Materials Literature
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The tilings of rhombi in two dimensions and of rhomboedra in three dimensions are studied when they are constrained by fixed boundary conditions. We establish a link between those conditions and free or periodic boundary ones: the entropy is written as a functional integral which is treated via a saddle-point method.…
Digital x-ray imaging techniques of today require electronic detectors that can be applied to all modalities of medical imaging. This paper presents work showing that selenium, when used as a direct converter, can be competitive with present day scintillator technologies targeting mammographic, radiographic and fluoro…
The evolution of cross-linked polymer chain clusters in a solvent from a monomer solution has been investigated by dynamic light scattering. The characteristic decay time distribution, P (Γ -1 ), of the gelling system has been examined as a function of the initial monomer concentration, C, where Γ -1 and Γ are the cha…
The templating organoammonium cations of as-synthesized MCM-41 mesoporous silicas are ion-exchanged with [Co(en)3]3+or trans-[Co(en)2Cl2]+ in DMSO or ethanol neutral solutions, respectively. Pure electrostatic adsorption or complex grafting takes place at the inner MCM-41 surface depending on the nature of the complex…
A series of carbosilane dendrimer generations, G x RF6 ( x = 1−3) with perfluorohexyl (−C 6 F 13 ) groups on the surface and one dendrimer G3 without these end groups, have been studied using X-ray scattering and quasielastic neutron scattering. The G x RF6 form generation dependent superstructures as a result of the…
The accurate control of a system that exhibits hysteresis requires a control strategy that incorporates some form of compensation for the hysteresis. One approach is to develop an accurate model P of the hysteresis and then use the inverse P<SUP>-1</SUP> as a compensator (inverse compensation). This paper focuses on t…
The photoluminescence behavior of dicyanoargentate(I) ions doped in KCl host crystals has been studied. Several ultraviolet and visible emission bands are observed in this system. Each emission band becomes dominant at a characteristic excitation wavelength; that is, the energy of the emission can be tuned by site-sel…
Novel Ru(II) and Ru(III) complexes having TPA (tris(2-pyridylmethyl)amine, L1) and 5-Me(3)-TPA (tris(5-methyl-2-pyridylmethyl)amine, L2) were prepared to establish their synthetic routes and to elucidate coordination geometry and interactions between tightly bound tripodal tetradentate ligands and Ru(II)/Ru(III) cente…
The secondary relaxations of a series of glassy copolymers based on poly(ethylene terephthalate) (PET) and poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) involve cooperative motions of the cyclohexylene rings. The cooperativity gives rise to longer range motions which create significant volume fluctuations tha…
We present numerical simulations of avalanches and critical phenomena associated with hysteresis loops, modeled using the zero-temperature random-field Ising model. We study the transition between smooth hysteresis loops and loops with a sharp jump in the magnetization, as the disorder in our model is decreased. In a…
The thermal properties of silver are calculated within the quasi-harmonic approximation, by using phonon dispersions from density-functional perturbation theory, and the pseudopotential plane-wave method. The resulting free energy provides predictions for the temperature dependence of various quantities such as the eq…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationDirect Observation of Size-Dependent Optical Enhancement in Single Metal NanoparticlesSteven R. Emory, William E. Haskins, and Shuming NieView Author Information Department of Chemistry, Indiana University Bloomington, Indiana 47405 Cite this: J. Am. Chem. Soc. 1998, 120,…
Titania, zirconia, and alumina samples with periodic three-dimensional arrays of macropores were synthesized from the corresponding metal alkoxides, using latex spheres as templates. In a fast, single-step reaction, the monomeric alkoxide precursors permeate the array of bulk polystyrene spheres and condense in air at…
We investigate morphology evolution under melt blending of an immiscible mixture of two polymers, to which small amounts of a block copolymer are added as an emulsifier. We demonstrate the effect on blend morphology of an exothermic interaction between the major component, which constitutes the continuous matrix, and…
The Raman spectrum of dihydrofolate (H 2 folate) complexed with dihydrofolate reductase (DHFR) and NADP +, believed to be an accurate mimic of the productive DHFR/NADPH/H 2 folate complex involved in the reaction catalyzed by DHFR, contains bands associated with stretch motions of N5 C6 of bound substrate. However, th…
The mechanism of poly( p -phenylenebenzoxazole) formation from terephthalic acid (TA) and diaminodihydroxybenzene dihydrochloride (DADHB) in polyphosphoric acid (PPA) was studied. The solubility of TA in PPA with 86% P 2 O 5 content was determined to be 0.02% at 100 °C and 0.06% at 140 °C. Dissolved TA existed as thre…
The sequential reaction of (OEP)Os(CO) with NOPF 6 (in CH 2 Cl 2 ) followed by RMgX (in THF) gives variable isolated yields of the new (OEP)Os(NO)R (5−44%), (OEP)Os(R) 2 (1−10%), (OEP)Os(NO)X (14−19%), and [(OEP)Os(NO)] 2 (μ-O) (up to 24%) compounds, depending on the reaction conditions and the nature of R and X (OEP…
This paper reports a systematic experimental and theoretical study of the second-order nonlinear optical properties of multichromophoric molecules that range from dipolar symmetry to three-dimensional octupolar symmetry. The four possible conformers of tetranitrotetrapropoxycalix[4]arene ( cone, paco, 1,2-alt, 1,3-alt…
The degree of polymerization (DP n ) of poly( p -phenylene) (PPP) 3 with appendant third-generation, Fréchet-type dendrons was determined as 110 after a chemical modification. This DP n is extraordinarily high and shows that the mechanistically complex Suzuki polycondensation can thus be employed even in the case of s…
The effects of a metal ion-bound carboxylate group on the acidity of a water molecule bound to the same cation have been assessed by ab initio molecular orbital calculations. In the hexahydrate Mg[H 2 O] 6 2+ the free energy required to deprotonate one coordinated water molecule is only 40% of that required to deproto…