| 1. |
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| 2. |
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| 3. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 4. |
- Albani, Giorgia, et al.
(författare)
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Evolution in boron-based GEM detectors for diffraction measurements : From planar to 3D converters
- 2016
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Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 27:11
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Tidskriftsartikel (refereegranskat)abstract
- The so-called '3He-crisis' has motivated the neutron detector community to undertake an intense R&D programme in order to develop technologies alternative to standard 3He tubes and suitable for neutron detection systems in future spallation sources such as the European spallation source (ESS). Boron-based GEM (gas electron multiplier) detectors are a promising '3He-free' technology for thermal neutron detection in neutron scattering experiments. In this paper the evolution of boron-based GEM detectors from planar to 3D converters with an application in diffraction measurements is presented. The use of 3D converters coupled with GEMs allows for an optimization of the detector performances. Three different detectors were used for diffraction measurements on the INES instrument at the ISIS spallation source. The performances of the GEM-detectors are compared with those of conventional 3He tubes installed on the INES instrument. The conceptual detector with the 3D converter used in this paper reached a count rate per unit area of about 25% relative to the currently installed 3He tube. Its timing resolution is similar and the signal-to-background ratio (S/B) is 2 times lower.
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| 5. |
- Bakoglidis, Konstantinos, et al.
(författare)
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Rolling performance of carbon nitride-coated bearing components in different lubrication regimes
- 2017
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Ingår i: Tribology International. - : Pergamon Press. - 0301-679X .- 1879-2464. ; 114, s. 141-151
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Tidskriftsartikel (refereegranskat)abstract
- The performance of carbon nitride (CN) coated roller bearings is investigated, using a micropitting rig. The rolling performance is evaluated using Stribeck test, with a continuously varying rolling speed (0.2 - 2 m/s). Rolling contact fatigue tests with constant speeds (0.5, 1, 2, and 3.5 m/s) are also conducted in order to study the high-cycle performance of the rollers. The obtained Stribeck curve shows that the presence of coatings eliminates run-in, resulting in low friction coefficients (similar to 0.08). Raman spectroscopy, performed at the wear tracks, reveals that CNx maintain stable chemical state. Coatings show abrasion although the wear rate is not detrimental for the performance of the rollers, since a CNx to-steel contact is retained during the entire rolling contact fatigue test.
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| 6. |
- Berggren Newton, Benny
(författare)
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Business Basics : A Grounded Theory for Managing Ethical Behavior in Sales Organizations
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Managing co-workers’ ethical behavior in sales organizations is a complex social process. To start, sales organizations incorporate several actors to manage, often simultaneously, all with their own agendas. Ethics as a topic is convoluted because it encompasses context-based scenarios which may not have clear-cut right and wrong answers. The management process is an ongoing task managers deal with on daily basis, where mismanagement can lead to severe consequences. The majority of existing research on this area tends to focus on single factors in the management process, not the whole process. While there are some research studies that presents models or integrated frameworks describing the management process, they are few in number.Aim: The aim of this study is to derive empirical concepts and thereby try to develop a theory to facilitate an understanding of the process of managing co-workers’ ethical behavior, where the purpose is to ultimately build an integrated framework. More specifically, this study aims to describe the involved actors’ main concerns and the process by which these are continuously resolved.Methodology: In order to achieve the aim, a method with an inductive approach was necessary. The orthodox Grounded Theory methodology was chosen as research approach since it can generate conceptualizations in an integrated framework which help explain the occurring social processes. Working from this approach means that the researcher develops a new theory that is grounded in empirical data, where the researcher inductively describes the social process. The empirical data was mainly derived from interviews with actors within the field. The data was collected, coded and conceptualized in an overlapping procedure until an empirically derived theory emerged After the emergence of the theory, the empirical data was validated with existing academic literature.Findings: The core category in this study is Business Basics and concerns the desire to continuously conduct business where the management of ethical behavior is a fundamental basis to achieve this. Five distinct categories, all related to the core category were revealed: Bureaucratization, Relationship Investing, Educationing, Monetary Managing and Intuiting. These categories are expressed in social and dynamic processes. They represent different activities, tools, influences and practices that managers can adopt in order to reach their main concern.Contribution: As a contribution, this dissertation provides an integrated framework based on the actors own subjective experiences, describing the dynamic and social processes of managing co-workers ethical behavior in sales organizations.
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| 7. |
- Brosché, Johan, 1978-, et al.
(författare)
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Nio punkter för global fred (Nine Points for Global Peace)
- 2015
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Annan publikation (populärvet., debatt m.m.)abstract
- Insatserna för global fred måste stärkas skriver tolv företrädare för institutionen för freds- och konfliktforskning apropå att världens ledare samlas i dag i New York för att anta 17 nya globala mål för en bättre värld och mer hållbar utveckling.
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| 8. |
- Chen, J. T., et al.
(författare)
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A GaN-SiC hybrid material for high-frequency and power electronics
- 2018
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 113:4
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that 3.5% in-plane lattice mismatch between GaN (0001) epitaxial layers and SiC (0001) substrates can be accommodated without triggering extended defects over large areas using a grain-boundary-free AlN nucleation layer (NL). Defect formation in the initial epitaxial growth phase is thus significantly alleviated, confirmed by various characterization techniques. As a result, a high-quality 0.2-μm thin GaN layer can be grown on the AlN NL and directly serve as a channel layer in power devices, like high electron mobility transistors (HEMTs). The channel electrons exhibit a state-of-the-art mobility of >2000 cm2/V-s, in the AlGaN/GaN heterostructures without a conventional thick C- or Fe-doped buffer layer. The highly scaled transistor processed on the heterostructure with a nearly perfect GaN-SiC interface shows excellent DC and microwave performances. A peak RF power density of 5.8 W/mm was obtained at VDSQ= 40 V and a fundamental frequency of 30 GHz. Moreover, an unpassivated 0.2-μm GaN/AlN/SiC stack shows lateral and vertical breakdowns at 1.5 kV. Perfecting the GaN-SiC interface enables a GaN-SiC hybrid material that combines the high-electron-velocity thin GaN with the high-breakdown bulk SiC, which promises further advances in a wide spectrum of high-frequency and power electronics.
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| 9. |
- de Zwarte, Sonja M. C., et al.
(författare)
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Intelligence, educational attainment, and brain structure in those at familial high-risk for schizophrenia or bipolar disorder
- 2022
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Ingår i: Human Brain Mapping. - : John Wiley & Sons. - 1065-9471 .- 1097-0193. ; 43:1, s. 414-430
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Tidskriftsartikel (refereegranskat)abstract
- First-degree relatives of patients diagnosed with schizophrenia (SZ-FDRs) show similar patterns of brain abnormalities and cognitive alterations to patients, albeit with smaller effect sizes. First-degree relatives of patients diagnosed with bipolar disorder (BD-FDRs) show divergent patterns; on average, intracranial volume is larger compared to controls, and findings on cognitive alterations in BD-FDRs are inconsistent. Here, we performed a meta-analysis of global and regional brain measures (cortical and subcortical), current IQ, and educational attainment in 5,795 individuals (1,103 SZ-FDRs, 867 BD-FDRs, 2,190 controls, 942 schizophrenia patients, 693 bipolar patients) from 36 schizophrenia and/or bipolar disorder family cohorts, with standardized methods. Compared to controls, SZ-FDRs showed a pattern of widespread thinner cortex, while BD-FDRs had widespread larger cortical surface area. IQ was lower in SZ-FDRs (d = -0.42, p = 3 × 10-5 ), with weak evidence of IQ reductions among BD-FDRs (d = -0.23, p = .045). Both relative groups had similar educational attainment compared to controls. When adjusting for IQ or educational attainment, the group-effects on brain measures changed, albeit modestly. Changes were in the expected direction, with less pronounced brain abnormalities in SZ-FDRs and more pronounced effects in BD-FDRs. To conclude, SZ-FDRs and BD-FDRs show a differential pattern of structural brain abnormalities. In contrast, both had lower IQ scores and similar school achievements compared to controls. Given that brain differences between SZ-FDRs and BD-FDRs remain after adjusting for IQ or educational attainment, we suggest that differential brain developmental processes underlying predisposition for schizophrenia or bipolar disorder are likely independent of general cognitive impairment.
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| 10. |
- de Zwarte, Sonja M. C., et al.
(författare)
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The association between familial risk and brain abnormalities is disease specific : an ENIGMA-relatives study of schizophrenia and bipolar disorder
- 2019
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Ingår i: Biological Psychiatry. - : Elsevier. - 0006-3223 .- 1873-2402. ; 86:7, s. 545-556
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Schizophrenia and bipolar disorder share genetic liability, and some structural brain abnormalities are common to both conditions. First-degree relatives of patients with schizophrenia (FDRs-SZ) show similar brain abnormalities to patients, albeit with smaller effect sizes. Imaging findings in first-degree relatives of patients with bipolar disorder (FDRs-BD) have been inconsistent in the past, but recent studies report regionally greater volumes compared with control subjects.METHODS: We performed a meta-analysis of global and subcortical brain measures of 6008 individuals (1228 FDRs-SZ, 852 FDRs-BD, 2246 control subjects, 1016 patients with schizophrenia, 666 patients with bipolar disorder) from 34 schizophrenia and/or bipolar disorder family cohorts with standardized methods. Analyses were repeated with a correction for intracranial volume (ICV) and for the presence of any psychopathology in the relatives and control subjects.RESULTS: FDRs-BD had significantly larger ICV (d = +0.16, q < .05 corrected), whereas FDRs-SZ showed smaller thalamic volumes than control subjects (d = -0.12, q < .05 corrected). ICV explained the enlargements in the brain measures in FDRs-BD. In FDRs-SZ, after correction for ICV, total brain, cortical gray matter, cerebral white matter, cerebellar gray and white matter, and thalamus volumes were significantly smaller; the cortex was thinner (d < -0.09, q < .05 corrected); and third ventricle was larger (d = +0.15, q < .05 corrected). The findings were not explained by psychopathology in the relatives or control subjects.CONCLUSIONS: Despite shared genetic liability, FDRs-SZ and FDRs-BD show a differential pattern of structural brain abnormalities, specifically a divergent effect in ICV. This may imply that the neurodevelopmental trajectories leading to brain anomalies in schizophrenia or bipolar disorder are distinct.
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| 11. |
- Fjelde, Hanne, 1978-, et al.
(författare)
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Introducing the Ethnic One-Sided Violence Dataset
- 2021
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Ingår i: Conflict Management and Peace Science. - : SAGE Publications. - 0738-8942 .- 1549-9219. ; 38:1, s. 109-126
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Tidskriftsartikel (refereegranskat)abstract
- This article introduces the Ethnic One-Sided Violence dataset (EOSV) that provides information on the ethnic identity of civilian victims of direct and deliberate killings by state and non-state actors from 1989 to 2013. The EOSV dataset disaggregates the civilian victims in the one-sided violence dataset from the Uppsala Conflict Data Program by identifying which ethnic group they belong to, using the list of politically relevant ethnic groups from the Ethnic Power Relations data. By providing information on the ethnic targets of violence, EOSV enables researchers to explore new questions about the logic and dynamics of violence against civilians.
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| 12. |
- Ganna, Andrea, et al.
(författare)
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Utilizing Twins as Controls for Non-Twin Case-Materials in Genome Wide Association Studies
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:12, s. e83101-
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Tidskriftsartikel (refereegranskat)abstract
- Twin registries around the globe have collected DNA samples from large numbers of monozygotic and dizygotic twins. The twin sample collections are frequently used as controls in disease-specific studies together with non-twins. This approach is unbiased under the hypothesis that twins and singletons are comparable in terms of allele frequencies; i.e. there are no genetic variants associated with being a twin per se. To test this hypothesis we performed a genome-wide association study comparing the allele frequency of 572,352 single nucleotide polymorphisms (SNPs) in 1,413 monozygotic (MZ) and 5,451 dizygotic (DZ) twins with 3,720 healthy singletons. Twins and singletons have been genotyped using the same platform. SNPs showing association with being a twin at P-value < 1 × 10-5 were selected for replication analysis in 1,492 twins (463 MZ and 1,029 DZ) and 1,880 singletons from Finland. No SNPs reached genome-wide significance (P-value < 5 × 10-8) in the main analysis combining MZ and DZ twins. In a secondary analysis including only DZ twins two SNPs (rs2033541 close to ADAMTSL1 and rs4149283 close to ABCA1) were genome-wide significant after meta-analysis with the Finnish population. The estimated proportion of variance on the liability scale explained by all SNPs was 0.08 (P-value=0.003) when MZ and DZ were considered together and smaller for MZ (0.06, P-value=0.10) compared to DZ (0.09, P-value=0.003) when analyzed separately. In conclusion, twins and singletons can be used in genetic studies together with general population samples without introducing large bias. Further research is needed to explore genetic variances associated with DZ twinning.
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| 13. |
- Greczynski, Grzegorz, et al.
(författare)
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X-ray photoelectron spectroscopy of thin films
- 2023
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Ingår i: NATURE REVIEWS METHODS PRIMERS. - : SPRINGERNATURE. - 2662-8449. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectroscopy (XPS) is a popular analytical technique in materials science as it can assess the surface chemistry of a broad range of samples. This Primer concerns best practice in XPS analysis, aimed at both entry-level and advanced users, with a focus on thin film samples synthesized under vacuum conditions. The high surface to volume ratio of thin films means that factors such as substrate choice and air exposure time are important for the final result. Essential concepts are introduced, such as binding energy, photoelectric effect, spectral referencing and chemical shift, as well as practical aspects including surface sensitivity, probing depth, energy resolution, sample handling and sputter etching. Correct procedures for experimental planning, instrument set-up, sample preparation, data acquisition, results analysis and presentation are reviewed in connection with physical principles and common applications. Typical problems, including charging, spectral overlap, sputter damage and binding energy referencing, are discussed along with possible solutions or workarounds. Finally, a workflow is presented for arriving at high-quality results. X-ray photoelectron spectroscopy (XPS) can be used to investigate chemical bonding and elemental composition. This Primer discusses how XPS can be used to characterize thin films, including key considerations for sample preparation, experimental set-up and data analysis.
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| 14. |
- Havarinasab, Said, 1964-, et al.
(författare)
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Dose and Hg species determine the T-helper cell activation in murine autoimmunity
- 2007
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Ingår i: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 229:1-2, s. 23-32
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Tidskriftsartikel (refereegranskat)abstract
- Inorganic mercury (mercuric chloride-HgCl2) induces in mice an autoimmune syndrome (HgIA) with T cell-dependent polyclonal B cell activation and hypergammaglobulinemia, dose- and H-2-dependent production of autoantibodies targeting the 34 kDa nucleolar protein fibrillarin (AFA), and systemic immune-complex deposits. The organic mercury species methylmercury (MeHg) and ethylmercury (EtHg-in the form of thimerosal) induce AFA, while the other manifestations of HgIA seen after treatment with HgCl2 are present to varying extent. Since these organic Hg species are converted to the autoimmunogen Hg2+ in the body, their primary autoimmunogen potential is uncertain and the subject of this study. A moderate dose of HgCl2 (8 mg/L drinking water - internal dose 148 μg Hg/kg body weight [bw]/day) caused the fastest AFA response, while the induction was delayed after higher (25 mg/L) and lower (1.5 and 3 mg/L) doses. The lowest dose of HgCl2 inducing AFA was 1.5 mg/L drinking water which corresponded to a renal Hg2+ concentration of 0.53 μg/g. Using a dose of 8 mg HgCl2/L this threshold concentration was reached within 24 h, and a consistent AFA response developed after 8-10 days. The time lag for the immunological part of the reaction leading to a consistent AFA response was therefore 7-9 days. A dose of thimerosal close to the threshold dose for induction of AFA (2 mg/L drinking water-internal dose 118 μg Hg/kg bw per day), caused a renal Hg2+ concentration of 1.8 μg/g. The autoimmunogen effect of EtHg might therefore be entirely due to Hg2+ formed from EtHg in the body. The effect of organic and inorganic Hg species on T-helper type 1 and type 2 cells during induction of AFA was assessed as the presence and titre of AFA of the IgG1 and IgG2a isotype, respectively. EtHg induced a persistent Th1-skewed response irrespectively of the dose and time used. A low daily dose of HgCl2 (1.5-3 mg/L) caused a Th1-skewed AFA response, while a moderate dose (8 mg/L) after 2 weeks resulted in a balanced or even Th2-skewed response. Higher daily doses of HgCl2 (25 mg/L) caused a balanced Th2-Th1 response already from onset. In conclusion, while metabolically formed Hg2+ might be the main AFA-inducing factor also after treatment with EtHg, the quality of the Hg-induced AFA response is modified by the species of Hg as well as the dose. © 2006 Elsevier Ireland Ltd. All rights reserved.
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| 15. |
- Havarinasab, Said, et al.
(författare)
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Dose and Hg species determine the T-helper cell activation in murine autoimmunity.
- 2007
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Ingår i: Toxicology. - 0300-483X. ; 229:1-2, s. 23-32
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Tidskriftsartikel (refereegranskat)abstract
- Inorganic mercury (mercuric chloride--HgCl(2)) induces in mice an autoimmune syndrome (HgIA) with T cell-dependent polyclonal B cell activation and hypergammaglobulinemia, dose- and H-2-dependent production of autoantibodies targeting the 34 kDa nucleolar protein fibrillarin (AFA), and systemic immune-complex deposits. The organic mercury species methylmercury (MeHg) and ethylmercury (EtHg--in the form of thimerosal) induce AFA, while the other manifestations of HgIA seen after treatment with HgCl(2) are present to varying extent. Since these organic Hg species are converted to the autoimmunogen Hg(2+) in the body, their primary autoimmunogen potential is uncertain and the subject of this study. A moderate dose of HgCl(2) (8 mg/L drinking water--internal dose 148 micro gHg/kg body weight [bw]/day) caused the fastest AFA response, while the induction was delayed after higher (25 mg/L) and lower (1.5 and 3 mg/L) doses. The lowest dose of HgCl(2) inducing AFA was 1.5 mg/L drinking water which corresponded to a renal Hg(2+) concentration of 0.53 micro g/g. Using a dose of 8 mg HgCl(2)/L this threshold concentration was reached within 24 h, and a consistent AFA response developed after 8-10 days. The time lag for the immunological part of the reaction leading to a consistent AFA response was therefore 7-9 days. A dose of thimerosal close to the threshold dose for induction of AFA (2 mg/L drinking water--internal dose 118 micro gHg/kg bw per day), caused a renal Hg(2+) concentration of 1.8 micro g/g. The autoimmunogen effect of EtHg might therefore be entirely due to Hg(2+) formed from EtHg in the body. The effect of organic and inorganic Hg species on T-helper type 1 and type 2 cells during induction of AFA was assessed as the presence and titre of AFA of the IgG1 and IgG2a isotype, respectively. EtHg induced a persistent Th1-skewed response irrespectively of the dose and time used. A low daily dose of HgCl(2) (1.5-3 mg/L) caused a Th1-skewed AFA response, while a moderate dose (8 mg/L) after 2 weeks resulted in a balanced or even Th2-skewed response. Higher daily doses of HgCl(2) (25 mg/L) caused a balanced Th2-Th1 response already from onset. In conclusion, while metabolically formed Hg(2+) might be the main AFA-inducing factor also after treatment with EtHg, the quality of the Hg-induced AFA response is modified by the species of Hg as well as the dose.
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| 16. |
- Havarinasab, Said, et al.
(författare)
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Immunosuppressive and autoimmune effects of thimerosal in mice
- 2005
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Ingår i: TOXICOLOGY AND APPLIED PHARMACOLOGY. - : Elsevier BV. - 0041-008X. ; 204:2, s. 109-21
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Tidskriftsartikel (refereegranskat)abstract
- The possible health effects of the organic mercury compound thimerosal (ethylmercurithiosalicylate), which is rapidly metabolized to ethylmercury (EtHg), have recently been much debated and the effect of this compound on the immune system is largely unknown. We therefore studied the effect of thimerosal by treating A.SW (H-2(s)) mice, susceptible to induction of autoimmunity by heavy metals, with 10 mg thimerosal/L drinking water (internal dose ca 590 mu g Hg/kg body weight/day) for up to 30 days. The lymph node expression of IL-2 and IL-15 mRNA was increased after 2 days, and of IL-4 and IFN-gamma rnRNA after 6 and 14 days. During the first 14 days treatment, the number of splenocytes, including T and B cells as well as Ig-secreting cells decreased. A strong immunostimulation superseded after 30 days treatment xvith increase in splenic weight, number of splenocytes including T and B cells and Ig-secreting cells, and Th2- as well as Th-l-dependent serum immunoglobulins. Antinucleolar antibodies (ANoA) targeting the 34-kDa nucleolar protein fibrillarin, and systemic immune-complex deposits developed. The H-2(s) strains SJL and B10.S also responded to thimerosal treatment with ANoA. The A.TL and B10.TL strain, sharing background genes with the A.SW and B10.S strain, respectively, but with a different H-2 haplotype (tl), did not develop ANoA, linking the susceptibility to H-2. Thimerosal-treated H-2(s) mice homozygous for the nu mutation (SJL-nu/nu), or lacking the T-cell costimulatory molecule CD28 (B10.S-CD28(-/-)), did not develop ANoA, which showed that the autoimmune response is T-cell dependent. Using H-2(s) strains with targeted mutations, we found that IFN-gamma and IL-6, but not IL-4, is important for induction of ANoA by thimerosal. The maximum added renal concentration of thimerosal (EtHg) and inorganic mercury occurred after 14 days treatment and was 8 1 mu g Hg/g. EtHg made tip 59% and inorganic mercury 41% of the renal mercury. In conclusion, the organic mercury compound thimerosal (EtHg) has initial immunosuppressive effects similar to those of MeHg. However, in contrast to MeHg, thimerosal treatment leads in genetically susceptible mice to a second phase with strong immunostimulation and autoimmunity, which is T-cell dependent, H-2 linked and may at least partly be due to the inorganic mercury derived from the metabolism of ethyl mercury.
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| 17. |
- Havarinasab, Said, 1964-, et al.
(författare)
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Mercury species in lymphoid and non-lymphoid tissues after exposure to methyl mercury: Correlation with autoimmune parameters during and after treatment in susceptible mice
- 2007
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 221:1, s. 21-8
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Tidskriftsartikel (refereegranskat)abstract
- Methylmercury (MeHg) is present in the environment as a result of the global cycling of mercury, although anthropogenic sources may dramatically increase the availability in confined geographical areas. Accumulation of MeHg in the aquatic food chain is the dominating way of exposure in mammals, which accumulate MeHg in all organs, including the brain. Demethylation has been described in the organs, especially in phagocytic cells, but mainly in the flora of the intestinal tract. While most of the inorganic mercury (Hg2+) formed in the intestine is excreted, a fraction is reabsorbed which together with the local demethylation increases the organ Hg2+ concentration. MeHg is a well-known immunosuppressive agent, while Hg2+ is associated with immunostimulation and autoimmunity especially in genetically susceptible rodents, creating a syndrome, i.e. mercury-induced autoimmunity (HgIA). This study aimed at exploring the effect of MeHg with regard to HgIA, and especially the immunological events after stopping treatment, correlated with the presence of MeHg and Hg2+ in the organs.Treatment of A.SW mice for 30 days with 4.2 mg MeHg/L drinking water (corresponding to approximately 420 μg Hg/kg body weight/day) caused all the HgIA features observed after primary treatment with inorganic Hg, except systemic immune complex deposits. The total Hg concentration was 5-fold higher in the kidneys as compared with lymph nodes, but the fraction of Hg2+ was similar (17–20%). After stopping treatment, the renal and lymph node MeHg concentration declined according to first order kinetics during the initial 4–6 weeks, but then slower. A similar decline in the organ Hg2+ concentration occurred during the initial 2 weeks after stopping treatment but then ceased, causing the Hg2+ concentration to exceed that of MeHg in the lymph nodes and kidneys after 3 and 8 weeks, respectively. The selective increase in lymph node Hg2+ fraction is likely to be due to demethylation of MeHg in the macrophage-rich lymphoid tissue. The major autoantibody in HgIA, anti-fibrillarin antibodies, tended to increase during the initial 6 weeks after stopping treatment, while all other HgIA features including antichromatin antibodies declined to control levels after 2–4 weeks. This indicates differences in either dose requirement or induction mechanisms for the different HgIA parameters.The selective accumulation of Hg2+ in lymph nodes following MeHg treatment should be taken into account when the effect of MeHg on the immune system is evaluated.
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| 18. |
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| 19. |
- Heir, Trond, et al.
(författare)
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Tsunami-affected Scandinavian tourists : Disaster exposure and post-traumatic stress symptoms
- 2011
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Ingår i: Nordic Journal of Psychiatry. - : Informa UK Limited. - 0803-9488 .- 1502-4725. ; 65:1, s. 9-15
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Tidskriftsartikel (refereegranskat)abstract
- Background: Studies of short- and long-term mental effects of natural disasters have reported a high prevalence of post-traumatic stress. Less is known about disaster-exposed tourists repatriated to stable societies. Aims: To examine the association between exposure to the 2004 Southeast Asian tsunami and symptoms of post-traumatic stress in three Scandinavian tourist populations. Methods: Postal survey of Norwegian, Danish and Swedish Southeast Asia tourists registered by the police when arriving at national airports. Follow-up time was 6 (Norway), 10 (Denmark) and 14 months (Sweden) post-disaster; 6772 individuals were included and categorized according to disaster exposure: danger exposed (caught or chased by the waves), non-danger exposed (other disaster-related stressors) and non-exposed. Outcome measures were the Impact of Event Scale-Revised (IES-R) and Post Traumatic Stress Disorder Check List (PCL). Results: Danger exposed reported more post-traumatic stress than non-danger exposed, and the latter reported more symptoms than non-exposed (each P<0.001). Comparison of the Norwegian and Swedish data suggested that symptoms were attenuated at 14 months follow-up (P<0.001). Female gender and low education, but not age, predicted higher levels of symptoms. Conclusions: Disaster-exposed tourists repatriated to unaffected home environments show long-term post-traumatic stress disorder symptoms related to the severity of exposure.
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| 20. |
- Hsu, Chih-Wei, et al.
(författare)
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Controlled Growth of GaN Pyramidal template hosting InGaN Quantum Dots
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The emission properties of InGaN grown on hexagonal GaN pyramids with various pitch distances (PD) are studied. Emissions associated with InGaN quantum wells (QWs) and InGaN quantum dots (QDs) can be identified. The emission energies of InGaN QWs and QDs shift toward opposite directions with increasing PD; red-shift for QWs and blue-shift for QDs. Based on the source supply mechanism in a selective area growth process, the formation of InGaN QDs on GaN pyramids is believed to be a combined effect of Stranski-Krastanow growth mode and spinodal decomposition taking place at the microscopic (0001) surfaces on GaN pyramids.
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| 21. |
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| 22. |
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| 23. |
- Hultman, Erik, et al.
(författare)
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A cable feeder tool for robotized cable winding
- 2014
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Ingår i: Robotics and Computer-Integrated Manufacturing. - : Elsevier BV. - 0736-5845 .- 1879-2537. ; 30:6, s. 577-588
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Tidskriftsartikel (refereegranskat)abstract
- Cable winding is an alternative technology to create stator windings in large electrical machines. Today such cable winding is performed manually, which is very repetitive, time-consuming and therefore also expensive. This paper presents the design, function and control system of a developed cable feeder tool for robotized stator cable winding. The presented tool was able to catch a cable inside a cable guiding system and to grab the cable between two wheels. One of these wheels was used to feed cable through the feeder. A control system was integrated in the tool to detect feeding slippage and to supervise the feeding force on the cable. Functions to calculate the cable feed length, to release the cable from the tool and for positional calibration of the stator to be wound were also integrated in the tool. In validating the function of the cable feeder tool, the stator of the linear generator used in the Wave Energy Converter generator developed at Uppsala University was used as an example. Through these experiments, it was shown that the developed robot tool design could be used to achieve automated robotized cable winding. These results also complied with the cycle time assumptions for automated cable winding from earlier research. Hence, it was theoretically indicated that the total winding cycle time for one Uppsala University Wave Energy Converter stator could be reduced from about 80 h for manual winding with four personnel to less than 20 h in a fully developed cable winding robot cell. The same robot tool and winding automation could also be used, with minor adjustments, for other stator designs.
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| 24. |
- Hultman, Erik, et al.
(författare)
-
A robotized 6-DOF dry test rig for wave power
- 2023
-
Ingår i: Sustainable Energy Technologies and Assessments. - : Elsevier. - 2213-1388 .- 2213-1396. ; 59
-
Tidskriftsartikel (refereegranskat)abstract
- Wave power has the potential to contribute significantly to sustainability by reducing our global dependence on fossil fuels. Due to harsh conditions and high costs associated with offshore testing, lab experiments are favourable for resource-efficient validation and optimization in developing Wave Energy Converter (WEC) technologies. The limited scale and availability of existing wave tanks, and the limited flexibility of existing dry test rigs does however put significant restraints on such experiments. In this paper we introduce an alternative novel robotized dry test rig concept for wave power, evaluate its performance and discuss its potential. A full-scale robotized dry test rig demonstrator is constructed and used for experiments with a WEC prototype device. High motion flexibility and accuracy is thereby validated, also for repeating recorded wave and buoy motions. Compared to other dry test rigs, no special components were used and the motion trajectories were defined in full 6-Degrees-Of-Freedom. Two real-time hydrodynamic motion response methods are also demonstrated in the test rig, enabling emulation of actual offshore operation as well as development of advanced WEC control strategies. With a larger industrial robot manipulator, the introduced test rig concept could achieve realistic scaled force and power experiments with most point absorber WECs.
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| 25. |
- Hultman, Erik, et al.
(författare)
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An updated cable feeder tool design for robotized stator cable winding
- 2018
-
Ingår i: Mechatronics. - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 49, s. 197-210
-
Tidskriftsartikel (refereegranskat)abstract
- We have previously suggested a method for robotized stator winding of cable wound electric machines and demonstrated the method successfully in full-scale experiments. The cable feeder tool used to handle the cable during the complete winding process is an essential component of this robot cell. To take the robot winding method to the next level, into an industrial product, require further developments regarding durability, independency, flexibility and implementability. In this paper, we present an updated cable feeder tool design. This tool is designed to be used in a robot cell for cable winding of the third-generation design of the Uppsala University Wave Energy Converter generator stator. In this work, three cable feeder tool prototypes have been constructed, experimentally evaluated and validated for the intended application. Key performance parameters are presented and discussed, including suggestions for further developments. We completed a durable, compact, high performance tool design, with fully integrated control into industrial robot controllers. The experimental results presented in this article are very promising and hence, the updated cable feeder tool design represents another important step towards an industrial solution for robotized stator cable winding.
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| 26. |
- Hultman, Erik, et al.
(författare)
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Automated Cable Preparation for Robotized Stator Cable Winding
- 2017
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 5:2
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Tidskriftsartikel (refereegranskat)abstract
- A method for robotized cable winding of the Uppsala UniversityWave Energy Converter generator stator has previously been presented and validated. The purpose of this study is to present and validate further developments to the method: automated stand-alone equipment for the preparation of the winding cables. The cable preparation consists of three parts: feeding the cable from a drum, forming the cable end and cutting the cable. Forming and cutting the cable was previously done manually and only small cable drums could be handled. Therefore the robot cell needed to be stopped frequently. The new equipment was tested in an experimental robot stator cable winding setup. Through the experiments, the equipment was validated to be able to perform fully automated and robust cable preparation. Suggestions are also given on how to further develop the equipment with regards to performance, robustness and quality. Hence, this work represents another important step towards demonstrating completely automated robotized stator cable winding.
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| 27. |
- Hultman, Erik, et al.
(författare)
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Electromagnetic, Mechanical and Manufacturing Properties for Cable Wound Direct-Drive PM Linear Generators for Offshore Environments
- 2012
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Ingår i: Proceedings of the ASME 31st International Conference on Ocean, Offshore and Arctic Engineering, 2012, VOL 4. - 9780791844915 ; , s. 441-447
-
Konferensbidrag (refereegranskat)abstract
- Renewable energy conversion in offshore environments, such as wave, wind and tidal energy, can potentially give a considerable contribution to the global electric energy demand. These harsh environments require robust generators with minimal need for maintenance at competitive costs. To reduce the generator cost, the electromagnetic design must be done with manufacturing in mind. An optimal design provides high electric efficiency, long device life-time, little need for maintenance and low manufacturing costs. Modern simulation tools can be used to optimize the electromagnetic design of a generator for a specific task and operation mode. Hereby both electromagnetic losses and material stresses can be reduced. Industrial robots might provide new possibilities to automate generator-specific manufacturing tasks. A generator design with a cable wound stator, surface mounted permanent magnets on the translator and direct-drive linear technology is investigated in this article. This concept has a simpler and more robust mechanical design, while both the electromagnetic losses and the need for maintenance are reduced. By reducing the number of generator assembly steps, manufacturing might also be facilitated. Further work is however needed in developing automated assembly methods and comparing them to conventional generator manufacturing.
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| 28. |
- Hultman, Erik, et al.
(författare)
-
Integration of real-world project tasks in a course on automation and robot engineering
- 2019
-
Ingår i: IEEE Global Engineering Education Conference, EDUCON. - : Institute of Electrical and Electronics Engineers (IEEE). - 2165-9567 .- 2165-9559. ; April-2019, s. 107-114, s. 107-114
-
Konferensbidrag (refereegranskat)abstract
- © 2019 IEEE. The modern engineering profession requires classical technical skills combined with creativity and a high proficiency in cooperation and sustainable development. Research indicates that the engineering education should adapt better to this. This paper introduces a teaching approach where open-ended project tasks are fully integrated into a complete course, in a context relating to the students' future working life. The teaching approach was implemented in a course on automation and robot engineering. Extensive written student course evaluations, the students' examination results and the teachers' experience were used for evaluation and compared with the previous classical course. Both the students and the teachers greatly appreciated the course. It was strongly indicated that the students' theoretical knowledge and understanding of the subject had benefited, both with regards to the technical depth and to the non-technical engineering skills. It is likely that the presented teaching approach can be used also in other engineering courses.
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| 29. |
- Hultman, Erik
(författare)
-
Introducing robotized stator cable winding to rotating electric machines
- 2022
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 10:8
-
Tidskriftsartikel (refereegranskat)abstract
- Following environmental concerns and the rapid digitalization of our society, we are currently experiencing an extensive electrification and industrial revolution. High numbers of electric machines thus need to be assembled for varying applications, including vehicle propulsion and renewable energy conversion. Cable winding is an alternative stator winding technology for electric machines that has been utilized for such applications, so far in smaller series or in prototype machines. The presented work introduces the first concept for automated stator cable winding of rotating electric machines. This concept could enable higher production volumes of cable wound machines and a unique flexibility in handling different machines, in line with Industry 4.0. Robotized stator cable winding is evaluated here for five very different rotating machine designs, through simulations and analytical extrapolation of previous experimental winding results. Potential cycle time and assembly cost savings are indicated compared to manual and lower volume conventional automation, while it is not possible to compete in the present form with existing very high-volume conventional winding automation for smaller machines. Future experimental work is pointed out on handling larger winding cables and special machine designs, and on increased robustness and optimization.
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| 30. |
- Hultman, Erik, et al.
(författare)
-
Learnings from the rapid online transition of a real-world project task-based engineering course
- 2022
-
Ingår i: 2022 IEEE Frontiers in Education Conference (FIE). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665462457 - 9781665462440
-
Konferensbidrag (refereegranskat)abstract
- This Innovative Practice Full Paper presents the results and learnings from a rapid and forced transition to online teaching of a campus-based and practical lab exercise intense course in robot engineering. Founded in previous pedagogical development work, we continued with activating and varied teaching methods connected through integrated project tasks. The online transition is evaluated from student course evaluations, examination results and the teachers’ experiences from ten campus course occasions and four online course occasions during ten years. The paper focuses specifically on the combination of an innovative online lecturing format and fully virtual robot lab exercises. Our aim is to present learnings of interest for the engineering education community. The results highlight a successful and appreciated online course transition, with possibly improved student learning. In particular the prerecorded video lectures were praised, the virtual labs was similarly appreciated as campus labs and it was demonstrated that online robot programming can be performed virtually, while practical lab exercises and study visits were still missed.
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| 31. |
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| 32. |
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| 33. |
- Hultman, Erik
(författare)
-
Robotized Production Methods for Special Electric Machines
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A research project on renewable energy conversion from ocean waves to electricity was started at the Division of Electricity at Uppsala University (UU) in 2001. The Wave Energy Converter (WEC) unit developed in this project is intended to be used in large offshore WEC farms and has therefore been designed with large-scale production in mind. The concept has now also been commercialized by the spin-off company Seabased Industry AB.An essential part of the UU WEC is the linear direct-drive generator. This thesis presents the pilot work on developing robotized production methods for this special electric machine. The generator design is here investigated and four different backbreaking, monotone, potentially hazardous and time consuming manual production tasks are selected for automation. A robot cell with special automation equipment is then developed and constructed for each task. Simplicity, reliability and flexibility are prioritized and older model pre-owned industrial robots are used throughout the work. The robot cells are evaluated both analytically and experimentally, with focus on full scale experiments. It is likely that the developed production methods can be applied also for other similar electric machines.The main focus in the thesis is on robotized stator cable winding. The here presented robot cell is, to the knowledge of the author, the first fully automated stator cable winding setup. Fully automated winding with high and consistent quality and high flexibility is demonstrated. Significant potential cost savings compared to manual winding are also indicated. The robot cell is well prepared for production, but further work is required to improve its reliability.The other three developed robot cells are used for stator stacking, surface mounting of permanent magnets on translators and machining of rubber discs. All robot cell concepts are experimentally validated and considerable potential cost savings compared to manual production are indicated. Further work is however required with regards to autonomy and reliability.Finally, the thesis presents a pedagogical development work connected to the research on robotized production methods. A first cycle course on automation and robot engineering is here completely reworked, as it is structured around three real-world group project tasks. The new course is evaluated from the examination results, the students’ course evaluations and the feedback from the teachers during six years. The students greatly appreciated the new course. It is indicated that the developed teaching approach is effective in teaching both classical and modern engineering skills.
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| 34. |
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| 35. |
- Hultman, Erik, et al.
(författare)
-
Robotized stator cable winding
- 2018
-
Ingår i: Robotics and Computer-Integrated Manufacturing. - : Elsevier BV. - 0736-5845 .- 1879-2537. ; 53, s. 197-214
-
Tidskriftsartikel (refereegranskat)abstract
- Automated stator winding assembly has been available for small and medium sized conventional electric machines for a long time. Cable winding is an alternative technology developed for medium and large sized machines in particular. In this paper we present, evaluate and validate the first fully automated stator cable winding assembly equipment in detail. A full-scale prototype stator cable winding robot cell has been constructed, based on extensive previous work and experience, and used in the experiments. While the prototype robot cell is adapted for the third design generation of the Uppsala University Wave Energy Converter generator stator, the winding method can be adapted for other stator designs. The presented robot cell is highly flexible and well prepared for future integration in a smart production line. Potential cost savings are indicated compared to manual winding, which is a backbreaking task. However, further work is needed to improve the reliability of the robot cell, especially when it comes to preventing the kinking of the winding cable during the assembly.
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| 36. |
- Hultman, Erik, et al.
(författare)
-
Robotized Surface Mounting of Permanent Magnets
- 2014
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 2:4, s. 219-232
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Tidskriftsartikel (refereegranskat)abstract
- Using permanent magnets on a rotor can both simplify the design and increase the efficiency of electric machines compared to using electromagnets. A drawback, however, is the lack of existing automated assembly methods for large machines. This paper presents and motivates a method for robotized surface mounting of permanent magnets on electric machine rotors. The translator of the Uppsala University Wave Energy Converter generator is used as an example of a rotor. The robot cell layout, equipment design and assembly process are presented and validated through computer simulations and experiments with prototype equipment. A comparison with manual assembly indicates substantial cost savings and an improved work environment. By using the flexibility of industrial robots and a scalable equipment design, it is possible for this assembly method to be adjusted for other rotor geometries and sizes. Finally, there is a discussion on the work that remains to be done on improving and integrating the robot cell into a production line.
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| 37. |
- Hultman, Erik, et al.
(författare)
-
Six-Degrees-of-Freedom (6-DOF) Work Object Positional Calibration Using a Robot-Held Proximity Sensor
- 2013
-
Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 1:2, s. 63-80
-
Tidskriftsartikel (refereegranskat)abstract
- Industrial automation has been recognized as a fundamental key to build and keep manufacturing industries in developed countries. In most automation tasks, knowing the exact position of the objects to handle is essential. This is often done using a positional calibration system, such as a camera-based vision system. In this article, an alternative six-degrees-of-freedom work object positional calibration method using a robot-held proximity sensor, is presented. A general trigonometry-based measurement and calculation procedure, which, step-by-step, adjusts a work object coordinate system to the actual work object position, is explained. For suitable robot tasks and work object geometries, the benefits with the presented method include its robustness, large work area and low investment cost. Some drawbacks can be longer cycle time and its limited capacity to handle unsorted and complicated objects. To validate the presented method, it was implemented in an experimental robot setup. In this robot cell, it was used to calibrate the position of a stator section work object, which is used in the Uppsala University Wave Energy Converter generator. Hereby the function of the positional calibration procedure was validated. Sufficient positioning accuracy for the stator winding task was achieved and theoretically validated based on the experiments.
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| 38. |
- Hultman, Erik, et al.
(författare)
-
Utilizing cable winding and industrial robots to facilitate the manufacturing of electric machines
- 2013
-
Ingår i: Robotics and Computer-Integrated Manufacturing. - : Elsevier BV. - 0736-5845 .- 1879-2537. ; 29:1, s. 246-256
-
Tidskriftsartikel (refereegranskat)abstract
- Cable wound electric machines are used mainly for high voltage and direct-drive applications. They can be found in areas such as wind power, hydropower, wave power and high-voltage motors. Compared to conventional winding techniques, cable winding includes fewer manufacturing steps and is therefore likely to be better suited for automated production. Automation of the cable winding production step is a crucial task in order to lower the manufacturing costs of these machines. This article presents a production method using industrial robots for automation of cable winding of electric machine stators. The concept presented is validated through computer simulations and full-scale winding experiments, including a constructed robot-held cable feeder tool prototype. A cable wound linear stator section of an Uppsala University Wave Energy Converter and its winding process is used as a reference in this article. From this example, it is shown that considerable production cycle time and manufacturing cost savings can be anticipated compared to manual winding. The suggested automation method is very flexible. It can be used for the production of cable wound stators with different shapes and sizes, for different cable dimensions and with different winding patterns.
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| 39. |
- Hultman, Glenn, 1947-, et al.
(författare)
-
Avslutande reflektioner och slutsatser.
- 2004
-
Ingår i: Lärande och förändring i organisationer. Om pedagogik i arbetslivet.. - Lund : Studentlitteratur. - 9144035152 - 9789144035154 ; , s. 295-305
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- I fokus för denna antologi står frågor om lärande, förändring och ledarskap inom olika typer av verksamhet. Syftet är att bidra till en bred genomlysning av dessa begrepp utifrån såväl teoretiska som empiriska analyser. Vi vill härigenom försöka utmana vanligt förekommande uppfattningar om lärande, förändring och ledarskap. Framställningen baseras i stor utsträckning på egna studier som genomförts under de senaste åren. Dessa studier har i samtliga fall utgått från människors dagliga arbete i olika lokala verksamheter - inom företag, hälso- och sjukvård, omsorgsverksamhet och skola. De studier som redovisas speglar därmed också vardagen på arbetsplatser inom olika sektorer av svenskt arbetsliv. I flera av studierna har det också varit möjligt att studera dessa verksamheter över längre tid och på så sätt belysa de studerade processernas drivkrafter och inre dynamik. Boken kan användas som kurslitteratur vid universitet och högskolor samt som fördjupningslitteratur i anslutning till ledar- eller personalutbildningar. Den vänder sig också till forskare, politiker, företrädare för arbetsmarknadens parter samt praktiskt verksamma med intresse för frågor om lärande, kompetensutveckling och förändringsprocessser i organisationer.
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| 40. |
- Häggqvist, Bo, 1962-, et al.
(författare)
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The immunosuppressive effect of methylmercury does not preclude development of autoimmunity in genetically susceptible mice
- 2005
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Ingår i: TOXICOLOGY. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 208:1, s. 149-64
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Tidskriftsartikel (refereegranskat)abstract
- Methylmercury (MeHg) is a common environmental pollutant due to both natural and anthropogenic sources. Although the central nervous system (CNS) is considered the critical organ for the toxic effect of MeHg, it has recently been suggested that the immune system might be at least as sensitive as the CNS.We have examined the effects of MeHg on the immune system in genetically metal-susceptible mice. Subcutaneous (sc) injections of 2 mg MeHg/kg body weight (bw) every third day (internal dose ca. 540 μg Hg/kg bw/day) to A.SW mice of the H-2s haplotype, caused during the first week a 47 and 9% reduction of B- and T-cells, respectively, which indicates immunosuppression. Subsequently, an autoimmune syndrome developed which shared certain features with the syndrome induced by inorganic mercury in H-2s mice, including antibodies targeting the 34 kDa nucleolar protein fibrillarin, increased expression of IL-4 mRNA, increase of Th2-type of immunoglobulins (IgE and IgG1), and increased MHC class II expression on B-cells. However, the response using MeHg was attenuated compared with even lower doses of Hg in the form of inorganic mercury, and specifically lacked the increased expression of IL-2 and IFN-γ mRNA, the polyclonal B-cell activation (PBA), and the systemic immune-complex (IC) deposits which are induced by inorganic mercury. Increasing the dose of MeHg increased the titre of anti-nucleolar antibodies and shortened the induction time, but did not lead to stronger immunostimulation or systemic IC-deposits. The kidney and liver selectively accumulated MeHg, while the blood, spleen and lymph nodes showed lower levels of MeHg. The accumulation of MeHg and Hg2+ increased throughout the 30-day period. The fraction of Hg2+ in the kidney varied between 4 and 22%, and the lymph nodes showed a maximum of 30% Hg2+.We conclude first that MeHg has quantitatively different effect on the immune system compared with inorganic mercury, and secondly that an initial immunosuppression induced by a xenobiotic does not preclude subsequent immunostimulation and autoimmunity.
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| 41. |
- Innings, Fredrik, et al.
(författare)
-
Understanding and analysis of wear in homogenizers for processing liquid food
- 2011
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 271:9-10, s. 2588-2598
-
Tidskriftsartikel (refereegranskat)abstract
- The tribological research pertaining to homogenizers in processing liquid food has received much less attention compared to its potential in enhancing the efficiency and durability of the homogenization process equipment. Homogenization is a process used to disrupt fat globules in dairy products to reduce the formation of creamy layer (separation) and also to enhance the viscosity of certain products. This process takes place in a narrow gap in the homogenizer machine and this region is highly prone to wear. The occurrence of wear during processing not only impairs the homogenization effect but also leads to increased downtime of the machine. The aim of this work is to understand the occurrence of wear and wear mechanisms in the homogenization gap using both experimental and analytical approaches. Two experimental test rigs were used to study the differences in wear during operation, i.e. with and without particles. The trajectories of the particles have been simulated without the influence of cavitation using a CFD-code to investigate whether the particles are the cause of wear. The homogenizer gap has been simulated for a worn geometry to see how the occurrence of wear changes the particles trajectories. The results have shown that the presence of particles accelerates wear and most important parameters are the particle hardness and mass. When cavitation and particles are combined they create a synergistic effect on wear. This can be explained by the fact that cavitation can accelerate particles in random directions through the imploding action of cavities. A change in impact angle and increased velocity increases the amount of wear significantly. CFD-simulations and calculations show that the particles do not fully follow the streamlines and therefore create wear on the gap surfaces.
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| 42. |
- Kakanakova-Georgieva, Anelia, 1970-, et al.
(författare)
-
AlGaInN metal-organic-chemical-vapor-deposition gas-phase chemistry in hydrogen and nitrogen diluents : First-principles calculations
- 2006
-
Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 431:4-6, s. 346-351
-
Tidskriftsartikel (refereegranskat)abstract
- Direct impact of H2 and N2 diluents on the metal-organic-chemical-vapor-deposition gas-phase chemistry in M(CH3)3/NH3 (M = Al, Ga, In) systems is identified in the framework of Density Functional Theory in terms of cohesive energy differences. While both diluents destabilize model reaction species, i.e. adducts, transition states and chain complexes, the effect is particularly strong with respect to N2 in the Al(CH3)3/NH3 system, and can be a factor to restrain the expansion of chain complexes that deplete the gas-phase from precursors. Theoretical results are supported by experimental evidences of higher growth rate and superior optical properties of AlN grown in N2 vs. H2 diluent. © 2006 Elsevier B.V. All rights reserved.
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| 43. |
- Kakanakova-Georgieva, Anelia, 1970-, et al.
(författare)
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Epitaxial growth of AlN layers on SiC substrates in a hot-wall MOCVD system
- 2002
-
Ingår i: Phys. Stat. Sol. (c), Vol. 0, Issue 1. - : Wiley. ; , s. 205-208
-
Konferensbidrag (refereegranskat)abstract
- In this study we report the successful growth of AlN and AlN/GaN on SiC substrates in a MOCVD process based on a hot-wall susceptor design. Different features of AlN growth are established depending on the total reactor pressure, temperature, off-cut SiC substrate orientation and V-to-III gas-flow ratio. The feasibility of the hot-wall MOCVD concept is demonstrated by the performance of AlN/GaN structures with state-of-the-art properties with strong potential for further optimization. A narrower X-ray rocking curve over the asymmetric 10.4 than the symmetric 00.2 reflection clearly underlines the high overall crystal quality of the GaN layers on AlN buffers grown in this type of MOCVD reactor.
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| 44. |
- Kakanakova-Georgieva, A, et al.
(författare)
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Implementation of hot-wall MOCVD in the growth of high-quality GaN on SiC
- 2003
-
Ingår i: Materials Science Forum, Vols. 433-436. - : Trans Tech Publications. ; , s. 991-994
-
Konferensbidrag (refereegranskat)abstract
- This paper reports on the growth of high-quality GaN layers on SiC substrates by hotwall MOCVD. Use of AlN buffer with a thickness exceeding 50 nm is employed for the GaN deposition and it is found to encompass most of the misfit defects. A narrower X-ray rocking curve over asymmetric than over symmetric reflection is measured - full width at a half maximum (FWHM) of 350 arcsec vs. FWHM of 490 arcsec for 10.4 and 00.2 peaks, respectively, indicating high overall quality of the film. The free exciton photoluminescence emission peak has rather narrow FWHM of 5 meV. The typical thickness of the GaN layers is about 2 mum and they are completely depleted according to the capacitance-voltage profiling, which corresponds to estimated residual doping of less than 5x10(14) cm(-3). Only in some cases when the GaN layer is not depleted, deep level transient spectroscopy is performed and two deep traps with activation energies of 0.26 and 0.59 eV below the conduction band are measured.
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| 45. |
- Kakanakova-Georgieva, Anelia, 1970-, et al.
(författare)
-
Sublimation epitaxy of AlN on SiC : Growth morphology and structural features
- 2004
-
Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 273:1-2, s. 161-166
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Tidskriftsartikel (refereegranskat)abstract
- In order to study the development of individual AlN crystallites, sublimation epitaxy of AlN was performed on 4H-SiC, off-axis substrates in an inductively heated setup. Growth process variables like temperature, extrinsic nitrogen pressure and time were changed in an attempt to favor the lateral growth of individual AlN crystallites and thus open possibilities to prepare continuous patterns. Scanning and transmission electron microscopy and cathodoluminescence were used to obtain plan-view and cross-sectional images of the grown patterns and to study their morphology and structural features. The growth at 1900°C/200mbar results in AlN pattern consisting of individual single wurzite AlN crystallites with plate-like shape aligned along [1 1̄ 0 0] direction. The only defects these AlN crystallites contain are threading dislocations, some of which are terminated by forming half-loops. Because of the uniform distribution of the crystallites and their high structural perfection, this AlN pattern could represent interest as a template for bulk AlN growth. Alternative growth approaches to AlN crystallite formation are possible resulting in variation of the final AlN pattern structure. From a viewpoint of obtaining continuous patterns, the more favorable growth conditions involve applying of increased extrinsic gas pressure, 700 mbar in our case. © 2004 Elsevier B.V. All rights reserved.
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| 46. |
- Kakanakova-Georgieva, Anelia, 1970-, et al.
(författare)
-
Superior material properties of AlN on vicinal 4H-SiC
- 2006
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 100:3
-
Tidskriftsartikel (refereegranskat)abstract
- The crystal structure and optical properties of thick (>100 nm) AlN layers grown by hot-wall metalorganic chemical vapor deposition are characterized by infrared spectroscopic ellipsometry, cathodoluminescence, and transmission electron microscopy. The choice of substrates among the available SiC wafer polytype modifications (4H/6H) and misorientations (on-/off-axis cut) is found to determine the AlN defect interaction, stress homogeneity, and luminescence. The growth of thick AlN layers benefits by performing the epitaxy on off-axis substrates because, due to stacking faults, the propagation of threading defects in AlN layers is stopped in a narrow interface region. © 2006 American Institute of Physics.
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| 47. |
- Krag Jakobsen, Ane, et al.
(författare)
-
Is Nephrolithiasis an Unrecognized Extra-Articular Manifestation in Ankylosing Spondylitis? A Prospective Population-Based Swedish National Cohort Study with Matched General Population Comparator Subjects
- 2014
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 9:11
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Ankylosing spondylitis (AS) is associated with several extra-articular manifestations. Nephrolithiasis (NL) has not been recognized as one of those, however, several factors known to increase the risk of NL are at play in AS patients. The objective was to estimate rates and predictors of NL in Swedish patients with AS compared to the general population. Methods and Findings: We performed a prospective population-based nationwide cohort study based on linkage of data from Swedish registries. 8,572 AS patients were followed for 49,258 person-years (py) and 39,639 matched general population comparators were followed for 223,985 py. Patients were followed prospectively together with comparator subjects from January 2001 through December 2009. The first occurrence of NL during follow-up was the primary outcome. Hazard Ratios (HR) were used to compare these rates adjusting for comorbidities and treatment, and to assess predictors for NL. Mean age at study entry was 46 years (inter quartile range 36-56 years), 65% were males. Based on 250 vs. 466 NL events, the adjusted HR of NL in AS patients was 2.1 (95% CI 1.8 to 2.4). Predictors of NL within the AS group included prior diagnosis of inflammatory bowel disease (IBD) (HR 2.3; 95% CI 1.7 to 3.3), prior diagnosis of NL (HR 16.4; 95% CI 11.5 to 23.4), and patients receiving anti-TNF treatment (HR 1.6; 95% CI 1.2 to 2.1). Male sex was a risk factor for NL both in AS patients and in the general population. Limitations: The risk for residual confounding and inability to study the chemical nature of NL were considered the main limitations of the study. Conclusions: Patients with AS are at increased risk of NL, which may be considered a novel extra-articular manifestation. Previous history of NL, IBD, AS disease severity and male sex were identified as predictors of NL in AS.
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| 48. |
- Krag Jakobsen, Ane, et al.
(författare)
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Surgical interventions for nephrolithiasis in ankylosing spondylitis and the general population
- 2015
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Ingår i: Scandinavian Journal of Urology. - : Medical Journals Sweden AB. - 2168-1805 .- 2168-1813. ; 49:6, s. 486-491
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Tidskriftsartikel (refereegranskat)abstract
- Objective. The aim of this study was to estimate rates and type of definitive surgical interventions for nephrolithiasis in Swedish patients with ankylosing spondylitis (AS) compared to the general population. Materials and methods. This national prospective cohort study linked data from Swedish population and healthcare registries. Incidence rates and interventions for nephrolithiasis during follow-up in patients with AS were compared to general population comparator (GPC) subjects. Results. In total, 8572 AS patients were followed for 49,959 person-years and 39,639 matched GPCs were followed for 225,221 person-years. Mean age at study entry was 46 years [interquartile range (IQR) 36-56 years] and 65% were male. In AS patients with a diagnosis of nephrolithiasis during the study period, 29% (72/250) underwent similar intervention for nephrolithiasis compared to 24% (114/466) GPCs (p = 0.21). The incidence rate ratio (RR) in overall AS patients was 2.9 [95% confidence interval (CI) 2.1-3.8] during a median follow-up of 6.2 years (IQR 3.2-8.6 years). With prior diagnosis of nephrolithiasis, the RR for AS patients compared to GPCs was 3.7 (95% CI 1.8-7.7); without prior nephrolithiasis the RR was 2.1 (95% CI 1.5-3.0). Increasing age [odds ratio (OR) 1.02, 95% CI 1.01-1.03], prior nephrolithiasis diagnosis (OR 3.3, 95% CI 1.97-5.62) and atherosclerotic cardiac disease (OR 2.0, 95% CI 1.03-3.91) were identified as predictors of intervention for nephrolithiasis. Conclusions. Patients with AS have an almost three-fold increased risk of surgical intervention for kidney stones, with similar management, compared to the general population.
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| 49. |
- Landälv, Ludvig, 1982-, et al.
(författare)
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Phase evolution of radio frequency magnetron sputtered Cr-rich (Cr,Zr)(2)O-3 coatings studied by in situ synchrotron X-ray diffraction during annealing in air or vacuum
- 2019
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Ingår i: Journal of Materials Research. - : CAMBRIDGE UNIV PRESS. - 0884-2914 .- 2044-5326. ; 34:22, s. 3735-3746
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Tidskriftsartikel (refereegranskat)abstract
- The phase evolution of reactive radio frequency (RF) magnetron sputtered Cr0.28Zr0.10O0.61 coatings has been studied by in situ synchrotron X-ray diffraction during annealing under air atmosphere and vacuum. The annealing in vacuum shows t-ZrO2 formation starting at similar to 750-800 degrees C, followed by decomposition of the alpha-Cr2O3 structure in conjunction with bcc-Cr formation, starting at similar to 950 degrees C. The resulting coating after annealing to 1140 degrees C is a mixture of t-ZrO2, m-ZrO2, and bcc-Cr. The air-annealed sample shows t-ZrO2 formation starting at similar to 750 degrees C. The resulting coating after annealing to 975 degrees C is a mixture of t-ZrO2 and alpha-Cr2O3 (with dissolved Zr). The microstructure coarsened slightly during annealing, but the mechanical properties are maintained, with no detectable bcc-Cr formation. A larger t-ZrO2 fraction compared with alpha-Cr2O3 is observed in the vacuum-annealed coating compared with the air-annealed coating at 975 degrees C. The results indicate that the studied pseudo-binary oxide is more stable in air atmosphere than in vacuum.
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| 50. |
- Landälv, Ludvig, 1982-
(författare)
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Thin Film and Plasma Characterization of PVD Oxides
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The state-of-the-art tools for machining metals are primarily based on a metal-ceramic composite(WC-Co) coated with different combinations of carbide, nitride and oxide coatings. Combinations of these coating materials are optimized to withstand specific wear conditions. Oxide coatings are especially desired because of their possible high hot hardness, chemical inertness with respect to the workpiece, and their low friction.This thesis deals with process and coating characterization of new oxide coatings deposited by physical vapor deposition (PVD) techniques, focusing on the Cr-Zr-O and Al-Cr-Si-O systems.The thermal stability of α-Cr0.28Zr0.10O0.61 deposited by reactive radio frequency (RF)-magnetron sputtering at 500 °C was investigated after annealing up to 870 °C. The annealed samples showed transformation of α-(Cr,Zr)2O3 and amorphous ZrOx-rich areas into tetragonal ZrO2 and bcc Cr. The instability of the α-(Cr,Zr)2O3 is surprising and possibly related to the annealing being done under vacuum, facilitating the loss of oxygen. The stabilization of the room temperature metastable tetragonal ZrO2 phase, due to surface energy effects, may prove to be useful for metal cutting applications. The observed phase segregation of α-(Cr,Zr)2O3 and formation of tetragonal ZrO2 with corresponding increase in hardness for this pseudo-binary oxide system also opens up design routes for pseudo-binary oxides with tunable microstructural and mechanical properties.The inherent difficulties of depositing insulating oxide films with PVD, demanding a closed circuit, makes the investigation of process stability an important part of this research. In this context, we investigated the influence of adding small amount of Si in Al-Cr cathode on plasma characteristics ,process parameters, and coating properties. Si was chosen here due to a previous study showing improved erosion behavior of Al-Cr-Si over pure Al-Cr cathode without Si incorporation in the coating.This work shows small improvements in cathode erosion and process stability (lower pressure and cathode voltage) when introducing 5 at % Si in the Al70Cr30-cathode. This also led to fewer droplets at low cathode current and intermediate O2 flow. A larger positive effect on cathode erosion was observed with respect to cleaning the cathode from oxide contamination by increasing cathode current with 50%. However, higher cathode current also resulted in increased amount of droplets in the coating which is undesirable. Through plasma analysis the presence of volatile SiO species could be confirmed but the loss of Si through volatile SiO species was negligible, since the coating composition matched the cathode composition. The positive effect of added Si on the process stability at the cathode surface should be weighed against Si incorporation in the coating. This incorporation may or may not be beneficial for the final application since literature states that Si promotes the metastable γ-phase over the thermodynamically stable α-phase of pure Al2O3, contrary to the effect of Cr, which stabilizes the α-phase.
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