| 1. |
- Abbasi, Saeed, et al.
(författare)
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A pin-on-disc study of the rate of airborne wear particle emissions from railway braking materials
- 2012
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Ingår i: Wear. - UK : Elsevier. - 0043-1648 .- 1873-2577. ; 284, s. 18-29
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Tidskriftsartikel (refereegranskat)abstract
- The current study investigates the characteristics of particles generated from the wear of braking materials, and provides an applicable index for measuring and comparing wear particle emissions. A pin-on-disc tribometer equipped with particle measurement instruments was used. The number concentration, size, morphology, and mass concentration of generated particles were investigated and reported for particles 10 nm-32 mu m in diameter. The particles were also collected on filters and investigated using EDS and SEM. The effects of wear mechanisms on particle morphology and changes in particle concentration are discussed. A new index, the airborne wear particle emission rate (AWPER), is suggested that could be used in legislation to control non-exhaust emissions from transport modes, particularly rail transport.
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| 2. |
- Abbasi, Saeed, 1973-, et al.
(författare)
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A field test study of airborne wear particles from a running regional train
- 2012
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Ingår i: IMechE, Part F: Journal of Rail and Rapid Transit. - UK : Sage Publications. - 0954-4097 .- 2041-3017. ; 226:1, s. 95-109
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Tidskriftsartikel (refereegranskat)abstract
- Inhalable airborne particles have inverse health affect. In railways, mechanical brakes, the wheel–rail contact, current collectors, ballast, sleepers, and masonry structures yield particulate matter. Field tests examined a Swedish track using a train instrumented with particle measurement devices, brake pad temperature sensors, and speed and brake sensors. The main objective of this field test was to study the characteristics of particles generated from disc brakes on a running train with an on-board measuring set-up.Two airborne particle sampling points were designated, one near a pad–rotor disc brake contact and a second under the frame, not near a mechanical brake or the wheel–rail contact; the numbers and size distributions of the particles detected were registered and evaluated under various conditions (e.g. activating/deactivating electrical brakes or negotiating curves). During braking, three speed/temperature-dependent particle peaks were identified in the fine region, representing particles 280 nm, 350 nm, and 600 nm in diameter. In the coarse region, a peak was discerned for particles 3–6 μm in diameter. Effects of brake pad temperature on particle size distribution were also investigated. Results indicate that the 280 nm peak increased with increasing temperature, and that electrical braking significantly reduced airborne particle numbers. FESEM images captured particles sizing down to 50 nm. The ICP-MS results indicated that Fe, Cu, Zn, Al, Ca, and Mg were the main elements constituting the particles.
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| 3. |
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| 4. |
- Abbasi, Saeed, et al.
(författare)
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Particle emissions from rail traffic : a literature review
- 2013
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Ingår i: Critical reviews in environmental science and technology. - USA : Taylor & Francis. - 1064-3389 .- 1547-6537. ; 43:23, s. 2211-2244
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Forskningsöversikt (refereegranskat)abstract
- Particle emissions are a drawback of rail transport. This work is a comprehensive presentation of recent research into particle emissions from rail vehicles. Both exhaust and non-exhaust particle emissions are considered when examining particle characteristics such as PM10, and PM2.5 concentration levels, size, morphology, composition, as well as adverse health effects, current legislation, and available and proposed solutions for reducing such emissions. High concentration levels in enclosed rail traffic environments are reported and some toxic effects of the particles. We find that only a few limited studies have examined the adverse health effects of non-exhaust particle emissions and that no relevant legislation exists. Thus further research in this area is warranted.
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| 5. |
- Alami, Jones, et al.
(författare)
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High-power impulse magnetron sputtering of Ti-Si-C thin films from a Ti3SiC2 compound target
- 2006
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Ingår i: Thin Solid Films. - : Institutionen för fysik, kemi och biologi. - 0040-6090 .- 1879-2731. ; 515:4, s. 1731-1736
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Tidskriftsartikel (refereegranskat)abstract
- We have deposited Ti-Si-C thin films using high-power impulse magnetron sputtering (HIPIMS) from a Ti3SiC2 compound target. The as-deposited films were composite materials with TiC as the main crystalline constituent. X-ray diffraction and photoelectron spectroscopy indicated that they also contained amorphous SiC, and for films deposited on inclined substrates, crystalline Ti5Si3Cx. The film morphology was dense and flat, while films deposited with dc magnetron sputtering under comparable conditions were rough and porous. Due to the high degree of ionization of the sputtered species obtained in HIPIMS, it is possible to control the film composition, in particular the C content, by tuning the substrate inclination angle, the Ar process pressure, and the bias voltage.
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| 6. |
- Berndt, Sonja I., et al.
(författare)
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Genome-wide meta-analysis identifies 11 new loci for anthropometric traits and provides insights into genetic architecture
- 2013
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 45:5, s. 501-U69
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Tidskriftsartikel (refereegranskat)abstract
- Approaches exploiting trait distribution extremes may be used to identify loci associated with common traits, but it is unknown whether these loci are generalizable to the broader population. In a genome-wide search for loci associated with the upper versus the lower 5th percentiles of body mass index, height and waist-to-hip ratio, as well as clinical classes of obesity, including up to 263,407 individuals of European ancestry, we identified 4 new loci (IGFBP4, H6PD, RSRC1 and PPP2R2A) influencing height detected in the distribution tails and 7 new loci (HNF4G, RPTOR, GNAT2, MRPS33P4, ADCY9, HS6ST3 and ZZZ3) for clinical classes of obesity. Further, we find a large overlap in genetic structure and the distribution of variants between traits based on extremes and the general population and little etiological heterogeneity between obesity subgroups.
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| 7. |
- Bonow, Madeleine A
(författare)
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Gård, gräns, giftermål : Familjestrategiers betydelse för markens och landskapets utformning i Norra Åsarps socken, Västergötland ca 1640-1880
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation deals with property rights and the implications of these for people, landscape and settlement in Norra Åsarp Parish in the province of Västergötland.The overarching aim of the thesis is to investigate systems of social rules and how these influence the structure of settlement and land use/ownership. The central question concerns how the peasant family reproduced and maintained social and physical boundaries and if there are any relationships between territoriality and social class.The analysis has led us to the unexpected result that there was a surprising degree of continuity concerning the individual field strips. This is remarkable since the social system otherwise showed a rather rapid rotation in farm occupancy. The intriguing question here is why it was like this in this area? Why were there no changes in the allotment system? To solve this question special attention is given to reproduction and farm practice at the individual level. The social structure was primarily characterised by families who farmed on a small scale. The farms belonging to a larger kinship group circulated between the relatives and were farmed by the most suitable couple available. The marital strategy made group identity well connected and the family identity become strong. The social system was to some extent readable in the landscape: the family tree was more or less written on the ground. This investigation may provide an explanation to why there were no changes in the allotment system.The basis of the taxation in Norra Åsarp may have been the allotment system itself and this may explain why nothing happens on the ground: land had to stay fixed and tied to specific homesteads, otherwise it would be hard to calculate the rights and duties of the farm.
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| 8. |
- Jansson, Anna, et al.
(författare)
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Magnetron sputtering of the high entropy alloy CoCrFeMnNi on 316L : Influence of substrate grain orientations
- 2023
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Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 466
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Tidskriftsartikel (refereegranskat)abstract
- This study explores the influence of a 316L stainless steel substrate on the magnetron sputtering of the Cantor alloy CoCrFeMnNi at different substrate bias. The study was carried out on a polycrystalline 316L substrate where the growth behavior of the coating could be investigated on grains with different orientations. By combining electron backscatter diffraction (EBSD) before and after deposition and characterization of the same area, it was possible to determine growth behaviour and surface morphologies on individual substrate grains. No strong influence of the substrate was observed at a floating bias. At a bias of -100V, however, the coating was strongly influenced by the orientation of the individual substrate grains. Epitaxial coating grains with a smooth surface were observed on the [102]-oriented grains while a more columnar growth was observed on [111]-oriented grains. Furthermore, a small difference in growth rate was observed on different substrate orientations. The growth behaviour could be related to differences in surface energies and diffusion rates on different surface orientations.
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| 9. |
- Marklund, Matti, et al.
(författare)
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Biomarkers of Dietary Omega-6 Fatty Acids and Incident Cardiovascular Disease and Mortality : An Individual-Level Pooled Analysis of 30 Cohort Studies
- 2019
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Ingår i: Circulation. - : American Heart Association. - 0009-7322 .- 1524-4539. ; 139:21, s. 2422-2436
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Tidskriftsartikel (refereegranskat)abstract
- Background:Global dietary recommendations for and cardiovascular effects of linoleic acid, the major dietary omega-6 fatty acid, and its major metabolite, arachidonic acid, remain controversial. To address this uncertainty and inform international recommendations, we evaluated how in vivo circulating and tissue levels of linoleic acid (LA) and arachidonic acid (AA) relate to incident cardiovascular disease (CVD) across multiple international studies.Methods:We performed harmonized, de novo, individual-level analyses in a global consortium of 30 prospective observational studies from 13 countries. Multivariable-adjusted associations of circulating and adipose tissue LA and AA biomarkers with incident total CVD and subtypes (coronary heart disease, ischemic stroke, cardiovascular mortality) were investigated according to a prespecified analytic plan. Levels of LA and AA, measured as the percentage of total fatty acids, were evaluated linearly according to their interquintile range (ie, the range between the midpoint of the first and fifth quintiles), and categorically by quintiles. Study-specific results were pooled using inverse-variance-weighted meta-analysis. Heterogeneity was explored by age, sex, race, diabetes mellitus, statin use, aspirin use, omega-3 levels, and fatty acid desaturase 1 genotype (when available).Results:In 30 prospective studies with medians of follow-up ranging 2.5 to 31.9 years, 15198 incident cardiovascular events occurred among 68659 participants. Higher levels of LA were significantly associated with lower risks of total CVD, cardiovascular mortality, and ischemic stroke, with hazard ratios per interquintile range of 0.93 (95% CI, 0.88-0.99), 0.78 (0.70-0.85), and 0.88 (0.79-0.98), respectively, and nonsignificantly with lower coronary heart disease risk (0.94; 0.88-1.00). Relationships were similar for LA evaluated across quintiles. AA levels were not associated with higher risk of cardiovascular outcomes; in a comparison of extreme quintiles, higher levels were associated with lower risk of total CVD (0.92; 0.86-0.99). No consistent heterogeneity by population subgroups was identified in the observed relationships.Conclusions:In pooled global analyses, higher in vivo circulating and tissue levels of LA and possibly AA were associated with lower risk of major cardiovascular events. These results support a favorable role for LA in CVD prevention.
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| 10. |
- Samuelsson, Mattias, 1976-, et al.
(författare)
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Growth of Ti-C nanocomposite films by reactive high power impulse magnetron sputtering under industrial conditions
- 2012
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 206:8-9, s. 2396-2402
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Tidskriftsartikel (refereegranskat)abstract
- Titanium carbide (TiC) films were deposited employing high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) in an Ar-C2H2 atmosphere of various compositions. Analysis of the structural, bonding and compositional characteristics revealed that the deposited films are either TiC and hydrogenated amorphous carbon (a-C:H) nanocomposites, nanocrystalline TiC, or Ti/Tic, depending on the C/Ti ratio. It was found that Ti-C films grown by HiPIMS show a C/Ti ratio of close to 1 for a wide C2H2 flow range (4-15 sccm), with free C ranging from 0 to 20%. Thus, films ranging from near stoichiometric single phase TiC to TiC/a-C:H nanocomposites can be synthesized. This was not the case for DCMS, where films grown using similar deposition rates as for HiPIMS formed larger fractions of amorphous C matrix, thus being nanocomposites in the same C2H2 (above 4 sccm) flow range. For a C/Ti ratio of 1 the resistivity is low (4-8 x 10(2) mu Omega cm) for the HiPIMS films, and high (>100x 10(2) mu Omega cm) for the DCMS films. The hardness also shows a big difference with 20-27 and 6-10 GPa for HiPIMS and DCMS grown films, respectively.
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| 11. |
- Sarwar, Nadeem, et al.
(författare)
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Interleukin-6 receptor pathways in coronary heart disease : a collaborative meta-analysis of 82 studies
- 2012
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Ingår i: The Lancet. - New York, NY, USA : Elsevier. - 0140-6736 .- 1474-547X. ; 379:9822, s. 1205-1213
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Tidskriftsartikel (refereegranskat)abstract
- Background: Persistent inflammation has been proposed to contribute to various stages in the pathogenesis of cardiovascular disease. Interleukin-6 receptor (IL6R) signalling propagates downstream inflammation cascades. To assess whether this pathway is causally relevant to coronary heart disease, we studied a functional genetic variant known to affect IL6R signalling. Methods: In a collaborative meta-analysis, we studied Asp358Ala (rs2228145) in IL6R in relation to a panel of conventional risk factors and inflammation biomarkers in 125 222 participants. We also compared the frequency of Asp358Ala in 51 441 patients with coronary heart disease and in 136 226 controls. To gain insight into possible mechanisms, we assessed Asp358Ala in relation to localised gene expression and to postlipopolysaccharide stimulation of interleukin 6. Findings: The minor allele frequency of Asp358Ala was 39%. Asp358Ala was not associated with lipid concentrations, blood pressure, adiposity, dysglycaemia, or smoking (p value for association per minor allele >= 0.04 for each). By contrast, for every copy of 358Ala inherited, mean concentration of IL6R increased by 34.3% (95% CI 30.4-38.2) and of interleukin 6 by 14.6% (10.7-18.4), and mean concentration of C-reactive protein was reduced by 7.5% (5.9-9.1) and of fibrinogen by 1.0% (0.7-1.3). For every copy of 358Ala inherited, risk of coronary heart disease was reduced by 3.4% (1.8-5.0). Asp358Ala was not related to IL6R mRNA levels or interleukin-6 production in monocytes. Interpretation: Large-scale human genetic and biomarker data are consistent with a causal association between IL6R-related pathways and coronary heart disease.
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| 12. |
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| 13. |
- Adolfsson, Johanna, 1986-
(författare)
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A new storm over the Naqab : The temporality of space in Israeli settler colonialism
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- How can a posthumanist conceptualization of landscape, one that embraces temporality and practice, help us to better understand contemporary settler colonialism? This thesis explores this proposition through its analyses of the desire of the Israeli state to ‘settle’ the Naqab. The Naqab, an area located in the south of modern-day Israel and within its borders, is continuously narrated as under threat of being lost to the Palestinian Bedouins. In contrast to the breadth of scholarly attention given to the occupied Palestinian Territories, there is a relative paucity of studies focusing on the Naqab and on the Palestinian citizens of Israel living therein. Inspired by the concept of taskscape and, more broadly, by a posthumanist political ecology approach, in this thesis I seek to remedy the determinist undertones quite often found in settler colonial studies.The thesis’ empirical data draw from qualitative methods and field research in the Naqab, undertaken during multiple field visits between the 2018 and 2021. The thesis comprises a comprehensive summary (kappa) and three research papers. In Paper 1, I show how a schism between the Jewish National Fund and the civil society green movement surfaced amid land conflicts between the state and Bedouin villagers east of Beersheva. I argue that this schism offers insights into how nature is negotiated in relation to environmentalism and Zionist ideology. Further, I discuss how these negotiations point to an emerging new self-image of a post-settlement state that has abandoned pioneering, and replaced it with a planted forest (and natural) landscape as an emblem for Zionist nature. In Paper 2, I focus my attention on a network of Jewish villages in the Naqab. Based on a discourse analysis of YouTube videos produced by two Zionist organizations, I show how the narrative of Jewish relocation to the Naqab encompasses a modern re-enactment of the pioneering ideal, one mediated by a new neoliberal ethos of Israel as a ‘start-up nation’ and the Naqab as a new Israeli tech-hub. Finally, in Paper 3, I trace the cultural and political context of forest grazing in the Naqab. I argue that while the state uses afforestation as a proxy for territorialization, the irony is that it is the Bedouins who are largely responsible for everyday management of these forest areas, as grazing is a cost-effective method for keeping shrubs and other undergrowth low. I argue that in trying to accommodate grazing in the forest, policy makers struggle to juggle Bedouin land claims via continuous use and cultural connection to the land. Throughout the papers I affirm the performance of Israeli settler colonialism through the making of the natural environment. I assert that the tendency towards forest and grazing regulation, also articulated in planning policy, represents a move beyond the ‘era of pioneering’ towards a more formal type of society. I conclude by contending that the multiple spaces and temporalities presented in the paper’s case studies are indicative of contradictory narratives in the portrayal of the Naqab is and thus assemble as a necessity of the settlement ambition.
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| 14. |
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| 15. |
- Agardh, Carl-David, et al.
(författare)
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Varning för okritisk användning av överviktskirurgi vid typ 2-diabetes
- 2012
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Ingår i: Läkartidningen. - Stockholm : Läkartidningen förlag. - 0023-7205 .- 1652-7518. ; 109:25, s. 1208-1209
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Tidskriftsartikel (refereegranskat)abstract
- Överviktskirurgi diskuteras nu som ett behandlingsalternativ även för patienter med typ 2-diabetes där BMI inte överstiger nuvarande indikationsgräns 35 kg/m2. Artikelförfattarna vill varna för en sådan utveckling i avvaktan på kritisk värdering av denna typ av kirurgi.
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| 16. |
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| 17. |
- Ahlberg, Patrik, et al.
(författare)
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Defect formation in graphene during low-energy ion bombardment
- 2016
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Ingår i: APL Materials. - : AIP Publishing. - 2166-532X. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- This letter reports on a systematic investigation of sputter induced damage in graphene caused by low energy Ar+ ion bombardment. The integral numbers of ions per area (dose) as well as their energies are varied in the range of a few eV's up to 200 eV. The defects in the graphene are correlated to the dose/energy and different mechanisms for the defect formation are presented. The energetic bombardment associated with the conventional sputter deposition process is typically in the investigated energy range. However, during sputter deposition on graphene, the energetic particle bombardment potentially disrupts the crystallinity and consequently deteriorates its properties. One purpose with the present study is therefore to demonstrate the limits and possibilities with sputter deposition of thin films on graphene and to identify energy levels necessary to obtain defect free graphene during the sputter deposition process. Another purpose is to disclose the fundamental mechanisms responsible for defect formation in graphene for the studied energy range.
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| 18. |
- Ahlberg, Patrik, 1985-
(författare)
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Graphene Implementation Study in Semiconductor Processing
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Graphene, with its two-dimensional nature and unique properties, has for over a decade captured enormous interests in both industry and academia. This work tries to answer the question of what would happen to graphene when it is subjected to various processing conditions and how this would affect the graphene functionality. The focus is placed on its ability to withstand different thin-film deposition environments with regard to the implementation of graphene in two application areas: as a diffusion barrier and in electronic devices.With single-layer graphene films grown in-house by means of chemical vapor deposition (CVD), four techniques among the well-established thin-film deposition methods are studied in detail: atomic layer deposition (ALD), evaporation, sputter-deposition and spray-deposition. And in this order, these methods span a large range of kinetic impact energies from low to high. Graphene is known to have a threshold displacement energy of 22 eV above which carbon atoms are ejected from the lattice. Thus, ALD and evaporation work with energies below this threshold, while sputtering and spraying may involve energies above. The quality of the graphene films undergone the various depositions is mainly evaluated using Raman spectroscopy.Spray deposition of liquid alloy Ga-In-Sn is shown to require a stack of at least 4 layers of graphene in order to act as an effective barrier to the Ga diffusion after the harsh spray-processing. Sputter-deposition is found to benefit from low substrate temperature and high chamber pressure (thereby low kinetic impact energy) so as to avoid damaging the graphene. Reactive sputtering should be avoided. Evaporation is non-invasiveness with low kinetic impact energy and graphene can be subjected to repeated evaporation and removal steps without losing its integrity. With ALD, the effects on graphene are of different nature and they are investigated in the field-effect-transistor (FET) configuration. The ALD process for deposition of Al2O3 films is found to remove undesired dopants from the prior processing and the Al2O3 films are shown to protect the graphene channel from doping by oxygen. When the substrate is turned hydrophobic by chemical treatment prior to graphene transfer-deposition, a unipolar transistor behavior is obtained.
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| 19. |
- Ahlberg, Patrik, et al.
(författare)
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Toward synthesis of oxide films on graphene with sputtering based processes
- 2016
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 34:4
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Tidskriftsartikel (refereegranskat)abstract
- The impact of energetic particles associated with a sputter deposition process may introduce damage to single layer graphene films, making it challenging to apply this method when processing graphene. The challenge is even greater when oxygen is incorporated into the sputtering process as graphene can be readily oxidized. This work demonstrates a method of synthesizing ZnSn oxide on graphene without introducing an appreciable amount of defects into the underlying graphene. Moreover, the method is general and applicable to other oxides. The formation of ZnSn oxide is realized by sputter deposition of ZnSn followed by a postoxidation step. In order to prevent the underlying graphene from damage during the initial sputter deposition process, the substrate temperature is kept close to room temperature, and the processing pressure is kept high enough to effectively suppress energetic bombardment. Further, in the subsequent postannealing step, it is important not to exceed temperatures resulting in oxidation of the graphene. The authors conclude that postoxidation of ZnSn is satisfactorily performed at 300 degrees C in pure oxygen at reduced pressure. This process results in an oxidized ZnSn film while retaining the initial quality of the graphene film.
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| 20. |
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| 21. |
- Ahlman, Håkan, 1947, et al.
(författare)
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Interventional treatment of gastrointestinal neuroendocrine tumours.
- 2000
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Ingår i: Digestion. - 0012-2823. ; 62 Suppl 1, s. 59-68
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Tidskriftsartikel (refereegranskat)abstract
- Neuroendocrine (NE) tumours of the gastrointestinal tract (carcinoids and endocrine pancreatic tumours) are rare diseases. In the presence of liver metastases these patients may suffer from disabling symptoms due to hormone overproduction. Patients with localized disease can be resected for cure and also patients with liver metastases can undergo potentially curative tumour resection. However, long-term follow-up of the latter cases indicates frequent recurrence of tumour. Using close biochemical monitoring of tumour markers combined with newer techniques for tumour visualization, these recurrences can often be diagnosed at an early stage so that repeat surgical procedures can be performed. During the last years very active surgery has been recommended for NE tumours, many of which have a relatively slow growth. Even in patients not amenable to curative liver surgery, debulking can be considered if the main tumour burden can be safely excised. The primary aim of this type of treatment is palliation of hormonal symptoms. An important question is whether the aggressive treatment actually prolongs survival. No prospective studies have been performed. Such studies are hampered by the lack of strict surgical programs running over long periods and the relative rarity of NE tumours. Liver transplantation may be another treatment modality in selected cases.
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| 22. |
- Ahlman, Håkan, 1947, et al.
(författare)
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Management of disseminated midgut carcinoid tumours.
- 1991
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Ingår i: Digestion. - 0012-2823. ; 49:2, s. 78-96
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Tidskriftsartikel (refereegranskat)abstract
- Forty-one patients with disseminated midgut carcinoid tumours were treated over a 6-year period according to a strict programme including primary surgical treatment. In 10 patients, a total remission of the disease was obtained. Patients with bilobar hepatic disease had ischaemic treatment of their liver metastases by hepatic arterial embolisation after primary surgical and medical treatment (low dose octreotide). Thus, by combining surgical, radiological and medical treatment modalities, we wanted to offer these patients optimal palliation. This treatment programme resulted in good symptomatic relief in all patients accompanied by a marked reduction in 5-hydroxyindoleacetic acid (5-HIAA) levels. At recurrence of symptoms in combination with rising 5-HIAA levels, embolisation was repeated. Ten of the treated patients have deceased during the observation period, but only 5 from their carcinoid disease.
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| 23. |
- Akhtar, Sultan, et al.
(författare)
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Visualization of functionalization of nano-particles and graphene in the TEM
- 2010
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Ingår i: Advanced Materials Workshop 2010.
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Konferensbidrag (refereegranskat)abstract
- Recently, the activity on functionalized nano-objects has strongly increased. Yet, there are, to our knowledge no techniques available that visualize the attachment of molecules to nano-entities such as nanoparticles and graphene. In this work, we show a methodology to analyse the attachment of molecules to nanoparticles and graphene. The difficulty of such transmission electron microscopy (TEM) characterization consists in the high beam sensitivity of these nanoobjects. We employed a high resolution- as well as diffraction contrast-imaging methods to characterize graphene. First, we have developed a method to measure the thickness of free-standing graphene-like layers. The refinement of these imaging techniques enabled the imaging of functionalized C60 (fullerene) on top of a few-layer graphene flake by TEM. We also developed a methodology to visualize the attachment of functionalized gold and magnetic nanoparticles (different sizes) to nonstained and unlabeled single strand DNA-coils. This technique can be used to understand the interaction of a large variety of functionalized nanoparticles with their solution environment and/or macromolecular structures for their large applications.
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| 24. |
- Alvi, Sajid Ali
(författare)
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Refractory High Entropy Alloys and Films for High Temperature Applications
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High-entropy alloy (HEA) is a multi-component alloy constituting five or more principal elements in equi- or near equi-atomic percentages. The high configurational entropy in a HEA composition, in contrast to conventional alloys, leads to the stabilisation of the alloying elements in stable solid solutions of face-centred-cubic (FCC), body-centred-cubic (BCC) and/or amorphous structures. The characteristic properties of HEAs are mainly governed by lattice distortion, sluggish diffusion and entropy- and cocktail-effects. Refractory high-entropy alloys (RHEAs), consisting of refractory elements, are considered as a paradigm shift in developing materials for high temperature applications.The current PhD project investigates four different aspects of RHEAs. First, it involves developing CuMoTaWV RHEA by spark plasma sintering (SPS) and utilising the cocktail effect of HEAs for high temperature tribological application. The use of the cocktail effect, defined as selecting favourable compositions for particular applications, is utilised for RHEA compositions in order to yield adaptive tribological behaviour at changing temperatures or environments. The sintered CuMoTaWV showed formation of BCC solid solution and a composite microstructure. The high temperature tribological investigations showed an adaptive behaviour at different temperatures. At lower temperatures Cu lowered the wear rate through formation of CuO, and at higher temperatures V enhanced the tribological resistance through formation of lubricating V2O5 phases.The second aspect involves studying the effect of lattice distortion on mechanical properties of magnetron sputtered thin film after adding Cu to the refractory elements of Mo, Ta, W and V. A target of CuMoTaWV was developed through partial sintering and used to deposit thin film on different substrates. The deposited film showed formation of BCC solid solution, which was verified through DFT calculations. The lattice distortion in CuMoTaWV film showed high hardness and nano-pillar compressive strength. Furthermore, the tribological properties were enhanced at temperatures up to 400oC due to the addition of Cu.The third aspect involves studying the effect of configurational entropy on the formation and high temperature stability of refractory high-entropy thin film metallic glass and its nitrides, by increasing the number of principal elements. A partially sintered target of TiVZrNbMoHfTaW was used to deposit thin films of metallic glass and nitrides through magnetron sputtering. The metallic glass thin films and its nitrides were found to have high hardness of 7.3 GPa and 19–43 GPa, respectively. Furthermore, the metallic glass thin films showed a high nano-pillar compressive strength of up to 3 GPa, almost twice as high as conventional metallic glass films. The phase stability of metallic glass and its nitride thin films were found to be stable at temperatures up to 750oC and 950oC, respectively. The exceptionally superior mechanical properties and high temperature stability has been attributed to the presence of high configurational entropy. The last part of this PhD thesis consists of studying high-entropy-based W-rich alloys for high temperature applications. A W-based alloy of composition W0.5(TaTiVCr)0.5 was consolidated using SPS. The resulting alloy revealed a BCC solid solution structure. The microstructure of W-rich alloys consist of a combination of W-rich, high-entropy and TiC phases. The BCC solid solution structure in W-rich alloys was found to be stable with exceptionally high compressional strength up to 1,400oC. A high compressive yield strength of 1136 ± 40 MPa, 830 ± 60 MPa and 425 ± 15 MPa was found at test temperatures of 1,000oC, 1,200oC and 1,400oC, respectively. The resulting high strength has been related to the formation of high-entropy phases, which in return induces sluggish diffusion at higher temperatures. The high temperature tribology at 400oC showed an average COF and low wear rate of 0.5 and 1.37 x 10-5 mm3/Nm, respectively. The high temperature wear resistance at 400oC was enhanced due to the presence of HEA and TiC phases. The studies carried out in this thesis suggest the possibility of utilising the full potential of the cocktail effect, lattice distortion and configurational entropy in designing new high-entropy compositions for applications requiring adaptive tribological behaviour, superior mechanical properties and high temperature phase stability.
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| 25. |
- Alvåsen, Karin, et al.
(författare)
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Accuracy of the “index finger test” to determine type of death of dairy cows at destruction plants
- 2012
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Dead cows are routinely brought to destruction plants and monitoring the influx may be useful for early detection of emerging (infectious) diseases. A prerequisite is that it can be determined if the cow was euthanized or died unassisted, because a sudden increase in the latter may be indicative of an outbreak. The objective of this study was to evaluate the accuracy of visual inspection at the destruction plant as a means to distinguish between the two types of deaths. The two main destruction plants in Sweden were visited 3 times, 3 days each, in spring, summer and autumn during 2011. The identity, and whether the cow was shot in the forehead or not, was recorded for all dairy cows entering the destruction plants during these days. We phoned the owner of the cow within 3 weeks after the cow was examined and asked whether the cow died unassisted or was euthanized. A total of 468 cows examined, also had information from the farmers. The comparison demonstrated that there were discrepancies between the observations. According to the farmers (gold standard) the proportion of cows that died unassisted was 30%, while the visual inspection (test) found that the proportion was 40%. Three cows were euthanized by an overdose of an anesthetic, which explained some of the discrepancy. The sensitivity and the specificity of the visual examination were 93% and 83%, respectively. The positive predictive value was 70% and the negative predicted value was 97%. This study showed that visual inspection of dairy cows at destruction plants overestimate the proportion of cows that died unassisted. The accuracy of the method is however judged to be sufficient to monitor the proportion of unassisted death.
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