Materials Literature
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A new approach is proposed for the synthesis of extra-large-pore (diameter > 7 nm) MCM-41 analogues, potentially useful as hosts for the synthesis of nanowires and as model porous solids for fundamental research. The approach is based on the recently demonstrated opportunity for elimination of the connecting pores in…
2-Amino-3-ketobutyrate CoA ligase (KBL, EC 2.3.1.29) is a pyridoxal phosphate (PLP) dependent enzyme, which catalyzes the second reaction step on the main metabolic degradation pathway for threonine. It acts in concert with threonine dehydrogenase and converts 2-amino-3-ketobutyrate, the product of threonine dehydroge…
The growth and structuring of polyelectrolyte self-assemblies (so-called “multilayers”) made from a lyotropic ionene and a strong polyelectrolyte are examined in depth using X-ray reflectometry among other techniques. We show that highly ordered polyelectrolyte films may be obtained, consisting of a regular lamellar n…
In this paper the glass transition temperature ( T g ) in thin polymer films has been studied. Ellipsometry has been used to measure T g of poly(α-methylstyrene) (PAMS) thin films as a function of the film thickness for two molecular weights. When the films were thinner than a few hundred angstroms, substantial reduct…
In many oxides of the perovskite and pseudoperovskite families there are phase transitions between insulating and normal metallic (Fermi liquid) phases that are separated by an intermediate phase that is often called a non-Fermi liquid (NFL). The dc resistivity of the intermediate or NFL phase often exhibits a T tempe…
High real-space resolution atomic pair distribution functions (PDF's) have been obtained from ${\mathrm{ZnSe}}_{1\ensuremath{-}x}{\mathrm{Te}}_{x}$ using neutron powder diffraction. Distinct Zn-Se and Zn-Te nearest-neighbor (nn) bonds, differing in length by $\ensuremath{\Delta}r=0.14$ \AA{}, are resolved in the measu…
In order to tailor the properties of nanodots, it is essential to separate the effects of quantum confinement from those due to the surface, and to determine the mechanisms by which preparation conditions can influence the properties of the dot. We address these issues for the case of small Ge clusters (1--2.5 nm), us…
Superconducting transition temperatures ($T_c$'s) of MgB$_2$, Mg$_{1-x}$Ca$_x$B$_2$, Mg$_{1-x}$Na$_x$B$_2$, and Mg$_{1-x}$Al$_x$B$_2$ are studied within the McMillan approximation using electronic and structural information obtained from density functional theory within the generalized gradient approximation. The dens…
Fascinating properties of nanotubes arise when they form intermolecular junctions. In this rapid communication, we demonstrate that such nanotube junctions have atomic scale characteristics and the contact resistance between the tubes depends strongly on atomic structure in the contact region. Our calculations show th…
We report high-pressure Raman measurements (up to 19 GPa) on the perovskite-type relaxor ferroelectric sodium-bismuth-titanate, ${\mathrm{Na}}_{0.5}{\mathrm{Bi}}_{0.5}{\mathrm{TiO}}_{3}$ (NBT). Distinct changes in the Raman spectra have been analyzed in the light of a rhombohedral-to-orthorhombic $(R3c\ensuremath{-}\m…
We are reporting here on the inexpensive fabrication of large three-dimensional and highly oriented porous microrod array of n-type ZnO semiconductor with a unique designed architecture consisting of well-defined, length-tailored, monodisperse, perpendicularly oriented single-crystalline hexagonal rods, grown directly…
Zinc II hexacyanoferrate III, Zn 1.5 [Fe(CN) 6 ]·6H 2 O, was prepared by coprecipitation method. The precipitated powder possessed a face-centred cubic structure with a lattice parameter of 10.32 Å. Phase transformation in this cyanide compound was encountered after heat treatment at a temperature at 75 °C or above, f…
Abstract Three series of new thermoplastic, high molecular weight, segmented thiopolyurethanes were synthesized by a one‐step melt polymerization from newly obtained thiodiols, including bis[4‐(2‐hydroxyethyl)thiomethylphenyl]methane, bis[4‐(3‐hydroxypropyl)thiomethylphenyl]methane, and bis[4‐(6‐hydroxyhexyl)thiomethy…
Abstract Rotational molding of polyethylene foams has increasingly become an important process in industry because of its resultant thicker walls, low sound transfer, high stiffness, and good thermal insulation. This report assesses the rotomoldability of two‐layer polyethylene foamed parts. The polymeric material use…
The ab initio structures and energies of a series of gas-phase aluminum chlorides have been calculated at the RHF/6-31G* and MP2/6-31G* levels. The vibrational spectra of AlCl 3, Al 2 Cl 6, AlCl 4 -, EtAlCl 3 -, Al 2 Cl 7 -, Et 2 Al 2 Cl 5 -, and trans -Et 2 Al 2 Cl 4 are calculated at the RHF/6-31G* level. The theore…
Barium titanate (BaTiO 3 ) nanopowders were prepared through a combined polymerization and pyrolysis of a metallo-organic precursor. The mean particle size d m could be adjusted by choosing appropriate reaction temperatures and tempering atmospheres. In the present in situ study of this particular solid-phase reaction…
The effect of electron-electron interactions on the electronic properties of nonchiral single-wall carbon nanotubes is investigated by an extended Hubbard model resolved within the generalized unrestricted Hartree-Fock approximation. On-site U and nearest-neighbor $u$ Coulomb interactions are considered in tubules wit…
We report the observation of a “superquenching” for water-soluble poly- l -lysine derivatives containing an appended cationic cyanine dye on each repeat unit. The formally nonconjugated cyanine dye chromophores strongly associate in a “J” aggregate structure characterized by a sharp red-shifted absorption (compared to…
A novel donor−acceptor conjugated copolymer consisting of the electron-accepting moiety 2,7-diethynylfluorene and the electron-donating moiety tetraphenyldiaminobiphenyl (TPD), i.e., poly{(2,7-diethynyl-9,9-di-2-ethylhexylfluorene)- alt - co -[ N, N ‘-diphenyl- N, N ‘-bis(4-phenyl)-1,1‘-biphenyl-4,4‘-diamine]} (TPD-PF…
Extended data sets for the relative intensity variation of x-ray Bragg reflections of GaAs and ZnSe caused by an external electric field were collected using a modulation demodulation technique. In particular, the functional dependence of the intensity variation on field strength and wavelength of the synchrotron radi…