bluuebunny/crossref_metadata_2025 huggingface dataset:
Biological Synthesis of Ag Nanoparticles through In Vitro Cultures of Brassica Juncea C. zern
Authors: Shekhawat G.S. , Arya Vedpriya
Published: September 2009

In modern nanotechnology one of the most exciting area of research is the formation of nanoparticles through the biological interventions. Microbes and plants have inherent capacity to reduce metal through their specific metabolic pathway. In the present study Brassica juncea have been used to produce silver nanoparticles. Seedlings of B. juncea prepared in vitro and 14-days old plants were transferred into nutrient solution augmented with silver nitrate (25-2000 μM) allow the plants to grow in hydroponic culture for seven days. Then, the plants are harvested and analyzed through UV-VIS spectrophotometer and by Transmission Electron Microscopy (TEM) that confirms the nanoscale silver nanoparticles. We have found absorption peak in visible range (420-430 nm) of spectrum that is chiefly due to the silver nanoparticles. These biological synthesis methods considered as environmentally safe because of no toxic byproducts. Moreover, size of the nanoparticles can also be controlled by altering some conditions like pH, concentration of AgNO3 and temperature. Silver nanoparticles have large number of applications in non-linear optics, spectrally selective coating for solar energy absorption, biolabelling intercalation materials for electrical batteries, as optical receptors, catalyst in chemical reactions and as antibacterial capacities. So if these nanoparticles are synthesized by the biological methods, this would be more eco-friendly than the other common methods.
Effect of Annealing on Structural and Optical Properties of Pulsed Laser Deposited Titanium Dioxide Thin Films
Authors: Shukla Gaurav , Khare Alika K.
Published: September 2009

TiO2 is a widely studied material for many important applications in areas such as environmental purification, photocatalyst, gas sensors, cancer therapy and high effect solar cell. However, investigations demonstrated that the properties and applications of titanium oxide films depend upon the nature of the crystalline phases present in the films, i.e. anatase and rutile phases. We report on the pulsed laser deposition of high quality TiO2 thin films. Pulsed Laser deposition of TiO2 thin films were performed in different ambient viz. oxygen, argon and vacuum, using a second harmonic of Nd:YAG laser of 6 ns pulse width. These deposited films of TiO2 were further annealed for 5hrs in air at different temperatures. TiO2 thin films were characterized using x-ray diffraction, SEM, photoluminescence, transmittance and reflectance. We observed effect of annealing over structural, morphological and optical properties of TiO2 thin films. The anatase phase of as-deposited TiO2 thin films is found to change into rutile phase with increased annealing temperature. Increase in crystalline behaviour of thin films with post-annealing temperature is also observed. Surface morphology of TiO2 thin films is dependent upon ambient pressure and post- annealing temperature. TiO2 thin films are found to be optically transparent with very low reflectivity hence will be suitable for antireflection coating applications.
A Comparative Study of the Synthesis of Carbon Nanotubes Using Ni and Fe as Catalyst
Authors: Sengupta Joydip , Panda Sovan Kumar , Jacob Chacko
Published: September 2009

The effect of Fe and Ni catalysts on the synthesis of carbon nanotubes (CNTs) using atmospheric pressure chemical vapor deposition (APCVD) was investigated. Distribution of the catalyst particles over the Si substrate was analyzed by atomic force microscopy (AFM). Characterization by X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopic measurements over the grown species is reported. The study clearly shows that the catalyst strongly influences morphology and microstructure of the grown CNTs.
Application of High Aspect Ratio Scanning Probe in Microstructure Measurement
Authors: Fu M.M. , Guo K.K. , Chen Y. , Yang Y.H. , Ju Bing Feng
Published: September 2009

An experiment, which is based on a self-developed pure tungsten high aspect ratio scanning probe, was conducted to measure the topography of a micro channel and a complex microstructure respectively. Comparison and analysis of both results by the tungsten probe and a single-crystal diamond probe were carried out. It indicates that the newly developed pure tungsten scanning probe has the capability in topography measurement, particularly fit for the high aspect ratio surface measurement.
Material Removal Mechanism in Vibration-Assisted Finishing
Authors: Wang Yu , Yin Shao Hui , Shinmura Takeo
Published: September 2009

In this paper, it is explored the material removal mechanism in vibration-assisted finishing process. On the basis of some experiments, the finishing characteristics are represented summarily. Though the analysis, it is shown that the vibration assistance method may increase cutting distance and speed of abrasive and material removal in per unit finishing distance which is affected by vibration frequency and amplitude, in-process abrasives behavior. What more, the increase in material removal rate is mainly due to an increase in material removal per unit finishing distance which is affected by the effects of abrasives cross-cutting.
Cutting Force Modeling in Precision Turning 3J33 Alloy for Tool with Nose Radius
Authors: Zhai Yuan Sheng , Wang Yu , Liang Ying Chun
Published: September 2009

Based on experimental results, a predictive model with certain constraints of cutting parameters (feed rate and depth of cut) and nose radius for cutting forces is solved in precision turning 3J33 alloy. The proposed model is adequate with F-ratio test and multiple correlation coefficient of it. Regression analysis shows that depth of cut and feed rate influence the principal cutting force significantly. The goal of this study is to predict cutting forces under certain constraints of cutting parameters and nose radius.
A Survey of the Machining Characteristics and Mechanical Polishing Technology of CVD Diamond Films
Authors: Zhang Li , Wen Dong Hui , Ji Shi Ming , Yuan Qiao Ling , Xu Zhen Hao
Published: September 2009

The rough surfaces and non-uniform thicknesses of chemically vapor-deposited (CVD) diamond films and substrates affect their industrial application. In recent years, many polishing and planarization methods have been reported, but each method has its relative merits. This paper reviews the necessity for processing of the CVD diamond films first. Then the processing mechanism of micro-cracking and the characteristics of mechanical polishing of diamond films are discussed. The remove form of the material and surface characteristics are compared by three mechanical polishing method, including free abrasive polishing, fixation abrasive polishing and membrane on the membrane polishing method. No matter what form of mechanical polishing process is adopted, because of its inherent characteristics and the principles of processing, mechanical polishing CVD diamond films can only be as polish processing to remove large residual. The macro-surface roughness of processing is about the 2μm. The micro-rough surface roughness is for the 40nm or so. The material removal rate is 10nm/h.
Investigation of Material Removal and Grain Wear Mechanism in Single Point Diamond Scratching Tests on SiC
Authors: Zhao Q.L. , Chen J.Y.
Published: September 2009

There has been increased interest in the use of SiC due to its excellent physical and mechanical properties. The diamond grinding process of SiC has been largely investigated in recent years, but the interface between diamond grain and SiC in grinding has not been completely understood. In this paper, a single diamond scratching method was presented in order to insight into the interface realizing on a SRV friction and abrasion test machine using three types of diamond grains with different shapes. The results analysis for material removal and diamond grain wear mechanisms in the interacting between the diamond grain and SiC can be useful to improve the grinding process of SiC.
Fabrication of Micro-Structures by Micro-ECM
Authors: Wang Ming Huan , Zhang Qiao Fang , Yao C.Y. , Peng Wei
Published: September 2009

The machining of materials on microscopic scales is considered to be great importance to a wide variety of fields. Electrochemical Micro-machining (EMM) appears to be promising to machine the micro-structures in future due to the material is dissolved at the unit of ion. This paper is focused on developing a micro electrochemical machining system in which the micro-structures such as micro-cylinder, multiple micro-electrodes, micro-holes and micro-slot were processed. The micro-electrodes were prepared in a precisely controlling the electrochemical etching process. Mathematical model controlling the diameters of electrodes was built up. Furthermore, the obtained micro-electrodes were selected as the cathode tool for micro holes drilling and micro-slot milling using pulse power in Micro-ECM.
Analytical and Experimental Investigation of the Nickel Based Superalloy Using Cryogenic Cooling Grinding
Authors: Li Chang He , Ding Yu Cheng , Lu Bing Heng , Cai Guang Qi
Published: September 2009

Grinding processes are mainly technique employed widely as a finishing and difficult-to machine such as hardness and brittleness materials machining. However in grinding process, high grinding zone temperature may lead to thermal damage to the work surface, induces micro-cracks and tensile residual stresses at the ground surfaces, which deteriorate surface quality and integrality of the ground surface. The work presented in this paper aims at evaluating the grindability and surface integrity of the nickel base superalloy resulting from the application of cryogenic cooling. Grinding experiments were conducted under three different environments: dry, mineral oil and cryogenic cooling jet. The grindability results have shown that while the cryogenic cooling generates the lowest grinding temperature, no significant differences over the specific grinding force components were observed. As for the ground surface integrity, however, substantial improvements were realized. The novel process not only obviously enhances surface quality and integrality of grinding surface, but also enables retention of the wheel sharpness for a longer period and reduces pollution of grinding fluid to nature.
Study on an Open CNC System of 3-Axis Micro Milling Machine Tool
Authors: Huang Liang , He Ning , Li Liang
Published: September 2009

The traditional CNC system is established on conventional machine tool mainly using ball screws. This could not suitable for micro mechanical machining with linear motor which could provide high speed, high precision, fast response and zero backlash. In this paper, a 3-axis micro milling machine tool with an open CNC system has been developed based on motion controller and linear motors. Considering the requirements of micro milling several special functions just like micro cutting tool setting are provided in exploited control software. The system dynamic characteristics are evaluated through experiments with servo parameters adjustments. In the following machining experiments, the whole system is proved economically and effectively.
Cutting Forces in High Speed Milling of Hardened Steel by Coated Tool
Authors: Wu L.D. , Wang Cheng Yong , Yu D.H. , Song Yue Xian
Published: September 2009

Hardened steel P20 at 50 HRC is milled at high speed by TiN coated and TiAlN coated solid carbide straight end mills, and the cutting forces and tool wear are measured. The result shows that TiAlN coated tool is more suitable for cutting hardened steel at high speed. Then the hardened steel is milled under different cutting parameters. It is indicated that the effect of cutting speed on cutting forces is small, but the effect of cutting speed on machine vibration should be considered. Increase feed per tooth or radial depth of cut will increase the cutting forces.
Research on the Adaptive Machining Technology of Blisk
Authors: Zhang Ding Hua , Zhang Ying , Wu Bao Hai
Published: September 2009

Due to different datum position and inevitable distortion from the linear friction welding process, the nominal CAD model from the design stage is no longer suitable for the use of the final NC machining, and that is the main problem for precisely machining complex blisk. In this paper, an adaptive machining approach based on adaptive process model for high precision manufacturing of blisk is proposed and developed. Comparing the nominal model with the inspection result, adaptive process model is reconstructed to describe workpiece localization, allowance distribution and composite error compensation for NC machining of blisk accurately. Firstly, the transformation matrix for allowance optimization is searched fleetly by genetic algorithm with constraint conditions. Secondly, using the cross-section curve blending and deformation compensation method, adaptive model for shape distortion is constructed to solve the part-to-part variation machining problem and to realize precision machining for complex geometry blisk. Finally, based on the adaptive process model, tool paths used for the last NC machining process can then be adaptively generated to implement the different processes work. Example shows that the adaptive machining technology of blisk is feasible and the result is of high precision and efficiency.
Machinability Evaluation of TC11 Titanium Alloy in Finish Hard Turning Based on the Response Surface Methodology
Authors: Liu M. , Ming Wei Wei , Zhang Yun Shan , Xu H. , Chen Ming
Published: September 2009

TC11 is an α+β heat resistance titanium alloy with high strength to weight ratio, good corrosion resistance and high service temperature up to 500°C. Response Surface Methodology (RSM) is an empirical statistical modeling technique employed for multiple regression analysis using quantitative data obtained from properly designed experiments to solve multivariable equations simultaneously. In this paper, a series of experiments were carried out to evaluate the machinability of TC11 alloy based on RSM. Optimum results show feed rate at 0.05mm/r, depth of cut at 0.25mm and moderate cutting speed at 110.9m/min giving the satisfied machining quality.
Study on the Residual Stress Induced by Dry Turning of Buttress Thread
Authors: Wang X.Y. , An Qing Long , Zhang Yun Shan , Xu H. , Chen Ming
Published: September 2009

Stainless 2Cr13 is used as petroleum pipe material for its good performance in condition of high temperature, high pressure and corrosive environment. Buttress thread turning is a type of heavy machining, which has a great influence on the residual stress of workpiece. Residual stress is usually determined by cutting parameters and tool geometries. Experiments with different geometrical tools were carried out and a finite element model was used to study the influence of tool geometries on the residual stress. Experimental and simulated results showed that relatively bigger rake angle and smaller corner radius make a relatively lower tensile residual stress of workpiece surface in dry turning buttress thread.
An Improved Strategy of Automatic Triangular Mesh Generation over 3D Surface
Authors: Jia Hong , Wang Yu Huai , Lu Yan Lin
Published: September 2009

A quadratic mapping method based on curvature for mesh generation is presented in this paper. The method starts from the triangulation of 2D parametric surface by applying the Advancing Front Technique (AFT) and Delaunay Triangulation (DT) together with 3D feature information. Then 3D surface mapping from 2D elements is realized by quadratic mapping method with curvature measure information. After that, triangular mesh over 3D surface is automatically generated. Besides, graded mesh control strategy is discussed in the paper for the sake of generating mesh with higher quality. Finally, several application examples are given to show the characteristics of the presented method.
Error-Prone Business Process Study in Small and Medium Enterprises
Authors: Lu Cong Da , Zhang Y. , Jiang Shao Fei , Xu R.
Published: September 2009

A small and medium enterprise using ERP system as an example, this paper analyzes its business processes to reengine critical business processes more likely to have errors for the necessity and urgency of process reengineering. The use of AHP identifies weights of evaluation indexes determining whether the critical business processes are error-prone and using the improved flow prioritization matrix method prioritizes business processes. Select the first five business processes as the critical business processes, and choose the first two critical business processes as examples to reengine with the cause-effect analysis method.
Torque Transmission Analysis and Design of a 3-DOF Spherical Parallel Manipulator
Authors: Li Y.B. , Ji Shi Ming , Yuan Qiao Ling , Zhang Li , Jin Ming Sheng
Published: September 2009

Static analysis plays an important role on the design and applications of manipulator. In this paper, The torque balance equations of the spherical 3-DOF manipulator was derived in closed forms by analyzing the relationship of its input and output torques, then the torque transmission evaluation index and the global torque transmission evaluation index were defined based on the torque balance equation and discussed in detail, at last, by using the physical model technique, the parameters of the spherical 3-DOF manipulator were optimized based upon the global torque transmission evaluation index. Moreover, an integrated design scheme of the spherical 3-DOF manipulator was confirmed when satisfied the assembly conditions, which can provide theoretical base for the applications of the spherical 3-DOF manipulator. The spherical 3-DOF manipulator can be used as the waist, wrist and the ultra-precision machine in which the requirements for high stiffness, high accuracy and good technological efficiency.
Free-Form Surface Reconstruction Based on Interpolate Subdivision
Authors: Jin Chu Yun , Lan R. , Zhao W.Y.
Published: September 2009

The subdivision calculation method of a subdivision surface plays an important role on the precision of a surface reconstruction. This paper, with the fundamental of current research on subdivision surface, present a calculation method of recursive interpolation with general meaning based on initial triangular mesh. Optimization of selection on weighting coefficient for abnormal vertices and boundary interpolate calculation improves the modeling capacity of interpolate subdivision surface. The subdivision surface is carried out on an example of complicate free-form surface, and compared with other subdivision models through tolerance analysis.
Dynamic Numerical Simulation of Mould Free-Form Curved Surface Gasbag Polishing
Authors: Ji Shi Ming , Zhang Li , Jin Ming Sheng , Yuan Qiao Ling , Shen Ya Qi
Published: September 2009

Polishing is an important technics processing in order to obtain the high quality surface of mould in industry mould manufacture. For the moment, polishing of the free-form curved surfaces of mould is performed by manpower. So it is important to research gasbag polishing technology. This paper has been developed dynamic numerical simulation for gasbag polishing process based on the new type of polishing tools by FEM. On the material removal theory, influence of the shape of the structure of the gasbag, angular velocity and the air pressure inside the air gasbag on the campaign polishing process are explored. It can be used to provide technology support to establish polishing process database.
Design on 3D Complex Groove of Turning Inserts with MATLAB
Authors: Feng X.M. , Tan Guang Yu , Li Guan Hui , Zhang Yu Hua
Published: September 2009

The paper presented a method of designing grooves of turning insert with 3D complex groove; and deduced equation calculating the width of the grooves using condition equation of the chip breaking, the parameters included in the equation was taken place by equivalent ones. And the grooves width is computed by MATLAB, and then the curve of the groove is fitted. The width can be used to create model of the turning inserts with 3D complex groove by Pro/Engineer, and the model can be imported in ANSYS soft to simulate turning process and analysis groove performance. All this work provides a base for the groove design and optimization
Research on the Apple Non-Destructive Selection Technology Based on the Fuzzy Arithmetic
Authors: Wang Ya Liang , Ji Shi Ming , Zhang Li , Chen Yong , Zhang Y.
Published: September 2009

This paper studies mainly apples non-destructive selection technology, and presents the principle and implementation of non-destructive selection system for apple quality based on the theory of the fuzzy and neural network. Firstly, we can differentiate the kinds of apples by neural network theory. Then, the apple’s quality greatly depends on its size, shape, and color, which are considered as three input parameters in selection system. The pick-up of three character parameters is handled by computer image processing. Only one output parameter is apple rating, which is fall into three grades: A, B and C. Regarding three character parameters as input, we obtain the apple grade based on fuzzy arithmetic. Finally, we set forth the archetypal non-destructive selection system, which includes robot, AGV, conveyor, sensors and etc. Results of experiments show that this method can distinguish the apple’s quality as well as we set before the experiments, and the non-destructive system is feasible.
Narrow Beam Machining on Micro-WEDM
Authors: Chu Xu Yang , Di Shi Chun , Wei Dong Bo , Wang Zhen Long , Dong Ying Huai
Published: September 2009

This paper aims to investigate the performance of narrow beam machined by MWEDM. The narrow beam machining experiments are carried out on self-development Micro-WEDM with Φ30μm electrode wire. Narrow beams with the width around 10μm are machined on E52100 steel under different machine conditions (discharge energy, servo reference voltage). Based on the analysis of the experiments results, the coupled temperature and stress analysis using ANSYS finite element analysis software is performed to investigate causes of the failures on process.
Long Term Studies on the Impact of Thionic Bacteria on the Global Pollution of Waters with Toxic Ions
Authors: Beškoski Vladimir P. , Papić P. , Dragišić V. , Matić V. , Vrvić Miroslav M.
Published: September 2009

The biogeochemical activity of microorganisms from sulphide biogeocoenosis in the zones of sulphide copper ores deposits in East Serbia has been studied by us since 1975. All deposits of copper mineralization were dominantly sulphides and arsenic sulphides with the constant presence of pyrite.
The obtained results proved that the biochemical and chemical activity of thionic bacteria have an influence on the global pollution of waters. All the waters were characterized by a low pH value and by high Eh values, mineralization (over 7 gL-1) and in total iron (even more than 4 gL-1) dominantly as Fe3+ ions. These waters were characterized by toxic concentrations of copper ions, within the limits from about 2 to almost 200 mgL-1 and arsenic, up to more than 4 mgL-1. These waters partly arrive in an aquifer and the major part flows into surface water¬ courses gravitating towards the Danube River, which empties into the Black Sea. In a hypothetical case, if maximum concentrations of copper and arsenic and maximum capacity of the springs are considered, under the assumption that the pollutants do not precipitate on the way to the main recipient, the striking information is obtained that the Danube River receives about 31 t of copper and more than 0.6 t of arsenic per annum from one place alone, which undoubtedly points to the contribution of thionic bacteria as "biological agents" to global pollution of surface and ground waters.
Isolation of Novel Iron-Oxidizing Bacteria from an Acid Mine Water Treatment Plant
Authors: Hedrich Sabrina , Heinzel Elke , Seifert Jana , Schlömann Michael
Published: September 2009

The capacity of a microbiological mine water treatment plant may to be enhanced by understanding the microbiological processes. Therefore different samples from the pilot plant were analyzed by culture-independent and cultivation methods. Dominant bacteria could be isolated on overlay plates or enriched in gradient cultures. To immobilize biomass in the pilot plant, various carrier materials were tested. Sessil, the material currently used in the pilot plant, was the most favored and appropriate material.
Diversity of Culturable Bacteria in an Alkaliphilic Sulfur-Oxidizing Microbial Consortium
Authors: Granada C. , Revah S. , Le Borgne Sylvie
Published: September 2009

Alkaliphilic sulfur-oxidizing bacteria were isolated from an alkaliphilic microbial consortium used to treat H2S at pH>9 in a laboratory scale biofilter. Nineteen isolates were obtained. These isolates could be grouped based on their colonial morphology on a solid medium containing thiosulfate as sole energy source. Half of the isolates presented yellow colonies (group I). This yellowish colonial morphology is typically found in the genus Thioalkalivibrio. For the rest of the isolates, the colonies were white (group II) or transparent (group III). The isolates of each group were characterized by ribosomal intergenic spacer analysis and restriction analysis of their 16S rRNA genes. One of the yellow isolates presented 85% of homology with Thioalkalivibrio jannaschii by partial sequencing of its 16S rRNA gene. The genus Thioalkalivibrio comprises extremely haloalkaliphilic sulfur-oxidizing bacteria that have been proposed as suitable biocatalysts for natural gas desulfurization.
C-di-GMP Pathway in Biomining Bacteria
Authors: Castro M. , Ruíz Lina María , Barriga A. , Jerez Carlos A. , Holmes David S. , Guiliani Nicolas
Published: September 2009

Acidithiobacillus ferrooxidans, A. thiooxidans, and A. caldus are acidophilic Gram-negative -proteobacteria involved in the bioleaching of metal sulfides. Bacterial attachment to mineral surface and biofilm development play a pivotal role in this process. Therefore, the understanding of biofilm formation has relevance to the design of biological strategies to improve the efficiency of bioleaching processes. For this reason, our laboratory is focused on the characterization of the molecular mechanisms involved in biofilm formation in biomining bacteria. In many bacteria, the intracellular level of c-di-GMP molecules regulates the transition from the motile planktonic state to sessile community-based behaviors, such as biofilm development. Thus, we recently started the study of c-di-GMP pathway in biomining bacteria. C-di-GMP molecules are synthesized by diguanylate cyclases (DGCs) and degraded by phosphodiesterases (PDEs). So far, two kinds of effectors have been identified, including three protein families (pilZ, PleD and FleQ) and a conserved RNA domain (GEMM) which acts as a riboswitch. We previously reported the existence of different molecular players involved in c-di-GMP pathway in A. ferrooxidans ATCC 23270. Here, we expanded our work to other Acidithioibacillus species: A. thiooxidans ATCC 19377 and A. caldus ATCC 51756. In both, we identified several putative-ORFs encoding DGC, PDE and effector proteins. By using total RNA extracted from A. ferrooxidans and A. caldus cells in RT-PCR and qPCR experiments, we demonstrated that these genes are expressed. In addition, we characterized the presence of c-di-GMP in A. ferrooxidans ATCC 23270 and A. caldus ATCC 51756 cell extracts. Taken together, these results strongly suggest that A. ferrooxidans, A. caldus and A. thiooxidans possess functional c-di-GMP pathways. As it occurs in other Gram-negative bacteria, this pathway should be involved in the regulation of the planktonic/biofilm switch. In the future, we have to integrate this new biological dimension to improve the biological understanding of bioleaching.
Normalization of Quantitative Real-Time PCR Data of Identified Genes from an Industrial Bioleaching Operation
Authors: Olmos L. , Muñoz M. , Galleguillos F. , Remonsellez Francisco , Serón M. , Meneses Claudio , Demergasso Cecilia
Published: September 2009

A strategy for the monitoring and control of genetic expression in an industrial bioleaching process of copper sulphide minerals is developed in order to understand more fully this process and investigate optimization possibilities. The aim of this research is to find a group of housekeeping genes to normalize the genetic expression data associated to the metabolic functions from industrial bioleaching samples obtained through specific real-time PCR. The data includes the quantification of the previously identified genes in the industrial process in samples from different strips (heap sections) and times. Two studies were carried out, one with the gene expression data associated to each species and the other with the expression data from all the genes detected in the industrial process, during a period of 18 months, using the VBA applet geNorm [1]. The first analysis showed that for the archaea Ferroplasma acidiphilum, the gene with the most stable expression codifies to the ribosomal protein S4 (rpS4) and secondly the mercury reductase gene (merA). In the case of Acidithiobacillus ferrooxidans DM and D2 strains, genes merA and pyruvate dehydrogenase (pdhA) presented similar factors of stability. In the community analysis it was concluded that the gene with the most stable expression was pdhA of A.ferrooxidans. A new analysis was done including other genes using geNorm to define the most stable genes for the whole community. In the community analysis it was concluded that the gene with the most stable expression was pdhA of A.ferrooxidans and merA of F.acidiphilum.
Understanding and Modelling of Interactions in Bioleach Processes
Authors: Petersen Jochen
Published: September 2009

This paper gives a brief introduction to the modelling of bioleach processes developed from a careful analysis of the fundamental process steps at the gas-liquid, biological and mineral interfaces and how these interact in a given reactor environment (tanks and heaps). The insights gained from modelling work can guide both engineers in the optimisation of processes and scientist in directing their research at areas not yet well understood. Some perspectives of future directions of the bioleaching field are offered.
Effect of Sulfuric Acid Concentration on Chalcopyrite Concentrate Chemical Leaching
Authors: Joe Seong Jin , Chida Tadashi , Sakoda Masatoshi , Nakamura Hidekatsu , Tamura Muneyuki , Sato N.
Published: September 2009

This study reports the effect of sulfuric acid concentration on chalcopyrite chemical leaching in very simple H2SO4 solution systems ranging from 23g/L to 30g/L, with 2.5% chalcopyrite concentrate at 30°C. Copper extraction from chalcopyrite increases with an increase in sulfuric acid concentration, e.g. 86%, 90% and 92% after 96 days at 23g/L, 25/L and 27g/L H2SO4 solution respectively. Sulfur element formed on the surface of chalcopyrite was very porous as the result of an electron probe microanalyzer (EPMA). Copper extraction, however, leveled out at 35% after 20 days when the sulfuric acid concentration was higher than 28g/L on 25g/L of chalcopyrite concentrate. Sulfur element was detected by X-ray analysis as only a leaching reaction product. The passivation may be caused by thick elemental surface formed on the surface of chalcopyrite.
Respirometry Studies of the Bioleaching of a Copper Ore in a Large Isothermal Column
Authors: Petersen Jochen , Minnaar Sanet H. , du Plessis Chris A.
Published: September 2009

During large-scale column tests at BHP Billiton’s Johannesburg Technology Centre (JTC) during 2005/6 on a low-grade copper ore, the concentrations of both oxygen and CO2 were continuously monitored in feed and exit gas as well as at various intermediate positions over the height of the column. This paper describes results from a test run at 40 °C fed with an air stream enriched to between 1000 and 2000 ppm CO2. Oxygen consumption very closely tracks iron and copper leaching. CO2 is consumed rapidly from the bottom up, resulting in significant depletion midway through the column, even though an enriched feed was used. Oxidation rates decline in CO2 depleted zones, but were not observed to cease completely. This rate of decline is postulated to be linked to a slowly decaying population unable to regenerate itself.
Comparison between O2 and CO2 consumption rates shows a linear correlation beyond a minimum oxidation rate. This minimum rate corresponds to a non-growth maintenance energy requirement, and the slope of the linear correlation to the growth yield. Both are functions of available CO2 in the range 50 to 1000 ppm, with maintenance declining and yield increasing.
The findings of this study imply that CO2 supplementation in bioheaps will stimulate microbial growth and CO2 consumption, but not necessarily increase the rate of oxygen uptake and hence leaching. Absence of CO2 is expected to result in gradual population decline, but a degree of oxidation continues on the basis of maintenance. In tall heaps CO2 depletion with height is likely and may therefore result in impaired leaching in the upper zones.
Thermodynamic Modelling of Iron Solubility in Sulphide Mineral Leaching
Authors: Nurmi Pauliina , Ahonen Lasse , Tuovinen Olli H.
Published: September 2009

In this study the effects of pH and temperature on iron solubility were predicted using the geochemical modelling code PHREEQC and the thermodynamic database WATEQ4F. The modelling results demonstrated that the solubility of secondary solid phases formed under acid bioleaching conditions decreases with increasing temperature and also with increasing pH. Modelling calculations showed that bioleaching solutions are typically supersaturated with respect to K-, Na-, NH4-, and H3O-jarosites and the precipitates are typically solid solutions containing their mixtures. Jarosite solubility modelling results were also compared with a data set from jarosite synthesis experiments. Model-derived temperature dependence of hydronium-jarosite correlated very well with the actual experimental data.
Oxidative Capacity of Native Strains from Copahue Geothermal System in the Pretreatment of a Gold Sulfide Ore
Authors: Giaveno Alejandra , Chiacchiarini P. , Cordero Cintia , Lavalle L. , Huergo J. , Donati Edgardo R.
Published: September 2009

In this report we evaluate the oxidative capacity of native microorganisms from Copahue geothermal system applied to a gold concentrate (71.1 g/t) compared to that showed by some culture collection strains. The sulphide ore, in which gold is present as submicroscopic particles contained in a pyrite matrix, came from several reservoirs of polymetallic ores located in Neuquén, Patagonia Argentina. The ore was processed in Andacollo treatment plant for gold concentration. After biooxidation tests, the highest percentages of solubilised iron were reached in the inoculated system (100% mixed native cultures, 47.8% Leptospirillum ferrooxidans ATCC 29047 and 28.5% for Acidithiobacillus ferrooxidans DSM 11477) while in the sterile control it was only 8.8%. The gold recovery was 96.3% and 45.3% for the treated and untreated concentrate respectively.
Biooxidation of Refractory Gold Sulfide Concentrate of Olympiada Deposit
Authors: Sovmen V.K. , Belyi Alexander V. , Danneker M.Yu. , Gish A.A. , Teleutov A.N.
Published: September 2009

Results of research on technological processes for treatment of refractory gold-arsenic ores using bioleaching of concentrates are presented. In October 2001 the first line of bioreactors on Mill-2 began operation with projected throughput of 3 million tons a year. In July 2007 Mill-3 began operation with projected throughput of 5 million tons a year. At present the closed joint stock company Gold Mining Company «Polyus» occupies a leading position in gold extraction from hard rocks in the Russian Federation. Processing of refractory gold-arsenic ores is conducted on Mill-2 and Mill-3 by a flotation-cyanide scheme using a unique biooxidation technology, BIONORD®, designed to process concentrates in the extreme climatic conditions of the North, . The achieved productivity of the Olympiada Mining Combine, from the processing of both oxidized and refractory ores of the Olympiada deposit, is 26.7 tons of gold a year. The gold is mostly present as finely dispersed and submicroscopic particles in close association with sulfide minerals, usually pyrite, pyrrhotite, arsenopyrite and antimonite. The average productivity of the lines is 1000 t/day. The process time is 100-150 h. The pulp density is 150-200 g/l. The working temperature is 39-40oC. The microbial association is represented by three species of chemolithotrophs: “Sulfobacillus olympiadicus”, Leptospirillum ferrooxidans, and Ferroplasma acidiphilum present in proportions 60-80%, 10-20%, and 10-17%, respectively. During the process 87% of sulfide minerals are oxidized. Thus, 98% of the pyrrhotite, 95.4% of the arsenopyrite, 70% of the antimony sulfides and 60% of the pyrite is oxidised. Biooxidation enables 97% of the gold to be released.
Improvement in Metal Recovery from Laterite Tailings by Bioleaching
Authors: Hernández Díaz Ianeya , Galizia Federico , Coto Orquidea , Donati Edgardo R.
Published: September 2009

In previous studies it has been showed that sulphuric bio-acid is a good leaching agent for laterite tailings. In this work we evaluated nickel and cobalt recoveries from tailings of Caron technology process using sulphuric acid produced by Acidithiobacillus thiooxidans cultures under different conditions. In studies where tailings were initially added to the cultures, high nickel and cobalt recoveries (about 60 % for cobalt and 85-100 % for nickel) were reached after 13 days when low pulp densities (1 % and 2.5 %) of laterite tailings were used. These high recoveries fitted very well with the low pH values measured in these cultures. However, metal recoveries were negligible when higher pulp densities were used. Due to such reason, the performance of pre-cultivation configuration was evaluated; for that laterite tailings were added to the cultures after 24 or 48 hours of bacterial growth. This configuration was very efficient even at high pulp density (like 10 %) reaching recoveries (almost 50 % for cobalt and 80 % for nickel) close to those observed where tailings at low pulp densities were initially added to the cultures.
Acidithiobacillus Played Important Role in Zijinshan Commercial Low-Grade Copper Bioleaching Heap
Authors: Liu X. , Chen Bo Wei , Wen Jian Kang
Published: September 2009

The distribution and diversity of acidophilic microbe at the ore surface of Zijinshan commercial low-grade copper bioleaching heap operated at pH 0.8 were investigated. Samples taken from -1m, -2 m, -3m from the top of heap surface were investigated by 16S rRNA gene clone library. Phylogenetic analyses of 16S rRNA fragments revealed that the retrieved bacterial sequences mainly related to genus Acidithiobacillus (64.6%), genus Leptospirillum (27.3%), genus Sulfobacillus (3.1%) and genus Ferrimicrobium(1.6%). For archaea, only Ferroplasma acidiphilum was detected. Bacterial diversity in the heap was increased from surface layer to underground. The proportion of genus Leptospirillum was sharply reduced (from 48.5% to 5%) from higher depth to lower depth and reverse correlation of increased A.ferrooxidans (from 0.9% to 15%) and S. thermotolerans (from undetectable to 7%) were found in the heap. Sulfur oxidizers including A.albertensis, A.caldus and A.thiooxidans also vertically increased from higher depth to lower depth (from 50.5% to 80%). These results indicated that genus Acidithiobacillus especially sulfur oxidizers A.albertensis, A.caldus and A.thiooxidans may play very important roles in the commercial low-grade copper bioleaching heap.
Aerobic Reduction of Uranium(VI) by Acidithiobacillus Thiooxidans Cultures
Authors: Gargarello R.M. , Di Gregorio D. , Huck H. , Fernandez Niello J. , Curutchet G.
Published: September 2009

Acidithiobacillus thiooxidans was grown in the presence of uranium and its redox processes were studied in aerobic conditions for the first time. Results so far obtained may suggest an indirect uranium reduction, mediated by metabolically produced reducing compounds.
Comparison of Differently Remediated Hard Coal Overburden and Tailings Dumps: Conclusions a few Decades after Remediation
Authors: Willscher Sabine , Hertwig Thomas , Frenzel M. , Felix Manfred
Published: September 2009

. The historical hard coal mining area of the districts of Zwickau and Lugau/ Oelsnitz in Saxonia (Germany) is a source of heavy metals and arsenic polluting the adjacent ground- and surface waters. Heavy metals and metalloids like Zn, Cd, Ni, Co, As and Mn are transported, partially as fine precipitates, to the adjacent river Zwickauer Mulde and with that to the river Elbe. Some of the dumps are partially older than 150 years, and some of them were remediated more than 50 years ago. Today we still can learn from the more or less successful remediation measures after some decades of application. In this paper, three different dumps are presented and differences between their remediation measures and the long-term success of it shall be pointed out. As a result, especially a sealing and covering of a dump turned out as very successful for the prevention of AMD generation. A further utilization of such a remediated and revegetated area is possible, or it can be “given back” to the nature. In contrast, a revegetation without covering results in a long-term AMD-generation of such a mining dump site.
Bioremediation of a Cyanide-Contaminated Site Using EH-/PH-Controlled Conditions (ENA)
Authors: Harborth P. , Thieme M. , Fricke K.
Published: September 2009

In the course of remedial investigations for a former gasworks site, high cyanide pollution of the soil (74.6 - 101.7 mg/kgDS total cyanide) and of the groundwater (3,840 µg/l total cyanide /approx. 300 µg/l free cyanides) were particularly problematic. Extensive investigations in the laboratory as well as in field studies finally resulted in a 2-step oxic/anoxic concept. Both the free cyanides as well as the complex bound cyanides could be biodegraded at more than 90% through a combination of H2O2-treatment (ISCO) and denitrification by in situ conditions. Furthermore a destruction of the iron cyanide complexes under fermentative conditions could be observed for the first time.
Photothermal Techniques for Materials Characterization and Live Cells Monitoring
Authors: Chen George C.K. , Vasudevan Srivathsan , Kiat Teu Choon
Published: September 2009

Photothermal technology can be applied for thermal characterization of thin films and studying biological live cells. Using pulsed photothermal reflectance technique, thermal conductivity of thin films ranging from 20 nm to a few microns can be determined. Photothermal imaging (PTI) technique can provide ultra high spatial resolution and no fluorescence molecules are required. Comparison with normal phase contrast images, PT images reveal temperature distribution and more information on the intracellular components. Photothermal response (PTR) technique can provide high temporal resolutions. In monitoring the dying process of MDCK cells, significant changes in the PTR signals can be observed whereas unnoticeable changes are found in the images.
Plasmonics NanoSensor
Authors: Khoo E.H. , Bai Ping , Gu M.X. , Chu H.S. , Ewe W.B. , Ahmed I. , Li E.P.
Published: September 2009

This paper presents a number of plasmonics based nanosensors that is currently being investigated in IHPC. In the first case, the influence of external magnetic field and electron on the field distribution of active semiconductor microcavity with elliptical shape is studied. It is observed that high amount of electron pumped into the elliptical microcavity demonstrate the plasmonics field distribution, which can be used to sense the change in wavelength and electron/holes densities. The second case will discuss about using plasmonics to enhance the electromagnetic wave from metallic waveguide slot. The enhancement is more than 100 times and this is important for the generation of electron-holes pair in PIN based photo-detector. The third case will discuss using the metallic nanowire to sense different surrounding materials. The small differences in the refractive index of the surrounding materials show the different plasmonics resonance frequencies.
High Accuracy Pressure Sensor Based on Optical MEMS Technology
Authors: Zhang Wu , Tao Ji Fang , Zhu Wei Ming , Liu Ai Qun
Published: September 2009

The optical sensor achieves its sense function generally by measuring the change of intensity or the phase of the light beams. Compared to conventional sensor types, the optical sensor enjoys the advantages such as great sensitivity, wide dynamic sense range and multiplexing capabilities. In recent years, MEMS technology is widely used on the design of optical sensor due to the small feature of MEMS, which could be high sensitive with tiny change of the detected objective.

In this paper, instead of observing the change of intensity and phase, the author studied how the shift of wavelength spectrum can be utilized to sense the physical change of the object such as the pressure, vibration, velocity and electrical field. The author designed and simulated a FP-resonator-like structure which consists of 2 resonant cavities with 2 multi-layer mirrors located on two ends and 1 multi-layer mirror in the middle of the two cavities. The mirror in the middle is movable by physical pressure. In the simulation, it was found that this structure is able to have certain wavelength light resonate inside the cavities. The resonant mode will shift 1nm when the mirror in the center moves forward/backward for every 14nm, which is sensitive enough to detect the small change of the objectives.
A Wideband Electromagnetic Energy Harvester for Random Vibration Sources
Authors: Yang Bin , Lee Cheng Kuo
Published: September 2009

A novel non-resonant energy harveser with wide band frequency is proposed for collecting energy from ambient vibration at low frequency. A free-standing magnet is packaged inside a sealed hole which is created by stacking 5 pieces of printed circuit board (PCB) substrates with multi-layer copper coils made on double-sides. When the energy harvester is shook from 10 to 300 Hz at 1.9g acceleration along longitudinal direction of hole, a 65 Hz flat-band-like output voltage of 4.5 mV at the case of only one side with drilled air holes on acrylic plate is generated within 35 to 100 Hz. The output power from the coils is measured as 0.1µW under matched loading resistance of 50 Ω within this flat band range under 1.9 g ambient vibration.
Manufacturing Issues and Considerations in Thermal Bonding of Polymer Based Lab-on-a-Chip
Authors: Koh Yu Xin , Ng Sum Huan , May Khin Thet , Chan Cong Zhi , Wang Zhi Ping
Published: September 2009

The sealing of microchannels is a key step in the fabrication of microfluidic devices and thermal bonding is a common technique used. Here, major manufacturing issues and considerations in thermal bonding are investigated, including bonding quality and microchannel deformations. Flatness of substrate is extremely crucial to the uniformity in bonding. While increased bonding pressure helps to overcome problems related to surface topography and to enhance bond strength, its significant impact on geometrical changes of microchannel due to viscoelastic effect should also be taken into consideration.