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The molecular weight dependence of the lower critical solution temperature of polystyrene (PS) and poly(vinyl methyl ether) blends was studied by laser light transmission. The temperature of phase separation was found to decrease ...
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The molecular weight dependence of the lower critical solution temperature of polystyrene (PS) and poly(vinyl methyl ether) blends was studied by laser light transmission. The temperature of phase separation was found to decrease with increasing PS molecular weight. In the steady shear flow conditions and near the critical temperature, shear was found to enhance fluctuations of concentration at relatively small shear rates, whereas it suppresses such fluctuations at high shear rates. The shift in Flory-interaction parameter Δχ was calculated from experimental data and its sign was used to predict shear-induced mixing or shear-induced demixing under flow field. The obtained experimental results were compared to Criado-Sancho et al. and Clarke-Mcleish models.
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Viruses must efficiently and specifically package their genomes while excluding cellular nucleic acids and viral subgenomic fragments. Some viruses use specific packaging signals, which are conserved sequence or structure motifs p...
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Viruses must efficiently and specifically package their genomes while excluding cellular nucleic acids and viral subgenomic fragments. Some viruses use specific packaging signals, which are conserved sequence or structure motifs present only in the full-length genome. Recent work has shown that viral proteins important for packaging can undergo liquid-liquid phase separation (LLPS), in which one or two viral nucleic acid binding proteins condense with the genome. The compositional simplicity of viral components lends itself well to theoretical modeling compared with more complex cellular organelles. Viral LLPS can be limited to one or two viral proteins and a single genome that is enriched in LLPS-promoting features. In our previous study, we observed that LLPS-promoting sequences of severe acute respiratory syndrome coronavirus 2 are located at the 50 and 30 ends of the genome, whereas the middle of the genome is predicted to consist mostly of solubilizing elements. Is this arrangement sufficient to drive single genome packaging, genome compaction, and genome cyclization? We addressed these questions using a coarse-grained polymer model, LASSI, to study the LLPS of nucleocapsid protein with RNA sequences that either promote LLPS or solubilization. With respect to genome cyclization, we find the most optimal arrangement restricts LLPS-promoting elements to the 50 and 30 ends of the genome, consistent with the native spatial patterning. Genome compaction is enhanced by clustered LLPS-promoting binding sites, whereas single genome packaging is most efficient when binding sites are distributed throughout the genome. These results suggest that many and variably positioned LLPS-promoting signals can support packaging in the absence of a singular packaging signal which argues against necessity of such a feature. We hypothesize that this model should be generalizable to multiple viruses as well as cellular organelles such as paraspeckles, which enrich specific long RNA sequences in a defined arrangement.
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The increasing amount of liquid, especially water, in the product stream of offshore gas wells, requires improvement of current separation methods. Nowadays, separation methods are mainly based on gravitational settling of the dis...
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The increasing amount of liquid, especially water, in the product stream of offshore gas wells, requires improvement of current separation methods. Nowadays, separation methods are mainly based on gravitational settling of the dispersed phases. In these separators low gas velocities are required to achieve a sufficient separating efficiency. As a result these devices are voluminous, heavy, and expensive. As platforms are restricted to space and weight and the liquid amount is increasing, compact and efficient phase separation equipment is required to keep the exploitation of the wells profitable. A device which fulfils these requirements is the naturally driven Rotational Particle Separator (RPS). In this study the operating characteristics of such a separator was measured. For this purpose a full-scale prototype was built, which is capable to handle the volume flow of one typical wellhead under high pressure (80 bar) and which separates droplets down to 2 micron. In order to validate the operating characteristics of the prototype both hydrodynamic and separation performance measurements were performed. Overall, the performance of the prototype agrees well with expectations.
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A new approach is proposed to describe the spinodal decomposition, in particular, in polymer binary blends. In the framework of this approach, the spinodal decomposition is described as a relaxation of one-time structure factor S(...
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A new approach is proposed to describe the spinodal decomposition, in particular, in polymer binary blends. In the framework of this approach, the spinodal decomposition is described as a relaxation of one-time structure factor S(q,t) treated as an independent dynamic object (a peculiar two-point order parameter). The dynamic equation for S(q,t), including the explicit expression for the corresponding effective kinetic coefficient, is derived. In the first approximation this equation is identical to the Langer equation. We first solved it both in terms of higher transcendental functions and numerically. The asymptotic behaviour of S(q,t) at large (from the onset of spinodal decomposition) times is analytically described. The values obtained for the power-law growth exponent for the large-time peak value and position of S(q,t) are in good agreement with experimental data and results of numerical integration of the Cahn-Hilliard equation. [References: 9]
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The microstructure of a monotectic Ni54Nb23Y23 alloy, prepared under different casting conditions, was investigated. The alloy exhibits both a liquid miscibility gap and a high glass-forming ability. It was shown that, at moderate...
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The microstructure of a monotectic Ni54Nb23Y23 alloy, prepared under different casting conditions, was investigated. The alloy exhibits both a liquid miscibility gap and a high glass-forming ability. It was shown that, at moderate cooling rates, a change in the process parameters can drastically alter the morphology of microstructures, whereas the fractions of the Nb7Ni6, NiY and Ni2Y constituent phases themselves remain virtually unchanged. For rapid quenching from melt temperatures T > T-crit, the temperature of liquid phase separation, a phase separated glass is formed, which exhibits compositional heterogeneities with fractal character between 10 and 500 nm size.
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The authors investigated the transformation of state of silica particles and inorganic salts during the calcination of solid mixtures of silica/potassium halide (KX), which separated the mixture components producing microporous st...
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The authors investigated the transformation of state of silica particles and inorganic salts during the calcination of solid mixtures of silica/potassium halide (KX), which separated the mixture components producing microporous structures, at temperatures below the melting point of either materials. The silica sol (SiO2-Na2O)/KX solid was examined at high temperatures using thermal analysis, X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The data suggest the crystalline inorganic salt component transformed into an amorphous state ca. 100-200degreesC lower than its melting point, while the silica particle component coagulated, spontaneously separating the two components ("coagulation/phase separation"). Upon cooling, the inorganic salt was dispersed in water, resulting in porous silica with a narrow pore size distribution. However, at calcination temperatures above 800degreesC, formation of silica crystal existed as a separate domain without creating porous structures. (C) 2003 Kluwer Academic Publishers. [References: 22]
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A transparent separation unit with an apertured baffle for liquid-gas separation was constructed using acrylic resin. The phase-separation characteristics were examined using air and water as working fluids. The drain limit, flood...
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A transparent separation unit with an apertured baffle for liquid-gas separation was constructed using acrylic resin. The phase-separation characteristics were examined using air and water as working fluids. The drain limit, flooding limit, and liquid level in the header of the unit were determined under different inlet liquid and gas superficial velocities. The performances of the unit were evaluated by analyzing the effects of pressure, gravity, and capillary force. The liquid-separation efficiency of the separator was determined by the inlet flow patterns. The unit showed strong liquid-gas separation effects at optimal inlet conditions. The liquid-separation efficiency was higher than 45% for an annular flow inlet, higher than 80% for a slug flow inlet at low liquid inlet superficial velocities, and approached 100% for a stratified flow inlet. The flow distribution in the header was visually observed using a high-speed camera to determine the effects of the inlet flow patterns on the drain limit as well as on the liquid-separation efficiency.
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In this paper an experimental study to investigate two-phase flow distribution in compact heat exchanger manifolds is presented. An experimental test rig to measure the flow distribution in realistic manifold geometries and under ...
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In this paper an experimental study to investigate two-phase flow distribution in compact heat exchanger manifolds is presented. An experimental test rig to measure the flow distribution in realistic manifold geometries and under relevant operating conditions was built. To elucidate the effect on the flow distribution, the following factors are investigated: vapour fraction at the manifold inlet, heating load on the heat exchanger tubes, diameter of the manifold and manifold inlet tube length. The experimental system simulated an evaporator for an automobile air conditioner with a design cooling capacity of 5 kW. From the horizontal manifold, the two-phase refrigerant flow was distributed in 10 parallel heat exchanger tubes. The orientation of the test rig could be varied to measure both upward and downward flow out of the manifold. To ensure similarity to an actual heat exchanger, counterflowing water was used as heat source in the evaporator section. The experimental setup made it possible to measure the heat added to the evaporating refrigerant in each tube by using separate water flow circuits. Refrigerant R134a was used as refrigerant. (C) 2003 Elsevier Inc. All rights reserved. [References: 15]
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We study active surface wetting using a minimal model of bacteria that takes into account the intrinsic motility diversity of living matter. A mixture of "fast" and "slow" self-propelled Brownian particles is considered in the pre...
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We study active surface wetting using a minimal model of bacteria that takes into account the intrinsic motility diversity of living matter. A mixture of "fast" and "slow" self-propelled Brownian particles is considered in the presence of a wall. The evolution of the wetting layer thickness shows an overshoot before stationarity and its composition evolves in two stages, equilibrating after a slow elimination of excess particles. Nonmonotonic evolutions are shown to arise from delayed avalanches towards the dilute phase combined with the emergence of a transient particle front.
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