Opaque phase

The rocks of the NS-N dyke group range from nepheline syenite to sodalite-bearing nephelinolite. The primary phases in the NS-N dyke group are k-feldspar and nepheline, with variable abundances of amphibole, plagioclase, phlogopite, calcite, sodalite, titanite, cancrinite, apatite, clinopyroxene, zircon, chlorite, quartz, pyrochlore, and opaque phases. 

Aii iamprophyres have been ciassified as sannaite iamprophyres, except an uitramafic damtjernite. The sannaite iamprophyres contain kfs, amp cai, cpx, phi, ap, pi, sodaiite, ms, ttn, ep, white mica, chi, zrn, and opaque phases. The coarse-grained damtjernite consists of phenocrystic phiogopite, with groundmass caicite, aikaii feidspar, and apatite. 

Chondrules. Chondrules are major constituents of chondrites, which are millimeter- to submillimeter-sized spherules consisting of silicate phenocrysts (relatively large crystals), glassy mesostasis, and a small fraction of opaque phases (Lauretta et al. 2006 and references therein Chapter 8). Their textural, mineralog-ical, and chemical features suggest that chondrules formed from dust aggregates that were melted by localized transient high-temperature events and were cooled relatively rapidly. 

A similar thermally-induced inversion of the cholesteric sense was observed for the PBLG liquid crystal in benzyl alcohol. In this solution, a gel-like opaque phase coexists with the cholesteric phase at lower temperatures. The opaque phase disappears around 70 °C, where endothermic peaks are observed in the differential scanning calorimetry curve. The value of S below 70 °C remains constant, and then changes with temperature above 70 °C. The compensation occurs at about 103 °C, and the transition from biphasic phase to the isotropic phase is observed above 150 °C in this case. The results are summarized in Fig. 12, where the reciprocal of the half-pitch is plotted against temperature. The sign of 1/S is taken as positive when the cholesteric sense is the right-handed. 

Modern analytical ultracentrifuges allow the separation of emulsions to be followed in a quantitative manner. With typical oil-in water (O/W) emulsions, three layers are generally observed (i) a clear aqueous phase (ii) an opaque phase consisting of distorted polyhedral oil droplets and (iii) a clear separated oil phase, resulting from coalescence of the polyhedra. 

The degree of emulsion stability may be taken as the volume of the opaque phase remaining after time t. Alternatively, the volume of oil separated at infinite time may be used as an index of stability. 

Typical Formulation of a Multiphase Toothpaste Comprising Clear and Opaque Phases... 

Figure 2.11. Polarized light microscopy of polyacrylate-silica aerogel composites obtained by phoVipolymeriza-tion of octylcyanobiphenyl liquid crystal infiltrated in the porosity of the aerogel (in the cliche, liquid crystal and silica aerogel are, respectively, the brilliant and opaque phases). Courtesy ofPesce da Silveira N (UFRGS, Porto Alegre, Brazil) and Rigacci A. [99].

PEI blends have also been further modified with silicone polyether-imide copolymer to improve impact strength, especially at lower temperatures. Use of a sihcone polyetherimide as an impact modifier has the added benefit of retaining or even improving flame retardance, as it has a lower fuel value than traditional rubbery impact modifiers. The sili-cone-PEI copolymer also has the stabihty needed to survive high PEI processing temperatures without decomposition. These PEI-sdicone copolymer blends are hazy or opaque, phase-separated systems. 

There are, however, several limitations to overcome before designing hydrogels based on PDMS. The primary obstacle is that PDMS is hydrophobic and insoluble in hydrophilic monomers. Thus, when attempts are made to copolymerize methacrylate functionalized siloxanes with hydrophilic monomers, opaque, phase-separated materials are usually obtained. In many cases, a co-solvent such as hexanol or isopropanol can be used to solubilize the siloxane and hydrophilic monomer. In addition, the copolymerization of methacrylate fimctionalized silicones with hydrophilic monomers results in materials with a reduction in water content, loss of surface wettability and an increase in lipophilic character. Lipid uptake can lead to a loss in material wettability. 

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