Tourmaline of the elbaite-dravite series from an elbaite-subtype pegmatite at Bližná, southern Bohemia, Czech Republic
Tourmaline of the elbaite-dravite series from an elbaite-subtype pegmatite at Bližna, southern Bohemia, Czech Republic.
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Photoinduced Alignment of Polymer Liquid Crystals Containing Azobenzene Moieties in the Side Chain. 5. Effect of the Azo Contents on Alignment Behavior and Enhanced Response
A series of side-chain polymer liquid crystals (PLCs) of 6-[4-(4-ethylphenyl)diazenylphenyloxy]hexyl methacrylate and 4‘-[6-(methacryloyloxy)hexyloxy]-4-cyanobiphenyl were synthesized and characterized. The effects of contents of the azo units and the wavelength of irradiation light on photoinduced alignment behavior…
Kinetics of Wet Oxidation of Propionic and 3-Hydroxypropionic Acids
Oxidation of aqueous solutions of 3-hydroxypropionic (3-HPA) and propionic acids (PA) was studied in a titanium high-pressure reactor at 280−310 °C using oxygen partial pressures between 10 and 45 bar. Oxidation of both acids was found to obey first-order kinetic with respect to their concentrations as well as to thei…
Transient Kinetics of SO2 Oxidation Over SCR-DeNOx Monolith Catalysts
A dynamic kinetic study of the undesired oxidation of SO 2 over a commercial V 2 O 5 −WO 3 /TiO 2 monolith catalyst for the SCR-DeNO x process is herein presented. Transient SO 2 conversion data were systematically collected during experiments involving step changes of temperature, area velocity, and feed composition…
Cyclization Phenomena in the Sol−Gel Polymerization of α,ω-Bis(triethoxysilyl)alkanes and Incorporation of the Cyclic Structures into Network Silsesquioxane Polymers
Intramolecular cyclizations during acid-catalyzed sol−gel polymerizations of α,ω-bis(triethoxysilyl)alkanes substantially lengthen gel times for monomers with ethylene ( 1 ), propylene ( 2 ), and butylene ( 3 ) bridging groups. These cyclization reactions were found, using mass spectrometry and 29 Si NMR spectroscopy,…
Study of Bulk and Surface Reduction by Hydrogen of CexZr1-xO2 Mixed Oxides Followed by FTIR Spectroscopy and Magnetic Balance
The CeO 2 and Ce x Zr 1 - x O 2 reduction by hydrogen was studied using IR spectroscopy to follow the evolution of the ν(OH) vibrational modes and a magnetic balance to estimate the global reduction percentage from the magnetic susceptibility. H 2 was introduced between 298 and 873 K on activated samples. On ceria, di…
Small-Angle X-ray Scattering Study of Sol−Gel-Derived Siloxane−PEG and Siloxane−PPG Hybrid Materials
Hybrid organic−inorganic two-phase nanocomposites of siloxane−poly(ethylene glycol) (SiO 3/2 −PEG) and siloxane−poly(propylene glycol) (SiO 3/2 −PPG) have been obtained by the sol−gel process. In these composites, nanometric siloxane heterogeneities are embedded in a polymeric matrix with covalent bonds in the interfa…
Star and Hyperbranched Polymers
Synthesis of branched polymers - an introduction star-shaped polymers bia anionic polymerization methods branched polymers via group transfer polymerization star-shaped polymers via living cationic polymerization star and hyperbranched polymers by transition metal catalysis star polymers by immobilizing functional blo…
Filling dependence of the Mott transition in the degenerate Hubbard model
Describing the doped Fullerenes using a generalized Hubbard model, we study the Mott transition for different integer fillings of the t_1u band. We use the opening of the energy-gap E_g as a criterion for the transition. E_g is calculated as a function of the on-site Coulomb interaction U using fixed-node diffusion Mo…
Anion Exchange of Methyl Orange into Zn−Al Synthetic Hydrotalcite and Photophysical Characterization of the Intercalates Obtained
The intercalation via ion exchange of the azoic dye methyl orange (MO - ) into the hydrotalcite-like compound Zn 0.67 Al 0.33 (OH) 2 Cl 0.33 ·0.6H 2 O has been investigated. X-ray diffraction patterns of samples with increasing dye loading showed that Cl - /MO - exchange occurs with a first-order phase transition from…
Sol−Gel Synthesis of KVII[CrIII(CN)6]·2H2O: A Crystalline Molecule-Based Magnet with a Magnetic Ordering Temperature above 100 °C
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSol−Gel Synthesis of KVII[CrIII(CN)6]·2H2O: A Crystalline Molecule-Based Magnet with a Magnetic Ordering Temperature above 100 °CStephen M. Holmes and Gregory S. GirolamiView Author Information School of Chemical Sciences and Frederick Seitz Materials Research Laborato…
Chatzidimitriou-Dreismann and Abdul-Redah Reply:
A Reply to the Comment by M. Grimsditch.Received 7 January 1999DOI:https://doi.org/10.1103/PhysRevLett.82.4369©1999 American Physical Society
Piezoelectric and electro-optic coefficients of the molecular nonlinear optical crystal 2-furyl methacrylic anhydride
Large crystals of 2-furyl methacrylic anhydride were successfully grown, making it possible to measure accurately their piezoelectric and electro-optic coefficients. Low modulation frequency electro-optic coefficients at a wavelength of 632.8 nm are: r33=7.1±0.4 pm/V and r13=4.5±0.2 pm/V, whereas the inverse piezoelec…
Controlled Polymerization of Methyl Methacrylate with Porphinatocobalt(II) Catalysts in Supercritical Carbon Dioxide
We report the successful controlled polymerization of methyl methacrylate in the presence of the catalytic chain transfer agents 5,10,15,20-tetraphenylporphinatocobalt(II) and 5,10,15,20-tetra(pentafluorophenyl)porphinatocobalt(II) (CoTFPP) in supercritical carbon dioxide (scCO 2 ). Low molecular weight polymers with…
(Ba,Sr)TiO 3 thin films with conducting perovskite electrodes for dynamic random access memory applications
Interfaces and hence electrodes determine the performance of (Ba,Sr)TiO3 (BST) capacitors for ultralarge scale integration dynamic random access memories. Electrode materials forming a rectifying contact on BST drastically reduce the dielectric constant and hence the capacitance and charge storage density of the capac…
Depth-resolved imaging of nematic liquid crystals by third-harmonic microscopy
Third-harmonic microscopy is shown to be a powerful tool for the study of liquid crystal structures. The third-harmonic probe enables the investigation of molecular order well inside a liquid crystal cell. The observation of phase transition in various nematic liquid crystal samples is presented as a demonstration for…
Instant holography
Instant photography, epitomized by Polaroid films is characterized by the rapid appearance of an image after exposure. We describe here an instant off-axis holographic process, characterized by exposures as short as 5 ns and an instant display process, not requiring any wet chemical processing. The holograms are made…
Two-Dimensional Charge-Transport and Spin-Valve Effect in the Layered AntiferromagnetNd0.45Sr0.55MnO3
Below the N\`eel temperature $({T}_{N})$ a layered antiferromagnetic (AF) ${\mathrm{Nd}}_{0.45}{\mathrm{Sr}}_{0.55}{\mathrm{MnO}}_{3}$ crystal is metallic within the ferromagnetic (F) layers ( $\mathrm{ab}$ plane), while insulating along the AF-coupling direction ( $c$ axis), showing an extremely large anisotropy in r…
Enhanced photoluminescence in epitaxial ZnGa2O4:Mn thin-film phosphors using pulsed-laser deposition
The growth and properties of ZnGa2O4:Mn thin-film phosphors on single crystal substrates using pulsed-laser deposition were investigated. Epitaxial film properties were compared to polycrystalline films deposited on glass substrates. Green photoluminescence was observed for as-deposited films with no postannealing req…
Sum-Frequency Vibrational Spectroscopic Study of a Rubbed Polymer Surface
Sum-frequency vibrational spectroscopy has been used to probe the chain orientation of polyvinyl alcohol at the surface after rubbing. The distribution function of the chain orientation is determined quantitatively. The orientational order parameter of the chains deduced from the distribution matches well with that of…