Subjects -> CHEMISTRY (Total: 928 journals)
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PHYSICAL CHEMISTRY (65 journals)

Showing 1 - 64 of 64 Journals sorted alphabetically
ACS Central Science     Open Access   (Followers: 9)
ACS Physical Chemistry Au     Open Access   (Followers: 8)
ACS Sensors     Hybrid Journal   (Followers: 7)
Acta Physico-Chimica Sinica     Free  
Advances in Image and Video Processing     Open Access   (Followers: 20)
Advances in Physical Chemistry     Open Access   (Followers: 13)
Annual Review of Physical Chemistry     Full-text available via subscription   (Followers: 14)
Applied Materials Today     Hybrid Journal   (Followers: 1)
Biophysical Chemistry     Hybrid Journal   (Followers: 8)
Catalysis, Structure & Reactivity     Open Access   (Followers: 2)
Chemical Physics     Hybrid Journal   (Followers: 19)
Chemical Physics Letters     Hybrid Journal   (Followers: 18)
Chemistry and Physics of Lipids     Hybrid Journal   (Followers: 2)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Colloids and Surfaces A: Physicochemical and Engineering Aspects     Hybrid Journal   (Followers: 7)
Current Physical Chemistry     Hybrid Journal   (Followers: 1)
Doklady Physical Chemistry     Hybrid Journal  
EPJ B - Condensed Matter and Complex Systems     Hybrid Journal   (Followers: 1)
EPJ E - Soft Matter and Biological Physics     Hybrid Journal   (Followers: 3)
Friction     Open Access   (Followers: 4)
Geochemistry, Geophysics, Geosystems     Full-text available via subscription   (Followers: 35)
Glass Physics and Chemistry     Hybrid Journal  
Handbook on the Physics and Chemistry of Rare Earths     Full-text available via subscription   (Followers: 2)
Indian Journal of Biochemistry and Biophysics (IJBB)     Open Access   (Followers: 3)
Indian Journal of Chemistry - Section A     Open Access   (Followers: 9)
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 6)
International Journal of Quantum Chemistry     Hybrid Journal   (Followers: 5)
International Reviews in Physical Chemistry     Hybrid Journal   (Followers: 3)
Journal of Biophysical Chemistry     Open Access   (Followers: 3)
Journal of Chemical Physics     Hybrid Journal   (Followers: 37)
Journal of Chromatographic Science     Hybrid Journal   (Followers: 15)
Journal of Macromolecular Science, Part B: Physics     Hybrid Journal   (Followers: 2)
Journal of Physical and Chemical Reference Data     Hybrid Journal   (Followers: 4)
Journal of Physical Chemistry A     Hybrid Journal   (Followers: 28)
Journal of Physical Chemistry B     Hybrid Journal   (Followers: 48)
Journal of Physical Chemistry C     Hybrid Journal   (Followers: 36)
Journal of Physical Chemistry Letters     Hybrid Journal   (Followers: 26)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 3)
Journal of Quantum Chemistry     Open Access   (Followers: 1)
Journal of Radiation Research     Open Access   (Followers: 3)
Macromolecular Chemistry and Physics     Hybrid Journal   (Followers: 2)
Molecular Physics: An International Journal in the Field of Chemical Physics     Hybrid Journal   (Followers: 24)
Nature Communications     Open Access   (Followers: 340)
Open Journal of Physical Chemistry     Open Access  
Physical Chemistry     Open Access   (Followers: 2)
Physical Chemistry Chemical Physics     Hybrid Journal   (Followers: 29)
Physical Chemistry Research     Open Access   (Followers: 1)
Physical Review A     Full-text available via subscription   (Followers: 23)
Physical Review Accelerators and Beams     Open Access   (Followers: 3)
Physical Review B     Full-text available via subscription   (Followers: 33)
Physical Review D     Full-text available via subscription   (Followers: 11)
Physical Review E     Full-text available via subscription   (Followers: 41)
Physical Review Letters     Full-text available via subscription   (Followers: 142)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription  
Physics and Chemistry of Liquids: An International Journal     Hybrid Journal  
Physics and Chemistry of the Earth, Parts A/B/C     Hybrid Journal   (Followers: 10)
Plasma Processes and Polymers     Hybrid Journal   (Followers: 2)
Protection of Metals and Physical Chemistry of Surfaces     Hybrid Journal   (Followers: 15)
Revista Fuentes     Open Access  
Russian Journal of Physical Chemistry A, Focus on Chemistry     Hybrid Journal  
Russian Journal of Physical Chemistry B, Focus on Physics     Hybrid Journal  
Solid State Ionics     Hybrid Journal   (Followers: 5)
The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics     Hybrid Journal   (Followers: 29)
The European Physical Journal Special Topics     Hybrid Journal   (Followers: 1)
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EPJ E - Soft Matter and Biological Physics
Journal Prestige (SJR): 0.489
Citation Impact (citeScore): 1
Number of Followers: 3  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1292-8941 - ISSN (Online) 1292-895X
Published by Springer-Verlag Homepage  [2469 journals]
  • Analysis of a microfluidic device for diffusion coefficient determination
           of high molecular weight solutes detectable in the visible spectrum

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      Abstract: We developed a procedure to measure diffusion coefficients using microfluidic devices that contributes to the transport analysis of high molecular weight solutes with low diffusion coefficient. This procedure allows a quick determination of diffusion coefficients and a precise evaluation of measurement errors. Making use of color variation of a pH indicator, we determined its diffusion coefficient in its own solvent (water). The value obtained was compared with previously published ones and was found to be similar to those cited. The microfluidic device has a serpentine-shaped channel that allows monitoring the solution evolution in different regions of the path in a single visual field without the need to move the camera or the microchip. This kind of device also allows the spatial and temporal tracking of the diffusion process. The solution color intensity is used to determine solute concentration; therefore, this method presents an advantage compared to those based on fluorescence detection. A complete analysis of the diffusive behavior along the channel path was performed in order to test the accuracy of these kinds of methodologies. This analysis can be used with similar devices, and the techniques employed for diffusion analysis can be applied to a µTAS-type microfluidic platform, allowing obtain variations of the diffusion coefficient as a function of time due to variations in external factors, e.g., temperature, etc. Graphical abstract
      PubDate: 2022-06-25
       
  • Effects of hydrocarbon chain on the vesicle size distribution, kinetics of
           average size, bending modulus, and elastic modulus of lipid membranes

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      Abstract: The effects of the hydrocarbon chain of lipids on the size distribution of giant unilamellar vesicles (GUVs), kinetics of average size, bending modulus, and elastic modulus of membranes have been investigated. 1,2-dioleoyl-sn-glycero-3-phosphocholine (18:1 (Δ9-Cis) PC (DOPC)), 1,2-dipalmitoleoyl-sn-glycero-3-phosphocholine (16:1 (Δ9-Cis) PC), and 1,2-ditridecanoyl-sn-glycerol-3-phosphocholine (13:0 PC (DTPC)) lipids were considered. The number of hydrocarbons in a chain of the corresponding lipid was 18, 16, and 13. GUVs were prepared using the natural swelling method under incubation times of 20, 40, 60, 90, 120, and 180 min. The size distribution of vesicles was fitted using the lognormal distribution. The average sizes of DOPC, 16:1 (Δ9-Cis) PC, and DTPC-GUVs increased with the incubation time until 120 min, and then remained steady at 16.7 ± 0.2, 15.2 ± 0.4 and 12.0 ± 0.3 µm for the corresponding lipids. The average size at equilibrium state increased with the number of hydrocarbons. The incubation time-dependent average size was fitted with an exponential growth equation, and then the kinetic constants of 0.028 ± 0.004, 0.036 ± 0.007, and 0.083 ± 0.009 min−1 for DOPC, 16:1 (Δ9-Cis) PC, and DTPC-GUVs, respectively, were obtained. The equilibrium size distribution was fitted by the theoretical equation, and the bending modulus for DOPC, 16:1 (Δ9-Cis) PC, and DTPC membranes were 19.5 ± 0.2, 18.5 ± 0.1 and 14.3 ± 0.1 kBT, respectively. The bending modulus increased with the number of hydrocarbons. The elastic modulus of these membranes was 261 mN/m with a 4% fluctuation. The correlation between the average size and the square root of the bending modulus was supported by theoretical analysis. Graphical abstract
      PubDate: 2022-06-24
       
  • Size segregation of disk particle in two-dimensional chute

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      Abstract: Size segregation will lead to stratification of a particle system. At present, people have not fully understood the segregation mechanism. In this work, we have studied the size segregation behavior of two-component disk particles in chute flows. The effects of particle size ratio η, particle density ρ, static friction coefficient μ and chute angle α on size segregation are discussed. We use the discrete element method to simulate and calculate the force of disk large particles during segregation. Results show that the ‘squeeze expulsion’ mechanism plays a key role in the size segregation of a disk particle flow. We establish a physical model of ‘squeeze expulsion’ of disk particles and obtain the conditions for the formation of ‘squeeze expulsion’ mechanism. Graphic abstract
      PubDate: 2022-06-14
       
  • Thickness of epithelia on wavy substrates: measurements and continuous
           models

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      Abstract: We measured the thickness of MDCK epithelia grown on substrates with a sinusoidal profile. We show that while at long wavelength the profile of the epithelium follows that of the substrate, at short wavelengths cells are thicker in valleys than on ridges. This is reminiscent of the so-called «healing length in the case of a thin liquid film wetting a rough solid substrate. We explore the ability of continuum mechanics models to account for these observations. Modeling the epithelium as a thin liquid film, with surface tension, does not fully account for the measurements. Neither does modeling the epithelium as a thin incompressible elastic film. On the contrary, the addition of an apical active stress gives satisfactory agreement with measurements, with one fitting parameter, the ratio between the active stress and the elastic modulus. Graphic
      PubDate: 2022-06-04
       
  • Stabilized convection in a ternary mixture with two Soret coefficients of
           opposite sign

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      Abstract: We performed ground-based experiments on the sample polystyrene–toluene–cyclohexane in order to complement the experimental activities in microgravity conditions related to the ESA projects DCMIX4 and Giant Fluctuations. After applying a stabilizing thermal gradient by heating from above a layer of the fluid mixture, we studied over many hours the density variations in the bidimensional horizontal field by means of a Shadowgraph optical setup. The resulting images evidence the appearance of convective instability after a diffusive time associated with the binary molecular solvent consisting of toluene and cyclohexane, confirming the negative sign of the Soret coefficient of this mixture. After a larger diffusive time related to mass diffusion of the polystyrene in the binary solvent, convection was suppressed by the increasing stabilizing density gradient originated by the Soret-induced concentration gradient of the polymer. This is compatible with a positive sign of the Soret coefficient of the polymer in the binary solvent. Graphic
      PubDate: 2022-05-28
       
  • The memory of thin polymer films generated by spin coating

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      Abstract: We present results from isothermal and temperature-sweep creep experiments adapted to filaments which were derived from spin coated and subsequently crumpled thin polystyrene films. Due to the existence of residual stresses induced by preparation, the filaments showed significant shrinkage which we followed as a function of time at various temperatures. In addition, the influence of preparation conditions and subsequent annealing of supported thin polymer films on shrinkage and relaxation behavior was investigated. The temporal evolution of shrinkage revealed a sequence of relaxation regimes. We explored the temperature dependence of this relaxation and compared our observations with published results on drawn melt-spun fibers. This comparison revealed intriguing similarities between both systems prepared along different pathways. For instance, the magnitudes of shrinkage of melt-spun fibers and of filaments from crumpled spin coated polymer films are similar. Thus, our results suggest the existence of generic mechanisms of “forgetting”, i.e., how non-equilibrated polymers lose their memory of past processing events. Graphical abstract
      PubDate: 2022-05-25
       
  • Non-invasive measurement of nuclear relative stiffness from quantitative
           analysis of microscopy data

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      Abstract: The connection between the properties of a cell tissue and those of the single constituent cells remains to be elucidated. At the purely mechanical level, the degree of rigidity of different cellular components, such as the nucleus and the cytoplasm, modulates the interplay between the cell inner processes and the external environment, while simultaneously mediating the mechanical interactions between neighboring cells. Being able to quantify the correlation between single-cell and tissue properties would improve our mechanobiological understanding of cell tissues. Here we develop a methodology to quantitatively extract a set of structural and motility parameters from the analysis of time-lapse movies of nuclei belonging to jammed and flocking cell monolayers. We then study in detail the correlation between the dynamical state of the tissue and the deformation of the nuclei. We observe that the nuclear deformation rate linearly correlates with the local divergence of the velocity field, which leads to a non-invasive estimate of the elastic modulus of the nucleus relative to the one of the cytoplasm. We also find that nuclei belonging to flocking monolayers, subjected to larger mechanical perturbations, are about two time stiffer than nuclei belonging to dynamically arrested monolayers, in agreement with atomic force microscopy results. Our results demonstrate a non-invasive route to the determination of nuclear relative stiffness for cells in a monolayer. Graphic abstract
      PubDate: 2022-05-23
       
  • Interplay between cell height variations and planar pulsations in
           epithelial monolayers

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      Abstract: Biological tissues change their shapes through collective interactions of cells. This coordination sets length and time scales for dynamics where precision is essential, in particular during morphogenetic events. However, how these scales emerge remains unclear. Here, we address this question using the pulsatile domains observed in confluent epithelial MDCK monolayers where cells exhibit synchronous contraction and extension cycles of \(\approx 5\)  h duration and \(\approx 200~ \upmu \hbox {m}\) length scale. We report that the monolayer thickness changes gradually in space and time by more than twofold in order to counterbalance the contraction and extension of the incompressible cytoplasm. We recapitulate these pulsatile dynamics using a continuum model and show that incorporation of cell stiffness dependent height variations is critical both for generating temporal pulsations and establishing the domain size. We propose that this feedback between height and mechanics could be important in coordinating the length scales of tissue dynamics. Graphic abstract
      PubDate: 2022-05-19
       
  • Actomyosin contractility requirements and reciprocal cell–tissue
           mechanics for cancer cell invasion through collagen-based channels

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      Abstract: The interstitial tumor microenvironment is composed of heterogeneously organized collagen-rich porous networks as well as channel-like structures and interfaces which provide both barriers and guidance for invading cells. Tumor cells invading 3D random porous collagen networks depend upon actomyosin contractility to deform and translocate the nucleus, whereas Rho/Rho-associated kinase-dependent contractility is largely dispensable for migration in stiff capillary-like confining microtracks. To investigate whether this dichotomy of actomyosin contractility dependence also applies to physiological, deformable linear collagen environments, we developed nearly barrier-free collagen-scaffold microtracks of varying cross section using two-photon laser ablation. Both very narrow and wide tracks supported single-cell migration by either outward pushing of collagen up to four times when tracks were narrow, or cell pulling on collagen walls down to 50% of the original diameter by traction forces of up to 40 nN when tracks were wide, resulting in track widths optimized to single-cell diameter. Targeting actomyosin contractility by synthetic inhibitors increased cell elongation and nuclear shape change in narrow tracks and abolished cell-mediated deformation of both wide and narrow tracks. Accordingly, migration speeds in all channel widths reduced, with migration rates of around 45-65% of the original speed persisting. Together, the data suggest that cells engage actomyosin contraction to reciprocally adjust both own morphology and linear track width to optimal size for effective cellular locomotion. Graphic abstract
      PubDate: 2022-05-16
       
  • Translation–deformation coupling effects on the Rayleigh instability of
           an electrodynamically levitated charged droplet

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      Abstract: The breakup pathway of the Rayleigh fission process observed in the past experiments carried out using high-speed imaging of a charged drop levitated in an AC quadrupole trap has shown to exhibit several cycles of shape and center-of-mass oscillations followed by asymmetric breakup by ejecting a jet in the upward direction (i.e., opposite to the direction of gravity). We recently attempted to explain this using boundary integral simulations in the Stokes flow limit, wherein the position of the droplet and the polarity of the end cap electrodes were assigned using physical arguments, and the center-of-mass motion was not estimated consistently invoking quasi-static conditions. In this work, we explain the experimental observation of upward breakup of charged droplets in a quadrupolar field, using numerical calculations based on the boundary element method considering inviscid droplets levitated electrodynamically using quadrupole electric fields. The center-of-mass motion and the end cap are consistently calculated in the numerical scheme. The simulations show that the gravity-induced downward shift in the equilibrium position of the drop in the trap causes significant, large-amplitude shape oscillations superimposed over the center-of-mass oscillations of the drop. An important observation here is that the shape oscillations due to the applied quadrupole fields result in sufficient deformations that act as triggers for the onset of the instability below the Rayleigh limit, thereby admitting a subcritical instability. The center-of-mass oscillations of the droplet within the trap, which follow the applied frequency, are out of phase with the applied AC signal. Thus the combined effect of shape deformations and dynamic position of the drop leads to an asymmetric breakup such that the Rayleigh fission occurs upward via the ejection of a jet at the north pole of the deformed drop. Graphical abstract
      PubDate: 2022-05-13
       
  • Correction to: A biaxial tensional model for early vertebrate
           morphogenesis

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      Abstract: A Correction to this paper has been published: 10.1140/epje/s10189-022-00184-4
      PubDate: 2022-05-12
       
  • Thermogravitational separation in porous vertical and horizontal
           cylindrical annular cells saturated by a binary mixture

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      Abstract: In this paper, analytical and numerical studies of species separation in vertical and horizontal porous, cylindrical annular cells were presented. The binary fluid, saturating the porous medium, is a water–ethanol mixture. The thickness e of the horizontal and vertical columns is equal to \(R_o-R_i\) , where \(R_i\) and \(R_o\) are, respectively, the internal and the external radii. H is the height of the vertical cell, and the length of the horizontal cell. Constant temperatures, \(T_{\mathrm{hot}}\) and \(T_{\mathrm{cold}}\) , were imposed on the inner and outer cylinders. Since an important species separation, in thermogravitational column (TGC), is obtained for \(e<<H\) , the same assumption was made for the two configurations. The analytical solution was obtained using the parallel flow approximation for both configurations. The governing equations were solved numerically for 2D and 3D configurations using two different software (Comsol Multiphysics and a spectral collocation method with Gauss–Lobatto–Chebyshev points). Velocity, temperature, mass fraction fields and time to reach steady state were compared for the two configurations. The amount of species separated at the top or the bottom of each cell was also compared for each configuration. Graphical abstract
      PubDate: 2022-05-12
       
  • Measuring the average cell size and width of its distribution in cellular
           tissues using Fourier transform

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      Abstract: We present an in-depth investigation of a fully automated Fourier-based analysis to determine the cell size and the width of its distribution in 3D biological tissues. The results are thoroughly tested using generated images, and we offer valuable criteria for image acquisition settings to optimize accuracy. We demonstrate that the most important parameter is the number of cells in the field of view, and we show that accurate measurements can already be made on volume only containing \(3\times 3\times 3\) cells. The resolution in z is also not so important, and a reduced number of in-depth images, of order of one per cell, already provides a measure of the mean cell size with less than 5% error. The technique thus appears to be a very promising tool for very fast live local volume cell measurement in 3D tissues in vivo while strongly limiting photobleaching and phototoxicity issues. Graphic abstract
      PubDate: 2022-05-09
       
  • Effect of an excess of surfactant on thermophoresis, mass diffusion and
           viscosity in an oily surfactant-stabilized ferrofluid

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      Abstract: The effect of an excess of surfactant on the thermophoresis of a sterically stabilized ferrofluid is investigated experimentally by forced Rayleigh scattering (FRS). The experiments are performed with a stable magnetic fluid sample to which controlled amounts of surfactant are added. A decrease in the thermally induced transport of magnetic nanoparticles is observed while increasing the temperature T. The positive Soret coefficient \(S_{\mathrm{T}}\) decreases by adding 2 vol% of surfactant at room temperature. As shown by FRS relaxation, this decreasing is mainly associated with a reduction of the interaction between the carrier fluid and individual nanoparticles. No significant effect of extra surfactant on the sign of \(S_{\mathrm{T}}\) is observed at higher T’s (up to \(\sim \,85\,^{\circ }\) C). Dynamic light scattering at room temperature reveals the presence of a small amount of clusters/aggregates in the samples, which are hardly detectable by FRS relaxation. The presence of these small clusters/aggregates is confirmed by a rheological probing of the fluid properties. Whatever T, a small amount of added surfactant first causes a decrease of the ferrofluid viscosity, associated with a 10% decreasing of the flow activation energy. Further on, viscosity and activation energy both recover at higher excess surfactant concentrations. These results are analyzed in terms of saturation of the surfactant layer, concentration of free surfactant chains and heat of transport of the nanoparticles. Graphic abstract
      PubDate: 2022-05-05
       
  • Predicting thermodiffusion in simple binary fluid mixtures

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      Abstract: The predictive capabilities of some existing theoretical models to quantify thermodiffusion have been investigated in this work. To do so, the tests have been performed on two model fluids, the hard-sphere and the Lennard-Jones (including spheres and dimers) ones, exploring different mixtures and thermodynamic conditions thanks to extensive molecular simulations. It has been confirmed that the thermal diffusion factor should be expressed as the sum of one term related to the isotope effect and one term related to the “chemical” effects and that a kinetic term is required to quantify thermodiffusion from the gas state to the liquid state. In addition, regarding the isotope effects, it has been obtained that none of the available theoretical models are able to yield a reasonable prediction relatively to the molecular simulations results and that the moment of inertia contribution is one order of magnitude smaller than the mass contribution in the liquid state. Finally, concerning the chemical effects, it has been shown the Shukla and Firoozabadi model, complemented with a kinetic term, is probably the most reasonable option to estimate the chemical contribution to the thermal diffusion factor, even if it fails in capturing the effect of the asymmetry in size and in shape between the species. Overall, this works confirms that there is still a lack of a generic model able to predict accurately thermal diffusion factors, or equivalently Soret coefficient, in simple binary mixtures from the gas state to the liquid state. Graphical abstract
      PubDate: 2022-05-04
       
  • Soret separation and thermo-osmosis in porous media

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      Abstract: When a temperature difference is applied over a porous medium soaked with a fluid mixture, two effects may be observed, a component separation (the Ludwig–Soret effect, thermodiffusion) and a pressure difference due to thermo-osmosis. In this work, we have studied both effects using non-equilibrium thermodynamics and molecular dynamics. We have derived expressions for the two characteristic parameters, the Soret coefficient and the thermo-osmotic coefficient in terms of phenomenological transport coefficients, and we show how they are related. Numerical values for these coefficients were obtained for a two-component fluid in a solid matrix where both fluid and solid are Lennard–Jones/spline particles. We found that both effects depend strongly on the porosity of the medium and weakly on the interactions between the fluid components and the matrix. The Soret coefficient depends strongly on whether the fluid is sampled from inside the porous medium or from bulk phases outside, which must be considered in experimental measurements using packed columns. If we use a methane/decane mixture in bulk as an example, our results for the Soret coefficient give that a temperature difference of 10 K will separate the mixture to about 49.5/50.5 and give no pressure difference. In a reservoir with 30% porosity, the separation will be 49.8/50.2, whereas the pressure difference will be about 15 bar. Thermo-osmotic pressures with this order or magnitude have been observed in frost-heave experiments. Graphic abstract
      PubDate: 2022-05-03
       
  • Nonlinearities in shadowgraphy experiments on non-equilibrium fluctuations
           in polymer solutions

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      Abstract: Giant thermal and solutal non-equilibrium fluctuations are observed in shadowgraphy experiments on liquid mixtures subjected to a temperature gradient. For large temperature differences, both the temperature and the composition dependence of the relevant thermophysical parameters and the nonlinear terms in the diffusion equation need to be taken into account, leading to a nonlinear concentration profile. For temperature differences exceeding the inverse of the Soret coefficient, in our example approximately 10 K, the usual data evaluation yields increasingly wrong diffusion and Soret coefficients that are off by almost a factor of two for a temperature difference of 50 K. A local model that treats the measured shadowgraph signal as a superposition of the contributions from every layer of the sample is able to capture the essential trend and yields a good agreement with experimental data. The results are important for the application of shadowgraphy as a tool for the measurement of Soret and diffusion coefficients, where large temperature gradients promise a good signal-to-noise ratio. Graphical abstract
      PubDate: 2022-04-26
       
  • Hydrodynamics of electro-capillarity propelled non-Newtonian droplets
           through micro-confinements

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      Abstract: In this article, we theoretically explore the dynamics of droplet motion and its evolution during electro-capillarity propelled actuation within microfluidic systems. The study covers a wide gamut of fluids, wherein we investigate the dynamics of both pseudoplastic and dilatant fluid droplets. It is observed that change in the fluid rheology of the non-Newtonian fluids leads to significant morphing of the droplet dynamics during the actuation and propulsion event when compared to the Newtonian counterparts. We validate the theory using experimental reports on similar systems employing Newtonian droplets. The influence of governing parameters such as the actuation voltage and its transients, dielectric layer thickness on the electrodes and electrode spacing is probed. We also explore the influence of the interfacial properties of the system, such as channel wall friction, droplet wettability, and capillary friction, and establish that the fluid rheology, in conjunction with the interfacial features regulate the electro-actuation and propulsion of the droplets. We further provide theoretical estimates on the optimal design of the electro-actuation system in terms of a proposed electro-interfacial tension parameter. The findings may hold significance towards design and development of microfluidics with electro-actuation systems. Graphical
      PubDate: 2022-04-25
       
  • Traveling waves of a colloidal suspension in a closed cell

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      Abstract: Two-dimensional oscillatory flows in the convective cell filled with a colloidal suspension are investigated. We consider transient and permanent evolution scenarios of the traveling wave that were found in experimental investigation (Donzelli et al. in Phys Rev Lett 102:104503, 2009). The nanoparticle transport mechanisms (thermodiffusion and gravity settling) are analyzed and elucidated with the help of finite-difference numerical simulations for Hyflon MFA colloidal suspension. The spatiotemporal characteristics of the stable (permanent) traveling waves are determined. The dependence of the Rayleigh number on the Lewis number at the boundary of existence of the stable traveling wave is obtained. Graphic abstract
      PubDate: 2022-04-25
       
  • Mass effects for thermodiffusion in dilute aqueous solutions

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      Abstract: Thermodiffusion is the phenomenon by which molecules in a mixture present concentration gradients in response to an imposed temperature gradient. Despite decades of investigations, this effect remains poorly understood at a molecular level. A common, phenomenological approach is to individuate the molecular factors that influence the Soret coefficient, the parameter that quantifies the resulting concentration-gradient. Experimental studies, often performed on organic mixtures, as well as simulations of model particle systems have evidenced that the difference in masses between the mixture components has an important effect on the amplitude of the Soret coefficient. Here, we use molecular dynamics simulations of a thermophoretic setting to investigate the mass dependence of the Soret coefficient in dilute aqueous solutions. An advantage of simulation approaches is that they are not limited in the range of explored molecular masses, which is often limited to isotopic substitutions in the experiments. Our simulations reveal that the mass dependence of the Soret coefficient in these solutions is in agreement with previous experimental and simulation work on molecular-size systems. In particular, it is sensitive to the relative mass difference between the solute and the solvent, but not to their absolute mass. Adjusting the mass of the solvent and of the solute can turn a thermophobic solution into a thermophilic one, where solute accumulation is reversed. This demonstrates that the mass effect can indeed compensate for the other contributions to the Soret coefficient. Finally, we find that changing the molecular moments of inertia has a much more limited impact as compared to a change in the total molecular mass. Graphical
      PubDate: 2022-04-21
       
 
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