Materials Literature
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One-electron oxidation of nickel(II) 5,10,15,20-tetraaryl-2-aza-21-carbaporphyrin ((CTPP)Ni II ) and nickel(II) 2-methyl-5,10,15,20-tetraaryl-2-aza-21-carbaporphyrin ((MeCTPP)Ni II ) resulted in formation of rare organonickel(III) derivatives. The half-wave potential for the first oxidation of (CTPP)Ni II and (MeCTPP)…
Crack profile measurements near the crack tip in the SEM were used to measure crack tip toughness of alumina as a function of grain size (average grain size 0.9–16 μm). For comparative tests, two crack configurations were included in the present study: straight cracks (CT specimen) loaded with an in situ device; and r…
We present two sets of rules for constructing quasiperiodic tilings that suggest a simpler structural model of quasicrystals and a more plausible explanation of why quasicrystals form. First, we show that quasiperiodic tilings can be constructed from a single prototile with matching rules which constrain the way that…
Spectroscopic evidence is presented to indicate that local screening effects are important in polymer mixtures. Essentially, a polymer segment has a locally higher concentration of like segments because of this factor. A simple modification to existing theories is presented to account for this local screening.
The effects of solid-state structures on the rate of enzymatic erosion for melt-crystallized films of bacterial poly(hydroxyalkanoic acids) (PHAs) have been studied at 37 °C and pH 7.4 in the aqueous solution of an extracellular PHB depolymerase from Alcaligenes faecalis . In this study, the following PHA homopolymer…
The metastable state silk I structures of Bombyx mori silk fibroin in the solid state were studied on the basis of 15N- and 13C-nmr chemical shifts of Ala, Ser, and Gly residues. The 15N cross-polarization magic angle spinning (CP/MAS) nmr spectra of the precipitated fraction after chymotrypsin hydrolysis of B. mori s…
In this study, the adsorption of single-stranded oligodeoxyribonucleotides (ODN) onto well-characterized polymer latex particles has been investigated. At first, the case of poly(thymidylic acid) (dT 35 ) was thoroughly examined as a function of pH and ionic strength in the presence of cationic polystyrene colloids pr…
Effective-medium theory is often helpful for understanding the behavior of subwavelength gratings with small period-to-wavelength ratios. By analytically solving Maxwell’s equations in the small-depth limit, we show that the effective properties of subwavelength gratings strongly depend on the grating depth. Moreover,…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTModel Systems for Flavoenzyme Activity. Modulation of Flavin Redox Potentials through π-Stacking InteractionsEric C. Breinlinger and Vincent M. RotelloView Author Information Department of Chemistry, University of Massachusetts Amherst, Massachusetts 01003 Cite this: J…
Polystyrene/polyisoprene (PS/PI) diblocks suspended in decane serve as a model system for the investigation of highly concentrated diblock copolymer solutions. Bulk melts of PS/PI with no solvent exhibit ordered morphologies including lamellae, close-packed cylinders, etc. that depend on the block asymmetry. These sam…
The paper presents a survey on the dielectric analysis of integrated ceramic capacitors. The thin film examples are based on high–permittivity paraelectric SrTiO3, solid–solution (Ba,Sr)TiO3, ferroelectric Pb(Zr,Ti)O3, and superparaelectric BaTiO3. The current state of knowledge concerning the temperature dependence,…
The metalloporphyrin-catalyzed oxidation of 2-methynaphthalene (1) by potassium monopersulfate produced mainly two naphthoquinones: 2-methyl-1,4-naphthoquinone (2) (menadione or vitamin K(3)) and 6-methyl-1,4-naphthoquinone (3). In aqueous solution and at room temperature in the presence of 5 mol % of the water-solubl…
The complexation of TTF 2 and cyclobis(paraquat- p -phenylene) 1 4+ has been studied by cyclic voltammetry and by spectroelectrochemistry: shifts in the redox potentials for the TTF and the 1 4+ components of 45 and 30 mV, respectively, occur upon complexation. Decomplexation of 2·1 4+ upon oxidation of the TTF unit t…
The preparation and catalytic properties of bimetallic colloids consisting of a ligand-stabilized Pt shell on Au or Pd cores supported by alumina are described. The aim of this work is to study the influence of the electronegativity of the colloidal core metals on the activity and selectivity of the surface Pt in hydr…
Highly nonlinear chromophores with good thermal stabilities (> 250 °C) are required if organic polymeric materials are to be developed for electro‐optical (EO) applications. The synthesis and characterization of highly efficient and thermally stable diphenylamino‐substituted thiophene stilbenes (e.g., see Figure) a…
In the present paper, we analyse several activation configurations of embryonic dislocations nucleated from the tip of a cleavage crack. The activation configurations include nucleation on inclined planes, on oblique planes and on cleavage ledges and are treated within the classical framework of Peierls. A variational…
Type V collagen became solubilized in softened sardine muscle after 1 day of chilled storage with the concomitant weakening of pericellular connective tissue induced by disintegration of thin collagen fibrils. However, no significant changes were observed in the structure of interstitial connective tissue or biochemic…
F s + (H) color centers at the surface of MgO have been studied using a combined EPR and quantum chemical approach. F s + (H) are paramagnetic excess electrons centers where the unpaired electron is trapped in a surface anion vacancy. They are formed at the surface of thoroughly dehydrated MgO (1073K) upon UV irradiat…
We report the derivatization of hyperbranched poly(acrylic acid) (PAA) films with a wide range of amino- or alcohol-terminated molecules. These molecules can include moieties such as pyrene, ferrocene, poly(ethylene glycol), 15-crown-5, and a dye. To derivatize PAA films, we activate their carboxylic acid groups with…
We have studied the variation of the paramagnetic to ferromagnetic transition temperature TC and of the ferromagnetic to antiferromagnetic transition temperature TN as a function of the average size of the A site cations (Ln, Sr) in the manganite perovskites Ln0.5Sr0.5MnO3 (Ln=Gd, Sm, Y, Pr, La). For our investigation…