Materials Literature
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Classical continuum models, i.e. continuum models that do not incorporate an internal length scale, suffer from excessive mesh dependence when strain‐softening models are used in numerical analyses and cannot reproduce the size effect commonly observed in quasi‐brittle failure. In this contribution three different app…
Heat conduction in dielectric thin films is a critical issue in the design of electronic devices and packages. Depending on the material properties, there exists a range of film thickness where the Fourier law, used for macroscale heat conduction, cannot be applied. This paper shows that in this microscale regime, hea…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAssembly, structural characterization, and thermal behavior of layer-by-layer deposited ultrathin films of poly(vinyl sulfate) and poly(allylamine)Yuri Lvov, Gero Decher, and Helmuth MoehwaldCite this: Langmuir 1993, 9, 2, 481–486Publication Date (Print):February 1, 1993Publ…
Simulated annealing is a probabilistic method proposed in Kirkpatrick, Gelett and Vecchi (1983) and Cerny (1985) for finding the global minimum of a cost function that may possess several local minima. It works by emulating the physical process whereby a solid is slowly cooled so that when eventually its structure is…
Crystals of bovine trypsin were acylated at the reactive residue, serine 195, to form the transiently stable p-guanidinobenzoate. Hydrolysis of this species was triggered in the crystals by a jump in pH. The hydrolysis was monitored by three-dimensional Laue crystallography, resulting in three x-ray diffraction struct…
Fumarase A, a product of the fumA gene of Escherichia coli, has been found to catalyze the isomerization of enol to keto oxalacetic acid (OAA) in addition to catalyzing the fumarase reaction. The kcat/Km for the isomerization is almost identical to that for the fumarase reaction. The isomerization reaction apparently…
We have examined the interaction of Citrobacter freundii tyrosine phenol-lyase with both L- and D-alanine. This enzyme catalyzes the racemization of alanine as a side reaction, in addition to the physiological beta-elimination of L-tyrosine to give phenol and ammonium pyruvate. The steady-state kinetic parameters for…
Glycine is found as every third residue along the entire length of triple helices in fibrillar collagens, but the triple-helix regions of nonfibrillar collagens and other proteins usually contain one or more interruptions in this repeating pattern. A set of four peptides was designed to model the effect of interruptio…
The technique of Raman scattering has been used to investigate the properties of ferroelectric PbTiO3 thin films grown on both single-crystal KTaO3 and fused quartz substrates by means of metalorganic chemical vapor deposition. The ‘‘difference Raman’’ technique was employed in which substrate contributions were subtr…
The atomic structure of the (310) twin in Nb was predicted using interatomic potentials derived from the embedded atom method (EAM), Finnis-Sinclair theory (FS), and the model generalized pseudopotential theory (MGPT). The EAM and FS predicted structures with crystal translations which break mirror symmetry. The MGPT…
Using a time-of-flight technique, different transport mechanisms, deep trapping, multiple shallow trapping, and ideal itrinsic transport, can be observed in the different temperature and phase regions of the liquid-crystalline photoconductor hexapentyloxytriphenylene. The temperature and field dependences of carrier m…
A new mathematical representation of the cluster model for dielectric relaxation, in a bound dipole case, is established by employing the extremal value theory. Two distinct probabilistic mechanisms, which drive the dielectric response function to acquire the power-law form, are presented. Consequently, two forms of s…
The results of an experimental and theoretical study to compare the attributes of Pr3+-doped sulphide, chloride, mixed halide, fluoride and chlorotellurite glasses for 1.3 μm fibre amplifiers are presented. Quantum efficiencies based on measured and calculated radiative and nonradiative rates are presented for each gl…
Abstract The plane strain shear yield stress and the triaxial crazing stress were determined for several commercial glassy polymers as a function of temperature. The polymers considered were: polycarbonate (Lexan ® ), polysulfone (Udel ® ), polyetherimide (Ultem ® ), polyarylate (Arylon ® ), and an amorphous nylon (Zy…
The solutions of the pseudo 1-dimensional compound Li 2 Mo 6 Se 6 in N -methyl-formamide (NMF) previously obtained by Tarascon, Di Salvo et al. are shown to be of a liquid crystalline nature. A lyotropic nematic phase is observed within the concentration range (4 ·10 −2 ÷ 10 −1 ) mol/l Li 2 Mo 6 Se 6 /NMF. The gel pha…
Enzymes deposited on solid support usually show good stability when operated in organic solvents. Decreased stability of the enzyme preparations was noticed when low enzyme loadings were used (e.g., with Celite as support; less than 1 mg enzyme/g). It was possible to avoid the activity loss by the addition of an addit…
Binary mixtures of suspended, nearly hard-sphere, sterically stabilized colloidal silica particles of diameter ratio 6 were observed to phase-separate at comparable volume fractions of the two particle species. The occurrence of phase separation as a function of the particle concentrations was studied visually and by…
Abstract The effects of copper, mercury, nickel, zinc, cadmium, indium, magnesium, and calcium stearates on the course of N ‐cyclohexyl‐2‐benzthiazylsulphenamide‐accelerated sulfur vulcanization of natural rubber have been investigated on the basis of curemeter measurements at 145°C. The differences in the efficiencie…
(Ba,Ca)TiO3 samples with the ratio of (Ba+Ca) to Ti as unity but prepared by (i) a semiwet route involving (Ba,Ca)CO3 solid solution precursors and TiO2 and (ii) the conventional dry route involving BaCO3, CaCO3, and TiO2 powders, exhibit diffuse and BaTiO3-type sharp ferroelectric phase transitions, respectively. Rie…
Surface segregation in thin films of symmetric polyolefin diblock copolymers containing a lamellar microstructure, cast on a variety of substrates, has been investigated. In all cases, the conformationally smaller block preferentially segregated to both the solid and air interfaces even though the surface energy of th…