| 1. |
|
|
| 2. |
- Mishra, A., et al.
(författare)
-
Stroke genetics informs drug discovery and risk prediction across ancestries
- 2022
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 611, s. 115-123
-
Tidskriftsartikel (refereegranskat)abstract
- Previous genome-wide association studies (GWASs) of stroke - the second leading cause of death worldwide - were conducted predominantly in populations of European ancestry(1,2). Here, in cross-ancestry GWAS meta-analyses of 110,182 patients who have had a stroke (five ancestries, 33% non-European) and 1,503,898 control individuals, we identify association signals for stroke and its subtypes at 89 (61 new) independent loci: 60 in primary inverse-variance-weighted analyses and 29 in secondary meta-regression and multitrait analyses. On the basis of internal cross-ancestry validation and an independent follow-up in 89,084 additional cases of stroke (30% non-European) and 1,013,843 control individuals, 87% of the primary stroke risk loci and 60% of the secondary stroke risk loci were replicated (P < 0.05). Effect sizes were highly correlated across ancestries. Cross-ancestry fine-mapping, in silico mutagenesis analysis(3), and transcriptome-wide and proteome-wide association analyses revealed putative causal genes (such as SH3PXD2A and FURIN) and variants (such as at GRK5 and NOS3). Using a three-pronged approach(4), we provide genetic evidence for putative drug effects, highlighting F11, KLKB1, PROC, GP1BA, LAMC2 and VCAM1 as possible targets, with drugs already under investigation for stroke for F11 and PROC. A polygenic score integrating cross-ancestry and ancestry-specific stroke GWASs with vascular-risk factor GWASs (integrative polygenic scores) strongly predicted ischaemic stroke in populations of European, East Asian and African ancestry(5). Stroke genetic risk scores were predictive of ischaemic stroke independent of clinical risk factors in 52,600 clinical-trial participants with cardiometabolic disease. Our results provide insights to inform biology, reveal potential drug targets and derive genetic risk prediction tools across ancestries.
|
|
| 3. |
- Jaworek, T., et al.
(författare)
-
Contribution of Common Genetic Variants to Risk of Early-Onset Ischemic Stroke
- 2022
-
Ingår i: Neurology. - : Ovid Technologies (Wolters Kluwer Health). - 0028-3878 .- 1526-632X. ; 99:16
-
Tidskriftsartikel (refereegranskat)abstract
- Background and Objectives Current genome-wide association studies of ischemic stroke have focused primarily on late-onset disease. As a complement to these studies, we sought to identify the contribution of common genetic variants to risk of early-onset ischemic stroke. Methods We performed a meta-analysis of genome-wide association studies of early-onset stroke (EOS), ages 18-59 years, using individual-level data or summary statistics in 16,730 cases and 599,237 nonstroke controls obtained across 48 different studies. We further compared effect sizes at associated loci between EOS and late-onset stroke (LOS) and compared polygenic risk scores (PRS) for venous thromboembolism (VTE) between EOS and LOS. Results We observed genome-wide significant associations of EOS with 2 variants in ABO, a known stroke locus. These variants tag blood subgroups O1 and A1, and the effect sizes of both variants were significantly larger in EOS compared with LOS. The odds ratio (OR) for rs529565, tagging O1, was 0.88 (95% confidence interval [CI]: 0.85-0.91) in EOS vs 0.96 (95% CI: 0.92-1.00) in LOS, and the OR for rs635634, tagging A1, was 1.16 (1.11-1.21) for EOS vs 1.05 (0.99-1.11) in LOS; p-values for interaction = 0.001 and 0.005, respectively. Using PRSs, we observed that greater genetic risk for VTE, another prothrombotic condition, was more strongly associated with EOS compared with LOS (p = 0.008). Discussion The ABO locus, genetically predicted blood group A, and higher genetic propensity for venous thrombosis are more strongly associated with EOS than with LOS, supporting a stronger role of prothrombotic factors in EOS.
|
|
| 4. |
- Bonkhoff, A. K., et al.
(författare)
-
Sex-specific lesion pattern of functional outcomes after stroke
- 2022
-
Ingår i: Brain Communications. - : Oxford University Press (OUP). - 2632-1297. ; 4:2
-
Tidskriftsartikel (refereegranskat)abstract
- Relying on neuroimaging and clinical data of 822 acute stroke patients, Bonkhoff et al. report substantially more detrimental effects of lesions in left-hemispheric posterior circulation regions on functional outcomes in women compared to men. These findings may motivate a sex-specific clinical stroke management to improve outcomes in the longer term. Stroke represents a considerable burden of disease for both men and women. However, a growing body of literature suggests clinically relevant sex differences in the underlying causes, presentations and outcomes of acute ischaemic stroke. In a recent study, we reported sex divergences in lesion topographies: specific to women, acute stroke severity was linked to lesions in the left-hemispheric posterior circulation. We here determined whether these sex-specific brain manifestations also affect long-term outcomes. We relied on 822 acute ischaemic patients [age: 64.7 (15.0) years, 39% women] originating from the multi-centre MRI-GENIE study to model unfavourable outcomes (modified Rankin Scale >2) based on acute neuroimaging data in a Bayesian hierarchical framework. Lesions encompassing bilateral subcortical nuclei and left-lateralized regions in proximity to the insula explained outcomes across men and women (area under the curve = 0.81). A pattern of left-hemispheric posterior circulation brain regions, combining left hippocampus, precuneus, fusiform and lingual gyrus, occipital pole and latero-occipital cortex, showed a substantially higher relevance in explaining functional outcomes in women compared to men [mean difference of Bayesian posterior distributions (men - women) = -0.295 (90% highest posterior density interval = -0.556 to -0.068)]. Once validated in prospective studies, our findings may motivate a sex-specific approach to clinical stroke management and hold the promise of enhancing outcomes on a population level.
|
|
| 5. |
- Soderholm, M., et al.
(författare)
-
Genome-wide association meta-analysis of functional outcome after ischemic stroke
- 2019
-
Ingår i: Neurology. - : Ovid Technologies (Wolters Kluwer Health). - 0028-3878 .- 1526-632X. ; 92:12
-
Tidskriftsartikel (refereegranskat)abstract
- Objective To discover common genetic variants associated with poststroke outcomes using a genome-wide association (GWA) study. Methods The study comprised 6,165 patients with ischemic stroke from 12 studies in Europe, the United States, and Australia included in the GISCOME (Genetics of Ischaemic Stroke Functional Outcome) network. The primary outcome was modified Rankin Scale score after 60 to 190 days, evaluated as 2 dichotomous variables (0-2 vs 3-6 and 0-1 vs 2-6) and subsequently as an ordinal variable. GWA analyses were performed in each study independently and results were meta-analyzed. Analyses were adjusted for age, sex, stroke severity (baseline NIH Stroke Scale score), and ancestry. The significance level was p < 5 x 10(-8). Results We identified one genetic variant associated with functional outcome with genome-wide significance (modified Rankin Scale scores 0-2 vs 3-6, p = 5.3 x 10(-9)). This intronic variant (rs1842681) in the LOC105372028 gene is a previously reported trans-expression quantitative trait locus for PPP1R21, which encodes a regulatory subunit of protein phosphatase 1. This ubiquitous phosphatase is implicated in brain functions such as brain plasticity. Several variants detected in this study demonstrated suggestive association with outcome (p < 10(-5)), some of which are within or near genes with experimental evidence of influence on ischemic stroke volume and/or brain recovery (e.g., NTN4, TEK, and PTCH1). Conclusions In this large GWA study on functional outcome after ischemic stroke, we report one significant variant and several variants with suggestive association to outcome 3 months after stroke onset with plausible mechanistic links to poststroke recovery. Future replication studies and exploration of potential functional mechanisms for identified genetic variants are warranted.
|
|
| 6. |
- Bjordal, K, et al.
(författare)
-
A 12 country field study of the EORTC QLQ-C30 (version 3.0) and the head and neck cancer specific module (EORTC QLQ-H&N35) in head and neck patients
- 2000
-
Ingår i: European Journal of Cancer. - 1879-0852. ; 36:14, s. 1796-1807
-
Tidskriftsartikel (refereegranskat)abstract
- This study tests the reliability and validity of the European Organization for Research and Treatment of Cancer (EORTC) head and neck cancer module (QLQ-H&N35) and version 3.0 of the EORTC Core Questionnaire (QLQ-C30) in 622 head and neck cancer patients from 12 countries. The patients completed the QLQ-C30, the QLQ-H&N35 and a debriefing questionnaire before antineoplastic treatment or at a follow-up. 232 patients receiving treatment completed a second questionnaire after treatment. Compliance was high and the questionnaire was well accepted by the patients. Multitrait scaling analysis confirmed the proposed scale structure of the QLQ-H&N35. The QLQ-H&N35 was responsive to differences between disease status, site and patients with different Karnofsky performance status, and to changes over time. The new physical functioning scale (with a four-point response format) of version 3.0 of the QLQ-C30 was shown to be more reliable than previous versions. Thus, the QLQ-H&N35, in conjunction with the QLQ-C30, appears to be reliable, valid and applicable to broad multicultural samples of head and neck cancer patients.
|
|
| 7. |
|
|
| 8. |
- Vasanthakumar, A., et al.
(författare)
-
Reduced ITPase activity and favorable IL28B genetic variant protect against ribavirin-induced anemia in interferon-free regimens
- 2018
-
Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 13:5
-
Tidskriftsartikel (refereegranskat)abstract
- Background Genetic variants of inosine triphosphatase (ITPA) that confer reduced ITPase activity are associated with protection against ribavirin(RBV)-induced hemolytic anemia in peginterferon(IFN)/RBV-based treatment of hepatitis C virus (HCV). Patients with reduced ITPase activity showed improved treatment efficacy when treated with IFN/RBV. In addition, a genetic polymorphism near the IL28B gene is associated with an improved response to IFN/RBV treatment. RBV has been an important component of IFN-containing regimens, and is currently recommended in combination with several IFN-free regimens for treatment of harder to cure HCV infections. To evaluate whether genetic variations that reduce ITPase activity impact RBV-induced anemia in IFN-free/RBV regimens In this study, genetic analyses were conducted in the PEARL-IV trial to investigate the effect of activity-reducing ITPA variants as well as IL28B polymorphism on anemia, platelet (PLT) counts, and virologic response in HCV genotype1a-infected patients treated with the direct acting antiviral (DAA) regimen of ombitasvir/paritaprevir/ritonavir and dasabuvir RBV. Reduction in ITPase activity and homozygosity for the IL28Brs12979860 CC genotype protected against RBV-induced anemia. In patients receiving RBV, reduced ITPase activity was associated with reduced plasma RBV concentration and higher PLT counts. ITPase activity had no impact on response to DAA treatment, viral kinetics, or baseline IP-10 levels. Our study demonstrates that genetics of ITPA and IL28B may help identify patients protected from RBV-induced anemia when treated with IFN-free regimens. Our work demonstrates for the first time that IL28B genetics may also have an impact on RBV-induced anemia. This may be of particular significance in patients with difficult-to-cure HCV infections, such as patients with decompensated cirrhosis where RBV-containing regimens likely will continue to be recommended.
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
- Busch, K., et al.
(författare)
-
Prevalence and comorbidities of chronic hepatitis C: a nationwide population-based register study in Sweden
- 2017
-
Ingår i: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 0036-5521 .- 1502-7708. ; 52:1, s. 61-68
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: The aim of this study was to estimate the prevalence of physician-diagnosed and registered chronic hepatitis C (CHC), and to estimate the reported frequencies of Charlson comorbidities compared with matched comparators from the general population. Materials and methods: Patients were identified according to ICD codes for CHC in the Swedish National Patient Register (1997-2013). Prevalence was estimated according to different patient identification algorithms and for different subgroups. Charlson comorbidities were ascertained from the same register and compared with age/sex/county of residence matched general population comparators. Results: A total of 34,633 individuals with physician-diagnosed CHC were alive in Sweden in 2013 (mean age, 49 years; 64% men), corresponding to a physician-diagnosed prevalence of 0.36%. The prevalence varied by case definition (0.22%-0.36%). The estimate dropped to 0.14% for monitored CHC disease (defined as >= 1 CHC-related visit in 2013). Overall, 41.3% of the CHC patients had >= 1 physician-registered Charlson comorbidity; the most common was liver diseases (22.1%). Compared with matched comparators from the general population (n = 171,338), patients with CHC had more physician-diagnosed and registered diseases such as chronic pulmonary disease (10.2% vs. 4.0%), diabetes (10.6% vs. 5.5%) and liver-related cancer (1.3% vs. 0.2%; all p<.01). No information on behavioural factors, such as smoking, alcohol consumption or on-going illicit drug use, was available. Conclusion: The physician-diagnosed prevalence of CHC was slightly lower than previously reported estimates, and varied by case definition. The additional comorbidities observed in the CHC group should be taken into consideration, as these comorbidities add to the disease burden.
|
|
| 17. |
- Busch, K., et al.
(författare)
-
Sick leave and disability pension in patients with chronic hepatitis C compared with a matched general population: a nationwide register study
- 2020
-
Ingår i: BMJ Open. - : BMJ. - 2044-6055. ; 10:9
-
Tidskriftsartikel (refereegranskat)abstract
- Objective The objective of this study was to evaluate sick leave and disability pension in patients with chronic hepatitis C virus (HCV) infection as compared with a matched general population cohort. Design Retrospective register study. Setting Nationwide in Sweden. Participants This register-based study used the Swedish National Patient Register to identify working-age patients with HCV in 2012 (n=32 021) who were diagnosed between 1999 and 2007 (n=19 362). Sick leave and disability pension data were retrieved from Statistics Sweden (1994-2012), with up to five matched individuals from the general population. Primary and secondary outcome measures The primary outcome was workdays lost due to sick leave episodes (>14 days) and disability pension overall. The secondary outcome was workdays lost per subgroup of patients with chronic HCV. Results In 2012, 14% of the HCV patients had >= 1 registered sick leave episode compared with 10% in the matched comparator cohort. For disability pension benefits, results were 30% versus 8%, respectively. Overall, in 2012, 57% of patients with HCV did not have any registered workdays lost, whereas 30% were absent >= 360 days compared with 83% and 9% in the matched cohort, respectively. The mean total number of annual workdays lost in 2012 was 126 days in the HCV patient cohort compared with 40 days in the matched general population comparator cohort. Annual days lost increased from a mean of 86 days 5 years before diagnosis to 136 days during the year of diagnosis. Conclusions These results show that Swedish HCV patients used more sick days and have a higher frequency of disability pension compared with a comparator cohort from the general Swedish population. Whether earlier diagnosis of HCV and treatment might impact work absence in Sweden warrants further investigation.
|
|
| 18. |
|
|
| 19. |
|
|
| 20. |
|
|
| 21. |
|
|
| 22. |
|
|
| 23. |
|
|
| 24. |
|
|
| 25. |
|
|
| 26. |
|
|
| 27. |
|
|
| 28. |
- Soderholm, J., et al.
(författare)
-
Lower risk of multiple sclerosis in patients with chronic hepatitis C: a nationwide population-based registry study
- 2019
-
Ingår i: Journal of Neurology. - : Springer Science and Business Media LLC. - 0340-5354 .- 1432-1459. ; 266:9, s. 2208-2215
-
Tidskriftsartikel (refereegranskat)abstract
- Background Multiple sclerosis (MS) is an immune-mediated neurological disease that causes demyelination. The etiology is unknown, but patients with a previous viral infection, such as Epstein-Barr virus, have been shown to be at a higher risk of developing MS. In contrast, people living with HIV have a lower risk of developing MS. Hepatitis C virus (HCV) mainly infects the liver, but patients with HCV can experience several extrahepatic manifestations and studies have shown an association with several autoimmune conditions such as neuropathy and myelitis. The present study aimed to investigate the risk of MS in patients with chronic HCV infection compared with matched comparators. Methods Patients were identified using the nationwide Swedish inpatient (2001-2013) and outpatient care registers (2001-2013) for HCV (B18.2) and MS (G35) according to the International Classification of Diseases-10. Up to five comparators (matched on age/sex/place of residency) were drawn from the general population for each HCV patient. Follow-up started at the first HCV visit from 2001 and the patients' accrued person-time until death, emigration or 31 December 2013. Risk of MS diagnosis was calculated as standardized incidence ratio (SIR) with 95% confidence intervals (CIs). Results HCV patients were at lower risk of MS diagnosis (SIR 0.37; 95% CI 0.26-0.50). The incidence of MS during the study in the HCV cohort was 0.087% compared with 0.27% in the matched comparator cohort. Conclusion Surprisingly, these data suggest HCV patients to have a lower risk of MS diagnosis.
|
|
| 29. |
|
|
| 30. |
|
|
| 31. |
- Björk, Gunnar, et al.
(författare)
-
A theory of the relative phase and number difference of two quantized harmonic oscillators
- 2002
-
Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T102, s. 133-146
-
Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive and self-consistent theory of relative-phase measurements and the associated Hermitian relative-phase operator of two harmonic oscillators. We find that since Nature does not favor any particular initial condition of the two oscillators, the relative-phase operator is not unique. We show that the relative-phase eigenstates; are maximally entangled. Therefore. most relative-phase operators lack a classical correspondence, even in the high-excitation limit. Furthermore, we find that the relative phase and the excitation number difference are noncommuting, noncanonical observables and we derive a commutation relation.
|
|
| 32. |
- Björk, Gunnar, et al.
(författare)
-
Entangled-state lithography : Tailoring any pattern with a single state
- 2001
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 86:20, s. 4516-4519
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a systematic approach to Heisenberg-Limited lithographic image formation using four-mode reciprocal binomial states. By controlling the exposure pattern with a simple bank of birefringent plates, any pixel pattern on a (N + 1) X (N + 1) grid, occupying a square with the side half a wavelength long, can be generated from a 2N-photon state.
|
|
| 33. |
- Björk, Gunnar, et al.
(författare)
-
Hilbert space factorization and partial measurements
- 2003
-
Ingår i: Optics and Spectroscopy. - : Pleiades Publishing Ltd. - 0030-400X .- 1562-6911. ; 94:5, s. 695-699
-
Tidskriftsartikel (refereegranskat)abstract
- A quantum system whose state vector belongs to a finite-dimensional Hilbert space is considered. If this space has a dimension that is a composite number, one can factor the space into a tensor product of subspaces. An observable that acts only in one of these subspaces is called a partial measurement. Some of the properties and the interpretation of such partial measurements are discussed.
|
|
| 34. |
- Björk, Gunnar, et al.
(författare)
-
Subwavelength lithography over extended areas
- 2001
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 6401:1
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a systematic approach to subwavelength resolution Lithographic image formation on films covering areas larger than a wavelength squared. For example, it is possible to make a lithographic pattern with a feature size resolution of lambda/[2(N+1)] by using a particular 2M-photon, multimode entangled state, where N less than or equal toM, and banks of birefringent plates. By preparing such a statistically mixed state, one can form any pixel pattern on a 2(M-N)(N+1) x 2(M-N)(N+1) pixel grid occupying a square with side L = 2(M-N-1)lambda. Hence, there is a trade off between the exposed area, the minimum lithographic feature size resolution, and the number of photons used for the exposure. We also show that the proposed method will work even under nonideal conditions, albeit with somewhat poorer performance.
|
|
| 35. |
- Björk, Gunnar, et al.
(författare)
-
Visibility is not a good measure of a well-defined relative phase
- 2000
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 6202:2
-
Tidskriftsartikel (refereegranskat)abstract
- In a recent paper Marburger and Das [J. H. Marburger III and K. K. Das, Phys. Rev. A 59, 2213 (1999)] considered an interference visibility experiment involving two weakly interacting Bose-Einstein condensates. It was shown that condensate eigenstates of the Hermitian relative phase operator do not give interference fringes with unit visibility in a Young's double slit type of experiment. The authors concluded that ... these states are not especially well suited to describe weakly interacting multiply occupied coherent bosonic systems. In this work we suggest a criterion for states with a well-defined relative phase. Subsequently we show that the relative phase operator eigenstates satisfy this criterion. This suggests that the concept of interference visibility can, and should, be generalized, since it is widely believed that interference visibility is a measure of the relative phase properties. We therefore propose a broader, but still operational, definition of interference visibility, which we call generalized visibility, and prove that the relative phase operator eigenstates indeed can show unit generalized visibility. We also derive a simple, but general, criterion for states which can display a unit generalized visibility. Somewhat surprisingly, this criterion is weaker than the criterion for a well-defined relative phase. Finally, we discuss which two-mode states can display unit (ordinary) visibility.
|
|
| 36. |
|
|
| 37. |
|
|
| 38. |
- Emami, N., et al.
(författare)
-
Effect of light power density variations on bulk curing properties of dental composites
- 2003
-
Ingår i: Journal of Dentistry. - : Elsevier BV. - 0300-5712 .- 1879-176X. ; 31:3, s. 189-196
-
Tidskriftsartikel (refereegranskat)abstract
- Objective. The hypothesis that low light intensity and long but sufficient curing time can produce composites with volumetric shrinkage, degree of conversion (DC%) and Young's modulus (E-modulus) comparable to those of high light intensity cured composite was tested, when the contraction strain and heat generation were lower with Low Light intensity curing. Methods. Dental composites (Z100 and Z250, 3M ESPE) were investigated. Specimens were cured with Light intensities of 200, 450 and 800 mW/cm(2) for 140, 60 and 35 s from a distance of 7 mm. Strain-gages were used for contraction strain measurements. DC% was measured at the top and the bottom of 4 mm thick samples using FT-Raman spectroscopy. Volumetric polymerization shrinkage was determined using a water displacement method. E-modulus was determined in tension on composite specimens. Results. The results were analyzed using ANOVA and Duncan's multiple range tests and regular t-test. Polymerization stress Level decreased significantly (p < 0.05) when cured with 200 mW/cm(2) rather than with 800 mW/cm(2). Temperature rises were significantly different (p < 0.05) for different composites and light intensity values. Reduction in light intensity did not decrease the DC% values significantly at the top surfaces. The most dramatic differences existed between top and bottom surfaces (p < 0.05) rather than among curing groups. Measured E-modulus and volumetric shrinkage values were not significantly different (p > 0.05) between different light intensity groups. Conclusion. DC%, E-modulus and the volumetric shrinkage values in cured composites were not affected by low Light intensity, however, the contraction strain and polymerization's exotherm were decreased. Thus our results support the proposed hypothesis. Published by Elsevier Science Ltd.
|
|
| 39. |
|
|
| 40. |
|
|
| 41. |
|
|
| 42. |
|
|
| 43. |
- Hessmo, B., et al.
(författare)
-
Entangled states in interferometry
- 2002
-
Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 101:1, s. 37-46
-
Tidskriftsartikel (refereegranskat)abstract
- We show how some entangled quantum states can be used to improve interferometric measurements. We describe why Schrodinger-cat states are very sensitive to relative-phase shifts and why relative-phase states as described by A. Luis and L.L. Sanchez-Soto resolve the interval [0, 2pi] well. We also describe how the quantum concept of well-defined relative-phase and the classical visibility of an interference pattern are related.
|
|
| 44. |
- Klimov, A. B., et al.
(författare)
-
Distance-based degrees of polarization for a quantum field
- 2005
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 72:3
-
Tidskriftsartikel (refereegranskat)abstract
- It is well established that unpolarized light is invariant with respect to any SU(2) polarization transformation. This requirement fully characterizes the set of density matrices representing unpolarized states. We introduce the degree of polarization of a quantum state as its distance to the set of unpolarized states. We use two different candidates of distance, namely the Hilbert-Schmidt and the Bures metric, showing that they induce fundamentally different degrees of polarization. We apply these notions to relevant field states and we demonstrate that they avoid some of the problems arising with the classical definition.
|
|
| 45. |
- Nyholm, R., et al.
(författare)
-
ELECTRONIC AND STRUCTURAL-PROPERTIES OF THE CU-BI2CASR2CU2O8 INTERFACE
- 1991
-
Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 180:1-4, s. 120-123
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of the Cu-Bi2CaSr2Cu2O8 interface has been studied by photoelectron spectroscopy using synchrotron radiation. Photon energies in the range 20-1000 eV were utilized in order to probe both the valence band and to monitor chemical changes upon Cu deposition, as revealed by the core-level shifts. A strong chemical reaction between Bi2CaSr2CuO8 and Cu is manifested by the formation of metallic Bi. From the intensity variations as a function of electron emission angle it is shown that the metallic Bi segregates to the top surface layer.
|
|
| 46. |
- Nyholm, R., et al.
(författare)
-
SYNCHROTRON-RADIATION SOFT-X-RAY PHOTOEMISSION-STUDY OF LEAD ON BI2CASR2CU2O8
- 1992
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 46:10, s. 6488-6494
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a study of the interaction of Pb with a clean single-crystal Bi2CaSr2Cu2O8 superconductor surface based on photoemission and low-energy electron diffraction (LEED). Deposition of Pb on a Bi2CaSr2Cu2O8 Crystal kept at room temperature gives rise to the formation of metallic Bi and oxidized Pb at the interface. This behavior could not be observed when the crystal was kept at 100 K during Pb deposition. For all investigated Pb overlayers on a cold crystal (100 K), surface-sensitive photoelectron spectroscopy revealed the growth of a covering metallic Pb overlayer film. The growth at 100 K, contrary to the growth at room temperature, preserved the original LEED 5 X 1 pattern even for Pb depositions corresponding to a 24-angstrom thick overlayer indicating epitaxial growth. Furthermore, a rigid 0.4-eV shift of the valence band and the Bi 5d core levels is observed upon initial Pb deposition and is tentatively attributed to electron doping.
|
|
| 47. |
- Qvarford, M, et al.
(författare)
-
Doping dependence of the O 1s is core-level photoemission in bi-Sr-Ca-Cu-O superconductors
- 1996
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 53:22, s. 14753-14756
-
Tidskriftsartikel (refereegranskat)abstract
- The O 1s core level of three different Bi-Sr-Ca-Cu-O superconductors has been studied by means of high-resolution x-ray-photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS). The O 1a XPS spectra could be decomposed into three components that were unambiguously assigned to the emission from the three different oxide layers in the crystal structure. These are, in order of increasing binding energy, Cu-O-2, Sr-O, and Bi-O. Furthermore, the component assigned to the Cu-O-2 layers exhibits a shift which depends on the hole doping as monitored by the XAS spectra.
|
|
| 48. |
- Qvarford, M, et al.
(författare)
-
Photoemission and x-ray absorption study of superconducting and semiconducting Ba1-xKxBiO3 single crystals
- 1996
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 54:9, s. 6700-6707
-
Tidskriftsartikel (refereegranskat)abstract
- Semiconducting Ba0.9K0.1BiO3 and superconducting Ba0.6K0.4BiO3 single crystals cleaved in situ have been studied by core level and valence band photoelectron spectroscopy and O K edge x-ray absorption spectroscopy. It was found that the general shape of the valence band spectrum agrees with the shape predicted by band structure calculations, but the intensity near the Fermi level, was lower in the experimental spectrum as compared to the calculated. The O K edge spectra showed that the metallic phase is not related to the presence of doping inducted O 2p holes. This property of Ba1-xKxBiO3 shows that the semiconductor-metal transition of this system is of a different nature than that of the hole doped cuprate high-T-c superconductors. The core level photoemission spectra of the cations showed a small asymmetry for Ba0.9K0.1BiO3. Corresponding spectra for Ba0.6K0.4BiO3 showed a larger asymmetry resulting in a resolved high binding energy shoulder in the Bi 4f spectrum. The origin of this feature is discussed.
|
|
| 49. |
|
|
| 50. |
- QVARFORD, M, et al.
(författare)
-
X-RAY-ABSORPTION AND RESONANT-PHOTOEMISSION STUDY OF CA IN THE HIGH-TEMPERATURE SUPERCONDUCTOR BI2SR2CACU2O8
- 1992
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 46:21, s. 14126-14133
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of Ca in the high-temperature superconductor Bi2Sr2CaCu2O8 has been studied by x-ray-absorption spectroscopy and resonant-photoemission at the Ca L2,3 absorption edge. In the x-ray-absorption spectrum no edge structure is seen at the energy corresponding to the Ca 2p3/2 core-level binding energy, in agreement with the very low Ca density of states at the Fermi level predicted by band-structure calculations. Furthermore, the crystal-field splitting of the Ca 3d level, which is characteristic of ionic Ca compounds, is clearly observed in the x-ray-absorption spectrum. The photoemission spectra display strong resonant enhancements of the Ca 3s and 3p core levels as well as strong changes in the intensity and the line shape of the Ca L2,3M2,3M2,3 Auger structure at the Ca L2,3 threshold, showing the localized nature of the 3d states in core ionized Ca. The 3d induced spectator shift of the Ca L2,3M2,3M2,3 complex is fairly small as compared to what has been reported for CaF2, indicating that the screening of the normal Auger final state by the charge carriers in the surrounding Cu-O2 layers is quite efficient. From the Ca L2,3M2,3M2,3 data it is also suggested that, at the Ca L2 threshold, the excited 3d electron participates in a Coster-Kronig-type decay resulting in a 2p3/2 core hole followed by a normal L3M2,3M2,3 Auger decay.
|
|
