Unstable Mixtures Research Articles

Surface Modes and Ordered Patterns during Spinodal Decomposition of anABvModel Alloy

We study a lattice gas model for a binary alloy with vacancies by means of a mean-field kinetic equation. Simulations of droplets of unstable mixture immersed in a stable vapor show the emergence of ordered structures at the surface which propagate into the bulk. We calculate characteristic wavelengths and propagation velocities of these patterns by a linear stability analysis. The thickness of the ordered layer depends on the model parameters and the strength of the initial noise.

ABC Shock Crisis Threat

The ABC has weathered many crises. Its relationships with government are always potentially explosive on account of its character as a statutory authority, its dependence on government for each year's revenue, and its capacity to generate information and opinions useful and harmful to people in public life. The particular type of statutory authority provided for the ABC creates another source of conflict by separating the part-time chairmanship, appointed by government, from the full-time office of chief executive, chosen by chairman and board. Finally, ABC people work in an unstable mixture of hierarchy and consultation, and are apt to consider themselves, as workers in commercial media seldom do, not merely employees but guardians. These themes are illustrated by accounts of ten crises. The present crisis is judged to be the worst.

Study of the formation of α-U 2N 3+ x using unstable ammonia — reaction sequence and control of nitrogen activity

The formation of α-U 2N 3+ x by the reactions between U and NH 3 or a gas mixture of NH 3 and H 2 was examined at 300 °C. It was found that there were two routes for the reaction process. One route was the direct formation of α-U 2N 3+ x by the reaction of U and NH 3; the other included the formation of UH 3. Although the UH 3 formed in this way was finally converted to α-U 2N 3+ x , the reaction rate was very slow compared with the rates of nitride and hydride formation. It was presumed that the conversion of UH 3 to α-U 2N 3+ x was the rate-determining step in the series of reactions. It was also confirmed that the nitrogen content of α-U 2N 3+ x varied when the composition of the reactant gas mixture was changed. This result implies that the nitrogen activity of the unstable gas mixture is dependent on the composition.

Aquinas on Mind (review)

338 JOURNAL OF THE HISTORY OF PHILOSOPHY 33:z APRIL 1995 characterize philosophers during this period, and one sometimes wonders how useful it is to attempt such characterization. Suhrawardi's connection with Peripateticism seems to be close, and yet it is far from clear that his Illuminationist philosophy is very distant from his Peripateticism. Since the latter was thoroughly mediated by Neoplatonism , it was always a rather unstable mixture of Aristotelian and Platonic doctrines, and as such could be taken in a variety of ways. What Qu.tb al-Din managed to do with Suhrawardi's ontology is adapt it so that it could incorporate science. According to the latter, everything which is not a concrete individual is a mental abstraction, with the implication that the regularities which we observe in the world may be nothing more than arbitrary combinations of ideas. Qu.tb al-Din, who was after all mainly a scientist, managed to avoid this conclusion by identifying the formal aspect of our experience with the Platonic Forms and relating these to angels who keep species in existence through their position in the order of existence as abstract intellects. He goes on to develop Suhrawardi's account of the realm of visions, imagination, and dreams in such a way as to render it capable of analytical treatment. Since both Avicenna and Suhrawardi argue that the world of images constitutes yet another epistemological realm in addition to the worlds of body, soul, and intellect, this realm should be capable of philosophical clarification, and it is precisely this which Qu.tb M-DIn provides . The short essay which Walbridge translates deals with this issue, and reveals the considerable philosophical skills which its author could deploy. Although Qu.tb al-Din is working in an area replete with mystical language, he does not abandon the task of trying to understand analytically where the language of images is taking us. His main contribution is shown to be converting the esoteric into the exoteric, bringing mystical language closer to ordinary language, and so questioning the nature of the esoteric as a distinctive approach. This is an impressive book, and John Walbridge is to be congratulated for having clarified such a difficult yet rewarding set of ideas in the history of Islamic philosophy. OLIVER LEAMAN LiverpoolJohn Moores University Anthony Kenny. Aquinas on Mind. New York: Routledge, 1993. Topics in Medieval Philosophy. Pp. ii + a82. Cloth, $35.oo. In Aquinas on Mind, Anthony Kenny offers an interpretation of Aquinas's philosophy of mind based principally on a reading of the section of the Summa theologiaetraditionally referred to as the "Treatise on Man," that is, questions 75 through 89 of the prima pars (although the last two questions are omitted on the grounds that their concerns are principally theological). The book opens with Kenny's reflections on the relevance of Aquinas's philosophy of mind for contemporary philosophers; the second chapter provides the reader with an overview of some of the basic principles of Aristotelian metaphysics which come into play in Aquinas's philosophy; and the remaining chapters are devoted to the analysis of the texts themselves. Chapter 3 is devoted to perception and imagination (q. 78), chapter 4 to the intellecual powers (q. 79), chapters 5 and BOOK REVIEWS 339 6 to will and appetite (qq. 8o-83), chapters 7 through 9 to Aquinas's account of how we know the physical world (qq. 84-86 ), and chapter 1o to the problem of self-knowledge (q. 87). Kenny concludes with two chapters on Aquinas's general account of the soul and its relation to the body (qq. 75-76). While a few references to other relevant texts of Aquinas are made in the course of Kenny's work, by and large Kenny confines himself to what can be gleaned of Aquinas's views from this series of articles alone. Kenny's opening chapter defending the relevance of Aquinas's views for contemporary philosophers presents a generally convincing and eloquent case for the study of the history of philosophy, arguing against the claim that there is progress in all areas of philosophical endeavor. Kenny does admit that certain aspects of the history of philosophy have been...

Modelling and optimization of semi-batch and continuous nitration of chlorobenzene from safety and technical viewpoints

Abstract Performing nitration reactions in a semi-batch plant is potentially hazardous due to the handling of large quantities of unstable reaction mixture. This risk may be reduced by performing the nitration in a continuous way in a small well-stirred multi-stage reaction column. Based on new calorimetric measurements and data from the literature, the heterogeneous synthesis of dinitrochlorobenzene can be modelled and simulated in different types of reactors. The calculations show that a continuous process may be a favourable alternative to the semi-batch process both from an economic and a safety point of view.

Hydrogen/deuterium isotope effects on microphase separation in unstable crystalline mixtures of binary n-alkanes

We have observed large hydrogen-deuterium isotope effects on the microphase separation that occurs in unstable crystalline binary mixtures of n-alkanes rapidly quenched from the melt. These effects were studied in C 30 /C 36 mixtures at room temperature, mainly by infrared spectroscopy and electron diffraction. The isotope effects are manifest in a number of different ways: (i) immediately after the quench, the D/H (C 30 D /C 36 H ) mixture is significantly more demixed than the H/D (C 30 D /C 36 H ) mixture; (ii) the spontaneous demixing, which begins immediately after the quench to room temperature, is faster for D/H by a factor of about 3

C-S-Fe geochemistry of some modern and ancient anoxic marine muds and mudstones

Most sedimentary C, S and Fe occurs in marine muds and is originally present as an unstable mixture of dissolved sulphate, organic matter and detrital Fe minerals. During early diagenesis, key reactants are either destroyed (reduction of Fe(III) and SO 2- 4 to form pyrite), created (organically bound sulphur (OBS)) or preserved (Fe-bearing silicates). Pyrite formation is commonly limited not by sulphide availability but by the rate at which detrital Fe minerals react with sulphide. At low temperatures, detrital Fe(II) and Fe(III)-bearing clay minerals react very slowly with sulphide and are buried intact. The uptake of sulphur into organic matter is not, as commonly assumed, sulphide-limited. We believe that polysulphides react rapidly with organic matter and that the availability of reactive polysulphides may also influence the sulphur content of kerogen. Polysulphide formation is favoured at stable aerobic-anaerobic interfaces and sediments deposited under weakly oxygenated bottom waters are most likely to contain sulphur-rich kerogen. Deep burial (greater than 70 °C) C-S-Fe diagenesis is characterized by the loss and partial reduction of Fe(III) from smectitic and illitic clays and the conversion of limited amounts of obs to lower molecular mass S compounds. Pyrite formation is volumetrically insignificant. More than 90% of obs remains within organic-rich mudrocks during petroleum generation and expulsion, preserving a sulphur-enriched residual kerogen. The extent to which obs is eventually converted to H 2 S, and at what level of thermal maturity, is unclear. If, as may be likely, much of the sulphur in residual kerogen is thiophenic, it will be stable to at least 200 °C.

Measurement of the critical properties of thermally unstable substances and mixtures by the pulse-heating method

A method of measuring the critical temperatures and pressures of thermally unstable substances has been developed. The method is based on measuring the temperature of the attainable superheat with the help of a thin wire probe heated with electric-current pulses. With increasing pressure the temperature of the attainable superheat tends to the critical temperature. The authors have obtained a formula by which the dependence of the apparent critical temperature on the heating time is extrapolated to the critical temperature of an undecomposed substance. The results of measurement of the critical temperature and pressure of ethene glycol (ethane-1,2-diol), glycerin (propane-1,2,3-triol), dicumylmethane (di-1-methylethyldiphenylmethane), and (hexadecane + carbon dioxide) are given.

Unstable Mixtures, Dilated Spheres: Negt and Kluge's The Public Sphere and Experience, Twenty Years Later

Unstable Mixtures, Dilated Spheres: Negt and Kluge's <i>The Public Sphere and Experience</i>, Twenty Years Later

Reaction of uranium with ammonia

NH 3 can remain without being decomposed over a long period of time at temperatures of 300 °C or less. In this case NH 3 must be considered to be in a thermodynamically unstable state with respect to the dissociation equilibrium NH 3 = 1 2 N 2 + 3 2 H 2 and high nitrogen and hydrogen activities may be brought about by its instability. To gain some insight to the role of unstable NH 3 in chemical reactions with metals, reactions of U with static NH 3 were performed at 250 and 300 °C. The experimental results are discussed in terms of the nitrogen activity a N and hydrogen activity a H of unstable gaseous mixtures consisting of NH 3, H 2 and N 2.

The critical properties of dilute n-alkane mixtures

Abstract The critical properties of several dilute mixtures of n-hexane (solvent) with n-decane, n- tetradecane, n-octadecane, and n-docosane were measured using two experimental methods developed in our laboratory. The two methods are a sealed ampoule method for the measure- ment of the critical temperature and the critical density; and a flow method, which is used for the measurement of the critical temperature and pressure. Both methods have been used successfully by us to measure the critical properties of many thermally stable and unstable fluids and fluid mixtures. In the present work, the limiting slopes of the critical lines at infinite dilution were determined and compared with predictions from an equation of state. The appli- cation of these slopes for the prediction of phase equilibria in the dilute critical region was also explored, making use of recent theoretical developments in this field.

Polymerization in Microemulsion Systems

Abstract Polymerization of monomers in microemulsion systems has achieved widespread attention in recent days [1–11]. This new type of polymerization can be considered as an extension of emulsion polymerization [12]. Microemulsions are the colloidal dispersion of oil and water stabilized by certain alkali metal soaps, conventionally known as surfactants [13, 14] (Fig. 1). A microemulsion may be either oil continuous, where water is solubilized in oil phase (i.e., water-in-oil); or water continuous, where oil is dispersed in water, making it an oil-in-water microemulsion. Microemulsions differ completely from macroemulsions or miniemulsions in respect to their thermodynamic stability. Macroemulsions, conventionally known as emulsions, are opaque, milky, and thermodynamically unstable mixtures of two immiscible liquids having droplet size more than 100 nm. Microemulsions, on the other hand, are isotropic, transparent or translucent, and thermodynamically stable systems. This is due to the low interfacial tensions between oil and water microdomains. It is supposed that these microemulsions exist in the form of droplet structure having sizes in the range of 10–30 nm. However, a bicontinuous lamellar structure has also been postulated which is consistent with their transparency [15, 16].

Potential Hazard of Ferrocyanide Salts in High-Level Waste Tanks Within the Hanford Tank Farm

ABSTRACTOver the past few years, there has been an increased awareness of the potential hazard of energetic chemical reactions in high-level radioactive waste tanks at the Hanford tank farm. In particular, a mixture of Na2NiFe(CN)6 with NaNO3 and NaNO2 in several high-level waste tanks has caused concern. The problem of the FeCN tanks is fundamentally one of a potentially unstable mixture of fuel (the CN- moiety) and oxidizer (NO3- or NO2-).At Los Alamos National Laboratory, we have performed an extensive reanalysis of the safety problems associated with the presence of Na2NiFe(CN)6 mixed with NaNO3/NO2 for a particular tank (104-BY) that contains by far the largest amount of the nickel ferrocyanide salt (∼2E5 mol). Our approach is to use conservative assumptions to bound both the energy density for a potential runaway reaction and the mass that could participate if we assume ignition as the result of bounding radionuclide concentrations. The subsequent progress of the accident is analyzed using an advanced hydrodynamics computer code called MESA to evaluate the loads on the structure and the generation of aerosols. The subsequent doses are shown to be low both on and off the site. The conservatism in the analysis is quite large, and the expected results using more realistic assumptions are discussed.

Scanning thin-layer chromatography—liquid secondary ion mass spectrometry and its application for investigation of drug metabolites

Thin-layer chromatography—mass spectrometry including both direct and scanning thin-layer chromatography—liquid secondary ion mass spectrometry, has been used to obtain good separation and good mass spectra of non-volatile and thermally unstable mixtures. The methods are very simple, useful and easy to perform, and they can overcome the problems associated with indirect and direct coupling of liquid chromatography and mass spectrometry. Scanning thin-layer chromatography—liquid secondary ion mass spectrometry can be carried out like gas chromatography—mass spectrometry, and gives good quality chromatograms and mass spectra. These methods were used to analyse drug metabolites and mixtures of other organic compounds.

Merit in Courtly Literature: Castiglione, Rabelais, Marguerite de Navarre, and Le Caron

Spesse volte mi viene un dubbio, s'é dato dal nascimento (come nell'altre cose ancora) ch'i Principi siano propitii &amp; favorevoli verso questi, iniqui &amp; crudeli verso quegli altri, o se pure è posto nella industria nostra…. (Francesco Sansovino,Propositioni in materia di cose di Stato, Vinegia, 1583, fol. 110)Castiglione'sLibro del cortegiano(1528) and Renaissance courtesy literature in general chart an uneven course between the description of an illustrious courtly ideal never fully incarnate and the establishment of a set of rules enabling courtly practice and prescription. These two intentions, one roughly Platonic and the other roughly Aristotelian, are in the end contradictory, for the more substantial the ideal becomes, the less can it accommodate varying experience and therefore practice. The impulse to set forth an ideal as something outside of variety through which experience is to be judged is incompatible with the production of that ideal through the experiential mean of varying extremes.

ChemInform Abstract: Substituent Effects on Nitrosation of 1,3‐Diarylureas with Nitrosyl Chloride, Dinitrogen Trioxide and Dinitrogen Tetroxide.

Twenty-eight para-substituted and eleven ortho-substituted 1, 3-diarylureas were prepared.Their proton nuclear magnetic resonance (1H-NMR) spectra were measured to evaluate the acidity of the ureido protons in the para-substituted ureas, and to estimate the conformations of ortho-substituted molecules. The chemical shifts and acidities of two ureido protons were additively controlled by the two para-substituents in the 1, 3-diarylureas. The sixteen para-substitued diarylureas were nitrosated with gaseous nitrosating reagents (dinitrogen trioxide, dinitrogen tetroxide or nitroxyl chloride) to give unstable isomeric mixtures of 1, 3-diaryl-1-nitrosoureas [R1-C6H4-N(NO)-CO-NH-C6H4-R2] and 1, 3-diaryl-3-nitrosoureas [R1-C6H4-NH-CO-N(NO)-C6H4-R2]. The isomer ratio of each nitrosated urea was correlated with the difference between the chemical shifts (d[NH]) of the two ureido protons in the 1H-NMR spectrum of the starting urea. When d[NH] was below 0.25 ppm (with NOCl) or 0.45 ppm (with N2O3), good linearity was obtained (r(NOCl)=0.943, n=11; r(N2O3)=0.869, n=15). When d[NH] was over 0.25 ppm (NOCl) or 0.45 ppm (N2O3), the 1-nitrosated isomer [R1-C6H4-N(NO)-CO-NH-C6H4-R2] was the sole product. These principles ould not be extended to dinitrogen tetroxide.Thirteen para-substituted diarylureas gave 1- or 3-nitrosated ureido derivatives as sole products and only four gave nitrosated isomeric mixtures.The 1H-NMR spectra of 5 types of ortho-substituted 1, 3-diarylureas were measured for comformational analysis. Their conformations seem to be different from those of para-substituted diarylureas. Eleven ortho-substituted 1, 3-diarylureas were nitrosated with nitrosyl chloride and dinitrogen tetroxide. In many cases, the nitroso group was predominantly introduced at the ureido nitrogen, which is less hindered sterically, and isomeric mixtures of 1- and 3-nitrosated ureas were obtained.

Static and dynamic cross correlation in thermodynamically stable and unstable mixtures

Static and dynamic cross correlation in thermodynamically stable and unstable mixtures

Substituent effects on nitrosation of 1,3-diarylureas with nitrosyl chloride, dinitrogen trioxide, and dinitrogen tetroxide.

Twenty-eight para-substituted and eleven ortho-substituted 1, 3-diarylureas were prepared.Their proton nuclear magnetic resonance (1H-NMR) spectra were measured to evaluate the acidity of the ureido protons in the para-substituted ureas, and to estimate the conformations of ortho-substituted molecules. The chemical shifts and acidities of two ureido protons were additively controlled by the two para-substituents in the 1, 3-diarylureas. The sixteen para-substitued diarylureas were nitrosated with gaseous nitrosating reagents (dinitrogen trioxide, dinitrogen tetroxide or nitroxyl chloride) to give unstable isomeric mixtures of 1, 3-diaryl-1-nitrosoureas [R1-C6H4-N(NO)-CO-NH-C6H4-R2] and 1, 3-diaryl-3-nitrosoureas [R1-C6H4-NH-CO-N(NO)-C6H4-R2]. The isomer ratio of each nitrosated urea was correlated with the difference between the chemical shifts (d[NH]) of the two ureido protons in the 1H-NMR spectrum of the starting urea. When d[NH] was below 0.25 ppm (with NOCl) or 0.45 ppm (with N2O3), good linearity was obtained (r(NOCl)=0.943, n=11; r(N2O3)=0.869, n=15). When d[NH] was over 0.25 ppm (NOCl) or 0.45 ppm (N2O3), the 1-nitrosated isomer [R1-C6H4-N(NO)-CO-NH-C6H4-R2] was the sole product. These principles ould not be extended to dinitrogen tetroxide.Thirteen para-substituted diarylureas gave 1- or 3-nitrosated ureido derivatives as sole products and only four gave nitrosated isomeric mixtures.The 1H-NMR spectra of 5 types of ortho-substituted 1, 3-diarylureas were measured for comformational analysis. Their conformations seem to be different from those of para-substituted diarylureas. Eleven ortho-substituted 1, 3-diarylureas were nitrosated with nitrosyl chloride and dinitrogen tetroxide. In many cases, the nitroso group was predominantly introduced at the ureido nitrogen, which is less hindered sterically, and isomeric mixtures of 1- and 3-nitrosated ureas were obtained.

薄層クロマトグラフィーと質量分析法の直接結合 新しい焼結クロマトプレートによるＤｉｒｅｃｔ ＴＬＣ／ＭＳ

Mass spectrometry for nonvolatile and thermally unstable mixture samples still remains as a difficult problem. Thin-layer chromatography (TLC) is a simple and very effective method for the separation of mixtures. For coupling of TLC with mass spectrometry, a new TLC glass plate was devised. The plate has many linear grooves engraved on the rear, which guide a cutter to cleave to a strip. The strip is set on a usual holder for a mass spectrometer. This system provides a very simple and effective result for separation and measurement of mass spectra of the nonvolatile and thermally unstable mixtures.

薄層クロマトグラフィーと質量分析法の直接結合 薄層クロマトプレートを用いたＳＩＭＳ

A new technique, direct combination of thin-layer chromatography (TLC) with liquid secondary ion mass spectrometry (SIMS) enables very simple and excellent measuring method for thermally unstable mixture samples such as peptides and drug metabolites. For this technique a small strip of TLC aluminium sheet coated with silica gel taken from the usual developed TLC plate was used as a primary ion target in place of usual silver (metal) plate. In addition to this single spot measuring way, a TLC plate scanning technique was described.