Inhibitory effect of iron-oxidizing bacteria on ferrous-promoted chalcopyrite leaching

It is generally accepted that iron-oxidizing bacteria, Thiobacillus ferrooxidans, enhance chalcopyrite leaching. However, this article details a case of the bacteria suppressing chalcopyrite leaching. Bacterial leaching experiments were performed with sulfuric acid solutions containing 0 or 0.04 mol/dm3 ferrous sulfate. Without ferrous sulfate, the bacteria enhance copper extraction and oxidation of ferrous ions released from chalcopyrite. However, the bacteria suppressed chalcopyrite leaching when ferrous sulfate was added. This is mainly due to the bacterial consumption of ferrous ions which act as a promoter for chalcopyrite oxidation with dissolved oxygen. Coprecipitation of copper ions with jarosite formed by the bacterial ferrous oxidation also causes the bacterial suppression of copper extraction. Copyright 1999 John Wiley & Sons, Inc.

A new light-activated adhesive composite: shear bond strength and microleakage.

A new light-activated adhesive composite has been formulated. Its shear bond strength and marginal microleakage were compared with glass ionomer cements: Fuji Ionomer Type II, Ketac-Fil and Ketac-Bond. The new material showed significantly (p < 0.05) higher bond strength to non-etched enamel (7.9 MPa) and dentin (7.3 MPa) than commercially available materials. It also performed significantly better (p < 0.05) in the microleakage test. Ease of use and the excellent marginal sealing ability of the new material are expected to allow considerable innovation in restorations of root caries, cervical erosion and other conditions where the marginal seal of the gingival cavosurface is difficult.

A new light-activated adhesive cavity liner: an in vitro bond strength and microleakage study.

A new formulation of a light-activated calcium hydroxide-based cavity liner was developed for this study. Its shear bond strength and marginal microleakage in a Class V cavity preparation were compared to those of commercially available light-activated liners and conventional glass ionomer liners: GC Lining Cement (GC), Ketac-Bond (ESPE), Time Line (Caulk), Vitrabond (3M), XR lonomer (Kerr), and Zionomer (DenMat). The new formulation had significantly higher shear bond strength to dentin than the commercially available materials. Its microleakage along gingival (cemento-dentin) walls was statistically equivalent to one of the other materials and significantly better than all the others.

[Objective evaluation of apparent accommodation of pseudophakic eyes].

In 23 (9 males and 14 females) pseudophakic eyes which had a biconvex type intraocular lens (IOL) implanted after cataract extraction, we objectively measured changes in the anterior chamber (AC) depth caused by axial movement of the IOL accompanying accommodation of the contralateral phakic fellow eye, using a Schimpflug slit image with an anterior eye segment image analysis system (Nidek, EAS-1000, Japan). In 114 phakic eyes of 57 persons as controls, AC depths accompanying accommodation from distances of 5 m to 30 cm and 10 cm decreased with increasing age. The decreased mean value of AC depth with accommodation from distances of 5 m to 30 cm was 0.17 mm in patients in their teens, 0.15 mm in patients in their 20 s, 0.10 mm in the 30 s, 0.06 mm in the 40 s, 0.05 mm in the 50 s, and 0.03 mm in the 60 s. The decrease of AC depth with accommodation at a distance of 10 cm was 0 in patients in their 60 s. In the pseudophakic eye changes in anterior chamber depth caused by focusing at short distances were less than 0.04 mm, and decreasing rate of anterior chamber depth (DRAC) was less than 1% in all the pseudophakic eyes. Movement of IOL on the optical axis was too subtle to account for apparent accommodation of the pseudophakic eye.