趣说黄金与保健

“吞金自尽”以致“香消玉殒”的故事,在古典小说中时有所闻。黄金果真有毒吗?明代李时珍在《本草纲目》中记载说:“金屑辛,平,有毒”。但查阅近代的有关医学书刊,却未见纯金有毒的说法,也未发现有纯金中毒的报道。反之,近些年来在世界各地,一些餐馆。

Effect of Cr content on microstructure and properties of aged Cu−Cr−P alloys

The role of Cr in affecting the precipitates and the properties of aged Cu−Cr−P alloys was investigated and discussed.The results show that there are mainly three sizes of Cr phase in aged Cu−Cr−P alloys,among them,the nano-sized Cr phase plays an important role in the strength of Cu−Cr−P alloys.The strengthening effect of Cr phase(less than 5 nm)with FCC structure completely coherent with the matrix is calculated to be about 200 MPa on the basis of dislocation cut-through mechanism.The strengthening effect of Cr phase(10−20 nm)with BCC structure incoherent with the matrix is calculated to be about 100 MPa on the basis of the Orowan dislocation bypass mechanism.The increase of Cr content changes the number and size of nano-sized Cr phase,which causes the mechanical properties of the Cu−Cr−P alloys to increase first and then decrease.The tensile strength of Cu−0.36Cr−0.01P alloy is 572 MPa and its electrical conductivity is 80%IACS after solid solution treatment at 980°C for 2 h followed by 95%cold rolling and then aging treatment at 450°C for 1 h.

Directional migration behavior of cerium during sintering process of mischmetal doped cemented carbide

Three observation methods were used to investigate the existing form and the behavior of rare earth during the sintering process of high activity mischmetal （RE, with lanthanum and cerium） doped WC-8%Co-0.048%RE（mass fraction） alloy with low carbon-containing level by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDXS）, considering the fact that the addition amount of rare earth in the alloy is very minute. The directional migration process and mechanism of cerium were discussed. First, the sinter skin （surface） is observed. oxide on the sinter skin, and lanthanum in these cerium observed, and lanthanum containing phase/micro-zone in It is shown that there exists a dispersedly distributed cerium containing enrichment positions is very minute. Secondly, the polished section is the alloy is identified. Finally, based on the fact that the fracture of cemented carbide is resulted from the heterogeneous phase or other defects within the microstructure, the fracture surface is observed and cerium containing phase/micro-zone in the fracture source approximately 260 μm from the surface is identified. These combined observations reveal adequately the fact that lanthanum and cerium get separated and cerium predominantly migrates towards the surface during the sintering process.

Effects of Different Lead Compounds on Growth and Heavy Metal Uptake of Wetland Rice

Effects of different lead compounds, PbCl2, Pb(NO3)2 and Pb(OAc)2, on the rice growth and uptake of lead and some microelements by wetland rice were studied. The results showed that the seed germination, rice seedling growth, chlorophyl content, grain yield and uptake of Pb, Cu, Zn, Fe and Mn by rice plant were affected by the chemical forms of Pb compounds added in soil to a certain degree. The germination rate and the amount of chlorophyl decreased remarkably with increasing Pb concentration, the root extension was restrained obviously by the presence of Pb, and the effect of PbCl2 was more evident than that of Pb(NO3)2 or Pb(OAc)2. The pot incubation test with yellow brown soil and red soil showed that there was no significant regularity in effect of Pb on grain yield, but the difference in the influence of various Pb compounds on yield was clearer. The effect on the amount of Pb in straw and brown rice was in the sequence of Pb(NO3)2> Pb(OAc)2> PbCl2. In case the content of Pb in brown rice was 0.5 mg/ kg, the relative loading capacities of yellow brown soil for Pb added as PbCl2, Pb(OAc)2 and Pb(NO3)2 were 100, 90 and 60 respectively. Pb uptake by wetland rice was closely related to the chemical species of Pb in soil, but there was no comparability among chemical forms of different Pb compounds in the same soil. The uptake of Cu, Zn, Fe and Mn by wetland rice was markedly affected by the addition of Pb, and different Pb compounds varied in their impacts on the uptake of other metals by different organs of wetland rice, e.g. the concentration of Fe in root increased significantly (r = 0.92), while opposite was true for Fe in brown rice (r =-0.92) due to the application of Pb(OAc), in soil. These results demonstrate that the effect of accompanying anions of Pb on the physiological and biochemical processes of wetland rice was rather complex.

Influence of minor Sc additions on grain refinement and microstructure characteristics of a high Zn-containing Al-Zn-Mg-Cu-Zr alloy

In the present work, scandium elements with a series of contents(0.06 wt.%, 0.10 wt.%, 0.14 wt.%,0.17 wt.%, 0.20 wt.% and 0.25 wt.%) were added in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and the corresponding as-cast microstructure characteristics including grains and phases were thoroughly investigated. The results indicated that fine grain boundaries existed in these alloys and fine MgZn2phases discontinuously distributed on them. Besides,AlZnMgCu eutectic phases and Sc, Zr-containing phases with flocculent morphology were observed. As scandium contents vary from 0.06 wt.% to 0.17 wt.%, the average grain size continuously decreased and its equiaxial characteristics were strengthened. Meanwhile, the content of AlZnMgCu eutectic phase showed a decrease trend. When scandium contents were 0.20 wt.% and 0.25 wt.%, no further enhancement on grain refinement was observed, so as to the reduction of AlZnMgCu eutectic phase content. Besides, Sc, Zr-containing phases with blocky morphology were observed and the alloy with a scandium content of 0.25 wt.% possessed a larger amount of blocky Sc, Zr-containing phase than the alloy with a scandium content of 0.20 wt.%. Grain refinement and reduction of AlZnMgCu eutectic phase content associated with scandium addition were discussed.

The Role of Saturated Hydrocarbon in Enrichment of Cu, Pb, Zn in Kupferschiefer, Southwestern Poland

In order to clarify the role of organic matter in the enrichment of base metal, 10 samples of the Permian Kupferschiefer from southwestern Poland were analyzed by using microscopic and geochemical methods. The results indicate that the solvent extracts have been depleted in the samples with high Cu, Pb, Zn contents. This depletion occurred preferably in saturated hydrocarbons. Saturated hydrocarbons served as hydrogen donor for thermochemical sulfate reduction (TSR). The GC traces of saturated hydrocarbon show that the depletion occurred mainly in long chain n alkanes.

Determination of Selected Toxic Elements in Apples from Organic Farming

Due to the elevated ecological awareness nowadays the consumption of products of organic agriculture is increasing. Organic farming means excluding the use of synthetic inputs, such as synthetic fertilizers and pesticides or genetically modified organisms, but there are only a few regulations regarding heavy metal concentrations in soils. Thus a not negligible uptake of metals from the soil where the apple trees are grown may occur. Furthermore inorganic copper compounds being traditional fertilizers for apple trees are not considered as synthetic fertilizers, thus they are still used in organic apple farming for soil or foliar application. Thus also apples produced by organic agriculture may contain toxic elements, such as cadmium, chromium, copper, and lead. The concentrations of these elements were determined in whole apples, as well as in the flesh and peel in order to estimate the possible risk for human health. Prior to analysis using ICP-AES samples underwent a microwave assisted digestion. The LODs obtained are below the recommended maximum levels in vegetables/fruits by WHO. In all samples no Cu, Cr, and Pb could be detected. Only Ca was found in the peel of about a third of samples investigated in concentrations between LOD and LOQ （1-3 μg/g）.

Grain Size and Metallic Trace Element Contents in Sediments of Kemaman Coast, Terengganu, Malaysia, South China Sea

A total of 43 sediment samples were collected at Kemaman coast, Terengganu, by using Smith Mclntyre grab. These sediments were analyzed to determine the grain size, sediment texture and metallic trace elements. Lazer diffraction method using PSA （particle size analyzer） was used to determine the grain size and sediment texture. Teflon bomb was used to digest the sediments for metallic trace elements concentration. Results showed that the study area was dominated with sand particles （60.5%） followed by loamy sand （20.9%）, sandy clay （16.3%） and silt loam （2.3%）. On the other hand, the average concentrations of each metallic trace elements were 0.12 pg/g for Cd; 36.6 lag/g for Cr; 9.51 pg/g for Cu; 11.6 ~tg/g for N： 41.5 ~tg/g for Zn and 29.3/ag/g for Pb. Based on the results, it was found out that coarse sediments showed lower levels of metallic trace elements and higher levels in fine sediments. In addition, enrichment factor was calculated to assess the pollution status of the study area. Based on the calculation, the enrichment of metallic trace elements ranked in the following order： Pb 〉 Cd 〉 Zn 〉 Cu 〉 Ni 〉 Cr. The significant enrichment of Pb and moderate enrichment of Cd and Zn indicated that there are anthropogenic inputs while the rest of the metals can be considered from natural sources although there are effects of anthropogenic inputs in some sampling location.

In vitro degradation and biocompatibility of Mg-Li-Ca alloys—the influence of Li content

Mg-Li based alloys hold much attention as potential biomedical materials due to their excellent ductility. A reduced mechanical strength and concern for biocompatibility are exhibited for Mg-Li binary alloys due to the presence of Li element. Addition of the Ca element into Mg-Li alloys leads to an improvement in mechanical strength and biocompatibility.In the present work, the microstructure, mechanical property and corrosion behaviors of three kinds（α, α＋β, β） of as-extruded Mg-Li（1, 9 and 15 wt.%）-1 Ca alloys were investigated using optical microscope, X-ray diffraction（XRD）, tensile,immersion and electrochemical polarization measurements.In vitro biocompatibility was evaluated by cytotoxicity assays,hemolysis and four coagluation tests. The results indicated that the Mg-1 Li-1 Ca and Mg-15 Li-1 Ca alloys were characterized by α-Mg and β-Li phases besides Mg2 Ca particles, respectively; while the Mg-9 Li-1 Ca by dual（α-Mg＋β-Li） phase together with Mg2 Ca phase. The Mg-1 Li-1 Ca alloy had the highest ultimate tensile strength（UTS） and yield strength（YS）and the lowest elongation（EL） to failure（10.1±1.24%） as well.The EL for the Mg-9 Li-1 Ca alloy was the highest（52.2±0.01%）.The long-term immersion tests revealed a decrease in corrosion resistance with increasing Li content. The results of cytotoxicity assays clearly showed that the Mg-Li-Ca alloys demonstrated no toxicity to L-929 cells in 10% concentration of extracts. The Mg-1 Li-1 Ca alloy also exhibited an acceptable hemolysis ratio. The results of four coagulation tests designated no sign of thrombogenicity for the Mg-Li-Ca alloys except for the Mg-15 Li-1 Ca alloy.