Materials Literature
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Mesoporous materials have been synthesized that are composed of hybrid frameworks in which inorganic and organic components have a fixed stoichiometry and are covalently bonded. The creation of UOFMN (unified organically functionalized mesoporous networks) materials incorporates concepts employed in the synthesis of M…
A theoretical study of Heisenberg exchange and double exchange interactions in iron–sulphur superclusters is presented. The clusters can play an important role in biological systems (proteins and enzymes) acting as so-called active centers. The cluster with valence 4+ can be modeled by four Fe(III) and two Fe(II) ions…
It is shown that fluids consisting of particles that interact with potentials containing an accessible hard core have elastic moduli at infinite frequency that are infinite in magnitude. A consequence of this is that such a fluid, at any density or temperature, is not viscoelastic as are all real fluids. The viscosity…
Raman spectroscopy of matrix-isolated, mass-selected Fe3 and Ag3 reveal that both are Jahn–Teller distorted triangular molecules. The observed spectrum of Ag3 can be accounted for adequately using an approximate Jahn–Teller potential truncated at the quadratic term [Wedum et al., J. Chem. Phys. 100, 6312 (1994)] with…
This paper describes the characterizations of structural and electrochemical properties of nanoparticle thin films derived by a one-step exchange−cross-linking−precipitation route. While there exists a stepwise layer-by-layer construction method, our motivation stems from seeking an alternative and simpler pathway to…
The superconducting proximity effect in single-walled carbon nanotubes connected to niobium electrodes was controlled with the use of nearby gates that tune the niobium-nanotube transparency. At 4.2 kelvin, when the transparency was tuned to be high, a dip in the low-bias differential resistance was observed, indicati…
p-type doping of molecular-beam-epitaxy grown layers of the diluted magnetic semiconductor Zn(1-x)MnxTe is achieved by using an active nitrogen cell. The strong interaction between the localized Mn spins and the holes deeply modifies the transport properties (metal-insulator transition, spin-dependent Hall effect). In…
The scaling behavior of cyclical surface growth (e.g. deposition/desorption), with the number of cycles n, is investigated. The roughness of surfaces grown by two linear primary processes follows a scaling behavior with asymptotic exponents inherited from the dominant process while the effective amplitudes are determi…
A large first-order magnetic phase transition in an organic radical, 1,3,5-trithia-2,4,6-triazapentalenyl, is described. The transition occurs with a wide thermal hysteresis loop over the temperature range 230 to 305 kelvin. The high-temperature phase is paramagnetic, and its structure consists of a uniform one-dimens…
Ferroelectric and paraelectric films deposited on dielectric and semiconductor substrates were studied at the frequency range 0.3-100 GHz and temperature interval 300-700 K in comparison with chemically equivalent bulk materials. A dielectric spectroscopy method helps to trace the change of dielectric polarization and…
Dynamical properties of bulk poly(propylene sulfide) (PPS) were investigated for a range of molar masses between 600 and 50 000 g/mol. The primary and secondary relaxation (α-relaxation and β-relaxation) were studied using dielectric spectroscopy. The local segmental relaxation (α-relaxation) and the chain backbone co…
Structures of water-insoluble complexes of polyethyleneimine (PEI) and fluorinated acids, varying in chain length from 4 to 16, were examined via contact angle measurements, X-ray diffraction, and infrared spectroscopy. The wettability of complex surfaces was shown to decrease with increasing chain length. The surface…
New heterobinucleating ligands for heme−Cu O2-reactivity studies feature a variably appended tridentate chelate {N,N-bis[2-(2-pyridyl)ethyl]amine} possessing an already established copper(I)/O2 chemistry. Reduced metal complexes have been synthesized and characterized. (3L)FeII (1a), a heme−Fe(II) empty-tether complex…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTTransverse Cylindrical Microdomain Orientation in an LC Diblock Copolymer under Oscillatory ShearChinedum Osuji, Yuanming Zhang, Guoping Mao, Christopher K. Ober, and Edwin L. ThomasView Author Information Program in Polymer Science…
The kaolinite−mullite reaction process has been studied by single- and triple-quantum 27 Al magic-angle spinning (MAS) NMR. All materials have also been characterized by 29 Si MAS NMR and powder X-ray diffraction. It has been shown that in order to record reliable 27 Al MAS NMR spectra it is important to use very fast…
11-Aminoundecanoic acid capped titanium dioxide (capped-TiO 2 ) nanoparticles (63 ± 2 Å total diameter and 20−24 Å core diameter) and polyallylamine hydrochloride, PAH, have been layer-by-layer self-assembled onto precoated (by poly(diallyldimethylammonium chloride), PDDA, or PAH) substrates. The ultrathin S-PDDA(capp…
Reactions of Cu(hfacac)(2).H(2)O (hfacac = hexafluoroacetylacetonate) with pyrazine, 3-cyanopyridine, 1,2-bis(4-pyridyl)ethane, and 4,4'-trimethylenebipyridine in methylene chloride have been studied. Two types of products were obtained and crystallographically characterized: compounds 1 (Cu(hfacac)(2)(pyrazine)(2), o…
Pancake vortices in stacks of thin superconducting films or layers are considered. It is stressed that in the absence of Josephson coupling topological restrictions upon possible configurations of vortices are removed and various examples of structures forbidden in bulk superconductors are given. In particular, it is…
Thermoreversible gelation of relatively short n -alkanes and a variety of other organic liquids has been accomplished using low concentrations of long n -alkanes (chain lengths from 24 to 36 carbon atoms) as gelators. The stability of the gels is discussed in terms of gelator concentration, gelation temperature, and t…
The effects of “short term shearing” on the subsequent crystallization of a polydisperse Ziegler−Natta isotactic polypropylene are observed using in situ optical measurements and ex situ microscopy. Imposition of brief intervals of shear (0.25−20 s, less than a thousandth of the quiescent crystallization time) can red…