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- Andreasson, Björn Pererik, 1979-, et al.
(författare)
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Detecting oxygen vacancies in SrTiO3 by 3d transition-metal tracer ions
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - College Park, MD : American Physical Society. - 1098-0121 .- 1550-235X. ; 80:21, s. Article number: 212103-
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption experiments on 3d transition-metal tracer ions in SrTiO3 are presented. The absorption spectra of the tracer-ion changed upon reduction in the SrTiO3. This change is due to an oxygen vacancy created at the tracer-ion site. This finding is supported by density-functional theory calculations, which prove that the oxygen vacancies preferentially are created at the tracer-ion sites. Using the chemical sensitivity of x-ray absorption spectroscopy, tracer ions can be used to detect oxygen vacancies in SrTiO3 and possibly in other oxide systems. © 2009 The American Physical Society.
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- Andreasson, Björn Pererik, 1979-, et al.
(författare)
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Origin of oxygen vacancies in resistive switching memory devices
- 2009
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Ingår i: Journal of Physics, Conference Series. - Bristol : Institute of Physics Publishing (IOPP). - 1742-6588 .- 1742-6596. ; 190, s. Article number: 012074-
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Tidskriftsartikel (refereegranskat)abstract
- The resistive switching state in Cr-doped SrTiO3 was induced by applying an electric field. This was done in ambient air and in an atmosphere of H2/Ar. The distribution of the thereby introduced oxygen vacancies was studied by spatially resolved X-ray fluorescence images. It was concluded that the oxygen vacancies were introduced in the interface between the SrTiO3 and the positively biased electrode. © 2009 IOP Publishing Ltd.
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- Andreasson, Björn Pererik, 1979-, et al.
(författare)
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Resistive switching in Cr-doped SrTiO3 : An X-ray absorption spectroscopy study
- 2007
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Ingår i: Materials Science & Engineering. - Amsterdam : Elsevier. - 0921-5107 .- 1873-4944. ; 144:1-3, s. 60-63
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption spectroscopy was used to study the microscopic origin of conductance and resistive switching in chromium-doped strontium titanate (Cr:SrTiO3). Differences in the X-ray absorption near edge spectroscopy (XANES) at the Cr K-edge indicate that the valence of Cr changes from 3+ to 4+ underneath the anode of our sample device after the application of an electric field. Spatially resolved X-ray fluorescence microscopy (μ-XRF) maps show that the Cr4+ region retracts from the anode-Cr:SrTiO3 interface after a conducting state has been achieved. This interface region is studied with extended X-ray absorption fine structure (EXAFS) and the results are compared with structural parameters obtained from density functional theory (DFT) calculations. They confirm that oxygen vacancies which are localized at the octahedron with a Cr at its center are introduced at the interface. It is proposed that the switching state is not due to a valence change of chromium but caused by changes of oxygen vacancies at the interface. © 2007 Elsevier B.V. All rights reserved.
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- Andreasson, Björn Pererik, 1979-, et al.
(författare)
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Spatial distribution of oxygen vacancies in Cr-doped SrTiO3 during an electric-field-driven insulator-to-metal transition
- 2009
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Ingår i: Applied Physics Letters. - College Park, MD : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 94:1, s. Article number: 013513-
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Tidskriftsartikel (refereegranskat)abstract
- Spatially resolved x-ray fluorescence maps are presented that show the introduction and the evolution of oxygen vacancies in chromium-doped strontium titanate during an electric-field-driven insulator-to-metal transition. The vacancies are introduced at the anode and diffuse through the crystal toward the cathode. The spatial distribution of vacancies is explained by a model describing the electrical breakdown as a percolation process. Strong differences in the vacancy distribution were found when the transition took place in air and in a hydrogen-enriched atmosphere. In air, the vacancies disappeared from the surface, whereas in the reducing hydrogen atmosphere, they remained at the surface. © 2009 American Institute of Physics.
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- Beijer, U, et al.
(författare)
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Physical diseases among homeless people: gender differences and comparisons with the general population
- 2009
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Ingår i: Scandinavian journal of public health. - : SAGE Publications. - 1403-4948 .- 1651-1905. ; 37:1, s. 93-100
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To study morbidity amongst homeless men and women by comparing prevalence of hospital care for somatic diseases and injuries with a control group of men and women from the general population. Methods: A cohort of 1,364 men and 340 women were documented as homeless in 1996. Comparisons are made concerning hospital care for somatic diseases and injuries (1996-2002) among 3,750 men and 1,250 women from the general population. Results: The relative risk (RR) for homeless men and women of being hospitalised was double that of the men and women in the controls (1.93 and 1.96 respectively). Homeless women had a slightly, not significant, increased risk compared to homeless men (RR 1.10). Younger homeless women had a significant higher risk. Among diagnostic categories, the highest prevalence was found among homeless men in the diagnosis group injury/poisoning (22%). The highest risk was found for skin diseases (RR 36.96) and concerned homeless women. There were a number of gender specific diagnoses, where risks were considerably elevated, such as diseases of the genital organs, viral hepatitis, and poisoning for homeless women, and cerebrovascular diseases, diseases of the liver, and concussion for homeless men. Conclusions: Homeless people had twice the risk of being hospitalised for physical diseases compared to the general population. Younger women were particularly at risk compared to homeless men and to women in the controls. There were a number of gender specific diagnoses that are important to take into account when planning services for homeless people.
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- Kohl, S, et al.
(författare)
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CNGB3 mutations account for 50% of all cases with autosomal recessive achromatopsia
- 2005
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Ingår i: European Journal of Human Genetics. - : Springer Science and Business Media LLC. - 1476-5438 .- 1018-4813. ; 13:3, s. 302-308
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Tidskriftsartikel (refereegranskat)abstract
- Achromatopsia is a congenital, autosomal recessively inherited disorder characterized by a lack of color discrimination, low visual acuity (<0.2), photophobia, and nystagmus. Mutations in the genes for CNGA3, CNGB3, and GNAT2 have been associated with this disorder. Here, we analyzed the spectrum and prevalence of CNGB3 gene mutations in a cohort of 341 independent patients with achromatopsia. In 163 patients, CNGB3 mutations could be identified. A total of 105 achromats carried apparent homozygous mutations, 44 were compound (double) heterozygotes, and 14 patients had only a single mutant allele. The derived CNGB3 mutation spectrum comprises 28 different mutations including 12 nonsense mutations, eight insertions and/or deletions, five putative splice site mutations, and three missense mutations. Thus, the majority of mutations in the CNGB3 gene result in significantly altered and/or truncated polypeptides. Several mutations were found recurrently, in particular a 1 bp deletion, c.1148delC, which accounts for over 70% of all CNGB3 mutant alleles. In conclusion, mutations in the CNGB3 gene are responsible for approximately 50% of all patients with achromatopsia. This indicates that the CNGB3/ACHM3 locus on chromosome 8q21 is the major locus for achromatopsia in patients of European origin or descent.
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