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Sample records for pure magnetite crystals

  1. Thermal Decomposition of an Impure (Roxbury) Siderite: Relevance to the Presence of Chemically Pure Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    McKay, D.S.; Gibson, E.K.; Thomas-Keprta, K.L.; Clemett, S.J.; Wentworth, S.J.

    2009-01-01

    The question of the origin of nanophase magnetite in Martian meteorite ALH84001 has been widely debated for nearly a decade. Golden et al. have reported producing nearly chemically pure magnetite from thermal decomposition of chemically impure siderite [(Fe, Mg, Mn)CO3]. This claim is significant for three reasons: first, it has been argued that chemically pure magnetite present in the carbonate disks in Martian meteorite ALH84001 could have formed by the thermal decomposition of the impure carbonate matrix in which they are embedded; second, the chemical purity of magnetite has been previously used to identify biogenic magnetite; and, third, previous studies of thermal decomposition of impure (Mg,Ca,Mn)-siderites, which have been investigated under a wide variety of conditions by numerous researchers, invariably yields a mixed metal oxide phase as the product and not chemically pure magnetite. The explanation for this observation is that these siderites all possess the same crystallographic structure (Calcite; R3c) so solid solutions between these carbonates are readily formed and can be viewed on an atomic scale as two chemically different but structurally similar lattices.

  2. Formation of "Chemically Pure" Magnetite from Mg-Fe-Carbonates Implications for the Exclusively Inorganic Origin of Magnetite and Sulfides in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, Douglas W.; Lauer, H. V., Jr.; Morris, R. V.; Trieman, A. H.; McKay, G. A.

    2006-01-01

    Magnetite and sulfides in the black rims of carbonate globules in Martian meteorite ALH84001 have been studied extensively because of the claim by McKay et al. that they are biogenic in origin. However, exclusively inorganic (abiotic) processes are able to account for the occurrence of carbonate-sulfide-magnetite assemblages in the meteorite. We have previously precipitated chemically zoned and sulfide-bearing carbonate globules analogous to those in ALH84001 (at less than or equal to 150 C) from multiple fluxes of variable-composition Ca-Mg-Fe-CO2-S-H2O solutions. Brief heating of precipitated globules to approx. 470 C produced magnetite and pyrrhotite within the globules by thermal decomposition of siderite and pyrite, respectively. We have also shown that morphology of magnetite formed by inorganic thermal decomposition of Fe-rich carbonate is similar to the morphology of so-called biogenic magnetite in the carbonate globules of ALH84001. Magnetite crystals in the rims of carbonate globules in ALH84001 are chemically pure [Note: "Chemically pure" is defined here as magnetite with Mg at levels comparable or lower than Mg detected by [8] in ALH84001 magnetite]. A debate continues on whether or not chemically pure magnetite can form by the thermal decomposition of mixed Mg-Fe-carbonates that have formed under abiotic conditions. Thomas-Keprta et al. argue that it is not possible to form Mg-free magnetite from Mg-Fe-carbonate based on thermodynamic data. We previously suggested that chemically pure magnetite could form by the thermal decomposition of relatively pure siderite in the outer rims of the globules. Mg-Fe-carbonates may also thermally decompose under conditions conducive for formation of chemically pure magnetite. In this paper we show through laboratory experiments that chemically pure magnetite can form by an inorganic process from mixed Mg-Fe-carbonates.

  3. Non-chemically Pure Magnetites Produced from Thermal Decomposition of Ankerites

    NASA Astrophysics Data System (ADS)

    Jiménez López, C.; Romanek, C.; Rodríguez-Navarro, A.; Pérez-González, T.; Rodríguez Navarro, C.

    2008-12-01

    It has been claimed that chemically pure magnetites (Fe3O4) can be obtained from thermal decomposition of (Fe, Mg, Ca)CO3 (Golden et al., 2004). Such an observation is critical, since it opens the possibility of an inorganic way of formation of the magnetites found on Martian meteorite ALH84001. Such a chemical purity is one of the parameters used, so far, to recognize bacterial origin of natural magnetites (Thomas-Keptra et al., 2001), since it has been demonstrated that biologically-controlled magnetites are chemically pure (Bazylinski and Frankel, 2004) . However, while Golden et al. (2004) obtained pure magnetite from an almost pure precursor, the ankerite cores in ALH84001 in which magnetites are embedded are far from being chemically pure, since they contain considerable amounts of Ca and Mg (Kopp and Humayun, 2003). In this study we have performed several experiments to analyze the chemical purity of magnetites produced by thermal decomposition of four ankerite samples sinthetized in the laboratory, and containing different amounts of Ca, Fe and Mg. Such a thermal decomposition was achieved by two procedures: (1) by heating the samples at 470°C under CO2 pressure and (2) by decomposing the ankerite "in situ" under the TEM (Transmission electron Microscopy) electron beam. Magnetite produced by the first procedure was analyzed by XRD to determine whether or not the resulting solid was a mixture of oxides or rather a solid solution of (Ca, Fe and Mg)oxide. Magnetites formed by the two methods were studied by High Resolution TEM. The chemical composition of about 20 crystals of each experiment was analyzed by EDAX. Under our experimental conditions, ankerites decomposed in magnetite crystals of about 5 nanometers in size. Magentite crystals arranged to keep the morphology of the precursor. Our results confirm that any of these magnetites is chemically pure, but rather, each one of them is a solid solution of Ca and Mg. Therefore, chemically pure magnetites

  4. Truncated hexa-octahedral magnetite crystals in ALH84001: presumptive biosignatures

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Bazylinski, D. A.; Kirschvink, J. L.; McKay, D. S.; Wentworth, S. J.; Vali, H.; Gibson, E. K. Jr; McKay, M. F.; Romanek, C. S.

    2001-01-01

    McKay et al. [(1996) Science 273, 924-930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe(3)O(4)) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found.

  5. Truncated hexa-octahedral magnetite crystals in ALH84001: presumptive biosignatures.

    PubMed

    Thomas-Keprta, K L; Clemett, S J; Bazylinski, D A; Kirschvink, J L; McKay, D S; Wentworth, S J; Vali, H; Gibson, E K; McKay, M F; Romanek, C S

    2001-02-27

    McKay et al. [(1996) Science 273, 924-930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe(3)O(4)) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found.

  6. Process for Making Single-Domain Magnetite Crystals

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, Douglas W.; Morris, Richard V.; Lofgren, Gary E.; McKay, Gordan A.; Schwandt, Craig S.; Lauer, Howard V., Jr.; Socki, Richard A.

    2004-01-01

    A process for making chemically pure, single-domain magnetite crystals substantially free of structural defects has been invented as a byproduct of research into the origin of globules in a meteorite found in Antarctica and believed to have originated on Mars. The globules in the meteorite comprise layers of mixed (Mg, Fe, and Ca) carbonates, magnetite, and iron sulfides. Since the discovery of the meteorite was announced in August 1996, scientists have debated whether the globules are of biological origin or were formed from inorganic materials by processes that could have taken place on Mars. While the research that led to the present invention has not provided a definitive conclusion concerning the origin of the globules, it has shown that globules of a different but related chemically layered structure can be grown from inorganic ingredients in a multistep precipitation process. As described in more detail below, the present invention comprises the multistep precipitation process plus a subsequent heat treatment. The multistep precipitation process was demonstrated in a laboratory experiment on the growth of submicron ankerite crystals, overgrown by submicron siderite and pyrite crystals, overgrown by submicron magnesite crystals, overgrown by submicron siderite and pyrite. In each step, chloride salts of appropriate cations (Ca, Fe, and Mg) were dissolved in deoxygenated, CO2- saturated water. NaHCO3 was added as a pH buffer while CO2 was passed continuously through the solution. A 15-mL aliquot of the resulting solution was transferred into each of several 20 mL, poly(tetrafluoroethylene)-lined hydrothermal pressure vessels. The vessels were closed in a CO2 atmosphere, then transferred into an oven at a temperature of 150 C. After a predetermined time, the hydrothermal vessels were removed from the oven and quenched in a freezer. Supernatant solutions were decanted, and carbonate precipitates were washed free of soluble salts by repeated decantations with

  7. Growing ZnO crystals on magnetite nanoparticles.

    PubMed

    Turgeman, Rachel; Tirosh, Shay; Gedanken, Aharon

    2004-04-02

    We report herein on the oriented growth of ZnO crystals on magnetite nanoparticles. The ZnO crystals were grown by hydrolyzing a supersaturated aqueous solution of zinc nitrate. The seeds for the growth were magnetite nanoparticles with a diameter of 5.7 nm and a narrow size distribution. Hollowed ZnO hexagons of 0.15 microm width and 0.5 microm length filled with Fe(3)O(4) particles were obtained. HR-TEM (high-resolution transmission electron microscopy) and selected-area EDS (energy-dispersive spectroscopy) show that the nanoparticles are homogenously spread in the ZnO tubes. Zeta potential measurements were employed to understand the relationship between the nanoparticles and the oriented growth of the ZnO crystals. The results show that the surfactants induced the directional growth of the ZnO crystals.

  8. Experimental study of chemical and crystallization remanent magnetizations in magnetite

    NASA Astrophysics Data System (ADS)

    Nguyen, T. K. T.; Pechersky, D. M.

    1987-06-01

    Crystallization magnetization (KRM) of magnetite is experimentally studied by the oxidation of fine grains of pyrite and by the oxidation (unmixing) of titanomagnetite with Tc = 150-200°C at the temperature of 400-450°C in the magnetic field of 50-100 mkT. Chemical remanence (CRM) of magnetite, which forms by the unmixing of titanomaghemite with Tc = 380-450°C at the temperature of 350°C in a magnetic field, is investigated. The main properties of KRM and CRM are: (1) the relation of KRM/ARM t = 1.0-1.4 and CRM/ARM 1 = 0.7-0.9, where ARM t is anhysteretic remanent magnetization after thermal demagnetization to the temperature of KRM or CRM acquisition; (2) the relative distance NT between linear portions of coercive force spectra of normal remanence from KRM or CRM state and from zero state is less than 0.2; for the same samples when absolute zero state and zero state are comparing NT ⩾ 0.3 (Sholpo-Luzianina NT-test of TRM); and (3) the spontaneous growth of KRM is small, but the spontaneous growth of CRM is not less than that of ARM or TRM. The properties of artificial KRM and CRM are similar to the properties of some rocks with natural KRM and CRM. As CRM/ARM t and KRM/ARM t ratio varies in the narrow limit, it can be used for the palaeointensity estimation. The first palaeointensity results are demonstrated: Holocene deep sea nodules—51 ± 4 mkT, Palaeocene magnetite ore —47 ± 3 mkT and Devonian baked rocks—6.1 ± 2.1 mkT.

  9. Effect of crystal morphology on magnetic structure of nano-magnetites

    NASA Astrophysics Data System (ADS)

    Chen, Y. H.; Zhang, J. F.

    2017-01-01

    The nano-magnetites with particle, rod, tube, and ring crystal morphologies were synthesized and the differences between macroscopic and microscopic magnetic properties were studied. The macroscopic magnetic properties of nano-magnetites obtained via a superconducting quantum interference device (SQUID) showed that both coercive magnetic field and saturation magnetization per unit volume followed the orders of ring > particle > tube > rod, respectively. This indicated that the crystal morphology affected macroscopic magnetic properties. The particle nano-magnetite contained a single domain while the others contained multiple domains measured by a magnetic force microscope (MFM). However, the domain structure of nano-magnetites calculated from SQUID data showed that all were pseudo-single domains. This suggested that the MFM may be a precise tool to determine magnetic structures. Moreover, the crystal morphology of nano-magnetites affected magnetic properties owing to different magnetic-domain structures.

  10. Iron et al.: Incorporation of Manganese in the Crystal Lattice of Magnetosome Magnetite

    NASA Astrophysics Data System (ADS)

    Prozorov, Tanya; Perez-Gonzalez, Teresa; Jimenez-Lopez, Concepcion; Mallapragada, Surya K.; Howse, Paul; Bazylinski, Dennis A.; Prozorov, Ruslan

    2010-03-01

    Incorporation of foreign metal into the crystal matrix of the magnetotactic bacterial magnetite has been attempted worldwide. Recently, presence of small amounts of cobalt and manganese in magnetosome magnetite crystals in cultured and uncultured magnetotactic bacteria, respectively, was reported. Magnetization of the uncultured cells and their magnetosomes were not determined, while only marginal changes in the magnetic properties of the cultured cobalt-grown cells and their magnetosomes were observed, however no evidence of incorporation of these metals into the crystalline lattice was presented. We grew cells of a magnetotactic bacterium, Magnetospirillum gryphiswaldense strain MSR-1, in the presence of manganese, ruthenium, zinc and vanadium, of which only manganese was incorporated within the magnetosome magnetite crystals. For the first time we demonstrate that the magnetic properties of magnetite crystals of magnetotactic bacteria can be significantly altered by the incorporation of metal ions, other than iron, in the crystal structure, as signaled by a major shift in the Verwey transition.

  11. Ferromagnetic resonance of intact cells and isolated crystals from cultured and uncultured magnetite-producing magnetotactic bacteria

    NASA Astrophysics Data System (ADS)

    Abraçado, Leida G.; Wajnberg, Eliane; Esquivel, Darci M. S.; Keim, Carolina N.; Silva, Karen T.; Moreira, Emílio T. S.; Lins, Ulysses; Farina, Marcos

    2014-06-01

    Most magnetotactic bacteria (MB) produce stable, single-domain magnetite nanocrystals with species-specific size, shape and chain arrangement. In addition, most crystals are elongated along the [111] direction, which is the easy axis of magnetization in magnetite, chemically pure and structurally perfect. These special characteristics allow magnetite crystal chains from MB to be recognized in environmental samples including old sedimentary rocks. Ferromagnetic resonance (FMR) has been proposed as a powerful and practical tool for screening large numbers of samples possibly containing magnetofossils. Indeed, several studies were recently published on FMR of cultured MB, mainly Magnetospirillum gryphiswaldense. In this work, we examined both uncultured magnetotactic cocci and the cultured MB M. gryphiswaldense using transmission electron microscopy (TEM) and FMR from 10 K to room temperature (RT). The TEM data supported the FMR spectral characteristics of our samples. The FMR spectra of both bacteria showed the intrinsic characteristics of magnetite produced by MB, such as extended absorption at the low field region of the spectra and a Verwey transition around 100 K. As previously observed, the spectra of M. gryphiswaldense isolated crystals were more symmetrical than the spectra obtained from whole cells, reflecting the loss of chain arrangement due to the small size and symmetrical shape of the crystals. However, the FMR spectra of magnetic crystals isolated from magnetotactic cocci were very similar to the FMR spectra of whole cells, because the chain arrangement was maintained due to the large size and prismatic shape of the crystals. Our data support the use of FMR spectra to detect magnetotactic bacteria and magnetofossils in samples of present and past environments. Furthermore, the spectra suggest the use of the temperature transition of spectral peak-to-peak intensity to obtain the Verwey temperature for these systems.

  12. Analysis of magnetite crystals and inclusion bodies inside magnetotactic bacteria from different environmental locations

    NASA Astrophysics Data System (ADS)

    Oestreicher, Z.; Lower, B.; Lower, S.; Bazylinski, D. A.

    2011-12-01

    Biomineralization occurs throughout the living world; a few common examples include iron oxide in chiton teeth, calcium carbonate in mollusk shells, calcium phosphate in animal bones and teeth, silica in diatom shells, and magnetite crystals inside the cells of magnetotactic bacteria. Biologically controlled mineralization is characterized by biominerals that have species-specific properties such as: preferential crystallographic orientation, consistent particle size, highly ordered spatial locations, and well-defined composition and structure. It is well known that magnetotactic bacteria synthesize crystals of magnetite inside of their cells, but how they mineralize the magnetite is poorly understood. Magnetosomes have a species-specific morphology that is due to specific proteins involved in the mineralization process. In addition to magnetite crystals, magnetotactic bacteria also produce inclusion bodies or granules that contain different elements, such as phosphorus, calcium, and sulfur. In this study we used the transmission electron microscope to analyze the structure of magnetite crystals and inclusion bodies from different species of magnetotactic bacteria in order to determine the composition of the inclusion bodies and to ascertain whether or not the magnetite crystals contain elements other than iron and oxygen. Using energy dispersive spectroscopy we found that different bacteria from different environments possess inclusion bodies that contain different elements such as phosphorus, calcium, barium, magnesium, and sulfur. These differences may reflect the conditions of the environment in which the bacteria inhabit.

  13. The Origin of Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Wentworth, S. J.; McKay, D. S.; Gibson, E. K., Jr.

    2012-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks believed to have formed approx 3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships between the carbonate disks, their associated magnetites and the orthopyroxene matrix in which they are embedded. Comparison of these results with experimental thermal decomposition studies of sideritic carbonates conducted under a range of heating scenarios suggests that the magnetite nanocrystals in the ALH84001 carbonate disks are not the products of thermal decomposition.

  14. Crystal growth of bullet-shaped magnetite in magnetotactic bacteria of the Nitrospirae phylum

    PubMed Central

    Li, Jinhua; Menguy, Nicolas; Gatel, Christophe; Boureau, Victor; Snoeck, Etienne; Patriarche, Gilles; Leroy, Eric; Pan, Yongxin

    2015-01-01

    Magnetotactic bacteria (MTB) are known to produce single-domain magnetite or greigite crystals within intracellular membrane organelles and to navigate along the Earth's magnetic field lines. MTB have been suggested as being one of the most ancient biomineralizing metabolisms on the Earth and they represent a fundamental model of intracellular biomineralization. Moreover, the determination of their specific crystallographic signature (e.g. structure and morphology) is essential for palaeoenvironmental and ancient-life studies. Yet, the mechanisms of MTB biomineralization remain poorly understood, although this process has been extensively studied in several cultured MTB strains in the Proteobacteria phylum. Here, we show a comprehensive transmission electron microscopy (TEM) study of magnetic and structural properties down to atomic scales on bullet-shaped magnetites produced by the uncultured strain MYR-1 belonging to the Nitrospirae phylum, a deeply branching phylogenetic MTB group. We observed a multiple-step crystal growth of MYR-1 magnetite: initial isotropic growth forming cubo-octahedral particles (less than approx. 40 nm), subsequent anisotropic growth and a systematic final elongation along [001] direction. During the crystal growth, one major {111} face is well developed and preserved at the larger basal end of the crystal. The basal {111} face appears to be terminated by a tetrahedral–octahedral-mixed iron surface, suggesting dimensional advantages for binding protein(s), which may template the crystallization of magnetite. This study offers new insights for understanding magnetite biomineralization within the Nitrospirae phylum. PMID:25566884

  15. Crystal growth of bullet-shaped magnetite in magnetotactic bacteria of the Nitrospirae phylum.

    PubMed

    Li, Jinhua; Menguy, Nicolas; Gatel, Christophe; Boureau, Victor; Snoeck, Etienne; Patriarche, Gilles; Leroy, Eric; Pan, Yongxin

    2015-02-06

    Magnetotactic bacteria (MTB) are known to produce single-domain magnetite or greigite crystals within intracellular membrane organelles and to navigate along the Earth's magnetic field lines. MTB have been suggested as being one of the most ancient biomineralizing metabolisms on the Earth and they represent a fundamental model of intracellular biomineralization. Moreover, the determination of their specific crystallographic signature (e.g. structure and morphology) is essential for palaeoenvironmental and ancient-life studies. Yet, the mechanisms of MTB biomineralization remain poorly understood, although this process has been extensively studied in several cultured MTB strains in the Proteobacteria phylum. Here, we show a comprehensive transmission electron microscopy (TEM) study of magnetic and structural properties down to atomic scales on bullet-shaped magnetites produced by the uncultured strain MYR-1 belonging to the Nitrospirae phylum, a deeply branching phylogenetic MTB group. We observed a multiple-step crystal growth of MYR-1 magnetite: initial isotropic growth forming cubo-octahedral particles (less than approx. 40 nm), subsequent anisotropic growth and a systematic final elongation along [001] direction. During the crystal growth, one major {111} face is well developed and preserved at the larger basal end of the crystal. The basal {111} face appears to be terminated by a tetrahedral-octahedral-mixed iron surface, suggesting dimensional advantages for binding protein(s), which may template the crystallization of magnetite. This study offers new insights for understanding magnetite biomineralization within the Nitrospirae phylum.

  16. Hydrothermal growth of fine magnetite and ferrite crystals

    NASA Astrophysics Data System (ADS)

    Byrappa, Shayan; Vicas, C. S.; Dhanaraj, Neel; Namratha, K.; Keerthana, S. D.; Dey, Ravi; Byrappa, K.

    2016-10-01

    In the present work, magnetite (Fe3O4, avg. 70 nm) synthesis employing Azadirachta indica (neem) leaf extract is reported originally using hydrothermal conditions and the results obtained were compared with that of D-glucose. Fourier transform infrared spectroscopy confirms the presence of polysaccharides and proteins in the extract which act as both surfactants and reducing agents, aided the formation of magnetite nanostructures. Authors also reported the selective doping of Zn, Cu and Co on nickel ferrite for the enhancement of adsorptive dye removal property, adopting and investigating the use of eloquent one-step green hydrothermal approach (T=180 °C, t=4 h, pH=12) with sodium dodecyl sulfate as surfactant. X-ray diffraction studies reveal that all the materials synthesized are isometric spinel structures and furthermore, morphological evidences using scanning electron microscopy are accounted. Adsorptive dye removal ability of synthesized materials was investigated using trypan blue as a probe. It was evident from the results that magnetite using neem extract showed enhanced adsorption ability (75%) than that of D-glucose (62%). Also, exponential increase in dye removal efficiency from 55% to 81% due to the presence of copper in nickel ferrite was duly noted.

  17. Chains of magnetite crystals in the meteorite ALH84001: evidence of biological origin.

    PubMed

    Friedmann, E I; Wierzchos, J; Ascaso, C; Winklhofer, M

    2001-02-27

    The presence of magnetite crystal chains, considered missing evidence for the biological origin of magnetite in ALH84001 [Thomas-Keprta, K. L., Bazylinski, D. A., Kirschvink, J. L., Clemett, S. J., McKay, D. S., Wentworth, S. J., Vali, H., Gibson, E. K., Jr., & Romanek, C. S. (2000) Geochim. Cosmochim. Acta 64, 4049-4081], is demonstrated by high-power stereo backscattered scanning electron microscopy. Five characteristics of such chains (uniform crystal size and shape within chains, gaps between crystals, orientation of elongated crystals along the chain axis, flexibility of chains, and a halo that is a possible remnant of a membrane around chains), observed or inferred to be present in magnetotactic bacteria but incompatible with a nonbiological origin, are shown to be present. Although it is unlikely that magnetotactic bacteria were ever alive in ALH84001, decomposed remains of such organisms could have been deposited in cracks in the rock while it was still on the surface on Mars.

  18. Truncated Hexa-Octahedral Magnetite Crystals in Martian Meteorite ALH84001: Evidence of Biogenic Activity on Early Mars

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K.; Clemett, S. J.; Schwartz, C.; McIntosh, J. R.; Bazylinski, D. A.; Kirschvink, J.; McKay, D. S.; Gibson, E. K.; Vali, H.; Romanek, C. S.

    2004-01-01

    The landmark paper by McKay et al. [1] cited four lines of evidence associated with the Martian meteorite ALH84001 to support the hypothesis that life existed on Mars approximately 4 Ga ago. Now, more than five years later, attention has focused on the ALH84001 magnetite grains embedded within carbonate globules in the ALH84001 meteorite. We have suggested that up to approx.25% of the ALH84001 magnetite crystals are products of biological activity [e.g., 2]. The remaining magnetites lack sufficient characteristics to constrain their origin. The papers of Thomas Keprta et al. were criticized arguing that the three dimensional structure of ALH84001 magnetite crystals can only be unambiguously determined using electron tomographic techniques. Clemett et al. [3] confirmed that magnetites produced by magnetotactic bacteria strain MV-I display a truncated hexa-octahedral geometry using electron tomography and validated the use of the multi-tilt classical transmission microscopy technique used by [2]. Recently the geometry of the purported martian biogenic magnetites was shown be identical to that for MV-1 magnetites using electron tomography [6].

  19. Intrinsic response of crystals to pure dilatation

    SciTech Connect

    Wang, Jinghan; Yip, S.; Phillpot, S.; Wolf, D.

    1991-12-31

    The response of an f.c.c. lattice with Lennard-Jones interaction under symmetric lattice extension has been studied by Monte Carlo simulation at several temperatures. The critical strain at which the crystal undergoes a structural change is found to be well predicted by the mechanical stability limit expressed in terms of either the elastic constants or the bulk modulus. At low temperature (reduced temperature T = 0.125), lattice decohesion is observed in the form of cleavage fracture, whereas at higher temperature (T = 0.3) the strained system deforms by cavitation with some degree of local plasticity. At still higher temperature (T = 0.5) the lattice undergoes homogeneous disordering with all the attendant characteristics of melting.

  20. Intrinsic response of crystals to pure dilatation

    SciTech Connect

    Wang, Jinghan; Yip, S. . Dept. of Nuclear Engineering); Phillpot, S.; Wolf, D. )

    1991-01-01

    The response of an f.c.c. lattice with Lennard-Jones interaction under symmetric lattice extension has been studied by Monte Carlo simulation at several temperatures. The critical strain at which the crystal undergoes a structural change is found to be well predicted by the mechanical stability limit expressed in terms of either the elastic constants or the bulk modulus. At low temperature (reduced temperature T = 0.125), lattice decohesion is observed in the form of cleavage fracture, whereas at higher temperature (T = 0.3) the strained system deforms by cavitation with some degree of local plasticity. At still higher temperature (T = 0.5) the lattice undergoes homogeneous disordering with all the attendant characteristics of melting.

  1. A first test of the hypothesis of biogenic magnetite-based heterogeneous ice-crystal nucleation in cryopreservation.

    PubMed

    Kobayashi, Atsuko; Golash, Harry N; Kirschvink, Joseph L

    2016-06-01

    An outstanding biophysical puzzle is focused on the apparent ability of weak, extremely low-frequency oscillating magnetic fields to enhance cryopreservation of many biological tissues. A recent theory holds that these weak magnetic fields could be inhibiting ice-crystal nucleation on the nanocrystals of biological magnetite (Fe3O4, an inverse cubic spinel) that are present in many plant and animal tissues by causing them to oscillate. In this theory, magnetically-induced mechanical oscillations disrupt the ability of water molecules to nucleate on the surface of the magnetite nanocrystals. However, the ability of the magnetite crystal lattice to serve as a template for heterogeneous ice crystal nucleation is as yet unknown, particularly for particles in the 10-100 nm size range. Here we report that the addition of trace-amounts of finely-dispersed magnetite into ultrapure water samples reduces strongly the incidence of supercooling, as measured in experiments conducted using a controlled freezing apparatus with multiple thermocouples. SQUID magnetometry was used to quantify nanogram levels of magnetite in the water samples. We also report a relationship between the volume change of ice, and the degree of supercooling, that may indicate lower degassing during the crystallization of supercooled water. In addition to supporting the role of ice-crystal nucleation by biogenic magnetite in many tissues, magnetite nanocrystals could provide inexpensive, non-toxic, and non-pathogenic ice nucleating agents needed in a variety of industrial processes, as well as influencing the dynamics of ice crystal nucleation in many natural environments.

  2. Molarity (Aromic Density) of the Elements as Pure Crystals.

    ERIC Educational Resources Information Center

    Pauling, Linus; Herman, Zelek S.

    1985-01-01

    Provides background information for teachers on the atomic density of the elements as pure crystals. Atomic density is defined as the reciprocal of the atomic volume. Includes atomic-density diagrams which were prepared using the atomic-volume values given by Singman, supplemented by additional values for some allotropes. (JN)

  3. Combined Experimental and Theoretical Approach to the Kinetics of Magnetite Crystal Growth from Primary Particles

    PubMed Central

    2017-01-01

    It is now recognized that nucleation and growth of crystals can occur not only by the addition of solvated ions but also by accretion of nanoparticles, in a process called nonclassical crystallization. The theoretical framework of such processes has only started to be described, partly due to the lack of kinetic or thermodynamic data. Here, we study the growth of magnetite nanoparticles from primary particles—nanometer-sized amorphous iron-rich precursors—in aqueous solution at different temperatures. We propose a theoretical framework to describe the growth of the nanoparticles and model both a diffusion-limited and a reaction-limited pathway to determine which of these best describes the rate-limiting step of the process. We show that, based on the measured iron concentration and the related calculated concentration of primary particles at the steady state, magnetite growth is likely a reaction-limited process, and within the framework of our model, we propose a phase diagram to summarize the observations.

  4. Transmission Electron Microscopy of Magnetite Plaquettes in Orgueil

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Han, J.; Zolensky, M.

    2016-01-01

    Magnetite sometimes takes the form of a plaquette - barrel-shaped stack of magnetite disks - in carbonaceous chondrites (CC) that show evidence of aqueous alteration. The asymmetric nature of the plaquettes caused Pizzarello and Groy to propose magnetite plaquettes as a naturally asymmetric mineral that can indroduce symmetry-breaking in organic molecules. Our previous synchrotron X-ray computed microtomography (SXRCT) and electron backscatter diffraction (EBSD) analyses of the magnetite plaquettes in fifteen CCs indicate that magnetite plaquettes are composed of nearly parallel discs, and the crystallographic orientations of the discs change around a rotational axis normal to the discs surfaces. In order to further investigate the nanostructures of magnetite plaquettes, we made two focused ion beam (FIB) sections of nine magnetite plaquettes from a thin section of CI Orgueil for transmission electron microscope (TEM) analysis. The X-ray spectrum imaging shows that the magnetite discs are purely iron oxide Fe3O4 (42.9 at% Fe and 57.1 at% O), which suggest that the plaquettes are of aqueous origin as it is difficult to form pure magnetite as a nebular condensate. The selected area electron diffraction (SAED) patterns acquired across the plaquettes show that the magnetite discs are single crystals. SEM and EBSD analyses suggest that the planar surfaces of the magnetite discs belong to the {100} planes of the cubic inverse spinel structure, which are supported by our TEM observations. Kerridge et al. suggested that the epitaxial relationship between magnetite plaquette and carbonate determines the magnetite face. However, according to our TEM observation, the association of magnetite with porous networks of phyllosilicate indicates that the epitaxial relationship with carbonate is not essential to the formation of magnetite plaquettes. It was difficult to determine the preferred rotational orientation of the plaquettes due to the symmetry of the cubic structure

  5. Structural and magnetic characterization of electro-crystallized magnetite nanoparticles under constant current

    SciTech Connect

    Mosivand, Saba; Kazeminezhad, Iraj

    2015-10-15

    Graphical abstract: Structural and magnetic properties of electro-crystallized magnetite nanoparticles under constant current were studied. All samples were characterized using XRD, SEM, VSM, and Mössbauer spectrometry. - Highlights: • The effect of applied current on morphology and properties of Fe{sub 3}O{sub 4} is studied. • The particle size and morphology are controllable by adjusting the current. • The magnetization depends on particle size, type of surfactant and applied current. • The clear correlation between magnetization and the mean particle size is observed. - Abstract: The effect of applied current on the morphology, particle size, structure, and magnetic properties of magnetite nanoparticles prepared by electro-crystallization method was studied. The synthesis was performed in an electrochemical cell containing two iron electrodes and an aqueous solution of sodium sulfate, and either thiourea, sodium butanoate, or β-cyclodextrine as organic stabilizer. All the samples were characterized by XRD, SEM, VSM, and Mössbauer spectroscopy. X-ray diffraction patterns, clearly confirmed that all products have the cubic spinel Fe{sub 3}O{sub 4} crystal structure. Electron microscope images of the samples showed that their mean particle size is in the range 20–80 nm, and depends critically on the applied current and type of the organic additives. Specific magnetization of the samples at room temperature ranges from 60 to 90 A m{sup 2} kg{sup −1}, depending on the growth conditions. Room temperature Mössbauer spectra are typical of nonstoichiometric Fe{sub 3−δ}O{sub 4}, with a small excess of Fe{sup 3+}, 0.06 ≤ δ ≤ 0.17.

  6. Discovery of superparamagnetism in sub-millimeter-sized magnetite porous single crystals

    NASA Astrophysics Data System (ADS)

    Ma, Ji; Chen, Kezheng

    2016-10-01

    In this work, sub-millimeter-sized magnetite porous single crystals were found to exhibit unique superparamagnetism rather than the known ferrimagnetism. This superparamagnetism was intimately related to the hydrothermal formation process, during which high lattice stress of ca. 6 GPa and large lattice strain of ca. - 1.21 ×10-2 would change the exchange constants of α, β, and ν to concurrently meet criterions of (i) ν1 =ν2 = β, (ii) α1 =α2 = α, and (iii) αβ = 1. These criterions, deduced from the molecular-field theory, were proposed to be the general transition conditions for any ferrimagnetic material exhibiting superparamagnetism when their size was beyond their superparamagnetic size limit.

  7. Stress Wave Isolation by Purely Mechanical Topological Phononic Crystals

    PubMed Central

    Chaunsali, Rajesh; Li, Feng; Yang, Jinkyu

    2016-01-01

    We present an active, purely mechanical stress wave isolator that consists of short cylindrical particles arranged in a helical architecture. This phononic structure allows us to change inter-particle stiffness dynamically by controlling the contact angles of the cylinders. We use torsional travelling waves to control the contact angles, thereby imposing a desired spatio-temporal stiffness variation to the phononic crystal along the longitudinal direction. Such torsional excitation is a form of parametric pumping in the system, which results in the breakage of the time-reversal symmetry. We report that, in quasi-static sense, the system shows topologically non-trivial band-gaps. However, in a dynamic regime where the pumping effect is significant, these band-gaps become asymmetric with respect to the frequency and wavenumber domains in the dispersion relationship. By using numerical simulations, we show that such asymmetry has a direct correspondence to the topological invariant, i.e., Chern number, of the system. We propose that this asymmetry, accompanied by selective inter-band transition, can be utilized for directional isolation of the stress wave propagating along the phononic crystal. PMID:27477236

  8. Stress Wave Isolation by Purely Mechanical Topological Phononic Crystals

    NASA Astrophysics Data System (ADS)

    Chaunsali, Rajesh; Li, Feng; Yang, Jinkyu

    2016-08-01

    We present an active, purely mechanical stress wave isolator that consists of short cylindrical particles arranged in a helical architecture. This phononic structure allows us to change inter-particle stiffness dynamically by controlling the contact angles of the cylinders. We use torsional travelling waves to control the contact angles, thereby imposing a desired spatio-temporal stiffness variation to the phononic crystal along the longitudinal direction. Such torsional excitation is a form of parametric pumping in the system, which results in the breakage of the time-reversal symmetry. We report that, in quasi-static sense, the system shows topologically non-trivial band-gaps. However, in a dynamic regime where the pumping effect is significant, these band-gaps become asymmetric with respect to the frequency and wavenumber domains in the dispersion relationship. By using numerical simulations, we show that such asymmetry has a direct correspondence to the topological invariant, i.e., Chern number, of the system. We propose that this asymmetry, accompanied by selective inter-band transition, can be utilized for directional isolation of the stress wave propagating along the phononic crystal.

  9. Sub-micrometer-scale mapping of magnetite crystals and sulfur globules in magnetotactic bacteria using confocal Raman micro-spectrometry.

    PubMed

    Eder, Stephan H K; Gigler, Alexander M; Hanzlik, Marianne; Winklhofer, Michael

    2014-01-01

    The ferrimagnetic mineral magnetite Fe3O4 is biomineralized by magnetotactic microorganisms and a diverse range of animals. Here we demonstrate that confocal Raman microscopy can be used to visualize chains of magnetite crystals in magnetotactic bacteria, even though magnetite is a poor Raman scatterer and in bacteria occurs in typical grain sizes of only 35-120 nm, well below the diffraction-limited optical resolution. When using long integration times together with low laser power (<0.25 mW) to prevent laser induced damage of magnetite, we can identify and map magnetite by its characteristic Raman spectrum (303, 535, 665 cm(-1)) against a large autofluorescence background in our natural magnetotactic bacteria samples. While greigite (cubic Fe3S4; Raman lines of 253 and 351 cm(-1)) is often found in the Deltaproteobacteria class, it is not present in our samples. In intracellular sulfur globules of Candidatus Magnetobacterium bavaricum (Nitrospirae), we identified the sole presence of cyclo-octasulfur (S8: 151, 219, 467 cm(-1)), using green (532 nm), red (638 nm) and near-infrared excitation (785 nm). The Raman-spectra of phosphorous-rich intracellular accumulations point to orthophosphate in magnetic vibrios and to polyphosphate in magnetic cocci. Under green excitation, the cell envelopes are dominated by the resonant Raman lines of the heme cofactor of the b or c-type cytochrome, which can be used as a strong marker for label-free live-cell imaging of bacterial cytoplasmic membranes, as well as an indicator for the redox state.

  10. New Insights into the Origin of Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keptra, Katie L.; Clemett, S. J.; Wentworth S. J.; Mckay, D. S.; Gibson, E. K., Jr.

    2010-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks believed to have formed approx.3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose ori gins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated: that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships between the carbonate disks, their associated magnetites and the orthopyroxene matrix in which they are embedded [1]. Comparison of these results with experimental thermal decomposition studies of sideritic carbonates conducted under a range of heating scenarios suggests that the magnetite nanocrystals in the ALH84001 carbonate disks are not the products of thermal decomposition.

  11. Field Ion Microscopy and Atom Probe Tomography of Metamorphic Magnetite Crystals

    NASA Technical Reports Server (NTRS)

    Kuhlman, K.; Martens, R. L.; Kelly, T. F.; Evans, N. D.; Miller, M. K.

    2001-01-01

    Magnetite has been analysed using Field Ion Microscopy (FIM) and Atom Probe Tomography (APT), highly attractive techniques for the nanoanalysis of geological materials despite the difficulties inherent in analyzing semiconducting and insulating materials. Additional information is contained in the original extended abstract.

  12. Origin of Magnetite Crystals in Martian Meteorite ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K.L.; Clemett, S.J.; McKay, D.S.; Gibson, E. K.; Wentworth, S. J.

    2010-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks which are believed to have precipitated approx.3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these Fe3O4 are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of Fe3O4 and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded [1]. We focus this discussion on the composition of ALH84001 magnetites and then compare these observations with those from our thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios.

  13. New insights into the origin of magnetite crystals in ALH84001 carbonate disks

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S. J.; Wentworth, S. J.; McKay, D. S.; Gibson, E. K.

    2009-01-01

    Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks which are believed to have precipitated approximately 3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these Fe3O4 are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of Fe3O4 and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. We focus this discussion on the composition of ALH84001 magnetites and then compare these observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios.

  14. Unidirectional growth of pure and L-lysine added ADP crystals from aqueous solution

    NASA Astrophysics Data System (ADS)

    Salarian, Samaneh; Dizaji, Hamid Rezagholipour

    2014-01-01

    Pure and L-lysine added ammonium dihydrogen phosphate (ADP) crystals were grown in the <001> direction by Sankaranarayanan-Ramasamy (S-R) method. The grown crystals were characterized by X-Ray diffractometry (XRD), UV-Vis spectroscopy, Fourier Transform Infrared (FT-IR) and Vicker's Microhardness analysis. XRD spectrum of each of the grown crystals proved its crystallinity. The crystals showed good transparency in the entire visible region. FT-IR spectra of the specimens revealed the presence of functional groups in them. The hardness of the pure and L-lysine added ADP crystals were measured and that of the added one was found higher. Meanwhile, it was found that the ADP crystals (pure and L-lysine added) grown by S-R method had higher hardness compared to ADP crystal grown by conventional method.

  15. Growth and characterization of pure and glycine doped cadmium thiourea sulphate (GCTS) crystals

    NASA Astrophysics Data System (ADS)

    Lawrence, M.; Thomas Joseph Prakash, J.

    2012-06-01

    The pure and glycine doped cadmium thiourea sulphate (GCTS) single crystals were grown successfully by slow evaporation method at room temperature. The concentration of dopant in the mother solution was 1 mol%. There is a change in unit cell. The Fourier transform infrared spectroscopy study confirms the incorporation of glycine into CTS crystal. The doped crystals are optically better and more transparent than the pure ones. The dopant increases the hardness value of the material. The grown crystals were also subjected to thermal and NLO studies.

  16. Study of radiation hardness of pure CsI crystals for Belle-II calorimeter

    NASA Astrophysics Data System (ADS)

    Boyarintsev, A.; Boyarintseva, Y.; Gektin, A.; Shiran, N.; Shlyakhturov, V.; Taranyuk, V.; Timoshenko, N.; Bobrov, A.; Garmash, A.; Golkovski, M.; Kuzmin, A.; Matvienko, D.; Savrovski, P.; Shebalin, V.; Shwartz, B.; Vinokurova, A.; Vorobyev, V.; Zhilich, V.; Krumshtein, Z. V.; Nozdrin, A. A.; Olshevsky, A. G.

    2016-03-01

    A study of the radiation hardness of pure CsI crystals 30 cm long was performed with a uniformly absorbed dose of up to 14.3 krad. This study was initiated by the proposed upgrade of the end cap calorimeter of the Belle-II detector, using pure CsI crystals. A set of 14 crystals of truncated pyramid shape used in this study was produced at the Institute for Scintillation Materials NAS from 14 different ingots grown with variations of the growing technology. Interrelationship of crystal scintillation characteristics, radiation hardness and the growing technology was observed.

  17. Isolation of isoelectrically pure cholera toxin for crystallization

    NASA Astrophysics Data System (ADS)

    Spangler, Brenda D.; Westbrook, Edwin M.

    1991-03-01

    We have determined that the failure of cholera toxin to crystallize well results from its isoelectric heterogeneity, which is probably due to a post-translational process such as deamidation of its B subunit. Every sample of cholera toxin we have examined from commercial or academic suppliers has been heterogeneous; heterogeneous cholera toxin does not crystallize satisfactorily. We have overcome this problem by using ion-exchange fast protein liquid chromatography (FPLC) to obtain an isoelectrically homogeneous species of cholera toxin. Homogeneous cholera toxin crystallizes readily, forming single, nonmosaic crystals suitable for X-ray diffraction studies. For this process, protein was applied to a MonoQ ion-exchange column, then eluted with an isocratic low salt buffer followed by a linear salt gradient (0-100 mM NaCl). Column fractions were analyzed on isoelectric focusing gels, and those fractions containing the desired homogeneous species were pooled and concentrated. Crystals formed within 24 to 48 h in a MOPS/PEG buffer, which made use of slow isoelectric precipitation to induce crystallization.

  18. Isolation of isoelectrically pure cholera toxin for crystallization

    SciTech Connect

    Spangler, B.D.; Westbrook, E.M.

    1989-01-01

    We have determined that the failure of cholera toxin to crystallize well results from its isoelectric heterogeneity, which is probably due to a post-translational process such as deamidation of its B subunit. Every sample of cholera toxin we have examined from commercial or academic suppliers has been heterogeneous; heterogeneous cholera toxin does not crystallize satisfactorily. We have overcome this problem by using ion-exchange fast protein liquid chromatography (FPLC) to obtain an isoelectrically homogeneous species of cholera toxin. Homogeneous cholera toxin crystallizes readily, forming single, nonmosaic crystals suitable for x-ray diffraction studies. For this process, protein was applied to a MonoQ ion-exchange column, then eluted with an isocratic low salt buffer followed by a linear salt gradient (0-100 mM NaCl). Column fractions were analyzed on isoelectric focusing gels, and those fractions containing the desired homogeneous species were pooled and concentrated. Crystals formed within 24 to 48 hours in a MOPS/PEG buffer, which made use of slow isoelectric precipitation to induce crystallization. 23 refs., 6 figs.

  19. Studies on various properties of pure and Li-doped Barium Hydrogen Phosphate (BHP) single crystals

    NASA Astrophysics Data System (ADS)

    Nallamuthu, D.; Selvarajan, P.; Freeda, T. H.

    2010-12-01

    Single crystals of pure and Li-doped barium hydrogen phosphate (BHP) were grown by solution method with gel technique. Various properties of the harvested crystals were studied by carrying out single crystal and powder XRD, FTIR, TG/DTA, microhardness and dielectric studies. Atomic absorption study was carried out for Li-doped BHP crystal to check the presence of Li dopants. Unit cell dimensions and diffracting planes of the grown crystals have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Density of the grown crystals was calculated using the XRD data. Thermal stability of the samples was checked by TG/DTA studies. Mechanical and dielectric characterizations of the harvested pure and Li-doped BHP crystals reveal the mechanical strength and ferroelectric transition. The observed results are reported and discussed.

  20. Growth and characterization of pure and Cadmium chloride doped KDP Crystals grown by gel medium

    NASA Astrophysics Data System (ADS)

    Kalaivani, M. S.; Asaithambi, T.

    2016-10-01

    Crystal growth technology provides an important basis for many industrial branches. Crystals are the unrecognized pillars of modern technology. Without crystals, there is no electronic industry, no photonic industry, and no fiber optic communications. Single crystals play a major role and form the strongest base for the fast growing field of engineering, science and technology. Crystal growth is an interdisciplinary subject covering physics, chemistry, material science, chemical engineering, metallurgy, crystallography, mineralogy, etc. In past few decades, there has been a keen interest on crystal growth processes, particularly in view of the increasing demand of materials for technological applications. Optically good quality pure and metal doped KDP crystals have been grown by gel method at room temperature and their characterization have been studied. Gel method is a much uncomplicated method and can be utilized to synthesize crystals which are having low solubility. Potassium dihydrogen orthophosphate KH2PO4 (KDP) continues to be an interesting material both academically and industrially. KDP is a representative of hydrogen bonded materials which possess very good electro - optic and nonlinear optical properties in addition to interesting electrical properties. Due to this interesting properties, we made an attempt to grow pure and cadmium chloride doped KDP crystals in various concentrations (0.002, 0.004, 0.006, 0.008 and 0.010) using gel method. The grown crystals were collected after 20 days. We get crystals with good quality and shaped. The dc electrical conductivity (resistance, capacitance and dielectric constant) values were measured at frequencies in the range of 1 KHZ and 100 HZ of pure and cadmium chloride added crystal with a temperature range of 400C to 1300C using simple two probe setup with Q band digital LCR meter present in our lab. The electrical conductivity increases with increase of temperature. The dielectric constants of metal doped KDP

  1. Influence of Growth Conditions on Magnetite Nanoparticles Electro-Crystallized in the Presence of Organic Molecules

    PubMed Central

    Mosivand, Saba; Monzon, Lorena M. A.; Kazeminezhad, Iraj; Coey, J. Michael D.

    2013-01-01

    Magnetite nanoparticles were synthesized by electrocrystallization in the presence of thiourea or sodium butanoate as an organic stabilizer. The synthesis was performed in a thermostatic electrochemical cell containing two iron electrodes with an aqueous solution of sodium sulfate as electrolyte. The effects of organic concentration, applied potential and growth temperature on particle size, morphology, structure and magnetic properties were investigated. The magnetite nanoparticles were characterized by X-ray diffraction, electron microscopy, magnetometry and Mössbauer spectrometry. When the synthesis is performed in the presence of sodium butanoate at 60 °C, a paramagnetic ferric salt is obtained as a second phase; it is possible to avoid formation of this phase, increase the specific magnetization and improve the structure of the oxide particles by tuning the growth conditions. Room-temperature magnetization values range from 45 to 90 Am2kg−1, depending on the particle size, type of surfactant and synthesis conditions. Mössbauer spectra, which were recorded at 290 K for all the samples, are typical of nonstoichiometric Fe3−δO4, with a small excess of Fe3+, 0.05 ≤ δ ≤ 0.15. PMID:23685871

  2. Studies on optical properties of pure and Mg2+ doped ZTS single crystal

    NASA Astrophysics Data System (ADS)

    Sumithra Devi, M.; Arthi, A. P.; Thamizharasan, K.

    2014-09-01

    Single crystal of semiorganic nonlinear optical material of pure and Mg2+ doped ZTS were grown by slow evaporation technique from its aqueous solution. The grown crystal was characterized by single crystal XRD to determine the cell parameters. The Mg2+ doped was characterized by SEM and EDX spectrum. The chemical composition of both the pure ZTS and doped Mg2+ crystals were determined by Fourier transform infrared (FTIR). The optical absorption spectrum recorded in the wavelength was ranged from 200 to 2500 nm and its energy gap (Eg) for both pure ZTS is 4.47 eV and doped Mg2+ is 4.42 eV. The mechanical strength of the grown crystal was found from Vicker's microhardness measurements. It showed that pure and doped ZTS crystals are soft in nature. The dielectric measurement was carried out to study the different polarization mechanism and conductivity of the crystal. Photoconductivity studies revealed that the positive photoconductivity of the both were considered as grown crystals.

  3. Crystal nucleation in glass-forming alloy and pure metal melts under containerless and vibrationless conditions

    NASA Technical Reports Server (NTRS)

    Turnbull, D.

    1979-01-01

    Crystal nucleation behavior in metallic alloys known to form glasses in melt quenching was characterized and from this characterization the possibility that massive amounts of certain alloys could be slow cooled to the glass state was assessed. Crystal nucleation behavior of pure liquid metals was examined experimentally, under containerless conditions, and theoretically.

  4. Experimental Deformation of Magnetite

    NASA Astrophysics Data System (ADS)

    Till, J. L.; Rybacki, E.; Morales, L. F. G.

    2015-12-01

    Magnetite is an important iron ore mineral and the most prominent Fe-oxide phase in the Earth's crust. The systematic occurrence of magnetite in zones of intense deformation in oceanic core complexes suggests that it may play a role in strain localization in some silicate rocks. We performed a series of high-temperature deformation experiments on synthetic magnetite aggregates and natural single crystals to characterize the rheological behavior of magnetite. As starting material, we used fine-grained magnetite powder that was hot isostatically pressed at 1100°C for several hours, resulting in polycrystalline material with a mean grain size of around 40 μm and containing 3-5% porosity. Samples were deformed to 15-20% axial strain under constant load (approximating constant stress) conditions in a Paterson-type gas apparatus for triaxial deformation at temperatures between 900 and 1100°C and 300 MPa confining pressure. The aggregates exhibit typical power-law creep behavior. At high stresses, samples deformed by dislocation creep exhibit stress exponents close to 3, revealing a transition to near-Newtonian creep with stress exponents around 1.3 at lower stresses. Natural magnetite single crystals deformed at 1 atm pressure and temperatures between 950°C and 1150 °C also exhibit stress exponents close to 3, but with lower flow stresses and a lower apparent activation energy than the aggregates. Such behavior may result from the different oxygen fugacity buffers used. Crystallographic-preferred orientations in all polycrystalline samples are very weak and corroborate numerical models of CPO development, suggesting that texture development in magnetite may be inherently slow compared with lower symmetry phases. Comparison of our results with experimental deformation data for various silicate minerals suggests that magnetite should be weaker than most silicates during ductile creep in dry igneous rocks.

  5. Growth of pure and doped KMgF 3 single crystals

    NASA Astrophysics Data System (ADS)

    Darabont, Al.; Neamţu, C.; Fǎrcaş, S. I.; Borodi, Gh.

    1996-11-01

    The preparation of pure and doped KMgF 3 single crystals using the Czochralski and Bridgman methods is described. The crystals were obtained using a home-made Czochralski-type device that allows also the growth of single crystals by the vertical Bridgman method (which we used mainly for the preparation of doped single crystals). The starting materials were KF or KHF 2, MgF 2 and, for the preparation of Mn 2+ or Ni 2+ doped crystals, KMnF 3 or KNiF 3. The crystals were produced using pulling rates of 4-5 mm h -1 and a rotation of 4-6 rpm. We have obtained good quality, transparent, both pure and Mn 2+ or Ni 2+ doped KMgF 3 single crystals of approximately 1 cm in diameter and 7.5-8.0 cm long. The transmission spectrum (in the range of 200-800 nm) and the absorption spectrum (in the range of 400-5000 cm -1) of the pure single crystals are given.

  6. DC electrical conductivity measurements for pure and titanium oxide doped KDP Crystals grown by gel medium

    NASA Astrophysics Data System (ADS)

    Mareeswaran, S.; Asaithambi, T.

    2016-10-01

    Now a day's crystals are the pillars of current technology. Crystals are applied in various fields like fiber optic communications, electronic industry, photonic industry, etc. Crystal growth is an interesting and innovative field in the subject of physics, chemistry, material science, metallurgy, chemical engineering, mineralogy and crystallography. In recent decades optically good quality of pure and metal doped KDP crystals have been grown by gel growth method in room temperature and its characterizations were studied. Gel method is a very simple and one of the easiest methods among the various crystal growth methods. Potassium dihydrogen phosphate KH2PO4 (KDP) continues to be an interesting material both academically and technologically. KDP is a delegate of hydrogen bonded materials which possess very good electrical and nonlinear optical properties in addition to interesting electro-optic properties. We made an attempt to grow pure and titanium oxide doped KDP crystals with various doping concentrations (0.002, 0.004, 0.006, 0.008 and 0.010) using gel method. The grown crystals were collected after 20 days. We get crystals with good quality and shaped crystals. The dc electrical conductivity (resistance, capacitance and dielectric constant) values of the above grown crystals were measured at two different frequencies (1KHz and 100 Hz) with a temperature range of 500C to 1200C using simple two probe setup with Q band digital LCR meter present in our lab. The electrical conductivity increases with the increase of temperature. Dielectric constants value of titanium oxide doped KDP crystal was slightly decreased compared with pure KDP crystals. Results were discussed in details.

  7. Morphological Evidence for an Exclusively Inorganic Origin for Magnetite in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.; Morris, R. V.; Brearley, A. J.; Lauer, H. V., Jr.; Treiman, A.; Zolensky, M. E.; Schwandt, C. S.; Lofgren, G. E.; McKay, G. A.

    2003-01-01

    The origin of magnetite crystals in Martian Meteorite ALH84001 is the focus of a debate about the possibility of past (and present) life on Mars. McKay et al. originally suggested that some of the magnetite crystals associated with carbonate globules in Martian Meteorite ALH84001 are biogenic in ori-gin, because they are single magnetic domain, free of crystalline defects, chemically pure, and coexist with other metastable phases in apparent disequilibrium. Thomas-Keprta et al. reported that a subpopulation of magnetite crystals (approx. 25%) associated with carbonate globules in ALH84001 and magnetite crystals produced by magnetotactic bacterial strain MV-1 have similar morphologies with crystal elongation along the [111] crystallographic axis that they describe as "truncated hexa-octahedral" ([111-THO]) magnetite. Along with several other properties, the [111]-THO morphology has been proposed to constitute a biomarker (i.e., formed only in biogenic processes), so that the presence of [111]-THO magnetite in ALH84001 may be evidence for past life on Mars.

  8. Nonlinear anisotropic description for shocked single crystals: Thermoelastic response and pure mode wave propagation

    NASA Astrophysics Data System (ADS)

    Winey, J. M.; Gupta, Y. M.

    2004-08-01

    An anisotropic continuum framework for describing the nonlinear thermoelastic response of shocked single crystals has been developed. Using this framework, the propagation of large amplitude stress waves along arbitrary directions in crystals of any symmetry can be examined. We developed an incremental approach, where the reference state for the dynamical variables and the material properties is updated throughout the calculation. Results from our incremental approach are in excellent agreement with the results from a finite strain formulation. Using a finite-difference wave propagation code, we performed numerical simulations of large amplitude elastic wave propagation in single crystals. Results of impact loading simulations for quartz and sapphire single crystals are presented. The framework developed was also useful for examining the propagation of pure mode nonlinear waves for various crystal symmetries. Our calculations showed that pure longitudinal waves resulted from impact loading along any rotational symmetry axis for all crystal symmetry classes. Differences between pure mode wave propagation for linear and nonlinear elastic deformation are discussed.

  9. Growth and characterization of pure and semiorganic nonlinear optical Lithium Sulphate admixtured l-alanine crystal

    NASA Astrophysics Data System (ADS)

    Vela, T.; Selvarajan, P.; Freeda, T. H.; Balasubramanian, K.

    2013-04-01

    Lithium sulphate admixtured l-alanine (LSLA) salt was synthesized and the solubility of the commercially available l-alanine and the synthesized LSLA sample was determined in de-ionized water at various temperatures. In accordance with the solubility data, the saturated aqueous solutions of l-alanine and lithium admixtured l-alanine were prepared separately and the single crystals of the samples were grown by the solution method with a slow evaporation technique. Studying single x-ray diffraction shows that pure and LSLA crystal belong to the orthorhombic system with a non-centrosymmetric space group P212121. Using the powder x-ray diffraction study, the crystallinity of the grown crystals is confirmed and the diffraction peaks are indexed. The various functional groups present in the pure and LSLA crystal are elucidated from Fourier transform infrared spectroscopy study. UV-visible transmittance is recorded to study the optical transmittance range for the grown crystals. The powder second harmonic generation test confirms the nonlinear optical property of the grown crystals. From the microhardness test, the hardness of the grown crystals is estimated. The dielectric behaviour, such as the dielectric constant and the loss of the sample, are measured as a function of temperature and frequency. The ac conductivity of the grown crystals is also studied and the activation energy is calculated.

  10. Near-pure vapor condensation in the Martian atmosphere: CO2 ice crystal growth

    NASA Astrophysics Data System (ADS)

    Listowski, C.; Määttänen, A.; Riipinen, I.; Montmessin, F.; Lefèvre, F.

    2013-10-01

    A new approach is presented to model the condensational growth of carbon dioxide (CO2) ice crystals on Mars. These condensates form in very particular conditions. First, ˜95% of the atmosphere is composed of CO2 so that near-pure vapor condensation takes place. Second, the atmosphere is rarefied, having dramatic consequences on the crystal growth. Indeed, the subsequently reduced efficiency of heat transport helps maintain a high temperature difference between the crystal surface and the environment, inhibiting the growth. Besides, the Stefan flow which would have been expected to increase the growth rate of the crystal, because of the near-pure vapor condensation, is negligible. We show that the heritage of the convenient and explicit linearized crystal growth rate formula used for Earth clouds, initially derived for a trace gas, has to be reconsidered in the case of near-pure vapor condensation for high saturation ratios that appear to be common in the Martian mesosphere. Nevertheless, by comparing our approach with a more complex condensation model, valid for all atmospheric conditions and all vapor abundances, we show that a very simple set of equations can still be used to efficiently reproduce the CO2 ice crystal growth rate. Our model, referred to as the CLASSIC model here, provides similar crystal growth rates than the traditionally used linearized growth rate models at low supersaturations but predicts lower crystal growth rates at high supersaturations. It can thus be used to model the condensational growth of CO2 ice crystals in the mesosphere where high supersaturations are observed.

  11. Structure and morphology of magnetite anaerobically-produced by a marine magnetotactic bacterium and a dissimilatory iron-reducing bacterium

    USGS Publications Warehouse

    Sparks, N.H.C.; Mann, S.; Bazylinski, D.A.; Lovley, D.R.; Jannasch, H.W.; Frankel, R.B.

    1990-01-01

    Intracellular crystals of magnetite synthesized by cells of the magnetotactic vibroid organism, MV-1, and extracellular crystals of magnetite produced by the non-magnetotactic dissimilatory iron-reducing bacterium strain GS-15, were examined using high-resolution transmission electron microscopy, electron diffraction and 57Fe Mo??ssbauer spectroscopy. The magnetotactic bacterium contained a single chain of approximately 10 crystals aligned along the long axis of the cell. The crystals were essentially pure stoichiometric magnetite. When viewed along the crystal long axis the particles had a hexagonal cross-section whereas side-on they appeared as rectangules or truncated rectangles of average dimension, 53 ?? 35 nm. These findings are explained in terms of a three-dimensional morphology comprising a hexagonal prism of {110} faces which are capped and truncated by {111} end faces. Electron diffraction and lattice imaging studies indicated that the particles were structurally well-defined single crystals. In contrast, magnetite particles produced by the strain, GS-15 were irregular in shape and had smaller mean dimensions (14 nm). Single crystals were imaged but these were not of high structural perfection. These results highlight the influence of intracellular control on the crystallochemical specificity of bacterial magnetites. The characterization of these crystals is important in aiding the identification of biogenic magnetic materials in paleomagnetism and in studies of sediment magnetization. ?? 1990.

  12. Magnetite nano-islands on silicon-carbide with graphene

    DOE PAGES

    Anderson, Nathaniel A.; Zhang, Qiang; Hupalo, Myron; ...

    2017-01-05

    X-ray magnetic circular dichroism (XMCD) measurements of iron nano-islands grown on graphene and covered with a Au film for passivation reveal that the oxidation through defects in the Au film spontaneously leads to the formation of magnetite nano-particles (i.e, Fe3O4). The Fe nano-islands (20 and 75 monolayers; MLs) are grown on epitaxial graphene formed by thermally annealing 6HSiC( 0001) and subsequently covered, in the growth chamber, with nominal 20 layers of Au. Our X-ray absorption spectroscopy and XMCD measurements at applied magnetic fields show that the thin film (20 ML) is totally converted to magnetite whereas the thicker lm (75more » ML) exhibits properties of magnetite but also those of pure metallic iron. Temperature dependence of the XMCD signal (of both samples) shows a clear transition at TV ≈ 120 K consistent with the Verwey transition of bulk magnetite. These results have implications on the synthesis of magnetite nano-crystals and also on their regular arrangements on functional substrates such as graphene.« less

  13. Electromagnetic waves in uniaxial crystals with metallized boundaries: Mode conversion, pure reflections, and bulk polaritons

    SciTech Connect

    Alshits, V. I. Lyubimov, V. N.; Radowicz, A.

    2007-02-15

    A theory is constructed for the reflection of plane electromagnetic waves in uniaxial crystals with a positive definite permittivity tensor and an arbitrarily oriented metallized boundary. The problem is solved both for general-position orientations corresponding to three-partial reflection and for special conditions allowing two-partial reflections: mode conversions when the incident and reflected waves belong to different sheets of the refraction surface and 'pure' reflections when both waves belong to the same sheet. The space of pure reflections is shown to be formed by two types of optical-axis orientations: arbitrary directions in the plane of the crystal surface and in the plane of incidence. The configurations of the conversion surface for optically positive and negative crystals are investigated. A subspace of pure reflections that transform into one-partial bulk polaritons with the energy flux parallel to the surface at grazing incidence has been found. The domain of existence of such bulk eigenmodes is bounded by two 'lines' of solutions. These are any directions along the boundary containing the optical axis for ordinary polaritons and the direction along the projection of the optical axis onto the surface at an arbitrary orientation of the axis with respect to the boundary for extraordinary polaritons.

  14. Submicron magnetite grains and carbon compounds in Martian meteorite ALH84001: inorganic, abiotic formation by shock and thermal metamorphism.

    PubMed

    Treiman, Allan H

    2003-01-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe(3)O(4), reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered).

  15. Rheology of Pure Glasses and Crystal Bearing Melts: from the Newtonian Field to the Brittle Onset

    NASA Astrophysics Data System (ADS)

    Cordonnier, B.; Caricchi, L.; Pistone, M.; Castro, J. M.; Hess, K.; Dingwell, D. B.

    2010-12-01

    The brittle-ductile transition remains a central question of modern geology. If rocks can be perceived as a granular flow on geological time-scale, their behavior is brittle in dynamic areas. Understanding rock failure conditions is the main parameter in mitigating geological risks, more specifically the eruptive style transitions from effusive to explosive. If numerical simulations are the only way to fully understanding the physical processes involved, we are in a strong need of an experimental validation of the proposed models. here we present results obtained under torsion and uni-axial compression on both pure glasses and crystal bearing melts. We characterized the brittle onset of two phases magmas from 0 to 65% crystals. The strain-rates span a 5 orders magnitude range, from the Newtonian flow to the Brittle field (10-5 - 100 s-1). We particularly emphasize the time dependency of the measured rheology. The materials tested are a borosilicate glass from the National Bureau of Standards, a natural sample from Mt Unzen volcano and a synthetic sample. The lattest is an HPG8 melt with 7% sodium mole excess. The particles are quasi-isometric corundum crystalschosen for their shape and integrity under the stress range investigated. The crystal fraction ranges from 0 to 0.65. Concerning pure magmas, we recently demonstrated that the material passes from a Newtonian to a non-Nemtonian behavior with increasing strain-rate. This onset can mostly be explained by viscous-heating effects. However, for even greater strain-rates, the material cracks and finally fail. The brittle onset is here explained with the visco-elastic theory and corresponds to a Deborah number greater than 10-2. Concerning crystal bearing melts the departure from the Newtonian state is characterized by two effects: a shear-thinning and a time weakening effect. The first one is instantaneous and loading-unloading cyclic tests suggest an elastic contribution of the crystal network. The second one

  16. Studies on gel-grown pure and strontium-modified lanthanum tartrate crystals

    NASA Astrophysics Data System (ADS)

    Firdous, A.; Quasim, I.; Ahmad, M. M.; Kotru, P. N.

    2009-07-01

    Crystals of pure and strontium-modified lanthanum tartrate bearing composition (La) 1-x(Sr) xC 4H 4O 6· nH 2O (where x=0, 0.04, 0.10, 0.15; n=5,5,6,8) were obtained using gel method. The materials were studied using CH analysis, X-ray powder diffraction, FTIR, EDAX and thermoanalytical techniques. X-ray powder diffraction results analyzed by using suitable software suggest that while unmodified lanthanum tartrate has a monoclinic structure with the space group P 21, the entry of strontium into its lattice changes the system to orthorhombic with the space group P 2121. The unit cell volume is observed to decrease with increase in the concentration of strontium in lanthanum tartrate. Thermal analysis suggests that pure lanthanum tartrate starts decomposing at 41.31 °C whereas the strontium-modified lanthanum tartrate brings about better thermal stability which increases with an increase in strontium concentration. The percentage weight loss calculations from the thermogram supplemented by EDAX, CH analysis and FTIR spectroscopy suggest that both unmodified and strontium-modified lanthanum tartrate spherulitic crystals contain water of hydration; the amount of water of hydration being different for crystals with different content of strontium.

  17. Pure crystal orientation and anisotropic charge transport in large-area hybrid perovskite films

    PubMed Central

    Cho, Namchul; Li, Feng; Turedi, Bekir; Sinatra, Lutfan; Sarmah, Smritakshi P.; Parida, Manas R.; Saidaminov, Makhsud I.; Murali, Banavoth; Burlakov, Victor M.; Goriely, Alain; Mohammed, Omar F.; Wu, Tom; Bakr, Osman M.

    2016-01-01

    Controlling crystal orientations and macroscopic morphology is vital to develop the electronic properties of hybrid perovskites. Here we show that a large-area, orientationally pure crystalline (OPC) methylammonium lead iodide (MAPbI3) hybrid perovskite film can be fabricated using a thermal-gradient-assisted directional crystallization method that relies on the sharp liquid-to-solid transition of MAPbI3 from ionic liquid solution. We find that the OPC films spontaneously form periodic microarrays that are distinguishable from general polycrystalline perovskite materials in terms of their crystal orientation, film morphology and electronic properties. X-ray diffraction patterns reveal that the film is strongly oriented in the (112) and (200) planes parallel to the substrate. This film is structurally confined by directional crystal growth, inducing intense anisotropy in charge transport. In addition, the low trap-state density (7.9 × 1013 cm−3) leads to strong amplified stimulated emission. This ability to control crystal orientation and morphology could be widely adopted in optoelectronic devices. PMID:27830694

  18. Pure crystal orientation and anisotropic charge transport in large-area hybrid perovskite films

    NASA Astrophysics Data System (ADS)

    Cho, Namchul; Li, Feng; Turedi, Bekir; Sinatra, Lutfan; Sarmah, Smritakshi P.; Parida, Manas R.; Saidaminov, Makhsud I.; Murali, Banavoth; Burlakov, Victor M.; Goriely, Alain; Mohammed, Omar F.; Wu, Tom; Bakr, Osman M.

    2016-11-01

    Controlling crystal orientations and macroscopic morphology is vital to develop the electronic properties of hybrid perovskites. Here we show that a large-area, orientationally pure crystalline (OPC) methylammonium lead iodide (MAPbI3) hybrid perovskite film can be fabricated using a thermal-gradient-assisted directional crystallization method that relies on the sharp liquid-to-solid transition of MAPbI3 from ionic liquid solution. We find that the OPC films spontaneously form periodic microarrays that are distinguishable from general polycrystalline perovskite materials in terms of their crystal orientation, film morphology and electronic properties. X-ray diffraction patterns reveal that the film is strongly oriented in the (112) and (200) planes parallel to the substrate. This film is structurally confined by directional crystal growth, inducing intense anisotropy in charge transport. In addition, the low trap-state density (7.9 × 1013 cm-3) leads to strong amplified stimulated emission. This ability to control crystal orientation and morphology could be widely adopted in optoelectronic devices.

  19. pH-responsive lyotropic liquid crystals for the preparation of pure cubic zirconia nanoparticles

    NASA Astrophysics Data System (ADS)

    He, Wei Yan; Liu, Jin Rong; He, Zhang; Cao, Zhen Zhu; Li, Cai Hong; Gao, Yan Fang

    2016-07-01

    We present a lyotropic liquid crystal system consisting of SDS/Triton X-100/water at 25 °C. This system is respond to pH variations with a phase switch. When pH is altered from alkaline (pH 13) to acidic (pH 2) conditions, phase change occurs from a bicontinuous hexagonal phase to a partially hexagonal phase until it disappears. The hexagonal phase under alkaline conditions is stable. Thus, this system is an ideal candidate for the preparation of pure cubic ZrO2 nanoparticles. XRD results confirm that the as-synthesized powder is composed of pure cubic ZrO2. These nanoparticles also exhibit a thermal stability of up to 800 °C. The size and morphological characteristics of the nanoparticles are greatly affected by ZrOCl2 concentration. The mechanism of zirconia nanoparticle synthesis in a lyotropic hexagonal phase was proposed.

  20. Morphology evolution and pure red upconversion mechanism of β-NaLuF4 crystals

    PubMed Central

    Lin, Hao; Xu, Dekang; Li, Anming; Teng, Dongdong; Yang, Shenghong; Zhang, Yueli

    2016-01-01

    A series of β-NaLuF4 crystals were synthesized via a hydrothermal method. Hexagonal phase microdisks, microprisms, and microtubes were achieved by simply changing the amount of citric acid in the initial reaction solution. Pure red upconversion (UC) luminescence can be observed in β-NaLuF4:Yb3+, Tm3+, Er3+ and Li+ doped β-NaLuF4:20% Yb3+, 1% Tm3+, 20% Er3+. Based on the rate equations, we report the theoretical model about the pure red UC mechanism in Yb3+/Tm3+/Er3+ doped system. It is proposed that the pure red UC luminescence is mainly ascribed to the energy transfer UC from Tm3+:3F4 → 3H6 to Er3+:4I11/2 → 4F9/2 and the cross-relaxation (CR) effect [Er3+:4S3/2 + 4I15/2 → 4I9/2 + 4I13/2] rather than the long-accepted mechanism [CR process among Er3+:4F7/2 + 4I11/2 → 4F9/2 + 4F9/2]. In addition, compared to the Li+-free counterpart, the pure red UC luminescence in β-NaLuF4:20% Yb3+, 1% Tm3+, 20% Er3+ with 15 mol% Li+ doping is enhanced by 13.7 times. This study provides a general and effective approach to obtain intense pure red UC luminescence, which can be applied to other synthetic strategies. PMID:27306720

  1. Morphology evolution and pure red upconversion mechanism of β-NaLuF4 crystals.

    PubMed

    Lin, Hao; Xu, Dekang; Li, Anming; Teng, Dongdong; Yang, Shenghong; Zhang, Yueli

    2016-06-16

    A series of β-NaLuF4 crystals were synthesized via a hydrothermal method. Hexagonal phase microdisks, microprisms, and microtubes were achieved by simply changing the amount of citric acid in the initial reaction solution. Pure red upconversion (UC) luminescence can be observed in β-NaLuF4:Yb(3+), Tm(3+), Er(3+) and Li(+) doped β-NaLuF4:20% Yb(3+), 1% Tm(3+), 20% Er(3+). Based on the rate equations, we report the theoretical model about the pure red UC mechanism in Yb(3+)/Tm(3+)/Er(3+) doped system. It is proposed that the pure red UC luminescence is mainly ascribed to the energy transfer UC from Tm(3+):(3)F4 → (3)H6 to Er(3+):(4)I11/2 → (4)F9/2 and the cross-relaxation (CR) effect [Er(3+):(4)S3/2 + (4)I15/2 → (4)I9/2 + (4)I13/2] rather than the long-accepted mechanism [CR process among Er(3+):(4)F7/2 + (4)I11/2 → (4)F9/2 + (4)F9/2]. In addition, compared to the Li(+)-free counterpart, the pure red UC luminescence in β-NaLuF4:20% Yb(3+), 1% Tm(3+), 20% Er(3+) with 15 mol% Li(+) doping is enhanced by 13.7 times. This study provides a general and effective approach to obtain intense pure red UC luminescence, which can be applied to other synthetic strategies.

  2. Crystal growth of pure substances: Phase-field simulations in comparison with analytical and experimental results

    NASA Astrophysics Data System (ADS)

    Nestler, B.; Danilov, D.; Galenko, P.

    2005-07-01

    A phase-field model for non-isothermal solidification in multicomponent systems [SIAM J. Appl. Math. 64 (3) (2004) 775-799] consistent with the formalism of classic irreversible thermodynamics is used for numerical simulations of crystal growth in a pure material. The relation of this approach to the phase-field model by Bragard et al. [Interface Science 10 (2-3) (2002) 121-136] is discussed. 2D and 3D simulations of dendritic structures are compared with the analytical predictions of the Brener theory [Journal of Crystal Growth 99 (1990) 165-170] and with recent experimental measurements of solidification in pure nickel [Proceedings of the TMS Annual Meeting, March 14-18, 2004, pp. 277-288; European Physical Journal B, submitted for publication]. 3D morphology transitions are obtained for variations in surface energy and kinetic anisotropies at different undercoolings. In computations, we investigate the convergence behaviour of a standard phase-field model and of its thin interface extension at different undercoolings and at different ratios between the diffuse interface thickness and the atomistic capillary length. The influence of the grid anisotropy is accurately analyzed for a finite difference method and for an adaptive finite element method in comparison.

  3. Magnetic microbes: Bacterial magnetite biomineralization

    SciTech Connect

    Prozorov, Tanya

    2015-09-14

    Magnetotactic bacteria are a diverse group of prokaryotes with the ability to orient and migrate along the magnetic field lines in search for a preferred oxygen concentration in chemically stratified water columns and sediments. These microorganisms produce magnetosomes, the intracellular nanometer-sized magnetic crystals surrounded by a phospholipid bilayer membrane, typically organized in chains. Magnetosomes have nearly perfect crystal structures with narrow size distribution and species-specific morphologies, leading to well-defined magnetic properties. As a result, the magnetite biomineralization in these organisms is of fundamental interest to diverse disciplines, from biotechnology to astrobiology. As a result, this article highlights recent advances in the understanding of the bacterial magnetite biomineralization.

  4. Magnetic microbes: Bacterial magnetite biomineralization.

    PubMed

    Prozorov, Tanya

    2015-10-01

    Magnetotactic bacteria are a diverse group of prokaryotes with the ability to orient and migrate along the magnetic field lines in search for a preferred oxygen concentration in chemically stratified water columns and sediments. These microorganisms produce magnetosomes, the intracellular nanometer-sized magnetic crystals surrounded by a phospholipid bilayer membrane, typically organized in chains. Magnetosomes have nearly perfect crystal structures with narrow size distribution and species-specific morphologies, leading to well-defined magnetic properties. As a result, the magnetite biomineralization in these organisms is of fundamental interest to diverse disciplines, from biotechnology to astrobiology. This article highlights recent advances in the understanding of the bacterial magnetite biomineralization.

  5. Antimicrobial activity and second harmonic studies on organic non-centrosymmetric pure and doped ninhydrin single crystals

    NASA Astrophysics Data System (ADS)

    Prasanyaa, T.; Jayaramakrishnan, V.; Haris, M.

    2013-03-01

    In this paper, we report the successful growth of pure, Cu2+ ions and Cd2+ ions doped on ninhydrin single crystals by slow solvent evaporation technique. The presence of Cu2+ and Cd2+ ions in the specimen of ninhydrin single crystal has been determined by atomic absorption spectroscopy. The powder X-ray diffraction analysis was done to calculate the lattice parameters of the pure and doped crystals. The percentage of transmittance of the crystal was recorded using the UV-Vis Spectrophotometer. Thermal behaviors of the grown crystals have been examined by the thermal gravimetric/differential thermal analysis. The hardness of the grown crystals was assessed and the results show the minor variation in the hardness value for the pure and doped ninhydrin samples. The value of the work hardening coefficient n was found to be 2.0, 1.0 and 1.06 for pure, copper and cadmium doped ninhydrin crystals respectively. The second harmonic generation efficiency of Cd2+ and Cu2+ doped ninhydrin is 8.3 and 6.3 times greater than well known nonlinear crystal of potassium dihydrogen phosphate respectively. The antibacterial and antifungal activities of the title compound were performed by disk diffusion method against the standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillis niger and Aspergillus flavus.

  6. Statistical Analyses Comparing Prismatic Magnetite Crystals in ALH84001 Carbonate Globules with those from the Terrestrial Magnetotactic Bacteria Strain MV-1

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Wentworth, Susan J.; Vali, H.; Gibson, Everett K.

    2000-01-01

    Here we use rigorous mathematical modeling to compare ALH84001 prismatic magnetites with those produced by terrestrial magnetotactic bacteria, MV-1. We find that this subset of the Martian magnetites appears to be statistically indistinguishable from those of MV-1.

  7. Microwave heating characteristics of magnetite ore

    NASA Astrophysics Data System (ADS)

    Rajavaram, Ramaraghavulu; Lee, Jaehong; Oh, Joon Seok; Kim, Han Gyeol; Lee, Joonho

    2016-11-01

    The heating characteristics of magnetite ore under microwave irradiation were investigated as a function of incident microwave power, particle size, and magnetite ore mass. The results showed that the heating rate of magnetite ore is highly dependent on microwave power and magnetite ore mass. The maximum heating rate was obtained at a microwave irradiation power of 1.70 kW with a mass of 25 g and particle size between 53-75 µm. The volumetric heating rate of magnetite ore was investigated by measuring the temperature at different depths during microwave irradiation. Microwave irradiation resulted in modification of the microstructure of the magnetite ore, but new phases such as FeO or Fe2O3 were not formed. In addition, the crystal size decreased from 115 nm to 63 nm after microwave irradiation up to 1573 K.

  8. Crystal orientation dependence of ion-irradiation hardening in pure tungsten

    NASA Astrophysics Data System (ADS)

    Hasenhuetl, Eva; Zhang, Zhexian; Yabuuchi, Kiyohiro; Song, Peng; Kimura, Akihiko

    2017-04-01

    Pure tungsten (W) single crystals of {0 0 1} and {0 1 1} surface orientations were irradiated with 6.4 MeV Fe3+ ions up to 1 dpa at 573 K. The TEM examination revealed that there was a very small orientation dependence in the radiation damaged microstructure, showing that both W{0 0 1} and W{0 1 1} exhibited a double black band structure with high number density of dislocation loop rafts in the black bands. However, the depth profile of ion-irradiation hardening evaluated by nanoindentation (NI) technique turned out to show a clear orientation dependence, namely, W{0 0 1} showed a deeper NI hardness profile than W{0 1 1}.

  9. Evidence for bulk superconductivity in pure bismuth single crystals at ambient pressure.

    PubMed

    Prakash, Om; Kumar, Anil; Thamizhavel, A; Ramakrishnan, S

    2017-01-06

    At ambient pressure, bulk rhombohedral bismuth is a semimetal that remains in the normal state down to at least 10 millikelvin. Superconductivity in bulk bismuth is thought to be unlikely because of the extremely low carrier density. We observed bulk superconductivity in pure bismuth single crystals below 0.53 millikelvin at ambient pressure, with an estimated critical magnetic field of 5.2 microteslas at 0 kelvin. Superconductivity in bismuth cannot be explained by the conventional Bardeen-Cooper-Schrieffer theory because its adiabatic approximation does not hold true for bismuth. Future theoretical work will be needed to understand superconductivity in the nonadiabatic limit in systems with low carrier densities and unusual band structures, such as bismuth.

  10. Growth and characterization of pure and potassium iodide-doped zinc tris-thiourea sulphate (ZTS) single crystals

    NASA Astrophysics Data System (ADS)

    Krishnan, C.; Selvarajan, P.; Freeda, T. H.; Mahadevan, C. K.

    2009-02-01

    Single crystals of pure and potassium iodide (KI)-doped zinc tris-thiourea sulphate (ZTS) were grown from aqueous solutions by the slow evaporation method. The grown crystals were transparent. The lattice parameters of the grown crystals were determined by the single-crystal X-ray diffraction technique. The grown crystals were also characterized by recording the powder X-ray diffraction pattern and by identifying the diffracting planes. The FT-IR spectrum was recorded in the range 400-4500 cm -1. Second harmonic generation (SHG) was confirmed by the Kurtz powder method. The thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) studies reveal that the materials have good thermal stability. Atomic absorption studies confirm the presence of dopant in ZTS crystals. The electrical measurements were made in the frequency range 10 2-10 6 Hz and in the temperature range 40-130 °C along a-, b- and c-directions of the grown crystals. The present study shows that the electrical parameters viz. dc conductivity, dielectric constant, dielectric loss factor and ac conductivity increase with increase in temperature. Activation energy values were also determined for the ac conduction process in grown crystals. The dc conductivity, dielectric constant, dielectric loss factor and ac conductivity of KI-doped ZTS crystal were found to be more than those of pure ZTS crystals.

  11. Growth and Characterization of Pure and Cd-Doped Zinc Tris-Thiourea Sulfate (ZTS) Single Crystals

    NASA Astrophysics Data System (ADS)

    Muley, G. G.

    2014-02-01

    Single crystals of pure and Cd-doped zinc tris-thiourea sulfate (ZTS) were grown for frequency conversion applications by a low temperature solution growth method, allowing slow evaporation of the water solvent at a constant temperature. The solubility of ZTS was found to increase with the concentration of Cd in the aqueous solution. The optical transparency was found to increase in the Cd-doped crystals as compared to that in the undoped crystals. The doping of Cd was confirmed quantitatively by the atomic absorption spectroscopy and qualitatively by Fourier transform infrared spectroscopy. From the powder x-ray diffraction study, it was found that the lattice constants (a, b and c) decrease with the concentration of Cd in ZTS, but the change in the crystal symmetry and space group has not been reported. A␣change in growth habit of Cd-doped crystals has been observed. Thermo-gravimetric and differential thermal analysis was employed to learn the thermal stability of the grown crystals, and 2 mol% Cd-doped ZTS crystal was found to thermally stable up to 230 °C. The second harmonic generation (SHG) efficiency measurement reveals improvement in the SHG efficiency, as 4 mol% Cd-doped ZTS crystal has 1.36 times more SHG efficiency as compared to the pure ZTS crystal.

  12. Growth and studies of pure and potassium iodide-doped zinc tris-thiourea sulphate (ZTS) single crystals

    NASA Astrophysics Data System (ADS)

    Krishnan, C.; Selvarajan, P.; Freeda, T. H.

    2008-12-01

    Single crystals of pure and potassium iodide (KI)-doped Zinc Tris-thiourea Sulphate (ZTS) were grown from aqueous solutions by slow evaporation technique. The grown crystals have been subjected to single crystal X-ray diffraction to determine the unit cell dimensions. The grown crystals were also characterized by recording the powder X-ray diffraction patterns and by identifying the diffracting planes. The Fourier Transform Infrared (FT-IR) spectra have been recorded in the range 400-4500 cm -1. Second harmonic generation (SHG) for the materials of this work was confirmed using Nd:YAG laser. The UV-visible spectra show that the grown crystals have wide optical transparency in the entire visible region. The Thermogravimetric/Differential Thermal Analyses (TG/DTA) thermograms reveal that the materials have good thermal stability. Atomic absorption study reveals the presence of potassium in the doped f crystals. The electrical measurements were made in the temperature range 40-130 °C along c-direction of the grown crystals. The dielectric studies show that there may be a ferroelectric transition at 50 °C for both pure and KI-doped ZTS crystals. DC conductivity for both the samples is found to be increasing with increase in temperature. Activation energy values were also determined for both AC and DC conduction processes in the samples.

  13. Composite Magnetite and Protein Containing CaCO3 Crystals. External Manipulation and Vaterite → Calcite Recrystallization-Mediated Release Performance.

    PubMed

    Sergeeva, Alena; Sergeev, Roman; Lengert, Ekaterina; Zakharevich, Andrey; Parakhonskiy, Bogdan; Gorin, Dmitry; Sergeev, Sergey; Volodkin, Dmitry

    2015-09-30

    Biocompatibility and high loading capacity of mesoporous CaCO3 vaterite crystals give an option to utilize the polycrystals for a wide range of (bio)applications. Formation and transformations of calcium carbonate polymorphs have been studied for decades, aimed at both basic and applied research interests. Here, composite multilayer-coated calcium carbonate polycrystals containing Fe3O4 magnetite nanoparticles and model protein lysozyme are fabricated. The structure of the composite polycrystals and vaterite → calcite recrystallization kinetics are studied. The recrystallization results in release of both loaded protein and Fe3O4 nanoparticles (magnetic manipulation is thus lost). Fe3O4 nanoparticles enhance the recrystallization that can be induced by reduction of the local pH with citric acid and reduction of the polycrystal crystallinity. Oppositely, the layer-by-layer assembled poly(allylamine hydrochloride)/poly(sodium styrenesulfonate) polyelectrolyte coating significantly inhibits the vaterite → calcite recrystallization (from hours to days) most likely due to suppression of the ion exchange giving an option to easily tune the release kinetics for a wide time scale, for example, for prolonged release. Moreover, the recrystallization of the coated crystals results in formulation of multilayer capsules keeping the feature of external manipulation. This study can help to design multifunctional microstructures with tailor-made characteristics for loading and controlled release as well as for external manipulation.

  14. Growth, mechanical, thermal and dielectric properties of pure and doped KHP single crystal

    NASA Astrophysics Data System (ADS)

    M, Lakshmipriya.; Babu, D. Rajan; Vizhi, R. Ezhil

    2015-06-01

    L-Arginine doped potassium hydrogen phthalate and L-Histidine doped potassium hydrogen phthalate single crystals were grown by slow evaporation method at room temperature. The grown crystal crystallizes in orthorhombic system which is confirmed by single crystal XRD analysis. The grown crystals are subjected to thermal, mechanical and dielectric analysis.

  15. Thermoluminescence in pure LiF crystals: Glow peaks and their connection with color centers

    SciTech Connect

    Baldacchini, G.; Montereali, R. M.; Nichelatti, E.; Kalinov, V. S.; Voitovich, A. P.; Davidson, A. T.; Kozakiewicz, A. G.

    2008-09-15

    Nominally pure LiF crystals were irradiated with the same dose (0.85 10{sup 6} R) of gamma rays at ambient and low temperatures (-60 deg. C) and the resulting thermoluminescence (TL) is reported. Various optical and thermal treatments were applied in order to change the concentration of color centers (CCs). The effect of such treatments on the glow curves is observed. Knowing the coloration from optical transmission and photoluminescence measurements made on the same samples, we attribute many of the glow peaks (GPs) to the annealing of F center aggregates. For the present conditions of irradiation and dose, TL processes begin with decay of F{sub 3}{sup +} centers that display a GP at 164 deg. C. F{sub 3}(R) centers follow and are responsible for GPs at 193 and 228 deg. C. A GP at 263 deg. C is ascribed to F{sub 2} centers. Several peaks at temperatures in the range of 280-380 deg. C are associated with impurity perturbed F centers. A GP at 410 deg. C is associated with a complex of aggregated F and H centers. These attributions are accomplished by means of TL spectra, optical transmission spectra, and annealing procedures, and are critically discussed. The experimental data confirm the general trend of thermal stability of CCs, which decreases by moving from simple F centers to more complex ones, and the existence of exchange dynamics among CCs.

  16. Growth and optical properties of ZnWO4 single crystals pure and doped with Ca and Eu

    NASA Astrophysics Data System (ADS)

    Kowalski, Z.; Kaczmarek, S. M.; Berkowski, M.; Głowacki, M.; Zhydachevskii, Y. A.; Suchocki, A.

    2017-01-01

    In frames of this work a series of ZnWO4 single crystals, pure and doped with either Ca (5 at%) or Ca (4 at%) and Eu (1 at%), has been grown by the Czochralski method. Phase analysis and structural refinement was performed X-ray powder diffraction and the powder diffraction and the patterns were analyzed by the Rietveld refinement method to analyze the lattice parameters of the crystal structure. Additionally, the absorbance, photoluminescence emission (PL) and photoluminescence excitation (PLE) and EPR spectra were measured and compared to investigate influence of Ca and Eu co-doping on optical properties of the obtained crystals. Furthermore the optical band-gap of the crystals has been calculated. The crystal structure of all mentioned ZnWO4 samples has also discussed in the scope of environment symmetry and possible sites of dopant ions.

  17. Influence of downsizing of zeolite crystals on the orthorhombic ↔ monoclinic phase transition in pure silica MFI-type

    NASA Astrophysics Data System (ADS)

    Kabalan, Ihab; Michelin, Laure; Rigolet, Séverinne; Marichal, Claire; Daou, T. Jean; Lebeau, Bénédicte; Paillaud, Jean-Louis

    2016-08-01

    The impact of crystal size on the transition orthorhombic ↔ monoclinic phase in MFI-type purely silica zeolites is investigated between 293 and 473 K using 29Si MAS NMR and powder X-ray diffraction. Three silicalite-1 zeolites are synthesized: a material constituted of micron-sized crystals, pseudospherical nanometer-sized crystals and hierarchical porous zeolites with a mesoporous network created by the use of a gemini-type diquaternary ammonium surfactant giving nanosheet zeolites. Our results show for the first time that the orthorhombic ↔ monoclinic phase transition already known for micron-sized particles also occurs in nanometer-sized zeolite crystals whereas our data suggest that the extreme downsizing of the zeolite crystal to one unit cell in thickness leads to an extinction of the phase transition.

  18. Critical Reexamination of Resonant Soft X-Ray Bragg Forbidden Reflections in Magnetite

    SciTech Connect

    Wilkins, S.B.; Di Matteo, S.; Beale, T.A.W.; Joly, Y.; Mazzoli, C.; Hatton, P.D.; Bencok, P.; Yakhou, F.; Brabers, V.A.M.

    2009-05-01

    Magnetite, Fe{sub 3}O{sub 4}, displays a highly complex low-temperature crystal structure that may be charge and orbitally ordered. Many of the recent experimental claims of such ordering rely on resonant soft x-ray diffraction at the oxygen K and iron L edges. We have reexamined this system and undertaken soft x-ray diffraction experiments on a high-quality single crystal. Contrary to previous claims in the literature, we show that the intensity observed at the Bragg forbidden (001/2){sub c} reflection can be explained purely in terms of the low-temperature structural displacements around the resonant atoms. This does not necessarily mean that magnetite is not charge or orbitally ordered but rather that the present sensitivity of resonant soft x-ray experiments does not allow conclusive demonstration of such ordering.

  19. Magnetite and its production

    SciTech Connect

    Koebbe, E.R.

    1993-12-31

    The supply of high quality magnetite for the cleaning of coal using dense medium cyclones and vessels is of concern to all coal preparation operations. This paper describes the production of high purity magnetite (Fe{sub 3}O{sub 4}) from a domestic underground mining operation in Missouri, Pea Ridge Iron Ore Company. Emphasis will be placed on the mining and processing of the magnetite ore into the various magnetite products required by coal preparation plants.

  20. Magnetic microbes: Bacterial magnetite biomineralization

    DOE PAGES

    Prozorov, Tanya

    2015-09-14

    Magnetotactic bacteria are a diverse group of prokaryotes with the ability to orient and migrate along the magnetic field lines in search for a preferred oxygen concentration in chemically stratified water columns and sediments. These microorganisms produce magnetosomes, the intracellular nanometer-sized magnetic crystals surrounded by a phospholipid bilayer membrane, typically organized in chains. Magnetosomes have nearly perfect crystal structures with narrow size distribution and species-specific morphologies, leading to well-defined magnetic properties. As a result, the magnetite biomineralization in these organisms is of fundamental interest to diverse disciplines, from biotechnology to astrobiology. As a result, this article highlights recent advances inmore » the understanding of the bacterial magnetite biomineralization.« less

  1. Strain and temperature characterization of LPGs written by CO2 laser in pure silica LMA photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Chaves, Roberta Cardoso; Pohl, Alexandre de Almeida Prado; Abe, Ilda; Sebem, Renan; Paterno, Aleksander

    2015-09-01

    This paper reports on the writing of long period gratings (LPGs) in a six-ring pure silica solid core, and large mode area photonic crystal fiber (fiber core diameter ρ = 10.1 μm) using a CO2 laser system, and the characterization of their strain and temperature sensitivities. Temperature and strain sensitivities in the order of -19.6 pm/°C and -88 pm/μɛ, respectively, were obtained, which were comparable or surpassed values of the similar photonic crystal fiber (PCF)-based LPG or sensor configurations found in the literature.

  2. Molecular tectonics: design of enantiomerically pure helical tubular crystals with controlled channel size and orientation.

    PubMed

    Lin, Mei-Jin; Jouaiti, Abdelaziz; Grosshans, Philippe; Kyritsakas, Nathalie; Hosseini, Mir Wais

    2011-07-21

    The combination of four enantiomerically pure organic tectons composed of a rigid chiral backbone bearing two terminal pyridyl coordinating sites with ZnSiF(6) behaving as an infinite pillar leads to the formation of tubular 2-D enantiomerically pure helical channels with controlled size and orientation.

  3. Biogenic Magnetite and EMF Effects

    NASA Astrophysics Data System (ADS)

    Kirschvink, Joseph L.

    1996-03-01

    Magnetite biomineralization is a genetically-controlled biochemical process through which organisms make perfect ferrimagnetic crystals, usually of single magnetic domain size. This process is an ancient one, having evolved about 2 billion years ago in the magnetotactic bacteria, and presumably was incorporated in the genome of higher organisms, including humans. During this time, DNA replication, protein synthesis, and many other biochemical processes have functioned in the presence of strong static fields of up to 400 mT adjacent to these magnetosomes without any obvious deleterious effects. Recent behavioral experiments using short but strong magnetic pulses in honeybees and birds demonstrates that ferromagnetic materials are involved in the sensory transduction of geomagnetic field information to the nervous system, and both behavioral and direct electrophysiological experiments indicate sensitivity thresholds to DC magnetic fields down to a few nT. However, far more biogenic magnetite is present in animal tissues than is needed for magnetoreception, and the biological function of this extra material is unknown. The presence of ferromagnetic materials in biological systems could provide physical transduction mechanisms for ELF magnetic fields, as well for microwave radiation in the .5 to 10 GHz band where magnetite has its peak ferromagnetic resonance. Elucidation of the cellular ultrastructure and biological function(s) of magnetite might help resolve the question of whether anthropogenic EMFs can cause deleterious biological effects. This work has been supported by grants from the NIH and EPRI.

  4. Pure & crystallized 2D Boron Nitride sheets synthesized via a novel process coupling both PDCs and SPS methods

    PubMed Central

    Yuan, Sheng; Linas, Sébastien; Journet, Catherine; Steyer, Philippe; Garnier, Vincent; Bonnefont, Guillaume; Brioude, Arnaud; Toury, Bérangère

    2016-01-01

    Within the context of emergent researches linked to graphene, it is well known that h-BN nanosheets (BNNSs), also referred as 2D BN, are considered as the best candidate for replacing SiO2 as dielectric support or capping layers for graphene. As a consequence, the development of a novel alternative source for highly crystallized h-BN crystals, suitable for a further exfoliation, is a prime scientific issue. This paper proposes a promising approach to synthesize pure and well-crystallized h-BN flakes, which can be easily exfoliated into BNNSs. This new accessible production process represents a relevant alternative source of supply in response to the increasing need of high quality BNNSs. The synthesis strategy to prepare pure h-BN is based on a unique combination of the Polymer Derived Ceramics (PDCs) route with the Spark Plasma Sintering (SPS) process. Through a multi-scale chemical and structural investigation, it is clearly shown that obtained flakes are large (up to 30 μm), defect-free and well crystallized, which are key-characteristics for a subsequent exfoliation into relevant BNNSs. PMID:26843122

  5. Pure & crystallized 2D Boron Nitride sheets synthesized via a novel process coupling both PDCs and SPS methods

    NASA Astrophysics Data System (ADS)

    Yuan, Sheng; Linas, Sébastien; Journet, Catherine; Steyer, Philippe; Garnier, Vincent; Bonnefont, Guillaume; Brioude, Arnaud; Toury, Bérangère

    2016-02-01

    Within the context of emergent researches linked to graphene, it is well known that h-BN nanosheets (BNNSs), also referred as 2D BN, are considered as the best candidate for replacing SiO2 as dielectric support or capping layers for graphene. As a consequence, the development of a novel alternative source for highly crystallized h-BN crystals, suitable for a further exfoliation, is a prime scientific issue. This paper proposes a promising approach to synthesize pure and well-crystallized h-BN flakes, which can be easily exfoliated into BNNSs. This new accessible production process represents a relevant alternative source of supply in response to the increasing need of high quality BNNSs. The synthesis strategy to prepare pure h-BN is based on a unique combination of the Polymer Derived Ceramics (PDCs) route with the Spark Plasma Sintering (SPS) process. Through a multi-scale chemical and structural investigation, it is clearly shown that obtained flakes are large (up to 30 μm), defect-free and well crystallized, which are key-characteristics for a subsequent exfoliation into relevant BNNSs.

  6. Polar Second-Harmonic Imaging to Resolve Pure and Mixed Crystal Phases along GaAs Nanowires.

    PubMed

    Timofeeva, Maria; Bouravleuv, Alexei; Cirlin, George; Shtrom, Igor; Soshnikov, Ilya; Reig Escalé, Marc; Sergeyev, Anton; Grange, Rachel

    2016-10-12

    In this work, we report an optical method for characterizing crystal phases along single-semiconductor III-V nanowires based on the measurement of polarization-dependent second-harmonic generation. This powerful imaging method is based on a per-pixel analysis of the second-harmonic-generated signal on the incoming excitation polarization. The dependence of the second-harmonic generation responses on the nonlinear second-order susceptibility tensor allows the distinguishing of areas of pure wurtzite, zinc blende, and mixed and rotational twins crystal structures in individual nanowires. With a far-field nonlinear optical microscope, we recorded the second-harmonic generation in GaAs nanowires and precisely determined their various crystal structures by analyzing the polar response for each pixel of the images. The predicted crystal phases in GaAs nanowire are confirmed with scanning transmission electron and high-resolution transmission electron measurements. The developed method of analyzing the nonlinear polar response of each pixel can be used for an investigation of nanowire crystal structure that is quick, sensitive to structural transitions, nondestructive, and on-the-spot. It can be applied for the crystal phase characterization of nanowires built into optoelectronic devices in which electron microscopy cannot be performed (for example, in lab-on-a-chip devices). Moreover, this method is not limited to GaAs nanowires but can be used for other nonlinear optical nanostructures.

  7. Growth and characterization of pure and KCl doped zinc thiourea chloride (ZTC) single crystals.

    PubMed

    Ruby Nirmala, L; Thomas Joseph Prakash, J

    2013-02-01

    Potassium Chloride (KCl) as an additive is added into zinc thiourea chloride solution in a small amount (1M%) by the method of slow evaporation solution growth technique at room temperature to get a new crystal. Due to the doping of the impurities on the crystals, remarkable changes in the physical properties were obtained. The grown crystals have been subjected to different instrumentation methods. The incorporation of the amount of potassium and zinc in the crystal lattices has been determined by AAS method. The lattice dimensions have been identified from single crystal X-ray diffraction measurements. The presence of functional group for the grown crystals has been identified by FTIR analysis. The optical, thermal and mechanical behaviors have been assessed by UV-Vis, TG/DTA and Vickers hardness methods respectively. The presence of dislocations of atoms has been identified by etching studies.

  8. Growth and characterization of pure and KCl doped zinc thiourea chloride (ZTC) single crystals

    NASA Astrophysics Data System (ADS)

    Ruby Nirmala, L.; Thomas Joseph Prakash, J.

    2013-02-01

    Potassium Chloride (KCl) as an additive is added into zinc thiourea chloride solution in a small amount (1 M%) by the method of slow evaporation solution growth technique at room temperature to get a new crystal. Due to the doping of the impurities on the crystals, remarkable changes in the physical properties were obtained. The grown crystals have been subjected to different instrumentation methods. The incorporation of the amount of potassium and zinc in the crystal lattices has been determined by AAS method. The lattice dimensions have been identified from single crystal X-ray diffraction measurements. The presence of functional group for the grown crystals has been identified by FTIR analysis. The optical, thermal and mechanical behaviors have been assessed by UV-Vis, TG/DTA and Vickers hardness methods respectively. The presence of dislocations of atoms has been identified by etching studies.

  9. Magnetite pollution nanoparticles in the human brain

    NASA Astrophysics Data System (ADS)

    Maher, Barbara A.; Ahmed, Imad A. M.; Karloukovski, Vassil; MacLaren, Donald A.; Foulds, Penelope G.; Allsop, David; Mann, David M. A.; Torres-Jardón, Ricardo; Calderon-Garciduenas, Lilian

    2016-09-01

    Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683-7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <˜200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health.

  10. Magnetite pollution nanoparticles in the human brain

    PubMed Central

    Maher, Barbara A.; Karloukovski, Vassil; MacLaren, Donald A.; Foulds, Penelope G.; Allsop, David; Mann, David M. A.; Torres-Jardón, Ricardo; Calderon-Garciduenas, Lilian

    2016-01-01

    Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683–7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <∼200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health. PMID:27601646

  11. Magnetite pollution nanoparticles in the human brain.

    PubMed

    Maher, Barbara A; Ahmed, Imad A M; Karloukovski, Vassil; MacLaren, Donald A; Foulds, Penelope G; Allsop, David; Mann, David M A; Torres-Jardón, Ricardo; Calderon-Garciduenas, Lilian

    2016-09-27

    Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 y ago [Kirschvink JL, Kobayashi-Kirschvink A, Woodford BJ (1992) Proc Natl Acad Sci USA 89(16):7683-7687]. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <∼200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health.

  12. Spectrally Pure States at Telecommunications Wavelengths from Periodically Poled M TiO X O4 (M =K , Rb, Cs; X =P , As) Crystals

    NASA Astrophysics Data System (ADS)

    Jin, Rui-Bo; Zhao, Pei; Deng, Peigang; Wu, Qing-Lin

    2016-12-01

    Significant successes have recently been reported in the study of the generation of a spectrally pure state in group-velocity-matched (GVM) nonlinear crystals. However, the GVM condition can be realized only in limited kinds of crystals and at limited wavelengths. Here, we investigate pure-state generation in the isomorphs of the PPKTP crystal: i.e., periodically poled RTP, KTA, RTA, and CTA crystals. By numerical simulation, we find that these crystals from the KTP family can generate pure photons with high spectral purity (over 0.8), wide tunability (more than 400 nm), and reasonable nonlinearity at a variety of wavelengths (from 1300 to 2100 nm). It is also discovered that the PPCTA crystal may achieve a purity of 0.97 at 1506 nm. This study may provide more and better choices for quantum-state engineering at telecom wavelengths.

  13. Growth of large, defect-free pure C60 single crystals

    NASA Technical Reports Server (NTRS)

    Meng, R. L.; Ramirez, D.; Jiang, X.; Chow, P. C.; Diaz, C.; Matsuishi, K.; Moss, S. C.; Hor, P. H.; Chu, C. W.

    1991-01-01

    Millimeter-sized single crystals of C60 were grown by sublimation of C60 powder in a vacuum for 6-24 h. The crystals had excellent facets, were free of C70 or solvent, and showed face-centered cubic symmetry with a very small mosaic spread down to 0.01 deg.

  14. Magnetite Nanoparticles Prepared By Spark Erosion

    NASA Astrophysics Data System (ADS)

    Maiorov, M.; Blums, E.; Kronkalns, G.; Krumina, A.; Lubane, M.

    2016-08-01

    In the present research, we study a possibility of using the electric spark erosion method as an alternative to the method of chemical co-precipitation for preparation of magnetic nanoparticles. Initiation of high frequency electric discharge between coarse iron particles under a layer of distilled water allows obtaining pure magnetite nanoparticles.

  15. The I-Xe Age of Orgueil Magnetite: New Results

    NASA Technical Reports Server (NTRS)

    Pravdivtseva, O. V.; Hohenberg, C. M.; Meshik, A. P.

    2003-01-01

    I-Xe ages of Murchison and Orgueil magnetites were reported to be the oldest [1] and interpreted as the condensation time of the solar nebula. More recent measurements, conducted on a highly magnetic separate from Orgueil (but not pure magnetite), gave much younger I-Xe ages [2]. We have since performed new studies on two pure separates of Orgueil magnetite, confirming the later closing time of the I-Xe system in this mineral phase. In the previous work of Lewis and Anders [1] special attention was paid to the purity of the analyzed material. It was shown, that the trapped Xe resided mostly in hydrated silicates and the radiogenic 129Xe in magnetite [3]. Therefore, Orgueil was finely ground and stirred with a saturated LiCl solution for 8 days at 60 C to remove the silicate-magnetite intergrowth. Although this procedure yields magnetic fractions that are at least 90% pure [1], it could potentially contaminate the magnetite with iodine and produce noncorrelated 128Xe and spurious I-Xe ages. To avoid this possibility, in our first work with Orgueil we deliberately omitted separation in LiCl solution. Instead, the meteorite was ground into a fine powder and the highly magnetic fraction was separated with a hand magnet and was confirmed to be largely magnetite [2]. The new work, reported here, was done in order to confirm our previous results and investigate the effects of the LiCl treatment on the I-Xe system in magnetite.

  16. Experimental study of NIR absorption due to Nb4+ polarons in pure and Cr- or Ce-doped SBN crystals

    NASA Astrophysics Data System (ADS)

    Gao, Ming; Kapphan, S.; Porcher, S.; Pankrath, R.

    1999-06-01

    A broad absorption band around 0.72 eV, assigned to the absorption of Nb4+ polarons, is observed in strontium barium niobate (SBN) crystals (nominally pure or Cr- or Ce-doped) either under illumination at low temperature or after a previous reduction treatment. The absorption spectra of Nb4+ polarons at low temperature show considerable dichroism, which in reduced SBN crystals exists even far above room temperature. The peak position of the Nb4+ polaron absorption in reduced SBN crystals shifts to higher energies with decreasing temperature. The dependence on light intensity and temperature of the Nb4+ polaron absorption during the build-up process under illumination and the decay process after the illumination is switched off are investigated in detail. Compared with pure SBN, doping with Ce or Cr creates additional absorption bands in the visible (2.6 eV) and red (1.9 eV for Cr doping) spectral regions. Illumination in these absorption bands at low temperature gives rise to strong Nb4+ polaron absorption in the NIR (0.72 eV), giving evidence of the enhanced sensitivity even in the red spectral region for SBN:Cr. The light-induced charge transfer process and formation of Nb4+ polarons in SBN are briefly discussed.

  17. Thermal expansion and magnetostriction of pure doped RAgSb2 (R = Y, Sm, La) single crystals

    SciTech Connect

    Bud'ko, S.; Law, S.; Canfield, P.; Samolyuk, G.; Torikachvili, M.; Schmiedeshoff, G.

    2008-02-20

    Data on temperature-dependent, anisotropic thermal expansion in pure and doped RAgSb{sub 2} (R = Y, Sm, La) single crystals are presented. Using the Ehrenfest relation and heat capacity measurements, uniaxial pressure derivatives for long range magnetic ordering and charge density wave transition temperatures are evaluated and compared with the results of the direct measurements under hydrostatic pressure. In-plane and c-axis pressure have opposite effects on the phase transitions in these materials, with in-plane effects being significantly weaker. Quantum oscillations in magnetostriction were observed for the three pure compounds, with the possible detection of new frequencies in SmAgSb{sub 2} and LaAgSb{sub 2}. The uniaxial (along the c-axis) pressure derivatives of the dominant extreme orbits ({beta}) were evaluated for YAgSb{sub 2} and LaAgSb{sub 2}.

  18. Thermal expansion and magnetostriction of pure and doped RAgSb(2) (R = Y, Sm, La) single crystals.

    PubMed

    Bud'ko, S L; Law, S A; Canfield, P C; Samolyuk, G D; Torikachvili, M S; Schmiedeshoff, G M

    2008-03-19

    Data on temperature-dependent, anisotropic thermal expansion in pure and doped RAgSb(2) (R = Y, Sm, La) single crystals are presented. Using the Ehrenfest relation and heat capacity measurements, uniaxial pressure derivatives for long range magnetic ordering and charge density wave transition temperatures are evaluated and compared with the results of the direct measurements under hydrostatic pressure. In-plane and c-axis pressure have opposite effects on the phase transitions in these materials, with in-plane effects being significantly weaker. Quantum oscillations in magnetostriction were observed for the three pure compounds, with the possible detection of new frequencies in SmAgSb(2) and LaAgSb(2). The uniaxial (along the c-axis) pressure derivatives of the dominant extreme orbits (β) were evaluated for YAgSb(2) and LaAgSb(2).

  19. Cavity-assisted atomic frequency comb memory in an isotopically pure 143Nd3+ :YLiF4 crystal

    NASA Astrophysics Data System (ADS)

    Akhmedzhanov, R. A.; Gushchin, L. A.; Kalachev, A. A.; Nizov, N. A.; Nizov, V. A.; Sobgayda, D. A.; Zelensky, I. V.

    2016-11-01

    In this work we present an implementation of cavity-assisted atomic frequency comb (AFC) memory protocol in an isotopically pure 143Nd3+ :YLiF4 crystal. We use a tunable confocal Fabry-Perot cavity that is placed inside the cryostat. For a 1 mm thick sample with optical depth of 0.2 we obtain total storage efficiency of 3%, which is a 15-fold enhancement compared to the no cavity case. The memory bandwidth is limited by the inhomogeneous broadening of the optical transition and allows us to store short 30 ns pulses.

  20. An Alignment Medium for Measuring Residual Dipolar Couplings in Pure DMSO: Liquid Crystals from Graphene Oxide Grafted with Polymer Brushes.

    PubMed

    Zong, Wen; Li, Gao-Wei; Cao, Jiang-Ming; Lei, Xinxiang; Hu, Mao-Lin; Sun, Han; Griesinger, Christian; Tan, Ren Xiang

    2016-03-07

    Residual dipolar couplings (RDCs) have attracted attention in light of their great impact on the structural elucidation of organic molecules. However, the effectiveness of RDC measurements is limited by the shortage of alignment media compatible with widely used organic solvents, such as DMSO. Herein, we present the first liquid crystal (LC) based alignment medium that is compatible with pure DMSO, thus enabling RDC measurements of polar and intermediate polarity molecules. The liquid crystals were obtained by grafting polymer brushes onto graphene oxide (GO) using free radical polymerization. The resulting new medium offers several advantages, such as absence of background signals, narrow line shapes, and tunable alignment. Importantly, this medium is compatible with π-conjugated molecules. Moreover, sonication-induced fragmentation can reduce the size of GO sheets. The resulting anisotropic medium has moderate alignment strength, which is a prerequisite for an accurate RDC measurement.

  1. Dielectric response of pure and doped-GaSe crystals studied by an indigenously developed broadband THz-TDS system

    NASA Astrophysics Data System (ADS)

    Das, Amit C.; Bhattacharya, S.; Mandal, K. C.; Mondal, S.; Jewariya, M.; Ozaki, T.; Bhaktha, S. N. B.; Datta, P. K.

    2016-04-01

    Publisher's Note: This paper, originally published on 12 July 2016, was replaced with a corrected/revised version on 26 July 2016. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance. We have developed a terahertz time domain spectroscopy system (THz TDS). For THz generation, optical rectification process and for detection, electro-optic sampling processes are used. Identical < 110 > cut ZnTe crystals are used for both generation and detection of THz radiation.This spectroscopy system can be used for the noninvasive and contactless electrical and optical characterizations of various samples. In this work spectroscopic measurements of pure, Chromium and Indium doped GaSe crystals within 0.4 THz to 3 THz range are taken by the developed set-up to study the dielectric response of the samples.

  2. Antimony oxofluorides - a synthesis concept that yields phase pure samples and single crystals.

    PubMed

    Ali, Sk Imran; Johnsson, Mats

    2016-07-26

    The single crystals of the new isostructural compounds Sb3O4F and Y0.5Sb2.5O4F and the two previously known compounds M-SbOF and α-Sb3O2F5 were successfully grown by a hydrothermal technique at 230 °C. The new compound Sb3O4F crystallizes in the monoclinic space group P21/c; a = 5.6107(5) Å, b = 4.6847(5) Å, c = 20.2256(18) Å, β = 94.145(8)°, z = 4. The replacing part of Sb with Y means a slight increase in the unit cell dimensions. The compounds M-SbOF and α-Sb3O2F5 have not been grown as single crystals before and it can be concluded that hydrothermal synthesis has proved to be a suitable technique for growing single crystals of antimony oxofluorides because of the relatively low solubility of such compounds compared to other antimony oxohalides that most often have been synthesised at high temperatures by solid state reactions or gas-solid reactions.

  3. Helium and neon diffusion in pure hematite (α-Fe2O3) crystal lattice

    NASA Astrophysics Data System (ADS)

    Balout, Hilal; Roques, Jérôme; Gautheron, Cécile; Tassan-Got, Laurent

    2016-04-01

    Hematite (α-Fe2O3) has the corundum-type structure and is relatively present on Earth and Mars surface associated to ore mineral precipitation or as a weathering phase. He and Ne retention in such mineral has been intensively investigated experimentally because of the potential use of (U-Th-Sm)/(He-Ne) chronometer and thermochronometer. Therefore, the He/Ne diffusion in hematite crystal is an important issue for the interpretation of (U-Th)/(He-Ne) thermochronometric ages. For this purpose an accurate investigation of helium and neon diffusion in hematite crystal lattice has been achieved by computational multi-scale approach. Different insertion sites and diffusion pathways are first characterized where the spin polarized density functional theory (sp-DFT) approach coupled to the nudged elastic band (NEB) method is used to determine the migration energies between the insertion sites. Then, a statistical method, based on transition state theory (TST), is used to compute the jump probability between sites. The previous results are used as input data in a 3D random walk simulation, which permits to determine the effective activation energy and diffusion coefficient. Using the He/Ne diffusion coefficients, the closure temperature Tc has been calculated. For typical grain size of 100 microns, Tc will be of 116° C and 297° C for He and Ne atoms, respectively. These results Show that He and Ne atoms are highly retained in the crystal lattice at surface temperature. The obtained diffusion coefficients confirm that He/Ne retentively power in hematite lattice is very important, allowing a large range of different geological applications such the measurement of hematite crystallization ages on Earth and Mars.

  4. A comparative study on pure, L-arginine and glycine doped ammonium dihydrogen orthophosphate single crystals grown by slow solvent evaporation and temperature-gradient method

    NASA Astrophysics Data System (ADS)

    Pattanaboonmee, N.; Ramasamy, P.; Yimnirun, R.; Manyum, P.

    2011-01-01

    Single crystals of pure, L-arginine and glycine doped ammonium dihydrogen orthophosphate (ADP) were grown by both the slow solvent evaporation method and the temperature-gradient method of Sankaranarayanan-Ramasamy (SR). The metastable zone width for different saturation temperatures of pure glycine and L-arginine added solutions were carried out. The grown crystals were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), optical transmission, dielectric constant, dielectric loss, and Vickers microhardness. The DSC and TG curves of the grown crystals indicated that they were stable up to 200 °C. The XRD study confirmed the structure of the grown crystal. The optical transmission analysis revealed that the pure and doped ADP crystals had very high percentage of transmission in the entire visible region. The important optical parameters such as reflectance and extinction coefficients of the grown crystals were calculated. L-arginine and glycine were used as dopants to reduce dielectric constant of ADP. The a.c. resistivity and a.c. conductivity were calculated. Dielectric loss of the doped ADP crystals grown by the SR method is lower than the doped ADP crystals grown by the conventional method. Larger hardness value for the SR method grown crystals confirmed greater crystalline perfection.

  5. Determination of Low Loss in Isotopically Pure Single Crystal 28Si at Low Temperatures and Single Microwave Photon Energy

    PubMed Central

    Kostylev, Nikita; Goryachev, Maxim; Bulanov, Andrey D.; Gavva, Vladimir A.; Tobar, Michael E.

    2017-01-01

    The low dielectric losses of an isotopically pure single crystal 28Si sample were determined at a temperature of 20 mK and at powers equivalent to that of a single photon. Whispering Gallery Mode (WGM) analysis revealed large Quality Factors of order 2 × 106 (dielectric loss ~5 × 10−7) at high powers, degrading to 7 × 10−5 (dielectric loss ~1.4 × 10−6 at single photon energy. A very low-loss narrow line width paramagnetic spin flip transition was detected with extreme sensitivity in 28Si, with very small concentration below 1010 cm−3 (less than 10 parts per trillion) and g-factor of 1.995 ± 0.008. Such determination was only possible due to the low dielectric photonic losses combined with the long lifetime of the spin transition (low magnetic loss), which enhances the magnetic AC susceptibility. Such low photonic loss at single photon energy combined with the narrow line width of the spin ensemble, indicate that single crystal 28Si could be an important crystal for future cavity QED experiments. PMID:28317908

  6. Determination of Low Loss in Isotopically Pure Single Crystal (28)Si at Low Temperatures and Single Microwave Photon Energy.

    PubMed

    Kostylev, Nikita; Goryachev, Maxim; Bulanov, Andrey D; Gavva, Vladimir A; Tobar, Michael E

    2017-03-20

    The low dielectric losses of an isotopically pure single crystal (28)Si sample were determined at a temperature of 20 mK and at powers equivalent to that of a single photon. Whispering Gallery Mode (WGM) analysis revealed large Quality Factors of order 2 × 10(6) (dielectric loss ~5 × 10(-7)) at high powers, degrading to 7 × 10(-5) (dielectric loss ~1.4 × 10(-6) at single photon energy. A very low-loss narrow line width paramagnetic spin flip transition was detected with extreme sensitivity in (28)Si, with very small concentration below 10(10) cm(-3) (less than 10 parts per trillion) and g-factor of 1.995 ± 0.008. Such determination was only possible due to the low dielectric photonic losses combined with the long lifetime of the spin transition (low magnetic loss), which enhances the magnetic AC susceptibility. Such low photonic loss at single photon energy combined with the narrow line width of the spin ensemble, indicate that single crystal (28)Si could be an important crystal for future cavity QED experiments.

  7. Formation of tabular single-domain magnetite induced by Geobacter metallireducens GS-15

    PubMed Central

    Vali, Hojatollah; Weiss, Benjamin; Li, Yi-Liang; Sears, S. Kelly; Kim, Soon Sam; Kirschvink, Joseph L.; Zhang, Chuanlun L.

    2004-01-01

    Distinct morphological characteristics of magnetite formed intracellularly by magnetic bacteria (magnetosome) are invoked as compelling evidence for biological activity on Earth and possibly on Mars. Crystals of magnetite produced extracellularly by a variety of bacteria including Geobacter metallireducens GS-15, thermophilic bacteria, and psychrotolerant bacteria are, however, traditionally not thought to have nearly as distinct morphologies. The size and shape of extracellular magnetite depend on the culture conditions and type of bacteria. Under typical CO2-rich culture conditions, GS-15 is known to produce superparamagnetic magnetite (crystal diameters of approximately <30 nm). In the current study, we were able to produce a unique form of tabular, single-domain magnetite under nontraditional (low-CO2) culture conditions. This magnetite has a distinct crystal habit and magnetic properties. This magnetite could be used as a biosignature to recognize ancient biological activities in terrestrial and extraterrestrial environments and also may be a major carrier of the magnetization in natural sediments. PMID:15525704

  8. Search for magnetite in lunar rocks and fines.

    PubMed

    Jedwab, J; Herbosch, A; Wollast, R; Naessens, G; Van Geen-Peers, N

    1970-01-30

    Magnetite crystals larger than 2 micrometers are absent from rocks and fines. Smaller opaque spheres in the fines can tentatively be identified as magnetite. Their concentration is not higher than 1 x 10(-6) particle per particle smaller than 1 millimeter. In the fines from the sampling site, the contribution of material similar to type 1 carbonaceous meteorites is insignificant, either because it never existed, or because it was evaporated or comminuted by impact or was diluted by indigenous material. Other magnetite habits typical of carbonaceous meteorites or possibly of cosmic dust or comets were also sought without success-such as rods, platelets, framboids, spherulites, and idiomorphic crystals.

  9. Trace elements in magnetite from massive iron oxide-apatite deposits indicate a combined formation by igneous and magmatic-hydrothermal processes

    NASA Astrophysics Data System (ADS)

    Knipping, Jaayke L.; Bilenker, Laura D.; Simon, Adam C.; Reich, Martin; Barra, Fernando; Deditius, Artur P.; Wälle, Markus; Heinrich, Christoph A.; Holtz, François; Munizaga, Rodrigo

    2015-12-01

    Iron oxide-apatite (IOA) deposits are an important source of iron and other elements (e.g., REE, P, U, Ag and Co) vital to modern society. However, their formation, including the namesake Kiruna-type IOA deposit (Sweden), remains controversial. Working hypotheses include a purely magmatic origin involving separation of an Fe-, P-rich, volatile-rich oxide melt from a Si-rich silicate melt, and precipitation of magnetite from an aqueous ore fluid, which is either of magmatic-hydrothermal or non-magmatic surface or metamorphic origin. In this study, we focus on the geochemistry of magnetite from the Cretaceous Kiruna-type Los Colorados IOA deposit (∼350 Mt Fe) located in the northern Chilean Iron Belt. Los Colorados has experienced minimal hydrothermal alteration that commonly obscures primary features in IOA deposits. Laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS) transects and electron probe micro-analyzer (EPMA) wavelength-dispersive X-ray (WDX) spectrometry mapping demonstrate distinct chemical zoning in magnetite grains, wherein cores are enriched in Ti, Al, Mn and Mg. The concentrations of these trace elements in magnetite cores are consistent with igneous magnetite crystallized from a silicate melt, whereas magnetite rims show a pronounced depletion in these elements, consistent with magnetite grown from an Fe-rich magmatic-hydrothermal aqueous fluid. Further, magnetite grains contain polycrystalline inclusions that re-homogenize at magmatic temperatures (>850 °C). Smaller inclusions (<5 μm) contain halite crystals indicating a saline environment during magnetite growth. The combination of these observations are consistent with a formation model for IOA deposits in northern Chile that involves crystallization of magnetite microlites from a silicate melt, nucleation of aqueous fluid bubbles on magnetite surfaces, and formation and ascent of buoyant fluid bubble-magnetite aggregates. Decompression of the fluid-magnetite aggregate

  10. Crystallography of magnetite plaquettes and their significance as asymmetric catalysts for the synthesis of chiral organics in carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Chan, Q. H. S.; Zolensky, M. E.

    2015-10-01

    We have previously observed the magnetite plaquettes in carbonaceous chondrites using scanning electron microscope (SEM) imaging, examined the crystal orientation of the polished surfaces of magnetite plaquettes in CI Orgueil using electron backscattered diffraction (EBSD) analysis, and concluded that these magnetite plaquettes are likely naturally asymmetric materials [1]. In this study, we expanded our EBSD observation to other magnetite plaquettes in Orgueil, and further examined the internal structure of these remarkable crystals with the use of X-ray computed microtomography.

  11. Crystallography of Magnetite Plaquettes and their Significance as Asymmetric Catalysts for the Synthesis of Chiral Organics in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Zolensky, M. E.

    2015-01-01

    We have previously observed the magnetite plaquettes in carbonaceous chondrites using scanning electron microscope (SEM) imaging, examined the crystal orientation of the polished surfaces of magnetite plaquettes in CI Orgueil using electron backscattered diffraction (EBSD) analysis, and concluded that these magnetite plaquettes are likely naturally asymmetric materials. In this study, we expanded our EBSD observation to other magnetite plaquettes in Orgueil, and further examined the internal structure of these remarkable crystals with the use of X-ray computed microtomography.

  12. Atomic frequency comb memory in an isotopically pure 143Nd3+:Y7LiF4 crystal

    NASA Astrophysics Data System (ADS)

    Akhmedzhanov, R. A.; Gushchin, L. A.; Kalachev, A. A.; Korableva, S. L.; Sobgayda, D. A.; Zelensky, I. V.

    2016-01-01

    We implemented the atomic frequency comb protocol for optical quantum memory in an isotopically pure crystal of Y7LiF4 doped by 143Nd3+ ions. Echo signals were observed on the 4I9/2(1)-4F3/2(1) transition, which had inhomogeneous broadening much smaller than the hyperfine splitting of the ground and excited states. We performed hole-burning spectroscopy measurements on several transitions, obtaining information about the hyperfine state lifetimes. An intrinsic hole structure was found on some of the transitions, which allowed us to prepare a comb structure with two clearly defined periods and to observe echo pulses with different time delays.

  13. Atomistic study of pyramidal slips in pure magnesium single crystal under nano-compression

    NASA Astrophysics Data System (ADS)

    Tang, Xiao-Zhi; Guo, Ya-Fang; Xu, Shuang; Wang, Yue-Sheng

    2015-07-01

    Pyramidal slip mechanism plays an important role in c-axis micro-compression of hexagonal closed-packed metals. In this article, the detailed slip paths, respectively, on ? and ? planes in magnesium single crystal are given by molecular dynamics. The pyramidal slip on ? plane is suggested to consist of an edge-type partial dislocation and opposite basal movements on neighbouring basal planes, while the ? slip dissociation is achieved by two partial dislocations with a strip of stacking fault. Results imply that the slip on ? plane is more likely to nucleate with a relatively easy dissociation type comparing to the one on ? plane. No twinning is found under c-axis compression by examining the stepwise movement of atoms involved, fully supporting the recent experimental observations of micro-compression and the theoretical analysis on twinning formation proposed by our previous work.

  14. Scaffold of Asymmetric Organic Compounds - Magnetite Plaquettes

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Zolensky, M. E.; Martinez, J.

    2015-01-01

    Life on Earth shows preference towards the set of organics with particular spatial configurations, this 'selectivity' is a crucial criterion for life. With only rare exceptions, life prefers the left- (L-) form over the right- (D-) form of amino acids, resulting in an L-enantiomeric excess (L-ee). Recent studies have shown Lee for alpha-methyl amino acids in some chondrites. Since these amino acids have limited terrestrial occurrence, the origin of their stereoselectivity is nonbiological, and it seems appropriate to conclude that chiral asymmetry, the molecular characteristic that is common to all terrestrial life form, has an abiotic origin. A possible abiotic mechanism that can produce chiral asymmetry in meteoritic amino acids is their formation with the presence of asymmetric catalysts, as mineral crystallization can produce spatially asymmetric structures. Magnetite is shown to be an effective catalyst for the formation of amino acids that are commonly found in chondrites. Magnetite 'plaquettes' (or 'platelets'), first described by Jedwab, show an interesting morphology of barrel-shaped stacks of magnetite disks with an apparent dislocation-induced spiral growth that seem to be connected at the center. A recent study by Singh et al. has shown that magnetites can self-assemble into helical superstructures. Such molecular asymmetry could be inherited by adsorbed organic molecules. In order to understand the distribution of 'spiral' magnetites in different meteorite classes, as well as to investigate their apparent spiral configurations and possible correlation to molecular asymmetry, we observed polished sections of carbonaceous chondrites (CC) using scanning electron microscope (SEM) imaging. The sections were also studied by electron backscattered diffraction (EBSD) in order to reconstruct the crystal orientation along the stack of magnetite disks.

  15. Stimulated Raman scattering-active isotopically pure 12C and 13C diamond crystals: A milestone in the development of diamond photonics

    NASA Astrophysics Data System (ADS)

    Kaminskii, A. A.; Ral'chenko, V. G.; Yoneda, H.; Bol'shakov, A. P.; Inyushkin, A. V.

    2016-09-01

    Isotopically pure 12C and 13C diamonds are synthesized by chemical vapor deposition and impulsive stimulated Raman scattering in these crystals is investigated. The thermal conductivity of 12C isotopically pure damond and natC diamond with natural isotopic composition is measured. Phonon-nondegenerate Stokes lasing based on the χ(3) nonlinearity in the 12C, 13C, and natC diamond "triad" is attained, which opens a new stage in the development of diamond photonics.

  16. Optimization of band gap in Ni-substituted magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Rana, Geeta; Johri, Umesh C.

    2013-06-01

    The excellent biocompatibility and magnetic properties of magnetite nanoparticles have encouraged a tremendous amount of research in the last decade. Lots of work has been reported on their magnetic and electric properties but little work is done to study the optical properties (band gap). In the present work Ni is substituted with varying concentration in magnetite nanoparticles. XRD patterns confirm their spinel phase and particle size is estimated using TEM. The UV-visible reflectance and Kubelka-Munk function plot gives the optical band gap of NixFe1-xFe2O4 which is found to be decreasing with respect to the pure magnetite samples.

  17. Gd-DTPA Adsorption on Chitosan/Magnetite Nanocomposites

    NASA Astrophysics Data System (ADS)

    Pylypchuk, Ie. V.; Kołodyńska, D.; Kozioł, M.; Gorbyk, P. P.

    2016-03-01

    The synthesis of the chitosan/magnetite nanocomposites is presented. Composites were prepared by co-precipitation of iron(II) and iron(III) salts by aqueous ammonia in the 0.1 % chitosan solution. It was shown that magnetite synthesis in the chitosan medium does not affect the magnetite crystal structure. The thermal analysis data showed 4.6 % of mass concentration of chitosan in the hybrid chitosan/magnetite composite. In the concentration range of initial Gd-DTPA solution up to 0.4 mmol/L, addition of chitosan to magnetite increases the adsorption capacity and affinity to Gd-DTPA complex. The Langmuir and Freundlich adsorption models were applied to describe adsorption processes. Nanocomposites were characterized by scanning electron microscopy (SEM), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and specific surface area determination (ASAP) methods.

  18. Laser-assisted one-pot fabrication of calcium phosphate-based submicrospheres with internally crystallized magnetite nanoparticles through chemical precipitation.

    PubMed

    Nakamura, Maki; Oyane, Ayako; Sakamaki, Ikuko; Ishikawa, Yoshie; Shimizu, Yoshiki; Kawaguchi, Kenji

    2015-04-14

    In this paper, we have further developed our simple (one-pot) and rapid (short irradiation time) laser fabrication process of submicrometer spheres composed of amorphous calcium iron phosphate. In our previous process, laser irradiation was applied to a calcium phosphate (CaP) reaction mixture supplemented with ferric ions (Fe(3+)) as a light-absorbing agent. Because the intention of the present study was to fabricate magnetite-encapsulated CaP-based submicrometer spheres, ferrous ions (Fe(2+)) were used as a light-absorbing agent rather than ferric ions. The ferrous ions served as a light-absorbing agent and facilitated the fabrication of submicrometer and micrometer spheres of amorphous calcium iron phosphate. The sphere formation and growth were better promoted by the use of ferrous ions as compared with the use of ferric ions. The chemical composition of the spheres was controllable through adjustment of the experimental conditions. By the addition of sodium hydroxide to the CaP reaction mixture supplemented with ferrous ions, fabrication of CaP-based magnetic submicrometer spheres was successfully achieved. Numerous magnetite and wüstite nanoparticles were coprecipitated or segregated into the CaP-based spherical amorphous matrix via light-material interaction during the CaP precipitation process. The magnetic properties of the magnetite and wüstite formed in the CaP-based spheres were investigated by magnetization measurements. The present process and the resulting CaP-based spheres are expected to have great potential for biomedical applications.

  19. Synthesis and characterization of Gd-doped magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhang, Honghu; Malik, Vikash; Mallapragada, Surya; Akinc, Mufit

    2017-02-01

    Synthesis of magnetite nanoparticles has attracted increasing interest due to their importance in biomedical and technological applications. Tunable magnetic properties of magnetite nanoparticles to meet specific requirements will greatly expand the spectrum of applications. Tremendous efforts have been devoted to studying and controlling the size, shape and magnetic properties of magnetite nanoparticles. Here we investigate gadolinium (Gd) doping to influence the growth process as well as magnetic properties of magnetite nanocrystals via a simple co-precipitation method under mild conditions in aqueous media. Gd doping was found to affect the growth process leading to synthesis of controllable particle sizes under the conditions tested (0-10 at% Gd3+). Typically, undoped and 5 at% Gd-doped magnetite nanoparticles were found to have crystal sizes of about 18 and 44 nm, respectively, supported by X-ray diffraction and transmission electron microscopy. Our results showed that Gd-doped nanoparticles retained the magnetite crystal structure, with Gd3+ randomly incorporated in the crystal lattice, probably in the octahedral sites. The composition of 5 at% Gd-doped magnetite was Fe(3-x)GdxO4 (x=0.085±0.002), as determined by inductively coupled plasma mass spectrometry. 5 at% Gd-doped nanoparticles exhibited ferrimagnetic properties with small coercivity ( 65 Oe) and slightly decreased magnetization at 260 K in contrast to the undoped, superparamagnetic magnetite nanoparticles. Templation by the bacterial biomineralization protein Mms6 did not appear to affect the growth of the Gd-doped magnetite particles synthesized by this method.

  20. Optimize the modulation response of twisted-nematic liquid crystal displays as pure phase spatial light modulators

    NASA Astrophysics Data System (ADS)

    Ma, Baiheng; Peng, Fei; Kang, Mingwu; Zhou, Jiawu

    2014-11-01

    Twisted-nematic liquid crystal displays (TN-LCD) are widely used in numerous research fields of optics working as spatial light modulators. Approaches to obtaining desired intensity or phase modulation by TN-LCD have been extensively studied based on the knowledge of TN-LCD's internal structure parameters, e.g., the orientation of LC molecules at the surfaces, the twist angle, the thickness of the LC layer, and the birefringence of the material. Generally TN-LCD placed between two linear polarizers (P) produces coupled intensity and phase modulation. To obtain the commonly used pure phase modulation, quarter wave plates (QWP) are often used in front of and/or behind the LCD. In this paper, we present a method to optimize the optical modulation properties of the TN-LCD to obtain pure phase modulation in the configuration of P-QWP-LCD-QWP-P each with proper orientation. Firstly an improved method for determining the Jones matrix of the TN-LCD without knowing its internal parameters is presented, which is based on the macroscopical Jones matrix descriptions for TN-LCD, linear polarizer and QWP. Only three sets of intensity measurements are needed for the complete determination of the TN-LCD's Jones matrix for a single wavelength. Then Jones matrix calculations are carried out to determine the orientations of the polarizers and QWPs for pure phase modulation response. In addition, we prove that the phase modulation depth (PMD) of the TN-LCD can be further increased provided that the mean intensity transmission is decreased to a lower level, which is very useful when the TN-LCD is used as a phase modulator and the ratio between the intensities of the desired diffracted order relative to the other diffracted orders is required higher. Experimental results coincide well with the optical modulation properties of the TN-LCD predicted by our determined Jones matrix. In contrast to the traditional method which requires knowledge of the TN-LCD's internal structure parameters

  1. First-principles Exploration of Crystal Structures of Pure Iron at Earth’s Inner Core Conditions

    NASA Astrophysics Data System (ADS)

    Ishikawa, T.; Tsuchiya, T.; Tsuchiya, J.

    2009-12-01

    Determining the structure of Earth’s inner core has been a long standing challenge for geoscience. Iron has been considered as a main composition of the inner core and expected to exist as an iron-nickel-light elements alloy there. In order to get some information about the structure of the inner core, pure iron has been also investigated by many experimental and ab-initio studies. Pure iron has been expected to take the hexagonal close-packed (hcp) structure at the inner core conditions (Jephcoat and Olson, Nature 325, 332-335, 1987.; Mao et al., Nature 396, 741-743, 1998.; Fiquet et al., Science 291, 468-471, 2001.; Uchida et al., J. Geophys. Res. 106, 21799-21810, 2001.). On the other hand, the face-centered cubic (fcc) structure (Mikhaylushkin et al., Phys. Rev. Lett. 99, 165505-165508, 2007.) and the body-centered cubic structure (Vocadlo et al., Phys. Earth Planet In. 170, 52-59, 2008.) have been also considered as the candidate structures. In this study, first we explored the crystal structures of pure iron at 400 GPa by our originally developing algorithm for the structure exploration, Free Energy Surface Trekking (FEST). In FEST, using a minus sign of driving force acting on a simulation cell, we force a system to climb up to a ridge of a free energy surface (ascent-run). Then, flipping the negative driving force to an original one, we make the system go down to a neighboring potential well (descent-run). The more different directions we examine in the ascent-run, the more accurate topography we capture of free energy surface. For the exploration of the ultrahigh-pressure structures of pure iron, we used 16 atoms supercell and explored 64 pathways around the initial local minimum corresponding to hcp. As the result, 30 pathways lead to a complex hcp (chcp) structure, which has ABCACABCBCAB stacking with 12 layers. Other 33 pathways lead to hcp and 1 pathway fcc. The enthalpy of chcp was found higher than that of hcp but only by 4 mRy/atom and lower than

  2. The DTA-TG Investigation of Non-Crystalizing Super-Pure (up to 8N) Gallium Melt Obtained by the Membrane Technology

    NASA Astrophysics Data System (ADS)

    Kutelia, E.; Tsurtsumia, O.; Markus, T.; Chatzicharalampous, Ch.; Kukava, T.

    2011-12-01

    In the given work the DTA-TG investigations were carried out for the determination of unique properties of the overcooled super-pure (8N) non-crystallizing big mass (not droplets) liquid-Ga obtained by the membrane technology of purification. The wide endothermic peak is observed in the 22÷31 °C temperature range on the heating up DTA curve received for the specimen of the super pure liquid gallium. The existence of the given peak could be explained based on the poly-cluster structure of non-crystalized overcooled sample of the super pure liquid gallium in which the clusters of liquid and clusters of the solid phases coexist (and permanently transform one into another) with the quantification of their settled energies in the melt.

  3. Control of magnetite nanocrystal morphology in magnetotactic bacteria by regulation of mms7 gene expression

    PubMed Central

    Yamagishi, Ayana; Tanaka, Masayoshi; Lenders, Jos J. M.; Thiesbrummel, Jarla; Sommerdijk, Nico A. J. M.; Matsunaga, Tadashi; Arakaki, Atsushi

    2016-01-01

    Living organisms can produce inorganic materials with unique structure and properties. The biomineralization process is of great interest as it forms a source of inspiration for the development of methods for production of diverse inorganic materials under mild conditions. Nonetheless, regulation of biomineralization is still a challenging task. Magnetotactic bacteria produce chains of a prokaryotic organelle comprising a membrane-enveloped single-crystal magnetite with species-specific morphology. Here, we describe regulation of magnetite biomineralization through controlled expression of the mms7 gene, which plays key roles in the control of crystal growth and morphology of magnetite crystals in magnetotactic bacteria. Regulation of the expression level of Mms7 in bacterial cells enables switching of the crystal shape from dumbbell-like to spherical. The successful regulation of magnetite biomineralization opens the door to production of magnetite nanocrystals of desired size and morphology. PMID:27417732

  4. How the Molecular Packing Affects the Room Temperature Phosphorescence in Pure Organic Compounds: Ingenious Molecular Design, Detailed Crystal Analysis, and Rational Theoretical Calculations.

    PubMed

    Xie, Yujun; Ge, Yuwei; Peng, Qian; Li, Conggang; Li, Qianqian; Li, Zhen

    2017-02-21

    Long-lived phosphorescence at room temperature (RTP) from pure organic molecules is rare. Recent research reveals various crystalline organic molecules can realize RTP with lifetimes extending to the magnitude of second. There is little research on how molecular packing affecting RTP. Three compounds are designed with similar optical properties in solution, but tremendously different solid emission characteristics. By investigating the molecular packing arrangement in single crystals, it is found that the packing style of the compact face to face favors of long phosphorescence lifetime and high photoluminescence efficiency, with the lifetime up to 748 ms observed in the crystal of CPM ((9H-carbazol-9-yl)(phenyl)methanone). Theoretical calculation analysis also reveals this kind of packing style can remarkably reduce the singlet excited energy level and prompt electron communication between dimers. Surprisingly, CPM has two very similar single crystals, labeled as CPM and CPM-A, with almost identical crystal data, and the only difference is that molecules in CPM-A crystal take a little looser packing arrangement. X-ray diffraction and cross-polarization under magic spinning (13) C NMR spectra double confirm that they are different crystals. Interestingly, CPM-A crystal shows negligible RTP compared to the CPM crystal, once again proving that the packing style is critical to the RTP property.

  5. Synthesis, characterization and anti-microbial activity of pure, Cu2+ and Cd2+ doped organic NLO l-arginine trifluoroacetate single crystals

    NASA Astrophysics Data System (ADS)

    Prasanyaa, T.; Haris, M.; Jayaramakrishnan, V.; Amgalan, M.; Mathivanan, V.

    2013-10-01

    Optically transparent Cu2+ and Cd2+ doped l-arginine trifluoroacetate (LATF) single crystals were grown from its aqueous solution using the slow solvent evaporation technique. The grown crystals were characterized by powder x-ray diffraction to confirm the monoclinic crystal structure. The percentage of transmittance measured using the ultraviolet-visible-near infrared spectrophotometer was found to be more than 80% for doped crystals. The functional group analysis of the grown crystals has been made by Fourier transform infrared spectroscopy. Thermogravimetric/differential thermal analysis was performed for the grown crystals. An atomic absorption study was carried out to determine the presence of Cu2+ and Cd2+. The hardness of the grown crystals was assessed and the results show a significant variation in the hardness value between the pure and doped LATF crystals. The second harmonic generation measurements show that Cu2+ doped LATF is 2.8 times greater and Cd2+ doped is 2.6 times greater than KDP. The anti-bacterial and anti-fungal activities of the title compound were performed using the disc diffusion method against standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillus niger and Aspergillus flavus.

  6. Exsolution of Iron-Titanium Oxides in Magnetite in Miller Range (MIL) 03346 Nakhlite: Evidence for Post Crystallization Reduction in the Nakhlite Cumulate Pile

    NASA Technical Reports Server (NTRS)

    Righter, Kevin; Keller, L. P.; Rahman, Z.; Christoffersen, R.

    2012-01-01

    MIL 03346 is one of the most mesostasis-rich nakhlites [1] and thought to have equilibrated at oxygen fugacities near the fayalite-magnetite-quartz oxygen (FMQ) buffer ([2,3]). Studies of FeTi oxides in nakhlites have led to additional constraints on their equilibration temperatures and fO2s [4,5,6,7]. Comparison of these results to fO2s calculated for shergottites indicates that nakhlites are among the most oxidized samples from the martian meteorite suite [2]. The mesostasis of MIL 03346 contains skeletal titanomagnetite. Several scientists noticed several years ago (e.g. [8]) that this titanomagnetite contains very fine oxidation-driven exsolution lamellae (Figure 1). However, the lamellae are so small that they cannot be characterized by electron microprobe analysis (EMPA). Here we select several areas for focused ion beam (FIB) extraction, prepare transmission electron microscopy (TEM) foils, and identify and analyze the lamellae using TEM at the Johnson Space Center (JSC). The resulting analyses are combined with previous work on nakhlites to interpret the thermal and oxidation history of this meteorite group.

  7. Multiple ordering in magnetite.

    NASA Technical Reports Server (NTRS)

    Cullen, J. R.; Callen, E. R.

    1973-01-01

    Results of a self-consistent band calculation of the ground-state energy and charge orderings based on a tight-binding scheme in magnetite are presented. They show that below a critical (about 2.2) value of the ratio of interatomic Coulomb energy to bandwidth the lowest energy state has no order. Between this critical value and 2.5, the preferred state is multiply ordered.

  8. Growth of phase-pure, crack-free single crystals and large-grained polycrystals of molybdenum disilicide

    NASA Technical Reports Server (NTRS)

    Rossetti, M.

    1970-01-01

    High purity molybdenum disilicide crystals are prepared by zone melting sintered compacts. This method yields single crystals or polycrystals free from macrocracks which allow better measurement and evaluation of mechanical properties.

  9. Nanophase Magnetite and Pyrrhotite in ALH84001 Martian Meteorite: Evidence for an Abiotic Origin

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Lauer, H. V., Jr. III; Ming, D. W.; Morris, R. V.

    2006-01-01

    The nanophase magnetite crystals in the black rims of pancake-shaped carbonate globules of the Martian meteorite ALH84001 have been studied extensively because of the claim by McKay et al.that they are biogenic in origin. A subpopulation of these magnetite crystals are reported to conform to a unique elongated shape called "truncated hexa-octahedral" or "THO" by Thomas-Keprta et al. They claim these THO magnetite crystals can only be produced by living bacteria thus forming a biomarker in the meteorite. In contrast, thermal decomposition of Fe-rich carbonate has been suggested as an alternate hypothesis for the elongated magnetite formation in ALH84001 carbonates. The experimental and observational evidence for the inorganic formation of nanophase magnetite and pyrrhotite in ALH84001 by decomposition of Fe-rich carbonate in the presence of pyrite are provided.

  10. Magnetite: What it reveals about the origin of the banded iron formations. [Abstract only

    NASA Technical Reports Server (NTRS)

    Schwartz, D. E.; Mancinelli, R. L.; White, M. R.

    1994-01-01

    Magnetite, Fe3O4 is produced abiotically and biotically. Abiotically, magnetite is a late magmatic mineral and forms as a consequence of the cooling of iron rich magma. Biotically, magnetite is produced by several organisms, including magnetotactic bacteria. Hematite, Fe2O3, is also produced abiotically and biotically. Abiotically, hematite rarely occurs as a primary mineral in igneous rocks, but is common as an alteration product, fumarole deposit, and in some metamorphosed Fe-rich rocks. Biotically, hematite is produced by several types of microorganisms. Biologically-produced magnetite and hematite are formed under the control of the host organism, and consequently, have characteristics not found in abiotically produced magnetite and hematite crystals. To determine if the magnetite and hematite in the Banded Iron Formation was biologically or abiotically produced, the characteristics of biologically-produced magnetite and hematite (concentrated from Aquaspirillum magnetotacticum) and abiotically-produced magnetite and hematite obtained from Wards Scientific Supply Company, were compared with characteristics of magnetite and hematite concentrated from the Gunflint Banded Iron Formation (Ontario, Canada) using thermal and crystallographic analytical techniques. Whole rock analysis of the Gunflint Banded Iron Formation by x-ray diffraction (XRD) and differential thermal analysis (DTA) revealed the presence of quartz, hematite, siderite and dolomite as the major minerals, and magnetite, greenalite, pyrite, pyrrhotite and apatite as the minor minerals. Analysis of a crude magnetic fraction of the Gunflint showed the minerals quartz, hematite, siderite, dolomite, and magnetite. Analysis of the crude magnetic fraction from Aquaspirillum magnetotacticum revealed organic compounds plus hematite and magnetite. The mineral identification and particle size distribution data obtained from the DTA along with XRD data indicate that the magnetite and hematite from the Gunflint

  11. Comments on recently published "L-threonine phthalate" and pure and doped "L-lysinium succinate" crystals

    NASA Astrophysics Data System (ADS)

    Petrosyan, A. M.

    2016-04-01

    It is shown that the recently published papers on "L-threonine phthalate" (Theras et al. (2015) [2]) and pure and doped "L-lysinium succinate" (Kalaivani et al. (2015) [11,16]) misidentified the targeted compounds.

  12. Mineral chemistry of magnetite from magnetite-apatite mineralization and their host rocks: examples from Kiruna, Sweden, and El Laco, Chile

    NASA Astrophysics Data System (ADS)

    Broughm, Shannon G.; Hanchar, John M.; Tornos, Fernando; Westhues, Anne; Attersley, Samuel

    2017-03-01

    Interpretation of the mineralizing environment of magnetite-apatite deposits remains controversial with theories that include a hydrothermal or magmatic origin or a combination of those two processes. To address this controversy, we have analyzed the trace element content of magnetite from precisely known geographic locations and geologic environments from the Precambrian magnetite-apatite ore and host rocks in Kiruna, Sweden, and the Pliocene-Holocene El Laco volcano in the Atacama desert of Chile. Magnetite samples from Kiruna have low trace element concentrations with little chemical variation between the ore, host, and related intrusive rocks. Magnetite from andesite at El Laco, and dacite from the nearby Láscar volcano, has high trace element concentrations typical of magmatic magnetite. El Laco ore magnetite have low trace element concentrations and displays growth zoning in incompatible elements (Si, Ca, and Ce), compatible elements (Mg, Al, and Mn), large-ion lithophile element (Sr), and high field strength element (Y, Nb, and Th). The El Laco ore magnetite are similar in composition to magnetite that has been previously interpreted to have crystallized from hydrothermal fluids; however, there is a significant difference in the internal zoning patterns. At El Laco, each zoned element is either enriched or depleted in the same layers, suggesting the magnetite crystallized from a volatile-rich, iron-oxide melt. In general, the compositions of magnetite from these two deposits plot in very wide fields that are not restricted to the proposed fields in published discriminant diagrams. This suggests that the use of these diagrams and genetic models based on them should be used with caution.

  13. Magnetic and ultrasonic investigations on magnetite nanofluids.

    PubMed

    Nabeel Rashin, M; Hemalatha, J

    2012-12-01

    Magnetite nanofluids of various concentrations have been prepared through co-precipitation method. The structural and magnetic properties of the magnetic nanofluids have been analyzed which respectively revealed their face centered cubic crystal structure and super paramagnetic behavior. Ultrasonic investigations have been made for the nanofluids at different temperatures and magnetic fields. Open- and close-packed water structure is considered to explain the temperature effects. The inter particle interactions of surface modified nanomagnetite particle and the cluster formation are realized through the variations in ultrasonic parameters.

  14. Natural Magnetite: an efficient catalyst for the degradation of organic contaminant

    PubMed Central

    HE, Hongping; ZHONG, Yuanhong; LIANG, Xiaoliang; TAN, Wei; ZHU, Jianxi; Yan WANG, Christina

    2015-01-01

    Iron (hydr)oxides are ubiquitous earth materials that have high adsorption capacities for toxic elements and degradation ability towards organic contaminants. Many studies have investigated the reactivity of synthetic magnetite, while little is known about natural magnetite. Here, we first report the reactivity of natural magnetites with a variety of elemental impurities for catalyzing the decomposition of H2O2 to produce hydroxyl free radicals (•OH) and the consequent degradation of p-nitrophenol (p-NP). We observed that these natural magnetites show higher catalytic performance than that of the synthetic pure magnetite. The catalytic ability of natural magnetite with high phase purity depends on the surface site density while that for the magnetites with exsolutions relies on the mineralogical nature of the exsolved phases. The pleonaste exsolution can promote the generation of •OH and the consequent degradation of p-NP; the ilmenite exsolution has little effect on the decomposition of H2O2, but can increase the adsorption of p-NP on magnetite. Our results imply that natural magnetite is an efficient catalyst for the degradation of organic contaminants in nature. PMID:25958854

  15. Natural Magnetite: an efficient catalyst for the degradation of organic contaminant

    NASA Astrophysics Data System (ADS)

    He, Hongping; Zhong, Yuanhong; Liang, Xiaoliang; Tan, Wei; Zhu, Jianxi; Yan Wang, Christina

    2015-05-01

    Iron (hydr)oxides are ubiquitous earth materials that have high adsorption capacities for toxic elements and degradation ability towards organic contaminants. Many studies have investigated the reactivity of synthetic magnetite, while little is known about natural magnetite. Here, we first report the reactivity of natural magnetites with a variety of elemental impurities for catalyzing the decomposition of H2O2 to produce hydroxyl free radicals (•OH) and the consequent degradation of p-nitrophenol (p-NP). We observed that these natural magnetites show higher catalytic performance than that of the synthetic pure magnetite. The catalytic ability of natural magnetite with high phase purity depends on the surface site density while that for the magnetites with exsolutions relies on the mineralogical nature of the exsolved phases. The pleonaste exsolution can promote the generation of •OH and the consequent degradation of p-NP; the ilmenite exsolution has little effect on the decomposition of H2O2, but can increase the adsorption of p-NP on magnetite. Our results imply that natural magnetite is an efficient catalyst for the degradation of organic contaminants in nature.

  16. Evidence for exclusively inorganic formation of magnetite in Martian meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.; Morris, R. V.; Brearley, A. J.; Lauer, H. V., Jr.; Treiman, A. H.; Zolensky, M. E.; Schwandt, C. S.; Lofgren, G. E.

    2004-01-01

    Magnetite crystals produced by terrestrial magnetotactic bacterium MV-1 are elongated on a [111] crystallographic axis, in a so-called truncated hexa-Octahedral shape. This morphology has been proposed to constitute a biomarker (i.e., formed only in biogenic processes). A subpopulation of magnetite crystals associated with carbonate globules in Martian meteorite ALH84001 is reported to have this morphology, and the observation has been taken as evidence for biological activity on Mars. In this study, we present evidence for the exclusively inorganic origin of [111]-elongated magnetite crystals in ALH84001. We report three-dimensional(3-D) morphologies for approx.1000 magnetite crystals extracted from: (1) thermal decomposition products of Fe-rich carbonate produced by inorganic hydrothermal precipitation in laboratory experiments; (2) carbonate globules in Martian meteoriteeALH84001; and (3) cells of magnetotactic bacterial strain MV-1. The 3-D morphologies were derived by fitting 3-D shape models to two-dimensional bright-field transmission-electron microscope (TEAM) images obtained at a series of viewing angles. The view down the {110} axes closest to the [111] elongation axis of magnetite crystals ([111]x{110) not equal to 0) provides a 2-D projection that uniquely discriminates among the three [111]-elongated magnetite morphologies found in these samples: [111]-elongated truncated hexaoctahedron ([111]-THO), [111]-elongated cubo-octahedron ([111]-ECO), and [111]-elongated simple octahedron ([111]-ESO). All [111] -elongated morphologies are present in the three types of sample, but in different proportions. In the ALH84001 Martian meteorite and in our inorganic laboratory products, the most common [111]-elongated magnetite crystal morphology is [111]-ECO. In contrast, the most common morphology for magnetotactic bacterial strain MV-1 is [111]-THO. These results show that: (1) the morphology of [111]-elongated magnetite crystals associated with the carbonate

  17. Iron isotopic fractionation factor between magnetite and hydrous silicic melt

    NASA Astrophysics Data System (ADS)

    Huang, F.; Lundstrom, C. C.

    2006-12-01

    analysis of pure melt and the magnetite-melt mush with knowledge of the modes providing the ability to back out the fractionation factor. If we can prove attainment of equilibrium, this technique will bypass the difficulty of making pure separates of magnetite and melt. Fe isotopic composition of the melt and melt-magnetite layers will be measured by MC-ICP-MS.

  18. Fluid-induced martitization of magnetite in BIFs from the Dharwar Craton, India.

    NASA Astrophysics Data System (ADS)

    Wagner, Christiane; Orberger, Beate; Tudryn, Alina; Wirth, Richard; Morgan, Rachael

    2013-04-01

    Banded iron formations (BIFs) represent the largest iron deposits on Earth, which mainly formed in the Late Archean and Early Proterozoic. The complex geological history of BIFs makes it difficult to reconstruct the primary mineralogy and thus the initial depositional environment. Magnetite and hematite are the most important iron oxide minerals in BIFs. Magnetite (FeOFe2O3) comprising of both ferrous and ferric iron, easily undergoes transformation at low temperature. Hematite (α-Fe2O3) is often a result of the pseudomorphic replacement of magnetite, in the processus called martitisation. Despite the process of martitization having been widely studied, in both synthetic and natural magnetites, the mechanics of the transformation are poorly understood. What is generally agreed is that the transformation from magnetite to hematite occurs via a maghemite (g-Fe2O3) intermediate. The 2.9 Ga BIF from the Western Dharwar Craton, Southern India (a 500 m thick Archean BIF), is characterized by millimetric to centrimetric alternating white quartz and grey Fe-oxide bands. The Fe-oxide bands consist of martite crystals (~20µm) which represent the hematitisation of euhedral magnetite. The hematite crystals are in part euhedral, cubic shaped pointing to the replacement of magnetite. The crystals show a trellis pattern. Magnetite patches occur within the hematite. Raman spectroscopy, X-Ray diffraction, Curie balance and magnetic hysteresis analyses and FIB-TEM investigation indicate the presence of maghemite, and the presence of subhedral magnetite and interstitial hematite crystal. The latter are characterized by dislocation with fluid inclusions and high porosity zones. The magnetite grains contain lamellae and the interfaces between magnetite-maghemite and hematite are curved suggesting grain boundary migrations with the growth of hematite at the expense of magnetite and maghemite. It is thus suggested that martite result from low-T exsolutions along cleavage resulting in

  19. Hydrothermal Preparation of Apatite Composite with Magnetite or Anatase

    SciTech Connect

    Murakami, Setsuaki; Ishida, Emile H.; Ioku, Koji

    2006-05-15

    Microstructure designed porous hydroxyapatite (Ca10(PO4)6(OH)2) composites with magnetite (Fe3O4) particles or anatase (TiO2) dispersion were prepared by hydrothermal treatment. These composites had micro-pores of about 0.1-0.5 {mu}m in size. Magnetite / Hydroxyapatite composites should be suitable for medical treatment of cancer, especially in bones, because HA can bond to bones directly and magnetite can generate heat. They must be used for hyperthermia therapies of cancer in bones. Meanwhile, anatase / Hydroxyapatite composite should be suitable for environmental purification, because HA rod-shape particles expose the specific crystal face, which adsorbs organic contaminants and so on.

  20. Mechanical properties of natural chitosan/hydroxyapatite/magnetite nanocomposites for tissue engineering applications.

    PubMed

    Heidari, Fatemeh; Razavi, Mehdi; E Bahrololoom, Mohammad; Bazargan-Lari, Reza; Vashaee, Daryoosh; Kotturi, Hari; Tayebi, Lobat

    2016-08-01

    Chitosan (CS), hydroxyapatite (HA), and magnetite (Fe3O4) have been broadly employed for bone treatment applications. Having a hybrid biomaterial composed of the aforementioned constituents not only accumulates the useful characteristics of each component, but also provides outstanding composite properties. In the present research, mechanical properties of pure CS, CS/HA, CS/HA/magnetite, and CS/magnetite were evaluated by the measurements of bending strength, elastic modulus, compressive strength and hardness values. Moreover, the morphology of the bending fracture surfaces were characterized using a scanning electron microscope (SEM) and an image analyzer. Studies were also conducted to examine the biological response of the human Mesenchymal Stem Cells (hMSCs) on different composites. We conclude that, although all of these composites possess in-vitro biocompatibility, adding hydroxyapatite and magnetite to the chitosan matrix can noticeably enhance the mechanical properties of the pure chitosan.

  1. Microwave absorption by magnetite: a possible mechanism for coupling nonthermal levels of radiation to biological systems.

    PubMed

    Kirschvink, J L

    1996-01-01

    The presence of trace amounts of biogenic magnetite (Fe3O4) in animal and human tissues and the observation that ferromagnetic particles are ubiquitous in laboratory materials (including tissue culture media) provide a physical mechanism through which microwave radiation might produce or appear to produce biological effects. Magnetite is an excellent absorber of microwave radiation at frequencies between 0.5 and 10.0 GHz through the process of ferromagnetic resonance, where the magnetic vector of the incident field causes precession of Bohr magnetons around the internal demagnetizing field of the crystal. Energy absorbed by this process is first transduced into acoustic vibrations at the microwave carrier frequency within the crystal lattice via the magnetoacoustic effect; then, the energy should be dissipated in cellular structures in close proximity to the magnetite crystals. Several possible methods for testing this hypothesis experimentally are discussed. Studies of microwave dosimetry at the cellular level should consider effects of biogenic magnetite.

  2. Gigantism in unique biogenic magnetite at the Paleocene–Eocene Thermal Maximum

    PubMed Central

    Schumann, Dirk; Raub, Timothy D.; Kopp, Robert E.; Guerquin-Kern, Jean-Luc; Wu, Ting-Di; Rouiller, Isabelle; Smirnov, Aleksey V.; Sears, S. Kelly; Lücken, Uwe; Tikoo, Sonia M.; Hesse, Reinhard; Kirschvink, Joseph L.; Vali, Hojatollah

    2008-01-01

    We report the discovery of exceptionally large biogenic magnetite crystals in clay-rich sediments spanning the Paleocene–Eocene Thermal Maximum (PETM) in a borehole at Ancora, NJ. Aside from previously described abundant bacterial magnetofossils, electron microscopy reveals novel spearhead-like and spindle-like magnetite up to 4 μm long and hexaoctahedral prisms up to 1.4 μm long. Similar to magnetite produced by magnetotactic bacteria, these single-crystal particles exhibit chemical composition, lattice perfection, and oxygen isotopes consistent with an aquatic origin. Electron holography indicates single-domain magnetization despite their large crystal size. We suggest that the development of a thick suboxic zone with high iron bioavailability—a product of dramatic changes in weathering and sedimentation patterns driven by severe global warming—drove diversification of magnetite-forming organisms, likely including eukaryotes. PMID:18936486

  3. Crystal Plasticity Analysis of Texture Evolution of Pure Aluminum During Processing by a New Severe Plastic Deformation Technique

    NASA Astrophysics Data System (ADS)

    Khajezade, Ali; Parsa, Mohammad Habibi; Mirzadeh, Hamed

    2016-02-01

    Texture evolution in a newly developed severe plastic deformation technique, named multi-axial incremental forging and shearing (MAIFS), was studied applying the visco-plastic self-consistent crystal plasticity formulation by consideration of macroscopic deformation history. The simulated texture evolutions revealed that although shear-like texture had developed by the MAIFS process, texture components rotated around normal to mid-plane section. This could be ascribed to the complex deformation history that naturally develops during processing by the MAIFS process. The increased complexity of the deformation history in the MAIFS process, compared to the techniques that are solely based on the simple shear deformation, causes more activated slip planes, which in turn can result in an enhanced grain refinement ability of this processing technique.

  4. Magnetite seeded precipitation of phosphate.

    PubMed

    Karapinar, Nuray; Hoffmann, Erhard; Hahn, Hermann H

    2004-07-01

    Seeded precipitation of Ca phosphate on magnetite mineral (Fe3O4) surfaces was investigated using a Jar Test system in supersaturated solutions at 20 degrees C and ionic strength 0.01 mol l(-1) with relative super saturation, 12.0-20.0 for HAP. pH of the solution, initial phosphorus concentration and molar Ca/P ratio were investigated as the main parameters, which effect the seeded precipitation of Ca phosphate. Results showed that there is no pronounced effect of magnetite seed, neither positive nor negative on the amount of calcium phosphate precipitation. pH was found to be the main parameter that determines the phosphate precipitated onto the seed surface. Increasing of the pH of precipitation reaction was resulted in the decrease in percentage amount of phosphate precipitated onto seed surfaces to total precipitation (magnetite seeded precipitation efficiency). It was concluded that the pH dependence of magnetite-seeded precipitation should be considered in the light of its effect on the supersaturated conditions of solution. Saturation index (SI) of solution with respect to the precipitate phase was considered the driving force for the precipitation. A simulation programme PHREEQC (Version 2) was employed to calculate the Saturation-index with respect to hydroxyapatite (HAP) of the chemically defined precipitation system. It was found a good relationship between SI of solution with respect to HAP and the magnetite seeded precipitation efficiency, a second order polynomial function. Results showed that more favorable solution conditions for precipitation (higher SI values of solution) causes homogenous nucleation whereas heterogeneous nucleation led to a higher magnetite seeded precipitation efficiency.

  5. Core Amino Acid Residues in the Morphology-Regulating Protein, Mms6, for Intracellular Magnetite Biomineralization

    PubMed Central

    Yamagishi, Ayana; Narumiya, Kaori; Tanaka, Masayoshi; Matsunaga, Tadashi; Arakaki, Atsushi

    2016-01-01

    Living organisms produce finely tuned biomineral architectures with the aid of biomineral-associated proteins. The functional amino acid residues in these proteins have been previously identified using in vitro and in silico experimentation in different biomineralization systems. However, the investigation in living organisms is limited owing to the difficulty in establishing appropriate genetic techniques. Mms6 protein, isolated from the surface of magnetite crystals synthesized in magnetotactic bacteria, was shown to play a key role in the regulation of crystal morphology. In this study, we have demonstrated a defect in the specific region or substituted acidic amino acid residues in the Mms6 protein for observing their effect on magnetite biomineralization in vivo. Analysis of the gene deletion mutants and transformants of Magnetospirillum magneticum AMB-1 expressing partially truncated Mms6 protein revealed that deletions in the N-terminal or C-terminal regions disrupted proper protein localization to the magnetite surface, resulting in a change in the crystal morphology. Moreover, single amino acid substitutions at Asp123, Glu124, or Glu125 in the C-terminal region of Mms6 clearly indicated that these amino acid residues had a direct impact on magnetite crystal morphology. Thus, these consecutive acidic amino acid residues were found to be core residues regulating magnetite crystal morphology. PMID:27759096

  6. Exchange bias in polycrystalline magnetite films made by ion-beam assisted deposition

    SciTech Connect

    Kaur, Maninder; Jiang, Weilin; Qiang, You; Burks, Edward; Liu, Kai; Namavar, Fereydoon; Mccloy, John S.

    2014-11-03

    Iron oxide films were deposited onto Si substrates using ion-beam-assisted deposition. The films were ~300 nm thick polycrystalline magnetite with an average crystallite size of ~6 nm. Additionally, incorporation of significant fractions of argon in the films from ion bombardment is evident from chemical analysis, and Fe/O ratios are lower than expected from pure magnetite. However, Raman spectroscopy and x-ray diffraction both indicate that the films are single-phase magnetite. Since no direct evidence of a second phase could be found, exchange bias likely arises due to defects at grain boundaries, possibly amorphous, creating frustrated spins. Since these samples have such small grains, a large fraction of the material consists of grain boundaries, where spins are highly disordered and reverse independently with external field. The high energy deposition process results in an oxygen-rich, argon-containing magnetite film with low temperature exchange bias due to defects at the high concentration of grain boundaries.

  7. Iron and oxygen isotope signatures of the Pea Ridge and Pilot Knob magnetite-apatite deposits, southeast Missouri, USA

    USGS Publications Warehouse

    Childress, Tristan; Simon, Adam C.; Day, Warren C.; Lundstrom, Craig C.; Bindeman, Ilya N.

    2016-01-01

    New O and Fe stable isotope ratios are reported for magnetite samples from high-grade massive magnetite of the Mesoproterozoic Pea Ridge and Pilot Knob magnetite-apatite ore deposits and these results are compared with data for other iron oxide-apatite deposits to shed light on the origin of the southeast Missouri deposits. The δ18O values of magnetite from Pea Ridge (n = 12) and Pilot Knob (n = 3) range from 1.0 to 7.0 and 3.3 to 6.7‰, respectively. The δ56Fe values of magnetite from Pea Ridge (n = 10) and Pilot Knob (n = 6) are 0.03 to 0.35 and 0.06 to 0.27‰, respectively. These δ18O and the δ56Fe values suggest that magnetite crystallized from a silicate melt (typical igneous δ56Fe ranges 0.06–0.49‰) and grew in equilibrium with a magmatic-hydrothermal aqueous fluid. We propose that the δ18O and δ56Fe data for the Pea Ridge and Pilot Knob magnetite-apatite deposits are consistent with the flotation model recently proposed by Knipping et al. (2015a), which invokes flotation of a magmatic magnetite-fluid suspension and offers a plausible explanation for the igneous (i.e., up to ~15.9 wt % TiO2 in magnetite) and hydrothermal features of the deposits.

  8. Magnetism of Al-substituted magnetite reduced from Al-hematite

    NASA Astrophysics Data System (ADS)

    Jiang, Zhaoxia; Liu, Qingsong; Zhao, Xiang; Roberts, Andrew P.; Heslop, David; Barrón, Vidal; Torrent, José

    2016-06-01

    Aluminum-substituted magnetite (Al-magnetite) reduced from Al-substituted hematite or goethite (Al-hematite or Al-goethite) is an environmentally important constituent of magnetically enhanced soils. In order to characterize the magnetic properties of Al-magnetite, two series of Al-magnetite samples were synthesized through reduction of Al-hematite by a mixed gas (80% CO2 and 20% CO) at 395°C for 72 h in a quartz tube furnace. Al-magnetite samples inherited the morphology of their parent Al-hematite samples, but only those transformed from Al-hematite synthesized at low temperature possessed surficial micropores, which originated from the release of structural water during heating. Surface micropores could thus serve as a practical fingerprint of fire or other high-temperature mineralogical alteration processes in natural environments, e.g., shear friction in seismic zones. In addition, Al substitution greatly affects the magnetic properties of Al-magnetite. For example, coercivity (Bc) increases with increasing Al content and then decreases slightly, while the saturation magnetization (Ms), Curie temperature (Tc), and Verwey transition temperature (Tv) all decrease with increasing Al content due to crystal defect formation and dilution of magnetic ions caused by Al incorporation. Moreover, different trends in the correlation between Tc and Bc can be used to discriminate titanomagnetite from Al-magnetite, which is likely to be important in environmental and paleomagnetic studies, particularly in soil.

  9. Hydrogen-bond-dynamics-based switching of conductivity and magnetism: a phase transition caused by deuterium and electron transfer in a hydrogen-bonded purely organic conductor crystal.

    PubMed

    Ueda, Akira; Yamada, Shota; Isono, Takayuki; Kamo, Hiromichi; Nakao, Akiko; Kumai, Reiji; Nakao, Hironori; Murakami, Youichi; Yamamoto, Kaoru; Nishio, Yutaka; Mori, Hatsumi

    2014-08-27

    A hydrogen bond (H-bond) is one of the most fundamental and important noncovalent interactions in chemistry, biology, physics, and all other molecular sciences. Especially, the dynamics of a proton or a hydrogen atom in the H-bond has attracted increasing attention, because it plays a crucial role in (bio)chemical reactions and some physical properties, such as dielectricity and proton conductivity. Here we report unprecedented H-bond-dynamics-based switching of electrical conductivity and magnetism in a H-bonded purely organic conductor crystal, κ-D3(Cat-EDT-TTF)2 (abbreviated as κ-D). This novel crystal κ-D, a deuterated analogue of κ-H3(Cat-EDT-TTF)2 (abbreviated as κ-H), is composed only of a H-bonded molecular unit, in which two crystallographically equivalent catechol-fused ethylenedithiotetrathiafulvalene (Cat-EDT-TTF) skeletons with a +0.5 charge are linked by a symmetric anionic [O···D···O](-1)-type strong H-bond. Although the deuterated and parent hydrogen systems, κ-D and κ-H, are isostructural paramagnetic semiconductors with a dimer-Mott-type electronic structure at room temperature (space group: C2/c), only κ-D undergoes a phase transition at 185 K, to change to a nonmagnetic insulator with a charge-ordered electronic structure (space group: P1). The X-ray crystal structure analysis demonstrates that this dramatic switching of the electronic structure and physical properties originates from deuterium transfer or displacement within the H-bond accompanied by electron transfer between the Cat-EDT-TTF π-systems, proving that the H-bonded deuterium dynamics and the conducting TTF π-electron are cooperatively coupled. Furthermore, the reason why this unique phase transition occurs only in κ-D is qualitatively discussed in terms of the H/D isotope effect on the H-bond geometry and potential energy curve.

  10. Biophysics of Magnetic Orientation: Radical Pairs, Biogenic Magnetite, or both?

    NASA Astrophysics Data System (ADS)

    Kirschvink, Joe

    2011-03-01

    Two major biophysical mechanisms for magnetoreception in terrestrial animals, one based on biogenic magnetite and another on radical-pair biochemical reactions, have been the subject of experiment and debate for the past 30 years. The magnetite hypothesis has stood the test of time: biogenic magnetite is synthesized biochemically in Bacteria, Protists, and numerous Animal phyla, as well as in some plants. Chains of single-domain crystals have been detected by clean-lab based SQUID magnetometry in animal tissues in all major phyla, followed by high-resolution TEM in selected model organisms, as well as by electrophysiological studies demonstrating the role of the ophthalmic branch of the trigeminal nerve in the magnetoreceptive process. Pulse-remagnetization - configured to uniquely flip the polarity of single-domain ferromagnets - has dramatic effects on the behavior of many birds, honeybees, mole rats, turtles, and bats, to cite a growing list. Magnetite-containing cells in the vicinity of these neurons in fish are now the subject of intense study by our consortium. The existence of a specialized class of magnetite-containing magnetoreceptor cells in animal tissues is no longer controversial. In contrast, less success has been achieved in gaining experimental support across a range of taxa for the radical-pair hypothesis. Although this mechanism was proposed to explain an early observation that birds would not respond to complete inversion of the magnetic vector, many organisms (even some birds) do indeed respond to the field polarity. We also note that few, if any, of these critical experiments have been done using fully double-blind methods. This is joint work with: M. M. Walker (University of Auckland, New Zealand) and M. Winklhofer (LMU Munich, Germany).

  11. Magnetite-Based Magnetoreceptor Cells in the Olfactory Organ of Rainbow Trout and Zebrafish

    NASA Astrophysics Data System (ADS)

    Kirschvink, J. L.; Cadiou, H.; Dixson, A. D.; Eder, S.; Kobayashi, A.; McNaughton, P. A.; Muhamad, A. N.; Raub, T. D.; Walker, M. M.; Winklhofer, M.; Yuen, B. B.

    2011-12-01

    Many vertebrate and invertebrate animals have a geomagnetic sensory system, but the biophysics and anatomy of how magnetic stimuli are transduced to the nervous system is a challenging problem. Previous work in our laboratories identified single-domain magnetite chains in olfactory epithelium in cells proximal to the ros V nerve, which, in rainbow trout, responds to magnetic fields. Our objectives are to characterize these magnetite-containing cells and determine whether they form part of the mechanism of magnetic field transduction in teleost fishes, as a model for other Vertebrates. Using a combination of reflection mode confocal microscopy and a Prussian Blue technique modified to stain specifically for magnetite, our Auckland group estimated that both juvenile rainbow trout (ca. 7 cm total length) olfactory rosettes have ~200 magnetite-containing cells. The magnetite present in two types of cells within the olfactory epithelium appears to be arranged in intracellular chains. All of our groups (Munich, Auckland, Cambridge and Caltech) have obtained different types of structural evidence that magnetite chains closely associate with the plasma membrane in the cells, even in disaggregated tissues. In addition, our Cambridge group used Ca2+ imaging to demonstrate a clear response by individual magnetite-containing cells to a step change in the intensity of the external magnetic field and a slow change in Ca2+ activity when the external magnetic field was cancelled. In the teleost, zebrafish (Danio rerio), a small (~4 cm adult length in captivity) genetic and developmental biology model organism, our Caltech group detected ferromagnetic material throughout the body, but concentrated in the rostral trunk, using NRM and IRM scans of whole adults. Our analysis suggests greater than one million, 80-100 nm crystals, with Lowrie-Fuller curves strongly consistent with single-domain magnetite in 100-100,000 magnetocytes. Ferromagentic resonance (FMR) spectra show crystals

  12. Dissolution and reduction of magnetite by bacteria

    NASA Technical Reports Server (NTRS)

    Kostka, J. E.; Nealson, K. H.

    1995-01-01

    Magnetite (Fe3O4) is an iron oxide of mixed oxidation state [Fe(II), Fe(III)] that contributes largely to geomagnetism and plays a significant role in diagenesis in marine and freshwater sediments. Magnetic data are the primary evidence for ocean floor spreading and accurate interpretation of the sedimentary magnetic record depends on an understanding of the conditions under which magnetite is stable. Though chemical reduction of magnetite by dissolved sulfide is well known, biological reduction has not been considered likely based upon thermodynamic considerations. This study shows that marine and freshwater strains of the bacterium Shewanella putrefaciens are capable of the rapid dissolution and reduction of magnetite, converting millimolar amounts to soluble Fe(II)in a few days at room temperature. Conditions under which magnetite reduction is optimal (pH 5-6, 22-37 degrees C) are consistent with an enzymatic process and not with simple chemical reduction. Magnetite reduction requires viable cells and cell contact, and it appears to be coupled to electron transport and growth. In a minimal medium with formate or lactate as the electron donor, more than 10 times the amount of magnetite was reduced over no carbon controls. These data suggest that magnetite reduction is coupled to carbon metabolism in S. putrefaciens. Bacterial reduction rates of magnetite are of the same order of magnitude as those estimated for reduction by sulfide. If such remobilization of magnetite occurs in nature, it could have a major impact on sediment magnetism and diagenesis.

  13. Dissolution and reduction of magnetite by bacteria.

    PubMed

    Kostka, J E; Nealson, K H

    1995-10-01

    Magnetite (Fe3O4) is an iron oxide of mixed oxidation state [Fe(II), Fe(III)] that contributes largely to geomagnetism and plays a significant role in diagenesis in marine and freshwater sediments. Magnetic data are the primary evidence for ocean floor spreading and accurate interpretation of the sedimentary magnetic record depends on an understanding of the conditions under which magnetite is stable. Though chemical reduction of magnetite by dissolved sulfide is well known, biological reduction has not been considered likely based upon thermodynamic considerations. This study shows that marine and freshwater strains of the bacterium Shewanella putrefaciens are capable of the rapid dissolution and reduction of magnetite, converting millimolar amounts to soluble Fe(II)in a few days at room temperature. Conditions under which magnetite reduction is optimal (pH 5-6, 22-37 degrees C) are consistent with an enzymatic process and not with simple chemical reduction. Magnetite reduction requires viable cells and cell contact, and it appears to be coupled to electron transport and growth. In a minimal medium with formate or lactate as the electron donor, more than 10 times the amount of magnetite was reduced over no carbon controls. These data suggest that magnetite reduction is coupled to carbon metabolism in S. putrefaciens. Bacterial reduction rates of magnetite are of the same order of magnitude as those estimated for reduction by sulfide. If such remobilization of magnetite occurs in nature, it could have a major impact on sediment magnetism and diagenesis.

  14. Magnetite-apatite mineralization in Khanlogh iron deposit, northwest of Neyshaboor, NE Iran

    NASA Astrophysics Data System (ADS)

    Najafzadeh Tehrani, Parvin; Asghar Calagari, Ali; Velasco Roldan, Francisco; Simmonds, Vartan; Siahcheshm, Kamal

    2016-04-01

    Khanlogh iron deposit lies on Sabzehvar-Ghoochan Cenozoic magmatic belt in northwest of Neyshaboor, NE Iran. The lithologic units in this area include a series of sub-volcanic intrusive rocks like diorite porphyry, quartz-diorite porphyry, and micro-granodiorite of Oligocene age. Mineralization in this area occurred as veins, dissemination, and open space filling in brecciated zones within the host sub-volcanic intrusive bodies. Three distinct types of mineral associations can be distinguished, (1) diopside-magnetite, (2) magnetite-apatite, and (3) apatite-calcite. Microscopic examinations along with SEM and EPMA studies demonstrated that magnetite is the most common ore mineral occurring as solitary crystals. The euhedral magnetite crystals are accompanied by lamellar destabilized ilmenite and granular fluorapatite in magnetite-apatite ores. The results of EPMA revealed that the lamellar ilmenite, relative to host magnetite crystal, is notably enriched in MgO and MnO (average of 3.3 and 2.6 wt%, respectively; n=5), whereas magnetite is slighter enriched in Ti (TiO2 around 1.8 wt%) being average of MgO, MnO and V2O3 of 0.6wt%, 0.2wt%, and 0.6 wt% (respectively; n=20). Minerals such as chlorapatite, calcite, and chalcedony are also present in the magnetite-apatite ores. The samples from apatite-calcite ores contain coarse crystals of apatite and rhomboedral calcite. The plot of the EPMA data of Khanlogh iron ore samples on diagram of TiO2-V2O5 (Hou et al, 2011) illustrated that the data points lies between the well-known Kiruna and El Laco (Chile) iron deposits. The magnetite crystals in the sub-volcanic host rocks were possibly formed by immiscible iron oxide fluids during magmatic stage. However, the magnetite and apatite existing in the veins and breccia zones may have developed by high temperature hydrothermal fluids. Studies done by Purtov and Kotelnikova (1993) proved that the proportion of Ti in magnetite is related to fluoride complex in the hydrothermal

  15. Thermal treatment of magnetite nanoparticles

    PubMed Central

    Wykowska, Urszula; Satula, Dariusz; Nordblad, Per

    2015-01-01

    Summary This paper presents the results of a thermal treatment process for magnetite nanoparticles in the temperature range of 50–500 °C. The tested magnetite nanoparticles were synthesized using three different methods that resulted in nanoparticles with different surface characteristics and crystallinity, which in turn, was reflected in their thermal durability. The particles were obtained by coprecipitation from Fe chlorides and decomposition of an Fe(acac)3 complex with and without a core–shell structure. Three types of ferrite nanoparticles were produced and their thermal stability properties were compared. In this study, two sets of unmodified magnetite nanoparticles were used where crystallinity was as determinant of the series. For the third type of particles, a Ag shell was added. By comparing the coated and uncoated particles, the influence of the metallic layer on the thermal stability of the nanoparticles was tested. Before and after heat treatment, the nanoparticles were examined using transmission electron microscopy, IR spectroscopy, differential scanning calorimetry, X-ray diffraction and Mössbauer spectroscopy. Based on the obtained results, it was observed that the fabrication methods determine, to some extent, the sensitivity of the nanoparticles to external factors. PMID:26199842

  16. Single crystalline superstructured stable single domain magnetite nanoparticles

    PubMed Central

    Reichel, Victoria; Kovács, András; Kumari, Monika; Bereczk-Tompa, Éva; Schneck, Emanuel; Diehle, Patrick; Pósfai, Mihály; Hirt, Ann M.; Duchamp, Martial; Dunin-Borkowski, Rafal E.; Faivre, Damien

    2017-01-01

    Magnetite nanoparticles exhibit magnetic properties that are size and organization dependent and, for applications that rely on their magnetic state, they usually have to be monodisperse. Forming such particles, however, has remained a challenge. Here, we synthesize 40 nm particles of magnetite in the presence of polyarginine and show that they are composed of 10 nm building blocks, yet diffract like single crystals. We use both bulk magnetic measurements and magnetic induction maps recorded from individual particles using off-axis electron holography to show that each 40 nm particle typically contains a single magnetic domain. The magnetic state is therefore determined primarily by the size of the superstructure and not by the sizes of the constituent sub-units. Our results fundamentally demonstrate the structure – property relationship in a magnetic mesoparticle. PMID:28358051

  17. The origin and stability of lunar goethite, hematite and magnetite.

    NASA Technical Reports Server (NTRS)

    Williams, R. J.; Gibson, E. K.

    1972-01-01

    Extra-lunar contamination, fumarolic activity, and exposure to oxidizing gases from comet or carbonaceous meteorite impacts have been previously proposed as the causes of magnetite, hematite, and goethite in lunar materials. However, these minerals can occur in the stable low-temperature gas-solid equilibrium assemblages of lunar rocks. Below 600 C magnetite is in equilibrium with C-O-H gases with compositions compatible with high-temperature equilibrium with metallic iron; below 150 C hematite is stable in these same gases. Goethite is not stable in carbonaceous gases at low total pressure, and thus gases from impacting carbonaceous material cannot have produced it. Goethite is stable at low temperatures and pressures in almost pure H2-H2O gases. Its minimum stability against hematite is 2 bars total pressure at 130 C and 0.001 bars at 30 C for H2 to H2O ratios compatible with the high-temperature redox state of lunar materials. Thus the traces of magnetite, hematite, and goethite in lunar materials may be the result of normal low-temperature processes indigenous to the moon and not special processes.

  18. Microwave-assisted fractional precipitation of magnetite nanoparticles using designed experiments

    NASA Astrophysics Data System (ADS)

    Edrissi, Mohammad; Norouzbeigi, Reza

    2010-05-01

    In this study, highly pure magnetite nanoparticle dispersed in water and an organic solvent ( n-hexane) and its powder form were prepared in laboratory scale by the fractional precipitation using ammonium hydroxide and microwave heating in the presence of linoleic acid as capping agent. In order to overcome the oxidation of Fe2+ during magnetite formation ferrous ammonium sulfate, sodium azide, and fractional precipitation technique were used. The Fe3O4 products were investigated by XRD, LLS, EDX, TEM, viscosity measurements, and chemical analysis. The effects of seven main factors on the average diameter of magnetite particles were studied by a screening design. The analysis of the samples showed that this new modified method is able to produce pure magnetite particles in the range of 1-15 nm. The most important factors on the particle size reduction of magnetite were found to be the capping agent used and the pH of solution at the end of precipitation process. Data analysis was performed using Qualitek-4 and Minitab softwares.

  19. From iron(III) precursor to magnetite and vice versa

    SciTech Connect

    Gotic, M.; Jurkin, T.; Music, S.

    2009-10-15

    and recrystallised as goethite. The {gamma}-irradiation of the microemulsion for 25 h at a lower dose rate of 16 kGy/h produced pure substoichiometric nanosize magnetite particles of about 25 nm in size and with the stoichiometry of Fe{sub 2.83}O{sub 4}.

  20. Vortex magnetic structure in framboidal magnetite reveals existence of water droplets in an ancient asteroid

    NASA Astrophysics Data System (ADS)

    Kimura, Yuki; Sato, Takeshi; Nakamura, Norihiro; Nozawa, Jun; Nakamura, Tomoki; Tsukamoto, Katsuo; Yamamoto, Kazuo

    2013-10-01

    The majority of water has vanished from modern meteorites, yet there remain signatures of water on ancient asteroids. How and when water disappeared from the asteroids is important, because the final fluid-concentrated chemical species played critical roles in the early evolution of organics and in the final minerals in meteorites. Here we show evidence of vestigial traces of water based on a nanometre-scale palaeomagnetic method, applying electron holography to the framboids in the Tagish Lake meteorite. The framboids are colloidal crystals composed of three-dimensionally ordered magnetite nanoparticles and therefore are only able to form against the repulsive force induced by the surface charge of the magnetite as a water droplet parches in microgravity. We demonstrate that the magnetites have a flux closure vortex structure, a unique magnetic configuration in nature that permits the formation of colloidal crystals just before exhaustion of water from a local system within a hydrous asteroid.

  1. Composition of coarse-grained magnetite from pegmatite dikes related to plutons of quartz monzonite in the Jabal Lababa area, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Overstreet, William C.; Mousa, Hassan; Matzko, John J.

    1985-01-01

    Crystals of magnetite as large as 30 mm long and 7 mm thick are locally present in quartz-rich zones of interior and exterior pegmatite dikes related to plutons of quartz monzonite in the Jabal Lababa area. Niobium, tin, and yttrium are strongly enriched in six specimens of magnetite from interior pegmatite dikes in a small pluton where these elements form geochemical anomalies in nonmagnetic heavy-mineral concentrates from wadi sediment. Less abundant anomalous elements in the magnetite are molybdenum, lead, and zirconium, which also tend to be present in anomalous amounts in the nonmagnetic concentrates from the niobium-bearing pluton. The most anomalous trace element in the magnetite is zinc, which is at least 10 times as abundant as it is in the quartz monzonite plutons or in the nonmagnetic concentrates. The capacity of magnetite to scavenge molybdenum, zinc, niobium, lead, tin, yttrium, and zirconium suggests the possible utility of magnetite as a geochemical sample medium.

  2. Understanding the biological stabilization of ferrihydrite and its transformation to magnetite

    NASA Astrophysics Data System (ADS)

    Gordon, Lyle; Joester, Derk

    2013-03-01

    The biosynthesis of magnetite in the chiton tooth begins with the formation of ferrihydrite, which is transformed into magnetite. This strategy, which employs crystallization of a precursor into the desired polymorph, is generalized across a range of organisms. However, the specific biological factors that control the transformation are not known. Our results employing atom probe tomography of chiton tooth magnetite revealed the presence of acidic proteins binding sodium and magnesium ions associated with chitin nanofibers. Using a model system we are investigating the influence of organic and inorganic additives on the stabilization of ferrihydrite and the transformation to magnetite. I will discuss the influence of a range of organic and inorganic additives on the formation and transformation of ferrihydrite within the gel. We have found that acidic polymers stabilize ferrihydrite and prevent the formation of the crystalline polymorphs. Transformation of the ferrihydrite to magnetite upon addition of ferrous iron is observed as early as 30 minutes. Taken together, the contribution of these factors to magnetite biomineralization in the presence of an organic matrix will help to elucidate biological mechanisms for nucleation, stabilization, and transformation of iron oxides.

  3. Experimental stress remagnetization of magnetite

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham J.

    1996-09-01

    Pseudo-single-domain (PSD) and multidomain (MD) magnetite grains remagnetize in weak magnetic field (30 μT) during experimental triaxial deformation. The magnetite is supported in a calcite-cement matrix. Minor remagnetization occurs with hydrostatic stress of 100 MPa. Significant remagnetization requires hydrostatic pressure of 150 MPa with differential stress of ≥5 MPa superposed on the sample. Intergranular differential stresses must be much higher due to amplification at grain asperities. Stress remagnetization does not need chemical or thermal energy. New components of magnetic remanence are added parallel to the remagnetizing field. However, this only happens in grains or parts of grains with coercivities of remanence < 15 and > 60 mT. Grains with coercivities of 20-55 mT remember the primary magnetization and are not stress magnetized. These coercivity limits do not depend on the differential stress or strain rate of the experiment. The spatial distribution of vector components of remanence was isolated by AF demagnetization. After deforming a magnetized sample, the components of remanence spread along a partial great circle between the initial remanence and the direction of the remagnetizing field. The directions of the original magnetization and the remagnetizing field are the only factors controlling the course of the remagnetization path. Triaxial deformation shortened these samples by < 17%. Thus, grain rotation fails to explain the changes in directions of magnetism. The remagnetization is attributed to the low field during stress deflection of domain walls that were possibly locked in place by deformation features. If the experimental results are transferable to nature, it is possible that a pulse of excess crustal stress > 25 MPa could partially remagnetize low-dislocation-density magnetite. The experiments show that the directions of the remagnetizing field and the primary magnetization are the only variables that affect the demagnetization

  4. Magnetite and magnetite/silver core/shell nanoparticles with diluted magnet-like behavior

    SciTech Connect

    Garza-Navarro, Marco; Gonzalez, Virgilio; Ortiz, Ubaldo; De la Rosa, Elder

    2010-01-15

    In the present work is reported the use of the biopolymer chitosan as template for the preparation of magnetite and magnetite/silver core/shell nanoparticles systems, following a two step procedure of magnetite nanoparticles in situ precipitation and subsequent silver ions reduction. The crystalline and morphological characteristics of both magnetite and magnetite/silver core/shell nanoparticles systems were analyzed by high resolution transmission electron microscopy (HRTEM) and nanobeam diffraction patterns (NBD). The results of these studies corroborate the core/shell morphology and the crystalline structure of the magnetite core and the silver shell. Moreover, magnetization temperature dependent, M(T), measurements show an unusual diluted magnetic behavior attributed to the dilution of the magnetic ordering in the magnetite and magnetite/silver core/shell nanoparticles systems. - Graphical abstract: Biopolymer chitosan was used as stabilization media to synthesize both magnetite and magnetite/silver core/shell nanoparticles. Results of HRTEM and NBD patterns confirm core/shell morphology of the obtained nanoparticles. It was found that the composites show diluted magnet-like behavior.

  5. High Efficiency DNA Extraction by Graphite Oxide/Cellulose/Magnetite Composites Under Na+ Free System

    NASA Astrophysics Data System (ADS)

    Akceoglu, Garbis Atam; Li, Oi Lun; Saito, Nagahiro

    2016-04-01

    DNA extraction is the key step at various research areas like biotechnology, diagnostic development, paternity determination, and forensic science . Solid support extraction is the most common method for DNA purification. In this method, Na+ ions have often been applied as binding buffers in order to obtain high extraction efficiency and high quality of DNA; however, the presence of Na+ ions might be interfering with the downstream DNA applications. In this study, we proposed graphite oxide (GO)/magnetite composite/cellulose as an innovative material for Na+-free DNA extraction. The total wt.% of GO was fixed at 4.15% in the GO/cellulose/magnetite composite . The concentration of magnetite within the composites were controlled at 0-3.98 wt.%. The extraction yield of DNA increased with increasing weight percentage of magnetite. The highest yield was achieved at 3.98 wt.% magnetite, where the extraction efficiency was reported to be 338.5 ng/µl. The absorbance ratios between 260 nm and 280 nm (A260/A280) of the DNA elution volume was demonstrated as 1.81, indicating the extracted DNA consisted of high purity. The mechanism of adsorption of DNA was provided by (1) π-π interaction between the aromatic ring in GO and nucleobases of DNA molecule, and (2) surface charge interaction between the positive charge magnetite and anions such as phosphates within the DNA molecules. The results proved that the GO/cellulose/magnetite composite provides a Na+-free method for selective DNA extraction with high extraction efficiency of pure DNA.

  6. Three-Dimensional Morphological Analysis of ALH84001 Magnetite Using Electron Tomography

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Shimmin, Joel; Morphew, Mary; McIntosh, J. Richard; Bazylinski, Dennis A.; Kirschvink, Joseph L.; Wentworth, Susan J.; McKay, David S.; Vali, Hojatollah

    2003-01-01

    We report here the crystal morphologies of MV-1 and ALH84001 magnetites as calculated by back-projection using electron tomography. In the present study, we used a 300 keV TEM with a field emission gun (Tecnai F-30 from FEI Inc.), equipped with a 2048 x 2048 pixel CCD camera from Gatan Inc. to image magnetite crystals over tilt ranges of approx. +/- 72 deg in 2 deg tilt intervals. The images were aligned for back-projection, either manually, or through the use of fiducial 5 nm Au spheres affixed to the specimen prior to microscopy. Three-dimensional (3-D) reconstructions were computed using weighted back-projection of the tilted views. The tomograms were viewed and analyzed as a series of slices 1.0 nm thick, taken parallel to the specimen-supporting grid, using the IMOD software package. The shape of each magnetite crystal was determined by defining the external contour of a given magnetite in each slice and assembling a stack of these contours in 3-D. To aid in visualization, the stacked contour array was reduced to an optimal mesh by Delaunay triangulation. The surface normal to each of the triangles in the mesh was calculated and the triangle faces colored according to the orientation of that surface normal relative to the principal crystallographic axis of magnetite. Green surfaces correspond to {111} orientations, blue surfaces to {100} orientations, and red surfaces to {110} orientations. Triangles whose surface normal did not correspond to one of the principal axes were colored gray. Within the experimental and numerical uncertainties of the deconvolution, the tomographic reconstruction of both MV-1 and ALH84001 magnetites are equivalent and correspond to a truncated hexa-octahedral morphology.

  7. Preparation of magnetite-fullerene nanocomposite with enzyme immobilization.

    PubMed

    Kalska-Szostko, B; Rogowska, M

    2012-09-01

    This study presents modification of magnetite nanoparticles and fullerene for biocompatibility. It show also specific fabrication of magnetite-carbon nanocomposite with immobilized biomolecule. The composites were created by joining individual components step-by-step manner (fullerene to magnetite and glucose oxidase or glucose oxidase to magnetite and fullerene). The resulting nanocomposites were characterized by infrared spectroscopy (IR) and transmission electron microscopy (TEM).

  8. Novel magnetite-producing magnetotactic bacteria belonging to the Gammaproteobacteria.

    PubMed

    Lefèvre, Christopher T; Viloria, Nathan; Schmidt, Marian L; Pósfai, Mihály; Frankel, Richard B; Bazylinski, Dennis A

    2012-02-01

    Two novel magnetotactic bacteria (MTB) were isolated from sediment and water collected from the Badwater Basin, Death Valley National Park and southeastern shore of the Salton Sea, respectively, and were designated as strains BW-2 and SS-5, respectively. Both organisms are rod-shaped, biomineralize magnetite, and are motile by means of flagella. The strains grow chemolithoautotrophically oxidizing thiosulfate and sulfide microaerobically as electron donors, with thiosulfate oxidized stoichiometrically to sulfate. They appear to utilize the Calvin-Benson-Bassham cycle for autotrophy based on ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) activity and the presence of partial sequences of RubisCO genes. Strains BW-2 and SS-5 biomineralize chains of octahedral magnetite crystals, although the crystals of SS-5 are elongated. Based on 16S rRNA gene sequences, both strains are phylogenetically affiliated with the Gammaproteobacteria class. Strain SS-5 belongs to the order Chromatiales; the cultured bacterium with the highest 16S rRNA gene sequence identity to SS-5 is Thiohalocapsa marina (93.0%). Strain BW-2 clearly belongs to the Thiotrichales; interestingly, the organism with the highest 16S rRNA gene sequence identity to this strain is Thiohalospira alkaliphila (90.2%), which belongs to the Chromatiales. Each strain represents a new genus. This is the first report of magnetite-producing MTB phylogenetically associated with the Gammaproteobacteria. This finding is important in that it significantly expands the phylogenetic diversity of the MTB. Physiology of these strains is similar to other MTB and continues to demonstrate their potential in nitrogen, iron, carbon and sulfur cycling in natural environments.

  9. A reductive dissolution study of magnetite

    SciTech Connect

    Hui-Jun Won; Jung-Soon Park; Chong-Hun Jung; Sang-Yoon Park; Wang-Kyu Choi; Jei-Kwon Moon

    2013-07-01

    Magnetite dissolution tests using a hydrazine base solution were performed at a temperature range of 90 to 150 deg. C. The dissolution rate of magnetite increased with [N{sub 2}H{sub 4}], time, and temperature. The optimum solution pH in the experimental range was 3. The addition of copper ion to the hydrazine base solution greatly increased the magnetite dissolution rate. This was explained by the complex formation between N{sub 2}H{sub 4} and Cu ions, and the reducing power of the hydrazine-Cu complex to the ferric ions of magnetite. The reductive decontamination solution can be applied below 100 deg. C by the addition of copper ions. The chemical decontamination of a Type 304 stainless steel specimen using a hydrazine base reductive decontamination solution was also performed. The contact dose rate was greatly decreased by the repetitive application of NP and the hydrazine base solution. (authors)

  10. CIRCUMSTELLAR MAGNETITE FROM THE LAP 031117 CO3.0 CHONDRITE

    SciTech Connect

    Zega, Thomas J.; Haenecour, Pierre; Floss, Christine; Stroud, Rhonda M.

    2015-07-20

    We report the first microstructural confirmation of circumstellar magnetite, identified in a petrographic thin section of the LaPaz Icefield 031117 CO3.0 chondrite. The O-isotopic composition of the grain indicates an origin in a low-mass (∼2.2 M{sub ⊙}), approximately solar metallicity red/asymptotic giant branch (RGB/AGB) star undergoing first dredge-up. The magnetite is a single crystal measuring 750 × 670 nm, is free of defects, and is stoichiometric Fe{sub 3}O{sub 4}. We hypothesize that the magnetite formed via oxidation of previously condensed Fe dust within the circumstellar envelope of its progenitor star. Using an empirically derived rate constant for this reaction, we calculate that such oxidation could have occurred over timescales ranging from approximately ∼9000–500,000 years. This timescale is within the lifetime of estimates for dust condensation within RGB/AGB stars.

  11. Using the chemical analysis of magnetite to constrain various stages in the formation and genesis of the Kiruna-type chadormalu magnetite-apatite deposit, Bafq district, Central Iran

    NASA Astrophysics Data System (ADS)

    Heidarian, Hassan; Lentz, David; Alirezaei, Saeed; Peighambari, Sima; Hall, Douglas

    2016-12-01

    Textural and compositional data are presented for different types of magnetite in the Chadormalu iron deposit to discern the genesis of various styles of mineralization. Samples were chosen according to their paragenetic relations to apatite and their host setting: magnetite-apatite veins in the altered host rocks, disseminated magnetite-apatite assemblages in the marginal parts of the main ore body, and massive magnetite associated with irregular apatite veinlets from internal part of the main ore body. Scanning electron microscopy - back scatter electron (SEM-BSE) images reveal that there are three main generations of magnetite in each of the different magnetite-apatite assemblages. Primary magnetite (Mag1) features abundant porosity and a dark appearance. A second generation of magnetite (Mag2) replacing Mag1 shows a lighter appearance with both sharp and gradational contacts with the primary magnetite crystals. The two magnetite types are related to dissolution-precipitation processes due to changing physico-chemical parameters of the ore fluids. A third type of magnetite (Mag3) with a recrystallized appearance and foam-like triple junctions was mostly observed in magnetite-apatite veins in the main ore body and in veins hosted by altered rocks. Electron probe microanalyses (EPMA) were utilized to discriminate the various magnetite generations in the different magnetite-apatite assemblages. Applying published elemental discrimination diagrams shows that most primary magnetites fall into the hydrothermal- and Kiruna-type fields. Primary magnetite contains lower FeO (88.77-93.65 wt.%; average 91.5 wt.%), and higher SiO2 (0.21-2.26 wt.%; ave. 0.32 wt.%), Al2O3 (0.001-0.45 wt.%; ave. 0.053 wt.%), and CaO (0.002-0.48 wt.%; ave. 0.078 wt.%) contents, which might be related to magmatically derived fluids. Secondary magnetites have higher FeO (89.23-93.49 wt.%; ave. 92.11 wt.%), lower SiO2 (0.037-0.189 wt.%; ave. 0.072 wt.%), Al2O3 (0.004-0.072 wt.%; ave. 0.019 wt

  12. Intercalation Crystallization of Phase-Pure ..alpha..-HC(NH2)2PbI3 upon Microstructurally Engineered PbI2 Thin Films for Planar Perovskite Solar Cells

    SciTech Connect

    Zhou, Yuanyuan; Yang, Mengjin; Kwun, Joonsuh; Game, Onkar S.; Zhao, Yixin; Pang, Shuping; Padture, Nitin P.; Zhu, Kai

    2016-03-28

    The microstructure of the solid-PbI2 precursor thin film plays an important role in the intercalation crystallization of the formamidinium lead triiodide perovskite (..alpa..-HC(NH2)2PbI3). It is shown that microstructurally engineered PbI2 thin films with porosity and low crystallinity are the most favorable for conversion into uniform-coverage, phase-pure ..alpha..-HC(NH2)2PbI3 perovskite thin films. Planar perovskite solar cells fabricated using these thin films deliver power conversion efficiency (PCE) up to 13.8%.

  13. Cassiterite exsolution with ilmenite lamellae in magnetite from the Huashan metaluminous tin granite in southern China

    NASA Astrophysics Data System (ADS)

    Wang, Ru Cheng; Yu, A.-Peng; Chen, Jun; Xie, Lei; Lu, Jian-Jun; Zhu, Jin-Chu

    2012-05-01

    Sn4+ is generally the dominant form of tin in magnetite-series granites as shown by the presence of cassiterite or its incorporation into Ti-bearing minerals such as biotite and titanite. Little is known about the behavior of tin in magnetite. The Huashan granite is an oxidized tin granite in the Nanling Range, southern China, where it contains magnetite as the dominant Fe oxide mineral. It is included in biotite as an early phase and also as interstitial grains spatially associated with ilmenite, cassiterite, Sn-rich titanite (SnO2 up to 5.9 wt.%), fluorite and apatite. This association indicates that tin enrichment occurred during the late stage of magma crystallization. Ilmenite lamellae display a trellis structure consistent with features of the "oxy-exsolution" process of Sn-bearing titanomagnetite precursor. Micro-inclusions of cassiterite (<1 μm in size) are found only within ilmenite lamellae. This suggests that magnetite with cassiterite inclusions is likely an indicator mineral of oxidized tin granites. Although rare in nature, Sn-bearing magnetite from weathered granites where concentrated in stream sediments, may serve as a strategic tracer for tin exploration in granite districts and in placer deposits, in general.

  14. Comparison of the inhibitory capacity of two groups of pure natural extract on the crystallization of two types of material compound urinary stones in vitro study

    NASA Astrophysics Data System (ADS)

    Beghalia, Mohamed; Ghalem, Said; Allali, Hocine

    2015-10-01

    Urolithiasis is defined as the result of an abnormal precipitation within the urinary tract. This precipitation is most often from the normal constituents of the urine. This is a fairly common condition in the population. She is happy and recurrent etiology is often unknown if hypothetical. In Algeria, as in many countries, a large number of patients use herbal medicines in the treatment of their diseases including urolithiasis. Thus the aim of this study is the most widely used to evaluate the effectiveness of aqueous extracts of medicinal plants, in the treatment of calcium urolithiasis oxalo-and magnesium-amoniaco in vitro. The study also examines the effect of these extracts on the states of crystallization (nucleation, crystal growth, crystal aggregation), followed by photography on polarized light microscope.In this regard, we are devoted to studying the crystallization steps from oxalo-calcium and phospho-calcic prepared as artificial urine and supersaturated aqueous solutions, maintained at 37 °C to remain close to biological conditions. Extracts of the first group of herbs: Ammodaucus leucotrichus, Ajuga iva, Globularia alypum, Atriplex halimus are studied on the crystallization calcium oxalate, we cite the Ammodaucus leucotrichus which acts on the stages of nucleation, growth and the aggregation with a total inhibition. The second group of extracts plants tested on calcium phosphate crystallization : Acacia raddiana, Citrullus colocynthis, Rhus tripartita, Pistacia lentiscu, Warionia saharae, are able to significantly reduce phosphate crystallization in vitro. It is easily proved by FTIR and optical microscope. In conclusion the results of our work allows us to confirm the use of these plants as an aqueous decoction, in the field of urolithiasis. These activities may help to strengthen the body in depressed situations.

  15. Formation of single domain magnetite by green rust oxidation promoted by microbial anaerobic nitrate-dependent iron oxidation

    NASA Astrophysics Data System (ADS)

    Miot, Jennyfer; Li, Jinhua; Benzerara, Karim; Sougrati, Moulay Tahar; Ona-Nguema, Georges; Bernard, Sylvain; Jumas, Jean-Claude; Guyot, François

    2014-08-01

    Biomineralization of magnetite is a central geomicrobiological process that might have played a primordial role over Earth’s history, possibly leaving traces of life in the geological record or controlling trace metal(loid)s and organic pollutants mobility in modern environments. Magnetite biomineralization has been attributed to two main microbial pathways to date (namely magnetotactic bacteria and dissimilatory iron-reducing bacteria). Here, we uncover a new route of magnetite biomineralization involving the anaerobic nitrate-reducing iron(II) oxidizing bacterium Acidovorax sp. strain BoFeN1. Using transmission electron microscopy, scanning transmission X-ray microscopy, transmission Mössbauer spectroscopy and rock magnetic analyses, this strain is shown to promote the transformation of hydroxychloride green rust in equilibrium with dissolved Fe(II) to (1) periplasmic lepidocrocite (γ-FeOOH) and (2) extracellular magnetite, thus leading to strong redox heterogeneities at the nanometer scale. On the one hand, lepidocrocite was associated with protein moieties and exhibited an anisotropic texture, with the elongated axis parallel to the cell wall. On the other hand, magnetite crystals exhibited grain sizes and magnetic properties consistent with stable single domain particles. By comparison, abiotic controls led to a very slow (4 months vs. 2 days in BoFeN1 cultures) and incomplete oxidation of hydroxychloride green rust towards magnetite. As this abiotic magnetite exhibited the same size and magnetic properties (stable single domain particles) as magnetite produced in BoFeN1 cultures, only the co-occurrence of textured Fe(III)-oxides and magnetite, associated with the persistence of organic carbon molecules, might constitute valuable biosignatures to be looked for in the geological record. Our results furthermore contribute to a more complex picture of Fe redox cycling in the environment, providing an additional process of Fe(II)-bearing phase

  16. Simultaneously discrete biomineralization of magnetite and tellurium nanocrystals in magnetotactic bacteria.

    PubMed

    Tanaka, Masayoshi; Arakaki, Atsushi; Staniland, Sarah S; Matsunaga, Tadashi

    2010-08-01

    Magnetotactic bacteria synthesize intracellular magnetosomes comprising membrane-enveloped magnetite crystals within the cell which can be manipulated by a magnetic field. Here, we report the first example of tellurium uptake and crystallization within a magnetotactic bacterial strain, Magnetospirillum magneticum AMB-1. These bacteria independently crystallize tellurium and magnetite within the cell. This is also highly significant as tellurite (TeO(3)(2-)), an oxyanion of tellurium, is harmful to both prokaryotes and eukaryotes. Additionally, due to its increasing use in high-technology products, tellurium is very precious and commercially desirable. The use of microorganisms to recover such molecules from polluted water has been considered as a promising bioremediation technique. However, cell recovery is a bottleneck in the development of this approach. Recently, using the magnetic property of magnetotactic bacteria and a cell surface modification technology, the magnetic recovery of Cd(2+) adsorbed onto the cell surface was reported. Crystallization within the cell enables approximately 70 times more bioaccumulation of the pollutant per cell than cell surface adsorption, while utilizing successful recovery with a magnetic field. This fascinating dual crystallization of magnetite and tellurium by magnetotactic bacteria presents an ideal system for both bioremediation and magnetic recovery of tellurite.

  17. The chemistry of hydrothermal magnetite: a review

    USGS Publications Warehouse

    Nadoll, Patrick; Angerer, Thomas; Mauk, Jeffrey L.; French, David; Walshe, John

    2014-01-01

    Magnetite (Fe3O4) is a well-recognized petrogenetic indicator and is a common accessory mineral in many ore deposits and their host rocks. Recent years have seen an increased interest in the use of hydrothermal magnetite for provenance studies and as a pathfinder for mineral exploration. A number of studies have investigated how specific formation conditions are reflected in the composition of the respective magnetite. Two fundamental questions underlie these efforts — (i) How can the composition of igneous and, more importantly, hydrothermal magnetite be used to discriminate mineralized areas from barren host rocks, and (ii) how can this assist exploration geologists to target ore deposits at greater and greater distances from the main mineralization? Similar to igneous magnetite, the most important factors that govern compositional variations in hydrothermal magnetite are (A) temperature, (B) fluid composition — element availability, (C) oxygen and sulfur fugacity, (D) silicate and sulfide activity, (E) host rock buffering, (F) re-equilibration processes, and (G) intrinsic crystallographic controls such as ionic radius and charge balance. We discuss how specific formation conditions are reflected in the composition of magnetite and review studies that investigate the chemistry of hydrothermal and igneous magnetite from various mineral deposits and their host rocks. Furthermore, we discuss the redox-related alteration of magnetite (martitization and mushketovitization) and mineral inclusions in magnetite and their effect on chemical analyses. Our database includes published and previously unpublished magnetite minor and trace element data for magnetite from (1) banded iron formations (BIF) and related high-grade iron ore deposits in Western Australia, India, and Brazil, (2) Ag–Pb–Zn veins of the Coeur d'Alene district, United States, (3) porphyry Cu–(Au)–(Mo) deposits and associated (4) calcic and magnesian skarn deposits in the southwestern United

  18. Magnetic Dinner Salads: The Role of Biogenic Magnetite in Cryopreservation for Common Food Plants

    NASA Astrophysics Data System (ADS)

    Chaffee, T. M.; Kirschvink, J. L.; Kobayashi, A. K.

    2015-12-01

    Biogenically-precipitated magnetite has been found in organisms ranging from Bacteria, single-celled protists, and many of the animal phyla, where its major function is navigation and magnetoreception. To date there is but a single report of biogenic magnetite in plants (essentially, magnetoferritin), and that is in common grass (Festuca species, from Gajdardziska-Josifovska et. al. doi:10.1127/0935-1221/2001/0013/0863). Recent developments in cryopreservation suggest that ~ 1 mT, ~ 10 Hz oscillating magnetic fields can drastically reduce ice nucleation during freezing, promote supercooling, and minimize cellular damage in living tissues (e.g., Kaku et al., doi: 10.1016/j.cryobiol.2012.02.001). Kobayashi & Kirschvink (2014, doi:10.1016/j.cryobiol.2013.12.002) suggest that biogenic magnetite crystals could be the nucleating site for damaging ice crystals, and that they would be driven magneto-mechanically to rotate in those oscillating fields which could inhibit the ice crystal nucleation process. This prompted our investigation into the magnetite content of ordinary fruit and vegetable food products, as knowledge of the natural levels of biogenic magnetite in the human food supply could guide the selection of which foods might work for this type of cryopreservation. Our study involved a range of common foods including avocados, bananas, garlic, and apples. Samples were prepared in a clean lab environment kept free of contaminant particles, and subjected to a variety of standard rock-magnetic tests including IRM and ARM acquisition, and the corresponding Af demagnetization, on a standard 2G™ SRM. Results are consistent with moderately interacting single-domain magnetite (see figure), with moderate inter-particle interaction effects. Typical magnetite concentrations in these samples are in the range of .1 to 1 ng/g for room temperature samples, increasing to the range of 1-10 ng/g when measured frozen (to inhibit thermal rotation of small particles and clumps). If

  19. Complete sets of elastic constants and photoelastic coefficients of pure and MgO-doped lithium niobate crystals at room temperature

    SciTech Connect

    Andrushchak, A. S.; Laba, H. P.; Yurkevych, O. V.; Mytsyk, B. G.; Solskii, I. M.; Kityk, A. V.; Sahraoui, B.

    2009-10-01

    This paper presents the results of ultrasonic measurements of LiNbO{sub 3} and LiNbO{sub 3}:MgO crystals. The tensors of piezoelectric coefficients, elastic stiffness constants, and elastic compliances are determined for both crystals at room temperature. Combining these data with the results of piezo-optical measurements, a complete set of photoelastic tensor coefficients is also calculated. Doping of LiNbO{sub 3} crystals by MgO does not lead to a considerable modification of their elastic and photoelastic properties. However, LiNbO{sub 3}:MgO is characterized by a considerably higher resistance with respect to powerful light radiation, making it promising for future application in acousto-optic devices that deal with superpowerful laser radiation. Presented here are the complete tensor sets of elastic constants and photoelastic coefficients of LiNbO{sub 3} and LiNbO{sub 3}:MgO crystals that may be used for a geometry optimization of acousto-optical interaction providing the best diffraction efficiency of acousto-optical cells made of these materials.

  20. Magnetofluidization of fine magnetite powder.

    PubMed

    Valverde, J M; Espin, M J; Quintanilla, M A S; Castellanos, A

    2009-03-01

    The behavior of a fluidized bed of fine magnetite particles as affected by a cross-flow magnetic field is investigated. A distinct feature of this naturally cohesive powder, as compared to noncohesive magnetic grains usually employed in magnetofluidized beds, is that the fluidized bed displays a range of stable fluidization even in the absence of an external magnetic field. Upon application of the magnetic field, the interval of stable fluidization is extended to higher gas velocities and bed expansion is enhanced. We have measured the tensile strength as affected by application of the external magnetic field according to two different operation modes. In the H off-on operation mode, the bed is driven to bubbling in the absence of external magnetic field. Once the gas velocity is decreased below the bubbling onset and the bed has returned to stable fluidization due to natural cohesive forces, the field is applied. In the H on-on mode, the field is maintained during the whole process of bubbling and return to stable fluidization. It is found that the tensile strength of the naturally stabilized bed is not essentially changed by application of the field ( H off-on) since the magnetic field cannot alter the bed structure once the particles are jammed in the stable fluidization state. Magnetic forces within the bulk of the jammed bed are partially canceled as a result of the anisotropic nature of the dipole-dipole interaction between the particles, which gives rise to just a small increment of the tensile strength. On the other hand, when the field is held on during bubbling and transition to stable fluidization ( H on-on mode), the tensile strength is appreciably increased. This suggests the formation of particle chains when the particles are not constrained due to the dipole-dipole attractive interaction which affects the mechanical strength of the stably fluidized bed. Experimental data are analyzed in the light of theoretical models on magnetic surface stresses.

  1. Geochemistry of magnetite from Proterozoic Fe-Cu deposits in the Kangdian metallogenic province, SW China

    NASA Astrophysics Data System (ADS)

    Chen, Wei Terry; Zhou, Mei-Fu; Gao, Jian-Feng; Hu, Ruizhong

    2015-10-01

    -sulfide stage have slightly higher Cu, Zn, and Mn and are thought to have crystallized from relatively low-temperature and Cu-Zn-Mn-rich fluids evolved from the fluids of the early Fe-oxide stage. Our results show that magnetite from the Fe-Cu deposits in the Kangdian Province, banded iron formation, Fe skarn deposits, diabase-hosted hydrothermal Fe deposits, and magmatic deposits has significantly different compositions. We propose that covariations of Co-Ni, Zn-Sn, and Co/Ni-Mn can be used to effectively discriminate different deposit types.

  2. Preparation of phase pure and well-crystallized Li4Ti5O12 nanoparticles by precision control of starting mixture and calcining at lowest possible temperatures

    NASA Astrophysics Data System (ADS)

    Abe, Y.; Matsui, E.; Senna, M.

    2007-05-01

    In an attempt to obtain spinel Li4Ti5O12 with smallest possible grain size and highest possible phase purity via a solid state route, we tried to elevate reactivity of the reactant mixture by mechanical activation and appropriate choice of the starting materials. From the stoichiometric mixture comprising Li2CO3 and 150 nm anatase, we needed to heat at 950 °C for 1 h to obtain 81 88% phase purity (PhP) of Li4Ti5O12 with its average grain size ca 600 nm. After mechanical activation with a multi-ring mill for 30 min, 850 °C was enough to obtain 85 87% pure 500 nm spinel. From a combination of LiNO3 and 50 nm anatase, 90 91% phase pure product with its grain size 240 nm was obtained at 750 °C due to fusion of the nitrate and shorter diffusion path. By using CH3COOLi.2H2O and 50 nm anatase we obtained 130 nm Li4Ti5O12 with its PhP ca 90% by milling the mixture preliminarily calcined at 500 °C for 1 h and heating subsequently at 700 for 1 h.

  3. Oxidation of pyrite in coal to magnetite

    USGS Publications Warehouse

    Thorpe, A.N.; Senftle, F.E.; Alexander, C.C.; Dulong, F.T.

    1984-01-01

    When bituminous coal is heated in an inert atmosphere (He) containing small amounts of oxygen at 393-455 ??C, pyrite (FeS2) in coal is partially converted to magnetite (Fe304). The maximum amount of Fe304 formed during the time of heating corresponds to 5-20% of the total pyrite present, depending on the coal sample. The magnetite forms as an outer crust on the pyrite grains. The fact that the magnetic properties of the pyrite grains are substantially increased by the magnetite crust suggests that pyrite can be separated from coal by use of a low magnetic field. In a laboratory test, 75% removal is obtained by means of a 500 Oe magnet on three samples, and 60% on a fourth sample. ?? 1984.

  4. Rock magnetism linked to human brain magnetite

    NASA Astrophysics Data System (ADS)

    Kirschvink, Joseph L.

    Magnetite has a long and distinguished career as one of the most important minerals in geophysics, as it is responsible for most of the remanent magnetization in marine sediments and the oceanic crust. It may come as a surprise to discover that it also ranks as the third or fourth most diverse mineral product formed biochemically by living organisms, and forms naturally in a variety of human tissues [Kirschvink et al., 1992].Magnetite was discovered in teeth of the Polyplacophora mollusks over 30 years ago, in magnetotactic bacteria nearly 20 years ago, in honey bees and homing pigeons nearly 15 years ago, but only recently in human tissue.

  5. Immobilization of Peroxidase onto Magnetite Modified Polyaniline

    PubMed Central

    Barbosa, Eduardo Fernandes; Molina, Fernando Javier; Lopes, Flavio Marques; García-Ruíz, Pedro Antonio; Caramori, Samantha Salomão; Fernandes, Kátia Flávia

    2012-01-01

    The present study describes the immobilization of horseradish peroxidase (HRP) on magnetite-modified polyaniline (PANImG) activated with glutaraldehyde. After the optimization of the methodology, the immobilization of HRP on PANImG produced the same yield (25%) obtained for PANIG with an efficiency of 100% (active protein). The optimum pH for immobilization was displaced by the effect of the partition of protons produced in the microenvironment by the magnetite. The tests of repeated use have shown that PANImG-HRP can be used for 13 cycles with maintenance of 50% of the initial activity. PMID:22489198

  6. Stabilization and encapsulation of magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Kawni, Issmat Al; Garcia, Ricardo; Youssef, Sami; Abboud, Maher; Podlecki, Jean; Habchi, Roland

    2016-12-01

    The goal is to stabilize magnetite nanoparticles (NPs) in order to prepare them for encapsulation and to obtain a core-shell structure. Magnetite NPs were obtained by a co-precipitation method and then treated with different stabilizing agents in order to get a full dispersion in an aqueous medium. The dispersed particles were then coated with silica using a TEOS solution. The samples were characterized by Raman spectroscopy, TEM, EDX analysis, and FTIR measurements. The particles are the basis of a core-shell structure where a potential polymer or drug could be anchored on the surface.

  7. Short-Range Correlations in Magnetite above the Verwey Temperature

    NASA Astrophysics Data System (ADS)

    Bosak, Alexey; Chernyshov, Dmitry; Hoesch, Moritz; Piekarz, Przemysław; Le Tacon, Mathieu; Krisch, Michael; Kozłowski, Andrzej; Oleś, Andrzej M.; Parlinski, Krzysztof

    2014-01-01

    Magnetite, Fe3O4, is the first magnetic material discovered and utilized by mankind in Ancient Greece, yet it still attracts attention due to its puzzling properties. This is largely due to the quest for a full and coherent understanding of the Verwey transition that occurs at TV=124 K and is associated with a drop of electric conductivity and a complex structural phase transition. A recent detailed analysis of the structure, based on single crystal diffraction, suggests that the electron localization pattern contains linear three-Fe-site units, the so-called trimerons. Here, we show that whatever the electron localization pattern is, it partially survives up to room temperature as short-range correlations in the high-temperature cubic phase, easily discernible by diffuse scattering. Additionally, ab initio electronic structure calculations reveal that characteristic features in these diffuse scattering patterns can be correlated with the Fermi surface topology.

  8. Remanent and induced magnetic anomalies over a layered intrusion: Effects from crystal fractionation and magma recharge

    NASA Astrophysics Data System (ADS)

    McEnroe, Suzanne A.; Brown, Laurie L.; Robinson, Peter

    2009-12-01

    The Bjerkreim-Sokndal (BKS) norite - quartz mangerite layered intrusion is part of the early Neoproterozoic Rogaland Anorthosite Province intruded into the Fennoscandian shield in south Norway at ~ 930 Ma. The BKS is exposed over an area of 230 km 2 with a thickness of ~ 7000 m and is of economic interest for ilmenite, magnetite and apatite deposits. From the point of view of magnetic minerals, in the course of fractional crystallization and magma evolution, the ilmenite becomes less Fe 3+-rich reflected by a change from ilmenite with hematite exsolution to nearly pure ilmenite. Magnetite starts to crystallize relatively late in the intrusive history, but its crystallization is interrupted by influxes of more primitive magma. The variations in aeromagnetic and ground-magnetic anomalies measured over the BKS can be explained in terms of the measured magnetic properties of NRM, susceptibility, and hysteresis presented here, and in terms of mineralogy. Early layers in the intrusion contain hemo-ilmenite. As the magma evolved and magnetite started to crystallize, this caused a distinct change over the layering from remanence-controlled negative anomalies to induced positive anomalies. When new, more primitive magma was injected into the system, hemo-ilmenite returned as the major oxide and the resulting magnetic anomalies are again negative. The most dramatic change in the magnetic signature is in the upper part of the intrusion in MCU IVe, where magnetite became a well established cumulate phase as indicated by susceptibility, but its induced magnetization is overcome by large NRMs associated either with hemo-ilmenite, or with hemo-ilmenite and magnetite exsolved from pyroxenes. The average natural remanent magnetizations change from ~ 3 A/m in MCU IVd, to 15 A/m in MCU IVe, and back to 2 A/m in the overlying MCU IVf, producing a strong negative remanent anomaly that has been followed along strike for at least 20 km by ground-magnetic measurements. The highly varied

  9. Magnetite Biomineralization: Fifty years of progress, from beach-combing to the SQUID microscope

    NASA Astrophysics Data System (ADS)

    Kirschvink, J. L.; Dixson, A. D.; Raub, T.

    2012-12-01

    Magnetite biomineralization was first discovered 50 years ago as a hardening agent in the teeth of the Polyplacophoran molluscs (chitons) by the late Prof. Heinz A. Lowenstam of Caltech, when he noticed unusual erosional effects produced by their grazing in the intertidal zones of Palau (Lowenstam, 1962). Since then, biogenic magnetite has been detected in a broad range of organisms, including magnetotactic bacteria, protists, insects, fish, amphibians, reptiles, birds, and mammals including humans. In many species, the role of ferromagnetic material as a neurophysiological transducer is demonstrated clearly through the effects of pulse-remagnetization on behavior. A brief (1 uS), properly configured magnetic discharge from a rectified LC circuit, tailored to exceed the coercivity of the magnetite, will often abolish a magnetic behavioral response, or in some cases make the organism go the wrong way. This is a unique ferromagnetic effect. The genes controlling magnetite biomineralization are well characterized in several species of bacteria, and the ability of some of these bacterial genes to initiate magnetite precipitation in mammalian cell lines argues for a common descent, probably via a magnetotactic mitochondrial ancestor. Previous studies in fish reported the presence of single-domain magnetite crystals in cells near projections of the trigeminal nerve, co-located in the olfactory epithelium. Although the cells are rare, the recent development of a spinning magnetic field technique allows easy identification and isolation of these cells for individual study (Eder et al., 2012). The cells are surprisingly magnetic, with moments hundreds of times larger than typical magnetotactic bacteria. Subsequent efforts to identify the anatomical seat of magnetoreceptors have focused on the same locations in new organisms, excluding other areas. Using SQUID moment magnetometry and SQUID scanning microscopy, we report here the unexpected presence of biogenic magnetite in

  10. Magnetite in Black Sea Turtles (Chelonia agassizi)

    NASA Astrophysics Data System (ADS)

    Fuentes, A.; Urrutia-Fucugauchi, J.; Garduño, V.; Sanchez, J.; Rizzi, A.

    2004-12-01

    Previous studies have reported experimental evidence for magnetoreception in marine turtles. In order to increase our knowledge about magnetoreception and biogenic mineralization, we have isolated magnetite particles from the brain of specimens of black sea turtles Chelonia agassizi. Our samples come from natural deceased organisms collected the reserve area of Colola Maruata in southern Mexico. The occurrence of magnetite particles in brain tissue of black sea turtles offers the opportunity for further studies to investigate possible function of ferrimagnetic material, its mineralogical composition, grain size, texture and its location and structural arrangement within the host tissue. After sample preparation and microscopic examination, we localized and identified the ultrafine unidimensional particles of magnetite by scanning electron microscope (SEM). Particles present grain sizes between 10.0 to 40.0Mm. Our study provides, for the first time, evidence for biogenic formation of this material in the black sea turtles. The ultrafine particles are apparently superparamagnetic. Preliminary results from rock magnetic measurements are also reported and correlated to the SEM observations. The black turtle story on the Michoacan coast is an example of formerly abundant resource which was utilized as a subsistence level by Nahuatl indigenous group for centuries, but which is collapsing because of intensive illegal commercial exploitation. The most important nesting and breeding grounds for the black sea turtle on any mainland shore are the eastern Pacific coastal areas of Maruata and Colola, in Michoacan. These beaches are characterized by important amounts of magnetic mineral (magnetites and titanomagnetites) mixed in their sediments.

  11. The metal-insulator transition in magnetite.

    NASA Technical Reports Server (NTRS)

    Cullen, J. R.; Callen, E.

    1972-01-01

    We describe an electronic model for the low temperature transition in magnetite, in which the average number of electrons on a site is non-integral. The solution of the one-dimensional problem is reviewed, and the connection of the model with the Verwey ordering is discussed. Some of the implication of the three dimensional problem are discussed.

  12. Charge ordering and ferroelectricity in magnetite

    NASA Astrophysics Data System (ADS)

    Khomskii, Daniel

    2007-03-01

    Magnetite Fe3O4 is one of the most fascinating material in solid state physics. Besides being the first magnetic material known to the mankind, it is also the first example of an insulator-metal transition in transition metal oxides -- the famous Verwey transition [1]. One usually connects this transition with the charge ordering of Fe^2+ and Fe^3+. However the detailed pattern of CO in Fe3O4 is still a matter of debate. Another aspect, which is not so widely known and which did not yet receive sufficient attention, is that below TV, besides being completely spin polarised, magnetite apparently is also ferroelectric (FE) [2]. Thus it seems that magnetite, besides being the first magnetic material and the first transition metal oxide with an insulator-metal transition, is also the first multiferroic material. Using the idea of a coexistence of site-centred and bond-centred charge ordering [3], I suggest a novel type of ordering in magnetite which explains the observed FE in Fe3O4 and which agrees with the structural data. [1] Verwey E.J.W., Nature 144, 327 (1939) [2] Rado G.T. and Ferrari J.M., Phys.Rev.B 12, 5166 (1975); Kato K. and Iida S., J.Phys.Soc.Japan 50, 2844 (1981) [3] Efremov D.V., van den Brink J. and Khomskii D.I., Nature Mater. 3, 853 (2004)

  13. Magnetite biomineralization and ancient life on Mars.

    PubMed

    Frankel, R B; Buseck, P R

    2000-04-01

    Certain chemical and mineral features of the Martian meteorite ALH84001 were reported in 1996 to be probable evidence of ancient life on Mars. In spite of new observations and interpretations, the question of ancient life on Mars remains unresolved. Putative biogenic, nanometer magnetite has now become a leading focus in the debate.

  14. Bisphosphonate release profiles from magnetite microspheres.

    PubMed

    Miyazaki, Toshiki; Inoue, Tatsuya; Shirosaki, Yuki; Kawashita, Masakazu; Matsubara, Takao; Matsumine, Akihiko

    2014-10-01

    Hyperthermia has been suggested as a novel, minimally invasive cancer treatment method. After implantation of magnetic nano- or microparticles around a tumour through blood vessels, irradiation with alternating magnetic fields facilitates the efficient in situ hyperthermia even for deep-seated tumours. On the basis of this idea, if the microspheres are capable of delivering drugs, they could be promising multifunctional biomaterials effective for chemotherapy as well as hyperthermia. In the present study, magnetite microspheres were prepared by aggregation of the iron oxide colloid in water-in-oil (W/O) emulsion. The release behaviour of alendronate, a typical bisphosphonate, from the microspheres was examined in vitro as a model of the bone tumour prevention and treatment system. The alendronate was successfully incorporated onto the porous magnetite microspheres in vacuum conditions. The drug-loaded microspheres maintained their original spherical shapes even after shaking in ultrapure water for 3 days, suggesting that they have sufficient mechanical integrity for clinical use. It was attributed to high aggregation capability of the magnetite nanoparticles through van der Waals and weak magnetic attractions. The microspheres showed slow release of the alendronate in vitro, resulting from tight covalent or ionic interaction between the magnetite and the alendronate. The release rate was diffusion-controlled type and well controlled by the alendronate concentration in drug incorporation to the microspheres.

  15. Remanent magnetism and ductile deformation in an experimentally deformed magnetite-bearing limestone

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham J.

    1991-07-01

    A limestone with pseudo-single-domain (PSD) pure magnetite is given an isothermal remanent magnetization (IRM). Samples are deformed triaxially at 200 MPa (2 kbar) confining pressure at room temperature and at a strain-rate of 10 -5 s -1. The limestone deforms in a ductile manner by twinning to produce sufficiently homogeneously strained specimens up to about 20% shortening. The uniform, saturation IRM rotates away from the shortening axis, approximately by an amount expected for the homogeneous strain of a non-material line marker. Hydrostatic compaction alone shows that this is time-dependent and compatible with progressive damage of the ferrimagnetic grains. Strain produces an increase in coercivity of the magnetite, an increase in its saturation remanence, and an increase in its anisotropy of magnetization (with respect to IRM). These observations are compatible with reduction in effective grain size and change of shape of magnetite. Experimental deformation reduces the intensity of magnetisation, chiefly by the removal of low-coercivity components of remanence when there is a pure IRM vector.

  16. Determination of the Three-Dimensional Morphology of ALH84001 and Biogenic MV-1 Magnetite: Comparison of Results from Electron Tomography and Classical Transmission Electron Microscopy

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Schwartz, Cindy; Morphew, Mary; McIntosh, J. Richard; Bazylinski, Dennis A.; Kirschvink, Joseph L.; Wentworth, Susan J.; McKay, David S.; Vali, Hojatollah

    2004-01-01

    Dated at approximately 3.9 billion years of age, carbonate disks, found within fractures of the host rock of Martian meteorite ALH84001, have been interpreted as secondary minerals that formed at low temperature in an aqueous medium. Heterogeneously distributed within these disks are magnetite nanocrystals that are of Martian origin. Approximately one quarter of these magnetites have morphological and chemical similarities to magnetite particles produced by magnetotactic bacteria strain MV-1, which are ubiquitous in aquatic habitats on Earth. Moreover, these types of magnetite particles are not known or expected to be produced by abiotic means either through geological processes or synthetically in the laboratory. The remaining three quarters of the ALH84001 magnetites are likely products of multiple processes including, but not limited to, precipitation from a hydrothermal fluid, thermal decomposition of the carbonate matrix in which they are embedded, and extracellular formation by dissimilatory Fe-reducing bacteria. We have proposed that the origins of magnetites in ALH84001 can be best explained as the products of multiple processes, one of which is biological. Recently the three-dimensional (3-D) external morphology of the purported biogenic fraction of the ALH84001 magnetites has been the subject of considerable debate. We report here the 3-D geometry of biogenic magnetite crystals extracted from MV-1 and of those extracted from ALH84001 carbonate disks using a combination of high resolution classical and tomographic transmission electron microscopy (TEM). We focus on answering the following questions: (1) which technique provides adequate information to deduce the 3-D external crystal morphology?; and, (2) what is the precise 3-D geometry of the ALH84001 and MV-1 magnetites?

  17. Title: Biogenic Magnetite Prevails in Oxic Pelagic Red Clay Core in the South Pacific Gyre

    NASA Astrophysics Data System (ADS)

    Shimono, T.; Yamazaki, T.

    2012-12-01

    Magnetotactic bacteria have been observed in wide variety of environments, including soils, freshwater lakes, and marine sediments, since Blakemore (1975) first described in 1975. Magnetotactic bacteria, which most commonly live within the oxic-anoxic transition zone (OATZ) of aquatic environments, produce intracellular crystals of magnetic minerals, specifically magnetite or greigite. It is considered that the magnetite/greigite crystals facilitate the bacteria's search for optimal conditions within the sharp chemical gradients of the OATZ. Petermann and Bleil (1993) reported living magnetotactic bacteria in pelagic and hemipelagic sediments near OATZ in the eastern South Atlantic at water depths to about 3,000 m, but they couldn't find actively swimming magnetotactic bacteria in sediments of deeper water depths. The South Pacific Gyre (SPG) is far from continents and the lowest productivity region on Earth. IODP site U1365 (water depth ~5,700 m) cored pelagic red clay of 75.5 m thick above ~100 Ma basement (except for the chart layer from ~42 to 63.5 m) in the western edge of the SPG. The core mainly consists of iron rich clay. The color is dark reddish and/or dark brown throughout the core. We conducted a paleomagnetic and environmental rock magnetic study of the pelagic clay core. The magnetostratigraphy revealed the top 5 m sediments cover the last 5 My, and sedimentation rate decreases downward from 1.7 to 0.6 m/m.y. Geochemical measurements of pore water indicate that dissolved oxygen was present throughout the core (>50 μM). Thus oxygen penetrates through the entire sediment column to the sediment/basalt interface, and there is no OATZ. Magnetic mineral assemblage of this core is dominated by biogenic magnetite despite no OATZ. First-order reversal curve (FORC) diagrams of all specimens have a narrow central ridge along the Hc axis with very small vertical spread. This indicates very weak magnetostatic interaction (Roberts et al., 2000), and is the

  18. Quantification of Biogenic Magnetite by Synchrotron X-ray Microscopy During the PETM

    NASA Astrophysics Data System (ADS)

    Wang, H.; Wang, J.; Kent, D. V.; Chen-Wiegart, Y. C. K.

    2014-12-01

    Exceptionally large biogenic magnetite crystals, including spearhead-like and spindle-like ones up to 4 microns, have been reported in clay-rich sediments recording the ~56 Ma Paleocene-Eocene thermal maximum (PETM) and carbon isotope excursion (CIE) in a borehole at Ancora, NJ and along with magnetotactic bacteria (MTB) chains, were suggested [Schumann et al. 2008 PNAS; Kopp et al. 2009 Paleoceanography] to account for the distinctive single domain (SD) rock magnetic properties of these sediments [Lanci et al. 2002 JGR]. However, because uncalibrated magnetic extraction techniques were used to provide material for TEM imaging of the biogenic magnetite, it is difficult to quantitatively analyze their concentration in the bulk clay. In this study, we use a synchrotron transmission X-ray microscope to image bulk CIE clay. We first take mosaic images of sub-millimeter-sized bulk clay samples, in which we can identify many of the various types of giant biogenic magnetite crystals, as well as several other types of iron minerals, such as pyrite framboids, siderite, and detrital magnetite. However, limited by the instrument resolution (~50 nm), we are not able to identify MTB chains let alone isolated magnetic nanoparticles that may be abundant the clay. To quantitatively estimate the concentration of the giant biogenic magnetite, we re-deposited the bulk clay sample in an alcohol solution on a silicon nitride membrane for 2D X-ray scans. After scanning a total area of 0.55 mm2 with average clay thickness of 4 μm, we identified ~40 spearheads, ~5 spindles and a few elongated rods and estimated their total magnetization as SD particles to be less than about 10% of the mass normalized clay for the scanned area. This result suggests that the giant biogenic magnetite is not a major source of the SD signal for the clay and is in good agreement with rock magnetic analyses using high-resolution first-order reversal curves and thermal fluctuation tomography on bulk CIE clay

  19. Ferromagnetic resonance and low-temperature magnetic tests for biogenic magnetite

    NASA Astrophysics Data System (ADS)

    Weiss, Benjamin P.; Sam Kim, Soon; Kirschvink, Joseph L.; Kopp, Robert E.; Sankaran, Mohan; Kobayashi, Atsuko; Komeili, Arash

    2004-07-01

    Magnetite is both a common inorganic rock-forming mineral and a biogenic product formed by a diversity of organisms. Magnetotactic bacteria produce intracellular magnetites of high purity and crystallinity (magnetosomes) arranged in linear chains of crystals. Magnetosomes and their fossils (magnetofossils) have been identified using transmission electron microscopy (TEM) in sediments dating back to ˜510-570 Ma, and possibly in 4 Ga carbonates in Martian meteorite ALH84001. We present the results from two rock magnetic analyses—the low-temperature Moskowitz test and ferromagnetic resonance (FMR)—applied to dozens of samples of magnetite and other materials. The magnetites in these samples are of diverse composition, size, shape, and origin: biologically induced (extracellular), biologically controlled (magnetosomes and chiton teeth), magnetofossil, synthetic, and natural inorganic. We confirm that the Moskowitz test is a distinctive indicator for magnetotactic bacteria and provide the first direct experimental evidence that this is accomplished via sensitivity to the magnetosome chain structure. We also demonstrate that the FMR spectra of four different strains of magnetotactic bacteria and a magnetofossil-bearing carbonate have a form distinct from all other samples measured in this study. We suggest that this signature also results from the magnetosomes' unique arrangement in chains. Because FMR can rapidly identify samples with large fractions of intact, isolated magnetosome chains, it could be a powerful tool for identifying magnetofossils in sediments.

  20. Biogenic magnetite as a basis for magnetic field detection in animals.

    PubMed

    Kirschvink, J L; Gould, J L

    1981-01-01

    Bacteria, sharks, honey bees, and homing pigeons as well as other organisms seem to detect the direction of the earth's magnetic field. Indirect but reproducible evidence suggests that the bees and birds can also respond to very minute changes in its intensity. The mechanisms behind this sensitivity are not known. Naturally magnetic, biologically precipitated magnetite (Fe3O4) has been found in chitons, magnetotactic bacteria, honey bees, homing pigeons, and dolphins. Its mineralization in localized areas may be associated with the ability of these animals to respond to the direction and intensity of the earth's magnetic field. The presence of large numbers (approximately 10(8)) of superparamagnetic magnetite crystals in honey bees and similar numbers of single-domain magnetite grains in pigeons suggests that there may be at least two basic types of ferrimagnetic magnetoreceptive organelles. Theoretical calculations show that ferrimagnetic organs using either type of grain when integrated by the nervous system are capable of accounting for even the most extreme magnetic field sensitivities reported. Indirect evidence suggests that organic magnetite may be a common biological component, and may account for the results of numerous high field and electromagnetic experiments on animals.

  1. Lanthanide-Substituted Magnetite Nanoparticles Using a New Mixed Precursor Method by Thermoanaerobacter ethanolicus

    NASA Astrophysics Data System (ADS)

    Moon, J.; Roh, Y.; Yeary, L. W.; Lauf, R. J.; Phelps, T. J.

    2006-12-01

    A metal reducing bacterium, Thermoanaerobacter ethanolicus successfully converted the precursor of L (lanthanide)-mixed akaganeite (LxFe1-xOOH) phase to L-substituted magnetite (LyFe3-yO4) while avoiding the potentially toxic effects of soluble L-ions. Antibiotic elements, lanthanide (Nd, Gd, Tb, Ho, and Er)-substituted magnetites were produced by microbial fermentation using LxFe1-xOOH, where x was up to 0.02 which is equivalent to 0.72 mM. Combining lanthanides into the akaganeite precursor phase mitigated some of the toxicity when compared to the traditional method by using pure akaganeite and the dissolved L-salt form. This new technique showed that an upper limit of L-concentrations between 0.02 and 0.1 mM might suppress bacterial activity. At the equivalent L-cation mole fraction, the traditional method increased the concentration of soluble toxic L ions in the final media. The precursor method enabled production of microbially synthesized L- substituted magnetite with an L-concentration 36-fold greater than could be obtained when the lanthanides were added as soluble salts. These results were confirmed by protein assay. The increase of L-concentration in the magnetite evidently manipulates its physical properties such as decreasing Curie temperature and decreasing saturation magnetism of L-substituted magnetite. This mixed precursor method can therefore be used to extend the application for nanofermentation and other bacterial synthesis fields where there is a need for economically low-energy consumable microbial production of nanoscale materials that should involve toxic or inhibitory elements to bacterial growth.

  2. Exchange bias in polycrystalline magnetite films made by ion-beam assisted deposition

    SciTech Connect

    Kaur, Maninder; Qiang, You; Jiang, Weilin; Burks, Edward C.; Liu, Kai; Namavar, Fereydoon; McCloy, John S.

    2014-11-07

    Iron oxide films were produced using ion-beam-assisted deposition, and Raman spectroscopy and x-ray diffraction indicate single-phase magnetite. However, incorporation of significant fractions of argon in the films from ion bombardment is evident from chemical analysis, and Fe/O ratios are lower than expected from pure magnetite, suggesting greater than normal disorder. Low temperature magnetometry and first-order reversal curve measurements show strong exchange bias, which likely arises from defects at grain boundaries, possibly amorphous, creating frustrated spins. Since these samples contain grains ∼6 nm, a large fraction of the material consists of grain boundaries, where spins are highly disordered and reverse independently with external field.

  3. Electron thermalization and trapping rates in pure and doped alkali and alkaline-earth iodide crystals studied by picosecond optical absorption

    NASA Astrophysics Data System (ADS)

    Ucer, K. B.; Bizarri, G.; Burger, A.; Gektin, A.; Trefilova, L.; Williams, R. T.

    2014-04-01

    Although light continues to be emitted from insulating crystals used as scintillators over a period of nanoseconds to microseconds after stopping of an energetic particle, much of what determines the nonlinearity of response goes on in the first picoseconds. On this time scale, free carriers and excitons are at high density near the track core and thus are subject to nonlinear quenching. The hot (free) electrons eventually cool to low enough energy that trapping on holes, dopants, or defects can commence. In the track environment, spatial distributions of trapped carriers determined on the picosecond time scale can influence the proportionality between light yield and the initial particle energy throughout the whole light pulse. Picosecond spectroscopy of optical absorption induced by a short pulse of above-gap excitation provides a useful window on what occurs during the crucial early evolution of excited populations. The laser excitation can be tuned to excite carriers that are initially very hot (˜3 eV) relative to the band edges, or that are almost thermalized (˜0.1 eV excess energy) at the outset. Undoped and doped samples of NaI:Tl(0%, 0.1%), CsI:Tl(0%, 0.01%, 0.04%, 0.3%), and SrI2:Eu(0%, 0.2%, 0.5%, 3%) are studied in this work.

  4. One step facile synthesis of ferromagnetic magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Suppiah, Durga Devi; Abd Hamid, Sharifah Bee

    2016-09-01

    The ferromagnetic properties of magnetite (Fe3O4) were influenced by the nanoparticle size, hence importance were given to the synthesis method. This paper clearly shows that magnetite nanoparticles were successfully synthesized by employing one step controlled precipitation method using a single salt (Iron(II) sulfate) iron precursor. The acquired titration curve from this method provides vital information on the possible reaction mechanism leading to the magnetite (Fe3O4) nanoparticles formation. Goethite (α-FeOOH) was obtained at pH 4, while the continuous addition of hydroxyl ions (OH-) forms iron hydroxides (Fe(OH)2). This subsequently reacts with the goethite, producing magnetite (Fe3O4) at pH 10. Spectroscopy studies validate the magnetite phase existence while structural and morphology analysis illustrates cubic shaped magnetite with an average size of 35 nm was obtained. The synthesized magnetite might be superparamagnetic though lower saturation magnetization (67.5 emu/g) measured at room temperature as compared to bulk magnetite. However the nanoparticles surface anisotropy leads to higher remanence (12 emu/g) and coercivity (117.7 G) making the synthesized magnetite an excellent candidate to be utilized in recording devices. The understanding of the magnetite synthesis mechanism can not only be used to achieve even smaller magnetite nanoparticles but also to prepare different types of iron oxides hydroxides using different iron precursor source.

  5. The contribution of vanadium and titanium on improving methylene blue decolorization through heterogeneous UV-Fenton reaction catalyzed by their co-doped magnetite.

    PubMed

    Liang, Xiaoliang; Zhong, Yuanhong; Zhu, Sanyuan; Ma, Lingya; Yuan, Peng; Zhu, Jianxi; He, Hongping; Jiang, Zheng

    2012-01-15

    This study investigated the methylene blue (MB) decolorization through heterogeneous UV-Fenton reaction catalyzed by V-Ti co-doped magnetites, with emphasis on comparing the contribution of V and Ti cations on improving the adsorption and catalytic activity of magnetite. In the well crystallized spinel structure, both Ti(4+) and V(3+) occupied the octahedral sites. Ti(4+) showed a more obvious effect on increasing specific surface area and superficial hydroxyl amount than V(3+) did, resulting in a significant improvement of the adsorption ability of magnetite to MB. The UV introduction greatly accelerated MB degradation. And magnetite with more Ti and less V displayed better catalytic activity in MB degradation through heterogeneous UV-Fenton reaction. The transformation of degradation products and individual contribution from vanadium and titanium on improving adsorption and catalytic activity of magnetite were also investigated. These new insights are of high importance for well understanding the interface interaction between contaminants and metal doped magnetites, and the environmental application of natural and synthetic magnetites.

  6. The magnetosome membrane protein, MmsF, is a major regulator of magnetite biomineralization in Magnetospirillum magneticum AMB-1

    PubMed Central

    Murat, Dorothée; Falahati, Veesta; Bertinetti, Luca; Csencsits, Roseann; Körnig, André; Downing, Kenneth; Faivre, Damien; Komeili, Arash

    2013-01-01

    Summary Magnetotactic bacteria (MTB) use magnetosomes, membrane bound crystals of magnetite or greigite, for navigation along geomagnetic fields. In Magnetospirillum magneticum sp. AMB-1, and other MTB, a magnetosome gene island (MAI) is essential for every step of magnetosome formation. An 8-gene region of the MAI encodes several factors implicated in control of crystal size and morphology in previous genetic and proteomic studies. We show that these factors play a minor role in magnetite biomineralization in vivo. In contrast, MmsF, a previously uncharacterized magnetosome membrane protein encoded within the same region plays a dominant role in defining crystal size and morphology and is sufficient for restoring magnetite synthesis in the absence of the other major biomineralization candidates. In addition, we show that the 18 genes of the mamAB gene cluster of the MAI are sufficient for the formation of an immature magnetosome organelle. Addition of MmsF to these 18 genes leads to a significant enhancement of magnetite biomineralization and an increase in the cellular magnetic response. These results define a new biomineralization protein and lay down the foundation for the design of autonomous gene cassettes for the transfer of the magnetic phenotype in other bacteria. PMID:22716969

  7. The HtrA/DegP family protease MamE is a bifunctional protein with roles in magnetosome protein localization and magnetite biomineralization

    PubMed Central

    Quinlan, Anna; Murat, Dorothée; Vali, Hojatollah; Komeili, Arash

    2011-01-01

    Summary Magnetotactic bacteria contain nanometer-sized, membrane-bound organelles, called magnetosomes, which are tasked with the biomineralization of small crystals of the iron oxide magnetite allowing the organism to use geomagnetic field lines for navigation. A key player in this process is the HtrA/DegP family protease MamE. In its absence, Magnetospirillum magneticum str AMB-1 is able to form magnetosome membranes but not magnetite crystals, a defect previously linked to the mislocalization of magnetosome proteins. In this work we use a directed genetic approach to find that MamE, and another predicted magnetosome-associated protease, MamO, likely function as proteases in vivo. However, as opposed to the complete loss of mamE where no biomineralization is observed, the protease-deficient variant of this protein still supports the initiation and formation of small, 20 nm-sized crystals of magnetite, too small to hold a permanent magnetic dipole moment. This analysis also reveals that MamE is a bifunctional protein with a protease-independent role in magnetosome protein localization and a protease-dependent role in maturation of small magnetite crystals. Together these results imply the existence of a previously unrecognized “checkpoint” in biomineralization where MamE moderates the completion of magnetite formation and thus committal to magneto-aerotaxis as the organism’s dominant mode of navigating the environment. PMID:21414040

  8. Origin of carbonate-magnetite-sulfide assemblages in Martian meteorite ALH84001

    NASA Astrophysics Data System (ADS)

    Scott, Edward R. D.

    1999-02-01

    A review of the mineralogical, isotopic, and chemical properties of the carbonates and associated submicrometer iron oxides and sulfides in Martian meteorite ALH84001 provides minimal evidence for microbial activity. Some magnetites resemble those formed by magnetotactic microorganisms but cubic crystals <50 nm in size and elongated grains <25 nm long are too small to be single-domain magnets and are probably abiogenic. Magnetites with shapes that are clearly unique to magnetotactic bacteria appear to be absent in ALH84001. Magnetosomes have not been reported in plutonic rocks and are unlikely to have been transported in fluids through fractures and uniformly deposited where abiogenic magnetite was forming epitaxially on carbonate. Submicrometer sulfides and magnetites probably formed during shock heating. Carbonates have correlated variations in Ca, Mg, and 18O/16O, magnetite-rich rims, and they appear to be embedded in pyroxene and plagioclase glass. Carbonates with these features have not been identified in carbonaceous chondrites and terrestrial rocks, suggesting that the ALH84001 carbonates have a unique origin. Carbonates and hydrated minerals in ALH84001, like secondary phases in other Martian meteorites, have O and H isotopic ratios favoring formation from fluids that exchanged with the Martian atmosphere. I propose that carbonates originally formed in ALH84001 from aqueous fluids and were subsequently shock heated and vaporized. The original carbonates were probably dolomite-magnesite-siderite assemblages that formed in pores at interstitial sites with minor sulfate, chloride, and phyllosilicates. These phases, like many other volatile-rich phases in Martian meteorites, may have formed as evaporite deposits from intermittent floods.

  9. [Interaction of fibrinogen with magnetite nanoparticles].

    PubMed

    Bychkova, A V; Sorokina, O N; Kovarskiĭ, A L; Shapiro, A B; Leonova, V B; Rozenfel'd, M A

    2010-01-01

    The interaction between fibrinogen and magnetite nanoparticles in solution has been studied by the methods of spin labeling, ferromagnetic resonance, dynamic and Rayleigh light scattering. It was shown that protein molecules adsorb on the surface of nanoparticles to form multilayer protein covers. The number of molecules adsorbed on one nanoparticle amounts to approximately 65 and the thickness of the adsorption layer amounts to approximately 27 nm. Separate nanoparticles with fibrinogen covers (clusters) form aggregates due to interactions of the end D-domains of fibrinogen. Under the influence of direct magnetic field, nanoparticles with adsorbed proteins form linear aggregates parallel to force lines. It was shown that the rate of protein coagulation during the formation of fibrin gel under the action of thrombin on fibrinogen decreases approximately 2 times in the presence of magnetite nanoparticles, and the magnitude of the average fiber mass-length ratio grows.

  10. Advancing Sustainable Catalysis with Magnetite Surface ...

    EPA Pesticide Factsheets

    This article surveys the recent developments in the synthesis, surface modification, and synthetic applications of magnetitenanoparticles. The emergence of iron(II,III) oxide (triiron tetraoxide or magnetite; Fe3O4, or FeO•Fe2O3) nanoparticles as a sustainable support in heterogeneous catalysis is highlighted. Use of an oxide of earth-abundant iron for various applications in catalysis and environmental remediation.

  11. Initial Test Determination of Cosmogenic Nuclides in Magnetite

    NASA Astrophysics Data System (ADS)

    Matsumura, H.; Caffee, M. W.; Nagao, K.; Nishiizumi, K.

    2014-12-01

    Long-lived radionuclides, such as 10Be, 26Al, and 36Cl, are produced by cosmic rays in surficial materials on Earth, and used for determinations of cosmic-ray exposure ages and erosion rates. Quartz and limestone are routinely used as the target minerals for these geomorphological studies. Magnetite also contains target elements that produce abundant cosmogenic nuclides when exposed to the cosmic rays. Magnetite has several notable merits that enable the measurement of cosmogenic nuclides: (1) the target elements for production of cosmogenic nuclides in magnetite comprise the dominant mineral form of magnetite, Fe3O4; (2) magnetite can be easily isolated, using a magnet, after rock milling; (3) multiple cosmogenic nuclides are produced by exposure of magnetite to cosmic-ray secondaries; and (4) cosmogenic nuclides produced in the rock containing the magnetite, but not within the magnetite itself, can be separated using nitric acid and sodium hydroxide leaches. As part of this initial study, magnetite was separated from a basaltic sample collected from the Atacama Desert in Chili (2,995 m). Then Be, Al, Cl, Ca, and Mn were separated from ~2 g of the purified magnetite. We measured cosmogenic 10Be, 26Al, and 36Cl concentrations in the magnetite by accelerator mass spectrometry at PRIME Lab, Purdue University. Cosmogenic 3He and 21Ne concentrations of aliquot of the magnetite were measured by mass spectrometry at the University of Tokyo. We also measured the nuclide concentrations from magnetite collected from a mine at Ishpeming, Michigan as a blank. The 10Be and 36Cl concentrations as well as 3He concentration produce concordant cosmic ray exposure ages of ~0.4 Myr for the Atacama basalt. However, observed high 26Al and 21Ne concentrations attribute to those nuclides incorporation from silicate impurity.

  12. Experimental Shock Decomposition of Siderite to Magnetite

    NASA Technical Reports Server (NTRS)

    Bell, M. S.; Golden, D. C.; Zolensky, M. E.

    2005-01-01

    The debate about fossil life on Mars includes the origin of magnetites of specific sizes and habits in the siderite-rich portions of the carbonate spheres in ALH 84001 [1,2]. Specifically [2] were able to demonstrate that inorganic synthesis of these compositionally zoned spheres from aqueous solutions of variable ion-concentrations is possible. They further demonstrated the formation of magnetite from siderite upon heating at 550 C under a Mars-like CO2-rich atmosphere according to 3FeCO3 = Fe3O4 + 2CO2 + CO [3] and they postulated that the carbonates in ALH 84001 were heated to these temperatures by some shock event. The average shock pressure for ALH 84001, substantially based on the refractive index of diaplectic feldspar glasses [3,4,5] is some 35-40 GPa and associated temperatures are some 300-400 C [4]. However, some of the feldspar is melted [5], requiring local deviations from this average as high as 45-50 GPa. Indeed, [5] observes the carbonates in ALH 84001 to be melted locally, requiring pressures in excess of 60 GPa and temperatures > 600 C. Combining these shock studies with the above inorganic synthesis of zoned carbonates it seems possible to produce the ALH 84001 magnetites by the shock-induced decomposition of siderite.

  13. Twisted partially pure spinors

    NASA Astrophysics Data System (ADS)

    Herrera, Rafael; Tellez, Ivan

    2016-08-01

    Motivated by the relationship between orthogonal complex structures and pure spinors, we define twisted partially pure spinors in order to characterize spinorially subspaces of Euclidean space endowed with a complex structure.

  14. Remanent and Induced Magnetic Anomalies over the Bjerkreim-Sokndal Layered Intrusion: Effects from Crystal Fractionation and Magma Recharge

    NASA Astrophysics Data System (ADS)

    McEnroe, S. A.; Brown, L. L.; Robinson, P.

    2013-12-01

    The Bjerkreim-Sokndal (BKS) norite-quartz mangerite layered intrusion is part of the early Neoproterozoic Rogaland Anorthosite Province intruded into the Fennoscandian shield in south Norway at ~930 Ma. The BKS is exposed over an area of 230 km2 with a thickness of ~7000m and is of economic interest for hemo-ilmenite, magnetite and apatite deposits. From the point of view of magnetic minerals, in the course of fractional crystallization and magma evolution, the ilmenite becomes less Fe3+-rich reflected by a change from ilmenite with hematite exsolution to nearly pure ilmenite. Magnetite starts to crystallize relatively late in the intrusive history, but its crystallization is interrupted by influxes of more primitive magma containing hemo-ilmenite. The variations in aeromagnetic and ground-magnetic anomalies measured over the BKS can be explained in terms of the magnetic properties of NRM, susceptibility, and hysteresis. Magnetic properties are correlated with the oxide mineralogy and mineral chemistry. Early layers in the intrusion contain hemo-ilmenite. As the magma evolved and magnetite started to crystallize, this caused a distinct change over the layering from remanence-controlled negative anomalies to induced positive anomalies. When new, more primitive magma was injected into the system, hemo-ilmenite returned as the major oxide and the resulting magnetic anomalies are again negative. The most dramatic change in the magnetic signature is in the upper part of the intrusion in MCU IVe, where magnetite became a well established cumulate phase as indicated by susceptibility, but its induced magnetization is overcome by large NRM's associated either with hemo-ilmenite or with hemo-ilmenite and magnetite exsolved from pyroxenes. The average natural remanent magnetizations change from ~3 A/m in MCU IVd, to 15 A/m in MCU IVe, and back to 2 A/m in the overlying MCU IVf, producing a strong negative remanent anomaly that has been followed along strike for at least 20

  15. Galvanostatic interruption of lithium insertion into magnetite: Evidence of surface layer formation

    DOE PAGES

    Nicholas W. Brady; Takeuchi, Esther S.; Knehr, K. W.; ...

    2016-04-24

    Magnetite is a known lithium intercalation material, and the loss of active, nanocrystalline magnetite can be inferred from the open-circuit potential relaxation. Specifically, for current interruption after relatively small amounts of lithium insertion, the potential first increases and then decreases, and the decrease is hypothesized to be due to a formation of a surface layer, which increases the solid-state lithium concentration in the remaining active material. Comparisons of simulation to experiment suggest that the reactions with the electrolyte result in the formation of a thin layer of electrochemically inactive material, which is best described by a nucleation and growth mechanism.more » Simulations are consistent with experimental results observed for 6, 8 and 32-nm crystals. As a result, simulations capture the experimental differences in lithiation behavior between the first and second cycles.« less

  16. Galvanostatic interruption of lithium insertion into magnetite: Evidence of surface layer formation

    SciTech Connect

    Nicholas W. Brady; Takeuchi, Esther S.; Knehr, K. W.; Cama, Christina A.; Lininger, Christianna N.; Lin, Zhou; Marschilok, Amy C.; Takeuchi, Kenneth J.; West, Alan C.

    2016-04-24

    Magnetite is a known lithium intercalation material, and the loss of active, nanocrystalline magnetite can be inferred from the open-circuit potential relaxation. Specifically, for current interruption after relatively small amounts of lithium insertion, the potential first increases and then decreases, and the decrease is hypothesized to be due to a formation of a surface layer, which increases the solid-state lithium concentration in the remaining active material. Comparisons of simulation to experiment suggest that the reactions with the electrolyte result in the formation of a thin layer of electrochemically inactive material, which is best described by a nucleation and growth mechanism. Simulations are consistent with experimental results observed for 6, 8 and 32-nm crystals. As a result, simulations capture the experimental differences in lithiation behavior between the first and second cycles.

  17. Galvanostatic interruption of lithium insertion into magnetite: Evidence of surface layer formation

    NASA Astrophysics Data System (ADS)

    Brady, Nicholas W.; Knehr, K. W.; Cama, Christina A.; Lininger, Christianna N.; Lin, Zhou; Marschilok, Amy C.; Takeuchi, Kenneth J.; Takeuchi, Esther S.; West, Alan C.

    2016-07-01

    Magnetite is a known lithium intercalation material, and the loss of active, nanocrystalline magnetite can be inferred from the open-circuit potential relaxation. Specifically, for current interruption after relatively small amounts of lithium insertion, the potential first increases and then decreases, and the decrease is hypothesized to be due to a formation of a surface layer, which increases the solid-state lithium concentration in the remaining active material. Comparisons of simulation to experiment suggest that the reactions with the electrolyte result in the formation of a thin layer of electrochemically inactive material, which is best described by a nucleation and growth mechanism. Simulations are consistent with experimental results observed for 6, 8 and 32-nm crystals. Furthermore, simulations capture the experimental differences in lithiation behavior between the first and second cycles.

  18. Preparation and adsorption properties of nano magnetite chitosan films for heavy metal ions from aqueous solution

    SciTech Connect

    Lasheen, M.R.; El-Sherif, Iman Y.; Tawfik, Magda E.; El-Wakeel, S.T.; El-Shahat, M.F.

    2016-08-15

    Highlights: • Nano magnetite–chitosan films were prepared by casting method. • The efficiency of the prepared films for removing heavy metals was investigated. • The adsorption mechanism was studied using different isotherm and kinetic models. • Films reuse and metals recovery were studied. - Abstract: Nano magnetite chitosan (NMag–CS) film was prepared and characterized with different analytical methods. X-ray diffraction (XRD) patterns confirmed the formation of a pure magnetite structure and NMag–CS nanocomposite. TEM image of the film, revealed the uniform dispersion of magnetite nanoparticles inside chitosan matrix. The adsorption properties of the prepared film for copper, lead, cadmium, chromium and nickel metal ions were evaluated. Different factors affecting the uptake behavior by the composite films such as time, initial pH and film dose were investigated. The adsorption equilibrium attained using 2 g/L of the film after 120 min of reaction. The equilibrium data were analyzed using Langmuir and Freundlich models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all metals. The metals regenerated from films with an efficiency greater than 95% using 0.1 M ethylene diamine tetra acetic acid (EDTA) and films were successfully reused for adsorption.

  19. Synthesis of non-aggregated nicotinic acid coated magnetite nanorods via hydrothermal technique

    NASA Astrophysics Data System (ADS)

    Attallah, Olivia A.; Girgis, E.; Abdel-Mottaleb, Mohamed M. S. A.

    2016-02-01

    Non-aggregated magnetite nanorods with average diameters of 20-30 nm and lengths of up to 350 nm were synthesized via in situ, template free hydrothermal technique. These nanorods capped with different concentrations (1, 1.5, 2 and 2.5 g) of nicotinic acid (vitamin B3); possessed good magnetic properties and easy dispersion in aqueous solutions. Our new synthesis technique maintained the uniform shape of the nanorods even with increasing the coating material concentration. The effect of nicotinic acid on the shape, particle size, chemical structure and magnetic properties of the prepared nanorods was evaluated using different characterization methods. The length of nanorods increased from 270 nm to 350 nm in nicotinic acid coated nanorods. Goethite and magnetite phases with different ratios were the dominant phases in the coated samples while a pure magnetite phase was observed in the uncoated one. Nicotinic acid coated magnetic nanorods showed a significant decrease in saturation magnetization than uncoated samples (55 emu/g) reaching 4 emu/g in 2.5 g nicotinic acid coated sample. The novel synthesis technique proved its potentiality to prepare coated metal oxides with one dimensional nanostructure which can function effectively in different biological applications.

  20. Extended release of vitamins from magnetite loaded polyanionic polymeric beads.

    PubMed

    Sonmez, Maria; Verisan, Cristina; Voicu, Georgeta; Ficai, Denisa; Ficai, Anton; Oprea, Alexandra Elena; Vlad, Mihaela; Andronescu, Ecaterina

    2016-08-30

    Here we explore a novel approach of increasing the release duration of folic and ascorbic acid from magnetite entrapped into calcium-alginate beads. Synthesis and characterization of magnetite-vitamins complexes are reported. The magnetite-vitamins complexes were characterized by FT-IR, XRD, SEM, BET and DTA-TG. Also calcium-alginate magnetic beads were prepared by dripping a mixture of sodium alginate with magnetite-vitamins complexes into calcium chloride solution. Extended release profile of the two experimental models was evaluated and quantified by UV-vis.

  1. A heterojunction photocatalyst composed of zinc rhodium oxide, single crystal-derived bismuth vanadium oxide, and silver for overall pure-water splitting under visible light up to 740 nm.

    PubMed

    Kobayashi, Ryoya; Takashima, Toshihiro; Tanigawa, Satoshi; Takeuchi, Shugo; Ohtani, Bunsho; Irie, Hiroshi

    2016-10-12

    We recently reported the synthesis of a solid-state heterojunction photocatalyst consisting of zinc rhodium oxide (ZnRh2O4) and bismuth vanadium oxide (Bi4V2O11), which functioned as hydrogen (H2) and oxygen (O2) evolution photocatalysts, respectively, connected with silver (Ag). Polycrystalline Bi4V2O11 (p-Bi4V2O11) powders were utilized to form ZnRh2O4/Ag/p-Bi4V2O11, which was able to photocatalyze overall pure-water splitting under red-light irradiation with a wavelength of 700 nm (R. Kobayashi et al., J. Mater. Chem. A, 2016, 4, 3061). In the present study, we replaced p-Bi4V2O11 with a powder obtained by pulverizing single crystals of Bi4V2O11 (s-Bi4V2O11) to form ZnRh2O4/Ag/s-Bi4V2O11, and demonstrated that this heterojunction photocatalyst had enhanced water-splitting activity. In addition, ZnRh2O4/Ag/s-Bi4V2O11 was able to utilize nearly the entire range of visible light up to a wavelength of 740 nm. These properties were attributable to the higher O2 evolution activity of s-Bi4V2O11.

  2. Zinc and Arsenic Immobilization and Magnetite Formation Upon Maghemite Reduction by Shewanella putrefaciens ATCC 8071

    NASA Astrophysics Data System (ADS)

    Cismasu, C.; Ona-Nguema, G.; Bonnin, D.; Menguy, N.; Brown, G. E.

    2007-12-01

    Dissimilatory reduction of ferric iron oxides is recognized as an important component of the iron biogeochemical cycle, causing the dissolution of iron oxide minerals and the possible formation of Fe(II)-bearing minerals such as magnetite, green rusts, siderite, etc. These mineralogical transformations affect the mobility of surface- associated toxic metal(loid)s, which may be released into solution, adsorbed, or incorporated into newly formed minerals. Maghemite (γ-Fe2O3) is an iron oxide mineral that is found in certain tropical soils and as isolated deposits in more temperate regions. In these settings, maghemite may play an important role in the biogeochemical cycling of iron and of surface-associated trace metal(loids). However, the reduction of maghemite by iron-respiring bacteria, the impact of reductive dissolution on the release of associated contaminants, and the nature of biogenic Fe(II)-containing reaction products are not well documented. In the present study, we incubated samples of pure maghemite and As(V)- and Zn-adsorbed maghemite with an iron reducing bacterium, Shewanella putrefaciens strain ATCC 8071, in a batch system under anoxic conditions. As a result of Fe(III) bioreduction, all mineral suspensions turned from brown to black during the first hour of incubation, indicating the onset of magnetite formation. The presence of this mineral was confirmed by transmission Mössbauer spectroscopy at room temperature, which showed the formation of an almost stoichiometric magnetite. High-resolution transmission electron microscopy images indicate that the parent maghemite and the biogenic magnetite particles are octahedral in shape and of similar size (5 to 20 nm). The presence of 50 mg/L adsorbed Zn(II) did not affect the initial rate of iron reduction with respect to the Zn-free maghemite sample (0.62 mM Fe(II)/h and 0.66 mM Fe(II)/h, respectively). However, adsorption of 50 and 100 mg/L As(V) on maghemite decreased the initial iron reduction rate

  3. Molecular simulation of the magnetite-water interface

    NASA Astrophysics Data System (ADS)

    Rustad, James R.; Felmy, Andrew R.; Bylaska, Eric J.

    2003-03-01

    This paper reports molecular dynamics simulations of the magnetite (001)-water interface, both in pure water and in the presence of a 2.3 molal solution of NaClO 4. The simulations are carried out using a potential model designed to allow the protonation states of the surface functional groups to evolve dynamically through the molecular dynamics trajectory. The primary structural quantities investigated are the populations of the surface functional groups, the distribution of electrolyte in the solution, and the surface hydrogen bonding relationships. The surface protonation states are dominated by extensive hydrolysis of interfacial water molecules, giving rise to a dipolar surface dominated by FeOH2+-OH 2-OH - arrangements. Triply coordinated, more deeply buried, surface sites are inert, probably due to the relative lack of solvent in their vicinity. The electrolyte distribution is oscillatory, arranging preferentially in layers defined by the solvating water molecules. The presence of electrolyte has a negligible effect on the protonation states of the surface functional groups. Steady-state behavior is obtained for the protonation states of the surface functional groups and hydrogen-bonding network. Although the overall structure of the electrolyte distribution is fairly well established, the electrolyte distribution has not fully equilibrated, as evidenced by the asymmetry in the distribution from the top to the bottom of the slab.

  4. Genes Necessary for Bacterial Magnetite Biomineralization Identified by Transposon Mutagenesis

    NASA Astrophysics Data System (ADS)

    Nash, C. Z.; Komeili, A.; Newman, D. K.; Kirschvink, J. L.

    2004-12-01

    Magnetic bacteria synthesize nanoscale crystals of magnetite in intracellular, membrane-bounded organelles (magnetosomes). These crystals are preserved in the fossil record at least as far back as the late Neoproterozoic and have been tentatively identified in much older rocks (1). This fossil record may provide deep time calibration points for molecular evolution studies once the genes involved in biologically controlled magnetic mineralization (BCMM) are known. Further, a genetic and biochemical understanding of BCMM will give insight into the depositional environment and biogeochemical cycles in which magnetic bacteria play a role. The BCMM process is not well understood, though proteins have been identified from the magnetosome membrane and genetic manipulation and biochemical characterization of these proteins are underway. Most of the proteins currently thought to be involved are encoded within the mam cluster, a large cluster of genes whose products localize to the magnetosome membrane and are conserved among magnetic bacteria (2). In an effort to identify all of the genes necessary for bacterial BCMM, we undertook a transposon mutagenesis of Magnetospirillum magneticum AMB-1. Non-magnetic mutants (MNMs) were identified by growth in liquid culture followed by a magnetic assay. The insertion site of the transposon was identified two ways. First MNMs were screened with a PCR assay to determine if the transposon had inserted into the mam cluster. Second, the transposon was rescued from the mutant DNA and cloned for sequencing. The majority insertion sites are located within the mam cluster. Insertion sites also occur in operons which have not previously been suspected to be involved in magnetite biomineralization. None of the insertion sites have occurred within genes reported from previous transposon mutagenesis studies of AMB-1 (3, 4). Two of the non-mam cluster insertion sites occur in operons containing genes conserved particularly between MS-1 and MC-1. We

  5. Viscosity studies of water based magnetite nanofluids

    NASA Astrophysics Data System (ADS)

    Anu, K.; Hemalatha, J.

    2016-05-01

    Magnetite nanofluids of various concentrations have been synthesized through co-precipitation method. The structural and topographical studies made with the X-Ray Diffractometer and Atomic Force Microscope are presented in this paper. The density and viscosity studies for the ferrofluids of various concentrations have been made at room temperature. The experimental viscosities are compared with theoretical values obtained from Einstein, Batchelor and Wang models. An attempt to modify the Rosensweig model is made and the modified Rosensweig equation is reported. In addition, new empirical correlation is also proposed for predicting viscosity of ferrofluid at various concentrations.

  6. Fe atom exchange between aqueous Fe2+ and magnetite.

    PubMed

    Gorski, Christopher A; Handler, Robert M; Beard, Brian L; Pasakarnis, Timothy; Johnson, Clark M; Scherer, Michelle M

    2012-11-20

    The reaction between magnetite and aqueous Fe(2+) has been extensively studied due to its role in contaminant reduction, trace-metal sequestration, and microbial respiration. Previous work has demonstrated that the reaction of Fe(2+) with magnetite (Fe(3)O(4)) results in the structural incorporation of Fe(2+) and an increase in the bulk Fe(2+) content of magnetite. It is unclear, however, whether significant Fe atom exchange occurs between magnetite and aqueous Fe(2+), as has been observed for other Fe oxides. Here, we measured the extent of Fe atom exchange between aqueous Fe(2+) and magnetite by reacting isotopically "normal" magnetite with (57)Fe-enriched aqueous Fe(2+). The extent of Fe atom exchange between magnetite and aqueous Fe(2+) was significant (54-71%), and went well beyond the amount of Fe atoms found at the near surface. Mössbauer spectroscopy of magnetite reacted with (56)Fe(2+) indicate that no preferential exchange of octahedral or tetrahedral sites occurred. Exchange experiments conducted with Co-ferrite (Co(2+)Fe(2)(3+)O(4)) showed little impact of Co substitution on the rate or extent of atom exchange. Bulk electron conduction, as previously invoked to explain Fe atom exchange in goethite, is a possible mechanism, but if it is occurring, conduction does not appear to be the rate-limiting step. The lack of significant impact of Co substitution on the kinetics of Fe atom exchange, and the relatively high diffusion coefficients reported for magnetite suggest that for magnetite, unlike goethite, Fe atom diffusion is a plausible mechanism to explain the rapid rates of Fe atom exchange in magnetite.

  7. [Role of mexidol (2-ethyl-6-methyl-3-hydroxypyridine succinate) in the obtaining of stabilized magnetite nanoparticles for biomedical application].

    PubMed

    Vazhnichaya, Ye M; Mokliak, Ye V; Kurapov, Yu A; Zabozlaev, A A

    2015-01-01

    Magnetite nanoparticles (NPs) are studied as agents for magnetic resonance imaging, hyperthermia of malignant tumors, targeted drug delivery as well as anti-anemic action. One of the main problems of such NPs is their aggregation that requires creation of methods for magnetite NPs stabilization during preparation of liquid medicinal forms on their basis. The present work is devoted to the possibility of mexidol (2-ethyl-6-methyl-3-hydroxypyridine succinate) use for solubilization of magnetite NPs in hydrophilic medium. For this purpose, the condensate produced by electron-beam evaporation and condensation, with magnetite particles of size 5-8 nm deposited into the crystals of sodium chloride were used in conjunction with substance of mexidol (2-ethyl-6-methyl-3-hydroxypyridine succinate), and low molecular weight polyvinylpyrrolidone (PVP). The NP condensate was dispersed in distilled water or PVP or mexidol solutions. NPs size distribution in the liquid phase of the systems was determined by photon correlation spectroscopy, iron (Fe) concentration was evaluated by atomic emission spectrometry. It is shown that in the dispersion prepared in distilled water, the major amount of NPs was of 13-120 nm in size, in mexidol solution - 270-1700 nm, in PVP solution - 30-900 nm. In the fluid containing magnetite NPs together with mexidol and PVP, the main fraction (99.9%) was characterized by the NPs size of 14-75 nm with maximum of 25 nm. This system had the highest iron concentration: it was similar to that in the sample with mexidol solution and 6.6-7.3 times higher than the concentration in the samples with distilled water or PVP. Thus, in the preparation of aqueous dispersions based on magnetite NPs condensate, mexidol provides a transition of Fe to the liquid phase in amount necessary to achieve its biological activity, and PVP stabilizes such modified NPs.

  8. Magnetite as Possible Template for the Synthesis of Chiral Organics in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Zolensky, M. E.

    2014-01-01

    a perfect chance to attest this argument. In order to understand the distribution of spiral magnetites among different meteorite classes, as well as to investigate their spiral configurations and correlation to molecular asymmetry, we observed polished thin sections of CCs using scanning electron microscope (SEM) imaging. Individual magnetite grains were picked, embedded in epoxy, thin-sectioned using an ultra-microtome, and studied with electron backscatter diffraction (EBSD) in order to reconstruct the crystal orientation along the stack of magnetite disks.

  9. Magnetic monitoring of magnetite nucleation and growth: true or apparent monopolarity of natural CRMs ?

    NASA Astrophysics Data System (ADS)

    Cairanne, G.; Brunet, F.; Pozzi, J. P.; Aubourg, C.; Besson, P.

    2003-04-01

    The aim of this experimental study is to monitor magnetic reversal during the acquisition of an experimental chemical remanent magnetization (CRM) in a well constrained medium. Magnetite nucleation and growth have been performed hydrothermally at 450°C and 500 bars, according to a redox reaction involving pyrite, hematite, and portlandite. The experimental device is an amagnetic furnace-press coupled with a coil to control the induction (0.5 mT). We carried out experiments with one polarity, one reversal and two reversals. CRM acquisition is monitored magnetically during heating.The time dependence of the magnetic susceptibility was found to follow an Avrami law (nucleation and growth) with n=2.79 and k=0.055. Synthetic products were characterized by IRM acquisition, X-Ray powder diffraction, SEM and TEM. Magnetite is the only ferromagnetic product. Magnetite crystals display an octahedral habit and are 1-10 æm in size, i.e. the pseudo-single-domain range. The magnetic monitoring shows that the CRM acquired during more than one polarity is composed of opposite magnetic components. However, AF demagnetization shows in this case only one magnetic component. Therefore successive partial CRMs of opposite polarities have been recorded, but AF is not efficient to separate them. We propose that partial CRMs of opposite polarities are superposed in Néel's diagram (V, Hco). Our results suggest that magnetic reversals can be filtered during natural chemical remagnetizations.

  10. Elongated magnetite nanoparticle formation from a solid ferrous precursor in a magnetotactic bacterium

    PubMed Central

    Menguy, Nicolas; Gonzalez, Teresa Perez; Morin, Guillaume; Widdrat, Marc; Faivre, Damien

    2016-01-01

    Magnetotactic bacteria are aquatic microorganisms that intracellularly mineralize ferrimagnetic nanoparticles enabling the cells to align with the geomagnetic field. The bacteria produce a magnetic mineral of species-specific phase (magnetite Fe(II)Fe(III)2O4 or greigite Fe(II)Fe(III)2S4), size, morphology and particle assembly. Several species produce crystals of unusual elongated particle shapes, which break the symmetry of the thermodynamically favoured isometric morphology. Such morphologies are thought to affect domain size and orientation of the internal magnetization. Therefore, they are interesting study objects to develop new synthetic strategies for the morphological control of nanoparticles. We investigate the formation of such irregularly shaped nanomagnets in the species Desulfovibrio magneticus RS-1. In contrast to previously described organisms, this bacterium accumulates iron predominantly as Fe(II) rather than Fe(III) consistent with an alternative oxidative biomineralization route. Further, using high-resolution electron microscopy, we observe an epitaxial relationship between precursor and the final mineral phase supporting the notion of a solid-state transformation pathway. The precursor is likely a green rust previously thought to convert to magnetite only by dissolution and re-precipitation. Our findings represent a novel observation in the interconversion of iron (oxyhydr)oxide materials and suggest that solid-state growth processes could be required to produce irregularly shaped, elongated magnetite nanocrystals. PMID:27881802

  11. Lymphatic mapping and sentinel node location with magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Jung, Chu W.; Rogers, James M.; Groman, Ernest V.

    1999-04-01

    Subcutaneously administered magnetite nanoparticles were used to locate sentinel lymph nodes in normal rats. Nanoparticles sequestered in brachial and axillary lymph nodes produced magnetic susceptibility artifacts in gradient recall echo magnetic resonance images. The artifact sizes enabled the determination of nanoparticle nodal uptake rates and lymphatic drainage patterns. These studies were confirmed by use of 59Fe labeled magnetite nanoparticles.

  12. Magnetic process for removing heavy metals from water employing magnetites

    DOEpatents

    Prenger, F. Coyne; Hill, Dallas D.; Padilla, Dennis D.; Wingo, Robert M.; Worl, Laura A.; Johnson, Michael D.

    2003-07-22

    A process for removing heavy metals from water is provided. The process includes the steps of introducing magnetite to a quantity of water containing heavy metal. The magnetite is mixed with the water such that at least a portion of, and preferably the majority of, the heavy metal in the water is bound to the magnetite. Once this occurs the magnetite and absorbed metal is removed from the water by application of a magnetic field. In most applications the process is achieved by flowing the water through a solid magnetized matrix, such as steel wool, such that the magnetite magnetically binds to the solid matrix. The magnetized matrix preferably has remnant magnetism, but may also be subject to an externally applied magnetic field. Once the magnetite and associated heavy metal is bound to the matrix, it can be removed and disposed of, such as by reverse water or air and water flow through the matrix. The magnetite may be formed in-situ by the addition of the necessary quantities of Fe(II) and Fe(III) ions, or pre-formed magnetite may be added, or a combination of seed and in-situ formation may be used. The invention also relates to an apparatus for performing the removal of heavy metals from water using the process outlined above.

  13. Magnetic process for removing heavy metals from water employing magnetites

    DOEpatents

    Prenger, F. Coyne; Hill, Dallas D.

    2006-12-26

    A process for removing heavy metals from water is provided. The process includes the steps of introducing magnetite to a quantity of water containing heavy metal. The magnetite is mixed with the water such that at least a portion of, and preferably the majority of, the heavy metal in the water is bound to the magnetite. Once this occurs the magnetite and absorbed metal is removed from the water by application of a magnetic field. In most applications the process is achieved by flowing the water through a solid magnetized matrix, such as steel wool, such that the magnetite magnetically binds to the solid matrix. The magnetized matrix preferably has remnant magnetism, but may also be subject to an externally applied magnetic field. Once the magnetite and associated heavy metal is bound to the matrix, it can be removed and disposed of, such as by reverse water or air and water flow through the matrix. The magnetite may be formed in-situ by the addition of the necessary quantities of Fe(II) and Fe(III) ions, or pre-formed magnetite may be added, or a combination of seed and in-situ formation may be used. The invention also relates to an apparatus for performing the removal of heavy metals from water using the process outlined above.

  14. 7 CFR 916.16 - Pure grower or pure producer.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Pure grower or pure producer. 916.16 Section 916.16... Order Regulating Handling Definitions § 916.16 Pure grower or pure producer. (a) Pure grower means any...); or (2) Who produces and handles his or her own product; Provided, That a pure grower can pack...

  15. 7 CFR 917.8 - Pure grower or pure producer.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Pure grower or pure producer. 917.8 Section 917.8... CALIFORNIA Order Regulating Handling Definitions § 917.8 Pure grower or pure producer. (a) For peaches, pure... packing business); or (2) Who produces and handles his or her own product; Provided, That a pure...

  16. 7 CFR 916.16 - Pure grower or pure producer.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Pure grower or pure producer. 916.16 Section 916.16... Order Regulating Handling Definitions § 916.16 Pure grower or pure producer. (a) Pure grower means any...); or (2) Who produces and handles his or her own product; Provided, That a pure grower can pack...

  17. 7 CFR 917.8 - Pure grower or pure producer.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Pure grower or pure producer. 917.8 Section 917.8... CALIFORNIA Order Regulating Handling Definitions § 917.8 Pure grower or pure producer. (a) For peaches, pure... packing business); or (2) Who produces and handles his or her own product; Provided, That a pure...

  18. Magnetic and conductive magnetite nanowires by DNA-templating.

    PubMed

    Mohamed, Hasan Daw A; Watson, Scott M D; Horrocks, Benjamin R; Houlton, Andrew

    2012-09-28

    The synthesis of nanowires made of magnetite (Fe(3)O(4)) phase iron oxide was achieved using DNA as a template to direct formation of the metal oxide and confine its growth in two dimensions. This simple solution-based approach involves initial association of Fe(2+) and Fe(3+) to the DNA "template" molecules, and subsequent co-precipitation of the Fe(3)O(4) material, upon increasing the solution pH, to give the final metal oxide nanowires. Analysis of the DNA-templated material, using a combination of FTIR, XRD, XPS, and Raman spectroscopy, confirmed the iron oxide formed to be the Fe(3)O(4) crystal phase. Investigation of the structural character of the nanowires, carried out by AFM, revealed the metal oxide to form regular coatings of nanometre-scale thickness around the DNA templates. Statistical analysis showed the size distribution of the nanowires to follow a trimodal model, with the modal diameter values identified as 5-6 nm, 14-15 nm, and 23-24 nm. Additional scanning probe microscopy techniques (SCM, MFM) were also used to verify that the nanowire structures are electrically conducting and exhibit magnetic behaviour. Such properties, coupled with the small dimensions of these materials, make them potentially good candidates for application in a host of future nanoscale device technologies.

  19. Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy.

    PubMed

    de la Figuera, Juan; Vergara, Lucía; N'diaye, Alpha T; Quesada, Adrian; Schmid, Andreas K

    2013-07-01

    Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (001) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the magnetization vector with high spatial and angular resolution. We find that domains are magnetized along the surface <110> directions, and domain wall structures include 90° and 180° walls. A type of unusually curved domain walls are interpreted as Néel-capped surface terminations of 180° Bloch walls.

  20. Hexagonal Platelet-like Magnetite as a Biosignature of Thermophilic Iron-Reducing Bacteria and Its Applications to the Exploration of the Modern Deep, Hot Biosphere and the Emergence of Iron-Reducing Bacteria in Early Precambrian Oceans

    PubMed Central

    2012-01-01

    Abstract Dissimilatory iron-reducing bacteria are able to enzymatically reduce ferric iron and couple to the oxidation of organic carbon. This mechanism induces the mineralization of fine magnetite crystals characterized by a wide distribution in size and irregular morphologies that are indistinguishable from authigenic magnetite. Thermoanaerobacter are thermophilic iron-reducing bacteria that predominantly inhabit terrestrial hot springs or deep crusts and have the capacity to transform amorphous ferric iron into magnetite with a size up to 120 nm. In this study, I first characterize the formation of hexagonal platelet-like magnetite of a few hundred nanometers in cultures of Thermoanaerobacter spp. strain TOR39. Biogenic magnetite with such large crystal sizes and unique morphology has never been observed in abiotic or biotic processes and thus can be considered as a potential biosignature for thermophilic iron-reducing bacteria. The unique crystallographic features and strong ferrimagnetic properties of these crystals allow easy and rapid screening for the previous presence of iron-reducing bacteria in deep terrestrial crustal samples that are unsuitable for biological detection methods and, also, the search for biogenic magnetite in banded iron formations that deposited only in the first 2 billion years of Earth with evidence of life. Key Words: Biosignatures—Magnetite—Iron-reducing bacteria—Deep subsurface biosphere—Banded iron formation. Astrobiology 12, 1100–1108. PMID:23145573

  1. Hexagonal platelet-like magnetite as a biosignature of thermophilic iron-reducing bacteria and its applications to the exploration of the modern deep, hot biosphere and the emergence of iron-reducing bacteria in early precambrian oceans.

    PubMed

    Li, Yi-Liang

    2012-12-01

    Dissimilatory iron-reducing bacteria are able to enzymatically reduce ferric iron and couple to the oxidation of organic carbon. This mechanism induces the mineralization of fine magnetite crystals characterized by a wide distribution in size and irregular morphologies that are indistinguishable from authigenic magnetite. Thermoanaerobacter are thermophilic iron-reducing bacteria that predominantly inhabit terrestrial hot springs or deep crusts and have the capacity to transform amorphous ferric iron into magnetite with a size up to 120 nm. In this study, I first characterize the formation of hexagonal platelet-like magnetite of a few hundred nanometers in cultures of Thermoanaerobacter spp. strain TOR39. Biogenic magnetite with such large crystal sizes and unique morphology has never been observed in abiotic or biotic processes and thus can be considered as a potential biosignature for thermophilic iron-reducing bacteria. The unique crystallographic features and strong ferrimagnetic properties of these crystals allow easy and rapid screening for the previous presence of iron-reducing bacteria in deep terrestrial crustal samples that are unsuitable for biological detection methods and, also, the search for biogenic magnetite in banded iron formations that deposited only in the first 2 billion years of Earth with evidence of life.

  2. Did the massive magnetite "lava flows" of El Laco (Chile) form by magmatic or hydrothermal processes? New constraints from magnetite composition by LA-ICP-MS

    NASA Astrophysics Data System (ADS)

    Dare, Sarah A. S.; Barnes, Sarah-Jane; Beaudoin, Georges

    2015-06-01

    The El Laco magnetite deposits consist of more than 98 % magnetite but show field textures remarkably similar to mafic lava flows. Therefore, it has long been suggested that they represent a rare example of an effusive Fe oxide liquid. Field and petrographic evidence, however, suggest that the magnetite deposits represent replacement of andesite flows and that the textures are pseudomorphs. We determined the trace element content of magnetite by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) from various settings at El Laco and compared them with magnetite from both igneous and hydrothermal environments. This new technique allows us to place constraints on the conditions under which magnetite in these supposed magnetite "lava flows" formed. The trace element content of magnetite from the massive magnetite samples is different to any known magmatic magnetite, including primary magnetite phenocrysts from the unaltered andesite host rocks at El Laco. Instead, the El Laco magnetite is most similar in composition to hydrothermal magnetite from high-temperature environments (>500 °C), such as iron oxide-copper-gold (IOCG) and porphyry-Cu deposits. The magnetite trace elements from massive magnetite are characterised by (1) depletion in elements considered relatively immobile in hydrothermal fluids (e.g. Ti, Al, Cr, Zr, Hf and Sc); (2) enrichment in elements that are highly incompatible with magmatic magnetite (rare earth elements (REE), Si, Ca, Na and P) and normally present in very low abundance in magmatic magnetite; (3) high Ni/Cr ratios which are typical of magnetite from hydrothermal environments; and (4) oscillatory zoning of Si, Ca, Mg, REE and most high field strength elements, and zoning truncations indicating dissolution, similar to that formed in hydrothermal Fe skarn deposits. In addition, secondary magnetite in altered, brecciated host rock, forming disseminations and veins, has the same composition as magnetite from the massive

  3. Experimental evidence for non-redox transformations between magnetite and hematite under H 2-rich hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Otake, Tsubasa; Wesolowski, David J.; Anovitz, Lawrence M.; Allard, Lawrence F.; Ohmoto, Hiroshi

    2007-05-01

    Transformations of magnetite (Fe IIFe 2IIIO 4) to hematite (Fe 2IIIO 3) (and vice versa) have been thought by many scientists and engineers to require molecular O 2 and/or H 2. Thus, the presence of magnetite and/or hematite in rocks has been linked to a specific oxidation environment. However, the availability of reductants or oxidants in many geologic and industrial environments appears to have been too low to account for the transformations of iron oxides through redox reactions. Here, we report the results of hydrothermal experiments in mildly acidic and H 2-rich aqueous solutions at 150 °C, which demonstrate that transformations of magnetite to hematite, and hematite to magnetite, occur rapidly without involving molecular O 2 or H 2: Fe3O 4(Mt) + 2H (aq)+ ↔ Fe 2O 3(Hm) + Fe (aq)2+ + H 2O. The transformation products are chemically and structurally homogeneous, and typically occur as euhedral single crystals much larger than the precursor minerals. This suggests that, in addition to the expected release of aqueous ferrous species to solution, the transformations involve release of aqueous ferric species from the precursor oxides to the solution, which reprecipitate without being reduced by H 2. These redox-independent transformations may have been responsible for the formation of some iron oxides in natural systems, such as high-grade hematite ores that developed from Banded Iron Formations (BIFs), hematite-rich deposits formed on Mars, corrosion products in power plants and other industrial systems.

  4. Controlled cobalt doping in biogenic magnetite nanoparticles

    PubMed Central

    Byrne, J. M.; Coker, V. S.; Moise, S.; Wincott, P. L.; Vaughan, D. J.; Tuna, F.; Arenholz, E.; van der Laan, G.; Pattrick, R. A. D.; Lloyd, J. R.; Telling, N. D.

    2013-01-01

    Cobalt-doped magnetite (CoxFe3 −xO4) nanoparticles have been produced through the microbial reduction of cobalt–iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by superconducting quantum interference device magnetometry, X-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to less than 4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe2+ site with Co2+, with up to 17 per cent Co substituted into tetrahedral sites. PMID:23594814

  5. Refractory Behaviors of Magnetite-Kaolin Bricks

    NASA Astrophysics Data System (ADS)

    Adeosun, S. O.; Akpan, E. I.; Gbenebor, O. P.; Taiwo, O. O.; Eke, I. J.

    2016-11-01

    In this work, the suitability of using kaolin-magnetite-plastic clay to produce refractory bricks has been experimentally explored. Thirty bricks of different compositions were produced and fired at 1200°C. The density, shrinkage moisture content, loss on ignition, porosity and permeability of the bricks were examined. Results show that the bricks remained stable during firing and thus possess good insulating characteristics. The highest (2.23 g/cm3) and lowest (2.00 g/cm3) bulk densities obtained in this study are higher than the highest bulk density reported for Al dross-filled refractories (1.23 g/cm3). The bricks also possessed very low effective moisture content (10-23%) and very high compression modulus (16-100 MPa) desirable in insulating refractory bricks with high resistance to abrasion.

  6. Refinement of Magnetite Nanoparticles by Coating with Organic Stabilizers

    PubMed Central

    Cîrcu, Monica; Nan, Alexandrina; Borodi, Gheorghe; Liebscher, Jürgen; Turcu, Rodica

    2016-01-01

    Magnetite nanoparticles are of great importance in nanotechnology and nanomedicine and have found manifold applications. Here, the effect of coating of magnetite nanoparticles with organic stabilizers, such as O-phosphoryl ethanolamine, glycerol phosphate, phospho-l-ascorbic acid, phospho-d,l-serine, glycolic acid, lactic acid, d,l-malic acid, and d,l-mandelic acid was studied. Remarkably, this procedure led to an improvement of saturation magnetization in three cases rather than to an unfavorable decrease as usually observed. Detailed X-ray powder diffraction investigations revealed that changes in the average crystallite occurred in the coating process. Surprisingly, changes of the average crystallite sizes in either direction were further observed, when the exposure time to the stabilizer was increased. These results imply a new mechanism for the well-known coating of magnetite nanoparticles with stabilizers. Instead of the hitherto accepted simple anchoring of the stabilizers to the magnetite nanoparticle surfaces, a more complex recrystallization mechanism is likely, wherein partial re-dispersion of magnetite moieties from the nanoparticles and re-deposition are involved. The results can help producers and users of magnetite nanoparticles to obtain optimal results in the production of core shell magnetite nanoparticles. PMID:28335356

  7. LA-ICP-MS of magnetite: Methods and reference materials

    USGS Publications Warehouse

    Nadoll, P.; Koenig, A.E.

    2011-01-01

    Magnetite (Fe3O4) is a common accessory mineral in many geologic settings. Its variable geochemistry makes it a powerful petrogenetic indicator. Electron microprobe (EMPA) analyses are commonly used to examine major and minor element contents in magnetite. Laser ablation ICP-MS (LA-ICP-MS) is applicable to trace element analyses of magnetite but has not been widely employed to examine compositional variations. We tested the applicability of the NIST SRM 610, the USGS GSE-1G, and the NIST SRM 2782 reference materials (RMs) as external standards and developed a reliable method for LA-ICP-MS analysis of magnetite. LA-ICP-MS analyses were carried out on well characterized magnetite samples with a 193 nm, Excimer, ArF LA system. Although matrix-matched RMs are sometimes important for calibration and normalization of LA-ICP-MS data, we demonstrate that glass RMs can produce accurate results for LA-ICP-MS analyses of magnetite. Cross-comparison between the NIST SRM 610 and USGS GSE-1G indicates good agreement for magnetite minor and trace element data calibrated with either of these RMs. Many elements show a sufficiently good match between the LA-ICP-MS and the EMPA data; for example, Ti and V show a close to linear relationship with correlation coefficients, R2 of 0.79 and 0.85 respectively. ?? 2011 The Royal Society of Chemistry.

  8. Bats use magnetite to detect the earth's magnetic field.

    PubMed

    Holland, Richard A; Kirschvink, Joseph L; Doak, Thomas G; Wikelski, Martin

    2008-02-27

    While the role of magnetic cues for compass orientation has been confirmed in numerous animals, the mechanism of detection is still debated. Two hypotheses have been proposed, one based on a light dependent mechanism, apparently used by birds and another based on a "compass organelle" containing the iron oxide particles magnetite (Fe(3)O(4)). Bats have recently been shown to use magnetic cues for compass orientation but the method by which they detect the Earth's magnetic field remains unknown. Here we use the classic "Kalmijn-Blakemore" pulse re-magnetization experiment, whereby the polarity of cellular magnetite is reversed. The results demonstrate that the big brown bat Eptesicus fuscus uses single domain magnetite to detect the Earths magnetic field and the response indicates a polarity based receptor. Polarity detection is a prerequisite for the use of magnetite as a compass and suggests that big brown bats use magnetite to detect the magnetic field as a compass. Our results indicate the possibility that sensory cells in bats contain freely rotating magnetite particles, which appears not to be the case in birds. It is crucial that the ultrastructure of the magnetite containing magnetoreceptors is described for our understanding of magnetoreception in animals.

  9. Pure-quartic solitons

    PubMed Central

    Blanco-Redondo, Andrea; Martijn, de Sterke C.; Sipe, J.E.; Krauss, Thomas F.; Eggleton, Benjamin J.; Husko, Chad

    2016-01-01

    Temporal optical solitons have been the subject of intense research due to their intriguing physics and applications in ultrafast optics and supercontinuum generation. Conventional bright optical solitons result from the interaction of anomalous group-velocity dispersion and self-phase modulation. Here we experimentally demonstrate a class of bright soliton arising purely from the interaction of negative fourth-order dispersion and self-phase modulation, which can occur even for normal group-velocity dispersion. We provide experimental and numerical evidence of shape-preserving propagation and flat temporal phase for the fundamental pure-quartic soliton and periodically modulated propagation for the higher-order pure-quartic solitons. We derive the approximate shape of the fundamental pure-quartic soliton and discover that is surprisingly Gaussian, exhibiting excellent agreement with our experimental observations. Our discovery, enabled by precise dispersion engineering, could find applications in communications, frequency combs and ultrafast lasers. PMID:26822758

  10. Geomorphology: Pure and applied

    SciTech Connect

    Hart, M.G.

    1986-01-01

    The book summarizes the history of intellectual debate in geomorphology and describes modern developments both ''pure'' and ''applied.'' The history begins well before W.M. Davis and follows through to such debates as those concerned with the Pleistocene. Modern developments in pure geomorphology are cast in terms of chapters on form, process, materials, and methods analysis. The applied chapters concentrate on environmental hazards and resources, and their management.

  11. Occurrence of gigantic biogenic magnetite during the Paleocene-Eocene Thermal Maximum

    NASA Astrophysics Data System (ADS)

    Schumann, D.; Raub, T. D.; Kopp, R. E.; Guerquin-Kern, J. L.; Wu, T. D.; Rouiller, I.; Smirnov, A. V.; Sears, S. K.; Lücken, U.; Tikoo, S. M.; Hesse, R.; Kirschvink, J. L.; Vali, H.

    2009-04-01

    The Paleocene-Eocene Thermal Maximum (PETM) is one of the most severe climatic events of the Cenozoic Era. A massive injection of light carbon into the oceans and atmosphere over a few thousand of years triggered drastic perturbation of Earth's climate resulting in abrupt global warming of ~5-9oC [Sluijs et al., 2007] that persisted for ~180,000 years. This episode is marked by the diversification and radiation of terrestrial plants and mammals while in the marine realm numerous deep-sea benthic foraminifera species disappeared and new forms evolved. Sediments deposited during the PETM are clay-rich and contain distinct evidence of these climatic changes. Kopp et al., (2007) and Lippert & Zachos (2007) report an extraordinary magnetofossil ‘Lagerstätte' in lowermost Eocene kaolinite-rich clay sediments deposited at subtropical paleolatitude in the Atlantic Coastal Plain of New Jersey, USA. Magnetofossils are magnetic particles produced most abundantly by magnetotactic bacteria. Kopp et al. (2007) and Lippert & Zachos (2007) used ferromagnetic resonance (FMR) spectroscopy, other rock magnetic methods, and transmission electron microscopy (TEM) of magnetic separates to characterize sediments from boreholes at Ancora (ODP Leg 174AX) and Wilson Lake, NJ, respectively. These sediments contain abundant ~40- to 300-nm cuboidal, elongate-prismatic and bullet-shaped magnetofossils, sometimes arranged in short chains, resembling crystals in living magnetotactic bacteria. Despite the scarcity of intact magnetofossil chains, the asymmetry ratios of the FMR spectra reflects a profusion of elongate single domain (SD) crystals and/or chains. Here we address both conundrums by reporting the discovery from these same sediments of exceptionally large and novel biogenic magnetite crystals unlike any previously reported from living organisms or from sediments. Aside from abundant bacterial magnetofossils, electron microscopy reveals novel spearhead-like and spindle-like magnetite

  12. Magnetite Plaquettes Provide an Extraterrestrial Source of Asymmetric Components

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Zolensky, M. E.; Martinez, J. E.

    2015-01-01

    Molecular selectivity is a crucial criterion for life. A possible abiotic mechanism that can produce chiral asymmetry in meteoritic amino acids is their formation with the presence of asymmetric catalysts. Magnetite (Fe3O4), a common mineral in some carbonaceous chondrites (CCs), has been shown to be an effective catalyst for the formation of amino acids that are commonly found in these meteorites. Magnetite sometimes takes the form of plaquettes that consist of barrel-shaped stacks of magnetite disks that resemble a spiral. However, a widely accepted description of the internal morphology of this particular magnetite form is still lacking, which is necessary in order to confirm or disprove the spiral configuration.

  13. Starch-modified magnetite nanoparticles for impregnation into cartilage

    NASA Astrophysics Data System (ADS)

    Soshnikova, Yulia M.; Roman, Svetlana G.; Chebotareva, Natalia A.; Baum, Olga I.; Obrezkova, Mariya V.; Gillis, Richard B.; Harding, Stephen E.; Sobol, Emil N.; Lunin, Valeriy V.

    2013-11-01

    The paper presents preparation and characterization of starch-modified Fe3O4 nanoparticles (NPs) in aqueous dispersion after impregnation into healthy and damaged types of cartilage. We show that starch-modified dispersion has a narrower size distribution than a non-stabilized one. The average hydrodynamic radius of magnetite NPs in a dispersion used for impregnation into cartilage is (48 ± 1) nm with the width of the distribution from 5 to 200 nm. We investigate stability of aqueous magnetite NPs dispersions during storage and with increase in temperature (up to 70 °C). We find that polydisperse magnetite NPs can penetrate into cartilage and the size and concentration of impregnated particles depend on the organization of the tissue structure. The results confirm the possibility of application of magnetite NPs in diagnostics and laser treatment of degenerative cartilage deceases.

  14. Synthesis of magnetite nanoparticles in the presence of aminoacids

    NASA Astrophysics Data System (ADS)

    Marinescu, Gabriela; Patron, Luminita; Culita, Daniela C.; Neagoe, Cristian; Lepadatu, Costinel I.; Balint, Ioan; Bessais, Lotfi; Cizmas, Corneliu Bazil

    2006-12-01

    A new synthesis route to prepare magnetite nanoparticles in only one step is described. The precipitation of magnetite is performed in the presence of aminoacid solution. The experimental protocol is original and the nanomagnetites are characterized by XRD, FTIR, TEM and SQUID magnetometry. A theoretical study of the consistent experimental results was performed using QSPR (Quantitative Structure Property Relationsheep). According with these studies the synthesized nanoparticles seem to be organized into a core-shell system, where the inner-core is formed from unit cells of magnetite. A way to control the self-assembly and the physical properties of the synthesized nanoparticles consists in their correlation with descriptors representing the aminoacid chemical structures. Using quantum chemical as well as the other simplest original descriptors it was found a relationship between the used aminoacids and the magnetization, nanoparticles diameter, magnetite core diameter and the (Fe3O4)8 cells in each nanoparticle core.

  15. Hexagonal plate-like magnetite nanocrystals produced in komatiite-H2O-CO2 reaction system at 450°C

    NASA Astrophysics Data System (ADS)

    Hao, Xi-Luo; Li, Yi-Liang

    2015-10-01

    Batch experiments of komatiite-H2O-CO2 system with temperatures from 200 to 450°C were performed to simulate the interactions between the newly formed ultramafic crust and the proto-atmosphere on Earth before the formation of its earliest ocean. Particularly, magnetite nanocrystals were observed in the experiment carried out at 450°C that are characterized by their hexagonal platelet-like morphology and porous structure. Exactly the same set of lattice fringes on the two opposite sides of one pore suggests post-crystallization erosion. The results demonstrate that magnetite could be produced by the direct interactions between the ultramafic rocky crust and the atmosphere before the formation of the ocean on the Hadean Earth. These magnetite nanoparticles could serve as a catalyst in the synthesis of simple organic molecules during the organochemical evolution towards life.

  16. Electrophoretic mobility of magnetite particles in high temperature water

    SciTech Connect

    Vidojkovic, Sonja; Rodriguez-Santiago, V; Fedkin, Mark V.; Wesolowski, David J; Lvov, Serguei N.

    2011-01-01

    Magnetite(Fe3O4) isoneofthemostcommonoxidesformingdepositsandparticulatephasesin industrialhightemperaturewatercircuits.Itscolloidalcharacteristicsplayaprincipalroleinthe mechanismofdepositformationandcanbeusedascontrollingfactorstopreventorminimizedeposit formationanddamageofindustrialpipelinesduetounder-depositcorrosion.Inthisstudy,ahigh temperatureparticleelectrophoresistechniquewasemployedtomeasurethezetapotentialatthe magnetite/waterinterface the parameterthatcontrolscolloidalstabilityofparticles,theiraggrega- tion, anddeposition.Themeasurementsweremadeattemperaturesupto200 1C overawiderangeofpH. The isoelectricpointsofmagnetite,atwhichthedepositionofparticlesisincreased,weredeterminedatpH 6.35, 6.00,5.25,and5.05fortemperatures25,100,150,and200 1C, respectively.Theobserved temperaturedependenceofzetapotentialandtheisoelectricpHpointofmagnetitecanhelptoexplain the extentofinteractionsbetweenthecolloidalparticlesandthesteelwallsurfacesunderhydro- thermalconditions,andindicatemethodsforcontrollingandmitigatingoxidedepositioninhigh temperaturewatercycles.

  17. EPR evidence for maghemitization of magnetite in a tropical soil

    NASA Astrophysics Data System (ADS)

    Fischer, H.; Luster, J.; Gehring, A. U.

    2007-06-01

    Electron paramagnetic spectroscopy (EPR) was used in combination with standard rock magnetic methods to study magnetic minerals in a tropical soil. The susceptibility and hysteresis measurements showed magnetite grains with a Curie temperature near 850 K as the dominant magnetic remanence carriers in the soil. A minor Ti content in the magnetite was found by energy dispersive X-ray analysis. In order to get insight into the weathering status of the magnetite, different chemical treatments, including oxalate and citrate-bicarbonate-dithionite (CBD) extraction, were applied to the soil samples. The hysteretic properties exhibited no significant differences between the untreated and the CBD or oxalate treated samples. By contrast, the comparison of the EPR spectra revealed a significant broadening of the linewidth (δB) and a shift of the g-values (geff) to lower fields after the CBD treatment. Furthermore, the spectral parameters geff and δB exhibited an angular dependence. At low temperature, the CBD treated samples showed a jump in δB between 120 and 100 K, the temperature range characteristic for the Verwey transition in magnetite. The changes in the spectral properties after the CBD treatment, which dissolves ferric oxides, were attributed to the removal of maghemite formed by the oxidation of magnetite, that is, during the maghemitization of the magnetite grains.

  18. Bioengineered magnetic crystals

    NASA Astrophysics Data System (ADS)

    Kasyutich, O.; Sarua, A.; Schwarzacher, W.

    2008-07-01

    In this paper we report on the successful application of a protein crystallization technique to fabricate a three-dimensionally ordered array of magnetic nanoparticles, i.e. a novel type of metamaterial with unique magnetic properties. We utilize ferritin protein cages for the template-constrained growth of superparamagnetic nanoparticles of magnetite/maghemite Fe3O4-γ-Fe2O3 (magnetoferritin), followed by thorough nanoparticle bioprocessing and purification, and finally by protein crystallization. Protein crystallization is driven by the natural response of proteins to the supersaturation of the electrolyte, which leads to spontaneous nucleation and 3D crystal growth. Within a short period of time (hours to days) we were able to grow functional crystals on the meso-scale, with sizes of the order of tens, up to a few hundred micrometres. We present initial magnetic and Raman spectroscopy characterization results for the obtained 3D arrays of magnetic nanoparticles.

  19. Production of pure metals

    NASA Technical Reports Server (NTRS)

    Philipp, W. H.; Marsik, S. J.; May, C. E. (Inventor)

    1974-01-01

    A process for depositing elements by irradiating liquids is reported. Ultra pure elements are precipitated from aqueous solutions or suspensions of compounds. A solution of a salt of a metal to be prepared is irradiated, and the insoluble reaction product settles out. Some chemical compounds may also be prepared in this manner.

  20. Dahlbeck and Pure Ontology

    ERIC Educational Resources Information Center

    Mackenzie, Jim

    2016-01-01

    This article responds to Johan Dahlbeck's "Towards a pure ontology: Children's bodies and morality" ["Educational Philosophy and Theory," vol. 46 (1), 2014, pp. 8-23 (EJ1026561)]. His arguments from Nietzsche and Spinoza do not carry the weight he supposes, and the conclusions he draws from them about pedagogy would be…

  1. Language as Pure Potential

    ERIC Educational Resources Information Center

    Park, Joseph Sung-Yul

    2016-01-01

    Language occupies a crucial position in neoliberalism, due to the reimagination of language as commodified skill. This paper studies the role of language ideology in this transformation by identifying a particular ideology that facilitates this process, namely the ideology which views language as pure potential. Neoliberalism treats language as a…

  2. Formation of Core-Shell Nanoparticles Composed of Magnetite and Samarium Oxide in Magnetospirillum magneticum Strain RSS-1.

    PubMed

    Shimoshige, Hirokazu; Nakajima, Yoshikata; Kobayashi, Hideki; Yanagisawa, Keiichi; Nagaoka, Yutaka; Shimamura, Shigeru; Mizuki, Toru; Inoue, Akira; Maekawa, Toru

    2017-01-01

    Magnetotactic bacteria (MTB) synthesize magnetosomes composed of membrane-enveloped magnetite (Fe3O4) or greigite (Fe3S4) particles in the cells. Recently, several studies have shown some possibilities of controlling the biomineralization process and altering the magnetic properties of magnetosomes by adding some transition metals to the culture media under various environmental conditions. Here, we successfully grow Magnetospirillum magneticum strain RSS-1, which are isolated from a freshwater environment, and find that synthesis of magnetosomes are encouraged in RSS-1 in the presence of samarium and that each core magnetic crystal composed of magnetite is covered with a thin layer of samarium oxide (Sm2O3). The present results show some possibilities of magnetic recovery of transition metals and synthesis of some novel structures composed of magnetic particles and transition metals utilizing MTB.

  3. Formation of Core-Shell Nanoparticles Composed of Magnetite and Samarium Oxide in Magnetospirillum magneticum Strain RSS-1

    PubMed Central

    Shimoshige, Hirokazu; Nakajima, Yoshikata; Kobayashi, Hideki; Yanagisawa, Keiichi; Nagaoka, Yutaka; Shimamura, Shigeru; Mizuki, Toru; Inoue, Akira; Maekawa, Toru

    2017-01-01

    Magnetotactic bacteria (MTB) synthesize magnetosomes composed of membrane-enveloped magnetite (Fe3O4) or greigite (Fe3S4) particles in the cells. Recently, several studies have shown some possibilities of controlling the biomineralization process and altering the magnetic properties of magnetosomes by adding some transition metals to the culture media under various environmental conditions. Here, we successfully grow Magnetospirillum magneticum strain RSS-1, which are isolated from a freshwater environment, and find that synthesis of magnetosomes are encouraged in RSS-1 in the presence of samarium and that each core magnetic crystal composed of magnetite is covered with a thin layer of samarium oxide (Sm2O3). The present results show some possibilities of magnetic recovery of transition metals and synthesis of some novel structures composed of magnetic particles and transition metals utilizing MTB. PMID:28125741

  4. Synthesis and characterization of magnetite/silver/antibiotic nanocomposites for targeted antimicrobial therapy.

    PubMed

    Ivashchenko, Olena; Lewandowski, Mikołaj; Peplińska, Barbara; Jarek, Marcin; Nowaczyk, Grzegorz; Wiesner, Maciej; Załęski, Karol; Babutina, Tetyana; Warowicka, Alicja; Jurga, Stefan

    2015-10-01

    The article is devoted to preparation and characterization of magnetite/silver/antibiotic nanocomposites for targeted antimicrobial therapy. Magnetite nanopowder was produced by thermochemical technique; silver was deposited on the magnetite nanoparticles in the form of silver clusters. Magnetite/silver nanocomposite was investigated by XRD, SEM, TEM, AFM, XPS, EDX techniques. Adsorptivity of magnetite/silver nanocomposite towards seven antibiotics from five different groups was investigated. It was shown that rifampicin, doxycycline, ceftriaxone, cefotaxime and doxycycline may be attached by physical adsorption to magnetite/silver nanocomposite. Electrostatic surfaces of antibiotics were modeled and possible mechanism of antibiotic attachment is considered in this article. Raman spectra of magnetite, magnetite/silver and magnetite/silver/antibiotic were collected. It was found that it is difficult to detect the bands related to antibiotics in the magnetite/silver/antibiotic nanocomposite spectra due to their overlap by the broad carbon bands of magnetite nanopowder. Magnetic measurements revealed that magnetic saturation of the magnetite/silver/antibiotic nanocomposites decreased on 6-19 % in comparison with initial magnetite nanopowder. Pilot study of antimicrobial properties of the magnetite/silver/antibiotic nanocomposites were performed towards Bacillus pumilus.

  5. Origins of Magnetite Nanocrystals in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Mckay, David S.; Gibson, Everett K.; Wentworth, Susan J.

    2009-01-01

    The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of mag- netite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterized of the compo- sitional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the car- bonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates.

  6. Effect of La{sub 2}O{sub 3}, CoO, Cr{sub 2}O{sub 3} and MoO{sub 3} nucleating agents on crystallization behavior and magnetic properties of ferromagnetic glass-ceramic in the system Fe{sub 2}O{sub 3}{center_dot}CaO{center_dot}ZnO{center_dot}SiO{sub 2}

    SciTech Connect

    Abdel-Hameed, Salwa A.M.; Elwan, Rawhia L.

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Crystallization of magnetic glass ceramic with different nucleating agents. Black-Right-Pointing-Pointer The effect of La{sub 2}O{sub 3}, CoO, Cr{sub 2}O{sub 3} and MoO{sub 3} as nucleating agents was studied. Black-Right-Pointing-Pointer XRD for as prepared samples revealed crystallization of pure magnetite. Black-Right-Pointing-Pointer Heat treatment revealed minor calcium silicate, hematite and cristobalite. Black-Right-Pointing-Pointer TEM revealed crystallization of crystallite size in the range 50-100 nm. -- Abstract: Preparation and characterization of ferromagnetic glass ceramic in the system Fe{sub 2}O{sub 3}{center_dot}CaO{center_dot}ZnO{center_dot}SiO{sub 2} with different nucleating agents was studied. The effect of La{sub 2}O{sub 3}, CoO, Cr{sub 2}O{sub 3} and MoO{sub 3} as nucleating agents was investigated. Differential thermal analysis; X-ray diffraction and transmission electron microscope were used to investigate thermal behavior, sequence of crystallization and microstructure of the samples. XRD analysis for as prepared samples revealed the crystallization of single magnetite phase. Heat treatment at 900 Degree-Sign C/2 h revealed the appearance of minor amounts of calcium silicate, hematite and cristobalite beside magnetite. TEM revealed crystallization of crystallite size in the range 50-100 nm. Lattice parameters, cell volume and crystallite size were stimulated from XRD data. Magnetic properties of quenched samples were measured under 20 kG.

  7. TEA controllable preparation of magnetite nanoparticles (Fe3O4 NPs) with excellent magnetic properties

    NASA Astrophysics Data System (ADS)

    Han, Chengliang; Zhu, Dejie; Wu, Hanzhao; Li, Yao; Cheng, Lu; Hu, Kunhong

    2016-06-01

    A fast and controllable synthesis method for superparamagnetic magnetite nanoparticles (Fe3O4 NPs) was developed in Fe(III)-triethanolamine (TEA) solution. The phase structure, morphology and particle size of the as-synthesized samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the magnetic particles were pure Fe3O4 with mean sizes of approximately 10 nm. The used TEA has key effects on the formation of well dispersing Fe3O4 NPs. Vibrating sample magnetometer (VSM) result indicated that the as-obtained Fe3O4 NPs exhibited superparamagnetic behavior and the saturation magnetization (Ms) was about 70 emu/g, which had potential applications in magnetic science and technology.

  8. Electrochemistry and dissolution kinetics of magnetite and ilmenite

    USGS Publications Warehouse

    White, A.F.; Peterson, M.L.; Hochella, M.F.

    1994-01-01

    Natural samples of magnetite and ilmenite were experimentally weathered in pH 1-7 anoxic solutions at temperatures of 2-65 ??C. Reaction of magnetite is described as [Fe2+Fe23+]O4(magnetite) + 2H+ ??? ??[Fe23+]O3(maghemite) + Fe2+ + H2O. Dynamic polarization experiments using magnetite electrodes confirmed that this reaction is controlled by two electrochemical half cells, 3[Fe2+Fe23+]O4(magnetite) ??? 4??[Fe23+]O3(maghemite) + Fe2+ + 2e- and [Fe2+Fe23+]O4(magnetite) + 8 H+ + 2e- ??? 3Fe2+ + 4H2O, which result in solid state Fe3+ reduction, formation of an oxidized layer and release of Fe(II) to solution. XPS data revealed that iron is present in the ferric state in the surfaces of reacted magnetite and ilmenite and that the Ti Fe ratio increased with reaction pH for ilmenite. Short-term (<36 h) release rates of Fe(II) were linear with time. Between pH 1 and 7, rates varied between 0.3 and 13 ?? 10-14 mol ?? cm-2 ?? s-1 for magnetite and 0.05 and 12.3 ?? 10-14 mol ?? cm-2 ?? s-1 for ilmenite. These rates are two orders of magnitude slower than electrochemical rates determined by Tafel and polarization resistance measurements. Discrepancies are due to both differences in geometric and BET surface area estimates and in the oxidation state of the mineral surface. In long-term closed-system experiments (<120 days), Fe(II) release slowed with time due to the passivation of the surfaces by increasing thicknesses of oxide surface layers. A shrinking core model, coupling surface reaction and diffusion transport, predicted that at neutral pH, the mean residence time for sand-size grains of magnetite and ilmenite will exceed 107 years. This agrees with long-term stability of these oxides in the geologic record. ?? 1994.

  9. Magnetic Separations with Magnetite: Theory, Operation, and Limitations

    SciTech Connect

    G. B. Cotten

    2000-08-01

    This dissertation documents the theory development and experimental plan followed to describe how a magnetite-based column under the influence of an external magnetic field functions as a magnetic separator. Theoretical simulations predict that weekly paramagnetic particles in the sub-micron range can be magnetically separated while diamagnetic particles as large as 2 microns in diameter may pass. Magnetite-based columns were evaluated as magnetically-controllable enhanced filtration devices. There was no evidence of enhanced filtration for diamagnetic particles by the magnetite-based bed. Magnetite-based magnetic separators have proven to be effective in specific laboratory experiments, indicating a potential feasibility for scale-up operations. Column media-filter type filtration effects indicate a magnetite-based column would not be suitable for treatment of a waste stream with a high diamagnetic solids content or high volume throughput requirements. Specific applications requiring removal of sub-micron para- or ferromagnetic particles under batch or Stokes flow conditions would be most applicable.

  10. Fabrication of chitosan-magnetite nanocomposite strip for chromium removal

    NASA Astrophysics Data System (ADS)

    Sureshkumar, Vaishnavi; Kiruba Daniel, S. C. G.; Ruckmani, K.; Sivakumar, M.

    2016-02-01

    Environmental pollution caused by heavy metals is a serious threat. In the present work, removal of chromium was carried out using chitosan-magnetite nanocomposite strip. Magnetite nanoparticles (Fe3O4) were synthesized using chemical co-precipitation method at 80 °C. The nanoparticles were characterized using UV-visible spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction spectrometer, atomic force microscope, dynamic light scattering and vibrating sample magnetometer, which confirm the size, shape, crystalline nature and magnetic behaviour of nanoparticles. Atomic force microscope revealed that the particle size was 15-30 nm and spherical in shape. The magnetite nanoparticles were mixed with chitosan solution to form hybrid nanocomposite. Chitosan strip was casted with and without nanoparticle. The affinity of hybrid nanocomposite for chromium was studied using K2Cr2O7 (potassium dichromate) solution as the heavy metal solution containing Cr(VI) ions. Adsorption tests were carried out using chitosan strip and hybrid nanocomposite strip at different time intervals. Amount of chromium adsorbed by chitosan strip and chitosan-magnetite nanocomposite strip from aqueous solution was evaluated using UV-visible spectroscopy. The results confirm that the heavy metal removal efficiency of chitosan-magnetite nanocomposite strip is 92.33 %, which is higher when compared to chitosan strip, which is 29.39 %.

  11. Observations of magnetite dissolution in poorly drained soils

    USGS Publications Warehouse

    Grimley, D.A.; Arruda, N.K.

    2007-01-01

    Dissolution of strongly magnetic minerals is a common and relatively rapid phenomenon in poorly drained soils of the central United States, resulting in low magnetic susceptibility (MS). Low Eh reducing conditions are primarily responsible for magnetic mineral dissolution; a process likely mediated by iron-reducing bacteria in the presence of soil organic matter. Based on transects across drainage sequences from nine sites, natural magnetic minerals (>5 ??m) extracted from surface soil consist of 54% ?? 18% magnetite, 21% ?? 11% titanomagnetite, and 17% ?? 14% ilmenite. Magnetite and titanomagnetite dissolution, assessed by scanning electron microscopy on a 0-to-3 scale, inversely correlates with surface soil MS (r = 0.53), a proxy for soil drainage at studied transects. Altered magnetite typically displays etch pits 5 ??m) include 26% ?? 18% anthropogenic fly ash that also exhibits greater dissolution in low MS soils (r = 0.38), indicating detectable alteration can occur within 150 years in low Eh soils. Laboratory induced reduction of magnetite, titanomagnetite, and magnetic fly ash, with a citrate-bicarbonate- dithionite solution, resulted in dissolution textures similar to those of in situ soil particles. Although experiments indicate that reductive dissolution of magnetite can occur abiotically under extreme conditions, bacteria likely play an important role in the natural environment. ?? 2007 Lippincott Williams & Wilkins, Inc.

  12. Functionalization of Magnetite Nanoparticles as Oil Spill Collector

    PubMed Central

    Atta, Ayman M.; Al-Lohedan, Hamad A.; Al-Hussain, Sami A.

    2015-01-01

    In the present study, a new magnetic powder based on magnetite can be used as a petroleum crude oil collector. Amidoximes based on rosin as a natural product can be prepared from a reaction between hydroxylamine and rosin/acrylonitrile adducts. The produced rosin amidoximes were used as capping agents for magnetite nanoparticles to prepare hydrophobic coated magnetic powders. A new class of monodisperse hydrophobic magnetite nanoparticles was prepared by a simple and inexpensive co-precipitation method. Iron ions and iodine were prepared by the reaction between ferric chloride and potassium iodide. The structure and morphology of magnetite capped with rosin amidoxime were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), zeta potential, thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The magnetic properties were determined from vibrating sample magnetometer (VSM) analyses. These prepared magnetite nanoparticles were tested as bioactive nanosystems and their antimicrobial effects were investigated. The prepared nanomaterials were examined as a crude oil collector using magnetic fields. The results show promising data for the separation of the petroleum crude oil from aqueous solution in environmental pollution cleanup. PMID:25822876

  13. The MagA Protein of Magnetospirilla Is Not Involved in Bacterial Magnetite Biomineralization

    PubMed Central

    Uebe, René; Henn, Verena

    2012-01-01

    Magnetotactic bacteria have the ability to orient along geomagnetic field lines based on the formation of magnetosomes, which are intracellular nanometer-sized, membrane-enclosed magnetic iron minerals. The formation of these unique bacterial organelles involves several processes, such as cytoplasmic membrane invagination and magnetosome vesicle formation, the accumulation of iron in the vesicles, and the crystallization of magnetite. Previous studies suggested that the magA gene encodes a magnetosome-directed ferrous iron transporter with a supposedly essential function for magnetosome formation in Magnetospirillum magneticum AMB-1 that may cause magnetite biomineralization if expressed in mammalian cells. However, more recent studies failed to detect the MagA protein among polypeptides associated with the magnetosome membrane and did not identify magA within the magnetosome island, a conserved genomic region that is essential for magnetosome formation in magnetotactic bacteria. This raised increasing doubts about the presumptive role of magA in bacterial magnetosome formation, which prompted us to reassess MagA function by targeted deletion in Magnetospirillum magneticum AMB-1 and Magnetospirillum gryphiswaldense MSR-1. Contrary to previous reports, magA mutants of both strains still were able to form wild-type-like magnetosomes and had no obvious growth defects. This unambiguously shows that magA is not involved in magnetosome formation in magnetotactic bacteria. PMID:22194451

  14. Mesoporous silica magnetite nanocomposite synthesized by using a neutral surfactant

    NASA Astrophysics Data System (ADS)

    Souza, K. C.; Salazar-Alvarez, G.; Ardisson, J. D.; Macedo, W. A. A.; Sousa, E. M. B.

    2008-05-01

    Magnetite nanoparticles coated by mesoporous silica were synthesized by an alternative chemical route using a neutral surfactant and without the application of any functionalization method. The magnetite (Fe3O4) nanoparticles were prepared by precipitation from aqueous media, and then coated with mesoporous silica by using nonionic block copolymer surfactants as the structure-directing agents. The mesoporous SiO2-coated Fe3O4 samples were characterized by x-ray diffraction, Fourier-transform infrared spectroscopy, N2 adsorption-desorption isotherms, transmission electron microscopy, 57Fe Mössbauer spectroscopy, and vibrating sample magnetometry. Our results revealed that the magnetite nanoparticles are completely coated by well-ordered mesoporous silica with free pores and stable (~8 nm thick) pore walls, and that the structural and magnetic properties of the Fe3O4 nanoparticles are preserved in the applied synthesis route.

  15. Synthesis and characterization of magnetite/PLGA/chitosan nanoparticles

    NASA Astrophysics Data System (ADS)

    Ibarra, Jaime; Melendres, Julio; Almada, Mario; Burboa, María G.; Taboada, Pablo; Juárez, Josué; Valdez, Miguel A.

    2015-09-01

    In this work, we report the synthesis and characterization of a new hybrid nanoparticles system performed by magnetite nanoparticles, loaded in a PLGA matrix, and stabilized by different concentrations of chitosan. Magnetite nanoparticles were hydrophobized with oleic acid and entrapped in a PLGA matrix by the emulsion solvent evaporation method, after that, magnetite/PLGA/chitosan nanoparticles were obtained by adding dropwise magnetite/PLGA nanoparticles in chitosan solutions. Magnetite/PLGA nanoparticles produced with different molar ratios did not show significant differences in size and the 3:1 molar ratio showed best spherical shapes as well as uniform particle size. Isothermal titration calorimetry studies demonstrated that the first stage of PLGA-chitosan interaction is mostly regulated by electrostatic forces. Based on a single set of identical sites model, we obtained for the average number of binding sites a value of 3.4, which can be considered as the number of chitosan chains per nanoparticle. This value was confirmed by using a model based on the DLVO theory and fitting zeta potential measurements of magnetite/PLGA/chitosan nanoparticles. From the adjusted parameters, we found that an average number of chitosan molecules of 3.6 per nanoparticle are attached onto the surface of the PLGA matrix. Finally, we evaluated the effect of surface charge of nanoparticles on a membrane model of endothelial cells performed by a mixture of three phospholipids at the air-water interface. Different isotherms and adsorption curves show that cationic surface of charged nanoparticles strongly interact with the phospholipids mixture and these results can be the basis of future experiments to understand the nanoparticles- cell membrane interaction.

  16. Simple and Rapid Synthesis of Magnetite/Hydroxyapatite Composites for Hyperthermia Treatments via a Mechanochemical Route

    PubMed Central

    Iwasaki, Tomohiro; Nakatsuka, Ryo; Murase, Kenya; Takata, Hiroshige; Nakamura, Hideya; Watano, Satoru

    2013-01-01

    This paper presents a simple method for the rapid synthesis of magnetite/hydroxyapatite composite particles. In this method, superparamagnetic magnetite nanoparticles are first synthesized by coprecipitation using ferrous chloride and ferric chloride. Immediately following the synthesis, carbonate-substituted (B-type) hydroxyapatite particles are mechanochemically synthesized by wet milling dicalcium phosphate dihydrate and calcium carbonate in a dispersed suspension of magnetite nanoparticles, during which the magnetite nanoparticles are incorporated into the hydroxyapatite matrix. We observed that the resultant magnetite/hydroxyapatite composites possessed a homogeneous dispersion of magnetite nanoparticles, characterized by an absence of large aggregates. When this material was subjected to an alternating magnetic field, the heat generated increased with increasing magnetite concentration. For a magnetite concentration of 30 mass%, a temperature increase greater than 20 K was achieved in less than 50 s. These results suggest that our composites exhibit good hyperthermia properties and are promising candidates for hyperthermia treatments. PMID:23629669

  17. The Verwey transition in nanostructured magnetite produced by a combination of chimie douce and spark plasma sintering

    SciTech Connect

    Gaudisson, T.; Nowak, S.; Ammar, S.; Vázquez-Victorio, G.; Valenzuela, R.; Bañobre-López, M.; Rivas, J.; Mazaleyrat, F.

    2014-05-07

    Magnetite nanoparticles about 10 nm sized were synthesized by the polyol method. Zero-field-cooled (ZFC)-FC measurements showed a blocking temperature ∼170 K and the absence of the Verwey transition. They were subsequently consolidated by spark plasma sintering at 750 °C for 15 min, leading to a high density (92% of the theoretical density), solid body, with grains in the 150 nm range. X-ray diffraction patterns exhibited a spinel single phase with cell parameters corresponding to the magnetite structure. Magnetic measurements showed a decrease of coercivity from 685 Oe (54.5 kA/m) at 118 K to 90 Oe (7.2 kA/m) at 139 K. ZFC measurements at 25 Oe presented a three-fold magnetization increase as temperature increased; a small transition between 116 and 117.5 K, followed by a larger one from 117.6 to 124 K. The first transition can be associated with a complex crystallographic transition and delocalization of Fe{sup 2+}-Fe{sup 3+}, while the second one can be attributed to spin reorientation due to the magnetocrystalline anisotropy constant (K{sub 1}) change of sign as previously observed only in magnetite single crystals.

  18. Magnetite-based magnetoreception in birds: the effect of a biasing field and a pulse on migratory behavior.

    PubMed

    Wiltschko, Wolfgang; Munro, Ursula; Wiltschko, Roswitha; Kirschvink, Joseph L

    2002-10-01

    To test the hypothesis that single domain magnetite is involved in magnetoreception, we treated Australian silvereyes Zosterops l. lateralis with a strong, brief pulse designed to alter the magnetization of single domain particles. This pulse was administered in the presence of a 1 mT biasing field, either parallel to the direction of the biasing field (PAR group) or antiparallel (ANTI group). In the case of magnetoreceptors based on freely moving single domain particles, the PAR treatment should have little effect, whereas the ANTI treatment should cause remagnetization of the magnetite particles involved in a receptor and could produce a maximum change in that receptor's output for some receptor configurations. Migratory orientation was used as a criterion to assess the effect on the receptor. Before treatment, both groups preferred their normal northerly migratory direction. Exposure to the biasing field alone did not affect their behavior. Treatment with the pulse in the presence of the biasing field caused both the PAR and the ANTI birds to show an axial preference for the east-west axis, with no difference between the two groups. Although these results are in accordance with magnetite-based magnetoreceptors playing a role in migratory orientation, they do not support the hypothesis that single domains in polarity-sensitive receptors are free to move through all solid angles. Possible interpretations, including other arrangements of single domains and superparamagnetic crystals, are discussed.

  19. The Disruption of an OxyR-Like Protein Impairs Intracellular Magnetite Biomineralization in Magnetospirillum gryphiswaldense MSR-1

    PubMed Central

    Zhang, Yunpeng; Wen, Tong; Guo, Fangfang; Geng, Yuanyuan; Liu, Junquan; Peng, Tao; Guan, Guohua; Tian, Jiesheng; Li, Ying; Li, Jilun; Ju, Jing; Jiang, Wei

    2017-01-01

    Magnetotactic bacteria synthesize intracellular membrane-enveloped magnetite bodies known as magnetosomes which have been applied in biotechnology and medicine. A series of proteins involved in ferric ion transport and redox required for magnetite formation have been identified but the knowledge of magnetosome biomineralization remains very limited. Here, we identify a novel OxyR homolog (named OxyR-Like), the disruption of which resulted in low ferromagnetism and disfigured nano-sized iron oxide crystals. High resolution-transmission electron microscopy showed that these nanoparticles are mainly composed of magnetite accompanied with ferric oxide including α-Fe2O3 and 𝜀-Fe2O3. Electrophoretic mobility shift assay and DNase I footprinting showed that OxyR-Like binds the conserved 5′-GATA-N{9}-TATC-3′ region within the promoter of pyruvate dehydrogenase (pdh) complex operon. Quantitative real-time reverse transcriptase PCR indicated that not only the expression of pdh operon but also genes related to magnetosomes biosynthesis and tricarboxylic acid cycle decreased dramatically, suggesting a link between carbon metabolism and magnetosome formation. Taken together, our results show that OxyR-Like plays a key role in magnetosomes formation. PMID:28261169

  20. Low-temperature oxidation of magnetite - a humidity sensitive process?

    NASA Astrophysics Data System (ADS)

    Appel, Erwin; Fang, Xiaomin; Herb, Christian; Hu, Shouyun

    2015-04-01

    Extensive multi-parameter palaeoclimate records were obtained from two long-term lacustrine archives at the Tibetan Plateau: the Qaidam basin (2.69-0.08 Ma) and Heqing basin (0.90-0.03 Ma). At present the region of the Qaidam site has an arid climate (<100 mm mean annual precipitation) while the Heqing site is located in the sub-tropical region with monsoonal rainfall. Magnetic properties play a prominent role for palaeoclimate interpretation in both records. Several parameters show a 100 kyr eccentricity cyclicity; in the Qaidam record also the Mid-Pleistocene Transition is seen. Both magnetic records are controlled by different absolute and relative contributions of magnetite and its altered (maghemitized) phases as well as hematite. Weathering conditions likely cause a systematic variation of magnetic mineralogy due to low-temperature oxidation (LTO). Maghemitization is well recognized as an alteration process in submarine basalts but about its relevance for climate-induced weathering in continental environments little is known. Various factors i.e., humidity, temperature, seasonality, duration of specific weathering conditions, and bacterial activity could be responsible for maghemitization (LTO) and transformation to hematite (or goethite) when a critical degree of LTO is reached. These factors may lead to a complex interplay, but one has to note that water acts as an electrolyte for Fe(II) to Fe(III) oxidation at the crystal surface and due to maghemitization-induced lattice shrinking a larger internal particle surface area becomes exposed to oxidation. We suggest that humidity is the most crucial driver for the two studied archives - for the following reasons: (1) The overall parameter variations and catchment conditions are well in agreement with an LTO scenario. (2) In the Qaidam record we observe a direct relationship of a humidity sensitive pollen Ratio with magnetic susceptibility (reflecting the degree of alteration by LTO). (3) In the Heqing record

  1. Experimental evidence for non-redox transformations between magnetite and hematite under H-2-rich hydrothermal conditions.

    SciTech Connect

    Otake, Tsubasa; Wesolowski, David J; Anovitz, Lawrence {Larry} M

    2007-05-01

    Transformations of magnetite (Fe{sup II}Fe{sub 2}{sup III}O{sub 4}) to hematite (Fe{sub 2}{sup III}O{sub 3}) (and vice versa) have been thought by many scientists and engineers to require molecular O{sub 2} and/or H{sub 2}. Thus, the presence of magnetite and/or hematite in rocks has been linked to a specific oxidation environment. However, the availability of reductants or oxidants in many geologic and industrial environments appears to have been too low to account for the transformations of iron oxides through redox reactions. Here, we report the results of hydrothermal experiments in mildly acidic and H{sub 2}-rich aqueous solutions at 150 C, which demonstrate that transformations of magnetite to hematite, and hematite to magnetite, occur rapidly without involving molecular O{sub 2} or H{sub 2}: Fe{sub 3}O{sub 4}(Mt) + 2H{sub (aq)}{sup +} {leftrightarrow} Fe{sub 2}O{sub 3}(Hm) + Fe{sub (aq)}{sup 2+} + H{sub 2}O. The transformation products are chemically and structurally homogeneous, and typically occur as euhedral single crystals much larger than the precursor minerals. This suggests that, in addition to the expected release of aqueous ferrous species to solution, the transformations involve release of aqueous ferric species from the precursor oxides to the solution, which reprecipitate without being reduced by H{sub 2}. These redox-independent transformations may have been responsible for the formation of some iron oxides in natural systems, such as high-grade hematite ores that developed from Banded Iron Formations (BIFs), hematite-rich deposits formed on Mars, corrosion products in power plants and other industrial systems.

  2. Experimental Evidence for Non-Redox Transformation Between Magnetite and Hermatite Under H2-Rich Hydrothermal Conditions

    SciTech Connect

    Otake, Tsubasa; Ohmoto, Hiroshi; Wesolowski, David J; Anovitz, Lawrence {Larry} M; Allard Jr, Lawrence Frederick

    2007-01-01

    Transformations of magnetite (Fe{sup II}Fe{sub 2}{sup III}O{sub 4}) to hematite (Fe{sub 2}{sup III}O{sub 3}) (and vice versa) have been thought by many scientists and engineers to require molecular O{sub 2} and/or H{sub 2}. Thus, the presence of magnetite and/or hematite in rocks has been linked to a specific oxidation environment. However, the availability of reductants or oxidants in many geologic and industrial environments appears to have been too low to account for the transformations of iron oxides through redox reactions. Here, we report the results of hydrothermal experiments in mildly acidic and H{sub 2}-rich aqueous solutions at 150 C, which demonstrate that transformations of magnetite to hematite, and hematite to magnetite, occur rapidly without involving molecular O{sub 2} or H{sub 2}: Fe{sub 3}O{sub 4}(Mt) + 2H{sub (aq)}{sup +} {leftrightarrow} Fe{sub 2}O{sub 3}(Hm) + Fe{sub (aq)}{sup 2+} + H{sub 2}O The transformation products are chemically and structurally homogeneous, and typically occur as euhedral single crystals much larger than the precursor minerals. This suggests that, in addition to the expected release of aqueous ferrous species to solution, the transformations involve release of aqueous ferric species from the precursor oxides to the solution, which reprecipitate without being reduced by H{sub 2}. These redox-independent transformations may have been responsible for the formation of some iron oxides in natural systems, such as high-grade hematite ores that developed from Banded Iron Formations (BIFs), hematite-rich deposits formed on Mars, corrosion products in power plants and other industrial systems.

  3. Pure right ventricular infarction.

    PubMed

    Inoue, Katsuji; Matsuoka, Hiroshi; Kawakami, Hideo; Koyama, Yasushi; Nishimura, Kazuhisa; Ito, Taketoshi

    2002-02-01

    A 76-year-old man with chest pain was admitted to hospital where electrocardiography (ECG) showed ST-segment elevation in leads V1-4, indicative of acute anterior myocardial infarction. ST-segment elevation was also present in the right precordial leads V4R-6R. Emergency coronary angiography revealed that the left coronary artery was dominant and did not have significant stenosis. Aortography showed ostial occlusion of the right coronary artery (RCA). Left ventriculography showed normal function and right ventriculography showed a dilated right ventricle and severe hypokinesis of the right ventricular free wall. Conservative treatment was selected because the patient's symptoms soon ameliorated and his hemodynamics was stable. 99mTc-pyrophosphate and 201Tl dual single-photon emission computed tomography showed uptake of 99mTc-pyrophosphate in only the right ventricular free wall, but no uptake of 99mTc-pyrophosphate and no perfusion defect of 201Tl in the left ventricle. The peak creatine kinase (CK) and CK-MB were 1,381 IU/L and 127 IU/L, respectively. His natural course was favorable and the chest pain disappeared under medication. Two months after the onset, the ECG showed poor R progression in leads V1-4 indicating an old anterior infarction. Coronary angiography confirmed the ostial stenosis of the hypoplastic RCA. This was a case of pure right ventricular free wall infarction because of the occlusion of the ostium of the hypoplastic RCA, but not of the right ventricular branch. Because the electrocardiographic findings resemble those of an acute anterior infarction, it is important to consider pure right ventricular infarction in the differential diagnosis.

  4. Low-temperature and high-temperature hysteresis of small multidomain magnetites (215-540 nm)

    NASA Astrophysics Data System (ADS)

    Argyle, Kenneth S.; Dunlop, David J.

    1990-05-01

    Approximately equidimensional magnetite crystals, with mean sizes of 215, 390, and 540 nm, respectively, have been produced by reducing hematite crystals. Isothermal magnetic hysteresis properties show a clear progression toward multidomain-like behavior as the mean grain size increases. Saturation remanences Mrs are only 5-10% of saturation magnetization Ms, coercive forces HC are low (5.5-8 mT), and both Mrs and HC have grain-size dependences compatible with those previously established for smaller and larger hydrothermally produced magnetites. Coercivities during remanence acquisition are greater than those measured during demagnetization. The difference between acquisition and destructive fields increases in the larger grains as a result of the increasing importance of the internal demagnetizing field. The low-temperature transition is well expressed in the Mrs and HC data of the 540-nm sample but is more subdued for smaller grains. Magnetostrictive, magnetocrystalline, and magnetostatic mechanisms in turn govern coercivity as the temperature rises. Remanence and coercivity ratios, Mrs/Ms and HR/HC, are almost temperature independent up to 500°C, indicating that domain wall configurations resulting from saturating fields are about the same at any temperature. A thermal fluctuation analysis of high-temperature coercive force data suggests that regions 200-250 nm in size are thermally activated as a unit in grains of all sizes; these are likely domain walls. Apparent demagnetizing factors calculated from both low- and high-temperature data are consistent with a mixture of two-domain (2D) and three-domain (3D) grains in all samples. However, theories of remanence in conventional 2D and 3D grains or in mixtures of 2D, 3D, and metastable single-domain grains do not explain the data in a satisfying way.

  5. High-pressure Raman spectroscopic study of magnetite Fe3O4

    NASA Astrophysics Data System (ADS)

    Kyono, A.; Ahart, M.; Yamanaka, T.; Mysen, B.; Mao, H.; Hemley, R. J.

    2010-12-01

    We report in situ Raman spectroscopic studies of magnetite in a diamond-anvil cell under hydrostatic conditions up to 60 GPa at room temperature. Magnetite with ideal chemical formula Fe3O4 crystallizes in the face-centered cubic spinel-type structure. There are five first-order Raman active modes (A1g + Eg + 3F2g) in the Fd3m space group of the spinel structure. Three modes at nearby 300, 600 and 700 cm-1 are observed under pressure conditions. In the cubic spinels including ferrites, the highest frequency at about 700 cm-1 corresponds to the stretching vibrations of oxygen atoms in the tetrahedral coordination and can be assigned to the A1g symmetry. The other strong peak centered at about 600 and 300 cm-1 can be assigned to the F2g and Eg symmetries. The remaining two modes could not be observed unambiguously in the measurements. The peak positions and shapes of the Raman spectra agree well with previously published data measured under ambient condition. With increasing pressure, the frequencies of the two modes A1g , F2g and Eg increase continuously up to about 30 GPa with pressure derivatives of 2.7, 4.5 and 1.4 cm-1/GPa, respectively. There is no obvious degradation of crystal symmetry or structural change within this pressure range. Upon elevation of pressure to nearby 30 GPa, the F2g mode starts to display a variation in the spectra and its intensity gradually decreases due to the tetragonal-orthorhombic phase transition. The splitted mode into B1g, B2g, B3g from F2g completely disappears at a pressure of 40 GPa. The most striking characteristic of Raman spectroscopy of magnetite is that the pressure-induced suppression leads to a significant extinction of the Raman active mode derived from F2g symmetry. Only one peak resulting from A1g mode can be observed continuously up to 60 GPa. Consequently, the results of the Raman spectroscopic study about phase transformation are in good agreement with that of the X-ray diffraction study.

  6. Intracellular hyperthermia for cancer using magnetite cationic liposomes

    NASA Astrophysics Data System (ADS)

    Shinkai, Masashige; Yanase, Mitsugu; Suzuki, Masataka; Honda, Hiroyuki; Wakabayashi, Toshihiko; Yoshida, Jun; Kobayashi, Takeshi

    1999-04-01

    We have developed `magnetite cationic liposomes' (MCLs) as a new heating mediator for hyperthermia. The hyperthermic effect on solid glioma tissue grown subcutaneously in F344 rats was investigated. Complete tumor regression was observed in about 90% of the rats by three times of repeated heating. Furthermore, induction of antitumor immunity for T-9 rat glioma using MCLs was investigated.

  7. SEPARATION OF TECHNETIUM FROM AQUEOUS SOLUTIONS BY COPRECIPITATION WITH MAGNETITE

    DOEpatents

    Rimshaw, S.J.

    1961-10-24

    A method of separating technetium in the 4+ oxidation state from an aqueous basic solution containing products of uranium fission is described. The method consists of contacting the solution with finely divided magnetite and recovering a technetium-bearing precipitate. (AEC)

  8. Avian magnetite-based magnetoreception: a physiologist's perspective

    PubMed Central

    Cadiou, Hervé; McNaughton, Peter A.

    2010-01-01

    It is now well established that animals use the Earth's magnetic field to perform long-distance migration and other navigational tasks. However, the transduction mechanisms that allow the conversion of magnetic field variations into an electric signal by specialized sensory cells remain largely unknown. Among the species that have been shown to sense Earth-strength magnetic fields, birds have been a model of choice since behavioural tests show that their direction-finding abilities are strongly influenced by magnetic fields. Magnetite, a ferromagnetic mineral, has been found in a wide range of organisms, from bacteria to vertebrates. In birds, both superparamagnetic (SPM) and single-domain magnetite have been found to be associated with the trigeminal nerve. Electrophysiological recordings from cells in the trigeminal ganglion have shown an increase in action potential firing in response to magnetic field changes. More recently, histological evidence has demonstrated the presence of SPM magnetite in the subcutis of the pigeon's upper beak. The aims of the present review are to review the evidence for a magnetite-based mechanism in birds and to introduce physiological concepts in order to refine the proposed models. PMID:20106875

  9. Advancing Sustainable Catalysis with Magnetite Surface Modification and Synthetic Applications

    EPA Science Inventory

    This article surveys the recent developments in the synthesis, surface modification, and synthetic applications of magnetitenanoparticles. The emergence of iron(II,III) oxide (triiron tetraoxide or magnetite; Fe3O4, or FeO•Fe2O3) nanoparticles as a sustainable support in heteroge...

  10. Clay and Magnetite Formation at Yellowknife Bay, Mars

    NASA Astrophysics Data System (ADS)

    Bridges, J. C.; Schwenzer, S. P.; Leveille, R.; Westall, F.; Wiens, R. C.; Mangold, N.; Bristow, T.; Edwards, P.; Berger, G.

    2014-09-01

    Sheepbed mudstone contains a clay-magnetite assemblage formed by dissolution of approximately 70% amorphous phase, 20% olivine, 10% host rock mixture, by a pore fluid at moderate W/R ratio. The clay is similar to Lafayette's ferric saponite and gel.

  11. Enhancing of Fe removal in pyrophyllite using magnetite ore susceptor

    NASA Astrophysics Data System (ADS)

    Hack Lim, Dae; Myung, Eun Ji; Kim, Hyun Soo; Choul Choi, Nag; Cho, Kang Hee; Park, Cheon Young

    2016-04-01

    Pyrite and hematite are an impurity that reduces the grade of pyrophyllite in the final products. Because the impurity in pyrophyllite which was associated with hydrothermally altered rocks. Microwave has been extensively explored in various fields of materials processing. This technology exhibits unique characteristics including volumetric and selective heating, which eventually lead to many exceptional advantages over conventional processing methods including both energy and cost savings, improved product quality and faster processing. The aim of this study was to investigate the application possibility of microwave process for Fe removal in pyrophyllite. The pyrite and quartz of the pyrophyllite was determined by reflected light microscopy and XRD. The result of Fe removal experiment in pyrophyllite using microwave susceptor(magnetite ore included ilmenite and magnetite) showed to decrease of Fe content in pyrophyllite. The Fe removal of 93.62% and parameters were obtained under the following conditions by magnetite ore was 20.0 g, the pyrophyllite was 10.0 g, and the microwave heating time was 10.0 min. By means of microwave, Fe removal in pyrophyllite can be rapidly and efficiently pyrolyze. if some of the magnetite ore, which acts as a microwave susceptor, is mixed with the raw material. Acknowledgment : This subject is supported by Korea Ministry of Environment as "Advanced Technology Program for Environmental Industry"

  12. Benefaction studies on the Hasan Celebi magnetite deposit, Turkey

    USGS Publications Warehouse

    Pressler, Jean W.; Akar, Ali

    1972-01-01

    Bench-scale and semicontinuous tests were performed on surface, trench, and diamond drill core samples from the Hasan Celebi low-grade magnetite deposit to determine the optimum benefication procedures utilizing wet magnetic separation techniques. Composite core samples typically contain about 27 percent recoverable magnetite and require crushing and grinding through 1 mm in size to insure satisfactory separation of the gangue from the magnetite. Regrinding and cleaning the magnetite concentrate to 80 percent minus 150-mesh is necessary to obtain an optimum of 66 percent iron. Semicontinuous pilot-plant testing with the wet magnetic drum using the recycled middling technique indicates that as much as 83 percent of the acid-soluble iron can be recovered into a concentrate containing 66 percent iron, with minimum deleterious elements. This represents 27 weight percent of the original ore. Further tests will continue when the Maden Tetkik ve Arama Enstitusu (MTA) receives 24 tons of bulk sample from an exploratory drift and cross-cut now being driven through a section of the major reserve area.

  13. Synthesis of a stable magnetite (magnetic fluid) colloid solution

    NASA Astrophysics Data System (ADS)

    Evdokimov, S. I.; Evdokimov, V. S.

    2017-01-01

    The article is dedicated to the development and investigation of conditions for obtaining the aggregate stable colloid solutions of magnetite – magnetic fluids. The developed method differs from the known ones and involves new ways of producing and stabilizing magnetic nanoparticles with a narrow particle size distribution.

  14. Physics with chemically and isotopically pure semiconductors

    NASA Astrophysics Data System (ADS)

    Haller, E. E.

    1993-05-01

    Chemically and isotopically pure semiconductors offer a wealth of interesting physics. We review a number of impurity complexes which were discovered in ultrapure Germanium. They have led the way to the widely pursued studies of hydrogen in numerous semiconductors. Isotope related effects and processes include neutron transmutation doping, a technique used for a number of silicon and germanium devices. Isotopically pure and deliberately mixed crystals of germanium have been grown recently and have been used to study the dependence of the indirect bandgap and phonon properties on the mass and mass disorder of the nuclei. The large number of stable isotopes of the various semiconductors present a great potential for basic and applied studies. Semi-conductor isotope engineering may become a reality because of the new economic and political world order.

  15. Intensified magneto-resistance by rapid thermal annealing in magnetite (Fe3O4) thin film on SiO2 glass substrate

    NASA Astrophysics Data System (ADS)

    Kobori, H.; Morii, K.; Yamasaki, A.; Sugimura, A.; Taniguchi, T.; Horie, T.; Naitoh, Y.; Shimizu, T.

    2012-12-01

    We have observed large magneto-resistance (MR) intensified by rapid thermal annealing (RTA) in magnetite (Fe3O4) thin film (MTF) on SiO2 glass (a-SiO2) substrate. The MTF was produced by the RF magnetron sputtering method by using a magnetite target. The electrical resistivity (ER) of as-grown MTF (AG-MTF) showed the Mott's variable range hopping behavior, which implies that the AG-MTF is amorphous-like. Although the magneto-resistance (MR) ratio of bulk single crystal is very small except around the Verwey transition temperature (VTT), that of the AG-MTF showed moderately large below room temperature. Due to RTA of the AG-MTF by use of an IR image furnace, the MR ratio of MTFs was intensified, and especially by the annealing around the Curie temperature (585°C) of magnetite. Furthermore the ER of the rapid thermally annealed MTF (RTA-MTF) showed a slight kink at around the VTT, which indicates that the crystallinity of the RTA-MTF is higher than that of the AG-MTF The MTF produced by the RF magnetron sputtering method are composed of magnetite fine particles (MFPs). We consider that the directions of magnetic moments of MFPs in the MTF were spatially randomized by the RTA and the strong spin scattering of itinerant electrons transferring between adjacent MFPs caused the intensification of the MR ratio.

  16. Surface reactions kinetics between nanocrystalline magnetite and uranyl.

    PubMed

    Missana, Tiziana; Maffiotte, César; García-Gutiérrez, Miguel

    2003-05-01

    Magnetite is the most important end member of iron corrosion products under reducing environment, which is the condition expected in a deep geological high level radioactive waste disposal. Nanocrystalline magnetite was synthesized in the laboratory and its physicochemical properties were analyzed in detail. The kinetics of the adsorption of U(VI) and the kinetics of the actinide reduction to a lower oxidation state, in presence of the oxide, were studied by means of batch sorption techniques and X-ray photoelectron spectroscopy (XPS) analysis. The results showed that the uranium sorption and reduction processes on the magnetite surface have very fast kinetics (hours), the reduction process being triggered by sorption. XPS measurements showed that the speciation of uranium at the surface does not show significant changes with time (from 1 day to 3 months), as well as the quantity of uranium detected at the surface. The surface speciation depended on the initial pH of the contact solution. Considering that the Eh of equilibrium between magnetite and the solution, under our experimental conditions, is slightly positive (50-100 mV), the uranium reduction would also be thermodynamically possible within the liquid phase. However, the kinetics of reduction in the liquid occur at a much slower rate which, in turn, has to depend on the attainment of the magnetite/solution equilibrium. The decrease of uranium in solution, observed after the uranyl adsorption stage, and particularly at acidic pH, is most probably due to the precipitation of U(IV) formed in the solution.

  17. Variation in magnetic properties of serpentinized peridotites exposed on the Yokoniwa Rise, Central Indian Ridge: Insights into the role of magnetite in serpentinization

    NASA Astrophysics Data System (ADS)

    Fujii, Masakazu; Okino, Kyoko; Sato, Hiroshi; Nakamura, Kentaro; Sato, Taichi; Yamazaki, Toshitsugu

    2016-12-01

    Magnetic properties in serpentinized peridotites are of increasing interest in seafloor mapping and petrologic studies because such data can promote the understanding of serpentinization reactions and hydrogen creation in ultramafic rocks. In order to reveal the magnetic properties and magnetite growth in serpentinized peridotites, we analyzed 30 serpentinized peridotite samples from a nontransform offset massif called the Yokoniwa Rise in the Central Indian Ridge. The results from multiple rock magnetic analyses and petrological observations illustrate the details of the creation and growth of magnetite in serpentinized peridotites that have undergone 17-100% serpentinzation. The magnetic carrier of these samples is pure magnetite, which did not suffer from maghemitization (low-temperature oxidation). The magnetic susceptibility ranged from 0.002 to 0.087 SI and increased nonlinearly with the progression of the serpentinization reaction. The natural remanent magnetization intensities of 0.2-8.4 A/m are comparable to those of basalts, which suggests that the remanence as well as induced magnetization of highly serpentinized peridotite can contribute to magnetization of the oceanic lithosphere. The amount of magnetite estimated from saturation magnetization increased nonlinearly from 0.1 to 5.5 wt % with the progression of the serpentinization. Highly serpentinized peridotites have a well-developed serpentine mesh texture. Pseudo-single-domain (PSD) and multidomain (MD) grains were formed during igneous processes in the mantle and/or during the initial stages of serpentinization. Superparamagnetic (SP) particles were formed during the initial stages of serpentinization. Single-domain (SD) magnetite was formed during the later stage of serpentinization, and it is assembled inside of mesh structures with strong magnetostatic interactions.

  18. Pressure effect on the low-temperature remanences of multidomain magnetite: Change in the Verwey transition temperature

    NASA Astrophysics Data System (ADS)

    Sato, M.; Yamamoto, Y.; Nishioka, T.; Kodama, K.; Mochizuki, N.; Tsunakawa, H.

    2011-12-01

    The Verwey transition of magnetite is the basic issues for the rock magnetism, since main magnetic mineral of terrestrial rocks is magnetite and its associates. One of the most important issues concerning the Verwey transition is the change in transition temperature (Tv) due to pressure, which is thought to improve our understanding of its electric and magnetic nature in relation to the phase diagram. Recently, the opposite pressure effects of the transition temperature were reported applying the different experimental method. Measuring the electrical resistivity of single crystalline samples, Môri et al. [2002] reported that Tv becomes lower with increasing pressure by 9 GPa. In contrast, Pasternak et al. [2003] reported from Mössbauer experiment that transition temperature becomes higher with increasing pressure by 30 GPa. Thus the change in transition temperature with pressure has been controversial, and nature of the Verwey transition is still unclear. The magnetic property measurements using low temperature cycle are a powerful tool for identifying the state of magnetic minerals. Carporzen and Gilder [2010] conducted the thermal demagnetization experiment of low-temperature remanences of magnetite, and observed an increase in Tv with increasing pretreated pressure. From this result, they suggested that the Verwey transition of magnetite have the potential of a geobarometer. Modern techniques of high-pressure experiments enable us to measure sample magnetizations under pressure [Gilder et al., 2002; Kodama and Nishioka, 2005; Sadykov et al., 2008]. In the present study, systematic experiments of low-temperature remanences have been conducted for powder samples of stoichiometric magnetite under pressure up to 0.7 GPa using the high-pressure cell specially designed for MPMS, which was made of CuBe and ZrO2 [Kodama and Nishioka, 2005]. Natural magnetite of large single crystals were crushed by hand and sieved in an ultrasonic bath to be ~50 μm in size. For

  19. Influence of silver content on rifampicin adsorptivity for magnetite/Ag/rifampicin nanoparticles

    NASA Astrophysics Data System (ADS)

    Ivashchenko, Olena; Coy, Emerson; Peplinska, Barbara; Jarek, Marcin; Lewandowski, Mikołaj; Załęski, Karol; Warowicka, Alicja; Wozniak, Anna; Babutina, Tatiana; Jurga-Stopa, Justyna; Dolinsek, Janez; Jurga, Stefan

    2017-02-01

    Magnetite nanoparticles (NPs) decorated with silver (magnetite/Ag) are intensively investigated due to their application in the biomedical field. We demonstrate that the increase of silver content on the surface of nanoparticles improves the adsorptivity of antibiotic rifampicin as well as antibacterial properties. The use of ginger extract allowed to improve the silver nucleation on the magnetite surface that resulted in an increase of silver content. Physicochemical and functional characterization of magnetite/Ag NPs was performed. Our results show that 5%-10% of silver content in magnetite/Ag NPs is already sufficient for antimicrobial properties against Streptococcus salivarius and Staphylococcus aureus. The rifampicin molecules on the magnetite/Ag NPs surface made the spectrum of antimicrobial activity wider. Cytotoxicity evaluation of the magnetite/Ag/rifampicin NPs showed no harmful action towards normal human fibroblasts, whereas the effect on human embryonic kidney cell viability was time and dose dependent.

  20. Magnetite-based Magnetoreception in Animals: 25+ Years of Theory & Experimentation

    NASA Astrophysics Data System (ADS)

    Kirschvink, J. L.; Walker, M. M.

    2005-12-01

    Living organisms ranging from bacteria through higher vertebrates rely on orientation, navigation, and homing to survive. Any sensory cue that enhances these behaviors will be subject to intense natural selection over geological time. Reproducible behavioral responses to earth-strength magnetic fields(1) have been documented in Bacteria, Protoctists, and in nearly every major group of animals, and are possibly also present in the Archaea. Several groups of animals, including birds and cetaceans, respond behaviorally to magnetic anomalies below 100 nT in magnitude, implying that their magnetoreception ability approaches the thermal noise limit. This approach to thermal noise is commonly observed in other sensory systems, including hearing, olfaction, and electroreception. The hypothesis of magnetite-based magnetoreception(2) is the only theory proposed so far that is capable of explaining all of the magnetic behavioral data. Tiny crystals of single-domain magnetite (or in some bacteria, greigite) rotate the cells of microorganisms passively like a simple compass needle. The initial detection of biogenic magnetite with rock magnetic techniques in birds and bees over 25 years ago has led progressively to the identification of a group of specialized cells in fish and birds which contain organized magnetite-containing structures. In these animals (and presumably all vertebrates) magnetic signals are transmitted to the brain via the ophthalmic branch of the trigeminal nerve(3, 4). Experiments with pulse-remagnetization, like those that convert North-seeking bacteria into South-seekers, have dramatic effects on animal behavior, confirming the role of magnetite in the sensory system. This is therefore a general mechanism for a highly sensitive magnetic sense, the origin of which probably dates to the ancestral metazoan, and perhaps earlier. The largest debate presently occurring in the field concerns the interpretation of magnetic compass responses that vary with intensity

  1. Fe2 + and Fe3 + ions distinguishable by x-ray anomalous scattering: Method and its application to magnetite

    NASA Astrophysics Data System (ADS)

    Sasaki, Satoshi

    1995-02-01

    A chemical shift of about 5 eV was observed between ferrous and ferric ions in the XANES absorption spectra of FeO and Fe2O3 where the Fe ions coordinate in regular octahedra. Experimental f'e was estimated based on the cross-section data in the 108 eV region at the Fe K edge using the Cromer and Liberman's equation. The result shows that the maximum difference in f'e between Fe2+ and Fe3+ is about 2.5 at the longer wavelength side of the Fe2+K edge. The XANES spectrum of Fe3O4 (magnetite) lies between those of FeO and Fe2O3. Synchrotron x-ray-diffraction data of a magnetite crystal were measured on a vertical-type four-circle diffractometer and used for evaluation at seven wavelengths of 1.7415, 1.7420, 1.7425, 1.7431, 1.7452, 1.7499, and 1.7567 Å. The difference-Fourier technique promises the possibility of mapping valence differences for atoms of the same atomic species in a mixed-valence crystal.

  2. Geochemistry of magnetite from porphyry Cu and skarn deposits in the southwestern United States

    USGS Publications Warehouse

    Nadoll, Patrick; Mauk, Jeffrey L.; LeVeille, Richard A.; Koenig, Alan E.

    2015-01-01

    A combination of petrographic observations, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and statistical data exploration was used in this study to determine compositional variations in hydrothermal and igneous magnetite from five porphyry Cu–Mo and skarn deposits in the southwestern United States, and igneous magnetite from the unmineralized, granodioritic Inner Zone Batholith, Japan. The most important overall discriminators for the minor and trace element chemistry of magnetite from the investigated porphyry and skarn deposits are Mg, Al, Ti, V, Mn, Co, Zn, and Ga—of these the elements with the highest variance for (I) igneous magnetite are Mg, Al, Ti, V, Mn, Zn, for (II) hydrothermal porphyry magnetite are Mg, Ti, V, Mn, Co, Zn, and for (III) hydrothermal skarn magnetite are Mg, Ti, Mn, Zn, and Ga. Nickel could only be detected at levels above the limit of reporting (LOR) in two igneous magnetites. Equally, Cr could only be detected in one igneous occurrence. Copper, As, Mo, Ag, Au, and Pb have been reported in magnetite by other authors but could not be detected at levels greater than their respective LORs in our samples. Comparison with the chemical signature of igneous magnetite from the barren Inner Zone Batholith, Japan, suggests that V, Mn, Co, and Ga concentrations are relatively depleted in magnetite from the porphyry and skarn deposits. Higher formation conditions in combination with distinct differences between melt and hydrothermal fluid compositions are reflected in Al, Ti, V, and Ga concentrations that are, on average, higher in igneous magnetite than in hydrothermal magnetite (including porphyry and skarn magnetite). Low Ti and V concentrations in combination with high Mn concentrations are characteristic features of magnetite from skarn deposits. High Mg concentrations (<1,000 ppm) are characteristic for magnetite from magnesian skarn and likely reflect extensive fluid/rock interaction. In porphyry deposits

  3. Geochemistry of magnetite from porphyry Cu and skarn deposits in the southwestern United States

    NASA Astrophysics Data System (ADS)

    Nadoll, Patrick; Mauk, Jeffrey L.; Leveille, Richard A.; Koenig, Alan E.

    2015-04-01

    A combination of petrographic observations, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and statistical data exploration was used in this study to determine compositional variations in hydrothermal and igneous magnetite from five porphyry Cu-Mo and skarn deposits in the southwestern United States, and igneous magnetite from the unmineralized, granodioritic Inner Zone Batholith, Japan. The most important overall discriminators for the minor and trace element chemistry of magnetite from the investigated porphyry and skarn deposits are Mg, Al, Ti, V, Mn, Co, Zn, and Ga—of these the elements with the highest variance for (I) igneous magnetite are Mg, Al, Ti, V, Mn, Zn, for (II) hydrothermal porphyry magnetite are Mg, Ti, V, Mn, Co, Zn, and for (III) hydrothermal skarn magnetite are Mg, Ti, Mn, Zn, and Ga. Nickel could only be detected at levels above the limit of reporting (LOR) in two igneous magnetites. Equally, Cr could only be detected in one igneous occurrence. Copper, As, Mo, Ag, Au, and Pb have been reported in magnetite by other authors but could not be detected at levels greater than their respective LORs in our samples. Comparison with the chemical signature of igneous magnetite from the barren Inner Zone Batholith, Japan, suggests that V, Mn, Co, and Ga concentrations are relatively depleted in magnetite from the porphyry and skarn deposits. Higher formation conditions in combination with distinct differences between melt and hydrothermal fluid compositions are reflected in Al, Ti, V, and Ga concentrations that are, on average, higher in igneous magnetite than in hydrothermal magnetite (including porphyry and skarn magnetite). Low Ti and V concentrations in combination with high Mn concentrations are characteristic features of magnetite from skarn deposits. High Mg concentrations (<1,000 ppm) are characteristic for magnetite from magnesian skarn and likely reflect extensive fluid/rock interaction. In porphyry deposits

  4. Investigation of heteroepitaxial growth of magnetite thin films.

    SciTech Connect

    Sterbinsky, G. E.; Cheng, J.; Chiu, P. T.; Wessels, B. W.; Keavney, D. J.; X-Ray Science Division; Northwestern Univ.

    2007-07-01

    Epitaxial magnetite (Fe{sub 3}O{sub 4}) thin films were deposited by molecular beam epitaxy using molecular oxygen as the oxidant. Films deposited on (001) SrTiO{sub 3}, (001) MgO, and (001) BaTiO{sub 3} surfaces are epitaxial with the film (001) parallel to the substrate (001) and the film <100> parallel to the substrate <100>. X-ray magnetic circular dichroism was used to determine the relative Fe{sup 2+}/Fe{sup 3+} stoichiometry of the magnetite films, which was nearly independent of oxygen partial pressure over the range studied. All films show no in-plane magnetic anisotropy. Coercive fields ranged from 0.019 to 0.039 T and depended on film roughness.

  5. Preparation of magnetite aqueous dispersion for magnetic fluid hyperthermia

    NASA Astrophysics Data System (ADS)

    Kikuchi, Teppei; Kasuya, Ryo; Endo, Shota; Nakamura, Akira; Takai, Toshiyuki; Metzler-Nolte, Nils; Tohji, Kazuyuki; Balachandran, Jeyadevan

    2011-05-01

    An aqueous magnetic suspension was prepared by dispersing amphiphilic co-polymer-coated monodispersed magnetite nanoparticles synthesized through thermal decomposition of iron acetylacetonate (Fe(acac) 3) in a mixture of oleic acid and oleylamine. The average diameter of narrow-size-distributed magnetite nanoparticles varied between 5 and 12 nm depending on the experimental parameters such as reaction temperature, metal salt concentration and oleic acid/oleylamine ratio. Though the as-synthesized particles were coated with oleate and were dispersible in organic solvent, their surfaces were modified using amphiphilic co-polymers composed of poly(maleic anhydride-alt-1-octadecene) and polyethylene glycol-methyl ether and made dispersible in water. Infrared spectra of the sample indicated the existence of -COOH groups on the surface for further conjugation with biomolecules for targeted cancer therapy.

  6. Magnetite-doped polydimethylsiloxane (PDMS) for phosphopeptide enrichment.

    PubMed

    Sandison, Mairi E; Jensen, K Tveen; Gesellchen, F; Cooper, J M; Pitt, A R

    2014-10-07

    Reversible phosphorylation plays a key role in numerous biological processes. Mass spectrometry-based approaches are commonly used to analyze protein phosphorylation, but such analysis is challenging, largely due to the low phosphorylation stoichiometry. Hence, a number of phosphopeptide enrichment strategies have been developed, including metal oxide affinity chromatography (MOAC). Here, we describe a new material for performing MOAC that employs a magnetite-doped polydimethylsiloxane (PDMS), that is suitable for the creation of microwell array and microfluidic systems to enable low volume, high throughput analysis. Incubation time and sample loading were explored and optimized and demonstrate that the embedded magnetite is able to enrich phosphopeptides. This substrate-based approach is rapid, straightforward and suitable for simultaneously performing multiple, low volume enrichments.

  7. Field Evidence for Magnetite Formation by a Methanogenic Microbial Community

    NASA Astrophysics Data System (ADS)

    Rossbach, S.; Beaver, C. L.; Williams, A.; Atekwana, E. A.; Slater, L. D.; Ntarlagiannis, D.; Lund, A.

    2015-12-01

    The aged, subsurface petroleum spill in Bemidji, Minnesota, has been surveyed with magnetic susceptibility (MS) measurements. High MS values were found in the free-product phase around the fluctuating water table. Although we had hypothesized that high MS values are related to the occurrence of the mineral magnetite resulting from the activity of iron-reducing bacteria, our microbial analysis pointed to the presence of a methanogenic microbial community at the locations and depths of the highest MS values. Here, we report on a more detailed microbial analysis based on high-throughput sequencing of the 16S rRNA gene of sediment samples from four consecutive years. In addition, we provide geochemical data (FeII/FeIII concentrations) to refine our conceptual model of methanogenic hydrocarbon degradation at aged petroleum spills and demonstrate that the microbial induced changes of sediment properties can be monitored with MS. The methanogenic microbial community at the Bemidji site consisted mainly of the syntrophic, hydrocarbon-degrading Smithella and the hydrogenotrophic, methane-generating Methanoregula. There is growing evidence in the literature that not only Bacteria, but also some methanogenic Archaea are able to reduce iron. In fact, a recent study reported that the methanogen Methanosarcina thermophila produced magnetite during the reduction of ferrihydrite in a laboratory experiment when hydrogen was present. Therefore, our finding of high MS values and the presence of magnetite in the methanogenic zone of an aged, subsurface petroleum spill could very well be the first field evidence for magnetite formation during methanogenic hydrocarbon degradation.

  8. Hematite Versus Magnetite as the Signature for Planetary Magnetic Anomalies?

    NASA Technical Reports Server (NTRS)

    Kletetshka, Gunther; Taylor, Patrick T.; Wasilewski, Peter J.

    1999-01-01

    Crustal magnetic anomalies are the result of adjacent geologic units having contrasting magnetization. This magnetization arises from induction and/or remanence. In a planetary context we now know that Mars has significant crustal magnetic anomalies due to remanent magnetization, while the Earth has some anomalies where remanence can be shown to be important. This picture, however, is less clear because of the nature and the magnitude of the geomagnetic field which is responsible for superimposed induced magnetization. Induced magnetization assumes a magnetite source, because of its much greater magnetic susceptibility when compared with other magnetic minerals. We investigated the TRM (thermoremanent magnetization) acquisition of hematite, in weak magnetic fields up to 1 mT, to determine if the remanent and induced magnetization of hematite could compete with magnetite. TRM acquisition curves of magnetite and hematite show that multi-domain hematite reaches TRM saturation (0.3 - 0.4 A sq m/kg) in fields as low as 100 microT. However, multi-domain magnetite reaches only a few percent of its TRM saturation in a field of 100 microT (0.02 - 0.06 A sq m/kg). These results suggest that a mineral such as hematite and, perhaps, other minerals with significant remanence and minor induced magnetization may play an important role in providing requisite magnetization contrast. Perhaps, and especially for the Mars case, we should reevaluate where hematite and other minerals, with efficient remanence acquisition, exist in significant concentration, allowing a more comprehensive explanation of Martian anomalies and better insight into the role of remanent magnetization in terrestrial crustal magnetic anomalies.

  9. Detection of magnetite particles in coal by ferromagnetic resonance

    SciTech Connect

    Malhotra, V.M.; Graham, W.R.M.

    1985-02-15

    The techniques of ferromagnetic (FMR) and electron paramagnetic resonance have been applied in studies of Pittsburgh No. 8 bituminous coal. The specimen has been found to be magnetically very heterogeneous, with paramagnetic Mn/sup 2 +/ and Fe/sup 3 +/, free radicals, and at least one ferromagnetic specie which is identified and characterized in the present paper. The temperature dependence of the spectral line shapes indicates the occurrence of a phase transition at 123 K for a finely ground powder sample and at 121 K for a hand-picked fragment; these temperatures are characteristic of the Verwey transition in magnetite, and confirm its presence in both samples. Linewidth data provide an upper limit of 0.07 ..mu..m on the particle size in the powdered sample. The chemical composition of the magnetite in the powdered sample is estimated, on the basis of the observed transition temperature, to be between Fe/sub 2.988/O/sub 4/ and Fe/sub 2.997/O/sub 4/. Spectra of the residue and the glass extract obtained after treatment of the powdered sample with HCl confirm the identification of magnetite, and indicate that it is not embedded in the organic matter in the coal, but should be easily removed either by acid treatment or magnetic separation. The results suggest the potential usefulness in the identification and physical and chemical characterization of ferro- and ferrimagnetic minerals in coals.

  10. Lanthanide sorbent based on magnetite nanoparticles functionalized with organophosphorus extractants

    PubMed Central

    Basualto, Carlos; Gaete, José; Molina, Lorena; Valenzuela, Fernando; Yañez, Claudia; Marco, Jose F

    2015-01-01

    In this work, an adsorbent was prepared based on the attachment of organophosphorus acid extractants, namely, D2EHPA, CYANEX 272, and CYANEX 301, to the surface of superparamagnetic magnetite (Fe3O4) nanoparticles. The synthesized nanoparticles were coated with oleic acid, first by a chemisorption mechanism and later by the respective extractant via physical adsorption. The obtained core–shell functionalized magnetite nanoparticle composites were characterized by dynamic light scattering, scanning electron microscopy, transmission electron microscopy, thermogravimetry, infrared absorption and vibrating sample magnetometry. All the prepared nanoparticles exhibited a high saturation magnetization capacity that varied between 72 and 46 emu g−1 and decreased as the magnetite nanoparticle was coated with oleic acid and functionalized. The scope of this study also included adsorption tests for lanthanum, cerium, praseodymium, and neodymium and the corresponding analysis of their results. Sorption tests indicated that the functionalized nanoparticles were able to extract the four studied lanthanide metal ions, although the best extraction performance was observed when the sorbent was functionalized with CYANEX 272, which resulted in a loading capacity of approximately 12–14 mgLa/gMNP. The magnetization of the synthesized nanoparticles was verified during the separation of the lanthanide-loaded sorbent from the raffinate by using a conventional magnet. PMID:27877811

  11. Characterization of Magnetite Scale Formed in Naphthenic Acid Corrosion

    NASA Astrophysics Data System (ADS)

    Jin, Peng; Robbins, Winston; Bota, Gheorghe; Nesic, Srdjan

    2017-02-01

    Naphthenic acid corrosion (NAC) is one of the major concerns for corrosion engineers in refineries. Traditionally, the iron sulfide (FeS) scale, formed when sulfur compounds in crudes corrode the metal, is expected to be protective and limit the NAC. Nevertheless, no relationship has been found between protectiveness and the characteristics of FeS scale. In this study, lab scale tests with model sulfur compounds and naphthenic acids replicated corrosive processes of refineries with real crude fractions behavior. The morphology and chemical composition of scales were analyzed with scanning electron microscopy and transmission electron microscopy. These high-resolution microscopy techniques revealed the presence of an iron oxide (Fe3O4 or magnetite) scale and discrete particulates on metal surfaces under FeS scales, especially on a low chrome steel. The presence of the iron oxide was correlated with the naphthenic acid activity during the experiments. It is postulated that the formation of the magnetite scale resulted from the decomposition of iron naphthenates at high temperatures. It is further postulated that a nano-particulate form of magnetite may be providing corrosion resistance.

  12. Stable ferrofluids of magnetite nanoparticles in hydrophobic ionic liquids.

    PubMed

    Mestrom, Luuk; Lenders, Jos J M; de Groot, Rick; Hooghoudt, Tonnis; Sommerdijk, Nico A J M; Artigas, Marcel Vilaplana

    2015-07-17

    Ferrofluids (FFs) of metal oxide nanoparticles in ionic liquids (ILs) are a potentially useful class of magnetic materials for many applications because of their properties related to temperature/pressure stability, hydrophobicity, viscosity and recyclability. In this work, the screening of several designer surfactants for their stabilizing capabilities has resulted in the synthesis of stable FFs of superparamagnetic 7 ± 2 nm magnetite (Fe3O4) nanoparticles in the hydrophobic IL 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(R)MIM][NTf2]). The designed and synthesized 1-butyl-3-(10-carboxydecyl)-1H-imidazol-3-ium bromide (ILC10-COOH) surfactant that combines the same imidazole moiety as the IL with a long alkyl chain ensured compatibility with the IL and increased the steric repulsion between the magnetite nanoparticles sufficiently such that stable dispersions of up to 50 wt% magnetite were obtained according to stability tests in the presence of a magnetic field (0.5-1 Tesla). Cryo-transmission electron microscopy (cryo-TEM) of the IL-based FFs allowed direct visualization of the surfactant-stabilized nanoparticles in the ILs and the native, hardly aggregated state of their dispersion.

  13. Biogenic Magnetite in Humans and New Magnetic Resonance Hazard Questions

    NASA Astrophysics Data System (ADS)

    Strbak, O.; Kopcansky, P.; Frollo, I.

    2011-01-01

    The widespread use of magnetic resonance (MR) techniques in clinical practice, and recent discovery of biogenic ferrimagnetic substances in human tissue, open new questions regarding health hazards and MR. Current studies are restricted just to the induction of Faraday currents and consequent thermal effects, or ‘inoffensive’ interaction with static magnetic field. We outlined that magnetic energies associated with interaction of ferrimagnetic particles and MR magnetic fields can be dangerous for sensitive tissues like the human brain is. To simulate the interaction mechanism we use our. ‘Cube’ model approach, which allows more realistic calculation of the particle's magnetic moments. Biogenic magnetite nanoparticles face during MR examination three principal fields: (i) main B0 field, (ii) gradient field, and (iii) B1 field. Interaction energy of biogenic magnetite nanoparticle with static magnetic field B0 exceeds the covalent bond energy 5 times for particles from 4 nm up to 150 nm. Translation energy in gradient field exceeds biochemical bond energy for particles bigger than 50 nm. Biochemical bond disruption and particle release to the tissue environment, in the presence of all MR fields, are the most critical points of this interaction. And together with relaxation processes after application of RF pulses, they make biogenic magnetite nanoparticles a potential MR health hazard issue.

  14. Stable ferrofluids of magnetite nanoparticles in hydrophobic ionic liquids

    NASA Astrophysics Data System (ADS)

    Mestrom, Luuk; Lenders, Jos J. M.; de Groot, Rick; Hooghoudt, Tonnis; Sommerdijk, Nico A. J. M.; Vilaplana Artigas, Marcel

    2015-07-01

    Ferrofluids (FFs) of metal oxide nanoparticles in ionic liquids (ILs) are a potentially useful class of magnetic materials for many applications because of their properties related to temperature/pressure stability, hydrophobicity, viscosity and recyclability. In this work, the screening of several designer surfactants for their stabilizing capabilities has resulted in the synthesis of stable FFs of superparamagnetic 7 ± 2 nm magnetite (Fe3O4) nanoparticles in the hydrophobic IL 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([CRMIM][NTf2]). The designed and synthesized 1-butyl-3-(10-carboxydecyl)-1H-imidazol-3-ium bromide (ILC10-COOH) surfactant that combines the same imidazole moiety as the IL with a long alkyl chain ensured compatibility with the IL and increased the steric repulsion between the magnetite nanoparticles sufficiently such that stable dispersions of up to 50 wt% magnetite were obtained according to stability tests in the presence of a magnetic field (0.5-1 Tesla). Cryo-transmission electron microscopy (cryo-TEM) of the IL-based FFs allowed direct visualization of the surfactant-stabilized nanoparticles in the ILs and the native, hardly aggregated state of their dispersion.

  15. Characterization of Magnetite Scale Formed in Naphthenic Acid Corrosion

    NASA Astrophysics Data System (ADS)

    Jin, Peng; Robbins, Winston; Bota, Gheorghe; Nesic, Srdjan

    2016-10-01

    Naphthenic acid corrosion (NAC) is one of the major concerns for corrosion engineers in refineries. Traditionally, the iron sulfide (FeS) scale, formed when sulfur compounds in crudes corrode the metal, is expected to be protective and limit the NAC. Nevertheless, no relationship has been found between protectiveness and the characteristics of FeS scale. In this study, lab scale tests with model sulfur compounds and naphthenic acids replicated corrosive processes of refineries with real crude fractions behavior. The morphology and chemical composition of scales were analyzed with scanning electron microscopy and transmission electron microscopy. These high-resolution microscopy techniques revealed the presence of an iron oxide (Fe3O4 or magnetite) scale and discrete particulates on metal surfaces under FeS scales, especially on a low chrome steel. The presence of the iron oxide was correlated with the naphthenic acid activity during the experiments. It is postulated that the formation of the magnetite scale resulted from the decomposition of iron naphthenates at high temperatures. It is further postulated that a nano-particulate form of magnetite may be providing corrosion resistance.

  16. Large pure intracranial vagal schwannoma.

    PubMed

    Gazzeri, Roberto; Galarza, Marcelo; Costanzo, De Bonis; Carotenuto, Vincenzo; D'Angelo, Vincenzo

    2009-04-01

    We report a patient with a large, pure intracranial vagal schwannoma, compressing the medulla who presented with essential hypertension. Based on this and on previous cases, we suggest that a differentiation of pure intracranial schwannomas (subtype A1) from intracranial schwannomas with some extension in the jugular foramen (type A) should be used.

  17. Bench-Scale Testing of the Micronized Magnetite Process

    SciTech Connect

    Edward R. Torak; Peter J. Suardini

    1997-11-01

    A recent emphasis of the Department of Energy's (DOE's), Coal Preparation Program has been the development of high-efficiency technologies that offer near-term, low-cost improvements in the ability of coal preparation plants to address problems associated with coal fines. In 1992, three cost-shared contracts were awarded to industry, under the first High-Efficiency Preparation (HEP I) solicitation. All three projects involved bench-scale testing of various emerging technologies, at the Federal Energy Technology Center*s (FETC*s), Process Research Facility (PRF). The first HEP I project, completed in mid-1993, was conducted by Process Technology, Inc., with the objective of developing a computerized, on-line system for monitoring and controlling the operation of a column flotation circuit. The second HEP I project, completed in mid-1994, was conducted by a team led by Virginia Polytechnic Institute to test the Mozely Multi-Gravity Separator in combination with the Microcel Flotation Column, for improved removal of mineral matter and pyritic sulfur from fine coal. The last HEP I project, of which the findings are contained in this report, was conducted by Custom Coals Corporation to evaluate and advance a micronized-magnetite-based, fine-coal cycloning technology. The micronized-magnetite coal cleaning technology, also know as the Micro-Mag process, is based on widely used conventional dense-medium cyclone applications, in that it utilizes a finely ground magnetite/water suspension as a separating medium for cleaning fine coal, by density, in a cyclone. However, the micronized-magnetite cleaning technology differs from conventional systems in several ways: ! It utilizes significantly finer magnetite (about 5 to 10 micron mean particle size), as compared to normal mean particle sizes of 20 microns. ! It can effectively beneficiate coal particles down to 500M in size, as compared to the most advanced, existing conventional systems that are limited to a particle bottom

  18. Magnetite-Binding Flagellar Filaments Displaying the MamI Loop Motif.

    PubMed

    Bereczk-Tompa, Éva; Pósfai, Mihály; Tóth, Balázs; Vonderviszt, Ferenc

    2016-11-03

    This work aimed at developing a novel method for fabricating 1 D magnetite nanostructures with the help of mutated flagellar filaments. We constructed four different flagellin mutants displaying magnetite-binding motifs: two contained fragments of magnetosome-associated proteins from magnetotactic bacteria (MamI and Mms6), and synthetic sequences were used for the other two. A magnetic selection method identified the MamI mutant as having the highest binding affinity to magnetite. Filaments built from MamI loop-containing flagellin subunits were used as templates to form chains of magnetite nanoparticles along the filament by capturing them from suspension. Our study represents a proof-of-concept that flagellar filaments can be engineered to facilitate formation of 1 D magnetite nanostructures under ambient conditions. In addition, it proves the interaction between MamI and magnetite, with implications for the role of this protein in magnetotactic bacteria.

  19. Fourier transform infrared and Raman spectroscopy studies on magnetite/Ag/antibiotic nanocomposites

    NASA Astrophysics Data System (ADS)

    Ivashchenko, Olena; Jurga-Stopa, Justyna; Coy, Emerson; Peplinska, Barbara; Pietralik, Zuzanna; Jurga, Stefan

    2016-02-01

    This article presents a study on the detection of antibiotics in magnetite/Ag/antibiotic nanocomposites using Fourier transform infrared (FTIR) and Raman spectroscopy. Antibiotics with different spectra of antimicrobial activities, including rifampicin, doxycycline, cefotaxime, and ceftriaxone, were studied. Mechanical mixtures of antibiotics and magnetite/Ag nanocomposites, as well as antibiotics and magnetite nanopowder, were investigated in order to identify the origin of FTIR bands. FTIR spectroscopy was found to be an appropriate technique for this task. The spectra of the magnetite/Ag/antibiotic nanocomposites exhibited very weak (for doxycycline, cefotaxime, and ceftriaxone) or even no (for rifampicin) antibiotic bands. This FTIR "invisibility" of antibiotics is ascribed to their adsorbed state. FTIR and Raman measurements show altered Csbnd O, Cdbnd O, and Csbnd S bonds, indicating adsorption of the antibiotic molecules on the magnetite/Ag nanocomposite structure. In addition, a potential mechanism through which antibiotic molecules interact with magnetite/Ag nanoparticle surfaces is proposed.

  20. Defense Mechanisms in "Pure" Anxiety and "Pure" Depressive Disorders.

    PubMed

    Colovic, Olga; Lecic Tosevski, Dusica; Perunicic Mladenovic, Ivana; Milosavljevic, Maja; Munjiza, Ana

    2016-10-01

    Our study was intended to test whether there are any differences in the way defense mechanisms are used by patients suffering from pure anxiety and those with pure depressive disorders. The sample size was as follows: depressive disorders without psychotic symptoms 30, anxiety disorders 30, and the healthy control group 30. The assessment of defense mechanisms was made using the DSQ-40 questionnaire. Our findings show that "pure" anxiety disorders differ from "pure" depressive disorders only in the use of immature defense mechanisms. The group with depressive disorders was significantly more prone to use immature defense mechanisms than the group with anxiety disorders (p = 0.005), primarily projection (p = 0.001) and devaluation (p = 0.003). These defense mechanisms may therefore be used both to differentiate between anxiety and depressive disorders and also to determine which symptoms (anxiety or depressive disorders) are dominant at any given stage of treatment.

  1. Experimental Shock Decomposition of Siderite and the Origin of Magnetite in Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Bell, Mary Sue

    2007-01-01

    Shock recovery experiments to determine whether magnetite could be produced by the decomposition of iron-carbonate were initiated. Naturally occurring siderite was first characterized by electron microprobe (EMP), transmission electron microscopy (TEM), Mossbauer spectroscopy, and magnetic susceptibility measurements to be sure that the starting material did not contain detectable magnetite. Samples were shocked in tungsten-alloy holders (W=90%, Ni=6%, Cu=4%) to further insure that any iron phases in the shock products were contributed by the siderite rather than the sample holder. Each sample was shocked to a specific pressure between 30 to 49 GPa. Previously reported results of TEM analyses on 49 GPa experiments indicated the presence of nano-phase spinel-structured iron oxide. Transformation of siderite to magnetite as characterized by TEM was found in the 49 GPa shock experiment. Compositions of most magnetites are greater than 50% Fe sup(+2) in the octahedral site of the inverse spinel structure. Magnetites produced in shock experiments display the same range of single-domain, superparamagnetic sizes (approx. 50 100 nm), compositions (100% magnetite to 80% magnetite-20% magnesioferrite), and morphologies (equant, elongated, euhedral to subhedral) as magnetites synthesized by Golden et al. (2001) or magnetites grown naturally by MV1 magnetotactic bacteria, and as the magnetites in Martian meteorite ALH84001. Fritz et al. (2005) previously concluded that ALH84001 experienced approx. 32 GPa pressure and a resultant thermal pulse of approx. 100 - 110 C. However, ALH84001 contains evidence of local temperature excursions high enough to 1 melt feldspar, pyroxene, and a silica-rich phase. This 49 GPa experiment demonstrates that magnetite can be produced by the shock decomposition of siderite as a result of local heating to greater than 470 C. Therefore, magnetite in the rims of carbonates in Martian meteorite ALH84001 could be a product of shock devolatilization of

  2. Reaction of U(VI) with titanium-substituted magnetite: influence of Ti on U(IV) speciation.

    PubMed

    Latta, Drew E; Pearce, Carolyn I; Rosso, Kevin M; Kemner, Kenneth M; Boyanov, Maxim I

    2013-05-07

    Reduction of hexavalent uranium (U(VI)) to less soluble tetravalent uranium (U(IV)) through enzymatic or abiotic redox reactions has the potential to alter U mobility in subsurface environments. As a ubiquitous natural mineral, magnetite (Fe3O4) is of interest because of its ability to act as a rechargeable reductant for U(VI). Natural magnetites are often impure with titanium, and structural Fe(3+) replacement by Ti(IV) yields a proportional increase in the relative Fe(2+) content in the metal sublattice to maintain bulk charge neutrality. In the absence of oxidation, the Ti content sets the initial bulk Fe(2+)/Fe(3+) ratio (R). Here, we demonstrate that Ti-doped magnetites (Fe3 - xTixO4) reduce U(VI) to U(IV). The U(VI)-Fe(2+) redox reactivity was found to be controlled directly by R but was otherwise independent of Ti content (xTi). However, in contrast to previous studies with pure magnetite where U(VI) was reduced to nanocrystalline uraninite (UO2), the presence of structural Ti (xTi = 0.25-0.53) results in the formation of U(IV) species that lack the bidentate U-O2-U bridges of uraninite. Extended X-ray absorption fine structure spectroscopic analysis indicated that the titanomagnetite-bound U(IV) phase has a novel U(IV)-Ti binding geometry different from the coordination of U(IV) in the mineral brannerite (U(IV)Ti2O6). The observed U(IV)-Ti coordination at a distance of 3.43 Å suggests a binuclear corner-sharing adsorption/incorporation U(IV) complex with the solid phase. Furthermore, we explored the effect of oxidation (decreasing R) and solids-to-solution ratio on the reduced U(IV) phase. The formation of the non-uraninite U(IV)-Ti phase appears to be controlled by availability of surface Ti sites rather than R. Our work highlights a previously unrecognized role of Ti in the environmental chemistry of U(IV) and suggests that further work to characterize the long-term stability of U(IV) phases formed in the presence of Ti is warranted.

  3. Reaction of U-VI with titanium-substituted magnetite: Influence of Ti on U-IV speciation

    SciTech Connect

    Latta, Drew; Pearce, Carolyn I.; Rosso, Kevin M.; Kemner, Kenneth M.; Boyanov, Maxim I.

    2013-07-01

    Reduction of hexavalent uranium (UVI) to less soluble tetravalent uranium (UIV) through enzymatic or abiotic redox reactions has the potential to alter U mobility in subsurface environments. As a ubiquitous natural mineral, magnetite (Fe3O4) is of interest because of its ability to act as a rechargeable reductant for UVI. Natural magnetites are often impure with titanium, and structural Fe3+ replacement by TiIV yields a proportional increase in the relative Fe2+ content in the metal sublattice to maintain bulk charge neutrality. In the absence of oxidation, the Ti content sets the initial bulk Fe2+/Fe3+ ratio (R). Here, we demonstrate that Ti-doped magnetites (Fe3 xTixO4) reduce UVI to UIV. The UVI-Fe2+ redox reactivity was found to be controlled directly by R, but was otherwise independent of Ti content (xTi). However, in contrast to previous studies with pure magnetite where UVI was reduced to nanocrystalline uraninite (UO2), the presence of structural Ti (xTi = 0.25 0.53) results in the formation of UIV species that lack the bidentate U-O2-U bridges of uraninite. Extended x-ray absorption fine structure spectroscopic analysis indicated that the titanomagnetite-bound UIV phase has a novel UIV-Ti binding geometry, different from the coordination of UIV in the mineral brannerite (UIVTi2O6). The observed UIV-Ti coordination at a distance of 3.43 Å suggests a binuclear corner-sharing adsorption/incorporation UIV complex with the solid phase. Furthermore, we explored the effect of oxidation (decreasing R) and solids-to-solution ratio on the reduced UIV phase. The formation of the non-uraninite UIV-Ti phase appears to be controlled by availability of surface Ti sites, rather than R. Our work highlights a previously unrecognized role of Ti in the environmental chemistry of UIV and suggests that further work to characterize the long-term stability of UIV phases formed in the presence of Ti is warranted.

  4. Soft X-ray Spectroscopy Study of the Electronic Structure of Oxidized and Partially Oxidized Magnetite Nanoparticles

    SciTech Connect

    Gilbert, Benjamin; Katz, Jordan E.; Denlinger, Jonathan D.; Yin, Yadong; Falcone, Roger; Waychunas, Glenn A.

    2010-10-24

    The crystal structure of magnetite nanoparticles may be transformed to maghemite by complete oxidation, but under many relevant conditions the oxidation is partial, creating a mixed-valence material with structural and electronic properties that are poorly characterized. We used X-ray diffraction, Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, and soft X-ray absorption and emission spectroscopy to characterize the products of oxidizing uncoated and oleic acid-coated magnetite nanoparticles in air. The oxidization of uncoated magnetite nanoparticles creates a material that is structurally and electronically indistinguishable from maghemite. By contrast, while oxidized oleic acid-coated nanoparticles are also structurally indistinguishable from maghemite, Fe L-edge spectroscopy revealed the presence of interior reduced iron sites even after a 2-year period. We used X-ray emission spectroscopy at the O K-edge to study the valence bands (VB) of the iron oxide nanoparticles, using resonant excitation to remove the contributions from oxygen atoms in the ligands and from low-energy excitations that obscured the VB edge. The bonding in all nanoparticles was typical of maghemite, with no detectable VB states introduced by the long-lived, reduced-iron sites in the oleic acid-coated sample. However, O K-edge absorption spectroscopy observed a 0.2 eV shift in the position of the lowest unoccupied states in the coated sample, indicating an increase in the semiconductor band gap relative to bulk stoichiometric maghemite that was also observed by optical absorption spectroscopy. The results show that the ferrous iron sites within ferric iron oxide nanoparticles coated by an organic ligand can persist under ambient conditions with no evidence of a distinct interior phase and can exert an effect on the global electronic and optical properties of the material. This phenomenon resembles the band gap enlargement caused by electron accumulation in the

  5. Modeling Magnetite Reflectance Spectra Using Hapke Theory and Existing Optical Constants

    NASA Technical Reports Server (NTRS)

    Roush, T. L.; Blewett, D. T.; Cahill, J. T. S.

    2016-01-01

    Magnetite is an accessory mineral found in terrestrial environments, some meteorites, and the lunar surface. The reflectance of magnetite powers is relatively low [1], and this property makes it an analog for other dark Fe- or Ti-bearing components, particularly ilmenite on the lunar surface. The real and imaginary indices of refraction (optical constants) for magnetite are available in the literature [2-3], and online [4]. Here we use these values to calculate the reflectance of particulates and compare these model spectra to reflectance measurements of magnetite available on-line [5].

  6. Rotating Flow of Magnetite-Water Nanofluid over a Stretching Surface Inspired by Non-Linear Thermal Radiation

    PubMed Central

    Mustafa, M.; Mushtaq, A.; Hayat, T.; Alsaedi, A.

    2016-01-01

    Present study explores the MHD three-dimensional rotating flow and heat transfer of ferrofluid induced by a radiative surface. The base fluid is considered as water with magnetite-Fe3O4 nanoparticles. Novel concept of non-linear radiative heat flux is considered which produces a non-linear energy equation in temperature field. Conventional transformations are employed to obtain the self-similar form of the governing differential system. The arising system involves an interesting temperature ratio parameter which is an indicator of small/large temperature differences in the flow. Numerical simulations with high precision are determined by well-known shooting approach. Both uniform stretching and rotation have significant impact on the solutions. The variation in velocity components with the nanoparticle volume fraction is non-monotonic. Local Nusselt number in Fe3O4–water ferrofluid is larger in comparison to the pure fluid even at low particle concentration. PMID:26894690

  7. Rotating Flow of Magnetite-Water Nanofluid over a Stretching Surface Inspired by Non-Linear Thermal Radiation.

    PubMed

    Mustafa, M; Mushtaq, A; Hayat, T; Alsaedi, A

    2016-01-01

    Present study explores the MHD three-dimensional rotating flow and heat transfer of ferrofluid induced by a radiative surface. The base fluid is considered as water with magnetite-Fe3O4 nanoparticles. Novel concept of non-linear radiative heat flux is considered which produces a non-linear energy equation in temperature field. Conventional transformations are employed to obtain the self-similar form of the governing differential system. The arising system involves an interesting temperature ratio parameter which is an indicator of small/large temperature differences in the flow. Numerical simulations with high precision are determined by well-known shooting approach. Both uniform stretching and rotation have significant impact on the solutions. The variation in velocity components with the nanoparticle volume fraction is non-monotonic. Local Nusselt number in Fe3O4-water ferrofluid is larger in comparison to the pure fluid even at low particle concentration.

  8. Pure autonomic failure without synucleinopathy.

    PubMed

    Isonaka, Risa; Holmes, Courtney; Cook, Glen A; Sullivan, Patti; Sharabi, Yehonatan; Goldstein, David S

    2017-04-01

    Pure autonomic failure is a rare form of chronic autonomic failure manifesting with neurogenic orthostatic hypotension and evidence of sympathetic noradrenergic denervation unaccompanied by signs of central neurodegeneration. It has been proposed that pure autonomic failure is a Lewy body disease characterized by intra-neuronal deposition of the protein alpha-synuclein in Lewy bodies and neurites. A middle-aged man with previously diagnosed pure autonomic failure experienced a sudden, fatal cardiac arrest. He was autopsied, and tissues were harvested for neurochemical and immunofluorescence studies. Post-mortem microscopic neuropathology showed no Lewy bodies, Lewy neurites, or alpha-synuclein deposition by immunohistochemistry anywhere in the brain. The patient had markedly decreased immunofluorescent tyrosine hydroxylase in sympathetic ganglion tissue without detectable alpha-synuclein even in rare residual nests of tyrosine hydroxylase-containing ganglionic fibers. In pure autonomic failure, sympathetic noradrenergic denervation can occur without concurrent Lewy bodies or alpha-synuclein deposition in the brain or sympathetic ganglion tissue.

  9. Highly active Pd-on-magnetite nanocatalysts for aqueous phase hydrodechlorination reactions.

    PubMed

    Hildebrand, Heike; Mackenzie, Katrin; Kopinke, Frank-Dieter

    2009-05-01

    Nanoscale catalyst particles are already in focus as excellent tools in catalytic processes and intensive research is currently optimizing their performance. As known from nanosized metal particles, nanocatalysts have the potential of very high reaction rates due to their high specific surface areas and low mass transfer restrictions. In this study, we generated extremely active palladium catalysts on the basis of colloidal magnetic carriers. The most active catalyst contains only traces of Pd (0.15 wt %) on nanomagnetite as carrier. Pd-on-magnetite was successfully tested in batch experiments for the hydrodechlorination (HDC) of the chlorohydrocarbons trichloroethene (TCE) and chlorobenzene. For the HDC of TCE, second-order rate coefficients of approximately 1.6 x 10(4) L g(-1) min(-1) were measured. Such high activities have never been described before for Pd-containing catalysts in aqueous phase HDC reactions. The ferrimagnetism of the carrier enables a separation of the nanocatalyst from the treated water by means of magnetic separation. This allows the catalyst to be reused several times, which is an important advantage compared to other nanoscale catalytic systems such as pure Pd or Pd-on-Au colloids.

  10. Sticking polydisperse hydrophobic magnetite nanoparticles to lipid membranes.

    PubMed

    Paulus, Michael; Degen, Patrick; Brenner, Thorsten; Tiemeyer, Sebastian; Struth, Bernd; Tolan, Metin; Rehage, Heinz

    2010-10-19

    The formation of a layer of hydrophobic magnetite (Fe(3)O(4)) nanoparticles stabilized by lauric acid is analyzed by in situ X-ray reflectivity measurements. The data analysis shows that the nanoparticles partially disperse their hydrophobic coating. Consequently, a Langmuir layer was formed by lauric acid molecules that can be compressed into an untilted condensed phase. A majority of the nanoparticles are attached to the Langmuir film integrating lauric acid residue on their surface into the Langmuir film. Hence, the particles at the liquid-gas interface can be identified as so-called Janus beads, which are amphiphilic solids having two sides with different functionality.

  11. Superexchange coupling on oleylsarcosine-coated magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Bakuzis, A. F.; Pereira, A. R.; Santos, J. G.; Morais, P. C.

    2006-04-01

    Room temperature ferromagnetic resonance was used to investigate particle-particle interaction in magnetic fluid samples containing magnetite nanoparticles surface coated with dimercaptosuccinic acid (DMSA) or oleylsarcosine (OLEL). The DMSA sample showed a decrease of the magnetic resonance field (MRF) increasing the nanoparticle concentration (phi), whereas the OLEL sample showed the opposite behavior. The DMSA MRF concentration dependence was explained using a dipolar interaction model beyond the point dipole approximation. In addition, the magnetic resonance spectra of the OLEL sample showed an optical mode suggesting an antiferromagnetic superexchange coupling between magnetic nanoparticles forming dimers.

  12. Magnetite nanoparticles functionalized with α-tocopheryl succinate (α-TOS) promote selective cervical cancer cell death

    NASA Astrophysics Data System (ADS)

    Angulo-Molina, Aracely; Méndez-Rojas, Miguel Ángel; Palacios-Hernández, Teresa; Contreras-López, Oscar Edel; Hirata-Flores, Gustavo Alonso; Flores-Alonso, Juan Carlos; Merino-Contreras, Saul; Valenzuela, Olivia; Hernández, Jesús; Reyes-Leyva, Julio

    2014-08-01

    The vitamin E analog α-tocopheryl succinate (α-TOS) selectively induces apoptosis in several cancer cells, but it is sensitive to esterases present in cervical cancer cells. Magnetite nanoparticles (Nps) were prepared by a reduction-coprecipitation method; their surface was silanized and conjugated to α-TOS to enhance its resistance. Morphology, size, and crystal structure were analyzed by scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. Chemical composition was analyzed by energy-dispersive X-ray spectroscopy; functional groups were determined by Fourier transform infrared spectroscopy; and α-TOS content was estimated by thermogravimetric analysis. The cytotoxic activity of α-TOS-Nps was evaluated in non-malignant fibroblasts and cervical cancer cells by means of the colorimetric MTT viability test. Intracellular localization was identified by confocal laser scanning microscopy. Characterization of α-TOS-Nps revealed sphere-like Nps with 15 nm average size, formed by mineral and organic constituents with high stability. α-TOS-Nps were internalized in the nucleus and selectively affected the viability of cervical cancer cells in a dose- and time-dependent manner but were biocompatible with non-malignant fibroblasts. In conclusion, functionalization of magnetite Nps protected the cytotoxic activity of α-TOS in non-sensitive cervical cancer cells.

  13. Rock-magnetic properties of single zircon crystals sampled from the Tanzawa tonalitic pluton, central Japan

    NASA Astrophysics Data System (ADS)

    Sato, M.; Yamamoto, S.; Yamamoto, Y.; Ohno, M.; Tsunakawa, H.; Maruyama, S.

    2015-12-01

    This paper reports on the rock-magnetic properties of single zircon crystals, which are essential for future work establishing the paleointensity method using single zircon crystals. Zircon crystals used in this study were sampled from the Nakagawa River, which crosses the Tanzawa tonalitic pluton in central Japan. Rock-magnetic measurements were conducted on 1037 grains of zircons, but many of these measurements are below the limits of the sensitivity of the magnetometers employed. Isothermal remanent magnetizations (IRMs) of 876 zircon crystal are below the practical resolution of this study; we infer that these crystal contain no or only minute quantities of ferromagnetic minerals. The other zircon crystals contain enough magnetic minerals to be measured in the DC SQUID magnetometer. For 81 zircon crystals, IRM intensity (MIRM) are larger than 4 × 10-12 Am2, while natural remanent magnetization (NRM) intensity (MNRM) are below 4 × 10-12 Am2, indicating that these crystals are inappropriate for the paleomagnetic study. For the samples that had values of MNRM ≥ 4 × 10-12 Am2 and MIRM ≥ 4 × 10-12 Am2, combining the rock-magnetic parameter, we proposed the sample selection criteria for future study of paleointensity experiments using single zircon crystals. In the case that the samples had high Bc values (>10 mT) or high MNRM/MIRM values (>~0.1), main remanence carriers are probably pyrrhotite and these samples are inappropriate for the paleointensity study. In the case that the samples had low Bc values (<10 mT) and low MNRM/MIRM values (<~0.1), main remanence carrier seem to be nearly pure magnetite with PSD grain sizes and these samples are expected to appropriate for the paleointensity study. Total thermoremanent magnetization (TRM) acquisition experiments were also carried out for 12 samples of the zircon crystals satisfying the above criteria. The TRM intensity was comparable with that of NRM, and a rough estimation of the paleointensity using NRM

  14. Ferrous Iron Binding Key to Mms6 Magnetite Biomineralisation: A Mechanistic Study to Understand Magnetite Formation Using pH Titration and NMR Spectroscopy.

    PubMed

    Rawlings, Andrea E; Bramble, Jonathan P; Hounslow, Andrea M; Williamson, Michael P; Monnington, Amy E; Cooke, David J; Staniland, Sarah S

    2016-06-01

    Formation of magnetite nanocrystals by magnetotactic bacteria is controlled by specific proteins which regulate the particles' nucleation and growth. One such protein is Mms6. This small, amphiphilic protein can self-assemble and bind ferric ions to aid in magnetite formation. To understand the role of Mms6 during in vitro iron oxide precipitation we have performed in situ pH titrations. We find Mms6 has little effect during ferric salt precipitation, but exerts greatest influence during the incorporation of ferrous ions and conversion of this salt to mixed-valence iron minerals, suggesting Mms6 has a hitherto unrecorded ferrous iron interacting property which promotes the formation of magnetite in ferrous-rich solutions. We show ferrous binding to the DEEVE motif within the C-terminal region of Mms6 by NMR spectroscopy, and model these binding events using molecular simulations. We conclude that Mms6 functions as a magnetite nucleating protein under conditions where ferrous ions predominate.

  15. Formation of a Network Structure in the Gaseous Reduction of Magnetite Doped with Alumina

    NASA Astrophysics Data System (ADS)

    Kapelyushin, Yury; Sasaki, Yasushi; Zhang, Jianqiang; Jeong, Sunkwang; Ostrovski, Oleg

    2017-04-01

    Reduction of un-doped magnetite is developed topochemically with the formation of a dense iron shell. However, the reduction of alumina-doped magnetite to wüstite proceeds with the formation of a network-like structure which consists of criss-crossed horizontal and vertical plates of wüstite. Reduction of magnetite includes the conversion of Fe3+ to Fe2+ and the movement of iron cations from the tetrahedral sites on the {400} and {220} planes of magnetite to the octahedral sites on the {200} planes of wüstite. Alumina has a negligibly small solubility in wüstite. In the reduction of magnetite doped with Al2O3, rejected Al3+ cations from wüstite diffuse to the magnetite-hercynite solid solution. Enrichment of the Fe3O4-FeAl2O4 solution with alumina in the vicinity of the reduction interface restricts the growth of {220} planes of wüstite and nucleation of {220} planes adjusted to the existing planes, preventing the merging of wüstite plates during the reduction process. Reduction of magnetite from the magnetite-hercynite solid solution practically stops when the Al3+ content at the interface approaches the solubility limit. Wüstite in the separated plates is reduced further to iron.

  16. Coating of Sulfonic Silica onto Magnetite from Marina Beach Iron sand, Semarang, Indonesia

    NASA Astrophysics Data System (ADS)

    Azmiyawati, C.; Suyati, L.; Taslimah; Anggraeni, R. D.

    2017-02-01

    The mineral iron oxide is the main component of sand iron that are abundant in nature. Mineral iron oxide not yet widely applied into more useful products. The main component of iron ore is magnetite. Magnetite can be used as a basic ingredient in the manufacture of magnetite-modified silica adsorbent sulfonate. In this research, the adsorbent made from sulfonic functionalized silica-coated magnetic particle has been successfully produced, with the magnetite was obtained from iron sand at Marina Beach, Semarang Indonesia. This adsorbent was then used as a metal ion preconcentration media. From the research that it was found that the sulfonic has been bound to the silica marked by the emergence of element S on EDX. Whilst, the evidence that silica has coated on the magnetite could be seen from the SEM images which showed the morphology of sulfonic functionalized silica-coated magnetic particles were larger than the sulfonic functionalized silica without magnetite. From the DSC results showed that the addition of magnetite on sulfonic functionalized silica did not change the heat resistance of the sulfonic functionalized silica. Based on the XRD patterns show that magnetite sulfonate silica was formed.

  17. Formation of a Network Structure in the Gaseous Reduction of Magnetite Doped with Alumina

    NASA Astrophysics Data System (ADS)

    Kapelyushin, Yury; Sasaki, Yasushi; Zhang, Jianqiang; Jeong, Sunkwang; Ostrovski, Oleg

    2017-01-01

    Reduction of un-doped magnetite is developed topochemically with the formation of a dense iron shell. However, the reduction of alumina-doped magnetite to wüstite proceeds with the formation of a network-like structure which consists of criss-crossed horizontal and vertical plates of wüstite. Reduction of magnetite includes the conversion of Fe3+ to Fe2+ and the movement of iron cations from the tetrahedral sites on the {400} and {220} planes of magnetite to the octahedral sites on the {200} planes of wüstite. Alumina has a negligibly small solubility in wüstite. In the reduction of magnetite doped with Al2O3, rejected Al3+ cations from wüstite diffuse to the magnetite-hercynite solid solution. Enrichment of the Fe3O4-FeAl2O4 solution with alumina in the vicinity of the reduction interface restricts the growth of {220} planes of wüstite and nucleation of {220} planes adjusted to the existing planes, preventing the merging of wüstite plates during the reduction process. Reduction of magnetite from the magnetite-hercynite solid solution practically stops when the Al3+ content at the interface approaches the solubility limit. Wüstite in the separated plates is reduced further to iron.

  18. Trace-element fingerprints of chromite, magnetite and sulfides from the 3.1 Ga ultramafic-mafic rocks of the Nuggihalli greenstone belt, Western Dharwar craton (India)

    NASA Astrophysics Data System (ADS)

    Mukherjee, Ria; Mondal, Sisir K.; González-Jiménez, José M.; Griffin, William L.; Pearson, Norman J.; O'Reilly, Suzanne Y.

    2015-06-01

    andesitic melts, suggesting that magnetite crystallized from an evolved gabbroic melt. Enrichments of Ni, Co, Te, As and Bi in disseminated millerite and niccolite occurring within chromitites, and in disseminated bravoite within magnetites, reflect element mobility during serpentinization. Monosulfide solid solution inclusions within pyroxenes (altered to actinolite) in pyroxenite, and interstitial pyrites and chalcopyrites in magnetite, retain primary characteristics except for Fe-enrichment in chalcopyrite, probably due to sub-solidus re-equilibration with magnetite. Disseminated sulfides are depleted in platinum-group elements (PGE) due to late sulfide saturation and the PGE-depleted nature of the mantle source of the sill-like ultramafic-mafic plutonic rocks in the Nuggihalli greenstone belt.

  19. Oxygen vacancy induced surface stabilization: (110) terminated magnetite

    NASA Astrophysics Data System (ADS)

    Walls, B.; Lübben, O.; Palotás, K.; Fleischer, K.; Walshe, K.; Shvets, I. V.

    2016-10-01

    Scanning tunneling microscopy (STM) measurements of the (110) surface of magnetite showed the coexistence of two reconstructions: the known (1 ×3 ) row reconstruction and a surprising atomic structure of high complexity which occupies a small fraction of the surface. Oxygen vacancies on the Fe3O4 (110) B-terminated surface have previously been determined to be the most energetically favorable surface termination of those considered [Li et al., Surf. Sci. 601, 876 (2007), 10.1016/j.susc.2006.10.037]. However, this study only investigated oxygen vacancies which were threefold coordinated. Here, first principles calculations indicate that twofold coordinated oxygen represents the most energetically stable oxygen vacancy on the B-terminated (110) surface of magnetite. STM simulations reveal that the structure that occupies a small fraction of the surface corresponds to this energetically favorable B-terminated Fe3O4 (110) surface. The oxygen vacancies form an ordered array: Along the [1 ¯10 ] direction, every second twofold coordinated oxygen atom is vacant, and vacancies are separated by 6 Å. In adjacent twofold coordinated oxygen rows, the vacancies are shifted in the [1 ¯10 ] direction by 3 Å. Density functional theory calculations of the spin density distributions indicate that surface and subsurface octahedrally coordinated iron atoms are charge ordered. The charge ordering and existence of oxygen vacancies act to reduce the surface charge. However, other polarity compensation mechanisms may be at play to stabilize the surface.

  20. Moessbauer Characterization of Magnetite/Polyaniline Magnetic Nanocomposite

    SciTech Connect

    Rodriguez, Anselmo F. R.; Faria, Fernando S. E. D. V.; Lopez, Jorge L.; Mesquita, Antonio G. G.; Coaquira, Jose A. H.; Oliveira, Aderbal C.; Morais, Paulo C.; Azevedo, Ricardo B.; Araujo, Ana C. V. de; Alves, Severino Jr.; Azevedo, Walter M. de

    2010-12-02

    Aniline surface coated Fe{sub 3}O{sub 4} nanoparticles have been successfully synthesized by UV irradiation varying the time and the acid media (HCl, HNO{sub 3}, or H{sub 2}SO{sub 4}). The synthesized material represents a promising platform for application in nerve regeneration. XRD patterns are consistent with the crystalline structure of magnetite. Nevertheless, for UV irradiation times longer than 2 h, extra XRD lines reveal the presence of goethite. The mean crystallite size of uncoated particles is estimated to be 25.4 nm, meanwhile that size is reduced to 19.9 nm for the UV irradiated sample in HCl medium for 4 h. Moessbauer spectra of uncoated nanoparticles reveal the occurrence of thermal relaxation at room temperature, while the 77 K-Moessbauer spectrum suggests the occurrence of electron localization effects similar to that expected in bulk magnetite. The Mossbauer spectra of UV irradiated sample in HCl medium during 4 h, confirms the presence of the goethite phase. For this sample, the thermal relaxation is more evident, since the room temperature spectrum shows larger spectral area for the nonmagnetic component due to the smaller crystallite size. Meanwhile, the 77 K-Moessbauer spectrum suggests the absence of the electron localization effect above 77 K.

  1. Magnetic Core-Shell Morphology of Structurally Uniform Magnetite Nanoparticles

    NASA Astrophysics Data System (ADS)

    Krycka, Kathryn

    2011-03-01

    Magnetic nanoscale structures are intriguing, in part, because of the exotic properties that emerge compared with bulk. The reduction of magnetic moment per atom in magnetite with decreasing nanoparticle size, for example, has been hypothesized to originate from surface disordering to anisotropy-induced radial canting, which are difficult to distinguish using conventional magnetometry. Small-angle neutron scattering (SANS) is ideal for probing structure, both chemical and magnetic, from nm to microns across an ensemble of particles. Adding polarization analysis (PASANS) of the neutron spin orientation before and after interaction with the scattering particles allows the magnetic structure to be separated into its vector components. Application of this novel technique to 9 nm magnetite nanoparticles closed-packed into face-centered crystallites with order of a micron revealed that at nominal saturation the missing magnetic moments unexpectedly interacted to form well-ordered shells 1.0 to 1.5 nm thick canted perpendicular to their ferrimagnetic cores between 160 to 320 K. These shells additionally displayed intra-particle ``cross-talk'', selecting a common orientation over clusters of tens of nanoparticles. However, the shells disappeared when the external field was removed and interparticle magnetic interactions were negligible (300 K), confirming their magnetic origin. This work has been carried out in collaboration with Ryan Booth, Julie Borchers, Wangchun Chen, Liv Dedon, Thomas Gentile, Charles Hogg, Yumi Ijiri, Mark Laver, Sara Majetich, James Rhyne, and Shannon Watson.

  2. Synthesis and characterization of magnetite nanoparticles coated with lauric acid

    SciTech Connect

    Mamani, J.B.; Costa-Filho, A.J.; Cornejo, D.R.; Vieira, E.D.; Gamarra, L.F.

    2013-07-15

    Understanding the process of synthesis of magnetic nanoparticles is important for its implementation in in vitro and in vivo studies. In this work we report the synthesis of magnetic nanoparticles made from ferrous oxide through coprecipitation chemical process. The nanostructured material was coated with lauric acid and dispersed in aqueous medium containing surfactant that yielded a stable colloidal suspension. The characterization of magnetic nanoparticles with distinct physico-chemical configurations is fundamental for biomedical applications. Therefore magnetic nanoparticles were characterized in terms of their morphology by means of TEM and DLS, which showed a polydispersed set of spherical nanoparticles (average diameter of ca. 9 nm) as a result of the protocol. The structural properties were characterized by using X-ray diffraction (XRD). XRD pattern showed the presence of peaks corresponding to the spinel phase of magnetite (Fe{sub 3}O{sub 4}). The relaxivities r{sub 2} and r{sub 2}* values were determined from the transverse relaxation times T{sub 2} and T{sub 2}* at 3 T. Magnetic characterization was performed using SQUID and FMR, which evidenced the superparamagnetic properties of the nanoparticles. Thermal characterization using DSC showed exothermic events associated with the oxidation of magnetite to maghemite. - Highlights: • Synthesis of magnetic nanoparticles coated with lauric acid • Characterization of magnetic nanoparticles • Morphological, structural, magnetic, calorimetric and relaxometric characterization.

  3. Solution voltammetry of 4 nm magnetite iron oxide nanoparticles.

    PubMed

    Roberts, Joseph J P; Westgard, John A; Cooper, Laura M; Murray, Royce W

    2014-07-30

    The voltammetry of solution-dispersed magnetite iron oxide Fe3O4 nanoparticles is described. Their currents are controlled by nanoparticle transport rates, as shown with potential step chronoamperometry and rotated disk voltammetry. In pH 2 citrate buffer with added NaClO4 electrolyte, solution cyclic voltammetry of these nanoparticles (average diameter 4.4 ± 0.9 nm, each containing ca. 30 Fe sites) displays an electrochemically irreversible oxidation with E(PEAK) at ca. +0.52 V and an irreversible reduction with E(PEAK) at ca. +0.2 V vs Ag/AgCl reference electrode. These processes are presumed to correspond to the formal potentials for one-electron oxidation of Fe(II) and reduction of Fe(III) at their different sites in the magnetite nanoparticle structure. The heterogeneous electrode reaction rates of the nanoparticles are very slow, in the 10(-5) cm/s range. The nanoparticles are additionally characterized by a variety of tools, e.g., TEM, UV/vis, and XPS spectroscopies.

  4. Magnetite nanoparticles for biosensor model based on bacteria fluorescence

    NASA Astrophysics Data System (ADS)

    Poita, A.; Creanga, D.-E.; Airinei, A.; Tupu, P.; Goiceanu, C.; Avadanei, O.

    2009-06-01

    Fluorescence emission of pyoverdine - the siderophore synthesized by iron scavenger bacteria - was studied using in vitro cultures of Pseudomonas aeruginosa with the aim to design a biosensor system for liquid sample iron loading. Diluted suspensions of colloidal magnetite nanoparticles were supplied in the culture medium (10 microl/l and 100 microl/l) to simulate magnetic loading with iron oxides of either environmental waters or human body fluids. The electromagnetic exposure to radiofrequency waves of bacterial samples grown in the presence of magnetic nanoparticles was also carried out. Cell density diminution but fluorescence stimulation following 10 microl/l ferrofluid addition and simultaneous exposure to radiofrequency waves was evidenced. The inhibitory influence of 100 microl/l ferrofluid combined with RF exposure was evidenced by fluorescence data. Mathematical model was proposed to approach quantitatively the dynamics of cell density and fluorescence emission in relation with the consumption of magnetite nanoparticle supplied medium. The biosensor scheme was shaped based on the response to iron loading of bacterial sample fluorescence.

  5. Preparing a magnetically responsive single-wall carbon nanohorn colloid by anchoring magnetite nanoparticles.

    PubMed

    Utsumi, Shigenori; Urita, Koki; Kanoh, Hirofumi; Yudasaka, Masako; Suenaga, Kazutomo; Iijima, Sumio; Kaneko, Katsumi

    2006-04-13

    A single-wall carbon nanohorn (SWNH) colloid was made to be magnetically responsive by anchoring magnetite nanoparticles prepared by the homogeneous mixing of FeCl(2)-FeCl(3) and NaOH solutions. Transmission electron microscopy observation showed the high dispersion of magnetite particles of 2-9 nm on the surface of the SWNH colloid, coinciding with the broad X-ray diffraction peaks of the magnetites. The magnetization measurements showed that the magnetite nanoparticles-anchored SWNH (mag-SWNH) colloid has the hybrid property of ferrimagnetism and superparamagnetism. It was demonstrated that mag-SWNH colloid dispersed in water by sonication responded to an external magnetic field, gathering toward a magnet. N(2) adsorption experiments showed the high nanoporosity of mag-SWNHs and that magnetite nanoparticles were preferably anchored at "nanowindow" sites and the entrance sites of interstitial pores. This magnetically responsive SWNH colloid should contribute to the field of drug delivery.

  6. Avian orientation: the pulse effect is mediated by the magnetite receptors in the upper beak.

    PubMed

    Wiltschko, Wolfgang; Munro, Ursula; Ford, Hugh; Wiltschko, Roswitha

    2009-06-22

    Migratory silvereyes treated with a strong magnetic pulse shift their headings by approximately 90 degrees , indicating an involvement of magnetite-based receptors in the orientation process. Structures containing superparamagnetic magnetite have been described in the inner skin at the edges of the upper beak of birds, while single-domain magnetite particles are indicated in the nasal cavity. To test which of these structures mediate the pulse effect, we subjected migratory silvereyes, Zosterops l. lateralis, to a strong pulse, and then tested their orientation, while the skin of their upper beak was anaesthetized with a local anaesthetic to temporarily deactivate the magnetite-containing structures there. After the pulse, birds without anaesthesia showed the typical shift, whereas when their beak was anaesthetized, they maintained their original headings. This indicates that the superparamagnetic magnetite-containing structures in the skin of the upper beak are most likely the magnetoreceptors that cause the change in headings observed after pulse treatment.

  7. Renewable hybrid nanocatalyst from magnetite and cellulose for treatment of textile effluents.

    PubMed

    Arantes, Ana Carolina Cunha; Almeida, Crislaine das Graças; Dauzacker, Ligiane Carolina Leite; Bianchi, Maria Lucia; Wood, Delilah F; Williams, Tina G; Orts, William J; Tonoli, Gustavo Henrique Denzin

    2017-05-01

    A hybrid catalyst was prepared using cellulose nanofibrils and magnetite to degrade organic compounds. Cellulose nanofibrils were isolated by mechanical defibrillation producing a suspension used as a matrix for magnetite particles. The solution of nanofibrils and magnetite was dried and milled resulting in a catalyst with a 1:1 ratio of cellulose and magnetite that was chemically and physically characterized using light, scanning electron and transmission electron microscopies, specific surface area analysis, vibrating sample magnetometry, thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction, catalytic potential and degradation kinetics. Results showed good dispersion of the active phase, magnetite, in the mat of cellulosic nanofibrils. Leaching and re-use tests showed that catalytic activity was not lost over several cycles. The hybrid material produced was tested for degradation of methylene blue dye in Fenton-like reactions resulting in a potential catalyst for use in degradation of organic compounds.

  8. Spontaneous Symmetry-Breaking Vortex Lattice Transitions in Pure Niobium

    SciTech Connect

    Laver, M.; Forgan, E.M.; Brown, S.P.; Bowell, C.; Ramos, S.; Lycett, R.J.; Charalambous, D.; Fort, D.; Christen, D.K.; Kohlbrecher, J.; Dewhurst, C.D.; Cubitt, R.

    2006-04-28

    We report an extensive investigation of magnetic vortex lattice (VL) structures in single crystals of pure niobium with the magnetic field applied parallel to a fourfold symmetry axis, so as to induce frustration between the cubic crystal symmetry and hexagonal VL coordination expected in an isotropic situation. We observe new VL structures and phase transitions; all the VL phases observed (including those with an exactly square unit cell) spontaneously break some crystal symmetry. One phase even has the lowest possible symmetry of a two-dimensional Bravais lattice. This is quite unlike the situation in high-T{sub c} or borocarbide superconductors, where VL structures orient along particular directions of high crystal symmetry. The causes of this behavior are discussed.

  9. Synthesis of magnetite particles by pulsed alexandrite laser processing of metallic glass precursors

    SciTech Connect

    Sorescu, M.; Schafer, S.A.; Knobbe, E.T.

    1996-12-31

    Samples of Fe{sub 78}B{sub 13}Si{sub 9} and Fe{sub 81}B{sub 13.5}Si{sub 3.5}C{sub 2} metallic glasses were irradiated with a pulsed alexandrite laser ({lambda} = 750 nm, {tau} = 60 {micro}s) using different laser fluences. Kinetics of laser-induced phase transformations and fluence dependence of magnetic properties were studied by scanning electron microscopy (SEM) and Moessbauer spectroscopy. Low laser fluences were found to induce changes in magnetic texture and onset of crystallization. High laser fluences, however, correlated with additional oxidation effects and the formation of stoichiometric Fe{sub 3}O{sub 4} particles in the irradiated alloy system. An activation energy of 11.9 eV was estimated for the laser-driven synthesis of magnetite nanoparticles. Pulsed alexandrite laser processing is an intriguing alternative technique for the controlled synthesis of iron oxide phases from ferromagnetic glass precursors.

  10. Controlled Biomineralization of Magnetite (Fe(inf3)O(inf4)) and Greigite (Fe(inf3)S(inf4)) in a Magnetotactic Bacterium

    PubMed Central

    Bazylinski, D. A.; Frankel, R. B.; Heywood, B. R.; Mann, S.; King, J. W.; Donaghay, P. L.; Hanson, A. K.

    1995-01-01

    A slowly moving, rod-shaped magnetotactic bacterium was found in relatively large numbers at and below the oxic-anoxic transition zone of a semianaerobic estuarine basin. Unlike all magnetotactic bacteria described to date, cells of this organism produce single-magnetic-domain particles of an iron oxide, magnetite (Fe(inf3)O(inf4)), and an iron sulfide, greigite (Fe(inf3)S(inf4)), within their magnetosomes. The crystals had different morphologies, being arrowhead or tooth shaped for the magnetite particles and roughly rectangular for the greigite particles, and were coorganized within the same chain(s) in the same cell with their long axes along the chain direction. Because the two crystal types have different crystallochemical characteristics, the findings presented here suggest that the formation of the crystal types is controlled by separate biomineralization processes and that the assembly of the magnetosome chain is controlled by a third ultrastructural process. In addition, our results show that in some magnetotactic bacteria, external environmental conditions such as redox and/or oxygen or hydrogen sulfide concentrations may affect the composition of the nonmetal part of the magnetosome mineral phase. PMID:16535116

  11. Production of substantially pure fructose

    DOEpatents

    Hatcher, Herbert J.; Gallian, John J.; Leeper, Stephen A.

    1990-01-01

    A process is disclosed for the production of substantially pure fructose from sucrose-containing substrates. The process comprises converting the sucrose to levan and glucose, purifying the levan by membrane technology, hydrolyzing the levan to form fructose monomers, and recovering the fructose.

  12. Rock-magnetic properties of single zircon crystals sampled from the Tanzawa tonalitic pluton, central Japan

    NASA Astrophysics Data System (ADS)

    Sato, Masahiko; Yamamoto, Shinji; Yamamoto, Yuhji; Okada, Yoshihiro; Ohno, Masao; Tsunakawa, Hideo; Maruyama, Shigenori

    2015-09-01

    This paper reports on the rock-magnetic properties of single zircon crystals, which are essential for future work establishing the reliable paleointensity method using single zircon crystals. Zircon crystals used in this study were sampled from the Nakagawa River, which crosses the Tanzawa tonalitic pluton in central Japan. Rock-magnetic measurements were conducted on 1037 grains of zircons, but many of these measurements are below the limits of the sensitivity of the magnetometers employed. Isothermal remanent magnetizations (IRMs) of 876 zircon crystal are below the practical resolution of this study; we infer that these crystals contain no or only minute quantities of ferromagnetic minerals. The other zircon crystals contain enough magnetic minerals to be measured in the DC SQUID magnetometer. For 81 zircon crystals, IRM intensities ( M IRM) are larger than 4 × 10-12 Am2, while natural remanent magnetization (NRM) intensities ( M NRM) are below 4 × 10-12 Am2, indicating that these crystals are inappropriate for the paleomagnetic study. For the samples that had values of M NRM ≥ 4 × 10-12 Am2 and M IRM ≥ 4 × 10-12 Am2 (80 zircons), combining the rock-magnetic parameter, we proposed the sample-selection criteria for future study of paleointensity experiments using single zircon crystals. In the case that the samples had high coercivity ( B c) values (>10 mT) or high M NRM/ M IRM values (>~0.1), main remanence carriers are probably pyrrhotite and these samples are inappropriate for the paleointensity study. In the case that the samples had low B c values (<10 mT) and low M NRM/ M IRM values (<~0.1), main remanence carriers seem to be nearly pure magnetite with pseudo-single-domain grain sizes, and these samples are expected to appropriate for the paleointensity study. Total thermoremanent magnetization (TRM) acquisition experiments were also carried out for 12 samples satisfying the above criteria. The TRM intensity was comparable with that of NRM, and a

  13. Biophysical Puzzles Concerning Magnetite-Based Magnetoreception in the Common Nematode, Caenorhabditis elegans.

    NASA Astrophysics Data System (ADS)

    Kirschvink, J. L.; Kobayashi, A. K.

    2015-12-01

    magnetic field. If correct, the results of Vidal-Gadea et al. make clear predictions for the inheritance of single-domain magnetite crystals through ontogeny, and demand the presence of a gravity receptor. But if they have a gravity receptor, why would they need magnetotaxis? These are puzzles.

  14. Influence of Magnetite Nanoparticles on Human Leukocyte Activity

    NASA Astrophysics Data System (ADS)

    Džarová, Anežka; Dubničková, Martina; Závišová, Vlasta; Koneracká, Martina; Kopčanský, Peter; Gojzewski, Hubert; Timko, Milan

    2010-12-01

    Chemically synthesized magnetite particles coated by sodium oleate and PEG (MNP), and magnetosomes (MS) influence the process of phagocytosis and the metabolic activity (lysozyme and peroxidase activity) in leukocytes. Lysozyme activity is oxygen-independent liquidation mechanisms of engulfed microorganism, peroxidase activity is an oxygen-dependent mechanism. Both tested types of nanoparticles lysed leukocyte cells during incubation. MNP at concentrations of 10 and 20 μg/mL lysed almost all leukocytes and their cell viability was in the 14±0.05% range. On the other hand MS begin to influence leukocytes activity at the concentration of 1 μg/ml and this influence grows with increasing concentration up to 20 μg/ml. MS are more suitable for biological applications than MNP which are more aggressive material than MS. MS should not be used above 10 μg/mL.

  15. Hydrocolloid-stabilized magnetite for efficient removal of radioactive phosphates.

    PubMed

    Vellora Thekkae Padil, Vinod; Rouha, Michael; Cerník, Miroslav

    2014-01-01

    Liquid radioactive waste is a common by-product when using radioactive isotopes in research and medicine. Efficient remediation of such liquid waste is crucial for increasing safety during the necessary storage of the material. Herein, we present a novel Gum Karaya stabilized magnetite for the efficient removal of radioactive phosphorus (32)P from liquid radioactive waste. This environmentally friendly material is well suited to be used as a nanohydrogel for the removal of liquid waste, which can then be stored in a smaller space and without the risk of the spills inherent to the initial liquid material. The maximum adsorption capacity of the GK/M in this study was found to be 15.68 GBq/g. We present a thorough morphological characterization of the synthesised GK/M, as well as a discussion of the possible phosphorus adsorption mechanisms.

  16. Hydrocolloid-Stabilized Magnetite for Efficient Removal of Radioactive Phosphates

    PubMed Central

    Vellora Thekkae Padil, Vinod; Rouha, Michael; Černík, Miroslav

    2014-01-01

    Liquid radioactive waste is a common by-product when using radioactive isotopes in research and medicine. Efficient remediation of such liquid waste is crucial for increasing safety during the necessary storage of the material. Herein, we present a novel Gum Karaya stabilized magnetite for the efficient removal of radioactive phosphorus 32P from liquid radioactive waste. This environmentally friendly material is well suited to be used as a nanohydrogel for the removal of liquid waste, which can then be stored in a smaller space and without the risk of the spills inherent to the initial liquid material. The maximum adsorption capacity of the GK/M in this study was found to be 15.68 GBq/g. We present a thorough morphological characterization of the synthesised GK/M, as well as a discussion of the possible phosphorus adsorption mechanisms. PMID:24696854

  17. Magnetite decorated activated carbon composites for water purification

    NASA Astrophysics Data System (ADS)

    Barala, Sunil Kumar; Arora, Manju; Saini, Parveen

    2013-06-01

    Activated carbon decorated with magnetite (ACMG) nanoparticles composites have been prepared by facile method via impregnation of AC with stable dispersion of superparamagnetic MG nanoparticles followed by drying. These composites exhibit both magnetic and porosity behavior which can be easily optimized by controlling the weight ratio of two phases. The structural, magnetic, thermal and morphological properties of these as synthesized ACMG samples were characterized by powder XRD, FTIR, VSM and SEM techniques. The ACMG powder has been used for water purification having methylene blue (MB) dye as an impurity. The nanoporosity of these composites allow rapid adsorption of MB and their magnetic behavior helps in single step separation of MB adsorbed ACMG particles by the application of external magnetic field.

  18. Electromagnetic nanocomposite of bacterial cellulose using magnetite nanoclusters and polyaniline.

    PubMed

    Park, Minsung; Cheng, Jie; Choi, Jaeyoo; Kim, Jaehwan; Hyun, Jinho

    2013-02-01

    Magnetic BC was biosynthesized by culturing Gluconacetobacter xylinus in a medium containing magnetite nanoparticle (MNP) clusters. The stable dispersion of MNP clusters in an aqueous solution was achieved using amphiphilic comb-like polymer (CLP) stabilizers to disperse the MNPs. Subsequently, a conducting polymer was synthesized on the magnetic BC fibers by the chemical oxidative polymerization of aniline. The BC fiber was fully coated with polyaniline, forming hydrogen bonds. The colloidal stability of the CLP-modified MNPs was characterized by optical imaging and UV-visible spectroscopy. The chemical structure and morphology of the hybrid BC layers were observed using Fourier transform infrared spectroscopy and scanning electron microscopy. Magnetic and conductive properties were measured to confirm the immobilization of MNPs and polyaniline.

  19. Sorption of inorganic salts on carbon nanomaterials and magnetite

    NASA Astrophysics Data System (ADS)

    Lyu, Sh. T.; Troshkina, I. D.; Rakov, E. G.

    2016-11-01

    Magnetic composites based on graphene oxides and functionalized carbon nanotubes containing magnetite nanoparticles are synthesized. The dispersing ability of these composites in water at different pH values is studied. It is shown that the solubility of Fe3O4 composites is constant in the pH range of 3.5-10, though these composites are unstable at both lower and higher pH values. Magnetic sorbents for extracting Ce(NO3)3 and La(NO3)3 from solutions are tested. Dependences of the volume on the sorbent's composition, pH value, and salt concentration in the solution are found. Maximum sorption capacity in relation to Ce3+ and La3+ at pH 7.5 and 8.5 are found to be 1040 and 920 mg/g respectively.

  20. A molecular dynamics investigation of surface reconstruction on magnetite (001)

    NASA Astrophysics Data System (ADS)

    Rustad, J. R.; Wasserman, E.; Felmy, A. R.

    1999-07-01

    Molecular dynamics calculations using analytical potential functions with polarizable oxygen ions have been used to identify a novel mode of reconstruction on the half-occupied tetrahedral layer termination of the magnetite (Fe 3O 4) (001) surface. In the proposed reconstruction, the twofold coordinated iron ion in the top monolayer rotates downward to occupy a vacant half-octahedral site in the plane of the second-layer iron ions. At the same time, half of the tetrahedral iron ions in the third iron layer are pushed upward to occupy an adjacent octahedral vacancy at the level of the second-layer iron ions. The other half of the third-layer iron ions remain roughly in their original positions. The proposed reconstruction is consistent with recent low-energy electron diffraction and X-ray photoelectron spectroscopy results. It also provides a compelling interpretation for the arrangement of atoms suggested by high-resolution scanning-tunneling microscopy studies.

  1. Highly sensitive magnetite nano clusters for MR cell imaging.

    PubMed

    Li, Mingli; Gu, Hongchen; Zhang, Chunfu

    2012-03-31

    High sensitivity and suitable sizes are essential for magnetic iron oxide contrast agents for cell imaging. In this study, we have fabricated highly MR sensitive magnetite nanoclusters (MNCs) with tunable sizes. These clusters demonstrate high MR sensitivity. Especially, water suspensions of the MNCs with average size of 63 nm have transverse relaxivity as high as 630 s-1mM-1, which is among the most sensitive iron oxide contrast agents ever reported. Importantly, such MNCs have no adverse effects on cells (RAW 264.7). When used for cell imaging, they demonstrate much higher efficiency and sensitivity than those of SHU555A (Resovist), a commercially available contrast agent, both in vitro and in vivo, with detection limits of 3,000 and 10,000 labeled cells, respectively. The studied MNCs are sensitive for cell imaging and promising for MR cell tracking in clinics.

  2. Highly sensitive magnetite nano clusters for MR cell imaging

    PubMed Central

    2012-01-01

    High sensitivity and suitable sizes are essential for magnetic iron oxide contrast agents for cell imaging. In this study, we have fabricated highly MR sensitive magnetite nanoclusters (MNCs) with tunable sizes. These clusters demonstrate high MR sensitivity. Especially, water suspensions of the MNCs with average size of 63 nm have transverse relaxivity as high as 630 s-1mM-1, which is among the most sensitive iron oxide contrast agents ever reported. Importantly, such MNCs have no adverse effects on cells (RAW 264.7). When used for cell imaging, they demonstrate much higher efficiency and sensitivity than those of SHU555A (Resovist), a commercially available contrast agent, both in vitro and in vivo, with detection limits of 3,000 and 10,000 labeled cells, respectively. The studied MNCs are sensitive for cell imaging and promising for MR cell tracking in clinics. PMID:22462693

  3. Decrease of dissolved sulfide in sewage by powdered natural magnetite and hematite.

    PubMed

    Zhang, Lehua; Verstraete, Willy; de Lourdes Mendoza, María; Lu, Zhihao; Liu, Yongdi; Huang, Guangtuan; Cai, Lankun

    2016-12-15

    Natural magnetite and hematite were explored to decrease sulfide in sewage, compared with iron salts (FeCl3 and FeSO4). A particle size of magnetite and hematite ranging from 45 to 60μm was used. The results showed that 40mgL(-1) of powdered magnetite and hematite addition decreased the sulfide in sewage by 79%and 70%, respectively. The achieved decrease of sulfide production capacities were 197.3, 210.6, 317.6 and 283.3mgSg(-1)Fe for magnetite, hematite, FeCl3 and FeSO4 at the optimal dosage of 40mgL(-1), respectively. Magnetite and hematite provided a higher decrease of sulfide production since more iron ions are capable of being released from the solid phase, not because of adsorption capacity of per gram iron. Besides, the impact on pH and oxidation-reduction potential (ORP) of hematite addition was negligible; while magnetite addition resulted in slight increase of 0.3-0.5 on pH and 10-40mV on ORP. Powdered magnetite and hematite thus appear to be suitable for sulfide decrease in sewage, for their sparing solubility, sustained-release, long reactive time in sewage as well as cost-effectiveness, compared with iron salts. Further investigation over long time periods under practical conditions are needed to evaluate the possible settlement in sewers and unwanted (toxic) metal elements presenting as impurities.

  4. Synthesis and magnetic characterization of magnetite obtained by monowavelength visible light irradiation

    SciTech Connect

    Lin, Yulong; Wei, Yu; Sun, Yuhan; Wang, Jing

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Magnetite was synthesized under monowavelength LED irradiation at room temperature. Black-Right-Pointing-Pointer Different wavelength irradiations led to distinctive characteristics of magnetite. Black-Right-Pointing-Pointer Particle sizes of magnetite were controlled by different irradiation wavelengths. Black-Right-Pointing-Pointer Wavelength affects the magnetic characteristics of magnetite. -- Abstract: Magnetite (Fe{sub 3}O{sub 4}) nanoparticles were controllably synthesized by aerial oxidation Fe{sup II}EDTA solution under different monowavelength light-emitting diode (LED) lamps irradiation at room temperature. The results of the X-ray diffraction (XRD) spectra show the formation of magnetite nanoparticle further confirmed by Fourier transform infrared spectroscope (FTIR) and the difference in crystallinity of as-prepared samples. Fe{sub 3}O{sub 4} particles are nearly spherical in shape based on transmission electron microscopy (TEM). Average crystallite sizes of magnetite can be controlled by different irradiation light wavelengths from XRD and TEM: 50.1, 41.2, and 20.3 nm for red, green, and blue light irradiation, respectively. The magnetic properties of Fe{sub 3}O{sub 4} samples were investigated. Saturation magnetization values of magnetic nanoparticles were 70.1 (sample M-625), 65.3 (sample M-525), and 58.2 (sample M-460) emu/g, respectively.

  5. Effect of purification pretreatment on the recovery of magnetite from waste ferrous sulfate

    NASA Astrophysics Data System (ADS)

    Yu, Wang; Peng, Ying-lin; Zheng, Ya-jie

    2016-08-01

    The present study was conducted to elucidate the influence of impurities in waste ferrous sulfate on its recovery of magnetite. Ferrous sulfate solution was purified by the addition of NaOH solution to precipitate impurities, and magnetite was recovered from ferrous sulfate solution without and with purification pretreatment. Calcium hydroxide was added to the solution of ferrous sulfate as a precipitator. A mixed product of magnetite and gypsum was subsequently obtained by air oxidation and heating. Wet-milling was performed prior to magnetic separation to recover magnetite from the mixed products. The results show that with the purification pretreatment, the grade of iron in magnetite concentrate increased from 62.05% to 65.58% and the recovery rate of iron decreased from 85.35% to 80.35%. The purification pretreatment reduced the conglutination between magnetite and gypsum, which favors their subsequent magnetic separation. In summary, a higher-grade magnetite with a better crystallinity and a larger particle size of 2.35 μm was obtained with the purification pretreatment.

  6. Electrodeposition of Nanostructured Permalloy and Permalloy-Magnetite Composite Coatings and Investigation of Their Magnetic Properties

    NASA Astrophysics Data System (ADS)

    Fazli, Sara; Bahrololoom, M. E.

    2016-08-01

    Permalloy and permalloy-magnetite coatings were electrodeposited with the average thickness of 100 µm with certain operating parameters, such as the current density of 100 mA/cm2, pH 3.8, and the temperature of 298 K (25 °C), to fabricate alloy and composite coatings, respectively. The aim was to promote the magnetic properties of permalloy coating in order to extend its magnetic applications. For this purpose, nanocrystalline permalloy and permalloy-magnetite coatings were electrodeposited. The effect of the content of magnetite particles in the bath on magnetic properties of the samples was investigated. Vibrating sample magnetometry was performed to investigate the variation of magnetic properties of the coatings. The optimum amount of magnetite (2 g/L) was determined according to the highest amount of saturated magnetization and a sensible amount of coercivity. The morphology, phase, elemental analyses of the coatings and the chemical composition analysis of the bath were performed by scanning electron microscopy, X-ray diffraction pattern, quantometry, energy-dispersive X-ray spectroscopy, and ultraviolet-visible spectroscopy. The magnetization was increased initially and then decreased (after a limited amount of magnetite) by enhancing the content of magnetite particles in the bath. Also, the coercivity was decreased by increasing the amount of magnetite particles in the coatings, which was due to the reduction of the grain size of the permalloy matrix.

  7. Removal of azo dye from water by magnetite adsorption-Fenton oxidation.

    PubMed

    Rongcheng, Wu; Jiuhui, Qu

    2004-01-01

    The aim of this study is to highlight the possibility of using powder magnetite adsorption-Fenton oxidation as a method for removal of azo dye acid red B (ARB) from water. The adsorption properties of magnetite powder towards ARB were studied. The oxidation of adsorbed ARB and regeneration of magnetite adsorbent at the same time by Fenton reagent (hydrogen peroxide [H2O2] + iron (II) [Fe2+]) in another treatment unit with a smaller volume was also investigated. The efficiency of Fenton oxidation of ARB was compared for the reaction carried out in solution and on magnetite. The magnetic separation method was used to recover magnetite after adsorption or regeneration. The results indicated that the adsorption rate was fast. The capacity was strongly dependent on pH and inorganic anions, and pH 3.8 was optimal for the adsorption of ARB. The adsorption can be described well using the Langmuir model. The oxidation was more efficient for ARB adsorbed on magnetite than in solution. The adsorption capacity of magnetite increased significantly after regeneration, which was the result of an increase in surface area of the adsorbent and change of elemental ratio (oxygen:iron [O:Fe]) on the surface. The maximum adsorption capacity for ARB was 32.4 mg/g adsorbent.

  8. Anaerobic production of magnetite by a dissimilatory iron-reducing microorganism

    USGS Publications Warehouse

    Lovley, D.R.; Stolz, J.F.; Nord, G.L.; Phillips, E.J.P.

    1987-01-01

    The potential contribution of microbial metabolism to the magnetization of sediments has only recently been recognized. In the presence of oxygen, magnetotactic bacteria can form intracellular chains of magnetite while using oxygen or nitrate as the terminal electron acceptor for metabolism1. The production of ultrafine-grained magnetite by magnetotactic bacteria in surficial aerobic sediments may contribute significantly to the natural remanent magnetism of sediments2-4. However, recent studies on iron reduction in anaerobic sediments suggested that bacteria can also generate magnetite in the absence of oxygen5. We report here on a sediment organism, designated GS-15, which produces copious quantities of ultrafine-grained magnetite under anaerobic conditions. GS-15 is not magnetotactic, but reduces amorphic ferric oxide to extracellular magnetite during the reduction of ferric iron as the terminal electron acceptor for organic matter oxidation. This novel metabolism may be the mechanism for the formation of ultrafine-grained magnetite in anaerobic sediments, and couldaccount for the accumulation of magnetite in ancient iron formations and hydrocarbon deposits. ?? 1987 Nature Publishing Group.

  9. Transformation products of submicron-sized aluminum-substituted magnetite: Color and reductant solubility

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.; Lauer, H. V., Jr.

    1991-01-01

    Magnetite, when present as fine particles, is soluble in acid ammonium oxalate (pH equals 3). However, the commonly used extractant for free iron oxides (i.e., citrate dithionite-bicarbonate (CDB) is not very effective in dissolving magnetite in soils and geologic materials. Upon oxidation, magnetite transforms to maghemite; at elevated temperatures, maghemite inverts to hematite. This transformation causes a change in color from black to red and may affect the reductant solubility as well. The objectives here were to examine the color and reflectance spectral characteristics of products during the transformation of magnetite to maghemite to hematite and to study the effect of Al-substitution in magnetite on the above process. Reductant solubility of Al-substituted magnetite, maghemite, and hematite was also studied. In summary, the transformation of magnetite to maghemite was accompanied by a change in color from black to red because of the oxidation of Fe2(+) to Fe3(+). The phase change maghemite to hematite had a relatively minor effect on the color and the reflectance spectra.

  10. Antimicrobial Properties of Lysosomal Enzymes Immobilized on NH₂Functionalized Silica-Encapsulated Magnetite Nanoparticles.

    PubMed

    Bang, Seung Hyuck; Sekhon, Simranjeet Singh; Cho, Sung-Jin; Kim, So Jeong; Le, Thai-Hoang; Kim, Pil; Ahn, Ji-Young; Kim, Yang-Hoon; Min, Jiho

    2016-01-01

    The immobilization efficiency, antimicrobial activity and recovery of lysosomal enzymes on NH2 functionalized magnetite nanoparticles have been studied under various conditions. The immobi- lization efficiency depends upon the ratio of the amount of enzyme and magnetite and it shows an increase with magnetite concentration which is due to the presence of amine group at the magnetite surface that leads to a strong attraction. The optimized reaction time to immobilize the lysosomal enzymes on magnetite was determined by using a rolling method. The immobilization efficiency increases with reaction time and reached a plateau after 5 minutes and then remained constant for 10 minutes. However, after 30 minutes the immobilization efficiency decreased to 85%, which is due to the weaker electrostatic interactions between magnetite and detached lysosomal enzymes. The recovery and stability of immobilized lysosomal enzymes has also been studied. The antimicrobial activity was almost 100% but it decreased upon reuse and no activity was observed after its reuse for seven times. The storage stability of lysosomal enzymes as an antimicrobial agent was about 88%, which decreased to 53% after one day and all activity of immobilized lysosomal enzymes was maintained after five days. Thus, the lysosomal enzymes immobilized on magnetite nanoparticles could potentially be used as antimicrobial agents to remove bacteria.

  11. Synthesis of Enantiomerically Pure Anthracyclinones

    NASA Astrophysics Data System (ADS)

    Achmatowicz, Osman; Szechner, Barbara

    The anthracycline antibiotics are among the most important clinical drugs used in the treatment of human cancer. The search for new agents with improved therapeutic efficacy and reduced cardiotoxicity stimulated considerable efforts in the synthesis of new analogues. Since the biological activity of anthracyclines depends on their natural absolute configuration, various strategies for the synthesis of enantiomerically pure anthracyclinones (aglycones) have been developed. They comprise: resolution of racemic intermediate, incorporation of a chiral fragment derived from natural and non-natural chiral pools, asymmetric synthesis with the use of a chiral auxiliary or a chiral reagent, and enantioselective catalysis. Synthetic advances towards enantiopure anthracyclinones reported over the last 17 years are reviewed.

  12. Toxicological evaluation of pure hydroxytyrosol.

    PubMed

    Auñon-Calles, David; Canut, Lourdes; Visioli, Francesco

    2013-05-01

    Of all the phenolic constituents of olives and extra virgin olive oil, hydroxytyrosol is currently being actively exploited as a potential supplement or preservative to be employed in the nutraceutical, cosmeceutical, and food industry. In terms of safety profile, hydroxytyrosol has only been investigated as the predominant part of raw olive mill waste water extracts, due to the previous unavailability of appropriate quantities of the pure compound. We report the toxicological evaluation of hydroxytyrosol and, based on the results, propose a No Observed Adverse Effects Level (NOAEL) of 500mg/kg/d.

  13. Ferrihydrite Alteration to Magnetite, Maghemite and Hematite; Implications for Iron Oxides on Mars

    NASA Technical Reports Server (NTRS)

    Zent, A. P.; Bishop, J. L.; Mancinelli, R. L.; Olsen, M.; Wagner, P. A.

    2000-01-01

    Synthetic ferrihydrites have been altered to form magnetite, maghemite and hematite through low-temperature heating experiments (some with an organic reductant). Maghemite formed in this manner could become an indicator for Astrobiology on Mars.

  14. A unique type 3 ordinary chondrite containing graphite-magnetite aggregates - Allan Hills A77011

    NASA Technical Reports Server (NTRS)

    Mckinley, S. G.; Scott, E. R. D.; Taylor, G. J.; Keil, K.

    1982-01-01

    ALHA 77011, which is the object of study in the present investigation, is a chondrite of the 1977 meteorite collection from Allan Hills, Antarctica. It contains an opaque and recrystallized silicate matrix (Huss matrix) and numerous aggregates consisting of micron- and submicron-sized graphite and magnetite. It is pointed out that no abundant graphite-magnetite aggregates could be observed in other type 3 ordinary chondrites, except for Sharps. Attention is given to the results of a modal analysis, relations between ALHA 77011 and other type 3 ordinary chondrites, and the association of graphite-magnetite and metallic Fe, Ni. The discovery of graphite-magnetite aggregates in type 3 ordinary chondrites is found to suggest that this material may have been an important component in the formation of ordinary chondrites.

  15. Magnetic and Structural Properties of Magnetite in Radular Teeth of Chiton Acanthochiton Rubrolinestus

    NASA Astrophysics Data System (ADS)

    Han, Y. N.; Liu, C. L.; Yao, L. D.; Wang, Y.; Han, X. F.

    2008-03-01

    The major radular lateral teeth of Polyplacophora Chiton comprise a magnetite biomineral cap.We have investigated the structure and magnetic properties of the biomineralized magnetite crystallites in mature teeth of Chiton Acanthochiton Rubrolinestus. From the measurement of magnetic properties of tooth particles using SQUID magnetometry we find that the saturation magnetization and the Verwey transition temperature (Tv) are 78.4 emu/g and 105 K, respectively. An in situ examination of the structure of magnetite-bearing region within individual tooth using the high resolution TEM, together with electron diffraction (ED) pattern and energy-dispersive X-ray (EDX) analyses indicates magnetite microcrystal form electron-dense polycrystalline sheets with typical length 800 nm and width 150 nm or so. These polycrystalline sheets are arranged regularly along the longitude direction of the tooth cutting surface. Furthermore, the microcrystallites in polycrystalline sheet take on the generally good crystallinity.

  16. Truncated Hexa-Octahedral Magnetites: Biosignatures in Terrestrial Samples and Martian Meteorite ALH84001

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Wentworth, Susan J.; Vali, H.; Gibson, Everett K.

    2001-01-01

    We suggest that the observation of truncated hexa-octahedral magnetites in ALH84001 are both consistent with, and in the absence of terrestrial inorganic analogs, likely formed by biogenic processes. Additional information is contained in the original extended abstract.

  17. Controllable in situ synthesis of magnetite coated silica-core water-dispersible hybrid nanomaterials.

    PubMed

    Qu, Haiou; Tong, Sheng; Song, Kejing; Ma, Hui; Bao, Gang; Pincus, Seth; Zhou, Weilie; O'Connor, Charles

    2013-08-20

    Magnetite nanoparticle coated silica (Fe3O4@SiO2) hybrid nanomaterials hold an important position in the fields of cell imaging and drug delivery. Here we report a large scale synthetic procedure that allows attachment of magnetite nanoparticles onto a silica surface in situ. Many different silica nanomaterials such as Stöber silica nanospheres, mesoporous silica nanoparticles, and hollow silica nanotubes have been coated with a high density layer of water-dispersible magnetite nanoparticles. The size and attachment efficiency of the magnetite nanoparticle can be well tuned by adjusting the precursor concentration and reflux time. The functionalization of Fe3O4@SiO2 nanoparticles with dye molecules and biocompatible polymers impart optical imaging modality and good colloidal stability in either buffer solution or serum. The functionalized materials also exhibited strong potential as negative contrast agents in T2 weighted magnetic resonance imaging.

  18. Water-dispersible magnetite-reduced graphene oxide composites for arsenic removal.

    PubMed

    Chandra, Vimlesh; Park, Jaesung; Chun, Young; Lee, Jung Woo; Hwang, In-Chul; Kim, Kwang S

    2010-07-27

    Magnetite-graphene hybrids have been synthesized via a chemical reaction with a magnetite particle size of approximately 10 nm. The composites are superparamagnetic at room temperature and can be separated by an external magnetic field. As compared to bare magnetite particles, the hybrids show a high binding capacity for As(III) and As(V), whose presence in the drinking water in wide areas of South Asia has been a huge problem. Their high binding capacity is due to the increased adsorption sites in the M-RGO composite which occurs by reducing the aggregation of bare magnetite. Since the composites show near complete (over 99.9%) arsenic removal within 1 ppb, they are practically usable for arsenic separation from water.

  19. Use of different rapid mixing devices for controlling the properties of magnetite nanoparticles produced by precipitation

    NASA Astrophysics Data System (ADS)

    Wei, Li; Hervé, Muhr; Edouard, Plasari

    2012-03-01

    Magnetite nanoparticles were precipitated by the classic Massart's method in a 2.5 L stirred tank reactor where the injection of reagent solutions was effectuated by different micro-mixers (T-tube and Hartridge-Roughton rapid mixing devices). The specific surface area, the average particle size and the particle size distribution were highly influenced by changing operating parameters. Laser Diffraction, BET adsorption, Energy-Dispersive X-ray Spectroscopy (EDX), Raman spectroscopy and Transmission Electron Microscopy (TEM) were used for characterizing magnetite nanoparticles. Especially, Hartridge-Roughton micromixer appears to be the most efficient mixing device for producing magnetite nanoparticles. The average particle size of magnetite nanoparticles prepared by Hartridge-Roughton rapid mixing device was less than 10 nm and the EDX and Raman spectroscopy shows that the particle purity is quite high.

  20. Magnetite-supported sulfonic acid: a retrievable nanocatalyst for the Ritter reaction and multicomponent reactions

    EPA Science Inventory

    Magnetite-sulfonic acid (NanocatFe-OSO3H), prepared by wet-impregnation method, serves as a magnetically retrievable sustainable catalyst for the Ritter reaction which can be used in several reaction cycles without any loss of activity.

  1. Laboratory verification of submicron magnetite production in pseudotachylytes: relevance for paleointensity studies

    NASA Astrophysics Data System (ADS)

    Nakamura, Norihiro; Hirose, Takehiro; Borradaile, Graham J.

    2002-07-01

    Pseudotachylytes generally possess stable remanent magnetizations but the processes by which pseudotachylytes are magnetized remain poorly understood. Magnetic hysteresis and scanning electron microscope studies reveal that experimental frictional melting of granites produces dispersed submicron inclusions of weakly interacting pseudo-single-domain (PSD) magnetite, in artificial pseudotachylyte. The magnetite inclusions are absent in the undeformed granite protolith and result from oxidation of Fe in melt-susceptible mafic minerals during the melt-quenched event. The pseudotachylytes acquired a stable thermal remanence in fine-grained PSD magnetites during the rapid cooling of the melt, implying that fine-grained magnetite has the potential for paleointensity determinations of contemporaneous magnetic fields with co-seismic faulting in granitoids.

  2. Crystal size distribution (CSD) in rocks and the kinetics and dynamics of crystallization

    NASA Astrophysics Data System (ADS)

    Cashman, Katharine V.; Ferry, John M.

    1988-08-01

    Crystal size distributions (CSDs) measured in metamorphic rocks yield quantitative information about crystal nucleation and growth rates, growth times, and the degree of overstepping ( ΔT) of reactions during metamorphism. CSDs are described through use of a population density function n=dN/dL, where N is the cumulative number of crystals per unit volume and L is a linear crystal size. Plots of ln ( n) vs. L for olivine+pyroxene and magnetite in high-temperature (1000° C) basalt hornfelses from the Isle of Skye define linear arrays, indicating continuous nucleation and growth of crystals during metamorphism. Using the slope and intercept of these linear plots in conjunction with growth rate estimates we infer minimum mineral growth times of less than 100 years at ΔT<10° C, and nucleation rates between 10-4 and 10-1/cm3/s. Garnet and magnetite in regionally metamorphosed pelitic schists from south-central Maine have CSDs which are bell-shaped. We interpret this form to be the result of two processes: 1) initial continuous nucleation and growth of crystals, and 2) later loss of small crystals due to annealing. The large crystals in regional metamorphic rocks retain the original size frequency distribution and may be used to obtain quantitative information on the original conditions of crystal nucleation and growth. The extent of annealing increases with increasing metamorphic grade and could be used to estimate the duration of annealing conditions if the value of a rate constant were known. Finally, the different forms of crystal size distributions directly reflect differences in the thermal histories of regional vs. contact metamorphosed rocks: because contact metamorphism involves high temperatures for short durations, resulting CSDs are linear and unaffected by annealing, similar to those produced by crystallization from a melt; because regional metamorphism involves prolonged cooling from high temperatures, primary linear CSDs are later modified by annealing

  3. Dependence of microbial magnetite formation on humic substance and ferrihydrite concentrations

    NASA Astrophysics Data System (ADS)

    Piepenbrock, Annette; Dippon, Urs; Porsch, Katharina; Appel, Erwin; Kappler, Andreas

    2011-11-01

    Iron mineral (trans)formation during microbial Fe(III) reduction is of environmental relevance as it can influence the fate of pollutants such as toxic metal ions or hydrocarbons. Magnetite is an important biomineralization product of microbial iron reduction and influences soil magnetic properties that are used for paleoclimate reconstruction and were suggested to assist in the localization of organic and inorganic pollutants. However, it is not well understood how different concentrations of Fe(III) minerals and humic substances (HS) affect magnetite formation during microbial Fe(III) reduction. We therefore used wet-chemical extractions, magnetic susceptibility measurements and X-ray diffraction analyses to determine systematically how (i) different initial ferrihydrite (FH) concentrations and (ii) different concentrations of HS (i.e. the presence of either only adsorbed HS or adsorbed and dissolved HS) affect magnetite formation during FH reduction by Shewanella oneidensis MR-1. In our experiments magnetite formation did not occur at FH concentrations lower than 5 mM, even though rapid iron reduction took place. At higher FH concentrations a minimum fraction of Fe(II) of 25-30% of the total iron present was necessary to initiate magnetite formation. The Fe(II) fraction at which magnetite formation started decreased with increasing FH concentration, which might be due to aggregation of the FH particles reducing the FH surface area at higher FH concentrations. HS concentrations of 215-393 mg HS/g FH slowed down (at partial FH surface coverage with sorbed HS) or even completely inhibited (at complete FH surface coverage with sorbed HS) magnetite formation due to blocking of surface sites by adsorbed HS. These results indicate the requirement of Fe(II) adsorption to, and subsequent interaction with, the FH surface for the transformation of FH into magnetite. Additionally, we found that the microbially formed magnetite was further reduced by strain MR-1 leading to

  4. Uranium reduction on magnetite: Probing for pentavalent uranium using electrochemical methods

    NASA Astrophysics Data System (ADS)

    Yuan, Ke; Renock, Devon; Ewing, Rodney C.; Becker, Udo

    2015-05-01

    Pentavalent uranium is generally treated as an unstable intermediate when uranyl, U(VI)O22+, is reduced to U4+. However, mineral surfaces have been shown to stabilize pentavalent uranium, thus hindering further reduction (Ilton et al., 2005, 2010). The subject of this study is to identify the kinetic pathways that lead to U(V)O2+ being a metastable species. Electrochemical methods provide an in situ approach for the investigation of the intermediate reaction of U(V)O2+ on the surfaces of magnetite. Redox reactions of uranyl ions on particulate (∼3 μm) and bulk magnetite surfaces were investigated using cyclic voltammetry and potential step chronoamperometry using cavity microelectrodes and bulk (planar) mineral electrodes. The estimated redox potentials are consistent with the standard redox potential of UO22+/UO2+, indicating UO22+ is first reduced to UO2+ on the surfaces of both powder and bulk magnetite. The one-electron reduction of UO22+ to UO2+ was further confirmed by directly measuring the number of electrons transferred during the reduction process on the bulk magnetite electrode. Based on the charge conservation analysis and the positive correlation between the pH and the peak current for the UO2+ transformation to UO22+, the peak corresponding to the oxidation of U4+ to UO22+ was assigned in the voltammograms of particulate magnetite. The presence of U4+ indicates that the disproportionation of UO2+ (2U(V) ↔ U(IV) + U(VI)) is occurring on the surface of particulate magnetite within the timeframe of the experiment. The lack of a peak for U4+ in voltammograms for bulk magnetite suggests that the rate of the UO2+ disproportionation reaction is slower on bulk magnetite than that on particulate magnetite. The catalytic property of particulate magnetite surfaces on the disproportionation reaction is explained by its ability to adsorb and desorb protons, which could facilitate the proton-coupled disproportionation reaction of UO2+. This increased catalytic

  5. Pure dysarthria due to an insular infarction.

    PubMed

    Hiraga, Akiyuki; Tanaka, Saiko; Kamitsukasa, Ikuo

    2010-06-01

    Cortical infarction presenting with pure dysarthria is rarely reported. Previous studies have reported pure dysarthria due to cortical stroke at the precentral gyrus or middle frontal gyrus. We report a 72-year-old man who developed pure dysarthria caused by an acute cortical infarction in the insular cortex. The role of the insula in language has been difficult to assess clinically because of the rarity of pure insular strokes. Our patient showed pure dysarthria without aphasia, indicating that pure dysarthria can be the sole manifestation of insular infarctions.

  6. Novel one-pot synthesis of magnetite latex nanoparticles by ultrasound irradiation.

    PubMed

    Teo, Boon M; Chen, Fei; Hatton, T Alan; Grieser, Franz; Ashokkumar, Muthupandian

    2009-03-03

    A simple and efficacious procedure for the synthesis of magnetite nanoparticles has been achieved via a sonochemical miniemulsion polymerization process. The sonochemically synthesized magnetite encapsulated polymer latex particles exhibit excellent colloidal stability and strong magnetic properties, and are of a size that makes them technologically relevant. This novel method may be readily extended to the preparation of multiple combinations of different polymers and encapsulated materials.

  7. Introduction of biotin or folic acid into polypyrrole magnetite core-shell nanoparticles

    SciTech Connect

    Nan, Alexandrina; Turcu, Rodica; Liebscher, Jürgen

    2013-11-13

    In order to contribute to the trend in contemporary research to develop magnetic core shell nanoparticles with better properties (reduced toxicity, high colloidal and chemical stability, wide scope of application) in straightforward and reproducible methods new core shell magnetic nanoparticles were developed based on polypyrrole shells functionalized with biotin and folic acid. Magnetite nanoparticles stabilized by sebacic acid were used as magnetic cores. The morphology of magnetite was determined by transmission electron microscopy TEM, while the chemical structure investigated by FT-IR.

  8. Magnetite Nucleation in Mantle Xenoliths During Quasi-Adiabatic Ascent

    NASA Astrophysics Data System (ADS)

    Walsh, K. B., Jr.; Filiberto, J.; Friedman, S. A.; Knafelc, J.; Conder, J. A.; Ferre, E. C.; Khakhalova, E.; Feinberg, J. M.; Neal, C. R.; Ionov, D. A.; Hernandez, F. M.

    2014-12-01

    Can magnetite be a stable phase in the lithospheric mantle? Equilibrium-based thermodynamic calculations and petrologic models predict that it should not be stable. Studies of mantle xenoliths during the 1980s concluded that even though there were rare exceptions, mantle rocks do not host sufficient concentrations of ferromagnetic minerals and are too hot to allow any magnetic remanence. Thus, conventional wisdom dictates that the Moho constitutes a fundamental magnetic boundary. Yet, growing evidence from a more complete global mantle xenolith survey indicates the presence of ferromagnetic minerals in mantle materials. Examination of mantle xenoliths devoid of serpentinization and meteoric alteration show the presence of ferromagnetic minerals within primary silicate mineral phases, including olivine, pyroxene, and spinel. Nucleation of these magnetic minerals could occur at three different stages: in-situ in the mantle, upon ascent, and at the surface. This study reports the results of laboratory-based quasi-adiabatic decompression experiments that aim to simulate the ascent of mantle xenoliths through the lithosphere and test if magnetite growth is promoted during the process. The starting material for these experiments is San Carlos olivine, which holds a magnetic remanence of less than ~10-10 A/m2-1kg2 (the detection limit of the vibrating sample magnetometer). This low starting remanence will allow us to identify whether new magnetic minerals are formed during the decompression experiments using either vibrating sample magnetometry or SQUID-based rock magnetometers. All olivine grains in these experiments were hand-picked under a light microscope in an effort to avoid the inclusion of grains with spurious magnetic minerals. Olivine powders from these carefully selected grains will be used to represent average mantle olivine compositions (Fo90-Fo92). Experiments will start at 1 GPa and be decompressed to 0.3 GPa over 60 hrs at constant temperature (1200° C

  9. Multiple pure tone noise prediction

    NASA Astrophysics Data System (ADS)

    Han, Fei; Sharma, Anupam; Paliath, Umesh; Shieh, Chingwei

    2014-12-01

    This paper presents a fully numerical method for predicting multiple pure tones, also known as “Buzzsaw” noise. It consists of three steps that account for noise source generation, nonlinear acoustic propagation with hard as well as lined walls inside the nacelle, and linear acoustic propagation outside the engine. Noise generation is modeled by steady, part-annulus computational fluid dynamics (CFD) simulations. A linear superposition algorithm is used to construct full-annulus shock/pressure pattern just upstream of the fan from part-annulus CFD results. Nonlinear wave propagation is carried out inside the duct using a pseudo-two-dimensional solution of Burgers' equation. Scattering from nacelle lip as well as radiation to farfield is performed using the commercial solver ACTRAN/TM. The proposed prediction process is verified by comparing against full-annulus CFD simulations as well as against static engine test data for a typical high bypass ratio aircraft engine with hardwall as well as lined inlets. Comparisons are drawn against nacelle unsteady pressure transducer measurements at two axial locations as well as against near- and far-field microphone array measurements outside the duct. This is the first fully numerical approach (no experimental or empirical input is required) to predict multiple pure tone noise generation, in-duct propagation and far-field radiation. It uses measured blade coordinates to calculate MPT noise.

  10. Effects of pH and anions on the sorption of selenium ions onto magnetite.

    PubMed

    Kim, Seung Soo; Min, Je Ho; Lee, Jae Kwang; Baik, Min Hoon; Choi, Jong-Won; Shin, Hyung Seon

    2012-02-01

    This study analyzes the influence of carbonate and silicate, which are generally abundant in granitic groundwater, on the sorption of selenium ions onto magnetite in order to understand the behaviors of selenium in a radioactive waste repository. Selenite was sorbed onto magnetite very well below pH 10, but silicate and carbonate hindered the sorption of selenite onto magnetite. On the other hand, little selenate was sorbed onto magnetite in neutral and weak alkaline solutions of 0.02 M NaNO(3) or NaClO(4), matching the ionic strength in a granitic groundwater, even though silicate or carbonate was not contained in the solutions. The surface complexation constants between selenite and magnetite were obtained by using a geochemical program, FITEQL 4.0, from the experimental data, and the formation of an inner-sphere surface complex such as =FeOSeO(2)(-) was suggested for the sorption of selenite onto magnetite from the diffuse double layer model calculation.

  11. Amyloid Aβ 42, a promoter of magnetite nanoparticle formation in Alzheimer’s disease

    NASA Astrophysics Data System (ADS)

    Bogachan Tahirbegi, Islam; Pardo, Wilmer Alfonso; Alvira, Margarita; Mir, Mònica; Samitier, Josep

    2016-11-01

    The accumulation of iron oxides—mainly magnetite—with amyloid peptide is a key process in the development of Alzheimer’s disease (AD). However, the mechanism for biogeneration of magnetite inside the brain of someone with AD is still unclear. The iron-storing protein ferritin has been identified as the main magnetite-storing molecule. However, accumulations of magnetite in AD are not correlated with an increase in ferritin, leaving this question unresolved. Here we demonstrate the key role of amyloid peptide Aβ 42, one of the main hallmarks of AD, in the generation of magnetite nanoparticles in the absence of ferritin. The capacity of amyloid peptide to bind and concentrate iron hydroxides, the basis for the formation of magnetite, benefits the spontaneous synthesis of these nanoparticles, even under unfavorable conditions for their formation. Using scanning and transmission electron microscopy, electron energy loss spectroscopy and magnetic force microscopy we characterized the capacity of amyloid peptide Aβ 42 to promote magnetite formation.

  12. Quantum dot capped magnetite nanorings as high performance nanoprobe for multiphoton fluorescence and magnetic resonance imaging.

    PubMed

    Fan, Hai-Ming; Olivo, Malini; Shuter, Borys; Yi, Jia-Bao; Bhuvaneswari, Ramaswamy; Tan, Hui-Ru; Xing, Gui-Chuan; Ng, Cheng-Teng; Liu, Lei; Lucky, Sasidharan S; Bay, Boon-Huat; Ding, Jun

    2010-10-27

    In the present study, quantum dot (QD) capped magnetite nanorings (NRs) with a high luminescence and magnetic vortex core have been successfully developed as a new class of magnetic-fluorescent nanoprobe. Through electrostatic interaction, cationic polyethylenimine (PEI) capped QD have been firmly graft into negatively charged magnetite NRs modified with citric acid on the surface. The obtained biocompatible multicolor QD capped magnetite NRs exhibit a much stronger magnetic resonance (MR) T2* effect where the r2* relaxivity and r2*/r1 ratio are 4 times and 110 times respectively larger than those of a commercial superparamagnetic iron oxide. The multiphoton fluorescence imaging and cell uptake of QD capped magnetite NRs are also demonstrated using MGH bladder cancer cells. In particular, these QD capped magnetite NRs can escape from endosomes and be released into the cytoplasm. The obtained results from these exploratory experiments suggest that the cell-penetrating QD capped magnetite NRs could be an excellent dual-modality nanoprobe for intracellular imaging and therapeutic applications. This work has shown great potential of the magnetic vortex core based multifunctional nanoparticle as a high performance nanoprobe for biomedical applications.

  13. Acceleration of microwave-assisted enzymatic digestion reactions by magnetite beads.

    PubMed

    Chen, Wei-Yu; Chen, Yu-Chie

    2007-03-15

    In this study, we demonstrated that microwave-assisted enzymatic digestion could be greatly accelerated by multifunctional magnetite beads. The acceleration of microwave-assisted enzymatic digestion by the presence of the magnetite beads was attributable to several features of the beads. Their capacity to absorb microwave radiation leads to rapid heating of the beads. Furthermore, their negatively charged functionalities cause adsorption of proteins with opposite charges onto their surfaces by electrostatic interactions, leading to a concentration on the surfaces of the beads of proteins present in trace amounts in the solution. The adsorbed proteins are denatured and hence rendered vulnerable to enzymatic digestion and are digested on the beads. For microwave heating, 30 s was sufficient for carrying out the tryptic digestion of cytochrome c, in the presence of magnetite beads, while 1 min was adequate for tryptic digestion of myoglobin. The digestion products were characterized by MALDI-MS. This rapid enzymatic digestion allowed the entire time for identification of proteins to be greatly reduced. Furthermore, specific proteins present in trace quantities were enriched from the sample on the magnetite beads and could be rapidly isolated from the sample by employing an external magnetic field. These multiple roles of magnetite beads, as the absorber for microwave irradiation, the concentrating probe, and the agent for unfolding proteins, contributed to their capability of accelerating microwave-assisted enzymatic digestion. We also demonstrated that trypsin immobilized magnetite beads were suitable for use in microwave-assisted enzymatic digestion.

  14. Magnetic and structural properties of magnetite in radular teeth of chiton Acanthochiton rubrolinestus.

    PubMed

    Han, Yunan; Liu, Chuanlin; Zhou, Dong; Li, Fashen; Wang, Yong; Han, Xiufeng

    2011-04-01

    The teeth of the Polyplacophora Chiton Acanthochiton Rubrolinestus contain biomineralized magnetite crystallites whose biological functions in relation to structure and magnetic properties are not well understood. Here, using superconducting quantum interference device (SQUID) magnetometry, we find that the saturation magnetization (σ(s)) and the Verwey transition temperature (T(v)) of tooth particles are 78.4 emu/g and 105 K, respectively. These values are below those of the stoichiometric magnetite. An in situ examination of the structure of the magnetite-bearing region within an individual tooth using high-resolution transmission electron microscopy indicates magnetite microcrystals form electron dense polycrystalline sheets with typical lengths of about 800 nm and widths of about 150 nm. These polycrystalline sheets are arranged regularly along the longitudinal direction of the tooth cutting surface. In addition, the crystallites in polycrystalline sheets take on generally good crystallinity. The magnetic microstructures of in situ magnetic force microscopy demonstrate that the [111] easy direction of magnetite microcrystals are aligned along the length of the tooth, whereas the [111] direction is parallel to the thickness of the tooth. Both Mössbauer spectra and magnetization versus temperature measurements under field cooled and zero-field cooled conditions do not detect superparamagnetic magnetite crystallites in the mature major lateral tooth particles of this chiton.

  15. Estimation of Sintering Kinetics of Oxidized Magnetite Pellet Using Optical Dilatometer

    NASA Astrophysics Data System (ADS)

    Sandeep Kumar, T. K.; Viswanathan, Neelakantan Nurni; Ahmed, Hesham M.; Andersson, Charlotte; Björkman, Bo

    2015-04-01

    The quality of magnetite pellet is primarily determined by the physico-chemical changes the pellet undergoes as it makes excursion through the gaseous and thermal environment in the induration furnace. Among these physico-chemical processes, the oxidation of magnetite phase and the sintering of oxidized magnetite (hematite) and magnetite (non-oxidized) phases are vital. Rates of these processes not only depend on the thermal and gaseous environment the pellet gets exposed in the induration reactor but also interdependent on each other. Therefore, a systematic study should involve understanding these processes in isolation to the extent possible and quantify them seeking the physics. With this motivation, the present paper focusses on investigating the sintering kinetics of oxidized magnetite pellet. For the current investigation, sintering experiments were carried out on pellets containing more than 95 pct magnetite concentrate from LKAB's mine, dried and oxidized to completion at sufficiently low temperature to avoid sintering. The sintering behavior of this oxidized pellet is quantified through shrinkage captured by Optical Dilatometer. The extent of sintering characterized by sintering ratio found to follow a power law with time i.e., Kt n . The rate constant K for sintering was determined for different temperatures from isothermal experiments. The rate constant, K, varies with temperature as and the activation energy ( Q) and reaction rate constant ( K') are estimated. Further, the sintering kinetic equation was also extended to a non-isothermal environment and validated using laboratory experiments.

  16. Stability of magnetite nanoparticles with different coatings in a simulated blood plasma

    NASA Astrophysics Data System (ADS)

    Favela-Camacho, Sarai E.; Pérez-Robles, J. Francisco; García-Casillas, Perla E.; Godinez-Garcia, Andrés

    2016-07-01

    Magnetite nanoparticles (MNPs) have demonstrated to be a potential platform for simultaneous anticancer drug delivery and magnetic resonance imaging (MRI). However, magnetite is unstable at the blood plasma conditions. Therefore, to study their stability in a broad range of particle size, the MNPs were synthesized using two methods, the fast injection co-precipitation method (FIC) and the reflux co-precipitation method (RC). The MNPs obtained by the RC and the FIC methods have an average size of agglomerates of 200 and 45 nm respectively. They were dispersed using sodium citrate as surfactant and were coated with silica and chitosan. A total of four kind of coated MNPs were synthesized: magnetite/sodium citrate, magnetite/silica, magnetite/sodium citrate/silica and magnetite/sodium citrate/silica/chitosan. Different samples of the coated MNPs were immersed in a simulated blood plasma solution (Phosphate-Buffered Saline, PBS, Gibco®), for periods of 24, 48 and 72 h. Inductively coupled plasma (ICP) technique was used to analyze the composition of the simulated plasma after those periods of time. The obtained results suggest that the uncoated samples showed an appreciable weight loss, and the iron composition in the simulated plasma increased. This last means that the used coatings avoid iron dissolution from the MNPs.

  17. Temperature-dependent structure of Tb-doped magnetite nanoparticles

    SciTech Connect

    Rice, Katherine P.; Russek, Stephen E. Shaw, Justin M.; Usselman, Robert J.; Evarts, Eric R.; Silva, Thomas J.; Nembach, Hans T.; Geiss, Roy H.; Arenholz, Elke; Idzerda, Yves U.

    2015-02-09

    High quality 5 nm cubic Tb-doped magnetite nanoparticles have been synthesized by a wet-chemical method to investigate tailoring of magnetic properties for imaging and biomedical applications. We show that the Tb is incorporated into the octahedral 3+ sites. High-angle annular dark-field microscopy shows that the dopant is well-distributed throughout the particle, and x-ray diffraction measurements show a small lattice parameter shift with the inclusion of a rare-earth dopant. Magnetization and x-ray magnetic circular dichroism data indicate that the Tb spins are unpolarized and weakly coupled to the iron spin lattice at room temperature, and begin to polarize and couple to the iron oxide lattice at temperatures below 50 K. Broadband ferromagnetic resonance measurements show no increase in magnetic damping at room temperature for Tb-doped nanoparticles relative to undoped nanoparticles, further confirming weak coupling between Fe and Tb spins at room temperature. The Gilbert damping constant, α, is remarkably low for the Tb-doped nanoparticles, with α = 0.024 ± 0.003. These nanoparticles, which have a large fixed moment, a large fluctuating moment and optically active rare-earth elements, are potential high-relaxivity T1 and T2 MRI agents with integrated optical signatures.

  18. Temperature-dependent structure of Tb-doped magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Rice, Katherine P.; Russek, Stephen E.; Geiss, Roy H.; Shaw, Justin M.; Usselman, Robert J.; Evarts, Eric R.; Silva, Thomas J.; Nembach, Hans T.; Arenholz, Elke; Idzerda, Yves U.

    2015-02-01

    High quality 5 nm cubic Tb-doped magnetite nanoparticles have been synthesized by a wet-chemical method to investigate tailoring of magnetic properties for imaging and biomedical applications. We show that the Tb is incorporated into the octahedral 3+ sites. High-angle annular dark-field microscopy shows that the dopant is well-distributed throughout the particle, and x-ray diffraction measurements show a small lattice parameter shift with the inclusion of a rare-earth dopant. Magnetization and x-ray magnetic circular dichroism data indicate that the Tb spins are unpolarized and weakly coupled to the iron spin lattice at room temperature, and begin to polarize and couple to the iron oxide lattice at temperatures below 50 K. Broadband ferromagnetic resonance measurements show no increase in magnetic damping at room temperature for Tb-doped nanoparticles relative to undoped nanoparticles, further confirming weak coupling between Fe and Tb spins at room temperature. The Gilbert damping constant, α, is remarkably low for the Tb-doped nanoparticles, with α = 0.024 ± 0.003. These nanoparticles, which have a large fixed moment, a large fluctuating moment and optically active rare-earth elements, are potential high-relaxivity T1 and T2 MRI agents with integrated optical signatures.

  19. Improving biohydrogen production using Clostridium beijerinckii immobilized with magnetite nanoparticles.

    PubMed

    Seelert, Trevor; Ghosh, Dipankar; Yargeau, Viviane

    2015-05-01

    In order to supplement the need for alternative energy resources within the near future, enhancing the production of biohydrogen with immobilized Clostridium beijerinckii NCIMB8052 was investigated. Magnetite nanoparticles were functionalized, with chitosan and alginic acid polyelectrolytes using a layer-by-layer method, to promote bacterial attachment. Cultivating C. beijerinckii with these nanoparticles resulted in a shorter lag growth phase and increased total biohydrogen production within 100-ml, 250-ml and 3.6-L reactors compared with freely suspended organisms. The greatest hydrogen yield was obtained in the 250-ml reactor with a value of 2.1 ± 0.7 mol H2/mol glucose, corresponding to substrate conversion and energy conversion efficiencies of 52 ± 18 and 10 ± 3 %, respectively. The hydrogen yields obtained using the immobilized bacteria are comparable to values found in literature. However, to make this process viable, further improvements are required to increase the substrate and energy conversion efficiencies.

  20. Water treatment using activated carbon supporting silver and magnetite.

    PubMed

    Valušová, Eva; Vandžurová, Anna; Pristaš, Peter; Antalík, Marián; Javorský, Peter

    2012-01-01

    Recent efforts in water purification have led to the development of novel materials whose unique properties can offer effective biocidal capabilities with greater ease of use and at lower cost. In this study, we introduce a novel procedure for the preparation of activated carbon (charcoal) composite in which magnetite and silver are incorporated (MCAG); we also describe the use of this material for the disinfection of surface water. The formation process of magnetic MCAG composite was studied using ultraviolet-visible spectroscopy. The results demonstrated the high sorption efficiency of AgNO₃ to magnetic activated carbon. The antimicrobial capabilities of the prepared MCAG were examined and the results clearly demonstrate their inhibitory effect on total river water bacteria and on Pseudomonas koreensis and Bacillus mycoides cultures isolated from river water. The bacterial counts in river water samples were reduced by five orders of magnitude following 30 min of treatment using 1 g l⁻¹ of MCAG at room temperature. The removal of all bacteria from the surface water samples implies that the MCAG material would be a suitable disinfectant for such waters. In combination with its magnetic character, MCAG would be an excellent candidate for the simple ambulatory disinfection of surface water.

  1. Vacancy diffusion in magnetite-hercynite solid solution

    NASA Astrophysics Data System (ADS)

    Yamauchi, Shigeru; Nakamura, Akio; Shimizu, Toshiaki; Fueki, Kazuo

    1983-11-01

    To extend the chemical relaxation technique to ternary oxide systems, theoretical analysis was made to obtain an expression for the chemical diffusion coefficient in terms of the vacancy diffusion coefficient. An equation, D˜ = [ {C O}/{(C 1 + C 2) }] D v( {1}/{2})( {∂ ln P( O2) }/{∂ ln C v}) , was derived. This is similar to the one for the binary oxide system. Chemical relaxation experiments were made on the magnetite-hercynite solid solutions, (Fe 1- yAl y) 3-δO 4 with y = 0.0, 0.067, 0.133, and 0.20, at temperatures between 1300 and 1400°C. The vacancy diffusion coefficient decreased remarkably with an increase in y. The activation energy was found to be 20.8 ± 3.7, 33.5 ± 4.2, 50.4 ± 3.6, and 66.3 ± 4.5 kcal/mole for y = 0.0, 0.067, 0.133, and 0.20, respectively. A strong dependence on y was also found. The dependence of the vacancy diffusion coefficient on y was interpreted to indicate that the jump frequency of cation vacancies is decreased by the introduction of aluminium ion.

  2. Adsorption of copper ion on magnetite-immobilised chitin.

    PubMed

    Wong, K S; Wong, K H; Ng, S; Chung, W K; Wong, P K

    2007-01-01

    The adsorption of Cu2+ from aqueous solution by magnetite-immobilised chitin (MC) was studied in batch mode. Two conventional adsorbents, cation exchange resin (CER) and activated carbon (AC) were used for the comparison. The physicochemical parameters including pH, concentration of adsorbent, temperature and initial Cu2+ concentration were optimised. Under the optimised conditions, the removal efficiencies of Cu2+ for MC, CER and AC were 91.67, 93.36 and 89.16%, respectively. In addition, the removal capacities of Cu2+ for MC, CER and AC were 56.71, 74.84 and 6.55 mg/g, respectively. The adsorption isotherm studies indicated that the adsorptive behaviour of Cu2+ on three adsorbents could be well described by the Langmuir model. The maximum adsorption capacities (qmax) for MC, CER and AC were 53.19, 89.29 and 5.82 mg/g, respectively. The applicability of the kinetic model has been investigated for MC. Experimental results indicated that a pseudo-second-order reaction model provided the best description of the data with a correlation coefficient 0.999 for different initial Cu2+ concentrations. The rate constants were also determined. Various thermodynamic parameters such as standard free energy (DeltaG 0), enthalpy (DeltaH 0) and entropy (DeltaS 0) were calculated for predicting the adsorption nature of MC. The results indicated that this system was a spontaneous and endothermic process.

  3. Lipolytic biocatalyst based on recyclable magnetite-polysiloxane nanoparticles

    NASA Astrophysics Data System (ADS)

    Durdureanu-Angheluta, Anamaria; Ignat, Maurusa-Elena; Maier, Stelian Sergiu; Pricop, Lucia; Coroaba, Adina; Fifere, Adrian; Pinteala, Mariana; Chiriac, Anca

    2014-02-01

    This work presents a novel hydrophobic magnetizable nanosupport able to load and valorize the lipase derived from Candida cylindracea (CCL). Nude magnetite nanoparticles (MP) were coated by covalent binding with an ester-polysiloxane (PS). The chemical composition, dimensions, morphology and magnetic properties of the resulted core-shell nanoparticles (MP-PS-CCL) are analyzed. The amount of immobilized lipase increase when loaded from aqueous solutions of up to 12.8 mg/mL CCL, when a lipolytic activity of 74.76 U/g is achieved. For higher concentrations of the loading solution, the activity of immobilized lipase decreases, probably due to the enzyme steric hindrance. MP-PS-CCL exhibits a good lipolytic activity against 4-nitrophenyl laurate (4-NPL), which allows the kinetic study of lipolysis reaction by measuring the amount of released 4-nitrophenol (4-NP), when working at room temperature, in TRIS buffer (pH 8.2). Even after three months of storage, the product is able to sustain up to 4 reusing cycles.

  4. Novel hybrid nanostructured materials of magnetite nanoparticles and pectin

    NASA Astrophysics Data System (ADS)

    Sahu, Saurabh; Dutta, Raj Kumar

    2011-04-01

    A novel hybrid nanostructured material comprising superparamagnetic magnetite nanoparticles (MNPs) and pectin was synthesized by crosslinking with Ca2+ ions to form spherical calcium pectinate nanostructures, referred as MCPs, which were typically found to be 100-150 nm in size in dried condition, confirmed from transmission electron microscopy and scanning electron microscopy. The uniform size distribution was revealed from dynamic light scattering measurement. In aqueous medium the MCPs showed swelling behavior with an average size of 400 nm. A mechanism of formation of spherical MCPs is outlined constituting a MNP-pectin interface encapsulated by calcium pectinate at the periphery, by using an array of characterization techniques like zeta potential, thermogravimetry, Fourier transformed infrared and X-ray photoelectron spectroscopy. The MCPs were stable in simulated gastrointestinal fluid and ensured minimal loss of magnetic material. They exhibited superparamagnetic behavior, confirmed from zero field cooled and field cooled profiles and showed high saturation magnetization (Ms) of 46.21 emu/g at 2.5 T and 300 K. Ms decreased with increasing precursor pectin concentrations, attributed to quenching of magnetic moments by formation of a magnetic dead layer on the MNPs.

  5. Atomic layer deposition of superparamagnetic and ferrimagnetic magnetite thin films

    SciTech Connect

    Zhang, Yijun; Liu, Ming E-mail: wren@mail.xjtu.edu.cn Ren, Wei E-mail: wren@mail.xjtu.edu.cn; Zhang, Yuepeng; Chen, Xing; Ye, Zuo-Guang E-mail: wren@mail.xjtu.edu.cn

    2015-05-07

    One of the key challenges in realizing superparamagnetism in magnetic thin films lies in finding a low-energy growth way to create sufficiently small grains and magnetic domains which allow the magnetization to randomly and rapidly reverse. In this work, well-defined superparamagnetic and ferrimagnetic Fe{sub 3}O{sub 4} thin films are successfully prepared using atomic layer deposition technique by finely controlling the growth condition and post-annealing process. As-grown Fe{sub 3}O{sub 4} thin films exhibit a conformal surface and poly-crystalline nature with an average grain size of 7 nm, resulting in a superparamagnetic behavior with a blocking temperature of 210 K. After post-annealing in H{sub 2}/Ar at 400 °C, the as-grown α−Fe{sub 2}O{sub 3} sample is reduced to Fe{sub 3}O{sub 4} phase, exhibiting a ferrimagnetic ordering and distinct magnetic shape anisotropy. Atomic layer deposition of magnetite thin films with well-controlled morphology and magnetic properties provides great opportunities for integrating with other order parameters to realize magnetic nano-devices with potential applications in spintronics, electronics, and bio-applications.

  6. IDENTIFICATION OF MAGNETITE IN B-TYPE ASTEROIDS

    SciTech Connect

    Yang Bin; Jewitt, David E-mail: jewitt@ucla.ed

    2010-09-15

    Spectrally blue (B-type) asteroids are rare, with the second discovered asteroid, Pallas, being the largest and most famous example. We conducted a focused, infrared spectroscopic survey of B-type asteroids to search for water-related features in these objects. Our results show that the negative optical spectral slope of some B-type asteroids is due to the presence of a broad absorption band centered near 1.0 {mu}m. The 1 {mu}m band can be matched in position and shape using magnetite (Fe{sub 3}O{sub 4}), which is an important indicator of past aqueous alteration in the parent body. Furthermore, our observations of B-type asteroid (335) Roberta in the 3 {mu}m region reveal an absorption feature centered at 2.9 {mu}m, which is consistent with the absorption due to phyllosilicates (another hydration product) observed in CI chondrites. The new observations suggest that at least some B-type asteroids are likely to have incorporated significant amounts of water ice and to have experienced intensive aqueous alteration.

  7. ac susceptibility study of a magnetite magnetic fluid

    NASA Astrophysics Data System (ADS)

    Ayala-Valenzuela, O. E.; Matutes-Aquino, J. A.; Galindo, J. T. Elizalde; Botez, C. E.

    2009-04-01

    Magnetite nanometric powder was synthesized from metal salts using a coprecipitation technique. The powders were used to produce magnetic fluid via a peptization method, with hydrocarbon Isopar M as liquid carrier and oleic acid as surfactant. The complex magnetic susceptibility χ =χ'+iχ″ was measured as a function of temperature T in steps of 2.5 K from 3 to 298 K for frequencies ranging from f =10 to 10 000 Hz. The magnetic fluid real and imaginary components of the ac susceptibility show a prominent maximum at temperatures that increase with the measuring frequency, which is attributed to a spin-glass-like behavior. The peak temperature Tp1 of χ″ depends on f following the Vogel-Fulcher law f =f0 exp[E /kB(Tp1-T0)], where f0 and E are positive constants and T0 is a parameter related to particle interactions. There is another kind of peak temperature, Tp2, in the loss factor tan δ =χ″/χ' which is related to a magnetic aftereffect. The peak temperature Tp2 is far less than Tp1 and shows an Arrhenius-type dependence on f.

  8. Enhanced thermal stability of phosphate capped magnetite nanoparticles

    SciTech Connect

    Muthukumaran, T.; Philip, John

    2014-06-14

    We have studied the effect of phosphate capping on the high temperature thermal stability and magnetic properties of magnetite (Fe{sub 3}O{sub 4}) nanoparticles synthesized through a single-step co-precipitation method. The prepared magnetic nanoparticles are characterized using various techniques. When annealed in air, the phosphate capped nanoparticle undergoes a magnetic to non-magnetic phase transition at a temperature of 689 °C as compared to 580 °C in the uncoated nanoparticle of similar size. The observed high temperature phase stability of phosphate capped nanoparticle is attributed to the formation of a phosphocarbonaceous shell over the nanoparticles, which acts as a covalently attached protective layer and improves the thermal stability of the core material by increasing the activation energy. The phosphocarbonaceous shell prevents the intrusion of heat, oxygen, volatiles, and mass into the magnetic core. At higher temperatures, the coalescence of nanoparticles occurs along with the restructuring of the phosphocarbonaceous shell into a vitreous semisolid layer on the nanoparticles, which is confirmed from the small angle X-ray scattering, Fourier transform infra red spectroscopy, and transmission electron microscopy measurements. The probable mechanism for the enhancement of thermal stability of phosphocarbonaceous capped nanoparticles is discussed.

  9. Synthesis and Characterization of Magnetite/Zinc Oxide and Magnetite/Zinc Manganese Sulfide Core-Shell Heterostructured Nanoparticles

    NASA Astrophysics Data System (ADS)

    Beltran Huarac, Juan Carlos

    Currently, core-shell heterostructured nanosystems are emerging as next-generation materials due to their potential multifunctionalities in contrast with the more limited single-component counterparts. Systematic investigation of core-shell nanostructures of ZnO and bare-and-doped-Mn2+ ZnS nanocrystals on the surface of magnetite nanoparticles (Fe3O 4) was performed. The magnetite cores were prepared via the co-precipitation method and were next treated with an appropriate surfactant. The Fe3 O4/(S) (S=ZnO and ZnMnS) core-shell nanoparticles were obtained by an aqueous solution method at room temperature. The structural tests were carried out using an x-ray diffractometer (XRD) which showed the development of crystalline phases of cubic Fe3O4, hexagonal ZnO wurtzite and cubic ZnS. These patterns also established the matching between bare and doped-Mn2+ ZnS diffraction peaks. Broadness of the diffraction peaks evidenced the formation of nanosize phases. The transmission electron microscopy (TEM) confirmed the deposition of a semiconductor shell on the surface of superparamagnetic Fe3O4 nanoparticles. The UV-Vis spectra showed the presence of a strong absorption peak and photoluminescence (PL) spectra displayed the emission peak due to excitonic recombination and a very weak defect-related emission peak suggesting the rearrangement of electronic configuration in the core-shell structures when ZnO is surrounding the core. These spectra also displayed the strong emission peak attributed to paramagnetic ion Mn2+ when acted as dopant in the host ZnS structure. The study of the magnetic properties was carried out using a vibrating sample magnetometer (VSM) which evidenced considerable drop in the saturation magnetization of the Fe3O4/ZnO nanoparticles in comparison to individual Fe3O4 ones. For the Fe3O4/ZnMnS system a slight ferromagnetic behavior at room temperature was observed. The chemical composition of these nanomaterials was performed by x-ray photoelectron

  10. 76 FR 69284 - Pure Magnesium From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-08

    ... COMMISSION Pure Magnesium From China Determination On the basis of the record \\1\\ developed in the subject... order on pure magnesium from China would be likely to lead to continuation or recurrence of material... USITC Publication 4274 (October 2011), entitled Pure Magnesium from China: Investigation No....

  11. The synthesis and characterization of poly(γ-glutamic acid)-coated magnetite nanoparticles and their effects on antibacterial activity and cytotoxicity

    NASA Astrophysics Data System (ADS)

    Inbaraj, B. Stephen; Kao, T. H.; Tsai, T. Y.; Chiu, C. P.; Kumar, R.; Chen, B. H.

    2011-02-01

    Magnetite nanoparticles (MNPs) modified with sodium and calcium salts of poly(γ-glutamic acid) (NaPGA and CaPGA) were synthesized by the coprecipitation method, followed by characterization and evaluation of their antibacterial and cytotoxic effects. Superparamagnetic MNPs are particularly attractive for magnetic driving as well as bacterial biofilm and cell targeting in in vivo applications. Characterization of synthesized MNPs by the Fourier transform infrared spectra and magnetization curves confirmed the PGA coating on MNPs. The mean diameter of NaPGA- and CaPGA-coated MNPs as determined by transmission electron microscopy was 11.8 and 14 nm, respectively, while the x-ray diffraction pattern revealed the as-synthesized MNPs to be pure magnetite. Based on agar dilution assay, both NaPGA- and CaPGA-coated MNPs showed a lower minimum inhibitory concentration in Salmonella enteritidis SE 01 than the commercial antibiotics linezolid and cefaclor, but the former was effective against Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 10832, whereas the latter was effective against Escherichia coli O157:H7 TWC 01. An in vitro cytotoxicity study in human skin fibroblast cells as measured by MTT assay implied the as-synthesized MNPs to be nontoxic. This outcome demonstrated that both γ-PGA-modified MNPs are cytocompatible and possess antibacterial activity in vitro, and thereby should be useful in in vivo studies for biomedical applications.

  12. Core-shell magnetite-silica dithiocarbamate-derivatised particles achieve the Water Framework Directive quality criteria for mercury in surface waters.

    PubMed

    Lopes, C B; Figueira, P; Tavares, D S; Lin, Z; Daniel-da-Silva, A L; Duarte, A C; Rocha, J; Trindade, T; Pereira, E

    2013-09-01

    The sorption capacity of nanoporous titanosilicate Engelhard titanosilicate number 4 (ETS-4) and silica-coated magnetite particles derivatised with dithiocarbamate groups towards Hg(II) was evaluated and compared in spiked ultra-pure and spiked surface-river water, for different batch factors. In the former, and using a batch factor of 100 m(3)/kg and an initial Hg(II) concentrations matching the maximum allowed concentration in an effluent discharge, both materials achieve Hg(II) uptake efficiencies in excess of 99 % and a residual metal concentration lower than the guideline value for drinking water quality. For the surface-river water and the same initial concentration, the Hg(II) uptake efficiency of magnetite particles is outstanding, achieving the quality criteria established by the Water Framework Directive (concerning Hg concentration in surface waters) using a batch factor of 50 m(3)/kg, while the efficiency of ETS-4 is significantly inferior. The dissimilar sorbents' Hg(II) removal efficiency is attributed to different uptake mechanisms. This study also highlights the importance of assessing the effective capacity of the sorbents under realistic conditions in order to achieve trustable results.

  13. Effects of common groundwater ions on chromate removal by magnetite: Importance of chromate adsorption

    SciTech Connect

    Meena, Amanda H.; Arai, Yuji

    2016-04-29

    Reductive precipitation of hexavalent chromium (Cr(VI)) with magnetite is a well-known Cr(VI) remediation method to improve water quality. The rapid (< a few hr) reduction of soluble Cr(VI) to insoluble Cr(III) species by Fe(II) in magnetite has been the primary focus of the Cr(VI) removal process in the past. However, the contribution of simultaneous Cr(VI) adsorption processes in aged magnetite has been largely ignored, leaving uncertainties in evaluating the application of in situ Cr remediation technologies for aqueous systems. In this study, effects of common groundwater ions (i.e., nitrate and sulfate) on Cr(VI) sorption to magnetite were investigated using batch geochemical experiments in conjunction with X-ray absorption spectroscopy. As a result, in both nitrate and sulfate electrolytes, batch sorption experiments showed that Cr(VI) sorption decreases with increasing pH from 4 to 8. In this pH range, Cr(VI) sorption decreased with increasing ionic strength of sulfate from 0.01 to 0.1 M whereas nitrate concentrations did not alter the Cr(VI) sorption behavior. This indicates the background electrolyte specific Cr(VI) sorption process in magnetite. Under the same ionic strength, Cr(VI) removal in sulfate containing solutions was greater than that in nitrate solutions. This is because the oxidation of Fe(II) by nitrate is more thermodynamically favorable than by sulfate, leaving less reduction capacity of magnetite to reduce Cr(VI) in the nitrate media. X-ray absorption spectroscopy analysis supports the macroscopic evidence that more than 75 % of total Cr on the magnetite surfaces was adsorbed Cr(VI) species after 48 h. In conclusion, this experimental geochemical study showed that the adsorption process of Cr(VI) anions was as important as the reductive precipitation of Cr(III) in describing the removal of Cr(VI) by magnetite, and these interfacial adsorption processes could be impacted by common groundwater ions like sulfate and nitrate. The results of

  14. Effects of common groundwater ions on chromate removal by magnetite: Importance of chromate adsorption

    DOE PAGES

    Meena, Amanda H.; Arai, Yuji

    2016-04-29

    Reductive precipitation of hexavalent chromium (Cr(VI)) with magnetite is a well-known Cr(VI) remediation method to improve water quality. The rapid (< a few hr) reduction of soluble Cr(VI) to insoluble Cr(III) species by Fe(II) in magnetite has been the primary focus of the Cr(VI) removal process in the past. However, the contribution of simultaneous Cr(VI) adsorption processes in aged magnetite has been largely ignored, leaving uncertainties in evaluating the application of in situ Cr remediation technologies for aqueous systems. In this study, effects of common groundwater ions (i.e., nitrate and sulfate) on Cr(VI) sorption to magnetite were investigated using batchmore » geochemical experiments in conjunction with X-ray absorption spectroscopy. As a result, in both nitrate and sulfate electrolytes, batch sorption experiments showed that Cr(VI) sorption decreases with increasing pH from 4 to 8. In this pH range, Cr(VI) sorption decreased with increasing ionic strength of sulfate from 0.01 to 0.1 M whereas nitrate concentrations did not alter the Cr(VI) sorption behavior. This indicates the background electrolyte specific Cr(VI) sorption process in magnetite. Under the same ionic strength, Cr(VI) removal in sulfate containing solutions was greater than that in nitrate solutions. This is because the oxidation of Fe(II) by nitrate is more thermodynamically favorable than by sulfate, leaving less reduction capacity of magnetite to reduce Cr(VI) in the nitrate media. X-ray absorption spectroscopy analysis supports the macroscopic evidence that more than 75 % of total Cr on the magnetite surfaces was adsorbed Cr(VI) species after 48 h. In conclusion, this experimental geochemical study showed that the adsorption process of Cr(VI) anions was as important as the reductive precipitation of Cr(III) in describing the removal of Cr(VI) by magnetite, and these interfacial adsorption processes could be impacted by common groundwater ions like sulfate and nitrate. The

  15. Redox equilibria of iron oxides in aqueous-based magnetite dispersions: effect of pH and redox potential.

    PubMed

    Pang, Suh Cem; Chin, Suk Fun; Anderson, Marc A

    2007-07-01

    The effect of pH and redox potential on the redox equilibria of iron oxides in aqueous-based magnetite dispersions was investigated. The ionic activities of each dissolved iron species in equilibrium with magnetite nanoparticles were determined and contoured within the Eh-pH framework of a composite stability diagram. Both standard redox potentials and equilibrium constants for all major iron oxide redox equilibria in magnetite dispersions were found to differ from values reported for noncolloidal systems. The "triple point" position of redox equilibrium among Fe(II) ions, magnetite, and hematite shifted to a higher standard redox potential and an equilibrium constant which was several orders of magnitude higher. The predominant area of magnetite stability was enlarged to cover a wider range of both pH and redox potentials as compared to that of a noncolloidal magnetite system.

  16. Scintillation properties of pure CaF 2

    NASA Astrophysics Data System (ADS)

    Mikhailik, V. B.; Kraus, H.; Imber, J.; Wahl, D.

    2006-10-01

    The temperature dependence of the decay time and scintillation light yield of pure CaF 2 crystal was measured over the temperature range 8-305 K using the multiphoton coincidence counting technique. Pure CaF 2 exhibits emission of triplet self-trapped excitons at 280 nm with a slow decay, the time constant of which changes significantly with temperature. The main decay time constant increases by three orders of magnitude when cooled, from 0.96±0.06 μs at 295 K to 930±40 μs at 8 K. The results obtained demonstrate that the scintillation light yield of pure CaF 2 increases with decreasing temperature down to 20 K below which it is roughly constant. At low temperatures the light yield of CaF 2 is estimated to be 60% relative to that of pure CaWO 4. It is concluded that undoped calcium fluoride is a very attractive target material for experimental searches for rare events based on the detection of phonon and scintillation signals.

  17. Platinum-group element geochemistry of the Zhuqing Fe-Ti-V oxide ore-bearing mafic intrusions in western Yangtze Block, SW China: control of platinum-group elements by magnetite

    NASA Astrophysics Data System (ADS)

    Fan, Hong-Peng; Zhu, Wei-Guang; Zhong, Hong; Bai, Zhong-Jie; He, De-Feng; Ye, Xian-Tao; Chen, Cai-Jie; Cao, Chong-Yong

    2014-06-01

    Platinum-group element (PGE) geochemistry combined with elemental geochemistry and magnetite compositions are reported for the Mesoproterozoic Zhuqing Fe-Ti-V oxide ore-bearing mafic intrusions in the western Yangtze Block, SW China. All the Zhuqing gabbros display extremely low concentrations of chalcophile elements and PGEs. The oxide-rich gabbros contain relatively higher contents of Cr, Ni, Ir, Ru, Rh, and lower contents of Pt and Pd than the oxide-poor gabbros. The abundances of whole-rock concentrations of Ni, Ir, Ru, and Rh correlate well with V contents in the Zhuqing gabbros, implying that the distributions of these elements are controlled by magnetite. The fractionation between Ir-Ru-Rh and Pt-Pd in the Zhuqing gabbros is mainly attributed to fractional crystallization of chromite and magnetite, whereas Ru anomalies are mainly due to variable degrees of compatibility of PGE in magnetite. The order of relative incompatibility of PGEs is calculated to be Pd < Pt < Rh < Ir < Ru. The very low PGE contents and Cu/Zr ratios and high Cu/Pd ratios suggest initially S-saturated magma parents that were highly depleted in PGE, which mainly formed due to low degrees of partial melting leaving sulfides concentrating PGEs behind in the mantle. Moreover, the low MgO, Ni, Ir and Ru contents and high Cu/Ni and Pd/Ir ratios for the gabbros suggest a highly evolved parental magma. Fe-Ti oxides fractionally crystallized from the highly evolved magma and subsequently settled in the lower sections of the magma chamber, where they concentrated and formed Fe-Ti-V oxide ore layers at the base of the lower and upper cycles. Multiple episodes of magma replenishment in the magma chamber may have been involved in the formation of the Zhuqing intrusions.

  18. Ferrous Iron Binding Key to Mms6 Magnetite Biomineralisation: A Mechanistic Study to Understand Magnetite Formation Using pH Titration and NMR Spectroscopy

    PubMed Central

    Rawlings, Andrea E.; Bramble, Jonathan P.; Hounslow, Andrea M.; Williamson, Michael P.; Monnington, Amy E.; Cooke, David J.

    2016-01-01

    Abstract Formation of magnetite nanocrystals by magnetotactic bacteria is controlled by specific proteins which regulate the particles’ nucleation and growth. One such protein is Mms6. This small, amphiphilic protein can self‐assemble and bind ferric ions to aid in magnetite formation. To understand the role of Mms6 during in vitro iron oxide precipitation we have performed in situ pH titrations. We find Mms6 has little effect during ferric salt precipitation, but exerts greatest influence during the incorporation of ferrous ions and conversion of this salt to mixed‐valence iron minerals, suggesting Mms6 has a hitherto unrecorded ferrous iron interacting property which promotes the formation of magnetite in ferrous‐rich solutions. We show ferrous binding to the DEEVE motif within the C‐terminal region of Mms6 by NMR spectroscopy, and model these binding events using molecular simulations. We conclude that Mms6 functions as a magnetite nucleating protein under conditions where ferrous ions predominate. PMID:27112228

  19. Pure climb creep mechanism drives flow in Earth's lower mantle.

    PubMed

    Boioli, Francesca; Carrez, Philippe; Cordier, Patrick; Devincre, Benoit; Gouriet, Karine; Hirel, Pierre; Kraych, Antoine; Ritterbex, Sebastian

    2017-03-01

    At high pressure prevailing in the lower mantle, lattice friction opposed to dislocation glide becomes very high, as reported in recent experimental and theoretical studies. We examine the consequences of this high resistance to plastic shear exhibited by ringwoodite and bridgmanite on creep mechanisms under mantle conditions. To evaluate the consequences of this effect, we model dislocation creep by dislocation dynamics. The calculation yields to an original dominant creep behavior for lower mantle silicates where strain is produced by dislocation climb, which is very different from what can be activated under high stresses under laboratory conditions. This mechanism, named pure climb creep, is grain-size-insensitive and produces no crystal preferred orientation. In comparison to the previous considered diffusion creep mechanism, it is also a more efficient strain-producing mechanism for grain sizes larger than ca. 0.1 mm. The specificities of pure climb creep well match the seismic anisotropy observed of Earth's lower mantle.

  20. Trichloroethylene degradation by persulphate with magnetite as a heterogeneous activator in aqueous solution.

    PubMed

    Ruan, Xiaoxin; Gu, Xiaogang; Lu, Shuguang; Qiu, Zhaofu; Sui, Qian

    2015-01-01

    Iron oxide-magnetite (Fe3O4) as a heterogeneous activator to activate persulphate anions (S2O8(2-)) for trichloroethylene (TCE) degradation was investigated in this study. The experimental results showed that TCE could be completely oxidized within 5 h by using 5 g L(-1) magnetite and 63 mM S2O8(2-), indicating the effectiveness of the process for TCE removal. Various factors of the process, including. (S2O8(2-) and magnetite dosages, and initial solution pH, were evaluated, and TCE degradation fitted well to the pseudo-first-order kinetic model. The calculated kinetic rate constant was increased with increasing S2O8(2-) and magnetite dosages, but it was independent of solution pH. In addition, the changes of magnetite morphology examined by scanning electron microscopy and X-ray powder diffraction, respectively, confirmed the slight corrosion with α-Fe2O3 coated on the magnetite surface. The probe compounds tests clearly identified the generation of the reactive oxygen species in the system. While the free radical quenching studies further demonstrated that •SO4- and •OH were the major radicals responsible for TCE degradation, whereas •O2- contributed less in the system, and therefore the roles of reactive oxygen species on TCE degradation mechanisms were proposed accordingly. To our best knowledge, this is the first time the performance and mechanism of magnetite-activated persulphate oxidation for TCE degradation are reported. The findings of this study provided a new insight into the heterogeneous catalysis mechanism and showed a great potential for the practical application of this technique in in situ TCE-contaminated groundwater remediation.

  1. Fayalite Oxidation Processes: Experimental Evidence for the Stability of Pure Ferric Fayalite?

    NASA Technical Reports Server (NTRS)

    Martin, A. M.; Righter, K.; Keller, L. P.; Medard, E.; Devouard, B.; Rahman, Z.

    2011-01-01

    Olivine is one of the most important minerals in Earth and planetary sciences. Fayalite Fe2(2+)SiO4, the ferrous end-member of olivine, is present in some terrestrial rocks and primitive meteorites (CV3 chondrites). A ferric fayalite (or ferri-fayalite), Fe(2+) Fe2(3+)(SiO4)2 laihunite, has been reported in Earth samples (magnetite ore, metamorphic and volcanic rocks...) and in Martian meteorites (nakhlites). Laihunite was also synthesized at 1 atmosphere between 400 and 700 C. We show evidence for the stability of a pure ferrifayalite end-member and for potential minerals with XFe(3+) between 2/3 and 1.

  2. Montmorillonite-supported magnetite nanoparticles for the removal of hexavalent chromium [Cr(VI)] from aqueous solutions.

    PubMed

    Yuan, Peng; Fan, Mingde; Yang, Dan; He, Hongping; Liu, Dong; Yuan, Aihua; Zhu, JianXi; Chen, TianHu

    2009-07-30

    Montmorillonite-supported magnetite nanoparticles were prepared by co-precipitation and hydrosol method. The obtained materials were characterized by X-ray diffraction, nitrogen adsorption, elemental analysis, differential scanning calorimetry, transmission electron microscopy and X-ray photoelectron spectroscopy. The average sizes of the magnetite nanoparticles without and with montmorillonite support are around 25 and 15 nm, respectively. The montmorillonite-supported magnetite nanoparticles exist on the surface or inside the interparticle pores of clays, with better dispersing and less coaggregation than the ones without montmorillonite support. Batch tests were carried out to investigate the removal mechanism of hexavalent chromium [Cr(VI)] by these synthesized magnetite nanoparticles. The Cr(VI) uptake was mainly governed by a physico-chemical process, which included an electrostatic attraction followed by a redox process in which Cr(VI) was reduced into trivalent chromium. The adsorption of Cr(VI) was highly pH-dependent and the kinetics of the adsorption followed the Pseudo-second-order model. The adsorption data of unsupported and clay-supported magnetite nanoparticles fit well with the Langmuir and Freundlich isotherm equations. The montmorillonite-supported magnetite nanoparticles showed a much better adsorption capacity per unit mass of magnetite (15.3mg/g) than unsupported magnetite (10.6 mg/g), and were more thermally stable than their unsupported counterparts. These fundamental results demonstrate that the montmorillonite-supported magnetite nanoparticles are readily prepared, enabling promising applications for the removal of Cr(VI) from aqueous solution.

  3. One-step continuous synthesis of functionalized magnetite nanoflowers

    NASA Astrophysics Data System (ADS)

    Thomas, G.; Demoisson, F.; Chassagnon, R.; Popova, E.; Millot, N.

    2016-04-01

    For the first time, functionalized magnetite nanoparticles (Fe3O4 NPs) that form aggregates with a nanoflower morphology were synthesized using a rapid (11 s) one-step continuous hydrothermal process, which was recently modified, and their application as a T 2 magnetic resonance imaging (MRI) contrast agent was evaluated. The nanoparticles functionalized with 3,4-dihydroxy-L-phenylalanine (LDOPA) or 3,4-dihydroxyhydrocinnamic acid (DHCA) consisted of small crystallites of approximately 15 nm of diameter that assembled to form flower-shaped aggregate structures. The Fe3O4-LDOPA nanoflowers exhibited a high transverse relaxivity, r 2 of 418 ± 10 l mmolFe -1 s-1 at 3 T owing to magnetic dipolar interactions, which is twice as that of the commercial Feridex®/Endorem®. The prepared nanostructures were compared with bare Fe3O4 NPs and citrated Fe3O4 NPs. DHCA, LDOPA, and citric acid (CA) were found to have an anti-oxidizing effect and to influence the crystallite size and the lattice parameter of the NPs. DHCA and LDOPA increased the crystallite size, whereas CA decreased it. Surface modification increased the colloidal stability of NPs as compared to bare NPs. Nanoflower suspensions of Fe3O4-LDOPA NPs were found to be stable in the phosphate-buffered saline, saline medium, and minimal essential medium and formed aggregates of sizes smaller than 120 nm. All samples were found to be superparamagnetic in nature and the highest saturation magnetization was obtained for the Fe3O4-LDOPA samples. These NPs can bind to polymers such as PEG, and to fluorescent and chelating agents owing to the presence of free -NH2 or -COOH groups on the surface of NPs, allowing their use in dual imaging applications.

  4. Direct observations of field-induced assemblies in magnetite ferrofluids

    NASA Astrophysics Data System (ADS)

    Mousavi, N. S. Susan; Khapli, Sachin D.; Kumar, Sunil

    2015-03-01

    Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ≤ 10 nm) is studied with an emphasis on examining the effects of particle concentration (ϕ) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ϕ = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05-0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity.

  5. Microwave resonant and zero-field absorption study of doped magnetite prepared by a co-precipitation method.

    PubMed

    Aphesteguy, Juan Carlos; Jacobo, Silvia E; Lezama, Luis; Kurlyandskaya, Galina V; Schegoleva, Nina N

    2014-06-19

    Fe3O4 and ZnxFe3-xO4 pure and doped magnetite magnetic nanoparticles (NPs) were prepared in aqueous solution (Series A) or in a water-ethyl alcohol mixture (Series B) by the co-precipitation method. Only one ferromagnetic resonance line was observed in all cases under consideration indicating that the materials are magnetically uniform. The shortfall in the resonance fields from 3.27 kOe (for the frequency of 9.5 GHz) expected for spheres can be understood taking into account the dipolar forces, magnetoelasticity, or magnetocrystalline anisotropy. All samples show non-zero low field absorption. For Series A samples the grain size decreases with an increase of the Zn content. In this case zero field absorption does not correlate with the changes of the grain size. For Series B samples the grain size and zero field absorption behavior correlate with each other. The highest zero-field absorption corresponded to 0.2 zinc concentration in both A and B series. High zero-field absorption of Fe3O4 ferrite magnetic NPs can be interesting for biomedical applications.

  6. Aqueous dispersions of magnetite nanoparticles complexed with copolyether dispersants: experiments and theory.

    PubMed

    Zhang, Qian; Thompson, M Shane; Carmichael-Baranauskas, Anita Y; Caba, Beth L; Zalich, Michael A; Lin, Yin-Nian; Mefford, O Thompson; Davis, Richey M; Riffle, Judy S

    2007-06-19

    Magnetite (Fe3O4) nanoparticles have been synthesized and complexed with carboxylate-functional block copolymers, and then aqueous dispersions of the complexes were investigated as functions of their chemical and morphological structures. The block copolymer dispersants had either poly(ethylene oxide), poly(ethylene oxide-co-propylene oxide), or poly(ethylene oxide-b-propylene oxide) outer blocks, and all of them had a polyurethane center block that contained pendent carboxylate groups. The complexes were formed through interactions of the carboxylates with the surfaces of the magnetite nanoparticles. The magnetite cores of the magnetite-copolymer complexes were near 10 nm in diameter, and the particles were superparamagnetic. Complexes with mass ratios of polymer to magnetite varying from 50:50 to 85:15 were studied. One of our objectives is to design complexes that form stable dispersions of discrete particles in water, yet that can be actuated (moved together) upon exposure to a uniform magnetic field. DLVO calculations that accounted for magnetic attractive interparticle forces, as well as van der Waals, steric, and electrostatic forces are presented. Compositions were identified wherein a shallow, attractive interparticle potential minimum appears once the magnetic term is applied. This suggests that it may be possible to tune the structures of superparamagnetic nanoparticle shells to allow discrete dispersions without a field, yet weak flocculation could be induced upon exposure to a field.

  7. Synthesis of Zn(II)-Doped Magnetite Leaf-Like Nanorings for Efficient Electromagnetic Wave Absorption

    PubMed Central

    Yang, Shuang; Jiang, Jian-Tang; Xu, Cheng-Yan; Wang, Yang; Xu, Yan-Yan; Cao, Lei; Zhen, Liang

    2017-01-01

    We report the thermal annealing-induced formation of ring-like structure of Zn(II)-doped magnetite from iron alkoxide leaf-like nanoplate precusor. The phase, structure and morphology of magnetite nanorings were comprehensively characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscope, scanning electron microscope, and transmission electron microscope. The obtained Zn(II)-doped magnetite nanorings are of 13–20 nm in edge width, 70–110 nm in short axis length and 100–150 nm in long axis length. The growth mechanism was possibly due to a combined effect of decomposition of the organic component and diffusion growth. Zn(II)-doped magnetite nanorings delivered saturation magnetization of 66.4 emu/g and coercivity of 33 Oe at room temperature. In addition, the coatings containing Zn(II)-doped magnetite nanorings as fillers exhibit excellent microwave absorption properties with a maximum reflection loss of −40.4 dB and wide effective absorbing band obtained in coating with thin thickness of 1.50 mm. PMID:28368010

  8. Magnetite biomineralization in Magnetospirillum gryphiswaldense: time-resolved magnetic and structural studies.

    PubMed

    Fdez-Gubieda, M Luisa; Muela, Alicia; Alonso, Javier; García-Prieto, Ana; Olivi, Luca; Fernández-Pacheco, Rodrigo; Barandiarán, José Manuel

    2013-04-23

    Magnetotactic bacteria biosynthesize magnetite nanoparticles of high structural and chemical purity that allow them to orientate in the geomagnetic field. In this work we have followed the process of biomineralization of these magnetite nanoparticles. We have performed a time-resolved study on magnetotactic bacteria Magnetospirillum gryphiswaldense strain MSR-1. From the combination of magnetic and structural studies by means of Fe K-edge X-ray absorption near edge structure (XANES) and high-resolution transmission electron microscopy we have identified and quantified two phases of Fe (ferrihydrite and magnetite) involved in the biomineralization process, confirming the role of ferrihydrite as the source of Fe ions for magnetite biomineralization in M. gryphiswaldense. We have distinguished two steps in the biomineralization process: the first, in which Fe is accumulated in the form of ferrihydrite, and the second, in which the magnetite is rapidly biomineralized from ferrihydrite. Finally, the XANES analysis suggests that the origin of the ferrihydrite could be at bacterial ferritin cores, characterized by a poorly crystalline structure and high phosphorus content.

  9. Control of nanoparticle size, reactivity and magnetic properties during the bioproduction of magnetite by Geobacter sulfurreducens

    NASA Astrophysics Data System (ADS)

    Byrne, J. M.; Telling, N. D.; Coker, V. S.; Pattrick, R. A. D.; van der Laan, G.; Arenholz, E.; Tuna, F.; Lloyd, J. R.

    2011-11-01

    The bioproduction of nanoscale magnetite by Fe(III)-reducing bacteria offers a potentially tunable, environmentally benign route to magnetic nanoparticle synthesis. Here, we demonstrate that it is possible to control the size of magnetite nanoparticles produced by Geobacter sulfurreducens by adjusting the total biomass introduced at the start of the process. The particles have a narrow size distribution and can be controlled within the range of 10-50 nm. X-ray diffraction analysis indicates that controlled production of a number of different biominerals is possible via this method including goethite, magnetite and siderite, but their formation is strongly dependent upon the rate of Fe(III) reduction and total concentration and rate of Fe(II) produced by the bacteria during the reduction process. Relative cation distributions within the structure of the nanoparticles have been investigated by x-ray magnetic circular dichroism and indicate the presence of a highly reduced surface layer which is not observed when magnetite is produced through abiotic methods. The enhanced Fe(II)-rich surface, combined with small particle size, has important environmental applications such as in the reductive bioremediation of organics, radionuclides and metals. In the case of Cr(VI), as a model high-valence toxic metal, optimized biogenic magnetite is able to reduce and sequester the toxic hexavalent chromium very efficiently to the less harmful trivalent form.

  10. Control of nanoparticle size, reactivity and magnetic properties during the bioproduction of magnetite by Geobacter sulfurreducens

    SciTech Connect

    Byrne, J. M.; Telling, N. D.; Coker, V. S.; Pattrick, R. A. D.; Laan, G. van der; Arenholz, E.; Tuna, F.; Lloyd, J. R.

    2011-08-02

    The bioproduction of nano-scale magnetite by Fe(III)-reducing bacteria offers a potentially tunable, environmentally benign route to magnetic nanoparticle synthesis. Here, we demonstrate that it is possible to control the size of magnetite nanoparticles produced by Geobacter sulfurreducens, by adjusting the total biomass introduced at the start of the process. The particles have a narrow size distribution and can be controlled within the range of 10-50 nm. X-ray diffraction analysis indicates that controlled production of a number of different biominerals is possible via this method including goethite, magnetite and siderite, but their formation is strongly dependent upon the rate of Fe(III) reduction and total concentration and rate of Fe(II) produced by the bacteria during the reduction process. Relative cation distributions within the structure of the nanoparticles has been investigated by X-ray magnetic circular dichroism and indicates the presence of a highly reduced surface layer which is not observed when magnetite is produced through abiotic methods. The enhanced Fe(II)-rich surface, combined with small particle size, has important environmental applications such as in the reductive bioremediation of organics, radionuclides and metals. In the case of Cr(VI), as a model high-valence toxic metal, optimised biogenic magnetite is able to reduce and sequester the toxic hexavalent chromium very efficiently in the less harmful trivalent form.

  11. Fe{sup II} induced mineralogical transformations of ferric oxyhydroxides into magnetite of variable stoichiometry and morphology

    SciTech Connect

    Usman, M.; Abdelmoula, M.; Hanna, K.; and others

    2012-10-15

    The Moessbauer spectroscopy was used to monitor the mineralogical transformations of ferrihydrite (F), lepidocrocite (L) and goethite (G) into magnetite as a function of aging time. Ferric oxyhydroxides were reacted with soluble Fe{sup II} and OH{sup -} in stoichiometric amounts to form magnetite at an initial pH of {approx}9.7. Observed transformation extent into magnetite followed the order: F>L>G with almost 30% of untransformed G after 1 month. The departure from stoichiometry, {delta}, of magnetite (Fe{sub 3-{delta}}O{sub 4}) generated from F ({delta}{approx}0.04) and L ({delta}{approx}0.05) was relatively low as compared to that in magnetite from G ({delta}{approx}0.08). The analysis by transmission electron microscopy and BET revealed that generated magnetite was also different in terms of morphology, particle size and surface area depending on the nature of initial ferric oxyhydroxide. This method of preparation is a possible way to form nano-sized magnetite. - Graphical abstract: Moessbauer spectrum of the early stage of magnetite formation formed from the interaction of adsorbed Fe{sup II} species with goethite. Highlights: Black-Right-Pointing-Pointer Ferric oxides were reacted with hydroxylated Fe{sup II} to form magnetite. Black-Right-Pointing-Pointer Magnetite formation was quantified as a function of aging time. Black-Right-Pointing-Pointer Complete transformation of ferrihydrite and lepidocrocite was achieved. Black-Right-Pointing-Pointer Almost 70% of initial goethite was transformed. Black-Right-Pointing-Pointer Resulting magnetites have differences in stoichiometry and morphological properties.

  12. FAST TRACK COMMUNICATION: A new crossover in Fe3O4 magnetite under pressure near 6 GPa: modification to 'ideal' inverse cubic spinel?

    NASA Astrophysics Data System (ADS)

    Ovsyannikov, Sergey V.; Shchennikov, Vladimir V.; Todo, Sakae; Uwatoko, Yoshiya

    2008-04-01

    The results of the first study on the thermoelectric power (Seebeck effect) of single crystals of Fe3O4 magnetite at high pressure P up to 20 GPa and room temperature are reported. The electrical resistance and a sample's contraction (relative compressibility) were also investigated over a P range of 0-20 GPa. A smooth bend (crossover) in the pressure dependence of the thermopower was firmly established near 6 GPa. This feature was attributed to a modification of Fe3O4 to an 'ideal' inverse configuration, the case where equivalent amounts of charges (the Fe2+ ions) and vacancies (the Fe3+ ions) at the octahedral sites provide nearly metallic polaron hopping conductivity via the octahedral network. The origin of this transformation might lie in (i) a P-tuning 'perfection' of the electronic transport in the inverse spinel, and/or in (ii) a transfer of a minor group of the charges from the tetrahedral sites to the octahedral ones, i.e. a \\mathrm {normal \\to inverse} configuration transition. Opportunities for the opposite valence transition in magnetite, from the inverse spinel to the normal (direct) one, are also discussed. At ambient pressure the samples of Fe3O4 were probed by Raman spectroscopy and using the electrical resistivity across the Verwey transition.

  13. Synthesizing and Characterizing Functionalized Short Multiwall Carbon Nanotubes with Folate, Magnetite and Polyethylene Glycol as Multi- targeted Nanocarrier of Anti-cancer Drugs

    PubMed Central

    Jafari, Mahmoud; Heidari, Danial; Ebrahimnejad, Pedram

    2016-01-01

    Multifunctional nanomaterials showed great advantages in drug delivery. Folic acid (FA) binding protein, a glycosyl phosphatidyl inositol anchored cell surface receptor for folate, is overexpressed in several human tumors, whereas it is highly restricted in normal tissues. Therefore, in this study, FA, polyethylene glycol (PEG), and Fe3O4 nanoparticles multifunctionalized short multiwall carbon nanotubes (PEG-FA-SMWCNT@Fe3O4) were synthesized by conjugating folate, PEG, and magnetite nanoparticles with carboxylated multiwall carbon nanotubes. The prepared c-SMWCNT@Fe3O4 was characterized by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) in order to investigate crystal and magnetic properties, respectively. The images obtained by scanning electron microscopy (SEM) showed that the magnetite nanoparticles were attached to the surfaces of carbon nanotubes and SMWCNT@Fe3O4 was formed. Investigation of functional groups using Fourier transform infrared (FTIR) spectra indicated that PEG-FA was successfully linked to SMWCNT@Fe3O4.  PMID:27642315

  14. Oxygen, hydrogen, sulfur, and carbon isotopes in the Pea Ridge magnetite-apatite deposit, southeast Missouri, and sulfur isotope comparisons to other iron deposits in the region

    USGS Publications Warehouse

    Johnson, Craig A.; Day, Warren C.; Rye, Robert O.

    2016-01-01

    Oxygen, hydrogen, sulfur, and carbon isotopes have been analyzed in the Pea Ridge magnetite-apatite deposit, the largest historic producer among the known iron deposits in the southeast Missouri portion of the 1.5 to 1.3 Ga eastern granite-rhyolite province. The data were collected to investigate the sources of ore fluids, conditions of ore formation, and provenance of sulfur, and to improve the general understanding of the copper, gold, and rare earth element potential of iron deposits regionally. The δ18O values of Pea Ridge magnetite are 1.9 to 4.0‰, consistent with a model in which some magnetite crystallized from a melt and other magnetite—perhaps the majority—precipitated from an aqueous fluid of magmatic origin. The δ18O values of quartz, apatite, actinolite, K-feldspar, sulfates, and calcite are significantly higher, enough so as to indicate growth or equilibration under cooler conditions than magnetite and/or in the presence of a fluid that was not entirely magmatic. A variety of observations, including stable isotope observations, implicate a second fluid that may ultimately have been meteoric in origin and may have been modified by isotopic exchange with rocks or by evaporation during storage in lakes.Sulfur isotope analyses of sulfides from Pea Ridge and seven other mineral deposits in the region reveal two distinct populations that average 3 and 13‰. Two sulfur sources are implied. One was probably igneous melts or rocks belonging to the mafic- to intermediate-composition volcanic suite that is present at or near most of the iron deposits; the other was either melts or volcanic rocks that had degassed very extensively, or else volcanic lakes that had trapped rising magmatic gases. The higher δ34S values correspond to deposits or prospects where copper is noteworthy—the Central Dome portion of the Boss deposit, the Bourbon deposit, and the Vilander prospective area. The correspondence suggests that (1) sulfur either limited the deposition

  15. Preparation of hollow magnetite microspheres and their applications as drugs carriers

    PubMed Central

    2012-01-01

    Hollow magnetite microspheres have been synthesized by a simple process through a template-free hydrothermal approach. Hollow microspheres were surface modified by coating with a silica nanolayer. Pristine and modified hollow microparticles were characterized by field-emission electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, FT-IR and Raman spectroscopy, and VSM magnetometry. The potential application of the modified hollow magnetite microspheres as a drug carrier was evaluated by using Rhodamine B and methotrexate as model drugs. The loading and release kinetics of both molecules showed a clear pH and temperature dependent profile. Graphical abstract Hollow magnetite microspheres have been synthesized. Load-release experiments with Rhodamine-B as a model drug and with Methotrexate (chemotherapy drug used in treating certain types of cancer) demonstrated the potential applications of these nanostructures in biomedical applications. PMID:22490731

  16. Magnetite nanoparticles coated glass wool for As(V) removal from drinking water

    SciTech Connect

    Kango, Sarita; Kumar, Rajesh

    2015-08-28

    Arsenic (As) removal from contaminated groundwater is a key environmental concern worldwide. In this study, glass wool was coated with magnetite nanoparticles under argon gas flow and magnetite coated glass wool have been investigated for application as an adsorbent for As(V) removal from water. The adsorbent was characterized by using Scanning Electron Microscopy (SEM) and arsenic contaminated water treated with adsorbent was analyzed by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The ICP-MS results showed that 10 g/L of adsorbent removed 99.4% of As(V) within 5 hours at pH-7 and initial arsenic concentration of 360µg/L. Adsorption kinetics data fitted well in pseudo-first-order kinetics model with high correlation coefficient (R{sup 2} = 0.995). As magnetite nanoparticles coated glass wool showed favorable adsorption behavior for As(V), it can be a promising tool for water purification.

  17. Sustained release of doxorubicin from zeolite magnetite nanocomposites prepared by mechanical activation

    NASA Astrophysics Data System (ADS)

    Arruebo, Manuel; Fernández-Pacheco, Rodrigo; Irusta, Silvia; Arbiol, Jordi; Ibarra, M. Ricardo; Santamaría, Jesús

    2006-08-01

    Nanocomposites consisting of magnetite and FAU zeolite with a high surface area and adsorption capacity have been prepared by mechanical activation using high-energy milling at room temperature. FTIR results, as well as HRTEM, EFTEM, and XPS measurements, show that the resulting magnetic nanoparticles are covered by a thin aluminosilicate coating. A saturation magnetization as high as 16 emu g-1 and 94.2 Oe of coercivity were observed for the obtained composites. The main advantages of this synthesis procedure are (i) simplicity of the preparation procedure, (ii) prevention of agglomeration of the magnetite nanoparticles to a large extent, and (iii) absence of free magnetite outside the zeolitic matrix. In addition, in vitro experiments revealed that the nanoparticles prepared were able to store and release substantial amounts of doxorubicin. In view of these advantages, these magnetic nanoparticles can be considered as potential candidates for drug-delivery applications.

  18. Magnetite nanoparticles-chitosan composite containing carbon paste electrode for glucose biosensor application.

    PubMed

    Kavitha, A L; Prabu, H Gurumallesh; Babu, S Ananda; Suja, S K

    2013-01-01

    This work was aimed to develop reusable magnetite chitosan composite containing carbon paste electrode for biosensor application. Glucose oxidase (GOx) enzyme was used to prepare GOx-magnetite-chitosan nanocomposite containing carbon paste electrode for sensitive detection of glucose. The immobilized enzyme retained its bioactivity, exhibited a surface confined reversible electron transfer reaction, and had good stability. The surface parameters like surface coverage (tau), Diffusion coefficient (D0), and rate constant (kS) were studied. The carbon paste modified electrode virtually eliminated the interference during the detection of glucose. The excellent performance of the biosensor is attributed to large surface-to-volume ratio, high conductivity and good biocompatibility of chitosan, which enhances the enzyme absorption and promotes electron transfer between redox enzymes and the surface of electrode. The shelf life of the developed electrode system is about 12 weeks under refrigerated conditions. We report for the first time in the fabrication of carbon paste bioelectrode containing magnetite-chitosan-GOx.

  19. Magnetite nanoparticles coated glass wool for As(V) removal from drinking water

    NASA Astrophysics Data System (ADS)

    Kango, Sarita; Kumar, Rajesh

    2015-08-01

    Arsenic (As) removal from contaminated groundwater is a key environmental concern worldwide. In this study, glass wool was coated with magnetite nanoparticles under argon gas flow and magnetite coated glass wool have been investigated for application as an adsorbent for As(V) removal from water. The adsorbent was characterized by using Scanning Electron Microscopy (SEM) and arsenic contaminated water treated with adsorbent was analyzed by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The ICP-MS results showed that 10 g/L of adsorbent removed 99.4% of As(V) within 5 hours at pH-7 and initial arsenic concentration of 360µg/L. Adsorption kinetics data fitted well in pseudo-first-order kinetics model with high correlation coefficient (R2 = 0.995). As magnetite nanoparticles coated glass wool showed favorable adsorption behavior for As(V), it can be a promising tool for water purification.

  20. Bench-scale testing of a micronized magnetite, fine-coal cleaning process

    SciTech Connect

    Suardini, P.J.

    1995-11-01

    Custom Coals, International has installed and is presently testing a 500 lb/hr. micronized-magnetite, fine-coal cleaning circuit at PETC`s Process Research Facility (PRF). The cost-shared project was awarded as part of the Coal Preparation Program`s, High Efficiency Preparation Subprogram. The project includes design, construction, testing, and decommissioning of a fully-integrated, bench-scale circuit, complete with feed coal classification to remove the minus 30 micron slimes, dense medium cycloning of the 300 by 30 micron feed coal using a nominal minus 10 micron size magnetite medium, and medium recovery using drain and rinse screens and various stages and types of magnetic separators. This paper describes the project circuit and goals, including a description of the current project status and the sources of coal and magnetite which are being tested.

  1. Verwey Metal-Insulator Transition in Magnetite from the Slave-Boson Approach

    NASA Astrophysics Data System (ADS)

    Sherafati, Mohammad; Satpathy, Sashi; Pettey, Dix

    2013-03-01

    We study the Verwey metal-insulator transition in magnetite (Ref.1) by solving a three-band extended Hubbard Hamiltonian for spinless fermions using the slave-boson approach, which also includes coupling to the local phonon modes. This model is suggested from the earlier density-functional studies of magnetite.(Ref.2) We first solve the 1D Hubbard model for the spinless fermions with nearest-neighbor interaction by both Gutzwiller variational and slave-boson methods and show that these two approaches yield different results unlike in the case of the standard Hubbard model, thereby clarifying some of the discrepancies in the literature (Ref.3), then we extend the formalism to three-band Hamiltonian for magnetite. The results suggest a metal-insulator transition at a critical value for the intersite interaction.

  2. Synthesis of functionalized magnetite nanoparticles to use as liver targeting MRI contrast agent

    NASA Astrophysics Data System (ADS)

    Yazdani, Farshad; Fattahi, Bahare; Azizi, Najmodin

    2016-05-01

    The aim of this research was the preparation of functionalized magnetite nanoparticles to use as a liver targeting contrast agent in magnetic resonance imaging (MRI). For this purpose, Fe3O4 nanoparticles were synthesized via the co-precipitation method. The synthesized nanoparticles were coated with silica via the Stober method and finally the coated nanoparticles were functionalized with mebrofenin. Formation of crystalline magnetite particles was confirmed by X-ray diffraction (XRD) analysis. The Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray analyzer (EDX) of the final product showed that silica had been effectively bonded onto the surface of the magnetite nanoparticles and the coated nanoparticles functionalized with mebrofenin. The magnetic resonance imaging of the functional nanoparticles showed that the Fe3O4-SiO2-mebrofenin composite is an effective MRI contrast agent for liver targeting.

  3. Mesoporous silica-magnetite nanocomposite synthesized by using a neutral surfactant.

    PubMed

    Souza, K C; Salazar-Alvarez, G; Ardisson, J D; Macedo, W A A; Sousa, E M B

    2008-05-07

    Magnetite nanoparticles coated by mesoporous silica were synthesized by an alternative chemical route using a neutral surfactant and without the application of any functionalization method. The magnetite (Fe(3)O(4)) nanoparticles were prepared by precipitation from aqueous media, and then coated with mesoporous silica by using nonionic block copolymer surfactants as the structure-directing agents. The mesoporous SiO(2)-coated Fe(3)O(4) samples were characterized by x-ray diffraction, Fourier-transform infrared spectroscopy, N(2) adsorption-desorption isotherms, transmission electron microscopy, (57)Fe Mössbauer spectroscopy, and vibrating sample magnetometry. Our results revealed that the magnetite nanoparticles are completely coated by well-ordered mesoporous silica with free pores and stable (∼8 nm thick) pore walls, and that the structural and magnetic properties of the Fe(3)O(4) nanoparticles are preserved in the applied synthesis route.

  4. Keeping Nanoparticles Fully Functional: Long-Term Storage and Alteration of Magnetite

    PubMed Central

    Widdrat, Marc; Kumari, Monika; Tompa, Éva; Pósfai, Mihály; Hirt, Ann M; Faivre, Damien

    2014-01-01

    Magnetite is an iron oxide found in rocks. Its magnetic properties are used for paleoclimatic reconstructions. It can also be synthesized in the laboratory to exploit its magnetic properties for bio- and nanotechnological applications. However, although the magnetic properties depend on particle size in a well-understood manner, they also depend on the structure of the oxide, because magnetite oxidizes to maghemite under environmental conditions. The dynamics of this process have not been well described. Here, a study of the alteration of magnetite particles of different sizes as a function of their storage conditions is presented. Smaller nanoparticles are shown to oxidize more rapidly than larger ones, and that the lower the storage temperature, the lower the measured oxidation. In addition, the magnetic properties of the altered particles are not decreased dramatically, thus suggesting that this alteration will not impact the use of such nanoparticles as medical carriers. PMID:26366334

  5. Controls on soluble Pu concentrations in PuO2/magnetite suspensions.

    PubMed

    Felmy, Andrew R; Moore, Dean A; Pearce, Carolyn I; Conradson, Steven D; Qafoku, Odeta; Buck, Edgar C; Rosso, Kevin M; Ilton, Eugene S

    2012-11-06

    Time-dependent reduction of PuO(2)(am) was studied over a range of pH values in the presence of aqueous Fe(II) and magnetite (Fe(3)O(4)) nanoparticles. At early time frames (up to 56 days) very little aqueous Pu was mobilized from PuO(2)(am), even though measured pH and redox potentials, coupled to equilibrium thermodynamic modeling, indicated the potential for significant reduction of PuO(2)(am) to relatively soluble Pu(III). Introduction of Eu(III) or Nd(III) to the suspensions as competitive cations to displace possible sorbed Pu(III) resulted in the release of significant concentrations of aqueous Pu. However, the similarity of aqueous Pu concentrations that resulted from the introduction of Eu(III)/Nd(III) to suspensions with and without magnetite indicated that the Pu was solubilized from PuO(2)(am), not from magnetite.

  6. Influence of Dynamical Conditions on the Reduction of UVI at the Magnetite-Solution Interface

    SciTech Connect

    Ilton, Eugene S.; Boily, Jean F.; Buck, Edgar C.; Skomurski, Frances N.; Rosso, Kevin M.; Cahill, Christopher L.; Bargar, John R.; Felmy, Andrew R.

    2010-01-14

    The heterogeneous reduction of UVI to UIV by ferrous iron is a potentially key process influencing the fate and transport of U in the environment. The reactivity of both sorbed and structural FeII has been studied for numerous substrates, including magnetite. The results from UVI-magnetite experiments have been variable, ranging from no reduction to clear evidence for the formation of UIV. In this contribution, we used XAS and high resolution (+cryogenic) XPS to study the interaction of UVI with nano-particulate magnetite. The results indicated that UVI was partially reduced to UV with no evidence of UIV. However, thermodynamic calculations indicated that mixed-valence U phases with average oxidation states below (V) should have been stable, indicating that the system was not in redox equilibrium. A reaction pathway that involves incorporation of U and stabilization of UV and UVI in secondary phases is invoked to explain the observations.

  7. Magnetic properties of magnetite nanoparticles coated with mesoporous silica by sonochemical method

    SciTech Connect

    Ursachi, Irina; Vasile, Aurelia; Chiriac, Horia; Postolache, Petronel; Stancu, Alexandru

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer MCM-41-coating of magnetite nanoparticles performed under ultrasonic irradiation. Black-Right-Pointing-Pointer Ultrasonic irradiation accelerates the formation of the MCM-41 framework. Black-Right-Pointing-Pointer The hysteretic response to an applied field was investigated applying FORC diagram. Black-Right-Pointing-Pointer The average coercive field of the Fe{sub 3}O{sub 4} nanoparticles increased after coating. -- Abstract: In this paper we present the magnetic properties of mesoporous silica-coated Fe{sub 3}O{sub 4} nanoparticles. The coating of magnetite nanoparticles with mesoporous silica shell was performed under ultrasonic irradiation. The obtained mesoporous silica-coated magnetite nanoparticles were characterized by powder X-ray diffraction, focused ion beam-scanning electron microscopy, nitrogen adsorption-desorption isotherms and vibrating sample magnetometer. The hysteretic behavior was studied using first-order reversal curves diagrams. The X-ray diffraction result indicates that the extreme chemical and physical conditions created by acoustic cavitations have an insignificant effect on crystallographic structural characteristic of magnetite nanoparticles. Changes in the coercivity distributions of the magnetite nanoparticles were observed on the first-order reversal curves diagrams for the samples with coated particles compared with the samples containing uncoated particles of magnetite. The coated particles show an increased most probable coercivity of about 20% compared with the uncoated particles which can be associated with an increased anisotropy due to coating even if the interaction field distribution measured on the diagrams are virtually identical for coated/uncoated samples.

  8. Effects of Temperature and Gas Composition on Reduction and Swelling of Magnetite Concentrates

    NASA Astrophysics Data System (ADS)

    Kapelyushin, Yury; Sasaki, Yasushi; Zhang, Jianqiang; Jeong, Sunkwang; Ostrovski, Oleg

    2016-08-01

    The gaseous reduction of magnetite ore concentrates was studied using CO-CO2 and CO-CO2-H2 gas mixtures at different temperatures and gas compositions. The reduction of magnetite ore by CO-CO2 gas mixture was examined at temperatures 973 K to 1173 K (700 °C to 900 °C) at CO/CO2 ratio 80/20, and at varied CO/CO2 ratio from 60/40 to 85/15 at 1023 K (750 °C). In the reduction of magnetite ore by CO-CO2-H2 gas mixture, temperature was 1173 K (800 °C) and hydrogen content changed from 5 to 25 vol pct at constant CO/CO2 ratio of 80/20. Reduction of magnetite ore did not go to completion in both CO-CO2 and CO-CO2-H2 gas mixtures. Addition of H2 to the CO-CO2 gas mixture accelerated the reduction in the first 10 to 30 minutes of reaction. However, the degree of reduction by gas containing 5 to 25 vol pct H2 after 60 to 120 minutes of reaction was in the range 60 to 65 pct, while the degree of reduction by CO-CO2 gas (80 vol pct CO) after 120 minutes of reaction was close to 70 pct. Significant swelling of magnetite ore pellets was observed in the reduction by CO-CO2 gas mixture. Addition of H2 to the CO-CO2 gas mixture decreased swelling. Swelling of magnetite ore during the reduction was attributed to the breakout of iron layer caused by the increase of the inner pressure in the voids at the wüstite/iron phase boundary.

  9. Four decades of paleomagnetic studies of magnetite in carbonate rocks: a history of remagnetizations

    NASA Astrophysics Data System (ADS)

    Van Der Voo, R.

    2011-12-01

    With the advent of cryogenic magnetometers in the early 1970's, paleomagnetic studies of carbonate rocks became possible and it was quickly established that magnetite generally was the carrier of an ancient remanence in non-red limestones. For about a decade, this magnetite was thought to be detrital, implying that the magnetizations were primary, i.e., dating back to the time of deposition of the strata. Gray Devonian limestones from Ohio, Arizona's Grand Canyon, Arkansas, and New York revealed directions similar to those of Permian rocks in North America, resulting in APWP loops and erroneous large-scale tectonic conclusions about an "Acadia" displaced terrane and Europe-Laurentia reconstructions. However, when syn-folding magnetizations became documented, the prevailing interpretations quickly changed. Remagnetizations became the rule rather than the exception. The carrier was no longer thought to be detrital, and abundant magnetite in the form of spherules and framboids imaged in scanning electron microscopy (SEM) seemed to be the answer to the quest for a growth mechanism of this mineral. In some cases, magnetite could be seen as oxidation rims to Fe-sulfide cores. Also, at about this time, hysteresis parameters of remagnetized carbonates, plotted in Day diagrams, revealed unique patterns, which did not match the parameters measured on individual spherules. Growth of the magnetite from a superparamagnetic size to single- and pseudo-single-domain size is currently the favored mode of occurrence of the magnetite, and some SEM images support this. Important unresolved questions remain, however. Notably, it remains puzzling why the remagnetizations most often appear to have been acquired at the time the nearest orogeny occurred, and what role fluids played in this process.

  10. Crystallization Stages of the Bishop Tuff Magma Body Recorded in Crystal Textures in Pumice Clasts

    SciTech Connect

    Pamukcu, Ayla; Gualda, Guilherme A.R.; Anderson, Jr. , Alfred T.

    2012-07-25

    The Bishop Tuff is a giant silicic ignimbrite erupted at 0.76 Ma in eastern California, USA. Five pumice clasts from the late-erupted Bishop Tuff (Aeolian Buttes) were studied in an effort to better understand the pre- and syn-eruptive history of the Bishop magma body and place constraints on the timescales of its existence. This study complements and expands on a previous study that focused on early-erupted Bishop Tuff pumice clasts. Bulk densities of pumice clasts were measured using an immersion method, and phenocryst crystal contents were determined using a sieving and winnowing procedure. X-ray tomography was used to obtain qualitative and quantitative textural information, particularly crystal size distributions (CSDs). We have determined CSDs for crystals ranging in size from {approx}10 to {approx}1000 {micro}m for three groups of mineral phases: magnetite ({+-}ilmenite), pyroxene + biotite, quartz + feldspar. Similar to early-erupted pumice, late-erupted pumice bulk density and crystal contents are positively correlated, and comparison of crystal fraction vs size trends suggests that the proportion of large crystals is the primary control on crystallinity. Porosity is negatively correlated with crystal content, which is difficult to reconcile with closed-system crystallization. Magnetite and pyroxene + biotite size distributions are fractal in nature, often attributed to fragmentation; however, crystals are mostly whole and euhedral, such that an alternative mechanism is necessary to explain these distributions. Quartz + feldspar size distributions are kinked, with a shallow-sloped log-linear section describing large crystals (> 140 {micro}m) and a steep-sloped log-linear section describing small crystals (< 140 {micro}m). We interpret these two crystal populations as resulting from a shift in crystallization regime. We suggest that the shallow-sloped section describes a pre-eruptive quartz + feldspar growth-dominated regime, whereas the steep

  11. High stable suspension of magnetite nanoparticles in ethanol by using sono-synthesized nanomagnetite in polyol medium

    SciTech Connect

    Bastami, Tahereh Rohani; Entezari, Mohammad H.

    2013-09-01

    Graphical abstract: - Highlights: • The sonochemical synthesis of magnetite nanoparticles was carried out in EG without any surfactant. • The nanoparticles with sizes ∼24 nm were composed of small building blocks with sizes ∼2 nm. • The hydrophilic magnetite nanoparticles were stable in ethanol even after 8 months. • Ultrasonic intensity showed a crucial role on the obtained high stable magnetite nanoparticles in ethanol. - Abstract: The sonochemical synthesis of magnetite nanoparticles was carried out at relatively low temperature (80 °C) in ethylene glycol (EG) as a polyol solvent. The particle size was determined by transmission electron microscopy (TEM). The magnetite nanoparticles with an average size of 24 nm were composed of small building blocks with an average size of 2–3 nm and the particles exhibited nearly spherical shape. The surface characterization was investigated by using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The stability of magnetite nanoparticles was studied in ethanol as a polar solvent. The nanoparticles showed an enhanced stability in ethanol which is due to the hydrophilic surface of the particles. The colloidal stability of magnetite nanoparticles in ethanol was monitored by UV–visible spectrophotometer. According to the results, the nanoparticles synthesized in 30 min of sonication with intensity of 35 W/cm{sup 2} (50%) led to a maximum stability in ethanol as a polar solvent with respect to the other applied intensities. The obtained magnetite nanoparticles were stable for more than12 months.

  12. Arsenate and Arsenite Sorption on Magnetite: Relations to Groundwater Arsenic Treatment Using Zerovalent Iron and Natural Attenuation

    EPA Science Inventory

    Magnetite (Fe3O4) is a zerovalent iron corrosion product; it is also formed in natural soil and sediment. Sorption of arsenate (As(V)) and arsenite (As(III)) on magnetite is an important process of arsenic removal from groundwater using zerovalent iron-based permeable reactive ba...

  13. Non-stoichiometric magnetite and maghemite in the mature teeth of the chiton Acanthopleura hirtosa

    NASA Astrophysics Data System (ADS)

    St. Pierre, T. G.; Evans, L. A.; Webb, J.

    1992-04-01

    Mature radula pieces from the chiton Acanthopleura hirtosa were studied using Mössbauer spectroscopy. The magnetite present in the radulae was found to have a distribution of Verwey transition temperatures in the range 85-100K. It was deduced that the magnetite was non-stoichiometric with an average formula Fe2.98O3. About 10% of the Fe in the radulae was in the form of maghemite and about 19% was in the form of paramagnetic or superparamagnetic phases.

  14. Evidence for a ubiquitous, sub-microscopic 'magnetite-like' constituent in the lunar soils

    NASA Technical Reports Server (NTRS)

    Griscom, D. L.; Friebele, E. J.; Marquardt, C. L.

    1973-01-01

    Electron spin resonance (ESR) has been employed in a study of the ferromagnetic constituents of a wide variety of soils from six sampled regions of the moon as well as glasses made to simulate lunar compositions. A significant result has been that magnetite-like phases (magnetic iron spinel) precipitated in and on simulated lunar glasses as a result of sub-solidus oxidation yield room-temperature ESR spectra virtually identical with the line shape predicted for spherical, single domain particles of metallic Fe. It is shown that such magnetite-like phases can nevertheless be distinguished from metallic iron on the basis of the temperature dependence of the ESR intensity.

  15. Novel protocol for the solid-state synthesis of magnetite for medical practices

    NASA Astrophysics Data System (ADS)

    Paiva, D. L.; Andrade, A. L.; Pereira, M. C.; Fabris, J. D.; Domingues, R. Z.; Alvarenga, M. E.

    2015-06-01

    It is reported a novel approach to prepare nanoparticles of magnetite (Fe3O4) by heating a mixture of synthetic commercial maghemite ( γFe2O3) with sucrose. This solid-state reaction leads to the chemical reduction of part of the Fe3+ of the precursor oxide to render Fe2+ and Fe3+ in octahedral and Fe3+ in tetrahedral sites of the Fe-O coordination framework. Powder X-ray diffraction patterns, FTIR and 298 K Mössbauer spectra confirm the conversion of maghemite into magnetite. Based on these results, the optimal sucrose:maghemite rate was found to be 4.

  16. Quenched magnetite in cretaceous-tertiary boundary microtekite-like spheroid

    NASA Technical Reports Server (NTRS)

    Smit, J.; Kyte, F. T.; Wasson, J. T.

    1984-01-01

    The magnetite containing spheres collected from a kt boundary localities in Italy were analyzed. It was found that these spheres contain relatively high concentrations of Ir. The spheres were analyzed for siderophile elements Ir, Pt, Au, Pd, Os, and Re. Elements Ir, Pt, Pd, and Au were found in high concentrations in magnetic spheres and their concentrations are similar to those in most meteorites. It is suggested that the magnetite spheres do not contain a meteorite component which may be a relic of the kt event.

  17. Adsorption of alkenyl succinic anhydride from solutions in carbon tetrachloride on a fine magnetite surface

    NASA Astrophysics Data System (ADS)

    Balmasova, O. V.; Ramazanova, A. G.; Korolev, V. V.

    2016-06-01

    The adsorption of alkenyl succinic anhydride from a solution in carbon tetrachloride on a fine magnetite surface at a temperature of 298.15 K is studied using fine magnetite, which forms the basis of magnetic fluids, as the adsorbent. An adsorption isotherm is recorded and interpreted in terms of the theory of the volume filling of micropores (TVFM). Adsorption process parameters are calculated on the basis of the isotherm. It is shown that at low equilibrium concentrations, the experimental adsorption isotherm is linear in the TVFM equation coordinates.

  18. Thiol-functionalized magnetite/graphene oxide hybrid as a reusable adsorbent for Hg2+ removal

    NASA Astrophysics Data System (ADS)

    Bao, Jian; Fu, You; Bao, Zhihao

    2013-11-01

    A thiol-functionalized magnetite/graphene oxide (MGO) hybrid as an adsorbent of Hg2+ was successfully synthesized by a two-step reaction. It exhibited a higher adsorption capacity compared to the bare graphene oxide and MGO due to the combined adsorption of thiol groups and magnetite nanocrystals. Its capacity reached 289.9 mg g-1 in a solution with an initial Hg2+ concentration of 100 mg l-1. After being exchanged with H+, the adsorbent could be reused. The adsorption of Hg2+ by the thiol-functionalized MGO fits well with the Freundlich isotherm model and followed pseudo-second-order kinetics.

  19. Magnetotactic bacteria form magnetite from a phosphate-rich ferric hydroxide via nanometric ferric (oxyhydr)oxide intermediates

    PubMed Central

    Baumgartner, Jens; Morin, Guillaume; Menguy, Nicolas; Perez Gonzalez, Teresa; Widdrat, Marc; Cosmidis, Julie; Faivre, Damien

    2013-01-01

    The iron oxide mineral magnetite (Fe3O4) is produced by various organisms to exploit magnetic and mechanical properties. Magnetotactic bacteria have become one of the best model organisms for studying magnetite biomineralization, as their genomes are sequenced and tools are available for their genetic manipulation. However, the chemical route by which magnetite is formed intracellularly within the so-called magnetosomes has remained a matter of debate. Here we used X-ray absorption spectroscopy at cryogenic temperatures and transmission electron microscopic imaging techniques to chemically characterize and spatially resolve the mechanism of biomineralization in those microorganisms. We show that magnetite forms through phase transformation from a highly disordered phosphate-rich ferric hydroxide phase, consistent with prokaryotic ferritins, via transient nanometric ferric (oxyhydr)oxide intermediates within the magnetosome organelle. This pathway remarkably resembles recent results on synthetic magnetite formation and bears a high similarity to suggested mineralization mechanisms in higher organisms. PMID:23980143

  20. Magnetotactic bacteria form magnetite from a phosphate-rich ferric hydroxide via nanometric ferric (oxyhydr)oxide intermediates.

    PubMed

    Baumgartner, Jens; Morin, Guillaume; Menguy, Nicolas; Perez Gonzalez, Teresa; Widdrat, Marc; Cosmidis, Julie; Faivre, Damien

    2013-09-10

    The iron oxide mineral magnetite (Fe3O4) is produced by various organisms to exploit magnetic and mechanical properties. Magnetotactic bacteria have become one of the best model organisms for studying magnetite biomineralization, as their genomes are sequenced and tools are available for their genetic manipulation. However, the chemical route by which magnetite is formed intracellularly within the so-called magnetosomes has remained a matter of debate. Here we used X-ray absorption spectroscopy at cryogenic temperatures and transmission electron microscopic imaging techniques to chemically characterize and spatially resolve the mechanism of biomineralization in those microorganisms. We show that magnetite forms through phase transformation from a highly disordered phosphate-rich ferric hydroxide phase, consistent with prokaryotic ferritins, via transient nanometric ferric (oxyhydr)oxide intermediates within the magnetosome organelle. This pathway remarkably resembles recent results on synthetic magnetite formation and bears a high similarity to suggested mineralization mechanisms in higher organisms.

  1. REE Mineralization in Kiruna-type Magnetite-Apatite Ore Deposits: Magmatism and Metasomatism

    NASA Astrophysics Data System (ADS)

    Harlov, D. E.

    2015-12-01

    Magnetite-apatite ore bodies of the Kiruna type occur worldwide and are generally associated with volcanic rocks or volcanism. They also show strong evidence of extensive metasomatism over a wide P-T range. Notable examples include the Kiirunavaara ore body, northern Sweden (Harlov et al., 2002, Chem. Geol., 191, 47-72); the Grängesberg ore body, central Sweden (Jonsson et al., 2010, NGF abstracts, vol 1, 88-89); the Mineville ore body, Adirondacks, New York, USA (McKeown and Klemc, 1956, U.S. Geol Sur Bull (1956), pp. 9-23); the Pea Ridge ore body, SE Missouri, USA (Kerr, 1998, MS Thesis, Univ. Windsor, Windsor, Ontario, Canada 113 pp); the Jurassic Marcona ore body in south-central Peru (Chen et al., 2010, Econ Geol, 105, 1441-1456); and a collection of ore bodies from the Bafq Region, central Iran (Daliran et al., 2010, Geol. Assoc. Canada, Short Course Notes, v. 20, p.147-159). In these ore bodies, low Th and U monazite, xenotime, allanite, REE carbonates, and/or REE fluorides are commonly associated with the apatite as inclusions, rim grains, or as independent grains in the surrounding mineral matrix. High contrast BSE imaging, coupled with EMPA and LA-ICPMS, indicates that the apatite has experienced fluid-induced alteration in the form of (Y+REE) + Na + Si + Cl depletion implying that it served as the source for the (Y+REE) (e.g. Kiirunavaara, northern Sweden; Harlov et al., 2002). Formation of monazite and xenotime associated with fluorapatite, as inclusions or rim grains, has experimentally been demonstrated to originate from the fluorapatite as the result of fluid-aided, coupled dissolution-reprecipitation processes (Harlov et al., 2005, Contrib. Mineral. Petrol. 150, 268-286). This is explains the low Th and U content of the monazite and xenotime. Fluid sources could range from 700-900 °C, residual, acidic (HCl, H2HSO4) grain boundary fluids, remaining after the last stages of ore body crystallization, to later stage, cooler (< 600 °C) (H2O-CO2-(Na

  2. Method of preparing pure fluorine gas

    DOEpatents

    Asprey, Larned B.

    1976-01-01

    A simple, inexpensive system for purifying and storing pure fluorine is described. The method utilizes alkali metal-nickel fluorides to absorb tank fluorine by forming nickel complex salts and leaving the gaseous impurities which are pumped away. The complex nickel fluoride is then heated to evolve back pure gaseous fluorine.

  3. Pure ovarian choriocarcinoma: report of two cases

    PubMed Central

    Mood, Narges Izadi; Samadi, Nasrin; Rahimi-Moghaddam, Parvaneh; Sarmadi, Soheila; Eftekhar, Zahra; Yarandi, Fariba

    2009-01-01

    Pure primary ovarian choriocarcinoma is an extremely rare condition of gestational or nongestational origin. The possibility of gestational origin can be suspected by the presence of a corpus luteum of pregnancy but definite diagnosis would be based on genetic analysis. Here, we present two cases of pure ovarian choriocarcinoma in the forth decade of life with the possibility of gestational origin. PMID:21772904

  4. Nonuniform Growth of Composite Layer-by-Layer Assembled Coatings via Three-Dimensional Expansion of Hydrophobic Magnetite Nanoparticles.

    PubMed

    Voronin, Denis V; Grigoriev, Dmitry; Möhwald, Helmuth; Shchukin, Dmitry G; Gorin, Dmitry A

    2015-12-30

    Nanocomposite coatings are promising for a range of practical applications, and layer-by-layer assembly (LbL) is a versatile tool for nanocomposite formation. However, conventional LbL is a quite laborious procedure taking a lot of time to reach a sufficient thickness of the coatings required for practical applications. Herein, we proposed a novel variant of the LbL approach based on the deposition of hydrophilic polyelectrolyte molecules from a polar solvent and hydrophobic magnetite nanoparticles (NPs) from a nonpolar dispersion medium with an intermediate washing in the same polar solvent. The composite multilayers formed in this way exhibit exponential growth of the thickness and mass. On the basis of quartz crystal microbalance (QCM), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and surface profile measurements, we propose a model describing the driving force of multilayer formation and the factors leading to nonlinear growth of their mass and thickness. The results allow one to expand the understanding of the mechanism of the LbL assembly in order to form multifunctional nanocomposites in a more efficient way.

  5. MamO Is a Repurposed Serine Protease that Promotes Magnetite Biomineralization through Direct Transition Metal Binding in Magnetotactic Bacteria

    SciTech Connect

    Hershey, David M.; Ren, Xuefeng; Melnyk, Ryan A.; Browne, Patrick J.; Ozyamak, Ertan; Jones, Stephanie R.; Chang, Michelle C. Y.; Hurley, James H.; Komeili, Arash

    2016-03-16

    Many living organisms transform inorganic atoms into highly ordered crystalline materials. An elegant example of such biomineralization processes is the production of nano-scale magnetic crystals in magnetotactic bacteria. Previous studies have implicated the involvement of two putative serine proteases, MamE and MamO, during the early stages of magnetite formation in Magnetospirillum magneticum AMB-1. Here, using genetic analysis and X-ray crystallography, we show that MamO has a degenerate active site, rendering it incapable of protease activity. Instead, MamO promotes magnetosome formation through two genetically distinct, noncatalytic activities: activation of MamE-dependent proteolysis of biomineralization factors and direct binding to transition metal ions. By solving the structure of the protease domain bound to a metal ion, we identify a surface-exposed di-histidine motif in MamO that contributes to metal binding and show that it is required to initiate biomineralization in vivo. Finally, we find that pseudoproteases are widespread in magnetotactic bacteria and that they have evolved independently in three separate taxa. In conclusion, our results highlight the versatility of protein scaffolds in accommodating new biochemical activities and provide unprecedented insight into the earliest stages of biomineralization.

  6. Magnetite (Fe3O4)-filled carbon nanofibers as electro-conducting/superparamagnetic nanohybrids and their multifunctional polymer composites

    NASA Astrophysics Data System (ADS)

    Das, Arindam; Raffi, Muhammad; Megaridis, Constantine; Fragouli, Despina; Innocenti, Claudia; Athanassiou, Athanassia

    2015-01-01

    A mild-temperature, nonchemical technique is used to produce a nanohybrid multifunctional (electro-conducting and magnetic) powder material by intercalating iron oxide nanoparticles in large aspect ratio, open-ended, hollow-core carbon nanofibers (CNFs). Single-crystal, superparamagnetic Fe3O4 nanoparticles (10 nm average diameter) filled the CNF internal cavity (diameter <100 nm) after successive steps starting with dispersion of CNFs and magnetite nanoparticles in aqueous or organic solvents, sequencing or combining sonication-assisted capillary imbibition and concentration-driven diffusion, and finally drying at mild temperatures. The influence of several process parameters—such as sonication type and duration, concentration of solids dispersed in solvent, CNF-to-nanoparticle mass ratio, and drying temperature—on intercalation efficiency (evaluated in terms of particle packing in the CNF cavity) was studied using electron microscopy. The magnetic CNF powder was used as a low-concentration filler in poly(methyl methacrylate) to demonstrate thin free-standing polymer films with simultaneous magnetic and electro-conducting properties. Such films could be implemented in sensors, optoelectromagnetic devices, or electromagnetic interference shields.

  7. MamO Is a Repurposed Serine Protease that Promotes Magnetite Biomineralization through Direct Transition Metal Binding in Magnetotactic Bacteria

    DOE PAGES

    Hershey, David M.; Ren, Xuefeng; Melnyk, Ryan A.; ...

    2016-03-16

    Many living organisms transform inorganic atoms into highly ordered crystalline materials. An elegant example of such biomineralization processes is the production of nano-scale magnetic crystals in magnetotactic bacteria. Previous studies have implicated the involvement of two putative serine proteases, MamE and MamO, during the early stages of magnetite formation in Magnetospirillum magneticum AMB-1. Here, using genetic analysis and X-ray crystallography, we show that MamO has a degenerate active site, rendering it incapable of protease activity. Instead, MamO promotes magnetosome formation through two genetically distinct, noncatalytic activities: activation of MamE-dependent proteolysis of biomineralization factors and direct binding to transition metal ions.more » By solving the structure of the protease domain bound to a metal ion, we identify a surface-exposed di-histidine motif in MamO that contributes to metal binding and show that it is required to initiate biomineralization in vivo. Finally, we find that pseudoproteases are widespread in magnetotactic bacteria and that they have evolved independently in three separate taxa. In conclusion, our results highlight the versatility of protein scaffolds in accommodating new biochemical activities and provide unprecedented insight into the earliest stages of biomineralization.« less

  8. Crystal Meth

    MedlinePlus

    ... from Other Parents Stories of Hope Crystal meth Crystal meth Story of Hope by giovanni January 3, ... about my drug addiction having to deal with Crystal meth. I am now in recovery and fighting ...

  9. Crystal Meth

    MedlinePlus

    ... Navigation Home / Stories of Hope / Crystal meth Crystal meth Story Of Hope By giovanni January 3rd, 2013 ... my drug addiction having to deal with Crystal meth. I am now in recovery and fighting my ...

  10. Crystal Creations.

    ERIC Educational Resources Information Center

    Whipple, Nona; Whitmore, Sherry

    1989-01-01

    Presents a many-faceted learning approach to the study of crystals. Provides instructions for performing activities including crystal growth and patterns, creating miniature simulations of crystal-containing rock formations, charcoal and sponge gardens, and snowflakes. (RT)

  11. Adsorption and kinetic studies of seven different organic dyes onto magnetite nanoparticles loaded tea waste and removal of them from wastewater samples

    NASA Astrophysics Data System (ADS)

    Madrakian, Tayyebeh; Afkhami, Abbas; Ahmadi, Mazaher

    2012-12-01

    Adsorption of seven different organic dyes from aqueous solutions onto magnetite nanoparticles loaded tea waste (MNLTW) was studied. MNLTW was prepared via a simple method and was fully characterized. The properties of this magnetic adsorbent were characterized by scanning electron microscopy and X-ray diffraction. Adsorption characteristics of the MNLTW adsorbent was examined using Janus green, methylene blue, thionine, crystal violet, Congo red, neutral red and reactive blue 19 as adsorbates. Dyes adsorption process was thoroughly studied from both kinetic and equilibrium points of view for all adsorbents. The experimental isotherm data were analyzed using Langmuir, Freundlich, Sips, Redlich-Peterson, Brouers-Sotolongo and Temkin isotherms. The results from Langmuir isotherm indicated that the capacity of MNLTW for the adsorption of cationic dyes was higher than that for anionic dyes. The adsorption kinetics was tested for the pseudo-first order and pseudo-second order kinetic models at different experimental conditions.

  12. Methane production from hydrothermal transformation of siderite to magnetite

    NASA Astrophysics Data System (ADS)

    Muratbayev, T.; Schroeder, C.; Kappler, A.; Haderlein, S.

    2012-12-01

    Mumma et al. (2009) observed a methane (CH4) plume above the Nili Fossae region on Mars, a region rich in carbonate minerals. Morris et al. (2010) suggest this to be (Mg,Fe)-carbonate. McCollom (2003) demonstrated that the hydrothermal transformation of siderite (FeCO3), to magnetite (Fe3O4) produces CH4. This reaction may thus contribute to the formation of methane on Mars, but is also relevant in the context of such diverse topics as diagenesis of Precambrian banded iron formations, sources of prebiotic organic compounds on early Earth, oil and gas accumulations in Earth's crust, or geological sequestration and storage of CO2. However, neither the thermodynamics of this reaction nor the conditions of maximum CH4 yield have been investigated to date. In order to estimate how pressure and temperature influence CH4 yield we derived a thermodynamic model with a numerical solution implemented in MATLAB. We used the equation 12FeCO3 + 2H2O → 4Fe3O4 + 11CO2 + CH4 (Frost et al. 2007) and thermodynamic calculations of the stability field of FeCO3 by Thoms-Keprta et al. (2009) as a template. At 1 bar pressure, the Gibbs energy turns negative (favorable reaction conditions) at a temperature of 200°C. Increasing pressure to 1000 bar changes that temperature to 250°C. An increase in temperature has a larger effect on shifting the Gibbs energy to more negative values. We therefore chose ambient pressure and temperatures of 300°C, 400°C, and 500°C as experimental conditions. We added 100 mg of either natural or synthetic FeCO3 and 25 μL of MilliQ water into long tip Pasteur pipettes inside an anoxic glove box to avoid contamination by free oxygen. The Pasteur pipettes were sealed with butyl stoppers and then melted shut outside of the glove box. The glass capsules were heated for 48 hours in a muffle furnace at 300°C, 400 0C or 5000C. The composition of the gas phase and the formation of methane in particular were analyzed using gas chromatography with a flame

  13. Multicolor photonic crystal laser array

    SciTech Connect

    Wright, Jeremy B; Brener, Igal; Subramania, Ganapathi S; Wang, George T; Li, Qiming

    2015-04-28

    A multicolor photonic crystal laser array comprises pixels of monolithically grown gain sections each with a different emission center wavelength. As an example, two-dimensional surface-emitting photonic crystal lasers comprising broad gain-bandwidth III-nitride multiple quantum well axial heterostructures were fabricated using a novel top-down nanowire fabrication method. Single-mode lasing was obtained in the blue-violet spectral region with 60 nm of tuning (or 16% of the nominal center wavelength) that was determined purely by the photonic crystal geometry. This approach can be extended to cover the entire visible spectrum.

  14. Magnetite nanoparticle (NP) uptake by wheat plants and its effect on cadmium and chromium toxicological behavior.

    PubMed

    López-Luna, J; Silva-Silva, M J; Martinez-Vargas, S; Mijangos-Ricardez, O F; González-Chávez, M C; Solís-Domínguez, F A; Cuevas-Díaz, M C

    2016-09-15

    The aim of this work was to assess the uptake of citrate-coated magnetite nanoparticles (NPs) by wheat plants and its effect on the bioaccumulation and toxicity of individual and joint Cd(2+) and Cr(6+) levels. Seven-day assays were conducted using quartz sand as the plant growth substrate. The endpoints measured were seed germination, root and shoot lengths, and heavy metal accumulation. Magnetite exhibited very low toxicity, regardless of the wheat seedling NP uptake and distribution into roots and shoots. The seed germination and shoot length were not sensitive enough, while the root length was a more sensitive toxicity endpoint. The root length of wheat seedlings exposed to individual metals decreased by 50% at 2.67mgCd(2)(+)kg(-1) and 5.53mgCr(6+)kg(-1). However, when magnetite NPs (1000mgkg(-1)) were added, the root length of the plants increased by 25 and 50%. Cd(2+) and Cr(6+) showed similar and noninteractive joint action, but strongly impaired the wheat seedlings. In contrast, an interactive infra-additive or antagonistic effect was observed upon adding magnetite NPs. Thus, cadmium and chromium accumulation in vegetable tissues was considerately diminished and the toxicity alleviated.

  15. Cranberry magnetite deposits Avery County, N.C., and Carter County, Tenn.

    USGS Publications Warehouse

    Kline, M.H.; Ballard, T.J.

    1948-01-01

    The Cranberry magnetite deposits occur in pre-Cambrian granite-gneiss in a belt extending from 3 miles southeast of Cranberry, N.C., to about 6 miles southwest of Magnetic City, Tenn. The belt forms a curve, elongated to the north, approximately 26 miles in length.

  16. New kind of type 3 chondrite with a graphite-magnetite matrix

    NASA Technical Reports Server (NTRS)

    Scott, E. R. D.; Rubin, A. E.; Taylor, G. J.; Keil, K.

    1981-01-01

    Four clasts in three ordinary-chondrite regolith breccias are discovered which are a new kind of type 3 chondrite. As with ordinary and carbonaceous type 3 chondrites, they have distinct chondrules, some of which contain glass, highly heterogeneous olivines and pyroxenes, and predominantly monoclinic low-Ca pyroxenes. Instead of the usual, fine-grained, Fe-rich silicate matrix, however, the clasts have a matrix composed largely of aggregates of micron- and submicron-sized graphite and magnetite. The bulk compositions of the clasts, as well as the types of chondrules (largely porphyritic), are characteristic of type 3 ordinary chondrites, although chondrules in the clasts are somewhat smaller (0.1-0.5 mm). A close relationship with ordinary chondrites is also suggested by the presence of similar graphite-magnetite aggregates in seven type 3 ordinary chondrites. It is thought that this new kind of chondrite is probably the source of the abundant graphite-magnetite inclusions in ordinary-chondrite regolith breccias and that it may be more common than indicated by the absence of whole meteorites made of chondrules and graphite-magnetite.

  17. Precipitation synthesis and magnetic properties of self-assembled magnetite-chitosan nanostructures

    NASA Astrophysics Data System (ADS)

    Bezdorozhev, Oleksii; Kolodiazhnyi, Taras; Vasylkiv, Oleg

    2017-04-01

    This paper reports the synthesis and magnetic properties of unique magnetite-chitosan nanostructures synthesized by the chemical precipitation of magnetite nanoparticles in the presence of chitosan. The influence of varying synthesis parameters on the morphology of the magnetic composites is determined. Depending on the synthesis parameters, magnetite-chitosan nanostructures of spherical (9-18 nm), rice-seed-like (75-290 nm) and lumpy (75-150 nm) shapes were obtained via self-assembly. Spherical nanostructures encapsulated by a 9-15 nm chitosan layer were assembled as well. The prospective morphology of the nanostructures is combined with their excellent magnetic characteristics. It was found that magnetite-chitosan nanostructures are ferromagnetic and pseudo-single domain. Rice-seed-like nanostructures exhibited a coercivity of 140 Oe and saturation magnetization of 56.7 emu/g at 300 K. However, a drop in the magnetic properties was observed for chitosan-coated spherical nanostructures due to the higher volume fraction of chitosan.

  18. Magnetite nanoparticles facilitate methane production from ethanol via acting as electron acceptors.

    PubMed

    Yang, Zhiman; Shi, Xiaoshuang; Wang, Chuanshui; Wang, Lin; Guo, Rongbo

    2015-11-12

    Potential for interspecies hydrogen transfer within paddy soil enrichments obtained via addition of magnetite nanoparticles and ethanol (named as PEM) was investigated. To do this, PEM derived from rice field of Hangzhou (named as PEM-HZ) was employed, because it offered the best methane production performance. Methane production and Fe (III) reduction proceeded in parallel in the presence of magnetite. Inhibition experiments with 2-bromoethane sulfonate (BES) or phosphate showed that interspecies hydrogen transfer and Fe (III) reduction also occurred in methane production from ethanol. 16S rRNA-based Illumina sequencing results showed that Dechloromonas, Thauera, Desulfovibrio and Clostridium were the dominant putative Fe (III) -reducers, and that hydrogenotrophic Methanobacterium accounted for about 88% of the total archaeal community. These results indicated that magnetite nanoparticles that acted as electron acceptor could facilitate rapid oxidation of ethanol by members of the Fe (III) -reducers in PEM-HZ and establishment of the syntrophic relationship of Fe (III) -reducers with Methanobacterium via interspecies hydrogen transfer. Our results could offer a model to understand the microbial interaction with magnetite from a novel angle during methanogenesis.

  19. Magnetite nanoparticles facilitate methane production from ethanol via acting as electron acceptors

    PubMed Central

    Yang, Zhiman; Shi, Xiaoshuang; Wang, Chuanshui; Wang, Lin; Guo, Rongbo

    2015-01-01

    Potential for interspecies hydrogen transfer within paddy soil enrichments obtained via addition of magnetite nanoparticles and ethanol (named as PEM) was investigated. To do this, PEM derived from rice field of Hangzhou (named as PEM-HZ) was employed, because it offered the best methane production performance. Methane production and Fe (III) reduction proceeded in parallel in the presence of magnetite. Inhibition experiments with 2-bromoethane sulfonate (BES) or phosphate showed that interspecies hydrogen transfer and Fe (III) reduction also occurred in methane production from ethanol. 16S rRNA-based Illumina sequencing results showed that Dechloromonas, Thauera, Desulfovibrio and Clostridium were the dominant putative Fe (III) -reducers, and that hydrogenotrophic Methanobacterium accounted for about 88% of the total archaeal community. These results indicated that magnetite nanoparticles that acted as electron acceptor could facilitate rapid oxidation of ethanol by members of the Fe (III) -reducers in PEM-HZ and establishment of the syntrophic relationship of Fe (III) -reducers with Methanobacterium via interspecies hydrogen transfer. Our results could offer a model to understand the microbial interaction with magnetite from a novel angle during methanogenesis. PMID:26559132

  20. Magnetite nanoparticles facilitate methane production from ethanol via acting as electron acceptors

    NASA Astrophysics Data System (ADS)

    Yang, Zhiman; Shi, Xiaoshuang; Wang, Chuanshui; Wang, Lin; Guo, Rongbo

    2015-11-01

    Potential for interspecies hydrogen transfer within paddy soil enrichments obtained via addition of magnetite nanoparticles and ethanol (named as PEM) was investigated. To do this, PEM derived from rice field of Hangzhou (named as PEM-HZ) was employed, because it offered the best methane production performance. Methane production and Fe (III) reduction proceeded in parallel in the presence of magnetite. Inhibition experiments with 2-bromoethane sulfonate (BES) or phosphate showed that interspecies hydrogen transfer and Fe (III) reduction also occurred in methane production from ethanol. 16S rRNA-based Illumina sequencing results showed that Dechloromonas, Thauera, Desulfovibrio and Clostridium were the dominant putative Fe (III) -reducers, and that hydrogenotrophic Methanobacterium accounted for about 88% of the total archaeal community. These results indicated that magnetite nanoparticles that acted as electron acceptor could facilitate rapid oxidation of ethanol by members of the Fe (III) -reducers in PEM-HZ and establishment of the syntrophic relationship of Fe (III) -reducers with Methanobacterium via interspecies hydrogen transfer. Our results could offer a model to understand the microbial interaction with magnetite from a novel angle during methanogenesis.

  1. Size dependent microbial oxidation and reduction of magnetite nano- and micro-particles

    PubMed Central

    Byrne, James M.; van der Laan, Gerrit; Figueroa, Adriana I.; Qafoku, Odeta; Wang, Chongmin; Pearce, Carolyn I.; Jackson, Michael; Feinberg, Joshua; Rosso, Kevin M.; Kappler, Andreas

    2016-01-01

    The ability for magnetite to act as a recyclable electron donor and acceptor for Fe-metabolizing bacteria has recently been shown. However, it remains poorly understood whether microbe-mineral interfacial electron transfer processes are limited by the redox capacity of the magnetite surface or that of whole particles. Here we examine this issue for the phototrophic Fe(II)-oxidizing bacteria Rhodopseudomonas palustris TIE-1 and the Fe(III)-reducing bacteria Geobacter sulfurreducens, comparing magnetite nanoparticles (d ≈ 12 nm) against microparticles (d ≈ 100–200 nm). By integrating surface-sensitive and bulk-sensitive measurement techniques we observed a particle surface that was enriched in Fe(II) with respect to a more oxidized core. This enables microbial Fe(II) oxidation to occur relatively easily at the surface of the mineral suggesting that the electron transfer is dependent upon particle size. However, microbial Fe(III) reduction proceeds via conduction of electrons into the particle interior, i.e. it can be considered as more of a bulk electron transfer process that is independent of particle size. The finding has potential implications on the ability of magnetite to be used for long range electron transport in soils and sediments. PMID:27492680

  2. Formation of magnetite and iron-rich carbonates by thermophilic iron-reducing bacteria

    SciTech Connect

    Zhang, C.; Liu, S.; Roh, Y.; Cole, D.; Phelps, T.; Vali, H.; Kirschvink, J.L.; Onsttot, T.; McKay, D.

    1997-06-01

    Laboratory experiments were performed to study the formation of iron minerals by a thermophilic (45 to 75 C) fermentative iron-reducing bacterial culture (TOR39) obtained from the deep subsurface. Using amorphous Fe(III) oxyhydroxide as an electron acceptor and glucose as an electron donor, TOR39 produced magnetite and iron-rich carbonates at conditions consistent, on a thermodynamic basis, with Eh ({minus}200 mV to {minus}415 mV) and pH (6.2 to 7.7) values determined for these experiments. Analyses of the precipitating solid phases by X-ray diffraction showed that the starting amorphous Fe(III) oxyhydroxide was nearly completely converted to magnetite and Fe-rich carbonate after 20 days of incubation. Increasing bicarbonate concentration in the chemical milieu resulted in increased proportions of siderite relative to magnetite and the addition of MgCl{sub 2} caused the formation of magnesium-rich carbonate in addition to siderite. The results suggest that the TOR39 bacterial culture may have the capacity to form magnetite and iron-rich carbonates in a variety of geochemical conditions. These results may have significant implications for studying the past biogenic activities in the Martian meteorite ALH84001.

  3. Cell surface receptor interactions of C 27-steroid hormone ecdysterone immobilized on nanodispersed magnetite

    NASA Astrophysics Data System (ADS)

    Mykhaylyk, O. M.; Kotzuruba, A. V.; Buchanevich, O. M.; Gula, N. M.; Bakai, E. A.

    1999-04-01

    Concurrent binding of ecdysterone immobilized on the nanodispersed magnetite with intact rat cells in the presence of free ecdysterone was investigated. The results imply the existence of high affinity ecdysterone-specific binding sites on the surface of liver and spleen macrophages, thymus and spleen lymphocytes, erythrocytes and hepatocytes. Membrane effects may be involved in the signal transduction mechanisms activated by ecdysterone.

  4. Evaluation of the sediment remediation potential of magnetite impregnated activated carbons and biochars

    NASA Astrophysics Data System (ADS)

    Werner, David; Han, Zhantao; Karapanagioti, Hrissi

    2014-05-01

    We evaluated the sediment remediation potential of magnetic composite materials synthesized by precipitating magnetite minerals onto activated carbons and biochars. Magnetite impregnation did not reduce the phenanthrene sorption capacity of the activated carbon or biochar component of the composite materials. The phenanthrene sorption capacity of the composite materials correlated with the surface areas of the pristine carbonaceous sorbents. XRD data and mass magnetic susceptibility data indicate that the mineral component of the composites is indeed nearly 100% magnetite. Addition of magnetic activated carbon to River Tyne sediment slurries reduced polycyclic aromatic hydrocarbon availability by more than 90%. After 3 months of mixing, 77% of the added magnetic activated carbon could be recovered with a magnetic rod. Continued monitoring showed that polycyclic aromatic hydrocarbon availability remained low following the magnetic recovery of most of the added sorbent mass. XRD analysis confirmed the presence of magnetite in the recovered sorbent material, with some other mineral phases such as calcite and quartz also being identifiable. Magnetic activated carbon has potential as a recoverable sorbent amendment for the treatment of sediment polluted with hydrophobic organic compounds. Further work will include an evaluation of the long-term magnetic sorbent effectiveness and stability in unmixed sediments under aerobic and anaerobic conditions and regeneration and re-use options for the recovered sorbent materials.

  5. Sorptive uptake of selenium with magnetite and its supported materials onto activated carbon.

    PubMed

    Kwon, Jae H; Wilson, Lee D; Sammynaiken, R

    2015-11-01

    Kinetic and equilibrium uptake studies of selenite in aqueous solution with synthetic magnetite (Mag-P), commercial magnetite (Mag-C), goethite, activated carbon (AC), and a composite material containing 19% magnetite supported on activated carbon (CM-19) were investigated. Kinetic uptake studies used a one-pot setup at pH 5.26 at variable temperature. Sampling of unbound selenite in-situ was achieved with analytical detection by atomic absorbance. The sorptive uptake at equilibrium and kinetic conditions are listed in descending order: goethite>Mag-P>Mag-C>CM-19. Kinetic uptake parameters reveal that Mag-P showed apparent negative values for the activation energy (E(a)) and the enthalpy of activation (ΔH(‡)), in agreement with a multi-step process for the kinetic uptake of selenite. By contrast, Mag-C, CM-19, and goethite showed positive values for E(a) and ΔH(‡). The uptake properties of the various sorbent materials with selenite are in accordance with the formation of inner- and out-sphere complexes. Leaching of iron from the composite material (CM-19) was attenuated due to the stabilizing effect of the magnetite within the pore sites and the surface of AC. Supported iron oxide nanomaterial composites represent a unique sorbent material with tunable uptake properties toward inorganic selenite in aqueous solution.

  6. Structure of magnetite lodes at the Estyunino iron deposit in the central Urals

    NASA Astrophysics Data System (ADS)

    Rudnitsky, V. F.; Aleshin, K. B.; Kuznetsov, A. Zh.; Ivanchenko, V. S.

    2013-11-01

    The structure of magnetite lodes is determined by iron and sulfur distribution, as well as texture and structure of ore. These features have been revealed by documentation of cores from ore intervals in exploration boreholes penetrating two main lodes 21 and 22 of the Estyunino iron deposit. The documentation of cores was accompanied by sampling for microscopic examination of texture and structure of ore and selection of Fe and S contents in ore. Then these data were summarized as sections of the lodes. It was established that the structure of magnetite lodes is characterized by conformable ore layers distinguished by texture, structure, and Fe and S contents. Banded and spotty ores containing less than 50% magnetite are predominant. Layers of homogeneous massive ore are infrequent. The textural pattern indicates a volcaniclastic nature of host rocks. The spotty texture is characteristic of hyaloclastites with vitreous shards. The banded texture with oriented distribution of fiamme is inherent to volcaniclastic rocks. In both cases, magnetite selectively replaces dark-colored vitreous fragments and is also dispersed in the salic matrix and lava fragments. No indications of crosscutting superposed relationships are observed. The available data can be satisfactorily explained by an impregnation-metasomatic mode of ore deposition.

  7. Size dependent microbial oxidation and reduction of magnetite nano- and micro-particles

    NASA Astrophysics Data System (ADS)

    Byrne, James M.; van der Laan, Gerrit; Figueroa, Adriana I.; Qafoku, Odeta; Wang, Chongmin; Pearce, Carolyn I.; Jackson, Michael; Feinberg, Joshua; Rosso, Kevin M.; Kappler, Andreas

    2016-08-01

    The ability for magnetite to act as a recyclable electron donor and acceptor for Fe-metabolizing bacteria has recently been shown. However, it remains poorly understood whether microbe-mineral interfacial electron transfer processes are limited by the redox capacity of the magnetite surface or that of whole particles. Here we examine this issue for the phototrophic Fe(II)-oxidizing bacteria Rhodopseudomonas palustris TIE-1 and the Fe(III)-reducing bacteria Geobacter sulfurreducens, comparing magnetite nanoparticles (d ≈ 12 nm) against microparticles (d ≈ 100–200 nm). By integrating surface-sensitive and bulk-sensitive measurement techniques we observed a particle surface that was enriched in Fe(II) with respect to a more oxidized core. This enables microbial Fe(II) oxidation to occur relatively easily at the surface of the mineral suggesting that the electron transfer is dependent upon particle size. However, microbial Fe(III) reduction proceeds via conduction of electrons into the particle interior, i.e. it can be considered as more of a bulk electron transfer process that is independent of particle size. The finding has potential implications on the ability of magnetite to be used for long range electron transport in soils and sediments.

  8. In situ formation of magnetite reactive barriers in soil for waste stabilization

    DOEpatents

    Moore, Robert C.

    2003-01-01

    Reactive barriers containing magnetite and methods for making magnetite reactive barriers in situ in soil for sequestering soil contaminants including actinides and heavy metals, organic materials, iodine and technetium are disclosed. According to one embodiment, a two-step reagent introduction into soil takes place. In the first step, free oxygen is removed from the soil by separately injecting into the soil aqueous solutions of iron (II) salt, for example FeCl.sub.2, and base, for example NaOH or NH.sub.3 in about a 1:1 volume ratio. Then, in the second step, similar reagents are injected a second time (however, according to about a 1:2 volume ratio, iron to salt) to form magnetite. The magnetite formation is facilitated, in part, due to slow intrusion of oxygen into the soil from the surface. The invention techniques are suited to injection of reagents into soil in proximity to a contamination plume or source allowing in situ formation of the reactive barrier at the location of waste or hazardous material. Mixing of reagents to form. precipitate is mediated and enhanced through movement of reagents in soil as a result of phenomena including capillary action, movement of groundwater, soil washing and reagent injection pressure.

  9. Multiple morphologies of gold-magnetite heterostructure nanoparticles are effectively functionalized with protein for cell targeting.

    PubMed

    Krystofiak, Evan S; Mattson, Eric C; Voyles, Paul M; Hirschmugl, Carol J; Albrecht, Ralph M; Gajdardziska-Josifovska, Marija; Oliver, Julie A

    2013-08-01

    Nanoparticles composed of a magnetic iron oxide core surrounded by a metal shell have utility in a broad range of biomedical applications. However, the presence of surface energy differences between the two components makes wetting of oxide with metal unfavorable, precluding a "core-shell" structure of an oxide core completely surrounded by a thin metal shell. Three-dimensional island growth followed by island coalescence into thick shells is favored over the two-dimensional layer-by-layer growth of a thin, continuous metal coating of a true core-shell. Aqueous synthesis of gold-coated magnetite nanoparticles with analysis by infrared, energy-dispersive X-ray, and electron energy loss spectroscopies; high-resolution transmission electron microscopy; selected area electron diffraction; and high-angle annular dark-field scanning transmission electron microscopy showed two distinct morphologies that are inconsistent with an idealized core-shell. The majority were isolated ~16-22-nm-diameter nanoparticles consisting of ~7-nm-diameter magnetite and a thick deposition of gold, most often discontinuous, with some potentially "sandwiched" morphologies. A minority were aggregates of agglomerated magnetite decorated with gold but displaying significant bare magnetite. Both populations were successfully conjugated to fibrinogen and targeted to surface-activated platelets, demonstrating that iron oxide-gold nanoparticles produced by aqueous synthesis do not require an ideal core-shell structure for biological activity in cell labeling and targeting applications.

  10. The role of polymer films on the oxidation of magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Letti, C. J.; Paterno, L. G.; Pereira-da-Silva, M. A.; Morais, P. C.; Soler, M. A. G.

    2017-02-01

    A detailed investigation about the role of polymer films on the oxidation process of magnetite nanoparticles (∼7 nm diameter), under laser irradiation is performed employing micro Raman spectroscopy. To support this investigation, Fe3O4-np are synthesized by the co-precipitation method and assembled layer-by-layer with sodium sulfonated polystyrene (PSS). Polymer films (Fe3O4-np/PSS)n with n=2,3,5,7,10 and 25 bilayers are employed as a model system to study the oxidation process under laser irradiation. Raman data are further processed by principal component analysis. Our findings suggest that PSS protects Fe3O4-np from oxidation when compared to powder samples, even for the sample with the greater number of bilayers. Further, the oxidation of magnetite to maghemite occurs preferably for thinner films up to 7 bilayers, while the onset for the formation of the hematite phase depends on the laser intensity for thicker films. Water takes part on the oxidation processes of magnetite, the oxidation/phase transformation of Fe3O4-np is intensified in films with more bilayers, since more water is included in those films. Encapsulation of Fe3O4-np by PSS in layer-by-layer films showed to be very efficient to avoid the oxidation process in nanosized magnetite.

  11. Titaniferous magnetite in the layered intrusive complex at Lakathah, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Martin, Conrad; Roberts, Ralph Jackson; Stoeser, D.B.

    1979-01-01

    The Lakathah layered intrusive complex about 90 km east of Qunfudhah contains significant resources of low-grade titanium-bearing rock. The complex is about 10 km in diameter and consists of three principal units: an outer syenite ring, an intermediate diorite-gabbro zone, and a central pyroxenite-hornblendite core. The principal mineralization zone is in the ultramafic core of the complex. The titanium is mainly in titaniferous magnetite, but some is in ilmenite intergrown with magnetite and in the titanium-bearing hornblende, kaersutite. The titaniferous magnetite is in concordant lenses and veinlets and is disseminated throughout the host rock. The lenses and veins range from a few centimeters to 3 m in width and are as much as 50 m long. The layered disseminated bodies contain as much as 25 percent magnetite. Exploratory drilling showed that an area 500 by 1000 m contains titaniferous rock averaging about 6.2 percent TiO2. This mineralized zone contains about 175,000,000 tons per 100 m depth. Material of this grade is not commercial at this time, but may be a future resource. Alluvial deposits along the Red Sea near Al Qunfudhah should be tested for possible deposits of titaniferous sand.

  12. First-order metal-insulator transition and infrared identification of shape-controlled magnetite nanocrystals

    NASA Astrophysics Data System (ADS)

    Zheng, Lei; Su, Wei; Qi, Zeming; Xu, Yang; Zhou, Min; Xie, Yi

    2011-12-01

    The first-order metal-insulator transition (MIT) in magnetite has been known for a long time but is still controversial in its nature. In this study, well-defined magnetite nanocrystals (NCs) with controllable size, shape and terminated surface are first employed to elucidate this important issue, and new discoveries such as a highly suppressed phase transition temperature are identified by monitoring the variable-temperature electric resistance and infrared spectroscopy. Significantly, by carefully comparing the infrared vibrational bands of the as-prepared magnetite NCs with octahedral and cubic shapes, respectively, we found that these two forms of magnetite NCs exhibited different transmittance changes and frequency shifts of the infrared characteristics, presumably due to the differences in the lattice distortions on the corresponding {001} and {111} terminal surfaces. This result produced evidence in support of the charge ordering of Fe atoms along the low dimensionality at octahedral B sites undergoing the MIT. Taken together, infrared identification was proposed to be an available characterization strategy for MIT, which can reflect more information on the elusive lattice distortion of crystallographic structure or exposed surfaces.

  13. Light scattering in colloidal solution of magnetite in electric and magnetic fields.

    PubMed

    Yerin, Constantine V

    2007-04-15

    Light scattering by magnetite particles in kerosene under the simultaneous action of crossed electric and magnetic fields was studied. Decreasing of variation of light scattering intensity at some values of electric and magnetic fields have been found. Values of fields at which a minimum of light scattering intensity occur depend on the angle between laser beam and the plane of crossed fields.

  14. A&M. Special shielding materials. Stockpile of magnetite, used for making ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    A&M. Special shielding materials. Stockpile of magnetite, used for making high-density concrete, and loading conveyor near TAN-607 construction site. Date: September 25, 1953. INEEL negative no. 8710 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  15. Magnetically recyclable magnetite-palladium (Nanocat-Fe-Pd) nanocatalyst for the Buchwald-Hartwig reaction

    EPA Science Inventory

    The immobilization of Pd on magnetite surface afforded (Nanocat-Fe-Pd) using inexpensive precursors and its catalytic role in the Buchwald-Hartwig reaction for arylation of amines and amides was investigated; C-N bond formation was achieved in moderate to excellent yields and the...

  16. Morphological analysis of mouse lungs after treatment with magnetite-based magnetic fluid stabilized with DMSA

    NASA Astrophysics Data System (ADS)

    Garcia, Mônica Pereira; Miranda Parca, Renata; Braun Chaves, Sacha; Paulino Silva, Luciano; Djalma Santos, Antonio; Guerrero Marques Lacava, Zulmira; César Morais, Paulo; Azevedo, Ricardo Bentes

    2005-05-01

    Mouse lungs injected with magnetic fluids based on magnetite nanoparticles stabilized by 2,3-dimercaptosuccinic acid were studied. We observed clusters of magnetic nanoparticles inside blood vessels, within the organ parenchyma and cells, as well as increased numbers of leukocytes in the organ. Both the particle concentration and organ inflammation diminished in a time-dependent manner.

  17. Synthesis of superparamagnetic silica-coated magnetite nanoparticles for biomedical applications

    SciTech Connect

    Kaur, Navjot Chudasama, Bhupendra

    2015-05-15

    Multifunctional superparamagnetic iron oxide nanoparticles (SPIONs) coated with silica are widely researched for biomedical applications such as magnetic resonance imaging, tissue repair, cell separation, hyperthermia, drug delivery, etc. In this article synthesis of magnetite (Fe{sub 3}O{sub 4}) nanoparticles and their coating with SiO{sub 2} is reported. Fe{sub 3}O{sub 4} nanoparticles were synthesized by chemical co-precipitation and it was coated with silica by hydrolysis and condensation of tetraethylorthosilicate. XRD, FTIR, TEM and VSM techniques were used to characterize bare and coated nanoparticles. Results indicated that the average size of SPIONS was 8.4 nm. X-ray diffraction patterns of silica coated SPIONS were identical to that of SPIONS confirming the inner spinal structure of SPIONS. FTIR results confirmed the binding of silica with the magnetite and the formation of the silica shell around the magnetite core. Magnetic properties of SPIONS and silica coated SPIONS are determined by VSM. They are superparamagnetic. The major conclusion drawn from this study is that the synthesis route yields stable, non-aggregated magnetite-silica core-shell nanostructures with tailored morphology and excellent magnetic properties.

  18. Dispersion in photonic crystals

    NASA Astrophysics Data System (ADS)

    Witzens, Jeremy

    2005-11-01

    fabricated and characterized. A purely theoretical section of the thesis investigates advanced data processing techniques for the finite-difference time-domain method. In particular it is shown that an inner product can be used to filter out specific photonic crystal modes or photonic crystal waveguide modes (Bloch-modes). However it is also shown that the numerical accuracy of this inner product severely worsens for Bloch modes with very low group velocities.

  19. Method for solid state crystal growth

    DOEpatents

    Nolas, George S.; Beekman, Matthew K.

    2013-04-09

    A novel method for high quality crystal growth of intermetallic clathrates is presented. The synthesis of high quality pure phase crystals has been complicated by the simultaneous formation of both clathrate type-I and clathrate type-II structures. It was found that selective, phase pure, single-crystal growth of type-I and type-II clathrates can be achieved by maintaining sufficient partial pressure of a chemical constituent during slow, controlled deprivation of the chemical constituent from the primary reactant. The chemical constituent is slowly removed from the primary reactant by the reaction of the chemical constituent vapor with a secondary reactant, spatially separated from the primary reactant, in a closed volume under uniaxial pressure and heat to form the single phase pure crystals.

  20. Conformal pure radiation with parallel rays

    NASA Astrophysics Data System (ADS)

    Leistner, Thomas; Nurowski, Paweł

    2012-03-01

    We define pure radiation metrics with parallel rays to be n-dimensional pseudo-Riemannian metrics that admit a parallel null line bundle K and whose Ricci tensor vanishes on vectors that are orthogonal to K. We give necessary conditions in terms of the Weyl, Cotton and Bach tensors for a pseudo-Riemannian metric to be conformal to a pure radiation metric with parallel rays. Then, we derive conditions in terms of the tractor calculus that are equivalent to the existence of a pure radiation metric with parallel rays in a conformal class. We also give analogous results for n-dimensional pseudo-Riemannian pp-waves.