The synthesis of a new 22 π-electron macrocycle: pentaphyrin
The first synthesis of pentapyrrole macrocycle analogous to the porphyrins is described.
Materials Literature
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Toxicity of some charged lipids used in liposome preparations.
The inhibition of 3H-thymidine incorporation into DNA of L1210 cells in culture by liposomes was used as an index of liposome toxicity. Inhibition of 3H-thymidine incorporation appeared to be dose dependent for some lipid compositions tested. The commonly used neutral lipids, phosphatidylcholine and cholesterol did no…
Studies of the thermal decomposition of βNiO(OH) and nickel peroxide by X-ray photoelectron spectroscopy
The thermal decomposition of both βNiO(OH) and ‘nickel peroxide’ have been studied by combining X-ray photoelectron spectroscopic (X.p.s.) studies of the solid with mass-spectrometric analysis of the gas phase. Through monitoring the O(1s) and Ni(2p) spectra of the as-prepared solids during decomposition, with simulta…
On estimators for the reduced second moment measure of point processes
For the reduced second moment measure of stationary point processes several estimators are presented. In order to show the most general conditions under which the estimators are applicable, some properties of non-stationary point processes are introduced making it possible to reduce the second moment measure as in the…
Electrochemistry of ruthenates. Part 1.—Oxygen reduction on pyrochlore ruthenates
The reduction of dioxygen to water has been investigated on ternary ruthenium(IV) oxides having the pyrochlore structure; in particular, compounds of the general form Bi2–2xPb2xRu2O7-y have been studied. Oxygen reduction on these materials appears to proceed by a rate-determining outer-sphere electron transfer, follow…
Modification of radiation damage microstructure by helium
Current experimental findings on the effects of helium on the evolution of radiation damage microstructure in metals at temperatures where vacancies are mobile are reviewed. It is shown that helium concentrations as low as a few parts per million promote the formation of cavities and dislocations, may increase or decr…
Heat Capacity and Other Thermodynamic Properties of Linear Macromolecules. VIII. Polyesters and Polyamides
Heat capacity of polyglycolide, poly(ε-caprolactone), poly(ethylene terephthalate), poly(ethylene sebacate), polyglycine, poly(L-alanine), poly(L-valine),nylon 6, nylon 6.6 and nylon 6.12 is reviewed on the basis of measurements on 35 samples reported in the literature. All heat capacity data are compiled and a set of…
A review of the stainless steel surface
The characteristics of the surface of various stainless steels are reviewed. The property of these alloys that makes them stainless is the formation of Cr2O3 on the surface. It has been found that this protective layer can be modified relatively easily by heating, abrading, chemical treatment, or ion bombardment. Modi…
Scaling theory of polymer adsorption : proximal exponent
We interpret some recent calculations of Eisenriegler, Kremer, and Binder [1], and related multi-critical results of Diehl and Dietrich [2]. They show that the monomer concentration profile Φ(x) for isolated polymer chains in a good solvent and in close proximity to an adsorbing wall exhibits a singular behaviour ; i.…
Polyetherimide: A new high‐performance thermoplastic resin
Abstract A new high‐performance amorphous thermoplastic, named polyetherimide, has been developed by the General Electric Company. This resin is characterized by high deflection temperature (200°C at 264 psi), high tensile strength and flexural modulus (480,000 psi), and very good retention of mechanical properties at…
Computer modelling of barium titanate
Barium titanate is an important material for both scientific and industrial applications. Much of the interest centres around its ferroelectric properties, since it is structurally the most simple in this class. In addition rare-earth doped ceramics are found to exhibit a very steep positive temperature coefficient of…
Effect of Microstructure on the Properties of TiB 2 Ceramics
Samples of a TiB 2 ceramic containing 0 to 10 wt% Ni were fabricated by hot‐pressing. Several properties, including fracture strength, indentation fracture toughness, and thermal expansion (between 25° and 1000°C) were measured. Resulting data were correlated with sample microstructure and composition.
Structural properties of cellulose and cellulase reaction mechanism
The effects of structural properties and their changes during cellulose hydrolysis on the enzymatic hydrolysis rate have been studied from the reaction mechanism point of view. Important findings are the following: (1) The crystallinity index (CrI) of partially crystalline cellulose increases as the hydrolysis reactio…
Isothermal and nonisothermal crystallization of polyethylene
Abstract Differential scanning calorimetry is employed to study the crystallization kinetics of two commercial injection‐molding high‐density polyethylene resins. Also, polarized light microscopy has been used to elucidate the morphological structures formed at various crystallization conditions. Corrections and opera…
Platinum/titanium dioxide catalysts. A photoconductivity study of electron transfer from the ultraviolet-illuminated support to the metal and of the influence of hydrogen
Photoconductivity measurements have been carried out for a series of powder Pt/TiO2 catalysts containing from 0.05 to 10 wt% Pt as well homodispersed particles (mean diameter ca. 2 nm). The presence of platinum, at least for contents ca. 1 wt%, caused a decrease in the anatase photoconductance σeq at equilibrium under…
Plastic composites for electromagnetic interference shielding applications
Abstract Research in the past eight years has established the ability of polymer composites made with sufficient electrical conductivity to be suitable as shields against electromagnetic interference (EMI). A number of conductive fillers have been used to produce such composites. These include carbon black, carbon fib…
A Liquid Silazane Precursor To Silicon Nitride
The reaction of dichlorosilane, H 2 SiCl 2 , with gaseous NH 3 in dichloromethane or diethyl ether solution results in the formation of a silazane oil containing silicon, hydrogen, and nitrogen in good yield. This ammonolysis product can be pyrolyzed in an N 2 atmosphere (temperature to 1150°C) to give α‐Si 3 N 4 in ∼…
Surface Anchoring of Liquid Crystal Molecules on Various Substrates
Ever since Mauguin described the fabrication of liquid crystal cells by rubbing glass plates with paper to obtain uniform homogeneous alignment, scientists have been attempting to study and understand the mechanism of anchoring and the subsequent alignment of these materials on various substrates. More than 35 differe…
Polycaprolactone degradation by mixed and pure cultures of bacteria and a yeast
Abstract The degradability of three high molecular weight polycaprolactones (M̄ w = 35,000, 18,600, and 7,130) and one low molecular weight polycaprolactone diol(M̄ w = 2060) by mixed and pure cultures of microorganisms was assayed. A yeast, Cryptococcus laurentii , a gram‐negative rod, Acinetobacter calcoaceticus var…
Microstructure and unit‐cell orientation in α‐polypropylene
Abstract The microstructure of melt‐grown dendritic aggregates of the monoclinic α phase of isotactic polypropylene has been examined by optical microscopy, electron microscopy, and electron diffraction. Whereas the tightly crosshatched structure of such dendrites grown in the usual manner from the melt had not hereto…