Materials Literature
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Liquid crystals were discovered about ninety years ago. The Austrian botonist Reinitzer [1] observed that cholesteryl benzoate has two sharp melting points at ∼145 and 179°C. At 145°C the solid crystalline material changed to a hazy anisotropic liquid which at 179°C became a clear, transparent, and isotropic phase. Th…
X-ray photoelectron spectroscopy with variable takeoff angles has been used to study the nitridation of Si(100). The air-oxidized layer on the silicon film has been cleaned off by an Ar radio frequency (rf) plasma, and nitridation was obtained at temperatures around 400 °C in a rf plasma of a NH3 (5%)-N2(95%) mixture.…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructure and magnetism in ACuCl3 salts containing bibridged chains with square-pyramidal coordination geometryU. Geiser, R. M. Gaura, R. D. Willett, and D. X. WestCite this: Inorg. Chem. 1986, 25, 23, 4203–4212Publication Date (Print):November 1, 1986Publication History Pub…
Abstract The role of organic ligands of different ability to complex with Al 3+ in affecting the formation of allophane and imogolite and the nature of the precipitation (>0.01 µm) and soluble (<0.01 µm) products was investigated at initial Si concentration of 1.6 × 10 −3 mol.L −1 , Si/Al molar ratios of 0.5 and…
Abstract The molecular order and mobility of two liquid‐crystalline polyacrylates with phenyl benzoate moieties as mesogenic side groups and (CH 2 ) m spacers ( m = 2 and m = 6) were investigated by pulsed 2 H NMR. The mesogenic side groups were isotopically labelled at the terminal phenylene ring. In the glassy state…
The dc conductivity of a sintered sample of Y 2 O 3 containing an excess of lower‐valent metal (Ml) impurities has been measured at 600° to 1100°C in air as a function of the water vapor pressure (0.4 to 3000 Pa). The logarithm of the p ‐type conductivity vs log P H2o has a slope of – 1/2 in certain regions of F H2o a…
When a nematic liquid-crystal cell is driven by a dc electric field, the capacitance of the cell increases in the first several tens of milliseconds, but after that the capacitance tends to decrease with a rather long relaxation time of the order of 1 s. This phenomenon can be explained by impurity ions which form the…
Densification of two‐dimensional arrays of nearly monosized copper spheres was examined by hot‐stage optical microscopy. The evolution of the particle arrangement was studied with computer methods, and statistical correlations were sought. Color graphics were found useful for displaying the spatial relationship of the…
Abstract Several classes of organosilicon polymers are effective precursors for silicon carbide ceramic compositions. These include polydimethylsilane (via a two‐step process), ‘polysilastyrene’, polycarbosilazanes or polysilazanes, and certain siloxanes, plus the branched polycarbosilanes, branched polysilahydrocarbo…
We report, for the first time to our knowledge, on high-resolution x-ray scattering measurements of the liquid crystal 4'-butoxyphenylester 4-decyloxybenzoic acid (4OP10OB) with emphasis on the smectic-C phase and the smectic-A to smectic-C phase transition. From angular scans in reciprocal space we found that the sme…
Abstract A novel addition polymerization of 1,4‐diethynylbenzene ( 1 ) with 1,4‐benzenedithiol ( 2 ) was studied under UV‐irradiation in toluene solution at −20°C. The addition polymerization was found to proceed rapidly and a pale‐yellowish polymer precipitated with the progress of the reaction ( M̄ n = 7500). A solu…
Abstract A greenhouse experiment was conducted with soil from the A horizon of an acid Mountview silt loam (Typic Paleudult) to measure the relative influence of soil P retention capacity on P availability from Bayovar (also known as Sechura) phosphate rock (Peru) with that from triple superphosphate (TSP). The P rete…
At room temperature, a kink in negative fields appears in the hysteresis loops of Nd-Fe-B permanent magnets. This phenomenon can be related to the fact that the grains at the surface of the magnet exhibit a strongly reduced coercivity compared to those of the bulk. Below 130 K a kink of another nature develops. It is…
Abstract The temperature dependence of electrical resistivity and thermoelectric power of the intercalation compounds of M x TiS 2 (M = Mn, Fe, Co, and Ni; 0 ≦ x ≦ 1/3) with layered structures are measured over the temperature range 1.5 to 300 K. These experimental results can be explained by a simple model, which tak…
A product consisting of two vinylogous amidinium ions is formed when the title compounds gives up two electrons to iodide. The resulting salt forms diamagnetic, blackish-violet crystals. The two mesomeric π-electron systems are almost planar; the sixmembered ring in 1 has a twist-conformation.
The properties of a soluble endoprotease from rat liver were studied. The enzyme was purified in a latent form. It sedimented as a single component with a sedimentation coefficient (S(0)20,w) of 19.8 S. Measurement by quasi-elastic light scattering gave a diffusion coefficient (D(0)20,w) of 2.5 X 10(-7) cm2 X s-1 and…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCopper(II) and nickel(II) trinuclear species with dithiooxamide derivative ligands: structural, magnetic, spectroscopic, and electrochemical propertiesRichard Veit, Jean Jacques Girerd, Olivier Kahn, Francis Robert, and Yves JeanninCite this: Inorg. Chem. 1986, 25, 23, 4175–…
Lonberg and Meyer [Phys. Rev. Lett. 55, 718 (1985)] have recently discovered in polymer nematics the existence of a critical value ${r}_{c}$=0.303 for the ratio r=${K}_{2}$/${K}_{1}$ between the twist and splay Frank elastic constants, below which a periodic splay-twist distortion is energetically favored with respect…
Electrostatic membrane mirrors are potentially useful as aberration generators. To realize this capability, it is necessary to know the influence functions (each giving mirror response to a single electrode) and then to use a fitting procedure to determine the optimal voltage settings for reproducing a desired surface…
The authors present a theory for the static, paramagnetic, spin susceptibility for metals at finite temperatures. It is based on a 'first principles' mean-field theory of itinerant magnetism and provides an expression which resembles that of a classical Heisenberg model added to an itinerant component. The quantities…