Development ofThiobacillus ferrooxidans ATCC 19859 strains tolerant to copper and zinc

A study was carried out to develop strains ofThiobacillus ferrooxidans ATCC 19859 tolerant to higher levels of heavy metal ions. Strains ofT. ferrooxidans capable of growing in Cu²⁺ (30 g/L) and Zn²⁺ (60 g/L) have been obtained. The ability of strains tolerant to either copper or zinc to grow in medium containing both the metals has been examined. The copper-tolerant strain (25 g/L) grows better in the medium containing both metals (Cu²⁺ 25 g/L and Zn²⁺ 40 g/L) compared to the zinc-tolerant strain (40 g/L).     

Fe2+ oxidation rate drastically affect the formation and phase of secondary iron hydroxysulfate mineral occurred in acid mine drainage

During the processes of secondary iron hydroxysulfate mineral formation, Fe²⁺ ion was oxidized by the following three methods: (1) biooxidation treatment by Acidithiobacillus ferrooxidans (A. ferrooxidans); (2) rapid abiotic oxidation of Fe²⁺ with H₂O₂ (rapid oxidation treatment); (3) slow abiotic oxidation of Fe²⁺ with H₂O₂ (slow oxidation treatment). X-ray diffraction (XRD) patterns, element composition, precipitate weight and total Fe removal efficiency were analyzed. The XRD patterns and element composition of precipitates synthesized through the biooxidation and the slow oxidation treatments well coincide with those of potassium jarosite, while precipitates formed at the initial stage of incubation in the rapid oxidation treatment showed a similar XRD pattern to schwertmannite. With the ongoing incubation, XRD patterns and element composition of the precipitates that occurred in the rapid oxidation treatment were gradually close to those in the biooxidation and the slow oxidation treatments. Due to the inhibition of A. ferrooxidans itself and its extracellular polymeric substances (EPS) in aggregation of precipitates, the amount of precipitates and soluble Fe removal efficiency were lower in the biooxidation treatment than in the slow oxidation treatment. Therefore, it is concluded that Fe²⁺ oxidation rate can greatly affect the mineral phase of precipitates, and slow oxidation of Fe²⁺ is helpful in improving jarosite formation.     

Thermal decomposition of ferric and ammonium sulphates obtained by bio-oxidation of water pickling liquors with Thiobacillus ferrooxidans

Sulphuric water pickling liquor containing ferrous sulphates was oxidized by Thiobacillus ferrooxidans at different pHs. The oxidized solution was then evaporated and crystallized, and products characterized by X-ray powder diffraction, X-ray high temperature powder diffraction and Fourier transform infrared (FTIR) spectrometry. The thermal decomposition of these materials, studied by calorimetric and thermogravimetric techniques, shows that iron(III) hydroxysalts and monoammonium and triammonium salts are formed during the oxidation-evaporation-crystallization process. However, this formation depends upon pH.     

Immobilization of Acidithiobacillus ferrooxidans on sulfonated microporous poly(styrene–divinylbenzene) copolymer with granulated activated carbon and its use in bio-oxidation of ferrous iron

The immobilization efficiencies of Acidithiobacillus ferrooxidans cells on different immobilization matrices were investigated for biooxidation of ferrous iron (Fe^2 +) to ferric iron (Fe^3 +). Six different matrices were used such as the polyurethane foam (PUF), granular activated carbon (GAC), raw poly(styrene–divinylbenzene) copolymer (rawSDVB), raw poly(styrene–divinylbenzene) copolymer with granular activated carbon (rawSDVB-GAC), sulfonated poly(styrene–divinylbenzene) copolymer (sulfSDVB) and sulfonated poly(styrene–divinylbenzene) copolymer with granular activated carbon (sulfSDVB-GAC). The sulfSDVB-GAC polymer showed the best performance for Fe^2 + biooxidation. It was used at packed-bed bioreactor and the kinetic parameters were obtained. The highest Fe^2 + biooxidation rate (R) was found to be 4.02 g/L h at the true dilution rate (D_t) of 2.47 1/h and hydraulic retention time (τ) of 0.4 h. The sulfSDVB-GAC polymer was used for the first time as immobilization material for A. ferrooxidans for Fe^2 + biooxidation.     

Band theory analysis of shock velocity-particle velocity relations for metals

The systematics of the shock constants in shock velocity-particle velocity relations for metals have been examined by energy band theory methods. The causes of non-linearity of this relation at high pressure are discussed in terms ofs ⇌d electron transfer.     

Viscosity and density of liquid mixtures ofn-alkanes with squalane

Viscosity and density measurements are reported for binary liquid mixtures ofn-butane andn-hexane with squalane in the temperature range from 273 to 333 K. The viscosity measurements have been carried out by using a capillary viscometer calibrated with standard liquids. that is. JS5, JSIO, JS20, and water. The uncertainty in the viscosity data was estimated to be ± 1.7%. The density needed for the calculation of the viscosity has been measured by using a glass pycnometer within an accuracy of ±0.04%. In the prediction of the viscosity, the scheme of Assael et al. fails for mixtures of this type differing greatly in size.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994. Boulder, Colorado, U.S.A.     

1/f Noise properties of swift heavy ion irradiated epitaxial thin films of YBCO

Effect of 250 MeV¹⁰⁷Ag ion irradiation induced columnar defects on the noise properties of the YBCO superconductor in the normal and superconducting state have been investigated. Magnitude of the spectral density of the noise is found to scale inversely with the frequency and exhibit a quadratic dependence on the bias current confirming that the noise arises due to the resistance fluctuations. The magnitude ofS _v has been found to decrease with decrease in temperature and shows a noise peak in the transition region. The noise performance of these materials in the vicinity of the superconducting transition as well as in the normal state is found to improve by an order of magnitude after irradiation with 250 MeV¹⁰⁷Ag ions. The decrease in the magnitude of 1/f noise peak is due the irradiation induced enhanced flux pinning of the material which suppresses the flux motion induced noise in the vicinity ofT _c.     

Isobaric thermal expansivities of binary mixtures ofn-Hexane with 1-hexanol at pressures from 0.1 to 350 MPa and at temperatures from 303 to 503 K

Isobaric thermal expansivities, α_p(p, T), of seven binary mixtures ofn-hexane with l-hexanol (0.0553, 0.1088, 0.2737, 0.2983, 0.4962, 0.6036, and 0.7455 mol fraction of l-hexanol) have been measured with a pressure-controlled scanning calorimeter over the pressure range from just above the saturation pressures to 350 MPa and at temperatures from 302.6 to 503.1 K. The low-temperature isotherms of α_p for particular mixtures observed with respect to the unique crossing point ofn-hexane isotherms reveal an association effect which is reduced when the temperature increases. The high-temperature isotherms of α_p are very similar to the isotherms of puren-hexane, especially for lower mole fractions ofn-hexanol. No known equation of state can reproduce these properties.     

Low temperature preparation ofβ-alumina by an alkoxide route

β-alumina has been prepared by the thermal decomposition of a mixture of sodium and aluminium isopropoxides followed by heating up to 1000°C. It has been found necessary to use sodium isopropoxide in excess (25–30%) for the complete formation ofβ-alumina at 1000°C. On the other hand one obtains a mixture ofβ-alumina andα-alumina when the starting materials are taken in the stoichiometric ratio Na₂O:11Al₂O₃. DTA, TG and DTG studies of a mixture of sodium and aluminium isopropoxide showedβ-alumina formation at 1000°C. NCL Communication No. 4446.     

Thermal analysis of used and radiation treated polycarbonate (L-MW) biomaterial

γ-radiation treatment of radiation sterilized polycarbonate biomaterials has been carried out to ensure efficient disposal by incineration. Low molecular weight polycarbonate sterilized with 2·5 Mrad dose ofγ-radiation was further treated with different doses ofγ-radiation. The radiation-treated samples were subjected to thermogravimetry. The sterilized sample and the 7·5 Mrad-treated sample showed similar properties. These samples do not leave any residue during thermal decomposition.     

Biocompatibility evaluation of magnetosomes formed by Acidithiobacillus ferrooxidans

Magnetite nanocrystal has been extensively used in biomedical field. Currently, an interesting alternative to synthetic magnetic Fe₃O₄ nanoparticles, called magnetosome, has been found in magnetotactic bacteria. It has been reported that Acidithiobacillus ferrooxidans (At. ferrooxidans) has a potential to synthesize magnetosome. In this study, transmission electron microscope (TEM) was used to analyze the magnetite particles in At. ferrooxidans BY-3. The magnetosomes formed by this bacterium were isolated by a method combining ultracentrifugation and magnetic separation. Crystalline phase and surface functional group of the magnetosomes were investigated by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), respectively. Biocompatibility of the magnetosomes was systematically evaluated at various concentrations (0.5, 1.0, 2.0 and 4.0 mg/ml). MTT test, hemolysis assay and Micronucleus Test were carried out to evaluate in vitro cytotoxicity, blood toxicity and genotoxicity of magnetosomes, respectively. Under these conditions, magnetosomes showed no cytotoxic, genotoxic and hemolytic effects up to 4.0 mg/ml indicating good biocompatibility of these biological nanoparticles. These revealed that the magnetosomes might have a potential for biotechnological and biomedical applications in the future.     

Oxygen incorporation duringin situ growth of YBCO films on both sides of substrates

Oxygen out-diffusion during cooling and heating ofin situ grown {ie685-1} (YBCO) films in low oxygen pressure used during growth by pulsed laser deposition was studied in the temperature range 700−450°C usingin situ resistance measurements. Results indicate that irrespective of the number of cooling and heating cycles seen by the films, full oxygenation of the films can be realized by the final cooling from the growth temperature in 500 torr oxygen pressure. This result has been successfully used to sequentially grow high quality YBCO films on both sides of LaAlO₃ substrates. These films have been used for the fabrication of X-band microstrip resonators with superconducting ground plane.     

Esperanza condicionada para probabilidades finitamente aditivas

Let (Ω, θ,J) be a finitely additive probabilistic space formed by any set Ω, an algebra of subsets θ and a finitely additive probabilityJ. In these conditions ifF belongs toV ¹ (Ω, θ,J) there existsf, element of the completion ofL ¹ (Ω, θ,J), such thatF(E)=∫ _E fdJ for allE of θ and conversely. This integral representation gives sense to the following result, which is the objetive of this paper, in terms of the, point function: If β is a subalgebra of θ, for everyF ofV ¹ (Ω, θ,J) there exists a unique element ofV ¹ (Ω, β,J) which we note down byE(F/gb), conditional expetation ofF given β. E(F/β) is characterized by (E(F/β),G)=(F, G) for every ofV ^∞(Ω,β, J). Aside from this, the mappingE(./β):V ¹ (Ω, θ,J)→V ¹ (Ω, β,J) is linear, positive, contractive, idempotent andE(J/β)=J. IfF is ofV ^p (Ω, θ,J),p>1,E(F/β) is ofV ^p (Ω, β,J).

     

In situ grown superconducting YBCO films on buffered silicon substrates for device applications

Thin films of YBa₂Cu₃O_7– (YBCO) have been grownin situ on silicon single-crystal (100) substrate by using SrTiO₃ as a buffer layer. The deposition has been carried out by on-axis rf magnetron sputtering method. The deposition condition have been optimized by studying the plasma characteristics and correlating them with the superconducting performance of the film. Films deposited at substrate temperature in the range of 680–700°C from stoichiometric YBCO targets in an argon + oxygen mixture (31) are superconducting and showc-axis epitaxy. Compositional confirmation has been carried out using Rutherford backscattering. Scanning tunneling microscopy of the films reveal formation of well-defined layered structure with some defects in the initial stages ofin situ growth of the films. Films grown on SrTiO₃ substrates have excellent crystalline quality (XRD), transition temperatureT _c0=81 K and the critical current densityJ _c >2×10⁵ A/cm² for unpatterned films at 77 K. On silicon substrates using buffer layers thein situ deposited YBCO films shows a higher transition width andT _c0 is also slightly less (71 K).     

An isomorphism theorem between the 7-adic integers and a ring associated with a hexagonal lattice

The primary goal of this paper is to prove that a ring defined by L. Gibson and D. Lucas is isomorphic to the ring of 7-adic integers. The ring, denoted byR ₂, arises naturally as an algebraic structure associated with a hexagonal lattice. The elements ofR ₂ consist of all infinite sequences in /(7). The addition and multiplication operations are given in terms of remainder and carries tables. The Generalized Balanced Ternary, denoted byG, is the subring ofR ₂ consisting of all the finite sequences ofR ₂. IfI _k is the ideal ofG consisting of all those sequences whose firstk digits are zero, then the second goal of the paper is to show that the inverse limit ofG/I _k is also isomorphic to the 7-adic integers.     

Role of lead in the growth of the highT c phase in the Bi2−x Pb x Sr2Ca2Cu3O y systems

Bi_2−x Pb _x Sr₂Ca₂Cu₃O _y superconducting samples with 0<x<0·3 have been synthesized and characterized using X-ray powder diffraction.T _c and superconducting volume fraction have been measured using a.c. magnetic susceptibility, d.c. electrical resistivity as well as X-band microwave surface resistance in the normal state. The data indicate the growth of the highT _c (2223) phase with corresponding reduction of the lowT _c (2122) phase with increasingx, up to 0·25. Beyond this value ofx there is a slight deterioration of the superconducting behaviour.     

An improved representation forn-alkane liquid densities

New experimental density data have been used to improve a recently published correlation ofn-alkane densities, based on the Tait equation. The new correlation covers then-alkanes from methane ton-hexadecane in an extended pressure range of up to 500 MPa in some cases. The overall average deviation of the experimental measurements of the density from those calculated by the correlation is ±0.10%. A simple extension to n-alkane mixtures gives a satisfactory prediction of the density compared with experimental data.     

t-Model mechanism of high-Tc cuprates

A doublon formalism ofd-p model Hubbard Hamiltonian is studied only with transfer integrals, and without the superexchange term. This gives excellent doping-dependent features ofT _c in high-T _c cuprates.     

High-pressure dc sputtering of High-Tc BPSCCO thin films withTc(0) above 100 K

High-T _c Bi(Pb)-Sr-Ca-Cu-O thin films have been made on single-crystal MgO substrates using high-pressure dc sputtering technique. X-ray studies confirm the crystallinity and highly oriented structure withc-axis perpendicular to the substrate. By optimizing the annealing schedule the formation of the high-T _c phase is stabilized. The best film exhibited superconducting transition temperature with zero-resistance temperature,T _c(0), as high as 101 K. Temperature dependence ofJ _c indicates the presence of Josephson-type weak links.     

Systematic investigation of electronic structure in BEDT-TTF based organic superconductors withTc above 10 K; κ-(BEDT-TTF)2X (X=Cu(NCS)2, Cu[N(CN)2]Br, and Cu(CN)[N(CN)2])

The electronic structure of the title superconductors has been investigated by electrical resistivity, complex susceptibility, and electron paramagnetic resonance (EPR) measurements. The superconducting properties (pressure dependence ofT _c , magnetic penetration depth, upper critical field, and so on) of these three salts are similar to each other, while transport properties in the normal state have shown a large variety in the temperature dependence. In order to clarify the electronic structure in the normal state, the EPR parameters, the spin susceptibility ( _spin), and the linewidth (H _pp), are compared. An anomalous temperature dependence of theg-value has been observed below 150 K in the Cu(NCS)₂ and Cu(CN)[N(CN)₂] salts.