| 1. |
- Toth, Luca, et al.
(författare)
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The Effect of Mild Traumatic Brain Injury on Cerebral Microbleeds in Aging
- 2021
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Ingår i: Frontiers in Aging Neuroscience. - : Frontiers Media S.A.. - 1663-4365. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- A traumatic brain injury (TBI) induces the formation of cerebral microbleeds (CMBs), which are associated with cognitive impairments, psychiatric disorders, and gait dysfunctions in patients. Elderly people frequently suffer TBIs, especially mild brain trauma (mTBI). Interestingly, aging is also an independent risk factor for the development of CMBs. However, how TBI and aging may interact to promote the development of CMBs is not well established. In order to test the hypothesis that an mTBI exacerbates the development of CMBs in the elderly, we compared the number and cerebral distribution of CMBs and assessed them by analysing susceptibility weighted (SW) MRI in young (25 +/- 10 years old, n = 18) and elder (72 +/- 7 years old, n = 17) patients after an mTBI and in age-matched healthy subjects (young: 25 +/- 6 years old, n = 20; aged: 68 +/- 5 years old, n = 23). We found significantly more CMBs in elder patients after an mTBI compared with young patients; however, we did not observe a significant difference in the number of cerebral microhemorrhages between aged and aged patients with mTBI. The majority of CMBs were found supratentorially (lobar and basal ganglion). The lobar distribution of supratentorial CMBs showed that aging enhances the formation of parietal and occipital CMBs after mTBIs. This suggests that aging and mTBIs do not synergize in the induction of the development of CMBs, and that the different distribution of mTBI-induced CMBs in aged patients may lead to specific age-related clinical characteristics of mTBIs.
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| 2. |
- Környei, Bálint S., et al.
(författare)
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Cerebral microbleeds may be less detectable by susceptibility weighted imaging MRI from 24 to 72 hours after traumatic brain injury
- 2021
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Ingår i: Frontiers in Neuroscience. - : Frontiers Media S.A.. - 1662-4548 .- 1662-453X. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: A former rodent study showed that cerebral traumatic microbleeds (TMBs) may temporarily become invisible shortly after injury when detected by susceptibility weighted imaging (SWI). The present study aims to validate this phenomenon in human SWI.Methods: In this retrospective study, 46 traumatic brain injury (TBI) patients in various forms of severity were included and willingly complied with our strict selection criteria. Clinical parameters potentially affecting TMB count, Rotterdam and Marshall CT score, Mayo Clinic Classification, contusion number, and total volume were registered. The precise time between trauma and MRI [5 h 19 min to 141 h 54 min, including SWI and fluid-attenuated inversion recovery (FLAIR)] was individually recorded; TMB and FLAIR lesion counts were assessed. Four groups were created based on elapsed time between the trauma and MRI: 0-24, 24-48, 48-72, and >72 h. Kruskal-Wallis, ANOVA, Chi-square, and Fisher's exact tests were used to reveal differences among the groups within clinical and imaging parameters; statistical power was calculated retrospectively for each comparison.Results: The Kruskal-Wallis ANOVA with Conover post hoc analysis showed significant (p = 0.01; 1-β > 0.9) median TMB number differences in the subacute period: 0-24 h = 4.00 (n = 11); 24-48 h = 1 (n = 14); 48-72 h = 1 (n = 11); and 72 h ≤ 7.5 (n = 10). Neither clinical parameters nor FLAIR lesions depicted significant differences among the groups.Conclusion: Our results demonstrate that TMBs on SWI MRI may temporarily become less detectable at 24-72 h following TBI.
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| 3. |
- Toth, Luca, et al.
(författare)
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Age-related decline in circulating IGF-1 associates with impaired neurovascular coupling responses in older adults
- 2022
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Ingår i: GeroScience. - : Springer. - 2509-2715 .- 2509-2723. ; 44:6, s. 2771-2783
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Tidskriftsartikel (refereegranskat)abstract
- Impairment of moment-to-moment adjustment of cerebral blood flow (CBF) to the increased oxygen and energy requirements of active brain regions via neurovascular coupling (NVC) contributes to the genesis of age-related cognitive impairment. Aging is associated with marked deficiency in the vasoprotective hormone insulin-like growth factor-1 (IGF-1). Preclinical studies on animal models of aging suggest that circulating IGF-1 deficiency is causally linked to impairment of NVC responses. The present study was designed to test the hypotheses that decreases in circulating IGF-1 levels in older adults also predict the magnitude of age-related decline of NVC responses. In a single-center cross-sectional study, we enrolled healthy young (n = 31, 11 female, 20 male, mean age: 28.4 + / - 4.2 years) and aged volunteers (n = 32, 18 female, 14 male, mean age: 67.9 + / - 4.1 years). Serum IGF-1 level, basal CBF (phase contrast magnetic resonance imaging (MRI)), and NVC responses during the trail making task (with transcranial Doppler sonography) were assessed. We found that circulating IGF-1 levels were significantly decreased with age and associated with decreased basal CBF. Age-related decline in IGF-1 levels predicted the magnitude of age-related decline in NVC responses. In conclusion, our study provides additional evidence in support of the concept that age-related circulating IGF-1 deficiency contributes to neurovascular aging, impairing CBF and functional hyperemia in older adults.
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| 4. |
- Toth, Luca, et al.
(författare)
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Traumatic brain injury-induced cerebral microbleeds in the elderly
- 2021
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Ingår i: GeroScience. - : Springer. - 2509-2715 .- 2509-2723. ; 43:1, s. 125-136
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Forskningsöversikt (refereegranskat)abstract
- Traumatic brain injury (TBI) was shown to lead to the development of cerebral microbleeds (CMBs), which are associated with long term cognitive decline and gait disturbances in patients. The elderly is one of the most vulnerable parts of the population to suffer TBI. Importantly, ageing is known to exacerbate microvascular fragility and to promote the formation of CMBs. In this overview, the effect of ageing is discussed on the development and characteristics of TBI-related CMBs, with special emphasis on CMBs associated with mild TBI. Four cases of TBI-related CMBs are described to illustrate the concept that ageing exacerbates the deleterious microvascular effects of TBI and that similar brain trauma may induce more CMBs in old patients than in young ones. Recommendations are made for future prospective studies to establish the mechanistic effects of ageing on the formation of CMBs after TBI, and to determine long-term consequences of CMBs on clinically relevant outcome measures including cognitive performance, gait and balance function.
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| 5. |
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| 6. |
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| 7. |
- Alvarado, Gerardo, et al.
(författare)
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Heme-induced contractile dysfunction in Human cardiomyocytes caused by oxidant damage to thick filament proteins.
- 2015
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Ingår i: Free Radical Biology & Medicine. - : Elsevier BV. - 0891-5849. ; 89:sep 23, s. 248-262
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Tidskriftsartikel (refereegranskat)abstract
- Intracellular free heme predisposes to oxidant-mediated tissue damage. We hypothesized that free heme causes alterations in myocardial contractility via disturbed structure and/or regulation of the contractile proteins. Isometric force production and its Ca(2+)-sensitivity (pCa50) were monitored in permeabilized human ventricular cardiomyocytes. Heme exposure altered cardiomyocyte morphology and evoked robust decreases in Ca(2+)-activated maximal active force (Fo) while increasing Ca(2+)-independent passive force (Fpassive). Heme treatments, either alone or in combination with H2O2, did not affect pCa50. The increase in Fpassive started at 3µM heme exposure and could be partially reversed by the antioxidant dithiothreitol. Protein sulfhydryl (SH) groups of thick myofilament content decreased and sulfenic acid formation increased after treatment with heme. Partial restoration in the SH group content was observed in a protein running at 140kDa after treatment with dithiothreitol, but not in other proteins, such as filamin C, myosin heavy chain, cardiac myosin binding protein C, and α-actinin. Importantly, binding of heme to hemopexin or alpha-1-microglobulin prevented its effects on cardiomyocyte contractility, suggesting an allosteric effect. In line with this, free heme directly bound to myosin light chain 1 in human cardiomyocytes. Our observations suggest that free heme modifies cardiac contractile proteins via posttranslational protein modifications and via binding to myosin light chain 1, leading to severe contractile dysfunction. This may contribute to systolic and diastolic cardiac dysfunctions in hemolytic diseases, heart failure, and myocardial ischemia-reperfusion injury.
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| 8. |
- Alvarado, Gerardo, et al.
(författare)
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Heme-induced oxidation of cysteine groups of myofilament proteins leads to contractile dysfunction of permeabilized human skeletal muscle fibres
- 2020
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 21:21
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Tidskriftsartikel (refereegranskat)abstract
- Background: Heme released from red blood cells targets a number of cell components including the cytoskeleton. The purpose of the present study was to determine the impact of free heme (20–300 µM) on human skeletal muscle fibres made available during orthopedic surgery. Methods: Isometric force production and oxidative protein modifications were monitored in permeabilized skeletal muscle fibre segments. Results: A single heme exposure (20 µM) to muscle fibres decreased Ca2+-activated maximal (active) force (Fo) by about 50% and evoked an approximately 3-fold increase in Ca2+-independent (passive) force (Fpassive). Oxidation of sulfhydryl (SH) groups was detected in structural proteins (e.g., nebulin, α-actinin, meromyosin 2) and in contractile proteins (e.g., myosin heavy chain and myosin-binding protein C) as well as in titin in the presence of 300 µM heme. This SH oxidation was not reversed by dithiothreitol (50 mM). Sulfenic acid (SOH) formation was also detected in the structural proteins (nebulin, α-actinin, meromyosin). Heme effects on SH oxidation and SOH formation were prevented by hemopexin (Hpx) and α1-microglobulin (A1M). Conclusions: These data suggest that free heme has a significant impact on human skeletal muscle fibres, whereby oxidative alterations in structural and contractile proteins limit contractile function. This may explain and or contribute to the weakness and increase of skeletal muscle stiffness in chronic heart failure, rhabdomyolysis, and other hemolytic diseases. Therefore, therapeutic use of Hpx and A1M supplementation might be effective in preventing heme-induced skeletal muscle alterations.
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| 9. |
- Büki, Andras, 1966-, et al.
(författare)
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Minor and repetitive head injury
- 2014
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Ingår i: Advances and Technical Standards in Neurosurgery. - Cham : Springer. - 9783319090658 - 9783319090665 ; , s. 147-192
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Bokkapitel (refereegranskat)abstract
- Traumatic brain injury (TBI) is the leading cause of death and disability in the young, active population and expected to be the third leading cause of death in the whole world until 2020. The disease is frequently referred to as the silent epidemic, and many authors highlight the "unmet medical need" associated with TBI.The term traumatically evoked brain injury covers a heterogeneous group ranging from mild/minor/minimal to severe/non-salvageable damages. Severe TBI has long been recognized to be a major socioeconomical health-care issue as saving young lives and sometimes entirely restituting health with a timely intervention can indeed be extremely cost efficient.Recently it has been recognized that mild or minor TBI should be considered similarly important because of the magnitude of the patient population affected. Other reasons behind this recognition are the association of mild head injury with transient cognitive disturbances as well as long-term sequelae primarily linked to repeat (sport-related) injuries.The incidence of TBI in developed countries can be as high as 2-300/100,000 inhabitants; however, if we consider the injury pyramid, it turns out that severe and moderate TBI represents only 25-30 % of all cases, while the overwhelming majority of TBI cases consists of mild head injury. On top of that, or at the base of the pyramid, are the cases that never show up at the ER - the unreported injuries.Special attention is turned to mild TBI as in recent military conflicts it is recognized as "signature injury."This chapter aims to summarize the most important features of mild and repetitive traumatic brain injury providing definitions, stratifications, and triage options while also focusing on contemporary knowledge gathered by imaging and biomarker research.Mild traumatic brain injury is an enigmatic lesion; the classification, significance, and its consequences are all far less defined and explored than in more severe forms of brain injury.Understanding the pathobiology and pathomechanisms may aid a more targeted approach in triage as well as selection of cases with possible late complications while also identifying the target patient population where preventive measures and therapeutic tools should be applied in an attempt to avoid secondary brain injury and late complications.
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| 10. |
- Cseplo, Peter, et al.
(författare)
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Hemolyzed Blood Elicits a Calcium Antagonist and High CO2 Reversible Constriction via Elevation of [Ca2+]i in Isolated Cerebral Arteries
- 2017
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Ingår i: Journal of Neurotrauma. - : Mary Ann Liebert. - 0897-7151 .- 1557-9042. ; 34:2, s. 529-534
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Tidskriftsartikel (refereegranskat)abstract
- During acute subarachnoid hemorrhage, blood is hemolyzed, which is followed by a significant cerebrovascular spasm resulting in a serious clinical condition. Interestingly, however, the direct vasomotor effect of perivascular hemolyzed blood (HB) has not yet been characterized, preventing the assessment of contribution of vasoconstrictor mechanisms deriving from brain tissue and/or blood and development of possible treatments. We hypothesized that perivascular HB reduces the diameter of the cerebral arteries (i.e., basilar artery [BA]; middle cerebral artery [MCA]) by elevating vascular tissue [Ca2+](i) level. Vasomotor responses were measured by videomicroscopy and intracellular Ca2+ by the Fura2-AM ratiometric method. Adding HB to the vessel chamber reduced the diameter significantly (BA: from 264 +/- 7 to 164 +/- 11 mu m; MCA: from 185 +/- 15 to 155 +/- 14 mu m), which was reversed to control level by wash-out of HB. Potassium chloride (KCl), HB, serum, hemolyzed red blood cell (RBC), plasma, and platelet suspension (PLTs) elicited significant constrictions of isolated basilar arteries. There was a significant increase in K+ concentration in hemolyzed HB (7.02 +/- 0.22 mmol/L) compared to Krebs' solution (6.20 +/- 0.01 mmol/L). Before HB, acetylcholine (ACh), sodium-nitroprussid (SNP), nifedipin, and CO2 elicited substantial dilations in cerebral arteries. In contrast, in the presence of HB dilations to ACh, SNP decreased, but not to nifedipine and CO2. After washout of HB, nitric oxide-mediated dilations remained significantly reduced compared to control. HB significantly increased the ratiometric Ca signal, which returned to control level after washout. In conclusion, perivascular hemolyzed blood elicits significant-nifedipine and high CO2 reversible-constrictions of isolated BAs and MCAs, primarily by increasing intracellular Ca2+, findings that can contribute to the refinement of local treatment of subarachnoid hemorrhage.
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| 11. |
- Diószegi, Attila, 1962-, et al.
(författare)
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Modelling and simulation of heat conduction in 1-D polar spherical coordinates using control volume-based finite difference method
- 2016
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Ingår i: International journal of numerical methods for heat & fluid flow. - 0961-5539 .- 1758-6585. ; 26:1, s. 2-17
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Tidskriftsartikel (refereegranskat)abstract
- Purpose - The purpose of this paper is to obtain a finite difference method (FDM) solution using control volume for heat transport by conduction and the heat absorption by the enthalpy model in the sand mixture used in casting manufacturing processes. A mixture of sand and different chemicals (binders) is used as moulding materials in the casting processes. The presence of various compounds in the system improve the complexity of the heat transport due to the heat absorption as the binders are decomposing and transformed into gaseous products due to significant heat shock. Design/methodology/approach - The geometrical domain were defined in a 1D polar coordinate system and adapted for numerical simulation according to the control volume-based FDM. The simulation results were validated by comparison to the temperature measurements under laboratory conditions as the sand mould mixture was heated by interacting with a liquid alloy. Findings - Results of validation and simulation methods were about high correspondence, the numerical method presented in this paper is accurate and has significant potential in the simulation of casting processes. Originality/value - Both numerical solution (definition of geometrical domain in 1D polar coordinate system) and verification method presented in this paper are state-of-the-art in their kinds and present high scientific value especially regarding to the topic of numerical modelling of heat flow and foundry technology.
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| 12. |
- Garami, Attila, et al.
(författare)
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Reaction zone monitoring in biomass combustion
- 2018
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Ingår i: Control Engineering Practice. - : Elsevier Ltd. - 0967-0661 .- 1873-6939. ; 74, s. 95-106
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Tidskriftsartikel (refereegranskat)abstract
- In this work we demonstrate the utilization of a machine vision-based combustion monitoring system in biomass combustion. The proposed system monitored the location of the reaction zone in a 3 MW, grate-fired biomass boiler operated at varying loads and with fluctuating fuel quality. The system can help guarantee equal primary air supply to different regions of the grate and avoid the elutriation of fly ash by providing information on the location of the reaction zone. Strong correlation was found between the reaction zone boundary location and most process parameters, indicating that the location of the reaction zone can be a useful metric in monitoring and control by providing supplementary measurements to already existing monitoring to avoid over-emissions and improve economics.
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| 13. |
- Munoz-Fuentes, Violeta, et al.
(författare)
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Strong Artificial Selection in Domestic Mammals Did Not Result in an Increased Recombination Rate
- 2015
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Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 32:2, s. 510-523
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Tidskriftsartikel (refereegranskat)abstract
- Recombination rates vary in intensity and location at the species, individual, sex and chromosome levels. Despite the fundamental biological importance of this process, the selective forces that operate to shape recombination rate and patterns are unclear. Domestication offers a unique opportunity to study the interplay between recombination and selection. In domesticates, intense selection for particular traits is imposed on small populations over many generations, resulting in organisms that differ, sometimes dramatically, in morphology and physiology from their wild ancestor. Although earlier studies suggested increased recombination rate in domesticates, a formal comparison of recombination rates between domestic mammals and their wild congeners was missing. In order to determine broad-scale recombination rate, we used immunolabeling detection of MLH1 foci as crossover markers in spermatocytes in three pairs of closely related wild and domestic species (dog and wolf, goat and ibex, and sheep and mouflon). In the three pairs, and contrary to previous suggestions, our data show that contemporary recombination rate is higher in the wild species. Subsequently, we inferred recombination breakpoints in sequence data for 16 genomic regions in dogs and wolves, each containing a locus associated with a dog phenotype potentially under selection during domestication. No difference in the number and distribution of recombination breakpoints was found between dogs and wolves. We conclude that our data indicate that strong directional selection did not result in changes in recombination in domestic mammals, and that both upper and lower bounds for crossover rates may be tightly regulated.
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| 14. |
- Pethő, Dávid, et al.
(författare)
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Ferryl hemoglobin and heme induce Α1‐microglobulin in hemorrhaged atherosclerotic lesions with inhibitory function against hemoglobin and lipid oxidation
- 2021
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 22:13
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Tidskriftsartikel (refereegranskat)abstract
- Infiltration of red blood cells into atheromatous plaques and oxidation of hemoglobin (Hb) and lipoproteins are implicated in the pathogenesis of atherosclerosis. α1‐microglobulin (A1M) is a radical‐scavenging and heme‐binding protein. In this work, we examined the origin and role of A1M in human atherosclerotic lesions. Using immunohistochemistry, we observed a significant A1M immunoreactivity in atheromas and hemorrhaged plaques of carotid arteries in smooth muscle cells (SMCs) and macrophages. The most prominent expression was detected in macrophages of organized hemorrhage. To reveal a possible inducer of A1M expression in ruptured lesions, we exposed aortic endothelial cells (ECs), SMCs and macrophages to heme, Oxy‐ and FerrylHb. Both heme and FerrylHb, but not OxyHb, upregulated A1M mRNA expression in all cell types. Importantly, only FerrylHb induced A1M protein secretion in aortic ECs, SMCs and macrophages. To assess the possible function of A1M in ruptured lesions, we analyzed Hb oxidation and heme‐catalyzed lipid peroxidation in the presence of A1M. We showed that recombinant A1M markedly inhibited Hb oxidation and heme‐driven oxidative modification of low‐density lipoproteins as well plaque lipids derived from atheromas. These results demonstrate the presence of A1M in atherosclerotic plaques and suggest its induction by heme and FerrylHb in the resident cells.
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| 15. |
- Stanzione, Marcello, et al.
(författare)
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Meiotic DNA break formation requires the unsynapsed chromosome axis-binding protein IHO1 (CCDC36) in mice
- 2016
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Ingår i: Nature Cell Biology. - : Springer Science and Business Media LLC. - 1465-7392 .- 1476-4679. ; 18, s. 1208-1220
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 Macmillan Publishers Limited. part of Springer Nature All rights reserved. DNA double-strand breaks (DSBs) are induced by SPO11 during meiosis to initiate recombination-mediated pairing and synapsis of homologous chromosomes. Germline genome integrity requires spatiotemporal control of DSB formation, which involves the proteinaceous chromosome axis along the core of each meiotic chromosome. In particular, a component of unsynapsed axes, HORMAD1, promotes DSB formation in unsynapsed regions where DSB formation must occur to ensure completion of synapsis. Despite its importance, the underlying mechanism has remained elusive. We identify CCDC36 as a direct interactor of HORMAD1 (IHO1) that is essential for DSB formation. Underpinning this function, IHO1 and conserved SPO11-auxiliary proteins MEI4 and REC114 assemble chromatin-bound recombinosomes that are predicted activators of DSB formation. HORMAD1 is needed for robust recruitment of IHO1 to unsynapsed axes and efficient formation and/or stabilization of these recombinosomes. Thus, we propose that HORMAD1-IHO1 interaction provides a mechanism for the selective promotion of DSB formation along unsynapsed chromosome axes.
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| 16. |
- Svidró, József Tamás, 1984-, et al.
(författare)
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Heat absorption capacity and binder degradation characteristics of 3D printed cores investigated by inverse Fourier thermal analysis
- 2015
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Ingår i: Transactions Of The American Foundry Society. - : The American Foundry Society. - 9780874334340 ; , s. 135-143
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Konferensbidrag (refereegranskat)abstract
- The application of 3D printing techniques is a recently developing area used within foundry technology. Digital production of sand molds and cores eliminates the need for hard tooling, drastically reduces lead times and offers design freedoms not possible in the traditional pattern making. Even though mold and core making technologies are refined from both scientific and practical points of view, casting defects may still occur in the final products. Thus, molding material related casting research is required to generate state-of-the-art methods and understandings to avoid the formation of casting defects. In this paper, a pioneering method is presented which is suitable to determine novel thermophysical and heat transfer properties of various types of molding materials. These properties are strongly connected to the cooling capacity and the gas evolution features of the cores used in casting production. The method is based on temperature measurements inside spherical shaped core sand specimens and evaluated by a special application of Fourier thermal analysis. Temperature measurements were performed in test samples produced by two different 3D core printing systems. The registered temperature data were processed by Fourier thermal analysis to calculate the thermal properties and the decomposition characteristics of the 3D printed cores. The experiments were executed under different heating conditions analogous to aluminium and cast iron production.
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| 17. |
- Svidró, József Tamás, et al.
(författare)
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The novel application of Fourier thermal analysis in foundry technologies
- 2014
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Ingår i: Journal of thermal analysis and calorimetry (Print). - : Springer Science and Business Media LLC. - 1388-6150 .- 1588-2926. ; 115:1, s. 331-338
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Tidskriftsartikel (refereegranskat)abstract
- The process of casting in sand moulds is used for a large volume of castings manufactured in the world. Internal channels and complex geometries of these products are formed by the placement of cores within the mould cavity. Resin-bound sand mixtures are essential ingredients in engine component manufacturing. In this study, a state-of-the-art application of Fourier thermal analysis in foundry technologies is presented. Investigation of decomposition phenomena of resin-bound moulding materials during casting production is a brand new area to use the potential of thermal sciences. Temperature measurements in test samples of standard types of moulding mixtures were performed. The registered cooling curves were processed by a numerical iteration algorithm to determine the amount of heat absorbed during degradation of the moulding material. Thermogravimetric analysis (TG) and differential thermal analysis (DTA) of sand mixtures were carried out to compare the results of the Fourier thermal analysis with TG and DTA curves.
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| 18. |
- Svidró, Judit, et al.
(författare)
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The influence of thermal expansion of unbonded foundry sands on the deformation of resin bonded cores
- 2017
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Ingår i: Archives of Metallurgy and Materials. - : De Gruyter Open. - 1733-3490 .- 2300-1909. ; 62:2, s. 795-798
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Tidskriftsartikel (refereegranskat)abstract
- Depending on the preparation and the applied materials, moulds and cores can be of high rigidity or can be flexible. Although, chemically bonded moulding materials have relatively good flexibility, their high temperature behaviour determines the dimensional accuracy, the stresses in the castings and can induce several casting defects, such as rattail, veining, etc. The phenomenon is based on two major effects: the thermal expansion of the unbonded foundry sands and the deformation of the sand mixtures. The main objective of the present work was to study the relationship between these two effects, and to improve the knowledge related to the thermo-mechanical interactions between the casting and the mould. Dilatometric analysis of unbonded sand samples were performed and compared to the results of hot distortion tests of moulding mixture specimens. The results showed, that the thermal expansion of foundry sand largely influences the hot distortion behaviour, but depending on the type of binder used.
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| 19. |
- Toth, Arnold, et al.
(författare)
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Both hemorrhagic and non-hemorrhagic traumatic MRI lesions are associated with the microstructural damage of the normal appearing white matter
- 2018
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Ingår i: Behavioural Brain Research. - : Elsevier. - 0166-4328 .- 1872-7549. ; 340, s. 106-116
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Tidskriftsartikel (refereegranskat)abstract
- Traumatic microbleeds (TMBs) and non-hemorrhagic lesions (NHLs) on MRI are regarded as surrogate markers of diffuse axonal injury. However, the actual relation between lesional and diffuse pathology remained unclear, since lesions were related to clinical parameters, largely influenced by extracranial factors. The aim of this study is to directly compare TMBs, NHLs and their regional features with the co-existing diffuse injury of the normal appearing white matter (NAWM) as measured by diffusion tensor imaging (DTI). Thirty-eight adults with a closed traumatic brain injury (12 mild, 4 moderate and 22 severe) who underwent susceptibility weighted imaging (SWI), Tl-, T2 weighted and FLAIR MRI and routine CT were included in the study. TMB (on SWI) and NHL (on T1-, T2 weighted and FLAIR images) features and Rotterdam scores were evaluated. DTI metrics such as fractional anisotropy (FA) and mean diffusivity (MD) were measured over different NAWM regions. Clinical parameters including age; Glasgow Coma Scale; Rotterdam score; TMB and NHL features were correlated to regional NAWM diffusivity using multiple regression. Overall NHL presence and basal ganglia area TMB load were significantly, negatively correlated with the subcortical NAWM FA values (partial r = -0.37 and -0.36; p = 0.006 and 0.025, respectively). The presence of any NHL, or TMBs located in the basal ganglia area indicates diffuse NAWM damage even after adjusting for clinical and CT parameters. To estimate DAI, a conventional lesional MRI pathology evaluation might at least in part substitute the use of quantitative DTI, which is yet not widely feasible in a clinical setting. (C) 2017 Elsevier B.V. All rights reserved.
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| 20. |
- Tóth, Arnold, et al.
(författare)
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Cerebral Microbleeds Temporarily Become Less Visible or Invisible in Acute Susceptibility Weighted Magnetic Resonance Imaging : A Rat Study
- 2019
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Ingår i: Journal of Neurotrauma. - : Mary Ann Liebert. - 0897-7151 .- 1557-9042. ; 36:10, s. 1670-1677
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Tidskriftsartikel (refereegranskat)abstract
- Previously, we reported human traumatic brain injury cases demonstrating acute to subacute microbleed appearance changes in susceptibility-weighted imaging (SWI-magnetic resonance imaging [MRI]). This study aims to confirm and characterize such temporal microbleed appearance alterations in an experimental model. To elicit microbleed formation, brains of male Sprague Dawley rats were pierced in a depth of 4 mm, in a parasagittal position bilaterally using 159 mu m and 474 mu m needles, without the injection of autologous blood or any agent. Rats underwent 4.7 T MRI immediately, then at multiple time points until 125 h. Volumes of hypointensities consistent with microbleeds in SWI were measured using an intensity threshold-based approach. Microbleed volumes across time points were compared using repeated measures analysis of variance. Microbleeds were assessed by Prussian blue histology at different time points. Hypointensity volumes referring to microbleeds were significantly decreased (corrected p < 0.05) at 24 h compared with the immediate or the 125 h time points. By visual inspection, microbleeds were similarly detectable at the immediate and 125 h imaging but were decreased in extent or completely absent at 24 h or 48 h. Histology confirmed the presence of microbleeds at all time points and in all animals. This study confirmed a general temporary reduction in visibility of microbleeds in the acute phase in SWI. Such short-term appearance dynamics of microbleeds should be considered when using SWI as a diagnostic tool for microbleeds in traumatic brain injury and various diseases.
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| 21. |
- Tóth, Arnold, et al.
(författare)
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Lateral ventricle volume asymmetry predicts midline shift in severe traumatic brain injury
- 2015
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Ingår i: Journal of Neurotrauma. - : Mary Ann Liebert. - 0897-7151 .- 1557-9042. ; 32:17, s. 1307-1311
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Tidskriftsartikel (refereegranskat)abstract
- Midline shift following severe traumatic brain injury (sTBI) detected on computed tomography (CT) scans is an established predictor of poor outcome. We hypothesized that lateral ventricular volume (LVV) asymmetry is an earlier sign of developing asymmetric intracranial pathology than midline shift. This retrospective analysis was performed on data from 84 adults with blunt sTBI requiring a ventriculostomy who presented to a Level I trauma center. Seventy-six patients underwent serial CTs within 3 h and an average of three scans within the first 10 d of sTBI. Left and right LVVs were quantified by computer-assisted manual volumetric measurements. LVV ratios (LVR) were determined on the admission CT to evaluate ventricular asymmetry. The relationship between the admission LVR value and subsequent midline shift development was tested using receiver operating characteristic (ROC) analysis, and odds ratio (OR) and relative risk tests. Sixty patients had no >5 mm midline shift on the initial admission scan. Of these, 15 patients developed it subsequently (16 patients already had >5 mm midline shift on admission scans). For >5 mm midline shift development, admission LVR of >1.67 was shown to have a sensitivity of 73.3% and a specificity of 73.3% (area under the curve=0.782; p<0.0001). LVR of >1.67 as exposure yielded an OR of 7.56 (p<0.01), and a risk ratio of 4.42 (p<0.01) for midline shift development as unfavorable outcome. We propose that LVR captures LVV asymmetry and is not only related to, but also predicts the development of midline shift already at admission CT examination. Lateral ventricles may have a higher "compliance" than midline structures to developing asymmetric brain pathology. LVR analysis is simple, rapidly accomplished and may allow earlier interventions to attenuate midline shift and potentially improve ultimate outcomes.
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| 22. |
- Toth, Arnold, et al.
(författare)
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Microbleeds may expand acutely after traumatic brain injury
- 2016
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Ingår i: Neuroscience Letters. - : Elsevier. - 0304-3940 .- 1872-7972. ; 617, s. 207-212
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Susceptibility weighted imaging (SWI) is a very sensitive tool for the detection of microbleeds in traumatic brain injury (TBI). The number and extent of such traumatic microbleeds (TMBs) have been shown to correlate with the severity of the injury and the clinical outcome. However, the acute dynamics of TMBs have not been revealed so far. Since TBI is known to constitute dynamic pathological processes, we hypothesized that TMBs are not constant in their appearance, but may progress acutely after injury.Materials and methods: We present here five closed moderate/severe (Glasgow coma scale≤13) TBI patients who underwent SWI very early (average=23.4 h), and once again a week (average=185.8 h) after the injury. The TMBs were mapped at both time points by a conventional radiological approach and their numbers and volumes were measured with manual tracing tools by two observers. TMB counts and extents were compared between time points.Results: TMBs were detected in four patients, three of them displaying an apparent TMB change. In these patients, TMB confluence and apparent growth were detected in the corpus callosum, coronal radiation or subcortical white matter, while unchanged TMBs were also present. These changes caused a decrease in the TMB count associated with an increase in the overall TMB volume over time.Conclusion: We have found a compelling evidence that diffuse axonal injury-related microbleed development is not limited strictly to the moment of injury: the TMBs might expand in the acute phase of TBI. The timing of SWI acquisition may be relevant for optimizing the prognostic utility of this imaging biomarker.
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| 23. |
- Toth, Arnold, et al.
(författare)
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Multi-modal magnetic resonance imaging in the acute and sub-acute phase of mild traumatic brain injury : can we see the difference?
- 2013
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Ingår i: Journal of Neurotrauma. - : Mary Ann Liebert. - 0897-7151 .- 1557-9042. ; 30:1, s. 2-10
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Tidskriftsartikel (refereegranskat)abstract
- Advanced magnetic resonance imaging (MRI) methods were shown to be able to detect the subtle structural consequences of mild traumatic brain injury (mTBI). The objective of this study was to investigate the acute structural alterations and recovery after mTBI, using diffusion tensor imaging (DTI) to reveal axonal pathology, volumetric analysis, and susceptibility weighted imaging (SWI) to detect microhemorrhage. Fourteen patients with mTBI who had computed tomography with negative results underwent MRI within 3 days and 1 month after injury. High resolution T1-weighted imaging, DTI, and SWI, were performed at both time points. A control group of 14 matched volunteers were also examined following the same imaging protocol and time interval. Tract-Based Spatial Statistics (TBSS) were performed on DTI data to reveal group differences. T1-weighted images were fed into Freesurfer volumetric analysis. TBSS showed fractional anisotropy (FA) to be significantly (corrected p<0.05) lower, and mean diffusivity (MD) to be higher in the mTBI group in several white matter tracts (FA=40,737; MD=39,078 voxels) compared with controls at 72 hours after injury and still 1month later for FA. Longitudinal analysis revealed significant change (i.e., normalization) of FA and MD over 1 month dominantly in the left hemisphere (FA=3408; MD=7450 voxels). A significant (p<0.05) decrease in cortical volumes (mean 1%) and increase in ventricular volumes (mean 3.4%) appeared at 1 month after injury in the mTBI group. SWI did not reveal microhemorrhage in our patients. Our findings present dynamic micro- and macrostructural changes occurring in the acute to sub-acute phase in mTBI, in very mildly injured patients lacking microhemorrhage detectable by SWI. These results underscore the importance of strictly defined image acquisition time points when performing MRI studies on patients with mTBI.
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| 24. |
- Tóth, Judit, et al.
(författare)
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Heat absorption capacity and binder degradation characteristics of 3D printed cores investigated by inverse fourier thermal analysis
- 2016
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Ingår i: International Journal of metalcasting. - : Springer. - 1939-5981 .- 2163-3193. ; 10:3, s. 306-314
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Tidskriftsartikel (refereegranskat)abstract
- The application of 3D printing techniques is a recently developing area used within foundry technology. Digital production of sand molds and cores eliminates the need for hard tooling, drastically reduces lead times and offers design freedoms not possible in the traditional pattern making. Even though mold and core making technologies are refined from both scientific and practical points of view, casting defects may still occur in the final products. Thus, molding material related casting research is required to generate state-of-the-art methods and understandings to avoid the formation of casting defects. In this paper, a pioneering method is presented which is suitable to determine novel thermophysical and heat transfer properties of various types of molding materials. These properties are strongly connected to the cooling capacity and the gas evolution features of the cores used in casting production. The method is based on temperature measurements inside spherical shaped core sand specimens and evaluated by a special application of Fourier thermal analysis. Temperature measurements were performed in test samples produced by two different 3D core printing systems. The registered temperature data were processed by Fourier thermal analysis to calculate the thermal properties and the decomposition characteristics of the 3D printed cores. The experiments were executed under different heating conditions analogous to aluminium and cast iron production.
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| 25. |
- Ögren, Yngve, et al.
(författare)
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Development of a vision-based soft sensor for estimating equivalence ratio and major species concentration in entrained flow biomass gasification reactors
- 2018
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 226, s. 450-460
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Tidskriftsartikel (refereegranskat)abstract
- A combination of image processing techniques and regression models was evaluated for predicting equivalence ratio and major species concentration (H2, CO, CO2 and CH4) based on real-time image data from the luminous reaction zone in conditions and reactors relevant to biomass gasification. Two simple image pre-processing routines were tested: reduction to statistical moments and pixel binning (subsampling). Image features obtained by using these two pre-processing methods were then used as inputs for two regression algorithms: Gaussian Process Regression and Artificial Neural Networks. The methods were evaluated by using a laboratory-scale flat-flame burner and a pilot-scale entrained flow biomass gasifier. For the flat-flame burner, the root mean square error (RMSE) were on the order of the uncertainty of the experimental measurements. For the gasifier, the RMSE was approximately three times higher than the experimental uncertainty – however, the main source of the error was the quantization of the training dataset. The accuracy of the predictions was found to be sufficient for process monitoring purposes. As a feature extraction step, reduction to statistical moments proved to be superior compared to pixel binning.
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| 26. |
- Aad, G., et al.
(författare)
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- 2011
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Tidskriftsartikel (refereegranskat)
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