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At least 289 records · Page 16Linked to original sources
PubMed2004

Effective Raman gain characteristics in germanium- and fluorine-doped optical fibers.

We describe the dopant dependence of Raman gain in germanium- and fluorine-doped optical fibers. We clarify, both theoretically and experimentally, the effective Raman gain characteristic in an optical fiber, which is closely related to the fiber's refractive-index profile and electromagnetic field profile. We also show that this experimentally determined relationship can be used to evaluate the effective Raman gain characteristic in a germaninum- or a fluorine-doped optical fiber with an arbitrary index profile.

Journal Article↗
PubMed2004

Bismuth- and aluminum-codoped germanium oxide glasses for super-broadband optical amplification.

Broadband infrared luminescence from bismuth-doped germanium oxide glasses prepared by a conventional melting-quenching technique was discovered. The absorption spectrum of the glasses covered a wide range from the visible to the near-infrared wavelength regions and consisted of five broad peaks below 370, 500, 700, 800, and 1000 nm. The fluorescence spectrum exhibited broadband characteristics (FWHM) greater than 300 nm with a maximum at 1300 nm pumped by an 808-nm laser. The fluorescence lifetime at room temperature decreased with increasing Bi2O3 concentration in the glass. Codoping of aluminum and bismuth was indispensable for the broadband infrared luminescence in GeO2:Bi, Al glass.

Journal Article↗
PubMed1965

GERMANIUM AND SILICON DISULFIDES: STRUCTURE AND SYNTHESIS.

A series of carbon-14 measurements of 18th- and 19-century wood revealed an excellent correlation between the variations in carbon-14 content and average sunspot activity. It seems probable, therefore, that the predominant cause of the short-term fluctuations in carbon-14 activity is the variability of solar activity.

Carbon Radioisotopes↗
PubMed1991

Diatomic monocations and dications containing germanium and a rare gas atom.

Diatomic dications and monocations GeY2+ and GeY+, where Y = Ne, Ar, Kr or Xe, have been detected on the microsecond time scale. They are characterized via appearance energies, charge stripping of GeY+ ions, and mass-analysed ion kinetic energy spectroscopy. The formation of GeAr+ is found to involve an excited state of Ar in a Hornbeck-Molnar process.

Cations, Divalent↗
PubMed2004

Comparative chemistry of isolable divalent compounds of silicon, germanium, and tin.

Recent studies of the synthesis, structures, spectroscopic properties, and reactions of a series of isolable metallylenes (R2E:, E = Si (1), Ge (2), and Sn (3); R2 = 1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl) are summarized. Because these group-14 metallylenes bear the same helmet-like ligand, a straightforward discussion of the element-dependence of the intrinsic properties of the group-14 element divalent compounds is possible. All these metallylenes were monomeric both in solution and in the solid state, indicating the effective steric protection by the ligand against dimerization. A small sigma-pi conjugation between C-Si(substituent) sigma orbitals and the vacant npz orbitals of divalent atoms in R2E: exists and the extent decreases in the order E = Si > Ge > Sn, as evidenced by UV-vis and NMR spectroscopies and X-ray crystallography. However, the extent of the sigma-pi conjugation in metallylenes 1-3 was much smaller than the electron-donating effects of neighboring nitrogen atoms in known stable cyclic diamino-substituted metallylenes, and hence metallylenes 1-3 are regarded as the least electronically perturbed. Comparative studies of the unique reactions among these metallylenes are also discussed.

Butanes↗
PubMed1992

Germanium-68 as a possible marker for silicon transport in rat brain.

Silicon (Si) is an essential trace element normally present in brain and cerebrospinal fluid, although the mechanism by which it enters and distributes in brain is largely unknown. Due to the short radioactive half-life of 31Si (156 min) we have investigated the use of 68Germanium (68-Ge, half-life 282 days) as a possible marker for Si transport in rat brain over longer periods than are possible with 31Si. Adult male anaesthetised rats were given a bolus of 68Ge I.V. and arterial blood samples taken during experiments that lasted between 5 min and 3 days. At termination, the brain was removed and analysed for radioactivity as were the plasma samples. Data were analyzed by Graphical Analysis which showed that the blood-brain barrier permeability to 68Ge (Kin approximately 10(-4) ml/min/g) is similar to that for many non protein-bound electrolytes in plasma and that 68Ge fluxes across cerebral capillaries are bidirectional. The autoradiographic distribution of 68Ge in brain was homogenous. Our results are in agreement with those of previous studies using 31Si or 68Ge, which suggest 68Ge may be a useful marker for Si when investigating the role of this element in conditions such as neurodegenerative diseases.

Animals↗