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Objective The re-greasing process and kinetics of the human scalp, post-shampooing, have been previously documented, in vivo, on a few Caucasian subjects. The objective of the presented research was to extend such knowledge over seven different ethnic groups. Methods The post-shampooing re-greasing kinetics of the scalp was studied on 1325 subjects (women and men of two distinct age classes) from seven different ethnic groups in their residential and native country. Sebum amounts were determined onto small shaved scalp areas at various times post-shampooing, using the Sebumeter® technique. Results As previously published on Caucasian subjects, scalp re-greasing process follows a hyperbolic-like kinetics over days. However, amounts of collected sebum highly vary with ethnicity. As recorded through the casual level (CL) at the equilibrium phase, 2–3 days post-shampooing, the highest amount of sebum was found in African American subjects, followed in descending order by Caucasian American, Japanese, Chinese, Thai, Caucasian European and Indian subjects, the latter showing very low values. Lower amounts of sebum were recorded in the older age class in all ethnics, as compared to the younger one, and male subjects were found higher sebum producers than women, irrespective of ethnicity. Conclusion The kinetics and slopes of the re-greasing process of the human scalp appear similar in all ethnic groups studied. However, striking quantitative differences are found between the seven ethnic groups, resulting from different sebaceous production levels and scalp hygiene routines.

In six-coordinate complexes, flexible tridentate ligands enable mer, cis-fac, and trans-fac stereoisomers. With labile metal ions of the first transition metal series, typically only the final thermodynamic product is available because of the rapid isomerization processes. Here we report on the structural characterization of a so far elusive kinetic intermediate of [Co(ddpd)2](BF4)2 (1; ddpd = N,N′-dimethyl-N,N′-dipyridine-2-yl-pyridine-2,6-diamine). Microcrystals of the cis-fac isomer of 1 were obtained by rapid precipitation. The solid-state structure of cis-fac-1 was determined from electron diffraction data.

Telluride misfit layer compounds are reported for the first time. These compounds were synthesized using a novel approach of structurally designing a precursor that would form the desired product upon low-temperature annealing, which allows the synthesis of kinetically stable products that do not appear on the equilibrium phase diagram. Four new compounds of the [(PbTe)1.17]m(TiTe2)n family are reported, and their structures were examined by a variety of X-ray diffraction techniques.

In this study, a series of solid-state dewetting experiments of pure and Hf-doped Ni films on sapphire and HfO2 substrates were conducted in order to measure the change in interfacial energy of the Ni–Al2O3 interface in the presence of Hf, and to study Hf interfacial segregation. It was found that Hf oxidizes under the conditions of the experiment (P(O2)=10−20 atm), Hf does not segregate to the Ni–Al2O3 interface, and that the interface energy of Ni–HfO2 is 2.7 ± 0.4 J/m2 vs 2.16 ± 0.2 J/m2 for the Ni–Al2O3 interface. This contradicts several theoretical studies that predict that Hf segregates to the interface to stabilize it thermodynamically. The solubility of Hf in bulk Ni was found to be significantly lower than the value reported in the equilibrium phase diagram.

We describe a method, called the iterative method, which can be used to construct equilibrium N -body models with a given mass distribution and with given kinematic properties, parameters, or constraints. This method is both very simple and very powerful and can be used for mass distributions with an arbitrary geometry and a large variety of kinematical constraints. Applications of this method include the creation of initial conditions forN -body simulations and the modelling of galaxies from their photometric and kinematic observations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Liquid–liquid phase separation is undesirable in crystallization as it leads to slow crystal growth and uncontrollable crystal morphology. Therefore, it is necessary to identify the conditions under which liquid–liquid phase split occurs, so as to avoid crystallization process taking place at such conditions. In this study, an experimental approach is developed to systematically construct the solid-liquid-liquid equilibrium (SLLE) phase diagram. A four-component system is used to demonstrate the experimental technique and the overall workflow in developing an SLLE phase diagram. 2007 American Institute of Chemical Engineers AIChE J, 53: 1608–1619, 2007

The Cd—Gd equilibrium phase diagram is investigated by powder XRD, SEM, and DTA of samples obtained from melts of the elements (Ta tubes in evacuated silica tubes

In a recent publication [Maćkowiak et al., J. Chem. Phys. 145, 164704 (2016)] the results of Non-Equilibrium Molecular Dynamics (NEMD) simulations of confined sheared Lennard-Jones molecular films have been presented. The present work builds on that study by focusing on the low wall speed (shear rate) regime. Maps are given of the steady-state structures and corresponding friction coefficients in the region where a transition from static to kinetic friction is observed. The boundary between static and kinetic friction regions is determined as a function of wall speed and applied pressure, which is located for wall speeds up to about 0.8 m s−1. It was found that stick-slip behavior extends to pressures as high as 1000 MPa. The NEMD equations of motion are shown to be consistent with the Prandtl–Tomlinson model in the ‘soft spring’ limit, which leads to a new expression for the friction coefficient. This study provides new details and insights into the nature of anomalous friction behavior in the so-called Plug-Slip part of the nonquilibrium phase diagram regime.

Telluride misfit layer compounds are reported for the first time. These compounds were synthesized using a novel approach of structurally designing a precursor that would form the desired product upon low-temperature annealing, which allows the synthesis of kinetically stable products that do not appear on the equilibrium phase diagram. Four new compounds of the [(PbTe)1.17]m(TiTe2)n family are reported, and their structures were examined by a variety of X-ray diffraction techniques.

Investigations of changes in phase composition and mechanical properties of CeO 2 - and Y 2 O 3 - stabilized plasma-sprayed ZrO 2 -based thermal barrier coatings (TBC) after long-term heat treatments at typical service temperatures were performed. Experimental studies include X-ray diffraction and mechanical testing. TBCs with a high amount of the tetragonal equilibrium phase t (8 mol-% CeO 2 ) show strong degradation due to the high amount of transformation to the monoclinic phase and the related decrease in strength. TBCs with a high amount of tetragonal or cubic non-equilibrium phases t' or c' are more suitable. Among these, TBCs with higher CeO 2 -stabilizer contents (19.5 mol-% CeO 2 /1.5 mol-% Y 2 O 3 and 35 mol-% CeO 2 ) show less amounts of monoclinic phase with respect to Y 2 O 3 -stabilized TBCs (4.5 mol-% Y 2 O 3 ), as commercially used. Therefore they seem to have a high potential for long-term applications.

Equilibrium phase diagrams of mixtures of propoxylated glyceroltriacrylate (GPTA) and the low molecular weight liquid crystal 4-cyano-4′-pentyl-biphenyl (5CB) are studied. The diagrams of monomeric and electron beam (EB) cured GPTA/5CB blends are established using polarized optical microscopy and differential scanning calorimetry techniques. The experimental data are successfully analyzed using mean field models and a reasonable choice of parameters.

The effect of thermal vacancies on the hardness of the annealed Fe-40 at.% Al with additives (Zr + B and Zr + Cr) is measured. The effects observed in the temperature dependence of the hardness are compared with the subdivision of the B2 (FeAl) field of the Fe-Al equilibrium phase diagram. (orig.)

We discuss the progress in realistic calculations of the optical response of semiconductor surfaces. It concerns numerical developments as well as the better inclusion of many-body effects. We show that the starting point of such calculations, the atomic structure and the surface equilibrium phase, can be now derived with high accuracy. The different steps are described in detail for the computation of the reflectance anisotropy and the exploration of the In-rich InP(001)2 4 surfaces.

Equilibrium phase relationships for the ternary system sucrose-water-isobutanol have been determined at 30° and 60° and for the system with n-butanol at 60°. These relationships are illustrated to include tie-line equilibria in the two liquid-phase concentration ranges. At 30° occasional appearance of an acicular crystalline solid phase was observed at high butanol concentrations but was of low stability and was difficult to reproduce. It was not positively identified.

The isothermal cross-section through the temary phase diagram Sn-Ag-Sb at 220 was constructed by means of diffusion couples and equilibrated alloys. It is proposed that only two phases. Sn 4 Sb 3 and Sn 3 Sb 4 , exist in the binary Sn-Sb system, and no equiatomic compound SnSb is present as an equilibrium phase at this temperature. No ternary phases were found in the Sn-Ag-Sb system at 220°C; the topology of the isotherm is largely determined by the presence of the extended region of solid solution between the ζ-Ag 4 Sn and ζ-Ag 4 Sb intermetallic phases.

The structure of electrodeposited composite coatings of Ni–Al–Al2O3, with Ni as the matrix and Al and Al2O3 as second-phase particles, was investigated using light microscopy and scanning electron microscopy. Ni coatings with no particles, which were used as reference samples, had progressively coarser structures with increasing current density. Co-deposition with Al resulted in refinement of the Ni matrix structure at high (>10 A dm−2) current densities. For single-particle baths, the co-deposition of Al2O3 was more strongly affected by current density and bath particle content than was the co-deposition of Al. However, for baths containing both Al and Al2O3 the amount of incorporated Al2O3 no longer depended on current density. With the choice of appropriate conditions, coatings of Ni with up to 39 vol.% Al2O3 were made. Similar experiments with Al yielded a maximum of 17.5 vol.% only. Uniform and graded mixed-particle coatings were also produced. When coatings containing Al were annealed, the reaction of the two elements resulted in the formation of either single-phase γ or two-phase γ–γ′ alloys, in agreement with the equilibrium phase diagram.

A new non-equilibrium state of metal materials induced by irradiation has been found in preceding studies of the authors by the method of X-ray investigation. Now the morphology peculiarities accompanying this transition are described. There are three stages and three groups of microstructures depending on irradiation parameters. These are essentially different whether the microstructure corresponds to a state within a specific interval of the transition or out of this interval. There are some signs of microstructures observed which are similar to the structural elements in heavily deformed metals, in particular, the rotation mode and the appearance of hydrodynamical flow.

CoP ist bei hinreichender Zugabe von Iod als Transportmittel uber einen grosen Temperaturbereich (650°C ⩽ T ⩽ 1000°C; T (T1 + T2)/2, ΔT = 100 K) aufgrund endothermer Reaktionen transportierbar. Zentrale Bedeutung fur die Wanderung des Cobaltmonophosphids hat das heterogene Gleichgewicht Bei niedrigen Transporttemperaturen (T ≤ 800°C) und genugend hohen Transportmitteldichten (D ≥ 7,5 mg · cm−3) liegt CoI2,l neben CoP in der Senke vor. Thermodynamische Modellrechnungen zum chemischen Transport von CoP mit Iod unter Verwendung uberarbeiteter thermodynamischer Daten fur CoI2,l, CoI2,g und Co2I4,g geben die beobachteten Phasenverhaltnisse im Bodenkorper sowie die Transportraten fur CoP gut wieder. Detaillierte Aussagen zur Zusammensetzung der Gleichgewichtsgasphase sind moglich. Der Einflus von Feuchtigkeitsspuren auf das Transportverhalten wird erortert. On the Chemical Vapour Transport of Cobalt Monophosphide using Iodine. Experiments and Thermochemical Model Calculations CoP can be crystallized by chemical vapour transport using iodine as transport agent. Over a wide temperature range (650°C ≤ T ≤ 1000°C; T = (T1 + T2)/2; ΔT = 100 K) the migration from the higher to the lower temperature is based on the heterogeneous equilibrium CoI2,l is observed as second condensed equilibrium phase besides CoPs in experiments carried out at lower mean temperatures (T ⩽ 800°C) and with sufficiently high amounts of iodine. Thermochemical model calculations, based on modified data for CoI2,l, CoI2,g and Co2I4,g, reproduce the observed deposition rates as well as the compositions of the condensed equilibrium phases. These calculations allow a detailed description of the equilibrium gas phase in the system Co/P/I under variable experimental conditions. The influence of traces of moisture on the transport behavior will be discussed.

A mechanically stable [110] oriented tetragonal barium titanate layer of ≤50 μm thickness on a rutile substrate has been obtained by reactive coating of screen printed barium titanate submicrometer powder on the substrate and following a two-step firing cycle at 1400°C for 6 min and 1310°C for 60 min. The results have been explained taking into account the BaTiO3–TiO2 equilibrium phase diagram.

Equilibrium phase diagrams for the ternary systems Nd–{Cr,Fe,Co,Zn}–Sb at 870 K have been determined and analyzed for the first time. The phase field distributions in these systems at 870 K are characterized by the presence of only a small number of ternary compounds: For M=Cr, Fe, Co and Zn we observed one, two, and three ternary antimonides, respectively.

This paper reports that equilibrium phase diagrams for the systems NdCl[sub 3]---CaCl[sub 2] and NdCl[sub 3]---NaCl were determined by differential thermal analysis. A simple eutectic was observed at 59 [plus minus] 1 mol% CaCl[sub 2] and 600[degrees] [plus minus] 2 [degrees]C in the NdCl[sub 3]---CaCl[sub 2] system. A compound NaCl [center dot] 3NdCl[sub 3] which melts incongruently at 545[degrees] [plus minus] 5[degrees]C to NdCl[sub 3] and a liquid containing approximately 47 mol% NaCl, and a eutectic at 68 mol% NaCl and 439[degrees] [plus minus] 2[degrees]C were found in the NdCl[sub 3]---NaCl system. On the basis of agreements between the activities calculated by the Clausius-Clapeyron equation and Temkin's model using the present data for the NdCl[sub 3]---CaCl[sub 2] system and the literature data for the PrCl[sub 3]---CaCl[sub 2] system, the melts in the former system consist of Nd[sup 3+], Ca[sup 2+], and Cl[sup [minus]] ions and in the latter system of Pr[sup 3+], Ca[sup 2+], and Cl[sup [minus]] ions. The above approach indicates the presence of Na[sup +], Cl[sup [minus]], and NdCl[sub 4][sup [minus]] in the NdCl[sub 3]-rich melts in the NdCl[sub 3]--NaCl system.

Replacing Pb-Sn with Pb-free solders is one of the most important issues in the electronic industry. Melting, dissolution, solidification and interfacial reactions are encountered in the soldering processes. Phase diagrams contain equilibrium phase information and are important for the understanding and prediction of phase transformation and reactive phase formation at the solder joints. This study reviews the available phase diagrams of the promising Pb-free solders, and their related materials systems. The solders are Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Zn, Sn-Bi, Sn-In and Sn-Sb. The materials systems are the solders with the Ag, Au, Cu, Ni substrates, such as Sn-Ag-Au, Sn-Ag-Ni, Sn-Cu-Au, and Sn-Cu-Ni ternary systems. For the Pb-free solders and their related ternary and quaternary systems, preliminary phase equilibria information is available; however, complete and reliable phase diagrams over the entire compositional and temperature ranges of soldering interests are lacking.

We survey the portfolio of computational strategies available for tackling the generic problems of phase behavior - free-energy-estimation and coexistence-curve mapping.

The phases which result from the oxidation of III-V compound semiconductors can be predicted from a knowledge of the condensed phase portion of their equilibrium phase diagrams. Examples will be shown for arsenides, antimonides, and phosphides. Use of these diagrams explicitly presumes equilibrium growth conditions, and that assumption often fails. In such cases kinetic rather than thermodynamic factors dominate the determination of the observed phases. Examples of this phenomenon for anodic oxidation will be presented. Recent interest in high pressure oxidation conditions as a means of alleviating kinetic limitations will be discussed for InP. The phase diagrams can also be used to predict interfacial reactions under certain conditions and data for GaAs will serve to illustrate this point.

Silver has played a critical role in the fabrication of metal/ high-Tc superconductor composites. Phase equilibrium in the binary PbO–Ag and CuO–Ag systems has been investigated using differential thermal analysis (DTA), thermogravimetry (TG), and X-ray diffractometry (XRD) techniques. Composition versus temperature diagrams have been established for these systems in air. Eutectic reactions CuO + Ag = L at a composition of Ag = 98.6 mol% and 932°± 3°C for the CuO–Ag system and PbO + Ag = L at a composition of Ag = 8.3 mol% and 825°± 3°C for the PbO–Ag system have been detected. The CuO–Ag system has two immiscible liquid phases in the composition regime of Ag = 30.6–98 mol%, and there are two immiscible liquid phases at the composition range of Ag = 11.7–95.7 mol% in the PbO–Ag system.

The fluctuation theory based on the functional integration method is developed for a multimode Dicke-Hamiltonian with arbitrary spins and with antiresonant terms included. The effective classical Hamiltonian of the fluctuations is deduced and the equilibrium phase transition, the existence of soft modes as well as the general equations of state are discussed in this unified approach. The consequences of the rotating-wave approximation are clearly distinguished. The solid state phenomena of the cooperative Jahn-Teller effect and of spin-reorientation are implied in these considerations. Die auf der Funktional-Integrationsmethode gegrundete Fluktuationstheorie wird fur einen multimoden Dicke-Hamiltonoperator mit beliebigen Spins, einschlieslich der Antiresonanzglieder entwickelt. Eine effektive klassische Hamiltonfunktion fur die Fluktuationen wird abgeleitet und die Gleichgewichtsphasenumwandlung, die Existenz von Nullfrequenz-Moden, sowie die allgemeinen Zustandsgleichungen in diesem einheitlichen Bild diskutiert. Die Folgen der „rotating-wave approximation” werden klar gekennzeichnet. Die Festkorperphanomene des kooperativen Jahn-Teller-Effektes und der Spinumorientierung werden in diesen Betrachtungen miteinbegriffen.

The model proposed in 1978 for threshold switching is explained more fully in terms of the generation-recombination induced non-equilibrium phase transition involved. This is done l. by reference to the control parameter plane of band-trap impact ionisation coefficients in which the state of the system is represented by a trajectory on which the externally applied electric field is a parameter; 2. by a classification of various types of switching which are admitted by the model; 3. by the provision of more current–voltage curves to which the model leads; 4. by the derivation of approximate expressions for switching and delay times provided by the model, and 5. by the interpretation of these characteristic switching times in terms of phase portraits. Das 1978 fur das Schwellenschalten vorgeschlagene Modell wird mit dem Generations–Rekombinations-induzierten Nichtgleichgewichts-Phasenubergang vollstandiger erklart. Dies wird erreicht : 1. unter Bezugnahme auf die Ebene der Steuerparameter der Stosionisationskoeffizienten, in der der Zustand des Systems durch eine Trajektorie dargestellt wird, bei der das ausere angelegte elektrische Feld ein Parameter ist; 2. durch eine Klassifizierung der verschiedenen Schalttypen, die durch das Modell geliefert werden; 3. durch den Vorschlag mehrerer Strom-Spannungs. Kurven, zu denen das Modell fuhrt 4. durch die Ableitung von Naherungsausdrucken fur das Schalten und die Verzogerungszeiten, die das Modell angibt, und 5. durch die Erklarung dieser charakteristischen Schaltzeiten mit Phasenbildern.

The various phases and the respective ranges of their existence were determined during continuous cooling from temperatures close below the solidus line to R.T. with a rate of 2 K min−1 as well as during the subsequent heating in few AlZn(40 wt.%)–Mg(X) alloys (X = 0; 0.5; 1.0; and 3.0 wt.%) by means of X-ray phase-analysis, small angle X-ray scattering, differential thermo-analysis, optical microscopy, and X-ray micro-analysis. The most striking features are that even addition of only 0.5 wt.% Mg cause the formation of precursors of the MgZn2 equilibrium phase few degrees below the solidus line. Wahrend der kontinuierlichen Abkuhlung von Temperaturen nahe unterhalb der Soliduskurve auf Raumtemperatur und wahrend der nachfolgenden Aufheizung mit 2 K min−1 wurden in AlZn(40 Gew.%)–Mg(X)-Legierungen (X = 0; 0,5; 1,0; 3,0 Gew.%) mit Hilfe der Rontgen-Phasenanalyse, der Rontgenkleinwinkelstreuung, der Differential-thermoanalyse, lichtmikroskopischer Aufnahmen und der Rontgenmikroanalyse die verschiedenen Phasen und deren Existenzbereiche bestimmt. Als uberraschendes Ergebnis zeigte es sich, das schon ein Zusatz von nur 0,5 Gew.% Mg die Bildung von Vorlaufern der MgZn2-Gleichgewichtsphase wenige Grade unter der Soliduskurve bewirkt.

The Tungsten oxides WO3, W20O59, W18O49 and WO2 have been transported by TeCl4 in monocrystalline Form. W3O is not a equilibrium phase of the system, and therefore it is impossible to obtain this phase by CTR. The value of the lower phase boundary of tungsten trioxide is 2.96. Die Wolframoxide WO3, W20O59, W18O49 und WO2 werden mit TeCl4 transportiert und einkristallin abgeschieden. W3O ist keine Gleichgewichtsphase des Systems und kann durch Transport nicht dargestellt werden. Die untere Phasengrenzzusammensetzung von Wolframtrioxid kann mit x = 2,96 angenommen werden.

Effective distribution coefficients of silicon in Fe—Si alloys with 1.0–12.1 at.% Si in floating zone melting at various solidification rates were determined. The dependence of kef on the solidification rate was compared with the Burton-Prim-Slichter equation. Effective distribution coefficients extrapolated to a zero solidification rate were compared with equilibrium distribution coefficients taken from the equilibrium phase diagram of Fe—Si.

Solubilities of MgO in aqueous HC1 solutions at 23°±3°C were measured and combined with analyses of neat magnesium oxychloride cements, cured in sealed containers, to construct an equilibrium phase diagram for the system MgO-MgCl2-H2O. Specific gravities and acidities of solutions saturated with MgO and relative humidities of vapor phases over sealed samples were measured and combined with XRD data to define the compositions in equilibrium with two crystalline phases. Studies of relative reaction rates indicated that the 5–1–8 phase crystallizes more rapidly than the 3·1·8 phase and that cements near the 3·1·8 composition react rapidly with atmospheric CO2 to form the chlorocarbonate phase.

Vapor and liquid equilibrium phase compositions have been determined at 310.9, 394.3, and 477.6 K for the mesitylene–methane binary system and at 310.9, 338.7, 394.3, and 477.6 K for the mesitylene–carbon dioxide system. At each temperature, the pressure ranged from the vapor pressure of mesitylene to about 15 MPa, although in the case of the mesitylene–carbon dioxide system, pressures were extended to the vicinity of the critical region at about 18 MPa. The data were used to calculate equilibrium ratios for each component in the binary system. On a determine les compositions a l'equilibre liquide-vapeur, a 310,9, 394,9, 394,3 et 477,8 K, pour le systeme binaire mesitylene-methane, et a 3 10,9,338,7,394,3 et 477.6 K pour le systeme mesitylene-anhydride carbonique. A chaque temperature, la pression a varie depuis la tension de vapeur du mesitylene et une pression d'environ 15 MPa; toutefois, dans le cas du systeme mesitylene-anhydride carbonique, la pression a ete elevee jusqu'au voisinage de la region critique, soit environ 18 MPa. On a employe les donnees obtenues pour calculer les rapports a I'equilibre pour chacun des composants du systeme binaire.

A theoretical investigation is presented of the approach of chemical reactions to their steady states in a continuous stirred tank reactor (CSTR). We define a approach time tϵ which is a measure of the time required for any perturbation to decrease below a certain value where ϵ = 1/e is a convenient choice for linear networks. We shown analytically for any first order network that the approach time is less than or equal to the average residence time but never longer regardless whether „overshoot” or „false start” occurs if the sum of the initial CSTR concentrations does not exceed the sum of the input concentrations. For higher order single step CSTR reactions we present analytical solutions for small perturbations from their steady states. We show that the longest relaxation time is equal to the average residence time for all non-autocatalytic higher order reactions in the CSTR. For autocatalytic reactions, however, the relaxation time constant in the CSTR may become infinite at critical flow rates. This interesting phenomenon is called critical slowing down and it has an analogy in second order equilibrium phase transitions. We show that critical slowing down may occur also in higher order autocatalysis. It may act as a tunable low pass filter i.e. the open autocatalytic reaction may resemble a kinetic buffer system that absorbs even large perturbations. As illustrations a number of examples of reaction types are presented. In der theoretischen Untersuchung behandeln wir die Naherung chemischer Reaktionen an den stationaren Zustand im Flusruhrreaktor (CSTR). Wir definieren eine Naherungszeit tϵ, die ein Mas darstellt fur die von einer beliebigen Storung benotigten Zeit, unter einen bestimmten Wert abzusinken, wobei ϵ = 1/e eine praktische Grose fur lineare Reaktionsnetzwerte ist. Wir zeigen analytisch, das diese Naherungszeit kleiner oder gleich der mittleren Verweilzeit, jedoch nie groser als dieselbe ist, selbst wenn „overshoot” oder „falscher Start” vorliegt . Dies gilt, wenn die Summe der Anfangskonzentrationen im CSTR die Summe der Zufluskonzentrationen nicht ubersteigt. Fur Einschrittreaktionen hoherer Ordnung im CSTR geben wir analytische Losungen fur kleine Storungen vom stationaren Zustand. Wir zeigen, das die langste Relaxationszeit gleich der mittleren Verweilzeit fur alle nicht-autokatalytischen Reaktionen hoherer Ordnung im CSTR ist. Fur autokatalytische Reaktionen kann jedoch die Relaxationszeit unendlich gros bei einer kritischen Flusgeschwindigkeit werden. Dieses interessante Phanomen wird als kritische Verlangsamung bezeichnet. Es zeigt eine Analogie mit Gleichgewichtsphasenumwandlungen zweiter Art. Wir zeigen, das die kritische Verlangsamung auch in der Autokatalyse hoherer Ordnung vorkommen kann. Die kritische Verlangsamung verhalt sich wie ein Tiefpassfilter, d. h. die offene autokatalytische Reaktion ist wie ein kinetischer Puffer, der selbst grose Storungen absorbieren kann. Mehrere Reaktionstypen werden als Beispiele durchgerechnet.

The lattice constant of the Al-rich matrix in equilibrium with (metastable) Guinier-Preston (GP) zones and the β(Zn) equilibrium phase is followed by the X-ray diffraction method during the decomposition of two Al–(8 and 24) at% Zn alloys. The respective decomposition states are determined by means of small-angle X-ray scattering and transmission electron microscopic investigations. The most striking result of these investigations is that the measured lattice constant fo the Al-rich matrix in metastable equilibrium with GP zones is considerably lower than expected according to literature data. This effect is explained by assuming that in the Al–Zn alloys containing a sufficiently dense system of GP zones the lattice spacing inside the zinc-rich GP zones and the zinc depleted matrix does not differ as expected. Die Gitterkonstante der Al-reichen Matrix im Gleichgewicht mit (metastabilen) Guinier-Preston(GP)-Zonen und der β(Zn)-Gleichgewichtsphase wird mit der Rontgenbeugungsmethode wahrend der Entmischung von zwei AlZn[(8 und 24) At%]-Legierungen verfolgt. Die zugehorigen Entmischungszustande werden mittels Rontgenkleinwinkelstreuung und Transmissionselektronenmikroskop ermittelt. Das uberraschendste Ergebnis dieser Untersuchungen ist, das die gemessene Gitterkonstante der Al-reichen Matrix im metastabilen Gleichgewicht mit GP-Zonen betrachtlich geringer ist als es nach den Literaturwerten zu erwarten ware. Dieser Effekt wird unter der Annahme erklart, das in AlZn-Legierungen, die ein ausreichend dichtes System von GP-Zonen enthalten, die Gitterabstande in den GP-Zonen und in der Matrix sich nicht so stark wie erwartet unterscheiden.

The crystal structures of the RTy intermetallic compounds, where y = (5n + 4)/(n + 2), n = 0, 1, 2, 3, …, are one-dimensional long-period superstructures of the CaCu5-type structure, with period, P, given by P = 2(n + 1). The period of these superstructures is related with the valence electron concentration, i.e. number of valence electrons per atom, e/a, as follows: e/a = 1/2 + 1/P. Since the value of e/a, according to this equation, becomes nearly constant for P value greater than eight, RTy one-dimensional long-period superstructures having periods greater than this value are not likely to exist distinctly. Variation of lattice parameters with composition of RTy supports this conclusion, too. The equilibrium phase diagram of the YCo system is presented. Die Kristallstrukturen der intermetallischen RTy Verbindungen, wobei y = (5n + 4)/(n + 2), n = 0, 1, 2, 3, …, ist, sind lineare Verwerfungsuberstrukturen von der CaCu5-Typ-Struktur. Die relative Verwerfungslange P dieser Verwerfungsuberstrukturen wird durch die folgende Gleichung gegeben: P = 2(n + 1). Diese Verwerfungslange hangt von der Valenzelektronkonzentration, d. h. der Anzahl der Valenzelektronen pro Atom, e/a, in folgender Weise ab: e/a = 1/2 + 1/P. Da e/a nach dieser Gleichung fur P groser als acht zu einem konstanten Wert strebt, wird erwartet, das die RTy Verwerfungsuberstrukturen fur P groser als acht nicht eindeutig existenzfahig sind. Die Gitterparameteranderungen mit der Zusammensetzung dieser Verwerfungsuberstrukturen unterstutzen auch diesen Befund. Das Gleichgewichtsphasendiagramm des YCo-Systems wird angegeben.

A quantitative mass fragmentographic method for the simultaneous determination of labeled and unlabeled propoxyphene in plasma is described. Dogs treated daily with propoxyphene-d0 were treated with a pulse dose of propoxyphene-d2 at day 20. It was found that following an initial rapid equilibrium phase levels of propoxyphene-d2 fell more rapidly than those of propoxyphene-d0. This result suggests that ‘deep’ pools of tissue bound propoxyphene exist which exchange very slowly with drug present in the central compartment. Experimental evidence is presented which demonstrates that the difference in behavior of propoxyphene-d0 and -d2 is not due to unanticipated secondary isotope effects.

A new compound with the composition PbCrO3, with Cr in the valence state of 4, was synthesized at high pressures above a pressure-temperature line extending from about 50 kbars at 750°C to 60 kbars at 1450°C. PbCrO3 can be quenched and retained at 1 atm but decomposes on heating above 275° C at the same pressure. PbCrO3 is considered to be an equilibrium phase at high pressures because it was synthesized from mixtures of PbO: CrO2 as well as from several other mixtures of compounds in the Pb-Cr-0 system. The new phase has the cubic perovskite structure and is the only known compound with Cr4+ in an octahedral site. PbCrO3 crystallizes primarily as black cubes which are often twinned on (111).

Equilibrium phase diagrams for the systems MgCl2-MgF2, CaCl2-MgF2 and NaCl-MgF2 were determined by differential thermal analysis, thermal analysis, and temperature-composition equilibrium techniques. Simple eutectics were observed at 78.0±0.5 mol% MgCl2 and 628°±2°C in the MgCl2-MgF2 system, at 87.5±0.5 mol% CaCl2 and 694°±2°C in the CaCl2-MgF2 system, and at 95.5±0.5 mol% NaCl and 786°±3°C in the NaCl-MgF2 system. The phase diagrams determined for these systems were compared with phase diagrams that were computed using Temkin's model. The phase diagrams of the CaCl2-MgF2 and NaCl-MgF2 systems were also compared with diagrams that were computed using the expression suggested by Flood et al. for reciprocal systems. The experimentally determined and computed phase diagrams agreed for the MgCl2-MgF2 system but not for the CaCl2-MgF2 and NaCl-MgF2 systems.

The equilibrium phase diagram for the system Li2O-BeO-SiO2 contains only one ternary compound, Li2BeSi04. Liquidus relations for compositions containing 33 mol% SiO2 were determined; 10 liquidus invariant points were located and 7 subsolidus compatibility triangles. The most refractory compositions lie on the join BeO-Li2BeSiO4, with a solidus temperature of 1320°C. Metastable phases observed were a high-quartz phase, Li2x(Si1-xBex)O2, x 0.33; phase X which is probably a metastable orthosilicate between Li2BeSiO4 and Be2SiO4; and phase Y which lies on the join Li2BeSiO4-SiO2. The crystal chemistry and glass network-forming properties of BeO are discussed.

On the basis of this extensive reinvestigation, an accurate equilibrium phase diagram of the entire Zr-Rh system is presented.

The high average thermal expansion required for thermal compatibility of dental porcelains with their substrate alloys is supplied by the mineral leucite (K2O Al2O3 4SiO2). Since leucite is not an equilibrium phase at the composition of component No. 1 of the Weinstein et al. patent, phase changes in this leucitecontaining frit could be responsible for the observed thermally induced changes in dental porcelain expansion behavior. This study sought to explore such phase changes.