Spectro-microscopic Characterization of Physical Properties and Phase Separations in Individual Atmospheric Particles

NASA Astrophysics Data System (ADS)

OBrien, R. E.; Wang, B.; Neu, A.; Kelly, S. T.; Lundt, N.; Epstein, S. A.; MacMillan, A.; You, Y.; Laskin, A.; Nizkorodov, S.; Bertram, A. K.; Moffet, R.; Gilles, M.

2013-12-01

The phase state and liquid-liquid phase separations of ambient and laboratory generated aerosol particles were investigated using (1) scanning transmission x-ray microscopy/near-edge x-ray absorption fine structure spectroscopy (STXM/NEXAFS) coupled to a relative humidity (RH) controlled in-situ chamber and (2) environmental scanning electron microscopy (ESEM). The phase states of the particles were determined from measurements of their size and optical density. A comparison is made between the observed phase states of ambient samples and of laboratory generated aerosols to determine how well laboratory samples represent the phase of ambient samples. In addition, liquid-liquid phase separations in laboratory generated particles were investigated. Preliminary results showing that liquid-liquid phase separations occur at RH's between the deliquescence and efflorescence points and that the organic phase surrounds the inorganic phase will be presented. The STXM/NEXAFS technique provides insight into the degree of mixing at the deliquescence point and the degree of phase separation for particles of atmospherically relevant sizes.

Study Of Phase Separation In Glass

NASA Technical Reports Server (NTRS)

Neilson, George F.; Weinberg, Michael C.; Smith, Gary L.

1989-01-01

Report describes an experimental study of effect of hydroxide content on phase separation in soda/silica glasses. Ordinary and gel glasses melted at 1,565 degree C, and melts stirred periodically. "Wet" glasses produced by passing bubbles of N2 saturated with water through melts; "dry" glasses prepared in similar manner, except N2 dried before passage through melts. Analyses of compositions of glasses performed by atomic-absorption and index-of-refraction measurements. Authors conclude hydroxide speeds up phase separation, regardless of method (gel or ordinary) by which glass prepared. Eventually helps material scientists to find ways to control morphology of phase separation.

Stability and Oil Migration of Oil-in-Water Emulsions Emulsified by Phase-Separating Biopolymer Mixtures.

PubMed

Yang, Nan; Mao, Peng; Lv, Ruihe; Zhang, Ke; Fang, Yapeng; Nishinari, Katsuyoshi; Phillips, Glyn O

2016-08-01

Oil-in-water (O/W) emulsions with varying concentration of oil phase, medium-chain triglyceride (MCT), were prepared using phase-separating gum arabic (GA)/sugar beet pectin (SBP) mixture as an emulsifier. Stability of the emulsions including emulsion phase separation, droplet size change, and oil migration were investigated by means of visual observation, droplet size analysis, oil partition analysis, backscattering of light, and interfacial tension measurement. It was found that in the emulsions prepared with 4.0% GA/1.0% SBP, when the concentration of MCT was greater than 2.0%, emulsion phase separation was not observed and the emulsions were stable with droplet size unchanged during storage. This result proves the emulsification ability of phase-separating biopolymer mixtures and their potential usage as emulsifiers to prepare O/W emulsion. However, when the concentration of MCT was equal or less than 2.0%, emulsion phase separation occurred after preparation resulting in an upper SBP-rich phase and a lower GA-rich phase. The droplet size increased in the upper phase whereas decreased slightly in the lower phase with time, compared to the freshly prepared emulsions. During storage, the oil droplets exhibited a complex migration process: first moving to the SBP-rich phase, then to the GA-rich phase and finally gathering at the interface between the two phases. The mechanisms of the emulsion stability and oil migration in the phase-separated emulsions were discussed. © 2016 Institute of Food Technologists®

Gas-Liquid Flows and Phase Separation

NASA Technical Reports Server (NTRS)

McQuillen, John

2004-01-01

Common issues for space system designers include:Ability to Verify Performance in Normal Gravity prior to Deployment; System Stability; Phase Accumulation & Shedding; Phase Separation; Flow Distribution through Tees & Manifolds Boiling Crisis; Heat Transfer Coefficient; and Pressure Drop.The report concludes:Guidance similar to "A design that operates in a single phase is less complex than a design that has two-phase flow" is not always true considering the amount of effort spent on pressurizing, subcooling and phase separators to ensure single phase operation. While there is still much to learn about two-phase flow in reduced gravity, we have a good start. Focus now needs to be directed more towards system level problems .

Electronic Phase Separation in Iron Selenide (Li,Fe)OHFeSe Superconductor System

NASA Astrophysics Data System (ADS)

Mao, Yiyuan; Li, Jun; Huan, Yulong; Yuan, Jie; Li, Zi-an; Chai, Ke; Ma, Mingwei; Ni, Shunli; Tian, Jinpeng; Liu, Shaobo; Zhou, Huaxue; Zhou, Fang; Li, Jianqi; Zhang, Guangming; Jin, Kui; Dong, Xiaoli; Zhao, Zhongxian

2018-05-01

The phenomenon of phase separation into antiferromagnetic (AFM) and superconducting (SC) or normal-state regions has great implication for the origin of high-temperature (high-Tc) superconductivity. However, the occurrence of an intrinsic antiferromagnetism above the Tc of (Li, Fe)OHFeSe superconductor is questioned. Here we report a systematic study on a series of (Li, Fe)OHFeSe single crystal samples with Tc up to ~41 K. We observe an evident drop in the static magnetization at Tafm ~125 K, in some of the SC (Tc < ~38 K, cell parameter c < ~9.27 {\\AA}) and non-SC samples. We verify that this AFM signal is intrinsic to (Li, Fe)OHFeSe. Thus, our observations indicate mesoscopic-to-macroscopic coexistence of an AFM state with the normal (below Tafm) or SC (below Tc) state in (Li, Fe)OHFeSe. We explain such coexistence by electronic phase separation, similar to that in high-Tc cuprates and iron arsenides. However, such an AFM signal can be absent in some other samples of (Li, Fe)OHFeSe, particularly it is never observed in the SC samples of Tc > ~38 K, owing to a spatial scale of the phase separation too small for the macroscopic magnetic probe. For this case, we propose a microscopic electronic phase separation. It is suggested that the microscopic static phase separation reaches vanishing point in high-Tc (Li, Fe)OHFeSe, by the occurrence of two-dimensional AFM spin fluctuations below nearly the same temperature as Tafm reported previously for a (Li, Fe)OHFeSe (Tc ~42 K) single crystal. A complete phase diagram is thus established. Our study provides key information of the underlying physics for high-Tc superconductivity.

Rationalizing the light-induced phase separation of mixed halide organic–inorganic perovskites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Draguta, Sergiu; Sharia, Onise; Yoon, Seog Joon

Mixed halide hybrid perovskites, CH 3NH 3Pb(I 1-xBrx) 3' represent good candidates for lowcost, high efficiency photovoltaic, and light-emitting devices. Their band gaps can be tuned from 1.6 to 2.3 eV, by changing the halide anion identity. Unfortunately, mixed halide perovskites undergo phase separation under illumination. This leads to iodide- and bromide-rich domains along with corresponding changes to the material’s optical/electrical response. Here, using combined spectroscopic measurements and theoretical modeling, we quantitatively rationalize all microscopic processes that occur during phase separation. Our model suggests that the driving force behind phase separation is the bandgap reduction of iodiderich phases. It additionallymore » explains observed non-linear intensity dependencies, as well as self-limited growth of iodide-rich domains. Most importantly, our model reveals that mixed halide perovskites can be stabilized against phase separation by deliberately engineering carrier diffusion lengths and injected carrier densities.« less

Rationalizing the light-induced phase separation of mixed halide organic–inorganic perovskites

DOE PAGES

Draguta, Sergiu; Sharia, Onise; Yoon, Seog Joon; ...

2017-08-04

Mixed halide hybrid perovskites, CH 3NH 3Pb(I 1-xBrx) 3' represent good candidates for lowcost, high efficiency photovoltaic, and light-emitting devices. Their band gaps can be tuned from 1.6 to 2.3 eV, by changing the halide anion identity. Unfortunately, mixed halide perovskites undergo phase separation under illumination. This leads to iodide- and bromide-rich domains along with corresponding changes to the material’s optical/electrical response. Here, using combined spectroscopic measurements and theoretical modeling, we quantitatively rationalize all microscopic processes that occur during phase separation. Our model suggests that the driving force behind phase separation is the bandgap reduction of iodiderich phases. It additionallymore » explains observed non-linear intensity dependencies, as well as self-limited growth of iodide-rich domains. Most importantly, our model reveals that mixed halide perovskites can be stabilized against phase separation by deliberately engineering carrier diffusion lengths and injected carrier densities.« less

Phase separation of self-propelled ballistic particles

NASA Astrophysics Data System (ADS)

Bruss, Isaac R.; Glotzer, Sharon C.

2018-04-01

Self-propelled particles phase-separate into coexisting dense and dilute regions above a critical density. The statistical nature of their stochastic motion lends itself to various theories that predict the onset of phase separation. However, these theories are ill-equipped to describe such behavior when noise becomes negligible. To overcome this limitation, we present a predictive model that relies on two density-dependent timescales: τF, the mean time particles spend between collisions; and τC, the mean lifetime of a collision. We show that only when τF<τC do collisions last long enough to develop a growing cluster and initiate phase separation. Using both analytical calculations and active particle simulations, we measure these timescales and determine the critical density for phase separation in both two and three dimensions.

Motility-Induced Phase Separation

NASA Astrophysics Data System (ADS)

Cates, Michael E.; Tailleur, Julien

2015-03-01

Self-propelled particles include both self-phoretic synthetic colloids and various microorganisms. By continually consuming energy, they bypass the laws of equilibrium thermodynamics. These laws enforce the Boltzmann distribution in thermal equilibrium: The steady state is then independent of kinetic parameters. In contrast, self-propelled particles tend to accumulate where they move more slowly. They may also slow down at high density for either biochemical or steric reasons. This creates positive feedback, which can lead to motility-induced phase separation (MIPS) between dense and dilute fluid phases. At leading order in gradients, a mapping relates variable-speed, self-propelled particles to passive particles with attractions. This deep link to equilibrium phase separation is confirmed by simulations but generally breaks down at higher order in gradients: New effects, with no equilibrium counterpart, then emerge. We give a selective overview of the fast-developing field of MIPS, focusing on theory and simulation but including a brief speculative survey of its experimental implications.

Wetting and phase separation in soft adhesion

PubMed Central

Jensen, Katharine E.; Sarfati, Raphael; Style, Robert W.; Boltyanskiy, Rostislav; Chakrabarti, Aditi; Chaudhury, Manoj K.; Dufresne, Eric R.

2015-01-01

In the classic theory of solid adhesion, surface energy drives deformation to increase contact area whereas bulk elasticity opposes it. Recently, solid surface stress has been shown also to play an important role in opposing deformation of soft materials. This suggests that the contact line in soft adhesion should mimic that of a liquid droplet, with a contact angle determined by surface tensions. Consistent with this hypothesis, we observe a contact angle of a soft silicone substrate on rigid silica spheres that depends on the surface functionalization but not the sphere size. However, to satisfy this wetting condition without a divergent elastic stress, the gel phase separates from its solvent near the contact line. This creates a four-phase contact zone with two additional contact lines hidden below the surface of the substrate. Whereas the geometries of these contact lines are independent of the size of the sphere, the volume of the phase-separated region is not, but rather depends on the indentation volume. These results indicate that theories of adhesion of soft gels need to account for both the compressibility of the gel network and a nonzero surface stress between the gel and its solvent. PMID:26553989

Kinetics of phase separation and coarsening in dilute surfactant pentaethylene glycol monododecyl ether solutions

NASA Astrophysics Data System (ADS)

Tanaka, S.; Kubo, Y.; Yokoyama, Y.; Toda, A.; Taguchi, K.; Kajioka, H.

2011-12-01

We investigated the phase separation phenomena in dilute surfactant pentaethylene glycol monodedecyl ether (C12E5) solutions focusing on the growth law of separated domains. The solutions confined between two glass plates were found to exhibit the phase inversion, characteristic of the viscoelastic phase separation; the majority phase (water-rich phase) nucleated as droplets and the minority phase (micelle-rich phase) formed a network temporarily, then they collapsed into an usual sea-island pattern where minority phase formed islands. We found from the real-space microscopic imaging that the dynamic scaling hypothesis did not hold throughout the coarsening process. The power law growth of the domains with the exponent close to 1/3 was observed even though the coarsening was induced mainly by hydrodynamic flow, which was explained by Darcy's law of laminar flow.

Evolutionary Calculations of Phase Separation in Crystallizing White Dwarf Stars

NASA Astrophysics Data System (ADS)

Montgomery, M. H.; Klumpe, E. W.; Winget, D. E.; Wood, M. A.

1999-11-01

We present an exploration of the significance of carbon/oxygen phase separation in white dwarf stars in the context of self-consistent evolutionary calculations. Because phase separation can potentially increase the calculated ages of the oldest white dwarfs, it can affect the age of the Galactic disk as derived from the downturn in the white dwarf luminosity function. We find that the largest possible increase in ages due to phase separation is ~1.5 Gyr, with a most likely value of approximately 0.6 Gyr, depending on the parameters of our white dwarf models. The most important factors influencing the size of this delay are the total stellar mass, the initial composition profile, and the phase diagram assumed for crystallization. We find a maximum age delay in models with masses of ~0.6 Msolar, which is near the peak in the observed white dwarf mass distribution. In addition, we note that the prescription that we have adopted for the mixing during crystallization provides an upper bound for the efficiency of this process, and hence a maximum for the age delays. More realistic treatments of the mixing process may reduce the size of this effect. We find that varying the opacities (via the metallicity) has little effect on the calculated age delays. In the context of Galactic evolution, age estimates for the oldest Galactic globular clusters range from 11.5 to 16 Gyr and depend on a variety of parameters. In addition, a 4-6 Gyr delay is expected between the formation of the globular clusters and the formation of the Galactic thin disk, while the observed white dwarf luminosity function gives an age estimate for the thin disk of 9.5+1.1-0.8 Gyr, without including the effect of phase separation. Using the above numbers, we see that phase separation could add between 0 and 3 Gyr to the white dwarf ages and still be consistent with the overall picture of Galaxy formation. Our calculated maximum value of <~1.5 Gyr fits within these bounds, as does our best-guess value of

Binary Colloidal Alloy Test-5: Phase Separation

NASA Technical Reports Server (NTRS)

Lynch, Matthew; Weitz, David A.; Lu, Peter J.

2008-01-01

The Binary Colloidal Alloy Test - 5: Phase Separation (BCAT-5-PhaseSep) experiment will photograph initially randomized colloidal samples onboard the ISS to determine their resulting structure over time. This allows the scientists to capture the kinetics (evolution) of their samples, as well as the final equilibrium state of each sample. BCAT-5-PhaseSep studies collapse (phase separation rates that impact product shelf-life); in microgravity the physics of collapse is not masked by being reduced to a simple top and bottom phase as it is on Earth.

Separation of aqueous two-phase polymer systems in microgravity

NASA Technical Reports Server (NTRS)

Vanalstine, J. M.; Harris, J. M.; Synder, S.; Curreri, P. A.; Bamberger, S. B.; Brooks, D. E.

1984-01-01

Phase separation of polymer systems in microgravity is studied in aircraft flights to prepare shuttle experiments. Short duration (20 sec) experiments demonstrate that phase separation proceeds rapidly in low gravity despite appreciable phase viscosities and low liquid interfacial tensions (i.e., 50 cP, 10 micro N/m). Ostwald ripening does not appear to be a satisfactory model for the phase separation mechanism. Polymer coated surfaces are evaluated as a means to localize phases separated in low gravity. Contact angle measurements demonstrate that covalently coupling dextran or PEG to glass drastically alters the 1-g wall wetting behavior of the phases in dextran-PEG two phase systems.

In Situ Observations of Thermoreversible Gelation and Phase Separation of Agarose and Methylcellulose Solutions under High Pressure.

PubMed

Kometani, Noritsugu; Tanabe, Masahiro; Su, Lei; Yang, Kun; Nishinari, Katsuyoshi

2015-06-04

Thermoreversible sol-gel transitions of agarose and methylcellulose (MC) aqueous solutions on isobaric cooling or heating under high pressure up to 400 MPa have been investigated by in situ observations of optical transmittance and falling-ball experiments. For agarose, which undergoes the gelation on cooling, the application of pressure caused a gradual rise in the cloud-point temperature over the whole pressure range examined, which is almost consistent with the pressure dependence of gelling temperature estimated by falling-ball experiments, suggesting that agarose gel is stabilized by compression and that the gelation occurs nearly in parallel with phase separation under ambient and high-pressure conditions. For MC, which undergoes the gelation on heating, the cloud-point temperature showed a slight rise with an initial elevation of pressure up to ∼150 MPa, whereas it showed a marked depression above 200 MPa. In contrast, the gelling temperature of MC, which is nearly identical to the cloud-point temperature at ambient pressure, showed a monotonous rise with increasing pressure up to 350 MPa, which means that MC undergoes phase separation prior to gelation on heating under high pressure above 200 MPa. Similar results were obtained for the melting process of MC gel on cooling. The unique behavior of the sol-gel transition of MC under high pressure has been interpreted in terms of the destruction of hydrophobic hydration by compression.

Texas A&M vortex type phase separator

NASA Astrophysics Data System (ADS)

Best, Frederick

2000-01-01

Phase separation is required for regenerative biological and chemical process systems as well as thermal transport and rejection systems. Liquid and gas management requirements for future spacecraft will demand small, passive systems able to operate over wide ranges of inlet qualities. Conservation and recycling of air and water is a necessary part of the construction and operation of the International Space Station as well as future long duration space missions. Space systems are sensitive to volume, mass, and power. Therefore, it is necessary to develop a method to recycle wastewater with minimal power consumption. Regenerative life support systems currently being investigated require phase separation to separate the liquid from the gas produced. The microgravity phase separator designed and fabricated at Texas A&M University relies on centripetal driven buoyancy forces to form a gas-liquid vortex within a fixed, right-circular cylinder. Two-phase flow is injected tangentially along the inner wall of this cylinder producing a radial acceleration gradient. The gradient produced from the intrinsic momentum of the injected mixture results in a rotating flow that drives the buoyancy process by the production of a hydrostatic pressure gradient. Texas A&M has flown several KC-135 flights with separator. These flights have included scaling studies, stability and transient investigations, and tests for inventory instrumentation. Among the hardware tested have been passive devices for separating mixed vapor/liquid streams into single-phase streams of vapor only and liquid only. .

Polymerization- and Solvent-Induced Phase Separation in Hydrophilic-rich Dentin Adhesive Mimic

PubMed Central

Abedin, Farhana; Ye, Qiang; Good, Holly J; Parthasarathy, Ranganathan; Spencer, Paulette

2014-01-01

Current dental resin undergoes phase separation into hydrophobic-rich and hydrophilic-rich phases during infiltration of the over-wet demineralized collagen matrix. Such phase separation undermines the integrity and durability of the bond at the composite/tooth interface. This study marks the first time that the polymerization kinetics of model hydrophilic-rich phase of dental adhesive has been determined. Samples were prepared by adding varying water content to neat resins made from 95 and 99wt% hydroxyethylmethacrylate (HEMA) and 5 and 1wt% (2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl1]-propane (BisGMA) prior to light curing. Viscosity of the formulations decreased with increased water content. The photo-polymerization kinetics study was carried out by time-resolved FTIR spectrum collector. All of the samples exhibited two-stage polymerization behavior which has not been reported previously for dental resin formulation. The lowest secondary rate maxima were observed for water content of 10-30%wt. Differential scanning calorimetry (DSC) showed two glass transition temperatures for the hydrophilic-rich phase of dental adhesive. The DSC results indicate that the heterogeneity within the final polymer structure decreased with increased water content. The results suggest a reaction mechanism involving both polymerization-induced phase separation (PIPs) and solvent-induced phase separation (SIPs) for the model hydrophilic-rich phase of dental resin. PMID:24631658

Polymer depletion-driven cluster aggregation and initial phase separation in charged nanosized colloids

NASA Astrophysics Data System (ADS)

Gögelein, Christoph; Nägele, Gerhard; Buitenhuis, Johan; Tuinier, Remco; Dhont, Jan K. G.

2009-05-01

We study polymer depletion-driven cluster aggregation and initial phase separation in aqueous dispersions of charge-stabilized silica spheres, where the ionic strength and polymer (dextran) concentration are systematically varied, using dynamic light scattering and visual observation. Without polymers and for increasing salt and colloid content, the dispersions become increasingly unstable against irreversible cluster formation. By adding nonadsorbing polymers, a depletion-driven attraction is induced, which lowers the stabilizing Coulomb barrier and enhances the cluster growth rate. The initial growth rate increases with increasing polymer concentration and decreases with increasing polymer molar mass. These observations can be quantitatively understood by an irreversible dimer formation theory based on the classical Derjaguin, Landau, Verwey, and Overbeek pair potential, with the depletion attraction modeled by the Asakura-Oosawa-Vrij potential. At low colloid concentration, we observe an exponential cluster growth rate for all polymer concentrations considered, indicating a reaction-limited aggregation mechanism. At sufficiently high polymer and colloid concentrations, and lower salt content, a gas-liquidlike demixing is observed initially. Later on, the system separates into a gel and fluidlike phase. The experimental time-dependent state diagram is compared to the theoretical equilibrium phase diagram obtained from a generalized free-volume theory and is discussed in terms of an initial reversible phase separation process in combination with irreversible aggregation at later times.

Polymer depletion-driven cluster aggregation and initial phase separation in charged nanosized colloids.

PubMed

Gögelein, Christoph; Nägele, Gerhard; Buitenhuis, Johan; Tuinier, Remco; Dhont, Jan K G

2009-05-28

We study polymer depletion-driven cluster aggregation and initial phase separation in aqueous dispersions of charge-stabilized silica spheres, where the ionic strength and polymer (dextran) concentration are systematically varied, using dynamic light scattering and visual observation. Without polymers and for increasing salt and colloid content, the dispersions become increasingly unstable against irreversible cluster formation. By adding nonadsorbing polymers, a depletion-driven attraction is induced, which lowers the stabilizing Coulomb barrier and enhances the cluster growth rate. The initial growth rate increases with increasing polymer concentration and decreases with increasing polymer molar mass. These observations can be quantitatively understood by an irreversible dimer formation theory based on the classical Derjaguin, Landau, Verwey, and Overbeek pair potential, with the depletion attraction modeled by the Asakura-Oosawa-Vrij potential. At low colloid concentration, we observe an exponential cluster growth rate for all polymer concentrations considered, indicating a reaction-limited aggregation mechanism. At sufficiently high polymer and colloid concentrations, and lower salt content, a gas-liquidlike demixing is observed initially. Later on, the system separates into a gel and fluidlike phase. The experimental time-dependent state diagram is compared to the theoretical equilibrium phase diagram obtained from a generalized free-volume theory and is discussed in terms of an initial reversible phase separation process in combination with irreversible aggregation at later times.

Hybrid films with phase-separated domains: A new class of functional materials

NASA Astrophysics Data System (ADS)

Kang, Minjee; Leal, Cecilia

The cell membrane is highly compartmentalized over micro-and nano scale. The compartmentalized domains play an important role in regulating the diffusion and distribution of species within and across the membrane. In this work, we introduced nanoscale heterogeneities into lipid films for the purpose of developing nature-mimicking phase-separated materials. The mixtures of phospholipids and amphiphilic block copolymers self-assemble into supported 1D multi-bilayers. We observed that in each lamella, mixtures of lipid and polymer phase-separate into domains that differ in their composition akin to sub-phases in cholesterol-containing lipid bilayers. Interestingly, we found evidence that like-domains are in registry across multilayers, making phase separation three-dimensional. To exploit such distinctive domain structure for surface-mediated drug delivery, we incorporated pharmaceutical molecules into the films. The drug release study revealed that the presence of domains in hybrid films modifies the diffusion pathways of drugs that become confined within phase-separated domains. A comprehensive domain structure coupled with drug diffusion pathways in films will be presented, offering new perspectives in designing a thin-film matrix system for controlled drug delivery. This work was supported by the National Science Foundation under Grant No. DMR-1554435.

Chromatographic Separations Using Solid-Phase Extraction Cartridges: Separation of Wine Phenolics

NASA Astrophysics Data System (ADS)

Brenneman, Charles A.; Ebeler, Susan E.

1999-12-01

We describe a simple laboratory experiment that demonstrates the principles of chromatographic separation using solid-phase extraction columns and red wine. By adjusting pH and mobile phase composition, the wine is separated into three fractions of differing polarity. The content of each fraction can be monitored by UV-vis spectroscopy. When the experiment is combined with experiments involving HPLC or GC separations, students gain a greater appreciation for and understanding of the highly automated instrumental systems currently available. In addition, they learn about the chemistry of polyphenolic compounds, which are present in many foods and beverages and which are receiving much attention for their potentially beneficial health effects.

Phase separation and large deviations of lattice active matter

NASA Astrophysics Data System (ADS)

Whitelam, Stephen; Klymko, Katherine; Mandal, Dibyendu

2018-04-01

Off-lattice active Brownian particles form clusters and undergo phase separation even in the absence of attractions or velocity-alignment mechanisms. Arguments that explain this phenomenon appeal only to the ability of particles to move persistently in a direction that fluctuates, but existing lattice models of hard particles that account for this behavior do not exhibit phase separation. Here we present a lattice model of active matter that exhibits motility-induced phase separation in the absence of velocity alignment. Using direct and rare-event sampling of dynamical trajectories, we show that clustering and phase separation are accompanied by pronounced fluctuations of static and dynamic order parameters. This model provides a complement to off-lattice models for the study of motility-induced phase separation.

Phase separation in artificial vesicles driven by light and curvature

NASA Astrophysics Data System (ADS)

Rinaldin, Melissa; Pomp, Wim; Schmidt, Thomas; Giomi, Luca; Kraft, Daniela; Physics of Life Processes Team; Soft; Bio Mechanics Collaboration; Self-Assembly in Soft Matter Systems Collaboration

The role of phase-demixing in living cells, leading to the lipid-raft hypothesis, has been extensively studied. Lipid domains of higher lipid chain order are proposed to regulate protein spatial organization. Giant Unilamellar Vesicles provide an artificial model to study phase separation. So far temperature was used to initiate the process. Here we introduce a new methodology based on the induction of phase separation by light. To this aim, the composition of the lipid membrane is varied by photo-oxidation of lipids. The control of the process gained by using light allowed us to observe vesicle shape fluctuations during phase-demixing. The presence of fluctuations near the critical mixing point resembles features of a critical process. We quantitatively analyze these fluctuations using a 2d elastic model, from which we can estimate the material parameters such as bending rigidity and surface tension, demonstrating the non-equilibrium critical behaviour. Finally, I will describe recent attempts toward tuning the membrane composition by controlling the vesicle curvature.

Role of lipid phase separations and membrane hydration in phospholipid vesicle fusion.

PubMed

Hoekstra, D

1982-06-08

The relationship between lipid phase separation and fusion of small unilamellar phosphatidylserine-containing vesicles was investigated. The kinetics of phase separation were monitored by following the increase of self-quenching of the fluorescent phospholipid analogue N-(7-nitro-2,1,3-benzoxadiazol-4-yl)phosphatidylethanolamine, which occurs when the local concentration of the probe increases upon Ca2+-induced phase separation in phosphatidylserine (PS) bilayers [Hoekstra, D. (1982) Biochemistry 21, 1055-1061]. Fusion was determined by using the resonance energy transfer fusion assay [Struck, D. K., Hoekstra, D., & Pagano, R. E. (1981) Biochemistry 20, 4093-4099], which monitors the mixing of fluorescent lipid donor and acceptor molecules, resulting in an increase in energy transfer efficiency. The results show that in the presence of Ca2+, fusion proceeds much more rapidly (t 1/2 less than 5 s) than the process of phase separation (T 1/2 congruent to 1 min). Mg2+ also induced fusion, albeit at higher concentrations than Ca2+. Mg2+-induced phase separation were not detected, however. Subthreshold concentrations of Ca2+ (0.5 mM) or Mg2+ (2 mM) induced extensive fusion of PS-containing vesicles in poly(ethylene glycol) containing media. This effect did not appear to be a poly(ethylene glycol)-facilitated enhancement of cation binding to the bilayer, and consequently Ca2+-induced phase separation was not observed. The results suggest that macroscopic phase separation may facilitate but does not induced the fusion process and is therefore, not directly involved in the actual fusion mechanism. The fusion experiments performed in the presence of poly(ethylene glycol) suggest that the degree of bilayer dehydration and the creation of "point defects" in the bilayer without rigorous structural rearrangements in the membrane are dominant factors in the initial fusion events.

Stress reduction in phase-separated, cross-linked networks: influence of phase structure and kinetics of reaction

PubMed Central

Szczepanski, Caroline R.; Stansbury, Jeffrey W.

2014-01-01

A mechanism for polymerization shrinkage and stress reduction was developed for heterogeneous networks formed via ambient, photo-initiated polymerization-induced phase separation (PIPS). The material system used consists of a bulk homopolymer matrix of triethylene glycol dimethacrylate (TEGDMA) modified with one of three non-reactive, linear prepolymers (poly-methyl, ethyl and butyl methacrylate). At higher prepolymer loading levels (10–20 wt%) an enhanced reduction in both shrinkage and polymerization stress is observed. The onset of gelation in these materials is delayed to a higher degree of methacrylate conversion (~15–25%), providing more time for phase structure evolution by thermodynamically driven monomer diffusion between immiscible phases prior to network macro-gelation. The resulting phase structure was probed by introducing a fluorescently tagged prepolymer into the matrix. The phase structure evolves from a dispersion of prepolymer at low loading levels to a fully co-continuous heterogeneous network at higher loadings. The bulk modulus in phase separated networks is equivalent or greater than that of poly(TEGDMA), despite a reduced polymerization rate and cross-link density in the prepolymer-rich domains. PMID:25418999

Phase separation in solutions of monoclonal antibodies and the effect of human serum albumin

PubMed Central

Wang, Ying; Lomakin, Aleksey; Latypov, Ramil F.; Benedek, George B.

2011-01-01

We report the observation of liquid-liquid phase separation in a solution of human monoclonal antibody, IgG2, and the effects of human serum albumin, a major blood protein, on this phase separation. We find a significant reduction of phase separation temperature in the presence of albumin, and a preferential partitioning of the albumin into the antibody-rich phase. We provide a general thermodynamic analysis of the antibody-albumin mixture phase diagram and relate its features to the magnitude of the effective interprotein interactions. Our analysis suggests that additives (HSA in this report), which have moderate attraction with antibody molecules, may be used to forestall undesirable proetin condensation in antibody solutions. Our findings are relevant to understanding the stability of pharmaceutical solutions of antibodies and the mechanisms of cryoglobulinemia. PMID:21921237

Laser-induced phase separation of silicon carbide

PubMed Central

Choi, Insung; Jeong, Hu Young; Shin, Hyeyoung; Kang, Gyeongwon; Byun, Myunghwan; Kim, Hyungjun; Chitu, Adrian M.; Im, James S.; Ruoff, Rodney S.; Choi, Sung-Yool; Lee, Keon Jae

2016-01-01

Understanding the phase separation mechanism of solid-state binary compounds induced by laser–material interaction is a challenge because of the complexity of the compound materials and short processing times. Here we present xenon chloride excimer laser-induced melt-mediated phase separation and surface reconstruction of single-crystal silicon carbide and study this process by high-resolution transmission electron microscopy and a time-resolved reflectance method. A single-pulse laser irradiation triggers melting of the silicon carbide surface, resulting in a phase separation into a disordered carbon layer with partially graphitic domains (∼2.5 nm) and polycrystalline silicon (∼5 nm). Additional pulse irradiations cause sublimation of only the separated silicon element and subsequent transformation of the disordered carbon layer into multilayer graphene. The results demonstrate viability of synthesizing ultra-thin nanomaterials by the decomposition of a binary system. PMID:27901015

The effect of protein on phase separation in giant unilamellar lipid vesicles.

NASA Astrophysics Data System (ADS)

Hutchison, J. B.; Weis, R. M.; Dinsmore, A. D.

2009-03-01

We explore the coarsening and out of plane curvature (budding) of domains in lipid bilayer vesicles composed of DOPC (unsaturated), PSM (saturated), and cholesterol. Green fluorescent protein (GFP) was added to the membrane in controlled amounts by binding to the Ni-chelating lipid, Ni-DOGS. Vesicles with diameters between 10 and 50 microns were prepared via a standard electroformation procedure. As a sample is lowered through temperature Tmix, a previously homogeneous vesicle phase separates into two fluid phases with distinct compositions. Phase-separated domains have a line tension (energy/length) at the boundary with the major phase which competes with bending energy and lateral tension to determine the overall configuration of the vesicle. Domain budding and coarsening were observed and recorded using both bright field and fluorescence microscopy during temperature scans and with varying concentrations of GFP. The addition of a model protein into our system allows for a broader understanding of the effect of protein, which are ubiquitous in cell membranes, on phase separation, budding, and coarsening.

Superfluid helium 2 liquid-vapor phase separation: Technology assessment

NASA Technical Reports Server (NTRS)

Lee, J. M.

1984-01-01

A literature survey of helium 2 liquid vapor phase separation is presented. Currently, two types of He 2 phase separators are being investigated: porous, sintered metal plugs and the active phase separator. The permeability K(P) shows consistency in porous plug geometric characterization. Both the heat and mass fluxes increase with K(P). Downstream pressure regulation to adjust for varying heat loads and both temperatures is possible. For large dynamic heat loads, the active phase separator shows a maximum heat rejection rate of up to 2 W and bath temperature stability of 0.1 mK. Porous plug phase separation performance should be investigated for application to SIRTF and, in particular, that plugs of from 10 to the minus ninth square centimeters to 10 to the minus eighth square centimeters in conjunction with downstream pressure regulation be studied.

Low gravity phase separator

NASA Technical Reports Server (NTRS)

Smoot, G. F.; Pope, W. L.; Smith, L. (Inventor)

1977-01-01

An apparatus is described for phase separating a gas-liquid mixture as might exist in a subcritical cryogenic helium vessel for cooling a superconducting magnet at low gravity such as in planetary orbit, permitting conservation of the liquid and extended service life of the superconducting magnet.

Phase Separation in Lean Grade Duplex Stainless Steel 2101

DOE PAGES

Garfinkel, D.; Poplawsky, Jonathan D.; Guo, Wei; ...

2015-08-19

The use of duplex stainless steels (DSS) in nuclear power generation systems is limited by thermal instability that leads to embrittlement in the temperature range of 204°C - 538°C. New lean grade alloys, such as 2101, offer the potential to mitigate these effects. Thermal embrittlement was quantified through impact toughness and hardness testing on samples of alloy 2101 after aging at 427°C for various durations (1-10,000 hours). Additionally, atom probe tomography (APT) was utilized in order to observe the kinetics of α-α’ separation and G-phase formation. Mechanical testing and APT data for two other DSS alloys, 2003 and 2205 weremore » used as a reference to 2101. The results show that alloy 2101 exhibits superior performance compared to the standard grade DSS alloy, 2205, but inferior to the lean grade alloy, 2003, in mechanical testing. APT data demonstrates that the degree of α-α’ separation found in alloy 2101 closely resembles that of 2205, and greatly exceeds 2003. Additionally, contrary to what was observed in 2003, 2101 demonstrated G-phase like precipitates after long aging times, though precipitates were not as abundant as was observed in 2205.« less

Microscopic origin of the magnetoelectronic phase separation in Sr-doped LaCoO3

NASA Astrophysics Data System (ADS)

Németh, Zoltán; Szabó, András; Knížek, Karel; Sikora, Marcin; Chernikov, Roman; Sas, Norbert; Bogdán, Csilla; Nagy, Dénes Lajos; Vankó, György

2013-07-01

The nanoscopic magnetoelectronic phase separation in doped La1-xSrxCoO3 perovskites was studied with local probes. The phase separation is directly observed by Mössbauer spectroscopy in the studied doping range of 0.05 ≤ x ≤ 0.25 both at room temperature and in the low-temperature magnetic phase. Extended with current synchrotron-based x-ray spectroscopies, these data help to characterize the volume as well as the local electric and magnetic properties of the distinct phases. A simple model based on a random distribution of the doping Sr ions describes well both the evolution of the separated phases and the variation of the Co spin state. The experiments suggest that Sr doping initiates small droplets and a high degree of doping-driven cobalt spin-state transition, while the Sr-free second phase vanishes rapidly with increasing Sr content.

Phase Separation of Superconducting Phases in the Penson-Kolb-Hubbard Model

NASA Astrophysics Data System (ADS)

Jerzy Kapcia, Konrad; Czart, Wojciech Robert; Ptok, Andrzej

2016-04-01

In this paper, we determine the phase diagrams (for T = 0 as well as T > 0) of the Penson-Kolb-Hubbard model for two dimensional square lattice within Hartree-Fock mean-field theory focusing on an investigation of superconducting phases and on a possibility of the occurrence of the phase separation. We obtain that the phase separation, which is a state of coexistence of two different superconducting phases (with s- and η-wave symmetries), occurs in definite ranges of the electron concentration. In addition, increasing temperature can change the symmetry of the superconducting order parameter (from η-wave into s-wave). The system considered exhibits also an interesting multicritical behaviour including bicritical points. The relevance of the results to experiments for real materials is also discussed.

Exploring the dynamics of phase separation in colloid-polymer mixtures with long range attraction.

PubMed

Sabin, Juan; Bailey, Arthur E; Frisken, Barbara J

2016-06-28

We have studied the kinetics of phase separation and gel formation in a low-dispersity colloid - non-adsorbing polymer system with long range attraction using small-angle light scattering. This system exhibits two-phase and three-phase coexistence of gas, liquid and crystal phases when the strength of attraction is between 2 and 4kBT and gel phases when the strength of attraction is increased. For those samples that undergo macroscopic phase separation, whether to gas-crystal, gas-liquid or gas-liquid-crystal coexistence, we observe dynamic scaling of the structure factor and growth of a characteristic length scale that behaves as expected for phase separation in fluids. In samples that gel, the power law associated with the growth of the dominant length scale is not equal to 1/3, but appears to depend mainly on the strength of attraction, decreasing from 1/3 for samples near the coexistence region to 1/27 at 8kBT, over a wide range of colloid and polymer concentrations.

Spatially resolved micro-Raman observation on the phase separation of effloresced sea salt droplets.

PubMed

Xiao, Han-Shuang; Dong, Jin-Ling; Wang, Liang-Yu; Zhao, Li-Jun; Wang, Feng; Zhang, Yun-Hong

2008-12-01

We report on the investigation of the phase separation of individual seawater droplets in the efflorescence processes with the spatially resolved Raman system. Upon decreasing the relative humidity (RH), CaSO4.0.5H2O separated out foremost fromthe droplet atan unexpectedly high RH of approcimately 90%. Occasionally, CaSO4.2H2O substituted for CaSO4.O.5H2O crystallizing first at approximately 78% RH. Relatively large NaCI solids followed to crystallize at approximately 55% RH and led to the great loss of the solution. Then, the KMgCl3.6H2O crystallites separated out from the residual solutions, adjacentto NaCl at approximately 44% RH. Moreover, a shell structure of dried sea salt particle was found to form at low RHs, with the NaCl crystals in the core and minor supersaturated solutions covered with MgSO4 gel coating on the surface. Ultimately, the shielded solution partly effloresced into MgSO4 hydrates at very dry state (<5% RH).

Experimental study of phase separation in dividing two phase flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian Yong; Yang Zhilin; Xu Jijun

1996-12-31

Experimental study of phase separation of air-water two phase bubbly, slug flow in the horizontal T-junction is carried out. The influences of the inlet mass quality X1, mass extraction rate G3/G1, and fraction of extracted liquid QL3/QL1 on phase separation characteristics are analyzed. For the first time, the authors have found and defined pulsating run effect by the visual experiments, which show that under certain conditions, the down stream flow of the T-junction has strangely affected the phase redistribution of the junction, and firstly point out that the downstream geometric condition is very important to the study of phase separationmore » phenomenon of two-phase flow in a T-junction. This kind of phenomenon has many applications in the field of energy, power, petroleum and chemical industries, such as the loss of coolant accident (LOCA) caused by a small break in a horizontal coolant pipe in nuclear reactor, and the flip-flop effect in the natural gas transportation pipeline system, etc.« less

The Role of RNA in Biological Phase Separations.

PubMed

Fay, Marta M; Anderson, Paul J

2018-05-10

Phase transitions that alter the physical state of ribonucleoprotein particles contribute to the spacial and temporal organization of the densely packed intracellular environment. This allows cells to organize biologically coupled processes as well as respond to environmental stimuli. RNA plays a key role in phase separation events that modulate various aspects of RNA metabolism. Here, we review the role that RNA plays in ribonucleoprotein phase separations. Copyright © 2018 Elsevier Ltd. All rights reserved.

Origin of Reversible Photoinduced Phase Separation in Hybrid Perovskites.

PubMed

Bischak, Connor G; Hetherington, Craig L; Wu, Hao; Aloni, Shaul; Ogletree, D Frank; Limmer, David T; Ginsberg, Naomi S

2017-02-08

The distinct physical properties of hybrid organic-inorganic materials can lead to unexpected nonequilibrium phenomena that are difficult to characterize due to the broad range of length and time scales involved. For instance, mixed halide hybrid perovskites are promising materials for optoelectronics, yet bulk measurements suggest the halides reversibly phase separate upon photoexcitation. By combining nanoscale imaging and multiscale modeling, we find that the nature of halide demixing in these materials is distinct from macroscopic phase separation. We propose that the localized strain induced by a single photoexcited charge interacting with the soft, ionic lattice is sufficient to promote halide phase separation and nucleate a light-stabilized, low-bandgap, ∼8 nm iodide-rich cluster. The limited extent of this polaron is essential to promote demixing because by contrast bulk strain would simply be relaxed. Photoinduced phase separation is therefore a consequence of the unique electromechanical properties of this hybrid class of materials. Exploiting photoinduced phase separation and other nonequilibrium phenomena in hybrid materials more generally could expand applications in sensing, switching, memory, and energy storage.

Fine mist versus large droplets in phase separated manganites

NASA Astrophysics Data System (ADS)

Khomskii, D.; Khomskii, L.

2003-02-01

The properties of phase-separated systems, e.g., manganites close to a first-order phase transition between charge-ordered insulator and ferromagnetic metal, are usually described by percolation picture. We argue that the correlated occupation of metallic sites leads to the preferential formation of larger metallic clusters, and their size distribution depends on the thermal history. This can explain several puzzling effects in manganites, such as the often observed inverse, or “overshot” hysteresis, and the recently discovered thermal cycling effect. Thus in treating this and similar systems in percolation picture, not only the total concentration of metallic phase, but also the distribution of metallic clusters by shape and size may significantly influence the properties of the system and has to be taken into account.

Electronic phase separation at the LaAlO₃/SrTiO₃ interface.

PubMed

Ariando; Wang, X; Baskaran, G; Liu, Z Q; Huijben, J; Yi, J B; Annadi, A; Barman, A Roy; Rusydi, A; Dhar, S; Feng, Y P; Ding, J; Hilgenkamp, H; Venkatesan, T

2011-02-08

There are many electronic and magnetic properties exhibited by complex oxides. Electronic phase separation (EPS) is one of those, the presence of which can be linked to exotic behaviours, such as colossal magnetoresistance, metal-insulator transition and high-temperature superconductivity. A variety of new and unusual electronic phases at the interfaces between complex oxides, in particular between two non-magnetic insulators LaAlO(3) and SrTiO(3), have stimulated the oxide community. However, no EPS has been observed in this system despite a theoretical prediction. Here, we report an EPS state at the LaAlO(3)/SrTiO(3) interface, where the interface charges are separated into regions of a quasi-two-dimensional electron gas, a ferromagnetic phase, which persists above room temperature, and a (superconductor like) diamagnetic/paramagnetic phase below 60 K. The EPS is due to the selective occupancy (in the form of 2D-nanoscopic metallic droplets) of interface sub-bands of the nearly degenerate Ti orbital in the SrTiO(3). The observation of this EPS demonstrates the electronic and magnetic phenomena that can emerge at the interface between complex oxides mediated by the Ti orbital.

Electron irradiation induced phase separation in a sodium borosilicate glass

NASA Astrophysics Data System (ADS)

Sun, K.; Wang, L. M.; Ewing, R. C.; Weber, W. J.

2004-06-01

Electron irradiation induced phase separation in a sodium borosilicate glass was studied in situ by analytical electron microscopy. Distinctly separate phases that are rich in boron and silicon formed at electron doses higher than 4.0 × 10 11 Gy during irradiation. The separated phases are still in amorphous states even at a much high dose (2.1 × 10 12 Gy). It indicates that most silicon atoms remain tetrahedrally coordinated in the glass during the entire irradiation period, except some possible reduction to amorphous silicon. The particulate B-rich phase that formed at high dose was identified as amorphous boron that may contain some oxygen. Both ballistic and ionization processes may contribute to the phase separation.

Therapeutic Antibody Engineering To Improve Viscosity and Phase Separation Guided by Crystal Structure.

PubMed

Chow, Chi-Kin; Allan, Barrett W; Chai, Qing; Atwell, Shane; Lu, Jirong

2016-03-07

Antibodies at high concentrations often reveal unanticipated biophysical properties suboptimal for therapeutic development. The purpose of this work was to explore the use of point mutations based on crystal structure information to improve antibody physical properties such as viscosity and phase separation (LLPS) at high concentrations. An IgG4 monoclonal antibody (Mab4) that exhibited high viscosity and phase separation at high concentration was used as a model system. Guided by the crystal structure, four CDR point mutants were made to evaluate the role of hydrophobic and charge interactions on solution behavior. Surprisingly and unpredictably, two of the charge mutants, R33G and N35E, showed a reduction in viscosity and a lower propensity to form LLPS at high concentration compared to the wild-type (WT), while a third charge mutant S28K showed an increased propensity to form LLPS compared to the WT. A fourth mutant, F102H, had reduced hydrophobicity, but unchanged viscosity and phase separation behavior. We further evaluated the correlation of various biophysical measurements including second virial coefficient (A2), interaction parameter (kD), weight-average molecular weight (WAMW), and hydrodynamic diameters (DH), at relatively low protein concentration (4 to 15 mg/mL) to physical properties, such as viscosity and liquid-liquid phase separation (LLPS), at high concentration. Surprisingly, kD measured using dynamic light scattering (DLS) at low antibody concentration correlated better with viscosity and phase separation than did A2 for Mab4. Our results suggest that the high viscosity and phase separation observed at high concentration for Mab4 are mainly driven by charge and not hydrophobicity.

Cell separation in immunoaffinity partition in aqueous polymer two-phase systems

NASA Technical Reports Server (NTRS)

Karr, Laurel J.; Van Alstine, James M.; Snyder, Robert S.; Shafer, Steven G.; Harris, J. Milton

1989-01-01

Two methods for immunoaffinity partitioning are described. One technique involves the covalent coupling of poly (ethylene glycol) (PEG) to immunoglobulin G antibody preparations. In the second method PEG-modified Protein A is used to complex with cells and unmodified antibody. The effects of PEG molecular weight, the degree of modification, and varying phase system composition on antibody activity and its affinity for the upper phase are studied. It is observed that both methods resulted in effective cell separation.

Pharmaceutical Perspective on Opalescence and Liquid-Liquid Phase Separation in Protein Solutions.

PubMed

Raut, Ashlesha S; Kalonia, Devendra S

2016-05-02

Opalescence in protein solutions reduces aesthetic appeal of a formulation and can be an indicator of the presence of aggregates or precursor to phase separation in solution signifying reduced product stability. Liquid-liquid phase separation of a protein solution into a protein-rich and a protein-poor phase has been well-documented for globular proteins and recently observed for monoclonal antibody solutions, resulting in physical instability of the formulation. The present review discusses opalescence and liquid-liquid phase separation (LLPS) for therapeutic protein formulations. A brief discussion on theoretical concepts based on thermodynamics, kinetics, and light scattering is presented. This review also discusses theoretical concepts behind intense light scattering in the vicinity of the critical point termed as "critical opalescence". Both opalescence and LLPS are affected by the formulation factors including pH, ionic strength, protein concentration, temperature, and excipients. Literature reports for the effect of these formulation factors on attractive protein-protein interactions in solution as assessed by the second virial coefficient (B2) and the cloud-point temperature (Tcloud) measurements are also presented. The review also highlights pharmaceutical implications of LLPS in protein solutions.

Synthetic oligonucleotide separations by mixed-mode reversed-phase/weak anion-exchange liquid chromatography.

PubMed

Zimmermann, Aleksandra; Greco, Roberto; Walker, Isabel; Horak, Jeannie; Cavazzini, Alberto; Lämmerhofer, Michael

2014-08-08

Synthetic oligonucleotides gain increasing importance in new therapeutic concepts and as probes in biological sciences. If pharmaceutical-grade purities are required, chromatographic purification using ion-pair reversed-phase chromatography is commonly carried out. However, separation selectivity for structurally closely related impurities is often insufficient, especially at high sample loads. In this study, a "mixed-mode" reversed-phase/weak anion exchanger stationary phase has been investigated as an alternative tool for chromatographic separation of synthetic oligonucleotides with minor sequence variations. The employed mixed-mode phase shows great flexibility in method development. It has been run in various gradient elution modes, viz. one, two or three parameter (mixed) gradients (altering buffer pH, buffer concentration, and organic modifier) to find optimal elution conditions and gain further insight into retention mechanisms. Compared to ion-pair reversed-phase and mere anion-exchange separation, enhanced selectivities were observed with the mixed-mode phase for 20-23 nucleotide (nt) long oligonucleotides with similar sequences. Oligonucleotides differing by 1, 2 or 3 nucleotides in length could be readily resolved and separation factors for single nucleotide replacements declined in the order Cytosine (C)/Guanine (G)>Adenine (A)/Guanine∼Guanine/Thymine (T)>Adenine/Cytosine∼Cytosine/Thymine>Adenine/Thymine. Selectivities were larger when the modification was at the 3' terminal-end, declined when it was in the middle of the sequence and was smallest when it was located at the 5' terminus. Due to the lower surface area of the 200Å pore size mixed-mode stationary phase compared to the corresponding 100Å material, lower retention times with equal selectivities under milder elution conditions were achievable. Considering high sample loading capacities of the mixed-mode anion-exchanger phase, it should have great potential for chromatographic

Phase separation and the formation of cellular bodies

NASA Astrophysics Data System (ADS)

Xu, Bin; Broedersz, Chase P.; Meir, Yigal; Wingreen, Ned S.

Cellular bodies in eukaryotic cells spontaneously assemble to form cellular compartments. Among other functions, these bodies carry out essential biochemical reactions. Cellular bodies form micron-sized structures, which, unlike canonical cell organelles, are not surrounded by membranes. A recent in vitro experiment has shown that phase separation of polymers in solution can explain the formation of cellular bodies. We constructed a lattice-polymer model to capture the essential mechanism leading to this phase separation. We used both analytical and numerical tools to predict the phase diagram of a system of two interacting polymers, including the concentration of each polymer type in the condensed and dilute phase.

Dynamics of crowding-induced mixing in phase separated lipid bilayers

DOE PAGES

Zeno, Wade F.; Johnson, Kaitlin E.; Sasaki, Darryl Y.; ...

2016-10-10

We use fluorescence microscopy to examine the dynamics of the crowding-induced mixing transition of liquid ordered (L o)–liquid disordered (L d) phase separated lipid bilayers when the following particles of increasing size bind to either the L o or L d phase: Ubiquitin, green fluorescent protein (GFP), and nanolipoprotein particles (NLPs) of two diameters. These proteinaceous particles contained histidine-tags, which were phase targeted by binding to iminodiacetic acid (IDA) head groups, via a Cu 2+ chelating mechanism, of lipids that specifically partition into either the Lo phase or Ld phase. The degree of steric pressure was controlled by varying themore » size of the bound particle (10–240 kDa) and the amount of binding sites present (i.e., DPIDA concentrations of 9 and 12 mol%) in the supported lipid multibilayer platform used here. We develop a mass transfer-based diffusional model to analyze the observed L o phase domain dissolution that, along with visual observations and activation energy calculations, provides insight into the sequence of events in crowding-induced mixing. Furthermore, our results suggest that the degree of steric pressure and target phase influence not only the efficacy of steric-pressure induced mixing, but the rate and controlling mechanism for which it occurs.« less

Variation in pH of Model Secondary Organic Aerosol during Liquid-Liquid Phase Separation.

PubMed

Dallemagne, Magda A; Huang, Xiau Ya; Eddingsaas, Nathan C

2016-05-12

The majority of atmospheric aerosols consist of both organic and inorganic components. At intermediate relative humidity (RH), atmospheric aerosol can undergo liquid-liquid phase separation (LLPS) in which the organic and inorganic fractions segregate from each other. We have extended the study of LLPS to the effect that phase separation has on the pH of the overall aerosols and the pH of the individual phases. Using confocal microscopy and pH sensitive dyes, the pH of internally mixed model aerosols consisting of polyethylene glycol 400 and ammonium sulfate as well as the pH of the organic fraction during LLPS have been directly measured. During LLPS, the pH of the organic fraction was observed to increase to 4.2 ± 0.2 from 3.8 ± 0.1 under high RH when the aerosol was internally mixed. In addition, the high spatial resolution of the confocal microscope allowed us to characterize the composition of each of the phases, and we have observed that during LLPS the organic shell still contains large quantities of water and should be characterized as an aqueous organic-rich phase rather than simply an organic phase.

Scaling behavior of nonisothermal phase separation.

PubMed

Rüllmann, Max; Alig, Ingo

2004-04-22

The phase separation process in a critical mixture of polydimethylsiloxane and polyethylmethylsiloxane (PDMS/PEMS, a system with an upper critical solution temperature) was investigated by time-resolved light scattering during continuous quenches from the one-phase into the two-phase region. Continuous quenches were realized by cooling ramps with different cooling rates kappa. Phase separation kinetics is studied by means of the temporal evolution of the scattering vector qm and the intensity Im at the scattering peak. The curves qm(t) for different cooling rates can be shifted onto a single mastercurve. The curves Im(t) show similar behavior. As shift factors, a characteristic length Lc and a characteristic time tc are introduced. Both characteristic quantities depend on the cooling rate through power laws: Lc approximately kappa(-delta) and tc approximately kappa(-rho). Scaling behavior in isothermal critical demixing is well known. There the temporal evolutions of qm and Im for different quench depths DeltaT can be scaled with the correlation length xi and the interdiffusion coefficient D, both depending on DeltaT through critical power laws. We show in this paper that the cooling rate scaling in nonisothermal demixing is a consequence of the quench depth scaling in the isothermal case. The exponents delta and rho are related to the critical exponents nu and nu* of xi and D, respectively. The structure growth during nonisothermal demixing can be described with a semiempirical model based on the hydrodynamic coarsening mechanism well known in the isothermal case. In very late stages of nonisothermal phase separation a secondary scattering maximum appears. This is due to secondary demixing. We explain the onset of secondary demixing by a competition between interdiffusion and coarsening. (c) 2004 American Institute of Physics

Bioinspired phase-separated disordered nanostructures for thin photovoltaic absorbers.

PubMed

Siddique, Radwanul H; Donie, Yidenekachew J; Gomard, Guillaume; Yalamanchili, Sisir; Merdzhanova, Tsvetelina; Lemmer, Uli; Hölscher, Hendrik

2017-10-01

The wings of the black butterfly, Pachliopta aristolochiae , are covered by micro- and nanostructured scales that harvest sunlight over a wide spectral and angular range. Considering that these properties are particularly attractive for photovoltaic applications, we analyze the contribution of these micro- and nanostructures, focusing on the structural disorder observed in the wing scales. In addition to microspectroscopy experiments, we conduct three-dimensional optical simulations of the exact scale structure. On the basis of these results, we design nanostructured thin photovoltaic absorbers of disordered nanoholes, which combine efficient light in-coupling and light-trapping properties together with a high angular robustness. Finally, inspired by the phase separation mechanism of self-assembled biophotonic nanostructures, we fabricate these bioinspired absorbers using a scalable, self-assembly patterning technique based on the phase separation of binary polymer mixture. The nanopatterned absorbers achieve a relative integrated absorption increase of 90% at a normal incident angle of light to as high as 200% at large incident angles, demonstrating the potential of black butterfly structures for light-harvesting purposes in thin-film solar cells.

Bioinspired phase-separated disordered nanostructures for thin photovoltaic absorbers

PubMed Central

Siddique, Radwanul H.; Donie, Yidenekachew J.; Gomard, Guillaume; Yalamanchili, Sisir; Merdzhanova, Tsvetelina; Lemmer, Uli; Hölscher, Hendrik

2017-01-01

The wings of the black butterfly, Pachliopta aristolochiae, are covered by micro- and nanostructured scales that harvest sunlight over a wide spectral and angular range. Considering that these properties are particularly attractive for photovoltaic applications, we analyze the contribution of these micro- and nanostructures, focusing on the structural disorder observed in the wing scales. In addition to microspectroscopy experiments, we conduct three-dimensional optical simulations of the exact scale structure. On the basis of these results, we design nanostructured thin photovoltaic absorbers of disordered nanoholes, which combine efficient light in-coupling and light-trapping properties together with a high angular robustness. Finally, inspired by the phase separation mechanism of self-assembled biophotonic nanostructures, we fabricate these bioinspired absorbers using a scalable, self-assembly patterning technique based on the phase separation of binary polymer mixture. The nanopatterned absorbers achieve a relative integrated absorption increase of 90% at a normal incident angle of light to as high as 200% at large incident angles, demonstrating the potential of black butterfly structures for light-harvesting purposes in thin-film solar cells. PMID:29057320

Self-assembly of amorphous biophotonic nanostructures by phase separation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dufresne, Eric R.; Noh, Heeso; Saranathan, Vinodkumar

2009-04-23

Some of the most vivid colors in the animal kingdom are created not by pigments, but by wavelength-selective scattering of light from nanostructures. Here we investigate quasi-ordered nanostructures of avian feather barbs which produce vivid non-iridescent colors. These {beta}-keratin and air nanostructures are found in two basic morphologies: tortuous channels and amorphous packings of spheres. Each class of nanostructure is isotropic and has a pronounced characteristic length scale of variation in composition. These local structural correlations lead to strong backscattering over a narrow range of optical frequencies and little variation with angle of incidence. Such optical properties play important rolesmore » in social and sexual communication. To be effective, birds need to precisely control the development of these nanoscale structures, yet little is known about how they grow. We hypothesize that multiple lineages of birds have convergently evolved to exploit phase separation and kinetic arrest to self-assemble spongy color-producing nanostructures in feather barbs. Observed avian nanostructures are strikingly similar to those self-assembled during the phase separation of fluid mixtures; the channel and sphere morphologies are characteristic of phase separation by spinodal decomposition and nucleation and growth, respectively. These unstable structures are locked-in by the kinetic arrest of the {beta}-keratin matrix, likely through the entanglement or cross-linking of supermolecular {beta}-keratin fibers. Using the power of self-assembly, birds can robustly realize a diverse range of nanoscopic morphologies with relatively small physical and chemical changes during feather development.« less

Cluster formation and phase separation in heteronuclear Janus dumbbells

NASA Astrophysics Data System (ADS)

Munaò, G.; O'Toole, P.; Hudson, T. S.; Costa, D.; Caccamo, C.; Sciortino, F.; Giacometti, A.

2015-06-01

We have recently investigated the phase behavior of model colloidal dumbbells constituted by two identical tangent hard spheres, with the first being surrounded by an attractive square-well interaction (Janus dumbbells, Munaó et al 2014 Soft Matter 10 5269). Here we extend our previous analysis by introducing in the model the size asymmetry of the hard-core diameters and study the enriched phase scenario thereby obtained. By employing standard Monte Carlo simulations we show that in such ‘heteronuclear Janus dumbbells’ a larger hard-sphere site promotes the formation of clusters, whereas in the opposite condition a gas-liquid phase separation takes place, with a narrow interval of intermediate asymmetries wherein the two phase behaviors may compete. In addition, some peculiar geometrical arrangements, such as lamellæ, are observed only around the perfectly symmetric case. A qualitative agreement is found with recent experimental results, where it is shown that the roughness of molecular surfaces in heterogeneous dimers leads to the formation of colloidal micelles.

Conducting polymer networks synthesized by photopolymerization-induced phase separation

NASA Astrophysics Data System (ADS)

Yamashita, Yuki; Komori, Kana; Murata, Tasuku; Nakanishi, Hideyuki; Norisuye, Tomohisa; Yamao, Takeshi; Tran-Cong-Miyata, Qui

2018-03-01

Polymer mixtures composed of double networks of a polystyrene derivative (PSAF) and poly(methyl methacrylate) (PMMA) were alternatively synthesized by using ultraviolet (UV) and visible (Vis) light. The PSAF networks were generated by UV irradiation to photodimerize the anthracene (A) moieties labeled on the PSAF chains, whereas PMMA networks were produced by photopolymerization of methyl methacrylate (MMA) monomer and the cross-link reaction using ethylene glycol dimethacrylate (EGDMA) under Vis light irradiation. It was found that phase separation process of these networks can be independently induced and promptly controlled by using UV and Vis light. The characteristic length scale distribution of the resulting co-continuous morphology can be well regulated by the UV and Vis light intensity. In order to confirm and utilize the connectivity of the bicontinuous morphology observed by confocal microscopy, a very small amount, 0.1 wt%, of multi-walled carbon nanotubes (MWCNTs) was introduced into the mixture and the current-voltage (I-V) relationship was subsequently examined. Preliminary data show that MWCNTs are preferentially dispersed in the PSAF-rich continuous domains and the whole mixture became electrically conducting, confirming the connectivity of the observed bi-continuous morphology. The experimental data obtained in this study reveal a promising method to design various scaffolds for conducting soft matter taking advantages of photopolymerization-induced phase separation.

Dynamic evolution of liquid–liquid phase separation during continuous cooling

DOE PAGES

Imhoff, Seth D.; Gibbs, Paul J.; Katz, Martha R.; ...

2015-01-06

Solidification from a multiphase fluid involves many unknown quantities due to the difficulty of predicting the impact of fluid flow on chemical partitioning. Real-time x-ray radiography was used to observe liquid-liquid phase separation in Al 90In 10 prior to solidification. Quantitative image analysis was used to measure the motion and population characteristics of the dispersed indium-rich liquid phase during cooling. Here we determine that the droplet growth characteristics resemble well known steady-state coarsening laws with likely enhancement by concurrent growth due to supersaturation. Simplistic views of droplet motion are found to be insufficient until late in the reaction due tomore » a hydrodynamic instability caused by the large density difference between the dispersed and matrix liquid phases.« less

Phase separation and long-wavelength charge instabilities in spin-orbit coupled systems

NASA Astrophysics Data System (ADS)

Seibold, G.; Bucheli, D.; Caprara, S.; Grilli, M.

2015-01-01

We investigate a two-dimensional electron model with Rashba spin-orbit interaction where the coupling constant g=g(n) depends on the electronic density. It is shown that this dependence may drive the system unstable towards a long-wavelength charge density wave (CDW) where the associated second-order instability occurs in close vicinity to global phase separation. For very low electron densities the CDW instability is nesting-induced and the modulation follows the Fermi momentum kF. At higher density the instability criterion becomes independent of kF and the system may become unstable in a broad momentum range. Finally, upon filling the upper spin-orbit split band, finite momentum instabilities disappear in favor of phase separation alone. We discuss our results with regard to the inhomogeneous phases observed at the LaAlO3/SrTiO3 or LaTiO3/SrTiO3 interfaces.

Stress granule formation via ATP depletion-triggered phase separation

NASA Astrophysics Data System (ADS)

Wurtz, Jean David; Lee, Chiu Fan

2018-04-01

Stress granules (SG) are droplets of proteins and RNA that form in the cell cytoplasm during stress conditions. We consider minimal models of stress granule formation based on the mechanism of phase separation regulated by ATP-driven chemical reactions. Motivated by experimental observations, we identify a minimal model of SG formation triggered by ATP depletion. Our analysis indicates that ATP is continuously hydrolysed to deter SG formation under normal conditions, and we provide specific predictions that can be tested experimentally.

Simulations of irradiated-enhanced segregation and phase separation in Fe–Cu–Mn alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Boyan; Hu, Shenyang; Li, Chengliang

2017-06-13

For reactor pressure vessel steels, the addition of Cu, Mn, and Ni has a positive effect on mechanical, corrosion and radiation resistance properties. However, experiments show that radiation-enhanced segregation and/or phase separation is one of important material property degradation processes. In this work, we developed a model integrating rate theory and phase-field approaches to investigate the effect of irradiation on solute segregation and phase separation. The rate theory is used to describe the accumulation and clustering of radiation defects while the phase-field approach describes the effect of radiation defects on phase stability and microstructure evolution. The Fe-Cu-Mn ternary alloy ismore » taken as a model system. The free energies used in the phase-field model are from CALPHAD. Spatial dependent radiation damage from atomistic simulations is introduced into the simulation cell for a given radiation dose rate. The radiation effect on segregation and phase separation is taken into account through the defect concentration dependence of solute mobility. With the model the effect of temperatures and radiation rates on Cu and Mn segregation and Cu-rich phase nucleation are systematically investigated. The segregation and nucleation mechanisms are analyzed. The simulations demonstrated that the nucleus of Cu precipitates has a core-shell composition profile, i.e., Cu rich at center and Mn rich at the interface, in good agreement with the theoretical calculation as well as experimental observations.« less

Simulations of irradiated-enhanced segregation and phase separation in Fe-Cu-Mn alloys

NASA Astrophysics Data System (ADS)

Li, Boyan; Hu, Shenyang; Li, Chengliang; Li, Qiulin; Chen, Jun; Shu, Guogang; Henager, Chuck, Jr.; Weng, Yuqing; Xu, Ben; Liu, Wei

2017-09-01

For reactor pressure vessel steels, the addition of Cu, Mn, and Ni has a positive effect on their mechanical, corrosion and radiation resistance properties. However, experiments show that radiation-enhanced segregation and/or phase separation is one of the important material property degradation processes. In this work, we develop a model integrating rate theory and phase-field approaches to investigate the effect of irradiation on solute segregation and phase separation. The rate theory is used to describe the accumulation and clustering of radiation defects, while the phase-field approach describes the effect of radiation defects on phase stability and microstructure evolution. The Fe-Cu-Mn ternary alloy is taken as a model system. The free energies used in the phase-field model are from CALPHAD. Spatial dependent radiation damage from atomistic simulations is introduced into the simulation cell for a given radiation dose rate. The radiation effect on segregation and phase separation is taken into account through the defect concentration dependence of solute mobility. Using the model, the effect of temperature and radiation rates on Cu and Mn segregation and Cu-rich phase nucleation were systematically investigated. The segregation and nucleation mechanisms were analyzed. The simulations demonstrate that the nucleus of Cu precipitates has a core-shell composition profile, i.e. Cu-rich at the center and Mn-rich at the interface, in good agreement with theoretical calculations as well as experimental observations.

TES buffer-induced phase separation of aqueous solutions of several water-miscible organic solvents at 298.15 K: phase diagrams and molecular dynamic simulations.

PubMed

Taha, Mohamed; Lee, Ming-Jer

2013-06-28

Water and the organic solvents tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, tert-butanol, acetonitrile, or acetone are completely miscible in all proportions at room temperature. Here, we present new buffering-out phase separation systems that the above mentioned organic aqueous solutions can be induced to form two liquid phases in the presence of a biological buffer 2-[[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]amino]ethanesulfonic acid (TES). The lower liquid phase is rich in water and buffer, and the upper phase is organic rich. This observation has both practical and mechanistic interests. The phase diagrams of these systems were constructed by experimental measurements at ambient conditions. Molecular dynamic (MD) simulations were performed for TES + water + THF system to understand the interactions between TES, water, and organic solvent at molecular level. Several composition-sets for this system, beyond and inside the liquid-liquid phase-splitting region, have been simulated. Interestingly, the MD simulation for compositions inside the phase separation region showed that THF molecules are forced out from the water network to start forming a new liquid phase. The hydrogen-bonds, hydrogen-bonds lifetimes, hydrogen-bond energies, radial distribution functions, coordination numbers, the electrostatic interactions, and the van der Waals interactions between the different pairs have been calculated. Additionally, MD simulations for TES + water + tert-butanol∕acetonitrile∕acetone phase separation systems were simulated. The results from MD simulations provide an explanation for the buffering-out phenomena observed in [TES + water + organic solvent] systems by a mechanism controlled by the competitive interactions of the buffer and the organic solvent with water. The molecular mechanism reported here is helpful for designing new benign separation materials.

Effect of atomic disorder on the magnetic phase separation

NASA Astrophysics Data System (ADS)

Groshev, A. G.; Arzhnikov, A. K.

2018-05-01

The effect of disorder on the magnetic phase separation between the antiferromagnetic and incommensurate helical and phases is investigated. The study is based on the quasi-two-dimensional single-band Hubbard model in the presence of atomic disorder (the Anderson–Hubbard model). A model of binary alloy disorder is considered, in which the disorder is determined by the difference in energy between the host and impurity atomic levels at a fixed impurity concentration. The problem is solved within the theory of functional integration in static approximation. Magnetic phase diagrams are obtained as functions of the temperature, the number of electrons and impurity concentration with allowance for phase separation. It is shown that for the model parameters chosen, the disorder caused by impurities whose atomic-level energy is greater than that of the host atomic levels, leads to qualitative changes in the phase diagram of the impurity-free system. In the opposite case, only quantitative changes occur. The peculiarities of the effect of disorder on the phase separation regions of the quasi-two-dimensional Hubbard model are discussed.

Precipitation phase separation schemes in the Naqu River basin, eastern Tibetan plateau

NASA Astrophysics Data System (ADS)

Liu, Shaohua; Yan, Denghua; Qin, Tianling; Weng, Baisha; Lu, Yajing; Dong, Guoqiang; Gong, Boya

2018-01-01

Precipitation phase has a profound influence on the hydrological processes in the Naqu River basin, eastern Tibetan plateau. However, there are only six meteorological stations with precipitation phase (rainfall/snowfall/sleet) before 1979 within and around the basin. In order to separate snowfall from precipitation, a new separation scheme with S-shaped curve of snowfall proportion as an exponential function of daily mean temperature was developed. The determinations of critical temperatures in the single/two temperature threshold (STT/TTT2) methods were explored accordingly, and the temperature corresponding to the 50 % snowfall proportion (SP50 temperature) is an efficiently critical temperature for the STT, and two critical temperatures in TTT2 can be determined based on the exponential function and SP50 temperature. Then, different separation schemes were evaluated in separating snowfall from precipitation in the Naqu River basin. The results show that the S-shaped curve methods outperform other separation schemes. Although the STT and TTT2 slightly underestimate and overestimate the snowfall when the temperature is higher and colder than SP50 temperature respectively, the monthly and annual separation snowfalls are generally consistent with the observed snowfalls. On the whole, S-shaped curve methods, STT, and TTT2 perform well in separating snowfall from precipitation with the Pearson correlation coefficient of annual separation snowfall above 0.8 and provide possible approaches to separate the snowfall from precipitation for hydrological modelling.

Hydrodynamic effects on phase separation morphologies in evaporating thin films of polymer solutions

NASA Astrophysics Data System (ADS)

Zoumpouli, Garyfalia A.; Yiantsios, Stergios G.

2016-08-01

We examine effects of hydrodynamics on phase separation morphologies developed during drying of thin films containing a volatile solvent and two dissolved polymers. Cahn-Hilliard and Flory-Huggins theories are used to describe the free energy of the phase separating systems. The thin films, considered as Newtonian fluids, flow in response to Korteweg stresses arising due to concentration non-uniformities that develop during solvent evaporation. Numerical simulations are employed to investigate the effects of a Peclet number, defined in terms of system physical properties, as well as the effects of parameters characterizing the speed of evaporation and preferential wetting of the solutes at the gas interface. For systems exhibiting preferential wetting, diffusion alone is known to favor lamellar configurations for the separated phases in the dried film. However, a mechanism of hydrodynamic instability of a short length scale is revealed, which beyond a threshold Peclet number may deform and break the lamellae. The critical Peclet number tends to decrease as the evaporation rate increases and to increase with the tendency of the polymers to selectively wet the gas interface. As the Peclet number increases, the instability moves closer to the gas interface and induces the formation of a lateral segregation template that guides the subsequent evolution of the phase separation process. On the other hand, for systems with no preferential wetting or any other property asymmetries between the two polymers, diffusion alone favors the formation of laterally separated configurations. In this case, concentration perturbation modes that lead to enhanced Korteweg stresses may be favored for sufficiently large Peclet numbers. For such modes, a second mechanism is revealed, which is similar to the solutocapillary Marangoni instability observed in evaporating solutions when interfacial tension increases with the concentration of the non-volatile component. This mechanism may lead

Dynamics of polymerization induced phase separation in reactive polymer blends

NASA Astrophysics Data System (ADS)

Lee, Jaehyung

Mechanisms and dynamics of phase decomposition following polymerization induced phase separation (PIPS) of reactive polymer blends have been investigated experimentally and theoretically. The phenomenon of PIPS is a non-equilibrium and non-linear dynamic process. The mechanism of PIPS has been thought to be a nucleation and growth (NG) type originally, however, newer results indicate spinodal decomposition (SD). In PIPS, the coexistence curve generally passes through the reaction temperature at off-critical compositions, thus phase separation has to be initiated first in the metastable region where nucleation occurs. When the system farther drifts from the metastable to unstable region, the NG structure transforms to the SD bicontinuous morphology. The crossover behavior of PIPS may be called nucleation initiated spinodal decomposition (NISD). The formation of newer domains between the existing ones is responsible for the early stage of PIPS. Since PIPS is non- equilibrium kinetic process, it would not be surprising to discern either or both structures. The phase separation dynamics of DGEBA/CTBN mixtures having various kinds of curing agents from low reactivity to high reactivity and various amount of curing agents were examined at various reaction temperatures. The phase separation behavior was monitored by a quantity of scattered light intensity experimentally and by a quantity of collective structure factor numerically. Prior to the study of phase separation dynamics, a preliminary investigation on the isothermal cure behavior of the mixtures were executed in order to determine reaction kinetics parameters. The cure behavior followed the overall second order reaction kinetics. Next, based on the knowledge obtained from the phase separation dynamics study of DGEBA/CTBN mixtures, the phase separation dynamics of various composition of DGEBA/R45EPI mixtures having MDA as a curing agent were investigated. The phase separation behavior was quite dependent upon the

Ordering-separation phase transitions in a Co3V alloy

NASA Astrophysics Data System (ADS)

Ustinovshchikov, Yu. I.

2017-01-01

The microstructure of the Co3V alloy formed by heat treatment at various temperatures is studied by transmission electron microscopy. Two ordering-separation phase transitions are revealed at temperatures of 400-450 and 800°C. At the high-temperature phase separation, the microstructure consists of bcc vanadium particles and an fcc solid solution; at the low-temperature phase separation, the microstructure is cellular. In the ordering range, the microstructure consists of chemical compound Co3V particles chaotically arranged in the solid solution. The structure of the Co3V alloy is shown not to correspond to the structures indicated in the Co-V phase diagram at any temperatures.

Observations and implications of liquid–liquid phase separation at high relative humidities in secondary organic material produced by α-pinene ozonolysis without inorganic salts

DOE PAGES

Renbaum-Wolff, Lindsay; Song, Mijung; Marcolli, Claudia; ...

2016-07-01

Particles consisting of secondary organic material (SOM) are abundant in the atmosphere. In order to predict the role of these particles in climate, visibility and atmospheric chemistry, information on particle phase state (i.e., single liquid, two liquids and solid) is needed. Our paper focuses on the phase state of SOM particles free of inorganic salts produced by the ozonolysis of α-pinene. Phase transitions were investigated in the laboratory using optical microscopy and theoretically using a thermodynamic model at 290 K and for relative humidities ranging from < 0.5 to 100%. In the laboratory studies, a single phase was observed frommore » 0 to 95% relative humidity (RH) while two liquid phases were observed above 95% RH. For increasing RH, the mechanism of liquid–liquid phase separation (LLPS) was spinodal decomposition. The RH range over which two liquid phases were observed did not depend on the direction of RH change. In the modeling studies, the SOM took up very little water and was a single organic-rich phase at low RH values. At high RH, the SOM underwent LLPS to form an organic-rich phase and a water-rich phase, consistent with the laboratory studies. The presence of LLPS at high RH values can have consequences for the cloud condensation nuclei (CCN) activity of SOM particles. In the simulated Köhler curves for SOM particles, two local maxima were observed. Depending on the composition of the SOM, the first or second maximum can determine the critical supersaturation for activation. Recently researchers have observed inconsistencies between measured CCN properties of SOM particles and hygroscopic growth measured below water saturation (i.e., hygroscopic parameters measured below water saturation were inconsistent with hygroscopic parameters measured above water saturation). Furthermore, the work presented here illustrates that such inconsistencies are expected for systems with LLPS when the water uptake at subsaturated conditions represents the

Structural and hydrodynamic properties of an intrinsically disordered region of a germ cell-specific protein on phase separation

PubMed Central

Brady, Jacob P.; Farber, Patrick J.; Sekhar, Ashok; Lin, Yi-Hsuan; Huang, Rui; Bah, Alaji; Chan, Hue Sun; Forman-Kay, Julie D.; Kay, Lewis E.

2017-01-01

Membrane encapsulation is frequently used by the cell to sequester biomolecules and compartmentalize their function. Cells also concentrate molecules into phase-separated protein or protein/nucleic acid “membraneless organelles” that regulate a host of biochemical processes. Here, we use solution NMR spectroscopy to study phase-separated droplets formed from the intrinsically disordered N-terminal 236 residues of the germ-granule protein Ddx4. We show that the protein within the concentrated phase of phase-separated Ddx4, Ddx4cond, diffuses as a particle of 600-nm hydrodynamic radius dissolved in water. However, NMR spectra reveal sharp resonances with chemical shifts showing Ddx4cond to be intrinsically disordered. Spin relaxation measurements indicate that the backbone amides of Ddx4cond have significant mobility, explaining why high-resolution spectra are observed, but motion is reduced compared with an equivalently concentrated nonphase-separating control. Observation of a network of interchain interactions, as established by NOE spectroscopy, shows the importance of Phe and Arg interactions in driving the phase separation of Ddx4, while the salt dependence of both low- and high-concentration regions of phase diagrams establishes an important role for electrostatic interactions. The diffusion of a series of small probes and the compact but disordered 4E binding protein 2 (4E-BP2) protein in Ddx4cond are explained by an excluded volume effect, similar to that found for globular protein solvents. No changes in structural propensities of 4E-BP2 dissolved in Ddx4cond are observed, while changes to DNA and RNA molecules have been reported, highlighting the diverse roles that proteinaceous solvents play in dictating the properties of dissolved solutes. PMID:28894006

Operation of a separated-type x-ray interferometer for phase-contrast x-ray imaging

NASA Astrophysics Data System (ADS)

Yoneyama, Akio; Momose, Atsushi; Seya, Eiichi; Hirano, Keiichi; Takeda, Tohoru; Itai, Yuji

1999-12-01

Aiming at large-area phase-contrast x-ray imaging, a separated-type x-ray interferometer system was designed and developed to produce 25×20 mm interference patterns. The skew-symmetric optical system was adopted because of the feasibility of alignment. The rotation between the separated crystal blocks was controlled within a drift of 0.06 nrad using a feedback positioning system. This interferometer generated a 25×15 mm interference pattern with 0.07 nm synchrotron x-rays. A slice of a rabbit's kidney was observed, and its tubular structure could be revealed in a measured phase map.

Nanoscale ferromagnetism in phase-separated manganites

NASA Astrophysics Data System (ADS)

Mori, S.; Horibe, Y.; Asaka, T.; Matsui, Y.; Chen, C. H.; Cheong, S. W.

2007-03-01

Magnetic domain structures in phase-separated manganites were investigated by low-temperature Lorentz electron microscopy, in order to understand some unusual physical properties such as a colossal magnetoresistance (CMR) effect and a metal-to-insulator transition. In particular, we examined a spatial distribution of the charge/orbital-ordered (CO/OO) insulator state and the ferromagnetic (FM) metallic one in phase-separated manganites; Cr-doped Nd0.5Ca0.5MnO3 and ( La1-xPrx)CaMnO3 with x=0.375, by obtaining both the dark-field images and Lorentz electron microscopic ones. It is found that an unusual coexistence of the CO/OO and FM metallic states below a FM transition temperature in the two compounds. The present experimental results clearly demonstrated the coexisting state of the two distinct ground states in manganites.

EXOPLANET ALBEDO SPECTRA AND COLORS AS A FUNCTION OF PLANET PHASE, SEPARATION, AND METALLICITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cahoy, Kerri L.; Marley, Mark S.; Fortney, Jonathan J., E-mail: kerri.l.cahoy@nasa.go

2010-11-20

First generation space-based optical coronagraphic telescopes will obtain images of cool gas- and ice-giant exoplanets around nearby stars. Exoplanets lying at planet-star separations larger than about 1 AU-where an exoplanet can be resolved from its parent star-have spectra that are dominated by reflected light to beyond 1 {mu}m and punctuated by molecular absorption features. Here, we consider how exoplanet albedo spectra and colors vary as a function of planet-star separation, metallicity, mass, and observed phase for Jupiter and Neptune analogs from 0.35 to 1 {mu}m. We model Jupiter analogs with 1x and 3x the solar abundance of heavy elements, andmore » Neptune analogs with 10x and 30x the solar abundance of heavy elements. Our model planets orbit a solar analog parent star at separations of 0.8 AU, 2 AU, 5 AU, and 10 AU. We use a radiative-convective model to compute temperature-pressure profiles. The giant exoplanets are found to be cloud-free at 0.8 AU, possess H{sub 2}O clouds at 2 AU, and have both NH{sub 3} and H{sub 2}O clouds at 5 AU and 10 AU. For each model planet we compute moderate resolution (R = {lambda}/{Delta}{lambda} {approx} 800) albedo spectra as a function of phase. We also consider low-resolution spectra and colors that are more consistent with the capabilities of early direct imaging capabilities. As expected, the presence and vertical structure of clouds strongly influence the albedo spectra since cloud particles not only affect optical depth but also have highly directional scattering properties. Observations at different phases also probe different volumes of atmosphere as the source-observer geometry changes. Because the images of the planets themselves will be unresolved, their phase will not necessarily be immediately obvious, and multiple observations will be needed to discriminate between the effects of planet-star separation, metallicity, and phase on the observed albedo spectra. We consider the range of these combined effects

Formation of structural steady states in lamellar/sponge phase-separating fluids under shear flow

NASA Astrophysics Data System (ADS)

Panizza, P.; Courbin, L.; Cristobal, G.; Rouch, J.; Narayanan, T.

2003-05-01

We investigate the effect of shear flow on a lamellar-sponge phase-separating fluid when subjected to shear flow. We show the existence of two different steady states (droplets and ribbons structures) whose nature does not depend on the way to reach the two-phase unstable region of the phase diagram (temperature quench or stirring). The transition between ribbons and droplets is shear thickening and its nature strongly depends on what dynamical variable is imposed. If the stress is fixed, flow visualization shows the existence of shear bands at the transition, characteristic of coexistence in the cell between ribbons and droplets. In this shear-banding region, the viscosity oscillates. When the shear rate is fixed, no shear bands are observed. Instead, the transition exhibits a hysteretic behavior leading to a structural bi-stability of the phase-separating fluid under flow.

Modeling phase separation in mixtures of intrinsically-disordered proteins

NASA Astrophysics Data System (ADS)

Gu, Chad; Zilman, Anton

Phase separation in a pure or mixed solution of intrinsically-disordered proteins (IDPs) and its role in various biological processes has generated interest from the theoretical biophysics community. Phase separation of IDPs has been implicated in the formation of membrane-less organelles such as nucleoli, as well as in a mechanism of selectivity in transport through the nuclear pore complex. Based on a lattice model of polymers, we study the phase diagram of IDPs in a mixture and describe the selective exclusion of soluble proteins from the dense-phase IDP aggregates. The model captures the essential behaviour of phase separation by a minimal set of coarse-grained parameters, corresponding to the average monomer-monomer and monomer-protein attraction strength, as well as the protein-to-monomer size ratio. Contrary to the intuition that strong monomer-monomer interaction increases exclusion of soluble proteins from the dense IDP aggregates, our model predicts that the concentration of soluble proteins in the aggregate phase as a function of monomer-monomer attraction is non-monotonic. We corroborate the predictions of the lattice model using Langevin dynamics simulations of grafted polymers in planar and cylindrical geometries, mimicking various in-vivo and in-vitro conditions.

Effect of atomic disorder on the magnetic phase separation.

PubMed

Groshev, A G; Arzhnikov, A K

2018-05-10

The effect of disorder on the magnetic phase separation between the antiferromagnetic and incommensurate helical [Formula: see text] and [Formula: see text] phases is investigated. The study is based on the quasi-two-dimensional single-band Hubbard model in the presence of atomic disorder (the [Formula: see text] Anderson-Hubbard model). A model of binary alloy disorder is considered, in which the disorder is determined by the difference in energy between the host and impurity atomic levels at a fixed impurity concentration. The problem is solved within the theory of functional integration in static approximation. Magnetic phase diagrams are obtained as functions of the temperature, the number of electrons and impurity concentration with allowance for phase separation. It is shown that for the model parameters chosen, the disorder caused by impurities whose atomic-level energy is greater than that of the host atomic levels, leads to qualitative changes in the phase diagram of the impurity-free system. In the opposite case, only quantitative changes occur. The peculiarities of the effect of disorder on the phase separation regions of the quasi-two-dimensional Hubbard model are discussed.

Liquid-liquid phase separation in aerosol particles: Imaging at the Nanometer Scale

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Brien, Rachel; Wang, Bingbing; Kelly, Stephen T.

2015-04-21

Atmospheric aerosols can undergo phase transitions including liquid-liquid phase separation (LLPS) while responding to changes in the ambient relative humidity (RH). Here, we report results of chemical imaging experiments using environmental scanning electron microscopy (ESEM) and scanning transmission x-ray microscopy (STXM) to investigate the LLPS of micron sized particles undergoing a full hydration-dehydration cycle. Internally mixed particles composed of ammonium sulfate (AS) and either: limonene secondary organic carbon (LSOC), a, 4-dihydroxy-3-methoxybenzeneaceticacid (HMMA), or polyethylene glycol (PEG-400) were studied. Events of LLPS with apparent core-shell particle morphology were observed for all samples with both techniques. Chemical imaging with STXM showed thatmore » both LSOC/AS and HMMA/AS particles were never homogeneously mixed for all measured RH’s above the deliquescence point and that the majority of the organic component was located in the shell. The shell composition was estimated as 65:35 organic: inorganic in LSOC/AS and as 50:50 organic: inorganic for HMMA/AS. PEG-400/AS particles showed fully homogeneous mixtures at high RH and phase separated below 89-92% RH with an estimated 50:50% organic to inorganic mix in the shell. These two chemical imaging techniques are well suited for in-situ analysis of the hygroscopic behavior, phase separation, and surface composition of collected ambient aerosol particles.« less

Effect of applied strain on phase separation of Fe-28 at.% Cr alloy: 3D phase-field simulation

NASA Astrophysics Data System (ADS)

Zhu, Lihui; Li, Yongsheng; Liu, Chengwei; Chen, Shi; Shi, Shujing; Jin, Shengshun

2018-04-01

A quantitative simulation of the separation of the α‧ phase in Fe-28 at.% Cr alloy under the effects of applied strain is performed by utilizing a three-dimensional phase-field model. The elongation of the Cr-enriched α‧ phase becomes obvious with the influence of applied uniaxial strain for the phase separation transforms from spinodal decomposition of 700 K to nucleation and growth of 773 K. The applied strain shows a significant influence on the early stage phase separation, and the influence is enlarged with the elevated temperature. The steady-state coarsening with the mechanism of spinodal decomposition is substantially affected by the applied strain for low-temperature aging, while the influence is reduced as the temperature increases and as the phase separation mechanism changes to nucleation and growth. The peak value of particle size distribution decreases, and the PSD for 773 K becomes more widely influenced by the applied strain. The simulation results of separation of the Cr-enriched α‧ phase with the applied strain provide a further understanding of the strain effect on the phase separation of Fe-Cr alloys from the metastable region to spinodal regions.

Continuum theory of phase separation kinetics for active Brownian particles.

PubMed

Stenhammar, Joakim; Tiribocchi, Adriano; Allen, Rosalind J; Marenduzzo, Davide; Cates, Michael E

2013-10-04

Active Brownian particles (ABPs), when subject to purely repulsive interactions, are known to undergo activity-induced phase separation broadly resembling an equilibrium (attraction-induced) gas-liquid coexistence. Here we present an accurate continuum theory for the dynamics of phase-separating ABPs, derived by direct coarse graining, capturing leading-order density gradient terms alongside an effective bulk free energy. Such gradient terms do not obey detailed balance; yet we find coarsening dynamics closely resembling that of equilibrium phase separation. Our continuum theory is numerically compared to large-scale direct simulations of ABPs and accurately accounts for domain growth kinetics, domain topologies, and coexistence densities.

Tube radial distribution phenomenon with a two-phase separation solution of a fluorocarbon and hydrocarbon organic solvent mixture in a capillary tube and metal compounds separation.

PubMed

Kitaguchi, Koichi; Hanamura, Naoya; Murata, Masaharu; Hashimoto, Masahiko; Tsukagoshi, Kazuhiko

2014-01-01

A fluorocarbon and hydrocarbon organic solvent mixture is known as a temperature-induced phase-separation solution. When a mixed solution of tetradecafluorohexane as a fluorocarbon organic solvent and hexane as a hydrocarbon organic solvent (e.g., 71:29 volume ratio) was delivered in a capillary tube that was controlled at 10°C, the tube radial distribution phenomenon (TRDP) of the solvents was clearly observed through fluorescence images of the dye, perylene, dissolved in the mixed solution. The homogeneous mixed solution (single phase) changed to a heterogeneous solution (two phases) with inner tetradecafluorohexane and outer hexane phases in the tube under laminar flow conditions, generating the dynamic liquid-liquid interface. We also tried to apply TRDP to a separation technique for metal compounds. A model analyte mixture, copper(II) and hematin, was separated through the capillary tube, and detected with a chemiluminescence detector in this order within 4 min.

Nanoscopy of Phase Separation in InxGa1-xN Alloys.

PubMed

Abate, Yohannes; Seidlitz, Daniel; Fali, Alireza; Gamage, Sampath; Babicheva, Viktoriia; Yakovlev, Vladislav S; Stockman, Mark I; Collazo, Ramon; Alden, Dorian; Dietz, Nikolaus

2016-09-07

Phase separations in ternary/multinary semiconductor alloys is a major challenge that limits optical and electronic internal device efficiency. We have found ubiquitous local phase separation in In1-xGaxN alloys that persists to nanoscale spatial extent by employing high-resolution nanoimaging technique. We lithographically patterned InN/sapphire substrates with nanolayers of In1-xGaxN down to few atomic layers thick that enabled us to calibrate the near-field infrared response of the semiconductor nanolayers as a function of composition and thickness. We also developed an advanced theoretical approach that considers the full geometry of the probe tip and all the sample and substrate layers. Combining experiment and theory, we identified and quantified phase separation in epitaxially grown individual nanoalloys. We found that the scale of the phase separation varies widely from particle to particle ranging from all Ga- to all In-rich regions and covering everything in between. We have found that between 20 and 25% of particles show some level of Ga-rich phase separation over the entire sample region, which is in qualitative agreement with the known phase diagram of In1-xGaxN system.

Phase separation like dynamics during Myxococcus xanthus fruiting body formation

NASA Astrophysics Data System (ADS)

Liu, Guannan; Thutupalli, Shashi; Wigbers, Manon; Shaevitz, Joshua

2015-03-01

Collective motion exists in many living organisms as an advantageous strategy to help the entire group with predation, forage, and survival. However, the principles of self-organization underlying such collective motions remain unclear. During various developmental stages of the soil-dwelling bacterium, Myxococcus xanthus, different types of collective motions are observed. In particular, when starved, M. xanthus cells eventually aggregate together to form 3-dimensional structures (fruiting bodies), inside which cells sporulate in response to the stress. We study the fruiting body formation process as an out of equilibrium phase separation process. As local cell density increases, the dynamics of the aggregation M. xanthus cells switch from a spatio-temporally random process, resembling nucleation and growth, to an emergent pattern formation process similar to a spinodal decomposition. By employing high-resolution microscopy and a video analysis system, we are able to track the motion of single cells within motile collective groups, while separately tuning local cell density, cell velocity and reversal frequency, probing the multi-dimensional phase space of M. xanthus development.

A Temperature-Dependent Phase-Field Model for Phase Separation and Damage

NASA Astrophysics Data System (ADS)

Heinemann, Christian; Kraus, Christiane; Rocca, Elisabetta; Rossi, Riccarda

2017-07-01

In this paper we study a model for phase separation and damage in thermoviscoelastic materials. The main novelty of the paper consists in the fact that, in contrast with previous works in the literature concerning phase separation and damage processes in elastic media, in our model we encompass thermal processes, nonlinearly coupled with the damage, concentration and displacement evolutions. More particularly, we prove the existence of "entropic weak solutions", resorting to a solvability concept first introduced in Feireisl (Comput Math Appl 53:461-490, 2007) in the framework of Fourier-Navier-Stokes systems and then recently employed in Feireisl et al. (Math Methods Appl Sci 32:1345-1369, 2009) and Rocca and Rossi (Math Models Methods Appl Sci 24:1265-1341, 2014) for the study of PDE systems for phase transition and damage. Our global-in-time existence result is obtained by passing to the limit in a carefully devised time-discretization scheme.

Solvent annealing induced phase separation and dewetting in PMMA∕SAN blend film: film thickness and solvent dependence.

PubMed

You, Jichun; Zhang, Shuangshuang; Huang, Gang; Shi, Tongfei; Li, Yongjin

2013-06-28

The competition between "dewetting" and "phase separation" behaviors in polymer blend films attracts significant attention in the last decade. The simultaneous phase separation and dewetting in PMMA∕SAN [poly(methyl methacrylate) and poly(styrene-ran-acrylonitrile)] blend ultrathin films upon solvent annealing have been observed for the first time in our previous work. In this work, film thickness and annealing solvent dependence of phase behaviors in this system has been investigated using atomic force microscopy and grazing incidence small-angle X-ray scattering (GISAXS). On one hand, both vertical phase separation and dewetting take place upon selective solvent vapor annealing, leading to the formation of droplet∕mimic-film structures with various sizes (depending on original film thickness). On the other hand, the whole blend film dewets the substrate and produces dispersed droplets on the silicon oxide upon common solvent annealing. GISAXS results demonstrate the phase separation in the big dewetted droplets resulted from the thicker film (39.8 nm). In contrast, no period structure is detected in small droplets from the thinner film (5.1 nm and 9.7 nm). This investigation indicates that dewetting and phase separation in PMMA∕SAN blend film upon solvent annealing depend crucially on the film thickness and the atmosphere during annealing.

Steric Pressure among Membrane-Bound Polymers Opposes Lipid Phase Separation.

PubMed

Imam, Zachary I; Kenyon, Laura E; Carrillo, Adelita; Espinoza, Isai; Nagib, Fatema; Stachowiak, Jeanne C

2016-04-19

Lipid rafts are thought to be key organizers of membrane-protein complexes in cells. Many proteins that interact with rafts have bulky polymeric components such as intrinsically disordered protein domains and polysaccharide chains. Therefore, understanding the interaction between membrane domains and membrane-bound polymers provides insights into the roles rafts play in cells. Multiple studies have demonstrated that high concentrations of membrane-bound polymeric domains create significant lateral steric pressure at membrane surfaces. Furthermore, our recent work has shown that lateral steric pressure at membrane surfaces opposes the assembly of membrane domains. Building on these findings, here we report that membrane-bound polymers are potent suppressors of membrane phase separation, which can destabilize lipid domains with substantially greater efficiency than globular domains such as membrane-bound proteins. Specifically, we created giant vesicles with a ternary lipid composition, which separated into coexisting liquid ordered and disordered phases. Lipids with saturated tails and poly(ethylene glycol) (PEG) chains conjugated to their head groups were included at increasing molar concentrations. When these lipids were sparse on the membrane surface they partitioned to the liquid ordered phase. However, as they became more concentrated, the fraction of GUVs that were phase-separated decreased dramatically, ultimately yielding a population of homogeneous membrane vesicles. Experiments and physical modeling using compositions of increasing PEG molecular weight and lipid miscibility phase transition temperature demonstrate that longer polymers are the most efficient suppressors of membrane phase separation when the energetic barrier to lipid mixing is low. In contrast, as the miscibility transition temperature increases, longer polymers are more readily driven out of domains by the increased steric pressure. Therefore, the concentration of shorter polymers required

Pi-Pi contacts are an overlooked protein feature relevant to phase separation.

PubMed

Vernon, Robert McCoy; Chong, Paul Andrew; Tsang, Brian; Kim, Tae Hun; Bah, Alaji; Farber, Patrick; Lin, Hong; Forman-Kay, Julie Deborah

2018-02-09

Protein phase separation is implicated in formation of membraneless organelles, signaling puncta and the nuclear pore. Multivalent interactions of modular binding domains and their target motifs can drive phase separation. However, forces promoting the more common phase separation of intrinsically disordered regions are less understood, with suggested roles for multivalent cation-pi, pi-pi, and charge interactions and the hydrophobic effect. Known phase-separating proteins are enriched in pi-orbital containing residues and thus we analyzed pi-interactions in folded proteins. We found that pi-pi interactions involving non-aromatic groups are widespread, underestimated by force-fields used in structure calculations and correlated with solvation and lack of regular secondary structure, properties associated with disordered regions. We present a phase separation predictive algorithm based on pi interaction frequency, highlighting proteins involved in biomaterials and RNA processing. © 2018, Vernon et al.

Pi-Pi contacts are an overlooked protein feature relevant to phase separation

PubMed Central

Vernon, Robert McCoy; Chong, Paul Andrew; Tsang, Brian; Kim, Tae Hun; Bah, Alaji; Farber, Patrick; Lin, Hong

2018-01-01

Protein phase separation is implicated in formation of membraneless organelles, signaling puncta and the nuclear pore. Multivalent interactions of modular binding domains and their target motifs can drive phase separation. However, forces promoting the more common phase separation of intrinsically disordered regions are less understood, with suggested roles for multivalent cation-pi, pi-pi, and charge interactions and the hydrophobic effect. Known phase-separating proteins are enriched in pi-orbital containing residues and thus we analyzed pi-interactions in folded proteins. We found that pi-pi interactions involving non-aromatic groups are widespread, underestimated by force-fields used in structure calculations and correlated with solvation and lack of regular secondary structure, properties associated with disordered regions. We present a phase separation predictive algorithm based on pi interaction frequency, highlighting proteins involved in biomaterials and RNA processing. PMID:29424691

Origin of Reversible Photoinduced Phase Separation in Hybrid Perovskites

NASA Astrophysics Data System (ADS)

Bischak, Connor G.; Hetherington, Craig L.; Wu, Hao; Aloni, Shaul; Ogletree, D. Frank; Limmer, David T.; Ginsberg, Naomi S.

2017-02-01

Nonequilibrium processes occurring in functional materials can significantly impact device efficiencies and are often difficult to characterize due to the broad range of length and time scales involved. In particular, mixed halide hybrid perovskites are promising for optoelectronics, yet the halides reversibly phase separate when photo-excited, significantly altering device performance. By combining nanoscale imaging and multiscale modeling, we elucidate the mechanism underlying this phenomenon, demonstrating that local strain induced by photo-generated polarons promotes halide phase separation and leads to nucleation of light-stabilized iodide-rich clusters. This effect relies on the unique electromechanical properties of hybrid materials, characteristic of neither their organic nor inorganic constituents alone. Exploiting photo-induced phase separation and other nonequilibrium phenomena in hybrid materials, generally, could enable new opportunities for expanding the functional applications in sensing, photoswitching, optical memory, and energy storage.

Conserved interdomain linker promotes phase separation of the multivalent adaptor protein Nck

PubMed Central

Banjade, Sudeep; Wu, Qiong; Mittal, Anuradha; Peeples, William B.; Pappu, Rohit V.; Rosen, Michael K.

2015-01-01

The organization of membranes, the cytosol, and the nucleus of eukaryotic cells can be controlled through phase separation of lipids, proteins, and nucleic acids. Collective interactions of multivalent molecules mediated by modular binding domains can induce gelation and phase separation in several cytosolic and membrane-associated systems. The adaptor protein Nck has three SRC-homology 3 (SH3) domains that bind multiple proline-rich segments in the actin regulatory protein neuronal Wiskott-Aldrich syndrome protein (N-WASP) and an SH2 domain that binds to multiple phosphotyrosine sites in the adhesion protein nephrin, leading to phase separation. Here, we show that the 50-residue linker between the first two SH3 domains of Nck enhances phase separation of Nck/N-WASP/nephrin assemblies. Two linear motifs within this element, as well as its overall positively charged character, are important for this effect. The linker increases the driving force for self-assembly of Nck, likely through weak interactions with the second SH3 domain, and this effect appears to promote phase separation. The linker sequence is highly conserved, suggesting that the sequence determinants of the driving forces for phase separation may be generally important to Nck functions. Our studies demonstrate that linker regions between modular domains can contribute to the driving forces for self-assembly and phase separation of multivalent proteins. PMID:26553976

Freezing-induced phase separation and spatial microheterogeneity in protein solutions.

PubMed

Dong, Jinping; Hubel, Allison; Bischof, John C; Aksan, Alptekin

2009-07-30

Amid decades of research, the basic mechanisms of lyo-/cryostabilization of proteins and more complex organisms have not yet been fully established. One major bottleneck is the inability to probe into and control the molecular level interactions. The molecular interactions are responsible for the significant differences in the outcome of the preservation processes. (1) In this communication, we have utilized confocal Raman microspectroscopy to quantify the freezing-induced microheterogeneity and phase separation (solid and liquid) in a frozen solution composed of a model protein (lysozyme) and a lyo-/cryoprotectant (trehalose), which experienced different degrees of supercooling. Detailed quantitative spectral analysis was performed across the ice, the freeze-concentrated liquid (FCL) phases, and the interface region between them. It was established that the characteristics of the microstructures observed after freezing depended not only on the concentration of trehalose in the solution but also on the degree of supercooling. It was shown that, when samples were frozen after high supercooling, small amounts of lysozyme and trehalose were occluded in the ice phase. Lysozyme preserved its native-like secondary structure in the FCL region but was denatured in the ice phase. Also, it was observed that induction of freezing after a high degree of supercooling of high trehalose concentrations resulted in aggregation of the sugar and the protein.

A fracture mechanics study of the phase separating planar electrodes: Phase field modeling and analytical results

NASA Astrophysics Data System (ADS)

Haftbaradaran, H.; Maddahian, A.; Mossaiby, F.

2017-05-01

It is well known that phase separation could severely intensify mechanical degradation and expedite capacity fading in lithium-ion battery electrodes during electrochemical cycling. Experiments have frequently revealed that such degradation effects could be substantially mitigated via reducing the electrode feature size to the nanoscale. The purpose of this work is to present a fracture mechanics study of the phase separating planar electrodes. To this end, a phase field model is utilized to predict how phase separation affects evolution of the solute distribution and stress profile in a planar electrode. Behavior of the preexisting flaws in the electrode in response to the diffusion induced stresses is then examined via computing the time dependent stress intensity factor arising at the tip of flaws during both the insertion and extraction half-cycles. Further, adopting a sharp-interphase approximation of the system, a critical electrode thickness is derived below which the phase separating electrode becomes flaw tolerant. Numerical results of the phase field model are also compared against analytical predictions of the sharp-interphase model. The results are further discussed with reference to the available experiments in the literature. Finally, some of the limitations of the model are cautioned.

3D CFD simulation of Multi-phase flow separators

NASA Astrophysics Data System (ADS)

Zhu, Zhiying

2017-10-01

During the exploitation of natural gas, some water and sands are contained. It will be better to separate water and sands from natural gas to insure favourable transportation and storage. In this study, we use CFD to analyse the effect of multi-phase flow separator, whose detailed geometrical parameters are designed in advanced. VOF model and DPM are used here. From the results of CFD, we can draw a conclusion that separated effect of multi-phase flow achieves better results. No solid and water is carried out from gas outlet. CFD simulation provides an economical and efficient approach to shed more light on details of the flow behaviour.

Selectivity differences of water-soluble vitamins separated on hydrophilic interaction stationary phases.

PubMed

Yang, Yuanzhong; Boysen, Reinhard I; Hearn, Milton T W

2013-06-01

In this study, the retention behavior and selectivity differences of water-soluble vitamins were evaluated with three types of polar stationary phases (i.e. an underivatized silica phase, an amide phase, and an amino phase) operated in the hydrophilic interaction chromatographic mode with ESI mass spectrometric detection. The effects of mobile phase composition, including buffer pH and concentration, on the retention and selectivity of the vitamins were investigated. In all stationary phases, the neutral or weakly charged vitamins exhibited very weak retention under each of the pH conditions, while the acidic and more basic vitamins showed diverse retention behaviors. With the underivatized silica phase, increasing the salt concentration of the mobile phase resulted in enhanced retention of the acidic vitamins, but decreased retention of the basic vitamins. These observations thus signify the involvement of secondary mechanisms, such as electrostatic interaction in the retention of these analytes. Under optimized conditions, a baseline separation of all vitamins was achieved with excellent peak efficiency. In addition, the effects of water content in the sample on retention and peak efficiency were examined, with sample stacking effects observed when the injected sample contained a high amount of water. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Current-induced transition from particle-by-particle to concurrent intercalation in phase-separating battery electrodes.

PubMed

Li, Yiyang; El Gabaly, Farid; Ferguson, Todd R; Smith, Raymond B; Bartelt, Norman C; Sugar, Joshua D; Fenton, Kyle R; Cogswell, Daniel A; Kilcoyne, A L David; Tyliszczak, Tolek; Bazant, Martin Z; Chueh, William C

2014-12-01

Many battery electrodes contain ensembles of nanoparticles that phase-separate on (de)intercalation. In such electrodes, the fraction of actively intercalating particles directly impacts cycle life: a vanishing population concentrates the current in a small number of particles, leading to current hotspots. Reports of the active particle population in the phase-separating electrode lithium iron phosphate (LiFePO4; LFP) vary widely, ranging from near 0% (particle-by-particle) to 100% (concurrent intercalation). Using synchrotron-based X-ray microscopy, we probed the individual state-of-charge for over 3,000 LFP particles. We observed that the active population depends strongly on the cycling current, exhibiting particle-by-particle-like behaviour at low rates and increasingly concurrent behaviour at high rates, consistent with our phase-field porous electrode simulations. Contrary to intuition, the current density, or current per active internal surface area, is nearly invariant with the global electrode cycling rate. Rather, the electrode accommodates higher current by increasing the active particle population. This behaviour results from thermodynamic transformation barriers in LFP, and such a phenomenon probably extends to other phase-separating battery materials. We propose that modifying the transformation barrier and exchange current density can increase the active population and thus the current homogeneity. This could introduce new paradigms to enhance the cycle life of phase-separating battery electrodes.

On the phase form of a deformation quantization with separation of variables

NASA Astrophysics Data System (ADS)

Karabegov, Alexander

2016-06-01

Given a star product with separation of variables on a pseudo-Kähler manifold, we obtain a new formal (1, 1)-form from its classifying form and call it the phase form of the star product. The cohomology class of a star product with separation of variables equals the class of its phase form. We show that the phase forms can be arbitrary and they bijectively parametrize the star products with separation of variables. We also describe the action of a change of the formal parameter on a star product with separation of variables, its formal Berezin transform, classifying form, phase form, and canonical trace density.

Separation of Iron Phase and P-Bearing Slag Phase from Gaseous-Reduced, High-Phosphorous Oolitic Iron Ore at 1473 K (1200 °C) by Super Gravity

NASA Astrophysics Data System (ADS)

Gao, Jintao; Zhong, Yiwei; Guo, Lei; Guo, Zhancheng

2016-04-01

In situ observation on the morphology evolution and phosphorous migration of gaseous-reduced, high-phosphorous oolitic iron ore during the melting process was carried out with a high-temperature confocal scanning laser microscope. The results showed that 1473 K (1200 °C) was a critical temperature at which the gangue minerals started to form into the slag phase while the iron grains remained in a solid state; in addition, the phosphorus remained in the slag phase. Since the separation of iron grains and P-bearing slag was not achieved at the low temperature under the conventional conditions, separate experiments of the iron phase and the P-bearing slag phase from gaseous-reduced, high-phosphorous oolitic iron ore at 1473 K (1200 °C) by super gravity were carried out in this study. Based on the iron-slag separation by super gravity, phosphorus was removed effectively from the iron phase at the temperature below the melting point of iron. Iron grains moved along the super-gravity direction, joined, and concentrated as the iron phase on the filter, whereas the slag phase containing apatite crystals broke through the barriers of the iron grains and went through the filter. Consequently, increasing the gravity coefficient was definitely beneficial for the separation of the P-bearing slag phase from the iron phase. With the gravity coefficient of G = 1200, the mass fractions of separated slag and iron phases were close to their respective theoretical values, and the mass fraction of MFe in the separated iron phase was up to 98.09 wt pct and that of P was decreased to 0.083 wt pct. The recovery of MFe in the iron phase and that of P in the slag phase were up to 99.19 and 95.83 pct, respectively.

Prediction of Phase Separation of Immiscible Ga-Tl Alloys

NASA Astrophysics Data System (ADS)

Kim, Yunkyum; Kim, Han Gyeol; Kang, Youn-Bae; Kaptay, George; Lee, Joonho

2017-06-01

Phase separation temperature of Ga-Tl liquid alloys was investigated using the constrained drop method. With this method, density and surface tension were investigated together. Despite strong repulsive interactions, molar volume showed ideal mixing behavior, whereas surface tension of the alloy was close to that of pure Tl due to preferential adsorption of Tl. Phase separation temperatures and surface tension values obtained with this method were close to the theoretically calculated values using three different thermodynamic models.

Anisotropic imprint of amorphization and phase separation in manganite thin films via laser interference irradiation.

PubMed

Ding, Junfeng; Lin, Zhipeng; Wu, Jianchun; Dong, Zhili; Wu, Tom

2015-02-04

Materials with mesoscopic structural and electronic phase separation, either inherent from synthesis or created via external means, are known to exhibit functionalities absent in the homogeneous counterparts. One of the most notable examples is the colossal magnetoresistance discovered in mixed-valence manganites, where the coexistence of nano- to micrometer-sized phase-separated domains dictates the magnetotransport. However, it remains challenging to pattern and process such materials into predesigned structures and devices. In this work, a direct laser interference irradiation (LII) method is employed to produce periodic stripes in thin films of a prototypical phase-separated manganite Pr0.65 (Ca0.75 Sr0.25 )0.35 MnO3 (PCSMO). LII induces selective structural amorphization within the crystalline PCSMO matrix, forming arrays with dimensions commensurate with the laser wavelength. Furthermore, because the length scale of LII modification is compatible to that of phase separation in PCSMO, three orders of magnitude of increase in magnetoresistance and significant in-plane transport anisotropy are observed in treated PCSMO thin films. Our results show that LII is a rapid, cost-effective and contamination-free technique to tailor and improve the physical properties of manganite thin films, and it is promising to be generalized to other functional materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultrafast Dynamics in Vanadium Dioxide: Separating Spatially Segregated Mixed Phase Dynamics in the Time-domain

NASA Astrophysics Data System (ADS)

Hilton, David

2011-10-01

In correlated electronic systems, observed electronic and structural behavior results from the complex interplay between multiple, sometimes competing degrees-of- freedom. One such material used to study insulator-to-metal transitions is vanadium dioxide, which undergoes a phase transition from a monoclinic-insulating phase to a rutile-metallic phase when the sample is heated to 340 K. The major open question with this material is the relative influence of this structural phase transition (Peirels transition) and the effects of electronic correlations (Mott transition) on the observed insulator-to-metal transition. Answers to these major questions are complicated by vanadium dioxide's sensitivity to perturbations in the chemical structure in VO2. For example, related VxOy oxides with nearly a 2:1 ratio do not demonstrate the insulator-to- metal transition, while recent work has demonstrated that W:VO2 has demonstrated a tunable transition temperature controllable with tungsten doping. All of these preexisting results suggest that the observed electronic properties are exquisitely sensitive to the sample disorder. Using ultrafast spectroscopic techniques, it is now possible to impulsively excite this transition and investigate the photoinduced counterpart to this thermal phase transition in a strongly nonequilibrium regime. I will discuss our recent results studying the terahertz-frequency conductivity dynamics of this photoinduced phase transition in the poorly understood near threshold temperature range. We find a dramatic softening of the transition near the critical temperature, which results primarily from the mixed phase coexistence near the transition temperature. To directly study this mixed phase behavior, we directly study the nucleation and growth rates of the metallic phase in the parent insulator using non-degenerate optical pump-probe spectroscopy. These experiments measure, in the time- domain, the coexistent phase separation in VO2 (spatially

Adhesive phase separation at the dentin interface under wet bonding conditions.

PubMed

Spencer, Paulette; Wang, Yong

2002-12-05

Under in vivo conditions, there is little control over the amount of water left on the tooth and, thus, there is the danger of leaving the dentin surface so wet that the bonding resin undergoes physical separation into hydrophobic and hydrophilic-rich phases. The purpose of this study was to investigate phase separation in 2,2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl] propane (BisGMA)-based adhesive using molecular microanalysis and to examine the effect of phase separation on the structural characteristics of the hybrid layer. Model BisGMA/HEMA (hydroxyethl methacrylate) mixtures with/without ethanol and commercial BisGMA-based adhesive (Single Bond) were combined with water at concentrations from 0 to 50 vol%. Macrophase separation in the BisGMA/HEMA/water mixtures was detected using cloud point measurements. In parallel with these measurements, the BisGMA/HEMA and adhesive/water mixtures were cast as films and polymerized. Molecular structure was recorded from the distinct features in the phase-separated adhesive using confocal Raman microspectroscopy (CRM). Human dentin specimens treated with Single Bond were analyzed with scanning electron microscopy (SEM) and CRM mapping across the dentin/adhesive interface. The model BisGMA/HEMA mixtures with ethanol and the commercial BisGMA-based adhesive experienced phase separation at approximately 25 vol% water. Raman spectra collected from the phase-separated adhesive indicated that the composition of the particles and surrounding matrix material was primarily BisGMA and HEMA, respectively. Based on SEM analysis, there was substantial porosity at the adhesive interface with dentin. Micro-Raman spectral analysis of the dentin/adhesive interface indicates that the contribution from the BisGMA component decreases by nearly 50% within the first micrometer. The morphologic results in corroboration with the spectroscopic data suggest that as a result of adhesive phase separation the hybrid layer is not an

Phase separation and second-order phase transition in the phenomenological model for a Coulomb-frustrated two-dimensional system

NASA Astrophysics Data System (ADS)

Mamin, R. F.; Shaposhnikova, T. S.; Kabanov, V. V.

2018-03-01

We have considered the model of the phase transition of the second order for the Coulomb frustrated 2D charged system. The coupling of the order parameter with the charge was considered as the local temperature. We have found that in such a system, an appearance of the phase-separated state is possible. By numerical simulation, we have obtained different types ("stripes," "rings," "snakes") of phase-separated states and determined the parameter ranges for these states. Thus the system undergoes a series of phase transitions when the temperature decreases. First, the system moves from the homogeneous state with a zero order parameter to the phase-separated state with two phases in one of which the order parameter is zero and, in the other, it is nonzero (τ >0 ). Then a first-order transition occurs to another phase-separated state, in which both phases have different and nonzero values of the order parameter (for τ <0 ). Only a further decrease of temperature leads to a transition to a homogeneous ordered state.

Tubing modifications for countercurrent chromatography (CCC): Stationary phase retention and separation efficiency.

PubMed

Englert, Michael; Vetter, Walter

2015-07-16

Countercurrent chromatography (CCC) is a separation technique in which two immiscible liquid phases are used for the preparative purification of synthetic and natural products. In CCC the number of repetitive mixing and de-mixing processes, the retention of the stationary phase and the mass transfer between the liquid phases are significant parameters that influence the resolution and separation efficiency. Limited mass transfer is the main reason for peak broadening and a low number of theoretical plates along with impaired peak resolution in CCC. Hence, technical improvements with regard to column design and tubing modifications is an important aspect to enhance mixing and mass transfer. In this study we constructed a crimping tool which allowed us to make reproducible, semi-automated modifications of conventional round-shaped tubing. Six crimped tubing modifications were prepared, mounted onto multilayer coils which were subsequently installed in the CCC system. The stationary phase retention of the tubing modifications were compared to the conventional system with unmodified tubing in a hydrophobic, an intermediate and a hydrophilic two-phase solvent system. Generally, the tubing modifications provided higher capabilities to retain the stationary phase depending on the solvent system and flow rates. In the intermediate solvent system the separation efficiency was evaluated with a mixture of six alkyl p-hydroxybenzoates. The peak resolution could be increased up to 50% with one of the tubing modifications compared to the unmodified tubing. Using the most convincing tubing modification at fixed values for the stationary phase retention, a reasonable comparison to the unmodified tubing was achieved. The peak width could be reduced up to 49% and a strong positive impact at increased flow rates regarding peak resolution and theoretical plate number was observed compared to unmodified tubing. It could be concluded that the tubing modification enhanced the interphase

Phase separations in mixtures of a liquid crystal and a nanocolloidal particle.

PubMed

Matsuyama, Akihiko

2009-11-28

We present a mean field theory to describe phase separations in mixtures of a liquid crystal and a nanocolloidal particle. By taking into account a nematic, a smectic A ordering of the liquid crystal, and a crystalline ordering of the nanoparticle, we calculate the phase diagrams on the temperature-concentration plane. We predict various phase separations, such as a smectic A-crystal phase separation and a smectic A-isotropic-crystal triple point, etc., depending on the interactions between the liquid crystal and the colloidal surface. Inside binodal curves, we find new unstable and metastable regions, which are important in the phase ordering dynamics. We also find a crystalline ordering of the nanoparticles dispersed in a smectic A phase and a nematic phase. The cooperative phenomena between liquid-crystalline ordering and crystalline ordering induce a variety of phase diagrams.

Intrinsic Tunneling in Phase Separated Manganites

NASA Astrophysics Data System (ADS)

Singh-Bhalla, G.; Selcuk, S.; Dhakal, T.; Biswas, A.; Hebard, A. F.

2009-02-01

We present evidence of direct electron tunneling across intrinsic insulating regions in submicrometer wide bridges of the phase-separated ferromagnet (La,Pr,Ca)MnO3. Upon cooling below the Curie temperature, a predominantly ferromagnetic supercooled state persists where tunneling across the intrinsic tunnel barriers (ITBs) results in metastable, temperature-independent, high-resistance plateaus over a large range of temperatures. Upon application of a magnetic field, our data reveal that the ITBs are extinguished resulting in sharp, colossal, low-field resistance drops. Our results compare well to theoretical predictions of magnetic domain walls coinciding with the intrinsic insulating phase.

Separation of piracetam derivatives on polysaccharide-based chiral stationary phases.

PubMed

Kažoka, H; Koliškina, O; Veinberg, G; Vorona, M

2013-03-15

High-performance liquid chromatography was used for the enantiomeric separation of two chiral piracetam derivatives. The suitability of six commercially available polysaccharide-based chiral stationary phases (CSPs) under normal phase mode for direct enantioseparation has been investigated. The influence of the CSPs as well the nature and content of an alcoholic modifier in the mobile phase on separation and elution order was studied. It was established that CSP Lux Amylose-2 shows high chiral recognition ability towards 4-phenylsubstituted piracetam derivatives. Copyright © 2013 Elsevier B.V. All rights reserved.

Liquid-liquid phase separation in internally mixed magnesium sulfate/glutaric acid particles

NASA Astrophysics Data System (ADS)

Wu, Feng-Min; Wang, Xiao-Wei; Jing, Bo; Zhang, Yun-Hong; Ge, Mao-Fa

2018-04-01

The confocal Raman microscopy is utilized to investigate the liquid-liquid phase separation (LLPS) of mixed magnesium sulfate/glutaric acid (MgSO4/GA) droplets deposited on a hydrophobic polytetrafluoroethylene (PTFE) substrate and a hydrophilic quartz substrate. Raman spectra collected from different regions of the mixed droplets provide detailed information of component distributions for MgSO4 and GA. During the dehydration process, the MgSO4/GA mixed particles show the initial liquid-liquid phase separation between 85% and 80% relative humidity (RH) on both the hydrophobic and hydrophilic substrates. For the droplets deposited on the two substrates, the inner phase of droplets is dominated by aqueous MgSO4, which is surrounded by a rich GA organic layer due to the surface tension effects. In addition, the crystallization of GA could be observed in the organic aqueous phase while it is inhibited in the inner MgSO4 phase due to the effects of gel formation of MgSO4 at low RH. The Raman spectra reveal that with decreasing RH the morphology of the mixed droplet evolves from a uniform droplet to the structure of LLPS with the GA crystallizing in the outer layer and MgSO4 gel formed in the inner phase. These findings contribute to the further understanding of the role of interactions between inorganic salts and organic acids on the morphological evolution and environmental effects of atmospheric aerosols under ambient RH conditions.

Microgravity Passive Phase Separator

NASA Technical Reports Server (NTRS)

Paragano, Matthew; Indoe, William; Darmetko, Jeffrey

2012-01-01

A new invention disclosure discusses a structure and process for separating gas from liquids in microgravity. The Microgravity Passive Phase Separator consists of two concentric, pleated, woven stainless- steel screens (25-micrometer nominal pore) with an axial inlet, and an annular outlet between both screens (see figure). Water enters at one end of the center screen at high velocity, eventually passing through the inner screen and out through the annular exit. As gas is introduced into the flow stream, the drag force exerted on the bubble pushes it downstream until flow stagnation or until it reaches an equilibrium point between the surface tension holding bubble to the screen and the drag force. Gas bubbles of a given size will form a front that is moved further down the length of the inner screen with increasing velocity. As more bubbles are added, the front location will remain fixed, but additional bubbles will move to the end of the unit, eventually coming to rest in the large cavity between the unit housing and the outer screen (storage area). Owing to the small size of the pores and the hydrophilic nature of the screen material, gas does not pass through the screen and is retained within the unit for emptying during ground processing. If debris is picked up on the screen, the area closest to the inlet will become clogged, so high-velocity flow will persist farther down the length of the center screen, pushing the bubble front further from the inlet of the inner screen. It is desired to keep the velocity high enough so that, for any bubble size, an area of clean screen exists between the bubbles and the debris. The primary benefits of this innovation are the lack of any need for additional power, strip gas, or location for venting the separated gas. As the unit contains no membrane, the transport fluid will not be lost due to evaporation in the process of gas separation. Separation is performed with relatively low pressure drop based on the large surface

Film thickness dependence of phase separation and dewetting behaviors in PMMA/SAN blend films.

PubMed

You, Jichun; Liao, Yonggui; Men, Yongfeng; Shi, Tongfei; An, Lijia

2010-09-21

Film thickness dependence of complex behaviors coupled by phase separation and dewetting in blend [poly(methyl methacrylate) (PMMA) and poly(styrene-ran-acrylonitrile) (SAN)] films on silicon oxide substrate at 175 °C was investigated by grazing incidence ultrasmall-angle X-ray scattering (GIUSAX) and in situ atomic force microscopy (AFM). It was found that the dewetting pathway was under the control of the parameter U(q0)/E, which described the initial amplitude of the surface undulation and original thickness of film, respectively. Furthermore, our results showed that interplay between phase separation and dewetting depended crucially on film thickness. Three mechanisms including dewetting-phase separation/wetting, dewetting/wetting-phase separation, and phase separation/wetting-pseudodewetting were discussed in detail. In conclusion, it is relative rates of phase separation and dewetting that dominate the interplay between them.

Particle separation by phase modulated surface acoustic waves.

PubMed

Simon, Gergely; Andrade, Marco A B; Reboud, Julien; Marques-Hueso, Jose; Desmulliez, Marc P Y; Cooper, Jonathan M; Riehle, Mathis O; Bernassau, Anne L

2017-09-01

High efficiency isolation of cells or particles from a heterogeneous mixture is a critical processing step in lab-on-a-chip devices. Acoustic techniques offer contactless and label-free manipulation, preserve viability of biological cells, and provide versatility as the applied electrical signal can be adapted to various scenarios. Conventional acoustic separation methods use time-of-flight and achieve separation up to distances of quarter wavelength with limited separation power due to slow gradients in the force. The method proposed here allows separation by half of the wavelength and can be extended by repeating the modulation pattern and can ensure maximum force acting on the particles. In this work, we propose an optimised phase modulation scheme for particle separation in a surface acoustic wave microfluidic device. An expression for the acoustic radiation force arising from the interaction between acoustic waves in the fluid was derived. We demonstrated, for the first time, that the expression of the acoustic radiation force differs in surface acoustic wave and bulk devices, due to the presence of a geometric scaling factor. Two phase modulation schemes are investigated theoretically and experimentally. Theoretical findings were experimentally validated for different mixtures of polystyrene particles confirming that the method offers high selectivity. A Monte-Carlo simulation enabled us to assess performance in real situations, including the effects of particle size variation and non-uniform acoustic field on sorting efficiency and purity, validating the ability to separate particles with high purity and high resolution.

Rapid Separation of Copper Phase and Iron-Rich Phase From Copper Slag at Low Temperature in a Super-Gravity Field

NASA Astrophysics Data System (ADS)

Lan, Xi; Gao, Jintao; Huang, Zili; Guo, Zhancheng

2018-03-01

A novel approach for quickly separating a metal copper phase and iron-rich phase from copper slag at low temperature is proposed based on a super-gravity method. The morphology and mineral evolution of the copper slag with increasing temperature were studied using in situ high-temperature confocal laser scanning microscopy and ex situ scanning electron microscopy and X-ray diffraction methods. Fe3O4 particles dispersed among the copper slag were transformed into FeO by adding an appropriate amount of carbon as a reducing agent, forming the slag melt with SiO2 at low temperature and assisting separation of the copper phase from the slag. Consequently, in a super-gravity field, the metallic copper and copper matte were concentrated as the copper phase along the super-gravity direction, whereas the iron-rich slag migrated in the opposite direction and was quickly separated from the copper phase. Increasing the gravity coefficient (G) significantly enhanced the separation efficiency. After super-gravity separation at G = 1000 and 1473 K (1200 °C) for 3 minutes, the mass fraction of Cu in the separated copper phase reached 86.11 wt pct, while that in the separated iron-rich phase was reduced to 0.105 wt pct. The recovery ratio of Cu in the copper phase was as high as up to 97.47 pct.

Rapid Separation of Copper Phase and Iron-Rich Phase From Copper Slag at Low Temperature in a Super-Gravity Field

NASA Astrophysics Data System (ADS)

Lan, Xi; Gao, Jintao; Huang, Zili; Guo, Zhancheng

2018-06-01

A novel approach for quickly separating a metal copper phase and iron-rich phase from copper slag at low temperature is proposed based on a super-gravity method. The morphology and mineral evolution of the copper slag with increasing temperature were studied using in situ high-temperature confocal laser scanning microscopy and ex situ scanning electron microscopy and X-ray diffraction methods. Fe3O4 particles dispersed among the copper slag were transformed into FeO by adding an appropriate amount of carbon as a reducing agent, forming the slag melt with SiO2 at low temperature and assisting separation of the copper phase from the slag. Consequently, in a super-gravity field, the metallic copper and copper matte were concentrated as the copper phase along the super-gravity direction, whereas the iron-rich slag migrated in the opposite direction and was quickly separated from the copper phase. Increasing the gravity coefficient (G) significantly enhanced the separation efficiency. After super-gravity separation at G = 1000 and 1473 K (1200 °C) for 3 minutes, the mass fraction of Cu in the separated copper phase reached 86.11 wt pct, while that in the separated iron-rich phase was reduced to 0.105 wt pct. The recovery ratio of Cu in the copper phase was as high as up to 97.47 pct.

Development of a novel amide-silica stationary phase for the reversed-phase HPLC separation of different classes of phytohormones.

PubMed

Aral, Hayriye; Aral, Tarık; Ziyadanoğulları, Berrin; Ziyadanoğulları, Recep

2013-11-15

A novel amide-bonded silica stationary phase was prepared starting from N-Boc-phenylalanine, cyclohexylamine and spherical silica gel (4 µm, 60 Å). The amide ligand was synthesised with high yield. The resulting amide bonded stationary phase was characterised by SEM, IR and elemental analysis. The resulting selector bearing a polar amide group is used for the reversed-phase chromatography separation of different classes of thirteen phytohormones (plant hormones). The chromatographic behaviours of these analytes on the amide-silica stationary phase were compared with those of RP-C18 column under same conditions. The effects of different separation conditions, such as mobile phase, pH value, flow rate and temperature, on the separation and retention behaviours of the 13 phytohormones in this system were studied. The optimum separation was achieved using reversed-phase HPLC gradient elution with an aqueous mobile phase containing pH=6.85 potassium phosphate buffer (20 mM) and acetonitrile with a 22 °C column temperature. Under these experimental conditions, the 12 phytohormones could be separated and detected at 230 or 270 nm within 26 min. Copyright © 2013 Elsevier B.V. All rights reserved.

A review of molecular phase separation in binary self-assembled monolayers of thiols on gold surfaces

NASA Astrophysics Data System (ADS)

Ong, Quy; Nianias, Nikolaos; Stellacci, Francesco

2017-09-01

Binary self-assembled monolayers (SAMs) on gold surfaces have been known to undergo molecular phase separation to various degrees and have been subject to both experimental and theoretical studies. On gold nanoparticles in particular, binary SAMs ligand shells display intriguing morphologies. Consequently, unexpected behaviors of the nanoparticles with respect to their biological, chemical, and interfacial properties have been observed. It is critical that the phase separation of binary SAMs be understood at both molecular and macroscopic level to create, and then manipulate, the useful properties of the functionalized surfaces. We look into the current understanding of molecular phase separation of binary SAMs on gold surfaces, represented by Au(111) flat surfaces and Au nanoparticles, from both theoretical and experimental aspects. We point out shortcomings and describe several research strategies that will address them in the future. Contribution to the Focus Issue Self-assemblies of Inorganic and Organic Nanomaterials edited by Marie-Pule Pileni.

Phase Separation and Crystallization of Hemoglobin C in Transgenic Mouse and Human Erythrocytes

PubMed Central

Canterino, Joseph E.; Galkin, Oleg; Vekilov, Peter G.; Hirsch, Rhoda Elison

2008-01-01

Individuals expressing hemoglobin C (β6 Glu→Lys) present red blood cells (RBC) with intraerythrocytic crystals that form when hemoglobin (Hb) is oxygenated. Our earlier in vitro liquid-liquid (L-L) phase separation studies demonstrated that liganded HbC exhibits a stronger net intermolecular attraction with a longer range than liganded HbS or HbA, and that L-L phase separation preceded and enhanced crystallization. We now present evidence for the role of phase separation in HbC crystallization in the RBC, and the role of the RBC membrane as a nucleation center. RBC obtained from both human homozygous HbC patients and transgenic mice expressing only human HbC were studied by bright-field and differential interference contrast video-enhanced microscopy. RBC were exposed to hypertonic NaCl solution (1.5–3%) to induce crystallization within an appropriate experimental time frame. L-L phase separation occurred inside the RBC, which in turn enhanced the formation of intraerythrocytic crystals. RBC L-L phase separation and crystallization comply with the thermodynamic and kinetics laws established through in vitro studies of phase transformations. This is the first report, to the best of our knowledge, to capture a temporal view of intraerythrocytic HbC phase separation, crystal formation, and dissolution. PMID:18621841

Vapor-liquid phase separator permeability results

NASA Technical Reports Server (NTRS)

Yuan, S. W. K.; Frederking, T. H. K.

1981-01-01

Continued studies are described in the area of vapor-liquid phase separator work with emphasis on permeabilities of porous sintered plugs (stainless steel, nominal pore size 2 micrometer). The temperature dependence of the permeability has been evaluated in classical fluid using He-4 gas at atmospheric pressure and in He-2 on the basis of a modified, thermosmotic permeability of the normal fluid.

Separation of gas from liquid in a two-phase flow system

NASA Technical Reports Server (NTRS)

Hayes, L. G.; Elliott, D. G.

1973-01-01

Separation system causes jets which leave two-phase nozzles to impinge on each other, so that liquid from jets tends to coalesce in center of combined jet streams while gas phase is forced to outer periphery. Thus, because liquid coalescence is achieved without resort to separation with solid surfaces, cycle efficiency is improved.

Effect of temperature gradient on liquid-liquid phase separation in a polyolefin blend.

PubMed

Jiang, Hua; Dou, Nannan; Fan, Guoqiang; Yang, Zhaohui; Zhang, Xiaohua

2013-09-28

We have investigated experimentally the structure formation processes during phase separation via spinodal decomposition above and below the spinodal line in a binary polymer blend system exposed to in-plane stationary thermal gradients using phase contrast optical microscopy and temperature gradient hot stage. Below the spinodal line there is a coupling of concentration fluctuations and thermal gradient imposed by the temperature gradient hot stage. Also under the thermal gradient annealing phase-separated domains grow faster compared with the system under homogeneous temperature annealing on a zero-gradient or a conventional hot stage. We suggest that the in-plane thermal gradient accelerates phase separation through the enhancement in concentration fluctuations in the early and intermediate stages of spinodal decomposition. In a thermal gradient field, the strength of concentration fluctuation close to the critical point (above the spinodal line) is strong enough to induce phase separation even in one-phase regime of the phase diagram. In the presence of a temperature gradient the equilibrium phase diagrams are no longer valid, and the systems with an upper critical solution temperature can be quenched into phase separation by applying the stationary temperature gradient. The in-plane temperature gradient drives enhanced concentration fluctuations in a binary polymer blend system above and below the spinodal line.

Effects of temperature and solvent condition on phase separation induced molecular fractionation of gum arabic/hyaluronan aqueous mixtures.

PubMed

Hu, Bing; Han, Lingyu; Gao, Zhiming; Zhang, Ke; Al-Assaf, Saphwan; Nishinari, Katsuyoshi; Phillips, Glyn O; Yang, Jixin; Fang, Yapeng

2018-05-14

Effects of temperature and solvent condition on phase separation-induced molecular fractionation of gum arabic/hyaluronan (GA/HA) mixed solutions were investigated. Two gum arabic samples (EM10 and STD) with different molecular weights and polydispersity indices were used. Phase diagrams, including cloud and binodal curves, were established by visual observation and GPC-RI methods. The molecular parameters of control and fractionated GA, from upper and bottom phases, were measured by GPC-MALLS. Fractionation of GA increased the content of arabinogalactan-protein complex (AGP) from ca. 11% to 18% in STD/HA system and 28% to 55% in EM10/HA system. The phase separation-induced molecular fractionation was further studied as a function of temperature and solvent condition (varying ionic strength and ethanol content). Increasing salt concentration (from 0.5 to 5 mol/L) greatly reduced the extent of phase separation-induced fractionation. This effect may be ascribed to changes in the degree of ionization and shielding of the acid groups. Increasing temperature (from 4 °C to 80 °C) also exerted a significant influence on phase separation-induced fractionation. The best temperature for GA/HA mixture system was 40 °C while higher temperature negatively affected the fractionation due to denaturation and possibly degradation in mixed solutions. Increasing the ethanol content up to 30% showed almost no effect on the phase separation induced fractionation. Copyright © 2018 Elsevier B.V. All rights reserved.

Polymer-induced phase separation and crystallization in immunoglobulin G solutions.

PubMed

Li, Jianguo; Rajagopalan, Raj; Jiang, Jianwen

2008-05-28

We study the effects of the size of polymer additives and ionic strength on the phase behavior of a nonglobular protein-immunoglobulin G (IgG)-by using a simple four-site model to mimic the shape of IgG. The interaction potential between the protein molecules consists of a Derjaguin-Landau-Verwey-Overbeek-type colloidal potential and an Asakura-Oosawa depletion potential arising from the addition of polymer. Liquid-liquid equilibria and fluid-solid equilibria are calculated by using the Gibbs ensemble Monte Carlo technique and the Gibbs-Duhem integration (GDI) method, respectively. Absolute Helmholtz energy is also calculated to get an initial coexisting point as required by GDI. The results reveal a nonmonotonic dependence of the critical polymer concentration rho(PEG) (*) (i.e., the minimum polymer concentration needed to induce liquid-liquid phase separation) on the polymer-to-protein size ratio q (equivalently, the range of the polymer-induced depletion interaction potential). We have developed a simple equation for estimating the minimum amount of polymer needed to induce the liquid-liquid phase separation and show that rho(PEG) (*) approximately [q(1+q)(3)]. The results also show that the liquid-liquid phase separation is metastable for low-molecular weight polymers (q=0.2) but stable at large molecular weights (q=1.0), thereby indicating that small sizes of polymer are required for protein crystallization. The simulation results provide practical guidelines for the selection of polymer size and ionic strength for protein phase separation and crystallization.

Separation of multiphosphorylated peptide isomers by hydrophilic interaction chromatography on an aminopropyl phase.

PubMed

Singer, David; Kuhlmann, Julia; Muschket, Matthias; Hoffmann, Ralf

2010-08-01

The separation of isomeric phosphorylated peptides is challenging and often impossible for multiphosphorylated isomers using chromatographic and capillary electrophoretic methods. In this study we investigated the separation of a set of single-, double-, and triple-phosphorylated peptides (corresponding to the human tau protein) by ion-pair reversed-phase chromatography (IP-RPC) and hydrophilic interaction chromatography (HILIC). In HILIC both hydroxyl and aminopropyl stationary phases were tested with aqueous acetonitrile in order to assess their separation efficiency. The hydroxyl phase separated the phosphopeptides very well from the unphosphorylated analogue, while on the aminopropyl phase even isomeric phosphopeptides attained baseline separation. Thus, up to seven phosphorylated versions of a given tau domain were separated. Furthermore, the low concentration of an acidic ammonium formate buffer allowed an online analysis with electrospray ionization tandem mass spectrometry (ESI-MS/MS) to be conducted, enabling peptide sequencing and identification of phosphorylation sites.

Separating homeologs by phasing in the tetraploid wheat transcriptome.

PubMed

Krasileva, Ksenia V; Buffalo, Vince; Bailey, Paul; Pearce, Stephen; Ayling, Sarah; Tabbita, Facundo; Soria, Marcelo; Wang, Shichen; Akhunov, Eduard; Uauy, Cristobal; Dubcovsky, Jorge

2013-06-25

The high level of identity among duplicated homoeologous genomes in tetraploid pasta wheat presents substantial challenges for de novo transcriptome assembly. To solve this problem, we develop a specialized bioinformatics workflow that optimizes transcriptome assembly and separation of merged homoeologs. To evaluate our strategy, we sequence and assemble the transcriptome of one of the diploid ancestors of pasta wheat, and compare both assemblies with a benchmark set of 13,472 full-length, non-redundant bread wheat cDNAs. A total of 489 million 100 bp paired-end reads from tetraploid wheat assemble in 140,118 contigs, including 96% of the benchmark cDNAs. We used a comparative genomics approach to annotate 66,633 open reading frames. The multiple k-mer assembly strategy increases the proportion of cDNAs assembled full-length in a single contig by 22% relative to the best single k-mer size. Homoeologs are separated using a post-assembly pipeline that includes polymorphism identification, phasing of SNPs, read sorting, and re-assembly of phased reads. Using a reference set of genes, we determine that 98.7% of SNPs analyzed are correctly separated by phasing. Our study shows that de novo transcriptome assembly of tetraploid wheat benefit from multiple k-mer assembly strategies more than diploid wheat. Our results also demonstrate that phasing approaches originally designed for heterozygous diploid organisms can be used to separate the close homoeologous genomes of tetraploid wheat. The predicted tetraploid wheat proteome and gene models provide a valuable tool for the wheat research community and for those interested in comparative genomic studies.

Quantitative analysis of aqueous phase composition of model dentin adhesives experiencing phase separation

PubMed Central

Ye, Qiang; Park, Jonggu; Parthasarathy, Ranganathan; Pamatmat, Francis; Misra, Anil; Laurence, Jennifer S.; Marangos, Orestes; Spencer, Paulette

2013-01-01

There have been reports of the sensitivity of our current dentin adhesives to excess moisture, for example, water-blisters in adhesives placed on over-wet surfaces, and phase separation with concomitant limited infiltration of the critical dimethacrylate component into the demineralized dentin matrix. To determine quantitatively the hydrophobic/hydrophilic components in the aqueous phase when exposed to over-wet environments, model adhesives were mixed with 16, 33, and 50 wt % water to yield well-separated phases. Based upon high-performance liquid chromatography coupled with photodiode array detection, it was found that the amounts of hydrophobic BisGMA and hydrophobic initiators are less than 0.1 wt % in the aqueous phase. The amount of these compounds decreased with an increase in the initial water content. The major components of the aqueous phase were hydroxyethyl methacrylate (HEMA) and water, and the HEMA content ranged from 18.3 to 14.7 wt %. Different BisGMA homologues and the relative content of these homologues in the aqueous phase have been identified; however, the amount of crosslinkable BisGMA was minimal and, thus, could not help in the formation of a crosslinked polymer network in the aqueous phase. Without the protection afforded by a strong crosslinked network, the poorly photoreactive compounds of this aqueous phase could be leached easily. These results suggest that adhesive formulations should be designed to include hydrophilic multimethacrylate monomers and water compatible initiators. PMID:22331596

Rapid variations in fluid chemistry constrain hydrothermal phase separation at the Main Endeavour Field

NASA Astrophysics Data System (ADS)

Love, Brooke; Lilley, Marvin; Butterfield, David; Olson, Eric; Larson, Benjamin

2017-02-01

Previous work at the Main Endeavour Field (MEF) has shown that chloride concentration in high-temperature vent fluids has not exceeded 510 mmol/kg (94% of seawater), which is consistent with brine condensation and loss at depth, followed by upward flow of a vapor phase toward the seafloor. Magmatic and seismic events have been shown to affect fluid temperature and composition and these effects help narrow the possibilities for sub-surface processes. However, chloride-temperature data alone are insufficient to determine details of phase separation in the upflow zone. Here we use variation in chloride and gas content in a set of fluid samples collected over several days from one sulfide chimney structure in the MEF to constrain processes of mixing and phase separation. The combination of gas (primarily magmatic CO2 and seawater-derived Ar) and chloride data, indicate that neither variation in the amount of brine lost, nor mixing of the vapor phase produced at depth with variable quantities of (i) brine or (ii) altered gas rich seawater that has not undergone phase separation, can explain the co-variation of gas and chloride content. The gas-chloride data require additional phase separation of the ascending vapor-like fluid. Mixing and gas partitioning calculations show that near-critical temperature and pressure conditions can produce the fluid compositions observed at Sully vent as a vapor-liquid conjugate pair or as vapor-liquid pair with some remixing, and that the gas partition coefficients implied agree with theoretically predicted values.