Site symmetry and crystal field splittings of Ce 3+ in LiLuF 4 and LiSr 0.8 Ca 0.2 AlF 6

Electron paramagnetic resonance (EPR) spectra of Ce 3+ in LiLuF 4 (LLF) and LiSr 0.8 Ca 0.2 AlF 6 (LSCAF) observed at low temperatures (<20 v K) show that the Ce 3+ centers have tetragonal and pseudo-trigonal symmetry with ( g , g )=(2.751, 1.467) and (2.14, 0.80), respectively. The EPR lines of Ce 3+ in LSCAF are inhomogeneously broadened by different Ce 3+ configurations which correspond to the random occupation of the second nearest neighbor cation sites by Ca 2+ and Sr 2+ and/or charge compensators. These EPR results indicate that the Ce 3+ centers in LLF and LSCAF are associated with substitution of Ce 3+ for Lu 3+ with eight-fold coordination and Sr 2+ /Ca 2+ with six-fold coordination, respectively. Fourier transform infrared absorption has been used to measure transitions between the 2 F 5/2 ground state and the 2 F 7/2 multiplet of Ce 3+ in LLF at 10 v K. The optical absorption and luminescence of Ce 3+ :LLF and Ce 3+ :LSCAF in the UV range are strongly polarized. The energy levels and polarization dependence of the optical transitions can be accounted for in terms of the crystal field potential experienced by the Ce 3+ ions under the action of the different point group symmetries.     

Sensitive determination of tyrosine metabolites, p-hydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenyl-acetic acid and 4-hydroxy-3-methoxymandelic acid, by gas chromatography-negative-ion chemical-ionization mass spectrometry. Application to a stable isotope-labelled tracer experiment to investigate their metabolism in man

A method has been established for studying the dynamic metabolism of tyrosine to its metabolites in humans using a deuterium-labelled amino acid. Phenylalanine-d5 was administered orally to human subjects (5 mg/kg) and the levels of p-hydroxyphenylacetic acid-d4, 4-hydroxy-3-methoxyphenylacetic acid-d3, and 4-hydroxy-3-methoxymandelic acid-d3 excreted into urine every hour were determined by gas chromatography-negative-ion chemical-ionization mass spectrometry. This method was also applied to some patients with depression and it was possible to detect a slight alteration in the excretion of some compounds compared with the control.     

An analytical determination of speed factor in gear designs

In practical gear design, the “speed factor” is usually employed which is defined as a ratio of the allow-able stress at required running speed of the gear system to the stress at zero speed. At present, several expressions for the speed factor are recommended by several authorities; however, those are almost all empirical and not analytical. The present paper aims to contribute to an analytical determination of the speed factor for spur gears as stated below. First, from a dynamic photoelastic test of a pair of spur gears, the following results were obtained:

1. (1)
   At a contant speed and torque and at the same point of engagement, the maximum fillet stress did not have a specific constant value but had somewhat scattered values due to the vibration of gear system under operation.     

Self-trapping of a wannier exciton in the optical phonon field

Stability for self-trapping of a Wannier exciton in the polarization field of optical phonons is studied by means of variational calculations based on the adiabatic approximation. The phase diagram of free and self-trapped states is presented for 1s, 2s and 2p excitons. It is shown that optical phonons can be responsible for self-trapping of 2s (2p) exciton as a trigger of self-trapping.     

Aktive Polykondensatino von Diestern, die heterocyclische Kerne enthalten

Ohne Zusammenfassung     

Application of Spectral Analysis for Crystal Shape Improvement during Czochralski Growth of Oxide Crystals

The automatic diameter control system using the results of spectral analysis of weight sensor data as a criterion for the amount of feedback tuning was applied successfully for the growth of La₃Ga₅SiO₁₄ single crystals. The developed method enabled to determine timely the appearance of oscillations in the control system and to adapt the amplification factor automatically for the maintenance of stable crystal shape. Furthermore, the developed system made it possible to estimate the formation of a second phase at a very early stage.