nanocrystalline hydroxyapatite was precipitated from calcium hydroxide and phosphoric acid. effects of precipitation temperature and different calcium to phosphate ratios (ca/p) on the obtained powders were investigated. characteriza-tion of the powders was performed using xrd and ftir spectra, scanning electron microscopy, and transmission electron microscopy. increase in precipitation tempera...

In this paper, concrete specimens are immersed in ultrapure water, to study the evolutions of surface permeability, pore structure and paste microstructure following the prolonging of immersion period. According to the results, after 30-day immersion, the surface permeability of concrete becomes higher as compared with the value before immersion. However, further immersion makes the surface per...

Meta l impregnat ion , or "s ta in ing ," of tissue sections for electron microscopy has become the accepted practice in recent years. Salts of metals of h igh atomic weight such as u ran ium, chromium, thor ium, lead, or tungsten, among many tested, have been found suitable (6, 1). "Lead hydroxide ," as prepar ted by Watson (6), is now widely used, hu t this solution is extremely unstable in a...

Retention of heavy metal ions on soil mineral surfaces is an important process for maintaining environmental quality. A thorough understanding of the kinetics and mechanisms of heavy metal sorption on soil mineral surfaces is therefore of fundamental importance. The present study examines the kinetics and mechanisms of Ni(II) sorption onto pyrophyllite, kaolinite, gibbsite, and montmorillonite....

The one-step cyclocondensation of substituted isoflavones with cyanothioacetamide in the presence of sodium hydroxide gave an array of 3-cyano-5,6-diaryl pyridine-2(1H)-thiones in good yields. The procedure involves base-mediated ring opening of the isoflavones and subsequent Knoevenagel condensation between the 1,3-dicarbonyl intermediate generated from the isoflavones and cyanothioacetamide, ...

The Sn(IV) atom in the centrosymmetric title complex, [Sn2(CH3)4(NCS)2(OH)2], adopts a distorted trigonal-bipyramidal coordination environment defined by two methyl C atoms and one bridging hydroxide group in the equatorial plane while the other bridging hydroxide group and the N atom of the thio-cyanate anion are in the apical >positions. The dinuclear species are linked through O-H⋯S and C-H⋯...