Materials Literature
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Particles which undergo a stress‐induced martensitic transformation are known to toughen certain brittle materials. The enhanced toughness can be considered to originate from the residual strain fields which develop following transformation and tend to limit the crack opening. The increased toughness can estimated fro…
At -30 degrees C the ferroelectric dicalcium strontium propionate (DSP), is tetragonal with space group P4 1 (C 4 2 ) or P4 3 (C 4 4 ), with a=12.452(2) AA, c=17.217(4) AA, Z=4. There are six independent propionate groups in the structure, two of which have statistical disorder (static or dynamic) of their methyl carb…
Estimates were obtained of the intrinsic optical losses in glassy As 2 S 3 and As 2 Se 3 in the high-transparency range. It was found that minimum losses of 0.5 dB/km could be reached in the wavelength range 5–6 μ .
The properties of magnetic insulators containing orbitally degenerate transition metal ions (Jahn-Teller ions) are discussed. The Jahn-Teller effect in these insulators causes structural phase transitions, lowers the lattice symmetry, and gives rise to an orbital ordering. Various interactions responsible for these ef…
The microstructure of ortical thin films is strongly columnar with a large internal surface area and void volume. This structure has great influence on the optical and mechanical properties of the films and is responsible for many of the difficulties experienced with the fabrication and subsequent performance of optic…
The detailed proof of the 437-residue amino acid sequence (Mr 48,969) of porcine heart citrate synthase (EC 4.13.7) is described. The S-carboxymethylated protein has been cleaved at methionine (cyanogen bromide) and arginine (trypsin digest of citraconylated enzyme) residues to yield 14 and 17 major peptides, respecti…
Molecular-dynamics calculations have been used to investigate the nature of critical fluctuations in the paraelectric phase of NaN${\mathrm{O}}_{2}$. Although the ${(\mathrm{N}{\mathrm{O}}_{2})}^{\ensuremath{-}}$ anions are found to reorient rapidly, predominantly about the crystal $c$ axis, the simulation reveals the…
The Mossbauer spectra have been recorded from room temperature to above the Neel temperature for the spinel ferrites Cu 1-x Ni x Fe 2 O 4 and Cu 1-x Mn x Fe 2 O 4 for x=0.2, 0.4, 0.6 and 0.8. The spectra have been fitted with two sextets in the ferrimagnetic state. Iron is found to be in the trivalent high-spin state.…
ESR measurements on X-irradiated undoped CaSO 4 single crystals at 77K reveal two related radiation damage centres. Step annealing measurements suggest a connection between these centres and the thermoluminescent glow peaks at approximately 395 and 465K. An analysis of the g-values (centre I: g x =2.006, g y =2.0091 a…
The stiffness constants of a nematic liquid crystal are calculated for the situation of perfect orientational order with the aid of a model of distributed harmonic forces. Both attractive and repulsive forces are taken as distributed along the molecules, and thus are only important for the parts of two molecules that…
A novel geometry in which it is possible to do x-ray diffraction from a horizontal surface of fluids is applied to liquid crystals. A large-diameter drop of octyloxycyanobiphenyl (8OCB) on a glass plate treated for homeotropic alignment yields perfect alignment of the smectic-$A$ layers at the top surface over an area…
Abstract Isothermal crystallization of polypropylene in two temperature steps has been investigated by means of polarizing optical microscopy. On the edges of growing β‐spherulites a β → α modification change is observed when the temperature is raised beyond 140°C. The growth rate of the β‐modification exceeds that of…
Physical-chemical conditions of synthesis are found and trigonal GdF3-CaF2 crystals with Nd3+ ions are grown using the Bridgman technique. Detailed investigations are made of their spectroscopic intensity characteristics. Intermanifold luminescence branching ratios from the 4F3/2 state and transition cross-sections ar…
Variable range hopping conductivity (i.e. resistivity proportional to exp T−1/4) has been observed in Al implanted sapphire. The conductivity of these implanted layers was studied as a function of implanted doses.
We consider the interaction of electrons in unfilled shells of an ion substituted as an impurity in an insulating host crystal with their self-fields induced through polarizable ligands. All orders of the interaction (dipole, quadrupole, etc.) are considered, thereby extending previous treatments that included induced…
Absorption spectra of Pr3+ and Nd3+ diluted in LuPO4 and YPO4 crystals have been measured from 4000 to 30 000 cm−1, at liquid He and N2 temperatures. Fluorescence was observed for Pr3+ and Nd3+ in YPO4, and Zeeman spectra were obtained in the visible region. The transitions were assigned and fit to a semiempirical Ham…
The chelating agents EDTA, o-phenanthroline, nitrilotriacetic acid (NTA), ethylenediamine-bis(o-hydroxyphenylacetic acid) (EDDA) or dimethylglyoxime prevented the expression of hydrogenase activity in batch cultures of nitrogen-fixing Azotobacter chroococcum, but did not inhibit preformed enzyme. The inhibition was re…
Some important statistical properties of the self-avoiding freely jointed ring-polymer model are studied. Using dynamic Monte Carlo techniques, which yield proper ring configurations, the probability distribution function Pn(r) of intrachain distances, the bond correlation function 〈u0u0+n〉 and related quantities as m…
High-resolution electron-energy-loss spectra are reported which describe the oxidation of Al(111) surfaces. The initial stage of oxidation is characterized by both surface and subsurface atomic oxygen. The surface oxygen phase is unstable and converts to subsurface oxygen at room temperature. No evidence of molecular…
Results of the temperature-dependent Raman spectra of graphite-bromine intercalation compounds are reported in the temperature range $290<T<380$ K. Of particular importance is the first observation of phase transitions in intercalated graphite using the Raman scattering technique, including (1) a commensurate-in…