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Enthalpies of formation of kornelite [Fez(S[O.sub.4]).sub.3]-7.75[H.sub.2]O] and paracoquimbite [[Fe.sub.2](S[O.sub.4]).sub.3] 9[H.sub.2]0] were measured by acid (5 N HCI) solution calorimetry at T = 298.15 K. The samples were characterized chemically by an electron microprobe, and structurally by the means of single-crystal, in-house powder, and synchrotron powder X-ray diffraction. The refined structures for the two phases are provided, including estimates of the positions and concentration of non-stoichimetric water in structural channels of kornelite, location of the hydrogen atoms and the hydrogen bonding system in this phase. The measured enthalpies of formation from the elements (crystalline Fe, orthorhombic S, ideal gases [O.sub.2] and[H.sup.2]) at T = 298.15 K are -4916.2 [+ or -] 4.2 kJ/mol for kornelite and -5295.4 [+ or -] 4.2 k J/tool for paracoquimbite. We have used several algorithms to estimate the standard entropy of the two phases. Afterward, we calculated their Gibbs free energy of formation and constructed a phase diagram for kornelite, paracoquimbite, [Fe.sub.2][(SO.sub.4]).sub.3] * 5[H.sub.2]O, and [Fe..sub.2][(S[O.sub.4]).sub.3] as a function of temperature and relative humidity of air. The topology of the phase diagram is very sensitive to the entropy estimates and the construction of a reliable phase diagram must await better constraints on entropy or Gibbs free energy of formation. Possible remedies of these problems are also discussed. Keywords: Kornelite, paracoquimbite, thermodynamic properties, enthalpy of formation DOI: 10.2138/am.2009.3179

The effect of partial substitutions of Zr by Hf in the perovskite-type crystalline structure of PbZr[O.sub.3] is determined. The crystalline structure of pure PbZr[O.sub.3] and PbHf[O.sub.3] perovskites, the phase diagram of the Pb[Zr.sub.1-x][Hf.sub.x][O.sub.3] family is described.

For cellular biochemical reaction systems where the numbers of molecules is small, significant noise is associated with chemical reaction events. This molecular noise can give rise to behavior that is very different from the predictions of deterministic rate equation models. Unfortunately, there are few analytic methods for examining the qualitative behavior of stochastic systems. Here we describe such a method that extends deterministic analysis to include leading-order corrections due to the molecular noise. The method allows the steady-state behavior of the stochastic model to be easily computed, facilitates the mapping of stability phase diagrams that include stochastic effects, and reveals how model parameters affect noise susceptibility in a manner not accessible to numerical simulation. By way of illustration we consider two genetic circuits: a bistable positive-feedback loop and a negative-feedback oscillator. We find in the positive feedback circuit that translational activation leads to a far more stable system than transcriptional control. Conversely, in a negative-feedback loop triggered by a positive-feedback switch, the stochasticity of transcriptional control is harnessed to generate reproducible oscillations. intrinsic noise | phase diagram | synthetic biology | oscillations

A general theoretical model is described for the NMR spectra of mixtures of sterols and deuterium-labeled phospholipids. In the case of homogeneous membranes, the average quadrupole splittings are determined by equilibria between lipids in cholesterol-phospholipid complexes and lipids not in complexes. Chemical exchange of lipids between those in the free state and those in the complex state affects the deuterium resonance line shapes. The lifetime of a phospholipid molecule in an ergosterol-dipalmitoylphosphatidylcholine complex is estimated to be of the order of 10-s s on the basis of the observed line broadenings. In the vicinity of a critical point of a cholesterol-phospholipid mixture, fluctuations in the concentration of complexes also can contribute to the deuterium nuclear resonance line broadening. At the critical point, the temperature derivative of the concentration of complexes is discontinuous. There is a corresponding jump in the calculated heat capacity as well as in the temperature derivative of the deuterium NMR first moment. condensed complexes | critical point fluctuations | order parameters | phase diagrams | reaction kinetics

Whether salt is or is not melting when it dissolves in water, a matter of some significance in the teaching of introductory science, is discussed. Elementary school teachers are concerned when students talk about melting or disappearing when they see solid substances dissolving in a liquid. Definitions and data are examined. When a mixture of two or more solids is heated the resulting process can be called melting or dissolving. Teachers can still be learners and share that learning with other teachers without disgrace, as learning is to be celebrated. Students may profit by knowing that teachers are also learning.

Phase diagrams of one-component systems and their use for the general chemistry course are discussed. Topics include equilibrium and the Gibbs phase rule, illustrative high-pressure phase diagrams (carbon dioxide, water, hydrogen, iron). Students can gain appreciation for the concept of equilibrium before it is formally introduced through work with acid-base chemistry, thermodynamics and solubility products. Information about structural chemistry and phase equilibria in the full phase diagrams of common substances is much richer than general chemistry students think it is. Textbooks use these very little.

Experiments at 70-224 kbar, using a split-sphere anvil apparatus, reveal the melting relations on the enstatite-diopside join. For low pressures, melting in the enstatite-rich compositions is peritectic that turns eutectic at higher pressures. The diopside-rich clinopyroxene experiences azeotropic melting at 70-165 kbar and at temperatures lower than the eutectic. Relationships with the coexisting garnets and perovskites are studied with the help of the melting curve of diopside. Applications of the calculated temperature-pressure phase diagram from the study are discussed.

A model based on phase diagrams facilitates the determination of the fractional crystallization paths in olivine-plagioclase-augite basalts. Empirical equations are used as a thermobarometer to estimate the variations in temperature and composition in these rocks for different pressures. Augite composition plays an important role in the crystallization history. Detailed results of 190 anhydrous experiments are provided. Glasses from the east limb of the East Pacific Rise have been used to illustrate the workability of the proposed model.

The amount of hydrogen or oxygen released or consumed during mineral reactions determines the composition of C-O-H fluid in graphite rocks. The mass balance constraints acting during the fluid-rock interaction are explained by the compositional degree of freedom. The calculation of the C-O-H-FeO-TiO2-SiO2 system petrogenetic grid confirms the pressure-temperature stability field of this assemblage.

Differential scanning calorimetry is used in the determination of the enthalpies of formation of metastable fcc Ag-Cu solid solutions, prepared by ball milling of elemental powders. The calculation of phase diagrams and atomistic simulation predictions are used in the experimental determination of the thermodynamic data for these metastable alloys. The free-energy minimization methods of the enthalpy of formation and lattice parameters of the metastable solid solutions are used in the evaluation of the equilibrium of Ag-Cu phase diagram.

Phase diagrams of inorganic compounds in aqueous solutions are a useful way of illustrating phase properties such as the ability of Plaster of Paris to become a rigid mass after moistening. These aqueous solutions are often used as chemical reagents in industrial and laboratory processes and so students should be aware of their phase behavior. Two- or three-dimensional graphs can be used to illustrate binary systems' behavior through comparing temperature, pressure and composition. Some examples of two-dimensional graphs for water and potassium iodide among other solutions are included.

Abstract--In this contribution, an efficient active power filter (APF) technique in phase coordinates abc is proposed, which can mitigate the harmonics generated by nonlinear components and loads. It avoids the transformation between different frameworks and allows a control circuit design to be relatively simpler and easier to implement. The effective operation of the proposed APF is demonstrated and the potentials are illustrated with a case study. Index Terms--Active power filter (APF), harmonic mitigation, phase coordinates.

Using the micromagnetics package MAGPAR, we study the ground states of NiFe nanorings with sub-100-nm lateral dimensions, in zero external field. We solve the Landau-Lifschitz-Gilbert equation for three different initial magnetizations (in plane, out of plane, and vortex) to obtain the lowest energy state. Plotting the total energy as a function of thickness, along with its corresponding magnetostatic and exchange energies, we are able to identify various phase transitions and derive phase diagrams as a function of thickness and outer radius, normalized to the exchange length, for rings with different inner to outer radius ratios. We discuss the results in terms of shape anisotropy and its effect on the magnetostatic and exchange energies. We also compare the results of our numerical method to the phase diagram of a nanodot and the phase diagrams of rings obtained by analytical models. Finally, we present a new ground state configuration, the helix, found along the boundary between the vortex and out of plane phases, where the magnetization is vortex like, but with moments canted along the z direction. Index Terms--Micromagnetics, nanoring, phase diagram.

A modified phase diagram can be used to help students of chemistry understand the relationship between melting point range and purity. In many organic chemistry laboratory textbooks a two-component phase diagram is used to illustrate melting point lowering and eutectic mixtures. Discussions in such books usually cover the relationship of melting point and melting point range to purity in terms that refer only to an idealized two-component phase diagram. Some point out that the melting at a temperature at which it begins will usually not be detectable except for mixtures close to the eutectic composition and that the first appearance of liquid will be at a temperature below the one where all the solid disappears and above the point where it begins. That helps, but students find the diagram and the generalizations difficult to reconcile. A diagram that makes it easy for a student to understand that the most easily recognized difference between a very pure sample and an almost-pure sample will be significantly wider melting point range of the less purer sample can be created. The difference is not the slightly lower temperature at which all solid is liquefied.

A modified eight-order Landau potential is described for the BaTi[O.sub.3] single crystal by considering the quantum mechanical effects at low temperature. The new Landau potential is used for calculating the dielectric coefficients, spontaneous polarizations, temperature-electric field phase diagram and piezoelectric coefficients.

The analysis of Cr-Mn alloy films that are epitaxially stabilized on GaSb (100) by suing molecular beam epitaxy is described. The structural and magnetic phase diagrams of the epitaxial Cr-Mn alloy films are presented.

The magnetization switching behavior in a nanostructured magnetic thin film, under combined in-plane fields along the longitudinal and the transverse directions, is examined. The results have shown that the switching phase diagram is constructed analytically with the use of a total energy equation.

The Sn-In-Me (Me = Ag, Cu) systems belong to the group of potential candidates for lead-free solder materials. Samples, representing two vertical sections: with In : Ag = 7 : 3 from Sn-In-Ag ternary system and with Cu : In = 1 : 9 from Sn-In-Cu ternary system, were measured with Differential Scanning Calorimetry (DSC). The experimental transformation temperatures were compared with CALPHAD-type calculation results based on thermodynamic parameter values from COST531 database. The characterisation of investigated samples was done using Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX), Light Optical Microscopy (LOM), electroconductivity and microhardness measurements.

The scanning tunneling microscopy in the sub-monolayer regime is employed to study the 'in vacuo' self-assembly of a two-component porphyrin system on a metal surface. The results obtained are discussed consistently on the basis of molecule-surface and molecule-molecule interactions as well as thermodynamic aspects for qualitative comprehension of the phase behavior of the two-dimensional bimolecular system.

Several modular studies are conducted to explain the phase stability, dielectric response and the various properties of the ultrathin epitaxial (001)-oriented lead zirconate titanate films. The combinations of the in-plane misfit strains are shown to be the best alternatives to attain high dielectric and piezoelectric coefficients.

The operation of a MEMS-based micro heat engine at resonant and off-resonant conditions are described where the model and experiment are used for examining the resonant and off-resonant operation of the engine. The pressure-volume (PV) diagrams of an engine operated at resonance and off-resonance have shown that resonant operation is beneficial.

Multiferroic Y-type hexaferrite [Ba.sub.0.5][Sr.sub.1.5][Zn.sub.2][Fe.sub.12][O.sub.22] ceramics are prepared and their magnetic and dielectric properties are compared with single crystal. Ferroelectric (FE) phase is induced by external magnetic field in all samples and the phase diagram in ceramics has resembled that of the single crystal.

The article discusses the approach, which employs the mechanical alloying of melt-spun ribbon for the synthesis of metastable [gamma]-FeNi nanostructures. The mechanisms employed for the stabilization and the tuning of the Curie temperature of these nanostructures are also discussed.

The functioning of microevaporators is examined by using numerics and analytical arguments. The stationary gradients have displayed exact exponential or Gaussian shapes depending on a Peclet number (Pe) that has compared the mobility of the solute to the convection in the microevaporator.

Multilayers of [(F/NF).sub.N] composition, where F is a ferromagnetic layers, NF is a nonferromagnetic one and N the number of repetitions, are analyzed theoretically for different magnetic anisotropy characterized by the quality factor Q. The studies have shown that a [(F/NF}.sub.N] multilayer is a soft magnetic system in which the domain size is changed by a few orders of magnitude by small variations of Q, N, and the NF spacer thickness.

The phase diagram and compressibility of wolframite-type tungstates are examined by using x-ray powder diffraction and absorption in a diamond-anvil cell and ab initio calculations. The studies have shown that monoclinic wolframite-type MgW[O.sub.4] has suffered at least two phase transitions and they have also disclosed details of the local-atomic compression in MgW[O.sub.4] and ZnW[O.sub.4].

An external magnetic field B perpendicular to the ring's plane is considered to calculate the electronic states of an array of [N.sub.d] quantum dots (QDs) patterned in an isolated quantum ring. The phase diagrams for the insulating band from half to integer filling shed light on a rich variety of ground states revealing transitions in which the total spin changes.

The complete phase diagram of NdFeAs[O.sub.1-x][F.sub.x] solid solution is provided as a function of electron doping by the determination of F- and O-content and phase content. The method has indicated that in order to provide reliable results on the complex new superconducting materials, a rigorous control of the chemical composition of the phase is carried out.

A study was conducted to demonstrate the contribution of sweeping rate (SR) of the applied magnetic field as another parameter towards the appearance of the vortex avalanche. The results shed light on the strong dependence of the appearance of the vortex avalanche on the SR, particularly at low temperature and also allowed to obtain H-T phase diagram that distinguished the regions of magnetic stability and instability for each SR.