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Abstract The Al/Si atomic ratio of allophane was obtained from analyses of soil horizons for a range of New Zealand soils and for a wide range of volcanic soils from around the world. Imogolite‐like allophane (Al/Si = 2) occurs very frequently in soil horizons with >1 or 2% allophane, suggesting that it is more sta…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRegiospecific aryl nitration of meso-substituted tetraarylporphyrins: a simple route to bifunctional porphyrinsWilliam J. Kruper Jr., Thomas A. Chamberlin, and Monica KochannyCite this: J. Org. Chem. 1989, 54, 11, 2753–2756Publication Date (Print):May 1, 1989Publication Hist…
Equilibrium configurations for linear and closed arrays (rings and regular polyhedra containing a single pore) of identical particles (cylinders or spheres) were determined by minimizing the array's surface and grain‐boundary energies with the assumption that each particle conserves its mass. The change in free energy…
The structure of activated pig heart aconitase [citrate(isocitrate) hydro-lyase, EC 4.2.1.3] containing a [4Fe-4S] cluster has been refined at 2.5-A resolution to a crystallographic residual of 18.2%. Comparison of this structure to the recently determined 2.1-A resolution structure of the inactive enzyme containing a…
The anodic current‐potential characteristics of four types of silicon in aqueous solutions have been studied. According to the surface condition of the samples anodized at different potentials, there are generally three regions on a current‐potential curve: porous silicon formation in the region where current changes…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLuminescence and metal-metal interactions in binuclear gold(I) compoundsChristopher King, Ju Chun Wang, M. Nazrul I. Khan, and John P. Fackler Jr.Cite this: Inorg. Chem. 1989, 28, 11, 2145–2149Publication Date (Print):May 1, 1989Publication History Published online1 May 2002…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConductive-polymer bronzes. Intercalated polyaniline in vanadium oxide xerogelsMercouri G. Kanatzidis, Chun Guey Wu, Henry O. Marcy, and Carl R. KannewurfCite this: J. Am. Chem. Soc. 1989, 111, 11, 4139–4141Publication Date (Print):May 1, 1989Publication History Published on…
Synthetic diamonds grown using a solvent-catalyst containing nickel give optical absorption and luminescence with zero-phonon structure at 1.401 and 1.404 eV. We show that the zero-phonon lines are split as a result of the different natural isotopes of nickel. The sign and magnitude of the splitting are consistent wit…
A complex analysis of the nonlinear diffusion problem in ferromagnetic materials under steady-state excitation is presented. The problem is solved by considering an equivalent fictitious material where the relative permeability is assumed to be constant in time but different from point to point and is related to the n…
We study the failure properties of a defected square lattice of Born springs under uniaxial tensile strain. The springs fail completely and irreversibly once a critical strain energy is exceeded. The Born potential provides an effective bending force that yields realistic crack microstructures, which are analyzed in d…
We consider the partial differential equation which describes phase separation in a block copolymer melt. We construct numerically the periodic solution which minimizes the free energy. The lamellar thickness of the final equilibrium pattern is found to scale with the molecular weight as a power law ${\ensuremath{\lam…
Metal silos and tanks are subject to axial compressive stresses in their cylindrical shell walls. The buckling strength is very sensitive to geometric imperfections in the wall. The most regular and well‐defined imperfection is the local depression adjacent to a circumferential weld, caused by the plate rolling proces…
The processing problems associated with boron carbide and the limitations of its mechanical properties can be significantly reduced when a metal phase (e.g., aluminum) is added. Lower densification temperatures and higher fracture toughness will result. Based on fundamental capillarity ther modynamics, reaction thermo…
We obtain explicit predictions for velocity selection in two- and three-dimensional, symmetric, and one-sided models of dendritic solidification. We do this by using WKB techniques to derive a solvability condition, which is then solved numerically, for the existence of steady-state needle crystals. The comparison wit…
Defects are local breakings of symmetry in an ordered medium. The physics of defects has long been reduced to the study of dislocations in solids, and to the main physical phenomena they are responsible for, like plastic deformation. Dislocations break translational symmetries. Disclinations break rotational symmetrie…
We present a study which reveals that the switching speed for the redox reaction of polyaniline is very fast. With a 1200Å film in 2 M sulfuric acid, switching speeds of up to 100 μs with current densities of 100 A/cm 2 are observed with the appropriate compensation for IR loss. The true switching speed is higher stil…
Summary The mobilities of aqueous foams of known texture have been measured in homogeneous bead packs. To correlate the data, a theory developed recently to describe the apparent viscosity of foams in smooth capillaries is extended to account for (1) the capillary pressure imposed by the porous medium and (2) constric…
A review is given of some simplified concepts that will contribute to a better understanding of corrosion fundamentals. The corrosion process involves not only electrochemical reactions but also acid-base reactions, and it is the acid-base nature that diversifies the corrosion phenomena. Anions either catalyze or inhi…
Several techniques are reviewed with which thermal conductivity and phonon scattering can be measured in films of thicknesses ranging from angstroms to millimeters. Recent experimental results are compared critically with previous measurements. It is shown that phonons are very sensitive probes of the structural perfe…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTransition-metal-catalyzed epoxidationsKarl Anker JoergensenCite this: Chem. Rev. 1989, 89, 3, 431–458Publication Date (Print):May 1, 1989Publication History Published online1 May 2002Published inissue 1 May 1989https://doi.org/10.1021/cr00093a001RIGHTS & PERMISSIONSArticle…