Materials Literature
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The optical properties of a series of high refractive index polyphosphazenes were investigated. The wavelength-dependent change in refractive index (optical dispersion) associated with two selected polymers was examined using variable-angle spectroscopic ellipsometry. Values of the Abbé number for these polymers were…
Abstract Supramolecular structure of initially wet bacterial cellulose of Acetobacter xylinum has been investigated by X‐ray scattering including synchrotron radiation, transmission electron microscopy, and 13 C‐CP/MAS‐NMR‐spectroscopy. As a result a model is given of never dried swollen microfibrillar ribbons consist…
Many polymeric materials, including structural adhesives, exhibit a nonlinear viscoelastic response. The nonlinear free volume approach is based on the Doolittle concept that the “free volume” controls the mobility of polymer molecules and, thus, the inherent time scale of the material. It then follows that factors su…
Composite materials have become very attractive as personal and vehicle armors because of their light weight and high performance. Unfortunately, these materials are difficult to simulate numerically or analytically, and the only way to check their performance is experimentally. A first step could be the study of the…
Reactive species of nitrogen cold plasma could interact with a polymeric surface, leading to an important surface functionalization (mostly as amino group attachment) and consequently to a surface having a Lewis base character. Under certain conditions, the surface functionalization is not the only modification; a mor…
The synthesis of azobenzene-substituted polythiophenes (poly[3-(2-(4-((4‘-ethoxyphenyl)azo)phenoxy)ethoxy)-4-methylthiophene] (P3A), poly[3-((6-(4-((4‘-ethoxyphenyl)azo)phenoxy)hexyl)oxy)-4-methylthiophene] (P3B)) and poly[3-(((6-(4-((4-ethoxyphenyl)azo)phenoxy)ethyl)tri(ethoxy)oxy)-4-methylthiophene] (P3C) has led to…
Thermal factors of protein atoms as determined by X-ray crystallographic techniques show a tendency to be larger in side chains with unfavourable local conformations rather than in those displaying conformational energy minima. It follows that side chain atoms are more mobile if they are in a non-rotameric configurati…
The distribution of framework aluminum inside micrometer-size particles of the mesoporous molecular sieve MCM-41 has been investigated using transmission electron microscopic (TEM) images, after supporting platinum clusters inside the aluminum-containing region selectively via the ion exchange of Pt(NH 3 ) 4 2+ . The…
The synthesis and spectroscopic investigation of a number of push–pull ethenes in which the donor moiety is represented by a π-excessive five-membered heterocycle (pyrrole, indole and thiophene) and the acceptor group is a π-deficient heterocyclic azine ring (pyridine, pyrazine, pyrimidine, pyridazine) are described.…
To relax many of the assumptions used in continuum approaches, a general stochastic model has been developed. The stochastic model can be used not only for an accurate description of the fraction of solid evolution, and therefore accurate cooling curves, but also for simulation of microstructure formation in castings.…
Summary: A heavy-metal-accumulating Citrobacter sp. has been used for the treatment of metal-laden industrial wastes. Metal uptake is mediated via a cell-bound phosphatase that liberates inorganic phosphate which precipitates with heavy metals as cell-bound metal phosphate. A phosphatase-deficient mutant accumulated l…
It is shown that the magnon spectrum of magnetically ordered crystals can be calculated using a frozen magnon scheme and spin density functional theory in the local approximation. Ab initio calculated magnon spectra for Fe and Ni are presented. Kohn anomalies are predicted for the magnon spectrum of Fe. Considering th…
We have measured the Flory−Huggins interaction parameter (χ) for blends of polystyrene (PS) and poly(4-vinylpyridine) (P4VP) by three different methods. First, we measured the micelle spacings in microphase-separated films of PS−P4VP diblock copolymers by secondary ion mass spectrometry and atomic force microscopy. Se…
Five layered silicates in which the octahedral sheet contained differing amounts of Al, Mg, Fe, and Li were acid leached using acid concentrations and treatment temperatures selected to produce materials in which the octahedral sheet was depopulated in a controlled, stepwise (yet comparable) manner. SAz-1 and JP are d…
The synthesis of mesoporous silica sell‐shapes , with spiral and gyroid forms and ornate surface designs (see the inside front cover for examples), is described. High‐resolutioin SEM, TEM, and AFM were used to establish the spatial relationship between the bulk and surface mesosstructure and the overall morphpology of…
The first time-resolved infrared difference spectra for metal-to-ligand charge transfer (MLCT) excited states in the fingerprint region from 1400 to 1625 cm -1 are reported for [Ru(bpy) 3 ] 2+ * and [Re(bpy)(CO) 3 (4-Etpy)] + * in CD 3 CN at 298 K (bpy is 2,2‘-bipyridine; 4-Etpy is 4-ethylpyridine). The spectra are as…
A hybrid electrochemical/chemical (E/C) method is employed to synthesize epitaxially oriented CdS nanocrystallites size selectively on graphite surfaces. The E/C synthesis involves three steps: (1) cadmium metal nanocrystals (NCs) are electrochemically deposited on the graphite basal plane surface; (2) cadmium NCs are…
The effect of particle solubility and the dissolution rate on agglomeration was studied by drying silica and titania particles from aqueous slurries with pH values in the range of 2–12. The agglomerate strength and strength distribution were measured by a calibrated ultrasonic force, and the strength increased as the…
Novel semicrystalline, poly(vinyl alcohol) (PVA)-based phase erosion systems were developed. The rate of drug release from these systems is controlled by the rate of crystal dissolution. PVA devices loaded with metronidazole were exposed to temperatures ranging from 90 to 120 C for times of 10-90 min to obtain samples…
We report a scheme for the II−VI chalcogenide sol−gel synthesis, using cadmium sulfide as a model system. Highly concentrated sols are obtained by surface complexation of CdS nanocrystals with 4-fluorophenylthiol. Controlled aggregation and gelation is then achieved by a progressive decomplexation of the particles via…