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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…
<div class="htmlview paragraph">This paper describes the results of durability tests of monolithic catalytic converters with mechanical devices used to tailor the exhaust gas flow. Deflectors of several different shapes show promise of extending the useful life of the converter by improving conversion efficienci…
Abstract The lattice dynamics of graphite have been studied using a tensor force model. Force constant values for interactions between atoms in‐plane have been transferred from the naphthalene molecule. It is shown that the agreement between theory and neutron scattering data is very good, indicating that the molecula…
Abstract The measurement of the polarization resistance using AC enables the corrosion losses to be determined with certain difficulties only, Despite that the AC methods are of technical interest because they allow the determination of corrosion rate/time curves without difficulties and enable potentiel fluctuation t…
Abstract The formation of polyion complexes in aqueous medium between polycations carrying charges in the chain backbone and poly(carboxylic acid)s, such as poly(methacrylic acid) (PMAA), poly(carboxylic acid) (PAA), and poly(itaconic acid) (PIA), were studied. It was found that polycations formed more stable complexe…
The two-dimensional solubility parameter approach has been applied to the prediction of solubility of one polymer in another. The solubility parameters of a number of polymers have been calculated and the second dimension shown to improve the agreement between the calculated solubility and that measured using a ternar…
The effect on the diffusion coefficient of nondissipative interactions between diffusing macromolecules is evaluated for two-component solvent-macromolecule solutions. For linear concentration gradients, the generalized Stokes-Einstein relation is obtained from purely microscopic arguments. Application of these result…