Search results for "phase transition"
showing 10 items of 1281 documents
A new approach to simulate coating thickness in cold spray
2020
Abstract In the process of cold spray on complex components, the coating thickness is an important indicator to monitor and control. Current methods such as destructive tests or direct mechanical measurements can only be performed after spraying. Besides, these methods lead to production shutdown and additional costs . This article presents a novel approach predicting coating thickness for components with complex curved surfaces, especially in the case of shadow effects. Firstly, a three-dimensional geometric model of the coating profile based on Gaussian distribution was developed. In addition, the relative deposition efficiency (RDE) resulting from the different robot kinematic parameters…
Microstructural, mechanical and energy demand characterization of alternative WAAM techniques for Al-alloy parts production
2020
Abstract Additive manufacturing (AM) processes are gathering momentum as an alternative to conventional manufacturing processes. A research effort is being made worldwide to identify the most promising AM approaches. Within this category, wire arc additive manufacturing (WAAM) is among the most interesting, especially when large parts must be manufactured. In this paper, two different WAAM deposition techniques suitable for the deposition of Aluminum alloys, Cold Metal Transfer (CMT) and CMT mix drive, are analyzed and compared. With the aim of obtaining a clear picture concerning the two different techniques, microstructural analyses, mechanical property evaluation and electrical energy de…
Bioactive potential of silica coatings and its effect on the adhesion of proteins to titanium implants
2018
There is an ever-increasing need to develop dental implants with ideal characteristics to achieve specific and desired biological response in the scope of improve the healing process post-implantation. Following that premise, enhancing and optimizing titanium implants through superficial treatments, like silica sol-gel hybrid coatings, are regarded as a route of future research in this area. These coatings change the physicochemical properties of the implant, ultimately affecting its biological characteristics. Sandblasted acid-etched titanium (SAE-Ti) and a silica hybrid sol-gel coating (35M35G30T) applied onto the Ti substrate were examined. The results of in vitro and in vivo tests and t…
Wavelength selection of rippling patterns in myxobacteria
2016
Rippling patterns of myxobacteria appear in starving colonies before they aggregate to form fruiting bodies. These periodic traveling cell density waves arise from the coordination of individual cell reversals, resulting from an internal clock regulating them, and from contact signaling during bacterial collisions. Here we revisit a mathematical model of rippling in myxobacteria due to Igoshin et al.\ [Proc. Natl. Acad. Sci. USA {\bf 98}, 14913 (2001) and Phys. Rev. E {\bf 70}, 041911 (2004)]. Bacteria in this model are phase oscillators with an extra internal phase through which they are coupled to a mean-field of oppositely moving bacteria. Previously, patterns for this model were obtaine…
Physical mechanisms of micro- and nanodomain formation in multicomponent lipid membranes.
2016
This article summarizes a variety of physical mechanisms proposed in the literature, which can generate micro- and nanodomains in multicomponent lipid bilayers and biomembranes. It mainly focusses on lipid-driven mechanisms that do not involve direct protein-protein interactions. Specifically, it considers (i) equilibrium mechanisms based on lipid-lipid phase separation such as critical cluster formation close to critical points, and multiple domain formation in curved geometries, (ii) equilibrium mechanisms that stabilize two-dimensional microemulsions, such as the effect of linactants and the effect of curvature-composition coupling in bilayers and monolayers, and (iii) non-equilibrium me…
Linoleic acid: Is this the key that unlocks the quantum brain? Insights linking broken symmetries in molecular biology, mood disorders and personalis…
2017
Abstract In this paper we present a mechanistic model that integrates subneuronal structures, namely ion channels, membrane fatty acids, lipid rafts, G proteins and the cytoskeleton in a dynamic system that is finely tuned in a healthy brain. We also argue that subtle changes in the composition of the membrane’s fatty acids may lead to down-stream effects causing dysregulation of the membrane, cytoskeleton and their interface. Such exquisite sensitivity to minor changes is known to occur in physical systems undergoing phase transitions, the simplest and most studied of them is the so-called Ising model, which exhibits a phase transition at a finite temperature between an ordered and disorde…
Intramolecular structural parameters are key modulators of the gel-liquid transition in coarse grained simulations of DPPC and DOPC lipid bilayers
2018
The capability of coarse-grained models based on the MARTINI mapping to reproduce the gel-liquid phase transition in saturated and unsaturated model lipids was investigated. We found that the model is able to reproduce a lower critical temperature for 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with respect to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). Nonetheless, the appearance of a gel phase for DOPC is strictly dependent on the intramolecular parameters chosen to model its molecular structure. In particular, we show that the bending angle at the coarse-grained bead corresponding to the unsaturated carbon-carbon bond acts as an order parameter determining the temperature of …
Fractional hereditariness of lipid membranes: Instabilities and linearized evolution
2016
In this work lipid ordering phase changes arising in planar membrane bilayers is investigated both accounting for elas- ticity alone and for effective viscoelastic response of such assemblies. The mechanical response of such membranes is studied by minimizing the Gibbs free energy which penalizes perturbations of the changes of areal stretch and their gradients only [1]. As material instabilities arise whenever areal stretches characterizing homogeneous configurations lie inside the spinoidal zone of the free energy density, bifurcations from such configurations are shown to occur as oscillatory perturbations of the in-plane displacement. Experimental observations [2] show a power-law in-pl…
Stability of the human microbiome. Health and disease imprinted in the time variability of the human microbiota.
2019
Animal microbiota plays an essential role in keeping the physiological status of the host healthy. This microbiota consists of hundreds of different species that inhabit the host, and whose composition varies on a daily basis due to multiple factors as diets, medicine intakes, lifestyle or diseases. It is a highly dynamical system that shows variability even when the host is in a healthy condition, but visible changes happen when the system is perturbed. Thus, the main objective of this thesis aimed to study the temporal variability of human microbiota, and link it to the health status of the host. For this, we proposed a formal definition of stability in microbial systems based on the use …
Mossbauer spectroscopic study of the thermal spin crossover in [Fe(II)(isoxazole)(6)](ClO(4))(2)
2008
The (57)Fe Mossbauer spectroscopy of mononuclear [Fe(II)(isoxazole)(6)](ClO(4))(2) has been studied to reveal the thermal spin crossover of Fe(II) between low-spin (S = 0) and high-spin (S = 2) states.Temperature-dependent spin transition curves have been constructed with the least-square fitted data obtained from the Mossbauer spectra measured at various temperatures between 84 and 270 K during a cooling and heating cycle. This compound exhibits an unusual temperature-dependent spin transition behaviour with T(C)(down arrow) = 223 and T(C)(up arrow) = 213 K occurring in the reverse order in comparison to those observed in SQUID observation and many other spin transition compounds. The comp…