Materials Literature
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Abstract By the oxidation of tetraphenylpyrrole, two types of dimers of tetraphenylpyrryl were obtained. One dimer showed piezochromism and thermochromism, while the other showed photochromism and thermochromism. These phenomena were found to correspond to those of the piezochromic and photochromic dimers of triphenyl…
Jørgensen (1944) showed that young specimens of the siliceous freshwater sponge Spongilla lacustris L. obtained their skeletal silica from the water and demonstrated that, under experimental conditions, a relationship existed between the size of the microscleric spicules produced and the concentration of dissolved sil…
The metallic and non-metallic behaviour of certain transition metal oxides is discussed, taking into account the effects of crystalline structure and of polaron formation as well as those of correlation. It is shown that the former have an important role in explaining recent experimental results.
The RSM can be used to detect magnetic moment (vM≥5×10−6 emu), rotational hysteresis (vWR/H≥10−2 emu), spin flop (vM≥5×10−5 emu), and properties related to anisotropy energy [vK/H, v(χ⊥−χ∥)H and vMx≥5×10−6 emu], i.e., anisotropy constants, anisotropic susceptibility, and anisotropic spontaneous magnetization. Samples…
Abstract While the results of our study leave many questions regarding vulcanization still open, it is concluded that: 1. Effective, practical vulcanization of polymers containing simple monoolefinic residues by sulfur/accelerator, sulfur donor/accelerator, p -quinone dioxime (or dinitroso benzene), and halogenated al…
The salamander limb regenerate develops from a mesenchymatous bud of cells called the blastema. This review briefly considers the local origin and major features of blastemal cells and then discusses their role in the histogenesis of the regenerate. The capacity of blastemal cells to form the various cell types of the…
By DTA and visual methods the phase diagrams of the ten binary systems formed by lithium, sodium, potassium, rubidium and cesium bromide with barium or strontium bromide have been drawn. Moreover, the fusion thermal effects regarding the eutectics and the congruent compounds singled out in the systems have been evalua…
The integrated intensities of the K alpha emission satellite groups alpha alpha 3 alpha 4 and alpha 5 alpha 6 have been measured in secondary excitation for Na + in NaF, NaCl and NaBr and of F - in LiF, NaF and KF. The results are generally in agreement with calculations based on the assumption that the satellites are…
The penetration of a small-amplitude high-frequency electromagnetic wave into a plasma slab is calculated making allowance for the thermal motion of electrons. For low collision rates the electromagnetic field distribution in the plasma is strongly dependent on the ratio of the wave period to the transit time of elect…
Radiation dose may be measured by means of the increase which it produces in the thermoluminescence sensitivity of quartz. The measurement is possible even if the quartz was heated after the dose was received (for example for several hours at temperatures up to 300°C). This makes the quartz suitable as a heat-resistan…
Vegetative cells of a Cyclotella clone (03A) form male gametes and auxospores in response to salinity changes in the medium. Two different valve patterns which characterize described species of diatoms, Cyclotella meneghiniana and C. cryptica, may occur during clonal development of the auxospores of clone 03A. Evidenc…
Abstract The nonvolatile products of polypropylene that has been process degraded in the melt by a Brabender torque rheometer have been quantitatively identified by infrared analysis and chemical reactions carried out on molded sheets. The molecular weight changes with degradation have been determined by gel‐permeatio…
Research over a period of about 20 years into the mechanism of the protection of steel by paint films is reviewed. possibilities are: cathodic protection achieved with zinc-rich paints; anodic passivation, by degradation products of metal soaps, notably those of lead, formed by pigment/media interaction; and resistanc…
Abstract A new macromolecular model for branched PVC was synthesized by copolymerization of vinyl chloride with 2,4‐dichloropentene‐1. The composition and the properties of this new copolymer were studied and the phenolysis reaction to determine the content of chlorine atom bound to the tertiary carbon atom (Cl T ) wa…
Summary The properties of amorphous germanium and silicon, vitreous selenium chalcogenide glasses and transition-metal oxide glasses are described and discussed. Much of the current experimental data can be interpreted within the framework of the theoretical models developed in Part I, in which the main influence of d…
Previously published results on the propagation characteristics of sound waves in K${\mathrm{D}}_{2}$P${\mathrm{O}}_{4}$ are analyzed phenomenologically to give the electric susceptibility and the polarization relaxation rate above and below the transition temperature. These results are then compared with the predicti…
The values of Slater–Condon (F2, F4, F6) and Racah (E1, E2, E3) interelectronic repulsion and Landé (ζ4f) spin–orbit interaction parameters have been computed from already observed visible and near infrared absorption spectra of 24 Nd3+ complexes. Using these parameters the energies of 27 energy levels of each complex…
The intramolecular contribution to the entropy of fusion of crystalline polymers is treated through calculation of the change in configurational entropy on melting of a single isolated polymer chain. Perfect backbone conformational order is assumed in the crystalline polymer chain, and the configurational entropy of t…
The ‘weak-beam’ technique of Cockayne, Ray and Whelan (1969) for resolving very closely spaced dislocations in the electron microscope has been applied to the dissociation of BZ-type superlattice dislocations in highly ordered Fe-35 at. % Al. By plotting the separation of the partials as a function of orientation a va…
The second-order perturbation method of Parmenter and the theories of Kane and of Halperin and Lax are employed to calculate self-consistently the conduction band density of states in heavily doped n-type GaAs using a screened Coulomb potential for impurity atoms. The three models all show that the total number of sta…