| 1. |
- Syväjärvi, Mikael, et al.
(författare)
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Cubic silicon carbide as a potential photovoltaic material
- 2016
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier. - 0927-0248 .- 1879-3398. ; 145, s. 104-108
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present a significant advancement in cubic silicon carbide (3C-SiC) growth in terms of crystal quality and domain size, and indicate its potential use in photovoltaics. To date, the use of 3C-SiC for photovoltaics has not been considered due to the band gap of 2.3 eV being too large for conventional solar cells. Doping of 3C-SiC with boron introduces an energy level of 0.7 eV above the valence band. Such energy level may form an intermediate band (IB) in the band gap. This IB concept has been presented in the literature to act as an energy ladder that allows absorption of sub-bandgap photons to generate extra electron-hole pairs and increase the efficiency of a solar cell. The main challenge with this concept is to find a materials system that could realize such efficient photovoltaic behavior. The 3C-SiC bandgap and boron energy level fits nicely into the concept, but has not been explored for an IB behavior. For a long time crystalline 3C-SiC has been challenging to grow due to its metastable nature. The material mainly consists of a large number of small domains if the 3C polytype is maintained. In our work a crystal growth process was realized by a new approach that is a combination of initial nucleation and step-flow growth. In the process, the domains that form initially extend laterally to make larger 3C-SiC domains, thus leading to a pronounced improvement in crystalline quality of 3C-SiC. In order to explore the feasibility of IB in 3C-SiC using boron, we have explored two routes of introducing boron impurities; ion implantation on un-doped samples and epitaxial growth on un-doped samples using pre-doped source material. The results show that 3C-SiC doped with boron is an optically active material, and thus is interesting to be further studied for IB behavior. For the ion implanted samples the crystal quality was maintained even after high implantation doses and subsequent annealing. The same was true for the samples grown with pre-doped source material, even with a high concentration of boron impurities. We present optical emission and absorption properties of as-grown and boron implanted 3C-SiC. The low-temperature photoluminescence spectra indicate the formation of optically active deep boron centers, which may be utilized for achieving an IB behavior at sufficiently high dopant concentrations. We also discuss the potential of boron doped 3C-SiC base material in a broader range of applications, such as in photovoltaics, biomarkers and hydrogen generation by splitting water.
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| 2. |
- Galeckas, A., et al.
(författare)
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Optical and microstructural investigation of heavy B-doping effects in sublimation-grown 3C-SiC
- 2018
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Ingår i: Materials Science Forum. - : Trans Tech Publications Ltd. - 9783035711455 ; , s. 221-224
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Konferensbidrag (refereegranskat)abstract
- In this work, a complementary microstructural and optical approach is used to define processing conditions favorable for the formation of deep boron-related acceptor centers that may provide a pathway for achieving an intermediate band behavior in highly B-doped 3C-SiC. The crystallinity, boron solubility and precipitation mechanisms in sublimation-grown 3C-SiC crystals implanted to 1-3 at.% B concentrations were investigated by STEM. The revealed defect formation and boron precipitation trends upon thermal treatment in the range 1100-2000oC have been crosscorrelated with the optical characterization results provided by imaging PL spectroscopy. We discuss optical activity of the implanted B ions in terms of both shallow acceptors and deep D-centers, a complex formed by a boron atom and a carbon vacancy, and associate the observed spectral developments upon annealing with the strong temperature dependence of the D-center formation efficiency, which is further enhanced by the presence of implantation-induced defects. © 2018 Trans Tech Publications, Switzerland.
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| 3. |
- Berggård, T, et al.
(författare)
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Alpha1-microglobulin chromophores are located to three lysine residues semiburied in the lipocalin pocket and associated with a novel lipophilic compound
- 1999
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Ingår i: Protein Science. - : Wiley. - 0961-8368. ; 8:12, s. 20-2611
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Tidskriftsartikel (refereegranskat)abstract
- Alpha1-microglobulin (alpha1m) is an electrophoretically heterogeneous plasma protein. It belongs to the lipocalin superfamily, a group of proteins with a three-dimensional (3D) structure that forms an internal hydrophobic ligand-binding pocket. Alpha1m carries a covalently linked unidentified chromophore that gives the protein a characteristic brown color and extremely heterogeneous optical properties. Twenty-one different colored tryptic peptides corresponding to residues 88-94, 118-121, and 122-134 of human alpha1m were purified. In these peptides, the side chains of Lys92, Lys118, and Lys130 carried size heterogeneous, covalently attached, unidentified chromophores with molecular masses between 122 and 282 atomic mass units (amu). In addition, a previously unknown uncolored lipophilic 282 amu compound was found strongly, but noncovalently associated with the colored peptides. Uncolored tryptic peptides containing the same Lys residues were also purified. These peptides did not carry any additional mass (i.e., chromophore) suggesting that only a fraction of the Lys92, Lys118, and Lys130 are modified. The results can explain the size, charge, and optical heterogeneity of alpha1m. A 3D model of alpha1m, based on the structure of rat epididymal retinoic acid-binding protein (ERABP), suggests that Lys92, Lys118, and Lys130 are semiburied near the entrance of the lipocalin pocket. This was supported by the fluorescence spectra of alpha1m under native and denatured conditions, which indicated that the chromophores are buried, or semiburied, in the interior of the protein. In human plasma, approximately 50% of alpha1m is complex bound to IgA. Only the free alpha1m carried colored groups, whereas alpha1m linked to IgA was uncolored.
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| 4. |
- Di Cori, Andrea, et al.
(författare)
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Clinical impact of antithrombotic therapy in transvenous lead extraction complications : a sub-analysis from the ESC-EORP EHRA ELECTRa (European Lead Extraction ConTRolled) Registry
- 2019
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Ingår i: Europace. - : Oxford University Press. - 1099-5129 .- 1532-2092. ; 21:7, s. 1096-1105
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: A sub-analysis of the ESC-EHRA European Lead Extraction ConTRolled (ELECTRa) Registry to evaluate the clinical impact of antithrombotic (AT) on transvenous lead extraction (TLE) safety and efficacy.METHODS AND RESULTS: ELECTRa outcomes were compared between patients without AT therapy (No AT Group) and with different pre-operative AT regimens, including antiplatelets (AP), anticoagulants (AC), or both (AP + AC). Out of 3510 pts, 2398 (68%) were under AT pre-operatively. AT patients were older with more comorbidities (P < 0.0001). AT subgroups, defined as AP, AC, or AP + AC, were 1096 (31.2%), 985 (28%), and 317 (9%), respectively. Regarding AP patients, 1413 (40%) were under AP, 1292 (91%) with a single AP, interrupted in 26% about 3.8 ± 3.7 days before TLE. In total, 1302 (37%) patients were under AC, 881 vitamin K antagonist (68%), 221 (17%) direct oral anticoagulants, 155 (12%) low weight molecular heparin, and 45 (3.5%) unfractionated heparin. AC was 'interrupted without bridging' in 696 (54%) and 'interrupted with bridging' in 504 (39%) about 3.3 ± 2.3 days before TLE, and 'continued' in 87 (7%). TLE success rate was high in all subgroups. Only overall in-hospital death (1.4%), but not the procedure-related one, was higher in the AT subgroups (P = 0.0500). Age >65 years and New York Heart Association Class III/IV, but not AT regimens, were independent predictors of death for any cause. Haematomas were more frequent in AT subgroups, especially in AC 'continued' (P = 0.025), whereas pulmonary embolism in the No-AT (P < 0.01).CONCLUSIONS: AT minimization is safe in patients undergoing TLE. AT does not seem to predict death but identifies a subset of fragile patients with a worse in-hospital TLE outcome.
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| 5. |
- Thøgersen-Ntoumani, Cecilie, et al.
(författare)
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Does self-compassion help to deal with dietary lapses among overweight and obese adults who pursue weight-loss goals?
- 2021
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Ingår i: British Journal of Health Psychology. - : John Wiley & Sons. - 1359-107X .- 2044-8287. ; 26:3, s. 767-788
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Self‐compassion can facilitate self‐improvement motivation. We examined the effects of self‐compassion in response to dietary lapses on outcomes relevant to weight‐loss strivings using a longitudinal design. The indirect effects of self‐compassion via guilt and shame were also explored.Design: An Ecological Momentary Assessment methodology was employed with a sample of adults who were overweight or obese attempting to lose weight via dietary restriction (N = 56; Mage = 34.88; SD = 13.93; MBMI = 32.50; SD = 6.88) and who responded to brief surveys sent to their mobile phones twice daily for two weeks.Methods: Dietary temptations and lapses were assessed at each diary entry, and self‐compassion in response to dietary lapses, intention to continue dieting, weight‐loss‐related self‐efficacy, negative reactions to the lapse, and self‐conscious emotions were surveyed on occasions when participants reported having experienced a dietary lapse. The participants were also weighed in a laboratory prior to the EMA phase and via self‐report straight after the EMA phase. Weight was measured again in the laboratory 12 weeks after the EMA period.Results: Bayesian multilevel path analyses showed that self‐compassion did not predict weight loss. However, at the within‐person level, self‐compassion was positively related to intentions and self‐efficacy to continue dieting, and negatively related to negative affective reactions to the lapses. Guilt mediated the associations of self‐compassion with intention, self‐efficacy, and negative reactions.Conclusion: Self‐compassion may be a powerful internal resource to cultivate when dieters experience inevitable setbacks during weight‐loss strivings which could facilitate weight‐loss perseverance.
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