Systematics of EPR spectra of GD3+ in some isostructural rare-earth trisulphate octahydrate hosts

X-band data on Gd³⁺ ions doping some isostructural single crystals of rare-earth trisulphate octahydrate [R₂(SO₄)₃·8H₂O] single crystals (RSH) have been obtained at room temperature for the hosts characterized by R = Pr, Nd, Sm, Eu, Yb and Y, and at liquid nitrogen and liquid helium temperatures for the hosts characterized by R = Pr, Sm, Eu and Y. The data are analyzed using a rigorous least-squares fitting procedure in which all resonant line positions obtained for various orientations of the external magnetic field are fitted simultaneously to the same spin Hamiltonian parameters. The intensities of the lines obtained at liquid helium temperatures indicate the absolute sign of the parameter b₂⁰ to be negative for R = Pr, Eu and Y, whereas for the Sm host the sign of b₂⁰ is found to be positive. While the parameter b₂⁰ does not exhibit a clear cut linear dependence upon the host ion radius, the parameter b₂⁰ is found to behave approximately linearly as a function of the host-ion radius. On the other hand, the zero-field splitting is found to be a linear function of the host ion radius at all three temperatures—room, liquid nitrogen and liquid helium.A comparison is presented of the systematics of the EPR spectra for the RSH hosts with those for some other isostructural rare-earth hosts.     

A physical model for the stress-induced electromagnetic effect in metals

Observations of the fracture-induced electromagnetic effect in metals have recently been reported by the author. This paper presents a physical model for explaining this new effect. The reasoning attributes the observed electromagnetic effect to dislocationelectron interactions in a metal. The frequency of the emitted radiation has been calculated from Bohr's correspondence principle and potential on the basis of Hertzian dipole radiation. The proposed physical model predicts emission of electromagnetic waves at distinct transition stages of elastic-plastic deformations. The paper also presents some of the experimental results, being obtained by the author, which confirm the practicability of this approach.     

EPR studies of Gd3+-doped Ce2(SO4)3.8H2O and La2(SO4)3.9H2O single crystals

EPR spectra of Gd³⁺-doped Ce₂(SO₄)₃.8H₂O and La₂(SO₄)₃.9H₂O single crystals have been measured with an X-band spectrometer at room and low temperatures. The absolute signs of spin Hamiltonian parameters have been determined for the La₂(SO₄)₃.9H₂O host from intensities of lines at liquid helium temperature; for the Ce₂(SO₄).8H₂O host the lines broaden considerably below 60 K, not permitting the determination of absolute signs of spin Hamiltonian parameters. The data are analysed using a rigourous least-squares procedure, fitting simultaneously all lines obtained for several orientations of the external magnetic field. The zero-field splittings have been computed for both the hosts. The characteristics of EPR spectra of Gd³⁺ in these hosts are compared with those obtained in other rare-earth trisulphate octahydrate hosts.     

Adsorption von Jodid und Jod durch Phosphate

Ohne Zusammenfassung     

Adh?sive Bindung verschiedener Materialien an harten Zahnmaterialien. VIII. Nickel- und Kupfer-Ionen an Hydroxyapatit. Die Rolle des Ionenaustausches und der Oberfl?chenkernbildung

Ohne Zusammenfassung     

Stress-induced crystallization of poly(ethylene terephthalate)

Quenched amorphous films of poly(ethylene terephthalate) (PET) are stretched at temperatures less than T_g; changes in density, wide-angle x-ray diffraction, and small-angle light scattering are observed. The density increase upon stretching is attributed to an increase in crystallinity accompanied by an increase in the intensity of somewhat diffuse wide-angle x-ray diffraction and of both V_V and H_V small-angle light scattering patterns. The formation of oriented rodlike superstructure may be discerned from small-angle light scattering. Annealing of these samples increases the crystallinity as measured from density and leads to an increase in the perfection of crystalline and supercrystalline structure as measured by wide-angle x-ray diffraction and small-angle light scattering. The rodlike morphology changes to form spherulitelike aggregates as observed by small-angle light scattering and light micrographs. A model is proposed to explain the observations. Studies are extended to stretching films of PET above their T_g and observing changes in birefringence, density, wide-angle x-ray diffraction and small-angle light scattering as a function of elongation and stretching temperature. The formation of defomed spherulitelike superstructure may be discèrned from light micrographs. Results are compared with those obtained upon stretching films below T_g.     

Surface remodeling of bones induced by intra-medullary nailing

The paper is devoted to a study on the surface remodeling of bones. Anisotropy and piezoelectricity of bone tissue (as per previous experimental studies) are incorporated in the analysis. Surface remodeling induced by intra-medullary nailing is of primary concern in the study.     

Effect of meso aryl substituents on the synthesis of core-modified expanded porphyrins

[reaction: see text] Synthesis and characterization of core-modified [26]hexaphyrin (1.1.1.1.0.0). A meso aryl rubyrin isomer and a new 54pi-modified dodecaphyrin are reported.     

TiO2 nanoparticles synthesis for application in proton exchange membranes

In the present paper, suitable TiO₂ nanoparticles are successfully synthesized by sol‐gel method, in order to utilize the freshly prepared TiO₂ nanoparticles for proton exchange membrane (PEM) preparation. Titanium tetrachloride (TiCl₄) is used as precursor and ethanol as a solvent. The optimum and suitable TiO₂ nanoparticles were obtained by varying gelatinisation time (4–120 h), concentration of precursor (TiCl₄) in ethanol (2–15 vol%), and reaction temperature (15–35 °C). The morphology, size and purity of the nanoparticles are investigated by transmission electron microscope (TEM), dynamic light scattering (DLS) and X‐ray diffraction (XRD). Optimum results were found at 4 h of gelatinisation time, 10% precursor concentration and 25 °C temperature for preparation of TiO₂ nanoparticles. Thus prepared nanoparticles are found to be suitable for preparation of nanocomposite PEM, and consequently the prepared PEM indicates enhanced properties, such as, higher thermal stability (high glass transition temperature of 184.1 °C), excellent proton conductivity (0.0822 S cm⁻¹ at room temperature) and low methanol permeability (1.11 × 10⁻⁹ cm2 s⁻¹).