Materials Literature
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The synthesis of "designer" dendrimers and dendrons with sulfonimide units at every branching point is reported. The synthesis is based on a series of (regio)selective functionalization reactions of amines and sulfonamides allowing precise control of the dendrimers' shape, the number of branches in each generation, an…
The influence of rotational and geometrical isomerism on the nonlinear optical (NLO) properties, specifically the first-order hyperpolarizability beta, of chromophores of current interest has been investigated with density functional theory (DFT). In the first of this two-part study, the rotational isomerism of a line…
Concerted proton and electron transfers (CPET) currently attract considerable theoretical and experimental attention, notably in view of their likely involvement in many enzymatic reactions. The role of carboxylate groups as proton-accepting sites in CPET reactions is explored by means of a cyclic voltammetric investi…
Pyridoxal 5'-phosphate (PLP) dependent tryptophanase has been isolated from Escherichia coli and its crystal structure has been determined. The structure shares the same fold with and has similar quaternary structure to Proteus vulgaris tryptophanase and tyrosine-phenol lyase, but is found in a closed conformation whe…
Multi-axial compressions/forgings (MAC/F) were conducted at room temperature to obtain severe plastic deformation (SPD) of AA6061 alloy. Microhardness measurements taken across the cross-section of each of the MAC/F processed samples indicated that the hardness distribution is nonuniform during initial compressions/fo…
Poly(vinyl pyrrolidone)-capped multiple twinned gold (Au) particles with decahedral shape have been synthesized by a simple and convenient solvothermal wet chemical method. In the process, hydrogen tetrachloroauric acid (HAuCl(4).3H(2)O) was reduced by ethylene glycol (EG) to form the multiple twinned Au nanocrystals…
A novel technique for the preparation of water-soluble carbon nanotubes was demonstrated using a pulsed streamer discharge generated in water. The technique involved chemical reactions between radicals generated by the pulsed streamer discharge and carbon nanotubes. The pulsed streamer-treated carbon nanotubes were ho…
ABSTRACT A number of regulatory circuits in biological systems function through the exchange of phosphoryl groups from one protein to another. Spo0F and Spo0B are components of a phosphorelay that control sporulation in the bacterium Bacillus subtilis through the exchange of a phosphoryl group. Using beryllofluoride a…
A simple two-dimensional model was developed for the growth of fractures in a chemically decomposing solid. Simulations were carried out under rapid chemical decomposition conditions for which the kinetics of fracture growth is controlled by diffusion of the volatile reaction product or the kinetics of evaporation. Th…
We investigate the two-dimensional flow of a liquid foam around circular obstacles by measuring all the local fields necessary to describe this flow: velocity, pressure, bubble deformations and rearrangements. We show how our experimental setup, a quasi-2D "liquid pool" system, is adapted to the determination of these…
Colloidal CdSe/ZnSe core/shell nanocrystals were prepared via the conventional TOP/TOPO process and their shell thickness was controlled varying the ZnSe precursor concentration. X-ray diffraction (XRD) on the nanocrystals showed gradual peak shifts to high two-theta angles due to a decrease in the lattice parameter o…
In this article we describe electro-optical properties of recently discovered ferroelectric particles/liquid crystal colloids. We show that the presence of ferroelectric particles in a liquid crystal changes its birefringence and dielectric anisotropy. In contrast to the traditional time consuming and expensive chemic…
ZrO2-carbon nanotube (CNT) composites have been successfully synthesized via decomposition of Zr(NO3)4.5H2O in supercritical carbon dioxide-ethanol solution with dispersed CNTs at relatively low temperatures. The samples were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction spectroscopy (XRD)…
Size, Shape, and Synthesis Key toTuning Properties The discovery and rapid evolution of carbon nanotubes have led to a vastly improved understanding of nanotechnology, as well as dozens of possible applications for nanomaterials of different shapes and sizes ranging from composites to biology, medicine, energy, transp…
First Self-Contained Source Entirely Dedicated to Nanocarbons Carbon nanotubes (CNTs) attract a good deal of attention for their electronic, mechanical, optical, and chemical characteristics. But nanostructured carbons are not limited to nanotubes and fullerenes-they also exist as nano-diamonds, fibers, cones, scrolls…
High-resolution x-ray powder diffraction and extended x-ray-absorption fine-structure (EXAFS) measurements have been performed on the iso-structural framework crystals ${\mathrm{Cu}}_{2}\mathrm{O}$ and ${\mathrm{Ag}}_{2}\mathrm{O}$ as a function of temperature. According to diffraction, both compounds exhibit a negati…
The ribulose monophosphate (RuMP) pathway, involving 3-hexulose-6-phosphate synthase (HPS) and 6-phospho-3-hexuloisomerase (PHI), is now recognized as a widespread prokaryotic pathway for formaldehyde fixation and detoxification. Interestingly, HPS and PHI homologs are also found in a variety of archaeal strains, and…
In tightly confined one-dimensional (1D) systems, the effective Coulomb interaction is greatly enhanced and optical transitions generally lead to the formation of strongly bound excitons. When more than one exciton is present, the Coulomb interaction also leads to rapid exciton-exciton annihilation through an Auger re…
The physisorption and chemisorption of hydrogen in BN nanotubes, investigated by density functional theory (DFT), were compared with carbon nanotubes. The physisorption of H2 on BN nanotubes is less favorable energetically than on carbon nanotubes; BN nanotubes cannot adsorb hydrogen molecules effectively in this mann…
We present ab initio calculations for single-atom vacancies in graphene. In agreement with earlier work, we find that vacancies are responsible for the magnetism recently observed experimentally, creating a center with net spin. For small supercells, there is a strong symmetry breaking in the supercell with respect to…