Science.gov

Sample records for mg inyectable liofilizado

  1. Pincharse sin infectarse: estrategias para prevenir la infección por el VIH y el VHC entre usuarios de drogas inyectables

    PubMed Central

    MATEU-GELABERT, P.; FRIEDMAN, S.; SANDOVAL, M.

    2011-01-01

    Resumen Objetivo Desde principios de los noventa, en la ciudad de Nueva York se han implementado con éxito programas para reducir la incidencia del virus de la inmunodeficiencia humana (VIH) y, en menor medida, del virus de la hepatitis C (VHC). A pesar de ello, aproximadamente el 70% de los usuario de drogas inyectables (UDI) están infectados por el VHC. Queremos investigar cómo el 30% restante se las ha arreglado para no infectarse. El Staying safe (nombre original del estudio) explora los comportamientos y mecanismos que ayudan a evitar la infección por el VHC y el VIH a largo plazo. Material y métodos Hemos utilizado el concepto de «desviación positiva» aplicado en otros campos de salud pública. Estudiamos las estrategias, prácticas y tácticas de prevención de aquellos UDI que, viviendo en contextos de alta prevalencia, se mantienen sin infectar por VIH y el VHC, a pesar de haberse inyectado heroína durante años. Los resultados preliminares presentados en este artículo incluyen el análisis de las entrevistas realizadas a 25 UDI (17 doble negativos, 3 doble positivos y 5 con infección por el VHC y sin infección por el VIH). Se usaron entrevistas semiestructuradas que exploraban con detalle la historia de vida de los sujetos, incluyendo su consumo de drogas, redes sociales, contacto con instituciones, relaciones sexuales y estrategias de protección y vigilancia. Resultados La intencionalidad es importante para no infectarse, especialmente durante períodos de involución (períodos donde hay un deterioro económico y/o social que llevan al que se inyecta a situaciones de mayor riesgo). Presentamos tres dimensiones independientes de intencionalidad que conllevan comportamientos que pueden ayudar a prevenir la infección: a) evitar «el mono» (síntomas de abstención) asegurando el acceso a la droga; b) «llevarlo bien» para no convertirse en un junkie y así evitar la «muerte social» y la falta de acceso a los recursos, y c) seguir sin

  2. Role of Mg interlayers in Fe/Mg/MgO/Fe and Fe/Mg/MgO/Mg/Fe magnetic tunnel junctions

    SciTech Connect

    Wang, Y.; Zhang, J.; Zhang, Xiaoguang; Cheng, Hai-Ping; Han, Prof. X. F.

    2010-01-01

    -Fe(001)/Mg/MgO/Fe- and -Fe(001)/Mg/MgO/Mg/Fe- magnetic tunnel junctions (MTJs) with Mg interlayers are studied by first-principles calculation. An important role of the Mg interlayer is identified to be preserving the preferential transmission of the majority-spin states with \\Delta_1 symmetry, which dominate the spin-dependent electron transport of MTJs with MgO barrier. One layer of Mg at the electrode/barrier interface does not decrease the tunneling magnetoresistance (TMR) ratio nearly as much as one layer of oxide. At certain Mg thickness case the TMR could be strongly influenced by the resonance tunneling states in minority-spin channel, these states are mainly raised from the quantum-well states formed in the Mg interlayer and coupled with interfacial resonance states which are very sensitive to the interface structures.

  3. Porous Mg thin films for Mg-air batteries.

    PubMed

    Xin, Gongbiao; Wang, Xiaojuan; Wang, Chongyun; Zheng, Jie; Li, Xingguo

    2013-12-28

    An alkaline primary Mg-air battery made from a porous Mg thin film displayed superior discharge performances, including a flat discharge plateau, a high open-circuit voltage of 1.41 V and a large discharge capacity of 821 mAh g(-1), suggesting that the electrochemical performances of Mg-air batteries can be improved by controlling the Mg anode morphology. PMID:24158667

  4. Observations of Local Interstellar Mg I and Mg II

    NASA Technical Reports Server (NTRS)

    Bruhweiler, F. C.; Oegerle, W.; Weiler, E.; Stencel, R. E.; Kondo, Y.

    1984-01-01

    Copernicus and IUE observations of 5 stars within 50 pc of the Sun were combined to study the ionization of magnesium in the local interstellar medium (LISM). The high resolution Copernicus spectrometer was used to detect interstellar MG I 2852 in the spectra of alpha Gru, alpha Eri, and alpha Lyr, while placing upper limits on Mg I in the spectra of alpha CMa and alpha PsA. Observations of Mg II 2795, 2802 for these stars were also obtained with IUE and Copernicus. The column densities of Mg I and Mg II are used to place constraints on the temperature of the LISM.

  5. Mg(+)-ligand binding energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry

    1991-01-01

    Ab initio calculations are used to optimize the structures and determine the binding energies of Mg(+) to a series of ligands. Mg(+) bonds electrostatically with benzene, acetone, H2, CO, and NH3 and a self-consistent-field treatment gives a good description of the bonding. The bonding in MgCN(+) and MgCH3(+) is largely covalent and a correlated treatment is required.

  6. Substitution of Mn for Mg in MgB_2*

    NASA Astrophysics Data System (ADS)

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

    2002-03-01

    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 0.01<= x<= 0.15. We attempted to obtain single-phase samples with x<= 0.25 by reacting the constituent elements in sealed Ta tubes and/or using prereacted MnBx synthesized using an arc furnace. The results of x-ray diffraction and magnetization measurements on those samples will be presented. * Supported by the USDOE under contract no. W-7405-Eng-82. [1] "Mn-substitution effects on MgB2 superconductor", Y.Moritomo et al. J. Phys. Soc. Japan b70, 1889 (2001).; “Effects of transition metal doping in MgB2 superconductor", Y. Moritomo at al. arXiv:cond-mat/0104568.

  7. Subdivision of the Mg-suite noritic rocks into Mg-gabbronorites and Mg-norites

    NASA Technical Reports Server (NTRS)

    James, O. B.; Flohr, M. K.

    1983-01-01

    Mg-suite noritic rocks can be divided into two groups, the Mg-gabbronorites and the Mg-norites. The rocks of these groups differ in ratios of high-Ca pyroxene to total pyroxene, compositions of pyroxene and plagioclase, assemblages of Ti-, Nb-, and Zr-bearing minerals, compositions of chrome spinel, bulk-rock Ti/Sm and Sc/Sm, and measured ages. The two groups probably crystallized from different types of parent magmas. Two hypotheses are offered for the differences in composition of the parent magmas. One hypothesis ascribes the differences to compositional heterogeneity of the mantle source areas. The other hypothesis ascribes the differences to variations in extent of partial melting of the mantle source regions and variations in extent of assimilation of the anorthosite and the highly differentiated residual liquid that were produced during the primordial lunar differentiation.

  8. Spin assignments of 22Mg states through a 24Mg(p,t)22Mg measurement

    SciTech Connect

    Chae, K. Y.; Jones, K. L.; Moazen, Brian; Pittman, S. T.; Bardayan, Daniel W; Blackmon, Jeff C; Liang, J Felix; Smith, Michael Scott; Chipps, K.; Hatarik, Robert; O'Malley, Patrick; Pain, Steven D; Kozub, R. L.; Matei, Catalin; Nesaraja, Caroline D

    2009-01-01

    The {sup 18}Ne({alpha},p){sup 21}Na reaction plays a crucial role in the ({alpha},p) process, which leads to the rapid proton capture process in X-ray bursts. The reaction rate depends upon properties of {sup 22}Mg levels above the {alpha} threshold at 8.14 MeV. Despite recent studies of these levels, only the excitation energies are known for most with no constraints on the spins. We have studied the {sup 24}Mg(p,t){sup 22}Mg reaction at the Oak Ridge National Laboratory (ORNL) Holifield Radioactive Ion Beam Facility (HRIBF), and by measuring the angular distributions of outgoing tritons, we provide the first experimental constraints on the spins of astrophysically-important {sup 18}Ne({alpha},p){sup 21}Na resonances.

  9. The Arabidopsis Mg Transporter, MRS2-4, is Essential for Mg Homeostasis Under Both Low and High Mg Conditions.

    PubMed

    Oda, Koshiro; Kamiya, Takehiro; Shikanai, Yusuke; Shigenobu, Shuji; Yamaguchi, Katsushi; Fujiwara, Toru

    2016-04-01

    Magnesium (Mg) is an essential macronutrient, functioning as both a cofactor of many enzymes and as a component of Chl. Mg is abundant in plants; however, further investigation of the Mg transporters involved in Mg uptake and distribution is needed. Here, we isolated an Arabidopsis thaliana mutant sensitive to high calcium (Ca) conditions without Mg supplementation. The causal gene of the mutant encodes MRS2-4, an Mg transporter.MRS2-4 single mutants exhibited growth defects under low Mg conditions, whereas an MRS2-4 and MRS2-7 double mutant exhibited growth defects even under normal Mg concentrations. Under normal Mg conditions, the Mg concentration of the MRS2-4 mutant was lower than that of the wild type. The transcriptome profiles of mrs2-4-1 mutants under normal conditions were similar to those of wild-type plants grown under low Mg conditions. In addition, both mrs2-4 and mrs2-7 mutants were sensitive to high levels of Mg. These results indicate that both MRS2-4 and MRS2-7 are essential for Mg homeostasis, even under normal and high Mg conditions. MRS2-4-green fluorescent protein (GFP) was mainly detected in the endoplasmic reticulum. These results indicate that these two MRS2 transporter genes are essential for the ability to adapt to a wide range of environmental Mg concentrations. PMID:26748081

  10. First-principles study of Mg(0001)/MgO(1-11) interfaces

    NASA Astrophysics Data System (ADS)

    Song, Hong-Quan; Zhao, Ming; Li, Jian-Guo

    2016-06-01

    By means of first-principles density-functional calculations, we studied the surface energy of a nonstoichiometric MgO(1-11) slab, the interfacial energy and interfacial bonding characteristics of Mg-terminated and O-terminated Mg/MgO(1-11) interfaces with three stacking-site (TOP, HCP and FCC sites) models, and the effect of the thickness of Mg films on the O-terminated MgO(1-11) surface. The results indicate that the surface energies of the nonstoichiometric MgO(1-11) slab and interfacial energies of Mg/Mg(1-11) interface depend on Mg chemical potential. We found that the Mg-terminated MgO(1-11) surface is more stable than the O-terminated MgO(1-11) surface at high Mg chemical potential, and Mg/MgO(1-11) with FCC stacking-site model is the most stable configuration in the Mg/MgO(1-11) interfaces. The results of the electronic structure reveals that the interfacial bonding of Mg-terminated interface with FCC site model mainly consists of metallic bond and of the O-terminated interface with FCC site model is mainly ionic with a small degree of σ-type covalent bond. Although the interfacial energy of Mg-terminated Mg/MgO interface with FCC stacking-site model is slightly higher than that of O-terminated Mg/MgO interface, the molten Mg would epitaxially grow on the FCC sites of the Mg-terminated MgO(1-11) surface because of the high evaporation pressure of Mg at high temperature.

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

    NASA Astrophysics Data System (ADS)

    Jimbo, K.; Nakagawa, S.

    2011-01-01

    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.

  12. Bacterial Mg2+ Homeostasis, Transport, and Virulence

    PubMed Central

    Hollands, Kerry; Kriner, Michelle A.; Lee, Eun-Jin; Park, Sun-Yang; Pontes, Mauricio H.

    2014-01-01

    Organisms must maintain physiological levels of Mg2+ because this divalent cation is critical for the stabilization of membranes and ribosomes, the neutralization of nucleic acids, and as a cofactor in a variety of enzymatic reactions. In this review, we describe the mechanisms that bacteria utilize to sense the levels of Mg2+ both outside and inside the cytoplasm. We examine how bacteria achieve Mg2+ homeostasis by adjusting the expression and activity of Mg2+ transporters, and by changing the composition of their cell envelope. We discuss the connections that exist between Mg2+ sensing, Mg2+ transport and bacterial virulence. Additionally, we explore the logic behind the fact that bacterial genomes encode multiple Mg2+ transporters and distinct sensing systems for cytoplasmic and extracytoplasmic Mg2+. These analyses may be applicable to the homeostatic control of other cations. PMID:24079267

  13. A Facile Approach Using MgCl2 to Formulate High Performance Mg2+ Electrolytes for Rechargeable Mg Batteries

    SciTech Connect

    Liu, Tianbiao L.; Shao, Yuyan; Li, Guosheng; Gu, Meng; Hu, Jian Z.; Xu, Suochang; Nie, Zimin; Chen, Xilin; Wang, Chong M.; Liu, Jun

    2014-01-01

    Rechargeable Mg batteries have been regarded as a viable battery technology for grid scale energy storage and transportation applications. However, the limited performance of Mg2+ electrolytes has been a primary technical hurdle to develop high energy density rechargeable Mg batteries. In this study, MgCl2 is demonstrated as a non-nucleophilic and cheap Mg2+ source in combining with Al Lewis acids (AlCl3, AlPh3 and AlEtCl2) to formulate a series of Mg2+ electrolytes characteristic of high oxidation stability (up to 3.4 V vs Mg), sulfur compatibility and electrochemical reversibility (up to 100% coulombic efficiency). Three electrolyte systems (MgCl2-AlCl3, MgCl2-AlPh3, and MgCl2-AlEtCl2) were prepared free of purification and fully characterized by multinuclear NMR (27Al{1H} and 25Mg{1H}) spectroscopies, single crystal X-ray diffraction, and electrochemical analysis. The reaction mechanism of MgCl2 and the Al Lewis acids in THF is discussed to highlight the formation of the electrochemically active [(µ-Cl)3Mg2(THF)6]+ monocation in these electrolytes. We are grateful for the financial support from the Pacific Northwest National Laboratory (PNNL)-Laboratory Directed Research and Development (LDRD) program for developing magnesium battery technology. The XRD and SEM data were collected at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL. PNNL is a multiprogram laboratory operated by Battelle Memorial Institute for the Department of Energy under Contract DE-AC05-76RL01830.

  14. Interstellar fossil Mg-26 and its possible relationship to excess meteoritic Mg-26

    NASA Technical Reports Server (NTRS)

    Clayton, Donald D.

    1986-01-01

    A plausible scenario is advanced for explainig a linear correlation found in some solar system solids between their Mg-26/Mg-24 isotopic ratios and their Al/Mg elemental abundance ratios. This scenario involves three stages: (1) the mechanical aggregation of an average ensemble of Al-bearing dust particles that is postulated to be modestly enriched in the Al/Mg abundance ratio because the aggregated particles themselves are; (2) the extraction, perhaps but not necessarily by hot distillation, of almost all Mg, leaving an aggregate with a large Al/Mg ratio and a large Mg-26 excess; and (3) the uptake of normal ambient Mg by the resulting hot Al-rich solid as it cools in Mg-rich vapor. A linear correlation in solids between their Mg-26/Mg-24 isotopic ratio and their aluminum enrichment may be a fossil correlation inherited from interstellar dust.

  15. X-ray photoelectron spectroscopy studies of MgB 2 for valence state of Mg

    NASA Astrophysics Data System (ADS)

    A. Talapatra; Bandyopadhyay, S. K.; Sen, Pintu; Barat, P.; Mukherjee, S.; Mukherjee, M.

    2005-03-01

    Core level X-ray photoelectron spectroscopy (XPS) studies have been carried out on polycrystalline MgB 2 pellets over the whole binding energy range with a view to having an idea of the charge state of magnesium (Mg). We observe three distinct peaks in Mg 2p spectra at 49.3 eV (trace), 51.3 eV (major) and 54.0 eV (trace), corresponding to metallic Mg, MgB 2 and MgCO 3 or, divalent Mg species, respectively. Similar trend has been noticed in Mg 2s spectra. The binding energy of Mg in MgB 2 is lower than that corresponding to Mg(2+), indicative of the fact that the charge state of Mg in MgB 2 is less than (2+). Lowering of the formal charge of Mg promotes the σ → π electron transfer in boron (B) giving rise to holes on the top of the σ-band which are involved in coupling with B E 2g phonons for superconductivity. Through this charge transfer, Mg plays a positive role in hole superconductivity. B 1s spectra consist of three peaks corresponding to MgB 2, boron and B 2O 3. There is also evidence of MgO due to surface oxidation as seen from O 1s spectra.

  16. Transformation of Mg-bearing amorphous calcium carbonate to Mg-calcite - In situ monitoring

    NASA Astrophysics Data System (ADS)

    Purgstaller, Bettina; Mavromatis, Vasileios; Immenhauser, Adrian; Dietzel, Martin

    2016-02-01

    The formation of Mg-bearing calcite via an amorphous precursor is a poorly understood process that is of relevance for biogenic and abiogenic carbonate precipitation. In order to gain an improved insight on the controls of Mg incorporation in calcite formed via an Mg-rich amorphous calcium carbonate (Mg-ACC) precursor, the precipitation of Mg-ACC and its transformation to Mg-calcite was monitored by in situ Raman spectroscopy. The experiments were performed at 25.0 ± 0.03 °C and pH 8.3 ± 0.1 and revealed two distinct pathways of Mg-calcite formation: (i) At initial aqueous Mg/Ca molar ratios ⩽ 1:6, Mg-calcite formation occurs via direct precipitation from solution. (ii) Conversely, at higher initial Mg/Ca molar ratios, Mg-calcite forms via an intermediate Mg-rich ACC phase. In the latter case, the final product is a calcite with up to 20 mol% Mg. This Mg content is significant higher than that of the Mg-rich ACC precursor phase. Thus, a strong net uptake of Mg ions from the solution into the crystalline precipitate throughout and also subsequent to ACC transformation is postulated. Moreover, the temporal evolution of the geochemical composition of the reactive solution and the Mg-ACC has no significant effect on the obtained "solubility product" of Mg-ACC. The enrichment of Mg in calcite throughout and subsequent to Mg-ACC transformation is likely affected by the high aqueous Mg/Ca ratio and carbonate alkalinity concentrations in the reactive solution. The experimental results have a bearing on the formation mechanism of Mg-rich calcites in marine early diagenetic environments, where high carbonate alkalinity concentrations are the rule rather than the exception, and on the insufficiently investigated inorganic component of biomineralisation pathways in many calcite secreting organisms.

  17. Mg Isotopic Compositions of Modern Marine Carbonates

    NASA Astrophysics Data System (ADS)

    Krogstad, E.; Bizzarro, M.; Hemming, N.

    2003-12-01

    We have used a MC-ICP-MS to measure the isotopic composition of magnesium in a number of samples of modern marine carbonate. Due to the large mass difference between 26Mg and 24Mg (similar to that between 13C and 12C), there is potential for mass fractionation during geologic and biologic processes that may make this isotope system useful for geochemical studies. These samples are from the study of Hemming and Hanson (1992, GCA 56: 537-543). The carbonate minerals analyzed include aragonite, low-Mg calcite, and high-Mg calcite. The samples include corals, echinoderms, ooids, etc., from subtropical to Antarctic settings. Mg purification was accomplished by ion-exchange chromatography, using Bio-Rad AG50W-X12 resin on which greater than 99 percent recovery of Mg is achieved. Samples were introduced into the MC-ICP-MS (VG Axiom) using a Cetac MCN-6000 nebuliser. We use a standard-sample-standard bracketing technique, and samples are analysed at least three times. For lab standards we find that the reproducibility on the 26Mg/24Mg to be about ñ 0.12 permil (2 s.d.). We monitored our separated samples for Na and Ca, as we have found that high Ca/Mg and Na/Mg produce variable magnesium isotopic fractionation during mass spectrometry due to as yet unclear matrix effects. We have normalized our results to our measured values for seawater. We observed a d26Mg(s.w.) range of -1.4 to -2.4 permil in our modern carbonate samples relative to present day seawater. Due to the long residence time of Mg in the oceans (ca. 50 my), this must be due to kinetic or biologic effects. Our d25Mg(s.w.) variations as a function of d26Mg(s.w.) plot along the terrestrial fractionation trend. With an average d26Mg(s.w.) of ca. +0.5 permil in all samples of mantle lithologies and mantle-derived igneous rocks (Bizzarro et al., Goldschmidt abs., 2003), we can assume that the Mg isotopic composition of Earth's river water lies between ca. -2.4 and +0.5 permil (relative to seawater). The actual

  18. The potential energy curves of HeBe, HeMg and BeMg

    NASA Astrophysics Data System (ADS)

    Chiles, Richard A.; Dykstra, Clifford E.

    1982-01-01

    Correlated calculations have been performed on the potential curves of mixed dimers of He, Be and Mg He interacts weakly with all partners. BeMg appears to be intermediate in well-depth to Be 2 and Mg 2 and has electronic structure features similar to Be 2 but different from Mg 2.

  19. Mechanical Properties of Mg2Si/Mg Composites via Powder Metallurgy Process

    NASA Astrophysics Data System (ADS)

    Muramatsu, Hiroshi; Kondoh, Katsuyoshi; Yuasa, Eiji; Aizawa, Tatsuhiko

    The mechanical properties of the Mg2Si/Mg composites solid-state synthesized from the mixed Mg-Si powders have been investigated. The macro-hardness (HRE) and the tensile strength of the composites increase with increasing the Si content and decreasing the Si size. The particle size of the synthesized Mg2Si depends on the initial Si size; the mechanical properties of the Mg2Si/Mg composite are remarkably improved by using fine Si particles or by decreasing the grain size of Mg matrix grains when the powder mixture was prepared via bulk mechanical alloying process.

  20. Antibacterial biodegradable Mg-Ag alloys.

    PubMed

    Tie, D; Feyerabend, F; Müller, W D; Schade, R; Liefeith, K; Kainer, K U; Willumeit, R

    2013-01-01

    The use of magnesium alloys as degradable metals for biomedical applications is a topic of ongoing research and the demand for multifunctional materials is increasing. Hence, binary Mg-Ag alloys were designed as implant materials to combine the favourable properties of magnesium with the well-known antibacterial property of silver. In this study, three Mg-Ag alloys, Mg2Ag, Mg4Ag and Mg6Ag that contain 1.87 %, 3.82 % and 6.00 % silver by weight, respectively, were cast and processed with solution (T4) and aging (T6) heat treatment. The metallurgical analysis and phase identification showed that all alloys contained Mg4Ag as the dominant β phase. After heat treatment, the mechanical properties of all Mg-Ag alloys were significantly improved and the corrosion rate was also significantly reduced, due to presence of silver. Mg(OH)₂ and MgO present the main magnesium corrosion products, while AgCl was found as the corresponding primary silver corrosion product. Immersion tests, under cell culture conditions, demonstrated that the silver content did not significantly shift the pH and magnesium ion release. In vitro tests, with both primary osteoblasts and cell lines (MG63, RAW 264.7), revealed that Mg-Ag alloys show negligible cytotoxicity and sound cytocompatibility. Antibacterial assays, performed in a dynamic bioreactor system, proved that the alloys reduce the viability of two common pathogenic bacteria, Staphylococcus aureus (DSMZ 20231) and Staphylococcus epidermidis (DSMZ 3269), and the results showed that the killing rate of the alloys against tested bacteria exceeded 90%. In summary, biodegradable Mg-Ag alloys are cytocompatible materials with adjustable mechanical and corrosion properties and show promising antibacterial activity, which indicates their potential as antibacterial biodegradable implant materials. PMID:23771512

  1. Hydrogen storage systems from waste Mg alloys

    NASA Astrophysics Data System (ADS)

    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.

    2014-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    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.

  3. The puzzle of {sup 32}Mg

    SciTech Connect

    Fortune, H. T.

    2011-08-15

    An analysis of results of the {sup 30}Mg(t,p) {sup 32}Mg reaction demonstrates that the ground state is the normal state and the excited 0{sup +} state is the intruder, contrary to popular belief. Additional experiments are suggested.

  4. Twinning-mediated formability in Mg alloys

    PubMed Central

    Suh, Byeong-Chan; Kim, Jae H.; Hwang, Ji Hyun; Shim, Myeong-Shik; Kim, Nack J.

    2016-01-01

    Mg alloys are promising candidates for automotive applications due to their low density and high specific strength. However, their widespread applications have not been realized mainly because of poor formability at room temperature, arising from limited number of active deformation systems and strong basal texture. It has been recently shown that Mg-Zn-Ca alloys have excellent stretch formability, which has been ascribed to their weak basal texture. However, the distribution of basal poles is orthotropic, which might result in anisotropy during deformation and have adverse effect on formability. Here, we show that tension twinning is mainly responsible for enhanced formability of Mg-Zn-Ca alloys. We found that tension twinning is quite active during both uniaxial deformation and biaxial deformation of Mg-Zn-Ca alloy even under the stress conditions unfavourable for the formation of tensile twins. Our results provide new insights into the development of Mg alloys having high formability. PMID:26926655

  5. Twinning-mediated formability in Mg alloys

    NASA Astrophysics Data System (ADS)

    Suh, Byeong-Chan; Kim, Jae H.; Hwang, Ji Hyun; Shim, Myeong-Shik; Kim, Nack J.

    2016-03-01

    Mg alloys are promising candidates for automotive applications due to their low density and high specific strength. However, their widespread applications have not been realized mainly because of poor formability at room temperature, arising from limited number of active deformation systems and strong basal texture. It has been recently shown that Mg-Zn-Ca alloys have excellent stretch formability, which has been ascribed to their weak basal texture. However, the distribution of basal poles is orthotropic, which might result in anisotropy during deformation and have adverse effect on formability. Here, we show that tension twinning is mainly responsible for enhanced formability of Mg-Zn-Ca alloys. We found that tension twinning is quite active during both uniaxial deformation and biaxial deformation of Mg-Zn-Ca alloy even under the stress conditions unfavourable for the formation of tensile twins. Our results provide new insights into the development of Mg alloys having high formability.

  6. Role of MgO impurity on the superconducting properties of MgB2

    NASA Astrophysics Data System (ADS)

    Singh, Dharmendra Kumar; Tiwari, Brajesh; Jha, Rajveer; Kishan, H.; Awana, V. P. S.

    2014-10-01

    We address the effect of MgO impurity on the superconducting properties of MgB2. The synthesis of MgB2 is very crucial because of sensitivity of Mg to oxidation which may lead to MgO as a secondary phase. Rietveld refinement was performed to determine the quantitative volume fraction of MgO in the samples synthesized by two different techniques. Both the samples were subjected to magnetization measurements under dc and a.c. applied magnetic fields and the observed results were compared as a function of temperature. Paramagnetic Meissner effect has been observed in a sample of MgB2 having more amount of MgO (with Tc = 37.1 K) whereas the pure sample MgB2 having minor quantity of MgO shows diamagnetic Meissner effect with Tc = 38.8 K. M-H measurements at 10 K reveal a slight difference in irreversibility field which is due to MgO impurity along with wide transition observed from ac magnetic susceptibility measurements. The magnetotransport measurements ρ(T) using ρN = 90%, 50% and 10% criterion on pure sample of MgB2 has been used to determine the upper critical field whereas the sample having large quantity of MgO does not allow these measurements due to its high resistance.

  7. Effect of ambient Mg/Ca ratio on Mg fractionation in calcareous marine invertebrates: A record of the oceanic Mg/Ca ratio over the Phanerozoic

    NASA Astrophysics Data System (ADS)

    Ries, Justin B.

    2004-11-01

    The Mg/Ca ratio of seawater has changed significantly over the Phanerozoic, primarily as a function of the rate of ocean-crust production. Echinoids, crabs, shrimps, and calcareous serpulid worms grown in artificial seawaters encompassing the range of Mg/Ca ratios that existed throughout the Phanerozoic exhibit a direct nonlinear relationship between skeletal and ambient Mg/Ca. Specimens grown in seawater with the lowest Mg/Ca (˜1) changed their mineralogy to low-Mg calcite (<4 mol% MgCO3), suggesting that these high-Mg calcareous organisms would have produced low-Mg calcite in the Cretaceous, when oceanic Mg/Ca was lowest (˜1). These results support the empirical evidence that the skeletal chemistry of calcareous organisms has varied significantly over the Phanerozoic as a function of the Mg/Ca of seawater, and that the Mg/Ca of unaltered fossils of such organisms may be a record of oceanic Mg/Ca throughout the Phanerozoic. Mg fractionation algorithms, which relate skeletal Mg/Ca, seawater Mg/Ca, and temperature, were derived from these and other experiments. They can be used to estimate paleoceanic Mg/ Ca ratios and temperatures from fossil skeletal Mg/Ca of the organisms evaluated. Pale oceanic Mg/Ca ratios, recalculated by using the echinoderm Mg fractionation algorithm from published fossil echinoid Mg/Ca, crinoid Mg/Ca, and paleotemperature data, are consistent with other estimates and models of oceanic Mg/Ca over the Phanerozoic.

  8. Diffusion of Ca and Mg in Calcite

    SciTech Connect

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

    1999-02-10

    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.

  9. Valsartan 160 mg/Amlodipine 5 mg Combination Therapy versus Amlodipine 10 mg in Hypertensive Patients with Inadequate Response to Amlodipine 5 mg Monotherapy

    PubMed Central

    Sung, Jidong; Jeong, Jin-Ok; Kwon, Sung Uk; Won, Kyung Heon; Kim, Byung Jin; Cho, Byung Ryul; Kim, Myeong-Kon; Lee, Sahng; Kim, Hak Jin; Lim, Seong-Hoon; Park, Seung Woo

    2016-01-01

    Background and Objectives When monotherapy is inadequate for blood pressure control, the next step is either to continue monotherapy in increased doses or to add another antihypertensive agent. However, direct comparison of double-dose monotherapy versus combination therapy has rarely been done. The objective of this study is to compare 10 mg of amlodipine with an amlodipine/valsartan 5/160 mg combination in patients whose blood pressure control is inadequate with amlodipine 5 mg. Subjects and Methods This study was conducted as a multicenter, open-label, randomized controlled trial. Men and women aged 20-80 who were diagnosed as having hypertension, who had been on amlodipine 5 mg monotherapy for at least 4 weeks, and whose daytime mean systolic blood pressure (SBP) ≥135 mmHg or diastolic blood pressure (DBP) ≥85 mmHg on 24-hour ambulatory blood pressure monitoring (ABPM) were randomized to amlodipine (A) 10 mg or amlodipine/valsartan (AV) 5/160 mg group. Follow-up 24-hour ABPM was done at 8 weeks after randomization. Results Baseline clinical characteristics did not differ between the 2 groups. Ambulatory blood pressure reduction was significantly greater in the AV group compared with the A group (daytime mean SBP change: -14±11 vs. -9±9 mmHg, p<0.001, 24-hour mean SBP change: -13±10 vs. -8±8 mmHg, p<0.0001). Drug-related adverse events also did not differ significantly (A:AV, 6.5 vs. 4.5 %, p=0.56). Conclusion Amlodipine/valsartan 5/160 mg combination was more efficacious than amlodipine 10 mg in hypertensive patients in whom monotherapy of amlodipine 5 mg had failed. PMID:27014353

  10. Formation of Mg{sub 2}Ni with enhanced kinetics: Using MgH{sub 2} instead of Mg as a starting material

    SciTech Connect

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

    2012-08-15

    At a temperature over the decomposition point (375 Degree-Sign C) of MgH{sub 2}, the formation of Mg{sub 2}Ni is greatly enhanced from the 2MgH{sub 2}+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 2MgH{sub 2}+Ni system than in the 2Mg+Ni system. Furthermore, theoretical modeling also shows that Mg atoms are readily released from MgH{sub 2} using much less energy and thus are more available to react with Ni once the dehydrogenation of MgH{sub 2} occurs, as compared to normal Mg. - Graphical Abstract: The formation of Mg{sub 2}Ni is greatly enhanced by using MgH{sub 2} instead of Mg at a temperature higher than the MgH{sub 2} decomposition point. Highlights: Black-Right-Pointing-Pointer A new and efficient synthesis of Mg-based compounds at a reduced temperature. Black-Right-Pointing-Pointer Mg{sub 2}Ni formation is enhanced by using MgH{sub 2} instead of Mg as a starting material. Black-Right-Pointing-Pointer XAFS results show that Mg---Ni bonds are formed faster in 4MgH{sub 2}+Ni than in 4Mg+Ni. Black-Right-Pointing-Pointer DFT calculations show that Mg atoms are released from MgH{sub 2} more readily than from Mg. Black-Right-Pointing-Pointer Mg formed by MgH{sub 2} dehydrogenation is more available to react with Ni than normal Mg.

  11. Mg Content Dependence of EML-PVD Zn-Mg Coating Adhesion on Steel Strip

    NASA Astrophysics Data System (ADS)

    Jung, Woo Sung; Lee, Chang Wook; Kim, Tae Yeob; De Cooman, Bruno C.

    2016-09-01

    The effect of coating thickness and Mg concentration on the adhesion strength of electromagnetic levitation physical vapor deposited Zn-Mg alloy coatings on steel strip was investigated. The phase fraction of Zn, Mg2Zn11, and MgZn2 was determined for a coating Mg concentration in the 0 to 15 wt pct range. Coatings with a Mg content less than 5 pct consisted of an Zn and Mg2Zn11 phase mixture. The coatings showed good adhesion strength and ductile fracture behavior. Coatings with a higher Mg concentration, which consisted of a Mg2Zn11 and MgZn2 phase mixture, had a poor adhesion strength and a brittle fracture behavior. The adhesion strength of PVD Zn-Mg alloy coatings was found to be related to the pure Zn phase fraction. The effect of coating thickness on adhesion strength was found to be negligible. The microstructure of the interface between steel and Zn-Mg alloy coatings was investigated in detail by electron microscopy, electron diffraction, and atom probe tomography.

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

    PubMed

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

    2016-04-01

    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. PMID:26838918

  13. Mg Content Dependence of EML-PVD Zn-Mg Coating Adhesion on Steel Strip

    NASA Astrophysics Data System (ADS)

    Jung, Woo Sung; Lee, Chang Wook; Kim, Tae Yeob; De Cooman, Bruno C.

    2016-07-01

    The effect of coating thickness and Mg concentration on the adhesion strength of electromagnetic levitation physical vapor deposited Zn-Mg alloy coatings on steel strip was investigated. The phase fraction of Zn, Mg2Zn11, and MgZn2 was determined for a coating Mg concentration in the 0 to 15 wt pct range. Coatings with a Mg content less than 5 pct consisted of an Zn and Mg2Zn11 phase mixture. The coatings showed good adhesion strength and ductile fracture behavior. Coatings with a higher Mg concentration, which consisted of a Mg2Zn11 and MgZn2 phase mixture, had a poor adhesion strength and a brittle fracture behavior. The adhesion strength of PVD Zn-Mg alloy coatings was found to be related to the pure Zn phase fraction. The effect of coating thickness on adhesion strength was found to be negligible. The microstructure of the interface between steel and Zn-Mg alloy coatings was investigated in detail by electron microscopy, electron diffraction, and atom probe tomography.

  14. The Mg impurity in nitride alloys

    SciTech Connect

    Zvanut, M. E.; Willoughby, W. R.; Sunay, U. R.; Koleske, D. D.; Allerman, A. A.; Wang, Ke; Araki, Tsutomu; Nanishi, Yasushi

    2014-02-21

    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.

  15. MgO Solubility in Steelmaking Slags

    NASA Astrophysics Data System (ADS)

    Tayeb, Mohammed A.; Assis, Andre N.; Sridhar, Seetharaman; Fruehan, Richard J.

    2015-04-01

    A predominantly liquid and MgO-saturated slag is preferred in EAF and BOF steelmaking. Fully liquid slag provides a better environment for faster mass transfer due to lower bulk viscosities and larger liquid slag volume and these help dephosphorization and desulfurization. Also, an MgO-saturated slag would be preferable in order to increase the lifetime of furnace refractory lining by reducing the extent of dissolution. This article will demonstrate the factors that would influence MgO saturation, which includes FeO, CaO, P2O5, and Al2O3 contents and temperature. In addition, this paper comments on the applicability and accuracy of FactSage prediction, which are compared to laboratory experiments. The results indicate that FactSage may underestimate MgO solubility by up to 2.5 wt pct at higher basicities while there is reasonable agreement with current measurements at lower basicities.

  16. AB Initio Characterization of MgCCH, MgCCH(+), and MgC2, and Pathways to their Formation in the Interstellar Medium

    NASA Technical Reports Server (NTRS)

    Woon, David E.

    1996-01-01

    A study of Mg-bearing compounds has been performed in order to determine molecular properties which are critical for planning new astronomical searches and laboratory studies. The primary focus of the work is on MgCCH, MgCCH(+), and the isomers of MgC2. Only MgCCH has been identified in laboratory studies. Additional calculations have been carried out on MgH, MgNC, MgCN, and their cations in an effort to evaluate pathways to the formation of MgCCH and MgCCH(+) in the InterStellar Medium (ISM) or in circumstellar envelopes. Correlated ab initio methods and correlation-consistent basis sets have been employed. Properties including structures, rotational constants, dipole moments, and harmonic frequencies are reported. A transition state between linear MgCC and cyclic MgC2 has been characterized and was found to yield a minimal barrier (approx. 0.5 kcal/mole), indicating easy interconversion to the cyclic form. Direct reactions in the ISM between Mg or Mg(+) and HCCH are precluded by energetic considerations, but a number of ion- molecule or neutral-neutral exchange reactions between CCH and various Mg-containing species offer plausible pathways to MgCCH or MgCCH(+). Weakly bound MgH may react with CCH to form MgCCH, but MgH has not been detected. Both MgNC and MgCN have been observed, but reactions with CCH are slightly endothermic by 1-3 kcal/mole. Although MgH(+), MgNC(+), and MgCN(+) have not been detected, their reactions with CCH to form MgCCH(+) are all exothermic. With only a small barrier separating linear MgCC and cyclic MgC2, the dissociative recombination of MgCCH(+) with an electron is expected to yield cyclic MgC2, and regenerate Mg and CCH. New astronomical searches for MgCCH, MgCCH(+), cyclic MgC2, MgNC(+), and MgCN(+) will provide further insight into organo-magnesium astrochemistry.

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

    PubMed Central

    Carbonell, Josep Lluis; Garcia, Ramon; Gonzalez, Adriana; Breto, Andres; Sanchez, Carlos

    2015-01-01

    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 un ≥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. PMID:25624773

  18. The study of MgB2/BN/MgB2 trilayer films

    NASA Astrophysics Data System (ADS)

    Hu, Hui; Feng, Qingrong; Wang, Yue; Zhang, Yan

    2015-12-01

    MgB2/BN/MgB2 trilayer films have been fabricated by using hybrid physical-chemical vapor deposition (HPCVD) method for the MgB2 layers and chemical vapor deposition (CVD) method for the BN layers in the same reactor. The films are studied by X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD) and magnetization measurements. These test outcomes indicate the trilayer films are grown without deteriorating the superconductivity of MgB2 films. Our results show that it is feasible to grow MgB2/BN/MgB2 trilayer films in the same reactor sequentially, which has the advantage of reducing contamination during the growth. This therefore opens the door for fabricating all-MgB2 Josephson junctions by using the BN film as the insulating layer.

  19. Spontaneously intermixed Al-Mg barriers enable corrosion-resistant Mg/SiC multilayer coatings

    SciTech Connect

    Soufli, Regina; Fernandez-Perea, Monica; Baker, Sherry L.; Robinson, Jeff C.; Alameda, Jennifer; Walton, Christopher C.

    2012-07-24

    Magnesium/silicon carbide (Mg/SiC) has the potential to be the best-performing reflective multilayercoating in the 25–80 nm wavelength region but suffers from Mg-related corrosion, an insidious problem which completely degrades reflectance. We have elucidated the origins and mechanisms of corrosion propagation within Mg/SiC multilayers. Based on our findings, we have demonstrated an efficient and simple-to-implement corrosion barrier for Mg/SiC multilayers. In conclusion, the barrier consists of nanometer-scale Mg and Al layers that intermix spontaneously to form a partially amorphous Al-Mg layer and is shown to prevent atmospheric corrosion while maintaining the unique combination of favorable Mg/SiC reflective properties.

  20. Spontaneously intermixed Al-Mg barriers enable corrosion-resistant Mg/SiC multilayer coatings

    NASA Astrophysics Data System (ADS)

    Soufli, Regina; Fernández-Perea, Mónica; Baker, Sherry L.; Robinson, Jeff C.; Alameda, Jennifer; Walton, Christopher C.

    2012-07-01

    Magnesium/silicon carbide (Mg/SiC) has the potential to be the best-performing reflective multilayer coating in the 25-80 nm wavelength region but suffers from Mg-related corrosion, an insidious problem which completely degrades reflectance. We have elucidated the origins and mechanisms of corrosion propagation within Mg/SiC multilayers. Based on our findings, we have demonstrated an efficient and simple-to-implement corrosion barrier for Mg/SiC multilayers. The barrier consists of nanometer-scale Mg and Al layers that intermix spontaneously to form a partially amorphous Al-Mg layer and is shown to prevent atmospheric corrosion while maintaining the unique combination of favorable Mg/SiC reflective properties.

  1. Mg deficiency affects leaf Mg remobilization and the proteome in Brassica napus.

    PubMed

    Billard, Vincent; Maillard, Anne; Coquet, Laurent; Jouenne, Thierry; Cruz, Florence; Garcia-Mina, José-Maria; Yvin, Jean-Claude; Ourry, Alain; Etienne, Philippe

    2016-10-01

    In order to cope with variable mineral nutrient availability, higher plants have developed numerous strategies including the remobilization of nutrients from source to sink tissues. However, such processes remain relatively unknown for magnesium (Mg), which is the third most important cation in plant tissues. Using Mg depletion of Brassica napus, we have demonstrated that Mg is remobilized from old leaves to young shoot tissues. Moreover, this study showed that Mg depletion induces modification of nutrient uptake, especially Zn and Mn. Finally, comparative proteomic analysis of old leaves (source of Mg) revealed amongst other results that some proteins requiring Mg for their functionality (isocitrate dehydrogenase for example) were up-regulated. Moreover, down-regulation of proteases suggested that mobilization of Mg from old leaves was not associated with senescence. PMID:27362297

  2. Fourier transform infrared emission spectra of MgH and MgD

    NASA Astrophysics Data System (ADS)

    Shayesteh, A.; Appadoo, D. R. T.; Gordon, I.; Le Roy, R. J.; Bernath, P. F.

    2004-06-01

    High resolution Fourier transform infrared emission spectra of MgH and MgD have been recorded. The molecules were generated in an emission source that combines an electrical discharge with a high temperature furnace. Several vibration-rotation bands were observed for all six isotopomers in the X 2Σ+ ground electronic state: v=1→0 to 4→3 for 24MgH, v=1→0 to 3→2 for 25MgH and 26MgH, v=1→0 to 5→4 for 24MgD, v=1→0 to 4→3 for 25MgD and 26MgD. The new data were combined with the previous ground state data, obtained from diode laser vibration-rotation measurements and pure rotation spectra, and spectroscopic constants were determined for the v=0 to 4 levels of 24MgH and the v=0 to 5 levels of 24MgD. In addition, Dunham constants and Born-Oppenheimer breakdown correction parameters were obtained in a combined fit of the six isotopomers. The equilibrium vibrational constants (ωe) for 24MgH and 24MgD were found to be 1492.776(7) cm-1 and 1077.298(5) cm-1, respectively, while the equilibrium rotational constants (Be) are 5.825 523(8) cm-1 and 3.034 344(4) cm-1. The associated equilibrium bond distances (re) were determined to be 1.729 721(1) Å for 24MgH and 1.729 157(1) Å for 24MgD.

  3. Electronic states of MgO: Spectroscopy, predissociation, and cold atomic Mg and O production

    SciTech Connect

    Maatouk, A.; Ben Houria, A.; Yazidi, O.; Jaidane, N.; Hochlaf, M.

    2010-10-14

    We used multiconfigurational methods and a large basis set to compute the potential energy curves of the valence and valence-Rydberg electronic states of MgO molecule. New bound electronic states are found. Using these highly correlated wave functions, we evaluated their mutual spin-orbit couplings and transition moment integrals. For the bound electronic states of MgO, we deduced an accurate set of spectroscopic constants that agree remarkably well with experimental results. Moreover, our potentials, transition moments, and spin-orbit coupling evolutions are incorporated into Fermi golden rule calculations to deduce the radiative lifetimes of MgO(B {sup 1}{Sigma}{sup +}) rovibrational levels and the natural lifetimes of MgO(A {sup 1}{Pi}) vibrational levels, where a good agreement is found with experimental values. Finally, we suggest new routes for the production of cold Mg and O atoms and cold MgO molecules.

  4. The millimeter-wave spectrum of the MgH and MgD radicals

    NASA Technical Reports Server (NTRS)

    Ziurys, L. M.; Barclay, W. L., Jr.; Anderson, M. A.

    1993-01-01

    The pure rotational spectrum of MgH radical (X 2 Sigma (+)) in its ground state v = 0 and v = 1 vibrational modes has been observed in the laboratory using millimeter/submillimeter direct absorption spectroscopy. The rotational spectra of two isotopically substituted species, MgD and (Mg-26)H, have been detected as well. All six hyperfine components of the N = 0 -1 transition of MgH in its v = 0 and v = 1 states have been directly measured to an accuracy of +/-50 kHz, and the five components have been observed for (Mg-26)H. The N = 0 +/-1 and N = 1 -2 transitions of MgD have also been detected. Rotational, fine structure, and hyperfine constants were determined for all species from a nonlinear least-squared fit to the data using a 2 Sigma Hamiltonian.

  5. Superconductivity in MgPtSi: An orthorhombic variant of MgB2

    NASA Astrophysics Data System (ADS)

    Kudo, Kazutaka; Fujimura, Kazunori; Onari, Seiichiro; Ota, Hiromi; Nohara, Minoru

    2015-05-01

    A ternary compound, MgPtSi, was synthesized by solid-state reaction. An examination of the compound by powder x-ray diffraction revealed that it crystallizes in the orthorhombic TiNiSi-type structure with the P n m a space group. The structure comprises alternately stacked layers of Mg and PtSi honeycomb network, which is reminiscent of MgB2, and the buckling of the honeycomb network causes orthorhombic distortion. Electrical and magnetic studies revealed that MgPtSi exhibited superconductivity with a transition temperature of 2.5 K. However, its isostructural compounds, namely, MgRhSi and MgIrSi, were not found to exhibit superconductivity.

  6. Spontaneous polarization driven Mg concentration profile reconstruction in MgZnO/ZnO heterostructures

    SciTech Connect

    Imasaka, K.; Falson, J.; Kozuka, Y. Kawasaki, M.; Tsukazaki, A.

    2014-06-16

    Atomic reconstruction at the interface of MgZnO and ZnO in molecular beam epitaxy grown heterostructures is investigated. Using secondary ion mass spectroscopy, we experimentally find that Mg atomic reconstruction depends on the polarity of the interface; it is not observed in n-type interfaces (MgZnO on Zn-polar ZnO) owing to electron accumulation, while in p-type interfaces (ZnO on Zn-polar MgZnO), Mg drastically redistributes into the ZnO layer. Combined with self-consistent calculation of band profiles and carrier distributions, we reveal that the observed Mg reconstruction is not due to thermal diffusion but consequences in order to avoid hole accumulation. This tendency implies inherent significant asymmetry of energy scales of atomic and electronic reconstructions between n-type and p-type interfaces.

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

    PubMed

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

    2012-07-28

    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. PMID:22715459

  8. Interdiffusion in the Mg-Al system and Intrinsic Diffusion in (Al3Mg2) Phase

    SciTech Connect

    Brennan, Sarah; Bermudez, Katrina; Kulkarni, Nagraj S; Sohn, Yong Ho

    2011-01-01

    Increasing use and development of lightweight Mg-alloys have led to the desire for more fundamental research in and understanding of Mg-based systems. As a strengthening component, Al is one of the most important and common alloying elements for Mg-alloys. In this study, solid-to-solid diffusion couple techniques were employed to examine the interdiffusion between pure Mg and Al. Diffusion anneals were carried out at 300 , 350 , and 400 C for 720, 360, and 240 hours, respectively. Optical and scanning electron microscopies (SEM) were employed to observe the formation of the intermetallics -Al12Mg17 and -Al3Mg2, but not -phase. Concentration profiles were determined using X-ray energy dispersive spectroscopy (XEDS). The growth constants and activation energies were determined for each intermetallic phase.

  9. Unraveling the role of Mg(++) in osteoarthritis.

    PubMed

    Li, Yaqiang; Yue, Jiaji; Yang, Chunxi

    2016-02-15

    Mg(++) is widely involved in human physiological processes that may play key roles in the generation and progression of diseases. Osteoarthritis (OA) is a complex joint disorder characterized by articular cartilage degradation, abnormal mineralization and inflammation. Magnesium deficiency is considered to be a major risk factor for OA development and progression. Magnesium deficiency is active in several pathways that have been implicated in OA, including increased inflammatory mediators, cartilage damage, defective chondrocyte biosynthesis, aberrant calcification and a weakened effect of analgesics. Abundant in vitro and in vivo evidence in animal models now suggests that the nutritional supplementation or local infiltration of Mg(++) represent effective therapies for OA. The goal of this review is to summarize the current understanding of the role of Mg(++) in OA with particular emphasis on the related molecular mechanisms involved in OA progression. PMID:26800786

  10. Influence of RCS on Al-3Mg and Al-3Mg-0.25Sc alloys

    NASA Astrophysics Data System (ADS)

    Bhovi, Prabhakar M.; Venkateswarlu, K.

    2016-02-01

    An influence of repetitive corrugation and straightening (RCS) was studied on Al-3Mg and Al-3Mg-0.25Sc alloys up to eight passes. Each pass consist of a corrugation and followed by straightening. This has resulted in introducing large plastic strain in sample, and thus led to formation of sub-micron grain sizes with high angle grain boundaries. These sub grain formation was eventually resulted in improved mechanical properties. The average grain size of Al-3Mg-0.25Sc alloy after 8 passes yielded to ∼0.6pm. Microhardness, strength properties were evaluated and it suggests that RCS was responsible for high hardness values as compared to the as cast samples. The microhardness values after RCS were 105 HV and 130 HV for Al-3Mg and Al-3Mg-0.25Sc alloys, respectively. Similarly, ∼ 40% improvement in tensile strength from 240 MPa to 370 MPa was observed for Al- 3Mg-0.25Sc alloy after RCS process.Al-3Mg and Al-3Mg-0.25Scalloys exhibited maximum strength of 220 MPa and 370 MPa, respectively. It is concluded that RCS process has a strong influence on Al- 3Mg and Al-3Mg-0.25Sc alloys for obtaining improved mechanical properties and grain refinement. In addition to RCS process and presence of AESc precipitates in Al-3Mg-0.25Sc alloy had a significant role in grain refinement and improved mechanical properties as compared to Al-3Mg alloy.

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

    PubMed

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

    2016-01-13

    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. PMID:26636472

  12. Excited states in ^22Mg and the ^21Na(p,γ)^22Mg reaction

    NASA Astrophysics Data System (ADS)

    Jewett, C.; Chipps, K.; Greife, U.; Bishop, S.; D'Auria, J.; Lamey, M.; Trinczek, M.; Hutcheon, D.; Ottewell, D.; Olin, A.; Buchmann, L.; Rogers, J.; Pearson, J.; Engel, S.; Gigliotti, D.; Ruiz, C.; Ruprecht, G.; Vockenhuber, C.; Gross, C.; Radford, D.; Yu, C.-H.; Blackmon, J.; Bardayan, D.; Smith, M. S.; Kozub, R.

    2004-10-01

    In explosive astrophysical scenarios like novae or x-ray bursts, the ^21Na(p,γ)^22Mg reaction is believed to play an important role. The proton capture proceeds predominantly via isolated excited states in the ^22Mg nucleus. This talk will present results from a search for excited states in ^22Mg via the ^12C + ^12C reaction measured at HRIBF (ORNL) and from a direct measurement of ^21Na(p,γ)^22Mg with a radioactive ion beam at ISAC (TRIUMF).

  13. Excited intruder states in {sup 32}Mg

    SciTech Connect

    Tripathi, Vandana; Tabor, S. L.; Bender, P.; Hoffman, C. R.; Lee, Sangjin; Pepper, K.; Perry, M.; Utsuno, Y.; Otsuka, T.; Mantica, P. F.; Pinter, J. S.; Stoker, J. B.; Cook, J. M.; Pereira, J.; Weisshaar, D.

    2008-03-15

    The low energy level structure of N=20 {sup 32}Mg obtained via {beta}-delayed {gamma} spectroscopy is reported. The level structure of {sup 32}Mg is found to be completely dominated by intruders. An inversion between the 1p-1h and 3p-3h states is observed for the negative parity states, similar to the 0p-0h and 2p-2h inversion for the positive parity states in these N{approx}20 nuclei. The intruder excited states, both positive and negative parity, are reasonably explained by Monte Carlo shell model calculations, which suggest a shrinking N=20 shell gap with decreasing Z.

  14. Preliminary study of the characteristics of a high Mg containing Al-Mg-Si alloy

    NASA Astrophysics Data System (ADS)

    Yan, F.; McKay, B. J.; Fan, Z.; Chen, M. F.

    2012-01-01

    An Al-20Mg-4Si high Mg containing alloy has been produced and its characteristics investigated. The as-cast alloy revealed primary Mg2Si particles evenly distributed throughout an α-Al matrix with a β-Al3Mg2 fully divorced eutectic phase observed in interdendritic regions. The Mg2Si particles displayed octahedral, truncated octahedral, and hopper morphologies. Additions of Sb, Ti and Zr had a refining influence reducing the size of the Mg2Si from 52 ± 4 μm to 25 ± 0.1 μm, 35 ± 1 μm and 34 ± 1 μm respectively. HPDC tensile test samples could be produced with a 0.6 wt.% Mn addition which prevented die soldering. Solution heating for 1 hr was found to dissolve the majority of the Al3Mg2 eutectic phase with no evidence of any effect on the primary Mg2Si. Preliminary results indicate that the heat treatment has a beneficial effect on the elongation and the UTS.

  15. Mg2+-sensing mechanism of Mg2+ transporter MgtE probed by molecular dynamics study

    PubMed Central

    Ishitani, Ryuichiro; Sugita, Yuji; Dohmae, Naoshi; Furuya, Noritaka; Hattori, Motoyuki; Nureki, Osamu

    2008-01-01

    Proper regulation of the intracellular ion concentration is essential to maintain life and is achieved by ion transporters that transport their substrates across the membrane in a strictly regulated manner. MgtE is a Mg2+ transporter that may function in the homeostasis of the intracellular Mg2+ concentration. A recent crystallographic study revealed that its cytosolic domain undergoes a Mg2+-dependent structural change, which is proposed to gate the ion-conducting pore passing through the transmembrane domain. However, the dynamics of Mg2+ sensing, i.e., how MgtE responds to the change in the intracellular Mg2+ concentration, remained elusive. Here we performed molecular dynamics simulations of the MgtE cytosolic domain. The simulations successfully reproduced the structural changes of the cytosolic domain upon binding or releasing Mg2+, as well as the ion selectivity. These results suggested the roles of the N and CBS domains in the cytosolic domain and their respective Mg2+ binding sites. Combined with the current crystal structures, we propose an atomically detailed model of Mg2+ sensing by MgtE. PMID:18832160

  16. New FCC Mg-Zr and Mg-Zr-ti deuterides obtained by reactive milling

    NASA Astrophysics Data System (ADS)

    Guzik, Matylda N.; Deledda, Stefano; Sørby, Magnus H.; Yartys, Volodymyr A.; Hauback, Bjørn C.

    2015-03-01

    Results for binary Mg-Zr and ternary Mg-Zr-Ti mixtures ball milled at room temperature under reactive deuterium atmosphere (5.6-6.7 MPa) are reported. X-ray and neutron powder diffraction combined with Rietveld refinements show that two new cubic phases were formed during milling. Mg0.40Zr0.60D1.78 and Mg0.40Zr0.26Ti0.34D1.98 crystallize with disordered face centered cubic metal atom arrangements. Results of differential scanning calorimetry and termogravimetric measurements demonstrate that both deuterides desorb deuterium at lower temperatures than MgD2, ZrD2 or TiD2; 528 and 575 K in the Mg-Zr-D and Mg-Zr-Ti-D system, respectively. Interestingly, Mg0.40Zr0.26Ti0.34D1.98 stores deuterium reversibly at 673 K and 10 MPa of D2.

  17. Single crystal growth of MgB 2 by evaporating Mg-flux method

    NASA Astrophysics Data System (ADS)

    Du, Wei; Xu, Huizhong; Zhang, Hongbin; Xu, Dong; Wang, Xinqiang; Hou, Xianqin; Wu, Yongzhong; Jiang, Fuyi; Qin, Lianjie

    2006-04-01

    Well hexagonal plate-shaped single crystal of magnesium diboride (MgB 2) with the size of 100 μm has been grown at ambient pressure by evaporating Mg-flux method which is a new practice to grow MgB 2 single crystal. The superconducting transition of as-prepared crystals was measured to be at about 33.7 K by superconducting quantum interference device (dc-SQUID) magnetometer. The X-ray powder diffraction (XRD) confirmed the MgB 2 phase, and the electron diffraction patterns measured by using high-resolution transmission electron microscope (HRTEM) confirmed the structure of MgB 2 single crystal. The single crystal images were observed by scanning electron microscope (SEM) and metallographic microscope (MM). The micromechanism of crystal growth is also proposed through the investigations of SEM and MM.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

  19. Role of MgCo compound on the sorption properties of the Mg-Co milled mixtures

    NASA Astrophysics Data System (ADS)

    Verón, M. G.; Gennari, F. C.; Meyer, G. O.

    The influence of MgCo on the reaction paths during hydriding and dehydriding processes of Mg-Co mixtures was studied using a combined HP-DSC and XRD approach. Mg-Co mixtures with different compositions were mechanically milled under argon to prepare Mg-Co nanocomposites and then submitted to thermal treatment at 300 °C for 5 days to induce MgCo formation. The local Mg-Co composition in the milled and milled-heated samples determines the nature of the phases obtained after hydriding/dehydriding cycling. The formation of Mg 6Co 2H 11, Mg 2CoH 5 and MgH 2 hydrides occurs after the first hydriding stage of the 2Mg-Co and Mg-Co milled mixtures due to kinetic restrictions. On the contrary, Mg-Co milled-heated mixture exhibits the selective formation of Mg 2CoH 5 during first hydriding via two-step reaction. In the first one, MgCo disproportion to MgH 2 and Co takes place simultaneously with Mg hydriding (<200 °C). The second step involves MgCo hydriding to Mg 2CoH 5 through MgH 2 as intermediate phase (>200 °C). Dehydriding reaction is enhanced by dispersion of Co into Mg-matrix, which reduces more than 100 °C the hydrogen desorption temperature when compared with the Mg-Co milled sample without previous heating.

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

    PubMed

    Wu, Xinxing; Zhang, Ruiqi; Yang, Jinlong

    2016-07-28

    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. PMID:27376680

  1. Highly Reversible Mg Insertion in Nanostructured Bi for Mg Ion Batteries

    SciTech Connect

    Shao, Yuyan; Gu, Meng; Li, Xiaolin; Nie, Zimin; Zuo, Pengjian; Li, Guosheng; Liu, Tianbiao L.; Xiao, Jie; Cheng, Yingwen; Wang, Chong M.; Zhang, Jiguang; Liu, Jun

    2014-01-08

    Rechargeable magnesium batteries have attracted wide attention for energy storage. Currently, most studies focus on Mg metal as the anode, but this approach is still limited by the properties of the electrolyte and poor control of the Mg plating/stripping processes.1,2 Here we report the synthesis and application of Bi nanotubes as a high performance anode material for rechargeable Mg ion batteries. The nanostructured Bi anode delivers a high reversible specific capacity (350 mAh/gBi, or 3430 mAh/cm3 Bi), excellent stability, and high columbic efficiency (95 % initial and very close to 100% afterwards). The good performance is attributed to the unique properties of in-situ formed, interconnected nanoporous bismuth. Such nanostructures can effectively accommodate the large volume change without losing electric contact and significantly reduce diffusion length for Mg2+. Significantly, the nanostructured Bi anode can be used with conventional electrolytes which will open new opportunities to study Mg ion battery chemistry and further improve the properties. The performance and the stability of a full cell Mg ion battery have been demonstrated with conventional electrolytes. This work suggests that other high energy density alloy compounds may also be considered for Mg-ion chemistry for high capacity electrode materials.

  2. A preliminary study for novel use of two Mg alloys (WE43 and Mg3Gd).

    PubMed

    Guo, Yu; Liu, Weiwei; Ma, Shanshan; Wang, Jia; Zou, Jingting; Liu, Zhenzhen; Zhao, Jinghui; Zhou, Yanmin

    2016-05-01

    In this study, two types of magnesium alloys (WE43 and Mg3Gd) were compared with Heal-All membrane (a biodegradable membrane used in guided bone regeneration) in vitro to determine whether the alloys could be used as biodegradable membranes. Degradation behavior was assessed using immersion testing with simulated body fluid (SBF). Microstructural characteristics before and after immersion were evaluated through scanning electron microscopy, and degradation products were analyzed with energy dispersive spectrometry (EDS). To evaluate the biocompatibility of the three types of materials, we performed cytotoxicity, adhesion, and mineralization tests using human osteoblast-like MG63 cells. Immersion testing results showed no significant difference in degradation rate between WE43 and Mg3Gd alloys. However, both Mg alloys corroded faster than the Heal-All membrane, with pitting corrosion as the main corrosion mode for the alloys. Degradation products mainly included P- and Ca-containing apatites on the surface of WE43 and Mg3Gd, whereas these apatites were rarely detected on the surface of the Heal-All membrane. All three type of materials exhibited good biocompatibility. In the mineralization experiment, the alkaline phosphatase (ALP) activity of 10 % Mg3Gd extract was significantly higher than the extracts of the two other materials and the negative control. This study highlighted the potential of these Mg-REE alloys for uses in bone regeneration and further studies and refinements are obviously required. PMID:26968757

  3. Hydroxyl Motion in Mg(OH)2

    NASA Astrophysics Data System (ADS)

    Itoh, Yutaka; Isobe, Masahiko

    2015-11-01

    We report on pulsed 1H NMR studies of the hydroxyl OH groups in magnesium hydroxide Mg(OH)2 at 77-355 K at 42.5772 MHz. The Fourier-transformed NMR spectra show the superposition of broad and narrow components. The broad NMR spectrum is assigned to dipole-coupled protons on a rigid lattice in the bulk Mg(OH)2, while the narrow NMR spectrum is assigned to extrinsic protons, e.g., conduction protons facilitated by lattice defects. We found a monotonically decreasing linewidth of the broad NMR spectrum on heating. The monotonic decrease in the linewidth is associated with hopping protons around a threefold axis (rotational hydroxyl protons).

  4. Experimental Mg IX photorecombination rate coefficient

    NASA Astrophysics Data System (ADS)

    Schippers, S.; Schnell, M.; Brandau, C.; Kieslich, S.; Müller, A.; Wolf, A.

    2004-07-01

    The rate coefficient for radiative and dielectronic recombination of beryllium-like magnesium ions was measured with high resolution at the Heidelberg heavy-ion storage ring TSR. In the electron-ion collision energy range 0-207 eV resonances due to 2s -> 2p (Δ N = 0) and 2s -> 3l (Δ N=1) core excitations were detected. At low energies below 0.15 eV the recombination rate coefficient is dominated by strong 1s2 (2s 2p 3P) 7l resonances with the strongest one occuring at an energy of only 21 meV. These resonances decisively influence the Mg IX recombination rate coefficient in a low temperature plasma. The experimentally derived Mg IX dielectronic recombination rate coefficient (±15% systematical uncertainty) is compared with the recommendation by Mazzotta et al. (1998, A&AS, 133, 403) and the recent calculations by Gu (2003, ApJ, 590, 1131) and by Colgan et al. (2003, A&A, 412, 597). These results deviate from the experimental rate coefficient by 130%, 82% and 25%, respectively, at the temperature where the fractional abundance of Mg IX is expected to peak in a photoionized plasma. At this temperature a theoretical uncertainty in the 1s2 (2s 2p 3P) 7l resonance positions of only 100 meV would translate into an uncertainty of the plasma rate coefficient of almost a factor 3. This finding emphasizes that an accurate theoretical calculation of the Mg IX recombination rate coefficient from first principles is challenging.

  5. The significance of Mg in prebiotic geochemistry

    PubMed Central

    Holm, N G

    2012-01-01

    Magnesium plays a special role in biochemistry because of its ability to coordinate six oxygen atoms efficiently in its first coordination shell. Such oxygen atoms may be part of one or two charged oxyanions, which means that Mg2+ can, for instance, tie together two different phosphate groups that are located at distance from each other in a macromolecule, and in this way be responsible for the folding of molecules like RNA. This property of Mg2+ also helps the stabilization of diphosphate and triphosphate groups of nucleotides, as well as promoting the condensation of orthophosphate to oligophosphates, like pyrophosphate and trimetaphosphate. Borates, on the other hand, are known to promote the formation of nucleobases and carbohydrates, ribose in particular, which is yet another constituent of nucleotides. The oldest borate minerals that we find on Earth today are magnesium borates. Dissolved borate stabilizes pentose sugars by forming complexes with cis-hydroxyl groups. In the furanose form of ribose, the preferential binding occurs to the 2 and 3 carbon, leaving the 5 carbon free for phosphorylation. The central role of Mg2+ in the function of ribozymes and its ‘archaic’ position in ribosomes, and the fact that magnesium generally has coordination properties different from other cations, suggests that the inorganic chemistry of magnesium had a key position in the first chemical processes leading to the origin and early evolution of life. PMID:22429303

  6. Interstitial Fe in MgO

    SciTech Connect

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

    2014-01-14

    Isolated {sup 57}Fe atoms were studied in MgO single-crystals by emission Mössbauer spectroscopy following implantation of {sup 57}Mn decaying to {sup 57}Fe. Four Mössbauer spectral components were found corresponding to different Fe lattice positions and/or charge states. Two components represent Fe atoms substituting Mg as Fe{sup 2+} and Fe{sup 3+}, 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.

  7. Roaming dynamics in the MgH + H→Mg + H 2 reaction: Quantum dynamics calculations

    NASA Astrophysics Data System (ADS)

    Takayanagi, Toshiyuki; Tanaka, Tomokazu

    2011-03-01

    Reaction mechanisms of the MgH + H→Mg + H 2 reaction have been investigated using quantum reactive scattering methods on a global ab initio potential energy surface. There exist two microscopic mechanisms in the dynamics of this reaction. One is a direct hydrogen abstraction reaction and the other proceeds via initial formation of a HMgH complex in the deep potential well. The result of the present quantum dynamics calculations suggests that the HMgH complex formed in the reaction mainly decays into the Mg + H 2 channel via a 'roaming mechanism' without going through the saddle point region.

  8. NEXAFS Study of Air Oxidation for Mg Nanoparticle Thin Film

    NASA Astrophysics Data System (ADS)

    Ogawa, S.; Murakami, S.; Shirai, K.; Nakanishi, K.; Ohta, T.; Yagi, S.

    2013-03-01

    The air oxidation reaction of Mg nanoparticle thin film has been investigated by Mg K-edge NEXAFS technique. It is revealed that MgO is formed on the Mg nanoparticle surfaces at the early stage of the air oxidation for Mg nanoparticle thin film. The simulation of NEXAFS spectrum using standard spectra indicates the existence of complex magnesium carbonates (x(MgCO3).yMg(OH2).z(H2O)) in addition to MgO at the early stage of the air oxidation.

  9. A fundamental study on the [(μ-Cl)3Mg2(THF)6]+ dimer electrolytes for rechargeable Mg batteries†

    PubMed Central

    Cox, Jonathan T.; Hu, Dehong; Deng, Xuchu; Hu, Jianzhi; Hu, Mary Y.; Xiao, Jie; Shao, Yuyan; Tang, Keqi; Liu, Jun

    2016-01-01

    The long sought solvated [MgCl]+ species in the Mg-dimer electrolytes was characterized by soft mass spectrometry. The presented study provides an insightful understanding on the electrolyte chemistry of rechargeable Mg batteries. PMID:25562393

  10. Mg intercalation in layered and spinel host crystal structures for Mg batteries.

    PubMed

    Emly, Alexandra; Van der Ven, Anton

    2015-05-01

    We investigate electrochemical properties of Mg in layered and spinel intercalation compounds from first-principles using TiS2 as a model system. Our calculations predict that Mg(x)TiS2 in both the layered and spinel crystal structures exhibits sloping voltage profiles with steps at stoichiometric compositions due to Mg-vacancy ordering. Mg ions are predicted to occupy the octahedral sites in both layered and spinel TiS2 with diffusion mediated by hops between octahedral sites that pass through adjacent tetrahedral sites. Predicted migration barriers are substantially higher than typical Li-migration barriers in intercalation compounds. The migration barriers are shown to be very sensitive to lattice parameters of the host crystal structure. We also discuss the possible role of rehybridization between the transition metal and the anion in affecting migration barriers. PMID:25905428

  11. Theoretical Investigation of the Electronic Structure and Spectra of Mg(2+)He and Mg(+)He.

    PubMed

    Bejaoui, M; Dhiflaoui, J; Mabrouk, N; El Ouelhazi, R; Berriche, H

    2016-02-11

    The ground and many excited states of the Mg(+)He van der Waals molecular system have been explored using a one-electron pseudopotential approach. In this approach, effective potentials are used to consider the Mg(2+) core and the electron-He effects. Furthermore, a core-core interaction is included. This has reduced the number of active electrons of the Mg(+)He, to be considered in the calculation, to a single valence electron. This has permitted to use extended Gaussian basis sets for Mg and He. Therefore, the potentianl energy and dipole moments calculations are carried out at the Hartree-Fock level of theory, and the spin-orbit effect is included using a semiclassical approach. The core-core interaction for the Mg(2+)He ground state is included using accurate CCSD(T) calculations. The spectroscopic constants of the Mg(+)He electronic states are extracted and compared with the existing theoretical works, where very good agreement is observed. Moreover, the transition dipole function has been determined for a large and dense grid of internuclear distances including the spin-orbit effect. PMID:26783874

  12. A thermokinetic model for Mg-Si couple formation in Al-Mg-Si alloys

    NASA Astrophysics Data System (ADS)

    Svoboda, J.; Shan, Y. V.; Kozeschnik, E.; Fischer, F. D.

    2016-03-01

    Mg-Si couples formed from atomic Mg and Si represent the first step in Mg-Si cluster formation in a dilute Al-Mg-Si system. Based on the thermodynamic extremal principle, a kinetic model for Mg-Si couple formation is developed. The model utilizes the trapping concept for the calculation of Gibbs energy of the non-equilibrium system and provides a generalized (multiplicative) form of the Oriani equation for description of the equilibrium state. The dissipation in the system accounts for diffusion of both Mg and Si atoms in the lattice. The model is compared with the classical Lidiard and Howard equilibrium theory. Some demonstrative examples are presented. Finally the model is applied to an experimentally studied system. Good quantitative agreement with quenching experiments is obtained, if, simultaneously, the impact of excess quenched-in vacancies and their gradual annihilation in the system, which has been already treated in a previous paper, are accounted for. The model is generally applicable for any couple (and pair) formation.

  13. Laser cooling of MgCl and MgBr in theoretical approach

    SciTech Connect

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

    2015-07-14

    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.

  14. Dipole transition strengths in Mg26

    NASA Astrophysics Data System (ADS)

    Schwengner, R.; Wagner, A.; Fujita, Y.; Rusev, G.; Erhard, M.; de Frenne, D.; Grosse, E.; Junghans, A. R.; Kosev, K.; Schilling, K. D.

    2009-03-01

    Excited states with Jπ=1+ and 1- in Mg26 were studied in a photon-scattering experiment using bremsstrahlung produced by an electron beam of 13.0 MeV kinetic energy provided by the superconducting electron linear accelerator ELBE. We determined the transition strengths from the 1+ and 1- states to the ground state as well as to low-lying excited states. In addition, we observed a J=1 state at 11.154 MeV, above the neutron-separation energy of 11.093 MeV, and determined its partial γ decay width for the first time.

  15. On the dissociation energy of Mg2

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Bauschlicher, Charles W., Jr.; Pettersson, Lars G. M.; Mclean, A. D.; Liu, Bowen

    1990-01-01

    The bonding in the X 1Sigma(+)g state of Mg2 is investigated using near-complete valence one-particle Slater and Gaussian basis sets containing up to h functions. It is shown that the four-electron complete CI limit can be approached using a sequence of either second-order CI (SOCI) or interacting correlated fragment (ICF) calculations. At the valence level, the best estimate of the dissociation energy D(e) was 464/cm. This is a lower limit and is probably within 5/cm of the complete basis value.

  16. The Atomization Energy of Mg4

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Arnold, James O. (Technical Monitor)

    1999-01-01

    The atomization energy of Mg4 is determined using the MP2 and CCSD(T) levels of theory. Basis set incompleteness, basis set extrapolation, and core-valence effects are discussed. Our best atomization energy, including the zero-point energy and scalar relativistic effects, is 24.6+/-1.6 kcal per mol. Our computed and extrapolated values are compared with previous results, where it is observed that our extrapolated MP2 value is good agreement with the MP2-R12 value. The CCSD(T) and MP2 core effects are found to have the opposite signs.

  17. Variable Stars from the MG-1 Catalog

    NASA Astrophysics Data System (ADS)

    Flurchick, K. M.; Griego, Ben; Culver, Roger B.

    2014-06-01

    This work describes the recent efforts at North Carolina A&T(NCAT) mining the MG catalogs for variable stars. NCAT is a node in both the GNAT network and the SKYNET collaboration which forms the basis of the collaboration including access to instruments. The initial data analysis to obtain the light curves (LC) for MG-1 has been performed and a number of candidate variable stars have been identified including brown dwarf stars, eclipsing binaries and long period variable stars.Many of the identified candidate variable stars are now the subject of coordinated multi-site follow-on observations to elucidate the details of the variability. The coordinated observing includes researchers in Australia, Arizona, Colorado and North Carolina. As a node in both the GNAT network and the SKYNET collaboration NCAT has access to a number of instruments. Much of the observational work is performed using the SKYNET node in Chile.For the North Carolina work reported here, the observational work and initial LC generation is performed using telescopes and applications from the SKYNET program. In this work the instrumentation, the LC analysis and status of the coordinated follow-on observations arepresented.

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

    NASA Technical Reports Server (NTRS)

    Kindler, Andrew; Huang, Yuhong

    2010-01-01

    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.

  19. Highly reversible Mg insertion in nanostructured Bi for Mg ion batteries.

    PubMed

    Shao, Yuyan; Gu, Meng; Li, Xiaolin; Nie, Zimin; Zuo, Pengjian; Li, Guosheng; Liu, Tianbiao; Xiao, Jie; Cheng, Yingwen; Wang, Chongmin; Zhang, Ji-Guang; Liu, Jun

    2014-01-01

    Rechargeable magnesium batteries have attracted wide attention for energy storage. Currently, most studies focus on Mg metal as the anode, but this approach is still limited by the properties of the electrolyte and poor control of the Mg plating/stripping processes. This paper reports the synthesis and application of Bi nanotubes as a high-performance anode material for rechargeable Mg ion batteries. The nanostructured Bi anode delivers a high reversible specific capacity (350 mAh/gBi or 3430 mAh/cm(3)Bi), excellent stability, and high Coulombic efficiency (95% initial and very close to 100% afterward). The good performance is attributed to the unique properties of in situ formed, interconnected nanoporous bismuth. Such nanostructures can effectively accommodate the large volume change without losing electric contact and significantly reduce diffusion length for Mg(2+). Significantly, the nanostructured Bi anode can be used with conventional electrolytes which will open new opportunities to study Mg ion battery chemistry and further improve its properties. PMID:24279987

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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. Toward Understanding the Roaming Mechanism in H + MgH → Mg + HH Reaction.

    PubMed

    Mauguière, Frédéric A L; Collins, Peter; Stamatiadis, Stamatis; Li, Anyang; Ezra, Gregory S; Farantos, Stavros C; Kramer, Zeb C; Carpenter, Barry K; Wiggins, Stephen; Guo, Hua

    2016-07-14

    The roaming mechanism in the reaction H + MgH →Mg + HH is investigated by classical and quantum dynamics employing an accurate ab initio three-dimensional ground electronic state potential energy surface. The reaction dynamics are explored by running trajectories initialized on a four-dimensional dividing surface anchored on three-dimensional normally hyperbolic invariant manifold associated with a family of unstable orbiting periodic orbits in the entrance channel of the reaction (H + MgH). By locating periodic orbits localized in the HMgH well or involving H orbiting around the MgH diatom, and following their continuation with the total energy, regions in phase space where reactive or nonreactive trajectories may be trapped are found. In this way roaming reaction pathways are deduced in phase space. Patterns similar to periodic orbits projected into configuration space are found for the quantum bound and resonance eigenstates. Roaming is attributed to the capture of the trajectories in the neighborhood of certain periodic orbits. The complex forming trajectories in the HMgH well can either return to the radical channel or "roam" to the MgHH minimum from where the molecule may react. PMID:26918375

  2. Apollo 15 Mg- and Fe-norites - A redefinition of the Mg-suite differentiation trend

    NASA Technical Reports Server (NTRS)

    Lindstrom, M. M.; Marvin, U. B.; Mittlefehldt, D. W.

    1989-01-01

    The Apollo 15 highland rocks from the Apennine Front include clasts of mafic plutonic rocks from deep in the lunar crust that were brought to the surface by the Imbrium and Serenitatis impacts. The Apollo 15 norites exhibit wide variations in mineral and bulk compositions and include Fe-norites that plot between the three major pristine rock fields on a diagram of Mg' in mafic minerals vs An in paglioclase. Based on assemblages and compositions of minerals, and on ratios of elemental abundances, it is concluded that these Apollo 15 Fe-norites are differentiated members of the Mg-norite suite. The Apollo 15 and 17 norites and troctolites form a closely related suite of rocks, whose variations in mineral compositions represent the main differentiation trend of the Mg-suite. This trend in mineral compositions has a steeper slope than the previous Mg-suite field. The parent magmas for these Mg-suite rocks formed by partial melting deep in the lunar mantle. Differentiation by fractional crystallization may also have included assimilation of crustal components as the magmas rose from the mantle and crystallized plutons in the lower crust.

  3. Phase transition and optoelectronic properties of MgH2

    NASA Astrophysics Data System (ADS)

    Nayak, Vikas; Verma, U. P.

    2016-05-01

    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.

  4. Role of dopants in LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P detectors

    SciTech Connect

    Mohammadi, Kh. Moussavi Zarandi, A.; Afarideh, H.; Shahmaleki, S.

    2013-06-15

    In this study, electronic structure of LiF crystal doped with Mg,Cu,P impurities was studied with WIEN2k code on the basis of FPLAPW+lo method. Results show that in Mg-doped LiF composition, an electronic trap was created with impurity concentration of 1.56% and 3.125%. In this condition, the electronic trap with increasing the percentage of the impurities up to 4.687% is annihilated. It was found, that by doping of Mg and Cu or P simultaneously, a hole-trap is created in valence band. It was realized that in LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P, Cu impurity and Li atom, have a key role in creation of levels which lead to create electronic and hole traps. Mg impurity and F atom, only have a role in creation of electronic traps. In addition, P impurity has a main role in creation of the electronic and hole traps in LiF:Mg,Cu,P. The activation energy of electronic and hole trap in LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P crystalline lattice were obtained as 0.3 and 5.5 eV, 0.92 and 3.4 eV and 0.75 and 3.1 eV, respectively. - Graphical abstract: Figure (a) and (b) shows changes in electronic structure and band gap energy of LiF crystal due to presence of Mg and Cu, Mg and P ions respectively. - Highlights: • Electronic structure of LiF, LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P materials were studied with WIEN2K code. • In LiF:Mg,Cu and LiF:Mg,Cu,P, Li atom and Cu impurity have a key role in creation of levels. • F atom and Mg impurity only have a role in creation of electronic traps. • In LiF:Mg,Cu,P, P impurity has a main role in creation of electronic and hole traps.

  5. Neural depolarization triggers Mg2+ influx in rat hippocampal neurons.

    PubMed

    Yamanaka, R; Shindo, Y; Karube, T; Hotta, K; Suzuki, K; Oka, K

    2015-12-01

    Homeostasis of magnesium ion (Mg(2+)) plays key roles in healthy neuronal functions, and deficiency of Mg(2+) is involved in various neuronal diseases. In neurons, we have reported that excitotoxicity induced by excitatory neurotransmitter glutamate increases intracellular Mg(2+) concentration ([Mg(2+)]i). However, it has not been revealed whether neuronal activity under physiological condition modulates [Mg(2+)]i. The aim of this study is to explore the direct relationship between neural activity and [Mg(2+)]i dynamics. In rat primary-dissociated hippocampal neurons, the [Mg(2+)]i and [Ca(2+)]i dynamics were simultaneously visualized with a highly selective fluorescent Mg(2+) probe, KMG-104, and a fluorescent Ca(2+) probe, Fura Red, respectively. [Mg(2+)]i increase concomitant with neural activity by direct current stimulation was observed in neurons plated on an indium-tin oxide (ITO) glass electrode, which enables fluorescent imaging during neural stimulation. The neural activity-dependent [Mg(2+)]i increase was also detected in neurons whose excitability was enhanced by the treatment of a voltage-gated K(+) channel blocker, tetraethylammonium (TEA) at the timings of spontaneous Ca(2+) increase. Furthermore, the [Mg(2+)]i increase was abolished in Mg(2+)-free extracellular medium, indicating [Mg(2+)]i increase is due to Mg(2+) influx induced by neural activity. The direct neuronal depolarization by veratridine, a Na(+) channel opener, induced [Mg(2+)]i increase, and this [Mg(2+)]i increase was suppressed by the pretreatment of a non-specific Mg(2+) channel inhibitor, 2-aminoethoxydiphenyl borate (2-APB). Overall, activity-dependent [Mg(2+)]i increase results from Mg(2+) influx through 2-APB-sensitive channels in rat hippocampal neurons. PMID:26455951

  6. The Influence of MgH2 on the Assessment of Electrochemical Data to Predict the Degradation Rate of Mg and Mg Alloys

    PubMed Central

    Mueller, Wolf-Dieter; Hornberger, Helga

    2014-01-01

    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. PMID:24972140

  7. PLD growth of multilayered MgO/Ag(001)/MgO photocathode

    NASA Astrophysics Data System (ADS)

    Velazquez, Daniel; Yusof, Zikri; Spentzouris, Linda; Terry, Jeff

    2014-03-01

    Films of of Ag, MgO and multilayers of these were grown via pulsed laser deposition on clean Si(111) 7x7 substrates. The films were studied using reflection high-energy electron diffraction, Kelvin probe and ellipsometry. Information about crystalline and atomic structure as well as surface condition, work function and film thickness was obtained using these techniques. Deposition at various substrate temperatures and partial oxygen pressures was performed in order to understand the parameter settings that lead to higher quality crystalline films. Epitaxial films of Ag(111) were found to grow at an optimal substrate temperature of 256 °C (fig 1.). The superstructure Ag(111) √3 x √3 occurs when deposition takes place at a substrate temperature of 620 °C. In addition, MgO films were found to grow with small grain size on both, Si(111) 7x7 and Ag(111)/Si(111) at room temperature with a partial oxygen pressure of 5x10-5 Torr (fig. 2). Highly-oriented, polycrystalline growth of MgO films is evidenced by their RHEED pattern. In addition, the obliquely-shaped diffraction spots indicate the growth of secondary phase precipitates, most likely due to oxygen deficit. Measurements of the work function of these multilayers indicate that the Ag(111) work function (4.75 eV) is sharply suppressed with the first few MgO shots and has a quasi-linear increase for the first few monolayers (fig. 3). As the thickness of MgO increases (a few nanometers) the work function drops again and stabilizes at the level of MgO (~ 4.2 eV).

  8. On nanoparticle surface growth: MgO nanoparticle formation during a Mg particle combustion

    NASA Astrophysics Data System (ADS)

    Altman, Igor S.; Agranovski, Igor E.; Choi, Mansoo

    2004-06-01

    It is demonstrated that formation of MgO nanoparticles during a Mg particle combustion occurs in the vapor adsorption regime and the particle coagulation and coalescence do not play any significant role in the process in question. Analysis of the particle size distributions shows that the rate of the nanoparticle condensation growth strongly depends on the actual particle size. The revealed dependence of the growth rate upon the size is consistent with the exponential law recently predicted. This finding can shed light on the long-standing general problem of gas-phase nanotechnology—the origin of lognormal size distribution behavior of generated nanoparticles.

  9. Porous composite materials ZrO2(MgO)-MgO for osteoimplantology

    NASA Astrophysics Data System (ADS)

    Buyakov, Ales; Litvinova, Larisa; Shupletsova, Valeria; Kulbakin, Denis; Kulkov, Sergey

    2016-08-01

    The pore structure and phase composition of ceramic composite material ZrO2(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.

  10. Atomistically informed solute drag in Al Mg

    NASA Astrophysics Data System (ADS)

    Zhang, F.; Curtin, W. A.

    2008-07-01

    Solute drag in solute-strengthened alloys, caused by diffusion of solute atoms around moving dislocations, controls the stress at deformation rates and temperatures useful for plastic forming processes. In the technologically important Al-Mg alloys, the solute drag stresses predicted by classical theories are much larger than experiments, which is resolved in general by eliminating the singularity of the dislocation core via Peierls-Nabarro-type models. Here, the drag stress versus dislocation velocity is computed numerically using a realistic dislocation core structure obtained from an atomistic model to investigate the role of the core and obtain quantitative stresses for comparison with experiment. The model solves a discrete diffusion equation in a reference frame moving with the dislocation, with input solute enthalpies and diffusion activation barriers in the core computed by or estimated from atomistic studies. At low dislocation velocities, the solute drag stress is controlled by bulk solute diffusion because the core diffusion occurs too quickly. In this regime, the drag stress can be obtained using a Peierls-Nabarro model with a core spreading parameter tuned to best match the atomistic models. At intermediate velocities, both bulk and core diffusion can contribute to the drag, leading to a complex stress-velocity relationship showing two peaks in stress. At high velocities, the drag stress is controlled solely by diffusion within and across the core. Like the continuum models, the drag stress is nearly linear in solute concentration. The Orowan relationship is used to connect dislocation velocity to deformation strain rate. Accounting for the dependence of mobile dislocation density on stress, the simulations are in good agreement with experiments on Al-Mg alloys over a range of concentrations and temperatures.

  11. Microstructural formation in a hypereutectic Mg-Si alloy

    SciTech Connect

    Pan Yichuan . E-mail: riverpan@mail.sdu.edu.cn; Liu Xiangfa; Yang Hua

    2005-09-15

    In the present work, the microstructure of an ingot metallurgy hypereutectic Mg-8 wt.% Si alloy was studied using electron probe microanalysis (EPMA) and the solidification process was discussed. The components of the alloy are Mg{sub 2}Si and Mg. The solidified microstructure of the alloy contains three constituents: Mg{sub 2}Si primary dendrites that are surrounded by Mg sub-primary particles and the Mg-Mg{sub 2}Si eutectic. The primary Mg{sub 2}Si dendrites have a secondary dendrite arm spacing d {sub 2} of approximately 17 {mu}m or show polygonal morphologies with a mean size of 30 {mu}m. An Mg phase appearing as halos surround the Mg{sub 2}Si constituents. The Mg-Mg{sub 2}Si eutectic has a regular morphology of rod-like Mg{sub 2}Si distributed in a continuous matrix of Mg having an interphase spacing r of approximately 0.8 {mu}m.

  12. Mg intercalation into Ti2C building block

    NASA Astrophysics Data System (ADS)

    Yu, Xue-fang; Cheng, Jianbo; Liu, Zhenbo; Li, Qingzhong; Li, Wenzuo; Yang, Xin; Xiao, Bo

    2015-06-01

    Generally, intercalation occurs when foreign atoms intercalate into multi-layer structures, while adsorption occurs when foreign atoms interact with monolayer structures or surfaces. We performed an investigation on the Mg intercalation into Ti2C building block (MXene) from first-principles simulation. We found that Mg can favorably intercalate into MXene, forming the stable compound Ti2MgC, which corresponds to the stage I in the Li intercalation into graphite. Based on the evaluation of the average cell potential and the energy barrier of Mg diffusion for the most energetically stable structure, our results suggest that Ti2MgC is a potential anode for Mg ion batteries.

  13. ZnO/(ZnMg)O single quantum wells with high Mg content graded barriers

    SciTech Connect

    Laumer, Bernhard; Schuster, Fabian; Wassner, Thomas A.; Stutzmann, Martin; Rohnke, Marcus; Schoermann, Joerg; Eickhoff, Martin

    2012-06-01

    ZnO/Zn{sub 1-x}Mg{sub x}O single quantum wells (SQWs) were grown by plasma-assisted molecular beam epitaxy on c-plane sapphire substrates. Compositional grading allows the application of optimized growth conditions for the fabrication of Zn{sub 1-x}Mg{sub x}O barriers with high crystalline quality and a maximum Mg content of x = 0.23. High resolution x-ray diffraction reveals partial relaxation of the graded barriers. Due to exciton localization, the SQW emission is found to consist of contributions from donor-bound and free excitons. While for narrow SQWs with well width d{sub W}{<=}2.5nm, the observed increase of the exciton binding energy is caused by quantum confinement, the drop of the photoluminescence emission below the ZnO bulk value found for wide SQWs is attributed to the quantum-confined Stark effect. For a Mg content of x = 0.23, a built-in electric field of 630 kV/cm is extracted, giving rise to a decrease of the exciton binding energy and rapid thermal quenching of the SQW emission characterized by an activation energy of (24 {+-} 4) meV for d{sub W} = 8.3 nm.

  14. Rupatadine 20 mg and 40 mg are Effective in Reducing the Symptoms of Chronic Cold Urticaria.

    PubMed

    Abajian, Marina; Curto-Barredo, Laia; Krause, Karoline; Santamaria, Eva; Izquierdo, Iñaki; Church, Martin K; Maurer, Marcus; Giménez-Arnau, Ana

    2016-01-01

    Chronic cold urticaria (ColdU) is a rare disease characterized by mast cell-mediated wheals and angioedema following cold exposure. Second-generation H1-antihistamines, such as rupatadine, are the recommended first-line therapy. As of yet, the effects of rupatadine up-dosing on development of ColdU symptom have only been partially characterized. Two-centre, randomized, double-blind, 3-way crossover, placebo-controlled study in patients with a confirmed ColdU was designed to assess the effects of up-dosing of rupatadine. A total of 23 patients were randomized to receive placebo, rupatadine 20 mg/day, and rupatadine 40 mg/day for 1 week. The primary outcome was change in critical temperature thresholds and critical stimulation time thresholds after treatment. Secondary endpoints included assessment of safety and tolerability of rupatadine. Both 20 and 40 mg rupatadine were highly effective in reducing critical temperature thresholds (p < 0.001) and critical stimulation time thresholds (p < 0.001). In conclusion, rupatadine 20 and 40 mg significantly reduced the development of chronic cold urticaria symptom without an increase in adverse effects. PMID:26038847

  15. Superplasticity in a thermomechanically processed High-Mg, Al-Mg alloy

    NASA Astrophysics Data System (ADS)

    McNelley, T. R.; Lee, E. W.; Mills, M. E.

    1986-06-01

    Superplastic elongations in excess of 400 pct have been observed in tension testing at 573 K (300 °C) and strain rate έ = 2 × 10-3 s-1 for a thermomechanically processed Al-10.2 pct Mg-0.52 pct Mn alloy. The thermomechanical processing consists of solution treatment and hot working, followed by extensive warm rolling at 573 K (300 °C), a temperature below the solvus for Mg in the alloy. This processing results in a fine subgrain structure in conjunction with refined and homogeneously distributed β(Al8Mg5) and MnAl6 precipitates. This structure does not statically recrystallize when annealed at 573 K (300 °C) but appears to recrystallize continuously during deformation at such a temperature and the resulting fine grain structure deforms with minimal cavitation. At temperatures above the Mg-solvus, e.g., 673 K (400 °C), recrystallization and growth occur readily resulting in rela tively coarser structures which deform superplastically but with extensive grain boundary sliding and cavitation.

  16. Mg2+ coordinating dynamics in Mg:ATP fueled motor proteins

    NASA Astrophysics Data System (ADS)

    Bojovschi, A.; Liu, Ming S.; Sadus, Richard J.

    2014-03-01

    The coordination of Mg2+ with the triphosphate group of adenosine triphosphate (ATP) in motor proteins is investigated using data mining and molecular dynamics. The possible coordination structures available from crystal data for actin, myosin, RNA polymerase, DNA polymerase, DNA helicase, and F1-ATPase are verified and investigated further by molecular dynamics. Coordination states are evaluated using structural analysis and quantified by radial distribution functions, coordination numbers, and pair interaction energy calculations. The results reveal a diverse range of both transitory and stable coordination arrangements between Mg2+ and ATP. The two most stable coordinating states occur when Mg2+ coordinates two or three oxygens from the triphosphate group of ATP. Evidence for five-site coordination is also reported involving water in addition to the triphosphate group. The stable states correspond to a pair interaction energy of either ˜-2750 kJ/mol or -3500 kJ/mol. The role of water molecules in the hydration shell surrounding Mg2+ is also reported.

  17. Effects of MgO and Mg(OH)2 on Phase Formation and Properties of MgTiO3 Microwave Dielectric Ceramics

    NASA Astrophysics Data System (ADS)

    Liou, Yi-Cheng; Yang, Song-Ling; Chu, Sheng-Yuan

    2015-04-01

    This study investigates the effects of MgO and Mg(OH)2 on the phase formation and properties of MgTiO3 ceramics prepared via a reaction-sintering process. A mixture of raw materials was sintered into MgTiO3 ceramics by bypassing calcination and subsequent pulverization stages. The second phase MgTi2O5 forms in pellets with added MgO (MT) and disappears in pellets with added Mg(OH)2 (MHT). Abnormal grain growth is observed in MHT due to different reactions during the heating process. Microwave dielectric properties ɛ r = 18.5-19.2, Q × f = 53,300-76,300 GHz and τ f = -58.7 to -53.2 ppm/°C are measured for MT. ɛ r = 15.3-15.9, Q × f = 118,800-144,400 GHz and τ f = -52.8 to -49.8 ppm/°C are measured for MHT. The lower ɛ r for MHT is caused by a lower density. Q × f increases and τ f shifts to less negative values when Mg(OH)2 is used instead of MgO. The reaction-sintering process is then a simple and effective method to produce MgTiO3 ceramics for applications in microwave dielectric resonators.

  18. Report on the sintering and properties of MgO and MgO-5% TiC

    SciTech Connect

    Bengisu, M.; Inal, O.T.

    1992-07-01

    Sintering of technical grade MgO yields higher fractional densities compared to pure MgO. TiC reacts with MgO under sintering of MgO-TiC composites in air, yielding Mg{sub 2}TiO{sub 4} and CO or CO{sub 2}. This can be suppressed in vacuum by plasma sintering. Plasma sintering of MgO at 1300 C and short times does not produce satisfactory results. 5 vol% TiC increases the sinterability of MgO during conventional air sintering; larger additions (50 vol%) decrease sinterability due to macropores formed by gaseous reaction product. Microwave sintering of MgO is possible. Mechanical properties of MgO are improved by additions of small amounts of TiC to starting powders.

  19. A fundamental study on the [(μ-Cl)3 Mg2 (THF)6 ]+ dimer electrolytes for rechargeable Mg batteries

    DOE PAGESBeta

    Liu, Tianbiao; Cox, Jonathan T.; Hu, Dehong; Deng, Xuchu; Hu, Jianzhi; Hu, Mary Y.; Xiao, Jie; Shao, Yuyan; Tang, Keqi; Liu, Jun

    2015-01-05

    We present a fundamental study on [(μ-Cl)3 Mg2 (THF)6 ]+ dimer electrolytes using various physical methods including Subambient Pressure Ionization with Nanoelectrospray Mass spectrometry (SPIN-MS), Raman spectroscopy, 25Mg{1H} NMR, 27Al{1H} NMR and electrochemical analysis. For the first time, long time sought THF solvated [MgCl]+ species was experimentally characterized by SPIN mass spectrometry in the solution of the Mgdimer containing electrolyte, confirming the mono-Cl- abstraction reaction between MgCl2 and an Al Lewis acid. Solvated MgCl2 in the electrolyte was confirmed by Raman spectroscopy. The experimental results establish the previously proposed dimerization equilibrium of solvated [MgCl]+ and MgCl2 with [(μ-Cl)3Mg2(THF)6]+.more » 25Mg{1H} NMR, 27Al{1H} NMR and electrochemical analysis on chloration reaction of [(μ-Cl)3Mg2(THF)6]AlPh3Cl with external Cl- led to further insights on the coordination chemistry of the dimer electrolyte. Finally, a comprehensive mechanism is proposed for the reversible electrochemical Mg deposition and stripping and Mg2+ and Cl- ion transports of the Mg dimer electrolytes in rechargeable Mg batteries.« less

  20. The effect of Mg location on Co-Mg-Ru/γ-Al2O3 Fischer–Tropsch catalysts

    PubMed Central

    Combes, Gary B.; Ozkaya, Don; Enache, Dan I.; Ellis, Peter R.; Kelly, Gordon; Rosseinsky, Matthew J.

    2016-01-01

    The effectiveness of Mg as a promoter of Co-Ru/γ-Al2O3 Fischer–Tropsch catalysts depends on how and when the Mg is added. When the Mg is impregnated into the support before the Co and Ru addition, some Mg is incorporated into the support in the form of MgxAl2O3+x if the material is calcined at 550°C or 800°C after the impregnation, while the remainder is present as amorphous MgO/MgCO3 phases. After subsequent Co-Ru impregnation MgxCo3−xO4 is formed which decomposes on reduction, leading to Co(0) particles intimately mixed with Mg, as shown by high-resolution transmission electron microscopy. The process of impregnating Co into an Mg-modified support results in dissolution of the amorphous Mg, and it is this Mg which is then incorporated into MgxCo3−xO4. Acid washing or higher temperature calcination after Mg impregnation can remove most of this amorphous Mg, resulting in lower values of x in MgxCo3−xO4. Catalytic testing of these materials reveals that Mg incorporation into the Co oxide phase is severely detrimental to the site-time yield, while Mg incorporation into the support may provide some enhancement of activity at high temperature. PMID:26755760

  1. The effect of Mg location on Co-Mg-Ru/γ-Al2O3 Fischer-Tropsch catalysts.

    PubMed

    Gallagher, James R; Boldrin, Paul; Combes, Gary B; Ozkaya, Don; Enache, Dan I; Ellis, Peter R; Kelly, Gordon; Claridge, John B; Rosseinsky, Matthew J

    2016-02-28

    The effectiveness of Mg as a promoter of Co-Ru/γ-Al2O3 Fischer-Tropsch catalysts depends on how and when the Mg is added. When the Mg is impregnated into the support before the Co and Ru addition, some Mg is incorporated into the support in the form of MgxAl2O3+x if the material is calcined at 550°C or 800°C after the impregnation, while the remainder is present as amorphous MgO/MgCO3 phases. After subsequent Co-Ru impregnation MgxCo3-xO4 is formed which decomposes on reduction, leading to Co(0) particles intimately mixed with Mg, as shown by high-resolution transmission electron microscopy. The process of impregnating Co into an Mg-modified support results in dissolution of the amorphous Mg, and it is this Mg which is then incorporated into MgxCo3-xO4. Acid washing or higher temperature calcination after Mg impregnation can remove most of this amorphous Mg, resulting in lower values of x in MgxCo3-xO4. Catalytic testing of these materials reveals that Mg incorporation into the Co oxide phase is severely detrimental to the site-time yield, while Mg incorporation into the support may provide some enhancement of activity at high temperature. PMID:26755760

  2. A Fundamental Study on the [(μ-Cl)3Mg2(THF)6]+ Dimer Electrolytes for Rechargeable Mg Batteries

    SciTech Connect

    Liu, Tianbiao L.; Cox, Jonathan T.; Hu, Dehong; Deng, Xuchu; Hu, Jian Z.; Hu, Mary Y.; Xiao, Jie; Shao, Yuyan; Tang, Keqi; Liu, Jun

    2015-01-01

    We present a fundamental study on [(μ-Cl)3Mg2(THF)6]+dimer electrolytes using various physical methods including Subambient Pressure Ionization with Nanoelectrospray Mass spectrometry (SPIN-MS), Raman spectroscopy, 25Mg{1H} NMR, 27Al{1H} NMR and electrochemical analysis. For the first time, long time sought THF solvated [MgCl]+ species was experimentally characterized by SPIN mass spectrometry in the solution of the Mgdimer containing electrolyte, confirming the mono-Cl- abstraction reaction between MgCl2 and an Al Lewis acid. Solvated MgCl2 in the electrolyte was confirmed by Raman spectroscopy. The experimental results establish the previously proposed dimerization equilibrium of solvated [MgCl]+ and MgCl2 with [(μ-Cl)3Mg2(THF)6]+. 25Mg{1H} NMR, 27Al{1H} NMR and electrochemical analysis on chloration reaction of [(μ-Cl)3Mg2(THF)6]AlPh3Cl with external Cl- led to further insights on the coordination chemistry of the dimer electrolyte. Finally, a comprehensive mechanism is proposed for the reversible electrochemical Mg deposition and stripping and Mg2+ and Cl- ion transports of the Mg dimer electrolytes in rechargeable Mg batteries.

  3. Mg Isotopes of the Late Permian Evaporites, New Mexico, USA

    NASA Astrophysics Data System (ADS)

    Feng, C.; Gao, C. H.; Chang, S. C.

    2015-12-01

    Mg isotope holds promise to decipher the evaporative environment of evaporites. High-precision Mg isotope compositions of the late Permian langbeinites have been measured by using MC-ICPMS. The equilibrium Mg isotope fractionation factor between langbeinite and aqueous Mg2+ solutions has been determined using quantum chemistry calculations. All computations are employed at B3LYP/6-311++G(2d,2p) level and solvation effects are treated by solvent model ("water-droplet" approach), mineral structures are constructed using volume variable cluster models (VVCM). The Mg isotope compositions of the langbeinite samples, whose total formation thickness ranges up to 100 meters, are extremely isotopically lighter than that of modern seawater and relatively homogeneous (δ26MgDSM3 is from -4.12±0.03‰ to -3.81±0.07‰ v.s. -0.83‰ of modern seawater). The computed equilibrium Mg isotope fractionation factors between langbeinite and aqueous Mg2+ solutions are -2.73‰, -2.66‰ and -2.53‰ at 25, 30 and 40 ℃, respectively. These significant equilibrium fractionation factors indicate that a huge equilibrium Mg isotope fractionation between langbeinite and its parent brine can happen during langbeinite depositions, and langbeinites are enriched in isotopically light 24Mg comparing to the brine. Using the computed fractionation factors to simulate a Rayleigh fractionation process of langbeinite Mg precipitation, we find that a significant Mg isotope difference between langbeinite and its growing brine (seawater) is indeed present but the Mg isotope composition of langbeinite merely increase monotonically in a closed system. Because of that, the homogenous Mg isotope compositions of such a thick evaporite sequence suggest a disequlibrium effect rather than an equilibrium Mg isotope fractionation behavior during its formation. Combined with its prevailing Mg-bearing character, the homogenous Mg isotope compositions reveal that this the late Permian langbeinite sequence has

  4. Texture and microstructure in co-sputtered Mg-M-O (M = Mg, Al, Cr, Ti, Zr, and Y) films

    NASA Astrophysics Data System (ADS)

    Saraiva, M.; Depla, D.

    2012-05-01

    Mg-M-O solid solution films (M = Mg, Al, Cr, Ti, Zr, and Y) with various M contents are grown employing reactive co-sputtering by varying the target-to-substrate distance. It is shown that all films are biaxially aligned. When the two cathodes are equipped with the same target material (Mg), the in-plane alignment is determined by the cathode closest to the substrate, i.e., by the largest material flux. In the case of nearly equal material fluxes from the two cathodes, double in-plane orientation is observed. This is also the case for the Mg-Al-O and Mg-Cr-O films, while the Mg-Ti-O, Mg-Zr-O and Mg-Y-O films exhibit single in-plane orientation. Pole figures indicate that the grains in Mg-M-O (M different than Mg) are titled; in the Mg-Al-O, Mg-Cr-O, and Mg-Ti-O films, the grains tilt towards the Al, Cr, and Ti metal flux, respectively, while the grain tilt of the Mg-Zr-O and Mg-Y-O films is found to be towards the Mg metal flux. Furthermore, SEM cross-sectional images of the Mg-M-O films reveal columnar microstructure with columns tilted to the same direction as the grains. A mechanism which is based on the cation radius change upon the incorporation of an M atom in the MgO lattice is proposed to explain the tilting.

  5. The possibility of forming a sacrificial anode coating for Mg

    SciTech Connect

    Dudney, Nancy J; Li, Juchuan; Sacci, Robert L; Thomson, Jeffery K

    2014-01-01

    Mg is the most active engineering metal, and is often used as a sacrificial anode/coating to protect other engineering metals from corrosion attack. So far no sacrificial anode coating has been developed or considered for Mg. This study explores the possibility of forming a sacrificial coating for Mg. A lithiated carbon coating and a metaphosphated coating are applied on the Mg surface, respectively, and their open-circuit-potentials are measured in saturated Mg(OH)2 solution. They exhibit more negative potentials than bare Mg. SEM reveals that the metaphosphated coating offers more effective and uniform protection for Mg than the lithiated carbon coating. These preliminary results indicate that development of a sacrificial anode coating for Mg is indeed possible.

  6. Rotational Band Structure in 32Mg

    NASA Astrophysics Data System (ADS)

    Crawford, Heather; NSCL E11029 Collaboration Team

    2016-03-01

    There is significant evidence supporting the existence of deformed ground states within the neutron-rich N =20 neon, sodium, and magnesium isotopes that make up what is commonly called the ``Island of Inversion''. However, rotational band structures, a characteristic fingerprint of a rigid non-spherical shape, have yet to be observed. We report on a measurement and analysis of the yrast (lowest lying) rotational band in 32Mg up to spin I = 6+, produced in a two-step projectile fragmentation reaction and observed using the state-of-the-art γ-ray tracking detector array, GRETINA. Large-scale shell model calculations using the SDPF-U-MIX effective interaction show excellent agreement with the new data. Moreover, a theoretical analysis of the spectrum of rotational states as a function of the pairing gap, together with cranked shell model calculations, provides intriguing evidence for a reduction in pairing correlations with increased angular momentum, also in line with the shell-model results. This material is based upon work supported by the U.S. DOE, Office of Science, NP Office under Contract No. DE-AC02-05CH11231 (LBNL). GRETINA was funded by the U.S. DOE Office of Science. Operation of the array at NSCL was supported by NSF.

  7. Rotational band structure in 32Mg

    NASA Astrophysics Data System (ADS)

    Crawford, H. L.; Fallon, P.; Macchiavelli, A. O.; Poves, A.; Bader, V. M.; Bazin, D.; Bowry, M.; Campbell, C. M.; Carpenter, M. P.; Clark, R. M.; Cromaz, M.; Gade, A.; Ideguchi, E.; Iwasaki, H.; Langer, C.; Lee, I. Y.; Loelius, C.; Lunderberg, E.; Morse, C.; Richard, A. L.; Rissanen, J.; Smalley, D.; Stroberg, S. R.; Weisshaar, D.; Whitmore, K.; Wiens, A.; Williams, S. J.; Wimmer, K.; Yamamato, T.

    2016-03-01

    There is significant evidence supporting the existence of deformed ground states within the neutron-rich N ≈20 neon, sodium, and magnesium isotopes that make up what is commonly called the "island of inversion." However, the rotational band structures, which are a characteristic fingerprint of a rigid nonspherical shape, have yet to be observed. In this work, we report on a measurement and analysis of the yrast (lowest lying) rotational band in 32Mg up to spin I =6+ produced in a two-step projectile fragmentation reaction and observed using the state-of-the-art γ -ray tracking detector array, GRETINA (γ -ray energy tracking in-beam nuclear array). Large-scale shell-model calculations using the SDPF-U-MIX effective interaction show excellent agreement with the new data. Moreover, a theoretical analysis of the spectrum of rotational states as a function of the pairing gap, together with cranked-shell-model calculations, provides intriguing evidence for a reduction in pairing correlations with increased angular momentum, also in line with the shell-model results.

  8. Fabrication of decorated MgO crystalline fibers

    SciTech Connect

    Chen, Y.J.; Li, J.B.; Han, Y.S.; Yang, X.Z.; Dai, J.H

    2003-02-20

    By depositing Mg vapor generated via carbothermal reduction on boron powder in the presence of different additives, dumbbell-like MgO nanofibers, NaCl particle-decorated MgO nanofibers and camphor tree stalk-like MgO fibers were produced. SEM, TEM and EDS analysis showed that the additives of Si and NaCl deposited in the sites of stacking faults in fiber, which resulted in the growth of different morphologies of decorated fibers.

  9. Transition of interface oxide layer from porous Mg(OH)2 to dense MgO induced by polyaniline and corrosion resistance of Mg alloy therefrom

    NASA Astrophysics Data System (ADS)

    Luo, Yizhong; Sun, Yang; Lv, Jinlong; Wang, Xianhong; Li, Ji; Wang, Fosong

    2015-02-01

    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.

  10. Enhancing phosphate adsorption by Mg/Al layered double hydroxide functionalized biochar with different Mg/Al ratios.

    PubMed

    Li, Ronghua; Wang, Jim J; Zhou, Baoyue; Awasthi, Mukesh Kumar; Ali, Amjad; Zhang, Zengqiang; Gaston, Lewis A; Lahori, Altaf Hussain; Mahar, Amanullah

    2016-07-15

    Mg/Al ratio plays a significant role for anion adsorption by Mg/Al-layered double hydroxides (Mg/Al-LDHs) modified biochar. In this study, Mg/Al-LDHs biochar with different Mg/Al ratios (2, 3, 4) were prepared by co-precipitation for phosphate removal from aqueous solution. Factors on phosphate adsorption including Mg/Al ratio, pH, and the presence of other inorganic anions were investigated through batch experiments. Increasing Mg/Al ratio in the Mg/Al-LDHs biochar composites generally enhanced phosphate adsorption with Langmuir adsorption maximum calculated at 81.83mg phosphorous (P) per gram of 4:1Mg/Al-LDHs biochar at pH3.0. The adsorption process was best described by the pseudo-second-order kinetic model. Solution pH had greater effects on the phosphate adsorption by Mg/Al LDHs biochar composites with lower Mg/Al ratios. The presence of other inorganic anions decreased the phosphate adsorption efficiency in the order of F(-) > SO4(2-) > NO2(-) >Cl(-). Phosphate adsorption mechanism involves ion exchange, electrostatic attraction and surface inner-sphere complex formation. Overall, Mg/Al-LDHs biochar composites offer a potential alternative of carbon-based adsorbent for phosphate removal from aqueous solution. PMID:27058131

  11. Osteopenic effects of MgSO4 in multiple pregnancies.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To describe the effects of prolonged maternal treatment with MgSO4 in infants who were products of multiple pregnancies. Case series of infants presenting with osteopenia secondary to MgSO4 administration for preterm labor. Ten premature infants with hypermagnesemia (4.5+/-0.2 mg/dl), hypocalcemia (...

  12. Mg-lattice associations in red coralline algae

    NASA Astrophysics Data System (ADS)

    Kamenos, N. A.; Cusack, M.; Huthwelker, T.; Lagarde, P.; Scheibling, R. E.

    2009-04-01

    Recent investigations have shown red coralline algae to record ambient temperature in their calcite skeletons. Temperature recorded by variation in Mg concentrations within algal growth bands has sub-annual resolution and high accuracy. The conversion of Mg concentration to temperature is based on the assumption of Ca replacement by Mg within the algal calcite skeleton at higher temperatures. While Mg-temperature relationships in coralline algae have been calibrated for some species, the location of Mg within the calcite lattice remains unknown. Critically, if Mg is not a lattice component but associated with organic components this could lead to erroneous temperature records. Before coralline algae are used in large scale climate reconstructions it is therefore important to determine the location of Mg. Synchrotron Mg-X-ray absorbance near edge structure (XANES) indicates that Mg is associated with the calcite lattice in Lithothamnion glaciale (contemporary free-living, contemporary encrusting and sub-fossil free-living) and Phymatolithon calcareum (contemporary free-living) coralline algae. Mg is deposited within the calcite lattice in all seasons ( L. glaciale & P. calcareum) and thallus areas ( P. calcareum). These results suggest L. glaciale and P. calcareum are robust Mg-palaeotemperature proxies. We suggest that similar confirmation be obtained for Mg associations in other species of red coralline algae aiding our understanding of their role in climate reconstruction at large spatial scales.

  13. Mg-lattice associations in red coralline algae

    NASA Astrophysics Data System (ADS)

    Kamenos, N. A.; Cusack, M.,; Huthwelker, T.; Lagarde, P.; Scheibling, R. E.

    2009-04-01

    Recent investigations have shown red coralline algae to record ambient temperature in their calcite skeletons. Temperature recorded by variation in Mg concentrations within algal growth bands has sub-annual resolution and high accuracy. The conversion of Mg concentration to temperature is based on the assumption of Ca replacement by Mg within the algal calcite skeleton at higher temperatures. While Mg-temperature relationships in coralline algae have been calibrated for some species, the location of Mg within the calcite lattice remains unknown. Critically, if Mg is not a lattice component but associated with organic components this could lead to erroneous temperature records. Before coralline algae are used in large scale climate reconstructions it is therefore important to determine the location of Mg. Synchrotron Mg-X-ray absorbance near edge structure (XANES) indicates that Mg is associated with the calcite lattice in Lithothamnion glaciale (contemporary free-living, contemporary encrusting and sub-fossil free-living) and Phymatolithon calcareum (contemporary free-living) coralline algae. Mg is deposited within the calcite lattice in all seasons (L. glaciale & P. calcareum) and thallus areas (P. calcareum). These results suggest L. glaciale and P. calcareum are robust Mg-palaeotemperature proxies. We suggest that similar confirmation be obtained for Mg associations in other species of red coralline algae aiding our understanding of their role in climate reconstruction at large spatial scales.

  14. LOW Mg/Si PLANETARY HOST STARS AND THEIR Mg-DEPLETED TERRESTRIAL PLANETS

    SciTech Connect

    Carter-Bond, Jade C.; O'Brien, David P.; Delgado Mena, Elisa; Israelian, Garik; Gonzalez Hernandez, Jonay I.; Santos, Nuno C.

    2012-03-15

    Simulations have shown that a diverse range of extrasolar terrestrial planet bulk compositions are likely to exist based on the observed variations in host star elemental abundances. Based on recent studies, it is expected that a significant proportion of host stars may have Mg/Si ratios below 1. Here we examine this previously neglected group of systems. Planets simulated as forming within these systems are found to be Mg-depleted (compared to Earth), consisting of silicate species such as pyroxene and various feldspars. Planetary carbon abundances also vary in accordance with the host star C/O ratio. The predicted abundances are in keeping with observations of polluted white dwarfs, lending validity to this approach. Further studies are required to determine the full planetary impacts of the bulk compositions predicted here.

  15. Room-temperature perpendicular magnetic anisotropy of MgO/Fe/MgO ultrathin films

    SciTech Connect

    Kozioł-Rachwał, A.; Ślęzak, T.; Przewoźnik, J.; Skowroński, W.; Stobiecki, T.; Wilgocka-Ślęzak, D.; Qin, Q. H.; Dijken, S. van; Korecki, J.

    2013-12-14

    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}.

  16. The dependence of Raman scattering on Mg concentration in Mg-doped GaN grown by MBE

    NASA Astrophysics Data System (ADS)

    Flynn, Chris; Lee, William

    2014-04-01

    Magnesium-doped GaN (GaN:Mg) films having Mg concentrations in the range 5 × 1018-5 × 1020 cm-3 were fabricated by molecular beam epitaxy. Raman spectroscopy was employed to study the effects of Mg incorporation on the positions of the E2 and A1(LO) lines identifiable in the Raman spectra. For Mg concentrations in excess of 2 × 1019 cm-3, increases in the Mg concentration shift both lines to higher wave numbers. The shifts of the Raman lines reveal a trend towards compressive stress induced by incorporation of Mg into the GaN films. The observed correlation between the Mg concentration and the Raman line positions establish Raman spectroscopy as a useful tool for optimizing growth of Mg-doped GaN.

  17. Solid Solution Effects on the MgAl2O4-MgGa2O4 System

    SciTech Connect

    O'Hara, Kelley; Smith, Jeffrey D; Hemrick, James Gordon

    2009-01-01

    Phase relations between two spinel compounds (MgAl2O4 and MgGa2O4) were studied. Stoichiometric MgAl2O4 was formed in the laboratory through a coprecipitation method. Complete solid solution formation int eh MgAl2O4-MgGa2O4 systems was confirmed through X-ray diffraction analysis. Solid solution between MgAl2O4-MgGa2O4 decreases thermal conductivity at all temperatures up to 900oC. At 200oC with 10 mol% additoin of MgGa2O4 thermal conductivity decreases approximately 25%, and at 900oC there was still an 8% decrease. Additionally, preliminary studies show that porosity between 5% and 10% does not have an appreciable effect on the thermal conductivity in this study.

  18. Impact of Mg Content on (Mg,Zn)O Native Point Defects

    NASA Astrophysics Data System (ADS)

    Ball, Molly; Restrepo, Oscar; Brillson, Leonard; Windl, Wolfgang; Department of Material Science; Engineering Collaboration; Department of Physics Collaboration

    2015-03-01

    The two most thermodynamically stable defects in ZnO are oxygen vacancies (VO) and zinc vacancies (VZn) . These native point defects are electrically charged and can contribute to free carrier densities. Experiment shows that Mg addition to ZnO significantly changes native defect densities. To better understand this dramatic decrease in VZn and VO-related defects with increasing Mg content up to x =0.44 and the subsequent increase, we performed density functional theory (DFT) calculations using PAW potentials within PBE using VASP. The results showed to be very sensitive to DFT method used and chemical-potential calculation. For the latter, the literature shows that one can assume that the oxygen chemical potential equals that of the atoms in the oxygen molecules at a given surrounding partial oxygen pressure. However, one can also postulate that the total defect concentrations conserve the stoichiometry, or limiting potentials from elemental equilibrium phases can be used. The experimentally observed dependence helped identify the correct way to reproduce the experimental dependence of formation energy on Mg concentration, which will be discussed in detail in this presentation.

  19. Formation and stability of hollow MgO nanoshells.

    PubMed

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

    2010-07-01

    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 facets, which is followed by nanoshell size reduction and collapse within a few minutes. However, in ambient conditions the nanoshells remain stable for significant periods of time and further degrade by becoming filled with carbon while lossing any MgO identity. Finally, in moderate low vacuum they remained stable for months indicating promise for applications. PMID:21128428

  20. A Computational Investigation of Precipitates in Mg-RE Alloys With Applications To Mg-X Systems

    NASA Astrophysics Data System (ADS)

    Issa, Ahmed

    Increasing fuel efficiency in transportation vehicles is a major policy goal for both government and auto and aerospace manufacturers. Lightweight structural materials, such as magnesium alloys, hold great promise in enabling such fuel efficiency gains. Understanding the controlling factors in Mg alloy strengthening is crucial for the rational design of structurally strong and inexpensive Mg alloys. In this work, we seek to understand the energetic underpinnings giving rise to a class of remarkably strong Mg alloys: Mg-RE systems. We use first-principles methods to efficiently explore seventeen Mg-RE systems, drawing out broad patterns and distilling our knowledge into simple design rules for Mg alloys. We begin by investigating the controlling factors for the Mg-strengthening prismatic plate precipitates in Mg-RE systems, discovering the critical role of strain in such systems. We then proceed to investigate the surprising role of interfacial energies in determining the course of the Mg-RE precipitation reactions. Using strain and interfacial energies, we construct a phase-field model which accurately depicts the precipitate morphology as a function of time and size in a Mg-Nd system. Finally, we combine our gained insights to implement a computational alloy design scheme on a large portion of the periodic table where we seek Mg-strengthening solutes. Our work advances the understanding of strengthening in Mg alloys and lays the groundwork for full scale computational alloy design.

  1. The Strength of the Spatially Interconnected Eutectic Network in HPDC Mg-La, Mg-Nd, and Mg-La-Nd Alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Bao; Gavras, Serge; Nagasekhar, Anumalasetty V.; Cáceres, Carlos Horacio; Easton, Mark A.

    2014-09-01

    3D numerical images of the intergranular percolating eutectic of two binary alloys, Mg-0.62 at. pctLa and Mg-0.60 at. pctNd, created using dual beam FIB tomography, were incorporated into an FEM code to model their tensile behavior. Due to its high volume fraction (29.9 pct), the behavior of the Mg-La network was akin to that of a stretch-dominated micro-truss structure, whereas the Mg-Nd's, with a relatively low volume fraction (7.5 pct), mimicked that of a bending-dominated structure. The 3D network contributed some 37 MPa to the strength of the Mg-La alloy casting, whereas it only added about 1.4 MPa to the Mg-Nd's. The model predictions based on the binary alloys were verified using cast-to-shape specimens of the Mg-La and two ternary Mg-La-Nd alloys, subjected to a flash-annealing aiming at breaking up the continuity of the 3D network, while preserving the rest of the microstructure unchanged. The flash-annealed specimens exhibited a decrease in strength that matched closely the computed values. Implications regarding alloy design involving the eutectic network and solid solution hardening of more complex alloys are discussed.

  2. Mg segregation in Mg-rich Mg-Ni switchable mirror studied by Rutherford backscattering, elastic recoil detection analysis, and nuclear reaction analysis

    SciTech Connect

    Sekiba, D.; Horikoshi, M.; Abe, S.; Ishii, S.

    2009-12-01

    Pd/Mg{sub 3.3}Ni films were prepared by dc sputtering deposition on three different substrates of glass, diamondlike carbon/Si, and Si. Hydrogenation and dehydrogenation cycles were performed on these samples simultaneously. The optical switching property due to the hydrogenation and dehydrogenation was monitored by the transmission of laser light via the glass substrate. The switching ability was totally lost after 120 cycles. We made comparative study of the composition change between the new (as-deposited) and old (after 120 switching cycles) samples by Rutherford backscattering (RBS), elastic recoil detection analysis (ERDA), and nuclear reaction analysis (NRA). From the RBS results we found out the segregation of a Mg layer between the Pd cap layer and the rest of the Mg-Ni layer. At the Pd/Mg interface in the old sample, thin MgO layer formed probably during the dehydrogenation process with O{sub 2}. ERDA showed that there is much hydrogen in the old sample. NRA displayed the depth profiles of hydrogen distribution in the old sample. It is revealed that much hydrogen is accumulated at the interface between the Pd cap layer and the segregated Mg layer. It can be concluded that the formations of oxide and hydride of the segregated Mg layer are the main reasons for the degradation of the Mg{sub 3.3}Ni switchable mirror.

  3. The Mg isotopic composition of Cenozoic seawater - evidence for a link between Mg-clays, seawater Mg/Ca, and climate

    NASA Astrophysics Data System (ADS)

    Higgins, John A.; Schrag, Daniel P.

    2015-04-01

    Cooling of Earth's climate over the Cenozoic has been accompanied by large changes in the magnesium and calcium content of seawater whose origins remain enigmatic. The processes that control these changes affect the magnesium isotopic composition of seawater, rendering it a useful tool for elucidating the processes that control seawater chemistry on geologic timescales. Here we present a Cenozoic magnesium isotope record of carbonate sediments and use a numerical model of seawater chemistry and the carbon cycle to test hypotheses for the covariation between Cenozoic seawater chemistry and climate. Records are consistent with a 2-3× increase in seawater Mg/Ca and little change in the Mg isotopic composition of seawater. These observations are best explained by a change in the cycling of Mg-silicates. We propose that Mg/Ca changes were caused by a reduction in removal of Mg from seawater in low-temperature marine clays, though an increase in the weathering of Mg-silicates cannot be excluded. We attribute the reduction in the Mg sink in marine clays to changes in ocean temperature, directly linking the major element chemistry of seawater to global climate and providing a novel explanation for the covariation of seawater Mg/Ca and climate over the Cenozoic.

  4. Diffusion Couple Investigation of the Mg-Zn System

    SciTech Connect

    Brennan, Sarah; Bermudez, Katrina; Sohn, Yong Ho; Kulkarni, Nagraj S

    2012-01-01

    Phase layer growth and interdiffusion in the binary Mg-Zn system was investigated utilizing solid-to-solid diffusion couples annealed at 295 , 315 and 325 C for 21, 7 and 5 days, respectively. The diffusion microstructure was examined by scanning electron microscopy and concentration profiles were determined using X-ray energy dispersive spectroscopy and electron microprobe analysis. The Mg solid solution, Mg2Zn11, MgZn2 and Mg2Zn3 in all three couples were observed in addition to the high temperature, Mg51Zn20 phase at 325 C. The MgZn2 phase was observed to grow the thickest layer, followed by the Mg2Zn3 and the Mg2Zn11 phases. Activation energies for the parabolic growth were calculated to be 105 kJ/mol and 207 kJ/mol for the Mg2Zn3 and MgZn2, respectively. Relevant interdiffusion coefficients were calculated for the phases present by analyses of concentration profiles. This study was sponsored by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program (DE-AC05-00OR22725).

  5. Energy band bowing parameter in MgZnO alloys

    SciTech Connect

    Wang, Xu; Saito, Katsuhiko; Tanaka, Tooru; Nishio, Mitsuhiro; Guo, Qixin; Nagaoka, Takashi; Arita, Makoto

    2015-07-13

    We report on bandgap bowing parameters for wurtzite and cubic MgZnO alloys from a study of high quality and single phase films in all Mg content range. The Mg contents in the MgZnO films were accurately determined using the energy dispersive spectrometer and X-ray photoelectron spectroscopy (XPS). The measurement of bandgap energies by examining the onset of inelastic energy loss in core-level atomic spectra from XPS is proved to be valid for determining the bandgap of MgZnO films. The dependence of the energy bandgap on Mg content is found to deviate downwards from linearity. Fitting of the bandgap data resulted in two bowing parameters of 2.01 ± 0.04 eV and 1.48 ± 0.11 eV corresponding to wurtzite and cubic MgZnO films, respectively.

  6. Mechanical Properties of High Strength Al-Mg Alloy Sheet

    NASA Astrophysics Data System (ADS)

    Choi, Bong-Jae; Hong, Kyung-Eui; Kim, Young-Jig

    The aim of this research is to develop the high strength Al alloy sheet for the automotive body. For the fabrication Al-Mg alloy sheet, the composition of alloying elements was designed by the properties database and CALPHAD (Calculation Phase Diagram) approach which can predict the phases during solidification using thermodynamic database. Al-Mg alloys were designed using CALPHAD approach according to the high content of Mg with minor alloying elements. After phase predictions by CALPHAD, designed Al-Mg alloys were manufactured. Addition of Mg in Al melts were protected by dry air/Sulphur hexafluoride (SF6) mixture gas which can control the severe Mg ignition and oxidation. After rolling procedure of manufactured Al-Mg alloys, mechanical properties were examined with the variation of the heat treatment conditions.

  7. Transformation of echinoid Mg calcite skeletons by heating

    NASA Astrophysics Data System (ADS)

    Dickson, J. A. D.

    2001-02-01

    Interambularcral plates of echinoid Heterocentrotus trigonarius, composed of Mg calcite 1 (≈14 mol% MgCO 3), were heated in three timed series of experiments at 300°C. Dried plate fragments and fragments with added water were heated separately in pressurized bombs. X-ray powder diffractometry, unit cell dimensions, and phase compositions are used to monitor reaction progress. After 10 h heating in the bombs dolomite (43.5 mol% MgCO 3) and Mg calcite appear (4-7 mol% MgCO 3); by 20 h all Mg calcite 1 is consumed, and at 120 h dolomite composition has evolved to ≈47 mol% MgCO 3 and calcite to ≈2 mol% MgCO 3. Whole plates heated at 300°C in an open muffle furnace develop dolomite (≈42 mol% MgCO 3) and Mg calcite 2 (≈6 mol% MgCO 3) after 10 h and remain compositionally invariant throughout subsequent heating to 620 h. Limited skeletal water catalyzes the early reaction but escapes from the open furnace and consequently reaction ceases after ≈10 h. The experimentally produced dolomite has relative Mg-Ca ordering of 75% to 79%. The stabilization of echinoid Mg calcite by heating at 300°C to a mixture of dolomite and calcite occurs through a dissolution/precipitation reaction. The alteration fabric produced within the stereom consists of irregularly shaped, branched dolomite crystals > 5 μm homoaxially set in a calcite 2 (bomb) or Mg calcite 2 (furnace) matrix. Round and tubular pores 1 to 5 μm are randomly distributed throughout this fabric. The stereom pore system remains intact during furnace heating but is destroyed during heating in bombs. The texture of experimentally stabilized echinoid skeletons is different from that of fossil echinoderms that are composed of microrhomic dolomite homoaxially set in a single calcite crystal.

  8. Formation and Thermodynamics of Mg-Al-Ti-O Complex Inclusions in Mg-Al-Ti-Deoxidized Steel

    NASA Astrophysics Data System (ADS)

    Ren, Ying; Zhang, Lifeng; Yang, Wen; Duan, Haojian

    2014-12-01

    The formation of Mg-Al-Ti-O complex inclusions in steel was investigated by laboratory experiments and thermodynamic calculation. The composition evolutions of Mg-Al-Ti-O inclusions in steel with different contents of [Al], [Mg], and [Ti] were discussed. Mg-Al-Ti-O complex inclusion with high TiOx content was liquid at 1873 K (1600 °C), indicating MgAl2O4 spinel inclusions can be modified to low melting temperature ones by combining TiOx component. The stability diagram of Al-Mg-Ti-O system inclusions in the molten steel at 1873 K (1600 °C) was calculated, considering many kinds of oxide inclusions such as MgO, Al2O3, TiOx, MgTi2O4, MgAl2O4, Al2TiO5, and liquid inclusion. The thermodynamic calculations are in good agreement with experimental results, which can predict the formation of Al-Mg-Ti-O complex inclusions in molten steel with a large concentration range of [Al], [Mg], and [Ti].

  9. Structural and optical properties of ZnMgO nanostructures formed by Mg in-diffused ZnO nanowires

    SciTech Connect

    Pan, C.-J.; Hsu, H.-C.; Cheng, H.-M.; Wu, C.-Y.; Hsieh, W.-F.

    2007-04-15

    ZnMgO nanostructures with wurtzite phase were prepared by thermal diffusion of Mg into the ZnO nanowires. As ZnO light-emitting devices have been operated by using ZnMgO layers as energy barrier layers to confine the carriers, it is essential to realize the characterization of ZnMgO particularly. In this work, the Mg content in Zn{sub 1} {sub -x} Mg {sub x} O alloy determined by X-ray diffraction (XRD) and photoluminescence (PL) shows a good coincidence. The variation of lattice constant and the blueshift of near-band-edge emission indicate that Zn{sup 2+} ions are successfully substituted by Mg{sup 2+} ions in the ZnO lattice. In Raman-scattering studies, the change of E {sub 2}(high) phonon line shape in ZnO:Mg nanostructures reveals the microscopic substitutional disorder. In addition to the host phonons of ZnO, two additional bands around 383 and 510 cm{sup -1} are presumably attributed to the Mg-related vibrational modes. - Graphical abstract: We reported the synthesis of the ZnMgO nanostructures prepared by a simple vapor transport method. Magnesium-related anomalous modes are observed by Raman spectra for the first time in ZnMgO system.

  10. Interdiffusion and Intrinsic Diffusion in the Mg-Al System

    SciTech Connect

    Brennan, Sarah; Bermudez, Katrina; Sohn, Yong Ho; Kulkarni, Nagraj S

    2012-01-01

    Solid-to-solid diffusion couples were assembled and annealed to examine the diffusion between pure Mg (99.96%) and Al (99.999%). Diffusion anneals were carried out at 300 , 350 , and 400 C for 720, 360, and 240 hours, respectively. Optical and scanning electron microscopes were utilized to identify the formation of the intermetallic phases, -Al12Mg17 and -Al3Mg2 and absence of the -phase in the diffusion couples. Thicknesses of the -Al12Mg17 and -Al3Mg2 phases were measured and the parabolic growth constants were calculated to determine the activation energies for the growth, 165 and 86 KJ/mole, respectively. Concentration profiles were determined with electron microprobe analysis using pure elemental standards. Composition-dependent interdiffusion coefficients in Mg-solid solution, -Al12Mg17 and - Al3Mg2 and Al-solid solutions were calculated based on the Boltzmann-Matano analysis. Average effective interdiffusion coefficients for each phase were also calculated, and the magnitude was the highest for the -Al3Mg2 phase, followed by -Al12Mg17, Al-solid solution and Mg-solid solution. Intrinsic diffusion coefficients based on Huemann s analysis (e.g., marker plane) were determined for the ~38 at.% Mg in the -Al3Mg2 phase. Activation energies and the pre-exponential factors for the inter- and intrinsic diffusion coefficients were calculated for the temperature range examined. The -Al3Mg2 phase was found to have the lowest activation energies for growth and interdiffusion among all four phases studied. At the marker location in the -Al3Mg2 phase, the intrinsic diffusion of Al was found to be faster than that of Mg. Extrapolations of the impurity diffusion coefficients in the terminal solid solutions were made and compared to the available self- and impurity diffusion data from literature. Thermodynamic factor, tracer diffusion coefficients and atomic mobilities at the marker plane composition were approximated using available literature values of Mg activity in the -Al

  11. Dual-color ultraviolet photodetector based on mixed-phase-MgZnO/i-MgO/p-Si double heterojunction

    NASA Astrophysics Data System (ADS)

    Xie, X. H.; Zhang, Z. Z.; Shan, C. X.; Chen, H. Y.; Shen, D. Z.

    2012-08-01

    We report a dual-color ultraviolet (UV) photodetector based on mixed-phase-MgZnO/i-MgO/p-Si double heterojunction. The device exhibits distinct dominant responses at solar blind (250 nm) and visible blind (around 330 nm) UV regions under different reverse biases. By using the energy band diagram of the structure, it is found that the bias-tunable two-color detection is originated from different valence band offset between cubic MgZnO/MgO and hexagonal MgZnO/MgO. Meanwhile, due to the large conduction band offset at the Si/MgO interface, the visible-light photoresponse from Si substrate is suppressed.

  12. MgO platelets and high critical field in MgB2 thin films doped with carbon from methane

    NASA Astrophysics Data System (ADS)

    Zhu, Y.; Hunte, F.; Zhuang, C. G.; Feng, Q. R.; Gan, Z. Z.; Xi, X. X.; Larbalestier, D. C.; Voyles, P. M.

    2009-12-01

    We report that C-doped MgB2 thin films deposited by hybrid physical-chemical vapor deposition (HPCVD) using CH4 as the carbon source have Hc2(0 K)~60 T, similar to that of HPCVD films obtained using (MeCp)2Mg for the carbon. Using transmission electron microscopy, we show that in the films doped using CH4 there is a MgB2C2 layer on top of the MgB2 film, which does not degrade the MgB2 connectivity or Jc. We also find a high density of coherent MgO nanoplatelets in the MgB2 which create strain fields which may give rise to strong π-band scattering and the very high Hc2.

  13. Magnesium and cadmium containing Heusler phases REPd2Mg, REPd2Cd, REAg2Mg, REAu2Mg and REAu2Cd

    NASA Astrophysics Data System (ADS)

    Johnscher, Michael; Stein, Sebastian; Niehaus, Oliver; Benndorf, Christopher; Heletta, Lukas; Kersting, Marcel; Höting, Christoph; Eckert, Hellmut; Pöttgen, Rainer

    2016-02-01

    Twenty-eight new Heusler phases REPd2Mg, REPd2Cd, REAg2Mg, REAu2Mg and REAu2Cd with different rare earth elements were synthesized from the elements in sealed niobium ampoules in a water-cooled sample chamber of an induction furnace. The samples were characterized by powder X-ray diffraction. The cell volumes show the expected lanthanide contraction. The structures of YPd2Cd, GdPd2Cd, GdAu2Cd, Y1.12Ag2Mg0.88 and GdAg2Mg were refined based on single crystal diffractometer data. The magnetic properties were determined for fifteen phase pure samples. LuAu2Mg is a weak Pauli paramagnet with a susceptibility of 1.0(2) × 10-5 emu mol-1 at room temperature. The remaining samples show stable trivalent rare earth ions and most of them order magnetically at low temperatures. The ferromagnet GdAg2Mg shows the highest ordering temperature of TC = 98.3 K. 113Cd and 89Y MAS NMR spectra of YAu2Cd and YPd2Cd confirm the presence of unique crystallographic sites. The resonances are characterized by large Knight shifts, whose magnitude can be correlated with electronegativity trends.

  14. Mg Isotope Fractionation During Hydrothermal Ultramafic Rock Alteration

    NASA Astrophysics Data System (ADS)

    Beinlich, A.; Mavromatis, V.; Austrheim, H.; Oelkers, E. H.

    2013-12-01

    Both riverine and ocean waters are enriched in 24Mg compared to the homogenous chondritic Mg isotopic composition of the Earth's mantle requiring a fractionation step that is generally attributed to low temperature continental crust weathering [1,2,3]. Here we present new observations on the Mg isotope fractionation during hydrothermal alteration of ultramafic rocks from three different localities in Norway, the Linnajavri Ultramafic Complex (LUC), the Feragen Ultramafic Body (FUB), and the Solund Sedimentary Basin (SSB). Mineral separates of coexisting olivine and serpentine from serpentinized peridotite samples from the FUB and SSB exhibit invariant Mg isotope ratios suggesting that serpentinization does not fractionate Mg isotopes. In contrast, antigorite carbonation at the LUC resulted in significant inter-mineral Mg isotope fractionation among the antigorite, magnesite, and talc. The carbonation of the natural samples is constrained by O isotope thermometry at ~275 °C [4] and hence closes the temperature gap between previous investigations of the natural distribution of Mg isotopes during surface weathering and magmatic processes. Textures, mass-balance, and reaction path considerations indicate that antigorite carbonation conserved Mg and Si. The precursor antigorite has an isotopic composition of δ26Mg (DSM3)=-0.11×0.05 ‰, whereas the talc is enriched in 26Mg with mean δ26Mg=0.17×0.08 ‰ and the magnesite is depleted in 26Mg with mean δ26Mg=-0.95×0.15 ‰. This hydrothermal fractionation has significant implications for the Mg isotopic compositions of natural surface waters. Our results suggest that carbonation reactions beneath off-axis low temperature hydrothermal vent sites may exert an important control on the Mg isotope ratio in ocean water. As carbonate minerals dissolve significantly faster than silicate minerals [5,6], the chemical weathering of carbonated ultramafic and by analogy mafic rocks on the continents will yield isotopically

  15. Clustering effects in 48Cr composite nuclei produced via the 24Mg+24Mg reaction

    NASA Astrophysics Data System (ADS)

    Di Nitto, A.; Vardaci, E.; Brondi, A.; La Rana, G.; Cinausero, M.; Gelli, N.; Moro, R.; Nadtochy, P. N.; Prete, G.; Vanzanella, A.

    2016-04-01

    The nuclear properties of 48Cr composite α -like nuclei produced at 60 MeV of excitation energy via the 24Mg+24Mg reaction were investigated. This excitation energy corresponds to a resonance with a narrow width (170 keV) observed in the elastic and inelastic channels, which was interpreted as a highly deformed state. To gain insight on the deformation of this state exclusive measurements of light charged particles were carried out with 8 π LP apparatus at Laboratori Nazionali di Legnaro and compared to statistical model predictions. The measured of α -particle energy spectra, α -evaporation residues, α -α , and α -α -α correlations indicate the limitation of the rotating liquid drop model in describing the nuclear shape of the compound nucleus along the decay cascade. To reproduce the full set of experimental data very elongated nuclear shapes had to be considered, with an axis ratio 3 :1 at the resonance angular momentum. This large deformation is consistent with previous findings for α -like nuclei and with the predictions of the cranked cluster model.

  16. Dihydroxyprogesterone acetophenide 150 mg + estradiol enantate 10 mg as monthly injectable contraceptives.

    PubMed

    Jarquín González, J D; Elda de Aguirre, L; Rodríguez, C; Abrego de Aguilar, M; Carrillo, F; León, D A; Lima, M; Trigueros, S; Acosta, R

    1996-09-01

    A survey among users and health personnel participating in the Salvadorian Social Security Institute (ISSS) Family Planning Program revealed interest in including a monthly preparation for injection as a contraceptive method offered by this Institution. The formulation containing dihydroxyprogesterone acetophenide (DHPA) 150 mg + estradiol enantate (E2EN) 10 mg was chosen for conducting an open and prospective study of efficacy and tolerability. Between January 1992 and March 1994, 7054 women were treated with this product for a total of 60010 months. A sample composed of 4505 women treated at this Institution confirmed that average users are young, have one or two children, do not show a particular geographical distribution and choose the monthly injection instead of oral contraceptives as the first contraceptive method or for the puerperium. The study formulation showed a high efficacy (Pearl Index: 0.018) and tolerability (general withdrawal rate throughout the study: 27.09%). The most frequent adverse events included bleeding disorders, headache and mastalgia; their incidence decreased spontaneously from the sixth month (3.9%), reaching 0% after two years. Treatment was discontinued due to adverse events in 3.47% of women. No significant bodyweight or systolic and diastolic blood pressure alterations were observed. Based on these results, the monthly injectable contraceptive was included in the basic product list at ISSS. PMID:8910663

  17. Magnetoresistance and electronic structure of granular films with MgO or MgF2 matrices

    NASA Astrophysics Data System (ADS)

    Fujiwara, Y.; Matsuda, H.; Sato, K.; Jimbo, M.; Kobayashi, T.

    2011-01-01

    The magneto-transport properties and electronic structures of FeCo-MgO, FeCoB-MgO, FeCo-MgF2 and FeCoB-MgF2 granular films were investigated. From the X-ray photoelectron spectroscopy (XPS) measurements, it was recognized that the oxide layer formed on the surface of granules in FeCo-MgO. Especially Fe oxides were preferentially formed. By using (Fe50Co50)80B20, the formation of Fe oxides on the granule surface was suppressed since B was oxidized instead of Fe. The MR ratio of FeCoB-MgO was approximately 2%. By using MgF2 matrix, the surface states of granules were drastically improved. XPS measurements indicated that an amount of metallic Fe in FeCoB-MgF2 increased compared with FeCoB-MgO. Reflecting the improvement of surface states of granules, a large MR ratio of approximately 6 % was obtained in FeCoB-MgF2.

  18. Enhanced voltage-controlled magnetic anisotropy in magnetic tunnel junctions with an MgO/PZT/MgO tunnel barrier

    NASA Astrophysics Data System (ADS)

    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.

    2016-03-01

    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.

  19. A high resolution atlas of Mg II profiles

    NASA Technical Reports Server (NTRS)

    Ewald, R.; Nichols-Bohlin, Joy Y.; Kondo, Yoji

    1990-01-01

    An atlas of high dispersion Mg II profiles for standard stars of spectral types B0 through G9 is presented. The atlas contains plots of the Mg II profiles for approximately 65 stars and associated equivalent width measurements for both absorption and emission components, and the subordinate lines. The atlas is used to investigate systematic behavior of the Mg II profiles and correlation of the behavior with spectral classification.

  20. Proximity Effect in Nb/Mg/CoFe Trilayers.

    NASA Astrophysics Data System (ADS)

    Choi, Seong Kook; Kwon, Jun Hyung; Char, Kookrin

    2007-03-01

    We have fabricated the Nb/Mg bilayer and Nb/Mg/CoFe trilayer samples by varying Mg layer thickness and measured their superconducting transition temperature Tc electrically using the 4-prove method. Mg normal layer was used to investigate the effect of its small atomic number, since we have observed previously the largely different behavior when Au, Cu and Al were used. When the Al layer was used, a very unusual behavior was found. Because of chemical interaction between Nb and Mg, the Tc transition curves did not show sharp Tc transition. In order to prevent this interaction, we inserted 2 nm thick Al layer between Nb and Mg. In the case of Nb/Al(2nm)/Mg, we observed Tc behavior consistent with a conventional SN theory. In the case of Nb/Al(2nm)/Mg/CoFe with fixed thicknesses of Nb and CoFe layer, the Tc values exhibited two distinct behavior as the thickness of Mg increased. The Tc value of S/N/F trialyer increased rapidly until the Mg thickness reached a few nm. As Mg thickness increased further to 200 nm, the Tc value of S/N/F decreased again, following closely those of the S/N data. Overall, the Mg data basically followed those of Al data, suggesting that the low atomic number of the normal layer is important in observing the unusual proximity effect in SNF trilayers. Our analysis of the interface effect using an Usadel picture will be presented.

  1. Defect structure of ultrafine MgB{sub 2} nanoparticles

    SciTech Connect

    Bateni, Ali; Somer, Mehmet E-mail: msomer@ku.edu.tr; Repp, Sergej; Erdem, Emre E-mail: msomer@ku.edu.tr; Thomann, Ralf; Acar, Selçuk

    2014-11-17

    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.

  2. A determination of Mg(+)-ligand binding energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry

    1991-01-01

    Theoretical calculations employing large basis sets and including correlation are carried out for Mg(+) with methanol, water, and formaldehyde. For Mg(+) with ethanol and acetaldehyde, the trends in the binding energies are studied at the self-consistent-field level. The predictions for the binding energy of Mg(+) to methanol and water of 41 + or - 5 and 36 + or - 5 kcal/mol, respectively, are much less than the experimental upper bounds, of 61 + or - 5 and 60 + or - 5 kcal mol, determined by using photodissociation techniques. The theoretical results are inconsistent with the onset of Mg(+) production observed in the photodissociation experiments, as the smallest absorptions are calculated at about 80 kcal/mol for both Mg(+)-CH3OH and Mg(+)-H2O, and these transitions are to bound excited states. The binding energy for Mg(+) with formaldehyde is predicted to be similar to Mg(+)-H2O. The relative binding energies are in reasonable agreement with experiment. The binding energy of a second water molecule to Mg(+) is predicted to be similar to the first. This suggests that the reduced reaction rate observed for the second ligand is not a consequence of a significantly smaller binding energy, at least for the smaller ligards such as those considered in this work.

  3. Superconducting gap parameters of MgB 2 obtained on MgB 2/Ag and MgB 2/In junctions

    NASA Astrophysics Data System (ADS)

    Plecenik, A.; Beňačka, Š.; Kúš, P.; Grajcar, M.

    2002-03-01

    MgB 2 superconducting wires with the critical temperature Tc approaching 40 K were used for the preparation of MgB 2/Ag and MgB 2/In junctions. The differential conductance vs. voltage characteristics of N-S junctions exhibit a clear contribution of the Andreev reflection. Using a modified BTK theory for s-wave superconductors two order parameters Δdirty≈4 meV and Δ3D≈2.6 meV were determined from the temperature dependencies. Surprisingly, the larger order parameter Δdirty vanishes at a lower temperature T c dirty≈20 K compared with the smaller one Δ3D with Tc≈38 K. Both the magnitudes of the order parameters and their critical temperatures are in good agreement with theoretical calculations of electron-phonon coupling in MgB 2 carried out by Liu et al. [cond-mat/0103570 (2001)].

  4. Solidification Pathways of Alloys in the Mg-Rich Corner of the Mg-Al-Ba Ternary System

    NASA Astrophysics Data System (ADS)

    Bryan, Zachary L.; Hooper, Ryan J.; Henderson, Hunter B.; Manuel, Michele V.

    2015-04-01

    An experimental investigation of the solidification reactions and microstructures of alloys in the Mg-rich corner of the Mg-Al-Ba ternary system has been conducted. Four distinct exothermic reactions involving the formation of α-Mg, Mg17Ba2, Mg17Al12, and a fourth phase designated as τ were observed and their onset temperatures were recorded as functions of composition. Using compositional and microstructural analysis, the Mg17Ba2 intermetallic was found to have significant solubility of Al, up to 20 at. pct. The solidification pathways of the investigated alloys involved both a Class I and Class II equilibrium reaction. A flow block diagram that outlines the observed solidification reactions is presented and discussed in reference to cast microstructures.

  5. Effect of sterilization process on surface characteristics and biocompatibility of pure Mg and MgCa alloys.

    PubMed

    Liu, X L; Zhou, W R; Wu, Y H; Cheng, Y; Zheng, Y F

    2013-10-01

    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. PMID:23910326

  6. Growth of high Mg content wurtzite MgZnO epitaxial films via pulsed metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Alema, Fikadu; Ledyaev, Oleg; Miller, Ross; Beletsky, Valeria; Osinsky, Andrei; Schoenfeld, Winston V.

    2016-02-01

    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.

  7. Shape and size of crystalline MgO particles formed by the decomposition of Mg(OH)/sub 2/

    SciTech Connect

    Dahmen,; Kim, M.G.; Searcy, A.W.

    1988-08-01

    Decomposition of Mg(OH)/sub 2/ at 300/sup 0/ to 400/sup 0/C yields MgO crystals with often unequal edge lengths which, from counting of crystal planes in high-resolution transmission electron micrographs, range from 0.8 to 2.4 nm, in agreement with conclusions of Moodie and Warble. Optical diffractograms and electron diffraction patterns yield concordant results. An origin for discordant X-ray diffraction estimates of particle size for MgO produced from Mg(OH)/sub 2/ in the same temperature range is suggested.

  8. Spin and charge transport in double-junction Fe/MgO/GaAs/MgO/Fe heterostructures

    SciTech Connect

    Wolski, S. Szczepański, T.; Dugaev, V. K.; Barnaś, J.; Landgraf, B.; Slobodskyy, T.; Hansen, W.

    2015-01-28

    We present theoretical and experimental results on tunneling current in single Fe/MgO/GaAs and double Fe/MgO/GaAs/MgO/Fe tunnel junctions. The charge and spin currents are calculated as a function of external voltage for different sets of parameters characterizing the semiconducting GaAs layer. Transport characteristics of a single Fe/MgO/GaAs junction reveal typical diode as well as spin diode features. The results of numerical calculations are compared with current-voltage characteristics measured experimentally for double tunnel junction structures, and a satisfactory agreement of the theoretical and experimental results has been achieved.

  9. High-precision Mg isotopic systematics of bulk chondrites

    NASA Astrophysics Data System (ADS)

    Schiller, Martin; Handler, Monica R.; Baker, Joel A.

    2010-08-01

    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

  10. Projectile deformation effects in the breakup of 37Mg

    NASA Astrophysics Data System (ADS)

    Shubhchintak; Chatterjee, R.; Shyam, R.

    2016-05-01

    We study the breakup of 37Mg on Pb at 244MeV/u with the recently developed extended theory of Coulomb breakup within the postform finite range distorted wave Born approximation that includes deformation of the projectile. Comparing our calculated cross section with the available Coulomb breakup data we determine the possible ground state configuration of 37Mg.

  11. Optical properties and electronic band structure of BiMg2PO6, BiMg2VO6, BiMg2VO6:Pr3+ and BiMg2VO6:Eu3+

    NASA Astrophysics Data System (ADS)

    Barros, A.; Deloncle, R.; Deschamp, J.; Boutinaud, P.; Chadeyron, G.; Mahiou, R.; Cavalli, E.; Brik, M. G.

    2014-08-01

    The luminescence properties of the yellow pigment BiMg2VO6 are revisited and those of BiMg2PO6, BiMg2VO6:Pr3+ and BiMg2VO6:Eu3+ are described. It is shown that the undoped systems exhibit broad band emission in the green or orange spectral regions, but only upon UV or near UV excitation. In contradiction with a previous report, we found that the blue, host absorbed, photons are lost non-radiatively and do not contribute to the luminescence processes in BiMg2VO6. To understand these experimental results, the optical properties of BiMg2VO6 and BiMg2PO6 are theoretically analysed on the basis of electronic structure diagrams calculated by the DFT method. It is found that the optical transitions are mostly localised within [VO4]3- units or non-regular Bi3+ ions and occur in the UV or near UV regions. The luminescence of the trivalent lanthanide dopants is weak (Eu3+) or unobserved (Pr3+) in BiMg2VO6 which is explained by inefficient energy migration in the host lattice to the impurity sites.

  12. Mg-based compounds for hydrogen and energy storage

    NASA Astrophysics Data System (ADS)

    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.

    2016-02-01

    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. Size effects in MgO cube dissolution.

    PubMed

    Baumann, Stefan O; Schneider, Johannes; Sternig, Andreas; Thomele, Daniel; Stankic, Slavica; Berger, Thomas; Grönbeck, Henrik; Diwald, Oliver

    2015-03-10

    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. PMID:25668706

  14. Nanostructured Layered Cathode for Rechargeable Mg-Ion Batteries.

    PubMed

    Tepavcevic, Sanja; Liu, Yuzi; Zhou, Dehua; Lai, Barry; Maser, Jorg; Zuo, Xiaobing; Chan, Henry; Král, Petr; Johnson, Christopher S; Stamenkovic, Vojislav; Markovic, Nenad M; Rajh, Tijana

    2015-08-25

    Nanostructured bilayered V2O5 was electrochemically deposited within a carbon nanofoam conductive support. As-prepared electrochemically synthesized bilayered V2O5 incorporates structural water and hydroxyl groups, which effectively stabilizes the interlayers and provides coordinative preference to the Mg(2+) cation in reversible cycling. This open-framework electrode shows reversible intercalation/deintercalation of Mg(2+) ions in common electrolytes such as acetonitrile. Using a scanning transmission electron microscope we demonstrate that Mg(2+) ions can be effectively intercalated into the interlayer spacing of nanostructured V2O5, enabling electrochemical magnesiation against a Mg anode with a specific capacity of 240 mAh/g. We employ HRTEM and X-ray fluorescence (XRF) imaging to understand the role of environment in the intercalation processes. A rebuilt full cell was tested by employing a high-energy ball-milled Sn alloy anode in acetonitrile with Mg(ClO4)2 salt. XRF microscopy reveals effective insertion of Mg ions throughout the V2O5 structure during discharge and removal of Mg ions during electrode charging, in agreement with the electrode capacity. We show using XANES and XRF microscopy that reversible Mg intercalation is limited by the anode capacity. PMID:26169073

  15. Model for nonprotective oxidation of Al-Mg alloys

    SciTech Connect

    Zayan, M.H. )

    1990-12-01

    The oxidation of Al-5Mg alloy has been studied at 550 C in dry air. Morphological details of the MgO layers which develop on this alloy during high-temperature oxidation have been studied by scanning electron microscopy (SEM). A localized detachment of the protective, adherent MgO layer was found, which is caused by voids formed by vacancy condensation at the metal-oxide interface. The source of these vacancies was the outward diffusion of Mg though the oxide layer. Continuing growth of these voids was responsible for cracking of oxide ridges and nodules, as well as the growth of new MgO having a cauliflower morphology. A model describing the process of the outward diffusion is given.

  16. The anodic surface film and hydrogen evolution on Mg

    DOE PAGESBeta

    Song, Guang -Ling; Unocic, Kinga A.

    2015-06-04

    This paper clarifies that the inner and outer layers of the anodic film consist of a nano/micro-porous MgO+Mg(OH)2 mixture. The film becomes thicker and more porous with increasing potential. It can rupture when potential is too positive in a non-corrosive Mg(OH)2 solution. Hydrogen evolution becomes more intensive as polarization potential increases, particularly when the potential at the film-covered Mg surface is close to or more positive than the hydrogen equilibrium potential, suggesting that an “anodic hydrogen evolution” (AHE) reaction occurs on the substrate Mg in film pores, and the significantly intensified AHE causes film rupture at high potential.

  17. The anodic surface film and hydrogen evolution on Mg

    SciTech Connect

    Song, Guang -Ling; Unocic, Kinga A.

    2015-06-04

    This paper clarifies that the inner and outer layers of the anodic film consist of a nano/micro-porous MgO+Mg(OH)2 mixture. The film becomes thicker and more porous with increasing potential. It can rupture when potential is too positive in a non-corrosive Mg(OH)2 solution. Hydrogen evolution becomes more intensive as polarization potential increases, particularly when the potential at the film-covered Mg surface is close to or more positive than the hydrogen equilibrium potential, suggesting that an “anodic hydrogen evolution” (AHE) reaction occurs on the substrate Mg in film pores, and the significantly intensified AHE causes film rupture at high potential.

  18. Preparation of MgB2 superconducting tapes using electrophoresis

    NASA Astrophysics Data System (ADS)

    Xu, J. D.; Wang, S. F.; Zhou, Y. B.; Zhou, Y. L.; Chen, Z. H.; Cui, D. F.; Lu, H. B.; He, M.; Dai, S. Y.; Yang, G. Z.

    2002-08-01

    Superconducting MgB2/Ta tapes with a critical temperature of 34 K have been prepared successfully by ex situ annealing of electrophoresis-grown boron in the presence of Mg vapour at 920 °C. Scanning electron microscopy was used to examine the surface morphology of the MgB2/Ta tapes, and well-formed MgB2 crystals with sizes up to 2 μm were observed. The x-ray diffraction patterns showed randomly orientated growth of MgB2 phase in the tapes. Estimates using hysteresis loops and the Bean model give a value of 6.8 × 105 A cm-2 for the critical current density.

  19. Oxygen Segregation and Ordering in MgB2

    NASA Astrophysics Data System (ADS)

    Idrobo, Juan; Klie, Robert; Browning, Nigel D.

    2002-03-01

    Polycrystalline MgB2 has been studied by atomic resolution scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). We find that within the detection limits of the techniques, there is no oxygen within the bulk of the grains, but significant oxygen segregated to the grain boundaries. The majority of the grain boundaries contain ordered crystalline MgB_2-xOx and amorphous BOy phases smaller than the coherence length, explaining the high conductivity of the material. Other kinds of grain boundaries containing larger areas of MgO sandwiched between BOy layers were also found. Furthermore, coherent Mg(B,O) precipitates can be formed within the bulk of the MgB2 grains. We will discuss the formation mechanisms of these secondary phases, the presence of oxygen ordering within the precipitates and the effect of the oxide precipitates on the bulk transport properties.

  20. Mg Isotope Fractionation Between E. coli and Growth Medium

    NASA Astrophysics Data System (ADS)

    Basset, R.; Lemelle, L.; Albalat, E.; Telouk, P.; Albarède, F.

    2008-12-01

    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

  1. The role of Mg in the crystallization of monohydrocalcite

    NASA Astrophysics Data System (ADS)

    Rodriguez-Blanco, Juan Diego; Shaw, Samuel; Bots, Pieter; Roncal-Herrero, Teresa; Benning, Liane G.

    2014-02-01

    Monohydrocalcite is a member of the carbonate family which forms in Mg-rich environments at a wide range of Mg/Ca ratios Mg2+aq/Ca2+aq≥0.17<65. Although found in modern sedimentary deposits and as a product of biomineralization, there is a lack of information about its formation mechanisms and about the role of Mg during its crystallization. In this work we have quantitatively assessed the mechanism of crystallization of monohydrocalcite through in situ synchrotron-based small and wide angle X-ray scattering (SAXS/WAXS) and off-line spectroscopic, microscopic and wet chemical analyses. Monohydrocalcite crystallizes via a 4-stage process beginning with highly supersaturated solutions from which a Mg-bearing, amorphous calcium carbonate (ACC) precursor precipitates. This precursor crystallizes to monohydrocalcite via a nucleation-controlled reaction in stage two, while in stage three it is further aged through Ostwald-ripening at a rate of 1.8 ± 0.1 nm/h1/2. In stage four, a secondary Ostwald ripening process (66.3 ± 4.3 nm/h1/2) coincides with the release of Mg from the monohydrocalcite structure and the concomitant formation of minor hydromagnesite. Our data reveal that monohydrocalcite can accommodate significant amounts of Mg in its structure (χMgCO3 = 0.26) and that its Mg content and dehydration temperature are directly proportional to the saturation index for monohydrocalcite (SIMHC) immediately after mixing the stock solutions. However, its crystallite and particle size are inversely proportional to these parameters. At high supersaturations (SIMHC = 3.89) nanometer-sized single crystals of monohydrocalcite form, while at low values (SIMHC = 2.43) the process leads to low-angle branching spherulites. Many carbonates produced during biomineralization form at similar conditions to most synthetic monohydrocalcites, and thus we hypothesize that some calcite or aragonite deposits found in the geologic record that have formed at high Mg/Ca ratios could be

  2. Reactions of Mg and Mg2 with SO2 in low-temperature matrices: association or insertion?

    PubMed

    Liu, Xing; Xing, Xiaopeng; Zhao, Jie; Wang, Xuefeng

    2015-01-29

    Laser-ablated magnesium species were codeposited with SO2 in excess argon or neon on the substrate at 4 K. The reactions mainly produced Mg(η(2)-O2S), Mg(η(2)-O2S)2, Mg2(η(2)-O2S), OMg2(η(2)-SO), and Mg(η(2)-SO) complexes, which were identified by isotopic substitutions and density functional frequency calculations (B3LYP and BPW91). In addition, the collected infrared spectra suggest that the single Mg atoms could react with SO2 to form the Mg(η(2)-O2S) complex on annealing, which further reacts with SO2 to produce the Mg(η(2)-O2S)2 complex on irradiation. In contrast, the reactions of magnesium dimers lead to cleavage of the S═O bond in SO2 on irradiating. Structural and bonding characteristics of these generated complexes, which shed light on the different performances of single Mg atom and its dimer in their reactions with small molecules, are discussed. PMID:25521504

  3. Effect of Synthesized MgNi4Y Catalyst on Hydrogen Desorption Properties of Milled MgH2

    NASA Astrophysics Data System (ADS)

    ChitsazKhoyi, Leila; Raygan, Shahram; Pourabdoli, Mehdi

    2015-03-01

    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.

  4. Effect of Mg content on the bioactivity and biocompatibility of Mg-substituted fluorapatite nanopowders fabricated via mechanical activation.

    PubMed

    Kheradmandfard, M; Fathi, M H; Ansari, F; Ahmadi, T

    2016-11-01

    The aim of this work was preparation, characterization, bioactivity and biocompatibility evaluation of Mg-substituted fluorapatite (Mg-FA) nanopowders. Mg-FA nanopowders with a chemical composition of Ca10-xMgx(PO4)6F2, with x=0, 0.5, 1, and 2 were prepared by mechanically activated method. The in vitro bioactivity was investigated by soaking the powders in simulated body fluid (SBF) for various time periods to analyze the nucleation and growth of bone-like apatite on the surface of the samples. Cell viability and cell attachment were studied by MTT assay. Results indicated that the bioactivity of all of samples with different Mg content was improved compared with the pure FA. However, the mechanism of bioactivity is different and depends on the amount of Mg substitution. Finally, cell culture suggested that the addition of Mg(2+) has no adverse effect and Mg-FA samples have good biocompatibility. The Mg-FA material shows potential in satisfying the requirements of biomedical applications. PMID:27524005

  5. Synthesis, crystal growth and structure of Mg containing {beta}-rhombohedral boron: MgB{sub 17.4}

    SciTech Connect

    Adasch, Volker; Hess, Kai-Uwe; Vojteer, Natascha; Hillebrecht, Harald . E-mail: harald.hillebrecht@ac.uni-freiburg.de

    2006-09-15

    For the first time, single crystals of Mg containing {beta}-rhombohedral boron MgB{sub 17.4} were synthesised from the elements in a Mg/Cu melt at 1600deg. C. The crystal structure determined by the refinement of single crystal data (space group R-3m, a=10.991(2)A, c=24.161(4)A, 890 reflections, 123 variables, R{sub 1}(F)=0.049, wR{sub 2}(I)=0.122) improves and modifies the former structure model derived from earlier investigations on powder samples. Mg is located on four different positions with partial occupation. While the occupation of the sites D (53.3%), E (91%) and F (7.2%) is already known from other boron-rich borides related to {beta}-rhombohedral boron, the occupation of the fourth position (18h, 6.7%) is observed for the first time. Two boron positions show partial occupation. The summation reveals the composition MgB{sub 17.4} and Mg{sub 5.85}B{sub 101.9}, respectively, confirmed by WDX measurements. The single crystals of MgB{sub 17.4} show the highest Mg content ever found. Preliminary measurements indicate no superconductivity.

  6. Laser cladding of a Mg based Mg-Gd-Y-Zr alloy with Al-Si powders

    NASA Astrophysics Data System (ADS)

    Chen, Erlei; Zhang, Kemin; Zou, Jianxin

    2016-03-01

    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.

  7. Structural, electronic and bonding properties of antifluorite crystals of Be2C, BeMgC and Mg2C

    NASA Astrophysics Data System (ADS)

    Joshi, K. B.; Trivedi, D. K.; Paliwal, U.; Galav, K. L.

    2016-05-01

    Structure prediction methods are coupled with the first-principles linear combination of atomic orbitals method to propose the crystal parameters and bulk modulus of antifluorite BeMgC. The binary antifluorite methanides Be2C, Mg2C are also studied. Electronic structure calculations and Mulliken population analyses (MPA) are performed to unravel bands dispersion and bonding properties. The values of the indirect band gap Γ → X for Be2C, Mg2C and BeMgC, in order, are 2.90, 2.05 and 1.86 eV. The calculated energies of a few occupied bands in Be2C are in very good agreement with the available experimental data. The application of pressure causes change in the band gap of three carbides. The Γ-Γ, Γ-X and Γ-K band gaps exhibit different trends with pressure. Effective charges on the basis of MPA in the three compounds are {(B{e}+1.095)}2{C}-2.19, {(M{g}+1.615)}2{C}-3.23 and B{e}+1.12M{g}+1.682{C}-2.802. It signifies covalent bonding in Be2C, ionic in Mg2C, and intermediate in the BeMgC.

  8. Possibility of a 2D SiC monolayer formation on Mg(0001) and MgO(111) substrates

    NASA Astrophysics Data System (ADS)

    Kuzubov, A. A.; Eliseeva, N. S.; Krasnov, P. O.; Tomilin, F. N.; Fedorov, A. S.; Tolstaya, A. V.

    2013-08-01

    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.

  9. Electrochromism of Mg-Ni hydride switchable mirrors

    NASA Astrophysics Data System (ADS)

    Isidorsson, Jan; Giebels, I. A. M. E.; Di Vece, M.; Griessen, Ronald

    2001-11-01

    Switchable mirrors have so far been made of rare-earth and rare-earth-magnesium based metal-hydrides. In this investigation we study Mg-Ni-hydrides, which have been shown by Richardson et al. to exhibit switchable properties similar to those of the rare-earth hydrides. Cyclic voltammetry on MgzNiHx samples with 0.8 less than z less than 3.7 shows that addition of one Mg atom per Mg2Ni gives the best ab/desorption kinetics for hydrogen. X- ray diffraction reveals a structural change as hydrogen is absorbed. The metal-insulator transition is confirmed with simultaneous resistivity measurements. A pressure- composition isotherm of Mg2NiHx is also determined electrochemically. Optical spectrometry during gas loading gives an optical band gap of 1.6 eV for Mg2NiH4. This gap increases with increasing Mg content in a way similar to that of the Mg-doped rare-earth hydrides.

  10. Synthesis and crystal structure of MgB{sub 12}

    SciTech Connect

    Adasch, Volker; Hess, Kai-Uwe; Vojteer, Natascha; Hillebrecht, Harald . E-mail: harald.hillebrecht@ac.uni-freiburg.de

    2006-09-15

    Single crystals of MgB{sub 12} were synthesized from the elements in a Mg/Cu melt at 1600deg. C. MgB{sub 12} crystallizes orthorhombic in space group Pnma with a=16.632(3)A, b=17.803(4)A and c=10.396(2)A. The crystal structure (Z=30, 5796 reflections, 510 variables, R{sub 1}(F)=0.049, wR{sub 2}(I)=0.134) consists of a three dimensional net of B{sub 12} icosahedra and B{sub 21} units in a ratio 2:1. The B{sub 21} units are observed for the first time in a solid compound. Mg is on positions with partial occupation. The summation reveals the composition MgB{sub 12.35} or Mg{sub 0.97}B{sub 12} , respectively. This is in good agreement with the value of MgB{sub 11.25} as expected by electronic reasons to stabilize the boron polyhedra B{sub 12}{sup 2-} and B{sub 21}{sup 4-}.

  11. A Redetermination of the Dissociation Energy of MgO(+)

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Partridge, Harry

    1994-01-01

    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.

  12. Mg II 2800 A emission in late type stars

    NASA Technical Reports Server (NTRS)

    Doherty, L. R.

    1972-01-01

    The largest body of data on ultraviolet spectra of late-type stars now available is the series of scans made with the long wavelength spectrometer onboard OAO-2. Some features of selected scans from this series and estimates of Mg II emission fluxes were reported earlier. Since that time, the effects of sky background, scattered light and variable instrumental sensitivity have become better understood. Additional stars are used to define more clearly the transition from Mg II 2800 A absorption to emission with advancing spectral type, and additional scans of alpha Sco provide a better estimate of Mg II emission strength for this supergiant in OAO observations.

  13. Matter radii of {sup 32-35}Mg

    SciTech Connect

    Kanungo, R.; Perro, C.; Prochazka, A.; Farinon, F.; Knoebel, R.; Horiuchi, W.; Nociforo, C.; Aumann, T.; Geissel, H.; Gerl, J.; Kindler, B.; Lommel, B.; Mahata, K.; Scheidenberger, C.; Weick, H.; Winkler, M.; Boutin, D.; Lenske, H.; Cortina-Gil, D.; Davids, B.

    2011-02-15

    The interaction cross sections of {sup 32-35}Mg at 900A MeV have been measured using the fragment separator at GSI. The deviation from the r{sub 0}A{sup 1/3} trend is slightly larger for {sup 35}Mg, signaling the possible formation of a longer tail in the neutron distribution for {sup 35}Mg. The radii extracted from a Glauber model analysis with Fermi densities are consistent with models predicting the development of neutron skins.

  14. Inversion of ferromagnetic proximity polarization by MgO interlayers.

    PubMed

    Li, Yan; Chye, Y; Chiang, Y F; Pi, K; Wang, W H; Stephens, J M; Mack, S; Awschalom, D D; Kawakami, R K

    2008-06-13

    We investigate the spin-dependent reflection properties in Fe/MgO/GaAs heterostructures by optical pump-probe measurement of the ferromagnetic proximity polarization (FPP). As a function of MgO thickness, the FPP is initially enhanced (<2.0 A) and then exhibits an unexpected sign reversal at approximately 5.0 A. The identification of two competing thresholds in the intensity dependence of FPP and the observation of FPP sign reversal in Fe/Mg/GaAs suggest that the inversion of FPP is related to an interfacial bonding effect. PMID:18643542

  15. Phase stability in the Cd-Mg system

    SciTech Connect

    Asta, M.; McCormack, R.; de Fontaine, D.

    1993-12-31

    This paper reports on results of a theoretical study of solid-state phase equilibria and short-range order in Cd-Mg alloys. Results of first-principles linear muffin-tin orbital method total-energy calculations for seven hcp-based superstructures have been combined with cluster-variation-method calculations of thermodynamic properties in order to compute the Cd-Mg phase diagram. Effect on the calculated phase diagram of contributions to the alloy free energy arising from atomic vibrations and structural relaxations are assessed using available experimental information for ordered and disordered alloys in the Cd-Mg system.

  16. Structural and magnetic properties of Mg substituted Co nanoferrites

    NASA Astrophysics Data System (ADS)

    Sharma, Jyoti; Sharma, Neha; Yadav, Premlata; Parashar, Jyoti; Jadoun, Priya; Saxena, V. K.; Bhatnagar, D.; Sharma, K. B.

    2016-05-01

    The structural and magnetic properties of magnesium substituted cobalt nano ferrites CoxMg1-xFe2O4 (x= 0.2, 0.4 and 1.0) have been investigated. The structural characterization has been done by X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). The magnetic studies indicate that the samples show ferromagnetic behaviour at room temperature as well as at low temperature. The magnetization decreases with Mg content in both the cases due to the less magnetic nature of Mg ions than that of the Co ions.

  17. PROPERTIES OF DEFECTS AND IMPLANTS IN Mg+ IMPLANTED SILICON CARBIDE

    SciTech Connect

    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

    2013-09-25

    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.

  18. Calculation of Mg(+)-ligand relative binding energies

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Bauschlicher, Charles W., Jr.

    1992-01-01

    The calculated relative binding energies of 16 organic molecules to Mg(+) are compared with experimental results where available. The geometries of the ligands and the Mg(+)-ligand complexes arc optimized at the self-consistent field level using a 6-31G* basis set. The Mg(+) binding energies are evaluated using second-order perturbation theory and basis sets of triple-sigma quality augmented with two sets of polarization functions. This level of theory is calibrated against higher levels of theory for selected systems. The computed binding energies are accurate to about 2 kcal/mol.

  19. Control of carbonate alkalinity on Mg incorporation in calcite: Insights on the occurrence of high Mg calcites in diagenetic environments

    NASA Astrophysics Data System (ADS)

    Purgstaller, Bettina; Mavromatis, Vasileios; Dietzel, Martin

    2015-04-01

    High Mg calcites (HMC), with up to 25 mol % of Mg, are common features in early diagenetic environments and are frequently associated with bio-induced anaerobic oxidation of methane (AOM). Such archives hold valuable information about the biogeochemical processes occurring in sedimentary environments in the geological past. Despite the frequency AOM-induced HMC observed in marine diagenetic settings and their potential role in dolomitization, only a minor number of experimental studies has been devoted on deciphering their formation conditions. Thus, in order to improve our understanding on the formation mechanism of HMC induced by elevated carbonate ion concentrations, we precipitated HMC by computer controlled titration of a (Mg,Ca)Cl2 solution at different Mg/Ca ratios into a NaHCO3 solution under precisely defined physicochemical conditions (T = 25.00 ±0.03°C; pH = 8.3 ±0.1). The formation of carbonates was monitored at a high temporal resolution using in situ Raman spectroscopy as well as by continuous sampling and analyzing of precipitates and reactive solutions. We identified two distinct mechanisms of HMC formation. In solutions with molar Mg/Ca ratios ≤ 1/8 calcium carbonate was precipitated as crystalline phases directly from homogeneous solution. In contrast, higher Mg/Ca ratios induced the formation of Mg-rich ACC (up to 10 mol % of Mg), which was subsequently transformed to HMC with up 20 mol % of Mg. Our experimental results highlight that the finally formed HMC has a higher Mg content than the ACC precursor phase. Considering experimental data for Mg containing ACC transformation to crystalline calcium carbonate from literature, the continuous enrichment of Mg in the precipitate throughout transformation of amorphous to crystalline CaCO3 most likely occurs due to the high carbonate alkalinity (DIC about 0.1 M) of our reactive solutions. The Mg incorporation into calcite lattice seems to be favored by intensive supply of carbonate ions as

  20. Basolateral Mg2+ Extrusion via CNNM4 Mediates Transcellular Mg2+ Transport across Epithelia: A Mouse Model

    PubMed Central

    Miura, Jiro; Sato, Sunao; Toyosawa, Satoru; Furutani, Kazuharu; Kurachi, Yoshihisa; Omori, Yoshihiro; Furukawa, Takahisa; Tsuda, Tetsuya; Kuwabata, Susumu; Mizukami, Shin; Kikuchi, Kazuya; Miki, Hiroaki

    2013-01-01

    Transcellular Mg2+ 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 Mg2+ 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 Mg2+ extrusion to the inner parts of body. Imaging analyses revealed that CNNM4 can extrude Mg2+ by exchanging intracellular Mg2+ 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 Mg2+ extrusion activity. These results demonstrate the crucial importance of Mg2+ extrusion by CNNM4 in organismal and topical regulation of magnesium. PMID:24339795

  1. Optical transitions of Er3+ ions in RbMgF3 and RbMgF3: Mn

    NASA Astrophysics Data System (ADS)

    Shinn, M. D.; Windscheif, J. C.; Sardar, D. K.; Sibley, W. A.

    1982-09-01

    Optical absorption, emission, and excitation spectra, as well as lifetime values, are presented for Er3+ ions in RbMgF3. Previous workers have demonstrated that Er3+ ions can reside in a number of different site symmetries in crystalline hosts such as CaF2 and CdF2. The numerous sites in this type lattice are most likely due to compensating fluorine interstitials which are necessarily present for charge compensation. In a unit cell of RbMgF3 there are two nonequivalent Mg2+ sites with C3v symmetry. Evidence is presented in this paper that Er3+ ions in RbMgF3 substitute for Mg2+ ions in both types of sites. The charge compensation is not local, which leaves the symmetry of the Er3+ sites unchanged. Absorption data for Er3+-ion transitions in both sites are shown. Emission from Er3+ ions is observed from one type of site in RbMgF3 and from both types of sites in RbMgF3: Mn. Lifetime values for the 4S32 and 4F92 transitions are shorter than those normally measured in fluoride host lattices, and the emissions are quenched above 200 K. Energy migration among Er3+ ions and subsequent energy transfer to Mn2+-ion impurities are responsible for the steady-state and transient-emission behavior.

  2. Bending strain tolerance of MgB2 superconducting wires

    NASA Astrophysics Data System (ADS)

    Kováč, P.; Hušek, I.; Melišek, T.; Kulich, M.; Kopera, L.

    2016-04-01

    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.

  3. Solute effect on basal and prismatic slip systems of Mg.

    PubMed

    Moitra, Amitava; Kim, Seong-Gon; Horstemeyer, M F

    2014-11-01

    In an effort to design novel magnesium (Mg) alloys with high ductility, we present a first principles data based on the Density Functional Theory (DFT). The DFT was employed to calculate the generalized stacking fault energy curves, which can be used in the generalized Peierls-Nabarro (PN) model to study the energetics of basal slip and prismatic slip in Mg with and without solutes to calculate continuum scale dislocation core widths, stacking fault widths and Peierls stresses. The generalized stacking fault energy curves for pure Mg agreed well with other DFT calculations. Solute effects on these curves were calculated for nine alloying elements, namely Al, Ca, Ce, Gd, Li, Si, Sn, Zn and Zr, which allowed the strength and ductility to be qualitatively estimated based on the basal dislocation properties. Based on our multiscale methodology, a suggestion has been made to improve Mg formability. PMID:25273695

  4. ZnCdMgSe-Based Semiconductors for Intersubband Devices

    SciTech Connect

    Tamargo, Maria C.

    2008-11-13

    This paper presents a review of recent results on the application of ZnCdMgSe-based wide bandgap II-VI compounds to intersubband devices such as quantum cascade lasers and quantum well infrared photodetectors operating in the mid-infrared region. The conduction band offset of ZnCdSe/ZnCdMgSe quantum well structures was determined from contactless electroreflectance measurements to be as high as 1.12 eV. FT-IR was used to measure intersubband absorption in multi-quantum well structures in the mid-IR range. Electroluminescence at 4.8 {mu}m was observed from a quantum cascade emitter structure made from these materials. Preliminary results are also presented on self assembled quantum dots of CdSe on ZnCdMgSe, and novel quantum well structures with metastable binary MgSe barriers.

  5. Photoluminescence properties of Mg-doped InN nanowires

    SciTech Connect

    Zhao, Songrui; Liu, Xuedong; Mi, Zetian

    2013-11-11

    In this work, photoluminescence (PL) properties of nearly defect-free Mg-doped InN nanowires were investigated in detail. The low-doped sample exhibits two PL emission peaks up to 152 K, which can be ascribed to the band-to-band recombination and the Mg-acceptor energy level related recombination, respectively. For the high-doped sample, the Mg-acceptor energy level related transition dominates. Detailed power dependent PL studies further indicate that the Mg-acceptor energy level related PL emission is due to the donor-acceptor pair recombination process, which subsequently evolves into the free-to-acceptor recombination with increasing temperature.

  6. Co/Mg/X Multilayer Mirrors For the EUV Range

    SciTech Connect

    Hu, M.-H.; Le Guen, K.; Andre, J.-M.; Jonnard, P.; Zhou, S. K.; Li, H. Ch.; Zhu, J. T.; Wang, Z. S.

    2010-04-06

    A new material combination namely Co/Mg multilayer designed for optics applications in the EUV range, is reported. Simulations show that reflectivity value of the Co/Mg multilayer can reach a reflectivity of 55% at 25.2 nm (49.2 eV), when the grazing incidence angle is set to 45 deg. and s polarization is considered. The introduction of additional materials, e.g., Y and Zr can improve the reflectivity to 61%. Co/Mg and Co/Mg/B{sub 4}C multilayers have been deposited following the parameters deduced from the simulations. The introduction of a B{sub 4}C barrier layer would in principle increase the multilayer reflectivity to 61%. In fact the reflectivity measurements at 0.154 nm show that the introduction of B{sub 4}C does not improve the structural quality of the multilayers.

  7. A simple immersion approach for fabricating superhydrophobic Mg alloy surfaces

    NASA Astrophysics Data System (ADS)

    Song, Jinlong; Lu, Yao; Huang, Shuai; Liu, Xin; Wu, Libo; Xu, Wenji

    2013-02-01

    A simple immersion approach for fabricating superhydrophobic Mg alloy surfaces is present here. Micro/nanometer-scale rough structures composed of micrometer-scale island-like rough structures and nanometer-scale sheets are generated on the Mg alloy surfaces after immersion in the aqueous CuSO4 solution. After ultrasonic cleaning, the micro/nanometer-scale rough structures are disappeared, whereas the lump-like rough structures appear on the Mg alloy surfaces. After modification with stearic acid, the as-prepared micro/nanometer-scale rough structures and the micrometer-scale lump-like rough structures all show superhydrophobicity. The contact angles of the water droplet on the aforementioned two structures are respectively 151.3° and 161.8°. The rolling angles are respectively 3° and 13°. The results indicate that the cooperation of suitable rough structures and stearic acid modification is responsible for the obtained superhydrophobicity on the Mg alloy surfaces.

  8. Laser-Ultrasonic Inspection of MG/AL Castings

    SciTech Connect

    Blouin, Alain; Levesque, Daniel; Monchalin, Jean-Pierre; Baril, Eric; Fischersworring-Bunk, Andreas

    2005-04-09

    Laser-ultrasonics is used to assess the metallurgical bond between Mg/Al materials in die-cast Magnesium/Aluminum composite. The acoustic impedances of Mg, Al and air are such that the amplitude of ultrasonic echoes reflected back from a void is many times larger than the amplitude of those reflected back from a well-bonded interface. In addition, the polarity of echoes from a void is inverted compared to that from a well-bonded interface. Laser-ultrasonic F-SAFT is also used for imaging tilted Mg/Al interfaces. Experimental setup, signal processing and results for detecting voids in the Mg/Al interface of cast parts are presented.

  9. Spark Plasma Sintering of MgO-Strengthened Aluminum

    NASA Astrophysics Data System (ADS)

    Ben-Haroush, M.; Dikovsky, G.; Kalabukhov, S.; Aizenshtein, M.; Hayun, S.

    2016-02-01

    The effects of MgO as a sintering additive, sintering duration, and post-heat treatment on mechanical properties and microstructure of spark plasma-sintered aluminum powders were investigated. The sinterability of aluminum with or without MgO was found to be sensitive to the aluminum average particle size, meaning the amount of native oxide within the raw aluminum powders. The fracture mode changes gradually from a brittle mode (after short SPS), through a mixed brittle-ductile fracture mode (after long SPS), ending with the pure ductile form (short SPS followed by heat treatment). Maxima flexural strength and elongation were found in samples with particles size of about 44 μm and the addition of 2 wt.% MgO after short SPS process followed by an additional heat treatment. The addition of MgO may contribute to perforation of the aluminum native oxide and enhance aluminum diffusion during the heat treatment.

  10. Improving properties of Mg with Al–Cu additions

    SciTech Connect

    Rashad, Muhammad; Pan, Fusheng; Asif, Muhammad; Hussain, Shahid; Saleem, Muhammad

    2014-09-15

    The present work reports improvement in tensile properties of the Mg matrix reinforced with micron-sized copper–aluminum particulate hybrids. The Al–Cu particulate hybrids were incorporated into the Mg matrix through powder metallurgy method. The synthesized alloys exhibited homogeneously dispersed Mg{sub 2}Cu particles in the matrix, therefore leading to a 110% increase in yield strength (221 MPa) and a 72% enhancement in ultimate tensile strength (284 MPa) by addition of 1.0 wt.%Al–0.6 wt.%Cu particle hybrids. Optical microscopy, scanning election microscopy, transmission electron microscopy and X-ray diffraction were used to investigate the microstructure and intermetallic phases of the synthesized alloys. - Highlights: • Mg matrix is reinforced with Al–Cu particulate hybrids. • Powder metallurgic method is used to fabricate the alloys. • Tensile strength and ductility were increased simultaneously.

  11. Nucleosynthesis in AGB stars: Observation of Mg-25 and Mg-26 in IRC+10216 and possible detection of Al-26

    NASA Technical Reports Server (NTRS)

    Guelin, M.; Forestini, M.; Valiron, P.; Ziurys, L. M.; Anderson, M. A.; Cernicharo, J.; Kahane, C.

    1995-01-01

    We report the detection in the circumstellar envelope IRC+10216 of millimeter lines of the rare isotopomers (25)MgNC and (26)MgNC, as well as of a line at 234433 MHz, which could be the J= 7-6 transition of (26)AlF (an alternate, although less likely identified would be the J= 9-8 transition of NaF). The derived Mg-24:Mg-25:Mg-26 isotopic abundance ratios (78 : 11+/- 1 : 11 +/-1) are consistent with the solar system values (79.0:10.0:11.0), following Anders & Grevesse 1989). According to new calculations of evolutionary models of 3 solar mass and 5 solar mass asymptotic giant branch (AGB) stars, these ratios and the previously measured N, O and Si isotopic ratios imply that the central star had an initial mass 3 solar mass (less than or equal to M(sub *, ini) less than 5 solar mass and has already experienced many 3rd dredge-up events. From this, it can be predicted that the Al-26/Al-27 isotopics ratio lies between 0.01 and 0.08; in fact, the value derived in the case that U234433 arises from (26)AlF is Al-26/Al-27 = 0.04. The identification of the (25)MgNC and (26)MgNC lines was made possible by ab-initio quantum mechanical calculations of the molecule geometrical structure. It was confirmed through millimeter-wave laboratory measurements. The quantum mechanical calculations are briefly described and the laboratory results presented in some detail. The rotation constants B, D, H and the spin-rotation constant gamma of (25)MgNC and (26)MgNC are determined from a fit of laboratory and astronomical data.

  12. Synthesis of Mg(OH)2, MgO, and Mg nanoparticles using laser ablation of magnesium in water and solvents

    SciTech Connect

    Tran, P.X.; Howard, B.H.; Martello, D.V.; Soong, Y.; Chyu, M.K.

    2008-01-01

    laser ablation of magnesium in deionized water (OW), solutions of OW and sodium dodecyl sulfate (50S) with different concentrations, acetone and 2-propanol has been conducted, The results showed that ablation in acetone and 2-propanol yielded MgO and Mg nanocrystallites as isolated particles and agglomerated chains probably intermixed with organic residues resulting from the alterationj decomposition of the solvents under the high-energy conditions. Brucite-like Mg(OH)2 particles were mainly produced by laser ablation of Mg in either OW or OW~SOS solutions. Ablation in OW yielded particles of fiber-like shapes having a diameter of about 5-lOnm and length as long as 150nm. Materials produced in DW-SOS solutions were composed of various size and shape particles, Some had rough surfaces with irregular shapes. Small particles were about 20-30nm and larger particles were about 120 nm. Particles with rod-like, triangular, and plate-like shapes were also observed.

  13. Synthesis of Mg(OH)2, MgO, and Mg nanoparticles using laser ablation of magnesium in water and solvents

    SciTech Connect

    Phuoc, Tran X.; Howard, Bret H.; Martello, Donald V.; Soong, Yee; Chyu, Minking K.

    2008-11-01

    Laser ablation of magnesium in deionized water (DW), solutions of DW and sodium dodecyl sulfate (SDS) with different concentrations, acetone and 2-propanol has been conducted. The results showed that ablation in acetone and 2-propanol yielded MgO and Mg nanocrystallites as isolated particles and agglomerated chains probably intermixed with organic residues resulting from the alteration/decomposition of the solvents under the high-energy conditions. Brucite-like Mg(OH)2 particles were mainly produced by laser ablation of Mg in either DW or DW-SDS solutions. Ablation in DW yielded particles of fiber-like shapes having a diameter of about 5-10nm and length-as long as 150 nm. Materials produced in DW-SDS solutions were composed of various size and shape particles. Some had rough surfaces with irregular shapes. Small particles were about 20-30 nm and larger particles were about 120 nm. Particles with rodlike, triangular, and plate-like shapes were also observed.

  14. ELECTRON-ION RECOMBINATION OF Mg{sup 6+} FORMING Mg{sup 5+} AND OF Mg{sup 7+} FORMING Mg{sup 6+}: LABORATORY MEASUREMENTS AND THEORETICAL CALCULATIONS

    SciTech Connect

    Lestinsky, M.; Hahn, M.; Novotny, O.; Savin, D. W.; Badnell, N. R.; Bernhardt, D.; Mueller, A.; Schippers, S.; Bing, D.; Grieser, M.; Hoffmann, J.; Jordon-Thaden, B.; Krantz, C.; Orlov, D. A.; Repnow, R.; Shornikov, A.; Wolf, A.

    2012-10-10

    We have measured electron-ion recombination for C-like Mg{sup 6+} forming Mg{sup 5+}, and for B-like Mg{sup 7+} forming Mg{sup 6+}. These studies were performed using a merged electron-ion beam arrangement at the TSR heavy ion storage ring located in Heidelberg, Germany. Both primary ions have metastable levels with significant lifetimes. Using a simple cascade model we estimate the population fractions in these metastable levels. For the Mg{sup 6+} results, we find that the majority of the stored ions are in a metastable level, while for Mg{sup 7+} the metastable fraction is insignificant. We present the Mg{sup 6+} merged beams recombination rate coefficient for DR via N = 2 {yields} N' = 2 core electron excitations ({Delta}N = 0 DR) and for Mg{sup 7+} via 2 {yields} 2 and 2 {yields} 3 core excitations. Taking the estimated metastable populations into account, we compare our results to state-of-the-art multiconfiguration Breit-Pauli theoretical calculations. Significant differences are found at low energies where theory is known to be unreliable. Moreover, for both ions we observe a discrepancy between experiment and theory for {Delta}N = 0 DR involving capture into high-n Rydberg levels and where the stabilization is primarily due to a radiative transition of the excited core electron. This is consistent with previous DR experiments on M-shell iron ions which were performed at TSR. The large metastable content of the Mg{sup 6+} ion beam precludes generating a plasma recombination rate coefficient (PRRC). However, this is not an issue for Mg{sup 7+} and we present an experimentally derived Mg{sup 7+} PRRC for plasma temperatures from 400 K to 10{sup 7} K with an estimated uncertainty of less than 27% at a 90% confidence level. We also provide a fit to our experimentally derived PRRC for use in plasma modeling codes.

  15. Thermoelectric transport properties of CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2

    SciTech Connect

    May, Andrew F; McGuire, Michael A; Ma, Jie; Delaire, Olivier A; Huq, Ashfia; Singh, David J; Cai, Wei; Wang, Hsin

    2012-01-01

    The thermoelectric transport properties of CaMg{sub 2}Bi{sub 2}, EuMg{sub 2}Bi{sub 2}, and YbMg{sub 2}Bi{sub 2} were characterized between 2 and 650 K. As synthesized, the polycrystalline samples are found to have lower p-type carrier concentrations than single-crystalline samples of the same empirical formula. These low carrier concentration samples possess the highest mobilities yet reported for materials with the CaAl{sub 2}Si{sub 2} structure type, with a mobility of {approx}740 cm{sup 2}/V/s observed in EuMg{sub 2}Bi{sub 2} at 50 K. Despite decreases in the Seebeck coefficient ({alpha}) and electrical resistivity ({rho}) with increasing temperature, the power factor ({alpha}{sup 2}{rho}) increases for all temperatures examined. This behavior suggests a strong asymmetry in the conduction of electrons and holes. The highest figure of merit (zT) is observed in YbMg{sub 2}Bi{sub 2}, with zT approaching 0.4 at 600 K for two samples with carrier densities of approximately 2 x 10{sup 18} cm{sup -3} and 8 x 10{sup 18} cm{sup -3} at room temperature. Refinements of neutron powder diffraction data yield similar behavior for the structures of CaMg{sub 2}Bi{sub 2} and YbMg{sub 2}Bi{sub 2}, with smooth lattice expansion and relative expansion in c being {approx}35% larger than relative expansion in a at 973 K. First-principles calculations reveal an increasing band gap as Bi is replaced by Sb and then As, and subsequent Boltzmann transport calculations predict an increase in {alpha} for a given n associated with an increased effective mass as the gap opens. The magnitude and temperature dependence of {alpha} suggests higher zT is likely to be achieved at larger carrier concentrations, roughly an order of magnitude higher than those in the current polycrystalline samples, which is also expected from the detailed calculations.

  16. Growth of large single crystals of MgO

    SciTech Connect

    Boatner, L.A.; Urbanik, M.

    1997-06-12

    The progressive identification of new high-technology applications and requirements for MgO single crystals in the commercial realm, as well as in DOE and other government-agency project areas, has resulted in an increased demand and international market for this material. Specifically, the demand for MgO crystals in large sizes and quantities is presently increasing due to existing and developing applications that include: (a) MgO substrates for the formation of electro-optic thin films and devices, (b) epitaxial substrates for high-temperature thin-film superconducting devices MgO optical components - including high-temperature windows, lenses, and prisms, and (d) specialty MgO crucibles and evaporation sources for thin-film production. In the course of CRADA ORNL92-0091, carried out with Commercial Crystal Laboratories of Naples, Florida as the commercial participant, we have made major progress in increasing the size of single crystals of MgO produced by means of the submerged-arc-fusion technique-thereby increasing the commercial utility of this material. Prior to the accomplishments realized in the course of this CRADA, the only commercially available single crystals of MgO were produced in Japan, Israel, and Russia. The results achieved in the course of CRADA ORNL92-0091 have now led to the establishment of a domestic commercial source of MgO single-crystal substrates and components, and the U.S. is no longer totally dependent on foreign sources of this increasingly important material.

  17. On Interpreting the Photoelectron Spectra of MgO

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Arnold, James (Technical Monitor)

    2001-01-01

    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.

  18. Structures and stabilities of (MgO)n nanoclusters.

    PubMed

    Chen, Mingyang; Felmy, Andrew R; Dixon, David A

    2014-05-01

    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. PMID:24716776

  19. High Resolution Laser Spectroscopy of Mg12C12CD, Mg13C13CH and Mg12C_4H

    NASA Astrophysics Data System (ADS)

    Forthomme, D.; Linton, C.; Tokaryk, D. W.; Adam, A. G.; Granger, A. D.

    2010-06-01

    Carbon and magnesium are abundant elements in the interstellar medium, so it is possible that carbon chain molecules containing a magnesium atom may exist in this environment. With this in mind, radical molecules of the form MgC2nH (n = 1,2,3) have been frequent subjects of both experimental and theoretical studies In this presentation we will discuss our high-resolution experiments of the ~A2Π-~X2Σ+ transitions in the isotopologues Mg12C12CD and Mg13C13CH, which complement our earlier investigation of this spectrum in Mg12C12CH^b. The data permit us to determine the lengths of individual bonds to high precision. In addition, we have expanded on previous studies of the ~A2Π-~X2Σ+ transition of Mg12C_4H, conducted at medium resolution. The parameters obtained from our high-resolution spectra are compared with those obtained from theoretical structure calculations. H. Ding, C. Apetrei, L. Chacaga, J. P. Maier, Astrophys. J. 677 (2008) 348-352 D. W. Tokaryk, A. G. Adam, W. S. Hopkins, J. Mol. Spectrosc. 230 (2005) 54-61 D. E. Woon, Chem. Phys. Lett. 274 (1997) 299-305 C. A. Thompson and L. Andrews, J. Am. Chem. Soc. 118 (1996) 10242-10249 X. Guo, J. Zhang, J. Li, L. Jiang, J. Zhang, Chem. Phys 360 (2009) 27-31 E. Chasovskikh, E. B. Jochnowitz, J. P. Maier, J. Phys. Chem. A. 112 (2008) 8686-8689.

  20. Bioactivity of Mg-ion-implanted zirconia and titanium

    NASA Astrophysics Data System (ADS)

    Liang, H.; Wan, Y. Z.; He, F.; Huang, Y.; Xu, J. D.; Li, J. M.; Wang, Y. L.; Zhao, Z. G.

    2007-01-01

    Titanium and zirconia are bioinert materials lacking bioactivity. In this work, surface modification of the two typical biomaterials is conducted by Mg-ion-implantation using a MEVVA ion source in an attempt to increase their bioactivity. Mg ions were implanted into zirconia and titanium with fluences ranging from 1 × 10 17 to 3 × 10 17 ions/cm 2 at 40 keV. The Mg-implanted samples, as well as control (unimplanted) samples, were immersed in SBF for 7 days and then removed to identify the presence of calcium and phosphate (Ca-P) coatings and to characterize their morphology and structure by SEM, XRD, and FT-IR. SEM observations confirm that globular aggregates are formed on the surfaces of the Mg-implanted zirconia and titanium while no precipitates are observed on the control samples. XRD and FT-IR analyses reveal that the deposits are carbonated hydroxyapatite (HAp). Our experimental results demonstrate that Mg-implantation improves the bioactivity of zirconia and titanium. Further, it is found that the degree of bioactivity is adjustable by the ion dose. Mechanisms are proposed to interpret the improvement of bioactivity as a result of Mg implantation and the difference in bioactivity between zirconia and titanium.

  1. In vitro degradation of pure Mg in response to glucose

    NASA Astrophysics Data System (ADS)

    Zeng, Rong-Chang; Li, Xiao-Ting; Li, Shuo-Qi; Zhang, Fen; Han, En-Hou

    2015-08-01

    Magnesium and its alloys are promising biodegradable biomaterials but are still challenging to be used in person with high levels of blood glucose or diabetes. To date, the influence of glucose on magnesium degradation has not yet been elucidated, this issue requires more attention. Herein, we present pure Mg exhibiting different corrosion responses to saline and Hank’s solutions with different glucose contents, and the degradation mechanism of pure Mg in the saline solution with glucose in comparison with mannitol as a control. On one hand, the corrosion rate of pure Mg increases with the glucose concentration in saline solutions. Glucose rapidly transforms into gluconic acid, which attacks the oxides of the metal and decreases the pH of the solution; it also promotes the absorption of chloride ions on the Mg surface and consequently accelerates corrosion. On the other hand, better corrosion resistance is obtained with increasing glucose content in Hank’s solution due to the fact that glucose coordinates Ca2+ ions in Hank’s solution and thus improves the formation of Ca-P compounds on the pure Mg surface. This finding will open up new avenues for research on the biodegradation of bio-Mg materials in general, which could yield many new and interesting results.

  2. Recycling practices of spent MgO-C refractories

    SciTech Connect

    Kwong, Kyei-Sing; Bennett, James P.

    2002-10-01

    The recycling options of spent MgO-C refractories from an electrical arc furnace (EAF) have been evaluated. The economic, quality of spent refractories and products made from it, the ease of implementation of a recycling practice and the interest of steel melt shops were considered. It was decided that the best option of most EAF shops would be to recycle spent MgO-C refractory as a foaming slag conditioner because of their MgO content. Crushed MgO-C spent refractories can be reused directly back into an EAF without complex and costly beneficiation. Even though this practice is simple, it is critical to know the optimum amount of MgO in the slag to achieve the best foaming quality. A computer model was designed to find the optimum MgO amount. This modeling also helps the melt shop extend refractory service life, increase the energy efficiency, increase productivity, and decrease the amount of slag. Issues related to the refractory recycling will be discussed.

  3. Mg rechargeable batteries: an on-going challenge

    SciTech Connect

    Yoo, HD; Shterenberg, I; Gofer, Y; Gershinsky, G; Pour, N; Aurbach, D

    2013-08-01

    The first working Mg rechargeable battery prototypes were ready for presentation about 13 years ago after two breakthroughs. The first was the development of non-Grignard Mg complex electrolyte solutions with reasonably wide electrochemical windows in which Mg electrodes are fully reversible. The second breakthrough was attained by demonstrating high-rate Mg cathodes based on Chevrel phases. These prototypes could compete with lead-acid or Ni-Cd batteries in terms of energy density, very low self-discharge, a wide temperature range of operation, and an impressive prolonged cycle life. However, the energy density and rate capability of these Mg battery prototypes were not attractive enough to commercialize them. Since then we have seen gradual progress in the development of better electrolyte solutions, as well as suggestions of new cathodes. In this article we review the recent accumulated experience, understandings, new strategies and materials, in the continuous R&D process of nonaqueous Mg batteries. This paper provides a road-map of this field during the last decade.

  4. Inhibition of DNA ejection from bacteriophage by Mg+2 counterions

    NASA Astrophysics Data System (ADS)

    Lee, Sell; Tran, C. V.; Nguyen, T. T.

    2011-03-01

    The problem of inhibiting viral DNA ejection from bacteriophages by multivalent counterions, specifically Mg+2 counterions, is studied. Experimentally, it is known that MgSO4 salt has a strong and nonmonotonic effect on the amount of DNA ejected. There exists an optimal concentration at which the minimum amount of DNA is ejected from the virus. At lower or higher concentrations, more DNA is ejected from the capsid. We propose that this phenomenon is the result of DNA overcharging by Mg+2 multivalent counterions. As Mg+2 concentration increases from zero, the net charge of DNA changes from negative to positive. The optimal inhibition corresponds to the Mg+2 concentration where DNA is neutral. At lower/higher concentrations, DNA genome is charged. It prefers to be in solution to lower its electrostatic self-energy, which consequently leads to an increase in DNA ejection. By fitting our theory to available experimental data, the strength of DNA-DNA short range attraction energies, mediated by Mg+2, is found to be -0.004 kBT per nucleotide base. This and other fitted parameters agree well with known values from other experiments and computer simulations. The parameters are also in agreement qualitatively with values for tri- and tetravalent counterions.

  5. In vitro degradation of pure Mg in response to glucose

    PubMed Central

    Zeng, Rong-Chang; Li, Xiao-Ting; Li, Shuo-Qi; Zhang, Fen; Han, En-Hou

    2015-01-01

    Magnesium and its alloys are promising biodegradable biomaterials but are still challenging to be used in person with high levels of blood glucose or diabetes. To date, the influence of glucose on magnesium degradation has not yet been elucidated, this issue requires more attention. Herein, we present pure Mg exhibiting different corrosion responses to saline and Hank’s solutions with different glucose contents, and the degradation mechanism of pure Mg in the saline solution with glucose in comparison with mannitol as a control. On one hand, the corrosion rate of pure Mg increases with the glucose concentration in saline solutions. Glucose rapidly transforms into gluconic acid, which attacks the oxides of the metal and decreases the pH of the solution; it also promotes the absorption of chloride ions on the Mg surface and consequently accelerates corrosion. On the other hand, better corrosion resistance is obtained with increasing glucose content in Hank’s solution due to the fact that glucose coordinates Ca2+ ions in Hank’s solution and thus improves the formation of Ca-P compounds on the pure Mg surface. This finding will open up new avenues for research on the biodegradation of bio-Mg materials in general, which could yield many new and interesting results. PMID:26264413

  6. Surface exciton emission of MgO crystals

    NASA Astrophysics Data System (ADS)

    Kuang, Wen-Jian; Li, Qing; Chen, Yu-Xiang; Hu, Kai; Wang, Ning-Hui; Xing, Fang-Li; Yan, Qun; Sun, Shuai-Shuai; Huang, Yan; Tao, Ye; Tolner, Harm

    2013-09-01

    MgO crystals have been exposed to vacuum ultraviolet (VUV) radiation from a synchrotron, with energies up to 9 eV, and the emitted light, at wavelengths above 200 nm, was observed. It is concluded that bulk excitons, play an important role in the diffusion of energy inside MgO crystals, resulting in 5.85 eV (212 nm) emission from the MgO terraces of large (0.2-2 µm) MgO : F crystals. In the case of aliovalent impurity doping, then the bulk exciton energy is also transferred to the Vk centres and 5.3 eV (235 nm) light is emitted. Both fluorine and silicon doping appear to promote UV surface emission, acting similarly to an ns2 ion inside MgO, while strong scandium doping is killing the surface emission completely. The 212 nm surface UV emission and the 235 nm bulk UV emission can be excited only at the bandgap edge. Broadband visible light, centred around 400 nm, is also emitted. Contrary to the UV emission, this is not generated when excited at the bandgap edge; instead, we find that it is only excited at sub-bandgap energies, with a maximum at the 5C surface excitation energy of 5.71 eV (217 nm) for the MgO terraces.

  7. Secondary Ionization Coefficient of MgO and Accumulated Charge

    NASA Astrophysics Data System (ADS)

    Suzuki, Susumu; Sekizawa, Takashi; Kashiwagi, Yasuhide; Itoh, Haruo

    2011-10-01

    An experimental study on Townsend's secondary ionization coefficient γ of MgO is carried out in accordance with a previously reported sequential procedure. A sinusoidal voltage is applied between the MgO film electrode and a stainless-steel electrode in the frequency range of 0.1 Hz-2 kHz. The breakdown voltage is determined from the observed waveforms of applied voltage and accumulated charge on the MgO film electrode. The influence on the breakdown voltage of the voltage induced by the accumulated charge is investigated. We found that the accumulated charge does not affect the breakdown voltage at low frequency or the DC voltage, but it affects the breakdown voltage at high frequency. Using the breakdown voltage, we determine Townsend's secondary ionization coefficient γ of MgO. The obtained γ for MgO in the study is compared with other reported values. It is found that γ for MgO is larger than those of metallic electrodes.

  8. On the Incidence and Kinematics of Strong Mg II Absorbers

    NASA Astrophysics Data System (ADS)

    Prochter, Gabriel E.; Prochaska, Jason X.; Burles, Scott M.

    2006-03-01

    We present the results of two complementary investigations into the nature of strong (rest equivalent width, Wr>1.0 Å) Mg II absorption systems at high redshift. The first line of questioning examines the complete Sloan Digital Sky Survey Data Release 3 set of quasar spectra to determine the evolution of the incidence of strong Mg II absorption. This search resulted in 7421 confirmed Mg II systems of Wr>1.0 Å, yielding a >95% complete statistical sample of 4835 absorbers (systems detected in S/N>7 spectral regions) spanning a redshift range 0.35Mg(X), is characterized by a roughly constant value at z>0.8, indicating that the product of the number density and gas cross section of halos hosting strong Mg II is unevolving at these redshifts. In contrast, one observes a decline in lMg(X) at z<0.8, which we interpret as a decrease in the gas cross section to strong Mg II absorption and therefore a decline in the physical processes relevant to strong Mg II absorption. Perhaps uncoincidentally, this evolution roughly tracks the global evolution of the star formation rate density. Dividing the systems in Wr subsamples, the lMg(X) curves show similar shape with lower normalization at higher Wr values and a more pronounced decrease in lMg(X) at z<0.8 for larger Wr systems. We also present the results of a search for strong Mg II absorption in a set of 91 high-resolution quasar spectra collected on the ESI and HIRES spectrographs. These data allow us to investigate the kinematics of such systems at 0.81.0 Å were discovered. These systems are characterized by the presence of numerous components spread over an average velocity width of Δv~200 km s-1. Also, absorption due to more highly ionized species (e.g., Al III, C IV, Si IV) tends to display kinematic profiles similar to the corresponding Mg II and Fe II absorption. We consider all of these

  9. A SIMS Calibration of Benthic Foraminiferal Mg/Ca

    NASA Astrophysics Data System (ADS)

    Curry, W. B.; Marchitto, T. M.

    2005-12-01

    Using a suite of multi-core tops, we have produced a calibration of C. pachyderma Mg/Ca versus temperature spanning the temperature range of 5 to 18 °C. The core tops are located along the Florida margin south of Dry Tortugas (KNR166), along the Bahamas west of Andros Island and Great Bahama Bank (KNR166), and along the southeastern margin of Brazil (KNR159). Water depths range from about 200 to 800 m for the Florida Straits multi-cores and 400 to 800 m for the Brazil margin multi-cores. Five of the KNR166 core tops contain post-1950 bomb radiocarbon with Fmodern> 1; several others have bomb radiocarbon mixed in with pre-bomb sediments to give ages less than 0 BP. Core top ages are generally older for the KNR159 multi-cores, but each is from a location with a well documented Holocene section. Sedimentation rates for KNR166 multi-cores vary from 10 to 100 cm kyr-1; for KNR159 multi-cores, sedimentation rates vary from 5 to 10 cm kyr-1. Elemental ratios were determined by Secondary Ionization Mass Spectrometry (SIMS) using a Cameca IMS 3f ion probe calibrated for Mg/Ca and Sr/Ca using two standards which were independently measured using ICP-MS. Using SIMS, the external precision of the calibration standards averages ±3.5% (1σ RSD) for Mg/Ca and ± 1.7% (1σ RSD) for Sr/Ca. SIMS elemental measurements were performed on one to three individual C. pachyderma tests in each core top; more than 30 tests have been measured from 18 multi-core tops. Mg/Ca variability within C. pachyderma tests averages ± 20% (1σ RSD) with a small but significant trend toward higher variability at higher Mg/Ca. Higher Mg/Ca is observed in warmer waters, but the Mg/Ca values are generally lower (at comparable warm temperatures) than observed in previous calibration studies. At temperatures below 8 °C, C. pachyderma Mg/Ca values are less than 2 mmole/mole. At temperatures warmer than 15 °C, C. pachyderma Mg/Ca values exceed 3 mmole/mole. The slope of Mg/Ca versus temperature (~0.14 mmole

  10. The role of Mg in the crystallization of monohydrocalcite

    NASA Astrophysics Data System (ADS)

    Rodriguez-Blanco, Juan Diego; Shaw, Samuel; Bots, Pieter; Roncal-Herrero, Teresa; Benning, Liane G.

    2014-02-01

    Monohydrocalcite is a member of the carbonate family which forms in Mg-rich environments at a wide range of Mg/Ca ratios Mg2+aq/Ca2+aq≥0.17<65. Although found in modern sedimentary deposits and as a product of biomineralization, there is a lack of information about its formation mechanisms and about the role of Mg during its crystallization. In this work we have quantitatively assessed the mechanism of crystallization of monohydrocalcite through in situ synchrotron-based small and wide angle X-ray scattering (SAXS/WAXS) and off-line spectroscopic, microscopic and wet chemical analyses. Monohydrocalcite crystallizes via a 4-stage process beginning with highly supersaturated solutions from which a Mg-bearing, amorphous calcium carbonate (ACC) precursor precipitates. This precursor crystallizes to monohydrocalcite via a nucleation-controlled reaction in stage two, while in stage three it is further aged through Ostwald-ripening at a rate of 1.8 ± 0.1 nm/h1/2. In stage four, a secondary Ostwald ripening process (66.3 ± 4.3 nm/h1/2) coincides with the release of Mg from the monohydrocalcite structure and the concomitant formation of minor hydromagnesite. Our data reveal that monohydrocalcite can accommodate significant amounts of Mg in its structure (χMgCO3 = 0.26) and that its Mg content and dehydration temperature are directly proportional to the saturation index for monohydrocalcite (SIMHC) immediately after mixing the stock solutions. However, its crystallite and particle size are inversely proportional to these parameters. At high supersaturations (SIMHC = 3.89) nanometer-sized single crystals of monohydrocalcite form, while at low values (SIMHC = 2.43) the process leads to low-angle branching spherulites. Many carbonates produced during biomineralization form at similar conditions to most synthetic monohydrocalcites, and thus we hypothesize that some calcite or aragonite deposits found in the geologic record that have formed at high Mg/Ca ratios could be

  11. Loss of Endothelial Barrier in Marfan Mice (mgR/mgR) Results in Severe Inflammation after Adenoviral Gene Therapy

    PubMed Central

    Weymann, Alexander; Arif, Rawa; Weber, Antje; Zaradzki, Marcin; Richter, Karsten; Ensminger, Stephan; Robinson, Peter Nicholas; Wagner, Andreas H.; Karck, Matthias; Kallenbach, Klaus

    2016-01-01

    Objectives 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. Methods 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). Results 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

  12. In Vitro Degradation Behavior of Ternary Mg-Zn-Se and Mg-Zn-Cu Alloys as Biomaterials

    PubMed Central

    Persaud-Sharma, Dharam; Budiansky, Noah

    2013-01-01

    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

  13. Density functional theory (DFT) study on the hydrolysis behavior of degradable Mg/Mg alloys for biomedical applications

    NASA Astrophysics Data System (ADS)

    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

  14. Effect of organic ligands on Mg partitioning and Mg isotope fractionation during low-temperature precipitation of calcite

    NASA Astrophysics Data System (ADS)

    Mavromatis, Vasileios; Immenhauser, Adrian; Buhl, Dieter; Purgstaller, Bettina; Baldermann, Andre; Dietzel, Martin

    2016-04-01

    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. Mg2+ dependence of guanine nucleotide binding to tubulin.

    PubMed

    Correia, J J; Baty, L T; Williams, R C

    1987-12-25

    The relationship between the concentration of Mg2+ and the binding of GDP and GTP to tubulin dimers was investigated by measuring the displacement of the nucleotide bound at the exchangeable site (E-site) by radiolabeled GDP and GTP. A wide range of concentrations of GTP, GDP, and Mg2+ was explored. In the near absence of Mg2+, the affinity of tubulin for GDP was found to be much greater than its affinity for GTP. In the presence of 1.0 mM Mg2+, however, its affinity for GDP was slightly less than for GTP. The results could be quantitatively described in terms of a small number of reversible equilibria. Equilibrium constants, pertaining to measurements at 0 degrees C, in 0.1 M piperazine-N,N'-bis(2-ethanesulfonic acid), 0.2 mM dithioerythritol, 2 mM EGTA, pH 6.9, were obtained by nonlinear least squares fitting of the data. When the association constant of tubulin for GDP uncomplexed with Mg2+ was taken to be 1.6 X 10(7) M-1, that for uncomplexed GTP was found to be no larger than 1.4 x 10(4) M-1, at least 1100-fold smaller. The association constant of tubulin for the GDP.Mg2+ complex was found to be 2.5-2.7 x 10(7) M-1, while that for the GTP.Mg2+ complex is 6.4-9.0 x 10(7) M-1. PMID:2826416

  16. Nanoscale order in ZnSe:(Mg, O)

    SciTech Connect

    Elyukhin, Vyacheslav A.

    2014-02-21

    Self-assembling of 1O4Mg identical tetrahedral clusters resulting in the nanoscale order in ZnSe:(Mg, O) is presented. Co-doping transforms ZnSe into Mg{sub x}Zn{sub 1−x}O{sub y}Se{sub 1−y} alloy of MgO, MgSe, ZnO and ZnSe. The decrease of a sum of the enthalpies of the constituent compounds and diminution of the strain energy are the causes of this phenomenon. The self-assembling conditions are obtained from the free energy minimum when magnesium and oxygen are in the dilute and ultra dilute limits, correspondingly. The occurrence of 1O4Mg clusters and completion of self-assembling when all oxygen atoms are in clusters are results of the continuous phase transitions. The self-assembling occurrence temperature does not depend on the oxygen content and it is a function of magnesium concentration. Mg{sub x}Zn{sub 1−x}O{sub y}Se{sub 1−y} with all oxygen atoms in clusters can be obtained in temperature ranges from T = 206 °C (x = 0.001, y = 1×10{sup −4}) to T = 456 °C (x = 0.01, y = 1×10{sup −4}) and from T = 237 °C (x = 0.001, y = 1×10{sup −6}) to T = 462 °C (x = 0.01, y = 1×10{sup −6})

  17. Contributions of Mycorrhizal Trees to Mg Isotopic Variations in Weathering

    NASA Astrophysics Data System (ADS)

    Bryce, J. G.; Hobbie, E. A.; Blichert-Toft, J.; Colpaert, J.; Hoff, C.; Prado, M. F.; Pettitt, E.; Telouk, P.

    2013-12-01

    Although it is well established that organisms contribute significantly to the weathering process and to the distribution of elements within continental environments, the degree to which biota actively drive weathering versus the degree to which organisms benefit from nutrients released during largely inorganic weathering processes remains shrouded in mystery. Furthermore, the relative influence of different organisms on key emerging isotopic systems, especially Mg, remains poorly understood. To address these questions, we have carried out a series of Mg isotopic investigations on semi-hydroponically cultured trees (pine, Pinus sylvestris and sugar maple, Acer saccharum) grown with appropriate mycorrhizal symbionts (ectomycorrhizal, Suillus, or arbuscular, Glomus, respectively) in different geologic substrates (carbonate and granitic) under low nutrient supply. Plant tissues and eluting solutions across these biogeochemical experiments were studied for elemental abundances and Mg isotopic signatures. Eluting solutions were most distinctive from the abiotic control for those trees grown in granite-bearing cultures, an observation we attribute to biotite weathering. Foliar and root tissues recorded distinctive isotopic compositions (e.g., differences up to 0.6 ‰ δ26/24Mg) in both the pines and sugar maples. Foliar δ26/24Mg varied amongst the trees grown in the different experiments: compared to the substrate, ectomycorrhizal pine had more depleted Mg isotopic signatures in foliage than nonmycorrhizal pine and arbuscular mycorrhizal sugar maple. Taken together our results indicate that ectomycorrhizal symbioses contribute to Mg isotopic variations during weathering and that this effect may be more pronounced in soils forming over biotite-bearing terrains.

  18. MG132 reverse the malignant characteristics of hypopharyngeal cancer.

    PubMed

    Ma, Juke; Yu, Liang; Tian, Jiajun; Mu, Yakui; Lv, Zhenghua; Zou, Jidong; Li, Jianfeng; Wang, Haibo; Xu, Wei

    2014-06-01

    In order to reverse the malignant characteristics of hypopharyngeal cancer, the proteasome inhibitor MG132 was introduced into FaDu/T cells and the mechanisms underlying its effects were investigated. The multi-drug resistance (MDR) sensitivities of FaDu/T and FaDu/T-MG132 cancer cells to several chemotherapeutics were investigated by a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide (MTT) assay. Apoptosis was measured by staining cells with Annexin V and propidium iodide (PI) double staining. Reverse transcription-polymerase chain reaction and western blot analysis were conducted to detect mRNA and corresponding protein levels of the MDR- and apoptosis-related genes P-glycoprotein (P-gp), caspase-3, Bcl-2 and Bax. The nuclear protein of nuclear factor κ-light-chain-enhancer of activated B cells. (NF-κB) and p53 were also investigated via western blot analysis. Compared with FaDu/T cells, the drug resistance of FaDu/T + MG132 cells to cisplatin (DDP), 5-fluorouracil (5-FU), doxorubicin (Dox) and vincristine (VCR) decreased. With increased expression of caspase-3 and Bax and decreased expression of Bcl-2, the anti-apoptotic ability markedly decreased in FaDu/T + MG132 cells. P-gp and NF-κB significantly decreased; however, p53 increased in FaDu/T + MG132 cells. These results suggested that the proteasome inhibitor MG132 reversed the malignant characteristics of FaDu/T by enhancing apoptosis and inhibiting P-gp. MG132 was also able to inhibit the nuclear translocation of NF-κB and increase the expression of p53. PMID:24691740

  19. Cardiac myosin isoforms exhibit differential rates of MgADP release and MgATP binding detected by myocardial viscoelasticity.

    PubMed

    Wang, Yuan; Tanner, Bertrand C W; Lombardo, Andrew T; Tremble, Sarah M; Maughan, David W; Vanburen, Peter; Lewinter, Martin M; Robbins, Jeffrey; Palmer, Bradley M

    2013-01-01

    We measured myosin crossbridge detachment rate and the rates of MgADP release and MgATP binding in mouse and rat myocardial strips bearing one of the two cardiac myosin heavy chain (MyHC) isoforms. Mice and rats were fed an iodine-deficient, propylthiouracil diet resulting in ~100% expression of β-MyHC in the ventricles. Ventricles of control animals expressed ~100% α-MyHC. Chemically-skinned myocardial strips prepared from papillary muscle were subjected to sinusoidal length perturbation analysis at maximum calcium activation pCa 4.8 and 17°C. Frequency characteristics of myocardial viscoelasticity were used to calculate crossbridge detachment rate over 0.01 to 5mM [MgATP]. The rate of MgADP release, equivalent to the asymptotic value of crossbridge detachment rate at high MgATP, was highest in mouse α-MyHC (111.4±6.2s(-1)) followed by rat α-MyHC (65.0±7.3s(-1)), mouse β-MyHC (24.3±1.8s(-1)) and rat β-MyHC (15.5±0.8s(-1)). The rate of MgATP binding was highest in mouse α-MyHC (325±32 mM(-1) s(-1)) then mouse β-MyHC (152±23 mM(-1) s(-1)), rat α-MyHC (108±10 mM(-1) s(-1)) and rat β-MyHC (55±6 mM(-1) s(-1)). Because the events of MgADP release and MgATP binding occur in a post power-stroke state of the myosin crossbridge, we infer that MgATP release and MgATP binding must be regulated by isoform- and species-specific structural differences located outside the nucleotide binding pocket, which is identical in sequence for these four myosins. We postulate that differences in the stiffness profile of the entire myosin molecule, including the thick filament and the myosin-actin interface, are primarily responsible for determining the strain on the nucleotide binding pocket and the subsequent differences in the rates of nucleotide release and binding observed among the four myosins examined here. PMID:23123290

  20. Magnesium phthalocyanine(MgPc) thin films as nanomaterials

    NASA Astrophysics Data System (ADS)

    Puri, Munish; Bedi, R. K.; Prakash, G. V.

    2006-05-01

    MgPc is a promising candidate for photovoltaic applications. It can be easily synthesized and is non-toxic to the envioronment. It is a self assembly molecule developed from deep-blue-green pigment. It exhibits a characteristic structural self organization which is reflected in an efficient energy migration in the form of extinction transport. MgPc relates to the similarity with chlorophyll. In the present work thin films of MgPc have been prepared on glass substrate under strict vacuum conditions(10 Â6 torr), thickness of few nanometers. Absorption spectra in Visible and IR regions have been observed which is good for fabrication of Photovoltaic cells and Nanostructures for Photodynamic Cancer Therapy. Appreciable amount of cytotoxicity can be observed while using MgPc as photosensitizers which is a promising PDT agent. The films thus prepared have been studied for their electrical and optical characterizations. Investigations have been made from different stacking positions of molecular MgPc thin films for studying their self-assembling nature that can be useful for their applications as Molecular-Recognition in Drug delivery and sensors which is one of the key features of Nanotechnology.

  1. DIFFUSION OF MAGNESIUM AND MICROSTRUCTURES IN Mg+ IMPLANTED SILICON CARBIDE

    SciTech Connect

    Jiang, Weilin; Edwards, Danny J.; Jung, Hee Joon; Wang, Zheming; Zhu, Zihua; Roosendaal, Timothy J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2014-08-28

    Following our previous reports [ 1- 3], further isochronal annealing (2 hrs.) of the monocrystalline 6H-SiC and polycrystalline CVD 3C-SiC was performed at 1573 and 1673 K in Ar environment. SIMS data indicate that observable Mg diffusion in 6H-SiC starts and a more rapid diffusion in CVD 3C-SiC occurs at 1573 K. The implanted Mg atoms tend to diffuse deeper into the undamaged CVD 3C-SiC. The microstructure with Mg inclusions in the as-implanted SiC has been initially examined using high-resolution STEM. The presence of Mg in the TEM specimen has been confirmed based on EDS mapping. Additional monocrystalline 3C-SiC samples have been implanted at 673 K to ion fluence 3 times higher than the previous one. RBS/C analysis has been performed before and after thermal annealing at 1573 K for 12 hrs. Isothermal annealing at 1573 K is being carried out and Mg depth profiles being measured. Microstructures in both the as-implanted and annealed samples are also being examined using STEM.

  2. MAGNESIUM PRECIPITATION AND DIFUSSION IN Mg+ ION IMPLANTED SILICON CARBIDE

    SciTech Connect

    Jiang, Weilin; Jung, Hee Joon; Kovarik, Libor; Wang, Zhaoying; Roosendaal, Timothy J.; Zhu, Zihua; Edwards, Danny J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2015-03-02

    As a candidate material for fusion reactor applications, silicon carbide (SiC) undergoes transmutation reactions under high-energy neutron irradiation with magnesium as the major metallic transmutant; the others include aluminum, beryllium and phosphorus in addition to helium and hydrogen gaseous species. Calculations by Sawan et al. predict that at a dose of ~100 dpa (displacements per atom), there is ~0.5 at.% Mg generated in SiC. The impact of these transmutants on SiC structural stability is currently unknown. This study uses ion implantation to introduce Mg into SiC. Multiaxial ion-channeling analysis of the as-produced damage state indicates a lower dechanneling yield observed along the <100> axis. The microstructure of the annealed sample was examined using high-resolution scanning transmission electron microscopy. The results show a high concentration of likely non-faulted tetrahedral voids and possible stacking fault tetrahedra near the damage peak. In addition to lattice distortion, dislocations and intrinsic and extrinsic stacking faults are also observed. Magnesium in 3C–SiC prefers to substitute for Si and it forms precipitates of cubic Mg2Si and tetragonal MgC2. The diffusion coefficient of Mg in 3C–SiC single crystal at 1573 K has been determined to be 3.8 ± 0.4E-19 m2/s.

  3. Multifunctional MgO Layer in Perovskite Solar Cells.

    PubMed

    Guo, Xudong; Dong, Haopeng; Li, Wenzhe; Li, Nan; Wang, Liduo

    2015-06-01

    A multifunctional magnesium oxide (MgO) layer was successfully introduced into perovskite solar cells (PSCs) to enhance their performance. MgO was coated onto the surface of mesoporous TiO(2) by the decomposition of magnesium acetate and, therefore, could block contact between the perovskite and TiO(2). X-ray photoelectron spectroscopy and infrared spectroscopy showed that the amount of H(2)O/hydroxyl absorbed on the TiO(2) decreased after MgO modification. The UV/Vis absorption spectra of the perovskite with MgO modification revealed an enhanced photoelectric performance compared with that of unmodified perovskite after UV illumination. In addition to the photocurrent, the photovoltage and fill factor also showed an enhancement after modification, which resulted in an increase in the overall efficiency of the cell from 9.6 to 13.9 %. Electrochemical impedance spectroscopy (EIS) confirmed that MgO acts as an insulating layer to reduce charge recombination. PMID:25851999

  4. Hot Tearing Susceptibility of Mg-Ca Binary Alloys

    NASA Astrophysics Data System (ADS)

    Song, Jiangfeng; Wang, Zhi; Huang, Yuanding; Srinivasan, Amirthalingam; Beckmann, Felix; Kainer, Karl Ulrich; Hort, Norbert

    2015-12-01

    Hot tearing is known as one of the most critical solidification defects commonly encountered during casting practice. As most Mg alloys are initially prepared by casting, ingots must have superior quality with no casting defects for the further processing. Due to the extensive potential biodegradable applications of binary Mg-Ca alloys, it is of great importance to investigate their hot tearing behavior. In the present study, the influence of Ca content (0.1, 0.2, 0.5, 1.0, and 2.0 wt pct) on hot tearing susceptibility (HTS) of Mg-Ca binary alloys was investigated using a constrained rod casting apparatus equipped with a load cell and data acquisition system. Tear volumes were quantified with 3D X-ray tomography. Results showed that the influence of Ca content on HTS followed a "Λ" shape: the HTS increased with increase in Ca content, reached a maximum at 0.5 to 1 wt pct Ca, and then decreased with further increasing the Ca content to 2.0 wt pct. The wide solidification range and reasonably high volume of intermetallic in the Mg-0.5 wt pct Ca and Mg-1 wt pct Ca alloys resulted in high HTS. Microstructure analysis suggested that the hot tear initiated at grain boundaries and propagated along them through thin film rupture or across the eutectic.

  5. Harvesting of microalgae species using Mg-sericite flocculant.

    PubMed

    Lee, Seung-Mok; Choi, Hee-Jeong

    2015-12-01

    In this study, Mg-sericite was used as a flocculant to harvest freshwater microalgae Chlorella vulgaris. Mg-sericite separated successfully >99% of the C. vulgaris at the following optimal parameters: sericite and MgCl2 ratio (S/M ratio) of 45 to 15, mixing time of 5 min, mixing rate 100 to 150 rpm and settling time of 5 min. The harvesting efficiency was pH dependent. The highest harvesting efficiency (99 ± 0.3%) was obtained at S/M ratio 40 and pH 9-11. These results indicated that a biopolymer, Mg-sericite, can be a promising flocculant due to its high efficiency, low-dose requirements, and short mixing and settling times. In addition, Mg-sericite does not contaminate the growth medium, which can be recycled to reduce not only the cost and the demand for water, but also the extra operational costs for reusing the growth medium. This harvesting method is helpful to lower the production cost of algae for biodiesel. PMID:26341111

  6. Atomic simulation of mechanical behavior of Mg in a super-lattice of nanocrystalline Mg and amorphous Mg-Al alloy

    SciTech Connect

    Song, H. Y.; An, M. R.; Li, Y. L. Deng, Q.

    2014-12-07

    The mechanical properties of a super-lattice architecture composed of nanocrystalline Mg and Mg-Al amorphous alloy are investigated using molecular dynamics simulation. The results indicate that deformation mechanism of nanocrystalline Mg is obviously affected by the amorphous boundary spacing and temperature. The strength of the material increases with the decrease of amorphous boundary spacing, presenting a Hall-Petch effect at both 10 K and 300 K. A stress platform and following stiffness softening, as well as a linear strengthening in the plastic stage, are observed when the amorphous boundary spacing below 8.792 nm at 10 K. The implying reason may be that the amorphous boundary acts as the dislocations emission and absorption source. However, the second stress peak is not observed for the models at 300 K. Instead, the flow stress in plastic stage is a nearly constant value. The simulation demonstrates the emergence of the new grain, accompanied by the deformation twins and stacking faults associated with the plastic behaviors at 300 K. The general conclusions derived from this work may provide a guideline for the design of high-performance hexagonal close-packed metals.

  7. The MG-RAST metagenomics database and portal in 2015.

    PubMed

    Wilke, Andreas; Bischof, Jared; Gerlach, Wolfgang; Glass, Elizabeth; Harrison, Travis; Keegan, Kevin P; Paczian, Tobias; Trimble, William L; Bagchi, Saurabh; Grama, Ananth; Chaterji, Somali; Meyer, Folker

    2016-01-01

    MG-RAST (http://metagenomics.anl.gov) is an open-submission data portal for processing, analyzing, sharing and disseminating metagenomic datasets. The system currently hosts over 200,000 datasets and is continuously updated. The volume of submissions has increased 4-fold over the past 24 months, now averaging 4 terabasepairs per month. In addition to several new features, we report changes to the analysis workflow and the technologies used to scale the pipeline up to the required throughput levels. To show possible uses for the data from MG-RAST, we present several examples integrating data and analyses from MG-RAST into popular third-party analysis tools or sequence alignment tools. PMID:26656948

  8. The MG-RAST Metagenomics Database and Portal in 2015

    DOE PAGESBeta

    Wilke, Andreas; Bischof, Jared; Gerlach, Wolfgang; Glass, Elizabeth; Harrison, Travis; Keegan, Kevin; Paczian, Tobias; Trimble, William L.; Bagchi, Saurabh; Grama, Ananth; et al

    2015-12-09

    MG-RAST (http://metagenomics.anl.gov) is an opensubmission data portal for processing, analyzing, sharing and disseminating metagenomic datasets. Currently, the system hosts over 200 000 datasets and is continuously updated. The volume of submissions has increased 4-fold over the past 24 months, now averaging 4 terabasepairs per month. In addition to several new features, we report changes to the analysis workflow and the technologies used to scale the pipeline up to the required throughput levels. Lastly, to show possible uses for the data from MG-RAST, we present several examples integrating data and analyses from MG-RAST into popular third-party analysis tools or sequence alignmentmore » tools.« less

  9. The MG-RAST Metagenomics Database and Portal in 2015

    SciTech Connect

    Wilke, Andreas; Bischof, Jared; Gerlach, Wolfgang; Glass, Elizabeth; Harrison, Travis; Keegan, Kevin; Paczian, Tobias; Trimble, William L.; Bagchi, Saurabh; Grama, Ananth; Chaterji, Somali; Meyer, Folker

    2015-12-09

    MG-RAST (http://metagenomics.anl.gov) is an opensubmission data portal for processing, analyzing, sharing and disseminating metagenomic datasets. Currently, the system hosts over 200 000 datasets and is continuously updated. The volume of submissions has increased 4-fold over the past 24 months, now averaging 4 terabasepairs per month. In addition to several new features, we report changes to the analysis workflow and the technologies used to scale the pipeline up to the required throughput levels. Lastly, to show possible uses for the data from MG-RAST, we present several examples integrating data and analyses from MG-RAST into popular third-party analysis tools or sequence alignment tools.

  10. The corrosivity and passivity of sputtered Mg-Ti alloys

    SciTech Connect

    Song, Guang -Ling; Unocic, Kinga A.; Meyer, III, Harry M.; Cakmak, Ercan; Brady, Michael P.; Gannon, Paul E.; Himmer, Phil; Andrews, Quinn

    2015-11-30

    Our study explored the possibility of forming a “stainless” Mg–Ti alloy. The electrochemical behavior of magnetron-sputtered Mg–Ti alloys was measured in a NaCl solution, and the surface films on the alloys were examined by XPS, SEM and TEM. Increased corrosion resistance was observed with increased Ti content in the sputtered Mg–Ti alloys, but passive-like behavior was not reached until the Ti level (atomic %) was higher than the Mg level. Moreover, the surface film that formed on sputtered Mg–Ti based alloys in NaCl solution was thick, discontinuous and non-protective, whereas a thin, continuous and protective Mg and Ti oxide film was formed on a sputtered Ti–Mg based alloy.

  11. Mechanical properties of alloy Mg-Li rod in tension

    NASA Astrophysics Data System (ADS)

    Zhang, Xueyi; Zou, Guangping; Cao, Yang; Yue, Baocheng

    2009-12-01

    Light-weight metal or alloy was widespread in aerospace and aeronautical engineering. Alloy Li-Mg was the lightest metal structural materials. Focus was recently on this alloy. Static mechanical properties were important for materials before they were applied into practical use. Static Testing of a new alloy Li-Mg was accomplished in this paper by universal materials testing system Model INSTRON 5500R. Stress-strain curve was acquired. And ultimate stress, yield stress, elongation in percentage and reduce of area in percentage were measured in detail. The result showed that alloy had higher strength to 250MPa in tension. But the deformation was hardly changed in length or section before it cracked. All the experimental result proved that this material was typical brittle materials. Fractography had been observed by scanning electron microscope (SEM). SEM Photos were also verified alloy Li-Mg was ductile material.

  12. Mechanical properties of alloy Mg-Li rod in tension

    NASA Astrophysics Data System (ADS)

    Zhang, Xueyi; Zou, Guangping; Cao, Yang; Yue, Baocheng

    2010-03-01

    Light-weight metal or alloy was widespread in aerospace and aeronautical engineering. Alloy Li-Mg was the lightest metal structural materials. Focus was recently on this alloy. Static mechanical properties were important for materials before they were applied into practical use. Static Testing of a new alloy Li-Mg was accomplished in this paper by universal materials testing system Model INSTRON 5500R. Stress-strain curve was acquired. And ultimate stress, yield stress, elongation in percentage and reduce of area in percentage were measured in detail. The result showed that alloy had higher strength to 250MPa in tension. But the deformation was hardly changed in length or section before it cracked. All the experimental result proved that this material was typical brittle materials. Fractography had been observed by scanning electron microscope (SEM). SEM Photos were also verified alloy Li-Mg was ductile material.

  13. Hydrothermal synthesis of Mg-Al hydrotalcites by urea hydrolysis

    SciTech Connect

    Rao, M. Mohan . E-mail: mandapati@iict.res.in; Reddy, B. Ramachandra; Jayalakshmi, M.; Jaya, V. Swarna; Sridhar, B.

    2005-02-15

    We report a simple method to prepare hydrotalcites involving both urea hydrolysis and hydrothermal synthetic conditions. Out of a series of Mg/Al ratios tried, pure hydrotalcite like phase was obtained for Mg/Al ratios of 1:1 and 2:1. Unlike in conventional co-precipitation method we succeeded in preparing Mg/Al ratio of 1:1 by this route. The high temperature (180 deg. C) applied and pressure developed in the autoclave during the synthesis might have altered the topochemical transformation. The materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, thermo gravimetric and differential thermal analysis and transmission electron microscopy.

  14. The Mg II h and k lines in Vega

    NASA Technical Reports Server (NTRS)

    Ferrero, R. F.; Gouttebroze, P.; Kondo, Y.

    1983-01-01

    High resolution h (2802.7 A) and k (2795.5 A) lines Mg II obtained for the star Vega (Alpha Lyr, A0V) with Copernicus satellite and a balloon-borne ultraviolet stellar spectrometer (BUSS) are interpreted by means of theoretical NLTE line profiles in the frame work of complete (CR) and partial (PR) redistribution hypothesis. The PR profiles are remarkably coincident with the observed ones for a magnesium abundance Mg/H = 0.00001 and a projected rotation velocity v sin i = 17 km/s. LTE and NLTE atmospheric models with a temperature plateau or with temperature rises (depending on whether the atmosphere is in radiative equilibrium or not) are used to account for the possible presence of a chromosphere on Vega. The possible presence of an interstellar Mg II absorption line superimposed on the stellar ones is also discussed.

  15. Improved Mg-based alloys for hydrogen storage

    SciTech Connect

    Sapru, K.; Ming, L.; Stetson, N.T.; Evans, J.

    1998-08-01

    The overall objective of this on-going work is to develop low temperature alloys capable of reversibly storing at least 3 wt.% hydrogen, allowing greater than for 2 wt.% at the system level which is required by most applications. Surface modification of Mg can be used to improve its H-sorption kinetics. The authors show here that the same Mg-transition metal-based multi-component alloy when prepared by melt-spinning results in a more homogeneous materials with a higher plateau pressure as compared to preparing the material by mechanical grinding. They have also shown that mechanically alloyed Mg{sub 50}Al{sub 45}Zn{sub 5} results in a sample having a higher plateau pressure.

  16. Metagenomes from Argonne's MG-RAST Metagenomics Analysis Server

    DOE Data Explorer

    MG-RAST has a large number of datasets that researchers have deposited for public use. As of July, 2014, the number of metagenomes represented by MG-RAST numbered more than 18,500, and the number of available sequences was more than 75 million! The public can browse the collection several different ways, and researchers can login to deposit new data. Researchers have the choice of keeping a dataset private so that it is viewable only by them when logged in, or they can choose to make a dataset public at any time with a simple click of a link. MG-RAST was launched in 2007 by the Mathematics and Computer Science Division at Argonne National Laboratory (ANL). It is part of the toolkit available to the Terragenomics project, which seeks to do a comprehensive metagenomics study of U.S. soil. The Terragenomics project page is located at http://www.mcs.anl.gov/research/projects/terragenomics/.

  17. The MG-RAST metagenomics database and portal in 2015

    PubMed Central

    Wilke, Andreas; Bischof, Jared; Gerlach, Wolfgang; Glass, Elizabeth; Harrison, Travis; Keegan, Kevin P.; Paczian, Tobias; Trimble, William L.; Bagchi, Saurabh; Grama, Ananth; Chaterji, Somali; Meyer, Folker

    2016-01-01

    MG-RAST (http://metagenomics.anl.gov) is an open-submission data portal for processing, analyzing, sharing and disseminating metagenomic datasets. The system currently hosts over 200 000 datasets and is continuously updated. The volume of submissions has increased 4-fold over the past 24 months, now averaging 4 terabasepairs per month. In addition to several new features, we report changes to the analysis workflow and the technologies used to scale the pipeline up to the required throughput levels. To show possible uses for the data from MG-RAST, we present several examples integrating data and analyses from MG-RAST into popular third-party analysis tools or sequence alignment tools. PMID:26656948

  18. Interpretation of Na-K-Mg relations in geothermal waters

    USGS Publications Warehouse

    Fournier, R.O.

    1990-01-01

    When using a Na-K-???Mg triangular diagram as an aid in the interpretation of a geothermal water, the estimated temperature of last water-rock equilibration may change by as much as 50??C, depending on which of the many Na/K geothermometers one assumes is correct. A particular geothermometer may work well in one place and not in another because of differences in the mineralogy of the phases that are in contact with the reservoir fluid. The position of the full equilibrium line that is used for geothermometry and for assessing degrees of departure from equilibrium also changes as the assumed K/???Mg geothermometer equation changes. The degree of ambiguity can be evaluated by utilizing the results of all the recently published Na/K geothermometers on a single Na-K-???Mg triangular plot.

  19. Preparation and properties of high purity Mg-Y biomaterials.

    PubMed

    Peng, Qiuming; Huang, Yuanding; Zhou, Le; Hort, Norbert; Kainer, Karl Ulrich

    2010-01-01

    An effective zone solidification method has been found to prepare high purity Mg-Y biomaterials. The corrosion and mechanical properties of the purified middle region are improved remarkably compared with common casting method. The average gain size and secondary dendrite space decrease from the top layer to the bottom layer of the ingot. The oxides, defects and precipitates are mainly enriched in the top layer of the ingot under the impulsion of high thermal gradient. These results are in agreement with that simulated by finite elemental method using FLOW-3D software. It is confirmed that the mode of scallop symmetric solidification attributes to the purifying process. This zone solidification method not only contributes to high purity Mg-based biomaterials, but also provides a new approach to prepare high performance Mg alloys. PMID:19800117

  20. Mg II line profiles of the Mira S Carinae

    NASA Technical Reports Server (NTRS)

    Brugel, Edward W.; Bookbinder, Jay A.; Brown, Alexander

    1988-01-01

    High-dispersion IUE observations obtained to investigate the evolution of the shock structure of the Mira S Carinae (S Car) produced, despite very limited phase coverage, a set of five spectra of the Mg II h and k lines. There is significant emission from both the h and k lines at velocities of -150 km/sec relative to the stellar photosphere. The h-to-k ratio of the Mg II doublet remains below the theoretically predicated values of 2:1 to 1:1, and shows a smooth dependence on the optical phase. Archival studies of other Miras (e.g., R Car) indicate that S Car is not unique in possessing unusual and highly variable Mg II h and k line profiles.

  1. EBSD analysis of MgB2 bulk superconductors

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Schmauch, J.; Inoue, K.; Muralidhar, M.; Berger, K.; Noudem, J.

    2016-04-01

    The grain orientation, the texture and the grain boundary misorientations are important parameters for the understanding of the magnetic properties of the bulk MgB2 samples intended for super-magnet applications. Such data can be provided by electron backscatter diffraction (EBSD) analysis. However, as the grain size (GS) of the MgB2 bulks is preferably in the 100-200 nm range, the common EBSD technique working in reflection operates properly only on highly dense samples. In order to achieve a reasonably good Kikuchi pattern quality on all samples, we apply here the newly developed transmission EBSD (t-EBSD) technique to several bulk MgB2 samples. This method requires the preparation of TEM slices by means of focused ion-beam milling, which are then analyzed within the SEM, operating with a specific sample holder. We present several EBSD mappings of samples prepared with different techniques and at various reaction temperatures.

  2. Synthesis of Si, Mg substituted hydroxyapatites and their sintering behaviors.

    PubMed

    Kim, S R; Lee, J H; Kim, Y T; Riu, D H; Jung, S J; Lee, Y J; Chung, S C; Kim, Y H

    2003-04-01

    Si, Mg-substituted hydroxyapatites, alone and co-substituted, have been prepared to obtain biomaterials having an improved biocompatibility. From FT-IR, XRD and ICP analyses, it was confirmed that single phases of hydroxyapatite substituted by Si alone or co-substituted by Si, Mg. The XRD data indicated the absence of extra phases related to silicon and magnesium oxide or other calcium phosphate species. Si-substituted hydroxyapatite of up to 2 wt% for Si and Si, Mg co-substituted hydroxyapatite of 1 wt% for the each ion keep their original structures intact for the sintering temperatures of up to 1200 degrees C. However, it is observed that ion substitutions by an amount higher than the above ratios for each hydroxyapatite lead to destabilization of original structures of the hydroxyapatite and to the production of tricalcium phosphate and calcium phosphate silicate phases when the samples were sintered at 1100 degrees C or higher. PMID:12527280

  3. The corrosivity and passivity of sputtered Mg-Ti alloys

    DOE PAGESBeta

    Song, Guang -Ling; Unocic, Kinga A.; Meyer, III, Harry M.; Cakmak, Ercan; Brady, Michael P.; Gannon, Paul E.; Himmer, Phil; Andrews, Quinn

    2015-11-30

    Our study explored the possibility of forming a “stainless” Mg–Ti alloy. The electrochemical behavior of magnetron-sputtered Mg–Ti alloys was measured in a NaCl solution, and the surface films on the alloys were examined by XPS, SEM and TEM. Increased corrosion resistance was observed with increased Ti content in the sputtered Mg–Ti alloys, but passive-like behavior was not reached until the Ti level (atomic %) was higher than the Mg level. Moreover, the surface film that formed on sputtered Mg–Ti based alloys in NaCl solution was thick, discontinuous and non-protective, whereas a thin, continuous and protective Mg and Ti oxide filmmore » was formed on a sputtered Ti–Mg based alloy.« less

  4. Fabrication of Single Crystal MgO Capsules

    NASA Technical Reports Server (NTRS)

    Danielson, Lisa

    2012-01-01

    A method has been developed for machining MgO crystal blocks into forms for containing metallic and silicate liquids at temperatures up to 2,400 C, and pressures up to at least 320 kilobars. Possible custom shapes include tubes, rods, insulators, capsules, and guides. Key differences in this innovative method include drilling along the crystallographic zone axes, use of a vibration minimizing material to secure the workpiece, and constant flushing of material swarf with a cooling medium/lubricant (water). A single crystal MgO block is cut into a section .5 mm thick, 1 cm on a side, using a low-speed saw with a 0.004 blade. The cut is made parallel to the direction of cleavage. The block may be cut to any thickness to achieve the desired length of the piece. To minimize drilling vibrations, the MgO block is mounted on a piece of adhesive putty in a vise. The putty wad cradles the bottom half of the entire block. Diamond coring tools are used to drill the MgO to the desired custom shape, with water used to wet and wash the surface of swarf. Compressed air may also be used to remove swarf during breaks in drilling. The MgO workpiece must be kept cool at all times with water. After all the swarf is rinsed off, the piece is left to dry overnight. If the workpiece is still attached to the base of the MgO block after drilling, it may be cut off by using a diamond cutoff wheel on a rotary hand tool or by using a low-speed saw.

  5. THE Mg II CROSS-SECTION OF LUMINOUS RED GALAXIES

    SciTech Connect

    Bowen, David V.; Chelouche, Doron

    2011-01-20

    We describe a search for Mg II {lambda}{lambda}2796, 2803 absorption lines in Sloan Digital Sky Survey (SDSS) spectra of QSOs whose lines of sight pass within impact parameters {rho} {approx} 200 kpc of galaxies with photometric redshifts of z = 0.46-0.6 and errors {Delta}z {approx} 0.05. The galaxies selected have the same colors and luminosities as the Luminous Red Galaxy (LRG) population previously selected from the SDSS. A search for Mg II lines within a redshift interval of {+-}0.1 of a galaxy's photometric redshift shows that absorption by these galaxies is rare: the covering fraction is f({rho}) {approx_equal} 10%-15% between {rho} = 20 kpcand{rho} = 100 kpc, for Mg II lines with rest equivalent widths of W{sub r} {>=} 0.6 A, falling to zero at larger {rho}. There is no evidence that W{sub r} correlates with impact parameter or galaxy luminosity. Our results are consistent with existing scenarios in which cool Mg II-absorbing clouds may be absent near LRGs because of the environment of the galaxies: if LRGs reside in high-mass groups and clusters, either their halos are too hot to retain or accrete cool gas, or the galaxies themselves-which have passively evolving old stellar populations-do not produce the rates of star formation and outflows of gas necessary to fill their halos with Mg II-absorbing clouds. In the rarer cases where Mg II is detected, however, the origin of the absorption is less clear. Absorption may arise from the little cool gas able to reach into cluster halos from the intergalactic medium, or from the few star-forming and/or AGN-like LRGs that are known to exist.

  6. A DNA enzyme with Mg(2+)-Dependent RNA Phosphoesterase Activity

    NASA Technical Reports Server (NTRS)

    Breaker, Ronald R.; Joyce, Gerald F.

    1995-01-01

    Previously we demonstrated that DNA can act as an enzyme in the Pb(2+)-dependent cleavage of an RNA phosphoester. This is a facile reaction, with an uncatalyzed rate for a typical RNA phosphoester of approx. 10(exp -4)/ min in the presence of 1 mM Pb(OAc)2 at pH 7.0 and 23 C. The Mg(2+) - dependent reaction is more difficult, with an uncatalyzed rate of approx. 10(exp -7)/ min under comparable conditions. Mg(2+) - dependent cleavage has special relevance to biology because it is compatible with intracellular conditions. Using in vitro selection, we sought to develop a family of phosphoester-cleaving DNA enzymes that operate in the presence of various divalent metals, focusing particularly on the Mg(2+) - dependent reaction. Results: We generated a population of greater than 10(exp 13) DNAs containing 40 random nucleotides and carried out repeated rounds of selective amplification, enriching for molecules that cleave a target RNA phosphoester in the presence of 1 mM Mg(2+), Mn(2+), Zn(2+) or Pb(2+). Examination of individual clones from the Mg(2+) lineage after the sixth round revealed a catalytic motif comprised of a three-stem junction.This motif was partially randomized and subjected to seven additional rounds of selective amplification, yielding catalysts with a rate of 0.01/ min. The optimized DNA catalyst was divided into separate substrate and enzyme domains and shown to have a similar level of activity under multiple turnover conditions. Conclusions: We have generated a Mg(2+) - dependent DNA enzyme that cleaves a target RNA phosphoester with a catalytic rate approx. 10(exp 5) - fold greater than that of the uncatalyzed reaction. This activity is compatible with intracellular conditions, raising the possibility that DNA enzymes might be made to operate in vivo.

  7. Foram Farming in the Mid-Continent: Culturing Low-Mg Benthic Foraminifera to Calibrate the Mg/Ca Paleothermometer

    NASA Astrophysics Data System (ADS)

    Jennings, D.; Hasiuk, F.; Thomas, E.; Varekamp, J. C.

    2014-12-01

    The initiation of Cenozoic continental ice sheets and the history of their growth/decay is difficult to reconstruct because of the mixed effects of polar ice volume and temperature on benthic foraminiferal oxygen isotope values. Coupled measurements of foraminiferal δ18O and Mg/Ca are a promising tool to unlock the history of past continental glaciation by calculating the oxygen isotopic composition of paleo-seawater. This method has been applied on Quaternary timescales with success, but uncertainty about secular changes in seawater Mg/Ca and potential changes in carbonate saturation have produced varying results with deeper time data. Currently, no experimentally-calibrated model explains how the Mg/Ca of low-Mg calcite, such as secreted by benthic foraminifera, responds to variations in seawater temperature and Mg/Ca. Our "Foram Farm" is a culture system for low-Mg calcite benthic foraminifera, composed of a colony and an experimental line. Currently, the colony hosts several species of rotaliids, miliolids, and buliminids obtained from Qatar, the Dominican Republic, Scotland, and Long Island Sound, USA. In addition, two tanks contain "live sand," a mixture of sandy material and seawater obtained from tropical reefs, and commonly used to condition hobbyist saltwater aquaria. This sand contains foraminifera and numerous other microorganisms. "Live sand" could be a source for cheap and easy to obtain test subjects. The foram farm gives access to a constant supply and variety of test subjects for the experimental line, which consists of several analytical refrigerators with varying temperatures. Each refrigerator houses petri dishes where forams are grown in water with varying Mg/Ca compositions. Elphidium excavatum, a well-researched, eurytopic taxon, will be the first to be cultured in the experimental line. After growing under experimental conditions, specimens will be analyzed using LA-ICP-MS, in order to model effects of seawater T and Mg/Ca on foram Mg

  8. Level structure of {sup 21}Mg: Nuclear and astrophysical implications

    SciTech Connect

    St Murphy, A.J.; Aliotta, M.; Davinson, T.; Ruiz, C.; Woods, P.J.; D'Auria, J.M.; Buchmann, L.; Chen, A.A.; Laird, A.M.; Sarazin, F.; Walden, P.; Fulton, B.R.; Pearson, J.E.; Brown, B.A.

    2006-03-15

    Resonant elastic scattering of a radioactive {sup 20}Na beam incident upon protons in a polyethylene target has been used to probe the level structure of {sup 21}Mg above the proton decay threshold. Three states have been observed, and their properties deduced through analysis based on the R-matrix formalism. The results improve and extend previous studies of this nucleus. An estimate of the {sup 20}Na(p,{gamma}){sup 21}Mg reaction rate, including these new data, suggests this reaction will not play a significant role in explosive hydrogen burning in astrophysical sites such as novae and x-ray bursts.

  9. NMR structure of hypothetical protein MG354 from Mycoplasmagenitalium

    SciTech Connect

    Pelton, Jeffrey G.; Shi, Jianxia; Yokotoa, Hisao; Kim, Rosalind; Wemmer, David E.

    2005-04-12

    Mycoplasma genitalium (Mg) and M. pneumoniae (Mp) are human pathogens with two of the smallest genomes sequenced to date ({approx} 480 and 680 genes, respectively). The Berkeley Structural Genomics Center is determining representative structures for gene products in these organisms, helping to understand the set of protein folds needed to sustain this minimal organism. The protein coded by gene MG354 (gi3844938) from M. genitalium has a relatively unique sequence, related only to MPN530 from M. pneumoniae (68% identity, coverage 99%) and MGA{_}0870 from the avian pathogen M. gallisepticum (23% identity, coverage 94%), has no homologue with a determined structure, and no functional annotations.

  10. Divorced Eutectic Solidification of Mg-Al Alloys

    NASA Astrophysics Data System (ADS)

    Monas, Alexander; Shchyglo, Oleg; Kim, Se-Jong; Yim, Chang Dong; Höche, Daniel; Steinbach, Ingo

    2015-08-01

    We present simulations of the nucleation and equiaxed dendritic growth of the primary hexagonal close-packed -Mg phase followed by the nucleation of the -phase in interdendritic regions. A zoomed-in region of a melt channel under eutectic conditions is investigated and compared with experiments. The presented simulations allow prediction of the final properties of an alloy based on process parameters. The obtained results give insight into the solidification processes governing the microstructure formation of Mg-Al alloys, allowing their targeted design for different applications.

  11. Continuous monitoring of Mg oxidation by internal exoemission.

    PubMed

    Glass, S; Nienhaus, H

    2004-10-15

    Thin-film Mg/Si(111) Schottky diodes are exposed to oxygen to detect chemicurrents in the devices. The detected charge is created by nonadiabatic energy dissipation and due to either internal exoemission currents or surface chemiluminescence induced photocurrents. Both contributions can be distinguished by changing the metal film thickness of the device. Auger electron spectroscopy to study the oxygen uptake demonstrates that the chemicurrent transients represent truly the time dependent reaction rate at the surface. Model calculations indicate that the current monitors Mg oxide island nucleation and growth. PMID:15525041

  12. Continuous Monitoring of Mg Oxidation by Internal Exoemission

    NASA Astrophysics Data System (ADS)

    Glass, S.; Nienhaus, H.

    2004-10-01

    Thin-film Mg/Si(111) Schottky diodes are exposed to oxygen to detect chemicurrents in the devices. The detected charge is created by nonadiabatic energy dissipation and due to either internal exoemission currents or surface chemiluminescence induced photocurrents. Both contributions can be distinguished by changing the metal film thickness of the device. Auger electron spectroscopy to study the oxygen uptake demonstrates that the chemicurrent transients represent truly the time dependent reaction rate at the surface. Model calculations indicate that the current monitors Mg oxide island nucleation and growth.

  13. Aging of magnetic properties in MgO films

    SciTech Connect

    Balcells, Ll.; Konstantinovic, Z.; Martinez, B.; Beltran, J. I.; Martinez-Boubeta, C.; Arbiol, J.

    2010-12-20

    In this work we report on the magnetic behavior of MgO thin films prepared by sputtering. A severe aging process of the ferromagnetic properties is detected in magnetic samples exposed to ambient atmosphere. However, ferromagnetism can be successively switched on again by annealing samples in vacuum. We suggest this behavior reflects the key role played by defects in stabilizing ferromagnetism in MgO films and is likely to be closely related to the hydrogen-driven instability of V-type centers in this material.

  14. Microstructure and superconductivity of MgB2 single crystals

    SciTech Connect

    Kim, Kijoon H.P.; Jung, C.U.; Kang, B.W.; Kim, Kyung Hee; Lee, Hyun-Sook; Lee, Sung-Ik; Tamura, N.; Caldwell, W.A.; Patel, J.R.

    2004-07-19

    The hexagonal-disc-shaped MgB2 single crystals were synthesized under the high-pressure conditions. The crystal symmetry, lattice constants as well as the Laue pattern of these single crystals were obtained from X-ray micro-diffraction. A crystallographic mapping showed that the edge and the c-axis of hexagonal-disc shape exactly matched the [1 0 1 bar 0] and [0 0 0 1] directions of the MgB2 phase. This clearly confirmed that above well-shaped single crystals could be excellent samples to study the unsolved direction dependencies of the physical properties.

  15. Predicting the optimized thermoelectric performance of MgAgSb

    NASA Astrophysics Data System (ADS)

    Sheng, C. Y.; Liu, H. J.; Fan, D. D.; Cheng, L.; Zhang, J.; Wei, J.; Liang, J. H.; Jiang, P. H.; Shi, J.

    2016-05-01

    Using first-principles method and Boltzmann theory, we provide an accurate prediction of the electronic band structure and thermoelectric transport properties of α-MgAgSb. Our calculations demonstrate that only when an appropriate exchange-correlation functional is chosen can we correctly reproduce the semiconducting nature of this compound. By fine tuning the carrier concentration, the thermoelectric performance of α-MgAgSb can be significantly optimized, which exhibits a strong temperature dependence and gives a maximum ZT value of 1.7 at 550 K. We also provide a simple map by which one can efficiently find the best doping atoms and optimal doping content.

  16. Multicore MgB 2 wires made by hydrostatic extrusion

    NASA Astrophysics Data System (ADS)

    Kováč, P.; Pachla, W.; Hušek, I.; Kulczyk, M.; Melišek, T.; Holúbek, T.; Diduszko, R.; Reissner, M.

    2008-12-01

    Seven-filament MgB2/Fe and MgB2/Nb/Cu wires have been made by in situ process using hydrostatic extrusion, drawing and two-axial drawing deformation into the wire size of 1.1 × 1.1 mm2. The conductors were sintered at 650 °C/0.5 h and studied in terms of field-dependent transport critical current density and thermal stability. XRD, SEM and EDX analysis were applied for structural characterization. Transport current property and compositional/structural differences are compared and discussed in connection to used powders and metallic materials.

  17. Effect of amorphous lamella on the crack propagation behavior of crystalline Mg/amorphous Mg-Al nanocomposites

    NASA Astrophysics Data System (ADS)

    Hai-Yang, Song; Yu-Long, Li

    2016-02-01

    The effects of amorphous lamella on the crack propagation behavior in crystalline/amorphous (C/A) Mg/Mg-Al nanocomposites under tensile loading are investigated using the molecular dynamics simulation method. The sample with an initial crack of orientation [0001] is considered here. For the nano-monocrystal Mg, the crack growth exhibits brittle cleavage. However, for the C/A Mg/Mg-Al nanocomposites, the ‘double hump’ behavior can be observed in all the stress-strain curves regardless of the amorphous lamella thickness. The results indicate that the amorphous lamella plays a critical role in the crack deformation, and it can effectively resist the crack propagation. The above mentioned crack deformation behaviors are also disclosed and analyzed in the present work. The results here provide a strategy for designing the high-performance hexagonal-close-packed metal and alloy materials. Project supported by the National Natural Science Foundation of China (Grant Nos. 11372256 and 11572259), the 111 Project (Grant No. B07050), the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-12-1046), and the Program for New Scientific and Technological Star of Shaanxi Province, China (Grant No. 2012KJXX-39).

  18. New quaternary semiconductor Cu2MgSnS4 and Cu2MgSnSe4 for photovoltaics

    NASA Astrophysics Data System (ADS)

    Tse, Kinfai; Zhong, Guohua; Zhang, Yiou; Li, Xiaoguang; Yang, Chunlei; Zhu, Junyi; Zeng, Zhi; Zhang, Zhenyu; Xiao, Xudong

    Element substitution of Zn by Mg and Ca is attempted to overcome the problem of potential fluctuation in Cu2ZnSnS4 and Cu2ZnSnSe4 (CZTSSe) due to prevalence of CuZn + ZnCu defect complex. Through density function theory calculation with hybrid functional, we have shown that Cu2MgSnS4 and Cu2MgSnSe4 (CMTSSe) are stable with respect to secondary phases considered under suitable chemical potential. Stannite CMTSSe is thermodynamically more favorable over the kesterite structure. The alternating Cu and Mg/Sn cation layer of stannite structure may suppress the formation of MgCu antisite due to large stress induced. The electronic and optical properties of CMTSSe are similar to that of CZTSSe with comparable absorption coefficient at the band-edge suggests CMTSSe to be a promising photovoltaic material. The work was supported by the National Major Science Research Program of China under Grant No. 2012CB933700, the Natural Science Foundation of China (Grant Nos. 61274093, 61574157, 11274335, 11504398, 51302303, and 51474132), and the Shenzhen Basic Resear.

  19. Mg-chelatase I subunit 1 and Mg-protoporphyrin IX methyltransferase affect the stomatal aperture in Arabidopsis thaliana.

    PubMed

    Tomiyama, Masakazu; Inoue, Shin-Ichiro; Tsuzuki, Tomo; Soda, Midori; Morimoto, Sayuri; Okigaki, Yukiko; Ohishi, Takaya; Mochizuki, Nobuyoshi; Takahashi, Koji; Kinoshita, Toshinori

    2014-07-01

    To elucidate the molecular mechanisms of stomatal opening and closure, we performed a genetic screen using infrared thermography to isolate stomatal aperture mutants. We identified a mutant designated low temperature with open-stomata 1 (lost1), which exhibited reduced leaf temperature, wider stomatal aperture, and a pale green phenotype. Map-based analysis of the LOST1 locus revealed that the lost1 mutant resulted from a missense mutation in the Mg-chelatase I subunit 1 (CHLI1) gene, which encodes a subunit of the Mg-chelatase complex involved in chlorophyll synthesis. Transformation of the wild-type CHLI1 gene into lost1 complemented all lost1 phenotypes. Stomata in lost1 exhibited a partial ABA-insensitive phenotype similar to that of rtl1, a Mg-chelatase H subunit missense mutant. The Mg-protoporphyrin IX methyltransferase (CHLM) gene encodes a subsequent enzyme in the chlorophyll synthesis pathway. We examined stomatal movement in a CHLM knockdown mutant, chlm, and found that it also exhibited an ABA-insensitive phenotype. However, lost1 and chlm seedlings all showed normal expression of ABA-induced genes, such as RAB18 and RD29B, in response to ABA. These results suggest that the chlorophyll synthesis enzymes, Mg-chelatase complex and CHLM, specifically affect ABA signaling in the control of stomatal aperture and have no effect on ABA-induced gene expression. PMID:24840863

  20. Hydrothermal replacement of calcite by Mg-carbonates

    NASA Astrophysics Data System (ADS)

    Jonas, Laura; Mueller, Thomas; Dohmen, Ralf

    2014-05-01

    The transport of heat and mass through the Earth's crust is coupled to mineral reactions and the exchange of isotopes and elements between different phases. Carbonate minerals are a major constituent of the Earth's crust and play an important role in different physical, chemical and even biological processes. In this experimental study, the element exchange reaction between calcite (CaCO3) and a Mg-rich fluid phase is investigated under hydrothermal conditions. Single crystals of calcite (2x2x2 mm) react with 1 ml of a 1 M MgCl2 solution at 200° C in a Teflon-lined steel autoclave for different times between one day and four weeks. The reaction leads to the formation of a porous reaction front and the pseudomorphic replacement of calcite by dolomite [CaMg(CO3)2] and magnesite (MgCO3). Scanning electron microscopy revealed that the reaction rim consists of small Mg-carbonate rhombs closely attached to each other, suggesting that the replacement reaction takes place by a dissolution-precipitation mechanism. Typically, the observed reaction front can be divided into two different domains. The outer part of the reaction rim, i.e. from the mineral surface in contact to the fluid inwards, consists of magnesite, whereas the inner part of the rim surrounding the unreacted calcite core consists of Ca-rich dolomite. The formation of a porous microstructure that varies in different parts of the reaction rim is a direct result of the large molar volume change induced by the replacement of calcite by magnesite and dolomite. The developing porosity therefore creates fluid pathways that promote the progress of the reaction front towards the unreacted core of the single crystal. Compositional profiles measured perpendicular to the mineral surface across the reactions rims using electron microprobe (EMPA) further revealed a compositional gradient within the reaction rim with regard to the structure-forming elements Mg and Ca. Here, the amount of Mg incorporated in both product

  1. Reflection polarizers for the vacuum ultraviolet using Al + MgF2 mirrors and an MgF2 plate

    NASA Technical Reports Server (NTRS)

    Hass, G.; Hunter, W. R.

    1978-01-01

    Consideration is given to the design and operation of a three-mirror reflecting polarizer where one of the reflecting surfaces is an MgF2 plate, the other surfaces are Al + MgF2 coatings, and one reflection occurs at or near the true Brewster angle. It is found that the polarizer is most efficient in the 1200-2000 A wavelength region, and that by optimum selection of the angle of incidence on the MgF2 plate, polarization values of 100 and over are yielded from 900 to 3000 A. The polarizer may be used at wavelengths as short as 500 A, although it is observed that at such wavelengths the polarization value decreases to about 10. It is noted that all reflecting polarizers operating in the vacuum ultraviolet wavelength may manifest changing characteristics as their mirrors become contaminated, and that polarization must therefore be occasionally remeasured.

  2. Tunneling conductance studies in the ion-beam sputtered CoFe/Mg/MgO/NiFe magnetic tunnel junctions

    SciTech Connect

    Singh, Braj Bhusan; Chaudhary, Sujeet

    2013-06-03

    Magnetic tunnel junctions consisting of CoFe(10 nm)/Mg(1 nm)/MgO(3.5 nm)/NiFe(10 nm) are grown at room temperature using dual ion beam sputtering via in-situ shadow masking. The effective barrier thickness and average barrier height are estimated to be 3.5 nm (2.9 nm) and 0.69 eV (1.09 eV) at 290 K (70 K), respectively. The tunnel magnetoresistance value of 0.2 % and 2.3 % was observed at 290 K and 60 K, respectively. The temperature dependence of tunneling conductance revealed the presence of localized states present within the forbidden gap of the MgO barrier leading to finite inelastic spin independent tunneling contributions, which degrade the TMR value.

  3. Ru Catalyst-Induced Perpendicular Magnetic Anisotropy in MgO/CoFeB/Ta/MgO Multilayered Films.

    PubMed

    Liu, Yiwei; Zhang, Jingyan; Wang, Shouguo; Jiang, Shaolong; Liu, Qianqian; Li, Xujing; Wu, Zhenglong; Yu, Guanghua

    2015-12-01

    The high oxygen storage/release capability of the catalyst Ru is used to manipulate the interfacial electronic structure in spintronic materials to obtain perpendicular magnetic anisotropy (PMA). Insertion of an ultrathin Ru layer between the CoFeB and Ta layers in MgO/CoFeB/Ta/MgO films effectively induces PMA without annealing. Ru plays a catalytic role in Fe-O-Ta bonding and isolation at the metal-oxide interface to achieve moderate interface oxidation. In contrast, PMA cannot be obtained in the sample with a Mg insertion layer or without an insertion layer because of the lack of a catalyst. Our work would provide a new approach toward catalyst-induced PMA for future CoFeB-based spintronic device applications. PMID:26565747

  4. Noncontact atomic force and Kelvin probe force microscopy on MgO(100) and MgO(100)-supported Ba

    NASA Astrophysics Data System (ADS)

    Pang, Chi Lun; Sasahara, Akira; Onishi, Hiroshi

    2016-08-01

    Atomically-flat MgO(100) surfaces were prepared by sputtering and annealing. Noncontact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM) were used to characterize the MgO(100) surfaces. The NC-AFM images revealed the presence of point defects on an atomically-resolved surface. The surface potential at these point defects, as well as features such as step edges and deposited Ba nanoparticles were mapped using KPFM. The Kelvin images show that the surface potential increases at the point defects and at the step edges. On the other hand, a decrease in the potential was found over Ba nanoparticles which can be explained by electron charge transfer from the Ba to the MgO.

  5. EELS of colloids in Mg{sup +} implanted MgAl{sub 2}O{sub 4} spinel

    SciTech Connect

    Evans, N.D.; Zinkle, S.J.

    1994-06-01

    During 2-MeV Mg{sup +} implantation at 25 C to 2.8{times}10{sup 21}/m{sup 2}, dislocation loops are formed at midrange depths (0.5-1.0{mu}m) on {l_brace}110{r_brace} and {l_brace}111{r_brace}. No evidence was found for the dark field images to be hexagonal metallic Mg; the colloids are suggested to be either metallic Al or another phase coherent with surrounding spinel. Regression analysis of low-loss spectra and diffraction data are consistent with the colloids in the implanted ion region being metallic Al, although the colloids could be metallic Mg in a metastable cubic structure.

  6. Positron lifetime studies of decomposition in 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) alloys

    SciTech Connect

    Dlubek, G. |; Lademann, P.; Krause, H.; Krause, S.; Unger, R.

    1998-09-04

    In the current paper, the decomposition behavior of the engineering alloys 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) is studied using positron lifetime measurements. Positrons probe open volume defects such as vacancies and dislocations. However, they may also be used to investigate coherent zones and incoherent precipitates. In order to understand the rather complicated precipitation sequences and the response of positrons to different type of precipitates occurring in 2024 and 7010 alloys, binary and ternary laboratory alloys were also investigated under the same experimental conditions as the engineering alloys. The interpretations of the results are based on experiences of the group from extensive positron studies of laboratory alloys such as Al-Zn, Al-Zn-Mg, Al-Cu, and further Al alloys (see also the review (4)). Their collected results are shown as lifetimes and curve-shape parameters S of the electron-positron momentum distribution curves characteristic for different precipitates in Al alloys.

  7. The role of Mg interface layer in MgO magnetic tunnel junctions with CoFe and CoFeB electrodes

    SciTech Connect

    Yang, Hyunsoo; Yang, See-Hun; Parkin, Stuart

    2012-03-15

    The tunneling spin polarization (TSP) is directly measured from reactively sputter deposited crystalline MgO tunnel barriers with various CoFe(B) compositions using superconducting tunneling spectroscopy. We find that the Mg interface layer thickness dependence of TSP values for CoFeB/Mg/MgO junctions is substantially different from those for CoFe/Mg/MgO especially in the pre-annealed samples due to the formation of boron oxide at the CoFeB/MgO interface. Annealing depletes boron at the interface thus requiring a finite Mg interface layer to prevent CoFeOx formation at the CoFeB/MgO interface so that the TSP values can be optimized by controlling Mg thickness.

  8. Bioequivalence of ondansetron oral soluble film 8 mg (ZUPLENZ) and ondansetron orally disintegrating tablets 8 mg (ZOFRAN) in healthy adults.

    PubMed

    Dadey, Eric

    2015-01-01

    Oral formulations of ondansetron are used to prevent nausea and vomiting associated with chemotherapy, radiotherapy, and surgery. An oral soluble film formulation of ondansetron (OND OSF) was developed using MonoSol Rx's proprietary PharmFilm technology and was formulated to dissolve rapidly on the tongue, without the need for water. This product provides an oral antiemetic treatment option for patients who experience difficulty swallowing. The purpose of this study was to compare the bioequivalence of OND OSF 8 mg (ZUPLENZ, Monosol Rx, Warren, NJ) with ondansetron orally disintegrating tablets (OND ODT) 8 mg (ZOFRAN, GlaxoSmithKline, Research Triangle Park). In 3 individual open-label, randomized studies, healthy adult subjects received a single dose of OND OSF 8 mg and a single dose of OND ODT 8 mg, under fasted conditions (study 1, n = 48), fed conditions (study 2, n = 48), and fasted with and without water (study 3, n = 18). Each dosing period was followed by a 3- or 7-day washout period. Ondansetron pharmacokinetics were assessed predose to 24 hours postdose for the single 8-mg doses of OND OSF and OND ODT. All analyses were conducted on natural log-transformed pharmacokinetic parameters for OND OSF and OND ODT. Under both fasted and fed conditions, the 90% confidence interval for the comparisons of OND OSF and OND ODT plasma ondansetron area under the curve from time 0 to the last measured concentration (AUC0-t), area under the concentration vs. time curve from time 0 to infinity (AUC0-∞), and maximum plasma concentration (Cmax) were within the 80%-125% range, indicating bioequivalence between the formulations. With features designed to make it portable and easy to take, OND OSF 8 mg provides an alternative treatment option, particularly for patients with dysphagia and others who find it difficult to take oral tablets. PMID:25581856

  9. PD/MG BIMETALLIC CORROSION CELLS FOR DECHLORINATING PCBS

    EPA Science Inventory

    Two dissimilar metals immersed in a conducting solution develop different corrosion potentials forming a bimetallic corrosion cell. Enhanced corrosion of an active metal like Mg combined with catalytic hydrogenation properties of a noble metal like Pd in such bimetallic cells can...

  10. Draft Genome Sequence of the Fungus Penicillium brasilianum MG11.

    PubMed

    Horn, Fabian; Linde, Jörg; Mattern, Derek J; Walther, Grit; Guthke, Reinhard; Brakhage, Axel A; Valiante, Vito

    2015-01-01

    The genus Penicillium belongs to the phylum Ascomycota and includes a variety of fungal species important for food and drug production. We report the draft genome sequence of Penicillium brasilianum MG11. This strain was isolated from soil, and it was reported to produce different secondary metabolites. PMID:26337871

  11. Rotation Period Determination for (9773) 1993 MG1

    NASA Astrophysics Data System (ADS)

    Benishek, Vladimir; Brincat, Stephen M.

    2016-01-01

    Photometric observations of the Mars-crossing asteroid (9773) 1993 MG1 were conducted over seven nights in 2015 July from Malta and Serbia. A synodic rotation period of 2.74595 ± 0.00006 h and lightcurve amplitude of 0.29 ± 0.02 mag were determined from the data.

  12. Preparation of Mg-vermiculite nanoparticles using potassium persulfate treatment.

    PubMed

    Matĕjka, Vlastimil; Supová-Krístková, Monika; Kratosvá, Gabriela; Valásková, Marta

    2006-08-01

    Delamination/exfoliation process of the Mg-vermiculite (Letovice, Czech Republic), particles with size less than 5 microm, was studied after potassium persulfate treatment and compared with known method utilized hydrogen peroxide treatment. X-ray powder diffraction (XRPD) patterns showed that treatment of Mg-vermiculite with different molar concentration of potassium persulfate: c = 0.02, 0.04, and 0.08 mol x dm(-3) at the temperature 60 degrees C for 2 hr caused reduction of relative intensity (I(rel.)) of the basal 001 diffraction to the 15%, 9%, and 4%, respectively, compared to intensity of 001 diffraction of untreated Mg-vermiculite (I(rel.) = 100%). On the other hand I(rel.) of the 001 diffraction of Mg-vermiculite after treatment with 30% and 50% (c = 9.8 and 17.4 mol x dm(-3)) hydrogen peroxide at the 60 degrees C for 2 hr decreased only to I(rel.) = 36% and 32%, respectively. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) verified effect of potassium persulfate treatment on structure degradation which is connected with higher degree of delamination/exfoliation of the particles and their cracking into nano-sized particles. PMID:17037860

  13. The CorA Mg2+ Transporter Is a Homotetramer

    SciTech Connect

    Warren, Mary A.; Kucharski, Lisa M.; Veenstra, Alexander; Shi, Liang; Grulich, Paul F.; Maguire, Michael E.

    2004-07-01

    Salmonella enterica serovar Typhimurium has three transport systems mediating influx of Mg2+: CorA, MgtA, and MgtB (6, 7, 22, 24). The CorA system is encoded by the corA gene that constitutively expresses a 37-kDa integral membrane protein (19).

  14. Permanent magnet with MgB2 bulk superconductor

    NASA Astrophysics Data System (ADS)

    Yamamoto, Akiyasu; Ishihara, Atsushi; Tomita, Masaru; Kishio, Kohji

    2014-07-01

    Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging. The recent global helium shortage has quickened research into high-temperature superconductors (HTSs)—materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB2) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (<0.1 ppm/h). The magnetic field trapped in this magnet is uniformly distributed, as for single-crystalline neodymium-iron-boron. Magnetic hysteresis loop of the MgB2 permanent bulk magnet was detrmined. Because MgB2 is a simple-binary-line compound that does not contain rare-earth metals, polycrystalline bulk material can be industrially fabricated at low cost and with high yield to serve as strong magnets that are compatible with conventional compact cryocoolers, making MgB2 bulks promising for the next generation of Tesla-class permanent-magnet applications.

  15. Selective nitrite reduction at heterobimetallic CoMg complexes.

    PubMed

    Uyeda, Christopher; Peters, Jonas C

    2013-08-14

    Heme-containing nitrite reductases bind and activate nitrite by a mechanism that is proposed to involve interactions with Brønsted acidic residues in the secondary coordination sphere. To model this functionality using synthetic platforms that incorporate a Lewis acidic site, heterobimetallic CoMg complexes supported by diimine-dioxime ligands are described. The neutral (μ-NO2)CoMg species 3 is synthesized from the [(μ-OAc)(Br)CoMg](+) complex 1 by a sequence of one-electron reduction and ligand substitution reactions. Data are presented for a redox series of nitrite adducts, featuring a conserved μ-(η(1)-N:η(1)-O)-NO2 motif, derived from this synthon. Conditions are identified for the proton-induced N-O bond heterolysis of bound NO2(-) in the most reduced member of this series, affording the [(NO)(Cl)CoMg(H2O)](+) complex 6. Reduction of this complex followed by protonation leads to the evolution of free N2O. On the basis of these stoichiometric reactivity studies, the competence of complex 1 as a NO2(-) reduction catalyst is evaluated using electrochemical methods. In bulk electrolysis experiments, conducted at -1.2 V vs SCE using Et3NHCl as a proton source, N2O is produced selectively without the competing formation of NH3, NH2OH, or H2. PMID:23865638

  16. Characteristics of laser welded wrought Mg-Al-Mn alloy

    SciTech Connect

    Quan Yajie Chen Zhenhua; Yu Zhaohui; Gong Xiaosan; Li Mei

    2008-12-15

    Magnesium alloys have gained increased attention in recent years as a structural metal because of their property merits, which necessitates the development of welding techniques qualified for applications in the aeronautic and automotive industries. Laser welding is known to be an excellent method for joining metals. In this paper, a 3 kW CO{sub 2} laser beam was used to weld the wrought Mg-Al-Mn alloy. The characteristics of the microstructure and the mechanical properties of the joints were analyzed by optical microscopy (OM), energy dispersive spectrometry (EDS), scanning electron microscopy (SEM), tensile testing and hardness testing. The experimental results show that the wrought Mg-Al-Mn alloy can be joined successfully using optimized welding conditions. The results of tensile testing show that the highest ultimate tensile strength (UTS) of the joints is up to 94% of that of the base metal. The base metal consists of a typical rolled structure, the narrow heat affected zone (HAZ) has no obvious grain coarsening, and the fusion zone consists of fine grains with a high density of {gamma}-Mg{sub 17}Al{sub 12} precipitates. The hardness test results indicate that the microhardness in the fusion zone is higher than that of the base metal. The elemental analysis reveals that the Mg content in the weld is lower than that of the base metal, but the Al content is slightly higher.

  17. The Low-Lying Electronic States of Mg2(+)

    NASA Technical Reports Server (NTRS)

    Ricca, Alessandra; Bauschlicher, Charles W., Jr.

    1994-01-01

    The low-lying doublet and quartet states of Mg+ have been studied using a multireference configuration interaction approach. The effect of inner-shell correlation has been included using the core-polarization potential method. The computed spectroscopic constants, lifetimes, and oscillator strengths should help resolve the difference between the recent experiments and previous theoretical calculations.

  18. Flux Pinning and Connectivity in MgB2

    NASA Astrophysics Data System (ADS)

    Sumption, M. D.; Susner, M.; Bhatia, M.; Collings, E. W.

    2008-03-01

    The transport and pinning properties of in-situ MgB2 bulks and strands are discussed. The influence of SiC, excess Mg, B4C, TiC, and their combination on Birr and Bc2 as distinct from connectivity and flux pinning is the focus of the work. SiC dopants increase Bc2 and Birr predominantly, with little influence on connectivity or flux pinning. Excess Mg improves the transport current, changes the grain microstructure, and also leads local maxima in Bc2 and Birr at excess Mg levels of 15% mol fraction. Fp curves are consistent with grain boundary pinning for the binary materials over the whole temperature range. This is also true for SiC and TiC doped materials at lower fields and temperatures, while higher temperatures show a deviation from surface pinning. These higher temperature deviations are consistent with the size and distribution of these nanoparticulate additions. Normal state resistivity measurements and models are used to extract residual resistivity values, percent connectivity, and Debye temperatures. Debye temperatures are seen to be depressed by SiC doping, an effect which is confirmed by heat capacity measurements. Residual resistivity values are seen to correlate with Bc2 and Birr enhancements, consistent with B site substitution with C as evidenced by XRD extracted lattice parameter shifts.

  19. Permanent magnet with MgB{sub 2} bulk superconductor

    SciTech Connect

    Yamamoto, Akiyasu; Ishihara, Atsushi; Tomita, Masaru; Kishio, Kohji

    2014-07-21

    Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging. The recent global helium shortage has quickened research into high-temperature superconductors (HTSs)—materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB{sub 2}) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (<0.1 ppm/h). The magnetic field trapped in this magnet is uniformly distributed, as for single-crystalline neodymium-iron-boron. Magnetic hysteresis loop of the MgB{sub 2} permanent bulk magnet was determined. Because MgB{sub 2} is a simple-binary-line compound that does not contain rare-earth metals, polycrystalline bulk material can be industrially fabricated at low cost and with high yield to serve as strong magnets that are compatible with conventional compact cryocoolers, making MgB{sub 2} bulks promising for the next generation of Tesla-class permanent-magnet applications.

  20. Reaction mechanisms in {sup 24}Mg+{sup 12}C and {sup 32}S+{sup 24}Mg

    SciTech Connect

    Beck, C.; Sanchez i Zafra, A.; Papka, P.; Thummerer, S.; Azaiez, F.; Courtin, S.; Curien, D.; Dorvaux, O.; Lebhertz, D.; Nourreddine, A.; Rousseau, M.; Oertzen, W. von; Gebauer, B.; Kokalova, Tz.; Wheldon, C.; De Angelis, G.; Gadea, A.; Lenzi, S.; Napoli, D. R.; Szilner, S.

    2009-03-04

    The occurrence of 'exotic' shapes in light N = Z{alpha}-like nuclei is investigated for {sup 24}Mg+{sup 12}C and {sup 32}S+{sup 24}Mg. Various approaches of superdeformed and hyperdeformed bands associated with quasimolecular resonant structures with low spin are presented. For both reactions, exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON Tandem facility of Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their associated {gamma}-decays studied. The analysis of the binary and ternary reaction channels is discussed.

  1. STORAGE RING MEASUREMENT OF ELECTRON IMPACT IONIZATION FOR Mg{sup 7+} FORMING Mg{sup 8+}

    SciTech Connect

    Hahn, M.; Lestinsky, M.; Novotny, O.; Savin, D. W.; Bernhardt, D.; Mueller, A.; Schippers, S.; Wolf, A.

    2010-04-01

    We report electron impact ionization cross section measurements for Mg{sup 7+} forming Mg{sup 8+} at center of mass energies from approximately 200 eV to 2000 eV. The experimental work was performed using the heavy-ion storage ring TSR located at the Max-Planck-Institut fuer Kernphysik in Heidelberg, Germany. We find good agreement with distorted wave calculations using both the GIPPER code of the Los Alamos Atomic Physics Code suite and using the Flexible Atomic Code.

  2. Four treatment failures of pharyngeal gonorrhoea with ceftriaxone (500 mg) or cefotaxime (500 mg), Sweden, 2013 and 2014.

    PubMed

    Golparian, D; Ohlsson, Ak; Janson, H; Lidbrink, P; Richtner, T; Ekelund, O; Fredlund, H; Unemo, M

    2014-01-01

    We describe four cases in Sweden of verified treatment failures of pharyngeal gonorrhoea with ceftriaxone (500 mg; n=3) or cefotaxime (500 mg; n=1) monotherapy. All the ceftriaxone treatment failures were caused by the internationally spreading multidrug-resistant gonococcal NG-MAST genogroup 1407 clone. Increased awareness of treatment failures is crucial particularly when antimicrobial monotherapy is used. Frequent test of cure and appropriate verification/falsification of suspected treatment failures, as well as implementation of recommended dual antimicrobial therapy are imperative. PMID:25108533

  3. Signal-to-Noise Characteristics of Solar MG II Indices

    NASA Astrophysics Data System (ADS)

    Crane, P. C.; Floyd, L. E.

    1999-05-01

    Knowledge of the variations in solar ultraviolet irradiances is essential to understanding both the Sun and the behavior of the Earth's upper atmosphere. Since the solar ultraviolet radiation is absorbed by the atmosphere, the requisite measurements must be done from space. Reliable, approximately daily measurements of solar ultraviolet irradiances have been made since November 1978 by a variety of instruments (Numbus-7 SBUV, NOAA-9 and NOAA-11 SBUV/2, UARS SUSIM and SOLSTICE, and ERS-2 GOME). To overcome differences in spectral coverage and resolution and the challenges involved in the long-term calibrations of the instruments, a solar index suitable for use as a proxy for the solar ultraviolet (i.e., 100-400 nm) irradiances has been sought. The most popular indices for this purpose are the several Mg II indices based upon the Mg II k and h doublet near 280 nm; starting with the core-to-wing index developed by Heath and Schlesinger (J. Geophys. Res. 91, 8672, 1986) for the Nimbus-7 SBUV, they are calculated by taking the ratio of adjacent parts of the Mg II feature: one originating in the upper chromosphere that exhibits solar ultraviolet variations and the other, in the upper photosphere which is insensitive to solar variations. Because the ratio is of irradiances at nearby wavelengths, the Mg II indices mostly are not affected by temporal and spectral variations in the instrument responses. While there is an ongoing effort to combine the available Mg II indices into a single 20-year time series (i.e., Viereck and Puga, J. Geophys. Res., in press), we are investigating an alternate approach. We report here on the first step in that study: the characterization of the signal and noise properties of the several Mg II indices available. We use Fourier analysis to determine the amplitudes of a common signal (the 27-day variations) and of the high-frequency, day-to-day errors. Ultimately, the corresponding signal-to-noise ratios may be used to derive statistical

  4. Mg2(Si,Sn)-based thermoelectric materials and devices

    NASA Astrophysics Data System (ADS)

    Gao, Peng

    Thermoelectric effects are phenomena found in materials that can achieve direct conversion between heat flow and electricity. One important application of thermoelectric effects is thermoelectric generators, which can generate electricity when a temperature gradient is applied. Thermoelectric generators make use of various sources of heat and it is considered a promising solution for waste heat recovery. The conversion efficiency of thermoelectric generators depends on the materials used in the devices. Significant improvement in the performance of thermoelectric materials has been made in the past few decades. However, most of the good thermoelectric materials being investigated have limitations, such as the high materials cost, high materials density and toxicity of the constituent elements. The Mg2(Si,Sn)-based materials studied in this work are promising candidates for thermoelectric generators in the mid-temperature range and have drawn increasing research interest in recent years because these materials are high performance thermoelectrics that are low cost, low-density and non-toxic. In this work, systematic studies were performed on the Mg2(Si,Sn) thermoelectric materials. Thermal phase stability was studied for different compositions of Mg2Si1-xSnx and Mg2Si0.4Sn 0.6 was used as base material for further optimization. Both n-type and p-type samples were obtained by doping the materials with different elements. Peak ZT ˜ 1.5 for the n-type and ZT ˜ 0.7 for the p-type materials were obtained, both of which are among the best reported results so far. Experimental work was also done to study the techniques to develop the Mg2Si 0.4Sn0.6 materials into working devices. Different electrode materials were tested in bonding experiment for this compound, and copper was found to be the best electrode material for Mg2Si 0.4Sn0.6. Preliminary work was done to demonstrate the possibility of fabricating a Mg2Si0.4Sn0.6-based thermoelectric generator and the result is

  5. Interstellar MG II Absorption Lines from Low-Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Bowen, David V.; Blades, J. Chris; Pettini, Max

    1995-08-01

    We have used the GHRS aboard HST to search for interstellar Mg II 2796, 2803 absorption from the disks and halos of 17 low-redshift galaxies, using as probes QSOs and extragalactic supernovae whose sight lines pass close to, or through, intervening galaxies. The galaxies studied are of diverse morphological type, reside in different environments, and lie at separations of p' ≃ 2-113 h-1 kpc from a QSO line of sight. Ten of 11 galaxies at separations 31-113 h-1 kpc show no absorption to equivalent width limits of W(λ2796) <40-90 mÅ, which corresponds to N(Mg II) ≃1-4 × 1012 cm-2. Six galaxies lie at p' ≤ 9 kpc, and of these, four (NGC 4319, the LMC, M81, and the Milky Way) show absorption. Two early-type galaxies (NGC 1380 and Leo I) show no absorption at p' < 9 kpc: these nondetections are surprising because the separations are small and point to the possibility that the existence of extended absorbing halos may be a function of galaxy type. All of the galaxies which produce absorption are plausibly members of interacting systems. For absorbing galaxies probed below 9 kpc, the sight line passes within the optical radius of the galaxy, where the interstellar medium (ISM) is expected to have a high covering factor, and we do not attribute the absorption to the interactions. However, we do find that the environment of the absorbing galaxies affects the characteristics of the absorption detected the strength of lines, the complexity of line components, the ionization state of the gas and we warn of the dangers inherent in constructing models of generic halos based on statistical properties of QSO absorption-line surveys. Our data suggest that the covering factor of Mg II absorption is high for galaxies within ≍10 kpc, but very small beyond ≍30 h-1 kpc, a result consistent with the size found of Mg II halos deduced for galaxies at redshifts z > 0.2. The low-redshift galaxies observed in this study which show Mg II absorption are probably drawn from the same

  6. Improved hydrogen storage kinetics of the Li-Mg-N-H system by addition of Mg(BH4)2.

    PubMed

    Pan, Hongge; Shi, Songbo; Liu, Yongfeng; Li, Bo; Yang, Yanjing; Gao, Mingxia

    2013-03-21

    A Mg(BH(4))(2)-added Mg(NH(2))(2)-2LiH system was prepared by ball milling the corresponding chemicals. The hydrogen storage properties of the Mg(NH(2))(2)-2LiH-xMg(BH(4))(2) (x = 0, 0.1, 0.2, 0.3) samples and the role played by Mg(BH(4))(2) were systematically investigated. The results show that the onset and peak temperatures for hydrogen desorption from the Mg(BH(4))(2)-added Mg(NH(2))(2)-2LiH sample shifted to lower temperatures. In particular, the Mg(NH(2))(2)-2LiH-0.1Mg(BH(4))(2) sample could reversibly absorb ~4.5 wt% of hydrogen in the temperature range of 120-150 °C, which is superior to the pristine sample. During ball milling, a metathesis reaction between Mg(BH(4))(2) and LiH readily occurred to form LiBH(4) and MgH(2) and subsequently, the newly formed MgH(2) reacted with Mg(NH(2))(2) to generate MgNH. Upon heating, the presence of LiBH(4) not only decreased the recrystallization temperature of Mg(NH(2))(2) but also reacted with LiNH(2) to form the Li(4)(BH(4))(NH(2))(3) intermediate, which weakens the N-H bonding and enhances the ion conductivity. Meanwhile, MgNH may act as the nucleation center for the dehydrogenation product of Li(2)MgN(2)H(2) due to the structural similarity. Thus, the in situ formed LiBH(4) and MgNH provide a synergetic effect to improve the hydrogen storage performances of the Mg(NH(2))(2)-2LiH system. PMID:23178338

  7. Production of Mg and Al Auger electrons by noble gas ion bombardment of Mg and Al surfaces

    NASA Technical Reports Server (NTRS)

    Ferrante, J.; Pepper, S. V.

    1976-01-01

    Relative production efficiencies of Mg and Al Auger electrons by He, Ne, Ar, Kr, and Xe ion bombardment are reported as a function of ion energy for energies not exceeding 3 keV. The experimental apparatus employed consisted of a LEED-Auger system equipped with an ion gun and a four-grid retarding-potential analyzer. It is found that: (1) the shape of the ion-excited Auger signal was independent of the rare gas and quite symmetric; (2) the Al signal was about an order of magnitude smaller than the Mg signal for a given bombarding species and ion-gun voltage; (3) no signal was observed for He(+) bombardment under any of the experimental conditions; (4) signal strengths were independent of temperature and ion dose; (5) the Auger production efficiencies differed by no more than a factor of two among the different gases - except for He(+) - on a given metal; (6) all the signal strengths increased with increasing ion-gun voltage, with no maximum exhibited; and (7) the apparent threshold energy for the Al signal was higher than that for the Mg signal. The differences between the results for the two metals are attributed to the fact that the Al 2p orbital lies deeper in energy and closer to the nucleus than the corresponding Mg orbital.

  8. Pd/MgO: Catalyst characterization and phenol hydrogenation activity

    SciTech Connect

    Claus, P.; Berndt, H.; Mohr, C.; Radnik, J.; Shin, E.J.; Keane, M.A.

    2000-05-15

    The gas-phase hydrogenation of phenol has been studied over a 1% w/w Pd/MgO catalyst prepared by impregnation of MgO with (NH{sub 4}){sub 2}PdCl{sub 6}. The catalyst precursor was activated by precalcination in air at 473 K followed by reduction in hydrogen at 573 K. Temperature-programmed reduction/desorption has revealed the presence of ammonium carbonate and/or ammonium hydrogen carbonate on the active surface in addition to a metallic palladium component. Whereas the latter was not detectable by X-ray diffraction due to the high metal dispersion, transmission electron microscopy revealed that the mean palladium particle diameter is 1.3 {+-} 0.2 nm, which corresponds to a palladium dispersion of D{sub Pd} = 71%. Impregnation followed by calcination is shown to transform MgO to Mg(OH){sub 2} while the additional reduction step generates a surface phase that is composed of both needle-like Periclase MgO and Mg(OH){sub 2}. X-ray photoelectron spectrometric analyses of the activated catalyst has established the presence of zero-valent palladium which appears to be electron rich as a result of metal-support interaction; a degree of palladium charging is also evident as well as residual surface chlorine. The effects on fractional phenol conversion and reaction selectivity of varying such process variables as reaction time, temperature, and phenol molar feed rate are considered and the possibility of thermodynamic limitations is addressed. Hydrogenation was observed to proceed in a stepwise fashion with cyclohexanone as the partially hydrogenated product and cyclohexanol as the fully hydrogenated product. The catalyst delivered a 96% selectivity with respect to cyclohexanone production at 423 K but the cyclohexanone yield decreased at higher temperatures as conversion declined and cyclohexanol was increasingly preferred. Conversion and selectivity were both stable with prolonged catalyst use, i.e., time on stream in excess of 55 h.

  9. Theoretical studies on the two-dimensional electron-gas properties of MgZnO/MgO/ZnO heterostructures

    NASA Astrophysics Data System (ADS)

    Park, Seoung-Hwan; Hong, Woo-Pyo; Kim, Jong-Jae

    2016-07-01

    The polarization effects on the two-dimensional electron-gas (2DEG) of the ZnO/MgO/MgZnO heterostructure were theoretically investigated. The carrier confinement in the MgZnO/MgO/ZnO high-electron-mobility transistor (HEMT) structure is shown to be superior to that in the conventional MgZnO/ZnO HEMT structure. The electron density is shown to be very sensitive to the layer thickness and to become a maximum at a layer thickness of 2 nm. Also, the MgZnO/MgO/ZnO HEMT structure shows a larger saturation drain current than the conventional MgZnO/ZnO HEMT structure does. This is mainly due to the increased channel electron density induced by the enhanced polarization charge with the inclusion of the MgO layer.

  10. Superconducting MgB2 thin films grown by pulsed laser deposition on Al2O3(0001) and MgO(100) substrates

    NASA Astrophysics Data System (ADS)

    Wang, S. F.; Dai, S. Y.; Zhou, Y. L.; Chen, Z. H.; Cui, D. F.; Xu, J. D.; He, M.; Lu, H. B.; Yang, G. Z.; Fu, G. S.; Han, L.

    2001-11-01

    Superconducting MgB2 thin films were fabricated on Al2O3(0001) and MgO(100) substrates by a two-step method. Boron thin films were deposited by pulsed laser deposition followed by an ex-situ annealing process. Resistance measurements of the deposited MgB2 films show a Tc of 38.6 K for MgB2/Al2O3 and 38.1 K for MgB2/MgO. Atomic force microscopy, scanning electron microscopy and x-ray diffraction were used to study the properties of the films. The results indicate that the MgB2/Al2O3 films consist of well-crystallized grains with a highly c-axis-oriented structure while the MgB2/MgO films have a dense uniform appearance with an unfixed orientation.

  11. Recovery of SO2 and MgO from By-Products of MgO Wet Flue Gas Desulfurization

    PubMed Central

    Yan, Liyun; Lu, Xiaofeng; Wang, Quanhai; Guo, Qiang

    2014-01-01

    Abstract An industrial demonstration unit using natural gas as a heat source was built to calcine the by-products of MgO wet flue gas desulfurization from power plants; influencing factors on the SO2 content in calciner gas were comprehensively analyzed; and an advantageous recycling condition of MgO and SO2 from by-products was summarized. Results showed that the SO2 content in the calciner gas was increased by more than 10 times under a lower excess air coefficient, a higher feed rate, a lower crystal water in by-products, and a higher feed port position. For the tests conducted under the excess air coefficient above and below one, the effect of the furnace temperature on the SO2 content in the calciner gas was reversed. Results of activity analysis indicate that particles of MgO generated under the calcination temperature of 900–1,000°C had a high activity. In contrast, due to the slight sintering, MgO generated under the calcination temperature of 1,100°C had a low activity. To recycle SO2 as well as MgO, a temperature range of 900–927°C for TE103 is proposed. These studies will prompt the desulfurization market diversification, reduce the sulfur's dependence on imports for making sulfuric acid, be meaningful to balance the usage of the natural resource in China, and be regarded as a reference for the development of this technology for other similar developing countries. PMID:25371652

  12. Recovery of SO2 and MgO from By-Products of MgO Wet Flue Gas Desulfurization.

    PubMed

    Yan, Liyun; Lu, Xiaofeng; Wang, Quanhai; Guo, Qiang

    2014-11-01

    An industrial demonstration unit using natural gas as a heat source was built to calcine the by-products of MgO wet flue gas desulfurization from power plants; influencing factors on the SO2 content in calciner gas were comprehensively analyzed; and an advantageous recycling condition of MgO and SO2 from by-products was summarized. Results showed that the SO2 content in the calciner gas was increased by more than 10 times under a lower excess air coefficient, a higher feed rate, a lower crystal water in by-products, and a higher feed port position. For the tests conducted under the excess air coefficient above and below one, the effect of the furnace temperature on the SO2 content in the calciner gas was reversed. Results of activity analysis indicate that particles of MgO generated under the calcination temperature of 900-1,000°C had a high activity. In contrast, due to the slight sintering, MgO generated under the calcination temperature of 1,100°C had a low activity. To recycle SO2 as well as MgO, a temperature range of 900-927°C for TE103 is proposed. These studies will prompt the desulfurization market diversification, reduce the sulfur's dependence on imports for making sulfuric acid, be meaningful to balance the usage of the natural resource in China, and be regarded as a reference for the development of this technology for other similar developing countries. PMID:25371652

  13. Mg(PF6)2-Based Electrolyte Systems: Understanding Electrolyte-Electrode Interactions for the Development of Mg-Ion Batteries.

    PubMed

    Keyzer, Evan N; Glass, Hugh F J; Liu, Zigeng; Bayley, Paul M; Dutton, Siân E; Grey, Clare P; Wright, Dominic S

    2016-07-20

    Mg(PF6)2-based electrolytes for Mg-ion batteries have not received the same attention as the analogous LiPF6-based electrolytes used in most Li-ion cells owing to the perception that the PF6(-) anion decomposes on and passivates Mg electrodes. No synthesis of the Mg(PF6)2 salt has been reported, nor have its solutions been studied electrochemically. Here, we report the synthesis of the complex Mg(PF6)2(CH3CN)6 and its solution-state electrochemistry. Solutions of Mg(PF6)2(CH3CN)6 in CH3CN and CH3CN/THF mixtures exhibit high conductivities (up to 28 mS·cm(-1)) and electrochemical stability up to at least 4 V vs Mg on Al electrodes. Contrary to established perceptions, Mg electrodes are observed to remain electrochemically active when cycled in the presence of these Mg(PF6)2-based electrolytes, with no fluoride (i.e., MgF2) formed on the Mg surface. Stainless steel electrodes are found to corrode when cycled in the presence of Mg(PF6)2 solutions, but Al electrodes are passivated. The electrolytes have been used in a prototype Mg battery with a Mg anode and Chevrel (Mo3S4)-phase cathode. PMID:27359196

  14. New CeMgCo4 and Ce2MgCo9 compounds: Hydrogenation properties and crystal structure of hydrides

    NASA Astrophysics Data System (ADS)

    Denys, R. V.; Riabov, A. B.; Černý, R.; Koval'chuk, I. V.; Zavaliy, I. Yu.

    2012-03-01

    Two new ternary intermetallic compounds, CeMgCo4 (C15b pseudo-Laves phase, MgCu4Sn type) and Ce2MgCo9 (substitution derivative of PuNi3 type) were synthesized by mechanical alloying method. The structural and hydrogenation properties of these compounds were studied by X-ray diffraction and Pressure-Composition-Temperature measurements. Both compounds absorb hydrogen at room temperature and pressures below 10 MPa forming hydrides with maximum compositions CeMgCo4H6 and Ce2MgCo9H12. Single plateau behavior was observed in P-C isotherm during hydrogen absorption/desorption by Ce2MgCo9 alloy. The CeMgCo4-H2 system is characterized by the presence of two absorption/desorption plateaus corresponding to formation of β-CeMgCo4H4 and γ-CeMgCo4H6 hydride phases. The structure of β-hydride CeMgCo4H(D)4 was determined from X-ray and neutron powder diffraction data. In this structure initial cubic symmetry of CeMgCo4 is preserved and hydrogen atoms fill only one type of interstitial sites, triangular MgCo2 faces. These positions are occupied by 70% and form octahedron around Mg atom with Mg-D bond distances 1.84 Å.

  15. Electrochemical Codeposition of Al-Li-Mg Alloys at Solid Aluminum Electrode from LiCl-KCl-MgCl2 Molten Salt System

    NASA Astrophysics Data System (ADS)

    Ye, Ke; Zhang, Mi Lin; Chen, Ye; Han, Wei; de Yan, Yong; Cao, Peng

    2010-06-01

    The electrochemical codeposition of Mg and Li at an aluminium electrode in LiCl-KCl (50:50 wt pct) melts containing different concentrations of MgCl2 at 893 K (620 °C) to form Al-Li-Mg alloys was investigated. Cyclic voltammograms showed that the potential of Li metal deposition at an Al electrode, before the addition of MgCl2, is more positive than that of Li metal deposition at an Mo electrode, which indicated the formation of an Al-Li alloy. The underpotential deposition of magnesium at an aluminium electrode leads to the formation of Al-Mg alloys, and the succeeding underpotential deposition of lithium on predeposited Al-Mg alloys leads to the formation of Al-Li-Mg alloys. Chronopotentiometric measurements indicated that the codeposition of Mg and Li occurs at current densities lower than -0.668 A cm-2 in LiCl-KCl-MgCl2 (8 wt pct) melts at an aluminium electrode. The chronoamperometric studies indicated that the onset potential for the codeposition of Mg and Li is -2.000 V, and the codeposition of Mg and Li at an aluminium electrode is formed into Al-Li-Mg alloys when the applied potentials are more negative than -2.000 V. X-ray diffraction and inductively coupled plasma analysis indicated that Al-Li-Mg alloys with different lithium and magnesium contents were prepared via potentiostatic and galvanostatic electrolysis. The microstructure of typical dual phases of the Al-Li-Mg alloy was characterized by an optical microscope and by scanning electron microscopy. The analysis of energy dispersive spectrometry showed that the elements of Al and Mg distribute homogeneously in the Al-Li-Mg alloy. The lithium and magnesium contents of Al-Li-Mg alloys can be controlled by MgCl2 concentrations and by electrolytic parameters.

  16. Field trial on efficacy of supervised monthly dose of 600 mg rifampin, 400 mg ofloxacin and 100 mg minocycline for the treatment of leprosy; first results.

    PubMed

    Mane, I; Cartel, J L; Grosset, J H

    1997-06-01

    In 1995, a field trial was implemented in Senegal in order to evaluate the efficacy of a regimen based on the monthly supervised intake of rifampin 600 mg, ofloxacin 400 mg and minocycline 100 mg to treat leprosy. During the first year of the trial, 220 patients with active leprosy (newly detected or relapsing after dapsone monotherapy) were recruited: 102 paucibacillary (PB) (60 males and 42 females) and 118 multibacillary (MB) (71 males and 47 females). All of them accepted the new treatment (none requested to be preferably put under standard WHO/MDT), no clinical sign which could be considered as a toxic effect of the drug was noted, and none of the patients refused to continue treatment because of any clinical trouble. The compliance was excellent: the 113 patients (PB and MB) detected during the first 6 months of the trial have taken six monthly doses in 6 months, as planned. The rate of clearance and the progressive decrease of cutaneous lesions was satisfactory. Although it is too soon to give comprehensive results, it should be noted that no treatment failure was observed in the 56 PB patients who have completed treatment and have been followed up for 6 months. The long-term efficacy of the new regimen is to be evaluated on the rate of relapse during the years following the cessation of treatment. If that relapse rate is acceptable (similar to that observed in patients after treatment with current standard WHO/ MDT), the new regimen could be a solution to treat, for instance, patients very irregular and/or living in remote or inaccessible areas since no selection of rifampin-resistant Mycobacterium leprae should be possible (a monthly dose of ofloxacin and minocycline being as effective as a dose of dapsone and clofazimine taken daily for 1 month). Nevertheless, until longer term results of this and other trials become available, there is no justification for any change in the treatment strategy, and all leprosy patients should be put under standard WHO

  17. Superior hydrogen absorption and desorption behavior of Mg thin films

    NASA Astrophysics Data System (ADS)

    Qu, Jianglan; Wang, Yuntao; Xie, Lei; Zheng, Jie; Liu, Yang; Li, Xingguo

    Pd-capped Mg films prepared by magnetron sputtering achieved complete dehydrogenation in air at room temperature and behaved as favorable gasochromic switchable mirrors. Their cyclic hydrogen absorption and desorption kinetics in air were investigated by using the Bruggeman effective medium approximation. The overall activation energy was 80 kJ mol -1, while the reaction orders controlling desorption were deduced to be n = 2 at 328 K and n = 1 at lower temperatures by analyzing the transmittance data. The hydrogen diffusion coefficient and the corresponding activation energy were calculated by electrochemical measurements. Mg thin films exhibited the smaller activation energy and remarkable diffusion kinetics at room temperature which implied potential applications in smart windows.

  18. Deformation effects on isoscalar giant resonances in 24Mg

    NASA Astrophysics Data System (ADS)

    Gupta, Y. K.; Garg, U.; Hoffman, J.; Matta, J.; Rao, P. V. Madhusudhana; Patel, D.; Peach, T.; Yoshida, K.; Itoh, M.; Fujiwara, M.; Hara, K.; Hashimoto, H.; Nakanishi, K.; Yosoi, M.; Sakaguchi, H.; Terashima, S.; Kishi, S.; Murakami, T.; Uchida, M.; Yasuda, Y.; Akimune, H.; Kawabata, T.; Harakeh, M. N.

    2016-04-01

    Strength distributions for isoscalar giant resonances with multipolarity L ≤2 have been determined in 24Mg from "instrumental background-free" inelastic scattering of 386-MeV α particles at extreme forward angles, including 0∘. The isoscalar E 0 , E 1 , and E 2 strengths are observed to be 57 ±7 % , 111 .1-7.2+10.9% , and 148.6 ±7.3 % , respectively, of their energy-weighted sum rules in the excitation energy range of 6 to 35 MeV. The isoscalar giant monopole (ISGMR) and quadrupole (ISGQR) resonances exhibit a prominent K splitting which is consistent with microscopic theory for a prolate-deformed ground state of 24Mg. For the ISGQR it is due to splitting of the three K components, whereas for the ISGMR it is due to its coupling to the K =0 component of the ISGQR. Deformation effects on the isoscalar giant dipole resonance are less pronounced, however.

  19. Paramagnetic Meissner effect in MgB 2

    NASA Astrophysics Data System (ADS)

    Sözeri, Hüseyin; Dorosinskii, Lev; Topal, Uǧur; Ercan, İsmail

    2004-08-01

    We observed the paramagnetic Meissner effect (PME) in MgB 2 pellets after cooling in low fields of less than 1 Oe. As external magnetic field increases, the paramagnetic response of the sample decreases and disappears completely at 1 Oe. Effect of gamma irradiation on magnetic properties of MgB 2 has been investigated at low fields. In irradiated samples, the magnitude of the PME was found to be lower. To understand that whether this effect is of geometrical origin (so called flux compression model) or whether it is intrinsic to the material (e.g., π-junctions), measurements were performed with two samples having different geometries. Our results showed that paramagnetic response did not change as the geometry changes.

  20. Doublet 2800 MgII in close binary systems

    NASA Technical Reports Server (NTRS)

    Gurzadian, G. A.; Perez, M.

    1991-01-01

    The origin of the intercomponent ultraviolet emission from binary radio stars is discussed following an examination of observed emission parameters. Observations are used to consider four arguments which suggest that the Mg emission originates in the space between the components of the binary and not in the chromosphere. Parameters examined include the ratio of Mg emission to that of other binaries, the direct variation of emission with brightness strength, the derivation and nature of the radial velocity, and comparisons of absolute luminosities. Emission (A) and absorption (B) streams or clouds generate the emission, and the observed wavelength distortions are caused by B. An examination of the nature of the emission yields both qualitative and quantitative criteria, including the notion of weak ionization of the hydrogen atoms in B clouds relative to the ionization in A clouds.

  1. Neutron capture of 26Mg at thermonuclear energies

    NASA Astrophysics Data System (ADS)

    Mohr, P.; Beer, H.; Oberhummer, H.; Staudt, G.

    1998-08-01

    The neutron capture cross section of 26Mg was measured relative to the known gold cross section at thermonuclear energies using the fast cyclic activation technique. The experiment was performed at the 3.75 MV Van-de-Graaff accelerator, Forschungszentrum Karlsruhe. The experimental capture cross section is the sum of resonant and direct contributions. For the resonance at En,lab=220 keV our new results are in disagreement with the data from Weigmann, Macklin, and Harvey [Phys. Rev. C 14, 1328 (1976)]. An improved Maxwellian averaged capture cross section is derived from the new experimental data taking into account s- and p-wave capture and resonant contributions. The properties of so-called potential resonances which influence the p-wave neutron capture of 26Mg are discussed in detail.

  2. Molecular Dynamics Simulation of MgSiO3 Perovskite

    NASA Astrophysics Data System (ADS)

    Lin-xiang, Zhou; L, Zhou X.; J, Hardy R.; Xin, Xu; X, Xu

    1998-06-01

    Using molecular dynamics to simulate MgSiO3 perovskite is performed to investigate its phase transitions and superionicity. These simulations has used parameter-free Gordon-Kim potentials and a novel technique to monitor the motion of ions which clearly demonstrates the sublattice melting of ions O2- and the rotations of SiO6 octahedra. MgSiO3 has to undergo a few of phase transitions, then enter into the cubic phase. In particular, there is a transitional phase between orthorhombic phase and cubic phase. There are a superionic phase and the cubic phase in magnesium-rich silicate perovskite. This superionic phase occurs after the onset of cubic phase before the melting point. The onset temparature Tc for superionicity is about 200-700 K below the melting point Tm, Tc / Tm similar 0.92.

  3. Fourier Transform Infrared Emission Spectra of MgF_2

    NASA Astrophysics Data System (ADS)

    Frohman, Daniel J.; Bernath, Peter F.; Koput, Jacek

    2014-06-01

    High resolution infrared emission spectra of hot MgF2 in the 700 to 1300 cm-1 region have been recorded. The molecules were generated by heating solid MgF2 to 1675 °C. Four vibrational bands were rotationally analyzed yielding band origins and rotational constants. Observed bands are: 001-000 (Σu+ - Σg+), 0111 - 0110 (Πg - Πu), 0221 (f parity) - 0220 (f parity) (Δu - Δg), and 0331 - 0330 (Φg - Φu). High level ab initio calculations were essential in making assignments and in helping to fit the data. The Δu - Δg band was only observed for f-parity because the e-parity is significantly perturbed by l-resonance.

  4. Fusion in the 20Ne+24Mg system

    NASA Astrophysics Data System (ADS)

    Albinska, M.; Belery, P.; Delbar, Th.; El Masri, Y.; Grégoire, Gh.; Michel, C.; Vervier, J.; Albinski, J.; Grotowski, K.; Kopta, S.; Kozik, T.; Płaneta, R.; Paič, G.

    1983-01-01

    Inclusive γ spectra from the 20Ne+24Mg interaction have been measured using from 45 up to 105 MeV 20Ne beams. Experimental mass and charge spectra are compared with statistical model calculations. Total reaction and fusion cross sections are extracted. The optical, Glas and Mosel, and Bass model calculations are presented and compared with the data. The limitation of the fusion cross section by the statistical yrast line is also discussed. NUCLEAR REACTIONS 20Ne+24Mg, Elab=45, 55, 60, 70, 80, 85, 105 MeV; measured mass spectra for 12<=A<=44, charge spectra for 6<=Z<=22 measured total reaction and fusion cross sections σR, σf deduced critical angular momentum and radius lf and rcr.

  5. Active Protection of an MgB2 Test Coil

    PubMed Central

    Park, Dong Keun; Hahn, Seungyong; Bascuñán, Juan; Iwasa, Yukikazu

    2011-01-01

    This paper presents results of a study, experimental and computational, of a detect-and-activate-the-heater protection technique applied to a magnesium diboride (MgB2) test coil operated in semi-persistent mode. The test coil with a winding ID of 25 cm and wound with ~500-m long reacted MgB2 wire was operated at 4.2 K immersed in a bath of liquid helium. In this active technique, upon the initiation of a “hot spot” of a length ~10 cm, induced by a “quench heater,” a “protection heater” (PH) of ~600-cm long planted within the test coil is activated. The normal zone created by the PH is large enough to absorb the test coil’s entire initial stored energy and still keeps the peak temperature within the winding below ~260 K. PMID:22081754

  6. Flexible MgO Barrier Magnetic Tunnel Junctions.

    PubMed

    Loong, Li Ming; Lee, Wonho; Qiu, Xuepeng; Yang, Ping; Kawai, Hiroyo; Saeys, Mark; Ahn, Jong-Hyun; Yang, Hyunsoo

    2016-07-01

    Flexible MgO barrier magnetic tunnel junction (MTJ) devices are fabricated using a transfer printing process. The flexible MTJ devices yield significantly enhanced tunneling magnetoresistance of ≈300% and improved abruptness of switching, as residual strain in the MTJ structure is released during the transfer process. This approach could be useful for flexible electronic systems that require high-performance memory components. PMID:27119207

  7. Phase Transitions of MgO Along the Hugoniot (Invited)

    NASA Astrophysics Data System (ADS)

    Root, S.; Shulenburger, L.; Lemke, R. W.; Cochrane, K. R.; Mattsson, T. R.

    2013-12-01

    The formation of terrestrial planets and planetary structure has become of great interest because of recent exoplanet discoveries of super earths. MgO is a major constituent of Earth's mantle, the rocky cores of gas giants such as Jupiter, and likely constitutes the interiors of many exoplanets. The high pressure - high temperature behavior of MgO directly affects equation of state models for planetary structure and formation. In this work, we examine single crystal MgO under shock compression utilizing experimental and density functional theory (DFT) methods to determine phase transformations along the Hugoniot. We perform plate impact experiments using Sandia's Z - facility on MgO up to 11.6 Mbar. The plate impact experiments generate highly accurate Hugoniot state data. The experimental results show the B1 - B2 solid - solid phase transition occurs near 4 Mbar on the Hugoniot. The solid - liquid transition is determined to be near 7 Mbar with a large region of B2-liquid coexistence. Using DFT methods, we also determine melt along the B1 and B2 solid phase boundaries as well as along the Hugoniot. The combined experimental and DFT results have determined the phase boundaries along the Hugoniot, which can be implemented into new planetary and EOS models. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Securities Administration under Contract No. DE-AC04-94AL85000.

  8. Enhanced magnetization at the Cr/MgO(001) interface

    SciTech Connect

    Leroy, M.-A.; Bataille, A. M. Ott, F.; Wang, Q.; Fitzsimmons, M. R.; Bertran, F.; Le Fèvre, P.; Taleb-Ibrahimi, A.; Vlad, A.; Coati, A.; Garreau, Y.; Hauet, T.; Andrieu, S.; Gatel, C.

    2015-12-21

    We report on the magnetization at the Cr/MgO interface, which we studied through two complementary techniques: angle-resolved photoemission spectroscopy and polarized neutron reflectivity. We experimentally observe an enhanced interface magnetization at the interface, yet with values much smaller than the ones reported so far by theoretical and experimental studies on Cr(001) surfaces. Our findings cast some doubts on the interpretations on previous works and could be useful in antiferromagnetic spin torque studies.

  9. Anisotropic high field superconductinng behavior in MgB_2

    NASA Astrophysics Data System (ADS)

    Gurevich, Alexander

    2004-03-01

    I will discuss new effects resulting from the two-gap superconductivity in MgB_2, focusing on: 1. Current-induced interband breakdown and dynamic interband phase textures caused by nonequilibrium charge imbalance [1], 2. Anomalous enhancement of the upper critical field H_c2(T) by nonmagnetic impurities in dirty two-gap superconductors. A theory of H_c2 based on generalized two-gap Usadel equations, which include both intra and interband scattering channels and paramagnetic pairbreaking is presented. Solutions of these equations show that H_c2(T) can exhibit a strong upward curvature and an unusual temperature dependence of the anisotropy parameter H_c2^||/H_c2^⊥, which can both increase and decrease with T depending on the ratio of the intraband electron diffusivities D_π/D_σ [2]. The theory explains recent high-field transport experiments on resistive MgB2 films in which the upper critical field was increased by 3-10 times as compared to single crystals [3], H_c2 exceeding 50 Tesla for H||ab and 35T for H⊥ ab. The results suggest that nonmagnetic impurities due to selective atomic substitution on Mg and B sites can increase H_c2 of MgB2 to a much greater extend than in one-gap superconductors. [1]. A. Gurevich and V.M. Vinokur, PRL 90, 047004 (2003). [2]. A. Gurevich, PRB 67, 1845151 (2003) and unpublished. [3]. A. Gurevich et al. Supercond. Sci. Technol. (2003, to appear). *In collaboration with V.M. Vinokur, V. Braccini, S. Patnaik, X. Song, D.C. Larbalestier, C.B. Eom, X. Pan, X. Xi, V. Ferrando, C. Ferdighini, A. Siri, K.H. Kim and C. Mielke. Work supported by NSF Nanostructured Materials and Interfaces MRSEC at the University of Wisconsin.

  10. Lattice dynamics of Mg 2SiO 4

    NASA Astrophysics Data System (ADS)

    Łażewski, J.; Jochym, P. T.; Parlinski, K.; Piekarz, P.

    2001-09-01

    Total energy calculations within the density functional theory (DFT), generalized gradient approximation and ultrasoft pseudopotentials have been used to investigate structural, dynamical and thermodynamical properties of the high-pressure structure of the magnesium orthosilicate (Mg 2SiO 4, γ-spinel, ringwoodite). The phonon dispersion curves and phonon density of states have been calculated using the direct method. The results show agreement with the available experimental Raman data.

  11. MAGIICAT I. THE Mg II ABSORBER-GALAXY CATALOG

    SciTech Connect

    Nielsen, Nikole M.; Churchill, Christopher W.; Kacprzak, Glenn G.; Murphy, Michael T.

    2013-10-20

    We describe the Mg II Absorber-Galaxy Catalog, MAGIICAT, a compilation of 182 spectroscopically identified intermediate redshift (0.07 ≤ z ≤ 1.1) galaxies with measurements of Mg II λλ2796, 2803 absorption from their circumgalactic medium within projected distances of 200 kpc from background quasars. In this work, we present 'isolated' galaxies, which are defined as having no spectroscopically identified galaxy within a projected distance of 100 kpc and a line of sight velocity separation of 500 km s{sup –1}. We standardized all galaxy properties to the ΛCDM cosmology and galaxy luminosities, absolute magnitudes, and rest-frame colors to the B- and K-band on the AB system. We present galaxy properties and rest-frame Mg II equivalent width, W{sub r} (2796), versus galaxy redshift. The well-known anti-correlation between W{sub r} (2796) and quasar-galaxy impact parameter, D, is significant to the 8σ level. The mean color of MAGIICAT galaxies is consistent with an Sbc galaxy for all redshifts. We also present B- and K-band luminosity functions for different W{sub r} (2796) and redshift subsamples: 'weak absorbing' [W{sub r} (2796) < 0.3 Å], 'strong absorbing' [W{sub r} (2796) ≥ 0.3 Å], low redshift (z < (z)), and high redshift (z ≥ (z)), where (z) = 0.359 is the median galaxy redshift. Rest-frame color B – K correlates with M{sub K} at the 8σ level for the whole sample but is driven by the strong absorbing, high-redshift subsample (6σ). Using M{sub K} as a proxy for stellar mass and examining the luminosity functions, we infer that in lower stellar mass galaxies, Mg II absorption is preferentially detected in blue galaxies and the absorption is more likely to be weak.

  12. Effect of Fe and Mg on crystallization in granitic systems

    SciTech Connect

    Naney, M.T.; Swanson, S.E.

    1980-07-01

    Single-step and multistep undercooling experiments using both Fe, Mg-free and Fe, Mg-bearing model granitic compositions were conducted to investigate the influence of mafic components on the crystallization of granitic melts. Crystallization of granite and granodiorite compositions in the system NaAlSi/sub 3/O/sub 8/-KAlSi/sub 3/O/sub 8/-CaAl/sub 2/Si/sub 2/O/sub 8/-SiO/sub 2/-H/sub 2/O produces assemblages containing one or more of the following phases: plagioclase, alkali feldspar, quartz, silicate liquid, and vapor. The observed phase assemblages are generally in good agreement with equilibrium data reported in the literature on the same bulk compositions. With the addition of Fe and Mg to these bulk compositions six new phases participate in the equilibria (orthopyroxene, clinopyroxene, biotite, hornblende,epidote, and magnetite). However, crystalline assemblages produced in phase equilibrium and crystal growth experiments brought to the same final P-T-X/sub H/sub 2/O/ conditions are in general not equivalent. Perhaps the addition of Fe and Mg has caused a breakdown of the Si-O framework in the melt, thereby promoting the more rapid nucleation of the ino- and phyllosilicates rather than the framework silicates. Border zones of granitic plutons, commonly rich in mafic minerals, may result from the more rapid nucleation of mafic phases from the silicate liquid. These zones are thought to develop by early crystallization along the walls of the pluton. Our results suggest the mafic phases should nucleate more quickly than the feldspars and quartz and thus should enrich the early crystallization products in ferromagnesian minerals.

  13. Characterisation of Mg biodegradable stents produced by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Elmrabet, N.; Botterill, N.; Grant, D. M.; Brown, P. D.

    2015-10-01

    Novel Mg-minitubes for biodegradable stent applications have been produced using PVD magnetron sputtering. The minitubes were characterised, as a function of annealing temperature, using a combination of SEM/EDS, XRD and hardness testing. The as-deposited minitubes exhibited columnar grain structures with high levels of porosity. Slight alteration to the crystal structure from columnar to equiaxed grain growth was demonstrated at elevated temperature, along with increased material densification, hardness and corrosion resistance.

  14. Superconductivity in MgB2 irradiated with energetic protons

    NASA Astrophysics Data System (ADS)

    Sandu, Viorel; Craciun, Liviu; Ionescu, Alina Marinela; Aldica, Gheorghe; Miu, Lucica; Kuncser, Andrei

    2016-09-01

    A series of MgB2 samples were irradiated with protons of 11.3 and 13.2 MeV. Magnetization data shows an insignificant reduction of the critical temperatures but a continuous decrease of the Meissner fraction with increasing fluence or energy. All samples show a consistent improvement of the critical current density compared to the virgin sample and an increase of the pinning energy at high fields as resulted from relaxation data.

  15. Helium diffraction from the MgO(001) surface

    NASA Astrophysics Data System (ADS)

    Jung, David R.; Mahgerefteh, Massoud; Frankl, Daniel R.

    1989-05-01

    Helium diffraction beam intensity measurements from an in situ cleaved, oxygen-treated, room-temperature surface of MgO(001) are reported. The in-plane spectra obtained at several angles in the main azimuthal planes at beam energies of 17.3 and 63 meV were analyzed using a hard corrugated surface model. A corrugation amplitude of about 0.17 Å gives a fair fit, in agreement with most previous work.

  16. Quadruplex-and-Mg2+ Connection (QMC) of DNA

    PubMed Central

    Kankia, Besik

    2015-01-01

    This work highlights a novel method of coupling of nucleic acids through formation of an extraordinary stable, specific and fully reversible quadruplex-and-Mg2+ connection (QMC). QMC employs the monomolecular tetrahelical architecture of DNA and has two key components: (i) shape complementarity between QMC partners, which is introduced by specific modifications of the quadruplexes, and (ii) Mg2+ ions. The on-rate of QMC formation is between 105–106 M−1 s−1, while the off-rate is undetectable even at 80 °C. However, QMC dissociates rapidly upon removal of Mg2+ ions (i.e., by EDTA). QMC is characterized by high specificity, as even a single-nucleotide modification of one of the connectors inhibits complex-formation. QMC has the potential to revolutionize biotechnology by introducing a new class of capture molecules with major advantages over traditional systems such as streptavidin-biotin. The advantages include reversibility, multiplexing, higher stability and specificity, longer shelf life and low cost. PMID:26265243

  17. Carbon Doped MgB2 Thin Films using TMB

    NASA Astrophysics Data System (ADS)

    Wilke, R. H. T.; Li, Qi; Xi, X. X.; Lamborn, D. R.; Redwing, J.

    2007-03-01

    The most effective method to enhance the upper critical field in MgB2 is through carbon doping. In the case of thin films, ``alloying'' with carbon has resulted in enhanced Hc2 values estimated to be as high as 70 T for H parallel to ab and 40 T for H perpendicular ab [1]. ``Alloying'' refers to the in-situ Hybrid Physical-Chemical Vapor Deposition (HPCVD) of carbon containing MgB2 films using (C5H5)2Mg as the carbon source. While these films exhibit enhanced Hc2 values, there are amorphous boron- carbon phases in the grain boundaries that reduce the cross section area for superconducting current. We present here the results of our attempts to make more homogeneously carbon doped thin films using gaseuous trimethyl-boron (TMB) as the carbon source. Initial results indicate different behavior upon carbon doping using TMB from carbon-alloying. The microstructures and upper critical fields of the carbon doped films using TMB and carbon alloyed films will be compared. [1] V. Braccini et al., Phys. Rev. B 71 (2005) 012504. [2] A.V. Pogrebnyakov et al., Appl. Phys. Lett 85 (2004) 2017.

  18. Inhomogeneities and Effective Mass in Doped Mg2Si

    NASA Astrophysics Data System (ADS)

    Stefanaki, E. C.; Polymeris, G. S.; Ioannou, M.; Pavlidou, E.; Hatzikraniotis, E.; Kyratsi, Th.; Paraskevopoulos, K. M.

    2016-03-01

    Magnesium silicide (Mg2Si)-based materials are promising candidates as thermoelectric components for mid-temperature range (500-900 K) energy conversion. Many different approaches for determining the parabolicity of the conduction band have been suggested in the literature, while the values of the effective mass m* dL reported, lie between 0.46 and 1.1 m0. The aim of this work is to contribute in elucidating the discrepancy observed in the effective mass values of the lower conduction band of highly doped Mg2Si and examine whether this discrepancy could be attributed to the method of determination or to the sample's characteristics. We present the results of effective mass calculations at room temperature (RT) by applying different experimental methods and models (parabolic and non-parabolic) in two different groups of samples; one yielding profound inhomogeneities (Sb-doped) and one yielding homogeneous (Bi-doped) samples. Concluding this analysis, it seems that the lower conduction band of Mg2Si is more likely described as non-parabolic. Comparing the two groups of samples, our analysis indicated that the effective mass may be significantly underestimated for samples with dopant and content-modulated composition.

  19. Hydrogen generation by means of catalyzed Mg-Al hydrolysis

    NASA Astrophysics Data System (ADS)

    Hoehne, K.; Jaeger, P.

    Based on considerations of reactivity, costs, and the volume of hydrogen which can be expected per mass fraction of metal, Al and Mg offer good possibilities in metal hydrolysis. Since these metals hardly react with water, however, a catalyst is used to accelerate the Mg-Al hydrolysis process. Experiments show that a mixture of Mg and Al reacts strongly with water in the presence of CO3O4, MoO3, and Cl-ions; with an optimum combination of all the participants in the reaction, the H2 yield can amount to 100%. Various methods are discussed for constructing a hydrogen generator using this new method of metal hydrolysis. A hydrogen generator plant is described, in which pressed powder pellets are used. An aluminum-magnesium-cobalt oxide powder mixture is introduced into the reactor in the form of cylindrical pellets, which are pulverized in the reactor chamber. The powder falls into the salt water in the reactor and is converted. The hydrogen produced has a purity potentially greater than 99.9%.

  20. Mg II line profiles of the Mira S Carinae

    SciTech Connect

    Bookbinder, J.A.; Brown, A.; Brugel, E.W.; Colorado Univ., Boulder )

    1989-07-01

    A series of high-dispersion IUE observations obtained to investigate the evolution of the shock structure of the Mira variable S Carinae have produced (despite limited phase coverage) a set of five exceptionally interesting spectra of the Mg II h and k lines. The two primary findings of these observations are (1) there is significant emission from both the h and k lines at positions corresponding to velocities of -150 km/s relative to the stellar photosphere and (2) the k/h flux ratio of the Mg II doublet remains below the theoretically predicted values which lie in the range 2:1 to 1:1 and shows a smooth dependence on the optical phase. Archival studies of other Miras (e.g., R Car) indicate that S Car is not unique in possessing unusual and highly variable Mg II h and k line profiles. Several possible physical processes that may explain these results, including radiative transfer effects in a shocked atmosphere, circumstellar scattering, and circumstellar absorption, are discussed. 10 refs.

  1. Mg II line profiles of the Mira S Carinae

    NASA Technical Reports Server (NTRS)

    Bookbinder, Jay A.; Brown, Alexander; Brugel, Edward W.

    1989-01-01

    A series of high-dispersion IUE observations obtained to investigate the evolution of the shock structure of the Mira variable S Carinae have produced (despite limited phase coverage) a set of five exceptionally interesting spectra of the Mg II h and k lines. The two primary findings of these observations are (1) there is significant emission from both the h and k lines at positions corresponding to velocities of -150 km/s relative to the stellar photosphere and (2) the k/h flux ratio of the Mg II doublet remains below the theoretically predicted values which lie in the range 2:1 to 1:1 and shows a smooth dependence on the optical phase. Archival studies of other Miras (e.g., R Car) indicate that S Car is not unique in possessing unusual and highly variable Mg II h and k line profiles. Several possible physical processes that may explain these results, including radiative transfer effects in a shocked atmosphere, circumstellar scattering, and circumstellar absorption, are discussed.

  2. Synthesis and characterization of Mn intercalated Mg-Al hydrotalcite.

    PubMed

    Yang, Chengxue; Liao, Libing; Lv, Guocheng; Wu, Limei; Mei, Lefu; Li, Zhaohui

    2016-10-01

    Mn intercalated hydrotalcite was prepared using a reconstruction method. And Mn intercalation was confirmed by XRD, FTIR, and thermal analyses. The different valences of Mn were present as determined by XPS. Calcination slightly promoted the isomorphic replacement of Mn(2+) and Mn(3+) for Mg(2+) and Al(3+), especially the replacement of Mn(2+) for Mg(2+) and Al(3+), and to some extent, reduced Mn intercalation. Ultrasonic treatment significantly increased Mn intercalation in permanganate form (Mn(7+)), and promoted the replacement of Mn(2+) for Mg(2+) and Al(3+). XRF analysis showed that ultrasonic treatment decreased the unbalanced layer charge of Mn intercalated hydrotalcite, while prolonged calcination increased it. These results may provide guidance on the preparation and application of Mn intercalated hydrotalcite. Extended calcination time and ultrasonic vibration increased the interlayer spacing of hydrotalcite, as a result of reduction in layer charge. As the layer charge was not completely balanced after Mn intercalation, a certain amount of CO3(2-) was re-adsorbed into the interlayer space. Mn-hydrotalcites with different layer charges, different contents of Mn with varying valences are expected to have different performances in the process of adsorption, degradation, and catalysis. PMID:27380016

  3. Mg+ and other metallic emissions observed in the thermosphere

    SciTech Connect

    Gardner, J.A.; Viereck, R.A.; Murad, E.; Lai, S.T.; Knecht, D.J.

    1994-11-17

    Limb observations of UV dayglow emissions from 80 to 300 km tangent heights were made in December 1992, using the GLO instrument, which flew on STS-53 as a Hitchhiker-G experiment. STS-53 was at 330 km altitude and had an orbit inclination of 57 deg. The orbit placed the shuttle near the terminator for the entire mission, resulting in a unique set of observations. The GLO instrument consisted of 12 imagers and 9 spectrographs on an Az/El gimbal system. The data was obtained over 6 days of the mission. Emissions from Mg+ and Ca+ were observed, as were emissions from the neutral metallic species Mg and Na. The ultimate source of the metals is ablation of meteors; however, the spatial distribution of the emissions is controlled by upper mesospheric and thermospheric winds and, in the case of the ions, by the electromagnetic fields of the ionosphere. The observed Mg+ emission was the brightest of the metal emissions, and was observed near the poles and around the geomagnetic equator near sunset. The polar emissions were short-lived and intense, indicative of auroral activity. The equatorial emissions were more continuous, with several luminous patches propagation poleward over the period of several orbits. The instrumentation will be described, as will spatial and temporal variations of the metal emissions with emphasis on the metal ions. These observations will be compared to previous observations of thermospheric metallic species.

  4. The electric dipole moment of magnesium deuteride, MgD

    NASA Astrophysics Data System (ADS)

    Steimle, Timothy C.; Zhang, Ruohan; Wang, Hailing

    2014-06-01

    The (0,0) A2Π-X 2Σ+ band of a cold molecular beam sample of magnesium monodeuteride, MgD, has been recorded field-free and in the presence of a static electric field of up to 11 kV/cm. The lines associated with the lowest rotational levels are detected for the first time. The field-free spectrum was analyzed to produce an improved set of fine structure parameters for the A2Π (v = 0) state. The observed electric field induced splittings and shifts were analyzed to produce permanent electric dipole moments, ěc μ _{el} of 2.567(10)D and 1.31(8)D for A2Π (v = 0) and X2Σ+(v = 0) states, respectively. The recommended value for ěc μ _{el}(X2Σ+ (v = 0)) for MgH, based upon the measured value for MgD, is 1.32(8)D.

  5. The electric dipole moment of magnesium deuteride, MgD

    SciTech Connect

    Steimle, Timothy C. Zhang, Ruohan; Wang, Hailing

    2014-06-14

    The (0,0) A{sup 2}Π–X {sup 2}Σ{sup +} band of a cold molecular beam sample of magnesium monodeuteride, MgD, has been recorded field-free and in the presence of a static electric field of up to 11 kV/cm. The lines associated with the lowest rotational levels are detected for the first time. The field-free spectrum was analyzed to produce an improved set of fine structure parameters for the A{sup 2}Π (v = 0) state. The observed electric field induced splittings and shifts were analyzed to produce permanent electric dipole moments, μ{sup -vector}{sub el} of 2.567(10)D and 1.31(8)D for A{sup 2}Π (v = 0) and X{sup 2}Σ{sup +}(v = 0) states, respectively. The recommended value for μ{sup -vector}{sub el}(X{sup 2}Σ{sup +} (v = 0)) for MgH, based upon the measured value for MgD, is 1.32(8)D.

  6. Arsenic mobility in sediments from Paracatu River Basin, MG, Brazil.

    PubMed

    Rezende, Patrícia Sueli; Costa, Letícia Malta; Windmöller, Cláudia Carvalhinho

    2015-04-01

    Paracatu River Basin, Minas Gerais, Brazil, houses long areas of irrigated agriculture and gold-, lead-, and zinc-mining activities. This region has a prevalence of sulfide minerals and a natural occurrence of high levels of arsenopyrite. In this work, surface water, groundwater, sediments and local vegetable samples were collected in October 2010 and November 2011 and were analyzed to evaluate arsenic (As) distribution, mobility, and transport in these environmental compartments. All sediment samples (738-2,750 mg kg(-1)) and 37 % of the water samples [less than the limit of detection (LOD) to 110 µg L(-1)] from the rivers and streams of Paracatu had As concentrations greater than the quality standards established by national and international environmental organizations (5.9 mg kg(-1) for sediments and 10 µg L(-1) for water). Most vegetable samples had As concentrations within the normal range for plants (lower than the LOD to 120 mg kg(-1)). A correlation among As concentrations in water, sediment, and vegetable samples was verified. PMID:25672271

  7. Ostracode Mg/Ca Paleothermometry: Applications and Complications

    NASA Astrophysics Data System (ADS)

    Cronin, T. M.; Dwyer, G. S.

    2007-12-01

    Ostracode (bivalved Crustacea) shell Mg/Ca paleothermometry has wide applicability in Cenozoic paleoclimatology over 101 to 107 year timescales because they are commonly fossilized, live in freshwater, shallow- and deep-marine habitats, and grow by molting, which minimizes Mg/Ca variability due to ontogenetic variability. Two empirically derived Mg/Ca-temperature calibrations based on core top and culturing include one for the shallow marine, estuarine genus Loxoconcha (5 to 30°C) and another for deep-sea genus Krithe (<1 to 14°C). The former produced a temperature history for Chesapeake Bay for the last millennium, which has been intensively analyzed in the context of the hockey stick temperature curve. The latter produced evidence for decreased deep-sea temperature during glacial intervals and the first Atlantic-wide reconstruction of deep-sea temperature during the warm mid-Pliocene. In addition to temperature, however, factors such as host-water magnesium concentrations, salinity, intra-shell, intra-population, and interspecific variabilility, seasonality, biological factors (shell secretion rate), and post-mortem dissolution can contribute to scatter in calibration datasets and uncertainty in paleotemperature estimates. We will review these processes, present a new 2000 year Chesapeake temperature record, and discuss its relation to twentieth century climate change.

  8. Fine-Filament MgB2 Superconductor Wire

    NASA Technical Reports Server (NTRS)

    Cantu, Sherrie

    2015-01-01

    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 (<10 micrometers) could reduce alternating current (AC) losses that occur due to hysteresis, eddy currents, and coupling losses. The company refined a manufacturing method that incorporates a magnesium-infiltration process and provides a tenfold enhancement in critical current density over wire made by a conventional method involving magnesium-boron powder mixtures. Hyper Tech also improved its wire-drawing capability to fabricate fine multifilament strands. In Phase II, the company developed, manufactured, and tested the wire for superconductor and engineering current density and AC losses. Hyper Tech also fabricated 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.

  9. Grain boundary mobility in anion doped MgO

    NASA Technical Reports Server (NTRS)

    Kapadia, C. M.; Leipold, M. H.

    1973-01-01

    Certain anions OH(-), F(-) and Gl(-) are shown to enhance grain growth in MgO. The magnitude of their effect decreases in the order in which the anions are listed and depends on their location (solid-solution, second phase) in the MgO lattice. As most anions exhibit relatively high vapor pressures at sintering temperatures, they retard densification and invariably promote residual porosity. The role of anions on grain growth rates was studied in relation to their effect on pore mobility and pore removal; the atomic process controlling the actual rates was determined from observed kinetics in conjunction with the microstructural features. With respect to controlling mechanisms, the effects of all anions are not the same. OH(-) and F(-) control behavior through creation of a defect structure and a grain boundary liquid phase while Cl(-) promotes matter transport within pores by evaporation-condensation. Studies on an additional anion, S to the minus 2nd power gave results which were no different from undoped MgO, possibly because of evaporative losses during hot pressing. Hence, the effect of sulphur is negligible or undetermined.

  10. Effect of Heavy Carbon Doping of MgB_2

    NASA Astrophysics Data System (ADS)

    Kasinathan, Deepa; Pickett, W. E.

    2003-03-01

    Superconductivity in MgB2 seems to be beginning to be understood, but behavior under changes of hole concentration remain to be established and understood. Recently Ribeiro, Bud'ko, Petrovic, and Canfield (cond-mat/0210530) have reported MgB_2-xC_x, where Tc ˜ 20 K for x 0.1 -- 0.2. Rigid band arguments would say that the σ-band hole states in MgB2 should be filled by x=1/6, with no superconductivity. We have carried all-electron, full potential LAPW studies [WIEN2K] of ordered supercells corresponding to x=1/6 and 1/8 to assess the effects of the C, whose potential is more attractive and size is smaller than B, on the structure and the electronic bands and density of states. The behavior is non-rigid-band in important ways. We report on the magnitude of B atom relaxation around the C impurities, the effect that the relaxation has on the band filling, and the degree to which the experimental data can be accounted for.

  11. Automotive Mg Research and Development in North America

    SciTech Connect

    Carpenter, Joseph A.; Jackman, Jennifer; Li, Naiyi; Osborne, Richard J.; Powell, Bob R.; Sklad, Philip S

    2006-01-01

    Expanding world economic prosperity and probable peaking of conventional petroleum production in the coming decades require efforts to increase the efficiency of, and the development of alternatives to, petroleum-based fuels used in automotive transportation. North America has been aggressively pursuing both approaches for over ten years. Mainly as a result of lower prices due to global sourcing, magnesium has recently emerged as a serious candidate for lightweighting, and thus increasing the fuel efficiency of, automotive transportation. Automotive vehicles produced in North America currently use more Mg than vehicles produced elsewhere in the world, but the amounts per vehicle are very small in comparison to other materials such as steel, aluminum and plastics. The reasons, besides price, are primarily a less-developed state of technology for Mg in automotive transportation applications and lack of familiarity by the vehicle manufacturers with the material. This paper reviews some publicly-known, recent, present and future North American research and development activities in Mg for automotive applications.

  12. Parenteral magnesium load testing with /sup 28/Mg in weanling and young adult rats

    SciTech Connect

    Caddell, J.L.; Calhoun, N.R.; Howard, M.P.; Patterson, K.Y.; Smith, J.C. Jr.

    1981-06-01

    A sound diagnostic test for Mg deficiency is needed. This is a report of the parenteral Mg load test conducted in weanling and young adult rats fed a purified basal diet containing 3 mg magnesium/100 g with 150 mg of added magnesium/100 g (control) or 0 added magnesium (deficient). Weanlings were studied at about 1 week of dietary treatment and young adults at 2 weeks. The protocol included: a) a 6-hour preload urinary collection; b) an intraperitoneal load of 15 mg of magnesium/kg (weanlings) or 12 mg/kg (young adults) with 2 microCi 28Mg given simultaneously with each load; c) a 6-hour postload urinary collection; d) chemical analysis of selected tissues and urine for Mg; and e) 28Mg counting 6 and 24 hours postload. Controls all excreted large amounts of Mg pre- and postload, retaining less than 26% of nonradioactive loads. They had high urinary 28Mg counts. In Mg-deficient animals, the concentration of Mg in bone more than halved. These animals avidly conserved Mg and retained over 85% of nonradioactive Mg loads. Their 28Mg activity in vital organs was 3--6 times greater than in controls. We concluded that the parenteral Mg load test reliably identifies severe Mg deficiency.

  13. Electron microscopy of Mg/TiO2 photocatalyst morphology for deep desulfurization of diesel

    NASA Astrophysics Data System (ADS)

    Yin, Yee Cia; Kait, Chong Fai; Fatimah, Hayyiratul; Wilfred, Cecilia

    2015-07-01

    A series of Mg/TiO2 photocatalysts were prepared and characterized using Field Emission Scanning Electron Microscopy (FESEM) and High-Resolution Transmission Electron Microscopy (HRTEM). The average particle sizes of the photocatalysts were ranging from 25.7 to 35.8 nm. Incorporation of Mg on TiO2 did not lead to any surface lattice distortion to TiO2. HRTEM data indicated the presence of MgO and Mg(OH)2 mixture at low Mg loading while at higher Mg loading, the presence of lamellar Mg-oxyhydroxide intermediates and Mg(OH)2.

  14. Electron microscopy of Mg/TiO{sub 2} photocatalyst morphology for deep desulfurization of diesel

    SciTech Connect

    Yin, Yee Cia; Kait, Chong Fai Fatimah, Hayyiratul Wilfred, Cecilia

    2015-07-22

    A series of Mg/TiO{sub 2} photocatalysts were prepared and characterized using Field Emission Scanning Electron Microscopy (FESEM) and High-Resolution Transmission Electron Microscopy (HRTEM). The average particle sizes of the photocatalysts were ranging from 25.7 to 35.8 nm. Incorporation of Mg on TiO{sub 2} did not lead to any surface lattice distortion to TiO{sub 2}. HRTEM data indicated the presence of MgO and Mg(OH){sub 2} mixture at low Mg loading while at higher Mg loading, the presence of lamellar Mg-oxyhydroxide intermediates and Mg(OH){sub 2}.

  15. Kinetic analysis of MgB2 layer formation in advanced internal magnesium infiltration (AIMI) processed MgB2 wires

    PubMed Central

    Li, G. Z.; Sumption, M. D.; Collings, E. W.

    2015-01-01

    Significantly enhanced critical current density (Jc) for MgB2 superconducting wires can be obtained following the advanced internal Mg infiltration (AIMI) route. But unless suitable precautions are taken, the AIMI-processed MgB2 wires will exhibit incomplete MgB2 layer formation, i.e. reduced superconductor core size and hence suppressed current-carrying capability. Microstructural characterization of AIMI MgB2 wires before and after the heat treatment reveals that the reaction mechanism changes from a “Mg infiltration-reaction” at the beginning of the heat treatment to a “Mg diffusion-reaction” once a dense MgB2 layer is formed. A drastic drop in the Mg transport rate from infiltration to diffusion causes the termination of the MgB2 core growth. To quantify this process, a two-stage kinetic model is built to describe the MgB2 layer formation and growth. The derived kinetic model and the associated experimental observations indicate that fully reacted AIMI-processed MgB2 wires can be achieved following the optimization of B particle size, B powder packing density, MgB2 reaction activation energy and its response to the additions of dopants. PMID:26973431

  16. Thermodynamics and Kinetics of the Formation of Al2O3/ MgAl2O4/MgO in Al-Silica Metal Matrix Composite

    NASA Astrophysics Data System (ADS)

    Sreekumar, V. M.; Ravi, K. R.; Pillai, R. M.; Pai, B. C.; Chakraborty, M.

    2008-04-01

    The formation of Al2O3, MgAl2O4, and MgO has been widely studied in different Al base metal matrix composites, but the studies on thermodynamic aspects of the Al2O3/ MgAl2O4/MgO phase equilibria have been limited to few systems such as Al/Al2O3 and Al/SiC. The present study analyzes the Al2O3/MgAl2O4 and MgAl2O4/MgO equilibria with respect to the temperature and the Mg content in Al/SiO2 system using an extended Miedema model. There is a linear and parabolic variation in Mg with respect to the temperature for MgAl2O4/MgO and Al2O3/MgAl2O4 equilibria, respectively, and the influence of Si and Cu in the two equilibria is not appreciable. The experimental verification has been limited to MgAl2O4/MgO equilibria due to the high Mg content (≥0.5 wt pct) required for composite processing. The study has been carried out on two varieties of Al/SiO2 composites, i.e., Al/Silica gel and Al/Micro silica processed by liquid metallurgy route (stir casting route). MgO is found to be more stable compared to MgAl2O4 at Mg levels ≥5 and 1 wt pct in Al/Silica gel and Al/Micro silica composites, respectively, at 1073 K. MgO is also found to be more stable at lower Mg content (3 wt pct) in Al/Silica gel composite with decreasing particle size of silica gel from 180 micron to submicron and nanolevels. The MgO to MgAl2O4 transformation has taken place through a series of transition phases influenced by the different thermodynamic and kinetic parameters such as holding temperature, Mg concentration in the alloy, holding time, and silica particle size.

  17. "Quasi-Antiferromagnetic" Ordering in the R-Mg-Zn Icosahedral Alloys? The Case of Tb-Mg-Zn

    NASA Astrophysics Data System (ADS)

    Goldman, A. I.; Islam, Z.; Fisher, I. R.; Panchula, A. F.; Cheon, K. O.; Canfield, P. C.; Stassis, C.; Zarestky, J.

    1998-03-01

    Recently, it was reported that long-range magnetic ordering was observed in several of the new rare earth containing icosahedral alloys, R-Mg-Zn (R=Tb, Dy, Ho, Er) (B. Charrier et al., Phys. Rev. Lett. 78, 4637, 1997.). At low temperatures, the antiferromagnetic Bragg peaks, while weak, could be indexed to the icosahedral parent phase with good accuracy. In addition, significant magnetic diffuse scattering, indicating only short-range magnetic order, was also observed. However, bulk magnetization measurements have evidenced only a spin-glass transition at low temperatures, and no antiferromagnetic transition. We will report on new neutron scattering measurements of the magnetic order in Tb-Mg-Zn powder samples produced from crushed single-crystals, used to improve sample purity. Our results for these samples show only the diffuse component of the magnetic scattering at low temperature, and no antiferromagnetic Bragg peaks. We will discuss several possibilities for the discrepencies between the two experiments.

  18. High-power high-brightness solar laser approach for renewable Mg recovery from MgO

    NASA Astrophysics Data System (ADS)

    Almeida, Joana; Liang, Dawei

    2014-08-01

    Hydrogen and heat energy from the reaction of magnesium with water can be used for engines and fuel cells. However, at least 4000 K is necessary for magnesium oxide reduction. Ultra high brightness solar-pumped lasers become essential to make this renewable process technology efficient and economically competitive. 2.3 mg/kJ solar laser - induced magnesium production efficiency has been achieved by T. Yabe et al., in 2012, by focusing a 53 W solar laser beam on a mixture of MgO with Si as reducing agent. This result is however far from the 12.1 mg/kJ attained with 2 kW/mm2 CO2 laser beam. To improve substantially the solar laser - induced Mg production efficiency, a simple high-power, high brightness Nd:YAG solar laser pumping approach is proposed. The solar radiation is both collected and concentrated by four Fresnel lenses, and redirected towards a Nd:YAG laser head by four plane folding mirrors. A fused-silica secondary concentrator is used to compress the highly concentrated solar radiation to a laser rod. Optimum pumping conditions and laser resonator parameters are found through ZEMAXand LASCADnumerical analysis. High-record solar laser beam brightness figure of merit - defined as the ratio between laser power and the product of Mx 2 and My 2 - of 10.5 W is numerically achieved, being 5.5 times higher than the previous record and about 1600 times more than that of the most powerful Nd:YAG solar laser. 8340 W/mm2 is numerically achieved at its focal region, which can quadruple the magnesium production efficiency with clean energy.

  19. Rutherford Backscattering and Channeling Studies of Mg and Fe Diffusion at the Interface of gamma-Fe₂O₃(001)/MgO(001)

    SciTech Connect

    Thevuthasan, Suntharampillai; Jiang, Weilin; McCready, David E.; Chambers, Scott A.

    1999-12-01

    Investigates the crystalline quality of an epitaxially grown gamma-FeO(001) film on Mg/O(001) substrate along with the Mg and Fe inter-diffusion using Rutherford Backscattering and channeling experiments.

  20. THE Mg2+ TRANSPORTER MagT1 PARTIALLY RESCUES CELL-GROWTH AND Mg2+ UPTAKE IN CELLS LACKING THE CHANNEL-KINASE TRPM7

    PubMed Central

    Deason-Towne, Francina; Perraud, Anne-Laure; Schmitz, Carsten

    2011-01-01

    Magnesium (Mg2+) transport across membranes plays an essential role in cellular growth and survival. TRPM7 is the unique fusion of a Mg2+ permeable pore with an active cytosolic kinase domain, and is considered a master regulator of cellular Mg2+ homeostasis. We previously found that the genetic deletion of TRPM7 in DT40 B-cells results in Mg2+ deficiency and severe growth impairment, which can be rescued by supplementation with excess extracellular Mg2+. Here, we show that gene expression of the Mg2+ selective transporter MagT1 is upregulated in TRPM7−/− cells. Furthermore, overexpression of MagT1 in TRPM7−/− cells augments their capacity to uptake Mg2+, and improves their growth behavior in the absence of excess Mg2+. PMID:21627970

  1. Stellar neutrino energy loss rates due to {sup 24}Mg suitable for O+Ne+Mg core simulations

    SciTech Connect

    Nabi, Jameel-Un

    2008-10-15

    Neutrino losses from proto-neutron stars play a pivotal role to decide if these stars would be crushed into black holes or explode as supernovae. Recent observations of subluminous Type II-P supernovae (e.g., 2005cs, 2003gd, 1999br, 1997D) were able to rejuvenate the interest in 8-10 M{sub {center_dot}} stars that develop O+Ne+Mg cores. Simulation results of O+Ne+Mg cores show varying results in converting the collapse into an explosion. The neutrino energy loss rates are important input parameters in core collapse simulations. Proton-neutron quasiparticle random-phase approximation (pn-QRPA) theory has been used for calculation of neutrino energy loss rates due to {sup 24}Mg in stellar matter. The rates are presented on a detailed density-temperature grid suitable for simulation purposes. The calculated neutrino energy loss rates are enhanced up to more than one order of magnitude compared to the shell-model calculations and favor a lower entropy for the core of these massive stars.

  2. Synthesis of Ultra-Thin Single Crystal MgO/Ag/MgO Multilayer for Controlled Photocathode Emissive Properties

    NASA Astrophysics Data System (ADS)

    Velazquez, Daniel; Seibert, Rachel; Yusof, Zikri; Terry, Jeff; Spentzouris, Linda

    2015-03-01

    Developments of new accelerator technologies such as free-electron lasers and high-energy accelerators, among others, continuously set requirements for particle sources to produce higher beam flux. The emissive properties of these photocathodes directly influence the accelerator beam flux and thus the performance of the accelerator as a whole. The objective of this project is to test the possibility of engineering the photoemissive properties of materials for potential use as photocathodes. For this purpose we use a Density Functional Theory calculations by collaborator Karoly Nemeth et al. [Phys. Rev. Lett. 104, 046801, 2010], which predict a thickness dependent change in the band structure that results in a change in the work function and dispersion of occupied states at the Fermi level. Multilayered MgO/Ag/MgO in the crystallographic orientations (001) and (111) were grown on Ag/MgO(001) and Ag/Si(111), respectively using pulsed laser deposition (PLD). A series of surface probing techniques were used to characterize physical, chemical and photoemissive properties of the films.

  3. Electronic structure and thermoelectric properties of (Mg2X)2 / (Mg2Y)2 (X, Y = Si, Ge, Sn) superlattices from first-principle calculations

    NASA Astrophysics Data System (ADS)

    Guo, San-Dong

    2016-05-01

    To identify thermoelectric materials containing abundant, low-cost and non-toxic elements, we have studied the electronic structures and thermoelectric properties of (Mg2X)2/ (Mg2Y)2 (X, Y = Si, Ge, Sn) superlattices with state-of-the-art first-principles calculations using a modified Becke and Johnson (mBJ) exchange potential. Our results show that (Mg2Ge)2/ (Mg2Sn)2 and (Mg2Si)2/ (Mg2Sn)2 are semi-metals using mBJ plus spin-orbit coupling (mBJ + SOC), while (Mg2Si)2/ (Mg2Ge)2 is predicted to be a direct-gap semiconductor with a mBJ gap value of 0.46 eV and mBJ + SOC gap value of 0.44 eV. Thermoelectric properties are predicted by through solving the Boltzmann transport equations within the constant scattering time approximation. It is found that (Mg2Si)2/ (Mg2Ge)2 has a larger Seebeck coefficient and power factor than (Mg2Ge)2/ (Mg2Sn)2 and (Mg2Si)2/ (Mg2Sn)2 for both p-type and n-type doping. The detrimental influence of SOC on the power factor of p-type (Mg2X)2/ (Mg2Y)2 (X, Y = Si, Ge, Sn) is analyzed as a function of the carrier concentration, but there is a negligible SOC effect for n-type. These results can be explained by the influence of SOC on their valence and conduction bands near the Fermi level.

  4. Precise calibration of Mg concentration in Mg{sub x}Zn{sub 1-x}O thin films grown on ZnO substrates

    SciTech Connect

    Kozuka, Y.; Falson, J.; Tsukazaki, A.; Segawa, Y.; Makino, T.; Kawasaki, M.

    2012-08-15

    The growth techniques for Mg{sub x}Zn{sub 1-x}O thin films have advanced at a rapid pace in recent years, enabling the application of this material to a wide range of optical and electrical applications. In designing structures and optimizing device performances, it is crucial that the Mg content of the alloy be controllable and precisely determined. In this study, we have established laboratory-based methods to determine the Mg content of Mg{sub x}Zn{sub 1-x}O thin films grown on ZnO substrates, ranging from the solubility limit of x {approx} 0.4 to the dilute limit of x < 0.01. For the absolute determination of Mg content, Rutherford backscattering spectroscopy is used for the high Mg region above x = 0.14, while secondary ion mass spectroscopy is employed to quantify low Mg content. As a lab-based method to determine the Mg content, c-axis length is measured by x-ray diffraction and is well associated with Mg content. The interpolation enables the determination of Mg content to x = 0.023, where the peak from the ZnO substrate overlaps the Mg{sub x}Zn{sub 1-x}O peak in standard laboratory equipment, and thus limits quantitative determination. At dilute Mg contents below x = 0.023, the localized exciton peak energy of the Mg{sub x}Zn{sub 1-x}O films as measured by photoluminescence is found to show a linear Mg content dependence, which is well resolved from the free exciton peak of ZnO substrate down to x = 0.0043. Our results demonstrate that x-ray diffraction and photoluminescence in combination are appropriate methods to determine Mg content in a wide Mg range from x = 0.004 to 0.40 in a laboratory environment.

  5. Multistage growth of Fe-Mg-carpholite and Fe-Mg-chloritoid, from field evidence to thermodynamic modelling

    NASA Astrophysics Data System (ADS)

    Pourteau, Amaury; Bousquet, Romain; Vidal, Olivier; Plunder, Alexis; Duesterhoeft, Erik; Candan, Osman; Oberhänsli, Roland

    2015-04-01

    We provide new insights into the prograde evolution of HP/LT meta-sedimentary rocks on the basis of detailed petrologic examination, element-partitioning analysis, and thermodynamic modelling of well-preserved Fe-Mg-carpholite- and chloritoid-bearing rocks from the Afyon zone (Anatolia). Study samples, stemming from three different areas of the metamorphic belt, include typical quartz-carpholite veins as well as quartz-free and quartz-bearing phyllites. All samples exhibit multiple stages of carpholite, whereas zoning was until now rarely documented in this type of rocks. We document continuous, and discontinuous compositional (ferro-magnesian substitution) zoning of carpholite (overall XMg = 0.27-0.73) and chloritoid (overall XMg = 0.07-0.30), as well as clear equilibrium, and disequilibrium (i.e. reaction-related) textures involving carpholite and chloritoid, which consistently account for the consistent enrichment in Mg of both minerals through time, and the progressive replacement of carpholite by chloritoid. Mg/Fe distribution coefficients calculated between carpholite and chloritoid vary widely within samples (2.2-20.0). Among this range, only values of 7-11 correlate with equilibrium textures, in agreement with data from the literature. Equilibrium phase diagrams for (NaK)FMASH rock compositions are calculated using a newly modified thermodynamic dataset, including most recent data for carpholite, chloritoid, chlorite, and white mica, as well as further refinements for Fe-carpholite, and both chloritoid end-members, as required to reproduce accurately petrologic observations (phase relations, experimental constraints, Mg/Fe partitioning). Modelling reveals that Mg/Fe partitioning between carpholite and chloritoid is greatly sensitive to temperature, and calls for a future evaluation of possible use as a thermometer, valid for blueschist-facies conditions, which has so far been missing. In addition, calculations show significant effective bulk composition

  6. Microstructure and dielectric tunable properties of Ba0.6Sr0.4TiO3-Mg2SiO4-MgO composite.

    PubMed

    He, Yanyan; Xu, Yebin; Liu, Ting; Zeng, Chunlian; Chen, Wanping

    2010-07-01

    Ba(0.6)Sr(0.4)TiO(3)-Mg(2)SiO(4)-MgO composite ceramics were prepared by a solid-state reaction method and their dielectric tunable characteristics were investigated for the potential application as microwave tunable materials. The addition of Mg(2)SiO(4)-MgO into Ba(0.6)Sr(0.4)TiO(3) forms ferroelectric (Ba(0.6)Sr(0.4)TiO(3))-dielectric (Mg(2)SiO(4)-MgO) composites and shifts the Curie temperature to a lower temperature. The dielectric constant and loss tangent of Ba(0.6)Sr(0.4)TiO(3)-Mg(2)Si(O4)- MgO composites have been decreased and the overall tunability is maintained at a sufficiently high level. The microwave dielectric properties of Ba(0.6)Sr(0.4)TiO(3)-Mg(2)Si(O4)-MgO composites were evaluated. Ba(0.6)Sr(0.4)TiO(3)-Mg(2)SiO(4)-MgO composites have tunability of 9.2 to 10.5% at 100 kHz under 2 kV/mm, indicating that it is a promising candidate material for tunable microwave applications requiring a low dielectric constant. PMID:20639146

  7. Adsorption of small Au clusters on MgO and MgO/Mo: the role of oxygen vacancies and the Mo-support

    NASA Astrophysics Data System (ADS)

    Frondelius, P.; Häkkinen, H.; Honkala, K.

    2007-09-01

    We report a systematic density functional theory investigation of adsorption of small Aun (n =1-6) clusters on ideal and defected MgO(100) single crystal surfaces and Mo(100) supported thin MgO(100) films. As a model defect, we consider a neutral surface oxygen vacancy (Fs). Optimal adsorption geometries and energies, cluster formation energies and cluster charges are discussed and compared in detail over four different substrates. For a given cluster size, the adsorption energy among these substrates increases in the order MgO, Fs/MgO, MgO/Mo and Fs/MgO/Mo. While cluster growth by association of atoms from gas phase is exothermic on all the substrates, cluster growth by diffusion and aggregation of pre-adsorbed Au atoms is an endothermic process for Au1→Au2, Au3→Au4 and Au5→Au6 on MgO/Mo and Au2→Au3 and Au5→Au6 on Fs/MgO/Mo. The adsorbed clusters are close to neutral on MgO, but adopt a significant anionic charge on other supports with the increasing order: MgO/Mo, Fs/MgO and Fs/MgO/Mo. The adsorption strength thus correlates with the amount of negative charge transferred from the substrate to gold.

  8. The magnesium isotope (δ26Mg) signature of dolomites

    NASA Astrophysics Data System (ADS)

    Geske, A.; Goldstein, R. H.; Mavromatis, V.; Richter, D. K.; Buhl, D.; Kluge, T.; John, C. M.; Immenhauser, A.

    2015-01-01

    Dolomite precipitation models and kinetics are debated and complicated due to the complex and temporally fluctuating fluid chemistry and different diagenetic environments. Using well-established isotope systems (δ18O, δ13C, 87Sr/86Sr), fluid inclusions and elemental data, as well as a detailed sedimentological and petrographic data set, we established the precipitation environment and subsequent diagenetic pathways of a series of Proterozoic to Pleistocene syn-depositional marine evaporative (sabkha) dolomites, syn-depositional non-marine evaporative (lacustrine and palustrine) dolomites, altered marine ("mixing zone") dolomites and late diagenetic hydrothermal dolomites. These data form the prerequisite for a systematic investigation of dolomite magnesium isotope ratios (δ26Mgdol). Dolomite δ26Mg ratios documented here range, from -2.49‰ to -0.45‰ (δ26Mgmean = -1.75 ± 1.08‰, n = 42). The isotopically most depleted end member is represented by earliest diagenetic marine evaporative sabkha dolomites (-2.11 ± 0.54‰ 2σ, n = 14). In comparing ancient compositions to modern ones, some of the variation is probably due to alteration. Altered marine (-1.41 ± 0.64‰ 2σ, n = 4), and earliest diagenetic lacustrine and palustrine dolomites (-1.25 ± 0.86‰ 2σ, n = 14) are less negative than sabkha dolomites but not distinct in composition. Various hydrothermal dolomites are characterized by a comparatively wide range of δ26Mg ratios, with values of -1.44 ± 1.33‰ (2σ, n = 10). By using fluid inclusion data and clumped isotope thermometry (Δ47) to represent temperature of precipitation for hydrothermal dolomites, there is no correlation between fluid temperature (∼100 to 180 °C) and dolomite Mg isotope signature (R2 = 0.14); nor is there a correlation between δ26Mgdol and δ18Odol. Magnesium-isotope values of different dolomite types are affected by a complex array of different Mg sources and sinks, dissolution/precipitation and non

  9. Observed Variability of the Solar Mg II h Spectral Line

    NASA Astrophysics Data System (ADS)

    Schmit, D.; Bryans, P.; De Pontieu, B.; McIntosh, S.; Leenaarts, J.; Carlsson, M.

    2015-10-01

    The Mg ii h&k doublet are two of the primary spectral lines observed by the Sun-pointing Interface Region Imaging Spectrograph (IRIS). These lines are tracers of the magnetic and thermal environment that spans from the photosphere to the upper chromosphere. We use a double-Gaussian model to fit the Mg ii h profile for a full-Sun mosaic data set taken on 2014 August 24. We use the ensemble of high-quality profile fits to conduct a statistical study on the variability of the line profile as it relates the magnetic structure, dynamics, and center-to-limb viewing angle. The average internetwork profile contains a deeply reversed core and is weakly asymmetric at h2. In the internetwork, we find a strong correlation between h3 wavelength and profile asymmetry as well as h1 width and h2 width. The average reversal depth of the h3 core is inversely related to the magnetic field. Plage and sunspots exhibit many profiles that do not contain a reversal. These profiles also occur infrequently in the internetwork. We see indications of magnetically aligned structures in plage and network in statistics associated with the line core, but these structures are not clear or extended in the internetwork. The center-to-limb variations are compared to predictions of semi-empirical model atmospheres. We measure a pronounced limb darkening in the line core that is not predicted by the model. The aim of this work is to provide a comprehensive measurement baseline and preliminary analysis on the observed structure and formation of the Mg ii profiles observed by IRIS.

  10. MG Isotopic Measurement of FIB-Isolated Presolar Silicate Grains

    NASA Technical Reports Server (NTRS)

    Messenger, Scott R.; Nguyen, A.; Ito, M.; Rahman, Z.

    2010-01-01

    The majority of presolar oxide and silicate grains are ascribed to origins in low-mass red giant and asymptotic giant branch (AGB) stars based on their O isotopic ratios. However, a minor population of these grains (< 10%) has O isotopic ratios incompatible with these sources. Two principle alternative sources are higher-than-solar metallicity (Z) stars or, more likely, supernovae (SN) [1-3]. These rare (Group 4) grains [3] are characterized by enrichments in O-18, and typically also enrichments in O-17. An even rarer subset of grains with extremely large enrichments in O-17 and smaller depletions in O-18 were suggested to come from binary star systems [2]. To establish the origins of these isotopically unusual grains, it is necessary to examine isotopic systems in addition to O. Presolar silicates offer several elements diagnostic of their stellar sources and nuclear processes, including O, Si, Mg, Fe and Ca. However, the database for minor element isotopic compositions in silicates is seriously lacking. To date only two silicate grains have been analyzed for Mg [4] or Fe [5]. One major complicating factor is their small size (average 230 nm), which greatly limits the number of measurements that can be performed on any one grain and makes it more difficult to obtain statistically relevant data. This problem is compounded because the grains are identified among isotopically solar silicates, which contribute a diluting signal in isotopic measurements [1]. Thus, relatively small isotopic anomalies are missed due to this dilution effect. By applying focused ion beam (FIB) milling, we obtain undiluted Mg isotopic ratios of isolated rare presolar silicate grains to investigate their sources.

  11. The Evolution of ONeMg Cores with MESA

    NASA Astrophysics Data System (ADS)

    Schwab, Josiah; Quataert, Eliot; Bildsten, Lars

    2015-01-01

    We present calculations of the evolution of degenerate cores composed primarily of oxygen, neon, and magnesium which are undergoing compression. We make use of the state-of-the-art MESA stellar evolution code, with updated weak reaction rates from Martinez-Pinedo et al. (2014). We perform a detailed parameter study of the effects a number of quantities, including the accretion rate, magnesium mass fraction, and initial core temperature. We discuss the final fate of these ONeMg cores, focusing on cores formed as a result of the merger of two carbon-oxygen white dwarfs.

  12. Mn2 luminescence in Mg-Ai spinels

    NASA Astrophysics Data System (ADS)

    Rodríguez-Mendoza, U. R.; Rodríguez, V. D.; Ibarra, A.

    Luminescence of Mn2+ in A sites in natural and synthetic MgAl2O4 spinel has been studied. In the near perfect structure of the natural crystals the degenerate levels of the Mn2+ are splitted due to a symmetry lower than tetrahedral. In synthetic crystals the structure of the spectra is lost as a consequence of the superposition of partial spectra related to Mn2+ ions perturbed by the cationic disorder of the lattice. Thermal annealing modifies the spectra of natural crystals making them similar to those of the synthetic ones due to an order-disorder transition.

  13. Studies on ZnS-MgS Nano Composites

    NASA Astrophysics Data System (ADS)

    Rajkumar, M.; Raj, S. Alfred Cecil

    2011-10-01

    ZnS-MgS nanocomposites was successfully prepared by the microwave assisted solvothermal method using a domestic microwave oven. The prepared sample was annealed at 100 °C for 1 hr to improve the ordering. Grain sizes and lattice parameters were determined by carrying out X-ray powder diffraction measurements. Scanning electron microscopy (SEM) shows the morphology. AC electrical measurements were carried out on pelletised samples at various temperatures ranging from 40-150 °C. Results of the present study reveal that the space charge contribution plays a significant role in the charge transport process and polarizability.

  14. Selective adsorption in 4MgO scattering

    NASA Astrophysics Data System (ADS)

    Mahgerefteh, Massoud; Jung, David R.; Frankl, Daniel R.

    1989-02-01

    Helium scattering data from an in situ cleaved, oxygen-treated, room-temperature surface of MgO(100) are reported. The sharpness of the selective adsorption line shapes as well as the strength of the scattered beams indicate an improvement over previous studies on air-cleaved surfaces. Selective adsorption line shapes in azimuthal scans of the specular intensity at many closely spaced angles of incidence are presented. Analysis of the resonances at several reciprocal lattice vectors yielded binding energies of 5.52, 2.57, 1.16, 0.54, and 0.26 meV.

  15. Preparation of MgH{sub 2} composite with a composition of 40%MgH{sub 2} + 30%LiBH{sub 4} + 30%(2LiBH{sub 4} + MgF{sub 2})

    SciTech Connect

    Hong, Seong-Hyeon; Song, Myoung Youp

    2012-09-15

    Graphical abstract: Hydrogen content vs. desorption time curves for consecutive 1st desorptions of 40 wt%MgH{sub 2} + 30 wt%LiBH{sub 4} + 30 wt%(2LiBH{sub 4} + MgF{sub 2}) at 533–873 K. Highlights: ► Addition of MgF{sub 2} and LiBH{sub 4} with a higher hydrogen storage capacity to MgH{sub 2}. ► Preparation of 40%MgH{sub 2} + 30%LiBH{sub 4} + 30% (2LiBH{sub 4} + MgF{sub 2}) composite. ► Examination of desorption properties of the composite. ► Total desorbed hydrogen quantity for consecutive 1st desorptions of 7.07 wt%. ► Reactions of LiBH{sub 4} → LiH + B + (3/2)H{sub 2}, and 2LiBH{sub 4} + MgF{sub 2} → 2LiF + MgB{sub 2} + 4H{sub 2}. -- Abstract: A mixture of containing two chemical equivalents of lithium borohyride and one equivalent of magnesium fluoride is known to yield hydrogen in an amount of about 7.6 wt% of the mixture when heated to about 150 °C at atmospheric pressure by the following reaction; 2LiBH{sub 4} + MgF{sub 2} = 2LiF + MgB{sub 2} + 4H{sub 2}. In order to increase hydrogen storage capacity of Mg-based materials, a mixture with a composition of 2LiBH{sub 4} + MgF{sub 2} and LiBH{sub 4}with a higher hydrogen storage capacity of 18.4 wt% were added to MgH{sub 2}. MgH{sub 2} composite with a composition of 40 wt%MgH{sub 2} + 30 wt%LiBH{sub 4} + 30 wt%(2LiBH{sub 4} + MgF{sub 2}) was prepared by reactive mechanical grinding. The hydrogen storage properties of the sample were then examined. Hydrogen content vs. desorption time curves for consecutive 1st desorptions of 40 wt%MgH{sub 2} + 30 wt%LiBH{sub 4} + 30 wt%(2LiBH{sub 4} + MgF{sub 2}) at 533–873 K showed that the total desorbed hydrogen quantity for consecutive 1st desorptions is 7.07 wt%.

  16. Prediction of novel stable compounds in the Mg-Si-O system under exoplanet pressures.

    PubMed

    Niu, Haiyang; Oganov, Artem R; Chen, Xing-Qiu; Li, Dianzhong

    2015-01-01

    The Mg-Si-O system is the major Earth and rocky planet-forming system. Here, through quantum variable-composition evolutionary structure explorations, we have discovered several unexpected stable binary and ternary compounds in the Mg-Si-O system. Besides the well-known SiO2 phases, we have found two extraordinary silicon oxides, SiO3 and SiO, which become stable at pressures above 0.51 TPa and 1.89 TPa, respectively. In the Mg-O system, we have found one new compound, MgO3, which becomes stable at 0.89 TPa. We find that not only the (MgO)x · (SiO2)y compounds, but also two (MgO3)x · (SiO3)y compounds, MgSi3O12 and MgSiO6, have stability fields above 2.41 TPa and 2.95 TPa, respectively. The highly oxidized MgSi3O12 can form in deep mantles of mega-Earths with masses above 20 M⊕ (M⊕:Earth's mass). Furthermore, the dissociation pathways of pPv-MgSiO3 are also clarified, and found to be different at low and high temperatures. The low-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ SiO2 + Mg2SiO4 ⇒ MgO + SiO2, while the high-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ MgO + MgSi2O5 ⇒ MgO + SiO2. Present results are relevant for models of the internal structure of giant exoplanets, and for understanding the high-pressure behavior of materials. PMID:26691903

  17. Impact of seawater [Ca2+] on the calcification and calciteMg / Ca of Amphistegina lessonii

    NASA Astrophysics Data System (ADS)

    Mewes, A.; Langer, G.; Thoms, S.; Nehrke, G.; Reichart, G.-J.; de Nooijer, L. J.; Bijma, J.

    2015-04-01

    Mg / Ca ratios in foraminiferal tests are routinely used as paleotemperature proxies, but on long timescales, they also hold the potential to reconstruct past seawater Mg / Ca. The impact of both temperature and seawater Mg / Ca on Mg incorporation in Foraminifera has been quantified by a number of studies. The underlying mechanism responsible for Mg incorporation in foraminiferal calcite and its sensitivity to environmental conditions, however, has not been fully identified. A recently published biomineralization model (Nehrke et al., 2013) proposes a combination of transmembrane transport and seawater leakage or vacuolization to link calcite Mg / Ca to seawater Mg / Ca and explains inter-species variability in Mg / Ca ratios. To test the assumptions of this model, we conducted a culture study in which seawater Mg / Ca was manipulated by varying [Ca2+] and keeping [Mg2+] constant. Foraminiferal growth rates, test thickness and calcite Mg / Ca of newly formed chambers were analyzed. Results showed optimum growth rates and test thickness at Mg / Ca closest to that of ambient seawater. Calcite Mg / Ca is positively correlated to seawater Mg / Ca, indicating that it is not absolute seawater [Ca2+] and [Mg2+] but their ratio that controls Mg / Ca in tests. These results demonstrate that the calcification process cannot be based only on seawater vacuolization, supporting the mixing model proposed by Nehrke et al. (2013). Here, however, we suggest transmembrane transport fractionation that is not as strong as suggested by Nehrke et al. (2013).

  18. Impact of seawater Ca2+ on the calcification and calcite Mg/Ca of Amphistegina lessonii

    NASA Astrophysics Data System (ADS)

    Mewes, A.; Langer, G.; Thoms, S.; Nehrke, G.; Reichart, G.-J.; de Nooijer, L. J.; Bijma, J.

    2014-12-01

    Mg/Ca ratios in foraminiferal tests are routinely used as paleo temperature proxy, but on long timescales, also hold the potential to reconstruct past seawater Mg/Ca. Impact of both temperature and seawater Mg/Ca on Mg incorporation in foraminifera have been quantified by a number of studies. The underlying mechanism responsible for Mg incorporation in foraminiferal calcite and its sensitivity to environmental conditions, however, is not fully identified. A recently published biomineralization model (Nehrke et al., 2013) proposes a combination of transmembrane transport and seawater leakage or vacuolization to link calcite Mg/Ca to seawater Mg/Ca and explains inter-species variability in Mg/Ca ratios. To test the assumptions of this model, we conducted a culture study in which seawater Mg/Ca was manipulated by varying [Ca2+] and keeping [Mg2+] constant. Foraminiferal growth rates, test thickness and calcite Mg/Ca of newly formed chambers were analyzed. Results showed optimum growth rates and test thickness at Mg/Ca closest to that of ambient seawater. Calcite Mg/Ca is positively correlated to seawater Mg/Ca, indicating that not absolute seawater [Ca2+] and [Mg2+], but the telative ratio controls Mg/Ca in tests. These results demonstrate that the calcification process cannot be based only on seawater vacuolization, supporting the mixing model proposed by Nehrke et al. (2013). Here we, however, suggest a transmembrane transport fractionation that is not as strong as suggested by Nehrke et al. (2013).

  19. A culture study with benthic foraminifers at different [Mg2+]: Implications for biomineralization and proxies

    NASA Astrophysics Data System (ADS)

    Funcke, A.; Langer, G.; de Nooijer, L. J.; Bijma, J.; Reichart, G.

    2012-12-01

    The elemental composition of foraminiferal calcium carbonate (CC) tests is a widely used tool for paleoceanographic reconstructions. Especially Mg/CaCC is used extensively to reconstruct past seawater temperatures. But besides temperature, the Mg/CaCC of foraminiferal tests also depends on seawater (SW) Mg/Ca. The aim of this study was to investigate the impact of different Mg/CaSW on Mg incorporation into the tests of two different foraminiferal species that have contrasting Mg/CaCC. For this purpose, juveniles of the benthic foraminifers Ammonia tepida (producing low-Mg calcite) and Amphistegina lessonii (producing intermediate-Mg calcite) were cultured at constant temperatures in seawater with varying [Mg2+]. Foraminiferal Mg/CaCC was analyzed using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). Results show that Mg partitioning (DMg=[Mg/CaCC]/[Mg/CaSW]) varies as a function of Mg/CaSW in both species. The observed trend matches the previously established trend for inorganic calcite and other biogenic calcites, e.g. coccoliths, and hence suggests a common underlying mechanism. For foraminifers we suggest an adsorption of Mg ions to transmembrane proteins that changes the Mg/Ca at the protein seawater interface. We conclude that since both calcite precipitation, as well as cell physiology influences element partitioning in biogenic calcite it is mandatory to consider both when element to Ca ratios are used as proxies in paleo-reconstructions.

  20. In vitro biocompatibility of Ti-Mg alloys fabricated by direct current magnetron sputtering.

    PubMed

    Hieda, Junko; Niinomi, Mitsuo; Nakai, Masaaki; Cho, Ken

    2015-09-01

    Ti-xMg (x=17, 33, and 55 mass%) alloy films, which cannot be prepared by conventional melting processes owing to the absence of a solid-solution phase in the phase diagram, were prepared by direct current magnetron sputtering in order to investigate their biocompatibility. Ti and Mg films were also prepared by the same process for comparison. The crystal structures were examined by X-ray diffraction (XRD) analysis and the surfaces were analyzed by X-ray photoelectron spectroscopy. The Ti, Ti-xMg alloy, and Mg films were immersed in a 0.9% NaCl solution at 310 K for 7d to evaluate the dissolution amounts of Ti and Mg. In addition, to evaluate the formation ability of calcium phosphate in vitro, the Ti, Ti-xMg alloy, and Mg films were immersed in Hanks' solution at 310 K for 30 d. Ti and Mg form solid-solution alloys because the peaks attributed to pure Ti and Mg do not appear in the XRD patterns of any of the Ti-xMg alloy films. The surfaces of the Ti-17 Mg alloy and Ti-33 Mg alloy films contain Ti oxides and MgO, whereas MgO is the main component of the surface oxide of the Ti-55 Mg alloy and Mg films. The dissolution amounts of Ti from all films are below or near the detection limit of inductively coupled plasma-optical emission spectroscopy. On the other hand, the Ti-17 Mg alloy, Ti-33 Mg alloy, Ti-55 Mg alloy, and Mg films exhibit Mg dissolution amounts of approximately 2.5, 1.4, 21, and 41 μg/cm(2), respectively. The diffraction peaks attributed to calcium phosphate are present in the XRD patterns of the Ti-33 Mg alloy, Ti-55 Mg alloy, and Mg films after the immersion in Hanks' solution. Spherical calcium phosphate particles precipitate on the surface of the Ti-33 Mg film. However, many cracks are observed in the Ti-55 Mg film, and delamination of the film occurs after the immersion in Hanks' solution. The Mg film is dissolved in Hanks' solution and calcium phosphate particles precipitate on the glass substrate. Consequently, it is revealed that the Ti-33 Mg

  1. A declaration of independence for Mg/Si. [Al/Si intensity ratio predictive usefulness for Mg/Si intensity ratio in lunar X-ray fluorescence

    NASA Technical Reports Server (NTRS)

    Hubbard, N.; Keith, J. E.

    1978-01-01

    The weak covariation that exists between Al/Si and Mg/Si for large areas of the lunar surface is little, if any, stronger than that forced on a random set of numbers that are subject to closure. The Mg and Al variations implied by the Mg/Si and Al/Si intensity ratio data are qualitatively like those seen in lunar soil sample data. Two petrogenetic provinces are suggested for terra materials; one appears to have 50% higher Mg values than the other. Using the improved data, Mg/Si variations can be studied at a signal-to-noise ratio greater than 5/1.

  2. Multilayer MgB2 superconducting quantum interference filter magnetometers

    NASA Astrophysics Data System (ADS)

    Galan, Elias; Melbourne, Thomas; Davidson, Bruce A.; Xi, X. X.; Chen, Ke

    2016-04-01

    We report two types of all-MgB2 superconductive quantum interference filter (SQIF) magnetometers that can measure absolute magnetic fields with high sensitivity. In one configuration, the SQIFs were made of 20 multilayer nonplanar all-MgB2 superconducting quantum interference devices (SQUIDs) connected in parallel with loop areas ranging in size from 0.4 to 3.6 μm2. These devices are sensitive to magnetic fields parallel to the substrate and show a single antipeak from 3 to 16 K with a maximum transfer function of ˜16 V/T at 3 K and a field noise of ˜110 pT/Hz1/2 above 100 Hz at 10 K. In a second configuration, the SQIFs were made with 16 planar SQUIDs connected in parallel with loop areas ranging in size from 4 μm2 to 25 μm2 and are sensitive to the magnetic fields perpendicular to the substrate. The planar SQIF shows a single antipeak from 10 to 22 K with a maximum transfer function of 7800 V/T at 10 K and a field noise of ˜70 pT/Hz1/2 above 100 Hz at 20 K.

  3. Density Functional Study of Perovskite Superconductor MgCNi3

    NASA Astrophysics Data System (ADS)

    Kumar, Jagdish; Sharma, Devina; Kumar, Ranjan; Awana, V. P. S.; Ahluwalia, P. K.

    2011-12-01

    We here report the first principle density functional study of MgCNi3 which crystallize in cubic perovskite structure having critical transition temperature of 8 K. The interesting aspect of this compound is that in normal state it is non magnetic in nature despite conduction electrons in it are derived from partially filled Ni d states, which typically lead to ferromagnetism in metallic Ni and many Ni-based binary alloys. To investigate the detailed microscopic origin of the non magnetic nature we have done density functional based calculations on this compound. The lattice constant is calculated using minimum energy criteria from total energy versus lattice constant plot. By taking the calculated values of lattice constant we have done the precise calculations on the compound using Full Potential Linear Augmented Plane Wave (FP-LAPW) method implemented in ELK code. The electronic density of states is found spin degenerate that corresponds to a non-magnetic ground state. The density of states (DOS) at Fermi level, N(EF) is dominated by Ni-d states. The sharp peak observed just below Fermi level corresponds to van Hove singularity (vHs). The projected density of states (PDOS) suggests a strong hybridization of Ni-3d and C-2p states which is responsible for the observed non magnetic nature of MgCNi3.

  4. Antibacterial polyelectrolyte-coated Mg alloys for biomedical applications

    NASA Astrophysics Data System (ADS)

    Seraz, Md. S.; Asmatulu, R.; Chen, Z.; Ceylan, M.; Mahapatro, A.; Yang, S. Y.

    2014-04-01

    This study deals with two biomedical subjects: corrosion rates of polyelectrolyte-coated magnesium (Mg) alloys, mainly used for biomedical purposes, and antibacterial properties of these alloys. Thin sheets of Mg alloys were coated with cationic polyelectrolyte chitosan (CHI) and anionic polyelectrolyte carboxymethyl cellulose (CMC) using a layer-by-layer coating method and then embedded with antibacterial agents under vacuum. Electrochemical impedance spectroscopy was employed to analyze these samples in order to detect their corrosion properties at different conditions. In the electrochemical analysis section, a corrosion rate of 72 mille inches per year was found in a salt solution for the sample coated with a 12 phosphonic acid self-assembled monolayer and 9 CHI/CMC multilayers. In the antibacterial tests, gentamicin was used to investigate the effects of the drug embedded with the coated surfaces against the Escherichia coli (E. coli) bacteria. Antibacterial studies were tested using the disk diffusion method. Based on the standard diameter of the zone of inhibition chart, the antibacterial diffusion from the surface strongly inhibited bacterial growth in the regions. The largest recorded diameter of the zone of inhibition was 50 mm for the pre-UV treated and gentamicin-loaded sample, which is more than three times the standard diameter.

  5. NMR Studies of the Li-Mg-N-H Phases.

    NASA Astrophysics Data System (ADS)

    Bowman, Robert; Reiter, J. W.; Kulleck, J. G.; Hwang, S.-J.; Luo, Weifang

    2007-03-01

    Solid state NMR including magic-angle-spinning (MAS) and cross-polarization (CP) MAS experiments have been used to characterize various amide and imide phases containing Li and/or Mg. MAS-NMR spectra for the ^1H, ^6Li, ^7Li, and ^15N nuclei have been obtained to improve understanding on formation, processing, and degradation behavior. Only limited information could be obtained from the proton and ^7Li MAS-NMR spectra to due large dipolar interactions and small chemical shifts. However, more success was obtained from the ^6Li and ^15N nuclei although their very long spin-lattice relaxation times did impact signal acquisition times. For example, three distinct ^6Li peaks were resolved from LiNH2 phases that were clearly separated from the LiH secondary phase in these samples. While the ^15N spectra for LiNH2 phase in isotopically enriched samples exhibited only a single peak at least three distinct ^15N peaks were observed from the similarly enriched Mg amide samples. These differences will be related to crystal structures. The NMR spectra also revealed very little motion in these hydrides upon to nearly 500 K.

  6. Chemically Sensitive Imaging of MgP with STM

    NASA Astrophysics Data System (ADS)

    Yu, Arthur; Li, Shaowei; Czap, Greg; Ho, Wilson

    2014-03-01

    Since its invention, the STM has been limited by its lack of sensitivity to chemical structures in molecules. Recent advances in scanning probe microscopy techniques, such as non-contact AFM and scanning tunneling hydrogen microscopy have enabled imaging of the internal structure and bonding of aromatic molecules such as pentacene and PTCDA. Here, we present a novel method of using the STM to image magnesium porphyrin molecules adsorbed on Au(110) with chemical sensitivity. In our previous study, we have shown that hydrogen molecules weakly adsorb on Au(110), exhibiting both vibrational and rotational IETS spectra. Exploiting the sensitivity of the vibrational and rotational mode energies to the local chemical environment, we perform dI/dV and d2I/dV2 imaging at different bias voltages, highlighting the various parts of the MgP molecule. In particular, we are able to image the positions of the nitrogen atoms in MgP. d2I/dV2 spectral mapping reveals that the origin of the chemical sensitivity comes from an energy shift of the rotational peak as the tip is scanned across the molecule, indicating a changing potential landscape for the H2. Similar d2I/dV2 imaging with a CO terminated tip reveals no chemical sensitivity to nitrogen.

  7. Regulation of CFTR ion channel gating by MgATP.

    PubMed

    Aleksandrov, A A; Riordan, J R

    1998-07-10

    Single channel currents of wild-type CFTR reconstituted in lipid bilayers were recorded to study the temperature dependence of channel gating between +20 degrees C and +40 degrees C. The opening of the channel was highly temperature dependent and required an activation energy of about 100 kJ/mol. Closing of the channel was only weakly temperature dependent with an activation energy close to that of diffusion in water. We found no significant difference in the free energy between the open and closed states. Most of the excess energy needed to activate channel opening is used to diminish the entropy of the open state. This structural reorganization is initiated by ATP binding followed by interconversion to the open channel structure as the CFTR-ATP-Mg complex passes to the transition state for hydrolysis. The energy of the CFTR-ATP-Mg interaction in the transition state is responsible for the CFTR ion channel opening rather than the energy of ATP hydrolysis. Channel closing is a diffusion limited process and does not require additional ATP binding. PMID:9684873

  8. Characterization of MgB2 Superconducting Hot Electron Bolometers

    NASA Technical Reports Server (NTRS)

    Cunnane, D.; Kawamura, J. H.; Wolak, M. A.; Acharya, N.; Tan, T.; Xi, X. X.; Karasik, B. S.

    2014-01-01

    Hot-Electron Bolometer (HEB) mixers have proven to be the best tool for high-resolution spectroscopy at the Terahertz frequencies. However, the current state of the art NbN mixers suffer from a small intermediate frequency (IF) bandwidth as well as a low operating temperature. MgB2 is a promising material for HEB mixer technology in view of its high critical temperature and fast thermal relaxation allowing for a large IF bandwidth. In this work, we have fabricated and characterized thin-film (approximately 15 nanometers) MgB2-based spiral antenna-coupled HEB mixers on SiC substrate. We achieved the IF bandwidth greater than 8 gigahertz at 25 degrees Kelvin and the device noise temperature less than 4000 degrees Kelvin at 9 degrees Kelvin using a 600 gigahertz source. Using temperature dependencies of the radiation power dissipated in the device we have identified the optical loss in the integrated microantenna responsible as a cause of the limited sensitivity of the current mixer devices. From the analysis of the current-voltage (IV) characteristics, we have derived the effective thermal conductance of the mixer device and estimated the required local oscillator power in an optimized device to be approximately 1 microwatts.

  9. MgB2 superconducting joints for persistent current operation

    NASA Astrophysics Data System (ADS)

    Patel, Dipak; Hossain, Md Shahriar Al; See, Khay Wai; Xu, Xun; Barua, Shaon; Ma, Zongqing; Choi, Seyong; Tomsic, Mike; Kim, Jung Ho

    2015-06-01

    High-performance superconducting joints are essential for realizing persistent-mode magnets. Herein, we propose a concept and fabrication of such superconducting joints, which yielded reliable performance in the operating temperature range of 4.2-25 K. MgB2-MgB2 joints in magnets are known to result in deterioration of localized electrical, thermal, and mechanical properties. To overcome these problems, the ends of the two wires are inserted into a pellet press, which is then filled with a mixture of unreacted magnesium and boron powders, followed by heat treatment. The critical current capacity and joint resistance were precisely evaluated by the standard four-probe method in open-circuit and by field-decay measurements in a closed-loop, respectively. These joints demonstrated up to 66% of the current-carrying capacity of unjoined wire at 20 K, 2 T and joint resistance of 1.4 × 10-12 Ω at 4.2 K in self-field.

  10. Novel Co:MgF2 lidar for aerosol profiler

    NASA Technical Reports Server (NTRS)

    Acharekar, M. A.

    1993-01-01

    Lidars are of great interest because of their unique capabilities in remote sensing applications in sounding of the atmosphere, meteorology, and climatology. In this small business innovative research (SBIR) phase II program, laser sources including Co:MgF2, CTH:YAG, CTH:YSGG, CT:YAG, and Er:Glass were evaluated. Modulator of fused silica and TeO2 materials with Brewster's angle end faces were used with these lasers as acousto-optical (AO) Q-switches. A higher hold-off energy and hence a higher Q-switched energy was obtained by using a high power RF driver. The report provides performance characteristics of these lasers. The tunable (1.75-2.50 microns) Co:MgF2 laser damaged the TeO2 Q-switch cell. However, the CTH:YAG laser operating at 2.09 microns provided output energy of over 300 mJ/p in 50 ns pulse width using the fused silica Q-switch. This Q-switched CTH:YAG laser was used in a breadboard vertical aerosol profiler. A 40 cm diameter telescope, InSb and InGaAs detectors were used in the receiver. The data obtained using this lidar is provided in the report. The data shows that the eye safe lidar using CTH:YAG laser for the vertical aerosol density and range measurements is the viable approach.

  11. NH AND Mg INDEX TRENDS IN ELLIPTICAL GALAXIES

    SciTech Connect

    Serven, Jedidiah; Worthey, Guy; Toloba, Elisa; Sanchez-Blazquez, Patricia

    2011-06-15

    We examine the spectrum in the vicinity of the NH3360 index of Davidge and Clark, which was defined to measure the NH absorption around 3360 A and shows almost no trend with velocity dispersion, unlike other N-sensitive indices, which show a strong trend. Computing the effect of individual elements on the integrated spectrum with synthetic stellar population integrated spectra, we find that, while being well correlated with nitrogen abundance, NH3360 is almost equally well anti-correlated with Mg abundance. This prompts the definition of two new indices, Mg3334, which is mostly sensitive to magnesium, and NH3375, which is mostly sensitive to nitrogen. Rather surprisingly, we find that the new NH3375 index shows a trend versus optical absorption feature indices that is as shallow as the NH3360 index. We hypothesize that the lack of a strong index trend in these near-UV indices is due to the presence of an old metal-poor component of the galactic population. Comparison of observed index trends and those predicted by models shows that a modest fraction of an old, metal-poor stellar population could easily account for the observed flat trend in these near-UV indices while still allowing substantial N abundance increase in the larger galaxies.

  12. Al-26-Mg-26 ages of iron meteorites

    NASA Technical Reports Server (NTRS)

    Herzog, G. F.; Souzis, A. E.; Xue, S.; Klein, J.; Juenemann, D.; Middleton, R.

    1993-01-01

    An exposure age for an iron meteorite can be calculated from measurements of a radioactive nuclide and a stable nuclide that are produced by similar sets of nuclear reactions, provided that the stable nuclide is present with low initial abundance. The standard methods rely on either K-40 (t(sub 1/2) = 1.26 Gy), K-39, and K-41 or on a shorter-lived radionuclide and a stable, noble gas isotope. Widely used pairs of this type include Cl-36/Ar-36 and Al-26/Ne-21. Other pairs that may serve the purpose for iron meteorites contain many stable isotopes besides those of K and the noble gases that are produced partly by cosmic rays. We consider here the calculation of exposure ages, t(sub 26), from measurements of Al-26 (t(sub 1/2) = 0.7 My) and (stable) Mg-26. Ages based on Al-26/Mg-26 ratios, like those based on Cl-36/Ar-36 ratios, are 'buffered' against changes in relative production rates due to shielding because decay of the radioactive nuclide accounts for a good part of the inventory of the stable nuclide.

  13. Superior hydrogen desorption kinetics of Mg(NH{sub 2}){sub 2} hollow nanospheres mixed with MgH{sub 2} nanoparticles

    SciTech Connect

    Xie Lei; Li Yaoqi; Yang Rong; Liu Yang; Li Xingguo

    2008-06-09

    Mg{sub 3}N{sub 2} nanocubes were prepared by vaporized bulk magnesium in ammonia atmosphere associated with plasma metal reaction. Then the product transformed to Mg(NH{sub 2}){sub 2} hollow nanospheres after it was reacted with NH{sub 3} based on the Kirkendall effect. The electron microscopy results suggested that the obtained hollow nanospheres were around 100 nm and the shell thickness was about 10 nm. Because of its short distance for Mg{sup 2+} diffusion and large specific surface area for interaction between Mg(NH{sub 2}){sub 2} and MgH{sub 2}, the structure dramatically enhanced the hydrogen desorption kinetics of Mg(NH{sub 2}){sub 2}-2MgH{sub 2}.

  14. Rupatadine 10 mg and cetirizine 10 mg in seasonal allergic rhinitis: a randomised, double-blind parallel study.

    PubMed

    Martínez-Cócera, C; De Molina, M; Martí-Guadaño, E; Pola, J; Conde, J; Borja, J; Pérez, I; Arnaiz, E; Izquierdo, I

    2005-01-01

    This randomised, double-blind, parallel-group, multicentre clinical trial evaluated the efficacy and safety of rupatadine, a new antihistamine with antiplatelet-activating factor (PAF) activity, and cetirizine in the treatment of patients with seasonal allergic rhinitis (SAR). A total 249 patients were randomised to receive rupatadine 10 mg once daily (127 patients) or cetirizine 10 mg (122 patients) for two weeks. The main efficacy variable was the mean total daily symptom score (mTDSS) and was based on the daily subjective assessment of the severity of each rhinitis symptom--nasal (runny nose, sneezing, nasal itching and nasal obstruction) and non-nasal (conjunctival itching, tearing, and pharyngeal itching)--recorded by patients in their diaries. The mTDSS was 0.7 for both treatment groups (intention to treat analysis). In the investigator's global evaluation of efficacy at the seventh day, 93.3% and 83.7% patients in the rupatadine and cetirizine groups, respectively, showed some or great improvement (p = 0.022). In the per protocol analysis (n = 181), runny nose at the seventh day of treatment was absent or mild in 81.1% of patients in the rupatadine group and in 68.6% of patients in the cetirizine group (p = 0.029). In any case statistical significance was not maintained at the second week. Overall, all treatments were well tolerated. Adverse events (AEs) were similar in both treatment groups, i.e. headache, somnolence and fatigue/asthenia as the most often reported. Somnolence was reported in 9.6% and 8.5% of patients treated with rupatadine or cetirizine, respectively. The most reported AEs (67%) were mild in intensity. Our results suggest that rupatadine 10 mg may be a valuable and safe alternative for the symptomatic treatment of SAR. PMID:15864879

  15. Effect of different seawater Mg2 + concentrations on calcification in two benthic foraminifers

    PubMed Central

    Mewes, Antje; Langer, Gerald; de Nooijer, Lennart Jan; Bijma, Jelle; Reichart, Gert-Jan

    2014-01-01

    Magnesium, incorporated in foraminiferal calcite (Mg/CaCC), is used intensively to reconstruct past seawater temperatures but, in addition to temperature, the Mg/CaCC of foraminiferal tests also depends on the ratio of Mg and Ca in seawater (Mg/CaSW). The physiological mechanisms responsible for these proxy relationships are still unknown. This culture study investigates the impact of different seawater [Mg2 +] on calcification in two benthic foraminiferal species precipitating contrasting Mg/CaCC: Ammonia aomoriensis, producing low-Mg calcite and Amphistegina lessonii, producing intermediate-Mg calcite. Foraminiferal growth and test thickness were determined and, Mg/Ca was analyzed using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). Results show that at present-day seawater Mg/CaSW of ~ 5, both species have highest growth rates, reflecting their adaptation to modern seawater element concentrations. Test thickness is not significantly affected by different Mg/CaSW. The relationship between Mg/CaSW and Mg/CaCC shows a distinct positive y-axis intercept, possibly reflecting at least two processes involved in foraminiferal biomineralization. The associated Mg partition (DMg) changes non-linearly with increasing Mg/CaSW, hence suggesting that the DMg is best described by an exponential function approaching an asymptote. PMID:26089590

  16. Solute carrier 41A3 encodes for a mitochondrial Mg(2+) efflux system.

    PubMed

    Mastrototaro, Lucia; Smorodchenko, Alina; Aschenbach, Jörg R; Kolisek, Martin; Sponder, Gerhard

    2016-01-01

    The important role of magnesium (Mg(2+)) in normal cellular physiology requires flexible, yet tightly regulated, intracellular Mg(2+) homeostasis (IMH). However, only little is known about Mg(2+) transporters of subcellular compartments such as mitochondria, despite their obvious importance for the deposition and reposition of intracellular Mg(2+) pools. In particular, knowledge about mechanisms responsible for extrusion of Mg(2+) from mitochondria is lacking. Based on circumstantial evidence, two possible mechanisms of Mg(2+) release from mitochondria were predicted: (1) Mg(2+) efflux coupled to ATP translocation via the ATP-Mg/Pi carrier, and (2) Mg(2+) efflux via a H(+)/Mg(2+) exchanger. Regardless, the identity of the H(+)-coupled Mg(2+) efflux system is unknown. We demonstrate here that member A3 of solute carrier (SLC) family 41 is a mitochondrial Mg(2+) efflux system. Mitochondria of HEK293 cells overexpressing SLC41A3 exhibit a 60% increase in the extrusion of Mg(2+) compared with control cells. This efflux mechanism is Na(+)-dependent and temperature sensitive. Our data identify SLC41A3 as the first mammalian mitochondrial Mg(2+) efflux system, which greatly enhances our understanding of intracellular Mg(2+) homeostasis. PMID:27302215

  17. Solute carrier 41A3 encodes for a mitochondrial Mg2+ efflux system

    PubMed Central

    Mastrototaro, Lucia; Smorodchenko, Alina; Aschenbach, Jörg R.; Kolisek, Martin; Sponder, Gerhard

    2016-01-01

    The important role of magnesium (Mg2+) in normal cellular physiology requires flexible, yet tightly regulated, intracellular Mg2+ homeostasis (IMH). However, only little is known about Mg2+ transporters of subcellular compartments such as mitochondria, despite their obvious importance for the deposition and reposition of intracellular Mg2+ pools. In particular, knowledge about mechanisms responsible for extrusion of Mg2+ from mitochondria is lacking. Based on circumstantial evidence, two possible mechanisms of Mg2+ release from mitochondria were predicted: (1) Mg2+ efflux coupled to ATP translocation via the ATP-Mg/Pi carrier, and (2) Mg2+ efflux via a H+/Mg2+ exchanger. Regardless, the identity of the H+-coupled Mg2+ efflux system is unknown. We demonstrate here that member A3 of solute carrier (SLC) family 41 is a mitochondrial Mg2+ efflux system. Mitochondria of HEK293 cells overexpressing SLC41A3 exhibit a 60% increase in the extrusion of Mg2+ compared with control cells. This efflux mechanism is Na+-dependent and temperature sensitive. Our data identify SLC41A3 as the first mammalian mitochondrial Mg2+ efflux system, which greatly enhances our understanding of intracellular Mg2+ homeostasis. PMID:27302215

  18. Sustained efficacy of agomelatine 10 mg, 25 mg, and 25-50 mg on depressive symptoms and functional outcomes in patients with major depressive disorder. A placebo-controlled study over 6 months.

    PubMed

    Kennedy, Sidney H; Avedisova, Alla; Belaïdi, Carole; Picarel-Blanchot, Françoise; de Bodinat, Christian

    2016-02-01

    This randomized placebo-controlled "dose relation study" was conducted in patients who met criteria for major depressive disorder, to evaluate the efficacy and safety of agomelatine during 24 weeks at 3 doses (i) low fixed dosage (10 mg/day, n=100 patients entered the extension period), (ii) fixed dosage (25 mg/day, n=111) and (iii) a flexible dosage with up-titration in case of insufficient improvement at week 2 (25-50 mg/day, n=115) versus placebo (n=85). Mood was evaluated using the Hamilton rating scale for depression (HAM-D17) and Clinical Global Impression (CGI) scale. The functional status was examined with the Sheehan Disability Scale (SDS). At last post-baseline assessment, there were significant placebo-agomelatine differences on mean HAM-D17 total scores in favour of each agomelatine dose regimen (4.51±1.06 points, p<0.0001 at 10 mg; 7.74±1.05 points, p<0.0001 at 25 mg and 7.72±1.05 points, p<0.0001 at 25-50 mg). The response rate according to HAM-D17 was significantly higher in patients taking agomelatine than those taking placebo (difference of 21.8% at 10mg p<0.001; 36.4% and 35.4% respectively at 25 mg and 25-50 mg, p<0.0001). The remitter rate was significantly higher in patients taking agomelatine than those taking placebo (difference of 16.7% at 10 mg p=0.003; 33.8% and 35.4% respectively at 25 mg and 25-50 mg, p<0.0001). The effects of agomelatine were corroborated by CGI scores. Agomelatine improved symptom-related functional impairment on all domains of the SDS scale for the fixed dose 25 mg, and the one step titration 25-50 mg dose regimen. Similar findings were obtained for all measures in the subgroup of severely depressed patients. All dose regimens of agomelatine were well tolerated and no unexpected adverse event was reported. Long term agomelatine treatment improves both mood symptoms and social and occupational functioning of moderately to severely depressed patients. There is a dose effect between 10 mg and higher dose regimens of

  19. Gallium-assisted growth of flute-like MgO nanotubes, Ga2O3-filled MgO nanotubes, and MgO/Ga2O3 co-axial nanotubes.

    PubMed

    Jie, Jiansheng; Wu, Chunyan; Yu, Yongqiang; Wang, Li; Hu, Zhizhong

    2009-02-18

    Flute-like MgO nanotubes were successfully synthesized via a simple thermal evaporation method by using Mg(3)N(2) and Ga(2)O(3) as the source materials. The nanotubes are single-crystal cubic MgO, and have [100] orientation. In contrast to conventional nanotubes with intact walls, the flute-like MgO nanotubes possess a unique porous structure. On the nanotubes there are series of holes aligned along the nanotube length with approximate equidistance. Ga(2)O(3)-filled MgO nanotubes and MgO/Ga(2)O(3) co-axial nanotubes were also found in the product. Further investigation confirms that the inner beta-Ga(2)O(3) has an epitaxial growth relation with the outer MgO nanotube due to their perfect lattice matching. A gallium-assisted growth mechanism was proposed to interpret the growth of the flute-like MgO nanotubes. The thermal expansion and evaporation of the filled liquid gallium in MgO nanotubes are likely responsible for the formation of the hole structures on the side walls. PMID:19417423

  20. Modelling dislocation cores in MgSiO3 perovskite

    NASA Astrophysics Data System (ADS)

    Cordier, P.; Carrez, P.; Gouriet, K.; Kraych, A.

    2012-12-01

    MgSiO3 perovskite is the most abundant mineral of the Earth's lower mantle (i.e. between 700 and 2900 km depth) and accounts for half of Earth's mass. At lower mantle pressures (25-135 GPa) MgSiO3 crystallises in a distorted (orthorhombic) perovskite structure (described in the following using the Pbnm space group). In this structure, SiO6 octahedra are tilted with tilt angles increasing with increasing pressure. Since it is very difficult to perform deformation experiments under the extreme P, T conditions of the lower mantle, little is known about plastic deformation of MgSiO3 perovskite and its slip systems are still a matter of debate. To overcome this difficulty, we model dislocation core structures in this mineral taking into account the influence of pressure. In this study, we focus on dislocation core structures of dislocations with [100] and [010] Burgers vectors (which derive from <110> Burgers vectors of the underlying pseudo-cubic structure). Atomistic calculations are performed using pair-wise potentials as implemented in the LAMMPS code. The choice of potentials was initially validated by comparing generalized stacking fault (GSF) energies to similar calculations performed with the density functional theory (DFT). The core structures of screw dislocations are calculated using two independent methods. The first one is based on Peierls-Nabarro-Galerkin simulations involving GSF as an input. Direct calculations have also bee performed using cluster approach. It turns out that screw dislocations with [100] Burgers vector are characterised by a core mostly spread in the (010) plane. The core exhibits two edge-sharing octahedra in a configuration very similar to that modelled in SrTiO3 cubic perovskite. The structure of [010] screw dislocations is more complex with dissociation into two, non-collinear partial dislocations with a significant non-screw component. Both dislocations exhibit high Peierls stresses. This illustrates the effect of orthorhombic

  1. Grain Boundary Diffusion of Sulfur in MgO

    NASA Astrophysics Data System (ADS)

    Watson, H. C.; Watson, E. B.

    2013-12-01

    From being a candidate light element in the Earth's core to recording biosignatures on the surface, sulfur is a minor, but critical, element throughout the Earth. A deeper understanding the behaviour of sulfur under a wide scope of Earth relevant conditions will provide insight into geochemical cycles and reservoirs from the crust to the core. Sulfur isotope ratios in particular may be used to record specific geochemical processes such as ongoing core/mantle interaction, as well as shallower processes including cycling between the atmosphere/hydrosphere and lithosphere. The mobility of sulfur under these conditions will affect the reliability of using observed signatures to distinguish past processes and events. Grain boundary diffusion has often been shown to be orders of magnitude more rapid than diffusion through the crystal lattice of many materials. This effect is particularly important in cases where the diffusant is incompatible in the crystal lattice, and thus resides predominantly on grain boundaries. This is the case for sulfur and many of the minerals that comprise the interior of the Earth. If S diffusion is fast enough, the retention of some pristine signatures could be compromised. In other cases fast diffusion may allow for detection of signatures at large distances from their original source, as suggested by [1]. Experiments have been conducted in a piston-cylinder device at 1GPa and temperatures ranging from 1100°C to 1500°C to determine the rate of S grain boundary diffusion in an MgO matrix. A source-sink method similar to that used by [1] was employed using either FeS or FeS2 as a source and Mo foil as a sink separated by up to 3mm of pure MgO polycrystalline matrix. The foil sink was analyzed by electron microprobe and laser ablation ICP-MS for S content. Preliminary results show substantial diffusion of S through the MgO matrix. The results from these experiments, potential applications, and relevant numerical simulations will be presented

  2. Epitaxial growth of tungsten layers on MgO(001)

    SciTech Connect

    Zheng, Pengyuan; Ozsdolay, Brian D.; Gall, Daniel

    2015-11-15

    Smooth single crystal W(001) layers were grown on MgO(001) substrates by magnetron sputtering at 900 °C. X-ray diffraction ω–2θ scans, ω-rocking curves, pole figures, and reciprocal space maps indicate a 45°-rotated epitaxial relationship: (001){sub W}‖(001){sub MgO} and [010]{sub W}‖[110]{sub MgO}, and a relaxed lattice constant of 3.167 ± 0.001 nm. A residual in-plane biaxial compressive strain is primarily attributed to differential thermal contraction after growth and decreases from −0.012 ± 0.001 to −0.001 ± 0.001 with increasing layer thickness d = 4.8–390 nm, suggesting relaxation during cooling by misfit dislocation growth through threading dislocation glide. The in-plane x-ray coherence length increases from 3.4 to 33.6 nm for d = 4.8–390 nm, while the out-of-plane x-ray coherence length is identical to the layer thickness for d ≤ 20 nm, but is smaller than d for d ≥ 49.7 nm, indicating local strain variations along the film growth direction. X-ray reflectivity analyses indicate that the root-mean-square surface roughness increases from 0.50 ± 0.05 to 0.95 ± 0.05 nm for d = 4.8–19.9 nm, suggesting a roughness exponent of 0.38, but remains relatively constant for d > 20 nm with a roughness of 1.00 ± 0.05 nm at d = 47.9 nm.

  3. Structural characterization of MG and pre-MG states of proteins by MD simulations, NMR, and other techniques.

    PubMed

    Naiyer, Abdullah; Hassan, Md Imtaiyaz; Islam, Asimul; Sundd, Monica; Ahmad, Faizan

    2015-01-01

    Almost all proteins fold via a number of partially structured intermediates such as molten globule (MG) and pre-molten globule states. Understanding the structure of these intermediates at atomic level is often a challenge, as these states are observed under extreme conditions of pH, temperature, and chemical denaturants. Furthermore, several other processes such as chemical modification, site-directed mutagenesis (or point mutation), and cleavage of covalent bond of natural proteins often lead to MG like partially unfolded conformation. However, the dynamic nature of proteins in these states makes them unsuitable for most structure determination at atomic level. Intermediate states studied so far have been characterized mostly by circular dichroism, fluorescence, viscosity, dynamic light scattering measurements, dye binding, infrared techniques, molecular dynamics simulations, etc. There is a limited amount of structural data available on these intermediate states by nuclear magnetic resonance (NMR) and hence there is a need to characterize these states at the molecular level. In this review, we present characterization of equilibrium intermediates by biophysical techniques with special reference to NMR. PMID:25586676

  4. Depletion of intracellular free Mg2+ in Mg2(+)- and Ca2(+)-free solution in the taenia isolated from guinea-pig caecum.

    PubMed Central

    Nakayama, S; Tomita, T

    1990-01-01

    1. In isolated strips of the taenia of guinea-pig caecum removal of Mg2+ alone from the external solution had no clear effects on contractions produced by carbachol. However, after treatment with Mg2(+)- and Ca2(+)-free solution, readmission of 2.4 mM-Ca2+ caused only limited recovery, and addition of Mg2+ was necessary for full recovery. 2. When Mg2+ was removed in the absence of Ca2+, oxygen consumption increased, but gradually decreased again in the prolonged absence of the divalent cations. The increase in O2 consumption was blocked by ouabain or by decreasing the external sodium concentration to 20 mM. 3. Under normal conditions, the intracellular free Mg2+ concentration [( Mg2+]i) was estimated to be 310 +/- 30 microM (n = 17) from the chemical shift of the ATP peaks obtained with 31P nuclear magnetic resonance (NMR), assuming the dissociation constant of MgATP to be 41 microM. 4. Removal of external Mg2+ did not alter [Mg2+]i within 100 min. However, when both Mg2+ and Ca2+ were omitted, [Mg2+]i decreased to 8.3 +/- 3.6 microM (n = 12) in 100 min. The [Mg2+]i recovered completely on readmission of 1.2 mM-Mg2+. 5. When Mg2+ and Ca2+ were omitted, the phosphocreatine (PCr) content of the tissue slowly decreased to about 90% and the ATP concentration was reduced to about 60% of the control in 100 min. On Mg2+ readmission the ATP levels recovered partially, whereas PCr decreased further. 6. It is concluded that free [Mg2+]i slowly decreases when both Mg2+ and Ca2+ are removed from the external solution, due to an increased permeability of the plasma membrane, and that when [Mg2+]i is reduced to less than about 10% of the normal internal concentration, energy metabolism, membrane transport, and contraction are impaired. PMID:2348397

  5. Investigations on hydrogen storage properties of Mg{sub 2}Ni+x wt% LaMg{sub 2}Ni (x=0, 10, 20, 30) composites

    SciTech Connect

    Zhao Xin; Han Shumin; Zhu Xilin; Liu Baozhong; Liu Yanqing

    2012-06-15

    Mg{sub 2}Ni+x wt% LaMg{sub 2}Ni (x=0, 10, 20, 30) composites have been prepared by ball milling Mg{sub 2}Ni and LaMg{sub 2}Ni hydrides. X-ray Diffraction indicates that the composites consist of LaH{sub 3} and Mg{sub 2}NiH{sub 4} phases. Mg{sub 2}NiH{sub 4} phase transforms between with Mg{sub 2}Ni phase during hydriding/dehydriding cycling, while the LaH{sub 3} phase exists still after dehydriding process. Backscatter Electron results reveal that the LaH{sub 3} phase, which is decomposed from hydrided LaMg{sub 2}Ni, distributes in Mg{sub 2}Ni alloy homogeneously after ball milling procedure. Hydriding/Dehydriding measurements indicate significant improvement in reversible hydrogen storage properties of the composites over Mg{sub 2}Ni at low temperature. At 473 K, the hydrogen storage capacity of Mg{sub 2}Ni+20 wt% LaMg{sub 2}Ni composite reaches 3.22 wt% and can reversely desorb hydrogen completely, while the pure Mg{sub 2}Ni hydride is hardly desorbs hydrogen at this temperature. The improvement in the hydrogen storage properties is attributed to the existence of LaH{sub 3} phase in the composites. - Graphical abstract: The Mg{sub 2}Ni + x wt% LaMg{sub 2}Ni (x=10, 20, 30) composites display enhancement on reversible hydrogen storage properties compared with that of pure Mg{sub 2}Ni. Highlights: Black-Right-Pointing-Pointer Tittle La is introduced into Mg{sub 2}Ni alloy without multiphase created. Black-Right-Pointing-Pointer La is introduced into Mg{sub 2}Ni by hydrogen decomposed ball-milling. Black-Right-Pointing-Pointer Reversible hydrogen storage properties at low temperature are improved. Black-Right-Pointing-Pointer Hydrogen storage capacity of composites is beyond 3 wt% at 473 K.

  6. Pressure Effects on Mg70Zn30 Superconductor

    NASA Astrophysics Data System (ADS)

    Vora, Aditya M.

    Theoretical computation of the pressure dependence of superconducting state parameters of binary Mg70Zn30 is reported using model potential formalism. Explicit expressions have been derived for the volume dependence of the electron-phonon coupling strength λ and the Coulomb pseudopotential μ* considering the variation of Fermi momentum kF and Debye temperature θD with volume. The well-known Ashcroft's empty core (EMC) model pseudopotential and five different types of the local field correction functions viz. Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) have been used for obtaining pressure dependence of transition temperature TC and the logarithmic volume derivative Φ of the effective interaction strength N0V for metallic glass. It has been observed that the μ* curve shows a linear nature and an elbow is formed in the Φ graph.

  7. Internal reduction of (Mg,Ni)O: Morphology and kinetics

    SciTech Connect

    Rogers, K.A.; Trumble, K.P.

    1996-12-31

    Internal reduction microstructures in the (Mg{sub 1{minus}x}Ni{sub x})O system were studied as a function of temperature from 800 to 1350 {degrees}C and composition from 0.10 {le} x {le} 0.75. The microstructural variety extends from very fine Ni particles to a large scale interpenetrating vermiculite structures. Reduction microstructures are discussed in terms of composition and reduction temperature as a function of homologous temperature. The reduction kinetics in same composition range were studied, resulting in reduction rates an order of magnitude faster that observed previously with single crystals. The reduction rate was found to decrease with increasing composition, counter to most of the experimental evidence to date.

  8. Electrical and magnetic properties of Co-Zn-Mg ferrite

    NASA Astrophysics Data System (ADS)

    Oza, M. H.; Baldha, G. J.

    2016-05-01

    The series Co(0.8)Zn0.2-XMgXFe2O4 has been synthesized using standard ceramic technique and characterized using different techniques. The XRD analysis shows single phase cubic structure of the sample. It was also observed from XRD that lattice constant values calculated from these data were found to increase on increasing value of concentration X. The a.c susceptibility was carried out which exhibited ferromagnetic ordering. The Neel's temperature Tc determined from it increases with increasing X. There is an agreement in ferrimagnetic behaviour between magnetization and susceptibility data. This also suggests that A-B interaction increases with increasing X. The electrical properties of Zn - Mg substituted Co ferrite were found through DC resistivity measurements.

  9. An Unusual yet "Mg"nificent Indication for Hemodialysis.

    PubMed

    Bansal, Amar D; Negoianu, Dan; Warburton, Karen M

    2016-05-01

    Hypermagnesemia is an uncommon electrolyte abnormality, due to the fact that magnesium toxicity is only seen in the setting of a massive exposure to exogenous magnesium, often in the setting of renal insufficiency. Here, we report a case of severe hypermagnesemia that resulted in complete paralysis that was secondary to Renacidin administration, a rarely used agent used for intra-renal pelvic or intra-vesicular instillation dissolution of struvite stones. The patient also had concurrent acute kidney injury (AKI). The patient's magnesium was as high as 16.7 mg/dL, and he initially received hemodialysis followed by continuous venovenous hemodialysis. These therapies resulted in a rapid reduction in magnesium levels and eventual resolution of the muscular weakness. The case discussion highlights several key aspects of magnesium homeostasis, the limited mechanistic understanding of Renacidin-induced hypermagnesemia, and the role of renal replacement therapies in the treatment of hypermagnesemia. PMID:26915350

  10. Bismuth-doped Mg - Al silicate glasses and fibres

    SciTech Connect

    Bufetov, Igor' A; Vel'miskin, V V; Galagan, B I; Denker, B I; Sverchkov, S E; Semjonov, S L; Firstov, Sergei V; Shulman, I L; Dianov, Evgenii M

    2012-09-30

    This paper compares the optical properties of bulk bismuth-doped Mg - Al silicate glasses prepared in an iridium crucible to those of optical fibres prepared by the powder-in-tube method and having a core identical in composition to the glasses. The bulk glasses and fibres are shown to be similar in luminescence properties. The optical loss in the fibres in their IR luminescence band is about one order of magnitude lower than that in the crucible-melted glasses. The level of losses in the fibres and their luminescence properties suggest that such fibres can be made to lase near 1.15 {mu}m. (optical fibres, lasers and amplifiers. properties and applications)

  11. Al-Mg Isotope Study of Allende 5241

    NASA Technical Reports Server (NTRS)

    Kerekgyarto, A. G.; Jeffcoat, C. R.; Lapen, T. J.; Andreasen, R.; Righter, M.; Ross, D. K.; Simon, J. I.

    2016-01-01

    The defining characteristic of type B1 CAIs is a large (.5- 3mm) concentric melilite mantle [1]. In [2] we presented two isochrons from separate traverses across the melilite mantle of Allende EK 459-5-1. The primary petrographic differences between the traverses was the preservation of strong oscillatory zoning. The traverse that crossed the distinctive oscillatory zone produced a pristine internal isochron, while the other that did not have a strongly preserved oscillatory zone produced a disturbed isochron indicated by more scatter (higher MSWD) and a positive (delta)26Mg* intercept. The implication simply being that the oscillatory zone may represent varying conditions during the mantle formation event. We targeted a similar texture in Allende 5241 using the same methodology in an attempt to achieve similar results.

  12. Electronic, optical and bonding properties of MgCO 3

    NASA Astrophysics Data System (ADS)

    Hossain, Faruque M.; Dlugogorski, B. Z.; Kennedy, E. M.; Belova, I. V.; Murch, Graeme E.

    2010-05-01

    The electronic, optical and bonding properties of MgCO 3 (magnesite, rhombohedral calcite-type structure) are calculated using a first-principles density-functional theory (DFT) method considering the exchange-correlation function within the local density approximation (LDA) and the generalized gradient approximation (GGA). The indirect band gap of magnesite is estimated to be 5.0 eV, which is underestimated by ˜1.0 eV. The fundamental absorption edge, which indicates the exact optical transitions from occupied valence bands to the unoccupied conduction band, is estimated by calculating the photon energy dependent imaginary part of the dielectric function using scissors approximations (rigid shift of unoccupied bands). The optical properties show consistent results with the experimental calcite-type structure and also show a considerable optical anisotropy of the magnesite structure. The density of states and Mulliken population analyses reveal the bonding nature between the atoms.

  13. Novel electrolyte chemistries for Mg-Ni rechargeable batteries.

    SciTech Connect

    Garcia-Diaz, Brenda; Kane, Marie; Au, Ming

    2010-10-01

    Commercial hybrid electric vehicles (HEV) and battery electric vehicles (BEV) serve as means to reduce the nation's dependence on oil. Current electric vehicles use relatively heavy nickel metal hydride (Ni-MH) rechargeable batteries. Li-ion rechargeable batteries have been developed extensively as the replacement; however, the high cost and safety concerns are still issues to be resolved before large-scale production. In this study, we propose a new highly conductive solid polymer electrolyte for Mg-Ni high electrochemical capacity batteries. The traditional corrosive alkaline aqueous electrolyte (KOH) is replaced with a dry polymer with conductivity on the order of 10{sup -2} S/cm, as measured by impedance spectroscopy. Several potential novel polymer and polymer composite candidates are presented with the best-performing electrolyte results for full cell testing and cycling.

  14. Effect of amorphous Mg{sub 50}Ni{sub 50} on hydriding and dehydriding behavior of Mg{sub 2}Ni alloy

    SciTech Connect

    Guzman, D.; Ordonez, S.; Fernandez, J.F.; Sanchez, C.; Serafini, D.; Rojas, P.A.; Aguilar, C.; Tapia, P.

    2011-04-15

    Composite Mg{sub 2}Ni (25 wt.%) amorphous Mg{sub 50}Ni{sub 50} was prepared by mechanical milling starting with nanocrystalline Mg{sub 2}Ni and amorphous Mg{sub 50}Ni{sub 50} powders, by using a SPEX 8000 D mill. The morphological and microstructural characterization of the powders was performed via scanning electron microscopy and X-ray diffraction. The hydriding characterization of the composite was performed via a solid gas reaction method in a Sievert's-type apparatus at 363 K under an initial hydrogen pressure of 2 MPa. The dehydriding behavior was studied by differential thermogravimetry. On the basis of the results, it is possible to conclude that amorphous Mg{sub 50}Ni{sub 50} improved the hydriding and dehydriding kinetics of Mg{sub 2}Ni alloy upon cycling. A tentative rationalization of experimental observations is proposed. - Research Highlights: {yields} First study of the hydriding behavior of composite Mg{sub 2}Ni (25 wt.%) amorphous Mg{sub 50}Ni{sub 50}. {yields} Microstructural characterization of composite material using XRD and SEM was obtained. {yields} An improved effect of Mg{sub 50}Ni{sub 50} on the Mg{sub 2}Ni hydriding behavior was verified. {yields} The apparent activation energy for the hydrogen desorption of composite was obtained.

  15. Simultaneous desorption behavior of M borohydrides and Mg2FeH6 reactive hydride composites (M = Mg, then Li, Na, K, Ca)

    NASA Astrophysics Data System (ADS)

    Chaudhary, Anna-Lisa; Li, Guanqiao; Matsuo, Motoaki; Orimo, Shin-ichi; Deledda, Stefano; Sørby, Magnus H.; Hauback, Bjørn C.; Pistidda, Claudio; Klassen, Thomas; Dornheim, Martin

    2015-08-01

    Combinations of complex metal borohydrides ball milled with the transition metal complex hydride, Mg2FeH6, are analysed and compared. Initially, the Reactive Hydride Composite (RHC) of Mg2+ cation mixtures of Mg2FeH6 and γ-Mg(BH4)2 is combined in a range of molar ratios and heated to a maximum of 450 °C. For the molar ratio of 6 Mg2FeH6 + Mg(BH4)2, simultaneous desorption of the two hydrides occurred, which resulted in a single event of hydrogen release. This single step desorption occurred at temperatures between those of Mg2FeH6 and γ-Mg(BH4)2. Keeping this anionic ratio constant, the desorption behavior of four other borohydrides, Li-, Na-, K-, and Ca-borohydrides was studied by using materials ball milled with Mg2FeH6 applying the same milling parameters. The mixtures containing Mg-, Li-, and Ca-borohydrides also released hydrogen in a single event. The Mass Spectrometry (MS) results show a double step reaction within a narrow temperature range for both the Na- and K-borohydride mixtures. This phenomenon, observed for the RHC systems at the same anionic ratio with all five light metal borohydride mixtures, can be described as simultaneous hydrogen desorption within a narrow temperature range centered around 300 °C.

  16. Complex transition metal hydrides incorporating ionic hydrogen: thermal decomposition pathway of Na2Mg2FeH8 and Na2Mg2RuH8.

    PubMed

    Humphries, Terry D; Matsuo, Motoaki; Li, Guanqiao; Orimo, Shin-Ichi

    2015-03-28

    Complex transition metal hydrides have potential technological application as hydrogen storage materials, smart windows and sensors. Recent exploration of these materials has revealed that the incorporation of anionic hydrogen into these systems expands the potential number of viable complexes, while varying the countercation allows for optimisation of their thermodynamic stability. In this study, the optimised synthesis of Na2Mg2TH8 (T = Fe, Ru) has been achieved and their thermal decomposition properties studied by ex situ Powder X-ray Diffraction, Gas Chromatography and Pressure-Composition Isotherm measurements. The temperature and pathway of decomposition of these isostructural compounds differs considerably, with Na2Mg2FeH8 proceeding via NaMgH3 in a three-step process, while Na2Mg2RuH8 decomposes via Mg2RuH4 in a two-step process. The first desorption maxima of Na2Mg2FeH8 occurs at ca. 400 °C, while Na2Mg2RuH8 has its first maxima at 420 °C. The enthalpy and entropy of desorption for Na2Mg2TH8 (T = Fe, Ru) has been established by PCI measurements, with the ΔHdes for Na2Mg2FeH8 being 94.5 kJ mol(-1) H2 and 125 kJ mol(-1) H2 for Na2Mg2RuH8. PMID:25732233

  17. Evidence for boron diffusion into sub-stoichiometric MgO (001) barriers in CoFeB/MgO-based magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Harnchana, V.; Hindmarch, A. T.; Sarahan, M. C.; Marrows, C. H.; Brown, A. P.; Brydson, R. M. D.

    2013-04-01

    Evidence of boron diffusion into the MgO barrier of a CoFeB/MgO based magnetic tunnel junction has been identified using analytical scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy. Structures were deposited by DC/RF-magnetron sputtering, where defective, sub-stoichiometric MgO barriers degrading device performance have been previously mitigated against by deposition of thin Mg layers prior to MgO deposition. We show that despite the protection offered by the Mg layer, disorder in the MgO barrier is still evident by STEM analysis and is a consequence of the oxidation of the Co40Fe40B20 surface during MgO deposition. Evidence of boron diffusion from CoFeB into the MgO barrier in the as-deposited and annealed structure is also presented, which in the as-deposited case we suggest results from the defective structures at the barrier interfaces. Annealing at 375 °C results in the presence of B in the trigonal coordination of [BO3]3- in the MgO barrier and partial crystallization of the top electrode (we presume there is also some boron diffusion into the Ta capping layer). The bottom electrode, however, fails to crystallize and much of the boron is retained in this thicker electrode. A higher annealing temperature or lower initial boron content is required to crystallize the bottom electrode.

  18. Synthesis and Characterization of Bismuth Magnesium Phosphate and Arsenate: BiMg 2PO 6 and BiMg 2AsO 6

    NASA Astrophysics Data System (ADS)

    Huang, Jinfan; Gu, Qiuyi; Sleight, Arthur W.

    1993-08-01

    Two new compounds, BiMg 2PO 6 and BiMg 2AsO 6, have been synthesized and structurally characterized by single crystal and powder X-ray diffraction. Both compounds crystallize in the orthorhombic space group Cmcm (No. 63) with four formula units per unit cell. They are isostructural with bismuth magnesium vanadate, BiMg 2VO 6. The cell parameters for BiMg 2PO 6 are a = 7.801(2), b = 11.888(3), c = 5.273(2) Å, V = 489.0(2) Å 3 and for BiMg 2AsO 6 are a = 7.9142(5), b = 12.1637(8), c = 5.3898(4) Å, V = 518.9(2) Å 3. The formula for this series of compounds may be written as (BiO 2)Mg AO 4 to emphasize the (BiO 2) 1- chains and the (AO 4) 3- tetrahedral groups isolated from one another. Between these chains and tetrahedral groups sit Mg 2+ cations in an unusual fivefold coordination to oxygen. No emission bands were observed from BiMg 2PO 6 and BiMg 2AsO 6 under excitation with UV or visible radiation. The IR spectra of these compounds are compared to that of BiMg 2VO 6.

  19. Properties of YBCO on LaMnO3-capped IBAD MgO-templates without Homo-epitaxial MgO layer.

    SciTech Connect

    Aytug, Tolga; Paranthaman, Mariappan Parans; Kim, Kyunghoon; Zhang, Yifei; Cantoni, Claudia; Zuev, Yuri L; Goyal, Amit; Thompson, James R; Christen, David K

    2009-01-01

    Previously, it has been well established that in an IBAD architecture for coated conductors, (1) LaMnO3 (LMO) buffer layers are structurally and chemically compatible with an underlying homo-epitaxial MgO layer and (2) high current density YBCO films can be grown on these LMO templates. In the present work, the homo-epi MgO layer has been successfully eliminated and a LMO cap layer was grown directly on the IBAD (MgO) template. The performance of the LMO/IBAD (MgO) samples has been qualified by depositing 1 m-thick YBCO coatings by pulsed laser deposition. Electrical transport measurements of YBCO films on the standard (with homo-epi MgO) and simplified (without homo-epi MgO) IBAD architectures were carried out. The angular dependencies of critical current density (Jc) are similar for both IBAD architectures. XRD measurements indicate good, c-axis aligned YBCO films. Transmission electron microscopy (TEM) images reveal that microstructures of YBCO/LMO/IBAD (MgO) and YBCO/LMO/homo-epi MgO/IBAD (MgO) templates are similar. These results demonstrate the strong potential of using LMO as a single cap layer directly on IBAD (MgO) for the development of a simplified IBAD architecture.

  20. Enhanced cycling stability and high rate dischargeability of (La,Mg)2Ni7-type hydrogen storage alloys with (La,Mg)5Ni19 minor phase

    NASA Astrophysics Data System (ADS)

    Liu, Jingjing; Han, Shumin; Han, Da; Li, Yuan; Yang, Shuqin; Zhang, Lu; Zhao, Yumeng

    2015-08-01

    The A2B7-type lanthanum (La)-magnesium (Mg)-nickel (Ni)-based alloy with single (La,Mg)2Ni7 phase and different amounts of (La,Mg)5Ni19 minor phase was obtained by step-wise sintering. The impact of (La,Mg)5Ni19 phase on the alloy's microstructure and electrochemical performance was subsequently studied. It was found that the average subunit volume in (La,Mg)5Ni19 phase is smaller than that in (La,Mg)2Ni7 phase, resulting in increases of strains inside the alloys and decreases of cell volumes. During battery charge/discharge, the (La,Mg)5Ni19 phase network scattered in the alloys relieves internal stress, alleviates pulverization and oxidation of the alloys, stabilizes the stacking structures against amorphization, and finally improves the cycling stability of the alloys. Furthermore, (La,Mg)5Ni19 phase with higher Ni content desorbs hydrogen ahead of (La,Mg)2Ni7 phase. The reduced hydrogen pressure in (La,Mg)5Ni19 phase can subsequently lead to the fast discharge of (La,Mg)2Ni7 phase, thus making a remarkable improvement in high rate dischargeability at 1500 mA g-1 from 46.2% to 58.9% with increasing (La,Mg)5Ni19 phase abundance from 0 to 37.4 wt.%. Therefore, it is believed that A2B7-type La-Mg-Ni-based alloys with A5B19-type minor phase are promising prototypes for high-power and long-lifetime nickel/metal hydride battery electrode materials.

  1. New antimony substituted Mg-Al layered double hydroxides.

    PubMed

    Kim, Jin A; Hwang, Seong-Ju; Choy, Jin-Ho

    2008-10-01

    No antimony hydroxide has been previously reported not only in solid state but also in aqueous solution, surely due to the fact that the formation of antimony oxide, Sb2O3, is thermodynamically more favorable than that of the hydroxide phase, Sb(OH)3. According to the pH dependent solubility diagram of Sb2O3, antimony (III) hydroxide may not exist as a definite compound but be proposed as a hydrated monomeric molecular species, Sb(OH)3(aq), which is in equilibrium with Sb2O3, under a condition of very small ionic strength. This is probably the reason why no Sb(3+)-containing layered double hydroxide, LDH, has been reported as yet. In the present study, an attempt has been made to prepare new Sb(3+)-LDH by substituting the Al3+ in octahedral site partially with Sb3+ up to approximately 10%. From the X-ray diffraction analysis, we found that the lattice constants (a = 3.075 angstroms, c = 23.788 angstroms) of the pristine, Mg-Al LDH, increased gradually upto those (a = 3.087 angstroms, c = 24.167 angstroms) of Sb-LDH (8%-substituted). Beyond 10%, the Sb substitution does not lead to any further increases of lattice constants but the impurity Sb2O3 phase is formed. It is, therefore, concluded that the solubility limit of Sb3+ in LDH would be around 10%. In addition, we were able to determine the chemical formula of Sb-substituted LDHs as follows, Mg4Al(1-x)Sb(x)OH10(CO3)(1/2) x H2O (x = 0 approximately 0.08) on the basis of energy dispersive X-ray spectroscopy. PMID:19198414

  2. MG132, a proteasome inhibitor, induces apoptosis in tumor cells.

    PubMed

    Guo, Na; Peng, Zhilan

    2013-03-01

    The balance between cell proliferation and apoptosis is critical for normal development and for the maintenance of homeostasis in adult organisms. Disruption of this balance has been implicated in a large number of disease processes, ranging from autoimmunity and neurodegenerative disorders to cancer. The ubiquitin-proteasome pathway, responsible for mediating the majority of intracellular proteolysis, plays a crucial role in the regulation of many normal cellular processes, including the cell cycle, differentiation and apoptosis. Apoptosis in cancer cells is closely connected with the activity of ubiquitin-proteasome pathway. The peptide-aldehyde proteasome inhibitor MG132 (carbobenzoxyl-L-leucyl-L-leucyl-L-leucine) induces the apoptosis of cells by a different intermediary pathway. Although the pathway of induction of apoptosis is different, it plays a crucial role in anti-tumor treatment. There are many cancer-related molecules in which the protein levels present in cells are regulated by a proteasomal pathway; for example, tumor inhibitors (P53, E2A, c-Myc, c-Jun, c-Fos), transcription factors (transcription factor nuclear factor-kappa B, IκBα, HIFI, YYI, ICER), cell cycle proteins (cyclin A and B, P27, P21, IAP1/3), MG132 induces cell apoptosis through formation of reactive oxygen species or the upregulation and downregulation of these factors, which is ultimately dependent upon the activation of the caspase family of cysteine proteases. In this article we review the mechanism of the induction of apoptosis in order to provide information required for research. PMID:22897979

  3. Aberrant tropoelastin secretion in MG-63 human osteosarcoma cells

    SciTech Connect

    Curtiss, S.W.

    1989-01-01

    The secretion of newly synthesized tropoelastin, the soluble precursor of the extracellular matrix protein elastin, is not well understood. MG-63 human osteosarcoma cells were found by immunoblot analysis to synthesize 62 kD and 64 kD tropoelastins. Media from 63 cells labelled for five hours with ({sup 3}H)-valine contain no detectable tropoelastin, unlike media from other tropoelastin-synthesizing cells. Immunoblots of conditioned media and 1Ox-concentrated conditioned media left on the cells for six days also show an absence of tropoelastin from the cell media. No insoluble elastin is associated with the cell layer, as determined by amino acid analysis and electron microscopy of 18-21 day cell cultures. The absence of tropoelastin from the cell medium and elastin from the extracellular matrix indicates that MG63 cells do not secrete tropoelastin as expected, but accumulate it intracellularly. This accumulation is transient: immunoblots and immunofluorescence microscopy show that cells three days after passage have the highest steady-state levels of tropoelastin per cell, that day 8 cells contain lower but still significant amounts of tropoelastin, and that by day 22 tropoelastin is no longer present in the cell cultures. Cell density is a critical factor in the observed pattern of tropoelastin expression. Cells seeded at ten fold their usual initial density have high tropoelastin levels at one day after passage, sooner than cells seeded normally. Tropoelastin also disappears from high density-seeded cells more quickly and is no longer detectable at day 10. Lysosome-like vesicles containing membranous structures appear by immunoelectron microscopy to be the primary site of intracellular tropoelastin localization.

  4. Divacancies and the hydrogenation of Mg-Ti films with short range chemical order

    SciTech Connect

    Leegwater, H.; Schut, H.; Eijt, S. W. H.; Egger, W.; Baldi, A.; Dam, B.

    2010-03-22

    We obtained evidence for the partial chemical segregation of as-deposited and hydrogenated Mg{sub 1-y}Ti{sub y} films (0<=y<=0.30) into nanoscale Ti and Mg domains using positron Doppler-broadening. We exclusively monitor the hydrogenation of Mg domains, owing to the large difference in positron affinity for Mg and Ti. The electron momentum distribution broadens significantly upon transformation to the MgH{sub 2} phase over the whole compositional range. This reveals the similarity of the metal-insulator transition for rutile and fluorite MgH{sub 2}. Positron lifetime studies show the presence of divacancies in the as-deposited and hydrogenated Mg-Ti metal films. In conjunction with the relatively large local lattice relaxations we deduce to be present in fluorite MgH{sub 2}, these may be responsible for the fast hydrogen sorption kinetics in this MgH{sub 2} phase.

  5. Mass spectrometric determination of the dissociation energy of the AuMg diatomic molecule

    NASA Astrophysics Data System (ADS)

    Balducci, G.; Ciccioli, A.; Gigli, G.; Kudin, L. S.

    2003-02-01

    The dissociation energy of the intermetallic molecule AuMg was for the first time determined by the Knudsen-effusion mass spectrometry technique. Partial pressures of Au(g), Mg(g), AuMg(g) and Au 2(g) species produced under equilibrium vaporization of an appropriate alloy were monitored in the temperature range 1870-2333 K. The collected data were analyzed by the second- and third-law methods for the gaseous equilibria AuMg(g)=Au(g) + Mg(g) and AuMg(g) + Au(g)=Au 2(g) + Mg(g). The selected value for the dissociation energy of AuMg at 0 K is D0∘(AuMg)= 175.4±2.7 kJ/mol.

  6. Phase stability, mechanical property, and electronic structure of an Mg-Ca system.

    PubMed

    Zhou, Peng; Gong, H R

    2012-04-01

    First principle calculations reveal that Mg-Ca phases are energetically favorable with negative heats of formation within the entire composition range, and that a strong chemical bonding is formed between Mg and Ca atoms. Calculations also show that the composition has an important effect on mechanical properties of Mg-Ca, and that the Mg-Ca phases with an Mg composition of less than 50 at.% would be good candidates as degradable bone materials in terms of Young's modulus and ductility. In addition, it is found out that Mg(3)Ca, MgCa and MgCa(3) have phase sequences of BCC→HCP, BCC→HCP and FCC→HCP under high pressure, respectively, and that Ca plays a dominant role in determining the electronic structures and stable crystal structures of various Mg-Ca phases. PMID:22402162

  7. Erythrocyte intracellular Mg2+ concentration as an index of recognition and memory

    PubMed Central

    Xiong, Wenxiang; Liang, Yaru; Li, Xue; Liu, Guosong; Wang, Zhao

    2016-01-01

    Magnesium (Mg2+) plays an important role in the neural system, and yet scarcely any research has quantitatively analyzed the link between endogenous Mg2+ level and memory. Using our original technique, we measured erythrocyte intracellular ionized Mg2+ concentration (RBC [Mg2+]i), which linearly correlated to recognition and spatial memory in normal aging rats. In the brain, RBC [Mg2+]i significantly correlated to hippocampus extracellular fluid Mg2+ concentration, and further correlated to hippocampal synapse density. Elevation of Mg2+ intake in aged rats demonstrated an association between RBC [Mg2+]i increase and memory recovery. The therapeutic effect of Mg2+ administration was inversely correlated to individual basal RBC [Mg2+]i. In summary, we provide a method to measure RBC [Mg2+]i, an ideal indicator of body Mg2+ level. RBC [Mg2+]i represents rodent memory performance in our study, and might further serve as a potential biomarker for clinical differential diagnosis and precise treatment of Mg2+-deficiency-associated memory decline during aging. PMID:27253451

  8. Magnesium relaxes arterial smooth muscle by decreasing intracellular Ca2+ without changing intracellular Mg2+.

    PubMed Central

    D'Angelo, E K; Singer, H A; Rembold, C M

    1992-01-01

    Elevations in extracellular [Mg2+] ([Mg2+]o) relax vascular smooth muscle. We tested the hypothesis that elevated [Mg2+]o induces relaxation through reductions in myoplasmic [Ca2+] and myosin light chain phosphorylation without changing intracellular [Mg2+] ([Mg2+]i). Histamine stimulation of endothelium-free swine carotid medial tissues was associated with increases in both Fura 2- and aequorin-estimated myoplasmic [Ca2+], myosin phosphorylation, and force. Elevated [Mg2+]o decreased myoplasmic [Ca2+] and force to near resting values. However, elevated [Mg2+]o only transiently decreased myosin phosphorylation values: sustained [Mg2+]o-induced decreases in myoplasmic [Ca2+] and force were associated with inappropriately high myosin phosphorylation values. The elevated myosin phosphorylation during [Mg2+]o-induced relaxation was entirely on serine 19, the Ca2+/calmodulin-dependent myosin light chain kinase substrate. Myoplasmic [Mg2+] (estimated with Mag-Fura 2) did not significantly increase with elevated [Mg2+]o. These results are consistent with the hypothesis that increased [Mg2+]o induces relaxation by decreasing myoplasmic [Ca2+] without changing [Mg2+]i. These data also demonstrate dissociation of myosin phosphorylation from myoplasmic [Ca2+] and force during Mg(2+)-induced relaxation. This finding suggests the presence of a phosphorylation-independent (yet potentially Ca(2+)-dependent) mechanism for regulation of force in vascular smooth muscle. Images PMID:1602005

  9. Erythrocyte intracellular Mg(2+) concentration as an index of recognition and memory.

    PubMed

    Xiong, Wenxiang; Liang, Yaru; Li, Xue; Liu, Guosong; Wang, Zhao

    2016-01-01

    Magnesium (Mg(2+)) plays an important role in the neural system, and yet scarcely any research has quantitatively analyzed the link between endogenous Mg(2+) level and memory. Using our original technique, we measured erythrocyte intracellular ionized Mg(2+) concentration (RBC [Mg(2+)]i), which linearly correlated to recognition and spatial memory in normal aging rats. In the brain, RBC [Mg(2+)]i significantly correlated to hippocampus extracellular fluid Mg(2+) concentration, and further correlated to hippocampal synapse density. Elevation of Mg(2+) intake in aged rats demonstrated an association between RBC [Mg(2+)]i increase and memory recovery. The therapeutic effect of Mg(2+) administration was inversely correlated to individual basal RBC [Mg(2+)]i. In summary, we provide a method to measure RBC [Mg(2+)]i, an ideal indicator of body Mg(2+) level. RBC [Mg(2+)]i represents rodent memory performance in our study, and might further serve as a potential biomarker for clinical differential diagnosis and precise treatment of Mg(2+)-deficiency-associated memory decline during aging. PMID:27253451

  10. Powder metallurgical low-modulus Ti-Mg alloys for biomedical applications.

    PubMed

    Liu, Yong; Li, Kaiyang; Luo, Tao; Song, Min; Wu, Hong; Xiao, Jian; Tan, Yanni; Cheng, Ming; Chen, Bing; Niu, Xinrui; Hu, Rong; Li, Xiaohui; Tang, Huiping

    2015-11-01

    In this work, powder metallurgical (PM) Ti-Mg alloys were prepared using combined techniques of mechanical alloying and spark plasma sintering. The alloys mainly consist of super saturations of Mg in Ti matrix, and some laminar structured Ti- and Mg-rich phases. The PM Ti-Mg alloys contain a homogeneous mixtures of nanocrystalline Mg and Ti phases. The novel microstructures result in unconventional mechanical and biological properties. It has been shown that the PM Ti-Mg alloys have a much lower compression modulus (36-50GPa) compared to other Ti alloys, but still remain a very high compressive strength (1500-1800MPa). In addition, the PM Ti-Mg alloys show good biocompatibility and bioactivity. Mg can dissolve in the simulated body fluids, and induce the formation of the calcium phosphate layer. The compression modulus of PM Ti-Mg alloys decreases with the amount of Mg, while the bioactivity increases. Although the corrosion resistance of Ti-Mg alloys decreases with the content of Mg, the alloys still show good stability in simulated body fluid under electrochemical conditions. The indirect and direct cytotoxicity results show that PM Ti-Mg alloys have a good biocompatibility to NIH-3T3 cells. Therefore, the PM Ti-Mg alloys are promising candidates in biomedical applications. PMID:26249586

  11. 3D [Ag-Mg] polyanionic frameworks in the La{sub 4}Ag{sub 10}Mg{sub 3} and La{sub 4}Ag{sub 10.3}Mg{sub 12} new ternary compounds

    SciTech Connect

    Solokha, Pavlo; De Negri, Serena; Pavlyuk, Volodymyr; Saccone, Adriana

    2010-12-15

    The crystal structures of two new ternary phases, La{sub 4}Ag{sub 10}Mg{sub 3} and La{sub 4}Ag{sub 10.3}Mg{sub 12}, were refined from X-ray single crystal diffraction data. La{sub 4}Ag{sub 10}Mg{sub 3} crystallizes in the Ca{sub 4}Au{sub 10}In{sub 3} structure type, an ordered variant of the binary Zr{sub 7}Ni{sub 10} compound: orthorhombic, Cmce, oS68, a=14.173(5), b=10.266(3), c=10.354(3) A, Z=4, wR{sub 2}=0.0826, 676 F{sup 2} values, 50 variables. La{sub 4}Ag{sub 10.3}Mg{sub 12} represents a new structure type: orthorhombic, Cmmm, oS116-10.32, a=9.6130(3), b=24.9663(8), c=9.6333(2) A, Z=4, wR{sub 2}=0.0403, 1185 F{sup 2} values, 101 variables. The structural analysis of both compounds, highlighting a significant contraction of the Ag-Mg distances, suggests the existence of three-dimensional [Ag-Mg] networks hosting La atoms. LMTO calculations applied to La{sub 4}Ag{sub 10}Mg{sub 3} indicate that the strongest bonds occur for Ag-Ag and Ag-Mg interactions, and confirm the presence of a 3D{sub {infinity}}[Ag{sub 10}Mg{sub 3}]{sup {delta}}{sup -} polyanionic framework balanced by positively charged La atoms. -- Graphical abstract: An independent fragment of the 3D [Ag-Mg] framework in La{sub 4}Ag{sub 10}Mg{sub 3} together with an ELF section (1/2 0 0 basal plane). Display Omitted

  12. Aging and thermal stability of Mg/SiC and Mg/Y2O3 reflection multilayers in the 25-35 nm region

    SciTech Connect

    Ejima, Takeo; Yamazaki, Atsushi; Banse, Takanori; Saito, Katsuhiko; Kondo, Yuji; Ichimaru, Satoshi; Takenaka, Hisataka

    2005-09-10

    Reflection measurements in the 25-35 nm region were made for Mg/SiC and Mg/Y2O3 multilayers kept in a low-humidity atmosphere for 4 or 5 years. Aged Mg/SiC multilayers keep their reflectances, and the reflectance value at 31.2 nm is 0.44 at 10 deg. of the normal angle of incidence. Aged Mg/Y2O3 multilayers change reflectance as top layer materials, and the best value at 30.1 nm is 0.40 at 10 deg. . Reflection measurements are also made for Mg-based multilayers that are annealed from room temperature to 400 deg. C at 50 deg. C intervals. Both multilayers keep their reflectance at annealing temperatures of 200 deg. C. These results suggest that both Mg-based multilayers can be applied to practical optics.

  13. Method for making MgO buffer layers on rolled nickel or copper as superconductor substrates

    DOEpatents

    Paranthaman, Mariappan; Goyal, Amit; Kroeger, Donald M.; List, III, Frederic A.

    2002-01-01

    Buffer layer architectures are epitaxially deposited on biaxially-textured rolled-Ni and/or Cu substrates for high current conductors, and more particularly buffer layer architectures such as MgO/Ag/Pt/Ni, MgO/Ag/Pd/Ni, MgO/Ag/Ni, MgO/Ag/Pd/Cu, MgO/Ag/Pt/Cu, and MgO/Ag/Cu. Techniques used to deposit these buffer layers include electron beam evaporation, thermal evaporation, rf magnetron sputtering, pulsed laser deposition, metal-organic chemical vapor deposition (MOCVD), combustion CVD, and spray pyrolysis.

  14. MgO buffer layers on rolled nickel or copper as superconductor substrates

    DOEpatents

    Paranthaman, Mariappan; Goyal, Amit; Kroeger, Donald M.; List, III, Frederic A.

    2001-01-01

    Buffer layer architectures are epitaxially deposited on biaxially-textured rolled-Ni and/or Cu substrates for high current conductors, and more particularly buffer layer architectures such as MgO/Ag/Pt/Ni, MgO/Ag/Pd/Ni, MgO/Ag/Ni, MgO/Ag/Pd/Cu, MgO/Ag/Pt/Cu, and MgO/Ag/Cu. Techniques used to deposit these buffer layers include electron beam evaporation, thermal evaporation, rf magnetron sputtering, pulsed laser deposition, metal-organic chemical vapor deposition (MOCVD), combustion CVD, and spray pyrolysis.

  15. Functional Mn–Mg{sub k} cation complexes in GaN featured by Raman spectroscopy

    SciTech Connect

    Devillers, T. Bonanni, A.; Leite, D. M. G.; Dias da Silva, J. H.

    2013-11-18

    The evolution of the optical branch in the Raman spectra of (Ga,Mn)N:Mg epitaxial layers as a function of the Mn and Mg concentrations, reveals the interplay between the two dopants. We demonstrate that the various Mn-Mg-induced vibrational modes can be understood in the picture of functional Mn–Mg{sub k} complexes formed when substitutional Mn cations are bound to k substitutional Mg through nitrogen atoms, the number of ligands k being driven by the ratio between the Mg and the Mn concentrations.

  16. Al-doped MgB2 materials studied using electron paramagnetic resonance and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Bateni, Ali; Erdem, Emre; Repp, Sergej; Weber, Stefan; Somer, Mehmet

    2016-05-01

    Undoped and aluminum (Al) doped magnesium diboride (MgB2) samples were synthesized using a high-temperature solid-state synthesis method. The microscopic defect structures of Al-doped MgB2 samples were systematically investigated using X-ray powder diffraction, Raman spectroscopy, and electron paramagnetic resonance. It was found that Mg-vacancies are responsible for defect-induced peculiarities in MgB2. Above a certain level of Al doping, enhanced conductive properties of MgB2 disappear due to filling of vacancies or trapping of Al in Mg-related vacancy sites.

  17. Mg3(VO4)2-MgO-ZrO2 nano-catalysts for oxidative dehydrogenation of n-butane.

    PubMed

    Lee, Jong Kwon; Seo, Hyun; Hong, Ung Gi; Yoo, Yeonshick; Cho, Young-Jin; Lee, Jinsuk; Park, Gle; Chang, Hosik; Song, In Kyu

    2014-11-01

    A series of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts with different vanadium content (X = 3.3, 5.3, 7.0, 10.2, and 13.4) were prepared by a single-step citric acid-derived sol-gel method for use in the oxidative dehydrogenation of n-butane to n-butene and 1,3-butadiene. The effect of vanadium content of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts on their physicochemical properties and catalytic activities in the oxidative dehydrogenation of n-butane was investigated. Successful formation of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts was confirmed by XRD, Raman spectroscopy, and ICP-AES analyses. The catalytic performance of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts strongly depended on vanadium content. All the X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts showed a stable catalytic performance without catalyst deactivation during the reaction. Among the catalysts tested, 7.0-Mg3(VO4)2-MgO-ZrO2 nano-catalyst showed the best catalytic performance in terms of yield for total dehydrogenation products (TDP, n-butene and 1,3-butadiene). TPRO (temperature-programmed reoxidation) experiments were carried out to measure the oxygen capacity of the catalyst. Experimental results revealed that oxygen capacity of the catalyst was closely related to the catalytic performance. Yield for TDP increased with increasing oxygen capacity of the catalyst. PMID:25958621

  18. Extraction of Mg(OH)2 from Mg silicate minerals with NaOH assisted with H2O: implications for CO2 capture from exhaust flue gas.

    PubMed

    Madeddu, Silvia; Priestnall, Michael; Godoy, Erik; Kumar, R Vasant; Raymahasay, Sugat; Evans, Michael; Wang, Ruofan; Manenye, Seabelo; Kinoshita, Hajime

    2015-01-01

    The utilisation of Mg(OH)2 to capture exhaust CO2 has been hindered by the limited availability of brucite, the Mg(OH)2 mineral in natural deposits. Our previous study demonstrated that Mg(OH)2 can be obtained from dunite, an ultramafic rock composed of Mg silicate minerals, in highly concentrated NaOH aqueous systems. However, the large quantity of NaOH consumed was considered an obstacle for the implementation of the technology. In the present study, Mg(OH)2 was extracted from dunite reacted in solid systems with NaOH assisted with H2O. The consumption of NaOH was reduced by 97% with respect to the NaOH aqueous systems, maintaining a comparable yield of Mg(OH)2 extraction, i.e. 64.8-66%. The capture of CO2 from a CO2-N2 gas mixture was tested at ambient conditions using a Mg(OH)2 aqueous slurry. Mg(OH)2 almost fully dissolved and reacted with dissolved CO2 by forming Mg(HCO3)2 which remained in equilibrium storing the CO2 in the aqueous solution. The CO2 balance of the process was assessed from the emissions derived from the power consumption for NaOH production and Mg(OH)2 extraction together with the CO2 captured by Mg(OH)2 derived from dunite. The process resulted as carbon neutral when dunite is reacted at 250 °C for durations of 1 and 3 hours and CO2 is captured as Mg(HCO3)2. PMID:26391815

  19. Interchangeability of two 500 mg amoxicillin capsules with one 1000 mg amoxicillin tablet after a single oral administration.

    PubMed

    Zaid, A N; Cortesi, R; Kort, J; Sweileh, W

    2010-07-01

    The aim of the study was to evaluate if two capsules (Amoxil(®) capsules, 500 mg/capsule) and one tablet (Amoxicare(®) tablets, 1000 mg/tablet) of amoxicillin have similar bioequivalence parameters. For this purpose a randomized, two-way, crossover, bioequivalence study was performed in 24 healthy, male volunteers, divided into two groups of 12 subjects each. One group was treated with the reference standard (Amoxil(®)) and the other one with the generic tablet Amoxicare(®), with a crossover after a wash-out period of 7 days. Blood samples were collected at fixed time intervals and amoxicillin was determined by a validated HPLC method. The pharmacokinetic parameters AUC(0-8), AUC(0-∞), C(max), T(max), K(e) and T(1/2) were determined for both formulations and statistically compared to evaluate the bioequivalence between the two brands of amoxicillin, using the statistical model recommended by the FDA. C(max) and AUC(0-∞) were statistically analyzed using analysis of variance (ANOVA); no statistically significant difference was observed between the two formulations. The 90% confidence intervals between the mean values of C(max) and AUC(0-∞) fall within the FDA specified bioequivalent limits (80-125%) suggesting that the two products are bioequivalent and the two formulations are interchangeable. Based on these findings it was concluded that the practice of interchangeability between the above formulations to achieve better patient compliance could be followed without compromising the extent of amoxicillin absorption. PMID:21218049

  20. Electrochemical Formation of Mg-Li-Sm Alloys by Codeposition from LiCl-KCl-MgCl2-SmCl3 Molten Salts

    NASA Astrophysics Data System (ADS)

    Han, Wei; Wang, Fengli; Tian, Yang; Zhang, Milin; Yan, Yongde

    2011-12-01

    In this article, the electrochemical method of preparing Mg-Li-Sm alloys by codeposition in LiCl-KCl-MgCl2-SmCl3 melts was investigated. Transient electrochemical techniques, such as cyclic voltammetry, chronopotentiometry, and chronoamperometry were used to explore the electrochemical formation of Mg-Li-Sm alloys. Chronopotentiograms demonstrated that the codepositon of Mg, Li, and Sm occurred when current densities were more negative than -0.31 A cm-2. Chronoamperograms indicated that the onset potential for the codeposition of Mg, Li, and Sm was -2.40 V, and the codeposition of Mg, Li, and Sm was formed when the applied potentials were more negative than -2.40 V. The different phases of Mg-Li-Sm alloys were prepared by galvanostatic electrolysis and characterized by X-ray diffraction (XRD), optical microscope (OM), and scanning electron microscopy (SEM). An inductively coupled plasma (ICP) analysis showed that the lithium and samarium contents in Mg-Li-Sm alloys could be controlled by the concentrations of MgCl2 and SmCl3. The results demonstrated that Sm could refine the grains dramatically. When the Sm content was 0.8 wt pct, the grain size was the finest.

  1. Cathodoluminescence study of Mg activation in non-polar and semi-polar faces of undoped/Mg-doped GaN core-shell nanorods

    NASA Astrophysics Data System (ADS)

    Hortelano, V.; Martínez, O.; Cuscó, R.; Artús, L.; Jiménez, J.

    2016-03-01

    Spectrally and spatially resolved cathodoluminescence (CL) measurements were carried out at 80 K on undoped/Mg-doped GaN core-shell nanorods grown by selective area growth metalorganic vapor phase epitaxy in order to investigate locally the optical activity of the Mg dopants. A study of the luminescence emission distribution over the different regions of the nanorods is presented. We have investigated the CL fingerprints of the Mg incorporation into the non-polar lateral prismatic facets and the semi-polar facets of the pyramidal tips. The amount of Mg incorporation/activation was varied by using several Mg/Ga flow ratios and post-growth annealing treatment. For lower Mg/Ga flow ratios, the annealed nanorods clearly display a donor-acceptor pair band emission peaking at 3.26-3.27 eV and up to 4 LO phonon replicas, which can be considered as a reliable indicator of effective p-type Mg doping in the nanorod shell. For higher Mg/Ga flow ratios, a substantial enhancement of the yellow luminescence emission as well as several emission subbands are observed, which suggests an increase of disorder and the presence of defects as a consequence of the excess Mg doping.

  2. In vitro and in vivo corrosion and histocompatibility of pure Mg and a Mg-6Zn alloy as urinary implants in rat model.

    PubMed

    Zhang, Shiying; Zheng, Yang; Zhang, Liming; Bi, Yanze; Li, Jianye; Liu, Jiao; Yu, Youbin; Guo, Heqing; Li, Yan

    2016-11-01

    Pure Mg and a Mg-6wt.% Zn alloy were investigated as potential candidates for biodegradable implants for the urinary system. The in vitro corrosion behavior was studied by potentiodynamic polarization and immersion tests in simulated body fluid (SBF) at 37°C. The in vivo degradation and histocompatibility were examined through implantation into the bladders of Wistar rats. The alloying element Zn elevated the passivation potential and increased the cathodic current density. Both in vitro and in vivo degradation tests showed a faster corrosion rate for the Mg-6Zn alloy. Tissues stained with hematoxylin and eosin (HE) suggested that both pure Mg and Mg-6Zn alloy exhibited good histocompatibility in the bladder indwelling implantation and no differences between pure Mg and Mg-6Zn groups were found in bladder, liver and kidney tissues during the 2weeks implantation. Overall, this work presented instructive information on the degradation properties and histocompatibility of pure Mg and the Mg-6Zn alloy in the urinary system. PMID:27524036

  3. Synthesis and characterization of the divalent samarium Zintl-phases SmMg2Bi2 and SmMg2Sb2

    NASA Astrophysics Data System (ADS)

    Ramirez, D.; Gallagher, A.; Baumbach, R.; Siegrist, T.

    2015-11-01

    Single crystals of LnMg2Bi2 (Ln=Yb, Eu, Sm) and SmMg2Sb2 were synthesized using Mg-Bi metal and Mg-Sb metal fluxes, respectively. The crystal structures are of the CaAl2Si2 type with space group P 3 ̅m1 (#164, Z=1): SmMg2Bi2 (a=4.7745(1) Å, c=7.8490(2) Å), EuMg2Bi2 (a=4.7702(1) Å, c=7.8457(2) Å), YbMg2Bi2 (a=4.7317(2) Å, c=7.6524(3) Å), and SmMg2Sb2 (a=4.6861(1) Å, c=7.7192(2) Å). Heat capacity, electrical transport, and magnetization of all bismuth containing phases were measured. The materials behave as "poor metals" with resistivity between 2 and 10 mΩ cm. Temperature independent Van Vleck paramagnetism is observed in SmMg2Bi2 indicative of divalent samarium (Sm2+) ions.

  4. Comparative studies on radioluminescent and thermoluminescent spectra of LiF:Mg,Cu,P and LiF:Mg,Cu,Si.

    PubMed

    Tang, K; Fan, H; Cui, H; Zhu, H; Liu, Z

    2016-03-01

    The influence of various annealing treatments on radioluminescent (RL) and thermoluminescent (TL) spectra of LiF:Mg,Cu,Si and LiF:Mg,Cu,P was investigated. The TL and RL emission bands for LiF:Mg,Cu,P are not the same; however, the emission band peaking at ∼383 nm is predominant in the TL and RL emission for LiF:Mg,Cu,Si. With the increase in annealing temperatures in the range of 240-300°C, for LiF:Mg,Cu,P, the intensity of TL decreases much more rapidly than that of RL. For LiF:Mg,Cu,Si, the area ratios of the two bands of RL and TL remain constant within experimental errors. It suggests that there is a significant decrease in the concentration of recombination centres in LiF:Mg,Cu,P after the annealing, in addition to the decrease in trapping centres, the recombination centres for main TL emission and RL emission in LiF:Mg,Cu,Si are the same, and the recombination centres for TL emission and RL emission in LiF:Mg,Cu,P are not the same. P is a more effective dopant than Si. PMID:26264711

  5. Enhanced bioactivity of Mg-Nd-Zn-Zr alloy achieved with nanoscale MgF2 surface for vascular stent application.

    PubMed

    Mao, Lin; Shen, Li; Chen, Jiahui; Wu, Yu; Kwak, Minsuk; Lu, Yao; Xue, Qiong; Pei, Jia; Zhang, Lei; Yuan, Guangyin; Fan, Rong; Ge, Junbo; Ding, Wenjiang

    2015-03-11

    Magnesium (Mg) alloys have revolutionized the application of temporary load-bearing implants as they meet both engineering and medical requirements. However, rapid degradation of Mg alloys under physiological conditions remains the major obstacle hindering the wider use of Mg-based implants. Here we developed a simple method of preparing a nanoscale MgF2 film on Mg-Nd-Zn-Zr (denoted as JDBM) alloy, aiming to reduce the corrosion rate as well as improve the biological response. The corrosion rate of JDBM alloy exposed to artificial plasma is reduced by ∼20% from 0.337 ± 0.021 to 0.269 ± 0.043 mm·y(-1) due to the protective effect of the MgF2 film with a uniform and dense physical structure. The in vitro cytocompatibility test of MgF2-coated JDBM using human umbilical vein endothelial cells indicates enhanced viability, growth, and proliferation as compared to the naked substrate, and the MgF2 film with a nanoscale flakelike feature of ∼200-300 nm presents a much more favorable environment for endothelial cell adhesion, proliferation, and alignment. Furthermore, the animal experiment via implantation of MgF2-coated JDBM stent to rabbit abdominal aorta confirms excellent tissue compatibility of the well re-endothelialized stent with no sign of thrombogenesis and restenosis in the stented vessel. PMID:25705919

  6. Structural, Electronic and Elastic Properties of MgH2, CaH2 and Ca4Mg3H14 for Hydrogen Storage Materials

    NASA Astrophysics Data System (ADS)

    Djellab, Sihem; Bouhadda, Youcef; Bououdina, Mohamed; Fenineche, Noureddine; Boudouma, Youcef

    2016-08-01

    The structural, electronic and elastic properties of MgH2, CaH2 and Ca4Mg3H14 have been determined using first principles calculation based on density functional theory. The calculated lattice constants were in good agreement with the experimental values. The electronic density of states revealed that these hydrides are insulators. The calculated elastic constants of MgH2, CaH2 and Ca4Mg3H14 indicated that these hydrides are mechanically stable at zero pressure. The bulk modulus B, shear modulus G, Young's modulus E, and Poisson's ratio ν were derived, and the ductility was discussed.

  7. Preparation and characterization of thin films of MgO, Al2O3 and MgAl2O4 by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Huang, Ron; Kitai, Adrian H.

    1993-02-01

    MgO, Al2O3 and MgAl2O4 thin films were deposited on silicon substrates at various temperatures by the atomic layer deposition (ALD) method using bis(cyclopentadienyl)magnesium, triethylaluminum, and H2O and were characterized systematically. High-quality polycrystalline MgO films were deposited for a substrate temperature above 500°C, and amorphous thin films were deposited around 400°C. The deposited Al2O3 and MgAl2O4 thin films were characterized as amorphous in structure. Applicability of ALD to complex oxides is discussed.

  8. Polytypism in wagnerite, Mg2PO4(F,OH)

    NASA Astrophysics Data System (ADS)

    Chopin, C.; Armbruster, T.; Leyx, C.

    2003-04-01

    The Mg, Fe and Mn phosphates with formula Me2+_2PO_4(F,OH) belong to two groups which share the same fundamental monoclinic structure type, but in one of which the b parameter is doubled. Specifically, magniotriplite (Mg), zwieselite (Fe) and triplite (Mn) are F-dominant and have space group I2/a, with Z = 8, b_0 ≈ 6.5 Å, whereas wagnerite (Mg, F dominant), wolfeite (Fe, OH dominant) and triploidite (Mn, OH dominant) have space group P2_1/a, Z = 16 and b = 2 b_0 ≈ 13 Å. In I2/a magniotriplite, eight F atoms are distributed over two eightfold equipoints with 50% occupancy. Periodic ordering of the F atoms into each of these equipoint positions (say A and B), each alternately void and fully occupied along b, leads to a new, double cell with space group P2_1/a and a 2b_0 parameter, i.e. the wagnerite cell, in which the succession of the occupied F positions along b is ABAB (Tadini 1981). Ren et al. (2002) reported from granulite-facies rocks of East Antarctica a wagnerite "polymorph" structurally very close to wagnerite, but with space group Ia, b = 5b_0 ≈ 32 Å and Z = 40. We studied wagnerite crystals from granulite-facies rocks of central Australia (Vry and Cartwright 1994). CCD area-detector imaging revealed either 7b_0 ≈ 45 Å or 9b_0 ≈ 57 Å superstructures (Z = 56 and 72, respectively). The structure of the 9b_0 phase was refined in space group Ia to R = 6% from 11903 unique reflections. We show that wagnerite and the 5b_0, 7b_0 and 9b_0 phases share the same topological arrangement of cations and oxygen atoms, differ only by the periodic faulting of the A-B succession of the F atoms along b, and are all members of a polytypic series based on the magniotriplite cell (b_0). The relevant polytypes and F ordering schemes are wagnerite-a2bc (AB), wagnerite-a5bc (ABAAB), wagnerite-a7bc (ABAABAB) and wagnerite-a9bc (ABAABABAB). Reinvestigation of OH-rich wagnerite from Miregn (Central Alps) and of OH-rich to OH-dominant wagnerite from Dora-Maira (W. Alps

  9. Microstructures and Thermal Properties of Mg-Sn-Ca Alloys: Casts and Extrusions

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Han; Choi, Jeong-Won; Kim, Yong-Ho; Yoo, Hyo-Sang; Woo, Kee-Do; Lee, Seong-Hee; Son, Hyeon-Taek

    2015-11-01

    Microstructure and thermal properties of Mg-(3 mass% or 5 mass%) Sn-2 mass% Ca alloys as casts and extrusions have been investigated with different ram speeds and extrusion temperatures. Mg-(3 mass% or 5 mass%) Sn-2 mass% Ca alloys are composed of \\upalpha -Mg, MgSnCa, and {Mg}2{Ca} phases. By adding Sn content from 3 mass% to 5 mass%, the MgSnCa phase is increased and the {Mg}2{Ca} phase is decreased. During hot extrusion, the average grain sizes are increased with increasing ram speed and temperature. The ultimate tensile strength ( UTS) and elongation for the Mg-5Sn-2Ca alloy at 2.3 {mm}{\\cdot }{s}^{-1} are 227.73 MPa and 18.43 %, respectively. With increasing extrusion ram speed, the UTS and elongation for the Mg-5Sn-2Ca alloy are remarkably decreased to 215.95 MPa, 206.33 MPa, and 14.74 %, 6.88 %, respectively. The thermal conductivity for the Mg-3Sn-2Ca alloy is dramatically improved, compared to commercialized Mg alloys such as AZ31 and AZ91 due to formation of MgSnCa and {Mg}2{Ca} phases.

  10. Enhanced Glucose 6-Phosphatase Activity in Liver of Rats Exposed to Mg2+-Deficient Diet

    PubMed Central

    Barfell, Andrew; Crumbly, Ashlee; Romani, Andrea

    2011-01-01

    Total hepatic Mg2+ content decreases by >25% in animals maintained for two weeks on Mg2+ deficient diet, and results in a >25% increase in glucose 6-phosphatase (G6Pase) activity in isolated liver microsomes in the absence of significant changed in enzyme expression. Incubation of Mg2+-deficient microsomes in the presence of 1mM external Mg2+ returned G6Pase activity to levels measured in microsomes from animals on normal Mg2+ diet. EDTA addition dynamically reversed the Mg2+ effect. The effect of Mg2+ or EDTA persisted in taurocholic acid permeabilized microsomes. An increase in G6Pase activity was also observed in liver microsomes from rats starved overnight, which presented a ~15% decrease in hepatic Mg2+ content. In this model, G6Pase activity increased to a lesser extent than in Mg2+-deficient microsomes, but it could still be dynamically modulated by addition of Mg2+ or EDTA. Our results indicate that 1) hepatic Mg2+ content rapidly decreases following starvation or exposure to deficient diet, and 2) the loss of Mg2+ stimulates G6P transport and hydrolysis as a possible compensatory mechanism to enhance intrahepatic glucose availability. The Mg2+ effect appears to take place at the level of the substrate binding site of the G6Pase enzymatic complex or the surrounding phospholipid environment. PMID:21402051

  11. Behavior of mammalian cells on magnesium substituted bare and hydroxyapatite deposited (Ti,Mg)N coatings.

    PubMed

    Onder, Sakip; Calikoglu-Koyuncu, Ayse Ceren; Kazmanli, Kursat; Urgen, Mustafa; Torun Kose, Gamze; Kok, Fatma Nese

    2015-12-25

    TiN and (Ti,Mg)N thin film coatings were deposited on titanium substrates by using cathodic arc physical vapor deposition (arc-PVD) technique with magnesium contents of 0, 4.24 at% (low Mg) and 10.42 at% (high Mg). The presence of magnesium on both normal (hFOB) and cancer (SaOS-2) osteoblast cell behavior was investigated in (Ti,Mg)N surfaces with or without prior hydroxyapatite (HA) deposition (in simulated body fluid, SBF). Mg incorporation on TiN films was found to have no apparent effect on the cell proliferation in bare surfaces but cell spreading was better on low Mg content surface for hFOB cells. SaOS-2 cells, on the other hand, showed an increased extra cellular matrix (ECM) deposition on low Mg surfaces but ECM deposition almost disappeared when Mg content was increased above 10 at%. HA deposited surfaces with high Mg content was shown to cause a significant decrease in cell viability. While the cells were flattened, elongated and spread over the surface in contact with each other via cellular extensions on unmodified and low Mg doped surfaces, unhealthy morphologies of cells with round shape with a limited number of extended arms was visualized on high Mg containing samples. In summary, Mg incorporation into the TiN coatings by arc-PVD technique and successive HA deposition led to promising cell responses on low Mg content surfaces for a better osteointegration performance. PMID:25556119

  12. MgB2: Novel properties due to multibands

    NASA Astrophysics Data System (ADS)

    Blumberg, Girsh

    2008-03-01

    About 40 years ago A.J. Leggett proposed a new collective mode arising from cross-tunneling of Cooper pairs residing on different Fermi surfaces of a multiband superconductor: Leggett's collective mode is caused by a counter flow of the interacting superfluids leading to small fluctuations of the relative phase of the condensates while the total electron density is locally conserved.ootnotetextA.J. Leggett, Progr. Theor. Phys. 36, 901 (1966). Here we present direct spectroscopic observation of the Leggett's excitation in the MgB2 superconductor containig two pairs of Fermi surfaces resulting from π- and σ-bands. Electronic Raman scattering studies have revealed three distinct superconducting (SC) features: (i) a clean threshold of Raman intensity at 4.6 meV consistent with the π-band SC gap; (ii) the SC pair breaking coherence peak at 13.5 meV consistent with excitations above the σ-band gap; and (iii) the SC collective mode at 9.4 meV which we assign to an excitation first discussed by Leggett.ootnotetextG. Blumberg et al., Phys. Rev. Lett. 99 (2007); arXiv:0710.2803http://arxiv.org/pdf/0710.2803. Our calculation of the Raman response function for MgB2 superconductor based on multiband interaction matrices by first principle computations show good agreement with spectroscopic observations. The temperature and field dependencies for all three features (i) -- (iii) have been established;ootnotetextG. Blumberg et al., Physica (Amsterdam) 456C, 75 (2007). the effects of magnetic field on the pair cross-tunneling in multiband system will be discussed. In addition, anharmonicity and superconductivity-induced self-energy effects for the E2g boron stretching phonon have been studied.ootnotetextA. Mialitsin et al., Phys. Rev. B 75, 020509(R) (2007). We show that anharmonic two-phonon decay is mainly responsible for the unusually large linewidth of the E2g mode. We observe 2.5% hardening of the E2g phonon frequency upon cooling into the SC state and estimate the

  13. Biodegradable Magnesium (Mg) Implantation Does Not Impose Related Metabolic Disorders in Rats with Chronic Renal Failure

    NASA Astrophysics Data System (ADS)

    Wang, Jiali; Xu, Jiankun; Liu, Waiching; Li, Yangde; Qin, Ling

    2016-05-01

    Mg and its alloys have been considered as one of the most promising biodegradable medical devices, but it was still unclear whether hypermagnesemia involved health risks would occur in persons with kidney disease due to their deteriorated kidney function for Mg ions excretion from their body. In this study, we established a chronic renal failure (CRF) model in rats induced by adenine administration prior to Mg implantation, aiming to predict if CRF patients are suitable for the use of Mg implants. The results showed that Mg levels in serum, urine, feces and internal organs had no significant changes after Mg implantation for both normal and CRF rats. Biochemical indices detection and histopathological analysis in kidney, liver and heart tissue confirmed that Mg implants did not induce any extra damage in animals even with renal failure. Our study indicates that Mg based orthopaedic medical device may be considered for use in CRF patients without biosafety concerns.

  14. Biodegradability engineering of biodegradable Mg alloys: Tailoring the electrochemical properties and microstructure of constituent phases

    NASA Astrophysics Data System (ADS)

    Cha, Pil-Ryung; Han, Hyung-Seop; Yang, Gui-Fu; Kim, Yu-Chan; Hong, Ki-Ha; Lee, Seung-Cheol; Jung, Jae-Young; Ahn, Jae-Pyeong; Kim, Young-Yul; Cho, Sung-Youn; Byun, Ji Young; Lee, Kang-Sik; Yang, Seok-Jo; Seok, Hyun-Kwang

    2013-08-01

    Crystalline Mg-based alloys with a distinct reduction in hydrogen evolution were prepared through both electrochemical and microstructural engineering of the constituent phases. The addition of Zn to Mg-Ca alloy modified the corrosion potentials of two constituent phases (Mg + Mg2Ca), which prevented the formation of a galvanic circuit and achieved a comparable corrosion rate to high purity Mg. Furthermore, effective grain refinement induced by the extrusion allowed the achievement of much lower corrosion rate than high purity Mg. Animal studies confirmed the large reduction in hydrogen evolution and revealed good tissue compatibility with increased bone deposition around the newly developed Mg alloy implants. Thus, high strength Mg-Ca-Zn alloys with medically acceptable corrosion rate were developed and showed great potential for use in a new generation of biodegradable implants.

  15. Investigating the behaviour of Mg isotopes during the formation of clay minerals

    NASA Astrophysics Data System (ADS)

    Wimpenny, Joshua; Colla, Christopher A.; Yin, Qing-Zhu; Rustad, James R.; Casey, William H.

    2014-03-01

    We present elemental and isotopic data detailing how the Mg isotope system behaves in natural and experimentally synthesized clay minerals. We show that the bulk Mg isotopic composition (δ26Mg) of a set of natural illite, montmorillonite and kaolinite spans a 2‰ range, and that their isotopic composition depends strongly on a balance between the relative proportions of structural and exchangeable Mg. After acid leaching, these natural clays become relatively enriched in isotopically heavy Mg by between 0.2‰ and 1.6‰. Results of exchange experiments indicate that the Mg that has adsorbed to interlayer spaces and surface charged sites is relatively enriched in isotopically light Mg compared to the residual clay. The isotopic composition of this exchangeable Mg (-1.49‰ to -2.03‰) is characteristic of the isotopic composition of Mg found in many natural waters. Further experiments with an isotopically characterized MgCl2 solution shows that the clay minerals adsorb this exchangeable Mg with little or no isotopic fractionation, although we cannot discount the possibility that the uptake of exchangeable Mg does so with a slight preference for 24Mg. To characterize the behaviour of Mg isotopes during clay mineral formation we synthesized brucite (Mg(OH)2), which we consider to be a good analogue for the incorporation of Mg into the octahedral sheet of Mg-rich clay minerals or into the brucitic layer of clays such as chlorite. In our experiment the brucite mineral becomes enriched in the heavy isotopes of Mg while the corresponding solution is always relatively enriched in isotopically light Mg. The system reaches a steady state after 10 days with a final fractionation factor (αsolid-solution) of 1.0005 at near-neutral pH. This result is consistent with the general consensus that secondary clay minerals preferentially take up isotopically heavy Mg during their formation. However our results also show that exchangeable Mg is an important component within bulk

  16. Biodegradable Magnesium (Mg) Implantation Does Not Impose Related Metabolic Disorders in Rats with Chronic Renal Failure.

    PubMed

    Wang, Jiali; Xu, Jiankun; Liu, Waiching; Li, Yangde; Qin, Ling

    2016-01-01

    Mg and its alloys have been considered as one of the most promising biodegradable medical devices, but it was still unclear whether hypermagnesemia involved health risks would occur in persons with kidney disease due to their deteriorated kidney function for Mg ions excretion from their body. In this study, we established a chronic renal failure (CRF) model in rats induced by adenine administration prior to Mg implantation, aiming to predict if CRF patients are suitable for the use of Mg implants. The results showed that Mg levels in serum, urine, feces and internal organs had no significant changes after Mg implantation for both normal and CRF rats. Biochemical indices detection and histopathological analysis in kidney, liver and heart tissue confirmed that Mg implants did not induce any extra damage in animals even with renal failure. Our study indicates that Mg based orthopaedic medical device may be considered for use in CRF patients without biosafety concerns. PMID:27210744

  17. Biodegradable Magnesium (Mg) Implantation Does Not Impose Related Metabolic Disorders in Rats with Chronic Renal Failure

    PubMed Central

    Wang, Jiali; Xu, Jiankun; Liu, Waiching; Li, Yangde; Qin, Ling

    2016-01-01

    Mg and its alloys have been considered as one of the most promising biodegradable medical devices, but it was still unclear whether hypermagnesemia involved health risks would occur in persons with kidney disease due to their deteriorated kidney function for Mg ions excretion from their body. In this study, we established a chronic renal failure (CRF) model in rats induced by adenine administration prior to Mg implantation, aiming to predict if CRF patients are suitable for the use of Mg implants. The results showed that Mg levels in serum, urine, feces and internal organs had no significant changes after Mg implantation for both normal and CRF rats. Biochemical indices detection and histopathological analysis in kidney, liver and heart tissue confirmed that Mg implants did not induce any extra damage in animals even with renal failure. Our study indicates that Mg based orthopaedic medical device may be considered for use in CRF patients without biosafety concerns. PMID:27210744

  18. Ames test mutagenicity studies of the subfractions of the mild gasification composite material, MG-120

    SciTech Connect

    Not Available

    1992-04-17

    Mutagenicity of six mild gasification product samples was studied using the Ames Salmonella/microsomal assay system. The results of the Ames testing of the MG-119 and MG-120 subfractions indicate significant mutagenic activity only in the nonpolar neutral fraction. The activity was evident on bacterial strains, TA98 and TA100, with and without metabolic activation for MG-120, and with metabolic activation for MG-119. Previous testing of MG-119 and MG-120 when solvated in DMSO had shown possible, but unconfirmable, mutagenic activity. Tween 80-solvated MG-119 and MG-120 showed low, but significant, mutagenic activity only on TA98 with metabolic activation. Comparison of these results indicate an inhibition of the mutagenic components by nonmutagenic components in the complex mixture. 4 refs., 2 tabs.

  19. Dielectric behavior of MgO:Li/sup +/ crystals

    SciTech Connect

    Puma, M.; Lorincz, A.; Andrews, J.F.; Crawford, J.H Jr.

    1980-01-01

    Measurements of the dielectric constant in crystals of MgO doped with Li/sup +/ ions have been carried out after quenching from anneals at 1300/sup 0/C in static air. Prior to heat treatment the crystals showed no discernible dielectric loss but afterwards the loss tangent exceeded 0.4. For 10 min anneals the dielectric relaxation is very close to a Debye process and the temperature dependence of the maximum of the loss peak corresponds to an activation energy of 0.72 eV. When plotted in the form of a Cole-Cole arc the data indicate that deviation from a Debye relaxation amounts to a distribution of relaxation time no greater than that which can be accounted for with a distribution of activation energies only 0.007 eV. For longer heating times overlapping relaxation processes appear. The lack of broadening of the loss peak and the magnitude of the relaxation time yield clues as to possible loss mechanisms.

  20. Dielectric behavior of MgO:Li/sup +/ crystals

    SciTech Connect

    Puma, M.; Lorincz, A.; Andrews, J.F.; Crawford, J.H. Jr.

    1982-06-01

    Measurements of the dielectric constant in crystals of MgO doped with Li/sup +/ ions have been carried out after quenching from anneals at 1300 /sup 0/C in static air. Prior to heat treatment, the crystals showed no discernible dielectric loss, but afterwards, the loss tangent exceeded 0.4. For 10-min anneals, the dielectric relaxation is very close to a Debye process, and the temperature dependence of the maximum of the loss peak corresponds to an activation energy of 0.724 eV. When plotted in the form of a Cole-Cole arc, the data indicate that deviation from a Debye relaxation amounts to a distribution of relaxation time no greater than that which can be accounted for with a distribution of activation energies of only 0.007 eV. For longer heating times, overlapping relaxation processes appear. The lack of broadening of the loss peak, and the magnitude of the relaxation time, yield clues as to possible loss mechanisms.

  1. Covalence and ionicity in MgAgAs-type compounds.

    PubMed

    Bende, David; Grin, Yuri; Wagner, Frank R

    2014-07-28

    MgAgAs-type "half-Heusler" compounds are known to realize two out of three possible atomic arrangements of this structure type. The number of transition metal components typically determines which of the alternatives is favored. On the basis of DFT calculations for all three variants of 20 eight- and eighteen-valence-electron compounds, the experimentally observed structural variant was found to be determined by basically two different bonding patterns. They are quantified by employing two complementary position-space bonding measures. The Madelung energy E((M)(QTAIM)) calculated with the QTAIM effective charges reflects contributions of the ionic interactions to the total energy. The sum of nearest-neighbor delocalization indices ςnn characterizes the covalent interactions through electron sharing. With the aid of these quantities, the energetic sequence of the three atomic arrangements for each compound is rationalized. The resulting systematic is used to predict a scenario in which an untypical atomic arrangement becomes most favorable. PMID:24990108

  2. Microencapsulation of Mg-Ni hydrogen storage alloy

    SciTech Connect

    Akiyama, Tomohiro; Fukutani, Takashi; Ohta, Hiromichi; Takahashi, Reijiro; Yagi, Junichiro; Waseda, Yoshio

    1995-05-01

    Metal-hydrogen systems are currently used in a heat storage and other applications; however, some difficulties still exist in the actual process. It is well-known that hydrogen storage alloys, particularly powders, have very poor thermal conductivity and disintegrate into a very fine powder easily with the repeated cycling of hydrogen charging and discharging. Ishikawa et al. (1985) proposed a copper microencapsulation method for hydrogen storage alloy. With this method, powder was coated in a thin layer of copper by a plating technique. They showed that the compacts obtained by this method have enough strength without the loss of storage capacity, although they have been compressed at room temperature. However, data on both thermal property and kinetics of the Cu-micro-encapsulated hydrogen storage alloy is needed for predicting temperature distribution in the heat storage unit where simultaneous hydrogen and heat transfer occurs. In this article, an experimental study of thermal conductivity, diffusivity and dehydrating rate of Mg-Ni hydrogen storage alloy is described, in which a main attempt was made to assess the effect of Cu-encapsulation on them.

  3. Transition probabilities and radiative lifetimes of Mg III

    NASA Astrophysics Data System (ADS)

    Alonso-Medina, A.; Colón, C.; Moreno-Díaz, C.

    2015-03-01

    There have been calculated transition probabilities for 365 lines arising from 2p5 n s(n = 3 , 4 , 5) , 2p5 n p(n = 3 , 4) , 2p5 n d(n = 3 , 4) , 2p5 n f(n = 4 , 5) and 2p5 5g configurations of Mg III and radiative lifetimes corresponding to 89 levels. These values were obtained in intermediate coupling (IC) by using ab initio relativistic Hartree-Fock (HFR) calculations. Later, we use the standard method of least square fitting of experimental energy levels for the IC calculations by means of Cowan's computer codes. The vast majority of the calculated transition probabilities correspond to lines lying in the ultraviolet range (UV) which are of high interest in astrophysics. Our results are compared to those previously reported in the literature. Furthermore, the values of transition probabilities of configuration levels 2p5 4d, 2p5 n f(n = 4 , 5) and 2p5 5g are presented for the first time. In light of these findings, it is possible to extend the range of wavelengths which allows us to estimate the temperature in plasma diagnostic. In addition, our results for radiative lifetimes have been compared to the available experimental values.

  4. Lightweight MgB2 superconducting 10 MW wind generator

    NASA Astrophysics Data System (ADS)

    Marino, I.; Pujana, A.; Sarmiento, G.; Sanz, S.; Merino, J. M.; Tropeano, M.; Sun, J.; Canosa, T.

    2016-02-01

    The offshore wind market demands a higher power rate and more reliable turbines in order to optimize capital and operational costs. The state-of-the-art shows that both geared and direct-drive conventional generators are difficult to scale up to 10 MW and beyond due to their huge size and weight. Superconducting direct-drive wind generators are considered a promising solution to achieve lighter weight machines. This work presents an innovative 10 MW 8.1 rpm direct-drive partial superconducting generator using MgB2 wire for the field coils. It has a warm iron rotor configuration with the superconducting coils working at 20 K while the rotor core and the armature are at ambient temperature. A cooling system based on cryocoolers installed in the rotor extracts the heat from the superconducting coils by conduction. The generator's main parameters are compared against a permanent magnet reference machine, showing a significant weight and size reduction. The 10 MW superconducting generator concept will be experimentally validated with a small-scale magnetic machine, which has innovative components such as superconducting coils, modular cryostats and cooling systems, and will have similar size and characteristics as the 10 MW generator.

  5. Polarimetry in the MG II H and K lines

    NASA Astrophysics Data System (ADS)

    Henze, W.; Stenflo, J. O.

    1987-09-01

    The Ultraviolet Spectrometer and Polarimeter (UVSP) on the SMM satellite has been used to record the linear polarization profile across the Mg II h and k lines, including its center-to-limb variation. Linear polarization with an orientation of the electric vector parallel to the solar limb is detected in the line wings on the short wavelength side of the k line and on the long wavelength side of the h line, in agreement with theoretical predictions of Auer et al. (1980). The predicted negative polarization (electric vector perpendicular to the limb) between the h and k lines is however not confirmed by the observations. Instead values close to zero are indicated there, although the statistical significance of the results is marginal. Possible explanations of such a discrepancy between theory and observations are examined. After having rejected other alternatives (e.g., opacity effects, different continuum polarization, or deviations from a plane-parallel stratification), it is suggested that the solution may be found in a treatment of partial redistribution of the polarized radiation with the quantum-mechanical interference between the two scattering transitions being included as an integral part of the redistribution problem.

  6. Residual edema evaluation with ranibizumab 0.5 mg and 2.0 mg formulations for diabetic macular edema (REEF study)

    PubMed Central

    Dhoot, D S; Pieramici, D J; Nasir, M; Castellarin, A A; Couvillion, S; See, R F; Steinle, N; Bennett, M; Rabena, M; Avery, R L

    2015-01-01

    Purpose To compare the efficacy of ranibizumab 0.5-mg and 2.0-mg intravitreal injections for persistent diabetic macular edema (DME) previously treated with bevacizumab. Methods In all, 43 patients with residual center-involved DME following intravitreal bevacizumab were included in this 12-month prospective, nonrandomized, multicenter study. Enrolled patients received three monthly ranibizumab 0.5-mg injections. At month 3, patients with residual macular edema switched to three monthly injections of ranibizumab 2.0-mg. Assessments included monthly visual acuity and spectral-domain optical coherence tomography. Results Mean visual acuity improved by +6.4 letters at month 3 and +8.8 letters at month 6. Mean central subfield thickness (CST) decreased by –113 μm at month 3 and –165 μm at month 6. Before enrollment, 29/43 (67.4%) patients showed <10% CST reduction following monthly bevacizumab treatment. After three monthly ranibizumab 0.5-mg injections, 22/29 (75.9%) patients showed >10% reduction in CST, whereas 6 showed <10% reduction. Of these six, three (50%) showed >10% reduction in CST after switching to three monthly ranibizumab 2.0-mg doses. No serious adverse events were observed to month 6. Conclusion Ranibizumab 0.5-mg or 2.0-mg may improve visual and anatomic outcomes in patients with DME who demonstrated minimal or no response to bevacizumab therapy. Moreover, increased dosage of ranibizumab (2.0-mg) may provide additional benefit over ranibizumab 0.5-mg in some patients. However, 2.0-mg ranibizumab is not currently commercially licensed or available. PMID:25633882

  7. Synthesis of Na2Mg3X2 (X = Sn, Pb) and Na4Mg4Sn3 and their crystal structures and thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Yamada, Takahiro; Ishiyama, Ryo; Yamane, Hisanori

    2015-07-01

    Novel ternary stannides and a plumbide, Na2Mg3X2 (X = Sn, Pb) and Na4Mg4Sn3, were synthesized by heating the corresponding elements. The crystal structures were determined by single-crystal X-ray diffraction analysis, and the electrical conductivities and Seebeck coefficients were measured. The crystal structures of Na2Mg3X2 [orthorhombic, a = 7.3066(9) Å, b = 14.4559(13) Å, c = 6.6433(7) Å for X = Sn, a = 7.4272(11), b = 14.770(3), c = 6.6852(11) Å for X = Pb] are based on the Mg5Ga2-type structure (space group Ibam, Z = 4). Na4Mg4Sn3 crystallizes in an orthorhombic cell [a = 6.879(3) Å, b = 7.154(2) Å, c = 22.285(7) Å, space group Fmmm, Z = 4] with layers of disordered Na atom arrangement with defects. The electrical conductivities measured for the polycrystalline sintered samples of Na2Mg3Sn2, Na4Mg4Sn3, and Na2Mg3Pb2 were 1.9 × 105 S m-1 at 300 K, 1.6 × 105 S m-1 at 307 K and 3.3 × 105 S m-1 at 300 K, respectively. The Seebeck coefficients (S) of Na2Mg3Sn2, Na4Mg4Sn3, and Na2Mg3Pb2 were +47 to +72, +29 to +67, and +10 to +24 µV K-1, respectively, and increased with increasing temperature of 300-600 K.

  8. Interplay of Mg2+, ADP, and ATP in the cytosol and mitochondria: Unravelling the role of Mg2+ in cell respiration

    PubMed Central

    Gout, Elisabeth; Rébeillé, Fabrice; Douce, Roland; Bligny, Richard

    2014-01-01

    In animal and plant cells, the ATP/ADP ratio and/or energy charge are generally considered key parameters regulating metabolism and respiration. The major alternative issue of whether the cytosolic and mitochondrial concentrations of ADP and ATP directly mediate cell respiration remains unclear, however. In addition, because only free nucleotides are exchanged by the mitochondrial ADP/ATP carrier, whereas MgADP is the substrate of ATP synthase (EC 3.6.3.14), the cytosolic and mitochondrial Mg2+ concentrations must be considered as well. Here we developed in vivo/in vitro techniques using 31P-NMR spectroscopy to simultaneously measure these key components in subcellular compartments. We show that heterotrophic sycamore (Acer pseudoplatanus L.) cells incubated in various nutrient media contain low, stable cytosolic ADP and Mg2+ concentrations, unlike ATP. ADP is mainly free in the cytosol, but complexed by Mg2+ in the mitochondrial matrix, where [Mg2+] is tenfold higher. In contrast, owing to a much higher affinity for Mg2+, ATP is mostly complexed by Mg2+ in both compartments. Mg2+ starvation used to alter cytosolic and mitochondrial [Mg2+] reversibly increases free nucleotide concentration in the cytosol and matrix, enhances ADP at the expense of ATP, decreases coupled respiration, and stops cell growth. We conclude that the cytosolic ADP concentration, and not ATP, ATP/ADP ratio, or energy charge, controls the respiration of plant cells. The Mg2+ concentration, remarkably constant and low in the cytosol and tenfold higher in the matrix, mediates ADP/ATP exchange between the cytosol and matrix, [MgADP]-dependent mitochondrial ATP synthase activity, and cytosolic free ADP homeostasis. PMID:25313036

  9. Solidification Paths and Phase Components at High Temperatures of High-Zn Al-Zn-Mg-Cu Alloys with Different Mg and Cu Contents

    NASA Astrophysics Data System (ADS)

    Shu, W. X.; Hou, L. G.; Liu, J. C.; Zhang, C.; Zhang, F.; Liu, J. T.; Zhuang, L. Z.; Zhang, J. S.

    2015-11-01

    Studies were carried out systematically on a series of Al-8.5 wt pct Zn- xMg- yCu alloys ( x is about 1.5, 2.0, and 2.5 wt pct, and y is about 1.5, 2.0, 2.5, and 2.9 wt pct). The effects of alloying elements Mg and Cu on the microstructures of as-cast and homogenized alloys were investigated using the computational/experimental approach. It shows that Mg(Zn,Al,Cu)2 ( σ) phase can exist in all the as-cast alloys without any observable Mg32(Al,Zn)49/Al2Mg3Zn3 ( T) or Al2CuMg ( S) phase, whereas Al2Cu ( θ) phase is prone to exist in the alloys with low Mg and high Cu contents. Thermodynamic calculation shows that the real solidification paths of the designed alloys fall in between the Scheil and the equilibrium conditions, and close to the former. After the long-time homogenization [733 K (460 °C)/168 hours] and the two-step homogenization [733 K (460 °C)/24 hours + 748 K (475 °C)/24 hours], the phase components of the designed alloys are generally consistent with the calculated phase diagrams. At 733 K (460 °C), the phase components in the thermodynamic equilibrium state are greatly influenced by Mg content, and the alloys with low Mg content are more likely to be in single-Al phase field even if the alloys contain high Cu content. At 748 K (475 °C), the dissolution of the second phases is more effective, and the phase components in the thermodynamic equilibrium state are dominated primarily by (Mg + Cu) content, except the alloys with (Mg + Cu) ≳ 4.35 wt pct, all designed alloys are in single-Al phase field.

  10. Strengthening and toughening of poly(L-lactide) composites by surface modified MgO whiskers

    NASA Astrophysics Data System (ADS)

    Wen, Wei; Luo, Binghong; Qin, Xiaopeng; Li, Cairong; Liu, Mingxian; Ding, Shan; Zhou, Changren

    2015-03-01

    To improve both the strength and toughness of poly(L-lactide) (PLLA), fibrous-like MgO whiskers with diameters of 0.15-1 μm and lengths of 15-110 μm were prepared, and subsequently surface modified with L-lactide to obtain grafted MgO whiskers (g-MgO whiskers). The structures and properties of MgO whiskers and g-MgO whiskers were studied. Then, a series of MgO whiskers/PLLA and g-MgO whiskers/PLLA composites were prepared by solution casting method, for comparison, MgO particles/PLLA composite was prepared too. The resulting composites were evaluated in terms of hydrophilicity, crystallinity, dispersion of whiskers, interfacial adhesion and mechanical performance by means of polarized optical microscopy (POM), contact angle measurement, field emission scanning electron microscope (FSEM), transmission electron microscopy (TEM) and tensile testing. The results revealed that the crystallization rate and hydrophilicity of PLLA were improved by the introduction of MgO whiskers and g-MgO whiskers. The g-MgO whiskers can disperse more uniformly in and show stronger interfacial adhesion with the matrix than MgO whiskers as a result of the surface modification. Due to the bridge effect of the whiskers and the excellent interfacial adhesion between g-MgO whiskers and PLLA, g-MgO whiskers/PLLA composites exhibited remarkably higher strength, modulus and toughness compared to the pristine PLLA, MgO particles/PLLA and MgO whiskers/PLLA composites.

  11. Role of Chloride for a Simple, Non-Grignard Mg Electrolyte in Ether-Based Solvents.

    PubMed

    Sa, Niya; Pan, Baofei; Saha-Shah, Anumita; Hubaud, Aude A; Vaughey, John T; Baker, Lane A; Liao, Chen; Burrell, Anthony K

    2016-06-29

    Mg battery operates with Chevrel phase (Mo6S8, ∼1.1 V vs Mg) cathodes that apply Grignard-based or derived electrolytes, which allow etching of the passivating oxide coating forms at the magnesium metal anode. Majority of Mg electrolytes studied to date are focused on developing new synthetic strategies to achieve a better reversible Mg deposition. While most of these electrolytes contain chloride as a component, and there is a lack of literature which investigates the fundamental role of chloride in Mg electrolytes. Further, ease of preparation and potential safety benefits have made simple design of magnesium electrolytes an attractive alternative to traditional air sensitive Grignard reagents-based electrolytes. Work presented here describes simple, non-Grignard magnesium electrolytes composed of magnesium bis(trifluoromethane sulfonyl)imide mixed with magnesium chloride (Mg(TFSI)2-MgCl2) in tetrahydrofuran (THF) and diglyme (G2) that can reversibly plate and strip magnesium. Based on this discovery, the effect of chloride in the electrolyte complex was investigated. Electrochemical properties at different initial mixing ratios of Mg(TFSI)2 and MgCl2 showed an increase of both current density and columbic efficiency for reversible Mg deposition as the fraction content of MgCl2 increased. A decrease in overpotential was observed for rechargeable Mg batteries with electrolytes with increasing MgCl2 concentration, evidenced by the coin cell performance. In this work, the fundamental understanding of the operation mechanisms of rechargeable Mg batteries with the role of chloride content from electrolyte could potentially bring rational design of simple Mg electrolytes for practical Mg battery. PMID:27255422

  12. Effect of secular variation in oceanic Mg/Ca on calcareous biomineralization

    NASA Astrophysics Data System (ADS)

    Ries, J. B.; Stanley, S. M.

    2006-12-01

    The polymorph mineralogy of simple, hypercalcifying marine organisms has generally varied in synchroneity with the polymorph mineralogy of abiotic CaCO3 precipitates (ooids, marine cements) throughout the Phanerozoic Eon. This synchroneity is caused by secular variation in the Mg/Ca ratio of seawater (SW; mMg/Ca > 2 = aragonite + high-Mg calcite; mMg/Ca < 2 = calcite), determined primarily by the mixing rate of mid-ocean-ridge/large-igneous-province hydrothermal brines and river water, driven by the global rate of ocean crust production. Here, we present experiments evaluating the effect of seawater Mg/Ca on the biomineralization and growth of extant representatives of hypercalcifying taxa that have been subjected to fluctuations in oceanic Mg/Ca in the past. Codiacean algae (arag), scleractinian corals (arag), coccolithophores (low-high Mg-calc), coralline algae (high Mg-calc), various reef-dwelling animals (echinoids, crabs, shrimp, calcareous serpulid worms; high Mg- calc), and calcifying microbial mats (arag + high-Mg calc) were grown in artificial SW formulated over the range of mMg/Ca (1.0 to 5.2) that occurred throughout each taxon's history. Codiacean algae and scleractinian corals exhibited higher rates of calcification and growth in artificial SW favoring their aragonite mineralogy and, significantly, produced a portion of their CaCO3 as calcite in the artificial calcite SW. Coccolithophores (low-high Mg calc.) showed higher calcification and growth rates and produced low-Mg calcite in the calcite SW. Likewise, coralline algae and the reef-dwelling animals (high-Mg calc) varied skeletal Mg/Ca with seawater Mg/Ca. The calcifying microbial mats grew equally well in the calcite and aragonite SW and varied their mineral polymorph commensurate with the SW (mMg/Ca<2 = low- Mg calc; mMg/Ca>2 = arag + high-Mg calc), suggesting a nearly abiotic mode of calcification. The precipitation of low-Mg calcite + aragonite by codiacean algae and scleractinian corals (arag

  13. Mg-isotopic fractionation in the manila clam (Ruditapes philippinarum): New insights into Mg incorporation pathway and calcification process of bivalves

    NASA Astrophysics Data System (ADS)

    Planchon, Frédéric; Poulain, Céline; Langlet, Denis; Paulet, Yves-Marie; André, Luc

    2013-11-01

    We estimate the magnesium stable isotopic composition (δ26Mg) of the major compartments involved in the biomineralisation process of euryhaline bivalve, the manila clam Ruditapes philippinarum. Our aim is to identify the fractionation processes associated with Mg uptake and its cycling/transport in the bivalve organism, in order to better assess the controlling factors of the Mg isotopic records in bivalve shells. δ26Mg were determined in seawater, in hemolymph, extrapallial fluid (EPF), soft tissues and aragonitic shell of adult clams collected along the Auray River estuary (Gulf of Morbihan, France) at two sites showing contrasted salinity regimes. The large overall δ26Mg variations (4.16‰) demonstrate that significant mass-dependent Mg isotopic fractionations occur during Mg transfer from seawater to the aragonitic shell. Soft tissues span a range of fractionation factors relative to seawater (Δ26Mgsoft tissue-seawater) of 0.42 ± 0.12‰ to 0.76 ± 0.12‰, and show evidence for biological isotopic fractionation of Mg. Hemolymph and EPF are on average isotopically close to seawater (Δ26Mghemolymph-seawater = -0.20 ± 0.27‰; 2 sd; n = 5 and Δ26MgEPF-seawater = -0.23 ± 0.25‰; 2 sd; n = 5) indicating (1) a predominant seawater origin for Mg in the intercellular medium and (2) a relatively passive transfer route through the bivalve organism into the calcifying fluid. The lightest isotopic composition is found in shell, with δ26Mg ranging from -1.89 ± 0.07‰ to -4.22 ± 0.06‰. This range is the largest in the dataset and is proposed to result from a combination of abiotic and biologically-driven fractionation processes. Abiotic control includes fractionation during precipitation of aragonite and accounts for Δ26Mgaragonite-seawater ≈ 1000 ln αaragonite-seawater = -1.13 ± 0.28‰ at 20 °C based on literature data. Deviations from inorganic precipitate (expressed as Δ26MgPhysiol) appear particularly variable in the clam shell, ranging from 0

  14. Incorporation of Mg particles into PDLLA regulates mesenchymal stem cell and macrophage responses.

    PubMed

    Cifuentes, Sandra C; Bensiamar, Fátima; Gallardo-Moreno, Amparo M; Osswald, Tim A; González-Carrasco, José L; Benavente, Rosario; González-Martín, María L; García-Rey, Eduardo; Vilaboa, Nuria; Saldaña, Laura

    2016-04-01

    In this work, we investigated a new approach to incorporate Mg particles within a PDLLA matrix using a solvent-free commercially available process. PDLLA/Mg composites were manufactured by injection moulding and the effects of Mg incorporated into PDLLA on MSC and macrophage responses were evaluated. Small amounts of Mg particles (≤ 1 wt %) do not cause thermal degradation of PDLLA, which retains its mechanical properties. PDLLA/Mg composites release hydrogen, alkaline products and Mg(2+) ions without changing pH of culture media. Mg-containing materials provide a noncytotoxic environment that enhances MSC viability. Concentration of Mg(2+) ions in extracts of MSCs increases with the increment of Mg content in the composites. Incorporation of Mg particles into PDLLA stimulates FN production, ALP activity, and VEGF secretion in MSCs, an effect mediated by degradation products dissolved from the composites. Degradation products of PDLLA induce an increase in MCP-1, RANTES, and MIP-1α secretion in macrophages while products of composites have minimal effect on these chemokines. Regulation of MSC behavior at the biomaterial's interface and macrophage-mediated inflammatory response to the degradation products is related to the incorporation of Mg in the composites. These findings suggest that including small amounts of Mg particles into polymeric devices can be a valuable strategy to promote osseointegration and reduce host inflammatory response. PMID:26662548

  15. Synthesis and crystal growth of Mg2Si by the liquid encapsulated vertical gradient freezing method

    NASA Astrophysics Data System (ADS)

    Nakagawa, Reo; Katsumata, Hiroshi; Hashimoto, Satoshi; Sakuragi, Shiro

    2015-08-01

    The synthesis of Mg2Si bulk crystals was performed by the vertical gradient freezing method using a KCl-MgCl2 eutectic liquid encapsulant. Stoichiometric polycrystalline Mg2Si bulk crystals were successfully grown by changing the composition ratio of starting Mg and Si powders (Mg/Si) from 2.0 to 3.5. A chemical reaction between Mg2Si and the crucible materials was inhibited using encapsulant materials, and the contamination by K or Cl originating from the encapsulant materials was not detected in almost all the samples. However, Mg evaporation could not be prevented completely during the synthesis and crystal growth. The optical band-gap energy of Mg2Si bulk crystals became minimal (0.79 eV) at a Mg/Si ratio of 2.5, at which the maximum electron mobility of 202 cm2·V-1·s-1 was obtained. These results indicate that the composition ratio of Mg/Si = 2.5 for starting Mg and Si powders was optimal for synthesizing Mg2Si bulk crystals with high crystalline quality.

  16. Investigation of Barrier-Layer Materials for Mg2Si/Ni Interfaces

    NASA Astrophysics Data System (ADS)

    Sakamoto, Tatsuya; Taguchi, Yutaka; Kutsuwa, Takeshi; Ichimi, Kiyohide; Kasatani, Shinichi; Inada, Minoru

    2016-03-01

    The durability of Ni electrodes, which are often used for Mg2Si thermoelectric chips, is poor at high working temperatures because of deposition of Mg at the Mg2Si/Ni interface and on the surface. Hence, a "Mg2Si/barrier material/Ni" structure was adopted instead of direct adhesion of Ni to Mg2Si. Ti, TiSi2, and TiN were selected as candidate materials for the barrier layer between Mg2Si and Ni, and the barrier effect, adhesion, and contact resistance of each of these materials were evaluated. After the samples had been annealed at 873 K for 1 h, Mg appeared on the Ti surface and TiSi2 deposited on Mg2Si; however, no Mg was detected on the surface of TiN or in the inner part of the Ni electrode. Continuous, low contact resistance was also observed for Mg2Si/TiN/Ni samples. TiN does not adhere strongly to Mg2Si but is a promising barrier material for Mg2Si/Ni interfaces.

  17. The synthesis and characterization of Mg-Zn-Ca alloy by powder metallurgy process

    NASA Astrophysics Data System (ADS)

    Annur, Dhyah; Franciska P., L.; Erryani, Aprilia; Amal, M. Ikhlasul; Sitorus, Lyandra S.; Kartika, Ika

    2016-04-01

    Known for its biodegradation and biocompatible properties, magnesium alloys have gained many interests to be researched as implant material. In this study, Mg-3Zn-1Ca, Mg-29Zn-1Ca, and Mg-53Zn-4.3Ca (in wt%) were synthesized by means of powder metallurgy method. The compression strength and corrosion resistance of magnesium alloy were thoroughly examined. The microstructures of the alloy were characterized using optical microscopy, Scanning Electron Microscope, and also X-ray diffraction analysis. The corrosion resistance were evaluated using electrochemical analysis. The result indicated that Mg- Zn- Ca alloy could be synthesized using powder metallurgy method. This study showed that Mg-29Zn-1Ca would make the highest mechanical strength up to 159.81 MPa. Strengthening mechanism can be explained by precipitation hardening and grain refinement mechanism. Phase analysis had shown the formation of α Mg, MgO, and intermetallic phases: Mg2Zn11 and also Ca2Mg6Zn3. However, when the composition of Zn reach 53% weight, the mechanical strength will be decreasing. In addition, all of Mg-Zn-Ca alloy studied here had better corrosion resistance (Ecorr around -1.4 VSCE) than previous study of Mg. This study indicated that Mg- 29Zn- 1Ca alloy can be further analyzed to be a biodegradable implant material.

  18. Liquation Cracking in Arc and Friction-Stir Welding of Mg-Zn Alloys

    NASA Astrophysics Data System (ADS)

    Wagner, Dustin C.; Chai, Xiao; Tang, Xin; Kou, Sindo

    2015-01-01

    As compared to Al alloys, which are known to be susceptible to liquation ( i.e., liquid formation) and liquation-induced cracking, most Mg alloys have a lower eutectic temperature and thus are likely to be even more susceptible. The present study was conducted to study liquation and liquation cracking in Mg alloys during arc welding and friction-stir welding (FSW). Binary Mg-Zn alloys were selected as a model material in view of their very low eutectic temperature of 613 K (340 °C). Mg-Zn alloys with 2, 4, and 6 wt pct of Zn were cast and welded in the as-cast condition by both gas-tungsten arc welding (GTAW) and FSW. A simple test for liquation cracking was developed, which avoided interference by solidification cracking in the nearby fusion zone. Liquation and liquation cracking in GTAW were found to be in the decreasing order of Mg-6Zn, Mg-4Zn, and Mg-2Zn. Liquation cracking occurred in FSW of Mg-6Zn but not Mg-4Zn or Mg-2Zn. Instead of a continuous ribbon-like flash connected to the weld edge, small chips, and powder covered the weld surface of Mg-6Zn. The results from GTAW and FSW were discussed in light of the binary Mg-Zn phase diagram and the curves of temperature vs fraction solid during solidification.

  19. Improvement of Corrosion Resistance of Binary Mg-Ca Alloys Using Duplex Aluminum-Chromium Coatings

    NASA Astrophysics Data System (ADS)

    Daroonparvar, Mohammadreza; Yajid, Muhamad Azizi Mat; Yusof, Noordin Mohd; Bakhsheshi-Rad, Hamid Reza; Adabi, Mohsen; Hamzah, Esah; Kamali, Hussein Ali

    2015-07-01

    Al-AlCr was coated on Mg-Ca and Mg-Zn-Ce-La alloys using physical vapor deposition method. The surface morphology of the specimens was characterized by x-ray diffraction, scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and atomic force microscopy (AFM). The AFM results indicated that the average surface roughness of Al-AlCr coating on the Mg-Ca alloy is much lower than that of Al-AlCr coating on the Mg-Zn-Ce-La alloy. However, Al-AlCr coating on the Mg-Ca alloy presented a more compact structure with fewer pores, pinholes, and cracks than Al-AlCr coating on the Mg-Zn-Ce-La alloy. Electrochemical studies revealed that the novel coating (Al-AlCr) can remarkably reduce the corrosion rate of the Mg-Ca alloy in 3.5 wt.% NaCl solution. It was seen that the anodic current density of the Al-AlCr-coated Mg-Ca alloy was very small when compared to the Al-AlCr-coated Mg-Zn-Ce-La and uncoated alloys. Impedance modulus ( Z) of the Al-AlCr-coated samples was higher than that of the bare Mg alloys. Z of Al-AlCr-coated Mg-Ca alloy was higher than that of the Al-AlCr-coated Mg-Zn-Ce-La alloy at low frequency.

  20. Mg-based multilayers and their thermal stabilities for EUV range

    NASA Astrophysics Data System (ADS)

    Zhu, Jingtao; Zhou, Sika; Li, Haochuan; Huang, Qiushi; Jiang, Li; Wang, Fengli; Zhang, Zhong; Wang, Zhanshan; Zhou, Hongjun; Huo, Tonglin

    2011-09-01

    We have investigated the optical properties and thermal stabilities of a serial of Mg-based multilayers including Mg/SiC, Mg/Co and Mg/Zr in extreme ultraviolet (EUV) range. Mg/X multilayer mirrors were deposited by magnetron sputtering technique onto polished silicon wafers. In order to study their stabilities under heat resistance, annealing experiments were carried out in vacuum environment keeping 1hour at different temperatures from 200°C to 550°C. Their EUV reflectivities were measured by using synchrotron radiation. Grazing incident X-ray and EUV reflection measurements were used to estimate the thermal stability of these multilayer systems. Mg/SiC and Mg/Co are stable up to 200°C and the reflectivity decreases drastically with the increase of temperature, while the reflectivity of Mg/Zr keeps constant during annealing at 300°C and falls slowly as the temperature increases. Up to 550°C, Bragg peaks of Mg/Zr multilayer are still sharp in X-ray reflectivity curve, and EUV reflectivity is 25% at 26.2nm at 30 degree incidence. These measurement results indicate that Mg/Co and Mg/SiC should be used in application requiring no heating above 200°C, while the new material combination Mg/Zr is a promising multilayer for practical application requiring stronger heat resistance in EUV range.

  1. Microstructure and superconducting properties of nanocarbon-doped internal Mg diffusion-processed MgB2 wires fabricated using different boron powders

    NASA Astrophysics Data System (ADS)

    Xu, Da; Wang, Dongliang; Li, Chen; Yuan, Pusheng; Zhang, Xianping; Yao, Chao; Dong, Chiheng; Huang, He; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2016-04-01

    MgB2/Nb/Monel monofilament wires were fabricated using four different boron powders by an internal Mg diffusion (IMD) process. The microstructure, morphology and the critical current density (J c) of the used boron powders and the formative MgB2 layers were analyzed and compared. It was found that the purity and particle size of the boron powder influence the superconducting properties of MgB2 wires; further that the optimized heat-treatment condition also depends on the quality of the boron powder. The highest J c was obtained in the MgB2 layer made using amorphous boron (AB) powder, although a certain amount of voids existed in the superconducting layer. The IMD-processed MgB2 layer fabricated using high-purity boron (HB) powder had also a high J c compared with the powder-in-tube (PIT) process and a few unreacted boron particles remained in it. MgB2 wire fabricated using low-purity boron (LB) powder had a high cost-performance ratio compared with the others, which is expected to allow the fabrication of large-scale and low-cost superconducting wires for practical application. However, the enhancement of the J c was not found in the MgB2 layer manufactured using the ball-milled LB (MLB) powder as expected due to the increased percentage of impurity.

  2. The Electrochemical Co-reduction of Mg-Al-Y Alloys in the LiCl-NaCl-MgCl2-AlF3-YCl3 Melts

    NASA Astrophysics Data System (ADS)

    Li, Mei; Liu, Yaochen; Han, Wei; Wang, Shanshan; Zhang, Milin; Yan, Yongde; Shi, Weiqun

    2015-04-01

    The electrochemical formation of Mg-Al-Y alloys was studied in the LiCl-NaCl-MgCl2 melts by the addition of AlF3 and YCl3 on a molybdenum electrode at 973 K (700 °C). In order to reduce the volatilization of salt solvent in the electrolysis process, the volatile loss of LiCl-NaCl-MgCl2 and LiCl-KCl-MgCl2 melts was first measured in the temperature range from 873 K to 1023 K (600 °C to 750 °C). Then, the electrochemical behaviors of Mg(II), Al(III), Y(III) ions and alloy formation processes were investigated by cyclic voltammetry, chronopotentiometry, and open circuit chronopotentiometry. The cyclic voltammograms indicate that the under-potential deposition of magnesium and yttrium on pre-deposited Al leads to formation of Mg-Al and Al-Y intermetallic compounds. The Mg-Al-Y alloys were prepared by galvanostatic electrolysis in the LiCl-NaCl-MgCl2-AlF3-YCl3 melts and characterized by X-ray diffraction and scanning electron microscopy with energy dispersive spectrometry. Composition of the alloys was analyzed by inductively coupled plasma-atomic emission spectrometer, and current efficiency was also determined by the alloy composition.

  3. Phosphate adsorption ability of biochar/Mg-Al assembled nanocomposites prepared by aluminum-electrode based electro-assisted modification method with MgCl₂ as electrolyte.

    PubMed

    Jung, Kyung-Won; Jeong, Tae-Un; Hwang, Min-Jin; Kim, Kipal; Ahn, Kyu-Hong

    2015-12-01

    In this work, the textural properties and phosphate adsorption capability of modified-biochar containing Mg-Al assembled nanocomposites prepared by an effective electro-assisted modification method with MgCl2 as an electrolyte have been determined. Structure and chemical analyses of the modified-biochar showed that nano-sized stonelike or flowerlike Mg-Al assembled composites, MgO, spinel MgAl2O4, AlOOH, and Al2O3, were densely grown and uniformly dispersed on the biochar surface. The adsorption isotherm and kinetics data suggested that the biochar/Mg-Al assembled nanocomposites have an energetically heterogeneous surface and that phosphate adsorption could be controlled by multiple processes. The maximum phosphate adsorption capacity was as high as 887 mg g(-1), as fitted by the Langmuir-Freundlich model, and is the highest value ever reported. It was concluded that this novel electro-assisted modification is a very attractive method and the biochar/Mg-Al assembled nanocomposites provide an excellent adsorbent that can effectively remove phosphate from aqueous solutions. PMID:26433157

  4. Effect of inorganic and organic ligands on the sorption/desorption of arsenate on/from Al-Mg and Fe-Mg layered double hydroxides.

    PubMed

    Caporale, A G; Pigna, M; Dynes, J J; Cozzolino, V; Zhu, J; Violante, A

    2011-12-30

    This paper describes the sorption of arsenate on Al-Mg and Fe-Mg layered double hydroxides as affected by pH and varying concentrations of inorganic and organic ligands, and the effect of residence time on the desorption of arsenate by ligands. The capacity of ligands to inhibit the fixation of arsenate followed the sequence: nitrateMg-LDH and nitrateMg-LDH. The inhibition of arsenate sorption increased by increasing the initial ligand concentration and was greater on Al-Mg-LDH than on Fe-Mg-LDH. The longer the arsenate residence time on the LDH surfaces the less effective the competing ligands were in desorbing arsenate from sorbents. A greater percentage of arsenate was removed by phosphate from Al-Mg-LDH than from Fe-Mg-LDH, due to the higher affinity of arsenate for iron than aluminum. PMID:22071258

  5. Effect of Mg diffusion on photoluminescence spectra of MgZnO/ZnO bi-layers annealed at different temperatures

    NASA Astrophysics Data System (ADS)

    Das, Amit K.; Misra, P.; Ajimsha, R. S.; Bose, A.; Joshi, S. C.; Porwal, S.; Sharma, T. K.; Oak, S. M.; Kukreja, L. M.

    2013-11-01

    MgZnO/ZnO bilayers (Mg concentration of ˜30%) have been grown and subsequently annealed at different temperatures in the range of 600-900 °C with the specific interest of studying the effect of inter-diffusion of Mg on the photoluminescence (PL) properties of the bilayers. The influence of Mg diffusion and material homogenization is evaluated through absorption, PL, and secondary ion mass spectrometry (SIMS) measurements. No appreciable change in the spectral positions is seen either in PL or absorption up to an annealing temperature of 700 °C, which is also supported by SIMS. However at higher annealing temperatures, diffusion of Mg into the ZnO layer is clearly evident in SIMS profile, which results in the red-shift (blue-shift) of spectral positions of MgZnO (ZnO) layer, respectively. Finally, for the sample annealed at 900 °C, the two layers are completely merged providing a single peak at ˜3.60 eV in PL/absorption corresponding to a completely homogenized MgZnO layer. Spectroscopic results are corroborated by the numerical simulations based on a simple theoretical model, which correlates the observed PL spectra of the heterostructures with the experimental Mg diffusion profiles across the heterointerface, as measured by SIMS.

  6. Influence of crystallization front direction on the Mg-related impurity centers incorporation in bulk GaN:Mg grown by HNPS method

    NASA Astrophysics Data System (ADS)

    Sadovyi, B.; Amilusik, M.; Litwin-Staszewska, E.; Bockowski, M.; Grzegory, I.; Porowski, S.; Fijalkowski, M.; Rudyk, V.; Tsybulskyi, V.; Panasyuk, M.; Karbovnyk, I.; Kapustianyk, V.

    2016-08-01

    We studied the incorporation of Mg-related impurity centers in GaN crystals depending on the direction of the crystallization front. Two series of GaN crystals - (i) undoped and (ii) Mg-doped - were grown by High Nitrogen Pressure Solution (HNPS) method under otherwise identical conditions. Each series contained four samples with (10 1 bar 0) , (11 2 bar 0) , (20 2 bar 1 bar) and (20 2 bar 1) orientations. The low-temperature photoluminescence (PL) spectroscopy was used for characterization of the obtained crystals. The observed differences in the PL spectra of GaN:Mg crystals suggested that Mg incorporation in GaN grown by HNPS method depends considerably on the orientation of crystallization front. The concentration of Mg impurity incorporated into the GaN crystals subsequently increases for the following sequence of planes: (10 1 bar 0) , (11 2 bar 0) , (20 2 bar 1 bar) and (20 2 bar 1) . For (10 1 bar 0) , (11 2 bar 0) and (20 2 bar 1 bar) planes the blue band is related only to ON - MgGa donor-acceptor pair (DAP) transitions, while for (20 2 bar 1) plane the incorporation of Mg-H complexes occurs additionally to the formation ON - MgGa DAP.

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

    PubMed

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

    2013-08-20

    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. PMID:23895233

  8. Highly Active Electrolytes for Rechargeable Mg Batteries Based on [Mg2(μ-Cl)2]2+ Cation Complex in Dimethoxyethane

    SciTech Connect

    Cheng, Yingwen; Stolley, Ryan M.; Han, Kee Sung; Shao, Yuyan; Arey, Bruce W.; Washton, Nancy M.; Mueller, Karl T.; Helm, Monte L.; Sprenkle, Vincent L.; Liu, Jun; Li, Guosheng

    2015-01-01

    Highly active electrolytes based on a novel [Mg2(μ-Cl)2]2+ cation complex for reversible Mg deposition were developed and analyzed in this work. These electrolytes were formulated in dimethoxyethane through dehalodimerization of non-nucleophilic MgCl2 by reacting with either Mg salts (such as Mg(TFSI)2, TFSI= bis(trifluoromethane)sulfonylimide) or Lewis acid salts (such as AlEtCl2 or AlCl3). The cation complex was identified for the first time as [Mg2(μ-Cl)2(DME)4]2+ (DME=dimethoxyethane) and its molecular structure was characterized by single crystal X-ray diffraction, Raman spectroscopy and NMR. The electrolyte synthesis process was studied and rational approaches for formulating highly active electrolytes were proposed. Through control of the anions, electrolytes with efficiency close to 100%, wide electrochemical window (up to 3.5V) and high ionic conductivity (> 6 mS/cm) were obtained. The electrolyte synthesis and understandings developed in this work could bring significant opportunities for rational formulation of electrolytes with the general formula [Mg2(μ-Cl)2(DME)4][anion]x for practical Mg batteries.

  9. Wide pH range for fluoride removal from water by MHS-MgO/MgCO₃ adsorbent: kinetic, thermodynamic and mechanism studies.

    PubMed

    Zhang, Kaisheng; Wu, Shibiao; Wang, Xuelong; He, Junyong; Sun, Bai; Jia, Yong; Luo, Tao; Meng, Fanli; Jin, Zhen; Lin, Dongyue; Shen, Wei; Kong, Lingtao; Liu, Jinhuai

    2015-05-15

    A novel environment friendly adsorbent, micro-nano hierarchical structured flower-like MgO/MgCO3 (MHS-MgO/MgCO3), was developed for fluoride removal from water. The adsorbent was characterized and its defluoridation properties were investigated. Adsorption kinetics fitted well the pseudo-second-order model. Kinetic data revealed that the fluoride adsorption was rapid, more than 83-90% of fluoride could be removed within 30 min, and the adsorption equilibrium was achieved in the following 4 h. The fluoride adsorption isotherm was well described by Freundlich model. The maximum adsorption capacity was about 300 mg/g at pH=7. Moreover, this adsorbent possessed a very wide available pH range of 5-11, and the fluoride removal efficiencies even reached up to 86.2%, 83.2% and 76.5% at pH=11 for initial fluoride concentrations of 10, 20 and 30 mg/L, respectively. The effects of co-existing anions indicated that the anions had less effect on adsorption of fluoride except phosphate. In addition, the adsorption mechanism analysis revealed that the wide available pH range toward fluoride was mainly resulted from the exchange of the carbonate and hydroxyl groups on the surface of the MHS-MgO/MgCO3 with fluoride anions. PMID:25668780

  10. MgCO3·3H2O and MgO complex nanostructures: controllable biomimetic fabrication and physical chemical properties.

    PubMed

    Wu, Xiaoming; Cao, Huaqiang; Yin, Gui; Yin, Jiefu; Lu, Yuexiang; Li, Baojun

    2011-03-21

    In this paper, we report a method of biomimetic synthesis of MgCO(3)·3H(2)O and MgO Viburnum opulus-like complex nanostructures with superhydrophobicity and adsorption properties. The MgCO(3)·3H(2)O complex nanostructures can be obtained by changing experimental parameters, including concentrations of reactants (dextran and MgCl(2)), molar ratios of reactants, and reaction time. The phase structure of as-synthesized samples was characterized by X-ray diffraction (XRD). The morphology and structure are studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The MgCO(3)·3H(2)O complex nanostructures exhibited superhydrophobicity, due to their unique superstructures, and was proved by the contact angle (CA) measurement. We also show that a simple calcination of these unusually shaped MgCO(3)·3H(2)O results in spontaneous formation of MgO complex nanostructures while the unique shape can be maintained, and the as-synthesized MgO nanostructures show excellent adsorption property. These unique structures and properties will open up a wide range of potential applications in material and environmental protection. PMID:21170433

  11. Experimental and calculated phases in two as-cast and annealed Mg-Zn-Y alloys

    SciTech Connect

    Farzadfar, S.A.; Sanjari, M.; Jung, I.-H.; Essadiqi, E.; Yue, S.

    2012-01-15

    The CALPHAD (Calculation of Phase Diagram) method was used to select ternary alloys from Mg-Zn-Y system, aimed at determining the role of precipitates in the microstructure and texture evolution of Mg during and after deformation. The selected alloys are Mg-6Zn-1.2Y and Mg-5Zn-2Y. The constituent phases in the as-cast Mg-6Zn-1.2Y alloy are {alpha}-Mg solid solution phase and I (Mg{sub 3}YZn{sub 6}) intermetallic phase. The as-cast Mg-5Zn-2Y alloy is composed of {alpha}-Mg, I and W (Mg{sub 3}Y{sub 2}Zn{sub 3}) phases. The intermetallics in the two alloys form by eutectic reaction, which in Mg-5Zn-2Y alloy results in initially W-phase formation and ultimately I-phase formation during solidification. After heat treatment, the Mg-6Zn-1.2Y and Mg-5Zn-2Y alloys contain nearly the same amount of ternary intermetallics (I and W phases, respectively) in equilibrium with {alpha}-Mg solid solution phase. The main solute in {alpha}-Mg phase is Zn with the same amount in the two alloys. The type and quantity of the phases obtained experimentally disagree with the results obtained from the thermodynamic database. One important discrepancy is that, in Mg-6Zn-1.2Y alloy, the I phase is not stable at the temperature of 430 Degree-Sign C, and that the W phase is the stable phase at this temperature. The differences in the experimental and calculated data indicate that the Mg-Zn-Y system requires to be reassessed with more experimental data. - Highlights: Black-Right-Pointing-Pointer Mg-6Zn-1.2Y and Mg-5Zn-2Y alloys were selected by FactSage Trade-Mark-Sign Thermodynamic software. Black-Right-Pointing-Pointer The I and W intermetallics in the two alloys form by eutectic reaction. Black-Right-Pointing-Pointer The alloys contain similar amounts of different intermetallics in equilibrium with {alpha}-Mg. Black-Right-Pointing-Pointer In Mg-6Zn-1.2Y, the I phase is not stable at the temperature of 430 Degree-Sign C. Black-Right-Pointing-Pointer The hardness of W phase is determined to be

  12. Prediction of novel stable compounds in the Mg-Si-O system under exoplanet pressures

    PubMed Central

    Niu, Haiyang; Oganov, Artem R.; Chen, Xing-Qiu; Li, Dianzhong

    2015-01-01

    The Mg-Si-O system is the major Earth and rocky planet-forming system. Here, through quantum variable-composition evolutionary structure explorations, we have discovered several unexpected stable binary and ternary compounds in the Mg-Si-O system. Besides the well-known SiO2 phases, we have found two extraordinary silicon oxides, SiO3 and SiO, which become stable at pressures above 0.51 TPa and 1.89 TPa, respectively. In the Mg-O system, we have found one new compound, MgO3, which becomes stable at 0.89 TPa. We find that not only the (MgO)x·(SiO2)y compounds, but also two (MgO3)x·(SiO3)y compounds, MgSi3O12 and MgSiO6, have stability fields above 2.41 TPa and 2.95 TPa, respectively. The highly oxidized MgSi3O12 can form in deep mantles of mega-Earths with masses above 20 M⊕ (M⊕:Earth’s mass). Furthermore, the dissociation pathways of pPv-MgSiO3 are also clarified, and found to be different at low and high temperatures. The low-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ SiO2 + Mg2SiO4 ⇒ MgO + SiO2, while the high-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ MgO + MgSi2O5 ⇒ MgO + SiO2. Present results are relevant for models of the internal structure of giant exoplanets, and for understanding the high-pressure behavior of materials. PMID:26691903

  13. Study on biodegradation of the second phase Mg17Al12 in Mg-Al-Zn alloys: in vitro experiment and thermodynamic calculation.

    PubMed

    Liu, Chen; Yang, Huazhe; Wan, Peng; Wang, Kehong; Tan, Lili; Yang, Ke

    2014-02-01

    The in vitro biodegradation behavior of Mg17Al12 as a second phase in Mg-Al-Zn alloys was investigated via electrochemical measurement and immersion test. The Hank's solutions with neutral and acidic pH values were adopted as electrolytes to simulate the in vivo environment during normal and inflammatory response process. Furthermore, the local orbital density functional theory approach was employed to study the thermodynamical stability of Mg17Al12 phase. All the results proved the occurrence of pitting corrosion process with crackings for Mg17Al12 phase in Hank's solution, but with a much lower degradation rate compared with both AZ31 alloy and pure magnesium. Furthermore, a preliminary explanation on the biodegradation behaviors of Mg17Al12 phase was proposed. PMID:24411344

  14. Effect of MgO Cap Layer on Gilbert Damping of FeB Electrode Layer in MgO-Based Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Konoto, Makoto; Imamura, Hiroshi; Taniguchi, Tomohiro; Yakushiji, Kay; Kubota, Hitoshi; Fukushima, Akio; Ando, Koji; Yuasa, Shinji

    2013-07-01

    We investigated the Gilbert damping of thin films with a MgO-barrier/Fe80B20/MgO-cap/Ta structure, in which the Fe80B20 layer corresponds to a free layer of a perpendicularly magnetized magnetic tunnel junction, by using ferromagnetic resonance (FMR). We systematically varied the thickness of the MgO cap layer and estimated the damping constant (α) by measuring the dependence of the FMR spectrum on the magnetic field angle. The MgO cap layer was found to reduce α to about 0.005, which is less than half the value without the cap. The significant reduction can be explained by the suppression of spin pumping by the dielectric MgO cap layer.

  15. Effect of reaction time and (Ca+Mg)/Al molar ratios on crystallinity of Ca-Mg-Al layered double Hydroxide

    NASA Astrophysics Data System (ADS)

    Heraldy, E.; Nugrahaningtyas, K. D.; Sanjaya, F. B.; Darojat, A. A.; Handayani, D. S.; Hidayat, Y.

    2016-02-01

    Ca-Mg-Al Layered Double Hydroxides (Ca-Mg-Al-LDH) compounds were successfully synthesized from brine water and AlCl3.6H2O as the starting materials by coprecipitation method. The product result was characterized by X-ray powder diffraction (XRD) and Fourier transform infrared (FT-IR). The effects of the reaction time and the molar ratios of the raw material on the crystallinity of Ca-Mg-Al-LDH were examining. Results show that increasing reaction time (30; 60 and 90 min.) could improve the crystallinity and monodispersity of layered double hydroxide compounds particles. The well-defined Ca-Mg- Al-LDH could be prepared with (Ca+Mg)/Al molar ratios 0.5.

  16. Ab-initio modelling of defects in MgO

    NASA Astrophysics Data System (ADS)

    Gilbert, C. A.; Smith, R.; Kenny, S. D.

    2007-02-01

    The energetics of the key defects that are observed to occur during simulations of radiation damage in MgO are analysed using density functional theory. The results are compared with those from the empirical potentials used to carry out the radiation damage studies. The formation energies of vacancies, interstitials, Frenkel pairs, di-vacancies and di-interstitials are calculated as a function of the increasing supercell size in order to ensure good convergence. The supercell geometries were chosen to maximise the separation distance between periodic images. Their sizes ranged from cells containing 32 atoms up to cells containing 180 atoms. Results are presented for the formation energies of the first, second and third nearest neighbour defects. Results show that the di-vacancy formation energy is in the region of 4-6 eV and that formation energies for di-interstitials are more than double this, lying in the range 12-16 eV. Comparison of the results show that empirical potentials overestimate the formation energy of di-vacancies by 1-3 eV and underestimate the formation energies of di-interstitials by about 1-2 eV. The relative stability of the defects is, however, correctly predicted by the empirical potentials. The direction and the magnitude of the displacements of the atoms surrounding the defects are in good agreement for all the systems containing interstitials. For the systems containing vacancies the direction of the displacements are in agreement but the empirical potentials predict larger displacements in all cases.

  17. Phosphorus recovery from biogas fermentation liquid by Ca-Mg loaded biochar.

    PubMed

    Fang, Ci; Zhang, Tao; Li, Ping; Jiang, Rongfeng; Wu, Shubiao; Nie, Haiyu; Wang, Yingcai

    2015-03-01

    Shortage in phosphorus (P) resources and P wastewater pollution is considered as a serious problem worldwide. The application of modified biochar for P recovery from wastewater and reuse of recovered P as agricultural fertilizer is a preferred process. This work aims to develop a calcium and magnesium loaded biochar (Ca-Mg/biochar) application for P recovery from biogas fermentation liquid. The physico-chemical characterization, adsorption efficiency, adsorption selectivity, and postsorption availability of Ca-Mg/biochar were investigated. The synthesized Ca-Mg/biochar was rich in organic functional groups and in CaO and MgO nanoparticles. With the increase in synthesis temperature, the yield decreased, C content increased, H content decreased, N content remained the same basically, and BET surface area increased. The P adsorption of Ca-Mg/biochar could be accelerated by nano-CaO and nano-MgO particles and reached equilibrium after 360min. The process was endothermic, spontaneous, and showed an increase in the disorder of the solid-liquid interface. Moreover, it could be fitted by the Freundlich model. The maximum P adsorption amounts were 294.22, 315.33, and 326.63mg/g. The P adsorption selectivity of Ca-Mg/biochar could not be significantly influenced by the typical pH level of biogas fermentation liquid. The nano-CaO and nano-MgO particles of Ca-Mg/biochar could reduce the negative interaction effects of coexisting ions. The P releasing amounts of postsorption Ca-Mg/biochar were in the order of Ca-Mg/B600>Ca-Mg/B450>Ca-Mg/B300. Results revealed that postsorption Ca-Mg/biochar can continually release P and is more suitable for an acid environment. PMID:25766018

  18. In vitro degradation and cytotoxicity of Mg/Ca composites produced by powder metallurgy.

    PubMed

    Zheng, Y F; Gu, X N; Xi, Y L; Chai, D L

    2010-05-01

    Mg/Ca (1 wt.%, 5 wt.%, 10 wt.% Ca) composites were prepared from pure magnesium and calcium powders using the powder metallurgy method, aiming to enlarge the addition of Ca content without the formation of Mg(2)Ca. The microstructures, mechanical properties and cytotoxicities of Mg/Ca composite samples were investigated. The corrosion of Mg/Ca composites in Dulbecco's modified Eagle's medium (DMEM) for various immersion intervals was studied by electrochemical impedance spectroscopy measurements and environmental scanning electron microscope, with the concentrations of released Mg and Ca ions in DMEM for various immersion time intervals being measured. It was shown that the main constitutional phases were Mg and Ca, which were uniformly distributed in the Mg matrix. The ultimate tensile strength (UTS) and elongation of experimental composites decreased with increasing Ca content, and the UTS of Mg/1Ca composite was comparable with that of as-extruded Mg-1Ca alloy. The corrosion potential increased with increasing Ca content, whereas the current density and the impedance decreased. It was found that the protective surface film formed quickly at the initial immersion stage. With increasing immersion time, the surface film became compact, and the corrosion rate of Mg/Ca composites slowed down. The surface film consisted mainly of CaCO(3), MgCO(3)x3H(2)O, HA and Mg(OH)(2) after 72 h immersion in DMEM. Mg/1Ca and Mg/5Ca composite extracts had no significant toxicity (p>0.05) to L-929 cells, whereas Mg/10Ca composite extract induced approximately 40% reduced cell viability. PMID:19815098

  19. Structural and optical properties of ZnMgO thin films grown by pulsed laser deposition using ZnO-MgO multiple targets

    NASA Astrophysics Data System (ADS)

    Maemoto, Toshihiko; Ichiba, Nobuyasu; Ishii, Hiroaki; Sasa, Shigehiko; Inoue, Masataka

    2007-04-01

    We report on structural and optical properties for Zn1-xMgxO (ZMO) thin films produced by pulsed laser ablation. ZMO thin films were grown on a-plane Al2O3 substrates at 400°C. In order to efficiently incorporate Mg into ZnO thin films, we used multiple ZnO-MgO ablation targets. Pulses from a Nd:YAG laser (4th harmonic generation: 266 nm) were directed on the ZnO-MgO ablation targets, which consisted of MgO single crystals mounted on ZnO ceramic targets. The ZMO films were characterized by x-ray diffraction, optical transmittance and cathodeluminescence (CL) measurements. Highly c-axis oriented ZMO(0002) reflections corresponding to the wurtzite-phase were observed. The c-axis lattice constants of the films were determined from the ZnMgO(0002) peak. The c-axis length of the ZMO films decreased linearly with Mg content. From the optical transmittance spectra of ZMO films, we observed a blue shift in the absorption edge with increasing Mg content. Band gap energies of ZMO thin films were determined from the optical transmittance and CL spectra. We found that the band gap energy changed from 3.27 eV to 3.95 eV. The Mg content of ZMO films increased monotonically with the number of laser pulses which struck the MgO target. These results show that laser ablation using multiple targets of ZnO and MgO is effective for band engineering of ZMO.

  20. Crystal Structure Refinement of Mg 5Nb 4O 15and Mg 5Ta 4O 15by Rietveld Analysis of Neutron Powder Diffraction Data

    NASA Astrophysics Data System (ADS)

    Pagola, S.; Carbonio, R. E.; Fernández-Díaz, M. T.; Alonso, J. A.

    1998-05-01

    The crystal structure of the isomorphous phases Mg5Nb4O15and Mg5Ta4O15was refined from neutron powder diffraction data. These compounds are isostructural with pseudobrookite, Fe2TiO5. The two kinds of metal sites of this structure are randomly occupied by Mg(II) and Nb(V) or Ta(V). The structure consists of double chains of (Mg,M)O6units (whereM=Nb or Ta), sharing edges on thebcplane, interconnected through common oxygens along theaaxis to give a three-dimensional array. The (Mg,M)O6polyhedra at both metal positions can be described as very distorted octahedra, with (Mg,M)-O distances ranging from 1.93 to 2.22 Å. The crystallographic formulas can be written as (Mg0.73(2)Nb0.27(2))4c(Mg0.94(2)Nb1.06(2))8fO5and (Mg0.66(2)Ta0.34(2))4c(Mg1.01(2)Ta0.99(2))8fO5respectively, where 4c and 8f are the Wyckoff sites of the two metal positions of the structure. The space group is Cmcm (orthorhombic) andZ=4. Unit cell parameters, cell volume,RwpandRIvalues obtained werea=3.8068(1) Å,b=10.0561(1) Å,c=10.2566(1) Å,V=392.64(2) Å3, and 6.72% and 2.94% for the niobium compound; anda=3.81884(6) Å,b=10.0574(2) Å,c=10.2343(2) Å,V=393.07(2) Å3, and 4.46%, and 2.36% for the tantalum compound.

  1. Electrochemical synthesis of superconductive MgB 2 from molten salts

    NASA Astrophysics Data System (ADS)

    Yoshii, Kenji; Abe, Hideki

    2003-05-01

    We have found that superconductive MgB2 can be electrochemically synthesized from molten salts. The electrolysis was performed in an Ar flow at 600 °C on fused mixtures composed of MgCl2, MgB2O4, Na2B2O4 and alkali halides such as KCl, NaCl, and LiCl. Superconductivity was observed for a wide variety of electrolytes. It was also found that the magnetic and electrical transport properties are the most improved for samples prepared from MgCl2-NaCl-KCl-MgB2O4 electrolytes.

  2. Nanostructured BN-Mg composites: features of interface bonding and mechanical properties.

    PubMed

    Kvashnin, Dmitry G; Krasheninnikov, Arkady V; Shtansky, Dmitry; Sorokin, Pavel B; Golberg, Dmitri

    2016-01-14

    Magnesium (Mg) is one of the lightest industrially used metals. However, wide applications of Mg-based components require a substantial enhancement of their mechanical characteristics. This can be achieved by introducing small particles or fibers into the metal matrix. Using first-principles calculations, we investigate the stability and mechanical properties of a nanocomposite made of magnesium reinforced with boron nitride (BN) nanostructures (BN nanotubes and BN monolayers). We show that boron vacancies at the BN/Mg interface lead to a substantial increase in BN/Mg bonding establishing an efficient route towards the development of BN/Mg composite materials with enhanced mechanical properties. PMID:26662205

  3. Nucleation and growth of dense phase in compressed MgB2

    NASA Astrophysics Data System (ADS)

    Mikheenko, P.; Bevan, A. I.; Abell, J. S.

    2006-06-01

    We report nucleation and growth of dense MgB2 phase in two advanced methods for compacting MgB2 powder: hot isostatic pressing (HIP) and resistive sintering (RS). Both methods produce a compact with nearly theoretical mass density and high critical current density: up to 8 . 105 A/cm2 at 20 K. A liquid phase is responsible for the propagation of dense MgB2. The additions of Mg and Ni are beneficial for rapid formation of dense compact. The process of compacting is further improved by introducing single crystal-dense MgB2 seeds.

  4. Chemical Interaction of Mg-CARBONATE and the Earth's Lower Mantle Minerals

    NASA Astrophysics Data System (ADS)

    Spivak, Anna; Solopova, Natalia; Litvin, Yuriy; Dubrovinsky, Leonid

    2013-04-01

    Diamonds of lower mantle origin are rare but important guests at Earth surface currying crucial information about deep interiors. Apart minerals expected to be similar in Earth lower mantle (particularly Mg-Fe-Al silicates and MgO-FeO oxides) ultra-deep diamonds contain primary inclusions of carbonates indicating that they are presented in the Earth lower mantle. Carbonates of magnesium, calcium, iron and sodium are stable at wide pressure-temperature conditions close to the geotherm. We studied interaction of Mg-carbonates with ferropericlase, perovskite employing laser-heated diamond anvil cell (DAC) at pressures up to 60 GPa and temperatures over 3000 K. Melting of Mg-carbonate is determined as congruent under PT-conditions of the lower mantle. The MgCO3 melts are stable in an expanded high-pressure high-temperature field. We observed formation of diamond at 18 and 40 GPa as a result of decomposition of MgCO3 melt at temperatures above 3500 K on the high-temperature boundary of the field. Melting reactions of the MgCO3-(Mg,Fe)O system were studied in the 30-63 GPa range at high temperatures up to 3600 K. It was found that decomposition boundary of MgCO3-(Mg,Fe)O melt is close to the pure MgCO3 decomposition one within ± 150 K (accuracy of DAC experiment). Preliminary data shows that perovskite -(Mg,Fe)(Si,Al)O3reacts with MgCO3 at PT-conditions of 24GPa/2000K and 60GPa/2500K, that is close to the boundary of congruent MgCO3 melting. The reaction is accompanied with formation of diamond and MgO. The experimental data on melting phase relations MgCO3, MgCO3 - (Mg,Fe)O and MgCO3-(Mg,Fe)(Si,Al)O3 systems combined with diamond crystallization are applied to the problem of ultra-deep diamond formation in carbonate-bearing parental media of the Earth's lower mantle. This work was funded by the Ministry of education and science of Russian Federation, project 8317, 16.740.11.0621, grants RFBR 12-05-33044 and 11-05-000401.

  5. Olivine vitrophyres - A nonpristine high-Mg component in lunar breccia 14321

    NASA Technical Reports Server (NTRS)

    Shervais, John W.; Taylor, Lawrence A.; Lindstrom, Marilyn M.

    1988-01-01

    The presence of olivine vitrophyres in breccia 14321 is discussed, suggesting that olivine vitrophyres could account for the high-Mg component of soils and breccias in the lunar highlands. The olivine vitrophyre clasts from 14321 have high bulk MgO and the Mg/(Mg+Fe) ratio is 78 percent. The olivine vitrophyres are impact melt rocks and are rich in KREEP. The high MgO concentration is manifest by skeletal quench crystals of olivine that constitute about 30 percent of the mode.

  6. Removal of borate by coprecipitation with Mg/Al layered double hydroxide

    NASA Astrophysics Data System (ADS)

    Kurashina, Masashi; Inoue, Tatsuki; Tajima, Chihiro; Kanezaki, Eiji

    2015-03-01

    Borate has been used for various industrial products and excessive dose of boron is harmful to humans. We investigated the removal of borate by direct coprecipitation with Mg/Al layered double hydroxide. In this study, the maximum removal of boron was 90% when Mg 30 mmol and Al 15 mmol at pH = 10 were used for 498 mg/l as B. The boron adsorption isotherms could be fitted to Langmuir model. The calculated constant Ws, saturation limit of boron adsorption, is 25 ± 2 mg/g and it is larger than that of ion exchange reaction (Ws = 15±1 mg/g).

  7. Tunable electronic structures of p-type Mg doping in AlN nanosheet

    SciTech Connect

    Peng, Yuting; Xia, Congxin Zhang, Heng; Wang, Tianxing; Wei, Shuyi; Jia, Yu

    2014-07-28

    The p-type impurity properties are investigated in the Mg-doped AlN nanosheet by means of first-principles calculations. Numerical results show that the transition energy levels reduce monotonously with the increase in Mg doping concentration in the Mg-doped AlN nanosheet systems, and are lower than that of the Mg-doped bulk AlN case for the cases with larger doping concentration. Moreover, Mg substituting Al atom is energy favorably under N-rich growth experimental conditions. These results are new and interesting to further improve p-type doping efficiency in the AlN nanostructures.

  8. Slip, twinning and transformation in Laves phases. [Ti-TiCr[sub 2]; Fe-ZrFe[sub 2]; Ni-Cu-Mg containing MgNi[sub 2] and MgCu[sub 2

    SciTech Connect

    Allen, S.M.; Livingston, J.D.

    1993-01-26

    Research was concentrated on two-phase Ti-TiCr[sub 2] alloys, two- phase Fe-ZrFe[sub 2] alloys, and two-phase ternary Ni-Cu-Mg alloys containing MgNi[sub 2] and MgCu[sub 2] phases. Work demonstrated that a variety of room-temperature deformation processes are possible in Laves phases. A strain-induced phase transformation from C36[r arrow]C15 structures is one mechanism for plastic deformation in ZrFe[sub 2]. The C15 structure in TiCr[sub 2] deforms by slip and twinning. The microstructure after indentation of specimens containing C36 phases ZrFe[sub 2] and MgNi[sub 2] indicates that a variety of slip systems operate in this form. 8 figs.

  9. Isopiestic Investigation of the Osmotic and Activity Coefficients of {yMgCl2 + (1 - y)MgSO4}(aq) and the Osmotic Coefficients of Na2SO4.MgSO4(aq) at 298.15 K

    SciTech Connect

    Miladinovic, J; Ninkovic, R; Todorovic, M; Rard, J A

    2007-06-06

    Isopiestic vapor pressure measurements were made for {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) solutions with MgCl{sub 2} ionic strength fractions of y = 0, 0.1997, 0.3989, 0.5992, 0.8008, and (1) at the temperature 298.15 K, using KCl(aq) as the reference standard. These measurements for the mixtures cover the ionic strength range I = 0.9794 to 9.4318 mol {center_dot} kg{sup -1}. In addition, isopiestic measurements were made with NaCl(aq) as reference standard for mixtures of {l_brace}xNa{sub 2}SO{sub 4} + (1-x)MgSO{sub 4}{r_brace}(aq) with the molality fraction x = 0.50000 that correspond to solutions of the evaporite mineral bloedite (astrakanite), Na{sub 2}Mg(SO{sub 4}){sub 2} {center_dot} 4H{sub 2}O(cr). The total molalities, m{sub T} = m(Na{sub 2}SO{sub 4}) + m(MgSO{sub 4}), range from m{sub T} = 1.4479 to 4.4312 mol {center_dot} kg{sup -1} (I = 5.0677 to 15.509 mol {center_dot} kg{sup -1}), where the uppermost concentration is the highest oversaturation molality that could be achieved by isothermal evaporation of the solvent at 298.15 K. The parameters of an extended ion-interaction (Pitzer) model for MgCl2(aq) at 298.15 K, which were required for an analysis of the {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) mixture results, were evaluated up to I = 12.025 mol {center_dot} kg{sup -1} from published isopiestic data together with the six new osmotic coefficients obtained in this study. Osmotic coefficients of {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) solutions from the present study, along with critically-assessed values from previous studies, were used to evaluate the mixing parameters of the extended ion-interaction model.

  10. Phase, microstructure and hydrogen storage properties of Mg-Ni materials synthesized from metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Shao, Huaiyu; Chen, Chunguang; Liu, Tong; Li, Xingguo

    2014-04-01

    After Mg and Ni nanoparticles were fabricated by hydrogen plasma metal reaction, Mg-rich MgxNi100-x(75 < x < 90) materials were synthesized from these metal nanoparticles to study the synergistic effects for hydrogen storage in these samples to show both good kinetics and high capacity. These MgxNi100-x materials may absorb hydrogen with a capacity of around 3.3-5.1 wt% in 1 min at 573 K. The Mg90Ni10 sample shows a hydrogen capacity of 6.1 wt%. The significant kinetic enhancement is thought to be due to the unique nanostructure from the special synthesis route, the catalytic effect of the Mg2Ni nano phase, and the synergistic effects between the Mg2Ni and Mg phases in the materials. An interesting phenomenon which has never been reported before was observed during pressure composition isotherm (PCT) measurements. One steep step in the absorption process and two obviously separated steps in the desorption process during PCT measurements of Mg80Ni20 and Mg90Ni10 samples were observed and a possible reason from the kinetic performance of the Mg2Ni and Mg phases in absorption and desorption processes was explained. These MgxNi100-x materials synthesized from Mg and Ni nanoparticles show high capacity and good kinetics, which makes these materials very promising candidates for thermal storage or energy storage and utilization for renewable power.

  11. Synthesis and characterization of excess magnesium MgB 2 superconductor under inert carbon environment

    NASA Astrophysics Data System (ADS)

    Sinha, B. B.; Kadam, M. B.; Mudgel, M.; Awana, V. P. S.; Kishan, Hari; Pawar, S. H.

    2010-01-01

    The structural, transport and magnetic properties of MgB 2 superconductor heavily blended with Mg is studied. The samples are synthesized with a new approach in both, pressed carbon environment and in flowing argon. The excess magnesium used is observed to play dual role: one being the prevention of Mg losses during the synthesis process and hence maintaining the stoichiometry of MgB 2 phase, and second being the formation of Mg milieu probably all around the MgB 2 grains to give a dense structure. Excess Mg also improves the grain connectivity by going into the pores and there by minimizing the insulating junctions. The residual resistivity of the sample is observed to decrease from 57.02 μΩ cm to 10.042 μΩ cm as it is progressively filled with superconductor-normal-superconductor (SNS) type junctions amongst the grains by the virtue of increased magnesium content. The synthesized samples devoid of porosity show the superconducting transition, T c in the range of 39-34 K as of clean MgB 2 samples, though overloaded with Mg. The excess Mg resulted in enhanced critical current density, J c from 6.8 × 10 3 A cm -2 to 5.9 × 10 4 A cm -2 at 20 K and 10 kOe, with reasonable decrease in the superconducting transition. Thus our samples being overloaded with Mg impart mechanical strength and competitive superconducting properties, which forms a part of interest.

  12. Mitochondrial Mg2+ homeostasis decides cellular energy metabolism and vulnerability to stress

    PubMed Central

    Yamanaka, Ryu; Tabata, Sho; Shindo, Yutaka; Hotta, Kohji; Suzuki, Koji; Soga, Tomoyoshi; Oka, Kotaro

    2016-01-01

    Cellular energy production processes are composed of many Mg2+ dependent enzymatic reactions. In fact, dysregulation of Mg2+ homeostasis is involved in various cellular malfunctions and diseases. Recently, mitochondria, energy-producing organelles, have been known as major intracellular Mg2+ stores. Several biological stimuli alter mitochondrial Mg2+ concentration by intracellular redistribution. However, in living cells, whether mitochondrial Mg2+ alteration affect cellular energy metabolism remains unclear. Mg2+ transporter of mitochondrial inner membrane MRS2 is an essential component of mitochondrial Mg2+ uptake system. Here, we comprehensively analyzed intracellular Mg2+ levels and energy metabolism in Mrs2 knockdown (KD) cells using fluorescence imaging and metabolome analysis. Dysregulation of mitochondrial Mg2+ homeostasis disrupted ATP production via shift of mitochondrial energy metabolism and morphology. Moreover, Mrs2 KD sensitized cellular tolerance against cellular stress. These results indicate regulation of mitochondrial Mg2+ via MRS2 critically decides cellular energy status and cell vulnerability via regulation of mitochondrial Mg2+ level in response to physiological stimuli. PMID:27458051

  13. Effect of carbon on hydrogen desorption and absorption of mechanically milled MgH 2

    NASA Astrophysics Data System (ADS)

    Shang, C. X.; Guo, Z. X.

    The use of MgH 2, instead of pure Mg, in the mechanical synthesis of Mg-based hydrogen storage materials offers added benefit to powder size refinement and reduced oxygen contamination. Alloying additions can further improve the sorption kinetics at a relatively low temperature. This paper examines the effect of graphitic carbon on the desorption and absorption of MgH 2. Graphite powder of different concentrations were mechanically milled with MgH 2 particles. The milled powder was characterised by XRD, SEM and simultaneous TG and DSC techniques. The results show that graphite poses little influence on the desorption properties of MgH 2. However, it does benefit the absorption process, leading to rapid hydrogen uptake in the re-hydrogenated sample. After dehydrogenation, 5 wt.% of hydrogen was re-absorbed within 30 min at 250 °C for the ( MgH 2+10 G) mixture prior-milled for 8 h, while only 0.8 wt.% for the pure MgH 2 milled for 8 h, the effect may be attributed to the interaction between crystalline graphite with H 2 disassociation close to the MgH 2 or Mg surface. Moreover, graphite can also inhibit the formation of a new oxide layer on the surface of Mg particles.

  14. Direct observation of solid-state reversed transformation from crystals to quasicrystals in a Mg alloy

    NASA Astrophysics Data System (ADS)

    Liu, Jian-Fang; Yang, Zhi-Qing; Ye, Heng-Qiang

    2015-06-01

    Phase transformation of quasicrystals is of interest in various fields of science and technology. Interestingly, we directly observed unexpected solid-state epitaxial nucleation and growth of Zn6Mg3Y icosahedral quasicrystals in a Mg alloy at about 573 K which is about 300 K below the melting point of Zn6Mg3Y, in contrast to formation of quasicrystals through solidification that was usually found in many alloys. Maximizing local packing density of atoms associated with segregation of Y and Zn in Mg adjacent to Mg/Zn3MgY interfaces triggered atomic rearrangement in Mg to form icosahedra coupled epitaxially with surface distorted icosahedra of Zn3MgY, which plays a critical role in the nucleation of icosahedral clusters. A local Zn:Mg:Y ratio close to 6:3:1, corresponding to a valence electron concentration of about 2.15, should have been reached to trigger the formation of quasicrystals at Mg/Zn3MgY interfaces. The solid-state icosahedral ordering in crystals opens a new window for growing quasicrystals and understanding their atomic origin mechanisms. Epitaxial growth of quasicrystals onto crystals can modify the surface/interface structures and properties of crystalline materials.

  15. On the synthesis, structural, optical and magnetic properties of nano-size Zn-MgO

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Dwivedi, Sonam

    2015-09-01

    Chemical co-precipitation method is employed to synthesize ZnO, MgO and Zn0.5Mg0.5O nanoparticles. X-ray diffraction (XRD) pattern infers that the sample of ZnO is in single-phase wurtzite structure (hexagonal phase, P63mc), MgO crystallizes in cubic Fd3m space group and Zn0.5Mg0.5O represents mixed nature of ZnO and MgO lattices. MgO nanocrystals band around 1078 cm-1 is ascribed to the TO-LO surface phonon modes in MgO lattice. In case of Zn0.5Mg0.5O lattice illustrating two bands at 436 and 1087 cm-1. FTIR spectra clearly show the broad band within 450-600 cm-1 is associated with the special vibration of magnesium oxide. FT-IR spectrum of Zn0.5Mg0.5O represents the combined bands of both ZnO-MgO oxides. Further the optical study obtained value of MgO (4.08 eV) is much lower than the corresponding bulk value (7.08 eV). All samples show diamagnetic nature at room temperature.

  16. Solubility of Mg-containing β-tricalcium phosphate at 25 °C

    PubMed Central

    Li, Xia; Ito, Atsuo; Sogo, Yu; Wang, Xiupeng; LeGeros, R.Z.

    2008-01-01

    The equilibrium solubility of Mg-containing β-tricalcium phosphate (βMgTCP) with various magnesium contents was determined by immersing βMgTCP powder for 27 months in a CH3COOH–CH3COONa buffer solution at 25 °C under a nitrogen gas atmosphere. The negative logarithm of the solubility product (pKsp) of βMgTCP was expressed as pKsp = 28.87432 + 1.40348C − 0.3163C2 + 0.04218C3 − 0.00275C4 + 0.0000681659C5, where C is the magnesium content in βMgTCP (mol.%). The solubility of βMgTCP decreased with increasing magnesium content owing to the increased structural stability and possible formation of a whitlockite-type phase on the surface. As a result, βMgTCP with 10.1 mol.% magnesium had a lower solubility than that of hydroxyapatite below pH 6.0. βMgTCP was found to be more soluble than zinc-containing β-tricalcium phosphate given the same molar content of zinc or magnesium. The solubility of βMgTCP and release rate of magnesium from βMgTCP can be controlled by adjusting the Mg content by selecting the appropriate pKsp. PMID:18644755

  17. Mitochondrial Mg(2+) homeostasis decides cellular energy metabolism and vulnerability to stress.

    PubMed

    Yamanaka, Ryu; Tabata, Sho; Shindo, Yutaka; Hotta, Kohji; Suzuki, Koji; Soga, Tomoyoshi; Oka, Kotaro

    2016-01-01

    Cellular energy production processes are composed of many Mg(2+) dependent enzymatic reactions. In fact, dysregulation of Mg(2+) homeostasis is involved in various cellular malfunctions and diseases. Recently, mitochondria, energy-producing organelles, have been known as major intracellular Mg(2+) stores. Several biological stimuli alter mitochondrial Mg(2+) concentration by intracellular redistribution. However, in living cells, whether mitochondrial Mg(2+) alteration affect cellular energy metabolism remains unclear. Mg(2+) transporter of mitochondrial inner membrane MRS2 is an essential component of mitochondrial Mg(2+) uptake system. Here, we comprehensively analyzed intracellular Mg(2+) levels and energy metabolism in Mrs2 knockdown (KD) cells using fluorescence imaging and metabolome analysis. Dysregulation of mitochondrial Mg(2+) homeostasis disrupted ATP production via shift of mitochondrial energy metabolism and morphology. Moreover, Mrs2 KD sensitized cellular tolerance against cellular stress. These results indicate regulation of mitochondrial Mg(2+) via MRS2 critically decides cellular energy status and cell vulnerability via regulation of mitochondrial Mg(2+) level in response to physiological stimuli. PMID:27458051

  18. In vitro biodegradation behavior, mechanical properties, and cytotoxicity of biodegradable Zn-Mg alloy.

    PubMed

    Gong, Haibo; Wang, Kun; Strich, Randy; Zhou, Jack G

    2015-11-01

    Zinc-Magnesium (Zn-Mg) alloy as a novel biodegradable metal holds great potential in biodegradable implant applications as it is more corrosion resistant than Magnesium (Mg). However, the mechanical properties, biodegradation uniformity, and cytotoxicity of Zn-Mg alloy remained as concerns. In this study, hot extrusion process was applied to Zn-1 wt % Mg (Zn-1Mg) to refine its microstructure. Effects of hot extrusion on biodegradation behavior and mechanical properties of Zn-1Mg were investigated in comparison with Mg rare earth element alloy WE43. Metallurgical analysis revealed significant grain size reduction, and immersion test found that corrosion rates of WE43 and Zn-1Mg were reduced by 35% and 57%, respectively after extrusion. Moreover, hot extrusion resulted in a much more uniform biodegradation in extruded Zn-1Mg alloy and WE43. In vitro cytotoxicity test results indicated that Zn-1Mg alloy was biocompatible. Therefore, hot extruded Zn-1Mg with homogenous microstructure, uniform as well as slow degradation, improved mechanical properties, and good biocompatibility was believed to be an excellent candidate material for load-bearing biodegradable implant application. PMID:25581552

  19. Direct observation of solid-state reversed transformation from crystals to quasicrystals in a Mg alloy

    PubMed Central

    Liu, Jian-Fang; Yang, Zhi-Qing; Ye, Heng-Qiang

    2015-01-01

    Phase transformation of quasicrystals is of interest in various fields of science and technology. Interestingly, we directly observed unexpected solid-state epitaxial nucleation and growth of Zn 6 Mg 3 Y icosahedral quasicrystals in a Mg alloy at about 573 K which is about 300 K below the melting point of Zn 6 Mg 3 Y, in contrast to formation of quasicrystals through solidification that was usually found in many alloys. Maximizing local packing density of atoms associated with segregation of Y and Zn in Mg adjacent to Mg/Zn 3 MgY interfaces triggered atomic rearrangement in Mg to form icosahedra coupled epitaxially with surface distorted icosahedra of Zn 3 MgY, which plays a critical role in the nucleation of icosahedral clusters. A local Zn:Mg:Y ratio close to 6:3:1, corresponding to a valence electron concentration of about 2.15, should have been reached to trigger the formation of quasicrystals at Mg/Zn 3 MgY interfaces. The solid-state icosahedral ordering in crystals opens a new window for growing quasicrystals and understanding their atomic origin mechanisms. Epitaxial growth of quasicrystals onto crystals can modify the surface/interface structures and properties of crystalline materials. PMID:26066096

  20. Reactive wetting of amorphous silica by molten Al-Mg alloys and their interfacial structures

    NASA Astrophysics Data System (ADS)

    Shi, Laixin; Shen, Ping; Zhang, Dan; Jiang, Qichuan

    2016-07-01

    The reactive wetting of amorphous silica substrates by molten Al-Mg alloys over a wide composition range was studied using a dispensed sessile drop method in a flowing Ar atmosphere. The effects of the nominal Mg concentration and temperature on the wetting and interfacial microstructures were discussed. The initial contact angle for pure Al on the SiO2 surface was 115° while that for pure Mg was 35° at 1073 K. For the Al-Mg alloy drop, it decreased with increasing nominal Mg concentration. The reaction zone was characterized by layered structures, whose formation was primarily controlled by the variation in the alloy concentration due to the evaporation of Mg and the interfacial reaction from the viewpoint of thermodynamics as well as by the penetration or diffusion of Mg, Al and Si from the viewpoint of kinetics. In addition, the effects of the reaction and the evaporation of Mg on the movement of the triple line were examined. The spreading of the Al-Mg alloy on the SiO2 surface was mainly attributed to the formation of Mg2Si at the interface and the recession of the triple line to the diminishing Mg concentration in the alloy.