Materials Literature
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The shear response of a Nicalon‐reinforced ceramic‐matrix composite was investigated using Iosipescu tests. Damage was characterized by X‐ray, optical, and SEM techniques. The large inelastic strains which were observed were attributed to rigid body sliding of longitudinal blocks of material. These blocks are created…
Using an off-lattice Monte Carlo bead-spring model of a chain in a random environment, we study chain conformations and dynamic scaling of diffusivity and relaxation times with chain length N and density of the host matrix ${\mathrm{C}}_{\mathrm{obs}}$. Our simulational results show that with growing ${\mathrm{C}}_{\m…
Ab initio geometry optimizations and normal mode analysis have been performed on a series of oligomers of leucoemeraldine base (LB, the fully reduced amine form of polyaniline) over conformational variations with the HF/6-31G* basis set. Aniline was used to obtain 12 force constant scaling factors with the best vibrat…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTInclusion Adduct Formation between Tris(o-phenylenedioxy)cyclotriphosphazene and Poly(ethylene oxide) or PolyethyleneA. Paul Primrose, Masood Parvez, and Harry R. AllcockView Author Information Department of Chemistry, The Pennsylva…
Abstract Polymerisation conditions have a remarkable effect on the electrochemical properties of polyaniline. Care has to be taken to ensure identical conditions for electrochemical experiments when films electropolymerised differently are examined in comparison, especially when films are prepared potentiodynamically.…
A careful study of the existing literature available in the field of cavitation reveals the potential of ultrasonics as a tool for controlling and, if possible, eliminating certain types of hydrodynamic cavitation through the manipulation of nuclei size present in a flow. A glass venturi is taken to be an ideal device…
A laboratory study was conducted on the cavitation corrosion behavior of a commercial cast duplex stainless steel (DSS) in seawater using an ultrasonically-induced cavitation facility. Mass loss, free-corrosion potential, potentiodynamic polarization, and microscopic examinations were compared in the absence and prese…
A facile preparation of polyimide–silica gel hybrids by the simultaneous in-situ formation of polyimides during the hydrolysis–condensation of tetramethoxysilane (TMOS) is reported here. The hydrolysis and condensation of TMOS was carried out in a solution of DMAc containing 5% LiCl, CaCl2 or ZnCl2 and the seven-membe…
The noncollinear magnetic structure of ferrimagnetic ${\mathrm{Mn}}_{4}$N is calculated ab initio. The magnetic exchange contributions of the different magnetic sites are estimated and compared with ordinary fcc-Mn. For this purpose we present a model which allows us to explain the noncollinear spin configurations of…
The syntheses and mesomorphism of novel octaalkoxymethyl-substituted tetra-2,3-thiophenophorphyrazines, heterocyclic phthalocyanine analogues in which the benzene rings are replaced by thiophene rings, are reported. NMR analysis indicates that these materials exist as isomeric mixtures due to the asymmetry induced by…
Polycrystalline thin films of n-CdSe0.6Te0.4 were deposited in a vacuum of 5×10−5 Torr by thermal flash evaporation with a deposition rate of 20±1 Å/s on indium oxide coated glass plates [σ=1.25×104 (Ω cm)−1] held at 200 °C. Application of surface treatment techniques such as annealing and photoelectrochemical etching…
In a systematic investigation of the effect of dopant composition on dosimetric characteristics of thermoluminescent LiF:Mg,Cu,P phosphor, 130 samples were prepared with different concentrations of all activators over the following ranges: Mg (0-1.0 mol%), Cu (0-0.5 mol%) and P (0-5.0 mol%). From each material a group…
The effect of proline on the prevention of trichloroacetic acid (TCA)-induced protein precipitation is studied. It is found that proline at high concentrations (> 4.0 M) completely prevents TCA-induced precipitation of hen egg white lysozyme. Other osmolytes such as ethylene glycol, glycerol and sucrose fail to preven…
Ni and mixed Ni‐Co oxide films were formed at Pt substrates by the sol‐gel technique and studied electrochemically in 1 M NaOH solutions. All sol‐gel films under study have to be found amorphous. The charge densities of these films are quite high compared to oxides formed by the anodic oxidation of metallic substrates…
In this paper we describe the peculiar structures and preferential codon usage found in wild silkworm fibroin genes. We determined a 1350 bp nucleotide sequence from the Chinese oak silkworm, Antheraea pernyi. The deduced amino acid sequence was partitioned into thirteen polyalanine-containing repetitive motifs, which…
A variety of phenyl-containing polymer surfaces have been oxidized using low pressure non-equilibrium O 2 glow discharges. Characterization by X-ray photoelectron spectroscopy has shown that the level of oxygen incorporation can be correlated to the intensity of the C(1s) π−π* valence transition measured for the untre…
The energy states of oxygen-deficient type defects in the vacuum ultraviolet region are discussed based on the experimental results of vacuum ultraviolet absorption, temperature dependence of the photoluminescence (PL) intensities at 4.3 and 3.1 eV, and lifetimes of the PLs. It was found that the oxygen-deficient type…
We have measured the fracture toughness, G c, of an interface between polystyrene (PS) and poly (2-vinylpyridine) (PVP) reinforced with triblock copolymers (PVP- b -dPS- b -PVP) as a function of the areal chain density, Σ, of the copolymers at the interface. The failure mechanisms of the interface are studied by trans…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTRational Design of a Hexagonal Columnar Mesophase in Telechelic Alternating Multicomponent Semifluorinated Polyethylene OligomersV. Percec, D. Schlueter, and G. UngarView Author Information The W. M. Keck Laboratories for Organic Synthesis, Department of Macromolecular Science,…
The peroxy radical (ROO) is unique among reactive oxygen species implicated in the production of DNA damage in that it possesses an extremely long half-life (order of seconds) and is predicted to have a relatively greater chemical selectivity in its reactions relative to other radical intermediates. Yet no product stu…