Materials Literature
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Abstract The iron chelates of polymethyl-substituted dipyrromethenes were prepared. The ferrous ion was found to form complexes having a ligand to metal ratio of 2 : 1 with 5,5′-substituted dipyrromethenes, 3,3′,5,5′-tetramethyl- and 3,3′,4,4′,5,5′-hexamethyl-dipyrromethene. On the other hand, the ferric ion gave a co…
The structure of the interstitially ordered lattice formed in zirconium–oxygen alloys has been studied with use of single-crystal data obtained by X-ray and neutron diffraction methods. The structure belongs to space group P312 and the lattice parameters a and c are related to a0 and c0 of the host hexagonal metal lat…
Copper single crystals which appeared free from dislocations in X-ray topographs were deformed in tension. Very sharp and large yield drops, up to 70% of the upper yield stress, were observed. The lower yield stress was about 20g/mm2 for all dislocation-free crystals. Lüders band propagation was observed by X-ray topo…
Abstract The way in which polymer molecular structure controls structure on higher levels of organization in a solid polymer is briefly reviewed, as is also the way in which structure, on all levels, controls physical properties. The “line of descent” from molecular structure to physical properties is then illustrated…
Rather sharp zero-phonon lines accompanied by many vibronic lines are observed in the near-ultraviolet luminescence and excitation spectra due to the 4f-5d transitions of Ce 3+ ion in YPO 4 and LuPO 4 crystals at low temperature. Comparing the vibrational energies of the vibronic lines with the results of infrared and…
The morphology and cell wall composition of Bacillus coagulans, a facultative thermophile, were examined as a function of growth temperature. The morphology of the organism varied when it was grown at different temperatures; at 37 C the organism grew as individual cells which increased in length with increasing growth…
RESUME Le cortex de la face dorsale (non ciliée) ne contient pas de cinétosomes; sous des alvéoles bien développés se trouve un épiplasme épais, puis une couche irrégulière de microtubules longitudinaux; de nombreux pores cylindriques traversent le cortex. La région ventrale, limitée aux faces internes des 2 lèvres ap…
The ordered structures of Cu–Pt alloys containing 65–78 at. % Pt have been investigated by a combined technique of selected-area electron diffraction and dark-field electron microscopy using thin foils prepared from bulk specimens, and three different types of ordered structure have been observed. Below the order–diso…
Relaxation times T1 and T2 of 207Pb in liquid PbCl4 have been studied for the purpose of establishing an absolute nuclear shielding scale for lead. T1 has been decomposed into scalar and spin-rotation contributions using variable temperature measurements at the two field strengths 6.59 and 16.90 kG. T2 is much shorter…
Abstract The concentration of impurity–vacancy dipoles in potassium bromide crystals doped with strontium bromide was measured using the ionic thermocurrent (ITC) technique. The parameters of the dipole relaxation are: fundamental relaxation time 4 × 10 −14 s , activation enthalpy 0.66 eV. The effect of 60 Co γ‐irradi…
Abstract It is shown that the presently available information on the structure of bulk amorphous polymers is consistent with the concept of the existence of a substantial amount of short‐range segmental order. It is suggested that the sharp change of molecular‐weight dependence of NEWTONian viscosity of polymer melts…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLow-valent metal isocyanide complexes. IV. Crystal and molecular structure of cis-antibis-(pentahaptocyclopentadienyl)dicarbonyldi(.mu.-methyl isocyanide)diiron(Fe-Fe), (.eta.5-C5H5)2F2(CO)2(.mu.-CHCH3)2F. A. Cotton and B. A. FrenzCite this: Inorg. Chem. 1974, 13, 2, 253–256…
Given a model which represents a certain specimen, a method is described for computing the expected Mossbauer spectrum for transmission or reflection geometries which includes the effects of thickness, imperfect geometry, nonlinearity of the spectrometer scale and arbitrary source line shape.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNovel metalloporphyrins. Syntheses and implicationsDavid Ostfeld and Minoru TsutsuiCite this: Acc. Chem. Res. 1974, 7, 2, 52–58Publication Date (Print):February 1, 1974Publication History Published online1 May 2002Published inissue 1 February 1974https://doi.org/10.1021/ar50…
Optical absorption and emission spectra of Cr3+ ions in YAlO3 have been investigated at 300 and 77°K. In the cubic field approximation, the spectra can be fitted by the parameters Dq = 1800 cm−1, B = 590 cm−1, C = 2980 cm−1. An intense vibronic spectrum is associated with 2E → 4A2 fluorescence transitions. Measurement…
Determination of the crystal structure of ethyl chlorophyllide a.2H(2)O by single crystal x-ray diffraction techniques has provided the first detailed molecular structural data available for a magnesium-containing derivative of chlorophyll. At the same time the aggregation observed in this structure serves as the basi…
Low-density polyethylene films strained up to 35% exhibit an initial increase of diffusivity and permeability which soon reach a maximum and subsequently drop to steadily decreasing values below those of the unstrained starting material. The sorption steadily increases and seems to approach a plateau. The maximum and…
Lattice vibrational dispersion curves for the ``intermolecular'' modes in the triclinic, one molecule per unit cell β phase of p-C6D4Cl2 and p-C6H4Cl2 have been obtained by inelastic neutron scattering. The deuterated sample was investigated at 295 and at 90°K and a linear extrapolation to 0°K was applied in order to…
Abstract Two Cu ++ centres in NH 4 Cl single crystals grown from acid (I) and neutral (II) aqueous solution were investigated by ESR and ENDOR at 4.2 °K. From the superhyperfine and quadrupole data obtained for several shells of neighbour nuclei the following centre models are proposed: in both centres Cu ++ is at an…
Abstract To demonstrate the cooperativity in the formation of an interpolymer complex, the stability of polyanion‐polycation complexes as a function of their chain length was studied. Poly(methacrylic acid) (PMAA; P̄ n ≈ 800) was used as source for the polyanion and quaternized alkylamines and polyethyleneimines with…