Purification and properties of Aspartate aminotransferase (E.C. 2.6.1.1) from skeletal muscle of Cirrhina mrigala

Aspartate aminotransferase (E.C. 2.6.1.1.) from the skeletal muscle of fresh water fish Cirrhina mrigala has been purified 40 fold by ammonium sulphate fractionation, adsorption on alumina Csub(8) gel and chromatography using DEAE-cellulose column and the properties of the purified enzyme studied. The pH optimum of the enzyme is 7.8. The Km value of aspartic acid and 2-oxoglutaric acid are found to be 2.8 x 10sub(-3) M and 1.0 x 10sub(-4) M respectively. The activity of enzyme is inhibited by p-chloromercurybenzoate, hydroxylamine hydrochloride and sodium cyanide. The inhibition by pchloromercurybenzoate is reversed by reduced glutathione, B-mercaptoethanol and cysteine. Dicarboxylic acids such as maleic acid, malic acid and succinic acid inhibit the enzyme activity. The enzyme is not activated by any of the metal ions tested and heavy metal ions such as mercury and silver strongly inhibit the enzyme activity.

Plans for laser spectroscopy of trapped cold hydrogen-like HCI

Laser spectroscopy studies are being prepared to measure the 1s ground state hyperfine splitting in trapped cold highly charged ions. The purpose of such experiments is to test quantum electrodynamics in the strong electric field regime. These experiments form part of the HITRAP project at GSI. A brief review of the planned experiments is presented. © 2005 Elsevier B.V. All rights reserved.

Local structure of Mn in (La1-xHox) 2/3Ca1/3MnO3 studied by X-ray absorption fine structure

Results of X-ray absorption fine structure measurements in manganites (La1-xHox)2/3Ca1/3MnO3 with 0.15 < x < 0.50 are presented. When LaMnO3 is doped with a, divalent element such as Ca2+, substituting for La3+, holes are induced in the filled Mn d orbitais. This leads to a, strong ferromagnetic coupling between Mn sites. Ca ions in La1-xCa xMnO3 introduce a distortion of the crystal lattice and mixed valence Mn ions (Mn3+ and Mn4+). On the other hand, in manganites (La1-xHox)2/3Ca 1/3MnO3 the substitution of La for Ho causes a lattice distortion and induces a disorder, which reduces a magnetic interaction. The ferromagnetic transition temperature and conductivity decrease very quickly with increasing x. The magnetic and transport properties of compounds depend on the local atomic structure around Mn ions. The information on the bond lengths and Debye-Waller factor are obtained from the extended X-ray absorption fine structure (EXAFS) data analysis. The charge state of Mn is determined from the position of the absorption edge in X-ray absorption near edge structure (XANES) data. XAFS results are in good agreement with magnetic characteristics of the studied materials.

Polishing Treatment of Molasses Wastewater with Iron Salts: the Role of Counter-ions

The effect of counter-ions on the coagulation of biologically treated molasses wastewater using iron-based coagulants was investigated. Parameters such as removals of chemical oxygen demand (COD) and color, and residual turbidity, were measured to evaluate coagulation performance. Experimental results showed that ferric chloride and ferric nitrate were more effective than ferric sulfate at optimal dosages, achieving 89 to 90% and 98 to 99% of COD and color removals, respectively, with residual turbidity of less than 5 NTU. High-performance size exclusion chromatography (HPSEC) results revealed differences in the removal of the molecular weight fraction of organic compounds using iron salts. Scanning electron microscopy (SEM) showed randomly formed coagulated flocs characterized with irregular, sheet-like shapes. Nitrate and chloride counter-ions had similar effects on coagulation performance compared to sulfate. Both FeCl3 and Fe(NO3)(3) yielded better results than Fe(SO4)(2) under underdosed and optimum dosage conditions. Coagulation efficiency was less adversely affected in the overdosed regions, however, if sulfate rather than chloride or nitrate was present. Water Environ. Res., 81, 2293 (2009).

Modelling and comparison of trapped fields in (RE)BCO bulk superconductors for activation using pulsed field magnetization

The ability to generate a permanent, stable magnetic field unsupported by an electromotive force is fundamental to a variety of engineering applications. Bulk high temperature superconducting (HTS) materials can trap magnetic fields of magnitude over ten times higher than the maximum field produced by conventional magnets, which is limited practically to rather less than 2 T. In this paper, two large c-axis oriented, single-grain YBCO and GdBCO bulk superconductors are magnetized by the pulsed field magnetization (PFM) technique at temperatures of 40 and 65 K and the characteristics of the resulting trapped field profile are investigated with a view of magnetizing such samples as trapped field magnets (TFMs) in situ inside a trapped flux-type superconducting electric machine. A comparison is made between the temperatures at which the pulsed magnetic field is applied and the results have strong implications for the optimum operating temperature for TFMs in trapped flux-type superconducting electric machines. The effects of inhomogeneities, which occur during the growth process of single-grain bulk superconductors, on the trapped field and maximum temperature rise in the sample are modelled numerically using a 3D finite-element model based on the H-formulation and implemented in Comsol Multiphysics 4.3a. The results agree qualitatively with the observed experimental results, in that inhomogeneities act to distort the trapped field profile and reduce the magnitude of the trapped field due to localized heating within the sample and preferential movement and pinning of flux lines around the growth section regions (GSRs) and growth sector boundaries (GSBs), respectively. The modelling framework will allow further investigation of various inhomogeneities that arise during the processing of (RE)BCO bulk superconductors, including inhomogeneous Jc distributions and the presence of current-limiting grain boundaries and cracks, and it can be used to assist optimization of processing and PFM techniques for practical bulk superconductor applications. © 2014 IOP Publishing Ltd.

Ferromagnetic modification of GaN film by Cu+ ions implantation

The structural and magnetic properties of Cu+ ions-implanted GaN films have been reported. Eighty kilo-electron-volt Cu+ ions were implanted into n-type GaN film at room temperature with fluences ranging from 1 x 10(16) to 8 x 10(16) cm(-2) and subsequently annealed at 800 degrees C for 1 h in N-2 ambient. PIXE was employed to determine the Cu-implanted content. The magnetic property was measured by the Quantum Design MPMS SQUID magnetometer. No secondary phases or clusters were detected within the sensitivity of XRD. Raman spectrum measurement showed that the Cu ions incorporated into the crystal lattice positions of GaN through substitution of Ga atoms. Apparent ferromagnetic hysteresis loops measured at 10 K were presented. The experimental result showed that the ferromagnetic signal strongly increased with Cu-implanted fluence from 1 x 10(16) to 8 x 10(16) cm(-2).

New observations on the pressure dependence of luminescence from Eu2+-doped MF2 (M = Ca, Sr, Ba) fluorides

The luminescence from Eu2+ ions in MF2 (M = Ca, Sr, Ba) fluorides has been investigated under the pressure range of 0-8 GPa. The emission band originating from the 4f(6)5d(1) -> 4f(7) transition of Eu2+ ions in CaF2 and SrF2 shows the red-shift as increasing pressure with pressure coefficients of -17 meV/GPa for CaF2 and -18 meV/GPa for SrF2. At atmospheric pressure, the emission spectrum of BaF2:Eu2+ comprises two peaks at 2.20 and 2.75 eV from the impurity trapped exciton (ITE) and the self-trapped exciton (STE), respectively. As the pressure is increased, both emission peaks shift to higher energies, and the shifting rate is slowed by the phase transition from the cubic to orthorhombic phase at 4 GPa. Due to the phase transition at 4-5 GPa pressure, the ITE emission disappears gradually, and the STE emission is gradually replaced by the 4f(6)5d(1) -> 4f(7) transition of Eu2+. Above 5 GPa, the pressure behavior of the 4f(6)5d(1) -> 4f(7) transition of EU2+ in BaF2: EU2+ is the same as the normal emission of Eu2+ in CaF2 and SrF2 phosphors.

Raman scattering study on Ga1-xMnxAs prepared by Mn ions implantation, deposition and post-annealing

Raman scattering measurements have been performed in Ga1-xMnxAs crystals prepared by Mn ions implantation, deposition, and post-annealing. The Raman spectrum measured from the implanted surface of the sample shows some weak phonon modes in addition to GaAs-like phonon modes, where the GaAs-like LO and TO phonons are found to be shifted by approximately 4 and 2 cm(-1), respectively, in the lower frequency direction compared to those observed from the unimplanted surface of the sample. The weak vibrational modes observed are assigned to hausmannite Mn3O4 like. The coupled LO-phonon plasmon mode (CLOPM), and defects and As related vibrational modes caused by Mn ions implantation, deposition, and post-annealing are also observed. The compositional dependence of GaAs-like LO phonon frequency is developed for strained and unstrained conditions and then using the observed LOGaAs peak, the Mn composition is evaluated to be 0.034. Furthermore, by analyzing the intensity of CLOPM and unscreened LOGaAs phonon mode, the hole density is evaluated to be 1.84 x 10(18) cm(-3). (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Luminescence temperature and pressure studies of Zn2SiO4 phosphors doped with Mn2+ and Eu3+ ions

Zn2SiO4:Mn2+, Zn2SiO4:Eu3+ and Zn2SiO4:Mn2+ Eu3+ phosphors were prepared by a sol-gel process and their luminescence spectra were investigated. The emission bands from intra-ion transitions of Mn2+ and Eu3+ samples were studied as a function of pressure. The pressure coefficient of Mn2+ emission was found to be -25.3 +/- 0.5 and -28.5 +/- 0.9 meV/GPa for Zn2SiO4:Mn2+ and Zn2SiO4:Mn2+ Eu3+, respectively. The Eu3+ emission shows only weak pressure dependence. The pressure dependences of the Mn2+ and Eu3+ emissions in Zn2SiO4:Mn2+ Eu3+ are slightly different from that in Zn2SiO4:Mn2+ and Zn2SiO4:Eu3+ samples, which can be attributed to the co-doping of Mn2+ and Eu3+ ions. The Mn2+ emission in the two samples, however, exhibits analogous temperature dependence and similar luminescence lifetimes, indicating no energy transfer from Mn2+ to Eu3+ occurs. (c) 2005 Elsevier B.V. All rights reserved.

Anomalous photoluminescence of InAs quantum dots implanted by Mn ions

The photoluminescence (PL) of Mn-implanted quantum dot (QD) samples after rapid annealing is studied. It is found that the blue shift of the PL peak of the QDs, introduced by the rapid annealing, decreases abnormally as the implantation dose increases. This anomaly is probably related to the migration of Mn atoms to the InAs QDs during annealing, which leads to strain relaxation when Mn atoms enter InAs QDs or to the suppression of the inter-diffusion of In and Ga atoms when Mn atoms surround QDs. Both effects will suppress the blue shift of the QD PL peaks. The temperature dependence of the PL intensity of the heavily implanted QDs confirms the existence of defect traps around the QDs. (c) 2006 Elsevier B.V. All rights reserved.

Violet/blue emission from hydrogenated amorphous carbon films deposited from energetic CH3+ ions and ion bombardment

Considering the complexity of the general plasma techniques, pure single CH3+ ion beams were selected for the deposition of hydrogenated amorphous (a) carbon films with various ion energies and temperatures. Photoluminescence (PL) measurements have been performed on the films and violet/blue emission has been observed. The violet/blue emission is attributed to the small size distribution of sp(2) clusters and is related to the intrinsic properties of CH3 terminals, which lead to a very high barrier for the photoexcited electrons. Ion bombardment plays an important role in the PL behavior. This would provide further insight into the growth dynamics of a-C:H films. (C) 2002 American Institute of Physics.

Photoluminescence of erbium-doped hydrogenated amorphous SiOx(0 < x < 2)

Hydrogenated amorphous SiOx films are fabricated via plasma enhanced chemical vapor deposition technique. After erbium implantation and rapid thermal annealing, photoluminescence (PL) are measured at 77 K and room temperature (RT), respectively. We observed the strong PL at 1.54 mu m at RT. The 1.54 mu m PL intensity changes with the variation of concentration of oxygen. The most intense PL at 77 K in a-SiOx:H (Er) corresponds to O/Si = 1.0 and at RT to O/Si = 1.76. Based on our results, we propose that Er ions contributed to PL come from O-rich region in the film. Er ions in Si-rich region have no relation with FL. Temperature dependence of the intensity of the 1.54 mu m line of the Er3+ transition displays a very weak temperature quenching in Er-doped hydrogenated amorphous Si. The PL intensity at 250 K is a little more one half of that at 15 K.

Intense room temperature near infrared emission from Al (3+) and Yb3+ ions

Intense near infrared emission was observed from Al3+ and Yb3+ ions co-implanted SiO2 film on silicon. It was found that the addition of Al3+ ions could remarkably improve the photoluminescence efficiency of Yb3+-implanted SiO2 film. No excitation power saturation was observed and trivial temperature quenching factor of 2 was achieved.

Broad-spectrum and long-lifetime emissions of Nd3+ ions in lead fluorosilicate glass

A novel Nd3+-doped lead fluorosilicate glass (NPS glass) is prepared by a two-step melting process. Based on the absorption spectrum a Judd-Ofelt theory analysis is made. The emission line width of NPS glass is 44.2nm. The fluorescence decay lifetime of the 4F3/2 level is 586±20μsec, and the stimulated emission cross-section is 0.87×10-20cm2 at 1056nm. A laser oscillation is occurred at 1062nm when pumped by 808nm Diode Laser. The slope efficiency is 23.7% with a 415mJ threshold. It is supposed that NPS glass is a good candidate for using in ultra-short pulse generation and amplification by the broad emission bandwidth and long fluorescence lifetime.