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Characterization of the Open Porosity of Brake Pads. I. Development of 2-D Porosity Image Analysis Techniques

Congresos, Seminarios y Cursos. Noticias

On the question of silk in pre-Han Eurasia

When was silk first brought across the steppe from far China towards the European world? There is silk from the Middle Bronze Age of Uzbekistan, in Scythian burials of Siberia and among the Hallstatt grave-goods of western Europe. Teasing out the story of silk depends on identifying the textile, and distinguishing its…

Chemical Preparation of Manganese Dioxide/Polypyrrole Composites and Their Use as Cathode Active Materials for Rechargeable Lithium Batteries

Chemical preparation of composite powders of polypyrrole and either , , or spinel has been successfully achieved by injecting liquid pyrrole into an acidic medium containing suspended manganese dioxide powder as an oxidizing agent. The content of manganese dioxide in the composites increased with increasing amount of…

The reaction of ammonia with nitrogen dioxide in a flow reactor: Implications for the NH2 + NO2 reaction

Abstract The NH 3 /NO 2 system has been investigated experimentally in an isothermal flow reactor in the temperature range 850–1350 K. The experimental data were interpreted in terms of a detailed reaction mechanism. The flow reactor results, supported by a theoretical analysis of the NH 2 NO 2 complex, suggest that…

Morphology of Polymer-Stabilized Liquid Crystals

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMorphology of Polymer-Stabilized Liquid CrystalsC. V. Rajaram, S. D. Hudson, and L. C. ChienCite this: Chem. Mater. 1995, 7, 12, 2300–2308Publication Date (Print):December 1, 1995Publication History Published online1 May 2002Published inissue 1 December 1995https://pubs.acs.…

Stability of Liquid Crystalline Macroemulsions

The topological stability of emulsions of liquid crystal in water (glycerol) matrices is demonstrated for a wide range of materials and concentrations. Coalescence is prevented by an energy barrier for a topological ring defect formation in a neck between the two merging droplets. There is a characteristic size of emu…

From Porphyrin Isomers to Octapyrrolic “Figure Eight” Macrocycles

Cyclooctapyrroles such as 1–3 tend to form during the condensation of dipyrrolic units if cyclization to cyclotetrapyrroles is hindered for conformational reasons. These macrocycles are chiral and might afford interesting complexes with metal ions. Their most intriguing feature is their unusual figure-eight conformati…

CO chemisorption on TiO2(110): Oxygen vacancy site influence on CO adsorption

CO chemisorption has been studied on TiO2(110) under surface conditions where oxygen anion vacancy sites are not present (oxidized surface), compared to conditions where the vacancy sites are present (annealed surface). The binding energy of CO on the nondefective TiO2(110) surface is 9.9 kcal/mole in the limit of zer…

Electron density and optical anisotropy in rhombohedral carbonates. III. Synchrotron X-ray studies of CaCO3, MgCO3 and MnCO3

Diffraction-deformation electron-density (Δp) images for small, naturally faced single crystals of synthetic calcite (CaCO 3 ), magnesite (MgCO 3 ) and mineral rhodochrosite (MnCO 3 ) were measured with focused λ = 0.7 and 0.9 A synchrotron (SR) X-radiation. Mo Kα (λ = 0.71073 A) structure factors were also measured f…

The Role of Porphyrin‐to‐Porphyrin Linkage Topology in the Extensive Modulation of the Absorptive and Emissive Properties of a Series of Ethynyl‐ and Butadiynyl‐Bridged Bis‐ and Tris(porphinato)zinc Chromophores

Abstract A new method for the regulation of the photophysical properties of highly conjugated porphyrin arrays is described. The absorptive and emissive signatures of such supramolecular structures can be modulated to an impressive degree by regulation of: i) the extent of the steric interactions that define the barri…

Magnetic Exchange through Oxalate Bridges: Synthesis and Characterization of (.mu.-Oxalato)dimetal(II) Complexes of Manganese, Iron, Cobalt, Nickel, Copper, and Zinc

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagnetic Exchange through Oxalate Bridges: Synthesis and Characterization of (.mu.-Oxalato)dimetal(II) Complexes of Manganese, Iron, Cobalt, Nickel, Copper, and ZincJorgen Glerup, Patricia A. Goodson, Derek J. Hodgson, and Kirsten MichelsenCite this: Inorg. Chem. 1995, 34, 2…

An Improved Model for Structural Transformations of Heat-Treated Aluminous Dioctahedral 2:1 Layer Silicates

Abstract An improved model for the interpretation of thermal effects during dehydroxylation in aluminous dioctahedral 2:1 layer phyllosilicates considers trans- vacant (tv) and cis- vacant (cv) 2:1 layers and leads to very different temperatures of dehydroxylation for these tv and cv vacant modifications. In particula…

Doxorubicin encapsulated in sterically stabilized liposomes for the treatment of a brain tumor model: biodistribution and therapeutic efficacy

Anthracyclines entrapped in small-sized, sterically stabilized liposomes have the advantage of long circulation time, reduced systemic toxicity, increased uptake into systemic tumors, and gradual release of their payload. To date, there is no information on the behavior of these liposomes in brain tumors. The objectiv…

Partial Conductivities in SrTiO 3 : Bulk Polarization Experiments, Oxygen Concentration Cell Measurements, and Defect‐Chemical Modeling

Knowledge of the exchange kinetics of O 2 in SrTiO 3 allows us to design appropriate strategies to separate the ionic and the electronic conductivity. In the low‐temperature range, where the overall surface reaction is very slow compared to bulk diffusion and measuring time, electrochemical cells of the type Pt|SrTiO…

The chemical bond and atomic displacements in SrTiO3 from X-ray diffraction analysis

The deformation electron-density (dynamic Fourier) maps and the anharmonicity of atomic displacements in strontium titanate, SrTiO 3 (Gram-Charlier model), were studied by high-precision single-crystal X-ray diffraction analysis at 145(1) and 296(2) K. Space group Pm3m, cubic, λ(Mo Kα) = 0.71069 A, Z = 1, F(000) = 84,…

Cryo-TEM and SANS Microstructural Study of Pluronic Polymer Solutions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCryo-TEM and SANS Microstructural Study of Pluronic Polymer SolutionsKell Mortensen and Yeshayahu TalmonCite this: Macromolecules 1995, 28, 26, 8829–8834Publication Date (Print):December 1, 1995Publication History Published online1 May 2002Published inissue 1 December 1995ht…

Evaluation of spectroscopic properties ofYb3+-doped glasses

The absorption and emission properties of numerous glasses doped with ${\mathrm{Yb}}^{3+}$ ions have been investigated. The emission cross sections have been evaluated using the measured absorption spectra and principle of reciprocity, and again using the Fuchtbauer-Ladenburg formula. Agreement between the two methods…

Synthesis and Rietveld crystal structure refinement of mackinawite, tetragonal FeS

Abstract Mackinawite, tetragonal FeS, has been synthesised by reacting iron with Na 2 S solutions. A Rietveld structure refinement of X-ray powder diffraction data, recorded using X-rays monochromated from synchrotron radiation with a wavelength of 0.6023 Å, has been performed. The structure has been refined in the te…

Polarized Laser Induced Holographic Surface Relief Gratings on Polymer Films

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolarized Laser Induced Holographic Surface Relief Gratings on Polymer FilmsD. Y. Kim, Lian Li, X. L. Jiang, V. Shivshankar, J. Kumar, and S. K. TripathyCite this: Macromolecules 1995, 28, 26, 8835–8839Publication Date (Print):December 1, 1995Publication History Published on…