| 1. |
- Rothen, Hans Ulrich, et al.
(författare)
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Influence of gas composition on recurrence of atelectasis after a reexpansion maneuver during general anaesthesia
- 1995
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Ingår i: Anesthesiology. - 0003-3022 .- 1528-1175. ; 82:4, s. 832-842
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:Atelectasis, an important cause of impaired gas exchange during general anesthesia, may be eliminated by a vital capacity maneuver. However, it is not clear whether such a maneuver will have a sustained effect. The aim of this study was to determine the impact of gas composition on reappearance of atelectasis and impairment of gas exchange after a vital capacity maneuver.METHODS:A consecutive sample of 12 adults with healthy lungs who were scheduled for elective surgery were studied. Thirty minutes after induction of anesthesia with fentanyl and propofol, the lungs were hyperinflated manually up to an airway pressure of 40 cmH2O. FIO2 was either kept at 0.4 (group 1, n = 6) or changed to 1.0 (group 2, n = 6) during the recruitment maneuver. Atelectasis was assessed by computed tomography. The amount of dense areas was measured at end-expiration in a transverse plane at the base of the lungs. The ventilation-perfusion distributions (VA/Q) were estimated with the multiple inert gas elimination technique. The static compliance of the total respiratory system (Crs) was measured with the flow interruption technique.RESULTS:In group 1 (FIO2 = 0.4), the recruitment maneuver virtually eliminated atelectasis for at least 40 min, reduced shunt (VA/Q < 0.005), and increased at the same time the relative perfusion to poorly ventilated lung units (0.005 < VA/Q < 0.1; mean values are given). The arterial oxygen tension (PaO2) increased from 137 mmHg (18.3 kPa) to 163 mmHg (21.7 kPa; before and 40 min after recruitment, respectively; P = 0.028). In contrast to these findings, atelectasis recurred within 5 min after recruitment in group 2 (FIO2 = 1.0). Comparing the values before and 40 min after recruitment, all parameters of VA/Q were unchanged. In both groups, Crs increased from 57.1/55.0 ml.cmH2O-1 (group 1/group 2) before to 70.1/67.4 ml.cmH2O-1 after the recruitment maneuver. Crs showed a slow decrease thereafter (40 min after recruitment: 61.4/60.0 ml.cmH2O-1), with no difference between the two groups.CONCLUSIONS:The composition of inspiratory gas plays an important role in the recurrence of collapse of previously reexpanded atelectatic lung tissue during general anesthesia in patients with healthy lungs. The reason for the instability of these lung units remains to be established. The change in the amount of atelectasis and shunt appears to be independent of the change in the compliance of the respiratory system.
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| 2. |
- Al-Saadi, Munir, 1965-
(författare)
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Thermomechanical Processing of Nickel-Base Alloy 825
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Alloy 825 material was studied using a Gleeble-3800 thermosimulatorby performing single-hot compression experiments.Optical microscopy and electron backscatter diffraction wereutilized to characterize the microstructure. Dynamicrecrystallization is not considerable in the as-cast alloy anddislocation recovery is deemed to be dominant. Based on thisfinding, the effect of adding trace amounts of alloying additionson the mechanical properties of cast alloy 825 was studied, withemphasis on whether or not dynamic recrystallization occurred.The results show that dynamic recrystallization was moreprevalent under all test conditions in samples containing a traceamount of magnesium, but not for the conventional alloy.However, alloying with trace magnesium did not lead to animprovement of the mechanical properties. Instead, processingmaps for hot forging of conventional Alloy 825 were required toidentify optimal working parameters and to achieve dynamicrecrystallization. The hot deformation behavior of cast Alloy 825was characterized by using dynamic materials modelling of hotcompression data. The results show that the maximum powerdissipation efficiency is over 35%. The highest efficiency isachieved in the temperature range of 1100 ℃ - 1250 ℃ and instrain rates in the range of 0.01 ≤ strain rate / s ≤ 0.1. The optimumprocessing parameters for good strain hardening are obtained inthe temperature range between 950 ℃ and 1100 ℃ with strainrates of 0.3 ≤ strain rate/ s ≤ 10.0. In addition, the influence of thedeformation level on the recrystallization and microstructuralchanges in Alloy 825 during hot forging operations attemperatures between 950 °C and 1200 °C was studied. Themaximum yield strength and ultimate tensile strength wereobtained after forging to achieve a true strain of 0.9 were 413 MPa and 622 MPa , respectively, with a ductility of 40%.However, Alloy 825 is often supplied as annealed bars.Therefore, the effect of the forging strain magnitude andsubsequent annealing on the microstructure, strengtheningmechanisms and room temperature mechanical properties wereinvestigated to assess the suitability of current industrialpractice. The results showed that the majority of strengtheningwas attributed to grain refinement, the dislocation densities thatarise due to the large forging strain, and due to solid solutionstrengthening. The results of calculations are in excellentagreement with experimental data, with less than 1% difference.These results can be used by future researchers and industry topredict the strength of Alloy 825 and similar alloys, especially inmaterial after a completed hot forging operation.
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| 3. |
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| 4. |
- Berggård, Cecilia, 1975-
(författare)
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Transcription Factor AP-2 in Relation to Personality and Antidepressant Drugs
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The CNS monoaminergic systems are considered as the head engine regulating neuropsychiatric functions and personality. Transcription factor AP-2 is known to be essential for the development of the brainstem including the monoaminergic nuclei, and has the ability to regulate many genes in the monoaminergic systems. The ability of transcription factors to regulate specific gene expression, has lately made them hot candidates as drug targets. In this thesis, results indicating a role of AP-2 in the molecular effects of the antidepressant drugs citalopram and phenelzine, are presented. A polymorphism in the second intron of the gene encoding AP-2ß has previously been associated with anxiety-related personality traits as estimated by the Karolinska Scales of Personality (KSP). In this thesis, results confirming this association, gained by using a larger material and several different personality scales, are presented. Furthermore, data is presented showing an association between the activity of platelet monoamine oxidase, a trait-dependent marker for personality, and the genotype of the AP-2ß intron 2 polymorphism. The functional importance of the AP-2ß intron 2 polymorphism has not yet been elucidated. Included in this thesis are results showing that the AP-2ß intron 2 polymorphism is not in linkage disequilibrium with the only other described polymorphism in the AP-2ß gene, i.e. in the AP-2ß promoter (-67 G/A). Introns have in several studies been shown to include binding sites for regulatory proteins, and thus, to be important in transcriptional regulation. Results are presented demonstrating that one human brain nuclear protein binds only to the long variant of the AP-2ß intron 2 polymorphism. If this protein is involved in the regulation of the AP-2ß gene, it would affect the expression levels of the AP-2ß protein. In general, this thesis further establishes the role of transcription factor AP-2 as a regulatory factor of importance for personality and monoaminergic functions.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Calmunger, Mattias
(författare)
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High-Temperature Behaviour of Austenitic Alloys : Influence of Temperature and Strain Rate on Mechanical Properties and Microstructural Development
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The global increase in energy consumption and the global warming from greenhouse gas emission creates the need for more environmental friendly energy production processes. Biomass power plants with higher efficiency could generate more energy but also reduce the emission of greenhouse gases, e.g. CO2. Biomass is the largest global contributor to renewable energy and offers no net contribution of CO2 to the atmosphere. One way to increase the efficiency of the power plants is to increase temperature and pressure in the boiler parts of the power plant.The materials used for the future biomass power plants, with higher temperature and pressure, require improved properties, such as higher yield strength, creep strength and high-temperature corrosion resistance. Austenitic stainless steels and nickel-base alloys have shown good mechanical and chemical properties at the operation temperatures of today’s biomass power plants. However, the performance of austenitic stainless steels at the future elevated temperatures is not fully understood.The aim of this licentiate thesis is to increase our knowledge about the mechanical performance of austenitic stainless steels at the demanding conditions of the new generation power plants. This is done by using slow strain rate tensile deformation at elevated temperature and long term hightemperature ageing together with impact toughness testing. Microscopy is used to investigate deformation, damage and fracture behaviours during slow deformation and the long term influence of temperature on toughness in the microstructure of these austenitic alloys. Results show that the main deformation mechanisms are planar dislocation deformations, such as planar slip and slip bands. Intergranular fracture may occur due to precipitation in grain boundaries both in tensile deformed and impact toughness tested alloys. The shape and amount of σ-phase precipitates have been found to strongly influence the fracture behaviour of some of the austenitic stainless steels. In addition, ductility is affected differently by temperature depending on alloy tested and dynamic strain ageing may not always lead to a lower ductility.
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| 9. |
- ENGBERG, ARON, et al.
(författare)
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'A Fool for Christ' : Sense-Making and Negotiation of Identity in the Life Story of a Christian Soldier
- 2014
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Ingår i: Comprehending Christian Zionism : Perspectives in Comparison - Perspectives in Comparison. - Minneapolis : Fortress Press. - 9781451472264 - 9781451489644 ; , s. 33-59
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Bokkapitel (refereegranskat)abstract
- This chapter presents a narrative analysis of the life story of a Swedish Pentecostal who decided to join the Israeli Defense Forces out of his conviction that God wanted him to protect the chosen people. His story is treated as an example of lived Christian Zionism; as one of many manifestations that contemporary Christian affection for Israel can take. The analysis focuses on the central narrative pattern of calling-test of faith-confirmation, 'Jacob's' sense-making of his life choices, and the negotiation of his identity in relation to larger religious and cultural narratives.
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| 10. |
- Engberg, Elisabeth, 1961-
(författare)
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I fattiga omständigheter : Fattigvårdens former och understödstagare i Skellefteå socken under 1800-talet
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis is to shed light upon the Swedish nineteenth century poor relief system, how it operated in a local rural context, how it changed over time, and not least, who was supported and why. It raises questions about how the poor laws were interpreted on the parish level, how the welfare systems interacted with local society and about who was considered to be poor and entitled to support. The geographical setting of the thesis is Skellefteå, a rural parish in northern Sweden, and it concentrates upon the period 1830–1875.Swedish poor relief was governed by the fundamental principle that each parish had a duty to support their own poor and each parish was allowed a large amount of freedom to adjust their welfare arrangements according to local conditions. In Skellefteå, the main incentive for modification of the poor relief system was not new regulations from the national level, but social and economic transformations on the local level. This implies that local requirements were put before national legislation and suggests the existence of several regional, and perhaps also local, poor relief systems in nineteenth-century Sweden.On the local level, the results indicate the existence of a parochial social citizenship based upon a common understanding of social rights and duties in the community, and grounded in a strong sense of affiliation with the local society. Generally there was a larger distance between the poor and their providers in the wealthier and more socially stratified villages, hence a more egalitarian context seem to have facilitated identification and empathy with the poor. The local provision for the poor created and maintained bonds within a community, as well as it helped to build and reinforce boundaries towards those who did not belong. A sometimes suspicious and negative attitude towards outsiders was to some extent caused by a fear of increased poor relief expenses, but it also bears witness to a rural culture with a strong sense of belonging to one’s own village or hamlet.The majority of men and women supported by poor relief in Skellefteå belonged to the lower strata of society long before they became welfare recipients. They were landless rural people with weak kinship networks, that in most cases were unable to mobilize any significant support in times of need. Childhood, early middle age, and old age were identified as phases in the life cycle that seem to have entailed an increased risk of poverty and dependence. A substantial proportion of the poor were breadwinners, middle aged men with large households to support, while the widowed and unmarried paupers usually were women. For many of these households the life cycles’ vulnerable periods were further reinforced by other factors: a breadwinner’s illness or disability, the death of a spouse, a major subsistence crisis, or a larger marginalization caused by a deviation from society’s moral standards. In most cases there seems to have been a delicate interplay between several social risks that determined if and when a person or a household was to end up being supported by poor relief.
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| 11. |
- Engberg, Göran, et al.
(författare)
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A Physically based Microstructure Model for Predicting the Microstructure Evolution of a C-Mn Steel during and after Deformation
- 2008
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Ingår i: Steel Research International. - Düsseldorf : Verlag Stahleisen GMBH. - 1611-3683 .- 1869-344X. ; 79:1, s. 47-58
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Tidskriftsartikel (refereegranskat)abstract
- A physically based model for predicting microstructural evolution has been developed. The model is based on a physical description of dislocation density evolution, where the generation and recovery of dislocations determine 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. To verify that the model is able to describe dynamic, static and metadynamic recrystallization of C-Mn steels, hot compression tests combined with relaxation were performed at various temperatures, strains and strain rates. The model showed reasonable agreement with the experimental data for the compression tests performed at temperatures ranging from 850?C to 1200?C and strain rates ranging from 0.1 to 10 s-1. Also, the calculations of the stress relaxation tests show good agreement with experimental data. A validation of the model was done by calculating a multi-step test where good agreement with both flow-stress values and grain sizes was obtained. The main purpose of the model is to be able to predict the microstructural evolution during hot rolling and this investigation presents very promising results.
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| 12. |
- Engberg, Göran, et al.
(författare)
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Analysing metal working processes
- 2005
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Ingår i: Fundamentals of metallurgy. - Cambridge : Woodhead Publishing ltd. - 9781855739277 ; , s. 453-470
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Metal working processes encompass a wide range of strain, strain rates and temperatures. Strains range from less than 0.01 (for example in skin-pass rolling of interstitial free steel) up to around 1 (cold rolling of strip, extrusion, etc.). Typical strain rates and temperatures are given in Table 11.1 (which is partly an extract from Frost and Ashby (1982). For plastic forming processes the most important characteristics of the material are: the ability to distribute strains; the deformation resistance; and the resulting properties of the formed part. The ability to distribute strains is mainly governed by the work hardening and strain-rate sensitivity. It is also affected by the strain path. The purpose of this paper is to outline the, in our view, most essential material properties for metal working processes and the microstructural reasons for them. We recognise that the presence and development of crystallographic texture is quite an important part but our purpose is not to give an extensive description of this, only to point out some consequences. For further reading we recommend a book by Kocks, Tomé and Wenk (1998). Another aspect that is only briefly covered is the influence of stress states and changes in strain paths during processing or between consecutive process steps.
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| 13. |
- Engberg, Göran, et al.
(författare)
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Analysis of the plastic deformation behavior for two austenitic NiCr-steels with different stacking fault energies
- 2018
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Ingår i: International Journal of Computational Physics Series. - : NSSEL Publishing. - 2631-8350. ; 1:1, s. 137-141
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Tidskriftsartikel (refereegranskat)abstract
- Two austenitic stainless steels, with low and medium stacking fault energies (SFE), 20 mJ/m2 and 30 mJ/m2 respectively, have been studied by conventional tensile tests and in situ tensile tests in a FEG-SEM equipped for EBSD. High angle boundaries (HAB) and low angle boundaries (LAB) with misorientations >= 10o and >= 2o respectively have been determined, and size distributions for the LABs have been derived by linear intercepts. It was found that the size distributions could be described by bimodal lognormal functions. For the steel with highest SFE plastic deformation took place by dislocation slip only while the steel with low SFE deformed by slip and twinning. Using a model for slip based on the evolution of the dislocation density with the generation of dislocations inversely proportional to the mean free distance of slip and recovery of dislocations proportional to the dislocation density the stress strain-curves were analyzed and the results compared with the measured quantities. The mean free distance of slip as evaluated from the stress-strain curve for the steel with the highest SFE correlates very well with the mean size of the LABs intercept. The rate of recovery also gave an expected stress dependence. The stress needed to start deformation twinning was based on the assumption that Shockley partials become completely separated in the slip plane. The thus calculated values for the twinning stress showed an excellent agreement with the observed start of twinning as given by EBSD evaluation of twin boundaries (TB). For the alloy with low SFE both surface grains (in situ test) and bulk grains (from interrupted conventional tests) were studied. The stress needed for slip and twinning of surface grains was, as expected, in the order of 0.5-0.6 times the applied stress.
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| 14. |
- Engberg, Göran, 1946-
(författare)
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Constitutive models, physically based models for plasticity
- 2014
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Ingår i: Encyclopedia of Thermal Stresses. - Dordrecht, Heidelberg, New York, London : Springer. - 9789400727397 ; , s. 649-662
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Bokkapitel (refereegranskat)abstract
- Physically based models for the plastic behavior of crystalline, metallic materials are discussed. However, deformation by twinning and phase transformations as well as the evolution of texture are omitted.
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| 15. |
- Engberg, Göran, et al.
(författare)
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Modeling microstructure development during hot working of an austenitic stainless steel
- 2013
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 753, s. 423-426
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Tidskriftsartikel (refereegranskat)abstract
- A number of physically based models are combined in order to predict microstructure development during hot deformation. The models treat average values for the generation and recovery of vacancies and dislocations, recrystallization and grain growth and the dissolution and precipitation of second phase particles. The models are applied to a number of laboratory experiments made on 304 austenitic stainless steel and the model parameters are adjusted from those used for low alloyed steel mainly in order to obtain the right kinetics for the influence of solute drag on climb of dislocations and on grain growth. The thermodynamic data are obtained using Thermo-Calc© to create solubility products for the possible secondary phases. One case of wire rolling has been analyzed mainly concerning the evolution of recrystallization and grain size. The time, temperature and strain history has been derived using process information. The models are shown to give a fair description of the microstructure development during hot working of the studied austenitic stainless steel. © (2013) Trans Tech Publications, Switzerland.
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| 16. |
- Engberg, Isak, et al.
(författare)
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Fatigue in the general population-associations to age, sex, socioeconomic status, physical activity, sitting time and self-rated health : the northern Sweden MONICA study 2014
- 2017
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Ingår i: BMC Public Health. - : BIOMED CENTRAL LTD. - 1471-2458. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Background: Fatigue is widespread in the population and a common complaint in primary care. Little is known about prevalence of fatigue in the population and its predictors. We aimed to describe the pattern of fatigue in the general population and to explore the associations with age, sex, socioeconomic status, self-reported physical activity, sitting time and self-rated health.Methods: One thousand, five hundred and fifty-seven out of 2500 invited subjects in the Northern Sweden MONICA Study 2014, aged 25-74 years, filled out the Multidimensional Fatigue Inventory (MFI-20), consisting of four subscales: General fatigue (GF), Physical fatigue (PF), Reduced activity (RA) and Mental fatigue (MF). Questions regarding age, sex, socioeconomic status, physical activity, sitting time and self-rated health were also included.Results: Higher age correlated significantly with lower fatigue scores for the GF and MF subscales. Women had higher fatigue scores than men on all subscales (p < 0.05). Among men, higher socioeconomic status was related to lower fatigue for the GF, PF and RA subscales (age adjusted p < 0.05). Among women, higher socioeconomic status was related to lower fatigue for the PF and MF subscales (age adjusted p < 0.05). Higher physical activity was connected to lower levels of fatigue for all subscales (age and sex adjusted p < 0.001) except for MF. Longer time spent sitting was also related to more fatigue on all subscales (age and sex adjusted p < 0.005) except for MF. Better self-rated health was strongly associated with lower fatigue for all subscales (age and sex adjusted p < 0.001).Conclusion: Older, highly educated, physically active men, with little sedentary behavior are generally the least fatigued. Self-rated health is strongly related to fatigue. Interventions increasing physical exercise and reducing sedentary behavior may be important to help patients with fatigue and should be investigated in prospective studies.
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| 17. |
- Eren, Feride, et al.
(författare)
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Immunological protein profiling of first-episode psychosis patients identifies CSF and blood biomarkers correlating with disease severity
- 2023
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Ingår i: Brain, behavior, and immunity. - : Elsevier. - 0889-1591 .- 1090-2139. ; 111, s. 376-385
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Tidskriftsartikel (refereegranskat)abstract
- Background and HypothesisImmune activation is suggested to play an important role in psychosis. In this study, a large number of immune-related proteins were analyzed to obtain a more comprehensive picture of immune aberrations in schizophrenia.Study DesignNinety-two immune markers were analyzed by the Olink Protein Extension Assay (Inflammatory Panel) in plasma and cerebrospinal fluid (CSF) from 77 first-episode psychosis (FEP) patients (of which 43 later received the diagnosis of schizophrenia) and 56 healthy controls, all recruited from the Karolinska Schizophrenia Project (KaSP), Stockholm, Sweden.Study ResultsDifferential analysis showed that 12 of 92 inflammatory proteins were significantly higher in the plasma of FEP patients (n = 77) than in controls, and several proteins were positively correlated with disease severity. Patients from the same cohort diagnosed with schizophrenia (n = 43), showed significantly higher levels of 15 plasma proteins compared to controls whereas those not receiving this diagnosis showed no significant differences. The presently used OLINK inflammatory panel allowed the detection of only 47 CSF proteins of which only CD5 differed between patients and controls.ConclusionsThe levels of several peripheral immune markers, particularly those interfering with WNT/β-catenin signaling, were significantly higher in patients with FEP than in healthy controls and associated with illness severity.
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| 18. |
- Erhardt, Sophie, et al.
(författare)
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Kynurenic acid levels ae elevated in the cerebrospinal fluid of patients with schizophrenia
- 2001
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Ingår i: Neuroscience Letters. - 0304-3940 .- 1872-7972. ; 313:1-2, s. 96-98
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Tidskriftsartikel (refereegranskat)abstract
- Kynurenic acid is an endogenous glutamate antagonist with a preferential action at the glycine-site of the N-methyl D-aspartate-receptor. Mounting evidence indicate that the compound is significantly involved in basal neurophysiological processes in the brain. In the present investigation, cerebrospinal fluid (CSF) level of kynurenic acid was analyzed in 28 male schizophrenic patients and 17 male healthy controls by means of high pressure liquid chromatography and fluorescence detection. Schizophrenic patients showed elevated CSF levels of kynurenic acid (1.67 ▒ 0.27 nM) compared to the control group (0.97 ▒ 0.07 nM). Furthermore, CSF levels of kynurenic acid in schizophrenic patients were also found to correlate with age. The present finding is indicative of a contribution of kynurenic acid in the pathogenesis of schizophrenia. ⌐ 2001 Elsevier Science Ireland Ltd. All rights reserved.
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| 19. |
- Eskilsson, Anna, 1986-
(författare)
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Inflammatory Signaling Across the Blood-Brain Barrier and the Generation of Fever
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fever is a cardinal sign of inflammation and is evolutionary conserved. Fever is known to be beneficial during acute inflammation, but over time and if very high it can be detrimental. The signaling pathways by which fever is initiated by the brain and the peripheral mechanisms through which the temperature increase is generated were studied from several point of views. Fever is known to be dependent on prostaglandin E2 (PGE2) binding to its receptors in the median preoptic nucleus of the hypothalamus, which signals to the brainstem and through sympathetic nerves to heat conserving and heat producing effector organs. This thesis focuses on identifying the cells that produce the PGE2 critical for the fever response; showing where in the brain the critical PGE2 production takes place; demonstrating how peripheral inflammation activates these cells to produce PGE2; and finally, identifying the effector mechanisms behind the temperature elevation in fever. By using a newly developed specific antibody we showed that the enzyme responsible for the terminal step in the production of PGE2, microsomal prostaglandin E-synthase 1 (mPGES-1), is expressed in endothelial cells of brain blood vessels in mice where it is co-expressed with the enzyme cyclooxygenase-2 (Cox-2), which is known to be induced in these cells and to be rate limiting for the PGE2 production. The mPGES-1 enzyme was also expressed in several other cell types and structures which however did not express Cox-2, such as capillary-associated pericytes, astroglial cells, leptomeninges, and the choroid plexus. The role of the mPGES-1 in these other cells/structures remains unknown. Next, by using mice with selective deletion of Cox-2 in brain endothelial cells, we showed that local PGE2 production in deep brain areas, such as the hypothalamus, is critical for the febrile response to peripheral inflammation. In contrast, PGE2 production in other brain areas and the overall PGE2 level in the brain were not critical for the febrile response. Partly restoring the PGE2 synthesizing capacity in the anterior hypothalamus of mice lacking such capacity with a lentiviral vector resulted in a temperature elevation in response to an intraperitoneal injection of bacterial wall lipopolysaccharide (LPS). The data show that the febrile response is dependent on the local release of PGE2 onto its target neurons, possibly by a paracrine mechanism. Deletion of the receptor for the pyrogenic cytokine IL-6 on brain endothelial cells, but not on neurons or peripheral nerves, strongly attenuated the febrile response to LPS and reduced the induction of the Cox-2 expression in the hypothalamus. Furthermore, mice deficient of the IL- 6Rα gene in the brain endothelial cells showed a reduced SOCS3 mRNA induction, whereas IκB mRNA-levels were unaffected, suggesting that the IL-6 signaling occurs via STAT3 activation and not signaling through the transcription factor NF-κB. This idea was confirmed by the observation of attenuated fever in mice deficient of STAT3 in brain endothelial cells. These data show that IL-6, when endogenously released during systemic inflammation, is pyrogenic by binding to IL-6R on brain endothelial cells to induce prostaglandin synthesis in these cells. Finally, we demonstrate that mice with genetic deletion of uncoupling protein-1 (UCP-1), hence lacking functional brown adipose tissue, had a normal fever response to LPS, and that LPS caused no activation of brown adipose tissue in wild type mice. However, blocking peripheral cutaneous vasoconstriction resulted in a blunted fever response to LPS, suggesting that heat conservation, possibly together with shivering or non-shivering thermogenesis in the musculature, is responsible for the generation of immune-induced fever, whereas brown adipose tissue thermogenesis is not involved.
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| 20. |
- Farooq, Muhammad, 1976-
(författare)
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Strengthening and degradation mechanisms in austenitic stainless steels at elevated temperature
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With rapid economic developments and rising living standards, the demand for electricity all over the world is greatly increased. Due to high fuel costs, the steam boilers with higher steam temperature and pressure are needed to decrease the cost of power generation throughout the world extensively. In recent years, human awareness of the gradual strengthening of environmental protection increases, therefore to reduce the CO2 emissions the power generation efficiency needs to be improved. The development of high temperature materials with improved creep rupture strength and oxidation resistance is critically needed. Materials for these demanding conditions are austenitic stainless steels such as 310, 310NbN and Sanicro 25.Fundamental models have been developed for the precipitation of coarse particles during long time ageing of austenitic stainless steels and the influence of the particles on the mechanical properties. The models have been verified by ageing experiments. The austenitic stainless steel 310 was aged for up to 5000 h at 800 ºC. The precipitation models could satisfactorily describe the influence of ageing time on the radii and the volume fractions of particles. Models for the influence of the coarse precipitates on the tensile properties and the toughness were developed and reproduce the measured mechanical properties without the use of any fitting parameters. These developed models were utilised to investigate the influence of bands on ductility and toughness at room temperature. Up to 10 % σ-phase was observed to precipitate, which has a pronounced influence of the mechanical properties. Thermodynamic analysis demonstrated that the amount of precipitates due to ageing can significantly be reduced if the nitrogen or the carbon content is increased.Microstructure investigations of austenitic stainless steel 310NbN and Sanicro 25 were carried out by light microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The austenitic stainless steel 310NbN was aged for up to 10000 h at 650 and 750 ºC. The austenitic stainless steel Sanicro 25 was also aged for up to 10000 h at 650 and 700 ºC. Phase fractions and mean radii evolution of precipitates were calculated and compared to the experimental results. Size distributions of the precipitates in these steels were determined. Models for the different contributions to the creep strength have been applied: i) a recovery creep model for the dislocation hardening; ii) a climb controlled model for the precipitation hardening; iii) solid solution hardening from Cottrell clouds of solutes around the dislocations, and iv) A modified Dobes model for the effective stress. The total contributions can describe the experimental creep strength satisfactorily without the use of adjustable parameters.
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| 21. |
- Gyhlesten Back, Jessica, et al.
(författare)
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Investigation of parent austenite grains from martensite structure using EBSD in a wear resistant steel
- 2017
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Ingår i: Materials. - : MDPI. - 1996-1944. ; 10:5
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Tidskriftsartikel (refereegranskat)abstract
- Crystallographic reconstruction of parent austenite grain boundaries from the martensitic microstructure in a wear resistant steel was carried out using electron backscattered diffraction (EBSD). The present study mainly aims to investigate the parent austenite grains from the martensitic structure in an as-rolled (reference) steel sample and samples obtained by quenching at different cooling rates with corresponding dilatometry. Subsequently, this study is to correlate the nearest cooling rate by the dilatometer which yields a similar orientation relationship and substructure as the reference sample. The Kurdjumov-Sachs orientation relationship was used to reconstruct the parent austenite grain boundaries from the martensite boundaries in both reference and dilatometric samples using EBSD crystallographic data. The parent austenite grain boundaries were successfully evaluated from the EBSD data and the corresponding grain sizes were measured. The parent austenite grain boundaries of the reference sample match the sample quenched at 100 °C/s (CR100). Also the martensite substructures and crystallographic textures are similar in these two samples. The results from hardness measurements show that the reference sample exhibits higher hardness than the CR100 sample due to the presence of carbides in the reference sample.
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| 22. |
- Gyhlesten Back, Jessica
(författare)
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Modelling and Characterisation of the Martensite Formation in Low Alloyed Carbon Steels
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The current work contains experimental and theoretical work about the formation of martensite from the austenitic state of the steel Hardox 450. Simulation of rolling and subsequent quenching of martensitic steel plates requires a model that can account for previous deformation, current stresses and the temperature history, therefore dilatometry experiments were performed, with and without deformation. Two austenitization schedules were used and in the standard dilatometry the cooling rates varied between 5-100 °C/s, in order to find the minimum cooling rate that gives a fully martensitic microstructure. Cooling rates larger than 40°C/s gave a fully martensitic microstructure. The cooling rate of 100 °C/s was used in the deformation dilatometry tests where the uniaxial deformation varied from 5-50 %. The theoretical work involved modelling of the martensite formation and the thermal/transformation strains they cause in the steel. Characterizations were done using light optical microscopy, hardness tests and electron backscatter diffraction technique. The parent austenite grains of the martensitic structure were reconstructed using the orientation relationship between the parent austenite and the martensite. Kurdjumov-Sachs orientation relationships have previously been proven to work well for low-carbon steels and was therefore selected.The standard implementation of the Koistinen-Marburger equation for martensite formation and a more convenient approach were compared. The latter approach does not require the storage of initial austenite fraction at start of martensite formation. The comparison shows that the latter model works equally well for the martensite formation. The results showed that the use of martensite start and finish temperatures calibrated versus experiments for Hardox 450 works better when computing thermal expansion than use of general relations based on the chemistry of the steel.The results from deformation dilatometry showed that deformation by compressive uniaxial stresses impedes the martensite transformation. The simplified incremental model works well for deformation with 5 % and 10 %. However, the waviness in the experimental curve for deformation 50 % does not fit the model due vi to large barrelling effect and the large relative expansion for the material that the sample holders are made of.Crystallographic reconstruction of parent austenite grains were performed on a hot-rolled as-received reference sample and dilatometry samples cooled with 60 °C/s and 100 °C/s. The misorientation results showed that the samples match with the Kurdjumov-Sachs orientation relationship in both hot rolled product and dilatometry samples. When misorientation between adjacent pixels are between 15° and 48°, then the boundary between them was considered as a parent austenite grain. The austenitic grain boundaries of the sample cooled at 100 °C/s is in general identical with the hot rolled sample when considering high angle boundaries (15°-48°). The results from the hardness tests showed that the rolled product exhibits higher hardness as compared to samples cooled by 100 °C/s and 60 °C/s. This can be attributed to the formation of transition-iron-carbides in the hot rolled product due to longer exposure of coiling temperature.
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| 23. |
- Haroon, Humza, et al.
(författare)
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Cerebrospinal fluid proteomic signatures are associated with symptom severity of first-episode psychosis
- 2024
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Ingår i: Journal of Psychiatric Research. - : Elsevier. - 0022-3956 .- 1879-1379. ; 171, s. 306-315
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Tidskriftsartikel (refereegranskat)abstract
- Apart from their diagnostic, monitoring, or prognostic utility in clinical settings, molecular biomarkers may be instrumental in understanding the pathophysiology of psychiatric disorders, including schizophrenia. Using untargeted metabolomics, we recently identified eight cerebrospinal fluid (CSF) metabolites unique to first-episode psychosis (FEP) subjects compared to healthy controls (HC). In this study, we sought to investigate the CSF proteomic signatures associated with FEP. We employed 16-plex tandem mass tag (TMT) mass spectrometry (MS) to examine the relative protein abundance in CSF samples of 15 individuals diagnosed with FEP and 15 age-and-sex-matched healthy controls (HC). Multiple linear regression model (MLRM) identified 16 differentially abundant CSF proteins between FEP and HC at p < 0.01. Among them, the two most significant CSF proteins were collagen alpha-2 (IV) chain (COL4A2: standard mean difference [SMD] = -1.12, p = 1.64 × 10-4) and neuron-derived neurotrophic factor (NDNF: SMD = -1.03, p = 4.52 × 10-4) both of which were down-regulated in FEP subjects compared to HC. We also identified several potential CSF proteins associated with the pathophysiology and the symptom profile and severity in FEP subjects, including COL4A2, NDNF, hornerin (HRNR), contactin-6 (CNTN6), voltage-dependent calcium channel subunit alpha-2/delta-3 (CACNA2D3), tropomyosin alpha-3 chain (TPM3 and TPM4). Moreover, several protein signatures were associated with cognitive performance. Although the results need replication, our exploratory study suggests that CSF protein signatures can be used to increase the understanding of the pathophysiology of psychosis.
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| 24. |
- Hashimoto, Kenji, et al.
(författare)
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Elevated glutamine/glutamate ratio in cerebrospinal fluid of first episode and drug naive schizophrenic patients
- 2005
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Ingår i: BMC Psychiatry. - 1471-244X. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Background: Recent magnetic resonance spectroscopy (MRS) studies report that glutamine is altered in the brains of schizophrenic patients. There were also conflicting findings on glutamate in cerebrospinal fluid (CSF) of schizophrenic patients, and absent for glutamine. This study aims to clarify the question of glutamine and glutamate in CSF of first episode and drug naive schizophrenic patients. Method: Levels of glutamine and glutamate in CSF of 25 first episode and drug-naive male schizophrenic patients and 17 age-matched male healthy controls were measured by a high performance liquid chromatography. Results: The ratio (126.1 (median), 117.7 ± 27.4 (mean ± S.D.)) of glutamine to glutamate in the CSF of patients was significantly (z = -3.29, p = 0.001) higher than that (81.01 (median), 89.1 ± 22.5 (mean ± S.D.)) of normal controls although each level of glutamine and glutamate in patients was not different from that of normal controls. Conclusion: Our data suggests that a disfunction in glutamate-glutamine cycle in the brain may play a role in the pathophysiology of schizophrenia. © 2005 Hashimoto et al, licensee BioMed Central Ltd.
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| 25. |
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