Materials Literature
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A new type of solid support for HPLC separation of nucleotides, oligonucleotides, N-protected amino acids, and perfluorinated biphenyls is revealed in the form of two distinct calix[4]pyrrole-modified silica gels (below).
Infrared spectra of hydrogenated lightly doped Czochralski silicon show absorption due to (a) modes of ${\mathrm{O}}_{i}\ensuremath{-}{\mathrm{H}}_{2}$ centers (binding energy 0.26 eV), and (b) a mode labeled ${\ensuremath{\nu}}_{3\mathrm{HH}}$ at $3618{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ due to ${\mathrm{H}}_{2}…
The atomic structure of ordered domains in Ba(Mg1/3Nb2/3)O3 and La-doped and undoped Pb(Mg1/3Nb2/3)O3 is studied by high-resolution Z-contrast imaging. The ordered domain structure in both doped and undoped Pb(Mg1/3Nb2/3)O3 is determined to be in agreement with the charge balanced random-layer model and inconsistent w…
A molecular dynamics simulation of water confined in a silica pore is performed in order to compare it with recent experimental results on water confined in porous Vycor glass at room temperature. A cylindrical pore of 40 Å is created inside a vitreous SiO2 cell, obtained by computer simulation. The resulting cavity o…
Collagenous matrices with entrapped anionic polypeptides can mimic biological processes of mineral deposition by controlling the crystallization of calcium carbonate polymorphs. The concentration and structure of the polypeptides and the collagenous environment play major roles in controlling polymorphism. Random and…
We spatially isolate and detect the luminescence from individual porous Si nanoparticles at room temperature. Our experiments show a variety of phenomena not previously observed in the emission from porous Si including a distribution of emission wavelengths, resolved vibronic structure, luminescence intermittency, and…
X-ray diffraction showed that the volume fraction of 90° domains in tetragonal Pb(Zr,Ti)O3 thin films could be substantially reduced by either hot dc poling or by a bipolar pulsed-field process. In both cases, the (001) Bragg peak increased and the (100) peak decreased. However, ferroelectric hysteresis loops look qui…
Fatigue of Pb(Zr0.53Ti0.47)O3 ferroelectric thin films has been studied with several novel electrode modifications. Doped amorphous silicon is used as a gating layer between the ferroelectric and metal electrode to regulate the type of charge carrier injection during switching of the ferroelectric. This configuration…
The validity of the actinometry method applied to H-atom mole fraction measurements has been analyzed. First, a theoretical approach allowed us to determine boundary conditions for which the validity of actinometry may be critical. For these specific conditions, corresponding to an upper limit of electron temperature…
In this work we develop a unifying and general method for calculating linear viscoelastic properties of multicomponent colloidal mixtures of spherical particles. Using linear response theory based on the many-body Smoluchowski diffusion equation, we derive an exact expression for the zero shear rate shear relaxation f…
We have measured the effect of elastic strain $\ensuremath{\epsilon}$ on the threshold field ${E}_{T}$ for the motion of the higher-temperature charge density wave (CDW) in ${\mathrm{NbSe}}_{3}$. We find that ${E}_{T}$ exhibits a critical behavior, ${E}_{T}\ensuremath{\sim}(1\ensuremath{-}\ensuremath{\epsilon}/{\ensur…
We use simple models and molecular dynamics simulations to determine the effects of polydispersity δ on the equation of state for hard sphere crystals. Experiments show that the osmotic pressure for poly-(methyl methacrylate) (PMMA) spheres with a poly-(12-hydroxy stearic acid) (PHSA) layer with a 5% polydispersity ex…
The $\ensuremath{\sigma}+\ensuremath{\pi}$ electron densities of states of chiral carbon nanotubes are computed with a tight-binding Hamiltonian. Our calculations show that the electronic structures of carbon nanotubes with chiral symmetry are similar to the zigzag and armchair ones. The implications of these results…
Electron-correlation effects on cohesive energy, lattice constant, and bulk compressibility of rutile are calculated using an ab initio scheme. A competition between the two groups of partially covalent Ti-O bonds is the reason that the correlation energy does not change linearly with deviations from the equilibrium g…
It has recently been shown that amorphization and melting of ice (O. Mishima, Nature , 384 (1996) 546) were intimately linked. In this letter, we infer from molecular-dynamics simulations on the SiO 2 system that the extension of the α-quartz melting line in the metastable pressure-temperature domain is the pressure-i…
The possibility of determining the temperature of diamond by noncontact Raman spectroscopy is assessed critically. The intensity ratio of Stokes to anti-Stokes lines is shown to be ill suited for temperatures above ∼750 K. Employing the temperature coefficient of the Raman line position, on the other hand, turns out t…
We consider the low-energy magnetic excitations of nanographite ribbons with zigzag edges. The zigzag ribbons possess almost flat bands at the Fermi level which cause a ferrimagnetic spin polarization localized at the edge sites. The spin wave mode of this magnetic state is investigated by a random phase approximation…
Electroluminescence (EL) and photoluminescence (PL) from heterostructure thin films made of organic poly (phenylene vinylene), PPV, and inorganic semiconductor CdSe nanocrystals are investigated. In these devices, the organic PPV structure is built next to an indium tin oxide anode, using the technique of molecular la…
Significant reductions in both the in-plane and cross-plane thermal conductivities of superlattices, in comparison to the values calculated from the Fourier heat conduction theory using bulk material properties, have been observed experimentally in recent years. Understanding the mechanisms controlling the thermal con…
The 3p photoelectron spectra of atomic Fe and Cu, and the Fe outer-shell satellites have been investigated. The complex multiline structure of the Fe spectra has been resolved using high-resolution electron spectroscopy. The thresholds of the direct 3p photoionization have been determined and are compared with experim…