Materials Literature
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A new class of biodegradable poly(ester-amide)s was prepared by a two step method. At first isosorbide or isomannide were esterified with α-amino acids in the presence of p-toluenesulfonic acid, and the resulting esters bisammonium tosylates were isolated. Second, the amino groups were liberated and polycondensed with…
Copolymers of ε-caprolactone and L-lactide (PCLLA) with different monomer ratio were synthesized by ring opening polymerization, and drug-loaded nanoparticles of poly-ε-caprolactone (PCL), poly-L-lactide (PLLA), and their copolymers were prepared by precipitation method, respectively. The results of differential scann…
A new technique for characterization of linear low-density polyethylene (LLDPE) is presented in this report. The molecular structure of two commercial LLDPEs, produced by copolymerization of ethylene with 1-butene over a Ziegler-Natta and a metallocene catalyst, was investigated. The LLDPE resins were fractionated by…
Slow structural relaxation ("aging") observed in many atomic, molecular, and polymeric glasses substantially alters their stress-strain relations and can produce a distinctive yield point. Using Monte Carlo simulation for a binary Lennard-Jones mixture, we have observed these phenomena and their cooling-rate dependenc…
New experimental data obtained mainly at the GSI/FRS facility allow one to modify the empirical parametrization of fragmentation cross sections. It will be shown that minor modifications of the parameters lead to a much better reproduction of measured cross sections. The most significant changes refer to the descripti…
We develop a variational mean-field theory of the ferromagnetic transition in compounds like Lanthanum-Manganite within the framework of the Double-Exchange Model supplemented by modest disorder. We obtain analytical expressions for the transition temperature, its variation with the valence electron-density and its de…
We present a new technique which allows the fully {\em ab initio} calculation of the chemical potential of a substitutional impurity in a high-temperature crystal, including harmonic and anharmonic lattice vibrations. The technique uses the combination of thermodynamic integration and reference models developed recent…
We develop a finite-element-based nodal dislocation dynamics model to simulate the structure and strength of dislocation junctions in fcc crystals. The model is based on anisotropic elasticity theory supplemented by the explicit inclusion of the separation of perfect dislocations into partial dislocations bounding a s…
The electrical noise characteristics of single-walled carbon nanotubes have been investigated. For all three cases of individual isolated nanotubes, thin films of interconnected nanotubes, and bulk nanotube mats, anomalously large bias-dependent 1/f noise is found. The noise magnitude greatly exceeds that commonly obs…
There are two classes of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase: the class I enzymes of eukaryotes and some archaea, and the class II enzymes of certain eubacteria. The activity of the class I Syrian hamster HMG-CoA reductase is regulated by phosphorylation-dephosphorylation of Ser871. Phosphorylati…
The preparation of β-SiC/MC (M = Ti, Nb, and Ta) nanocomposite ceramics by the pyrolysis under an inert atmosphere of precursors consisting in interpenetrating networks of poly[(dimethylsilylene)diacetylene], 1, and polymeric metal oxide is described. The precursors are obtained by in-situ precipitation of the desired…
Carbon single-wall nanotubes (SWNTs) are of great interest because of their expected novel electronic, mechanical, and adsorption properties. However, to test these properties and develop applications, it is necessary to isolate large aligned nanotube bundles. Here we demonstrate that SWNT samples may be converted fro…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTA New Method for the Synthesis of Tri-tert-butyl Diethylenetriaminepentaacetic Acid and Its DerivativesSamuel Achilefu, R. Randy Wilhelm, Hermo N. Jimenez, Michelle A. Schmidt, and Ananth SrinivasanView Author Information Discovery Research, Mallinckrodt, Inc., St. Louis, Misso…
Ultrathin cross sections of core−corona polymeric nanospheres, which were prepared by the free-radical polymerization of methacrylate-terminated poly(ethylene glycol) (MA-PEG) as a hydrophilic macromonomer and styrene (St) as a hydrophobic comonomer in a ethanol/water (4/1, v/v) mixed solvent, were observed by using t…
The notion of using support materials to achieve high dispersions of metal particles has been extended to the synthesis of carbon nanofibers from the catalyzed decomposition of ethylene. By using this approach it has been possible to generate nanofibers whose widths are dictated by the dimensions of the supported meta…
Solidlike and liquidlike linear viscoelastic responses were observed at low and high temperatures ( T ) for polystyrene−polyisoprene−polystyrene (SIS) triblock copolymers dissolved in an I-selective solvent, n -tetradecane (C14). These SIS systems behaved as thermoreversible physical gels, with the microphase-separate…
Surface and interface play an important role in controlling the properties of a broad range of materials. With the recent development of various advanced surface analytical techniques, our understanding of material surfaces and interfaces has been significantly increased, as with our ability to control and even to tai…
The alternating copolymer of alkyl sorbates with oxygen was prepared by photopolymerization or thermal polymerization in the presence of oxygen. Methyl sorbate provided an alternating copolymer with oxygen on exposure to sunlight at room temperature. The yield and molecular weight of the obtained polymers depended on…
Raman spectra of oriented alpha-helical protein molecules exhibit a prominent band near 1340-1345 cm(-)(1), the intensity of which is highly sensitive to molecular orientation. Polarization of the 1340-1345 cm(-)(1) marker is evident in Raman spectra of alpha-helical poly-L-alanine (alphaPLA) and alpha-helical poly-ga…
We present inelastic neutron scattering (INS) experiments on various types of cellulose revealing the universal nature of the disordered regions from the point of view of low-energy dynamics. Using INS in combination with the deuteration of polar groups technique, we have studied the dynamic response of hydroxyl group…