Materials Literature
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We have proposed the phenomenological description of dielectric hysteresis loops in ferroelectric semiconductors with charged defects and prevailing extrinsic conductivity. We have modified the Landau–Ginsburg approach and shown that the macroscopic state of the aforementioned inhomogeneous system can be described by…
We present a model for the leakage current in ferroelectric thin- film capacitors which explains two of the observed phenomena that have escaped satisfactory explanation, i.e. the occurrence of either a plateau or negative differential resistivity at low voltages, and the observation of a Positive Temperature Coeffici…
Cadmium selenide (CdSe) thin films were deposited on a glass substrate using the chemical bath deposition method at room temperature. The films were deposited using cadmium acetate as a Cd 2+ ion source and sodium selenosulfate as a Se 2− ion source. The ‘as-deposited’ CdSe thin films are red in colour and specularly…
The atomic structures of clean and hydrogen-adsorbed Pd(001) are investigated by low energy electron diffraction (LEED) I/V analysis. Clean Pd(001) shows little surface relaxation in sharp contrast to previous reports. Adsorbing 1 monolayer of hydrogen on Pd(001), we observe sizable expansion of the interlayer spacing…
It has been shown that the geometric Berry-phase shift acquired by the components of the light hole (LH) spinor during an adiabatic collision is equal to the angular distance traveled by the wave vector. For LH, geometric dephasing leads to equality between angular and crystal momentum relaxation time. I will show tha…
The reversible dephosphorylation of beta-aspartyl phosphate to L-aspartate-beta-semialdehyde (ASA) in the aspartate biosynthetic pathway is catalyzed by aspartate-beta-semialdehyde dehydrogenase (ASADH). The phosphate that is present to activate the aspartate carboxyl group is held in a separate and distinct binding s…
Abstract Tetragonal 0.88Pb(Zn 1/3 Nb 2/3 )O 3 –0.12PbTiO 3 (PZNT12) single crystals were found to possess high electromechanical coupling k 33 ∼ 86–88% and large coercive field ∼8 kV/cm, while exhibiting good temperature stability till its Curie temperature ( T C ) ∼190 °C. The role of dopants on the dielectric and pi…
The growth kinetics of passive films on iron and stainless steel (Fe−16.31%Cr) substrates in pH 8.4 borate buffer solution was investigated by using in situ specular X-ray reflectivity. The oxide growth rate decays exponentially with increasing oxide thickness consistent with the point defect model in which the electr…
The assignments of bands in the electronic spectra of Y 2 O 3:Er 3+ to Er 3+ ions situated at S 6 symmetry sites (Silver, J.; Martinez-Rubio, M. I.; Ireland, T. G.; Withnall, R. J. Phys. Chem. B 2001, 105, 7200; Silver, J.; Martinez-Rubio, M. I.; Ireland, T. G.; Fern, G. R.; Withnall, R. J. Phys. Chem. B 2001, 105, 94…
Genetic algorithms are powerful optimizers that have been underutilized in protein crystallography, given that many crystallographic problems have characteristics that would benefit from these algorithms: non-linearity, interdependent parameters and a complex function landscape. These functions have been implemented f…
Maximum-likelihood methods have now been applied to most areas of macromolecular crystallography, including data reduction, molecular replacement, experimental phasing and refinement. However, students of macromolecular crystallography are predominantly taught only traditional crystallographic methods and therefore ha…
Pores for thought: The channels of alumina membranes were used as templates for mesoporous silica. The interface between the precursor of the mesoporous material and the alumina wall plays a major role in the alignment of the mesopores. Novel membrane materials are obtained if hexagonal pores are aligned parallel to t…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTStructure Formation in Isotactic Poly(methacrylic acid)Edith van den Bosch, Quintin Keil, Genovéva Filipcsei, Hugo Berghmans, and Harry ReynaersView Author Information Polymer Research Devision, Department of Chemistry, Catholic Uni…
The process of refinement is such a large problem in function minimization that even the computers of today cannot perform the calculations to properly fit X-ray diffraction data. Each of the refinement packages currently under development reduces the difficulty of this problem by utilizing a unique combination of tar…
ZnO well-faceted microfibers with periodic junctions were prepared by an evaporation and deposition process. The junctions with spacings of 5−30 μm presented concavo−concave morphologies, and the spacings could be changed with the growth conditions. The anisotropic growth mechanism was investigated by X-ray diffractio…
Open cell polymer derived ceramic foams were prepared by a self-foaming process of a filler loaded poly(silsesquioxane) and subsequent pyrolysis at 1000°C in nitrogen atmosphere. A 1 : 1 mixture by weight of elemental Si and SiC was introduced as particulate filler. Foam samples without and with addition of a small am…
Methods for automated identification and building of protein-bound ligands in electron-density maps are described. An error model of the geometrical features of the molecular structure of a ligand based on a lattice distribution of positional parameters is obtained via simulation and is used for the construction of an…
In this study the replication process was applied to produce porous glass ceramic foams. Polyurethane (PU) sponges were impregnated by immersion in aqueous slurry of a parent glass (mean particle size around 3 μm) from the system Li2O–ZrO2–SiO2–Al2O3 and submitted to heat treatment. From TGA and IR analyses, two main…
This paper reports on the synthesis of a novel poly(ethylene oxide) (PEO) macromonomer, which can be copolymerized with ε-caprolactone (ε-CL) by ring-opening polymerization (ROP). PEO chains end-capped by an ε-caprolactone unit (γPEO·CL) have been synthesized by living anionic ring-opening polymerization of ethylene o…
A closer look at some natural materials from animal and plant sources and the phenomenon driving their use in day to day applications resulted in investigation of their potential in processing of ceramic foams. Ceramic foams were made using aqueous ceramic slurries based on chicken egg white, soap nut fruit extract an…