Materials Literature
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A homologous series of cellulose oligomers from two to eight repeating subunits have been isolated and size-fractionated from the hydrolysis products of microcrystalline cellulose. Chemical modification of cellotriose ( 1 ), cellotetraose ( 2 ), cellopentaose ( 3 ), and cellohexaose ( 4 ) to the corresponding β-methyl…
We conclude from 23Na and 51V NMR measurements in NaxV2O5(x=0.996) a charge ordering transition starting at T=37 K and preceding the lattice distortion and the formation of a spin gap Delta=106 K at Tc=34.7 K. Above Tc, only a single Na site is observed in agreement with the Pmmn space group of this first 1/4-filled l…
A continuum model of crystalline solid equilibrium is presented in which the underlying periodic lattice structure is taken explicitly into account. This model also allows for both point and line defects in the bulk of the lattice and at interfaces, and the kinematics of such defects is discussed in some detail. A Gib…
We develop a theoretical framework for the diffusion of a single unconstrained species of atoms on a crystal lattice that provides a generalization of the classical theories of atomic diffusion and diffusion-induced phase separation to account for constitutive nonlinearities, external forces, and the deformation of th…
Grand canonical Monte Carlo (GCMC) simulations of ethylene physisorption on the basal plane of graphite are reported. The calculated isotherms are compared with experimental results at several temperatures. The maximum surface coverage studied is close to one monolayer. The ethylene molecules are described as six Lenn…
A thermodynamic framework (UNIQUAC model with temperature dependent parameters) is applied to model the salt-induced protein crystallization equilibrium, i.e., protein solubility. The framework introduces a term for the solubility product describing protein transfer between the liquid and solid phase and a term for th…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTImproved Polypyrrole/Silicon Junctions by Surfacial Modification of Hydrogen-Terminated Silicon Using Organolithium ReagentsNamyong Y. Kim and Paul E. LaibinisView Author Information Departments of Chemistry and Chemical Engineering Massachusetts Institute of Technolog…
A stable aqueous lead sol (10 nm particles) is formed upon the γ-irradiation of Pb(ClO 4 ) 2 in the presence of (poly)ethyleneimine. Lead nanoparticles have an absorption band at 218 nm with ε = 3.2 × 10 4 M -1 cm -1; the band appears at the wavelength that is expected for a surface plasmon oscillation. The changes in…
The deformation behavior of poly(styrene- b -butyl methacrylate) diblock copolymers, PS- b -PBMA, is studied by high-voltage electron microscopy (HVEM) with in-situ deformation device and by TEM. This allows us to describe the craze growth and propagation in block copolymers with different morphologies. The influence…
Herein we introduce the concept of an “activated” monomer approach to the synthesis of convergent dendrimers. In this method a set of chemically orthogonal monomers, one of which is an “activated” analogue of the other, is used to rapidly synthesize large, perfect dendrimers with one additional generation being added…
The 364 nm negative ion photoelectron spectrum of WO 2 - is obtained. The spectrum reveals that four different electronic states are accessed in the neutral molecule following electron detachment. From the rich vibrational structure the vibrational frequencies of the bending and/or symmetric stretching vibrations are…
We report simulations of water confined between two parallel flat (hydrophobic) walls separated by 10.95 Å. Our results are consistent with the possibility of a liquid−liquid phase transition separating two phases of different densities. The low-density liquid phase displays tetrahedral “ice-like” local ordering, whil…
Several new Ni ( 7a − i ), Pd ( 8a − j ), and Pt ( 9a − j ) dithiolenes belonging to the general class [M(R,R‘timdt) 2 ] (R,R‘timdt = monoanion of di-substituted imidazolidine-2,4,5-trithione) have been synthesized by sulfuring the disubstituted imidazolidine-2-thione-4,5-diones ( 4 ) with Lawesson's reagent ( 5 ) in…
The reaction of H 2 S with activated Ag + -loaded zeolite A leads to silver sulfide zeolite A composites. The optical absorption spectra of samples with different loading densities of silver sulfide suggest the formation of small silver sulfide clusters which are stable under ambient conditions. To our knowledge, this…
We report the calculation of autocorrelation relaxation times, intrinsic viscosity, and the diffusion coefficient of a starburst dendrimer model, using both the preaveraging and variational-bound techniques. The model includes hydrodynamic effects, represented by the Rotne−Prager interaction, as well as excluded-volum…
The novel dimeric polyoxometalate [{beta-SiNi(2)W(10)O(36)(OH)(2)(H(2)O)}(2)](12)(-) (1) has been synthesized and characterized by IR spectroscopy, polarography, elemental analysis, thermogravimetric analysis, and magnetic measurements. An X-ray single-crystal analysis was carried out on K(12)[{beta-SiNi(2)W(10)O(36)(…
A smart structure is a system containing multifunctional parts that can perform sensing, control, and actuation; it is a primitive analogue of a biological body. Smart materials are used to construct these smart structures, which can perform both sensing and actuation functions. The “I.Q.” of smart materials is measur…
The optimized effective potential (OEP) method allows for calculation of the local, effective single particle potential of density functional theory for explicitly orbital-dependent approximations to the exchange-correlation energy functional. In the present work the OEP method is used together with the approximation…
We have prepared a number of GaAs structures delta-doped by Sn using the well-known molecular beam epitaxy growth technique. The samples obtained for a wide range of Sn doping densities were characterised by magnetotransport experiments at low temperatures and in high magnetic fields up to 38 T. Hall-effect and Shubni…
We describe instrumentation for conducting high sensitivity millimeter-wave cavity perturbation measurements over a broad frequency range (40-200 GHz) and in the presence of strong magnetic fields (up to 33 tesla). A Millimeter-wave Vector Network Analyzer (MVNA) acts as a continuously tunable microwave source and pha…