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| 2. |
- Furustig, Joel, et al.
(author)
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The measurement of wear using AFM and wear interpretation using a contact mechanics coupled wear model
- 2016
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In: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 350-351, s. 74-81
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Journal article (peer-reviewed)abstract
- Detailed understanding of wear processes is required to improve the wear resistance and lifetime of machine components. Atomic force microscopy (AFM) is used to measure surface height profiles with high precision, before and after a wear experiment. The distribution and depth of wear on steel surfaces is then calculated using a relocation method. A numerical investigation of wear based on Archard's equation is conducted on the same measured surfaces. A good correlation was found between the model and experiment for wear larger than a hundred nm. The wear mechanisms considered in the numerical simulation was thus found to be the cause of the majority of the wear. On the scale of tens of nm the correlation was limited, but the measured wear was still analysed in detail.
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| 3. |
- Hellberg, Magnus, et al.
(author)
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In situ scanning probe microscopy studies of morphology and growth kinetics in amyloid-peptide fibrillogenesis with custom designed tapping mode and pulsed force mode systems
- 2004
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In: Proceedings of 5th Nordic-Baltic Scanning Probe Microscopy Workshop. ; , s. 93-95
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Conference paper (peer-reviewed)abstract
- We have used a commercial Nanoscope II atomic force microscope (AFM) with a custom designedtapping mode (TM) system to in situ monitor amyloid β-peptide aggregation related to Alzheimer’sdisease (AD). The custom tapping mode setup was successfully used to image the real timeaggregation behaviour of the arctic mutation amyloid β-peptide, Aβ(1-40), in vitro in aphysiologically relevant buffer and compare with the behaviour of the normal wild type of theAlzheimer’s amyloid peptide Aβ(1-40) at the same conditions. The investigation revealed distinctdifferences in fibrillogenesis behaviour for the two peptides. Our results demonstrate a previouslysuggested alternative fibrillogenesis pathway, of highly distinct aggregates with orderedmorphology as on-pathway. Moreover, additional investigations using a pulsed force mode (PFM)are under way.
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| 4. |
- Norlin, Nils, et al.
(author)
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Aggregation and fibril morphology of the Arctic mutation of Alzheimer's Aβ peptide by CD, TEM, STEM and in situ AFM
- 2012
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In: Journal of Structural Biology. - San Diego, CA, USA : Academic Press. - 1047-8477 .- 1095-8657. ; 180:1, s. 174-189
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Journal article (peer-reviewed)abstract
- Morphology of aggregation intermediates, polymorphism of amyloid fibrils and aggregation kinetics of the "Arctic" mutant of the Alzheimer's amyloid β-peptide, Aβ((1-40))(E22G), in a physiologically relevant Tris buffer (pH 7.4) were thoroughly explored in comparison with the human wild type Alzheimer's amyloid peptide, wt-Aβ((1-40)), using both in situ atomic force and electron microscopy, circular dichroism and thioflavin T fluorescence assays. For arc-Aβ((1-40)) at the end of the 'lag'-period of fibrillization an abrupt appearance of ∼3nm size 'spherical aggregates' with a homogeneous morphology, was identified. Then, the aggregation proceeds with a rapid growth of amyloid fibrils with a variety of morphologies, while the spherical aggregates eventually disappeared during in situ measurements. Arc-Aβ((1-40)) was also shown to form fibrils at much lower concentrations than wt-Aβ((1-40)): ⩽2.5μM and 12.5μM, respectively. Moreover, at the same concentration, 50μM, the aggregation process proceeds more rapidly for arc-Aβ((1-40)): the first amyloid fibrils were observed after c.a. 72h from the onset of incubation as compared to approximately 7days for wt-Aβ((1-40)). Amyloid fibrils of arc-Aβ((1-40)) exhibit a large variety of polymorphs, at least five, both coiled and non-coiled distinct fibril structures were recognized by AFM, while at least four types of arc-Aβ((1-40)) fibrils were identified by TEM and STEM and their mass-per-length statistics were collected suggesting supramolecular structures with two, four and six β-sheet laminae. Our results suggest a pathway of fibrillogenesis for full-length Alzheimer's peptides with small and structurally ordered transient spherical aggregates as on-pathway immediate precursors of amyloid fibrils.
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| 5. |
- Spencer, Andrew, et al.
(author)
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Surface characterization with functional parameters
- 2011
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Conference paper (other academic/artistic)abstract
- Typically engineering surfaces are characterized with traditional roughness parameters that perform some type of height averaging over the surface. Although these parameters describe the topography of the surface none of them necessarily describe the ability of the surface to carry out its function in a tribological contact. In this study an ICE cylinder liner has been investigated.The traditional Rk parameters (based on the Abbott curve) have been calculated as well as functional ‘flow factors’which modify the Reynolds equation to incorporate the effects of surface topography.To calculate flow factors the homogenization technique has been implemented and a full 3D contact mechanics model has been incorporated so that surface functionality in mixed lubrication can be studied. Furthermore, the cylinder liner surface has been measured with both white light interferometery and an AFM so that the effect of measuring technique on roughness and functional parameters can be investigated.
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| 6. |
- Spencer, Andrew, et al.
(author)
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The influence of AFM and VSI techniques on the accurate calculation of tribological surface roughness parameters
- 2013
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In: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 57, s. 242-250
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Journal article (peer-reviewed)abstract
- Vertical Scanning Interferometry (VSI) may induce optical artefacts in surface topography measurements. The influence of these optical artefacts on the calculation of Rk surface roughness parameters, contact stiffness and flow factors were studied. Two surface measurement techniques were used: Atomic Force Microscopy (AFM) and VSI. Calibration grids were used to make it easier to isolate the causes of these artefacts, while a real engineering surface was used to compare these two techniques in an industrially applied case. It was found that the optical artefacts have a large influence on all the roughness parameters, contact stiffness and flow factors calculated on the calibration grids. However, for the engineering surface the differences between AFM and VSI measurements were much smaller.
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| 8. |
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| 9. |
- Almqvist, Nils, et al.
(author)
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AFM and STM characterization of surfaces exposed to high flux deuterium plasma
- 1995
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In: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 220-222:1-3, s. 917-921
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Journal article (peer-reviewed)abstract
- This paper reports the results of scanning tunneling (STM) and atomic force microscopy (AFM) studies of D+ irradiated graphite and graphite-silicon mixtures. The microscopes were used for studying surface topography and for measuring the surface roughness. The substrates were exposed at various temperatures (60 and 700°C) to different doses of deuterium ions in simulators of plasma - surface interactions and in the TEXTOR tokamak. Also nuclear reaction analysis (NRA) and Rutherford backscattering spectroscopy were applied for the qualitative and quantitative determination of surface composition. The initial stages of radiation damage, nanometer-sized bubbles/blisters, were found in plasma-eroded surfaces. These structures only appeared in the graphite phase on the multicomponent material. The microroughness of the surfaces was measured. We also used the AFM for probing the thickness of the plasma-modified layers. The results correlate with the presence of deuterium measured by NRA depth-profiling. Moreover, the AFM reveals the co-deposited layers formed on surfaces facing the tokamak plasma. The appearance of these layers is clearly correlated to the amount of co-deposited atoms.
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