Materials Literature
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A detailed study of doped LaMn${\mathrm{O}}_{3}$ with fixed carrier concentration reveals a direct relationship between the Curie temperature ${T}_{c}$ and the average ionic radius of the La site $〈{r}_{A}〉$, which is varied by substituting different rare earth ions for La. With decreasing $〈{r}_{A}〉$, magnetic order…
Abstract Six new polyether azomethines were synthesized by melt and solution polycondensation of six different diamines with 4,4′‐[1,4‐phenylene bis(oxy)] bisbenzaldehyde. The polymers synthesized by solution method are yellow to white in color and had inherent viscosities up to 0.59 dL/g in concentrated H 2 SO 4 . Th…
Abstract Six nearly monodisperse substituted poly(styrene) homopolymers, poly(styrene) (PS), poly(2‐methylstyrene) (P2MS), poly(3‐methylstyrene) (P3MS), poly(4‐methylstyrene) (P4MS), poly(tertiary‐butylstyrene) (PtBS), and poly(α‐methylstyrene) (FαMS) were anionically polymerized and subsequently saturated using heter…
Abstract 4,4′‐Binaphthyl‐1,1′,8,8′‐tetracarboxylic dianhydride was synthesized from 4‐chloro‐1,8‐naphthalic anhydride and polymerized with aromatic and pliphatic diamines in m ‐cresol or N ‐methyl‐2‐pyrrolidinone (NMP). The polyimides, except for two derived from p ‐phenylenediamine and hydrazine, are soluble in 1,1,2…
Abstract Three N , N ′‐bis (glycidyl ester imide) of pyromellitic acid (diepoxides) were prepared and were used as chain extenders for poly (ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT). The typical reaction conditions for the coupling of the polyester macromolecules were heating with the chai…
It is the intention of this paper to rigorously clarify the role of the occupation numbers in the current practical applications of the density functional formalism. In these calculations one has to decide how to distribute a given, fixed number of electrons over a set of single-particle orbitals. The conventional cho…
There are two stereochemical classes of hydratase-dehydratase enzymes. Those that catalyze the addition of water to alpha, beta-unsaturated thioesters give syn addition-elimination stereochemistry, whereas those that catalyze the addition of water to conjugated carboxylate substrates give anti stereochemistry. This di…
Classification of admixtures influence of admixtures on nucleation - homogeneous nucleation heterogeneous nucleation secondary nucleation influence of admixtures on crystal growth - the role of the solid surface, the role of the interphase solid - liquid influence of admixtures on crystal shape influence of solvents d…
We consider (AlAs)_n/(GaAs)_n superlattices with random thickness fluctuations Delta-n around the nominal period n. Using three-dimensional pseudopotential plane-wave band theory, we show that (i) any amount Delta-n/n of thickness fluctuations leads to band-edge wavefunction localization, (ii) for small Delta-n/n the…
Abstract Polymer blends based on high‐density polyethylene (HDPE) and acrylonitrile butadiene rubber (NBR) were prepared by a melt blending technique. The mixing parameters such as temperature, time, and speed of mixing were varied to obtain a wide range of properties. The mixing parameters were optimized by evaluatin…
Using a functional lactose permease mutant devoid of Cys (C-less permease), each amino acid residue in putative transmembrane helix V was replaced individually with Cys (from Met145 to Thr163). Of the 19 mutants, 13 are highly functional (60-125% of C-less permease activity), and 4 exhibit lower but significant lactos…
Abstract A numerical method to seek a solution for the solid‐state polycondensation (SSP) proces has been proposed to analyze the mechanism of SSP. Results expound that, for the industrial SSP process of PET, the overall reaction rate in a single pellet is appropriately simulated by the diffusion and reaction rate joi…
Three relaxation processes for frequencies from 10 Hz to 10 MHz and for various Ti concentrations in PbZr 1-x Ti x O 3 (x<or=0.03) are presented. The lowest relaxation process (below 100 Hz in the paraelectric phase) is attributed to electrochemical processes contributing to the dielectric polarization. The second is…
We have measured the complete 1.7 μm excited state absorption (ESA) spectrum in erbium-doped glasses. The spectrum is obtained by measuring the gain of an erbium-doped waveguide in the 1400–1800 nm region. Using the measured spectra, we estimate the 1.5 μm uniform upconversion rate by calculating the spectral overlap…
Diamond crystals of 1 μm mean size were grown on (100) silicon substrates by ArF (193 nm) laser ablation of graphite in a hydrogen atmosphere with a laser power density of 1.3×108 W/cm2 at relatively low substrate temperature (450 °C). Raman spectroscopy analysis confirmed the diamond cubic structure of the crystals b…
The formation of YBa2Cu3O7−y(YBCO)/BaTiO3(BTO)//SrTiO3(STO) (100) and BTO/ YBCO//STO(100) bilayer structures is demonstrated for the construction of a superconductor ferroelectric field transistor. The resulting films of the bilayers have highly c-axis oriented structure. Epitaxial YBCO films formed on the BTO//STO(10…
Colossal magnetoresistance in excess of 106% has been obtained (at 110 K, H=6 T) in epitaxially grown La–Ca–Mn–O thin films. The as-deposited film exhibits a substantial magnetoresistance value of 39 000%, which is further improved by heat treatment. The magnetoresistance is found to be strongly dependent on film thic…
Pulsed laser ablation deposition was used to synthesize polycrystalline SrBi2Ta2O9 layered ferroelectric thin films on platinized silicon substrates. Top electrodes were produced by dc magnetron sputter deposition to fabricate capacitors for electrical tests. The polarization electric field hysteresis loops showed sat…
We report measurements of chain diffusion in macroscopically oriented, well-entangled lamellar block copolymers. Diffusion in the lamellar plane is proposed to occur by an ``activated reptation'' mechanism when the composition profile is roughly sinusoidal. At higher degrees of segregation a crossover to an entropical…
A parameter-free, mean-field, multi-orbital Hubbard model with nonspherical Coulomb and exchange interactions, implemented around all-electron local-density approximation (LDA) calculations, correctly predicts the band-gap energy, the absence of dimerization, and the antiferromagnetic ground state of halogen-bridged l…