Phase separation

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Random resistivity network calculations for cuprate superconductors with an electronic phase separation transition

Random resistivity network calculations for cuprate superconductors with an electronic phase separation transition

which happens at lower temperatures, as can be seen in Fig. 4. Like the CH phase separation calculations shown in the pre- vious section, the resistivity calculations were made on 100 × 100 lattices. Periodic boundary conditions were used only on the sides without the V source terminals. The resulting linear systems that come from Kirchhoff laws were solved with the aid of the subroutine ma57 , provided by HSL, which makes use of a multifrontal algorithm [47], which speeded up the calculations. For each value of p and T we use 300 samples in order to obtain results independent of the random process of sharing the p ( i ) distribution. Results of simulations for typical samples near optimum doping are shown in Fig. 5 for the com- pound Y 0 . 80 Ca 0 . 20 Ba 2 Cu 3 O 7 −δ with nominal doping p = 0 . 136. 300 samples were used for each point in the graph. The phase separation begins at 400 K; SC links of resistivity 1 × 10 − 8 m Ω cm are introduced below 180 K, according to the T
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Micro-Raman spectroscopy studies of the phase separation mechanisms of transition-metal phosphate glasses.

Micro-Raman spectroscopy studies of the phase separation mechanisms of transition-metal phosphate glasses.

MICRO-RAMAN SPECTROSCOPY STUDIES OF THE PHASE SEPARATION MECHANISMS OF TRANSITION-METAL PHOSPHATE GLASSES. Glass-ceramics are prepared by controlled separation of crystal phases in glasses, leading to uniform and dense grain structures. On the other hand, chemical leaching of soluble crystal phases yields porous glass-ceramics with important applications. Here, glass/ceramic interfaces of niobo-, vanado- and titano-phosphate glasses were studied by micro-Raman spectroscopy, whose spatial resolution revealed the multiphase structures. Phase-separation mechanisms were also determined by this technique, revealing that interface composition remained unchanged as the crystallization front advanced for niobo- and vanadophosphate glasses (interface-controlled crystallization). For titanophosphate glasses, phase composition changed continuously with time up to the equilibrium composition, indicating a spinodal-type phase separation.
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Development of paper-based devices, using a simple phase separation process for the fabrication of biomimetic superhydrophobic paper substrates

Development of paper-based devices, using a simple phase separation process for the fabrication of biomimetic superhydrophobic paper substrates

Biomimetic rough paper substrates were obtained by a simple phase separation methodology, using PHB. Different characterization techniques were used to confirm the large increase of WCA after the modification with the PHB: the micro and nano structures resulting from the polymer precipitation, visible by the SEM, are directly related with the superhydrophobic properties assessed by WCA measurements. We hypothesize that such materials could find applicability in the biomedical and biological fields. Therefore, it was important to perform a protein adsorption study to complement the characterization of the SH paper substrates. We were able to conclude that the amount of adsorbed BSA was much less for rough SH paper surfaces, when compared with the original paper. This was explained using the Cassie-Baxter model, where the rough topography of the surface significantly reduced the liquid-surface contact. Other parameters such as the robustness of the surfaces and the ability to maintain their properties after ethylene oxide sterilization were also evaluated; the substrates exhibited resistance to manual handling and to EtO sterilization.
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Phase Separation and Phase Preferences in Pigmented, Impact-Modified, PCPBT Blends

Phase Separation and Phase Preferences in Pigmented, Impact-Modified, PCPBT Blends

Delimoy et al. (1988) (TEM studies), reported that, during annealing at 220 ºC, the PBT lamellae were growing from the interface, inside the PC-rich phase, depleting the PC from the dissolved PBT. This fact is quoted as being direct evidence of the limited miscibility of PC in PBT, above the crystallisation temperature of the PBT. TEM imaging confirmed the reported (Wahrmund et al. 1978; Birley and Chen 1984) partial miscibility of the PBT in PC. Moreover, it can be concluded that the extent of PBT crystallisation also influences its solubility in a PC blend (Bennekom et al. 1997a). Ratzsch et al. (1990) found that phase separation occurs upon the appearance of PBT crystallisation and, therefore, is said to be entropically promoted. Delimoy et al. (1995) presented further evidence of the partial miscibility of PC and PBT in PC/PBT blends. Complete inhibition of transesterification was assumed as triphenyl phosphite was used as a stabiliser. However the authors pointed to the problem of the limits of analytical methods needed to prove the absence of a copolyester content. The partial miscibility was interpreted from the observed behaviour of the glass transition with respect to the composition. A change in the melting temperature was not found.
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The Secondary Organic Aerosol Processor (SOAP v1.0) model: a unified model with different ranges of complexity based on the molecular surrogate approach

The Secondary Organic Aerosol Processor (SOAP v1.0) model: a unified model with different ranges of complexity based on the molecular surrogate approach

state. For the biogenic case at low humidity, if the structure of nonadecane is used to represent the compounds POAlP, POAmP, POAhP, SOAlP, SOAmP and SOAhP (with- out a molecular structure; these compounds only condense on the less oxidized phase without impacting phase separation), a third organic phase may be created. Com- pounds with low oxidation state may not readily mix with slightly oxidized compounds

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Adiabatic Differential Scanning Calorimetric Study of Divalent Cation Induced DNA - DPPC Liposome Formulation Compacted for Gene Delivery

Adiabatic Differential Scanning Calorimetric Study of Divalent Cation Induced DNA - DPPC Liposome Formulation Compacted for Gene Delivery

-induced phase separation with an increased gel - liquid crystal phase transition temperature, which indicated the divalent cation triggered high temperature DNA stabilization. Unilamellar vesicles treated with the same concentration of Mg 2+ did not produce such a shift, which was normally detected spectroscopically. Obviously, here divalent metal cation did not contribute essentially in stabilizing the zwitterionic lipid structure. Therefore, DNA contributed to stabilization of ternary complex towards higher temperatures. Apparently, Mg 2+ - DNA created polymorphic phase transitions in phosphatidylcholine moiety.
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Sistemas aquosos bifásicos: determinação de equilíbrio de fase e aplicação para partição de alfa-lactoalbumina e beta-lactoglobulina

Sistemas aquosos bifásicos: determinação de equilíbrio de fase e aplicação para partição de alfa-lactoalbumina e beta-lactoglobulina

3.2. Microcalorimetric studies of ATPS formation: Calorimetric measurements were carried out by da Silva and Loh [34] to investigate and explain the ATPS formation process. According to the proposed model, when PEO and salts are mixed, the ions and the polymer interact, releasing solvation water molecules in a process driven by this increase in entropy. The ion binding continues as more electrolytes are added until it reaches a saturation point, after which no more entropy is gained and the phase splitting becomes more favorable. After this saturation point, the addition of more salt would lead to a higher concentration in the bulk than around the polymer. The proposition that phase separation occurs in association with the saturation of the electrolyte –polymer binding may sound contradictory to features of the binodal curves for aqueous two –phase systems, which highlights that at lower concentrations of one component, more of the other component is necessary to induce phase splitting. At this point, it is important to stress that this saturation does not mean physical saturation of the binding sites around the polymer, but that a significant amount of electrolyte is left in solution without interacting with the polymer, destabilizing the system, hence, leading to phase separation.
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Selective synthesis under Microwave Irradiation of New Monomers for potential applications in PDLC films

Selective synthesis under Microwave Irradiation of New Monomers for potential applications in PDLC films

The microscopic images of the microstructure of the polymeric matrix were evaluated by scanning electronic microscopy (SEM). Some microscopic images can be assigned to the swiss cheese (figures 5.3, 5.4 (a) and 5.5) or polymer ball (figures 5.1 (a), 5.7 (a) and 5.8) types of morphology, but for some samples these morphologies are not uniform across the sample. For other samples it was not possible to identify any morphology as is show in figures 5.1 (b), 5.2, 5.4 (b), 5.6 and 5.7 (b). These results can suggest that the chemical affinity of polymerisable monomers with liquid crystal molecules due to their similarities in chemical structure produces a smaller phase separation and therefore the E7 liquid crystal molecules would be highly embedded in the matrix. It is also possible to observe that it cannot be established a correlation between the molecular structure of the polymerisable monomers and polymerisation conditions. Although the samples for analysis by GPC and SEM were not prepared with the same conditions, it is not possible to establish a correlation between the molecular weight of polymers and the microstructure of the polymer matrix.
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Effect of simplified chemical moisture control protocols on the bond durability of fiber posts cemented to root dentin / Efeito de protocolos simplificados de controle químico de umidade na durabilidade da união de pinos de fibra cimentados à dentina radi

Effect of simplified chemical moisture control protocols on the bond durability of fiber posts cemented to root dentin / Efeito de protocolos simplificados de controle químico de umidade na durabilidade da união de pinos de fibra cimentados à dentina radicular

The moisture in dentin tissue contributes to the degradation of the hybrid layer.6 Excess water generates the phenomenon of phase separation and compromises the diffusion of the adhesive.[7] However, the complete removal of moisture from the conditioned dentin significantly reduces bond strength,8 since water is essential to maintaining the integrity of the collagen network, which, in turn, enables the adequate penetration of resinous monomers.[9] Thus, the control of dentin moisture by chemical means to promote dehydration without drying the substrate (keeping it moist with ethanol) is a promising method that has demonstrated good results in terms of bond strength and durability.[10,11]
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What is spinodal decomposition?

What is spinodal decomposition?

A pair of partially miscible liquids, i.e. liquids that do not mix in all proportions at all temperatures, shows in a tem- perature-composition diagram a miscibility gap where phase separation occurs. Gibbs [1] showed that the condition for stability (or metastability) in respect to continuous change of phase is that the second derivative of the free energy of mix- ing to be positive. If negative, the system is unstable. If zero, the spinodal is defined. The free energy of mixing, ΔG mix , has the following general form:

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Braz. J. Pharm. Sci.  vol.49 número1

Braz. J. Pharm. Sci. vol.49 número1

In Figure 1, the original (unbuffered) (Anastassia- des et al., 2003) and the buffered (Lehotay, Mastovska, Lightield, 2005) QuEchERS methodologies applied in the present study can be compared. The buffered meth- odology with acetonitrile could be highly suitable for the extraction of SAs evaluated from chicken breast, as this solvent can precipitate proteins. After the addition of mag- nesium sulfate and buffering salts (pH 5-5.5), the mixture is shaken intensively and centrifuged for phase separation. An aliquot of the organic phase is cleaned up by dispersive SPE employing bulk sorbent (PSA) and MgSO 4 for the removal of residual water. The inal extract can be directly employed for HPLC analysis. In the present study, the dryness step was evaluated, and it provides an increment of the recovery of the analytes (Figure 1).
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Mat. Res.  vol.15 número4

Mat. Res. vol.15 número4

showed that incorporation of POSS decreased the rate of mass loss of TPU under isothermal conditions. The flexible phase showed an enhanced stability to temperature, probably due to increased phase separation between the rigid and flexible domains. The DSC showed that incorporation of 0.4 wt. (%) of POSS increased the glass transition temperature of the flexible phase. Moreover, addition of POSS modified the melting behaviour, providing samples with a higher melting enthalpy compared to neat TPU as a consequence of the formation of larger crystals. The capillary rheometry analysis revels that the POSS addition showed a clear tendency toward higher intrinsic viscosities as the amount of POSS was increased.
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Mat. Res.  vol.20 número1

Mat. Res. vol.20 número1

A Cu-10Fe alloy with magnetron sputtered Al ilms was irradiated by high current pulsed electron beam (HCPEB) with various pulse numbers, next changes of its microstructure and corrosion property were investigated. Compared with the initial sample, microhardness and corrosion resistance of the aluminized Cu-10Fe alloys after the HCPEB treatment are remarkably improved with increasing pulse numbers. This improvement could be attributed to formation of Al 2 Cu intermetallic compounds, occurrence of liquid phase separation and grain reinement in the surface layer of the Cu-10Fe alloy during the process of rapid remelting and solidiication induced by the HCPEB treatment.
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Dynamic formation of SEBS copolymer submicrometric structures

Dynamic formation of SEBS copolymer submicrometric structures

Fig. 1 shows AFM images of self-organized structures found in different regions of the same sample. Fig. 1a exhibits a region patterned with parallel stripes, while in another region a quasi- perfect 2D hexagonal lattice constituted by submicrometric drop- lets was recorded (Fig. 1b) [9]. Fig. 1c and d show, using a section profile analysis (a height profile), how regular these structures are, as well as the uniformity of shapes of stripes and droplets. Those images are the final result after dewetting and solvent evaporation of a thin liquid film that was formed by dipping the mica substrate in a SEBS/toluene solution for few seconds [9]. SEBS stripes and droplets adhered to the mica surface after the complete evapora- tion of the solvent, and inside each stripe or droplet the phase separation is such that parallel cylindrical structures of polystyrene remain embedded in the poly(ethene-co-butene) matrix, as shown in the AFM phase image (Fig. 2). It is clear that some perpendicular cylinders also appear in the structure, mainly in the borders where the thickness is smaller. PS-cylinders reached hundreds of micrometers, and from the AFM images we can estimate an average diameter of about 12 nm for the cylinders, and a mean distance between two neighbouring cylinders also of 12 nm. However, we need to advise that it exists a certain imprecision in the lateral interaction between the tip and the surface in the phase mode, which can artificially enlarge the dimension of the cylinders [21]. Even so, this is in agreement with accurate measurements of Transmission Electron Microscopy technique (TEM) carried out in similar SEBS films that were deposited on liquid phosphoric acid substrate [7].
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From biological membranes to biomimetic model membranes

From biological membranes to biomimetic model membranes

The concept that biological membranes are composed of two opposite layers of lipids was already found out in 1925 by Gorter et al. who observed using the Langmuir trough technique that the molecular area of lipids extracted from red blood cells was two times the area of the red blood cells measured by microscopy. The irst membrane model including proteins dates from 1935 and was proposed by Danielli et al. These researchers postulated that a protein layer is tightly associated to the polar heads of lipids composing the cell membranes. It was forced to wait more than thirty years to ind out that proteins may also span through membranes. Such discovery led to the so-called luid mosaic model proposed by Singer et al. in 1972. According to this model, each lealet of the bilayer is formed by a homogeneous environment of lipids in a luid state incorporating globular assembling of proteins and glycoproteins. Singer et al. also assumed that the lipid composition within the bilayers is most likely asymmetric. Since its conception in 1972, some developments and reinements were brought to the luid mosaic model especially in terms of composition and molecular organization. The most important evolution of this model was obtained in 1997 with the works of Simons et al. and of Brown et al. These authors showed that biological membranes do not form a homogeneous luid lipid phase as predicted by Singer et al. In contrast, they suggested that membrane lipids are organized into phase-separated microdomains, called lipid rafts, with both a speciic composition and a molecular dynamic that are different to the ones of the surrounding liquid crystalline phase. The discovery of such phase separation in the plane of the membrane has induced in the last decade an explosion in the research efforts related to the biology of the cell membrane as well as in the development of new technologies for detecting lateral heterogeneities in biological membranes. Nowadays, while there is no doubt about the presence of phase separation in the plane of the membrane, the existence of lipid rafts, which are believed to be enriched in sphingolipids and cholesterol, to present a high mobility in the plane of the membrane and to be involved in many biological processes such as signal transduction, membrane transport and protein sorting (Simons et al., 1997) is still controversial. A more
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Simulation of aromatic SOA formation using the lumping model integrated with explicit gas-phase kinetic mechanisms and aerosol-phase reactions

Simulation of aromatic SOA formation using the lumping model integrated with explicit gas-phase kinetic mechanisms and aerosol-phase reactions

In the presence of inorganic species (ammonium, sulfate and water), both toluene SOA and 135-TMB SOA are assumed to have two completely separated phases (an organic phase and inorganic aqueous phase). In a recent study by Bertram et al. (2011), the LLPS of organic/ammonium sulfate parti- cles has been parameterized using model organic compounds as a function of the elemental O : C ratio and organic : sulfate ratio. Based on the previously reported O : C ratios of toluene SOA (0.62 on average) (Sato et al., 2012) and our measured organic : sulfate ratio (ranging 1–6), the predicted RH value for the LLPS of toluene SOA is about 65 %. Similarly, based on the reported O : C ratio of 135-TMB SOA (0.46 on aver- age) (Sato et al., 2012), the predicted RH at LLPS for 135- TMB SOA is expected to be higher than 90 %. Thus, the as- sumption of phase separation for the two aromatic SOA is justified as the chamber experiments are largely conducted at RH below their respective LLPS RH values. The humid- ity conditions during chamber experiments were lower than 65 %, except for a short period at the beginning of each ex- periment, and SOA formation is negligible at this time (less than 1 h). Furthermore, the solubility of oligomeric products
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Mat. Res.  vol.18 suppl.1

Mat. Res. vol.18 suppl.1

The microstructure and phase formation of rapid solidiied Ag-rich Ag-Cu-Zr alloys were investigated. Two types of structure; interconnected- and droplet-type structures, were obtained due to phase separation mechanisms. The former was spinodal decomposition and the later was nucleation and growth mechanism. Depending on the alloy compositions, three crystalline phases; FCC-Ag, AgZr and Cu 10 Zr 7 phases were observed along with an in-situ nanocrystalline/amorphous composite.

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Braz. J. Phys.  vol.30 número4

Braz. J. Phys. vol.30 número4

universality lass at the ritial point marking phase. separation[r]

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Primary and secondary organic aerosol origin by combined gas-particle phase source apportionment

Primary and secondary organic aerosol origin by combined gas-particle phase source apportionment

Abstract. Secondary organic aerosol (SOA), a prominent fraction of particulate organic mass (OA), remains poorly constrained. Its formation involves several unknown precur- sors, formation and evolution pathways and multiple natu- ral and anthropogenic sources. Here a combined gas-particle phase source apportionment is applied to wintertime and summertime data collected in the megacity of Paris in order to investigate SOA origin during both seasons. This was pos- sible by combining the information provided by an aerosol mass spectrometer (AMS) and a proton transfer reaction mass spectrometer (PTR-MS). A better constrained appor- tionment of primary OA (POA) sources is also achieved us- ing this methodology, making use of gas-phase tracers. These tracers made possible the discrimination between biogenic and continental/anthropogenic sources of SOA. We found that continental SOA was dominant during both seasons (24– 50 % of total OA), while contributions from photochemistry- driven SOA (9 % of total OA) and marine emissions (13 % of total OA) were also observed during summertime. A semi- volatile nighttime component was also identified (up to 18 % of total OA during wintertime). This approach was success- fully applied here and implemented in a new source appor- tionment toolkit.
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J. Braz. Chem. Soc.  vol.28 número12

J. Braz. Chem. Soc. vol.28 número12

It was found that the small variation of dichloromethane ratio in the isopropanol (A):n-hexane (B):dichloromethane (C) system would affect the retention time and the separation degrees between NP and adjacent NPnEOs. Three gradient elution procedures with different dichloromethane ratios (A:B:C linear changed within 30 min: from 1:96:3 to 10:87:3, from 1:95:4 to 10:86:4, from 1:94:5 to 10:85:5) were performed to investigate the separation of NP1EO, NP2EO, NP and NP3EO. Under the dichloromethane ratio of 4% (Figure 2), NP1EO, NP2EO and NP achieved complete separation, while NP and NP3EO showed a little overlap, which could be improved by changing the
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