Materials Literature
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We investigated possible physical and chemical changes in inert polymers by means of mechanical milling. No chemical changes were observed. However, in polystyrene we found two glass temperatures after milling, in contrast to one glass temperature in the original material. Under certain conditions crystalline polyethy…
It has become possible in recent years to synthesize new materials under controlled conditions with constituent structures on a nanometer size scale (below 100 nm). These novel nanophase materials have grain-size dependent mechanical properties that are significantly different than those of their coarser-grained count…
A newly synthetic method has been developed for the preparation of block copoly(urethaneimide) (PUI). The copolymer was yielded from the direct reaction of the prepolyurethane terminated with isocyanate and the prepolyimide terminated with anhydride. The latter is prepared by reacting an excess amount of pyromellic di…
Polyurethanes were synthesized from polyester and butanediol with three different diisocyanates, i.e., 4,4´-diphenylmethane diisocyanate (MDI), m-xylene diisocyanate (XDI), and 2,4-toluene diiscynate (TDI). The effect of chemical structures of diisocyate compounds on the degree of crystallinity and the thermal stabili…
The influence of external factors on the formation of various polymorphic modifications of poly(vinylidene fluoride) (PVDF) and the copolymers and blends based on it is examined. It is shown that the formation of a particular conformational structure of the PVDF chains may be controlled by regulating, for example, the…
First principles linear response calculations are used to investigate the lattice dynamics of what is thought to be the third most abundant phase in the lower mantle, CaSiO_3 perovskite. The commonly assumed cubic structure (Pm3m) is found to be dynamically unstable at all pressures, exhibiting unstable modes along th…
Rational engineering of enzymes involves introducing key amino acids guided by a knowledge of protein structure to effect a desirable change in function. To date, all successful attempts to change specificity have been limited to substituting individual amino acids within a protein fold. However, the infant field of p…
To test whether the structure of a protein is determined in a manner akin to the assembly of a jigsaw puzzle, up to 10 adjacent residues within the core of T4 lysozyme were replaced by methionine. Such variants are active and fold cooperatively with progressively reduced stability. The structure of a seven-methionine…
Infrared and Raman spectra of lithium ammonium tartrate monohydrate were obtained in the frequency region at temperatures of 15 - 300 K. No soft phonon mode was observed, so the ferroelastic and ferroelectric phase transition at is of order - disorder type. The ordering of atoms below produces pronounced decreases in…
The frequency of optically excited plasmon oscillations in a metal cluster is studied as a function of cluster size. The model is based on the fact that a sphere filled with free-electron gas forms a cavity with size-dependent eigenfrequencies of the optically excitable TM plasmons. Excitation of plasmon resonances by…
The early stages of nucleation and growth in a mixture of high polymers were studied by time-resolved neutron scattering. During the first 160 min, a slow clustering was evident, indicating a buildup of concentration fluctuations. The clusters formed at the end of this stage had the characteristics of ``critical nucle…
For the first time quasicrystal surfaces produced by in situ cleavage in ultrahigh vacuum have been investigated by scanning tunneling microscopy. Twofold and fivefold surfaces of icosahedral AlPdMn single quasicrystals have been studied. The surfaces were found to be rough. Their structure is determined by cluster ag…
Low dielectric fluorocarbon/SiO2 composite films are developed that exhibit good thermal stability and low dielectric constant by using hexamethyldisiloxane (HMDSO) and prefluorobenzene (C6F6) as the monomer source gases, and argon and oxygen as the carrier gases in a dual frequency, inductively-coupled high-density p…
High-temperature surface metallization of Si(100) is observed at $T>900\mathrm{K}$ by high-resolution electron-energy-loss and ultraviolet photoemission spectroscopy. Metallization takes place well below the incomplete surface melting temperature and is consistent with the Si dimer dynamics, characterized by an ins…
Total Internal Reflection Fluorescence Spectroscopy, A.J. de Mello Total Internal Reflection Fluorescence Spectroscopy of Biomaterials, L.R. Fisher Surface Plasmon Resonance - Theory and Experimental Considerations, J. Davies and I. Faulkner Flow Cell Design Considerations for SPR Measurements, J. Davies and L. Skelto…
By using spin-polarized secondary electron spectroscopy, we have found that the surface of FeO(111) prepared by oxidation of Fe(110) is ferromagnetically ordered above the bulk N\'eel temperature of 198 K. A possible cause of the ordering is the reconstruction of a polar FeO(111) surface to reduce electrostatic surfac…
Universal curves are constructed that provide an immediate determination of the effect of a series resistor on the electron emission from a field emitter. These curves are applicable to both the low current and high current regime. The effects of space charge and of the series resistor are apparent from these curves,…
We report on electroluminescence at room temperature from forward biased n+–p silicon diodes containing high densities (108–109 cm−2) of dislocations at the junction interface. In addition to electroluminescence from band-to-band transitions, we observe a signal with a comparable intensity peaked at ∼1.6 μm (0.78 eV).…
The region of parameter space (acoustic pressure ${P}_{a}$, bubble radius ${R}_{0}$) in which stable single bubble sonoluminescence (SBSL) occurs in an air-water system is a small fraction of that which is accessible. This is due to the existence of an island of dissolution at high ${P}_{a}$ and small ${R}_{0}$. For d…
High energy resolution inelastic x-ray scattering measurements in the $1--6{\mathrm{nm}}^{\ensuremath{-}1}$ momentum transfer ( $Q$) region in vitreous silica ( $v{\ensuremath{-}\mathrm{S}\mathrm{i}\mathrm{O}}_{2}$) at $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1050\mathrm{K}$ show the existence of collectiv…