Materials Literature
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The urea-induced unfolding of the alpha subunit of tryptophan synthase from E. coli was monitored by optical spectroscopy and by urea-gradient gel electrophoresis. Three independent lines of evidence support the conclusion that one or more stable intermediates are present in this process: (i) Satisfactory fits of the…
Experimental results and a theoretical model are presented which give strong evidence that the ratio β/L2μM is a constant for a large class of disubstituted conjugated hydrocarbons, β is the second-order polarizability, μM the mesomeric dipole moment, and L the length of the hydrocarbon chain.
Segments of yeast genomic DNA containing two enolase structural genes have been isolated by subculture cloning procedures using a cDNA hybridization probe synthesized from purified yeast enolase mRNA. Based on restriction endonuclease and transcriptional maps of these two segments of yeast DNA, each hybrid plasmid con…
Utilizing field data obtained in Part I, laboratory studies to simulate flashovers on several insulator shapes and designs were carried out. Chemical composition of the contaminants used in these studies was based on our findings at the Sylmar HVDC Converter Station. The flashover characteristics thus derived are comp…
Abstract The structure of thermally denatured Type I collagen has been studied using laser light scattering. The results indicate that the diffusion coefficients of α‐chains and β‐ and γ‐components are 1.550 ± 0.08 × 10 −7 , 1.000 ± 0.05 × 10 −7 , and 0.835 ± 0.04 × 10 −7 cm 2 /sec, respectively, at temperatures betwe…
Abstract The chemisorption of SO 2 on a W and a Pt surface has been investigated by flash desorption mass spectrometry (FDMS) and AES. AES data indicate that the chemisorbed sulfur dioxide molecules oxidized the W surface, and produced a stable tungsten oxide during the heating (up to 1400 K) process. FDMS data indica…
SUMMARY Two devices for measuring the beam current in an electron microscope are described; a Faraday cage rod for accurate absolute measurements in the specimen position and a collector plate mounted in the viewing chamber, which may be used continuously during experiments, for relative current measurements. Results…
It is well established that diffusion and relaxation processes in polymers above Tg are closely related in that they are both governed by the polymer segmental motions, which are believed to be determined by the free volume present in the system. The diffusion coefficients of gases in elastomers can be accounted for b…
The interaction of anhydrous ferric chloride with nylon 6 has been inferred from Fourier transform infrared spectroscopy (FTIR), wide-angle x-ray diffraction (WAXD), thermal (DSC and TGA), and rheological (Rheometrics) measurements. At very low additive concentration of ∼0.25 wt %, an about 50-fold melt viscosity incr…
This study compares the grain sizes of dense, equiaxed gadolinia (Gd 2 O 3 ) specimens as determined by light microscope/polished surface and by scanning electron microscope/fracture surface techniques. The average intercept lengths (AIL) as determined by the two techniques were found to differ only slightly. For Gd 2…
Abstract A series of N ‐alkylene biscitraconimides was synthesized from the corresponding N ‐alkylene‐biscitraconamic acids or directly from itaconic anhydride and a homologous series of aliphatic diamines, H 2 N(CH 2 ) n NH 2 , where n = 2 through 12. The biscitraconamic acids were synthesized from the α,ω‐diamino‐al…
Abstract Film composition, temperature and humidity affect the oxygen transmission rates of some films used for the vacuum packaging of meat. Of the transparent films suitable for meat included in the investigation, those which include polyvinyl alcohol or polyvinylidene chloride offer the greatest barriers to oxygen.…
The X-ray powder diffraction pattern of the low-temperature form of carnegieite (T < 943 K) has been successfully indexed by means of electron diffraction on small particles (10 μm) and subsequent least-squares refinement of 103 reflections from a high-resolution Guinier Cu Kα1 photograph. The lattice constants a = 5.…
By comparing the propagation of electrical trees in polyethylene with the evolution of artificial air-filled cavities in epoxy, it is possible to envisage the dielectric breakdown as a treeing process. Experiments were carried out on epoxy resin specimens with voids of 0.250 mm thick and 3 mm in diameter. The propagat…
14C labeled ethylenediaminetetra (methylene phosphonic acid) and triethylenediaminetetra (methylene phosphonic acid) have been used to study their adsorption on calcium sulfate dihydrate crystals radiometrically under different conditions. Kinetics of crystal growth of calcium sulfate dihydrate crystals was studied bo…
Measurements of the internal friction of aluminium alloys containing hydrogen have been made from 77 to 300 K at 35 kHz using a composite resonator technique. Perfection of a metallic bonding technique for the transducer-specimen composite produced background dampings which were typically of the order Q −1 ≃ 10−6. Cri…
Ionomers based on propylene–acrylic acid copolymer have been prepared and their rheological behavior studied. With different cations the melt viscosity at any shear rate increases as tributylamine salt < acid < zinc salt < sodium salt. Similarly, the activation energies for viscous flow follow the order polypropylene…
This paper describes some of the unique properties and performance characteristics of triaxial woven fabrics. With three systems of yarn interlacing at sixty-degree angles with one another, triaxial woven fabrics provide less of an anistotropic behavior and offer an alternative to the inherent structural weaknesses of…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectron-transfer reactions accompanied by large structural changes. 1. Lucigenin-10,10'-dimethyl-9,9'-biacridylidene redox systemElisabet Ahlberg, Ole Hammerich, and Vernon D. ParkerCite this: J. Am. Chem. Soc. 1981, 103, 4, 844–849Publication Date (Print):February 1, 1981P…
The effect of direct interactions between suspended particles on their diffusion coefficient is investigated starting from the generalized Einstein relation. It is shown that an attractive potential added to the hard core repulsion leads to a decrease of the diffusion coefficient, whereas a repulsive term has the oppo…