硫化银比浊法测定液氨中微量硫

液氨样品经自然蒸发后,加甲醇蒸馏除去残液中溶解的氨,用硫化银比浊法测定微量硫。该方法准 确度较高,取得了满意的效果。

当前白银比黄金更具投资价值

近日,海外一些知名市场分析机构纷纷撰文,看好未来的白银市场,他们认为,当前白银比黄金更有投资价值(不过在市场波动很强的情况下,入市需谨慎)。全球头号咨讯集团--路透社和全球白银现货交易中心--伦敦金银协会(LBMA)都组织全球著名分析机构,对2004年全球白银市场进行分析预测(路透社组织了28家,LBMA组织了18家)。两家机构预测的总体趋势是。

Modeling of whole process of ageing precipitation and strengthening in Al-Cu-Mg-Ag alloys with high Cu-to-Mg mass ratio

A physically based numerical model to predict the microstructure evolution and yield strength of high Cu-to-Mg mass ratio Al-Cu-Mg-Ag alloys during the whole ageing process was developed.A thermodynamically-based precipitation model,employing the classical nucleation and growth theories,was adapted to deal with the precipitation kinetics (evolution of radius and volume fraction of precipitates for Ω phase) of aged Al-Cu-Mg-Ag alloys.The model gives an estimation of the precipitation kinetics (evolution of radius and density of precipitates for both θ' and Ω phases) of the alloy.The strengthening model based on Orowan mechanism was deduced.The microstructural development and strength predictions of the model are generally in good agreement with the experimental data.

Application of silver nitrate colorimetric method to non-steady-state diffusion test

NT build 443, or profile fitting method, is often used to measure the diffusion coefficient of chloride in concrete. However, this method is quite laborious and needs special equipment. Colorimetric method is a quick and simple method to measure the penetration depth of chloride by spraying 0.1 mol/L silver nitrate solution. The objective of this work is to study the possibility of the use of colorimetric method in the calculation of non-steady-state diffusion coefficient. Twelve concrete mixtures with different supplementary cementitious materials and water-to-cement ratios of 0.35, 0.48 and 0.6 were used for study. According to NT build 443, the concrete specimens were immersed in 165 g/L NaC1 （2.8 mol/L） solution for 42 d. Both water-soluble （convert to free chloride） chloride and acid-soluble chloride at different layers of specimens were measured. The results show that the mean value of free chloride concentration at the color change boundary Cd was 0.306 mol/L. The surface free chloride concentration cs was obtained by profile fitting method, which was 40% lower than the chloride concentration of exposure solution after an immersion period of 42 d. Chloride diffusion coefficients obtained by the colorimetric method was not well correlated with those obtained by profile fitting method.

Assessing Financial Performance of Malaysian Islamic and Conventional Commercial Banks Using Financial Ratios

A rapid growth of Islamic banking has led the Malaysian economy to gaining greater prosperity than before. Presently, there are more than 20 Islamic banks operating in Malaysia. Financial ratios calculated from the categories of liquidity, profitability, risk and solvency, and efficiency of banks can be used to gauge the overall financial performance of the banking industry. The objective is to assess the overall performance of Islamic banks as well as conventional banks in Malaysia using financial ratios. The findings indicated that conventional commercial banks in Malaysia do have better quality assets, are more liquid, and are more profitable than Islamic banks. Total expenses in conventional banks are much higher, which may affect profitability and the significant amount of non-performing loans （NPLs）, thus increasing solvency risk. The findings show positive insights of Islamic banks, whose confidence and trust are rising, over a short period with strong improvements in asset utilization, effective management, and expenditure control. This comparative study clearly identified that conventional banks are better financial performers compared to Islamic banks in Malaysia during the period of 2006-2010.

Assessment of the Presence of Chlorides in Mortar through the Silver Nitrate Colorimetric Spraying Method

This study aims to evaluate the presence of free chlorides by the silver nitrate colorimetric spraying method in mortars made with Portland cement CP II Z-32. In order to make an assessment beyond the qualitative analysis, a calculation of the contaminated areas by free chlorides was performed by measuring the regions using a computer image analysis software （IMAGEJ）. The experimental part of the research involved samples of 5 cm x 10 cm of mortar and 0.1 M solution of silver nitrate in distilled water. The mortar samples were made with cement CP II Z-32 with the following concentrations of chloride incorporated into the mixing water： 0%0, 0.4%, 0.6%, 0.8%, 1.0% and 2.0%, in relation to the mass of cement, totaling 108 samples. The average of percentage results from the contaminated area of the series of samples was respectively 0%, 14.9694%, 19.7444%, 46.0239%, 62.3311% and 96.0083% in relation to the total area, concluding that the method of silver nitrate spraying is applicable and that the white color indicates the presence of chloride ions and other possible aggressive salts to the structure or the concrete.

Investment Strategy of the Temasek Holdings

Sovereign Wealth Funds （SWFs） are generally known as investment funds owned by national governments and financed by the country＇s foreign currency reserves （dollar, euro, and yen）, often through their central banks or via direct investments. The study investigated the investment strategy of the Temasek Holdings as one of the most successful SWFs which is owned by the government of Singapore. Temasek Holdings was founded in 1974 to manage part of the government＇s revenues. Present turbulent times create a big pressure on healthy investment strategy of the SWFs. But total shareholder return for Temasek since its inception in 1974 has been a healthy 17% compounded annually. The main objective of the paper is to focus on the role of the Temasek Holdings as a company managed on commercial principles with an aim to achieve long-term sustainable returns. The study also analyzed Temasek Holdings＇investment strategy. The study provides answers to questions like： why Temasek is of the most successful SWFs and what is the fund risk management？ Another part of the paper compares investment strategy of the Temasek Holdings with other SWFs. The study has been conducted mainly on the basis of literature survey, secondary information and with using various web sites and research paper. The analysis has been also based on disclosures appearing in the Temasek annual reports over the period from 2008 to 2010.

A label-free colorimetric assay for detection of c-Myc mRNA based on peptide nucleic acid and silver nanoparticles

A label-free colorimetric protocol based on peptide nucleic acid/silver nanoparticles(PNA/Ag NPs) has been initially proposed for specific recognition of m RNA.Making use of the controlled silver nanoparticles aggregation/dispersion by PNA/PNA–RNA complex, proto-oncogene c-Myc m RNA detection can be achieved. Moreover, the PNA/Ag NPs platform can undergo color change in response to target c-Myc m RNA with single-base-mismatch sensitivity, which could further help in visually identify single nucleotide differences in target genes.

Late Mesozoic magmatism and tectonic evolution in the Southern margin of the North China Craton

Late Mesozoic granitic magmatism(158–112 Ma) are widespread in the southern margin of the North China Craton(NCC), contemporary with many world-class Mo-Au-Ag-Pb-Zn polymetallic deposits. There are abrupt changes in the elements and isotopic compositions of these granites at about 127 Ma. The early stage(158–128 Ma) granites show slightly or no negative Eu anomalies, large ion lithophile elements enriched and heavy REE depleted(such as Y and Yb), belonging to typical I-type granite. The late stage(126–112 Ma) granites are characterized by A-type and/or highly fractionated I-type granite, with higher contents of SiO2, K2 O, Y, Yb and Rb/Sr ratio and lower contents of Sr, δEu value and Sr/Y ratio than that of the early-stage granites.Moreover, the whole rock Nd and Hf isotopic compositions of the granites younger than 127 Ma show more depleted than those of the older one. The two stages of Late Mesozoic granites were derived from a source region of the ancient basement of the southern margin of the NCC incorporated the mantle material. The late stage(126–112 Ma) granites contain more fractions of mantle material with depleted isotopic composition than the early ones. The granites record evidence for a strong crust-mantle interaction. They formed in an intracontinental extensional setting which was related to lithospheric thinning and asthenospheric upwelling in this region, which was possibly caused by westward subduction of the Paleo-Pacific plate. 127 Ma is an critical period of the transformation of the tectonic regime.

Comparison of cellular responses across multiple passage numbers in Ba/F3-BCR-ABL cells induced by silver nanoparticles

With the rapid development of nanotechnology and increasingly broad bio-application of engineered nanomaterials, their bio- hazards have become a serious public concern. It is believed that the chemical nature, particle size, morphology, and surface chemistry of nanomaterials are key parameters that influence their toxicity. Although cultured ceils have been widely used to evaluate nanomaterial toxicity, it remains unclear whether the passage of these cells affects the evaluation results. In the pre- sent study, Ba/F3 cells transfected with the BCR-ABL gene were subcultured to study the effect of passage number on cell sta- bility and their cellular responses upon exposure to nanomaterials. The results demonstrated that proliferation, cellular senes- cence, BCR-ABL gene expression, cell cycle and apoptosis were stable across multiple passages. Senescence and BCR-ABL gene expression of cells from different passage cells were unchanged when treated with silver nanoparticles （AgNPs）. In addi- tion, the cells at multiple passage numbers were all arrested in the G2/M phase and apoptosis was induced by the AgNPs. These nanoparticles could enter cells via endocytosis and localize in the cndosomes, which were also not influenced by passage number. These data suggest that short-term passage would not affect cultured cell stability and toxicity assessment using these cells would be consistent when maintained appropriately.

Simple colorimetric detection of dopamine using modified silver nanoparticles

Dopamine(DA) plays an important role in health and peripheral nervous systems. Colorimetric detection of DA has the advantage of color change and simplicity in operation and instrumentation. Herein, we report a highly sensitive and selective colorimetric detection of DA by using two specific ligands modified Ag nanoparticles, where the DA molecules can make dual recognition with high specificity. The colloidal suspension of modified Ag nanoparticles was agglomerated after interacting with DA, while the color of Ag nanoparticles suspension changed from yellow to brown, arising from the interparticle plasmon coupling during the aggregation of Ag nanoparticles. The modified Ag nanoparticles suspension and agglomeration were confirmed by transmission electron microscope images. The optical properties behind the color change were thoroughly investigated by using UV-Vis and Raman techniques. The changes in p H, zeta potential, particle size and surface charge density by adding DA were also determined by using dynamic light scattering measurements. The detection limits of modified Ag probes for DA was calculated to be 6.13′10^(-6) mol L^(-1)(S/N=2.04) and the correlation co-efficient was determined to be 0.9878. Because of the simplicity in operation and instrumentation of the colorimetric method, this work may afford a feasible, fast approach for detecting and monitoring the DA levels in physiological and pathological systems.

Synthesis of polymer protected Au NPs for silver ions detection

Herein, a novel probe based on poly(N,N′-methylenebisacylamide) protected Au NPs(PDMAM-Au NPs) was developed for determination of silver ions. The thiol-terminated PDMAM was synthesized by the reversible addition fragmentation chain transfer radical polymerization. Then, the PDMAM-Au NPs were prepared by a simple, one-pot and green process. It has been observed that existence of the silver ions evoked a small red-shift to the emission peak of PDMAM-Au NPs and an obvious increase in UV absorption. The detection limit of the present method for silver ions was 0.5 ?mol/L, with a linear range of 1.0–1000 ?mol/L. Moreover, the possible mechanism for enhanced UV absorption intensity with enlarged diameter of PDMAM-Au NPs was explored and discussed briefly. The results demonstrated that silver ions could be detected by the PDMAM-Au NPs based colorimetric assays, further opening up new ways for the visualization and quantification of silver ions involved in our daily life.