Materials Literature
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Epoxidations of olefins and oxidations of alcohols can be carried out in the presence of peroxides at relatively low temperatures with Cu2+ histidine complexes that have been immobilized in zeolite cavities (structure from molecular modeling shown on the right). Combined diffuse reflectance and ESR spectroscopic studi…
The dragline silk spun by spiders exhibits unusual tensile strength and the energy required to break it can be higher than that of Kevlar. In his Perspective, Tirrell comments on a research report in the same issue by Simmons et al . ( p. 84 ) that elucidates some of the structural properties that give spider silk its…
The redox behavior is markedly different for the second generation dendrimer 1 (depicted on the right) from that of the first generation dendrimer without the densely packed dendritic structure. The unusually positive FeIII/FeII redox potential of 1 in water (+0.19 V vs. SCE) is attributable to the strong shielding of…
At least four types of silanol groups are present in MCM-41, a novel silicate with uniform mesopores, according to IR spectroscopy. Isolated silanol groups (type 1 in the picture on the right) and those involved in hydrogen bonds were distinguished by partial silylation with chlorotrimethylsilane (CTMS) and chlorotrip…
A complete and accurate set of experimental crystallographic phases to a resolution of 1.8 angstroms was obtained for a 230-residue dimeric fragment of rat mannose-binding protein A with the use of multiwavelength anomalous dispersion (MAD) phasing. An accurate image of the crystal structure could thus be obtained wit…
The first report of the formal potentials of a series of solid metal hexacyanometalates (M + ) n M′[M″ (CN) 6 ] is given (M + = Li + , K + , Na + , Rb + , Cs + ; M′ = Ag, Al, Cd, Co, Cr, Cu, Fe, Ga, In, Mn, Ni, Pb; M″ = Cr, Fe, Mn). A linear correlation exists between the ionic potential Φ = z /r eff of the nitrogen‐b…
The computation of the electron-electron Coulomb interaction is one of the limiting factors in ab initio electronic structure calculations. The computational requirements for calculating the Coulomb term with commonly used analytic integration techniques between Gaussian functions prohibit electronic structure calcula…
Molecular-based ferrimagnetic thin films with high critical temperatures ( T c ) composed of mixed-valence chromium cyanides were synthesized by means of a simple electrochemical route. The highest T c was 270 K, obtained for Cr 2.12 (CN) 6 . The T c values were easily controlled by changing the preparation conditions…
The molecular origin of the exceptional mechanical properties of spider silk is unclear. This paper presents solid-state 2H nuclear magnetic resonance data from unoriented, oriented, and supercontracted fibers, indicating that the crystalline fraction of dragline silk consists of two types of alanine-rich regions, one…
First-principles calculations of the relative stability, structure, and physical properties of carbon nitride polymorphs predict a cubic form of C 3 N 4 with a zero-pressure bulk modulus exceeding that of diamond. Like diamond, this new phase could potentially be synthesized at high pressure and quenched to ambient pr…
Many mineralizing organisms selectively form either calcite or aragonite, two polymorphs of calcium carbonate with very similar crystalline structures. Understanding how these organisms achieve this control has represented a major challenge in the field of biomineralization. Macromolecules extracted from the aragoniti…
The effect of the rate and time of mixing in a batch mixer on the phase structure of polypropylene/polystyrene (PP/PS) blends with various rheological properties of the components was studied. Regions with substantially different average sizes of the dispersed particles were found in the studied blends. Differences be…
Starting from aromatic diamines, a series of bismaleimides (BMIs) and maleimide-terminated structural resins were prepared in solution and characterized. Maleimide-terminated resins were prepared through Michael addition reaction with 3/2 molar ratio of bismaleimide and aromatic diamine as reactants. The structural an…
Differential scanning calorimetry (DSC) and dynamic and thermomechanical analyses are used to study the glass transition temperature (Tg) of the thermotropic liquid crystalline polyesters prepared by molten polycondensation of 4-acetoxyvanillic acid (V), 4-acetoxybenzoic acid (B), and poly(ethylene terephthalate) (E).…
Several samples of poly(lactic acid) with different molecular weights and tacticity have been prepared, and some PLLA injection moulded specimens have been annealed to promote their crystallization. From the characterization data, poly(L-lactide) showed more interesting mechanical properties than poly(D, L-lactide), a…
The electrochemistry and spectroscopic properties of three iron corroles were examined in benzonitrile, dichloromethane, and pyridine containing 0.1 M tetra-n-butylammonium perchlorate or tetra-n-ethylammonium hexafluorophosphate as supporting electrolyte. The investigated compounds are represented as (OEC)Fe(IV)(C(6)…
Several samples of poly(lactic acid) with different molecular weights and tacticity have been prepared, and some PLLA injection moulded specimens have been annealed to promote their crystallization. From the characterization data, poly(L-lactide) showed more interesting mechanical properties than poly(D, L-lactide), a…
We present a method to perform fully selfconsistent density-functional calculations, which scales linearly with the system size and which is well suited for very large systems. It uses strictly localized pseudoatomic orbitals as basis functions. The sparse Hamiltonian and overlap matrices are calculated with an $O(N)$…
The effect of ionizing radiation on nanoparticles can change the chemical and physical properties of materials. The study of these processes by means of Fourier infrared spectroscopy leads to a better understanding of the behavior of nanomaterials in the radiation environment and the development of new fields of appli…
The phenomenon of reaction anisotropy, i.e. forming of different products on different crystals' facets, is characteristic for 2-amino-5-aryl- 1,3,4-oxadiazoles solid-state acetylation. In this case, the ratio of products in reaction yield depends on the form of substrate crystal, hence, on the solvent from which the…