Materials Literature
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Abstract An ab initio LCAO SCF MO calculation was performed on planar Fe‐porphine with a double zeta basis set consisting of 300 CGTO 's. SCF wave functions of several states of Fe‐porphine and its cation were obtained. The net charge of Fe is in the range of 1.39 to 1.53. The highest occupied orbital is ascertained t…
Abstract Free volume fraction of the Williams‐Landel‐Ferry(WLF)‐Doolittle type has been applied to the analysis of the nonequilibrium state for the glassy polymers. The free volume fraction is a two parameter variable since it depends on the free volume and the occupied volume. The excess entropy is derived from the m…
The heat capacity of poly(oxymethylene), poly(oxyethylene), poly(oxytrimethylene), poly(oxytetramethylene), poly(oxyoctamethylene), poly(oxypropylene), Poly(oxymethyleneoxyethylene), poly(oxymethyleneoxytetramethylene), poly(oxy-1,4-phenylene), poly(oxy-2,6-dimethyl-1,4-phenylene), ploy(oxy-2,6-diphenyl-1,4-phenylene)…
Abstract A comprehensive model for a semibatch ester interchange reactor has been developed with a view to investigate the effect of various process and operational variables on the DMT conversion rate as well as the by‐product formation. The influence of important variables such as EG‐to‐DMT ratio, catalyst concentra…
Experimental evidence indicates that up to 90% of all hydrogen is generated at the metal/oxide interface during the corrosion of carbon and low alloy ferritic steels by high temperature water, in the absence of oxygen. None of the presently accepted mechanisms are able to account for this observation. After considerat…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe function of silicon dioxide colloids in photoinduced redox reactions. Interfacial effects on the quenching, charge separation, and quantum yieldsI. Willner, Jer-Ming Yang, Colja Laane, John W. Otvos, and Melvin CalvinCite this: J. Phys. Chem. 1981, 85, 22, 3277–3282Publi…
Strontium-barium niobate, (Sr, Ba)Nb2O6, was hot-pressed and the dielectric, piezoelectric and optical properties of samples with a transmission of 40–52% in a wavelength from 0.35 to 1.4 μm were measured. Anisotropies of about 1.5 times were found in both the permittivity and the electromechanical coupling factor in…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotocontrol of polypeptide helix sense by cis-trans isomerism of side-chain azobenzene moietiesAkihiko Ueno, Keiko Takahashi, Junichi Anzai, and Tetsuo OsaCite this: J. Am. Chem. Soc. 1981, 103, 21, 6410–6415Publication Date (Print):October 1, 1981Publication History Publis…
Organs that are rich in collagen such as liver, lungs, and bone are frequently sites of tumor cell metastasis. In this study, we have found that cultured tumor cells of human and rat origin migrated unidirectionally in response to collagen in vitro. Synthetic di- and tri-peptides that contained amino acid sequences fo…
The structural relaxation rates, which are crucial in understanding the liquid \ensuremath{\leftrightarrow} glass transition, are investigated within the free-volume theory. We discuss the origin of the observed dispersion of relaxation times and show that it is simply related to the dispersion of the total surface-to…
We persent tempeature measurements of the importnt parameter defming the properties of the semctic C* Phase in a series of schiff bases. The pitch of the helica texture is measured optically. The molecular tilt is deduced from optical observations and from X-ray measurements of the smectic layer thickness. The critica…
The solid state reactions that take place between many ceramics and metals can be utilised to produce strong vacuum-tight joints that maintain their strength and durability even at elevated temperatures. In this context platinum can play an especially important role because of its high melting point and resistance to…
The results are presented and discussed of previous and recent experiments concerning the mechanism of the anti ferroelectric phase transition in squaric acid. Special emphasis is laid upon an extended discussion of the static equation of state of the order parameter because of its importance for establishing microsco…
Cerium dioxide doped with Y3+ ions, which is of interest for its ionic conductivity, is here studied by anelastic methods. The internal friction peaks observed are analyzed into peaks A, B, C (with Hr = 0.64, 0.71 and 0.78 eV, respectively). Peak A, present at low Y3+ concentrations is established to be due to a YV Pa…
The reduction in the dielectric anomaly near Tc in improper ferroelectrics suggests that this behavior may be exploited to significantly enhance the figure-of-merit for pyroelectric infrared detection. This “reduction” is associated with a decoupling of the thermal and dielectric responses which, in turn, reflects the…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStrategy for the synthesis of cylindrical macropolycyclic hosts with hydrophilic interior surfaces: crown ether rings fused by the tetrahydroxymethylethylene (THYME) unitDavid M. Walba, Rodney M. Richards, Steven P. Sherwood, and R. Curtis HaltiwangerCite this: J. Am. Chem.…
Abstract Poly(methyl methacrylate) (PMMA) microspheres were swollen in methanol vapor, the swelling penetrant was quickly evacuated, and the subsequent relaxation of the polymer under vacuum was monitored by determination of the rate of settling of rapidly measured low pressure pseudoequilibrium CO 2 sorption isotherm…
Poly(vinyl chloride) resins are produced by four basic processes: suspension, emulsion, bulk and solution polymerization. PVC suspensions resins are usually relatively dust-free and granular with varying degrees of particle porosity. PVC emulsion resins are small particle powders containing very little free monomer. B…
Abstract Perfluoroalkyltin(IV) halides (RfSnX2I) were prepared in situ by the oxidative addition of perfluoroalkyl iodides to tin(II) halide in N,N-dimethylformamide. Aldehydes and ketones readily reacted with RfSnCl2I giving perfluoroalkylcarbinols in the N,N-dimethylformamide-pyridine system. RfSnF2I, however, did n…
Abstract Thermal polymerization of acrylamide was studied by differential scanning calorimetry. Latent heat of fusion Δ H f and enthalpy of polymerization Δ H p values were found to be 36 and −18.0 kcal mol −1 , respectively. The overall activation energy E for the polymerization was calculated to be 19 k cal mol −1 u…