Showing papers on "Phase (matter) published in 1980"
TL;DR: In this article, the ternary system potassium laurate-1-decanol-D${2}\mathrm{O}$ was studied over concentration ranges where nematic phases are likely to occur.
Abstract: The phase diagram of the ternary system potassium laurate-1-decanol-D$_{2}\mathrm{O}$ was studied over concentration ranges where nematic phases are likely to occur. Two uniaxial nematic phases which are separated by a biaxial nematic phase are found. In limited concentration range the following phase sequence may be observed reversibly on heating and on cooling: isotropic-uniaxial nematic (positive optical anisotropy)-biaxial nematic-uniaxial nematic (negative optical anisotropy)-biaxial nematic-uniaxial nematic (positive optical anisotropy)-isotropic.
629 citations
TL;DR: In this article, it is shown that the gravity current can pass through three states: a slumping phase, a viscous phase, and a purely inertial phase, where the buoyancy force of the intruding fluid is balanced by the inertial force.
Abstract: Experimental results for the release of a fixed volume of one homogeneous fluid into another of slightly different density are presented, From these results and those obtained by previous experiments, it is argued that the resulting gravity current can pass through three states. There is first a slumping phase, during which the current is retarded by the counterflow in the fluidinto which it is issuing. The current remains in this slumping phase until the depth ratio of current to intruded fluid is reduced to less than about 0,075. This may be followed by a (previously investigated) purely inertial phase, wherein the buoyancy force of the intruding fluid is balanced by the inertial force. Motion in the surrounding fluid plays a negligible role in this phase. There then follows a viscous phase, wherein the buoyancy force is balanced by viscous forces. It is argued and confirmed by experiment that the inertial phase is absent if viscous effects become important before the slumping phase has been completed. R’elationships between spreading distance and time for each phase are obtained for all three phases for both two-dimensional and axisymmetric geometries. Some consequences of the retardation of the gravity current during the slumping phase are discussed.
592 citations
TL;DR: A general outline of the relationship between phase structure and overall composition can be obtained from a consideration intra-and inter-micellar interactions as mentioned in this paper, which also gives some insight into the relationship of rheological properties and phase structure.
537 citations
TL;DR: The inclusion of bile salts in a fixed stoichiometry within the interior of the bilayers is shown to provide a quantitative explanation for the divergence of the mixed micellar sizes, their temperature dependence, and the origin of the lecithin-bile salt phase limit.
Abstract: From measurements of the autocorrelation function and time-averaged intensity of light scattered from aqueous bile salt-lecithin solutions, we deduced the mean hydrodynamic radius (Rh), shape, and polydispersity of bile salt-lecithin mixed micelles as functions of bile salt species, lecithin to bile salt (L/BS) molar ratio, total lipid concentration (0.625-10 g/dL), temperature (20-60 degrees C), and NaCl concentration (0.15-0.6 M). Our data suggest that at low L/BS ratios (0 to approximately 0.6) simple bile salt micelles coexist in varying proportions with minimum-sized mixed micelles (Rh, 18-35 A). These solutions are highly polydisperse and display features dependent upon the particular bile salt species. At high L/BS ratios (greater than 0.6), only mixed micelles are present, and their sizes increase markedly (Rh, 20 leads to 300 A) with increases in L/BS ratio and appear to diverge as the lecithin-bile salt phase limit is approached. The shape of the mixed micelles as deduced from light-scattering measurements and confirmed by transmission electron microscopy is disklike. The radii of the disks, however, are not compatible with Small's model of mixed micellar structure [Small, D.M. (1967a) Gastroenterology 52, 607-a1 but are consistent with a new model proposed here in which bile salts and lecithin interact to form a mixed bilayer disk which is surrounded on its perimeter by bile salts. The inclusion of bile salts in a fixed stoichiometry within the interior of the bilayers is shown to provide a quantitative explanation for the divergence of the mixed micellar sizes, their temperature dependence, and the origin of the lecithin-bile salt phase limit. The influence of total lipid concentration on both mixed micellar size and the lecithin-bile salt phase limit is explained by the "mixed disk" model by taking account of the equilibrium between mixed micelles and bile salt monomers in the intermicellar solution. By use of this concept, deductions of the intermicellar bile salt concentration in taurocholate-lecithin solutions are made and are shown to vary as a function of mixed micellar size and temperature. The range of values obtained, 3-6 mM, is comparable in magnitude to the critical micellar concentration of the pure bile salt.
489 citations
TL;DR: In this article, the authors describe the process of nucleation, growth and coarsening, which combines to dictate the final particle density produced by a phase transformation, illustrated in Fig. 1, which depicts the number of particles vs. time.
379 citations
TL;DR: In this article, the authors used experimental methane-krypton and methane-argon hydrate data to generate chemical-potential, enthalpy, and heat-capacity functions for Structure I hydrates for temperatures between -190/sup 0/ and 80/Sup 0/F (150 and 300 K) using a modified statistical model where the gas-water interactions were calculated from the spherical core Kihara intermolecular pair potential function.
Abstract: Because hydrate formation in pipelines, processing operations, and reservoirs is generally undesirable, studies of gas-hydrate thermodynamics, particularly examinations of conditions where a second hydrate phase or a hydrocarbon-rich phase exists in addition to the water, hydrate, and gas phases, are important to the natural gas industry. In this study, analysts used experimental methane-krypton and methane-argon hydrate data to generate chemical-potential, enthalpy, and heat-capacity functions for Structure I hydrates for temperatures between -190/sup 0/ and 80/sup 0/F (150 and 300 K). These properties were based upon a modified statistical model where the gas-water interactions were calculated from the spherical-core Kihara intermolecular pair potential function. (The model does not use any adjustable parameters that depend upon the gas species present.) Estimates of the Kihara water-energy and water-distance parameters were -251.57/sup 0/F (115.46 K) and 375.06 pm, respectively. The mixing rules for the Kihara parameters are probably the weakest point of the model, but they are necessary to the corresponding-states approach for predicting the hydrate phase equilibrium. Although the model does not allow satisfactory predictions for larger or highly asymmetric hydrate-forming molecules (such as propane and isobutane), the results of this study can serve as a base for modificatins that account for bothmore » size and asymmetry.« less
351 citations
TL;DR: An ab initio calculation of the solid-solid phase transformation, static structural properties, and the lattice dynamics of Si is presented in this article, with the atomic number as the only input.
Abstract: An ab initio calculation fof the solid-solid phase transformation, static structural properties, and the lattice dynamics of Si is presented. A density-functional pseudopotential scheme is used with the atomic number as the only input. The detailed properties of the diamond to ..beta..-tin transition are accurately reproduced. The phonon frequencies and mode-Grueneisen parameters at GAMMA and X, along with the lattice constant, bulk modulus, and cohesive energy, are calculated and found to be in excellent agreement with experiment.
308 citations
TL;DR: In this paper, the phase relationships in the ternary systems Cr Al C, V Al C and Ti Al C have been investigated, and the perovskite phase Ti3AlC has been found to be in equilibrium with Al4C3, Al(1), Al3V, V7Al8, V (solid solution with Al), V2C, V 2C, γ-VC1−x, and VC 1−x (including V8C7).
287 citations
TL;DR: It is concluded that in the gel phase, at all temperatures below the main transition, the acyl chains are predominantly in all-trans conformations and that the temperature-dependent variations of spectral parameters result from changes in interchain interactions.
Abstract: Fourier transform infrared spectroscopy has been used to study the infrared-active acyl chain vibrational modes of fully hydrated multibilayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (L-DPPC) over the temperature range 0-55 degrees C. Frequencies, bandwidths, and other spectral parameters were measured as a function of temperature for the methylene scissoring, rocking, and wagging modes, as well as for the C-H stretching modes, and they were used to monitor the packing of the acyl chains. Particular emphasis was placed on determining the nature of the pretransition event. It is shown that between 36 and 38 degrees C the spectral changes are indicative of a phase change in the acyl chain packing from an orthorhombid to a hexagonal subcell. It is also concluded that in the gel phase, at all temperatures below the main transition, the acyl chains are predominantly in all-trans conformations and that the temperature-dependent variations of spectral parameters result from changes in interchain interactions.
235 citations
TL;DR: In this paper, the influence of the chain length of n-alkyldimethylsilyl bonded phases (RP-1 to RP-22) on retention has been investigated using methanol-water mixtures as the mobile phase.
222 citations
TL;DR: In this paper, the fine structure of the carbon Auger peak was found to be a sensitive indicator of the chemical state of a carbonaceous layer and it is suggested that the CH x layer consists to a large degree of CH species.
TL;DR: In this article, the T-x phase diagram of the binary system Cu2S-In2S3 has been determined by differential thermal analysis and X-ray diffraction, and two ternary semiconducting phases are found, CuInS2 and CuIn5S8.
TL;DR: The proposed phase diagram provides an explanation for several conflicting literature proposals of stoichiometries for phosphatidylcholine-cholesterol complexes in membranes, and correspond to the boundaries of two-phase areas in the gel region of the phase diagram.
Abstract: We have investigated the phase behavior of dipalmitoylphosphatidylcholine-cholesterol bilayers using both the fluorescence of bilayer-associated 1,6-diphenyl-1,3,5-hexatriene (DPH) and freeze-fracture electron microscopy to elucidate specimen structure. Arrhenius analysis of the fluorescence-derived "microviscosity" parameter reveals temperature-induced structural changes in these membranes. In addition, isotherms of DPH fluorescence anisotropy and total intensity are used to detect alterations in membrane structure with varying cholesterol content. Freeze-fracture electron microscopic studies, utilizing rapid "jet-freezing" techniques, show strikingly different fracture-face morphologies for different combinations of sample cholesterol content and temperature. A phase diagram is proposed that offers a unifying interpretation of the fluorescence and freeze-fracture results. In this interpretation, inflections in temperature-scanning and isothermal fluorescence measurements reveal phase lines in the dipalmitoylphosphatidylcholine-cholesterol membranes Two-phase regions of the proposed phase diagram correspond to samples showing two coexisting fracture-face morphologies, while single-phase regions produce membranes having only one clearly identifiable structure. The proposed phase diagram provides an explanation for several conflicting literature proposals of stoichiometries for phosphatidylcholine-cholesterol complexes in membranes. These stoichiometric complexes correspond to the boundaries of two-phase areas in the gel region of the phase diagram. To better approximate the effect of cholesterol on natural membranes, the structure of egg phosphatidylcholine-cholesterol multilamellar vesicles was also investigated by using DPH fluorescence. The results for this complex natural phospholipid system are interpreted by comparison with the synthetic phospholipid results.
TL;DR: In this paper, the compositional variation of the chemical diffusion coefficient in the six intermediate phases LiSn, Li7Sn3, Li5Sn2, Li13Sn5 and Li22Sn5 of the lithium-tin system at 415°C has been measured.
TL;DR: In this paper, the transition from lamellar to cubic to hexagonal in aqueous system of sunflower oil monoglycerides is analyzed and a linear relationship between the lattices of the three phases is discussed on the basis of structures formed by lipid bilayer units.
TL;DR: The packing densities of spheres of two different sizes, regularly arranged in a few structures based on cubic or hexagonal packing, have been calculated for different ratios (γ) of the radii of the spheres as mentioned in this paper.
Abstract: The packing densities of spheres of two different sizes, regularly arranged in a few structures based on cubic or hexagonal packing, have been calculated for different ratios (γ) of the radii of the spheres. Apart from a series of structures ABn, formed by very small B spheres filling cavities in a close-packed array of A spheres, only two arrangements AB (NaCl-type) and AB2 (AlB2-type) have packing fractions greater than the 0·7405 of the separate close-packed phases. Thus it is likely that for 0·24 < γ < 0·458 a mixture of A and B spheres will contain the AB phase, and for 0·482 < γ < 0·624, AB2 should occur. An ideal cubic structure AB13, containing an icosahedral cluster of small (B) spheres cannot have a packing fraction greater than 0·738, but a small modification to the structure permits an increase in the packing to 0·76, and is suggested as the explanation for the appearance of this phase in the opal specimen described in Part I of this work.
TL;DR: In this article, an algorithm for the construction of complete vapour envelopes, capable of accurately determining the critical points and maxima in temperature and pressure is described, and a computationally more convenient formulation is suggested.
TL;DR: The phase diagram of the Bi2O3-Er 2O3 system was investigated in this article and a monophasic f c c c structure was stabilized for samples containing 17.5-45.5 mol% Er2O 3.
Abstract: The phase diagram of the Bi2O3-Er2O3 system was investigated. A monophasic f c c structure was stabilized for samples containing 17.5–45.5 mol% Er2O3. Above and below this concentration range polyphasic regions appear. The f c c phase showed high oxygen ion conduction. The ionic transference number is equal to one for specimens containing 30 mol% Er2O3 or less, while an electronic component is introduced at low temperatures for specimens containing 40–60 mol% Er2O3. Between 673 K and 873 K a maximum in the conductivity was found at 20 mol% Er2O3. (Bi2O3)0.8.(Er2O3)0.20 is found to be the best oxygen ion conductor so far known. The conductivity at 773 K and 973 K is 2.3 Ω−1m−1 and 37 Ω−1 m−1 respectively. These values are 2–3 times higher than the best oxygen ion conductor reported for substituted Bi2O3 systems and 50–100 times higher than those of stabilized zirconia (ZrO2)0.915(Y2O3)0.085 at corresponding temperatures.
TL;DR: In this paper, the hold-up time of the n-alkyldimethylsilyl-bonded methanol-water was investigated and a rough estimate of the holdup time can be obtained by using components of the mobile phase or highly concentrated salt solutions, but only for mobile phase compositions around 60% (v/v) methanoline.
Abstract: The determination of the hold-up time in reversed phase liquid chromatography has been studied extensively for the mobile phase system methanol-water. Hold-up times obtained by static methods, linearization of homologous series and so-called “unretained compounds” are discussed and mutually compared. Several n-alkyldimethylsilyl bonded phases have been used for this investigation. A rough estimate of the hold-up time can be obtained by using components of the mobile phase or highly concentrated salt solutions, but only for mobile phase compositions around 60% (v/v) methanol. Hold-up times accurate to 1% can be obtained over the complete range of mobile phase compositions from the linearization of net retention times of homologous series.
TL;DR: The geometric properties of polygranular microstructures of the Johnson-Mehl cellular types have been studied through computer simulation as mentioned in this paper, and their geometric features have been characterized through a combination of analytic and computer simulation studies.
TL;DR: In this paper, the Riemann problem with phase boundary has been studied in the context of dynamic elastic bar theory, and it has been shown to be consistent with the maximal rate of decay of entropy.
Abstract: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 1. Dynamic Elastic Bar Theory . . . . . . . . . . . . . . . . . . . . . . . 126 2. Existence of Solutions with Phase Boundaries . . . . . . . . . . . . . . . 129 3. Extensions of Theorem 1 . . . . . . . . . . . . . . . . . . . . . . . . . 133 A. Data prescribed on both sides of the phase boundary . . . . . . . . . . . 133 B. Global solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 C. Invariance groups . . . . . . . . . . . . . . . . . . . . . . . . . . 136 4. Interaction of Sound Waves with a Phase Boundary . . . . . . . . . . . . . 136 5. The Riemann Problem and Admissibility . . . . . . . . . . . . . . . . . 143 A. The Riemann problem. Single phase boundary . . . . . . . . . . . . . 143 B. The Riemann problem. Double phase boundary . . . . . . . . . . . . . 147 C. Admissibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 1. Consistency with static stability theory . . . . . . . . . . . . . . . . 150 2. Consistency with viscoelastic bar theory . . . . . . . . . . . . . . . 153 3. Consistency with the maximal rate of decay of entropy . . . . . . . . . 156 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
TL;DR: In this paper, phase equilibria data in the systems SiO2-P2O5, P2O-5-M(x)O(y), and P 2O5-m O(y)-SiO2 are employed in conjunction with chromatographic and spectral data to investigate the role of P2 O5 in silicate melts.
TL;DR: In this article, distribution phenomena associated with the elution of solutes of varying retention from reversed-phase chromatographic columns have been examined, and it was shown that the composition of the extracted modifier system could be varied by the addition of a second solvent to the mobile phase, such as occurs in ternary mobile phase systems.
TL;DR: The Galvani potential difference at the interface of two immiscible electrolyte solutions (ITIES), Δ α βϕ, can be determined, when concentrations, activity coefficients, standard Gibbs transfer energies of all ions, which are present in the system, volumes of each phase and temperature are known as discussed by the authors.
IBM1
TL;DR: In this article, the leading terms in the magnetic equation of state are calculated for models with random fields and random uniaxial anisotropies for dimensionalities $dl4$.
Abstract: The leading terms in the magnetic equation of state are calculated for models with random fields and random uniaxial anisotropies for dimensionalities $dl4$. In the random anisotropy case we find a new low-temperature phase, in which the magnetization vanishes but the zero-field susceptibility is infinite, because of algebraically decaying correlations. No phase transition is found for the random field case.
TL;DR: Natural mixtures of bacterial menaquinones were separated according to the length and degree of saturation of the polyisoprenyl side-chain using ready made Merck RP-18F254 reverse phase thin-layer chromatography plates to provide a simple and rapid means of menaquinone characterization.
Abstract: Natural mixtures of bacterial menaquinones were separated according to the length and degree of saturation of the polyisoprenyl side-chain using ready made Merck RP-18F254 reverse phase thin-layer chromatography plates. The system described affords a simple and rapid means of menaquinone characterization.
TL;DR: In this paper, the kinetics of corrosion were measured by accelerated oxidation tests on Co 30Cr and Ni 30Cr as a function of temperature from 600°-900°C, in the environment and deposit composition.
Abstract: The kinetics of corrosion were measured by accelerated oxidation tests on Co‐30Cr and Ni‐30Cr as a function of temperature from 600°–900°C, in the environment and deposit composition. The alloys were rapidly attacked at temperatures between 650° and 750°C when a liquid sulfate phase was obtained from an initially pure solid deposit. The rapid rate of attack resulted from sulfation of the transient surface nickel or cobalt oxides and the dissolution of these transition metal sulfates into to yield a liquid phase. This retarded the formation of a protective scale. The exposure conditions under which liquids could form from mixtures were calculated from thermodynamic considerations.
TL;DR: In this article, the volume fraction φ 0 of the dispersed phase in close-packed, uncompressed emulsions is predicted as a function of the thickness of the film separating neighboring droplets, and of the contact angle between the film and its adjacent Plateau border.