bluuebunny/crossref_metadata_2025 huggingface dataset:
Retrospective Study of Suicide Among Children and Young Adults
Authors: Mishra Navin , Shrestha Devendra , Poudyal Rakesh Babu , Mishra Pravin
Published: October 2013

Introduction: The prevalence of suicide has been increasing globally in all age groups. There is dearth of literature on suicide among younger patients from developing country. The objective of this study was to find out the prevalence and cause of suicide as well as to identify the vulnerable groups of children and young adults to suicide. Materials and Methods: This is a retrospective observational study. Data was collected from the Police Head Quarters in Kathmandu and included all completed suicide cases of less than twenty one years of age from January 2005 to December 2009. Results: There were a total of 2172 documented cases of completed suicide in the age group between 4 to 21 years. The majority were female and belonged to the adolescent age group. The incidence of suicide showed an increasing trend within the five years of the study. A monthly breakdown of the cases revealed that the incidence of suicide was lowest in January and February and peaked from April to October. Hanging was the most common mode of suicide followed by poisoning and drowning. The reason for suicide could be ascertained only among 25.5 % of cases. Domestic violence (35%), mental illness (24%), failure in academic achievement (15.8%) and end of a romantic relationship (8.7%) were found to be common causes of committing suicide. Of the 87 cases found who committed suicide because of academic failure 46.6% were at a grade ten level. Conclusions: Suicide in children and young adults in Nepal appears to be a concealed but serious problem requiring immediate attention and systematic efforts. DOI: http://dx.doi.org/10.3126/jnps.v33i2.7512   J Nepal Paediatr Soc. 2013; 33(2):110-116
Coffin-Siris Syndrome in Two Sisters in Nepal
Authors: Ojha Anil , Fong Chin-To , Pandey Arti Sharma
Published: October 2013

Coffin-Siris syndrome (CSS) has the characteristic feature of brachydactyly of the fifth digit of hands and feet accompanying cognitive and developmental delay. There is an overlap of symptoms with other conditions making the diagnosis of CSS difficult. An algorithm to look for a set of characters was followed for diagnosis of CSS in two sisters in Nepal. This is the first case of CSS reported from this country. DOI: http://dx.doi.org/10.3126/jnps.v33i2.8079 J Nepal Paediatr Soc. 2013; 33(2):132-135
In Vitro Estimation of Lead Content in Nepalese Traditional Ayurvedic Medicines Commonly Used in Children
Authors: Ojha Anil
Published: October 2013

Introduction: Ayurvedic remedies are popularly used in practice for long time in Nepal. It is regarded as safe and free from side effects. However there are published reports of the high content of heavy metals like lead in such preparations. No such study has been done in Nepal looking at the lead content in ayurvedic preparations. The aim of this study was to detect the level of lead in commonly used ayurvedic remedies used in paediatric population if any. Materials and Methods: Seventeen samples were selected for lead estimation based on frequency of prescription and over the counter dispense. All of them were analyzed using Atomic Absorption Spectrophotometer (AAS) 6300 using flame mode. Results: None of the samples had detectable level of lead in parts per billion. Conclusion: Though this study did not detect lead in the seventeen samples of ayurvedic medicine, a larger study is needed involving large samples of these medicines with use of more sensitive equipment for testing. DOI: http://dx.doi.org/10.3126/jnps.v33i2.8314   J Nepal Paediatr Soc. 2013; 33(2):103-105
“May everybody witness the Global Peace.”
Authors: Chief Editor In
Published: October 2013

Nepalese Journal of Radiology / Vol.3 / No.1 / Issue 4 / Jan-June, 2013 / i DOI: http://dx.doi.org/10.3126/njr.v3i1.8711
Comparative Study of Sonourethrography and Radiographic Urethrogaphy in Urethral Lesions
Authors: Rauniyar RK , Agrawal CS , Gupta MK , Ahmad K , Gupta A , Baboo S
Published: October 2013

Background: The radiographic urethrography is an invasive , time consuming procedure and due to risk of radiation exposure can’t be repeated when required, further it has failed to demonstrate periurethral abnormality as a cause of urethral lesion. Where as sonourethrography is a noninvasive, painless, cheap, quick, easy to perform and without radiation exposure and provide detail visualization of mucosal and periurethral soft tissue. Objectives: To establish the accuracy of sonourethrography in detecting urethral lesions. Materials and Methods: Study was conducted as single blind prospective study to compare the radiographic urethrography (RGU/MCU) and sonourethragraphy and to established their role and accuracy in evaluation of urethral abnormalities. The findings and results of radiographic urethrography and sonourethrography were correlated and considering radiographic urethrography as gold standard, accuracy of sonourethrography in diagnosis of urethral lesions were analyzed. Result: Total of 27 patients were included in the study. RGU showed normal anterior (penile and bulbar) urethra in 12 out of 27 cases while among these only 9 were normal on sonourethrography. The length of stricture measured on sonourethrography was slightly more than as measured on RGU. Periurethral causes for urethral abnormality were completely identified on sonourethrography while they were not identified on RGU. Conclusion: Radiographic urethrography though gold standard in evaluating urethral abnormalities, sonourethrography is equally accurate (sensitivity 100%) in the diagnosis of urethral lesions. Sonourethrography has advantage in better evaluating mucosal and periurethral abnormalities as cause of urethral lesions. Further sonourethrography is more accurate in measurement of stricture length and it is cheap, safe and does not provide any kind of radiation to the patients in gonad areas. Nepalese Journal of Radiology / Vol.3 / No.1 / Issue 4 / Jan-June, 2013 / 33-39 DOI: http://dx.doi.org/10.3126/njr.v3i1.8714
Largest Abdominal CSF Pseudocyst – An Uncommon Complication of VP Shunt
Authors: Lukhi Hiteshkumar D , Singh M , Chakravarthy S , Perwez N
Published: October 2013

Abdominal cerebrospinal fluid (CSF) pseudocyst is an unusual and important complication in patients with ventriculoperitoneal (VP) shunt. A 36yrs old male referred to the Department of Radiology for USG abdomen with complaints of gradually increasing distension of abdomen and provisional diagnosis of Alcoholic liver disease. Successive radiological investigations lead to diagnosis of malfunctioning VP shunt, secondary to abdominal CSF pseudocyst formation. Due to lack of suspiciousness patient had developed a giant abdominal CSF pseudocyst, size of which has not been reported in any literature so far. Hence, initial suspicion with appropriate investigation and early treatment can prevent morbidity and mortality. Nepalese Journal of Radiology / Vol.3 / No.1 / Issue 4 / Jan-June, 2013 / 89-90 DOI: http://dx.doi.org/10.3126/njr.v3i1.8820
Analogue Realization of Fractional-Order Dynamical Systems
Authors: Dorčák Ľubomír , Valsa Juraj , Gonzalez Emmanuel , Terpák Ján , Petráš Ivo , Pivka Ladislav
Published: October 2013

As it results from many research works, the majority of real dynamical objects are fractional-order systems, although in some types of systems the order is very close to integer order. Application of fractional-order models is more adequate for the description and analysis of real dynamical systems than integer-order models, because their total entropy is greater than in integer-order models with the same number of parameters. A great deal of modern methods for investigation, monitoring and control of the dynamical processes in different areas utilize approaches based upon modeling of these processes using not only mathematical models, but also physical models. This paper is devoted to the design and analogue electronic realization of the fractional-order model of a fractional-order system, e.g., of the controlled object and/or controller, whose mathematical model is a fractional-order differential equation. The electronic realization is based on fractional-order differentiator and integrator where operational amplifiers are connected with appropriate impedance, with so called Fractional Order Element or Constant Phase Element. Presented network model approximates quite well the properties of the ideal fractional-order system compared with e.g., domino ladder networks. Along with the mathematical description, circuit diagrams and design procedure, simulation and measured results are also presented.
Routes to rupture and folding of graphene on rough 6H-SiC(0001) and their identification
Authors: Temmen M , Ochedowski O , Bussmann B Kleine , Schleberger M , Reichling M , Bollmann T R J
Published: October 2013

Twisted few layer graphene (FLG) is highly attractive from an application point of view, due to its extraordinary electronic properties. In order to study its properties, we demonstrate and discuss three different routes to in situ create and identify (twisted) FLG. Single layer graphene (SLG) sheets mechanically exfoliated under ambient conditions on 6H-SiC(0001) are modified by (i) swift heavy ion (SHI) irradiation, (ii) by a force microscope tip and (iii) by severe heating. The resulting surface topography and the surface potential are investigated with non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM). SHI irradiation results in rupture of the SLG sheets, thereby creating foldings and bilayer graphene (BLG). Applying the other modification methods creates enlarged (twisted) graphene foldings that show rupture along preferential edges of zigzag and armchair type. Peeling at a folding over an edge different from a low index crystallographic direction can result in twisted BLG, showing a similar height as Bernal (or AA-stacked) BLG in NC-AFM images. The rotational stacking can be identified by a significant contrast in the local contact potential difference (LCPD) measured by KPFM.
Towards Personal, Social, and Urban Awareness
Authors: Guo Bin , Liang Yunji , Wang Zhu , Yu Zhiwen , Zhang Daqing , Zhou Xingshe
Published: October 2013

In the past decades, numerous research efforts have been made to model and extract the contexts of users in pervasive computing environments. The recent explosion of sensor-equipped mobile phone market and the phenomenal growth of geo-tagged data (Twitter messages, Foursquare check-ins, etc.) have enabled the analysis of new dimensions of contexts that involve the social and urban context. The technology trend towards pervasive sensing and large-scale social and community computing is making “Social and Community Intelligence (SCI)” a new research area that aims at investigating individual/group behavior patterns, community and urban dynamics based on the “digital footprints.” It is believed that the SCI technology has the potential to revolutionize the field of context-aware computing. The aim of this chapter is to identify this emerging research area, present the research background, define the general system framework, characterize its unique properties, discuss the open research challenges, and present this emerging research field.
Efficient Forwarding With Power Saving and Load Balancing In Wireless Sensor Networks
Authors: Idoudi Hanen
Published: October 2013

Energy efficiency is still a challenging issue in wireless sensor networks (WSNs). Balancing nodes’ activities and duty cycling are efficient ways that could enhance WSN’s performances. In this paper the authors introduce a new asynchronous power saving mechanism that provides an adaptive duty cycle and a minimum overhead to achieve load balancing and energy saving. This mechanism relies on two basic functions: an asynchronous duty cycling for activity balancing and a lightweight geographic routing. Extensive simulations showed the effectiveness of the proposed approach in terms of residual energy, energy consumption balancing and packet delivery ratio.
Learning Concept Drift Using Adaptive Training Set Formation Strategy
Authors: Hewahi Nabil M. , Kohail Sarah N.
Published: October 2013

We live in a dynamic world, where changes are a part of everyday life. When there is a shift in data, the classification or prediction models need to be adaptive to the changes. In data mining the phenomenon of change in data distribution over time is known as concept drift. In this research, the authors propose an adaptive supervised learning with delayed labeling methodology. As a part of this methodology, the atuhors introduce Adaptive Training Set Formation for Delayed Labeling Algorithm (SFDL), which is based on selective training set formation. Our proposed solution is considered as the first systematic training set formation approach which takes into account delayed labeling problem. It can be used with any base classifier without the need to change the implementation or setting of this classifier. The authors test their algorithm implementation using synthetic and real dataset from various domains which might have different drift types (sudden, gradual, incremental recurrences) with different speed of change. The experimental results confirm improvement in classification accuracy as compared to ordinary classifier for all drift types. The authors’ approach is able to increase the classifications accuracy with 20% in average and 56% in the best cases of our experimentations and it has not been worse than the ordinary classifiers in any case. Finally a comparison with other four related methods to deal with changing in user interest over time and handle recurrence drift is performed. These methods are simple incremental method, time window approach with different window size, instance weighting method and conceptual clustering and prediction framework (CCP). Results indicate the effectiveness of the proposed method over other methods in terms of classification accuracy.
Study on Hypereutectic Al-Si Alloy Fabricated by Liquid-Liquid Mixing
Authors: Li Yuan Dong , Hu Shao Hua , Li Xia , He Ming Tao , Ma Ying , Apelian Diran
Published: October 2013

The hypereutectic Al-20%Si alloy was fabricated by liquid-liquid mixing of Controlled Diffusion Solidification (CDS), and the mixing interface of two precursor alloys as well as the effects of pouring temperature during liquid-liquid mixing process on microstructure of size, morphology and distribution of primary silicon were studied. The results show that the size of primary phase decreases as the pouring temperature decreases, and the distribution of primary phase becomes uniform, but the morphology changes unobvious. Meanwhile, the liquid-liquid mixing interface is divided into four areas: low temperature alloy area, interface front area, fine grain area and high temperature alloy area.
Research on Hot Ductility Behavior of 800 MPa Grade Ultra High Strength Weathering Steel
Authors: Huang Chao Bin , Zhu Yan , Wu Ru Yi , Li Qing Shan , Zhang Mei , Zhong Yong , Li Lin
Published: October 2013

The hot ductility behavior of test steel was investigated by Gleeble-3500 thermo-mechanical simulator through high temperature tensile test. The reduction in area (RA) and tensile strength (TS) were acquired to draw hot ductility curve and hot strength curve. SEM fractograph and microstructure of the tensile samples were analyzed. The results show that the third brittle zone of test steel is between 700°C and 800°C and the occurrence of the third brittle zone is mainly related to the formation of film-like ferrite along the prior austenite grain boundary and the precipitation of second phase. Moreover, the drop of hot ductility at 900°C is rooted in the reduction of grain boundary strength owing to the precipitation of sulfides. Therefore, it is advised that the straightening temperature of test steel should be kept over 900°C.
Numerical Simulation and Experimental Research on the Deformation of Equal Channel Angular Pressing of Al-5Ti-1B Aluminum Alloy
Authors: Zhang Wen Yu , Liu Xian Lan , Jin Xiao Ming
Published: October 2013

The effective strain size and distribution of Al-5Ti-1B alloy deformed by equal channel angular pressing (ECAP) were investigated through the finite element simulation by the die with outer corner ψ=0°, 20°, 30° and the friction coefficient f=0, 0.2, 0.3. The simulation results show that the effective strains decrease with the increase of the outer corner ψ from 0° to 30° with a constant f; the more uniform deformation were obtained under the conditions of large friction than that of small friction. Al-5Ti-1B alloy was produced by once path ECAP at room temperature under the die with the corner angle φ=90° and ψ=20°. The optical microscope and compressing test machine were performed. The results indicate that the grain size was obviously refined. The yield strength increased by 37.5% from 142.0MPa to 195.3MPa, and hardness increased by 24% from 45.2HV to 55.9 HV.
Corn-Rice Powder Extrusion Key Parameters in Twin-Screw Extrusion Process
Authors: Li Xiao Ping , Zhang Zhi Sen , Xiao Hui Jin , Zeng Qiang , Zhang Xiao An
Published: October 2013

To find the inner relations of extrusion key parameters, 2-factor and 3-level orthogonal experiments are carried out on the twin-screw extruder with the corn-rice powder as the materials. The factors are: screw rate and feed rate; the indices are: inner pressure, die outlet temperature and generator current. The results are analyzed by single index regression method, the results show that the screw rate has the significant influence on the variables of barrel inner pressure, die outlet temperature and generator current, while the feed rate only impact significantly on the barrel inner pressure and generator current. After the response analysis of the original variables, the desired experimental conditions are obtained. The parameters should be: screw rate=150rpm, feed rate=14rpm.
Synthesis and Characterization of Novel Polyfluorene Derivatives
Authors: Zhou Li Di , Hu Xiao Dan , Wang Shao Hong , Hou Zhao Xia , Wang Mei Han
Published: October 2013

A novel series of copolymers containing fluorene units are synthesized by Sonogashira coupling reaction in mild condition. Benzene, naphthalene and anthracene are co-polymerized with ethynylfluorene, respectively. The structures are confirmed by NMR, Mass, Elemental analysis and GPC. The polymers have good thermal properties with glass-transition temperature of 90-155°C(Tg), and they have bandgaps from 2.21-2.77 eV. The results of photoluminescence in solid state show that introduction of huge chromophore could effectively suppress the formation of aggregates and excimers which typically cause red-shifted or new emission.
New Opportunities in Lead Selenide Nanolayers
Authors: Pashaev Arif M. , Davarashvili Omar I. , Enukashvili Megi I. , Akhvlediani Zaira G. , Gulyaev Revaz G. , Zlomanov Vladimir P.
Published: October 2013

The article deals with the peculiarities of creation of effective negative pressure and the increase in the forbidden gap width in PbSe nanolayers. The dielectric state that maybe realized under these conditions and their appropriate doping can be considered as a new resource in lead selenide nanolayers. The increasing of the tangential lattice constant with higher growth temperature and layer growth rate confirms this consideration. When determining the forbidden gap width, the optical transmission spectra were processed by a model of the Fabry-Perot interferometer, and, at high concentration of free current carriers, the absorption on them and their degeneracy were taken into consideration.
Preparation of Cationic Polyacrylamide Nanocomposite by Aqueous Two-Phase Polymerization Method
Authors: Wu Quan Cai , Li Shu
Published: October 2013

In order to improve the aqueous solutions viscosity and flocculation performance of cationic polyacrylamide, organic montmorillonite was added into polymerization system of polyacrylamide, the cationic polyacrylamide/dimethyl diallyl ammonium chloride/organic montmorillonite (CPAM/DMDAAC/MMT) nanocomposite was prepared by aqueous two-phase polymerization method. The influence of organic montmorillonite content, cationic monomer content, polyethylene glycol concentration, monomer concentration on the intrinsic viscosity of the CPAM/DMDAAC/MMT nanocomposite were discussed. The reaction conditions were optimized by orthogonal test. The chemical component and organic montmorillonite shape of the cationic CPAM/DMDAAC/MMT nanocomposite were analyzed by FTIR and XRD respectively. The results show that CPAM/DMDAAC/MMT nanocomposite with high aqueous solutions viscosity and beyond compare flocculation performance has been obtained by aqueous two-phase polymerization method. The CPAM/DMDAAC/MMT nanocomposite has been used very well as a flocculating agent.
Nano Structures Constructed by AFM Based Lithography
Authors: Zhang Hui Yong
Published: October 2013

Scanning probe lithography such as atom force microscopy (AFM) has the highest spatial resolution. SPM etching technique employed conductive SPM probe as cathode and metal or semiconductor surface as anode. This paper reports the construction of nanopatterns by conductive nanoetching method on HDT modified Au (111) surface. With Pt-plated probe tip, nanowires of a minimum width of 176 nm was fabricated. The study shows that AFM lithography could be an alternative technology to e-beam lithography and focused-ion-beam.
Corrosion Behavior of Five Commonly-Used Steels in Oily and Alcoholic Sewage from Gas Field
Authors: Ma Yun , Wang Qian , Wu Xin Min
Published: October 2013

The corrosion behavior of commonly-used steels in the oil-containing and alcoholic sewage from gas field was studied combined with polarization curves, electric impedance spectrum (EIS), dynamic corrosion weight loss test, scanning electron microscope (SEM) and energy spectrum (ES) of corrosion products. It was shown that corrosion rate increased with the sequence of 316L, 16Mn, 20#, L360 and 20R steels, and 316L steel was corroded more slightly than 16Mn, 20#, L360 and 20R steels. There were some spot corrosion pits on the surface of L360 and 20R steels. A higher Chromium content of 316L steel led to a stronger corrosion resistance. Ferrous carbonate was the mainly corrosion product on the surface of the four steels. While the corrosion product on the surface of L360 and 20R steels was poor adhered and easy to fall off, and formed some corrosion pits on the steels surface.
Study on Absorbing Properties of Honeycomb Absorbing Materials
Authors: Sun Hui Min , Gu Zhao Zhan , Yang Ran Ran
Published: October 2013

Honeycomb absorbing materials were measured using the method of free space in this paper. The reflectance of honeycomb absorbing materials was calculated and simulated, and it was verified based on the measured results. It was demonstrated that this test method was feasible. Through studying on absorbing properties of honeycomb, the results have showed that the radar absorbing properties of honeycomb are related to electromagnetic parameters, as well as thickness of the dip-coatings. With the increase of thickness of the dipping layer, the radar absorbing capability of high frequency and low frequency wave are significantly increased. It is worth noting that the resonance peak moved to the low frequency with the increase of dipping layer thickness. These results are useful for design of honeycomb absorbing materials.
A Contrast Experimental Study of C40 Concrete Tensile Strength
Authors: Li Ping , Li Yong Chi , Duan Shi Wei , Huang Rui Yuan
Published: October 2013

In order to obtain the tensile strength of the C40 concrete accurately, the comparative study between Brazilian disc splitting experiment and the direct tensile experiment is conducted with a self-modified tensile loading device. The study shows that the tensile strength observed from the direct tensile experiments (3.64MPa) is lower than that from the experiments (5.44MPa). A comprehensive analysis of experimental results is conducted focusing on the perspectives of the specimen failure forms, energy dissipation, the correlation of strength and hydrostatic pressure etc. The study suggests that the main reasons for the differences between Brazilian tensile experimental strength and direct tensile experimental strength include the surface energy required by the specimen destruction, the bond strength between the aggregate, the hydrostatic pressure in the process of loading and other factors.
Particle Size Distribution of Micropowder in Jet Milling/Electrostatic Dispersion
Authors: Li Yin Bing , Zhang Rong , Yin Peng Fei , Hu Jian Chang , Zhang Li Min , Li Ning
Published: October 2013

Jet milling is an innovative method to prepare micropowder with high efficiency and pureness, while the particles obtained through this way exhibit a prominent agglomeration due to the electrostatic attraction caused by friction of particles during jet milling progress. Recently, we have developed a new method to prepare micropowder by combination of jet milling and electrostatic dispersion. In this paper, both fine powders of calcium carbonate and talc were produced by J/E method, the particle size and its distribution were evaluated by SEM and LPSA as well. The results of our research reveal that the dispersion state of the micropowder thus prepared is influenced by its properties and the combined process is effectiveness in powder pulverization and dispersion.
Comparison of Kjeldahl and the Elemental Analysis Methods for Determination of Nitrogen Content in Raw Natural Rubber
Authors: Qi Ning Li , Li Pu Wang , Zeng Xian Hai , Huang Hong Hai , Yang Zi Ming , Gong Xiao
Published: October 2013

The nitrogen in raw natural rubber is mainly derived from crude protein of latex. In this study, the nitrogen content of six kinds of raw natural rubber was analyzed for evaluating Kjeldahl and elemental analysis methods. The nitrogen content ranged from 0.43% to 0.66% for Kjeldahl methods and from 0.45% to 0.75% for elemental analysis method. There was no significant difference between the two methods. The coefficient of variation was below 1%. The data of nitrogen content showed a simple linear correlation (r=0.9937) between the two methods. It was concluded that the elemental analysis method could replace Kjeldahl method in nitrogen analysis of raw natural rubber.
First-Principles Calculation of Intermetallics on Novel Anode Materials
Authors: Zhang Jin , Zhu Pei Xian , Zhou Sheng Gang , Guo Jia Xin
Published: October 2013

Our team proposes the design concept of layered composite electrode materials. Change the single substrate of traditional electrode material by using thermal pressing diffusion welding to synthesize sandwich structure electrode substrate of titanium cladding aluminum. Only Al3Ti phase is obtained in the composite interface. First-principles calculations have been used to calculate the formation enthalpy and binding energies, and the respective order of their value are as follows: AlTi3<AlTi<Al2Ti<Al3Ti,AlTi3<AlTi<Al2Ti<Al3Ti. AlTi3 near Fermi surface is zero and it has good conductivity. It has the strongest bonding capability and stability. Practical application of this new anode in the field of hydrometallurgy has good conductivity, strong adaptability.
Optimization of Biomechanical Systems For the Fighter Plane Ejection Seats
Authors: Wang Yu Fei , Wang Ban , Wang Jin Yuan , Meng Dong Qi
Published: October 2013

Restraint systems and protection devices, referred to as safety devices in this paper, are widely used in automobiles and aircraft for crashworthiness and safety. While such safety devices are designed to isolate, attenuate, and control the impact to the occupants, their performance for crashworthiness and safety may be ineffective or even counterproductive under certain circumstances.
Application of Remote Sensing Technology on Tobacco Planting in Fuquan City
Authors: Li Yu Peng , Ling Zhi Gang , Ma Zi Qiang , Gou Zheng Gui , Liu Xiang , Tang Yan Lin
Published: October 2013

Tobacco planting in Guizhou existed many problems such as exceed planting area, irregularity in quality, imprecise in crop estimate and kinds of disaster monitoring etc. In this article, to solve these problems some new schemes were given. The satellite remote sensing technology was applied on tobacco planting monitoring in Fuquan city of Guizhou province for the first time combining with ERDAS, GPS and ARCGIS in this paper. It put forward a specific implementation plan. And this plan could provide technical helps very well in planting area statistics, growth monitoring and yield estimation of tobacco in Fuquan city.
New Insights into the Biofilm Lifestyle and Metabolism of Acidithiobacillus Species from Analysis of High Throughput Proteomic Data
Authors: Vera Mario , Janosch Claudia , Bellenberg Sören , Krok Beate , Sand Wolfgang , Poetsch Ansgar
Published: October 2013

Bioleaching is the extraction of metals, such as copper or gold, from sulfidic ores by microorganisms. Their energy for growth is obtained by oxidation of ferrous iron and/or reduced inorganic sulfur compounds. Bacterial attachment to ores increase leaching activities through the formation of a special microenvironment between the bacterium and the metal sulfide surface, filled by extracellular polymeric substances (EPS). Recently, a high-throughput proteomic comparison from biofilm cells attached to pyrite (FeS2) and planktonic cells of the mesophilic iron and/or sulfur oxidizer Acidithiobacillus ferrooxidans ATCC 23270 was done. Several proteins were found to be up-regulated in biofilm cells. Among them, membrane and outer membrane proteins probably involved in osmotic regulation, polysaccharide biosynthesis and protein secretion, as well as proteins probably involved in cofactor metabolism were present. In order to extend our knowledge of the genus Acidithiobacilli, we started a high-throughput proteomic analysis of the sulfur oxidizer Acidithiobacillus caldus ATCC 51756 by comparing cells grown with an insoluble energy substrate such as elemental sulfur (S°) against cells grown on a soluble energy substrate, such as thiosulfate. The results revealed several differences in proteins related to sulfur metabolism, potential EPS biosynthesis pathways as well as membrane and transport functions. In both microorganisms several conserved hypothetical proteins were found. Some of them were also found to be induced in sessile cells, suggesting their potential involvement in biofilm formation. This study will provide new insights into the biology of Acidithiobacilli and will probably help assigning functions to poorly characterized and unknown proteins. Keywords: Biofilm, Proteomics, Acidithiobacilli
Functional Analysis of c-di-GMP Pathway in Biomining Bacteria Acidithiobacillus thiooxidans
Authors: Diaz Mauricio , Copaja Sylvia , Guiliani Nicolas
Published: October 2013

Bioleaching is the solubilization of metals catalyzed by acidophilic microorganisms. Among these, the Gram negative γ-proteobacteria from the genusAcidithiobacillusplay a relevant role. Biofilm formation has an impact on bioleaching performance. InAcidithiobacillussp. the molecular mechanisms involved in biofilm formation are still unknown. However, in many Gram-negative and some Gram-positive bacteria, the intracellular levels of the second messenger cyclic diguanilic acid (c-di-GMP) control the regulation of biofilm formation. These levels depend on the balance between the enzymatic activities of diguanylate cyclases (synthesis) and phosphodiesterases (degradation). Previously, functional c-di-GMP pathways have been characterized inAt.ferrooxidansandAt.caldus. Here, our main goal was to characterize the presence of a functional c-di-GMP pathway inAt.thiooxidans. By bioinformatic analysis, several putative-ORFs encoding DGCs, PDEs and effector proteins have been identified in the genome sequence ofAt.thiooxidansATCC 19377. RT-PCR experiments revealed that most of these ORFs are transcribed. In addition, the analysis of nucleotide-enriched fraction extracted fromAt.thiooxidanscells showed that this bacterium is able to produce c-di-GMP. These results strongly indicate thatAt.thiooxidanshas a functional c-di-GMP pathway.
Iberian Pyrite Belt Subsurface Life (IPBSL), a Drilling Project of Biohydrometallurgical Interest
Authors: Amils Ricardo , Fernández-Remolar David , Parro Victor , Rodríguez-Manfredi José Antonio , Timmis Ken , Oggerin Mónica , Sánchez-Román Mónica , J. López Francisco , Fernández José Pablo , Puente Fernando , Gómez-Ortiz David , Briones Carlos , Gómez Felipe , Omoregie Enoma O. , García Miriam , Rodríguez Nuria , Sanz Jose Luis
Published: October 2013

The geomicrobiological characterization of Río Tinto, an extreme acidic environment, has proven the importance of the iron cycle, not only in generating the extreme conditions of the habitat (low pH, high concentration of toxic heavy metals) but also in maintaining the high level of microbial diversity detected in the water column and the sediments. The extreme conditions detected in the Tinto basin are not the product of industrial contamination but the consequence of the presence of an underground bioreactor that obtains its energy from the massive sulfide minerals of the Iberian Pyrite Belt (IPB). To test this hypothesis, a drilling project (IPBSL) to intersect ground waters interacting with the mineral ore is under way, to provide evidence of subsurface microbial activities. A dedicated geophysical characterization of the area selected two drilling sites due to the possible existence of water with high ionic content. Two wells have been drilled in Peña de Hierro, BH11 and BH10, with depths of 340 and 630 meters respectively, with recovery of cores and generation of samples in anaerobic and sterile conditions. The geological analysis of the retrieved cores showed an important alteration of mineral structures associated with the presence of water, with production of expected products from the bacterial oxidation of pyrite. Ion chromatography of water soluble compounds from uncontaminated samples showed the existence of putative electron donors, electron acceptors, as well as variable concentration of metabolic organic acids, which suggest the presence of an active subsurface ecosystem associated to the high sulfidic mineral content of the IPB. Enrichment cultures from selected samples showed evidences of an active iron and sulfur cycle, together with unexpected methanogenic, methanotrophic and acetogenic activities. The geological, geomicrobiological and molecular biology analyses which are under way, should allow the characterization of this ecosystem of biohydrometallurgical interest
Analysis of Gene Expression in Response to Copper Stress in Acidithiobacillus ferrooxidans Strain D2, Isolated from a Copper Bioleaching Operation
Authors: Salazar Camila N. , Acosta Mauricio , Galleguillos Pedro A. , Shmaryahu Amir , Quatrini Raquel , Holmes David S. , Demergasso Cecilia
Published: October 2013

Acidithiobacillus ferrooxidans strain D2 was isolated from a copper bioleaching operation in Atacama Desert, Chile. Copper is widely used as cofactor in proteins but high concentrations of copper are toxic. Cells require certain mechanisms to maintain the copper homeostasis and avoid toxic effects of high intracellular concentration. The molecular response of A. ferrooxidans strain D2 grown in the presence/absence of copper was examined using a A. ferrooxidans whole-genome DNA microarrays. Roughly 23% of 3,147 genes represented on the microarray were differentially expressed; about 9% of them were upregulated in the presence of copper. Among the upregulated genes, those encoding for the copper efflux protein (CusA) and for the copper-translocating P-type ATPase (CopA) were upregulated. The expression of genes encoding proteins related to iron transport was repressed. Similarly, genes related with assimilative metabolism of sulfur (L-cysteine biosynthesis) cysB, cysJ, cysI, CysD-2 and cysN were upregulated. Our results show that when A. ferrooxidans strain D2 was challenged with high copper concentrations, genes related to copper stress response were upregulated as well as others that have not been reported to be related to that mechanism. In addition, some genes related to other metabolic pathways were repressed, probably because of the energy cost of the stress response.
Biogenesis and Transfer of Iron-Sulfur Clusters from Acidithiobacillus ferrooxidans
Authors: Liu Jian She , Qian Lin , Zheng Chun Li
Published: October 2013

Iron-sulfur (Fe-S) proteins are ubiquitous and participate in multiple essential functions of life. However, little is currently known about the mechanisms of iron-sulfur biosynthesis and transfer in acidophilic microorganisms. In this study, the IscS, IscU and IscA proteins from Acidithiobacillus ferrooxidans were successfully expressed in Escherichia coli and purified by affinity chromatography. The IscS was a cysteine desulfurase which catalyzes desulfurization of L-cysteine and transfer sulfur for iron-sulfur cluster assembly. Purified IscU did not have an iron-sulfur cluster but could act as a scaffold protein to assemble the [2Fe-2S] cluster in vitro. The IscA was a [4Fe-4S] cluster binding protein, but it also acted as an iron binding protein. Further studies indicated that the iron sulfur clusters could be transferred from pre-assembled scaffold proteins to apo-form iron sulfur proteins, the reconstituted iron sulfur proteins could restore their physiological activities.
Bioleaching of a Marine Hydrothermal Sulfide Ore with Mesophiles, Moderate Thermophiles and Thermophiles
Authors: Korehi Hananeh , Schippers Axel
Published: October 2013

Marine hydrothermal polymetallic sulfide ores contain high amounts of valuable metals such as Cu, Pb, Zn, Au, Ag, as well as In, Ge, Bi, and Se. Samples from a site in the Indian Ocean were taken during a BGR ship cruise, crushed and sieved for bioleaching experiments to reveal the extraction of the various metals. Chalcopyrite was the main mineral, the total copper content was 38.5 %wt. Comparative bioleaching with mesophilic, moderate thermophilic and thermophilic acidophilic iron- and sulfur-oxidizing bacteria and archaea was investigated. Batch culture experiments were conducted at 2% (w/v) pulp density in shake flasks in the presence of Acidithiobacillus ferrooxidans, Acidiphilium sp. and Acidithiobacillus thiooxidans as mesophiles (30°C), a mixed culture of moderate thermopilic iron- and sulfur oxidizing bacteria (50°C) and the thermophile Acidianus brierleyi (70°C). The results after four weeks showed most effective dissolution of copper in the presence of A. brierleyi (up to 4.3 g/l), compared with moderate thermophiles and mesophiles (3.3 g/l and 2.5 g/l, respectively). Furthermore, the bioleaching performance was approved with dissolved iron concentrations. Conclusively, an increase in temperature from 30 °C to 70 °C had a major impact on bioleaching efficiency. Copper and iron extraction efficiency occurred in the order thermophiles, moderate thermophiles, mesophiles.
A Two-Step Process for the Treatment of Refractory Sulphidic Concentrate
Authors: Muravyov Maxim I. , Bulaev Aleksander
Published: October 2013

Methods for improving the treatment efficiency of a refractory gold-bearing sulphidic concentrate are proposed. These methods consist of the oxidation of the concentrate through a two-step process: a high-temperature ferric leaching step and a subsequent biooxidation step, which further involves the use of organic nutrients. The concentrate contained 34.7% pyrite and 7.9% arsenopyrite. The biooxidation of the concentrate (in a one-step process) was conducted at 45°C in bioreactors under continuous conditions. The pyrite and arsenopyrite oxidation levels after 240 hours were 60.2 and 92.0%, and the gold recovery level by cyanidation was 65.7%. The two-step process involved the leaching of the concentrate by a Fe3+-containing solution and the subsequent biooxidation of the leach residue. The pyrite andarsenopyrite oxidation levels after 240 hours of biooxidation were 65.7 and 94.1%, and the gold recovery level was 71.7%. The effect of an organic nutrient (yeast extract) on biooxidation during the two-step process was studied. The pyrite and arsenopyrite oxidation levels after 240 hours of biooxidation under mixotrophic conditions were 73.5 and 95.1%, and the gold recovery level was 77.9%. The effect of the organic nutrient on the microbial population was determined. Sulfobacillus thermosulfidooxidans and Acidithiobacillus caldus were the predominant microorganisms studied under both autotrophic and mixotrophic conditions. Archaeon Acidiplasma sp. MBA-1 was a minor component of the microbial community under autotrophic conditions but was one of the predominant microorganisms studied under mixotrophic conditions. The strain MBA-1 could oxidise both ferrous iron and elemental sulphur in the presence of yeast extract. These results suggest that the organic nutrient changed the composition and increased the activity of the microbial population. Thus, a two-step process with organic nutrients added during biooxidation may be considered an effective strategy for treating refractory pyrite-arsenopyrite concentrates.
Biological, Chemical and Transport Phenomena which Control the Rate of Copper Leaching in Heap and Dump Operations
Authors: Vargas Tomas , Davis-Belmar Carol S.
Published: October 2013

Bioleaching of secondary and low grade copper ores in heaps and/or dumps is to day a well established technology. However, there is still a strong need to improve the copper leaching rates and recoveries currently reached at plant level in order to increase the economic outcome and range of application of this technology. This work presents a conceptual model which helps to elucidate when a bioleaching process is controlled either by biological, chemical or transport phenomena. This model, mathematically simplified but scientifically well grounded, it is expected will facilitate discussions among biologists, metallurgists and process engineers to develop collaborative approaches to improve this technology integrating different expertise.
Column Bioleaching of Low Grade Copper Sulfide Ore at Extreme Conditions for Most Mineral Processing Bacteria
Authors: Zou Gang , Wu Zeng Ling , Lai Xiao Kang , Zou Lai Chang , Ruan Ren Man , Papirio Stefano , Puhakka Jaakko
Published: October 2013

This study is prompted by the high leaching efficiency of Zijinshan copper bio-heap leaching industrial plant. Bioleaching columns with 100 mm diameter and 1 m height were used to investigate copper bioleaching at different operating conditions. Elevated temperature, high total iron concentration and high acidity significantly increased copper leaching rate as determined by solution and residue assays. At 60 °C with 50 g/L iron (initial Fe3+/Fe2+ gram ratio 2.5), pH 1.0 and no aeration, copper extraction was achieved 90% after 60 days. However, at 30°C, 5 g/L total Fe, pH 1.5 and no aeration, copper extraction reached 80% and 85% after 90 and 200 days, respectively. Real-time PCR assay showed that only 105 cells/ml and 2×105 cells/g are in solution and on the ore surface at the condition of 60 °C 50 g/L iron and pH 1.0, respectively. In addition, a similar leaching rate was observed in the tests with and without inoculation. The column without inoculation was directly irrigated with acid mine drainage (AMD). Our results indicate high copper leaching efficiency at extreme conditions for mineral oxidizing bacteria. Inoculation and aeration are not necessary in Zijinshan copper mine bio-heap leaching process.
Effects of Individual Use, Mixed Culture and Sulfur Addition on the Effectiveness of Nickel Laterite Ore Bioelaching with Penicillium verruculosum and Galactomyces geotrichum
Authors: Mubarok M. Zaki , Astuti Widi , Chaerun Siti Khodijah
Published: October 2013

The type of fungi used in fungal bioleaching influence the effectiveness of metals extraction due to the dissimilarity of each microorganism survival in environments with certain metals content. Several metals have prominent toxicities to certain type of fungi, which result in low metals extraction and leaching rate. In the present work, the influences of individual use of Penicillium verruculosum and Galactomyces geotrichum on the nickel extraction from Indonesian laterite ore are compared with the fungis mixed culture. The effect of sulfur addition in the mixed culture of Penicillium verruculosum and Galactomyces geotrichum on the sulfate ion formation was also investigated. Shake flask bioleaching assays have been performed in a medium growth of Indonesian food production waste over the course of 28 days. It was observed that mixed culture of Penicillium verruculosum and Galactomyces geotrichum has a higher effect in nickel extraction compared with the use of individual fungi for both saprolite and limonite ores. For saprolite ore, the fungi species of Galactomyces geotrichum demonstrated a greater nickel extraction than Penicillium verruculosum. In contrast, the extraction of nickel from limonite ore by Penicillium verruculosum was slightly more effective than Galactomyces geotrichum. The addition of elemental sulfur in the mixed culture was found to generate sulfate anion, having a significant increase in its concentration with time and decreasing solution pH within 28-day of incubation. The proportion of sulfur addition must be optimized in order to avoid ore surface passivation with the excess of sulfur. XRD analysis detected the presence of un-oxidized sulfur on surface of the leaching residues along with the biomass.
Hydrogen Sulphide Production at Alkaline, Neutral and Acid pH by a Bacterial Consortium Isolated from Peruvian Mine Tailing and Wetland
Authors: Mormontoy Juliet , Hurtado Jasmin E.
Published: October 2013

The gol aim of this study is to optimize the ability to produce hydrogen sulphide (H2S) in pure and mixed cultures of sulfate reducing bacteria (SRB) at pH variations from 9 to 5. Hydrogen sulphide produced by SRB reacts with dissolved metals in water or tailings generating highly insoluble metal sulfides and therefore the selective immobilization of different metals. Three strains of SRB were isolated from Orcopampa mine tailings and from the Pantanos de Villa wetlands, both located in Peru. Cultures were identified by microscopy, cultural characteristics and biochemical tests as production of desulfoviridin and growth in different substrates. The production of H2S by pure and mixed cultures was evaluated at: acid pH (5), neutral pH (7) and alkaline pH (9). The mixed culture consisted of all three isolated species:Desulfobactersp. from mine tailings andDesulfovibrio desulfuricansandDesulfovibrio sapovorans from wetland sludges. Pure cultures of these three strains grew and produced H2S at both neutral or alkaline pH. At low pH no pure culture was able to grow and no production of H2S was detected. A mixed culture formed by the three isolated SRB was the only culture that grew and produced sulphide at the three different pH tested in shorter time (24 hours). The improvement of bacterial activity can be based in the metabolic diversity of the mixed culture able to use lactate and acetate as a result of the joint activity of these species. Energy obtained from the substrate is thus used more efficiently.
The Bioleaching Characteristics of Chalcopyrite with Different Genetic Types
Authors: Bai Jing , Wen Jiang Kang , Huang Song Tao , Wu Biao , Chen Bo Wei
Published: October 2013

The copper extraction yield from thermophilic bioleaching of chalcopyrite depends on temperature, pH, and the oxidation-reduction potential (ORP), the activity of the thermophile used, as well as on the different genetic type of the chalcopyrite used. The bioleaching characteristics of chalcopyrite from marine volcanic type and porphyry type, and the influence of genetic type on microbial community were studied. The results indicated that the bioleaching of chalcopyrite is controlled by the ORP rather than by the pH. The thermophiles composition of marine volcanic type bioleaching wasMetallosphaeracuprinaandSulfobus spHB59.Metallosphaeracuprinawas the dominate bacteria during porphyry chalcopyrite bioleaching. The different leachability between marine volcanic type and porphyry type is attributed to their nature which caused by genetic type.