Materials Literature
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This paper describes the chemical modification of high surface area, photoluminescent porous silicon (PSi) by reaction at a moderately elevated temperature (<115 °C) with alkenes (RCH CH 2 ) and aldehydes (RCHO) to give organic monolayers covalently bonded to the surface through Si−C and Si−O−C linkages, respectively.…
A prismlike hollow structure was assembled when three pyridyl-substituted porphyrin panels were linked by six PdII ions. A dramatic D3h→C2 structural change of the prism (see scheme) was triggered by complexation of pyrene.
We report the magnetic susceptibility, specific heat and dielectric constant for high-purity polycrystalline samples of three hexagonal manganites: YMnO 3 , LuMnO 3 and ScMnO 3 . These materials can exhibit a ferroelectric transition at very high temperatures ( T FE >700 K). At lower temperatures there is magnetic ord…
Diastereoselectivities as high as 98 % were the result of the photochemical ring-closure of stereochemically pure copper(I) helicates of a chiral oxazoline-substituted 1,2-dithienylethene photochrome (see scheme). The variations in optical rotation that accompany the photochromic event provide a means to read stored i…
Weak localization has a strong influence on both the normal and superconducting properties of metals. In particular, since weak localization leads to the decoupling of electrons and phonons, the temperature dependence of resistance (i.e., $λ_{tr}$) is decreasing with increasing disorder, as manifested by Mooij's empir…
Informationsspeicherung in einzelnen magnetischen Nanodrähten? Die Grundlage hierfür könnten erste Hinweise auf die langsame Dynamik liefern, welche für eindimensionale magnetische Systeme mit Ising-Anisotropie vorhergesagt wurde: Langsame magnetische Relaxation und Hystereseeffekte dynamischen Ursprungs wurden oberha…
The phase diagram and stability limits of diatomic solid nitrogen have been explored in a wide pressure--temperature range by several optical spectroscopic techniques. A newly characterized narrow-gap semiconducting phase $η$ has been found to exist in a range of 80--270 GPa and 10--510 K. The vibrational and optical…
We study the static and dynamic properties of liquid silica over a wide range of temperature T and density using computer simulations. The results reveal a change in the potential energy landscape as T decreases that underlies a transition from a fragile liquid at high T to a strong liquid at low T. We also show that…
We present a statistical analysis of the acoustic emissions induced by dislocation motion during the creep of ice single crystals. The recorded acoustic waves provide an indirect measure of the inelastic energy dissipated during dislocation motion. Compression and torsion creep experiments indicate that viscoplastic d…
This article discusses advances in understanding the structural and physicochemical characteristics of suspensions of cellulose crystallites prepared by acid hydrolysis of natural cellulose fibres. Consideration of recent developments in visualization of crystallite ultrastructure may provide clues to suspension behav…
Weak localization leads to the same correction to both the conductivity and the McMillan's electron-phonon coupling constant $λ$ (and $λ_{tr}$). Consequently the temperature dependence of the thermal electrical resistivity is decreasing as the conductivity is decreasing due to weak localization, which results in the d…
Many crystalline solids cannot be prepared in the form of single crystals of sufficient size and/or quality for investigation using single-crystal X-ray diffraction techniques, and the opportunity to carry out structure determination using powder diffraction data is therefore essential to understand the structural pro…
Intimate electrical contact occurs between a substituted poly(metaphenylenevinylene) (PmPV) and bundles of single-walled nanotubes (SWNT) as evidenced by atomic force microscopy, optical, and electronic measurements carried out on single, isolated SWNT/PmPV structures (see picture). PmPV may provide a useful route tow…
Slow magnetic relaxation and hysteresis effects of dynamic origin have been observed above liquid helium temperature in a chain compound (see picture), comprising CoII centers and organic radicals, without any evidence of phase transition to three-dimensional magnetic order. These results are the first evidence of the…
Abstract The viscosity, ultrasonic velocity, refractive index, and density of cellulose acetate/carboxylated poly(vinyl chloride) (CA/C‐PVC) blends in cyclohexanone, a common solvent, were measured at 30°C. After casting films of the blend for a 50:50 composition, polarizing micrographs were taken. Using the viscosity…
The K -shell ionization cross sections of Cu and Ga are measured by electron impact and the data of Ga are reported for the first time. The method of a thin chemical compound target with a thick substrate is formally used in the experiment. The influence of electrons reflected from the substrate is corrected by means…
An electronic structure of ferroelectric PbZr 1/2 Ti 1/2 O 3 is presented. The full potential linearized augmented plane wave method is used and the exchange correlation effects are treated by the generalized gradient approximation. In order to understand the ferroelectricity of PbZr 1/2 Ti 1/2 O 3 , the density of st…
Abstract Young's moduli of a series of quenched isotactic polypropylene/high‐density polyethylene blends were measured. The moduli of many of the blends exceeded the upper bound, calculated from the parallel model with the moduli of the two quenched homopolymers as those of the two components. In fact, both components…
Two-dimensional maps of x-ray diffuse scattering (DS) in a reciprocal space for a real crystal containing Coulomb deformation centres (clusters or dislocation loops) were calculated using a new dynamical theory developed for a crystalline media with homogeneously distributed defects. Such maps were calculated for both…
The structural interface properties of layered Pt/Ti/SiO 2 /Si electrodes have been investigated using high-resolution specular and diffuse x-ray reflectivity under grazing angles. Currently this multilayer system represents a technological standard as bottom electrodes for ferroelectric thin-film applications. For th…