Development of a I source for its application in bone densitometry

This paper describes a method for the preparation of ¹²⁵I sources for their use in bone densitometer. The process consists of preparation of silver pellets of size ∼2.5 mm (?)×0.6 mm (l) by ‘Cold die compaction technique’, palladium coating of the silver pellets, adsorption of ¹²⁵I on the palladium coated silver pellets and encapsulation source matrix in a titanium capsule [ 3 mm (?)×10 mm(l)] using Nd:YAG laser. The texture and morphology of the source matrix were examined by SEM and EDS analyses. Encapsulated sources containing ¹²⁵I activity up to ∼1.85 GBq (50 mCi) were prepared. Quality control tests that were necessary before application were performed and gave satisfactory results.     

Effects of barriers on chemical and biological properties of two dual resin cements

The aim of this study was to investigate the degree of conversion, monomer release, and cytotoxicity of two dual‐cure resin cements (Cement‐One and SmartCem2), light‐cured across two indirect restorative materials in an attempt to simulate in vitro the clinical conditions. The results obtained show that the degree of conversion was influenced by both barriers, but the effect of the composite material was greater than that of the ceramic one. The amount of monomers released from the polymerized materials in the absence of barriers was significantly lower than that released in the presence of either the ceramic or the composite barrier. However, a higher amount of monomers was released in the presence of the ceramic barrier. All materials, in all the experimental conditions employed, induced slight cytotoxicity (5–10%) on human pulp cells. Our examinations showed that the two resin cements had similar chemical and biological properties. The decreased degree of conversion of the dual‐curing self‐adhesive composite showed that the light‐curing component of these materials has an important role in the polymerization process. In clinical practice, it is therefore important to pay attention to the thickness of the material used for the reconstruction.     

Characterization of trace metal leachability from highway construction solid waste using the toxicity characteristic leaching procedure

The potential risk of soil, surface and ground water contamination by trace metals leached from highway construction solid wastes is a major environmental concern. The objectives of this study were to evaluate trace metal leachability, toxicity of the leachate to aquatic organism and environmental impacts of highway construction solid waste (HCSW). Potential leachability, defined as the maximum metal pool that may become available for leaching at a constant pH 4 decreased in the following order: Zn > Ni > As > Pb > Cu. Potential metal leachability was controlled mainly by solid phase distribution of metals in wastes. The kinetics of metal release were determined using the cascade leaching test (CLT) with water at pH 4. With the exception of zinc in the first fraction, metal concentrations in all consecutive leaching fractions remained below the maximum permissible level in water for human consumption. The result of toxicity test showed that the leachates were in concentrations that did not exceed toxic concentrations for aquatic toxicity tests. The results indicate low risk of surface and ground water contamination resulting from highway construction solid wastes.     

义齿基托聚合物的溶出特性

目的:对我院临床常用的三种基托材料进行溶出物质的检测及溶出特性研究.方法:将基托材料(自凝基托一种,热凝基托两种)浸提在37℃的0.9%生理盐水中,于不同时相收集浸提液.利用HPLC对溶出成分进行定性定量分析.结果:①自凝基托的主要溶出成分是MMA,热凝基托的主要溶出成分是BA和MMA.②溶出主要发生在第一个24小时.③自凝基托的溶出性明显高于热凝基托.结论:义齿加工完毕后对其进行早期浸泡处理,特别是自凝基托材料,可望明显减少随后的溶出,进而减少或减轻不良反应.     

Effects of various light curing methods on the leachability of uncured substances and hardness of a composite resin

The purpose of this study was to evaluate the effect of the various light curing units (plasma arc, halogen and light-emitting diodes) and irradiation methods (one-step, two-step and pulse) using different light energy densities on the leachability of unreacted monomers (Bis-GMA and UDMA) and the surface hardness of a composite resin (Z250, 3M). Leachability of the specimens immersed for 7 days in ethanol was analysed by HPLC. Vicker's hardness number (VHN) was measured immediately after curing (IC) and after immersion in ethanol for 7 days. Various irradiation methods with three curing units resulted in differences in the amount of leached monomers and VHN of IC when light energy density was lower than 17.0 J cm(-2) (P = 0.05). However, regardless of curing units and irradiation methods, these results were not different when the time or light energy density increased. When similar light energy density was irradiated (15.6-17.7 J cm(-2)), the efficiency of irradiation methods was different by the following order: one-step > or = two-step > pulse. These results suggest that the amount of leached monomers and VHN were influenced by forming polymer structure in activation and initiation stages of polymerization process with different light source energies and curing times.     

Strength and Leaching Behavior of Contaminated Mining Sludge at High Water Content Stabilized with Lime Activated GGBS

Sludge management is one of the major challenges in mining activities. The direct disposal of contaminated mining sludge can bring severe damages to the environment and community. Solidification/stabilization (S/S) is a very efficient technology for the treatment of contaminated mining sludge because it improves the stability of sludge dumping sites and reduces the leachability of contaminants. Very few studies investigate the S/S of mining sludge, especially with high water content. This paper investigated the effectiveness of S/S for the treatment of mining sludge at high water content by using quick lime (CaO) activated ground granulated blast furnace slag (GGBS) in comparison to ordinary Portland cement (OPC). To evaluate the mechanical, leaching, and microstructural behavior of CMS at high water content stabilized by lime-activated GGBS and OPC, a series of laboratory experimental tests were performed. Experimental results indicated that increasing the dosage of binder led to increased strength and decreased leachability of the heavy metal. In contrast, an increase in the water content of the mixture resulted in a decrease in compressive strength and an increase in the leachability of heavy metals. On the other hand, lime-activated GGBS mixes had substantially better performance than OPC mixes in the aspect of strength development of treated mining sludge and showed comparable capability of heavy metal stabilization compared to OPC. The microstructural tests revealed the formation of different hydration products such as calcium silicate hydrate, calcium aluminum silicate hydrate, ettringite, hydrotalcite, and heavy metal complexes in CG and OPC mixes.     

Mechanical,Leaching, and Microstructure Properties of Mine Waste Rock Reinforced and Stabilised with Waste Oyster Shell for Road Subgrade Use

Two waste materials, oyster shell (NCOS; non-calcined oyster shell as coarse aggregate and COSP; calcined oyster shell powder as total and partial cement replacement) are used to reinforce and stabilise poorly graded and heavy metal-contaminated mine waste rock (MWR) for pavement subgrade use. Mechanical, leaching, and microstructural tests and analysis were performed on reinforced and stabilised samples to evaluate the effectiveness of the reinforcement and stabilisation of the MWR. Experimental results revealed NCOS and COSP improved the mechanical, leaching, and microstructural properties of the stabilised composite, with a 5% cement–15% COSP–15% NCOS mix being optimal when compared to the control mixes of cement only and no- NCOS. Higher COSP contents beyond 10% reduced the heavy metal contents significantly, but with relatively lower unconfined compressive strengths. Microstructural test results revealed the formation of calcium silicate hydrate (CSH), calcium aluminium silicate hydrate (CASH), ettringite, and calcite as the stabilisation products. Heavy metal complexes in both the cement-only and cement–NCOS–COSP mixes were also found. It is concluded that NCOS reinforced and improved the grading of poorly graded MWR, and that COSP stabilised and immobilised heavy metals present in MWR, thereby improving strength and other engineering properties for subgrade use.     

Long-Term Behavior of Cement Mortars Based on Municipal Solid Waste Slag and Natural Zeolite—A Comprehensive Physico-Mechanical,Structural and Chemical Assessment

Limitations in natural aggregate resources and the continuous increase in the demand for concrete as a building material, as well as the increase in the production of waste and the problem with its storage were the reasons for attempts to replace the sand fraction in cement matrices with a corresponding slag fraction. Municipal solid waste incineration (MSWI) slag, which is a product of waste incineration, can be used as an aggregate. This extends its service life and reduces landfill waste. Therefore, three types of cement mortars with different aggregate composition were prepared. In addition, to increase the durability of the cement matrix and the degree of immobilization of harmful heavy metals and salts present in the slag, a natural zeolite with pozzolanic properties was used. A set of tests was carried out on fresh mortar and hardened mortar, including strength tests after 7, 28 and 360 days. What is more, chemical tests were undertaken, including the content of chlorides and sulfates, leaching using the TCLP method and oxide composition. The conducted tests revealed that all mortars had similar strength properties and demonstrated the effectiveness of immobilizing harmful substances contained in the municipal solid waste incineration (MSWI) slag by cementing.