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Sample records for mg ca zn

  1. Microstructure, In Vitro Corrosion Behavior and Cytotoxicity of Biodegradable Mg-Ca-Zn and Mg-Ca-Zn-Bi Alloys

    NASA Astrophysics Data System (ADS)

    Bakhsheshi-Rad, H. R.; Hamzah, E.; Tok, H. Y.; Kasiri-Asgarani, M.; Jabbarzare, S.; Medraj, M.

    2017-01-01

    The effects of bismuth (Bi) addition on the microstructure and corrosion behavior of the Mg-Ca-Zn-Bi alloys were evaluated using electron microscopy, electrochemical test and electrochemical impedance spectroscopy. Microstructural observations showed that Mg-1.2Ca-1Zn-xBi (x = 0.5, 1.5, 3 wt.%) are composed of Mg2Ca, Ca2Mg6Zn3 and Mg3Bi2 phases while a new phase Mg2Bi2Ca appeared after the addition of 5 and 12 wt.% Bi to the Mg-1.2Ca-1Zn alloy. Furthermore, the additions of 0.5 wt.% Bi to the Mg-1.2Ca-1Zn alloy slightly improved the corrosion behavior of the alloy, while further increase in Bi amount from 1.5 to 12 wt.% has a deleterious effect on the corrosion behavior of the ternary Mg-1.2Ca-1Zn alloy which is driven by galvanic coupling effect. Cytotoxicity tests indicate that the Mg-1.2Ca-1Zn presents higher cell viability compared to Mg-1.2Ca-1Zn-0.5Bi alloy. In addition, the cell viability of both alloys increased with increasing incubation time while diluting the extracts to 50% and 10% improved the cell viabilities. The present results suggest that the Mg-1.2Ca-1Zn-0.5Bi can be interesting candidate for the development of degradable biomaterials and it is worthwhile for further investigation in an in vivo environment.

  2. Microstructure, In Vitro Corrosion Behavior and Cytotoxicity of Biodegradable Mg-Ca-Zn and Mg-Ca-Zn-Bi Alloys

    NASA Astrophysics Data System (ADS)

    Bakhsheshi-Rad, H. R.; Hamzah, E.; Tok, H. Y.; Kasiri-Asgarani, M.; Jabbarzare, S.; Medraj, M.

    2017-02-01

    The effects of bismuth (Bi) addition on the microstructure and corrosion behavior of the Mg-Ca-Zn-Bi alloys were evaluated using electron microscopy, electrochemical test and electrochemical impedance spectroscopy. Microstructural observations showed that Mg-1.2Ca-1Zn- xBi ( x = 0.5, 1.5, 3 wt.%) are composed of Mg2Ca, Ca2Mg6Zn3 and Mg3Bi2 phases while a new phase Mg2Bi2Ca appeared after the addition of 5 and 12 wt.% Bi to the Mg-1.2Ca-1Zn alloy. Furthermore, the additions of 0.5 wt.% Bi to the Mg-1.2Ca-1Zn alloy slightly improved the corrosion behavior of the alloy, while further increase in Bi amount from 1.5 to 12 wt.% has a deleterious effect on the corrosion behavior of the ternary Mg-1.2Ca-1Zn alloy which is driven by galvanic coupling effect. Cytotoxicity tests indicate that the Mg-1.2Ca-1Zn presents higher cell viability compared to Mg-1.2Ca-1Zn-0.5Bi alloy. In addition, the cell viability of both alloys increased with increasing incubation time while diluting the extracts to 50% and 10% improved the cell viabilities. The present results suggest that the Mg-1.2Ca-1Zn-0.5Bi can be interesting candidate for the development of degradable biomaterials and it is worthwhile for further investigation in an in vivo environment.

  3. Structure of Ca-Mg-Zn Metallic Glasses (Preprint)

    DTIC Science & Technology

    2011-07-01

    can be described as a mixture of Mg- and Zn- centered clusters, with Ca dominating in the first coordination shell of these clusters. The coordination...simulation. The amorphous structure can be described as a mixture of Mg- and Zn- centered clusters, with Ca dominating in the first coordination...in mm). The presence of the ternary eutectic reaction provides a strong liquidus temperature gradient in the selected composition area, which leads

  4. The synthesis and characterization of Mg-Zn-Ca alloy by powder metallurgy process

    SciTech Connect

    Annur, Dhyah; Franciska, P.L.; Erryani, Aprilia; Amal, M. Ikhlasul; Kartika, Ika; Sitorus, Lyandra S.

    2016-04-19

    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.

  5. Microstructures and Mechanical Study of Mg Alloy Foam Based on Mg-Zn-Ca-CaCO3 System

    NASA Astrophysics Data System (ADS)

    Erryani, A.; Pramuji, F.; Annur, D.; Amal, M. I.; Kartika, I.

    2017-05-01

    Magnesium alloy, a material that has potential to use some applications such as aerospace components, computer parts, and mobile phones. Magnesium alloy can also be a popular candidate as an orthopedic implant material for biodegradability, non-toxicity, and mechanical and physical properties that are excellent. Magnesium, one of the main macro elements required for the proper functioning of the human organism, is used to test the materials for biodegradable implants. The main objective of this study was to find out the microstructure, and mechanical characteristics of the Mg-Ca-Zn-CaCO3 alloy as porous implant materials are biodegradable. The presence of CaCO3 on the alloy functions as a foaming agent expected to produce gas bubbles during manufacturing process taken place that will form pores in the alloy. Mg-Ca-Zn-CaCO3 alloy was made by powder metallurgy method with three variations of composition (96Mg-Ca-3Zn-CaCO3, 91Mg-Ca-3Zn-5CaCO3, and 86Mg-Ca-3Zn-10CaCO3 wt%). Milling process was by using a shaker mill for 2 hours to produce a powder size distribution which was more homogeneous. The mixed powder was uniaxially pressed at a pressure of 100 MPa for 2 minutes and 200 MPa for 3 minutes into green compacts with dimensions of 10 mm in diameter and 10 mm in length. The sintering process was carried out at 650°C with a variation of holding time of 10 and 15 hours, and then the specimens were cooled down at room temperature. Microstructural analysis was performed by using X-Ray diffraction technique and Scanning electron microscopy equipped with an energy disperse spectrometry (EDS). The mechanical characteristics were analyzed by using Universal Testing Machine. The density and porosity of specimen were further measured by using Archimedes method. The results show that the optimum microstructure and mechanical characteristics are the holding time of 10 hours. The value of compression was 208.398 N/mm2, the density was 1.63 g/cc and a porosity was 18% on the

  6. High-Strength Low-Alloy (HSLA) Mg-Zn-Ca Alloys with Excellent Biodegradation Performance

    NASA Astrophysics Data System (ADS)

    Hofstetter, J.; Becker, M.; Martinelli, E.; Weinberg, A. M.; Mingler, B.; Kilian, H.; Pogatscher, S.; Uggowitzer, P. J.; Löffler, J. F.

    2014-04-01

    This article deals with the development of fine-grained high-strength low-alloy (HSLA) magnesium alloys intended for use as biodegradable implant material. The alloys contain solely low amounts of Zn and Ca as alloying elements. We illustrate the development path starting from the high-Zn-containing ZX50 (MgZn5Ca0.25) alloy with conventional purity, to an ultrahigh-purity ZX50 modification, and further to the ultrahigh-purity Zn-lean alloy ZX10 (MgZn1Ca0.3). It is shown that alloys with high Zn-content are prone to biocorrosion in various environments, most probably because of the presence of the intermetallic phase Mg6Zn3Ca2. A reduction of the Zn content results in (Mg,Zn)2Ca phase formation. This phase is less noble than the Mg-matrix and therefore, in contrast to Mg6Zn3Ca2, does not act as cathodic site. A fine-grained microstructure is achieved by the controlled formation of fine and homogeneously distributed (Mg,Zn)2Ca precipitates, which influence dynamic recrystallization and grain growth during hot forming. Such design scheme is comparable to that of HSLA steels, where low amounts of alloying elements are intended to produce a very fine dispersion of particles to increase the material's strength by refining the grain size. Consequently our new, ultrapure ZX10 alloy exhibits high strength (yield strength R p = 240 MPa, ultimate tensile strength R m = 255 MPa) and simultaneously high ductility (elongation to fracture A = 27%), as well as low mechanical anisotropy. Because of the anodic nature of the (Mg,Zn)2Ca particles used in the HSLA concept, the in vivo degradation in a rat femur implantation study is very slow and homogeneous without clinically observable hydrogen evolution, making the ZX10 alloy a promising material for biodegradable implants.

  7. Microstructure and mechanical properties of Mg-5Sn-5Zn-xCa alloys

    NASA Astrophysics Data System (ADS)

    Qiu, Ke-qiang; Liu, Bin; You, Jun-hua; Ren, Ying-lei

    Mg-5Sn-5Zn-xCa(x=0.5, 1, 2) alloys were melted by the vacuum melting furnace. The microstructures and phase compositions were analyzed by the scanning electron microscope (SEM) and X-ray diffraction (XRD). The mechanical properties were tested by the electronic universal test machine. The fracture surface were observed by scanning electron microscope (SEM). The results indicate that the microstructures of Mg-5Zn-5Sn-xCa alloys are composed of CaMgSn phases, layer MgZn2 phases and Mg2Sn phases. Matrix precipitates onset Mg2Ca phase, when the content of Ca is 2 wt%. With the increasing of the Ca content, the needle CaMgSn phases become rods gradually, the layer MgZn2 phases and plate Mg2Sn phases become continuous, ultimate tensile strength decrease. The ultimate tensile strength obtained by Mg-5Zn-5Sn-0.5Ca alloy is 184MPa.

  8. Microstructures, mechanical properties and corrosion resistances of extruded Mg-Zn-Ca-xCe/La alloys.

    PubMed

    Tong, L B; Zhang, Q X; Jiang, Z H; Zhang, J B; Meng, J; Cheng, L R; Zhang, H J

    2016-09-01

    Magnesium alloys are considered as good candidates for biomedical applications, the influence of Ce/La microalloying on the microstructure, mechanical property and corrosion performance of extruded Mg-5.3Zn-0.6Ca (wt%) alloy has been investigated in the current study. After Ce/La addition, the conventional Ca2Mg6Zn3 phases are gradually replaced by new Mg-Zn-Ce/La-(Ca) phases (T1'), which can effectively divide the Ca2Mg6Zn3 phase. The Ca2Mg6Zn3/T1' structure in Mg-Zn-Ca-0.5Ce/La alloy is favorably broken into small particles during the extrusion, resulting in an obvious refinement of secondary phase. The dynamic recrystallized grain size is dramatically decreased after 0.5Ce/La addition, and the tensile yield strength is improved, while further addition reverses the effect, due to the grain coarsening. However, the corrosion resistance of extruded Mg-Zn-Ca alloy deteriorates after Ce/La addition, because the diameter of secondary phase particle is remarkably decreased, which increases the amount of cathodic sites and accelerates the galvanic corrosion process.

  9. Production and Precipitation Hardening of Mg-Ca-Zn-Co Alloy for Tissue Engineering.

    PubMed

    Mutlu, Ilven

    2017-02-01

    In this study, Mg-Ca-Zn-Co alloy specimens for biomedical applications were produced by the powder metallurgy method. The Mg-Ca-Zn-Co alloy could be used as a scaffold material in tissue engineering applications. Electrochemical corrosion behavior of the specimens was investigated in simulated body fluid environment. Electrochemical corrosion resistance of the specimens was increased with increasing Zn and Ca contents of the alloy up to an optimum composition and then decreased. Optimum values for Ca and Zn additions were about 0.7 wt.% and 3.0 wt.% respectively. Young's modulus values of the specimens were determined by nondestructive ultrasonic measurement. Alloying element addition increased the Young's modulus of the specimens. Precipitation hardening of the Mg-Ca-Zn-Co alloy increased the Young's modulus and the corrosion rate of the specimens.

  10. Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr.

    PubMed

    Li, H F; Xie, X H; Zheng, Y F; Cong, Y; Zhou, F Y; Qiu, K J; Wang, X; Chen, S H; Huang, L; Tian, L; Qin, L

    2015-05-29

    Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals.

  11. Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr

    PubMed Central

    Li, H. F.; Xie, X. H.; Zheng, Y. F.; Cong, Y.; Zhou, F. Y.; Qiu, K. J.; Wang, X.; Chen, S. H.; Huang, L.; Tian, L.; Qin, L.

    2015-01-01

    Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals. PMID:26023878

  12. Investigation on microstructure characterization and property of rapidly solidified Mg-Zn-Ca-Ce-La alloys

    SciTech Connect

    Zhou Tao; Chen Zhenhua; Yang Mingbo; Hu Jianjun; Xia Hua

    2012-01-15

    Rapidly solidified (RS) Mg-Zn-Ca-Ce-La (wt.%) alloys have been produced via atomizing the alloy melt and subsequent splat-quenching on the water-cooled copper twin-rollers in the form of flakes. Microstructure characterization, phase compositions and thermal stability of the alloys have been systematically investigated. The results showed that with addition of RE (Ce and La) to the Mg-6Zn-5Ca alloy, the stable intermetallic compounds i.e. the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (about 3 at.%), shortened as the T Prime phase, were formed at the expense of the binary Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases, which was possibly beneficial to the enhanced thermal stability of the alloy. In the Mg-6Zn-5Ca-3Ce-0.5La alloy, the composition of the T Prime phase in the grain interior was different from that at the grain boundaries, in which the segregation of the La elements was found, and the atomic percentage ratio of Zn to Ce in the T Prime phase within the grains was close to 2. Moreover, the stable Mg{sub 2}Ca phases were detected around the T Prime phases at the grain boundaries in the alloy. - Research Highlights: Black-Right-Pointing-Pointer The phase constitution of RS Mg-6Zn-5Ca alloy can be improved by RE additions. Black-Right-Pointing-Pointer In the Mg-Zn-Ca-Ce-La alloys, the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (T Prime phase) is formed. Black-Right-Pointing-Pointer The formation of the T Prime phase leads to the loss of the Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases. Black-Right-Pointing-Pointer The composition of the T Prime phase differs from the grain interior to the grain boundary.

  13. Biodegradable CaMgZn bulk metallic glass for potential skeletal application.

    PubMed

    Wang, Y B; Xie, X H; Li, H F; Wang, X L; Zhao, M Z; Zhang, E W; Bai, Y J; Zheng, Y F; Qin, L

    2011-08-01

    A low density and high strength alloy, Ca65Mg15Zn20 bulk metallic glass (CaMgZn BMG), was evaluated by both in vitro tests on ion release and cytotoxicity and in vivo implantation, aimed at exploring the feasibility of this new biodegradable metallic material for potential skeletal applications. MTT assay results showed that the experimental CaMgZn BMG extracts had no detectable cytotoxic effects on L929, VSMC and ECV304 cells over a wide range of concentrations (0-50%), whereas for MG63 cells concentrations in the range ~5-20% promoted cell viability. Meanwhile, alkaline phosphatase (ALP) activity results showed that CaMgZn BMG extracts increased alkaline phosphatase (ALP) production by MG63 cells. However, Annexin V-fluorescein isothiocyanate and propidium iodide staining indicated that higher concentrations (50%) might induce cell apoptosis. The fluorescence observation of F-actin and nuclei in MG63 cells showed that cells incubated with lower concentrations (0-50%) displayed no significant change in morphology compared with a negative control. Tumor necrosis factor-α expression by Raw264.7 cells in the presence of CaMgZn BMG extract was significantly lower than that of the positive and negative controls. Animal tests proved that there was no obvious inflammation reaction at the implantation site and CaMgZn BMG implants did not result in animal death. The cortical thickness around the CaMgZn BMG implant increased gradually from 1 to 4 weeks, as measured by in vivo micro-computer tomography.

  14. Microstructure and mechanical properties of the as-cast Mg-Zn-Mn-Ca alloys

    NASA Astrophysics Data System (ADS)

    Fu, Junjian; Liu, Ke; Du, Wenbo; Wang, Zhaohui; Li, Shubo; Du, Xian

    2017-03-01

    As-cast Mg-Zn-Mn-Ca alloys are the candidates for medical implants. The microstructure and mechanical properties of the as-cast Mg-Zn-Mn-Ca alloys were investigated by using optical microscope (OM), X-ray diffraction (XRD) and scanning electron microscope (SEM). The results suggested that the addition of Zn significantly refined the grain size of the as-cast magnesium alloys, and hence improved the mechanical properties of the alloys. Meanwhile, the secondary phase mainly distributed in the grain boundaries and the solution treatment made parts of secondary phases dissolved into the matrix, resulting in enhancement of the plasticity of the as-cast Mg-Zn-Mn-Ca alloy.

  15. The Influence of Zn Content on the Corrosion and Wear Performance of Mg-Zn-Ca Alloy in Simulated Body Fluid

    NASA Astrophysics Data System (ADS)

    Li, Hua; Liu, Debao; Zhao, Yue; Jin, Feng; Chen, Minfang

    2016-09-01

    Mg-Zn-Ca alloy has been attracting increasing attention as a potential biodegradable implant material. In this paper, Mg-3Zn-0.2Ca and Mg-4Zn-0.2Ca alloys were prepared by means of vacuum melting and subsequent hot extrusion process. The influences of Zn content on the microstructure, mechanical properties, and corrosion and wear behavior of Mg-Zn-Ca alloys in simulated body fluid (SBF) were studied. The results show that with increased Zn content, the grain size and corrosion resistance were decreased, while the mechanical strength and wear resistance were increased, under both dry sliding and SBF-lubricated conditions. For the same Mg-Zn-Ca alloy, the wear loss rate under SBF lubrication was higher than dry sliding condition, indicating a strong corrosion-assisted wear effect of SBF to the Mg-Zn-Ca alloy.

  16. Cytotoxicity assessment of adipose-derived mesenchymal stem cells on synthesized biodegradable Mg-Zn-Ca alloys.

    PubMed

    Fazel Anvari-Yazdi, Abbas; Tahermanesh, Kobra; Hadavi, Seyed Mohammad Mehdi; Talaei-Khozani, Tahereh; Razmkhah, Mahboobeh; Abed, Seyedeh Mehr; Mohtasebi, Maryam Sadat

    2016-12-01

    Magnesium (Mg)-based alloys have been extensively considered as biodegradable implant materials for orthopedic surgery. Mg and its alloys are metallic biomaterials that can degrade in the body and promote new bone formation. In this study, the corrosion behavior and cytotoxicity of Mg-Zn-Ca alloys are evaluated with adipose-derived mesenchymal stem cells (ASCs). Mg-2Zn and Mg-2Zn-xCa (x=1, 2 and 3wt.%) alloys were designated. Mg alloys were analyzed with scanning electron microscopy and potentiodynamic polarization. To understand the in-vitro biocompatibility and cytotoxicity of Mg-2Zn and Mg-2Zn-xCa alloys, ASCs were cultured for 24 and 72h in contact with 10%, 50% and 100% extraction of all alloys prepared in DMEM. Cell cytotoxicity and viability of ASCs were examined by MTT assay. Alloying elements including Zn and Ca improved the corrosion resistance of alloys were compared with pure Mg. The cytotoxicity results showed that all alloys had no significant adverse effects on cell viability in 24h. After 72h, cell viability and proliferation increased in the cells exposed to pure Mg and Mg-2Zn-1Ca extracts. The release of Mg, Zn and Ca ions in culture media had no toxic impacts on ASCs viability and proliferation. Mg-2Zn-1Ca alloy can be suggested as a good candidate to be used in biomedical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Unique antitumor property of the Mg-Ca-Sr alloys with addition of Zn

    PubMed Central

    Wu, Yuanhao; He, Guanping; Zhang, Yu; Liu, Yang; Li, Mei; Wang, Xiaolan; Li, Nan; Li, Kang; Zheng, Guan; Zheng, Yufeng; Yin, Qingshui

    2016-01-01

    In clinical practice, tumor recurrence and metastasis after orthopedic prosthesis implantation is an intensely troublesome matter. Therefore, to develop implant materials with antitumor property is extremely necessary and meaningful. Magnesium (Mg) alloys possess superb biocompatibility, mechanical property and biodegradability in orthopedic applications. However, whether they possess antitumor property had seldom been reported. In recent years, it showed that zinc (Zn) not only promote the osteogenic activity but also exhibit good antitumor property. In our present study, Zn was selected as an alloying element for the Mg-1Ca-0.5Sr alloy to develop a multifunctional material with antitumor property. We investigated the influence of the Mg-1Ca-0.5Sr-xZn (x = 0, 2, 4, 6 wt%) alloys extracts on the proliferation rate, cell apoptosis, migration and invasion of the U2OS cell line. Our results show that Zn containing Mg alloys extracts inhibit the cell proliferation by alteration the cell cycle and inducing cell apoptosis via the activation of the mitochondria pathway. The cell migration and invasion property were also suppressed by the activation of MAPK (mitogen-activated protein kinase) pathway. Our work suggests that the Mg-1Ca-0.5Sr-6Zn alloy is expected to be a promising orthopedic implant in osteosarcoma limb-salvage surgery for avoiding tumor recurrence and metastasis. PMID:26907515

  18. Unique antitumor property of the Mg-Ca-Sr alloys with addition of Zn.

    PubMed

    Wu, Yuanhao; He, Guanping; Zhang, Yu; Liu, Yang; Li, Mei; Wang, Xiaolan; Li, Nan; Li, Kang; Zheng, Guan; Zheng, Yufeng; Yin, Qingshui

    2016-02-24

    In clinical practice, tumor recurrence and metastasis after orthopedic prosthesis implantation is an intensely troublesome matter. Therefore, to develop implant materials with antitumor property is extremely necessary and meaningful. Magnesium (Mg) alloys possess superb biocompatibility, mechanical property and biodegradability in orthopedic applications. However, whether they possess antitumor property had seldom been reported. In recent years, it showed that zinc (Zn) not only promote the osteogenic activity but also exhibit good antitumor property. In our present study, Zn was selected as an alloying element for the Mg-1Ca-0.5Sr alloy to develop a multifunctional material with antitumor property. We investigated the influence of the Mg-1Ca-0.5Sr-xZn (x = 0, 2, 4, 6 wt%) alloys extracts on the proliferation rate, cell apoptosis, migration and invasion of the U2OS cell line. Our results show that Zn containing Mg alloys extracts inhibit the cell proliferation by alteration the cell cycle and inducing cell apoptosis via the activation of the mitochondria pathway. The cell migration and invasion property were also suppressed by the activation of MAPK (mitogen-activated protein kinase) pathway. Our work suggests that the Mg-1Ca-0.5Sr-6Zn alloy is expected to be a promising orthopedic implant in osteosarcoma limb-salvage surgery for avoiding tumor recurrence and metastasis.

  19. Unique antitumor property of the Mg-Ca-Sr alloys with addition of Zn

    NASA Astrophysics Data System (ADS)

    Wu, Yuanhao; He, Guanping; Zhang, Yu; Liu, Yang; Li, Mei; Wang, Xiaolan; Li, Nan; Li, Kang; Zheng, Guan; Zheng, Yufeng; Yin, Qingshui

    2016-02-01

    In clinical practice, tumor recurrence and metastasis after orthopedic prosthesis implantation is an intensely troublesome matter. Therefore, to develop implant materials with antitumor property is extremely necessary and meaningful. Magnesium (Mg) alloys possess superb biocompatibility, mechanical property and biodegradability in orthopedic applications. However, whether they possess antitumor property had seldom been reported. In recent years, it showed that zinc (Zn) not only promote the osteogenic activity but also exhibit good antitumor property. In our present study, Zn was selected as an alloying element for the Mg-1Ca-0.5Sr alloy to develop a multifunctional material with antitumor property. We investigated the influence of the Mg-1Ca-0.5Sr-xZn (x = 0, 2, 4, 6 wt%) alloys extracts on the proliferation rate, cell apoptosis, migration and invasion of the U2OS cell line. Our results show that Zn containing Mg alloys extracts inhibit the cell proliferation by alteration the cell cycle and inducing cell apoptosis via the activation of the mitochondria pathway. The cell migration and invasion property were also suppressed by the activation of MAPK (mitogen-activated protein kinase) pathway. Our work suggests that the Mg-1Ca-0.5Sr-6Zn alloy is expected to be a promising orthopedic implant in osteosarcoma limb-salvage surgery for avoiding tumor recurrence and metastasis.

  20. MgZnCa glasses without clinically observable hydrogen evolution for biodegradable implants.

    PubMed

    Zberg, Bruno; Uggowitzer, Peter J; Löffler, Jörg F

    2009-11-01

    Corrosion is normally an undesirable phenomenon in engineering applications. In the field of biomedical applications, however, implants that 'biocorrode' are of considerable interest. Deploying them not only abrogates the need for implant-removal surgery, but also circumvents the long-term negative effects of permanent implants. In this context magnesium is an attractive biodegradable material, but its corrosion is accompanied by hydrogen evolution, which is problematic in many biomedical applications. Whereas the degradation and thus the hydrogen evolution of crystalline Mg alloys can be altered only within a very limited range, Mg-based glasses offer extended solubility for alloying elements plus a homogeneous single-phase structure, both of which may alter corrosion behaviour significantly. Here we report on a distinct reduction in hydrogen evolution in Zn-rich MgZnCa glasses. Above a particular Zn-alloying threshold (approximately 28 at.%), a Zn- and oxygen-rich passivating layer forms on the alloy surface, which we explain by a model based on the calculated Pourbaix diagram of Zn in simulated body fluid. We document animal studies that confirm the great reduction in hydrogen evolution and reveal the same good tissue compatibility as seen for crystalline Mg implants. Thus, the glassy Mg(60+x)Zn(35-x)Ca5 (0 < or = x < or = 7) alloys show great potential for deployment in a new generation of biodegradable implants.

  1. MgZnCa glasses without clinically observable hydrogen evolution for biodegradable implants

    NASA Astrophysics Data System (ADS)

    Zberg, Bruno; Uggowitzer, Peter J.; Löffler, Jörg F.

    2009-11-01

    Corrosion is normally an undesirable phenomenon in engineering applications. In the field of biomedical applications, however, implants that `biocorrode' are of considerable interest. Deploying them not only abrogates the need for implant-removal surgery, but also circumvents the long-term negative effects of permanent implants. In this context magnesium is an attractive biodegradable material, but its corrosion is accompanied by hydrogen evolution, which is problematic in many biomedical applications. Whereas the degradation and thus the hydrogen evolution of crystalline Mg alloys can be altered only within a very limited range, Mg-based glasses offer extended solubility for alloying elements plus a homogeneous single-phase structure, both of which may alter corrosion behaviour significantly. Here we report on a distinct reduction in hydrogen evolution in Zn-rich MgZnCa glasses. Above a particular Zn-alloying threshold (~28at.%), a Zn- and oxygen-rich passivating layer forms on the alloy surface, which we explain by a model based on the calculated Pourbaix diagram of Zn in simulated body fluid. We document animal studies that confirm the great reduction in hydrogen evolution and reveal the same good tissue compatibility as seen for crystalline Mg implants. Thus, the glassy Mg60+xZn35-xCa5 (0<=x<=7) alloys show great potential for deployment in a new generation of biodegradable implants.

  2. Exploring Mg-Zn-Ca-Based Bulk Metallic Glasses for Biomedical Applications Based on Thermodynamic Approach

    NASA Astrophysics Data System (ADS)

    Ramya, M.; Sarwat, Syed Ghazi; Udhayabanu, V.; Raj, Baldev; Ravi, K. R.

    2015-12-01

    Magnesium (Mg)-based metallic glasses are considered as possible candidates in orthopedic implant applications. This paper aims to theoretically predict the glass-forming ability (GFA) in Mg-Zn-Ca alloy using a newly proposed thermodynamic model ( P HHS), and the consistency of this model is verified through experimental analysis. P HHS is based on thermodynamic parameters such as enthalpy of chemical mixing, elastic enthalpy, and configurational entropy, thus incorporating the pivotal effects, i.e., electron transfer effects, effect of atomic size mismatch, and effect of randomness, which aid to high GFA. In essence, P HHS can be visualized as the energy barrier that exists between the transformations of random atomic structure of glass to ordered crystalline structure. When the P HHS value is more negative, the energy barrier will be high, supporting easy glass formation. Various Mg-Zn-Ca metallic glass compositions displayed almost an expected and supporting trend, where the critical diameter of the metallic glass rod increased with a more negative P HHS value. Among the predicted Mg-Zn-Ca systems, the Mg60Zn35Ca5 composition shows deviation from the expected trend. This discrepancy has been clearly elucidated using a eutectic phase diagram. In addition to the consistency of the P HHS parameter to verifying the GFA of various compositions, the unique ability of this model is to predict unexplored Mg-Zn-Ca glass-forming compositions using contour development. Thus, proving P HHS parameter to be used as an efficient tool in predicting new glass-forming compositions.

  3. On the biodegradability, mechanical behavior, and cytocompatibility of amorphous Mg72 Zn23 Ca5 and crystalline Mg70 Zn23 Ca5 Pd2 alloys as temporary implant materials.

    PubMed

    Pellicer, E; González, S; Blanquer, A; Suriñach, S; Baró, M D; Barrios, L; Ibáñez, E; Nogués, C; Sort, J

    2013-02-01

    The evolution of microstructure and mechanical properties of almost fully amorphous Mg(72) Zn(23) Ca(5) and crystalline Mg(70) Zn(23) Ca(5) Pd(2) alloys during immersion in Hank's balanced salt solution (HBSS), as well as their cytocompatibility, are investigated in order to assess the feasibility of both materials as biodegradable implants. Though the crystalline Mg(70) Zn(23) Ca(5) Pd(2) sample shows lower wettability and more positive corrosion potential, this sample degrades much faster upon incubation in HBSS as a consequence of the formation of micro-galvanic couples between the nobler Pd-rich dendrites and the surrounding phases. After 22-h immersion, the concentration of Mg ions in the HBSS medium containing the Mg(70) Zn(23) Ca(5) Pd(2) sample is six times larger than for Mg(72) Zn(23) Ca(5) . Due to the Zn enrichment and the incipient porosity, the mechanical properties of the Mg(72) Zn(23) Ca(5) sample improve within the first stages of biodegradation (i.e., hardness increases while the Young's modulus decreases, thus rendering an enhanced wear resistance). Cytocompatibility studies reveal that neither Mg(72) Zn(23) Ca(5) nor Mg(70) Zn(23) Ca(5) Pd(2) are cytotoxic, although preosteoblast cell adhesion is to some extent precluded, particularly onto the surface of Mg(70) Zn(23) Ca(5) Pd(2) , because of the relatively high hydrophobicity. Because of their outstanding properties and their time-evolution, the use of the Pd-free alloy in temporary implants such as screws, stents, and sutures is envisioned.

  4. Speciation of Zn, Fe, Ca and Mg in wine with the Donnan Membrane Technique.

    PubMed

    Lao, Mireia; Companys, Encarnació; Weng, Liping; Puy, Jaume; Galceran, Josep

    2018-01-15

    Free concentrations of Zn(2+), Fe(3+), Ca(2+) and Mg(2+) in a red wine (Raimat, Catalonia, Spain) have been determined, with the Donnan Membrane Technique (DMT) for the first time. The required equilibration time benefits from the acceptor solution including major cations. K(+) and Na(+), mainly unbound to any ligand in the sample, have been identified as suitable reference ions. A free Zn concentration of 1.76μmolL(-1) determined with DMT was in excellent agreement with the free Zn concentration independently provided by the electroanalytical technique Absence of Gradients and Nernstian Equilibrium Stripping (AGNES), 1.7μmolL(-1), amounting to 14.4% of the total Zn. The free concentrations found in this wine were 1.79μmolL(-1) Fe(3+), 1.11mmolL(-1) Ca(2+) and 3.4mmolL(-1)Mg(2+) (8.82%, 40% and 57% of their total concentrations). Prior to the application of the techniques to the red wine, they had been cross-validated in Zn-tartrate solutions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Microstructure and corrosion study of porous Mg-Zn-Ca alloy in simulated body fluid

    NASA Astrophysics Data System (ADS)

    Annur, Dhyah; Erryani, Aprilia; Lestari, Franciska P.; Nyoman Putrayasa, I.; Kartika, Ika

    2017-03-01

    Magnesium alloys had been considered as promising biomedical devices due to their biocompatibility and biodegradability. In this present work, microstructure and corrosion properties of Mg-Zn-Ca-CaCO3 porous magnesium alloy were examined. Porous metals were fabricated through powder metallurgy process with CaCO3 addition as a foaming agent. CaCO3 content was varied (1, 5, and 10%wt) followed by sintering process in 650 °C in Argon atmosphere for 10 and 15 h. The microstructure of the resulted alloys was analyzed by scanning electron microscopy (SEM) equipped with energy dispersive spectrometry data (EDS). Further, to examine corrosion properties, electrochemical test were conducted using G750 Gamry Instrument in accordance with ASTM standard G5-94 in simulated body fluid (Hank’s solution). As it was predicted, increasing content of foaming agent was in line with the increasing of pore formation. The electrochemical testing indicated corrosion rate would increase along with the increasing of foaming agent. The porous Mg-Zn-Ca alloy which has more porosity and connecting area will corrode much faster because it can transport the solution containing chloride ion which accelerated the chemical reaction. Highest corrosion resistance was given by Mg-Zn-Ca-1CaCO3-10 h sintering with potential corrosion of  -1.59 VSCE and corrosion rate of 1.01 mmpy. From the microstructure after electrochemical testing, it was revealed that volcano shaped structure and crack would occur after exposure to Hank’s solution

  6. Concentrations of morphologically normal, motile spermatozoa: Mg, Ca and Zn in the semen of infertile men.

    PubMed

    Pandy, V K; Parmeshwaran, M; Soman, S D; Dacosta, J C

    1983-03-01

    Semen from infertile men (n = 23) has been compared with that of control subjects (n = 25). Whereas the concentrations of morphologically normal, motile sperms, Mg, Ca and Zn fell within the acceptable limits for all the control subjects, only two infertile men qualified by all five parameters. Of the patient group, seven were abnormal on all counts; sperm motility, Mg and Zn were low in 16, Ca in 19 and abnormal morphology was encountered in 12. Since there was no linear correlation between any two parameters, it is possible that each factor may singly or jointly influence the physiological integrity of the spermatozoa. The results are discussed from a consideration of pathological manifestations known to occur in deficiency of these trace elements à propos their role in determining the fertility index of the semen.

  7. Effect of Ca and Zn additions on the mechanical properties of Mg produced by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Guleryuz, L. F.; Ipek, R.; Arıtman, I.; Karaoglu, S.

    2017-02-01

    Magnesium and its alloys are among important research topics in view of their excellent biocompatibility.In this study mechanical and microstructure properties of hot sintered Mg-Zn-Ca alloys were studied.The effects of the addition of different amounts Ca and Zn were added to the base material has been processed by powder metallurgy method.resulting microstructures densities and compression test behaviors of the Mg-based alloys were studied.Visual inspection using SEM (Scanning Electron Microscope) analyses indicates that the microstructure of the composite is also greatly effected by these parameters. In addition, EDS (Energy Dispersive X-Ray Spectroscopy) analyses were performed for reliable determination of the chemical composition.

  8. Thermodynamic analysis of glass-forming ability in a Ca-Mg-Zn ternary alloy system

    SciTech Connect

    Gorsse, S.; Orveillon, G.; Senkov, O. N.; Miracle, D. B.

    2006-06-01

    A thermodynamic analysis of the onset driving force for crystallization of super-cooled liquid has been conducted to explain strong composition dependency of the glass forming ability in the Ca-Mg-Zn ternary alloy system observed experimentally. In addition to the onset driving force, other energetic and kinetic factors are discussed to explain the observed glass stabilities. The universality of this method is discussed, thus establishing an analytic approach for determining the most stable glass in a given alloy system.

  9. Antioxidant response and carboxylate metabolism in Brassica rapa exposed to different external Zn, Ca, and Mg supply.

    PubMed

    Blasco, Begoña; Graham, Neil S; Broadley, Martin R

    2015-03-15

    Zinc (Zn), calcium (Ca), and magnesium (Mg) malnutrition are common deficiencies in many developed and developing countries, resulting in a widespread health problem. Biofortification of food crops is an agricultural strategy that can be used to increase the levels of these elements in the edible portions of crops. Deficiency or toxicity of these cations in soils reduces plant growth, crop yield, and the quality of plant foodstuff. The aim of this study was to investigate the effect of external Zn, Ca, and Mg supply on accumulation and distribution of this elements as well as antioxidant response and organic acid composition of Brassica rapa ssp. trilocularis line R-o-18. Plants were grown at low Zn (0.05 μM Zn) and high Zn (500 μM Zn), low Ca (0.4 mM) and high Ca (40 mM), and low Mg (0.2 mM), and high Mg (20 mM) to simulate deficiency and toxicity conditions. Larger shoot biomass reductions were observed under high Zn, Ca and Mg treatments, and superoxide dismutase (SOD), ascorbate peroxidase (APX), H2O2, malondialdehyde (MDA), and total ascorbate (AA) showed a marked increase in these treatments. Therefore, Brassica plants might be more sensitive to excess of these elements in the nutrient solution. The translocation factor (TF) and distribution coefficient (DC) values of Zn, Ca, and Mg indicated higher translocation and accumulation in deficient conditions. High biosynthesis and citrate content in Brassica plants may be associated mainly with a high-nutrient solution extraction ability of these plants. These results provide background data, which will be used to characterize TILLING mutants to study the effects of mutations in genes involved in regulating Zn, Ca, and Mg distribution and accumulation in plants.

  10. Understanding corrosion behavior of Mg-Zn-Ca alloys from subcutaneous mouse model: effect of Zn element concentration and plasma electrolytic oxidation.

    PubMed

    Jang, Yongseok; Tan, Zongqing; Jurey, Chris; Xu, Zhigang; Dong, Zhongyun; Collins, Boyce; Yun, Yeoheung; Sankar, Jagannathan

    2015-03-01

    Mg-Zn-Ca alloys are considered as suitable biodegradable metallic implants because of their biocompatibility and proper physical properties. In this study, we investigated the effect of Zn concentration of Mg-xZn-0.3Ca (x=1, 3 and 5wt.%) alloys and surface modification by plasma electrolytic oxidation (PEO) on corrosion behavior in in vivo environment in terms of microstructure, corrosion rate, types of corrosion, and corrosion product formation. Microstructure analysis of alloys and morphological characterization of corrosion products were conducted using x-ray computed tomography (micro-CT) and scanning electron microscopy (SEM). Elemental composition and crystal structure of corrosion products were determined using x-ray diffraction (XRD) and electron dispersive x-ray spectroscopy (EDX). The results show that 1) as-cast Mg-xZn-0.3Ca alloys are composed of Mg matrix and a secondary phase of Ca2Mg6Zn3 formed along grain boundaries, 2) the corrosion rate of Mg-xZn-0.3Ca alloys increases with increasing concentration of Zn in the alloy, 3) corrosion rates of alloys treated by PEO sample are decreased in in vivo environment, and 4) the corrosion products of these alloys after in vivo tests are identified as brucite (Mg(OH)2), hydroxyapatite (Ca10(PO4)6(OH)2), and magnesite (MgCO3·3H2O).

  11. Microstructure, mechanical properties and bio-corrosion properties of Mg-Si(-Ca, Zn) alloy for biomedical application.

    PubMed

    Zhang, Erlin; Yang, Lei; Xu, Jianwei; Chen, Haiyan

    2010-05-01

    Mg-Si alloy was investigated for biomedical application due to the biological function of Si in the human body. However, Mg-Si alloy showed a low ductility due to the presence of coarse Mg(2)Si. Ca and Zn elements were used to refine and modify the morphology of Mg(2)Si in order to improve the corrosion resistance and the mechanical properties. The cell toxicity of Mg, Zn and Ca metals was assessed by an MTT test. The test results indicated that increasing the concentrations of Mg, Zn and Ca ions did not cause cell toxicity, which showed that the release of these three elements would not lead to cell toxicity. Then, microstructure, mechanical properties and bio-corrosion properties of as-cast Mg-Si(-Ca, Zn) alloys were investigated by optical microscopy, scanning electronic microscopy, mechanical properties testing and electrochemical measurement. Ca element can slightly refine the grain size and the morphology Mg(2)Si phase in Mg-Si alloy. The bio-corrosion resistance of Mg-Si alloys was improved by the addition of Ca due to the reduction and refinement of Mg(2)Si phase; however, no improvement was observed in the strength and elongation. The addition of 1.6% Zn to Mg-0.6Si can modify obviously the morphology of Mg(2)Si phase from course eutectic structure to a small dot or short bar shape. As a result, tensile strength, elongation and bio-corrosion resistance were all improved significantly; especially, the elongation improved by 115.7%. It was concluded that Zn element was one of the best alloying elements of Mg-Si alloy for biomedical application.

  12. Microstructure, mechanical and bio-corrosion properties of Mn-doped Mg-Zn-Ca bulk metallic glass composites.

    PubMed

    Wang, Jingfeng; Huang, Song; Li, Yang; Wei, Yiyun; Xi, Xingfeng; Cai, Kaiyong

    2013-10-01

    The effects of Mn substitution for Mg on the microstructure, mechanical properties, and corrosion behavior of Mg69-xZn27Ca4Mnx (x=0, 0.5 and 1at.%) alloys were investigated using X-ray diffraction, compressive tests, electrochemical treatments, and immersion tests, respectively. Microstructural observations showed that the Mg69Zn27Ca4 alloy was mainly amorphous. The addition of Mn decreases the glass-forming ability, which results in a decreased strength from 545 MPa to 364 MPa. However, this strength is still suitable for implant application. Polarization and immersion tests in the simulated body fluid at 37 °C revealed that the Mn-doped Mg-Zn-Ca alloys have significantly higher corrosion resistance than traditional ZK60 and pure Mg alloys. Cytotoxicity test showed that cell viabilities of osteoblasts cultured with Mn-doped Mg-Zn-Ca alloys extracts were higher than that of pure Mg. Mg68.5Zn27Ca4Mn0.5 exhibits the highest bio-corrosion resistance, biocompatibility and has desirable mechanical properties, which could suggest to be used as biomedical materials in the future. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. Bio-corrosion characterization of Mg-Zn-X (X = Ca, Mn, Si) alloys for biomedical applications.

    PubMed

    Rosalbino, F; De Negri, S; Saccone, A; Angelini, E; Delfino, S

    2010-04-01

    The successful applications of magnesium-based alloys as biodegradable orthopedic implants are mainly inhibited due to their high degradation rates in physiological environment. This study examines the bio-corrosion behaviour of Mg-2Zn-0.2X (X = Ca, Mn, Si) alloys in Ringer's physiological solution that simulates bodily fluids, and compares it with that of AZ91 magnesium alloy. Potentiodynamic polarization and electrochemical impedance spectroscopy results showed a better corrosion behaviour of AZ91 alloy with respect to Mg-2Zn-0.2Ca and Mg-2Zn-0.2Si alloys. On the contrary, enhanced corrosion resistance was observed for Mg-2Zn-0.2Mn alloy compared to the AZ91 one: Mg-2Zn-0.2Mn alloy exhibited a four-fold increase in the polarization resistance than AZ91 alloy after 168 h exposure to the Ringer's physiological solution. The improved corrosion behaviour of the Mg-2Zn-0.2Mn alloy with respect to the AZ91 one can be ascribed to enhanced protective properties of the Mg(OH)(2) surface layer. The present study suggests the Mg-2Zn-0.2Mn alloy as a promising candidate for its applications in degradable orthopedic implants, and is worthwhile to further investigate the in vivo corrosion behaviour as well as assessed the mechanical properties of this alloy.

  14. In vitro degradation and mechanical integrity of Mg-Zn-Ca alloy coated with Ca-deficient hydroxyapatite by the pulse electrodeposition process.

    PubMed

    Wang, H X; Guan, S K; Wang, X; Ren, C X; Wang, L G

    2010-05-01

    The key to manufacturing magnesium-based alloys that are suitable as biodegradable orthopaedic implants is how to adjust their degradation rates and mechanical integrity in the physiological environment. In this study, to solve this challenge, a soluble Ca-deficient hydroxyapatite (Ca-def HA) coating was deposited on an Mg-Zn-Ca alloy substrate by pulse eletrodeposition. This deposition can be demonstrated by X-ray diffractometry and energy dispersion spectroscopy analyses, and the Ca/P atomic ratio of as-deposited coating is about 1.33 (within the range from 1.33 to 1.65). By regulating the appropriate pulse amplitude and width, the Ca-def HA coating shows better adhesion to Mg-Zn-Ca alloy, whose lap shear strength is increased to 41.8+/-2.7 MPa. Potentiodynamic polarization results in Kokubo's simulated body fluid (SBF) indicate that the corrosion potential of Mg alloy increases from -1645 to -1414 mV, while the corrosion current density decreases from 110 to 25 microA/cm(2), which illustrates that the Ca-def HA coating improves the substrate corrosion resistance significantly. Since orthopaedic implants generally serve under conditions of stress corrosion, the mechanical integrity of the Mg-Zn-Ca alloy was measured using the slow strain rate tensile (SSRT) testing technique in SBF. The SSRT results show that the ultimate tensile strength and time of fracture for the coated Mg-Zn-Ca alloy are higher than those of the uncoated one, which is beneficial in supporting fractured bone for a longer time. Thus Mg-Zn-Ca alloy coated with Ca-def HA is be a promising candidate for biodegradable orthopaedic implants, and is worthwhile to further investigate the in vivo degradation behavior. Copyright (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  15. Introducing Mg-4Zn-3Gd-1Ca/ZnO nanocomposite with compressive strengths matching/exceeding that of mild steel

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Tekumalla, S.; Guo, Y. B.; Gupta, M.

    2016-08-01

    This work introduces Mg-4Zn-3Gd-1Ca/2ZnO (wt.%) nanocomposite fabricated using the technique of disintegrated melt deposition and extrusion. Addition of ZnO nanoparticles enhanced the compressive strengths of alloy by ~100 MPa. Nanocomposite samples display high strength and good ductility: 0.2% compressive yield stress of 355 MPa, ultimate compressive stress of 703 MPa, and compressive failure strain of 10.6%. The significant enhancement of compressive yield stress is mainly attributed to the grain refinement by adding nanoparticles. The strength levels exceed that of commercial magnesium alloys (i.e. WE43, WE54, ZK60, and ME21) and mild steels (i.e. S275 and S355), making Mg-4Zn-3Gd-1Ca/2ZnO a very promising material for multiple engineering and biomedical applications.

  16. Introducing Mg-4Zn-3Gd-1Ca/ZnO nanocomposite with compressive strengths matching/exceeding that of mild steel

    PubMed Central

    Chen, Y.; Tekumalla, S.; Guo, Y. B.; Gupta, M.

    2016-01-01

    This work introduces Mg-4Zn-3Gd-1Ca/2ZnO (wt.%) nanocomposite fabricated using the technique of disintegrated melt deposition and extrusion. Addition of ZnO nanoparticles enhanced the compressive strengths of alloy by ~100 MPa. Nanocomposite samples display high strength and good ductility: 0.2% compressive yield stress of 355 MPa, ultimate compressive stress of 703 MPa, and compressive failure strain of 10.6%. The significant enhancement of compressive yield stress is mainly attributed to the grain refinement by adding nanoparticles. The strength levels exceed that of commercial magnesium alloys (i.e. WE43, WE54, ZK60, and ME21) and mild steels (i.e. S275 and S355), making Mg-4Zn-3Gd-1Ca/2ZnO a very promising material for multiple engineering and biomedical applications. PMID:27572903

  17. In vitro and in vivo studies on biodegradable CaMgZnSrYb high-entropy bulk metallic glass.

    PubMed

    Li, H F; Xie, X H; Zhao, K; Wang, Y B; Zheng, Y F; Wang, W H; Qin, L

    2013-11-01

    In order to enhance the corrosion resistance of the Ca65Mg15Zn20 bulk metallic glass, which has too fast a degradation rate for biomedical applications, we fabricated the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass because of the unique properties of high-entropy alloys. Our results showed that the mechanical properties and corrosion behavior were enhanced. The in vitro tests showed that the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass could stimulate the proliferation and differentiation of cultured osteoblasts. The in vivo animal tests showed that the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass did not show any obvious degradation after 4 weeks of implantation, and they can promote osteogenesis and new bone formation after 2 weeks of implantation. The improved mechanical properties and corrosion behavior can be attributed to the different chemical composition as well as the formation of a unique high-entropy atomic structure with a maximum degree of disorder.

  18. In vitro bioaccessibility of β-carotene, Ca, Mg and Zn in landrace carrots (Daucus carota, L.).

    PubMed

    Zaccari, Fernanda; Cabrera, María Cristina; Ramos, Ana; Saadoun, Ali

    2015-01-01

    Four landrace carrots ("Becaria", "CRS", "González" and "Rodríguez") and two marketable cultivars (Kuroda and Brasilia), raw and steamed, were characterised by the total content of β-carotene Ca, Mg and Zn, in vitro bioaccessibility and by colour and were evaluated to determine the effect of particle size in nutrient bioaccessibility. Steaming increased the content of β-carotene extracted from "CRS" and Brasilia (29% and 75%) and decreased the content of β-carotene extracted from "CRS" by 23% in "Rodríguez." In addition, steaming caused a loss of Ca (21%) but did not change the amount of Mg and Zn. The bioaccessibility of β-carotene in raw and pulped carrots was very low (<0.5%). Furthermore, steaming and a smaller particle size increased the bioaccessibility of β-carotene by 3-16 times. Additionally, cooking increased the in vitro bioaccessibility of Ca and Zn but had no effect on Mg. Moreover, homogenisation increased the bioaccessibility by 20% in Ca, 17% in Mg, and 10% in Zn compared to pulping. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Influence of solid-solution treatment on microstructure, mechanical property and corrosion behavior of biodegradable Mg-Zn-Ca alloy

    NASA Astrophysics Data System (ADS)

    Ly, Xuan Nam; Yang, S.; Qin, Y.

    2017-03-01

    The influence of solid-solution treatment on microstructure, mechanical property and corrosion behavior of Mg-Zn-Ca alloy was studied in the present investigation by SEM, tensile test, electrochemical and immersion test. The results show that the microstructure of Mg alloys after solid solution treatment significantly changed, a large number of the second phase (Ca2Mg6Zn3, Mg2Ca) dissolved into the α-Mg matrix reaching a supersaturated state, and the grains size was bigger than before solid solution treatment; the mechanical properties were obviously improved. In particular the tensile strength of 0.5wt.% Ca of Mg alloy reached 220MPa and the ductility reached 16.6%. Compared with the as-cast Mg alloys, the corrosion potential after solid-solution treatment slightly shifted negative, but the corrosion current density significantly decreased. After solid solution treatment, the surface corrosion was not serious and the result of weight gain was lower compared with those of the as-cast Mg alloys.

  20. Analysis of Relations Between the Level of Mg, Zn, Ca, Cu, and Fe and Depressiveness in Postmenopausal Women.

    PubMed

    Szkup, Małgorzata; Jurczak, Anna; Brodowska, Aleksandra; Brodowska, Agnieszka; Noceń, Iwona; Chlubek, Dariusz; Laszczyńska, Maria; Karakiewicz, Beata; Grochans, Elżbieta

    2017-03-01

    Numerous observations suggest a possible connection between the levels of Mg, Zn, Fe, and Zn and the incidence of depressive symptoms. Depression is two to three times more common in women than in men. The menopausal period is extremely conducive to depressive disorders. The aim of this study was to assess the severity of depressive symptoms in postmenopausal women depending on the levels of Mg, Zn, Ca, Cu, and Fe. The study included 198 healthy postmenopausal women at the average age of 56.26 ± 5.55 years. In the first part of the study, standardized research tools were used, namely the Primary Care Evaluation of Mental Disorders (PRIME-MD) and the Beck Depression Inventory (BDI). The second part involved biochemical analysis of Mg, Zn, Ca, Cu, and Fe levels in blood serum. The lowest Cu levels were observed in women without depressive symptoms (1.07 ± 0.22 mg/l) and the highest in those with severe depressive symptoms (1.19 ± 0.17 mg/l), (p ≤ 0.05). The lowest Mg levels were observed in women with depressive symptoms (14.28 ± 2.13 mg/l), and the highest in women without depressive symptoms (16.30 ± 3.51 mg/l), (p ≤ 0.05). The average serum Mg levels (15.75 ± 3.23 mg/l) decreased compared to the reference values (18.77-24 mg/l). What is striking is a potential relation between the levels of Mg and Cu and depressiveness. Our results indicate to a higher vulnerability to depression in a group of women with lower levels of Mg and higher levels of Cu.

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

    PubMed

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

    2004-01-01

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

  2. Improved mechanical performance and delayed corrosion phenomena in biodegradable Mg-Zn-Ca alloys through Pd-alloying.

    PubMed

    González, S; Pellicer, E; Fornell, J; Blanquer, A; Barrios, L; Ibáñez, E; Solsona, P; Suriñach, S; Baró, M D; Nogués, C; Sort, J

    2012-02-01

    The influence of partial substitution of Mg by Pd on the microstructure, mechanical properties and corrosion behaviour of Mg(72-x)Zn(23)Ca(5)Pd(x) (x=0, 2 and 6 at.%) alloys, synthesized by copper mould casting, is investigated. While the Mg(72)Zn(23)Ca(5) alloy is mainly amorphous, the addition of Pd decreases the glass-forming ability, thus favouring the formation of crystalline phases. From a mechanical viewpoint, the hardness increases with the addition of Pd, from 2.71 GPa for x=0 to 3.9 GPa for x=6, mainly due to the formation of high-strength phases. In turn, the wear resistance is maximized for an intermediate Pd content (i.e., Mg(70)Zn(23)Ca(5)Pd(2)). Corrosion tests in a simulated body fluid (Hank's solution) indicate that Pd causes a shift in the corrosion potential towards more positive values, thus delaying the biodegradability of this alloy. Moreover, since the cytotoxic studies with mouse preosteoblasts do not show dead cells after culturing for 27 h, these alloys are potential candidates to be used as biomaterials.

  3. Composition-dependent structural and electronic properties of Mg(95-x)Zn(x)Ca5 metallic glasses: an ab initio molecular dynamics study.

    PubMed

    Li, S N; Liu, J B; Li, J H; Wang, J; Liu, B X

    2015-02-26

    Recent progress in the synthesis of Mg-based metallic glasses (MGs) has allowed them to be considered as potential candidates for biodegradable and bioabsorbable implant materials. In this work, we use the Mg-Zn-Ca system as a representative to investigate the effect of composition on the atomic-level structure and local chemical environment in Mg-based MGs from ab initio molecular dynamics simulations. The results suggest that the short-range order of Mg(95-x)Zn(x)Ca5 (x = 21, 25, 29, and 33) MGs is characterized by Zn-centered icosahedral and icosahedral-like clusters, which show an increasing number and a rising tendency to interpenetrate each other with the enrichment of Zn constituents. A considerable degree of charge transfer between Zn and the surrounding Mg/Ca atoms is observed through electronic structure and bonding character analysis. At Zn-rich compositions, a percolated Zn-Zn network extended throughout the entire sample is formed, upon which the accumulated charges around Zn atoms are associated into a continuous conductivity path. Such results may shed light on the improved corrosion resistance of the Zn-rich Mg-Zn-Ca MGs.

  4. Effect of Ca addition on the damping capacity of Mg-Al-Zn casting alloys

    NASA Astrophysics Data System (ADS)

    Jun, Joong-Hwan; Moon, Jung-Hyun

    2015-07-01

    The influences of Ca addition on the microstructures and damping capacities of AZ91-(0˜2)%Ca casting alloys were investigated, on the basis of the results of X-ray diffractometry, optical microscopy, scanning electron microscopy and vibration tests in a single cantilever mode. The amount of intermetallic compounds decreased with increasing Ca content up to 0.5%, above which it increased; the average cell size showed the opposite tendency. All alloys exhibited similar damping levels in the strain-amplitude independent region. Considering the very low solubility of Ca in the matrix, and that most of the Ca elements are consumed by the formation of the Al2Ca phase and incorporation into the Mg17Al12 phase, this would be ascribed to the almost identical concentrations of Ca solutes distributed in the matrix. In the strain-amplitude dependent region, however, the AZ91-0.5%Ca alloy possessed the maximum damping capacity. From the viewpoint of microstructural evolution with Ca addition, the number density of compound particles is considered to be the principal factor affecting the damping behavior in the strain-amplitude dependent region.

  5. Bioaccessibility of Ca, Cu, Fe, Mg, Zn, and crude protein in beef, pork and chicken after thermal processing.

    PubMed

    Menezes, Eveline A; Oliveira, Aline F; França, Celia J; Souza, Gilberto B; Nogueira, Ana Rita A

    2018-02-01

    The bioaccessibility of Ca, Cu, Fe, Mg, Zn, and crude protein was evaluated after submitting beef, pork, and chicken to five different thermal treatments. The bioaccessibility of crude protein and metals were simulated by using in vitro enzymatic digestion with a gastric fluid solution and dialysability approach. Inductively coupled plasma optical spectrometry was used to quantify the dialyzable fraction and the total mineral content after microwave-assisted digestion. Graphite furnace atomic absorption spectrometry quantified Cu in chicken dialyzable fraction. The increase of temperature and heat exposure period decreased the protein bioaccessibility. Considering the total and dialyzable fraction, beef is an important source of Cu, Fe, Mg, and Zn to the human diet. The results of Fourier-transform infrared spectroscopy indicated physical changes in the treated samples related to protein denaturation, which was probably responsible for the decreased bioaccessibility of minerals and protein, mainly at higher temperatures. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Pt–Mg, Pt–Ca, and Pt–Zn lantern complexes and metal-only donor–acceptor interactions [Pt-Mg Pt-Ca and Pt-Zn compounds with metal-only donor-acceptor interactions

    DOE PAGES

    Baddour, Frederick G.; Hyre, Ariel S.; Guillet, Jesse L.; ...

    2016-12-12

    Here, Pt-based heterobimetallic lantern complexes of the form [PtM(SOCR)4(L)] have been shown previously to form intermolecular metallophilic interactions and engage in antiferromagnetic coupling between lanterns having M atoms with open shell configurations. In order to understand better the influence of the carboxylate bridge and terminal ligand on the electronic structure, as well as the metal–metal interactions within each lantern unit, a series of diamagnetic lantern complexes, [PtMg(SAc)4(OH2)] (1), [PtMg(tba)4(OH2)] (2), [PtCa(tba)4(OH2)] (3), [PtZn(tba)4(OH2)] (4), and a mononuclear control (Ph4P)2[Pt(SAc)4] (5) have been synthesized. Crystallographic data show close Pt–M contacts enforced by the lantern structure in each dinuclear case. 195Pt-NMR spectroscopymore » of 1–4, (Ph4P)2[Pt(SAc)4] (5), and several previously reported lanterns revealed a strong chemical shift dependence on the identity of the second metal (M), mild influence by the thiocarboxylate ligand (SOCR; R = CH3 (thioacetate, SAc), C6H5 (thiobenzoate, tba)), and modest influence from the terminal ligand (L). Fluorescence spectroscopy has provided evidence for a Pt···Zn metallophilic interaction in [PtZn(SAc)4(OH2)], and computational studies demonstrate significant dative character. In all of 1–4, the short Pt–M distances suggest that metal-only Lewis donor (Pt)–Lewis acceptor (M) interactions could be present. DFT and NBO calculations, however, show that only the Zn examples have appreciable covalent character, whereas the Mg and Ca complexes are much more ionic.« less

  7. Microstructure and Fatigue Behavior of Friction Stir-welded Noncombustive Mg-9Al-Zn-Ca Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Zhou, L.; Li, Z. Y.; Nakata, K.; Feng, J. C.; Huang, Y. X.; Liao, J. S.

    2016-06-01

    Microstructure and fatigue behavior of friction stir-welded noncombustive Mg-9Al-Zn-Ca magnesium alloy were investigated. The as-received hot-extruded material consisted of equiaxed α-Mg grains with β-Mg17Al12 and Al2Ca compounds distributed along the grain boundaries. Friction stir welding produced much refined α-Mg grains accompanied by the dissolution of the eutectic β-Mg17Al12 phase, while Al2Ca phase was dispersed homogenously into the Mg matrix. Friction stir welding produced slightly increased hardness and tensile strength in the defect-free welds compared with the base material due to microstructural refinement and uniform distribution of intermetallic compounds. The load-controlled uniaxial tensile high-cycle fatigue tests indicated that fatigue strength of 90 MPa was obtained for the friction stir-welded joint with fatigue crack initiated basically near the specimen's surface and at the retreating side of the joint. Crack propagation was characterized by cleavage and fatigue striations.

  8. Ca:Mg:Zn:CO3 and Ca:Mg:CO3-tri- and bi-elemental carbonate microparticles for novel injectable self-gelling hydrogel-microparticle composites for tissue regeneration.

    PubMed

    Douglas, Timothy E L; Sobczyk, Katarzyna; Łapa, Agata; Włodarczyk, Katarzyna; Brackman, Gilles; Vidiasheva, Irina; Reczyńska, Katarzyna; Pietryga, Krzysztof; Schaubroeck, David; Bliznuk, Vitaliy; Voort, Pascal Van Der; Declercq, Heidi A; Bulcke, Jan Van den; Samal, Sangram Keshari; Khalenkow, Dmitry; Parakhonskiy, Bogdan V; Van Acker, Joris; Coenye, Tom; Lewandowska-Szumieł, Małgorzata; Pamuła, Elżbieta; Skirtach, Andre G

    2017-03-24

    Injectable composites for tissue regeneration can be developed by dispersion of inorganic microparticles and cells in a hydrogel phase. In this study, multifunctional carbonate microparticles containing different amounts of calcium, magnesium and zinc were mixed with solutions of gellan gum (GG), an anionic polysaccharide, to form injectable hydrogel-microparticle composites, containing Zn, Ca and Mg. Zn and Ca were incorporated into microparticle preparations to a greater extent than Mg. Microparticle groups were heterogeneous and contained microparticles of differing shape and elemental composition. Zn-rich microparticles were 'star shaped' and appeared to consist of small crystallites, while Zn-poor, Ca- and Mg-rich microparticles were irregular in shape and appeared to contain lager crystallites. Zn-free microparticle groups exhibited the best cytocompatibility and, unexpectedly, Zn-free composites showed the highest antibacterial activity towards methicilin-resistant Staphylococcus aureus. Composites containing Zn-free microparticles were cytocompatible and therefore appear most suitable for applications as an injectable biomaterial. This study proves the principle of creating bi- and tri-elemental microparticles to induce the gelation of GG to create injectable hydrogel-microparticle composites.

  9. Acidity and metal (Mg2+, Ca2+, Zn2+) affinity of L-γ-carboxyglutamic acid and its peptide analog

    NASA Astrophysics Data System (ADS)

    Remko, Milan; Broer, Ria; Remková, Anna; Van Duijnen, Piet Th.

    2014-10-01

    Density functional theory methods with the B3LYP and B97D functionals with triple-zeta 6-311++G(d,p) basis set have been used to study the acidity, basicity and metal affinity of L-γ-carboxyglutamic acid (GLA) and its peptide derivative [2-acetylamino-3-(methylamino)-3-oxopropyl]malonic acid (AMD-GLA). The Gibbs interaction energies of the GLA2-…M2+ and AMD-GLA2-…M2+ (M = Mg, Ca, Zn) complexes show an increasing binding affinity in the order Ca2+ < Mg2+ < Zn2+ The transition metal Zn2+ is most effectively recognized by the dianions of GLA and AMD-GLA. Of the dianions studied the AMD-GLA dianion is the strongest Lewis base. Computations that include the effect of solvation showed that in water the relative stability of GLA2-…M2+ and AMD-GLA2-…M2+ ionic bonds is rapidly diminished. The computed interaction Gibbs energy in water is small and negative.

  10. Pt-Mg, Pt-Ca, and Pt-Zn Lantern Complexes and Metal-Only Donor-Acceptor Interactions.

    PubMed

    Baddour, Frederick G; Hyre, Ariel S; Guillet, Jesse L; Pascual, David; Lopez-de-Luzuriaga, José Maria; Alam, Todd M; Bacon, Jeffrey W; Doerrer, Linda H

    2017-01-03

    Pt-based heterobimetallic lantern complexes of the form [PtM(SOCR)4(L)] have been shown previously to form intermolecular metallophilic interactions and engage in antiferromagnetic coupling between lanterns having M atoms with open shell configurations. In order to understand better the influence of the carboxylate bridge and terminal ligand on the electronic structure, as well as the metal-metal interactions within each lantern unit, a series of diamagnetic lantern complexes, [PtMg(SAc)4(OH2)] (1), [PtMg(tba)4(OH2)] (2), [PtCa(tba)4(OH2)] (3), [PtZn(tba)4(OH2)] (4), and a mononuclear control (Ph4P)2[Pt(SAc)4] (5) have been synthesized. Crystallographic data show close Pt-M contacts enforced by the lantern structure in each dinuclear case. (195)Pt-NMR spectroscopy of 1-4, (Ph4P)2[Pt(SAc)4] (5), and several previously reported lanterns revealed a strong chemical shift dependence on the identity of the second metal (M), mild influence by the thiocarboxylate ligand (SOCR; R = CH3 (thioacetate, SAc), C6H5 (thiobenzoate, tba)), and modest influence from the terminal ligand (L). Fluorescence spectroscopy has provided evidence for a Pt···Zn metallophilic interaction in [PtZn(SAc)4(OH2)], and computational studies demonstrate significant dative character. In all of 1-4, the short Pt-M distances suggest that metal-only Lewis donor (Pt)-Lewis acceptor (M) interactions could be present. DFT and NBO calculations, however, show that only the Zn examples have appreciable covalent character, whereas the Mg and Ca complexes are much more ionic.

  11. Effects of secondary phase and grain size on the corrosion of biodegradable Mg-Zn-Ca alloys.

    PubMed

    Lu, Y; Bradshaw, A R; Chiu, Y L; Jones, I P

    2015-03-01

    The bio-corrosion behaviour of Mg-3Zn-0.3Ca (wt.%) alloy in simulated body fluid (SBF) at 37°C has been investigated using immersion testing and electrochemical measurements. Heat treatment has been used to alter the grain size and secondary phase volume fraction; the effects of these on the bio-corrosion behaviour of the alloy were then determined. The as-cast sample has the highest bio-corrosion rate due to micro-galvanic corrosion between the eutectic product (Mg+Ca2Mg6Zn3) and the surrounding magnesium matrix. The bio-corrosion resistance of the alloy can be improved by heat treatment. The volume fraction of secondary phases and grain size are both key factors controlling the bio-corrosion rate of the alloy. The bio-corrosion rate increases with volume fraction of secondary phase. When this is lower than 0.8%, the dependence of bio-corrosion rate becomes noticeable: large grains corrode more quickly.

  12. Pt–Mg, Pt–Ca, and Pt–Zn lantern complexes and metal-only donor–acceptor interactions [Pt-Mg Pt-Ca and Pt-Zn compounds with metal-only donor-acceptor interactions

    SciTech Connect

    Baddour, Frederick G.; Hyre, Ariel S.; Guillet, Jesse L.; Pascual, David; Lopez-de-Luzuriaga, Jose Maria; Alam, Todd M.; Bacon, Jeffrey W.; Doerrer, Linda H.

    2016-12-12

    Here, Pt-based heterobimetallic lantern complexes of the form [PtM(SOCR)4(L)] have been shown previously to form intermolecular metallophilic interactions and engage in antiferromagnetic coupling between lanterns having M atoms with open shell configurations. In order to understand better the influence of the carboxylate bridge and terminal ligand on the electronic structure, as well as the metal–metal interactions within each lantern unit, a series of diamagnetic lantern complexes, [PtMg(SAc)4(OH2)] (1), [PtMg(tba)4(OH2)] (2), [PtCa(tba)4(OH2)] (3), [PtZn(tba)4(OH2)] (4), and a mononuclear control (Ph4P)2[Pt(SAc)4] (5) have been synthesized. Crystallographic data show close Pt–M contacts enforced by the lantern structure in each dinuclear case. 195Pt-NMR spectroscopy of 1–4, (Ph4P)2[Pt(SAc)4] (5), and several previously reported lanterns revealed a strong chemical shift dependence on the identity of the second metal (M), mild influence by the thiocarboxylate ligand (SOCR; R = CH3 (thioacetate, SAc), C6H5 (thiobenzoate, tba)), and modest influence from the terminal ligand (L). Fluorescence spectroscopy has provided evidence for a Pt···Zn metallophilic interaction in [PtZn(SAc)4(OH2)], and computational studies demonstrate significant dative character. In all of 1–4, the short Pt–M distances suggest that metal-only Lewis donor (Pt)–Lewis acceptor (M) interactions could be present. DFT and NBO calculations, however, show that only the Zn examples have appreciable covalent character, whereas the Mg and Ca complexes are much more ionic.

  13. AB Initi Molecular Dynamics Simulation of the Amorphous Structure of Ca-Mg-Cu and Ca-Mg-Zn Alloys (Postprint)

    DTIC Science & Technology

    2012-09-26

    The Minerals , Metals & Materials Society and ASM International (outside the USA). The U.S. Government is joint author of the work and has the right...amorphous alloys. DOI: 10.1007/s11661-012-1406-z The Minerals , Metals & Materials Society and ASM International (outside the USA) 2012 I. INTRODUCTION...presence ofMRO in these alloys,[34,35] as well as the fluctuation in the atomic scattering cross-sections: the solutes , Cu, Zn and Mg, have larger neutron

  14. Effect of Mg(2+), Ca(2+), Sr(2+) and Ba(2+) metal ions on the antifungal activity of ZnO nanoparticles tested against Candida albicans.

    PubMed

    Haja Hameed, Abdulrahman Syedahamed; Karthikeyan, Chandrasekaran; Senthil Kumar, Venugopal; Kumaresan, Subramanian; Sasikumar, Seemaisamy

    2015-01-01

    The antifungal ability of pure and alkaline metal ion (Mg(2+), Ca(2+), Sr(2+) and Ba(2+)) doped ZnO nanoparticles (NPs) prepared by the co-precipitation method was tested against the pathogenic yeast, Candida albicans (C. albicans), and the results showed that the Mg-doped ZnO NPs possessed greater effect than the other alkaline metal ion doped ZnO NPs. The impact of the concentration of Mg doped ZnO sample on the growth of C. albicans was also studied. The Minimal Fungicidal Concentration (MFC) of the Mg doped ZnO NPs was found to be 2000 μg/ml for which the growth of C. albicans was completely inhibited. The ZnO:Mg sample (1.5mg/ml) with various concentrations of histidine reduced the fungicidal effect of the nanoparticles against C. albicans, which was deliberately explained by the role of ROS. The ZnO:Mg sample added with 5mM of histidine scavenged the ample amount of generated ROS effectively. The binding of the NPs with fungi was observed by their FESEM images and their electrostatic attraction is confirmed by the zeta potential measurement.

  15. Fabrication and characterization of a biodegradable Mg-2Zn-0.5Ca/1β-TCP composite.

    PubMed

    Huang, Yan; Liu, Debao; Anguilano, Lorna; You, Chen; Chen, Minfang

    2015-09-01

    A biodegradable magnesium matrix and beta-tricalcium phosphate (β-TCP) particles reinforced composite Mg-2Zn-0.5Ca/1beta-TCP (wt.%) was fabricated for biomedical applications by the novel route of combined high shear solidification (HSS) and equal channel angular extrusion (ECAE). The as-cast composite obtained by HSS showed a fine and equiaxed grain structure with globally uniformly distributed β-TCP particles in aggregates of 2-25 μm in size. The ECAE processing at 300 °C resulted in further microstructural refinement and the improvement of β-TCP particle distribution. During ECAE, the β-TCP aggregates were broken into smaller ones or individual particles, forming a dispersion in the matrix. Such fabricated composite exhibited enhanced hardness and in vitro corrosion resistance. The enhanced hardness was attributed to both the addition of β-TCP particles and grain refinement while the development of a Ca-P rich surface layer from β-TCP during corrosion was responsible for the improvement in corrosion resistance. The composite was characterized in terms of microstructural evolution during fabrication, mechanical properties and electrochemical performance during polarization and immersion tests in a simulated body fluid. Discussions are made on the benefits of both HSS and ECAE and the mechanisms responsible for the enhanced corrosion resistance.

  16. Levels of Se, Zn, Mg and Ca in commercial goat and cow milk fermented products: Relationship with their chemical composition and probiotic starter culture.

    PubMed

    Navarro-Alarcón, Miguel; Cabrera-Vique, Carmen; Ruiz-López, Ma Dolores; Olalla, Manuel; Artacho, Reyes; Giménez, Rafael; Quintana, Verónica; Bergillos, Triana

    2011-12-01

    We determined Se, Zn, Mg and Ca levels in 42 samples of goat and cow fermented milks which are widely consumed in Spain were determined. Atomic absorption spectrometry (hydride generation for Se and flame atomisation for remaining elements) was used as an analytical technique. Reliability of the procedure was checked. Only Mg levels in goat fermented milks were significantly higher to those found in cow fermented milks (p<0.022). Important similarities in concentrations and behaviours for Mg and Ca have been observed. Mg contents were significantly correlated with Zn (r=0.590; p<0.001) and Ca (r=0.344; p<0.028) concentrations, Zn, Mg and Ca levels with protein content (r=0.554, r=0.479, r=0.388, respectively), Mg levels with fats (r=0.403; p=0.011) and Se levels with carbohydrates (r=-0.379; p=0.031). Mineral and macronutrient levels in yogurts with traditional probiotic starter cultures were not significantly different to those found in fermented milks with additional probiotic microorganisms (p>0.05). It was concluded that goat fermented milks are a better source for Mg than cow samples.

  17. Influence of trace impurities on the in vitro and in vivo degradation of biodegradable Mg-5Zn-0.3Ca alloys.

    PubMed

    Hofstetter, J; Martinelli, E; Pogatscher, S; Schmutz, P; Povoden-Karadeniz, E; Weinberg, A M; Uggowitzer, P J; Löffler, J F

    2015-09-01

    The hydrogen evolution method and animal experiments were deployed to investigate the effect of trace impurity elements on the degradation behavior of high-strength Mg alloys of type ZX50 (Mg-5Zn-0.3Ca). It is shown that trace impurity elements increase the degradation rate, predominantly in the initial period of the tests, and also increase the material's susceptibility to localized corrosion attack. These effects are explained on the basis of the corrosion potential of the intermetallic phases present in the alloys. The Zn-rich phases present in ZX50 are nobler than the Mg matrix, and thus act as cathodic sites. The impurity elements Fe and Mn in the alloy of conventional purity are incorporated in these Zn-rich intermetallic phases and therefore increase their cathodic efficiency. A design rule for circumventing the formation of noble intermetallic particles and thus avoiding galvanically accelerated dissolution of the Mg matrix is proposed.

  18. Electrical and Optical Properties of Nanocrystalline A8ZnNb6O24 (A = Ba, Sr, Ca, Mg) Ceramics

    NASA Astrophysics Data System (ADS)

    John, Fergy; Thomas, Jijimon K.; Jacob, John; Solomon, Sam

    2017-08-01

    Nanoparticles of A8ZnNb6O24 (A = Ba, Sr, Ca, and Mg, abbreviated as BZN, SZN, CZN, and MZN) have been synthesized by an auto-igniting combustion technique and their structural and optical properties characterized. The phase purity, crystal structure, and particle size of the prepared nanopowders were examined by x-ray diffraction (XRD) analysis and transmission electron microscopy. The XRD results revealed that all the samples crystallized with hexagonal perovskite structure in space group P6 3 cm. The Fourier-transform infrared and Raman (FT-Raman) spectra of the samples were investigated in detail. The ultraviolet-visible (UV-Vis) absorption spectra of the samples were also recorded and their optical bandgap energy values calculated. The nanopowders synthesized by the combustion technique were sintered to 95% of theoretical density at temperature of 1250°C for 2 h. The surface morphology of the sintered pellets was studied by scanning electron microscopy. The photoluminescence spectra of the samples showed intense emission in the blue-green region. Complex impedance analysis was used to determine the grain and grain boundary effects on the dielectric behavior of the ceramics.

  19. Metallic elements (Ca, Hg, Fe, K, Mg, Mn, Na, Zn) in the fruiting bodies of Boletus badius.

    PubMed

    Kojta, Anna K; Falandysz, Jerzy

    2016-06-01

    The aim of this study was to investigate and compare the levels of eight metallic elements in the fruiting bodies of Bay Bolete (Boletus badius; current name Imleria badia) collected from ten sites in Poland to understand better the value of this popular mushroom as an organic food. Bay Bolete fruiting bodies were collected from the forest area near the towns and villages of Kętrzyn, Poniatowa, Bydgoszcz, Pelplin, Włocławek, Żuromin, Chełmno, Ełk and Wilków communities, as well as in the Augustów Primeval Forest. Elements such as Ca, Fe, K, Mg, Mn, Na and Zn were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-OES), and mercury by cold vapor atomic absorption spectrometry (CV-AAS). This made it possible to assess the nutritional value of the mushroom, as well as possible toxicological risks associated with its consumption. The results were subjected to statistical analysis (Kruskal-Wallis test, cluster analysis, principal component analysis).

  20. Influence of Applied Voltage and Film-Formation Time on Microstructure and Corrosion Resistance of Coatings Formed on Mg-Zn-Zr-Ca Bio-magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Yandong, Yu; Shuzhen, Kuang; Jie, Li

    2015-09-01

    The influence of applied voltage and film-formation time on the microstructure and corrosion resistance of coatings formed on a Mg-Zn-Zr-Ca novel bio-magnesium alloy has been investigated by micro-arc oxidation (MAO) treatment. Phase composition and microstructure of as-coated samples were analyzed by the x-ray diffraction, energy dispersive x-ray spectroscopy and scanning electron microscopy. And the porosity and average of micro-pore aperture of the surface on ceramic coatings were analyzed by general image software. Corrosion microstructure of as-coated samples was caught by a microscope digital camera. The long-term corrosion resistance of as-coated samples was tested in simulated body fluid for 30 days. The results showed that the milky white smooth ceramic coating formed on the Mg-Zn-Zr-Ca novel bio-magnesium alloy was a compound of MgO, Mg2SiO4 and MgSiO3, and its corrosion resistance was significantly improved compared with that of the magnesium substrate. In addition, when the MAO applied voltage were 450 V and 500 V and film-formation time were 9 min and 11 min, the surface micro-morphology and the corrosion resistance of as-coated samples were relatively improved. The results provided a theoretical foundation for the application of the Mg-Zn-Zr-Ca novel bio-magnesium alloy in biomedicine.

  1. Terahertz Spectroscopy of CaH (X^{2}Σ^{+}), MgH (X^{2}Σ^{+}), and ZnH (X^{2}Σ^{+}) : Extreme Hydride Synthesis

    NASA Astrophysics Data System (ADS)

    Bucchino, Matthew P.; Ziurys, Lucy M.

    2013-06-01

    Sub-millimeter spectra of CaH (X^{2}Σ^{+}), MgH (X^{2}Σ^{+}), and ZnH (X^{2}Σ^{+}) have been measured in the sub-mm{/}THz regime (500{-805} GHz) using direct{-absorption} methods. All species were produced by the reaction of metal vapor with H_{2} under DC discharge in a Broida-type oven. Because of efficient molecule production, spectra of ^{26}MgH, ^{66}ZnH, ^{68}ZnH and ^{70}ZnH could be recorded in their natural abundance as well, with high signal-to-noise. Additionally, the N = 0 {→} 1 and N = 1 {→} 2 transitions of ^{25}MgH and ^{67}ZnH were measured. Fermi contact, dipolar, and quadrupole constants for the ^{25}Mg and ^{67}Zn nuclei have been accurately determined for the first time in the gas phase, and are in good agreement with previous ESR studies. The hyperfine constants suggest a substantial amount of covalent character is present in metal hydrides.

  2. Fabrication and characterization of rod-like nano-hydroxyapatite on MAO coating supported on Mg-Zn-Ca alloy

    NASA Astrophysics Data System (ADS)

    Gao, J. H.; Guan, S. K.; Chen, J.; Wang, L. G.; Zhu, S. J.; Hu, J. H.; Ren, Z. W.

    2011-01-01

    The poor corrosion resistance of magnesium alloys is a dominant problem that limits their clinical application. In order to solve this challenge, micro-arc oxidation (MAO) was used to fabricate a porous coating on magnesium alloys and then electrochemical deposition (ED) was done to fabricate rod-like nano-hydroxyapatite (RNHA) on MAO coating. The cross-section morphology of the composite coatings and its corresponding energy dispersion spectroscopy (EDS) surficial scanning map of calcium revealed that HA rods were successfully deposited into the pores. The three dimensional morphology and scanning electron microscopy (SEM) image of the composite coatings showed that the distribution of the HA rods was dense and uniform. Atomic force microscope (AFM) observation of the composite coatings showed that the diameters of HA rods varied from 95 nm to 116 nm and the root mean square roughness (RMS) of the composite coatings was about 42 nm, which were favorable for cellular survival. The bonding strength between the HA film and MAO coating increased to 12.3 MPa, almost two times higher than that of the direct electrochemical deposition coating (6.3 MPa). Compared with that of the substrate, the corrosion potential of Mg-Zn-Ca alloy with composite coatings increased by 161 mV and its corrosion current density decreased from 3.36 × 10 -4 A/cm 2 to 2.40 × 10 -7 A/cm 2 which was due to the enhancement of bonding strength and the deposition of RNHA in the MAO pores. Immersion tests were carried out at 36.5 ± 0.5 °C in simulated body fluid (SBF). It was found that RNHA can induce the rapid precipitation of calcium orthophosphates in comparison with conventional HA coatings. Thus magnesium alloy coated with the composite coatings is a promising candidate as biodegradable bone implants.

  3. In vitro metal ion release and biocompatibility of amorphous Mg67Zn28Ca5 alloy with/without gelatin coating.

    PubMed

    Chan, W Y; Chian, K S; Tan, M J

    2013-12-01

    Amorphous zinc-rich Mg-Zn-Ca alloys have exhibited good tissue compatibility and low hydrogen evolution in vivo. However, suboptimal cell-surface interaction on magnesium alloy surface observed in vitro could lead to reduced integration with host tissue for regenerative purpose. This study aims to improve cell-surface interaction of amorphous Mg67Zn28Ca5 alloy by coating a gelatin layer by electrospinning. Coated/uncoated alloys were immersed and extracted for 3 days under different CO2. The immersion results showed that pH and metal ion release in the alloy extracts were affected by gelatin coating and CO2, suggesting their roles in alloy biocorrosion and a mechanism has been proposed for the alloy-CO2 system with/without coating. Cytotoxicity results are evident that gelatin-coated alloy with 2-day crosslinking not only exhibited no indirect cytotoxicity, but also supported attachment of L929 and MG63 cell lines around/on the alloy with high viability. Therefore, amorphous Mg67Zn28Ca5 alloy coated with gelatin by electrospinning technique provides a useful method to improve alloy biocompatibility.

  4. Biological and mechanical properties of an experimental glass-ionomer cement modified by partial replacement of CaO with MgO or ZnO

    PubMed Central

    Dong-Ae, KIM; Hany, ABO-MOSALLAM; Hye-Young, LEE; Jung-Hwan, LEE; Hae-Won, KIM; Hae-Hyoung, LEE

    2015-01-01

    Some weaknesses of conventional glass ionomer cement (GIC) as dental materials, for instance the lack of bioactive potential and poor mechanical properties, remain unsolved. Objective The purpose of this study was to investigate the effects of the partial replacement of CaO with MgO or ZnO on the mechanical and biological properties of the experimental glass ionomer cements. Material and Methods Calcium fluoro-alumino-silicate glass was prepared for an experimental glass ionomer cement by melt quenching technique. The glass composition was modified by partial replacement (10 mol%) of CaO with MgO or ZnO. Net setting time, compressive and flexural properties, and in vitro rat dental pulp stem cells (rDPSCs) viability were examined for the prepared GICs and compared to a commercial GIC. Results The experimental GICs set more slowly than the commercial product, but their extended setting times are still within the maximum limit (8 min) specified in ISO 9917-1. Compressive strength of the experimental GIC was not increased by the partial substitution of CaO with either MgO or ZnO, but was comparable to the commercial control. For flexural properties, although there was no significance between the base and the modified glass, all prepared GICs marked a statistically higher flexural strength (p<0.05) and comparable modulus to control. The modified cements showed increased cell viability for rDPSCs. Conclusions The experimental GICs modified with MgO or ZnO can be considered bioactive dental materials. PMID:26398508

  5. Dielectric Properties of a New Ceramic System (Mg0.95Zn0.05)2TiO4-CaTiO3 at Microwave Frequencies

    NASA Astrophysics Data System (ADS)

    Huang, Cheng-Liang; Liu, Shih-Sheng; Chen, Shih-Hsuan

    2009-07-01

    The microwave dielectric properties and microstructure of a two-phase (Mg0.95Zn0.05)2TiO4-CaTiO3 ceramic system prepared using the conventional solid-state route were investigated. The structure and microstructure were analyzed by X-ray diffraction and scanning electron microscopy, respectively. Ilmenite-structured (Mg0.95Zn0.05)TiO3 was detected as a second phase. The coexistence of the second phase, however, did not degrade the dielectric properties of the specimen because the phases were compatible. At 1270 °C, 0.92(Mg0.95Zn0.05)2TiO4-0.08CaTiO3 ceramic showed a good combination of microwave dielectric properties: a dielectric constant (ɛr) of ˜18.03, a quality factor (Q ×f) value of ˜153,000 GHz (at 10 GHz), and a temperature coefficient of resonant frequency (τf) of ˜ -16.82 ppm/°C. The τf value is strongly correlated to the composition and can be controlled by the compositional ratio. At x = 0.1, an ɛr of ˜19.15, a Q ×f value of ˜94,400 GHz (at 10 GHz), and a τf of ˜1.5 ppm/°C were obtained for 0.9(Mg0.95Zn0.05)2TiO4-0.1CaTiO3 ceramic sintered at 1270 °C for 4 h.

  6. Biological and mechanical properties of an experimental glass-ionomer cement modified by partial replacement of CaO with MgO or ZnO.

    PubMed

    Kim, Dong-Ae; Abo-Mosallam, Hany; Lee, Hye-Young; Lee, Jung-Hwan; Kim, Hae-Won; Lee, Hae-Hyoung

    2015-01-01

    Some weaknesses of conventional glass ionomer cement (GIC) as dental materials, for instance the lack of bioactive potential and poor mechanical properties, remain unsolved.Objective The purpose of this study was to investigate the effects of the partial replacement of CaO with MgO or ZnO on the mechanical and biological properties of the experimental glass ionomer cements.Material and Methods Calcium fluoro-alumino-silicate glass was prepared for an experimental glass ionomer cement by melt quenching technique. The glass composition was modified by partial replacement (10 mol%) of CaO with MgO or ZnO. Net setting time, compressive and flexural properties, and in vitrorat dental pulp stem cells (rDPSCs) viability were examined for the prepared GICs and compared to a commercial GIC.Results The experimental GICs set more slowly than the commercial product, but their extended setting times are still within the maximum limit (8 min) specified in ISO 9917-1. Compressive strength of the experimental GIC was not increased by the partial substitution of CaO with either MgO or ZnO, but was comparable to the commercial control. For flexural properties, although there was no significance between the base and the modified glass, all prepared GICs marked a statistically higher flexural strength (p<0.05) and comparable modulus to control. The modified cements showed increased cell viability for rDPSCs.Conclusions The experimental GICs modified with MgO or ZnO can be considered bioactive dental materials.

  7. Estimated equilibrated dietary intakes for nine minerals (Na, K, Ca, Mg, P, Fe, Zn, Cu, and Mn) adjusted by mineral balance medians in young Japanese females.

    PubMed

    Nishimuta, Mamoru; Kodama, Naoko; Shimada, Mieko; Yoshitake, Yutaka; Matsuzaki, Nobue; Morikuni, Eiko

    2012-01-01

    The present study sought to determine estimated equilibrated dietary intakes (EEDIs) for nine essential minerals: sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P), iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn), using data from 17 human mineral balance studies conducted from 1986 to 2007 (subjects=178). Among these studies, two used male subjects, two subjected some or all subjects to sodium restriction, and one study utilized a low protein diet; these subjects were not included in the present analysis. Consequently, data from 13 studies of young female subjects (n=131) consuming a standard diet were selected. Balance distribution medians for six of the minerals (Na, K, Mg, Fe, Zn and Cu) were positive, so the data were adjusted to set the medians of the balances to zero. Medians for the other minerals (Ca, P and Mn) were close to zero and were not adjusted. Intake and balance for each mineral were divided by body weight (BW), lean body mass (LBM), and standard body weight (SBW), which was calculated using height and standard body mass index (BMI=22), and EEDIs were calculated as the intercept of a simple regression equation. When relationships between intake and balance of a mineral were not significant in the regression equation, a significant regression equation comparing intake and balance of another mineral was used to calculate the intercept. Significant simple regression equations were not obtained from any of the three parameters of Na or Zn, or for two of the parameters of P; thus, K, Fe and Ca balances were used to determine the intercepts for Na, Zn and P, respectively. EEDIs for the minerals were: Na (67.9, 89.0, 62.5), K (39.5, 53.5, 37.4), Ca (11.0, 14.4, 10.1), Mg (4.18, 5.51, 3.86), P (18.7, 24.6, 17.3) (mg/kg BW/d, mg/kg LBM/d, mg/kg SBW/d), Fe (180, 237, 165), Zn (181, 241, 166), [corrected] Cu (32.3, 42.6, 29.7), [corrected] Mn (55.1, 72.1, 50.7) (µg/kg BW/d, µg/kg LBM/d, µg/kg SBW/d), respectively. These values

  8. Ultrafiltration of skimmed goat milk increases its nutritional value by concentrating nonfat solids such as proteins, Ca, P, Mg, and Zn.

    PubMed

    Moreno-Montoro, Miriam; Olalla, Manuel; Giménez-Martínez, Rafael; Bergillos-Meca, Triana; Ruiz-López, María Dolores; Cabrera-Vique, Carmen; Artacho, Reyes; Navarro-Alarcón, Miguel

    2015-11-01

    Goat milk has been reported to possess good nutritional and health-promoting properties. Usually, it must be concentrated before fermented products can be obtained. The aim of this study was to compare physicochemical and nutritional variables among raw (RM), skimmed (SM), and ultrafiltration-concentrated skimmed (UFM) goat milk. The density, acidity, ash, protein, casein, whey protein, Ca, P, Mg, and Zn values were significantly higher in UFM than in RM or SM. Dry extract and fat levels were significantly higher in UFM than in SM, and Mg content was significantly higher in UFM than in RM. Ultrafiltration also increased the solubility of Ca and Mg, changing their distribution in the milk. The higher concentrations of minerals and proteins, especially caseins, increase the nutritional value of UFM, which may therefore be more appropriate for goat milk yogurt manufacturing in comparison to RM or SM.

  9. Seven dietary minerals (Ca, P, Mg, Fe, Zn, Cu, and Mn) and their relationship with blood pressure and blood lipids in healthy adults with self-selected diet.

    PubMed

    Kim, Mi-Hyun; Choi, Mi-Kyeong

    2013-06-01

    The purpose of this study is to evaluate the dietary intakes of calcium (Ca), phosphorus (P), magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) and investigate their correlation with blood pressure and blood lipids. Targeting 258 healthy men and women, blood pressure was measured, and blood samples were collected to analyze serum lipids, and then the intakes of seven minerals were assessed through a food intake survey for 3 days using a 24-h recall method. The average age of the men and women was 49.55 and 49.19, respectively. The daily energy intake of the men was 1,830.57 kcal, which was significantly higher than that of women, 1,476.23 kcal (p < 0.001). The mineral intake of the subjects was as follows: 450.95 mg/day for Ca, 915.24 mg/day for P, 279.23 mg/day for Mg, 12.60 mg/day for Fe, 8.25 mg/day for Zn, 1.23 mg/day for Cu, and 4.22 mg/day for Mn. These accounted for 63.83, 130.76, 90.74, 129.75, 97.50, 154.49, and 113.50 % of adequate intake or the recommended intake of each mineral, respectively. Subjects who did not satisfy the estimated average requirement were 74.00 % for Ca, 63.18 % for Mg, and 41.86 % for Zn. After adjusting for age, sex, BMI, and energy intake, Mg intake had a negative correlation with systolic blood pressure (SBP), and Cu intake had a significant negative correlation with SBP and diastolic blood pressure (DBP). Also, Mn intake was negatively correlated with DBP, serum total cholesterol, and triglycerides. Thus, it is concluded that the dietary intakes of Mg, Cu, and Mn may play an important role in controlling blood pressure and lipids in Korean adults.

  10. [Mineral composition of different types of Canarian gofio; factors affecting the presence of Na, K, Mg, Ca, Mn, Fe, Cn and Zn].

    PubMed

    Caballero, J M; Tejera, R L; Caballero A, A; Rubio, C; González-Weller, D; Gutiérrez, A J; Hardisson, A

    2014-03-01

    The contents of Na, K, Mg, Ca, Mn, Fe, Cu and Zn were analyzed and evaluated in 181 samples of various types of gofio produced from different roasted cereal grains. Samples were analyzed by ICP-OES. Based on a daily gofio intake of 30 g/day for adults and 15 g/day for children, the daily intake of each metal, and its percentage contribution to the RDAs established for the Spanish population, were estimated. The metal with the highest concentration was K (2189 ± 766 mg/kg). The lowest concentration was observed for Cu in corn gofio samples (2.05 ± 0.36 mg/kg). With respect to daily intake, it is noteworthy that gofio contributes significantly to the recommended allowance of copper (53.77%-71.45% of the RDI), depending on the population group considered and on the type of gofio.

  11. Evaluation of sewage sludge, septic waste and sludge compost applications to corn and forage: Ca, Mg, S, Fe, Mn, Cu, Zn and B content of crops and soils.

    PubMed

    Warman, P R; Termeer, W C

    2005-06-01

    This is the second of two papers presenting the data from an experiment on the application of aerobically-digested sewage sludge (AES), anaerobic lagoon septic wastes (ANS), sewage sludge compost and fertilizer to soils for grass forage and feed corn production at two different sites in Nova Scotia. Crop yields, plant tissue and Mehlich-1 extractable soil nutrients were evaluated; 15 elements were analyzed in the plant tissue and 9 elements in the soil extracts. This paper describes the Ca, Mg, S, Fe, Mn, Cu, Zn and B content of the crops and the Mehlich-1 extractable content of the soils. The response to the amendments was not consistent at the two sites with the two different crops. We found that the septic sludge (ANS) produced the highest forage Fe, Cu and Zn levels and was equal to compost in elevating corn stover and forage S and the forage B content. The compost produced the highest forage Ca and corn Zn, the AES produced the highest corn Mn, and fertilizer produced the highest forage Mn. None of the amendments produced excessive levels of the above nutrients; rather, the amendments improved the feed quality of the forage and corn stover. Lastly, it was noted that the Mehlich-1 extract only had a significantly positive correlation with forage Cu content.

  12. Determination of Ca, Mg, Na, Cd, Cu, Fe, K, Li and Zn in acid mine and reference water samples by inductively coupled plasma atomic fluorescence spectrometry

    USGS Publications Warehouse

    Sanzolone, R.F.; Meier, A.L.

    1986-01-01

    An inductively coupled plasma atomic fluorescence spectrometric (ICP-AFS) method was used for the determination of nine elements in natural water. Reference and acid mine water samples were analysed by this method to demonstrate its usefulness for hydrogeochemical exploration. The elements were determined in two groups based on the compatibility of operating conditions and consideration of element abundance levels in natural water. Ca, Mg and Na were determined as a group using one set of instrumental conditions and a 1 + 99 dilution of the sample, and Cd, Cu, Fe, K, Li and Zn were determined using another set of conditions and the undiluted sample. The detection limits for the elements are as follows: Ca, 1.4; Mg, 1.7; Na, 2.0; Cd, 1.8; Cu, 6.2; Fe, 15.8; K, 3.5; Li, 0.3; and Zn, 1.2 ng m1-1. Each element has a linear range spanning about four orders of magnitude. The method has good precision and accuracy, as shown by statistics on replicate analyses and by the agreement between values obtained and those recommended for the reference water samples, and also those obtained by atomic absorption spectrometry for the acid mine water samples.

  13. Tululite, Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36: a new Ca zincate-aluminate from combustion metamorphic marbles, central Jordan

    NASA Astrophysics Data System (ADS)

    Khoury, Hani N.; Sokol, Ella V.; Kokh, Svetlana N.; Seryotkin, Yurii V.; Nigmatulina, Elena N.; Goryainov, Sergei V.; Belogub, Elena V.; Clark, Ian D.

    2016-02-01

    Tululite (Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36 (the hypothetical end-member formula Ca14{Fe3+O6}[SiO4][Zn5Al9]O26) (IMA2014-065) is a new natural Ca zincate-aluminate, identified in medium-temperature (800-850 °C) combustion metamorphic (CM) spurrite-fluorellestadite marbles from central Jordan. The type locality (Tulul Al Hammam area) is situated in the northern part of the Siwaqa complex, the largest area of the "Mottled Zone" Formation in the Dead Sea region. The marbles originated from bitumen-rich chalky marine sediments of the Maastrichtian-Paleogene Muwaqqar Chalk Marl Formation, which have low clay content (and, consequently, low Al) and high Zn, Cd, and U enrichments. The bulk CM rocks derived from the low-Al protolith have unusually high (Zn + Cd)/Al ratios ( 0.2) and, as a result, a mineralogy with negligibly small percentages of Ca aluminates having low Ca:Al molar ratios (minerals of mayenite supergroup, Ca:Al = 6:7) common to most of calcareous CM rocks in the Mottled Zone. Instead, the mineral assemblage of the Zn-rich marbles contains tululite, with high Ca:Al = 2.55 molar ratios and Zn substituting for a large portion of Al (Zn:Al = 1.1). Tululite occurs in thin clusters as irregular grains with indented outlines (20-100 μm in size), having typical open-work textures associated with rock-forming calcite, fluorellestadite, spurrite, and accessory Zn-rich periclase, lime-monteponite solid solutions, calcium uranates, and zincite. Marbles also bear brownmillerite, dorrite, fluormayenite, high-fluorine Ca aluminate, and lakargiite. Secondary phases are brucite, gel-like calcium silicate hydrates and calcium silicate aluminate hydrates, including Zn- and U-bearing and Cd-rich compounds, Si-bearing hydrated compounds after calcium uranates, and basic Cd chlorides. The empirical formula of the holotype tululite (a mean of 32 analyses) is (Ca13.29Cd0.75)Σ14.04(Al5.46Zn5.20Fe3+ 2.23Si0.95Mn3+ 1.01Mg0.78P0.41)Σ16.04O36. Tululite is cubic, space

  14. Stress corrosion cracking and corrosion fatigue characterisation of MgZn1Ca0.3 (ZX10) in a simulated physiological environment.

    PubMed

    Jafari, Sajjad; Raman, R K Singh; Davies, Chris H J; Hofstetter, Joelle; Uggowitzer, Peter J; Löffler, Jörg F

    2017-01-01

    Magnesium (Mg) alloys have attracted great attention as potential materials for biodegradable implants. It is essential that an implant material possesses adequate resistance to cracking/fracture under the simultaneous actions of corrosion and mechanical stresses, i.e., stress corrosion cracking (SCC) and/or corrosion fatigue (CF). This study investigates the deformation behaviour of a newly developed high-strength low-alloy Mg alloy, MgZn1Ca0.3 (ZX10), processed at two different extrusion temperatures of 325 and 400°C (named E325 and E400, respectively), under slow strain tensile and cyclic tension-compression loadings in air and modified simulated body fluid (m-SBF). Extrusion resulted in a bimodal grain size distribution with recrystallised grain sizes of 1.2 μm ± 0.8 μm and 7 ± 5 μm for E325 and E400, respectively. E325 possessed superior tensile and fatigue properties to E400 when tested in air. This is mainly attributed to a grain-boundary strengthening mechanism. However, both E325 and E400 were found to be susceptible to SCC at a strain rate of 3.1×10(-7)s(-1) in m-SBF. Moreover, both E325 and E400 showed similar fatigue strength when tested in m-SBF. This is explained on the basis of crack initiation from localised corrosion following tests in m-SBF.

  15. Improvement of the mechanical properties and corrosion resistance of biodegradable β-Ca3(PO4)2/Mg-Zn composites prepared by powder metallurgy: the adding β-Ca3(PO4)2, hot extrusion and aging treatment.

    PubMed

    Yan, Yang; Kang, Yijun; Li, Ding; Yu, Kun; Xiao, Tao; Deng, Youwen; Dai, Han; Dai, Yilong; Xiong, Hanqing; Fang, Hongjie

    2017-05-01

    In this study, 10%β-Ca3(PO4)2/Mg-6%Zn (wt.%) composites with Mg-6%Zn alloy as control were prepared by powder metallurgy. After hot extrusion, the as-extruded composites were aged for 72h at 150°C. The effects of the adding β-Ca3(PO4)2, hot extrusion and aging treatment on their microstructure, mechanical properties and corrosion resistance were investigated. The XRD results identified α-Mg, MgZn phase and β-Ca3(PO4)2 phase in these composites. After hot extrusion, grains were significantly refined, and the larger-sized β-Ca3(PO4)2 particles and coarse MgZn phases were broken into linear-distributed β-Ca3(PO4)2 and MgZn phases along the extrusion direction. After aging treatment, the elements of Zn, Ca, P and O presented a more homogeneous distribution. The compressive strengths of the β-Ca3(PO4)2/Mg-Zn composites were approximately double those of natural bone, and their densities and elastic moduli matched those of natural bone. The immersion tests and electrochemical tests revealed that the adding β-Ca3(PO4)2, hot extrusion and aging treatment could promote the formation of protective corrosion product layer on the sample surface in Ringer's solution, which improved corrosion resistance of the β-Ca3(PO4)2/Mg-Zn composites. The XRD results indicated that the corrosion product layer contained Mg(OH)2, β-Ca3(PO4)2 and hydroxyapatite (HA). The cytotoxicity assessments showed the as-extruded β-Ca3(PO4)2/Mg-Zn composite aged for 72h was harmless to L-929 cells. These results suggested that the β-Ca3(PO4)2/Mg-Zn composites prepared by powder metallurgy were promising to be used for bone tissue engineering.

  16. Synthesis of layered double hydroxides containing Mg2+, Zn2+, Ca2+ and Al3+ layer cations by co-precipitation methods-A review

    NASA Astrophysics Data System (ADS)

    Theiss, Frederick L.; Ayoko, Godwin A.; Frost, Ray L.

    2016-10-01

    Co-precipitation is a common method for the preparation of layered double hydroxides (LDHs) and related materials. This review article is aimed at providing newcomers to the field with some examples of the types of co-precipitation reactions that have been reported previously and to briefly investigate some of the properties of the products of these reactions. Due to the sheer volume of literature on the subject, the authors have had to limit this article to the synthesis of Mg/Al, Zn/Al and Ca/Al LDHs by co-precipitation and directly related methods. LDHs have been synthesised from various reagents including metal salts, oxides and hydroxides. Co-precipitation is also useful for the direct synthesis of LDHs with a wide range of interlayer anions and various bases have been successfully employed to prepare LDHs. Examples of other synthesis techniques including the urea method, hydrothermal synthesis and various mechanochemical methods that are undoubtedly related to co-precipitation have also been included in this review. The effect of post synthesis hydrothermal has also been summarised.

  17. Chemically anchoring of TiO2 coating on OH-terminated Mg3(PO3)2 surface and its influence on the in vitro degradation resistance of Mg-Zn-Ca alloy

    NASA Astrophysics Data System (ADS)

    Cao, Guoqin; Wang, Lijie; Fu, Zhenya; Hu, Junhua; Guan, Shaokang; Zhang, Caili; Wang, Liguo; Zhu, Shijie

    2014-07-01

    Surface treatment is of particular interest to slow down the in vitro degradation of Mg-based implants. In this work, micro arc oxidation (MAO) coating was fabricated on Mg-Zn-Ca alloy which has been developed by our group especially for the application of bio-implants. Evident improvement in corrosion resistance was obtained although the MAO coating was porous. In order to further diminish the contact with SBF, a composite coating was prepared by introducing a TiO2 layer by liquid phase deposition (LPD) method on the MAO pre-treated alloy. The coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results of the potentiodynamic polarization experiments showed that, compared with the bare alloy, the corrosion potential of TiO2/MAO/alloy increased from -1.771 to -1.607 V. At the same time, the corrosion current density decreased from 1.43 × 10-4 A cm-2 to 5.69 × 10-7 A cm-2. The improvement of degradation resistance in SBF was ascribed to both barrier effect and enhanced interface condition. The OH-terminated MAO layer surface can make the TiO2 layer anchor tightly on the MOA surface. The chemical bonding of composite layer induced by Mg2+ cations bridges was also analyzed.

  18. Analysis of six elements (Ca, Mg, Fe, Zn, Cu, and Mn) in several wild vegetables and evaluation of their intakes based on Korea National Health and Nutrition Examination Survey 2010-2011.

    PubMed

    Bae, Yun-Jung; Kim, Mi-Hyun; Lee, Je-Hyuk; Choi, Mi-Kyeong

    2015-03-01

    Wild vegetables, those edible among naturally grown vegetables, have been reported to contain many bioactive substances, dietary fibers, vitamins, and minerals. The purpose of this study is to examine the six elements of the wild vegetables frequently consumed by Koreans and assess the element intakes through them. Contents of six kinds of elements (Ca, Mg, Fe, Zn, Cu, and Mn) in 11 wild vegetables were analyzed by inductively coupled plasma optical emission spectroscopy. Using these analysis data, the 6-element intakes from the wild vegetables were evaluated in healthy Korean adults aged 19-64 years from the Korea National Health and Nutrition Examination Survey (2010-2011). Sedum and shepherd's purse contained over 100 mg of Ca in 100 g of their edible portion. The Mg content per 100 g of the 11 wild vegetables ranged from 12.1 mg to 43.4 mg. The wild vegetable with the highest mineral content per 100 g was sedum for Ca, spinach for Mg, shepherd's purse for Fe, spinach for Zn, bracken for Cu, and fragrant edible wild aster for Mn. The element intakes from the 11 wild vegetables compared with dietary reference intakes in the healthy Koreans were 1.0 % for Ca, 2.1 % for Mg, 5.3 % for Fe, 1.4 % for Zn, 0.3 % for Cu, and 1.8 % for Mn. Considering the low intake ratio (1.2 %) of the wild vegetable to total food intake, wild vegetables may contribute to some element intakes. Our results show the nutritional value of the wild vegetables in the aspect of mineral nutrition; however, further research is needed to evaluate the bioavailability of various elements in wild vegetables.

  19. MALDI time-of-flight mass spectrometry and thermogravimetric analysis of Mg(II), Ca(II), Cu(II), Zn(II) and Pt(II) adducts with monomethoxypolyethylene glycol 5000

    NASA Astrophysics Data System (ADS)

    Mwelase, S. R.; Bariyanga, J.

    2002-05-01

    We have prepared and isolated complexes of Mg(II), Ca(II), Cu(II), Zn(II) and Pt(II) with monomethoxypolyethylene glycol 5000 in a pH 7 buffer at 40 °C in order to study the interaction of this polymer carrier with the ions likely to be found in the human body. Their characterization was done by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, Fourier transform infrared, UV-Vis spectrophotometry, thermogravimetry and elemental analysis. The mass spectra allowed us to determine not only the molecular weights but also the nature of the complexes and the findings were in agreement with the elementary analysis data. The calcium ion was found not directly linked to polyethylene glycol but through water molecules. The overall results indicated strong bonding for Cu(II) and Zn(II) complexes and weak interactions for Mg(II), Ca(II) and Pt(II).

  20. 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.

  1. Synthesis of new brownmillerite-type systems A2(M2+,M4+,)2O5 (A = Ba, Sr, Ca; M2+ = Zn, Mg, Cd, Be; M4+, = Zr, Ce, Ti, Hf)

    NASA Astrophysics Data System (ADS)

    Ito, Shigeharu; Watanabe, Masayuki; Saito, Miwa; Yamamura, Hiroshi

    2011-06-01

    The A2(M,M')2O5 systems (A=Ba, Sr, Ca; M2+=Zn, Mg, Cd, Be; M4+'=Zr, Ce, Ti. Hf, Sn) having a brownmillerite-type compositions were prepared by a solid state reaction. X-ray diffraction analyses confirmed that only the combinations of (Ba-Zn-Zr), (Ba-Zr-Ce), (Ba-Zn-Hf), (Sr-Zn-Zr), (Sr-Zn-Ti) and (Sr-Zn-Hf) for the A-M2+-M4+' in the present systems showed single phases of cubic or orthorhombic perovskite-type structures at room temperature. When the average ionic radii of B site increased, the lattice constants and lattice volumes also increased. Although the samples have the brownmillerite composition, the obtained samples showed perovskite-type structure. The tolerance factor of single phased samples having the brownmillerite composition were estimated to be in the range of 0.9428 ~ 1.0061. It was found that the electrical comductivities of the new phases increased with increasing unit cell free volume.

  2. Chemical stability and dielectric properties of RO-La{sub 2}O{sub 3}-B{sub 2}O{sub 3} (R = Ca, Mg, Zn)-based ceramics

    SciTech Connect

    Jo, Yeon Hwa; Kang, Min Soo; Chung, Kyung Won; Cho, Yong Soo

    2008-02-05

    New lanthanum borate (La{sub 2}O{sub 3}-B{sub 2}O{sub 3}) glasses modified with divalent oxides, such as CaO, MgO and ZnO were investigated as potential low temperature dielectrics by understanding compositional dependence of dielectric properties and chemical leaching resistance. Firing behavior, such as densification and crystallization, depended strongly on the glass composition and is found to influence the resultant dielectric performance. Specifically, the dielectric composition of 20ZnO-20La{sub 2}O{sub 3}-60B{sub 2}O{sub 3} glass with 40 wt% Al{sub 2}O{sub 3} as a filler showed distinct enhancements of dielectric properties, i.e., k {approx} 8.3 and Q {approx} 1091 at the resonant frequency of 17.1 GHz, as a result of 850 deg. C firing. The result was believed related to earlier densification and unexpected evolvements of ZnAl{sub 2}O{sub 4} and La(BO{sub 2}){sub 3} phases during firing. The Mg-containing glass sample was most stable in strong acid solutions and did not show any significant changes in microstructure even after 300 min exposure. The Ca-containing glass sample was not regarded as a promising candidate for low temperature dielectrics from the observed low quality factor and weak chemical durability.

  3. Effects of the Oral Administration of K2Cr2O7 and Na2SeO3 on Ca, Mg, Mn, Fe, Cu, and Zn Contents in the Heart, Liver, Spleen, and Kidney of Chickens.

    PubMed

    Chen, Peng; Zhu, Yiran; Wan, Huiyu; Wang, Yang; Hao, Pan; Cheng, Ziqiang; Liu, Yongxia; Liu, Jianzhu

    2017-03-28

    This study aimed to investigate the effects of selenium on the ion profiles in the heart, liver, spleen, and kidney through the oral administration of hexavalent chromium. Approximately 22.14 mg/kg b.w. K2Cr2O7 was added to water to establish a chronic poisoning model. Different selenium levels (0.00, 0.31, 0.63, 1.25, 2.50, and 5.00 mg Na2SeO3/kg b.w.) around the safe dose were administered to the experimental group model. Ca, Mg, Mn, Fe, Cu, and Zn were detected in the organs through flame atomic absorption spectrometry after these organs were exposed to K2Cr2O7 and Na2SeO3 for 14, 28, and 42 days. Results showed that these elements exhibited various changes. Ca contents declined in the heart, liver, and spleen. Ca contents also decreased on the 28th day and increased on the 42nd day in the kidney. Mn contents declined in the heart and spleen but increased in the kidney. Mn contents also decreased on the 28th day and increased on the 42nd day in the liver. Cu contents declined in the heart and spleen. Cu contents increased on the 28th day and decreased on the 42nd day in the liver and kidney. Zn contents declined in the heart and spleen. Zn contents increased on the 28th day and decreased on the 42nd day in the liver and kidney. Fe contents decreased in the heart and liver. Fe contents increased on the 28th day and decreased on the 42nd day in the spleen and kidney. Mg contents did not significantly change in these organs. Appropriate selenium contents enhanced Mn and Zn contents, which were declined by chromium. Conversely, appropriate selenium contents reduced Ca, Fe, and Cu contents, which were increased by chromium. In conclusion, the exposure of chickens to K2Cr2O7 induced changes in different trace elements, and Na2SeO3 supplementation could alleviate this condition.

  4. Release of Zn from maternal tissues in pregnant rats deficient in Zn or Zn and Ca

    SciTech Connect

    Hurley, L.S.; Masters, D.G.; Lonnerdal, B.; Keen, C.L.

    1986-03-05

    Earlier studies have shown that diets that increase tissue catabolism reduce the teratogenic effects of Zn deficiency. The hypothesis that Zn may be released from body tissues when the metabolic state is altered was further tested. Nonpregnant Sprague Dawley females were injected with Zn-65; after equilibration, the two major pools of Zn, bone and muscle, had different specific activities (SA), muscle being much higher. Females were mated and fed diets adequate in Zn and Ca (C) or deficient in Zn (ZnD) or deficient in both Zn and Ca (ZnCaD). Calculations using weight loss in ZnD and ZnCaD rats, Zn content of maternal bone and muscle, and total fetal Zn at term indicated that in ZnCaD rats a relatively small amount of Zn from bone early in pregnancy was sufficient to prevent abnormal organogenesis, but most fetal Zn came from breakdown of maternal muscle in the last 3 days of pregnancy. Isotope data supported this conclusion. SA of Zn in ZnD fetuses was equal and high, indicating that most Zn came from the same maternal tissue. High muscle SA prior to mating, and increased SA in tibia and liver during pregnancy suggest that muscle provided Zn for other maternal tissues as well as fetuses. In contrast, SA in C fetuses was less than 30% of that of the D groups, consistent with the earlier hypothesis that most fetal Zn in C rats is accrued directly from the diet.

  5. 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.

  6. Mg/Ca of Continental Ostracode Shells

    NASA Astrophysics Data System (ADS)

    Ito, E.; Forester, R. M.; Marco-Barba, J.; Mezquita, F.

    2007-12-01

    Marine ionic chemistry is thought to remain constant. This, together with the belief that marine calcifiers partition Mg/Ca in a systematic manner as functions of temperature (and Mg/Ca) of water forms the basis of the Mg/Ca thermometer. In continental settings both of these assumptions are usually not true. Continental waters contain a wide variety of solutes in absolute and relative ion concentrations. Hence, waters with identical Mg/Ca may have very different concentrations of Mg and Ca and very different anions. Here we use two examples to focus on the effects of ion chemistry on Mg/Ca partitioning in continental ostracode shells and we ignore the complexities of solute evolution, which can change Mg/Ca over timescales of minutes to millennia. Palacios-Fest and Dettman (2001) conducted a monthly study of ,Cypridopsis vidua at El Yeso Lake in Sonora, Mexico. They established a relation between temperature and average shell Mg/Ca using regression analyses on averaged data. When their Mg/Ca-temperature relation is applied to monthly ,C. vidua data from Page Pond near Cleveland, Ohio, water temperatures of -8 to -1°C are obtained. The observed Mg/Ca ranges for El Yeso Lake (0.31 to 0.46) and Page Pond (0.33 to 0.46) are similar, as are their specific conductivities (700 to 850μS for El Yeso Lake; 400 to 600μS for Page Pond). However, [Ca] is 140-260 mg/L for El Yeso, but only 70-90 mg/L for Page Pond. Page Pond data, in fact, shows a good temperature shell Mg/Ca relation for .C. vidua, but the relation is different from that at El Yeso. Hence, shell Mg/Ca is a multi-valued, family of curves function of temperature and Mg/Ca of water that depends on the [Mg] and [Ca] values in water and perhaps other factors. Our second example comes from sites near Valencia, Spain and involves shell data for ,Cyprideis torosa, an estuarine ostracode that is tolerant of a wide range of salinity and can live in continental waters as long as the carbonate alkalinity to Ca ratio is

  7. An electrochemical study of Ni/2+/, Co/2+/, and Zn/2+/ ions in melts of composition CaMgSi2O6

    NASA Technical Reports Server (NTRS)

    Semkow, K. W.; Haskin, L. A.; Lindstrom, D. J.; Rizzo, R. A.

    1982-01-01

    Results are reported for a study of the behavior of Ni(2+), Co(2+), and Zn(2+) in molten diopside, determined by cyclic voltametry, as a first step in adapting electrochemical methods for use in experimental geochemistry. The techniques used are described, the theory is briefly discussed, and it is demonstrated that Ni(2+), Co(2+), and Zn(2+) can be reduced, then reoxidized in an uncomplicated case of reversible charge transfer at the Pt electrode. This implies that the neutral metal atoms remain undissolved in the melt. The kinetics of the reduction process, the effects of concentration, the standard reduction potentials, and the diffusion coefficients are discussed in detail. The observations are consistent with the mechanism of Ni(2+) diffusion by transport from site to site. As the proportion of SiO2 in the melt increases, a higher activation energy is required for Ni(2+) to move, and the rate of diffusion is lowered.

  8. Structural relationships among MgZn2 and Mg4Zn7 phases and transition structures in Mg-Zn-Y alloys

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

    Isothermal ageing of plastically deformed Mg-Zn-Y alloys resulted in precipitation along ? twin boundaries. The bulky precipitates so formed had structures similar to those recently reported for the rod-like ? precipitates, but afforded a more detailed study by high-resolution TEM due to their larger size. The core of the precipitates often had the structure of the monoclinic Mg4Zn7 phase, and had the orientation ? ; ? with either the matrix or the twin. On this Mg4Zn7 phase, the hexagonal MgZn2 phase grew in two orientations, both with ? . One of these orientations formed a known orientation relationship ? ; ? with the matrix. The part of the precipitate with the MgZn2 structure was usually in direct contact with the twin boundary. Both the Mg4Zn7 and MgZn2 phases have layered structures that can be described with similar building blocks of icosahedrally coordinated atoms. The atomic positions of zinc atoms comprise the vertices of these icosahedra and form 'thick' rhombic tiles. The orientations of these rhombuses remain unchanged across the interfaces between the two phases. Near the interface with MgZn2, transition structures formed in the Mg4Zn7 phase, with the Zn:Mg atom ratio between those of the Mg4Zn7 and MgZn2 phases. In these transition structures, the unit cell of the Mg4Zn7 phase is extended along [100] or [001] by half a unit cell length by continuation of the rhombic tiling. Structures of these extended unit cells are proposed.

  9. Zinc deficiency negatively affects alkaline phosphatase and the concentration of Ca, Mg and P in rats

    PubMed Central

    Cho, Young-Eun; Lomeda, Ria-Ann R.; Ryu, Sang-Hoon; Sohn, Ho-Yong; Shin, Hong-In; Beattie, John H.

    2007-01-01

    Zn is an essential nutrient that is required in humans and animals for many physiological functions, including immune and antioxidant function, growth, and reproduction. The present study evaluated whether Zn deficiency would negatively affect bone-related enzyme, ALP, and other bone-related minerals (Ca, P and Mg) in rats. Thirty Sprague Dawley rats were assigned to one of the three different Zn dietary groups, such as Zn adequate (ZA, 35 mg/kg), pair fed (PF, 35 mg/kg), Zn deficient (ZD, 1 mg/kg) diet, and fed for 10 weeks. Food intake and body weight were measured daily and weekly, respectively. ALP was measured by spectrophotometry and mineral contents were measured by inductively coupled plasma-mass spectrophotometer (ICP-MS). Zn deficient rats showed decreased food intake and body weight compared with Zn adequate rats (p<0.05). Zn deficiency reduced ALP activity in blood (RBC, plasma) and the tissues (liver, kidney and small intestine) (p<0.05). Also, Zn deficiency reduced mineral concentrations in rat tissues (Ca for muscle and liver, and Mg for muscle and liver) (p<0.05). The study results imply the requirement of proper Zn nurture for maintaining bone growth and formation. PMID:20535396

  10. 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.

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

    PubMed

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

    2009-08-07

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

  12. Synthesis of Al₂Ca Dispersoids by Powder Metallurgy Using a Mg-Al Alloy and CaO Particles.

    PubMed

    Fujita, Junji; Umeda, Junko; Kondoh, Katsuyoshi

    2017-06-28

    The elemental mixture of Mg-6 wt %Al-1 wt %Zn-0.3 wt %Mn (AZ61B) alloy powder and CaO particles was consolidated by an equal-channel angular bulk mechanical alloying (ECABMA) process to form a composite precursor. Subsequently, the precursor was subjected to a heat treatment to synthesize fine Al₂Ca particles via a solid-state reaction between the Mg-Al matrix and CaO additives. Scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) and electron probe micro-analysis on the precursor indicated that 4.7-at % Al atoms formed a supersaturated solid solution in the α-Mg matrix. Transmission electron microscopy-EDS and X-ray diffraction analyses on the AZ61B composite precursor with 10-vol % CaO particles obtained by heat treatment confirmed that CaO additives were thermally decomposed in the Mg-Al alloy, and the solid-soluted Ca atoms diffused along the α-Mg grain boundaries. Al atoms also diffused to the grain boundaries because of attraction to the Ca atoms resulting from a strong reactivity between Al and Ca. As a result, needle-like (Mg,Al)₂Ca intermetallics were formed as intermediate precipitates in the initial reaction stage during the heat treatment. Finally, the precipitates were transformed into spherical Al₂Ca particles by the substitution of Al atoms for Mg atoms in (Mg,Al)₂Ca after a long heat treatment.

  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. 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).

  15. Effects of annealing heat treatment on the corrosion resistance of Zn/Mg/Zn multilayer coatings

    NASA Astrophysics Data System (ADS)

    Bae, KiTae; La, JoungHyun; Lee, InGyu; Lee, SangYul; Nam, KyungHoon

    2017-05-01

    Zn coatings alloyed with magnesium offer superior corrosion resistance compared to pure Zn or other Zn-based alloy coatings. In this study, Zn/Mg/Zn multilayer coatings with various Mg layer thicknesses were synthesized using an unbalanced magnetron sputtering process and were annealed to form Zn-Mg intermetallic phases. The effects of the annealing heat treatment on the corrosion resistance of the Zn/Mg/Zn multilayer coatings were evaluated using electrochemical measurements. The extensive diffusion of magnesium species into the upper and lower zinc layer from the magnesium layer in the middle of the coating was observed after the heat treatment. This phenomenon caused (a) the porous microstructure to transition into a dense structure and (b) the formation of a MgZn2 intermetallic phase. The results of the electrochemical measurements demonstrated that the heat treated Zn/Mg/Zn multilayer coatings possessed higher levels of corrosion resistance than the non-heat treated coatings. A Zn/Mg/Zn multilayer coating with MgZn2 and (Zn) phases showed the best corrosion resistance among the heat treated coatings, which could be attributed to the reduced galvanic corrosion effects due to a small potential gradient between the MgZn2 and zinc.

  16. Study on the compounds of Mg12La and (Mg,Zn)11.5La

    NASA Astrophysics Data System (ADS)

    Huang, M. L.; Si, Z. Y.; Li, H. X.

    2017-01-01

    The composition, crystal structure and phase relationship of the main intermetallics of the Mg-Zn-La system on the low La side have been studied. The results show that there exists a binary solid solutions of Mg12La as (Mg,Zn)La12 and a linear ternary compound (Mg,Zn)11.5La. Though the composition formula of the two phases are similar, but the composition of Zn in them are different. The maximum Zn content of (Mg,Zn)12La is 7.2at% and the minimum Zn content of (Mg,Zn)11.5La is 8.5at%. What’s more, the crystal structures of (Mg,Zn)12La and (Mg,Zn)11.5La phase are also totally different. (Mg,Zn)La12 have the body centered tetragonal lattice structure, but the crystal structure of (Mg,Zn)11.5La is C-centered orthorhombic lattice structure.

  17. 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.

  18. Mixture designs to assess composition-structure-property relationships in SiO₂-CaO-ZnO-La₂O₃-TiO₂-MgO-SrO-Na₂O glasses: potential materials for embolization.

    PubMed

    Kehoe, Sharon; Langman, Maxine; Werner-Zwanziger, Ulli; Abraham, Robert J; Boyd, Daniel

    2013-09-01

    Embolization with micron-sized particulates is widely applied to treat uterine fibroids. The objective of this work was to develop mixture designs to predict materials composition-structure-property relationships for the SiO₂-CaO-ZnO-La₂O₃-TiO₂-MgO-SrO-Na₂O glass system and compare its fundamental materials properties (density and cytocompatibility), against a state-of-the-art embolic agent (contour polyvinyl alcohol) to assess the potential of these materials for embolization therapies. The glass structures were evaluated using ²⁹Si MAS NMR to identify chemical shift and line width; the particulate densities were determined using helium pycnometry and the cell viabilities were assessed via MTT assay. ²⁹Si MAS NMR results indicated peak maxima for each glass in the range of -82.3 ppm to -89.9 ppm; associated with Q² to Q³ units in silicate glasses. All experimental embolic compositions showed enhanced in vitro compatibility in comparison to Contour PVA with the exceptions of ORP9 and ORP11 (containing no TiO₂). In this study, optimal compositions for cell viability were obtained for the following compositional ranges: 0.095-0.188 mole fraction ZnO; 0.068-0.159 mole fraction La₂O₃; 0.545-0.562 mole fraction SiO₂ and 0.042-0.050 mole fraction TiO₂. To ensure ease of producibility in obtaining good melts, a maximum loading of 0.068 mole fraction La₂O₃ is required. This is confirmed by the desirability approach, for which the only experimental composition (ORP5) of the materials evaluated was presented as an optimum composition; combining high cell viability with ease of production (0.188 mole fraction ZnO; 0.068 mole fraction La₂O₃; 0.562 mole fraction SiO₂ and 0.042 mole fraction TiO₂).

  19. Mg-Ca Alloys Produced by Reduction of CaO: Understanding of ECO-Mg Alloy Production

    NASA Astrophysics Data System (ADS)

    Jung, In-Ho; Lee, Jin Kyu; Kim, Shae K.

    2017-04-01

    There have been long debates about the environment conscious (ECO) Mg technology which utilizes CaO to produce Ca-containing Mg alloys. Two key process technologies of the ECO-Mg process are the chemical reduction of CaO by liquid Mg and the maintenance of melt cleanliness during the alloying of Ca. Thermodynamic calculations using FactSage software were performed to explain these two key issues. In addition, an experimental study was performed to compare the melt cleanliness of the Ca-containing Mg alloys produced by the conventional route with metallic Ca and the ECO-Mg route with CaO.

  20. Mg-Ca Alloys Produced by Reduction of CaO: Understanding of ECO-Mg Alloy Production

    NASA Astrophysics Data System (ADS)

    Jung, In-Ho; Lee, Jin Kyu; Kim, Shae K.

    2016-12-01

    There have been long debates about the environment conscious (ECO) Mg technology which utilizes CaO to produce Ca-containing Mg alloys. Two key process technologies of the ECO-Mg process are the chemical reduction of CaO by liquid Mg and the maintenance of melt cleanliness during the alloying of Ca. Thermodynamic calculations using FactSage software were performed to explain these two key issues. In addition, an experimental study was performed to compare the melt cleanliness of the Ca-containing Mg alloys produced by the conventional route with metallic Ca and the ECO-Mg route with CaO.

  1. Ab initio simulation of elastic and mechanical properties of Zn- and Mg-doped hydroxyapatite (HAP).

    PubMed

    Aryal, Sitaram; Matsunaga, Katsuyuki; Ching, Wai-Yim

    2015-07-01

    Hydroxyapatite (HAP) is an important bioceramic which constitutes the mineral components of bones and hard tissues in mammals. It is bioactive and used as bioceramic coatings for metallic implants and bone fillers. HAP readily absorbs a large amount of impurities. Knowledge on the elastic and mechanical properties of impurity-doped HAP is a subject of great importance to its potential for biomedical applications. Zn and Mg are the most common divalent cations HAP absorbs. Using density function theory based ab initio methods, we have carried out a large number of ab initio calculations to obtain the bulk elastic and mechanical properties of HAP with Zn or Mg doped in different concentration at the Ca1 and Ca2 sites using large 352-atom supercells. Detailed information on their dependece on the concetraion of the substitued impurity is obtained. Our results show that Mg enhances overall elastic and bulk mechanical properties whereas Zn tends to degrade except at low concentrations. At a higher concentration, the mechanical properties of Zn and Mg doped HAP also depend significantly on impurity distribution between the Ca1 and Ca2 sites. There is a strong evidence that Zn prefers Ca2 site for substituion whereas Mg has no such preference. These results imply that proper control of dopant concentration and their site preference must carefully considered in using doped HAP for specific biomedical applications.

  2. Quaternary BeMgZnO by plasma-enhanced molecular beam epitaxy for BeMgZnO/ZnO heterostructure devices

    NASA Astrophysics Data System (ADS)

    Ullah, M. B.; Toporkov, M.; Avrutin, V.; Özgür, Ü.; Smith, D. J.; Morkoç, H.

    2017-02-01

    We investigated the crystal structure, growth kinetics and electrical properties of BeMgZnO/ZnO heterostructures grown by Molecular Beam Epitaxy (MBE). Transmission Electron Microscopy (TEM) studies revealed that incorporation of Mg into the BeZnO solid solution eliminates the high angle grain boundaries that are the major structural defects in ternary BeZnO. The significant improvement of x-ray diffraction intensity from quaternary BeMgZnO alloy compared to ternary BeZnO was attributed to the reduction of lattice strain, which is present in the latter due to the large difference of covalent radii between Be and Zn (1.22 Å for Zn, 0.96 Å for Be). Incorporation of Mg, which has a larger covalent radius of 1.41Å, reduced the strain in BeMgZnO thin films and also enhanced Be incorporation on lattice sites in the wurtzite lattice. The Zn/(Be + Mg) ratio necessary to obtain single-crystal O-polar BeMgZnO on (0001) GaN/sapphire templates was found to increase with increasing substrate temperature:3.9, 6.2, and 8.3 at substrate temperatures of 450°C, 475°C, and 500°C, respectively. Based on analysis of photoluminescence spectra from Be0.03MgyZn0.97-yO and evolution of reflection high-energy electron diffraction patterns observed in situ during the MBE growth, it has been deduced that more negative formation enthalpy of MgO compared to ZnO and the increased surface mobility of Mg adatoms at elevated substrate temperatures give rise to the nucleation of a MgO-rich wurtzite phase at relatively low Zn/(Be + Mg) ratios. We have demonstrated both theoretically and experimentally that the incorporation of Be into the barrier in Zn-polar BeMgZnO/ZnO and O-polar ZnO/BeMgZnO polarization doped heterostructures allows the alignment of piezoelectric polarization vector with that of spontaneous polarization due to the change of strain sign, thus increasing the amount of net polarization. This made it possible to achieve Zn-polar BeMgZnO/ZnO heterostructures grown on Ga

  3. Examining the Evidence for the Influence of Carbonate Saturation State on Benthic Foraminiferal Mg/Ca

    NASA Astrophysics Data System (ADS)

    Martin, P. A.; Lea, D. W.; McCorkle, D. C.

    2002-12-01

    Benthic foraminiferal Mg/Ca paleothermometry is based on an empirical relationship between the Mg/Ca of benthic foraminifera recovered from core tops and in situ bottom water temperatures (Rosenthal, 1997; Martin et al, in press; Lear et al, in review). While there is a tight correlation between shell Mg/Ca and temperature over a broad range of temperatures (-1 to 20 degrees C), Mg/Ca variation over the small range of deep water temperatures reveals departures from the calibration curve at low temperatures. Lower Mg/Ca values are generally associated with the deepest sites from the Atlantic and Pacific, contributing to an apparently steeper Mg/Ca-T response for abyssal benthics. The steeper response of abyssal benthics may reflect an influence of decreasing carbonate saturation with depth. Saturation related effects have already been documented for Mg in planktonic foraminifera and for other metals (Cd, Ba, and Zn) in benthic foraminifera shells (see Marchitto and ref. therein). Although it is difficult to definitively separate the effects of various environmental parameters (including temperature, depth, and relative saturation states), which often change in unison, we can use the core top Mg/Ca data to estimate the potential influence of saturation state. An alternative calibration of the benthic Mg/Ca - T relationship can be derived from core top benthic foraminifera based only on sites bathed in waters above carbonate saturation that yields a slightly smaller change in Mg/Ca per degree C (~9.5% vs. 11%) but better explains benthic Mg/Ca from the coldest sites (-1degrees C). Using this alternative Mg/Ca -T relation and a subset of data from the Ceara Rise and Ontong Java Plateau, we can estimate a maximum Mg/Ca offset attributable to saturation state. By comparing core top and downcore data, we can also address possible differences in the primary Mg-T response and carbonate saturation related effects between different genera (Cibicidoides and Uvigerina).

  4. A DFT study on the complex formation between desferrithiocin and metal ions (Mg(2+), Al(3+), Ca(2+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+)).

    PubMed

    Kaviani, Sadegh; Izadyar, Mohammad; Housaindokht, Mohammad Reza

    2017-04-01

    In recent years, Metal-chelating compounds, namely siderphores have been considered very much because of their crucial role in various fields of the environmental researches. Their importance lies in the fact that they are able to be bonded to a variety of metals in addition to iron. A theoretical study on the structures of desferrithiocin siderphore coordinated to Mg(2+), Al(3+), Ca(2+), Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+) and Zn(2+) metal ions was carried out, using the CAM-B3LYP/6-31G(d) level of the theory in the water. In order to understand the factors which control the stability, reactivity and the strength of toxic metals excretion as well as microbial uptake of the metal-siderphore complexes, we examined the stability and binding energies of the desferrithiocin and various metal ions with different spin states. The binding affinity of desferrithiocin to Fe(3+) (log β2=23.88) showed that the desferrithiocin can scavenge the excess iron(III) from the labile sources. Also, the binding energy values were well described by addition of the dispersion-corrected D3 functional. Because of the importance of the charge transfer in the complex formation, donor-acceptor interaction energies were evaluated. Based on this analysis, an increase in the effective nuclear charge increases E(2) values. Vibrational analysis showed that the critical bonds (CO stretching and CH bending) are in the range of 1300-1800cm(-1). Finally, some probable correlations between the complexation behavior and quantum chemistry descriptors have been analyzed.

  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. Transport characteristics of a ZnMgO/ZnO hetero junction and the effect of temperature and Mg content

    NASA Astrophysics Data System (ADS)

    Uslu, Salih; Yarar, Zeki

    2017-02-01

    The Ensemble Monte Carlo method is used to calculate the transport characteristics of two dimensional electron gas (2DEG) at a ZnMgO/ZnO hetero structure. The spontaneous and piezoelectric polarizations are considered and there is no intentional doping in either material. Numerical Schrödinger and Poisson equations are solved self consistently to obtain the scattering rates of various scattering mechanisms. The density of carriers, each energy sub bands, potential profile and corresponding wave functions are obtained from the self consistent calculations. The self consistent sub band wave functions of acoustic and optic phonon scattering and interface roughness scattering are used in Monte Carlo method to obtain transport characteristics at ZnMgO/ZnO junction. Two dimensional electron gas confined to ZnMgO/ZnO hetero structure is studied and the effect of temperature and Mg content are investigated.

  7. 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).

  8. 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).

  9. Selective antibacterial effects of mixed ZnMgO nanoparticles

    NASA Astrophysics Data System (ADS)

    Vidic, Jasmina; Stankic, Slavica; Haque, Francia; Ciric, Danica; Le Goffic, Ronan; Vidy, Aurore; Jupille, Jacques; Delmas, Bernard

    2013-05-01

    Antibiotic resistance has impelled the research for new agents that can inhibit bacterial growth without showing cytotoxic effects on humans and other species. We describe the synthesis and physicochemical characterization of nanostructured ZnMgO whose antibacterial activity was compared to its pure nano-ZnO and nano-MgO counterparts. Among the three oxides, ZnO nanocrystals—with the length of tetrapod legs about 100 nm and the diameter about 10 nm—were found to be the most effective antibacterial agents since both Gram-positive ( B. subtilis) and Gram-negative ( E. coli) bacteria were completely eradicated at concentration of 1 mg/mL. MgO nanocubes (the mean cube size 50 nm) only partially inhibited bacterial growth, whereas ZnMgO nanoparticles (sizes corresponding to pure particles) revealed high specific antibacterial activity to Gram-positive bacteria at this concentration. Transmission electron microscopy analysis showed that B. subtilis cells were damaged after contact with nano-ZnMgO, causing cell contents to leak out. Our preliminary toxicological study pointed out that nano-ZnO is toxic when applied to human HeLa cells, while nano-MgO and the mixed oxide did not induce any cell damage. Overall, our results suggested that nanostructured ZnMgO, may reconcile efficient antibacterial efficiency while being a safe new therapeutic for bacterial infections.

  10. Enhanced output power using MgZnO/ZnO/MgZnO double heterostructure in ZnO homojunction light-emitting diode

    NASA Astrophysics Data System (ADS)

    Chu, Sheng; Zhao, Jianze; Zuo, Zheng; Kong, Jieying; Li, Lin; Liu, Jianlin

    2011-02-01

    A diode with Sb-doped p-type ZnO, MgZnO/ZnO/MgZnO double heterojunction, and undoped n-type ZnO layers was grown on c-plane sapphire substrate by plasma-assisted molecular-beam epitaxy. Hall effect measurement showed that the top p-type Sb-doped ZnO layer has a hole concentration of 1×1017cm-3. Mesa geometry light emitting diodes were fabricated with Au/Ni and Au/Ti Ohmic contacts on top of the p-type and n-type layers, respectively. Strong ultraviolet emission was achieved, which yielded an output power of 457 nW at 140 mA. The drastic enhancement of the output power is attributed to carrier confinement in the good-quality intrinsic layer of the double heterojunction. The spatial distribution of light emission was characterized.

  11. Enhanced output power using MgZnO/ZnO/MgZnO double heterostructure in ZnO homojunction light emitting diode

    NASA Astrophysics Data System (ADS)

    Chu, Sheng; Zhao, Jianze; Zuo, Zheng; Kong, Jieying; Li, Lin; Liu, Jianlin

    2011-06-01

    A diode with Sb-doped p-type ZnO, MgZnO/ZnO/MgZnO double heterostructure, and undoped n-type ZnO layers was grown on c-plane sapphire substrate by plasma-assisted molecular-beam epitaxy. Hall effect measurement showed that the top p-type Sb-doped ZnO layer has a hole concentration of 1 × 1017cm-3. Mesa geometry light emitting diodes were fabricated with Au/Ni and Au/Ti Ohmic contacts on top of the p-type and n-type layers, respectively. Ultraviolet emission was achieved, which yielded an output power of 457 nW at 140 mA. The enhancement of the output power is attributed to carrier confinement in the good-quality intrinsic layer of the double heterostructure. The spatial distribution of light emission was characterized.

  12. Thermal Parameters and Microstructural Development in Directionally Solidified Zn-Rich Zn-Mg Alloys

    NASA Astrophysics Data System (ADS)

    Vida, Talita A.; Freitas, Emmanuelle S.; Brito, Crystopher; Cheung, Noé; Arenas, Maria A.; Conde, Ana; De Damborenea, Juan; Garcia, Amauri

    2016-06-01

    Transient directional solidification experiments have been carried out with Zn-Mg hypoeutectic alloys under an extensive range of cooling rates with a view to analyzing the evolution of microstructure. It is shown that the microstructure is formed by a Zn-rich matrix of different morphologies and competitive eutectic mixtures (Zn-Zn11Mg2 and Zn-Zn2Mg). For 0.3 wt-pct Mg and 0.5 wt-pct Mg alloys, the Zn-rich matrix is shown to be characterized by high-cooling rates plate-like cells (cooling rates >9.5 and 24 K/s, respectively), followed by a granular-dendritic morphological transition for lower cooling rates. In contrast, a directionally solidified Zn1.2 wt-pct Mg alloy casting is shown to have the Zn-rich matrix formed only by dendritic equiaxed grains. Experimental growth laws are proposed relating the plate-like cellular interphase, the secondary dendritic arm spacing, and the eutectic interphase spacings to solidification thermal parameters, i.e., cooling rate and growth rate. The experimental law for the growth of secondary dendritic spacings under unsteady-state solidifications is also shown to encompass results of hypoeutectic Zn-Mg alloys subjected to steady-state Bridgman growth.

  13. 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.

  14. Distribution of P, K, Ca, Mg, Cd, Cu, Fe, Mn, Pb and Zn in wood and bark age classes of willows and poplars used for phytoextraction on soils contaminated by risk elements.

    PubMed

    Zárubová, Pavla; Hejcman, Michal; Vondráčková, Stanislava; Mrnka, Libor; Száková, Jiřina; Tlustoš, Pavel

    2015-12-01

    Fast-growing clones of Salix and Populus have been studied for remediation of soils contaminated by risk elements (RE) using short-rotation coppice plantations. Our aim was to assess biomass yield and distributions of elements in wood and bark of highly productive willow (S1--[Salix schwerinii × Salix viminalis] × S. viminalis, S2--Salix × smithiana clone S-218) and poplar (P1--Populus maximowiczii × Populus nigra, P2--P. nigra) clones with respect to aging. The field experiment was established in April 2008 on moderately Cd-, Pb- and Zn- contaminated soil. Shoots were harvested after four seasons (February 2012) and separated into annual classes of wood and bark. All tested clones grew on contaminated soils, with highest biomass production and lowest mortality exhibited by P1 and S2. Concentrations of elements, with exception of Ca and Pb, decreased with age and were higher in bark than in wood. The Salix clones were characterised by higher removal of Cd, Mn and Zn compared to the Populus clones. Despite generally higher RE content in young shoots, partly due to lower wood/bark ratios and higher RE concentrations in bark, the overall removal of RE was higher in older wood classes due to higher biomass yield. Thus, longer rotations seem to be more effective when phytoextraction strategy is considered. Of the four selected clones, S1 exhibited the best removal of Cd and Zn and is a good candidate for phytoextraction.

  15. Distribution of calcium (Ca) and magnesium (Mg) in the leaves of Brassica rapa under varying exogenous Ca and Mg supply

    PubMed Central

    Rios, Juan Jose; Ó Lochlainn, Seosamh; Devonshire, Jean; Graham, Neil S.; Hammond, John P.; King, Graham J.; White, Philip J.; Kurup, Smita; Broadley, Martin R.

    2012-01-01

    Background and Aims Leafy vegetable Brassica crops are an important source of dietary calcium (Ca) and magnesium (Mg) and represent potential targets for increasing leaf Ca and Mg concentrations through agronomy or breeding. Although the internal distribution of Ca and Mg within leaves affects the accumulation of these elements, such data are not available for Brassica. The aim of this study was to characterize the internal distribution of Ca and Mg in the leaves of a vegetable Brassica and to determine the effects of altered exogenous Ca and Mg supply on this distribution. Methods Brassica rapa ssp. trilocularis ‘R-o-18’ was grown at four different Ca:Mg treatments for 21 d in a controlled environment. Concentrations of Ca and Mg were determined in fully expanded leaves using inductively coupled plasma-mass spectrometry (ICP-MS). Internal distributions of Ca and Mg were determined in transverse leaf sections at the base and apex of leaves using energy-dispersive X-ray spectroscopy (EDS) with cryo-scanning electron microscopy (cryo-SEM). Key Results Leaf Ca and Mg concentrations were greatest in palisade and spongy mesophyll cells, respectively, although this was dependent on exogenous supply. Calcium accumulation in palisade mesophyll cells was enhanced slightly under high Mg supply; in contrast, Mg accumulation in spongy mesophyll cells was not affected by Ca supply. Conclusions The results are consistent with Arabidopsis thaliana and other Brassicaceae, providing phenotypic evidence that conserved mechanisms regulate leaf Ca and Mg distribution at a cellular scale. The future study of Arabidopsis gene orthologues in mutants of this reference B. rapa genotype will improve our understanding of Ca and Mg homeostasis in plants and may provide a model-to-crop translation pathway for targeted breeding. PMID:22362665

  16. Distribution of calcium (Ca) and magnesium (Mg) in the leaves of Brassica rapa under varying exogenous Ca and Mg supply.

    PubMed

    Rios, Juan Jose; Lochlainn, Seosamh O; Devonshire, Jean; Graham, Neil S; Hammond, John P; King, Graham J; White, Philip J; Kurup, Smita; Broadley, Martin R

    2012-05-01

    Leafy vegetable Brassica crops are an important source of dietary calcium (Ca) and magnesium (Mg) and represent potential targets for increasing leaf Ca and Mg concentrations through agronomy or breeding. Although the internal distribution of Ca and Mg within leaves affects the accumulation of these elements, such data are not available for Brassica. The aim of this study was to characterize the internal distribution of Ca and Mg in the leaves of a vegetable Brassica and to determine the effects of altered exogenous Ca and Mg supply on this distribution. Brassica rapa ssp. trilocularis 'R-o-18' was grown at four different Ca:Mg treatments for 21 d in a controlled environment. Concentrations of Ca and Mg were determined in fully expanded leaves using inductively coupled plasma-mass spectrometry (ICP-MS). Internal distributions of Ca and Mg were determined in transverse leaf sections at the base and apex of leaves using energy-dispersive X-ray spectroscopy (EDS) with cryo-scanning electron microscopy (cryo-SEM). Leaf Ca and Mg concentrations were greatest in palisade and spongy mesophyll cells, respectively, although this was dependent on exogenous supply. Calcium accumulation in palisade mesophyll cells was enhanced slightly under high Mg supply; in contrast, Mg accumulation in spongy mesophyll cells was not affected by Ca supply. The results are consistent with Arabidopsis thaliana and other Brassicaceae, providing phenotypic evidence that conserved mechanisms regulate leaf Ca and Mg distribution at a cellular scale. The future study of Arabidopsis gene orthologues in mutants of this reference B. rapa genotype will improve our understanding of Ca and Mg homeostasis in plants and may provide a model-to-crop translation pathway for targeted breeding.

  17. Electrodeposition of Ca-P coatings on biodegradable Mg alloy: in vitro biomineralization behavior.

    PubMed

    Song, Yang; Zhang, Shaoxiang; Li, Jianan; Zhao, Changli; Zhang, Xiaonong

    2010-05-01

    Preparing stabilized apatite on biodegradable Mg alloy may improve biocompatibility and promote osteointegration. In the present work, three kinds of Ca-P coatings, brushite (DCPD, CaHPO(4).2H(2)O), hydroxyapatite (HA, Ca(10)(PO(4))(6)(OH)(2)) and fluoridated hydroxyapatite (FHA, Ca(5)(PO(4))(3)(OH)(1-)(x)F(x)) are fabricated by electrodeposition on a biodegradable Mg-Zn alloy. The crystalline structures, morphologies and compositions of these Ca-P coatings have been characterized by X-ray diffrection, scanning electron microscopy and energy-dispersive spectoscopy. The effects of these coatings on the degradation behavior and mineralization activity of the Mg-Zn alloy have also been investigated. The experimental results showed that these coatings decreased the degradation rate of Mg-Zn alloy, while the precipitates on the uncoated and DCPD-coated Mg-Zn alloy in modified simulated biological fluid had low Ca/P molar ratios, which delayed bone-like apatite formation. Both the HA and FHA coating could promote the nucleation of osteoconductive minerals (bone-like apatite or beta-TCP) for 1month. However, the HA coating transformed from DCPD through alkali heat treatment was fragile and less stable, and therefore its long-term corrosion resistance was not satisfactory. Instead, the FHA was more stable and had better corrosion resistance, and thus it should be better suited as a coating of Mg implants for orthopedic applications. Copyright (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  18. [Determination of Mg and Zn contents of Naruto "wakame" (Undaria pinnatifida)].

    PubMed

    Ito, S; Miyoshi, T

    1990-08-01

    The contents of Mg and Zn in the sea-weed "wakame" were determined and compared at different growth stages, in different parts, for different root cultivation intervals, and in processed foods. The results obtained were as follows: 1. Mg (2.09-2.60 g/100 g) and Zn (8.00-10.76 mg/100 g) contents were independent of growth stage with the exception of Zn (29.00-35.78 mg/100 g) in the natural young "wakame". 2. The mineral contents of leaves, stipes, fruiting bodies and rhizoids of "wakame" at different growth stages were determined. The contents of Mg (1.00-2.36 g/100 g) and Zn (3.93-12.01 mg/100 g) were richer in leaves and stipes than in fruiting bodies and rhizoids. 3. Densely cultured "wakame" showed higher contents of Zn (6.73 mg/100 g) than thinly cultured plants (5.99 mg/100 g), and Mg content was not affected by changes in environmental conditions. 4. The Mg/Ca ratios reached a maximum in the stipe (3.3) and at fruiting bodies (2.9) in the middle stage, and in the base of the stipe of the mature plant (3.5). 5. Contents of the minerals in processed foods were determined. "Suboshi" was rich in Mg (1.07 +/- 0.42 g/100 g), and "Haiboshi" was rich in Zn (10.90 +/- 1.20 mg/100 g). The mineral contents in "Enzo" were small.

  19. The van der Waals potentials of MgCa, MgSr, MgBa, CaSr, CaBa, and SrBa

    NASA Astrophysics Data System (ADS)

    Wei, L. M.; Li, P.; Tang, K. T.

    2015-08-01

    Based on the facts that the potential energy curves of the homo-nuclear group 2 dimers (group IIA metal), except Be2, are conformal, and they can be described by the Tang-Toennies potential model, a set of simple combining rules are proposed for the parameters of the reduced potentials of the hetero-nuclear dimers. Together with the well-established combining rules of the range parameters of the exponential repulsion and the known dispersion coefficients, these rules enable us to determine the ground state potential energy curves of MgCa, MgSr, MgBa, CaSr, CaBa, and SrBa from those of Mg2, Ca2, Sr2, and Ba2. The determined potentials are comparable to some ab initio calculations and in excellent agreement with the experiment.

  20. Ultraviolet emission from a multi-layer graphene/MgZnO/ZnO light-emitting diode

    SciTech Connect

    Kang, Jang-Won; Choi, Yong-Seok; Goo Kang, Chang; Hun Lee, Byoung; Kim, Byeong-Hyeok; Tu, C. W.; Park, Seong-Ju

    2014-02-03

    We report on ultraviolet emission from a multi-layer graphene (MLG)/MgZnO/ZnO light-emitting diodes (LED). The p-type MLG and MgZnO in the MLG/MgZnO/ZnO LED are used as transparent hole injection and electron blocking layers, respectively. The current-voltage characteristics of the MLG/MgZnO/ZnO LED show that current transport is dominated by tunneling processes in the MgZnO barrier layer under forward bias conditions. The holes injected from p-type MLG recombine efficiently with the electrons accumulated in ZnO, and the MLG/MgZnO/ZnO LED shows strong ultraviolet emission from the band edge of ZnO and weak red-orange emission from the deep levels of ZnO.

  1. 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

  2. Corrosion Fatigue of Al-Zn-Mg and and Al-Mg-Li Alloys.

    DTIC Science & Technology

    1986-01-01

    surface of a sample of the Al-Zn-Mg alloy tested in 0.5 M sodium chloride, at a constant potential of -0.8 I..* xiii ..:S: Vuce ...potential of -0.8 Vuce (10OX). 20g .71 179 eL 4 0.2 mm Figure 97 The fracture surface of a sample of the Al-Zn-Mg alloy tested in 0.5 N sodium...fracture surface of a sample of the Al-Zn-Mg alloy tested in 0.5 N sodium chloride at a constant potential of-1.0 Vuce (20X). : Figure 100 The fracture

  3. Application of calcite Mg partitioning functions to the reconstruction of paleocean Mg/Ca

    NASA Astrophysics Data System (ADS)

    Hasiuk, Franciszek J.; Lohmann, Kyger C.

    2010-12-01

    Calcite Mg/Ca is usually assumed to vary linearly with solution Mg/Ca, that a constant partition coefficient describes the relationship between these two ratios. Numerous published empirical datasets suggests that this relationship is better described by a power function. We provide a compilation of these literature data for biotic and abiotic calcite in the form of Calcite Mg/Ca = F(Solution Mg/Ca) H, where F and H are empirically determined fitting parameters describing the slope and deviation from linearity, respectively, of the function. This is equivalent to Freundlich sorption behavior controlling Mg incorporation in calcite. Using a power function, instead of a partition coefficient, lowers Phanerozoic seawater Mg/Ca estimates based on echinoderm skeletal material by, on average, 0.5 mol/mol from previous estimates. These functions can also be used to model the primary skeletal calcite Mg/Ca of numerous calcite phases through geologic time. Such modeling suggests that the Mg/Ca of all calcite precipitated from seawater has varied through the Phanerozoic in response to changing seawater Mg/Ca and that the overall range in Mg/Ca measured among various calcite phases would be greatest when seawater Mg/Ca was also high (e.g., "aragonite seas") and lowest when seawater Mg/Ca was low (e.g., "calcite seas"). It follows that, during times of "calcite seas" when the seawater Mg/Ca is presumed to have been lower, deposition of calcite with low Mg contents would have resulted in a depressed drive for diagenetic stabilization of shelfal carbonate and, in turn, lead to greater preservation of crystal and skeletal microfabrics and primary chemistries in biotic and abiotic calcites.

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

    NASA Astrophysics Data System (ADS)

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

    2017-06-01

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

  5. Towards reconstructing ancient seawater Mg/Ca by combining porcelaneous and hyaline foraminiferal Mg/Ca-temperature calibrations

    NASA Astrophysics Data System (ADS)

    Wit, J. C.; de Nooijer, L. J.; Haig, J.; Jorissen, F. J.; Thomas, E.; Reichart, G.-J.

    2017-08-01

    The temperature of the deep ocean plays a vital role in the Earth's climate system. Paleo-reconstructions of deep-sea temperatures have traditionally been based on the oxygen isotope composition of deep-sea benthic foraminiferal calcite shells, although this parameter depends upon polar ice volume as well as temperature. More recent reconstructions use Mg/Ca in these shells, with temperature calibrations based on empirical relationships observed in present-day oceans. Incorporation of Mg (DMg) into foraminiferal calcite is, however, not solely dependent on temperature, but also on seawater Mg/Ca. Due to its long oceanic residence time, Mg concentrations remained relatively constant over time scales of a few hundred thousand years, but varied significantly over longer geological time scales. Accurate reconstruction of past temperatures using foraminiferal Mg/Ca, therefore, hinges on our understanding of Mg/Ca seawater changes on geological timescales. We explore a novel, independent approach to reconstructing past seawater Mg/Ca using the temperature-dependent offset in DMg between porcelaneous (secreting intermediate- or high-Mg calcite, abbreviated as IMC or HMC, respectively) and hyaline (producing low-Mg calcite, abbreviated as LMC) benthic foraminifera. We calibrated the Mg/Ca-temperature dependence for Pyrgo spp. (one of the few common, large-sized porcelaneous taxa present in the deep-sea since the middle Miocene), and combined this with an existing calibration of hyaline Cibicidoides spp. to mathematically solve for changes in Mg/Ca seawater through time. We show that changes in Mg/Ca seawater can be reconstructed using the offset between porcelaneous and hyaline foraminifera, but absolute values are highly dependent on the species-specific offset between Mg/Ca seawater and Mg-partition coefficients.

  6. Different response of osteoblastic cells to Mg(2+), Zn(2+) and Sr(2+) doped calcium silicate coatings.

    PubMed

    Hu, Dandan; Li, Kai; Xie, Youtao; Pan, Houhua; Zhao, Jun; Huang, Liping; Zheng, Xuebin

    2016-03-01

    Mg(2+), Zn(2+) and Sr(2+) substitution for Ca(2+) in plasma sprayed calcium silicate (Ca-Si) coatings have been reported to impede their degradation in physiological environment and, more importantly, to improve their biological performance. The reason for the improved biological performance is still elusive and, especially, the contribution of the dopant ions is lack of obvious and direct evidence. In this study, we aim to identify the effect of Mg(2+), Zn(2+) and Sr(2+) incorporation on the osteogenic ability of Ca-Si based coatings (Ca2MgSi2O7, Ca2ZnSi2O7 and Sr-CaSiO3) by minimizing the influence of Ca and Si ions release and surface physical properties. Similar surface morphology, crystallinity and roughness were achieved for all samples by optimizing the spray parameters. As expected, Ca and Si ions release from all the coatings showed the comparable concentration with immersing time. The response of MC3T3-E1 cells onto Mg(2+), Zn(2+) and Sr(2+) doped Ca-Si coatings were studied in terms of osteoblastic adhesion, proliferation, differentiation and mineralization. The results showed that the level of cell adhesion and proliferation increased the most on the surface of Mg-modified coating. Gene expressions of early markers of osteoblast differentiation (COL-I and ALP mRNA) were obviously improved on Zn-modified coating. Gene expressions of later markers for osteoblast differentiation (OPN and OC mRNA) and mineralized nodules formation were obviously accelerated on the surface of Sr-modified coating. Since Mg(2+), Zn(2+) and Sr(2+) play a regulatory role in different stages of osteogenesis, it may be possible to utilize this in the development of new coating materials for orthopedic application.

  7. 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})

  8. Tunable zinc interstitial related defects in ZnMgO and ZnCdO films

    SciTech Connect

    Li, Wanjun; Qin, Guoping; Fang, Liang E-mail: kchy@163.com; Ye, Lijuan; Wu, Fang; Ruan, Haibo; Zhang, Hong; Kong, Chunyang E-mail: kchy@163.com; Zhang, Ping

    2015-04-14

    We report tunable band gap of ZnO thin films grown on quartz substrates by radio frequency magnetron sputtering. The zinc interstitial (Zn{sub i}) defects in ZnO films were investigated by X-ray diffraction, Raman scattering, Auger spectra, first-principle calculations, and Hall measurement. Undoped ZnO film exhibits an anomalous Raman mode at 275 cm{sup −1}. We first report that 275 cm{sup −1} mode also can be observed in ZnO films alloyed with Mg and Cd, whose Raman intensities, interestingly, decrease and increase with increasing Mg and Cd alloying content, respectively. Combined with the previous investigations, it is deduced that 275 cm{sup −1} mode is attributed to Zn{sub i} related defects, which is demonstrated by our further experiment and theoretical calculation. Consequently, the concentration of Zn{sub i} related defects in ZnO can be tuned by alloying Mg and Cd impurity, which gives rise to different conductivity in ZnO films. These investigations help to further understand the controversial origin of the additional Raman mode at 275 cm{sup −1} and also the natural n-type conductivity in ZnO.

  9. ZnO and MgZnO Nanocrystalline Flexible Films: Optical and Material Properties

    DOE PAGES

    Huso, Jesse; Morrison, John L.; Che, Hui; ...

    2011-01-01

    An emore » merging material for flexible UV applications is Mg x Zn 1 − x O which is capable of tunable bandgap and luminescence in the UV range of ~3.4 eV–7.4 eV depending on the composition x . Studies on the optical and material characteristics of ZnO and Mg 0.3 Zn 0.7 O nanocrystalline flexible films are presented. The analysis indicates that the ZnO and Mg 0.3 Zn 0.7 O have bandgaps of 3.34 eV and 4.02 eV, respectively. The photoluminescence (PL) of the ZnO film was found to exhibit a structural defect-related emission at ~3.316 eV inherent to the nanocrystalline morphology. The PL of the Mg 0.3 Zn 0.7 O film exhibits two broad peaks at 3.38 eV and at 3.95 eV that are discussed in terms of the solubility limit of the ZnO-MgO alloy system. Additionally, external deformation of the film did not have a significant impact on its properties as indicated by the Raman LO-mode behavior, making these films attractive for UV flexible applications.« less

  10. A comparison of Zn2+- and Ca2+- triggered depolarization of liver mitochondria reveals no evidence of Zn2+-induced permeability transition

    PubMed Central

    Devinney, Michael J.; Malaiyandi, Latha M.; Vergun, Olga; DeFranco, Donald B.; Hastings, Teresa G.; Dineley, Kirk E.

    2013-01-01

    Intracellular Zn2+ toxicity is associated with mitochondrial dysfunction. Zn2+ depolarizes mitochondria in assays using isolated organelles as well as cultured cells. Some reports suggest that Zn2+-induced depolarization results from the opening of the mitochondrial permeability transition pore (mPTP). For a more detailed analysis of this relationship, we compared Zn2+-induced depolarization with the effects of Ca2+ in single isolated rat liver mitochondria monitored with the potentiometric probe Rhodamine123. Consistent with previous work, we found that relatively low levels of Ca2+ caused rapid, complete and irreversible loss of mitochondrial membrane potential, an effect that was diminished by classic inhibitors of mPT, including high Mg2+, ADP and cyclosporine A. Zn2+ also depolarized mitochondria, but only at relatively high concentrations. Furthermore Zn2+-induced depolarization was slower, partial and sometimes reversible, and was not affected by inhibitors of mPT. We also compared the effects of Ca2+ and Zn2+ in a calcein-retention assay. Consistent with the well-documented ability of Ca2+ to induce mPT, we found that it caused rapid and substantial loss of matrix calcein. In contrast, calcein remained in Zn2+-treated mitochondria. Considered together, our results suggest that Ca2+ and Zn2+ depolarize mitochondria by considerably different mechanisms, that opening of the mPTP is not a direct consequence of Zn2+-induced depolarization, and that Zn2+ is not a particularly potent mitochondrial inhibitor. PMID:19349076

  11. Blood compatibility of zinc-calcium phosphate conversion coating on Mg-1.33Li-0.6Ca alloy

    NASA Astrophysics Data System (ADS)

    Zou, Yu-Hong; Zeng, Rong-Chang; Wang, Qing-Zhao; Liu, Li-Jun; Xu, Qian-Qian; Wang, Chuang; Liu, Zhi-Wei

    2016-09-01

    Magnesium alloys as a new class of biomaterials possess biodegradability and biocompatibility in comparison with currently used metal implants. However, their rapid corrosion rates are necessary to be manipulated by appropriate coatings. In this paper, a new attempt was used to develop a zinc-calcium phosphate (Zn-Ca-P) conversion coating on Mg-1.33Li-0.6Ca alloys to increase the biocompatibility and improve the corrosion resistance. In vitro blood biocompatibility of the alloy with and without the Zn-Ca-P coating was investigated to determine its suitability as a degradable medical biomaterial. Blood biocompatibility was assessed from the hemolysis test, the dynamic cruor time test, blood cell count and SEM observation of the platelet adhesion to membrane surface. The results showed that the Zn-Ca-P coating on Mg-1.33Li-0.6Ca alloys had good blood compatibility, which is in accordance with the requirements for medical biomaterials.

  12. 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

  13. Quantifying the Potential Influence of Carbonate Saturation State on Benthic Foraminiferal Mg/Ca

    NASA Astrophysics Data System (ADS)

    Martin, P. A.; Lea, D. W.; McCorkle, D. C.

    2002-05-01

    Benthic foraminiferal Mg/Ca paleothermometry is based on an empirical relationship between the Mg/Ca of benthic foraminifera recovered from core tops and in situ bottom water temperatures (Rosenthal, 1997; Martin et al, in press; Lear et al, in review). While there is a tight correlation between shell Mg/Ca and temperature over a broad range of temperatures (-1 to 20 degrees C), Mg/Ca variation over the small range of deep water temperatures reveals departures from the calibration curve at low temperatures. Lower Mg/Ca values are generally associated with the deepest sites from the Atlantic and Pacific, contributing to an apparently steeper Mg/Ca-T response for abyssal benthics. The steeper response of abyssal benthics may reflect an influence of decreasing carbonate saturation with depth. Dissolution or other saturation related effects have already been documented for Mg in planktonic foraminifera and for other metals (Cd, Ba, and Zn) in benthic foraminifera shells (see Marchitto and ref. therein). Although it is difficult to definitively separate the effects of various environmental parameters (including temperature, depth, and relative saturation states), which often change in unison, we can use to the core top Mg/Ca data to estimate the potential influence of saturation state. An alternative calibration of the benthic Mg/Ca - T relationship can be derived based on core top benthic foraminifera only from sites bathed in waters above carbonate saturation, which yields a slightly smaller change in Mg/Ca per degree C (~9.5% vs. 11%) but better explains benthic Mg/Ca from the coldest sites (-1oC). Using this alternative Mg/Ca -T relation and a subset of the data from the Ceara Rise and Ontong Java Plateau, we can estimate a maximum Mg/Ca offset attributable to saturation state. The uncertainty this implies for downcore reconstructions varies widely (exceeding 1.5oC), depending on the hydrographic setting and which proxy is used to estimate saturation state.

  14. Enhanced biocorrosion resistance and biocompatibility of degradable Mg-Nd-Zn-Zr alloy by brushite coating.

    PubMed

    Niu, Jialin; Yuan, Guangyin; Liao, Yi; Mao, Lin; Zhang, Jian; Wang, Yongping; Huang, Feng; Jiang, Yao; He, Yaohua; Ding, Wenjiang

    2013-12-01

    To further improve the corrosion resistance and biocompatibility of Mg-Nd-Zn-Zr alloy (JDBM), a biodegradable calcium phosphate coating (Ca-P coating) with high bonding strength was developed using a novel chemical deposition method. The main composition of the Ca-P coating was brushite (CaHPO4·2H2O). The bonding strength between the coating and the JDBM substrate was measured to be over 10 MPa, and the thickness of the coating layer was about 10-30 μm. The in vitro corrosion tests indicated that the Ca-P treatment improved the corrosion resistance of JDBM alloy in Hank's solution. Ca-P treatment significantly reduced the hemolysis rate of JDBM alloy from 48% to 0.68%, and induced no toxicity to MC3T3-E1 cells. The in vivo implantation experiment in New Zealand's rabbit tibia showed that the degradation rate was reduced obviously by the Ca-P treatment and less gas was produced from Ca-P treated JDBM bone plates and screws in early stage of the implantation, and at least 10weeks degradation time can be prolonged by the present coating techniques. Both Ca-P treated and untreated JDBM Mg alloy induced bone growth. The primary results indicate that the present Ca-P treatment is a promising technique for the degradable Mg-based biomaterials for orthopedic applications. © 2013.

  15. Biodegradable Mg-Zn-Y alloys with long-period stacking ordered structure: optimization for mechanical properties.

    PubMed

    Zhao, Xu; Shi, Ling-ling; Xu, Jian

    2013-02-01

    To optimize the mechanical properties for biodegradable orthopedic implant, microstructures and tensile properties of Mg-Zn-Y alloys containing long period stacking ordered (LPSO) phase were investigated. For the as-cast Mg(100-3x)(Zn(1)Y(2))(x) (1 ≤ x ≤ 3) alloys, volume fraction of 18R LPSO phase increases with increasing the contents of Zn and Y. Mg(97)Zn(1)Y(2) alloy exhibits the optimal combination of strength and plasticity. Substitution of bioactive element Ca for Y in the Mg(97)Zn(1)Y(2) does not favor the formation of LPSO phase, but involving the formation of Mg(2)Ca phase. By micro-alloying with Zr as grain refinement agent, morphology of α-Mg in the Mg(96.83)Zn(1)Y(2)Zr(0.17) alloy is changed into the equiaxial shape, together with a significant refinement in grain size to 30 μm. It brings about an improvement not only in strength but also in plasticity, in contrast to the Zr-free alloy. In comparison with the as-cast state, warm-extruded alloys manifest significantly improved properties not only in strength but also in plasticity due to the refinement of α-Mg grain by dynamic recrystallization and the alignment of LPSO phase along extrusion direction.

  16. Mg and Ca isotope fractionation during CaCO3 biomineralisation.

    PubMed

    Chang, Veronica T-C; Williams, R J P; Makishima, Akio; Belshawl, Nick S; O'Nions, R Keith

    2004-10-08

    The natural variation of Mg and Ca stable isotopes of carbonates has been determined in carbonate skeletons of perforate foraminifera and reef coral together with Mg/Ca ratios to assess the influence of biomineralisation processes. The results for coral aragonite suggest its formation, in terms of stable isotope behaviour, approximates to inorganic precipitation from a seawater reservoir. In contrast, results for foraminifera calcite suggest a marked biological control on Mg isotope ratios presumably related to its low Mg content compared with seawater. The bearing of these observations on the use of Mg and Ca isotopes as proxies in paleoceanography is considered. Copyright 2004 Elsevier Inc.

  17. The suitability of the simplified method of the analysis of coffee infusions on the content of Ca, Cu, Fe, Mg, Mn and Zn and the study of the effect of preparation conditions on the leachability of elements into the coffee brew.

    PubMed

    Stelmach, Ewelina; Pohl, Pawel; Szymczycha-Madeja, Anna

    2013-12-01

    A fast and straightforward method of the analysis of coffee infusions was developed for measurements of total concentrations of Ca, Cu, Fe, Mg, Mn and Zn by flame atomic absorption spectrometry. Its validity was proved by the analysis of spiked samples; recoveries of added metals were found to be within 98-104% while the precision was better than 4%. The method devised was used for the analysis of re-distilled water infusions of six popular ground coffees available in the Polish market. Using the mud coffee preparation it was established that percentages of metals leached in these conditions varied a lot among analysed coffees, especially for Ca (14-42%), Mg (6-25%) and Zn (1-24%). For remaining metals, the highest extractabilities were assessed for Mn (30-52%) while the lowest for Fe (4-16%) and Cu (2-12%). In addition, it was found that the water type and the coffee brewing preparation method influence the concentration of studied metals in coffee infusions the most.

  18. Thermal variation of MgZn nanoferrites for magnetic hyperthermia

    NASA Astrophysics Data System (ADS)

    Kim, Sam Jin; Hyun, Sung Wook; Kim, Chul Sung; Kim, Hyung Joon

    2014-08-01

    Mg1- x Zn x Fe2O4 (x = 0.2, 0.4, 0.5, 0.6, 0.8) nanoparticles were prepared for the characterization of the crystallographic and magnetic properties. The Rietveld refinement for x-ray diffraction was used to confirm that the Zn ion occupied on B-site for dopings over 0.5 doping. The lattice constant ( a 0) was increased from 8.3969 to 8.4100 ± 0.0001 Å with increasing Zn concentration. Mössbauer spectra of all samples were taken at room temperature and showed Fe3+ and Fe2+ valence states. The thermal properties of all samples were measured at 50 kHz and 25 mT. The heating temperature was increased up to 124 °C until 0.5 doping of Zn ions, however it was decreased down to 69 °C over 0.5 doping of Zn ions. These results can be explained by the fact that the saturation magnetization was increased by Fe2+ ion, but, the heating temperature was decreased due to occupation of Zn ions on B-site for dopings above 0.5.

  19. New procedure of quantitative mapping of Ti and Al released from dental implant and Mg, Ca, Fe, Zn, Cu, Mn as physiological elements in oral mucosa by LA-ICP-MS.

    PubMed

    Sajnóg, Adam; Hanć, Anetta; Koczorowski, Ryszard; Barałkiewicz, Danuta

    2017-12-01

    A new procedure for determination of elements derived from titanium implants and physiological elements in soft tissues by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is presented. The analytical procedure was developed which involved preparation of in-house matrix matched solid standards with analyte addition based on certified reference material (CRM) MODAS-4 Cormorant Tissue. Addition of gelatin, serving as a binding agent, essentially improved physical properties of standards. Performance of the analytical method was assayed and validated by calculating parameters like precision, detection limits, trueness and recovery of analyte addition using additional CRM - ERM-BB184 Bovine Muscle. Analyte addition was additionally confirmed by microwave digestion of solid standards and analysis by solution nebulization ICP-MS. The detection limits are in range 1.8μgg(-1) to 450μgg(-1) for Mn and Ca respectively. The precision values range from 7.3% to 42% for Al and Zn respectively. The estimated recoveries of analyte addition line within scope of 83%-153% for Mn and Cu respectively. Oral mucosa samples taken from patients treated with titanium dental implants were examined using developed analytical method. Standards and tissue samples were cryocut into 30µm thin sections. LA-ICP-MS allowed to obtain two-dimensional maps of distribution of elements in tested samples which revealed high content of Ti and Al derived from implants. Photographs from optical microscope displayed numerous particles with µm size in oral mucosa samples which suggests that they are residues from implantation procedure. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Purification and characteristics of Ca2+,Mg2+- and Ca2+,Mn2+-dependent and acid DNases from spermatozoa of the sea urchin Strongylocentrotus intermedius.

    PubMed

    Shastina, V V; Menzorova, N I; Sibirtsev, Yu T; Rasskazov, V A

    2003-05-01

    Ca2+,Mg2+- and Ca2+,Mn2+-dependent and acid DNases were isolated from spermatozoa of the sea urchin Strongylocentrotus intermedius. The enzymes have been purified by successive chromatography on DEAE-cellulose, phenyl-Sepharose, Source 15Q, and by gel filtration, and the principal physicochemical and enzymatic properties of the purified enzymes were determined. Ca2+,Mg2+-dependent DNase (Ca,Mg-DNase) is a nuclear protein with molecular mass of 63 kD as the native form and its activity optimum is at pH 7.5. The enzyme activity in the presence of bivalent metal ions decreases in the series (Ca2+ + Mg2+) > Mn2+ = (Ca2+ + Mn2+) > (Mg2+ + EGTA) > Ca2+. Ca,Mg-DNase retains its maximal activity in sea water and is not inhibited by G-actin and N-ethylmaleimide, whereas Zn(2+) inhibits the enzyme. The endogenous Ca,Mg-DNase is responsible for the internucleosomal cleavage of chromosomal DNA of spermatozoa. Ca2+,Mn2+-dependent DNase (Ca,Mn-DNase) has molecular mass of 25 kD as the native form and the activity optimum at pH 8.5. The enzyme activity in the presence of bivalent metal ions decreases in the series (Ca2+ + Mn2+) > (Ca2+ + Mg2+) > Mn2+ > (Mg2+ + EGTA). In seawater the enzyme is inactive. Zinc ions inhibit Ca,Mn-DNase. Acid DNase of spermatozoa (A-DNase) is not a nuclear protein, it has molecular mass of 37 kD as a native form and the activity optimum at pH 5.5, it is not activated by bivalent metal ions, and it is inhibited by N-ethylmaleimide and iodoacetic acid. Mechanisms of the endonuclease cleavage of double-stranded DNA have been established for the three enzymes. The possible involvement of DNases from sea urchin spermatozoa in programmed cell death is discussed.

  1. In vitro corrosion resistance and cytocompatibility of nano-hydroxyapatite reinforced Mg-Zn-Zr composites.

    PubMed

    Ye, Xinyu; Chen, Minfang; Yang, Meng; Wei, Jun; Liu, Debao

    2010-04-01

    Due to good biocompatibility and mechanical properties, magnesium (Mg) and its alloys are considered promising degradable materials for orthopedic applications. In this work, a Mg metal matrix composite (MMC) was fabricated using Mg-2.9Zn-0.7Zr alloy as the matrix and 1 wt% nano-hydroxyapatite (n-HA) particles as reinforcements. In vitro corrosion behavior and cytocompatibility of a Mg-Zn-Zr/n-HA composite and a Mg-Zn-Zr alloy were investigated. In contrast with the Mg-Zn-Zr alloy, the MMC has better properties. The average corrosion rate of MMC is 0.75 mm/yr after immersion in simulated body fluid (SBF) for 20 days, and the surface of MMC is covered with white Ca-P precipitates. The electrochemical test results show that the corrosion potential (E(corr)) of MMC increases to -1.615 V and its polarization resistance (R(p)) is 2.56 KOmega with the addition of n-HA particles. The co-cultivation of MMC with osteoblasts results in the adhesion and proliferation of cells on the surface of the composite. The maximum cell density is calculated to be (1.85+/-0.15) x 10(4)/l after 5 days of co-culture with osteoblasts. The average cell numbers for two groups after culturing for 3 and 5 days (P<0.05) are significantly different. All the results demonstrate that the Mg-Zn-Zr/n-HA composite can be potentially used as biodegradable bone fixation material.

  2. The electrochemical behaviors of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn in sodium chloride solution

    NASA Astrophysics Data System (ADS)

    Lv, Yanzhuo; Liu, Min; Xu, Yan; Cao, Dianxue; Feng, Jing

    2013-03-01

    The electrochemical oxidation behaviors of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn electrodes in 0.7 mol L-1 NaCl solution are investigated by methods of potentiodynamic polarization, potentiostatic oxidation, electrochemical impedance spectroscopy and scanning electron microscopy. The phase composition of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn alloys is analyzed conducted by X-ray diffraction. The performances of Mg-8Li-3Al-0.5Zn and Mg-8Li-3Al-1.0Zn as the anode of Mg-H2O2 semi fuel cells are determined. The effect of Zn content on the corrosion resistant of these Mg-Li-based alloys is studied. It is found that the Mg-8Li-3Al-0.5Zn electrode has higher discharge activity and less corrosion resistance than that of Mg-8Li-3Al-1.0Zn electrode in 0.7 mol L-1 NaCl solution. The Mg-H2O2 semi fuel cell with Mg-8Li-3Al-0.5Zn anode presents a maximum power density of 100 mW cm-2 at room temperature, which is higher than that of Mg-8Li-3Al-1.0Zn anode (80 mW cm-2). The performance of semi fuel cell with the Mg-8Li-3Al-0.5Zn electrode is better than that with Mg-8Li-3Al-1.0Zn electrode, especially at higher current density (>30 mA cm-2).

  3. Hall field-induced resistance oscillations in MgZnO/ZnO heterostructures

    NASA Astrophysics Data System (ADS)

    Shi, Q.; Zudov, M. A.; Falson, J.; Kozuka, Y.; Tsukazaki, A.; Kawasaki, M.; von Klitzing, K.; Smet, J.

    2017-01-01

    We report on nonlinear magnetotransport in a two-dimensional electron gas hosted in a MgZnO/ZnO heterostructure. Upon application of a direct current, we observe pronounced Hall field-induced resistance oscillations (HIRO), which are well known from experiments on high-mobility GaAs/AlGaAs quantum wells. The unique sensitivity of HIRO to the short-range component of the disorder potential allows us to unambiguously establish that the mobility of our MgZnO/ZnO heterostructure is limited by impurities residing within or near the two-dimensional (2D) channel. This demonstration that HIRO can be realized in a system with a much lower mobility, much higher density, and much larger effective mass than in previously studied systems highlights the remarkable universality of the phenomenon and its great promise for use in studies of a wide variety of emerging 2D materials.

  4. The ZnO p-n homojunctions modulated by ZnMgO barriers

    NASA Astrophysics Data System (ADS)

    Yang, Jing-Jing; Fang, Qing-Qing; Wang, Dan-Dan; Du, Wen-Han

    2015-04-01

    In this paper, we fabricated the ultrathin ZnO p-n homojunctions, which modulated by ZnMgO asymmetrical double barriers (ADB). The ADB p-n homojunctions displays step-like curve in the absorption spectrums, this is the first time that quantum confinement effect has been observed in the absorption spectrums at room temperature (RT). The Hall-effect data confirm there is 2-dimensional electron gas in the interface of the ZnMgO ADB p-n junctions. The quantum confinement effect enhances the hall-mobility μ to 103 cm2V -1s-1 based on the polarity of the films. There was no rectification property in the ZnO homojunctions with thickness of 250nm, however, when the ADB was added in the n-type layer of the homojunctions, it displays a typical Zener diode rectification property in the I-V curve.

  5. Rapidly solidified Mg-Al-Zn-rare earth alloys

    SciTech Connect

    Chang, C.F.; Das, S.K.; Raybould, D.

    1987-01-01

    Among the light metal alloys, magnesium is the lightest structural material except for beryllium, and yet magnesium alloys have not seen extensive use because of their poor strength and corrosion resistance. Rapid solidification technology offers a possible solution to these problems. A number of Mg-Al-Zn alloys containing rare earth (RE) elements (e.g. Ce, Pr, Y, and Nd) have been investigated using rapid solidification processing for possible structural applications. The processing consists of planar flow or jet casting into ribbons, pulverization of ribbon to powder, and consolidation of powder into bulk shapes. The mechanical properties of some of these alloys show attractive combinations of strength, ductility and corrosion resistance. The microstructures of these alloys are correlated with their mechanical properties. The rapidly solidified Mg-Al-Zn-RE alloys show great potential for applications in automotive and aerospace industries. 7 references.

  6. The solar chromospheric Ca and Mg indices from Aura OMI

    NASA Astrophysics Data System (ADS)

    Deland, Matthew; Marchenko, Sergey

    2013-04-01

    Direct observations of long-term variations in solar UV irradiance from satellites, although important for monitoring the energetic forcing of the Earth's atmosphere, is challenging because of the difficulty of accurately tracking instrument response changes. Proxy indexes based on core-to-wing ratios of solar Fraunhofer lines, such as the Mg II feature at 280 nm, can minimize the impact of both time- and wavelength-dependent instrument changes to better monitor solar UV activity. Here we present new data sets from the Ozone Monitoring Instrument (OMI) on the Aura satellite, which began operations in late 2004. The high quality of OMI irradiance measurements allows us to construct daily indexes for the Mg II, Ca II K (393.4 nm), Ca II H (396.8 nm), and Mg I (285.2 nm) lines. The OMI Ca II K index is well correlated with the Mg II index measured by multiple instruments, as well as the ground-based National Solar Observatory (NSO) Ca II K 1.0 Å index data derived from Integrated Sunlight Spectrometer measurements. OMI Ca II K data can be used to evaluate anomalous short-term features in the NSO data set. The OMI solar data products represent a valuable addition to current data sets.

  7. Near ultraviolet light emitting diodes using ZnMgO:N/ZnO hetero-junction grown by MOVPE

    NASA Astrophysics Data System (ADS)

    Fujita, Yasuhisa; Yanase, Shogo; Nishikori, Hirokazu; Hiragino, Yuto; Furubayashi, Yutaka; Lin, Jie; Yoshida, Toshiyuki

    2017-04-01

    A ZnMgO:N/ZnO/ZnO:Ga single hetero-junction light emitting diode structure on Al2O3 (11 2 ̅0) substrate was fabricated by metalorganic vapor phase epitaxy. By using ZnMgO:N as a substitute for a ZnO:N top layer of a homojunction LED, improved rectifying current-voltage characteristics were obtained. Although the device had a heating problem and the luminescent area was partly in the ZnMgO:N layer, a sharp ultraviolet electroluminescence emission at 3.17 eV was successfully observed at room temperature.

  8. Effect of Hydroxyapatite on the Mechanical Properties and Corrosion Behavior of Mg-Zn-Y Alloy

    PubMed Central

    Chiu, Chun; Lu, Chih-Te; Chen, Shih-Hsun; Ou, Keng-Liang

    2017-01-01

    Mg-Zn-Y alloys with a long period stacking ordered (LPSO) phase are potential candidates for biodegradable implants; however, an unfavorable degradation rate has limited their applications. Hydroxyapatite (HA) has been shown to enhance the corrosion resistance of Mg alloys. In this study, Mg97Zn1Y2-0.5 wt% HA composite was synthesized and solution treated at 500 °C for 10 h. The corrosion behavior of the composite was studied by electrochemical and immersion tests, while the mechanical properties were investigated by a tensile test. Addition of HA particles improves the corrosion resistance of Mg97Zn1Y2 alloy without sacrificing tensile strength. The improved corrosion resistance is due to the formation of a compact Ca-P surface layer and a decrease of the volume fraction of the LPSO phase, both resulting from the addition of HA. After solution-treatment, the corrosion resistance of the composite decreases. This is due to the formation of a more extended LPSO phase, which weakens its role as a corrosion barrier in protecting the Mg matrix. PMID:28773216

  9. Estrogen enhancement of Ca-, Mg-, and Ca-Mg-stimulated adenosine triphosphatase activity in the chick shell gland.

    PubMed

    Qin, X; Klandorf, H; Porter, D W; Holt, S B; Martin, W G

    1993-01-01

    The effect of 17 beta-estradiol (E2) on Ca-, Mg-, and Ca-Mg-ATPase activity was investigated in the shell gland of 6-week-old chicks. In the first study, each of 42 birds was implanted with three E2 (Compudose-200) pellets. An additional 6 sham-implanted birds served as controls for measurements of body weight and concentrations of E2 and Ca in plasma. The activities of Mg-, Ca-, and Ca-Mg-ATPase peaked coincident with maximum plasma E2 concentrations 8 days after implantation and then progressively declined in concert with the decline in plasma E2. By 29 days after implantation, the ATPase activities were similar to those measured in birds whose E2 pellets had been removed for 11 days. Concentrations of plasma E2 dropped from peak values of 1676 +/- 317 at Day 8 to 611 +/- 180 pg/ml at Day 29. When birds whose E2 pellets had been removed were reimplanted with three pellets per bird, plasma E2 again increased to 1637 +/- 227 pg/ml. ATPase activity in these reimplanted birds also was greater (P < 0.05) than activities measured in E2-removed or E2-maintained birds. In a second study the Ca-ATPase Km and Vmax were determined in E2-implanted chicks (three pellets per bird) and compared to E2-withdrawn chicks. Five days after reimplantation of chicks with E2, there was a significant increase in both Vmax (3.38 +/- 0.21 vs 2.37 +/- 0.28 micrograms Pi/mg protein/min; P < 0.05) and Km (0.31 +/- 0.02 vs 0.25 +/- 0.01 mM Ca; P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

  10. Phosphate Capacities of CaF2-MgO and CaF2-CaO-MgO Slags

    NASA Astrophysics Data System (ADS)

    Akbari, F.; Pickles, C. A.

    2015-02-01

    Previously published sulphide capacity data and thermodynamic arguments have been employed to calculate the phosphate capacities and the phosphorus partition ratios between a molten carbon saturated iron alloy and binary CaF2-MgO slags and also ternary CaF2 -CaO-MgO slags at 1450 °C. For the CaF2-MgO binary system, a linear relationship was found between the phosphate and the sulphide capacities as follows: log ? = 1.2 log Cs + 25.2. For the ternary CaF2-CaO-MgO system at 1450 °C, the logarithm of the calculated phosphate capacities ranged from 19.47 to 20.15. With the addition of CaO, the phosphate capacities initially increased, reached a maximum and then decreased slightly. The addition of MgO to the CaF2-CaO system resulted in a decrease in the phosphate capacity. The calculated phosphorus partition ratios increased slightly with increasing mole fraction of CaO in the ternary system.

  11. Synthesis and Characterization of Mg-doped ZnO Nanorods for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Gemar, H.; Das, N. C.; Wanekaya, A.; Delong, R.; Ghosh, K.

    2013-03-01

    Nanomaterials research has become a major attraction in the field of advanced materials research in the area of Physics, Chemistry, and Materials Science. Bio-compatible and chemically stable metal nanoparticles have biomedical applications that includes drug delivery, cell and DNA separation, gene cloning, magnetic resonance imaging (MRI). This research is aimed at the fabrication and characterization of Mg-doped ZnO nanorods. Hydrothermal synthesis of undoped ZnO and Mg-doped ZnO nanorods is carried out using aqueous solutions of Zn(NO3)2 .6H2O, MgSO4, and using NH4OH as hydrolytic catalyst. Nanomaterials of different sizes and shapes were synthesized by varying the process parameters such as molarity (0.15M, 0.3M, 0.5M) and pH (8-11) of the precursors, growth temperature (130°C), and annealing time during the hydrothermal Process. Structural, morphological, and optical properties are studied using various techniques such as XRD, SEM, UV-vis and PL spectroscopy. Detailed structural, and optical properties will be discussed in this presentation. This work is partially supported by National Cancer Institute (1 R15 CA139390-01).

  12. MgCaO Dry Etching on GaN

    NASA Astrophysics Data System (ADS)

    Hlad, M.; Ren, F.

    2005-11-01

    MgCaO films grown by rf plasma-assisted Molecular Beam Epitaxy and capped with Sc2O3 are promising candidates as surface passivation layers and gate dielectrics on GaN-based high electron mobility transistors (HEMTs) and metal-oxide semiconductor HEMTs (MOS-HEMTs) respectively. Two different plasma chemistries were examined for etching these thin films on GaN. Inductively Coupled Plasmas of CH4/H2/Ar produced etch rates only in the range 20-70 å/min, comparable to the Ar sputter rates under the same conditions. Similarly slow MgCaO etch rates (˜100 å/min) were obtained with Cl2/Ar discharges under the same conditions, but GaN showed rates almost an order of magnitude higher. The MgCaO removal rates are limited by the low volatilities of the respective etch products. The CH4/H2/Ar plasma chemistry produced a selectivity of around 2 or etching the MgCaO with respect to GaN.

  13. Fabrication of biodegradable Zn-Al-Mg alloy: Mechanical properties, corrosion behavior, cytotoxicity and antibacterial activities.

    PubMed

    Bakhsheshi-Rad, H R; Hamzah, E; Low, H T; Kasiri-Asgarani, M; Farahany, S; Akbari, E; Cho, M H

    2017-04-01

    In this work, binary Zn-0.5Al and ternary Zn-0.5Al-xMg alloys with various Mg contents were investigated as biodegradable materials for implant applications. Compared with Zn-0.5Al (single phase), Zn-0.5Al-xMg alloys consisted of the α-Zn and Mg2(Zn, Al)11 with a fine lamellar structure. The results also revealed that ternary Zn-Al-Mg alloys presented higher micro-hardness value, tensile strength and corrosion resistance compared to the binary Zn-Al alloy. In addition, the tensile strength and corrosion resistance increased with increasing the Mg content in ternary alloys. The immersion tests also indicated that the corrosion rates in the following order Zn-0.5Al-0.5Mg-0.5Al-0.3Mg-0.5Al-0.1Mg-0.5Al. The cytotoxicity tests exhibited that the Zn-0.5Al-0.5Mg alloy presents higher viability of MC3T3-E1 cell compared to the Zn-0.5Al alloy, which suggested good biocompatibility. The antibacterial activity result of both Zn-0.5Al and Zn-0.5Al-Mg alloys against Escherichia coli presented some antibacterial activity, while the Zn-0.5Al-0.5Mg significantly prohibited the growth of Escherichia coli. Thus, Zn-0.5Al-0.5Mg alloy with appropriate mechanical properties, low corrosion rate, good biocompatibility and antibacterial activities was believed to be a good candidate as a biodegradable implant material.

  14. Trimethyltin Selectively Alters Activity of Ca(++), Mg(++), and (Ca(++) + Mg(++))-ATPases of Human Neuroblastoma

    DTIC Science & Technology

    1990-05-01

    7 2. MATERIALS AND METHODS ..................... ... ....... 7 2.1 Materials...spectrophot mtrically by the method of Lanzetta and cow.rkers 32 C -h_ ase activity was determined by subtracting basal ATPase activity (no alded Ca++ or 1...Txijcl. Teratol. Vol. 4, pp 127- 133 (1982). 17. Dyer, R.S., Deshields, T.L., and Wonerlin, W.F. " Triz ltin- iruce Changes in Gross Morphology of the

  15. Effect of Sn:Zn Ratio on Corrosion Behavior of Mg-aSn-bZn Extrusions

    NASA Astrophysics Data System (ADS)

    Yim, Chang Dong; Woo, Sang Kyu; You, Bong Sun

    The effect of Sn:Zn ratio on corrosion behavior of magnesium alloys containing Sn and Zn was evaluated systematically by potentiodynamic polarization and immersion tests. The hydrogen evolution rate during cathodic polarization and the average corrosion rate measured by immersion test increased with increasing Sn content and Sn:Zn ratio. The changes of fraction of second phase with more positive corrosion potential and solute contents in the matrix phase were responsible for the change of corrosion behavior according to Sn content and Sn:Zn ratio. Mg2Sn particle accelerated the corrosion by formation of micro-galvanic cell, which resulted in faster corrosion rates of Mg-5Sn-xZn alloys than those of Mg-2Sn-xZn alloys. The increase of Zn in the matrix was harmful to the corrosion resistance because Zn accelerated the hydrogen evolution although ZnO was beneficial to the passivity of surface film.

  16. Growth rate effects on Mg/Ca and Sr/Ca ratios constrained by belemnite calcite

    NASA Astrophysics Data System (ADS)

    Vinzenz Ullmann, Clemens

    2016-04-01

    Multiple temperature proxies from single species are important to achieve robust palaeotemperature estimates. Besides the commonly employed oxygen isotope thermometer, also Mg/Ca and Sr/Ca ratios perform well as proxies for calcification temperature in the shells of some species. While salinity changes affect the ratios of earth alkaline elements much less than the δ18O thermometer, metabolic effects may exert a strong control on the expression of element ratios. Such effects are hard to study because biomineralization experiments have to overcome large intraspecific variability and can hardly ever isolate the controls of a single parameter on shell geochemistry. The unique geometry of the belemnite rostrum constitutes an exception to this rule. Its shape, large size, and the visibility of growth increments as bands enable the analysis of multiple, correlatable, high resolution geochemical profiles in a single fossil. The effects of the growth rate variability amongst these profiles on Mg/Ca and Sr/Ca ratios has been tested here. Within a specimen of Passaloteuthis bisulcata (Early Toarcian, Cleveland Basin, UK), Mg/Ca and Sr/Ca data were obtained from four profiles. With respect to growth rate in the first profile, which was taken as a reference, the relative growth rates in the remaining three profiles varied by a factor of 0.9 to 2.7. Results suggest that relative growth rate is linearly correlated with Mg/Ca and Sr/Ca, with a decrease of Mg/Ca by 8 % and increase of Sr/Ca by 6 % per 100 % increase in relative growth rate. The observed trends are consistent with abiogenic precipitation experiments and suggest that crystal precipitation rate exerts a significant, predictable control on the element distribution in biogenic calcite.

  17. A Bayesian, multivariate calibration for Globigerinoides ruber Mg/Ca

    NASA Astrophysics Data System (ADS)

    Khider, D.; Huerta, G.; Jackson, C.; Stott, L. D.; Emile-Geay, J.

    2015-09-01

    The use of Mg/Ca in marine carbonates as a paleothermometer has been challenged by observations that implicate salinity as a contributing influence on Mg incorporation into biotic calcite and that dissolution at the sea-floor alters the original Mg/Ca. Yet, these factors have not yet been incorporated into a single calibration model. We introduce a new Bayesian calibration for Globigerinoides ruber Mg/Ca based on 186 globally distributed core top samples, which explicitly takes into account the effect of temperature, salinity, and dissolution on this proxy. Our reported temperature, salinity, and dissolution (here expressed as deep-water ΔCO32-) sensitivities are (±2σ) 8.7±0.9%/°C, 3.9±1.2%/psu, and 3.3±1.3%/μmol.kg-1 below a critical threshold of 21 μmol/kg in good agreement with previous culturing and core-top studies. We then perform a sensitivity experiment on a published record from the western tropical Pacific to investigate the bias introduced by these secondary influences on the interpretation of past temperature variability. This experiment highlights the potential for misinterpretations of past oceanographic changes when the secondary influences of salinity and dissolution are not accounted for. Multiproxy approaches could potentially help deconvolve the contributing influences but this awaits better characterization of the spatio-temporal relationship between salinity and δ18Osw over millennial and orbital timescales.

  18. Ca2+, Mg2+-dependent endonuclease and ADP-ribosylation.

    PubMed

    Yoshihara, K; Tanaka, Y; Kamiya, T

    1983-01-01

    The molecular mechanism of the inhibition of Ca2+, Mg2+-dependent endonuclease by ADP-ribosylation was studied by using purified bull seminal plasma Ca2+, Mg2+-dependent endonuclease, endonuclease-stimulating proteins, and poly-(ADP-ribose) polymerase. The activity of an essentially homogeneous preparation of the endonuclease was markedly suppressed by its preincubation with NAD+, poly-(ADP-ribose) polymerase, DNA, and Mg2+. These four components of the incubation mixture were all essential for the suppression of the activity. Analyses of the initial and the chased reaction product by Sephadex G-100 column chromatography and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis revealed that Ca2+, Mg2+-dependent endonuclease was ADP-ribosylated during the incubation and its activity was markedly inhibited by the elongation of the ADP-ribose polymer covalently attached to the endonuclease. When the suppressed enzymes were mildly treated with an alkaline pH of 10.0, the activity was restored almost to the level of the unmodified control sample. These facts indicate that the linkage between the enzyme and poly(ADP-ribose) is hydrolyzed at this pH, and that the liberated polymer itself does not appreciably affect the endonuclease activity. These results also suggest that an electric repulsion between negative charges on DNA and poly(ADP-ribose) attached to Ca2+, Mg2+-dependent endonuclease is the basis for the observed suppression of the enzyme by ADP-ribosylation. Though histone H2B and H1 are shown to be as good endonuclease-stimulators (1) as they are good acceptors of ADP-ribose in poly(ADP-ribose) polymerase reaction (2), ADP-ribosylation of these two proteins did not affect their endonuclease-stimulating ability appreciably, at least under the conditions used.

  19. 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.

  20. Characterization of (Mg, La) Substituted Ni-Zn Spinel Ferrite

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Wei, S. C.; Wang, Y. J.; Tian, H. L.; Tong, H.; Xu, B. S.

    Spinel structure of (Mg, La) substituted spinel Ni-Zn ferrite has been synthesized by sol-gel auto combustion method. The ferrite exhibits a single-spinel structure. The ferrite is studied as a microwave absorbing material. The microwave measurements are carried out by a vector network analyzer. The reflection loss of the ferrite is calculated as a single-layer absorber. The results indicate that the ferrite annealed at 850°C has great potential for application in electromagnetic wave attenuation.

  1. 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.

  2. The Effect of Ca Content on the Microstructure, Hardness and Tensile Properties of AZ81 Mg Cast Alloy

    NASA Astrophysics Data System (ADS)

    Allameh, S. H.; Emamy, M.

    2017-05-01

    The effects of various Ca contents (0.1-4 wt.%) on the microstructure and tensile properties of AZ81 magnesium alloy were investigated with the contribution of an analytical method. Ca addition (up to 1.0 wt.%) refined the alloy microstructure but further addition of Ca resulted in a coarse structure and introduced large dendrites within the grains. The changes in the microstructures revealed that Al4Ca, Al2Ca, τ-Mg32(A1,Zn)49 and ɛ-MgZn intermetallics are formed in the alloy as a result of Ca addition and Al consumption. The assessment of tensile properties of AZ81-1.0 wt.%Ca alloy showed the optimum values of yield strength and ultimate tensile strength, while AZ81-0.7 wt.%Ca alloy showed maximum elongation. The reduction in tensile properties of the cast alloy by the addition of more Ca was attributed to grain coarsening and evolution of a network of intermetallic compounds. FF study of tensile fractured surfaces indicated that Ca addition encourages brittle mode of fracture propagating through precipitated intermetallics in the structure.

  3. Biocompatibility Assessment of Novel Bioresorbable Alloys Mg-Zn-Se and Mg-Zn-Cu for Endovascular Applications: In- Vitro Studies

    PubMed Central

    Budiansky, Noah; McGoron, Anthony J.

    2013-01-01

    Previous studies have shown that using biodegradable magnesium alloys such as Mg-Zn and Mg-Zn-Al possess the appropriate mechanical properties and biocompatibility to serve in a multitude of biological applications ranging from endovascular to orthopedic and fixation devices. The objective of this study was to evaluate the biocompatibility of novel as-cast magnesium alloys Mg-1Zn-1Cu wt.% and Mg-1Zn-1Se wt.% as potential implantable biomedical materials, and compare their biologically effective properties to a binary Mg-Zn alloy. The cytotoxicity of these experimental alloys was evaluated using a tetrazolium based- MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and a lactate dehydrogenase membrane integrity assay (LDH). The MTS assay was performed on extract solutions obtained from a 30-day period of alloy immersion and agitation in simulated body fluid to evaluate the major degradation products eluted from the alloy materials. Human foreskin fibroblast cell growth on the experimental magnesium alloys was evaluated for a 72 hour period, and cell death was quantified by measuring lactate dehydrogenase concentrations. Both Mg-Zn-Se and Mg-Zn-Cu alloys exhibit low cytotoxicity levels which are suitable for biomaterial applications. The Mg-Zn-Cu alloy was found to completely degrade within 72 hours, resulting in lower human foreskin fibroblast cell viability. The Mg-Zn-Se alloy was shown to be less cytotoxic than both the Mg-Zn-Cu and Mg-Zn alloys. PMID:24058329

  4. Biocompatibility Assessment of Novel Bioresorbable Alloys Mg-Zn-Se and Mg-Zn-Cu for Endovascular Applications: In- Vitro Studies.

    PubMed

    Persaud-Sharma, Dharam; Budiansky, Noah; McGoron, Anthony J

    2013-01-01

    Previous studies have shown that using biodegradable magnesium alloys such as Mg-Zn and Mg-Zn-Al possess the appropriate mechanical properties and biocompatibility to serve in a multitude of biological applications ranging from endovascular to orthopedic and fixation devices. The objective of this study was to evaluate the biocompatibility of novel as-cast magnesium alloys Mg-1Zn-1Cu wt.% and Mg-1Zn-1Se wt.% as potential implantable biomedical materials, and compare their biologically effective properties to a binary Mg-Zn alloy. The cytotoxicity of these experimental alloys was evaluated using a tetrazolium based- MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and a lactate dehydrogenase membrane integrity assay (LDH). The MTS assay was performed on extract solutions obtained from a 30-day period of alloy immersion and agitation in simulated body fluid to evaluate the major degradation products eluted from the alloy materials. Human foreskin fibroblast cell growth on the experimental magnesium alloys was evaluated for a 72 hour period, and cell death was quantified by measuring lactate dehydrogenase concentrations. Both Mg-Zn-Se and Mg-Zn-Cu alloys exhibit low cytotoxicity levels which are suitable for biomaterial applications. The Mg-Zn-Cu alloy was found to completely degrade within 72 hours, resulting in lower human foreskin fibroblast cell viability. The Mg-Zn-Se alloy was shown to be less cytotoxic than both the Mg-Zn-Cu and Mg-Zn alloys.

  5. Optical probing of MgZnO/ZnO heterointerface confinement potential energy levels

    SciTech Connect

    Solovyev, V. V.; Van'kov, A. B.; Kukushkin, I. V.; Falson, J.; Kozuka, Y.; Zhang, D.; Smet, J. H.; Maryenko, D.; Tsukazaki, A.; Kawasaki, M.

    2015-02-23

    Low-temperature photoluminescence and reflectance measurements were employed to study the optical transitions present in two-dimensional electron systems confined at Mg{sub x}Zn{sub 1–x}O/ZnO heterojunctions. Transitions involving A- and B-holes and electrons from the two lowest subbands formed within the confinement potential are detected. In the studied density range of 2.0–6.5 × 10{sup 11 }cm{sup −2}, the inter-subband splitting is measured and the first excited electron subband is shown to be empty of electrons.

  6. K -shell double photoionization of Be, Mg, and Ca

    NASA Astrophysics Data System (ADS)

    Kheifets, A. S.; Bray, Igor; Hoszowska, J.

    2009-04-01

    We perform convergent close-coupling calculations of double photoionization (DPI) of the K -shell of alkaline-earth metal atoms (Be, Mg, and Ca) from the threshold to the nonrelativistic limit of infinite photon energy. Theoretical double-to-single photoionization cross-section ratios for Mg and Ca are compared with experimental values derived from high-resolution x-ray spectra following the radiative decay of the K -shell double vacancy. We investigate the role of many-electron correlations in the ground and doubly-ionized final states played in the DPI process. Universal scaling of DPI cross section with an effective nuclear charge is examined in neutral atoms in comparison with corresponding heliumlike ions.

  7. In vitro degradation of ZnO flowered coated Zn-Mg alloys in simulated physiological conditions.

    PubMed

    Alves, Marta M; Prosek, Tomas; Santos, Catarina F; Montemor, Maria F

    2017-01-01

    Flowered coatings composed by ZnO crystals were successfully electrodeposited on Zn-Mg alloys. The distinct coatings morphologies were found to be dependent upon the solid interfaces distribution, with the smaller number of bigger flowers (ø 46μm) obtained on Zn-Mg alloy containing 1wt.% Mg (Zn-1Mg) contrasting with the higher number of smaller flowers (ø 38μm) achieved on Zn-Mg alloy with 2wt.% Mg (Zn-2Mg). To assess the in vitro behaviour of these novel resorbable materials, a detailed evaluation of the degradation behaviour, in simulated physiological conditions, was performed by electrochemical impedance spectroscopy (EIS). The opposite behaviours observed in the corrosion resistances resulted in the build-up of distinct corrosion layers. The products forming these layers, preferentially detected at the flowers, were identified and their spatial distribution disclosed by EDS and Raman spectroscopy techniques. The presence of smithsonite, simonkolleite, hydrozincite, skorpionite and hydroxyapatite were assigned to both corrosion layers. However the distinct spatial distributions depicted may impact the biocompatibility of these resorbable materials, with the bone analogue compounds (hydroxyapatite and skorpionite) depicted in-between the ZnO crystals and on the top corrosion layer of Zn-1Mg flowers clearly contrasting with the hindered layer formed at the interface of the substrate with the flowers on Zn-2Mg.

  8. 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.

  9. Thermoluminescence of K-Mg-Al-Zn fluorophosphate glass

    NASA Astrophysics Data System (ADS)

    Thomas, Sunil; Chithambo, M. L.

    2017-02-01

    The thermoluminescence of beta irradiated K-Mg-Al-Zn fluorophosphate glass is reported. A glow-curve corresponding to 10 Gy measured at 1 °C/s shows two peaks, a weaker-intensity one at 70 °C and a more prominent one at 235 °C, the subject of this report. The main peak was observed to fade with delay between irradiation and measurement and specifically, by 11% in 15 h. Its dose response is superlinear in the dose range 1-190 Gy although the change was linear for the initial 10 Gy. Regarding kinetic analysis, the activation energy of the higher temperature peak was evaluated as 1.31 eV and that of the lower temperature peak was found as 0.47 eV. It was also noted that the main peak is affected by thermal quenching with an activation energy for thermal quenching equal to 1.37 eV. It is proposed that the mechanism associated with the thermoluminescence in K-Mg-Al-Zn fluorophosphate glass is that electrons trapped by the metal cations are released during heating and then recombine with holes at oxygen sites.

  10. Formation of Zn Ca phyllomanganate nanoparticles in grass roots

    NASA Astrophysics Data System (ADS)

    Lanson, Bruno; Marcus, Matthew A.; Fakra, Sirine; Panfili, Frédéric; Geoffroy, Nicolas; Manceau, Alain

    2008-05-01

    It is now well established that a number of terrestrial and aquatic microorganisms have the capacity to oxidize and precipitate Mn as phyllomanganate. However, this biomineralization has never been shown to occur in plant tissues, nor has the structure of a natural Mn(IV) biooxide been characterized in detail. We show that the graminaceous plant Festuca rubra (red fescue) produces a Zn-rich phyllomanganate with constant Zn:Mn and Ca:Mn atomic ratios (0.46 and 0.38, respectively) when grown on a contaminated sediment. This new phase is so far the Zn-richest manganate known to form in nature (chalcophanite has a Zn:Mn ratio of 0.33) and has no synthetic equivalent. Visual examination of root fragments under a microscope shows black precipitates about ten to several tens of microns in size, and their imaging with backscattered and secondary electrons demonstrates that they are located in the root epidermis. In situ measurements by Mn and Zn K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) with a micro-focused beam can be quantitatively described by a single-phase model consisting of Mn(IV) octahedral layers with 22% vacant sites capped with tetrahedral and octahedral Zn in proportions of 3:1. The layer charge deficit is also partly balanced by interlayer Mn and Ca. Diffracting crystallites have a domain radius of 33 Å in the ab plane and contain only 1.2 layers (∼8.6 Å) on average. Since this biogenic Mn oxide consists mostly of isolated layers, basal 00l reflections are essentially absent despite its lamellar structure. Individual Mn layers are probably held together in the Mn-Zn precipitates by stabilizing organic molecules. Zinc biomineralization by plants likely is a defense mechanism against toxicity induced by excess concentrations of this metal in the rhizosphere.

  11. Characteristics of unannealed ZnMgO/ZnO p-n junctions on bulk (100) ZnO substrates

    SciTech Connect

    Yang, Hyuck Soo; Li, Y.; Norton, David P.; Pearton, S. J.; Jang, Soohwan; Ren, F.; Boatner, Lynn A

    2005-01-01

    Zn0.9Mg0.1O/ZnO p-n junctions were grown by pulsed laser deposition at 500 C on bulk n-type, s100d, nonpolar, a-plane ZnO substrates. No postgrowth annealing was performed, with the P-doped ZnMgO showing p-type conductivity shole density ,1016 cm 3, mobility ,6 cm2 V 1 s 1d in the as-grown state. Front-to-back p-n junctions were fabricated with Ni/Au used as the p-Ohmic contact and Ti/Au as the backside n-Ohmic contact. The p contacts showed improved characteristics after annealing up to 400 C, but the n contacts were Ohmic as deposited. The junctions showed rectifying behavior up to 200 C. The forward turn-on voltage was ,6.5 V at 25 C. The simple, low-temperature growth and processing sequence show the promise of ZnO for applications in transparent electronics and UV light emitters

  12. The ZnO p-n homojunctions modulated by ZnMgO barriers

    SciTech Connect

    Yang, Jing-Jing; Fang, Qing-Qing Wang, Dan-Dan; Du, Wen-Han

    2015-04-15

    In this paper, we fabricated the ultrathin ZnO p-n homojunctions, which modulated by ZnMgO asymmetrical double barriers (ADB). The ADB p-n homojunctions displays step-like curve in the absorption spectrums, this is the first time that quantum confinement effect has been observed in the absorption spectrums at room temperature (RT). The Hall-effect data confirm there is 2-dimensional electron gas in the interface of the ZnMgO ADB p-n junctions. The quantum confinement effect enhances the hall-mobility μ to 10{sup 3} cm{sup 2}V {sup −1}s{sup −1} based on the polarity of the films. There was no rectification property in the ZnO homojunctions with thickness of 250nm, however, when the ADB was added in the n-type layer of the homojunctions, it displays a typical Zener diode rectification property in the I-V curve.

  13. First-principles calculations of Zn-K XANES in Ca-deficient hydroxyapatite.

    PubMed

    Murata, Hidenobu; Shitara, Kazuki; Tanaka, Isao; Nakahira, Atsushi; Mizoguchi, Teruyasu; Matsunaga, Katsuyuki

    2010-09-29

    The local environment of substitutional Zn(2+) in Ca-deficient hydroxyapatite (HAp) was investigated using experimental and theoretical analyses of the x-ray absorption near edge structure (XANES). For Zn-K XANES calculations, two situations of Zn(2+) were considered. One was Zn(2+) substituted for Ca sites in perfect HAp, and the other was a Ca-deficient HAp model of substitutional Zn(2+) associated with a Ca(2+) vacancy charge compensated by two protons. The model of Zn(2+) in perfect HAp did not reproduce the experimental Zn-K XANES spectrum. In contrast, the Ca-deficient HAp model agreed well with the experimental spectrum. This indicates that substitutional Zn(2+) in Ca-deficient HAp is associated with the Ca(2+) vacancy complex in HAp.

  14. Evaluation of an Al, La Modified MgZn2Y2 Alloy

    DTIC Science & Technology

    2014-02-01

    of yttrium (Y) and zinc (Zn) atoms arranged in alternating layers of Mg and an intermetallic phase. For the MgZn1Y2 alloys, the LPSO phase has been...scanning electron microscope Tb terbium Y yttrium Zn zinc NO. OF COPIES ORGANIZATION 20 1 DEFENSE TECHNICAL (PDF) INFORMATION CTR

  15. Influence of valence electron concentration on Laves phases: Structures and phase stability of pseudo-binary MgZn2-xPdx

    DOE PAGES

    Thimmaiah, Srinivasa; Miller, Gordon J.

    2015-06-03

    A series of pseudo-binary compounds MgZn2-xPdx (0.15 ≤ x ≤ 1.0) were synthesized and structurally characterized to understand the role of valence electron concentration (vec) on the prototype Laves phase MgZn2 with Pd-substitution. Three distinctive phase regions were observed with respect to Pd content, all exhibiting fundamental Laves phase structures: 0.1 ≤ x ≤ 0.3 (MgNi2-type, hP24; MgZn1.80Pd0.20(2)), 0.4 ≤ x ≤ 0.6 (MgCu2-type, cF24; MgZn1.59Pd0.41(2)), and 0.62 ≤ x ≤ 0.8 (MgZn2-type, hP12: MgZn1.37Pd0.63(2)). Refinements from single-crystal X-ray diffraction indicated nearly statistical distributions of Pd and Zn atoms among the majority atom sites in these structures. Interestingly, the MgZn2-typemore » structure re-emerges in MgZn2–xPdx at x ≈ 0.7 with the refined composition MgZn1.37(2)Pd0.63 and a c/a ratio of 1.59 compared to 1.64 for binary MgZn2. Electronic structure calculations on a model “MgZn1.25Pd0.75” yielded a density of states (DOS) curve showing enhancement of a pseudogap at the Fermi level as a result of electronic stabilization due to the Pd addition. Moreover, integrated crystal orbital Hamilton population values show significant increases of orbital interactions for (Zn,Pd)–(Zn,Pd) atom pairs within the majority atom substructure, i.e., within the Kagomé nets as well as between a Kagomé net and an apical site, from binary MgZn2 to the ternary “MgZn1.25Pd0.75”. Multi-centered bonding is evident from electron localization function plots for “MgZn1.25Pd0.75”, an outcome which is in accordance with analysis of other Laves phases.« less

  16. Infrared spectroscopic method for analysis of Mg 2Ca(SO 4) 3 in mixtures with MgSO 4 and/or CaSO 4

    NASA Astrophysics Data System (ADS)

    Smith, Duane H.; Seshadri, Kal S.

    1999-04-01

    Mg 2Ca(SO 4) 3 is prepared from, and may be found in, mixtures with MgSO 4 and CaSO 4. Such mixtures frequently occur in the ash produced by various types of coal combustion, especially in filter cakes from pressurized fluidized bed combustion with dolomite as a SO x sorbent. Previously, qualitative analyses could be performed for Mg 2Ca(SO 4) 3 in these mixtures, but no quantitative analytical method was available. An infrared spectroscopic method has been developed that provides reasonably quantitative results for Mg 2Ca(SO 4) 3, MgSO 4,and CaSO 4 in their mixtures.

  17. The effect of Zn contents on phase composition, chemical stability and cellular bioactivity in Zn-Ca-Si system ceramics.

    PubMed

    Wu, Chengtie; Ramaswamy, Yogambha; Chang, Jiang; Woods, Joy; Chen, Yiqing; Zreiqat, Hala

    2008-11-01

    Ca-Si system ceramics, in particular CaSiO(3) ceramics, are regarded as potential bioactive bone repair/regeneration material. However, their high dissolution rate limits their biological applications. The aim of this study was to incorporate Zinc (Zn) into the Ca-Si system ceramics to produce part (at 10 and 20% Zn) or complete (at 50% Zn) new crystal phase (hardystonite: Ca(2)ZnSi(2)O(7)) with improved chemical stability and cellular activity. Zn-Ca-Si ceramics with four Zn contents (0, 10, 20, and 50%) were successfully prepared by sintering sol-gel-derived Zn-Ca-Si powder compacts. A new pure crystal phase Ca(2)ZnSi(2)O(7) was formed only when 50% Zn was added. The chemical stability of Zn-Ca-Si ceramics was evaluated by soaking in simulating body fluid (SBF), and the ion release from ceramics and the change in pH values of the SBF were measured. Their ability to form apatite in SBF was determined by analyzing the surface phase composition and morphology of the ceramics using X-ray diffraction and scanning electron microscopy (SEM). Results indicated that, with the increase of Zn contents, the chemical stability of ceramics increased while the apatite-formation ability decreased. The ability of Zn-Ca-Si ceramics to support attachment, proliferation, and differentiation of the human bone osteoblastic-like cells (HOB) was assessed using SEM, MTS, and alkaline phosphate activity assays, respectively. Zn-Ca-Si ceramics supported HOB attachment and their proliferation increased with the increase of Zn content. ALP activity of HOB on Zn-Ca-Si ceramics with 50% Zn (Ca(2)ZnSi(2)O(7)) was the highest among the levels obtained for the four ceramics tested. Taken together, Ca(2)ZnSi(2)O(7) ceramics possessed the best chemical stability and cellular bioactivity in Zn containing Ca-Si ceramics, indicating their potential application in skeletal tissue regeneration.

  18. High-efficiency ZnCdSe/ZnSSe/ZnMgSSe green and blue light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Nakayama, Norikazu; Itoh, Satoshi; Ishibashi, Akira; Mori, Yoshifumi

    1996-05-01

    Molecular beam epitaxy (MBE) has been used to grow our II-VI green and blue light-emitting diodes (LEDs) on n-GaAs substrates. The main structure consists of a ZnCdSe/ZnSSe triple quantum-well active region, ZnSSe carrier confining layers, ZnMgSSe cladding layers, and a p-ZnTe/p-ZnSe multiple quantum-well contact region. The LED chips, 0.3 multiplied by 0.3 mm2 in size, were mounted on LED leadframes and were encapsulated in epoxy. The devices produce light output powers of 3.5 mW (513 nm) and 1.5 mW (486 nm) for a direct current (dc) of 20 mA at room temperature. The corresponding external quantum efficiencies are 7.2% for the green, and 2.9% for the blue LEDs. In particular, the blue LED operated at a low applied voltage of 2.63 V for 20 mA. An aging test showed a half-intensity lifetime of 1000 hours for the candela-class blue LED under a constant dc drive current of 10 mA at an ambient temperature of 27 degrees Celsius.

  19. Structural and optical properties of MgO doped ZnO

    SciTech Connect

    Verma, Kavita; Shukla, S.; Varshney, Dinesh; Varshney, M.; Asthana, A.

    2014-04-24

    Samples of ZnO, Zn{sub 0.5}Mg{sub 0.5}O and MgO were prepared by co-precipitation method. X-ray diffraction (XRD) pattern infers that the sample of ZnO is in single-phase wurtzite structure (hexagonal phase, space group P6{sub 3}mc), MgO crystallizes in cubic Fd3m space group and Zn{sub 0.5}Mg{sub 0.5}O represents mixed nature of ZnO and MgO lattices. Similar features were observed from Raman spectroscopy. The energy band gaps estimated from UV-Vis spectroscopy are found to be 4.21 and 3.42 eV for ZnO and Zn{sub 0.5}Mg{sub 0.5}O samples respectively.

  20. Self-compensation induced high-resistivity in MgZnO

    NASA Astrophysics Data System (ADS)

    Liu, Lishu; Mei, Zengxia; Tang, Aihua; Liang, Huili; Du, Xiaolong

    2017-02-01

    The degradation of conductivity with increased Mg content for Mg x Zn1-x O wide bandgap materials has always been a fundamental application-motivated research issue. Herein, the study of self-compensating defects in Mg x Zn1-x O:F (0  ⩽  x  ⩽  0.29) thin films was performed to reveal their influence on increased resistivity. Our observations solidly evidence that the degradation of conductivity is mainly owing to the increased concentration of Zn vacancy (V Zn)-related compensating defects in Mg x Zn1-x O alloys. The formation enthalpy of intrinsic V Zn defects decreases as Mg content (x) increases. Thus, the compensation ratio increases from 0.23 at x  =  0 to 0.47 at x  =  0.29, resulting in deteriorated conductivity in Mg x Zn1-x O alloys. Cathodoluminescence (CL) spectra further confirm higher V Zn concentrations with increased Mg content. The electron transport is demonstrated to be dominated by an ionized scattering mechanism. Formation of F\\text{O}+ -V\\text{Zn}2- complexes could reduce the concentration of ionized scattering centers and thus increase mobility. These results clarify the reason of increasingly high resistivity in Mg x Zn1-x O, which is a long-sought-after physics problem in this area, and provide crucial information on controlling the conductivity of Mg x Zn1-x O alloys.

  1. Effect of Mg on the Microstructure and Corrosion Resistance of the Continuously Hot-Dip Galvanizing Zn-Mg Coating

    PubMed Central

    Dong, Anping; Li, Baoping; Lu, Yanling; Zhu, Guoliang; Xing, Hui; Shu, Da; Sun, Baode; Wang, Jun

    2017-01-01

    The microstructure of continuously hot-dip galvanizing Zn-Mg coating was investigated in order to obtain the mechanism of the effects of Mg on the corrosion resistance. In this paper, the vertical section of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner was calculated. The results indicates that the phase composition of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner is the same as Zn-Mg binary phase diagram, suggesting Al in the Zn-Mg (ZM) coatings mainly concentrates on the interfacial layer between the coating and steel substrate. The microstructure of continuously hot-dip galvanizing ZM coatings with 0.20 wt % Al containing 1.0–3.0 wt % Mg was investigated using tunneling electron microscopy (TEM). The morphology of Zn in the coating changes from bulk to strip and finally to mesh-like, and the MgZn2 changes from rod-like to mesh-like with the Mg content increasing. Al in the ZM coatings mainly segregates at the Fe2Al5 inhibition layer and the Mg added to the Zn bath makes this inhibition layer thinner and uneven. Compared to GI coating, the time of the first red rust appears increases by more than two-fold and expansion rate of red rust reduces by more than four-fold in terms of salt spray experiment. The ZM coating containing 2.0 wt % Mg has the best corrosion resistance. The enhanced corrosion resistance of ZM coatings mainly depends on different corrosion products. PMID:28829393

  2. Synthesis, Photocatalytic, and Antifungal Properties of MgO, ZnO and Zn/Mg Oxide Nanoparticles for the Protection of Calcareous Stone Heritage.

    PubMed

    Sierra-Fernandez, A; De la Rosa-García, S C; Gomez-Villalba, L S; Gómez-Cornelio, S; Rabanal, M E; Fort, R; Quintana, P

    2017-07-26

    More recently, the biological colonization of stone heritage and consequently its biodeterioration has become the focus of numerous studies. Among all microorganisms, fungi are considered to be one of the most important colonizers and biodegraders on stone materials. This is why the development of new antifungal materials requires immediate action. ZnMgO nanoparticles (NPs) have several exciting applications in different areas, highlighting as an efficient antimicrobial agent for medical application. In this research, the application of Zn-doped MgO (Mg1-xZnxO, x = 0.096) NPs obtained by sol-gel method as antifungal coatings on dolomitic and calcitic stones has been explored as a means to develop effective protective coatings for stone heritage. Moreover, the photocatalytic and antifungal activity of Mg1-xZnxO NPs were comparatively studied with single ZnO and MgO NPs. Thus, compared to the MgO and ZnO nanomaterials, the Mg1-xZnxO NPs exhibited an enhanced photocatalytic activity. After UV irradiation for 60 min, 87% methylene blue was degraded over Zn-doped MgO NPs, whereas only 58% and 38% of MB was degraded over ZnO and MgO NPs, respectively. These nanoparticles also displayed a better antifungal activity than that of single pure MgO or ZnO NPs, inhibiting the growth of fungi Aspergillus niger, Penicillium oxalicum, Paraconiothyrium sp., and Pestalotiopsis maculans, which are especially active in the bioweathering of stone. The improved photocatalytic and antifungal properties detected in the Mg1-xZnxO NPs was attributed to the formation of crystal defects by the incorporation of Zn into MgO. The application of the MgO- and Zn-doped MgO NPs as protective coatings on calcareous stones showed important antifungal properties, inhibiting successfully the epilithic and endolithic colonization of A. niger and P. oxalicum in both lithotypes, and indicating a greater antifungal effectiveness on Zn-doped MgO NPs. The use of Zn-doped MgO NPs may thus represent a highly

  3. 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.

  4. 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.

  5. Eocene sea temperatures for the mid-latitude southwest Pacific from Mg/Ca ratios in planktonic and benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Creech, John B.; Baker, Joel A.; Hollis, Christopher J.; Morgans, Hugh E. G.; Smith, Euan G. C.

    2010-11-01

    We have used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to measure elemental (Mg/Ca, Al/Ca, Mn/Ca, Zn/Ca, Sr/Ca, and Ba/Ca) ratios of 13 species of variably preserved early to middle Eocene planktonic and benthic foraminifera from New Zealand. The foraminifera were obtained from Ashley Mudstone, mid-Waipara River, South Island, which was deposited at bathyal depth ( ca. 1000 m) on the northern margin of the east-facing Canterbury Basin at a paleo-latitude of ca. 55°S. LA-ICP-MS data yield trace element depth profiles through foraminifera test walls that can be used to identify and exclude zones of surficial contamination and infilling material resulting from diagenetic coatings, mineralisation and detrital sediment. Screened Mg/Ca ratios from 5 species of foraminifera are used to calculate sea temperatures from late Early to early Middle Eocene ( ca. 51 to 46.5 Ma), a time interval that spans the termination of the Early Eocene Climatic Optimum (EECO). During this time, sea surface temperatures (SST) varied from 30 to 24 °C, and bottom water temperatures (BWT) from 21 to 14 °C. Comparison of Mg/Ca sea temperatures with published δ 18O and TEX 86 temperature data from the same samples (Hollis et al., 2009) shows close correspondence, indicating that LA-ICP-MS can provide reliable Mg/Ca sea temperatures even where foraminiferal test preservation is variable. Agreement between the three proxies also implies that Mg/Ca-temperature calibrations for modern planktonic and benthic foraminifera can generally be applied to Eocene species, although some species (e.g., V. marshalli) show significant calibration differences. The Mg/Ca ratio of the Eocene ocean is constrained by our data to be 35-50% lower than the modern ocean depending on which TEX 86 - temperature calibration (Kim et al., 2008; Liu et al., 2009) - is used to compare with the Mg/Ca sea temperatures. Sea temperatures derived from δ 18O analysis of foraminifera from Waipara show

  6. Effect of Mg on the Microstructure and Corrosion Resistance of the Continuously Hot-Dip Galvanizing Zn-Mg Coating.

    PubMed

    Dong, Anping; Li, Baoping; Lu, Yanling; Zhu, Guoliang; Xing, Hui; Shu, Da; Sun, Baode; Wang, Jun

    2017-08-22

    The microstructure of continuously hot-dip galvanizing Zn-Mg coating was investigated in order to obtain the mechanism of the effects of Mg on the corrosion resistance. In this paper, the vertical section of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner was calculated. The results indicates that the phase composition of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner is the same as Zn-Mg binary phase diagram, suggesting Al in the Zn-Mg (ZM) coatings mainly concentrates on the interfacial layer between the coating and steel substrate. The microstructure of continuously hot-dip galvanizing ZM coatings with 0.20 wt % Al containing 1.0-3.0 wt % Mg was investigated using tunneling electron microscopy (TEM). The morphology of Zn in the coating changes from bulk to strip and finally to mesh-like, and the MgZn₂ changes from rod-like to mesh-like with the Mg content increasing. Al in the ZM coatings mainly segregates at the Fe₂Al₅ inhibition layer and the Mg added to the Zn bath makes this inhibition layer thinner and uneven. Compared to GI coating, the time of the first red rust appears increases by more than two-fold and expansion rate of red rust reduces by more than four-fold in terms of salt spray experiment. The ZM coating containing 2.0 wt % Mg has the best corrosion resistance. The enhanced corrosion resistance of ZM coatings mainly depends on different corrosion products.

  7. Identification of a type I Ca2+/Mg2+-dependent endonuclease induced in maize cells exposed to camptothecin

    PubMed Central

    2013-01-01

    Background Camptothecin is a plant alkaloid that specifically binds topoisomerase I, inhibiting its activity and inducing double stranded breaks in DNA and activating the cell responses to DNA damage. Results Maize cultured cells were incubated in the presence of different concentrations of camptothecin. Camptothecin inhibits cultured cell growth, induces genomic DNA degradation, and induces a 32 kDa Ca2+/Mg2+-dependent nuclease activity. This nuclease, we called CaMNUC32, is inhibited by Zn2+ and by acid pH, it is mainly localized in the nucleus and it cleaves single- and double-stranded DNA, with a higher activity against single-stranded DNA. Two-dimensional electrophoresis combined with mass spectrometry suggests that CaMNUC32 is a member of the type I S1/P1 nuclease family. This type of nucleases are usually Zn2+-dependent but our results support previous indications that S1-type nucleases have a wide variety of enzyme activities, including Ca2+/Mg2+-dependent. Conclusions We have identified and characterized CaMNUC32, a 32 kDa Ca2+/Mg2+-dependent nuclease of the S1/P1 family induced by the topoisomerase I inhibitor camptothecin in maize cultured cells. PMID:24256432

  8. Schottky Diodes Prepared with Ag, Au, or Pd Contacts on a MgZnO/ZnO Heterostructure

    NASA Astrophysics Data System (ADS)

    Lee, Jong Hoon; Kim, Chang Hoi; Kim, Ah Ra; Kim, Hong Seung; Jang, Nak Won; Yun, Young; Kim, Jin-Gyu; Pin, Min Wook; Lee, Won Jae

    2012-09-01

    We successfully fabricated lateral Schottky diodes with a thin MgZnO layer inserted between the ZnO and Schottky contact metal layers. The MgZnO/ZnO heterostructure was deposited onto a c-sapphire substrate by pulsed laser deposition using Mg0.3Zn0.7O and ZnO targets. Ti/Au was used to achieve ohmic contact with the Mg0.3Zn0.7O thin film layer, whereas Schottky contacts were prepared using silver (Ag), gold (Au), and palladium (Pd). The Ag Schottky diode devices exhibited rectification ratios as high as ˜103 at a bias voltage of ±1 V, with an ideality factor of 2.37 and a work function of 0.73 eV. The possibility of preparing Schottky contacts with a high carrier concentration on the ZnO layer is discussed as a function of the presence or absence of a MgZnO thin layer and in terms of the measured current-voltage properties.

  9. Electrical properties of Mg x Zn1- x O thin films deposited by using RF magnetron co-sputtering with ZnO and Mg0.3Zn0.7O targets

    NASA Astrophysics Data System (ADS)

    Yue, Li Li; Yang, Yi Da; Kim, Hong Seung; Jang, Nak Won; Yun, Young

    2016-03-01

    We successfully deposited hexagonal wurtzite Mg x Zn1- x O (0 ≤ x ≤ 0.18) films on Si substrates by using RF magnetron co-sputtering with ZnO and Mg0.3Zn0.7O targets. The Mg content was varied by controlling the RF power of the Mg0.3Zn0.7O target while the RF power of the ZnO target was fixed at 100 W. The electrical properties of the Mg x Zn1- x O films were investigated by using a transmission line model (TLM) with Ti/Au electrode and Hall effect measurements. The X-ray diffraction (XRD) results demonstrate that some Zn atoms can be replaced by Mg atoms in the Mg x Zn1- x O films. As the Mg content was increased from 0 at.% to 18 at.%, the resistivity of Mg x Zn1- x O films increased and the carrier concentration decreased from 1.17 × 1019 cm-3 to 1.17 × 1017 cm-3, which indicates a decrease in the number of oxygen vacancies. Meanwhile, the Hall mobility increased to 15.3 cm2/Vs. The electrical properties of Mg x Zn1- x O films were tuned by using the Mg content.

  10. Atomic Structure of Ca40+xMg25Cu35-x Metallic Glasses (Preprint)

    DTIC Science & Technology

    2011-12-01

    Ca50Mg25Cu25 alloys forms three equally probable crystal phases, CaMg2 Cu2Mg and CaCu [5,6]. CaMg2 is a hexagonal Laves phase (space group P63/mmc...the first shell, and a Mg-centered (0,0,12,4) Friauf polyhedron with 12 Cu and 4 Mg atoms in the first shell. The CaCu phase has a primitive crystal...0,3,6,0) Cu-centered coordination polyhedron in the CaCu phase is also common in the studied amorphous structures. This (0,3,6,0) Cu-centered cluster is

  11. Exciton dynamics in individual semimagnetic (Zn,Mn)Te/(Zn,Mg)Te nanowires

    SciTech Connect

    Gałkowski, K.; Papierska, J.; Sawicki, K.; Kossacki, P.; Suffczyński, J.; Wojnar, P.; Janik, E.

    2015-09-07

    Dynamics and mechanisms of photocreated carriers decay in individual core/shell (Zn,Mn)Te/(Zn,Mg)Te semimagnetic nanowires are studied with a high temporal resolution. Exciton lifetime determined to 44 ± 5 ps is found to increase to 78 ± 5 ps upon application of magnetic field of up to 10 T. A quantitative modeling attributes the effects observed in time-resolved and time-integrated micro-photoluminescence to the magnetic field induced quenching of exchange Auger type, non-radiative carrier recombination related to Mn{sup 2+} ions. The reported properties of the semimagnetic nanowires are promising for their implementation in high-speed devices exploiting light-induced conductivity.

  12. Air-gap gating of MgZnO/ZnO heterostructures

    SciTech Connect

    Tambo, T.; Falson, J. Kozuka, Y.; Maryenko, D.; Tsukazaki, A.; Kawasaki, M.

    2014-08-28

    The adaptation of “air-gap” dielectric based field-effect transistor technology to controlling the MgZnO/ZnO heterointerface confined two-dimensional electron system (2DES) is reported. We find it possible to tune the charge density of the 2DES via a gate electrode spatially separated from the heterostructure surface by a distance of 5 μm. Under static gating, the observation of the quantum Hall effect suggests that the charge carrier density remains homogeneous, with the 2DES in the 3 mm square sample the sole conductor. The availability of this technology enables the exploration of the charge carrier density degree of freedom in the pristine sample limit.

  13. Spin-Selective Electron Quantum Transport in Nonmagnetic MgZnO/ZnO Heterostructures.

    PubMed

    Maryenko, D; Falson, J; Bahramy, M S; Dmitriev, I A; Kozuka, Y; Tsukazaki, A; Kawasaki, M

    2015-11-06

    We report magnetotransport measurements on a high-mobility two-dimensional electron system at the nonmagnetic MgZnO/ZnO heterointerface showing distinct behavior for electrons with spin-up and spin-down orientations. The low-field Shubnikov-de Haas oscillations manifest alternating resistance peak heights which can be attributed to distinct scattering rates for different spin orientations. The tilt-field measurements at a half-integer filling factor reveal that the majority spins show usual diffusive behavior, i.e., peaks with the magnitude proportional to the index of the Landau level at the Fermi energy. By contrast, the minority spins develop "plateaus" with the magnitude of dissipative resistivity that is fairly independent of the Landau level index and is of the order of the zero-field resistivity.

  14. ZnCdSe/ZnCdMgSe quantum well infrared photodetector.

    PubMed

    Ravikumar, Arvind P; Alfaro-Martinez, Adrian; Chen, Guopeng; Zhao, Kuaile; Tamargo, Maria C; Gmachl, Claire F; Shen, Aidong

    2012-09-24

    We report the design, fabrication and characterization of a II-VI Zn(0.51)Cd(0.49)Se / Zn0.45(Cd)0.42(Mg)(0.13)Se-based quantum well infrared photodetector (QWIP) with a bound to quasi-bound transition centered at 8.7 µm. The good growth quality of the epitaxial layers was verified by x-ray diffraction measurements. Absorption and photocurrent measurements yield results consistent with conventional III-V QWIPs. Photocurrent measurements reveal an exponential decrease with temperature. In addition, we also observe more than 4 orders of magnitude increase in photocurrent with applied bias. By compensating the drop in temperature performance with an increase in applied bias, we achieve an operating temperature of up to 140K and a responsivity of 1-10 µA/W.

  15. Spin-Selective Electron Quantum Transport in Nonmagnetic MgZnO /ZnO Heterostructures

    NASA Astrophysics Data System (ADS)

    Maryenko, D.; Falson, J.; Bahramy, M. S.; Dmitriev, I. A.; Kozuka, Y.; Tsukazaki, A.; Kawasaki, M.

    2015-11-01

    We report magnetotransport measurements on a high-mobility two-dimensional electron system at the nonmagnetic MgZnO /ZnO heterointerface showing distinct behavior for electrons with spin-up and spin-down orientations. The low-field Shubnikov-de Haas oscillations manifest alternating resistance peak heights which can be attributed to distinct scattering rates for different spin orientations. The tilt-field measurements at a half-integer filling factor reveal that the majority spins show usual diffusive behavior, i.e., peaks with the magnitude proportional to the index of the Landau level at the Fermi energy. By contrast, the minority spins develop "plateaus" with the magnitude of dissipative resistivity that is fairly independent of the Landau level index and is of the order of the zero-field resistivity.

  16. 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.

  17. 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.

  18. Mechanical Properties and Tensile Failure Analysis of Novel Bio-absorbable Mg-Zn-Cu and Mg-Zn-Se Alloys for Endovascular Applications

    PubMed Central

    Persaud-Sharma, Dharam; Budiansky, Noah; McGoron, Anthony J.

    2013-01-01

    In this paper, the mechanical properties and tensile failure mechanism of two novel bio-absorbable as-cast Mg-Zn-Se and Mg-Zn-Cu alloys for endovascular medical applications are characterized. Alloys were manufactured using an ARC melting process and tested as-cast with compositions of Mg-Zn-Se and Mg-Zn-Cu, being 98/1/1 wt.% respectively. Nanoindentation testing conducted at room temperature was used to characterize the elastic modulus (E) and surface hardness (H) for both the bare alloys and the air formed oxide layer. As compared to currently available shape memory alloys and degradable as-cast alloys, these experimental alloys possess superior as-cast mechanical properties that can increase their biocompatibility, degradation kinetics, and the potential for medical device creation. PMID:23543822

  19. Enhanced Mechanical Properties and Corrosion Behavior of Biodegradable Mg-Zn/HA Composite

    NASA Astrophysics Data System (ADS)

    Salleh, Emee Marina; Zuhailawati, Hussain; Ramakrishnan, Sivakumar; Dhindaw, Brij Kumar

    2017-05-01

    Magnesium (Mg) and its alloys have shown potential for use in the biomedical industry due to their excellent biological performance and biodegradability in the bioenvironment. Thus, the aim of the present study was to develop a reliable biodegradable hard tissue substituent. Biodegradable and bioactive Mg-Zinc (Zn) reinforced by hydroxyapatite (HA) composite was prepared using mechanically alloyed Mg-6.5 wt pct Zn and pure HA powders as starting materials. Various HA contents ( i.e., 5, 10, 15, and 20 wt pct) were introduced in forming the Mg-Zn/HA composite. The effect of bioactive HA incorporation in biodegradable Mg-6.5 wt pct Zn alloy matrix on mechanical and biodegradation properties as well as microstructural observation was investigated. As measured by the Williamson-Hall formula, the Mg crystallite size of the sintered composites containing 5, 10, 15, and 20 wt pct HA were 36.76, 29.08, 27.93, and 27.31 nm, respectively. According to X-ray diffraction (XRD) analysis, there was no new crystalline phase formed during milling, indicating that no mechanochemical reactions between Mg-Zn alloy and HA occurred. The -1.70 V shifted significantly toward the passive position of the plain Mg-6.5 wt pct Zn alloy and Mg-Zn/10 wt pct HA composite, which were -1.50 and -1.46 V, respectively, indicating that the Mg-Zn/10 wt pct HA composite was least susceptible to corrosion in the bioenvironment.

  20. Enhanced Mechanical Properties and Corrosion Behavior of Biodegradable Mg-Zn/HA Composite

    NASA Astrophysics Data System (ADS)

    Salleh, Emee Marina; Zuhailawati, Hussain; Ramakrishnan, Sivakumar; Dhindaw, Brij Kumar

    2017-03-01

    Magnesium (Mg) and its alloys have shown potential for use in the biomedical industry due to their excellent biological performance and biodegradability in the bioenvironment. Thus, the aim of the present study was to develop a reliable biodegradable hard tissue substituent. Biodegradable and bioactive Mg-Zinc (Zn) reinforced by hydroxyapatite (HA) composite was prepared using mechanically alloyed Mg-6.5 wt pct Zn and pure HA powders as starting materials. Various HA contents (i.e., 5, 10, 15, and 20 wt pct) were introduced in forming the Mg-Zn/HA composite. The effect of bioactive HA incorporation in biodegradable Mg-6.5 wt pct Zn alloy matrix on mechanical and biodegradation properties as well as microstructural observation was investigated. As measured by the Williamson-Hall formula, the Mg crystallite size of the sintered composites containing 5, 10, 15, and 20 wt pct HA were 36.76, 29.08, 27.93, and 27.31 nm, respectively. According to X-ray diffraction (XRD) analysis, there was no new crystalline phase formed during milling, indicating that no mechanochemical reactions between Mg-Zn alloy and HA occurred. The -1.70 V shifted significantly toward the passive position of the plain Mg-6.5 wt pct Zn alloy and Mg-Zn/10 wt pct HA composite, which were -1.50 and -1.46 V, respectively, indicating that the Mg-Zn/10 wt pct HA composite was least susceptible to corrosion in the bioenvironment.

  1. Understanding the light soaking effect of ZnMgO buffer in CIGS solar cells.

    PubMed

    Kim, Suncheul; Lee, Chang-Soo; Kim, Seungtae; Chalapathy, R B V; Al-Ammar, Essam A; Ahn, Byung Tae

    2015-07-15

    This study investigated the mechanism underlying the light soaking effect of a ZnMgO buffer in Cu(In,Ga)Se2 (CIGS) solar cells, where the cell efficiency increased with an increase of light soaking time. The ZnMgO buffer layer was deposited by an atomic layer deposition method. With light soaking, the cell efficiency of ZnMgO/CIGS cells increased mainly by the increase of the fill factor and partly by the increase of the open-circuit voltage. With light soaking, the electron carrier concentration of the ZnMgO layer increased and the XPS intensity of the hydroxyl bond in the ZnMgO layer decreased. Based on the above results and the comparison of other buffers in literature, we assumed that the hydrogen atoms broken away from the hydroxyl bond by photon irradiation occupied the interstitial sites of the ZnMgO layer as a donor atom and also passivated the defects at the ZnMgO/CIGS interface. The increase of the fill factor and open circuit voltage was explained based on H doping in the ZnMgO layer and H passivation at the ZnO/CIGS interface.

  2. 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.

  3. MOCVD growth and characterization of ZnS and Zn 1- xMg xS alloys

    NASA Astrophysics Data System (ADS)

    Sallet, V.; Lusson, A.; Rommeluere, M.; Gorochov, O.

    2000-12-01

    The growth of ZnS and Zn 1- xMg xS alloys on GaAs and GaP substrates oriented 2° off the (1 0 0) in the [1 1 0] direction, using metalorganic chemical vapor deposition, is reported. The photoluminescence of high-quality ZnS samples is presented. Strain effects are considered to explain the valence band splitting, and the energy shift between ZnS/GaAs and ZnS/GaP photoluminescence spectra. For Zn 1- xMg xS alloys, the composition as well as the optical and structural properties are investigated as a function of the growth parameters.

  4. 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.

  5. Microstructure evolution and mechanical properties of biomedical Mg-Zn-Gd alloy wires

    NASA Astrophysics Data System (ADS)

    Chunlei, Gan; Xiaohui, Li; Deng, Nong; Xiang, Zhang; Kaihong, Zheng; Zhenghua, Huang

    2017-03-01

    In order to manufacture the Mg-Zn-Gd alloy fine wires for the development of new biomedical Mg alloy implant devices, a hot extrusion and cold drawing process which is used to develop the Mg-Zn-Gd alloy fine wires were investigated. The results demonstrate that the Mg-Zn-Gd alloy has good formability. The microstructure and properties of the Mg-Zn-Gd alloy wires were studied by the observations of optical microscopy and scanning electron microscopy. The results show that the process is successfully developed to manufacture the high-quality wires with 3.00 mm diameter. The achievement of the high-quality Mg-Zn-Gd alloy wires is ascribed to the refined microstructure due to dynamic recrystallization during hot extrusion. Additionally, the grain morphology can play an important role in affecting the subsequent cold drawing performance.

  6. Study of ZnO and Mg doped ZnO nanoparticles by sol-gel process

    SciTech Connect

    Ansari, Mohd Meenhaz Arshad, Mohd; Tripathi, Pushpendra

    2015-06-24

    Nano-crystalline undoped and Mg doped ZnO (Mg-ZnO) nanoparticles with compositional formula Mg{sub x}Zn{sub 1-x}O (x=0,1,3,5,7,10 and 12 %) were synthesized using sol-gel process. The XRD diffraction peaks match with the pattern of the standard hexagonal structure of ZnO that reveals the formation of hexagonal wurtzite structure in all samples. SEM images demonstrates clearly the formation of spherical ZnO nanoparticles, and change of the morphology of the nanoparticles with the concentration of the magnesium, which is in close agreement with that estimated by Scherer formula based on the XRD pattern. To investigate the doping effect on optical properties, the UV–VIS absorption spectra was obtained and the band gap of the samples calculated.

  7. Luminescence properties of MgxZn1-xSe prepared by Mg diffusion

    NASA Astrophysics Data System (ADS)

    Łożykowski, H. J.; Holtz, P. O.; Monemar, B.

    1983-07-01

    The photoluminescence of ZnSe doped with the isoelectronic substituent Mg with a simple diffusion procedure has been studied. It was found that Mg easily enters substitutionally on Zn-site to form MgxZn1-xSe. The diffused samples therefore show a graded bandgap due to a composition gradient in the surface region. In contrast to ZnSe the photoluminescence spectrum of MgxZn1-xSe is dominated by a near bandgap emission at all temperatures between 1.5 and 300 K. The bandgap shift compared with “pure” ZnSe is estimated from photoluminescence excitation spectra. The luminous efficiency of MgxZn1-xSe makes the material promising for future applications as light emitting diodes with a well defined narrow emission band at a wavelength determined by the Mg content x.

  8. Preparation and structural properties of pure and codoped (Mg, Ag) ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Reddy, B. Sankara; Reddy, S. Venkatramana; Reddy, N. Koteeswara

    2013-06-01

    Pure and co-doped (Mg, Ag) ZnO nanoparticles (Zn0.90Mg0.05Ag0.05O) are synthesized by chemical co-precipitation method in the presence of capping agent Polyethylene glycol 600 (PEG 600) and annealed at 500°C in air ambient for 1h. The XRD measurements reveals that the pure and co-doped ZnO samples have hexagonal structure without any change and the size of ZnO nanoparicles were decreased from 17 nm to 13 nm. FESEM images indicates that they are flake like structures of the ZnO and co-doped ZnO samples and ED AX spectra reveals that the successful doping concentration of Mg and Ag. From the TEM results, the size of the ZnO nanoparticles which are in good agreement with the XRD results.

  9. Fire-Proof Evaluation of CaO Added Mg-3Al, Mg-6Al, and Mg-9Al Mg Cast Products

    NASA Astrophysics Data System (ADS)

    Lee, Jin-kyu; Kim, Shae K.

    Mg products are easily oxidized and burned when they are exposed to high temperature or fire by accident. In order to solve these problems, the fire-proof solution has been developed by adding CaO in Mg alloys. The fire-proof was evaluated by three methods: quantitative DTA for small sphere specimen, furnace ignition test for burrs and machined chips, and torch ignition test for products. DTA was carried out for obtaining quantitative ignition temperature data with respect to specimen geometry and test environment; the furnace ignition test for burr and chip ignition temperature data; and the torch test for ignition temperature data for manufactured products. This paper discusses the results of fire-proof properties of 1wt.%, and 1.5wt.% CaO added Mg-3Al, Mg-6Al, and Mg-9Al Mg alloys compared with other high temperature Mg alloys such as AE44, AS21, MRI153, and MRI230. Eco-Mg alloy will be low-cost and fire-proof Mg alloys for airplane and train applications in terms of preventing poisonous gas generation, inhalation bum, and ignition generation.

  10. Preparation of p-type ZnMgO thin films by Sb doping method

    NASA Astrophysics Data System (ADS)

    Pan, X. H.; Ye, Z. Z.; Zeng, Y. J.; Gu, X. Q.; Li, J. S.; Zhu, L. P.; Zhao, B. H.; Che, Y.; Pan, X. Q.

    2007-07-01

    We report on Sb-doped p-type Zn0.95Mg0.05O thin films grown by pulsed laser deposition. The Sb-doped Zn0.95Mg0.05O films show an acceptable p-type conductivity with a resistivity of 126 Ω cm, a Hall mobility of 1.71 cm2 V-1 s-1 and a hole concentration of 2.90 × 1016 cm-3 at room temperature. Secondary ion mass spectroscopy confirms that Sb has been incorporated into the Zn0.95Mg0.05O films. Guided by x-ray photoemission spectroscopy analysis and a model for large-size-mismatched group-V dopants in ZnO, an SbZn-2VZn complex is believed to be the most possible acceptor in the Sb-doped p-type Zn0.95Mg0.05O thin films.

  11. Study of p-type ZnO and MgZnO Thin Films for Solid State Lighting

    SciTech Connect

    Liu, Jianlin

    2015-07-31

    This project on study of p-type ZnO and MgZnO thin films for solid state lighting was carried out by research group of Prof. Jianlin Liu of UCR during the four-year period between August 2011 and July 2015. Tremendous progress has been made on the proposed research. This final report summarizes the important findings.

  12. 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.

  13. High Strength, Nano-Structured Mg-Al-Zn Alloy

    DTIC Science & Technology

    2011-01-01

    REPORT High strength, nano-structured Mg– Al – Zn alloy 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: The mechanical behavior and microstructure of...Prescribed by ANSI Std. Z39.18 - High strength, nano-structured Mg– Al – Zn alloy Report Title ABSTRACT The mechanical behavior and microstructure of...strength, nano-structured Mg– Al – Zn alloy Block 13: Supplementary Note © 2011 . Published in Materials Science and Engineering, Vol. 528, (54), Ed. 0 (2011

  14. Damage accumulation and annealing behavior in high fluence implanted MgZnO

    NASA Astrophysics Data System (ADS)

    Azarov, A. Yu.; Hallén, A.; Svensson, B. G.; Du, X. L.; Kuznetsov, A. Yu.

    2012-02-01

    Molecular beam epitaxy grown Mg xZn 1-xO ( x ⩽ 0.3) layers were implanted at room temperature with 150 keV 166Er + ions in a fluence range of 5 × 10 15-3 × 10 16 cm -2. Evolution of ion-induced damage and structural changes were studied by a combination of Rutherford backscattering spectrometry, nuclear reaction analysis and time-of-flight elastic recoil detection analysis. Results show that damage production enhances in both Zn- and O-sublattices with increasing the Mg content in the MgZnO. However, MgZnO as well as pure ZnO exhibits a high degree of dynamic annealing and MgZnO can not be amorphized even at the highest ion fluence used. Annealing of heavily damaged ZnO leads to a strong surface erosion and thinning of the film. Increasing the Mg content suppresses the surface evaporation in high fluence implanted MgZnO but leads to a strong surface decomposition accompanied with a Mg-rich surface layer formation during post-implantation annealing.

  15. Auger recombination rates in ZnMgO from first principles

    NASA Astrophysics Data System (ADS)

    Heinemann, Markus; Heiliger, Christian

    2011-10-01

    We investigate direct electron-electron-hole interband Auger recombination for wurtzite Zn1-xMgxO alloys in the range 0 ≤ x ≤ 1. Recombination rates are computed by interpolating the band structure and transition matrix elements from ab initio calculations of bulk ZnO, Zn0.5Mgn0.5O, and MgO primitive cells. We find that interband Auger recombination is most probable for Mg concentrations around 50%, where ZnMgO does not exist in a stable wurtzite phase. Since, for low Mg concentrations, the calculated Auger coefficients are far below 10-32 cm6/s, we do not expect significant nonradiative loss through direct interband recombination in wurtzite ZnMgO.

  16. Intramitochondrial Zn2+ accumulation via the Ca2+ uniporter contributes to acute ischemic neurodegeneration

    PubMed Central

    Medvedeva, Yuliya V.; Weiss, John H.

    2014-01-01

    Ca2+ and Zn2+ have both been implicated in the induction of acute ischemic neurodegeneration. We recently examined changes in intracellular Zn2+ and Ca2+ in CA1 pyramidal neurons subjected to oxygen glucose deprivation (OGD), and found that Zn2+ rises precede and contribute to the onset of terminal Ca2+ rises (“Ca2+ deregulation”), which are causatively linked to a lethal loss of membrane integrity. The present study seeks to examine the specific role of intramitochondrial Zn2+ accumulation in ischemic injury, using blockers of the mitochondrial Ca2+ uniporter (MCU), through which both Zn2+ and Ca2+ appear able to enter the mitochondrial matrix. In physiological extracellular Ca2+, treatment with the MCU blocker, Ruthenium Red (RR), accelerated the Ca2+ deregulation, most likely by disrupting mitochondrial Ca2+ buffering and thus accelerating the lethal cytosolic Ca2+ overload. However, when intracellular Ca2+ overload was slowed, either by adding blockers of major Ca2+ entry channels or by lowering the concentration of Ca2+ in the extracellular buffer, Ca2+ deregulation was delayed, and under these conditions either Zn2+ chelation or MCU blockade resulted in similar further delays of the Ca2+ deregulation. In parallel studies using the reactive oxygen species (ROS) indicator, hydroethidine, lowering Ca2+ surprisingly accelerated OGD induced ROS generation, and in these low Ca2+ conditions, either Zn2+ chelation or MCU block slowed the ROS generation. These studies suggest that, during acute ischemia, Zn2+ entry into mitochondria via the MCU induces mitochondrial dysfunction (including ROS generation) that occurs upstream of, and contributes to the terminal Ca2+ deregulation. PMID:24787898

  17. Synthesis, Structure, and Properties of Ca2ZnN2

    DTIC Science & Technology

    1990-04-30

    ternary nitride CaiZnN9, prepared by the reaction of Ca3N2 and Zn in NT gas at 680-. The structure, determined by x-ray powder diffraction and...ZnN 2, prepared by the reaction of Ca 3N2 and Zn in N2 gas at 680 0 C. The structure, determined by x-ray powder diffraction and refined by Rietveld...properties of Ca2ZnN2. Experimental Synthesis All manipulations were carried out in an argon-filled glove box. Calcium nitride was first prepared by

  18. 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.

  19. Preparation and characterization of laser-melted Mg-Sn-Zn alloys for biomedical application.

    PubMed

    Shuai, Cijun; Zhou, Yuanzhuo; Lin, Xin; Yang, Youwen; Gao, Chengde; Shuai, Xiong; Wu, Hong; Liu, Xinyan; Wu, Ping; Feng, Pei

    2017-01-01

    The rapid degradation rate of Magnesium (Mg) alloy limits its biomedical application even though it possesses outstanding biological performance and biomechanical compatibility. In this study, a combined method of laser rapid melting and alloying Zinc (Zn) was proposed to decrease the degradation rate of Mg-Sn alloy. The microstructure, degradation behaviors and mechanical properties of the laser-melted Mg-5Sn-xZn (x = 0, 2, 4, 6 and 8 wt.%) alloys were investigated. The results indicated that the grain size of the alloys decreased with increasing Zn content, due to the increased number of nucleation particles formed in the process of solidification. Moreover, the laser-melted Mg-Sn alloys possessed finer grains compared with traditional as-cast and as-rolled Mg-Sn alloys. The degradation rate of the alloys decreased with increasing Zn content (0-4 wt.%), which was ascribed to the grain refinement and the formation of Zn(OH)2 protective layer. However, the degradation rate increased as the Zn content further increased (4-8 wt.%), which was caused by the galvanic corrosion between the Mg matrix and the generated Mg7Zn3 phase. Besides, Zn also increased the hardness of the alloys owing to the grain refinement strengthening and solid solution strengthening.

  20. 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.

  1. Pressure induced increase of the exciton phonon interaction in ZnO/(ZnMg)O quantum wells

    SciTech Connect

    Jarosz, D.; Suchocki, A.; Kozanecki, A.

    2016-03-15

    It is a well-established experimental fact that exciton-phonon coupling is very efficient in ZnO. The intensities of the phonon-replicas in ZnO/(ZnMg)O quantum structures strongly depend on the internal electric field. We performed high-pressure measurements on the single ZnO/(ZnMg)O quantum well. We observed a strong increase of the intensity of the phonon-replicas relative to the zero phonon line. In our opinion this effect is related to pressure induced increase of the strain in quantum structure. As a consequence, an increase of the piezoelectric component of the electric field is observed which leads to an increase of the intensity of the phonon-replicas.

  2. Structural and electronic properties of wurtzite MgZnO and BeMgZnO alloys and their thermodynamic stability

    NASA Astrophysics Data System (ADS)

    Gorczyca, I.; Teisseyre, H.; Suski, T.; Christensen, N. E.; Svane, A.

    2016-12-01

    Structural and electronic properties of MgZnO and BeMgZnO alloys are studied by the ab-initio Density Functional Theory method. Large band gap bowings are found for both kinds of alloys. The total energies as functions of the lattice constants are calculated and used to determine the ranges of composition in which the alloys are stable in the wurtzite structure. It is shown that the addition of 6% of Be can already help in stabilization of the MgZnO alloy in the wurtzite structure. The band gap can reach 7 eV for the wurtzite BexMg0.5Zn0.5-xO alloys with x approaching 0.5 and about 5.0 eV for Be0.125MgxZn0.875-xO type alloys for x approaching 0.6. Varying the alloy composition according to the presented stabilization diagram showing ranges of the x, y, for which BexMgyZn1-x-yO is stable in the wurtzite phase, one may tune band gaps over a wide spectral range, which provides flexibility in band gap engineering.

  3. Fabrication of p-n junctions in as-grown ZnMgO/ZnO films

    SciTech Connect

    Yang, Hyuck Soo; Li, Y.; Norton, David P.; Pearton, S. J.; Jang, Soohwan; Ren, F.; Boatner, Lynn A

    2005-01-01

    We achieved p-(Zn,Mg)O by doping with phosphorous and the conduction type was confirmed by capacitance-voltage properties of metal/insulator/p-(Zn,Mg)O:P diode structures as well as Hall measurements. The p-(Zn,Mg)O:P/n-ZnO junction was grown by pulsed laser deposition on bulk ZnO doped with Sn. Without post-growth annealing, the phosphorous-doped ZnMgO showed p-type conductivity (hole density {approx}10{sup 16} cm{sup -3}, mobility {approx}6 cm{sup 2}V{sup -1}s{sup -1}) in the as-grown state. The metal contacts in top-to-bottom p-n junctions were made with Ni/Au as the p-ohmic and Ti/Au as the backside n-ohmic contact. The p-contacts showed improved characteristics after annealing up to 350-400 C, but the n-contacts were ohmic as-deposited. The simple, low temperature growth (<=500 C) and processing sequence (<=400 C) shows the promise of ZnO for applications such as low-cost UV light emitters and transparent electronics.

  4. Fossil Echinoderms As Monitor of the Mg/Ca Ratio of Phanerozoic Oceans

    NASA Astrophysics Data System (ADS)

    Dickson, J. A. D.

    2002-11-01

    Opinion has long been divided as to whether the Mg/Ca ratio of seawater remained constant during the Phanerozoic or underwent substantial secular change. Existing empirical evidence for the Mg/Ca of ancient seawater provides a poorly resolved and often controversial signal. Echinoderm fossils that have retained their bulk original chemistry, despite micrometer-scale changes, preserve a record of seawater Mg/Ca and confirm that major changes in Mg/Ca occurred during the Phanerozoic. Echinoderms from the Cambrian and from the Carboniferous to the Triassic indicate a seawater Mg/Ca of ~3.3, whereas echinoderms from the Jurassic to the Cretaceous indicate a Mg/Ca of ~1.4. The present seawater Mg/Ca is ~5.

  5. The Crystal Structures of Mg 3N 2and Zn 3N 2

    NASA Astrophysics Data System (ADS)

    Partin, D. E.; Williams, D. J.; O'Keeffe, M.

    1997-08-01

    The structures of Mg3N2and Zn3N2have been refined from neutron time-of-flight powder diffraction data. These compounds have the antibixbyite structure and are the first such to be fully refined. The space group isIaoverline3,a=9.9528(1) Å (Mg3N2) and 9.7691(1) Å (Zn3N2). A revised bond valence parameter for Mg-N bonds is suggested.

  6. Comparison of a SiO₂-CaO-ZnO-SrO glass polyalkenoate cement to commercial dental materials: ion release, biocompatibility and antibacterial properties.

    PubMed

    Wren, A W; Coughlan, A; Hall, M M; German, M J; Towler, M R

    2013-09-01

    Ion Release and biocompatibility of a CaO-SrO-ZnO-SiO₂ (BT 101) based glass polyalkenoate cement (GPC) was compared against commercial GPCs, Fuji IX and Ketac Molar. The radiopacity (R) was similar for each material, 2.0-2.8. Ion release was evaluated on each material over 1, 7, 30 and 90 days. BT 101 release included Ca (23 mg/L), Sr (23 mg/L) Zn (13 mg/L), Si (203 mg/L). Fuji IX release includes Ca (0.7 mg/L), Al (3 mg/L) Si (26 mg/L), Na (60 mg/L) and P (0.5 mg/L) while Ketac Molar release includes Ca (1 mg/L), Al (0.6 mg/L) Si (23 mg/L), Na (76 mg/L) and P (0.7 mg/L). Simulated body fluid trials revealed CaP surface precipitation on BT 101. No evidence of precipitation was found on Fuji IX or Ketac Molar. Cytotoxicity testing found similar cell viability values for each material (~60 %, P = 1.000). Antibacterial testing determined a reduced CFU count with BT 101 (2.5 × 10³) when compared to the control bacteria (2.4 × 10⁴), Fuji IX (1.5 × 10⁴) and Ketac Molar (1.2 × 10⁴).

  7. Conduction mechanism and dielectric properties of ZnO/MgO solid composites

    NASA Astrophysics Data System (ADS)

    Hafef, Olfa; Othman, Zayani Jaafar; Megdich, Makram; Matoussi, Adel

    2017-01-01

    In this paper, (1- x)ZnO/ xMgO solid composites, where x = 0, 10 and 20%, were prepared at high temperature 1200 °C by a solid-state method. The effect of increasing MgO content on structural, morphological, dielectric and the electrical properties of the ZnO/MgO composites has been investigated. The X-ray diffraction analysis indicates that all the samples have a prominent hexagonal crystalline structure with (002) and (101) as preferred growth directions and the segregation of MgO cubic phase took place for an MgO composition x ≥ 10 wt%. Analysis of infrared (IR) is in agreement with the diffraction results of X-ray diffraction. Morphological properties showed that the grain size was decreased with increasing MgO content. For the dielectric properties, a strong dispersion of permittivity constants was observed at low frequency, which can be attributed to interfacial relaxation. For the electrical properties, the frequency dependence of ac conductivity is interpreted in terms of Jonscher's law. The ac electrical conduction in ZnO/MgO composites is analyzed by different processes, which can be attributed to several models, the hopping correlated barrier (CBH) for the undoped ZnO sample, and the hopping correlated barrier (CBH) and the overlapping large polaron tunneling model for both composites ZnO/MgO:10% and ZnO/MgO:20%.

  8. Thermodynamic analysis and experimental study on the oxidation of the Zn-Al-Mg coating baths

    NASA Astrophysics Data System (ADS)

    Su, Xuping; Zhou, Jie; Wang, Jianhua; Wu, Changjun; Liu, Ya; Tu, Hao; Peng, Haoping

    2017-02-01

    Surface oxidation of molten Zn-6Al baths containing 0.0, 3.0 and 6.0 wt. % Mg were analyzed using X-ray photoelectron spectroscopy. γ-Al2O3 is formed on the surface of the Zn-6Al bath, while MgAl2O4 and MgO occur at 460 °C in the Zn-6Al-3Mg and Zn-6Al-6Mg baths, respectively. Thermodynamic analysis on the oxidation of the Zn-Al-Mg baths was performed. Calculated phase diagrams at 460 °C and 560 °C show good agreements with the experimental results. MgO or MgAl2O4 exists in almost the entire composition range of the calculated oxidation diagrams. According to the calculation, oxidation products depend on the composition and temperature of the baths. The primary and secondary oxidation products of the Zn-Al-Mg baths can be reasonably explained by oxidation phase diagrams. Utilizing these results, the favorable practical bath melts and operating conditions can be designed.

  9. Tuning Complexity by Lithiation: A Family of Intergrowth Structures Using Condensed hypho-Icosahedra in the Li-Doped Ca-Zn System.

    PubMed

    Lin, Qisheng; Zhu, Ran; Miller, Gordon J

    2016-05-16

    Cluster chemistry of intermetallics with valence electron counts (VECs) in the range of 2.0-3.0 is intriguing. Lithiation of polar intermetallics in this VEC region is found to be an effective chemical route to produce new complex structures with different stability mechanisms. In this work, two new complex intermetallic structures have been discovered in the Ca-Li-Zn system: Ca12LixZn59-x and Ca15LixZn75-x. Ca12LixZn59-x, x ≈ 5.65(3)-14.95(3), forms in the trigonal space group R3̅m, with a = 9.074(1)-9.1699(2) Å, c = 53.353(1)-53.602(1) Å, and Z = 3. In comparison, Ca15LixZn75-x, x ≈ 19.07(2), crystallizes in the space group P63/mmc, with a ≈ 9.183(1) Å, c ≈ 45.191(5) Å), and Z = 2. Both structures are members of a large intergrowth family featuring slabs of dimers (D) and trimers (T) stacking along [001], with the sequences DTDDTDDTD for Ca12LixZn59-x and TDDDTDDD for Ca15LixZn75-x. Each dimer consists of two face-sharing Zn-centered hypho-icosahedra, and each trimer comprises a Li-centered icosahedron sandwiched by two hypho-icosahedra. This intergrowth family includes several known intermetallic structure types involving very electropositive metals, e.g., SrMg5.2, Ba2Li4.21Al4.79, and Sr9Li17.5Al25.5. Because of cluster defects and condensation, both Ca12LixZn59-x and Ca15LixZn75-x are electronically akin to close-packed metals, and their structural stabilities can be interpreted by a Hume-Rothery mechanism rather than the Zintl-Klemm concept.

  10. AC conductivity and structural properties of Mg-doped ZnO ceramic

    NASA Astrophysics Data System (ADS)

    Othman, Zayani Jaafar; Hafef, Olfa; Matoussi, Adel; Rossi, Francesca; Salviati, Giancarlo

    2015-11-01

    Undoped ZnO and Zn1- x Mg x O ceramic pellets were synthesized by the standard sintering method at the temperature of 1200 °C. The influence of Mg doping on the morphological, structural and electrical properties was studied. The scanning electron microscopy images revealed rough surface textured by grain boundaries and compacted grains having different shapes and sizes. Indeed, the X-ray diffraction reveals the alloying of hexagonal ZnMgO phase and the segregation of cubic MgO phase. The crystallite size, strain and stress were studied using Williamson-Hall (W-H) method. The results of mean particle size of Zn1- x Mg x O composites showed an inter-correlation with W-H analysis and Sherrer method. The electrical conductivity of the films was measured from 173 to 373 K in the frequency range of 0.1 Hz-1 MHz to identify the dominant conductivity mechanism. The DC conductivity is thermally activated by electron traps having activation energy of about 0.09 to 0.8 eV. The mechanisms of AC conductivity are controlled by the correlated barrier hopping model for the ZnO sample and the small polaron tunneling (SPT) model for Zn0.64Mg0.36O and Zn0.60Mg0.40O composites.

  11. Zn- and Mg- Containing Tricalcium Phosphates-Based Adjuvants for Cancer Immunotherapy

    NASA Astrophysics Data System (ADS)

    Wang, Xiupeng; Li, Xia; Onuma, Kazuo; Sogo, Yu; Ohno, Tadao; Ito, Atsuo

    2013-07-01

    Zn-, and Mg-containing tricalcium phosphates (TCPs) loaded with a hydrothermal extract of a human tubercle bacillus (HTB) were prepared by immersing Zn-TCP and Mg-TCP in HTB-containing supersaturated calcium phosphate solutions. The in vitro and in vivo immunogenic activities of the HTB-loaded Zn-, and Mg-TCPs (Zn-Ap-HTB and Mg-Ap-HTB, respectively) were evaluated as potential immunopotentiating adjuvants for cancer immunotherapy. The Zn-Ap-HTB and Mg-Ap-HTB adjuvants showed no obvious cytotoxicity and more effectively stimulated granulocyte-macrophage colony-stimulating factor (GM-CSF) secretion by macrophage-like cells than unprocessed HTB or HTB-loaded TCP (T-Ap-HTB) in vitro. Zn-Ap-HTB and Mg-Ap-HTB mixed with liquid-nitrogen-treated tumor tissue markedly inhibited the in vivo development of rechallenged Lewis lung carcinoma (LLC) cells compared with T-Ap-HTB and the unprocessed HTB mixed liquid-nitrogen-treated tumor tissue. Zn-Ap-HTB and Mg-Ap-HTB contributed to eliciting potent systemic antitumor immunity in vivo.

  12. Sr/Ca and Mg/Ca in Aragonitic Bivalves: Do They Record Temperature?

    NASA Astrophysics Data System (ADS)

    Gillikin, D. P.; Ulens, H.; Dehairs, F.; Baeyens, W.; Navez, J.; Andre, L.; Keppens, E.; Calmars Group,.

    2003-12-01

    The chemical or isotopic composition of calcareous skeletons have long been recognized as archives of past and present environmental conditions. Oxygen isotopes (d18O) of biogenic carbonates are a powerful proxy of SST, however, although usually dominated by SST, salinity (SSS) also significantly effects the oxygen isotopic signal recorded in the carbonate. This has led researchers to explore new proxies, which are independent of SSS. Generally, Sr/Ca and Mg/Ca of seawater remains unchanged above salinities of 10 and marine animals will commonly live in habitats that do not fluctuate below this salinity. To solve the issue of SSS complicating paleotemperature records, these "new" proxies must be at least as reliable as d18O. If an environmental control is dominant, the proxies should be reproducible between specimens growing under the same field conditions. Both Sr and Mg have been used as paleotemperature proxies in corals and foraminifera, whereas a fewer attempts have been made to use these proxies in bivalves. Some report a clear seasonal periodicity in Sr/Ca profiles of bivalves, which covaries with d18O (i.e., temperature), whereas others have found no clear periodicity. We test the robustness of these proxies by analyzing the shell material from three species of aragonitic clams from around the world using a LA-ICP-MS. Three individuals of M. mercenaria from North Carolina, USA, three individuals of Saxidomus giganteus from Washington, USA and one Arctica islandica from Norway have been analyzed. As expected, there is excellent reproducibility of d18O between specimens (both M. mercenaria and S. giganteus) indicating external environmental conditions control this proxy (i.e. SST and SSS). Preliminary data analysis show that Sr and Mg are not reproducible between specimens from the same site nor do they exhibit a clear seasonal cyclicity, indicating individual metabolic effects (i.e., vital effects) dominate the incorporation of these elements. A. islandica

  13. In vitro and in vivo corrosion measurements of Mg-6Zn alloys in the bile.

    PubMed

    Chen, Yigang; Yan, Jun; Wang, Zhigang; Yu, Song; Wang, Xiaohu; Yuan, Ziming; Zhang, Xiaonong; Zhao, Changli; Zheng, Qi

    2014-09-01

    Mg-6Zn alloy was studied as candidate biodegradable metallic implants for the common bile duct (CBD) in terms of its in vitro corrosion and in vivo corrosion. Electrochemical measurements, immersion tests and hydrogen evolution were performed in the bile and Hanks' solution to evaluate the in vitro degradation behavior of Mg-6Zn alloy. The results showed that the degradation rate and hydrogen evolution were higher when Mg-6Zn alloy immersed in the bile than in the Hanks' solution. The polarization resistance of the samples in the Hanks' solution was about 1.5 times to that in the bile. In the in vivo experiment, Mg-6Zn alloy stents were inserted in CBD of 42 rabbits, and CT scans, the value of total bilirubin (TB) and in vivo corrosion rate were determined. From the results of CT images and the fluctuations of TB values, it can be seen that the stent was degraded gradually in CBD. After 1 week post-implantation, the majority of the Mg-6Zn alloy sample remained in the CBD. Usually the required support time for CBD stent was approximately 7-10 days, thus the Mg-6Zn alloy stent was very close to the clinical requirement for CBD support materials. After three weeks, the residual weight of the Mg-6Zn alloy was only 9% of the original weight. The in vivo corrosion rate of Mg-6Zn alloy was ~0.107 mm·year(-1), which was much lower than that calculated in vitro (~0.72 mm·year(-1) by electrochemical test). Based on our research, there is promising for the Mg-6Zn alloy in CBD applications.

  14. Excellent capability in degrading azo dyes by MgZn-based metallic glass powders.

    PubMed

    Wang, Jun-Qiang; Liu, Yan-Hui; Chen, Ming-Wei; Louzguine-Luzgin, Dmitri V; Inoue, Akihisa; Perepezko, John H

    2012-01-01

    The lack of new functional applications for metallic glasses hampers further development of these fascinating materials. In this letter, we report for the first time that the MgZn-based metallic glass powders have excellent functional ability in degrading azo dyes which are typical organic water pollutants. Their azo dye degradation efficiency is about 1000 times higher than that of commercial crystalline Fe powders, and 20 times higher than the Mg-Zn alloy crystalline counterparts. The high Zn content in the amorphous Mg-based alloy enables a greater corrosion resistance in water and higher reaction efficiency with azo dye compared to crystalline Mg. Even under complex environmental conditions, the MgZn-based metallic glass powders retain high reaction efficiency. Our work opens up a new opportunity for functional applications of metallic glasses.

  15. Excellent capability in degrading azo dyes by MgZn-based metallic glass powders

    PubMed Central

    Wang, Jun-Qiang; Liu, Yan-Hui; Chen, Ming-Wei; Louzguine-Luzgin, Dmitri V.; Inoue, Akihisa; Perepezko, John H.

    2012-01-01

    The lack of new functional applications for metallic glasses hampers further development of these fascinating materials. In this letter, we report for the first time that the MgZn-based metallic glass powders have excellent functional ability in degrading azo dyes which are typical organic water pollutants. Their azo dye degradation efficiency is about 1000 times higher than that of commercial crystalline Fe powders, and 20 times higher than the Mg-Zn alloy crystalline counterparts. The high Zn content in the amorphous Mg-based alloy enables a greater corrosion resistance in water and higher reaction efficiency with azo dye compared to crystalline Mg. Even under complex environmental conditions, the MgZn-based metallic glass powders retain high reaction efficiency. Our work opens up a new opportunity for functional applications of metallic glasses. PMID:22639726

  16. Room temperature ferromagnetism in Mg-doped ZnO nanoparticles

    SciTech Connect

    Singh, Jaspal Vashihth, A.; Gill, Pritampal Singh; Verma, N. K.

    2015-06-24

    Zn{sub 1-x}Mg{sub x}O (x = 0, 0,10) nanoparticles were successfully synthesized using sol-gel method. X-ray diffraction (XRD) confirms that the synthesized nanoparticles possess wurtzite phase having hexagonal structure. Morphological analysis was carried out using transmission electron microscopy (TEM) which depicts the spherical morphology of ZnO nanoparticles. Energy dispersive spectroscopy (EDS) showed the presence of Mg in ZnO nanoparticles. Electron spin resonance (ESR) signal was found to be decreasing with increasing of Mg-doping concentration. The room temperature ferromagnetism was observed in undoped and Mg-doped ZnO nanoparticles. The increase of Mg-doping concentration resulted in decrease of saturation magnetization value which could be attributed to decrease of oxygen vacancies present in host nanoparticles.

  17. Determination of the spontaneous polarization of wurtzite (Mg,Zn)O

    SciTech Connect

    Stölzel, Marko Müller, Alexander; Benndorf, Gabriele; Lorenz, Michael; Grundmann, Marius; Patzig, Christian; Höche, Thomas

    2014-05-12

    We report on the experimental determination of the spontaneous polarization of wurtzite-(Mg,Zn)O by examination of the recombination dynamics of polar ZnO/(Mg,Zn)O quantum wells (QWs). The thickness-dependent decay time of the unscreened single-exciton states inside the QWs was modeled by a self-consistent solution of Schrödinger- and Poisson-equation to deduce the total polarization across the QW for different Mg-contents inside the barriers. By the separation of the piezoelectric components of the polarization, a linear increase in spontaneous polarization with increasing Mg-content x of P/x = (0.151 ± 0.015) C/m{sup 2} was determined for Mg{sub x} Zn{sub 1−x} O.

  18. Segregation of Mg in Zn1-xMgxO single crystals grown from the melt

    NASA Astrophysics Data System (ADS)

    Schulz, Detlev; Bertram, Rainer; Klimm, Detlef; Schulz, Tobias; Thiede, Elvira

    2011-11-01

    Solid solutions between zinc oxide and magnesium oxide containing up to 4 at.% Mg were grown from the melt using a modified Bridgman technique. Chemical analysis (ICP-OES) and photoluminescence (PL) measurements revealed that the Mg concentration in the melt is larger compared with the starting material. This observation contradicts the commonly accepted assumption, that the ZnO-MgO phase diagram is of eutectic type. Peritectic melting of Zn-rich Zn1-xMgxO can explain the new experimental results, and a new ZnO-MgO phase diagram is proposed. Furthermore a distribution coefficient for Mg of keff=1.32…1.4 has been determined.

  19. Thermally stimulated luminescence of Mg-doped ZnO Nanophosphors

    NASA Astrophysics Data System (ADS)

    Cruz-Vázquez, C.; Borbón-Nuñez, H. A.; Bernal, R.; Gaspar-Armenta, J. A.; Castaño, V. M.

    2014-05-01

    Nanosized ZnO:Mg phosphors were synthesized through a controlled chemical reaction. X-ray diffraction patterns confirmed that Mg entered in a substitutive way in Zn sites. To investigate their thermoluminescence (TL) properties, some samples were exposed to beta-particle irradiation. The results reported here show that Mg doping improves ZnO TL features that are important for TL dosimetry applications, such as the shape of the glow curve, the temperature at which the maximum TL intensity is observed, and the TL fading and reproducibility. No saturation clues of the TL response as a function of the dose is observed for doses below 1600 Gy.

  20. Microcavities with distributed Bragg reflectors based on ZnSe/MgS superlattice grown by MOVPE

    NASA Astrophysics Data System (ADS)

    Tawara, T.; Yoshida, H.; Yogo, T.; Tanaka, S.; Suemune, I.

    2000-12-01

    Monolithic II-VI semiconductor microcavities for the blue-green region grown by metal-organic vapor-phase epitaxy have been demonstrated. ZnSe/MgS-superlattice (ZnSe/MgS-SL) layers were used for the distributed Bragg reflectors (DBRs). The DBR with only 5 periods showed the high reflectivity of 92% at the wavelength of 510 nm due to the large difference of refractive indices between ZnSe and MgS layers. In a monolithic II-VI microcavity structure based on these DBRs, a clear cavity resonance mode was observed in the blue-green region for the first time.

  1. Insulating NiO enhanced MgZnO-based single-barrier 340 nm photodetector

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Gu, Dawei; Shen, Linjiang

    2017-10-01

    Combining pulsed laser deposition and thermal oxidation techniques, an enhanced MgZnO-based photodetector was achieved by inserting an insulating NiO layer between Au electrode and the Mg0.21Zn0.79O active layer. Bias voltage dependent spectral response of the Au/NiO/MgZnO/In photodetector was investigated systematically and it exhibited a peak response of 340 nm with a cutoff wavelength at 355 nm. Under reverse bias, a negative differential resistance feature was observed in the dark and light current-voltage characteristic curves.

  2. Room temperature fabrication of dielectric Bragg reflectors composed of a CaF2/ZnS multilayered coating.

    PubMed

    Muallem, Merav; Palatnik, Alex; Nessim, Gilbert D; Tischler, Yaakov R

    2015-01-14

    We describe the design, fabrication, and characterization of mechanically stable, reproducible, and highly reflecting distributed Bragg reflectors (DBR) composed of thermally evaporated thin films of calcium fluoride (CaF2) and zinc sulfide (ZnS). CaF2 and ZnS were chosen as the low and high refractive index components of the multilayer DBR structures, with n = 1.43 and n = 2.38 respectively, because neither material requires substrate heating during the deposition process in order to produce optical quality thin films. DBRs consisting of seven pairs of CaF2 and ZnS layers, were fabricated with thicknesses of 96 and 58 nm, respectively, as characterized by high-resolution scanning electron microscopy (HR-SEM), and exhibited a center wavelength of λc = 550 nm and peak reflectance exceeding 99%. The layers showed good adhesion to each other and to the glass substrate, resulting in mechanically stable DBR coatings. Complete optical microcavities consisting of two such DBR coatings and a CaF2 spacer layer between them could be fabricated in a single deposition run. Optically, these structures exhibited a resonator quality factor of Q > 160. When a CaF2/ZnS DBR was grown, without heating the substrate during deposition, on top of a thin film containing the fluorescent dye Rhodamine 6G, the fluorescence intensity showed no degradation compared to an uncoated film, in contrast to a MgF2/ZnS DBR coating grown with substrate heating which showed a 92% reduction in signal. The ability to fabricate optical quality CaF2/ZnS DBRs without substrate heating, as introduced here, can therefore enable formation of low-loss high-reflectivity coatings on top of more delicate heat-sensitive materials such as organics and other nanostructured emitters, and hence facilitate the development of nanoemitter-based microcavity device applications.

  3. Multi-terminal Two-color ZnCdSe/ZnCdMgSe Based Quantum-well Infrared Photodetector

    NASA Astrophysics Data System (ADS)

    Kaya, Yasin; Ravikumar, Arvind; Chen, Guopeng; Tamargo, Maria C.; Shen, Aidong; Gmachl, Claire

    Target recognition and identification applications benefits from two-color infrared (IR) detectors in the mid and long-wavelength IR regions. Currently, InGaAs/AlGaAs and GaAs/AlGaAs multiple quantum wells (QWs) grown on GaAs substrate are the most commonly used two-color QW IR photodetectors (QWIPs). However, the lattice-mismatch and the buildup of strain limit the number of QWs that can be grown, in turn increasing the dark current noise, and limiting the device detectivity.In this work, we report on two-color QWIPs based on the large conduction band offset (~1.12ev) ZnCdSe/ZnCdMgSe material system lattice matched to InP. QWIPs were designed based on a bound to quasi-bound transition, centered at 4 μm and 7 μm and each QW is repeated 50 times to eliminate the high dark current and a contact layer is inserted between the two stacks of QWs for independent electrical contacts. Wafers are processed into two step rectangular mesas by lithography and wet etching. Experiments showed absorption spectra centered at 4.9 μm and 7.6 μm at 80 K and the full width at half maximums were Δλ / λ = 21 % and Δλ / λ = 23 % , respectively. Current work studies the Johnson and the background noise limited detectivities of these QWIPs. Current address: School of Earth, Energy and Environmental Sciences, Stanford, CA 94305, USA.

  4. Impact of strain on electronic defects in (Mg,Zn)O thin films

    SciTech Connect

    Schmidt, Florian Müller, Stefan; Wenckstern, Holger von; Benndorf, Gabriele; Pickenhain, Rainer; Grundmann, Marius

    2014-09-14

    We have investigated the impact of strain on the incorporation and the properties of extended and point defects in (Mg,Zn)O thin films by means of photoluminescence, X-ray diffraction, deep-level transient spectroscopy (DLTS), and deep-level optical spectroscopy. The recombination line Y₂, previously detected in ZnO thin films grown on an Al-doped ZnO buffer layer and attributed to tensile strain, was exclusively found in (Mg,Zn)O samples being under tensile strain and is absent in relaxed or compressively strained thin films. Furthermore a structural defect E3´ can be detected via DLTS measurements and is only incorporated in tensile strained samples. Finally it is shown that the omnipresent deep-level E3 in ZnO can only be optically recharged in relaxed ZnO samples.

  5. Growth of new ternary intermetallic phases from Ca/Zn eutectic flux

    SciTech Connect

    Stojanovic, Milorad Latturner, Susan E.

    2007-03-15

    The eutectic 7.3:2.7 molar ratio mixture of calcium and zinc metal melts at 394 deg. C and was explored as a solvent for the growth of new intermetallic phases for potential use as hydrogen storage materials. The reaction of nickel in this molten mixture produces two new phases-the CaCu{sub 5}-related structure CaNi{sub 2}Zn{sub 3} (P6/mmm, a=8.9814(5) A, c=4.0665(5) A) and a new cubic structure Ca{sub 21}Ni{sub 2}Zn{sub 36} (Fd-3m, a=21.5051(4) A). Palladium-containing reactions produced CaPd{sub 0.85}Zn{sub 1.15} with the orthorhombic TiNiSi structure type (Pnma, a=7.1728(9) A, b=4.3949(5) A, c=7.7430(9) A). Reactions of platinum in the Ca/Zn mixture produce Ca{sub 6}Pt{sub 3}Zn{sub 5}, with an orthorhombic structure related to that of W{sub 3}CoB{sub 3} (Pmmn, a=13.7339(9) A, b=4.3907(3) A, c=10.7894(7) A). - Graphical abstract: The calcium/zinc eutectic is a useful synthesis medium for the growth of new intermetallic phases. Addition of group 10 transition metals to this flux produces ternary phases CaNi{sub 2}Zn{sub 3}, Ca{sub 21}Ni{sub 2}Zn{sub 36}, CaPd{sub 0.85}Zn{sub 1.15}, and Ca{sub 6}Pt{sub 3}Zn{sub 5}. The nickel-centered zinc icosahedron surrounded by a pentagonal dodecahedron of calcium atoms is found in Ca{sub 21}Ni{sub 2}Zn{sub 36}.

  6. MgZnO/ZnO Two-Dimensional Electron Gas Photodetectors Fabricated by Radio Frequency Sputtering.

    PubMed

    Hwang, J D; Yang, C C; Chu, C M

    2017-07-19

    MgZnO/ZnO two-dimensional electron gas (2DEG) structures with ZnO annealed at various temperatures (600-900 °C) and photodetectors (PDs) with and without a 2DEG structure were fabricated using a radio frequency magnetron sputtering system. It was found that the carrier concentration and mobility increase with the annealing temperature owing to the improved crystalline in ZnO; however, high-temperature (800 °C or higher) annealing can degrade the crystalline of the ZnO layer. Hall measurements showed that compared with that of bulk ZnO, the sheet carrier concentration of the 2DEG sample increased from 1.3 × 10(13) to 1.2 × 10(14) cm(-2), and the mobility was enhanced from 5.1 to 17.5 cm(2)/V s. This is because the channel layer is the total thickness (300 nm) in bulk ZnO, whereas the carriers are confined to a 45 nm region beneath the MgZO layer in the 2DEG sample, confirming the 2DEG behavior at the MgZnO/ZnO interface. The PDs with 2DEG structures demonstrate a higher ultraviolet (UV) response and a UV/visible rejection ratio that is six times larger than that of the PDs without a 2DEG structure. The 2DEG structure also induces a photocurrent gain, which results in a 240% quantum efficiency for the 310 nm incident wavelength. The related mechanism is elucidated with a band diagram.

  7. Atomic Structure of Ca40+xMg25Cu35-x Metallic Glasses (Postprint)

    DTIC Science & Technology

    2012-06-21

    while solidification of Ca45Mg25Cu30 and Ca50Mg25Cu25 alloys forms three equally probable crystal phases, CaMg2 Cu2Mg and CaCu . 5,6 CaMg2 is a...The CaCu phase has a primitive crystal structure (space group P21/m, space group number 11) with lattice parameters a¼ 19.47 Å, b¼ 4.271 Å, c¼ 5.880...Cu-centered coordination polyhedron in the CaCu phase is also common in the studied amorphous structures. This (0,3,6,0) Cu-centered cluster is

  8. Interdiffusion and impurity diffusion in polycrystalline Mg solid solution with Al or Zn

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Sohn, Yong Ho

    2014-01-01

    Interdiffusion and impurity diffusion in Mg binary solid solutions, Mg(Al) and Mg(Zn) were investigated at temperatures ranging from 623 to 723 K. Interdiffusion coef cients were determined via the Boltzmann Matano Method using solid-to-solid diffusion couples assembled with polycrystalline Mg and Mg(Al) or Mg(Zn) solid solutions. In addition, the Hall method was employed to extrapolate the impurity diffusion coef cients of Al and Zn in pure polycrystalline Mg. For all diffusion couples, electron micro-probe analysis was utilized for the measurement of concentration pro les. The interdiffusion coef cient in Mg(Zn) was higher than that of Mg(Al) by an order of magnitude. Additionally, the interdiffusion coef cient increased signi cantly as a function of Al content in Mg(Al) solid solution, but very little with Zn content in Mg(Zn) solid solution. The activation energy and pre-exponential factor for the average effective interdiffusion coef cient in Mg(Al) solid solution were determined to be 186.8 ( 0.9) kJ/mol and 7.69 x 10-1 ( 1.80 x 10-1) m2/s, respectively, while those determined for Mg(Zn) solid solution were 139.5 ( 4.0) kJ/mol and 1.48 x 10-3 ( 1.13 x 10-3) m2/s. In Mg, the Zn impurity diffusion coef cient was an order of magnitude higher than the Al impurity diffusion coef cient. The activation energy and pre-exponential factor for diffusion of Al impurity in Mg were determined to be 139.3 ( 14.8) kJ/mol and 6.25 x 10-5 ( 5.37 x 10-4) m2/s, respectively, while those for diffusion of Zn impurity in Mg were determined to be 118.6 ( 6.3) kJ/mol and 2.90 x 10-5 ( 4.41 x 10-5) m2/s.

  9. Reconstructing past seawater Mg/Ca and Sr/Ca from mid-ocean ridge flank calcium carbonate veins.

    PubMed

    Coggon, Rosalind M; Teagle, Damon A H; Smith-Duque, Christopher E; Alt, Jeffrey C; Cooper, Matthew J

    2010-02-26

    Proxies for past seawater chemistry, such as Mg/Ca and Sr/Ca ratios, provide a record of the dynamic exchanges of elements between the solid Earth, the atmosphere, and the hydrosphere and the evolving influence of life. We estimated past oceanic Mg/Ca and Sr/Ca ratios from suites of 1.6- to 170-million-year-old calcium carbonate veins that had precipitated from seawater-derived fluids in ocean ridge flank basalts. Our data indicate that before the Neogene, oceanic Mg/Ca and Sr/Ca ratios were lower than in the modern ocean. Decreased ocean spreading since the Cretaceous and the resulting slow reduction in ocean crustal hydrothermal exchange throughout the early Tertiary may explain the recent rise in these ratios.

  10. The in vitro biocompatibility and macrophage phagocytosis of Mg17Al12 phase in Mg-Al-Zn alloys.

    PubMed

    Liu, Chen; He, Peng; Wan, Peng; Li, Mei; Wang, Kehong; Tan, Lili; Zhang, Yu; Yang, Ke

    2015-07-01

    Mg alloys are gaining interest for applications as biodegradable medical implant, including Mg-Al-Zn series alloys with good combination of mechanical properties and reasonable corrosion resistance. However, whether the existence of second phase particles in the alloys exerts influence on the biocompatibility is still not clear. A deeper understanding of how the particles regulate specific biological responses is becoming a crucial requirement for their subsequent biomedical application. In this work, the in vitro biocompatibility of Mg17Al12 as a common second phase in biodegradable Mg-Al-Zn alloys was investigated via hemolysis, cytotoxicity, cell proliferation, and cell adhesion tests. Moreover, osteogenic differentiation was evaluated by the extracellular matrix mineralization assay. The Mg17Al12 particles were also prepared to simulate the real situation of second phase in the in vivo environment in order to estimate the cellular response in macrophages to the Mg17Al12 particles. The experimental results indicated that no hemolysis was found and an excellent cytocompatibility was also proved for the Mg17Al12 second phase when co-cultured with L929 cells, MC3T3-E1 cells and BMSCs. Macrophage phagocytosis co-culture test revealed that Mg17Al12 particles exerted no harmful effect on RAW264.7 macrophages and could be phagocytized by the RAW264.7 cells. Furthermore, the possible inflammatory reaction and metabolic way for Mg17Al12 phase were also discussed in detail.

  11. Kinetics of rapid Ca2+ release by sarcoplasmic reticulum. Effects of Ca2+, Mg2+, and adenine nucleotides

    SciTech Connect

    Meissner, G.; Darling, E.; Eveleth, J.

    1986-01-14

    A radioisotope flux-rapid-quench-Millipore filtration method is described for determining the effects of Ca2+, adenine nucleotides, and Mg2+ on the Ca2+ release behaviour of heavy sarcoplasmic reticulum (SR) vesicles. Rapid 45Ca2+ efflux from passively loaded vesicles was blocked by the addition of Mg2+ and ruthenium red. At pH 7 and 10(-9) M Ca2+, vesicles released 45Ca2+ with a low rate (k = 0.1 s-1). An increase in external Ca2+ concentration to 4 microM or the addition of 5 mM ATP or the ATP analogue adenosine 5'-(beta,gamma-methylenetriphosphate) (AMP-PCP) resulted in intermediate 45Ca2+ release rates. The maximal release rate was observed in media containing 4 microM Ca2+ and 5 mM AMP-PCP and had a first-order rate constant of 30-100 s-1. Mg2+ partially inhibited Ca2+- and nucleotide-induced 45Ca2+ efflux. In the absence of AMP-PCP, 45Ca2+ release was fully inhibited at 5 mM Mg2+ or 5 mM Ca2+. The composition of the release media was systematically varied, and the flux data were expressed in the form of Hill equations. The apparent n values of activation of Ca2+ release by ATP and AMP-PCP were 1.6-1.9. The Hill coefficient of Ca2+ activation (n = 0.8-2.1) was dependent on nucleotide and Mg2+ concentrations, whereas the one of Mg2+ inhibition (n = 1.1-1.6) varied with external Ca2+ concentration. These results suggest that heavy SR vesicles contain a Ca2+ release channel which is capable of conducting Ca2+ at rates comparable with those found in intact muscle. Ca2+, AMP-PCP (ATP), and Mg2+ appear to act at noninteracting or interacting sites of the channel.

  12. Luminescence enhancement of CaZnGe2O6:Tb3+ afterglow phosphors synthesized using ZnO nanopowders

    SciTech Connect

    Woo, Boon K.; Luo, Zhiping; Li, Yang; Singh, Surinder P.; Joly, Alan G.; Hossu, Marius; Liu, Zhongxin; Chen, Wei

    2011-06-01

    CaZnGe2O6:Tb3+ afterglow phosphors were prepared by solid state reaction using organic coated ZnO 30 nanopowders and their photoluminescence, X-ray luminescence and afterglow properties were investigated. The CaZnGe2O6:Tb3+ samples emit a green luminescence at 548 nm attributed to the 5D4-7F5 transition of Tb3+. It was observed that the replacement of bulk ZnO by ZnO nanopowder in the sample synthesis increases the luminescence intensity. By adjusting the mass ratio of bulk ZnO to nanopowder ZnO, the photoluminescence intensity, X-ray luminescence intensity, and afterglow efficiency are improved. The optimized sample made with a 0.71 ratio of nano ZnO to bulk ZnO has a factor of four enhancement in X-ray luminescence, photoluminescence and afterglow intensities in comparison with the sample made with 100% bulk ZnO.

  13. Corrosion Behavior and Surface Modification of Mg-Zn Implant Alloys

    NASA Astrophysics Data System (ADS)

    Ghayad, I. M.; Maamoun, M. A.; Metwally, W. A.; El-Baradie, Z. M.; Abdel-Azim, A. N.

    2016-10-01

    In this study, Mg-Zn alloys (1-4 wt.% Zn) were fabricated with high-purity raw materials using a clean melting process (fluxless method) and a protective atmosphere of CO2 + 0.4 SF6. The as-cast microstructures of the investigated alloys were characterized by optical and scanning electron microscopes, EDS and XRD. Corrosion properties of the prepared alloys were examined in simulated body fluid by electrochemical techniques and immersion test (hydrogen evolution method). Surface modification of the prepared alloys was performed using micro-arc oxidation (MAO) treatment and hydroxyapatite (HA) coating. Microstructure observation revealed that Zn was completely dissolved in the α-Mg matrix up to 2 wt.%. Higher Zn content led to a reduction in the grain size and the development of a second phase (MgZn2). Corrosion testing results revealed that Mg-1,2,3 wt.% Zn have almost the same degradation rate, whereas Mg-4Zn has the highest degradation rate. HA coating on MAO-treated magnesium alloys formed a dense and compact layer on the alloy surface, which had largely improved surface properties and enhanced corrosion resistance of the prepared alloys.

  14. Structural properties and spatial ordering in multilayered ZnMgTe/ZnSe type-II quantum dot structures

    SciTech Connect

    Manna, U.; Noyan, I. C.; Neumark, G. F.; Zhang, Q.; Moug, R.; Salakhutdinov, I. F.; Dunn, K. A.; Novak, S. W.; Tamargo, M. C.; Kuskovsky, I. L.

    2012-02-01

    We report the structural properties and spatial ordering of multilayer ZnMgTe quantum dots (QDs) embedded in ZnSe, where sub-monolayer quantities of Mg were introduced periodically during growth in order to reduce the valence band offset of ZnTe QDs. The periodicity, period dispersion, individual layer thickness, and the composition of the multilayer structures were determined by comparing the experimental high resolution x-ray diffraction (HRXRD) spectra to simulated ones for the allowed (004) and quasi-forbidden (002) reflections in combination with transmission electron microscopy (TEM) results. Secondary ion mass spectroscopy (SIMS) profiles confirmed the incorporation of Mg inside the QD layers, and the HRXRD analysis revealed that there is approximately 32% Mg in the ZnMgTe QDs. The presence of Mg contributes to higher scattering intensity of the HRXRD, leading to the observation of higher order superlattice peaks in both the (004) and (002) reflections. The distribution of scattered intensity in the reciprocal space map (RSM) shows that the diffuse scattered intensity is elongated along the q{sub x} axis, indicating a vertical correlation of the dots, which is found to be less defined for the sample with larger periodicity. The diffuse scattered intensity is also found to be weakly correlated along the q{sub z} direction indicating a weak lateral correlation of the dots.

  15. Surface and cut-edge corrosion behavior of Zn-Mg-Al alloy-coated steel sheets as a function of the alloy coating microstructure

    NASA Astrophysics Data System (ADS)

    Oh, Min-Suk; Kim, Sang-Heon; Kim, Jong-Sang; Lee, Jae-Won; Shon, Je-Ha; Jin, Young-Sool

    2016-01-01

    The effects of Mg and Al content on the microstructure and corrosion resistance of hot-dip Zn-Mg-Al alloycoated steel sheets were investigated. Pure Zn and Zn-based alloy coatings containing Mg (0-5 wt%) and Al (0.2-55 wt%) were produced by a hot-dip galvanizing method. Mg and Al addition induced formation of intermetallic microstructures, like primary Zn, Zn/MgZn2 binary eutectic, dendric Zn/Al eutectoid, and Zn/Al/MgZn2/ternary eutectic structures in the coating layer. MgZn2-related structures (Zn/MgZn2, Zn/Al/MgZn2, MgZn2) played an important role in increasing the corrosion resistance of Zn-Mg-Al alloy-coated steel sheets. Zn-3%Mg-2.5%Al coating layer containing a large volume of lamellar-shaped Zn/MgZn2 binary eutectic structures showed the best cut-edge corrosion resistance. The analysis indicated that Mg dissolved from MgZn2 in the early stage of corrosion and migrated to the cathodic region of steel-exposed cut-edge area to form dense and ordered protective corrosion products, leading to prolonged cathodic protection of Zn-Mg-Al alloy-coated steel sheets.

  16. Adsorption and desorption of Zn(II) and Cu(II) on Ca- alginate immobilized activated rice bran

    NASA Astrophysics Data System (ADS)

    Suratman, A.; Kamalia, N. Z.; Kusumawati, W. A.

    2016-02-01

    Ca-alginate immobilized activated rice bran has been used for adsorption of Zn(II) and Cu(II) from aqueous solution. The effect of the pH, kinetics model, adsorption isotherm and desorption on the adsorption performance was investigated. Activated rice bran was immobilized by the entrapment in alginate beads. The adsorption strength of Ca-alginate immobilized activated rice bran was compared to Ca-alginate and non-immobilized activated rice bran. The concentrations of adsorbed ions were analyzed using Atomic Absorption Spectrophotometer (AAS). The result showed that pH of 4.0 and the contact time of 120 min are the optimum condition for adsorption of Zn(II) and Cu(II). The adsorption kinetic of Zn(II) and Cu(II) followed the pseudo-second-order model with adsorption rate constant 4.9 x 10-2 and 3.14 g.mg-1.min-1, respectively. The both adsorption processes obeyed Langmuir isotherm with adsorption capacity of 2.03 and 2.42 mg.g-1 of adsorbent, respectively. The strength of Zn adsorption on Ca-alginate immobilized activated rice bran (86.63%) was more effective compared to Ca-alginate beads (60.96%) and activated rice bran (43.85%). The strength of Cu adsorption was 80.00%, 61.50% and 22.10%, respectively. The desorption of Zn(II) and Cu(II) showed that recovery percentage of the adsorption was 76.56% and 57.80% with the condition of using HCl 0.1 M as desorption agent for 1 hour.

  17. Superconducting tunnel junctions on MgB2 using MgO and CaF2 as a barrier

    NASA Astrophysics Data System (ADS)

    Sakoda, Masahito; Aibara, Masato; Mede, Kazuya; Kikuchi, Motoyuki; Naito, Michio

    2016-11-01

    We report the fabrication of superconducting tunnel junctions, both of superconductor-insulator-normal metal (SIN) and superconductor-insulator-superconductor (SIS), on MgB2 using MgO and CaF2 as a barrier. The SIN junctions fabricated using an MgO barrier showed excellent quasi-particle characteristics, including a large superconducting gap (Δ) of 2.5-3 meV and a low zero-bias conductance. We have also fabricated SIS junctions with an MgO barrier, but the quasi-particle characteristics of the SIS junctions are not as good as those of the SIN junctions, namely a reduced superconducting gap and a high zero-bias conductance. It appears that top MgB2 electrodes do not grow well on an MgO barrier, which is also suggested from in-situ RHEED observation. The SIN junctions fabricated using a CaF2 barrier showed less sharp quasi-particle characteristics than using an MgO barrier. However, the SIS junctions using a CaF2 barrier showed a fairly large IcRN value at 4.2 K over 1 mV and also exhibited finite Josephson current up to almost the film's Tc (∼30 K). The RHEED observation revealed that top MgB2 electrodes grow well on a CaF2 barrier.

  18. Biological activity evaluation of magnesium fluoride coated Mg-Zn-Zr alloy in vivo.

    PubMed

    Jiang, Hongfeng; Wang, Jingbo; Chen, Minfang; Liu, Debao

    2017-06-01

    To explore the biodegradable characteristics and biological properties, which could promote new bone formation, of MgF2 coated magnesium alloy (Mg-3wt%Zn-0.5wt%Zr) in rabbits. Magnesium alloy with MgF2 coating was made and the MgF2/Mg-Zn-Zr was implanted in the femoral condyle of rabbits. Twelve healthy adult Japanese white rabbits in weight of 2.8-3.2kg were averagely divided into A(Mg-Zn-Zr) group and B(MgF2/MgZn-Zr) group. Indexes such as microstructural evolution, SEM scan, X-ray, Micro-CT and mechanical properties were observed and detected at 1th day, 2th, 4th, 8th, 12th, 24th week after implantation. Low-density regions occurred around the cancellous bone, and the regions gradually expanded during the 12weeks after implantation. The implant was gradually absorbed from 12 to 24weeks. The density of surrounding cancellous bone increased compared with the 12th week data. The degradation rate of B group was lower than that of A group (P<0.01), while the density of the surrounding cancellous bone increased more evenly. In B group, SEM images after 12weeks showed the rich bone tissues on the alloy surface that were attached by active fibers. Micro-CT also presented alloy residue potholes on the surfaces of alloy combinated with bone tissues. Additionally, the trabecular bone had relatively integrated structures with surrounding cavities. MgF2 can effectively decrease the degradation rate of Mg-Zn-Zr in vivo. Mg-Zn-Zr coated with MgF2 can effectively inhibit the corrosion, and delay the release of magnesium ions. The biological properties of the coating itself presented good biocompatibility and bioactivity. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Structural and photoluminescence properties of Mg substituted ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Mallika, A. N.; Ramachandra Reddy, A.; Sowri Babu, K.; Sujatha, Ch.; Venugopal Reddy, K.

    2014-03-01

    This paper reports on structural and optical properties of Mg doped ZnO nanoparticles prepared through sol-gel method using polyvinyl alcohol as chelating agent. X-ray diffractometer (XRD), Field Emission Scanning Electron Microscope (FE-SEM), UV-Vis (UV-Vis), Fourier Transform Infrared (FTIR) and Photoluminescence (PL) spectrophotometers were employed to study the structural and optical properties. XRD and FE-SEM results demonstrated that particle size of ZnO decreased with increase in Mg concentrations. It was observed that the absorption spectrum of ZnO blue shifted as the Mg concentration enhanced from 1 mol.% to 5 mol.%, presumably due to reduction in particle size. It was found that MgO secondary phase was not formed even above the solid solubility limit of Mg in ZnO. ZnO nanoparticles exhibited an intense and strong UV emission peak at 396 nm and this peak is attributed to the electron transition from the localized level slightly below conduction band to the valence band. The position of this emission peak remained same for all concentrations of Mg in ZnO.

  20. Identification and characteristics of ZnO/MgO core-shell nanowires

    SciTech Connect

    Yang, S. Wang, L.; Wang, Y.; Li, L.; Wang, T.; Jiang, Z.

    2015-03-15

    In this paper, ZnO/MgO core-shell nanowires are synthesized based on a one-step chemical vapor deposition (CVD) method. The scanning electron microscopy (SEM) images of core-shell nanowires indicate that Mg addition has little influence on the morphology of the synthesizing products. High crystalline quality ZnO/MgO core-shell nanowires instead of ZnMgO ternary compounds are identified by X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM) images, selected area electron diffraction (SAED) pattern and photoluminescence (PL) spectra. The experimental results show that the ultraviolet (UV) emission of these samples with MgO shell is 12 times higher than that of the corresponding bare ZnO nanowires, and the suppression of the green emission is only 1/45 of the bare ZnO nanowires. It is also found that PL properties are proportional to Mg ratio. The UV emission enhancement and green emission suppression are due to the passivation of surface defects and the improvement of ZnO crystalline quality. The results are very useful for the development of optical devices based on nanowires.

  1. Review: the effects of secular variation in seawater Mg/Ca on marine biocalcification

    NASA Astrophysics Data System (ADS)

    Ries, J. B.

    2009-07-01

    Synchronized transitions in the polymorph mineralogy of the major reef-building and sediment-producing calcareous marine organisms and abiotic CaCO3 precipitates (ooids, marine cements) throughout Phanerozoic time is believed to have been caused by tectonically-induced variations in seawater molar Mg/Ca (>2="aragonite seas"; <2="calcite seas"). Here, I review a series of experiments in which extant calcifying taxa were reared in experimental seawater formulated over the range of mMg/Ca ratios (1.0 to 5.2) that occurred throughout their geologic history. Aragonite-secreting bryopsidalean algae and scleractinian corals and calcite-secreting coccolithophores exhibited higher rates of calcification and growth in the experimental seawaters that favored their skeletal mineral. These results support the assertion that seawater Mg/Ca played an important role in determining which hypercalcifying marine organisms were the major reef-builders and sediment-producers throughout Earth history. The observation that primary production increased along with calcification in mineralogically-favorable seawater is consistent with the hypothesis that calcification promotes photosynthesis within autotrophs through the liberation of CO2. The Mg/Ca ratio of calcite secreted by the coccolithophores, coralline algae and reef-dwelling animals (crustacea, urchins, calcareous tube worms) declined with reductions in seawater Mg/Ca. Calcifying microbial biofilms varied their mineral polymorph with seawater Mg/Ca (mMg/Ca<2=low Mg calc; mMg/Ca>2=arag+high Mg calc), suggesting a nearly abiotic mode of calcification. These results indicate that biomineralogical control can be partially overridden by ambient seawater Mg/Ca and suggests that modern high Mg calcite organisms probably secreted low Mg calcite in calcite seas of the past. Notably, Mg fractionation in autotrophic organisms was more strongly influenced by changes in seawater Mg/Ca, a probable consequence of them inducing a less controlled

  2. 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

  3. Synthesis, characterization and antibacterial property of ZnO:Mg nanoparticles

    NASA Astrophysics Data System (ADS)

    Kompany, A.; Madahi, P.; Shahtahmasbi, N.; Mashreghi, M.

    2012-09-01

    Sol-gel method was successfully used for the synthesis of ZnO nanoparticles (NPs) doped with different concentrations of Mg and the structural, optical and antibacterial properties of the nanoparticles were studied. The synthesized ZnO:Mg powders were characterized using x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transformation Infrared (FTIR) and UV-Vis spectroscopy. It was revealed that the samples have hexagonal Wurtzite structure, and the phase segregation takes place for 15% Mg content. TEM images show that the average size of the particles is about 50 nm. Also, the antibacterial activities of the nanoparticles were tested against Escherichia coli (Gram negative) cultures. ZnO:Mg nanofluid showed good antibacterial activity which increases with the increase of NPs concentration, and decreases slightly with the amount of Mg.

  4. Effect of co substitution of Mg and Zn on electromagnetic properties of NiCuZn ferrites

    NASA Astrophysics Data System (ADS)

    Sujatha, Ch.; Reddy, K. Venugopal; Babu, K. Sowri; Reddy, A. Rama Chandra; Suresh, M. Buchi; Rao, K. H.

    2013-07-01

    Ni0.5-2xMgxCu0.05Zn0.45+xFe2O4 (x=0, 0.04, 0.08, 0.12, and 0.16) ferrite samples were prepared through sol-gel method using polyvinyl alcohol as a chelating agent. Structural, magnetic, dielectric and electrical properties of the sintered samples were investigated using the characterisation techniques such as X-ray Diffractometer, Vibration sample magnetometer and impedance analyser respectively. X-ray diffraction patterns confirmed the formation of single phase cubic spinel structure of the samples. FTIR spectra showed two prominent bands (400 cm-1 and 600 cm-1) corresponding to characteristic of ferrites. Substitution of Mg and Zn for Ni showed gradual decrease of both magnetisation and coercivity. Magnetic permeability showed increasing trend with composition due to low anisotropy constant of Mg and Zn compared to Ni. Dielectric properties of the samples showed that both the dielectric constant as well as the dielectric loss factor was decreased with the composition. Cole-Cole plots consist of distorted semicircle with increasing diameter as a function of composition indicating improved resistance of the samples. The effect of substitution of Mg and Zn for Ni in NiCuZn ferrite system resulted in improved permeability with high cut off frequency, reduced dielectric losses and enhanced resistance of the samples.

  5. Luminescence and electrical properties of single ZnO/MgO core/shell nanowires

    SciTech Connect

    Grinblat, Gustavo; Comedi, David; Bern, Francis; Barzola-Quiquia, José; Esquinazi, Pablo; Tirado, Mónica

    2014-03-10

    To neutralise the influence of the surface of ZnO nanowires for photonics and optoelectronic applications, we have covered them with insulating MgO film and individually contacted them for electrical characterisation. We show that such a metal-insulator-semiconductor-type nanodevice exhibits a high diode ideality factor of 3.4 below 1 V. MgO shell passivates ZnO surface states and provides confining barriers to electrons and holes within the ZnO core, favouring excitonic ultraviolet radiative recombination, while suppressing defect-related luminescence in the visible and improving electrical conductivity. The results indicate the potential use of ZnO/MgO nanowires as a convenient building block for nano-optoelectronic devices.

  6. Lubrication performance and mechanisms of Mg/Al-, Zn/Al-, and Zn/Mg/Al-layered double hydroxide nanoparticles as lubricant additives

    NASA Astrophysics Data System (ADS)

    Li, Shuo; Bhushan, Bharat

    2016-08-01

    Solid lubricant particles are commonly used as oil additives for low friction and wear. Mg/Al-, Zn/Al-, and Zn/Mg/Al-layered double hydroxides (LDH) were synthesized by coprecipitation method. The benefits of LDH nanoparticles are that they can be synthesized using chemical methods where size and shape can be controlled, and can be modified organically to allow dispersal in fluids. The LDH nanoparticles were characterized by X-ray diffraction, scanning electron microscope, thermogravimetry, and differential scanning calorimetry. A pin-on-disk friction and wear tester was used for evaluating the friction and wear properties of LDH nanoparticles as lubricant additives. LDH nanoparticles have friction-reducing and anti-wear properties compared to oil without LDHs. Mg/Al-LDH has the best lubrication, possibly due to better thermal stability in severe conditions.

  7. Microstructure evolution and photoluminescence in nanocrystalline Mg(x)Zn(1 - x)O thin films.

    PubMed

    Sahaym, U; Norton, M G; Huso, J; Morrison, J L; Che, H; Bergman, L

    2011-10-21

    The effects of Mg concentration and annealing temperature on the characteristics of nanocrystalline Mg(x)Zn(1 - x)O thin films (where x = 0-0.4) were studied using electron microscopy and photoluminescence. The films were prepared by a sol-gel method. The solid solubility limit of MgO in ZnO for the sol-gel-derived Mg(x)Zn(1 - x)O films in the present study was determined to be ∼ 20 at.%. Microstructural characterization of the films showed that the wurtzite crystallites decrease in size with increase in Mg concentration up to the solubility limit. Increasing Mg concentration beyond the solubility limit resulted in a decrease in crystallinity of the films. The bandgap energy was found to increase with Mg concentration whereas the linewidth first increased and then decreased when the Mg concentration was increased beyond the solubility limit. Photoluminescence properties have been correlated to the microstructure of the films. A growth mechanism for Mg(x)Zn(1 - x)O nanocrystalline films under the present processing conditions has also been proposed.

  8. The (Ca2+ + Mg2+)-stimulated ATPase of the rat parotid endoplasmic reticulum.

    PubMed Central

    Thiyagarajah, P; Lim, S C

    1986-01-01

    A membrane fraction enriched in endoplasmic reticulum was prepared from rat parotid glands by using sucrose-gradient centrifugation. The fraction showed a 10-fold increase in specific activity of NADPH: cytochrome c reductase activity over that of tissue homogenates and minimal contamination with plasma membranes or mitochondria. The endoplasmic reticulum fraction possessed both Mg2+ -stimulated ATPase as well as Ca2+, Mg2+-ATPase [( Ca2+ + Mg2+)-stimulated ATPase]activity. The Ca2+, Mg2+-ATPase required 2-5 mM-Mg2+ for optimal activity and was stimulated by submicromolar concentrations of free Ca2+. The Km for free Ca2+ was 0.55 microM and the average Vmax. was 60 nmol/min per mg of protein. The Km for ATP was 0.11 mM. Other nucleotides, such as GTP, CTP or ADP, could not substitute for ATP in supporting the Ca2+-activated nucleotidase activity. Increasing the K+ concentration from 0 to 100 mM caused a 2-fold activation of the Ca2+, Mg2+-ATPase. Trifluoperazine, W7 [N-(6-aminohexyl)-5-chloronaphthalene-1-sulphonamide] and vanadate inhibited the enzyme. The concentration of trifluoperazine and vanadate required for 50% inhibition of the ATPase were 52 microM and 28 microM respectively. Calmodulin, cyclic AMP, cyclic AMP-dependent protein kinase and inositol 1,4,5-trisphosphate had no effect on the ATPase. The properties of the Ca2+, Mg2+ -ATPase were distinct from those of the Mg2+-ATPase, but comparable with those reported for the parotid endoplasmic-reticulum Ca2+-transport system [Kanagasuntheram & Teo (1982) Biochem. J. 208, 789-794]. The results suggest that the Ca2+, Mg2+-ATPase is responsible for driving the ATP-dependent Ca2+ accumulation by this membrane. PMID:2943271

  9. Mg fractionation in crustose coralline algae: Geochemical, biological, and sedimentological implications of secular variation in the Mg/Ca ratio of seawater

    NASA Astrophysics Data System (ADS)

    Ries, Justin B.

    2006-02-01

    The Mg/Ca ratio of seawater has varied significantly throughout the Phanerozoic Eon, primarily as a function of the rate of ocean crust production. Specimens of the crustose coralline alga Neogoniolithon sp. were grown in artificial seawaters encompassing the range of Mg/Ca ratios shown to have existed throughout the Phanerozoic. Significantly, the coralline algae's skeletal Mg/Ca ratio varied in lockstep with the Mg/Ca ratio of the artificial seawater. Specimens grown in seawater treatments formulated with identical Mg/Ca ratios but differing absolute concentrations of Mg and Ca exhibited no significant differences in skeletal Mg/Ca ratios, thereby emphasizing the importance of the ambient Mg/Ca ratio, and not the absolute concentration of Mg, in determining the Mg/Ca ratio of coralline algal calcite. Specimens grown in seawater of the lowest molar Mg/Ca ratio ( mMg/Ca = 1.0) actually changed their skeletal mineralogy from high-Mg (skeletal mMg/Ca > 0.04) to low-Mg calcite (skeletal mMg/Ca < 0.04), suggesting that ancient calcitic red algae, which exhibit morphologies and modes of calcification comparable to Neogoniolithon sp., would have produced low-Mg calcite from the middle Cambrian to middle Mississippian and during the middle to Late Cretaceous, when oceanic mMg/Ca approached unity. By influencing the original Mg content of carbonate facies in which these algae have been ubiquitous, this condition has significant implications for the geochemistry and diagenesis of algal limestones throughout most of the Phanerozoic. The crustose coralline algae's precipitation of high-Mg calcite from seawater that favors the abiotic precipitation of aragonite indicates that these algae dictate the precipitation of the calcitic polymorph of CaCO 3. However, the algae's nearly abiotic pattern of Mg fractionation in their skeletal calcite suggests that their biomineralogical control is limited to polymorph specification and is generally ineffectual in the regulation of skeletal

  10. High-Mobility Two-Dimensional Electron Gases at ZnO/ZnMgO Interfaces for Ultra-Fast Electronics Applications

    DTIC Science & Technology

    2014-11-17

    THz sources and electronics, ZnO superlattices , ZnO/ZnMgO heterostructures 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18...5 2.3 Device Fabrication and Measurement...unlimited. 3 List of Figures Figure 1 : He-ion microscope image of a fabricated ZnMgO device with multiple Ti/Au wiring contacts for longitudinal and

  11. Intersubband spectroscopy of ZnO/ZnMgO quantum wells grown on m-plane ZnO substrates for quantum cascade device applications (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Quach, Patrick; Jollivet, Arnaud; Isac, Nathalie; Bousseksou, Adel; Ariel, Frédéric; Tchernycheva, Maria; Julien, François H.; Montes Bajo, Miguel; Tamayo-Arriola, Julen; Hierro, Adrián.; Le Biavan, Nolwenn; Hugues, Maxime; Chauveau, Jean-Michel

    2017-03-01

    Quantum cascade (QC) lasers opens new prospects for powerful sources operating at THz frequencies. Up to now the best THz QC lasers are based on intersubband emission in GaAs/AlGaAs quantum well (QW) heterostructures. The maximum operating temperature is 200 K, which is too low for wide-spread applications. This is due to the rather low LO-phonon energy (36 meV) of GaAs-based materials. Indeed, thermal activation allows non-radiative path through electron-phonon interaction which destroys the population inversion. Wide band gap materials such as ZnO have been predicted to provide much higher operating temperatures because of the high value of their LO-phonon energy. However, despite some observations of intersubband absorption in c-plane ZnO/ZnMgO quantum wells, little is known on the fundamental parameters such as the conduction band offset in such heterostructures. In addition the internal field inherent to c-plane grown heterostuctures is an handicap for the design of QC lasers and detectors. In this talk, we will review a systematic investigation of ZnO/ZnMgO QW heterostructures with various Mg content and QW thicknesses grown by plasma molecular beam epitaxy on low-defect m-plane ZnO substrates. We will show that most samples exhibit TM-polarized intersubband absorption at room temperature linked either to bound-to-quasi bound inter-miniband absorption or to bound-to bound intersubband absorption depending on the Mg content of the barrier material. This systematic study allows for the first time to estimate the conduction band offset of ZnO/ZnMgO heterostructures, opening prospects for the design of QC devices operating at THz frequencies. This was supported by the European Union's Horizon 2020 research and innovation programme under grant agreement #665107.

  12. Luminescent properties and energy level structure of CaZnOS:Eu2+

    NASA Astrophysics Data System (ADS)

    Budde, B.; Luo, H.; Dorenbos, P.; van der Kolk, E.

    2017-07-01

    In this work it is shown that CaZnOS:Eu2+ has no Eu2+ emission even at low temperature. The observed and earlier reported red emission originates from a CaS:Eu2+ impurity phase. By means of washing the as-prepared samples with diluted nitride acid, we were able to remove the CaS impurity phase and study the Eu2+ emission in the pure CaZnOS phase. A clear relation was found between the red emission intensity, the CaS XRD line intensities and the nitric acid solution washing time, with zero intensity after prolonged washing. A so-called VRBE (vacuum referred binding energy)-diagram was constructed showing the energy of the 4fn and 4fn-15d1 states of the divalent and trivalent rare earth ions as dopants in CaZnOS with respect to the vacuum energy. This diagram shows that the 5d-levels of Eu2+ are located in the conduction band, which explains the absence of 5d→4f emission. By comparing the VRBE diagram with diagrams of other related compounds like CaO, CaS, ZnO and ZnS it becomes clear that the Eu2+ luminescence quenching is caused by a low lying conduction band, typical for Zn-based compounds.

  13. Thermoluminescence studies of γ-irradiated ZnO:Mg2+ nanoparticles

    NASA Astrophysics Data System (ADS)

    Pushpa, N.; Kokila, M. K.; Nagabhushana, K. R.

    2016-07-01

    Pure and Mg2+ doped ZnO nanoparticles are synthesized by solution combustion method. X-ray diffraction studies of the samples confirm hexagonal phase. Crystallite size is calculated using Scherer formula and found to be ∼30 nm for undoped ZnO and 34-38 nm for Mg2+ doped ZnO. A broad PL emission in the range 400-600 nm with peaks at 400, 450, 468, 483, 492, 517, 553 nm are observed in both pure and Mg2+ doped nanoparticles. Near band edge emission of ZnO is observed at 400 nm. The broad band emissions are due to surface defects. PL emission intensity is found to increase with Mg2+ concentration up to 1.5 mol% and then decreases due to concentration quenching. Samples are irradiated with γ-rays in a dose range 0.05-8 kGy. Gamma irradiation doesn't affect PL properties. Undoped samples exhibit unstructured low intense TL glow with peak at 720 K. Whereas Mg2+ doped samples exhibit well structured TL glow curves with peak at ∼618 K. TL glow peak intensity of Mg2+ doped samples increases with Mg2+ concentration up to 2 mol%, thereafter decreases. TL curves of Mg2+ (2 mol%) doped ZnO exhibit two glows, a high intense peak at 618 K and a weak one with peak at ∼485 K. TL intensity of Mg2+ (2 mol%) doped ZnO samples increases with gamma dose up to 1 kGy and then decreases. Kinetic parameters of TL glows are calculated by deconvolution technique. Activation energy and frequency factor are found to be 1.5 eV and 3.38 × 1011 s-1 respectively.

  14. In vitro degradation and cell viability assessment of Zn-3Mg alloy for biodegradable bone implants.

    PubMed

    Dambatta, M S; Murni, N S; Izman, S; Kurniawan, D; Froemming, G R A; Hermawan, H

    2015-05-01

    This article reports the in vitro degradation and cytotoxicity assessment of Zn-3Mg alloy developed for biodegradable bone implants. The alloy was prepared using casting, and its microstructure was composed of Mg2Zn11 intermetallic phase distributed within a Zn-rich matrix. The degradation assessment was done using potentiodynamic polarization and electrochemical impedance spectrometry. The cell viability and the function of normal human osteoblast cells were assessed using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and alkaline phosphatase extracellular enzyme activity assays. The results showed that the degradation rate of the alloy was slower than those of pure Zn and pure Mg due to the formation of a high polarization resistance oxide film. The alloy was cytocompatible with the normal human osteoblast cells at low concentrations (<0.5 mg/mL), and its alkaline phosphatase activity was superior to pure Mg. This assessment suggests that Zn-3Mg alloy has the potential to be developed as a material for biodegradable bone implants, but the toxicity limit must be carefully observed.

  15. Near UV excitable yellow light emitting Zn doped MgO for WLED application

    NASA Astrophysics Data System (ADS)

    Vasanthi, V.; Kottaisamy, M.; Anitha, K.; Ramakrishnan, V.

    2017-06-01

    Nanoparticles of Mg1-xZnxO (x = 0, 0.05, 0.1, 0.15) were synthesized by sol-gel assisted combustion method and their optical properties has been investigated. Crystal structure, phase purity and doping of Zn2+ ions in MgO are confirmed from Powder X-ray diffraction method. Spherical shape porous particles are found with increasing particle density as a function of doping concentration. Doping of Zn ions in MgO has altered the optical band gap of MgO and reduced the band gap from 4.6 eV to 3.9 eV as the concentration of Zn increases. The optical absorption bands are observed in the visible region exhibited the presence of various defects such as F, F+, F2+ in MgO and these defects concentration increases with Zn doping. The photoluminescence emission spectra of Zn doped MgO shows a bright bluish green emission which starts from 450 nm to 570 nm and this light can be obtained at the excitation of near UV light from 330 to 380 nm. However, the same defective structure has led to a highly intense broad band emission which starts from 450 nm to 750 nm at the excitation of near UV LED (at 375 nm). This material can be used as a yellow emitting phosphor for phosphor converted white LEDs (PCWLEDs) at the excitation of near UV LEDs.

  16. Controls on shell Mg/Ca and Sr/Ca in cultured planktonic foraminiferan, Globigerinoides ruber (white)

    NASA Astrophysics Data System (ADS)

    Kısakürek, B.; Eisenhauer, A.; Böhm, F.; Garbe-Schönberg, D.; Erez, J.

    2008-09-01

    Mg/Ca and Sr/Ca ratios were determined on a single species of planktonic foraminiferan, Globigerinoides ruber (white), collected from the Gulf of Eilat and cultured in seawater at five different salinities (32 to 44), five temperatures (18 to 30 °C) and four pH values (7.9 to 8.4). The Mg/Ca-temperature calibration of cultured G. ruber (with an exponential slope of 8 ± 3%/°C) agrees well with previously published calibrations from core-tops and sediment traps. However, the dependence of Mg/Ca on salinity (with an exponential slope of 5 ± 3%/psu) is also significant and should be included in the calibration equation. With this purpose, we calculated a calibration equation for G. ruber dependent on both temperature and salinity within the 95% confidence limits: Mg/Ca(mmol/mol)=exp[0.06(±0.02)∗S(psu)+0.08(±0.02)∗T(°C)-2.8(±1.0)],R=0.95 The influence of pH on Mg/Ca ratios is negligible at ambient seawater pH (8.1 to 8.3). However, we observe a dominating pH control on shell Mg/Ca when the pH of seawater is lower than 8.0. Sr/Ca in G. ruber shows a significant positive correlation with average growth rate. Presumably, part of the variability in shell Sr/Ca in the geological record is linked to changes in growth rates of foraminifera as a response to changing environmental conditions.

  17. Phosphorescence quenching by mechanical stimulus in CaZnOS:Cu

    SciTech Connect

    Tu, Dong; Kamimura, Sunao; Xu, Chao-Nan; Fujio, Yuki; Sakata, Yoshitaro; Ueno, Naohiro

    2014-07-07

    We have found that phosphorescence intensity of CaZnOS:Cu decreased visibly under an applied load. This mechanical quenching (MQ) of phosphorescence in CaZnOS:Cu corresponded to the mechanical stimuli. We have thus demonstrated that the MQ of CaZnOS:Cu could be used for visualizing stress distributions in practical applications. We propose that MQ arises from non-radiative recombination due to electron-transfer from trap levels to non-radiative centers as a result of the mechanical load.

  18. Rapid and High-Efficiency Laser-Alloying Formation of ZnMgO Nanocrystals

    PubMed Central

    Liu, Peisheng; Wang, Hao; Chen, Jun; Li, Xiaoming; Zeng, Haibo

    2016-01-01

    Applications of ZnMgO nanocrystals (NCs), especially in photoelectric detectors, have significant limitations because of the unresolved phase separation in the synthesis process. Here, we propose a rapid and highly efficient ZnMgO NC alloying method based on pulsed laser ablation in liquid. The limit value of homogeneous magnesium (Mg) is pushed from 37% to 62%, and the optical band gap is increased to 3.7 eV with high doping efficiency (>100%). Further investigations on the lattice geometry of ZnMgO NCs indicate that all ZnMgO NCs are hexagonal wurtzite structures, and the (002) and (100) peaks shift to higher diffraction angles with the increase in Mg doping content. The calculated results of the lattice constants a and c slightly decrease based on Bragg’s law and lattice geometry equations. Furthermore, the relationship between annealing temperature and the limit value of homogeneous Mg is examined, and the results reveal that the latter decreases with the former because of the phase separation of MgO. A probable mechanism of zinc magnesium alloy is introduced to expound on the details of the laser-alloying process. PMID:27324296

  19. Structure and optical properties of ternary alloy BeZnO and quaternary alloy BeMgZnO films growth by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Su, Longxing; Zhu, Yuan; Zhang, Quanlin; Chen, Mingming; Wu, Tianzhun; Gui, Xuchun; Pan, Bicai; Xiang, Rong; Tang, Zikang

    2013-06-01

    Ternary alloy BeZnO and quaternary alloy BeMgZnO films were prepared on sapphire (0 0 1) substrate by radio-frequency plasma-assisted molecular beam epitaxy (RF-PAMBE). Based on X-ray diffraction (XRD) analysis, no phase segregation is observed for all the alloys. However, BexZn1-xO alloys exhibit a constantly worse crystal quality than BexMgyZn1-x-yO alloys at the similar incorporation contents (i.e. x in BeZnO approximately equals to x + y in BeMgZnO). Optical transmittance spectra were recorded to determine the energy band gap of the films. BeMgZnO was revealed more effective in widening the band gap. Finally, BeZnO and BeMgZnO based MSM structure UV detectors were fabricated. BeMgZnO alloys with better crystal quality showed a favorable optical response and the cutoff wavelength shifted continuously to deep ultraviolet range, while BeZnO based detectors were found no response. This is the first report on BeMgZnO based UV detector, which is a meaningful step forward to the real application.

  20. Experimental 25Mg and 13C NMR and Computational Modeling Studies of Amorphous Mg-Ca Carbonates

    NASA Astrophysics Data System (ADS)

    Singer, J. W.; Yazaydin, A. O.; Kirkpatrick, R. J.; Saharay, M.; Bowers, G. M.

    2012-12-01

    Nuclear magnetic resonance (NMR) spectroscopy of synthetic Mg-Ca amorphous carbonates (AMC-ACC) provides direct, element specific structural information about these complicated phases. The 13C, 25Mg, and 43Ca resonances are typically broad and span the chemical shift ranges of all the crystalline polymorphs in the Ca-Mg-CO3-H2O system. In a fashion similar to our previous analysis of 43Ca NMR results for ACC,1 here we integrate new experimental 13C and 25Mg spectra obtained at 20T for samples with Mg/(Ca+Mg) ratios from x=0 to x=1 with quantum chemical calculations of the NMR parameters of the crystalline phases using CASTEP calculations, simulations of the spectra using the SIMPSON software, and classical molecular dynamics calculations. XRD and 13C NMR results are in general agreement with the one-phase/two-phase model of ACC-AMC derived from thermochemical work by others.2 13C-NMR spectra of amorphous materials having intermediate compositions can not be completely fit by mechanical mixing of ACC and AMC end members—requiring a degree of Ca/Mg solid solution. Amorphous samples in two-phase region crystallize to assemblages of dolomite-like (x~0.5) and hydromagnesite-like (x~1) defective structures, but we also observe aragonite co-nucleation in the presence of excess water, indicative of a more complex evolution. While 43Ca NMR of X-ray amorphous materials shows featureless, symmetric, Gaussian line shapes, the large quadrupole moment of 25Mg gives rise to superposition of several quadrupolar line shapes representing different local structural environments. Singularities of static Mg spectra are best explained by local environments similar to nequehonite, hydromagnesite, and landsfordite. The spectra can not exclude minor contributions from anhydrous phases dolomite, huntite, and magnesite. Additional sites having very large quadrupolar coupling and/or site asymmetry are not explained by any known reference phases. CITATIONS (1) Singer, J. W.; Yazaydin, A. O

  1. Biological responses of human bone marrow mesenchymal stem cells to Sr-M-Si (M = Zn, Mg) silicate bioceramics.

    PubMed

    Zhang, Meili; Wu, Chengtie; Lin, Kaili; Fan, Wei; Chen, Lei; Xiao, Yin; Chang, Jiang

    2012-11-01

    Strontium (Sr), Zinc (Zn), magnesium (Mg), and silicon (Si) are reported to be essential trace elements for the growth and mineralization of bone. We speculated that the combination of these bioactive elements in bioceramics may be effective to regulate the osteogenic property of bone-forming cells. In this study, two Sr-containing silicate bioceramics, Sr(2)ZnSi(2)O(7) (SZS) and Sr(2)MgSi(2)O(7) (SMS), were prepared. The biological response of human bone marrow mesenchymal stem cells (BMSCs) to the two bioceramics (in the forms of powders and dense ceramic bulks) was systematically studied. In powder form, the effect of powder extracts on the viability and alkaline phosphatase (ALP) activity of BMSCs was investigated. In ceramic disc form, both direct and indirect coculture of BMSCs with ceramic discs were used to investigate their biological response, including attachment, proliferation, ALP activity, and bone-related genes expression. Beta-tricalcium phosphate (β-TCP) and akermanite (Ca(2)MgSi(2)O(7), CMS) were used as control materials. The results showed that the Sr, Zn, and Si (or Sr, Mg, and Si)-containing ionic products from SZS and SMS powders enhanced ALP activity of BMSCs, compared to those from β-TCP. Both SZS and SMS ceramic discs supported the growth of BMSCs, and most importantly, significantly enhanced the ALP activity and bone-related genes expression of BMSCs as compared to β-TCP. The results suggest that the specific combination of bioactive ions (Sr, Zn, Si, e.g.) in bioceramics is a viable way to improve the biological performance of biomaterials, and the form of materials and surface properties were nonnegligible factors to influence cell response.

  2. Mg/Ca Ratios in Planktonic Foraminifera Across a Strong Salinity Gradient in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Ferguson, J. E.; Henderson, G. M.; Kucera, M.; Rickaby, R. E.

    2007-12-01

    The Mediterranean Sea provides an ideal environment to conduct a field study of the effect of salinity on Mg incorporation into planktonic foraminifera. Its semi-enclosed nature results in the development of a considerable gradient (5 psu) in salinity while its west to east alignment leads to relatively small sea surface temperature gradients (a maximum of 8° C in the summer). Eleven box core tops were sampled from across the Mediterranean Sea. Orbulina universa, Globigerinoides ruber (white) and (pink) and Globigerinella siphonifera, were picked and thoroughly cleaned using standard techniques for trace-metal work. Samples were analysed for Mg/Ca, Cd/Ca, U/Ca, Sr/Ca, Fe/Ca, Al/Ca and Mn/Ca. Samples were screened for contamination using Mn/Ca ratios for ferro-manganese crusts and Fe/Ca and Al/Ca for clays. SEM images and sequential dissolution experiments indicated that most samples did not feature inorganic encrusting high-Mg calcite (which has previously been found in some high salinity regions such as the Red Sea). After rejecting samples that failed these screening tests, Mg/Ca ratios in all species are higher, for their calcification temperatures, than seen in previous studies. There is an overall increase in Mg/Ca from west to east and percentage increases per ° C are unusually high. Mg/Ca ratios are particularly high in samples from the high-salinity eastern Mediterranean. We present arguments to suggest that these high values are not the result of nutrient or carbonate ion changes, with both of these variables being similar to those in the open ocean. Correlations of Mg/Ca with salinity are generally more significant than with temperature, with Mg/Ca increases per salinity unit of 15-60% - much higher than suggested in previous culture studies. Our results suggest that salinity may act as a significant secondary control on Mg/Ca ratios in addition to the dominant temperature control. A re-analysis of previous calibrations from other settings also suggests

  3. Direct determination of the band alignment at the (Zn,Mg)O/CISSe interface

    SciTech Connect

    Erfurth, F.; Reinert, F.; Weinhardt, L.; Grimm, A.; Palm, J.; Niesen, T. P.; Umbach, E.

    2011-04-04

    The electronic and chemical properties of the (Zn{sub 1-x},Mg{sub x})O/CuIn(S,Se){sub 2} interface, prepared by sputtering of thin (Zn,Mg)O layers, were investigated with direct and inverse photoelectron spectroscopy on in situ prepared samples. With the combination of both techniques we have determined the band alignment at this interface as a function of Mg-content in the range 0{<=}x{<=}0.30. We find that the band alignment at the interface can be tailored between a ''cliff'' (downward step) in the conduction band for pure ZnO and a 'spike' (upward step) for high Mg-contents. A direct influence of the band alignment modifications on the solar cell parameters is found.

  4. Synthesis and optical properties of MgO-doped ZnO microtubes using microwave heating

    NASA Astrophysics Data System (ADS)

    Al-Naser, Qusay A. H.; Zhou, Jian; Wang, Han; Liu, Guizhen; Wang, Lin

    2015-08-01

    The Zn1-xMgxO (x = 0%, 2% and 5%) microtubes have been successfully synthesized via a microwave heating method. The as synthesized microtubes were carefully investigated. Field emission scanning electron microscope (FE-SEM) showed that all the microtubes exhibit an exact hexagonal hollow structure with smooth surfaces and straight characteristics throughout their whole lengths. UV-Vis measurement indicates that the absorption peak for ZnO microtube was shifted from 378.88 nm (3.27 eV) to 369.91 nm (3.35 eV) for Zn0.95Mg0.05O microtube. Room temperature photoluminescence (PL) spectra showed that the intensity of UV emission peak decreased with increase of MgO concentration and the visible emission band showed a blue shift from 538.06812 nm for ZnO microtube to 529.54114 nm for Zn0.95Mg0.05O microtube. Energy-dispersive spectrometer (EDS) analysis revealed the presence of Zn and O as the only elementary components with the absence of MgO as a doping material.

  5. High response solar-blind MgZnO photodetectors grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Schoenfeld, Winston V.; Wei, Ming; Boutwell, R. Casey; Liu, Huiyong

    2014-03-01

    High quality w-MgxZn1-xO thin films were grown epitaxially on c-plane sapphire substrates by plasma-assisted Molecular Beam Epitaxy. ZnO thin films with high crystalline quality, low defect and dislocation densities, and subnanometer surface roughness were achieved by applying a low temperature nucleation layer. By tuning Mg/Zn flux ratio, wurtzite MgxZn1-xO thin films with Mg composition as high as x=0.46 were obtained without phase segregation. Metal- Semiconductor-Metal (MSM) photoconductive and Schottky barrier devices with interdigitated electrode geometry and active surface area of 1 mm2 were fabricated and characterized. Resultant devices showed ~100 A/W peak responsivity at wavelength of ~260nm. We also report on cubic rock salt c-MgxZn1-xO thin films, following a non-traditional approach on MgO substrates, to demonstrate solar-blind photoresponse in MSM photodetectors, realizing a peak responsivity of 460 A/W (@ 250 nm) and 12.6 mA/W (@ 240nm) for mixed phase and single crystal films, respectively. A specific focus of the work is on identifying the impact of various growth parameters on the performance of the c- MgZnO detectors.

  6. Ammonia sensing properties of V-doped ZnO:Ca nanopowders prepared by sol–gel synthesis

    SciTech Connect

    Fazio, E.; Hjiri, M.; Dhahri, R.; El Mir, L.; Sabatino, G.; Barreca, F.; Neri, F.; Leonardi, S.G.; Pistone, A.; Neri, G.

    2015-03-15

    V-doped ZnO:Ca nanopowders with different V loading were prepared by sol–gel synthesis and successive drying in ethanol under supercritical conditions. Characterization data of nanopowders annealed at 700 °C in air, revealed that they have the wurtzite structure. Raman features of V-doped ZnO:Ca samples were found to be substantially modified with respect to pure ZnO or binary ZnO:Ca samples, which indicate the substitution of vanadium ions in the ZnO lattice. The ammonia sensing properties of V-doped ZnO:Ca thick films were also investigated. The results obtained demonstrate the possibility of a fine tuning of the sensing characteristics of ZnO-based sensors by Ca and V doping. In particular, their combined effect has brought to an enhanced response towards NH{sub 3} compared to bare ZnO and binary V-ZnO and Ca-ZnO samples. Raman investigation suggested that the presence of Ca play a key role in enhancing the sensor response in these ternary composite nanomaterials. - Graphical abstract: V-doped ZnO:Ca nanopowders prepared by sol–gel synthesis possess enhanced sensing characteristics towards NH{sub 3} compared to bare ZnO. - Highlights: • V-doped ZnO:Ca nanopowders with different V loading were prepared by sol–gel synthesis. • Raman features of V-doped ZnO:Ca samples indicate the substitution of V ions in the ZnO lattice. • Combined effects of dopants have brought to an enhanced response to NH{sub 3} compared to ZnO. • Ca play a key role in enhancing the sensor response of ternary V-doped ZnO:Ca composites.

  7. Influence of ZnO on the crystallization kinetics and properties of diopside-Ca-Tschermak based glasses and glass-ceramics

    SciTech Connect

    Goel, Ashutosh; Ferreira, Jose M. F.; Tulyaganov, Dilshat U.; Shaaban, Essam R.; Basu, Rajendra N.

    2008-08-15

    We report on the influence of ZnO on the structural, thermal, and crystallization behavior of the diopside-Ca-Tschermak based glasses, and on the processing, microstructure, and the properties of the sintered glass ceramics. Four glasses with nominal compositions of CaMg{sub 0.8}Al{sub 0.4}Si{sub 1.8}O{sub 6}, CaMg{sub 0.75}Zn{sub 0.05}Al{sub 0.4}Si{sub 1.8}O{sub 6}, CaMg{sub 0.70}Zn{sub 0.10}Al{sub 0.4}Si{sub 1.8}O{sub 6}, and CaMg{sub 0.60}Zn{sub 0.20}Al{sub 0.4}Si{sub 1.8}O{sub 6} were obtained by melting at 1580 deg. C for 1 h. Structural and thermal behavior of the glasses was investigated by Fourier-transform infrared spectroscopy, density measurements, dilatometry, and differential thermal analysis. Nonisothermal crystallization kinetics has been employed to study the crystallization mechanism in the glasses. Sintering, crystallization, microstructure, and properties of the glass ceramics were investigated under nonisothermal heating conditions in the temperature range of 850-1000 deg. C.

  8. Effect of Ca2+ and Zn2+ on UO2 dissolution rates.

    PubMed

    Cerrato, José M; Barrows, Charles J; Blue, Lisa Y; Lezama-Pacheco, Juan S; Bargar, John R; Giammar, Daniel E

    2012-03-06

    The dissolution of UO(2) in a continuously stirred tank reactor (CSTR) in the presence of Ca(2+) and Zn(2+) was investigated under experimental conditions relevant to contaminated groundwater systems. Complementary experiments were performed to investigate the effect of adsorption and precipitation reactions on UO(2) dissolution. The experiments were performed under anoxic and oxic conditions. Zn(2+) had a much greater inhibitory effect on UO(2) dissolution than did Ca(2+). This inhibition was most substantial under oxic conditions, where the experimental rate of UO(2) dissolution was 7 times lower in the presence of Ca(2+) and 1450 times lower in the presence of Zn(2+) than in water free of divalent cations. EXAFS and solution chemistry analyses of UO(2) solids recovered from a Ca experiment suggest that a Ca-U(VI) phase precipitated. The Zn carbonate hydrozincite [Zn(5)(CO(3))(2)(OH)(6)] or a structurally similar phase precipitated on the UO(2) solids recovered from experiments performed in the presence of Zn. These precipitated Ca and Zn phases can coat the UO(2) surface, inhibiting the oxidative dissolution of UO(2). Interactions with divalent groundwater cations have implications for the longevity of UO(2) and the mobilization of U(VI) from these solids in remediated subsurface environments, waste disposal sites, and natural uranium ores.

  9. A Mg2+-independent Ca2+-stimulated ATPase activity in the tegument of Schistosoma mansoni.

    PubMed

    Cunha, V M; Noël, F

    1988-01-01

    A tegumental fraction was prepared from Schistosoma mansoni. This fraction exhibited ATPase activity stimulated by Ca2+ in the absence of Mg2+. The Mg2+ independency was assessed by lowering contaminant Mg2+ using CDTA. The peak of activity was 220 mumol Pi mg-1 protein h-1 and the K0.5 for CaATP was 0.32 mM; the same K0.5 was obtained using MgATP as substrate, in the absence of Ca2+. Both activities may be promoted by the same enzyme since the addition of Ca2+ did not increase the ATPase activity measured in the presence of a saturating MgATP concentration.

  10. Chamber formation leads to Mg/Ca banding in the planktonic foraminifer Neogloboquadrina pachyderma

    NASA Astrophysics Data System (ADS)

    Jonkers, Lukas; Buse, Ben; Brummer, Geert-Jan A.; Hall, Ian R.

    2016-10-01

    Many species of planktonic foraminifera show distinct banding in the intratest distribution of Mg/Ca. This heterogeneity appears biologically controlled and thus poses a challenge to Mg/Ca paleothermometry. The cause of this banding and its relation with chamber formation are poorly constrained and most of what we know about intratest Mg/Ca variability stems from culture studies of tropical, symbiont-bearing foraminifera. Here we present data on the non-spinose, symbiont-barren Neogloboquadrina pachyderma from the subpolar North Atlantic where wintertime mixing removes vertical gradients in temperature and salinity. This allows investigation of biologically controlled Mg/Ca intratest variability under natural conditions. We find that intratest Mg/Ca varies between <0.1 and 7 mmol/mol, even in winter specimens. High Mg/Ca bands occur at the outer edge of the laminae, indicating reduced Mg removal at the end of chamber formation. Our data thus provide new constraints on the timing of the formation of such bands and indicate that their presence is intrinsic to the chamber formation process. Additionally, all specimens are covered with an outer crust consisting of large euhedral crystals. The composition of the crust is similar to the low Mg/Ca bands in the laminar calcite in winter and summer specimens, indicating a tight biological control on crust formation and composition. Nevertheless, despite high intratest variability, the median Mg/Ca of summertime tests is higher than that of wintertime tests. This provides support for Mg/Ca paleothermometry, but to improve the accuracy of paleotemperature estimates biological effects on Mg incorporation need to be better accounted for.

  11. The formation of FHA coating on biodegradable Mg-Zn-Zr alloy using a two-step chemical treatment method

    NASA Astrophysics Data System (ADS)

    Jiang, S. T.; Zhang, J.; Shun, S. Z.; Chen, M. F.

    2016-12-01

    To improve the corrosion resistance of the biomedical magnesium alloy, a two-step chemical treatment method has been employed to prepare an FHA coating on the alloy surface. Prior to forming an FHA layer, the samples of Mg-3 wt% Zn-0.5 wt% Zr alloy were soaked in HF with concentration of 20% (v/v) at 37 °C temperature for 2 h, and were then placed into an aqueous solution with 0.1 mol/L Ca(NO3).4H2O and 0.06 mol/L NH4H2PO4 at 90 °C to prepare the Ca-P coating. The concentrations of Mg2+, F- ions, and pH variation with immersing time in the solution were investigated to explore the growth mechanism of FHA. The surface morphologies and compositions of the coatings were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results showed that the alloy surface treated with acid formed a layer of MgF2 nanoparticles with a thickness of 0.7 μm. The corrosion resistance of coatings in SBF solution was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results showed that the substrate with FHA coating had good corrosion resistance. After immersing into the calcium phosphate solution, some small spherical particles were first formed on the surface; these then cover the surface completely after 20 min. Some clusters consisting of needle-like crystal were observed in the spherical particles covering the surface, and the Ca/P ratio of the needle-like crystal was 1.46, clearly growing along the c axis preferred orientation growth. After immersion for 60 min, the FHA coating with completely uniform growth was obtained on the Mg-Zn-Zr alloy surface with its thickness reaching about 120 μm.

  12. 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/Ca

  13. High-pressure modifications of CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}, and BaAl{sub 2}: Implications for Laves phase structural trends

    SciTech Connect

    Kal, Subhadeep; Stoyanov, Emil; Belieres, Jean-Philippe; Groy, Thomas L.; Norrestam, Rolf; Haeussermann, Ulrich

    2008-11-15

    High-pressure forms of intermetallic compounds with the composition CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}, and BaAl{sub 2} were synthesized from CeCu{sub 2}-type precursors (CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}) and Ba{sub 21}Al{sub 40} by multi-anvil techniques and investigated by X-ray powder diffraction (SrAl{sub 2} and BaAl{sub 2}), X-ray single-crystal diffraction (CaZn{sub 2}), and electron microscopy (SrZn{sub 2}). Their structures correspond to that of Laves phases. Whereas the dialuminides crystallize in the cubic MgCu{sub 2} (C15) structure, the dizincides adopt the hexagonal MgZn{sub 2} (C14) structure. This trend is in agreement with the structural relationship displayed by sp bonded Laves phase systems at ambient conditions. - Graphical abstract: CeCu{sub 2}-type polar intermetallics can be transformed to Laves phases upon simultaneous application of pressure and temperature. The observed structures are controlled by the valence electron concentration.

  14. Effect of Mn on microstructure and corrosion properties of extruded Mg-1%Zn alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Z. M.; Ma, Y.; Xi, Z. Z.; Xu, C. J.; Lv, Z. L.

    2017-03-01

    The microstructure of the extruded Mg-1Zn alloy doped with different content of manganese was analyzed by optical microscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffractometry. The mass-loss immersion method and electrochemical test were used to evaluate the corrosion properties. The results show that the microstructure of the extruded Mg-1%Zn-x%Mn (mass fraction, x=0.4, 0.8, 1.2) alloys consists of α-Mg and α-Mn, the grain size of α-Mg decreases with increasing Mn content. Electrochemical corrosion behavior of the alloys is similar. Mn has considerable effect on the corrosion rate, the corrosion process is exacerbated by the galvanic corrosion occurred at interface between α-Mg and α-Mn. The corrosion rate increases as the Mn content increases. Mg-1%Zn-0.4% Mn alloy exhibits the best corrosion resistance between the Mg-1%Zn-x%Mn alloys

  15. Compositional tuning of atomic layer deposited MgZnO for thin film transistors

    SciTech Connect

    Wrench, J. S.; Brunell, I. F.; Chalker, P. R.; Jin, J. D.; Shaw, A.; Mitrovic, I. Z.; Hall, S.

    2014-11-17

    Thin film transistors (TFTs) have been fabricated using magnesium zinc oxide (MgZnO) layers deposited by atomic layer deposition at 200 °C. The composition of the MgZnO is systematically modified by varying the ratio of MgO and ZnO deposition cycles. A blue-shift of the near band-edge photoluminescence after post-deposition annealing at 300 °C indicates significant activation of the Mg dopant. A 7:1 ratio of ZnO:MgO deposition cycles was used to fabricate a device with a TFT channel width of 2000 μm and a channel length of 60 μm. This transistor yielded an effective saturation mobility of 4 cm{sup 2}/V s and a threshold voltage of 7.1 V, respectively. The on/off ratio was 1.6×10{sup 6} and the maximum interface state density at the ZnO/SiO{sub 2} interface is ∼6.5×10{sup 12} cm{sup −2}.

  16. Synthesis and luminescence of ZnMgS:Mn2+ nanoparticles.

    PubMed

    Zhang, Jun; Su, Fuhai; Chen, Wei; Sammynaiken, Ramaswami; Westcott, Sarah L; McCready, David E; Li, Guohua; Joly, Alan G

    2005-09-01

    Efficient green emission from ZnMgS:Mn2+ nanoparticles prepared by co-doping Mg2+ and Mn2+ ions into ZnS lattices has been observed. The synthesis is carried out in aqueous solution, followed by a post-annealing process, thus showing the features of less complexity, low cost, and easy incorporation of dopants. In comparison with the emission of ZnS:Mn2+ nanoparticles, which is located generally around 590 nm, the photoluminescence of ZnMgS:Mn2+ nanoparticles is blue-shifted by 14 nm in wavelength, leading to the enhanced green emission. The X-ray diffraction, electron spin resonance, and pressure dependent photoluminescence measurements suggest that the change of the crystal field caused by Mg2+ ionic doping and the lower symmetry in the nanoparticles may account for the blue-shift of the photoluminescence. The ZnMgS:Mn2+ nanoparticles with 1% Mn2+ doping exhibit the strongest luminescence, which could potentially meet the requirements for the construction of green light emitting diodes.

  17. Investigations on structural, vibrational and dielectric properties of nanosized Cu doped Mg-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Yadav, Anand; Rajpoot, Rambabu; Dar, M. A.; Varshney, Dinesh

    2016-05-01

    Transition metal Cu2+ doped Mg-Zn ferrite [Mg0.5Zn0.5-xCuxFe2O4 (0.0 ≤ x ≤ 0.5)] were prepared by sol gel auto combustion (SGAC) method to probe the structural, vibrational and electrical properties. X-ray diffraction (XRD) pattern reveals a single-phase cubic spinel structure without the presence of any secondary phase corresponding to other structure. The average particle size of the parent Mg0.5Zn0.5Fe2O4 is found to be ~29.8 nm and is found to increase with Cu2+ doping. Progressive reduction in lattice parameter of Mg0.5Zn0.5Fe2O4 has been observed due to difference in ionic radii of cations with improved Cu doping. Spinel cubic structure is further confirmed by Raman spectroscopy. Small shift in Raman modes towards higher wave number has been observed in doped Mg-Zn ferrites. The permittivity and dielectric loss decreases at lower doping and increases at higher order doping of Cu2+.

  18. Investigations on structural, vibrational and dielectric properties of nanosized Cu doped Mg-Zn ferrites

    SciTech Connect

    Yadav, Anand; Rajpoot, Rambabu; Dar, M. A.; Varshney, Dinesh E-mail: anand.212@gmail.com

    2016-05-23

    Transition metal Cu{sup 2+} doped Mg-Zn ferrite [Mg{sub 0.5}Zn{sub 0.5-x}Cu{sub x}Fe{sub 2}O{sub 4} (0.0 ≤ x ≤ 0.5)] were prepared by sol gel auto combustion (SGAC) method to probe the structural, vibrational and electrical properties. X-ray diffraction (XRD) pattern reveals a single-phase cubic spinel structure without the presence of any secondary phase corresponding to other structure. The average particle size of the parent Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} is found to be ~29.8 nm and is found to increase with Cu{sup 2+} doping. Progressive reduction in lattice parameter of Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} has been observed due to difference in ionic radii of cations with improved Cu doping. Spinel cubic structure is further confirmed by Raman spectroscopy. Small shift in Raman modes towards higher wave number has been observed in doped Mg-Zn ferrites. The permittivity and dielectric loss decreases at lower doping and increases at higher order doping of Cu{sup 2+}.

  19. The role of ionic sizes in inducing the cubic to tetragonal distortion in AV2O4 and ACr2O4 (A = Zn, Mg and Cd) compounds

    NASA Astrophysics Data System (ADS)

    Lal, Sohan; Pandey, Sudhir K.

    2016-11-01

    Cubic to tetragonal distortion in AV2O4 and ACr2O4 (A = Zn, Mg and Cd) compounds have been a contentious issue for last two decades. Different groups have proposed different mechanisms to understand such a distortion in these spinels, which are: (i) spin lattice coupling mechanism known as the spin driven Jahn-Teller (JT) effect, (ii) the strong relativistic spin-orbit coupling, a moderate JT distortion and weak V-V interactions and (iii) the JT effect. Now, in order to know the possible cause for such a distortion, we have avoided these complexities (various interactions among spin, electronic, orbital and lattice degrees of freedom) by carrying out spin unpolarized calculations. The calculated values of bulk moduli for ZnV2O4 (ZnCr2O4), MgV2O4 (MgCr2O4) and CdV2O4 (CdCr2O4) are found to be ˜289 (˜254), ˜244 (˜243) and ˜230 (˜233) GPa, respectively which suggest that CdV2O4 (among vanadates) and CdCr2O4 (among chromates) are more compressible. For vanadates and chromates, the order of calculated values of lattice parameter a are found to CdV2O4 > MgV2O4 > ZnV2O4 and CdCr2O4 > MgCr2O4 > ZnCr2O4, respectively and are consistent with the experimental results. The calculated values of cubic to tetragonal distortion (c/a), with c/a < 1 for ZnV2O4 (ZnCr2O4), MgV2O4 (MgCr2O4) and CdV2O4 (CdCr2O4) are ˜0.996 (˜0.997), ˜0.995 (˜0.994) and ˜0.997 (˜0.998), respectively. These values are in good agreement with the experimental data for ZnV2O4, MgV2O4, ZnCr2O4 and MgCr2O4 compounds. The present study clearly shows the role of ionic sizes in inducing the cubic to tetragonal distortion in these spinels. However, the discrepancies between the calculated and experimental data for CdV2O4 and CdCr2O4 are expected to improve by considering the above mentioned mechanisms. These mechanisms also appear to be responsible for deciding the other physical properties of these compounds.

  20. Structure and Properties of Single Crystalline CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2

    SciTech Connect

    May, Andrew F; McGuire, Michael A; Singh, David J; Custelcean, Radu; Jellison Jr, Gerald Earle

    2011-01-01

    Single crystals of CaMg{sub 2}Bi{sub 2}, EuMg{sub 2}Bi{sub 2}, and YbMg{sub 2}Bi{sub 2} were obtained from a Mg-Bi flux cooled to 650 C. These materials crystallize in the CaAl{sub 2}Si{sub 2} structure-type (P3{bar m}1, No. 164), and crystal structures are reported from refinements of single crystal and powder X-ray diffraction data. EuMg{sub 2}Bi{sub 2} displays an antiferromagnetic transition near 7 K, which is observed via electrical resistivity, magnetization, and specific heat capacity measurements. Magnetization measurements on YbMg{sub 2}Bi{sub 2} reveal a weak diamagnetic moment consistent with divalent Yb. Despite charge-balanced empirical formulas, all three compounds are p-type conductors with Hall carrier concentrations of 2.0(3) x 10{sup 19} cm{sup -3} for CaMg{sub 2}Bi{sub 2}, 1.7(1) x 10{sup 19} cm{sup -3} for EuMg{sub 2}Bi{sub 2}, and 4.6(7) x 10{sup 19} cm{sup -3} for YbMg{sub 2}Bi{sub 2}, which are independent of temperature to 5 K. The electrical resistivity decreases with decreasing temperature and the resistivity ratios {rho}(300 K)/{rho}(10 K) {le} 1.6 in all cases, indicating significant defect scattering.

  1. MgSO4 relaxes porcine airway smooth muscle by reducing Ca2+ entry.

    PubMed

    Kumasaka, D; Lindeman, K S; Clancy, J; Lande, B; Croxton, T L; Hirshman, C A

    1996-03-01

    Magnesium sulfate (MgSO4) is used clinically, but its mechanism of action is unknown. To determine whether MgSO4 relaxes airway smooth muscle and to investigate the pathways involved, we compared effects of MgSO4 in porcine tracheal and bronchial muscles contracted with either carbachol or KCl and measured the effects of MgSO4 on the concentration of intracellular free calcium ([Ca2+]i). Lungs were dissected after anesthesia and exsanguination. Tracheal strips and bronchial rings were suspended in tissue baths for measurement of isometric tension in the presence of different concentrations of MgSO4. In separate experiments, tracheal smooth muscle tension and [Ca2+]i were measured simultaneously, using the fluorescent dye fura 2. MgSO4 (1.2, 2.2, 9.2 mM) produced a concentration dependent rightward shift of contraction dose-response curves to KCl but not to carbachol. MgSO4 relaxed trachealis muscles precontracted with KCl or carbachol and simultaneously decreased [Ca2+]i. These findings indicate that MgSO4 directly relaxes airway smooth muscle and that the mechanism involves a decrease in [Ca2+]i. Because initiation and maintenance of contraction during KCl stimulation and maintenance of contraction during carbachol stimulation require Ca2+ entry through voltage-dependent calcium channels, MgSO4-induced relaxation may involve a decrease in Ca2+ entry via these channels.

  2. Photon guiding characteristics of waveguide membranes coupled to a microdisk of ZnSe/(Zn,Mg)Se quantum well structures

    NASA Astrophysics Data System (ADS)

    Schmidt, G.; Rieger, T.; Trellenkamp, S.; Grützmacher, D.; Pawlis, A.

    2017-07-01

    Integrated optical devices composed of waveguides and microdisks emitting blue light were fabricated from ZnSe/(Zn,Mg)Se quantum well structures. Here we study the optical properties and photon guiding characteristics of such devices. The structures were fabricated by multi-step electron beam lithography and subsequent wet chemical etching. The transfer characteristic of photons through the waveguide was analyzed via spatial-resolved μ-photoluminescence spectroscopy. Spatial excitation of the microdisk revealed substantial overcoupling of photons from the microdisk into the waveguide.

  3. The effects of shell characteristics on the UV photoresponse behaviors of photoconductivity based on ZnO/ZnMgO core-shell nanowire arrays

    NASA Astrophysics Data System (ADS)

    Fang, F.; Wang, X. J.; Fang, X.; Li, T.; Wei, Zhipeng; Li, Jinhua; Chu, Xueying

    2015-07-01

    Through a facile hydrothermal process and atomic layer deposition (ALD) technology, we obtained a kind of ZnO/ZnMgO core-shell nanowire array. The x-ray diffraction (XRD) results show a dominant (002) peak appears in as-grown ZnO, while the strongest peak is assigned an intensity of (100) in ZnO/ZnMgO core-shell structure. After ZnMgO shell coating, the main ultraviolet emission peak in room photoluminescence (PL) spectrum splits into two peaks, which locate at 364 nm and 378 nm. Furthermore, significant enhancement (one order of magnitude) in photoconductivity has been demonstrated. It is possible that the ZnMgO layer acts as an interfacial carrier transport layer, reducing the probability of carrier recombination.

  4. P- T- X controls on Ca and Na distribution between Mg-Al tourmaline and fluid

    NASA Astrophysics Data System (ADS)

    Berryman, Eleanor J.; Wunder, Bernd; Rhede, Dieter; Schettler, Georg; Franz, Gerhard; Heinrich, Wilhelm

    2016-04-01

    Ca-Na partitioning between tourmaline and a coexisting fluid is investigated in the system CaO-Na2O-B2O3-Al2O3-MgO-SiO2-H2O-Cl between 0.2-4.0 GPa and 500-700 °C. The synthesis experiments produced a mineral assemblage of tourmaline, coesite/quartz, and in some cases additional phases, typically comprising <1 wt% of the solid product. The synthesized tourmalines are solid solutions of dravite [NaMg3Al6Si6O18(BO3)3(OH)3(OH)], "oxy-uvite" (i.e. "Ca-Mg-O root name") [CaMg3Al6Si6O18(BO3)3(OH)3O], and magnesio-foitite [☐(Mg2Al)Al6Si6O18(BO3)3(OH)3(OH)]. Starting materials comprised a fluid of constant ionic strength (2.00 m) and an oxide mixture with a constant Mg/Al ratio. As a result, the number of vacancies at the X site and the Mg/Al ratio of tourmaline crystals synthesized at the same temperature vary only slightly. The major solid solution is Ca-Na exchange at the X site via the exchange vector X Ca W O[ X Na W (OH)]-1, with the exchange vector X (Ca☐)[ X Na2]-1 serving as a secondary Ca-incorporation mechanism. Tourmaline's X-site composition reflects the fluid composition, whereby the Ca (or Na) concentration in the fluid corresponds with the Ca (or Na) content in tourmaline at each pressure and temperature. At 0.2 GPa, 700 °C, Ca preferentially partitions into tourmaline, producing the most Ca-rich tourmaline crystals synthesized here. At pressures >1.0 GPa, Ca partitions preferentially into the fluid, resulting in Na-dominant tourmaline compositions. Temperature has a secondary effect on Ca-Na partitioning, with higher temperatures correlating with increased Ca incorporation in tourmaline. Based on the experimental findings, tourmaline is expected to have Ca-rich compositions when it forms in low pressure, high-temperature Ca-rich rocks, consistent with the current record of tourmaline occurrence. The bulk Mg/Al ratio and the pH of the tourmaline-forming system may also affect Ca incorporation in tourmaline, but remain to be investigated experimentally.

  5. Using benthic foraminiferal B/Ca to constrain the effect of dissolution on key Pliocene Mg/Ca temperature records

    NASA Astrophysics Data System (ADS)

    White, S. M.; Ravelo, A. C.

    2015-12-01

    The state of the Pliocene tropical Pacific is currently the subject of heated debate. The debate hinges on the veracity of planktic foraminiferal Mg/Ca temperatures from the west Pacific warm pool (WPWP) and the eastern equatorial Pacific (EEP) that show Pliocene WPWP temperatures similar to today but a warmer Pliocene EEP, resulting in a much reduced east-west gradient [Wara et al., 2005]. These findings form the basis of the "permanent El Niño-like state" paradigm of Pliocene climate. However, recent studies using organic biomarker proxies produce temperature records that indicate a WPWP cooling trend since the Pliocene that differs markedly from Mg/Ca-temperature records [O'Brien et al., 2014; Zhang et al., 2014]. Though much of the debate has focused on changes in seawater Mg/Ca, spatial variations in proxy agreement point to dissolution as a key factor. Dissolution, which imparts a cool bias to Mg/Ca temperatures, varies across ocean basins depending on Δ[CO32-], the difference from the carbonate ion concentration needed for calcite saturation. By necessity, dissolution corrections use the modern value of Δ[CO32-] for the entire record, so it is possible that Pliocene proxy discrepancies could stem from varying Δ[CO32-] over time. Here we present benthic foraminiferal B/Ca data (a proxy for Δ[CO32-]) from the EEP and WEP spanning the past 5 Myr, to constrain the effect of dissolution on Pliocene Mg/Ca records. To account for possible changes in seawater B/Ca, we present paired epifaunal-infaunal B/Ca data. Infaunal species are much less sensitive to Δ[CO32-] than epifaunal species, but would still record long-term changes in seawater B/Ca. The true Δ[CO32-] can thus be calculated from the epifaunal-infaunal B/Ca difference [Brown et al., 2011]. Our study is the first to apply this approach downcore; by accounting for long-term changes in seawater, it greatly expands use of the B/Ca proxy and enables a first attempt at correcting for time

  6. Electrical properties of Mg doped ZnO nanostructure annealed at different temperature

    SciTech Connect

    Mohamed, R. Mamat, M. H. Rusop, M.; Ismail, A. S.; Khusaimi, Z.

    2016-07-06

    In this work, ZincOxide (ZnO) nanostructures doped with Mg were successfully grown on the glass substrate. Magnesium (Mg) metal element was added in the ZnO host which acts as a doping agent. Different temperature in range of 250°C to 500°C was used in order to investigate the effect of annealing temperature of ZnO thin films. Field Emission Scanning Electron Microscopy (FESEM) was used to investigate the physical characteristic of ZnO thin films. FESEM results have revealed that ZnO nanorods were grown vertically aligned. The structural properties were determined by using X-Ray Diffraction (XRD) analysis. XRD results showed Mg doped ZnO thin have highest crystalinnity at 500°C annealing temperature. The electrical properties were investigating by using Current-Voltage (I-V) measurement. I-V measurement showed the electrical properties were varied at different annealing temperature. The annealing temperature at 500°C has the highest electrical conductance properties.

  7. Ostracode Mg/Ca Ratios from Quaternary Sediments of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Dwyer, G. S.; Caverly, E. K.; Cronin, T. M.; Polyak, L. V.; DeNinno, L.; Rodriguez-Lazaro, J.

    2013-12-01

    We analyzed magnesium/calcium (Mg/Ca) ratios from adult, calcitic shells of the deep-sea ostracode Krithe from the Northwind and Mendeleev Ridges, Arctic Ocean, to reconstruct orbital-scale Quaternary bottom-water temperature history. Results show an early Pleistocene (~1.5 Ma to 500 ka) Mg/CaKrithe pattern with low-amplitude, possibly orbitally controlled, oscillations between 10.5 and 12.5 mmol/mol followed by a progressive trend towards higher ratios (> 17 mmol/mol) during the last 500 ka. This shift coincides with the mid-Pleistocene Transition and mid-Brunhes Event (~ 300-500 ka) recognized in microfaunal proxy records in the Arctic Ocean. Analyses of Mg/CaKrithe from intervals representing marine isotope stage 11 (MIS 11) in 5 cores from water depths from 700 to 1470 m show Mg/Ca ratios ranging from 10.5 to 14 mmol/mol. A 2 mmol/mol excursion in Mg/CaKrithe within MIS 11 seen in all cores likely corresponds to a brief stadial event recognized also in planktic and benthic microfaunas. We will discuss the implications of Mg/Ca paleothermometry for deep Arctic Ocean circulation and the evolution of Arctic sea ice during major Quaternary climatic transitions as well as possible factors other than water temperature that may influence Mg/Ca ratios in Krithe shells from Quaternary sediments from the Arctic Ocean.

  8. Timing and mechanism for intratest Mg/Ca variability in a living planktic foraminifer

    NASA Astrophysics Data System (ADS)

    Spero, Howard J.; Eggins, Stephen M.; Russell, Ann D.; Vetter, Lael; Kilburn, Matt R.; Hönisch, Bärbel

    2015-01-01

    Geochemical observations indicate that planktic foraminifer test Mg/Ca is heterogeneous in many species, thereby challenging its use as a paleotemperature proxy for paleoceanographic reconstructions. We present Mg/Ca and Ba/Ca data collected by laser ablation ICP-MS from the shells of Orbulina universa cultured in controlled laboratory experiments. Test calcite was labeled with Ba-spiked seawater for 12 h day or night calcification periods to quantify the timing of intratest Mg-banding across multiple diurnal cycles. Results demonstrate that high Mg bands are precipitated during the night whereas low Mg bands are precipitated during the day. Data obtained from specimens growing at 20 °C and 25 °C show that Mg/Ca ratios in both high and low Mg bands increase with temperature, and average test Mg/Ca ratios are in excellent agreement with previously published empirical calibrations based on bulk solution ICP-MS analyses. In general, Mg band concentrations decrease with increasing pH and/or [CO2-3] but this effect decreases as experimental temperatures increase from 20 °C to 25 °C. We suggest that mitochondrial uptake of Mg2+ from the thin calcifying fluid beneath streaming rhizopodial filaments may provide the primary locus for Mg2+ removal during test calcification, and that diurnal variations in either mitochondrial density or activity produce Mg banding. These results demonstrate that Mg banding is an inherent component of test biomineralization in O. universa and show that the Mg/Ca paleothermometer remains a fundamental tool for reconstructing past ocean temperatures from fossil foraminifers.

  9. The synthesis of CaZn2Sb2 and its thermoelectric properties

    NASA Technical Reports Server (NTRS)

    Snyder, J.; Starkll, D.

    2002-01-01

    CaZn2Sb2 was prepared and examined for use as a hightemperature thermoelectric material. It has a high Seebeck coefficient and high electrical conductivity-comparable to B-Zn4Sb3. These two properties are vital in determining the ability of the compound to change heat into electricity isentropically.

  10. [Adsorption of perchlorate by calcined Mg/Zn/Al layered double hydroxides].

    PubMed

    Wang, Hong-Yu; Liu, Yan

    2014-07-01

    The adsorption capacity of perchlorate by Mg/Zn/Al layered double hydroxides was investigated. The samples were characterized by X-ray diffraction (XRD) and the adsorption isothermal model and dynamic model were discussed. The effect of calcination temperature, Mg/Zn/Al molar ratio, pH value of solution, adsorption time and dosage on the adsorption capacity of samples were studied. The experiment results showed that the removal ratio and adsorption capacity reached the highest and the pH value had good applicability when the molar ratio was Mg/Zn/Al = 2: 1 : 1. The adsorption of perchlorate basically conformed to the pseudo-second kinetics and Langmuir, Freundlich isotherm model.

  11. Methane-Sensing Performance Enhancement in Graphene Oxide/Mg:ZnO Heterostructure Devices

    NASA Astrophysics Data System (ADS)

    Sarkar, Argha; Maity, Santanu; Joseph, Aneesh M.; Chakraborty, S. K.; Thomas, Tiju

    2017-10-01

    Methane-sensing using reduced doped graphene oxide (rGO)/Mg:ZnO heterostructure devices is reported here. All samples are tested with CH4 in dry air ambient by a gas-analyzing set-up. Crystallinity of the sensing film is improved through annealing treatment (at 800°C). The active device area (i.e., the rGO and rGO/Mg:ZnO heterostructures) are characterized using scanning electron microscope imaging, x-ray diffraction, and x-ray spectroscopy measurements. Electrical performance of the fabricated device is optimized. rGO/Mg:ZnO heterostructures are substantially more sensitive and have better transient response than bare rGO-based sensor devices. All fundamental parameters such as sensitivity and response-recovery time are examined and reported in detail.

  12. The softening effect of heat-treated strengthened Al-Zn-Mg alloy in welding process

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaohong; Chen, Jingqing; Zhang, Kang; Chen, Hui

    2017-07-01

    Weld joint softening occurs during the welding process of heat-treatable aluminum alloys and strongly influences the mechanical properties. In this work, the softening of heat-treated Al-Zn-Mg alloy was studied in the multipass welding process. By Gleeble-3500 thermal-mechanical simulator, the heat treatment and tensile test with welding thermal cycles were carried out to simulate the microstructure evolution and mechanical softening during multipass welding. After that, the softening mechanism of the HAZ was analyzed by microstructure analysis. The results indicate that the heat-treated Al-Zn-Mg alloy exhibited obvious softening after several thermal cycles with peak temperature higher than 200∘C, and this phenomenon is worse with increasing peak temperature. Based on the microstructure analysis, it was found that the reinforcement phase changes according to the applied thermal cycles, which strongly affects the strength of Al-Zn-Mg alloys.

  13. Novel Approach for the Reduction of ZnO and MgO Using a Direct Diode-Laser

    NASA Astrophysics Data System (ADS)

    Mahmoud, M. S.; Yabe, T.; Iida, E.

    2017-02-01

    In this work, we present the results of using the diode laser with an energy density of 6.6 × 1011 W/m3 for reducing ZnO to Zn in vacuum as a first step. Subsequently, we use the diode laser for the reduction of MgO using Zn as the reducing agent. Although Zn is one of the candidates proposed for the renewable energy cycle, it is more auspicious to use it as a recyclable reducing agent. Herein, the reduction efficiency was measured in terms of moles of Zn or Mg obtained per moles of ZnO or MgO ablated. The energy efficiency is measured in terms of mass of Zn or Mg produced per energy consumed by diode laser. For the first part, the largest reduction rate was 15.8 mg/s, corresponding to reduction and energy efficiencies of 76.6 pct and 16.14 mg/kJ, respectively. The yield for the process was 8.8 pct of the theoretically calculated one, which is only better than the solar ZnO reduction process. For the second part, the reduction of MgO with Zn was attainable by diode laser, the resultant Mg was associated with Zn traces, and the electron probe micro analysis results showed that the MgO reduction efficiency fluctuates between 14.4 and 26.6 pct. Different scenarios were suggested for the mechanism of the reaction.

  14. Homoepitaxial nonpolar (10-10) ZnO/ZnMgO monolithic microcavities: Towards reduced photonic disorder

    SciTech Connect

    Zuniga-Perez, J. Kappei, L.; Deparis, C.; Chenot, S.; Leroux, M.; Reveret, F.; Jamadi, O.; Leymarie, J.; Grundmann, M.; Prado, E. de

    2016-06-20

    Nonpolar ZnO/ZnMgO-based optical microcavities have been grown on (10-10) m-plane ZnO substrates by plasma-assisted molecular beam epitaxy. Reflectivity measurements indicate an exponential increase of the cavity quality factor with the number of layers in the distributed Bragg reflectors. Most importantly, microreflectivity spectra recorded with a spot size in the order of 2 μm show a negligible photonic disorder (well below 1 meV), leading to local quality factors equivalent to those obtained by macroreflectivity. The anisotropic character of the nonpolar heterostructures manifests itself both in the surface features, elongated parallel to the in-plane c direction, and in the optical spectra, with two cavity modes being observed at different energies for orthogonal polarizations.

  15. Effects of Zn content and initial grain size on double peak basal textures of Mg-Zn-Al alloys

    NASA Astrophysics Data System (ADS)

    Choi, Jung Woo; Shin, Kwang Seon

    2017-07-01

    This study investigates the effects of Zn content on the double peak basal textures of extruded Mg-Zn-Al alloys. Two-step plane strain compression (PSC) tests (PSC at room temperature as a first step and PSC at high temperature as a second step) were conducted under various temperatures (200-340 °C) and initial strain rates (0.0002 s-1 and 0.04 s-1) using the extruded ZA11, ZA31 and ZA61 alloys. Additionally, to examine the effects of initial grain size on the double peak basal texture, two-step PSC tests were conducted using annealed ZA61 and cast ZA63 alloys. Tilt angle corresponding to the peak in the double peak basal texture increased with increasing Zn content. This correlation was clearly shown especially at low temperature and high initial strain rate. The tilt angle corresponding to the peak increased with decreasing initial grain size.

  16. Mg/Ca, Sr/Ca and Ca isotope ratios in benthonic foraminifers related to test structure, mineralogy and environmental controls

    NASA Astrophysics Data System (ADS)

    Gussone, Nikolaus; Filipsson, Helena L.; Kuhnert, Henning

    2016-01-01

    We analysed Mg/Ca, Sr/Ca and Ca isotope ratios of benthonic foraminifers from sediment core tops retrieved during several research cruises in the Atlantic Ocean, in order to improve the understanding of isotope fractionation and element partitioning resulting from biomineralisation processes and changes in ambient conditions. Species include foraminifers secreting tests composed of hyaline low magnesium calcite, porcelaneous high magnesium calcite as well as aragonite. Our results demonstrate systematic isotope fractionation and element partitioning patterns specific for these foraminiferal groups. Calcium isotope fractionation is similar in porcelaneous and hyaline calcite tests and both groups demonstrate the previously described anomaly with enrichment of heavy isotopes around 3-4 °C (Gussone and Filipsson, 2010). Calcium isotope ratios of the aragonitic species Hoeglundina elegans, on the other hand, are about 0.4‰ lighter compared to the calcitic species, which is in general agreement with stronger fractionation in inorganic aragonite compared to calcite. However, the low and strongly variable Sr content suggests additional processes during test formation, and we propose that transmembrane ion transport or a precursor phase to aragonite may be involved. Porcelaneous tests, composed of high Mg calcite, incorporate higher amounts of Sr compared to hyaline low Mg calcite, in agreement with inorganic calcite systematics, but also porcelaneous tests with reduced Mg/Ca show high Sr/Ca. While calcium isotopes, Sr/Ca and Mg/Ca in benthonic foraminifers primarily appear to fractionate and partition with a dominant inorganic control, δ44/40Ca temperature and growth rate dependencies of benthonic foraminifer tests favour a dominant contribution of light Ca by transmembrane transport relative to unfractionated seawater Ca to the calcifying fluid, thus controlling the formation of foraminiferal δ44/40Ca and Sr/Ca proxy signals.

  17. Surface modification of an Mg-1Ca alloy to slow down its biocorrosion by chitosan.

    PubMed

    Gu, X N; Zheng, Y F; Lan, Q X; Cheng, Y; Zhang, Z X; Xi, T F; Zhang, D Y

    2009-08-01

    The surface morphologies before and after immersion corrosion test of various chitosan-coated Mg-1Ca alloy samples were studied to investigate the effect of chitosan dip coating on the slowdown of biocorrosion. It showed that the corrosion resistance of the Mg-Ca alloy increased after coating with chitosan, and depended on both the chitosan molecular weight and layer numbers of coating. The Mg-Ca alloy coated by chitosan with a molecular weight of 2.7 x 10(5) for six layers has smooth and intact surface morphology, and exhibits the highest corrosion resistance in a simulated body fluid.

  18. In vitro corrosion of Mg-Ca alloy — The influence of glucose content

    NASA Astrophysics Data System (ADS)

    Cui, Lan-Yue; Li, Xiao-Ting; Zeng, Rong-Chang; Li, Shuo-Qi; Han, En-Hou; Song, Liang

    2017-09-01

    Influence of glucose on corrosion of biomedical Mg-1.35Ca alloy was made using hydrogen evolution, pH and electrochemical polarization in isotonic saline solution. The corrosion morphologies, compositions and structures were probed by virtue of SEM, EDS, FTIR, XRD and XPS. Results indicate that the glucose accelerated the corrosion of the alloy. The elemental Ca has no visible effect on the corrosion mechanism of glucose for the Mg-1.35Ca alloy in comparison with pure Mg. In addition, the presence of CO2 has beneficial effect against corrosion due to the formation of a layer of carbonatecontaining products.

  19. The Dissolution Kinetics of MgO into CaO-MgO-Fe2O3 Slag

    NASA Astrophysics Data System (ADS)

    Wei, Ruirui; Lv, Xuewei; Yue, Zhiwen; Xiang, Shenglin

    2017-02-01

    Calcium ferrite is the main binding phase for high-basicity sinter. The production and structure of calcium ferrite greatly influence the quality of the sinter. With the change in gangue composition, MgO becomes an important factor in the generation of calcium ferrite. In this study, the rotating cylinder method was used to study the dissolution kinetics of MgO into CaO-MgO-Fe2O3 melt. The experimental variables included the temperature, the initial composition of the melt, the Fe2O3/CaO mass ratio, the rotation time, and the rotation speed. The results indicate that the dissolution rate increases with increasing dissolution time, temperature, and rotation speed but decreases with increasing MgO content and Fe2O3/CaO mass ratio in the initial slag. The dissolution rate was observed to increase and then decrease with the addition of SiO2 in the initial slag. The activation energy and diffusion coefficient for MgO dissolution were found to range from 117.31 to 234.24 kJ mol-1 and from 1.03 × 10-6 to 1.18 × 10-5 cm2 s-1, respectively. The concentration difference between the solid and liquid phases is the main driving force for dissolution, but the viscosity and magnesium ion diffusivity of the melt also affect the process.

  20. Ca2+, Mg2+-dependent DNase involvement in apoptotic effects in spermatozoa of sea urchin Strongylocentrotus intermedius induced by two-headed sphingolipid rhizochalin.

    PubMed

    Sibirtsev, Juriy T; Shastina, Valeria V; Menzorova, Natalia I; Makarieva, Tatyana N; Rasskazov, Valeriy A

    2011-06-01

    Previously, we have purified three distinct DNases from spermatozoa of sea urchin Strongylocentrotus intermedius and we suppose the role of Ca(2+), Mg(2+)-dependent DNase (Ca, Mg-DNase) in apoptosis of spermatozoa. Two-headed sphingolipid rhizochalin (Rhz) induced characteristic apoptotic nuclear chromatin changes, internucleosomal DNA cleavage, and activation of caspase-9, caspase-8, and caspase-3 in spermatozoa as was shown by fluorescence Hoechst 33342/PI/FDA analysis, DNA fragmentation assay, and fluorescence caspase inhibitors FAM-LEHD-fmk, FAM-IETD-fmk, and FAM-DEVD-fmk, respectively. Inhibitor of caspase-3 z-DEVD-fmk subdued Rhz-induced internucleosomal ladder formation, which confirmed the major role of caspase-3 in apoptotic DNA cleavage probably through Ca, Mg-DNase activation. Participation of sea urchin Ca, Mg-DNase in apoptosis of spermatozoa was demonstrated by ions Zn(2+) blocking of Rhz-induced DNA fragmentation due to direct inhibition of the Ca, Mg-DNase and internucleosomal cleavage of HeLa S and Vero E6 cell nuclei chromatin by highly purified Ca, Mg-DNase.

  1. Stable isotopes, Sr/Ca, and Mg/Ca in biogenic carbonates from Petaluma Marsh, northern California, USA

    SciTech Connect

    Ingram, B.L.; Deckker, P. de; Chivas, A.R.; Conrad, M.E.; Byrne, A.R.

    1998-10-01

    Stable isotope ({sup 18}O/{sup 16}O and {sup 13}C/{sup 12}C) and minor-element compositions (Sr/Ca and Mg/Ca ratios) of ostracodes and gastropods separated from marsh sediments from San Francisco Bay, Northern California, were used to reconstruct paleoenvironmental changes in Petaluma March over the past 700 yr. The value of {delta}{sup 18}O in the marsh carbonates reflects changes in freshwater inflow, evaporation, and temperature. Mg/Ca and Sr/Ca in ostracode calcite reflect changes in both freshwater inflow and temperature, although primarily reflect temperature changes in the salinity range of about 10--35{per_thousand}. Ostracode {delta}{sup 18}O values show a gradual increase by 5{per_thousand} between 500 yr BP and the present, probably reflecting rising sea level and increased evaporation in the marsh. Superimposed on this trend are higher frequency Mg/Ca and {delta}{sup 18}O variations (3--4{per_thousand}), probably reflecting changes in freshwater inflow and evaporation. A period of low Mg/Ca occurred between about 100--300 cal yr BP, suggesting wetter and cooler conditions during the Little Ice Age. Higher Mg/Ca ratios occurred 600--700 cal yr BP, indicating drier and warmer conditions during the end of the Medieval Warm Period. Both ostracode and gastropod {delta}{sup 13}C values decrease up-core, reflecting decomposition of marsh vegetation, which changes from C{sub 4} ({delta}{sup 13}C {approximately} {minus}12{per_thousand}) to CAM ({delta}{sup 13}C = {minus}26{per_thousand})-type vegetation over time.

  2. Stable isotopes, Sr/Ca, and Mg/Ca in biogenic carbonates from Petaluma Marsh, northern California, USA

    SciTech Connect

    Ingram, B.L.; De Deckker, P.; Chivas, A.R.; Conrad, M.E.; Byrne, A.R.

    2004-10-19

    Stable isotope ({sup 18}O/{sup 16}O and {sup 13}C/{sup 12}C) and minor-element compositions (Sr/Ca and Mg/Ca ratios) of ostracodes and gastropods separated from marsh sediments from San Francisco Bay, Northern California, were used to reconstruct paleoenvironmental changes in Petaluma Marsh over the past 700 yr. The value of {delta}{sup 18}O in the marsh carbonates reflects changes in freshwater inflow, evaporation, and temperature. Mg/Ca and Sr/Ca in ostracode calcite reflect changes in both freshwater inflow and temperature, although primarily reflect temperature changes in the salinity range of about 10-35 {per_thousand}. Ostracode {delta}{sup 18}O values show a gradual increase by 5 {per_thousand} between 500 yr BR and the present, probably reflecting rising sea level and increased evaporation in the marsh. Superimposed on this trend are higher frequency Mg/Ca and {delta}{sup 18}O variations (3-4 {per_thousand}), probably reflecting changes in freshwater inflow and evaporation. A period of low Mg/Ca occurred between about 100-300 cal yr BP, suggesting wetter and cooler conditions during the Little Ice Age. Higher Mg/Ca ratios occurred 600-700 cal yr BP, indicating drier and warmer conditions during the end of the Medieval Warm Period. Both ostracode and gastropod {delta}{sup 13}C values decrease up-core, reflecting decomposition of marsh vegetation, which changes from C{sub 4} ({delta}{sup 13}C {approx} -12{per_thousand}) to CAM ({delta}{sup 13}C = -26 {per_thousand})-type vegetation over time.

  3. Diffuse scattering and phason fluctuations in the Zn-Mg-Sc icosahedral quasicrystal and its Zn-Sc periodic approximant.

    PubMed

    de Boissieu, M; Francoual, S; Kaneko, Y; Ishimasa, T

    2005-09-02

    We report on the absolute scale measurement of the x-ray diffuse scattering in the ZnMgSc icosahedral quasicrystal and its periodic approximant. Whereas the diffuse scattering in the approximant is purely accounted for by thermal diffuse scattering, an additional signal is observed in the quasicrystal. It is related to phason fluctuations as indicated by its Q(2)(per) dependence. Moreover, when compared to previous measurements carried out on the i-AlPdMn phase, we find that the amount of diffuse scattering is smaller in the i-ZnMgSc phase, in agreement with larger phason elastic constants in this phase. This is confirmed by the observation of a large number of weak Bragg peaks having a high Q(per) reciprocal space component.

  4. Diffuse Scattering and Phason Fluctuations in the Zn-Mg-Sc Icosahedral Quasicrystal and Its Zn-Sc Periodic Approximant

    SciTech Connect

    Boissieu, M. de; Francoual, S.; Kaneko, Y.; Ishimasa, T.

    2005-09-02

    We report on the absolute scale measurement of the x-ray diffuse scattering in the ZnMgSc icosahedral quasicrystal and its periodic approximant. Whereas the diffuse scattering in the approximant is purely accounted for by thermal diffuse scattering, an additional signal is observed in the quasicrystal. It is related to phason fluctuations as indicated by its Q{sub per}{sup 2} dependence. Moreover, when compared to previous measurements carried out on the i-AlPdMn phase, we find that the amount of diffuse scattering is smaller in the i-ZnMgSc phase, in agreement with larger phason elastic constants in this phase. This is confirmed by the observation of a large number of weak Bragg peaks having a high Q{sub per} reciprocal space component.

  5. Na Partitioning During Thermomechanical Processing of an Mg-Sn-Zn-Na Alloy

    NASA Astrophysics Data System (ADS)

    TerBush, Jessica R.; Stanford, Nicole; Nie, Jian-Feng; Barnett, Matthew R.

    2013-11-01

    Microstructural characterization was used to examine the changes that occur in an Mg-6Sn-5Zn-0.3Na alloy from casting to extrusion at either 623 K or 723 K (350 °C or 450 °C) followed by artificial aging at 473 K (200 °C). In particular, the partitioning of Na was examined at each step using STEM-EDS mapping. Na atoms were found to preferentially partition to the Mg-Zn phase when present. After extrusion, when no Mg-Zn was observed, the spherical Mg2Sn particles were found to be enriched in Na, particularly at the higher extrusion temperature. Artificial aging following extrusion resulted in a change in Na partitioning, and a coarse distribution of Mg-Zn precipitate rods. Na microadditions led to a high as-extruded hardness, but a significant tension-compression yield asymmetry was still observed at room temperature. The compressive yield strength was found to decrease significantly after 1000 hours of aging.

  6. Combinatorial sputtering of Ga-doped (Zn,Mg)O for contact applications in solar cells

    SciTech Connect

    Rajbhandari, Pravakar P.; Bikowski, Andre; Perkins, John D.; Dhakal, Tara P.; Zakutayev, Andriy

    2016-09-20

    In this study, the development of tunable contact materials based on environmentally friendly chemical elements using scalable deposition approaches is necessary for existing and emerging solar energy conversion technologies. In this paper, the properties of ZnO alloyed with magnesium (Mg), and doped with gallium (Ga) are studied using combinatorial thin film experiments. As a result of these studies, the optical band gap of the sputtered Zn1-xMgxO thin films was determined to vary from 3.3 to 3.6 eV for a compositional spread of Mg content in the 0.04 < x < 0.17 range. Depending on whether or not Ga dopants were added, the electron concentrations were on the order of 1017 cm-3 or 1020 cm-3, respectively. Based on these results and on the Kelvin Probe work function measurements, a band diagram was derived using basic semiconductor physics equations. The quantitative determination of how the energy levels of Ga-doped (Zn, Mg)O thin films change as a function of Mg composition presented here, will facilitate their use as optimized contact layers for both Cu2ZnSnS4 (CZTS), Cu(In, Ga)Se2 (CIGS) and other solar cell absorbers.

  7. Fabrication of stable, wide-bandgap thin films of Mg, Zn and O

    DOEpatents

    Katiyar, Ram S.; Bhattacharya, Pijush; Das, Rasmi R.

    2006-07-25

    A stable, wide-bandgap (approximately 6 eV) ZnO/MgO multilayer thin film is fabricated using pulsed-laser deposition on c-plane Al2O3 substrates. Layers of ZnO alternate with layers of MgO. The thickness of MgO is a constant of approximately 1 nm; the thicknesses of ZnO layers vary from approximately 0.75 to 2.5 nm. Abrupt structural transitions from hexagonal to cubic phase follow a decrease in the thickness of ZnO sublayers within this range. The band gap of the thin films is also influenced by the crystalline structure of multilayer stacks. Thin films with hexagonal and cubic structure have band-gap values of 3.5 and 6 eV, respectively. In the hexagonal phase, Mg content of the films is approximately 40%; in the cubic phase Mg content is approximately 60%. The thin films are stable and their structural and optical properties are unaffected by annealing at 750.degree. C.

  8. Mechanisms of rapid reactive oxygen species generation in response to cytosolic Ca2+ or Zn2+ loads in cortical neurons.

    PubMed

    Clausen, Aaron; McClanahan, Taylor; Ji, Sung G; Weiss, John H

    2013-01-01

    Excessive "excitotoxic" accumulation of Ca(2+) and Zn(2+) within neurons contributes to neurodegeneration in pathological conditions including ischemia. Putative early targets of these ions, both of which are linked to increased reactive oxygen species (ROS) generation, are mitochondria and the cytosolic enzyme, NADPH oxidase (NOX). The present study uses primary cortical neuronal cultures to examine respective contributions of mitochondria and NOX to ROS generation in response to Ca(2+) or Zn(2+) loading. Induction of rapid cytosolic accumulation of either Ca(2+) (via NMDA exposure) or Zn(2+) (via Zn(2+)/Pyrithione exposure in 0 Ca(2+)) caused sharp cytosolic rises in these ions, as well as a strong and rapid increase in ROS generation. Inhibition of NOX activation significantly reduced the Ca(2+)-induced ROS production with little effect on the Zn(2+)- triggered ROS generation. Conversely, dissipation of the mitochondrial electrochemical gradient increased the cytosolic Ca(2+) or Zn(2+) rises caused by these exposures, consistent with inhibition of mitochondrial uptake of these ions. However, such disruption of mitochondrial function markedly suppressed the Zn(2+)-triggered ROS, while partially attenuating the Ca(2+)-triggered ROS. Furthermore, block of the mitochondrial Ca(2+) uniporter (MCU), through which Zn(2+) as well as Ca(2+) can enter the mitochondrial matrix, substantially diminished Zn(2+) triggered ROS production, suggesting that the ROS generation occurs specifically in response to Zn(2+) entry into mitochondria. Finally, in the presence of the sulfhydryl-oxidizing agent 2,2'-dithiodipyridine, which impairs Zn(2+) binding to cytosolic metalloproteins, far lower Zn(2+) exposures were able to induce mitochondrial Zn(2+) uptake and consequent ROS generation. Thus, whereas rapid acute accumulation of Zn(2+) and Ca(2+) each can trigger injurious ROS generation, Zn(2+) entry into mitochondria via the MCU may do so with particular potency. This may be of

  9. Effects of Mg doping content and annealing temperature on the structural properties of Zn1- x Mg x O thin films prepared by radio-frequency magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Du, Wen-han; Yang, Jing-jing; Zhao, Yu; Xiong, Chao

    2017-01-01

    The doping content of Mg plays an important role in the crystalline structure and morphology properties of Zn1- x Mg x O thin films. Here, using radio-frequency magnetron sputtering method, we prepared Zn1- x Mg x O thin films on single crystalline Si(100) substrates with a series of x values. By means of X-ray diffraction (XRD) and scanning electron microscope (SEM), the crystalline structure and morphology of Zn1- x Mg x O thin films with different x values are investigated. The crystalline structure of Zn1- x Mg x O thin film is single phase with x<0.3, while there is phase separation phenomenon with x>0.3, and hexagonal and cubic structures will coexist in Zn1- x Mg x O thin films with higher x values. Especially with lower x values, a shoulder peak of 35.1° appearing in the XRD pattern indicates a double-crystalline structure of Zn1- x Mg x O thin film. The crystalline quality has been improved and the inner stress has been released, after the Zn1- x Mg x O thin films were annealed at 600 °C in vacuum condition.

  10. Effect of sertraline on [Ca2+](i) and viability of human MG63 osteosarcoma cells.

    PubMed

    Lin, Ko-Long; Chi, Chao-Chuan; Lu, Ti; Tseng, Li-Ling; Wang, Jue-Long; Lu, Yi-Chau; Jan, Chung-Ren

    2013-04-01

    The antidepressant, sertraline, has been shown to have diverse in vitro effects. This study examined whether sertraline altered [Ca(2+)](i) in MG63 human osteosarcoma cells by using fura-2 as a Ca(2+)-sensitive fluorescent dye. At 50-200 µM, sertraline induced a [Ca(2+)](i) rise in a concentration-dependent manner. Ca(2+) response was decreased by removing extracellular Ca(2+), suggesting that Ca(2+) entry and release contributed to the [Ca(2+)](i) signal. Sertraline-induced Ca(2+) entry was inhibited by nifedipine, La(3+), Gd(3+), and SK&F96365. When extracellular Ca(2+) was removed, pretreatment with the endoplasmic reticulum (ER) Ca(2+) pump inhibitor, thapsigargin, or 2,5-di-tert-butylhydroquinone (BHQ) abolished the sertraline-evoked [Ca(2+)](i) rise. Incubation with sertraline also abolished the thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C (PLC) with U73122 abolished the sertraline-induced [Ca(2+)](i) rise. At 20-30 µM, overnight treatment with sertraline killed cells in a concentration-dependent manner. The cytotoxic effect of sertraline was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Annexin V/propidium iodide staining data demonstrate that sertraline (30 µM) evoked apoptosis. Sertraline (20 and 30 µM) also increased levels of reactive oxygen species. Together, in human osteosarcoma cells, sertraline evoked a [Ca(2+)](i) rise by inducing PLC-dependent Ca(2+) release from the ER and Ca(2+) entry by L-type Ca(2+) channels and store-operated Ca(2+) channels. Sertraline induced cell death that may involve apoptosis by mitochondrial pathways.

  11. The ternary system K2SO4MgSO4CaSO4

    USGS Publications Warehouse

    Rowe, J.J.; Morey, G.W.; Silber, C.C.

    1967-01-01

    Melting and subsolidus relations in the system K2SO4MgSO4CaSO4 were studied using heating-cooling curves, differential thermal analysis, optics, X-ray diffraction at room and high temperatures and by quenching techniques. Previous investigators were unable to study the binary MgSO4CaSO4 system and the adjacent area in the ternary system because of the decomposition of MgSO4 and CaSO4 at high temperatures. This problem was partly overcome by a novel sealed-tube quenching method, by hydrothermal synthesis, and by long-time heating in the solidus. As a result of this study, we found: (1) a new compound, CaSO4??3MgSO4 (m.p. 1201??C) with a field extending into the ternary system; (2) a high temperature form of MgSO4 with a sluggishly reversible inversion. An X-ray diffraction pattern for this polymorphic form is given; (3) the inversion of ??-CaSO4 (anhydrite) to ??-CaSO4 at 1195??C, in agreement with grahmann; (1) (4) the melting point of MgSO4 is 1136??C and that of CaSO4 is 1462??C (using sealed tube methods to prevent decomposition of the sulphates); (5) calcium langbeinite (K2SO4??2CaSO4) is the only compound in the K2SO4CaSO4 binary system. This resolved discrepancies in the results of previous investigators; (6) a continuous solid solution series between congruently melting K2SOP4??2MgSO4 (langbeinite) and incongruently melting K2SO4??2CaSO4 (calcium langbeinite); (7) the liquidus in the ternary system consists of primary phase fields of K2SO4, MgSO4, CaSO4, langbeinite-calcium langbeinite solid solution, and CaSO4??3MgSO4. The CaSO4 field extends over a large portion of the system. Previously reported fields for the compounds (K2SO4??MgSO4??nCaSO4), K2SO4??3CaSO4 and K2SO4??CaSO4 were not found; (8) a minimum in the ternary system at: 740??C, 25% MgSO4, 6% CaSO4, 69% K2SO4; and ternary eutectics at 882??C, 49% MgSO4, 19% CaSO4, 32% K2SO4; and 880??, 67??5% MgSO4, 5% CaSO4, 27??5% K2SO4. ?? 1967.

  12. Microstructural characteristics and aging response of Zn-containing Al-Mg-Si-Cu alloy

    NASA Astrophysics Data System (ADS)

    Cai, Yuan-hua; Wang, Cong; Zhang, Ji-shan

    2013-07-01

    Al-Mg-Si-Cu alloys with and without Zn addition were fabricated by conventional ingot metallurgy method. The microstructures and properties were investigated using optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), tensile test, hardness test, and electrical conductivity measurement. It is found that the as-cast Al-Mg-Si-Cu-Zn alloy is composed of coarse dendritic grains, long needle-like β/δ-AlFeSi white intermetallics, and Chinese script-like α-AlFeSi compounds. During high temperature homogenization treatment, only harmful needle-like β-AlFeSi phase undergoes fragmentation and spheroidizing at its tips, and the destructive needle-like δ-phase does not show any morphological and size changes. Phase transitions from β-AlFeSi to α-AlFeSi and from δ-AlFeSi to β-AlFeSi are also not found. Zn addition improves the aging hardening response during the former aging stage and postpones the peak-aged hardness to a long aging time. In T4 condition, Zn addition does not obviously increase the yield strength and decrease the elongation, but it markedly improves paint-bake hardening response during paint-bake cycle. The addition of 0.5wt% Zn can lead to an increment of 99 MPa in yield strength compared with the value of 69 MPa for the alloy without Zn after paint-bake cycle.

  13. Microstructural analysis of biodegradable Mg-0.9Ca-1.2Zr alloy

    NASA Astrophysics Data System (ADS)

    Istrate, B.; Munteanu, C.; Geanta, V.; Baltatu, S.; Focsaneanu, S.; Earar, K.

    2016-08-01

    Magnesium alloys have applications in aerospace and medical applications as biodegradable orthopedic implants. Alloying with biocompatible elements, such as calcium or zirconium contribute to refining the the microstructure and improves corrosion resistance with the formation of an eutectic compound - Mg2Ca at boundary alpha-Mg grains. The purpose of this paper is to present the microstructure throw optical and scanning electron methods and phase and constituents identification with X-ray analysis. The results showed the presence of alpha-Mg grains with formation of a mechanical compound - Mg2Ca and appearance of alpha- Zr phase relatively uniformly distributed in nests.

  14. Scleractinian corals cultured in low Mg/Ca seawater form aragonite skeleton

    NASA Astrophysics Data System (ADS)

    Stolarski, Jaroslaw; Reynaud, Stéphanie; Ferrier-Pages, Christine; Janiszewska, Katarzyna; Domart-Coulon, Isabelle; Beraud, Eric; Marrocchi, Yves; Mazur, Maciej; Szlachetko, Jakub; Meibom, Anders

    2010-05-01

    Scleractinian corals represent a testing ground for ideas regarding biologically vs. environmentally controlled calcification. The morphology of skeletal micro-structural units (arrangement of the skeletal fibers) and their biogeochemical composition have, for a long time, been interpreted from two opposite view points: (1) as a purely physico-chemical process involving simple supersaturation of a fluid close in composition to seawater, hypothesized to exist at the interface between the skeleton and the calicoblastic cell-layer, or (2) a complete physiological control of calcification by the organism by means of a presumed amorphous precursor phase and precisely utilized organic macromolecules that control mineralogy, crystal orientation etc. Paleontological data originally supported the second interpretation because the aragonitic skeletal mineralogy appeared to be stable through geological time despite of changes in seawater chemistry (e.g., the late Mesozoic decrease of Mg/Ca ratio), which was believed to promote inorganic precipitation of calcite. However, Ries et al. (Geology 2006, 34: 525-528) argued that scleractinians are so-called 'hyper-calcifiers' and limited in their mineralogical control. Accordingly, in modern seawater (Mg/Ca molar ratio = 5.2) such organisms form aragonite simply because the Mg/Ca ratio favors this mineralogy. However, if the Mg/Ca ratio drops below 3.5, the mineralogy of such 'hyper-calcifiers' are supposed to become calcitic. In low-Mg/Ca experiments, Ries et al. detected calcite by X-ray diffraction of the bulk skeleton of Acropora, Montipora, and Porites and also indicated, by electron microprobe analyses, the presence of calcite in the uppermost portion of coral skeleton, though the exact position of the mapped areas were not indicated. We have cultured Acropora, Porites, Pavona and Galaxea in low Mg/Ca (compared with normal seawater) artificial seawater (ASW). A low Mg/Ca ratio can be obtained either by lowering the Mg

  15. On the nature of the bonding in Mg4 and Ca4 clusters

    NASA Astrophysics Data System (ADS)

    Pacchioni, Gianfranco; Koutecký, Jaroslav

    1982-12-01

    The bonding in the Mg4 and Ca4 clusters is studied using a pseudopotential multireference double-excitation configuration interaction method. The results confirm the calculations of chiles et al5.(AIP)

  16. Surface plasmon-enhanced ultraviolet photodetectors by using Au nanoparticles embedded in MgZnO thin films

    NASA Astrophysics Data System (ADS)

    Guo, Z. X.; Jiang, D. Y.; Zhao, M.; Zheng, T.; Lv, J. W.; Pei, J. N.; Hu, N.; Gao, S.; Liang, Q. C.; Zhao, J. X.; Hou, J. H.; Qin, J. M.

    2017-09-01

    This paper demonstrates surface plasmons (SPs) enhanced MgZnO ultraviolet (UV) photodetectors grown by a radio frequency (RF) magnetron sputtering technique, and the magnesium concentration is 30%. Predominantly, well-defined Au NPs with different sizes were produced embedded in MgZnO thin films. Notably, at 30 V applied bias, the proper combination MgZnO/Au NPs (40 s), responsivity as high as 341.08 A/W is achieved after optimizing the process. Impressively, the excellent comprehensive performance of MgZnO/Au NPs UV photodetectors should have great applied potential, a physical mechanism is given to explain the above results.

  17. Isotopic fractionation of Mg 2+(aq), Ca 2+(aq), and Fe 2+(aq) with carbonate minerals

    NASA Astrophysics Data System (ADS)

    Rustad, James R.; Casey, William H.; Yin, Qing-Zhu; Bylaska, Eric J.; Felmy, Andrew R.; Bogatko, Stuart A.; Jackson, Virgil E.; Dixon, David A.

    2010-11-01

    Density-functional electronic structure calculations are used to compute the equilibrium constants for 26Mg/ 24Mg and 44Ca/ 40Ca isotope exchange between carbonate minerals and uncomplexed divalent aquo ions. The most reliable calculations at the B3LYP/6-311++G(2d,2p) level predict equilibrium constants K, reported as 10 3ln ( K) at 25 °C, of -5.3, -1.1, and +1.2 for 26Mg/ 24Mg exchange between calcite (CaCO 3), magnesite (MgCO 3), and dolomite (Ca 0.5Mg 0.5CO 3), respectively, and Mg 2+(aq), with positive values indicating enrichment of the heavy isotope in the mineral phase. For 44Ca/ 40Ca exchange between calcite and Ca 2+(aq) at 25 °C, the calculations predict values of +1.5 for Ca 2+(aq) in 6-fold coordination and +4.1 for Ca 2+(aq) in 7-fold coordination. We find that the reduced partition function ratios can be reliably computed from systems as small as M(CO)610- and M(HO)62+ embedded in a set of fixed atoms representing the second-shell (and greater) coordination environment. We find that the aqueous cluster representing the aquo ion is much more sensitive to improvements in the basis set than the calculations on the mineral systems, and that fractionation factors should be computed using the best possible basis set for the aquo complex, even if the reduced partition function ratio calculated with the same basis set is not available for the mineral system. The new calculations show that the previous discrepancies between theory and experiment for Fe 3+-hematite and Fe 2+-siderite fractionations arise from an insufficiently accurate reduced partition function ratio for the Fe 3+(aq) and Fe 2+(aq) species.

  18. Isotopic Fractionation of Mg2+(aq), Ca2+(aq), and Fe2+(aq) with Carbonate Minerals

    SciTech Connect

    Rustad, James R.; Casey, William H.; Yin, Qing-Zhu; Bylaska, Eric J.; Felmy, Andrew R.; Bogatko, Stuart A.; Jackson, Virgil E.; Dixon, David A.

    2010-11-15

    Density functional electronic structure calculations are used to compute the equilibrium constant (the isotope fractionation factor) for 26Mg/24Mg and 44Ca/40Ca isotope exchange between carbonate minerals and uncomplexed divalent aquo ions. The most reliable calculations at the B3LYP/6-311++G(2d,2p) level predict equilibrium constants K, reported as 103ln(K) at 25 °C, of -5.3, -1.1, and +1.1 for 26Mg/24Mg exchange between calcite (CaCO3), magnesite (MgCO3), and dolomite (Ca0.5Mg0.5CO3), respectively, and Mg2+(aq), with positive values indicating enrichment in the mineral phase. For 44Ca/40Ca exchange between calcite and Ca2+(aq), the calculations predict values of +1.5 for Ca2+(aq) in six-fold coordination and +4.1 for Ca2+(aq) in seven-fold coordination. We find that the reduced partition function ratios can be reliably computed from systems as small as M(CO3)610- and M2+(H2O)6 embedded in a set of fixed atoms representing the 2nd shell (and greater) coordination environment. We find that the aqueous cluster representing the aquo ion is much more sensitive to improvements in the basis set than the calculations on the mineral systems, and that fractionation factors should be computed using 2 the best possible basis set for the aquo complex, even if the reduced partition function ratio calculated with the same basis set is not available for the mineral system. The new calculations show that the previous discrepancies between theory and experiment for Fe3+-hematite and Fe2+-siderite fractionations arise from an insufficiently accurate reduced partition function ratio for the Fe3+(aq) and Fe2+(aq) species.

  19. Surface treatment to improve responsivity of MgZnO UV detectors

    NASA Astrophysics Data System (ADS)

    Zhao, Yajun; Jiang, Dayong; Liu, Rusheng; Duan, Qian; Tian, Chunguang; Sun, Long; Gao, Shang; Qin, Jieming; Liang, Qingcheng; Zhao, Jianxun

    2015-09-01

    MgZnO films were grown on quartz substrates by radio frequency (RF) magnetron sputtering technique with a combinatorial target. The structural and optical properties of the sputtering films were characterized. Based on the MgZnO films, planar geometry metal-semiconductor-metal (MSM) structured ultraviolet (UV) detectors were fabricated. At 30 V bias, a peak responsivity of 3.5 mA/W was achieved at 285 nm, and the visible rejection was about one order of magnitude with 25 pairs of electrodes. Afterward, in order to improve the responsivity, the surface of the MgZnO-based detector was sputtered ZnO within 20 s. The responsivity was improved significantly from 3.5 to 15.8 mA/W after surface treatment, and the corresponding visible rejection increased to three orders of magnitude. It revealed ZnO particles play a key role in enhancing the responsivity of detector, and the physical mechanism has been explained by a straightforward model.

  20. Refining Globigerinoides ruber Mg/Ca paleothermometry in the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Hertzberg, Jennifer E.; Schmidt, Matthew W.

    2013-12-01

    The Mg/Ca ratio of the planktonic foraminifera Globigerinoides ruber (white) has become a widely used proxy for reconstructing sea surface temperature (SST), as numerous studies have shown that temperature is the primary control on Mg/Ca ratios in foraminiferal calcite. However, a recent study of core-top sediments across an Atlantic meridional transect suggests that salinity might have a stronger control on foraminiferal Mg/Ca ratios than previously thought. By analyzing Mg/Ca ratios and δO18 values in G. ruber (white), Arbuszewski et al. (2010) found a 27% increase in G. ruber Mg/Ca ratios per 1 salinity unit increase for seawater salinities above 35.5. Here, we use shell weight analyses and SEM images from a subset of the core-tops used in the Arbuszewski et al. (2010) study across a narrow depth range (3197-3733 m) to show that G. ruber shells from the equatorial region are highly dissolved compared to those from the subtropical North and South Atlantic gyres, significantly impacting their Mg/Ca-SSTs. Shell weights from the higher-productivity equatorial region of the Atlantic are on average 20% and 15% lower than those from the oligotrophic North and South Atlantic gyres, respectively. Given the large preservation gradient along the transect studied by Arbuszewski et al. (2010), application of a single dissolution-corrected Mg/Ca:SST calibration equation (Dekens et al., 2002) on cores from the subtropical gyres and the equatorial region is not appropriate. When regional differences in preservation are considered, as well as realistic habitat depths and calcification seasons for G. ruber in temperate latitudes, we find a strong correlation between observational SSTs and calculated G. ruber Mg/Ca-SSTs in core-top samples spanning 43°N to 25°S in the Atlantic. In addition, our re-calibrated Mg/Ca-SSTs are more strongly correlated with isotopic calcification temperatures across the transect than originally reported by Arbuszewski et al. (2010). This study

  1. Impurity Diffusion Coefficients of Al and Zn in Mg Determined from Solid-to-Solid Diffusion Couples

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Perry, Kelly A; Belova, Irina; Murch, Prof. Graeme; Sohn, Yong Ho

    2013-08-01

    Increasing use and development of lightweight Mgalloys have led to the desire for more fundamental research in and understanding of Mg-based systems. As property enhancing components, Al and Zn are two of the most important and common alloying elements for Mg-alloys. We have investigated the concentration dependent interdiffusion of Al and Zn in Mg using diffusion couples of pure polycrystalline Mg mated to Mg solid solutions containing either <9 at.% Al or <3 at.% Zn. Concentration profiles were determined by electron micro-probe microanalysis of the diffusion zone. The interdiffusion coefficients were determined by the classical Boltzmann-Matano method within the Mg solid solution. As the concentration of Al or Zn approaches the dilute ends, we employ an analytical approach based on the Hall method to estimate the impurity diffusion coefficients. Results of Al and Zn impurity diffusion in Mg are reported and compared to published impurity diffusion coefficients typically determined by thin film techniques.

  2. Suppression of the internal electric field effects in ZnO/Zn(0.7)Mg(0.3)O quantum wells by ion-implantation induced intermixing.

    PubMed

    Davis, J A; Dao, L V; Wen, X; Ticknor, C; Hannaford, P; Coleman, V A; Tan, H H; Jagadish, C; Koike, K; Sasa, S; Inoue, M; Yano, M

    2008-02-06

    Strong suppression of the effects caused by the internal electric field in ZnO/ZnMgO quantum wells following ion-implantation and rapid thermal annealing, is revealed by photoluminescence, time-resolved photoluminescence, and band structure calculations. The implantation and annealing induces Zn/Mg intermixing, resulting in graded quantum well interfaces. This reduces the quantum-confined Stark shift and increases electron-hole wavefunction overlap, which significantly reduces the exciton lifetime and increases the oscillator strength.

  3. A Ca2+-stimulated, Mg2+-dependent ATPase activity in subcellular fractions from Schistosoma mansoni.

    PubMed

    Cunha, V M; de Souza, W; Noël, F

    1988-12-05

    A Ca2+-stimulated, Mg2+-dependent ATPase activity was found in subcellular fractions from Schistosoma mansoni. Its specific and relative activities were higher in the heterogeneous cuticle fraction and in the microsomal fraction. The K0.5 for ATPase activation by free Ca2+ was 0.2-0.5 microM. This is the first description of an ATPase activity stimulated by Ca2+ in the micromolar range in S. mansoni.

  4. Seawater Mg/Ca controls polymorph mineralogy of microbial CaCO3: a potential proxy for calcite-aragonite seas in Precambrian time.

    PubMed

    Ries, J B; Anderson, M A; Hill, R T

    2008-03-01

    A previously published hydrothermal brine-river water mixing model driven by ocean crust production suggests that the molar Mg/Ca ratio of seawater (mMg/Ca(sw)) has varied significantly (approximately 1.0-5.2) over Precambrian time, resulting in six intervals of aragonite-favouring seas (mMg/Ca(sw) > 2) and five intervals of calcite-favouring seas (mMg/Ca(sw) < 2) since the Late Archaean. To evaluate the viability of microbial carbonates as mineralogical proxy for Precambrian calcite-aragonite seas, calcifying microbial marine biofilms were cultured in experimental seawaters formulated over the range of Mg/Ca ratios believed to have characterized Precambrian seawater. Biofilms cultured in experimental aragonite seawater (mMg/Ca(sw) = 5.2) precipitated primarily aragonite with lesser amounts of high-Mg calcite (mMg/Ca(calcite) = 0.16), while biofilms cultured in experimental calcite seawater (mMg/Ca(sw) = 1.5) precipitated exclusively lower magnesian calcite (mMg/Ca(calcite) = 0.06). Furthermore, Mg/Ca(calcite )varied proportionally with Mg/Ca(sw). This nearly abiotic mineralogical response of the biofilm CaCO3 to altered Mg/Ca(sw) is consistent with the assertion that biofilm calcification proceeds more through the elevation of , via metabolic removal of CO2 and/or H+, than through the elevation of Ca2+, which would alter the Mg/Ca ratio of the biofilm's calcifying fluid causing its pattern of CaCO3 polymorph precipitation (aragonite vs. calcite; Mg-incorporation in calcite) to deviate from that of abiotic calcification. If previous assertions are correct that the physicochemical properties of Precambrian seawater were such that Mg/Ca(sw) was the primary variable influencing CaCO3 polymorph mineralogy, then the observed response of the biofilms' CaCO3 polymorph mineralogy to variations in Mg/Ca(sw), combined with the ubiquity of such microbial carbonates in Precambrian strata, suggests that the original polymorph mineralogy and Mg/Ca(calcite )of well

  5. Testing the cation-hydration effect on the crystallization of Ca-Mg-CO3 systems.

    PubMed

    Xu, Jie; Yan, Chao; Zhang, Fangfu; Konishi, Hiromi; Xu, Huifang; Teng, H Henry

    2013-10-29

    Dolomite and magnesite are simple anhydrous calcium and/or magnesium carbonate minerals occurring mostly at Earth surfaces. However, laboratory synthesis of neither species at ambient temperature and pressure conditions has been proven practically possible, and the lack of success was assumed to be related to the strong solvation shells of magnesium ions in aqueous media. Here, we report the synthesis of MgCO3 and MgxCa(1-x)CO3 (0 < x < 1) solid phases at ambient conditions in the absence of water. Experiments were carried out in dry organic solvent, and the results showed that, although anhydrous phases were readily precipitated in the water-free environment, the precipitates' crystallinity was highly dependent on the Mg molar percentage content in the solution. In specific, magnesian calcite dominated in low [Mg(2+)]/[Ca(2+)] solutions but gave way to exclusive formation of amorphous MgxCa(1-x)CO3 and MgCO3 in high-[Mg(2+)]/[Ca(2+)] and pure-Mg solutions. At conditions of [Mg(2+)]/[Ca(2+)] = 1, both nanocrystals of Ca-rich protodolomite and amorphous phase of Mg-rich MgxCa(1-x)CO3 were formed. These findings exposed a previously unrecognized intrinsic barrier for Mg(2+) and CO3(2-) to develop long-range orders at ambient conditions and suggested that the long-held belief of cation-hydration inhibition on dolomite and magnesite mineralization needed to be reevaluated. Our study provides significant insight into the long-standing "dolomite problem" in geochemistry and mineralogy and may promote a better understanding of the fundamental chemistry in biomineralization and mineral-carbonation processes.

  6. Influence of ZnO/MgO substitution on sintering, crystallisation, and bio-activity of alkali-free glass-ceramics.

    PubMed

    Kapoor, Saurabh; Goel, Ashutosh; Correia, Ana Filipa; Pascual, Maria J; Lee, Hye-Young; Kim, Hae-Won; Ferreira, José M F

    2015-08-01

    The present study reports on the influence of partial replacement of MgO by ZnO on the structure, crystallisation behaviour and bioactivity of alkali-free bioactive glass-ceramics (GCs). A series of glass compositions (mol%): 36.07 CaO-(19.24-x) MgO-x ZnO-5.61 P2O5-38.49 SiO2-0.59 CaF2 (x=2-10) have been synthesised by melt-quench technique. The structural changes were investigated by solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR), X-ray diffraction and differential thermal analysis. The sintering and crystallisation behaviours of glass powders were studied by hot-stage microscopy and differential thermal analysis, respectively. All the glass compositions exhibited good densification ability resulting in well sintered and mechanically strong GCs. The crystallisation and mechanical behaviour were studied under non-isothermal heating conditions at 850 °C for 1h. Diopside was the primary crystalline phase in all the GCs followed by fluorapatite and rankinite as secondary phases. Another phase named petedunnite was identified in GCs with ZnO content >4 mol. The proliferation of mesenchymal stem cells (MSCs) and their alkaline phosphatase activity (ALP) on GCs was revealed to be Zn-dose dependent with the highest performance being observed for 4 mol% ZnO. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Structural and electrical properties of ZnO/Zn0.85Mg0.15O thin film prepared by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Yang, Jing-Jing; Wang, Gang; Du, Wen-Han; Xiong, Chao

    2017-07-01

    The electrical transport properties are the key factors to determine the performance of ZnO-based quantum effect device. ZnMgO is a typical material to regulate the band of ZnO. In order to investigate the electrical properties of the interface of ZnO/Zn0.85Mg0.15O films, three kinds of ZnO/Zn0.85Mg0.15O films have been fabricated with different thickness. After comparing the structural and electrical properties of the samples, we found that the independent Zn0.85Mg0.15O hexagonal wurtzite structure (002) peak can be detected in XRD spectra. Hall-effect test data confirmed that the two-dimensional electron gas (2DEG) became lower because of the decrease of thickness of Zn0.85Mg0.15O films, increase of impurity scattering and lattice structure distortion caused by the increase of Mg content.

  8. Shape and Site Dependent in Vivo Degradation of Mg-Zn Pins in Rabbit Femoral Condyle

    PubMed Central

    Han, Pei; Tan, Moyan; Zhang, Shaoxiang; Ji, Weiping; Li, Jianan; Zhang, Xiaonong; Zhao, Changli; Zheng, Yufeng; Chai, Yimin

    2014-01-01

    A type of specially designed pin model of Mg-Zn alloy was implanted into the full thickness of lesions of New Zealand rabbits’ femoral condyles. The recovery progress, outer surface healing and in vivo degradation were characterized by various methods including radiographs, Micro-CT scan with surface rendering, SEM (scanning electron microscope) with EDX (Energy Dispersive X-ray analysis) and so on. The in vivo results suggested that a few but not sufficient bridges for holding force were formed between the bone and the implant if there was a preexisting gap between them. The rapid degradation of the implantation in the condyle would result in the appearance of cavities. Morphological evaluation of the specially designed pins indicated that the cusp was the most vulnerable part during degradation. Furthermore, different implantation sites with distinct components and biological functions can lead to different degradation rates of Mg-Zn alloy. The rate of Mg-Zn alloy decreases in the following order: implantation into soft tissue, less trabecular bone, more trabecular bone, and cortical bone. Because of the complexities of in vivo degradation, it is necessary for the design of biomedical Mg-Zn devices to take into consideration the implantation sites used in clinics. PMID:24566138

  9. Combinatorial sputtering of Ga-doped (Zn,Mg)O for contact applications in solar cells

    DOE PAGES

    Rajbhandari, Pravakar P.; Bikowski, Andre; Perkins, John D.; ...

    2016-09-20

    In this study, the development of tunable contact materials based on environmentally friendly chemical elements using scalable deposition approaches is necessary for existing and emerging solar energy conversion technologies. In this paper, the properties of ZnO alloyed with magnesium (Mg), and doped with gallium (Ga) are studied using combinatorial thin film experiments. As a result of these studies, the optical band gap of the sputtered Zn1-xMgxO thin films was determined to vary from 3.3 to 3.6 eV for a compositional spread of Mg content in the 0.04 < x < 0.17 range. Depending on whether or not Ga dopants weremore » added, the electron concentrations were on the order of 1017 cm-3 or 1020 cm-3, respectively. Based on these results and on the Kelvin Probe work function measurements, a band diagram was derived using basic semiconductor physics equations. The quantitative determination of how the energy levels of Ga-doped (Zn, Mg)O thin films change as a function of Mg composition presented here, will facilitate their use as optimized contact layers for both Cu2ZnSnS4 (CZTS), Cu(In, Ga)Se2 (CIGS) and other solar cell absorbers.« less

  10. Combinatorial sputtering of Ga-doped (Zn,Mg)O for contact applications in solar cells

    SciTech Connect

    Rajbhandari, Pravakar P.; Bikowski, André; Perkins, John D.; Dhakal, Tara P.; Zakutayev, Andriy

    2017-01-01

    Development of tunable contact materials based on environmentally friendly chemical elements using scalable deposition approaches is necessary for existing and emerging solar energy conversion technologies. In this paper, the properties of ZnO alloyed with magnesium (Mg), and doped with gallium (Ga) are studied using combinatorial thin film experiments. As a result of these studies, the optical band gap of the sputtered Zn1-xMgxO thin films was determined to vary from 3.3 to 3.6 eV for a compositional spread of Mg content in the 0.04 < x < 0.17 range. Depending on whether or not Ga dopants were added, the electron concentrations were on the order of 1017 cm-3 or 1020 cm-3, respectively. Based on these results and on the Kelvin Probe work function measurements, a band diagram was derived using basic semiconductor physics equations. The quantitative determination of how the energy levels of Ga-doped (Zn, Mg)O thin films change as a function of Mg composition presented here, will facilitate their use as optimized contact layers for both Cu2ZnSnS4 (CZTS), Cu(In, Ga)Se2 (CIGS) and other solar cell absorbers.

  11. Bandwidth enhancement of MgZnO-based MSM photodetectors by inductive gain peaking

    NASA Astrophysics Data System (ADS)

    Wang, Ping; Guo, Xinlu; Guo, Lixin; He, Jingfang; Yang, Yintang; Zhang, Zhiyong

    2016-08-01

    For high-speed optical communication applications, the bandwidth of photodetector would be a key limitation. In this work, the bandwidth property of MgZnO-based Metal-Semiconductor-Metal (MSM) photodetector considering RC and transit limitations is investigated on the basis of the series and enhanced gain peaked photodetector circuits proposed by us with different finger widths. To ensure the accuracy of parameters, the high-filed transportation characteristics of MgZnO are investigated by a three-valley ensemble Monte Carlo simulation combined with first principle calculations. The results show that the gain peaking technique, especially the enhanced gain peaking, can improve the bandwidth of MgZnO MSM photodetector to a maximum value of 61.28 GHz, corresponding to a bandwidth enhancement of 49% without undesired effects. Three-dimensional electromagnetic computation is further performed to design and simulate the on-chip-inductor. The value of the simulated inductor is approximately 0.0529 nH, which is in good agreement with the designed value of 0.0569 nH. This work benefits the development of high speed MgZnO MSM photodetector.

  12. Effects of Sm addition on electromagnetic interference shielding property of Mg-Zn-Zr alloys

    NASA Astrophysics Data System (ADS)

    Yang, Chubin; Pan, Fusheng; Chen, Xianhua; Luo, Ning

    2017-06-01

    The electromagnetic interference (EMI) shielding of Sm-containing magnesium alloys in the 30-1500 MHz testing frequency range was investigated by coaxial cable method. The results demonstrated that Mg-3Zn alloys displayed the best electromagnetic shielding property. When 0.5 wt% of Zr was added for crystal grain refinement, the shielding effectiveness (SE) was apparently reduced. The addition of the rare earth element Sm in ZK magnesium alloys can improve the electromagnetic interference shielding of magnesium alloys. The main reason for the differences in electromagnetic interference shielding of magnesium alloys was the change in conductivity. The addition of Zr in Mg-Zn alloys can refine the grains and consequently improve the grain boundary area significantly. Therefore, the number of irregularly arranged atoms at the grain boundaries increased, decreasing the conductivity of magnesium alloys and leading to a decrease in the electromagnetic interference shielding. Following the Sm addition, the Mg-Zn-Sm phase was precipitated at the grain boundaries and in cores. The precipitation of Sm-containing rare earth phases could consume the solid-soluted Zn atoms within the Mg, resulting in an increase in electrical conductivity and electromagnetic interference shielding improvement.

  13. Novel ZnO/MgO/Fe2O3 composite optomagnetic nanoparticles.

    PubMed

    Kamińska, I; Sikora, B; Fronc, K; Dziawa, P; Sobczak, K; Minikayev, R; Paszkowicz, W; Elbaum, D

    2013-05-15

    A facile sol-gel synthesis of novel ZnO/MgO/Fe2O3 nanoparticles (NPs) is reported and their performance is compared to that of ZnO/MgO. Powder x-ray diffraction (XRD) patterns reveal the crystal structure of the prepared samples. The average particle size of the sample was found to be 4.8 nm. The optical properties were determined by UV-vis absorption and fluorescence measurements. The NPs are stable in biologically relevant solutions (phosphate buffered saline (PBS), 20 mM, pH = 7.0) contrary to ZnO/MgO NPs which degrade in the presence of inorganic phosphate. Superparamagnetic properties were determined with a superconducting quantum interference device (SQUID). Biocompatible and stable in PBS ZnO/MgO/Fe2O3 core/shell composite nanocrystals show luminescent and magnetic properties confined to a single NP at room temperature (19-24 ° C), which may render the material to be potentially useful for biomedical applications.

  14. Structural and optoelectronic properties of Mg substituted ZTe (Z=Zn, Cd and Hg)

    NASA Astrophysics Data System (ADS)

    Khan, Imad; Subhan, Fazle; Ahmad, Iftikhar; Ali, Zahid

    2015-08-01

    Wide band gap semiconductor alloys, MgxZ1-xTe (Z=Zn, Cd and Hg), are investigated over a full range of Mg compositions (0≤x≤1) using density functional theory (DFT). The variation in the lattice constant of MgxZ1-xTe is linear with the composition x, and all these alloys obey Vegrd's law. The CdTe (6.50 Å) and MgTe (6.44 Å) are lattice matched compounds, therefore the lattice constant of MgCdTe decreases slightly with the concentration x, whereas the lattice constant also decreases for MgHgTe but increases for MgZnTe. It is due to the fact that Mg has larger size than Zn and smaller size than Cd and Hg. The band gap of these compounds are calculated using the modified Becke-Johnson (mBJ) exchange potential as LDA and GGA are not effective in producing the experimental band gap of a strongly correlated electron system. The calculated band gaps of these compounds cover the range 0-3.5 eV and are consistent with the experimental band gaps. The band gaps exhibit nonlinear behavior or bowing effect with the change in concentration. The frequency dependent optical properties like dielectric functions, and indices of refraction of these ternary systems are also calculated and discussed.

  15. The effect of sulfate on CaCO_{3} mineralogy and the incorporation of Mg^{2+}

    NASA Astrophysics Data System (ADS)

    Goetschl, Katja Elisabeth; Mavromatis, Vasileios; Dietzel, Martin

    2017-04-01

    Sulfate is the second most concentrated anion in seawater, and it forms strong complexes with Ca2+ and Mg2+ in aqueous solutions. However, up to now not much is known about the effect of dissolved SO42- on the formation of calcium carbonate minerals. For example, it has earlier been documented that the primary CaCO3 polymorph in marine sediments was oscillating between calcite and aragonite throughout the Phanerozoic, reflecting changes in seawater chemistry, among them SO42- concentration. Most of the previous experimental work, however, has focused mainly on the Mg/Ca ratio in seawater as the major driver for a preferential formation of calcite or aragonite. It has thus been shown that Mg substitution affects the thermodynamic stability of calcite, causing precipitation of aragonite instead of calcite at an aqueous Mg/Ca ratio higher than ˜1.3 [1]. To shed light on the mechanisms controlling the calcium carbonate mineral formation in the presence of sulfate, we performed steady-state precipitation experiments with calcite seed material at 25 ˚ C. Furthermore in this study we examine the Mg partitioning and isotope fractionation during its incorporation in calcite. For this, throughout the experimental runs, the aqueous Mg concentration was kept constant at different growth rates and different concentrations of dissolved SO42- have been used. Our data show that the presence of sulfate induces the formation of aragonite on calcite seeds at elevated growth rates, whereas we see no formation of aragonite in the experiments performed in the absence of sulfate, but at the same Mg/Ca ratio. On a further step the effect of sulfate on Mg partitioning and stable isotope fractionation of Mg in calcite will be examined. These results will improve the general understanding of the controls of solution chemistry on the formation of CaCO3 minerals and in specific the effect of sulfate on the incorporation of Mg into the crystal lattice. [1] Morse et al., 1997, Geology

  16. Synthesis, Characterization and Photocatalytic Activity of Mg-Impregnated ZnO-SnO2 Coupled Nanoparticles.

    PubMed

    Behnajady, Mohammad A; Tohidi, Yasamin

    2014-01-01

    ZnO-SnO2 nanoparticles were prepared by coprecipitation method; then Mg, with different molar ratios and calcination temperatures, was loaded on the coupled nanoparticles by impregnation method. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), and Brunauer-Emmett-Teller (BET) techniques. Based on XRD results, the ZnO-SnO2 and Mg/ZnO-SnO2 nanoparticles were made of ZnO and SnO2 nanocrystallites. According to DRS spectra, the band gap energy value of 3.13 and 3.18 eV were obtained for ZnO-SnO2 and Mg/ZnO-SnO2 nanoparticles, respectively. BET analysis revealed a Type III isotherm with a microporous structure and surface area of 32.051 and 49.065 m(2)  g(-1) for ZnO-SnO2 and Mg/ZnO-SnO2 , respectively. Also, the spherical shape of nanocrystallites was deduced from TEM and FESEM images. The photocatalytic performance of pure ZnO-SnO2 and Mg/ZnO-SnO2 was analyzed in the photocatalytic removal of methyl orange (MO). The results indicated that Mg/ZnO-SnO2 exhibited superior photocatalytic activity to bare ZnO-SnO2 photocatalyst due to high surface area, increased MO adsorption and larger band gap energy. Maximum photocatalytic activity of Mg/ZnO-SnO2 nanoparticles was obtained with 0.8 mol% Mg and calcination temperature of 350°C.

  17. Distribution of Metals in the Termite Tumulitermes tumuli (Froggatt): Two Types of Malpighian Tubule Concretion Host Zn and Ca Mutually Exclusively

    PubMed Central

    Stewart, Aaron D.; Anand, Ravi R.; Laird, Jamie S.; Verrall, Michael; Ryan, Chris G.; de Jonge, Martin D.; Paterson, David; Howard, Daryl L.

    2011-01-01

    The aim of this study was to determine specific distribution of metals in the termite Tumulitermes tumuli (Froggatt) and identify specific organs within the termite that host elevated metals and therefore play an important role in the regulation and transfer of these back into the environment. Like other insects, termites bio-accumulate essential metals to reinforce cuticular structures and utilize storage detoxification for other metals including Ca, P, Mg and K. Previously, Mn and Zn have been found concentrated in mandible tips and are associated with increased hardness whereas Ca, P, Mg and K are accumulated in Malpighian tubules. Using high resolution Particle Induced X-Ray Emission (PIXE) mapping of whole termites and Scanning Electron Microscope (SEM) Energy Dispersive X-ray (EDX) spot analysis, localised accumulations of metals in the termite T. tumuli were identified. Tumulitermes tumuli was found to have proportionally high Mn concentrations in mandible tips. Malpighian tubules had significant enrichment of Zn (1.6%), Mg (4.9%), P (6.8%), Ca (2.7%) and K (2.4%). Synchrotron scanning X-ray Fluorescence Microprobe (XFM) mapping demonstrated two different concretion types defined by the mutually exclusive presence of Ca and Zn. In-situ SEM EDX realisation of these concretions is problematic due to the excitation volume caused by operating conditions required to detect minor amounts of Zn in the presence of significant amounts of Na. For this reason, previous researchers have not demonstrated this surprising finding. PMID:22087339

  18. Dechlorination of endocrine disrupting chemicals using Mg 0/ZnCl 2 bimetallic system.

    PubMed

    Begum, Asfiya; Gautam, Sumit Kumar

    2011-03-01

    In the present study, Mg 0/ZnCl 2 bimetallic system was evaluated for its efficiency to dechlorinate endosulfan and lindane in aqueous phase. Presence of acetone in the reaction mixture played an important role by increasing the solubilities of both pesticides and thereby accelerating its mass transfer. Water acetone ratio of 2:1 and 1:1 (v/v) was found optimum for the dechlorination of endosulfan and lindane respectively. Presence of H+ ions in the reaction mixture (50 μl ml(-1) of glacial acetic acid) accelerated the degradation efficiency of 30 ppm initial concentration of endosulfan (96% removal) and lindane (98% removal) at Mg 0/ZnCl 2 dose of 5/1 mg ml(-1) within 30 min of reaction. Dechlorination kinetics for endosulfan and lindane (10, 30 and 50 ppm initial concentration of each pesticide) with varying Mg 0/ZnCl 2 doses and the time course profiles of each pesticide were well fitted into the first order dechlorination reaction. The optimum observed rate constant (k(obs)') values for endosulfan (0.2168, 0.1209 and 0.1614 min(-1) for 10, 30 and 50 ppm initial concentration respectively) and lindane (0.1746, 0.1968 and 0.2253 min(-1) for 10, 30 and 50 ppm initial concentration respectively) dechlorination were obtained when the reactions were conducted with doses of 7.5/1 mg ml(-1) and 5/1 mg ml(-1) Mg 0/ZnCl 2 respectively. Endosulfan and lindane were completely dechlorinated into their hydrocarbon skeletons namely, Bicyclo [2,2,1] hepta 2-5 diene and Benzene respectively as revealed by GCMS analysis. Copyright © 2011 Elsevier Ltd. All rights reserved.

  19. Comparison of serum Concentration of Se, Pb, Mg, Cu, Zn, between MS patients and healthy controls

    PubMed Central

    Alizadeh, Anahita; Mehrpour, Omid; Nikkhah, Karim; Bayat, Golnaz; Espandani, Mahsa; Golzari, Alireza; Jarahi, Lida; Foroughipour, Mohsen

    2016-01-01

    Introduction Multiple Sclerosis (MS) is defined as one of the inflammatory autoimmune disorders and is common. Its exact etiology is unclear. There are some evidences on the role of environmental factors in susceptible genetics. The aim of this study is to evaluate the possible role of Selenium, Zinc, Copper, Lead and Magnesium metals in Multiple Sclerosis patients. Methods In the present analytical cross-sectional study, 56 individuals including 26 patients and 30 healthy controls were enrolled in the evaluation. The serum level of Se, Zn, Cu, Pb were quantified in graphite furnace conditions and flame conditions by utilizing an atomic absorption Perkin Elmer spectrophotometer 3030. The serum levels of Mg were measured by auto analyzer 1500 BT. The mean level of minerals (Zn, Pb, Cu, Mg, Se) in serum samples were compared in both cases and controls. The mean level of minerals (Zn, Pb, Cu, Mg, Se) in serum samples were compared in both cases and controls by using independent-samples t-test for normal distribution and Mann-Whitney U test as a non-parametric test. All statistical analyses were carried out using SPSS 11.0. Results As well as the Zn, Cu, and Se, there was no significant difference between MS patients and healthy individuals in Pb concentrations (p-value = 0.11, 0.14, 0.32, 0.20 respectively) but the level of Mg was significantly different (p= 0.001). Conclusion All serum concentrations of Zn, Pb, Se, Cu in both groups were in normal ranges and there was no difference in MS patients compared with the healthy group who were matched in genetics. Blood level of Mg was significantly lower in MS patients. But it should be noted that even with the low level of serum magnesium in MS patients, this value is still in the normal range. PMID:27757186

  20. Inter-species and Seasonal Variability in Mg / Ca in Larger Benthic Foraminifera: Implications for Paleo-proxy

    NASA Astrophysics Data System (ADS)

    Singh, A.; Saraswati, P. K.; Pande, K.; Sanyal, P.

    2015-12-01

    The reports of inter-species variability to intra-test heterogeneity in Mg/Ca in several species of foraminifera have raised question about its use in estimation of seawater temperatures and necessitate field and culture studies to verify it for species from different habitats. In this study, we attempt to investigate if Mg/Ca in larger benthic foraminifera (LBF) could be a potential proxy of seawater temperatures for shallow marine carbonates. The samples were collected in different seasons from coral reef at Akajima (Okinawa, Japan). The Ca and Mg of 13 species of LBF and small benthic foraminifera from the same season were determined to examine variation in Mg/Ca among the species calcified under presumably the same temperature and salinity conditions. We also analyzed Amphistegina lessoni from different seasons for Ca, Mg and δ18O to determine variation in Mg/Ca with temperature and see how the two proxies of temperatures, Mg/Ca and δ18O, correlate in the same species. The species cluster about two distinctly separated Mg/Ca values. The first group comprising species of Amphistegina, Gypsina, Ammonia and Elphidium have relatively lower Mg/Ca, varying from 30 to 45 mmol/mol. The second group, having average Mg/Ca ranging from ~110 to 170 mmol/mol, includes species of Schlumbergerella, Baculogypsinoides, Baculogypsina, Heterostegina, Operculina, Calcarina, Amphisorus, Alveolinella and Poroeponides. The result suggests large interspecies variability implying vital effect in foraminiferal Mg/Ca. There is no distinct difference in Mg/Ca values between porcelaneous and hyaline types or symbiont-bearing and symbiont-free types. In Amphistegina lessoni the variation in Mg/Ca between individuals of the same season is as large as variation across the seasons. There is no correlation between Mg/Ca and seawater temperature. Lack of correlation between Mg/Ca and δ18O further suggests that Mg/Ca in the species is not primarily controlled by temperature.

  1. The effect of Mg/2+/ and Ca/2+/ on urea-catalyzed phosphorylation reactions

    NASA Technical Reports Server (NTRS)

    Handschuk, G. J.; Lohrmann, R.; Orgel, L. E.

    1973-01-01

    The effect of Mg(2+) and Ca(2+) on phosphorylation reactions catalyzed by urea is investigated, showing that Mg(2+) improves markedly the yield of products containing pyrophosphate bonds. Yields of up to 25% of uridine diphosphate can be obtained with struvite at temperatures as low as 65 C.

  2. The effect of Mg/2+/ and Ca/2+/ on urea-catalyzed phosphorylation reactions

    NASA Technical Reports Server (NTRS)

    Handschuk, G. J.; Lohrmann, R.; Orgel, L. E.

    1973-01-01

    The effect of Mg(2+) and Ca(2+) on phosphorylation reactions catalyzed by urea is investigated, showing that Mg(2+) improves markedly the yield of products containing pyrophosphate bonds. Yields of up to 25% of uridine diphosphate can be obtained with struvite at temperatures as low as 65 C.

  3. Reversible Hydrogen Storage Characteristics of Catalytically Enhanced Ca(Li)-nMg-B-N-H System

    NASA Astrophysics Data System (ADS)

    Srinivasan, Sesha; Emre Demircak, Dervis; Sharma, Prakash; Yogi, Goswami; Stefanakos, Elias

    2013-04-01

    The aim of the present investigation is to study the synergistic effects of multi-walled carbon nanotubes, Nb2O5 and other catalysts for reversible hydrogen storage characteristics of Ca(Li)-nMg-B-N-H systems. Multinary hydride using light weight, high capacity hydride compounds such as Ca(BH4)2, LiBH4, LiNH2, nanoMgH2 in 3:1:8:4 composition was synthesized using high energy planetary milling under Ar/H2 ambient. Various nano additives and bi-metallic catalysts were added in a very small concentration with the host hydride (Ca)Li-nMg-B-N-H. The TGA and DSC results demonstrated that the catalytically enhanced Ca(Li)-nMg-B-N-H with hydrogen release at lower temperatures when compared to the pristine systems such as either Ca-Li-B-H or Ca-Li-Mg-B-H. Analyses of metrological characterization using XRD, SEM and have revealed the effectiveness and the role of the catalytic nanoparticles and their enhanced reversible hydrogen storage behavior on the host hydride matrix. The mass spectrometric investigations employing RGA on these nanocrystalline, multi-component hydride systems exhibit the release of hydrogen in major proportion (˜80-90%) as compared to previously attributed ammonia.

  4. Observation of Room Temperature Photoluminescence from Asymmetric CuGaO2/ZnO/ZnMgO Multiple Quantum Well Structures.

    PubMed

    Aneesh, P M; Jayaraj, M K; Reshmi, R; Ajimsha, R S; Kukreja, L M; Aldrin, A; Rojas, F; Bertomeu, J; López-Vidrier, J; Hernández, S

    2015-05-01

    Asymmetric (CuGaO2/ZnO/ZnMgO) and symmetric (ZnMgO/ZnO/ZnMgO) multiple quantum well (MQW) structures were successfully fabricated using pulsed laser deposition (PLD) and their comparison were made. Efficient room temperature photoluminescent (PL) emission was observed from these MQWs and temperature dependent luminescence of asymmetric and symmetric MQWs can be explained using the existing theories. A systematic blue shift was observed in both MQWs with decrease in the confinement layer thickness which could be attributed to the quantum confinement effects. The PL emission from asymmetric and symmetric MQW structures were blue shifted compared to 150 nm thick ZnO thin film grown by PLD due to quantum confinement effects.

  5. Electron microprobe analyses of Ca, S, Mg and P distribution in incisors of Spacelab-3 rats

    NASA Technical Reports Server (NTRS)

    Rosenberg, G. D.; Simmons, D. J.

    1985-01-01

    The distribution of Ca, S, Mg and P was mapped within the incisors of Spacelab-3 rats using an electron microprobe. The data indicate that Flight rats maintained in orbit for 7 days have significantly higher Ca/Mg ratios in dentin due to both higher Ca and lower Mg content than in dentin of ground-based Controls. There is no statistical difference in distribution of either P or S within Fligth animals and Controls, but there is clear indication that, for P at least, the reason is the greater variability of the Control data. These results are consistent with those obtained on a previous NASA/COSMOS flight of 18.5 days duration, although they are not pronounced. The results further suggest that continuously growing rat incisors provide useful records of the effects of weightlessness on Ca metabolism.

  6. Deep-sea ostracode shell chemistry (Mg:Ca ratios) and late Quaternary Arctic Ocean history

    USGS Publications Warehouse

    Cronin, T. M.; Dwyer, G.S.; Baker, P.A.; Rodriguez-Lazaro, J.; Briggs, W.M.; ,

    1996-01-01

    The magnesium:calcium (Mg:Ca) and strontium:calcium (Sr:Ca) ratios were investigated in shells of the benthic ostracode genus Krithe obtained from 64 core-tops from water depths of 73 to 4411 m in the Arctic Ocean and Nordic seas to determine the potential of ostracode shell chemistry for paleoceanographic study. Shells from the abyssal plain and ridges of the Nansen, Amundsen and Makarov basins and the Norwegian and Greenland seas had a wide scatter of Mg:Ca ratios ranging from 0.007 to 0.012 that may signify post-mortem chemical alteration of the shells from Arctic deep-sea environments below about 1000 m water depth. There is a positive correlation (r2=0.59) between Mg:Ca ratios and bottom-water temperature in Krithe shells from water depths <900 m.

  7. Electron microprobe analyses of Ca, S, Mg and P distribution in incisors of Spacelab-3 rats

    NASA Technical Reports Server (NTRS)

    Rosenberg, G. D.; Simmons, D. J.

    1985-01-01

    The distribution of Ca, S, Mg and P was mapped within the incisors of Spacelab-3 rats using an electron microprobe. The data indicate that Flight rats maintained in orbit for 7 days have significantly higher Ca/Mg ratios in dentin due to both higher Ca and lower Mg content than in dentin of ground-based Controls. There is no statistical difference in distribution of either P or S within Fligth animals and Controls, but there is clear indication that, for P at least, the reason is the greater variability of the Control data. These results are consistent with those obtained on a previous NASA/COSMOS flight of 18.5 days duration, although they are not pronounced. The results further suggest that continuously growing rat incisors provide useful records of the effects of weightlessness on Ca metabolism.

  8. Characteristic chemical shifts of quasicrystalline Zn-Mg-Zr alloys studied by EELS and SXES

    NASA Astrophysics Data System (ADS)

    Koshiya, S.; Terauchi, M.; Ohhashi, S.; Tsai, A. P.

    2013-06-01

    Chemical shifts of the constituent atoms of primitive icosahedral quasicrystal (P-QC), face-centred icosahedral quasicrystal (F-QC) and 1/1-approximant (1/1-AP) of F-QC Zn-Mg-Zr alloys were investigated for the first time using high energy-resolution electron energy-loss spectroscopy (EELS) and soft-X-ray emission spectroscopy (SXES). Among Zn M-shell and Mg L-shell excitation EELS spectra of P-QC, F-QC and 1/1-AP alloys, only the quasicrystalline alloys showed a chemical shift towards the larger binding energy side. In Zn-L and Zr-L emission SXES spectra, the P-QC and F-QC alloys showed a chemical shift towards larger binding energy side. The magnitudes of the shifts in the Zn-L emission spectra of the quasicrystalline alloys were almost the same as for ZnO. These results strongly suggest a decrease in valence charge in quasicrystalline states. Therefore, it should be concluded that bonding in quasicrystalline states involves a characteristic increase in covalency compared with bonding in corresponding approximant and standard metal crystals.

  9. Zn2+ activates large conductance Ca2+-activated K+ channel via an intracellular domain.

    PubMed

    Hou, Shangwei; Vigeland, Leif E; Zhang, Guangping; Xu, Rong; Li, Min; Heinemann, Stefan H; Hoshi, Toshinori

    2010-02-26

    Zinc is an essential trace element and plays crucial roles in normal development, often as an integral structural component of transcription factors and enzymes. Recent evidence suggests that intracellular Zn(2+) functions as a signaling molecule, mediating a variety of important physiological phenomena. However, the immediate effectors of intracellular Zn(2+) signaling are not well known. We show here that intracellular Zn(2+) potently and reversibly activates large-conductance voltage- and Ca(2+)-activated Slo1 K(+) (BK) channels. The full effect of Zn(2+) requires His(365) in the RCK1 (regulator of conductance for K(+)) domain of the channel. Furthermore, mutation of two nearby acidic residues, Asp(367) and Glu(399), also reduced activation of the channel by Zn(2+), suggesting a possible structural arrangement for Zn(2+) binding by the aforementioned residues. Extracellular Zn(2+) activated Slo1 BK channels when coexpressed with Zn(2+)-permeable TRPM7 (transient receptor potential melastatin 7) channels. The results thus demonstrate that Slo1 BK channels represent a positive and direct effector of Zn(2+) signaling and may participate in sculpting cellular response to an increase in intracellular Zn(2+) concentration.

  10. Intrinsic scintillators: TlMgCl3 and TlCaI3

    NASA Astrophysics Data System (ADS)

    Hawrami, R.; Ariesanti, E.; Wei, H.; Finkelstein, J.; Glodo, J.; Shah, K. S.

    2017-10-01

    Two intrinsic scintillators TlMgCl3 and TlCaI3 with excellent energy resolution and fast scintillation decay are presented. Crack-free transparent crystals were successfully grown by the Bridgman method. The scintillation light yields of TlMgCl3 and TlCaI3 are approximately 30,600 ph/MeV and 42,200 ph/MeV, respectively. Their energy resolutions at 662 keV are 3.7% for TlMgCl3 and 6.2% for TlCaI3. The scintillation decay times of TlMgCl3 are 46 ns, 166 ns, and 449 ns. The scintillation decay times of TlCaI3 are 62 ns, 200 ns, and 1.44 μs. Under X-ray irradiation, the emission of TlMgCl3 is between 300 nm and 540 nm with the peak at 409 nm. TlCaI3 has a broad emission band between 300 nm and 750 nm. Due to their excellent scintillation properties, these two scintillators can be developed for gamma-ray detection. Additionally, TlMgCl3 is non-hygroscopic.

  11. Mechanical properties and corrosion behavior of Mg-Gd-Ca-Zr alloys for medical applications.

    PubMed

    Shi, Ling-Ling; Huang, Yuanding; Yang, Lei; Feyerabend, Frank; Mendis, Chamini; Willumeit, Regine; Ulrich Kainer, Karl; Hort, Norbert

    2015-07-01

    Magnesium alloys are promising candidates for biomedical applications. In this work, influences of composition and heat treatment on the microstructure, the mechanical properties and the corrosion behavior of Mg-Gd-Ca-Zr alloys as potential biomedical implant candidates were investigated. Mg5Gd phase was observed at the grain boundaries of Mg-10Gd-xCa-0.5Zr (x=0, 0.3, 1.2wt%) alloys. Increase in the Ca content led to the formation of additional Mg2Ca phase. The Ca additions increased both the compressive and the tensile yield strengths, but reduced the ductility and the corrosion resistance in cell culture medium. After solution heat treatment, the Mg5Gd particles dissolved in the Mg matrix. The compressive strength decreased, while the corrosion resistance improved in the solution treated alloys. After ageing at 200°C, metastable β' phase formed on prismatic planes and a new type of basal precipitates have been observed, which improved the compressive and tensile ultimate strength, but decreased the ductility.

  12. Enhanced antibacterial properties, biocompatibility, and corrosion resistance of degradable Mg-Nd-Zn-Zr alloy.

    PubMed

    Qin, Hui; Zhao, Yaochao; An, Zhiquan; Cheng, Mengqi; Wang, Qi; Cheng, Tao; Wang, Qiaojie; Wang, Jiaxing; Jiang, Yao; Zhang, Xianlong; Yuan, Guangyin

    2015-06-01

    Magnesium (Mg), a potential biodegradable material, has recently received increasing attention due to its unique antibacterial property. However, rapid corrosion in the physiological environment and potential toxicity limit clinical applications. In order to improve the corrosion resistance meanwhile not compromise the antibacterial activity, a novel Mg alloy, Mg-Nd-Zn-Zr (Hereafter, denoted as JDBM), is fabricated by alloying with neodymium (Nd), zinc (Zn), zirconium (Zr). pH value, Mg ion concentration, corrosion rate and electrochemical test show that the corrosion resistance of JDBM is enhanced. A systematic investigation of the in vitro and in vivo antibacterial capability of JDBM is performed. The results of microbiological counting, CLSM, SEM in vitro, and microbiological cultures, histopathology in vivo consistently show JDBM enhanced the antibacterial activity. In addition, the significantly improved cytocompatibility is observed from JDBM. The results suggest that JDBM effectively enhances the corrosion resistance, biocompatibility and antimicrobial properties of Mg by alloying with the proper amount of Zn, Zr and Nd. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Effects in Mg-Zn-based alloys strengthened by quasicrystalline phase

    NASA Astrophysics Data System (ADS)

    Vlček, M.; Čížek, J.; Lukáč, F.; Melikhova, O.; Hruška, P.; Procházka, I.; Vlach, M.; Stulíková, I.; Smola, B.; Jäger, A.

    2016-01-01

    Magnesium Mg-based alloys are promising lightweight structural materials for automotive, aerospace and biomedical applications. Recently Mg-Zn-Y system attracted a great attention due to a stable icosahedral phase (I-phase) with quasicrystalline structure which is formed in these alloys. Positron lifetime spectroscopy and in situ synchrotron X-ray diffraction were used to study thermal stability of I-phase and precipitation effects in Mg-Zn-Y and Mg- Zn-Al alloys. All alloys containing quasicrystalline I-phase exhibit misfit defects characterized by positron lifetime of ∼ 300 ps. These defects are associated with the interfaces between I- phase particles and Mg matrix. The quasicrystalline I-phase particles were found to be stable up to temperatures as high as ∼ 370°C. The W-phase is more stable and melts at ∼ 420°C. Concentration of defects associated with I-phase decreases after annealing at temperatures above ∼ 300°C.

  14. The effects of diagenesis and dolomitization on Ca and Mg isotopes in marine platform carbonates: Implications for the geochemical cycles of Ca and Mg

    NASA Astrophysics Data System (ADS)

    Fantle, Matthew S.; Higgins, John

    2014-10-01

    The Ca, Mg, O, and C isotopic and trace elemental compositions of marine limestones and dolostones from ODP Site 1196A, which range in depth (∼58 to 627 mbsf) and in depositional age (∼5 and 23 Ma), are presented. The objectives of the study are to explore the potential for non-traditional isotope systems to fingerprint diagenesis, to quantify the extent to which geochemical proxies are altered during diagenesis, and to investigate the importance of diagenesis within the global Ca and Mg geochemical cycles. The data suggest that Ca, which has a relatively high solid to fluid mass ratio, can be isotopically altered during diagenesis. In addition, the alteration of Ca correlates with the alteration of Mg in such a way that both can serve as useful tools for deciphering diagenesis in ancient rocks. Bulk carbonate δ44Ca values vary between 0.60 and 1.31‰ (SRM-915a scale); the average limestone δ44Ca is 0.97 ± 0.24‰ (1SD), identical within error to the average dolostone (1.03 ± 0.15 1SD ‰). Magnesium isotopic compositions (δ26Mg, DSM-3 scale) range between -2.59‰ and -3.91‰, and limestones (-3.60 ± 0.25‰) and dolostones (-2.68 ± 0.07‰) are isotopically distinct. Carbon isotopic compositions (δ13C, PDB scale) vary between 0.86‰ and 2.47‰, with average limestone (1.96 ± 0.31‰) marginally offset relative to average dolostone (1.68 ± 0.57‰). The oxygen isotopic compositions (δ18O, PDB scale) of limestones (-1.22 ± 0.94‰) are substantially lower than the dolostones measured (2.72 ± 1.07‰). The isotopic data from 1196A suggest distinct and coherent trends in isotopic and elemental compositions that are interpreted in terms of diagenetic trajectories. Numerical modeling supports the contention that such trends can be interpreted as diagenetic, and suggests that the appropriate distribution coefficient (KMg) associated with limestone diagenesis is ∼1 to 5 × 10-3, distinctly lower than those values (>0.015) reported in laboratory

  15. Effects of Mg II and Ca II ionization on ab-initio solar chromosphere models

    NASA Technical Reports Server (NTRS)

    Rammacher, W.; Cuntz, M.

    1991-01-01

    Acoustically heated solar chromosphere models are computed considering radiation damping by (non-LTE) emission from H(-) and by Mg II and Ca II emission lines. The radiative transfer equations for the Mg II k and Ca II K emission lines are solved using the core-saturation method with complete redistribution. The Mg II k and Ca II K cooling rates are compared with the VAL model C. Several substantial improvements over the work of Ulmschneider et al. (1987) are included. It is found that the rapid temperature rises caused by the ionization of Mg II are not formed in the middle chromosphere, but occur at larger atmospheric heights. These models represent the temperature structure of the 'real' solar chromosphere much better. This result is a major precondition for the study of ab-initio models for solar flux tubes based on MHD wave propagation and also for ab-initio models for the solar transition layer.

  16. Effects of Mg II and Ca II ionization on ab-initio solar chromosphere models

    NASA Technical Reports Server (NTRS)

    Rammacher, W.; Cuntz, M.

    1991-01-01

    Acoustically heated solar chromosphere models are computed considering radiation damping by (non-LTE) emission from H(-) and by Mg II and Ca II emission lines. The radiative transfer equations for the Mg II k and Ca II K emission lines are solved using the core-saturation method with complete redistribution. The Mg II k and Ca II K cooling rates are compared with the VAL model C. Several substantial improvements over the work of Ulmschneider et al. (1987) are included. It is found that the rapid temperature rises caused by the ionization of Mg II are not formed in the middle chromosphere, but occur at larger atmospheric heights. These models represent the temperature structure of the 'real' solar chromosphere much better. This result is a major precondition for the study of ab-initio models for solar flux tubes based on MHD wave propagation and also for ab-initio models for the solar transition layer.

  17. Ca2+ and Mg2+ modulate conformational dynamics and stability of downstream regulatory element antagonist modulator

    PubMed Central

    Pham, Khoa; Dhulipala, Gangadhar; Gonzalez, Walter G; Gerstman, Bernard S; Regmi, Chola; Chapagain, Prem P; Miksovska, Jaroslava

    2015-01-01

    Downstream Regulatory Element Antagonist Modulator (DREAM) belongs to the family of neuronal calcium sensors (NCS) that transduce the intracellular changes in Ca2+ concentration into a variety of responses including gene expression, regulation of Kv channel activity, and calcium homeostasis. Despite the significant sequence and structural similarities with other NCS members, DREAM shows several features unique among NCS such as formation of a tetramer in the apo-state, and interactions with various intracellular biomacromolecules including DNA, presenilin, Kv channels, and calmodulin. Here we use spectroscopic techniques in combination with molecular dynamics simulation to study conformational changes induced by Ca2+/Mg2+ association to DREAM. Our data indicate a minor impact of Ca2+ association on the overall structure of the N- and C-terminal domains, although Ca2+ binding decreases the conformational heterogeneity as evident from the decrease in the fluorescence lifetime distribution in the Ca2+ bound forms of the protein. Time-resolved fluorescence data indicate that Ca2+binding triggers a conformational transition that is characterized by more efficient quenching of Trp residue. The unfolding of DREAM occurs through an partially unfolded intermediate that is stabilized by Ca2+ association to EF-hand 3 and EF-hand 4. The native state is stabilized with respect to the partially unfolded state only in the presence of both Ca2+ and Mg2+ suggesting that, under physiological conditions, Ca2+ free DREAM exhibits a high conformational flexibility that may facilitate its physiological functions. PMID:25627705

  18. Influence of Zn Interlayer on Interfacial Microstructure and Mechanical Properties of TIG Lap-Welded Mg/Al Joints

    NASA Astrophysics Data System (ADS)

    Gao, Qiong; Wang, Kehong

    2016-03-01

    This study explored 6061 Al alloy and AZ31B Mg alloy joined by TIG lap welding with Zn foils of varying thicknesses, with the additional Zn element being imported into the fusion zone to alloy the weld seam. The microstructures and chemical composition in the fusion zone near the Mg substrate were examined by SEM and EDS, and tensile shear strength tests were conducted to investigate the mechanical properties of the Al/Mg joints, as well as the fracture surfaces, and phase compositions. The results revealed that the introduction of an appropriate amount of Zn transition layer improves the microstructure of Mg/Al joints and effectively reduces the formation of Mg-Al intermetallic compounds (IMCs). The most common IMCs in the fusion zone near the Mg substrate were Mg-Zn and Mg-Al-Zn IMCs. The type and distribution of IMCs generated in the weld zone differed according to Zn additions; Zn interlayer thickness of 0.4 mm improved the sample's mechanical properties considerably compared to thicknesses of less than 0.4 mm; however, any further increase in Zn interlayer thickness of above 0.4 mm caused mechanical properties to deteriorate.

  19. Effect of Mg/Ca ratios on microbially induced carbonate precipitation

    NASA Astrophysics Data System (ADS)

    Balci, Nurgul; Demirel, Cansu; Seref Sonmez, M.; Kurt, M. Ali

    2016-04-01

    Influence of Mg/Ca ratios on microbially induced carbonate mineralogy were investigated by series of experiments carried out under various environmental conditions (Mg/Ca ratio, temperature and salinity). Halophilic bacterial cultures used for biomineralization experiments were isolated from hypersaline Lake Acıgöl (Denizli, SW Turkey), displaying extreme water chemistry with an average pH around 8.6 (Balci eta l.,2015). Enriched bacterial culture used in the experiments consisted of Halomonas saccharevitans strain AJ275, Halomonas alimentaria strain L7B; Idiomarina sp. TBZ29, 98% Idiomarina seosensis strain CL-SP19. Biomineralization experiments were set up using above enriched culture with Mg/Ca ratios of 0.05, 1, 4 and 15 and salinity of 8% and 15% experiments at 30oC and 10oC. Additionally, long-term biomineralization experiments were set up to last for a year, for Mg/Ca=4 and Mg/Ca=15 experiments at 30oC. For each experimental condition abiotic experiments were also conducted. Solution chemistry throughout incubation was monitored for Na, K, Mg, Ca, bicarbonate, carbonate, ammonium and phosphate for a month. At the end of the experiments, precipitates were collected and morphology and mineralogy of the biominerals were investigated and results were evaluated using the software DIFFRAC.SUITE EVA. Overall the preliminary results showed chemical precipitation of calcite, halite, hydromagnesite and sylvite. Results obtained from biological experiments indicate that, low Mg/Ca ratios (0.05 and 1) favor chlorapatite precipitation, whereas higher Mg/Ca ratios favor struvite precipitation. Biomineralization of dolomite, huntite and magnesite is favorable at high Mg/Ca ratios (4 and 15), in the presence of halophilic bacteria. Moreover, results indicate that supersaturation with respect to Mg (Mg/Ca=15) combined with NaCl (15%) inhibits biomineralization and forms chemical precipitates. 15% salinity is shown to favor chemical precipitation of mineral phases more than

  20. Mg/Ca composition of benthic foraminifera Miliolacea as a new tool of paleoceanography

    NASA Astrophysics Data System (ADS)

    Sadekov, Aleksey Yu.; Bush, Flora; Kerr, Joanna; Ganeshram, Raja; Elderfield, Henry

    2014-10-01

    The Mg/Ca compositions of benthic foraminifera from the superfamily Miliolacea have been studied to explore the use of these high-Mg foraminifera as a proxy for deep ocean conditions. Taxonomic analyses, relative abundance, and depth distributions of different Miliolacea species were carried out on a collection of core top samples, covering a depth range of 131 m to 2530 m, along the Australian coast of the Timor Sea. Pyrgo sp., composed of Pyrgo sarsi and Pyrgo murrhina, was found to be the most suitable for proxy studies. Mg/Ca values of this group of foraminifera show a strong correlation with bottom water temperatures and carbonate ion saturation described by the linear relationship: Mg/Ca = 2.53(±0.22) × BWT + 0.129(±0.023) × Δ[CO32-] + 4.63(±0.53), within the -1°C to 8°C temperature range. Absolute Mg/Ca values of Pyrgo sp. calcite and their temperature sensitivity are similar to those observed for inorganic calcite, suggesting that Mg composition of Pyrgo sp. calcite is mainly controlled by inorganic processes. The Mg/Ca composition of Pyrgo sp. calcite provides a new tool for reconstructing both water temperature and carbonate ion saturation when combined with other proxies for one of these parameters. A down core record from the Eastern Equatorial Pacific has been generated to illustrate how Mg/Ca values can be used for paleoclimate studies. This down core record shows large changes in Pacific bottom waters [CO32-] across glacial-interglacial transition, implying an increase in [CO32-] during the glacial period.

  1. MgZnO/ZnO heterostructures with electron mobility exceeding 1 × 106 cm2/Vs

    PubMed Central

    Falson, Joseph; Kozuka, Yusuke; Uchida, Masaki; Smet, Jurgen H.; Arima, Taka-hisa; Tsukazaki, Atsushi; Kawasaki, Masashi

    2016-01-01

    The inherently complex chemical and crystallographic nature of oxide materials has suppressed the purities achievable in laboratory environments, obscuring the rich physical degrees of freedom these systems host. In this manuscript we provide a systematic approach to defect identification and management in oxide molecular beam epitaxy grown MgZnO/ZnO heterostructures which host two-dimensional electron systems. We achieve samples displaying electron mobilities in excess of 1 × 106 cm2/Vs. This data set for the MgZnO/ZnO system firmly establishes that the crystalline quality has become comparable to traditional semiconductor materials. PMID:27229479

  2. Influence of Zn Coating on Interfacial Reactions and Mechanical Properties During Laser Welding-Brazing of Mg to Steel

    NASA Astrophysics Data System (ADS)

    Li, Liqun; Tan, Caiwang; Chen, Yanbin; Guo, Wei; Hu, Xinbin

    2012-12-01

    To investigate the influence of Zn coating on the joining of magnesium alloy AZ31 to Zn-coated steel, dissimilar metal joining both with and without Zn coating was performed by the laser welding-brazing (LWB) process. Welding characteristics including joint appearance, identification of interfacial reaction layers, and mechanical properties were comparatively studied. The results indicated that the presence of Zn coating promoted the wetting of liquid filler wire on the steel substrate. Heterogeneous interfacial reaction layers formed along the interface between the Mg alloy and Zn-coated steel, whereas no distinct reaction layer and increased concentration of Al were identified at the interface between the Mg alloy and noncoated steel. The maximum tensile-shear strength of Mg/steel lap joint with Zn coating reached 180 N/mm, which was slightly higher than that achieved without Zn coating (160 N/mm). Failure of joint in both cases occurred at the interface; however, the fracture mode was found to differ. For Zn-coated steel, the crack propagated along the Mg-Zn reaction layer and Fe-Al phase, with little Mg-Zn reaction phases remaining on the steel side. As for noncoated steel, some remnants of the seam adhered to the steel substrate.

  3. Mechanochemical synthesis of MgF2 - MF2 composite systems (M = Ca, Sr, Ba)

    NASA Astrophysics Data System (ADS)

    Scholz, G.; Breitfeld, S.; Krahl, T.; Düvel, A.; Heitjans, P.; Kemnitz, E.

    2015-12-01

    The capability of mechanochemical synthesis for the formation of MgF2-MF2 (M: Ca, Sr, Ba) composites, solid solutions or well-defined compounds was tested applying a fluorination of different fluorine-free metal sources with NH4F directly at milling. No evidence was found for a substitution of Mg2+ with Ca2+ (Sr2+, Ba2+) ions, or vice versa, in rutile or fluorite structure. However, an equimolar ratio of Mg2+ to the second cation allows the mechanochemical synthesis of tetrafluoromagnesates, MMgF4, which is more and more hampered the smaller the radius of the cation M2+ is. BaMgF4 is formed even phase pure from the acetates, SrMgF4 can only be observed in a mixture accompanied by the binary fluorides. In addition, 19F MAS NMR spectra along with calculations of 19F isotropic chemical shift values according to the superposition model point to the formation of a metastable phase of CaMgF4, which disappears at thermal treatment and decomposes into the binary fluorides CaF2 and MgF2.

  4. Influence of surface pre-treatment on the cytocompatibility of a novel biodegradable ZnMg alloy.

    PubMed

    Jablonská, Eva; Vojtěch, Dalibor; Fousová, Michaela; Kubásek, Jiří; Lipov, Jan; Fojt, Jaroslav; Ruml, Tomáš

    2016-11-01

    Degradable zinc-based alloys with an appropriate corrosion rate are promising materials for the preparation of temporary orthopaedic implants. Previously, we prepared and characterised a novel Zn1.5Mg alloy. This paper is focused on the characterisation of this alloy after a surface pre-treatment, which should mimic processes occurring in vivo. The samples of the Zn1.5Mg alloy were immersed in a simulated body fluid (SBF) at 37°C for 14days in order to form a protective layer of corrosion products. Thereafter, these samples were used for the corrosion rate determination, an indirect in vitro cytotoxicity test, as well as for a direct contact test and were compared with the non-treated samples. The protective layer was characterized by SEM and its chemical composition was determined by EDS and XPS analysis. The corrosion rate was significantly decreased after the pre-incubation. The protective layer of corrosion products was rich in Ca and P. The pre-incubated samples exhibited increased cytocompatibility in the indirect test (metabolic activity of L929 cells was above 70%) and we also observed osteoblast-like cell growth directly on the samples during the contact tests. Thus, the pre-incubation in SBF leading to improved cytocompatibility could represent more appropriate model to in vivo testing.

  5. Lattice dynamics of the icosahedral quasicrystals i-ZnMgSc and i-ZnAgSc and the cubic 1/1-approximant Zn6Sc.

    PubMed

    Euchner, H; Yamada, T; Rols, S; Ishimasa, T; Ollivier, J; Schober, H; Mihalkovic, M; de Boissieu, M

    2014-02-05

    A comparison of periodic approximants and their quasicrystalline counterparts offers the opportunity to better understand the structure, physical properties and stabilizing mechanisms of these complex phases. We present a combined experimental and computational study of the lattice dynamics of the icosahedral quasicrystals i-ZnMgSc and i-ZnAgSc and compare these to the lattice dynamics of the cubic 1/1-approximant Zn6Sc. The two phases, quasicrystal and approximant, are built up from the same atomic clusters, which are packed either quasiperiodically or on a body centered cubic lattice, respectively. Using inelastic neutron scattering and atomic scale simulations, we show that the vibrational spectra of these three systems are very similar, however, they contain a clear signature of the increasing structural complexity from approximant to quasicrystal.

  6. Microstructure Evolution and Mechanical and Corrosion Behavior of Accumulative Roll Bonded Mg-2%Zn/Al-7075 Multilayered Composite

    NASA Astrophysics Data System (ADS)

    Anne, Gajanan; Ramesh, M. R.; Shivananda Nayaka, H.; Arya, Shashi Bhushan; Sahu, Sandeep

    2017-02-01

    Multilayered composite of Mg-2%Zn/Al-7075 was developed by accumulative roll bonding (ARB) of wrought Mg-2%Zn and aluminum 7075 alloy. The Mg-2%Zn/Al-7075 multilayered composite exhibited density of 2295 kg/m3 and an average grain size of 1 and 1.3 μm in Mg-2%Zn and Al-7075 layers, respectively. A thorough microstructural characterization was performed on the composites by scanning electron microscope, electron backscatter diffraction (EBSD), transmission electron microscope and phase analysis by x-ray diffraction. In addition, mechanical properties were evaluated by microhardness and tensile tests. Corrosion behavior of the multilayered composite was examined using electrochemical polarization test. EBSD analysis showed the presence of ultrafine grains with high-angle grain boundaries. The composite exhibited a significant improvement in ultimate tensile strength ( 1.82 times) and elongation ( 1.5 times) as compared with Mg-2%Zn alloy, after four-pass ARB process.

  7. Microstructure Evolution and Mechanical and Corrosion Behavior of Accumulative Roll Bonded Mg-2%Zn/Al-7075 Multilayered Composite

    NASA Astrophysics Data System (ADS)

    Anne, Gajanan; Ramesh, M. R.; Shivananda Nayaka, H.; Arya, Shashi Bhushan; Sahu, Sandeep

    2017-04-01

    Multilayered composite of Mg-2%Zn/Al-7075 was developed by accumulative roll bonding (ARB) of wrought Mg-2%Zn and aluminum 7075 alloy. The Mg-2%Zn/Al-7075 multilayered composite exhibited density of 2295 kg/m3 and an average grain size of 1 and 1.3 μm in Mg-2%Zn and Al-7075 layers, respectively. A thorough microstructural characterization was performed on the composites by scanning electron microscope, electron backscatter diffraction (EBSD), transmission electron microscope and phase analysis by x-ray diffraction. In addition, mechanical properties were evaluated by microhardness and tensile tests. Corrosion behavior of the multilayered composite was examined using electrochemical polarization test. EBSD analysis showed the presence of ultrafine grains with high-angle grain boundaries. The composite exhibited a significant improvement in ultimate tensile strength ( 1.82 times) and elongation ( 1.5 times) as compared with Mg-2%Zn alloy, after four-pass ARB process.

  8. Ca2+ and Zn2+ are transported by the electrogenic 2Na+/1H+ antiporter in echinoderm gastrointestinal epithelium

    PubMed

    Zhuang; Duerr; Ahearn

    1995-01-01

    45Ca2+ uptake by purified brush-border membrane vesicles of starfish (Pycnopodia helianthoides) pyloric ceca was stimulated by an outwardly directed H+ gradient and this stimulation was enhanced by the simultaneous presence of an induced membrane potential (inside negative; K+/valinomycin). External amiloride (competitive inhibitor; Ki=660 µmol l-1) and a monoclonal antibody raised against proteins associated with the lobster (Homarus americanus) electrogenic 2Na+/1H+ antiporter both inhibited approximately half of the proton-gradient-stimulated 45Ca2+ uptake. These results suggested that Ca2+ might be transported by the electrogenic antiporter and that the crustacean antibody was inhibitory to the exchange function in echinoderms, as was recently shown in crustacean epithelial brush-border membrane vesicles. Carrier-mediated 45Ca2+ influx by amiloride-sensitive and amiloride-insensitive systems displayed the following kinetic constants: (amiloride-sensitive) Kt=66±2 µmol l-1; Jmax=0.173±0.002 pmol µg-1 protein 8 s-1; (amiloride-insensitive) Kt=18±0.3 µmol l-1; Jmax=0.100±0.001 pmol µg-1 protein 8 s-1. Zn2+ was a mixed inhibitor of 45Ca2+ influx by carrier-mediated transport, displaying a Ki of 920 µmol l-1. Mn2+, Cu2+, Fe2+ and Mg2+ also inhibited 45Ca2+ uptake, but the mechanism(s) of inhibition by these other cations was not disclosed. An equilibrium shift experiment showed that both Na+ and Zn2+ were able to exchange with equilibrated 45Ca2+ in these vesicles, suggesting that both monovalent and divalent cations were able to enter pyloric cecal cells through a common carrier-mediated transport system. In addition, the echinoderm electrogenic system appeared to exhibit a molecular component recognized by the crustacean antibody that may imply a similar epitope in the two animals.

  9. Reinvestigating the "salinity effect" on Atlantic Globigerinoides ruber Mg/Ca ratios

    NASA Astrophysics Data System (ADS)

    Hertzberg, J. E.; Schmidt, M. W.

    2012-12-01

    Numerous culturing, core-top, and sediment trap studies show that temperature is the primary control on Mg/Ca ratios in foraminiferal calcite, and calibrations of this relationship have been applied successfully to the paleo-record to reconstruct ocean temperatures across a wide range of time periods. In addition, paired Mg/Ca temperatures and δ18Ocalcite measurements on surface dwelling foraminifera are often used to reconstruct past δ18Osw variability, a robust proxy for sea surface salinity. However, a recent study of core-top sediments across an Atlantic meridional transect suggests that salinity might have a stronger control on foraminiferal Mg/Ca ratios than previously thought. By analyzing Mg/Ca ratios and δ18O on the planktonic foraminifera Globigerinoides ruber (white), Arbuszewski et al. [2010] found a 27% increase in G. ruber Mg/Ca ratios per 1 salinity unit increase for seawater salinities above 35. In this study, we use shell weight analyses and SEM images from a subset of the core-tops used in the Arbuszewski et al. [2010] study across a narrow depth range (3197 - 3559 m) to show that G. ruber shells from the equatorial region are highly dissolved compared to those from the gyres, significantly impacting their Mg/Ca-SSTs. Shell weights from the higher-productivity equatorial regions of the Atlantic are on average 20% and 15% lower than those from the oligotrophic North and South Atlantic gyres, respectively. Given the large preservation gradient along the Mid Atlantic Ridge, Arbuszewski et al.'s [2010] application of a single depth-corrected Mg/Ca:SST equation [Dekens et al., 2002] on cores from the subtropical gyres and the equatorial region is not appropriate. When regional differences in preservation are considered, as well as realistic calcification seasons for G. ruber in temperate latitudes, we find a strong correlation between SST and G. ruber Mg/Ca ratios in core-top samples spanning 43°N to 25°S in the Atlantic. When we also consider

  10. Mg2+ and Ca2+ differentially regulate DNA binding and dimerization of DREAM.

    PubMed

    Osawa, Masanori; Dace, Alexandra; Tong, Kit I; Valiveti, Aswani; Ikura, Mitsuhiko; Ames, James B

    2005-05-06

    DREAM (calsenilin/KChIP3) is an EF-hand calcium-binding protein that represses transcription of prodynorphin and c-fos genes. Here we present structural and binding studies on single-site mutants of DREAM designed to disable Ca(2+) binding to each of the functional EF-hands (EF-2: D150N; EF-3: E186Q; and EF-4: E234Q). Isothermal titration calorimetry (ITC) analysis of Ca(2+) binding to the various mutants revealed that, in the absence of Mg(2+), Ca(2+) binds independently and sequentially to EF-3 (DeltaH = -2.4 kcal/mol), EF-4 (DeltaH = +5.2 kcal/mol), and EF-2 (DeltaH = +1 kcal/mol). By contrast, only two Ca(2+) bind to DREAM in the presence of physiological levels of Mg(2+) for both wild-type and D150N, suggesting that EF-2 binds constitutively to Mg(2+). ITC measurements demonstrate that one Mg(2+) binds enthalpically with high affinity (K(d) = 13 mum and DeltaH = -0.79 kcal/mol) and two or more Mg(2+) bind entropically in the millimolar range. Size-exclusion chromatography studies revealed that Mg(2+) stabilizes DREAM as a monomer, whereas Ca(2+) induces protein dimerization. Electrophoretic mobility shift assays indicated that Mg(2+) is essential for sequence-specific binding of DREAM to DNA response elements (DREs) in prodynorphin and c-fos genes. The EF-hand mutants bind specifically to DRE, suggesting they are functionally intact. None of the EF-hand mutants bind DRE at saturating Ca(2+) levels, suggesting that binding of a single Ca(2+) at either EF-3 or EF-4 is sufficient to drive conformational changes that abolish DNA binding. NMR structural analysis indicates that metal-free DREAM adopts a folded yet flexible molten globule-like structure. Both Ca(2+) and Mg(2+) induce distinct conformational changes, which stabilize tertiary structure of DREAM. We propose that Mg(2+) binding at EF-2 may structurally bridge DREAM to DNA targets and that Ca(2+)-induced protein dimerization disrupts DNA binding.

  11. The role of beryllium in the band structure of MgZnO: Lifting the valence band maximum

    NASA Astrophysics Data System (ADS)

    Chen, S. S.; Pan, X. H.; Chen, W.; Zhang, H. H.; Dai, W.; Ding, P.; Huang, J. Y.; Lu, B.; Ye, Z. Z.

    2014-09-01

    We investigate the effect of Be on the valence band maximum (VBM) of MgZnO by measuring the band offsets of MgxZn1-xO/BexMgyZn1-x-yO heterojunctions using X-ray photoelectron spectroscopy measurements. MgxZn1-xO and BexMgyZn1-x-yO films have been grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. The valence band offset ( Δ E V) of Mg0.15Zn0.85O ( E g = 3.62 eV)/Be0.005Mg0.19Zn0.805O ( E g = 3.73 eV) heterojunction is 0.01 eV and Be0.005Mg0.19Zn0.805O has a lower VBM. The increased Mg composition is the main factor for the reduction of VBM. The VBM of MgxZn1-xO is lower by 0.03 eV with the enlargement of E g from 3.62 eV to 3.73 eV by increasing Mg composition. Considering the effect of increased Mg composition, it is concluded that the little amount of Be makes the VBM go up by 0.02 eV when the E g of the alloy is 3.73 eV. The Δ E V of Mg0.11Zn0.89O ( E g = 3.56 eV)/Be0.007Mg0.12Zn0.873O ( E g = 3.56 eV) heterojunction is calculated to be 0.03 eV and Be0.007Mg0.12Zn0.873O has a higher VBM than Mg0.11Zn0.89O, which means that a little amount Be lifts the VBM by 0.03 eV when the E g of the alloy is 3.56 eV. The experimental measurements have offered a strong support for the theoretical research that alloying Be in MgxZn1-xO alloys is hopeful to form a higher VBM and to enhance the p-type dopability of MgZnO.

  12. Culture-based Calibration of the Benthic Foraminiferal Mg/Ca Paleothermometer: Initial Results

    NASA Astrophysics Data System (ADS)

    Lincoln, S. A.; Filipsson, H. L.; Bernhard, J. M.; McCorkle, D. C.; Shimizu, N.; Birdwhistell, S. P.

    2007-12-01

    The magnesium calcium (Mg/Ca) paleothermometer has become a widely used tool for estimating deep water temperatures. To date, calibrations of the proxy have relied on core-top samples; in such studies, water chemistry and biological factors including food supply often co-vary with temperature, making it difficult to isolate the true Mg/Ca / temperature relationship. A multi-temperature culture experiment was conducted at the Woods Hole Oceanographic Institution from December 2006 through May 2007 in order to study the relationship between Mg/Ca and temperature under controlled conditions. Several species of benthic foraminifera were collected from four locations (the Skagerrak and Gullmar Fjord, Sweden; the Bahamas; and the Charleston Bump, United States; 70 to 800 m water depth), and were grown in microcosms under known, constant physical and chemical conditions at 3.5, 7.0, 14.0, and 21 C. Bulimina species ( B. aculeata and B. marginata) were the most successful, reproducing at 7.0 and 14.0 C and adding chambers at all temperatures. These newly added chambers are the focus of our first Mg/Ca analyses. Because cultured benthic foraminifera are typically lightly calcified, sensitive microanalytical techniques with high spatial resolution are required to measure trace element concentrations in single chambers of cultured specimens. We have explored the use of both secondary ion mass spectrometry and laser ablation inductively coupled mass spectrometry for this application, and present preliminary Mg/Ca data from Bulimina species across the experimental temperature range.

  13. Electrically driven deep ultraviolet MgZnO lasers at room temperature.

    PubMed

    Suja, Mohammad; Bashar, Sunayna Binte; Debnath, Bishwajit; Su, Longxing; Shi, Wenhao; Lake, Roger; Liu, Jianlin

    2017-06-01

    Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. In this paper, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM) random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29~33 A/cm(2) are achieved. Numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.

  14. Electrically driven deep ultraviolet MgZnO lasers at room temperature

    DOE PAGES

    Suja, Mohammad; Bashar, Sunayna Binte; Debnath, Bishwajit; ...

    2017-06-01

    Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. Here, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM)more » random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29-33 A/cm2 are achieved. Furthermore, numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.« less

  15. Local structures of polar wurtzites Zn1-xMgxO studied by raman and 67Zn/25Mg NMR spectroscopies and by total neutron scattering

    SciTech Connect

    Proffen, Thomas E; Kim, Yiung- Il; Cadars, Sylvian; Shayib, Ramzy; Feigerle, Charles S; Chmelka, Bradley F; Seshadri, Ram

    2008-01-01

    Research in the area of polar semiconductor heterostructures has been growing rapidly, driven in large part by interest in two-dimensional electron gas (2DEG) systems. 2DEGs are known to form at heterojunction interfaces that bear polarization gradients. They can display extremely high electron mobilities, especially at low temperatures, owing to spatial confinement of carrier motions. Recent reports of 2DEG behaviors in Ga{sub 1-x}Al{sub x}N/GaN and Zn{sub 1-x}Mg{sub x}O/ZnO heterostructures have great significance for the development of quantum Hall devices and novel high-electron-mobility transistors (HEMTs). 2DEG structures are usually designed by interfacing a polar semiconductor with its less or more polar alloys in an epitaxial manner. Since the quality of the 2DEG depends critically on interface perfection, as well as the polarization gradient at the heterojunction, understanding compositional and structural details of the parent and alloy semiconductors is an important component in 2DEG design and fabrication. Zn{sub 1-x}Mg{sub x}O/ZnO is one of the most promising heterostructure types for studies of 2DEGs, due to the large polarization of ZnO, the relatively small lattice mismatch, and the large conduction band offsets in the Zn{sub 1-x}Mg{sub x}O/ZnO heterointerface. Although 2DEG formation in Zn{sub 1-x}Mg{sub x}O/ZnO heterostructures have been researched for some time, a clear understanding of the alloy structure of Zn{sub 1-x}Mg{sub x}O is currently lacking. Here, we conduct a detailed and more precise study of the local structure of Zn{sub 1-x}Mg{sub x}O alloys using Raman and solid-state nuclear magnetic resonance (NMR), in conjunction with neutron diffraction techniques.

  16. DC electrical and thermoelectric power measurement studies of Ni-Mg-Zn-Co ferrites

    NASA Astrophysics Data System (ADS)

    Patil, S. B.; Patil, R. P.; Chougule, B. K.

    2013-06-01

    Ni-Mg-Zn-Co ferrites having general formula, Ni0.5-xMgx-0.01Zn0.5-yCoy+0.01Fe2O4 (where x=0.1-0.4 and y=0.1-0.4) were prepared by a ceramic method. X-ray diffraction reveals formation of single-phase cubic spinel structures. The lattice parameter is found to increase linearly with increase in Zn content. The variation of the electrical resistivity vs. temperature is linear with a transition near the Curie temperature. The thermoelectric power was measured from room temperature to 500 °C by maintaining a temperature difference of 20 °C between the hot and cold ends. All samples show a negative Seebeck coefficient. This indicates n-type charge carriers in the samples.

  17. Mechanical, thermal, and physical properties of Mg-Ca compounds in the framework of the modified embedded-atom method.

    PubMed

    Groh, Sébastien

    2015-02-01

    Interatomic potentials for pure Ca and the Mg-Ca binary have been developed in the framework of the second nearest-neighbors modified embedded-atom method (MEAM). The validity and the transferability of the Ca MEAM potential was performed by calculating physical, mechanical, and thermal properties. These properties were compared to experimental data and numerical data obtained from existing Ca potentials, and a good agreement was found. In addition, the dissociation of the edge dislocation into two Shockley partials aligns with the linear elasticity solution. Furthermore, the velocity of an edge dislocation under static and dynamics loading conditions predicted in Ca using the MEAM formalism reproduces the expected behavior of an edge dislocation in fcc crystal structures. The Ca MEAM potential was then coupled to an existing Mg MEAM potential to describe the properties of the Mg-Ca alloys. Heat of formation, structural energy difference, and elastic constants were calculated for several ordered Mg-Ca compounds containing different concentrations of Ca. As expected from first-principle calculations based on DFT, Mg2Ca with the Laves phase C14 was found to be the most stable structure with the lowest heat of formation compared to compounds with other Ca concentrations (Mg3Ca, MgCa, and MgCa3). Moreover, the mechanical stability was recovered for the different tested compounds and is in agreement with first-principle data.

  18. Powder metallurgy preparation of Mg-Ca alloy for biodegradable implant application

    NASA Astrophysics Data System (ADS)

    Annur, D.; Suhardi, A.; Amal, M. I.; Anwar, M. S.; Kartika, I.

    2017-04-01

    Magnesium and its alloys is a promising candidate for implant application especially due to its biodegradability. In this study, Mg-7Ca alloys (in weight %) were processed by powder metallurgy from pure magnesium powder and calcium granule. Milling process was done in a shaker mill using stainless steel balls in various milling time (3, 5, and 8 hours) followed by compaction and sintering process. Different sintering temperatures were used (450°C and 550°C) to examine the effect of sintering temperature on mechanical properties and corrosion resistance. Microstructure evaluation was characterized by X-ray diffraction, scanning electron microscope and energy dispersive X-ray spectroscopy. Mechanical properties and corrosion behavior were examined through hardness testing and electrochemical testing in Hank’s solution (simulation body fluid). In this report, a prolonged milling time reduced particle size and later affected mechanical properties of Mg alloy. Meanwhile, the phase analysis showed that α Mg, Mg2Ca, MgO phases were formed after the sintering process. Further, this study showed that Mg-Ca alloy with different powder metallurgy process would have different corrosion rate although there were no difference of Ca content in the alloy.

  19. Multifunctions of dual Zn/Mg ion co-implanted titanium on osteogenesis, angiogenesis and bacteria inhibition for dental implants.

    PubMed

    Yu, Yiqiang; Jin, Guodong; Xue, Yang; Wang, Donghui; Liu, Xuanyong; Sun, Jiao

    2017-02-01

    In order to improve the osseointegration and long-term survival of dental implants, it is urgent to develop a multifunctional titanium surface which would simultaneously have osteogeneic, angiogeneic and antibacterial properties. In this study, a potential dental implant material-dual Zn/Mg ion co-implanted titanium (Zn/Mg-PIII) was developed via plasma immersion ion implantation (PIII). The Zn/Mg-PIII surfaces were found to promote initial adhesion and spreading of rat bone marrow mesenchymal stem cells (rBMSCs) via the upregulation of the gene expression of integrin α1 and integrin β1. More importantly, it was revealed that Zn/Mg-PIII could increase Zn(2+) and Mg(2+) concentrations in rBMSCs by promoting the influx of Zn(2+) and Mg(2+) and inhibiting the outflow of Zn(2+), and then could enhance the transcription of Runx2 and the expression of ALP and OCN. Meanwhile, Mg(2+) ions from Zn/Mg-PIII increased Mg(2+) influx by upregulating the expression of MagT1 transporter in human umbilical vein endothelial cells (HUVECs), and then stimulated the transcription of VEGF and KDR via activation of hypoxia inducing factor (HIF)-1α, thus inducing angiogenesis. In addition to this, it was discovered that zinc in Zn/Mg-PIII had certain inhibitory effects on oral anaerobic bacteria (Pg, Fn and Sm). Finally, the Zn/Mg-PIII implants were implanted in rabbit femurs for 4 and 12weeks with Zn-PIII, Mg-PIII and pure titanium as controls. Micro-CT evaluation, sequential fluorescent labeling, histological analysis and push-out test consistently demonstrated that Zn/Mg-PIII implants exhibit superior capacities for enhancing bone formation, angiogenesis and osseointegration, while consequently increasing the bonding strength at bone-implant interfaces. All these results suggest that due to the multiple functions co-produced by zinc and magnesium, rapid osseointegration and sustained biomechanical stability are enhanced by the novel Zn/Mg-PIII implants, which have the potential

  20. Thermal stability and magnetic properties of MgFe2O4@ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Mallesh, S.; Prabu, D.; Srinivas, V.

    2017-05-01

    Magnesium ferrite, MgFe2O4, (MgFO) nanoparticles (NPs) have been synthesized through sol-gel process. Subsequently, as prepared particles were coated with Zinc-oxide (ZnO) layer(s) through ultrasonication process. Thermal stability, structure and magnetic properties of as-prepared (AP) and annealed samples in the temperature range of 350 °C-1200 °C have been investigated. Structural data suggests that AP MgFO NPs and samples annealed below 500 °C in air exhibit stable ferrite phase. However, α-Fe2O3 and a small fraction of MgO secondary phases appear along with ferrite phase on annealing in the temperatures range 500 °C- 1000 °C. This results in significant changes in magnetic moment for AP NPs 0.77 μB increases to 0.92 μB for 1200 °C air annealed sample. The magnetic properties decreased at intermediate temperatures due to the presence of secondary phases. On the other hand, pure ferrite phase could be stabilized with an optimum amount of ZnO coated MgFO NPs for samples annealed in the temperature range 500 °C-1000 °C with improvement in magnetic behavior compared to that of MgFO samples.

  1. Sol-Gel Derived Hydroxyapatite Coating on Mg-3Zn Alloy for Orthopedic Application

    NASA Astrophysics Data System (ADS)

    Singh, Sanjay; Manoj Kumar, R.; Kuntal, Kishor Kumar; Gupta, Pallavi; Das, Snehashish; Jayaganthan, R.; Roy, Partha; Lahiri, Debrupa

    2015-04-01

    In recent years, magnesium and its alloys have gained a lot of interest as orthopedic implant constituents because their biodegradability and mechanical properties are closer to that of human bone. However, one major concern with Mg in orthopedics is its high corrosion rate that results in the reduction of mechanical integrity before healing the bone tissue. The current study evaluates the sol-gel-derived hydroxyapatite (HA) coating on a selected Mg alloy (Mg-3Zn) for decreasing the corrosion rate and increasing the bioactivity of the Mg surface. The mechanical integrity of the coating is established as a function of the surface roughness of the substrate and the sintering temperature of the coating. Coating on a substrate roughness of 15-20 nm and sintering at 400°C shows the mechanical properties in similar range of bone, thus making it suitable to avoid the stress-shielding effect. The hydroxyapatite coating on the Mg alloy surface also increases corrosion resistance very significantly by 40 times. Bone cells are also found proliferating better in the HA-coated surface. All these benefits together establish the candidature of sol-gel HA-coated Mg-3Zn alloy in orthopedic application.

  2. Ca and Mg Incorporation in Siderite at Low Temperatures (< 50° C): Results from Laboratory Experiments

    NASA Astrophysics Data System (ADS)

    Sanchez-Roman, M.; Romanek, C. S.; Xu, H.; Coleman, M.

    2008-12-01

    Siderite (FeCO3) is a common mineral found in modern environments and in ancient rocks produce usually by microbia mediation [1,2]. It usually forms concretions with strongly varying chemical compositions which are governed by both pore-water origin and by microbial influence. In addition, siderite has also been identified in extraterrestrial material such as meteorites and dust particles [3,4]. The geochemical information stored in siderite provides valuable insights into the environmental conditions of mineral formation and the processes by which it is modified over time [5]. To unerstand the inorganic constraints on precipitation relative to natural compositions we undertook free drift experiments under anaerobic conditions at 25, 35 and 45°C with variable concentrations of Fe, Ca and Mg in solution. Samples of solution and solid were withdrawn at different time intervals (15, 21 and 30 days) during time course experiments to determine the composition of the solution and mineral precipitates, and the morphology and mineralogy of the precipitates. After 15 days of incubation a metastable phase was formed, whereas after 21 and 30 days of incubation siderite, Ca-siderite, Mg-siderite Ca-Mg siderite and/or Fe-pokrovskite (a hydrated magnesium hydroxy carbonate) were formed depending on the aqueous Fe, Ca and Mg concentrations in the solution. The Mg and Ca contents in the siderite increased with increasing Mg and Ca concentrations in the medium and with increasing temperature. Siderite precipitates ranged from 1.5 to 50.81 mol percent CaCO3 and from 0.54 to 41.38 mol percent MgCO3. Pokrovskite precipitates ranged from 48.8 to 57.7 mol percent MgCO3 and from 42.34 to 51.17 mol percent FeCO3. The Fe content in the pokrovskite increased with increasing temperature. These inorganic experiments will help to understand the mechanism of Ca-Mg-Fe carbonate formation in natural systems and they are of fundamental importance not only for understanding modern and

  3. The in vitro biological properties of Mg-Zn-Sr alloy and superiority for preparation of biodegradable intestinal anastomosis rings

    PubMed Central

    Liu, Ling; Li, Nianfeng; Lei, Ting; Li, Kaimo; Zhang, Yangde

    2014-01-01

    Background Magnesium (Mg) alloy is a metal-based biodegradable material that has received increasing attention in the field of clinical surgery, but it is currently seldom used in intestinal anastomosis. This study was conducted to comprehensively assess a ternary magnesium (Mg)-zinc (Zn)-strontium (Sr) alloy’s biological superiorities as a preparation material for intestinal anastomosis ring. Material/Methods Mouse L-929 fibroblasts were cultured with Mg-Zn-Sr alloy extract and compared with both positive (0.64% phenol) and negative (original broth culture) controls. The cell morphology of different groups was examined using microscopy, and a cytotoxicity assessment was performed. Fresh anticoagulated human blood was mixed with Mg-Zn-Sr alloy extract and compared with both positive (distilled water) and negative (normal saline) controls. The absorbance of each sample at 570 nm was used to calculate the Mg-Zn-Sr alloy hemolysis ratio in order to test the Mg alloy’s blood compatibility. Bacterial cultures of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were added to Mg-Zn-Sr alloy block samples and compared with positive (Ceftazidime), negative (316LSS stainless steel), and blank controls. The broth cultures were sampled to compare their bacterial colony counts so as to evaluate the antibacterial properties of the Mg-Zn-Sr alloy. The Mg-Zn-Sr alloy was surface-coated with a layer of poly(lactic-co-glycolic acid) carrying everolimus. The surface morphology and degradability of the coating were examined so as to demonstrate feasibility of coating, which can release the drug evenly. Results The experiments proved that Mg-Zn-Sr alloy has good biocompatible, antibacterial, and drug-loaded coating performances, which are lacking in existing intestinal anastomosis devices/materials. Conclusions The Mg-Zn-Sr alloy increases biocompatibility, and yields a safer and better therapeutic effect; therefore, it is a novel biomaterial that is feasible for

  4. Antihypertensive effect of Cu and Mg enriched modified poultry eggPsi on Zn-induced hypertension in Wistar rat.

    PubMed

    Taneja, Satish Kumar; Mandal, Reshu

    2010-07-01

    Excessive bioavailability of Zn either due to genetic predisposition or its high concentration in diet has been linked to increase in the prevalence of hypertension (HT) implicating the resultant deficiencies of Cu and Mg as its cause in some populations. To combat their nutritional deficiencies, a modified poultry egg (ME(Psi)) was designed containing higher amounts of Cu, Mg and other antioxidants (vitamin E and linolenic acid) in their optimized concentrations. Prior to its human clinical trials, its efficacy was tested in Zn induced HT Wistar rat model in the present study. In one set, the rats were fed on equicaloric semi-synthetic basal diet containing 20 mg Zn/kg diet (control diet-I, control group-I), Zn-induced-hypertensive-diets-II and III (Zn-HT-diet-II and Zn-HT-diet-III) containing 40 and 80 mg Zn/kg diet (groups-II and III) for 180 days. In another set, the rats were initially fed Zn-HT-diet-II and Zn-HT-diet-III for 90 days and then shifted to ME(Psi) mixed Zn-HT-diet-II and III designated as groups-IIME and IIIME fed for another 90 days completing 180 days of feeding. The results revealed that increase in systolic pressure (SP) and heart rates (HR) were Zn concentration dependent and coincided well with higher serum Zn, Cu, Mg, aldosterone, cortisol, dyslipidemia and higher Zn, and low Cu and Mg concentrations in liver of groups-II and III rats. On feeding ME(Psi) mixed diets, a significant reduction in SP and HR were linked with decrease in serum Zn, Cu, Mg, aldosterone, cortisol and blood lipid profile along with fall in Zn and rise in Cu and Mg concentrations in liver of groups-IIME and IIIME approaching closer to control group-I. This study makes the basis for human clinical trials of ME(Psi) on HT patients who exhibit high Zn, Cu and Mg in their blood serum. Copyright 2010 Elsevier GmbH. All rights reserved.

  5. Liquidus (Ca+Mg)-rich exsolution phases in low-sulfur fly ash

    SciTech Connect

    O'Connor, J.T.; Meeker, G.M.

    1999-07-01

    Ca- and Mg-rich fly ash samples from an electric power plant burning low-sulfur Powder River Coal were analyzed using optical petrographic microscope (OPM), scanning electron microscope (SEM), electron microprobe analyzer (EMPA), and Gandolfi and bulk-powder X-ray diffraction (XRD) techniques. Abundant Ca and Mg in the fly ash, probably originating from dispersed authigenic and residual minerals in the coal feed stock, flux the molten fly ash, effectively allowing many crystalline phases to achieve ordering, to separate from each other, and to grow to appreciable size (>10{micro}m) in the brief time (<20 sec) they spend at high temperature. Phases identified from the (Ca+Mg)-rich fly ash are listed in a table and shown in figures.

  6. Mg/Ca and Sr/Ca as novel geochemical proxies for understanding sediment transport processes within coral reefs

    NASA Astrophysics Data System (ADS)

    Gacutan, J.; Vila-Concejo, A.; Nothdurft, L. D.; Fellowes, T. E.; Cathey, H. E.; Opdyke, B. N.; Harris, D. L.; Hamylton, S.; Carvalho, R. C.; Byrne, M.; Webster, J. M.

    2017-10-01

    Sediment transport is a key driver of reef zonation and biodiversity, where an understanding of sediment dynamics gives insights into past reef processes and allows the prediction of geomorphic responses to changing environmental conditions. However, modal conditions within the back-reef seldom promote sediment transport, hence direct observation is inherently difficult. Large benthic foraminifera (LBF) have previously been employed as 'tracers' to infer sediment transport pathways on coral reefs, as their habitat is largely restricted to the algal flat and post-mortem, their calcium carbonate test is susceptible to sediment transport forces into the back-reef. Foraminiferal test abundance and post-depositional test alteration have been used as proxies for sediment transport, although the resolution of these measures becomes limited by low test abundance and the lack of variation within test alteration. Here we propose the novel use of elemental ratios as a proxy for sediment transport. Two species, Baculogypsina sphaerulata and Calcarina capricornia, were analysed using a taphonomic index within One Tree and Lady Musgrave reefs, Great Barrier Reef (Australia). Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to determine Mg/Ca and Sr/Ca and these ratios were compared with taphonomic data. Decreases in test Mg/Ca accompany increases in Sr/Ca in specimens from algal-flat to lagoonal samples in both species, mirroring trends indicated by taphonomic values, therefore indicating a relationship with test alteration. To delineate mechanisms driving changes in elemental ratios, back-scattered electron (BSE) images, elemental mapping and in situ quantitative spot analyses by electron microprobe microanalysis (EPMA) using wavelength dispersive X-ray spectrometers (WDS) were performed on un-altered algal flat and heavily abraded tests for both species. EPMA analyses reveal heterogeneity in Mg/Ca between spines and the test wall, implying the loss of

  7. H2O2: a Ca(2+) or Mg(2+)-sensing function in statin passive diffusion.

    PubMed

    Guillaume, Yves Claude; Lethier, Lydie; André, Claire

    2015-09-01

    In a previous paper Guillaume's group demonstrated that magnesium (Mg(2+) concentration range 0.00-2.60 mm) increased the passive diffusion of statins and thus played a role in their potential toxicity. In order to confirm an increase in this passive diffusion by divalent salt cations, the role of calcium chloride (CaCl2) on the statin-immobilized artificial membrane (IAM) association was studied. It was demonstrated that calcium supplementation (Ca(2+) concentration range 0.00-3.25 mm) increases the statin passive diffusion. In addition, it was shown that the Ca(2+) effect on the statin-IAM association is higher than that of Mg(2+). These results show that Ca(2+) enhances the passive diffusion of drugs into biological membranes and thus their potential toxicity. Also, addition of H2O2 to the medium showed a hyperbolic response for the statin passive diffusion and this effect was enhanced for the highest Ca(2+) or Mg(2+) concentrations in the medium. H2O2 is likely to interact with the polar head groups of the IAM through dipole-dipole interactions. The conformational changes in H2O2-IAM result in a higher degree of exposure of hydrophobic areas, thus explaining why the binding of pravastatin, which showed the lowest logP value, was less affected by H2O2. This result shows the significant contribution of H2O2 and thus the oxidative stress on the statin passive diffusion. Much of the sensitivity derives from the action of Ca(2+) or Mg(2+), in turn supported the idea that H2O2 may serve a Ca(2+) or Mg(2+) sensing function in statin passive diffusion.

  8. Controlling spin-dependent tunneling by bandgap tuning in epitaxial rocksalt MgZnO films

    SciTech Connect

    Li, D. L.; Ma, Q. L.; Wang, S. G.; Ward, R. C. C.; Hesjedal, T.; Zhang, X. -G.; Kohn, A.; Amsellem, E.; Yang, G.; Liu, J. L.; Jiang, J.; Wei, H. X.; Han, X. F.

    2014-12-02

    Widespread application of magnetic tunnel junctions (MTJs) for information storage has so far been limited by the complicated interplay between tunnel magnetoresistance (TMR) ratio and the product of resistance and junction area (RA). An intricate connection exists between TMR ratio, RA value and the bandgap and crystal structure of the barrier, a connection that must be unravelled to optimise device performance and enable further applications to be developed. In this paper, we demonstrate a novel method to tailor the bandgap of an ultrathin, epitaxial Zn-doped MgO tunnel barrier with rocksalt structure. This structure is attractive due to its good Δ1 spin filtering effect, and we show that MTJs based on tunable MgZnO barriers allow effective balancing of TMR ratio and RA value. Finally, in this way spin-dependent transport properties can be controlled, a key challenge for the development of spintronic devices.

  9. Controlling spin-dependent tunneling by bandgap tuning in epitaxial rocksalt MgZnO films

    DOE PAGES

    Li, D. L.; Ma, Q. L.; Wang, S. G.; ...

    2014-12-02

    Widespread application of magnetic tunnel junctions (MTJs) for information storage has so far been limited by the complicated interplay between tunnel magnetoresistance (TMR) ratio and the product of resistance and junction area (RA). An intricate connection exists between TMR ratio, RA value and the bandgap and crystal structure of the barrier, a connection that must be unravelled to optimise device performance and enable further applications to be developed. In this paper, we demonstrate a novel method to tailor the bandgap of an ultrathin, epitaxial Zn-doped MgO tunnel barrier with rocksalt structure. This structure is attractive due to its good Δ1more » spin filtering effect, and we show that MTJs based on tunable MgZnO barriers allow effective balancing of TMR ratio and RA value. Finally, in this way spin-dependent transport properties can be controlled, a key challenge for the development of spintronic devices.« less

  10. Friction Stir Welding of a Thick Al-Zn-Mg Alloy Plate

    NASA Astrophysics Data System (ADS)

    Buchibabu, V.; Reddy, G. M.; Kulkarni, D.; De, A.

    2016-03-01

    Al-Zn-Mg alloys are widely used as structural materials due to high strength-to-weight ratio and impact toughness. As fusion welds in these alloys commonly face hot cracking and macro porosity, friction stir welding is increasingly becoming the preferred recourse. We report here a detailed experimental study on friction stir welding of a specific Al-Zn-Mg alloy with its chemical compositions close to AA7039. The effect of tool rotational speed and welding speed on the weld profile, joint microstructure, and mechanical properties is studied extensively. The results show sound weld profiles and joint properties within the selected range of process conditions. Within the selected range of welding conditions, the welds made at a tool rotational speed of 350 rpm and welding speed of 3 mm/s have showed joint structure, tensile, and impact toughness properties fairly close to that of the base material.

  11. Ultraviolet random lasing from asymmetrically contacted MgZnO metal-semiconductor-metal device

    SciTech Connect

    Morshed, Muhammad M.; Suja, Mohammad; Zuo, Zheng; Liu, Jianlin

    2014-11-24

    Nitrogen-doped Mg{sub 0.12}Zn{sub 0.88}O nanocrystalline thin film was grown on c-plane sapphire substrate. Asymmetric Ni/Au and Ti/Au Schottky contacts and symmetric Ni/Au contacts were deposited on the thin film to form metal-semiconductor-metal (MSM) laser devices. Current-voltage, photocurrent, and electroluminescence characterizations were performed. Evident random lasing with a threshold current of ∼36 mA is demonstrated only from the asymmetric MSM device. Random lasing peaks are mostly distributed between 340 and 360 nm and an output power of 15 nW is measured at 43 mA injection current. The electron affinity difference between the contact metal and Mg{sub 0.12}Zn{sub 0.88}O:N layer plays an important role for electron and hole injection and subsequent stimulated random lasing.

  12. Fabrication of artificially stacked ultrathin ZnS/MgF2 multilayer dielectric optical filters.

    PubMed

    Kedawat, Garima; Srivastava, Subodh; Jain, Vipin Kumar; Kumar, Pawan; Kataria, Vanjula; Agrawal, Yogyata; Gupta, Bipin Kumar; Vijay, Yogesh K

    2013-06-12

    We report a design and fabrication strategy for creating an artificially stacked multilayered optical filters using a thermal evaporation technique. We have selectively chosen a zinc sulphide (ZnS) lattice for the high refractive index (n = 2.35) layer and a magnesium fluoride (MgF2) lattice as the low refractive index (n = 1.38) layer. Furthermore, the microstructures of the ZnS/MgF2 multilayer films are also investigated through TEM and HRTEM imaging. The fabricated filters consist of high and low refractive 7 and 13 alternating layers, which exhibit a reflectance of 89.60% and 99%, respectively. The optical microcavity achieved an average transmittance of 85.13% within the visible range. The obtained results suggest that these filters could be an exceptional choice for next-generation antireflection coatings, high-reflection mirrors, and polarized interference filters.

  13. Controlling spin-dependent tunneling by bandgap tuning in epitaxial rocksalt MgZnO films

    PubMed Central

    Li, D. L.; Ma, Q. L.; Wang, S. G.; Ward, R. C. C.; Hesjedal, T.; Zhang, X.-G.; Kohn, A.; Amsellem, E.; Yang, G.; Liu, J. L.; Jiang, J.; Wei, H. X.; Han, X. F.

    2014-01-01

    Widespread application of magnetic tunnel junctions (MTJs) for information storage has so far been limited by the complicated interplay between tunnel magnetoresistance (TMR) ratio and the product of resistance and junction area (RA). An intricate connection exists between TMR ratio, RA value and the bandgap and crystal structure of the barrier, a connection that must be unravelled to optimise device performance and enable further applications to be developed. Here, we demonstrate a novel method to tailor the bandgap of an ultrathin, epitaxial Zn-doped MgO tunnel barrier with rocksalt structure. This structure is attractive due to its good Δ1 spin filtering effect, and we show that MTJs based on tunable MgZnO barriers allow effective balancing of TMR ratio and RA value. In this way spin-dependent transport properties can be controlled, a key challenge for the development of spintronic devices. PMID:25451163

  14. Comparison between Mg II k and Ca II H images recorded by SUNRISE/SuFI

    SciTech Connect

    Danilovic, S.; Hirzberger, J.; Riethmüller, T. L.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Berkefeld, T.; Schmidt, W.; Knölker, M.; Rodríguez, J. Blanco; Iniesta, J. C. Del Toro

    2014-03-20

    We present a comparison of high-resolution images of the solar surface taken in the Mg II k and Ca II H channels of the Filter Imager on the balloon-borne solar observatory SUNRISE. The Mg and Ca lines are sampled with 0.48 nm and 0.11 nm wide filters, respectively. The two channels show remarkable qualitative and quantitative similarities in the quiet Sun, in an active region plage and during a small flare. However, the Mg filtergrams display 1.4-1.7 times higher intensity contrast and appear more smeared and smoothed in the quiet Sun. In addition, the fibrils in a plage are wider. Although the exposure time is 100 times longer for Mg images, the evidence suggests that these differences cannot be explained only with instrumental effects or the evolution of the solar scene. The differences at least partially arise because of different line-formation heights, the stronger response of Mg k emission peaks to the higher temperatures, and the larger height range sampled by the broad Mg filter used here. This is evidently manifested during the flare when a surge in Mg evolves differently than in Ca.

  15. Automated cleaning of foraminifera shells before Mg/Ca analysis using a pipette robot

    NASA Astrophysics Data System (ADS)

    Johnstone, Heather J. H.; Steinke, Stephan; Kuhnert, Henning; Bickert, Torsten; Pälike, Heiko; Mohtadi, Mahyar

    2016-08-01

    The molar ratio of magnesium to calcium (Mg/Ca) in foraminiferal calcite is a widely used proxy for reconstructing past seawater temperatures. Thorough cleaning of tests is required before analysis to remove contaminant phases such as clay and organic matter. We have adapted a commercial pipette robot to automate an established cleaning procedure, the "Mg-cleaning" protocol of Barker et al. (2003). Efficiency of the automated nine-step method was assessed through monitoring Al/Ca of trial samples (GeoB4420-2 core catcher). Planktonic foraminifera Globigerinoides ruber, Globigerinoides sacculifer, and Neogloboquadrina dutertrei from this sample gave Mg/Ca consistent with the habitat range of the three species, and 40-60% sample recovery after cleaning. Comparison between manually cleaned and robot-cleaned samples of G. ruber (white) from a sediment core (GeoB16602) showed good correspondence between the two methods for Mg/Ca (r = 0.93, p < 0001, n = 27). Average Al/Ca in robot-cleaned samples was 0.05 mmol/mol, showing that the samples are cleaned effectively by the robot. The robot offers increased sample throughput as batch sizes of up to 88 samples/blanks can be processed in ˜7 h with little intervention.

  16. Mg/Ca and δ18O in the calcite of benthic foraminifera: does size matter?

    NASA Astrophysics Data System (ADS)

    de Nooijer, Lennart; Bijma, Jelle; -Jan Reichart, Gert; Hathorne, Ed

    2010-05-01

    Mg/Ca and del-18O are popular proxies for past sea water temperatures, ice volume and, together, salinity. The biological control that foraminifera have over calcification results in precipitation of calcium carbonate that has an isotope and element composition that is very different from those of inorganically precipitated calcium carbonates. Indications for an effect of ontogeny (i.e. size of a specimen) on the fractionation of oxygen isotopes are contradictory, while for the incorporation of most (trace) elements, data are lacking. The causes of size-based variability in element incorporation and isotope fractionation need to be understood and quantified in order to reliably use them as paleoproxies. In this study, we present Mg/Ca and oxygen isotope data from cultured specimens of the benthic foraminifer Ammonia tepida. When asexual reproduction takes place in this species, 50-300 genetically identical juveniles (i.e. clones) are produced. These juveniles are cultured at constant temperature, carbonate chemistry, salinity, etc to determine inter- and intra-specimen variability in Mg/Ca, Ba/Ca and Sr/Ca. From the same groups of clones, del-18O was determined from specimens with different sizes. Results show that the variability differs greatly between the analysed elements (e.g. relatively constant for Sr and Ba, variable for Mg) and isotopes, underscoring the need for a biological understanding of foraminiferal calcification pathways.

  17. Orientation Dependence of Cracking in Hot-Dip Zn-Al-Mg Alloy Coatings on a Sheet Steel

    NASA Astrophysics Data System (ADS)

    Park, Y. B.; Kim, I. G.; Kim, S. G.; Kim, W. T.; Kim, T. C.; Oh, M. S.; Kim, J. S.

    2017-03-01

    The present study was aimed at investigating a basic cause of cracking in hot-dip Zn-Al-Mg alloy coatings on an extra deep drawing quality sheet steel. The electron backscattering diffraction technique was employed to examine the crystallographic planes of the cracks generated before and after bending deformation of the coated steel sheets. It was clarified that the occurrence of cracking in the Zn-Al-Mg alloy coatings absolutely depends on the orientation of the primary Zn and eutectic Zn alloy phases. Finally, a cracking mechanism was proposed on the basis of the anisotropy of thermal expansion and the Young's modulus in the phases constituting the coatings.

  18. Orientation Dependence of Cracking in Hot-Dip Zn-Al-Mg Alloy Coatings on a Sheet Steel

    NASA Astrophysics Data System (ADS)

    Park, Y. B.; Kim, I. G.; Kim, S. G.; Kim, W. T.; Kim, T. C.; Oh, M. S.; Kim, J. S.

    2017-01-01

    The present study was aimed at investigating a basic cause of cracking in hot-dip Zn-Al-Mg alloy coatings on an extra deep drawing quality sheet steel. The electron backscattering diffraction technique was employed to examine the crystallographic planes of the cracks generated before and after bending deformation of the coated steel sheets. It was clarified that the occurrence of cracking in the Zn-Al-Mg alloy coatings absolutely depends on the orientation of the primary Zn and eutectic Zn alloy phases. Finally, a cracking mechanism was proposed on the basis of the anisotropy of thermal expansion and the Young's modulus in the phases constituting the coatings.

  19. Mechanical properties and phase composition of potential biodegradable Mg-Zn-Mn-base alloys with addition of rare earth elements

    SciTech Connect

    Stulikova, Ivana; Smola, Bohumil

    2010-10-15

    Mechanical properties and creep resistance of the MgY4Zn1Mn1 alloy in the as cast as well as in the T5 condition were compared to those of the MgCe4Zn1Mn1 alloy in the same conditions. Yield tensile stress and ultimate tensile strength of the MgY4Zn1Mn1 alloy are slightly better in the temperature range 20 deg. C-400 deg. C than these of the MgCe4Zn1Mn1 alloy. Better thermal stability of ultimate tensile strength was observed in the T5 treated MgCe4Zn1Mn1 alloy than in this material in the as cast condition. An outstanding creep resistance at 225 deg. C-350 deg. C found in the MgY4Zn1Mn1 alloy is due to the existence of the 18R long period stacking structure persisting in this alloy even a long heat treatment of 500 deg. C/32 h. No similar stacking effects happen when Ce substitutes Y in approximately the same concentration. The creep resistance deteriorates considerably in the MgCe4Zn1Mn1 alloy. Rectangular particles of the equilibrium Mg{sub 12}Ce phase dominate in the microstructure of as cast as well as of high temperature heat-treated MgCe4Zn1Mn1 alloy. A population of small oval particles containing Mg and Zn develops additionally during annealing of this alloy. These particles pin effectively dislocations and can be responsible for the better thermal stability of the T5 treated material.

  20. Mg and Ca isotope signatures of authigenic dolomite in siliceous deep-sea sediments

    NASA Astrophysics Data System (ADS)

    Blättler, Clara L.; Miller, Nathaniel R.; Higgins, John A.

    2015-06-01

    Authigenic carbonates in marine sediments frequently have carbon isotope ratios that reflect local organic carbon processing rather than the δ13C of the global DIC (dissolved inorganic carbon) reservoir, but their contributions to ancient sedimentary sections are difficult to assess. In this study of authigenic dolomite from the Miocene-age Monterey Formation of offshore California, Mg and Ca isotopes are shown to vary with stratigraphic depth as a result of early diagenetic processes. The dolomite is a pre-compaction authigenic phase that occurs as beds and nodules with δ13C ranging from -16 to + 9 ‰. Light δ13C values were likely acquired from the sedimentary zone of microbial sulfate reduction, while heavy δ13C values were acquired from the zone of methanogenesis. Mg and Ca isotopes are roughly anti-correlated, with intervals of negative δ13C associated with low δ26Mg and higher δ 44/40Ca values. The variability is observed over a wide range of length-scales, from 10-2 meters within individual authigenic beds/nodules, to 102 meters over the entire stratigraphic column, and can be understood as the consequence of dolomite precipitation in pore fluids where Mg supply is limited by diffusive transport. The relationship of δ26Mg and δ 44/40Ca to the more common stable isotope measurements of δ13C and δ18O represents a new, diagenetically robust, geochemical fingerprint for identifying synsedimentary authigenic carbonates in the geological record.

  1. Microstructure evolution and tensile mechanical properties of thixoformed high performance Al-Zn-Mg-Cu alloy

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Chen, Qiang; Wang, Bo; Du, Zhi-ming

    2015-09-01

    Al-Zn-Mg-Cu alloys are the strongest aluminum alloys which have been widely used for aerospace applications. They are usually machined from the wrought state usually with a high waste percentage. To reduce waste, it is important to thixoform these alloys in near net shape. In this work, the thixoformability of a commercial high performance Al-Zn-Mg-Cu alloy 7075 was studied. A novel multistep reheating regime was developed in recrystallization and partial melting (RAP) route to obtain spheroidal semi-solid microstructures. The as-extruded 7075 alloy was fully recrystallized for a short holding time using the multistep reheating regime. Semi-solid microstructures with fine and spherical solid grains with a grain size of 40-50 μm embedded in liquid matrix were obtained. The advantage of the multistep reheating regimes over those conventional routes was also discussed. Some wheel-shaped components were thixoformed from the as-received 7075 alloy. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed component based on multistep reheating regime, are 510 MPa, 446 MPa and 17.5% respectively. These values are superior to those of the products manufactured with the conventional RAP route. As the results indicated, thixoforming could be conducted based on commercial extruded Al-Zn-Mg-Cu alloys, which has important practical significance.

  2. Optical properties of NbCl5 and ZnMg intercalated graphite compounds

    NASA Astrophysics Data System (ADS)

    Jung, Eilho; Lee, Seokbae; Roh, Seulki; Meng, Xiuqing; Tongay, Sefaattin; Kang, Jihoon; Park, Tuson; Hwang, Jungseek

    2014-12-01

    We studied NbCl5 and ZnMg alloy intercalated graphite compounds using an optical spectroscopy technique. These intercalated metallic graphite samples were quite challenging to obtain optical reflectance spectra since they were not flat and quite thin. By using both a new method and an in situ gold evaporation technique we were able to obtain reliable reflectance spectra of our samples in the far and mid infrared range (80-7000 cm-1). We extracted the optical constants including the optical conductivity and the dielectric function from the measured reflectance spectra using a Kramers-Kronig analysis. We also extracted the dc conductivity and the plasma frequencies from the optical conductivity and dielectric functions. NbCl5 intercalated graphite samples show similar optical conductivity spectra as bare highly oriented pyrolytic graphite even though there are some differences in detail. ZnMg intercalated samples show significantly different optical conductivity spectra from the bare graphite. Optical spectroscopy is one of the most reliable experimental techniques to obtain the electronic band structures of materials. The obtained optical conductivities support the recent theoretically calculated electronic band structures of NbCl5 and ZnMg intercalated graphite compounds. Our results also provide important information of electronic structures and charge carrier properties of these two new intercalated materials for applications.

  3. Factors Affecting the Hydrogen Environment Assisted Cracking Resistance of an AL-Zn-Mg-(Cu) Alloy

    SciTech Connect

    Young, G A; Scully, J R

    2002-04-09

    Precipitation hardenable Al-Zn-Mg alloys are susceptible to hydrogen environment assisted cracking (HEAC) when exposed to aqueous environments. In Al-Zn-Mg-Cu alloys, overaged tempers are used to increase HEAC resistance at the expense of strength but overaging has little benefit in low copper alloys. However, the mechanism or mechanisms by which overaging imparts HEAC resistance is poorly understood. The present research investigated hydrogen uptake, diffusion, and crack growth rate in 90% relative humidity (RH) air for both a commercial copper bearing Al-Zn-Mg-Cu alloy (AA 7050) and a low copper variant of this alloy in order to better understand the factors which affect HEAC resistance. Experimental methods used to evaluate hydrogen concentrations local to a surface and near a crack tip include nuclear reaction analysis (NRA), focused ion beam, secondary ion mass spectroscopy (FIB/SIMS) and thermal desorption spectroscopy (TDS). Results show that overaging the copper bearing alloys both inhibits hydrogen ingress from oxide covered surfaces and decreases the apparent hydrogen diffusion rates in the metal.

  4. Synthesis and magnetic induction heating properties of Gd-substituted Mg-Zn ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Hirosawa, Fumie; Iwasaki, Tomohiro; Watano, Satoru

    2017-06-01

    Gadolinium-substituted magnesium-zinc ferrite (Mg x Zn1- x Gd y Fe2- y O4) nanoparticles with different metal compositions for x between 0 and 1 and y between 0 and 0.06 were synthesized via coprecipitation of metal hydroxides, followed by calcination. Their crystal structure was characterized via X-ray diffraction analysis, confirming that the Gd-substituted Mg-Zn ferrite samples had a single-phase spinel structure. The metal composition significantly affected the crystal structure, including the lattice parameters and crystallite size. Scanning electron microscopy (SEM) showed that the ferrite samples had a diameter of approximately 50-200 nm. Furthermore, the temperature rise in an alternating magnetic field was measured, and the magnetic induction heating properties were evaluated using the specific absorption rate (SAR) determined from the temperature profile. The SAR significantly varied depending on the compositions of x and y. When x = 0.5 and y = 0.02, the SAR was found to be at maximum. This reveals that the compositions can control the magnetic induction heating properties. The results suggest that Gd-substituted Mg-Zn ferrite nanoparticles are promising candidates for magnetic hyperthermia applications.

  5. Simultaneously enhanced mechanical and damping properties of Mg-Zn-Y alloys reinforced with LPSO phase

    NASA Astrophysics Data System (ADS)

    Wang, Jingfeng; Wang, Haibo; Li, Shun; Wang, Shaohua

    2017-07-01

    The microstructure, mechanical properties and damping capacities of Mg-Zn-Y alloys were investigated and compared systematically. The results showed that strength and damping of the alloy were increasing markedly with the increase of the volume fraction of long period stacking ordered (LPSO) phase (8%, 16%, 32%, 64%, respectively) on the whole. The corporate effect of LPSO phase and solid solution atoms was beneficial to the strengths. The Mg-1.36Zn-2.28Y can be classified as high damping metals (Q-1≧0.01) at strain amplitudes surpassing 1×10-3. With increasing of the LPSO phase, the critical strain amplitudes of alloys gradually decreased so that alloys can break away from pinning points more easily, thus, achieving a more superior damping performance. In addition, the strain amplitude-independent damping and strain amplitude-dependent damping of the Mg-Zn-Y alloys both increased. The damping capacities of the alloys cannot be explained by the Granato-Lücke theory exclusively.

  6. Ultrafast intramolecular relaxation dynamics of Mg- and Zn-bacteriochlorophyll a

    NASA Astrophysics Data System (ADS)

    Kosumi, Daisuke; Nakagawa, Katsunori; Sakai, Shunsuke; Nagaoka, Yuya; Maruta, Satoshi; Sugisaki, Mitsuru; Dewa, Takehisa; Nango, Mamoru; Hashimoto, Hideki

    2013-07-01

    Ultrafast excited-state dynamics of the photosynthetic pigment (Mg-)bacteriochlorophyll a and its Zn-substituted form were investigated by steady-state absorption/fluorescence and femtosecond pump-probe spectroscopic measurements. The obtained steady-state absorption and fluorescence spectra of bacteriochlorophyll a in solution showed that the central metal compound significantly affects the energy of the Qx state, but has almost no effect on the Qy state. Photo-induced absorption spectra were recorded upon excitation of Mg- and Zn-bacteriochlorophyll a into either their Qx or Qy state. By comparing the kinetic traces of transient absorption, ground-state beaching, and stimulated emission after excitation to the Qx or Qy state, we showed that the Qx state was substantially incorporated in the ultrafast excited-state dynamics of bacteriochlorophyll a. Based on these observations, the lifetime of the Qx state was determined to be 50 and 70 fs for Mg- and Zn-bacteriochlorophyll a, respectively, indicating that the lifetime was influenced by the central metal atom due to the change of the energy gap between the Qx and Qy states.

  7. Adsorption of methyl orange from aqueous solutions by calcined ZnMgAl hydrotalcite

    NASA Astrophysics Data System (ADS)

    Yuan, Dong; Zhou, Liangqin; Fu, Dayou

    2017-02-01

    The calcined ZnMgAl hydrotalcite was used for degration of methyl orange (MO). The adsorbent was characterized by XRD, SEM, and FT-IR. The results reveal that the ZnMgAl layered structures were disappeared after calcining for 5 h at 500 °C, then were recovered to layer hydrotalcite structure after adsorbing MO anions. The several important affecting factors of adsorption behavior, including the initial pH value of solution, adsorbent dosage, and the initial concentration of solution, were also discussed. The adsorption kinetic processes were fitted with the equations of pseudo-first-order, pseudo-second-order, and intraparticle diffusion, respectively, in which the pseudo-second-order equation fitting results was the better. The equilibrium isotherm of MO was described by both Langmuir and Freundlich model, but better complys with the Langmuir model ( R 2 > 0.98). The possible adsorption mechanism has been presumed. The adsorption experiments indicated that the ZnMgAl hydrotalcite had good adsorption ability to methyl orange in wastewater.

  8. Ultrafast intramolecular relaxation dynamics of Mg- and Zn-bacteriochlorophyll a

    SciTech Connect

    Kosumi, Daisuke; Nagaoka, Yuya; Maruta, Satoshi; Sugisaki, Mitsuru; Dewa, Takehisa; Hashimoto, Hideki

    2013-07-21

    Ultrafast excited-state dynamics of the photosynthetic pigment (Mg-)bacteriochlorophyll a and its Zn-substituted form were investigated by steady-state absorption/fluorescence and femtosecond pump-probe spectroscopic measurements. The obtained steady-state absorption and fluorescence spectra of bacteriochlorophyll a in solution showed that the central metal compound significantly affects the energy of the Q{sub x} state, but has almost no effect on the Q{sub y} state. Photo-induced absorption spectra were recorded upon excitation of Mg- and Zn-bacteriochlorophyll a into either their Q{sub x} or Q{sub y} state. By comparing the kinetic traces of transient absorption, ground-state beaching, and stimulated emission after excitation to the Q{sub x} or Q{sub y} state, we showed that the Q{sub x} state was substantially incorporated in the ultrafast excited-state dynamics of bacteriochlorophyll a. Based on these observations, the lifetime of the Q{sub x} state was determined to be 50 and 70 fs for Mg- and Zn-bacteriochlorophyll a, respectively, indicating that the lifetime was influenced by the central metal atom due to the change of the energy gap between the Q{sub x} and Q{sub y} states.

  9. Band gap engineering of ZnO by doping with Mg

    NASA Astrophysics Data System (ADS)

    Rana, N.; Chand, Subhash; Gathania, Arvind K.

    2015-08-01

    Mg-doped zinc oxide (MgxZn1-xO (0 ≤ x ≤ 0.20)) samples were synthesized by polymeric precursor method. The structural and optical properties were investigated by x-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM), UV-visible spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopy. XRD patterns reveal that synthesized samples have a wurtzite structure. Lattice parameters, the degree of distortion of the samples were calculated from the XRD. SEM images show that the synthesized samples contain the elongated spherical shaped grains. The Raman scattering investigation and FTIR spectra authenticate the presence of Mg in the system and also show phase segregation at the higher Mg doping concentration. Optical band gap energy is determined from the Tauc relation. It is interesting to know that optical band energy exhibits blue shift with the increase of Mg doping concentration up to 16 mole %.

  10. Manipulation of Mg(2+)-Ca(2+) Switch on the Development of Bone Mimetic Hydroxyapatite.

    PubMed

    Andrés, Nancy C; D'Elía, Noelia L; Ruso, Juan M; Campelo, Adrián E; Massheimer, Virginia L; Messina, Paula V

    2017-05-10

    Ionic substitution can affect essential physicochemical properties leading to a specific biological behavior upon implantation. Therefore, it has been proposed as a tool to increase the biological efficiency of calcium phosphate based materials. In the following study, we have evaluated the contribution of an important cation in nature, Mg(2+), into the structure of previously studied biocompatible and biodegradable hydroxyapatite (HA) nanorods and its subsequent effect on its chemical, morphology, and bone mimetic articulation. Mg(2+)-substituted HA samples were synthesized by an aqueous wet-chemical precipitation method, followed by an hydrothermal treatment involving a Mg(2+) precursor that partially replace Ca(2+) ions into HA crystal lattice; Mg(2+) concentrations were modulated to obtain a nominal composition similar to that exists in calcified tissues. Hydrothermally synthesized Mg(2+)-substituted HA nanoparticles were characterized by X-ray powder diffraction, FT-NIR and EDX spectroscopies, field emission scanning and high resolution transmission electron microscopies (FE-SEM, H-TEM). Molecular modeling combining ab initio methods and power diffraction data were also performed. Results showed that Mg(2+)-substitution promoted the formation of calcium deficient HA (cdHA) where Mg(2+) replacement is energetically favored at Ca(1) position in a limited and specific amount directing the additional Mg(2+) toward the surface of the crystal. The control of Mg(2+) incorporation into HA nanorods gave rise to a tailored crystallinity degree, cell parameters, morphology, surface hydration, solubility, and degradation properties in a dose-replacement dependent manner. The obtained materials show qualities that conjugated together to drive an optimal in vitro cellular viability, spreading, and proliferation confirming their biocompatibility. In addition, an improved adhesion of osteoblast was evidenced after Mg(2+)-Ca(2+) substitution.

  11. Structural relaxation and colour in the spinel-magnesiochromite (MgAl2O4-MgCr2O4) and gahnite-zincochromite (ZnAl2O4-ZnCr2O4) solid solution series

    NASA Astrophysics Data System (ADS)

    Hålenius, U.; Andreozzi, G. B.; Skogby, H.

    2009-04-01

    Recent studies on binary mineral solid solution series utilising synchrotron based x-ray absorption spectroscopies have indicated strong structural relaxation. For instance, it has been suggested that the real Cr-O bond distances remain nearly constant (relaxation parameter (ɛ) of 0.85, where ɛ=1 equals full relaxation) over the entire compositional range of the MgAl2O4-MgCr2O4 series (Juhin et al. 2007). In the present study we have measured room temperature optical absorption spectra of synthetic single crystals of the ZnAl2-2xCr2xO4 (0.03?x?1) and MgAl2-2xCr2xO4(0.02?x?1) series with the aim to explore the real architecture of the structure and in particular the Cr-O distance as function of composition. Our crystals were synthesized by means of flux-growth methods under atmospheric pressure and temperature profiles resulting in an estimated cation ordering temperature of ca 850 °C. Crystals close to the spinel (sensu stricto) and gahnite end-member compositions were faintly red in colour. With increasing Cr-content the crystals become more intensely red-coloured and at the higher Cr-contents there is a distinct shift towards a dark greenish colouration. These colour changes are reflected in the measured optical spectra by the position and intensity of the two spin-allowed electronic d-d transitions in octahedrally coordinated Cr3+ at ca 18000 (4A2g -4T2g (4F) transition) and 25000 cm-1(4A2g -4T1g (4F) transition). The energy of the first transition (?1-band) is ca 1200 cm-1 lower in magnesiochromite than in weakly Cr-doped spinel (x=0.02) and ca 1400 cm-1 lower in zincochromite than in gahnite with the lowest Cr-content (x=0.03). Concomitantly the energy of the second transition (?2-band) decreases with increasing Cr-content in both series by ca. 1800 cm-1. From the position of the ?1-band, a decrease in crystal field splitting, 10Dq, for six-coordinated Cr3+ with increasing Cr-content in the MgAl2-2xCr2xO4 and ZnAl2-2xCr2xO4 series of 6.5 and 7

  12. Removal of K+, Na+, Ca2+, and Mg2+ from saline-alkaline water using the microalga Scenedesmus obliquus

    NASA Astrophysics Data System (ADS)

    Yao, Zongli; Ying, Chengqi; Lu, Jianxue; Lai, Qifang; Zhou, Kai; Wang, Hui; Chen, Ling

    2013-11-01

    The capability of Scenedesmus obliquus to remove cations (K+, Na+, Ca2+, Mg2+) from saline-alkaline water was investigated at different salinities (0, 5, 10, 15, 20, 25) and carbonate alkalinities (0, 5, 10, 15, 20, 25, 30, 35 mmol/L). K+, Na+, Ca2+, and Mg2+ in saline-alkaline water were efficiently removed by S. obliquus. The maximum removal of the cations (29.37 mg for K+, 185.85 mg for Na+, 23.07 mg for Ca2+, 66.14 mg for Mg2+) occurred at salinity 25. The maximum removal of K+ (2.28 mg), Na+ (6.62 mg), Ca2+ (1.01 mg), and Mg2+ (0.62 mg) occurred at carbonate alkalinities of 25 mmol/L for K+, 35 mmol/L for Na+, 20 mmol/L for Ca2+, and 25 mmol/L for Mg2+, respectively. Under a salinity stress, the concentration of Na+ in S. obliquus increased significantly, while that of K+ decreased significantly. The concentrations of Ca2+ and Mg2+ decreased as well. The ratios of K+/Na+, Ca2+/Na+, and Mg2+/Na+ were significantly lower in all salinity treatments than those of the control. Under alkaline stress, the concentrations of Na+ and K+ in S. obliquus decreased significantly and the ratios of K+/Na+, Ca2+/Na+, and Mg2+/Na+ were significantly higher in all treatments than in the control. Moreover, the concentrations of Ca2+ and Mg2+ in S. obliquus at alkalinities of 5-10 mmol/L were significantly higher than those of the other treatments. The removal of Na+ by S. obliquus mainly occurs through biosorption, and Mg2+ and Ca2+ were removed through both biosorption and bioaccumulation.

  13. Three-dimensional analysis of the microstructure and bio-corrosion of Mg–Zn and Mg–Zn–Ca alloys

    SciTech Connect

    Lu, Y.; Chiu, Y.L.; Jones, I.P.

    2016-02-15

    The effects of the morphology and the distribution of secondary phases on the bio-corrosion properties of magnesium (Mg) alloys are significant. Focused Ion Beam (FIB) tomography and Micro X-Ray computed tomography (Micro-CT) have been used to characterise the morphology and distribution of (α-Mg + MgZn) and (α-Mg + Ca{sub 2} + Mg{sub 6} + Zn{sub 3}) eutectic phase mixtures in as-cast Mg–3Zn and Mg–3Zn–0.3Ca alloys, respectively. There were two different 3D distributions: (i) an interconnected network and (ii) individual spheres. The tomography informed our understanding of the relationship between the distribution of secondary phases and the development of localized corrosion in magnesium alloys. - Highlights: • Multi-scale tomography was used to characterise the morphology and distribution of secondary phases in Mg alloys. • The development of localized corrosion was investigated using tomography. • An improved understanding of the microstructure and corrosion was achieved using Micro-CT tomography.

  14. SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6} - two new Ae-Zn-Sn polar intermetallic compounds (Ae: alkaline earth metal)

    SciTech Connect

    Stegmaier, Saskia; Faessler, Thomas F.

    2012-08-15

    SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}, two closely related new polar intermetallic compounds, were obtained by high temperature reactions of the elements. Their crystal structures were determined with single crystal XRD methods, and their electronic structures were analyzed by means of DFT calculations. The Zn-Sn structure part of SrZn{sub 2}Sn{sub 2} comprises (anti-)PbO-like {l_brace}ZnSn{sub 4/4}{r_brace} and {l_brace}SnZn{sub 4/4}{r_brace} layers. Ca{sub 2}Zn{sub 3}Sn{sub 6} shows similar {l_brace}ZnSn{sub 4/4}{r_brace} layers and {l_brace}Sn{sub 4}Zn{r_brace} slabs constructed of a covalently bonded Sn scaffold capped by Zn atoms. For both phases, the two types of layers are alternatingly stacked and interconnected via Zn-Sn bonds. SrZn{sub 2}Sn{sub 2} adopts the SrPd{sub 2}Bi{sub 2} structure type, and Ca{sub 2}Zn{sub 3}Sn{sub 6} is isotypic to the R{sub 2}Zn{sub 3}Ge{sub 6} compounds (R=La, Ce, Pr, Nd). Band structure calculations indicate that both SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6} are metallic. Analyses of the chemical bonding with the electron localization function (ELF) show lone pair like basins at Sn atoms and Zn-Sn bonding interactions between the layers for both title phases, and covalent Sn-Sn bonding within the {l_brace}Sn{sub 4}Zn{r_brace} layers of Ca{sub 2}Zn{sub 3}Sn{sub 6}. - Graphical abstract: Crystal structures of the new Ae-Zn-Sn polar intermetallic phases SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}. Highlights: Black-Right-Pointing-Pointer New polar intermetallic phases SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}. Black-Right-Pointing-Pointer Obtained by high temperature reactions of the elements. Black-Right-Pointing-Pointer Single crystal XRD structure determination and DFT electronic structure calculations. Black-Right-Pointing-Pointer Closely related crystal and electronic structures. Black-Right-Pointing-Pointer Metallic conductivity coexisting with lone pairs and covalent bonding

  15. Diluted ferromagnetic semiconductor (LaCa)(ZnMn)SbO isostructural to ``1111'' type iron pnictide superconductors

    NASA Astrophysics Data System (ADS)

    Han, Wei; Zhao, Kan; Wang, XianCheng; Liu, QingQing; Ning, FanLong; Deng, Zheng; Liu, Ying; Zhu, JinLong; Ding, Cui; Man, HuiYuan; Jin, ChangQing

    2013-11-01

    We report discovery of ferromagnetism in (LaCa)(ZnMn)SbO isostructural to the well-studied iron-based superconductor LaFeAs(O1- x F x ). Spin is induced by partial substitution of Mn2+ for Zn2+, while charge is induced by substitution of Ca2+ for La3+ within the parent compound LaZnSbO. Ferromagnetism with Curie temperature ( T C) is observed up to 40 K at the spin doping 0.15 by introducing Mn2+ into the Zn2+ sites for (La0.95Ca0.05)(Zn1- x Mn x )SbO. The Hall coefficient measurement indicates p-type carrier for (La0.95Ca0.05)(Zn0.9Mn0.1)SbO with concentration of n˜1020 cm-3 showing anomalous Hall effect below T C.

  16. Effect of Zn and Mn Additions on the Wear Resistance of Cast Alloy Mg - 5% Al - 1% Si

    NASA Astrophysics Data System (ADS)

    Cug, Harun; Ahlatci, Hayrettin

    2017-07-01

    The effect of additions of Zn and Mn (from 0.5 to 4%) on the microstructure of alloy Mg - 5% Al - 1% Si is studied by the methods of x-ray diffractometry and light and scanning electron microscopy. The strength parameters are determined in tensile and wear tests. It is shown that particles of Mg2Si precipitate in the matrix and particles of Mg17Al12 precipitate on grain boundaries upon the introduction of low contents of Zn and Mn. Phases MgZn and Al6Mn precipitate at a high content of the additions. An optimum concentration of Zn and Mn is chosen for raising the wear resistance of alloy Mg - 5% Al - 1% Si.

  17. Magnetic field induced third order susceptibility of third order harmonic generation in a ZnMgSe strained quantum well

    SciTech Connect

    Mark, J. Abraham Hudson Peter, A. John

    2014-04-24

    Third order susceptibility of third order harmonic generation is investigated in a Zn{sub 0.1}Mg{sub 0.9}Se/Zn{sub 0.8}Mg{sub 0.2}Se/Zn{sub 0.1}Mg{sub 0.9}Se quantum well in the presence of magnetic field strength. The confinement potential is considered as the addition of energy offsets of the conduction band (or valence band) and the strain-induced potential in our calculations. The material dependent effective mass is followed throughout the computation because it has a high influence on the electron energy levels in low dimensional semiconductor systems.

  18. Magnetic field induced third order susceptibility of third order harmonic generation in a ZnMgSe strained quantum well

    NASA Astrophysics Data System (ADS)

    Mark, J. Abraham Hudson; Peter, A. John

    2014-04-01

    Third order susceptibility of third order harmonic generation is investigated in a Zn0.1Mg0.9Se/Zn0.8Mg0.2Se/Zn0.1Mg0.9Se quantum well in the presence of magnetic field strength. The confinement potential is considered as the addition of energy offsets of the conduction band (or valence band) and the strain-induced potential in our calculations. The material dependent effective mass is followed throughout the computation because it has a high influence on the electron energy levels in low dimensional semiconductor systems.

  19. Platelet and erythrocyte Mg2+, Ca2+, Na+, K+ and cell membrane adenosine triphosphatase activity in essential hypertension in blacks.

    PubMed

    Touyz, R M; Milne, F J; Reinach, S G

    1992-06-01

    To assess the relationship between intracellular Mg2+, Ca2+, Na+ and K+ and cell membrane adenosine triphosphatase (ATPase) activity in normotensive and hypertensive blacks. Intracellular cations and cell membrane ATPase activity were studied in black patients with untreated essential hypertension and age-, weight- and height-matched normotensive controls. Platelet, erythrocyte and serum Mg2+, Ca2+, Na+ and K+ levels as well as platelet and erythrocyte membrane Na+,K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase activities were measured in all subjects. Intracellular Na+ and K+ were measured by flame photometry and Mg+ and Ca+ by atomic absorption spectrophotometry. Cell membrane ATPase activity was determined by a colorimetric method. The hypertensive group consistently demonstrated depressed activity of each ATPase studied, with significantly lower serum Mg2+, serum K+, erythrocyte Mg2+ and platelet Mg2+ levels compared with the normotensive group. Platelet Na+ and Ca2+ and erythrocyte Ca2+ were significantly elevated in the hypertensive group. In the hypertensive group, mean arterial pressure (MAP) was inversely correlated with platelet and erythrocyte membrane Na+,K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase. Serum Mg2+, serum Ca2+ and platelet Mg2+ were negatively correlated with MAP in the hypertensive group whilst erythrocyte and platelet Ca2+ were positively correlated. In the normotensive group, platelet Mg2+ and MAP were negatively, and erythrocyte Ca2+ and MAP, positively correlated. Black patients with essential hypertension have widespread depression of cell membrane Na+,K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase activities with serum and intracellular Mg2+ depletion and cytosolic Na+ and Ca2+ overload, which may reflect an underlying membrane abnormality in essential hypertension. These cellular abnormalities may be related to the defective transport mechanisms that in turn may be aggravated by Mg2+ depletion.

  20. Photoluminescence performance enhancement of ZnO/MgO heterostructured nanowires and their applications in ultraviolet laser diodes.

    PubMed

    Shi, Zhi-Feng; Zhang, Yuan-Tao; Cui, Xi-Jun; Zhuang, Shi-Wei; Wu, Bin; Chu, Xian-Wei; Dong, Xin; Zhang, Bao-Lin; Du, Guo-Tong

    2015-06-07

    Vertically aligned ZnO/MgO coaxial nanowire (NW) arrays were prepared on sapphire substrates by metal-organic chemical vapor deposition combined with a sputtering system. We present a comparative investigation of the morphological and optical properties of the produced heterostructures with different MgO layer thicknesses. Photoluminescence measurements showed that the optical performances of ZnO/MgO coaxial NWs were strongly dependent on the MgO layer thickness. The intensity of deep-level emission (DLE) decreased monotonously with the increase of MgO thickness, while the enhancement of ultraviolet (UV) emission showed a critical thickness of 15 nm, achieving a maximum intensity ratio (∼226) of IUV/IDLE at the same time. The significantly improved exciton emission efficiency of the coaxial NW structures allows us to study the surface passivation effect, photogenerated carrier confinement and transfer in terms of energy band theory. More importantly, we achieved an ultralow threshold (4.5 mA, 0.58 A cm(-2)) electrically driven UV lasing action based on the ZnO/MgO NW structures by constructing an Au/MgO/ZnO metal/insulator/semiconductor diode, and the continuous-current-driven diode shows a good temperature tolerance. The results obtained on the unique optical properties of ZnO/MgO coaxial NWs shed light on the design and development of ZnO-based UV laser diodes assembled with nanoscale building blocks.

  1. Mg/Ca temperature calibration for the benthic foraminifer Cibicidoides pachyderma

    NASA Astrophysics Data System (ADS)

    Marchitto, T. M.; Bryan, S. P.; Curry, W. B.; McCorkle, D. C.

    2007-03-01

    The recent development of foraminiferal Mg/Ca as a paleotemperature proxy has enabled the extraction of global ice volume and local salinity from the more traditional paleotemperature proxy δ18O. The benthic foraminiferal genus Cibicidoides is widely used in paleoceanographic reconstructions because of its epifaunal habitat and cosmopolitan distribution, and it has received early attention in Mg/Ca work. However, existing temperature calibrations for Cibicidoides rely heavily on C. pachyderma core top data from one location, Little Bahamas Bank, where authigenic processes and/or reworking may result in elevated warm water Mg/Ca values. Here we present new C. pachyderma Mg/Ca data from a series of 29 high-quality multicore tops collected in the Florida Straits, spanning a temperature range of 5.8-18.6°C. In contrast to previous calibrations, we find no evidence for a strongly exponential response to temperature. The data are best explained by a linear relationship, with a sensitivity of 0.12 mmol mol-1 per °C.

  2. Dry etching of MgCaO gate dielectric and passivation layers on GaN

    NASA Astrophysics Data System (ADS)

    Hlad, M.; Voss, L.; Gila, B. P.; Abernathy, C. R.; Pearton, S. J.; Ren, F.

    2006-09-01

    MgCaO films grown by rf plasma-assisted molecular beam epitaxy and capped with Sc 2O 3 are promising candidates as surface passivation layers and gate dielectrics on GaN-based high electron mobility transistors (HEMTs) and metal-oxide semiconductor HEMTs (MOS-HEMTs), respectively. Two different plasma chemistries were examined for etching these thin films on GaN. Inductively coupled plasmas of CH 4/H 2/Ar produced etch rates only in the range 20-70 Å/min, comparable to the Ar sputter rates under the same conditions. Similarly slow MgCaO etch rates (˜100 Å/min) were obtained with Cl 2/Ar discharges under the same conditions, but GaN showed rates almost an order of magnitude higher. The MgCaO removal rates are limited by the low volatilities of the respective etch products. The CH 4/H 2/Ar plasma chemistry produced a selectivity of around 2 for etching the MgCaO with respect to GaN.

  3. Characterization and luminescence properties of CaMgSi2O6:Eu2+ blue phosphor.

    PubMed

    Chandrakar, P; Baghel, R N; Bisen, D P; Chandra, B P

    2015-11-01

    A blue CaMgSi2O6:Eu(2+) phosphor was prepared by the solid-state reaction method and the phosphor characterized in terms of crystal structure, particle size, photoluminescence (PL), thermoluminescence (TL) and mechanoluminescence (ML) properties using X-ray diffraction (XRD), transmission electron microscopy (TEM), PL spectroscopy, TLD reader and ML impact technique. The XRD result shows that phosphor is formed in a single phase and has a monoclinic structure with the space group C2/c. Furthermore, the PL excitation spectra of Eu(2+) -doped CaMgSi2 O6 phosphor showed a strong band peak at 356 nm and the PL emission spectrum has a peak at 450 nm. The depths and frequency factors of trap centers were calculated using the TL glow curve by deconvolution method in which the trap depths were found to be 0.48 and 0.61 eV. The formation of CaMgSi2O6:Eu(2+) phosphor was confirmed by Fourier transform infrared spectroscopy. The ML intensity increased linearly with the impact velocity of the piston used to deform the phosphor. It was shown that the local piezoelectricity-induced electron bombardment model is responsible for the ML emission. Finally, the optical properties of CaMgSi2O6:Eu(2+) phosphors are discussed. Copyright © 2015 John Wiley & Sons, Ltd.

  4. A DFT study of hydrogen adsorption on Be, Mg and Ca frameworks in erionite zeolite

    NASA Astrophysics Data System (ADS)

    Fellah, Mehmet Ferdi

    2017-02-01

    The molecular hydrogen adsorption was investigated on additional frameworks with earth alkaline metal atoms (Be, Mg and Ca) in 24T ERI zeolite cluster model by means of Density Functional Theory study. HOMO and LUMO energy values, chemical potential, chemical hardness, electronegativity, adsorption energy and adsorption enthalpy values have been calculated in this study. Mg-ERI and Ca-ERI clusters have much lower chemical potentials with much lower adsorption energy values when compared to the value of Be-ERI cluster. Additionally, they are softer than Be-ERI cluster with respect to their lower chemical hardness values. Hydrogen adsorption enthalpy values were computed as -3.6 and -3.9 kJ/mol on Mg-ERI and Ca-ERI clusters, respectively. These adsorption enthalpy values are significantly larger than the enthalpy value of liquefaction for hydrogen molecule. This consequently specifies that Mg-ERI and Ca-ERI zeolite structures which have higher chemical reactivity appear to be a promising candidate cryoadsorbent for hydrogen storage.

  5. High-Temperature Vaporization of Mg-Ca-Carbonate-Sulfate-Quartz-Alumina Targets

    NASA Astrophysics Data System (ADS)

    Dikov, Yu. P.; Gerasimov, M. V.; Yakovlev, O. I.; Wlotzka, F.

    1996-03-01

    In a series of experiments we studied the chemistry of high-temperature vaporization in the Ca-carbonate-sulfate-quartz system in relation to the Chicxulub impact. Since Mg-carbonates are a major constituent of the rocks in the Chicxulub crater area, it is important to study the evaporative chemistry of MgCO3 together with the cited system. We performed high-temperature vaporization of MgCO3 + CaCO3 + CaSO4/CaSO4 x 2H2O + SiO2 (in one experiment we used anhydrite and in another gypsum) targets using standard laser-pulse heating technique to simulate impact vaporization. In the third experimental run we added Al2O3 to simulate the alumo-silicate component of Chicxulub target rocks and to investigate the behavior of Al during vaporization. The results show a complex chemistry which occurs in the vapor cloud, resulting in (1) noticeable trapping of S, C, and of H2O by condensing products; (2) formation of Mg and Al sheet silicates in experiments with water-containing targets; and (3) strong reduction processes in experiments with water-containing targets.

  6. Novel structure, morphology, and optical property of Mg-doped ZnO nanostructures fabricated by PCVD method

    NASA Astrophysics Data System (ADS)

    Wang, Y. L.; Wei, X. Q.; Guo, N.; Xu, X. J.

    2017-02-01

    Mg -doped ZnO nanostructures with different growth temperature and Mg contents have been successfully fabricated on Si (111) substrates via physical chemical vapor deposition (PCVD) method. The influences of the growth temperature and Mg contents on the nanostructure, morphologies, and crystallinities were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The SEM results show that it is beneficial to grow regular ZnMgO nanorods with the growth temperature of 750 °C and Zn/Mg molar ratio of 50:1, respectively. XRD results indicate that the nanorods possess the preferential orientation along the c-axis with the best crystals. The nanorod arrays, dendritic, and like-caltrop nanostructure were achieved at various growth temperature and Mg contents, respectively. The photoluminescence (PL) spectra show that the UV emissions present the obvious blueshift owing to the increasing growth temperature and Mg contents.

  7. VizieR Online Data Catalog: NLTE corrections for Mg and Ca lines (Merle+ 2011)

    NASA Astrophysics Data System (ADS)

    Merle, T.; Thevenin, F.; Pichon, B.; Bigot, L.

    2012-05-01

    Non-LTE corrections for Mg and Ca lines in the stellar parameter range Teff=[3500,5250]K, log(g)=[0.5, 2.0], [Fe/H]=[-4.0,0.5] and [α/Fe]=[0.0,0.4]. The W/W* ratio can be applied to the measured equivalent widths to determine NLTE abundance with classical LTE radiative transfer codes. 45 files for 45 lines of MgI, CaI and CaII are given. In each file, 453 rows at max for a grid of 453 model atmospheres. Only models with W>=1mÅ are given. Only models with 0.0

  8. The content of Ca, Cu, Fe, Mg and Mn and antioxidant activity of green coffee brews.

    PubMed

    Stelmach, Ewelina; Pohl, Pawel; Szymczycha-Madeja, Anna

    2015-09-01

    A simple and fast method of the analysis of green coffee infusions was developed to measure total concentrations of Ca, Cu, Fe, Mg and Mn by high resolution-continuum source flame atomic absorption spectrometry. The precision of the method was within 1-8%, while the accuracy was within -1% to 2%. The method was used to the analysis of infusions of twelve green coffees of different geographical origin. It was found that Ca and Mg were leached the easiest, i.e., on average 75% and 70%, respectively. As compared to the mug coffee preparation, the rate of the extraction of elements was increased when infusions were prepared using dripper or Turkish coffee preparation methods. Additionally, it was established that the antioxidant activity of green coffee infusions prepared using the mug coffee preparation was high, 75% on average, and positively correlated with the total content of phenolic compounds and the concentration of Ca in the brew.

  9. Long phase coherence length and anisotropic magnetoresistance in MgZnO thin film

    SciTech Connect

    Lv, Meng; Xu, Yonggang; Yu, Guolin Lin, Tie; Hu, Gujin; Chu, Junhao; Wang, Hao; Zhang, Huahan; Dai, Ning

    2015-04-21

    We comprehensively investigate magnetotransport properties of MgZnO thin film grown on ZnO substrate by molecular-beam epitaxy. We measure the weak localization effect and extract the electron phase coherence length by fitting to a three-dimensional weak localization theory and by analyzing the different changing rate of the magnetoresistance, results of which are in good agreement with each other. The phase coherence length ranges from 38.4±1    nm at 50 K to 99.8±3.6 nm at 1.4  K, almost the same as that of ZnO nanoplates and In-doped ZnO nanowires, and its temperature dependence is found to scale as T{sup −3/4}. Meanwhile, we study the anisotropic magnetoresistance resulting from the geometric effect as well as the Lorentz force induced path-length effect, which will be enhanced in higher magnetic fields.

  10. Atomic structure of biodegradable Mg-based bulk metallic glass.

    PubMed

    Christie, J K

    2015-05-21

    We have used highly accurate first-principles molecular dynamics simulations to elucidate the structure of Mg60Zn35Ca5 and Mg72Zn23Ca5 bulk metallic glasses, which are candidate materials for biomedical implants; these two compositions exhibit different behaviours when implanted. The environments of each species are different, and average coordination numbers are ∼13 for Mg, ∼11 for Zn and ∼18-19 for Ca. A wide range of local environments were found and icosahedral motifs, often seen in bulk metallic glasses, were among the most common for both Mg and Zn. Through the computation of a chemical short-range order parameter, a moderate avoidance of Zn-Zn bonding over Zn-Mg or Zn-Ca was observed. No statistically significant difference in structure was observed between the two compositions.

  11. Tropical Pacific Mg/Ca paleo-thermometry: A contribution to the core top calibration

    NASA Astrophysics Data System (ADS)

    Clark, S.; Mekik, F.; Kienast, M.; Groeneveld, J.

    2009-12-01

    The magnesium to calcium ratio in foraminifera is widely used as a proxy to estimate ocean temperatures in Earth’s past. However, studies have shown that both dissolution within the sediments and seawater salinity influence the Mg/Ca in the shells of tropical foraminifera and skew paleo-temperature estimates. We measured Mg/Ca and d18O in shells of mixed layer-dwelling species (Globigernoides ruber sensu stricto, Globigernoides ruber sensu lato, and Globigerinoides sacculifer) from a series of core tops in the eastern equatorial Pacific. We specifically chose these three taxa because they are most commonly used for sea surface temperature estimates, particularly in down core work. We compared our results with global core top data from which paleo-temperature equations have already been derived and published (e.g. Brown and Elderfield, 1996; Lea et al., 2000; Dekens et al., 2002). We find that at the same surface ocean temperature, Mg/Ca values can range as much as 1.5 mmol/mol, and we find no influence of salinity on outliers from the expected exponential relationship between Mg/Ca and temperature. Nor do we see dissolution as the cause of this variation. Most samples used for core top calibration work are well above the calcite saturation horizon and show no evidence of dissolution. We demonstrate this both with carbonate dissolution proxies, like data using the Globorotalia menardii Fragmentation Index (MFI) (Mekik et al., 2002) from our same core tops, and with estimates of bottom water carbonate ion concentration. Potential other influences which cause these variations could include seasonality, differences in analytical methods, and potential differences among morphotypes of G. ruber. Brown S. and H. Elderfield, 1996. Variations in Mg/Ca in Sr/Ca ratios of planktonic foraminifera caused by postdepositional dissolution: Evidence of shallow Mg-dependant dissolution, Paleoceanography, 11,5,543-551. Dekens P., D. Lea, D. Pak, and H. Spero, 2002. Core top

  12. Evaluation of foraminiferal trace element cleaning methods on the Mg/Ca of marine ostracoda Krithe

    NASA Astrophysics Data System (ADS)

    Gray, W. R.; Holmes, J. A.; Shevenell, A.

    2012-12-01

    Mg/Ca of marine ostracod Krithe calcite is a potentially important tool for reconstructing oceanic bottom water (150-4000m) temperatures, as core top studies show ostracod Mg uptake is unaffected by carbonate ion saturation. Rigorous cleaning procedures, routinely used to remove clays, organic matter and Fe-Mn-oxides in trace element studies of foraminifera are not regularly applied to marine ostracods. Here we assess the possibility of reducing the analytical uncertainty in Krithe Mg/Ca analyses by employing foraminiferal trace element cleaning procedures and determining the effects of these cleaning procedures on valve chemistry. Using coretop samples of adult and juvenile male Krithe pernoides valves from boxcore OCE205-50BC (26.23oN, 77.7oW, 817m water depth), we apply methanol sonication, hydrogen peroxide oxidation, and hydrazine reduction to single ostracod valves, and sequentially assess the impact of each cleaning step. We compare the results from each cleaning step to valves cleaned using the traditional ethanol/DI rinse method. Significant correlation between Al/Fe and Mn/Fe respectively indicate that clays and Fe-Mn-oxides are detectable in traditionally cleaned samples. Mn and Al covary with Mg in juvenile but not in adult valves, indicating that clays and Fe-Mn-oxides exert a significant control on the Mg/Ca of low valve weight juveniles. Results of our Krithe cleaning experiments confirm that the removal of clays by sonication in methanol results in a decrease in average Fe, Al and Mn values, as well as a reduction in Mg/Ca by 1 mmol/mol in juveniles and 0.5 mmol/mol in adults. Following hydrogen peroxide oxidation samples show a reduction in Fe, Al and Mn concentrations with no significant change in valve Mg/Ca (±0.15 mmol/mol). After reductive cleaning we observe a significant decrease in valve Mg (>1 mmol/mol in juveniles), however there is little effect on Mn and Fe. Examination of adult and juvenile Krithe valves using scanning electron

  13. Effect of alloying elements Al and Ca on corrosion resistance of plasma anodized Mg alloys

    NASA Astrophysics Data System (ADS)

    Anawati, Asoh, Hidetaka; Ono, Sachiko

    2016-04-01

    Plasma anodizing is a surface treatment used to form a ceramic-type oxide film on Mg alloys by the application of a high anodic voltage to create intense plasma near the metal surface. With proper selection of the process parameters, the technique can produce high quality oxide with superior adhesion, corrosion resistance, micro-hardness, wear resistance and strength. The effect of alloying element Al on plasma anodizing process of Mg alloys was studied by comparing the anodizing curves of pure Mg, AZ31, and AZ61 alloys while the effect of Ca were studied on AZ61 alloys containing 0, 1, and 2 wt% Ca. Anodizing was performed in 0.5 M Na3PO4 solution at a constant current density of 200 Am-2 at 25°C. Anodic oxide films with lava-like structure having mix composition of amorphous and crystal were formed on all of the alloys. The main crystal form of the oxide was Mg3(PO4)2 as analyzed by XRD. Alloying elements Al and Ca played role in modifying the plasma lifetime during anodization. Al tended to extend the strong plasma lifetime and therefore accelerated the film thickening. The effect of Ca on anodizing process was still unclear. The anodic film thickness and chemical composition were altered by the presence of Ca in the alloys. Electrochemical corrosion test in 0.9% NaCl solution showed that the corrosion behavior of the anodized specimens depend on the behavior of the substrate. Increasing Al and Ca content in the alloys tended to increase the corrosion resistance of the specimens. The corrosion resistance of the anodized specimens improved significantly about two orders of magnitude relative to the bare substrate.

  14. Cation occupancies in Mg, Co, Ni, Zn, Al ferrite spinels: a multi-element EXAFS study

    NASA Astrophysics Data System (ADS)

    Henderson, C. M. B.; Charnock, J. M.; Plant, D. A.

    2007-02-01

    The distribution of cations between tetrahedral (A) sites and octahedral (B) sites in ferrite spinels has been studied using K-edge x-ray absorption spectroscopy. The samples include natural and synthetic end-member magnetites (Fe3O4), a natural Mn- and Zn-rich magnetite (franklinite) and synthetic binary, ternary and quaternary ferrites of stoichiometry M2+M23+O4, where M2+ = Mg, Co, Ni, Zn and M3+ = Fe, Al. XAS data were obtained for all metals. Complete, unfiltered, EXAFS spectra were refined to determine the percentage distribution of each element over the A and B sites and these data were combined with microprobe analyses to quantify the tetrahedral occupancy for each element in each sample. Measured site occupancies and an internally consistent set of (M-O)A and (M-O)B bond lengths were used to calculate unit-cell parameters, which show excellent agreement with measured values, pointing to the reliability of the measured occupancy factors. The average occupancies determined for the tetrahedral sites in ferrites are (atoms per formula unit) Mg 0.44, Co 0.24, Ni 0.11, Zn 0.76, Al 0.11 and Fe3+ 0.92-0.19. The wide range found for Fe3+ is consistent with it playing a relatively passive role by making good any A-site deficit left by the other competing cations.

  15. Cation occupancies in Mg, Co, Ni, Zn, Al ferrite spinels: a multi-element EXAFS study.

    PubMed

    Henderson, C M B; Charnock, J M; Plant, D A

    2007-02-21

    The distribution of cations between tetrahedral (A) sites and octahedral (B) sites in ferrite spinels has been studied using K-edge x-ray absorption spectroscopy. The samples include natural and synthetic end-member magnetites (Fe₃O₄), a natural Mn- and Zn-rich magnetite (franklinite) and synthetic binary, ternary and quaternary ferrites of stoichiometry M(²+)M₂(³+)O₄, where M(²+) = Mg, Co, Ni, Zn and M(³+) = Fe, Al. XAS data were obtained for all metals. Complete, unfiltered, EXAFS spectra were refined to determine the percentage distribution of each element over the A and B sites and these data were combined with microprobe analyses to quantify the tetrahedral occupancy for each element in each sample. Measured site occupancies and an internally consistent set of (M-O)(A) and (M-O)(B) bond lengths were used to calculate unit-cell parameters, which show excellent agreement with measured values, pointing to the reliability of the measured occupancy factors. The average occupancies determined for the tetrahedral sites in ferrites are (atoms per formula unit) Mg 0.44, Co 0.24, Ni 0.11, Zn 0.76, Al 0.11 and Fe(³+) 0.92-0.19. The wide range found for Fe(³+) is consistent with it playing a relatively passive role by making good any A-site deficit left by the other competing cations.

  16. Molecular-beam-epitaxy-grown ZnMgS ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    Sou, I. K.; Wu, Marcus C. W.; Sun, T.; Wong, K. S.; Wong, G. K. L.

    2001-03-01

    Epitaxial growth of Zn1-xMgxS alloy thin films on GaP(100) substrates was carried out using the molecular-beam-epitaxy technique. In situ reflection high-energy electron diffraction studies show that the alloys can be grown with a stable zinc-blende structure up to x around 30%. For x>30%, a structural transition will occur at a critical thickness which is sensitively dependent on the x composition. A near-band-edge peak with a full width at half maximum of about 10 nm was observed in room-temperature photoluminescence measurements made on as-grown alloy thin films. Several Zn1-xMgxS-based Schottky barrier photodetectors were fabricated. Room-temperature photoresponse measurements were performed on these detectors and abrupt long-wavelength cutoffs covering 325, 305, 295, and 270 nm were achieved for devices with Mg composition of 16%, 44%, 57%, and 75%, respectively. The response curve of the Zn0.43Mg0.57S device offers a close match to the erythemal action spectrum that describes human skin sensitivity to UV radiation.

  17. Stress Corrosion Cracking in Al-Zn-Mg-Cu Aluminum Alloys in Saline Environments

    NASA Astrophysics Data System (ADS)

    Holroyd, N. J. Henry; Scamans, G. M.

    2013-03-01

    Stress corrosion cracking of Al-Zn-Mg-Cu (AA7xxx) aluminum alloys exposed to saline environments at temperatures ranging from 293 K to 353 K (20 °C to 80 °C) has been reviewed with particular attention to the influences of alloy composition and temper, and bulk and local environmental conditions. Stress corrosion crack (SCC) growth rates at room temperature for peak- and over-aged tempers in saline environments are minimized for Al-Zn-Mg-Cu alloys containing less than ~8 wt pct Zn when Zn/Mg ratios are ranging from 2 to 3, excess magnesium levels are less than 1 wt pct, and copper content is either less than ~0.2 wt pct or ranging from 1.3 to 2 wt pct. A minimum chloride ion concentration of ~0.01 M is required for crack growth rates to exceed those in distilled water, which insures that the local solution pH in crack-tip regions can be maintained at less than 4. Crack growth rates in saline solution without other additions gradually increase with bulk chloride ion concentrations up to around 0.6 M NaCl, whereas in solutions with sufficiently low dichromate (or chromate), inhibitor additions are insensitive to the bulk chloride concentration and are typically at least double those observed without the additions. DCB specimens, fatigue pre-cracked in air before immersion in a saline environment, show an initial period with no detectible crack growth, followed by crack growth at the distilled water rate, and then transition to a higher crack growth rate typical of region 2 crack growth in the saline environment. Time spent in each stage depends on the type of pre-crack ("pop-in" vs fatigue), applied stress intensity factor, alloy chemistry, bulk environment, and, if applied, the external polarization. Apparent activation energies ( E a) for SCC growth in Al-Zn-Mg-Cu alloys exposed to 0.6 M NaCl over the temperatures ranging from 293 K to 353 K (20 °C to 80 °C) for under-, peak-, and over-aged low-copper-containing alloys (<0.2 wt pct) are typically ranging from

  18. Influence of hydrostatic pressure on the built-in electric field in ZnO/ZnMgO quantum wells

    SciTech Connect

    Teisseyre, Henryk; Young, Toby D.

    2016-06-07

    We used high hydrostatic pressure to perform photoluminescence measurements on polar ZnO/ZnMgO quantum well structures. Our structure oriented along the c-direction (polar direction) was grown by plasma-assisted molecular beam epitaxy on a-plane sapphire. Due to the intrinsic electric field, which exists in polar wurtzite structure at ambient pressure, we observed a red shift of the emission related to the quantum-confined Stark effect. In the high hydrostatic pressure experiment, we observed a strong decrease of the quantum well pressure coefficients with increased thickness of the quantum wells. Generally, a narrower quantum well gave a higher pressure coefficient, closer to the band-gap pressure coefficient of bulk material 20 meV/GPa for ZnO, while for wider quantum wells it is much lower. We observed a pressure coefficient of 19.4 meV/GPa for a 1.5 nm quantum well, while for an 8 nm quantum well the pressure coefficient was equal to 8.9 meV/GPa only. This is explained by taking into account the pressure-induced increase of the strain in our structure. The strain was calculated taking in to account that in-plane strain is not equal (due to fact that we used a-plane sapphire as a substrate) and the potential distribution in the structure was calculated self-consistently. The pressure induced increase of the built-in electric field is the same for all thicknesses of quantum wells, but becomes more pronounced for thicker quantum wells due to the quantum confined Stark effect lowering the pressure coefficients.

  19. Magnetic, Electric and Optical Properties of Mg-Substituted Ni-Cu-Zn Ferrites

    NASA Astrophysics Data System (ADS)

    Kabbur, S. M.; Ghodake, U. R.; Kambale, Rahul C.; Sartale, S. D.; Chikhale, L. P.; Suryavanshi, S. S.

    2017-10-01

    The Ni0.25- x Mg x Cu0.30Zn0.45Fe2O4 ( x = 0.00 mol, 0.05 mol, 0.10 mol, 0.15 mol, 0.20 mol and 0.25 mol) magnetic oxide system was prepared by a sol-gel auto-combustion method using glycine as a fuel. X-ray diffraction study reveals the formation of pure spinel lattice symmetry along with the presence of a small fraction of unreacted Fe2O3 phase as a secondary phase due to incomplete combustion reaction between fuel and oxidizer. The lattice constant ( a) was found to decrease with the increase of Mg2+ content; the average crystallite size ( D) is observed in the range of 26.78-33.14 nm. At room temperature, all the samples show typical magnetic hysteresis loops with the decrease of magnetic moment ( n B) of Ni-Cu-Zn ferrites with the increase of Mg2+ content. The intrinsic vibrational absorption bands for the tetrahedral and octahedral sites of the spinel structure were confirmed by infrared (IR) spectroscopy. The optical parameters such as refractive index ( η), velocity of IR waves ( v) and jump rates ( J 1, J 2, J) were studied and found to be dependent on the variation of the lattice constant. The Curie temperature ( T c) of Ni-Cu-Zn mixed ferrite was found to decrease with Mg2+ addition. The composition x = 0.15 mol.% with a low dielectric loss tangent of 2% seems to have potential for multilayer chip inductor applications at a wide range of frequencies.

  20. Magnetic, Electric and Optical Properties of Mg-Substituted Ni-Cu-Zn Ferrites

    NASA Astrophysics Data System (ADS)

    Kabbur, S. M.; Ghodake, U. R.; Kambale, Rahul C.; Sartale, S. D.; Chikhale, L. P.; Suryavanshi, S. S.

    2017-06-01

    The Ni0.25-x Mg x Cu0.30Zn0.45Fe2O4 (x = 0.00 mol, 0.05 mol, 0.10 mol, 0.15 mol, 0.20 mol and 0.25 mol) magnetic oxide system was prepared by a sol-gel auto-combustion method using glycine as a fuel. X-ray diffraction study reveals the formation of pure spinel lattice symmetry along with the presence of a small fraction of unreacted Fe2O3 phase as a secondary phase due to incomplete combustion reaction between fuel and oxidizer. The lattice constant (a) was found to decrease with the increase of Mg2+ content; the average crystallite size (D) is observed in the range of 26.78-33.14 nm. At room temperature, all the samples show typical magnetic hysteresis loops with the decrease of magnetic moment (n B) of Ni-Cu-Zn ferrites with the increase of Mg2+ content. The intrinsic vibrational absorption bands for the tetrahedral and octahedral sites of the spinel structure were confirmed by infrared (IR) spectroscopy. The optical parameters such as refractive index (η), velocity of IR waves (v) and jump rates (J 1, J 2, J) were studied and found to be dependent on the variation of the lattice constant. The Curie temperature (T c) of Ni-Cu-Zn mixed ferrite was found to decrease with Mg2+ addition. The composition x = 0.15 mol.% with a low dielectric loss tangent of 2% seems to have potential for multilayer chip inductor applications at a wide range of frequencies.

  1. Interplay of Ca(2+) and Mg (2+) in sodium-calcium exchanger and in other Ca(2+)-binding proteins: magnesium, watchdog that blocks each turn if able.

    PubMed

    Levitsky, Dmitri O; Takahashi, Masayuki

    2013-01-01

    Sodium-calcium exchange across plasma membrane is regulated by intracellular calcium ions. The sodium-calcium exchanger (NCX1) is activated by successive saturation of numerous Ca(2+)-binding sites located in the intracellular loop of the protein. The progressive saturation of the binding domain CBD12 by Ca(2+) results in a series of conformational changes of CBD12 as well as of entire NCX1 molecule. Like other soluble and membrane Ca(2+)-binding proteins, NCX1 can also be regulated by Mg(2+) that antagonises Ca(2+) at the level of divalent cation-binding sites. This chapter summarises data on Mg(2+) impacts in the cells. Regulatory action of Mg(2+) on intracellular Ca(2+)-dependent processes can be achieved due to changes of its cytoplasmic level, which take place in the range of [Mg(2+)](i) from 0.5 to 3 mM. Under normal conditions, these changes are ensured by activation of plasmalemmal Mg(2+) transport systems and by variations in ATP level in cytoplasm. In heart and in brain, some pathological conditions, such as hypoxia, ischemia and ischemia followed by reperfusion, are associated with an important increase in intracellular Ca(2+). The tissue damage due to Ca(2+) overload may be prevented by Mg(2+). The protective actions of Mg(2+) can be achieved due to its ability to compete with Ca(2+) for the binding sites in a number of proteins responsible for the rise in intracellular free Ca(2+), including NCX1, in case when the reverse mode of Na(+)/Ca(2+) exchange becomes predominant. Saturation of CBD12 by Mg(2+) results in important changes of NCX1 conformation. Modulating actions of Mg(2+) on the conformation of NCX1 were detected at a narrow range of Mg(2+) concentration, from 0.5 to 1 mM. These data support an idea that variations of intracellular Mg(2+) could modify transmembrane Ca(2+) movements ensured by NCX1.

  2. Stabilization calculations of the low-lying temporary anions states of Be, Mg, and Ca

    NASA Astrophysics Data System (ADS)

    Falcetta, Michael F.; Reilly, Nathan D.; Jordan, Kenneth D.

    2017-01-01

    The stabilization method is used in conjunction with the equation-of-motion electron-attachment coupled-cluster method to calculate the complex energies of the 2P temporary anion states of Be and Mg as well as of the 2D temporary anions states of Mg and Ca. The calcul