A novel method for tailoring the pore-opening size of MCM-41 materials
A novel pore tailoring method is proposed by which the pore-opening sizes of MCM-41 materials can be finely tuned without significant loss in pore volume and surface area.
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Combustion synthesis of nanometal particles supported on α-Al2O3: CO oxidation and NO reduction catalysts
Nanoparticles of Pt, Pd, Ag and Au supported on α-Al 2 O 3 have been synthesized by the combustion method for the first time and characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Catalytic activities of these nanosized materials have been investigated. For the C…
Solvothermal reaction route to nanocrystalline semiconductors AgMS2 (M=Ga, In)
Nanocrystalline semiconductors AgGaS2 and AgInS2 with particle sizes ranging from 5 to 12 nm are prepared by a solvothermal reaction in the temperature range 180–230 °C.
Effects of very fast transient overvoltages on transformer
An analytical solution is found using the Laplace transform to describe the very fast transient overvoltage (VFTO) in the gas insulated switchgear (GIS) connected directly to a transformer. The oscillation frequencies, and other properties, are explicitly given in terms of system parameters. The magnitude of VFTO at t…
Comparison of the structural behaviour of the low thermal expansion NZP phases MTi2(PO4)3 (M = Li, Na, K)
We present the results of high resolution neutron powder diffraction studies of the NZP phases LiTi2(PO4)3 (LiTP) and KTi2(PO4)3 (KTP). The thermal expansion coefficients for both materials are reported and compared to those of NaTi2(PO4)3. αa for LiTP is found to decrease from 0.75 to 0.27 × 10–6 °C–1 between 20 and…
A “breathing” model for the polarization response of relaxor ferroelectrics
The present paper proposes a model of relaxor ferroelectrics. which describes the polarization response of these materials in terms of vibration of the interphase boundary between the polar regions and nonpolar matrix. The model is formulated and is applied to explain various features of the polarization response of a…
Common protein architecture and binding sites in proteases utilizing a Ser/Lys dyad mechanism
Escherichia coli signal peptidase (SPase) and E. coli UmuD protease are members of an evolutionary clan of serine proteases that apparently utilize a serine-lysine catalytic dyad mechanism. Recently, the crystallographic structure of a SPase inhibitor complex was solved elucidating the catalytic residues and the subst…
Improved Dissolution Behavior of Fenbufen by Spherical Crystallization
Fenbufen is an analgesic, antipyretic and anti-inflammatory drug that is characterized by poor water solubility, a defect increased by very low wettability. Poor water solubility, particularly at low pH, could decrease absorption in the upper part of the gastrointestinal tract, which would be inconvenient for good bio…
Water blown free rise polyurethane foams
Abstract A model is developed in this work for predicting the bubble size distribution in polyurethane foams generated by using water as a chemical blowing agent. The model combines equations of energy balance, kinetics of the reactions of isocyanate with water and polyol, and nucleation and growth of CO 2 bubbles. It…
Henry reactions catalysed by modified Mg–Al hydrotalcite:
Henry reactions have been performed for the first time with suitably activated Mg–Al hydrotalcite as catalyst in quantitative yields in the liquid phase under mild reaction conditions and with low reaction times. Exclusive synthesis of β-nitroalkanols (3) is realised by the compatible basic Brönsted hydroxy sites of t…
Liquid crystal tetramers
The first homologous series of liquid crystal tetramers in which four mesogenic groups are linked via three alkyl spacers has been synthesised and characterised. The length of the outer two spacers is varied from 3 to 12 methylene units while the central spacer is held at 8 methylene units. All the members of the seri…
The influence of A-cation disorder on the Curie temperature of ferroelectric ATiO3 perovskites
The ferroelectric Curie temperature TC in ATiO3 perovskites is shown to increase linearly with the size variance of the A-site cation mixture [A = (Ba, Sr, Ca)] and this effect accounts for the unusual TC variation in the Ba1–xCaxTiO3 system.
Ion exchange of caesium and strontium on a titanosilicate analogue of the mineral pharmacosiderite
Ion exchange experiments were carried out for the removal of trace caesium ( 137 Cs) and trace strontium ( 89 Sr) by different cationic forms of a titanosilicate analogue of the mineral pharmacosiderite. Selectivity factors were estimated by determining batch distribution coefficients (K d ) as a function of sodium, p…
Characterization of a charge-coupled-device detector in the 1100–014-nm (1-eV to 9-keV) spectral region
The performances of a CCD detector have been evaluated in a wide spectral region, which ranges from the near IR to the soft x ray. Four different experimental setups have been used: a Czerny-Turner monochromator for the 1100-250-nm region, a normal-incidence Johnson-Onaka monochromator for the 250-30-nm region, a graz…
Use of 2-methyl-1-phenylpropan-2-yl hydroperoxide (MPPH) as a mechanistic probe for the heterolytic versus homolytic O–O bond cleavage of tert-alkyl hydroperoxide by iron(III) porphyrin complex
The mechanism of the O–O bond cleavage of tert-alkyl hydroperoxide by iron(III) porphyrin complexes has been studied using 2-methyl-1-phenylpropan-2-yl hydroperoxide (MPPH) as a mechanistic probe; the hydroperoxide O–O bond is cleaved both heterolytically and homolytically and partitioning between the two pathways sig…
First-principles characterization of the four phases of barium titanate
Using a first-principles approach, the four phases of perovskite barium titanate are studied. We determine the lattice parameter, the bulk modulus and the cohesive energy of the cubic phase; the relaxed atomic positions in the three ferroelectric structures; and the evolution of the electronic properties from one phas…
Magnon dispersion in
The four magnon branches in the antiferromagnetic ground state of were measured by inelastic neutron scattering for two directions. On the basis of a model including isotropic Heisenberg exchange and uniaxial anisotropy, analytical expressions were derived for the dispersion relations in the spin-wave approximation us…
Physical basis of the domain engineering in the bulk ferroelectrics
We present a review of our theoretical and experimental investigations of the domain engineering aspects of domain structure development. Particular attention is paid to the processes governing the fabrication of periodic domain patterns.
On the possibility of ferromagnetic, antiferromagnetic, ferroelectric, and ferroelastic domain reorientations in magnetic and electric fields
By combining the thermodynamic classification of Primary, Secondary and Tertiary Ferroics and the corresponding symmetry-allowed or symmetry-forbidden driving forces for domain switching and reorientation, with a classification of Aizu's 773 species (prototype/ferroic phase point group pairs) into 30 ensembles of prop…
A way to higher resolution: spherical-aberration correction in a 200 kV transmission electron microscope
A double hexapole corrector system was constructed for compensation of the spherical aberration of the objective lens of a transmission electron microscope. By implementing this system on a commercial 200 kV instrument with a field emission gun, the spherical aberration correction was demonstrated and an improvement o…