Vinyl Tellurides: Synthesis and Properties
Data The Synthesis, Reactivity, Structure, And Physicochemical Properties Of Vinyl Tellurides, Which Are Potential Monomers, Synthons, And Intermediates, Are Given In The Present Review.
Materials Literature
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Heterogeneous molecular aggregation and fractal structure in chitosan/acetic acid systems
Abstract The influence of deacetylation degree on heterogeneous molecular aggregation has been investigated for chitosan solution in 2 wt % acetic acid aqueous solution using rheological and small‐angle x‐ray scattering (SAXS) methods. Three samples of chitosan, which were designated CS62, CS79, and CS96, were used, a…
Effect of plasticizer type on gelation and fusion of PVC plastisol, dialkyl phthalate series
Abstract Different grades of PVC resins and a variety of plasticizers are used to adjust processability and properties of plastisol. The plastisol, which is a dispersion of fine particles of PVC in plasticizer, is coated on a substrate and heated in an oven to gel and fuse. In the gelation stage the resin particles be…
Growth and electronic properties of ultrathin lutetium–diphthalocyanine films studied by electron spectroscopy
We report on a systematic study of the thin-film growth and the electronic structure of the intrinsic molecular semiconductor lutetium–diphthalocyanine (LuPc2). The films were grown in ultrahigh vacuum. Starting from submonolayer coverage, thickness-dependent x-ray and ultraviolet photoemission spectroscopy (UPS) meas…
Potassium release and fixation in Ferralsols (Oxisols) from Southern Togo
SUMMARY Potassium release and fixation were studied on Ferralsols (typic Eutrustox) of Southern Togo both by isotopic exchange with 42 K+ ions and by exchange with 1 M ammonium acetate. Experiments were conducted on soil samples taken from surface (0–30 cm) and subsoil (80–100 cm) layers of four plots. These plats, wi…
Surface‐enhanced Raman scattering of the complexes of silver with adenine and dAMP
Abstract The behaviour of adenine and 2′‐deoxyadenosine‐5′‐monophosphate (dAMP) at positive surface potentials of a silver working electrode was investigated using surface‐enhanced Raman scattering (SERS). The use of positive potentials in the presence of adenine or dAMP leads to a rapid accumulation of an intense spe…
Highly‐ordered ultrathin lc multilayer films on solid substrates
Research News: Freely suspended thin film of smectic liquid crystalline materials can be described as two‐dimensinal fluids with a regular layer structure in the third dimention. By reducing the internal pressure in the set up shown in the figure the films can be transferred onto solid supports allowing their study, m…
Diagenesis of the Central Basque-Cantabrian Basin (Iberian Peninsula) based on illite-smectite distribution
Abstract X-ray diffraction was used to analyse the distribution of clay minerals in the <2 µ m fraction of the lutitic and marly facies from the centre of the Basque-Cantabrian Basin (Basque Arc), where the sedimentary section is 2000 to 10,000 m thick. Most of the deposits were laid down during the Cretaceous and…
Thermoluminescent processes ofMgAl2O4irradiated at room temperature
Two non-first-order kinetic peaks at about 350 and 500 K appear in the thermoluminescence (TL) spectra of single-crystal and polycrystalline ${\mathrm{MgAl}}_{2}$${\mathrm{O}}_{4}$ irradiated with ionizing radiation at room temperature. Among others, emission from ${\mathrm{Cr}}^{3+}$ and ${\mathrm{Mn}}^{2+}$ ions are…
Energy Considerations in the Deposition of High‐Quality Plasma‐Enhanced CVD Silicon Dioxide
Silicon dioxide films deposited from the plasma‐enhanced chemical vapor deposition (PECVD) reaction of silane and nitrous oxide in the presence of helium were studied to determine the effects of temperature and radio frequency (RF) power on the deposition process. Increased RF power density yielded oxides which were s…
Disclination interaction in an applied field: Stabilization of the Lehmann cluster
We study the interaction of disclinations in the presence of an applied magnetic or extensional flow field, which tends to align the director. Disclinations and inversion walls in the director field of nematic thermotropic liquid-crystal polymers are imaged at high resolution using the lamellar decoration technique of…
Thermal analysis of pyridine-treated sepiolite and palygorskite
Abstract The thermal behaviour of sepiolite and palygorskite treated with pyridine (Py) was investigated by DTA, TG, DTG and EGA (by MS) under a flow of air and inert gases (N 2 or Ar). The thermal analysis showed that the organic base was adsorbed by the clays, penetrating into the clay pores and replacing zeolitic a…
Addition curing thermosets endcapped with 4‐amino [2.2] paracyclophane
Abstract A new family of addition curing polyimides were prepared that contained 4‐amino [2.2]‐paracyclophane as the endcap. An improved synthesis of the endcap 4‐amino‐[2.2] cyclophane was accomplished increasing the yield to 60% and simplifying the procedure. DSC and rheological analysis of endcapped polyimide oligo…
Observation of a new metastable liquid-crystalline phase in supercooled blue phase systems
A new metastable liquid-crystalline phase BPS was observed in pure chiral compounds. The BPS is transformed reversibly from the supercooled BPI and is thermodynamically stable with respect to the BPI and metastable to the cholesteric phase. Rhombic single crystals of the BPS probably indicate a cubic lattice structure…
An x-ray crystallographic and single-crystal EPR investigation of the cationic, iron-centered radical tricarbonylbis(triphenylphosphine)iron(I), {Fe(CO)3(PPh3)2+}. A theoretical examination of the structural preferences of five-coordinated seventeen-electron complexes
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn x-ray crystallographic and single-crystal EPR investigation of the cationic, iron-centered radical tricarbonylbis(triphenylphosphine)iron(I), {Fe(CO)3(PPh3)2+}. A theoretical examination of the structural preferences of five-coordinated seventeen-electron complexesJoseph…
A Continuum Damage Model for Fracture of Brittle Solids Under Dynamic Loading
A continuum damage mechanics description of elastic-brittle fracture provides an appropriate constitutive model for impact simulations involving ceramic, rock, or similar materials. For an orthotropically damaged solid, a complementary energy function may be derived from a mesomechanical description of three orthogona…
High-Temperature Reactor Fuel Fission Product Release and Distribution at 1600 to 1800°C
The essential feature of small, modular high-temperature reactors (HTRs) is the inherent limitation in maximum accident temperature to below 1600°C combined with the ability of coated particle fuel to retain all safety-relevant fission products under these conditions. To demonstrate this ability, spherical fuel elemen…
rac-1,2-DIACYLOXYPROPYL-3-ARSONIC ACIDS: ARSONOLIPID ANALOGUES OF PHOSPHONOLIPIDS
A new class of lipids, arsonolipids or rac-1,2-diacyloxypropyl-3-arsonic acids, have been synthesized by acylating tetrabutyl ammonium hydrogen rac-1,2-dihydroxypropyl-3-arsonate with myristic, palmitic and stearic anhydrides in the presence of pyridine. The yields are moderate to low due to decomposition of rac-1,2-d…
An accelerated method for establishing the long term performance of polyethylene gas pipe materials
Abstract It was demonstrated in a previous investigation that both horizontal and vertical shifting is required to produce master curves for the relaxation moduli from elevated temperature data for polyethylene gas pipe materials. In this study, the shift functions obtained from these stress relaxation tests are appli…
Velocity and current measurements in electroconvecting smectic films
We have studied electrically driven convective flow in thin, freely suspended films of smectic-A liquid crystal. Here we report measurements of the two-dimensional velocity field of this flow as the driving voltage is varied. Our results are well described by the first few terms of an appropriate mode expansion over a…