Materials Literature
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Abstract Isothermal glassy‐state properties of cured thermosetting materials pass through maximum and minimum values with increasing fractional chemical conversion. In this work, a diglycidyl ether of bisphenol A (a diepoxide) and trimethylene glycol di‐ p ‐aminobenzoate (a tetrafunctional aromatic diamine) system was…
Abstract Different levels of β‐form crystallinity in isotactic polypropylene (iPP) were produced by blending a series of additives. X‐ray diffraction analyses showed that the Kx values varied from 0 to 0.05. Indigosol Brown IRRD, Indigosol Red Violet IRH, Cibantine Orange HR, Indigosol Pink IR, Cibantine Blue 2B, Indi…
The theory of statistical-mechanical lattice-gas modeling of adsorption is reviewed and shown to be applicable to a range of electrochemical problems dominated by effective, lateral adsorbate--adsorbate interactions. A general strategy for applying the method to specific systems is outlined, which includes microscopic…
In this paper, by introducing a factor f to denote the contraction effect of perovskite crystals along the trigonal axis in the cubic-to-trigonal phase transition, the expressions for calculating the zero-field splitting D, the first excited-state splitting Delta ( 2 E) and the anisotropy of the EPR g-factor (characte…
The recent measurements of the magnetic properties of Pd 2 TiIn and Pd 2 TiAl Heusler-type alloys motivated a study of the electronic structure of such compounds. The electronic structures of the ordered Pd 2 TiX (X=Al, Ga, In) Heusler-type alloys are calculated by the self-consistent spin-polarized TB LMTO method. Th…
The effect of substrate bias voltage was investigated for bias-enhanced diamond nucleation pretreatments of diamond thin films in a microwave plasma chemical vapor deposition reactor. A critical bias voltage of approximately −200 V was observed for nucleation density enhancement from ∼104 cm−2 to ∼1010 cm−2. Furthermo…
Detailed neutron powder diffraction data are presented which show that the phase transition (P6 3 /mmc-C2/m) at 754 K in sodium carbonate, Na 2 CO 3 , is a second-order proper ferroelastic m=2 transition. The order parameter is characterized by the shear strain epsilon 5 , with a coupled rotation of the carbonate grou…
We have studied experimentally phase separation in binary mixtures comprised of nearly monodisperse emulsion droplets of two different sizes. For three values of \ensuremath{\xi}, where $\ensuremath{\xi}<1$ is the size ratio, we have determined phase diagrams and find that segregation occurs for $\ensuremath{\xi}\e…
Atomistic simulations of the vibrational density of states of a space-filling nanocrystalline model material show low- and high-frequency tails not seen in the perfect crystal. The interface-related low-frequency phonon modes give rise to a pronounced, grain-size-dependent peak in the low-temperature excess specific h…
In a mixed ionic/covalent insulator the dynamical ionic charges are much larger than the static ones. The phenomenon is particularly relevant in ferroelectric perovskites, and is well understood at the mean-field level. Here we use a model Hamiltonian to investigate polarization in a strongly correlated, and partially…
Passive diamond layers fabricated using chemical vapor deposition can improve thermal conduction in electronic microstructures. The benefit of using diamond depends strongly on the thermal boundary resistance between active semiconducting regions, where heat is generated, and the diamond. Two independent experimental…
It is shown that the spectrum of the thermal surface height fluctuations on supercooled liquid close to the glass transition contains a narrow quasielastic component, which desribes slow fluctuation freezing in at the glass transition. The spectrum is obtained from a dynamic susceptibility which is calculated using th…
We performed a first-principles molecular dynamics study of liquid ${\mathrm{SiO}}_{2}$ at a temperature of 3500 K, followed by a rapid quench to 300 K obtaining a perfectly chemically ordered amorphous network. Structural and electronic properties of our amorphous sample are in good agreement with neutron diffraction…
Abstract Die Untersuchung der thermodynamischen Eigenschaften und der Reaktivität neu synthetisierter Substanzen ergibt interessante Einblicke in deren Chemie. Mit der Thermischen Analyse erhält man bei kleinen Probenmengen (oft nur wenigen Milligramm) umfangreiche Informationen. Daneben können die aus der Thermischen…
“The metallic bond still lives!” maintains the author of this highlight. In two recent papers theoreticians argue against the concept of the metallic bond as a distinct type of bond, and favor treating it as a limiting case of the covalent bond based on ab initio descriptions of bonding in solids. Still, J. C. Schön i…
The rate of intramolecular triplet energy transfer upon excitation of the RuII unit in the binuclear complex 1 decreases by roughly a third when the alkyne spacer is extended by a second ethynyl group (complex 2). The metal—metal distance increases by 2.4 Å, and correspondingly the attenuation factor for electron exch…
The cover picture shows the arrangement of two 1:1 complexes composed of a cyclic zinc porphyrin tetramer (Zn4−1) and a central meso-tetra-4-pyridyl-porphyrin unit (H2-Py4P) in the solid state (view along the c axis; purple = N, blue = C, yellow = Zn). The central porphyrin ligand, which is coordinated to each zinc ce…
Site-directed mutagenesis and Laue diffraction data to 2.5 A resolution were used to solve the structures of two sequential intermediates formed during the catalytic actions of isocitrate dehydrogenase. Both intermediates are distinct from the enzyme-substrate and enzyme-product complexes. Mutation of key catalytic re…
Locked into a tub geometry, the pentaporphyrin array illustrated has a well-defined conformation both in solution and in the crystal. Self-assembly of this light-harvesting antenna model quenches the fluorescence of both the central tetrapyridylporphyrin unit and the zinc porphyrin tetramer.
The reversible photochemical conversion between the open form 1, a strong fluorophore, and the closed form containing a central, hexyl-substituted six-membered ring, which fluoresces only weakly, makes modulation of emitted light possible. This readily adjustable system is of interest for optical data storage. R = CH,…