Binary and ternary inclusion complexes of dapsone in cyclodextrins and polymers: preparation, characterization and evaluation

Dapsone (DAP) is a synthetic sulfone drug with bacteriostatic activity, mainly against Mycobacterium leprae. In this study we have investigated the interactions of DAP with cyclodextrins, 2-hydroxypropyl-beta-cyclodextrin (HP beta CD) and beta-cyclodextrin (beta CD), in the presence and absence of water-soluble polymers, in order to improve its solubility and bioavailability. Solid systems DAP/HP beta CD and DAP/beta CD, in the presence or absence of polyvinylpyrrolidone (PVP K30) or hydroxypropyl methylcellulose (HPMC), were prepared. The binary and ternary systems were evaluated and characterized by SEM, DSC, XRD and NMR analysis as well as phase solubility assays, in order to investigate the interactions between DAP and the excipients in aqueous solution. This study revealed that inclusion complexes of DAP and cyclodextrins (HP beta CD and beta CD) can be produced in order to improve DAP solubility and bioavailability in the presence or absence of polymers (PVP K30 and HPMC). The more stable inclusion complex was obtained with HP beta CD, and consequently HP beta CD was more efficient in improving DAP solubility than beta CD, and the addition of polymers had no influence on DAP solubility or on the stability of the DAP/CDs complexes.

Boron site preference in ternary Ta and Nb boron suicides

X-ray single crystal (XSC) and neutron powder diffraction data (NPD) were used to elucidate boron site preference for five ternary phases. Ta3Si1-xBx (x=0.112(4)) crystallizes with the Ti3P-type (space group P4(2)/n) with B-atoms sharing the 8g site with Si atoms. Ta5Si3-x (x=0.03(1); Cr5B3- type) crystallizes with space group 14/mcm, exhibiting a small amount of vacancies on the 4 alpha site. Both, Ta-5(Si1-xBx)(3), X=0.568(3), and Nb-5(Si1-xBx)(3), x=0.59(2), are part of solid solutions of M5Si3 with Cr5B3-type into the ternary M-Si-B systems (M=Nb or Ta) with B replacing Si on the 8h site. The D8(8)-phase in the Nb-Si-B system crystallizes with the Ti5Ga4-type revealing the formula Nb5Si3B1-x (x=0.292(3)) with B partially filling the voids in the 2b site of the Mn5Si3 parent type. (C) 2012 Elsevier Inc. All rights reserved.

Rheological Measurements and Thermal Characterization of Lamellar Gel Phase Emulsions Developed with Cetearyl Alcohol/Nonionic Ethoxylated Surfactants

The aim of this research was to characterize emulsion systems (ES) containing nonionic ethoxylated surfactants by using rheological, microscopic, and thermogravimetric assays. Three formulations were developed: ES-1: 8.0% (w/w) oleth-20; ES-2: 4.0% (w/w) oleth-20/4.0% (w/w) steareth-21; and ES-3: 8.0% (w/w) steareth-21. The systems showed typical non-Newtonian pseudo-plastic behavior. The presence of a lamellar gel phase was observed for all systems, with ES-2 being more pronounced. Through thermogravimetry, the profiles of the three systems were found to be similar, consisting of two main events, the first one being characterized by loss of water and, beyond 110 degrees C, by loss of the oil phase.

Ternary lithium based compounds used for technological applications

Im Rahmen dieser Dissertation wurden ternäre Li-haltige Halb-Heusler Verbindungen sowie dazu strukturell-verwandte Verbindungen untersucht. Diese Verbindungen sind potentielle Kandidaten für optoelektronische und spintronische Anwendungen.rnEinige der untersuchten Verbindungen sind auch als Elektroden Materialien inrnLi-Batterien geeignet. Neben der Synthese und der Untersuchung der chemischenrnEigenschaften wurden daher insbesondere die physikalischen Eigenschaften näherrnuntersucht. Im speziellen wurden Halb-Heusler Verbindungen wie LiMgZ (Z = P,rnAs, Sb) und LiZn1−xMnxP synthetisiert und charakterisiert. Des Weiteren wurdenrndie Verbindungen LiMnAs, LaOMnAs und LiCuS näher studiert.rnVerbindungen des Typs LiMgZ (Z = P, As, Sb) sind potentielle Anode-Materialienrnin Li-Batterien. Im Rahmen der Arbeit gelang es diese Verbindungen einphasig zurnsynthetisieren. Mit Hilfe der UV-VIS Spektroskopie wurden Bandlücken im Bereichrnvon 0.9 und 2.3 eV bestimmt. 7Li NMR Spektroskopie zeigte eine ausreichende LirnMobilität, die sich mit steigender Temperatur erhöht.rnWeiterhin wurde die Mischkristallserie LiZn1−xMnxP mit x = 0.04, 0.08 und 0.10rnuntersucht. Ziel dieser Arbeit war es aus dem Halbleiter LiZnP durch Dotierungrneinen verdünnten magnetischen Halbleiter herzustellen. Diese Materialien werdenrninsbesondere in der Spintronik benötigt. Optische Messungen zeigten, dass diernDotierung bis x = 0.10 zu einer Reduzierung der Bandlücke von 1.80 eV für LiZnPrnzu 1.18 eV für LiZn0.90Mn0.10P führt. Magnetische Untersuchungen erwiesen paramagnetischesrnCurie-Weiss Verhalten und negative Weiss Konstanten, die auf einernantiferromagnetische Ordnung bei tiefen Temperaturen hindeuten.rnLiMnAs und LaOMnAs sind beides antiferromagnetische Halbleiter, die insbesonderernf¨ur spinelektronische Anwendungen von Bedeutung sind. Die magnetischernStruktur von LiMnAs wurde mit Hilfe der Neutronenbeugung näher untersucht. DiernNeel Temperatur wurde zu 374 K bestimmt. Bei einer Temperatur von T = 768 Krnkommt es zu einer Phasenumwandlung. Die tetragonale Struktur wandelt sich hierrnin einer kubischen Halb-Heusler Phase um. Dichte Funktional Rechnungen sind inrnguter Übereinstimmung mit den experimentellen Werten. Darüberhinaus wurde diernKopplung der magnetischen Momente näher bestimmt.rnrnEine Verbindung der Zusammensetzung LiCuS wurde in der Literatur beschriebenrnals eine Phase, die sich bei der Reaktion von Li mit CuS in Li/CuS Batteriesystemrnbildet. Diese Verbindung ist auch als Ersatz von CdS in Pufferschicht vonrnDünnfilm-Solarzellen von Interesse. Es gelang erstmals diese Verbindung einphasigrnherzustellen. Sie kristallisiert gelb mit der nicht-stöchiometrischen ZusammensetzungrnLi1.1Cu0.9S. Die Kristallstruktur wurde mit Hilfe von NMR, PXRD und Neutronenbeugungrnaufgeklärt. Die Bandlücke wurde aus den optischen Messungenrnvon Dünnschichten bestimmt und beträgt circa 2 eV. Dieser Wert ist in guter Übereinstimmung mit DFT Ergebnissen. Wird der Li-Gehalt erhöht, erhält manrnab circa Li1.7Cu0.3S eine kubische Phase. Sie ist isotyp mit Li2S, die im anti-CaF2 Typ kristallisiert. Diese Verbindung ist ein direkter Halbleiter mit einer Bandlücke von 2.4 eV nach DFT Rechnungen.

Structural characterization of intermediate and metastable phases by electron microscopy

Structure characterization of nanocrystalline intermediates and metastable phases is of primary importance for a deep understanding of synthetic processes undergoing solid-to-solid state phase transitions. Understanding the evolution from the first nucleation stage to the final synthetic product supports not only the optimization of existing processes, but might assist in tailoring new synthetic paths. A systematic investigation of intermediates and metastable phases is hampered because it is impossible to produce large crystals and only in few cases a pure synthetic product can be obtained. Structure investigation by X-ray powder diffraction methods is still challenging on nanoscale, especially when the sample is polyphasic. Electron diffraction has the advantage to collect data from single nanoscopic crystals, but is limited by data incompleteness, dynamical effects and fast deterioration of the sample under the electron beam. Automated diffraction tomography (ADT), a recently developed technique, making possible to collect more complete three-dimensional electron diffraction data and to reduce at the same time dynamical scattering and beam damage, thus allowing to investigate even beam sensitive materials (f.e. hydrated phases and organics). At present, ADT is the only technique able to deliver complete three-dimensional structural information from single nanoscopic grains, independently from other surrounding phases. Thus, ADT is an ideal technique for the study of on-going processes where different phases exist at the same time and undergo several structural transitions. In this study ADT was used as the main technique for structural characterization for three different systems and combined subsequently with other techniques, among which high-resolution transmission electron microscopy (HRTEM), cryo-TEM imaging, X-ray powder diffraction (XRPD) and energy disperse X-ray spectroscopy (EDX).rnAs possible laser host materials, i.e. materials with a broad band emission in the near-infrared region, two unknown phases were investigated in the ternary oxide system M2O-Al2O3-WO3 (M = K, Na). Both phases exhibit low purity as well as non-homogeneous size distribution and particle morphology. The structures solved by ADT are also affected by pseudo-symmetry. rnSodium titanate nanotubes and nanowires are both intermediate products in the synthesis of TiO2 nanorods which are used as additives to colloidal TiO2 film for improving efficiency of dye-sensitized solar cells (DSSC). The structural transition from nantubes to nanowires was investigated in a step by step time-resolved study. Nanowires were discovered to consist of a hitherto unknown phase of sodium titanate. This new phase, typically affected by pervasive defects like mutual layer shift, was structurally determined ab-initio on the basis of ADT data. rnThe third system is related with calcium carbonate nucleation and early crystallization. The first part of this study is dedicated to the extensive investigations of calcium carbonate formation in a step by step analysis, up to the appearance of crystalline individua. The second part is dedicated to the structure determination by ADT of the first-to-form anhydrated phase of CaCO3: vaterite. An exhaustive structure analysis of vaterite had previously been hampered by diffuse scattering, extra periodicities and fast deterioration of the material under electron irradiation. rn

Sonic log prediction in carbonates

This work is conducted to study the complications associated with the sonic log prediction in carbonate logs and to investigate the possible solutions to accurately predict the sonic logs in Traverse Limestone. Well logs from fifty different wells were analyzed to define the mineralogy of the Traverse Limestone by using conventional 4-mineral and 3-mineral identification approaches. We modified the conventional 3-mineral identification approach (that completely neglects the gamma ray response) to correct the shale effects on the basis of gamma ray log before employing the 3-mineral identification. This modification helped to get the meaningful insight of the data when a plot was made between DGA (dry grain density) and UMA (Photoelectric Volumetric Cross-section) with the characteristic ternary diagram of the quartz, calcite and dolomite. The results were then compared with the 4-mineral identification approach. Contour maps of the average mineral fractions present in the Traverse Limestone were prepared to see the basin wide mineralogy of Traverse Limestone. In the second part, sonic response of Traverse Limestone was predicted in fifty randomly distributed wells. We used the modified time average equation that accounts for the shale effects on the basis of gamma ray log, and used it to predict the sonic behavior from density porosity and average porosity. To account for the secondary porosity of dolomite, we subtracted the dolomitic fraction of clean porosity from the total porosity. The pseudo-sonic logs were then compared with the measured sonic logs on the root mean square (RMS) basis. Addition of dolomite correction in modified time average equation improved the results of sonic prediction from neutron porosity and average porosity. The results demonstrated that sonic logs could be predicted in carbonate rocks with a root mean square error of about 4μsec/ft. We also attempted the use of individual mineral components for sonic log prediction but the ambiguities in mineral fractions and in the sonic properties of the minerals limited the accuracy of the results.

Constitution and Specific Gravity of the Ternary Mattes Cu2S-Sb2S3-PbS

The constitution of the ternary mattes Cu2S PbS Sb2S3 has never been completely investigated nor has there been any attempt to draw the complete ternary diagram. The following work is intended to [be] a contribution towards completion of this diagram by determining the specific gravity of different mattes and by pointing out some which show peculiarities of structure.

Constitution and Specific Gravity of the Ternary Mattes Cu2S-FeS-PbS.

The constitution of the ternary mattes CU2S-FeS-PbS has never been completely investigated. Fulton and Goodner 1) have investigated the binary mattes CU2S-FeS, CU2S-PbS, PbSFeS and have shown that the three binaries show eutectics. There has been no attempt however to draw the complete ternary diagram. The following work is intended to be a contribution toward the completion of this diagram by first of all pointing out those mattes which separate on melting into two layers, and second by determining the specific gravities of mattes of different compositions.

Phase separation in aqueous solutions of lens gamma-crystallins: special role of gamma s.

We have studied liquid-liquid phase separation in aqueous ternary solutions of calf lens gamma-crystallin proteins. Specifically, we have examined two ternary systems containing gamma s--namely, gamma IVa with gamma s in water and gamma II with gamma s in water. For each system, the phase-separation temperatures (Tph (phi)) alpha as a function of the overall protein volume fraction phi at various fixed compositions alpha (the "cloud-point curves") were measured. For the gamma IVa, gamma s, and water ternary solution, a binodal curve composed of pairs of coexisting points, (phi I, alpha 1) and (phi II, alpha II), at a fixed temperature (20 degrees C) was also determined. We observe that on the cloud-point curve the critical point is at a higher volume fraction than the maximum phase-separation temperature point. We also find that typically the difference in composition between the coexisting phases is at least as significant as the difference in volume fraction. We show that the asymmetric shape of the cloud-point curve is a consequence of this significant composition difference. Our observation that the phase-separation temperature of the mixtures in the high volume fraction region is strongly suppressed suggests that gamma s-crystallin may play an important role in maintaining the transparency of the lens.

Correlation of the liquid–liquid equilibrium data for specific ternary systems with one or two partially miscible binary subsystems

This paper presents the results of a liquid–liquid equilibrium data correlation for 11 ternary systems which have not been previously fitted using the NRTL model or, when they have, the results presented in the literature are inconsistent with the experimental behavior of the system. These ternary systems include mixtures with one or two partially miscible pairs. During the correlation process, new restrictions were imposed on the values for the NRTL binary parameters to ensure correct prediction of the total or partial miscibility for the binary pairs involved. In addition, topological concepts related to the Gibbs stability test have been applied in order to validate the results in the whole range of compositions.

Modelling liquid–liquid equilibria for island type ternary systems

Closed miscibility gaps in ternary liquid mixtures, at constant temperature and pressure, are obtained if phase separations occur only in the ternary region, whilst all binary mixtures involved in the system are completely miscible. This type of behaviour, although not very frequent, has been observed for a certain number of systems. Nevertheless, we have found no information about the applicability of the common activity coefficient models, as NRTL and UNIQUAC, for these types of ternary systems. Moreover, any of the island type systems published in the most common liquid–liquid equilibrium data collections, are correlated with any model. In this paper, the applicability of the NRTL equation to model the LLE of island type systems is assessed using topological concepts related to the Gibbs stability test. A first attempt to correlate experimental LLE data for two island type ternary systems is also presented.

Pitfalls on computing liquid-liquid phase equilibria using the k-value method

Poster presented in the 11th Mediterranean Congress of Chemical Engineering, Barcelona, October 21-24, 2008.

Solubility, Density, Refractive Index, and Viscosity for the Polyhydric Alcohol + CsBr + H2O Ternary Systems at Different Temperatures

The solubility, density, refractive index, and viscosity data for the ethylene glycol + CsBr + H2O, 1,2-propanediol + CsBr + H2O, and glycerin + CsBr + H2O ternary systems have been determined at (288.15, 298.15, and 308.15) K. In all cases, the solubility of CsBr in aqueous solutions was decreased significantly due to the presence of polyhydric alcohol. The liquid–solid equilibrium experimental data were correlated using the NRTL (nonrandom two-liquid) activity coefficient model, considering nondissociation of the dissolved salt in the liquid phase, and new interaction parameters were estimated. The mean deviations between calculated and experimental compositions were low, showing the good descriptive quality and applicability of the NRTL model. The refractive indices, densities, and viscosities for the unsaturated solutions of the three ternary systems have also been measured at three temperatures. Values for all of the properties were correlated with the salt concentrations and proportions of polyhydric alcohol in the solutions.

Delta stabilized ternary alloys of plutonium /

A preliminary survey of the plutonium rich corners of the Pu-Al-Ga, Pu-Zn-Ga and Pu-Ce-Ga systems was made. Emphasis was placed on the determination of how well the delta phase of plutonium was stabilized by these alloy additions.

Mechanical alloying of MoSi2 with ternary alloying elements. Part 1: Experimental

Phase evolution during the mechanical alloying of Mo and Si elemental powders with a ternary addition of Al, Mg, Ti or Zr was monitored using X-ray diffraction. Rietveld analysis was used to quantify the phase proportions. When Mo and Si are mechanically alloyed in the absence of a ternary element, the tetragonal C11b polymorph of MoSi2 (t-MoSi2) forms by a self-propagating combustion reaction. With additional milling, the tetragonal phase transforms to the hexagonal C40 structure (h-MoSi2). The mechanical alloying of Al, Mg and Ti additions with Mo and Si tend to promote a more rapid transformation of t-MoSi2 to h-MoSi2. In high concentrations, the addition of these ternary elements inhibits the initial combustion reaction, instead promoting the direct formation of h-MoSi2. The addition of Zr tends to stabilise the tetragonal phase.