Materials Literature
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Abstract Crystallization of poly(tetrafluoroethylene) was observed by differential scanning calorimetry at constant cooling rates. A method for kinetic analysis of thermoanalytical data of nonisothermal crystallization was applied to analyze the data, and it was elucidated that poly(tetrafluoroethylene) crystallizes o…
Robert W. Work, Duality in Major Ampullate Silk and Precursive Material from Orb-Web-Building Spiders (Araneae), Transactions of the American Microscopical Society, Vol. 103, No. 2 (Apr., 1984), pp. 113-121
Soviet carbon steel CT-3 plates were exposed in five different places in Havana and the city of Havana (rural, industrial-marine and marine stations). Weight loss was evaluated in periods of six and twelve months at different starting times. Salinity and SO2 concentration in the atmosphere were determined. Relative hu…
On flux grown polydomain single crystals of Sr8[Al12O24] (CrO4)2 exploratory domain studies and measurements of birefringence, polarization, dielectric constant and transition enthalpy demonstrate the existence of a first order ferroelectric phase transition at about 2954↓-299↑K.
We have performed photoemission studies on samples of poorly crystallized MoS2 prepared in situ by thermal decomposition of (NH4)2MoS4 in a UHV-compatible chamber under mixed H2S/H2 gas conditions. The results reveal new electronic states which are not present on crystalline MoS2. These states are observed as a band t…
From a study of living materials and specimens in several regional herbaria, a list has been drawn up of all the common and several of the rarer tube-dwelling diatoms of eastern Canada. Descriptions, illustrations of living material and acid-cleaned valves, and a key to the species are provided. Most specimens were fr…
The compound [Cu2(dien)2Cl2](C1O4)2 crystallizes in the orthorhombic system, space group Pbn21, with unit cell dimensions: a = 7.637(1) A, b = 13.549(3) A, and c = 20.866(4) A, with four molecules in the unit cell (Z = 4). The structure consists of dimeric [Cu2(dien)2C12]2+ units in which the coordination about copper…
Abstract The decomposition of methyl formate to methanol and carbon monoxide was carried out in gaseous phase at 50–300 °C over alkaline earth metal oxides, Na/MgO, Al2O3, SrO/Al2O3, K/active carbon, and 13X-molecular sieves. The MgO catalyst pretreated at 1000 °C exhibited a high activity, the selectivity being 100%.…
We describe observations made with an optical microscope of the formation of two distinct types of disclinations during the shear of a small molecule nematic, MBBA. Once formed, these disclinations grow and deform in the shear field. We also report observations of the relaxation of these defects after the cessation of…
The influence of oxygen vacancies in PbZrO3 on the dielectric properties and phase transitions between the antiferroelectric, ferroelectric and paraelectric states has been investigated. Marked changes in dielectric parameters and in phase transition temperatures were found for the deficient samples. With increasing n…
Abstract A quantitative model which described the microscopic and macroscopic refractive index properties of uniaxially oriented crystalline polymers has been extended in relation to molecular bond polarizabilities in this work. Application of this extended modeling methodology in analyzing measured refractive index d…
We have examined the interaction of H2O vapor with three structurally different carbon surfaces. The edge and basal surface of crystalline graphite as well as a ‘‘paracrystalline’’ glassy carbon were characterized with LEED, UPS, and AES. Structural characterization by LEED showed the typical ‘‘ring’’ pattern for the…
Electrochemical polarization methods were utilized to study the galvanic corrosion of steel coupled to brass. Polarization of a 70Cu-30Zn brass cathode controlled galvanic corrosion rate (galvanic current) of the steel anode in the couple. The effect of cathode/anode surface area ratio was predicted successfully from…
The magnetic properties of Pb(Fe1/2Nb1/2)O3 have been studied by neutron diffraction on a polydomain single crystal and susceptibility measurements on a single ferroelectric domain. A Néel temperature of $$ 160K was found but no further anomalies were indicated by the susceptibility data. No evidence of a spontaneous…
Bacillus subtilis mutants deficient in the 2-ketoglutarate dehydrogenase enzymatic complex required aspartate for growth at wild-type rates on carbon sources for which synthesis of the degradative enzymes is sensitive to catabolite repression (e.g., poor carbon sources), but did not require aspartate for growth on car…
Abstract Dimethylsilanediol and other water-soluble dimethysiloxanols undergo aqueous photolytic oxidative demethylation with tropospheric ultraviolet radiation in the presence of suitable chromophores, such as nitrogen oxides, to give silicic acid and carbon dioxide. The “biosuitability” of the resulting silicic acid…
A crystal chemical study carried out on phosphate single crystals with the formula AIBIIPO4 (AI=Na, K; BII=Ca, Zn, Sr, Cd, Ba, Pb) has permitted to follow the evolution of the crystal symmetry inside these series. Second harmonic generation (SHG) tests held on powder or small single crystals and hysteresis loops displ…
Abstract The solid reaction products from pyrolysis of polyethylene terephthalate in the presence and absence of red phosphorus were characterized by CP/MAS 13 C‐NMR, FR‐IR, and MAS 31 P‐NMR spectroscopy. Over the temperature range of 300–400°C, polyethylene terephthalate was converted in a sealed vial to a highly cro…
Abstract From analysis of infrared spectra it was found that in syndiotactic ( s ) poly(methyl methacrylate) (PMMA) in solution, long s sequences contain an increased population of diads with a skeletal conformation tt (in the staggered approximation). Self‐aggregation of s ‐PMMA in solution leads to a further increas…
The review of the experimental investigations of the anomalous (bulk) photovoltaic effect in the crystals without a center of symmetry is presented. The linear and circular effects for piezo and ferroelectrics are investigated in the wide range of conditions (the extrinsic and intrinsic absorbtion, different impurity…