| 1. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 2. |
- Gebhardt, Thomas, et al.
(författare)
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Elastic properties of fcc Fe-Mn-X (X = Al, Si) alloys studied by theory and experiment
- 2011
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Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 59:8, s. 3145-3155
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the influence of Al and Si additions on the elastic properties of face-centered cubic (fcc) Fe-Mn random alloys with Fe/Mn ratios of 4.00 and 2.33 using ab initio calculations. When Al is added up to 8 at.% the shearing elastic constants (C-11-C-12)/2 and C-44 decrease, resulting in a drop of similar to 20% in shear and similar to 19% in Young's modulus. In fcc Fe-Mn-Si alloys, the trends in the elastic constants are similar, but less drastic, with a similar to 7% shear and similar to 6% Young's modulus decrease when Si is added up to 8 at.%. The Fe/Mn ratio exhibits a minor influence on the shear and Young's modulus values at constant Al and Si contents. To assess the quality of the ab initio data Fe-Mn-Al and Fe-Mn-Si thin films with an fcc structure were combinatorially synthesized and the elastic properties measured using nanoindentation. For both systems the measured and calculated lattice parameters are in good agreement. Although the measured Young's modulus data showed significant scatter due to the high surface roughness, they are in good agreement with the predicted values. For the Fe-Mn-Al system the calculations generally underestimate the experimental data by similar to 15%. For the Fe-Mn-Si system the calculated data are in general lower by similar to 10% than the experimentally determined values. The presented results are of relevance for multicomponent alloy design, since the effect of Si and Al addition on the elastic properties of Fe-Mn alloys can be predicted based on ab initio data.
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| 3. |
- Hostert, Carolin, et al.
(författare)
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Density, elastic and magnetic properties of Co–Fe–Ta–Si metallic glasses by theory and experiment
- 2012
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Ingår i: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456.
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Tidskriftsartikel (refereegranskat)abstract
- Ab initio molecular dynamics simulations were employed to study the density, elastic and magnetic properties of Co–Fe–Ta–Si10 metallic glass thin films. A density of 8.03 g cm3, a Young’s modulus of 187 GPa and a volume magnetization of 0.089 lBA ˚ 3 werecalculated and validated by thin film experiments. The extensive stiffness of this glass may be related to the existence of strong(Fe,Co)–Si clusters as revealed by ab initio chemical short-range order data.
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| 4. |
- Jiang, Kaiyun, et al.
(författare)
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Ab initio study of effects of substitutional additives on the phase stability of gamma-alumina
- 2010
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Ingår i: Journal of Physics. - : Institute of Physics. - 0953-8984 .- 1361-648X. ; 22:50, s. 505502-
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Tidskriftsartikel (refereegranskat)abstract
- Using ab initio calculations, we have evaluated two structural descriptions of gamma-Al(2)O(3), spinel and tetragonal hausmannite, and explored the relative stability of gamma-Al(2)O(3) with respect to alpha-Al(2)O(3) with 2.5 at.% of Si, Cr, Ti, Sc, and Y additives to identify alloying element induced electronic structure changes that impede the gamma to alpha transition. The total energy calculations indicate that Si stabilizes gamma-Al(2)O(3), while Cr stabilizes alpha-Al(2)O(3). As Si is added, a bond length increase in alpha-Al(2)O(3) is observed, while strong and short Si-O bonds are formed in gamma-Al(2)O(3), consequently stabilizing this phase. On the other hand, Cr additions induce a smaller bond length increase in alpha-Al(2)O(3) than in gamma-Al(2)O(3), therefore stabilizing the a-phase. The bulk moduli of gamma-Al(2)O(3) with these additives show no significant changes. The phase stability and elastic property data discussed here underline the application potential of Si alloyed gamma-Al(2)O(3) for applications at elevated temperatures. Furthermore it is evident that the tetragonal hausmannite structure is a suitable description for gamma-Al(2)O(3).
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| 5. |
- Jiang, Kaiyun, et al.
(författare)
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Low temperature synthesis of alpha-Al(2)O(3) films by high-power plasma-assisted chemical vapour deposition
- 2010
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Ingår i: Journal of Physics D. - : Institute of Physics. - 0022-3727 .- 1361-6463. ; 43:32, s. 325202-
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we deposit Al(2)O(3) films using plasma-assisted chemical vapour deposition (PACVD) in an Ar-H(2)-O(2)-AlCl(3) atmosphere. A novel generator delivering approximately 4 times larger power densities than those conventionally employed in PACVD enabling efficient AlCl(3) dissociation in the gas phase as well as a more intense energetic bombardment of the growing film is utilized. We demonstrate that these deposition conditions allow for the growth of dense alpha-Al(2)O(3) films with negligible Cl incorporation and elastic properties similar to those of the bulk alpha-Al(2)O(3) at a temperature of 560 +/- 10 degrees C.
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| 6. |
- Jiang, Kaiyun, et al.
(författare)
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On the high temperature stability of gamma-Al2O3/Ti0.33Al0.67N coated WC-Co cutting inserts
- 2012
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Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Carl Hanser Verlag GmbH. - 1862-5282 .- 2195-8556. ; 103:12, s. 1509-1516
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Tidskriftsartikel (refereegranskat)abstract
- The high temperature stability of gamma-Al2O3 films deposited using filtered cathodic arc and plasma assisted chemical vapor deposition on Ti0.33Al0.67N coated WC-Co cutting inserts is investigated. X-ray diffractometry reveals that filtered cathodic arc deposited films transform partially into the thermodynamically stable alpha-Al2O3 phase at a temperature of 1000 degrees C. The gamma to alpha-Al2O3 transformation for plasma assisted chemical vapor deposition grown films is observed at 900 degrees C. These results are in qualitative agreement with differential scanning calorimetry measurements. Transmission electron microscopy on filtered cathodic arc and plasma assisted chemical vapor deposition films annealed at 900 degrees C reveals the existence of hexagonal AlN in the Ti0.33Al0.67N interlayer, as well as Al depletion at the Al2O3/Ti0.33Al0.67N interface. After annealing the plasma assisted chemical vapor deposition sample at 900 degrees C, alpha-Al2O3 grains with a size of 100 nm are observed inside the gamma-Al2O3 matrix, while for filtered cathodic arc samples only the gamma-phase is identified. Transmission electron microscopy analysis on both filtered cathodic arc and plasma assisted chemical vapor deposition samples annealed at 1000 degrees C shows that the original Al2O3/Ti0.33Al0.67N/WC-Co layer architecture is no longer intact. The formation of TiO2 is detected along the growth direction of the Al2O3 films. The present study suggests that not only the morphology and the impurities incorporated into gamma-Al2O3 but also stability of the Ti0.33Al0.67N interlayer determine the high temperature stability of gamma-Al2O3/Ti0.33Al0.67N coated hard-metal.
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| 7. |
- Mockuté, Aurelija, et al.
(författare)
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Synthesis and ab initio calculations of nanolaminated (Cr,Mn)2AlC compounds
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 87:9
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Tidskriftsartikel (refereegranskat)abstract
- We present an ab initio theoretical analysis of the temperature-dependent stability of inherently nanolaminated (Cr1−xMnx)2AlC. The results indicate energetic stability over the composition range x = 0.0 to 0.5 for temperatures ≥600 K. Corresponding thin film compounds were grown by magnetron sputtering from four elemental targets. X-ray diffraction in combination with analytical transmission electron microscopy, including electron energy-loss spectroscopy and energy dispersive x-ray spectroscopy analysis, revealed that the films were epitaxial (0001)-oriented single-crystals with x up to 0.16.
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| 8. |
- Music, Denis, et al.
(författare)
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Ab initio molecular dynamics of Al irradiation-induced processes during Al(2)O(3) growth
- 2011
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Ingår i: Applied Physics Letters. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 98:11, s. 111908-
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Tidskriftsartikel (refereegranskat)abstract
- Al bombardment induced structural changes in alpha-Al(2)O(3) (R-3c) and gamma-Al(2)O(3) (Fd-3m) were studied using ab initio molecular dynamics. Diffusion and irradiation damage occur for both polymorphs in the kinetic energy range from 3.5 to 40 eV. However, for gamma-Al(2)O(3)(001) subplantation of impinging Al causes significantly larger irradiation damage and hence larger mobility as compared to alpha-Al(2)O(3). Consequently, fast diffusion along gamma-Al(2)O(3)(001) gives rise to preferential alpha-Al(2)O(3)(0001) growth, which is consistent with published structure evolution experiments.
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| 9. |
- Reeswinkel, Thomas, et al.
(författare)
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Structure and mechanical properties of TiAlN-WNI(x) thin films
- 2011
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Ingår i: Surface & Coatings Technology. - : Elsevier Science B.V., Amsterdam.. - 0257-8972 .- 1879-3347. ; 205:20, s. 4821-4827
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Tidskriftsartikel (refereegranskat)abstract
- A combinatorial method was employed to grow TiAlN-WNx films by DC sputtering as well as by High Power Pulsed Magnetron Sputtering (HPPMS) where the W concentration was varied between 10-52 at.% and 7-54 at.%, respectively. Experiments were paired with ab initio calculations to investigate the correlation between composition, structure, and mechanical properties. During all depositions the time averaged power was kept constant. As the W concentration was increased, the lattice parameter of cubic TiAlN-WNx films first increased and then decreased for W concentrations above approximate to 29 at.% (DCMS) and approximate to 27 at.% (HPPMS) as the N concentration decreased. Calculations helped to attribute the increase to the substitution of Ti and Al by W and the decrease to the presence of N vacancies. Youngs modulus and hardness were around 385-400 GPa and 29-31 GPa for DCMS and 430-480 GPa and 34-38 GPa for HPPMS, respectively, showing no significant trend as the W concentration was increased, whereas calculations showed a continuous decrease in Youngs modulus from 440 to 325 GPa as the W concentration was increased from 0 to 37.5 at.%. The presence of N vacancies was shown to increase the calculated Youngs modulus. Hence, the relatively constant values measured may be understood based on N vacancy formation as the W concentration was increased. HPPMS-deposited films exceed DCMS films in Youngs modulus and hardness, which may be a consequence of the larger degree of ionization in the HPPMS plasma. It is reasonable to assume that especially the ionized film forming species may contribute towards film densification and N vacancy formation.
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| 10. |
- Sundberg, Jill, 1986-
(författare)
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Triboactive Low-Friction Coatings Based on Sulfides and Carbides
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For sustainable development, it is highly important to limit the loss of energy and materials in machines used for transportation, manufacturing, and other purposes. Large improvements can be achieved by reducing friction and wear in machine elements, for example by the application of coatings. This work is focused on triboactive coatings, for which the outermost layer changes in tribological contacts to form so-called tribofilms. The coatings are deposited by magnetron sputtering (a physical vapor deposition method) and thoroughly chemically and structurally characterized, often theoretically modelled, and tribologically evaluated, to study the connection between the composition, structure and tribological performance of the coatings.Tungsten disulfide, WS2, is a layered material with the possibility of ultra-low friction. This work presents a number of nanocomposite or amorphous coatings based on WS2, which combine the low friction with improved mechanical properties. Addition of N can give amorphous coatings consisting of a network of W, S and N with N2 molecules in nanometer-sized pockets, or lead to the formation of a metastable cubic tungsten nitride. Co-deposition with C can also give amorphous coatings, or nanocomposites with WSx grains in an amorphous C-based matrix. Further increase in coating hardness is achieved by adding both C and Ti, forming titanium carbide. All the WS2-based materials can provide very low friction (down to µ<0.02) by the formation of WS2 tribofilms, but the performance is dependent on the atmosphere as O2 and H2O can be detrimental to the tribofilm functionality.Another possibility is to form low-friction tribofilms by tribochemical reactions between the two surfaces in contact. Addition of S to TiC/a-C nanocomposite coatings leads to the formation of a metastable S-doped carbide phase, TiCxSy, from which S can be released. This enables the formation of low-friction WS2 tribofilms when a Ti-C-S coating is run against a W counter-surface. Reduced friction, at a moderate level, also occurs for steel counter-surfaces, likely due to formation of beneficial iron sulfide tribofilms.The studied coatings, whether based on WS2 or TiC, are thus triboactive, with the ability to form low-friction tribofilms in a sliding contact.
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