Isolation, identification and characterization of cadmium-resistant Pseudomonas aeruginosa strain E1

Strain E₁ with resistance to 18 mmol/L cadmium (Cd), isolated from Cd-contaminated soil was identified by morphological observation, biochemical and physiological characterization and 16S rDNA sequence analysis. The resistance to heavy metals Cd, Cu, Co, Mn, Pb, Zn and 12 antibiotics was examined. The ability of removing Cd from solution was studied. The characterizations show that strain E₁ is affiliated to Pseudomonas aeruginosa (P. aeruginosa). Strain E₁ has high resistance to heavy metals and the order is found to be Cd>Mn>Zn>Cu>Pb>Co in solid media. Strain E₁ also exhibits the resistance to 12 antibiotics. Both living and non-living cells of strain E₁ can remove Cd from solution, and living cell has better biosorption than non-living cell. Foundation item: Project (50621063) supported by the National Natural Science Foundation of China; Project (2004CB619204) supported by the Major State Basic Research and Development Program of China     

Alkaline treatment kinetics of calcium phosphate by piezoelectric quartz crystal impedance

Calcium phosphate film was prepared by electrochemical deposition technology. Subsequently, the alkaline treatment process of calcium phosphate film in 0.1 mol/L NaOH solution was monitored on real time by the piezoelectric quartz crystal impedance (PQCI) technique. The variations of morphology and composition for the alkaline treatment products were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and X-ray diffraction (XRD), respectively. The dynamic variations of calcium phosphate can be characterized by the change of equivalent circuit parameters. The results show that the forming process of hydroxyapatite (HA) is composed of three stages: (1) acidic calcium phosphate dissolution; (2) phase transformation; and (3) HA formation. Furthermore, the correlative kinetic equations and parameters are obtained by fitting the static capacitance (C _s)—time curves. Foundation item: Project(2005CB623901) supported by the Major State Basic Research and Development Program of China     

Acidophilic bacterial community reflecting pollution level of sulphide mine impacted by acid mine drainage

To reveal the impact of mining on bacterial ecology around mining area, bacterial community and geochemical characteristics about Dabaoshan Mine (Guangdong Province, China) were studied. By amplified ribosomal DNA restriction analysis and phylogenetic analysis, it is found that mining pollution greatly impacts the bacterial ecology and makes the habitat type of polluted environments close to acid mine drainage (AMD) ecology. The polluted environment is acidified so greatly that neutrophil and alkaliphilic microbes are massively dead and decomposed. It provided organic matters that can make Acidiphilium sp. rapidly grow and become the most bacterial species in this niche. Furthermore, Acidithiobacillus ferrooxidans and Leptospirillum sp. are also present in this niche. The amount of Leptospirillum sp. is far more than that of Acidithiobacillus ferrooxidans, which indicates that the concentration of toxic ions is very high. The conclusions of biogeochemical analysis and microbiological monitor are identical. Moreover, because the growth of Acidithiobacillus ferrooxidans and Leptospirillum sp. depends on ferrous iron or inorganic redox sulfur compounds which can be supplied by continual AMD, their presence indicates that AMD still flows into the site. And the area is closer to the outfalls of AMD, their biomasses would be more. So the distinction of their biomasses among different areas can help us to find the effluent route of AMD. Foundation item: Project(50621063) supported by the Science Fund for Creative Research Groups of China; Project(2004CB619201) supported by the Major State Basic Research Development Program of China     

Speciation of chromium in soil inoculated with Cr（Ⅵ）-reducing strain, Bacillus sp. XW-4

Cr(VI)-amended soil was inoculated with Cr(VI)-reducing strain, Bacillus sp. XW-4 and incubated at 28 °C in an incubator. Cr(VI) reduction, available Cr and Cr fraction in soils were studied. The results show that addition of Bacillus sp. XW-4 can promote Cr(VI) reduction, but inoculation of this strain has a negative effect on the decrease of available Cr content in soil. In controls (without this strain) amended with 100 and 200 mg/kg of Cr(VI), Cr(VI) contents decrease to about 41 and 92 mg/kg respectively after incubation of 4 d, while in soil inoculated with XW-4, Cr(VI) contents decrease to about 18 and 60 mg/kg, respectively. The content of available Cr in soils with inoculation of XW-4 is higher than that in controls. Chromium is partitioned into water soluble Cr, exchangeable Cr, precipitated Cr, Cr bound to organics and residual Cr. The highest content of Cr is observed in residual form and water soluble Cr is not detected for all treatments after 42 d, but the soils inoculated with Bacillus sp. XW-4 contain higher content of exchangeable Cr and lower content of precipitated Cr than the soil without the inoculum. Inoculation of Bacillus sp. XW-4 can increase chromium activity in soils. Foundation item: Project(20050532009) supported by the Doctoral Foundation of Ministry of Education of China; Project supported by Program for Changjiang Scholars and Innovative Research Team in University     

Delay-independent decentralized H ∞ control for multi-channel discrete-time systems with uncertainties

A robust decentralized H∞ control problem was considered for uncertain multi-channel discrete-time systems with time-delay. The uncertainties were assumed to be time-invariant, norm-bounded, and exist in the system, the time-delay and the output matrices. Dynamic output feedback was focused on. A sufficient condition for the multi-channel uncertain discrete time-delay system to be robustly stabilizable with a specified disturbance attenuation level was derived based on the theorem of Lyapunov stability theory. By setting the Lyapunov matrix as block diagonal appropriately according to the desired order of the controller, the problem was reduced to a linear matrix inequality （LMI） which is sufficient to existence condition but much more tractable. An example was given to show the efficiency of this method.     

Isolation and characterization of YNTC-1, a novel Alicyclobacillus sendaiensis strain

A heterotrophic acidothermophilic bacterial strain, YNTC-1, was isolated from an acidic hot spring in Tengchong, Yunan, China. YNTC-1 grows at pH value of 1.5-8.0 and temperature of 40-70 ℃, with optimal pH and temperature at 3.0 and 55 ℃, respectively. The cells of the strain are in shape of short rod, with 1.0-1.2 μm in length and 0.7-0.8 μm in diameter, and with distinct spores at both poles of each cell. The predominant fatty acids in cellular membrane of the strain are C18：1 ω7c. 16s rRNA gene analysis reveals that this strain is closely related to Alicyclobacillus sendaiensis, with over 99% sequence similarity. Based on phenotypic and genotypic analyses, YNTC-1 is identified as a member ofA. sendaiensis. Considering some important morphological and biochemical differences between strain YNTC-1 and A. sendaiensis ATCC 27009T, YNTC-1 may be proposed to be a novel subspecies of A. sendaiensis. However, this viewpoint has to be confirmed by further studies. Co-bioleaching of pyrite and chalcopyrite with strain YN22, Sulfobacillus thermosulfidooxidans, shows that strain YNTC-1 has no evident influence on bioleaching rates of these two sulphide minerals.     

Bioleaching of sphalerite by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans cultured in 9K medium modified with pyrrhotite

Elective culture of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans in 9K medium modified with pyrrhotite was studied. Bioleaching of flotation concentrate of sphalerite by the selected bacteria was carried out. The results show that the microorganisms cultured by pyrrhotite are a mixture of Acidithiobacillusferrooxidans and Acidithiobacillus thiooxidans, of which the capability to oxidize ferrous to ferric irons is enhanced by the high mass ratio of Fe to S in pyrrhotite. Three pyrrhotite samples were separated into various parts with corresponding S/Fe ratios by magnetic separation and were used to culture the elective bacteria as the substrate. The association of the cultures could provide a more rapid and complete oxidation of sphalerite than that of bacteria cultivated by conventional methods.     

Synthesis and coloring properties of Cd（S1-xSex） pigments by precipitate-hydrothermal method

Cd（S1-xSex） pigments （red to yellow） were synthesized by precipitate-hydrothermal method. The structure, morphology and hue of the powder were characterized by X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDAX） and CIE chromaticity. The optimum synthesis conditions were obtained and reaction mechanism was further analyzed as well. The results show that molar ratio of S to Se, pH value and hydrothermal reaction conditions have great effects on the hues of the pigments. Pigments with vivid hues are obtained under the conditions that pH value is about 13.0, hydrothermal reaction condition is at 140 ℃ for 4 h or at 160 ℃ for 6 h. The reaction mechanism is that Se^2- of Cd（S1-xSex） substitutes S^2- of CdS and then forms a continuous solid solution.     

Isolation and characterization of Acidithiobacillus caldus from several typical environments in China

Six strains of moderately thermophilic sulfur-oxidizing bacteria were isolated from several different typical environments in China. The identities of the isolates were confirmed by analyses of their 16S rRNA genes, and some key physiological traits. The isolates are Gram negative, rod-shaped bacteria, their optimal temperature and pH value for growth are 45-50 ℃ and 2.5-3.5 respectively. They are autotrophic and used＇elemental sulfur, sodium thiosulfate and potassium tetrathionate as electron donor, while a little glucose stimulated their growth. 16S rDNA sequences analysis reveals that the strains are phylogenetically clustered to Acidithiobacillus caldus.     

A random adaptive method to adjust MAC parameters in IEEE802.11e WLAN

The IEEE 802.11e standard is proposed to provide QoS support in WLAN by providing prioritized differentiation of traffic. Since all the stations in the same priority access category (AC) have the same set of parameters, when the number of stations increases, the probability of different stations in the same AC choosing the same values will increase, which will result in collisions. Random adaptive MAC (medium access control) parameters scheme (RAMPS) is proposed, which uses random adaptive MAC differentiation parameters instead of the static ones used in the 802.11e standard. The performance of RAMPS is compared with that of enhanced distributed coordination access (EDCA) using NS2. The results show that RAMPS can reduce collision rate of the AC and improve the throughput by using adaptive random contention window size and inter-frame spacing values. RAMPS ensures that at any given time, several flows of the same priority have different MAC parameter values. By using the random offset for the inter-frame spacing value and the backoff time, RAMPS can provide intra-AC differentiation. The simulation results show that RAMPS outperforms EDCA in terms of both throughput and end-to-end delay irrespective of the traffic load. Foundation item: Project(60673164) supported by the National Natural Science Foundation of China; Project(06JJ10009) supported by the Natural Science Foundation of Hunan Province, China; Project(20060533057) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China; Project(2008CB317107) supported by the Major State Basic Research and Development Program of China; Project(NCET-05-0683) supported by the Program for New Century Excellent Talents in University     

Homology modeling and evolutionary trace analysis of superoxide dismutase from extremophile Acidithiobacillus ferrooxidans

The gene sod in Acidithiobacillus ferrooxidans may play a crucial role in its tolerance to the extremely acidic, toxic and oxidative environment of bioleaching. For insight into the anti-toxic mechanism of the bacteria, a three-dimensional (3D) molecular structure of the protein encoded by this gene was built by homology modeling techniques, refined by molecular dynamics simulations, assessed by PROFILE-3D and PROSTAT programs and its key residues were further detected by evolutionary trace analysis. Through these procedures, some trace residues were identified and spatially clustered. Among them, the residues of Asn38, Gly103 and Glu161 are randomly scattered throughout the mapped structure; interestingly, the other residues are all distinctly clustered in a subgroup near Fe atom. From these results, this gene can be confirmed at 3D level to encode the Fe-depending superoxide dismutase and subsequently play an anti-toxic role. Furthermore, the detected key residues around Fe binding site can be conjectured to be directly responsible for Fe binding and catalytic function. Foundation item: Project(2004CB619201) supported by the National Basic Research Program of China; Project (50321402) supported by the National Natural Science Foundation of China     

Isolation of Leptospirillum ferriphilum by single-layered solid medium

According to physiological and biochemical characteristics of Leptospirillum ferriphilum,a strain of object bacteria was isolated successfully.Bacteria were enriched by selective liquid medium and plated on designed single-layered agar solid medium.Colony was cultured and bacteria were collected.The morphologies of the object bacteria were observed using crystal violet staining,scanning electron microscope(SEM)and transmission electron microscope(TEM).The result of 16S rDNA identification shows that this bacterium belongs to Leptospirillum ferriphilum and it is named as Leptospirillum ferriphilum strain D1.These results indicate that this new single-layered agar solid medium is efficient and simple for isolation of Leptospirillum ferriphilum.Additionally,physiological-biochemical characteristics show that the optimum initial pH value and its growth temperature are 1.68 and 40 ℃,respectively.The culture of it is used to leach a complex concentrate chalcopyrite,the leaching efficiencies of copper and iron are 1.93 % and 13.74 %,respectively,and it is more effective than the A.ferrooxidans culture in the leaching of the complex concentrate chalcopyrite.     

Fluorescence spectroscopy characteristics of humic acid by inoculating white-rot fungus during different phases of agricultural waste composting

The white-rot fungus, Phanerochaete chrysosporium (P. chrysosporium), was inoculated during different phases of agricultural waste composting, and its effect on the fluorescence spectroscopy characteristics of humic acid (HA) was studied. The results show that the emission spectra have a sharp peak at 400 nm and a broad shoulder with the maximum centered at 460 nm. The excitation spectra have two peaks and exhibit red shift (shift to longer wavelengths) at 470 nm. The synchronous scan spectra present a number of peaks and shoulders, and the peaks at shorter wavelengths disappear gradually and form a shoulder. At the final stage of composting, the fluorescence spectra have similar shapes, but the fluorescence intensities decrease. P. chrysosporium increases the degree of aromatization and polymerization of HA when it is inoculated during the second fermentation phase, while it does not produce an obvious change on the humification degree of HA when it is inoculated during the first fermentation phase. Compared with the fluorescence spectroscopy characteristics of HA from soil, the structure of HA from compost is simpler and the activity is higher. Foundation item: Project(2005CB724203) supported by the Major State Basic Research and Development Program of China; Project(IRT0719) supported by the Program for Changjiang Scholars and Innovative Research Team in University of China; Projects(50608029, 50808073) supported by the National Natural Science Foundation of China; Project(2007185) supported by the Environmental Protection Technology Research Program of Hunan Province, China     

Structural and optical characteristics of Al x Ga1- x N/AlN superlattice

AlN/Al_0.3Ga_0.7N superlattices were grown on (0001) sapphire substrate by metal-organic chemical vapor deposition (MOCVD). The superlattice period varies from 6 to 30. The layer thickness of different period stack was designed. GaN or AlGaN template was employed for growing AlN/AlGaN superlattices. Reflectivity, SEM, AFM and XRD data of the Al _x Ga_1-x N/AlN superlattices are presented. It is found that the templates used have an intensive impact on surface roughness and interfacial properties of following AlN/AlGaN superlattices. The result of atomic force microscopy indicates that AlN/AlGaN superlattices grown on GaN template exhibit quasi-two-dimensional growth mode. The resulting superlattice has a smooth surface morphology and distinct interface. No crack is observed in the area of a 2-inch wafer. Supported by the Special Funds for Major State Basic Research Project (973 Project) (Grant No. 2006CB6049), the Hi-tech Research Project (Grant Nos. 2006AA03A103, 2006AA03A118, and 2006AA03A142), the National Natural Science Foundation of China (Grant No. 60676057), and the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20050284004)     

Adsorption characteristics of thiobacillus ferrooxidans on surface of sulfide minerals

By using thiobacillus ferroxidans (T. f) from Qixiashan, Hubei Province, China, the adsorption characteristics of T. f on surface of sulfide mineral were studied. The influences of adsorption time, pH value, temperature, initial inoculated concentration of bacteria, concentration of sulfide mineral powder, and variety of minerals on the adsorption characteristics were firstly investigated by using the ninhydrin colorimetric method, and the changes of contact angles and Zeta potentials of mineral surface during the bacterial adsorption were then determined. The results show that when the leaching experiments are performed for a long time from several days to a month, the maximal quantity of adsorption of T f on the surface of pyrite is obtained under the following conditions: leaching for 20 d, pH value in range of 1–2 and temperature at 30 °C, respectively; when the bio-leaching experiments are performed for a shorter leaching time, the maximal quantity of adsorption is obtained under the conditions: bio-leaching for 2 h, at 2.4×10⁷ cell/mL of initial inoculated bacteria concentration, and at 10% of mineral powder concentration; and the adsorption quantities are different from one sulfide mineral to another, and the adsorption of T. f on the surface of sulfide minerals includes three phases: increasing phase, stationary phase and decreasing phase. Foundation item: Project(50321402) supported by the National Natural Science Foundation of China; project (2004CB619204) supported by the National Key Fundamental Research and Development Program of China     

Microscopic phase-field simulation for coarsening behavior of L12 and DO22 phases of Ni75Cr x Al25? x alloy

Based on the microscopic phase-field dynamic model and the microelasticity theory, the coarsening behavior of L1₂ and DO₂₂ phases in Ni₇₅Cr _x Al_25−x alloy was simulated. The results show that the initial irregular shaped, randomly distributed L1₂ and DO₂₂ phases are gradually transformed into cuboidal shape with round corner, regularly aligned along directions [100] and [001], and highly preferential selected microstructure is formed during the later stage of precipitation. The elastic field produced by the lattice mismatch between the coherent precipitates and the matrix has a strong influence on the coarsening kinetics, and there is no linear relationship between the cube of the average size of precipitates and the aging time, which does not agree with the results predicted by the classical Lifshitz-Slyozov-Wagner. The coarsening processes of L1₂ and DO₂₂ phases are retarded in elastically constrained system. In the concurrent system of L1₂ and DO₂₂ phases, there are two types of coarsening modes: the migration of antiphase domain boundaries and the interphase Ostwald ripening. Foundation item: Project(50671084) supported by the National Natural Science Foundation of China; Project(20070420218) supported by China Postdoctoral Science Foundation     

Preparation of bioactive calcium phosphate coating on porous C/C substrate by a novel deposition technique

A novel heat substrate technique, high frequency inductive heat deposition （IHD）, was introduced to coat porous carbon materials, C/C and carbon felt to improve their bioactivity. The morphologies, composition and microstructure of the resulting coatings were examined by scanning electron microscopy （SEM）, energy dispersive spectra （EDS）, X-ray diffractometer （XRD） and Fourier transform infrared spectroscopy （FTIR）. The results show that, the calcium phosphate consisted of non-stoichiometric, CO3-containing and plate- like octacalcium phosphate （Ca8-xH2（PO4）6, OCP） could uniformly cover the entire porous surfaces of carbon materials. Good adhesion of the coating to carbon material substrates was observed.     

Bioleaching of soluble phosphorus from rock phosphate containing pyrite with DES-induced Acidithiobacillus ferrooxidans

The effects of Acidithiobacillus ferrooxidans (At. f) mutated with diethyl sulfate (DES) as a mutagen on the bioleaching of soluble phosphorus (P) from rock phosphate (RP) were investigated. The results show that the oxidative activity of At. f is greatly improved by 1.0% (volume fraction) of DES. Correspondingly, the highest leaching rate of soluble P is also obtained to be 14.9% by the At. f mutated, which is 85.8% higher than that of the adapted At. f without mutation. In addition, the SEM images are significantly performed that the corrosion of RP residue surfaces leached by 1.0% DES-induced At.f is much worse than that of leached by the adapted At. f. All the above indicate that the leaching efficiency of soluble P from RP with pyrite can be greatly improved by using DES-induced At. f to a certain extent.     

RobustH ∞ controller design for a class of uncertain systems

TheH ^∞ control problem for a class of systems with time-varying and nonlinear uncertainties is considcred. A new sufficient condition based on LMI is provided to judge their robust stability andL ₂-gain finiteness. Solvability conditions are presented for both state feedback and output feedback cases, which are all reduced to solutions of LMIs. The design procedure is also discussed via LMI approach. Project supported by the National Natural Science Foundation of China (Grant No. 59704004).