Browsing by Subject "DEFORMATION"

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  • Dusa, Filip; Chen, Wen; Witos, Joanna; Wiedmer, Susanne Kristina (2019)
    The importance of using biomimicking membranes for various biological applications is rising, as such models are relevant for imitating real organisms. In addition, biomimicking membranes are usually much more repeatable in preparation and easier to handle during analysis than real organisms or biological membranes. In this work, we developed a method for the adsorption of intact small unilamellar Escherichia coli (E. cols) vesicles (Z-average size of 73 nm) on SiO2 substrate material. We describe the adsorption process based on the use of two surface sensitive techniques, i.e., nanoplasmonic sensing (NPS) and quartz crystal microbalance (QCM). The acquired data show that the adsorption follows a two-step process. The first step is a slow adsorption of E coil vesicle aggregates held together by 5 mM of calcium (Z-average size of 531 nm). The Z-average of the aggregates decreased almost three times when the calcium concentration was decreased to 0.1 mM. This suggests that the aggregates were disassembling to some extent when calcium was removed from the system. With both techniques, i.e., NPS and QCM, we observed a second rapid adsorption step after the solution was changed to deionized water. In this second step, the aggregates started to fall apart as the calcium concentration dropped, and the released vesicles started to adsorb onto unoccupied spots at the SiO2 surface of the sensors. Extensive release of mass from the surface was confirmed by QCM, where it was reflected by a sharp increase of frequency, while NPS, due to its lower sensing depth of a few tens of nanometers, did not record such a change. Taken together, we have developed a protocol to form a supported vesicle layer (SVL) of E coli vesicles on SiO2 surface using sodium 4-(2-hydroxyethyppiperazine-1-ethanesulfonate buffer, thus enabling the preparation of E coli biomimicking SVLs for interaction studies of compounds of interest. The immobilization happens via a two-step adsorption process.
  • Schütt, Jorina Marlena; Whipp, David Michael (2020)
    Strain partitioning onto margin-parallel thrust and strike-slip faults is a common process at obliquely convergent plate margins, leading to the formation and migration of crustal slivers. The degree of strain partitioning and rate of sliver migration can be linked to several factors including the angle of convergence obliquity, the dip angle of subduction, frictional coupling between the plates and the strength of the upper plate, among others. Although these factors are known to be important, their relative influence on strain partitioning is unclear, particularly at natural margins where the factors often vary along strike. Here we use a 3-D mechanical finite-element model to investigate the relationship between continental crustal strength, the convergence obliquity angle, the subduction angle, and strain partitioning in the Northern Volcanic Zone (NVZ) of the Andes (5 degrees N-3 degrees S). In the NVZ the subduction dip and obliquity angles both vary along strike, weaknesses in the continental crust may be present in suture zones or regions of arc volcanism, and strain partitioning is only observed in some regions. Thus, it is an ideal location to gain insight in which of the factors have the largest influence on deformation and sliver formation in the upper plate. Our numerical experiments confirm that a moderately high obliquity angle is needed for partitioning and that a continental crustal weakness is also required for movement of a coherent continental sliver at rates similar to geodetic observations from the NVZ. In contrast, the subduction dip angle is only of secondary importance in controlling strain partitioning behavior. Key Points Factors influencing formation of continental slivers investigated using 3-D numerical models of finite-width oblique subduction systems Model results indicate that convergence obliquity and the presence of weak zones in the upper plate are key to formation of well-defined slivers Model predictions are in good agreement with geodetic observations of sliver motion in the Northern Volcanic Zone of the Andes
  • Vu, T. H. Y.; Dufour, C.; Khomenkov, V.; Leino, A. A.; Djurabekova, F.; Nordlund, K.; Coulon, P. -E.; Rizza, G.; Hayoun, M. (2019)
    The elongation process under swift heavy ion irradiation (74 MeV Kr ions) of gold NPs, with a diameter in the range 10-30 nm, and embedded in a silica matrix has been investigated by combining experiment and simulation techniques: three-dimensional thermal spike (3DTS), molecular dynamics (MD) and a phenomenological simulation code specially developed for this study. 3DTS simulations evidence the formation of a track in the host matrix and the melting of the NP after the passage of the impinging ion. MD simulations demonstrate that melted NPs have enough time to expand after each ion impact. Our phenomenological simulation relies on the expansion of the melted NP, which flows in the track in silica with modified (lower) density, followed by its recrystallization upon cooling. Finally, the elongation of the spherical NP into a cylindrical one, with a length proportional to its initial size and a width close to the diameter of the track, is the result of the superposition of the independent effects of each expansion/recrystallization process occurring for each ion impact. In agreement with experiment, the simulation shows the gradual elongation of spherical NPs in the ion-beam direction until their widths saturate in the steady state and reach a value close to the track diameter. Moreover, the simulations indicate that the expansion of the gold NP is incomplete at each ion impact.
  • Dusa, Filip; Chen, Wen; Witos, Joanna; Rantamäki, Antti; King, Alistair; Sklavounos, Evangelos; Roth, Michal; Wiedmer, Susanne (2020)
    The cell membrane is mainly composed of lipid bilayers with inserted proteins and carbohydrates. Lipid bilayers made of purified or synthetic lipids are widely used for estimating the effect of target compounds on cell membranes. However, the composition of such biomimetic membranes is much simpler than the composition of biological membranes. Interactions between compounds and simple composition biomimetic membranes might not demonstrate the effect of target compounds as precisely as membranes with compositions close to real organisms. Therefore, the aim of our study is to construct biomimetic membrane closely mimicking the state of natural membranes. Liposomes were prepared from lipids extracted from L-alpha-phosphatidylcholine, Escherichia coli, yeast (Saccharomyces cerevisiae) and bovine liver cells through agitation and sonication. They were immobilized onto silicon dioxide (SiO2) sensor surfaces using N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid buffer with calcium chloride. The biomimetic membranes were successfully immobilized onto the SiO2 sensor surface and detected by nanoplasmonic sensing. The immobilized membranes were exposed to choline carboxylates. The membrane disruption effect was, as expected, more pronounced with increasing carbohydrate chain length of the carboxylates. The results correlated with the toxicity values determined using Vibrio fischeri bacteria. The yeast extracted lipid membranes had the strongest response to introduction of choline laurate while the bovine liver lipid extracted liposomes were the most sensitive towards the shorter choline carboxylates. This implies that the composition of the cell membrane plays a crucial role upon interaction with choline carboxylates, and underlines the necessity of testing membrane systems of different origin to obtain an overall image of such interactions.
  • Cameli, Matteo; Miglioranza, Marcelo Haertel; Magne, Julien; Mandoli, Giulia Elena; Benfari, Giovanni; Ancona, Roberta; Sibilio, Gerolamo; Reskovic Luksic, Vlatka; Dejan, Dosen; Griseli, Leonardo; Van de Heyning, Caroline M.; Mortelmans, Philippe; Michalski, Blazej; Kupczynska, Karolina; Di Giannuario, Giovanna; Devito, Fiorella; Dulgheru, Raluca; Ilardi, Federica; Salustri, Alessandro; Abushahba, Galal; Morrone, Doralisa; Fabiani, Iacopo; Penicka, Martin; Katbeh, Asim; Sammarco, Giuseppe; Esposito, Roberta; Santoro, Ciro; Pastore, Maria Concetta; Comenale Pinto, Salvatore; Kalinin, Artem; Pickure, Zanna; Azman Juvan, Katja; Zupan Meznar, Anja; Coisne, Augustine; Coppin, Amandine; Opris, Mihaela Maria; Nistor, Dan Octavian; Paakkanen, Riitta; Biering-Sorensen, Tor; Olsen, Flemming Javier; Lapinskas, Tomas; Vaskelyte, Jolanta Justina; Galian-Gay, Laura; Casas, Guillem; Motoc, Andreea Iulia; Papadopoulos, Constantinos Hristou; Loizos, Savvas; Agoston, Gergely; Szabo, Istvan; Hristova, Krasimira; Tsonev, Svetlin Netkov; Galli, Elena; Vinereanu, Dragos; Mihaila Baldea, Sorina; Muraru, Denisa; Mondillo, Sergio; Donal, Erwan; Galderisi, Maurizio; Cosyns, Bernard; Edvardsen, Thor; Popescu, Bogdan A. (2020)
    Two methods are currently available for left atrial (LA) strain measurement by speckle tracking echocardiography, with two different reference timings for starting the analysis: QRS (QRS-LASr) and P wave (P-LASr). The aim of MASCOT HIT study was to define which of the two was more reproducible, more feasible, and less time consuming. In 26 expert centers, LA strain was analyzed by two different echocardiographers (young vs senior) in a blinded fashion. The study population included: healthy subjects, patients with arterial hypertension or aortic stenosis (LA pressure overload, group 2) and patients with mitral regurgitation or heart failure (LA volume-pressure overload, group 3). Difference between the inter-correlation coefficient (ICC) by the two echocardiographers using the two techniques, feasibility and analysis time of both methods were analyzed. A total of 938 subjects were included: 309 controls, 333 patients in group 2, and 296 patients in group 3. The ICC was comparable between QRS-LASr (0.93) and P-LASr (0.90). The young echocardiographers calculated QRS-LASr in 90% of cases, the expert ones in 95%. The feasibility of P-LASr was 85% by young echocardiographers and 88% by senior ones. QRS-LASr young median time was 110 s (interquartile range, IR, 78-149) vs senior 110 s (IR 78-155); for P-LASr, 120 s (IR 80-165) and 120 s (IR 90-161), respectively. LA strain was feasible in the majority of patients with similar reproducibility for both methods. QRS complex guaranteed a slightly higher feasibility and a lower time wasting compared to the use of P wave as the reference.
  • Xu, Zongwei; Liu, Lei; He, Zhongdu; Tian, Dongyu; Hartmaier, Alexander; Zhang, Junjie; Luo, Xichun; Rommel, Mathias; Nordlund, Kai; Zhang, Guoxiong; Fang, Fengzhou (2020)
    Nanocutting mechanism of single crystal 6H-SiC is investigated through a novel scanning electron microscope setup in this paper. Various undeformed chip thicknesses on (0001) orientation are adopted in the nanocutting experiments. Phase transformation and dislocation activities involved in the 6H-SiC nanocutting process are also characterized and analyzed. Two methods of stress-assisted and ion implant-assisted nanocutting are studied to improve 6H-SiC ductile machining ability. Results show that stress-assisted method can effectively decrease the hydrostatic stress and help to activate dislocation motion and ductile machining; ion implant-induced damages are helpful to improve the ductile machining ability from MD simulation and continuous nanocutting experiments under the online observation platform.
  • Amekura, H.; Kluth, P.; Mota-Santiago, P.; Jantunen, V.; Leino, A. A.; Vazquez, H.; Nordlund, K.; Djurabekova, F.; Sahlberg, I. (2020)
    The mechanism of the shape elongation of metal nanoparticles (NPs) in silica, which is induced under swift heavy ion irradiation, is discussed with comparing the two candidates: (i) the synergy between the ion hammering and the transient melting of NPs by the inelastic thermal spike and (ii) the thermal pressure and flow model. We show that three experimental results are inconsistent with (i). The latter is supported by two-temperature molecular dynamics simulations, which simulate not only the atomic motions but also the local electron temperatures. A remarkable correlation was observed between the temporal evolution of the silica density around the ion trajectory and that of the aspect ratio of the NP later than similar to 1 ps after the ion impact, while no correlation was observed earlier than similar to 1 ps, even under the assumption of the instantaneous energy deposition.
  • Moreau, Juulia-Gabrielle; Kohout, Tomas; Wünnemann, Kai; Halodova, Patricie; Haloda, Jakub (2019)
    Shock-darkening, the melting of metals and iron sulfides into a network of veins within silicate grains, altering reflectance spectra of meteorites, was previously studied using shock physics mesoscale modeling. Melting of iron sulfides embedded in olivine was observed at pressures of 40-50 GPa. This pressure range is at the transition between shock stage 5 (C-S5) and 6 (C-S6) of the shock metamorphism classification in ordinary and enstatite chondrites. To better characterize C-S5 and C-S6 with a mesoscale modeling approach and assess post-shock heating and melting, we used multi-phase (i.e. olivine/enstatite, troilite, iron, pores, and plagioclase) meshes with realistic configurations of grains. We carried out a systematic study of shock compression in ordinary and enstatite chondrites at pressures between 30 and 70 GPa. To setup mesoscale sample meshes with realistic silicate, metal, iron sulfide, and open pore shapes, we converted backscattered electron microscope images of three chondrites. The resolved macroporosity in meshes was 3-6%. Transition from shock C-S5 to C-S6 was observed through (1) the melting of troilite above 40 GPa with melt fractions of similar to 0.7-0.9 at 70 GPa, (2) the melting of olivine and iron above 50 GPa with melt fraction of similar to 0.001 and 0.012, respectively, at 70 GPa, and (3) the melting of plagioclase above 30 GPa (melt fraction of 1, at 55 GPa). Post-shock temperatures varied from similar to 540 K at 30 GPa to similar to 1300 K at 70 GPa. We also constructed models with increased porosity up to 15% porosity, producing higher post-shock temperatures (similar to 800 K increase) and melt fractions (similar to 0.12 increase) in olivine. Additionally we constructed a pre-heated model to observe post-shock heating and melting during thermal metamorphism. This model presented similar results (melting) at pressures 10-15 GPa lower compared to the room temperature models. Finally, we demonstrated dependence of post-shock heating and melting on the orientation of open cracks relative to the shock wave front. In conclusion, the modeled melting and post-shock heating of individual phases were mostly consistent with the current shock classification scheme (Stoffler et al., 1991, 2018).
  • Chopin, Francis; Korja, Annakaisa; Nikkila, Kaisa; Holtta, Pentti; Korja, Toivo; Zaher, Mohamed Abdel; Kurhila, Matti; Eklund, Olav; Ramo, Tapani (2020)
    Tectonic evolution of the Paleoproterozoic Vaasa migmatitic complex (VMC) in the central part of the Svecofennian accretionary orogen is deciphered using aeromagnetic and gravity maps, deep seismic and magnetotelluric profiles, and structural and metamorphic data. The VMC is a semicircular structure with migmatitic rim and granitic core composed of several subdomes. It evolved in three main tectonic events (D1-D3). The D1 event (ca. 1.89-1.88 Ga) corresponds to the stacking of supracrustal rocks and the formation of an inverted metamorphic gradient. Anatexis at LP-HT metamorphic conditions enabled the material to flow. The D2 event (ca. 1.88-1.87 Ga) corresponds to large-scale folding of the partially molten crust within an orocline. It is marked by folds with an E-W vertical axial planar foliation. The late D3 event resulted from mass redistribution owing to mechanical instabilities within the hinge of the orocline. It is marked by vertical shearing (ca. 1.87-1.85 Ga) in the marginal parts of the complex and along the granitoid subdomes. The seismic reflection profile (FIRE 3a) and magnetotelluric profiles (MT-PE and MT-B2) image large-scale D1 stacking structures within an accretionary prism. Near vertical breaks in crustal-scale reflectivity and conductivity models are interpreted as D3 shear zones. The VMC is an example of early mass and heat transfer within a collage of hot supracrustal rocks in an accretionary belt. Partial melting enhanced the flow of material, the production, and rise of magma as well as exhumation, marked by magmatic domes in the hinge of the orocline.