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Abstract Phase separation in a segmented polyurethane has been studied by differential scanning calorimetry. The glass transition temperature of the soft phase decreases logarithmically with time to a limiting value at each annealing temperature. The magnitude of the decrease is larger at low annealing temperatures, b…
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We consider the long-wavelength behavior of smectic liquid crystals (or any solid developing periodic order in only one direction) in the presence of anharmonic terms dictated by symmetry considerations. We analyze this anharmonic model of smectics with the use of analytic renormalization-group techniques directly in…
Infrared absorption and variable excitation (4067, 4131, 5145, and 5682 Å, near the B, Q, and Q0 absorption maxima) resonance Raman spectra are reported for NiPP (PP = protoporphyrin IX dimethyl ester) and for NiPP-dα (vinyl α-carbons deuterated) and NiPP-d2β (vinyl β-carbons dideuterated). The deuteration shifts and…
This work shows that molecular structural variations can be introduced in oxide systems, including AI 2 O 3 , ZrO 2 , TiO 2 , and SiO 2 , by controlled hydrolysis and polymerization reactions during the formation of oxides from metal alkoxides. The chemical and stoichiometric makeup of hydroxides and oxides is not fix…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagnetic circular dichroism studies. 61. Substituent-induced sign variation in the magnetic circular dichroism spectra of reduced porphyrins. 2. Perturbed molecular orbital analysisJoseph D. Keegan, Alan M. Stolzenberg, Yu Cheng Lu, Robert E. Linder, Guenter Barth, Albert Mo…
The solubility of magnesium ammonium phosphate hexahydrate (MgNH4PO4·6H2O) was determined in aqueous solution at 25, 35, 38, and 45C. The thermodynamic solubility product was determined at each temperature.
The environmental and metallurgical factors in the intergranular stress corrosion cracking of austenitic stainless steel at temperatures below 100 C has been examined. The behavior of annealed and sensitized microstructures in a variety of environments, including oxygen-containing pure water and aqueous solutions cont…
Abstract The various pathways of degradation of polyurethane based on MDI and propoxylated trimethylol propane were studied from the analysis of degradation gases sampled at various temperatures during the heating rise. From the beginning of degradation (250°C) to 400°C, we suggest that the main mechanism is the fract…
A crystal structure refineme-nt of a synthetic hafnon, HfSiO4, space group l4llamd with a: 6.5725(7)4, c = 59632(qA,Z: 4,D: 6.97 gmcm-3, produced positional parameters for oxygen ofy = 9.965t(13) and z: 0.1948(14) at R : 0.054. Hafnon has a zircon structure and the similar ionic radii of Hf (0.83A) and Zr (0.844) acco…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagnetic circular dichroism studies. 60. Substituent-induced sign variation in the magnetic circular dichroism spectra of reduced porphyrins. 1. Spectra and band assignmentsJoseph D. Keegan, Alan M. Stolzenberg, Yu Cheng Lu, Robert E. Linder, Guenter Barth, Albert Moscowitz,…
In the Rietveld method of analysing powder diffraction data, the crystal structure is refined by fitting the entire profile of the diffraction pattern to a calculated profile. There is no intermediate step of extracting structure factors. The method was applied first to diffraction patterns recorded with neutrons at a…
Abstract Poly( p ‐phenyleneterephthalamide) of high molecular weight was obtained when the polycondensation of terephthalic acid and p ‐phenylenediamine was carried out in N ‐methylpyrrolidone (NMP) that contained dissolved CaCl 2 and LiCl in the presence of pyridine. The molecular weight of the polymer obtained varie…
SUMMARY Focusing and correcting the astigmatism of an electron microscope can be time consuming and difficult to achieve accurately. An automatic method of performing these tasks using an on‐line computer system and a digital framestore has been developed. The method is applicable to noisy images in both scanning and…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHigh-spin-low-spin equilibriums of cobalt(2+) in the terpyridine complexes Co(terpy)2X2.nH2OS. Kremer, W. Henke, and D. ReinenCite this: Inorg. Chem. 1982, 21, 8, 3013–3022Publication Date (Print):August 1, 1982Publication History Published online1 May 2002Published inissue…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDissolution of perfluorinated ion-containing polymersCharles R. Martin, Teresa A. Rhoades, and James A. FergusonCite this: Anal. Chem. 1982, 54, 9, 1639–1641Publication Date (Print):August 1, 1982Publication History Published online1 May 2002Published inissue 1 August 1982ht…
Abstract The pressure‐volume‐temperature (PVT) relationships of bisphenol‐A polycarbonate, polyarylate, and phenoxy were studied at pressures to 1800 kg/cm 2 and in both the glassy and melt states. Earlier data on polysulfone are included in the analysis and discussion of the results. All four polymers contain the bis…
Electronic conductivity and Seebeck coefficients of LaFeO 3 were measured as a function of temperature (1000° to 1400°C) and P ( O 2 ) (10 5 to 10 −13 Pa). Electronic conduction was found to be n‐type in the lower P ( O 2 ) range, and p ‐type in a higher P(O 2 ) range. The calculated carrier mobilities suggest a hoppi…
Two ion‐transport mechanisms are described for ion transport in polyether‐alkali metal salt complexes: an intrahelical jumping process along crystalline (helical) regions of the polymer, and a transport process in the amorphous regions which is dependent on formation of fourfold coordination sites via mutual motion of…
The magnetic free energy in the so-called s-d model where the itinerant d electrons and localised spins coexist is expanded in a power series of the total magnetisation M. The first-order transition observed for DyCo 2 , HoCo 2 and ErCo 2 is explained from the negative values of the coefficient of the M 4 term at T C…