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1.	Nyberg, Harald, et al. (författare) Tribochemical formation of sulphide tribofilms from a Ti-C-S coating sliding against different counter surfaces 2014 Ingår i: Tribology letters. - : Springer Science+Business Media B.V.. - 1023-8883 .- 1573-2711. ; 56:3, s. 563-572 Tidskriftsartikel (refereegranskat)abstract Tribochemically active Ti-C-S coatings are nanocomposite coatings containing a S-doped titanium carbide, from which S can be released in a tribological contact. This work studies tribochemical reactions between a Ti-C-S coating and various counter surface materials, and their effect on the tribological performance. Tribological tests were performed in a ball-on-disc set-up, using balls of five different materials as sliding partners for the coating: 100Cr6 steel, pure W, WC, 316-L steel and Al2O3. For W balls, a WS2 tribofilm was formed, leading to low friction (down to A mu = 0.06). Furthermore, increasing normal load on the W balls was found to lead to a strong decrease in A mu and earlier formation of the low-friction WS2 tribofilm. Similar WS2 and MoS2 tribofilms were, however, not formed from WC- and Mo-containing 316-L balls. The performance when using WC and Al2O3 balls was significantly worse than for the two steel balls. It is suggested that this is due to sulphide formation from Fe, analogous to formation of anti-seizure tribofilms from S-containing extreme pressure additives and steel surfaces. The tribochemical activity of Ti-C-S coatings, with the possibility of S release, is thus beneficial not only for pure W counter surfaces, but also for Fe-based sliding partners.
2.	Sundberg, Jill, 1986-, et al. (författare) Influence of composition, structure and testing atmosphere on the tribological performance of W-S-N coatings 2014 Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 258, s. 86-94 Tidskriftsartikel (refereegranskat)abstract W-S-N coatings deposited by reactive magnetron sputtering offer the possibility of ultra-low friction in unlubricated sliding. In this work, W-S-N coatings of different composition and structure have been deposited, characterised and evaluated with respect to the tribological performance and tribofilm formation. The composition was varied by changing the flow of N-2 into the deposition chamber, leading to N contents ranging from 0 to 47 at.%. W-S-N coatings deposited without substrate heating are amorphous, while substrate heating results in coatings containing nanocystalline tungsten sulphide (WSx) for low N contents, and nanocrystalline tungsten nitride (WyN) at a high N content. The coatings were tribologically tested against steel balls in four different atmospheres dry N-2, dry air, humid N-2 and humid air to study the effects of atmospheric O-2 and H2O both separately and simultaneously. In dry N-2, all coatings exhibited an excellent performance with very low friction (mu approximate to 0.02) and wear. Notably, this included the N-richest and hardest coating, containing nanocrystalline WyN and only 13 at.% of S. The friction and wear increased on changing the atmosphere, in the order of dry air-humid N-2-humid air. In these three non-inert atmospheres, the friction and wear also increased with increasing N content of the coating. It is thus concluded that the presence of O-2, the presence of H2O, and a high N content (i.e., low Wand S contents) are three factors increasing the risk of high friction and wear, especially when occurring together. Raman spectroscopy mapping of the contact surfaces on the coatings and the balls showed that low friction and wear is connected to the presence of WS2 tribofilms in the contact, and that the three previously mentioned factors affect the formation and function of this tribofilm.
3.	Sundberg, Jill, 1986-, et al. (författare) Quaternary W-S-C-Ti films for tribological applications 2011 Konferensbidrag (refereegranskat)abstract IntroductionTransition metal dichalcogenides such as WS2 are well-known for their layered structure and solid lubricant properties. The addition of another element, such as carbon, can improve the mechanical properties of the material, such as the hardness, while still maintaining the solid lubrication.1,2 Different theories regarding the friction mechanisms in W-S-C have been proposed: the low friction could be solely due to the WS2 phase2 or both the WS2 and the carbon phase could be responsible.1 Despite the hardness increase compared to pure WS2, W-S-C films still exhibit a quite low hardness. One route to increasing the hardness is to add a fourth element, which is a strong carbide-former (e. g. titanium), to form a hard carbide phase. In this work, W-S-C-Ti films have been deposited by magnetron sputtering and characterized with a variety of techniques. The mechanical and tribological properties have been studied and related to the composition.Experimental ProceduresThe films were deposited by non-reactive DC magnetron sputtering using two targets: graphitic carbon and WS2, with a ring-shaped titanium component mounted on the latter. The titanium content was varied by the size of the metal component, while the carbon content was varied by the carbon target power. Four series of films were deposited at room temperature and at 300°C.The micro- and nanostructure of the films was investigated by SEM and TEM, and XRD was used to study the presence of crystalline phases. The composition was determined by EDS, and the chemical bonding was studied by XPS and Raman spectroscopy. Nanoindentation was used to probe the mechanical properties of the different films, and ball-on-disc tests were performed in order to evaluate the tribological properties.Results and DiscussionPrevious studies on W-S-C suggest that the material consists of WS2 nanocrystallites embedded in an amorphous matrix. Also in this study, the only phase detected with XRD is WS2, with the typical WS2 peaks becoming broader with the addition of carbon indicating a decrease in crystallinity. TEM shows WS2 nanocrystallites embedded in an amorphous matrix. However, our results indicate that the composition of the matrix is more complex than what has previously been suggested. Chemical information from XPS suggests that the matrix is not based on carbon alone, but that it also includes a carbidic component. Furthermore, the S/W ratio in the samples is approximately constant but significantly lower than 2; such substochiometry in WS2 films is well known and we will discuss possible mechanisms for this behaviour.By adding titanium to W-S-C, the chemical bonding in the material is changed. XPS indicates the presence of Ti-C bonds even when no crystalline TiC grains are observed by XRD. For high titanium and carbon contents, a crystalline phase with the sodium chloride structure is observed, which has a cell parameter significantly larger than TiC. Furthermore, the added titanium changes the mechanical properties of the films, and an increase in hardness up to 100% from 6 GPa to 12 GPa can be observed. The effect of titanium addition, however, is dependent on the film composition and the deposition temperature.Tribological testing show friction coefficients down to approximately 0.02 in ball-on-disc tests using a steel ball in dry atmosphere for W-S-C films. The effect of titanium addition varies with the composition; high titanium contents combined with suitable carbon levels yields films that exhibit low and stable friction coefficients well under 0.02 under the aforementioned conditions. Thus, it is possible to tune the mechanical properties of W-S-C films, while still obtaining low friction, by the addition of titanium.References[1] A.A. Voevodin, J.S. Zabinski, Thin Solid Films 370, 223-231 (2000)[2] T. Polcar, M. Evaristo, A. Cavaleiro, Plasma Process. Polym. 6, 417-424 (2009)
4.	Sundberg, Jill, 1986-, et al. (författare) Sulfur-doping of nc-TiC/a-C films by reactive sputtering 2012 Ingår i: Thirteenth International Conference on Plasma Surface Engineering, Garmisch-Partenkirchen, Germany, 10-14 September 2012. Konferensbidrag (refereegranskat)abstract Nanocomposite thin films with carbide grains in a matrix of amorphous carbon have been found interesting for various mechanical and electrical applications. An important advantage of these materials is the possibility to tune the properties by varying the composition and the microstructure. A well-known example is the nc-TiC/a-C system, which is interesting for its tribological as well as its electrical and chemically protective properties. One way to modify the material is doping with a third element. Usually, another metal or a p-element such as oxygen or nitrogen is considered. In this work, however, Ti-C films have been doped with sulfur. The doping was performed by introduction of increasing amounts of H2S to the chamber during DC magnetron sputtering from elemental Ti and C targets.An increased flow of H2S during deposition leads to an increase in the S content of the films, as well as a slight decrease in the C:Ti ratio. Pure TiC/a-C films were proved by GI-XRD and XPS to contain crystalline TiC with the NaCl structure in a matrix of amorphous carbon. The introduction of S leads to a significant and gradual increase of the cell parameter of the carbide phase – from 4.3 Å up to more than 4.8 Å for coatings with approximately 20 at-% of S. This clearly indicates that the S atoms enter the carbide phase, forming a previously unknown Ti-C-S solid solution. The addition of S also affects the mechanical properties, such as the hardness which was seen to decrease from 8 GPa for pure TiC in an amorphous carbon matrix, to 5 GPa when doped with sulfur.Thus, the introduction of S is shown to have effects on the chemistry as well as the properties of nc-TiC/a-C thin films. In the current work, the effect of S doping on the structure, chemical bonding and mechanical properties as well as tribological performance will be presented.
5.	Hansen, Jonny, et al. (författare) Elastohydrodynamic performance of a hydrocarbon mimicking ionic liquid additive 2017 Konferensbidrag (refereegranskat)abstract Machine elements operating under lubricated conditions will eventually fail due to high stresses and fatigue-related causes. In order to find optimum protective measures, it is important to understand how the stresses arise and what factors that influence their magnitude. With the current shift for more sever lubricating regimes, the role of tribo-improvers is becoming vital. At this point, the interplay between the chemisorption mechanism of various lubricant compounds and surface failure is not yet fully understood. To obtain a better understanding of this, a newly developed ionic structured tribo-improving additive, based on silicon, was investigated and benchmarked against conventional heavy-duty gearbox additives. A ball on disc device was operated under heavily loaded rolling/sliding conditions, at elevated temperature to simulate gear like conditions, and lubricating performance was subsequently evaluated in terms of friction and wear. Such results highlight the importance of properly designed lubricants for optimal tribo-performance under rolling-sliding conditions
6.	Kröll, Mirco, et al. (författare) Auswirkungen von vereinheitlichten Prozeduren auf tribologische Versuche 2021 Ingår i: 62. Tribologie-Fachtagung der Gesellschaft für Tribologie. Konferensbidrag (refereegranskat)abstract Anerkannte Institutionen stellen ihre Kompetenzen auf dem Gebiet tribologischer Charakterisierungen Industrie und Forschung zur Verfügung (https://www.i-tribomat.eu/). Ein Aspekt hierbei ist eine tribologische Datenbank. Um die nötige Qualität der Daten sicherzustellen, sind vereinheitlichte Prozeduren erforderlich, in deren Auswirkungen dieser Vortrag einen Einblick gibt.
7.	Kröll, Mirco, et al. (författare) Effects of harmonised procedures on tribological testing 2022 Konferensbidrag (refereegranskat)
8.	Kröll, M., et al. (författare) On the challenges in achieving comparable and reproducible tribological model tests 2022 Ingår i: Book of Abstracts: SICT 2022 / Plasma Tech 2022 / Tribology 2022 Hybrid Joint Conferences. ; , s. 91- Konferensbidrag (refereegranskat)
9.	Kröll, Mirco, et al. (författare) On the quality of wear volume data of laboratory model tests 2022 Ingår i: 63. Tribologie-Fachtagung der Gesellschaft für Tribologie. Konferensbidrag (refereegranskat)abstract This contribution will concentrate on wear as volume loss, which is a crucial part in quantifying the performance of a tribological system. Wear is an outcome of a tribological experiment and affected by the variables of the tribological system including the samples involved. It can be detected and assessed in various ways (e.g., via changes in volume, weight, geometry, morphology, and topography). There are several methods to measure the wear volume. Some of them are standardised, others aren’t. The comparability of these methods was analysed in two Inter-Partner Round-Robin Tests (IP-RRT) using reciprocating laboratory model tests. The evaluation of wear volumes was done on two levels for each IP-RRT. The first level focused on the comparison of wear volumes caused by different tribological experiments with the same parameters conducted by various operators at the partners with several tribometers. The second level focused on the methods used to determine the wear volume of circulated samples with wear scars produced by the tribological tests in those IP-RRTs. These considerations are especially important as within the European Tribology Centre “i-TRIBOMAT” (Grant Agreement no. 814494; call: H2020-NMBP-TO-IND-2018; https://www.i-tribomat.eu/) a shared infrastructure of more than 100 tribometers is formed. Additionally, this centre incorporates the capacities of tribological characterisation of different renowned institutions. To ensure that the wear results determined by this Open Innovative Test Bed are characteristic as well as descriptive, trustworthy, comparable, and reproducible, appropriate procedures are needed. Hence, they safeguard respective quality features, such as low standard deviations. An essential part in the development of these procedures is the continuous improvement process that was set in place within the quality management system. It contains IP-RRTs that collect data, methods used, expenses and suggestions for improvements. They also validate the procedures developed. The presentation will show that harmonised procedures and Best Practices reduce influences caused, for example, by the operators, which is necessary to reach the quality demands of the European Tribology Centre.
10.	Kröll, Mirco, et al. (författare) Trusted tribological materials characterisation services 2022 Ingår i: 23rd International Colloquium Tribology. ; , s. 503-505 Konferensbidrag (refereegranskat)
11.	Martin-Torres, Javier, et al. (författare) Brine-Induced Tribocorrosion Accelerates Wear on Stainless Steel: Implications for Mars Exploration 2021 Ingår i: Advances in Astronomy. - : Hindawi Publishing Corporation. - 1687-7969 .- 1687-7977. ; 2021 Tidskriftsartikel (refereegranskat)abstract Tribocorrosion is a degradation phenomenon of material surfaces subjected to the combined action of mechanical loading and corrosion attack caused by the environment. Although corrosive chemical species such as materials like chloride atoms, chlorides, and perchlorates have been detected on the Martian surface, there is a lack of studies of its impact on materials for landed spacecraft and structures that will support surface operations on Mars. Here, we present a series of experiments on the stainless-steel material of the ExoMars 2020 Rosalind Franklin rover wheels. We show how tribocorrosion induced by brines accelerates wear on the materials of the wheels. Our results do not compromise the nominal ExoMars mission but have implications for future long-term surface operations in support of future human exploration or extended robotic missions on Mars.
12.	Nyberg, Erik, 1986-, et al. (författare) Additive Technology for Halogen-free Room Temperature Ionic Liquids 2016 Ingår i: STLE 2016 Annual Meeting and Exhibition, 2016. - Las Vegas, NV, USA. Konferensbidrag (refereegranskat)abstract Room temperature ionic liquids (RTIL) are increasingly being studied as advanced lubricants due to inherent properties such as thermal stability, low volatility, and non-flammability. While traditional lubricants are being optimized by additive technology, researched RTILs have generally been additive-free due to a lack of miscible additives. Recently, new RTILs have been designed for improved solvency of synthetic lubricant additives. In this work, RTIL samples based on tetralkylphosphonium cations have been evaluated. They are halogen-free and hydrophobic to minimize corrosion. Five RTILs were evaluated in a steel-steel tribotest where the results showed excellent tribological performance for RTILs with friction modifying and anti-wear additives designed for synthetic lubricants. These novel RTILs combined with additives demonstrate high potential as advanced lubricants due to their persistent nature in combination with excellent tribological performance.
13.	Nyberg, Erik, 1986-, et al. (författare) Additives to Improve Tribological Properties of Ionic Liquid as Base Fluids 2017 Konferensbidrag (refereegranskat)abstract Room temperature ionic liquids (RTILs) have several properties which make them interesting candidates as base fluids for extreme conditions. However, a lack of compatibility with tribo-improving additives combined with an often overly aggressive nature is limiting their use as base fluids. To overcome these drawbacks, hydrocarbon-imitating RTIL base fluids have recently been developed. These lubricants aim for a more balanced interaction with metal surfaces while enabling compatibility with common additives, so that the reactivity with the lubricated surface can be tuned in a manner similar to hydrocarbon base oil–additive systems. In this work, the effects of several common additives in the novel RTIL were examined by laboratory tribotesting. Surface analysis was performed in order to study the lubrication mechanisms.
14.	Nyberg, Erik, 1986- (författare) AI-tools for competence matching 2023 Konferensbidrag (övrigt vetenskapligt/konstnärligt)
15.	Nyberg, Erik, 1986-, et al. (författare) Boundary Film Formation from Hydrocarbon-mimicking Ionic Liquids 2017 Konferensbidrag (refereegranskat)abstract Ionic liquids have properties that are very useful in high performance lubricants. However, they must be well tuned to the tribological system. Hydrocarbon-mimicking ionic liquids have been developed in an effort to overcome some of the compatibility problems that are holding back the use of ionic liquids in tribology. In this work, hydrocarbon-mimicking ionic liquids are evaluated as base fluids in steel-steel reciprocating tribotests. Wear and friction reducing boundary films are formed and found to be composed mainly of Si and O. An amine additive is found to stimulate the formation of this boundary film.
16.	Nyberg, Erik, 1986-, et al. (författare) Boundary Film Formation of P-SiSO in Reduced Oxygen Atmosphere 2018 Ingår i: NORDTRIB 2018. - Uppsala. Konferensbidrag (refereegranskat)abstract Modern space exploration missions, such as planetary exploration of Mars, have significantly different tribological concerns compared to conditions faced by mechanical devices in satellites. Space lubricants have traditionally implied extremely low vapor pressure, but limited performance in boundary lubrication. Mars devices on the other hand are subjected to heavier loads, while operating in an atmosphere composed of CO2 at <1 kPa. Ionic liquids are synthetic fluids with inherently low vapor pressure that are known to readily form boundary films under severe conditions. In an effort to improve the tribological performance of ILs, hydrocarbon-mimicking ionic liquids have recently been designed. This recent work has displayed significantly improved lubrication performance for steel – steel tribo-systems in air, compared to PFPEs or fluorine-based ILs. Also, as a consequence of the hydrocarbon-mimicking structure, compatibility with several conventional tribo-improving additives have been displayed. In this work, we evaluate these novel fluids in a reduced oxygen environment under boundary lubricated conditions to evaluate the effect of oxygen supply on boundary film formation.
17.	Nyberg, Erik, 1986-, et al. (författare) Formation of Boundary Film from Ionic Liquids Enhanced by Additives 2017 Ingår i: Applied Sciences. - Basel : MDPI. - 2076-3417. ; 7:5 Tidskriftsartikel (refereegranskat)abstract Room temperature ionic liquids (RTILs) have several properties that make them interesting candidates as base fluids for extreme conditions. However, a lack of compatibility with tribo-improving additives combined with an often overly aggressive nature is limiting their use as base fluids. To overcome these drawbacks, hydrocarbon-imitating RTIL base fluids have recently been developed. In this study, the effects of several common additives in the novel RTIL (P-SiSO) were examined by laboratory tribotesting. A reciprocating steel-steel ball-on-flat setup in an air atmosphere was used, where the lubricant performance was evaluated over a range of loads and temperatures. Surface analyses after testing were carried out using optical profilometry, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Neat P-SiSO displayed high performance in the tribotests. At an elevated load and temperature, a shift in lubrication mode was observed with an accompanying increase in friction and wear. Surface analysis revealed a boundary film rich in Si and O in the primary lubrication mode, while P was detected after a shift to the secondary lubrication mode. An amine additive was effective in reducing wear and friction under harsh conditions. The amine was determined to increase formation of the protective Si–O film, presumably by enhancing the anion activity.
18.	Nyberg, Erik, 1986-, et al. (författare) Improvement in the Tribological Performance of Room Temperature Ionic Liquids by Additive Technology 2016 Ingår i: Nordic Symposium on Tribology - NORDTRIB 2016. - Hämeenlinna, Finland. Konferensbidrag (refereegranskat)abstract Room temperature ionic liquids (RTILs) have interesting properties such as thermal stability, low volatility, and non-flammability. Most research on RTIL lubricants regard RTILs composed of fluorine-containing anions. In metal-metal contacts, these fluids form boundary films of iron fluoride which reduces friction and wear to some extent, but on the other hand cause corrosion under humid conditions. Additives are one way of improving RTIL performance, however; most additives are designed for conventional petroleum base oils, and are therefore hardly miscible with RTILs. In order to improve the performance of RTILs, halogen-free and additive compatible RTILs have recently been developed as potential base oils for advanced lubricants. In this work, RTILs based on phosphonium cations and silylalkyl-sulfonate anions have been evaluated. These fluids are halogen-free and hydrophobic, showing good results in Cu-corrosion testing. Five RTILs, prepared from different anion-cation combinations, were evaluated in steel-steel tribotest. Compared as neat fluids, the RTILs performed superior to perfluoropolyether (PFPE) -based reference lubricant in terms of wear and friction reduction. In the attached figure, it can be seen that the mean friction coefficient is significantly lower for the neat RTIL samples at both 100 and 150 N. Regarding wear volume; the results show that the investigated RTILs produce better protection against wear and are robust to increased load. The tribological performance of RTILs is further improved when adding friction modifying and anti-wear agents designed for synthetic lubricants. This excellent tribological performance, in combination with the inherently persistent nature of ionic liquids demonstrates the high potential as advanced lubricants for these novel RTILs.
19.	Nyberg, Erik, 1986-, et al. (författare) Influence of atmosphere on boundary film formation from ionic liquids 2018 Konferensbidrag (refereegranskat)abstract Modern space exploration missions, such as planetary exploration of Mars, have significantly different tribological concerns compared to conditions faced by mechanical devices in satellites. Space lubricants have traditionally implied extremely low vapor pressure, but limited performance in boundary lubrication. Mars devices on the other hand are subjected to heavier loads, while operating in an atmosphere composed of CO2 at <1 kPa. Ionic liquids are synthetic fluids with inherently low vapor pressure that are known to readily form boundary films under severe conditions. In our recent work, an ionic liquid designed as lubricant base fluid formed highly effective boundary films composed of silicate when evaluated in air. These boundary films include oxygen, which can possibly be supplied by the atmosphere or by the lubricant itself. In this work, we employ tribotesting in CO2, and N2, and perform surface analysis to evaluate the effect of oxygen supply on boundary film formation.
20.	Nyberg, Erik, 1986- (författare) Ionic Liquid Lubricants for Space Applications 2021 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Lubrication is critical to the efficient and reliable operation of machine elements such as gears, bearings, or any other moving mechanical assembly (MMA). On Earth, machine designers are accustomed to the access of a wide range of liquid lubricants that enable predictable and reliable long-term operations of high performance MMA. In space applications on the other hand, engineers are constrained to a comparatively limited choice of lubricant candidates that can meet the stringent demands of tribosystems operating in a space environment. At the same time, repair or maintenance are seldom options that are possible in space, and consequently lubricant failures are potentially critical. As international space agencies are converging on the goal of establishing a permanently crewed lunar Gateway for human presence on the Moon and eventually onwards to Mars, there is a need for radical improvements in many aspects of space exploration technology, including space tribology and space grade lubricants. Liquid lubricants are enablers of high performance. A thin fluid film – even in the submicron scale – is often sufficient to separate opposing surface boundaries from direct contact, and thereby prevent excessive friction and wear. Liquid lubricants are therefore attractive for use in space mechanisms. Unfortunately, liquid lubricants must overcome several issues in order to be effective in the space environment. Vacuum, microgravity, and low temperatures are all factors that oppose the effective supply of liquid lubricants into the tribological contact of MMA. If the tribological contact becomes starved of oil, the surfaces enter the boundary lubrication regime where seizure is an ever-present threat. There are very few types of fluids available that meet the stringent space grade lubricant requirements. Perfluoropolyalkylethers (PFPE), or multiply alkylated cyclopentanes (MAC) are two fluids with significant heritage in space applications. These fluids are currently employed as lubricants in a wide range of space applications, as they are rare examples of fluids that meet the high demands on resistance to vacuum outgassing. Unfortunately, these compounds are susceptible to degradation under boundary lubrication conditions, and unlike conventional lubricants employed on Earth, these fluids have poor compatibility with the boundary lubrication additives that are commonly employed in conventional oils. Ionic liquids (ILs) have emerged as potential liquid lubricant candidates in space. These synthetic fluids are composed of anions and cations. The resulting ionic interaction enables the substance to have low vapor pressure with relatively low molecular weight. For this reason, ILs have been advocated as one of the candidate lubricants for space applications. When employing ILs as lubricants, the ionic charge provides Coulombic interaction with surfaces to enable the formation of a boundary lubricating film. This is an important part of the IL lubricating mechanism, but successful lubricant performance requires integrating the lubricant candidate into the tribosystem, taking into account operating conditions and environment. Therefore, the boundary film formation should be tunable to the application at hand. Ionic liquids are designable fluids, with properties dependent on the combination of anion and cation as well as incorporated functional groups. Based on this background, this work focused on evaluating the feasibility of employing ionic liquid lubricants for space applications. In this thesis, the molecular design of an IL lubricant was described Paper [1], and the resulting hydrocarbon-mimicking ionic liquid (P-SiSO) was evaluated in tribological experiments in boundary lubricated conditions. Boundary film formation by neat P-SiSO was studied in Paper [2], and in Paper [3] we describe the use of P-SiSO as a multipurpose performance ingredient in MAC. A test methodology was devised in Paper [4] in order to evaluate the lubrication performance under component scale experiments in space relevant conditions. The designed ionic liquid lubricant was evaluated in Paper [5] by the specific methodology. Advanced surface analysis was employed to understand the tribo-mechanism of P-SiSO in both the model scale experiments as well as the component scale. The lubricated surfaces were analyzed in terms of surface topography- and chemistry, and mechanisms of lubrication are discussed. A highly effective boundary film based on ionic adsorption and formation of silicate was observed by these ionic liquids. This thesis demonstrates the feasibility of employing ionic liquids for lubrication of moving mechanical assemblies in space applications.
21.	Nyberg, Erik, 1986- (författare) Ionic liquids as lubricants for mechanical devices on Mars 2017 Konferensbidrag (övrigt vetenskapligt/konstnärligt)
22.	Nyberg, Erik, 1986-, et al. (författare) Ionic Liquids as Performance Ingredients in Space Lubricants 2021 Ingår i: Molecules. - Switzerland : MDPI. - 1431-5157 .- 1420-3049. ; 26:4 Tidskriftsartikel (refereegranskat)abstract Low vapor pressure and several other outstanding properties make room-temperature ionic liquids attractive candidates as lubricants for machine elements in space applications. Ensuring sufficient liquid lubricant supply under space conditions is challenging, and consequently, such tribological systems may operate in boundary lubrication conditions. Under such circumstances, effective lubrication requires the formation of adsorbed or chemically reacted boundary films to prevent excessive friction and wear. In this work, we evaluated hydrocarbon-mimicking ionic liquids, designated P-SiSO, as performance ingredients in multiply alkylated cyclopentane (MAC). The tribological properties under vacuum or various atmospheres (air, nitrogen, carbon dioxide) were measured and analyzed. Thermal vacuum outgassing and electric conductivity were meas- ured to evaluate ‘MAC & P-SiSO’ compatibility to the space environment, including the secondary effects of radiation. Heritage space lubricants—MAC and perfluoroalkyl polyethers (PFPE)—were employed as references. The results corroborate the beneficial lubricating performance of incorporating P-SiSO in MAC, under vacuum as well as under various atmospheres, and demonstrates the feasibility for use as a multifunctional additive in hydrocarbon base oils, for use in space exploration applications.
23.	Nyberg, Erik, 1986-, et al. (författare) Lubrication Concept Evaluated for Geared Actuators under Starved Conditions 2020 Ingår i: 45th Aerospace Mechanisms Symposium. - : National Aeronautics and Space Administration (NASA). ; , s. 255-260 Konferensbidrag (refereegranskat)abstract Lubricant starvation leads to the risk of a shift in the lubrication regime from (elasto)hydrodynamic towards boundary conditons. Effective tribofilm formation is essential to limit surface damages in these conditions, but additive technology for space-grade lubricants is lacking. This work evaluates the feasibility of a novel type of multifunctional ionic liquid lubricant, for use with multiply alkylated cyclopentane (MAC). Actuator gearboxes are operated under starved conditions in nitrogen atmosphere to evaluate the effectiveness of the tribofilm forming lubricant (designated P-SiSO). The effectiveness of P-SiSO was evaluated from macro to micro scale in both surface and sub-surface analysis by use of microscopy (optical, interferometric, SEM) and X-ray microtomography (XMT), and mechanisms of effective lubrication are discussed.
24.	Nyberg, Erik, 1986- (författare) Lubrication mechanism of hydrocarbon-mimicking ionic liquids 2017 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Lubrication is critical in order to achieve high efficiency and reliability of machine elements such as gears, bearings, and other moving mechanical assemblies (MMA). In space applications, tribological properties of lubricants are quickly growing more important. Traditional space systems such as satellites imply MMA such as gyroscopes, antenna pointing mechanisms, and solar array drives. These MMA operate in high vacuum (<10-5 Pa) under lightly loaded conditions. Modern space missions on the other hand, such as remotely operated vehicles used for in-situ Mars exploration relies on different types of MMA. In these robotic systems, electromechanical actuators are being used extensively to provide controlled motion. Gears and bearings in these actuators operate in an atmosphere mainly consisting of CO2 at ~10+3 Pa under heavily loaded contact conditions. In these conditions, the tribosystem is likely to operate in the boundary lubricated regime, with consequent risk of high friction and wear.High molecular weight fluids have significant heritage in space because of their low vapor pressure. They are currently employed as lubricants in a wide range of space applications, as they meet high demands on resistance to vacuum outgassing. Unfortunately, the large molecules are susceptible to degradation under heavy load.Ionic liquids (ILs) on the other hand, are synthetic fluids that consist entirely of ion pairs with opposing charge. The resulting ion bonds enable inherently low vapor pressure of the fluid without the need for a high molecular weight. For this reason ILs have been advocated as potential lubricants for space applications, but so far compatibility issues have hampered their use as lubricants. Countless IL variations are possible, and solutions are thus likely to exist. Constituent ions can be designed individually and combined in various configurations. However, the fundamental understanding of the lubricating mechanism of ionic liquids is still incomplete, and consequently the optimum molecular structure for IL lubricants remain unknown.In this thesis, a stepwise approach to molecular design of IL lubricants is described, and the resulting hydrocarbon-mimicking ionic liquids are evaluated in tribological experiments. In this thesis, the experiments focus on tribological performance, using steel-steel tribopairs in air environment under boundary lubrication (Paper I). Boundary film formation under a range of contact pressures and temperatures, is analyzed after tribotesting by optical profilometry, scanning electron microscopy (SEM), and energy dispersive X- iii ray spectroscopy (EDS) in Paper II. The analysis reveal formation of a highly effective boundary film based on silicate, that can be further enhanced by amine additives. This thesis demonstrates the feasibility of improving tribological performance of ionic liquids by molecular design.
25.	Nyberg, Erik, 1986-, et al. (författare) Molecular design of advanced lubricant base fluids : hydrocarbon-mimicking ionic liquids 2017 Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 7:11, s. 6364-6373 Tidskriftsartikel (refereegranskat)abstract This paper describes the molecular design and tribological evaluation of novel room-temperature ionic liquid (RTIL) lubricants{,} abbreviated as P-SiSOs. The RTILs are designed to mimic hydrocarbons{,} in order to ensure their compatibility with existing tribosystems as well as enable use of conventional additives. Steel-on-steel ball-on-flat reciprocating tribotests performed under atmospheric conditions show that the neat P-SiSOs exhibit favorable performances{,} resulting in friction and wear significantly lower than those in the case of the perfluoropolyether lubricants used as references. Tribotests performed at elevated loads and temperatures indicate the formation of friction-reducing boundary films of the neat P-SiSOs. The tribological performance of the P-SiSO is improved further by the incorporation of additives conventionally used in hydrocarbon oils. When used in a concentration of 5 wt%{,} the additives glycerol monooleate{,} dibenzyl disulfide{,} and oleylamine improve the tribological characteristics of P-SiSO. These results indicate that molecular-designed hydrocarbon-mimicking RTIL lubricants can exhibit suitable performances in the neat form and that their performances can be improved further by using conventional additives{,} as in the case of hydrocarbon base oil-additive systems.
26.	Nyberg, Erik, 1986-, et al. (författare) Tribology in Space Robotic Actuators : Experimental Method for Evaluation and Analysis of Gearboxes 2021 Ingår i: Aerospace. - : MDPI. - 2226-4310 .- 2226-4310. ; 8:3 Tidskriftsartikel (refereegranskat)abstract Liquid lubricants are critical to enable long-life operation of high-performance machinery, such as geared actuators employed in robotics. In space applications, actuator gearboxes must operate in low temperatures, where liquid lubricants face inherent problems related to low temperature rheology. Heaters are relied upon to provide acceptable gearbox temperatures. Unfortunately, heating is energy-intense and does not scale well with increasing mechanism mass and performance. Effective boundary lubrication (BL), on the other hand, can minimize problems of low temperature rheology. BL relies on tribofilm formation over conventional fluid film separation. Effective space grade boundary lubricants can potentially allow for drastically reduced amounts of oil and the accompanying rheological problems. In this work, we describe the design of a methodology to evaluate and analyze tribology of actuator gearboxes operated under cryogenic oil-starved conditions in N2 atmosphere. The devised methodology enables research pertinent to space actuator tribology by accelerated testing and advanced analysis, as demonstrated by a lubricant candidate case study. Complementary microscopy techniques are discussed, and a novel methodology devised for gear internal microstructure analysis by X-ray microtomography (XMT) is presented.
27.	Nylander, Erik, 1986-, et al. (författare) Growth hormone increases dendritic spine density in primary hippocampal cell cultures 2020 Ingår i: Growth Hormone & IGF Research. - : Elsevier BV. - 1096-6374 .- 1532-2238. ; 50, s. 42-47 Tidskriftsartikel (refereegranskat)abstract Objective: Growth hormone (GH) is widely known for its peripheral effects during growth and development. However, numerous reports also suggest that GH exert pro-cognitive, restorative, and protective properties in the brain. In in vitro studies, the detection of dendritic spines, small protrusions extending from axons, can act as a marker for cognition-related function as spine formation is considered to be associated with learning and memory. Here we show that an acute 24-hour treatment of GH can increase dendritic spine density in primary hippocampal cell cultures.Design: Primary hippocampal cells were harvested from embryonic Wistar rats and cultured for 14 days. Cells were treated with supra-physiological doses of GH (10-1000 nM) and subjected to a high-throughput screening protocol. Images were acquired and analyzed using automated image analysis and the number of spines, spines per neurite length, neurite length, and mean area of spines, was reported.Results: GH treatment increased dendritic spine density using the highest dose while the general health of the cells was unaffected.Conclusion: The results from the present study further confirms a potential role of GH in the treatment of cognitive dysfunction.
28.	Nylander, Erik, 1986-, et al. (författare) Growth hormone is protective against acute methadone-induced toxicity by modulating the NMDA receptor complex 2016 Ingår i: Neuroscience. - : Elsevier. - 0306-4522 .- 1873-7544. ; 339, s. 538-547 Tidskriftsartikel (refereegranskat)abstract Human growth hormone (GH) displays promising protective effects in the central nervous system after damage caused by various insults. Current evidence suggests that these effects may involve N-methyl-d-aspartate (NMDA) receptor function, a receptor that also is believed to play a role in opioid-induced neurotoxicity. The aims of the present study were to examine the acute toxic effects of methadone, an opioid receptor agonist and NMDA receptor antagonist, as well as to evaluate the protective properties of recombinant human GH (rhGH) on methadone-induced toxicity. Primary cortical cell cultures from embryonic day 17 rats were grown for 7 days in vitro. Cells were treated with methadone for 24 h and the 50% lethal dose was calculated and later used for protection studies with rhGH. Cellular toxicity was determined by measuring mitochondrial activity, lactate dehydrogenase release, and caspase activation. Furthermore, the mRNA expression levels of NMDA receptor subunits were investigated following methadone and rhGH treatment using quantitative PCR (qPCR) analysis. A significant protective effect was observed with rhGH treatment on methadone-induced mitochondrial dysfunction and in methadone-induced LDH release. Furthermore, methadone significantly increased caspase-3 and -7 activation but rhGH was unable to inhibit this effect. The mRNA expression of the NMDA receptor subunit GluN1, GluN2a, and GluN2b increased following methadone treatment, as assessed by qPCR, and rhGH treatment effectively normalized this expression to control levels. We have demonstrated that rhGH can rescue cells from methadone-induced toxicity by maintaining mitochondrial function, cellular integrity, and NMDA receptor complex expression.
29.	Nylander, Erik, 1986-, et al. (författare) Mitochondrial function and membrane integrity: an in vitro comparison between six commonly used opioids Annan publikation (övrigt vetenskapligt/konstnärligt)abstract Introduction: There is an ongoing opioid crisis in the United States where the illicit and non-medical use of prescription opioids is associated with an increasing number of overdose deaths. Few studies have investigated the effects of opioid-induced effects on cell viability, and comparative studies are scarce. Here we examine the toxic effect on cell viability from six commonly used opioids; methadone, morphine, oxycodone, hydromorphone, ketobemidone, and fentanyl with respect to mitochondrial and membrane function in vitro. Methods: The opioids were tested in four different cell cultures; primary cortical cell cultures, human neuroblastoma SH-SY5Y cells, and both differentiated and undifferentiated neuroblastoma/glioma hybrid NG108-15 cells. Results: The six different opioids displayed the same trend of reduced cell viability in all four cell cultures. The ranking of opioids, with respect to reduced cell viability were as follows; methadone, fentanyl, ketobemidone, oxycodone, hydromorphone, and morphine. Conclusion: Methadone was ranked as the most toxic opioid closely followed by fentanyl. Ketobemidone and oxycodone had modest effects while both hydromorphone and morphine only displayed little to no negative impact on cell viability.
30.	Nylander, Erik, 1986-, et al. (författare) The effects of morphine, methadone, and fentanyl on mitochondria : A live cell imaging study 2021 Ingår i: Brain Research Bulletin. - : Elsevier. - 0361-9230 .- 1873-2747. ; 171, s. 126-134 Tidskriftsartikel (refereegranskat)abstract The important role of mitochondria in maintaining normal brain cell function has been demonstrated in several neurodegenerative diseases where mitochondrial dysfunction is a prominent feature. Accumulating evidence indicates that opioids may induce neuronal cell death and inhibit neurogenesis, two factors that are dependent on normal mitochondrial function. The aim of the present study was to examine the effects of morphine, methadone, and fentanyl on mitochondrial morphology. Cells from the neuroblastoma/glioma hybrid cell-line NG108-15 were seeded on 96-well cell culture plates and treated with MitoTracker™ for 30 min prior to opioid treatment. Morphine, methadone, and fentanyl were added at various concentrations and images of mitochondria were acquired every 30 min for four hours using a high-content imaging device. The morphological parameters total mitochondrial area, mitochondrial network, number of mitochondrial objects, and the mean area of mitochondrial objects were analyzed using automated image analysis. Methadone and fentanyl, but not morphine, decreased the mitochondrial network, the number of mitochondrial objects, and increased the mean area of mitochondrial objects. Both methadone and fentanyl altered mitochondrial morphology with no effects seen from morphine treatment. These data suggest that methadone and fentanyl disrupt mitochondrial morphology, which may contribute to neuronal cell death.
31.	Nylander, Erik, 1986-, et al. (författare) The Protective and Restorative Effects of Growth Hormone and Insulin-Like Growth Factor-1 on Methadone-Induced Toxicity In Vitro 2018 Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 19:11, s. 1-16 Tidskriftsartikel (refereegranskat)abstract Evidence to date suggests that opioids such as methadone may be associated with cognitive impairment. Growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are suggested to be neuroprotective and procognitive in the brain and may therefore counteract these effects. This study aims to explore the protective and restorative effects of GH and IGF-1 in methadone-treated cell cultures. Primary cortical cell cultures were harvested from rat fetuses and grown for seven days in vitro. To examine the protective effects, methadone was co-treated with or without GH or IGF-1 for three consecutive days. To examine the restorative effects, methadone was added for the first 24 h, washed, and later treated with GH or IGF-1 for 48 h. At the end of each experiment, mitochondrial function and membrane integrity were evaluated. The results revealed that GH had protective effects in the membrane integrity assay and that both GH and IGF-1 effectively recovered mitochondrial function and membrane integrity in cells pretreated with methadone. The overall conclusion of the present study is that GH, but not IGF-1, protects primary cortical cells against methadone-induced toxicity, and that both GH and IGF-1 have a restorative effect on cells pretreated with methadone.
32.	Pirker, Franz, et al. (författare) Tribological Characterisation Services for Materials – i-TRIBOMAT 2020 Ingår i: Tribologie und Schmierungstechnik. - : Expert Verlag. - 0724-3472. ; 67:5-6, s. 35-50 Tidskriftsartikel (refereegranskat)abstract Um den Entwicklungsprozess von neuen Komponenten zu beschleunigen, ist die Vorrausage der Eigenschaften der eingesetzten Werkstoffe im Betrieb der Komponenten von enormer Bedeutung. Um neue Werkstoffe hinsichtlich Ihrer Performance (in einer Komponente) bewerten zu können, ist deshalb die Entwicklung neuer innovativer Methoden notwendig. Diese Methoden können auch unter dem Begriff „lab-to-field“ oder „materials“ – up-scaling zusammengefasst werden. D. h. Werkstoffe werden im Labor charakterisiert, und deren Eigenschaften mittels z.B. Simulation auf die Komponentenperformance hochskaliert (upscaling). i-TRIBOMAT ist ein EU gefördertes Projekt (H2020, GA Nr. 814494) mit dem Ziel ein Open Innovation Test Bed für tribologische Werkstoffcharakterisierung aufzubauen und ent-sprechende Services von der tribologischen Charakterisierung neuer Werkstoffe bis hin zu Simulationsmodellen zur Vorrausage der Perfomance von Komponenten der Industrie anzubieten. Durch die Bündelung von Knowhow und Infrastruktur zu Charakterisierung sowie den Aufbau einer digitalen Plattform, wird i-TRIBOMAT das weltgrößte Open Innovation Test Bed für tribologische Werkstoffcharakterisierung.
33.	Soria Salinas, Álvaro Tomás, et al. (författare) Improved Pressure-Volume-Temperature Gauging Method for Electric Propulsion Systems (PVT-GAMERS) : flight-model experiment for zero-g validation. 2018 Ingår i: IAC-18. - : International Astronautical Federation. Konferensbidrag (refereegranskat)abstract Current forecasts suggest that, by 2030, at least 50% of telecommunication satellites will use electric propulsion (EP) as the only propulsion system on board. The ever-increasing operations time has led to a substantial increment of the amount of propellant stored on-board, from the initial 200-350 kg to present-day masses of 800-1500 kg. Despite the need to know the available propellant mass during operations, the retrieval is still challenging, and inaccurate, as no technological alternatives have been proven to satisfy with the needed requirements for long duration missions.Recently we have proposed a new gauging method that uses TLR-9 hardware components. The method, called Improved-PVT method, is based on a better understanding of the thermal properties of the stored xenon. Laboratory experiments and theoretical work demonstrated an accuracy improved by a factor of 8 compared to classical Pressure-Volume-Temperature retrievals [A. Soria-Salinas et al., 2017]. In fact, it gives an error of mass gauging of 0.1% with respect to the initial mass, at a pressure of about 70 bar.This method has been implemented in the PVT-GAMERS experiment, selected to fly at the ESA Fly Your Thesis! parabolic flight campaign, between October 22 nd to November 2 nd . As a technology demonstrator, it consists of a suit of 6 small-scaled and pressurized CO2 tanks, sensed with pressure (P) and temperature (T) sensors, with a heating duty cycle and real-time data processing. The PVT-GAMERS experiment will fly on three Airbus A310 Zero-G flights, where micro/hyper gravity-loads will allow to demonstrate the robustness of the method against thermal gradients, and i) simulated thruster ignitions, ii) external accelerations and iii) propellant management operations scenarios. These flights will also increase the TRL of the full system from 4 to 6.In this work, we shall present the development, testing and ground calibration of the PVT-GAMERS experiment, including: 1) ground tests, assembly validation, expected results and operational procedures estimation; and 2) calibration of mass retrieval algorithm applied over a CO2 PVT-GAMERS engineering model (EM). Ground tests results indicates a relative error expected for the mass retrieval on flight model ground tests < 1.4% for CO2 gas at EOL conditions. Furthermore, a compromised solution shall be reached between retrieval expected accuracy, cooling rate for the retrieval application, and sensitivity to ambient condition changes. The EM tests suggest on this particular configuration to approximate the cooling ratio dP/dT using a least-squared-error procedure and over an interval of at least 900 seconds.
34.	Tanguay, Sophie, et al. (författare) Reference equations for quadriceps strength, endurance and power : a multicentre study 2023 Ingår i: ERJ Open Research. - : European Respiratory Society. - 2312-0541. ; 9:4 Tidskriftsartikel (refereegranskat)abstract Introduction: The lack of reference values of lower-limb muscle function hinders the clinical recommendations of its measurement in patients with COPD. Therefore, this study aimed to develop reference equations to predict reference values for quadriceps strength, endurance and power and evaluate their construct validity in patients with COPD.Methods: Quadriceps strength, endurance and power were assessed in 158 healthy individuals and 87 patients with COPD. In addition, patients with COPD performed a 6-min walk test (6MWT) and a 1-min sit-to-stand test (1STS). Multiple linear regressions were performed to develop reference equations. The proportion of patients with COPD with reduced quadriceps function was determined, and correlations between quadriceps strength, endurance and power expressed in percentage of predicted values and 6MWT and 1STS performance were used to document the construct validity of the reference equation.Results: Except for quadriceps isometric endurance, the proposed reference equations explained 50-70% of the variance of the quadriceps properties in healthy individuals. All quadriceps properties were systematically reduced in a large proportion of patients with COPD compared to healthy individuals. Correlation coefficients between quadriceps properties expressed in percentage of predicted values and 6MWT and 1STS performance ranged between 0.28 and 0.49 (all p<0.05).Conclusion: In healthy individuals, age, sex, height and body mass index explained 50-70% of the variance of quadriceps strength, endurance and power. When expressed in percentage of predicted values, these quadriceps properties correlated with 6MWT and 1STS performance, suggesting construct validity of the reference values in patients with COPD.
35.	Zelleroth, Sofia, 1990-, et al. (författare) Structurally different anabolic androgenic steroids reduce neurite outgrowth and neuronal viability in primary rat cortical cell cultures 2021 Ingår i: Journal of Steroid Biochemistry and Molecular Biology. - : Elsevier BV. - 0960-0760 .- 1879-1220. ; 210 Tidskriftsartikel (refereegranskat)abstract The illicit use of anabolic androgenic steroids (AAS) among adolescents and young adults is a major concern due to the unknown and unpredictable impact of AAS on the developing brain and the consequences of this on mental health, cognitive function and behaviour. The present study aimed to investigate the effects of supra-physiological doses of four structurally different AAS (testosterone, nandrolone, stanozolol and trenbolone) on neurite development and cell viability using an in vitro model of immature primary rat cortical cell cultures. A high-throughput screening image-based approach, measuring the neurite length and number of neurons, was used for the analysis of neurite outgrowth. In addition, cell viability and expression of the Tubb3 gene (encoding the protein beta-III tubulin) were investigated. Testosterone, nandrolone, and trenbolone elicited adverse effects on neurite outgrowth as deduced from an observed reduced neurite length per neuron. Trenbolone was the only AAS that reduced the cell viability as indicated by a decreased number of neurons and declined mitochondrial function. Moreover, trenbolone downregulated the Tubb3 mRNA expression. The adverse impact on neurite development was neither inhibited nor supressed by the selective androgen receptor (AR) antagonist, flutamide, suggesting that the observed effects result from another mechanism or mechanisms of action that are operating apart from AR activation. The results demonstrate a possible AAS-induced detrimental effect on neuronal development and regenerative functions. An impact on these events, that are essential mechanisms for maintaining normal brain function, could possibly contribute to behavioural alterations seen in AAS users.
36.	Zelleroth, Sofia, 1990-, et al. (författare) Toxic Impact of Anabolic Androgenic Steroids in Primary Rat Cortical Cell Cultures 2019 Ingår i: Neuroscience. - : Elsevier BV. - 0306-4522 .- 1873-7544. ; 397, s. 172-183 Tidskriftsartikel (refereegranskat)abstract The use of anabolic androgenic steroids (AASs) among non-athletes is a public health-problem, as abusers underestimate the negative effects associated with these drugs. The present study investigated the toxic effects of testosterone, nandrolone, stanozolol, and trenbolone, and aimed to understand how AAS abuse affects the brain. Mixed cortical cultures from embryonic rats were grown in vitro for 7 days and thereafter treated with increasing concentrations of AASs for 24 h (single-dose) or 3 days (repeated exposure). Cells were co-treated with the androgen-receptor (AR) antagonist flutamide, to determine whether the potential adverse effects observed were mediated by the AR. Cellular toxicity was determined by measuring mitochondrial activity, lactate dehydrogenase (LDH) release, and caspase-3/7 activity. Nandrolone, unlike the other AASs studied, indicated an effect on mitochondrial activity after 24 h. Furthermore, single-dose exposure with testosterone, nandrolone and trenbolone increased LDH release, while no effect was detected with stanozolol. However, all of the four steroids negatively affected mitochondrial function and resulted in LDH release after repeated exposure. Testosterone, nandrolone, and trenbolone caused their toxic effects by induction of apoptosis, unlike stanozolol that seemed to induce necrosis. Flutamide almost completely prevented AAS-induced toxicity by maintaining mitochondrial function, cellular integrity, and inhibition of apoptosis. Overall, we found that supra-physiological concentrations of AASs induce cell death in mixed primary cortical cultures, but to different extents, and possibly through various mechanisms. The data presented herein suggest that the molecular interactions of the AASs with the AR are primarily responsible for the toxic outcomes observed.

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