Mechanical and tribological characterization of human tooth

In order to develop new dental restorative materials, it is imperative to evaluate and understand the structure–property relationships of the human tooth. Three major structural parts of human tooth i.e. enamel, dentin and dentin–enamel junction have been characterized in the present work in terms of microstructure, phase analysis and compositional gradient. It has been observed that microindentation hardness varies from enamel to dentin with the highest hardness observed for enamel at the outermost surface (around 3.5 GPa). Hardness values monotonically decrease with depth to less than 1 GPa, measured at the interior dentin. Furthermore, the measured hardness variation is found to have a noticeable correlation with the compositional variation.

In order to evaluate the tribological properties of the human tooth, fretting wear tests were carried out against sintered alumina under a load of 1 N for 2000 to 10,000 cycles. A variation in coefficient of friction (ranging from 0.12 to 0.55) was measured in our experiments. The wear mechanism is dominated by fretting fatigue and adhesive wear, involving the formation of oxidized calcium phosphate based compounds and its subsequent transfer from tooth to alumina surface. The experimental results also reveal that the human tooth is more susceptible to adhesion wear than abrasion or attrition at fretting contacts.     

Effect of compost age and composition on the atrazine removal from solution

Compost samples from two composting facilities, the Urbana (Illinois) Landscape Recycling Center (ULRC) and Illinois State University (ISU), were selected to examine the effect of compost age on atrazine removal from solution. The ULRC samples were made from yard waste without an additional nitrogen source. The ISU samples were made from yard waste or sawdust with the addition of manure. The 6-month-old ULRC compost had the greater capacity to remove atrazine from solution, which we attributed to its greater organic carbon content. The addition of nitrate into ULRC compost could influence the extent of atrazine removal, but did not have a significant impact on atrazine removal when applied to ISU compost, probably because manure was added to the yard waste to produce the compost. For both ULRC and ISU samples, the presence of sodium azide inhibited atrazine removal, suggesting that microbial activity contributed to the atrazine removal. Metabolic analysis demonstrated that hydroxyatrazine was the major identified metabolite that accumulated in solution before significant ring mineralization could occur. When compared with the ISU compost, the ULRC compost sample had a greater capacity to remove atrazine from solution during the 120 days of study because of the larger humic acid content. The experimental results suggested that less-mature compost may be better suited for environmental applications such as removing atrazine from tile-drainage waters.     

Degradation of DMSO by ozone-based advanced oxidation processes

The present study investigates the oxidation of dimethyl sulfoxide (DMSO) by conventional ozonation and the advanced oxidation processes (AOPs). The major degradation products identified were methanesulfinate, methanesulfonate, formaldehyde, and formic acid in ozonation process. The subsequent degradation of intermediates shows that methanesulfonate is more resistance to ozonation, which reduces the mineralization rate of DMSO. The effect of t-butanol addition and ozone gas flow dosage on the degradation rate was evaluated. The rate constant of the reaction of ozone (k(D)) with DMSO was found to be 0.4162 M(-1)S(-1). In the second part of this study, DMSO degradation and TOC mineralization were investigated using O(3)/UV, O(3)/H(2)O(2) and UV/H(2)O(2) processes. In all theses processes the degradation of target organics is more pronounced than TOC removal. The efficiencies of these processes were evaluated and discussed. The formation of sulfate ion in all AOPs have been identified and compared with other processes. Overall it can be concluded that ozonation and ozone-based AOPs are promising processes for an efficient removal of DMSO in wastewater.     

花垣民乐沉积型锰矿床成矿地质特征

湘西花垣民乐锰矿床属沉积型碳酸锰矿床,地层古构造、岩相古地理、古气候、古生物和地球化学等诸因素决定其成矿机理。文章对该矿床地质特征、成矿条件和成矿物质来源进行了论述。     

胶西北郭家岭幔枝构造控矿作用分析

胶西北金矿集中区的控矿作用与深部过程密切相关。华北东部地区在经历了古生代漫长的稳定地台演化阶段后,于燕山运动时期进入了地幔热柱演化阶段,而胶西北成矿集中区则进入了以莱阳地幔亚热柱与其外围郭家店幔枝构造的发展演化阶段。核幔源Au元素以气—液的形式,经过地幔热柱—地幔亚热柱—幔枝构造—有利构造扩容带,迁移到幔枝构造的有利部位集聚成矿,从而构成了环绕郭家岭幔枝构造的一系列大、中型金矿床。同时,提出了焦家断裂为幔枝构造北西缘的主拆离（断裂蚀变岩）带,三山岛断裂是拆离带上盘铲状断裂的基本认识,并据此指出了该区进一步找矿方向。     

祁雨沟金矿床J4角砾岩体地质特征及矿化富集规律

祁雨沟金矿床为典型的角砾岩型金矿床,J 4角砾岩体是祁雨沟金矿区最重要的角砾岩体之一。重点阐述了J 4角砾岩体的地质特征,总结了矿化富集规律,为在河南省嵩县地区角砾岩型金矿床的找矿勘查工作提供了依据。     

Adhesion resistance surfaces against clay resulting from biomimetic adaptation

To improve the dewetting characteristic and reducing the clay adhesion of molds, a series of “morphological” and “functional” biomimetic roughness units was fabricated on 45^# steel mold surfaces by laser and machining methods. The anti-adhesion and wettability behaviors of samples with different roughness units were investigated. The results indicated that the adhesion forces of samples with different roughness units were lower than that of the smooth one and decreased with increasing the area ratio of roughness units. Contact angle measurements of water on biomimetic roughness surfaces showed that the apparent contact angle increased from 76.9° to 97.5° with the increase of area ratio of biomimetic units. The anti-adhesion mechanism of biomimetic mold was the dual roughness structure of biomimetic units that could decrease the wettability of mold surfaces and reduce the adhesion of clay.     

云南昭通炎山小田村铅锌矿床成矿控制条件分析

矿区位于滇黔川铅锌成矿区之巧家-金沙厂成矿带之上,处于金沙厂、茂租-东坪两大矿化集中区之间。区内震旦系灯影组上部硅质条带白云岩、顶部含藻白云岩为矿区赋矿地层,矿体呈似层状、透镜状及沿断裂带呈脉状产于以上地层中,其控矿因素为地层-岩性(相)-构造。找矿标志为灯影组上部、顶部的硅质条带白云岩、含藻白云岩,莲峰-茂租区域控矿断裂上盘和旁侧的次级断裂,相应的围岩蚀变发育的地区(段)。     

晋蒙地体集宁群金红石成矿规律研究

根据晋蒙地体集宁群上部孔兹岩系和下部麻粒岩系的不整合构造接触,将本区划分为4个构造单元。通过对集宁群岩石学特征的分析及变质原岩的恢复,分析出其沉积环境具有差异。同时依据麻粒岩系形成于晚太古代而孔兹岩系形成于早元古代,对金红石的形成过程进行反演,推断其第一次主成矿期为阜平期,含矿岩层为集宁群下部麻粒岩系,右所堡组含石墨黑云角闪片麻岩。后经吕梁期地层重熔成矿物质迁移,最终在集宁群上部孔兹岩系下白窑组下段富集成矿,矿石岩性为含夕线石榴二长浅粒岩。     

An efficient methodology for utilization of K-feldspar and phosphogypsum with reduced energy consumption and CO2 emissions

The issues of reducing CO2 emissions, sustainably utilizing natural mineral resources, and dealing with industrial waste offer challenges for sustainable development in energy and the environment. We propose an efficient methodology via the co-reaction of K-feldspar and phosphogypsum for the extraction of soluble potassium salts and recovery of SO2 with reduced CO2 emission and energy consumption. The results of characterization and reactivity evaluation indicated that the partial melting of K-feldspar and phosphogypsum in the high-temperature co-reaction significantly facilitated the reduction of phosphogypsum to SO2 and the exchange of K+(K-feldspar) with Ca2+(CaSO4 in phosphogypsum). The reaction parameters were systematical y investigat-ed with the highest sulfur recovery ratio of~60%and K extraction ratio of~87.7%. This novel methodology possesses an energy consumption reduction of~28%and CO2 emission reduction of~55%comparing with the present typical commercial technologies for utilization of K-feldspar and the treatment of phosphogypsum.