for distraction in any modality using both frequentist and Bayesian methods of analysis. The impact of the deviating sounds and vibrations on performance were similar between groups. However, the amount of missed trials, which possibly reflects mind wandering or attention away from the focal task, was higher in the high symptom group (0.5 % difference in missing data between groups). The findings indicate a difference in missed responses between groups, despite no differences in the likelihood of distraction being indicated between vibro-tactile and auditory modalities. Overall, the complexity of adult ADHD symptomatology, especially behavioral differences in attentional control is reflected in the results of this study.
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| 4. |
- Larsson, Erik G., 1974-, et al.
(författare)
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Teaching the Principles of Massive MIMO : Exploring reciprocity-based multiuser MIMO beamforming using acoustic waves
- 2017
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Ingår i: IEEE signal processing magazine (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-5888 .- 1558-0792. ; 34:1, s. 40-47
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Tidskriftsartikel (refereegranskat)abstract
- Massive multiple-input, multiple-output (MIMO) is currently the most compelling wireless physical layer technology and a key component of fifth-generation (5G) systems. The understanding of its core principles has emerged during the last five years, and material is becoming available that is rigorously refined to focus on timeless fundamentals [1], facilitating the instruction of the topic to both master- and doctoral-level students [2]. Meaningful laboratory work that exposes the operational principles of massive MIMO is more difficult to accomplish. At Linköping University, Sweden, this was achieved through a project course, based on the conceive-design-implement-operate (CDIO) concept [3], and through the creation of a specially designed experimental setup using acoustic signals.
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| 5. |
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| 6. |
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| 7. |
- Sörman, E., et al.
(författare)
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Silicon vacancy related defect in 4H and 6H SiC
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:4, s. 2613-2620
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Tidskriftsartikel (refereegranskat)abstract
- We report on an irradiation-induced photoluminescence (PL) band in 4H and 6H SiC and the corresponding optically detected magnetic resonance (ODMR) signals from this band. The deep PL band has the same number of no-phonon lines as there are inequivalent sites in the respective polytype. These lines are at 1352 and 1438 meV in the case of 4H and at 1366, 1398, and 1433 meV in the case of 6H. The intensity of the PL lines is reduced after a short anneal at 750░C. ODMR measurements with above-band-gap excitation show that two spin-triplet (S=1) states with a weak axial character are detected via each PL line in these bands. One of these two triplet states can be selectively excited with the excitation energy of the corresponding PL line. These triplet signals can therefore be detected separately and only then can the well documented and characteristic hyperfine interaction of the silicon vacancy in SiC be resolved. Considering the correlation between the irradiation dose and the signal strength, the well established annealing temperature and the characteristic hyperfine pattern, we suggest that this PL band is related to the isolated silicon vacancy in 4H and 6H SiC. The spin state (S=1) implies a charge state of the vacancy with an even number of electrons. By combining the knowledge from complementary electron-spin resonance measurements and theoretical calculations we hold the neutral charge state for the strongest candidate. ⌐2000 The American Physical Society.
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| 8. |
- Sörman, Erik
(författare)
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The silicon vacancy in SiC
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- SiC has for decades been considered to be a very promising semiconductor, but several problems related to the material quality, did earlier prevent an exploitation of the supreme electrical characteristics of the material. Now most of these problems have been overcome, high quality material can be grown and research around this material is going through an intense phase of development.The photoluminescence (PL) technique is simple, non-destructive and requires no sample preparation. If a PL signal can be associated with a fundamental defect it certainly is an important piece of information. A fingerprint signal obtainable with such a simple technique is very useful in routine characterisation of the material. In our ambition to reveal the origin of the PL signals from SiC, we have used a technique called optically detected magnetic resonance (ODMR). It is efficient in supplying microscopic information about defects and have enabled us to assign a deep PL band to the silicon vacancy in 3C, 4H and 6H SiC. To be more specific, we argue that the deep PL band originates from internal transitions of the silicon vacancy in its neutral charge state.SiC is the classical example of polytypism i. e. it appears in many different but closely related crystal structures. A substitutional atom or a vacancy can therefore occupy sites, with different arrangements of their neighbours. If a defect is sensitive to its immediate neighbourhood, the signals from the different sites can usually be separated and new possibilities opens up for a materials scientist. A certain defect system can then be investigated and compared between the polytypes and much more about how the local environment of the defect affects its properties can be learned, than otherwise would have been possible.Here we have been able to investigate the signals from the silicon vacancy in 3C, 4H and 6H SiC and by comparing the characteristics of the signals from the different sites, we have been able to correlate the individual signals to the corresponding sites in the 4H and 6H crystals (in the 3C crystal there is just one site). There are some pronounced differences in the signals from the different sites. Only the PL lines from the sites with a cubic environment are split by applied stress while the ODMR signals from the sites with a hexagonal environment have a stronger relation to the symmetry axis of the crystal.Substitutional nitrogen is a shallow donor in SiC. Our magnetic resonance measurements show that the loosely bound electron of the nitrogen atom is transferred to various deep defects. This direct transfer of electrons from a shallow defect to deeper ones opens up new efficient recombination channels. This type of recombination channels is not included in standard recombination models.
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| 9. |
- Wagner, Matthias, 1969-, et al.
(författare)
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Electronic structure of the neutral silicon vacancy in 4H and 6H SiC
- 2000
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Ingår i: Physical review. B, Condensed matter and materials physics. - 2469-9950. ; 62:24, s. 16555-16560
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Tidskriftsartikel (refereegranskat)abstract
- Detailed information about the electronic structure of the lowest-lying excited states and the ground state of the neutral silicon vacancy in 4H and 6H SiC has been obtained by high-resolution photoluminescence (PL), PL excitation (PLE), and Zeeman spectroscopy of both PL and PLE. The excited states and the ground states involved in the characteristic luminescence of the defect with no-phonon (NP) lines at 1.438 and 1.352 eV in 4H SiC and 1.433, 1.398, and 1.368 eV in 6H SiC are shown to be singlets. The orbital degeneracy of the excited states is lifted by the crystal field for the highest-lying NP lines corresponding to one of the inequivalent lattice sites in both polytypes, leading to the appearance of hot lines at slightly higher energies. Polarization studies of the NP lines show a different behavior for the inequivalent sites. A comparison of this behavior in the two polytypes together with parameters from spin resonance studies provides useful hints for the assignment of the no-phonon lines to the inequivalent sites. In strained samples an additional fine structure of the NP lines can be resolved. This splitting may be due to strain variations in the samples.
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