The linear and second-order nonlinear optical properties of single-crystal zinc tris(thiourea) sulfate, or ZTS, are determined. The deduced nonlinear coefficients are |d(31)| = 0.31, |d(32)| = 0.35, and |d(33)| = 0.23 pm/V compared with a |d(14)| value of 0.39 pm/V for potassium dihydrogen phosphate. Because it exhibits a low angular sensitivity (deltaDeltak/deltatheta), ZTS may prove useful for type-II second-harmonic generation from 1.06 to 1.027 microm. We present the phase-matching measurement data for ZTS and compare the calculated frequency conversion efficiency for ZTS with that of several other well-characterized materials.
Using noncritically phase-matched 1-cm(2) -aperture KTiOAsO(4) (KTA) crystals in an optical parametric oscillator (OPO), we have demonstrated a sustained average signal power of 33 W at 1534.7 nm. To our knowledge, this is the highest-average-power signal ever generated by an OPO. The pump source was a 100-Hz Q -switched 1064-nm Nd:YAG laser. Compared with that of the similar and more-common material KTiOPO>(4) , idler absorption in KTA is negligible, allowing high-power operation with minimal thermally induced refractive distortion in the OPO crystal.
The currently available phosphate binders are relatively inefficient and suffer from clinical side-effects of increased absorption of calcium and aluminium and the diarrhoea-inducing effects of magnesium. A new class of compounds based on mixed metal hydroxides has been developed and evaluated for their potential as phosphate binders. The mixed metal hydroxides were prepared using a standard procedure for hydrotalcite (Al2Mg6(OH)16.CO3.4H2O) by substituting Fe3+ for Al3+, with Mg2+ or Ca2+ as the divalent metal ion. Phosphate precipitation (binding) was examined at different pH values in aqueous solution and in various food mixtures in comparison with hydrotalcite, Al(OH)3, CaCO3 and Mg(OH)2 on the same weight-to-weight basis. A series of compounds with differing ratios of metal ions (Fe:Mg/Ca 1:2 or 1:3) gave analytically similar ratios to those predicted from the initial amounts added. CTFeCa bound > 90% phosphate in aqueous solution compared with 65% binding with CTFeMg, 85% binding with Mg(OH)2, and less than 30% binding for CaCO3 and Al(OH)3. The mixed metal compounds also bound up to 80% phosphate in various food matrices, which was relatively independent of changes in pH, compared with Mg(OH)2, where binding decreased from 85% at pH 3.0 to 25% at pH 8.0. Al(OH)3 and CaCO3 were relatively ineffective phosphate binders under all the conditions tested. The mixed metal hydroxides compounds show considerable promise as phosphate binders over those currently available and warrant further patient-based in-vivo testing.
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