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- Hattel, H. B., et al.
(författare)
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Lifelong endurance training keeps the mitochondria young.
- 2014
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Ingår i: Proceedings of the Physiological Society 2014. ; , s. 276P-277P
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Konferensbidrag (refereegranskat)abstract
- It is an ongoing debate whether mitochondrial function deteriorates with aging. Some studies demonstrate metabolic dysfunction and increased ROS production (Squier, 2001) while others find no bioenergetics alterations (Rasmussen, et al., 2003). The extent to which exercise maintains or restores mitochondrial function is unknown. Methods: A unique group of elderly lifelong trained males (64±2 yr, BMI=24.5±0.4 kg/m2, VO2max=3.5±0.07 L/min), who maintained road cycling training ~250 km/week 50 years were recruited for the experiment (group ET) along with a group of healthy age matched untrained males (age 65±2 yr, BMI=27±1, VO2max=2.4±0.1), who lived a sedentary lifestyle (group UT). A biopsy was obtained from Vastus lateralis under local anaesthesia. 15-25 mg muscle was immediately prepared and permeabilized for High Resolution Respirometry as previously described (Boushel, et al., 2011). LEAK respiration was assessed by addition of malate (2 mM) and octanoyl-carnitine (0.2 mM). Coupled ADP-stimulated respiration (OXPHOS) of complex I was assessed with pyruvate (5mM) and glutamate (10 mM), and ADP (5 mM). Maximal OXPHOS was determined by addition of succinate (10 mM) for convergent electron input to both complexes I and II. The isolated activity of cytochrome c oxidase (COX), was determined in a redox reaction with TMPD (N,N,N,N-tetramethyl-p-phenylenediamine dihydrochloride) (0.5 mM) and ascorbate (2mM) after blockade of electron flow through complex III with antimycin A (2.5μM) followed by sodium azide (100 mM). Findings: All values are mean±S.E.M. Preliminary findings show that mitochondrial OXPHOS capacity for CI (PI) is substantially higher (50±3 vs. 30±1 pmol.sec-1.mg-1, p<0.0001) in the ET compared to the UT, and maximal OXPHOS with CI+CII (PI+PII) was 2-fold higher (103±3 vs. 51±2 pmol.sec-1.mg-1, p<5*10-5). The higher substrate control ratio (CI+II/CI) in ET (2.05±0.09) compared to UT (1.7±0.06) suggests less substrate competition at the mitochondrial level. These findings indicate that exercise training throughout life induces both regulatory and mitochondrial density changes that optimize mitochondrial function. The observed OXPHOS capacities in the ET subjects are fully comparable to values reported in young elite trained subjects (Jacobs & Lundby, 2013), illustrating no mitochondrial age-related deteriorating in these subjects.
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| 2. |
- Safavi Nick, Arash, 1985-
(författare)
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Pores, inclusions and electromagnetic stirring : Topics from the continuous casting of steel
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with two topics of relevance to the continuous casting of steel,in view of their importance as regards the quality of the final solidified structure.The first concerns the precipitation of gas pores and inclusions in the interden-dritic region of the solidifying metal. Motivated by experimental results thatindicate the formation of pore-inclusion clusters in the final cast structure, a the-oretical model is developed to describe how thus might occur; the model makesuse of the basic principles of fluid mechanics and heat transfer, with asymptoticmethods then being used in order to obtain solutions. In particular, it is foundthat soluto-thermocapillary drift in a direction perpendicular to the direction ofcasting, as a consequence of the dependence of surface tension at the pore-metalinterface on temperature and sulphur concentration, could explain cluster forma-tion. The second is a theoretical study concerning longitudinal electromagneticstirring (EMS), which is often used in the continuous casting of blooms in order toimprove product quality. Via an analysis of the three-dimensional (3D) Maxwellequations for the components of the magnetic flux density, a flaw is found inthe way that the components of the stirring Lorentz force have previously beencalculated; this is corrected and the new results are confirmed by comparison ofsolutions obtained from asymptotic analysis and time-dependent 3D computa-tions using finite-element methods. The analysis identifies the importance of theproduct of the bloom width and the wave vector of the applied field as a keydimensionless parameter.
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| 3. |
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| 4. |
- Zhang, J., et al.
(författare)
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Designing against phase and property heterogeneities in additively manufactured titanium alloys
- 2022
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing (AM) creates digitally designed parts by successive addition of material. However, owing to intrinsic thermal cycling, metallic parts produced by AM almost inevitably suffer from spatially dependent heterogeneities in phases and mechanical properties, which may cause unpredictable service failures. Here, we demonstrate a synergistic alloy design approach to overcome this issue in titanium alloys manufactured by laser powder bed fusion. The key to our approach is in-situ alloying of Ti−6Al−4V (in weight per cent) with combined additions of pure titanium powders and iron oxide (Fe2O3) nanoparticles. This not only enables in-situ elimination of phase heterogeneity through diluting V concentration whilst introducing small amounts of Fe, but also compensates for the strength loss via oxygen solute strengthening. Our alloys achieve spatially uniform microstructures and mechanical properties which are superior to those of Ti−6Al−4V. This study may help to guide the design of other alloys, which not only overcomes the challenge inherent to the AM processes, but also takes advantage of the alloy design opportunities offered by AM.
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