Structural Studies of Novel Siloxysilsesquioxanes
Five silsesquioxanes (RSiO3/2)2n with R = siloxy and n = 4, 5 have been investigated by X-ray crystallography, MALDI-TOF mass spectrometry, and differential scanning calorimetry (DSC).
Materials Literature
文献浏览
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
Structure and Conformation of Tetra-meso-, Octa-β-, and Dodecasubstituted 22,24-Dihydroporphyrins (Porphyrin Dications)
A comparative crystallographic analysis of the conformation of porphyrin diacids with various substituent types reveals considerable differences in the degree of nonplanarity and distortion modes. Diacids of 5,10,15,20-tetraarylporphyrins generally exhibit typical saddledistorted macrocycles with displacements of the…
Thermal stability of methacrylic acid copolymers of Eudragits L, S, and L30D and the acrylic acid polymer of carbopol
The thermal stability of the powder or film forms of Eudragits L, S, and L30D and carbopol polymers was qualitatively investigated by microscopic reflectance Fourier transform infrared spectroscopy equipped with differential scanning calorimetry (FT-IR/DSC microscopic system). DSC and thermogravimetric analysis (TGA)…
Synthesis and ion conductivity of poly(oxyethylene) methacrylates containing a quaternary ammonium group
A quaternary ammonium salt of poly(oxyethylene) methacrylates containing a quaternary ammonium group was designed and synthesized as a single-ionic solid polyelectrolyte. The ionic conductivity of the polymer is about 10−5 S/cm at room temperature. Furthermore, when a small amount of water or aqueous KOH solution was…
Obtaining optical constants of thin GexSbyTez films from measurements of reflection and transmission
Phase change rewritable optical recording media contain a chalcogenide layer, e.g., GexSbyTez, that undergoes a transition between the amorphous and crystalline phases (by absorption of laser energy). Differences in their optical constants [n,k] result in reflectivity differences in the multilayer optical devices. We…
Lithium ion transport in Li 2 SO 4 -Li 2 O-B 2 O 3 glasses
Electrical conductivity and dielectric relaxation studies with a wide range of compositions of lithium ion conducting glasses belonging to the ternary glass system Li2SO4-Li2O-B2-O3- have been carried out over the temperature range 150-450 K and between 10 - 10(7) Hz. DC conductivities exhibit two different activation…
Nuclear magnetic resonance line shapes of methyl-like quantum rotors in low-temperature solids
Dissipative dynamics of a tunneling, methyl-like rotor, whose spatial coordinate is weakly coupled to a thermal bath, are described using the reduced density matrix (RDM) approach. It is found that, owing to selection rules imposed on thermally induced transitions by the symmetrization postulate, there are two sorts o…
Chemical heterogeneity analysis of high-conversion poly[styrene-co-(ethyl acrylate)]s by NMR and on-line coupled SEC-NMR
Copolymers of styrene and ethyl acrylate are prepared by radical polymerization and analysed with respect to microstructure by means of nuclear magnetic resonance. Using 13C NMR, the compositional styrene- and ethyl acrylate-centered triads can be determined and compared to theoretical values. Good agreement between e…
Development of Trickle‐Bed Electrolyzer for On‐Site Electrochemical Production of Hydrogen Peroxide
A practical‐scale cell with a trickle‐bed electrode was developed for on‐site electrochemical production of hydrogen peroxide by the cathodic reduction of oxygen. Terminal voltage and current efficiency were affected by the dispersions of liquid and oxygen gas in the trickle‐bed cathode and by the current density. Cur…
Structure of metal centres in proteins at subatomic resolution
Metalloproteins perform a wide variety of biological functions and, in doing so, in many cases exploit the redox properties and the coordination chemistry of the metal atom. The structural changes associated with the different coordination and redox changes can be quite small and can only be visualized at a very high…
A Square-Planar Dinickel(II) Complex with a Noninnocent Dinucleating Oxamate Ligand: Evidence for a Ligand Radical Species
The new bimetallic nickel(II) compound (PPh4)4[Ni2(2)]·6H2O (3), where H8[2] stands for N,N′,N′′,N′′′-1,2,4,5-benzene-tetrayltetrakis(oxamic acid), has been synthesized and its crystal structure determined by single-crystal X-ray diffraction. The structure of 3 consists of [Ni2(η4:η4-2)]4– anions, tetraphenylphosphoni…
Fabric Bagging
Aesthetic appearance is one of the most important criteria used by consumers in judging clothing wear performance. Bagging is a kind of three-dimensional residual deformation that deteriorates garment appearance during wear and causes dissatisfaction. To understand the psychophysical mechanisms of fabric bagging perce…
Oxygen Reduction on Pyrolytic Graphite Electrodes Modified with Electropolymerized Cobalt Salen Compounds
Electropolymerized cobalt salen compounds on pyrolytic graphite electrodes were first tested as oxygen reduction catalysts in aqueous solutions of various pH. N,N '‐Bis(salicylidene)ethylenediaminocobalt(II) [abbreviated Co(salen)] and its analogs were polymerized on a basal plane of pyrolytic graphite electrode by el…
Compilation of photon cross-sections: some historical remarks and current status
In x-ray diffraction spectrometry as well as in the many other scientific, engineering and medical disciplines involving photon radiation, x-ray attenuation coefficients are required as input data. Within a very few years after the discovery of x-rays by Röntgen in 1895, the transmission of a narrow (parallel) beam of…
Kinetics of thermally induced phase separation in ternary polymer solutions. I. Modeling of phase separation dynamics
Simulations based on Cahn-Hilliard spinodal decomposition theory for phase separation in thermally quenched polymer/solvent/nonsolvent systems are pre- sented. Two common membrane-forming systems are studied, cellulose acetate (CA)/ acetone/water, and poly(ethersulfone) (PES)/dimethylsulfoxide (DMSO)/water. The ef- fe…
Synthesis and properties of imidazole-blocked diisocyanates
Imidazole-, 2-methylimidazole- and benzimidazole-blocked hexamethylene diisocyanate and isophorone diisocyanate have been prepared and characterized by elemental analyses, IR and NMR spectroscopy. The structure–property relationship of these adducts has been established by reacting with hydroxyl-terminated polybutadie…
Bacteria isolated from a sugarcane agroecosystem: their potential production of polyhydroxyalcanoates and resistance to antibiotics
In this investigation, a sugarcane agroecosystem at a coastal tableland, in the northeast of Brazil, was screened to obtain bacteria strains able to synthesize poly-<FONT FACE="Symbol">b</font>-hydroxyalkanoates (PHA), using sucrose as the main carbon source. The potential to synthesize PHA was tested qual…
Effect of disorder produced by cationic vacancies at theBsites on the electronic properties of mixed valence manganites
An alloy series of single-phased polycrystalline ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Na}}_{x}{\mathrm{MnO}}_{3+\mathrm{\ensuremath{\delta}}} (0<~x<~0.15)$ has been synthesized in order to study the effect of disorder on the electronic properties of mixed valence manganites. The synthetic variables allow on…
The Molecular Dynamics Study of Lithium Ion Conduction in Phosphate Glasses and the Role of Non-Bridging Oxygen
Molecular dynamics (MD) simulation of lithium phosphate (Li 2 O−P 2 O 5 ) glasses with varying Li 2 O content has been carried out. Two different P O distances corresponding to phosphorus coordination with bridging oxygen (BO) and non-bridging oxygen (NBO) were identified in the simulated glasses. NBO−BO interconversi…
Structural stability of higher-energy phases and its relation to the atomic configurations of extended defects: The example of Cu
The total-energy calculations using a full-potential first-principles method have been performed for three displacive phase transformation modes in Cu. The structural and elastic properties of the ground-state (fcc) and higher-energy phases (bcc and $9R)$, as well as the energy barrier for sliding of ${111{}}_{\mathrm…