Materials Literature
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Homolysis of the C–Mn bond of [RMn(CO)5] or [RCOMn(CO)5] under u.v. irradiation has been studied using nitrosodurene as a spin-trap for both the radicals formed; irradiation of various metal–metal bonded compounds (LM–ML, M = Mn, Re, Fe, Mo, or Co) gives rise to metal-centred radicals which can similarly be trapped.
Rates of oxidative vaporization of on preoxidized resistively heated chromium were determined in flowing oxygen at a pressure of 0.115 Torr for temperatures from 1000° to 1300°C. Reaction controlled rates were obtained from experimental rates by a gold calibration technique, and these rates were shown to agree with th…
The influence of the addition of mainly 1st row of transition elements on the resistivity anomaly of BaTiO3 semiconducting ceramics has been examined. The results showed that Mn ion is the most effective in increasing the PTC anomaly by up to a factor of 109. The high temperature chemical behaviour of the ceramics was…
A survey is given of the results of five years electron fractography as conducted at the National Aerospace Laboratory N.L.R. and of the contribution of this work to the comprehension of fatigue cracking, ductile fracture, cleavage and stress corrosion.
W A Wooster Oxford: University Press 1973 pp x + 344 price £7 'The reader who died of boredom' is a built in hazard for the authors of books on group theory, and Dr Wooster sets his own critical standards when he confesses that he has difficulty in keeping awake while reading such books. As a fellow sufferer, I am hap…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStereochemistry of low-spin cobalt porphyrins. III. Crystal structure and molecular stereochemistry of bis(piperidine)-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinatocobalt(II)W. Robert ScheidtCite this: J. Am. Chem. Soc. 1974, 96, 1, 84–89Publication Date (Print):Janua…
The contrast in many-beam lattice images from very thin crystals of 4Nb2O5. 9WO3 is shown to be directly related to its known structure. On the basis of this correlation, the structure of 2Nb2O5.7WO3 is derived from the observed image contrast; it is an ordered intergrowth of the ReO3 and tetragonal tungsten bronze st…
Crystals of the title compound are monoclinic, space group C2/c, a= 18·14(1), b= 18·62(1), c= 18·51 (1)Å, β= 95·9(5)°, Z= 4. The heavy atoms were located by direct methods and the oxygen and sodium atoms by difference Fourier analyses, with block-diagonal least-squares refinement to R 0·083 for 2781 independent reflec…
SummaryTin coatings and some tin alloy coatings from various plating baths and on several substrates have been kept under observation for spontaneous whisker growth for periods up to 20 years. A review of the results and of information obtained elsewhere suggests that, although assured immunity from whiskers may be di…
The partial pressures of the gaseous species in equilibrium with solid silicon in the Si‐H‐Cl system are presented as a function of temperature for different Cl/H ratios and total pressures. Computations were performed using our recently determined value of Δ Hf ° 298 ( SiHCl 3 , g ) = − 116.9 kcal / mol . Experimenta…
The steady-state distribution of mobile point defects in a monatomic solid under irradiation has been calculated for a semi-infinite solid and for a foil. The calculation was performed for defect annihilation by mutual recombination, at internal sinks, and by diffusion to the surface. Simple approximations, accurate t…
Conditions for the nucleation of recrystallized grains are briefly reviewed with emphasis placed on the orientation-dependent aspects. Distinction is drawn between nucleation sites within grains, at grain boundaries, and at transition bands. These sites are shown to have different orientation dependences. The role of…
The inherent characteristics of the instrumented impact test are discussed. The hammer energy is reduced by deforming the test specimen, accelerating the specimen from rest, Brinell-type deformation at the load points, vibrations of the hammer assembly, and elastic deformation within the machine. The limitations of th…
Electron micrographs of calf-skin collagen in the reconstituted native-type fibril and the segmented long spacing (SLS) forms are matched with one another and with the distribution of charged residues in the known α1 chain sequence.It is shown that:a) the pattern of bands in SLS corresponds closely with the charge dis…
The lipids and fatty acids of two freshwater diatoms Nitzschia palea Kutz, Navicula muralis Lewin, and one marine species, Navicula incerta Grun. have been studied. The major lipid components in all species were triglycerides, monogalactosyl, digalactosyl and sulphoquinovosyl diglycerides, phosphatidyl glycerol, phosp…
Matrix reactions of H and D atoms from a microwave discharge source with oxygen molecules diluted in argon have produced significantly higher yields of HO2 and DO2 than the previous photolysis methods. Oxygen isotopic enrichment confirmed the previous vibrational assignments to HO2; significantly greater concentration…
Abstract
We have studied the simple shear flow, in the laminar regime, of a nematic (uniaxial) liquid film between two glass plates with carefully imposed boundary conditions. In the case considered here, the optical axis at rest is normal both to the flow velocity and to the velocity gradient. Using various methods of optical…
Abstract The nature of the distribution of ionic groups in cesium salts of ethylene‐methacrylic acid and ethylene‐acrylic acid copolymers containing 2.1 to 6.3 mol% acid was examined using the small‐angle and wide‐angle x‐ray scattering techniques. The low‐angle data containing a maximum characteristic of these materi…
A model has been proposed to account for the yield behaviour of amorphous glassy polymers. The critical step in the yield process is envisaged as being the nucleation under stress of small disc-shaped sheared regions (the strain fields of which are analogous to those of dislocation loops) that form with the aid of the…