Sample records for mg feii kg-1

  1. Rapacuronium 2.0 or 2.5 mg kg(-1) for rapid-sequence induction : comparison with succinylcholine 1.0 mg kg(-1)

    Blobner, M; Mirakhur, RK; Wierda, JMKH; Wright, PMC; Olkkola, KT; Debaene, B; Pendeville, P; Engbaek, J; Rietbergen, H; Sparr, HJ


    The purpose of this nine-centre study in 602 patients was to show that the frequency of acceptable intubating conditions after rapacuronium 2.0 or 2.5 mg kg(-1) is not more than 10% lower than the frequency after succinylcholine 1.0 mg kg(-1) during rapid-sequence induction of anaesthesia with fenta

  2. Sugammadex 4.0 mg kg-1 reversal of deep rocuronium-induced neuromuscular blockade

    Yu, Buwei; Wang, Xiangrui; Hansen, Søren Helbo


    Objective: Maintenance of deep Neuro Muscular Blockade (NMB) until the end of surgery may be beneficial in some surgical procedures. The selective relaxant binding agent sugammadex rapidly reverses deep levels of rocuronium-induced NMB. The purpose of this study was to evaluate the efficacy...... and safety of sugammadex 4.0 mg kg-1 for reversal of deep rocuronium-induced NMB in Chinese and Caucasian patients. Methods: This was an open-label, multicenter, prospective Phase III efficacy study in adult American Society of Anesthesiologists Class 1-3 patients scheduled for surgery under general...... anesthesia and requiring deep NMB. All patients received intravenous propofol and opioids for induction and maintenance of anesthesia, and a single intubation dose of rocuronium 0.6 mg/kg, with maintenance doses of 0.1-0.2 mg/kg as required. Sugammadex 4.0 mg/kg was administered after the last dose...

  3. Efficacy, safety and pharmacokinetics of sugammadex 4 mg kg-1 for reversal of deep neuromuscular blockade in patients with severe renal impairment.

    Panhuizen, I F; Gold, S J A; Buerkle, C; Snoeck, M M J; Harper, N J N; Kaspers, M J G H; van den Heuvel, M W; Hollmann, M W


    This study evaluated efficacy and safety of sugammadex 4 mg kg(-1) for deep neuromuscular blockade (NMB) reversal in patients with severe renal impairment (creatinine clearance [CLCR] Sugammadex 4 mg kg(-1) was administered at 1-2 post-tetanic counts for reversal of rocuronium NMB. Primary efficacy variable was time from sugammadex to recovery to train-of-four (T4/T1) ratio 0.9. Equivalence between groups was demonstrated if two-sided 95% CI for difference in recovery times was within -1 to +1 min interval. Pharmacokinetics of rocuronium and overall safety were assessed. The intent-to-treat group comprised 67 patients (renal n=35; control n=32). Median (95% CI) time from sugammadex to recovery to T4/T1 ratio 0.9 was 3.1 (2.4-4.6) and 1.9 (1.6-2.8) min for renal patients vs controls. Estimated median (95% CI) difference between groups was 1.3 (0.6-2.4) min; thus equivalence bounds were not met. One control patient experienced acceleromyography-determined NMB recurrence, possibly as a result of premature sugammadex (4 mg kg(-1)) administration, with no clinical evidence of NMB recurrence observed. Rocuronium, encapsulated by Sugammadex, was detectable in plasma at day 7 in 6 patients. Bioanalytical data for sugammadex were collected but could not be used for pharmacokinetics. Sugammadex 4 mg kg(-1) provided rapid reversal of deep rocuronium-induced NMB in renal and control patients. However, considering the prolonged sugammadex-rocuronium complex exposure in patients with severe renal impairment, current safety experience is insufficient to support recommended use of sugammadex in this population. NCT00702715. © The Author 2015. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email:

  4. Postoperative impairment of motor function at train-of-four ratio ≥0.9 cannot be improved by sugammadex (1 mg kg-1).

    Baumüller, E; Schaller, S J; Chiquito Lama, Y; Frick, C G; Bauhofer, T; Eikermann, M; Fink, H; Blobner, M


    A train-of-four ratio (TOFR) ≥0.9 measured by quantitative neuromuscular monitoring is accepted as an indication of sufficient neuromuscular recovery for extubation, even though many postsynaptic acetylcholine receptors may still be inhibited. We investigated whether antagonism with sugammadex after spontaneous recovery to TOFR≥0.9 further improves muscle function or subjective well-being. Following recovery to TOFR≥0.9 and emergence from anaesthesia, 300 patients randomly received either sugammadex 1.0 mg kg(-1) or placebo. Fine motor function (Purdue Pegboard Test) and maximal voluntary grip strength were measured before and after surgery (before and after test drug administration). At discharge from the postanaesthesia care unit, well-being was assessed with numerical analogue scales and the Quality-of-Recovery Score 40 (QoR-40). Patients' fine motor function [6 (sd 4) vs 15 (3) pegs (30 s)(-1), Psugammadex or placebo, motor function was significantly improved in both groups but did not reach the preoperative level. There was no difference between groups at any time. Global well-being was unaffected (QoR-40: placebo, 174 vs 185; sugammadex, 175 vs 186, P>0.05). Antagonizing rocuronium at TOF≥0.9 with sugammadex 1.0 mg kg(-) (1) did not improve patients' motor function or well-being when compared with placebo. Our data support the view that TOFR≥0.9 measured by electromyography signifies sufficient recovery of neuromuscular function. The trial is registered at (NCT01101139). © The Author 2014. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email:

  5. Children and parental anxiolysis in paediatric ambulatory surgery: a randomized controlled study comparing 0.3 mg kg-1 midazolam to tablet computer based interactive distraction.

    Marechal, C; Berthiller, J; Tosetti, S; Cogniat, B; Desombres, H; Bouvet, L; Kassai, B; Chassard, D; de Queiroz Siqueira, M


    The operating theatre, anaesthesia induction and separation from parents create fear and anxiety in children. Anxiety leads to adverse behavioral changes appearing and sometimes persisting during the postoperative period. Our aim was to compare the effects of midazolam (0.3 mg kg(-)(1): MDZ) for premedication with age-appropriate tablet game apps (TAB) on children anxiety during and after ambulatory surgery. A randomized controlled trial was conducted from May 16th, 2013 to March 25th, 2014 at the Children Hospital of Lyon. The primary outcome of this study was the change in m-YPAS score at the time of anaesthetic mask induction. Anxiety was also assessed in the waiting surgical area, at the time of separation with parents and when back in the ambulatory surgery ward. One hundred and eighteen patients aged four-11 yr were recruited, 60 in the TAB Group and 58 in the MDZ Group. Main endpoint was missing for three patients from the MDZ Group. At the time of mask induction, there was no significant difference between MDZ and TAB Group for the m-YPAS score (40.5 (18.6) vs 41.8 (20.7), P = 0.99). There was no significant correlation between m-YPAS score and its evolution over the four period of time between subjects. We were not able to show whether TAB is superior to MDZ to blunt anxiety in children undergoing ambulatory surgery. TAB is a non-pharmacological tool which has the capacity in reducing perioperative stress without any sedative effect in this population. NCT 02192710. © The Author 2017. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email:

  6. Fine-Structure FeII* Emission and Resonant MgII Emission in z = 1 Star-Forming Galaxies

    Kornei, K A; Martin, C L; Coil, A L; Lotz, J M; Weiner, B J


    We present a study of the prevalence, strength, and kinematics of ultraviolet FeII and MgII emission lines in 212 star-forming galaxies at z = 1 selected from the DEEP2 survey. We find FeII* emission in composite spectra assembled on the basis of different galaxy properties, indicating that FeII* emission is prevalent at z = 1. In these composites, FeII* emission is observed at roughly the systemic velocity. At z = 1, we find that the strength of FeII* emission is most strongly modulated by dust attenuation, and is additionally correlated with redshift, star-formation rate, and [OII] equivalent width, such that systems at higher redshifts with lower dust levels, lower star-formation rates, and larger [OII] equivalent widths show stronger FeII* emission. We detect MgII emission in at least 15% of the individual spectra and we find that objects showing stronger MgII emission have higher specific star-formation rates, smaller [OII] linewidths, larger [OII] equivalent widths, lower dust attenuations, and lower st...

  7. Strongly Variable z=1.48 MgII and FeII Absorption in the Spectra of z=4.05 GRB 060206

    Hao, H; Dobrzycki, A; Matheson, T; Bentz, M C; Kuraszkiewicz, J; Garnavich, P M; Howk, J C; Calkins, M L; Worthey, G; Modjaz, M; Serven, J


    We report on the discovery of strongly variable MgII and FeII absorption lines seen at z=1.48 in the spectra of the z=4.05 GRB 060206 obtained between 4.13 to 7.63 hours after the burst. In particular, the FeII line equivalent width (EW) decayed rapidly from 1.72+-0.25 AA to 0.28+-0.21 AA, only to increase to 0.96+-0.21 AA in a later date spectrum. The MgII doublet shows even more complicated evolution: the weaker line of the doublet drops from 2.05+-0.25 AA to 0.92+-0.32 AA, but then more than doubles to 2.47+-0.41 AA in later data. The ratio of the EWs for the MgII doublet is also variable, being closer to 1:1 (saturated regime) when the lines are stronger and becoming closer to 2:1 (unsaturated regime) when the lines are weaker, consistent with expectations based on atomic physics. We have investigated and rejected the possibility of any instrumental or atmospheric effects causing the observed strong variations. The possibility of variable intervening absorption in GRB spectra was recently predicted by Fra...

  8. Effects of waterborne Fe(II) on juvenile turbot Scophthalmus maximus: analysis of respiratory rate, hematology and gill histology

    Wu, Zhihao; You, Feng; Liu, Hongjun; Liu, Mengxia; Li, Jun; Zhang, Peijun


    The concentration of Fe(II) is high in some groundwater supplies used in turbot culture, and the toxicity of waterborne Fe(II) is unknown. We investigated the stress responses of juvenile turbot, Scophthalmus maximus, exposed to Fe(II) of different concentrations (0.01, 0.05, 0.1, 0.5, 1, and 2 mg/L) for 1, 7, 14, and 28 d, under the same ambient conditions of other parameters. Changes in respiratory rate, hematological parameters, and gill structure were determined. The results show that waterborne Fe(II) did not cause severe hematological perturbation to turbot. A low-medium Fe(II) concentration (lower than 0.1 mg/L) could boost the respiratory rate, and caused no or very limited damage to fish. A high Fe(II) concentration (0.1 mg/L or higher), however, caused gill damage, such as vacuoles in branchial lamellae, epithelial necrosis, and hypertrophy of epithelial cells, and even death after extended exposure time. Therefore, excess waterborne Fe(II) and long-term exposure to Fe(II) could be responsible for poor growth and high mortality of turbot in culture. The concentration of waterborne Fe(II) in turbot culture should be kept below 0.1 mg/L.

  9. Single doses of ivermectin 400 micrograms/kg-1: the most effective dosage in bancroftian filariasis.

    Moulia-Pelat, J P; Glaziou, P; Nguyen, L N; Cartel, J L


    Forty-three Wuchereria bancrofti carriers were given four successive semi-annual single doses of ivermectin 100 (IVER 100). The geometric mean microfilaremia (mf) recurrence percentage as compared to the pre-initial treatment mf level was 35%, 21%, 17% and 17% at 6, 12, 18 and 24 months, respectively. However, the recurrence of mf 6 months after the fourth treatment remained high in several individuals: 15 have been considered as 'bad responders' and 28 as 'good responders' individuals. At month 24 (M 24), they were randomly allocated into 2 groups. A first group was treated with a fifty and a sixth dose of IVER 100, at M24 and M30, respectively; the second one was treated, at the same time, with single doses of IVER 400 (IVER 400). At M 36, the mf recurrence percentage (mf M36/mf M0) was significantly higher in patients treated with IVER 100 than IVER 400 (11% vs 1%, p < 10(-4). From the group IVER 100, 6 out of the 8 'bad responders' remained 'bad responders' whereas there were none of the 7 in the group IVER 400. Moreover, there were only 2 more patients in the group IVER 100 showing sustained complete zero mf, whereas they were 13 in the group IVER 400. Single doses of IVER 400 were effective on 'bad responders'; IVER 400 must be recommended for semi-annual mass treatment in bancroftian filariasis.

  10. Effects of the combination of decitabine and homoharringtonine in SKM-1 and Kg-1a cells.

    Geng, Suxia; Yao, Han; Weng, Jianyu; Tong, Jiaqi; Huang, Xin; Wu, Ping; Deng, Chengxin; Li, Minming; Lu, Zesheng; Du, Xin


    The methylation inhibitor decitabine (DAC) has great therapeutic value for myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). However, DAC monotherapy is associated with relatively low rates of overall response and complete remission. Previous studies have shown promising results for combination treatment regimens including DAC. Homoharringtonine (HHT), an alkaloid from Chinese natural plants and Cephalotaxus, has demonstrated potential for leukemia treatment. Our studies have suggested that the combination of DAC and HHT has synergistic effects for inhibiting the viability of SKM-1 and Kg-1a cells. This combination leads to enhanced inhibition of colony formation and apoptosis induction compared with DAC alone in SKM-1 but not Kg-1a cells. Only high-dose DAC and HHT significantly up-regulate caspase-3 and caspase-9 and inhibit BCL-XL in the SKM-1 cell line. The combined effects of DAC plus HHT on apoptosis may not only depend on regulation of the apoptosis-related genes we examined but others as well. HHT had no demethylation effects, and HHT in combination with DAC had no enhanced effects on hypomethylation and DNMT1, DNMT3A and DNMT3B mRNA expression in SKM-1 cells. Overall, these results suggest that DAC used in combination with HHT may have clinical potential for MDS treatment.

  11. 白藜芦醇增强TRAIL对人髓系白血病KG-1a细胞的细胞毒作用%Resveratrol enhances cytotoxicity of TRAIL to human promyloblastic leukemia KG-1a cells

    胡亮杉; 孙茂本; 曾雅丽; 李玉华; 邓兰; 郭坤元


    目的:观察白藜芦醇作用前后TRAIL对人髓系白血病KG-1a细胞的细胞毒作用的变化.方法:流式细胞仪检测KG-1a细胞表面CD34 和CD38的表达,二甲氧唑黄(XTT)细胞增殖及细胞毒性检测试剂盒检测白藜芦醇作用前后TRAIL对KG-1a细胞增殖的影响,AnnexinV-FITC/PI染色流式细胞仪检测细胞凋亡变化.流式细胞仪检测白藜芦醇作用前后KG-1a细胞表面TRAIL死亡受体表达变化.结果:人髓系白血病KG-1a细胞 CD34+CD38-占(58.67±2.87)%,10~1 000 ng/ml 的TRAIL对KG-1a细胞增殖无明显影响,但对白藜芦醇作用后的KG-1a细胞的增殖有明显抑制作用,白藜芦醇能促进TRAIL诱导KG-1a细胞凋亡,并能上调KG-1a细胞表面TRAIL死亡受体DR5的表达.结论:白藜芦醇能增强TRAIL对人髓系白血病KG-1a细胞的细胞毒作用,其机制可能与白藜芦醇上调KG-1a细胞表面TRAIL死亡受体DR5的表达有关.%Objective :To explore the cytotoxicity of TRAIL to human acute promyeloblastic leukemia KG-1a cells treated with resvera trol .Methods :The expression of CD34 and CD38 on the Surface of KG-1 cells was detected by flow cytometry ;The effects of various concentration TRAIL on proliferation of KG-1a cells treated with or without resveratrol were analyzed by XTT cell proliferation and cytotoxicity assay kit ;The changes of apoptosis in KG-1a cells treated with or without resveratrol induced by TRAIL were detected by flow cytometry through the staining of AnnexinV-FITC /PI ;The effects of resveratrol on the expression of DR4/5 on the surface of KG-1a cells were detected by flow cytometry .Results :The CD34+ CD38- percent age of KG-1a cells was (58 .67±2 .87 )% ;10-1 000 ng/ml of TRAIL had no effects on the proliferation of KG-1a cells ,while could inhibit the proliferation of KG-1a cells treated with resveratrol ;Moreover ,resveratrol could enhance the apoptosis of KG-1a cells induced by TRAIL and up-regulate the expression of TIRAIL death receptors DR5

  12. Removal of Fe(II) from tap water by electrocoagulation technique

    Ghosh, D.; Solanki, H. [Department of Chemical Engineering, Indian Institute of Technology, Guwahati 781039 (India); Purkait, M.K. [Department of Chemical Engineering, Indian Institute of Technology, Guwahati 781039 (India)], E-mail:


    Electrocoagulation (EC) is a promising electrochemical technique for water treatment. In this work electrocoagulation (with aluminum as electrodes) was studied for iron Fe(II) removal from aqueous medium. Different concentration of Fe(II) solution in tap water was considered for the experiment. During EC process, various amorphous aluminum hydroxides complexes with high sorption capacity were formed. The removal of Fe(II) was consisted of two principal steps; (a) oxidation of Fe(II) to Fe(III) and (b) subsequent removal of Fe(III) by the freshly formed aluminum hydroxides complexes by adsorption/surface complexation followed by precipitation. Experiments were carried out with different current densities ranging from 0.01 to 0.04 A/m{sup 2}. It was observed that the removal of Fe(II) increases with current densities. Inter electrode distance was varied from 0.005 to 0.02 m and was found that least inter electrode distance is suitable in order to achieve higher Fe(II) removal. Other parameters such as conductivity, pH and salt concentration were kept constant as per tap water quality. Satisfactory iron removal of around 99.2% was obtained at the end of 35 min of operation from the initial concentration of 25 mg/L Fe(II). Iron concentration in the solution was determined using Atomic absorption spectrophotometer. By products obtained from the electrocoagulation bath were analyzed by SEM image and corresponding elemental analysis (EDAX). Cost estimation for the electrocoagulation was adopted and explained well. Up to 15 mg/L of initial Fe(II) concentration, the optimum total cost was 6.05 US$/m{sup 3}. The EC process for removing Fe(II) from tap water is expected to be adaptable for household use.

  13. TGF-β1对白血病KG-1细胞株Gli1表达的影响%Effect of TGF-β1 on Gli1 expression in KG-1 cell line

    李哲; 潘静


    Objective To prove that there was cross talk between Hh signaling pathway and TGF-β signaling pathway in KG-1 cells line. Methods (1) KG-1 cells were treated with 0. 1 ng/mL,l ng/mL,and 10 ng/mL TGF-β1 for 6 h,12 h,and 24 h respectively. Cells were collected after stimulation. Total mRNA was extracted. Glil expression was detected by real-time PCR. (2) KG-1 cells were treated with 5 ng/mL TGFβ1 and 5 ng/mL TGF-β1 +5 μmol SIS3 respectively for 24h. Cells were collected after stimulation. Total mRNA was extracted. Glil expression was detected. Results (1) When 1- 10 ng/mL TGF-β1 acted on the KG-1 cells respectively for 6 h, 12 h and 24 h, significant reduction of Glil mRNA in response to TGF-β1 was observed in KG-1 cells, emerging at 12 h and lasting at least 24 h,lower than that of the control group. (2) When 5 ng/mL TGF-β1 and 5 ng/mL TGF-β1 +5 μmol SIS3 acted on the KG-1 cells respectively for 24 h respectively,Glil expression of mRNA of control group was higher than that of TGF-β1 group, while much lower than that of TGF-β1 +SIS3 group. Conclusion TGF-β1significantly decreased Glil expression in KG-1 cells. Glil induction in KG-1 cells by TGF-β1 was a Smad3-dependent manner. This effect was independent from the Ptch/Smo axis.%目的 证明在白血病KG-1细胞株中存在TGF-β信号通路对Gli的调控作用.方法 (1)用0.1、1、10 ng/mL TGF-β1分别作用于KG-1细胞,时间分别为6、12、24 h.处理结束后收集细胞,提取mRNA,检测Gli1的表达.(2)5 ng/mL TGF-β1、5 ng/mL TGF-β1联合5 μmol SIS3分别作用于KG-1细胞24 h.处理结束后收集细胞,提取mRNA,检测Gli1的表达.结果 (1)1~10 ng/mL TGF-β1分别作用于KG-1细胞6、12、24 h,从12 h起并至少持续至24 h,其Gli1的mRNA表达较对照组明显减少;(2)5 ng/mL TGF-β1、5ng/mL TGF-β1联合5 μmol SIS3分别作用于KG-1细胞24 h,其Gli1的mRNA表达与对照组比较:5 ng/mL TGF-β1组较对照组降低,而5 ng/mL TGF-β1联合5 μmol SIS3组较

  14. Persistence of Fe(II) in Seawater Due to the Effect of Organic Exudates from D. tertiolecta

    Gonzalez, A.; Santana-Casiano, M.; González-Dávila, M.; Rico-Santos, M.; Lopez, A.; Perez-Almeida, N.; Suarez de Tangil, M. A.; Martel-Quintana, A.


    The chemistry of iron is highly affected by the presence of organic ligands in solution, where the exudates produced by microorganisms play a key role. In this sense, the Fe(II) oxidation was studied in the presence of exudates produced by Dunaliella tertiolecta. The Fe(II) oxidation rate was studied at different stages of growth, where the Dissolved Organic Carbon (DOC) increased from 2.1 to 7.1 mg L-1. The oxidation of Fe(II) was also studied as a function of pH (7.2 - 8.2), temperature (5-35 °C) and salinity (10-37). The presence of exudates invoked a decrease in Fe(II) rate constant with respect to the control seawater. On the other hand, the phenolic profile of the exudates and extracts of D. tertiolecta were studied in the stationary phase (8 days of culture) and compared with the control seawater. The phenolic profile revealed an enrichment in phenolic compounds that are able to reduce Fe(III) to Fe(II) acting as a source of Fe(II) in the surface waters. The two phenolic compounds, catechin and sinapic acid, were selected to study the reduction of Fe(III) in seawater from pH 8.0 to 6.0. The reduction of Fe(III) by these two phenolic compounds was a pH-dependent process. The organic exudates of D. tertiolecta favoured the persistence of Fe(II) in surface waters. This must be factored under ocean acidification conditions due to the key role played by them on the Fe(II) oxidation rate at lower pH values. As they are responsible for decreasing the Fe(II) oxidation rate, these experiments indicated that the exudates of D. tertiolecta can act as an important Fe(II) supplier to other marine organisms.

  15. Magnetic gold nanoparticles: synthesis, characterization and its application in the delivery of FITC into KG-1 cells.

    Hao, Yuzhi; Song, Steven; Yang, Xiaoyan; Xing, James; Chen, Jie


    In this article, we report a new method-a sonication method to disperse iron oxide nanoparticles into smaller nanoparticles and make gold ions absorb onto the surface or trapped in the micropores of the iron oxide nanoparticles using sonication action. By using quick reduction of ascorbic acid and post-HCI solution treatment, gold covered magnetic nanoparticles (mGNPs) with spherical morphology and uniform size were synthesized in a water solution. The size of the mGNPs was found to be 20-30 nm. Some ideal mGNPs possessed a core-shell structure. The mGNPs were non-cytotoxic and mGNP-fluorescein isothiocyanate (FITC) can enter KG-1 cells when driven by an external magnetic force, which was confirmed by confocal imaging. The confocal image also showed the FITC inside the KG-1 cells was near the nucleus. The fluorescein isothiocyanate (FITC) delivery efficiency is about 100% according to the flow cytometry results.

  16. Determination of Total Iron as Fe(II) in Multivitamins, Haematinics ...

    The determination of total iron in pharmaceutical products and natural waters as Fe(II) ... as a [Fe(phen)32+] complex at 515 nm with a UV/Vis spectrophotometer. The linear range of the system is between 1 and 60 mg/l with a detection limit of ...

  17. What controls the FeII strength in active galactic nuclei?

    Dong, Xiaobo; Wang, Tinggui; Wang, Huiyuan; Fan, Xiaohui; Zhou, Hongyan; Yuan, Weimin


    We have investigated the correlations of the equivalent widths (EWs) of narrow and broad FeII emission lines and the FeII/MgII intensity ratio with fundamental physical parameters of active galactic nuclei (AGNs), luminosity (L), black hole mass (M_{BH}) and Eddington ratio (L/Ledd), using a homogenous sample of z<0.8 Seyfert 1 galaxies and QSOs in the spectroscopic data set of Sloan Digital Sky Survey Fourth Data Release (SDSS DR4). The sample comprises 4178 spectra that are selected to suffer little from the host-galaxy starlight contamination. We find that the strongest correlations of almost all the emission-line intensity ratios and EWs are with L/Ledd, either positively (e.g. FeII EW) or negatively (e.g. MgII EW), rather than with L or M_{BH}; In particular, the intensity ratios of both the ultraviolet and optical FeII emissions to MgII 2800 correlate quite tightly with L/Ledd (e.g., Spearman r_s = 0.74 for the [narrow FeII]/MgII -- L/Ledd correlation). We have also investigated the FeII emission in ...

  18. Online spectrophotometric determination of Fe(II) and Fe(III) by flow injection combined with low pressure ion chromatography

    Chen, Shujuan; Li, Nan; Zhang, Xinshen; Yang, Dongjing; Jiang, Heimei


    A simple and new low pressure ion chromatography combined with flow injection spectrophotometric procedure for determining Fe(II) and Fe(III) was established. It is based on the selective adsorption of low pressure ion chromatography column to Fe(II) and Fe(III), the online reduction reaction of Fe(III) and the reaction of Fe(II) in sodium acetate with phenanthroline, resulting in an intense orange complex with a suitable absorption at 515 nm. Various chemical (such as the concentration of colour reagent, eluant and reductive agent) and instrumental parameters (reaction coil length, reductive coil length and wavelength) were studied and were optimized. Under the optimum conditions calibration graph of Fe(II)/Fe(III) was linear in the Fe(II)/Fe(III) range of 0.040-1.0 mg/L. The detection limit of Fe(III) and Fe(II) was respectively 3.09 and 1.55 μg/L, the relative standard deviation (n = 10) of Fe(II) and Fe(III) 1.89% and 1.90% for 0.5 mg/L of Fe(II) and Fe(III) respectively. About 2.5 samples in 1 h can be analyzed. The interfering effects of various chemical species were studied. The method was successfully applied in the determination of water samples.

  19. Removal of Fe(II) from the wastewater of a galvanized pipe manufacturing industry by adsorption onto bentonite clay.

    Tahir, S S; Rauf, Naseem


    Bentonite clay has been used for the adsorption of Fe(II) from aqueous solutions over a concentration range of 80-200 mg/l, shaking time of 1-60 min, adsorbent dosage from 0.02 to 2 g and pH of 3. The process of uptake follows both the Langmuir and Freundlich isotherm models and also the first-order kinetics. The maximum removal (>98%) was observed at pH of 3 with initial concentration of 100 mg/l and 0.5 g of bentonite. The efficiency of Fe(II) removal was also tested using wastewater from a galvanized pipe manufacturing industry. More than 90% of Fe(II) can be effectively removed from the wastewater by using 2.0 g of the bentonite. The effect of cations (i.e. zinc, manganese, lead, cadmium, nickel, cobalt, chromium and copper) on the removal of Fe(II) was studied in the concentration range of 10-500 mg/l. All the added cations reduced the adsorption of Fe(II) at high concentrations except Zn. Column studies have also been carried out using a certain concentration of wastewater. More than 99% recovery has been achieved by using 5 g of the bentonite with 3M nitric acid solution.

  20. Incidence of HI 21-cm absorption in strong FeII systems at $0.5

    Dutta, R; Gupta, N; Joshi, R; Petitjean, P; Noterdaeme, P; Ge, J; Krogager, J -K


    We present the results from our search for HI 21-cm absorption in a sample of 16 strong FeII systems ($W_{\\rm r}$(MgII $\\lambda2796$) $\\ge1.0$ \\AA\\ and $W_{\\rm r}$(FeII $\\lambda2600$) or $W_{\\rm FeII}$ $\\ge1$ \\AA) at $0.5MgII systems at this redshift range by $\\sim50$%. Combining our measurements with those in the literature, we find that the detection rate of HI 21-cm absorption increases with $W_{\\rm FeII}$, being four times higher in systems with $W_{\\rm FeII}$ $\\ge1$ \\AA\\ compared to systems with $W_{\\rm FeII}$ $<1$ \\AA. The $N$(HI) associated with the HI 21-cm absorbers would be $\\ge 2 \\times 10^{20}$ cm$^{-2}$, assuming a spin temperature of $\\sim500$ K (based on HI 21-cm absorption measurements of damped Lyman-$\\alpha$ systems at this redshift range) and unit covering factor. We find that ...

  1. Advanced oxidation removal of hypophosphite by O3/H2O2 combined with sequential Fe(II) catalytic process.

    Zhao, Zilong; Dong, Wenyi; Wang, Hongjie; Chen, Guanhan; Wang, Wei; Liu, Zekun; Gao, Yaguang; Zhou, Beili


    Elimination of hypophosphite (HP) was studied as an example of nickel plating effluents treatment by O3/H2O2 and sequential Fe(II) catalytic oxidation process. Performance assessment performed with artificial HP solution by varying initial pH and employing various oxidation processes clearly showed that the O3/H2O2─Fe(II) two-step oxidation process possessed the highest removal efficiency when operating under the same conditions. The effects of O3 dosing, H2O2 concentration, Fe(II) addition and Fe(II) feeding time on the removal efficiency of HP were further evaluated in terms of apparent kinetic rate constant. Under improved conditions (initial HP concentration of 50 mg L(-1), 75 mg L(-1) O3, 1 mL L(-1) H2O2, 150 mg L(-1) Fe(II) and pH 7.0), standard discharge (oxidation treatment favored the improvement of phosphorus removal due to the formation of more metal hydroxides. Moreover, as a comparison with lab-scale Fenton approach, the O3/H2O2─Fe(II) oxidation process had more competitive advantages with respect to applicable pH range, removal efficiency, sludge production as well as economic costs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Sorption and catalytic oxidation of Fe(II) at the surface of calcite

    Mettler, S.; Wolthers, M.; Charlet, L.; Von Gunten, U.


    The effect of sorption and coprecipitation of Fe(II) with calcite on the kinetics of Fe(II) oxidation was investigated. The interaction of Fe(II) with calcite was studied experimentally in the absence and presence of oxygen. The sorption of Fe(II) on calcite occurred in two distinguishable steps: (a

  3. Salinomycin overcomes ABC transporter-mediated multidrug and apoptosis resistance in human leukemia stem cell-like KG-1a cells

    Fuchs, Dominik [Research Group Molecular Neuro-Oncology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg (Germany); Institute of Immunology, University of Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg (Germany); Daniel, Volker; Sadeghi, Mahmoud; Opelz, Gerhard [Institute of Immunology, University of Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg (Germany); Naujokat, Cord, E-mail: [Institute of Immunology, University of Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg (Germany)


    Leukemia stem cells are known to exhibit multidrug resistance by expression of ATP-binding cassette (ABC) transporters which constitute transmembrane proteins capable of exporting a wide variety of chemotherapeutic drugs from the cytosol. We show here that human promyeloblastic leukemia KG-1a cells exposed to the histone deacetylase inhibitor phenylbutyrate resemble many characteristics of leukemia stem cells, including expression of functional ABC transporters such as P-glycoprotein, BCRP and MRP8. Consequently, KG-1a cells display resistance to the induction of apoptosis by various chemotherapeutic drugs. Resistance to apoptosis induction by chemotherapeutic drugs can be reversed by cyclosporine A, which effectively inhibits the activity of P-glycoprotein and BCRP, thus demonstrating ABC transporter-mediated drug resistance in KG-1a cells. However, KG-1a are highly sensitive to apoptosis induction by salinomycin, a polyether ionophore antibiotic that has recently been shown to kill human breast cancer stem cell-like cells and to induce apoptosis in human cancer cells displaying multiple mechanisms of drug and apoptosis resistance. Whereas KG-1a cells can be adapted to proliferate in the presence of apoptosis-inducing concentrations of bortezomib and doxorubicin, salinomycin does not permit long-term adaptation of the cells to apoptosis-inducing concentrations. Thus, salinomycin should be regarded as a novel and effective agent for the elimination of leukemia stem cells and other tumor cells exhibiting ABC transporter-mediated multidrug resistance.

  4. Abiotic oxidation of Fe(II) by reactive nitrogen species in cultures of the nitrate-reducing Fe(II) oxidizer Acidovorax sp. BoFeN1 - questioning the existence of enzymatic Fe(II) oxidation.

    Klueglein, N; Kappler, A


    Nitrate-reducing, Fe(II)-oxidizing bacteria were suggested to couple with enzymatic Fe(II) oxidation to nitrate reduction. Denitrification proceeds via intermediates (NO2 -, NO) that can oxidize Fe(II) abiotically at neutral and particularly at acidic pH. Here, we present a revised Fe(II) quantification protocol preventing artifacts during acidic Fe extraction and evaluate the contribution of abiotic vs. enzymatic Fe(II) oxidation in cultures of the nitrate-reducing, Fe(II) oxidizer Acidovorax sp. BoFeN1. Sulfamic acid used instead of HCl reacts with nitrite and prevents abiotic Fe(II) oxidation during Fe extraction. Abiotic experiments without sulfamic acid showed that acidification of oxic Fe(II) nitrite samples leads to 5.6-fold more Fe(II) oxidation than in anoxic samples because the formed NO becomes rapidly reoxidized by O(2) , therefore leading to abiotic oxidation and underestimation of Fe(II). With our revised protocol using sulfamic acid, we quantified oxidation of approximately 7 mm of Fe(II) by BoFeN1 within 4 days. Without addition of sulfamic acid, the same oxidation was detected within only 2 days. Additionally, abiotic incubation of Fe(II) with nitrite in the presence of goethite as surface catalyst led to similar abiotic Fe(II) oxidation rates as observed in growing BoFeN1 cultures. BoFeN1 growth was observed on acetate with N(2) O as electron acceptor. When adding Fe(II), no Fe(II) oxidation was observed, suggesting that the absence of reactive N intermediates (NO2 -, NO) precludes Fe(II) oxidation. The addition of ferrihydrite [Fe(OH)(3) ] to acetate/nitrate BoFeN1 cultures led to growth stimulation equivalent to previously described effects on growth by adding Fe(II). This suggests that elevated iron concentrations might provide a nutritional effect rather than energy-yielding Fe(II) oxidation. Our findings therefore suggest that although enzymatic Fe(II) oxidation by denitrifiers cannot be fully ruled out, its contribution to the observed Fe(II

  5. A Near-Infrared Template Derived from I Zw 1 for the FeII Emission in Active Galaxies

    Garcia-Rissmann, A; Sigut, T A A; Pradhan, A K


    In AGN spectra, a series of FeII multiplets form a pseudo-continuum that extends from the ultraviolet to the near-infrared (NIR). This emission is believed to originate in the Broad Line Region (BLR), and it has been known for a long time that pure photoionization fails to reproduce it in the most extreme cases, as does the collisional-excitation alone. The most recent models by Sigut & Pradhan (2003) include details of the FeII ion microphysics and cover a wide range in ionization parameter log U_ion= (-3.0 -> -1.3) and density log n_H = (9.6 -> 12.6). With the aid of such models and a spectral synthesis approach, we study for the first time in detail the NIR emission of I Zw 1. The main goals are to confirm the role played by Ly\\alpha-fluorescence mechanisms in the production of the FeII spectrum and to construct the first semi-empirical NIR FeII template that best represents this emission and can be used to subtract it in other sources. A good overall match between the observed FeII+MgII features with ...

  6. Long-term efficacy of single-dose treatment with 400 of ivermectin in bancroftian filariasis: results at one year.

    Moulia-Pelat, J P; Glaziou, P; Nguyen, L N; Chanteau, S; Martin, P M; Cartel, J L


    In April 1992, a safety trial was performed with a single dose of ivermectin 400 (IVER 400). In 37 bancroftian filariasis carriers, 6 and 12 months after IVER 400 treatment, the microfilaremia recurrences were 3.2% and 13.5%, respectively. As compared to results from other studies with diethylcarbamazine and IVER at different dosages and periodicities, the dosage of IVER 400 seems the most effective; but a yearly intake might not be sufficient.

  7. Chelation of Cu(II, Zn(II, and Fe(II by Tannin Constituents of Selected Edible Nuts

    Magdalena Karamać


    Full Text Available The tannin fractions isolated from hazelnuts, walnuts and almonds were characterised by colorimetric assays and by an SE-HPLC technique. The complexation of Cu(II and Zn(II was determined by the reaction with tetramethylmurexide, whereas for Fe(II, ferrozine was employed. The walnut tannins exhibited a significantly weaker reaction with the vanillin/HCl reagent than hazelnut and almond tannins, but the protein precipitation capacity of the walnut fraction was high. The SE-HPLC chromatogram of the tannin fraction from hazelnuts revealed the presence of oligomers with higher molecular weights compared to that of almonds. Copper ions were most effectively chelated by the constituents of the tannin fractions of hazelnuts, walnuts and almonds. At a 0.2 mg/assay addition level, the walnut tannins complexed almost 100% Cu(II. The Fe(II complexation capacities of the tannin fractions of walnuts and hazelnuts were weaker in comparison to that of the almond tannin fraction, which at a 2.5 mg/assay addition level, bound Fe(II by ~90%. The capacity to chelate Zn(II was quite varied for the different nut tannin fractions: almond tannins bound as much as 84% Zn(II, whereas the value for walnut tannins was only 8.7%; and for hazelnut tannins, no Zn(II chelation took place at the levels tested.

  8. 蝎毒多肽对白血病细胞株KG1a干细胞活性的影响%Study on the effects of PESV on the viability of leukemia stem cells line KG1a

    杨向东; 李红玉; 李德冠; 史哲新; 杨文华; 颜田赅; 闫理想; 王兴丽



  9. Resistance of Leukemia KG1 a Cells with Positive N-cadherin in Phase G0Against Killing Activity of VP16%N-cadherin阳性白血病KG1a细胞系在G0期抵抗VP16杀伤的作用

    何侃; 于沛; 邢海燕; 李艳; 田征; 王敏; 唐克晶; 饶青


    抗药性是白血病干细胞的重要特征,为探索N-cadherin阳性的白血病细胞耐受化疗药物VP16杀伤作用的机制,本研究以白血病细胞系KGla为研究模型,利用流式细胞术测定N-cadherin阳性和N-cadherin阴性细胞在G0期比例的差异,利用G-CSF诱导KG1a细胞进入细胞周期,观察G0期细胞比例的变化,并测定诱导后KG1a细胞对VP16的敏感性;再利用EGTA抑制N-cadherin介导的细胞间黏附后,观察KG1a细胞耐药性的变化.结果 显示,N-cadherin阳性的KG1a细胞G0期比例高于N-cadherin阴性的细胞;诱导KG1a细胞进入细胞周期后G0期细胞比例明显下降,KG1a细胞对VP16的敏感性显著升高;利用EGTA处理KG1a细胞24小时抑制N-cadherin的作用后,KG1a细胞在G0期比例降低,KG1a细胞对VP16的药物敏感性显著升高.结论:N-cadherin通过介导白血病细胞之间的黏附作用,使白血病细胞处于G0期的静息状态,从而耐受VP16的杀伤作用.%This study was aimed to investigate the methylation status of WTI gene in leukemia cell lines and its relation with expression of WTI gene. The WTI gene was silenced by DNA methylation or histone deacetylation, and the expression of WTI gene was induced by using HDAC inhibitor and/or demethylation agent of DNA. Some leukemia cell lines (U937, HL-60, K562, KG1) were detected by RT-PCR, MS-PCR, restriction analysis, and DNA sequencing. U937 leukemic cells without WTI mRNA expression were incubated with HDAC inhibitor Trichostatin A (TSA) and/or demethylation agent decitabine. The results showed that the U937 cells did not express WTI gene, but HL-60, K562 and KG1 cells hyghly expressed WTI gene; WTI gene was unmethylated in HL-60 cells, but methylated in K562 and U937 cells. WTI expression could be reactivated by co-incubation with TSA and decitabine, but not was observed by using single drug. It is concluded that WTI promoter is methylated in some leukemia cells, however, the methylation can not affect

  10. Study on the Functional Expression of P2X7 Receptor in Human Leukemic Cell Line KG1a%人白血病细胞系KG1a中P2X7受体的表达和功能研究

    张秀军; 孟丽君



  11. Pitzer ion-interaction parameters for Fe(II) and Fe(III) in the quinary {l_brace}Na + K + Mg + Cl + SO{sub 4} + H{sub 2}O{r_brace} system at T=298.15 K

    Christov, Christomir E-mail:


    This paper describes a chemical model that calculates (solid + liquid) equilibria in the {l_brace}m{sub 1}FeCl{sub 2} + m{sub 2}FeCl{sub 3}{r_brace}(aq), {l_brace}m{sub 1}FeSO{sub 4} + m{sub 2}Fe{sub 2}(SO{sub 4}){sub 3}{r_brace}(aq), {l_brace}m{sub 1}NaCl + m{sub 2}FeCl{sub 3}{r_brace}(aq), {l_brace}m{sub 1}Na{sub 2}SO{sub 4} + m{sub 2}FeSO{sub 4}{r_brace}(aq), {l_brace}m{sub 1}NaCl + m{sub 2}FeCl{sub 2}{r_brace}(aq), {l_brace}m{sub 1}KCl + m{sub 2}FeCl{sub 3}{r_brace}(aq), {l_brace}m{sub 1}K{sub 2}SO{sub 4} + m{sub 2}Fe{sub 2}(SO{sub 4}){sub 3}{r_brace}(aq), {l_brace}m{sub 1}KCl + m{sub 2}FeCl{sub 2}{r_brace}(aq), {l_brace}m{sub 1}K{sub 2}SO{sub 4} + m{sub 2}FeSO{sub 4}{r_brace}(aq), and {l_brace}m{sub 1}MgCl{sub 2} + m{sub 2}FeCl{sub 2}{r_brace}(aq) systems, where m denotes molality at T=298.15 K. The Pitzer ion-interaction model has been used for thermodynamic analysis of the experimental activity data in binary FeCl{sub 2}(aq) and FeCl{sub 3}(aq) solutions, and ternary solubility data, presented in the literature. The thermodynamic functions needed (binary and ternary parameters of ionic interaction, thermodynamic solubility products) have been calculated and the theoretical solubility isotherms have been plotted. The mixed solution model parameters {l_brace}{theta}(MN) and {psi}(MNX){r_brace} have been chosen on the basis of the compositions of saturated ternary solutions and data on the pure water solubility of the K{sub 2}SO{sub 4} {center_dot} FeSO{sub 4} {center_dot} 6H{sub 2}O double salt. The standard chemical potentials of four ferrous {l_brace}FeCl{sub 2} {center_dot} 4H{sub 2}O, Na{sub 2}SO{sub 4} {center_dot} FeSO{sub 4} {center_dot} 4H{sub 2}O, K{sub 2}SO{sub 4} {center_dot} FeSO{sub 4} {center_dot} 6H{sub 2}O, and MgCl{sub 2} {center_dot} FeCl{sub 2} {center_dot} 8H{sub 2}O{r_brace} and three ferric {l_brace}FeCl{sub 3} {center_dot} 6H{sub 2}O, 2KCl {center_dot} FeCl{sub 3} {center_dot} H{sub 2}O, and 2K{sub 2}SO{sub 4} {center_dot} Fe{sub 2}(SO

  12. Simultaneous surface-adsorbed organic matter desorption and cell integrity maintenance by moderate prechlorination to enhance Microcystis aeruginosa removal in KMnO4Fe(II) process.

    Qi, Jing; Lan, Huachun; Liu, Huijuan; Liu, Ruiping; Miao, Shiyu; Qu, Jiuhui


    The KMnO4Fe(II) process was proved to have good application potential in Microcystis aeruginosa removal, although at relatively high doses. This study aims to improve the algae removal in KMnO4Fe(II) process by moderate prechlorination, which can realize the desorption of surface-adsorbed organic matter (S-AOM) from algae cells without damaging cell integrity. S-AOM was proved to not only inhibit algae removal but also maintain cell integrity, using various dilution methods for algal suspension preparation. The dilution after filtration method mainly removed the dissolved organics in cultured M. aeruginosa, while the dilution after centrifugal cleaning method could also remove the S-AOM on algae cells. Compared with the S-AOM-removed algal suspension, the lower algae removal in KMnO4Fe(II) process and the reduced proportion of damaged cells during prechlorination of algal suspension without S-AOM removed indicated the inhibitory role of S-AOM in algae removal and the protective function of S-AOM toward cell integrity, respectively. Moderate prechlorination of directly diluted M. aeruginosa could be realized at chlorine doses of below 0.5 mg/L, and the damaged cell ratios were below 4% after 5-min prechlorination. The ability of the KMnO4Fe(II) process to remove algae was dramatically enhanced by the elevation of chlorine dose from 0 to 0.5 mg/L, as more S-AOM was desorbed during prechlorination. Additionally, algae cells were easily captured by flocs after moderate prechlorination, which benefited the floc aggregation for formation of tightly bounded algae flocs. Therefore, the desorption of S-AOM without damaging cell integrity is the key feature of moderate prechlorination, which can be applied in improving the algae removal of KMnO4Fe(II) process. Copyright © 2016. Published by Elsevier Ltd.

  13. $Ly \\alpha$ Fluorescent Excitation of FeII in Active Galactic Nuclei

    Sigut, T A A; Pradhan, Anil K.


    We have calculated FeII emission line strengths for Active Galactic Nuclei Broad-Line Regions using precise radiative transfer and Iron Project atomic data. We improve the treatment of all previously considered excitation mechanisms for the FeII emission, continuum fluorescence, collisional excitation, fluorescence by self-overlap among the iron lines, and fluorescent excitation by Lyman-alpha. We demonstrate that Lyman-alpha fluorescence is of fundamental importance in determining the strength of the FeII emission. In addition to enhancing the ultraviolet and optical FeII flux, Lyman-alpha fluorescence also results in significant near-infrared FeII emission in the 8500-9500 Angstrom wavelength range. New observations are suggested to probe this effect in strong FeII emitting quasars.

  14. Oxygen isotope indicators of selenate reaction with Fe(II) and Fe(III) hydroxides.

    Schellenger, Alexandra E P; Larese-Casanova, Philip


    Selenate (SeO(4)(2-)) reduction to elemental selenium is an important Se immobilization process in subsurface environments that could be mediated by Fe(II)-rich minerals or selenate-respiring microorganisms. We report the kinetic isotope effects for (18)O within selenate during abiotic reactions with iron-bearing hydroxides within laboratory experiments. Selenate was reduced to Se(0) by a green rust (chloride interlayer type) and ferrous hydroxide, the two known environmentally relevant mineral reductants for selenate. Reaction kinetics are described by a rapid, low-fractionating uptake step caused by diffusive exchange between selenate and chloride followed by a slower, high-fractionating reduction step caused by electron transfer from structural Fe(II). The dual-phase kinetics cannot be described with the traditional Rayleigh fractionation model; however, well after the initial uptake step, the extent of selenate reaction is well correlated with δ(18)O values in accordance with the Rayleigh model. Selenate-(18)O enrichment (εO) was nearly identical for reaction with chloride green rust (22.7 ± 2.2‰) and ferrous hydroxide (22.1 ± 1.1‰) which suggests a common reduction mechanism by structural Fe(II). The minor enrichment due to anion exchange alone (1.4 ± 0.2‰) was confirmed using iowaite, a nonredox active Mg(II)-Fe(III) layered double hydroxide. Our εO results may contribute to Se isotope forensics to identify selenate reduction within field sites and to possibly distinguish between abiotic and biotic reduction processes.

  15. Autotrophic denitrification by nitrate-dependent Fe(II) oxidation in a continuous up-flow biofilter.

    Zhou, Jun; Wang, Hongyu; Yang, Kai; Ji, Bin; Chen, Dan; Zhang, Huining; Sun, Yuchong; Tian, Jun


    A continuous-upflow biofilter packed with sponge iron was constructed for nitrate removal under an anaerobic atmosphere. Microbacterium sp. W5, a nitrate reducing and Fe(II) oxidizing strain, was added to the biofilter as an inoculum. The best results were achieved when NO3 (-)-N concentration was 30 mg/L and Fe(2+) was 800 mg/L. Nitrite in influent would inhibit nitrate removal and aqueous Fe(2+) resulted in encrustation. Fe(II)EDTA would prevent cells from encrustation and the maximum nitrogen removal efficiency was about 90 % with Fe(II)EDTA level of 1100 mg/L. Nitrate reduction followed first-order reaction kinetics. Characteristics of biofilms were analyzed by X-ray fluorescence spectroscopy.

  16. Oxygen dependency of neutrophilic Fe(II) oxidation by Leptothrix differs from abiotic reaction

    Vollrath, S.; Behrends, T.; Van Cappellen, P.


    Neutrophilic Fe(II) oxidizing microorganisms are found in many natural environments. It has been hypothesized that, at low oxygen concentrations, microbial iron oxidation is favored over abiotic oxidation. Here, we compare the kinetics of abiotic Fe(II) oxidation to oxidation in the presence of

  17. Adsorption and surface oxidation of Fe(II) on metal (hydr)oxides.

    Hiemstra, T.; Riemsdijk, van W.H.


    The Fe(II) adsorption by non-ferric and ferric (hydr)oxides has been analyzed with surface complexation modeling. The CD model has been used to derive the interfacial distribution of charge. The fitted CD coefficients have been linked to the mechanism of adsorption. The Fe(II) adsorption is

  18. Abiotic and microbial interactions during anaerobic transformations of Fe(II and NOx-

    Flynn ePicardal


    Full Text Available Microbial Fe(II oxidation using NO3- as the terminal electron acceptor (nitrate-dependent Fe(II oxidation; NDFO has been studied for over 15 years. Although there are reports of autotrophic isolates and stable enrichments, many of the bacteria capable of NDFO are known organotrophic NO3- -reducers that require the presence of an organic, primary substrate, e.g., acetate, for significant amounts of Fe(II oxidation. Although the thermodynamics of Fe(II oxidation are favorable when coupled to either NO3- or NO2- reduction, the kinetics of abiotic Fe(II oxidation by NO3- are relatively slow except under special conditions. NDFO is typically studied in batch cultures containing millimolar concentrations of Fe(II, NO3-, and the primary substrate. In such systems, NO2- is often observed to accumulate in culture media during Fe(II oxidation. Compared to NO3-, abiotic reactions of biogenic NO2- and Fe(II are relatively rapid. The kinetics and reaction pathways of Fe(II oxidation by NO2- are strongly affected by medium composition and pH, reactant concentration, and the presence of Fe(II-sorptive surfaces, e.g., Fe(III oxyhydroxides and cellular surfaces. In batch cultures, the combination of abiotic and microbial Fe(II oxidation can alter product distribution and, more importantly, results in the formation of intracellular precipitates and extracellular Fe(III oxyhydroxide encrustations that apparently limit further cell growth and Fe(II oxidation. Unless steps are taken to minimize or account for potential abiotic reactions, results of microbial NDFO studies can be obfuscated by artifacts of the chosen experimental conditions, the use of inappropriate analytical methods, and the resulting uncertainties about the relative importance of abiotic and microbial reactions.In this manuscript, abiotic reactions of NO3- and NO2- with aqueous Fe2+, chelated Fe(II, and solid-phase Fe(II are reviewed along with factors that can influence overall NDFO reac

  19. Characterization of the physiology and cell-mineral interactions of the marine anoxygenic phototrophic Fe(II) oxidizer Rhodovulum iodosum--implications for Precambrian Fe(II) oxidation.

    Wu, Wenfang; Swanner, Elizabeth D; Hao, Likai; Zeitvogel, Fabian; Obst, Martin; Pan, Yongxin; Kappler, Andreas


    Anoxygenic phototrophic Fe(II)-oxidizing bacteria (photoferrotrophs) are suggested to have contributed to the deposition of banded iron formations (BIFs) from oxygen-poor seawater. However, most studies evaluating the contribution of photoferrotrophs to Precambrian Fe(II) oxidation have used freshwater and not marine strains. Therefore, we investigated the physiology and mineral products of Fe(II) oxidation by the marine photoferrotroph Rhodovulum iodosum. Poorly crystalline Fe(III) minerals formed initially and transformed to more crystalline goethite over time. During Fe(II) oxidation, cell surfaces were largely free of minerals. Instead, the minerals were co-localized with EPS suggesting that EPS plays a critical role in preventing cell encrustation, likely by binding Fe(III) and directing precipitation away from cell surfaces. Fe(II) oxidation rates increased with increasing initial Fe(II) concentration (0.43-4.07 mM) under a light intensity of 12 μmol quanta m(-2) s(-1). Rates also increased as light intensity increased (from 3 to 20 μmol quanta m(-2) s(-1)), while the addition of Si did not significantly change Fe(II) oxidation rates. These results elaborate on how the physical and chemical conditions present in the Precambrian ocean controlled the activity of marine photoferrotrophs and confirm the possibility that such microorganisms could have oxidized Fe(II), generating the primary Fe(III) minerals that were then deposited to some Precambrian BIFs. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

  20. Sorption of As(V) on aluminosilicates treated with Fe(II) nanoparticles.

    Dousová, Barbora; Grygar, Tomás; Martaus, Alexandr; Fuitová, Lucie; Kolousek, David; Machovic, Vladimír


    Adsorption of arsenic on clay surfaces is important for the natural and simulated removal of arsenic species from aqueous environments. In this investigation, three samples of clay minerals (natural metakaoline, natural clinoptilolite-rich tuff, and synthetic zeolite) in both untreated and Fe-treated forms were used for the sorption of arsenate from model aqueous solution. The treatment of minerals consisted of exposing them to concentrated solution of Fe(II). Within this process the mineral surface has been laden with Fe(III) oxi(hydroxides) whose high affinity for the As(V) adsorption is well known. In all investigated systems the sorption capacity of Fe(II)-treated sorbents increased significantly in comparison to the untreated material (from about 0.5 to >20.0 mg/g, which represented more than 95% of the total As removal). The changes of Fe-bearing particles in the course of treating process and subsequent As sorption were investigated by the diffuse reflectance spectroscopy and the voltammetry of microparticles. IR spectra of treated and As(V)-saturated solids showed characteristic bands caused by Fe(III)SO(4), Fe(III)O, and AsO vibrations. In untreated As(V)-saturated solids no significant AsO vibrations were observed due to the negligible content of sorbed arsenate.

  1. Abiotic reduction of nitroaromatic compounds by Fe(II) associated with iron oxides and humic acid.

    Luan, Fubo; Xie, Li; Li, Jun; Zhou, Qi


    Experiments were conducted to examine the reduction of nitroaromatic compounds (NACs) by Fe(II) associated with iron oxides (goethite, hematite and magnetite) and humic acid. The reduction rate of nitrobenzene decreased in the order of Fe(II) associated with magnetite>Fe(II) associated with goethite>Fe(II) associated with hematite. We proposed a four-step model (adsorption, electron transfer to conduction band, electron transfer to nitrobenzene and electron transfer to crystal lattice) for nitrobenzene reduction by Fe(II) associated with iron oxides. Fe(II)-humic acid complexes did not present reduction capability of nitrobenzene. Furthermore, Humic acid significantly inhibited nitrobenzene reduction by Fe(II) associated with iron oxides. The inhibitory effect of humic acid toward the reduction of nitrobenzene decreased in the order of magnetite>goethite>hematite. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Fe hydroxyphosphate precipitation and Fe(II) oxidation kinetics upon aeration of Fe(II) and phosphate-containing synthetic and natural solutions

    van der Grift, B.; Behrends, T.; Osté, L. A.; Schot, P. P.; Wassen, M. J.; Griffioen, J.


    Exfiltration of anoxic Fe-rich groundwater into surface water and the concomitant oxidative precipitation of Fe are important processes controlling the transport of phosphate (PO4) from agricultural areas to aquatic systems. Here, we explored the relationship between solution composition, reaction kinetics, and the characteristics of the produced Fe hydroxyphosphate precipitates in a series of aeration experiments with anoxic synthetic water and natural groundwater. A pH stat device was used to maintain constant pH and to record the H+ production during Fe(II) oxidation in the aeration experiments in which the initial aqueous P/Fe ratios ((P/Fe)ini), oxygen concentration and pH were varied. In general, Fe(II) oxidation proceeded slower in the presence of PO4 but the decrease of the PO4 concentration during Fe(II) oxidation due to the formation of Fe hydroxyphosphates caused additional deceleration of the reaction rate. The progress of the reaction could be described using a pseudo-second-order rate law with first-order dependencies on PO4 and Fe(II) concentrations. After PO4 depletion, the Fe(II) oxidation rates increased again and the kinetics followed a pseudo-first-order rate law. The first-order rate constants after PO4 depletion, however, were lower compared to the Fe(II) oxidation in a PO4-free solution. Hence, the initially formed Fe hydroxyphosphates also affect the kinetics of continuing Fe(II) oxidation after PO4 depletion. Presence of aqueous PO4 during oxidation of Fe(II) led to the formation of Fe hydroxyphosphates. The P/Fe ratios of the precipitates ((P/Fe)ppt) and the recorded ratio of H+ production over decrease in dissolved Fe(II) did not change detectably throughout the reaction despite a changing P/Fe ratio in the solution. When (P/Fe)ini was 0.9, precipitates with a (P/Fe)ppt ratio of about 0.6 were formed. In experiments with (P/Fe)ini ratios below 0.6, the (P/Fe)ppt decreased with decreasing (P/Fe)ini and pH value. Aeration experiments with

  3. Fe(II) sorption on a synthetic montmorillonite. A combined macroscopic and spectroscopic study.

    Soltermann, Daniela; Fernandes, Maria Marques; Baeyens, Bart; Dähn, Rainer; Miehé-Brendlé, Jocelyne; Wehrli, Bernhard; Bradbury, Michael H


    Extended X-ray absorption fine structure (EXAFS) and Mössbauer spectroscopy combined with macroscopic sorption experiments were employed to investigate the sorption mechanism of Fe(II) on an iron-free synthetic montmorillonite (Na-IFM). Batch sorption experiments were performed to measure the Fe(II) uptake on Na-IFM at trace concentrations as a function of pH and as a function of sorbate concentration at pH 6.2 and 6.7 under anoxic conditions (O2 < 0.1 ppm). A two-site protolysis nonelectrostatic surface complexation and cation exchange sorption model was used to quantitatively describe the uptake of Fe(II) on Na-IFM. Two types of clay surface binding sites were required to model the Fe(II) sorption, the so-called strong (≡S(S)OH) and weak (≡S(W)OH) sites. EXAFS data show spectroscopic differences between Fe sorbed at low and medium absorber concentrations that were chosen to be characteristic for sorption on strong and weak sites, respectively. Data analysis indicates that Fe is located in the continuity of the octahedral sheet at trans-symmetric sites. Mössbauer spectroscopy measurements confirmed that iron sorbed on the weak edge sites is predominantly present as Fe(II), whereas a significant part of surface-bound Fe(III) was produced on the strong sites (∼12% vs ∼37% Fe(III) species to total sorbed Fe).

  4. Physiology and Mechanism of Phototrophic Fe(II) Oxidation by Rhodopseudomonas palustris TIE-1

    Jiao, Y.; Newman, D.


    Phototrophic Fe(II)-oxidizing bacteria use electrons from ferrous iron [Fe(II)] and energy from light to drive reductive CO2 fixation. This metabolism is thought to be ancient in origin, and plays an important role in environmental iron cycling. It has been implicated in the deposition of Banded Iron Formations, a class of ancient sedimentary iron deposits. Consistent with this hypothesis, we discovered that hydrogen gas, a thermodynamically favorable electron donor to Fe(II), in an Archean atmosphere would not have inhibited phototrophic Fe(II) oxidation. To understand this physiology and the connection to BIF formation at the molecular level, the mechanisms of phototrophic Fe(II) oxidation were examined in a model organism Rhodopseudomonas palustris TIE-1. Increased expression of a putative decaheme c-type cytochrome, encoded by pioA, was observed when cells were grown under Fe(II)-oxidizing conditions. Two genes located immediately downstream of pioA in the same operon, pioB and pioC, encode a putative outer membrane beta-barrel protein and a putative high potential iron-sulfur protein, respectively. Deletion studies demonstrated that all three genes are involved in phototrophic Fe(II) oxidation. This study provides our first insight into the molecular mechanisms of this metabolism, which will be further characterized by in vitro biochemical studies.

  5. Photochemical Formation of Fe(II) in the Aqueous Solutions of Fe(III)- Dicarboxylates

    Okada, K.; Arakaki, T.


    Although there have been many studies reporting the photochemical formation of Fe(II) in various aqueous-phase such as rain, cloud waters, seawater and aerosols, the detailed formation mechanisms are not well understood. To better understand the mechanisms of Fe(II) formation, we attempted to determine the molar absorptivity and the quantum yield of Fe(II) photoformation for individual Fe(III)-dicarboxylate species. The concentrations of Fe(II) and total dissolved Fe were measured by a Ferrozine-HPLC method. The Visual MINTEQ computer program was used to calculate the equilibrium concentrations of chemical species in the solutions of Fe(III)-dicarboxylate complexes. The molar absorptivity and the product of the quantum yield and the molar absorptivity of Fe(III)- dicarboxylate complex can be analysed by UV-VIS spectrophotometer and photochemical experiments, and these experimental data were combined with the calculated equilibrium Fe(III) speciation to determine individual molar absorptivity and quantum yield of Fe(II) photoformation for a specific Fe(III)-dicarboxylate complex. Preliminary results, using an oxalate whose quantum yield has been previously reported, indicate that this approach gives lower quantum yield values in air saturated solutions than previously reported.

  6. Production of hydroxyl radicals from Fe(II) oxygenation induced by groundwater table fluctuations in a sand column.

    Jia, Mengqi; Bian, Xiao; Yuan, Songhu


    Natural and artificial processes often cause the fluctuation of groundwater table, inducing the interaction of O2 from the unsaturated zone with reduced components such as Fe(II) from the saturated zone. In light of previous findings that hydroxyl radicals (OH) can be produced from Fe(II) oxygenation, we hypothesize that OH could be produced during groundwater table fluctuations. Therefore, this study aims to measure the production of OH during water table fluctuations in a simulated sand column. Deoxygenated water in the absence and presence of 20mg/L Fe(2+) (pH6.5) was fed into the sand column. Water table fluctuations were manipulated to observe O2 entrapment, Fe(2+)oxygenation and OH production. Results showed that O2 in the pore air was efficiently entrapped by the rise of water table at the tested rates of 0.16-0.34cm/min (or 0.10-0.20m/h), and the dissolution of entrapped O2 into the pore water led to the oxygenation of Fe(2+). Production of OH was presumably attributed to oxygenation of the Fe(2+) adsorbed on Fe(III) oxyhydroxides generated in situ. In a total of 4cycles of fluctuations, the cumulative OH at all the elevations increased progressively, attaining 2.7μM in the zone near the water table in the 4th cycle. We suggest that OH produced from water table fluctuations could induce an overlooked pathway for contaminant transformation in the fluctuation zone. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. A Comparison between Four Analytical Methods for the Measurement of Fe(II at Nanomolar Concentrations in Coastal Seawater

    Mark J. Hopwood


    Full Text Available Dissolved Fe(II in seawater is deemed an important micronutrient for microbial organisms, but its analysis is challenging due to its transient nature. We conducted a series of Fe(II method comparison experiments, where spikes of 5 to 31 nM Fe(II were added to manipulated seawaters with varying dissolved oxygen (37 to 156 μM concentrations. The observed Fe(II concentrations from four analytical methods were compared: spectrophotometry with ferrozine, stripping voltammetry, and flow injection analysis using luminol (with, and without, a pre-concentration column. Direct comparisons between the different methods were undertaken from the derived apparent Fe(II oxidation rate constant (k1. Whilst the two luminol based methods produced the most similar concentrations throughout the experiments, k1 was still subject to a 20–30% discrepancy between them. Contributing factors may have included uncertainty in the calibration curves, and different responses to interferences from Co(II and humic/fulvic organic material. The difference in measured Fe(II concentrations between the luminol and ferrozine methods, from 10 min–2 h after the Fe(II spikes were added, was always relatively large in absolute terms (>4 nM and relative to the spike added (>20% of the initial Fe(II concentration. k1 derived from ferrozine observed Fe(II concentrations was 3–80%, and 4–16%, of that derived from luminol observed Fe(II with, and without, pre-concentration respectively. The poorest comparability of k1 was found after humic/fulvic material was added to raise dissolved organic carbon to 120 μM. A luminol method without pre-concentration then observed Fe(II to fall below the detection limit (<0.49 nM within 10 min of a 17 nM Fe(II spike addition, yet other methods still observed Fe(II concentrations of 2.7 to 3.7 nM 30 min later. k1 also diverged accordingly with the ferrozine derived value 4% of that derived from luminol without pre-concentration. These apparent

  8. Anaerobic, Nitrate-Dependent Fe(II) Oxidation Under Advective Flow

    Weber, K. A.; Coates, J. D.


    Microbially-catalyzed nitrate-dependent Fe(II) oxidation has been identified as a ubiquitous biogeochemical process contributing to anaerobic iron redox cycling in sedimentary environments. Most probable number enumeration revealed nitrate-dependent Fe(II) oxidizing microbial communities in groundwater and subsurface sediments in the order of 0 - 2.04 x 103 cells mL-1 and 2.39 x 102 - 1.17 x 103 cells (g wet sediment)-1, respectively. The efficacy of nitrate-dependent Fe(II) oxidation under advective flow was evaluated in a meso-scale column reactor packed with sterile low iron sand amended with subsurface sediments collected from the NABIR FRC background field site (10% mass/mass). Continuous flow of minimal medium mimicked the natural groundwater. Periodic FeCl2 and nitrate injections over a period of 49 days resulted in the retention of 95% of the iron (290 mmol). Extraction of solid-phase Fe revealed a net increase in Fe(III) of 160 mmol above background Fe(III) content indicating that 55% of the injected Fe(II) was oxidized. Differential solubility analysis of 0.5M HCl-extractable Fe and 3M HCl-extractable Fe indicated that the oxidation product was crystalline in nature as only 20% was soluble in 0.5M HCl. This formation of crystalline biogenic Fe(III) oxides is consistent with previous studies. Periodic injections of nitrate and acetate did not result in significant changes in Fe(II) or Fe(III) throughout a control column. Together these results demonstrate that native subsurface sediments harbor microbial communities capable of nitrate-dependent Fe(II) oxidation under advective flow. The biogenic formation of reactive Fe(III) oxide minerals capable of immobilizing heavy metals and radionuclides presents a plausible bioremediative strategy for contaminated subsurface environments.

  9. Preparation and reactivity of a tetranuclear Fe(II) core in the metallothionein α-domain.

    Sano, Yohei; Onoda, Akira; Sakurai, Rie; Kitagishi, Hiroaki; Hayashi, Takashi


    Metallothioneins (MTs) are small cysteine-rich proteins which exhibit high affinities for various metal ions and play roles in storage of essential metals and detoxification of toxic metals. Studies on the redox properties of MTs have been quite limited. Recently, we focused on the α-domain of MT (MTα) as a protein matrix and incorporated a tetranuclear metal cluster as a reductant. UV-visible, CD and MS data indicate the formation of the stable tetranuclear metal-cysteine cluster in the MTα matrix with Fe(II)(4)-MTα and Co(II)(4)-MTα species existing in water. Furthermore, the Fe(II)(4)-MTα species was found to promote the reduction of met-myoglobin and azobenzene derivatives under mild conditions. Particularly, the stoichiometric reduction of methyl red with Fe(II)(4)-MTα (1:1) was found to proceed with a conversion of 98% over a period of 6h at 25°C. This indicates that all of the four Fe(II) cores contribute to the reduction. In this paper, we describe the preparation and reactivity of the tetranuclear iron cluster in the protein matrix.

  10. Dual-nanomaterial based electrode for voltammetric stripping of trace Fe(II) in coastal waters.

    Lin, Mingyue; Pan, Dawei; Zhu, Yun; Hu, Xueping; Han, Haitao; Wang, ChenChen


    In this work, a dual-nanomaterial based electrode was established for selective and sensitive detection of trace Fe(II) in the presence of complexing agent (2,2'-bipyridyl). Titanium carbide nanoparticles (TiCNPs) were used as the growth-template for the formation of three-dimensional platinum nanoflowers (PtNFs) due to their unique cubic structures. Nafion was employed as the conducting matrix to help TiCNPs better attached onto the surface of the electrode and slow down the crystal rate of PtNFs during electrodeposition, which resulted in flower structure and more active surface of PtNFs. Taking advantage of synergistic effects of TiCNPs and Nafion as well as the catalytic amplifying effect of PtNFs, the excellent anodic signal responses for the voltammetric stripping determination of Fe(II) were obtained. The linear range of Fe(II) on this dual-nanomaterial based electrode was from 1nmolL(-1) to 6μmolL(-1) with the lowest detectable concentration of 0.1nmolL(-1) and a detection limit of 0.03nmolL(-1). Additionally, the effect of several experimental parameters, such as concentration and pH value of buffer solution, concentration of modifier and ligand, deposition potential and time of electrochemical determination, and scan rate were studied for analytical applications. The fabricated sensor had been successfully applied for the sensitive determination of trace Fe(II) in coastal waters.

  11. Microbial Fe(II) oxidation at circumneutral pH: Reaction kinetics, mineral products, and distribution of neutrophilic iron oxidizers in wetland soils

    Vollrath, S.


    Multiple studies have shown that neutrophilic Fe(II) oxidizers can conserve energy from Fe(II) oxidation, however, it is still unclear how they can compete against the fast abiotic reaction at neutral pH, or to which extent these bacteria increase the overall Fe(II) oxidation rate. Similar to

  12. [Reduction of nitrobenzene by iron oxides bound Fe(II) system at different pH values].

    Luan, Fu-Bo; Xie, Li; Li, Jun; Zhou, Qi


    Batch tests were conducted to investigate the reductive transformation of nitrobenzene by goethite, hematite, magnetite and steel converter slag bound Fe(II) system. And the reduction mechanism was explored at different pH values. Experimental results showed that hematite, magnetite and steel converter slag could adsorb Fe(II) on surfaces and form iron oxides bound Fe(II) system at pH from 6.5 to 7.0. The systems had strong reductive capacity and could reduce nitrobenzene to aniline. The reduction efficiency of nitrobenzene in surface bound Fe(II) system followed the sequence of magnetite, hematite and steel converter slag from high to low. The reduction efficiency of hematite and magnetite system increased with pH increasing. While it was almost pH independent in steel converter slag system. Although goethite adsorbed most of Fe(II) in solution, the adsorbed Fe(II) had no reductive activity for nitrobenzene. At pH 6.0, small amount of Fe(II) was adsorbed on magnetite and hematite and the systems did not show reductive activity for nitrobenzene. However, steel converter slag could adsorb Fe(II) at pH 6.0 and reduction efficiency almost equaled to the value at pH 7.0. When pH was above 7.5, dissolved Fe(II) could be converted to Fe(OH)2 and the newly formed Fe(OH)2 became the main redactor in the system. Under alkali condition, the presence of iron oxides inhibited the reduction capacity of system.

  13. Fe(II) oxidation during acid mine drainage neutralization in a pilot-scale sequencing batch reactor

    Zvimba, JN


    Full Text Available the suspended solids impacted more positively on Fe(II) oxidation during pilot scale AMD neutralization in a SBR, a phenomenon ascribed to generation of acidity by hydrolysis of Fe(II) as shown in equation 2. Figure 3 shows the chemical behavior... to the acidity generation resulting from hydrolysis of Fe(III) (Reaction 2) that would require further neutralization by CaCO3 (Reaction 3), and as such promotes further CaCO3 dissolution with AMD pH increasing to above 6.8 following complete Fe(II) oxidation...

  14. Rate law of Fe(II) oxidation under low O2 conditions

    Kanzaki, Yoshiki; Murakami, Takashi


    Despite intensive studies on Fe(II) oxidation kinetics, the oxidation rate law has not been established under low O2 conditions. The importance of Fe(II) oxidation under low O2 conditions has been recently recognized; for instance, the Fe(II)/Fe(III) compositions of paleosols, ancient soils formed by weathering, can produce a quantitative pattern of the atmospheric oxygen increase during the Paleoproterozoic. The effects of partial pressure of atmospheric oxygen (PO2) on the Fe(II) oxidation rate were investigated to establish the Fe(II) oxidation rate - PO2 relationships under low O2 conditions. All oxidation experiments were carried out in a glove box by introducing Ar gas at ∼10-5-∼10-4 atm of PO2, pH 7.57-8.09 and 22 °C. Luminol chemiluminescence was adopted to measure low Fe(II) concentrations (down to ∼2 nM). Combining previous data under higher PO2 conditions (10-3-0.2 atm) with the present data, the rate law for Fe(II) oxidation over a wide range of PO2 (10-5-0.2 atm) was found to be written as: d[Fe(II)]/dt=-k[Fe(II)][[]2 where the exponent of [O2], x, and the rate constant, k, change from x = 0.98 (±0.04) and log k = 15.46 (±0.06) at ∼6 × 10-3-0.2 atm of PO2 to x = 0.58 (±0.02) and log k = 13.41 (±0.03) at 10-5-∼6 × 10-3 atm of PO2. The most plausible mechanism that explains the change in x under low O2 conditions is that, instead of O2, oxygen-derived oxidants, H2O2 and to some extent, O2rad -, dominate the oxidation reactions at oxygen in the Precambrian.

  15. Optical Waveguiding Organic Nanorods Coated with Reversibly Switchable Fe(II Spin Transition Nanoparticles

    Supratim Basak


    Full Text Available A dual functional nanohybrid object combining photonic and magnetic properties was successfully prepared through a “bottom-up” self-assembly approach. In this method, spin transition Fe(II coordination nanoparticles and optical wave guiding organic nanorods were generated in situ and successfully integrated together in a single pot through self-assembly. The Fe(II nanoparticles coated on organic nanorods (nanohybrids display temperature dependent reversible spin transition (Paramagnetic; diamagnetic; behavior. The nano-hybrids show efficient optical wave guiding behavior, which demonstrates the future possibility to perform light induced excited spin state trapping (LIESST experiments on a single spin transition nanoparticle level. These photonic and magnetic “nanohybrids” offer promising option to externally manipulate spin state of the spin transition nanoparticles using temperature as well as remote laser light.

  16. The reaction of hydrogen peroxide with Fe(II) ions at elevated temperatures

    Christensen, H.; Sehested, K.; Løgager, T.


    The rate constant for the reaction between Fe(II) ions and H2O2 has been determined at pH 0.4-2 as a function of temperature in the range 5-300-degrees-C. H2O2 was produced by irradiating the aqueous solution with a pulse of electrons. The rate constants at 20 and 300-degrees-C were determined to...

  17. Effect of aqueous Fe(II) on Sb(V) sorption on soil and goethite.

    Fan, Jian-Xin; Wang, Yu-Jun; Fan, Ting-Ting; Dang, Fei; Zhou, Dong-Mei


    The effects of Fe(II) on the sorption and precipitation of Sb(V) on soils and goethite were investigated using batch experiments and X-ray photoelectron spectroscopy (XPS) in this study. The sorption capacity of Sb(V) were much higher in anoxic soil than oxic soil. Typically, dissolved Fe(II) concentration in anoxic soils decreased significantly with increasing Sb(V), which may be suggestive of Fe-Sb precipitation. The elevated concentrations of Fe(II) (1 mM) enhanced the sorption capacity of Sb(V) on goethite significantly. However, synchrotron radiation X-ray diffraction showed no new characteristic peak, indicating that this Fe-Sb precipitate might be poor crystallinity or amorphous. Moreover, Sb(III) was detected in anoxic soil, and the reduction of Sb(V) to Sb (III) improved the sorption capacity of Sb in anoxic soil because of the low solubility and migration of Sb(III). Nevertheless, Fe-Sb co-precipitation and Sb(V) reduction to Sb(III) might contribute simultaneously to the increased sorption capacity of Sb(V) on anoxic soils. This research could improve our current understanding of soil Sb chemistry in paddy and wetland soils.

  18. Heterogeneous reduction of {sup 239}PuO{sub 2} by aqueous Fe(II) in the presence of hematite

    Felmy, A.R.; Moore, D.A.; Qafoku, O.; Buck, E.; Ilton, E.S. [Pacific Northwest National Laboratory, Richland, WA (United States); Conradson, S.D. [Los Alamos National Laboratory, NM (United States)


    The reduction of PuO{sub 2}(am) by Fe(II) in the presence and absence of hematite was studied over a range of pH values and oxidation/reduction potentials. In contrast to thermodynamic predictions, the presence of hematite did not have a major effect on the overall reduction of PuO{sub 2}(am) to aqueous Pu(III). Instead the aqueous Pu(III) concentrations at longer time frames were accurately predicted using the measured Fe(II) concentration and existing thermodynamic data for the reaction: H{sub 2}O + H{sup +} + Fe{sup 2+} + PuO{sub 2}(am) {r_reversible} Pu{sup 3+} + Fe(OH){sub 3}(am) with log K = -0.6. The accuracy of this approach in all solutions containing aqueous Fe(II), coupled with the apparent lack of oxidation of Fe(II) by O{sub 2}(g), suggests that the Fe(OH){sub 3}(am) is formed by the oxidation of Fe(II) to Fe(III) by radiolysis. The continued generation of reactive amorphous iron hydroxide by radiolysis prevents thermodynamic equilibrium from being reached with more stable ferric oxide compounds, except possibly under acidic conditions where amorphous ferric hydroxide is soluble. The use of measured pe values, instead of aqueous Fe(II) measurements, also yields reasonable predictions of the final Pu(III) concentrations although the predictions are more uncertain. (orig.)

  19. Uranium Immobilization through Fe(II) bio-oxidation: A Column study

    Coates, John D.


    Current research on the bioremediation of heavy metals and radionuclides is focused on the ability of reducing organisms to use these metals as alternative electron acceptors in the absence of oxygen and thus precipitate them out of solution. However, many aspects of this proposed scheme need to be resolved, not the least of which is the time frame of the treatment process. Once treatment is complete and the electron donor addition is halted, the system will ultimately revert back to an oxic state and potentially result in the abiotic reoxidation and remobilization of the immobilized metals. In addition, the possibility exists that the presence of more electropositive electron acceptors such as nitrate or oxygen will also stimulate the biological oxidation and remobilization of these contaminants. The selective nitrate-dependent biooxidation of added Fe(II) may offer an effective means of “capping off” and completing the attenuation of these contaminants in a reducing environment making the contaminants less accessible to abiotic and biotic reactions and allowing the system to naturally revert to an oxic state. Our previous DOE-NABIR funded studies demonstrated that radionuclides such as uranium and cobalt are rapidly removed from solution during the biogenic formation of Fe(III)-oxides. In the case of uranium, X-ray spectroscopy analysis indicated that the uranium was in the hexavalent form (normally soluble) and was bound to the precipitated Fe(III)-oxides thus demonstrating the bioremediative potential of this process. We also demonstrated that nitrate-dependent Fe(II)- oxidizing bacteria are prevalent in the sediment and groundwater samples collected from sites 1 and 2 and the background site of the NABIR FRC in Oakridge, TN. However, all of these studies were performed in batch experiments in the laboratory with pure cultures and although a significant amount was learned about the microbiology of nitrate-dependent bio-oxidation of Fe(II), the effects of

  20. Role of Fe(II) and phosphate in arsenic uptake by coprecipitation

    Sahai, N.; Lee, Y.J.; Xu, H.; Ciardelli, M.; Gaillard, J.-F. (NWU); (UW)


    Natural attenuation of arsenic by simple adsorption on oxyhydroxides may be limited due to competing oxyanions, but uptake by coprecipitation may locally sequester arsenic. We have systematically investigated the mechanism and mode (adsorption versus coprecipitation) of arsenic uptake in the presence of carbonate and phosphate, from solutions of inorganic composition similar to many groundwaters. Efficient arsenic removal, >95% As(V) and {approx}55% in initial As(III) systems, occurred over 24 h at pHs 5.5-6.5 when Fe(II) and hydroxylapatite (Ca{sub 5}(PO{sub 4}){sub 3}OH, HAP) 'seed' crystals were added to solutions that had been previously reacted with HAP, atmospheric CO{sub 2(g)} and O{sub 2(g)}. Arsenic adsorption was insignificant (<10%) on HAP without Fe(II). Greater uptake in the As(III) system in the presence of Fe(II) was interpreted as due to faster As(III) to As(V) oxidation by molecular oxygen in a putative pathway involving Fe(IV) and As(IV) intermediate species. HAP acts as a pH buffer that allows faster Fe(II) oxidation. Solution analyses coupled with high-resolution transmission electron microscopy (HRTEM), X-ray Energy-Dispersive Spectroscopy (EDS), and X-Ray Absorption Spectroscopy (XAS) indicated the precipitation of sub-spherical particles of an amorphous, chemically-mixed, nanophase, Fe{sup III}[(OH){sub 3}(PO{sub 4})(As{sup V}O{sub 4})] {center_dot} nH{sub 2}O or Fe{sup III}[(OH){sub 3}(PO{sub 4})(As{sup V}O{sub 4})(As{sup III}O{sub 3}){sub minor}] {center_dot} nH{sub 2}O, where As{sup III}O{sub 3} is a minor component. The mode of As uptake was further investigated in binary coprecipitation (Fe(II) + As(III) or P), and ternary coprecipitation and adsorption experiments (Fe(II) + As(III) + P) at variable As/Fe, P/Fe and As/P/Fe ratios. Foil-like, poorly crystalline, nanoparticles of Fe{sup III}(OH){sub 3} and sub-spherical, amorphous, chemically-mixed, metastable nanoparticles of Fe{sup III}[(OH){sub 3}, PO{sub 4}] {center_dot} n

  1. Biochemistry and Ecology of Novel Cytochromes Catalyzing Fe(II) Oxidation by an Acidophilic Microbial Community

    Singer, S. W.; Jeans, C. J.; Thelen, M. P.; Verberkmoes, N. C.; Hettich, R. C.; Chan, C. S.; Banfield, J. F.


    An acidophilic microbial community found in the Richmond Mine at Iron Mountain, CA forms abundant biofilms in extremely acidic (pHcytochromes with unique properties. Sulfuric acid extraction of biofilm samples liberated one of these proteins, a 16 kDa cytochrome with an unusual alpha-band absorption at 579 (Cyt579). Genomic sequencing of multiple biofilms indicated that several variants of Cyt579 were present in Leptospirillum strains. Intact protein MS analysis identified the dominant variants in each biofilm and documented multiple N-terminal cleavage sites for Cyt579. By combining biochemical, geochemical and microbiological data, we established that the sequence variation and N-terminal processing of Cyt579 are selected by ecological conditions. In addition to the soluble Cyt579, the second cytochrome appears as a much larger protein complex of ~210 kDa predominant in the biofilm membrane fraction, and has an alpha-band absorption at 572 nm. The 60 kDa cytochrome subunit, Cyt572, resides in the outer membrane of LeptoII, and readily oxidizes Fe(II) at low pH (0.95 - 3.0). Several genes encoding Cyt572 were localized within a recombination hotspot between two strains of LeptoII, causing a large range of variation in the sequences. Genomic sequencing and MS proteomic studies established that the variants were also selected by ecological conditions. A general mechanistic model for Fe(II) oxidation has been developed from these studies. Initial Fe(II) oxidation by Cyt572 occurs at the outer membrane. Cyt572 then transfers electrons to Cyt579, perhaps representing an initial step in energy flow to the biofilm community. Amino acid variations and post-translational modifications of these unique cytochromes may represent fine-tuning of function in response to local environmental conditions.

  2. Role of adsorbed arsenic and structural aluminum on Fe(II) retention and transformation of ferrihydrite (Invited)

    Sharma, R.; Masue-Slowey, Y.; Fendorf, S. E.


    Arsenic is a wide-spread toxin contaminating water from both natural (as in the case of South and Southeast Asia) and anthropogenic sources. Its high affinity for soil solids helps to regulate the deleterious impacts of this toxic element on ecosystem and human health. Iron (hydr)oxides are of particular importance in controlling dissolved concentrations of arsenic, making the behavior of these substrates crucial to understanding the transport and ultimate fate of arsenic. Ferrihydrite is one of the most active forms of Fe (hydr)oxides, and aluminum-substituted ferrihydrite is a common form of this phase in soils and sediment. Sorption of Fe(II) catalyzes the transformation of the thermodynamically unstable ferrihydrite to more thermodynamically stable Fe (hydr)oxides. Although the process of ferrihydrite transformation has been extensively studied, the role of structural aluminum and adsorbed arsenic on the Fe(II)-catalyzed transformation of ferrihydrite is unknown. Hence, the objective of this study was to compare how ferrihydrite and aluminum-substituted ferrihydrite differ in their retention of Fe(II) and the resulting transformation rates and products in the presence and absence of arsenic. Sand coated with ferrihydrite and aluminum-ferrihydrite (with and without adsorbed arsenic) was packed into columns and flow of circumneutral groundwater solution containing 0.2 to 4 mM Fe(II) was initiated. Breakthrough of Fe(II) was monitored using the ferrozine colorimetric assay to determine Fe(II) retention in the solid phase. The solid phase was characterized using Fe K-edge X-ray absorption spectroscopy and scanning electron microscopy. Structural aluminum limits Fe(II) sorption, and, as a consequence, the extent of the aluminum-substituted ferrihydrite transformation is much less than that of ferrihydrite. Adsorbed As further decreases Fe(II) retention on aluminum-ferrihydrite. In contrast, Fe(II) retention on ferrihydrite is enhanced in the presence of arsenic due


    О. Ciobanica


    Full Text Available The interaction of [Fe(DfgH2Py2] (where DfgH=monodeprotonated diphenylglyioxime, Py-pyridune and 1,3,5-triazine (Trz in chloroform resulted in a new coordination compound with the composition [Fe(DfgH2(Trz2]·2CHCl3 (1. The crystal structure of 1, determined by single crystal X-ray diffraction, revealed that Fe(II atom is coordinated by four oximic nitrogen atoms of two DfgH and two nitrogen atoms of two Trz ligands resulting in octahedral surrounding.

  4. The _ carinae like feii-rich spectrum of fbs0022-021

    S. Zharikov


    Full Text Available Informamos sobre los resultados de observaciones espectrosc opicas Echelle y B&C del objeto con l neas de emisi on FBS 0022 - 21 obtenidas en el Observatorio de San Pedro M artir, M exico. Analizamos los espectros de las l neas de emisi on junto con datos del optico e IR disponibles. El espectro rico en FeII del objeto se asemeja fuertemente al del sistema binario peculiar Car. Se discuten las condiciones f sicas que dan lugar a tal espectro y la naturaleza de este peculiar objeto.

  5. Effect of oxidation rate and Fe(II) state on microbial nitrate-dependent Fe(III) mineral formation.

    Senko, John M; Dewers, Thomas A; Krumholz, Lee R


    A nitrate-dependent Fe(II)-oxidizing bacterium was isolated and used to evaluate whether Fe(II) chemical form or oxidation rate had an effect on the mineralogy of biogenic Fe(III) (hydr)oxides resulting from nitrate-dependent Fe(II) oxidation. The isolate (designated FW33AN) had 99% 16S rRNA sequence similarity to Klebsiella oxytoca. FW33AN produced Fe(III) (hydr)oxides by oxidation of soluble Fe(II) [Fe(II)sol] or FeS under nitrate-reducing conditions. Based on X-ray diffraction (XRD) analysis, Fe(III) (hydr)oxide produced by oxidation of FeS was shown to be amorphous, while oxidation of Fe(II)sol yielded goethite. The rate of Fe(II) oxidation was then manipulated by incubating various cell concentrations of FW33AN with Fe(II)sol and nitrate. Characterization of products revealed that as Fe(II) oxidation rates slowed, a stronger goethite signal was observed by XRD and a larger proportion of Fe(III) was in the crystalline fraction. Since the mineralogy of Fe(III) (hydr)oxides may control the extent of subsequent Fe(III) reduction, the variables we identify here may have an effect on the biogeochemical cycling of Fe in anoxic ecosystems.

  6. The HH34 outflow as seen in [FeII]1.64um by LBT-LUCI

    Antoniucci, S; Nisini, B; Giannini, T; Lorenzetti, D; Paris, D; Sani, E


    Dense atomic jets from young stars copiously emit in [FeII] IR lines, which can, therefore, be used to trace the immediate environments of embedded protostars. We want to investigate the morphology of the bright [FeII] 1.64um line in the jet of the source HH34 IRS and compare it with the most commonly used optical tracer [SII]. We analyse a 1.64um narrow-band filter image obtained with the Large Binocular Telescope (LBT) LUCI instrument, which covers the HH34 jet and counterjet. A Point Spread Function (PSF) deconvolution algorithm was applied to enhance spatial resolution and make the IR image directly comparable to a [SII] HST image of the same source. The [FeII] emission is detected from both the jet, the (weak) counter-jet, and from the HH34-S and HH34-N bow shocks. The deconvolved image allows us to resolve jet knots close to about 1\\arcsec from the central source. The morphology of the [FeII] emission is remarkably similar to that of the [SII] emission, and the relative positions of [FeII] and [SII] pea...

  7. Biological Oxidation of Fe(II) in Reduced Nontronite Coupled with Nitrate Reduction by Pseudogulbenkiania sp. Strain 2002

    Zhao, Linduo; Dong, Hailiang; Kukkadapu, Ravi K.; Agrawal, A.; Liu, Deng; Zhang, Jing; Edelmann, Richard E.


    Nitrate contamination in soils, sediments, and water bodies is a significant issue. Although much is known about nitrate degradation in these environments, especially via microbial pathways, a complete understanding of all degradation processes, especially in clay mineral-rich soils, is still lacking. The objective of this study was to study the potential of removing nitrate contaminant using structural Fe(II) in clay mineral nontronite. Specifically, the coupled processes of microbial oxidation of Fe(II) in microbially reduced nontronite (NAu-2) and nitrate reduction by Pseudogulbenkiania species strain 2002 was investigated. Bio-oxidation experiments were conducted in bicarbonate-buffered medium under both growth and nongrowth conditions. The extents of Fe(II) oxidation and nitrate reduction were measured by wet chemical methods. X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and 57Fe-Mössbauer spectroscopy were used to observe mineralogical changes associated with Fe(III) reduction and Fe(II) oxidation in nontronite. The bio-oxidation extent under growth and nongrowth conditions reached 93% and 57%, respectively. Over the same time period, nitrate was completely reduced under both conditions to nitrogen gas (N2), via an intermediate product nitrite. Magnetite was a mineral product of nitrate-dependent Fe(II) oxidation, as evidenced by XRD data and TEM diffraction patterns. The results of this study highlight the importance of iron-bearing clay minerals in the global nitrogen cycle with potential applications in nitrate removal in soils.

  8. Influences of Alkyl and Aryl Substituents on Iminopyridine Fe(II- and Co(II-Catalyzed Isoprene Polymerization

    Lihua Guo


    Full Text Available A series of alkyl- and aryl-substituted iminopyridine Fe(II complexes 1a–7a and Co(II complexes 2b, 3b, 5b, and 6b were synthesized. The activator effect, influence of temperature, and, particularly, the alkyl and aryl substituents’ effect on catalytic activity, polymer molecular weight, and regio-/stereoselectivity were investigated when these complexes were applied in isoprene polymerization. All of the Fe(II complexes afforded polyisoprene with high molecular weight and moderate cis-1,4 selectivity. In contrast, the Co(II complexes produced polymers with low molecular weight and relatively high cis-1,4 selectivity. In the iminopyridine Fe(II system, the alkyl and aryl substituents’ effect exhibits significant variation on the isoprene polymerization. In the iminopyridine Co(II system, there is little influence observed on isoprene polymerization by alkyl and aryl substituents.

  9. Enhanced reductive degradation of carbon tetrachloride by biogenic vivianite and Fe(II)

    Bae, Sungjun; Lee, Woojin


    We demonstrated that reductive dechlorination of carbon tetrachloride (CT) can be enhanced by iron-bearing soil minerals (IBSMs) in the presence of Shewanella putrefaciens CN32 (CN32) due to the formation of biogenic vivianite and Fe(II). The bioreduction efficiency of magnetite was the highest (51.1%), followed by lepidocrocite (25.7%), goethite (3.6%), and hematite (1.8%). The dechlorination kinetic of CT by lepidocrocite (0.043 d-1) in the presence of CN32 was three times faster than that by microbial transformation with CN32 (0.014 d-1). Chloroform (16.1-29.4%), carbon monoxide (2.4-23.8%), and formate (0-58.0%) were measured as main products for the degradation of CT by magnetite and lepidocrocite in the presence of CN32. X-ray diffraction and electron microscope analyses revealed that the biogenic vivianite can form during the CT degradation in magnetite and lepidocrocite suspensions with CN32. The dechlorination kinetics of CT by chemogenic vivianite was much faster than that by magnetite and lepidocrocite with CN32. The highest formate production (84.2%) was observed during a full degradation of CT by the chemogenic vivianite. The experimental results showed that biogenic vivianite and sorbed Fe(II) formed during the bioreduction of IBSMs played a pivotal role for the reductive dechlorination of CT.

  10. Arsenic Uptake by Hydroxyapatite in the Presence of Fe(II)

    Sahai, N.; Lee, Y. J.; Xu, H.; Ciardelli, M.


    We have examined As(III) and As(V) uptake by hydroxyapatite (HAP) in the absence and presence of the commonly occurring geochemical species, Fe(II), in a system open to the atmosphere and at near-neutral pH. The immediate goal of our project is to develop an inexpensive, efficient remediation method for the acute As contamination problem in well-waters of Bangladesh and Eastern India. Our study also provide a conceptual model system for understanding cation, neutral species and anion uptake by a class of minerals (apatites) capable of multiple substitutions, the effect of co-ions on metal(loid) uptake and the geochemically ubiquitous, but relatively poorly-understood, process of coprecipitation. Batch experiments on HAP suspensions, equilibrated for 24 hours, indicate that As(III) and As(V) uptake is slightly greater in the presence of HAP compared to the control experiment. The addition of Fe(II) significantly improves As(III) and As(V) uptake from solutions, both, without and with HAP suspensions. Analyses of equilibrated solutions and High Resolution Transmission Electron Microscopy of solids formed suggest that precipitation of amorphous FePO4.nH2O nanoparticles (10-20 nm) is mainly responsible for As removal with additional uptake by HAP. The efficiency of the process suggests the potential for an effective remediation strategy of As-contaminated drinking water after it has been withdrawn from the affected well.

  11. Energetic Chromophores: Low-Energy Laser Initiation in Explosive Fe(II) Tetrazine Complexes.

    Myers, Thomas W; Bjorgaard, Josiah A; Brown, Kathryn E; Chavez, David E; Hanson, Susan K; Scharff, R Jason; Tretiak, Sergei; Veauthier, Jacqueline M


    The synthesis and characterization of air stable Fe(II) coordination complexes with tetrazine and triazolo-tetrazine ligands and perchlorate counteranions have been achieved. Time-dependent density functional theory (TD-DFT) was used to model the structural, electrochemical, and optical properties of these materials. These compounds are secondary explosives that can be initiated with Nd:YAG laser light at lower energy thresholds than those of PETN. Furthermore, these Fe(II) tetrazine complexes have significantly lower sensitivity than PETN toward mechanical stimuli such as impact and friction. The lower threshold for laser initiation was achieved by altering the electronic properties of the ligand scaffold to tune the metal ligand charge transfer (MLCT) bands of these materials from the visible into the near-infrared region of the electromagnetic spectrum. Unprecedented decrease in both the laser initiation threshold and the mechanical sensitivity makes these materials the first explosives that are both safer to handle and easier to initiate than PETN with NIR lasers.

  12. Mariprofundus ferrooxydans PV-1 the first genome of a marine Fe(II oxidizing Zetaproteobacterium.

    Esther Singer

    Full Text Available Mariprofundus ferrooxydans PV-1 has provided the first genome of the recently discovered Zetaproteobacteria subdivision. Genome analysis reveals a complete TCA cycle, the ability to fix CO(2, carbon-storage proteins and a sugar phosphotransferase system (PTS. The latter could facilitate the transport of carbohydrates across the cell membrane and possibly aid in stalk formation, a matrix composed of exopolymers and/or exopolysaccharides, which is used to store oxidized iron minerals outside the cell. Two-component signal transduction system genes, including histidine kinases, GGDEF domain genes, and response regulators containing CheY-like receivers, are abundant and widely distributed across the genome. Most of these are located in close proximity to genes required for cell division, phosphate uptake and transport, exopolymer and heavy metal secretion, flagellar biosynthesis and pilus assembly suggesting that these functions are highly regulated. Similar to many other motile, microaerophilic bacteria, genes encoding aerotaxis as well as antioxidant functionality (e.g., superoxide dismutases and peroxidases are predicted to sense and respond to oxygen gradients, as would be required to maintain cellular redox balance in the specialized habitat where M. ferrooxydans resides. Comparative genomics with other Fe(II oxidizing bacteria residing in freshwater and marine environments revealed similar content, synteny, and amino acid similarity of coding sequences potentially involved in Fe(II oxidation, signal transduction and response regulation, oxygen sensation and detoxification, and heavy metal resistance. This study has provided novel insights into the molecular nature of Zetaproteobacteria.

  13. Physiology, Fe(II oxidation, and Fe mineral formation by a marine planktonic cyanobacterium grown under ferruginous conditions

    Elizabeth D. Swanner


    Full Text Available Evidence for Fe(II oxidation and deposition of Fe(III-bearing minerals from anoxic or redox-stratified Precambrian oceans has received support from decades of sedimentological and geochemical investigation of Banded Iron Formations (BIF. While the exact mechanisms of Fe(II oxidation remains equivocal, reaction with O2 in the marine water column, produced by cyanobacteria or early oxygenic phototrophs, was likely. In order to understand the role of cyanobacteria in the deposition of Fe(III minerals to BIF, we must first know how planktonic marine cyanobacteria respond to ferruginous (anoxic and Fe(II-rich waters in terms of growth, Fe uptake and homeostasis, and Fe mineral formation. We therefore grew the common marine cyanobacterium Synechococcus PCC 7002 in closed bottles that began anoxic, and contained Fe(II concentrations that span the range of possible concentrations in Precambrian seawater. These results, along with cell suspension experiments, indicate that Fe(II is likely oxidized by this strain via chemical oxidation with oxygen produced during photosynthesis, and not via any direct enzymatic or photosynthetic pathway. Imaging of the cell-mineral aggregates with scanning electron microscopy (SEM and confocal laser scanning microscopy (CLSM are consistent with extracellular precipitation of Fe(III (oxyhydroxide minerals, but that >10% of Fe(III sorbs to cell surfaces rather than precipitating. Proteomic experiments support the role of reactive oxygen species (ROS in Fe(II toxicity to Synechococcus PCC 7002. The proteome expressed under low Fe conditions included multiple siderophore biosynthesis and siderophore and Fe transporter proteins, but most siderophores are not expressed during growth with Fe(II. These results provide a mechanistic and quantitative framework for evaluating the geochemical consequences of perhaps life’s greatest metabolic innovation, i.e. the evolution and activity of oxygenic photosynthesis, in ferruginous

  14. Physiology, Fe(II) oxidation, and Fe mineral formation by a marine planktonic cyanobacterium grown under ferruginous conditions

    Swanner, Elizabeth; Wu, Wenfang; Hao, Likai; Wuestner, Marina; Obst, Martin; Moran, Dawn; McIlvin, Matthew; Saito, Mak; Kappler, Andreas


    Evidence for Fe(II) oxidation and deposition of Fe(III)-bearing minerals from anoxic or redox-stratified Precambrian oceans has received support from decades of sedimentological and geochemical investigation of Banded Iron Formations (BIF). While the exact mechanisms of Fe(II) oxidation remains equivocal, reaction with O2 in the marine water column, produced by cyanobacteria or early oxygenic phototrophs, was likely. In order to understand the role of cyanobacteria in the deposition of Fe(III) minerals to BIF, we must first know how planktonic marine cyanobacteria respond to ferruginous (anoxic and Fe(II)-rich) waters in terms of growth, Fe uptake and homeostasis, and Fe mineral formation. We therefore grew the common marine cyanobacterium Synechococcus PCC 7002 in closed bottles that began anoxic, and contained Fe(II) concentrations that span the range of possible concentrations in Precambrian seawater. These results, along with cell suspension experiments, indicate that Fe(II) is likely oxidized by this strain via chemical oxidation with oxygen produced during photosynthesis, and not via any direct enzymatic or photosynthetic pathway. Imaging of the cell-mineral aggregates with scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) are consistent with extracellular precipitation of Fe(III) (oxyhydr)oxide minerals, but that >10% of Fe(III) sorbs to cell surfaces rather than precipitating. Proteomic experiments support the role of reactive oxygen species (ROS) in Fe(II) toxicity to Synechococcus PCC 7002. The proteome expressed under low Fe conditions included multiple siderophore biosynthesis and siderophore and Fe transporter proteins, but most siderophores are not expressed during growth with Fe(II). These results provide a mechanistic and quantitative framework for evaluating the geochemical consequences of perhaps life’s greatest metabolic innovation, i.e. the evolution and activity of oxygenic photosynthesis, in ferruginous

  15. Spin crossover in Fe(II) complexes with N4S2 coordination

    Arroyave, Alejandra; Lennartson, Anders; Dragulescu-Andrasi, Alina;


    A systematic study of a series of Fe(II) complexes with the tetradentate N2S2-binding ligand and NCX− coligands (X = S, Se, BH3) conclusively demonstrates the occurrence of temperature-driven spin crossover (SCO), which is rarely observed for the Fe(II) ion in the N4S2 coordination environment....... The SCO is confirmed by crystallography, magnetic measurements, and Mössbauer spectroscopy. The last two methods also reveal a light-induced excited spin state trapping (LIESST) effect at low temperatures....

  16. Heterogeneous reduction of PuO₂ with Fe(II): importance of the Fe(III) reaction product.

    Felmy, Andrew R; Moore, Dean A; Rosso, Kevin M; Qafoku, Odeta; Rai, Dhanpat; Buck, Edgar C; Ilton, Eugene S


    Heterogeneous reduction of actinides in higher, more soluble oxidation states to lower, more insoluble oxidation states by reductants such as Fe(II) has been the subject of intensive study for more than two decades. However, Fe(II)-induced reduction of sparingly soluble Pu(IV) to the more soluble lower oxidation state Pu(III) has been much less studied, even though such reactions can potentially increase the mobility of Pu in the subsurface. Thermodynamic calculations are presented that show how differences in the free energy of various possible solid-phase Fe(III) reaction products can greatly influence aqueous Pu(III) concentrations resulting from reduction of PuO₂(am) by Fe(II). We present the first experimental evidence that reduction of PuO₂(am) to Pu(III) by Fe(II) was enhanced when the Fe(III) mineral goethite was spiked into the reaction. The effect of goethite on reduction of Pu(IV) was demonstrated by measuring the time dependence of total aqueous Pu concentration, its oxidation state, and system pe/pH. We also re-evaluated established protocols for determining Pu(III) {[Pu(III) + Pu(IV)] - Pu(IV)} by using thenoyltrifluoroacetone (TTA) in toluene extractions; the study showed that it is important to eliminate dissolved oxygen from the TTA solutions for accurate determinations. More broadly, this study highlights the importance of the Fe(III) reaction product in actinide reduction rate and extent by Fe(II).

  17. Condutividade da Polianilina e Poliacrilonitrila Dopadas com Fe(II e Fe(III

    Yonis Fornazier Filho


    Full Text Available In this work we report O estudo da interação de íons Fe(II com a polianilina foi feito através da obtenção deste polímero na forma de salthe studies on Polyaniline Emeraldine (PANI-ES and Polyacrilonitrile (PAN doped with salt of Fe (II and Fe(III. We used the techniques of conductivity measurements with aplicação de pressão.application of pressure.  The results showed that conductivity of PANI-ES increase with pressure of range of 1.73 MPa until 20.0 MPa and PAN also increase with maximum of 6.0 mPa except to samples PAN-2-TT-FeIII and PAN-2-TTAA-FeIII.

  18. Role of Natural Organic Matter in Regulating the Partitioning of Fe(II, III) in Seawater

    Guo, L.; Chen, M.; Roberts, K.; Santschi, P. H.


    Iron (Fe) is an essential micronutrient and plays an important role in controlling ocean productivity and carbon cycling. Fe has been shown to be mostly complexed with dissolved organic matter in seawater. However, the interaction of Fe with natural organic matter and how the quality and quantity of organic matter affect the chemical speciation of Fe in seawater remain poorly understood. Controlled laboratory experiments have been conducted to examine the partitioning of Fe(II, III) between dissolved, colloidal and particulate phases using radiotracers, model organic compounds, and ultrafiltration. In natural seawater, Fe is mostly partitioned in the colloidal and particulate phases, resulting in a logKd value of 7.3 and a logKc of 6.1, respectively. On average, about 25% of dissolved Fe-55 was found in the complexation of Fe with DOM could depress the bioavailability of Fe in seawater, the resultant Fe reduction may significantly enhance its solubility and bioavailability to marine organisms.

  19. Atom exchange between aqueous Fe(II) and structural Fe in clay minerals.

    Neumann, Anke; Wu, Lingling; Li, Weiqiang; Beard, Brian L; Johnson, Clark M; Rosso, Kevin M; Frierdich, Andrew J; Scherer, Michelle M


    Due to their stability toward reductive dissolution, Fe-bearing clay minerals are viewed as a renewable source of Fe redox activity in diverse environments. Recent findings of interfacial electron transfer between aqueous Fe(II) and structural Fe in clay minerals and electron conduction in octahedral sheets of nontronite, however, raise the question whether Fe interaction with clay minerals is more dynamic than previously thought. Here, we use an enriched isotope tracer approach to simultaneously trace Fe atom movement from the aqueous phase to the solid ((57)Fe) and from the solid into the aqueous phase ((56)Fe). Over 6 months, we observed a significant decrease in aqueous (57)Fe isotope fraction, with a fast initial decrease which slowed after 3 days and stabilized after about 50 days. For the aqueous (56)Fe isotope fraction, we observed a similar but opposite trend, indicating that Fe atom movement had occurred in both directions: from the aqueous phase into the solid and from the solid into aqueous phase. We calculated that 5-20% of structural Fe in clay minerals NAu-1, NAu-2, and SWa-1 exchanged with aqueous Fe(II), which significantly exceeds the Fe atom layer exposed directly to solution. Calculations based on electron-hopping rates in nontronite suggest that the bulk conduction mechanism previously demonstrated for hematite1 and suggested as an explanation for the significant Fe atom exchange observed in goethite2 may be a plausible mechanism for Fe atom exchange in Fe-bearing clay minerals. Our finding of 5-20% Fe atom exchange in clay minerals indicates that we need to rethink how Fe mobility affects the macroscopic properties of Fe-bearing phyllosilicates and its role in Fe biogeochemical cycling, as well as its use in a variety of engineered applications, such as landfill liners and nuclear repositories.

  20. Effects of temperature on rates and mineral products of microbial Fe(II) oxidation by Leptothrix cholodnii at microaerobic conditions

    Vollrath, Susann; Behrends, Thilo; Koch, Christian Bender; Cappellen, Philippe Van


    Oxygen concentrations are important in constraining the geochemical niche of neutrophilic iron oxidizers. However, other factors like temperature may affect the competition between microbial and abiotic Fe(II) oxidation and may cause community changes. Here, rates and mineral products of Fe(II) oxidation (initial concentration 150 μmol Fe(II)/l) by the Fe(II) oxidizing bacterial strain Leptothrix cholodnii Appels were compared to those of abiotic oxidation in the temperature range 11-37 °C. Experiments were carried out in a batch reactor at 12-13 μmol O2/l (0.92-1% O2 saturation), pH 7 and, for the microbial experiments, a cell density of around 108 cells/ml. The iron precipitates formed at the different temperatures were characterized by SEM, XRD, FTIR and Mössbauer spectroscopy. Abiotic and microbial Fe(II) oxidation proceeded in two stages. During the initial stage, rates of microbial oxidation exhibited a temperature optimum curve. In contrast, the temperature dependency of abiotic Fe(II) oxidation rate followed the Arrhenius equation. As a consequence, microbial oxidation rates were about 10 times higher compared to the abiotic oxidation at 30 °C. During the second stage, microbial and abiotic rates and their temperature dependencies were similar. Independent of temperature or presence of bacteria, lepidocrocite and ferrihydrite were identified as reaction products, but the characteristics of the precipitates differed. At 37 °C, less lepidocrocite was precipitated in microbial and abiotic experiments due to high oxidation rates. Abiotic oxidation produced larger lepidocrocite crystals mixed with smaller, less crystalline oxides. Large crystals were absent in the microbial products, possibly due to growth inhibition of the minerals by EPS substances. Nevertheless, Mössbauer spectra revealed a better crystal structure of the smaller, microbial precipitates compared to the abiotically formed oxides.

  1. Dissolved Fe(II) in the Pacific Ocean: Measurements from the P16N CLIVAR/CO2 Repeat Hydrography Cruise

    Hansard, S. P.; Landing, W. M.; Measures, C. I.


    Vertical profiles of seawater Fe(II) concentration were obtained for 37 stations sampled in early 2006, in conjunction with the CLIVAR Repeat Hydrography P16N transect (152° W, Tahiti to Alaska). At each station, seawater samples were collected from 12 target depths (0-1000 m) using trace-metal clean Go-Flo bottles. Upon recovery, Go-Flo bottles were immediately transferred to a Class 100 clean van and sub-sampled for Fe(II) by passing sample water through a 0.2 μm Supor (polyethersulfone) cartridge filter into 125 mL containers, pre-loaded with 25 μL of 6M quartz-distilled HCl (final pH ~~ 6) to slow oxidation. Samples were immediately analyzed for Fe(II) using a luminol-based chemiluminescence method. Total dissolved iron was also determined shipboard by spectrophotometric flow injection analysis. The data collected from this cruise will be presented, along with corroborating data from another North Pacific cruise (PO2). Concentrations of Fe(II) ranged from below detection (meters. Photoreduction of Fe(III) has been cited as a source of Fe(II) in surface waters, and the pattern of attenuation with depth is consistent with this mechanism. Many samples collected at or near the bottom of the profile (500-1000 m) exhibited elevated Fe(II) relative to the mid-depths of the profile. Due to the higher total dissolved iron at depth, the percentage of Fe(II) was low in these samples. Recent studies support the presence of Fe(II) at depth, in association with low or suboxic conditions. In situ processes such as the remineralization of sinking biogenic particles may provide a source for this Fe(II).

  2. Multi-reverse flow injection analysis integrated with multi-optical sensor for simultaneous determination of Mn(II), Fe(II), Cu(II) and Fe(III) in natural waters.

    Youngvises, Napaporn; Suwannasaroj, Kittigan; Jakmunee, Jaroon; AlSuhaimi, Awadh


    Multi-reverse flow injection analysis (Mr-FIA) integrated with multi-optical sensor was developed and optimized for the simultaneous determination of multi ions; Mn(II), Fe(II), Cu(II) and Fe(III) in water samples. The sample/standard solutions were propelled making use of a four channels peristaltic pump whereas 4 colorimetric reagents specific for the metal ions were separately injected in sample streams using multi-syringe pump. The color zones that formed in the individual mixing coils were then streamed into multi-channels spectrometer, which comprised of four flows through cell and four pairs of light emitting diode and photodiode, whereby signals were measured concurrently. The linearity range (along with detection limit, µgL(-1)) was 0.050-3.0(16), 0.30-2.0 (11), 0.050-1.0(12) and 0.10-1.0(50)mgL(-1), for Mn(II), Fe(II), Cu(II) and Fe(III), respectively. In the interim, the correlation coefficients were 0.9924-0.9942. The percentages relative standard deviation was less than 3. The proposed system was applied successfully to determine targeted metal ions simultaneously in natural water with high sample throughput and low reagent consumption, thus it satisfies the criteria of Green Analytical Chemistry (GAC) and its goals.

  3. Final Report: Molecular mechanisms and kinetics of microbial anaerobic nitrate-dependent U(IV) and Fe(II) oxidation

    O' Day, Peggy A. [Univ. of California, Merced, CA (United States); Asta, Maria P. [Univ. of California, Merced, CA (United States); Kanematsu, Masakazu [Univ. of California, Merced, CA (United States); Beller, Harry [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Zhou, Peng [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Steefel, Carl [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)


    In this project, we combined molecular genetic, spectroscopic, and microscopic techniques with kinetic and reactive transport studies to describe and quantify biotic and abiotic mechanisms underlying anaerobic, nitrate-dependent U(IV) and Fe(II) oxidation, which influences the long-term efficacy of in situ reductive immobilization of uranium at DOE sites. In these studies, Thiobacillus denitrificans, an autotrophic bacterium that catalyzes anaerobic U(IV) and Fe(II) oxidation, was used to examine coupled oxidation-reduction processes under either biotic (enzymatic) or abiotic conditions in batch and column experiments with biogenically produced UIVO2(s). Synthesis and quantitative analysis of coupled chemical and transport processes were done with the reactive transport modeling code Crunchflow. Research focused on identifying the primary redox proteins that catalyze metal oxidation, environmental factors that influence protein expression, and molecular-scale geochemical factors that control the rates of biotic and abiotic oxidation.

  4. Two-step spin-switchable tetranuclear Fe(II) molecular solid: Ab initio theory and predictions

    Maldonado, Pablo; Kanungo, Sudipta; Saha-Dasgupta, Tanusri; Oppeneer, Peter M.


    Using density functional theory supplemented with on-site Coulomb U interaction in combination with ab initio molecular dynamics simulations, we investigate the spin-crossover (SCO) properties of a Fe(II) based cyanide-bridged square molecular system, [FeII4(μ-CN)4(bpy)4(tpa)2](PF6)4 (where bpy = 2,2'-bipyridine and tpa = tris(2-pyridylmethyl)amine], exhibiting a two-step SCO transition. The ab initio calculated SCO temperatures are found to show remarkably good agreement with experimentally measured spin conversion temperatures [M. Nihei , Angew. Chem., Int. Ed.1433-785110.1002/anie.200502216 44, 6484 (2005)]. Our theoretical study predicts further chemo switching of the spin state by introduction of guest molecules such as CO2, CS2, and H2O into the porous topology of the system, which would add another dimensionality to this interesting material.

  5. Formation of iron (hydr)oxides during the abiotic oxidation of Fe(II) in the presence of arsenate.

    Song, Jia; Jia, Shao-Yi; Yu, Bo; Wu, Song-Hai; Han, Xu


    Abiotic oxidation of Fe(II) is a common pathway in the formation of Fe (hydr)oxides under natural conditions, however, little is known regarding the presence of arsenate on this process. In hence, the effect of arsenate on the precipitation of Fe (hydr)oxides during the oxidation of Fe(II) is investigated. Formation of arsenic-containing Fe (hydr)oxides is constrained by pH and molar ratios of As:Fe during the oxidation Fe(II). At pH 6.0, arsenate inhibits the formation of lepidocrocite and goethite, while favors the formation of ferric arsenate with the increasing As:Fe ratio. At pH 7.0, arsenate promotes the formation of hollow-structured Fe (hydr)oxides containing arsenate, as the As:Fe ratio reaches 0.07. Arsenate effectively inhibits the formation of magnetite at pH 8.0 even at As:Fe ratio of 0.01, while favors the formation of lepidocrocite and green rust, which can be latterly degenerated and replaced by ferric arsenate with the increasing As:Fe ratio. This study indicates that arsenate and low pH value favor the slow growth of dense-structured Fe (hydr)oxides like spherical ferric arsenate. With the rapid oxidation rate of Fe(II) at high pH, ferric (hydr)oxides prefer to precipitate in the formation of loose-structured Fe (hydr)oxides like lepidocrocite and green rust. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Heterogeneous Reduction of PuO2 with Fe(II): Importance of the Fe(III) Reaction Product

    Felmy, Andrew R.; Moore, Dean A.; Rosso, Kevin M.; Qafoku, Odeta; Rai, Dhanpat; Buck, Edgar C.; Ilton, Eugene S.


    Abstract Heterogeneous reduction of actinides in higher and more soluble oxidation states to lower more insoluble oxidation states by reductants such as Fe(II) has been the subject of intensive study for more than two decades. However, Fe(II)-induced reduction of sparingly soluble Pu(IV) to the more soluble lower oxidation state Pu(III) has been much less studied even though such reactions can potentially increase the mobility of Pu in the subsurface. Thermodynamic calculations are presented that show how differences in the free energy of various possible solid-phase Fe(III) reaction products can greatly influence aqueous Pu(III) concentrations resulting from reduction of PuO2(am) by Fe(II). We present the first experimental evidence that reduction of PuO2(am) to Pu(III) by Fe(II) was enhanced when the Fe(III) mineral goethite was spiked into the reaction. The effect of goethite on reduction of Pu(IV) was demonstrated by measuring the time-dependence of total aqueous Pu concentration, its oxidation state, and system pe/pH. We also re-evaluated established protocols for determining Pu(III) [(Pu(III) + Pu(IV)) - Pu(IV)] by using thenoyltrifluoroacetone (TTA) in toluene extractions; the study showed that it is important to eliminate dissolved oxygen from the TTA solutions for accurate determinations. More broadly, this study highlights the importance of the Fe(III) reaction product in actinide reduction rate and extent by Fe(II).

  7. Coupling of Fe(II) oxidation in illite with nitrate reduction and its role in clay mineral transformation

    Zhao, Linduo; Dong, Hailiang; Edelmann, Richard E.; Zeng, Qiang; Agrawal, Abinash


    In pedogenic and diagenetic processes, clay minerals transform from pre-existing phases to other clay minerals via intermediate interstratified clays. Temperature, pressure, chemical composition of fluids, and time are traditionally considered to be the important geological variables for clay mineral transformations. Nearly ten years ago, the role of microbes was recognized for the first time, where microbial reduction of structural Fe(III) in smectite resulted in formation of illite under ambient conditions within two weeks. However, the opposite process, the oxidation of structural Fe(II) in illite has not been studied and it remains unclear whether or not this process would result in the back reaction, e.g., from illite to smectite. The overall objective of this study was to investigate biological oxidation of structural Fe(II) in illite coupled with nitrate reduction and the effect of this process on clay mineral transformation. Laboratory incubations were set up, where structural Fe(II) in illite served as electron donor, nitrate as electron acceptor, and Pseudogulbenkiania sp. strain 2002 as mediator. Solution chemistry and gas composition were monitored over time. Mineralogical transformation resulting from bio-oxidation was characterized with X-ray diffraction and scanning and transmission electron microscopy. Our results demonstrated that strain 2002 was able to couple oxidation of structural Fe(II) in illite with reduction of nitrate to N2 with nitrite as a transient intermediate. This oxidation reaction resulted in transformation of illite to smectite and ultimately to kaolinite (illite → smectite → kaolinite transformations). This study illustrates the importance of Fe redox process in mediating the smectite-illite mineral cycle with important implications for Fe redox cycling and mineral evolution in surficial earth environments.

  8. Incorporation of oxidized uranium into Fe (hydr)oxides during Fe(II) catalyzed remineralization

    Nico, Peter S.; Stewart, Brandy D.; Fendorf, Scott


    The form of solid phase U after Fe(II) induced anaerobic remineralization of ferrihydrite in the presence of aqueous and absorbed U(VI) was investigated under both abiotic batch and biotic flow conditions. Experiments were conducted with synthetic ground waters containing 0.168 mM U(VI), 3.8 mM carbonate, and 3.0 mM Ca{sup 2+}. In spite of the high solubility of U(VI) under these conditions, appreciable removal of U(VI) from solution was observed in both the abiotic and biotic systems. The majority of the removed U was determined to be substituted as oxidized U (U(VI) or U(V)) into the octahedral position of the goethite and magnetite formed during ferrihydrite remineralization. It is estimated that between 3% and 6% of octahedral Fe(III) centers in the new Fe minerals were occupied by U(VI). This site specific substitution is distinct from the non-specific U co-precipitation processes in which uranyl compounds, e.g. uranyl hydroxide or carbonate, are entrapped with newly formed Fe oxides. The prevalence of site specific U incorporation under both abiotic and biotic conditions and the fact that the produced solids were shown to be resistant to both extraction (30 mM KHCO{sub 3}) and oxidation (air for 5 days) suggest the potential importance of sequestration in Fe oxides as a stable and immobile form of U in the environment.

  9. On Spin Hamiltonian fits to Moessbauer spectra of high-spin Fe(II) porphyrinate systems

    Schulz, Charles E., E-mail: [Knox College, Department of Physics (United States); Hu Chuanjiang, E-mail:; Scheidt, W. Robert [University of Notre Dame, Department of Chemistry and Biochemistry (United States)


    Fits to Moessbauer spectra of high-spin iron(II) porphyrinates have been applied to the Fe(II) model compounds octaethylporphyrin(1,2-dimethylimidazole) and tetra-paramethoxyporphyrin(1,2-dimethylimidazole). Moessbauer spectra have been measured on these compounds at 4.2 K in large applied fields. Spin Hamiltonians were used for fitting both the electronic and nuclear interactions. The fits are done by adjusting the Hamiltonian parameters to simultaneously minimize the total {chi}{sup 2} for three different applied fields. In order to get best fits, the EFG tensor need to be rotated relative to the ZFS tensor. A comparative sensitivity analysis of their Spin Hamiltonian parameters has also been done on the ZFS parameters D, and the EFG asymmetry parameter {eta}. The best fits suggest that both systems definitely have a negative quadrupole splitting, and that largest EFG component is tilted far from the z-axis of the ZFS tensor, which is likely to be near the heme normal.

  10. Incorporation of oxidized uranium into Fe (hydr)oxides during Fe(II) catalyzed remineralization

    Nico, Peter S.; Stewart, Brandy D.; Fendorf, Scott


    The form of solid phase U after Fe(II) induced anaerobic remineralization of ferrihydrite in the presence of aqueous and absorbed U(VI) was investigated under both abiotic batch and biotic flow conditions. Experiments were conducted with synthetic ground waters containing 0.168 mM U(VI), 3.8 mM carbonate, and 3.0 mM Ca{sup 2+}. In spite of the high solubility of U(VI) under these conditions, appreciable removal of U(VI) from solution was observed in both the abiotic and biotic systems. The majority of the removed U was determined to be substituted as oxidized U (U(VI) or U(V)) into the octahedral position of the goethite and magnetite formed during ferrihydrite remineralization. It is estimated that between 3% and 6% of octahedral Fe(III) centers in the new Fe minerals were occupied by U(VI). This site specific substitution is distinct from the non-specific U co-precipitation processes in which uranyl compounds, e.g. uranyl hydroxide or carbonate, are entrapped with newly formed Fe oxides. The prevalence of site specific U incorporation under both abiotic and biotic conditions and the fact that the produced solids were shown to be resistant to both extraction (30 mM KHCO{sub 3}) and oxidation (air for 5 days) suggest the potential importance of sequestration in Fe oxides as a stable and immobile form of U in the environment.

  11. Abiotic process for Fe(II) oxidation and green rust mineralization driven by a heterotrophic nitrate reducing bacteria (Klebsiella mobilis).

    Etique, Marjorie; Jorand, Frédéric P A; Zegeye, Asfaw; Grégoire, Brian; Despas, Christelle; Ruby, Christian


    Green rusts (GRs) are mixed Fe(II)-Fe(III) hydroxides with a high reactivity toward organic and inorganic pollutants. GRs can be produced from ferric reducing or ferrous oxidizing bacterial activities. In this study, we investigated the capability of Klebsiella mobilis to produce iron minerals in the presence of nitrate and ferrous iron. This bacterium is well-known to reduce nitrate using an organic carbon source as electron donor but is unable to enzymatically oxidize Fe(II) species. During incubation, GR formation occurred as a secondary iron mineral precipitating on cell surfaces, resulting from Fe(II) oxidation by nitrite produced via bacterial respiration of nitrate. For the first time, we demonstrate GR formation by indirect microbial oxidation of Fe(II) (i.e., a combination of biotic/abiotic processes). These results therefore suggest that nitrate-reducing bacteria can potentially contribute to the formation of GR in natural environments. In addition, the chemical reduction of nitrite to ammonium by GR is observed, which gradually turns the GR into the end-product goethite. The nitrogen mass-balance clearly demonstrates that the total amount of ammonium produced corresponds to the quantity of bioreduced nitrate. These findings demonstrate how the activity of nitrate-reducing bacteria in ferrous environments may provide a direct link between the biogeochemical cycles of nitrogen and iron.

  12. Molar Absorptivity and Concentration-Dependent Quantum Yield of Fe(II) Photo-Formation for the Aqueous Solutions of Fe(III)-Dicarboxylate Complexes

    Hitomi, Y.; Arakaki, T.


    Redox cycles of iron in the aquatic environment affect formation of reactive oxygen species such as hydrogen peroxide and hydroxyl radicals, which in turn determines lifetimes of many organic compounds. Although aqueous Fe(III)-dicarboxylate complexes are considered to be important sources of photo-formed Fe(II), molar absorptivity and quantum yield of Fe(II) formation for individual species are not well understood. We initiated a study to characterize Fe(II) photo-formation from Fe(III)-dicarboxylates with the concentration ranges that are relevant to the natural aquatic environment. The Visual MINTEQ computer program was used to calculate the equilibrium concentrations of individual Fe(III)-dicarboxylate species. The molar absorptivity of Fe(III)-dicarboxylate species was obtained by UV-VIS spectrophotometer, and the product of the quantum yield and the molar absorptivity of Fe(III)-dicarboxylate species were obtained from photochemical experiments. These experimental data were combined with the calculated equilibrium Fe(III)-dicarboxylate concentrations to determine individual molar absorptivity and quantum yield of Fe(II) photo-formation for a specific Fe(III)-dicarboxylate species. We used initial concentrations of less than 10 micromolar Fe(III) to study the photochemical formation of Fe(II). Dicarboxylate compounds studied include oxalate, malonate, succinate, malate, and phthalate. We report molar absorptivity and concentration-dependent quantum yields of Fe(II) photo-formation of individual Fe(III)-dicarboxylates.

  13. Insights into Nitrate-Reducing Fe(II) Oxidation Mechanisms through Analysis of Cell-Mineral Associations, Cell Encrustation, and Mineralogy in the Chemolithoautotrophic Enrichment Culture KS.

    Nordhoff, M; Tominski, C; Halama, M; Byrne, J M; Obst, M; Kleindienst, S; Behrens, S; Kappler, A


    Most described nitrate-reducing Fe(II)-oxidizing bacteria (NRFeOB) are mixotrophic and depend on organic cosubstrates for growth. Encrustation of cells in Fe(III) minerals has been observed for mixotrophic NRFeOB but not for autotrophic phototrophic and microaerophilic Fe(II) oxidizers. So far, little is known about cell-mineral associations in the few existing autotrophic NRFeOB. Here, we investigate whether the designated autotrophic Fe(II)-oxidizing strain (closely related to Gallionella and Sideroxydans) or the heterotrophic nitrate reducers that are present in the autotrophic nitrate-reducing Fe(II)-oxidizing enrichment culture KS form mineral crusts during Fe(II) oxidation under autotrophic and mixotrophic conditions. In the mixed culture, we found no significant encrustation of any of the cells both during autotrophic oxidation of 8 to 10 mM Fe(II) coupled to nitrate reduction and during cultivation under mixotrophic conditions with 8 to 10 mM Fe(II), 5 mM acetate, and 4 mM nitrate, where higher numbers of heterotrophic nitrate reducers were present. Two pure cultures of heterotrophic nitrate reducers (Nocardioides and Rhodanobacter) isolated from culture KS were analyzed under mixotrophic growth conditions. We found green rust formation, no cell encrustation, and only a few mineral particles on some cell surfaces with 5 mM Fe(II) and some encrustation with 10 mM Fe(II). Our findings suggest that enzymatic, autotrophic Fe(II) oxidation coupled to nitrate reduction forms poorly crystalline Fe(III) oxyhydroxides and proceeds without cellular encrustation while indirect Fe(II) oxidation via heterotrophic nitrate-reduction-derived nitrite can lead to green rust as an intermediate mineral and significant cell encrustation. The extent of encrustation caused by indirect Fe(II) oxidation by reactive nitrogen species depends on Fe(II) concentrations and is probably negligible under environmental conditions in most habitats.IMPORTANCE Most described nitrate

  14. A dual nitrite isotopic investigation of chemodenitrification by mineral-associated Fe(II) and its production of nitrous oxide

    Grabb, Kalina C.; Buchwald, Carolyn; Hansel, Colleen M.; Wankel, Scott D.


    Under anaerobic conditions, the environmental reduction of nitrate (NO3-) and nitrite (NO2-) to more reduced forms is widely regarded as being microbially catalyzed. However, the chemical reduction of oxidized nitrogen species by reduced iron (Fe(II)), whether mineral-bound or surface-associated, may also occur under environmentally relevant conditions. Here we examine the nitrogen (N) and oxygen (O) stable isotope dynamics of the chemical reduction of NO2- by mineral associated Fe(II) (chemodenitrification) and its production of the potent greenhouse gas nitrous oxide (N2O). By shedding light on factors controlling kinetics of the reaction and its corresponding dual isotopic expression in the reactant NO2- and product N2O, this work contributes to a growing body of work aiming to improve our ability to identify chemodenitrification in the environment. Consistent with previous studies, we find that while homogenous reactions between aqueous NO2- and Fe(II) were kinetically slow, heterogeneous reactions involving Fe(II)-containing minerals often catalyzed considerable nitrite loss. In particular, rapid reduction of NO2- was catalyzed by the Fe-rich smectite clay mineral nontronite as well as the mixed Fe(II)-Fe(III) oxyhydroxide phase green rust. These minerals serve as both a source of reduced iron within the mineral structure as well as a surface for promoting the reactivity of Fe(II). However, even in the presence of aqueous Fe(II), experiments with low-Fe and non-Fe containing minerals showed little to no NO2- loss, perhaps suggesting a more dominant role for structural iron during chemodenitrification. When catalyzed by nontronite and green rust, N and O isotope effects for chemodenitrification (15εcDNF and 18εcDNF) ranged from 2 to 11‰ and 4 to 10‰, respectively, with lower values generally observed at higher reaction rates. Higher reaction rates were also linked to higher molar yields of N2O (up to 31%), highlighting a strong potential for

  15. The reactivity of Fe(II) associated with goethite formed during short redox cycles toward Cr(VI) reduction under oxic conditions

    Tomaszewski, Elizabeth J.; Lee, Seungyeol; Rudolph, Jared; Xu, Huifang; Ginder-Vogel, Matthew (UW)


    Chromium (Cr) is a toxic metal that causes a myriad of health problems and enters the environment as a result of anthropogenic activities and/or natural processes. The toxicity and solubility of chromium is linked to its oxidation state; Cr(III) is poorly soluble and relatively nontoxic, while Cr(VI) is soluble and a known carcinogen. Solid Fe(II) in iron-bearing minerals, such as pyrite, magnetite, and green rusts, reduce the oxidation state of chromium, reducing its toxicity and mobility. However, these minerals are not the only potential sources of solid-associated Fe(II) available for Cr(VI) reduction. For example, ferric (Fe(III)) (hydr)oxides, such as goethite or hematite, can have Fe(II) in the solid without phase transformation; however, the reactivity of Fe(II) within Fe(III) (hydr)oxides with contaminants, has not been previously investigated. Here, we cyclically react goethite with dissolved Fe(II) followed by dissolved O2, leading to the formation of reactive Fe(II) associated with goethite. In separate reactors, the reactivity of this Fe(II) is probed under oxic conditions, by exposure to chromate (CrO42 -) after either one, two, three or four redox cycles. Cr is not present during redox cycling; rather, it is introduced to a subset of the solid after each oxidation half-cycle. Analysis of X-ray absorption near edge structure (XANES) spectra reveals that the extent of Cr(VI) reduction to Cr(III) depends not only on solid Fe(II) content but also surface area and mean size of ordered crystalline domains, determined by BET surface area analysis and X-ray diffraction (XRD), respectively. Shell-by-shell fitting of the extended X-ray absorption fine structure (EXAFS) spectra demonstrates chromium forms both single and double corner sharing complexes on the surface of goethite, in addition to sorbed Cr(III) species. Finally, transmission electron microscope (TEM) imaging and X-ray energy-dispersive spectroscopy (EDS) illustrate that Cr preferentially

  16. Fe isotope fractionation during Fe(II) oxidation by the marine photoferrotroph Rhodovulum iodosum in the presence of Si - Implications for Precambrian iron formation deposition

    Wu, Wenfang; Swanner, Elizabeth D.; Kleinhanns, Ilka C.; Schoenberg, Ronny; Pan, Yongxin; Kappler, Andreas


    The iron (Fe) isotopic composition of Precambrian iron formations (IFs), besides providing geological context through its mineralogical properties, was suggested to function as a biosignature that can be used to infer a potential microbial role in the formation of the deposited Fe minerals. Anoxygenic phototrophic Fe(II)-oxidizing bacteria (photoferrotrophs), capable of oxidizing Fe(II) anoxically using light energy, were potentially involved in Fe(II) oxidation in anoxic or suboxic Precambrian oceans. The effect of Si on Fe isotopic fractionation between aqueous Fe(II) and Fe-Si-co-precipitates has been investigated before. However, it is currently unknown how stable Fe isotopes are fractionated during enzymatic Fe(II) oxidation under marine hydrogeochemical conditions, and particularly how the presence of Si affects the Fe isotope composition and the isotopic exchange among different Fe phases. We therefore studied Fe isotope fractionation during Fe(II) oxidation by the marine photoferrotroph Rhodovulum iodosum in simulated Precambrian seawater amended with 1 mM dissolved Si. Our results show that the change in the Fe isotope compositions over time for both the initial aqueous Fe(II) (Feaq) and the Fe(III) precipitates (Feppt) follow a Rayleigh distillation model. Moreover, the fractionation (ε56Feppt-aq) determined independently from either δ56Feaq or δ56Feppt data resulted in a value of 2.3 ± 0.3 (2SD, N = 6). This value differs from the fractionation factor determined previously for Fe(II) oxidation by R. iodosum in the absence of Si, where the fractionation calculated from δ56Feaq (i.e. 0.96-1.18) was different from that calculated from δ56Feppt (1.96-1.98). This difference was attributed to isotopic exchange processes with soluble and sorbed Fe species. The present study suggests that Si present in Precambrian oceans retards Fe isotopic exchange, likely through combined effects of complexation of dissolved Fe species by Si and sorption of Si to Fe

  17. Metagenomic insights into the dominant Fe(II oxidizing Zetaproteobacteria from an iron mat at Lōi’hi, Hawai’I

    Esther eSinger


    Full Text Available Zetaproteobacteria are among the most prevalent Fe(II oxidizing bacteria at deep-sea hydrothermal vents; however, knowledge about their environmental significance is limited. We provide metagenomic insights into an iron mat at the Lōʻihi Seamount, Hawai’I, revealing novel genomic information of locally dominant Zetaproteobacteria lineages. These lineages were previously estimated to account for ~13% of all local Zetaproteobacteria based on 16S clone library data. Biogeochemically relevant genes include nitrite reductases, which were previously not identified in Zetaproteobacteria, sulfide:quinone oxidases, and ribulose-1,5-bisphosphate carboxylase (RuBisCo. Genes assumed to be involved in Fe(II oxidation correlate in synteny and share 70% AASim with those previously identified in the related Zetaproteobacterium Mariprofundus ferrooxydans PV-1. Overall, Zetaproteobacteria genes appear to originate primarily from within the Proteobacteria and the Fe(II oxidizing Leptospirillum spp. and are predicted to facilitate adaptation to a deep-sea hydrothermal vent environment in addition to microaerophilic Fe(II and H2S oxidation. This dataset represents the first metagenomic study of Fe(II oxidizing bacteria (FeOB from an iron oxide mat at a deep-sea hydrothermal habitat.

  18. The metallomics approach: use of Fe(II) and Cu(II) footprinting to examine metal binding sites on serum albumins.

    Duff, Michael R; Kumar, Challa V


    Metal binding to serum albumins is examined by oxidative protein-cleavage chemistry, and relative affinities of multiple metal ions to particular sites on these proteins were identified using a fast and reliable chemical footprinting approach. Fe(ii) and Cu(ii), for example, mediate protein cleavage at their respective binding sites on serum albumins, in the presence of hydrogen peroxide and ascorbate. This metal-mediated protein-cleavge reaction is used to evaluate the binding of metal ions, Na(+), Mg(2+), Ca(2+), Al(3+), Cr(3+), Mn(2+), Co(2+), Ni(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Ce(3+) to albumins, and the relative affinities (selectivities) of the metal ions are rapidly evaluated by examining the extent of inhibition of protein cleavage. Four distinct systems Fe(II)/BSA, Cu(II)/BSA, Fe(II)/HSA and Cu(II)/HSA are examined using the above strategy. This metallomics approach is novel, even though the cleavage of serum albumins by Fe(II)/Cu(II) has been reported previously by this laboratory and many others. The protein cleavage products were analyzed by SDS PAGE, and the intensities of the product bands quantified to evaluate the extent of inhibition of the cleavage and thereby evaluate the relative binding affinities of specific metal ions to particular sites on albumins. The data show that Co(II) and Cr(III) showed the highest degree of inhibition, across the table, followed by Mn(II) and Ce(III). Alakali metal ions and alkaline earth metal ions showed very poor affinity for these metal sites on albumins. Thus, metal binding profiles for particular sites on proteins can be obtained quickly and accurately, using the metallomics approach.

  19. Confinement of a bioinspired nonheme Fe(II) complex in 2D hexagonal mesoporous silica with metal site isolation.

    Jollet, Véronique; Albela, Belén; Sénéchal-David, Katell; Jégou, Pascale; Kolodziej, Emilie; Sainton, Joëlle; Bonneviot, Laurent; Banse, Frédéric


    A mixed amine pyridine polydentate Fe(II) complex was covalently tethered in hexagonal mesoporous silica of the MCM-41 type. Metal site isolation was generated using adsorbed tetramethylammonium cations acting as a patterned silanol protecting mask and trimethylsilylazane as a capping agent. Then, the amine/pyridine ligand bearing a tethering triethoxysilane group was either grafted to such a pretreated silica surface prior to or after complexation to Fe(II). These two synthetic routes, denoted as two-step and one-step, respectively, were also applied to fumed silica for comparison, except that the silanol groups were capped after tethering the metal unit. The coordination of the targeted complex was monitored using UV-visible spectrophotometry and, according to XPS, the best control was achieved inside the channels of the mesoporous silica for the two-step route. For the solid prepared according to the one-step route, tethering of the complex occurred mainly at the entrance of the channel.

  20. Speciative Determination of Dissolved Inorganic Fe(II, Fe(III and Total Fe in Natural Waters by Coupling Cloud Point Extraction with FAAS

    Ramazan GÜRKAN


    Full Text Available A new cloud point extraction (CPE method for the preconcentration of trace iron speciation in natural waters prior to determination by flame atomic absorption spectrometry (FAAS was developed in the present study. In this method, Fe(II sensitively and selectively reacts with Calcon carboxylic acid (CCA in presence of cetylpyridinium chloride (CPC yielding a hydrophobic complex at pH 10.5, which is then entrapped in surfactant-rich phase. Total Fe was accurately and reliably determined after the reduction of Fe(III to Fe(II with sulfite. The amount of Fe(III in samples was determined from the difference between total Fe and Fe(II. CPC was used not only as an auxiliary ligand in CPE, but also as sensitivity enhancement agent in FAAS. The nonionic surfactant, polyethylene glycol tert-octylphenyl ether (Triton X-114 was used as an extracting agent. The analytical variables affecting CPE efficiency were investigated in detail. The preconcentration/enhancement factors of 50 and 82 respectively, were obtained for the preconcentration of Fe(II with 50 mL solution. Under the optimized conditions, the detection limit of Fe(II in linear range of 0.2-60 μg L-1 was 0.06 μg L-1. The relative standard deviation was 2.7 % (20 μg L-1, N: 5, recoveries for Fe(II were in range of 99.0-102.0% for all water samples including certified reference materials (CRMs. In order to verify its accuracy, two CRMs were analyzed and the results obtained were statistically in good agreement with the certified values.

  1. Green rust formation during Fe(II) oxidation by the nitrate-reducing Acidovorax sp. strain BoFeN1.

    Pantke, Claudia; Obst, Martin; Benzerara, Karim; Morin, Guillaume; Ona-Nguema, Georges; Dippon, Urs; Kappler, Andreas


    Green rust (GR) as highly reactive iron mineral potentially plays a key role for the fate of (in)organic contaminants, such as chromium or arsenic, and nitroaromatic compounds functioning both as sorbent and reductant. GR forms as corrosion product of steel but is also naturally present in hydromorphic soils and sediments forming as metastable intermediate during microbial Fe(III) reduction. Although already suggested to form during microbial Fe(II) oxidation, clear evidence for GR formation during microbial Fe(II) oxidation was lacking. In the present study, powder XRD, synchrotron-based XAS, Mössbauer spectroscopy, and TEM demonstrated unambiguously the formation of GR as an intermediate product during Fe(II) oxidation by the nitrate-reducing Fe(II)-oxidizer Acidovorax sp. strain BoFeN1. The spatial distribution and Fe redox-state of the precipitates associated with the cells were visualized by STXM. It showed the presence of extracellular Fe(III), which can be explained by Fe(III) export from the cells or extracellular Fe(II) oxidation by an oxidant diffusing from the cells. Moreover, GR can be oxidized by nitrate/nitrite and is known as a catalyst for oxidation of dissolved Fe(II) by nitrite/nitrate and may thus contribute to the production of extracellular Fe(III). As a result, strain BoFeN1 may contribute to Fe(II) oxidation and nitrate reduction both by an direct enzymatic pathway and an indirect GR-mediated process.

  2. Characterizing the production and retention of dissolved iron as Fe(II) across a natural gradient in chlorophyll concentrations in the Southern Drake Passage - Final Technical Report

    Katherine Barbeau


    Recent mesoscale iron fertilization studies in the Southern Ocean (e.g. SOIREE, EisenEx, SOFeX) have demonstrated the importance of iron as a limiting factor for phytoplankton growth in these high nutrient, low-chlorophyll (HNLC) waters. Results of these experiments have demonstrated that factors which influence the biological availability of the iron supplied to phytoplankton are crucial in bloom development, longevity, and generation of carbon export flux. These findings have important implications for the future development of iron fertilization protocols to enhance carbon sequestration in high-latitude oceans. In particular, processes which lead to the mobilization and retention of iron in dissolved form in the upper ocean are important in promoting continued biological availability of iron. Such processes can include photochemical redox cycling, which leads to the formation of soluble reduced iron, Fe(II), within iron-enriched waters. Creation of effective fertilization schemes will thus require more information about Fe(II) photoproduction in Southern Ocean waters as a means to retain new iron within the euphotic zone. To contribute to our knowledge base in this area, this project was funded by DOE with a goal of characterizing the production and retention of dissolved Fe as Fe(II) in an area of the southern Drake Passage near the Shackleton Transverse Ridge, a region with a strong recurrent chlorophyll gradient which is believed to be a site of natural iron enrichment in the Southern Ocean. This area was the focus of a multidisciplinary NSF/OPP-funded investigation in February 2004 (OPP02-30443, lead PI Greg Mitchell, SIO/UCSD) to determine the influence of mesoscale circulation and iron transport with regard to the observed patterns in sea surface chlorophyll in the region near the Shackleton Transverse Ridge. A number of parameters were assessed across this gradient in order to reveal interactions between plankton community structure and iron distributions

  3. MgII Absorption Lines in z=2.974 Damped Lyman-alpha System toward Gravitationally Lensed QSO APM 08279+5255 Detection of Small-scale Structure in MgII Absorbing Clouds

    Kobayashi, N; Goto, M; Tokunaga, A; Kobayashi, Naoto; Terada, Hiroshi; Goto, Miwa; Tokunaga, Alan


    1.02-1.16 micron spectra (R ~ 7,000) of the gravitationally lensed QSO APM 08279+5255 at z_em=3.911 were obtained during the commissioning run of IRCS, the 1-5 micron near-infrared camera and spectrograph for the Subaru 8.2 m Telescope. Strong MgII doublet at 2976,2800 angstrom and FeII (2600 angstrom), FeII (2587 angstrom) absorption lines at z_abs=2.974 were clearly detected in the rest-frame UV spectra, confirming the presence of a damped Lyman-alpha system at the redshift as suggested by Petitjean et al. Also MgI (2853 angstrom) absorption line is probably detected. An analysis of the absorption lines including velocity decomposition was performed. This is a first detailed study of MgII absorption system at high redshift (z > 2.5) where the MgII doublet shifts into the near-infrared in the observer's frame. The spectra of the lensed QSO pair A and B with 0.38 arcsec separation were resolved in some exposure frames under excellent seeing condition. We extracted the MgII doublet spectra of A and B separatel...

  4. Solid State Collapse of a High-Spin Square-Planar Fe(II) Complex, Solution Phase Dynamics, and Electronic Structure Characterization of an Fe(II)2 Dimer.

    Pascualini, Matias E; Stoian, Sebastian A; Ozarowski, Andrew; Abboud, Khalil A; Veige, Adam S


    Square-planar high-spin Fe(II) molecular compounds are rare, and until recently, the only four examples of non-macrocyclic or sterically driven molecular compounds of this kind shared a common FeO4 core. The trianionic pincer-type ligand [CF3-ONO]H3 (1) supports the high-spin square-planar Fe(II) complex {[CF3-ONO]FeCl}{Li(Sv)2}2 (2). In the solid state, 2 forms the dimer complex {[CF3-ONO]Fe}2{(μ-Cl)2(μ-LiTHF)4} (3) in 96% yield by simply applying a vacuum or stirring it with pentane for 2 h. A detailed high-frequency electron paramagnetic resonance and field-dependent (57)Fe Mössbauer investigation of 3 revealed a weak antiferromagnetic exchange interaction between the local iron spins which exhibit a zero-field splitting tensor characterized by negative D parameter. In solution, 2 is in equilibrium with the solvento complex {[CF3-ONO]FeCl(THF)}{Li2(Sv)4} (2·Sv) and the dimer 3. A combination of frozen solution (57)Fe Mössbauer spectroscopy and single crystal X-ray crystallography helped elucidate the solvent dependent equilibrium between these three species. The oxidation chemistry of 2·Sv was investigated. Complex 2 reacts readily with the one-electron oxidizing agent CuCl2 to give the Fe(III) complex {[CF3-ONO]FeCl2}{Li(THF)2}2 (4). Also, 2·Sv reacts with 2 equiv of TlPF6 to form the Fe(III) complex [CF3-ONO]Fe(THF)3 (5).

  5. Bis(imino)pyridine (BIMP) Fe(II) catalyses one-pot green condensation of resorcinol, malononitrile, aromatic aldehydes and cyclohexanone

    Saman Damavandi; Reza Sandaroos


    A novel, efficient and green approach for the synthesis of pyranopyridine derivatives through one-pot, four-component reaction of resorcinol, malononitrile, aromatic aldehydes and cyclohexanone using bis(imino)pyridine (BIMP) Fe(II) catalyst under solvent-free and ultrasonic irradiation is described.

  6. Electron transfer and atom exchange between aqueous Fe(II) and structural Fe(III) in clays. Role in U and Hg(II) transformations

    Scherer, Michelle [Univ. of Iowa, Iowa City, IA (United States)


    During this project, we investigated Fe electron transfer and atom exchange between aqueous Fe(II) and structural Fe(III) in clay minerals. We used selective chemical extractions, enriched Fe isotope tracer experiments, computational molecular modeling, and Mössbauer spectroscopy. Our findings indicate that structural Fe(III) in clay minerals is reduced by aqueous Fe(II) and that electron transfer occurs when Fe(II) is sorbed to either basal planes and edge OH-groups of clay mineral. Findings from highly enriched isotope experiments suggest that up to 30 % of the Fe atoms in the structure of some clay minerals exhanges with aqueous Fe(II). First principles calculations using a small polaron hopping approach suggest surprisingly fast electron mobility at room temperature in a nontronite clay mineral and are consistent with temperature dependent Mössbauer data Fast electron mobility suggests that electrons may be able to conduct through the mineral fast enough to enable exchange of Fe between the aqueous phase and clay mineral structure. over the time periods we observed. Our findings suggest that Fe in clay minerals is not as stable as previously thought.

  7. Fe(III) oxides protect fermenter-methanogen syntrophy against interruption by elemental sulfur via stiffening of Fe(II) sulfides produced by sulfur respiration.

    Igarashi, Kensuke; Kuwabara, Tomohiko


    Thermosipho globiformans (rod-shaped thermophilic fermenter) and Methanocaldococcus jannaschii (coccal hyperthermophilic hydrogenotrophic methanogen) established H2-mediated syntrophy at 68 °C, forming exopolysaccharide-based aggregates. Electron microscopy showed that the syntrophic partners connected to each other directly or via intercellular bridges made from flagella, which facilitated transfer of H2. Elemental sulfur (S(0)) interrupted syntrophy; polysulfides abiotically formed from S(0) intercepted electrons that were otherwise transferred to H(+) to produce H2, resulting in the generation of sulfide (sulfur respiration). However, Fe(III) oxides significantly reduced the interruption by S(0), accompanied by stiffening of Fe(II) sulfides produced by the reduction of Fe(III) oxides with the sulfur respiration-generated sulfide. Sea sand replacing Fe(III) oxides failed to generate stiffening or protect the syntrophy. Several experimental results indicated that the stiffening of Fe(II) sulfides shielded the liquid from S(0), resulting in methane production in the liquid. Field-emission scanning electron microscopy showed that the stiffened Fe(II) sulfides formed a network of spiny structures in which the microorganisms were buried. The individual fermenter rods likely produced Fe(II) sulfides on their surface and became local centers of a core of spiny structures, and the connection of these cores formed the network, which was macroscopically recognized as stiffening.

  8. Direct Detection of Fe(II) in Extracellular Polymeric Substances (EPS) at the Mineral-Microbe Interface in Bacterial Pyrite Leaching.

    Mitsunobu, Satoshi; Zhu, Ming; Takeichi, Yasuo; Ohigashi, Takuji; Suga, Hiroki; Jinno, Muneaki; Makita, Hiroko; Sakata, Masahiro; Ono, Kanta; Mase, Kazuhiko; Takahashi, Yoshio


    We herein investigated the mechanisms underlying the contact leaching process in pyrite bioleaching by Acidithiobacillus ferrooxidans using scanning transmission X-ray microscopy (STXM)-based C and Fe near edge X-ray absorption fine structure (NEXAFS) analyses. The C NEXAFS analysis directly showed that attached A. ferrooxidans produces polysaccharide-abundant extracellular polymeric substances (EPS) at the cell-pyrite interface. Furthermore, by combining the C and Fe NEXAFS results, we detected significant amounts of Fe(II), in addition to Fe(III), in the interfacial EPS at the cell-pyrite interface. A probable explanation for the Fe(II) in detected EPS is the leaching of Fe(II) from the pyrite. The detection of Fe(II) also indicates that Fe(III) resulting from pyrite oxidation may effectively function as an oxidizing agent for pyrite at the cell-pyrite interface. Thus, our results imply that a key role of Fe(III) in EPS, in addition to its previously described role in the electrostatic attachment of the cell to pyrite, is enhancing pyrite dissolution.

  9. Direct Detection of Fe(II) in Extracellular Polymeric Substances (EPS) at the Mineral-Microbe Interface in Bacterial Pyrite Leaching

    Mitsunobu, Satoshi; Zhu, Ming; Takeichi, Yasuo; Ohigashi, Takuji; Suga, Hiroki; Jinno, Muneaki; Makita, Hiroko; Sakata, Masahiro; Ono, Kanta; Mase, Kazuhiko; Takahashi, Yoshio


    We herein investigated the mechanisms underlying the contact leaching process in pyrite bioleaching by Acidithiobacillus ferrooxidans using scanning transmission X-ray microscopy (STXM)-based C and Fe near edge X-ray absorption fine structure (NEXAFS) analyses. The C NEXAFS analysis directly showed that attached A. ferrooxidans produces polysaccharide-abundant extracellular polymeric substances (EPS) at the cell-pyrite interface. Furthermore, by combining the C and Fe NEXAFS results, we detected significant amounts of Fe(II), in addition to Fe(III), in the interfacial EPS at the cell-pyrite interface. A probable explanation for the Fe(II) in detected EPS is the leaching of Fe(II) from the pyrite. The detection of Fe(II) also indicates that Fe(III) resulting from pyrite oxidation may effectively function as an oxidizing agent for pyrite at the cell-pyrite interface. Thus, our results imply that a key role of Fe(III) in EPS, in addition to its previously described role in the electrostatic attachment of the cell to pyrite, is enhancing pyrite dissolution. PMID:26947441

  10. Crystal structure of (NH42[FeII5(HPO36], a new open-framework phosphite

    Teresa Berrocal


    Full Text Available Diammonium hexaphosphitopentaferrate(II, (NH42[Fe5(HPO36], was synthesized under mild hydrothermal conditions and autogeneous pressure, yielding twinned crystals. The crystal structure exhibits an [FeII5(HPO36]2− open framework with NH4+ groups as counter-cations. The anionic skeleton is based on (001 sheets of [FeO6] octahedra (one with point-group symmetry 3.. and one with .2. linked along [001] through [HPO3]2− oxoanions. Each sheet is constructed from 12-membered rings of edge-sharing [FeO6] octahedra, giving rise to channels with a radius of ca 3.1 Å in which the disordered NH4+ cations are located. The IR spectrum shows vibrational bands typical for phosphite and ammonium groups.

  11. Emissão de hidrogênio molecular e [FeII] em núcleos Seyfert

    Rodríguez-Ardila, A.; Pastoriza, M. G.; Viegas, S.


    Um dos problemas fundamentais em núcleos ativos de galáxias (AGN) é determinar os mecanismos de excitação dominantes do gás emissor de linhas estreitas, seja este excitado por mecanismos não-estelares (fotoionização por uma fonte central ou choques produzidos por um jato rádio no gás circumnuclear) ou estelares (fotoionização por estrelas OB ou choques originados por um remanescente de supernova em expansão). Essa ambiguedade se faz mais evidente ao intepretar o espectro de espécies tais como H2 e [FeII]. Na primeira, fluorescência UV, processos térmicos (choques e/ou aquecimento por fótons) ou illuminação por raios-x, podem ser responsáveis pelo espectro observado enquanto que na segunda, os dois últimos mechanismos seriam relevantes. Neste trabalho, utilizando espectroscópia JHK de média resolução para uma amostra de AGN encontramos que o H2 observado é gerado principalmente por processos térmicos associados à presença de episódios de formação estelar circumnuclear. No entanto, em galáxias tais como NGC4151 as observações mostram que o hidrogênio molecular origina-se, principalmente, da interação entre o jato radio e o gás da NLR. Esses resultados baseiam-se nos valores das razões de linhas H2 2.24/2.12 mm e H2 2.03/2.22 mm. H2 2.24/2.12 separa claramente processos não-térmicos dos térmicos enquanto H2 2.03/2.22 serve como indicador de temperatura da componente térmica, e portanto, discrimina entre choques e associações OB. Já para o [FeII], as observações são compatíveis com excitação produzida diretamente pela fonte central ou choques associados com o jato rádio. A comparação da largura dos perfis de linhas observados permite concluir que não há correlação entre a emissão de H2 e [FeII]. Em praticamente todos os casos analisados, os perfis das linhas de H2 são não-resolvidos, enquanto que os perfis de [FeII] indicam, em alguns casos, velocidades de até 600 km/s.

  12. Redox cycling of Fe(II) and Fe(III) in magnetite by Fe-metabolizing bacteria

    Byrne, James M.; Klueglein, Nicole; Pearce, Carolyn; Rosso, Kevin M.; Appel, Erwin; Kappler, Andreas


    Microorganisms are a primary control on the redox-induced cycling of iron in the environment. Despite the ability of bacteria to grow using both Fe(II) and Fe(III) bound in solid-phase iron minerals, it is currently unknown whether changing environmental conditions enable the sharing of electrons in mixed-valent iron oxides between bacteria with different metabolisms. We show through magnetic and spectroscopic measurements that the phototrophic Fe(II)-oxidizing bacterium Rhodopseudomonas palustris TIE-1 oxidizes magnetite (Fe3O4) nanoparticles using light energy. This process is reversible in co-cultures by the anaerobic Fe(III)-reducing bacterium Geobacter sulfurreducens. These results demonstrate that Fe ions bound in the highly crystalline mineral magnetite are bioavailable as electron sinks and electron sources under varying environmental conditions, effectively rendering magnetite a naturally occurring battery.

  13. Preparation and XPS studies of macromolecule mixed-valent Cu(I, II) and Fe(II, III) complexes

    Wang Bo [Institute of Energy Chemistry, College of Chemistry and Materials Science, Shaanxi Normal University, Xi' An 710062 (China)]. E-mail:; Gao Fengqin [Institute of Energy Chemistry, College of Chemistry and Materials Science, Shaanxi Normal University, Xi' An 710062 (China); Department of Chemistry, Xianyang Normal University, Xianyang (China); Ma Hongzhu [Institute of Energy Chemistry, College of Chemistry and Materials Science, Shaanxi Normal University, Xi' An 710062 (China)


    A new macromolecule ligand and its mixed-valent Cu(I, II) and Fe(II, III) complexes have been prepared by using ethylenediamine as core and maleic anhydride as branched units and characterized by UV-vis, FT-IR, thermal analysis and X-ray photoelectron spectroscopy (XPS). The data obtained from these studies suggested that the coordinate bonds of N {sup {yields}} M, Cl {sup {yields}} M, Ph-OH {sup {yields}} M and H{sub 2}O {sup {yields}} M have been formed and possible binding models are proposed for these complexes. The thermal analysis (TG-DTG) reveals that these complexes possess thermal stable property below 800 deg. C.

  14. Fractionation of Fe isotopes during Fe(II) oxidation by a marine photoferrotroph is controlled by the formation of organic Fe-complexes and colloidal Fe fractions

    Swanner, Elizabeth D.; Wu, Wenfang; Schoenberg, Ronny; Byrne, James; Michel, F. Marc; Pan, Yongxin; Kappler, Andreas


    Much interest exists in finding mineralogical, organic, morphological, or isotopic biosignatures for Fe(II)-oxidizing bacteria (FeOB) that are retained in Fe-rich sediments, which could indicate the activity of these organisms in Fe-rich seawater, more common in the Precambrian Era. To date, the effort to establish a clear Fe isotopic signature in Fe minerals produced by Fe(II)-oxidizing metabolisms has been thwarted by the large kinetic fractionation incurred as freshly oxidized aqueous Fe(III) rapidly precipitates as Fe(III) (oxyhydr)oxide minerals at near neutral pH. The Fe(III) (oxyhydr)oxide minerals resulting from abiotic Fe(II) oxidation are isotopically heavy compared to the Fe(II) precursor and are not clearly distinguishable from minerals formed by FeOB isotopically. However, in marine hydrothermal systems and Fe(II)-rich springs the minerals formed are often isotopically lighter than expected considering the fraction of Fe(II) that has been oxidized and experimentally-determined fractionation factors. We measured the Fe isotopic composition of aqueous Fe (Feaq) and the final Fe mineral (Feppt) produced in batch experiment using the marine Fe(II)-oxidizing phototroph Rhodovulum iodosum. The δ56Feaq data are best described by a kinetic fractionation model, while the evolution of δ56Feppt appears to be controlled by a separate fractionation process. We propose that soluble Fe(III), and Fe(II) and Fe(III) extracted from the Feppt may act as intermediates between Fe(II) oxidation and Fe(III) precipitation. Based on 57Fe Mössbauer spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and X-ray total scattering, we suggests these Fe phases, collectively Fe(II/III)interm, may consist of organic-ligand bound, sorbed, and/or colloidal Fe(II) and Fe(III) mineral phases that are isotopically lighter than the final Fe(III) mineral product. Similar intermediate phases, formed in response to organic carbon produced by FeOB and inorganic

  15. Effects of Fe(II) and hydrogen peroxide interaction upon dissolving UO2 under geologic repository conditions.

    Amme, M; Bors, W; Michel, C; Stettmaier, K; Rasmussen, G; Betti, M


    Iron redox cycling is supposed to be one of the major mechanisms that control the geochemical boundary conditions in the near field of a geologic repository for UO2 spent nuclear fuel. This work investigates the impact of reactions between hydrogen peroxide (H2O2) and iron (Fe2+/Fe3+) on UO2 dissolution. The reaction partners were contacted with UO2 in oxygen-free batch reactor tests. The interaction in absence of UO2 gives a stoichiometric redox reaction of Fe2+ and H2O2 when the reactants are present in equal concentration. Predomination of H202 results in its delayed catalytic decomposition. With UO2 present, its dissolution is controlled by either a slow mechanism (as typical for anoxic environments) or uranium peroxide precipitation, depending strongly on the reactant ratio. Uranium peroxide (UO4 x nH2O, m-studtite), detected on UO2 surfaces after exposure to H2O2, was not found on the surfaces exposed to solutions with stoichometric Fe(II)/ H2O2 ratios. This suggests that H2O2 was deactivated in redox reactions before a formation of UO4 took place. ESR measurements employing the spin trapping technique revealed only the DMPO-OH adduct within the first minutes after the reaction start (high initial concentrations of the OH radical); however, in the case of Fe(II) and H2O2 reacting at 10(-4) mol/L with UO2, dissolved oxygen and Fe2+ concentrations indicate the participation of further Fe intermediates and, therefore, Fenton redox activities.

  16. A first principles investigation of electron transfer between Fe(II) and U(VI) on insulating Al- vs. semiconducting Fe-oxide surfaces via the proximity effect

    Taylor, S. D.; Marcano, M. C.; Becker, U.


    This study investigates how the intrinsic chemical and electronic properties of mineral surfaces and their associated electron transfer (ET) pathways influence the reduction of U(VI) by surface-associated Fe(II). Density functional theory (DFT), including the Hubbard U correction to the exchange-correlation functional, was used to investigate sorption/redox reactions and ET mechanisms between Fe(II) and U(VI) coadsorbed on isostructural, periodic (0 0 1) surfaces of the insulator corundum (α-Al2O3) vs. the semiconductor hematite (α-Fe2O3). Furthermore, the coadsorbed Fe(II) and U(VI) ions are spatially separated from one another on the surfaces (⩾5.9 Å) to observe whether electronic-coupling through the semiconducting hematite surface facilitates ET between the adsorbates, a phenomenon known as the proximity effect. The calculations show that the different chemical and electronic properties between the isostructural corundum and hematite (0 0 1) surfaces lead to considerably different ET mechanisms between Fe(II) and U(VI). ET on the insulating corundum (0 0 1) surface is limited by the adsorbates' structural configuration. When Fe(II) and U(VI) are spatially separated and do not directly interact with one another (e.g. via an inner-sphere complex), U(VI) reduction by Fe(II) cannot occur as there is no physical pathway enabling ET between the adsorbates. In contrast to the insulating corundum (0 0 1) surface, the hematite (0 0 1) surface can potentially participate in ET reactions due to the high number of electron acceptor sites from the Fe d-states near the Fermi level at the hematite surface. The adsorption of Fe(II) also introduces d-states near the Fermi level as well as shifts unoccupied d-states of the Fe cations at the hematite surface to lower energies, making the surface more conductive. In turn, electronic coupling through the surface can link the spatially separated adsorbates to one another and provide distinct ET pathways for an electron from Fe(II

  17. Anoxygenic growth of cyanobacteria on Fe(II) and their associated biosignatures: Implications for biotic contributions to Precambrian Banded Iron Formations

    Parenteau, M.; Jahnke, L. L.; Cady, S. L.; Pierson, B.


    Banded Iron Formations (BIFs) are widespread Precambrian sedimentary deposits that accumulated in deep ocean basins or shallow platformal areas with inputs of reduced iron (Fe(II)) and silica from deep ocean hydrothermal activity. There is debate as to whether abiotic or biotic mechanisms were responsible for the oxidation of aqueous Fe(II) and the subsequent accumulation of ferric iron (Fe(III)) mineral assemblages in BIFs. Biotic Fe(II) oxidation could have occurred indirectly as a result of the photosynthetic production of oxygen by cyanobacteria, or could have been directly mediated by anoxygenic phototrophs or chemolithotrophs. The anoxygenic use of Fe(II) as an electron donor for photosynthesis has also been hypothesized in cyanobacteria, representing another biotic mechanism by which Fe(II) could be oxidized in BIFs. This type of photoferrotrophic metabolism may also represent a key step in the evolution of oxygenic photosynthesis. Members of our group have speculated that an intermediate reductant such as Fe(II) could have acted as a transitional electron donor before water. The widespread abundance of Fe(II) in Archean and Neoproterozoic ferruginous oceans would have made it particularly suitable as an electron donor for photosynthesis. We have been searching for modern descendants of such an ancestral "missing link" cyanobacterium in the phototrophic mats at Chocolate Pots, a hot spring in Yellowstone National Park with a constant outflow of anoxic Fe(II)-rich thermal water. Our physiological ecology study of the Synechococcus-Chloroflexi mat using C-14 bicarbonate uptake and autoradiography experiments revealed that the cyanobacteria grow anoxygenically using Fe(II) as an electron donor for photosynthesis in situ. An initial set of similar experiments substituting C-13 bicarbonate as the tracer was used to characterize labeling of the community lipid biomarker signature and confirm the C-14 results. Under light conditions with and without Fe(II), the C

  18. As(III) removal and speciation of Fe (Oxyhydr)oxides during simultaneous oxidation of As(III) and Fe(II).

    Han, Xu; Song, Jia; Li, Yi-Liang; Jia, Shao-Yi; Wang, Wen-Hui; Huang, Fu-Gen; Wu, Song-Hai


    Abiotic oxidation of Fe(II) is an important pathway in the formation of Fe (oxyhydr)oxides. However, how can As(III) affect the oxidation rate of Fe(II) and the speciation of Fe (oxyhydr)oxides, and what's the extent of the newly formed Fe (oxyhydr)oxides on the removal of aqueous arsenic are still poorly understood. Oxidation of Fe(II) under neutral pH conditions was therefore investigated under different molar ratios of As:Fe. Our results suggest that co-existence of aqueous As(III) significantly slows down the oxidation rate of Fe(II). Speciation of Fe (oxyhydr)oxides is dependent on pH and As:Fe ratios. At pH 6.0, formation of lepidocrocite and goethite is apparently inhibited at low As:Fe ratios, and ferric arsenate is favored at high As:Fe ratios. At pH 7.0, lepidocrocite gradually degenerates with the increasing As:Fe ratios. At pH 8.0, arsenite significantly inhibits the development of magnetite and favors a formation of lepidocrocite. XPS analysis further reveals that more than half of As(III) is oxidized to As(V) at pH 6.0 and 7.0, whereas at pH 8.0, the rapid oxidation of Fe(II) as well as the rapid formation of Fe (oxyhydr)oxides facilitate a rapid removal of dissolved As(III) before its further oxidation to As(V). Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Monitoring, field experiments, and geochemical modeling of Fe(II) oxidation kinetics in a stream dominated by net-alkaline coal-mine drainage, Pennsylvania, USA

    Cravotta, Charles A.


    Watershed-scale monitoring, field aeration experiments, and geochemical equilibrium and kinetic modeling were conducted to evaluate interdependent changes in pH, dissolved CO2, O2, and Fe(II) concentrations that typically take place downstream of net-alkaline, circumneutral coal-mine drainage (CMD) outfalls and during aerobic treatment of such CMD. The kinetic modeling approach, using PHREEQC, accurately simulates observed variations in pH, Fe(II) oxidation, alkalinity consumption, and associated dissolved gas concentrations during transport downstream of the CMD outfalls (natural attenuation) and during 6-h batch aeration tests on the CMD using bubble diffusers (enhanced attenuation). The batch aeration experiments demonstrated that aeration promoted CO2 outgassing, thereby increasing pH and the rate of Fe(II) oxidation. The rate of Fe(II) oxidation was accurately estimated by the abiotic homogeneous oxidation rate law −d[Fe(II)]/dt = k1·[O2]·[H+]−2·[Fe(II)] that indicates an increase in pH by 1 unit at pH 5–8 and at constant dissolved O2 (DO) concentration results in a 100-fold increase in the rate of Fe(II) oxidation. Adjusting for sample temperature, a narrow range of values for the apparent homogeneous Fe(II) oxidation rate constant (k1′) of 0.5–1.7 times the reference value of k1 = 3 × 10−12 mol/L/min (for pH 5–8 and 20 °C), reported by Stumm and Morgan (1996), was indicated by the calibrated models for the 5-km stream reach below the CMD outfalls and the aerated CMD. The rates of CO2 outgassing and O2ingassing in the model were estimated with first-order asymptotic functions, whereby the driving force is the gradient of the dissolved gas concentration relative to equilibrium with the ambient atmosphere. Although the progressive increase in DO concentration to saturation could be accurately modeled as a kinetic function for the conditions evaluated, the simulation of DO as an instantaneous equilibrium process did not affect the

  20. Fe(II) sorption on pyrophyllite: Effect of structural Fe(III) (impurity) in pyrophyllite on nature of layered double hydroxide (LDH) secondary mineral formation

    Starcher, Autumn N.; Li, Wei; Kukkadapu, Ravi K.; Elzinga, Evert J.; Sparks, Donald L.


    Fe(II)-Al(III)-LDH (layered double hydroxide) phases have been shown to form from reactions of aqueous Fe(II) with Fe-free Al-bearing minerals (phyllosilicate/clays and Al-oxides). To our knowledge, the effect of small amounts of structural Fe(III) impurities in “neutral” clays on such reactions, however, were not studied. In this study to understand the role of structural Fe(III) impurity in clays, laboratory batch studies with pyrophyllite (10 g/L), an Al-bearing phyllosilicate, containing small amounts of structural Fe(III) impurities and 0.8 mM and 3 mM Fe(II) (both natural and enriched in 57Fe) were carried out at pH 7.5 under anaerobic conditions (4% H2 – 96% N2 atmosphere). Samples were taken up to 4 weeks for analysis by Fe-X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy. In addition to the precipitation of Fe(II)-Al(III)-LDH phases as observed in earlier studies with pure minerals (no Fe(III) impurities in the minerals), the analyses indicated formation of small amounts of Fe(III) containing solid(s), most probably hybrid a Fe(II)-Al(III)/Fe(III)-LDH phase. The mechanism of Fe(II) oxidation was not apparent but most likely was due to interfacial electron transfer from the sorbed Fe(II) to the structural Fe(III) and/or surface-sorption-induced electron-transfer from the sorbed Fe(II) to the clay lattice. Increase in the Fe(II)/Al ratio of the LDH with reaction time further indicated the complex nature of the samples. This research provides evidence for the formation of both Fe(II)-Al(III)-LDH and Fe(II)-Fe(III)/Al(III)-LDH-like phases during reactions of Fe(II) in systems that mimic the natural environments. Better understanding Fe phase formation in complex laboratory studies will improve models of natural redox systems.

  1. Iron Isotope Fractionation during Fe(II) Oxidation Mediated by the Oxygen-Producing Marine Cyanobacterium Synechococcus PCC 7002

    Swanner, E. D.; Bayer, T.; Wu, W.; Hao, L.; Obst, M.; Sundman, A.; Byrne, J. M.; Michel, F. M.; Kleinhanns, I. C.; Kappler, A.; Schoenberg, R.


    In this study, we couple iron isotope analysis to microscopic and mineralogical investigation of iron speciation during circumneutral Fe(II) oxidation and Fe(III) precipitation with photosynthetically produced oxygen. In the presence of the cyanobacterium Synechococcus PCC 7002, aqueous Fe(II) (Fe(II)aq) is oxidized and precipitated as amorphous Fe(III) oxyhydroxide minerals (iron precipitates, Feppt), with distinct isotopic fractionation (ε56Fe) values determined from fitting the δ56Fe(II)aq (1.79‰ and 2.15‰) and the δ56Feppt (2.44‰ and 2.98‰) data trends from two replicate experiments. Additional Fe(II) and Fe(III) phases were detected using microscopy and chemical extractions and likely represent Fe(II) and Fe(III) sorbed to minerals and cells. The iron desorbed with sodium acetate (FeNaAc) yielded heavier δ56Fe compositions than Fe(II)aq. Modeling of the fractionation during Fe(III) sorption to cells and Fe(II) sorption to Feppt, combined with equilibration of sorbed iron and with Fe(II)aq using published fractionation factors, is consistent with our resulting δ56FeNaAc. The δ56Feppt data trend is inconsistent with complete equilibrium exchange with Fe(II)aq. Because of this and our detection of microbially excreted organics (e.g., exopolysaccharides) coating Feppt in our microscopic analysis, we suggest that electron and atom exchange is partially suppressed in this system by biologically produced organics. These results indicate that cyanobacteria influence the fate and composition of iron in sunlit environments via their role in Fe(II) oxidation through O2 production, the capacity of their cell surfaces to sorb iron, and the interaction of secreted organics with Fe(III) minerals.

  2. Heteroleptic Fe(II) complexes of 2,2'-biimidazole and its alkylated derivatives: spin-crossover and photomagnetic behavior.

    Phan, Hoa V; Chakraborty, Pradip; Chen, Meimei; Calm, Yitzi M; Kovnir, Kirill; Keniley, Lawrence K; Hoyt, Jordan M; Knowles, Elisabeth S; Besnard, Céline; Meisel, Mark W; Hauser, Andreas; Achim, Catalina; Shatruk, Michael


    Three iron(II) complexes, [Fe(TPMA)(BIM)](ClO(4))(2)⋅0.5H(2)O (1), [Fe(TPMA)(XBIM)](ClO(4))(2) (2), and [Fe(TPMA)(XBBIM)](ClO(4))(2)⋅0.75CH(3)OH (3), were prepared by reactions of Fe(II) perchlorate and the corresponding ligands (TPMA=tris(2-pyridylmethyl)amine, BIM=2,2'-biimidazole, XBIM=1,1'-(α,α'-o-xylyl)-2,2'-biimidazole, XBBIM=1,1'-(α,α'-o-xylyl)-2,2'-bibenzimidazole). The compounds were investigated by a combination of X-ray crystallography, magnetic and photomagnetic measurements, and Mössbauer and optical absorption spectroscopy. Complex 1 exhibits a gradual spin crossover (SCO) with T(1/2) =190 K, whereas 2 exhibits an abrupt SCO with approximately 7 K thermal hysteresis (T(1/2) =196 K on cooling and 203 K on heating). Complex 3 is in the high-spin state in the 2-300 K range. The difference in the magnetic behavior was traced to differences between the inter- and intramolecular interactions in 1 and 2. The crystal packing of 2 features a hierarchy of intermolecular interactions that result in increased cooperativity and abruptness of the spin transition. In 3, steric repulsion between H atoms of one of the pyridyl substituents of TPMA and one of the benzene rings of XBBIM results in a strong distortion of the Fe(II) coordination environment, which stabilizes the high-spin state of the complex. Both 1 and 2 exhibit a photoinduced low-spin to high-spin transition (LIESST effect) at 5 K. The difference in the character of intermolecular interactions of 1 and 2 also manifests in the kinetics of the decay of the photoinduced high-spin state. For 1, the decay rate constant follows the single-exponential law, whereas for 2 it is a stretched exponential, reflecting the hierarchical nature of intermolecular contacts. The structural parameters of the photoinduced high-spin state at 50 K are similar to those determined for the high-spin state at 295 K. This study shows that N-alkylation of BIM has a negligible effect on the ligand field strength. Therefore

  3. Improvement of biological nitrogen removal with nitrate-dependent Fe(II) oxidation bacterium Aquabacterium parvum B6 in an up-flow bioreactor for wastewater treatment.

    Zhang, Xiaoxin; Li, Ang; Szewzyk, Ulrich; Ma, Fang


    Aquabacterium parvum strain B6 exhibited efficient nitrate-dependent Fe(II) oxidation ability using nitrate as an electron acceptor. A continuous up-flow bioreactor that included an aerobic and an anoxic section was constructed, and strain B6 was added to the bioreactor as inocula to explore the application of microbial nitrate-dependent Fe(II) oxidizing (NDFO) efficiency in wastewater treatment. The maximum NRE (anoxic section) and TNRE of 46.9% and 79.7%, respectively, could be obtained at a C/N ratio of 5.3:1 in the influent with HRT of 17. Meanwhile, the taxonomy composition of the reactor was assessed, as well. The NDFO metabolism of strain B6 could be expected because of its relatively dominant position in the anoxic section, whereas potential heterotrophic nitrification and aerobic denitrification developed into the prevailing status in the aerobic section after 50days of continuous operation.

  4. Incorporation of Pyrazine and Bipyridine Linkers with High-Spin Fe(II) and Co(II) in a Metal–Organic Framework

    Kawamura, Airi; Greenwood, Arin R.; Filatov, Alexander S.; Gallagher, Audrey T.; Galli, Giulia; Anderson, John S.


    A series of isoreticular metal organic frameworks (MOFs) of the formula M(BDC)(L) (M = Fe(II) or Co(II), BDC = 1,4-benzenedicarboxylate, L = pyrazine (pyz) or 4,4'-bipyridine (bipy)) has been synthesized and characterized by N-2 gas uptake Measurements, single crystal and powder X-ray diffraction, magnetometry, X-ray absorption spectroscopy, and Mossbauer spectroscopy. These studies indicate the formation of a permanently porous solid with high-spin Fe(II) and Co(II) centers that are weakly coupled, consistent with first-principles density functional theory calculations. This family of materials represents unusual examples of paramagnetic metal centers coordinated by linkers capable of mediating magnetic or electronic coupling in a porous framework. While only weak interactions are observed, the rigid 3D framework of the MOF dramatically impacts the properties of these materials when compared with close structural analogues.

  5. Thermal decomposition of solid solutions in systems of Fe(II), Co(II), and Ni(II) hydrogen maleates with the formation of bimetallic nanoparticles

    Yudanova, L. I.; Logvinenko, V. A.; Sheludyakova, L. A.; Ishchenko, A. V.; Rudina, N. A.


    XRD phase analysis and thermal analysis are used to confirm the formation of a continuous series of solid solutions in which one cation is substituted for another in the systems Co(II) hydrogen maleate-Ni(II) hydrogen maleate; Fe(II) hydrogen maleate-Co(II) hydrogen maleate; and Fe(II) hydrogen maleate-Ni(II) hydrogen maleate. The unit cell volume of these solid solutions is shown to depend linearly on their composition. The linear character of changes in the initial temperatures of dehydration and thermal decomposition is established. Using the example of the first of these systems, it is shown that when heated, bimetallic nanoparticles embedded in the polymeric matrix of composites obtained via the thermal decomposition of solid solutions of hydrogen maleates undergo a second-order phase transition, resulting in decomposition of the solid solutions of metals at the Curie temperature.

  6. FtmOx1, a non-heme Fe(II) and alpha-ketoglutarate-dependent dioxygenase, catalyses the endoperoxide formation of verruculogen in Aspergillus fumigatus.

    Steffan, Nicola; Grundmann, Alexander; Afiyatullov, Shamil; Ruan, Hanli; Li, Shu-Ming


    Verruculogen is a tremorgenic mycotoxin and contains an endoperoxide bond. In this study, we describe the cloning, overexpression and purification of a non-heme Fe(ii) and alpha-ketoglutarate-dependent dioxygenase FtmOx1 from Aspergillus fumigatus, which catalyses the conversion of fumitremorgin B to verruculogen by inserting an endoperoxide bond between two prenyl moieties. Incubation with (18)O(2)-enriched atmosphere demonstrated that both oxygen atoms of the endoperoxide bond are derived from one molecule of O(2). FtmOx1 is the first endoperoxide-forming non-heme Fe(ii) and alpha-ketoglutarate-dependent dioxygenase reported so far. A mechanism of FtmOx1-catalysed verruculogen formation is postulated and discussed.

  7. Formation of Fe(0-Nanoparticles via Reduction of Fe(II Compounds by Amino Acids and Their Subsequent Oxidation to Iron Oxides

    K. Klačanová


    Full Text Available Iron nanoparticles were prepared by the reduction of central Fe(II ion in the coordination compounds with amino acid ligands. The anion of the amino acid used as a ligand acted as the reducing agent. Conditions for the reduction were very mild; the temperature did not exceed 52°C, and the optimum pH was between 9.5 and 9.7. The metal iron precipitated as a mirror on the flask or as a colloid in water. Identification of the product was carried out by measuring UV/VIS spectra of the iron nanoparticles in water. The iron nanoparticles were oxidized by oxygen yielding a mixture of iron oxides. Oxidation of Fe(0 to Fe(II took several seconds under air. The size and properties of iron oxide nanoparticles were studied by UV/VIS, TEM investigation, RTG diffractometry, Mössbauer spectroscopy, magnetometry, thermogravimetry, and GC/MS.

  8. Dietary Supplementation of Magnesium Oxide (MgO) Nanoparticles for Better Survival and Growth of the Freshwater Prawn Macrobrachium rosenbergii Post-larvae.

    Srinivasan, Veeran; Bhavan, Periyakali Saravana; Rajkumar, Gopalan; Satgurunathan, Thangavelu; Muralisankar, Thirunavukkarasu


    This study was performed to assess the growth-promoting potential of dietary magnesium oxide nanoparticles (MgO NPs) in Macrobrachium rosenbergii post-larvae (PL). MgO NPs were supplemented at 0, 100, 200, 300, 400 and 500 mg kg(-1) with the basal diet (containing 0.95 g Mg kg(-1)); the concentrations of Mg in MgO NP-supplemented diets were increased correspondingly (1.07, 1.15, 1.24, 1.37 and 1.46 g Mg kg(-1) respectively). MgO NP-supplemented diets were fed to M. rosenbergii PL (initial weight 0.11 ± 0.04 g) for a period of 90 days. In the carcasses of experimental prawns, the content of Mg was found to be elevated significantly with respect to the individual diet (102.14, 183.29, 205.46, 221.03, 237.10 and 254.36 μg Mg g(-1) respectively) when compared with that of the control. The contents of Cu, Zn, Fe, Ca, Na and K levels were also found to be elevated in the carcasses of experimental prawns. Significant (P MgO NP-supplemented-feed-fed PL. There were no significant elevations recorded in activities of antioxidant enzymes [superoxide dismutase (SOD) and catalase (CAT)], lipid peroxidation (LPO) and metabolic enzymes [glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT)] recorded in any of the MgO NP-supplemented-feed-fed PL when compared with the control. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed increases in the staining intensity of polypeptide bands resolved in 500 mg kg(-1) MgO NP-supplemented-feed-fed PL when compared with the control. Based on the gradual improvement in attaining survival, growth, FCR, biochemical constituents and haemocyte population, this study recommends MgO NP supplementation of 500 mg kg(-1) for sustainable maintenance of M. rosenbergii PL. As the studied highest concentration of MgO NPs showed the best performance, it is necessary to study with beyond 500 mg kg(-1) of MgO NPs to optimize the actual concentration.

  9. Treatment of groundwater containing Mn(II), Fe(II), As(III) and Sb(III) by bioaugmented quartz-sand filters.

    Bai, Yaohui; Chang, Yangyang; Liang, Jinsong; Chen, Chen; Qu, Jiuhui


    High concentrations of iron (Fe(II)) and manganese (Mn(II)) often occur simultaneously in groundwater. Previously, we demonstrated that Fe(II) and Mn(II) could be oxidized to biogenic Fe-Mn oxides (BFMO) via aeration and microbial oxidation, and the formed BFMO could further oxidize and adsorb other pollutants (e.g., arsenic (As(III)) and antimony (Sb(III))). To apply this finding to groundwater remediation, we established four quartz-sand columns for treating groundwater containing Fe(II), Mn(II), As(III), and Sb(III). A Mn-oxidizing bacterium (Pseudomonas sp. QJX-1) was inoculated into two parallel bioaugmented columns. Long-term treatment (120 d) showed that bioaugmentation accelerated the formation of Fe-Mn oxides, resulting in an increase in As and Sb removal. The bioaugmented columns also exhibited higher overall treatment effect and anti-shock load capacity than that of the non-bioaugmented columns. To clarify the causal relationship between the microbial community and treatment effect, we compared the biomass of active bacteria (reverse-transcribed real-time PCR), bacterial community composition (Miseq 16S rRNA sequencing) and community function (metagenomic sequencing) between the bioaugmented and non-bioaugmented columns. Results indicated that the QJX1 strain grew steadily and attached onto the filter material surface in the bioaugmented columns. In general, the inoculated strain did not significantly alter the composition of the indigenous bacterial community, but did improve the relative abundances of xenobiotic metabolism genes and Mn oxidation gene. Thus, bioaugmentation intensified microbial degradation/utilization for the direct removal of pollutants and increased the formation of Fe-Mn oxides for the indirect removal of pollutants. Our study provides an alternative method for the treatment of groundwater containing high Fe(II), Mn(II) and As/Sb. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Spectroscopic and magnetic studies of wild-type and mutant forms of the Fe(II)- and 2-oxoglutarate-dependent decarboxylase ALKBH4.

    Bjørnstad, Linn G; Zoppellaro, Giorgio; Tomter, Ane B; Falnes, Pål Ø; Andersson, K Kristoffer


    The Fe(II)/2OG (2-oxoglutarate)-dependent dioxygenase superfamily comprises proteins that couple substrate oxidation to decarboxylation of 2OG to succinate. A member of this class of mononuclear non-haem Fe proteins is the Escherichia coli DNA/RNA repair enzyme AlkB. In the present work, we describe the magnetic and optical properties of the yet uncharacterized human ALKBH4 (AlkB homologue). Through EPR and UV-visible spectroscopy studies, we address the Fe-binding environment of the proposed catalytic centre of wild-type ALKBH4 and an Fe(II)-binding mutant. We could observe a novel unusual Fe(III) high-spin EPR-active species in the presence of sulfide with a g(max) of 8.2. The Fe(II) site was probed with NO. An intact histidine-carboxylate site is necessary for productive Fe binding. We also report the presence of a unique cysteine-rich motif conserved in the N-terminus of ALKBH4 orthologues, and investigate its possible Fe-binding ability. Furthermore, we show that recombinant ALKBH4 mediates decarboxylation of 2OG in absence of primary substrate. This activity is dependent on Fe as well as on residues predicted to be involved in Fe(II) co-ordination. The present results demonstrate that ALKBH4 represents an active Fe(II)/2OG-dependent decarboxylase and suggest that the cysteine cluster is involved in processes other than Fe co-ordination.

  11. Structural fold, conservation and Fe(II) binding of the intracellular domain of prokaryote FeoB

    Hung, Kuo-Wei; Chang, Yi-Wei; Eng, Edward T.; Chen, Jai-Hui; Chen, Yi-Chung; Sun, Yuh-Ju; Hsiao, Chwan-Deng; Dong, Gang; Spasov, Krasimir A.; Unger, Vinzenz M.; Huang, Tai-huang (Yale-MED); (Perutz Lab); (AS); (NTHU-Taiwan)


    FeoB is a G-protein coupled membrane protein essential for Fe(II) uptake in prokaryotes. Here, we report the crystal structures of the intracellular domain of FeoB (NFeoB) from Klebsiella pneumoniae (KpNFeoB) and Pyrococcus furiosus (PfNFeoB) with and without bound ligands. In the structures, a canonical G-protein domain (G domain) is followed by a helical bundle domain (S-domain), which despite its lack of sequence similarity between species is structurally conserved. In the nucleotide-free state, the G-domain's two switch regions point away from the binding site. This gives rise to an open binding pocket whose shallowness is likely to be responsible for the low nucleotide-binding affinity. Nucleotide binding induced significant conformational changes in the G5 motif which in the case of GMPPNP binding was accompanied by destabilization of the switch I region. In addition to the structural data, we demonstrate that Fe(II)-induced foot printing cleaves the protein close to a putative Fe(II)-binding site at the tip of switch I, and we identify functionally important regions within the S-domain. Moreover, we show that NFeoB exists as a monomer in solution, and that its two constituent domains can undergo large conformational changes. The data show that the S-domain plays important roles in FeoB function.

  12. Importance of out-of-state spin-orbit coupling for slow magnetic relaxation in mononuclear Fe(II) complexes.

    Lin, Po-Heng; Smythe, Nathan C; Gorelsky, Serge I; Maguire, Steven; Henson, Neil J; Korobkov, Ilia; Scott, Brian L; Gordon, John C; Baker, R Tom; Murugesu, Muralee


    Two mononuclear high-spin Fe(II) complexes with trigonal planar ([Fe(II)(N(TMS)(2))(2)(PCy(3))] (1) and distorted tetrahedral ([Fe(II)(N(TMS)(2))(2)(depe)] (2) geometries are reported (TMS = SiMe(3), Cy = cyclohexyl, depe = 1,2-bis(diethylphosphino)ethane). The magnetic properties of 1 and 2 reveal the profound effect of out-of-state spin-orbit coupling (SOC) on slow magnetic relaxation. Complex 1 exhibits slow relaxation of the magnetization under an applied optimal dc field of 600 Oe due to the presence of low-lying electronic excited states that mix with the ground electronic state. This mixing re-introduces orbital angular momentum into the electronic ground state via SOC, and 1 thus behaves as a field-induced single-molecule magnet. In complex 2, the lowest-energy excited states have higher energy due to the ligand field of the distorted tetrahedral geometry. This higher energy gap minimizes out-of-state SOC mixing and zero-field splitting, thus precluding slow relaxation of the magnetization for 2.

  13. A two-fold interpenetrated flexible bi-pillared-layer framework of Fe(II) with interesting solvent adsorption property

    Ritesh Haldar; Tapas Kumar Majia


    A two-fold interpenetrated microporous bi-pillared-layer framework of Fe(II), {[Fe(2,6-napdc)(4,4'-bipy)](EtOH)(H2O)} (1) (2,6-napdc =2,6-naphthalenedicarboxylate; 4,4'-bipy=4,4'-bipyridine) composed of mixed ligand system has been synthesized and structurally characterized. The 2,6-napdc linkers form a 2D corrugated sheet of {Fe(2,6-napdc)} by linking the secondary building unit of Fe2(CO2)2 in the plane, which are further connected by double 4,4'-bipy pillars resulting in a bi-pillared-layer type 3D framework. The 3D framework is two-fold interpenetrated and exhibits a 3D channel structure (4.0 × 3.5, 1.5 × 0.5 and 2.2 × 2.1 Å2) occupied by the guest water and ethanol molecules. Framework 1 shows high thermal stability, and the desolvated framework (1′) renders permanent porosity realized by N2 adsorption profile at 77K (BET surface area of ∼ 52 m2 g-1). Moreover, the framework 1′ also uptakes different solvent vapours (water, methanol and ethanol) and their type-I profile suggest strong interaction with pore surfaces and overall hydrophilic nature of the framework. Temperature dependent magnetic measurements suggest overall antiferromagnetic behaviour in compound 1.

  14. Uptake and Release of Cerium During Fe-Oxide Formation and Transformation in Fe(II) Solutions

    Nedel, Sorin; Dideriksen, Knud; Christiansen, Bo C.


    Fe-oxides are ubiquitous in soils and sediments and form during Fe(0) corrosion. Depending on redox conditions and solution composition, Fe-oxides such as ferrihydrite, goethite, magnetite, and green rust (GR) may form. These phases typically have high surface area and large affinity for adsorption...... of trace components. Further, Fe(II)-Fe(III) (hydr)oxides are redox active. Cerium, a member of the lanthanide family, can be used as an analogue for the tri- and tetra-valent actinides found in radioactive waste, expected to be stored in subsurface repositories. In experiments with ferrihydrite, Ce......(III) release. X-ray photoelectron spectroscopy revealed Ce(III) adsorbed on magnetite. When Fe-oxides were synthesized by air oxidation of Fe(II) solutions at pH 7, GR(Na,SO4) played a catalytic role in the oxidation of Ce(III) to Ce(IV) by O-2, removing more than 90% of the dissolved Ce. Transmission electron...

  15. Degradation of nitrates with the participation of Fe(II) and Fe(0) in groundwater: A review

    Vodyanitskii, Yu. N.; Mineev, V. G.


    Nitrates from soil and nitrogen fertilizers unused by plants become hazardous pollutants and contaminate surface and ground waters. In the water-saturated layers, into which nitrates are leached, the content of organic matter (i.e., electron donors necessary for nitrification) can be insufficient. The deficiency of electrons in the groundwater can be eliminated by Fe(II) minerals that remained in the heavy rocks and are available to microorganisms due to dispersion. However, when the groundwater table is shallow (less than at 10 m), the natural denitrification develops poorly; therefore, remediation is needed to enrich the contaminated water with electron donors. Zerovalent iron is most frequently used for this purpose. The efficiency of the Fe0 barriers for the purification of groundwater from nitrates increases due to the activation of anaerobic denitrifying bacteria. In addition, the geochemical conditions and the composition of the bacterial community change in the Fe0 barrier zone, which favors the development of a wide range of anaerobic hydrogenotrophic bacteria (primarily Fe(III) reductants).

  16. Ligand-field symmetry effects in Fe(ii) polypyridyl compounds probed by transient X-ray absorption spectroscopy

    Cho, Hana; Strader, Matthew L.; Hong, Kiryong; Jamula, Lindsey; Gullikson, Eric M.; Kim, Tae Kyu; de Groot, Frank M. F.; McCusker, James K.; Schoenlein, Robert W.; Huse, Nils


    Ultrafast excited-state evolution in polypyridyl FeII complexes are of fundamental interest for understanding the origins of the sub-ps spin-state changes that occur upon photoexcitation of this class of compounds as well as for the potential impact such ultrafast dynamics have on incorporation of these compounds in solar energy conversion schemes or switchable optical storage technologies. We have demonstrated that ground-state and, more importantly, ultrafast time-resolved x-ray absorption methods can offer unique insights into the interplay between electronic and geometric structure that underpin the photo-induced dynamics of this class of compounds. The present contribution examines in greater detail how the symmetry of the ligand field surrounding the metal ion can be probed using these x-ray techniques. In particular, we show that steady-state K-edge spectroscopy of the nearest-neighbour nitrogen atoms reveals the characteristic chemical environment of the respective ligands and suggests an interesting target for future charge-transfer femtosecond and attosecond spectroscopy in the x-ray water window.

  17. Speciation of Fe(II) and Fe(III) by the modified ferrozine method, FIA-spectrophotometry, and flame AAS after cloud-point extraction

    Giokas, Dimosthenis L.; Paleologos, Evangelos K.; Karayannis, Miltiades I. [Laboratory of Analytical Chemistry, Department of Chemistry, University of Ioannina (Greece)


    A method has been developed for the simultaneous determination of traces of Fe(III) and Fe(II) in water by on-line coupling of spectrophotometry with flame atomic absorption spectrometry (FAAS). The method involves cloud-point extraction (CPE) of both species with ammonium pyrrolidinecarbodithioate (APDC) under standard conditions, which facilitates the in situ complexation and extraction of both species. Differentiation of the oxidation states of iron is achieved by using mathematical equations to overcome the interference of Fe(III) in the spectrophotometric determination of Fe(II) when they are both present in the same solution. In this manner the time-consuming and labor-intensive steps of preoxidation of Fe(II) or reduction of Fe(III) are eliminated. By preconcentrating a 10-mL sample solution detection limits as low as 7 {mu}g L{sup -1}, were obtained after a single-step extraction procedure. The relative standard deviation (n=4, 30 {mu}g L{sup -1}) was 2.6 % and 1.8 % for spectrophotometry and FAAS, respectively. Recoveries in the range of 96-105 % were obtained by analysis of spiked real samples. The method was further verified by analyzing a certified reference material (IMEP-9); for this the recovery was 98.5 %. (orig.)

  18. UV-visible spectroscopic and electrochemical study of the complex formation between Fe(II) and 5-amino-1,10-phenantroline (5-Aphen) in aqueous solution.

    Lozano-Camargo, María Luisa; Rojas-Hernández, Alberto; Gómez-Hernández, Martín; Pacheco-Hernández, Ma de Lourdes; Galicia, Laura; Ramírez-Silva, María Teresa


    The system Fe(II)-5-Aphen-H(2)O was studied. The spectroscopic and electrochemical results show that only one stable complex between Fe(II) and 5-Aphen forms, having a 1:3 stoichiometric ratio. The spectrophotometry study allowed determination of the formation constant of the complex (logbeta(3)=23.42+/-0.06). Also, the stability of the complex was evaluated as a function of pH; it was found that it decomposed at low pH values depending on the concentration and a pseudo-first order kinetics constant associated with k'=0.011min(-1). The results are in agreement with the electrochemical behaviour observed in the system, which indicated that at pH 1.33 the destruction of the complex [Fe(5-Aphen)3](2+) took place as a function of time; however, when the experiments were carried out at pH 6.19 the complex was stable. The thermodynamic data obtained through the use of MEDUSA allowed construction of predominance zone diagrams of the system Fe(II)-5-Aphen-H(2)O under the experimental conditions used. The thermodynamic results represented in the PZD describe the experimental behaviour reported in this work.

  19. Molar Absorptivity and Quantum Yield of Fe(II) Photo-formation for the Aqueous Solutions of Fe(III)-Dicarboxylate Comlexes

    Hitomi, Y.; Arakaki, T.


    Fe(III)/Fe(II) cycle in the environment affects formation of active oxygen species such as hydrogen peroxide and hydroxyl radicals, which in turn determines lifetimes of many organic compounds. Although aqueous Fe(III)-dicarboxylate complexes are considered to be an important source of photo-chemically formed Fe(II), molar absorptivity and quantum yield of Fe(II) formation for individual species are not well understood. The Visual MINTEQ computer program was used to calculate the equilibrium concentrations of individual Fe(III)-dicarboxylate species in the aqueous solutions of Fe(III)-dicarboxylate complexes. The molar absorptivity and the product of the quantum yield and the molar absorptivity of Fe(III)-dicarboxylate species were obtained by UV-VIS spectrophotometer and photochemical experiments, and these experimental data were combined with the calculated equilibrium Fe(III)-dicarboxylate concentrations to determine individual molar absorptivity and quantum yield of Fe(II) photo-formation for a specific Fe(III)-dicarboxylate species. Dicarboxylate compounds studied were oxalate, malonate, succinate, malate, and phthalate.

  20. Characterization of recombinant nitrile-specifier proteins (NSPs) of Arabidopsis thaliana: dependency on Fe(II) ions and the effect of glucosinolate substrate and reaction conditions.

    Kong, Xiang Yi; Kissen, Ralph; Bones, Atle M


    Glucosinolates are plant secondary metabolites that are part of a plant defence system against pathogens and pests, the myrosinase-glucosinolate system, in which glucosinolates get activated by enzymic degradation through thioglucoside glucohydrolases called myrosinases. Epithiospecifier protein (ESP) and nitrile-specifier proteins (NSPs) divert myrosinase-catalyzed hydrolysis of a given glucosinolate from the formation of isothiocyanate to that of epithionitrile and/or nitrile. As the biological activity of glucosinolate hydrolysis products varies considerably, a detailed characterization of these specifier proteins is of utmost importance to understand their biological role. Therefore, the Arabidopsis thaliana AtNSP1, AtNSP2 and AtNSP5 and a supposed ancestor protein AtNSP-like1 were expressed in Escherichia coli and the activity of the purified recombinant proteins was tested in vitro on three highly different glucosinolates and compared to that of purified AtESP. As previously reported, only AtESP showed epithiospecifier activity on 2-propenylglucosinolate. We further confirmed that purified AtNSP1, AtNSP2 and AtNSP5, but not the ancestor AtNSP-like1 protein, show nitrile-specifier activity on 2-propenylglucosinolate and benzylglucosinolate. We now show for the first time that in vitro AtNSP1, AtNSP2 and AtNSP5 are able to generate nitrile from indol-3-ylmethylglucosinolate. We also tested the effect of different Fe(II) ion concentrations on the nitrile-specifier activity of purified AtNSP1, AtNSP2 and AtNSP5 on 2-propenylglucosinolate and benzylglucosinolate. AtNSP-related nitrile production was highly dependent on the presence of Fe(II) ions in the reaction assay. In the absence of added Fe(II) ions nitriles were only detected when benzylglucosinolate was incubated with AtNSP1. While AtNSP1 also exhibited overall higher nitrile-specifier activity than AtNSP2 and AtNSP5 at a given Fe(II) ion concentration, the pattern of nitrile formation in relation to Fe(II

  1. Stable iron isotope fractionation between aqueous Fe(II) and model Archean ocean Fe-Si coprecipitates and implications for iron isotope variations in the ancient rock record

    Wu, Lingling; Percak-Dennett, Elizabeth M.; Beard, Brian L.; Roden, Eric E.; Johnson, Clark M.


    Iron isotope fractionation between aqueous Fe(II) (Fe(II)aq) and two amorphous Fe(III) oxide-Si coprecipitates was investigated in an aqueous medium that simulated Archean marine conditions, including saturated amorphous silica, low sulfate, and zero dissolved oxygen. The equilibrium isotope fractionation (in 56Fe/54Fe) between Fe(II)aq and Fe(III)-Si coprecipitates at circum-neutral pH, as inferred by the three-isotope method, was -3.51 ± 0.20 (2σ)‰ and -3.99 ± 0.17 (2σ)‰ for coprecipitates that had Fe:Si molar ratios of 1:2 and 1:3, respectively. These results, when combined with earlier work, indicate that the equilibrium isotope fractionation factor between Fe(II)aq and Fe(III)-Si coprecipitates changes as a function of Fe:Si ratio of the solid. Isotopic fractionation was least negative when Fe:Si = 1:1 and most negative when Fe:Si = 1:3. This change corresponds with changes in the local structure of iron, as revealed by prior spectroscopic studies. The kinetics of isotopic exchange was controlled by movement of Fe(II) and Si, where sorption of Fe(II) from aqueous to solid phase facilitated atom exchange, but sorption of Si hindered isotopic exchange through blockage of reactive surface sites. Although Fe(II)-Fe(III) isotopic exchange rates were a function of solid and solution compositions in the current study, in all cases they were much higher than that determined in previous studies of aqueous Fe(III) and ferrihydrite interaction, highlighting the importance of electron exchange in promoting Fe atom exchange. When compared to analogous microbial reduction experiments of overlapping Fe(II) to Fe(III) ratios, isotopic exchange rates were faster in the biological experiments, likely due to promotion of atom exchange by the solid-phase Fe(II) produced in the biological experiments. These results provide constraints for interpreting the relatively large range of Fe isotope compositions in Precambrian marine sedimentary rocks, and highlight important

  2. High-Temperature CO2 Sorption on Hydrotalcite Having a High Mg/Al Molar Ratio.

    Kim, Suji; Jeon, Sang Goo; Lee, Ki Bong


    Hydrotalcites having a Mg/Al molar ratio between 3 and 30 have been synthesized as promising high-temperature CO2 sorbents. The existence of NaNO3 in the hydrotalcite structure, which originates from excess magnesium nitrate in the precursor, markedly increases CO2 sorption uptake by hydrotalcite up to the record high value of 9.27 mol kg(-1) at 240 °C and 1 atm CO2.

  3. The Physical Conditions of Intermediate Redshift MgII Absorbing Clouds from Voigt Profile Analysis

    Churchill, C W; Charlton, J; Churchill, Chris; Vogt, Steven; Charlton, Jane


    [Slightly Abridged] We present a detailed statistical analysis of the column densities, N, and Doppler parameters, b, of MgII absorbing clouds at redshifts 0.4~5 km/s for MgII and FeII and ~7 km/s for MgI. The clouds are consistent with being thermally broadened, with temperatures in the 30-40,000K range. (4) A two-component Gaussian model to the velocity two-point correlation function yielded velocity dispersions of 54 km/s and 166 km/s. The narrow component has roughly twice the amplitude of the broader component. The width and amplitude of the broader component decreases as equivalent width increases. (5) From photoionization models we find that the column density ratios are most consistent with photoionization by the extragalactic background, as opposed to stars. Based upon N(MgI)/N(MgII), it appears that at least two-phase ionization models are required to explain the data.

  4. Biochemical and Spectroscopic Characterization of the Non-Heme Fe(II)- and 2-Oxoglutarate-Dependent Ethylene-Forming Enzyme from Pseudomonas syringae pv. phaseolicola PK2.

    Martinez, Salette; Hausinger, Robert P


    The ethylene-forming enzyme (EFE) from Pseudomonas syringae pv. phaseolicola PK2 is a member of the mononuclear non-heme Fe(II)- and 2-oxoglutarate (2OG)-dependent oxygenase superfamily. This enzyme is reported to simultaneously catalyze the conversion of 2OG into ethylene and three CO2 molecules and the Cδ hydroxylation of l-arginine (l-Arg) while oxidatively decarboxylating 2OG to form succinate and carbon dioxide. A new plasmid construct for expression in recombinant Escherichia coli cells allowed for the purification of large amounts of EFE with activity greater than that previously recorded. A variety of assays were used to quantify and confirm the identity of the proposed products, including the first experimental demonstration of l-Δ(1)-pyrroline-5-carboxylate and guanidine derived from 5-hydroxyarginine. Selected l-Arg derivatives could induce ethylene formation without undergoing hydroxylation, demonstrating that ethylene production and l-Arg hydroxylation activities are not linked. Similarly, EFE utilizes the alternative α-keto acid 2-oxoadipate as a cosubstrate (forming glutaric acid) during the hydroxylation of l-Arg, with this reaction unlinked from ethylene formation. Kinetic constants were determined for both ethylene formation and l-Arg hydroxylation reactions. Anaerobic UV-visible difference spectra were used to monitor the binding of Fe(II) and substrates to the enzyme. On the basis of our results and what is generally known about EFE and Fe(II)- and 2OG-dependent oxygenases, an updated model for the reaction mechanism is presented.

  5. The Solubility of 242PuO2 in the Presence of Aqueous Fe(II): The Impact of Precipitate Preparation

    Felmy, Andrew R.; Moore, Dean A.; Buck, Edgar C.; Conradson, Steven D.; Kukkadapu, Ravi K.; Sweet, Lucas E.; Abrecht, David G.; Ilton, Eugene S.


    The solubility of different forms of precipitated 242PuO2(am) were examined in solutions containing aqueous Fe(II) over a range of pH values. The first series of 242PuO2(am) suspensions were prepared from a 242Pu(IV) stock that had been treated with thenoyltrifluoroacetone (TTA) to remove the 241Am originating from the decay of 241Pu. These 242PuO2(am) suspensions showed much higher solubilities at the same pH value and Fe(II) concentration than previous studies using 239PuO2(am). X ray absorption fine structure (XAFS) spectroscopy of the precipitates showed a substantially reduced Pu-Pu backscatter over that previously observed in 242PuO2(am) precipitates, indicating that the 242PuO2(am) precipitates purified using TTA lacked the long range order previously found in 239PuO2(am) precipitates. The Pu(IV) stock solution was subsequently repurified using an ion exchange resin and an additional series of 242PuO2(am) precipitates prepared. These suspensions showed higher redox potentials and total aqueous Pu concentrations than the TTA purified stock solution. The higher redox potential and aqueous Pu concentrations were in general agreement with previous studies on 242PuO2(am) precipitates, presumably due to the removal of possible organic compounds originally present in the TTA purified stock. 242PuO2(am) suspensions prepared with both stock solutions showed almost identical solubilities in Fe(II) containing solutions even though the initial aqueous Pu concentrations before the addition of Fe(II) were orders of magnitude different. By examining the solubility of 242PuO2(am) prepared from both stocks in this way we have essentially approached equilibrium from both the undersaturated and oversaturated

  6. The solubility of {sup 242}PuO{sub 2} in the presence of aqueous Fe(II). The impact of precipitate preparation

    Felmy, Andrew R.; Moore, Dean A.; Buck, Edgar; Kukkadapu, Ravi; Sweet, Lucas; Abrecht, David; Ilton, Eugene S. [Pacific Northwest National Laboratory, Richland, WA (United States); Conrados, Steven D. [Los Alamos National Laboratory, Los Alamos, NM (United States)


    The solubility of different forms of precipitated {sup 242}PuO{sub 2}(am) were examined in solutions containing aqueous Fe(II) over a range of pH values. The first series of {sup 242}PuO{sub 2}(am) suspensions were prepared from a {sup 242}Pu(IV) stock that had been treated with thenoyltrifluoroacetone (TTA) to remove the {sup 241}Am originating from the decay of {sup 241}Pu. These {sup 242}PuO{sub 2}(am) suspensions showed much higher solubilities at the same pH value and Fe(II) concentration than previous studies using {sup 239}PuO{sub 2}(am). X-ray absorption fine structure (XAFS) spectroscopy of the precipitates showed a substantially reduced Pu-Pu backscatter over that previously observed in {sup 239}PuO{sub 2}(am) precipitates, indicating that the {sup 242}PuO{sub 2}(am) precipitates purified using TTA lacked the long range order previously found in{sup 239}PuO{sub 2}(am) precipitates. The Pu(IV) stock solution was subsequently re-purified using an ion exchange resin and an additional series of {sup 242}PuO{sub 2}(am) precipitates prepared. These suspensions showed higher redox potentials and total aqueous Pu concentrations than the TTA purified stock solution. The higher redox potential and aqueous Pu concentrations were in general agreement with previous studies on {sup 242}PuO{sub 2}(am) precipitates, presumably due to the removal of possible organic compounds originally present in the TTA purified stock. {sup 242}PuO{sub 2}(am) suspensions prepared with both stock solutions showed almost identical solubilities in Fe(II) containing solutions even though the initial aqueous Pu concentrations before the addition of Fe(II) were orders of magnitude different. By examining the solubility of {sup 242}PuO{sub 2}(am) prepared from both stocks in this way we have essentially approached equilibrium from both the undersaturated and oversaturated conditions. The final aqueous Pu concentrations are predictable using a chemical equilibrium model which includes the

  7. Novel FeII and CoII Complexes of Natural Product Tryptanthrin: Synthesis and Binding with G-Quadruplex DNA

    Zhong, Yi-ning; Zhang, Yan; Gu, Yun-qiong; Wu, Shi-yun; Shen, Wen-ying


    Tryptanthrin is one of the most important members of indoloquinoline alkaloids. We obtained this alkaloid from Isatis. Two novel FeII and CoII complexes of tryptanthrin were first synthesized. Single-crystal X-ray diffraction analyses show that these complexes display distorted four-coordinated tetrahedron geometry via two heterocyclic nitrogen and oxygen atoms from tryptanthrin ligand. Binding with G-quadruplex DNA properties revealed that both complexes were found to exhibit significant interaction with G-quadruplex DNA. This study may potentially serve as the basis of future rational design of metal-based drugs from natural products that target the G-quadruplex DNA. PMID:27698647

  8. Hyperaccumulation of metals by Thlaspi caerulescens as affected by root development and Cd-Zn/Ca-Mg interactions.

    Saison, Carine; Schwartz, Christophe; Morel, Jean-Louis


    The aim of this work was to study, in a rhizobox experiment, the phytoextraction of metals by the hyperaccumulator plant Thlaspi caerulescens in relation to the heterogeneity of metal pollution. Six treatments were designed with soils containing various levels of metals. Homogeneous soils and inclusions of soils in other soil matrices were prepared in order to vary metal concentration and localization. Growth parameters of the plant (rosette diameter and shoot biomass) and localization of roots and shoot uptake of Zn, Cd, Ca, and Mg were determined after 10 weeks of growth. The plants grown on the polluted industrial soils provided a larger biomass and had lower mortality rates than those grown on the agricultural soil. Moreover, these plants accumulated more Zn and Cd (up to 17,516 and 375 mg kg(-1) DM, respectively) than plants grown on the agricultural soil (up to 7300 mg Zn kg(-1) and 83 mg Cd kg(-1) DM). The roots preferentially explored metal-contaminated areas. The exploration of polluted soil inclusions by the roots was associated with a higher extraction of metals. Zinc and Cd in the shoots of Thlaspi caerulescens were negatively correlated with Ca and Mg concentrations; however, the soil supply for these two elements was identical. This suggests that there is competition for the uptake of these elements and that Zn is preferentially accumulated.

  9. High velocity blue-shifted FeII absorption in the dwarf star-forming galaxy PHL293B: Evidence for a wind driven supershell?

    Terlevich, R; Bosch, G; Diaz, A I; Hagele, G; Cardaci, M; Firpo, V


    X-shooter and ISIS WHT spectra of the starforming galaxy PHL 293B also known as A2228-00 and SDSS J223036.79-000636.9 are presented in this paper. We find broad (FWHM = 1000km/s) and very broad (FWZI = 4000km/s) components in the Balmer lines, narrow absorption components in the Balmer series blueshifted by 800km/s, previously undetected FeII multiplet (42) absorptions also blueshifted by 800km/s, IR CaII triplet stellar absorptions consistent with [Fe/H] < -2.0 and no broad components or blushifted absorptions in the HeI lines. Based on historical records, we found no optical variability at the 5 sigma level of 0.02 mag between 2005 and 2013 and no optical variability at the level of 0.1mag for the past 24 years. The lack of variability rules out transient phenomena like luminous blue variables or SN IIn as the origin of the blue shifted absorptions of HI and FeII. The evidence points to either a young and dense expanding supershell or a stationary cooling wind, in both cases driven by the young cluster w...

  10. The Population of Weak MgII Absorbers. II The Properties of Single-Cloud Systems

    Rigby, J R; Churchill, C W; Rigby, Jane R.; Charlton, Jane C.; Churchill, Christopher W.


    We present an investigation of MgII absorbers characterized as single-cloud weak systems at z~1. We measured column densities and Doppler parameters for MgII and FeII in 15 systems found in HIRES/Keck spectra at 6.6 km/s. Using these quantities and CIV, Lyman alpha and Lyman limit absorption observed with FOS/HST (resolution ~230 km/s) we applied photoionization models to each system to constrain metallicities, densities, ionization conditions, and sizes. We find that: (1) Single-cloud weak systems are optically thin in neutral hydrogen and may have their origins in a population of objects distinct from the optically thick strong MgII absorbers, which are associated with bright galaxies. (2) Weak systems account for somewhere between 25% to 100% of the z < 1 Lyman alpha forest clouds in the range 15.8MgII absorber that we term ``iron-rich''. These clo...

  11. The effect of biogenic Fe(II) on the stability and sorption of Co(II)EDTA 2- to goethite and a subsurface sediment

    Zachara, John M.; Smith, Steven C.; Fredrickson, James K.


    Laboratory experiments were conducted with suspensions of goethite (α-FeOOH) and a subsurface sediment to assess the influence of bacterial iron reduction on the fate of Co(II)EDTA 2-, a representative metal-ligand complex of intermediate stability (log K Co(II)EDTA = 17.97). The goethite was synthetic (ca. 55 m 2/g) and the sediment was a Pleistocene age, Fe(III) oxide-containing material from the Atlantic coastal plain (Milford). Shewanella alga strain BrY, a dissimilatory iron reducing bacterium (DIRB), was used to promote Fe(III) oxide reduction. Sorption isotherms and pH adsorption edges were measured for Co 2+, Fe 2+, Co(II)EDTA 2-, and Fe(II)EDTA 2- on the two sorbents in 0.001 mol/L Ca(ClO 4) 2 to aid in experiment interpretation. Anoxic suspensions of the sorbents in PIPES buffer at pH 6.5-7.0 were spiked with Co(II)EDTA 2- (10 -5 mol/L, 60Co and 14EDTA labeled), inoculated with BrY (1-6 × 10 8 organisms/mL), and the headspace filled with a N 2/H 2 gas mix. The experiments were conducted under non-growth conditions. The medium did not contain PO 43- (with one exception), trace elements, or vitamins. The tubes were incubated under anoxic conditions at 25°C for time periods in excess of 100 d. Replicate tubes were sacrificed and analyzed at desired time periods for pH, Fe(II) TOT, Fe (aq)2+, 60Co, and 14EDTA. Abiotic analogue experiments were conducted where Fe (aq)2+ was added in increasing concentration to Co(II)EDTA 2-/mineral suspensions to simulate the influence of bacterial Fe(II) evolution. The DIRB generated Fe(II) from both goethite and the Milford sediment that was strongly sorbed by mineral surfaces. Aqueous Fe 2+ increased during the experiment as surfaces became saturated; Fe (aq)2+ induced the dissociation of Co(II)EDTA 2- into a mixture of Co 2+, Co(II)EDTA 2-, and Fe(II)EDTA 2- (log K Fe(II)EDTA = 15.98). The extent of dissociation of Co(II)EDTA 2- was greater in the subsurface sediment because it sorbed Fe(II) less strongly than did

  12. A Quadruple-Phase Strong Mg II Absorber at z~0.9902 Toward PG 1634+706

    Ding, J; Bond, N A; Zonak, S G; Churchill, C W


    The z=0.9902 system along the quasar PG 1634+706 line of sight is a strong MgII absorber (W(2796)>0.3A) with only weak CIV absorption (it is ``CIV-deficient''). To study this system, we used high-resolution spectra from both HST/STIS (R=30,000) and Keck/HIRES (R=45,000). These spectra cover key transitions, such as MgI, MgII, FeII, SiII, CII, SiIII, CIII, SiIV, and CIV. Assuming a Haardt and Madau extragalactic background spectrum, we modeled the system with a combination of photoionization and collisional ionization. Based on a comparison of synthetic spectra to the data profiles, we infer the existence of the following four phases of gas: i) Seven MgII clouds have sizes of 1-1000pc and densities of 0.002-0.1/cm^3, with a gradual decrease in density from blue to red. The MgII phase gives rise to most of the CIV absorption and resembles the warm, ionized inter-cloud medium of the Milky Way; ii) Instead of arising in the same phase as MgII, MgI is produced in separate, narrow components with b~0.75km/s. These ...

  13. Easy and quantitative access to Fe(II) and Fe(III) di(aryl)alkynylphosphine oxides featuring [Fe(dppe)Cp*] endgroups: terminal P=O functionality blocks the dimerisation of the Fe(III) derivatives.

    Tohmé, Ayham; Hagen, Charles T; Essafi, Stéphanie; Bondon, Arnaud; Roisnel, Thierry; Carmichael, Duncan; Paul, Frédéric


    A series of paramagnetic di(aryl)alkynylphosphine oxides [PF6] featuring an open-shell [Fe(κ(2)-dppe)(η(5)-C5Me5)](+) endgroup were obtained by oxidation of their neutral Fe(II) parents 3a-c, themselves obtained in a simple and nearly quantitative fashion from the corresponding Fe(II) metallophosphines 1a-c. The new organometallic radicals were characterised by NMR and ESR and were shown to be perfectly stable in solution, in contrast to species such as 1a-b[PF6] which readily dimerise.

  14. Comparison of rizatriptan 5 mg and 10 mg tablets and sumatriptan 25 mg and 50 mg tablets.

    Kolodny, A; Polis, A; Battisti, W P; Johnson-Pratt, L; Skobieranda, F


    This randomized, double-blind, two-attack, placebo-controlled, crossover study explored the efficacy and tolerability of rizatriptan 10 mg compared with sumatriptan 50 mg as well as rizatriptan 5 mg compared with sumatriptan 25 mg in the acute treatment of migraine. Following randomization to one of six possible treatment sequences, patients (n = 1447) treated two sequential attacks, of moderate or severe intensity, separated by at least 5 days. Patients assessed pain severity, migraine-associated symptoms, and functional disability at 0.5, 1, 1.5, and 2 h post treatment. Compared with placebo, all treatments were effective. On the primary endpoint of time to pain relief, rizatriptan 10 mg was not statistically different from sumatriptan 50 mg [odds ratio (OR) 1.10, P = 0.161], and rizatriptan 5 mg was statistically superior to sumatriptan 25 mg (OR 1.22, P = 0.007). In general, rizatriptan 10 mg and 5 mg treatment resulted in improvement compared with the corresponding doses of sumatriptan on measures of pain severity, migraine symptoms, and functional disability and the 5-mg dose reached statistical significance on almost all measures. All treatments were generally well tolerated.

  15. Substitution of Mn for Mg in MgB_2*

    Fitzpatrick, Michael D.; Johnston, David C.; Miller, Lance L.; Hill, Julienne M.


    The study of solid solutions in which the Mg in MgB2 is partially replaced by magnetic 3d or 4f atoms can potentially reveal important information on the superconducting state of MgB_2. As an end-member of the hypothetical Mg_1-xMn_xB2 system, MnB2 is isostructural with MgB2 and is an antiferromagnet below TN = 760 K which becomes canted at 157 K. A previous study by Moritomo et al.[1] examined the structure and properties of multi-phase samples with 0.01J. Phys. Soc. Japan b70, 1889 (2001).; “Effects of transition metal doping in MgB2 superconductor", Y. Moritomo at al. arXiv:cond-mat/0104568.

  16. Mesoporous carbon stabilized MgO nanoparticles synthesized by pyrolysis of MgCl2 preloaded waste biomass for highly efficient CO2 capture.

    Liu, Wu-Jun; Jiang, Hong; Tian, Ke; Ding, Yan-Wei; Yu, Han-Qing


    Anthropogenic CO2 emission makes significant contribution to global climate change and CO2 capture and storage is a currently a preferred technology to change the trajectory toward irreversible global warming. In this work, we reported a new strategy that the inexhaustible MgCl2 in seawater and the abundantly available biomass waste can be utilized to prepare mesoporous carbon stabilized MgO nanoparticles (mPC-MgO) for CO2 capture. The mPC-MgO showed excellent performance in the CO2 capture process with the maximum capacity of 5.45 mol kg(-1), much higher than many other MgO based CO2 trappers. The CO2 capture capacity of the mPC-MgO material kept almost unchanged in 19-run cyclic reuse, and can be regenerated at low temperature. The mechanism for the CO2 capture by the mPC-MgO was investigated by FTIR and XPS, and the results indicated that the high CO2 capture capacity and the favorable selectivity of the as-prepared materials were mainly attributed to their special structure (i.e., surface area, functional groups, and the MgO NPs). This work would open up a new pathway to slow down global warming as well as resolve the pollution of waste biomass.

  17. Avaliação de contaminação por mercúrio em Descoberto, MG Evaluation of mercury contamination in Descoberto, MG

    Ana Amélia Paulino Tinôco


    Full Text Available O mercúrio, elemento químico considerado não essencial a qualquer processo metabólico, é facilmente acumulado na maioria dos organismos. Ocorre naturalmente em formas orgânicas e inorgânicas, nos estados sólido, dissolvido e gasoso. Seu ciclo biogeoquímico envolve processos que ocorrem no solo, na água e na atmosfera. Em 2002, descobriu-se mercúrio elementar na zona rural do município de Descoberto, Minas Gerais, onde moram cerca de 70 famílias, e sua origem parece estar associada à exploração de ouro, que existiu na região no século 19. Neste trabalho, foram escolhidas três áreas para identificar possível contaminação da água, solo, sedimento e peixes por mercúrio, bem como para estabelecer valores de referência local e contraprova de resultados obtidos anteriormente. Verificaram-se elevadas concentrações no solo (0,26 a 0,55, sedimentos (0,13 a 0,61 e água (Mercury is a chemical element considered unessential to any metabolic process; however, it is easily accumulated in most organisms. It is naturally found in both organic and inorganic forms in solid, liquid and vapor states. Its biogeochemical cycle involves processes occurring in the soil, water and the atmosphere. In 2002, elementary mercury was found in the city of Descoberto, Minas Gerais, Brazil, where 70 families live, and its origin may be related to gold exploration that happened in this region in the 19th century. In this work, three areas were chosen to identify a possible mercury contamination of water, soil, sediment and fish samples and to establish local reference values and counter-evidence of the data previously obtained. Based on the results, high mercury concentrations in soil (0.26 to 0.55, sediments (0.13 to 0.61 and water (< 0.2 to 2,10 µg.L-1 were verified.

  18. Influence of organics and silica on Fe(II) oxidation rates and cell-mineral aggregate formation by the green-sulfur Fe(II)-oxidizing bacterium Chlorobium ferrooxidans KoFox - Implications for Fe(II) oxidation in ancient oceans

    Gauger, Tina; Byrne, James M.; Konhauser, Kurt O.; Obst, Martin; Crowe, Sean; Kappler, Andreas


    Most studies on microbial phototrophic Fe(II) oxidation (photoferrotrophy) have focused on purple bacteria, but recent evidence points to the importance of green-sulfur bacteria (GSB). Their recovery from modern ferruginous environments suggests that these photoferrotrophs can offer insights into how their ancient counterparts grew in Archean oceans at the time of banded iron formation (BIF) deposition. It is unknown, however, how Fe(II) oxidation rates, cell-mineral aggregate formation, and Fe-mineralogy vary under environmental conditions reminiscent of the geological past. To address this, we studied the Fe(II)-oxidizer Chlorobium ferrooxidans KoFox, a GSB living in co-culture with the heterotrophic Geospirillum strain KoFum. We investigated the mineralogy of Fe(III) metabolic products at low/high light intensity, and in the presence of dissolved silica and/or fumarate. Silica and fumarate influenced the crystallinity and particle size of the produced Fe(III) minerals. The presence of silica also enhanced Fe(II) oxidation rates, especially at high light intensities, potentially by lowering Fe(II)-toxicity to the cells. Electron microscopic imaging showed no encrustation of either KoFox or KoFum cells with Fe(III)-minerals, though weak associations were observed suggesting co-sedimentation of Fe(III) with at least some biomass via these aggregates, which could support diagenetic Fe(III)-reduction. Given that GSB are presumably one of the most ancient photosynthetic organisms, and pre-date cyanobacteria, our findings, on the one hand, strengthen arguments for photoferrotrophic activity as a likely mechanism for BIF deposition on a predominantly anoxic early Earth, but, on the other hand, also suggest that preservation of remnants of Fe(II)-oxidizing GSB as microfossils in the rock record is unlikely.

  19. Combined effects of Fe(II) and oxidizing radiolysis products on UO2 and PuO2 dissolution in a system containing solid UO2 and PuO2

    Amme, Marcus; Pehrman, Reijo; Deutsch, Rudolf; Roth, Olivia; Jonsson, Mats


    The stability of UO2 spent nuclear fuel in an oxygen-free geological repository depends on the absence of oxidizing reaction partners in the near field. This work investigates the reactions between the products of water radiolysis by alpha radiation and Fe(II) an the effect on UO2 dissolution. Solid 238PuO2 powder and UO2 pellet were allowed to react in Fe(II) solution in oxygen-free batch reactor tests and kinetics of the subsequent redox reactions were measured. Depending on the concentration of Fe(II) (tests with 10-5 and 10-4 mol L-1 were made), the induced redox reactions took place between 20 and 400 h. Dissolved uranium concentrations went first through a minimum caused by reduction, followed by a maximum caused by radiolytic oxidation, and eventually reached another minimum, probably due to sorption on precipitated Fe(III). Plutonium concentrations were decreasing steadily after going through a maximum about 70 h from the start of the experiments. The results show that in the presence of the strong alpha-radiolytic field induced by the presence of solid 238Pu, the behavior of the system is largely governed by Fe(II) as it controls the H2O2 concentration, reduces U(VI) in solution and drives the Fenton reaction leading to the oxidation of Pu(IV).

  20. Plausible mechanisms of the fenton-like reactions, M = Fe(II) and Co(II), in the presence of RCO2(-) substrates: are OH(•) radicals formed in the process?

    Kornweitz, Haya; Burg, Ariela; Meyerstein, Dan


    DFT calculations concerning the plausible mechanism of Fenton-like reactions catalyzed by Fe(II) and Co(II) cations in the presence of carboxylate ligands suggest that hydroxyl radicals are not formed in these reactions. This conclusion suggests that the commonly accepted mechanisms of Fenton-like reactions induced oxidative stress and advanced oxidation processes have to be reconsidered.

  1. Radiomimeticity of the system H{sub 2}O{sub 2}/Fe(II) on nucleic acid components. Kinetics study; Radiomimeticidad del sistema H{sub 2}O{sub 2}/Fe(II) sobre components de Acidos Nucleicos. Estudio Cinetico

    Cirauqui, R.; Mingot, F.; Davila, C. A.


    The kinetic study of the action of a redox system on DNA monomers allowed us to make criticisms on radiomimetic character of this system. Assuming that in both cases, gamma radiolysis of aerated aqueous solutions and action of H{sub 2}O{sub 2} / Fe(II) system in the same conditions, the reactive species is the OH radical, we propose the kinetic expressions that are confirmed by our experimental results. Some of the accepted G-values are corrected in view of our results. Al so these results put in evidence mechanisms of molecular repair after radical attack. (Author) 79 refs.

  2. P2X7 Receptor Mediated Growth-Inhibitory Effect in KG1 a Cell Line

    Xiujun Zhang; Lijun Meng


    This study was conducted to investigate ATP-induced growth inhibition in human leukemic cells KGla.METHoDS ATP inhibited cell growth was analyzed by MTSassay.Extemalization of phosphatidylserine could be detected byAnnexin-V-FITC apoptosis staining after activation of the P2X7 re-ceptor.P2X7 mediated pore formation was detected in KGla cellsby Yo-Pro-1 uptake assay.RESUlTS ATP inhibited cell growth in a dose-dependent man-ner.The cytotoxic effect could be blocked by P2X7 antagonists,oxidized ATP(OATP)and KN62.Externalization of phosphatidyl-serine could be detected in a time-dependent manner.P2X7 medi-ated pore forigation could be detected in KGla cells.These effectscould not be observed in P2X7 null Ramos cells.CONCLUSIoN The results and our previously reports thatmRNA,protein expression and calcium response of the P2X7receptor in KGla cells,suggested that extracellular ATP effectivelyinduces growth inhibition through apoptosis in KGla cells byactivation of P2X7 receptor,and that may be mediated by extracel-lular Ca2+ineux and pore formation.

  3. Spiral Dinuclear Complexes of Tetradentate N(4) Diazine Ligands with Mn(II), Fe(II), Fe(III), Co(III), and Ni(II) Salts.

    Xu, Zhiqiang; Thompson, Laurence K.; Miller, David O.; Clase, Howard J.; Howard, Judith A. K.; Goeta, Andrés E.


    A series of dinuclear complexes of the tetradentate dipyridyl-diazine ligand PAHAP with Mn(II), Fe(II), Fe(III), Co(III), and Ni(II) salts is reported in which three ligands wrap themselves around the six-coordinate metal centers in a rare spiral-like fashion. A similar Fe(II) complex is found for the dipyrazinyl-diazine ligand PZHPZ. The ligands are severely twisted with dihedral angles between the metal chelate ring mean planes on each ligand in the range 50-70 degrees, values close to the expected twist angle for orthogonality between the bridging nitrogen atom p orbitals. Full structures are reported for the dinuclear complexes [Mn(2)(PAHAP)(3)](ClO(4))(4).5H(2)O (1), [Fe(2)(PAHAP)(3)](NO(3))(4).3H(2)O (2), [Fe(2)(PZHPZ)(3)](NO(3))(4).5H(2)O (5), [Co(2)(PAHAP)(3)](NO(3))(6).5H(2)O (6), and [Ni(2)(PAHAP)(3)][Ni(H(2)O)(6)](NO(3))(6).4.5H(2)O (7). Other derivatives [Fe(2)(PAHAP)(3)](ClO(4))(4).4H(2)O (3), [Fe(2)(PAHAP)(3)](ClO(4))(6).4.5H(2)O (4), [Ni(2)(PAHAP)(3)](ClO(4))(4).5H(2)O (8), and [Fe(PHAAP-H)(H(2)O)(2)(NO(3))](NO(3))(2) (9) are also reported. Complex 1 crystallized in the monoclinic system, space group C2/c, with a = 13.4086(2) Å, b = 32.0249(1) Å, c = 14.3132(2) Å, alpha = 90 degrees, beta = 115.635(1) degrees, gamma = 90 degrees, and Z = 4. Complex 2 crystallized in the cubic system, space group Pa&thremacr;, with a = b = c = 21.0024(1) Å, alpha = beta = gamma = 90 degrees, and Z = 8. Complex 5 crystallized in the monoclinic system, space group P2/n, with a = 14.039(3) Å, b = 11.335(6) Å, c = 14.6517(15) Å, beta = 96.852(11) degrees, and Z = 1. Complex 6 crystallized in the trigonal system, space group R&thremacr;c(h), with a = b = 17.386(2) Å, c = 32.15(2) Å, alpha = beta = 90 degrees, gamma = 120 degrees, and Z = 4. Complex 7 crystallized in the trigonal system, space group R&thremacr;c, with a = b = 17.3737(3) Å, c = 33.235(6) Å, alpha = beta = 90 degrees, gamma = 120 degrees, and Z = 27. Weak ferromagnetic coupling was observed for 1

  4. Element-specific characterization of transient electronic structure of solvated Fe(II) complexes with time-resolved soft X-ray absorption spectroscopy.

    Hong, Kiryong; Cho, Hana; Schoenlein, Robert W; Kim, Tae Kyu; Huse, Nils


    Polypyridyl transition-metal complexes are an intriguing class of compounds due to the relatively facile chemical designs and variations in ligand-field strengths that allow for spin-state changes and hence electronic configurations in response to external perturbations such as pressure and light. Light-activated spin-conversion complexes have possible applications in a variety of molecular-based devices, and ultrafast excited-state evolution in these complexes is of fundamental interest for understanding of the origins of spin-state conversion in metal complexes. Knowledge of the interplay of structure and valence charge distributions is important to understand which degrees of freedom drive spin-conversion and which respond in a favorable (or unfavorable) manner. To track the response of the constituent components, various types of time-resolved X-ray probe methods have been utilized for a broad range of chemical and biological systems relevant to catalysis, solar energy conversions, and functional molecular devices. In particular, transient soft X-ray spectroscopy of solvated molecules can offer complementary information on the detailed electronic structures and valence charge distributions of photoinduced intermediate species: First-row transition-metal L-edges consist of 2p-3d transitions, which directly probe the unoccupied valence density of states and feature lifetime broadening in the range of 100 meV, making them sensitive spectral probes of metal-ligand interactions. In this Account, we present some of our recent progress in employing picosecond and femtosecond soft X-ray pulses from synchrotron sources to investigate element specific valence charge distributions and spin-state evolutions in Fe(II) polypyridyl complexes via core-level transitions. Our results on transient L-edge spectroscopy of Fe(II) complexes clearly show that the reduction in σ-donation is compensated by significant attenuation of π-backbonding upon spin-crossover. This underscores

  5. Mg spin affects adenosinetriphosphate activity

    Tulub, Alexander A


    The Schlegel-Frisch ab initio molecular dynamics (ADMP) (DFT:B3LYP), T = 310 K, is used to study complexation between adenosinetriphosphate (ATP), ATP subsystem, and magnesium cofactor [Mg(H2O)6]2+, Mg subsystem, in a water pool, modeled with 78 water molecules, in singlet (S) and triplet (T) states. The computations prove that the way of ATP cleavage is governed by the electron spin of Mg. In the S state Mg prefers chelation of \\gamma-\\beta-phosphate oxygens (O1-O2), whereas in the T state it chelates \\beta-\\alpha-phosphate oxygens (O2-O3) or produces a single-bonded intermediate. Unlike the chelates, which initiate ionic reaction paths, the single-bonded intermediate starts off a free-radical path of ATP cleavage, yielding a highly reactive adenosinemonophosphate ion-radical, .AMP-, earlier observed in the CIDNP (Chemically Induced Dynamic Nuclear Polarization) experiment (A.A. Tulub, 2006). The free-radical path is highly sensitive to Mg nuclear spin, which through a hyperfine interaction favors the produc...

  6. Synthesis and characterization of Fe(II) β-diketonato complexes with relevance to acetylacetone dioxygenase: insights into the electronic properties of the 3-histidine facial triad.

    Park, Heaweon; Baus, Jacob S; Lindeman, Sergey V; Fiedler, Adam T


    A series of high-spin iron(II) β-diketonato complexes have been prepared and characterized with the intent of modeling the substrate-bound form of the enzyme acetylacetone dioxygenase (Dke1). The Dke1 active site features an Fe(II) center coordinated by three histidine residues in a facial geometry--a departure from the standard 2-histidine-1-carboxylate (2H1C) facial triad dominant among nonheme monoiron enzymes. The deprotonated β-diketone substrate binds to the Fe center in a bidentate fashion. To better understand the implications of subtle changes in coordination environment for the electronic structures of nonheme Fe active sites, synthetic models were prepared with three different supporting ligands (L(N3)): the anionic (Me2)Tp and (Ph2)Tp ligands ((R2)Tp = hydrotris(pyrazol-1-yl)borate substituted with R-groups at the 3- and 5-pyrazole positions) and the neutral (Ph)TIP ligand ((Ph)TIP = tris(2-phenylimidazol-4-yl)phosphine). The resulting [(L(N3))Fe(acac(X))](0/+) complexes (acac(X) = substituted β-diketonates) were analyzed with a combination of experimental and computational methods, namely, X-ray crystallography, cyclic voltammetry, spectroscopic techniques (UV-vis absorption and (1)H NMR), and density functional theory (DFT). X-ray diffraction results for complexes with the (Me2)Tp ligand revealed six-coordinate Fe(II) centers with a bound MeCN molecule, while structures of the (Ph2)Tp and (Ph)TIP complexes generally exhibited five-coordinate geometries. Each [(L(N3))Fe(acac(X))](0/+) complex displays two broad absorption features in the visible region that arise from Fe(II)→acac(X) charge transfer and acac(X)-based transitions, consistent with UV-vis data reported for Dke1. These absorption bands, along with the Fe redox potentials, are highly sensitive to the identity of L(N3) and substitution of the β-diketonates. By interpreting the experimental results in conjunction with DFT calculations, detailed electronic-structure descriptions of the

  7. Schwertmannite and Fe oxides formed by biological low-pH Fe(II) oxidation versus abiotic neutralization: Impact on trace metal sequestration

    Burgos, William D.; Borch, Thomas; Troyer, Lyndsay D.; Luan, Fubo; Larson, Lance N.; Brown, Juliana F.; Lambson, Janna; Shimizu, Masayuki


    Three low-pH coal mine drainage (CMD) sites in central Pennsylvania were studied to determine similarities in sediment composition, mineralogy, and morphology. Water from one site was used in discontinuous titration/neutralization experiments to produce Fe(III) minerals by abiotic oxidative hydrolysis for comparison with the field precipitates that were produced by biological low-pH Fe(II) oxidation. Even though the hydrology and concentration of dissolved metals of the CMD varied considerably between the three field sites, the mineralogy of the three iron mounds was very similar. Schwertmannite was the predominant mineral precipitated at low-pH (2.5-4.0) along with lesser amounts of goethite. Trace metals such as Zn, Ni and Co were only detected at μmol/g concentrations in the field sediments, and no metals (other than Fe) were removed from the CMD at any of the field sites. Metal cations were not lost from solution in the field because of unfavorable electrostatic attraction to the iron mound minerals. Ferrihydrite was the predominant mineral formed by abiotic neutralization (pH 4.4-8.4, 4 d aging) with lesser amounts of schwertmannite and goethite. In contrast to low-pH precipitation, substantial metal removal occurred in the neutralized CMD. Al was likely removed as hydrobasaluminite and Al(OH) 3, and as a co-precipitate into schwertmannite or ferrihydrite. Zn, Ni and Co were likely removed via adsorption onto and co-precipitation into the freshly formed Fe and Al solids. Mn was likely removed by co-precipitation and, at the highest final pH values, as a Mn oxide. Biological low-pH Fe(II) oxidation can be cost-effectively used to pre-treat CMD and remove Fe and acidity prior to conventional neutralization techniques. A further benefit is that solids formed under these conditions may be of industrial value because they do not contain trace metal or metalloid contaminants.

  8. CsMgPO4

    Nikolay S. Slobodyanik


    Full Text Available Caesium magnesium orthophosphate is built up from MgO4 and PO4 tetrahedra (both with . m. symmetry linked together by corners, forming a three-dimensional framework. The Cs atoms have .m. site symmetry and are located in hexagonal channels running along the a- and b-axis directions.

  9. Transformation impacts of dissolved and solid phase Fe(II) on trichloroethylene (TCE) reduction in an iron-reducing bacteria (IRB) mixed column system: a mathematical model.

    Bae, Yeunook; Kim, Dooil; Cho, Hyun-Hee; Singhal, Naresh; Park, Jae-Woo


    In this research, we conducted trichloroethylene (TCE) reduction in a column filled with iron and iron-reducing bacteria (IRB) and developed a mathematical model to investigate the critical reactions between active species in iron/IRB/contaminant systems. The formation of ferrous iron (Fe(II)) in this system with IRB and zero-valent iron (ZVI, Fe(0)) coated with a ferric iron (Fe(III)) crust significantly affected TCE reduction and IRB respiration in various ways. This study presents a new framework for transformation property and reducing ability of both dissolved (Fe(II)(dissolved)) and solid form ferrous iron (Fe(II)(solid)). Results showed that TCE reduction was strongly depressed by Fe(II)(solid) rather than by other inhibitors (e.g., Fe(III) and lactate), suggesting that Fe(II)(solid) might reduce IRB activation due to attachment to IRB cells. Newly exposed Fe(0) from the released Fe(II)(dissolved) was a strong contributor to TCE reduction compared to Fe(II)(solid). In addition, our research confirmed that less Fe(II)(solid) production strongly supported long-term TCE reduction because it may create an easier TCE approach to Fe(0) or increase IRB growth. Our findings will aid the understanding of the contributions of iron media (e.g., Fe(II)(solid), Fe(II)(dissolved), Fe(III), and Fe(0)) to IRB for decontamination in natural groundwater systems.

  10. Biologically active new Fe(II, Co(II, Ni(II, Cu(II, Zn(II and Cd(II complexes of N-(2-thienylmethylenemethanamine

    C. SPÎNU


    Full Text Available Iron(II, cobalt(II, nickel (II, copper (II, zinc(II and cadmium(II complexes of the type ML2Cl2, where M is a metal and L is the Schiff base N-(2-thienylmethylenemethanamine (TNAM formed by the condensation of 2-thiophenecarboxaldehyde and methylamine, were prepared and characterized by elemental analysis as well as magnetic and spectroscopic measurements. The elemental analyses suggest the stoichiometry to be 1:2 (metal:ligand. Magnetic susceptibility data coupled with electronic, ESR and Mössbauer spectra suggest a distorted octahedral structure for the Fe(II, Co(II and Ni(II complexes, a square-planar geometry for the Cu(II compound and a tetrahedral geometry for the Zn(II and Cd(II complexes. The infrared and NMR spectra of the complexes agree with co-ordination to the central metal atom through nitrogen and sulphur atoms. Conductance measurements suggest the non-electrolytic nature of the complexes, except for the Cu(II, Zn(II and Cd(II complexes, which are 1:2 electrolytes. The Schiff base and its metal chelates were screened for their biological activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa and the metal chelates were found to possess better antibacterial activity than that of the uncomplexed Schiff base.

  11. Orientation towards asymmetric transfer hydrogenation of ketones catalyzed by (pyrazolyl)ethyl)pyridine Fe(II) and Ni(II) complexes

    Magubane, Makhosazane N.; Alam, Mohd Gulfam; Ojwach, Stephen O.; Munro, Orde Q.


    Compounds 2-[1-(3,5-dimethylpyrazol-1-yl)ethyl]pyridine (L1) and 2-[1-(3,5-diphenylpyrazol-1-yl)ethyl]pyridine (L2) were obtained in a three-step procedure which involved the reduction of acetylpyridine using NaBH4, chlorination of the alcohol intermediate using SOCl2 and subsequent reaction with appropriate pyrazoles. Reactions of L1 and L2 with Ni(II) and Fe(II) halides produced the respective complexes Ni(L1)Br2 (1), Ni(L1)Cl2 (2), Fe(L1)Cl2 (3) and Ni(L2)Br2 (4) as racemic mixtures in moderate yields. The molecular structures of complexes 1 and 4 are dinuclear and mononuclear respectively. All the complexes (1-4) formed active catalysts for the transfer hydrogenation of ketones (THK) in 2-propanol at 82 °C affording conversions of 58%-84% within 48 h. The influence of catalyst structure, reaction conditions and identity of ketone substrates in the TH reactions have been successfully established.

  12. Investigating the thermodynamics of the reduction of U(VI) to U(V) by Fe(II) using ab initio methods

    Wahlgren, Ulf [Stockholm Univ. (Sweden). Physics Dept.


    In the present work, we have addressed an important redox reaction, the reduction of U(VI) to U(V) in the presence of Fe(II). Redox reactions are not only of fundamental interest, to understand them is essential when describing how chemical reactions of actinides in surface and groundwater systems affect their mobility in the biosphere, and the function of engineered systems for the containment of radioactive waste in underground repositories. In this context it is important to notice that spent nuclear fuel is predominantly a matrix of UO{sub 2} in which fission products and higher actinides are dispersed. In contact with water the fuel matrix will dissolve with a resulting release of the different radionuclides; the dissolution is a result of oxidation by radiolysis products or by intruding oxygen. In most technical system the nuclear waste is contained in canisters of iron/steel, which provide a large reduction capacity to the system and thus may prevent the transformation of sparingly soluble UO{sub 2} to more soluble U(VI) species. Corrosion and other redox reactions involving iron species are therefore of key importance for the safe performance of many nuclear waste installations; as these have to function over very long time periods it is highly desirable to base predictions of their future environmental effects on molecular understanding of the chemical reactions taking place.

  13. Fluorinated Dodecaphenylporphyrins: Synthetic and Electrochemical Studies Including the First Evidence of Intramolecular Electron Transfer Between an Fe(II) Porphyrin -Anion Radical and an Fe(I) Porphyrin

    D' Souza, F.; Forsyth, T.P.; Fukuzumi, S.; Kadish, K.M.; Krattinger, B.; Lin, M.; Medforth, C.J.; Nakanishi, I.; Nurco, D.J.; Shelnutt, J.A.; Smith, K.M.; Van Caemelbecke, E.


    Dodecaphenylporphyrins with varying degrees of fluorination of the peripheral phenyl rings (FXDPPS) were synthesized as model compounds for studying electronic effects in nonplan~ porphyrins, and detailed electrochemical studies of the chloroiron(HI) complexes of these compounds were undertaken. The series of porphyrins, represented as FeDPPCl and as FeFXDPPCl where x = 4, 8 (two isomers), 12, 20,28 or 36, could be reversibly oxidized by two electrons in dichloromethane to give n-cation radicals and n-dications. All of the compounds investigated could also be reduced by three electrons in benzonitrile or pyridine. In benzonitrile, three reversible reductions were observed for the unfluorinated compound FeDPPC1, whereas the FeFXDPPCl complexes generally exhibited irreversible first and second reductions which were coupled to chemical reactions. The chemical reaction associated with the first reduction involved a loss of the chloride ion after generation of Fe FXDPPC1. The second chemical reaction involved a novel intramolecular electron transfer between the initially generated Fe(H) porphyrin n-anion radical and the final Fe(I) porphyrin reduction product. In pyridine, three reversible one electron reductions were observed with the second reduction affording stable Fe(II) porphyrin o - anion radicals for ail of the complexes investigated.

  14. Effect of phosphate, silicate, and Ca on the morphology, structure and elemental composition of Fe(III)-precipitates formed in aerated Fe(II) and As(III) containing water

    Kaegi, Ralf; Voegelin, Andreas; Folini, Doris; Hug, Stephan J.


    We investigated Fe(III)-precipitates formed from Fe(II) oxidation in water at pH 7 as a function of dissolved Fe(II), As(III), phosphate, and silicate in the absence and presence of Ca. We used transmission electron microscopy (TEM), including selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDX) to characterize the morphology, structure and elemental composition of the precipitates. Results from our companion X-ray absorption spectroscopy (XAS) study suggested that the oxidation of Fe(II) leads to the sequential formation of distinct polymeric units in the following order: Fe(III)-phosphate oligomers in the presence of phosphate, silicate-rich hydrous ferric oxide (HFO-Si) at high Si/Fe (>0.5) or 2-line ferrihydrite (2L-Fh) at lower Si/Fe (˜0.1-0.5), and lepidocrocite (Lp) in the absence of phosphate at low Si/Fe (arrangement of the different polymeric units within Fe(III)-precipitates. The resulting structural and compositional heterogeneity of short-range-ordered Fe(III)-precipitates likely affects their colloidal stability and their chemical reactivity and needs to be considered when addressing the fate of co-transformed trace elements such as arsenic.

  15. How to overcome inter-electrode variability and instability to quantify dissolved oxygen, Fe(II, mn(II, and S(−II in undisturbed soils and sediments using voltammetry

    Slowey Aaron J


    Full Text Available Abstract Background Although uniquely capable of measuring multiple redox constituents nearly simultaneously with no or minimal sample pretreatment, voltammetry is currently underutilized in characterizing redox conditions in aquatic and terrestrial systems. Investigation of undisturbed media such as pore water requires a solid-state electrode, and such electrodes can be difficult to fabricate reproducibly. An approach to determine the concentrations of electroactive constituents using indirectly calibrated electrodes has been developed, but the protocol for and accuracy of this approach—the pilot ion method—has not been documented in detail. Results A detailed procedure for testing electrode quality is provided, and the application and limitations of the pilot ion method have been documented. To quantify Fe(II and Mn(II, subtraction of non-linear baseline functions from voltammetric signals produced better calibration curves than did linear baselines, enabled lower detection limits and reliable deconvolution of overlapping signals, and was successfully applied to sediment pore water signals. We observed that electrode sensitivities often vary by tens of percent, and that the sensitivity declines over time. The ratio of calibration slopes of Mn(II to Fe(II varied by no more than 11% from one Hg/Au electrode to another and Fe(II concentrations predicted by the Mn(II pilot ion were, on average, 13% different from their actual values. However, concentration predictions by the pilot ion method were worse for less than 15 μM Fe(II (46% different on average. The ratio of calibration slopes of Mn(II to S(−II varied by almost 20% from one Hg/Au electrode to another, and S(−II predicted concentrations were as much as 58% different from their actual values. These predictions of Fe(II and S(−II concentrations indicate that the accuracy of the pilot ion method depends on how independent calibration slope ratios are from the electrode used. At

  16. Thermal spin-crossover in the [M(3)Zn(6)Cl(6)L(12)] (M = Zn, Fe(II); L = 5,6-dimethoxy-1,2,3-benzotriazolate) system: structural, electrochemical, Mössbauer, and UV-Vis spectroscopic studies.

    Biswas, Shyam; Tonigold, Markus; Kelm, Harald; Krüger, Hans-Jörg; Volkmer, Dirk


    Fusion of pentanuclear Kuratowski-type coordination units leads to homo- and heterononanuclear coordination compounds, two of which are presented, having structural formulae [Zn(9)Cl(6)(OMe(2)bta)(12)]·DMF (1), and [Fe(II)(3)Zn(6)Cl(6)(OMe(2)bta)(12)]·DMF (2), respectively; (OMe(2)btaH = 5,6-dimethoxy-1,2,3-benzotriazole; DMF = N,N'-dimethylformamide). Single crystal X-ray structure analyses reveal the presence of {M(3)Zn(6)L(12)}(6+) cores (M = Zn or Fe(II); L = 5,6-dimethoxy-1,2,3-benzotriazolate) in which the M(II) ions are bridged by μ(3)-OMe(2)bta ligands. In both compounds, the six peripheral Zn ions are tetracoordinated, whereas the remaining three metal ions M are hexacoordinated. The charge of each {M(3)Zn(6)L(12)}(6+) moiety is balanced by six chloride anions that are monodentately bound to the peripheral Zn ions. Based on differences in experimental Fe-N-donor bond lengths (deduced from single crystal data of 2 recorded at 223 K), two out of three Fe(II) ions are found in a high-spin (HS) state, whereas one Fe(II) ion shows a low-spin (LS) state. The assignment of different energetic ground states of Fe(II) ions is corroborated by spectroscopic studies: Both solid-state and solution UV-Vis spectra of 2 (at ambient temperature) display absorption bands owing to the presence of both HS and LS Fe(II) ions. Removal of occluded DMF molecules from the crystal lattices of 1 and 2 in high vacuum leads to fully desolvated powders, termed hereafter 1a and 2a, respectively. Mössbauer studies on 2a show that all three Fe(II) ions are in HS state at 160 K, and upon cooling to 7 K, the central Fe(II) ion undergoes a HS→LS transition while the HS states of the other Fe(II) ions remains unchanged. The cyclic voltammogram of 2 (chloroform solution) exhibits a single reversible oxidation regardless of different Fe(II) spin states in the nonanuclear core of 2.

  17. Binding affinities of Schiff base Fe(II) complex with BSA and calf-thymus DNA: Spectroscopic investigations and molecular docking analysis

    Rudra, Suparna; Dasmandal, Somnath; Patra, Chiranjit; Kundu, Arjama; Mahapatra, Ambikesh


    The binding interaction of a synthesized Schiff base Fe(II) complex with biological macromolecules viz., bovine serum albumin (BSA) and calf thymus(ct)-DNA have been investigated using different spectroscopic techniques coupled with viscosity measurements at physiological pH and 298 K. Regular amendments in emission intensities of BSA upon the action of the complex indicate significant interaction between them, and the binding interaction have been characterized by Stern Volmer plots and thermodynamic binding parameters. On the basis of this quenching technique one binding site with binding constant (Kb = (7.6 ± 0.21) × 105) between complex and protein have been obtained at 298 K. Time-resolved fluorescence studies have also been encountered to understand the mechanism of quenching induced by the complex. Binding affinities of the complex to the fluorophores of BSA namely tryptophan (Trp) and tyrosine (Tyr) have been judged by synchronous fluorescence studies. Secondary structural changes of BSA rooted by the complex has been revealed by CD spectra. On the other hand, hypochromicity of absorption spectra of the complex with the addition of ct-DNA and the gradual reduction in emission intensities of ethidium bromide bound ct-DNA in presence of the complex indicate noticeable interaction between ct-DNA and the complex with the binding constant (4.2 ± 0.11) × 106 M- 1. Life-time measurements have been studied to determine the relative amplitude of binding of the complex to ct-DNA base pairs. Mode of binding interaction of the complex with ct-DNA has been deciphered by viscosity measurements. CD spectra have also been used to understand the changes in ct-DNA structure upon binding with the metal complex. Density functional theory (DFT) and molecular docking analysis have been employed in highlighting the interactive phenomenon and binding location of the complex with the macromolecules.

  18. Binding affinities of Schiff base Fe(II) complex with BSA and calf-thymus DNA: Spectroscopic investigations and molecular docking analysis.

    Rudra, Suparna; Dasmandal, Somnath; Patra, Chiranjit; Kundu, Arjama; Mahapatra, Ambikesh


    The binding interaction of a synthesized Schiff base Fe(II) complex with biological macromolecules viz., bovine serum albumin (BSA) and calf thymus(ct)-DNA have been investigated using different spectroscopic techniques coupled with viscosity measurements at physiological pH and 298K. Regular amendments in emission intensities of BSA upon the action of the complex indicate significant interaction between them, and the binding interaction have been characterized by Stern Volmer plots and thermodynamic binding parameters. On the basis of this quenching technique one binding site with binding constant (Kb=(7.6±0.21)×10(5)) between complex and protein have been obtained at 298K. Time-resolved fluorescence studies have also been encountered to understand the mechanism of quenching induced by the complex. Binding affinities of the complex to the fluorophores of BSA namely tryptophan (Trp) and tyrosine (Tyr) have been judged by synchronous fluorescence studies. Secondary structural changes of BSA rooted by the complex has been revealed by CD spectra. On the other hand, hypochromicity of absorption spectra of the complex with the addition of ct-DNA and the gradual reduction in emission intensities of ethidium bromide bound ct-DNA in presence of the complex indicate noticeable interaction between ct-DNA and the complex with the binding constant (4.2±0.11)×10(6)M(-1). Life-time measurements have been studied to determine the relative amplitude of binding of the complex to ct-DNA base pairs. Mode of binding interaction of the complex with ct-DNA has been deciphered by viscosity measurements. CD spectra have also been used to understand the changes in ct-DNA structure upon binding with the metal complex. Density functional theory (DFT) and molecular docking analysis have been employed in highlighting the interactive phenomenon and binding location of the complex with the macromolecules.

  19. Peptide-based FeS4 complexes: the zinc ribbon fold is unsurpassed to stabilize both the FeII and FeIII states.

    Jacques, Aurélie; Latour, Jean-Marc; Sénèque, Olivier


    Whereas Zn(Cys)4 zinc fingers exist with different protein folds, only the zinc ribbon fold is found in rubredoxin Fe(Cys)4 sites. To assess the significance of this observation, we have investigated the binding and stability of Fe(2+) and Fe(3+) ions by a set of four peptides designed to model Zn(Cys)4 zinc fingers with various folds, i.e. zinc ribbon, treble clef and a loosened zinc ribbon fold. All peptides were shown by means of UV-Vis and CD spectroscopies to form stable 1 : 1 Fe(II)/peptide complexes with binding constants higher than 10(7) M(-1) at pH 7. Their oxidation into Fe(III) complexes and the stability of the latter were compared. The UV-Vis absorption and CD spectroscopic properties of the Fe(II) and Fe(III) complexes were analysed with respect to the structures of the zinc analogues in order to get insight into the local arrangement of the Fe(Cys)4 core around the metal ion. The chemical stability of these complexes was rationalized according to the shielding from the solvent provided by the various peptide folds to the FeS4 core. In addition, we showed that whereas UV-visible spectra inform only on the FeS4, the information derived from the corresponding CD spectra extend to the Cβ orientation and the peptide fold. The results presented here demonstrate that while the zinc ribbon fold is not strictly required to obtain a Fe(Cys)4 site, it affords a drastically superior protection of the site toward external redox agents. This finding brings new clues to engineer stable and redox-active Fe(Cys)4 sites in de novo proteins.

  20. Design, characterization, teratogenicity testing, antibacterial, antifungal and DNA interaction of few high spin Fe(II) Schiff base amino acid complexes

    Abdel-Rahman, Laila H.; El-Khatib, Rafat M.; Nassr, Lobna A. E.; Abu-Dief, Ahmed M.; Lashin, Fakhr El-Din


    In this study, new Fe(II) Schiff base amino acid chelates derived from the condensation of o-hydroxynaphthaldehyde with L-alanine, L-phenylalanine, L-aspartic acid, L-histidine and L-arginine were synthesized and characterized via elemental, thermogravimetric analysis, molar conductance, IR, electronic, mass spectra and magnetic moment measurements. The stoichiometry and the stability constants of the complexes were determined spectrophotometrically. Correlation of all spectroscopic data suggested that Schiff bases ligands exhibited tridentate with ONO sites coordinating to the metal ions via protonated phenolic-OH, azomethine-N and carboxylate-O with the general formulae [Fe(HL)2]·nH2O. But in case of L-histidine, the ligand acts as tetradentate via deprotonated phenolic-OH, azomethine-N, carboxylate-O and N-imidazole ring ([FeL(H2O)2]·2H2O), where HL = mono anion and L = dianion of the ligand. The structure of the prepared complexes is suggested to be octahedral. The prepared complexes were tested for their teratogenicity on chick embryos and found to be safe until a concentration of 100 μg/egg with full embryos formation. Moreover, the interaction between CT-DNA and the investigated complexes were followed by spectrophotometric and viscosity measurements. It was found that, the prepared complexes bind to DNA via classical intercalative mode and showed a different DNA activity with the sequence: nhi > nari > nali > nasi > nphali. Furthermore, the free ligands and their complexes are screened for their in vitro antibacterial and antifungal activity against three types of bacteria, Escherichia coli, Pseudomonas aeruginosa and Bacillus cereus and three types of anti fungal cultures, Penicillium purpurogenium, Aspergillus flavus and Trichotheium rosium in order to assess their antimicrobial potential. The results show that the metal complexes are more reactive with respect to their corresponding Schiff base amino acid ligands.

  1. Ab initio structural modeling of and experimental validation for Chlamydia trachomatis protein CT296 reveal structural similarity to Fe(II) 2-oxoglutarate-dependent enzymes

    Kemege, Kyle E.; Hickey, John M.; Lovell, Scott; Battaile, Kevin P.; Zhang, Yang; Hefty, P. Scott (Michigan); (Kansas); (HWMRI)


    Chlamydia trachomatis is a medically important pathogen that encodes a relatively high percentage of proteins with unknown function. The three-dimensional structure of a protein can be very informative regarding the protein's functional characteristics; however, determining protein structures experimentally can be very challenging. Computational methods that model protein structures with sufficient accuracy to facilitate functional studies have had notable successes. To evaluate the accuracy and potential impact of computational protein structure modeling of hypothetical proteins encoded by Chlamydia, a successful computational method termed I-TASSER was utilized to model the three-dimensional structure of a hypothetical protein encoded by open reading frame (ORF) CT296. CT296 has been reported to exhibit functional properties of a divalent cation transcription repressor (DcrA), with similarity to the Escherichia coli iron-responsive transcriptional repressor, Fur. Unexpectedly, the I-TASSER model of CT296 exhibited no structural similarity to any DNA-interacting proteins or motifs. To validate the I-TASSER-generated model, the structure of CT296 was solved experimentally using X-ray crystallography. Impressively, the ab initio I-TASSER-generated model closely matched (2.72-{angstrom} C{alpha} root mean square deviation [RMSD]) the high-resolution (1.8-{angstrom}) crystal structure of CT296. Modeled and experimentally determined structures of CT296 share structural characteristics of non-heme Fe(II) 2-oxoglutarate-dependent enzymes, although key enzymatic residues are not conserved, suggesting a unique biochemical process is likely associated with CT296 function. Additionally, functional analyses did not support prior reports that CT296 has properties shared with divalent cation repressors such as Fur.

  2. Formation of Mg2Ni with enhanced kinetics: Using MgH2 instead of Mg as a starting material

    Zhao, Bin; Fang, Fang; Sun, Dalin; Zhang, Qingan; Wei, Shiqiang; Cao, Fenglei; Sun, Huai; Ouyang, Liuzhang; Zhu, Min


    At a temperature over the decomposition point (375 °C) of MgH2, the formation of Mg2Ni is greatly enhanced from the 2MgH2+Ni system, as compared to the 2Mg+Ni system. In support of this finding, in-situ observation of X-ray absorption fine structure of the two systems indicates that MgNi bonds form faster in the 2MgH2+Ni system than in the 2Mg+Ni system. Furthermore, theoretical modeling also shows that Mg atoms are readily released from MgH2 using much less energy and thus are more available to react with Ni once the dehydrogenation of MgH2 occurs, as compared to normal Mg.

  3. Thermodynamic modeling of the La-Mg-Y system and Mg-based alloys database

    DU Zhenmin; GUO Cuiping; LI Changrong; ZHANG Weijing


    As an example of the La-Mg-Y system, the method how to set up the thermodynamic model of individual phases was introduced in the process of thermodynamic optimization. The solution phases (liquid, body-centered cubic,face-centered cubic, hexagonal close-packed and double hexagonal close-packed) were modeled with the Redlich-Kister equation. The compound energy model has been used to describe the thermodynamic functions of the intermetallic compounds in the La-Mg-Y systems. The compounds Mg2Y, Mg24Y5, Mg12La, Mg17La2, Mg41La5, Mg3La and Mg2La in the La-Mg-Y system were treated as the formulae (Mg, Y)2(La,Mg, Y), Mg24(La,Mg, Y)4Y, Mg12(La, Y), Mg17(La, Y)2,Mg41(La,Y)5, Mg3(La,Mg,Y) and Mg2(La,Y), respectively. A model (La,Mg,Y)0.5(La,Mg,Y)0.5 was applied to describe the compound MgM formed by MgLa and MgY in order to cope with the order-disorder transition between body-centered cubic solution (A2) and MgM with CsCl-type structure (B2) in the La-Mg-Y system. The Gibbs energies of individual phases were optimized in the La-Mg, La-Y and La-Mg-Y systems by CALPHAD technique. The projection of the liquidus surfaces for the La-Mg-Y system was predicted. The Mg-based alloys database including 36 binary and 15 ternary systems formed by Mg, Al, Cu, Ni, Mn, Zn and rare earth elements was set up in SGTE standard.

  4. Lipid peroxidation in the kidney of rats treated with V and/or Mg in drinking water.

    Scibior, Agnieszka; Zaporowska, Halina; Niedźwiecka, Irmina


    LPO induced by in vitro treatment of kidney supernatants with exogenous Fe or V or Mg (600, 800 and 1000 microm) were a consequence of independent action of those metals and they also resulted from the interactions between exogenous Fe (Fe(exog)) and endogenous V (V(end)) and between V(end) and exogenous V (V(exog)). In conclusion, V (as NaVO(3)) consumed by the rats with drinking water at a dose of 12.9 mg V kg(-1) b.w. per 24 h for 12 weeks increased the basal LPO and markedly enhanced TAS in the renal tissue. Its pro-oxidant potential was also found in in vitro conditions. The Mg dose (6 mg Mg kg(-1) b.w. per 24 h) ingested by the rats together with V (12.7 mg V kg(-1) b.w. per 24 h) neither reduced nor intensified the spontaneous LPO, compared with V-only intoxicated animals; however, the stimulating effect of Mg on LPO was revealed in in vitro conditions.

  5. Constraining the role of iron in environmental nitrogen transformations. Dual stable isotope systematics of abiotic NO2- reduction by Fe(II) and its production of N2O

    Johnston, David [Harvard Univ., Cambridge, MA (United States); Wankel, Scott David [Woods Hole Oceanographic Inst., MA (United States); Buchwald, Carolyn [Woods Hole Oceanographic Inst., MA (United States); Hansel, Colleen [Woods Hole Oceanographic Inst., MA (United States)


    Redox reactions involving nitrogen and iron have been shown to have important implications for mobilization of priority contaminants. Thus, an understanding of the linkages between their biogeochemical cycling is critical for predicting subsurface mobilization of radionuclides such as uranium. Despite mounting evidence for biogeochemical interactions between iron and nitrogen, our understanding of their environmental importance remains limited. Here we present an investigation of abiotic nitrite (NO2-) reduction by Fe(II) or ‘chemodenitrification,’ and its relevance to the production of nitrous oxide (N2O), specifically focusing on dual (N and O) isotope systematics under a variety of environmentally relevant conditions. We observe a range of kinetic isotope effects that are regulated by reaction rates, with faster rates at higher pH (~8), higher concentrations of Fe(II) and in the presence of mineral surfaces. A clear non-linear relationship between rate constant and kinetic isotope effects of NO2- reduction was evident (with larger isotope effects at slower rates) and is interpreted as reflecting the dynamics of Fe(II)-N reaction intermediates. N and O isotopic composition of product N2O also suggests a complex network of parallel and/or competing pathways. Our findings suggest that NO2- reduction by Fe(II) may represent an important abiotic source of environmental N2O, especially in iron-rich environments experiencing dynamic redox variations. This study provides a multi-compound, multi-isotope framework for evaluating the environmental occurrence of abiotic NO2- reduction and N2O formation, helping future studies constrain the relative roles of abiotic and biological N2O production pathways.

  6. Preparation and Hydrogen Storage Properties of Mg-Rich Mg-Ni Ultrafine Particles

    Jianxin Zou


    Full Text Available In the present work, Mg-rich Mg-Ni ultrafine powders were prepared through an arc plasma method. The phase components, microstructure, and hydrogen storage properties of the powders were carefully investigated. It is found that Mg2Ni and MgNi2 could be obtained directly from the vapor state reactions between Mg and Ni, depending on the local vapor content in the reaction chamber. A nanostructured MgH2 + Mg2NiH4 hydrogen storage composite could be generated after hydrogenation of the Mg-Ni ultrafine powders. After dehydrogenation, MgH2 and Mg2NiH4 decomposed into nanograined Mg and Mg2Ni, respectively. Thermogravimetry/differential scanning calorimetry (TG/DSC analyses showed that Mg2NiH4 phase may play a catalytic role in the dehydriding process of the hydrogenated Mg ultrafine particles.

  7. Complexation and coordination selectivities of the tetradentate ligand 7-[(2-hydroxy-5-sulfophenyl) azo]-8-hydroxyquinoline-5-sulfonic acid with Fe(II), Ni(II), Zn(II), Cd(II) and VO(IV)

    Huang, Hu; Kai, Fumiaki; Hirohata, Masaaki; Nakamura, Masaaki; Matsuzaki, Susumu; Komori, Kenji; Tsunematsu, Yuriko [Kumamoto Univ. (Japan)


    The new title tetradentate ligand (SPAHQS), containing both phenylazo and 8-quinolinol fragments, was prepared. Proton-dissociation processes of the ligand and complexing equilibria with Fe(II), Ni(II), Zn(II), Cd(II), and VO(IV) were analyzed spectrophotometrically. Coordination modes of SPAHQS with these metal ions have been investigated by means of polarography and Raman spectroscopy in aqueous solution. It was established that the coordination selectivity of SPAHQS for such metal ions is mainly dependent on steric factors in the chelate ring formed, not on HSAB properties. 18 refs., 6 figs., 2 tabs.

  8. Spin crossover behaviour in one-dimensional Fe(II) compounds based on the [M(CN)4](2-) (M = Pd, Pt) units.

    Zhang, Shao-Liang; Zhao, Xin-Hua; Wang, Yuan-Min; Shao, Dong; Wang, Xin-Yi


    Four one-dimensional heterobimetallic coordination polymers {Fe(pic)2[M(CN)4]}n (M = Pd(II) () and Pt(II) (), pic = 2-picolylamine), and {Fe(pypz)2[M(CN)4]}n (M = Pd(II) () and Pt(II) (), pypz = 2-(1H-pyrazol-3-yl)pyridine) have been synthesized and characterized by infrared spectroscopy, X-ray diffraction, magnetic measurements and differential scanning calorimetry (DSC). Single-crystal X-ray analyses show that all the compounds are 1D neutral zigzag chain structures in which the planar [M(CN)4](2-) anion acts as a μ2-bridging ligand, and the two pic/pypz molecules as chelating coligands. Examination of the intermolecular contacts in compounds reveals the existence of the hydrogen bonding interactions involving the hydrogen donor groups of the pic and pypz ligands and the nitrogen atoms of the non-bridging cyanide groups of the [M(CN)4](2-) anions. Weak π-π interactions were also found to be important for the formation of the 3D structures of compounds and . The SCO properties of all compounds were confirmed by the detailed structural analyses of the coordination environments of the Fe(II) centres, DSC analyses, and magnetic susceptibility measurements. Compounds and exhibit complete SCO behaviour with very narrow thermal hysteresis loops centred near the room temperature (T1/2↓ = 270 K and T1/2↑ = 272 K for and T1/2↓ = 272 K and T1/2↑ = 274 K for ), whereas and exhibit abrupt SCO at 186 and 180 K, respectively. Compared to the mononuclear species of the pic and pypz ligands, the SCO temperatures are adjusted by the different ligand field strength of the [M(CN)4)](2-) units. The cooperativity from both the coordination bonds and supramolecular interaction leads to the observation of the hysteresis loops in the Fe-pic systems and the abrupt SCO transition in the Fe-pypz systems. Furthermore, the light-induced excited-spin-state trapping (LIESST) effect was observed for .

  9. Highly (100) oriented MgO growth on thin Mg layer in MTJ structure

    Jimbo, K [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1-S3-42 O-okayama, Meguro, Tokyo 152-8552 (Japan); Nakagawa, S, E-mail:


    In order to apply Stress Assisted Magnetization Reversal (SAMR) method to perpendicular magnetoresistive random access memory (p-MRAM) with magnetic tunnel junction (MTJ) using MgO (001) oriented barrier layer, multilayer of Ta/ Terfenol-D/ Mg/ MgO and Ta/ Terfenol-D/ MgO were prepared. While the MgO layer, deposited directly on the Terfenol-D layer, did not show (100) orientatin, very thin metallic Mg layer, deposited prior to the MgO deposition, was effective to attain MgO (100) orientation. The crystalline orientation was very weak without Mg, however, the multilayer with Mg showed very strong MgO(100) peak and the MgO orientation was shifted depending on the Mg thickness.

  10. Fabrication and superconducting properties of internal Mg diffusion processed MgB2 wires using MgB4 precursors

    Xu, Da; Wang, Dongliang; Yao, Chao; Zhang, Xianping; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo


    Monofilament MgB2/Nb/Monel wires were fabricated using three different MgB4 precursors by an internal Mg diffusion (IMD) process. The wire geometry and heat-treatment conditions were optimized in order to improve the critical current density (J c) of the MgB2 wire. The influences of the quality of MgB4 powders, such as the particle size and MgO impurity, on the microstructure and superconducting properties of the wires were discussed. Although there were small amounts of voids, unreacted MgB4 particles and MgO impurity existed in the superconducting layers, and the transport layer J c of the wire with the MgB4 precursor reached 3.0 × 104 A cm-2 at 4.2 K and 10 T, which was comparable to that of IMD-processed wires fabricated using boron precursors. Both the non-barrier J c and engineering J c of MgB2 wire made using a MgB4 precursor were enhanced due to the improved grain connectivity and the enlarged fill factor.

  11. Determination of the 36Mg(n ,γ )37Mg reaction rate from Coulomb dissociation of 37Mg

    Shubhchintak; Chatterjee, R.; Shyam, R.


    We use the Coulomb dissociation (CD) method to calculate the rate of the 36Mg(n ,γ )37Mg radiative capture reaction. The CD cross sections of the 37Mg nucleus on a 208Pb target at the beam energy of 244 MeV/nucleon, for which new experimental data have recently become available, were calculated within the framework of a finite-range distorted-wave Born approximation theory that is extended to include the projectile deformation effects. Invoking the principle of detailed balance, these cross sections are used to determine the excitation function and subsequently the rate of the 36Mg(n ,γ )37Mg reaction. We compare these rates to those of the 36Mg(α ,n )39Si reaction calculated within a Hauser-Feshbach model. We find that for T9 as large as up to 1.0 (in units of 109 K) the 36Mg(n ,γ )37Mg reaction is much faster than the 36Mg(α ,n )39Si one. The inclusion of the effects of 37Mg projectile deformation in the breakup calculations enhances the (n ,γ ) reaction rate even further. Therefore, it is highly unlikely that the (n ,γ )β -decay r -process flow will be broken at the 36Mg isotope by the α process.

  12. The coordination of Mg in foraminiferal calcite

    Branson, Oscar; Redfern, Simon A. T.; Tyliszczak, Tolek; Sadekov, Aleksey; Langer, Gerald; Kimoto, Katsunori; Elderfield, Henry


    The Mg/Ca ratio of foraminiferal calcite is a widely accepted and applied empirical proxy for ocean temperature. The analysis of foraminifera preserved in ocean sediments has been instrumental in developing our understanding of global climate, but the mechanisms behind the proxy are largely unknown. Analogies have been drawn to the inorganic precipitation of calcite, where the endothermic substitution of Mg for Ca is favoured at higher temperatures. However, evidence suggests that foraminiferal Mg incorporation may be more complex: foraminiferal magnesium is highly heterogeneous at the sub-micron scale, and high Mg areas coincide with elevated concentrations of organic molecules, Na, S and other trace elements. Fundamentally, the incorporation mode of Mg in foraminifera is unknown. Here we show that Mg is uniformly substituted for Ca within the calcite mineral lattice. The consistency of Mg-specific X-ray spectra gathered from nano-scale regions across the shell (‘test’) reveals that the coordination of Mg is uniform. The similarity of these spectra to that produced by dolomite shows that Mg is present in an octahedral coordination, ideally substituted for Ca in a calcite crystal structure. This demonstrates that Mg is heterogeneous in concentration, but not in structure. The degree of this uniformity implies the action of a continuous Mg incorporation mechanism, and therefore calcification mechanism, across these compositional bands in foraminifera. This constitutes a fundamental step towards a mechanistic understanding of foraminiferal calcification processes and the incorporation of calcite-bound palaeoenvironment proxies, such as Mg.

  13. Modeling and stabilities of Mg/MgH2 interfaces: A first-principles investigation

    Tang, Jia-Jun; Yang, Xiao-Bao; Chen, Li-Juan; Zhao, Yu-Jun


    We have theoretically investigated the modeling and the structural stabilities of various Mg/MgH2 interfaces, i.e. Mg(10bar 10)/MgH2(210), Mg(0001)/MgH2(101) and Mg(10bar 10)/MgH2(101), and provided illuminating insights into Mg/MgH2 interface. Specifically, the main factors, which impact the interfacial energies, are fully considered, including surface energies of two phases, mutual lattice constants of interface model, and relative position of two phases. The surface energies of Mg and MgH2, on the one hand, are found to be greatly impacting the interfacial energies, reflected by the lowest interfacial energy of Mg(0001)/MgH2(101) which is comprised of two lowest energy surfaces. On the other hand, it is demonstrated that the mutual lattice constants and the relative position of two phases lead to variations of interfacial energies, thus influencing the interface stabilities dramatically. Moreover, the Mg-H bonding at interface is found to be the determinant of Mg/MgH2 interface stability. Lastly, interfacial and strain effects on defect formations are also studied, both of which are highly facilitating the defect formations. Our results provide a detailed insight into Mg/MgH2 interface structures and the corresponding stabilities.

  14. Modeling and stabilities of Mg/MgH2 interfaces: A first-principles investigation

    Jia-Jun Tang


    Full Text Available We have theoretically investigated the modeling and the structural stabilities of various Mg/MgH2 interfaces, i.e. Mg(101¯0/MgH2(210, Mg(0001/MgH2(101 and Mg(101¯0/MgH2(101, and provided illuminating insights into Mg/MgH2 interface. Specifically, the main factors, which impact the interfacial energies, are fully considered, including surface energies of two phases, mutual lattice constants of interface model, and relative position of two phases. The surface energies of Mg and MgH2, on the one hand, are found to be greatly impacting the interfacial energies, reflected by the lowest interfacial energy of Mg(0001/MgH2(101 which is comprised of two lowest energy surfaces. On the other hand, it is demonstrated that the mutual lattice constants and the relative position of two phases lead to variations of interfacial energies, thus influencing the interface stabilities dramatically. Moreover, the Mg-H bonding at interface is found to be the determinant of Mg/MgH2 interface stability. Lastly, interfacial and strain effects on defect formations are also studied, both of which are highly facilitating the defect formations. Our results provide a detailed insight into Mg/MgH2 interface structures and the corresponding stabilities.

  15. Análise de crescimento em Heteranthera reniformis, sob diferentes teores de Ca, Mg e S Growth analysis in Heteranthera reniformis under different contents of Ca, Mg and S

    Vanessa David Domingos


    Full Text Available O objetivo deste trabalho foi estudar o crescimento, alocação de biomassa e teores de nutrientes em Heteranthera reniformis Ruiz & Pav., sob o efeito de diferentes concentrações de Ca, Mg e S. As plantas foram cultivadas em vasos plásticos preenchidos com pedra rolada, em soluções nutritivas a 80% da concentração original de Sarruge, correspondente à solução-base. O experimento foi desenvolvido em delineamento experimental inteiramente casualizado, com quatro teores (0%, 25%, 50% e 75% da solução base de 80% avaliados em Ca, Mg e S, além da testemunha (solução-base, com quatro repetições no período de 35 dias em casa de vegetação. O aumento dos teores de Ca na solução propiciou uma redução significativa na área foliar. As maiores áreas foliares ocorreram em soluções a 25% de Ca e 50% de Mg e S. A maior proporção de biomassa seca está no caule, exceto a 25% de Ca (40 mg L-1 que propiciou maior área foliar e área foliar específica. Entre os teores de Mg na solução, as maiores biomassas foram observadas a 50% de Mg (19,2 mg.L-1 e, para o S, não houve diferenças significativas, exceto a 0%. A solução com 160 mg L-1 de Ca propiciou maior concentração de Ca na folha (56,6 g kg-1. Os teores de Ca, Mg e S em solução corresponderam a um aumento proporcional na planta. Os teores de enxofre nas folhas e nos caules aumentaram com a concentração de S na solução, enquanto o teor nas raízes reduziu nas concentrações entre 12,8 e 38,4 mg.L-1.The objective was to study the growth, biomass allocation and concentration of nutrients in Heteranthera reniformis Ruiz & Pav. under the effect of different concentrations of Ca, Mg and S. The plants were cultivated in plastic pots fulfilled with rolled stone, in nutrient solutions of 80% of the original concentration of Sarruge. The experiment was carried out in a complete randomized design, with 4 contents (0, 25, 50 and 75% of the base solution evaluated in Ca, Mg and

  16. Corrosion behavior of Mg and Mg-Zn alloys in simulated body fluid

    GAO Jia-cheng; WU Sha; QIAO Li-ying; WANG Yong


    The corrosion behavior of Mg and Mg-Zn in simulated body fluid was studied.The mass loss of pure Mg,Mg-Zn-Zr and Mg-Zn-Zr-Y in simulated body fluid was measured using photovoltaic scale meter.Corrosion rate was determined through electrochemical tests.Finally,the corrosion mechanism was tbermodynamically studied.The results show that the corrosion rate decreases with the lapse of time for both pure Mg and Mg alloys.The purer the alloy,the borer the corrosion resistance exhibits.The corrosion behavior of Mg alloy is improved by the addition of trace Y.

  17. Iron mediates catalysis of nucleic acid processing enzymes: support for Fe(II) as a cofactor before the great oxidation event.

    Okafor, C Denise; Lanier, Kathryn A; Petrov, Anton S; Athavale, Shreyas S; Bowman, Jessica C; Hud, Nicholas V; Williams, Loren Dean


    Life originated in an anoxic, Fe2+-rich environment. We hypothesize that on early Earth, Fe2+ was a ubiquitous cofactor for nucleic acids, with roles in RNA folding and catalysis as well as in processing of nucleic acids by protein enzymes. In this model, Mg2+ replaced Fe2+ as the primary cofactor for nucleic acids in parallel with known metal substitutions of metalloproteins, driven by the Great Oxidation Event. To test predictions of this model, we assay the ability of nucleic acid processing enzymes, including a DNA polymerase, an RNA polymerase and a DNA ligase, to use Fe2+ in place of Mg2+ as a cofactor during catalysis. Results show that Fe2+ can indeed substitute for Mg2+ in catalytic function of these enzymes. Additionally, we use calculations to unravel differences in energetics, structures and reactivities of relevant Mg2+ and Fe2+ complexes. Computation explains why Fe2+ can be a more potent cofactor than Mg2+ in a variety of folding and catalytic functions. We propose that the rise of O2 on Earth drove a Fe2+ to Mg2+ substitution in proteins and nucleic acids, a hypothesis consistent with a general model in which some modern biochemical systems retain latent abilities to revert to primordial Fe2+-based states when exposed to pre-GOE conditions.

  18. Fe(II) Spin Transition Materials Including an Amino-Ester 1,2,4-Triazole Derivative, Operating at, below, and above Room Temperature.

    Dîrtu, Marinela M; Naik, Anil D; Rotaru, Aurelian; Spinu, Leonard; Poelman, Dirk; Garcia, Yann


    A new family of one-dimensional Fe(II) 1,2,4-triazole spin transition coordination polymers for which a modification of anion and crystallization solvent can tune the switching temperature over a wide range, including the room temperature region, is reported. This series of materials was prepared as powders after reaction of ethyl-4H-1,2,4-triazol-4-yl-acetate (αEtGlytrz) with an iron salt from a MeOH/H2O medium affording: [Fe(αEtGlytrz)3](ClO4)2 (1); [Fe(αEtGlytrz)3](ClO4)2·CH3OH (2); [Fe(αEtGlytrz)3](NO3)2·H2O (3); [Fe(αEtGlytrz)3](NO3)2 (4); [Fe(αEtGlytrz)3](BF4)2·0.5H2O (5); [Fe(αEtGlytrz)3](BF4)2 (6); and [Fe(αEtGlytrz)3](CF3SO3)2·2H2O (7). Their spin transition properties were investigated by (57)Fe Mossbauer spectroscopy, superconducting quantum interference device (SQUID) magnetometry, and differential scanning calorimetry (DSC). The temperature dependence of the high-spin molar fraction derived from (57)Fe Mössbauer spectroscopy in 1 reveals an abrupt single step transition between low-spin and high-spin states with a hysteresis loop of width 5 K (Tc(↑) = 296 K and Tc(↓) = 291 K). The properties drastically change with modification of anion and/or lattice solvent. The transition temperatures, deduced by SQUID magnetometry, shift to Tc(↑) = 273 K and Tc(↓) = 263 K for (2), Tc(↑) = 353 K and Tc(↓) = 333 K for (3), Tc(↑) = 338 K and Tc(↓) = 278 K for (4), T(↑) = 320 K and T(↓) = 305 K for (5), Tc(↑) = 106 K and Tc(↓) = 92 K for (6), and T(↑) = 325 K and T(↓) = 322 K for (7). Annealing experiments of 3 lead to a change of the morphology, texture, and magnetic properties of the sample. A dehydration/rehydration process associated with a spin state change was analyzed by a mean-field macroscopic master equation using a two-level Hamiltonian Ising-like model for 3. A new structural-property relationship was also identified for this series of materials [Fe(αEtGlytrz)3](anion)2·nSolvent based on Mössbauer and DSC

  19. Non-resonant microwave absorption studies of superconducting MgB2 and MgB2 + MgO

    Janhavi P Joshi; Subhasis Sarangi; A K Sood; Dilip Pal; S V Bhat


    Non-resonant microwave absorption (NRMA) studies of superconducting MgB2 and a sample containing ∼ 10% by weight of MgO in MgB2 are reported. The NRMA results indicate near absence of intergranular weak links in the pure MgB2 sample. A linear temperature dependence of the lower critical field c1 is observed indicating a non- wave superconductivity. However, the phase reversal of the NRMA signal which could suggest wave symmetry is also not observed. In the MgB2 + MgO sample, much larger low field dependent absorption is observed indicating the presence of intergranular weak links. The hysteretic behavior of NRMA is compared and contrasted in the two samples. In the pure MgB2 sample, a large hysteresis is observed between the forward and the reverse scans of the magnetic field indicating strong pinning of flux lines. This hysteresis saturates a few degrees below c while in the MgB2 + MgO sample, a much slower increase of hysteresis with decreasing temperature is observed, a signature of weaker pinning.

  20. The conduction bands of MgO, MgS and HfO2

    Boer, P.K. de; Groot, R.A. de


    Electronic structure calculations for MgO, MgS and HfO2 are reported. It is shown that the conduction bands of MgO and MgS have predominantly anion character, contrary to the common picture of the conduction band being derived from cation states. In transition metal oxides, unoccupied anion states a

  1. TRPM6 forms the Mg2+ influx channel involved in intestinal and renal Mg2+ absorption.

    Voets, T.; Nilius, B.; Hoefs, S.J.G.; Kemp, J.W.C.M. van der; Droogmans, G.; Bindels, R.J.M.; Hoenderop, J.G.J.


    Mg2+ is an essential ion involved in a multitude of physiological and biochemical processes and a major constituent of bone tissue. Mg2+ homeostasis in mammals depends on the equilibrium between intestinal Mg2+ absorption and renal Mg2+ excretion, but little is known about the molecular nature of

  2. Hydrogen storage systems from waste Mg alloys

    Pistidda, C.; Bergemann, N.; Wurr, J.; Rzeszutek, A.; Møller, K. T.; Hansen, B. R. S.; Garroni, S.; Horstmann, C.; Milanese, C.; Girella, A.; Metz, O.; Taube, K.; Jensen, T. R.; Thomas, D.; Liermann, H. P.; Klassen, T.; Dornheim, M.


    The production cost of materials for hydrogen storage is one of the major issues to be addressed in order to consider them suitable for large scale applications. In the last decades several authors reported on the hydrogen sorption properties of Mg and Mg-based systems. In this work magnesium industrial wastes of AZ91 alloy and Mg-10 wt.% Gd alloy are used for the production of hydrogen storage materials. The hydrogen sorption properties of the alloys were investigated by means of volumetric technique, in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and calorimetric methods. The measured reversible hydrogen storage capacity for the alloys AZ91 and Mg-10 wt.% Gd are 4.2 and 5.8 wt.%, respectively. For the Mg-10 wt.% Gd alloy, the hydrogenated product was also successfully used as starting reactant for the synthesis of Mg(NH2)2 and as MgH2 substitute in the Reactive Hydride Composite (RHC) 2LiBH4 + MgH2. The results of this work demonstrate the concrete possibility to use Mg alloy wastes for hydrogen storage purposes.

  3. Coherent interface structures and intergrain Josephson coupling in dense MgO/Mg2Si/MgB2 nanocomposites

    Ueno, Katsuya; Nagashima, Yukihito; Seto, Yusuke; Matsumoto, Megumi; Sakurai, Takahiro; Ohta, Hitoshi; Takahashi, Kazuyuki; Uchino, Takashi


    Many efforts are under way to control the structure of heterointerfaces in nanostructured composite materials for designing functionality and engineering application. However, the fabrication of high-quality heterointerfaces is challenging because the crystal/crystal interface is usually the most defective part of the nanocomposite materials. In this work, we show that fully dense insulator (MgO)/semiconductor(Mg2Si)/superconductor(MgB2) nanocomposites with atomically smooth and continuous interfaces, including epitaxial-like MgO/Mg2Si interfaces, are obtained by solid phase reaction between metallic magnesium and a borosilicate glass. The resulting nanocomposites exhibit a semiconductor-superconducting transition at 36 K owing to the MgB2 nanograins surrounded by the MgO/Mg2Si matrix. This transition is followed by the intergrain phase-lock transition at ˜24 K due to the construction of Josephson-coupled network, eventually leading to a near-zero resistance state at 17 K. The method not only provides a simple process to fabricate dense nanocomposites with high-quality interfaces, but also enables to investigate the electric and magnetic properties of embedded superconducting nanograins with good intergrain coupling.

  4. The Coordination of Mg in Foraminiferal Calcite

    Branson, O.; Redfern, S. A.; Tyliszczak, T.; Sadekov, A.; Langer, G.; Elderfield, H.


    The Mg/Ca ratio in calcite shells ('tests') of foraminifera is an empirical ocean temperature proxy widely used to interpret palaeoclimates. We explore the distribution and local environment of Mg in foram tests using STXM and NEXAFS spectroscopy to test the fundamental assumptions behind the proxy, and shed light on the mechanisms underpinning this vital oceanographic tool. Throughout the development of the Mg/Ca proxy, it has been assumed that Mg in foraminifera tests substitutes directly into the calcite lattice (1). This assumption is based on XRD analyses of various high-Mg biogenic carbonates, where Mg concentrations are manifest in the shifted position of diffraction peaks (2, 3). The extrapolation of this trend to foraminiferal calcite links the proxy to inorganic precipitation experiments, and provides a theoretical mechanistic framework to understand the link between Mg/Ca and temperature: the substitution of Mg is endothermic, and favoured at higher temperatures. However, the concentration of Mg in most foraminifera (0-10 mmol/mol Mg/Ca) is below the detection limit of XRD methods, and the analogy to inorganic systems has not been explicitly tested. Electron microprobe (4-6), LA-ICP-MS (7) and high-resolution nanoSIMS mapping (Sadekov, unpub.) of foraminifera tests have revealed the presence of high 'trace element' bands running in plane with the test surface, enriched in Mg, Sr, S, organic molecules and other trace elements. This emphasises a key question highlighted by Dodd (1) when the proxy was still in its infancy: how is Mg incorporated into mineral skeletons? By direct substitution into the calcite lattice, interstitially in a separate distinct mineral phase, or associated with organic compounds? We address this fundamental question using scanning transmission X-ray microscopy (STXM) and X-ray absorption spectroscopy at ALS beamline 11.0.2 to examine the distribution and local atomic environment of Mg in two contrasting species of foraminifera

  5. Existing form and effect of zirconium in pure Mg, Mg-Yb, and Mg-Zn-Yb alloys

    YU Wenbin; HE Hong; LI Chunmei; LI Qing; LIU Zhiyi; QIN Bing


    The existing form and grain refining effects of small zirconium addition in pure Mg, Mg-Yb and Mg-Zn binary alloys, and Mg-Zn-Yb ternary alloy (ZK60-Yb) were investigated. The results show that Zr element exists mainly in single and cluster particles of pure α-Zr or Zn-Zr compounds inside grains and at grain boundaries. Only the particles located in the interior of grains can act as the nucleus for α-Mg growth and effectively promote the formation of Fine equiaxed grains. The broken and dispersed Zr-rich particles produced during the hot extrusion process can form nebulous banded structure in which these free particles may act as obstacles to dislocation motion in wrought magnesium alloys.

  6. Oxycline formation induced by Fe(II) oxidation in a water reservoir affected by acid mine drainage modeled using a 2D hydrodynamic and water quality model - CE-QUAL-W2.

    Torres, Ester; Galván, Laura; Cánovas, Carlos Ruiz; Soria-Píriz, Sara; Arbat-Bofill, Marina; Nardi, Albert; Papaspyrou, Sokratis; Ayora, Carlos


    The Sancho reservoir is an acid mine drainage (AMD)-contaminated reservoir located in the Huelva province (SW Spain) with a pH close to 3.5. The water is only used for a refrigeration system of a paper mill. The Sancho reservoir is holomictic with one mixing period per year in the winter. During this mixing period, oxygenated water reaches the sediment, while under stratified conditions (the rest of the year) hypoxic conditions develop at the hypolimnion. A CE-QUAL-W2 model was calibrated for the Sancho Reservoir to predict the thermocline and oxycline formation, as well as the salinity, ammonium, nitrate, phosphorous, algal, chlorophyll-a, and iron concentrations. The version 3.7 of the model does not allow simulating the oxidation of Fe(II) in the water column, which limits the oxygen consumption of the organic matter oxidation. However, to evaluate the impact of Fe(II) oxidation on the oxycline formation, Fe(II) has been introduced into the model based on its relationship with labile dissolved organic matter (LDOM). The results show that Fe oxidation is the main factor responsible for the oxygen depletion in the hypolimnion of the Sancho Reservoir. The limiting factors for green algal growth have also been studied. The model predicted that ammonium, nitrate, and phosphate were not limiting factors for green algal growth. Light appeared to be one of the limiting factors for algal growth, while chlorophyll-a and dissolved oxygen concentrations could not be fully described. We hypothesize that dissolved CO2 is one of the limiting nutrients due to losses by the high acidity of the water column. The sensitivity tests carried out support this hypothesis. Two different remediation scenarios have been tested with the calibrated model: 1) an AMD passive treatment plant installed at the river, which removes completely Fe, and 2) different depth water extractions. If no Fe was introduced into the reservoir, water quality would significantly improve in only two years

  7. Synthesis, characterization, DFT calculations and biological studies of Mn(II), Fe(II), Co(II) and Cd(II) complexes based on a tetradentate ONNO donor Schiff base ligand

    Abdel-Rahman, Laila H.; Ismail, Nabawia M.; Ismael, Mohamed; Abu-Dief, Ahmed M.; Ahmed, Ebtehal Abdel-Hameed


    This study highlights synthesis and characterization of a tetradentate ONNO Schiff base ligand namely (1, 1‧- (pyridine-2, 3-dimethyliminomethyl) naphthalene-2, 2‧-diol) and hereafter denotes as "HNDAP″ and selected metal complexes including Mn(II), Fe(II), Co(II) and Cd(II) as a central metal. HNDAP was synthesized from 1:2 M ratio condensation of 2, 3-diaminopyridine and 2- hydroxy-1-naphthaldhyde, respectively. The stoichiometric ratios of the prepared complexes were estimated using complementary techniques such as; elemental analyses (-C, H, N), FT-IR, magnetic measurements and molar conductivity. Furthermore, their physicochemical studies were carried out using thermal TGA, DTA and kinetic-thermodynamic studies along with DFT calculations. The results of elemental analyses showed that these complexes are present in a 1:1 metal-to- ligand molar ratio. Moreover, the magnetic susceptibilities values at room temperature revealed that Mn(II), Fe(II) and Co(II) complexes are paramagnetic in nature and have an octahedral (Oh) geometry. In contrast, Cd(II) is diamagnetic and stabilizes in square planar sites. The molar conductivity measurements indicated that all complexes are nonelectrolytes in dimethyl formamide. Spectral data suggested that the ligand is as tetradentate and coordinated with Co(II) ion through two phenolic OH and two azomethine nitrogen. However, for Mn(II), Fe(II) and Cd(II) complexes, the coordination occurred through two phenolic oxygen and two azomethine nitrogen with deprotonation of OH groups. The proposed chemical structures have been validated by quantum mechanics calculations. Antimicrobial activities of both the HNDAP Schiff base ligand and its metal complexes were tested against strains of Gram (-ve) E. coli and Gram (+ve) B. subtilis and S. aureus bacteria and C. albicans, A. flavus and T. rubrum fungi. All the prepared compounds showed good results of inhibition against the selected pathogenic microorganisms. The investigated

  8. Melatonin administration in diabetes: regulation of plasma Cr, V, and Mg in young male Zucker diabetic fatty rats.

    Navarro-Alarcon, Miguel; Ruiz-Ojeda, Francisco J; Blanca-Herrera, Rosa M; Kaki, Abdullah; Adem, Abdu; Agil, Ahmad


    The use of melatonin, a neurohormone present in plants, represents an exciting approach for the maintenance of optimum health conditions. Melatonin administration ameliorates glucose homeostasis in Zucker diabetic fatty (ZDF) rats. The objective of this study was to investigate the effects of melatonin in diabetes in relation to the levels and regulation of plasma chromium (Cr), vanadium (V), and magnesium (Mg) in Zucker diabetic fatty (ZDF) and Zucker lean (ZL) rats. At the age of 6 weeks, ZDF (n = 30) and ZL (n = 30) groups were each subdivided into three groups: control (C) (n = 10), vehicle-treated (V') (n = 10) and melatonin-treated (M) (10 mg kg(-1) per day; n = 10) groups for a 6 week period. After treatment, plasma mineral concentrations were measured by flame (Mg) and electrothermal (Cr and V) atomic absorption spectrometry. No significant differences were found between the C and V' groups (p > 0.05). Plasma Mg levels were significantly lower in C-ZDF vs. C-ZL rats, demonstrating the presence of hypomagnesemia in this diabetes mellitus model. Plasma V and Cr levels were significantly higher in M-ZDF vs. C-ZDF rats. Plasma Mg levels in ZDF rats were not affected by melatonin treatment (p > 0.05). Melatonin administration ameliorates the diabetic status of ZDF rats by enhancing plasma Cr and V concentrations. This appears to be the first report of a beneficial effect of melatonin treatment on plasma Cr and V regulation in ZDF rats.

  9. Theoretical simulation of CO2 capture by an \\text{A}{{\\text{l}}_{11}}\\text{Mg}_{3}^{-} cluster

    Jiang, Yuanyuan; Xie, Xuefang; Hamid, Ilyar; Chen, Chu; Duan, Haiming


    In order to have an impact on carbon emissions, new stable materials for carbon capture should be able to adsorb CO2 from a mixture of other gases efficiently. Based on density functional theory calculations, we showed that the \\text{A}{{\\text{l}}11}\\text{Mg}3- cluster has an excellent capture capacity of CO2 and high CO2 selectivity under ambient conditions. \\text{A}{{\\text{l}}11}\\text{Mg}3- has an O2-resist property because this cluster is similar to \\text{Al}13- which contains 40 electrons with a larger energy gap. The \\text{A}{{\\text{l}}11}\\text{Mg}3- cluster prefers to adsorb CO2 compared with CH4, H2 and N2, and the CO2 molecule can be chemically adsorbed on the cluster by overcoming a lower barrier, which originates from the introduction of the Mg atom. When seven CO2 molecules are chemically adsorbed on the cluster, the capture capacity of CO2 can reach up to 18.99 mol kg-1 this means that the \\text{A}{{\\text{l}}11}\\text{Mg}3- cluster can be viewed as a potential candidate material for CO2 capture.

  10. UHV and Ambient Pressure XPS: Potentials for Mg, MgO, and Mg(OH)2 Surface Analysis

    Head, Ashley R.; Schnadt, Joachim


    The surface sensitivity of x-ray photoelectron spectroscopy (XPS) has positioned the technique as a routine analysis tool for chemical and electronic structure information. Samples ranging from ideal model systems to industrial materials can be analyzed. Instrumentational developments in the past two decades have popularized ambient pressure XPS, with pressures in the tens of mbar now commonplace. Here, we briefly review the technique, including a discussion of developments that allow data collection at higher pressures. We illustrate the information XPS can provide by using examples from the literature, including MgO studies. We hope to illustrate the possibilities of ambient pressure XPS to Mg, MgO, and Mg(OH)2 systems, both in fundamental and applied studies.

  11. Diffusion of Ca and Mg in Calcite

    Cygan, R.T.; Fisler, D.K.


    The self-diffusion of Ca and the tracer diffusion of Mg in calcite have been experimentally measured using isotopic tracers of {sup 25}Mg and {sup 44}Ca. Natural single crystals of calcite were coated with a thermally-sputtered oxide thin film and then annealed in a CO{sub 2} gas at one atmosphere total pressure and temperatures from 550 to 800 C. Diffusion coefficient values were derived from the depth profiles obtained by ion microprobe analysis. The resultant activation energies for Mg tracer diffusion and Ca self-diffusion are respectively: E{sub a}(Mg) = 284 {+-} 74 kJ/mol and E{sub a}(Ca) = 271 {+-} 80 kJ/mol. For the temperature ranges in these experiments, the diffusion of Mg is faster than Ca. The results are generally consistent in magnitude with divalent cation diffusion rates obtained in previous studies and provide a means of interpreting the thermal histories of carbonate minerals, the mechanism of dolomitization, and other diffusion-controlled processes. The results indicate that cation diffusion in calcite is relatively slow and cations are the rate-limiting diffusing species for the deformation of calcite and carbonate rocks. Application of the calcite-dolomite geothermometer to metamorphic assemblages will be constrained by cation diffusion and cooling rates. The direct measurement of Mg tracer diffusion in calcite indicates that dolomitization is unlikely to be accomplished by Mg diffusion in the solid state but by a recrystallization process.

  12. Crystal structure of K0.75[FeII3.75FeIII1.25(HPO36]·0.5H2O, an open-framework iron phosphite with mixed-valent FeII/FeIII ions

    Edurne S. Larrea


    Full Text Available Single crystals of the title compound, potassium hexaphosphitopentaferrate(II,III hemihydrate, K0.75[FeII3.75FeIII1.25(HPO36]·0.5H2O, were grown under mild hydrothermal conditions. The crystal structure is isotypic with Li1.43[FeII4.43FeIII0.57(HPO36]·1.5H2O and (NH42[FeII5(HPO36] and exhibits a [FeII3.75FeIII1.25(HPO36]0.75− open framework with disordered K+ (occupancy 3/4 as counter-cations. The anionic framework is based on (001 sheets of two [FeO6] octahedra (one with point group symmetry 3.. and one with point group symmetry .2. linked along [001] through [HPO3]2− oxoanions. Each sheet is constructed from 12-membered rings of edge-sharing [FeO6] octahedra, giving rise to channels with a radius of ca 3.1 Å where the K+ cations and likewise disordered water molecules (occupancy 1/4 are located. O...O contacts between the water molecule and framework O atoms of 2.864 (5 Å indicate hydrogen-bonding interactions of medium strength. The infrared spectrum of the compound shows vibrational bands typical for phosphite and water groups. The Mössbauer spectrum is in accordance with the presence of FeII and FeIII ions.

  13. Treatment of patients with essential hypertension: amlodipine 5 mg/benazepril 20 mg compared with amlodipine 5 mg, benazepril 20 mg, and placebo.

    Kuschnir, E; Acuña, E; Sevilla, D; Vasquez, J; Bendersky, M; Resk, J; Glazer, R


    This multicenter, double-masked, randomized, parallel-group study compared the efficacy, tolerability, and safety of amlodipine 5 mg/benazepril 20 mg, amlodipine 5 mg, benazepril 20 mg, and placebo in patients with essential hypertension. After a placebo run-in period, 308 patients (all white) were randomized to treatment groups and took medication once daily for 8 weeks. Blood pressure was measured after 4 and 8 weeks of treatment in the 23- to 26-hour period after dosing. Patients wore a noninvasive blood pressure monitor for 24 hours before randomization and before the final visit. Investigators recorded adverse experiences at randomization and at study weeks 4 and 8, and obtained specimens for laboratory testing at randomization and at study week 8. Three hundred seven patients were evaluated for efficacy, and 308 for tolerability and safety. At end point (the last postrandomization measurement for each patient), the reduction in mean sitting diastolic blood pressure with the amlodipine 5 mg/benazepril 20 mg treatment was statistically significantly greater than with any comparative therapy. The results of 24-hour monitoring showed that the amlodipine/benazepril treatment, unlike monotherapy, maintained the hourly mean diastolic blood pressure at amlodipine 5 mg/benazepril 20 mg versus 67.5%, 53.3%, and 15.8% with amlodipine, benazepril, and placebo, respectively. This difference between the amlodipine/benazepril treatment group and each comparative single-agent treatment group was statistically significant. Drug-related adverse events occurred in 15.6% of patients in the amlodipine/benazepril group and in 24.7%, 6.5%, and 11.7% of patients in the amlodipine, benazepril, and placebo groups, respectively. Edema occurred less often in the amlodipine/benazepril group than in the amlodipine group. Overall, once-daily therapy with amlodipine 5 mg/benazepril 20 mg provided an antihypertensive effect that was statistically and clinically superior to amlodipine 5 mg

  14. Solvation of Mg in Helium-4: Are there Meta-stable Mg Dimers ?

    Krotscheck, Eckhard


    Experiments on the formation of magnesium complexes in $^4$He nanodroplets were interpreted as the observation of the formation of weakly bound magnesium complexes. We present results for single Mg and Mg dimer solvation using the hypernetted chain / Euler-Lagrange method as well as path integral Monte Carlo simulations. We find that the phonon-mediated, indirect Mg-Mg interaction adds an oscillatory component to the direct Mg-Mg interaction. We undertake a step-by-step examination of the ingredients of the calculation of the phonon-induced interaction, comparing the results of semi-analytic HNC-EL calculations for bulk and single impurity results with experiments as well as Monte Carlo data. We do not find evidence for a sufficiently strong secondary minimum in the effective Mg-Mg interaction to support a metastable state.

  15. The role of MgO content in ex situ MgB2 wires

    Kovac, P.; Hugek, I.; Meligek, T.;


    An experimental study of the effect of MgO content in the MgB2 powder used for ex situ made composite wires was carried out. Two single-core MgB2/Fe/Cu wires were made using commercial MgB2 powders from Alfa Aesar containing different fraction of MgO. Critical temperature and critical currents...... of as-deformed and heat-treated wires were measured. The differences between the wires are discussed and correlated with the MgO content. It was found that by increasing the amount of MgO, the inter-grain connectivity worsens, but well distributed and low size MgO particles improve flux pinning....

  16. Aging Behavior of Mg-Y-Zr and Mg-Nd-Zr Cast Alloys


    Aging behavior of Mg-3.6Y-0.5Zr and Mg-2.7Nd-0.5Zr alloys was investigated by microhardness measurement and transmission electron microscopy. In the case of Mg-Y-Zr alloy, the presence of β″ phase, a major strengthener, having base centered orthorhombic structure with its lattice constants of aβ″=0.64 nm, bβ″=2.22 nm,and cβ″=0.52 nm was identified. In the case of Mg-Nd-Zr alloy aged at 250℃, the presence ofβ″ and β′phases was identified. The crystal structure ofβ″ phase was found to be DO19 and its orientation relationships with Mg matrix were [0001]β″//[0001]Mg and [01-10]β″//[0110]Mg. The β′ phase had face centered cubicstructure and its orientation relationships with Mg matrix were [011]β′//[0001]Mg and [-11-1]β′//[-2110]Mg.The Mg-2.7Nd-0.5Zr alloy showed higher hardness compared with Mg-3.6Y-0.5Zr alloy.

  17. In vitro and in vivo comparison of binary Mg alloys and pure Mg.

    Myrissa, Anastasia; Agha, Nezha Ahmad; Lu, Yiyi; Martinelli, Elisabeth; Eichler, Johannes; Szakács, Gábor; Kleinhans, Claudia; Willumeit-Römer, Regine; Schäfer, Ute; Weinberg, Annelie-Martina


    Biodegradable materials are under investigation due to their promising properties for biomedical applications as implant material. In the present study, two binary magnesium (Mg) alloys (Mg2Ag and Mg10Gd) and pure Mg (99.99%) were used in order to compare the degradation performance of the materials in in vitro to in vivo conditions. In vitro analysis of cell distribution and viability was performed on discs of pure Mg, Mg2Ag and Mg10Gd. The results verified viable pre-osteoblast cells on all three alloys and no obvious toxic effect within the first two weeks. The degradation rates in in vitro and in vivo conditions (Sprague-Dawley® rats) showed that the degradation rates differ especially in the 1st week of the experiments. While in vitro Mg2Ag displayed the fastest degradation rate, in vivo, Mg10Gd revealed the highest degradation rate. After four weeks of in vitro immersion tests, the degradation rate of Mg2Ag was significantly reduced and approached the values of pure Mg and Mg10Gd. Interestingly, after 4 weeks the estimated in vitro degradation rates approximate in vivo values. Our systematic experiment indicates that a correlation between in vitro and in vivo observations still has some limitations that have to be considered in order to perform representative in vitro experiments that display the in vivo situation.

  18. The Mg impurity in nitride alloys

    Zvanut, M. E.; Willoughby, W. R.; Sunay, U. R. [Department of Physics, University of Alabama at Birmingham, Birmingham AL (United States); Koleske, D. D.; Allerman, A. A. [Sandia National Laboratory, Albuquerque NM (United States); Wang, Ke; Araki, Tsutomu [Department of Photonics, Ritsumeikan University, Kusatsu, Shiga (Japan); Nanishi, Yasushi [Department of Photonics, Ritsumeikan University, Kusatsu, Shiga, Japan and WCU Program, Department of Materials Science and Engineering, Seoul National University, Seoul (Korea, Republic of)


    Although several magnetic resonance studies address the Mg acceptor in GaN, there are few reports on Mg doping in the alloys, where hole production depends strongly on the Al or In content. Our electron paramagnetic resonance (EPR) measurements of the p-type alloys suggest that the Mg impurity retains the axial symmetry, characteristic of a p-type dopant in both alloys; however, In and Al produce additional, different characteristics of the acceptor. In InGaN, the behavior is consistent with a lowering of the acceptor level and increasing hole density as In concentration increases. For AlGaN, the amount of neutral Mg decreases with increasing Al content, which is attributed to different kinetics of hydrogen diffusion thought to occur in samples with higher Al mole fraction.

  19. Thermodynamic optimization of Mg-Nd system

    MENG Fan-gui; LIU Hua-shan; LIU Li-bin; JIN Zhan-peng


    Based on the reported experimental data, the phase diagram of Mg-Nd binary system was optimized using the CALPHAD approach. Gibbs energies of the disordered BCC_A2 and ordered BCC_B2 phases were modeled with a single expression based on a 2-sublattice model. Liquid and terminal solutions, such as dHCP and HCP, were modeled as substitutional solutions. Intermediate phases Mg2Nd, Mg3Nd and Mg41Nd5 were treated as stoichiometric compounds. The optimization was carried out in the Thermo-Calc package. A set of thermodynamic parameters is obtained. Calculated phase diagram, enthalpies of formation and Gibbs energies of formation are in reasonable agreement with the experimental data.

  20. MgH{sub 2} as dopant for improved activation of commercial Mg ingot

    Jain, P., E-mail: [Hydrogen Research Institute, Université du Québec à Trois-Rivières, 3351 des Forges, Trois-Rivières, Québec G9A 5H7 (Canada); Lang, J. [Hydrogen Research Institute, Université du Québec à Trois-Rivières, 3351 des Forges, Trois-Rivières, Québec G9A 5H7 (Canada); Skryabina, N.Y. [Department of Physics, Perm State University, 15, Bukireva, 614990 Perm (Russian Federation); Fruchart, D. [Institut Néel, BP 166, 38042 Grenoble Cedex 9 (France); Santos, S.F [CECS, Federal University of ABC, Rua Santa Adélia 166, Santo André, SP 09210-170 (Brazil); Binder, K.; Klassen, T. [Institute of Materials Technology, Helmut-Schmidt-University, University of the Federal Armed Forces, Holstenhofweg 85, 22043 Hamburg (Germany); Huot, J., E-mail: [Hydrogen Research Institute, Université du Québec à Trois-Rivières, 3351 des Forges, Trois-Rivières, Québec G9A 5H7 (Canada)


    Highlights: •We propose a simple method to reduce production cost of light weight materials for hydrogen storage applications. •Cheaper Mg ingot rather than expensive MgH{sub 2} is used as starting material. •Effect of MgH{sub 2} as catalytic powder for improved activation behavior of Mg is demonstrated. -- Abstract: In this paper, we propose a method to decrease the activation time (first hydrogenation) of commercial Mg. This new alternative processing route uses a combination of cold rolling and short time ball milling to obtain full hydrogen capacity quickly in the first hydrogenation. As ball milling of ductile materials leads to particle agglomeration, brittle Mg plates produced by repetitive cold rolling were used as starting material. These rolled plates were then ball milled for 30 min with and without the addition of 5 wt% Mg or MgH{sub 2} powders. All the synthesized samples were investigated for hydrogen storage, absorption–desorption behavior and microstructure using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and pressure-composition temperature (PCT) methods. Results showed slow activation behavior for cold rolled Mg plates, which was slightly improved after milling. Further improvement was obtained by adding 5 wt% of Mg powder during ball milling. In contrast, when the plates were ball milled with 5 wt% of MgH{sub 2} powder a drastic improvement in activation behavior was observed with hydrogen capacity reaching up to 6.2 wt% in comparison to 2.74 wt% for undoped and 3.57 wt% for Mg doped samples. These results reveal that ball milling with ductile Mg powder deforms only the surface of Mg plates while brittle MgH{sub 2} powders causes fracturing and cracks, increasing the surface area and generating heterogeneous nucleation sites within the bulk material.

  1. The influence of Mg-Zr master alloy microstructure on the corrosion of Mg

    Gandel, D. S.; Easton, M. A.; Gibson, M. A.; Abbott, T.; Birbilis, N.

    In this study, sixteen Mg-Zr alloys were produced to investigate the role of Zr on corrosion of Mg. Alloys were produced using two different commercial Mg-Zr master alloys commonly used for grain refining Mg, but which contain different Zr particle size distributions. It is seen that the master alloy with a smaller Zr particle size leads to an alloy containing more Zr in solid solution. The ratio of Zr in solid solution and in particle form was observed to have a marked effect on the corrosion of Mg.

  2. Features of Mg2Si Layer Growth in Si/Mg2Si Multilayers

    L.E. Konotopskyi


    Full Text Available Features of magnesium siliced layer growth in Si/Mg2Si multilayers in initial state and after thermal annealing were studied by methods of transmission electron microscopy and X-Ray scattering. As-deposited magnesium silicide layers are amorphous with nanocrystal inclusions of metastable h-Mg2Si. Formation of Mg2Si in hexagonal modification occurs under the influence of stress produced by silicon layers. At T = 723 К Mg2Si layers finished crystallizes in hexagonal modification, with some coarsening of grains. That is accompanied with 7.3 % reduction in period of the Si/Mg2Si multilayer.

  3. Influence of Mg Content on Deformability of AlMg Alloys during Extrusion

    Leśniak D.


    Full Text Available In this study the research on deformability of AlMg alloys with high Mg contents in extrusion was carried out. The different shapes from AlMg alloys containing 3.5%, 4.5% and 5.5% of Mg were extruded on 500 T semi-industrial press by using one-hole and multi-hole flat dies. The extrudates surface quality was under investigations in relation with the temperature-speed parameters of the extrusion process. The metal exit speed was estimated depending on the extrudates shape, wall thickness and Mg content. The alloy’s border solidus and liquidus temperatures were also determined.

  4. Preparation and estimation of thermodynamic properties of Fe(II)-, Co(II)-, Ni(II)- and Zr(IV)-containing layered double hydroxides

    Rozov, Konstantin; Curtius, Hilde; Bosbach, Dirk [Forschungszentrum Juelich GmbH (Germany). Inst. for Nuclear Waste Management and Reactor Safety (IEK-6)


    The investigation of layered double hydroxides (LDHs) was performed because they and similar 'green rust' phases were identified as specific secondary phases forming during the evolution of the disposed research reactor fuel elements under nuclear repository relevant conditions. LDHs or 'hydrotalcite-like' solids are of interest in environmental geochemistry because they can substitute various cations and especially due to the anion-exchange properties and, therefore, can be considered as buffer materials for retention of mobile and hazardous radionuclides (like, {sup 14}C, {sup 129}I, {sup 36}Cl, {sup 79}Se etc.). In our study Fe{sup 2+}-, Co{sup 2+}-, Ni{sup 2+}- and Zr{sup 4+}-containing LDHs have been synthesized by co-precipitation method and characterized (PXRD, FT-IR, SEM-EDX, TGA-DSC) in order to investigate the effect of substitution of 2- and 4-valent cations on the stability of LDHs. PXRD measurements demonstrated that: (1) pure Mg-Al-Fe(II) LDHs are existing in the range of the mole fraction of iron x{sub Fe} = Fe/(Mg+Fe) between 0 and 0.13. Unit-cell parameters (a{sub o}=b{sub o}) as a function of x{sub Fe} follow Vegard's law corroborating the existence of a solid solution when x{sub Fe} = 0 - 0.13. Products of syntheses with x{sub Fe} ≥ 0.13 contain detectable amounts (≥1-2 wt%) of additional phases (like, magnetite, maghemite, lepidocrocite); (2) pure Ni{sup 2+}- and Co{sup 2+}-containing LDHs (mole fractions of Ni and Co were equal to 0.1) have been synthesized successfully; (3) Mg-Al-Zr(IV) precipitates with mole fraction of zirconium x{sub Zr} = Zr/(Zr+Al) = 0.0 - 0.5 show PXRD patterns attributed to pure LDHs and the variation of lattice parameters a{sub o}=b{sub o} as a function of x{sub Zr} is in agreement with Vegard's law demonstrating the presence of solid solution. In contrast, PXRD analyses of precipitates with x{sub Zr} ≥ 0.5 have shown the presence of additional X-ray reflexes typical for brucite. The

  5. Elevated temperature properties of Mg- 12Li-Al-MgO composites

    WEI Xiao-wei; HUANG Qing-min


    The compressive creep of Mg-12Li-Al-MgO particulate composites was investigated, which were produced by the reaction of reinforcement materials (B2O3) with Mg-12Li-Al alloy melt in the temperature range of 100-190 ℃ and under different compressive stress in the range of 40-70 MPa with special apparatus. The content of MgO particulates is about 0, 5%, 10%,15%(volume fraction) in Mg-12Li-Al alloy respectively. The results reveal that the creep resistance of the particulate composites is increased with increasing the content of MgO particulates and considerable improvementin creep resistance is observed in Mg-12Li-Al-MgO composites. However, over all range of temperatures and stresses, the creep data for these composites can be correlated using an empirical equation εs =Aσnexp(-Q/RT), where n is 4.93 and Q is about 78.1 kJ/mol for Mg-14Li-Al alloy and n is between 7.48 and 9.47 and Q is 111.2-137.3 kJ/mol for Mg-12Li-Al-MgO composites. The different compressive creep behavior of the composites is associated with the different material constant A. The compressive creep rate is controlled by the lattice diffusion of Li and dislocation climb.

  6. Ultrafast Synthesis and Related Phase Evolution of Mg2Si and Mg2Sn Compounds

    Zhang, Qiang; Lu, Qiangbing; Yan, Yonggao; Su, Xianli; Tang, Xinfeng


    Both Mg2Si and Mg2Sn compounds were synthesized by an ultra-fast self-propagating high-temperature synthesis (SHS) method. The data regarding SHS were obtained via theoretical calculation combined with experiments, showing that the adiabatic temperature T ad and ignition temperature T ig of Mg2Si are a little higher than those of Mg2Sn. The mechanism of phase evolution and the concomitant microstructure evolution during the synthesis process of Mg2Si and Mg2Sn compounds were investigated by adopting SHS technique coupled with a sudden quenching treatment. Differential scanning calorimetry (DSC), field emission scanning electron microscopy (FESEM), and x-ray powder diffraction (XRD) results indicate that Mg2Si compound can be directly synthesized through the reaction of Mg and Si elements at around 850 K. Correspondingly, the formation of Mg2Sn needs to undergo melting of Sn and the subsequent feeble reaction between Mg and Sn elements before the large scale transformation at 730 K. As the groundwork, this research embodies great significance for future study on the ultrafast SHS process of the ternary Mg2Si1-x Sn x solid solutions.

  7. Formation and Corrosion Resistance of Mg-Al Hydrotalcite Film on Mg-Gd-Zn Alloy

    Ba, Z. X.; Dong, Q. S.; Kong, S. X.; Zhang, X. B.; Xue, Y. J.; Chen, Y. J.


    An environment-friendly technique for depositing a Mg-Al hydrotalcite (HT) (Mg6Al2(OH)16-CO3ṡ4H2O) conversion film was developed to protect the Mg-Gd-Zn alloy from corrosion. The morphology and chemical compositions of the film were analyzed by scanning electronic microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Raman spectroscopy (RS), respectively. The electrochemical test and hydrogen evolution test were employed to evaluate the biocorrosion behavior of Mg-Gd-Zn alloy coated with the Mg-Al HT film in the simulated body fluid (SBF). It was found that the formation of Mg-Al HT film was a transition from amorphous precursor to a crystalline HT structure. The HT film can effectively improve the corrosion resistance of magnesium alloy. It indicates that the process provides a promising approach to modify Mg-Gd-Zn alloy.

  8. Melting relations in the MgO-MgSiO3 system up to 70 GPa

    Ohnishi, Satoka; Kuwayama, Yasuhiro; Inoue, Toru


    Melting experiments in a binary system MgO-MgSiO3 were performed up to 70 GPa using a CO2 laser heated diamond anvil cell. The quenched samples were polished and analyzed by a dualbeam focused ion beam (FIB) and a field emission scanning electron microscope (FE-SEM), respectively. The liquidus phase and the eutectic composition were determined on the basis of textual and chemical analyses of sample cross sections. Our experimental results show that the eutectic composition is the Si/Mg molar ratio of 0.76 at 35 GPa and it decreases with increasing pressure. Above 45 GPa, it becomes relatively constant at about 0.64-0.65 Si/Mg molar ratio. Using our experimental data collected at a wide pressure range up to 70 GPa together with previous experimental data, we have constructed a thermodynamic model of the eutectic composition of the MgO-MgSiO3 system. The eutectic composition extrapolated to the pressure and temperature conditions at the base of the mantle is about 0.64 Si/Mg molar ratio. The modeled eutectic composition is quite consistent with a previous prediction from ab initio calculations (de Koker et al. in Earth Planet Sci Lett 361:58-63, 2013), suggesting that the simple assumption of a non-ideal regular solution model can well describe the melting relation of the MgO-MgSiO3 system at high pressure. Our results show that the liquidus phase changes from MgO-periclase to MgSiO3-bridgmanite at 35 GPa for the simplified pyrolite composition ( 0.7 Si/Mg molar ratio), while MgSiO3-bridgmanite is the liquidus phase at the entire lower mantle conditions for the chondritic composition ( 0.84 Si/Mg molar ratio).

  9. Hydrodechlorination of Tetrachloromethane over Palladium Catalysts Supported on Mixed MgF₂-MgO Carriers.

    Bonarowska, Magdalena; Wojciechowska, Maria; Zieliński, Maciej; Kiderys, Angelika; Zieliński, Michał; Winiarek, Piotr; Karpiński, Zbigniew


    Pd/MgO, Pd/MgF₂ and Pd/MgO-MgF₂ catalysts were investigated in the reaction of CCl₄ hydrodechlorination. All the catalysts deactivated in time on stream, but the degree of deactivation varied from catalyst to catalyst. The MgF₂-supported palladium with relatively large metal particles appeared the best catalyst, characterized by good activity and selectivity to C₂-C₅ hydrocarbons. Investigation of post-reaction catalyst samples allowed to find several details associated with the working state of hydrodechlorination catalysts. The role of support acidity was quite complex. On the one hand, a definite, although not very high Lewis acidity of MgF₂ is beneficial for shaping high activity of palladium catalysts. The MgO-MgF₂ support characterized by stronger Lewis acidity than MgF₂ contributes to very good catalytic activity for a relatively long reaction period (~5 h) but subsequent neutralization of stronger acid centers (by coking) eliminates them from the catalyst. On the other hand, the role of acidity evolution, which takes place when basic supports (like MgO) are chlorided during HdCl reactions, is difficult to assess because different events associated with distribution of chlorided support species, leading to partial or even full blocking of the surface of palladium, which plays the role of active component in HdCl reactions.

  10. Preparation of Metallic Isotope 26Mg

    WuXiaolei; ZhangFuming; GanZaiguo; GuoJunsheng; QinZhi


    Some special isotope material is usually used in nuclear experiments. It can be served as ion beam or target. When new superheavy nuclide 265Bh (Z=107) is synthesized, a reaction of 243Am target with 26Mg ion beamis selected to produce new isotope 265Bh. The preparation and production of this rare and extremely expensive isotope 26 Mg used for ion beam substance will be a key problem in synthesizing experiment of 265Bh. Theavailable chemical form of isotope 26Mg in commercial product usually is oxide or other compound, which are not required in our experiment. They need to be transformed to metal form as a proper working substance in ion source.

  11. Hydrogenation properties of Mg-Al alloys

    Andreasen, Anders


    In this paper the properties of Mg-Al alloys in relation to hydrogen storage are reviewed. The main topics of this paper are materials preparation, hydrogen capacity, thermodynamics of hydride formation, and the kinetics of hydride formation and decomposition. Hydrogenation of Mg-Al leads...... to disproportionation with the formation of magnesium hydride and metallic aluminum as the final product. Experimental evidence renders this process reversible. It is observed that the enthalpy of hydride formation of magnesium is lowered upon alloying with Al due to a slightly endothermic disproportionation reaction....... Further, it is found that the kinetics of hydrogenation, as well dehydrogenation, may be significantly improved by alloying compared to pure Mg. The expense of these improvements of the hydrogenation/dehydrogenation properties is a lower gravimetric hydrogen density in the hydrogenated product, (C) 2008...

  12. High Spin States in ^24Mg

    Schwartz, J.; Lister, C. J.; Wuosmaa, A.; Betts, R. R.; Blumenthal, D.; Carpenter, M. P.; Davids, C. N.; Fischer, S. M.; Hackman, G.; Janssens, R. V. F.


    The ^12C(^16O,α)^24Mg reaction was used at 51.5MeV to populate high angular momentum states in ^24Mg. Gamma-rays de-exciting high spin states were detected in a 20 detector spectrometer (the AYE-ball) triggered by the ANL Fragment Mass Analyser (FMA). Channel selection, through detection of ^24Mg nuclei with the appropriate time of flight, was excellent. All the known decays from high spin states were seen in a few hours, with the exception of the 5.04 MeV γ-decay of the J^π=9^- state at 16.904 MeV footnote A.E.Smith et al., Phys. Lett. \\underlineB176, (1986)292. which could not be confirmed. The potential of the technique for studying the radiative decay of states with very high spin in light nuclei will be discussed.

  13. Phase equilibrium in Mg-Cu-Y

    Mezbahul-Islam, Mohammad; Medraj, Mamoun


    Magnesium-based bulk metallic glasses (BMG) have potential in applications ranging from biomedical to sports equipment and the Mg-Cu-Y system offers some of the most promising alloys. Phase relations and ternary solubility of the binary and ternary compounds of this system have been experimentally investigated. The Isothermal section of Mg-Cu-Y system at 673 K for the entire composition range has been constructed. Phase relations in the Cu-rich (>66 at.% Cu) region of the Mg-Cu-Y system has been determined for the first time. The homogeneity range of three ternary compounds has been determined. Solidifications behavior of several key alloys have been discussed based on the differential scanning calorimetry (DSC) experiments and thermodynamic calculations. Extensive analysis of the DSC curves has been carried out to relate them to the corresponding phase transformation reactions and temperatures. Some of the most promising metallic glass forming regions have been analyzed using thermodynamic calculations.

  14. Superconductivity in MgB2


    In January of 2001 the superconductivity of the compound MgB2 with a critical temperature Tc of up to 39 K was discovered. This Tc is the highest in all intermetallic compound and alloy superconductors. MgB2 has a simple structure and its manufacturing capital cost is lower, therefore it could become a practical superconductor in the future. The recent progress is reviewed here which covers the progress in electronic structure, high Tc mechanism, superconducting parameters (Debye temperature, specific heat coefficient of electron, critical fields, coherent length, penetration depth, energy gap, critical current and relaxation rate of flux). Moreover the issue on power transmission is discussed.

  15. Electron microscopy observations of MgB 2 wire prepared by an internal Mg diffusion method

    Shimada, Y.; Kubota, Y.; Hata, S.; Ikeda, K.; Nakashima, H.; Matsumoto, A.; Togano, K.; Kumakura, H.


    Microstructure in a high-density MgB2 wire fabricated by an internal Mg diffusion (IMD) process has been investigated by electron microscopy imaging and analysis at different scales. In the IMD process, a pure Mg rod was used as Mg source, and nanosized SiC powders were mixed with amorphous B powders. In the case of a heat treatment at 640 °C for 1 h carried out after rolling and drawing processes, the wire has two microstructural features that degrade critical current density: uncrystallized zones composed mainly of unreacted B and SiC powders, and cracks partly filled with course Mg2Si crystals. Those cracks were formed in the uncrystallized zones as well as in crystallized MgB2 zones. It indicate that the cracks formed by the mechanical milling and drawing remain after the heat treatment.

  16. Vitamin K prophylaxis for premature infants: 1 mg versus 0.5 mg.

    Costakos, Dennis T; Greer, Frank R; Love, Laureen A; Dahlen, Lynn R; Suttie, John W


    We studied babies (22 to 32 weeks gestational age) of mothers wishing to breast-feed. Group 1 received 1 mg of vitamin K and Group 2 received 0.5 mg of vitamin K. The Day 2 plasma levels of vitamin K were 1900 to 2600 times higher on average, and the Day 10 vitamin K levels 550 to 600 times higher on average, relative to normal adult plasma values, whether an initial prophylaxis dose of 0.5 mg or 1 mg was used. We conclude that 0.5 mg as the initial dose of vitamin K intramuscularly or intravenously would likely be more than adequate to prevent hemorrhagic disease of the newborn, and that 0.3 mg/per kg may be used for babies with birth weights below 1000 g. To decrease vitamin K intakes in this population, new preparations of total parenteral nutrition multivitamins are needed.

  17. Efficient hydrogen storage with the combination of lightweight Mg/MgH2 and nanostructures.

    Cheng, Fangyi; Tao, Zhanliang; Liang, Jing; Chen, Jun


    Efficient hydrogen storage plays a key role in realizing the incoming hydrogen economy. However, it still remains a great challenge to develop hydrogen storage media with high capacity, favourable thermodynamics, fast kinetics, controllable reversibility, long cycle life, low cost and high safety. To achieve this goal, the combination of lightweight materials and nanostructures should offer great opportunities. In this article, we review recent advances in the field of chemical hydrogen storage that couples lightweight materials and nanostructures, focusing on Mg/MgH(2)-based systems. Selective theoretical and experimental studies on Mg/MgH(2) nanostructures are overviewed, with the emphasis on illustrating the influences of nanostructures on the hydrogenation/dehydrogenation mechanisms and hydrogen storage properties such as capacity, thermodynamics and kinetics. In particular, theoretical studies have shown that the thermodynamics of Mg/MgH(2) clusters below 2 nm change more prominently as particle size decreases.

  18. Mifepristone 5 mg versus 10 mg for emergency contraception: double-blind randomized clinical trial

    Carbonell JL


    Full Text Available Josep Lluis Carbonell,1 Ramon Garcia,2 Adriana Gonzalez,2 Andres Breto,2 Carlos Sanchez2 1Mediterranea Medica Clinic, Valencia, Spain; 2Eusebio Hernandez Gynecology and Obstetrics Teaching Hospital, Havana, Cuba Purpose: To estimate the efficacy and safety of 5 mg and 10 mg mifepristone for emergency contraception up to 144 hours after unprotected coitus. Methods: This double-blind randomized clinical trial was carried out at Eusebio Hernandez Hospital (Havana, Cuba. A total of 2,418 women who requested emergency contraception after unprotected coitus received either 5 mg or 10 mg mifepristone. The variables for assessing efficacy were the pregnancies that occurred and the fraction of pregnancies that were prevented. Other variables assessed were the side effects of mifepristone, vaginal bleeding, and changes in the date of the following menstruation. Results: There were 15/1,206 (1.2% and 9/1,212 (0.7% pregnancies in the 5 mg and 10 mg group, respectively (P=0.107. There were 88% and 93% prevented pregnancies in the 5 mg and 10 mg group, respectively. The side effect profiles were similar in both groups. Delayed menstruation ≥7 days was experienced by 4.9% and 11.0% of subjects in the 5 mg and 10 mg group, respectively (P=0.001. There was a significant high failure rate for women weighing >75 kg in the 5 mg group. Conclusion: It would be advisable to use the 10 mg dose of mifepristone for emergency contraception as there was a trend suggesting that the failure rate of the larger dose was lower. Keywords: mifepristone, emergency contraception

  19. The reactive Mg-liquid infiltration to obtain long superconducting MgB$_{2}$ cables

    Giunchi, G


    An alternative “in situ” process to the MgB2 wire manufacturing is represented by the Reactive Mg-Liquid Infiltration (Mg-RLI) process [1], in which the precursor wire is constituted by a metallic sheath encasing a central Mg rod, surrounded by the B powders. We demonstrated that this peculiar “internal Mg” assembly is able to produce very dense superconducting material of high critical current density, with an acceptable fill factor, up to 0.28. Furthermore the Mg-RLI allows also to easily dope the MgBB2 material either by carbon or nanoSiC powders. In order to realize long cables with this technique, two different approaches may be applied. The first one relies on the assembly of thin wires, fine enough that the liquid Mg cannot freely percolate along the wire during the reaction, and the second one relies on the assembly of thick hollow wires, reacted with a continuous supply of Mg to avoid deficiency of Mg in some part of the precursor wire. Both techniques have been demonstrated feasible and the ...

  20. The Interplay of Al and Mg Speciation in Advanced Mg Battery Electrolyte Solutions.

    See, Kimberly A; Chapman, Karena W; Zhu, Lingyang; Wiaderek, Kamila M; Borkiewicz, Olaf J; Barile, Christopher J; Chupas, Peter J; Gewirth, Andrew A


    Mg batteries are an attractive alternative to Li-based energy storage due to the possibility of higher volumetric capacities with the added advantage of using sustainable materials. A promising emerging electrolyte for Mg batteries is the magnesium aluminum chloride complex (MACC) which shows high Mg electrodeposition and stripping efficiencies and relatively high anodic stabilities. As prepared, MACC is inactive with respect to Mg deposition; however, efficient Mg electrodeposition can be achieved following an electrolytic conditioning process. Through the use of Raman spectroscopy, surface enhanced Raman spectroscopy, (27)Al and (35)Cl nuclear magnetic resonance spectroscopy, and pair distribution function analysis, we explore the active vs inactive complexes in the MACC electrolyte and demonstrate the codependence of Al and Mg speciation. These techniques report on significant changes occurring in the bulk speciation of the conditioned electrolyte relative to the as-prepared solution. Analysis shows that the active Mg complex in conditioned MACC is very likely the [Mg2(μ-Cl)3·6THF](+) complex that is observed in the solid state structure. Additionally, conditioning creates free Cl(-) in the electrolyte solution, and we suggest the free Cl(-) adsorbs at the electrode surface to enhance Mg electrodeposition.

  1. Effect of Ni on Mg based hydrogen storage alloy Mg3Nd

    TONG Yanqing; OUYANG Liuzhang; ZHU Min


    Magnesium-neodymium based alloys were prepared by induction melting in an alumina crucible under protection of pure argon atmosphere. XRD patterns show that the as-melted Mg-Nd and Mg3NdNi 0.1 diffraction peaks can be excellently indexed with D03 structure (BiF3 type, space group Fm3m ). The lattice constant of Mg3Nd phase is 0.7390 nm, which is determined by XRD analysis using Cohen's extrapolation method. The reversible hydrogen storage capacity reaches 1.95wt.% for Mg3Nd and 2.68wt.% for Mg3NdNi0.1 . The desorption of hydrogen takes place at 291 ℃ for Mg3Nd and at 250 ℃ for Mg3NdNi 0.1 . The alloys could absorb hydrogen at room temperature with rapid hydriding and dehydriding kinetics after only one cycle. The enthalpy (ΔH ) and entropy (ΔS ) of Mg3Nd-H dehydriding reaction were -68.2 kJ·mol-1 H2 and -0.121 kJ·(K·mol)-1 H2 determined by using van't Hoff plot according to the pressure-composition-isotherms (P-C-I) curve measured at different temperatures. Hydrogen absorption kinetic property of Mg3NdNi 0.1 alloy was also measured at room temperature.

  2. Comparing Doping Methodologies in Mg2Si/AgMg System

    Polymeris, G. S.; Theodorakakos, A.; Mars, K.; Godlewska, E.; Lioutas, Ch. B.; Hatzikraniotis, E.; Paraskevopoulos, K. M.


    Morphological and optical characterizations for the Mg2Si samples doped with Ag are presented. Two different doping methodologies with silver, namely in situ and ex situ doping, were studied for the case of Mg2Si of self-propagating high-temperature synthesis. Electron microscopy measurements in both scanning and transmission configurations verified the presence of AgMg precipitates embedded in the Mg2Si matrix and similar results were also yielded by FTIR spectroscopy. Finally, the dependence of silver content in both forms of dopant and inter-metallic constituent is studied upon doping technology.

  3. Confinement of Mg-MgH2 systems into carbon nanotubes changes hydrogen sorption energetics.

    Liang, Jian-jie; Kung, W-C Paul


    The density functional theory (DFT) method was used to study the effect of nanoconfinement on the energetics of Mg-MgH2 systems. Varying levels of loading of the Mg/MgH2 particles into a (10,10) carbon nanotube were examined, and the corresponding energetics were computed. A clear trend was observed that, as the level of loading increases (increasing confinement), the net energy change in the hydrogen sorption/desorption processes decreases to a significant level when the loading approaches the maximum. The confinement was found not to depend on the tube length of the confining nanotubes.

  4. 4-nitrocatechol as a probe of a Mn(II)-dependent extradiol-cleaving catechol dioxygenase (MndD): comparison with relevant Fe(II) and Mn(II) model complexes.

    Reynolds, Mark F; Costas, Miquel; Ito, Masami; Jo, Du-Hwan; Tipton, A Alex; Whiting, Adam K; Que, Lawrence


    Mn(II)-dependent 3,4-dihydroxyphenylacetate 2,3-dioxygenase (MndD) is an extradiol-cleaving catechol dioxygenase from Arthrobacter globiformis that has 82% sequence identity to and cleaves the same substrate (3,4-dihydroxyphenylacetic acid) as Fe(II)-dependent 3,4-dihydroxyphenylacetate 2,3-dioxygenase (HPCD) from Brevibacterium fuscum. We have observed that MndD binds the chromophoric 4-nitrocatechol (4-NCH(2)) substrate as a dianion and cleaves it extremely slowly, in contrast to the Fe(II)-dependent enzymes which bind 4-NCH(2) mostly as a monoanion and cleave 4-NCH(2) 4-5 orders of magnitude faster. These results suggest that the monoanionic binding state of 4-NC is essential for extradiol cleavage. In order to address the differences in 4-NCH(2) binding to these enzymes, we synthesized and characterized the first mononuclear monoanionic and dianionic Mn(II)-(4-NC) model complexes as well as their Fe(II)-(4-NC) analogs. The structures of [(6-Me(2)-bpmcn)Fe(II)(4-NCH)](+), [(6-Me(3)-TPA)Mn(II)(DBCH)](+), and [(6-Me(2)-bpmcn)Mn(II)(4-NCH)](+) reveal that the monoanionic catecholate is bound in an asymmetric fashion (Delta r(metal-O(catecholate))=0.25-0.35 A), as found in the crystal structures of the E(.)S complexes of extradiol-cleaving catechol dioxygenases. Acid-base titrations of [(L)M(II)(4-NCH)](+) complexes in aprotic solvents show that the p K(a) of the second catecholate proton of 4-NCH bound to the metal center is half a p K(a) unit higher for the Mn(II) complexes than for the Fe(II) complexes. These results are in line with the Lewis acidities of the two divalent metal ions but are the opposite of the trend observed for 4-NCH(2) binding to the Mn(II)- and Fe(II)-catechol dioxygenases. These results suggest that the MndD active site decreases the second p K(a) of the bound 4-NCH(2) relative to the HPCD active site.

  5. Effect of Mg-Nb oxides addition on hydrogen sorption in MgH{sub 2}

    Rahman, M.W.; Castellero, A. [Dipartimento di Chimica IFM, NIS Centre of Excellence, Universita di Torino, Via Pietro Giuria 9, 10125 Torino (Italy); Enzo, S. [Dipartimento di Chimica, Universita di Sassari, 07100 Sassari (Italy); Livraghi, S.; Giamello, E. [Dipartimento di Chimica IFM, NIS Centre of Excellence, Universita di Torino, Via Pietro Giuria 9, 10125 Torino (Italy); Baricco, M., E-mail: [Dipartimento di Chimica IFM, NIS Centre of Excellence, Universita di Torino, Via Pietro Giuria 9, 10125 Torino (Italy)


    Highlights: > H{sub 2} sorption reactions in MgH{sub 2} with 1 mol% MgNb{sub 2}O{sub 6}, Mg{sub 4}Nb{sub 2}O{sub 9} and Mg{sub 3}Nb{sub 6}O{sub 11} have been investigated. > Ball-milled samples showed the presence of a mixture of {beta} and {gamma} allotropes of MgH{sub 2}. > The presence of Mg-Nb oxides significantly accelerates the hydrogen absorption and desorption processes. > Experimental results are discussed on the basis of thermodynamic and kinetic arguments. - Abstract: H{sub 2} absorption and desorption reactions in MgH{sub 2} promoted by ball-milling with 1 mol% MgNb{sub 2}O{sub 6}, Mg{sub 4}Nb{sub 2}O{sub 9} and Mg{sub 3}Nb{sub 6}O{sub 11} have been investigated. MgH{sub 2} was milled with the bare oxides for 12 h under a high purity Ar atmosphere. Absorption and desorption reactions in the ball-milled samples were studied by in situ X-ray diffraction (XRD) in isothermal conditions with Anton Paar XRK 900 reaction chamber. XRD patterns for absorption were recorded at 573 K under hydrogen pressure of 0.9 MPa and for desorption at 623 K in vacuum. Experimental data were analysed according to the Rietveld method. Ball-milled samples showed the presence of a mixture of {beta} and {gamma} allotropes of MgH{sub 2}, with significantly broadened diffraction peaks due to reduced crystallite size and strain, together with bare additives. The presence of Mg-Nb oxides significantly accelerates the hydrogen absorption and desorption processes. The amount of hydrogen absorbed in the presence of Mg-Nb-O phases is lower than the maximum stoichiometric capacity, because of the presence of a non-reactive MgO layer on the surface of the powders or at the grain boundaries. Experimental results are discussed on the basis of thermodynamic and kinetic arguments.

  6. Preparation of an additive-free sample with a MgH2 phase by planetary ball milling of Mg with10 wt% MgH2

    Hong, Seong-Hyeon; Song, Myoung Youp


    In order to prepare an additive-free sample with a MgH2 phase, 90 wt% Mg+10 wt% MgH2 (named Mg-10MgH2) was milled under hydrogen atmosphere in a planetary ball mill for different durations (2 h, 5 h, and 10 h). The hydrogen absorption and release properties of the prepared samples were investigated and compared with those of purchased pure MgH2 samples. Mg-10MgH2 milled for 5 h had the largest quantity of hydrogen released at 648 K for 100 min of 5.96 wt%. Mg-10MgH2 milled for 5 h released 0.11 wt% H for 10 min, 4.85 wt% H for 30 min, and 5.83 wt% H for 60 min at 648 K at the first cycle. Mg-10MgH2 milled for 5 h absorbed 5.39 wt% H for 5 min and 5.92 wt% H for 60 min at 648 K at the second cycle. Dehydriding curves were also obtained at the first cycle of Mg-10MgH2 samples milled for 5 h using Mg powder with or without sieving (200 mesh). The dehydriding curve at 648 K of a Mg-10MgH2 sample milled for 5 h in the planetary ball mill was compared with that of the sample milled for 24 h in a horizontal ball mill.

  7. Destabilization of Mg Hydride by Self-Organized Nanoclusters in the Immiscible Mg-Ti System

    Asano, Kohta; Westerwaal, Ruud J.; Anastasopol, Anca; Mooij, Lennard P A; Boelsma, Christiaan; Ngene, Peter; Schreuders, Herman; Eijt, Stephan W H; Dam, Bernard


    Mg is an attractive hydrogen storage material not only because of its high gravimetric and volumetric hydrogen capacities but also because of it low material costs. However, the hydride of MgH2 is too stable to release hydrogen under moderate conditions. We demonstrate that the formation of

  8. Energy Bands and Fermi Surface for beta-MgMh and beta-MgTl

    Skriver, Hans Lomholt


    The energy bands of ordered β′-MgHg and β′-MgTl have been calculated by the relativistic linear-muffintin-orbital method. We show how the gross features of the energy bands may be estimated from Wigner-Seitz rules. The densities of states are calculated and the heat capacities derived. The Fermi...

  9. Destabilization of Mg Hydride by Self-Organized Nanoclusters in the Immiscible Mg-Ti System

    Asano, Kohta; Westerwaal, Ruud J.; Anastasopol, Anca; Mooij, Lennard P A; Boelsma, Christiaan; Ngene, Peter; Schreuders, Herman; Eijt, Stephan W H; Dam, Bernard


    Mg is an attractive hydrogen storage material not only because of its high gravimetric and volumetric hydrogen capacities but also because of it low material costs. However, the hydride of MgH2 is too stable to release hydrogen under moderate conditions. We demonstrate that the formation of nanomete

  10. Demonstration of Mg2FeH6 as heat storage material at temperatures up to 550 °C

    Urbanczyk, R.; Meggouh, M.; Moury, R.; Peinecke, K.; Peil, S.; Felderhoff, M.


    The storage of heat at high temperatures, which can be used to generate electricity after sunset in concentrating solar power plants, is one of the most challenging technologies. The use of metal hydride could be one possibility to solve the problem. During the endothermic heat storage process, the metal hydride is decomposed releasing hydrogen, which then can be stored. During the exothermic reaction of the metal with the hydrogen gas, the stored heat is then released. Previous research had shown that Mg and Fe powders can be used at temperatures up to 550 °C for heat storage and shows excellent cycle stability over hundreds of cycles without any degradation. Here, we describe the results of testing of a tube storage tank that contained 211 g of Mg and Fe powders in 2:1 ratio. Twenty-three dehydrogenations (storage) and 23 hydrogenations (heat release) in the temperature range between of 395 and 515 °C and pressure range between 1.5 and 8.6 MPa were done. During the dehydrogenation, 0.41-0.42 kWhth kg-1 of heat based on material 2 Mg/Fe can be stored in the tank. After testing, mainly Mg2FeH6 was observed and small amounts of MgH2 and Fe metal can be detected in the hydride samples. This means that the heat storage capacity of the system could be further increased if only Mg2FeH6 is produced during subsequent cycles.

  11. Modification effect of lanthanum on primary phase Mg2Si in Mg-Si alloys

    WANG Liping; GUO Erjun; MA Baoxia


    The modifying effect of La addition on primary phase Mg2Si in Mg-5Si alloys was investigated. The results showed that a proper amount of La could effectively modify the primary phase Mg2Si. Based on the present experiment, the optimal modification effect was obtained with an addition of about 0.5 wt.% La. The size of the primary phase Mg2Si was considerably reduced to 25 μm or less and the morphology was modified from a coarse dendritic shape to a polyhedral shape. However, when the addition of La increased to 0.8 wt.% or higher, the primary Mg2Si grew into a coarse dendritic morphology again. Moreover, it was found that some LaSi2 compounds were formed during solidification and the amount of the compounds appeared to increase gradually with increasing La content.

  12. Microstructure and hardness of Mg-based composites reinforced with Mg2Si particles

    Mustafa Aydin; Cem Ozgür; Osman San


    Magnesium powders were mechanically alloyed with SiO2 powder particles having different particle sizes using high-energy ball milling techniques under Ar atmosphere for 1 h. The powders were consolidated with cold pressing under 560 Mpa. They were then sintered at 550℃ for 45 min under Ar atmosphere. The composites obtained on the Mg-SiO2 system were investigated using the Archimedes principle, a differential scanning calorimeter, X-ray diffraction, optic microscopy, and scanning electron microscopy. For the mechanically alloyed powders, the solid-state reaction of the synthesis of Mg2Si and MgO progressed further during sintering of the materials. The results showed that the strengthening mechanisms were dependent on dispersion hardening of fine Mg2Si and MgO particulates dispersed homogeneously in the matrix.

  13. Growth of MgO on multi-layered graphene and Mg in PVA matrix

    Marka, Sandeep K.; Mohiddon, Md. Ahamad; Prasad, Muvva D.; Srikanth, Vadali V. S. S.


    An easy and low temperature in-situ growth of MgO micro-rods on multi-layered graphene (MLG) in poly vinyl alcohol (PVA) matrix is elucidated. MLG decked with nanosized fragments of MgO and PVA are used as the starting materials to form MgO micro-rods (width = ∼1 μm and length = ∼4 μm) and MLG filled PVA composite film. Simple solution mixing, spin coating and simple drying processes are used to obtain the PVA composite. The growth mechanism of MgO micro-rods and the role of PVA in the growth of MgO micro-rods are explained on the basis of the observed morphological, structural and phase characteristics and a further controlled synthesis experiment, respectively.

  14. Hydrothermal Synthesis and Properties of Open-Framework Mixed-valence Iron Phosphates FeIII2FeII1.5(PO4)3 with Three-dimensional Structure

    DUAN,Li-Ying(段丽颖); LIU,Fu-Chen(刘福臣); WANG,En-Bo(王恩波); LI,Yang-Guang(李阳光); HU,Chang-Wen(胡长文); XU,Lin(许林)


    The open-framework iron phosphate FeIII2FeII1.5(PO4)3 was hydrothermally synthesized and characterized by elemental analysis, IR, EPR, XPS and single crystal X-ray diffraction analysis. The title compound crystallized in the triclinic, space group P1 with a=0.64724(4) nm, b=0.79651(6) nm, c=0.94229(5) nm, α=104.447(2)°, β=108.919(4)°, γ=101.741(4)°, V=0.42302(5) nm3, Z=1 and R1 (wR2)=0.0307 (0.0793). Crystal data were collected on a Rigaku R-AXIS RAPID IP diffractometer with Mo Kα (λ=0.071073 nm) at 293(2) K in the range of 2.43°<θ<27.46°. The structure of 1 consists of 19 non-hydrogen atoms including three and a half crystallographically independent Fe and three P atoms. Fe(1) connects its symmetrical Fe(1A) through bridging oxygen forming a dimer and the dimers are connected by Fe(4) forming an infinite staircase-like chain. Fe(2) and Fe(3) connect the infinite chains into a layer with bridging oxygen. Layers are interconnected via Fe(4) forming the six-membered and eight-membered channel systems.

  15. Importance of reduced sulfur for the equilibrium chemistry and kinetics of Fe(II), Co(II) and Ni(II) supplemented to semi-continuous stirred tank biogas reactors fed with stillage.

    Shakeri Yekta, Sepehr; Lindmark, Amanda; Skyllberg, Ulf; Danielsson, Asa; Svensson, Bo H


    The objective of the present study was to assess major chemical reactions and chemical forms contributing to solubility and speciation of Fe(II), Co(II), and Ni(II) during anaerobic digestion of sulfur (S)-rich stillage in semi-continuous stirred tank biogas reactors (SCSTR). These metals are essential supplements for efficient and stable performance of stillage-fed SCSTR. In particular, the influence of reduced inorganic and organic S species on kinetics and thermodynamics of the metals and their partitioning between aqueous and solid phases were investigated. Solid phase S speciation was determined by use of S K-edge X-ray absorption near-edge spectroscopy. Results demonstrated that the solubility and speciation of supplemented Fe were controlled by precipitation of FeS(s) and formation of the aqueous complexes of Fe-sulfide and Fe-thiol. The relatively high solubility of Co (∼ 20% of total Co content) was attributed to the formation of compounds other than Co-sulfide and Co-thiol, presumably of microbial origin. Nickel had lower solubility than Co and its speciation was regulated by interactions with FeS(s) (e.g. co-precipitation, adsorption, and ion substitution) in addition to precipitation/dissolution of discrete NiS(s) phase and formation of aqueous Ni-sulfide complexes. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Kilogram-scale synthesis of iron oxy-hydroxides with improved arsenic removal capacity: study of Fe(II) oxidation--precipitation parameters.

    Tresintsi, Sofia; Simeonidis, Konstantinos; Vourlias, George; Stavropoulos, George; Mitrakas, Manassis


    Various iron oxy-hydroxides were synthesized in a continuous flow kilogram-scale production reactor through the precipitation of FeSO(4) and FeCl(2) in the pH range 3-12 under intense oxidative conditions to serve as arsenic adsorbents. The selection of the optimum adsorbent and the corresponding conditions of the synthesis was based not only on its maximum As(III) and As(V) adsorption capacity but also on its potential efficiency to achieve the arsenic health regulation limit in NSF challenge water. As a result, the adsorbent prepared at pH 4, which consists of schwertmannite, was selected because it exhibited the highest adsorption capacity of 13 μg As(V)/mg, while maintaining a residual arsenic concentration of 10 μg/L at an equilibrium pH 7. The high surface charge and the activation of an ion-exchange mechanism between SO(4)(2-) adsorbed in the Stern layer and arsenate ions were found to significantly contribute to the increased adsorption capacity. Adsorption capacity values observed in rapid scale column experiments illustrate the improved efficiency of the qualified adsorbent compared to the common commercial arsenic adsorbents.

  17. Synthesis, characterization and performance in arsenic removal of iron-doped activated carbons prepared by impregnation with Fe(III) and Fe(II).

    Muñiz, G; Fierro, V; Celzard, A; Furdin, G; Gonzalez-Sánchez, G; Ballinas, M L


    Arsenic removal from natural well water from the state of Chihuahua (Mexico) is investigated by adsorption using a commercial activated carbon (AC). The latter is used as such, or after oxidation by several chemicals in aqueous solution: nitric acid, hydrogen peroxide, and ammonium persulphate. Raw and oxidised activated carbons are fully characterised (elementary analysis, surface chemistry, pore texture parameters, pH(ZC), and TEM observation). Adsorption of As is measured in the aforementioned water, containing ca. 300 ppb of arsenic: removal of As is poor with the raw AC, and only the most oxidised carbons exhibit higher performances. By contrast, iron-doped ACs are much more efficient for that purpose, though their As uptake strongly depends on their preparation conditions: a number of samples were synthesised by impregnation of raw and oxidised ACs with HCl aqueous solutions of either FeCl(3) or FeCl(2) at various concentrations and various pH. It is shown that iron(II) chloride is better for obtaining high iron contents in the resultant ACs (up to 8.34 wt.%), leading to high As uptake, close to 0.036 mg As/g C. In these conditions, 100% of the As initially present in the natural well water is removed, as soon as the Fe content of the adsorbent is higher than 2 wt.%.

  18. Synthesis, characterization and performance in arsenic removal of iron-doped activated carbons prepared by impregnation with Fe(III) and Fe(II)

    Muniz, G. [Laboratoire de Chimie du Solide Mineral, Nancy-Universite, UMR CNRS 7555, BP 239, 54506 Vandoeuvre-les Nancy (France); Facultad de Ciencias Quimicas, Universidad Autonoma de Chihuahua, Circuito Universitario S/N, Chihuahua (Mexico); Fierro, V., E-mail: [Laboratoire de Chimie du Solide Mineral, Nancy-Universite, UMR CNRS 7555, BP 239, 54506 Vandoeuvre-les Nancy (France); Celzard, A. [Laboratoire de Chimie du Solide Mineral, UMR CNRS 7555, Nancy-Universite, ENSTIB, 27 rue du Merle Blanc, BP 1041, 88051 Epinal Cedex 9 (France); Furdin, G. [Laboratoire de Chimie du Solide Mineral, Nancy-Universite, UMR CNRS 7555, BP 239, 54506 Vandoeuvre-les Nancy (France); Gonzalez-Sanchez, G. [Centro de Investigacion en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chih., 31109 Chihuahua (Mexico); Ballinas, M.L. [Facultad de Ciencias Quimicas, Universidad Autonoma de Chihuahua, Circuito Universitario S/N, Chihuahua (Mexico)


    Arsenic removal from natural well water from the state of Chihuahua (Mexico) is investigated by adsorption using a commercial activated carbon (AC). The latter is used as such, or after oxidation by several chemicals in aqueous solution: nitric acid, hydrogen peroxide, and ammonium persulphate. Raw and oxidised activated carbons are fully characterised (elementary analysis, surface chemistry, pore texture parameters, pH{sub ZC}, and TEM observation). Adsorption of As is measured in the aforementioned water, containing ca. 300 ppb of arsenic: removal of As is poor with the raw AC, and only the most oxidised carbons exhibit higher performances. By contrast, iron-doped ACs are much more efficient for that purpose, though their As uptake strongly depends on their preparation conditions: a number of samples were synthesised by impregnation of raw and oxidised ACs with HCl aqueous solutions of either FeCl{sub 3} or FeCl{sub 2} at various concentrations and various pH. It is shown that iron(II) chloride is better for obtaining high iron contents in the resultant ACs (up to 8.34 wt.%), leading to high As uptake, close to 0.036 mg As/g C. In these conditions, 100% of the As initially present in the natural well water is removed, as soon as the Fe content of the adsorbent is higher than 2 wt.%.

  19. Mg based alloys obtained by mechanical alloying

    Ordonez, S. [Univ. de Santiago de Chile (Chile). Fac. de Ingenieria; Garcia, G.; Serafini, D.; San Martin, A.


    In the present work, we studied the production of magnesium alloys, of stoichiometry 2Mg + Ni, by mechanical alloying (MA) and the behavior of the alloys under hydrogen in a Sievert`s type apparatus. The elemental powders were milled under argon atmosphere in a Spex 8000 high energy ball mill. The milled materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Only minimum amounts of the Mg{sub 2}Ni intermetallic compound was obtained after 22 h of milling time. Most of the material was sticked to the inner surface of the container as well as to the milling balls. Powders milled only for 12 hours transforms to the intermetallic at around 433 K. Effects of the MA on the hydrogen absorption kinetics were also studied. (orig.) 10 refs.

  20. Bulk amorphous Mg-based alloys

    Pryds, Nini


    The present paper describes the preparation and properties of bulk amorphous quarternary Mg-based alloys and the influence of additional elements on the ability of the alloy to form bulk amorphous. The main goal is to find a Mg-based alloy system which shows both high strength to weight ratio...... and a low glass transition temperature. The alloys were prepared by using a relatively simple technique, i.e. rapid cooling of the melt in a copper wedge mould. The essential structural changes that are achieved by going from the amorphous to the crystalline state through the supercooled liquid state...... are discussed in this paper. On the basis of these measurements phase diagrams of the different systems were constructed. Finally, it is demonstrated that when pressing the bulk amorphous alloy onto a metallic dies at temperatures within the supercooled liquid region, the alloy faithfully replicates the surface...

  1. Novel alginate based coatings on Mg alloys

    Sangeetha, K.; Roy, Abhijit [Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Singh, Satish [Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Lee, Boeun [Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Kumta, Prashant N., E-mail: [Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Center for Complex Engineered Multifunctional Materials, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261 (United States)


    Coatings on yttrium doped magnesium (Mg4Y) alloy substrates were prepared using alginate hydrogels by dip coating method to improve the surface bioactive properties of the substrate. Furthermore, composite coatings containing nano-sized calcium phosphate corresponding to hydroxyapatite (HA) phase entrapped within alginate hydrogel were also synthesized on the Mg4Y substrates. Surface characteristics of these coated substrates have been investigated using FTIR-ATR, SEM and EDS. The results show that the coatings with alginate alone are not stable in vitro; however, incorporation of NanoCaPs slightly improves the stability of these coatings. In addition, these composite coatings showed cell attachments with fibronectin incorporation. These results indicate that alginate hydrogels have the potential to be used as bioactive coating materials for different biofunctional applications.

  2. Electronic structure of MgB2

    P Modak; R S Rao; B K Godwal; S K Sikka


    Results of ab initio electronic structure calculations on the compound MgB2 using the FPLAPW method employing GGA for the exchange-correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, / ratio and the bulk modulus, all of which are in excellent agreement with experiment. We obtain the mass enhancement parameter by using our calculated (F) and the experimental specific heat data. The c is found to be 24.7 K.

  3. Orientation relationships between icosahedral clusters in hexagonal MgZn2 and monoclinic Mg4Zn7 phases in Mg-Zn(-Y) alloys

    Rosalie, Julian M.; Somekawa, Hidetoshi; Singh, Alok; Mukai, Toshiji


    Intermetallic precipitates formed in heat-treated and aged Mg-Zn and Mg-Zn-Y alloys have been investigated via electron microscopy. Coarse spheroidal precipitates formed on deformation twin boundaries contained domains belonging to either the MgZn2 hexagonal Laves phase or the monoclinic Mg4Zn7 phase. Both phases are structurally related to the quasi-crystalline phase formed in Mg-Zn-Y alloys, containing icosahedrally coordinated zinc atoms arranged as a series of broad rhombohedral units. This rhombohedral arrangement was also visible in intragranular precipitates where local regions with the structures of hexagonal MgZn2 and Mg4Zn7 were found. The orientation adopted by the MgZn2 and Mg4Zn7 phases in twin-boundary and intragranular precipitates was such that the icosahedral clusters were aligned similarly. These results highlight the close structural similarities between the precipitates of the Mg-Zn-Y alloy system.

  4. Alteration of Basaltic Glass to Mg/Fe-Smectite under Acidic Conditions: A Potential Smectite Formation Mechanism on Mars

    Peretyazhko, Tanya; Sutter, Brad; Ming, Douglas W.


    phyllosilicates were examined by XRD analysis. Mineralogical changes were significant in Adirondack incubated with 10 mM MgCl2 at pH 4 and heated at 200 C. X-ray diffraction analysis revealed formation of phyllosilicate during 14 day incubation (Figure 1). Smectite was confirmed as the phyllosilicate after treatments with glycerol and KCl and heating to 550 C. The position of 02l (4.60 A) and 060 (1.54 A) diffraction bands were indicative of trioctahedral smectite such as saponite. Analysis of solution composition demonstrated that aqueous concentration of Mg decreased from 10 mM to approx.4 mM after 7 day incubation likely due to saponite formation. Smectite also formed in Adirondack incubated with 0 mM MgCl2 at pH 4 and heated at 200 C. However, diffraction peak positions of 02l (4.52 A) and 060 (1.51 A) suggested formation of dioctahedral nontronite. The 100degC Mg and Fe(II) treated basaltic glass experiments are ongoing and results will be presented.

  5. Interstitial Fe in MgO

    Mølholt, T E; Gunnlaugsson, H P; Svane, A; Masenda, H; Naidoo, D; Bharuth-Ram, K; Fanciulli, M; Gislason, H P; Johnston, K; Langouche, G; Ólafsson, S; Sielemann, R; Weyer, G


    Isolated Fe-57 atoms were studied in MgO single-crystals by emission Mossbauer spectroscopy following implantation of Mn-57 decaying to Fe-57. Four Mossbauer spectral components were found corresponding to different Fe lattice positions and/or charge states. Two components represent Fe atoms substituting Mg as Fe2+ and Fe3+, respectively; a third component is due to Fe in a strongly implantation-induced disturbed region. The fourth component, which is the focus of this paper, can be assigned to Fe at an interstitial site. Comparison of its measured isomer shift with ab initio calculations suggests that the interstitial Fe is located on, or close to, the face of the rock-salt MgO structure. To harmonize such an assignment with the measured near-zero quadrupole interaction a local motion process (cage motion) of the Fe has to be stipulated. The relation of such a local motion as a starting point for long range diffusion is discussed.

  6. Comparison of hydrogen storage properties of pure Mg and milled pure Mg

    Myoung Youp Song; Young Jun Kwak; Seong Ho Lee; Hye Ryoung Park


    Hydrogen storage properties of pure Mg were studied at 593 K under 12 bar H2. In order to increase the hydriding and dehydriding rates, pure Mg was ground under hydrogen atmosphere (reactive mechanical grinding, RMG) and its hydrogen storage properties were subsequently investigated. Pure Mg absorbed hydrogen very slowly. At the number of cycles () of 1, pure Mg absorbed 0.05 wt% H for 5 min, 0.08 wt% H for 10 min and 0.29 wt% H for 60 min at 593 K under 12 bar H2. Activation was completed at the fifth cycle. At = 6, pure Mg absorbed 1.76 wt% H for 5 min, 2.17 wt% H for 10 min and 3.40 wt% H for 60 min. The activation of pure Mg after RMG was completed at the sixth cycle. At = 7, pure Mg after RMG absorbed 2.57 wt% H for 5 min, 3.21 wt% H for 10 min and 4.15 wt% H for 60 min.

  7. Midazolam 12 mg is moderately counteracted by 250 mg caffeine in man.

    Mattila, M J; Vainio, P; Nurminen, M L; Vanakoski, J; Seppälä, T


    Caffeine (Caf) counteracts various effects of benzodiazepines (BZDs). Since the effects of zolpidem, a short-acting atypical GABA(A)-BZD agonist, were not antagonized by Caf, we studied an interaction between Caf and midazolam (Mid) in healthy volunteers. In Study 1, 108 healthy students divided to 6 parallel groups were given Mid 12 mg (capsule) and Caf 125 and 250 mg (in decaffeinated coffee), alone and in combinations in the double-blind placebo-controlled manner. Objective and subjective tests were done before and at 45 and 90 min after intake. Ranked delta-values (changes from baseline) were analyzed by one-way contrast ANOVA and Scheffe's tests. In Study 2, six healthy subjects took Mid 15 mg (tablet) with and without Caf 300 mg. The dynamic effects were analyzed as in Study 1 and the plasma concentrations were assayed. In Study 1, learn effects after placebo (ad + 15%) were seen for letter cancellation and digit symbol substitution tests. Midazolam alone significantly (p 0.05). In conclusion, in a parallel group study, sedative effects of Mid 12 mg were only moderately antagonized by Caf 250 mg but not by Caf 125 mg. In a cross-over study, a weak interaction was found subjectively but not in objective measures.

  8. Zolpidem 10 mg given at daytime is not antagonized by 300 mg caffeine in man.

    Mattila, M J; Nurminen, M L; Vainio, P; Vanakoski, J


    Caffeine counteracts various effects of traditional benzodiazepines (BZDs). As zolpidem, a short-acting hypnotic, is an atypical GABAA-BZD agonist, we investigated when caffeine would counteract the effects of zolpidem as well. In daytime study I, zolpidem 10 mg (capsule) and caffeine 150 or 300 mg (in decaffeinated coffee) were given, alone and in combinations, to parallel groups (n = 15-17) of healthy students in double-blind and placebo-controlled manner. Objective and subjective tests were done before and 45 min and 90 min after intake. Ranked delta values (changes from baseline) were analysed by one-way contrast ANOVA and Scheffe's tests. In daytime study II, four healthy subjects took zolpidem 10 mg alone, and together with blinded caffeine 250 mg or (at -45 min) erythromycin 750 mg. Objective and subjective effects were measured and plasma zolpidem concentrations assayed at baseline and 45 min and 90 min after zolpidem intake. In study I, practice effects after placebo (ad + 30%) were seen for letter cancellation and digit symbol substitution but not for flicker fusion tests. Zolpidem alone significantly impaired (P effects of zolpidem and either dose of caffeine matched those measured after zolpidem alone. Zolpidem + caffeine 300 mg was not stronger than zolpidem + caffeine 150 mg in impairing immediate memory and causing subjective sedation. In study II, zolpidem caused objective and subjective sedation; neither caffeine nor erythromycin modulated the effects of zolpidem or plasma zolpidem concentrations. The sedative effects of 10 mg of zolpidem are not antagonized by 150-300 mg of caffeine in pharmacodynamic or pharmacokinetic terms.

  9. Electronic structure of ferromagnet-insulator interfaces: Fe/MgO and Co/MgO

    Mueller, M.


    In this thesis the electronic structure of Fe/MgO{sub x} and Co/MgO{sub x} ferromagnet-insulator interfaces, representing material systems which are widely used in magnetic tunnel junctions, is studied by means of spin- and angle-resolved photoemission spectroscopy. The photoemission studies focus particularly on the response of the ferromagnetic electronic system in contact with MgO of varying stoichiometries, as this reflects the mechanisms of metal-oxide bonding at real ferromagnet-insulator interfaces. The correlation between chemical bonding and electronic structure formation is analyzed by combining information from core- and valence-band photoemission spectroscopy. The spectral features are compared to band structure calculations, which are performed using the SPR-KKR method. The Fe/MgO and Co/MgO systems are prepared by molecular beam epitaxy under ultrahigh vacuum conditions on well-defined (4 x 6) GaAs(001) substrates. A structural analysis by means of low-energy electron diffraction (LEED) reveals their body-centered cubic crystalline structure, whereas the chemical characterization by Auger electron spectroscopy is used to quantify the chemical environment at the sample surfaces. The magnetic analysis, using the magneto-optical Kerr effect, reveals the uniaxial anisotropy of the ferromagnetic layers. A crucial parameter is given by the MgO degree of oxidation, which is addressed by means of core-level spectroscopy and quantified by suitable fitting procedures of the Mg 2p core level. The results of the photoemission experiments show, that the electronic structure of the Fe/MgO and Co/MgO ferromagnet/insulator interfaces and, consequently, the interfacial spin polarization are sensitively controlled by the interface chemistry. In particular, three distinct scenarios are identified: the nearly stoichiometric, the oxygen-deficient and the over-oxidized ferromagnet/MgO interface. Each case is defined by innate characteristics of the electronic structure at

  10. FeII/MgII, [Fe/Mg] Ratios and High-z Quasars

    Korista, K; Corbin, M R; Freudling, W; Korista, Kirk; Kodituwakku, Nalaka; Corbin, Michael; Freudling, Wolfram


    It has been suggested in the literature that the (Fe/alpha) abundance ratio may be used as a chronometer, due to a delay in this ratio reaching its solar value as predicted by galactic chemical evolution models. Using grids of photoionization models along a sequence of the (Fe/Mg) abundance ratio vs.\\ metallicity with time in a giant elliptical starburst scenario, we investigate the relationship between the (Fe/Mg) abundance ratio and the FeII/MgII emission line flux ratio under the assumption that these lines originate in photoionized clouds within the broad emission line regions of quasars.

  11. Lipid peroxidation in the liver of rats treated with V and/or Mg in drinking water.

    Scibior, Agnieszka; Zaporowska, Halina; Niedźwiecka, Irmina


    revealed that the changes in LPO induced by in vitro treatment of liver supernatants with exogenous Fe or V or Mg (600, 800 and 1000 microm) were a consequence of independent action of those metals and they also resulted from the interactions between Fe(exog) and V(end) and between V(end) and V(exog). In conclusion, V consumed by the rats with drinking water at a dose of 12 mg V kg(-1) body weight per 24 h for 12 weeks decreased TAS and enhanced spontaneous LPO in the hepatic tissue, which confirms its pro-oxidant potential, was also found in in vitro conditions with regard to LPO. Mg administered to rats in combination with V, at the concentration used, neither reduced nor intensified the basal LPO, compared with V-only treated animals; however, its stimulating effect on LPO was revealed in in vitro conditions, which requires further study.

  12. A first-principles study of the thermodynamic and electronic properties of Mg and MgH2 nanowires.

    Wu, Xinxing; Zhang, Ruiqi; Yang, Jinlong


    In this article, we studied the thermodynamic and electronic properties of Mg and MgH2 nanowires with different diameters, and elucidated why MgH2 nanowires are good hydrogen storage materials through first-principles calculations. Previous experiments have shown that the orientation relationship between Mg and MgH2 nanowires is the Mg[0001] direction parallel to the MgH2[110] direction. In our calculations, Mg nanowires oriented along the [0001] direction and MgH2 nanowires oriented along the [110] direction were built from bulk Mg and MgH2 crystals, respectively. We found that as the diameters of Mg and MgH2 nanowires decrease, Mg and MgH2 nanowires become more unstable, and the hydrogen desorption energies and temperatures of MgH2 nanowires decrease. That is, the thinner the MgH2 nanowires get, the more dramatically hydrogen desorption temperatures (Td) will decrease. Meanwhile, we also found that when the diameters of MgH2 nanowires are larger than 1.94 nm, the Td almost maintain the same value at about 440 K, only about 40 K lower than that of bulk MgH2 crystal; if the diameters are less than 1.94 nm, the Td reduce very quickly. In particular, compared with bulk MgH2 crystal, the Td of the thinnest MgH2 nanowire with a diameter of 0.63 nm can be reduced by 164 K. In addition, the electronic structure calculations showed that Mg nanowires are metals, while MgH2 nanowires are semiconductors. In particular, our results showed that the electronic structures of MgH2 nanowires are influenced by the surface effect and quantum size effect. That is to say, the band gaps of MgH2 nanowires are controlled by surface electronic states and the size of MgH2 nanowires.

  13. Microstructural evolution of Mg-7Al-2Sn Mg alloy during multi-directional impact forging

    M.G. Jiang


    Full Text Available Multi-directional impact forging (MDIF was applied to a Mg-7Al-2Sn (wt.% Mg alloy to investigate its effect on the microstructural evolution. MDIF process exhibited high grain refinement efficiency. After MDIF 200 passes, the grain size drastically decreased to 20 µm from the initial coarse grains of ~500 µm due to dynamic recrystallization (DRX. Meanwhile, original grain boundaries remained during MDIF and large numbers of fine spherical β-Mg17Al12 particles dynamically precipitated along the original grain boundaries with high Al concentration, acting as effective pinning obstacles for the suppression of DRXed grain growth. Besides, micro-cracks nucleated during MDIF and propagated along the interface between the remained globular or cubic Al-Mn particles and Mg matrix.

  14. Proton resonance elastic scattering of $^{30}$Mg for single particle structure of $^{31}$Mg

    The single particle structure of $^{31}$Mg, which is located in the so-called “island of inversion”, will be studied through measuring Isobaric Analog Resonances (IARs) of bound states of $^{31}$Mg. They are located in the high excitation energy of $^{31}$Al. We are going to determine the spectroscopic factors and angular momenta of the parent states by measuring the excitation function of the proton resonance elastic scattering around 0 degrees in the laboratory frame with around 3 MeV/nucleon $^{30}$Mg beam. The present study will reveal the shell evolution around $^{32}$Mg. In addition, the spectroscopic factor of the (7/2)$^{−}$ state which was not yet determined experimentally, may allow one to study the shape coexistence in this nucleus.

  15. Thermodynamic Property Study of Nanostructured Mg-H, Mg-Ni-H, and Mg-Cu-H Systems by High Pressure DSC Method

    Huaiyu Shao


    Full Text Available Mg, Ni, and Cu nanoparticles were synthesized by hydrogen plasma metal reaction method. Preparation of Mg2Ni and Mg2Cu alloys from these Mg, Ni, and Cu nanoparticles has been successfully achieved in convenient conditions. High pressure differential scanning calorimetry (DSC technique in hydrogen atmosphere was applied to study the synthesis and thermodynamic properties of the hydrogen absorption/desorption processes of nanostructured Mg-H, Mg-Ni-H, and Mg-Cu-H systems. Van’t Hoff equation of Mg-Ni-H system as well as formation enthalpy and entropy of Mg2NiH4 was obtained by high pressure DSC method. The results agree with the ones by pressure-composition isotherm (PCT methods in our previous work and the ones in literature.

  16. Magnesium homeostasis in cardiac myocytes of Mg-deficient rats.

    Michiko Tashiro

    Full Text Available To study possible modulation of Mg(2+ transport in low Mg(2+ conditions, we fed either a Mg-deficient diet or a Mg-containing diet (control to Wistar rats for 1-6 weeks. Total Mg concentrations in serum and cardiac ventricular tissues were measured by atomic absorption spectroscopy. Intracellular free Mg(2+ concentration ([Mg(2+]i of ventricular myocytes was measured with the fluorescent indicator furaptra. Mg(2+ transport rates, rates of Mg(2+ influx and Mg(2+ efflux, were estimated from the rates of change in [Mg(2+]i during Mg loading/depletion and recovery procedures. In Mg-deficient rats, the serum total Mg concentration (0.29±0.026 mM was significantly lower than in control rats (0.86±0.072 mM after 4-6 weeks of Mg deficiency. However, neither total Mg concentration in ventricular tissues nor [Mg(2+]i of ventricular myocytes was significantly different between Mg-deficient rats and control rats. The rates of Mg(2+ influx and efflux were not significantly different in both groups. In addition, quantitative RT-PCR revealed that Mg deficiency did not substantially change mRNA expression levels of known Mg(2+ channels/transporters (TRPM6, TRPM7, MagT1, SLC41A1 and ACDP2 in heart and kidney tissues. These results suggest that [Mg(2+]i as well as the total Mg content of cardiac myocytes, was well maintained even under chronic hypomagnesemia without persistent modulation in function and expression of major Mg(2+ channels/transporters in the heart.

  17. Porous Ceramic Composite ZrO2(MgO)-MgO for Osteoimplantology

    Buyakov, A. S.; Kulkov, S. N.


    Pore and crystalline structure, biocompatibility of ceramic composite ZrO2(MgO)-MgO were studied. The main mechanical characteristics were determined and it has been shown that compression strength directly depends on microstresses obtained from X-ray data. In-vitro studies of mesenchymal stromal stem cells (MMSC), cultivated on material surface are shown that cell proliferation and differentiation of MMSC goes throw osteogenic type.

  18. Flunarizine in migraine prophylaxis: efficacy and tolerability of 5 mg and 10 mg dose levels.

    Centonze, V; Magrone, D; Vino, M; Caporaletti, P; Attolini, E; Campanale, G; Albano, O


    The use of flunarizine, a drug which has proven its efficacy in migraine, is often associated with important side effects. The aim of this paper has been to check their incidence at different dose levels (5 mg vs 10 mg). Our data confirm the occurrence of important side effects (in particular weight gain); on the other hand, they emphasize the dose-dependency of the side effects.

  19. Laser cooling of MgCl and MgBr in theoretical approach

    Wan, Mingjie; Shao, Juxiang; Huang, Duohui; Yang, Junsheng; Cao, Qilong; Jin, Chengguo; Wang, Fanhou, E-mail: [Computational Physics Key Laboratory of Sichuan Province, Yibin University, Yibin 644007 (China); Gao, Yufeng [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China)


    Ab initio calculations for three low-lying electronic states (X{sup 2}Σ{sup +}, A{sup 2}Π, and 2{sup 2}Π) of MgCl and MgBr molecules, including spin-orbit coupling, are performed using multi-reference configuration interaction plus Davidson correction method. The calculations involve all-electronic basis sets and Douglas–Kroll scalar relativistic correction. Spectroscopic parameters well agree with available theoretical and experimental data. Highly diagonally distributed Franck-Condon factors f{sub 00} for A{sup 2}Π{sub 3/2,1/2} (υ′ = 0) → X{sup 2}Σ{sup +}{sub 1/2} (υ″ = 0) are determined for both MgCl and MgBr molecules. Suitable radiative lifetimes τ of A{sup 2}Π{sub 3/2,1/2} (υ′ = 0) states for rapid laser cooling are also obtained. The proposed laser drives A{sup 2}Π{sub 3/2} (υ′ = 0) → X{sup 2}Σ{sup +}{sub 1/2} (υ″ = 0) transition by using three wavelengths (main pump laser λ{sub 00}; two repumping lasers λ{sub 10} and λ{sub 21}). These results indicate the probability of laser cooling MgCl and MgBr molecules.

  20. Fabrication of all-MgB Josephson junctions using MgO insulator layer

    Oba, T. [Graduate School of Engineering, Iwate University, 4-3-5, Ueda, Morioka 020-8551 (Japan); Goto, S. [Lightom, 95-2 Sugo, Takizawa 020-0173 (Japan); Sasaki, S.; Nakanishi, Y.; Fujino, T. [Graduate School of Engineering, Iwate University, 4-3-5, Ueda, Morioka 020-8551 (Japan); Harada, Y. [JST Satellite Iwate, Japan Science and Technology Agency, 3-35-2 Iiokashinden, Morioka, Iwate 020-0852 (Japan); Nakamura, M. [Graduate School of Engineering, Iwate University, 4-3-5, Ueda, Morioka 020-8551 (Japan); Saito, A. [Department of Electrical Engineering, Yamagata University, 4-3-16, Jonan, Yonezawa, Yamagata 992-8510 (Japan); Yoshizawa, M. [Graduate School of Engineering, Iwate University, 4-3-5, Ueda, Morioka 020-8551 (Japan)], E-mail:


    We report on the fabrication and properties of all-MgB{sub 2} tunnel junctions with an MgO barrier. Superconductor-insulator-superconductor (SIS) junctions were fabricated on C-plane sapphire substrates. MgB{sub 2} films were grown in an ultra-high vacuum in the 10{sup -9} Torr range. The MgO insulating layer was evaporated using an electron-beam gun. SIS junctions of 30 {mu}m in diameter were fabricated by standard photolithography and Ar ion milling techniques. The critical temperature (T{sub C}) of the lower MgB{sub 2} layer after the SIS junction fabrication process was 36.7 K, which remained the same as that of the bare MgB{sub 2} film. We observed tunneling behavior in the current-voltage (I-V) characteristics of the present junctions. A superconducting gap was clearly observed at around 2.7 mV (=2{delta})

  1. Preference for rizatriptan 10-mg wafer vs. eletriptan 40-mg tablet for acute treatment of migraine.

    Láinez, M J A; Evers, S; Kinge, E; Allais, G; Allen, C; Rao, N A; Massaad, R; Lis, K


    Preference is a composite, patient-oriented endpoint incorporating efficacy, tolerability, formulation, and convenience of medications. The objective of this study was to compare patient preference for rizatriptan 10-mg wafer vs. eletriptan 40-mg tablet for acute treatment of migraine. In this multicentre, open-label, two-period, crossover study, out-patients were randomly assigned to treat the first of two moderate to severe migraines with rizatriptan or eletriptan and the second with the alternate therapy. Patients completed diary assessments at baseline and up to 24 h after taking study medication. At the last visit, patients completed a psychometrically validated preference questionnaire. A total of 372 patients (mean age 38 years, 85% female) treated two migraine attacks, and 342 patients (92%) expressed a preference for treatment. Significantly more (P rizatriptan 10-mg wafer [61.1%; 95% confidence interval (CI) 55.7, 66.3] to eletriptan 40-mg tablet (38.9%; 95% CI 33.7, 44.3). The most common reason given for preference of either treatment was speed of headache relief. At 2 h, 80% and 69% of patients reported that rizatriptan and eletriptan, respectively, was convenient or very convenient to take (mean convenience score 1.99 vs. 2.31, respectively; P rizatriptan 10-mg wafer to the eletriptan 40-mg tablet for acute treatment of migraine. The single most important reason for preference was speed of relief, consistent with results from previous preference studies.

  2. Laser cooling of MgCl and MgBr in theoretical approach.

    Wan, Mingjie; Shao, Juxiang; Gao, Yufeng; Huang, Duohui; Yang, Junsheng; Cao, Qilong; Jin, Chengguo; Wang, Fanhou


    Ab initio calculations for three low-lying electronic states (X(2)Σ(+), A(2)Π, and 2(2)Π) of MgCl and MgBr molecules, including spin-orbit coupling, are performed using multi-reference configuration interaction plus Davidson correction method. The calculations involve all-electronic basis sets and Douglas-Kroll scalar relativistic correction. Spectroscopic parameters well agree with available theoretical and experimental data. Highly diagonally distributed Franck-Condon factors f00 for A(2)Π3/2,1/2 (υ' = 0) → X(2)Σ(+) 1/2 (υ″ = 0) are determined for both MgCl and MgBr molecules. Suitable radiative lifetimes τ of A(2)Π3/2,1/2 (υ' = 0) states for rapid laser cooling are also obtained. The proposed laser drives A(2)Π3/2 (υ' = 0) → X(2)Σ(+) 1/2 (υ″ = 0) transition by using three wavelengths (main pump laser λ00; two repumping lasers λ10 and λ21). These results indicate the probability of laser cooling MgCl and MgBr molecules.

  3. Raman scattering study of α-MgH2 and γ-MgH2

    Kuzovnikov, M. A.; Efimchenko, V. S.; Filatov, E. V.; Maksimov, A. A.; Tartakovskii, I. I.; Ramirez-Cuesta, A. J.


    Two modifications of MgH2 have been studied by Raman spectroscopy: α-MgH2 with the P42/mnm space group and γ-MgH2 with the Pbcn space group. The latter was prepared from α-MgH2 by exposing it to a pressure of 5.6 GPa at 470 °C for 1.5 h. A comparison of the experimental spectra with ab-initio calculations allowed identification of a few phonon modes. A broad feature in the Raman spectrum of α-MgH2 in the range 1470-1790 cm-1 was identified as the B2g phonon mode. A Raman spectrum of γ-MgH2 consists of five discernible peaks at 186 cm-1, 313 cm-1, 509 cm-1, 660 cm-1, 706 cm-1 and of three broad features in the regions 890-980 cm-1, 1010-1220 cm-1 and 1240-1430 cm-1. The peaks are identified as the 1Ag (186 cm-1), 3B3g (509 cm-1), 2Ag (660 cm-1) and 3B1g (706 cm-1) phonon modes.

  4. Dehydrogenation kinetics of air-exposed MgH2/Mg2Cu and MgH2/MgCu2 studied with in situ X-ray powder diffraction

    Andreasen, A.; Sørensen, M.B.; Burkarl, R.


    The dehydrogenation kinetics of air exposed samples of MgH2/Mg2Cu and MgH2/MgCu2 have been studied with in situ time resolved X-ray powder diffraction. The X-ray setup enabled the recording of full diffraction patterns within 150 s, thereby allowing the study of structural changes combined...... sample was found to be 108 kJ/mol and 160 kJ/mol, respectively. Furthermore, substantially improved dehydrogenation kinetics of MgH2 and resistance towards oxidation of Mg due to the presence of Mg2Cu/MgCu2 are discussed in relation to previous work....

  5. Two Proton Knockout from ^32Mg

    Fallon, P.; Rodriguez-Vieitez, E.; Macchiavelli, A. O.; Clark, R. M.; Lee, I.-Y.; Wiedeking, M.; Gade, A.; Adrich, P.; Bazin, D.; Bowen, M.; Campbell, C. M.; Cook, J. M.; Dinca, D. C.; Glasmacher, T.; McDaniel, S.; Mueller, W. F.; Ratiewicz, A. F.; Siwek, K.; Terry, J. R.; Wiesshaar, D.; Yoneda, K.; Brown, B. A.; Otsuka, T.; Tostevin, J. A.; Utsuno, Y.


    We present data and calculations on the near-dripline nucleus ^30Ne. Gamma-ray decays from excited states as well as inclusive and exclusive cross-sections were measured in the ^9Be(^32Mg,^30Ne γ)X two-proton knockout reaction at incident beam energies of 99.7 and 86.7 MeV/A. The measured inclusive cross section sigma = 0.22(4)mb is suppressed compared to calculation and is indicative of a reduced overlap of initial and final state wavefunctions. We interpret this reduction as a result of large 4p4h intruder components present in ^30Ne, but not ^32Mg. Large 4p4h amplitudes are predicted to generate increased T=1 paring strengths and to help stabilize the heavier fluorine isotopes against neutron decay. A new gamma-ray transition at 1443 keV is assigned to the decay of the 4^+ state based on the spin dependent sigma for 2 proton knockout from the (d5/2)^4 configuration.

  6. Materials science of Mg-Ni-based new hydrides

    Orimo, S.; Fujii, H. [Hiroshima Univ. (Japan). Faculty of Integrated Arts and Sciences


    One of the advantageous functional properties of Mg alloys (or compounds) is to exhibit the reversible hydriding reaction. In this paper, we present our systematic studies regarding the relationship between nanometer- or atomistic-scale structures and the specific hydriding properties of the Mg-Ni binary system, such as(1) nanostructured (n)-Mg{sub 2}Ni, (2) a mixture of n-Mg{sub 2}Ni and amorphous (a)-MgNi,(3) pure a-MgNi, and(4) n-MgNi{sub 2}. Further studies on(5) an a-MgNi-based system for clarifying the effect of the short-range ordering on the structural and hydriding properties and(6) a MgNi{sub 2}-based system for synthesizing the new Laves phase structure are also presented. The materials science of Mg-Ni-based new hydrides will provide indispensable knowledge for practically developing the Mg alloys as hydrogen-storage materials. (orig.)

  7. Factors Influencing MgO Content of RE-Mg Nodularizing Alloy%REMg球化剂中MgO含量的影响因素

    杨宇鹏; 肖勇


    The effect of Mg in nodularizing alloy was introduced.When the total content of Mg was constant,the formation of MgO reduced the content of the effective Mg that would influence the nodularizing capability of the nodualrizing alloy.The source of MgO in nodularizing alloy was analyzed as follows:the MgO formed during the melting process of the nodularizing alloy and the MgO formed during the analysis sample preparing process.It was pointed out after analyzing two cases:(1) the MgO content of nodularizing alloy is the main factor influencing its nodularzing capability,therefore the MgO content should be reduced by improving its melting process; (2)In order to ensure the veracity of MgO content test it's necessary to use correct sample preparing method.%介绍了Mg在球化剂中的作用.当w(Mg总)一定时,MgO的生成降低了w(Mg有效)的含量,影响到球化剂的球化能力.分析了球化剂中MgO的来源:球化剂熔炼过程中产生MgO、在制取分析样品过程中产生MgO.通过2个案例的分析,指出:(1)球化剂中MgO含量的高低是影响其球化能力的主要因素,应通过改进熔炼工艺来降低w(MgO)量;(2)为确保球化剂中w(MgO)量检测的准确性,应采用正确的样品制备方法.

  8. Comportamento do ácido fítico na presença de Fe(II e Fe(III Behaviour of phytic acid in the presence of iron(II and iron(III

    Hanna Raquel Quirrenbach


    Full Text Available O ácido fítico, dependendo do valor de pH, apresenta alto potencial quelante, complexando íons metálicos, inibindo, assim, a produção de espécies reativas de oxigênio, responsáveis pela destruição oxidativa em sistemas biológicos. Esse potencial quelante tem fundamentado diversos estudos aplicados à ação antioxidante em produtos alimentícios. O objetivo deste trabalho foi estudar o grau de interação do ácido fítico com os íons metálicos Fe(II e Fe(III, de importância biológica, em condições próximas às fisiológicas, e a estabilidade destes complexos. Titulações potenciométricas foram conduzidas para determinar as constantes de formação dos complexos ácido fítico-Fe(II e ácido fítico-Fe(III em solução aquosa, atmosfera inerte, força iônica 0,100 mol.L-1 de cloreto de potássio e à temperatura de 36 ± 0,1 ºC. Estudos espectroscópicos na região do UV-Vis foram realizados para acompanhar a formação dos complexos em solução. Os complexos ácido fítico-Fe(II e ácido fítico-Fe(III foram sintetizados e caracterizados por espectroscopia de absorção na região do infravermelho e por estudos termoanalíticos. Os resultados do conjunto de técnicas utilizadas evidenciaram, tanto em solução como no estado sólido, a presença dos íons metálicos coordenados ao ácido fítico.Depending on the pH value, phytic acid presents high chelating potential bonding metallic ions thus inhibiting the production of reactivated oxygen species, which are responsible for the oxidative destruction in biological systems. Such chelating potential has been the basis of several studies on the antioxidant action in food products. The objective of this work was to study the degree of interaction of the phytic acid with the metallic ions Fe(II and Fe(III, of biological importance, in near-physiological conditions and the stability of these complexes. Potentiometric titrations were applied to determine the constants of

  9. Effect of Mg and C contents in MgCNi3, and structure and superconductivity of MgCNi3-xCox


    The effect of Mg and C contents on TC in MgCNi3, and structure and superconductivity of MgCNi3-xCox were studied. It is found that the excess of Mg and C in initial material mixture is favorable to improvement in TC and helps to obtain single_phase samples. For preparing MgCNi3 superconductor, the optimum composition of starting materials is MgC1.45Ni3 with excess of Mg (20 wt.%) of the stoichiometric composition. In MgCNi3-xCox system, a continuous solid solution is formed, lattice parameter decreases slightly and TC decreases obviously with increasing x. A suppression of superconductivity is observed due to the substitution of Co (Mn) for Ni. The suppression effect is smaller for the substitution of Co than that of Mn.

  10. Importance of reduced sulfur for the equilibrium chemistry and kinetics of Fe(II), Co(II) and Ni(II) supplemented to semi-continuous stirred tank biogas reactors fed with stillage

    Shakeri Yekta, Sepehr, E-mail: [Department of Thematic Studies – Water and Environmental Studies, Linköping University, SE-581 83 Linköping (Sweden); Lindmark, Amanda [Department of Thematic Studies – Water and Environmental Studies, Linköping University, SE-581 83 Linköping (Sweden); Skyllberg, Ulf [Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå (Sweden); Danielsson, Åsa; Svensson, Bo H. [Department of Thematic Studies – Water and Environmental Studies, Linköping University, SE-581 83 Linköping (Sweden)


    Highlights: • Thermodynamics and kinetics of Fe, Co and Ni added to biogas reactors were studied. • Formation of Fe-sulfide and Fe-thiol aqueous complexes controlled the Fe solubility. • Cobalt solubility was controlled by processes independent of Co-sulfide interaction. • Iron added to the biogas reactors effected the Ni speciation and solubility. - Abstract: The objective of the present study was to assess major chemical reactions and chemical forms contributing to solubility and speciation of Fe(II), Co(II), and Ni(II) during anaerobic digestion of sulfur (S)-rich stillage in semi-continuous stirred tank biogas reactors (SCSTR). These metals are essential supplements for efficient and stable performance of stillage-fed SCSTR. In particular, the influence of reduced inorganic and organic S species on kinetics and thermodynamics of the metals and their partitioning between aqueous and solid phases were investigated. Solid phase S speciation was determined by use of S K-edge X-ray absorption near-edge spectroscopy. Results demonstrated that the solubility and speciation of supplemented Fe were controlled by precipitation of FeS(s) and formation of the aqueous complexes of Fe-sulfide and Fe-thiol. The relatively high solubility of Co (∼20% of total Co content) was attributed to the formation of compounds other than Co-sulfide and Co-thiol, presumably of microbial origin. Nickel had lower solubility than Co and its speciation was regulated by interactions with FeS(s) (e.g. co-precipitation, adsorption, and ion substitution) in addition to precipitation/dissolution of discrete NiS(s) phase and formation of aqueous Ni-sulfide complexes.

  11. Synthesis, characterization and antimicrobial activity of Fe(II), Zn(II), Cd(II) and Hg(II) complexes with 2,6-bis(benzimidazol-2-yl) pyridine ligand.

    Aghatabay, Naz M; Neshat, A; Karabiyik, T; Somer, M; Haciu, D; Dülger, B


    2,6-Bis(benzimidazol-2-yl)pyridine (L) ligand and complexes [M(L)Cl(2)] and [Fe(L)(2)](ClO(4))(2) (M=Zn, Cd, Hg) have been synthesized. The geometries of the [M(L)Cl(2)] complexes were derived from theoretical calculation in DGauss/DFT level (DZVP basis set) on CACHE. The central M(II) ion is penta-coordinated and surrounded by N(3)Cl(2) environment, adopting a distorted trigonal bipyramidal geometry. The ligand is tridentate, via three nitrogen atoms to metal centre and two chloride ions lie on each side of the distorted benzimidazole ring. In the [Fe(L)(2)](ClO(4))(2) complex, the central Fe(II) ion is surrounded by two (3N) units, adopting a octahedral geometry. The elemental analysis, molecular conductivity, FT-Raman, FT-IR (mid-, far-IR), (1)H, and (13)C NMR were reported. The antimicrobial activities of the free ligand, its hydrochloride salt, and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide (DMSO) as well as the minimal inhibitory concentration (MIC) dilution method, against 10 bacteria and the results compared with that for gentamycin. Antifungal activities were reported for Candida albicans, Kluyveromyces fragilis, Rhodotorula rubra, Debaryomyces hansenii, Hanseniaspora guilliermondii, and the results were referenced against nystatin, ketaconazole, and clotrimazole antifungal agents. In most cases, the compounds tested showed broad-spectrum (Gram positive and Gram negative bacteria) activities that were either more effective than or as potent as the references. The binding of two most biologically effective compounds of zinc and mercury to calf thymus DNA has also been investigated by absorption spectra.

  12. Some new nano-sized Fe(II), Cd(II) and Zn(II) Schiff base complexes as precursor for metal oxides: Sonochemical synthesis, characterization, DNA interaction, in vitro antimicrobial and anticancer activities.

    Abdel-Rahman, Laila H; Abu-Dief, Ahmed M; El-Khatib, Rafat M; Abdel-Fatah, Shimaa Mahdy


    The complexes of Fe(II), Cd(II) and Zn(II) with Schiff base derived from 2-amino-3-hydroxypyridine and 3-methoxysalicylaldehyde have been prepared. Melting points, decomposition temperatures, Elemental analyses, TGA, conductance measurements, infrared (IR) and UV-Visible spectrophotometric studies were utilized in characterizing the compounds. The UV-Visible spectrophotometric analysis revealed 1:1 (metal-ligand) stoichiometry for the three complexes. In addition to, the prepared complexes have been used as precursors for preparing their corresponding metal oxides nanoparticles via thermal decomposition. The structures of the nano-sized complexes and their metal oxides were characterized by X-ray powder diffraction and transmittance electron microscopy. Moreover, the prepared Schiff base ligand, its complexes and their corresponding nano-sized metal oxides have been screened in vitro for their antibacterial activity against three bacteria, gram-positive (Microccus luteus) and gram-negative (Escherichia coli, Serratia marcescence) and three strains of fungus. The metal chelates were shown to possess more antimicrobial activity than the free Schiff-base chelate and their nano-sized metal oxides have the highest activity. The binding behaviors of the complexes to calf thymus DNA have been investigated by absorption spectra, viscosity mensuration and gel electrophoresis. The DNA binding constants reveal that all these complexes interact with DNA through intercalative binding mode. Furthermore, the cytotoxic activity of the prepared Schiff base complexes on human colon carcinoma cells, (HCT-116 cell line) and hepatic cellular carcinoma cells, (HepG-2) showed potent cytotoxicity effect against growth of carcinoma cells compared to the clinically used Vinblastine standard. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Synthesis, investigation and spectroscopic characterization of piroxicam ternary complexes of Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with glycine and DL-phenylalanine

    Mohamed, Gehad G.; El-Gamel, Nadia E. A.


    The ternary piroxicam (Pir; 4-hydroxy-2-methyl- N-(2-pyridyl)-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide) complexes of Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with various amino acids (AA) such as glycine (Gly) or DL-phenylalanine (PhA) were prepared and characterized by elemental analyses, molar conductance, IR, UV-Vis, magnetic moment, diffuse reflectance and X-ray powder diffraction. The UV-Vis spectra of Pir and the effect of metal chelation on the different interligand transitions are discussed in detailed manner. IR and UV-Vis spectra confirm that Pir behaves as a neutral bidentate ligand coordinated to the metal ions via the pyridine- N and carbonyl group of the amide moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its carboxylic group, in addition PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its carboxylic and amino groups. All the chelates have octahedral geometrical structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. The molar conductance data reveal that most of these chelates are non electrolytes, while Fe(III)-Pir-Gly, Co(II)-, Ni(II)-, Cu(II)- and Zn(II)-Pir-PhA cheletes were 1:1 electrolytes. X-ray powder diffraction is used as a new tool to estimate the crystallinity of chelates as well as to elucidate their geometrical structures.

  14. 3-D analysis of bacterial cell-(iron)mineral aggregates formed during Fe(II) oxidation by the nitrate-reducing Acidovorax sp. strain BoFeN1 using complementary microscopy tomography approaches.

    Schmid, G; Zeitvogel, F; Hao, L; Ingino, P; Floetenmeyer, M; Stierhof, Y-D; Schroeppel, B; Burkhardt, C J; Kappler, A; Obst, M


    The formation of cell-(iron)mineral aggregates as a consequence of bacterial iron oxidation is an environmentally widespread process with a number of implications for processes such as sorption and coprecipitation of contaminants and nutrients. Whereas the overall appearance of such aggregates is easily accessible using 2-D microscopy techniques, the 3-D and internal structure remain obscure. In this study, we examined the 3-D structure of cell-(iron)mineral aggregates formed during Fe(II) oxidation by the nitrate-reducing Acidovorax sp. strain BoFeN1 using a combination of advanced 3-D microscopy techniques. We obtained 3-D structural and chemical information on different cellular encrustation patterns at high spatial resolution (4-200 nm, depending on the method): more specifically, (1) cells free of iron minerals, (2) periplasm filled with iron minerals, (3) spike- or platelet-shaped iron mineral structures, (4) bulky structures on the cell surface, (5) extracellular iron mineral shell structures, (6) cells with iron mineral filled cytoplasm, and (7) agglomerations of extracellular globular structures. In addition to structural information, chemical nanotomography suggests a dominant role of extracellular polymeric substances (EPS) in controlling the formation of cell-(iron)mineral aggregates. Furthermore, samples in their hydrated state showed cell-(iron)mineral aggregates in pristine conditions free of preparation (i.e., drying/dehydration) artifacts. All these results were obtained using 3-D microscopy techniques such as focused ion beam (FIB)/scanning electron microscopy (SEM) tomography, transmission electron microscopy (TEM) tomography, scanning transmission (soft) X-ray microscopy (STXM) tomography, and confocal laser scanning microscopy (CLSM). It turned out that, due to the various different contrast mechanisms of the individual approaches, and due to the required sample preparation steps, only the combination of these techniques was able to provide a

  15. Synthesis, characterization and biological activities of Cu(II), Co(II), Mn(II), Fe(II), and UO2(VI) complexes with a new Schiff Base hydrazone: O-hydroxyacetophenone-7-chloro-4-quinoline hydrazone.

    Al-Shaalan, Nora H


    The Schiff base hydrazone ligand HL was prepared by the condensation reaction of 7-chloro-4-quinoline with o-hydroxyacetophenone. The ligand behaves either as monobasic bidentate or dibasic tridentate and contain ONN coordination sites. This was accounted for be the presence in the ligand of a phenolic azomethine and imine groups. It reacts with Cu(II), Ni(II), Co(II), Mn(II), UO(2) (VI) and Fe(II) to form either mono- or binuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, NMR, Mass, and UV-Visible spectra. The magnetic moments and electrical conductance of the complexes were also determined. The Co(II), Ni(II) and UO(2) (VI) complexes are mononuclear and coordinated to NO sites of two ligand molecules. The Cu(II) complex has a square-planar geometry distorted towards tetrahedral, the Ni(II) complex is octahedral while the UO(2) (VI) complex has its favoured heptacoordination. The Co(II), Mn(II) complexes and also other Ni(II) and Fe(III) complexes, which were obtained in the presence of Li(OH) as deprotonating agent, are binuclear and coordinated via the NNNO sites of two ligand molecules. All the binuclear complexes have octahedral geometries and their magnetic moments are quite low compared to the calculated value for two metal ions complexes and thus antiferromagnetic interactions between the two adjacent metal ions. The ligand HL and metal complexes were tested against a strain of Gram +ve bacteria (Staphylococcus aureus), Gram -ve bacteria (Escherichia coli), and fungi (Candida albicans). The tested compounds exhibited high antibacterial activities.

  16. Synthesis, Characterization and Biological Activities of Cu(II, Co(II, Mn(II, Fe(II, and UO2(VI Complexes with a New Schiff Base Hydrazone: O-Hydroxyacetophenone-7-chloro-4-quinoline Hydrazone

    Nora H. Al-Shaalan


    Full Text Available The Schiff base hydrazone ligand HL was prepared by the condensation reaction of 7-chloro-4-quinoline with o-hydroxyacetophenone. The ligand behaves either as monobasic bidentate or dibasic tridentate and contain ONN coordination sites. This was accounted for be the presence in the ligand of a phenolic azomethine and imine groups. It reacts with Cu(II, Ni(II, Co(II, Mn(II, UO2 (VI and Fe(II to form either mono- or binuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, NMR, Mass, and UV-Visible spectra. The magnetic moments and electrical conductance of the complexes were also determined. The Co(II, Ni(II and UO2 (VI complexes are mononuclear and coordinated to NO sites of two ligand molecules. The Cu(II complex has a square-planar geometry distorted towards tetrahedral, the Ni(II complex is octahedral while the UO2 (VI complex has its favoured heptacoordination. The Co(II, Mn(II complexes and also other Ni(II and Fe(III complexes, which were obtained in the presence of Li(OH as deprotonating agent, are binuclear and coordinated via the NNNO sites of two ligand molecules. All the binuclear complexes have octahedral geometries and their magnetic moments are quite low compared to the calculated value for two metal ions complexes and thus antiferromagnetic interactions between the two adjacent metal ions. The ligand HL and metal complexes were tested against a strain of Gram +ve bacteria (Staphylococcus aureus, Gram −ve bacteria (Escherichia coli, and fungi (Candida albicans. The tested compounds exhibited high antibacterial activities.

  17. On the ortho-positronium quenching reactions promoted by Fe(II), Fe(III), Co(III), Ni(II), Zn(II) and Cd(II) cyanocomplexes

    Fantola Lazzarini, Anna L.; Lazzarini, Ennio

    The o-Ps quenching reactions promoted in aqueous solutions by the following six cyanocomplexes: [Fe(CN) 6] 4-; [Co(CN) 6] 3-; [Zn(CN) 4] 2-; [Cd(CN) 6] 2-; [Fe(CN) 6] 3-; [Ni(CN) 4] 2- were investigated. The first four reactions probably consist in o-Ps addition across the CN bond, their rate constants at room temperature, Tr, being ⩽(0.04±0.02) × 10 9 M -1 s -1, i.e. almost at the limit of experimental errors. The rate constant of the fifth reaction, in o-Ps oxydation, at Tr is (20.3±0.4) × 10 9 M -1 s -1. The [Ni(CN) 4] 2-k value at Tr, is (0.27±0.01) × 10 9 M -1 s -1, i.e. 100 times less than the rate constants of o-Ps oxydation, but 10 times larger than those of the o-Ps addition across the CN bond. The [Ni(CN) 4] 2- reaction probably results in formation of the following positronido complex: [Ni(CN) 4Ps] 2-. However, it is worth noting that the existence of such a complex is only indirectly deduced. In fact it arises from comparison of the [Ni(CN) 4] 2- rate constant with those of the Fe(II), Zn(II), Cd(II), and Co(III) cyanocomplexes, which, like the Ni(II) cyanocomplex, do not promote o-Ps oxydation or spin exchange reactions.

  18. Electrochemical formation of Mg-Li-Ca alloys by codeposition of Mg, Li and Ca from LiCl-KCl-MgCl2-CaCl2 melts.

    Yan, Yong De; Zhang, Mi Lin; Xue, Yun; Han, Wei; Cao, Dian Xue; Jing, Xiao Yan; He, Li Yi; Yuan, Yi


    This work presents electrochemical formation of Mg-Li-Ca alloys via codeposition of Mg, Li and Ca on a molybdenum electrode in KCl-LiCl-MgCl(2)-CaCl(2) melts at 943 K. Cyclic voltammograms (CVs) showed that the underpotential deposition (UPD) of calcium on pre-deposited magnesium leads to the formation of a liquid Mg-Ca alloy, and the succeeding underpotential deposition of lithium on pre-deposited Mg-Ca alloy leads to the formation of a liquid Mg-Li-Ca solution. Chronopotentiometric measurements indicated that the codepositon of Mg, Li and Ca occurs at current densities more negative than -0.31 A cm(-2) in LiCl-KCl-MgCl(2) (5 wt%) melts containing 1 wt% CaCl(2). Chronoamperograms demonstrated that the onset potential for the codeposition of Mg, Li and Ca is -2.200 V, and the codeposition of Mg, Li and Ca is formed when the applied potentials are more negative than -2.200 V. X-Ray diffraction (XRD) indicated that Mg-Li-Ca alloys with different phases were formed via galvanostatic electrolysis. The microstructures of typical alpha and beta phases of Mg-Li-Ca alloys were characterized by optical microscope (OM) and scanning electron microscopy (SEM). The analysis of energy dispersive spectrometry (EDS) showed that the element Ca mainly distributes along grain boundary in Mg-Li-Ca alloys. The results of inductively coupled plasma analysis determined that the chemical compositions of Mg-Li-Ca alloys correspond with the phase structures of XRD patterns, and the lithium and calcium contents of Mg-Li-Ca alloys depend on the concentrations of MgCl(2) and CaCl(2).

  19. Decay of a narrow and high spin {sup 24}Mg + {sup 24}Mg resonance

    Salsac, M.-D. [IPHC, Universite Louis Pasteur, CNRS-IN2P3, Strasbourg (France)], E-mail:; Haas, F.; Courtin, S. [IPHC, Universite Louis Pasteur, CNRS-IN2P3, Strasbourg (France); Algora, A. [INR, Debrecen (Hungary); Beck, C. [IPHC, Universite Louis Pasteur, CNRS-IN2P3, Strasbourg (France); Beghini, S. [Universita di Padova and INFN, Padova (Italy); Behera, B.R. [INFN Laboratori Nazionali di Legnaro, Legnaro (Italy); Chapman, R. [University of the West of Scotland, Paisley (United Kingdom); Corradi, L. [INFN Laboratori Nazionali di Legnaro, Legnaro (Italy); Dombradi, Z. [INR, Debrecen (Hungary); Farnea, E. [Universita di Padova and INFN, Padova (Italy); Fioretto, E.; Gadea, A. [INFN Laboratori Nazionali di Legnaro, Legnaro (Italy); Jenkins, D.G. [University of York, York (United Kingdom); Latina, A. [INFN Laboratori Nazionali di Legnaro, Legnaro (Italy); Lebhertz, D. [IPHC, Universite Louis Pasteur, CNRS-IN2P3, Strasbourg (France); Lenzi, S. [Universita di Padova and INFN, Padova (Italy); Liang, X. [University of the West of Scotland, Paisley (United Kingdom); Marginean, N. [INFN Laboratori Nazionali di Legnaro, Legnaro (Italy); Montagnoli, G. [Universita di Padova and INFN, Padova (Italy)] (and others)


    The {sup 24}Mg + {sup 24}Mg reaction has been studied at the Legnaro Tandem at a CM bombarding energy of 45.7 MeV where a narrow and high spin resonance has been reported previously. The decay of the resonance into the inelastic and fusion-evaporation channels has been investigated. The ON and OFF resonance decay yields have been measured using, for the inelastic channels, the fragment spectrometer PRISMA and the {gamma} array CLARA, and, for the fusion-evaporation channels, the Si array EUCLIDES and the {gamma} array GASP. Strong resonant effects have been observed in the inelastic channels involving the 2{sub 1}{sup +} and 4{sub 1}{sup +} states of the {sup 24}Mg ground state band. Weaker effects are also seen in certain fusion-evaporation channels. The properties of the studied resonance are in agreement with molecular model predictions. It is also proposed that the narrow and high spin {sup 24}Mg + {sup 24}Mg resonance corresponds to the formation of a fast rotating and highly prolate deformed {sup 48}Cr after a Jacobi shape transition and just before fission.

  20. Mechanical Properties of Mg-Gd and Mg-Y Solid Solutions

    Kula, Anna; Jia, Xiaohui; Mishra, Raj K.; Niewczas, Marek


    The mechanical properties of Mg-Gd and Mg-Y solid solutions have been studied under uniaxial tension and compression between 4 K and 298 K (-269 °C and 25 °C). The results reveal that Mg-Gd alloys exhibit higher strength and ductility under tension and compression attributed to the more effective solid solution strengthening and grain-boundary strengthening effects. Profuse twinning has been observed under compression, resulting in a material texture with strong dominance of basal component parallel to compression axis. Under tension, twining is less active and the texture evolution is controlled mostly by slip. The alloys exhibit pronounced yield stress asymmetry and significantly different work-hardening behavior under tension and compression. Increasing of Gd and/or Y concentration leads to the reduction of the tension-compression asymmetry due to the weakening of the recrystallization texture and more balanced twinning and slip activity during plastic deformation. The results suggest that under compression of Mg-Y alloys slip is more active than twinning in comparison to Mg-Gd alloys.

  1. Refinements in an Mg/MgH2/H2O-Based Hydrogen Generator

    Kindler, Andrew; Huang, Yuhong


    Some refinements have been conceived for a proposed apparatus that would generate hydrogen (for use in a fuel cell) by means of chemical reactions among magnesium, magnesium hydride, and steam. The refinements lie in tailoring spatial and temporal distributions of steam and liquid water so as to obtain greater overall energy-storage or energy-generation efficiency than would otherwise be possible. A description of the prior art is prerequisite to a meaningful description of the present refinements. The hydrogen-generating apparatus in question is one of two versions of what was called the "advanced hydrogen generator" in "Fuel-Cell Power Systems Incorporating Mg-Based H2 Generators" (NPO-43554), NASA Tech Briefs, Vol. 33, No. 1 (January 2009), page 52. To recapitulate: The apparatus would include a reactor vessel that would be initially charged with magnesium hydride. The apparatus would exploit two reactions: The endothermic decomposition reaction MgH2-->Mg + H2, which occurs at a temperature greater than or equal to 300 C, and The exothermic oxidation reaction MgH2 + H2O MgO + 2H2, which occurs at a temperature greater than or equal to 330 C.

  2. Formation and Stability of Hollow MgO Nanoshells

    Krishnan, G.; Palasantzas, G.; Kooi, B.J.


    High temperature annealing of gas phase synthesized Mg nanoparticles surrounded by an MgO shell leads to formation of hollow MgO nanoshells due to the evaporation assisted Kirkendall effect. Under electron beam exposure in TEM, the (220) MgO facets reduce their high surface energy by forming cube fa

  3. cDNA library Table: mg [KAIKOcDNA[Archive

    Full Text Available mg NA mg-- p50 midgut fifth instar larval stage D3 mixed pBluescript SK- EcoR1 for ...5' Xho1for 3' sequenced from T3 primer (5' -> 3') AU001868-AU002476,BY916287-BY916543 mg[number],mg[number]_1 ...

  4. The three shapes of 32Mg

    Poves A.


    Full Text Available The N=20 and N=28 “islands of inversion” are described by large scale shell model calculations which mix configurations with different Nħω or equivalently with different number of particles promoted from the sd-shell to the pf -shell. We pay particular attention to the properties of the states at fix Nħω which turn out to be the real protagonists of the physics at N=20. In particular we study the appearance of spherical, deformed and superdeformed structures in 32Mg at fixed 0p-0h, 2p-2h and 4p-4h configurations. Finally we submit that the islands of deformation at N=20 and N=28 merge in the Magnesium isotopes

  5. Simultaneous polymerization of Mg and Zr alkoxides

    Mendez-Vivar, J.; Lara, V.H. [Univ. Autonoma Metropolitana-Iztapalapa, Depto. de Quimica, Mexico, D. F. (Mexico); Mendoza-Serna, R.; Ayala-Morales, A. [Facultad de Estudios Superiores Zaragoza, UNAM, Carrera de Ingenieria Quimica, Mexico, D. F. (Mexico); Bosch, P. [Inst. de Investigaciones en Materiales, UNAM Circuito Exterior, Mexico, D. F. (Mexico)


    The preparation of homogeneous MgO-ZrO{sub 2} ceramics by the sol-gel process is of interest because of its potential technological applications as dielectric materials in thin films and membranes. In this work we used magnesium methoxide and zirconium n-propoxide as precursors. The simultaneous polymerization of the alkoxides was performed via the sol-gel process, using acetylacetone (acacH) and isoeugenol (isoH) separately as the chelating agents, in order to control the hydrolysis and condensation steps. Spectroscopic studies have been performed on the sols, gels, xerogels and oxides, including Fourier transform infrared (FTIR) spectroscopy and small Angle X-ray Scattering (SAXS). (orig.)

  6. Mg II Absorbing Galaxies: Morphologies and Kinematics

    Churchill, C; Kacprzak, G G; Churchill, Chris; Steidel, Chuck; Kacprzak, Glenn


    In this contribution, we review our current knowledge of the properties of galaxies, and their extended halos, selected by MgII absorption in the spectra of background quasars. We then describe recent efforts to quantify the morphologies and orientations of galaxies and explore how these relate to the gas kinematics. In a sample of 26 galaxies, we find no clear connection between the orientation of the quasar line of sight through the galaxy and the velocity spread of the gas. However, it appears that the quantity of gas "stirred up" in the halo may be correlated to asymmetry in the galaxy morphology. Since the galaxies have fairly normal morphologies, this connection may suggest that galaxies with extended halos experienced an interaction or merging event a few dynamical times prior to the epoch of observation.

  7. Multiaxial magnetic ordering in NdMg

    Deldem, M; Galera, R M; Morin, P; Schmitt, D; Ouladdiaf, B


    NdMg is a cubic compound (CsCl-type) which orders antiferromagnetically at T sub N =61 K. The magnetization measurements show a second transition at T sub R =35 K. Over the whole order range, the powder neutron diffraction pattern can be indexed on the hypothesis of a collinear structure, the magnetic moments being parallel to the wave vector. The neutron diffraction experiments on a single crystal, under an applied magnetic field, establish that the transition at T sub R corresponds to a change from a collinear structure to a multiaxial one. The magnetic moments successively point along a fourfold axis, in the collinear structure, and along twofold axes in the multiaxial one. This sequence of magnetic structures is consistent with the coexistence of ferroquadrupolar gamma-couplings and antiferroquadrupolar epsilon-couplings. (author)

  8. Preparation of Mg-MgH2 flakes by planetary ball milling with stearic acid and their hydrogen storage properties

    Hong, Seong-Hyeon; Song, Myoung Youp


    Many studies preparing magnesium hydride using catalyst addition were performed, resulting in the preparation of additive-containing magnesium hydride. Preparation of a sample with a MgH2 phase without additives requires high pressure and high temperature and is time-demanding. In order to prepare an additive-free sample with a MgH2 phase, 90 wt% Mg+10 wt% MgH2 (named 90Mg+10MgH2) was milled under a hydrogen atmosphere with 6 wt% stearic acid as a process-controlling agent, which led to a formation of Mg-MgH2 flakes. The hydrogen storing and releasing properties of the prepared flakes were investigated and compared with those of purchased MgH2. A sample with a majority fraction of MgH2 phase was prepared by planetary ball milling of 90 Mg+10 MgH2 with 6 wt% stearic acid. The resultant particles of 90 Mg+10 MgH2 obtained after hydridingdehydriding cycling were much smaller and had significantly more cracks and defects than those of MgH2 after hydriding-dehydriding cycling. 90 Mg+10 MgH2 released 0.12 wt% hydrogen for 4 min, 3.70 wt% for 20 min, and 5.30 wt% for 60 min at 648 K at the first cycle.

  9. Estabilidad de tabletas de Rifampicina 300 mg

    Lisette Martínez Miranda


    Full Text Available Se realizó el estudio de estabilidad de las tabletas de rifampicina 300 mg. Se utilizó para la cuantificación del principio activo un método analítico desarrollado y validado por cromatografía líquida de alta resolución en fase reversa y detección ultravioleta. El estudio de estabilidad de las tabletas se efectuó mediante los métodos de vida útil y acelerado en condiciones isotérmicas; no se obtuvo una variación notable de la concentración en el tiempo de estudio y se demostró así la estabilidad química y térmica del principio activo, por lo que se proponen 2 años como fecha de vencimiento. La humedad relativa de 75, 84 y 92 % tuvo influencia en la estabilidad de la formulación en el período analizado.The stability study of rifampicin 300 mg was conducted. An analytical method developed and validated by high pressure liquid chromatography in reverse phase and ultraviolet detection was used for the quantification of the actives principle. The stability study of the tablets was conducted by the method of useful life and the accelerated method under isothermic conditions. There was no significant variation of the concentration during the time of study and, thus, the chemical and thermal stability of the active principle was proved. A period of 2 years was proposed as expiration date. A relative humidity of 75, 84 and 92% influenced on the stability of the formulation in the analyzed period.

  10. Evidence for beta -delayed neutron emission from /sup 31/Mg and /sup 32/Mg

    Zaidins, C S; De Saint-Simon, M; Détraz, C; Epherre-Rey-Campagnolle, Marcelle; Guillemaud, D; Klapisch, Robert; Langevin, M; Naulin, F; Thibault, C; Touchard, F


    Investigates the time spectrum of beta -delayed neutron emission from /sup 30-34/Na and their descendants using beta -neutron coincidence detection. The authors have been able to assign an upper limit of 0,4% to the probability of beta -delayed neutron emission, p/sub n/, from the /sup 30/Na daugher isotope /sup 30/Mg. In fitting the time spectra of beta -delayed neutrons from /sup 31/Na and /sup 32/Na, we find a definitive component from subsequent daughter decay as well. This provides evidence for beta -delayed neutron emission from /sup 31/Mg and /sup 32/Mg with P/sub n/ values of the order of 2% for each. (7 refs).

  11. Ageing processes in Al-Cu-Mg alloys with different Cu/Mg ratios

    Macchi, C. [IFIMAT, UNCentro and CONICET, Pinto, Tandil (Argentina); Somoza, A. [IFIMAT, UNCentro and CICPBA, Pinto, Tandil (Argentina); Ferragut, R.; Dupasquier, A. [LNESS and CNISM, Politecnico di Milano, Como (Italy); Polmear, I.J. [Emeritus Professor, Department of Materials Engineering, Monash University, Melbourne, Vic. (Australia)


    Three age-hardenable Al-Cu-Mg alloys with different Cu/Mg ratios were studied by means of positron annihilation lifetime spectroscopy and Vickers hardness as a function of the artificial ageing time at 175 C. Complementary information on the decomposition sequence was obtained by means of differential scanning calorimetry. The results are discussed in terms of the different structures that are formed during the precipitation sequence of the supersaturated solid solution. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)



    The objective of the present work is to study the casting characteristics of various Al-Li alloys, which include fluidity and strengths of the alloys and their interaction with cast molds. Materials investigated are Al-Li-Mg and Al-Li-Cu-Mg alloys with Li content of 2.5 wt%. The results show that sand molds with resin binders are good for Al-Li casting. Ceramic coatings can further reduce the metal-mold interactions. However, the permeability is also reduced by coating. The fluidity of Li-bea...

  13. Porous composite materials ZrO{sub 2}(MgO)-MgO for osteoimplantology

    Buyakov, Ales, E-mail: [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Litvinova, Larisa, E-mail:; Shupletsova, Valeria, E-mail: [Immanuel Kant Baltic Federal University, Kaliningrad (Russian Federation); Kulbakin, Denis, E-mail: [Tomsk Cancer Research Institute, Tomsk, 634050 (Russian Federation); Kulkov, Sergey, E-mail: [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)


    The pore structure and phase composition of ceramic composite material ZrO{sub 2}(Mg)-MgO at different sintering temperatures were studied. The main mechanical characteristics of the material were determined and it was shown that they are close to the characteristics of natural bone tissues. It was shown that material structure has a positive effect on the pre-osteoblast cells proliferation. In-vitro studies of pre-osteoblast cells, cultivation on material surface showed a good cell adhesion, proliferation and differentiation of MMSC by osteogenic type.

  14. Phase transition and optoelectronic properties of MgH2

    Nayak, Vikas; Verma, U. P.


    In this article, structural and electronic properties of MgH2 have been studied. The aim behind this study was to find out the ground state crystal structure of MgH2. For the purpose, density functional theory (DFT)-based full-potential linearized augmented plane wave (FP-LAPW) calculations have been performed in three different space groups: P42/mnm (α-MgH2), Pa3 (β-MgH2) and Pbcn (γ-MgH2). It has been found that the ground state structure of MgH2 is α-MgH2. The present study shows that α-MgH2 transforms into γ-MgH2 at a pressure of 0.41 GPa. After further increase in pressure, γ-MgH2 transforms into β-MgH2 at a pressure of 3.67 GPa. The obtained results are in good agreement with previously reported experimental data. In all the studied phases, the behavior of MgH2 is insulating and its optical conductivity is around 6.0 eV. The α-MgH2 and γ-MgH2 are anisotropic materials while β-MgH2 is isotropic in nature.

  15. The Influence of MgH2 on the Assessment of Electrochemical Data to Predict the Degradation Rate of Mg and Mg Alloys

    Wolf-Dieter Mueller


    Full Text Available Mg and Mg alloys are becoming more and more of interest for several applications. In the case of biomaterial applications, a special interest exists due to the fact that a predictable degradation should be given. Various investigations were made to characterize and predict the corrosion behavior in vitro and in vivo. Mostly, the simple oxidation of Mg to Mg2+ ions connected with adequate hydrogen development is assumed, and the negative difference effect (NDE is attributed to various mechanisms and electrochemical results. The aim of this paper is to compare the different views on the corrosion pathway of Mg or Mg alloys and to present a neglected pathway based on thermodynamic data as a guideline for possible reactions combined with experimental observations of a delay of visible hydrogen evolution during cyclic voltammetry. Various reaction pathways are considered and discussed to explain these results, like the stability of the Mg+ intermediate state, the stability of MgH2 and the role of hydrogen overpotential. Finally, the impact of MgH2 formation is shown as an appropriate base for the prediction of the degradation behavior and calculation of the corrosion rate of Mg and Mg alloys.

  16. The influence of MgH2 on the assessment of electrochemical data to predict the degradation rate of Mg and Mg alloys.

    Mueller, Wolf-Dieter; Hornberger, Helga


    Mg and Mg alloys are becoming more and more of interest for several applications. In the case of biomaterial applications, a special interest exists due to the fact that a predictable degradation should be given. Various investigations were made to characterize and predict the corrosion behavior in vitro and in vivo. Mostly, the simple oxidation of Mg to Mg2+ ions connected with adequate hydrogen development is assumed, and the negative difference effect (NDE) is attributed to various mechanisms and electrochemical results. The aim of this paper is to compare the different views on the corrosion pathway of Mg or Mg alloys and to present a neglected pathway based on thermodynamic data as a guideline for possible reactions combined with experimental observations of a delay of visible hydrogen evolution during cyclic voltammetry. Various reaction pathways are considered and discussed to explain these results, like the stability of the Mg+ intermediate state, the stability of MgH2 and the role of hydrogen overpotential. Finally, the impact of MgH2 formation is shown as an appropriate base for the prediction of the degradation behavior and calculation of the corrosion rate of Mg and Mg alloys.

  17. Heavy Metals (Mg, Mn, Ni and Sn contamination in Soil Samples of Ahvaz II Industrial Estate of Iran in 2013

    Soheil l Sobhanardakani


    Full Text Available Background & Aims of the Study: Due to the rapid industrial development in Khuzestan province of Iran during recent years, this study was performed to analyze the variation of metals concentrations (Mg, Mn, Ni, and Sn in soil samples of Ahvaz II Industrial estate during the spring season of 2013. Materials & Methods: In this experimental study, 27 topsoil samples were collected from nine stations. The intensity of the soil contamination was evaluated, using a contamination factor (Cf and geo-accumulation index (I-geo. Results:  The mean soil concentrations (in mg kg-1 (dry weight were in ranged within 870-1144 (Mg, 188-300 (Mn, 93-199 (Ni and 9-15 (Sn. The data indicated that the I-geo value for all metals falls in class ‘1’. Also the Cf value for Mg and Mn falls in class ‘0’, the Cf value for Sn falls in class ‘1’ and the Cf value for Ni falls in the classes of ‘1’ and ‘2’. The result of the Pearson correlation showed that there were significant positive associations between all metals. Conclusions: According to the results which were achieved by a cluster analysis, there were significant positive associations among all metals based on Pearson correlation coefficient, especially between Ni and Sn; also both of them with Mn. Because the Ni originates from oil sources it can be resulted that Mn and Sn originate from oil sources, too. Therefore, industrial activities and exploitation of oil reservoirs are the main cause of pollution in that area. Also, it can be concluded that, with increasing the distance from the source of pollution, the accumulation of contaminants in the soil samples decreased.

  18. Calibration of the DH6500-MG02 and DH6500-MG03 antennas

    Nielsen, Jeppe Majlund; Pivnenko, Sergey

    frequencies. For the DH6500-MG03 horn the measurement comprises on-axis gain, and on-axis polarization at 601 frequencies. For both horns, the input reection coecient was measured at 601 frequencies. The measurement was carried out at the DTU-ESA Spherical Near-Field Antenna Test Facility in April 2013...

  19. Mechanical and Corrosive Properties of Two Magnesium Wires: Mg4Gd and Mg6Ag

    Maier, Petra; Szakács, Gabor; Wala, Marcin; Hort, Norbert

    The mechanical and corrosive properties of two Magnesium wires are studied in the field of microhardness, tension-, compression-and 3-point-bending tests, corrosion and its influence on the mechanical properties. Due to recrystallization during their complex forming processes (casting, extrusion, wire drawing), both wires show a fine grained microstructure resulting in high strength and ductility. However, the ductility is mostly evaluated by 3-point bending and compression; due to the notch effect in the clamp area, the maximum tensile strength and elongation under tension cannot be measured. Both alloys show a tensile-compressive yield asymmetry. Even RE-elements are known to reduce this asymmetry, the Mg-Gd alloy shows 100 MPa higher strength in tension than compression. The asymmetry of the Mg-Ag wire is similar. Overall the wires show very high strength and hardness, Mg6Ag slightly higher compared to Mg4Gd. Strong pitting corrosion is found and reduces strongly the tensile and bending strength.

  20. Nanometric MgFe2O4: Synthesis, characterization and its application towards supercapacitor and electrochemical uric acid sensor

    Majumder, S.; Kumar, S.; Banerjee, S.


    In this paper, we have synthesized nanocrystalline MgFe2O4 (S1) by auto-combustion assisted sol-gel method. The structure and morphology and elemental study of S1 are examined by powder X-ray diffraction (PXRD), field emission scanning electron microscopic (FESEM) and energy dispersive X-ray spectroscopic (EDS) techniques. The FESEM images reveal that the morphology of the sample is rough and average particle size is 50 nm. The PXRD study indicates that the samples are well crystalline and single phase in nature. Moreover, we have performed supercapacitor study by electrochemical galvanostatic charge-discharge (GCD) measurement, which shows pseudo capacitive behavior. S1 contains a high specific capacitance of 428.9 Fg-1 at the current density 0.0625 Ag-1 and can deliver high energy and power density of 18.01 Wh kg-1 and 21468 Wkg-1 respectively. Moreover, uric acid (UA) sensing study has also been performed by cyclic voltmetry (CV) and electrochemical impedance spectroscopy measurement (EIS) of S1. We can use nanocrystalline MgFe2O4 as supercapacitor and UA sensor applications purpose.


    Sikander A . K


    Full Text Available Macular edema is a frequent manifestation of diabetic retinopathy and animportant cause of visual disturbance in diabetic patients. AIM: To compare the efficacy and safety of 1mg and 4mg intravitreal triamcinolone acetonide (IVTA in the management of diabetic macular edema. SETTING: Sarojini Devi Eye Hospital, Hyderabad. MATERIAL AND METHODS: 42 eyes of 42 patients with diabetic macular edema were randomly assigned torecei ve either 1 - mg or 4 - mg dose of Intravitreal triamcinolone acetonide (IVTA. Each patient underwent a complete comprehensive eye examination at baseline andat each visit.Fundus fluorescein angiography and optical coherence angiographywas done at baseline an d at 1, 3 and 6 months.BCVA, lens status, IOP wererecorded at each follow up visit. Each patient’s BCVA was measured in snellen’s lines and converted into logarithm of minimum angle of resolution (log MAR scale for analysis. STATISTICAL ANALYSIS USED : The data were statistically evaluated using the Wilcoxon signedrank test, Mann - Whitney test and t tests wherever applicable. A p value of lessthan . 05 was considered significant. RESULTS: There was no statistically significant difference in the mean foveal thickness measurement at baseline (p=.723 or at 3 rd month (p=.878 between the sub - groups. BCVA significantly improved from baseline to subsequent visits in both the groups, but there was no statistically significant difference observed in the mean baseli ne BCVA between the two sub - groups (p=.754. There was no statistically significant difference observed in IOP between the two sub - groups at any follow up visit. CONCLUSIONS: The results of our study suggest that 1 - mg dose of IVTA is as effective as 4 - mgdo se of IVTA in improving the functional and anatomical outcome in macularedema associated with diabetic retinopathy.

  2. Comparison of initial loading doses of 5 mg and 10 mg for warfarin therapy

    Sidnei Lastória


    Full Text Available CONTEXT: The question of what is the best loading dosage of warfarin when starting anticoagulant treatment has been under discussion for ten years. We were unable to find any comparative studies of these characteristics conducted here in Brazil. OBJECTIVE: To compare the safety and efficacy of two initial warfarin dosage regimens for anticoagulant treatment. METHODS: One-hundred and ten consecutive patients of both sexes, with indications for anticoagulation because of venous or arterial thromboembolism, were analyzed prospectively. During the first 3 days of treatment, these patients were given adequate heparin to keep aPTT (activated partial thromboplastin time between 1.5 and 2.5, plus 5 mg of warfarin. From the fourth day onwards, their warfarin doses were adjusted using International Normalized Ratios (INR; target range: 2 to 3. This prospective cohort was compared with a historical series of 110 patients had been given 10 mg of warfarin on the first 2 days and 5 mg on the third day with adjustments based on INR thereafter. Outcomes analyzed were as follows: recurrence of thromboembolism, bleeding events and time taken to enter the therapeutic range. RESULTS: Efficacy, safety and length of hospital stay were similar in both samples. The sample that were given 10 mg entered the therapeutic range earlier (means: 4.5 days vs. 5.8 days, were on lower doses at discharge and had better therapeutic indicators at the first return appointment. CONCLUSIONS: The 10 mg dosage regimen took less time to attain the therapeutic range and was associated with lower warfarin doses at discharge and better INR at first out-patients follow-up visit.

  3. Pressure-induced structural transitions in MgH2.

    Vajeeston, P; Ravindran, P; Kjekshus, A; Fjellvåg, H


    The stability of MgH2 has been studied up to 20 GPa using density-functional total-energy calculations. At ambient pressure alpha-MgH2 takes a TiO2-rutile-type structure. alpha-MgH2 is predicted to transform into gamma-MgH2 at 0.39 GPa. The calculated structural data for alpha- and gamma-MgH2 are in very good agreement with experimental values. At equilibrium the energy difference between these modifications is very small, and as a result both phases coexist in a certain volume and pressure field. Above 3.84 GPa gamma-MgH2 transforms into beta-MgH2, consistent with experimental findings. Two further transformations have been identified at still higher pressure: (i) beta- to delta-MgH2 at 6.73 GPa and (ii) delta- to epsilon-MgH2 at 10.26 GPa.

  4. Magnetocaloric phenomena in Mg-ferrite nanoparticles

    Burianova, S; Holec, P; Plocek, J [Charles University, Faculty of Science, Department of Inorganic chemistry, Prague (Czech Republic); Poltierova-Vejpravova, J, E-mail: burianovasimona@email.c, E-mail: jana@mag.mff.cuni.c


    A comparative study of magnetocaloric effect (MCE) in superparamagnetic (SPM) regime is reported in two different types of magnesium ferrite nanostructures. The samples were prepared either by microemulsion method as MgFe{sub 2}O{sub 4} nanoparticles encapsulated in amorphous SiO{sub 2}, or as matrix-less nanoparticles using hydrothermal synthesis in supercritical water conditions. The particle diameter in all prepared samples was obtained from XRD measurements and TEM analysis. All samples show a SPM behavior above the blocking temperature, T{sub B}. The entropy change, {Delta}S was finally derived from the measurements of magnetization, M(H,T) curves at defined temperature intervals. We observed, that all samples show a broad peak of {Delta}S in the temperature range that is fairly above the T{sub B}. The values of the {Delta}S also depend on the particle size, and they are of about two orders lower than those reported in the famous giant magnetocaloric materials.

  5. Effect of heavy metals on pH buffering capacity and solubility of Ca, Mg, K, and P in non-spiked and heavy metal-spiked soils.

    Najafi, Sarvenaz; Jalali, Mohsen


    In many parts of the world, soil acidification and heavy metal contamination has become a serious concern due to the adverse effects on chemical properties of soil and crop yield. The aim of this study was to investigate the effect of pH (in the range of 1 to 3 units above and below the native pH of soils) on calcium (Ca), magnesium (Mg), potassium (K), and phosphorus (P) solubility in non-spiked and heavy metal-spiked soil samples. Spiked samples were prepared by cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) as chloride salts and incubating soils for 40 days. The pH buffering capacity (pHBC) of each sample was determined by plotting the amount of H(+) or OH(-) added (mmol kg(-1)) versus the related pH value. The pHBC of soils ranged from 47.1 to 1302.5 mmol kg(-1) for non-spiked samples and from 45.0 to 1187.4 mmol kg(-1) for spiked soil samples. The pHBC values were higher in soil 2 (non-spiked and spiked) which had higher calcium carbonate content. The results indicated the presence of heavy metals in soils generally decreased the solution pH and pHBC values in spiked samples. In general, solubility of Ca, Mg, and K decreased with increasing equilibrium pH of non-spiked and spiked soil samples. In the case of P, increasing the pH to about 7, decreased the solubility in all soils but further increase of pH from 7, enhanced P solubility. The solubility trends and values for Ca, Mg, and K did not differed significantly in non-spiked and spiked samples. But in the case of P, a reduction in solubility was observed in heavy metal-spiked soils. The information obtained in this study can be useful to make better estimation of the effects of soil pollutants on anion and cation solubility from agricultural and environmental viewpoints.

  6. Structural relationships among MgZn2 and Mg4Zn7 phases and transition structures in Mg-Zn-Y alloys

    Rosalie, Julian M.; Somekawa, Hidetoshi; Singh, Alok; Mukai, Toshiji


    Isothermal ageing of plastically deformed Mg-Zn-Y alloys resulted in precipitation along ? twin boundaries. The bulky precipitates so formed had structures similar to those recently reported for the rod-like ? precipitates, but afforded a more detailed study by high-resolution TEM due to their larger size. The core of the precipitates often had the structure of the monoclinic Mg4Zn7 phase, and had the orientation ? ; ? with either the matrix or the twin. On this Mg4Zn7 phase, the hexagonal MgZn2 phase grew in two orientations, both with ? . One of these orientations formed a known orientation relationship ? ; ? with the matrix. The part of the precipitate with the MgZn2 structure was usually in direct contact with the twin boundary. Both the Mg4Zn7 and MgZn2 phases have layered structures that can be described with similar building blocks of icosahedrally coordinated atoms. The atomic positions of zinc atoms comprise the vertices of these icosahedra and form 'thick' rhombic tiles. The orientations of these rhombuses remain unchanged across the interfaces between the two phases. Near the interface with MgZn2, transition structures formed in the Mg4Zn7 phase, with the Zn:Mg atom ratio between those of the Mg4Zn7 and MgZn2 phases. In these transition structures, the unit cell of the Mg4Zn7 phase is extended along [100] or [001] by half a unit cell length by continuation of the rhombic tiling. Structures of these extended unit cells are proposed.

  7. Effects of Ca additions on some Mg-alloy hydrides

    Lupu, D.; Biris, A.; Indrea, E.; Bucur, R.V.


    The hydrogenation of the alloy of composition CaMg/sub 1/ /sub 8/Ni/sub 0/ /sub 5/ containing CaMg/sub 2/ and MgNi/sub 2/ shows fast activation kinetics. The Mg/sub 2/Ni phase is observed in the dehydrided samples. The three plateaus on the hydrogen desorption isotherms correspond to the most stable magnesium hydrides observed up to now in Mg-alloy ( H = 20 to 24 kcal/mol H/sub 2/). The effects of Ca additions on the hydrogen storage capacity and desorption rates of some Mg-rich alloys have been studied. 16 references, 3 figures, 1 table.

  8. Pressureless sintering of translucent MgO ceramics

    Chen Dianying [Department of Chemical, Materials and Biomolecular Engineering, Institute of Materials Science, University of Connecticut, Storrs, CT 06269 (United States); Jordan, Eric H. [Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269 (United States)], E-mail:; Gell, Maurice [Department of Chemical, Materials and Biomolecular Engineering, Institute of Materials Science, University of Connecticut, Storrs, CT 06269 (United States)


    MgO nanocrystalline powders were synthesized via a wet precipitation process. X-ray diffraction analysis of the heat-treated precursor powders shows that a crystalline MgO phase forms at {approx}500 deg. C. Translucent MgO ceramics were prepared by pressureless sintering the nanocrystalline MgO powders at 1400 deg. C for 2 h under ambient atmosphere. The as-sintered MgO ceramics have a relative density of 98.1% with an average hardness of 6.8 GPa. Scanning electron microscope characterization revealed that the translucent MgO ceramics have an average grain size of {approx}6 {mu}m.

  9. Phase equilibria in the Mg-rich corner of the Mg-Zn-La system at 350℃

    LI Hongxiao; REN Yuping; HUANG Mingli; CHEN Qin; HAO Shiming


    The phase equilibria in the Mg-rich corner of the Mg-Zn-La system at 350℃ have been investigated by scanning electron microscopy, X-ray diffraction, and electron probe microanalysis. It has been shown that the linear compound (Mg,Zn)17La2 existed in the Mg-Zn-La system at 350℃. The linear compound (so-called T phase) was with the C-centred orthorhombic crystal structure induced by the solution of significant quantities of the third element. The three-phase region α(Mg) + MgZn(La) + T and the two-phase region composed of the α(Mg) and the linear-compound T phase existed in the Mg-rich corner of the Mg-Zn-La system at 350℃.

  10. Structural and electronic properties of Mg and Mg-Nb co-doped TiO2 (101) anatase surface

    Sasani, Alireza; Baktash, Ardeshir; Mirabbaszadeh, Kavoos; Khoshnevisan, Bahram


    In this paper, by using density functional theory, Mg and Nb-Mg co-doping of TiO2 anatase (101) surfaces are studied. By studying the formation energy of the defects and the bond length distribution of the surface, it is shown that Mg defects tend to stay as far as possible to induce least possible lattice distortion while Nb and Mg defects stay close to each other to cause less stress to the surface. By investigating band structure of the surface and changes stemmed from the defects, potential effects of Mg and Mg-Nb co-doping of TiO2 surface on dye-sensitized solar cells are investigated. In this study, it is shown that the Nb-Mg co-doping could increase JSC of the surface while slightly decreasing VOC compared to Mg doped surface, which might result in an increase in efficiency of the DSSCs compared to Nb or Mg doped surfaces.

  11. Synthesis kinetics of Mg_2Sn in Mg-Sn powder mixture using non-isothermal differential scanning calorimetry

    WU Yu-feng; DU Wen-bo; ZUO Tie-yong


    The non-isothermal heating process of Mg-Sn powder mixture was studied by differential scanning calorimetry(DSC) technique and the synthesis kinetics of Mg_2Sn was evaluated by the model-free and model-fitting methods. The activation energy and conversion function of Mg_2Sn synthesis reaction are calculated to be 281.7 kJ/mol and g(α)=[-ln(1-α)]~(1/4), respectively. The reaction mechanism of 2Mg+Sn→Mg_2Sn under non-isothermal condition is regarded as "nucleation and growth". During the non-isothermal heating process, the phase transformation occurred in the Mg-Sn powder mixture was analyzed by XRD and the microstructure evolution of Mg_2Sn was observed by optical microscopy, which is in good agreement with the reaction mechanism of 2Mg+Sn→Mg_2Sn deduced from the kinetic evaluation.

  12. Performance of Mg-14Li-1Al-0.1Ce as anode for Mg-air battery

    Ma, Yibin; Li, Deyu [School of Chemical Engineering and Technology, Harbin Institute of Technology, West Street No. 92, Harbin 150001 (China); Li, Ning [School of Chemical Engineering and Technology, Harbin Institute of Technology, West Street No. 92, Harbin 150001 (China); Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Zhang, Milin; Huang, Xiaomei [Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)


    In this research, a new Mg-air battery based on Mg-14Li-1Al-0.1Ce was prepared and the battery performance was investigated by constant current discharge test. The corrosion behavior of Mg, AZ31 and Mg-Li-Al-Ce were studied by self-corrosion rate measurement and potentiodynamic polarization measurement. The characteristics of Mg-Li-Al-Ce after discharge were investigated by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that Mg-Li-Al-Ce is more active than Mg and AZ31. The self-corrosion rate is found to be in the order: Mg-Li-Al-Ce < Mg < AZ31. It has been observed that the Mg-air battery based on Mg-Li-Al-Ce offers higher operating voltage, anodic efficiency and capacity than those with Mg and AZ31. SEM and EIS results show that the discharge product of Mg-Li-Al-Ce is loosely adhered to the alloy surface, and thus Mg-Li-Al-Ce could keep high discharge activity during discharge. (author)

  13. Enhanced ion anisotropy by nonconventional coordination geometry: single-chain magnet behavior for a [{Fe(II)L}2{Nb(IV)(CN)8}] helical chain compound designed with heptacoordinate Fe(II).

    Venkatakrishnan, Thengarai S; Sahoo, Shaon; Bréfuel, Nicolas; Duhayon, Carine; Paulsen, Carley; Barra, Anne-Laure; Ramasesha, S; Sutter, Jean-Pascal


    Nonconventional heptacoordination in combination with efficient magnetic exchange coupling is shown to yield a 1-D heteronuclear {Fe(II)Nb(IV)} compound with remarkable magnetic features when compared to other Fe(II)-based single chain magnets (SCM). Cyano-bridged heterometallic {3d-4d} and {3d-5d} chains are formed upon assembling Fe(II) bearing a pentadentate macrocycle as the blocking ligand with octacyano metallates, [M(CN)(8)](4-) (M = Nb(IV), Mo(IV), W(IV)). X-ray diffraction (single-crystal and powder) measurements reveal that the [{(H(2)O)Fe(L(1))}{M(CN)(8)}{Fe(L(1))}](infinity) architectures consist of isomorphous 1-D polymeric structures based on the alternation of {Fe(L(1))}(2+) and {M(CN)(8)}(4-) units (L(1) stands for the pentadentate macrocycle). Analysis of the magnetic susceptibility behavior revealed cyano-bridged {Fe-Nb} exchange interaction to be antiferromagnetic with J = -20 cm(-1) deduced from fitting an Ising model taking into account the noncollinear spin arrangement. For this ferrimagnetic chain a slow relaxation of its magnetization is observed at low temperature revealing a SCM behavior with Delta/k(B) = 74 K and tau(0) = 4.6 x 10(-11) s. The M versus H behavior exhibits a hysteresis loop with a coercive field of 4 kOe at 1 K and reveals at 380 mK magnetic avalanche processes, i.e., abrupt reversals in magnetization as H is varied. The origin of these characteristics is attributed to the combination of efficient {Fe-Nb} exchange interaction and significant anisotropy of the {Fe(L(1))} unit. High field EPR and magnetization experiments have revealed for the parent compound [Fe(L(1))(H(2)O)(2)]Cl(2) a negative zero field splitting parameter of D approximately = -17 cm(-1). The crystal structure, magnetic behavior, and Mossbauer data for [Fe(L(1))(H(2)O)(2)]Cl(2) are also reported.

  14. Understanding and Enhancing Hydrogen Diffusion in MgH2 and NaMgH3

    Sholl, David; Hao, Shiqiang


    The transport properties of hydrogen in metal hydrides are crucial to the kinetics of H2 storage in these materials. We use first-principles calculations to identify the defects that are relevant for H transport in MgH2 and NaMgH3. In both materials, the physically relevant defects are charged and H diffusion is dominated by mobility of negatively charged interstitial H. Interestingly, the diffusion of these species occurs via concerted mechanisms with low energy barriers. To improve the charged interstitial H diffusivity, a series of transition-metal additives are screened to lower the formation energy of mobile defects. Our results provide a practical way to examine and alter H diffusion in light metal hydrides.

  15. Secondary ageing in an Al-Cu-Mg alloy with high Cu/Mg ratio

    Dupasquier, A.; Folegati, P. [Politecnico di Milano (Italy). Ist. di Fisica della Materia; Ferragut, R. [Politecnico di Milano (Italy). Ist. di Fisica della Materia; IFIMAT, Univ. Nacional del Centro de la Provincia de Buenos Aires and CICPBA, Tandil (Argentina); Massazza, M.; Riontino, G. [Ist. Nazionale di Fisica della Materia, Dipt. di Chimica I.F.M., Univ. di Torino (Italy); Somoza, A. [IFIMAT, Univ. Nacional del Centro de la Provincia de Buenos Aires and CICPBA, Tandil (Argentina)


    The mechanisms governing secondary ageing (structural transformations occurring at low temperature after a heat treatment at higher temperature) were investigated by combined measurements of positron lifetimes, Vickers microhardness measurements and differential scanning calorimetry (DSC) on a laboratory alloy (Al-4.5 wt.% Cu-0.56 wt.% Mg). The results show that hardening occurs at a much slower rate than in case of primary ageing at RT. The positron lifetime data suggest that the hardening rate is controlled by slow release of vacancies from Cu-rich clusters formed during the initial high temperature treatment. The hardening stage is concomitant with an increase of the positron lifetime, and has probably the same origin, which is the formation of solute clusters containing vacancies and Mg as essential components. The formation at low temperature of new structures is also demonstrated by DSC. (orig.)

  16. Room-temperature perpendicular magnetic anisotropy of MgO/Fe/MgO ultrathin films

    Kozioł-Rachwał, A.; Ślęzak, T.; Przewoźnik, J. [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); Skowroński, W.; Stobiecki, T. [Department of Electronics, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); Wilgocka-Ślęzak, D. [Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Kraków (Poland); Qin, Q. H.; Dijken, S. van [NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto (Finland); Korecki, J. [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Kraków (Poland)


    We used the anomalous Hall effect to study the magnetic properties of MgO/Fe(t)/MgO(001) structures in which the Fe thickness t ranged from 4 Å to 14 Å. For the iron deposited at 140 K, we obtained perpendicular magnetization at room temperature below the critical thickness of t{sub c} = (9 ± 1) Å. In the vicinity of t{sub c}, the easy magnetization axis switched from an out-of-plane orientation to an in-plane orientation, and the observed spin-reorientation transition was considered in terms of the competition among different anisotropies. The perpendicular magnetization direction was attributed to magnetoelastic anisotropy. Finally, the temperature-dependent spin-reorientation transition was analyzed for Fe thicknesses close to t{sub c}.

  17. Transition of interface oxide layer from porous Mg(OH)2 to dense MgO induced by polyaniline and corrosion resistance of Mg alloy therefrom

    Luo, Yizhong; Sun, Yang; Lv, Jinlong; Wang, Xianhong; Li, Ji; Wang, Fosong


    The feasibility of polyaniline emeraldine base (EB) for enhancing long-term corrosion resistance of magnesium alloy (AZ91D Mg alloy) was confirmed, since the complex impedance of Mg alloy protected by EB/epoxy resin (ER) composite coating with 10 wt% EB loading maintained around 2 GΩ cm2 even after 80 day exposure in 0.5 M NaCl solution, while that of pure ER coated analogue decreased to 0.17 MΩ cm2 only after 31 days. The improvement in corrosion resistance was attributed to the transition of interface layer from porous Mg(OH)2 dominated one underneath pure ER coating to dense MgO dominated one underneath EB/ER coating, induced by the redox interaction of EB with Mg alloy. When the EB loading in EB/ER coating increased from 0 to 10 wt%, the relative XPS peak area ratio of MgO to Mg(OH)2 increased from 0.78 to 1.18, indicating that EB behaved as effective corrosion inhibitor causing the transformation of oxide layer from porous Mg(OH)2 to dense MgO.

  18. [Fluconazole 1200mg or 800mg for cryptococcal meningitis treatment in Ivory Coast].

    Kouakou, G A; Ello, N F; Kassi, N A; Keita, M; Doumbia, A; Mossou, C; Kassi, F K; Tanon, A; Ehui, E; Eholié, S P


    Assessing the use of high-dose fluconazol monotherapy (1200mg or 800mg) in the treatment and prognosis of HIV-associated cryptococcal meningitis in Ivory Coast. A retrospective study carried out from August 2008 to August 2011 based on patients charts suffering from CM in the Abidjan Tropicals and Infectious Disease Unit. Mortality rate and associated factors were analyzed. Forty-six cases of cryptococcal meningitis (2.5% of hospitalizations) were included. The sex-ratio was of 1.2. The median age was 40.5 [35-47] years. The symptomatology was subacute (93.5%). The main clinical symptoms were syndrome of pure meningeal irritation (65%), fever (100%); 35% of patients had encephalomeningits. Twenty-one (45.7%) was ART-naïve patients. Fluconazole 1200mg was prescribed to 29 (63%) patients. Therapeutic lumbar punctures were performed in 42 (91.3) patients. The mortality rate was 50%. Significant predictors of mortality were encephalomeningitis and therapeutic lumbar puncture. Cryptococcal meningitis associated mortality remains high despite the use of high-dose fluconazole monotherapy. Therapeutic lumbar punctures help to improving the prognosis. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  19. Combinatorial search for hydrogen storage alloys: Mg-Ni and Mg-Ni-Ti

    Oelmez, Rabia; Cakmak, Guelhan; Oeztuerk, Tayfur [Dept. of Metallurgical and Materials Engineering, Middle East Technical University, 06531 Ankara (Turkey)


    A combinatorial study was carried out for hydrogen storage alloys involving processes similar to those normally used in their fabrication. The study utilized a single sample of combined elemental (or compound) powders which were milled and consolidated into a bulk form and subsequently deformed to heavy strains. The mixture was then subjected to a post annealing treatment, which brings about solid state reactions between the powders, yielding equilibrium phases in the respective alloy system. A sample, comprising the equilibrium phases, was then pulverized and screened for hydrogen storage compositions. X-ray diffraction was used as a screening tool, the sample having been examined both in the as processed and the hydrogenated state. The method was successfully applied to Mg-Ni and Mg-Ni-Ti yielding the well known Mg{sub 2}Ni as the storage composition. It is concluded that a partitioning of the alloy system into regions of similar solidus temperature would be required to encompass the full spectrum of equilibrium phases. (author)

  20. Preparation of 24Mg-Fe-Cu Target

    FAN; Qi-wen; DU; Ying-hui; ZHANG; Rong


    <正>The three-layer-sandwich targets of 24Mg-Fe-Cu needed to be prepared in the physics experiment. The middle layers are thin ferromagnetic Fe layers of about 3.2 mg/cm2. The recoil stopper layers are thick crystallized and defect-free Cu layers of about 15 mg/cm2. The thickness of the 24Mg target layers is about 300 μg/cm2, and the uniformity should be better than 90%.

  1. MgB2 tunnel junctions and SQUIDs

    Brinkman, A.; Rowell, J.M.


    Recent advances in the realization and understanding of MgB2 tunnel junctions and SQUIDs are surveyed. High quality MgB2 junctions with suitable tunnel barriers have been realized based on both oriented and epitaxial thin MgB2 films. Multiband transport properties, such as the existence of two energ

  2. Hydrogen absorption and desorption in rapidly solidified Mg- Al alloys

    Urgnani, J.; Di Chio, M.; Palumbo, M.; Feuerbacher, M.; Fernandez, J. F.; Leardini, F.; Baricco, M.


    The addition of Al to Mg has been indicated as a suitable way to destabilise the hydride phase, in order to bring the absorption and desorption reactions close to reasonable temperatures and pressure values for hydrogen storage. Rapid solidification is known to refine the microstructure of Mg-Al alloys and it might improve the H2 absorption/desorption kinetics. In this paper, the interaction of H2 with rapidly solidified Mg-Al alloys have been studied for three different composition: Mg38.5Al61.5, Mg69Al31 and Mg72Al28. For Mg72Al28, no significant changes in the microstructure have been obtained by rapid solidification. In Mg69Al31, a significant grain refinement has been observed, whereas, for Mg38.5Al61.5, the formation of a metastable hexagonal phase has been found. In all cases, a disproportionation reaction has been observed after H2 absorption, leading to MgH2. After heating up to 430 °C the hydrogenated samples, a main desorption reaction from MgH2 has been observed, which brings again to the starting phases. Experimental results have been discussed on the basis of a thermodynamic assessment of the Mg-Al-H system.

  3. Thermodynamic assessment of the Bi-Mg binary system

    Chunju NIU; Changrong LI; Zhenmin DU; Cuiping GUO; Yongjuan JING


    The Bi-Mg binary system had been assessed by adopting the ionic melt and the modified quasi-chemical models to describe the liquid phase with short range ordering behavior.In general considerations of the development of the thermodynamic database of the multi-component Mg-based alloys and the consistency of the thermodynamic models of the related phases,the Gibbs energy descriptions of all the phases in the Bi-Mg binary system were reasonably re-modeled and critically re-assessed in the present work.Especially for the liquid phase,the associate model was used with the constituent species Bi,Mg and Bi2Mg3.The Mg-rich terminal phase hcp_A3 was modeled as a substitutional solution following Redlich-Kister equation and the Bi-rich terminal phase Rhombohedral_A7 was treated as a pure Bi substance since the extremely small solubility of Mg in Bi. The low and high temperature nonstoichiometric compounds β-Bi2Mg3 and α-Bi2Mg3 were described by the sublattice models (Bi,Va)2Mg3 and (Bi)1 (Bi,Va)aMg6 respectively based on their structure features.A set of self-consistent thermodynamic parameters of the Bi-Mg system was obtained and the experimental thermodynamic and phase equilibrium data were well reproduced by the optimized thermodynamic data.

  4. Hydrogen absorption and desorption in rapidly solidified Mg- Al alloys

    Urgnani, J; Di Chio, M; Palumbo, M; Baricco, M [Dipartimento di Chimica I.F.M. and NIS, Universita di Torino, via P. Giuria, 10125, Torino (Italy); Feuerbacher, M [Institut fuer Mikrostrukturforschung, Forschungszentrum Juelich GmbH, Leo-Brand- Strasse, 52428 Juelich (Germany); Fernandez, J F; Leardini, F, E-mail: jacopo.urgnani@unito.i [Departamento de Fisica de Materiales, Universidad Autonoma de Madrid, Cantoblanco, 28049, Madrid (Spain)


    The addition of Al to Mg has been indicated as a suitable way to destabilise the hydride phase, in order to bring the absorption and desorption reactions close to reasonable temperatures and pressure values for hydrogen storage. Rapid solidification is known to refine the microstructure of Mg-Al alloys and it might improve the H{sub 2} absorption/desorption kinetics. In this paper, the interaction of H{sub 2} with rapidly solidified Mg-Al alloys have been studied for three different composition: Mg{sub 38.5}Al{sub 61.5}, Mg{sub 69}Al{sub 31} and Mg{sub 72}Al{sub 28}. For Mg{sub 72}Al{sub 28}, no significant changes in the microstructure have been obtained by rapid solidification. In Mg{sub 69}Al{sub 31}, a significant grain refinement has been observed, whereas, for Mg{sub 38.5}Al{sub 61.5}, the formation of a metastable hexagonal phase has been found. In all cases, a disproportionation reaction has been observed after H{sub 2} absorption, leading to MgH{sub 2}. After heating up to 430 deg. C the hydrogenated samples, a main desorption reaction from MgH{sub 2} has been observed, which brings again to the starting phases. Experimental results have been discussed on the basis of a thermodynamic assessment of the Mg-Al-H system.

  5. Cardiovascular effect of dental anesthesia with articaine (40 mg with epinefrine 0,5 mg % and 40 mg with epinefrine 1 mg%) versus mepivacaine (30 mg and 20 mg with epinefrine 1 mg%) in medically compromised cardiac patients: a cross-over, randomized, single blinded study.

    Torres-Lagares, Daniel; Serrera-Figallo, María-Ángeles; Machuca-Portillo, Guillermo; Corcuera-Flores, José-Ramón; Machuca-Portillo, Carmen; Castillo-Oyagüe, Raquel; Gutiérrez-Pérez, José-Luis


    The aim of the present study is to compare cardiovascular safety profiles of two dental anesthetics: articaine versus two standard mepivacaine solutions used during etiological periodontal treatment in cardiovascular patients. Using a cross-over study design, ten cardiovascular patients were randomly assigned to dental treatment with 1.8 mL of a local anesthetic injected on each quadrant of the mouth: Articaine (40 mg with Epinephrine 0.5 mg % and 40 mg with Epinephrine 1mg %) or Mepivacaine (30 mg and 20 mg with Epinephrine 1mg %). A computer programme enabled continuous longitudinal data collection: O2 saturation, blood pressure (BP) and heart rate (HR). No severe clinical side effects were observed. During the treatment period, we observed statistically significant differences as regards HR between injections with and without adrenalin (p< 0.039) and as regards systolic (p< 0.046) and diastolic (p < 0.046) blood pressure during the stabilization period. In both cases, the parameters under study increase. Age, gender, jaw treated, treatment duration and the rest of cardiovascular variables did not affect the results. None of the patients underwent ischemic alterations or any other complication derived from the treatment or the anesthesia. According to the results of our study, dental anesthetics with standard concentrations of Epinephrine seem to alter HR and BP. Although no cardiac ischemic alterations or any other cardiovascular complications have been observed, we must be cautious with the administration of anesthetics containing vasoconstrictors in patients with cardiovascular diseases.

  6. Corrosion Resistance of the Superhydrophobic Mg(OH)2/Mg-Al Layered Double Hydroxide Coatings on Magnesium Alloys

    Zhang, Fen; Zhang, Changlei; Zeng, Rongchang; Song, Liang; Guo, Lian; Huang, Xiaowen


      Coatings of the Mg(OH)2/Mg-Al layered double hydroxide (LDH) composite were formed by a combined co-precipitation method and hydrothermal process on the AZ31 alloy substrate in alkaline condition...

  7. Fabrication of Mg-doped ZnO thin films by laser ablation of Zn:Mg target

    Kim, Tae Hyun; Park, Jin Jae; Nam, Sang Hwan; Park, Hye Sun; Cheong, Nu Ri [Department of Chemistry, Kyunghee University, Seoul 130-701 (Korea, Republic of); Song, Jae Kyu [Department of Chemistry, Kyunghee University, Seoul 130-701 (Korea, Republic of)], E-mail:; Park, Seung Min [Department of Chemistry, Kyunghee University, Seoul 130-701 (Korea, Republic of)], E-mail:


    Mg-doped ZnO thin films were fabricated by laser ablation of Zn:Mg targets consisting of Mg metallic strips and Zn disk in oxygen atmosphere with a goal to facilitate convenient control of Mg contents in the films. The characteristics of the deposited films were examined by analyzing their photoluminescence (PL), X-ray diffraction and X-ray photoelectron spectroscopy (XPS) spectra. Mg contents as analyzed by XPS indicate that the target composition is fairly transferred to the deposited films. The wurtzite structure of ZnO was conserved even for the highly doped ZnO films and there was no Mg- or MgO-related XRD peaks. With increase in the Mg content, the bandgap and PL peak energy shifted to blue and the Stokes shift became larger.

  8. Coherent interface structures and intergrain Josephson coupling in dense MgO/Mg{sub 2}Si/MgB{sub 2} nanocomposites

    Ueno, Katsuya; Takahashi, Kazuyuki; Uchino, Takashi, E-mail: [Department of Chemistry, Graduate School of Science, Kobe University, Nada, Kobe 657-8501 (Japan); Nagashima, Yukihito [Nippon Sheet Glass Co., Ltd., Konoike, Itami 664-8520 (Japan); Seto, Yusuke [Department of Planetology, Graduate School of Science, Kobe University, Nada, Kobe 657-8501 (Japan); Matsumoto, Megumi; Sakurai, Takahiro [Center for Support to Research and Education Activities, Kobe University, Nada, Kobe 657-8501 (Japan); Ohta, Hitoshi [Molecular Photoscience Research Center, Kobe University, Nada, Kobe 657-8501 (Japan)


    Many efforts are under way to control the structure of heterointerfaces in nanostructured composite materials for designing functionality and engineering application. However, the fabrication of high-quality heterointerfaces is challenging because the crystal/crystal interface is usually the most defective part of the nanocomposite materials. In this work, we show that fully dense insulator (MgO)/semiconductor(Mg{sub 2}Si)/superconductor(MgB{sub 2}) nanocomposites with atomically smooth and continuous interfaces, including epitaxial-like MgO/Mg{sub 2}Si interfaces, are obtained by solid phase reaction between metallic magnesium and a borosilicate glass. The resulting nanocomposites exhibit a semiconductor-superconducting transition at 36 K owing to the MgB{sub 2} nanograins surrounded by the MgO/Mg{sub 2}Si matrix. This transition is followed by the intergrain phase-lock transition at ∼24 K due to the construction of Josephson-coupled network, eventually leading to a near-zero resistance state at 17 K. The method not only provides a simple process to fabricate dense nanocomposites with high-quality interfaces, but also enables to investigate the electric and magnetic properties of embedded superconducting nanograins with good intergrain coupling.

  9. Structural and electronic properties of Mg and Mg-Nb co-doped TiO2 (101) anatase surface

    Sasani, Alireza [Department of Science, Karaj Islamic Azad University, Karaj, Alborz, P.O. Box 31485-313 (Iran, Islamic Republic of); Baktash, Ardeshir [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of); Mirabbaszadeh, Kavoos, E-mail: [Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, P. O. Box 15875-4413 (Iran, Islamic Republic of); Khoshnevisan, Bahram [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of)


    Highlights: • Formation energy of Mg and Mg-Nb co-doped TiO{sub 2} anatase surface (101) is studied. • Effect of Mg defect to the TiO{sub 2} anatase (101) surface and bond length distribution of the surface is studied and it is shown that Mg defects tend to stay far from each other. • Effect of Mg and Nb to the bond length distribution of the surface studied and it is shown that these defects tend to stay close to each other. • Effects of Mg and Mg-Nb defects on DSSCs using TiO{sub 2} anatase hosting these defects are studied. - Abstract: In this paper, by using density functional theory, Mg and Nb-Mg co-doping of TiO{sub 2} anatase (101) surfaces are studied. By studying the formation energy of the defects and the bond length distribution of the surface, it is shown that Mg defects tend to stay as far as possible to induce least possible lattice distortion while Nb and Mg defects stay close to each other to cause less stress to the surface. By investigating band structure of the surface and changes stemmed from the defects, potential effects of Mg and Mg-Nb co-doping of TiO{sub 2} surface on dye-sensitized solar cells are investigated. In this study, it is shown that the Nb-Mg co-doping could increase J{sub SC} of the surface while slightly decreasing V{sub OC} compared to Mg doped surface, which might result in an increase in efficiency of the DSSCs compared to Nb or Mg doped surfaces.

  10. NF3 Decomposition over Mn/MgO and Cr/MgO Without Water%NF3在Mn/MgO和Cr/MgO上的分解反应

    殷春晓; 毕翠玉; 张烽林; 徐秀峰


    用Mn (NO3)2和Cr(NO3)3溶液浸渍MgO制备了Mn/MgO和Cr/MgO系列脱氟剂;考察了无水条件下,NF3在Mn/MgO和Cr/MgO上的分解反应,并对反应前后的脱氟剂进行了XRD、N2吸附-脱附和EDX表征,分析了影响脱氟活性的原因.实验结果表明,Mn/MgO的脱氟活性显著高于MgO,但Cr/MgO的脱氟活性比MgO低;在反应气体积组成2%NF3/98%He、流量50 mL/min、脱氟剂用量2 g、400℃的条件下,NF3在10%(Mn原子与MgO的质量比)Mn/MgO上的全转化时间达460 min.依据表征结果和热力学计算数据,认为NF3与Mn/MgO反应生成的表层MnF3可与MgO进行氟/氧交换,促进了MgO的氟化反应,提高了Mn/MgO的脱氟活性;而NF3与Cr/MgO反应生成的表层CrF3不能与MgO进行氟/氧交换反应,且低比表面积、低孔体积的CrF3致密层附着在MgO表面,限制了NF3扩散至MgO孔中进行分解反应,降低了Cr/MgO的脱氟活性.

  11. Mg Alloy Foam Fabrication via Melt Foaming Method

    Donghui YANC; Changhwan SEO; Bo-Young HUR


    For the first time AZ91 (MgAl9Zn1) and AM60 (MgAl6) Mg alloy foams with homogeneous pore structures were prepared successfully via melt foaming method using CaCO3 as blowing agent. It is revealed that the blowing gas to foam the melt is not CO2 but CO, which comes from liquid-solid reaction between Mg melt. The reaction temperature is more than 100℃ lower than CaCO3 decomposition, which makes Mg alloy melts foam into cellular structure much more easily in the temperature range from 690℃ to 750℃.

  12. Study on Organization and Operation Mode of SMT-MG

    LI Chunquan; YU Tao; ZHOU Dejian


    SMT-MG is a typical application of grid in electric product manufacturing. The organization and operation mode are key problems in SMT-MG. In this paper, SMT-MG is taken as research object. Its mesh three-dimensional matrix organization mode is presented. Meanwhile from operation foundation, process, environment and target four aspects, operation principles are explored. Operation mechanisms of SMT-MG such as adaptive evolution, PUSH/PULL driving, cooperation and game, feedback, regulation/control, coordination, impetus mechanism and so on are studied. Finally, the operation flow of SMT-MG is introduced.

  13. The relation between the content of Al in Mg- Al alloy and the burning point of Mg - Al alloy%Mg-Al合金中Al含量对Mg-Al合金燃点影响的实验研究

    王世俊; 王泉; 汪岘


    研究了 Mg-Al合金中Al含量对Mg-Al合金燃点的影响,实验证明了保护熔剂能够有效的防止Mg-Al合金在熔炼中Mg和Al的氧化与燃烧,且在Al含量在10%~90%的Mg-Al合金中,Al含量40%的燃点最高,而在Al含量超过80%以后Mg-Al合金不发生燃烧现象.

  14. Administração inadvertida de 4 mg de morfina por via subaracnóidea: relato de caso Administración inadvertida de 4 mg de morfina por vía subaracnoidea: relato de caso Accidental subarachnoid administration of 4 mg of morphine: case report

    Bruno Salomé de Morais


    Full Text Available JUSTIFICATIVA E OBJETIVOS: A administração de morfina por via subaracnóidea é técnica bem estabelecida para analgesia pós-operatória devido a sua eficácia, segurança e baixo custo. A administração inadvertida de 4 mg de morfina por via subaracnóidea complicada por fibrilação atrial ap��s administração de naloxona foi o objetivo desse relato. RELATO DO CASO: Paciente do sexo masculino, 45 anos, 75 kg, 1,72 m, estado físico ASA II, hipertenso, a ser submetido à reconstrução do ligamento cruzado anterior do joelho esquerdo. Após a realização da raquianestesia, foi constatada troca da ampola de morfina, com administração de 4 mg (0,4 mL da ampola de 10 mg por via subaracnóidea. A freqüência respiratória oscilou entre 12 e 16 incursões respiratórias por minuto e o paciente manteve-se estável hemodinamicamente sem queixas no intra-operatório. Após 30 minutos da admissão na SRPA, apresentou vômitos e sudorese, tratados com 0,4 mg de naloxona seguidos de infusão contínua de 0,2 mg.h-1 até o desaparecimento dos sintomas. A infusão contínua de naloxona foi mantida na Unidade de Terapia Intensiva (UTI, onde a pressão arterial, freqüência cardíaca, freqüência respiratória, saturação de oxigênio foram monitoradas, assim como a presença de náusea, prurido, vômito, sedação, dor e retenção urinária observadas. Após 2 horas de admissão na UTI, o paciente apresentou fibrilação atrial aguda sem instabilidade hemodinâmica. O ritmo sinusal foi restabelecido após 150 mg de amiodarona e interrupção da infusão de naloxona. Nas 18 horas seguintes apresentou estabilidade hemodinâmica e evoluiu sem outras intercorrências até a alta hospitalar. CONCLUSÕES: O presente relato alerta para o risco de troca de medicamentos durante o ato anestésico e ressalta a importância do encaminhamento dos pacientes em tratamento de sobredose de opióides à UTI em virtude de seus potenciais efeitos adversos

  15. Intrinsic Conductivity in Magnesium-Oxygen Battery Discharge Products: MgO and MgO2

    Smith, Jeffrey G.; Naruse, Junichi; Hiramatsu, Hidehiko


    O, the equilibrium concentration of carriers in MgO2 is low, and moderate-to-poor mobility further limits conductivity. If equilibrium behavior is realized, then we conclude that (i) sluggish charge transport in MgO or MgO2 will limit battery performance when these compounds cover the cathode support and (ii) what...

  16. The structure of ? precipitates in Mg-Zn-Y alloys

    Singh, Alok; Rosalie, Julian M.; Somekawa, Hidetoshi; Mukai, Toshiji


    It is shown here by high-resolution electron microscopy that the structure of rod-like ? precipitates perpendicular to the basal planes of the magnesium matrix in Mg-Zn-Y alloys consist of complex domains at nanoscale. These domains can be recognized to be those of monoclinic Mg4Zn7 phase and hexagonal Laves phase MgZn2 with axial orientations ? . Due to disorder, often complete unit cells of the Mg4Zn7 structure cannot be recognized. Inside a domain of Mg4Zn7, the structure may locally transform to that of MgZn2. The structure of both the phases are composed of similar units of icosahedral coordinations. Maintaining the above axial orientation, the Mg4Zn7 can exhibit two orientation relationships with the matrix, ? or ? . The hexagonal MgZn2 forms in the monoclinic Mg4Zn7 in two different orientations, related to rhombic units (with angle ∼72°) in the Mg4Zn7 unit cell. With the common axial relationship given above, these two orientation relationships can be given as ? or ? . One of these two variants forms a known orientation relationship ? , ? with the matrix. The structure of the MgZn2 was found to be modified by the ordering of zinc layers perpendicular to the hexagonal axis.

  17. Interaction of hydrogen with an Mg-Al alloy (poster)

    Andreasen, A.; Andreasen, J.W.; Burkarl, R.;


    The properties of magnesium as a hydrogen storage medium may be positively altered by the addition of Al: thermodynamic properties, kinetics and heat transfer of the hydride bed can be improved. The interaction of hydrogen with a Mg-Al alloy pre-exposedto air has been studied with in-situ time...... energy for dehydrogenation of the Mg-Al alloy is found to be approx. 160 kJ/mol. This is not significantly higher than for pure and fully activated Mg.Furthermore, it is found that Mg-Al is hydrogenated to MgH2 + Al and upon dehydrogenation a Mg-Al alloy is reformed. Pure Mg is not observed during...

  18. Enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers by inhibiting Ta diffusion

    Li, Xu-Jing; Jiang, Shao-Long; Zhang, Jing-Yan; Liu, Qian-Qian; Liu, Yi-Wei; Zhao, Jian-Cheng [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Wu, Zheng-Long [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China); Feng, Chun, E-mail: [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Li, Ming-Hua [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Guang-Hua, E-mail: [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)


    Graphical abstract: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis have been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation to some extent due to the oxygen deficit MgO{sub x} (x < 1), and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent during the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (K{sub CoFeB/MgO}). As a result, the perpendicular magnetic anisotropy at high annealing temperatures was maintained. - Highlights: • High annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers was realized. • X-ray photoelectron spectroscopy analysis has been performed to explore the reasons. • The prevention of Ta diffusion was realized by introducing Mg at the CoFeB/MgO interface. - Abstracts: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis has been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation, and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent in the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (KCoFeB/MgO). As a result, the perpendicular magnetic anisotropy at high annealing temperatures is maintained.

  19. Thermodynamic description of the Mg-Nd-Zn ternary system

    Qi, H.Y.; Huang, G.X.; Bo, H.; Xu, G.L. [School of Material Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Liu, L.B., E-mail: [School of Material Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Education Ministry Key Laboratory of Non-ferrous Materials Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Center of Phase Diagram and Materials Design and Manufacture, Changsha, Hunan 410083 (China); Jin, Z.P. [School of Material Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Education Ministry Key Laboratory of Non-ferrous Materials Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Center of Phase Diagram and Materials Design and Manufacture, Changsha, Hunan 410083 (China)


    A thermodynamic description of the Mg-Nd-Zn system was developed by means of the CALPHAD (CALculation of PHAse Diagrams) method. The constituent binary systems Mg-Nd and Nd-Zn were re-optimized based on the experimental phase equilibria and thermodynamic properties available in the literature. Combining with the thermodynamic parameters of the Mg-Zn system cited from the reference, the Mg-Nd-Zn ternary system was evaluated. The Gibbs energies of the solution phases (liquid, BCC{sub A}2, DHCP, HCP{sub A}3 and HCP{sub Z}n) were described by the subregular solution model with the Redlich-Kister polynomial function, and those of the stoichiometric compounds, Nd{sub 2}Zn{sub 17}, NdZn{sub 11H}, NdZn{sub 11L}, Nd{sub 3}Zn{sub 22}, Nd{sub 13}Zn{sub 58}, Nd{sub 3}Zn{sub 11}, NdZn{sub 3}, NdZn{sub 2} and Mg{sub 2}Nd, were described by the sublattice model. The compounds Mg{sub 3}Nd and Mg{sub 41}Nd{sub 5} in the Mg-Nd-Zn system were treated as the formulae (Mg, Zn){sub 3}(Mg, Nd) and (Mg, Nd, Zn){sub 41}(Mg, Nd){sub 5}. The order-disorder transition between BCC{sub B}2 and BCC{sub A}2 phases was treated using a two-sublattice model (Mg, Nd, Zn){sub 0.5}(Mg, Nd, Zn){sub 0.5}. Based on experimental data, four stable ternary compounds {tau}{sub 1}(Mg{sub 7}Nd{sub 1}Zn{sub 12}), {tau}{sub 2}(Mg{sub 7}Nd{sub 2}Zn{sub 11}), {tau}{sub 3}(Mg{sub 6}Nd{sub 1}Zn{sub 3}) and {tau}{sub 4}(Mg{sub 6}Nd{sub 3}Zn{sub 11}) were taken into consideration in this system. A set of self-consistent thermodynamic parameters of the Mg-Nd-Zn system was obtained. Projection of the liquidus surface, selected vertical and isothermal sections were calculated using the proposed thermodynamic description. Comprehensive comparisons between the calculated and measured phase diagrams show that almost all the accurate experimental information is satisfactorily accounted for by the present thermodynamic description.

  20. Full-potential KKR-calculations for MgO and divalent impurities in MgO

    Baranov, A. N.; Stepanyuk, V. S.; Hergert, W.; Katsnelson, A. A.; Settels, A.; Zeller, R.; Dederichs, P. H.


    We present a detailed investigation of bulk properties of MgO and lattice relaxations around divalent impurities in MgO by means of the full-potential Korringa-Kohn-Rostoker Green's function method. The local-density approximation and the perturbative generalized gradient corrections are used to calculate the lattice constant and bulk modulus of MgO. We obtain a very good description of the ground properties of MgO. Lattice relaxations around divalent impurities in MgO are determined using an...

  1. Superior MgH2 Kinetics with MgO Addition: A Tribological Effect

    Kondo-Francois Aguey-Zinsou


    Full Text Available The kinetics of hydrogen absorption/desorption in magnesium can be improved without any catalysis assistance and MgO was found to be more effective than the best catalyst reported so far, i.e., Nb2O5. Herein, a quantitative analysis of the hydrogen kinetics in magnesium modified with MgO was performed in order to identify possible rate controlling mechanisms. While hydrogen absorption was found to be diffusion controlled as commonly reported, hydrogen desorption evolved from nucleation and growth to an interface controlled process depending on the desorption temperature. Comparison with the effect of Nb2O5 indicates that similar rate limiting steps occur regardless of the oxide additive. These findings are reconciled by considering the tribological effect of solid oxide additives, as a correlation between oxides electronegativity and improvement in hydrogen kinetics was found. Such a correlation clearly highlights the mechanical effect of solid oxides in facilitating the grinding and stabilisation of small magnesium particles for efficient and fast hydrogen kinetics.

  2. From $^{27}$Mg to ${33}$Mg transition to the "Island of inversion"

    Yordanov, Deyan

    Since introduced in nuclear physics, the concept of shell structure and magic numbers has governed our understanding of nuclear matter in atomic nuclei close to stability. Nuclear species with a magic number of protons and/or neutrons are known to be more stable and close to spherical in shape. Experimental studies of 30Ne, 31Na and 32Mg, systems with a closed neutron sd shell (N=20), provide evidence for a ground-state deformation in these nuclei. The observed phenomenon is understood as an inversion of the normal spherical ground-state configuration, expected according to the traditional shell model, with deformed states governed by particle-hole excitations over the N=20 shell gap. The properties of nuclei in this Island of inversion are of particular importance for the theoretical modeling of the region. The present doctoral dissertation reports on the first determination of the nuclear ground-state spins and magnetic moments of 31,33Mg, obtained by means of laser spectroscopy in combination with nuclear...

  3. Structure of Mg$_n$ and Mg$_n^+$ clusters up to n=30

    Janecek, Stefan


    We present structure calculations of neutral and singly ionized Mg clusters of up to 30 atoms, as well as Na clusters of up to 10 atoms. The calculations have been performed using density functional theory (DFT) within the local (spin-)density approximation, ion cores are described by pseudopotentials. We have utilized a new algorithm for solving the Kohn-Sham equations that is formulated entirely in coordinate space and, thus, permits straightforward control of the spatial resolution. Our numerical method is particularly suitable for modern parallel computer architectures; we have thus been able to combine an unrestricted simulated annealing procedure with electronic structure calculations of high spatial resolution, corresponding to a plane-wave cutoff of 954eV for Mg. We report the geometric structures of the resulting ground-state configurations and a few low-lying isomers. The energetics and HOMO-LUMO gaps of the ground-state configurations are carefully examined and related to their stability properties...

  4. Clustering effects in 48Cr composite nuclei produced via 24Mg + 24Mg reaction

    Cinausero M.


    Full Text Available In the framework of studying clustering effects in N=Z light nuclei, an experiment was carried out to get information on the properties of the 48Cr composite nuclei produced via the 24Mg +24Mg reaction. In particular, the study regards the 48Cr at 60 MeV of excitation energy where a resonance with a narrow width (170 KeV has been found by measuring the elastic and anelastic channels. To determine the deformation of this state, evaporative Light Charged Particles (LCP are measured and compared to the Statistical Model (SM predictions, which are very sensitive to nuclear deformation. The experiment was performed at LNL using the 8ĒLP apparatus to select LCPs and a Parallel Plate Avalanche Counter (PPAC system to detect the Evaporation Residues (ER. Preliminary results on the measurements of ER – LCP and LCP – LCP angular correlations are presented which indicate the presence of a very large deformation.The analysis will proceed with the extraction of the LCP energy spectra and with the angular correlations for high multiplicity channels to determine the deformation.

  5. Thermodynamic re-optimization of the Cu-Mg-Sn system at the Cu-Mg side

    Miettinen J.


    Full Text Available Thermodynamic description of the ternary Cu-Mg-Sn system at its Cu-Mg side is presented. The thermodynamic parameters of the binary sub-systems, Cu-Mg, Cu-Sn and Mg-Sn, are taken from the earlier SGTE-based assessments (modifying the Mg-Sn description slightly and those of the Cu-Mg-Si system are optimized in this study using the experimental thermodynamic and phase equilibrium data. The solution phases of the systems are described with the substitutional solution model and the intermetallic Cu2Mg compound (Laves C15, treated as simple semi-stoichiometric phases of the (A,BpCq type, is described with the twosublattice model. The present ternary description is valid for tin contents up to 45 wt% (xSn≈0.30.

  6. Recycling of AZ31 Mg alloy with high purity Mg deposition layer by hot working (solid recycling)

    Chino, Y.; Mabuchi, M. [Inst. for Structural and Engineering Materials, National Inst. of Advanced Industrial Science and Technology, Nagoya (Japan); Yamamoto, A.; Iwasaki, H.; Tsubakino, H. [Div. of Materials Science and Engineering, Graduate School of Himeji Inst. of Tech., Himeji (Japan)


    Solid recycling of AZ31 Mg alloy with vapor deposition coating layer of high purity Mg was evaluated. In the open die forging experiments, two AZ31 Mg alloy specimens with the pure Mg layer were sufficiently bonded by forging at 673 K. Furthermore, the Al and Zn of the AZ31 substrate diffused up to the center of the pure Mg layer. By the theoretical analysis, it is suggested that the grain boundary diffusion enhanced by grain refinement due to hot forging contributes to the solid state bonding of the specimens. Also, the solid recycled specimen was fabricated from the AZ31 Mg substrate with pure Mg layer by hot extrusion at 673 K. The solid recycled specimen showed almost the same tensile properties as the virgin extruded specimen. This is probably related not only to the grain boundary diffusion but also severe plastic deformation by hot extrusion. (orig.)

  7. Corrosion behavior of Mg/graphene composite in aqueous electrolyte

    Selvam, M. [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India); Saminathan, K., E-mail: [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India); Siva, P. [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India); Saha, P. [Department of Ceramic Engineering, National Institute of Technology, Rourkela, India-769008 (India); Rajendran, V. [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India)


    In the present work, the electrochemical corrosion behavior of magnesium (Mg) and thin layer graphene coated Mg (Mg/graphene) are studied in different salt electrolyte such as NaCl, KCl and Na{sub 2}SO{sub 4}. The phase structure, crystallinity, and surface morphology of the samples are investigated using X-ray diffraction (XRD) analysis, scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDAX), and Raman spectroscopy techniques. The electrochemical corrosion behavior of the Mg and graphene coated Mg are also investigated using Electrochemical Impedance Spectroscopy (EIS) analysis. The tafel plot reveals that the corrosion of Mg drastically drops when coated with thin layer graphene (Mg/graphene) compared to Mg in KCl electrolyte. Moreover, the EIS confirms that Mg/graphene sample shows improve corrosion resistance and lower corrosion rate in KCl solution compare to all other electrolytes studied in the present system. - Highlights: • The corrosion behavior of magnesium alloy (AZ91) was investigated in three different electrolyte solution. • To study the anti-corrosion behavior of graphene coated with magnesium alloy. • To improve the corrosion resistance for magnesium alloy. • Nyquist plots confirms that MgG shows better corrosion resistance and lower corrosion rate in KCl solution.

  8. Interaction of hydrogen with an Mg-Al alloy (poster)

    Andreasen, A.; Andreasen, J.W.; Burkarl, R.


    The properties of magnesium as a hydrogen storage medium may be positively altered by the addition of Al: thermodynamic properties, kinetics and heat transfer of the hydride bed can be improved. The interaction of hydrogen with a Mg-Al alloy pre-exposedto air has been studied with in-situ time...... energy for dehydrogenation of the Mg-Al alloy is found to be approx. 160 kJ/mol. This is not significantly higher than for pure and fully activated Mg.Furthermore, it is found that Mg-Al is hydrogenated to MgH2 + Al and upon dehydrogenation a Mg-Al alloy is reformed. Pure Mg is not observed during...... dehydrogenation, suggesting that the formation of Mg-Al is fast compared to the liberation of hydrogen fromMgH2. From thermodynamical calculations using the semi-empirical Miedema model a slightly lower heat of hydride formation is found. Based on comparison with previous experiments on Mg exposed to air...

  9. Neutron spectroscopy of gamma-MgH2

    Kolesnikov, Alexander; Antonov, Vladimir; Efimchenko, Vadim; Granroth, Garrett; Klyamkin, S. N.; Levchenko, A. V.; Sakharov, Michael; Ren, Yang; Ramirez-Cuesta, Timmy


    Under ambient conditions, magnesium dihydride exists in two forms, alpha-MgH2 (the most stable modification) and gamma-MgH2 (a less stable modification). The alpha-phase partly transforms to gamma-MgH2 in the course of ball-milling and under high pressure and temperature. Due to the high hydrogen content of 7.6 wt.%, MgH2 has been intensively studied as a prospective material for hydrogen storage. By exposing of alpha-MgH2 to a pressure of 5 GPa and temperature 840 K, we prepared a sample, in which about 60% of the alpha-MgH2 was transformed to gamma-MgH2. We have measured inelastic neutron scattering (INS) spectra of both the high pressure treated MgH2 and starting alpha-MgH2, and extracted the spectrum for gamma-MgH2. The differences between the INS spectra and their agreement with the first-principles calculations for these compounds will be discussed.

  10. Mg isotope fractionation during microbe-mineral interactions

    Kim, Insu; Ryu, Jong-sik; Lee, Kwang-sik; Lee, Dongho


    Magnesium is involved in various biogeochemical processes important to the global climate change over geological time-scale. Mg isotopes allow us to directly trace the Mg cycle in the Earth's surface but the factors controlling Mg isotopic compositions have not fully understood yet. Here, we conducted a batch experiment using two bacterial species (Shewanella putrefaciens and Burkholderia fungorum) and three major Mg-bearing minerals (biotite, dolomite and hornblende). All elemental concentrations increased by 336 h and then reached to steady-state values, of which Mg concentrations varied depending on minerals and bacterial species. This result indicates that the mineral dissolution is affect by the presence of microbes, which either provide organic acids or attach onto mineral surface. The Mg isotopic compositions of initial minerals biotite, dolomite and hornblende are -0.35o of biotite, -0.99o of dolomite, and -0.24o of hornblende, in δ26Mg. Similarly, δ26Mg values increased by 336 h and reached to steady-state values, which also varied with minerals and microbes. During dissolution of three minerals, the light isotope of Mg is preferentially incorporated into the dissolved phases and then the dissolved δ26Mg values become consistent with those of minerals with the time.

  11. Low-energy radioactive ion beam production of 22Mg

    Duy, N. N.; Kubono, S.; Yamaguchi, H.; Kahl, D.; Wakabayashi, Y.; Teranishi, T.; Iwasa, N.; Kwon, Y. K.; Khiem, L. H.; Kim, Y. H.; Song, J. S.; Hu, J.; Ayyad, Y.


    The 22Mg nucleus plays an important role in nuclear astrophysics, specially in the 22Mg(α,p)25Al and proton capture 22Mg(p,γ)23Al reactions. It is believed that 22Mg is a waiting point in the αp-process of nucleosynthesis in novae. We proposed a direct measurement of the 22Mg+α resonance reaction in inverse kinematics using a radioactive ion (RI) beam. A 22Mg beam of 3.73 MeV/u was produced at CRIB (Center for Nuclear Study (CNS) low-energy RI Beam) facility of the University of Tokyo located at RIKEN (Japan) in 2011. In this paper we present the results about the production of the 22Mg beam used for the direct measurement of the scattering reaction 22Mg(α,α)22Mg, and the stellar reaction 22Mg(α,p)25Al in the energy region concerning an astrophysical temperature of T9=1-3 GK.

  12. Laser multi-layer cladding of Mg-based alloys

    陈长军; 王东生; 王茂才


    By laser multi-layer cladding using a pulsed Nd-YAG irradiation the thickness of the cladding zone Mg-based alloys(ZM2 and ZM5) can reach about 1. 0 mm. The microstructure of the substrate and the cladding zone wasstudied using optical microscope, scanning electron microscopy(SEM), X-ray diffractometry(XRD) and micro hard-ness analysis. It is observed that constituent of ZM5 alloy is δ+Mg17 Al12, that of ZM2 alloy is α+MgZn+Mg9Ce.That of cladding layer ZM2 alloy(L-ZM2) is Mg+ Mg2 Zn11 +MgCe; while that of the cladding layer ZM5 alloy(L-ZM5) is Mg+Mg32 (Al, Zn)49. The hardness of the cladding area can be increased to values above HV127. Veryfine uniform microstructure and the produced new phases of nanometer/sub-micrometer order were obtained. Now,many repaired Mg-based alloy components have been passed by flying test in outside field.

  13. Adsorption of arginine, glycine and aspartic acid on Mg and Mg-based alloy surfaces: A first-principles study

    Fang, Zhe; Wang, Jianfeng; Yang, Xiaofan; Sun, Qiang; Jia, Yu; Liu, Hairong; Xi, Tingfei; Guan, Shaokang


    Studying the adsorption behaviors of biomolecules on the surface of Mg and Mg-based alloy has a fundamental and important role for related applications in biotechnology. In the present work, we systematically investigate and compare the adsorption properties of three typical amino acids, i.e., Arg (arginine), Gly (glycine) and Asp (aspartic acid), which form RGD tripeptide, on the Mg (0 0 0 1) surface with various doping (Zn, Y, and Nd), and aim to realize proper binding between biomolecules and Mg and Mg-based biomedical materials. Our results show that flat adsorption configurations of the functional groups binding to the surfaces are favored in energy for all the three selected amino acids. In specific, for the amino acids adsorped on clean Mg (0 0 0 1) surface, the adsorption energy (Eads) of Arg is found to be -1.67 eV for the most stable configuration, with amino and guanidyl groups binding with the surface. However, Gly (Asp) is found to binding with the surface through amino and carboxyl groups, with a -1.16 eV (-1.15 eV) binding energy. On the 2% Zn doped Mg (0 0 0 1) alloy surface (Mg-Zn (2%)), the Eads are significantly increased to be -1.91 eV, -1.32 eV and -1.35 eV for Arg, Gly and Asp, respectively. While the Mg-Y (1%) and Mg-Nd (1%) slightly weaken the adsorption of three amino acids. Moreover, we have performed detail discussions of the binding properties between amino acids and surfaces by projected density of states (PDOS) combined with charge transfer analyses. Our studies provide a comprehensive understanding on the interactions between amino acids and Mg and Mg-based alloy surfaces, with respect to facilitate the applications of Mg and Mg-based biomedical alloys in biosensing, drug delivery, biomolecule coating and other fields in biotechnology.

  14. Dinuclear Metallacycles with Single M-X-M Bridges (X = Cl(-), Br(-); M = Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II)): Strong Antiferromagnetic Superexchange Interactions.

    Reger, Daniel L; Pascui, Andrea E; Foley, Elizabeth A; Smith, Mark D; Jezierska, Julia; Wojciechowska, Agnieszka; Stoian, Sebastian A; Ozarowski, Andrew


    A series of monochloride-bridged, dinuclear metallacycles of the general formula [M2(μ-Cl)(μ-L)2](ClO4)3 have been prepared using the third-generation, ditopic bis(pyrazolyl)methane ligands L = m-bis[bis(1-pyrazolyl)methyl]benzene (Lm), M = Cu(II), Zn(II), and L = m-bis[bis(3,5-dimethyl-1-pyrazolyl)methyl]benzene (Lm*), M = Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II). These complexes were synthesized from the direct reactions of M(ClO4)2·6H2O, MCl2, and the ligand, Lm or Lm*, in the appropriate stoichiometric amounts. Three analogous complexes of the formula [M2(μ-Cl)(μ-L)2](BF4)3, L = Lm, M = Cu(II), and L = Lm*, M = Co(II), Cu(II), were prepared from the reaction of [M2(μ-F)(μ-L)2](BF4)3 and (CH3)3SiCl. The bromide-bridged complex [Cu2(μ-Br)(μ-Lm*)2](ClO4)3 was prepared by the first method. Three acyclic complexes, [Co2(μ-Lm)μ-Cl4], [Co2(μ-Lm*)Cl4], and [Co2(μ-Lm*)Br4], were also prepared. The structures of all [M2(μ-X)(μ-L)2](3+) (X = Cl(-), Br(-)) complexes have two ditopic bis(pyrazolyl)methane ligands bridging two metals in a metallacyclic arrangement. The fifth coordination site of the distorted trigonal bipyramidal metal centers is filled by a bridging halide ligand that has an unusual linear or nearly linear M-X-M angle. The NMR spectra of [Zn2(μ-Cl)(μ-Lm*)2](ClO4)3 and especially [Cd2(μ-Cl)(μ-Lm*)2](ClO4)3 demonstrate that the metallacycle structure is maintained in solution. Solid state magnetic susceptibility data for the copper(II) compounds show very strong antiferromagnetic exchange interactions, with -J values of 536 cm(-1) for [Cu2(μ-Cl)(μ-Lm)2](ClO4)3·xCH3CN, 720 cm(-1) for [Cu2(μ-Cl)(μ-Lm*)2](ClO4)3, and 945 cm(-1) for [Cu2(μ-Br)(μ-Lm*)2](ClO4)3·2CH3CN. Smaller but still substantial antiferromagnetic interactions are observed with other first row transition metals, with -J values of 98 cm(-1) for [Ni2(μ-Cl)(μ-Lm*)2](ClO4)3, 55 cm(-1) for [Co2(μ-Cl)(μ-Lm*)2](ClO4)3, and 34 cm(-1) for [Fe2(μ-Cl)(μ-Lm*)2](ClO4

  15. Thermodynamic modeling of the Ba - Mg binary system

    Ren, Xin; Li, Changrong; Du, Zhenmin; Guo, Cuiping; Chen, Sicheng [Univ. of Science and Technology, Beijing (China). School of Materials Science and Engineering


    On the basis of the thermochemical and phase equilibrium experimental data, the phase diagram of the Ba - Mg binary system has been assessed by means of the calculation of phase diagrams technique. The liquid phase is of unlimited solubility and modeled as a solution phase using the Redlich-Kister equation. The intermetallic compounds, Mg{sub 17}Ba{sub 2}, Mg{sub 23}Ba{sub 6} and Mg{sub 2}Ba, with no solubility ranges are treated as strict stoichiometric compounds with the formula Mg{sub m} Ba{sub n}. Two terminal phases, BccBa and HcpMg, are kept as solution phases, since the solubilities of the two phases are of considerable importance. After optimization, a set of self-consistent thermodynamic parameters has been obtained. The calculated values agree well with the available experimental data.

  16. Mg-ion indiffusion of lithium niobate single crystal fiber

    阙文修; 姚熹; 霍玉晶


    A core-cladding waveguide structure of lithium niobate single crystal fiber with different refractive index profiles has been obtained by using an Mg-ion indiffusion process. The propagation loss of the dadded crystal fiber is measured to be 14 times as low as that of the undadded crystal fibers. Mechanisms of Mg-ion indiffusion and reasons of lattice distortion are analyzed and discussed. It is found by X-ray diffraction analysis as well as scanning electron microscopy that MgO-rich layer in the magnesium diffused surface exhibits the crystal structure of a new compound from the Li-Mg-Nb-O ternary system. It is proposed, for the first time, that this new compound in MgO-rich layer is the real source of Mg-ion indiffusion lithium niobate.

  17. Aqueous magnesium ion battery based on carbon-coated FeVO4 as anode and Mg-OMS-1 as cathode with high energy density.

    Zhang, Hongyu; Ye, Ke; Zhu, Kai; Cang, Ruibai; Yan, Jun; Cheng, Kui; Wang, Guiling; Cao, Dianxue


    The porous FeVO4 is prepared by hydrothermal method and further modified by coating carbon to obtain the FeVO4/C with hierarchical pore structure, which are used as anodic electrodes in aqueous rechargeable magnesium ion battery. And the FeVO4/C material can not only improve the electrical conductivity by coating a carbon layer but also increase the specific surface area by hierarchical pore structure, which is more beneficial for magnesium ion insertion/deinsertion. Therefore, the aqueous rechargeable magnesium ion full battery is successfully constructed by FeVO4/C as anode, Mg-OMS-1 as cathode and in 1.0 mol L-1 MgSO4 as electrolyte. The discharge capacity of Mg-OMS-1 // FeVO4/C aqueous battery can be obtained 58.9 mAh g-1 at the current density of 100 mA g-1 by calculating the total mass of two electrodes and the capacity retention rate of this device is 97.7% after 100 cycles with the nearly 100% coulombic efficiency, which indicates that the system owns a good electrochemical reversibility. More than that, this system can achieve a high energy density of 70.4 Wh kg-1, which provides a powerful evidence to make the aqueous magnesium ion battery possible. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Gastroduodenal tolerance of 75 mg clopidogrel versus 325 mg aspirin in healthy volunteers. A gastroscopic study.

    Fork, F T; Lafolie, P; Tóth, E; Lindgärde, F


    Clopidogrel is a new antiplatelet agent that offers increased protection over aspirin in preventing vascular ischaemic events in patients with symptomatic atherosclerosis. In a large, randomized, international study of clopidogrel and aspirin (n = 19,185 patients) clopidogrel was associated with a lower incidence of gastrointestinal adverse events, including gastrointestinal haemorrhage and hospitalizations because of gastrointestinal haemorrhage. The aim of the study was to determine whether macroscopic differences in the gastric mucosa between aspirin- and clopidogrel-treated subjects could be detected by gastroscopy after short-term treatment. Thirty-six healthy volunteers were randomized in a double-blind, double-dummy, parallel design, to 75 mg/day of clopidogrel or 325 mg/day of aspirin for 8 days. Gastroscopy was performed at base line before administration of study drug and directly after treatment completion. Gastroduodenal effects were measured in accordance with a modified Lanza scale. At base line no difference between the groups was detected (median Lanza score, 0.0 in both groups). At the end of treatment the aspirin group showed a median score of 7.5, and the clopidogrel group showed an unchanged median score of 0.0 (P < 0.001). In the aspirin group 13 individuals reported 19 adverse events versus 8 individuals and 13 adverse events for clopidogrel, with approximately half of the adverse events being gastrointestinal in each group. No serious adverse events were reported. In contrast to aspirin, short-term treatment with clopidogrel does not induce macroscopic changes in the gastroduodenal mucosa. The study results show that in patients without gastroduodenal disease clopidogrel, but not aspirin, does not induce any gastroscopically evident erosions during short-term treatment.

  19. The van der Waals potentials of MgCa, MgSr, MgBa, CaSr, CaBa, and SrBa

    Wei, L. M.; Li, P.; Tang, K. T.


    Based on the facts that the potential energy curves of the homo-nuclear group 2 dimers (group IIA metal), except Be2, are conformal, and they can be described by the Tang-Toennies potential model, a set of simple combining rules are proposed for the parameters of the reduced potentials of the hetero-nuclear dimers. Together with the well-established combining rules of the range parameters of the exponential repulsion and the known dispersion coefficients, these rules enable us to determine the ground state potential energy curves of MgCa, MgSr, MgBa, CaSr, CaBa, and SrBa from those of Mg2, Ca2, Sr2, and Ba2. The determined potentials are comparable to some ab initio calculations and in excellent agreement with the experiment.

  20. MgO nanoparticles as antibacterial agent: preparation and activity

    Zhen-Xing Tang; Bin-Feng Lv


    Bacterial pollution is a great risk for human health. Nanotechnology offers a way to develop new inorganic antibacterial agents. Nano-inorganic metal oxide has a potential to reduce bacterial contamination. MgO is an important inorganic oxide and has been widely used in many fields. Many studies have shown that MgO nanoparticles have good antibacterial activity. Therefore, in this paper, the main synthesis methods, antibacterial activity and antibacterial mechanisms of MgO nanoparticles are r...

  1. MgO nanoparticles as antibacterial agent: preparation and activity

    Zhen-Xing Tang; Bin-Feng Lv


    Bacterial pollution is a great risk for human health. Nanotechnology offers a way to develop new inorganic antibacterial agents. Nano-inorganic metal oxide has a potential to reduce bacterial contamination. MgO is an important inorganic oxide and has been widely used in many fields. Many studies have shown that MgO nanoparticles have good antibacterial activity. Therefore, in this paper, the main synthesis methods, antibacterial activity and antibacterial mechanisms of MgO nanoparticles are r...

  2. Oxidation of Mg adsorbed on Ru(001): A photoemission study

    Malik, I.J.; Hrbek, J. (Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)); Shek, M. (National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973 (United States)); Bzowski, A.; Kristof, P.; Sham, T.K. (Department of Chemistry, University of Western Ontario, London, Ontario NA6 5B7 (Canada))


    We studied the interaction of oxygen with Mg overlayers adsorbed on Ru(001). Soft x-ray synchrotron radiation was used to explore photoemission from the valence band, the O 2{ital p}, O 2{ital s}, and Mg 2{ital p} levels, as well as intra- and interatomic Auger processes. The photoemission results are complemented by thermal desorption data. The O/Mg/Ru system shows photoemission features characteristic of molecular orbitals of a dioxygen species.

  3. MgO nanoparticles as antibacterial agent: preparation and activity

    Tang, Zhen-Xing, E-mail: [Department of Food Science, Anqing, Vocational and Technical College, Anqing, Anhui (China); Lv, Bin-Feng [Date Palm Research Center, King Faisal University, (Saudi Arabia)


    Bacterial pollution is a great risk for human health. Nanotechnology offers a way to develop new inorganic antibacterial agents. Nano-inorganic metal oxide has a potential to reduce bacterial contamination. MgO is an important inorganic oxide and has been widely used in many fields. Many studies have shown that MgO nanoparticles have good antibacterial activity. Therefore, in this paper, the main synthesis methods, antibacterial activity and antibacterial mechanisms of MgO nanoparticles are reviewed. (author)

  4. Attempts at doping indium in MgB2

    Grivel, Jean-Claude


    Indium (In) doped MgB2 polycrystalline samples were prepared by solid-liquid phase reaction in Ar. After reaction at 800 °C, less than 1 at.% Mg was replaced by In in the MgB2 phase, without significant influence on its lattice parameters and only a slight decrease of its superconducting transition...... in both the doped and undoped samples....

  5. Hydrodechlorination of Tetrachloromethane over Palladium Catalysts Supported on Mixed MgF2-MgO Carriers

    Magdalena Bonarowska


    Full Text Available Pd/MgO, Pd/MgF2 and Pd/MgO-MgF2 catalysts were investigated in the reaction of CCl4 hydrodechlorination. All the catalysts deactivated in time on stream, but the degree of deactivation varied from catalyst to catalyst. The MgF2-supported palladium with relatively large metal particles appeared the best catalyst, characterized by good activity and selectivity to C2-C5 hydrocarbons. Investigation of post-reaction catalyst samples allowed to find several details associated with the working state of hydrodechlorination catalysts. The role of support acidity was quite complex. On the one hand, a definite, although not very high Lewis acidity of MgF2 is beneficial for shaping high activity of palladium catalysts. The MgO-MgF2 support characterized by stronger Lewis acidity than MgF2 contributes to very good catalytic activity for a relatively long reaction period (~5 h but subsequent neutralization of stronger acid centers (by coking eliminates them from the catalyst. On the other hand, the role of acidity evolution, which takes place when basic supports (like MgO are chlorided during HdCl reactions, is difficult to assess because different events associated with distribution of chlorided support species, leading to partial or even full blocking of the surface of palladium, which plays the role of active component in HdCl reactions.

  6. Enhanced voltage-controlled magnetic anisotropy in magnetic tunnel junctions with an MgO/PZT/MgO tunnel barrier

    Chien, Diana; Li, Xiang; Wong, Kin; Zurbuchen, Mark A.; Robbennolt, Shauna; Yu, Guoqiang; Tolbert, Sarah; Kioussis, Nicholas; Khalili Amiri, Pedram; Wang, Kang L.; Chang, Jane P.


    Compared with current-controlled magnetization switching in a perpendicular magnetic tunnel junction (MTJ), electric field- or voltage-induced magnetization switching reduces the writing energy of the memory cell, which also results in increased memory density. In this work, an ultra-thin PZT film with high dielectric constant was integrated into the tunneling oxide layer to enhance the voltage-controlled magnetic anisotropy (VCMA) effect. The growth of MTJ stacks with an MgO/PZT/MgO tunnel barrier was performed using a combination of sputtering and atomic layer deposition techniques. The fabricated MTJs with the MgO/PZT/MgO barrier demonstrate a VCMA coefficient, which is ˜40% higher (19.8 ± 1.3 fJ/V m) than the control sample MTJs with an MgO barrier (14.3 ± 2.7 fJ/V m). The MTJs with the MgO/PZT/MgO barrier also possess a sizeable tunneling magnetoresistance (TMR) of more than 50% at room temperature, comparable to the control MTJs with an MgO barrier. The TMR and enhanced VCMA effect demonstrated simultaneously in this work make the MgO/PZT/MgO barrier-based MTJs potential candidates for future voltage-controlled, ultralow-power, and high-density magnetic random access memory devices.

  7. Comparing the Electrochemical Performance of LiFePO4/C Modified by Mg Doping and MgO Coating

    Jianjun Song


    Full Text Available Supervalent cation doping and metal oxide coating are the most efficacious and popular methods to optimize the property of LiFePO4 lithium battery material. Mg-doped and MgO-coated LiFePO4/C were synthesized to analyze their individual influence on the electrochemical performance of active material. The specific capacity and rate capability of LiFePO4/C are improved by both MgO coating and Mg doping, especially the Mg-doped sample—Li0.985Mg0.015FePO4/C, whose discharge capacity is up to 163 mAh g−1, 145.5 mAh g−1, 128.3 mAh g−1, and 103.7 mAh g−1 at 1 C, 2 C, 5 C, and 10 C, respectively. The cyclic life of electrode is obviously increased by MgO surface modification, and the discharge capacity retention rate of sample LiFePO4/C-MgO2.5 is up to 104.2% after 100 cycles. Comparing samples modified by these two methods, Mg doping is more prominent on prompting the capacity and rate capability of LiFePO4, while MgO coating is superior in terms of improving cyclic performance.

  8. Hydrogen generation via hydrolysis of nanocrystalline MgH2 and MgH2-based composites

    HU Lian-xi; WANG Er-de


    Nanocrystalline MgH2 and MgH2-based composites with 25% (mass fraction) of Al, Ca, or CaH2 as an individual additive respectively were prepared by ball milling. The crystallite size and morphology of the as-milled powders were characterized and their hydrolysis behaviours were investigated in comparison with commercial polycrystalline MgH2. The results show that the crystallite size of both MgH2 and MgH2-based composites is reduced to less than 13 nm after milling for 15 h. Due to its enhanced specific surface area and unique nanocrystalline structure, the as-milled MgH2 shows much better hydrolysis kinetics than the commercial polycrystalline MgH2, with the hydrolysed fraction upon hydrolysing for 70 min enhances from 7.5% to about 25%. As compared with the as-milled MgH2, the MgH2-based composites with either CaH2 or Ca as an additive present further greatly improved hydrolysis kinetics, with the hydrolysed fraction for 80 min achieving about 76% and 62% respectively.However, the addition of Al doesn't show any positive effect on the improvement of the hydrolysis kinetics of MgH2.

  9. Volumetric studies of some amino acids in binary aqueous solutions of MgCl2.6H2O at 288.15, and 308.15 K

    Amalendu Pal; Suresh Kumar


    Densities () of glycine, L-alanine, and L-valine in aqueous solutions of MgCl2.6H2O (0.1-0.8 mol kg-1) have been measured at 288.15, and 308.15 K. Apparent molar volumes (), and limiting partial molar volumes ($V^{0}_{\\phi}$) of each amino acid have been calculated. These data were combined with the earlier reported $V^{0}_{\\phi}$ values of glycine, L-alanine, and L-valine in aqueous MgCl2.6H2O solutions at 298.15 K in order to describe the temperature dependence behaviour of partial molar quantities. Group contributions to partial molar volumes have been determined for the amino acids. The trends of transfer volumes ($\\Delta V^{0}_{\\phi}$) have been interpreted in terms of solute-cosolute interactions on the basis of a cosphere overlap model. Pair and triplet interaction coefficients have also been calculated from transfer parameters.

  10. Effect of sterilization process on surface characteristics and biocompatibility of pure Mg and MgCa alloys

    Liu, X.L.; Zhou, W.R.; Wu, Y.H.; Cheng, Y. [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Zheng, Y.F., E-mail: [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); State Key Laboratory for Turbulence and Complex System, College of Engineering, Peking University, Beijing 100871 (China); Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China)


    The aim of this work was to investigate the effect of various sterilization methods on surface characteristics and biocompatibility of MgCa alloy, with pure Mg as a comparison, including steam autoclave sterilization (SA), ethylene oxide steam sterilization (EO), glutaraldehyde sterilization (GD), dry heat sterilization (DH) and Co60 γ ray radiation sterilization (R) technologies. The surface characterizations were performed by environmental scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, water contact angle and surface free energy measurement, whereas the cytotoxicity and hemocompatibility were evaluated by cellular adhesive experiment, platelet adhesion and hemolysis test. The results showed that the five sterilization processes caused more changes on the surface of MgCa alloy than that on the surface of pure Mg. The GD sterilization caused the most obvious changes on the surface of the pure Mg, and the SA sterilization made the largest alteration on the MgCa alloy surface. The GD and DH sterilization processes could cause increases on surface free energy for both pure Mg and MgCa alloys, while the other three sterilization processes reduced the surface free energy. The DH and GD sterilization processes caused the least alteration on the cell adhesion on pure Mg surface, whereas the EO sterilization performed the greatest impact on the cell adhesion on the Mg–Ca alloy surface. The hemolysis percentage of pure Mg and MgCa alloys were reduced by SA sterilization, meanwhile the other four sterilization processes increased their hemolysis percentages significantly, especially for the EO sterilization. - Highlights: • The effect of sterilization on surface chemistry and biocompatibility was studied. • Sterilization caused more surface changes on MgCa alloy than pure Mg. • Co60 γ ray radiation is the most appropriate sterilization process.

  11. Boron isotope effect in superconducting MgB2.

    Bud'ko, S L; Lapertot, G; Petrovic, C; Cunningham, C E; Anderson, N; Canfield, P C


    We report the preparation method of and boron isotope effect for MgB2, a new binary intermetallic superconductor with a remarkably high superconducting transition temperature T(c)(10B) = 40.2 K. Measurements of both temperature dependent magnetization and specific heat reveal a 1.0 K shift in T(c) between Mg11B2 and Mg10B2. Whereas such a high transition temperature might imply exotic coupling mechanisms, the boron isotope effect in MgB2 is consistent with the material being a phonon-mediated BCS superconductor.

  12. Debye Temperature of the MgCNi3 Superconductor

    魏志锋; 陈小龙; 王福明; 李文超; 贺蒙


    We have determined the Debye temperature of the MgCNi3 superconductor by using the Rietveld refinementmethod based on the powder x-ray diffraction data. MgCNi3 crystallizes in the cubic perovskite structure with space group Pm-3m and lattice constant a = 3.8089 . The temperature factors of the atoms Mg, C and Ni are 0.52, 0.45 and 0.44, respectively. The Debye temperature of MgCNi3 is calculated to be θD = 440K.

  13. Mg K-edge XANES of sepiolite and palygorskite

    Sanchez del Rio, M. [ESRF, BP 220 F-38043 Grenoble Cedex (France)]. E-mail:; Suarez, M. [Dpto. Geologia, Universidad de Salamanca, E-37008 Salamanca (Spain); Garcia Romero, E. [Dpto. Cristalografia y Mineralogia, U. Complutense de Madrid, E-28040 Madrid (Spain); Alianelli, L. [INFM, c/o ESRF, BP 220 F-38043 Grenoble Cedex (France); Felici, R. [INFM, c/o ESRF, BP 220 F-38043 Grenoble Cedex (France); Martinetto, P. [Lab. Cristallographie, CNRS, Grenoble BP 166, F-38042 Grenoble Cedex 09 (France); Dooryhee, E. [Lab. Cristallographie, CNRS, Grenoble BP 166, F-38042 Grenoble Cedex 09 (France); Reyes-Valerio, C. [INAH, Mexico DF (Mexico); Borgatti, F. [TASC-INFM Area Science Park, I-34012 Trieste (Italy); Doyle, B. [TASC-INFM Area Science Park, I-34012 Trieste (Italy); Giglia, A. [TASC-INFM Area Science Park, I-34012 Trieste (Italy); Mahne, N. [TASC-INFM Area Science Park, I-34012 Trieste (Italy); Pedio, M. [TASC-INFM Area Science Park, I-34012 Trieste (Italy); Nannarone, S. [TASC-INFM Area Science Park, I-34012 Trieste (Italy)


    We present a study of the Mg K-edge on sepiolite and palygorskite performed at the INFM BEAR beamline at Elettra synchrotron light source (Trieste). These two clays, although having very similar structures, show some different features in their near-edge. Mg is in octahedral coordination with oxygens, hydroxyl groups or water, for both palygorskite and sepiolite. The differences found in the near-edge seem to reflect the fact that, on average, an Mg atom in palygorskite 'sees' less Mg in higher coordination shells than sepiolite.

  14. Mg-Zr-Sr alloys as biodegradable implant materials.

    Li, Yuncang; Wen, Cuie; Mushahary, Dolly; Sravanthi, Ragamouni; Harishankar, Nemani; Pande, Gopal; Hodgson, Peter


    Novel Mg-Zr-Sr alloys have recently been developed for use as biodegradable implant materials. The Mg-Zr-Sr alloys were prepared by diluting Mg-Zr and Mg-Sr master alloys with pure Mg. The impact of Zr and Sr on the mechanical and biological properties has been thoroughly examined. The microstructures and mechanical properties of the alloys were characterized using optical microscopy, X-ray diffraction and compressive tests. The corrosion resistance was evaluated by electrochemical analysis and hydrogen evolution measurement. The in vitro biocompatibility was assessed using osteoblast-like SaOS2 cells and MTS and haemolysis tests. In vivo bone formation and biodegradability were studied in a rabbit model. The results indicated that both Zr and Sr are excellent candidates for Mg alloying elements in manufacturing biodegradable Mg alloy implants. Zr addition refined the grain size, improved the ductility, smoothed the grain boundaries and enhanced the corrosion resistance of Mg alloys. Sr addition led to an increase in compressive strength, better in vitro biocompatibility, and significantly higher bone formation in vivo. This study demonstrated that Mg-xZr-ySr alloys with x and y ≤5 wt.% would make excellent biodegradable implant materials for load-bearing applications. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  15. Mg2+ coordination in catalytic sites of F1-ATPase.

    Weber, J; Hammond, S T; Wilke-Mounts, S; Senior, A E


    Coordination of the Mg2+ ion in Mg-nucleotide substrates by amino acid residue side chains in the catalytic site of Escherichia coli F1-ATPase was investigated. From the X-ray structure of the mitochondrial enzyme [Abrahams, J. P., Leslie, A. G. W., Lutter, R., and Walker, J. E. (1994) Nature 370, 621-628], it may be inferred that the hydroxyl of betaThr-156 is a direct ligand of Mg2+, whereas the carboxyls of betaGlu-181, betaGlu-185, and betaAsp-242 might contribute via intervening water molecules. Elimination of each respective functional group by site-directed mutagenesis, followed by determination of Mg-nucleotide and uncomplexed nucleotide binding affinities using a tryptophan probe, showed that betaThr-156, betaGlu-185, and betaAsp-242 are all involved in Mg2+ coordination, whereas betaGlu-181 is not. A derived structural model for the octahedral coordination around the Mg2+ ion is presented. The results indicate that the ADP-containing site in the X-ray structure is the catalytic site of highest affinity. Correct Mg2+ coordination is required for catalytic activity at physiological rates. Elimination of any one of the Mg2+-coordinating residues led to complete loss of Mg2+-dependent nucleotide binding cooperativity of the catalytic sites.

  16. Defect structure of ultrafine MgB{sub 2} nanoparticles

    Bateni, Ali; Somer, Mehmet, E-mail:, E-mail: [Department of Chemistry, Koc University, Rumelifeneri Yolu, Sariyer, Istanbul (Turkey); Repp, Sergej; Erdem, Emre, E-mail:, E-mail: [Institut für Physikalische Chemie, Universität Freiburg, Albertstr. 21 79104 Freiburg (Germany); Thomann, Ralf [Freiburger Materialforschungzentrum (FMF) für Physikalische Chemie, Universität Freiburg, Stefan-Meier Str. 21 79104 Freiburg (Germany); Acar, Selçuk [Pavezyum Chemicals, Orhanlı Mah. Ulu Sokak, No. 3, 34956 Tuzla, Istanbul (Turkey)


    Defect structure of MgB{sub 2} bulk and ultrafine particles, synthesized by solid state reaction route, have been investigated mainly by the aid of X-band electron paramagnetic resonance spectrometer. Two different amorphous Boron (B) precursors were used for the synthesis of MgB{sub 2}, namely, boron 95 (purity 95%–97%, <1.5 μm) and nanoboron (purity >98.5%, <250 nm), which revealed bulk and nanosized MgB{sub 2}, respectively. Scanning and transmission electron microscopy analysis demonstrate uniform and ultrafine morphology for nanosized MgB{sub 2} in comparison with bulk MgB{sub 2}. Powder X-ray diffraction data show that the concentration of the by-product MgO is significantly reduced when nanoboron is employed as precursor. It is observed that a significant average particle size reduction for MgB{sub 2} can be achieved only by using B particles of micron or nano size. The origin and the role of defect centers were also investigated and the results proved that at nanoscale MgB{sub 2} material contains Mg vacancies. Such vacancies influence the connectivity and the conductivity properties which are crucial for the superconductivity applications.

  17. Mg(BH4)2和MgH2对RDX热分解特性的影响%Effect of Mg(BH4) 2 and MgH2 on Thermal Decomposition Performance of RDX

    姚淼; 陈利平; 堵平; 彭金华


    在黑索今(RDX)中加入具有高热值的金属氢化物(Mg(BH4)2和MgH2)有望提高RDX的爆炸性能,但同时给RDX的安全使用带来挑战.为了探索RDX与这2种金属氢化物的相容性与安定性,采用差示扫描量热法(DSC)研究Mg(BH4)2和MgH2对RDX热分解性能的影响,并由DSC得到的数据计算动力学参数,参照GJB770B——2005的方法分析这2种金属氢化物与RDX的相容性和安定性.结果表明,加入Mg(BH4)2使RDX的表观活化能从159.22 kJ/mol增加至180.27 kJ/mol,加入MgH2使RDX的表观活化能降低至133.69 kJ/mol; Mg(BH4)2与RDX的相容性为1级,MgH2与RDX的相容性为3级,加入Mg(BH4)2使RDX的安定性有所提高,加入MgH2降低了RDX的安定性.因此,在将MgH2作为RDX的高能添加剂以前,必须首先提高其与RDX的相容性以保证试验和存储过程的安全.%Metal hydrides ( Mg ( BH4) 2 and MgH2 ) with high heat values are expected to improve the explosion properties of RDX. However, they bring safety problems at the same time. In order to explore the consistencies between RDX and these two kinds of metal hydrides, the DSC was used to study the thermal decomposition characteristics of RDX influenced by the addition of Mg( BH4) 2 and MgH2. The consistencies between RDX and two kinds of metal hydrides were calculated and compared though the standard GJB770B - 2005 respectively. In addition, the stabilities of the mixtures were obtained, too. The results show that the addition of Mg(BH4)2 increases the apparent activation energy from 159. 22 kj/mol to 182.27 kj/mol and the addition of MgH2 decreases the apparent activation energy of RDX to 133. 69 kj/mol. The consistency grade of Mg( BH4 )2/RDX is 1 and the consistency grade of MgH2/RDX is 3 besides, the addition of Mg(BH4)2 is benefit to the stability of RDX and the addition of MgH2 lower the stability of RDX. So, how to enhance the consistency between RDX and MgH2 is the principal problem when adding MgH2 to RDX.

  18. Spectroscopic properties of MgH2, MgD2, and MgHD calculated from a new ab initio potential energy surface.

    Li, Hui; Le Roy, Robert J


    A three-dimensional potential energy surface for the ground electronic state of MgH2 has been constructed from 9030 symmetry-unique ab initio points calculated using the icMRCI+Q method with aug-cc-pVnZ basis sets for n=3, 4, and 5, with core-electron correlation calculated at the MR-ACPF level of theory using cc-pCVnZ basis sets, with both calculations being extrapolated to the complete basis set limit. Calculated spectroscopic constants of MgH2 and MgD2 are in excellent agreement with recent experimental results: for four bands of MgH2 and one band of MgD2 the root-mean-square (rms) band origin discrepancies were only 0.44 and 0.06 cm(-1), respectively, and the rms relative discrepancies in the inertial rotational constants (B[v]) were only 0.0196% and 0.0058%, respectively. Spectroscopic constants for MgHD were predicted using the same potential surface.

  19. The effects of Ni and Mg{sub 2}Ni interlayer on hydrogenation properties of Pd sandwiched Mg films

    Jain, Pragya, E-mail: [Centre for Non-Conventional Energy Resources, University of Rajasthan, Jaipur 302055 (India); Jain, Ankur; Vyas, Devendra; Verma, Reena [Centre for Non-Conventional Energy Resources, University of Rajasthan, Jaipur 302055 (India); Khan, S.A. [Inter University Accelerator Centre, New Delhi 110 067 (India); Jain, I.P., E-mail: [Centre for Non-Conventional Energy Resources, University of Rajasthan, Jaipur 302055 (India)


    Research highlights: > Hydrogen storage in solid state media has been centre of attraction due to several merits over other methods i.e. liquid and gaseous storage of hydrogen. > Particular attention has been focused on Mg based materials because high capacity storage can be achieved in these materials. However, problems regarding high thermodynamic stability and slow kinetics must be addressed before these hydrides can be used for transportation applications. > Thin films are a good approach to understand the mechanism of hydrogen sorption processes in Mg based materials, but on the other hand it is very difficult to measure hydrogen content in thin films using conventional Sievert type method due to low amount of available hydrogen in thin films. > ERDA technique has been proven as a useful tool for depth profiling and content measurement of hydrogen in thin films. > The present research is an attempt to measure hydrogen content in Pd sandwiched Mg thin films using ERDA. Additionally the effect of Ni and Mg2Ni layer on these systems has also been observed and discussed. - Abstract: The scope of present study is to investigate and compare the areal hydrogen concentration of Pd/Mg/Ni/Pd and Pd/Mg/Mg{sub 2}Ni/Pd films with the Pd/Mg/Pd base system using Elastic Recoil Detection Analysis (ERDA) technique. Metals were deposited on Si substrate by thermal evaporation and electron gun evaporation technique followed by hydrogenation for 2 h at 150 deg. C and 2 bar hydrogen pressure. ERDA study reveals that Pd/Mg/Ni/Pd and Pd/Mg/Mg{sub 2}Ni/Pd films absorb 7.08 x 10{sup 17} and 1.68 x 10{sup 18} hydrogen atoms/cm{sup 2}, respectively, in comparison to 4 x 10{sup 17} atoms/cm{sup 2} absorbed by base system. The influence of Ni and Mg{sub 2}Ni interlayer on the hydrogen storage properties of base system were investigated by changes in structural and surface topographical properties using XRD and AFM techniques, respectively. These results strongly supports the ERDA findings

  20. Effect of strontium on crystallization of Mg2Si phase in Al-Si-Mg casting alloys

    廖恒成; 丁毅; 孙国雄


    Optical microscope and SEM were used to observe the changes of the microstructure of Al-11.6%Si-0.4%Mg alloys with varying strontium additions and the effect of strontium on the crystallization of Mg2Si phase was discussed. It is found that Mg2Si phase nucleates on the surfaces of the eutectic silicon flakes in the unfully modified alloys, growing as meshwork or bamboo-shoot shape, however, very few and fine Mg2Si particles phase are isolated at the boundaries of the eutectic cells in the fully modified alloys. Strontium has an important influence on the crystallization of Mg2Si phase in Al-Si-Mg casting alloys and it is thought to be related to the increase of the amount of dendritic α phase and the modifying degree of eutectic silicon phase.

  1. Scleractinian Fossil Corals as Archives of Seawater δ26Mg

    Gothmann, A. O.; Higgins, J. A.; Adkins, J. F.; Stolarski, J.; Bender, M. L.


    The recovery of environmental signatures from coral skeletons is often made difficult by 'vital effects', which cause skeletal chemistry to deviate from the expected composition of aragonite in equilibrium with seawater. Recent studies show that Mg isotopes in scleractinian corals are subject to vital effects, which appear as a departure of the δ26Mg coral temperature dependence from that of inorganic aragonite [1]. However, different from the case for Mg/Ca or δ44Ca in coral, the magnitude of the observed Mg-isotope vital effect is small (on the order of 0.1 ‰ or less). In addition, measurements of different species of modern coral show similar fractionations, suggesting that coral δ26Mg is not species dependent [2]. Together, these observations indicate that corals should faithfully record the seawater Mg-isotope composition, and that vital effects will not bias reconstructions. We measured Mg isotopes in a set of extremely well-preserved fossil scleractinian corals, ranging in age from Jurassic through Recent, to reconstruct past seawater δ26Mg. Well-preserved fossil corals of similar age show a range in δ26Mg of ~0.2 ‰, pointing to the presence of vital effects. However, our results show little variability in the δ26Mg of fossil corals across different geologic ages, suggesting that seawater δ26Mg has remained relatively constant throughout the Cenozoic and Mesozoic. This pattern has implications for our understanding of the mechanisms driving secular variations in seawater Mg/Ca. In particular, our data imply that dolomitization rates have not changed enough during the Mesozoic and Cenozoic to account for secular variations in seawater Mg/Ca. Our coral δ26Mg record agrees with a Cenozoic record from bulk foraminifera, further supporting the faithfulness of the coral archive. However, both of these records disagree with a third Cenozoic Mg-isotope record, derived from species-specific planktic forams [3]. [1] Saenger, C. et al. (2014) Chem. Geol

  2. Growth of high Mg content wurtzite MgZnO epitaxial films via pulsed metal organic chemical vapor deposition

    Alema, Fikadu; Ledyaev, Oleg; Miller, Ross; Beletsky, Valeria; Osinsky, Andrei; Schoenfeld, Winston V.


    We report on the growth of high Mg content, high quality, wurtzite MgxZn1-xO (MgZnO) epitaxial films using a pulsed metal organic chemical vapor deposition (PMOCVD) method. Series of MgZnO films with variable Mg concentration were deposited on bare and AlN coated sapphire substrates. The band gap of the films estimated using UV-visible transmission spectra ranges from 3.24 eV to 4.49 eV, corresponding to fraction of Mg between x=0.0 and x=0.51, as determined by Rutherford backscattering spectroscopy. The cathodoluminescence (CL) measurement has shown a blue-shift in the peak position of MgZnO with an increasing Mg content. No multi-absorption edges and CL band splitting were observed, suggesting the absence of phase segregation in the as grown films. The crystal structure and phase purity of the films were also confirmed by XRD analysis. Hall effect measurement in van der Pauw configuration was employed to evaluate the electrical properties of the films. With a rise in Mg incorporation into the ZnO lattice, the films became very resistive, consistent with the widening of the band gap. The AFM measurement on the films has shown a decreasing surface roughness with an Mg content. To the best of our knowledge, the current result shows the highest Mg content (x=0.51), high quality, wurtzite MgZnO epitaxial film ever grown by MOCVD. The high Mg incorporation without phase separation is believed to be due to the non-equilibrium behavior of the PMOCVD in which the kinetic processes dominate the thermodynamic one.

  3. Microstructure, In Vitro Corrosion Behavior and Cytotoxicity of Biodegradable Mg-Ca-Zn and Mg-Ca-Zn-Bi Alloys

    Bakhsheshi-Rad, H. R.; Hamzah, E.; Tok, H. Y.; Kasiri-Asgarani, M.; Jabbarzare, S.; Medraj, M.


    The effects of bismuth (Bi) addition on the microstructure and corrosion behavior of the Mg-Ca-Zn-Bi alloys were evaluated using electron microscopy, electrochemical test and electrochemical impedance spectroscopy. Microstructural observations showed that Mg-1.2Ca-1Zn- xBi ( x = 0.5, 1.5, 3 wt.%) are composed of Mg2Ca, Ca2Mg6Zn3 and Mg3Bi2 phases while a new phase Mg2Bi2Ca appeared after the addition of 5 and 12 wt.% Bi to the Mg-1.2Ca-1Zn alloy. Furthermore, the additions of 0.5 wt.% Bi to the Mg-1.2Ca-1Zn alloy slightly improved the corrosion behavior of the alloy, while further increase in Bi amount from 1.5 to 12 wt.% has a deleterious effect on the corrosion behavior of the ternary Mg-1.2Ca-1Zn alloy which is driven by galvanic coupling effect. Cytotoxicity tests indicate that the Mg-1.2Ca-1Zn presents higher cell viability compared to Mg-1.2Ca-1Zn-0.5Bi alloy. In addition, the cell viability of both alloys increased with increasing incubation time while diluting the extracts to 50% and 10% improved the cell viabilities. The present results suggest that the Mg-1.2Ca-1Zn-0.5Bi can be interesting candidate for the development of degradable biomaterials and it is worthwhile for further investigation in an in vivo environment.

  4. Preparation of hydrogen by methanol decomposition over Fe/MgO, Co/MgO and Ni/MgO catalysts%甲醇在Fe/MgO、Co/MgO和Ni/MgO催化剂上裂解制备氢气

    朱刚; 焦宝娟


    The catalysts of Fe, Co and Ni supported on MgO were prepared by the means of impregnation. Methanol decomposition over Fe/MgO, Co/MgO and Ni/MgO catalysts were systematically investigated at 600℃. The results indicated that the production of H2 by methanol decomposition could be realized over these catalysts and carbon nano-tubes were produced at the same time. Ni/MgO was the best one among the three catalysts.%采用浸渍法制备出3种MgO负载型过渡金属催化剂Fe/MgO、Co/MgO和Ni/MgO,系统研究了甲醇在3种催化剂上于600℃下的裂解产物.结果表明,3种催化剂均能催化甲醇裂解产生富氢气体,同时产生碳纳米管.其中,Ni/MgO具有最佳的催化效果.

  5. High-precision Mg isotopic systematics of bulk chondrites

    Schiller, Martin; Handler, Monica R.; Baker, Joel A.


    Variations of the mass-independent abundance of 26Mg ( δ26Mg*) and stable Mg ( δ25Mg) isotope composition of chondrites are important because they constrain the homogeneity of 26Al and Mg isotopes in the proto-planetary disc and the validity of the short-lived 26Al-to- 26Mg chronometer applied to meteorites. We present high-precision Mg isotope data and Al/Mg ratios of chondrites representing nearly all major chondrite classes, including a step-leaching experiment on the CM2 chondrite Murchison. δ26Mg* variations in leachates of Murchison representing acid soluble material are ≤ 30 times smaller than reported for neutron-rich isotopes of Ti and Cr and do not reveal resolvable deficits in δ26Mg* (-0.002 to + 0.118‰). Very small variations in δ26Mg* anomalies in bulk chondrites (-0.006 to + 0.019‰) correlate with increasing 27Al/ 24Mg ratios and δ50Ti, reflecting the variable presence of calcium-aluminium-rich inclusions (CAIs) in some types of carbonaceous chondrites. Similarly, release of radiogenic 26Mg produced by 26Al decay from CAI material in the step-leaching of Murchison best explains the high δ26Mg* observed in the last, aggressive, leaching steps of this experiment. Overall, the observed variations in δ26Mg* are small and potential differences beyond that which result from the presence of CAI-like material cannot be detected within the analytical uncertainties of this study (± 0.004‰). The results do not allow radical heterogeneity of 26Al (≥±30%) or measurable Mg nucleosynthetic heterogeneity (≥±0.005‰) to have existed on a planetesimal scale in the proto-planetary disc. Combined with published δ26Mg* data for CAIs, the bulk chondrite data yield a precise initial ( 26Al/ 27Al) 0 = (5.21 ± 0.06) × 10 -5 and δ26Mg* = -0.0340 ± 0.0016‰ for the Solar System. However, it is not possible with the currently available data to determine with certainty whether CAIs and the material from which planetesimals accreted including

  6. Comparison of 1 mg and 2 mg overnight dexamethasone suppression tests for the screening of Cushing's syndrome in obese patients.

    Sahin, Mustafa; Kebapcilar, Levent; Taslipinar, Abdullah; Azal, Omer; Ozgurtas, Taner; Corakci, Ahmet; Akgul, Emin Ozgur; Taslipinar, Mine Yavuz; Yazici, Mahmut; Kutlu, Mustafa


    Obesity is currently a major public health problem and one of the potential underlying causes of obesity in a minority of patients is Cushing's syndrome (CS). Traditionally, the gold standard screening test for CS is 1 mg dexamethasone overnight suppression test. However, it is known that obese subjects have high false positive results with this test. We have therefore compared the 1 mg and 2 mg overnight dexamethasone suppression tests in obese subjects. Patients whose serum cortisol after ODST was >50 nM underwent and a low-dose dexamethasone suppression test (LDDST); 24-hour urine cortisol was collected for basal urinary free cortisol (UFC). For positive results after overnight 1-mg dexamethasone suppression test we also performed the overnight 2-mg dexamethasone suppression test. We prospectively evaluated 100 patients (22 men and 78 women, ranging in age from 17 to 73 years with a body mass index (BMI) >30 kg/m2 who had been referred to our hospital-affiliated endocrine clinic because of simple obesity. Suppression of serum cortisol to rate in 1 mg overnight test and 2% in 2 mg overnight test (p=0.001). There was no correlation between the cortisol levels after ODST and other parameters. Our results indicate that the 2 mg overnight dexamethasone suppression test (ODST) is more convenient and accurate than 1-mg ODST as a screening test for excluding CS in subjects with simple obesity.

  7. Perbandingan Efektivitas Pemberian Efedrin Oral Dosis 25 mg dengan 50 mg Preoperatif terhadap Kejadian Hipotensi Pascaanestesi Spinal pada Seksio Sesarea

    Selly Oktarina Rosita


    Full Text Available Oral ephedrine is one alternative to prevent hypotension with less adverse effects. The purpose of this study was to determine the effective dose of oral ephedrine given 30–45 minutes before spinal anesthesia to reduce incidence of hypotension. The research was a single-blind randomized experimental study involving 32 pregnant women, ASA II, who underwent caesarean section with spinal anesthesia at Dr. Hasan Sadikin Hospital Bandung from March to May 2012. Subjects were divided into two groups, 25 mg ephedrine and 50mg ephedrine groups. Data was analyzed using Mann Whitney and chi-square test, p<0.05 was considered significant. Statistical analysis showed there was a significant difference (p=0.049 in incidence of hypotension between 25 mg group and 50mg group. 25mg group required more intravenous ephedrine after spinal anesthesia (p=0.040. The conclusion of this study was that oral 50mg ephedrine given 30–45 minutes before performing spinal anesthesia will reduce the incidence of hypotension after spinal anesthesia in comparison to oral 25mg ephedrine. In 25mg group, the amount of ephedrine intravenous administered is higher compared with 50mg group.

  8. Melt Protection of Mg-Al Based Alloys

    María J. Balart


    Full Text Available This paper reports the current status of Mg melt protection in view to identify near-future challenges, but also opportunities, for Mg melt protection of Mg-Al based alloys. The goal is to design and manufacture sustainable Mg alloys for resource efficiency, recycling and minimising waste. Among alternative cover gas technologies for Mg melt protection other than SF6: commercially available technologies containing―HFC-134a, fluorinated ketone and dilute SO2―and developed technologies containing solid CO2, BF3 and SO2F2, can potentially produce toxic and/or corrosive by-products. On the other hand, additions of alkaline earth metal oxides to Mg and its alloys have developed a strong comparative advantage in the field of Mg melt protection. The near-future challenges and opportunities for Mg-Al based alloys include optimising and using CO2 gas as feedstock for both melt protection and grain refinement and TiO2 additions for melt protection.

  9. Multiband model for tunneling in MgB2 junctions

    Brinkman, A.; Golubov, A.A.; Rogalla, H.; Dolgov, O.V.; Kortus, J.; Kong, Y.; Jepsen, O.; Andersen, O.K.


    A theoretical model for quasiparticle and Josephson tunneling in multiband superconductors is developed and applied to MgB2-based junctions. The gap functions in different bands in MgB2 are obtained from an extended Eliashberg formalism, using the results of band structure calculations. The temperat

  10. Size effects in MgO cube dissolution.

    Baumann, Stefan O; Schneider, Johannes; Sternig, Andreas; Thomele, Daniel; Stankic, Slavica; Berger, Thomas; Grönbeck, Henrik; Diwald, Oliver


    Stability parameters and dissolution behavior of engineered nanomaterials in aqueous systems are critical to assess their functionality and fate under environmental conditions. Using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, we investigated the stability of cubic MgO particles in water. MgO dissolution proceeding via water dissociation at the oxide surface, disintegration of Mg(2+)-O(2-) surface elements, and their subsequent solvation ultimately leads to precipitation of Mg(OH)2 nanosheets. At a pH ≥ 10, MgO nanocubes with a size distribution below 10 nm quantitatively dissolve within few minutes and convert into Mg(OH)2 nanosheets. This effect is different from MgO cubes originating from magnesium combustion in air. With a size distribution in the range 10 nm ≤ d ≤ 1000 nm they dissolve with a significantly smaller dissolution rate in water. On these particles water induced etching generates (110) faces which, above a certain face area, dissolve at a rate equal to that of (100) planes.1 The delayed solubility of microcrystalline MgO is attributed to surface hydroxide induced self-inhibition effects occurring at the (100) and (110) microplanes. The present work underlines the importance of morphology evolution and surface faceting of engineered nanomaterials particles during their dissolution.

  11. Antioxidant status in MgO nanoparticle-exposed rats.

    Kiranmai, G; Reddy, A Rama Narsimha


    In this present study, antioxidant status was evaluated in rat serum following exposure to magnesium oxide (MgO) nanoparticles. The lungs of rats were intratracheally instilled with (single dose) phosphate-buffered saline (PBS) + 1% of Tween 80 (solvent control) or MgO or carbonyl iron (negative control) or quartz particles (positive control) at a dose of 1 and 5 mg/kg of body weight. The blood samples were collected at 1, 7, and 30 days of postinstillation of nanoparticles after their exposure, and different parameters were estimated to assess the oxidative stress induced by the instillation of MgO. Exposure of rats to MgO produced a significant (p MgO nanoparticle-exposed rats indicates the reduction in antioxidant defense mechanisms due to the instillation of MgO. These results indicate that exposure to MgO nanoparticles induces oxidative stress by reducing the total antioxidant capacity in rats. The findings suggest possible occupational health hazard in chronic exposures.

  12. Mg-based compounds for hydrogen and energy storage

    Crivello, J.-C.; Denys, R. V.; Dornheim, M.; Felderhoff, M.; Grant, D. M.; Huot, J.; Jensen, T. R.; de Jongh, P.; Latroche, M.; Walker, G. S.; Webb, C. J.; Yartys, V. A.


    Magnesium-based alloys attract significant interest as cost-efficient hydrogen storage materials allowing the combination of high gravimetric storage capacity of hydrogen with fast rates of hydrogen uptake and release and pronounced destabilization of the metal-hydrogen bonding in comparison with binary Mg-H systems. In this review, various groups of magnesium compounds are considered, including (1) RE-Mg-Ni hydrides (RE = La, Pr, Nd); (2) Mg alloys with p-elements (X = Si, Ge, Sn, and Al); and (3) magnesium alloys with d-elements (Ti, Fe, Co, Ni, Cu, Zn, Pd). The hydrogenation-disproportionation-desorption-recombination process in the Mg-based alloys (LaMg12, LaMg11Ni) and unusually high-pressure hydrides synthesized at pressures exceeding 100 MPa (MgNi2H3) and stabilized by Ni-H bonding are also discussed. The paper reviews interrelations between the properties of the Mg-based hydrides and p- T conditions of the metal-hydrogen interactions, chemical composition of the initial alloys, their crystal structures, and microstructural state.

  13. Multiwavelength observations of the Type IIb supernova 2009mg

    Oates, S. R.; Bayless, A. J.; Stritzinger, M. D.


    We present Swift Ultra-Violet Optical Telescope and X-Ray Telescope (XRT) observations, and visual wavelength spectroscopy of the Type IIb supernova (SN) 2009mg, discovered in the Sb galaxy ESO 121-G26. The observational properties of SN 2009mg are compared to the prototype Type IIb SNe 1993J...

  14. The luminescence properties of MgUO4

    Jong, K.P. de; Krol, D.M.; Blasse, G.


    The luminescence of MgUO4 has been investigated. Emission and excitation spectra as well as the decay time and the quantum efficiency of the emission were measured at 4.2 K. The temperature dependence of the emission spectrum and the emission intensity was studied. The results show that in MgUO4 the

  15. Mg2+ homeostasis: the balancing act of TRPM6.

    Wijst, J.A.J. van der; Bindels, R.J.; Hoenderop, J.G.J.


    PURPOSE OF REVIEW: The tight control of blood magnesium (Mg) levels is of central importance for numerous physiological processes. A persistent low Mg status (hypomagnesemia) is associated with severe health risks and is involved in the pathogenesis of type 2 diabetes mellitus, osteoporosis, asthma,

  16. Selective antibacterial effects of mixed ZnMgO nanoparticles

    Vidic, Jasmina, E-mail: [VIM, Institut de la Recherche Agronomique (France); Stankic, Slavica, E-mail:; Haque, Francia [CNRS, Institut des Nanosciences de Paris, UMR 7588 (France); Ciric, Danica; Le Goffic, Ronan; Vidy, Aurore [VIM, Institut de la Recherche Agronomique (France); Jupille, Jacques [CNRS, Institut des Nanosciences de Paris, UMR 7588 (France); Delmas, Bernard [VIM, Institut de la Recherche Agronomique (France)


    Antibiotic resistance has impelled the research for new agents that can inhibit bacterial growth without showing cytotoxic effects on humans and other species. We describe the synthesis and physicochemical characterization of nanostructured ZnMgO whose antibacterial activity was compared to its pure nano-ZnO and nano-MgO counterparts. Among the three oxides, ZnO nanocrystals-with the length of tetrapod legs about 100 nm and the diameter about 10 nm-were found to be the most effective antibacterial agents since both Gram-positive (B. subtilis) and Gram-negative (E. coli) bacteria were completely eradicated at concentration of 1 mg/mL. MgO nanocubes (the mean cube size {approx}50 nm) only partially inhibited bacterial growth, whereas ZnMgO nanoparticles (sizes corresponding to pure particles) revealed high specific antibacterial activity to Gram-positive bacteria at this concentration. Transmission electron microscopy analysis showed that B. subtilis cells were damaged after contact with nano-ZnMgO, causing cell contents to leak out. Our preliminary toxicological study pointed out that nano-ZnO is toxic when applied to human HeLa cells, while nano-MgO and the mixed oxide did not induce any cell damage. Overall, our results suggested that nanostructured ZnMgO, may reconcile efficient antibacterial efficiency while being a safe new therapeutic for bacterial infections.

  17. Electron beam induced oxidation of Al–Mg alloy surfaces

    Palasantzas, G.; Agterveld, D.T.L. van; Hosson, J.Th.M. De


    Electron beam currents of a few nanoamperes, currently used in nanometer scale scanning Auger/electron microscopy, induces severe oxidation of Al–Mg alloy surfaces at room temperature. Auger peak-to-peak oxygen curves for Al–Mg surfaces support the hypothesis that the electron beam creates

  18. Electron beam induced oxidation of Al–Mg alloy surfaces

    Palasantzas, G.; Agterveld, D.T.L. van; Hosson, J.Th.M. De


    Electron beam currents of a few nanoamperes, currently used in nanometer scale scanning Auger/electron microscopy, induces severe oxidation of Al–Mg alloy surfaces at room temperature. Auger peak-to-peak oxygen curves for Al–Mg surfaces support the hypothesis that the electron beam creates additiona

  19. Superconductivity in noncentrosymmetric Mg10Ir19B16

    Klimczuk, T.; Xu, Q.; Morosan, E.; Thompson, J.D.; Zandbergen, H.W.; Cava, R.J.


    Mg10Ir19B16, a previously unreported compound in the Mg-Ir-B chemical system, is found to be superconducting at temperatures near 5 K. The fact that the compound exhibits a range of superconducting temperatures between 4 and 5 K suggests that a range of stoichiometries is allowed, though no structur

  20. Multiwavelength observations of the Type IIb supernova 2009mg

    Oates, S. R.; Bayless, A. J.; Stritzinger, M. D.


    We present Swift Ultra-Violet Optical Telescope and X-Ray Telescope (XRT) observations, and visual wavelength spectroscopy of the Type IIb supernova (SN) 2009mg, discovered in the Sb galaxy ESO 121-G26. The observational properties of SN 2009mg are compared to the prototype Type IIb SNe 1993J...

  1. Flórula ruderal da cidade de Lavras, MG Ruderal plants from Lavras, MG

    Manuel Losada Gavilanes


    Full Text Available Efetuou-se o levantamento e a identificação das plantas ruderais ocorrentes na cidade de Lavras, MG. Foram identificadas 175 espécies, representando 122 gêneros, pertencentes a 41 famílias. As famílias. Compositae, Leguminosae, Graminese, Malvaceae, Convolvulaceae, Cyperaceae, Euphorbiaceae e Amaranthaceae, são as que apresentaram o maior número de espécies. O material foi coletado em áreas ajardinadas, beiras de caminhos, calçadas, muros e cercas, e em terrenos baldios.A survey and identification of ruderal plants occuring in Lavras City, state of Minas Gerais, Brazil, was carried out. One hundred and seventy five species, representing 122 genera belonging to 41 families were indentified. Families Compositae, Leguminosae, Gramineae, Malvaceae, Convolvulaceae, Cyperaceae, Euphorbiaceae, and Amaranthaceae presented the greatest numbers of species among all families. All plant materials were collected in garden areas, along roadsides and streets, walls and fences, and wastelands.

  2. Theoretical Limiting Potentials in Mg/O2 Batteries

    Smith, Jeffrey G.; Naruse, Junichi; Hiramatsu, Hidehiko


    A rechargeable battery based on a multivalent Mg/O2 couple is an attractive chemistry due to its high theoretical energy density and potential for low cost. Nevertheless, metal-air batteries based on alkaline earth anodes have received limited attention and generally exhibit modest performance....... In addition, many fundamental aspects of this system remain poorly understood, such as the reaction mechanisms associated with discharge and charging. The present study aims to close this knowledge gap and thereby accelerate the development of Mg/O2 batteries by employing first-principles calculations...... by the presence of large thermodynamic overvoltages. In contrast, MgO2-based cells are predicted to be much more efficient: superoxide-terminated facets on MgO2 crystallites enable low overvoltages and round-trip efficiencies approaching 90%. These data suggest that the performance of Mg/O2 batteries can...

  3. Electron Theory Research in Mg-Y Alloy

    郭旭涛; 何良菊; 李培杰; 曾大本


    Adding yttrium to magnesium can improve the mechanical properties,especially the mechanical behavior at high temperature.The valence electron structures of Mg-Y alloy were analyzed with the empirical electron theory of solids and molecules(EET).Calculation shows that yttrium is on the fifth hybrid level and magnesium is on the third one in pure metal crystals.By comparing with aluminum in Mg-Al alloy,it is shown that the reason why the solution strengthening effect of yttrium is better than that of aluminum in Mg-Al alloy is the enhanced bond energy according to EET.And it is concluded from EET analysis that intermetallics Mg24Y5 can significantly improve the properties of magnesium alloys because yttrium atoms occupy the centers of the octahedron and Mg-Y bonds efficiently strengthen the alloy matrix.

  4. Microstructure and properties of Mg-Al binary alloys

    ZHENG Wei-chao


    Full Text Available The effects of different amounts of added Al, ranging from 1 % to 9 %, on the microstructure and properties of Mg-Al binary alloys were investigated. The results showed that when the amount of added Al is less than 5%, the grain size of the Mg-Al binary alloys decreases dramatically from 3 097 μm to 151 μm with increasing addition of Al. Further addition of Al up to 9% makes the grain size decrease slowly to 111 μm. The α-Mg dendrite arms are also refined. Increasing the amount of added Al decreases the hot cracking susceptibility of the Mg-Al binary alloys remarkably, and enhances the micro-hardness of the α-Mg matrix.

  5. Microstructure and properties of Mg-Al binary alloys

    ZHENG Wei-chao; LI Shuang-shou; TANG Bin; ZENG Da-ben


    The effects of different amounts of added Al, ranging from 1% to 9%, on the microstructure and properties of Mg-Al binary alloys were investigated. The results showed that when the amount of added Al is less than 5%, the grain size of the Mg-Al binary alloys decreases dramatically from 3 097 μm to 151 μm with increasing addition of Al. Further addition of Al up to 9% makes the grain size decrease slowly to 111 μm. The α-Mg dendrite arms are also refined. Increasing the amount of added Al decreases the hot cracking susceptibility of the Mg-Al binary alloys remarkably, and enhances the micro-hardness of the α-Mg matrix.

  6. Chemical synthesis of superconducting MgB{sub 2} nanopowder

    Bansal, Narottam P., E-mail: [Materials and Structures Division, NASA Glenn Research Center, Cleveland, OH 44135 (United States); Goldsby, Jon C.; Rogers, Richard B. [Materials and Structures Division, NASA Glenn Research Center, Cleveland, OH 44135 (United States); Susner, Michael A.; Sumption, Michael D. [Center for Superconducting and Magnetic Materials, Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210 (United States)


    Highlights: • MgB{sub 2} nanopowder has been synthesized by chemical method. • Powder characterized by XRD and SEM. • Superconducting behavior confirmed by susceptibility and magnetization measurements. • Nanopowder will facilitate the fabrication of small diameter MgB{sub 2} filaments. - Abstract: Superconducting MgB{sub 2} nanopowder has been synthesized through chemical reaction between lithium borohydride and magnesium hydride at relatively low temperatures. From quantitative Rietveld analysis, the average crystallite size of MgB{sub 2} powder was evaluated to be 33 nm. The superconducting transition temperature of the MgB{sub 2} nanopowder was found to be 38.8-38.9 K from magnetization and DC susceptibility measurements. Powder morphology has been evaluated by scanning electron microscopy.

  7. The effect of iron plaque on uptake and translocation of norfloxacin in rice seedlings grown in paddy soil.

    Yan, Dafang; Ma, Wei; Song, Xiaojing; Bao, Yanyu


    Although the role of iron plaque on rice root surface has been investigated in recent years, its effect on antibiotic uptake remains uncertain. In the study, pot experiment was conducted to investigate the effect of iron plaque on uptake and translocation of norfloxacin (adding 10 and 50 mg·kg(-1) treatments) in rice seedlings grown in paddy soil. Iron plaque was induced by adding different amounts of Fe(II) in soil. The results showed that the presence of norfloxacin can decrease the amount of iron plaque induced. After rice with iron plaque induced, norfloxacin was mainly accumulated in iron plaque on root surface, followed by inside root, but its translocation from root to other rice tissues is not observed. Iron plaque played the role of a barrier for norfloxacin uptake into rice roots under high norfloxacin concentration of 50 mg·kg(-1), however not that under low concentration of 10 mg·kg(-1). And the barrier function was the most strongest with adding Fe(II) of 30 mg·kg(-1) as combined action of iron plaque and rhizosphere effect. Fluorescence microscope analysis showed that norfloxacin mainly distributed in the outside of root cell, which showed its translocation as apoplastic pathway in rice. Comparing with non-rhizosphere, more norfloxacin was accumulated in rhizosphere soil. Maybe, strong root oxidization (high Eh values) induced more iron oxide formation in rhizosphere and on root surface, which led to norfloxacin's mobility towards to rhizosphere through its strong adsorption of iron oxides and then promoted its uptake by rice on root surface.

  8. Mg Isotope Fractionation Between E. coli and Growth Medium

    Basset, R.; Lemelle, L.; Albalat, E.; Telouk, P.; Albarède, F.


    Magnesium is a major element in both microbial cells and minerals, immune to redox conditions and atmospheric interactions. In organic cells, Mg can be associated with membranes, with cytoplasm (either as an isolated ion or bound to proteins). Its isotope composition can be used to constrain the contribution of organic material to carbonate fluxes and the overall cycle of this element in the exogenous environment [1, 2]. Cells of DH5α E. coli strain were grown in Luria Broth medium and the Mg isotope fractionation between the cells and their growth medium determined after calcination in Pt crucibles, chemical purification by cation exchange chemistry in HCl medium [3] and isotopic analysis on a Nu HR MC-ICPMS. The yield is better than 96%. The Mg contents of 2.19 ± 0.08 mg per g DW in cells and 0.117 ± 0.001 mg per g DW in Luria Broth medium are consistent with literature data [4]. About half of the Mg initially present in the LB medium is taken up by the growing cells. At high cellular concentrations (OD600 = 3.5), cells are enriched in 26Mg by 0.97 ± 0.14 ‰ with respect to the culture medium. Although E. coli may not be a good proxy for oceanic plankton, such a substantial fractionation of Mg isotopes suggests that incorporation of even a few percent organic matter into oceanic oozes depletes oceanic Mg in its heavy isotopes and therefore accounts for the isotopic difference between riverine and marine Mg. [1] Drever, The Sea 5 (1974) 337-357 [2] Tipper et al., EPSL 250 (2006) 241-253 [3] Chang et al., JAAS 18 (2003) 296-301 [4] Outten et al., Science 292 (2001), 2488-2492

  9. Hydrogen reversibility of LiBH₄-MgH₂-Al composites.

    Hansen, Bjarne R S; Ravnsbæk, Dorthe B; Skibsted, Jørgen; Jensen, Torben R


    The detailed mechanism of hydrogen release in LiBH4-MgH2-Al composites of molar ratios 4 : 1 : 1 and 4 : 1 : 5 are investigated during multiple cycles of hydrogen release and uptake. This study combines information from several methods, i.e., in situ synchrotron radiation powder X-ray diffraction, (11)B magic-angle spinning (MAS) NMR, Sievert's measurements, Fourier transform infrared spectroscopy and simultaneous thermogravimetric analysis, differential scanning calorimetry and mass spectroscopy. The composites of LiBH4-MgH2-Al are compared with the behavior of the LiBH4-Al and LiBH4-MgH2 systems. The decomposition pathway of the LiBH4-MgH2-Al system is different for the two investigated molar ratios, although it ultimately results in the formation of LiAl, Mg(x)Al(1-x)B2 and Li2B12H12 in both cases. For the 4 : 1 : 1-molar ratio, Mg(0.9)Al(0.1) and Mg17Al12 are observed as intermediates. However, only Mg is observed as an intermediate in the 4 : 1 : 5-sample, which may be due to an earlier formation of Mg(x)Al(1-x)B2, reflecting the complex chemistry of Al-Mg phases. Hydrogen release and uptake reveals a decrease in the hydrogen storage capacity upon cycling. This loss reflects the formation of Li2B12H12 as observed by (11)B NMR and infrared spectroscopy for the cycled samples. Furthermore, it is shown that the Li2B12H12 formation can be limited significantly by applying moderate hydrogen partial pressure during decomposition.

  10. Resetting of Mg isotopes between calcite and dolomite during burial metamorphism: Outlook of Mg isotopes as geothermometer and seawater proxy

    Hu, Zhongya; Hu, Wenxuan; Wang, Xiaomin; Lu, Yizhou; Wang, Lichao; Liao, Zhiwei; Li, Weiqiang


    Magnesium isotopes are an emerging tool to study the geological processes recorded in carbonates. Calcite, due to its ubiquitous occurrence and the large Mg isotope fractionation associated with the mineral, has attracted great interests in applications of Mg isotope geochemistry. However, the fidelity of Mg isotopes in geological records of carbonate minerals (e.g., calcite and dolomite) against burial metamorphism remains poorly constrained. Here we report our investigation on the Mg isotope systematics of a dolomitized Middle Triassic Geshan carbonate section in eastern China. Magnesium isotope analysis was complemented by analyses of Sr-C-O isotopic compositions, major and trace element concentrations, and petrographic and mineralogical features. Multiple lines of evidence consistently indicated that post-depositional diagenesis of carbonate minerals occurred to the carbonate rocks. Magnesium isotope compositions of the carbonate rocks closely follow a mixing trend between a high δ26Mg dolomite end member and a low δ26Mg calcite end member, irrespective of sample positions in the section and calcite/dolomite ratio in the samples. By fitting the measured Mg isotope data using a two-end member mixing model, an inter-mineral Δ26Mgdolomite-calcite fractionation of 0.72‰ was obtained. Based on the experimentally derived Mg isotope fractionation factors for dolomite and calcite, a temperature of 150-190 °C was calculated to correspond to the 0.72‰ Δ26Mgdolomite-calcite fractionation. Such temperature range matches with the burial-thermal history of the local strata, making a successful case of Mg isotope geothermometry. Our results indicate that both calcite and dolomite had been re-equilibrated during burial metamorphism, and based on isotope mass balance of Mg, the system was buffered by dolomite in the section. Therefore, burial metamorphism may reset Mg isotope signature of calcite, and Mg isotope compositions in calcite should be dealt with caution in

  11. Effect of Mg content on microstructure and corrosion behavior of hot dipped Zn–Al–Mg coatings

    Yao, Caizhen; Lv, Haibing [Research Centre of Laser Fusion, CAEP, P.O.Box 919-988-5, Mianyang, Sichuan 621900 (China); Zhu, Tianping [Department of Chemical and Materials Engineering, The University of Auckland, PB 92019, Auckland 1142 (New Zealand); Zheng, Wanguo [Research Centre of Laser Fusion, CAEP, P.O.Box 919-988-5, Mianyang, Sichuan 621900 (China); Yuan, Xiaodong, E-mail: [Research Centre of Laser Fusion, CAEP, P.O.Box 919-988-5, Mianyang, Sichuan 621900 (China); Gao, Wei, E-mail: [Department of Chemical and Materials Engineering, The University of Auckland, PB 92019, Auckland 1142 (New Zealand)


    In this article, Zn–Al–Mg coatings were prepared by hot dipping method. The surface morphology, cross–section microstructure, microhardness, composition, corrosion behaviour of ZAM coatings were investigated by using X–ray diffraction (XRD), Optical microscope, Environmental scanning electron microscopy equipped with EDS (FESEM–EDS), Microhardness tester and Electrochemical analysis respectively. Corrosion test was also performed in a standard salt fog spray chamber. Microstructure studies indicates that Zn grain size was refined and eutectic areas at Zn grain boundary areas increased with increasing Mg content. ZA5M1.5 and ZA5M2 coatings have two distinct layers. Mg tends to exist in the outer layer while Al is in the inner layer. The inner layer is composed of Al{sub 5}Fe{sub 2}Zn{sub 0.4} intermetallic, which may to contribute to the microhardness. The outer layer is Zn grains surrounded by Zn–Mg etutectics, which may improve the corrosion resistance. The microhardness is more than 700 HV{sub 50g} for Al-rich layer and around 151 HV{sub 25g} for Mg-rich layer. The improved corrosion resistance of Zn–5%Al-1.5%Mg coating comes from the corrosion product of flocculent type simonkolleite, which prolongs the micro-path and impedes the movement of O{sub 2} and H{sub 2}O, ultimately retards the overall corrosion process. - Highlights: • Two-layer structured Zn–Al–Mg coatings were prepared by hot dipping method. • Mg exists in the outer layer while Al exists in the inner layer of Zn–Al–Mg coating. • Zn–Al–Mg coating has better protective ability than Zn and Zn–Al coatings. • The Mg-modified simonkolleite is the reason of the enhanced corrosion resistance.

  12. Improved hydrogen sorption kinetics in wet ball milled Mg hydrides

    Meng, Li


    In this work, wet ball milling method is used in order to improve hydrogen sorption behaviour due to its improved microstructure of solid hydrogen materials. Compared to traditional ball milling method, wet ball milling has benefits on improvement of MgH{sub 2} microstructure and further influences on its hydrogen sorption behavior. With the help of solvent tetrahydrofuran (THF), wet ball milled MgH{sub 2} powder has much smaller particle size and its specific surface area is 7 times as large as that of dry ball milled MgH{sub 2} powder. Although after ball milling the grain size is decreased a lot compared to as-received MgH{sub 2} powder, the grain size of wet ball milled MgH{sub 2} powder is larger than that of dry ball milled MgH{sub 2} powder due to the lubricant effect of solvent THF during wet ball milling. The improved particle size and specific surface area of wet ball milled MgH{sub 2} powder is found to be determining its hydrogen sorption kinetics especially at relatively low temperatures. And it also shows good cycling sorption behavior, which decides on its industrial applicability. With three different catalysts MgH{sub 2} powder shows improved hydrogen sorption behavior as well as the cyclic sorption behavior. Among them, the Nb{sub 2}O{sub 5} catalyst is found to be the most effective one in this work. Compared to the wet ball milled MgH{sub 2} powder, the particle size and specific surface area of the MgH{sub 2} powder with catalysts are similar to the previous ones, while the grain size of the MgH{sub 2} with catalysts is much finer. In this case, two reasons for hydrogen sorption improvement are suggested: one is the reduction of the grain size. The other may be as pointed out in some literatures that formation of new oxidation could enhance the hydrogen sorption kinetics, which is also the reason why its hydrogen capacity is decreased compared to without catalysts. After further ball milling, the specific surface area of wet ball milled Mg

  13. First-principles study on mechanical properties of LaMg3 and LaCuMg2

    王明辉; 潘荣凯; 李鹏博; 卞楠; 唐壁玉; 彭立明; 丁文江


    With the substitution of part Mg in LaMg3by Cu, the elastic constantsC11 andC12 increase whileC44 decreases, implying an enhanced Poisson effect and smaller resistance to (100) shear. Furthermore, the bulk modulusB increases, while the shear modulusG, elastic modulusE and anisotropic ratioA are reduced. The calculated Debye temperature of LaCuMg2 is lower, implying the weaker interaction between atoms in LaCuMg2. Then, the stress-strain curves in entire range and the ideal strength at critical strain are studied. The present results show that the lowest ideal tensile strength for LaMg3 and LaCuMg2is in the direction. The ideal shear strength on the (110) slip system of LaMg3 is greater than LaCuMg2. The density of states and charge density distribution are further studied to understand the inherent mechanism of the mechanical properties.

  14. Improved Hydrogen Storage Properties of Mg(BH4)2-Mg(AlH4)2 Combined Systems

    Xiao, Haoyuan; Leng, Haiyan; Yu, Zhigang; Li, Qian; Chou, Kuo-Chih

    Magnesium borohydride and Magnesium alanate were synthesized by mechanochemical metathesis reaction. The thermal decomposition behaviors of Mg(BH4)2-nMg(AlH4)2(n=0.5,1) systems were investigated as potential hydrogen storage materials. The results showed that the systems started to desorb H2 at 120 °C and desorbed 3.9 wt.% and 4.9 wt.% H2 below 300 °C when n equals 0.5 and 1, respectively, while individual Mg(BH4)2 started to desorb H2 at 250 °C and desorbed only 0.82 wt.% H2. Because of the exist of the Mg(AlH4)2, the isothermal desorption kinetics of Mg(BH4)2 in the Mg(BH4)2-0.5Mg(AlH4)2 systems was 50% faster than that of pristine Mg(BH4)2. In addition, the re-hydrogenation rates also increased 49.4% and 37.9%.

  15. Microstructures and mechanical properties of Al-Mg and Al-Zn-Mg based alloys containing minor scandium and zirconium

    尹志民; 姜锋; 潘青林; 郭飞跃; 朱大鹏; 宋练鹏; 曾渝; 王涛


    A series of Al-Mg and Al-Zn-Mg based alloys with and without Sc, Zr were prepared by ingot metallurgy. The mechanical properties and microstructures of the studied alloys under different treatment conditions were studied. In addition, the existing form and acting mechanism of minor Sc and Zr in Al-Mg and Al-Zn-Mg based alloys were analyzed and discussed. The following conclusions can be drawn. First, adding of minor Sc and Zr to those alloys can increase the strength of Al-Mg and Al-Zn-Mg based alloys by 25%, while the ductility can remain in 15% and 8%, respectively. Second, in Al-Mg and Al-Zn-Mg based alloys, minor Sc and Zr mainly exist in two forms of aluminides containing Sc and Zr, one is Al3(Sc,Zr)I precipitated from the melt during solidification, the other is Al3(Sc,Zr)Ⅱ precipitated during homogenization. The former is the most effective grain refiner for α(Al) solid solution matrix, and the latter is coherent with the matrix and can strongly pin dislocations and subboundaries, which can effectively restrain recrystallization of the alloys during hot deformation, annealing and solid solution. Third, strengthening caused by adding minor Sc and Zr to the studied alloys is mainly due to fine-grain strengthening, precipitation strengthening and substructure strengthening of Al3(Sc, Zr) caused by restraining recrystallization.

  16. The epithelial Mg2+ channel transient receptor potential melastatin 6 is regulated by dietary Mg2+ content and estrogens.

    Groenestege, W.M.; Hoenderop, J.G.J.; Heuvel, L.P.W.J. van den; Knoers, N.V.A.M.; Bindels, R.J.M.


    The kidney is the principal organ responsible for the regulation of the body Mg(2+) balance. Identification of the gene defect in hypomagnesemia with secondary hypocalcemia recently elucidated transient receptor potential melastatin 6 (TRPM6) as the gatekeeper in transepithelial Mg(2+) transport, wh

  17. Phosphatizing of Mg particles to improve the protective performance of Mg-rich primer on A2024 Al alloy

    Wang, Jianguo; Zuo, Yu; Tang, Yuming; Lu, Xiangyu


    Mg-rich primer as a new type protective coating provides cathodic protection for Al alloy. In this paper, a kind of phosphatizing surface treatment on Mg particles was studied in order to improve the protective performance of Mg-rich primer. After treated with phosphoric acid, a protective magnesium phosphate layer was formed on the surface of Mg particles, which had no negative influence on the cathodic protection of the Mg-rich primer for Al alloy. The coating resistance of the treated Mg-rich primer was bigger than that of untreated primer, meanwhile the coating capacitance of the treated Mg-rich primer was smaller than that of untreated primer, suggesting that the barrier effect of the primer was improved and the lifetime was extended. The magnesium phosphate layer could reduce the consumption rate of Mg particles. Meanwhile, the phosphate radicals transported to Al alloy substrate to form a product layer composed of magnesium phosphate and aluminum phosphate on the substrate surface, which decreased the corrosion rate of Al alloy and improved the protective performance of the primer.

  18. Laser cladding of a Mg based Mg-Gd-Y-Zr alloy with Al-Si powders

    Chen, Erlei; Zhang, Kemin; Zou, Jianxin


    In the present work, a Mg based Mg-Gd-Y-Zr alloy was subjected to laser cladding with Al-Si powders at different laser scanning speeds in order to improve its surface properties. It is observed that the laser clad layer mainly contains Mg2Si, Mg17Al12 and Al2(Gd,Y) phases distributed in the Mg matrix. The depth of the laser clad layer increases with decreasing the scanning speed. The clad layer has graded microstructures and compositions. Both the volume fraction and size of Mg2Si, Mg17Al12 and Al2(Gd,Y) phases decreases with the increasing depth. Due to the formation of these hardening phases, the hardness of clad layer reached a maximum value of HV440 when the laser scanning speed is 2 mm/s, more than 5 times of the substrate (HV75). Besides, the corrosion properties of the untreated and laser treated samples were all measured in a NaCl (3.5 wt.%) aqueous solution. The corrosion potential was increased from -1.77 V for the untreated alloy to -1.13 V for the laser clad alloy with scanning rate of 2 mm/s, while the corrosion current density was reduced from 2.10 × 10-5 A cm-2 to 1.64 × 10-6 A cm-2. The results show that laser cladding is an efficient method to improve surface properties of Mg-Rare earth alloys.

  19. Simulating GTP:Mg and GDP:Mg with a simple force field: a structural and thermodynamic analysis.

    Simonson, Thomas; Satpati, Priyadarshi


    Di- and tri-phosphate nucleotides are essential cofactors for many proteins, usually in an Mg(2+) -bound form. Proteins like GTPases often detect the difference between NDP and NTP and respond by changing conformations. To study such complexes, simple, fixed charge force fields have been used, which allow long simulations and precise free energy calculations. The preference for NTP or NDP binding depends on many factors, including ligand structure and Mg(2+) coordination and the changes they undergo upon binding. Here, we use a simple force field to examine two Mg(2+) coordination modes for the unbound GDP and GTP: direct, or "Inner Sphere" (IS) coordination by one or more phosphate oxygens and indirect, "Outer Sphere" (OS) coordination involving one or more bridging waters. We compare GTP: and GDP:Mg binding with OS and IS coordination; combining the results with experimental data then indicates that GTP prefers the latter. We also examine different kinds of IS coordination and their sensitivity to a key force field parameter: the optimal Mg:oxygen van der Waals distance Rmin . Increasing Rmin improves the Mg:oxygen distances, the GTP: and GDP:Mg binding affinities, and the fraction of GTP:Mg with β + γ phosphate coordination, but does not improve or change the GTP/GDP affinity difference, which remains much larger than experiment. It has no effect on the free energy of GDP binding to a GTPase. Copyright © 2012 Wiley Periodicals, Inc.

  20. Effect of Synthesized MgNi4Y Catalyst on Hydrogen Desorption Properties of Milled MgH2

    ChitsazKhoyi, Leila; Raygan, Shahram; Pourabdoli, Mehdi


    It has been reported that ball milling and adding catalyst can improve hydrogen desorption properties of MgH2. In this study, simultaneous effect of adding catalyst and ball milling on hydrogen desorption properties of MgH2 was studied. Mechanical alloying and heat treatment methods were used to synthesize MgNi4Y intermetallic as a catalyst. In this regard, pure Mg, Ni, and Y elemental powders were ball milled in different conditions and then heat treated at 1073 K (800 °C) for 4 hours. XRD and FESEM methods were used to investigate properties of the samples. It was found that, after 10 hours of ball milling and then heat treating at 1073 K (800 °C), MgNi4Y intermetallic was formed almost completely. The results of Sievert tests showed that as-received MgH2 did not release any significant amount of hydrogen at 623 K (350 °C). But, after ball milling for 10 hours, 0.8 wt pct hydrogen was released from MgH2 at 623 K (350 °C) in 40 minutes. Adding 10 wt pct catalyst via ball milling to MgH2 led to releasing 3.5 wt pct hydrogen in the same conditions. In addition, increasing ball milling time from 10 to 65 hours increased the amount of released hydrogen from 51 to 85 pct of theoretical hydrogen desorption value and improved kinetic of desorption process.

  1. Preparation of MgB2 Superconducting Materials%MgB2超导材料的制备




  2. Effects of Mg content on pore structure and electrochemical corrosion behaviors of porous Al-Mg alloys

    何文远; 肖逸锋; 吴靓; 许艳飞; 钱锦文; 贺跃辉; 郑学军


    Porous Al-Mg alloys with different nominal compositions were successfully fabricated via elemental powder reactive synthesis, and the phase composition, pore structure, and corrosion resistance were characterized with X-ray diffractometer, scanning electron microscope and electrochemical analyzer. The volume expansion ratio, open porosity and corrosion resistance in 3.5% (mass fraction) NaCl aqueous solution of the alloys increase at first and then decrease with the increase of Mg content. The maxima of volume expansion ratio and open porosity are 18.3% and 28.1% for the porous Al-56%Mg (mass fraction) alloy, while there is the best corrosion resistance for the porous Al-37.5% Mg (mass fraction) alloy. The pore formation mechanism can be explained by Kirkendall effect, and the corrosion resistance can be mainly affected by the phase composition for the porous Al-Mg alloys. They would be of the potential application for filtration in the chloride environment.

  3. Fabrication and spectroscopic properties of transparent Nd3+:MgO and Er3+:MgO ceramics

    Sanamyan, T.; Cooper, C.; Gilde, G.; Sutorik, A. C.; Dubinskii, M.


    We present the results of the development and comprehensive characterization of fully densified Er3+:MgO and Nd3+:MgO transparent ceramics fabricated from specially formulated nanopowders. Also presented are the spectroscopic characterization results (absorption, fluorescence and emission lifetimes) of Er3+ and Nd3+ dopant ions in MgO in the temperature range 10 to 300 K. To the best of our knowledge, this is the first reported successful demonstration of bulk MgO host material doped with rare earth (RE) ions. Spectroscopic results are indicative of a single-site RE ion incorporation with a nearly perfect single crystalline environment within the MgO ceramic grains. The results are presented with major emphasis on potential laser application and the outlook for substantially improved laser power scaling at room temperature based on the unique thermal properties of the host material.

  4. Possibility of a 2D SiC monolayer formation on Mg(0001) and MgO(111) substrates

    Kuzubov, A. A.; Eliseeva, N. S.; Krasnov, P. O.; Tomilin, F. N.; Fedorov, A. S.; Tolstaya, A. V.


    The geometrical characteristics of a 2D SiC monolayer on Mg(0001) and MgO(111) plates regarded as potential materials for growing two-dimensional silicon carbide were studied. The most favorable positions of the atoms of 2D SiC on the substrates were determined. In the 2D SiC/Mg(0001) system, unlike in 2D SiC/MgO(111), the deviation of the carbon atom from the silicon carbide monolayer was insignificant (0.08 Å). Consequently, magnesium can be used as a substrate for growing two-dimensional silicon carbide. The use of MgO(111) is not recommended because of a significant distortion of the 2D SiC surface.

  5. Superconductivity in dense MgB2 wires.

    Canfield, P C; Finnemore, D K; Bud'ko, S L; Ostenson, J E; Lapertot, G; Cunningham, C E; Petrovic, C


    MgB2 becomes superconducting just below 40 K. Whereas porous polycrystalline samples of MgB2 can be synthesized from boron powders, in this Letter we demonstrate that dense wires of MgB2 can be prepared by exposing boron filaments to Mg vapor. The resulting wires have a diameter of 160 microm, are better than 80% dense, and manifest the full chi = -1/4pi shielding in the superconducting state. Temperature-dependent resistivity measurements indicate that MgB2 is a highly conducting metal in the normal state with rho(40 K) = 0.38 microOmega cm. By using this value, an electronic mean-free path, l approximately 600 A can be estimated, indicating that MgB2 wires are well within the clean limit. Tc, Hc2(T), and Jc data indicate that MgB2 manifests comparable or better superconducting properties in dense wire form than it manifests as a sintered pellet.


    郭冬丽; 宁佩芳; 袁媛


    Objective: To study the dynamic change and its diagnostic significance of MG7 expression in the process of gastric cancer development. Methods: The expression level of antigen MG7 was determined by immunohistochemistry method in 406 cases of gastric mucosa. The classification of intestinal metaplasia of gastric mucosa was determined by histochemistry method in 82 cases. Results: The positive rate of MG7 expression in normal gastric mucosa, intestinal metaplasia and dysplasia of gastric mucosa and gastric cancer were increased gradually (P<0.01). The positive rate of MG7 expression in superficial gastritis, atrophic gastritis and gastric cancer were increased on sequence (P<0.01). The positive rate of antigen MG7 expression in type Ⅲ intestinal metaplasia of gastric mucosa had significant difference,compared with that in type Ⅰ an Ⅱ intestinal metaplasia (P<0.05). Conclusion: MG7 antigen had close relationship with gastric cancer. Type Ⅲ intestinal metaplasia, atrophic gastritis and dysplasia should be followed up in order to improve the early detection of gastric cancer. MG7 antigen had great clinical value in the dynamic follow-up of gastric precursors.

  7. Oxidation and growth of Mg thin films on Ru(001)

    Huang, H. H.; Jiang, X.; Siew, H. L.; Chin, W. S.; Sim, W. S.; Xu, G. Q.


    The oxidation and growth of ultra-thin Mg films on a Ru(001) substrate have been studied using X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS) in the temperature range of 300-1500 K. Our results suggest that the growth of Mg thin films follows a layer-by-layer mode. Upon oxygen adsorption at 300 K, two O 1s peaks were detected on the Mg film. The peak at 532.2-532.6 eV could be attributed to either dioxygen or partially reduced species (O δ-, δfilm to 800 K causes the conversion of the dioxygen or partially reduced species to the oxide state. Thermal desorption peaks of MgO were directly detected at 1000-1127 and 1350-1380 K, respectively. However, initial evaporation of Mg atoms onto an oxygen pre-adsorbed surface yields a fully oxidized MgO. Further Mg deposition results in the formation of a partially oxidized film with the observation of an O 1s peak at 532.2 eV.

  8. Combustion and sensitivity characteristics of Mg/TF pyrolants

    Kuwahara, T.; Matsuo, S.; Shinozaki, N. [Aerospace Division, Nissan Motor Co Ltd, Saitama (Japan)


    Burning rate and sensitivity characteristics of energetic mixtures composed of metal particles and oxidizers, the so called `pyrolants`, were studied experimentally. The pyrolants tested were made of various particle sizes of magnesium (Mg) and poly-tetrafluoroethylene (TF). Mg/TF pyrolant produces high combustion flame temperature, so it is used as heat sources and igniter pyrolants. The maximum flame temperature (Tf) of Mg/TF pyrolant is 3271 K at 0.1 MPa, and 3483 K at 1 MPa. These values are obtained when Mg concentration is 30 %. When the Mg concentrations are less than 50 %, the pyrolants are not able to burn stably at one atmosphere. The burning rate increases with increasing concentration of Mg and decreases with increasing the mean diameter of Mg particles at constant pressure. Sensitivity characteristics were evaluated with drop hammer test and the weight used was 5 kg. Explosive energy decreased with increasing burning rate, so there is strong relationship between burning rate and explosive energy. (authors) 8 refs.

  9. Characterization of Mg2+ Distributions around RNA in Solution


    Binding of metal ions is an important factor governing the folding and dynamics of RNA. Shielding of charges in the polyanionic backbone allows RNA to adopt a diverse range of folded structures that give rise to their many functions within the cell. Some RNA sequences fold only in the presence of Mg2+, which may be bound via direct interactions or occupy the more diffuse “ion atmosphere” around the RNA. To understand the driving forces for RNA folding, it is important to be able to fully characterize the distribution of metal ions around the RNA. In this work, a combined Grand Canonical Monte Carlo-Molecular Dynamics (GCMC-MD) method is applied to characterize Mg2+ distributions around folded RNA structures. The GCMC-MD approach identifies known inner- and outer-shell Mg2+ coordination, while also predicting new regions occupied by Mg2+ that are not observed in crystal structures but that may be relevant in solution, including the case of the Mg2+ riboswitch, for which alternate Mg2+ binding sites may have implications for its function. This work represents a significant step forward in establishing a structural and thermodynamic description of RNA–Mg2+ interactions and their role in RNA structure and function. PMID:27819065

  10. Electronic Structure of New Superconducting Perovskite MgCNi3

    Li CHEN; Hua LI; Liangmo MEI


    The electronic structures of new superconducting perovskite MgCNis and related compounds MgCNi2T (T=Co, Fe,and Cu) have been studied using MS-Xα method. In MgCNi3, the main peak of density of states is located below the Fermi level and dominated by Ni d. From the results of total energy calculations, it was found that the number of Ni valence electron decreases faster for the Fe-doped case than that for the Co-doped case. The valence state of Ni changes from +1.43 in MgCNi2Co to +3.02 in MgCNi2Fe. It was confirmed that Co and Fe dopants in MgCNi3 behave as a source of d-band holes and the suppression of superconductivity occurs faster for the Fe-doped case than that for the Co-doped case. In order to explain the fact that Co and Fe dopants in MgCNi3 behave as a source of d-band holes rather than magnetic scattering centers that quench superconductivity, we have also investigated the effects of electron (Cu) doping on the superconductivity and found that both electron (Cu) doping and hole (Co, Fe)doping quench superconductivity exist. Comparing with the hole (Co) doping, there was no much difference between Cu and Co doping. This suggests that Co and Fe doping do not actas magnetic impurity.

  11. Synthesis of superconductor MgCNi3 with carbon nanotubes

    Xia Qing-Lin; Yi Jian-Hong; Peng Yuan-Dong; Luo Shu-Dong; Wang Hong-Zhong; Li Li-Ya


    MgCNia, an intermetallic compound superconductor with a cubic perovskite crystal structure, has been synthesized using fine Mg and Ni powders and carbon nanotubes (CNTs) as starting materials by the conventional powder metallurgy method. The composition, microstructure and superconductivity are characterized using x-ray diffraction (XRD), energy dispersive x-ray (EDX) analysis, scanning electron microscopy (SEM), and superconducting quantum interference device (SQUID) magnetometer. The results indicate that the phases of the synthesized samples are MgCNi3 (major phase) and traces of C and MgO. The MgCNi3 particle sizes range from several hundreds of nanometres to several micrometres.The onset superconducting transition temperature Tc of the MgCNi3 sample is about 7.2 K. The critical current density Jc is about 3.44 × 104 A/cm2 calculated according to the Bean model from the magnetization hysteresis loop of the slab MgCNi3 sample at 5 K and zero applied field.

  12. Systematic study of the synthesis and coordination of 2-(1,2,3-triazol-4-yl)-pyridine to Fe(II), Ni(II) and Zn(II); ion-induced folding into helicates, mesocates and larger architectures, and application to magnetism and self-selection.

    Wu, Nan; Melan, Caroline F C; Stevenson, Kristina A; Fleischel, Olivier; Guo, Huan; Habib, Fatemah; Holmberg, Rebecca J; Murugesu, Muralee; Mosey, Nicholas J; Nierengarten, Hélène; Petitjean, Anne


    With its facile synthesis, the pyridine-1,2,3-triazole chelate is an attractive building block for coordination-driven self-assembly. When two such chelates are bridged by a spacer and exposed to cations of octahedral geometrical preference, they generally self-assemble into dinuclear triple-stranded structures in the solid state and in solution in the presence of non-coordinating counter-ions. In solution, a wider range of architectures may nevertheless form, depending on the nature of the spacer. A systematic study of the spacer and substitution pattern is therefore presented, which allows assessing the various factors affecting self-assembly around the pyridine-1,2,3-triazole chelate, as well as the stereochemical control in these architectures. Applications to chirality, magnetism and system selection are discussed, and involve Fe(ii), Ni(ii), Zn(ii) and Cu(i) cations.

  13. Nickel incorporation in Fe(II, III hydroxysulfate Green Rust: effect on crystal lattice spacing and oxidation products Incorporação de níquel em Fe (II-III Grenn Rust hidroxisulfato: efeito sobre a estrutura cristalina e produtos de oxidação

    Lucia Helena Garófalo Chaves


    Full Text Available Ni(II-Fe(II-Fe(III layered double hydroxides (LDH or Ni-containing sulfate green rust (GR2 samples were prepared from Ni(II, Fe(II and Fe(III sulfate salts and analyzed with X ray diffraction. Nickel is readily incorporated in the GR2 structure and forms a solid solution between GR2 and a Ni(II-Fe(III LDH. There is a correlation between the unit cell a-value and the fraction of Ni(II incorporated into the Ni(II-GR2 structure. Since there is strong evidence that the divalent/trivalent cation ratio in GR2 is fixed at 2, it is possible in principle to determine the extent of divalent cation substitution for Fe(II in GR2 from the unit cell a-value. Oxidation forms a mixture of minerals but the LDH structure is retained if at least 20 % of the divalent cations in the initial solution are Ni(II. It appears that Ni(II is incorporated in a stable LDH structure. This may be important for two reasons, first for understanding the formation of LDHs, which are anion exchangers, in the natural environment. Secondly, this is important for understanding the fate of transition metals in the environment, particularly in the presence of reduced Fe compounds.Amostras de hidróxidos de dupla camada (HDC, ou "sulfate green rust" (GR2, contendo Ni foram preparadas utilizando-se sulfatos de Ni(II, Fe(II e Fe(III e analisadas por difração de raios X. O Ni está incorporado na estrutura do GR2 e forma um sólido entre GR2 e um HDC contendo Ni(II-Fe(III. Há correlação entre os valores de "a" da célula unitária e os da fração de Ni(II incorporado na estrutura do Ni(II-GR2. Desde que haja forte evidência de que a razão entre os cátions divalente/trivalente no GR2 seja igual a 2, é possível, a princípio, determinar a extensão da substituição do cátion divalente por Fe(II no GR2 a partir dos valores de "a" da célula unitária do cristal. Sob o efeito da oxidação, é formada uma mistura de minerais, porém a estrutura do HDC não é alterada se pelo menos

  14. A Redetermination of the Dissociation Energy of MgO(+)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Partridge, Harry


    In 1986, we reported a dissociation energy (D(sub 0) of 2.31 eV for the X(sup 2)Pi ground state of MgO(+). This value was determined by computing the dissociation energy to the Mg(2+) + O(-) limit and adjusting the value to the Mg(+) + O limit using the experimental Ionization Potential (IP) of Mg(+) and the Electron Affinity (EA) of O. The success of this method relies on the assumption that there is little covalent contribution to the bonding. The very small (0.04 eV) correlation contribution to the binding energy was taken as corroboration for the validity of this approach. Our earlier theoretical value was estimated to be accurate to at least 0.2 eV. It is in excellent agreement with the subsequent value of 2.30 +/- 0.13 eV determined by Freiser and co-workers from photodissociation experiments. It is also consistent with the upper (less than 3.1 eV) and lower (greater than 1.1 eV) bounds determined by Rowe obtained by studying the reactions of Mg(+) with 03 and NO2. However, it is inconsistent with an upper bound of 1.7 eV reported by Kappes and Staley based on their failure to observe MgO(+) in the reaction of Mg(+) with N2O. The picture became somewhat clouded, however, by the recent guided-ion beam mass spectrometric studies of Dalleska and Armentrout. Their initial analysis of the reaction data for Mg(+) + O2 lead to a bond dissociation energy of 2.92 +/- 0.25 eV, which is considerably larger than the value of 2.47 +/- 0.06 eV deduced from their studies of the Mg(+)+NO2 reaction.

  15. Fabrication of Mg2Si/AZ91D Composites from Mg-SiO2%Mg-SiO2体系制备Mg2Si/AZ91D复合材料的研究

    王军; 陈刚; 赵玉涛; 徐萌; 张道理; 黄康; 彭蕾


    采用原位合成技术制备了Mg2Si/AZ91D复合材料, 并通过光学显微镜(OM)、扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)等对添加碱土、稀土元素的影响进行了研究. 结果表明: AZ91D镁合金中加入SiO2(其中Si占合金质量的3%)后, 出现多边形状或树枝晶状的初生Mg2Si相, 以及汉字状的共晶Mg2Si相, 树枝晶状Mg2Si的平均尺寸约25~50 μm, 汉字状Mg2Si的平均尺寸约12~15 μm;Mg2Si对镁合金中的β-Mg17Al12相有细化作用. 添加Ca, Sr, Y对Mg2Si形貌、尺寸有明显的改善, 当添加0.9%Ca, 0.1%Sr, 0.5%RE(80%Y)变质处理后, Mg2Si形貌全部变为多边形状, 平均尺寸约0.8~5 μm.

  16. Fine-Filament MgB2 Superconductor Wire

    Cantu, Sherrie


    Hyper Tech Research, Inc., has developed fine-filament magnesium diboride (MgB2) superconductor wire for motors and generators used in turboelectric aircraft propulsion systems. In Phase I of the project, Hyper Tech demonstrated that MgB2 multifilament wires (MgB2 rotor coil packs for a superconducting generator. The ultimate goal is to enable low-cost, round, lightweight, low-AC-loss superconductors for motor and generator stator coils operating at 25 K in next-generation turboelectric aircraft propulsion systems.

  17. Superconductivity of metallic boron in MgB2.

    Kortus, J; Mazin, I I; Belashchenko, K D; Antropov, V P; Boyer, L L


    Boron in MgB2 forms stacks of honeycomb layers with magnesium as a space filler. Band structure calculations indicate that Mg is substantially ionized, and the bands at the Fermi level derive mainly from B orbitals. Strong bonding with an ionic component and considerable metallic density of states yield a sizable electron-phonon coupling. Together with high phonon frequencies, which we estimate via zone-center frozen phonon calculations to be between 300 and 700 cm(-1), this produces a high critical temperature, consistent with recent experiments. Thus MgB2 can be viewed as an analog of the long sought, but still hypothetical, superconducting metallic hydrogen.

  18. Ultrasonic Properties of the MgB2 Superconductor

    YU Ri-Cheng; JIN Chang-Qing; LI Shao-Chun; WANG Ru-Ju; LI Feng-Ying; LIU Zhen-Xing; ZHU Jia-Lin


    The sound velocities of longitudinal and shear waves are measured on a polycrystalline MgB2 superconductor with Tc of 39 K. The specimen used in the experiments is pressed and heated using the MgB2 powder. The elastic moduli, Debye temperature and specific heat at room temperature are obtained based on sound velocity data. The results indicate that the velocities are much higher than those in the usual materials, while elastic constants remain reasonably soft, which may be due to the high transition temperature of the MgB2 superconductor.


    Jiang, Weilin; Zhu, Zihua; Varga, Tamas; Bowden, Mark E.; Manandhar, Sandeep; Roosendaal, Timothy J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang


    As a candidate material for fusion reactor designs, silicon carbide (SiC) under high-energy neutron irradiation undergoes atomic displacement damage and transmutation reactions that create magnesium as one of the major metallic products. The presence of Mg and lattice disorder in SiC is expected to affect structural stability and degrade thermo-mechanical properties that could limit SiC lifetime for service. We have initiated a combined experimental and computational study that uses Mg+ ion implantation and multiscale modeling to investigate the structural and chemical effects in Mg implanted SiC and explore possible property degradation mechanisms.

  20. Molecular dynamics of MgSiO3 perovskite melting

    Liu Zi-Jiang; Cheng Xin-Lu; Yang Xiang-Dong; Zhang Hong; Cai Ling-Cang


    The melting curve of MgSiO3 perovskite is simulated using molecular dynamics simulations method at high pressure. It is shown that the simulated equation of state of MgSiO3 perovskite is very successful in reproducing accurately the experimental data. The pressure dependence of the simulated melting temperature of MgSiO3 perovskite reproduces the stability of the orthorhombic perovskite phase up to high pressure of 13OGPa at ambient temperature, consistent with the theoretical data of the other calculations. It is shown that its transformation to the cubic phase and melting at high pressure and high temperature are in agreement with recent experiments.

  1. Efeitos do manganês sobre a soja cultivada em solo de Cerrado do Triângulo Mineiro Effects of manganese on soybean growth in a cerrado soil of Triângulo Mineiro, MG, Brazil



    Full Text Available A deficiência de Mn em soja [Glycine max (L. Merrill] e em outras culturas pode ser devida aos seus baixos teores no solo, ou à indisponibilidade do elemento induzida pela aplicação de calcário. O objetivo deste trabalho foi verificar a composição mineral da soja em relação à disponibilidade de Mn no solo. Em casa de vegetação foi conduzido um experimento utilizando um solo coletado no município de Patrocínio, MG, onde o café mostra sintomas de deficiência desse elemento. As doses de Mn foram: 0, 10, 50 e 100 mg kg-1 e um tratamento adicional com aplicação foliar de 0,6% de Mn e duas doses de calcário, ou seja: 0 e 2,7 t ha-1. Os teores de Mn na planta aumentaram com a dose de Mn no solo, e diminuíram com a aplicação de calcário. O menor teor de Mn encontrado nas folhas foi de 84 mg kg-1 na dose 0 de Mn com calcário. O Mn provocou um aumento na produção de matéria seca e de vagens, em relação a ambas as doses de calcário. A calagem não induziu o aparecimento de sintomas de deficiência de Mn. A aplicação foliar de Mn foi eficiente em aumentar e manter a produção.Manganese deficiency in soybean [Glycine max (L. Merrill and in other crops could be due to its low levels in the soil, or to its unavailability induced by liming. The objective of this research was to verify the soybean mineral composition in relation to Mn availability. An experiment was carried out in a greenhouse, using soil from Patrocínio, MG, Brazil, where the cultivated coffee shows symptoms of Mn deficiency. Mn was applied at the rates of zero, 10, 50 and 100 mg kg-1 with an additional treatment of 0.6% of foliar applied Mn and two rates of lime, namely: zero and 2.7 t ha-1. Mn concentration in the plant tissue was increased with the rate of lime application; liming, however, caused a Mn reduction. It must be pointed out that the lowest Mn level in the leaves was 84 mg kg-1, at the zero rate of Mn with lime. Mn ratio caused an increase both in

  2. Preparation of a sample with a single MgH2 phase by horizontal ball milling and the first hydriding reaction of 90 wt% Mg-10 wt% MgH2

    Hong, Seong-Hyeon; Song, Myoung Youp


    In order to prepare an additive-free sample with a single MgH2 phase, 90 wt% Mg-10 wt% MgH2 (named 90Mg-10MgH2) was milled under a hydrogen atmosphere in a horizontal ball mill, and then hydrided. The hydrogen absorption and desorption properties of the prepared samples were investigated, and compared with those of milled pure Mg and purchased MgH2. X-ray diffraction analysis, measurement of specific BET surface areas, and observation of the prepared samples by scanning electron microscope were performed. The 90Mg-10MgH2 sample after hydriding-dehydriding cycling had small and large particles with fine particles on their surfaces, and had much finer particles and more defects than the milled pure Mg sample after hydridingdehydriding cycling. The specific BET surface areas of the milled Mg and 90Mg-10MgH2 were measured as 7.81 and 99.81 m2/g, respectively. A sample that had almost a single MgH2 phase could be prepared by horizontal ball milling and the first hydriding reaction of 90Mg-10MgH2. 90Mg-10MgH2 released 5.82 wt% H for about 70 min, while unmilled MgH2 (Aldrich) released 6.04 wt% H for about 100 min, at 648 K.

  3. Improved efficacy of intramuscular weekly administration of clodronate 200 mg (100 mg twice weekly) compared with 100 mg (once weekly) for increasing bone mineral density in postmenopausal osteoporosis.

    Frediani, Bruno; Bertoldi, Ilaria; Pierguidi, Serena; Nicosia, Antonella; Picerno, Valentina; Filippou, Georgios; Cantarini, Luca; Galeazzi, Mauro


    Clodronate is a bisphosphonate used for the treatment of postmenopausal osteoporosis and all conditions characterized by excess bone resorption. We have previously reported that intramuscular (IM) therapy with clodronate at a dose of 100 mg/week displays significant effects on bone mineral density (BMD) although a plateau effect is observed after 1 year of treatment. Previous reports indicate that the densitometric effects of bisphosphonates directly correlate with the drug dosage and suggest that using IM clodronate at doses higher than 100 mg/week may result in improved efficacy. However, to the best of our knowledge, this has never been proved. The primary endpoint of the study was the effect on BMD of IM clodronate 100 mg once weekly or 100 mg twice weekly in patients with postmenopausal osteoporosis. The incidence of non-traumatic vertebral fractures and adverse events was also reported. The present study was a randomized, open-label, parallel-group trial conducted between January 2007 and December 2009 in the Osteoporosis and Osteoarticular Instrumental Diagnosis Centre (University of Siena, Siena, Italy). The study involved 60 women, aged 57-78 years, with a history of postmenopausal osteoporosis for more than 5 years. Patients were randomized to receive IM clodronate 100 mg once weekly (Group A, 30 patients) or 100 mg twice weekly (Group B, 30 patients), for 2 years. Significant increases compared with baseline in BMD were observed for both groups at 1 and 2 years, with significantly higher increases for Group B compared with Group A. Group B displayed a BMD increase (± SD) at the lumbar spine of +4.0 % (± 2.1) and +5.9 % (± 2.0) at 1 and 2 year(s), respectively, compared with +2.8 % (± 1.7) and +3.5 % (± 2.2), respectively, observed for Group A. Similarly, Group B showed better performance compared with Group A for BMD increase at the femoral neck, with an observed increase of +3.5 % (± 1.7) and +5.4 % (± 1.8) at 1 and 2 year(s), respectively

  4. Elastic and inelastic scattering of 0. 8 GeV polarized protons from /sup 24/Mg and /sup 26/Mg

    Blanpied, G.S.; Ritchie, B.G.; Barlett, M.L.; Hoffmann, G.W.; McGill, J.A.; Milner, E.C.; Jones, K.W.; Nanda, S.K.; de Swiniarski, R.


    Data on 800 MeV polarized proton scattering on /sup 24/Mg and /sup 26/Mg are presented. Angular distributions and analyzing power data have been extracted from fits to 26 peaks in the spectra for /sup 24/Mg and 23 peaks in /sup 26/Mg. Although there are a variety of shapes for the angular distributions, the analyzing power data for all states are positive and similar in magnitude and seem to be consistent with a two-body operator for the excitation with a spin structure much like that for the free proton-nucleon system. Evidence for a level in /sup 26/Mg at 8.03 MeV with J>4 is presented. Comparison between the observed angular distribution, coupled channels, and distorted wave Born approximation calculations, and the angular distributions of excited states in neighboring nuclei, support the assignment of J/sup ..pi../ = 5/sup -/ or 6/sup +/. Coupled channels calculations for the 0/sup +/, 2/sup +/, 4/sup +/, and 6/sup +/ members of the ground state rotational bands of /sup 24/Mg and /sup 26/Mg are compared to the data. Deformation parameters from distorted wave Born approximation calculations are determined for most of the angular distributions.

  5. Effect of Mg on microstructures and properties of Al-Mg-Si-Cu aluminium alloys for automotive body sheets

    LIU Hong; SONG Wen-ju; ZHAO Gang; LIU Chun-ming; ZUO Liang


    The effects of variation of Mg content on microstructures,the tensile properties and the formability of Al-Mg-Si-Cu alloys for automotive body sheets were investigated by means of scan electron microscopy,optical metallographic analysis,tensile and Ericsson tests.The results show that for Al-Mg-Si-Cu aluminium alloys with excessive Si,with an increment of Mg content,the strength enhances,the specific elongation and Erisson values of alloys decrease,and the number of Mg2 Si constituent increases and that of Al(MnFe)Si type constituents reduces.Al-MgSi-Cu aluminium alloys with excessive Si for automotive body sheets can present obviously the paint bake hardenability during the paint bake cycle (I.e.artificial aging at 170 ℃ for 30 min immediately after the solution treatment and quenching).Suitable Mg content should be controlled in the range of 0.8% and 1.2 % (mass fraction).

  6. As-cast microstructure of Al-Zn-Mg and Al-Zn-Mg-Cu alloys added erbium

    MAO Jian-wei; JIN Tou-nan; XU Guo-fu; NIE Zuo-ren


    The effects of different contents of rare earth element, and erbium, on the as-cast microstructures of Al-6Zn-2Mg and Al-6Zn-2Mg-1.8Cu alloys were studied by optical microscopy, scanning electron microscopy, X-ray diffractometry, transmission electron microscopy and EDS analysis. The results show that the netlike structure of as-cast alloys can be remarkably refined, and the distance of dendritic structure decreases, with Er addition. However, the improvement results on Al-Zn-Mg-Cu are not better than that of Al-Zn-Mg. Er and Al can interact to form Al3Er phase, which is coherent with α(Al) matrix, with trace Er addition to the Al-Zn-Mg alloy. The refinement effect of Al-Zn-Mg alloys is familiar with the formation and precipitation of coherent Al3Er phases. The ternary compound AlCuEr, similar with AlCuSc phase, will form when Er is added to Al-Zn-Mg-Cu alloy, which suppresses the formation of Al3Er phase and doesn't solve in the following heat treatment.

  7. Basolateral Mg2+ extrusion via CNNM4 mediates transcellular Mg2+ transport across epithelia: a mouse model.

    Daisuke Yamazaki

    Full Text Available Transcellular Mg(2+ transport across epithelia, involving both apical entry and basolateral extrusion, is essential for magnesium homeostasis, but molecules involved in basolateral extrusion have not yet been identified. Here, we show that CNNM4 is the basolaterally located Mg(2+ extrusion molecule. CNNM4 is strongly expressed in intestinal epithelia and localizes to their basolateral membrane. CNNM4-knockout mice showed hypomagnesemia due to the intestinal malabsorption of magnesium, suggesting its role in Mg(2+ extrusion to the inner parts of body. Imaging analyses revealed that CNNM4 can extrude Mg(2+ by exchanging intracellular Mg(2+ with extracellular Na(+. Furthermore, CNNM4 mutations cause Jalili syndrome, characterized by recessive amelogenesis imperfecta with cone-rod dystrophy. CNNM4-knockout mice showed defective amelogenesis, and CNNM4 again localizes to the basolateral membrane of ameloblasts, the enamel-forming epithelial cells. Missense point mutations associated with the disease abolish the Mg(2+ extrusion activity. These results demonstrate the crucial importance of Mg(2+ extrusion by CNNM4 in organismal and topical regulation of magnesium.

  8. Bending strain tolerance of MgB2 superconducting wires

    Kováč, P.; Hušek, I.; Melišek, T.; Kulich, M.; Kopera, L.


    This work describes the strain tolerance of MgB2 superconductors subjected to variable bending stresses. Bending of MgB2 wire was done at room temperature in different modes: (i) direct bending of straight annealed samples to variable diameters and by (ii) indirect bending by straightening of bent and annealed samples. I c-bending strain characteristics of samples made by in situ PIT and by the internal magnesium diffusion (IMD) process were measured at 4.2 K. The results show a good agreement between the direct and indirect bending mode, which allows easier estimation of limits important for the winding process of MgB2 superconductors with brittle filaments. A comparison of MgB2 wires made by in situ PIT and IMD processes showed improved strain tolerance for IMD due to better grain connectivity the low annealing temperature, which does not appear to reduce the mechanical strength of sheath material.


    mine, have a nearly ideal "picrotephroite" composition which is halfway between ... The iron and manganese ores, which are in proximity with each other but well .... From the chemical analysis of the studied Mn-Mg olivines, the numbers of.

  10. $^{31}$Mg $\\beta$-NMR applied in chemistry and biochemistry

    Magnesium ions, Mg$^{2+}$, are essential in biological systems, taking part in practically all phosphate chemistry, in photosynthesis as an integral component of chlorophyll, and they are regulated via transport through selective membrane proteins. Nonetheless, the function of magnesium ions in biochemistry is difficult to characterize, as it is practically invisible to current experimental techniques. With this proposal we aim to advance the use of $^{31}$Mg $\\beta$-NMR to liquid samples, building on the experience from the successful Letter of Intent INTC-I-088 “$\\beta$-NMR as a novel technique for biological applications”. Initially a series of experiments will be conducted aiming to characterize the coordination chemistry of Mg$^{2+}$ in ionic liquids (ILs), demonstrating that it is possible within the lifetime of the radioisotope to achieve binding of Mg$^{2+}$ to a molecule dissolved in the IL. ILs are chosen as they display a very low vapor pressure, and are thus straightforwardly compatible with t...

  11. Interpreting the Mg IIh andk Line Profiles of Mira Variables

    Wood, B. E.; Karovska, M.


    We use radiative transfer calculations to reproduce the basic appearance of Mg II lines observed from Mira variables. These lines have centroids that are blueshifted by at least 30 km s-1 from the stellar rest frame. It is unlikely that flow velocities in the stellar atmospheres are this fast, so radiative transfer effects must be responsible for this behavior. Published hydrodynamic models predict the existence of cool, downflowing material above the shocked material responsible for the Mg II emission, and we demonstrate that scattering in this layer can result in Mg II profiles as highly blueshifted as those that are observed. However, our models also show that scattering within the shock plays an equally strong role in shaping the Mg II profiles, and our calculations illustrate the importance of partial redistribution and the effects of being out of ionization equilibrium.

  12. Attempts at doping indium in MgB2

    Grivel, J.-C.


    Indium (In) doped MgB2 polycrystalline samples were prepared by solid-liquid phase reaction in Ar. After reaction at 800 °C, less than 1 at.% Mg was replaced by In in the MgB2 phase, without significant influence on its lattice parameters and only a slight decrease of its superconducting transition temperature. For all studied In concentrations in the nominal composition, the formation of InMg was evidenced by X-ray diffraction. The critical current density and accommodation field of the wires are decreased in the samples containing In. The flux pinning mechanism can be described by surface pinning in both the doped and undoped samples.

  13. Facile fabrication of hydrophobic surfaces on mechanically alloyed-Mg/HA/TiO{sub 2}/MgO bionanocomposites

    Khalajabadi, Shahrouz Zamani [Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Abdul Kadir, Mohammed Rafiq, E-mail: [Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Izman, Sudin; Mohd Yusop, Mohd Zamri [Department of Materials, Manufacturing and Industrial Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia)


    Highlights: • Mg/HA/TiO{sub 2}-based nanocomposite was produced using mechanical alloying. • The hydrophobic surface coverage was fabricated on the mechanical alloyed samples by annealing. • The morphological characteristics, phase evolution and wettability of nanocomposites and the hydrophobic surface coverage were investigated. • The activation energies and reaction kinetic of the powder mixture of nanocomposites were calculated. - Abstract: The effect of mechanical alloying and post-annealing on the phase evolution, microstructure, wettability and thermal stability of Mg–HA–TiO{sub 2}–MgO composites was investigated in this study. Phase evolution and microstructure analysis were performed using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy, as well as the wettability determined by contact angle measurements with SBF. The 16-h mechanical alloying resulted in the formation of MgTiO{sub 3}, CaTiO{sub 3}, Mg{sub 3}(PO{sub 4}){sub 2} and Mg(OH){sub 2} phases and a decrease in wettability of the nanocomposites. A hydrophobic film with hierarchical structures comprising nanoflakes of MgTiO{sub 3}, nano-cuboids of CaTiO{sub 3}, microspheres of Mg{sub 3}(PO{sub 4}){sub 2} and Mg(OH){sub 2} was successfully constructed on the surface of the Mg-based nanocomposites substrates as a result of the post-annealing process. After 1-h annealing at 630 °C, the synthesized hydrophobic surface on the nanocomposite substrates decreased the wettability, as the 8-h-mechanically alloyed samples exhibited a contact angle close to 93°. The formation activation energies and reaction kinetics of the powder mixture were investigated using differential thermal analysis and thermal gravimetric analysis. The released heat, weight loss percentage and reaction kinetics increased, while the formation activation energies of the exothermic reactions decreased following an increase in the milling time.

  14. On Interpreting the Photoelectron Spectra of MgO

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Arnold, James (Technical Monitor)


    The (sup 2)Sigma(+) and (sup 2)Pi states of MgO(-) and the (sup 1)Sigma(+), (sup 1)Pi, and (sup 3)Pi states of MgO are studied using the averaged coupled-pair functional (ACPF) approach. The computed spectroscopic constants are in good agreement with the available experimental data. The computed Franck-Condon factors and photodetachment overlaps are compared with experiment.

  15. Photoionization of excited states of neon-like Mg III

    Narendra Singh; Man Mohan


    The close coupling -matrix method is used to calculate cross-sections for photoionization of Mg III from its first three excited states. Configuration interaction wave functions are used to represent two target states of Mg III retained in the -matrix expansion. The positions and effective quantum numbers for the Rydberg series converging to the excited state 2226 \\ 2 of the residual ion, are predicted.

  16. Preparation and characterization of MgB2 superconductor

    Shashwati Sen; D K Aswal; Ajay Singh; T V Chandrasekhar Rao; K P Muthe; J C Vyas; L C Gupta; S K Gupta; V C Sahni


    The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties. The upper critical field, irreversibility line and critical current density have been determined using magnetization data. The current–voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition. The surface analysis using X-ray photoelectron spectroscopy shows that MgB2 is sensitive to atmospheric degradation.

  17. TEM microstructure of mechanically alloyed Ti-12Mg powders

    T. S. KIM; B. T. LEE; J. P. AHN; J. K. PARK; J. C. BAE


    The microstructures of mechanical alloyed(MA) Ti-12%Mg alloy powders were examined using a high resolution TEM (HRTEM). The effect of MA atmospheres such as argon gas and liquid isopropyl alcohol on the resultant microstructure was investigated. Both the MA powders form a homogeneous Ti-Mg solid solution, but the oxidation behavior is distinguished. The phase change was studied as a function of milling conditions and annealing temperatures.

  18. Structures and stabilities of (MgO)n nanoclusters.

    Chen, Mingyang; Felmy, Andrew R; Dixon, David A


    Global minima for (MgO)n structures were optimized using a tree growth-hybrid genetic algorithm in conjunction with MNDO/MNDO/d semiempirical molecular orbital calculations followed by density functional theory geometry optimizations with the B3LYP functional. New lowest energy isomers were found for a number of (MgO)n clusters. The most stable isomers for (MgO)n (n > 3) are 3-dimensional. For n < 20, hexagonal tubular (MgO)n structures are more favored in energy than the cubic structures. The cubic structures and their variations dominate after n = 20. For the cubic isomers, increasing the size of the cluster in any dimension improves the stability. The effectiveness of increasing the size of the cluster in a specific dimension to improve stability diminishes as the size in that dimension increases. For cubic structures of the same size, the most compact cubic structure is expected to be the more stable cubic structure. The average Mg-O bond distance and coordination number both increase as n increases. The calculated average Mg-O bond distance is 2.055 Å at n = 40, slightly smaller than the bulk value of 2.104 Å. The average coordination number is predicted to be 4.6 for the lowest energy (MgO)40 as compared to the bulk value of 6. As n increases, the normalized clustering energy ΔE(n) for the (MgO)n increases and the slope of the ΔE(n) vs n curve decreases. The value of ΔE(40) is predicted to be 150 kcal/mol, as compared to the bulk value ΔE(∞) = 176 kcal/mol. The electronic properties of the clusters are presented and the reactive sites are predicted to be at the corners.

  19. Thermodynamic modelling of Mg(BH{sub 4}){sub 2}

    Pinatel, E.R.; Albanese, E.; Civalleri, B.; Baricco, M.


    Highlights: • DFT calculations providing missing thermodynamic data for Mg(BH{sub 4}){sub 2}were performed. • A Calphad assessment of Mg(BH{sub 4}){sub 2} was performed, considering all the available data. • Stable and metastable phase diagrams have been calculated for Mg(BH{sub 4}){sub 2}. • Several dehydrogenation paths of Mg(BH{sub 4}){sub 2} have been analysed and discussed. - Abstract: Application of the Calphad method to the description of thermodynamic properties in complex borohydride-based systems may allow a faster development of hydrogen storage materials. It is, however, limited by the low number of available thermodynamic description for borohydrides in thermodynamic databases. In the present work, a Calphad assessment of Mg(BH{sub 4}){sub 2} has been performed, considering available thermodynamic data. DFT calculations have been performed in order to provide missing thermodynamic data and to calculate the relative stability of the α, β and γ polymorphs. Experimental results have been compared detecting inconsistencies between them. The database obtained has been used to estimate driving forces for several dehydrogenation reactions. The dehydrogenation reaction leading to the formation of MgB{sub 2} and gaseous hydrogen is the most favoured thermodynamically, even if at low temperatures the formation of MgB{sub 12}H{sub 12} is competitive. On the contrary, positive driving forces have been calculated for the decomposition into B{sub 2}H{sub 6} and Mg(B{sub 3}H{sub 8}){sub 2}.

  20. Preparation and properties of amorphous MgB2/MgO superstructures: A new model disordered superconductor

    Siemons, W.


    In this paper we introduce a novel method for fabricating MgB{sub 2}/MgO multilayers and demonstrate the potential for using them as a new model for disordered superconductors. In this approach we control the annealing of the MgB{sub 2} to yield an interesting new class of disordered (amorphous) superconductors with relatively high transition temperatures. The multilayers appear to exhibit quasi-two-dimensional superconductivity with controlled anisotropy. We discuss the properties of the multilayers as the thickness of the components of the bilayers vary.

  1. Thermodynamic Modeling of Poorly Complexing Metals in Concentrated Electrolyte Solutions: An X-Ray Absorption and UV-Vis Spectroscopic Study of Ni(II) in the NiCl2-MgCl2-H2O System

    Zhang, Ning; Brugger, Joël; Etschmann, Barbara; Ngothai, Yung; Zeng, Dewen


    Knowledge of the structure and speciation of aqueous Ni(II)-chloride complexes is important for understanding Ni behavior in hydrometallurgical extraction. The effect of concentration on the first-shell structure of Ni(II) in aqueous NiCl2 and NiCl2-MgCl2 solutions was investigated by Ni K edge X-ray absorption (XAS) and UV-Vis spectroscopy at ambient conditions. Both techniques show that no large structural change (e.g., transition from octahedral to tetrahedral-like configuration) occurs. Both methods confirm that the Ni(II) aqua ion (with six coordinated water molecules at RNi-O = 2.07(2) Å) is the dominant species over the whole NiCl2 concentration range. However, XANES, EXAFS and UV-Vis data show subtle changes at high salinity (> 2 mol∙kg-1 NiCl2), which are consistent with the formation of small amounts of the NiCl+ complex (up to 0.44(23) Cl at a Ni-Cl distance of 2.35(2) Å in 5.05 mol∙kg-1 NiCl2) in the pure NiCl2 solutions. At high Cl:Ni ratio in the NiCl2-MgCl2-H2O solutions, small amounts of [NiCl2]0 are also present. We developed a speciation-based mixed-solvent electrolyte (MSE) model to describe activity-composition relationships in NiCl2-MgCl2-H2O solutions, and at the same time predict Ni(II) speciation that is consistent with our XAS and UV-Vis data and with existing literature data up to the solubility limit, resolving a long-standing uncertainty about the role of chloride complexing in this system. PMID:25885410

  2. Ground-state properties of neutron-rich Mg isotopes

    Watanabe, Shin; Shimada, Mitsuhiro; Tagami, Shingo; Kimura, Masaaki; Takechi, Maya; Fukuda, Mitsunori; Nishimura, Daiki; Suzuki, Takeshi; Matsumoto, Takuma; Shimizu, Yoshifumi R; Yahiro, Masanobu


    We analyze recently-measured total reaction cross sections for 24-38Mg isotopes incident on 12C targets at 240 MeV/nucleon by using the folding model and antisymmetrized molecular dynamics(AMD). The folding model well reproduces the measured reaction cross sections, when the projectile densities are evaluated by the deformed Woods-Saxon (def-WS) model with AMD deformation. Matter radii of 24-38Mg are then deduced from the measured reaction cross sections by ?ne-tuning the parameters of the def-WS model. The deduced matter radii are largely enhanced by nuclear deformation. Fully-microscopic AMD calculations with no free parameter well reproduce the deduced matter radii for 24-36Mg, but still considerably underestimate them for 37,38Mg. The large matter radii suggest that 37,38Mg are candidates for deformed halo nucleus. AMD also reproduces other existing measured ground-state properties (spin-parity, total binding energy, and one-neutron separation energy) of Mg isotopes. Neutron-number (N) dependence of defor...

  3. Microstructure and crystal growth direction of Al-Mg alloy

    Ti-jun Chen


    Full Text Available The microstructures and crystal growth directions of permanent mould casting and directionally solidified Al-Mg alloys with different Mg contents have been investigated. The results indicate that the effect of Mg content on microstructure is basically same for the alloys prepared by these two methods. The primary grains change from cellular crystals to developed columnar dendrites, and then to equiaxed dendrites as the Mg content is increased. Simultaneously, both the cellular or columnar grain region and the primary trunk spacing decrease. All of these changes are mainly attributed to the constitutional supercooling resulting from Mg element. Comparatively, the cellular or columnar crystals of the directionally solidified alloys are straighter and more parallel than those of the permanent mould casting alloys. These have straight or wavy grain boundaries, one of the most important microstructure characteristics of feathery grains. However, the transverse microstructure and growth direction reveal that they do not belong to feathery grains. The Mg seemingly can affect the crystal growth direction, but does not result in the formation of feathery grains under the conditions employed in the study.

  4. A thermodynamic assessment of the Cd-Mg system

    Ren, Xin [School of Materials Science and Engineering, University of Science and Technology Beijing, No. 30 Xueyuan Road, Beijing 100083 (China); Li, Changrong, E-mail: [School of Materials Science and Engineering, University of Science and Technology Beijing, No. 30 Xueyuan Road, Beijing 100083 (China); Guo, Cuiping; Du, Zhenmin [School of Materials Science and Engineering, University of Science and Technology Beijing, No. 30 Xueyuan Road, Beijing 100083 (China)


    Highlights: Black-Right-Pointing-Pointer The Cd-Mg binary system is optimized on the basis of the experimental data. Black-Right-Pointing-Pointer A set of self-consistent thermodynamic parameters has been obtained. Black-Right-Pointing-Pointer The calculated values agree well with the available experimental data. - Abstract: On the basis of the experimental thermochemical and phase equilibrium data, the computational thermodynamic description of the Cd-Mg binary system is performed using CALPHAD technique. The solution phases, liquid and disordered Hcp{sub A}3, are described as a substitutional model, and the excess Gibbs energies formulated with Redlich-Kister expression. The ordered phases, Cd{sub 3}Mg, CdMg and CdMg{sub 3}, are treated as the AB{sub 3} phase and modeled using four-sublattices. The order-disorder transformation between the AB{sub 3} and the Hcp{sub A}3 phases is considered, so that the substitutional model for the Hcp{sub A}3 disordered phase is extended into the four-sublattice model for the AB{sub 3} ordered phase. The thermochemical properties as well as the phase diagram of the Cd-Mg binary system are predicted. A set of self-consistent thermodynamic parameters has been obtained. The consistency between the calculated results and the reported data of both the phase equilibria and the thermochemical properties has been achieved.

  5. Corrosion mechanism of MgO-C and MgO-C-Al refractories used in stainless steel electric arc furnace; Mecanismo de corrosion a refractarios de MgO-C y MgO-C-Al en horno electrico

    Pena, P.; Aza, A. H. de; Contreras, L.; Garcia-Crrodeguas, R.; Aza, S. de; Almagro, J. F.; Luna, C.; Guerrero Barranco, M.; Ferrer, F. J.


    This article presents the results of a post-mortem study of various MgO-C and MgO-C-Al pieces that are used in the electric furnaces at the Acerinox factory in Cadiz. From the chemical, thermal, mineralogical and microstructural characterization of the materials prior to use and post-mortem it has been established that, in both types of refractories, the corrosion has lead to the formation of reaction layers with different chemical and mineralogical composition, as a function of temperature and oxygen partial pressure, ranging from the hot to the cold face and strongly depending on the zone of the electric furnace where the piece is situated. Changes in graphite content have been observed in both types of materials by X-ray diffraction. These changes have been quantified by Differential Thermal Analysis. In MgO-C-Al refractories it has been observed the formation of small amounts of C{sub 3}Al{sub 4} inside the pieces and MgAl{sub 2}O{sub 4} in the refractories hot face. Keeping in mind the obtained results and the phase equilibrium diagram of Mg-C-Al-O it has been established a corrosion mechanism for both types of materials. It cannot be established by the present results that additions of Al ({approx}{approx} 2 % in weight) improve the performance of MgO-C materials. (Author)

  6. Colloidal processing of alumina with MgO additions

    Lyckfeldt, O. [Swedish Ceramic Inst., Goeteborg (Sweden); Ferreira, J.M.F. [Dept. of Ceramics and Glass Engineering, Univ. of Aveiro (Portugal)


    Both rheological studies and casting studies were made to evaluate the effects of adding MgO (0.10 wt%) to alumina slips with a solids loading of 45 vol%, stabilised either with a polyacrylic acid (Dispex A40, Allied Colloids Ltd, UK) or with a low M{sub w} sulphonic acid (Tiron, Aldrich Chemie, Germany). Tiron and Dispex are expected to give electrostatic and electrosteric stabilisation, respectively. The addition of MgO gave significant effects displayed by increased viscosity and elasticity of the slips and a considerable decrease in density of slip-cast and filter-pressed bodies. When the casting pressure increased, there was also a general tendency that the density of filter-pressed bodies decreased with well-stabilised slips (without MgO), but increased when the slip was weakly flocculated (with MgO). This was explained by the casting rate dependency under stabilised slip conditions, and the compressibility of the filter-pressed cakes formed using flocculated slips. Furthermore, it was shown that Tiron gave a higher degree of deflocculation both with addition of MgO and without MgO, indicating that the electrostatic stabilising mechanism dominates the particle interactions whereas steric effects are less important at the solids loading used. (orig.) 5 refs.

  7. In Vitro Degradation Behavior of Ternary Mg-Zn-Se and Mg-Zn-Cu Alloys as Biomaterials

    Persaud-Sharma, Dharam; Budiansky, Noah


    In this study, the corrosion behavior of Mg-Zn-Se and Mg-Zn-Cu alloys was investigated to evaluate their corrosion behavior related to use as implantable biomaterials. The corrosion behavior of these alloys and a commercially available Mg-Zn alloy were examined using static solution electrochemical testing, dynamic solution gravimetric testing, ion leaching testing, and microscopic evaluation. Fluctuations in the pH of the Dulbecco’s Modified Eagles Medium (DMEM) used for the gravimetric and ion leaching immersion testing were also recorded over the 30-day duration to assess whether the media conditions induced by the alloy degradation would permit for cellular survival. Weight loss experimentation and electrochemical tests revealed the Mg-Zn-Cu alloy to have the greatest corrosion rate. PMID:24465245

  8. Selection of dopants to enhance hydrogen diffusion rates in MgH2 and NaMgH3

    Hao, Shiqiang; Sholl, David S.


    The transport properties of hydrogen in metal hydrides are crucial to the kinetics of H2 storage in these materials. Previous first-principles calculations and experiments have shown that H transport in MgH2 and NaMgH3 is dominated by charged defects. This creates the possibility of enhancing hydrogen diffusion in these materials by adding dopants that alter the population of the relevant charged defects. We describe a comprehensive set of first-principles calculations examining dopants in MgH2 and NaMgH3 for this purpose. Only a small number of elemental dopants are found to have favorable properties, but these dopants could increase the diffusivity of H by two to three orders of magnitude relative to the undoped materials.

  9. Loss of Endothelial Barrier in Marfan Mice (mgR/mgR Results in Severe Inflammation after Adenoviral Gene Therapy.

    Philipp Christian Seppelt

    Full Text Available Marfan syndrome is an autosomal dominant inherited disorder of connective tissue. The vascular complications of Marfan syndrome have the biggest impact on life expectancy. The aorta of Marfan patients reveals degradation of elastin layers caused by increased proteolytic activity of matrix metalloproteinases (MMPs. In this study we performed adenoviral gene transfer of human tissue inhibitor of matrix metalloproteinases-1 (hTIMP-1 in aortic grafts of fibrillin-1 deficient Marfan mice (mgR/mgR in order to reduce elastolysis.We performed heterotopic infrarenal transplantation of the thoracic aorta in female mice (n = 7 per group. Before implantation, mgR/mgR and wild-type aortas (WT, C57BL/6 were transduced ex vivo with an adenoviral vector coding for human TIMP-1 (Ad.hTIMP-1 or β-galactosidase (Ad.β-Gal. As control mgR/mgR and wild-type aortas received no gene therapy. Thirty days after surgery, overexpression of the transgene was assessed by immunohistochemistry (IHC and collagen in situ zymography. Histologic staining was performed to investigate inflammation, the neointimal index (NI, and elastin breaks. Endothelial barrier function of native not virus-exposed aortas was evaluated by perfusion of fluorescent albumin and examinations of virus-exposed tissue were performed by transmission electron microscopy (TEM.IHC and ISZ revealed sufficient expression of the transgene. Severe cellular inflammation and intima hyperplasia were seen only in adenovirus treated mgR/mgR aortas (Ad.β-Gal, Ad.hTIMP-1 NI: 0.23; 0.43, but not in native and Ad.hTIMP-1 treated WT (NI: 0.01; 0.00. Compared to native mgR/mgR and Ad.hTIMP-1 treated WT aorta, the NI is highly significant greater in Ad.hTIMP-1 transduced mgR/mgR aorta (p = 0.001; p = 0.001. As expected, untreated Marfan grafts showed significant more elastolysis compared to WT (p = 0.001. However, elastolysis in Marfan aortas was not reduced by adenoviral overexpression of hTIMP-1 (compared to untreated

  10. Mechanical Spectroscopy of MgB2 Containing Sic / Spektroskopia Mechaniczna MgB2 Zawierającego Sic

    Silva M.R.


    Full Text Available The compound magnesium diboride (MgB2 has been well-known since the 1950s; however, its superconducting properties were unknown. Intrinsic characteristics of MgB2 make this material a promising candidate for technological applications, although the low value of the irreversibility field and the decrease in critical current density with the increase in the magnetic field considerably reduce its utility. The present work aimed to study the effect of carbon-based doping on anelastic properties of MgB2 as measured by mechanical spectroscopy. The samples were prepared by using the powder-intube method. The samples were made with 5, 7.5, and 10 wt.% of silicon carbide (SiC. The results reveal complex mechanical loss spectra caused by the interaction between point defects and surface defects in the crystalline lattice of MgB2.

  11. Ipilimumab 10 mg/kg versus ipilimumab 3 mg/kg in patients with unresectable or metastatic melanoma

    Ascierto, Paolo A; Del Vecchio, Michele; Robert, Caroline


    BACKGROUND: A phase 2 trial suggested increased overall survival and increased incidence of treatment-related grade 3-4 adverse events with ipilimumab 10 mg/kg compared with ipilimumab 3 mg/kg in patients with advanced melanoma. We report a phase 3 trial comparing the benefit-risk profile...... of ipilimumab 10 mg/kg versus 3 mg/kg. METHODS: This randomised, double-blind, multicentre, phase 3 trial was done in 87 centres in 21 countries worldwide. Patients with untreated or previously treated unresectable stage III or IV melanoma, without previous treatment with BRAF inhibitors or immune checkpoint...... for metastatic melanoma, and Eastern Cooperative Oncology Group performance status. The patients, investigators, and site staff were masked to treatment assignment. The primary endpoint was overall survival in the intention-to-treat population and safety was assessed in all patients who received at least one...

  12. HRTEM study of Mg{sub 2}Zr{sub 5}O{sub 12} in Mg-PSZ

    Liu, Z.W.; Spargo, A.E.C. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Hannink, R.H.J. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), East Melbourne, VIC (Australia). Minerals Research Labs.


    One of the toughest ceramics may be obtained by subjecting the sintered and control-cooled Mg-PSZ material to a final sub-eutectoid aging treatment at 1100 deg C. As a result, an ordered anion vacancy phase, termed {delta}-phase, with composition Mg{sub 2}Zr{sub 5}O{sub 12} is formed. High resolution Transmission Electron Microscopy (HRTEM) was used to study the formation and distribution of the {delta}-phase in a 9.4 mol% MgO-ZrO{sub 2} (Mg-PSZ) alloy. It is shown that the {delta} phase, nucleate at sites where two tetragonal precipitates impinged and then grows to consume the cubic matrix. Considerable strain was developed at these sites. 6 refs., 1 tab., 2 figs.

  13. Structures and Stabilities of Doubly-Charged $(MgO)nMg^{2+}$ (n=1-29) Cluster Ions

    López, F; López, J M; Lopez, Francisco; Aguado, Andres; Lopez, Jose M.


    Ab initio perturbed ion plus polarization calculations are reported for doubly-charged nonstoichiometric (MgO)nMg2+ (n=1--29) cluster ions. We consider a large number of isomers with full relaxations of the geometries, and add the correlation correction to the Hartree-Fock energies for all cluster sizes. The polarization contribution is included at a semiempirical level also for all cluster sizes. Comparison is made with theoretical results for neutral (MgO)n clusters and singly-charged alkali-halide cluster ions. Our method is also compared to phenomenological pair potential models in order to asses their reliability for calculations on small ionic systems. Bulk-like rocksalt structures are predominant from n=13 on. The relative stabilities of the cluster ions against evaporation of a MgO molecule shows variations that are in excellent agreement with the experimental abundance spectra.

  14. Effect of organic ligands on Mg partitioning and Mg isotope fractionation during low-temperature precipitation of calcite

    Mavromatis, Vasileios; Immenhauser, Adrian; Buhl, Dieter; Purgstaller, Bettina; Baldermann, Andre; Dietzel, Martin


    Calcite growth experiments have been performed at 25 oC and 1 bar pCO2 in the presence of aqueous Mg and six organic ligands in the concentration range from 10-5 to 10-3 M. These experiments were performed in order to quantify the effect of distinct organic ligands on the Mg partitioning and Mg stable isotope fractionation during its incorporation in calcite at similar growth rates normalized to total surface area. The organic ligands used in this study comprise of (i) acetate acid, (ii) citrate, (iii) glutamate, (iv) salicylate, (v) glycine and (vi) ethylenediaminetetraacetic acid (EDTA), containing carboxyl- and amino-groups. These fuctional groups are required for bacterial activity and growth as well as related to biotic and abiotic mineralization processes occurring in sedimentary and earliest diagenetic aquatic environments (e.g. soil, cave, lacustrine, marine). The results obtained in this study indicate that the presence of organic ligands promotes an increase in the partition coefficient of Mg in calcite (DMg = (Mg/Ca)calcite (Mg/Ca)fluid). This behaviour can be explained by the temporal formation of aqueous Mg-ligand complexes that are subsequently adsorbed on the calcite surfaces and thereby reducing the active growth sites of calcite. The increase of DMg values as a function of the supersaturation degree of calcite in the fluid phase can be described by the linear equation LogDMg =0.3694 (±0.0329)×SIcalcite - 1.9066 (±0.0147); R2=0.92 In contrast, the presence of organic ligands, with exception of citrate, does not significantly affect the Mg isotope fractionation factor between calcite and reactive fluid (Δ26Mgcalcite-fluid = -2.5 ±0.1). Citrate likely exhibits larger fractionation between the Mg-ligand complexes and free aqueous Mg2+, compared to the other organic ligands studied in this work, as evidenced by the smaller Δ26Mgcalcite-fluid values. These results indicate that in Earth's surface calcite precipitating environments that are

  15. Density functional theory (DFT) study on the hydrolysis behavior of degradable Mg/Mg alloys for biomedical applications

    Nezafati, Marjan

    Magnesium-based (Mg and/or Mg alloys) materials possess many advantageous physicochemical/biological characteristics such as good biocompatibility and similarity of the mechanical properties to the human bone tissue, which renders this material a promising candidate for the biomedical and implant applications. One of the most attractive features of Mg-based materials is the degradability in the physiological environment. With the burst of research on the biodegradable materials for the healthcare device applications, Mg and its alloys attracted a strong attention in the bioengineering field in recent years. However, the major limitation of applying Mg-based materials to biomedical applications is the fast degradation/corrosion rate with regards to the healing process time-span. In the present thesis, an atomistic model employing the density-functional theory (DFT) has been developed to study the hydrolysis process by understanding the influences of commonly used alloying elements (zinc (Zn), calcium (Ca), aluminum (Al), and yttrium (Y)) and the crystallographic orientation of the dissolution surfaces (basal (0001), prism (1010), and pyramidal (1011) planes) on the corrosion behavior. These parameters are known to strongly impact the initial hydrolysis phenomena of Mg-based materials. To develop the atomistic computational model, we have implemented the Dmol3 software package in conjunction with PBE (Perdew, Burke and Ernzerhof) correlation energy functional in the GGA (generalized gradient approximation) scheme. Throughout the thesis, we performed three sets of calculations, i) surface energy, ii) dissolution potential, and iii) water adsorption computations, to examine the hydrolysis mechanism and the subsequent corrosion/degradation of Mg/Mg alloys. The total energy changes of various Mg-based systems in different conditions for these surface energies, dissolution behavior, and tendency of the system for adsorbing the water molecule were quantified. The results

  16. Characterization and solubilization of nucleotide-specific, Mg/sup 2 +/-ATPase and Mg/sup 2 +/-pyrophosphatase of tonoplast

    Wagner, G.J.; Mulready, P.


    Nucleotide-specific, Mg/sup 2 +/-dependent ATPase and Mg/sup 2 +/-dependent pyrophosphatase were recovered with purified tonoplast obtained from isolated Tulipa petal vacuoles. Relative Mg/sup 2 +/-dependent hydrolysis of ATP, GTP and pyrophosphate, the only substrates hydrolyzed to a substantial degree, was 1.0, 0.3, and 0.6, respectively. Tonoplast ATPase required Mg/sup 2 +/, and essentially no Mg/sup 2 +/-dependent or Mg/sup 2 +/-independent p-nitrophenylphosphatase (which was associated with intact vacuoles) occurred with the membrane. Tonoplast ATPase was stimulated 10 to 30% by KCl, but was little effected by other cations (other than NH/sub 4//sup +/) or anions. No activity was observed with CaATP as substrate. The enzyme was cold stable and was inhibited by DCCD and Dio-9, but not by oligomycin. Its pH optimum was 7.0 and its specific activity was about 50 P/sub i//mg protein per h at 37/sup 0/C. Properties of membrane-bound and Polidocanol (polyoxyethylene ether, 9 lauryl ether) solubilized enzyme were similar. Reduced activity of solubilized enzyme was partially restored with phospholipids. Tonoplast ATPase appears to be an integral membrane component which requires phospholipids for maximal activity. Tonoplast Mg/sup 2 +/-pyrophosphatase had a pH optimum of greater than or equal to 8.5, was stimulated 2.5-fold by 50 mM KCl, and was largely lost upon detergent treatment. Properties of tonoplast ATPase observed are consistent with the characteristics of proton transport exhibited by isolated, intact Tulipa vacuoles. These observations suggest that tonoplast ATPase functions in proton transport. 34 references, 7 figures, 6 tables.

  17. Evaluation of sediment contamination by trace elements and the zooplankton community analysis in area affected by gold exploration in Southeast (SE of the Iron Quadrangle, Alto Rio Doce, (MG Brazil

    Cláudia de Lima e Silva


    Full Text Available AIM: The aim was to verify the geochemical composition of sediments samples (riverbed and bank and the relationship of the following elements: Al, As, Cd. Cr, Cu, Fe, Mn, Ni and Zn with the zooplankton community. METHODS: Bank and riverbed sediments were collected in four sampling points along the studied area, in June/2010 (dry season and March/2011 (rainy season. Three types of analysis were performed: granulometric, mineralogical (by X-Ray diffractometer and geochemical (by ICPOES, where for the last two types, only a fraction of silt/clay (<0.062 mm was used, and the results were compared with the following reference values: Local Reference Value (Costa et al., 2010, Quality Reference Values (São Paulo, 2005, PEC and TEC values (MacDonald et al., 2000. For identification of the zooplankton community, riverbed and bank samples were collected in polyethylene bottles, suspended with deionized water (bank sample only, stained with Rose Bengal and preserved in formalin at 4%. RESULTS: As concentrations at Col sampled point were 18 times greater than the Local Reference Value (3.84 Cd concentrations were greater than the values established by the QRV (<0.5 and PEC (4.98 in almost all the sampled points, regarding seasonality. The following zooplanktonic species were identified: Arcella costata (Ehrenberg, 1847, Arcella discoides (Ehrenberg, 1843, Arcella vulgaris (Ehrenberg, 1830, Centropyxis aculeata (Ehrenberg, 1838, Centropyxis ecornis (Ehrenberg, 1841, Difflugia sp., Difflugia acuminata (Ehrenberg, 1838, Euglypha laevis (Perty, 1849, Trynema enchelys (Ehrenberg, 1938, Asplanchna priodonta (Gosse, 1850, and Bedelloida, with, approximately 81% belonging to the Protozoa group. CONCLUSIONS: The studied area, with the exception of the Tripuí point, was found to be impacted by historical gold exploration in the region, as well as by the growing urbanization. Within the elements considered to be the most toxic to the biota

  18. Corrosion inhibition of powder metallurgy Mg by fluoride treatments.

    Pereda, M D; Alonso, C; Burgos-Asperilla, L; del Valle, J A; Ruano, O A; Perez, P; Fernández Lorenzo de Mele, M A


    Pure Mg has been proposed as a potential degradable biomaterial to avoid both the disadvantages of non-degradable internal fixation implants and the use of alloying elements that may be toxic. However, it shows excessively high corrosion rate and insufficient yield strength. The effects of reinforcing Mg by a powder metallurgy (PM) route and the application of biocompatible corrosion inhibitors (immersion in 0.1 and 1M KF solution treatments, 0.1M FST and 1M FST, respectively) were analyzed in order to improve Mg mechanical and corrosion resistance, respectively. Open circuit potential measurements, polarization techniques (PT), scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS) were performed to evaluate its corrosion behavior. SECM showed that the local current of attacked areas decreased during the F(-) treatments. The corrosion inhibitory action of 0.1M FST and 1M FST in phosphate buffered solution was assessed by PT and EIS. Under the experimental conditions assayed, 0.1M FST revealed better performance. X-ray photoelectron spectroscopy, energy dispersive X-ray and X-ray diffraction analyses of Mg(PM) with 0.1M FST showed the presence of KMgF(3) crystals on the surface while a MgF(2) film was detected for 1M FST. After fluoride inhibition treatments, promising results were observed for Mg(PM) as degradable metallic biomaterial due to its higher yield strength and lower initial corrosion rate than untreated Mg, as well as a progressive loss of the protective characteristics of the F(-)-containing film which ensures the gradual degradation process.

  19. Neutron scattering studies of superconducting MgB2 tapes

    Bellingeri, E.; Malagoli, A.; Modica, M.; Braccini, V.; Siri, A. S.; Grasso, G.


    The capability of manufacturing long superconducting MgB2 wires with already remarkable critical currents makes this material a very promising candidate for future applications. Tapes are prepared by the powder-in-tube technique. After the cold working procedure typically carried out by wire drawing and cold rolling, it has been found that a final sintering step carried out in argon atmosphere is a key process for further improving the superconducting properties of the conductors. To study the effect of the deformation and heat treatment processes, we performed neutron scattering experiment. Due to the high penetration depth of neutron inside matter, it was possible to analyse the MgB2 phase still wrapped in the Ni sheath. Our studies were carried out by a full spectra refinement by the Rietveld method. In the starting superconducting powder a large Mg deficiency was observed. In the tapes we found that the large forces applied during the cold working induced a large MgB2 lattice deformation, and that it is partly relaxed during the final sintering process. An important correlation of the residual stress with the critical temperature and the pinning properties was pointed out. We also observed the appearance of detrimental secondary phases during the sintering process. In particular, the MgB2 phase reacted with the nickel sheath and MgB2Ni2.5 was formed at temperatures higher than 850 °C. These results are of basic importance for a further optimization of the transport properties at moderate fields where applications of MgB2 tapes are already envisageable.


    Ravindra Waykar et al


    Full Text Available Generic drugs are lower-cost versions of patent-expired original brand-name medications. According to guidelines of regulatory agencies of the Canada, US and European Union, a generic drug must be “identical, or bioequivalent to a brand name drug in dosage form, safety, strength, route of administration, quality, performance characteristics and intended use”. Bioequivalence is decreed when the ratio of the generic to the reference compound for the area-under-the-curve and maximum plasma concentration (Cmax fall within a 0.80–1.25 range. The present study was to develop Olanzapine Tablets and compare pharmacokinetic profile of Zyprexa 10 mg film-coated tablets, Zyprexa Velotabs 10 mg orodispersible tablets and Olanzapine 10mg tablets. Multi media dissolution studies in 0.1N HCl, pH 4.5 acetate buffer and pH 6.8 phosphate buffer were carried out for Reference (Zyprexa Velotab 10 mg and Zyprexa 10 mg and test product (i.e. Olanzapine 10 mg. A single centre, open-label, single-dose, randomised, 3-way crossover bioequivalence study, performed under fasting conditions. Based on the results obtained, it can be concluded that the test olanzapine (Treatment A is bioequivalent to both references Zyprexa Velotab (Treatment B and Zyprexa (Treatment C following a 10 mg dose under fasting conditions. All formulations were well tolerated, with no major side effects and no relevant differences in safety profiles were observed between the preparations, particularly with respect to the number and pattern of adverse event.