| 26. |
- Karlsson, Maths, 1978, et al.
(författare)
-
Quasielastic neutron scattering of hydrated BaZr0.90A0.10O2.95 (A = Y and Sc)
- 2009
-
Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 180:1, s. 22-28
-
Tidskriftsartikel (refereegranskat)abstract
- Proton motions in hydrated proton conducting perovskites BaZr 0.90 A 0.10 O 2.95 (A = Y and Sc) have been investigated using quasielastic neutron scattering. The results reveal a localized motion on the ps time scale and with an activation energy of ~ 10-30 meV, in both materials. The temperature dependence of the total mean square displacement of the protons shows an onset of this motion at a temperature of about 300 K. The low activation energy, much lower than the activation energy for the macroscopic proton conductivity, suggests that this motion is not the rate-limiting process for the long-range proton diffusion, i.e. it is not linked to the two materials significantly different proton conductivities. In fact, a comparison of the QENS results with density functional theory calculations indicates that for both materials the observed motion may be ascribed to intra-octahedral proton transfers occurring close to a dopant atom. © 2008 Elsevier B.V. All rights reserved.
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| 27. |
- Karlsson, Maths, 1978, et al.
(författare)
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Using Neutron Spin-Echo To Investigate Proton Dynamics in Proton-Conducting Perovskites
- 2010
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 22:3, s. 740-742
-
Tidskriftsartikel (refereegranskat)abstract
- The applicability and potential of neutron spin-echo (NSE) to study proton dynamics in proton-conducting ceramics was studied. The experiment was performed on hydrated BaZr 0,90 Y 0.10 O 2.95 (10Y:BZO), a cubic perovskite with a relatively high proton conductivity. The NSE experiment was performed at the IN15 spectrometer at Institut Laue-Langevin (ILL) in Grenoble, France. The relaxation rate for two Q-values for the temperature 563 K was determined. The first-principles calculations were carried out within the framework of density functional theory (DFT). The calculated diffusion harriers far from Y-dopants are found to he 0.20 and 0.18 eV for the proton transfer and hydroxyl rotation motion, respectively. The binding energy to a Y-dopant is 0.16 eV, and the influence of the Y-dopant on the energetics for the proton is quite extended in space, including both the first and the second coordination shells.
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| 28. |
- Karlsson, Maths, 1978, et al.
(författare)
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Vibrational Properties of Protons in Hydrated BaInxZr1-xO3-x/2
- 2005
-
Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 72, s. 1-7
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the local proton dynamics in the proton conducting hydrated perovskite system BaInxZr1-xO3-x/2 (x=0.25-0.75) using infrared spectroscopy and first-principles calculations. We show that oxygen vacancies and dopant atoms in the vicinity of the proton tilt the proton toward a neighboring oxygen creating strongly hydrogen-bonded configurations. This is manifested as a strong redshift of the O-H stretch band in the infrared absorption spectrum. We also find considerable fluctuations of the nearest and next-nearest oxygen-proton distances with time, resulting in additional spectral broadening. By comparing the frequencies of computed O-H stretch modes we can relate specific local configurations to different parts of the broad O-H stretch band. Even though hydrogen-bonded configurations favor proton transfer they hinder the long-range migration by decreasing the reorientational rate. Thus, in order to optimize the proton mobility it is important to avoid extreme configurations caused by either oxygen vacancies or dopant atoms in the perovskite structure.
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| 29. |
- Kegel, Magdalena E., et al.
(författare)
-
Imbalanced Kynurenine Pathway in Schizophrenia
- 2014
-
Ingår i: International Journal of Tryptophan Research. - : Libertas Academica. - 1178-6469. ; 7, s. 15-22
-
Tidskriftsartikel (refereegranskat)abstract
- Several studies suggest a role for kynurenic acid (KYNA) in the pathophysiology of schizophrenia. It has been proposed that increased brain KYNA levels in schizophrenia result from a pathological shift in the kynurenine pathway toward enhanced KYNA formation, away from the other branch of the pathway leading to quinolinic acid (QUIN). Here we investigate the levels of QUIN in cerebrospinal fluid (CSF) of patients with schizophrenia and healthy controls, and relate those to CSF levels of KYNA and other kynurenine metabolites from the same individuals. CSF QUIN levels from stable outpatients treated with olanzapine (n = 22) and those of controls (n = 26) were analyzed using liquid chromatography-mass spectrometry. No difference in CSF QUIN levels between patients and controls was observed (20.6 ± 1.5 nM vs. 18.2 ± 1.1 nM, P = 0.36). CSF QUIN was positively correlated to CSF kynurenine and CSF KYNA in patients but not in controls. The CSF QUIN/KYNA ratio was lower in patients than in controls (P = 0.027). In summary, the present study offers support for an over-activated and imbalanced kynurenine pathway, favoring the production of KYNA over QUIN in patients with schizophrenia.
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| 30. |
- Kegel, Magdalena E., et al.
(författare)
-
Kynurenic acid and psychotic symptoms and personality traits in twins with psychiatric morbidity
- 2017
-
Ingår i: Psychiatry Research. - : Elsevier. - 0165-1781 .- 1872-7123. ; 247, s. 105-112
-
Tidskriftsartikel (refereegranskat)abstract
- Increased cytokines and kynurenic acid (KYNA) levels in cerebrospinal fluid (CSF) have been reported in patients with schizophrenia and bipolar disorder. The aim of the present study was to investigate cytokines and kynurenines in the CSF of twin pairs discordant for schizophrenia or bipolar disorder and to study these CSF markers in relation to psychotic symptoms and personality traits. CSF levels of tryptophan (TRP), KYNA, quinolinic acid (QUIN), interleukin (IL)-6, IL-8 and tumor necrosis factor-alpha (TNF-α) were analyzed in 23 twins with schizophrenia or bipolar disorder, and in their not affected co-twins. Ratings of psychotic symptoms and personality traits were made using the Scales for Assessment of Negative and Positive symptoms, the Structured Clinical Interview for DSM-IV - Axis II Disorders, and the Schizotypal Personality Questionnaire - Brief. A total score for psychotic symptoms and personality traits was constructed for analysis. CSF KYNA was associated with the score for psychotic symptom and personality traits. TNF-α and IL-8 were associated, and the intra-pair differences scores of TNF-α and IL-8 were highly correlated. Intraclass correlations indicated genetic influences on CSF KYNA, TRP, IL-8 and TNF-α. The association between KYNA and psychotic symptoms further supports a role of KYNA in psychotic disorders.
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| 31. |
- Kurbasic, Azra, et al.
(författare)
-
Gene-Lifestyle Interactions in Complex Diseases : Design and Description of the GLACIER and VIKING Studies
- 2014
-
Ingår i: Current nutrition reports. - : Springer Science and Business Media LLC. - 2161-3311. ; 3:4, s. 400-411
-
Tidskriftsartikel (refereegranskat)abstract
- Most complex diseases have well-established genetic and non-genetic risk factors. In some instances, these risk factors are likely to interact, whereby their joint effects convey a level of risk that is either significantly more or less than the sum of these risks. Characterizing these gene-environment interactions may help elucidate the biology of complex diseases, as well as to guide strategies for their targeted prevention. In most cases, the detection of gene-environment interactions will require sample sizes in excess of those needed to detect the marginal effects of the genetic and environmental risk factors. Although many consortia have been formed, comprising multiple diverse cohorts to detect gene-environment interactions, few robust examples of such interactions have been discovered. This may be because combining data across studies, usually through meta-analysis of summary data from the contributing cohorts, is often a statistically inefficient approach for the detection of gene-environment interactions. Ideally, single, very large and well-genotyped prospective cohorts, with validated measures of environmental risk factor and disease outcomes should be used to study interactions. The presence of strong founder effects within those cohorts might further strengthen the capacity to detect novel genetic effects and gene-environment interactions. Access to accurate genealogical data would also aid in studying the diploid nature of the human genome, such as genomic imprinting (parent-of-origin effects). Here we describe two studies from northern Sweden (the GLACIER and VIKING studies) that fulfill these characteristics.
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| 32. |
- Linderholm, Klas R, et al.
(författare)
-
Increased Levels of Kynurenine and Kynurenic Acid in the CSF of Patients With Schizophrenia
- 2012
-
Ingår i: Schizophrenia Bulletin. - : Oxford University Press. - 0586-7614 .- 1745-1701. ; 38:3, s. 426-432
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The kynurenic acid (KYNA) hypothesis for schizophrenia is partly based on studies showing increased brain levels of KYNA in patients. KYNA is an endogenous metabolite of tryptophan (TRP) produced in astrocytes and antagonizes N-methyl-D-aspartate and alpha7* nicotinic receptors. Methods: The formation of KYNA is determined by the availability of substrate, and hence, we analyzed KYNA and its precursors, kynurenine (KYN) and TRP, in the cerebrospinal fluid (CSF) of patients with schizophrenia. CSF from male patients with schizophrenia on olanzapine treatment (n = 16) was compared with healthy male volunteers (n = 29). Results: KYN and KYNA concentrations were higher in patients with schizophrenia (60.7 +/- 4.37nM and 2.03 +/- 0.23nM, respectively) compared with healthy volunteers (28.6 +/- 1.44nM and 1.36 +/- 0.08nM, respectively), whereas TRP did not differ between the groups. In all subjects, KYN positively correlated to KYNA. Conclusion: Our results demonstrate increased levels of CSF KYN and KYNA in patients with schizophrenia and further support the hypothesis that KYNA is involved in the pathophysiology of schizophrenia.
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| 33. |
- Lissel, Linda, et al.
(författare)
-
Modeling precipitation and its effect on recrystallization during hot strip rolling of niobium steels
- 2008
-
Ingår i: 3rd Int. Conf. on Thermomechanical Processing of Steels. - Padua, Italy.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Using a physically based model, the microstructural evolution of Nb microalloyed steels during rolling in SSAB Tunnplåt’s hot strip mill was modeled. The model describes the evolution of dislocation density, the creation and diffusion of vacancies, dynamic and static recovery through climb and glide, subgrain formation and growth, dynamic and static recrystallization and grain growth. Also, the model describes the dissolution and precipitation of particles. The impeding effect on grain growth and recrystallization due to solute drag and particles is accounted for. During hot strip rolling of Nb steels, Nb in solid solution retards recrystallization due to solute drag and at lower temperatures strain-induced precipitation of Nb(C,N) may occur which effectively retard recrystallization. The flow stress behavior during hot rolling was calculated where the mean flow stress values were calculated using both the model and measured mill data. The model showed that solute drag has an essential effect on recrystallization during hot rolling of Nb steels.
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| 34. |
|
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| 35. |
- Lissel, Linda, et al.
(författare)
-
Prediction of the microstructural evolution during hot strip rolling of Nb microalloyed steels
- 2007
-
Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 558-559:2, s. 1127-1132
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A physically based model is used to describe the microstructural evolution of Nb microalloyed steels during hot rolling. The model is based on a physical description of dislocation density evolution, where the generation and recovery of dislocations determines the flow stress and also the driving force for recrystallization. In the model, abnormally growing subgrains are assumed to be the nuclei of recrystallized grains and recrystallization starts when the subgrains reach a critical size and configuration. The model is used to predict the flow stress during rolling in SSAB Tunnplat's hot strip mill. The predicted flow stress in each stand was compared to the stresses calculated by a friction-hill roll-force model. Good fit is obtained between the predicted values by the microstructure model and the measured mill data, with an agreement generally within the interval +/-15%.
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| 36. |
- Magnusson, Hans, 1979-
(författare)
-
Creep modelling of particle strengthened steels
- 2007
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Materials to be used in thermal power plants have to resist creep deformation for time periods up to 30 years. The role of alloying elements for creep strength of 9-12% Cr steels is analysed. The creep strength in these steels relies on minor additions of alloying elements. Precipitates give rise to the main strengthening and remaining elements produce solid solution hardening. Nucleation, growth and coarsening of particles are predicted by thermodynamic modelling. Phase fractions and size distributions of M23C6 carbides, MX carbonitrides and Laves phase are presented. The size distributions are needed in order to determine the particle hardening during creep. At elevated temperatures the climb mobility is so high that the dislocations can climb across particles instead of passing by making Orowan loops. By solving Fick's second law the concentration profile around a moving dislocation can be determined. The results show an accumulation of solutes around the dislocation that slows down dislocation movement. When Laves phase grows a decrease in creep strength is observed due to a larger loss in solid solution hardening than strength increase by particle hardening. Solid solution hardening also gives an explanation of the low dislocation climb mobility in 9-12% Cr steels. Three different dislocation types are distinguished, free dislocations, immobile dislocation and immobile boundary dislocations. This distinction between types of dislocations is essential in understanding the decreasing creep with strain during primary creep. The empirical relation with subgrain size inversely proportional to stress has been possible to predict. The total creep strength can be predicted by adding the contribution from individual mechanisms.
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| 37. |
- Molnar, David, et al.
(författare)
-
Deformation properties of austenitic stainless steels with different stacking fault energies
- 2018
-
Ingår i: Materials Science Forum. - Switzerland : Trans Tech Publications Ltd. - 0255-5476 .- 1662-9752. ; 941, s. 190-197, s. 190-197
-
Tidskriftsartikel (refereegranskat)abstract
- In FCC metals a single parameter – stacking fault energy (SFE) – can help to predict the expectable way of deformation such as martensitic deformation, deformation twinning or pure dislocation glide. At low SFE one can expect the perfect dislocations to dissociate into partial dislocations, but at high SFE this separation is more restricted. The role of the magnitude of the stacking fault energy on the deformation microstructures and tensile behaviour of different austenitic steels have been investigated using uniaxial tensile testing and electron backscatter diffraction (EBSD). The SFE was determined by using quantum mechanical first-principles approach. By using plasticity models we make an attempt to explain and interpret the different strain hardening behaviour of stainless steels with different stacking fault energies.
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| 38. |
- Molnár, Dávid Sándor, et al.
(författare)
-
Effect of temperature on the stacking fault energy and deformation behaviour in 316L austenitic stainless steel
- 2019
-
Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 759, s. 490-497
-
Tidskriftsartikel (refereegranskat)abstract
- The stacking fault energy (SFE) is often used as a key parameter to predict and describe the mechanical behaviour of face centered cubic material. The SFE determines the width of the partial dislocation ribbon, and shows strong correlation with the leading plastic deformation modes. Based on the SFE, one can estimate the critical twinning stress of the system as well. The SFE mainly depends on the composition of the system, but temperature can also play an important role. In this work, using first principles calculations, electron backscatter diffraction and tensile tests, we show a correlation between the temperature dependent critical twinning stress and the developing microstructure in a typical austenitic stainless steel (316L) during plastic deformation. We also show that the deformation twins contribute to the strain hardening rate and gradually disappear with increasing temperature. We conclude that, for a given grain size there is a critical temperature above which the critical twinning stress cannot be reached by normal tensile deformation, and the disappearance of the deformation twinning leads to lower strain hardening rate and decreased ductility.
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| 39. |
- Molnár, Dávid Sándor, et al.
(författare)
-
Experimental study of the γ-surface of austenitic stainless steels
- 2019
-
Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 173, s. 34-43
-
Tidskriftsartikel (refereegranskat)abstract
- We introduce a theory-guided experimental approach to study the γ-surface of austenitic stainless steels. The γ-surface includes a series of intrinsic energy barriers (IEBs), which are connected to the unstable stacking fault (USF), the intrinsic stacking fault (ISF), the unstable twinning fault (UTF) and the extrinsic stacking fault (ESF) energies. The approach uses the relationship between the Schmid factors and the effective energy barriers for twinning and slip. The deformation modes are identified as a function of grain orientation using in situ electron backscatter diffraction measurements. The observed critical grain orientation separating the twinning and slip regimes yields the USF energy, which combined with the universal scaling law provides access to all IEBs. The measured IEBs and the critical twinning stress are verified by direct first-principles calculations. The present advance opens new opportunities for modelling the plastic deformation mechanisms in multi-component alloys.
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| 40. |
- Molnár, Dávid Sándor, 1990-
(författare)
-
Stacking fault energy and deformation behaviour of austenitic stainless steels: a joint theoretical-experimental study
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Austenitiska rostfria stål är främst kända för sin exceptionella korrosionsbeständighet. De har en ytcentrerad kubisk (FCC) struktur som stabiliseras genom att nickel, mangan eller kväve tillsätts till Fe-Cr legeringen. Fe-Cr-Ni-systemet kan utökas ytterligare genom tillsats av andra element såsom Mo, Cu, Ti, C, etc. för att förbättra egenskaperna. Eftersom austenitiska rostfria stål ofta används som konstruktionsmaterial är det viktigt att kunna förutsäga deras mekaniska egenskaper baserat på deras sammansättning, mikrostruktur, magnetiska tillstånd, etc. I denna avhandling är det plastiska deformationsbeteendet hos austenitiska rostfria stål undersökt med teoretiskt och experimentellt. I FCC material spelar staplingsfelsenergin (SFE) en viktig roll vid förutsägelsen och beskrivning av deformationsmekanism. Baserat på storleken av SFE kan olika deformationsmekanismer observeras, såsom martensitbildning, tvillingbildning, eller dislokationsglidning. Alla dessa funktioner påverkar beteendet, därför är det önskvärt att förutsäga och kontrollera deras förekomst. Legering och temperatur har stark inverkan på SFE och därmed legeringarnas mekaniska egenskaper. Flera modeller, baserade på SFE och mer nyligen på den så kallade generaliserade staplingsfelenergin (GSFE eller γ-surface), är tillgängliga för att förutsäga legeringens affinitet till tvillingbildning och den kritiska spänning som representerar den minsta upplösta skjuvspänningen som krävs för att initiera tvillingbildning. Man kan använda ab initio beräkningar baserade på täthetsfunktionalteori (DFT) för att beräkna GSFE för austenitiska stål och härleda parametrar som twinnability och kritisk tvillingsspänning.Korrelation mellan staplingsfelenergi och deformationsbeteendet för fyra olika austenitiska rostavstavning stål diskuteras i detta arbete. SFE för de valda legeringarna erhålls genom ab initio beräkningar och baserat på olika modeller, deras tendens till tvillingbildning och den kritiska tvillingsspänningen kan förutsägas. Deras mekaniska beteende och affinitet till tvilling och martensitisk transformation kartläggs över ett brett temperaturområde (−70°C to +500°C) för de fyra legeringarna. De teoretiska förutsägelserna jämförs med resultat från dragprov och bakåtspridd elektrondiffraktion (EBSD). Flera konventionella och in situ dragprov utfördes för att verifiera de teoretiska resultaten. Vi utförde EBSD-mätningar på dragprov som avbrutits vid olika töjningar och efter brott samt med in situ dragprov för att följa utvecklingen av mikrostrukturen noggrant. Vi tar hänsyn till de inre energibarriärernas roll i våra förutsägelser och presenterar ett nytt sätt att experimentellt få GSFE av austenitiska rostfria stål. Tidigare kunde endast SFE mätas tillförlitligt genom väl utformade experiment. I den aktuella avhandlingen går vi vidare och föreslår en teknik som kan ge noggranna värden för den instabila staplingsfelenergin för alla austenitiska legeringar som uppvisar tvillingbildning på låga spänningsnivåer. Betydelsen av temperatur och mellanliggande legering på mekaniskt beteende undersökt också i detta arbete.
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| 41. |
- Molnár, Dávid Sándor, et al.
(författare)
-
Study of the alternative mechanism behind the constant strain hardening rate in high‑nitrogen steels
- 2020
-
Ingår i: Materials Characterization. - : Elsevier BV. - 1044-5803 .- 1873-4189. ; 170
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, three austenitic stainless steels with different compositions are compared in terms of their deformation behaviour. Two of the investigated steels have considerable high nitrogen content which affects their deformation behaviour. The deformation properties and microstructure of the materials were studied by tensile testing and electron backscatter diffraction. We observe that the strain hardening rate curve of the alloy with low nitrogen content shows a continuously decreasing slope, whereas those of the high‑nitrogen steels exhibit a clear plateau. Since no twinning or ε-phase formation is observed at the corresponding strain levels, we suggest that the addition of a large amount of nitrogen suppresses cross-slip and promotes dislocation planarisation. The microstructural evolution of the materials during deformation supports the above scenario. Based on the results of the ab initio calculations, the deformation behaviour of high‑nitrogen alloys cannot be explained in terms of the stacking fault energy.
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| 42. |
- Mätlik, Kärt, et al.
(författare)
-
Elevated endogenous GDNF induces altered dopamine signalling in mice and correlates with clinical severity in schizophrenia.
- 2022
-
Ingår i: Molecular Psychiatry. - : Springer Nature. - 1359-4184 .- 1476-5578.
-
Tidskriftsartikel (refereegranskat)abstract
- Presynaptic increase in striatal dopamine is the primary dopaminergic abnormality in schizophrenia, but the underlying mechanisms are not understood. Here, we hypothesized that increased expression of endogenous GDNF could induce dopaminergic abnormalities that resemble those seen in schizophrenia. To test the impact of GDNF elevation, without inducing adverse effects caused by ectopic overexpression, we developed a novel in vivo approach to conditionally increase endogenous GDNF expression. We found that a 2-3-fold increase in endogenous GDNF in the brain was sufficient to induce molecular, cellular, and functional changes in dopamine signalling in the striatum and prefrontal cortex, including increased striatal presynaptic dopamine levels and reduction of dopamine in prefrontal cortex. Mechanistically, we identified adenosine A2a receptor (A2AR), a G-protein coupled receptor that modulates dopaminergic signalling, as a possible mediator of GDNF-driven dopaminergic abnormalities. We further showed that pharmacological inhibition of A2AR with istradefylline partially normalised striatal GDNF and striatal and cortical dopamine levels in mice. Lastly, we found that GDNF levels are increased in the cerebrospinal fluid of first episode psychosis patients, and in post-mortem striatum of schizophrenia patients. Our results reveal a possible contributor for increased striatal dopamine signalling in a subgroup of schizophrenia patients and suggest that GDNF-A2AR crosstalk may regulate dopamine function in a therapeutically targetable manner.
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| 43. |
- Nilsson, Linda K, et al.
(författare)
-
Cerebrospinal fluid kynurenic acid in male and female controls - Correlation with monoamine metabolites and influences of confounding factors
- 2007
-
Ingår i: Journal of Psychiatric Research. - : Elsevier BV. - 0022-3956 .- 1879-1379. ; 41:1-2, s. 144-151
-
Tidskriftsartikel (refereegranskat)abstract
- The concentrations of the tryptophan metabolite kynurenic acid (KYNA) and the monoamine metabolites homovanillic acid (HVA), 5-hydroxy-indoleacetic acid (5-HIAA) and 4-hydroxy-3-methoxyphenylglycol (HMPG) were determined in the cerebrospinal fluid (CSF) from 43 healthy volunteers (30 males and 13 females). Healthy female controls displayed higher CSF concentration of KYNA (1.91 nM ± 0.20) compared to healthy male controls (1.06 nM ± 0.07) and lower CSF levels of HMPG (39.2 nM ± 2.0 and 43.4 ± 1.2, respectively). CSF levels of HVA and 5-HIAA did not differ between females (181.3 nM ± 21.9 and 93.7 nM ± 11.4, respectively) and males (138.9 nM ± 12.6 and 74.8 nM ± 5.9, respectively). Positive intercorrelations were found between CSF KYNA, HVA and 5-HIAA while CSF content of HMPG did not correlate with KYNA or the other monoamine metabolites in CSF. A negative correlation was found between back length and CSF concentrations of KYNA, HVA and 5-HIAA and also between CSF KYNA levels and body height. The results of the present study suggest that concentrations of KYNA and the monoamine metabolites in CSF from healthy controls are dependent on gender and back length, which must be taken in consideration when analysing mixed groups of men and women. The higher KYNA concentration found in female controls compared to male might be attributed to a shorter back in women compared to men. Furthermore, these findings suggest that increased KYNA formation is associated with an increased dopamine and serotonin turnover. © 2005 Elsevier Ltd. All rights reserved.
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| 44. |
- Niskanen, Ilpo, et al.
(författare)
-
Determination of relative solids concentration in homogeneous dual component pulp-filler suspension by multi-spectrophotometer
- 2020
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 35:1, s. 71-77
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Tidskriftsartikel (refereegranskat)abstract
- The concentration of fibers and fillers in the pulp suspension is an important parameter in the monitoring process. This paper proposes a versatile optical measurement system to estimate the concentration of a solids mixture in water. The geometry used in a multi-spectrophotometer (MSM) enables the controlled observation of transmission, and forward scattering light from the suspension in the UV-visible spectral range. We have developed the new fibers mixing system which gives a homogenous distribution of the fines and fillers making it possible to increase the reproducibility and accuracy of the measurement. The data analysis is based on the Beer-Lambert law and CIELAB color space equations. The results show that the proposed method is accurate for measuring the fines and filler concentrations in multicomponent suspensions.
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| 45. |
- Olsson, Sara K, et al.
(författare)
-
Cerebrospinal fluid kynurenic acid is associated with manic and psychotic features in patients with bipolar I disorder.
- 2012
-
Ingår i: Bipolar disorders. - : Wiley. - 1399-5618 .- 1398-5647. ; 14:7, s. 719-26
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Tidskriftsartikel (refereegranskat)abstract
- Olsson SK, Sellgren C, Engberg G, Landén M, Erhardt S. Cerebrospinal fluid kynurenic acid is associated with manic and psychotic features in patients with bipolar I disorder. Bipolar Disord 2012: 14: 719-726. © 2012 The Authors. Journal compilation © 2012 John Wiley & Sons A/S. Objectives: Kynurenic acid (KYNA), an end metabolite of tryptophan degradation, antagonizes glutamatergic and cholinergic receptors in the brain. Recently, we reported elevated levels of cerebrospinal fluid (CSF) KYNA in male patients with bipolar disorder. Here, we investigate the relationship between symptomatology and the concentration of CSF KYNA in patients with bipolar I disorder. Methods: CSF KYNA levels from euthymic male {n=21; mean age: 41years [standard deviation (SD)=14]} and female [n=34; mean age: 37years (SD=14)] patients diagnosed with bipolar I disorder were analyzed using high-performance liquid chromatography (HPLC). Results: Euthymic bipolar I disorder patients with a lifetime occurrence of psychotic features had higher CSF levels of KYNA {2.0nm [standard error of the mean (SEM)=0.2]; n=43} compared to patients without any history of psychotic features [1.3nm (SEM=0.2); n=12] (p=0.01). Logistic regression, with age as covariate, similarly showed an association between a history of psychotic features and CSF KYNA levels [n=55; odds ratio (OR)=4.9, p=0.03]. Further, having had a recent manic episode (within the previous year) was also associated with CSF KYNA adjusted for age (n=34; OR=4.4, p=0.03), and the association remained significant when adjusting for a lifetime history of psychotic features (OR=4.1, p=0.05). Conclusions: Although the causality needs to be determined, the ability of KYNA to influence dopamine transmission and behavior, along with previous reports showing increased brain levels of the compound in patients with schizophrenia and bipolar disorder, may indicate a possible pathophysiological role of KYNA in the development of manic or psychotic symptoms.
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| 46. |
- Olsson, Sara K., et al.
(författare)
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Elevated levels of kynurenic acid in the cerebrospinal fluid of patients with bipolar disorder
- 2010
-
Ingår i: Journal of Psychiatry & Neuroscience. - : CMA Joule Inc.. - 1180-4882 .- 1488-2434. ; 35:3, s. 195-199
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Tidskriftsartikel (refereegranskat)abstract
- Background: Patients with schizophrenia show elevated brain levels of the neuroactive tryptophan metabolite kynurenic acid (KYNA) This astrocyte] derived mediator acts as a neuroprotectant and modulates sensory gating and cognitive functiona We measured the levels of KYNA in the cerebrospinal fluid T vSyU of patients with bipolar disorder and healthy volunteers to investigate the putative involvement of KYNA in bipolar disorder. Methods: We obtained CSF by lumbar puncture from 23 healthy men and 31 euthymic men with bipolar disorder. We analyzed the samples using high] performance liquid chromatography. Results: Patients with bipolar disorder had increased levels of KYNA in their CSF compared with healthy volunteers (1.71 nM, standard error of the mean [SEM] cad, va dad, nM, SEM cacln p = 0.002. The levels of KYNA were positively correlated with age among bipolar patients but not healthy volunteersa Limitations: The influence of ongoing drug treatment among patients cannot be ruled outa We conducted our study during the euthymic phase of the diseasea Conclusion: Brain KYNA levels are increased in euthymic men with bipolar disorder. In addition, KYNA levels increased with age in these patientsa These findings indicate shared mechanisms between bipolar disorder and schizophrenia. Elevated levels of brain KYNA may provide further insight to the pathophysiology and progression of bipolar disorder.
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| 47. |
- Orhan, Funda, et al.
(författare)
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CSF dopamine is elevated in first-episode psychosis and associates to symptom severity and cognitive performance.
- 2023
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Ingår i: Schizophrenia Research. - 0920-9964 .- 1573-2509. ; 257, s. 34-40
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The hypothesis of dopamine dysfunction in psychosis has evolved since the mid-twentieth century. However, clinical support from biochemical analysis of the transmitter in patients is still missing. The present study assessed dopamine and related metabolites in the cerebrospinal fluid (CSF) of first-episode psychosis (FEP) subjects.METHODS: Forty first-episode psychosis subjects and twenty healthy age-matched volunteers were recruited via the Karolinska Schizophrenia Project, a multidisciplinary research consortium that investigates the pathophysiology of schizophrenia. Psychopathology, disease severity, and cognitive performance were rated as well as cerebrospinal fluid concentrations of dopamine and related metabolites were measured using a sensitive high-pressure liquid chromatography assay.RESULTS: CSF dopamine was reliably detected in 50 % of healthy controls and in 65 % of first-episode psychosis subjects and significantly higher in first-episode psychosis subjects compared to age-matched healthy controls. No difference in CSF dopamine levels was observed between drug-naive subjects and subjects with short exposure to antipsychotics. The dopamine concentrations were positively associated with illness severity and deficits in executive functioning.CONCLUSIONS: Dopamine dysfunction has long been considered a cornerstone of the pathophysiology of schizophrenia, although biochemical support for elevated brain dopamine levels has been lacking. The results of the present study, showing that FEP subjects have increased CSF dopamine levels that correlate to disease symptoms, should fill the knowledge gap in this regard.
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| 48. |
- Pils, Marlene, et al.
(författare)
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Disrupted-in-schizophrenia 1 (DISC1) protein aggregates in cerebrospinal fluid are elevated in first-episode psychosis patients.
- 2023
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Ingår i: Psychiatry and Clinical Neurosciences. - 1323-1316 .- 1440-1819.
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Tidskriftsartikel (refereegranskat)abstract
- AIM: The Disrupted-in-schizophrenia 1 (DISC1) protein is a key regulator at the intersection of major signaling pathways relevant for adaptive behavior. It is prone to posttranslational changes such as misassembly and aggregation but the significance of such transformations for human mental illness has remained unclear. We aimed to demonstrate the occurrence of DISC1 protein aggregates in patients with first episode psychosis (FEP).METHOD: Cerebrospinal fluid (CSF) samples of patients with FEP (n = 50) and matched healthy controls (HC; n = 47) were measured by the highly sensitive surface-based fluorescence intensity distribution analysis (sFIDA) technology that enables single aggregate detection.RESULTS: Here we demonstrate that DISC1 protein aggregates are increased in CSF samples of FEP vs. HC. The concentration was in the low femtomolar range. No correlations were found to specific symptom levels, but the difference was particularly significant in the subset of patients receiving the diagnoses "schizophrenia, unspecified" (DSM IV 295.9) or schizoaffective disorder (DSM IV 295.70) at 18-month follow-up. DISC1 protein aggregate levels did not significantly change within the 18 months observation interval, and were in average higher for individuals carrying the major DISC1 rs821577 allele before correction.CONCLUSION: The occurrence of protein aggregates in vivo in patients with psychotic disorders has not been previously reported. It underscores the significance of posttranslational modifications of proteins both as pathogenetic mechanisms and as potential diagnostic markers in these disorders. This article is protected by copyright. All rights reserved.
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| 49. |
- Poveda, Alaitz, et al.
(författare)
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The heritable basis of gene–environment interactions in cardiometabolic traits
- 2017
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 60:3, s. 442-452
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Tidskriftsartikel (refereegranskat)abstract
- Aims/hypothesis: Little is known about the heritable basis of gene–environment interactions in humans. We therefore screened multiple cardiometabolic traits to assess the probability that they are influenced by genotype–environment interactions. Methods: Fourteen established environmental risk exposures and 11 cardiometabolic traits were analysed in the VIKING study, a cohort of 16,430 Swedish adults from 1682 extended pedigrees with available detailed genealogical, phenotypic and demographic information, using a maximum likelihood variance decomposition method in Sequential Oligogenic Linkage Analysis Routines software. Results: All cardiometabolic traits had statistically significant heritability estimates, with narrow-sense heritabilities (h2) ranging from 24% to 47%. Genotype–environment interactions were detected for age and sex (for the majority of traits), physical activity (for triacylglycerols, 2 h glucose and diastolic BP), smoking (for weight), alcohol intake (for weight, BMI and 2 h glucose) and diet pattern (for weight, BMI, glycaemic traits and systolic BP). Genotype–age interactions for weight and systolic BP, genotype–sex interactions for BMI and triacylglycerols and genotype–alcohol intake interactions for weight remained significant after multiple test correction. Conclusions/interpretation: Age, sex and alcohol intake are likely to be major modifiers of genetic effects for a range of cardiometabolic traits. This information may prove valuable for studies that seek to identify specific loci that modify the effects of lifestyle in cardiometabolic disease.
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| 50. |
- Safara, Nima, et al.
(författare)
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Study of the mean size and fraction of the second-phase particles in a 13% chromium steel at high temperature
- 2020
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Ingår i: Philosophical Magazine. - : Taylor & Francis. - 1478-6435 .- 1478-6443. ; 100:2, s. 217-233
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Tidskriftsartikel (refereegranskat)abstract
- The mean size and fraction of the second-phase particles in a 13% chromium steel are investigated, while no plastic deformation was applied. The results of the measurement are compared with the modelling results from a physicallybased model. The heating sequence is performed on samples using a Gleeble thermo-mechanical simulator over the temperature range of 850–1200°C. Using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), the size distribution and composition of the carbides were evaluated, respectively. For obtaining particle size distribution (PSD), an image-processing software was employed to analyse the SEM images. Additionally, the relation between the 2D shape factor and size of the particles is also studied at different temperatures and most of the particles turned out to have a shape factor close to two. In order to measure the carbide weight fraction, electrochemical phase isolation was employed. The Ms and fraction of the martensite phase after quenching of samples are calculated and the results were comparable with the measured hardness values at corresponding temperatures. The measured hardness of the samples is found to comply very well with the measured mean size of the precipitates. The calculated mean size of the particles from the model shows very good agreement with both hardness value and experimentally measured mean size, while the calculated volume fraction from simulation follows a slightly different trend.
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