Materials Literature
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。
The valence electronic properties of some unsubstituted and peripherally substituted oxo-titanium phthalocyanines are reported. Semiempirical quantum chemical calculations show that the nature of peripheral substituents has a strong bearing on the valence electronic properties, including the state dipole moments and a…
Elastomeric poly(propylene) with low percentages of isotactic pentads and high molecular weight was synthesized using unbridged “oscillating” metallocenes. The polymer sample with the highest [mmmm] content (22%) shows a small amount of crystallinity, which is highly influenced by the thermal history, and differs sign…
Star poly(lactides) with well defined molecular architectures have been synthesized from multifunctional dendritic initiators derived from 2,2′-bis(hydroxymethyl)propionic acid (bis-MPA) derivatives. The bis-MPA derivatives, in the presence of stannous 2-ethylhexanoate, generated new polymeric structures with accurate…
Director configurations in a nematic liquid crystal can be determined by minimizing its total elastic free energy, for given elastic constants and specific boundary conditions. In some cases, these configurations have been obtained by numerical procedures where the elastic free energy density plays the same role as th…
Abstract A hypothesis for formation of bi‐continuous phase structures in immiscible polymer blends is proposed. It is based on the observation that a critical volume fraction φ cr for the dual continuity of phases may be calculated considering the geometry of the dispersed phase. The knowledge of the form of discrete…
In practical applications, BSCCO/Ag tapes are exposed to external AC magnetic field and fed with an AC transport current. The total AC loss can be separated in two contributions: first, the transport current loss influenced by an external AC magnetic field, and second, the magnetisation loss that depends on the transp…
A series of semifluorinated 3-alkylthiophenes ((3-thienyl-(CH 2 ) m -CF 2 ) n F, Th- m, n ) were prepared by addition of perfluoroalkyl iodides to 3-(ω-alken-1-yl)thiophenes followed by treatment with NaBH 4 . Chemical and electrochemical oxidation gave the corresponding substituted polythiophenes. The fluorinated sid…
The relevance of measuring the melt strength of low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and their blends to their performance in terms of bubble stability in the film blowing process has been investigated. A good correlation between the melt strength values for two series of LLDPE/LDPE…
We report on the synthesis of cobalt 2,3,9,10,16,17,23,24-octakis(2-ethylhexyloxy)phthalocyanine. This complex, when pre-adsorbed onto graphite electrodes, is active for the electro-oxidation of 2-mercaptoethanol. Its activity is higher than that of cobalt phthalocyanine and cobalt tetrasulfonated phthalocyanine adsor…
The use of low-mobility photoconductors in x-ray imaging, especially amorphous selenium (a-Se), is currently of great interest. Detailed measurements of the photoconversion gain factor W± and gain fluctuations σ have been obtained to facilitate applications using a-Se and to provide a better understanding of the charg…
Carbon black is a common polymer additive that is used for reinforcement and for its ability to enhance physical properties, such as conductivity. This article pertains to an X-ray scattering (SAXS) study of a conductive grade of carbon black and carbon black–polymer composites. The scattering pattern for such blacks…
The accumulation of space charge in the crosslinked polyethylene (XLPE) insulation of a power cable sample under dc stress was investigated. The sample was held at 82/spl deg/C and atmospheric pressure, and at 82/spl deg/C and 0.1 Pa, for periods up to several days. Such conditioning removed pre-existing space charge,…
Serine hydroxymethyltransferase (SHMT) catalyzes the reversible cleavage of serine to form glycine and single carbon groups that are essential for many biosynthetic pathways. SHMT requires both pyridoxal phosphate (PLP) and tetrahydropteroylpolyglutamate (H4PteGlun) as cofactors, the latter as a carrier of the single…
The Upack program package for crystal structure generation was used to build hypothetical crystal structures for 32 pyranoses and 24 polyalcohols. A subset of these was used to compare six force fields in their ability to reproduce the experimentally observed structures, preferably with low energies and high rankings…
The oxygen vacancy ordering process in the system CaTiO3-CaFeO2.5 has been studied as a function of composition and temperature. The samples (CaTi1−x Fe x O3−x/2 with 0 ⩽x⩽ 1) were annealed at temperatures between 900°C and 1400°C and characterized, after drop quench, by means of XRD, Mössbauer spectroscopy and TEM. V…
The solid state of comb copolymer-like systems obtained by blending poly(4-vinylpyridine) with pentadecylphenol was studied by a combination of techniques. Depending on the amount of pentadecylphenol, several regimes are present. For 0.5 ≤ x ≤ 1.0 ( x is the ratio between the number of phenol and pyridine groups) the…
Accurate lattice parameters have been determined between 2 K and 520 K for the negative thermal expansion compound ZrW 2 O 8 , by high-resolution neutron powder diffraction measurements. Two different analyses of the temperature dependence of the lattice constant i) in terms of Debye and Einstein contributions and ii)…
An iron(III) porphyrin complex with highly electron-withdrawing substituents on the porphyrin ligand efficiently catalyzes the hydroxylation of alkanes by H2O2 via enzyme mimetic oxidation reactions in aprotic solvent. An “isolated” high-valent iron(IV) oxo porphyrin cation radical intermediate, prepared in situ by re…
Several experiments were conducted to examine the effects of the molar ratio of citric acid to cations and of the pH value on the chemistry of a solution prepared by the Pechini method. Two types of precipitates, barium titanium citrate (BTC) and barium citrate, developed, depending on the experimental conditions. Cha…
The effect of disorder arising from the mismatch between the average sizes of the A-site cations in the rare-earth manganates, ${L}_{0.5}{A}_{0.5}{\mathrm{MnO}}_{3}$ $(L=\mathrm{rare}\mathrm{}\mathrm{earth},$ $A=\mathrm{alkaline}\mathrm{}\mathrm{earth})$, on their charge-ordering behavior has been investigated. Measur…