Materials Literature
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The increase in proportion of the non-biological (D-) isomer of aspartic acid (Asp) relative to the L-isomer has been widely used in archaeology and geochemistry as a tool for dating. the method has proved controversial, particularly when used for bones. The non-linear kinetics of Asp racemization have prompted a numb…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Synthetic and Structural Chemistry of Heme Derivatives with Nitric Oxide LigandsW. Robert Scheidt and Mary K. EllisonView Author Information The Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 Cite this: Acc. Chem. Res. 1999,…
The design of predictable multichromophoric supramolecular arrays of freebase and metallo porphyrins constitutes an essential first step toward the synthesis of light-harvesting complexes. We now report crystal engineering strategies to achieve the synthesis of controllable and predictable porphyrinic multichromophore…
For mercury-free fluorescent lamps and plasma display panels, alternative luminescent materials are required for the efficient conversion of vacuum ultraviolet radiation to visible light. Quantum cutting involving the emission of two visible photons for each vacuum ultraviolet photon absorbed is demonstrated in Eu3+-d…
Cellulose samples were found to be soluble in PF/DMSO to form a genuine dilute solution without suffering obvious degradation under adequate conditions. The Mark-Houwink-Sakurada equation for cellulose in PF/DMSO at 30°C obtained here was [η] = 3.01 × DP0.81 where [η] is in the unit of cm3·g−1. The intrinsic viscosity…
An overview of the physics of glassy polymers and the relationships between molecular mechanisms and macroscopic physical, mechanical and transport properties of polymer glasses is presented. The importance of local translational and/or rotational motions of molecular segments in the glass is discussed in terms of the…
Adsorption of CO and NO individually and as a mixture of both on palladium catalysts has been investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The effect of sodium ions has been considered by comparing Pd/SiO 2 catalyst, sodium-doped Pd/SiO 2, and Pd on natural…
1H and 15N NMR studies have been undertaken on complexes of Lactobacillus casei dihydrofolate reductase (DHFR) formed with analogues of the antibacterial drug brodimoprim (2,4-diamino-5-(3', 5'-dimethoxy-4'-bromobenzyl)pyrimidine) in order to monitor interactions between carboxylate groups on the ligands and basic res…
Amorphous WO 3 films, doped with phosphorus, have been synthesized by chemical vapor deposition of volatile, low-melting P-substituted tungsten carbonyls. The presence of a small quantity of dopant released by the precursor during its decomposition is sufficient to inhibit the crystallization of the tungsten oxide on…
Chitosan crystallization, performed by simple drying of an oligomer or polymer solution on a glass or mica surface, was studied at room temperature. Polarizing microscopy revealed the formation of two-dimensional spherulites that were shown to have a negative birefringence. After metal shadowing, electron microscopy i…
We investigated binary low-molecular-weight glass formers as model systems for mixtures of small and large molecules. Tricresyl phosphate (TCP) in oligomeric styrenes (OS), benzene in OS and polystyrene (PS), and benzene in TCP were studied by applying dielectric spectroscopy as well as 1 H, 2 H, and 31 P NMR spectros…
The reaction of mononuclear [LFe(III)] where L represents the trianionic ligand 1,4,7-tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane with NiCl(2).6H(2)O and subsequent oxidations with [Ni(III)(tacn)(2)](ClO(4))(3) (tacn = 1,4,7-triazacyclononane) and PbO(2)/methanesulfonic acid produced an isostructural s…
An overview of the physics of glassy polymers and the relationships between molecular mechanisms and macroscopic physical, mechanical and transport properties of polymer glasses is presented. The importance of local translational and/or rotational motions of molecular segments in the glass is discussed in terms of the…
The dynamic viscoelastic properties of polypropylene (PP)–maleated PP blends in the molten state have been investigated with a dynamic mechanical thermal analyzer (PL-DMTA MKII) at a frequency range (ω) of 0.6 ∗︁ 10−1–3.14 ∗︁ 102 rad s−1. In the study, the blends were prepared by melt-blending in a twin-screw extruder…
Structure development during crystallization of isotactic polypropylene (iPP) at low undercooling is studied by small-angle light scattering (SALS) and light transmission. The structure development is related to network formation (gelation) as previously measured on the same sample in dynamic mechanical experiments. C…
A new cation deficient hexagonal perovskite with the unusual polytype 7H (hhchhcc) has been obtained in the Ba−Mo−Nb−O system for the Ba 7 Nb 4 MoO 20 composition. It crystallizes in the P 3̄ m 1 space group (No. 164) with hexagonal lattice parameters a = 5.8644(2) Å and c = 16.5272(4) Å. The crystal structure has bee…
It is crucial to have a good phenomenological model of electronic stopping power for modeling the physics of ion implantation into crystalline silicon. In the spirit of the Brandt-Kitagawa effective charge theory, we develop a model for electronic stopping power for an ion, which can be factorized into (i) a globally…
We present a highly efficient molecular dynamics scheme for calculating the concentration depth profile of dopants in ion irradiated materials. The scheme incorporates several methods for reducing the computational overhead, plus a rare event algorithm that allows statistically reliable results to be obtained over a r…
We simulate dopant profiles for phosphorus implantation into silicon using a new model for electronic stopping power. In this model, the electronic stopping power is factorized into a globally averaged effective charge Z1*, and a local charge density dependent electronic stopping power for a proton. There is only a si…
The nonlinear magneto-optical Kerr-effect (NOLIMOKE) is determined for freestanding Fe monolayers with several in-plane structures from first principles. Based on the theory of nonlinear magneto-optics by Hübner and Bennemann [Phys. Rev. B, {\bf 40}, 5973 (1989)] we calculate the nonlinear susceptibilities of the mono…