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Sample records for paz au-cu skarn

  1. Geology, mineralization, stable isotope geochemistry, and fluid inclusion characteristics of the Novogodnee-Monto oxidized Au-(Cu) skarn and porphyry deposit, Polar Ural, Russia

    NASA Astrophysics Data System (ADS)

    Soloviev, Serguei G.; Kryazhev, Sergey G.; Dvurechenskaya, Svetlana S.

    2013-06-01

    The Novogodnee-Monto oxidized Au-(Cu) skarn and porphyry deposit is situated in the large metallogenic belt of magnetite skarn and Cu-Au porphyry deposits formed along the Devonian-Carboniferous Urals orogen. The deposit area incorporates nearly contemporaneous Middle-Late Devonian to Late Devonian-Early Carboniferous calc-alkaline (gabbro to diorite) and potassic (monzogabbro, monzodiorite- to monzonite-porphyry, also lamprophyres) intrusive suites. The deposit is represented by magnetite skarn overprinted by amphibole-chlorite-epidote-quartz-albite and then sericite-quartz-carbonate assemblages bearing Au-sulfide mineralization. This mineralization includes early high-fineness (900-990 ‰) native Au associated mostly with cobaltite as well as with chalcopyrite and Co-pyrite, intermediate-stage native Au (fineness 830-860 ‰) associated mostly with galena, and late native Au (760-830 ‰) associated with Te minerals. Fluid inclusion and stable isotope data indicate an involvement of magmatic-hydrothermal high-salinity (>20 wt.% NaCl-equiv.) chloride fluids. The potassic igneous suite may have directly sourced fluids, metals, and/or sulfur. The abundance of Au mineralization is consistent with the oxidized character of the system, and its association with Co-sulfides suggests elevated sulfur fugacity.

  2. Gold-bearing skarns

    USGS Publications Warehouse

    Theodore, Ted G.; Orris, Greta J.; Hammerstrom, Jane M.; Bliss, James D.

    1991-01-01

    In recent years, a significant proportion of the mining industry's interest has been centered on discovery of gold deposits; this includes discovery of additional deposits where gold occurs in skarn, such as at Fortitude, Nevada, and at Red Dome, Australia. Under the classification of Au-bearing skarns, we have modeled these and similar gold-rich deposits that have a gold grade of at least 1 g/t and exhibit distinctive skarn mineralogy. Two subtypes, Au-skarns and byproduct Au-skarns, can be recognized on the basis of gold, silver, and base-metal grades, although many other geological factors apparently are still undistinguishable largely because of a lack of detailed studies of the Au-skarns. Median grades and tonnage for 40 Au-skarn deposits are 8.6 g/t Au, 5.0 g/t Ag, and 213,000 t. Median grades and tonnage for 50 byproduct and Au-skarn deposits are 3.7 g/t Au, 37 g/t Ag, and 330,000 t. Gold-bearing skarns are generally calcic exoskarns associated with intense retrograde hydrosilicate alteration. These skarns may contain economic amounts of numerous other commodities (Cu, Fe, Pb, Zn, As, Bi, W, Sb, Co, Cd, and S) as well as gold and silver. Most Au-bearing skarns are found in Paleozoic and Cenozoic orogenic-belt and island-arc settings and are associated with felsic to intermediate intrusive rocks of Paleozoic to Tertiary age. Native gold, electru, pyrite, pyrrhotite, chalcopyrite, arsenopyrite, sphalerite, galena, bismuth minerals, and magnetite or hematite are the most common opaque minerals. Gangue minerals typically include garnet (andradite-grossular), pyroxene (diopside-hedenbergite), wollastonite, chlorite, epidote, quartz, actinolite-tremolite, and (or) calcite.

  3. Ethylene binding to Au/Cu alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    Gammage, Michael D.; Stauffer, Shannon; Henkelman, Graeme; Becker, Michael F.; Keto, John W.; Kovar, Desiderio

    2016-11-01

    Weak chemisorption of ethylene has been shown to be an important characteristic in the use of metals for the separation of ethylene from ethane. Previously, density functional theory (DFT) has been used to predict the binding energies of various metals and alloys, with Ag having the lowest chemisorption energy amongst the metals and alloys studied. Here Au/Cu alloys are investigated by a combination of DFT calculations and experimental measurements. It is inferred from experiments that the binding energy between a Au/Cu alloy and ethylene is lower than to either of the pure metals, and DFT calculations confirm that this is the case when Au segregates to the particle surface. Implications of this work suggest that it may be possible to further tune the binding energy with ethylene by compositional and morphological control of films produced from Au-surface segregated alloys.

  4. The Thermal Stability of Nanocrystalline Au-Cu Alloys

    SciTech Connect

    Jankowski, A F; Saw, C K; Hayes, J P

    2006-02-15

    Grain refinement to the nanocrystalline scale is known to enhance physical properties as strength and surface hardness. For the case of Au-Cu alloys, development of the pulsed electroplating has led to the functional control of nanocrystalline grain size in the as-deposited condition. The thermal aging of Au-Cu electrodeposits is now investigated to assess the stability of the nanocrystalline grain structure and the difference between two diffusion mechanisms. The mobility of grain boundaries, dominant at low temperatures, leads to coarsening of grain size whereas at high temperature the process of bulk diffusion dominates. Although the kinetics of bulk diffusion are slow below 500 K at 10{sup -20} cm{sup 2} {center_dot} sec, the kinetics of grain boundary diffusion are faster at 10{sup -16} cm{sup 2} {center_dot} sec. The diffusivity values indicate that the grain boundaries of the as-deposited nanocrystalline Au-Cu are mobile and sensitive to low-temperature anneal treatments affecting the grain size, hence the strength of the material.

  5. Modification of TiO2 by Bimetallic Au-Cu Nanoparticles for Wastewater Treatment

    PubMed Central

    Hai, Zibin; Kolli, Nadia EL; Uribe, Daniel Bahena; Beaunier, Patricia; José-Yacaman, Miguel; Vigneron, Jackie; Etcheberry, Arnaud; Sorgues, Sébastien; Colbeau-Justin, Christophe; Chen, Jiafu; Remita, Hynd

    2016-01-01

    Au, Cu and bimetallic Au-Cu nanoparticles were synthesized on the surface of commercial TiO2 compounds (P25) by reduction of the metal precursors with tetrakis (hydroxymethyl) phosphonium chloride (THPC) (0.5 % in weight). The alloyed structure of Au-Cu NPs was confirmed by HAADF-STEM, EDS, HRTEM and XPS techniques. The photocatalytic properties of the modified TiO2 have been studied for phenol photodegradation in aqueous suspensions under UV-visible irradiation. The modification by the metal nanoparticles induces an increase in the photocatalytic activity. The highest photocatalytic activity is obtained with Au-Cu/TiO2 (Au/Cu 1:3). Their electronic properties have been studied by time resolved microwave conductivity (TRMC) to follow the charge-carrier dynamics. TRMC measurements show that the TiO2 modification with Au, Cu and Au-Cu nanoparticles plays a role in charge-carrier separations increasing the activity under UV-light. Indeed, the metal nanoparticles act as a sink for electron, decreasing the charge carrier recombination. The TRMC measurements show also that the bimetallic Au-Cu nanoparticles are more efficient in electron scavenging than the monometallic Au and Cu ones. PMID:27274844

  6. Surface plasmon resonance of two-segmented Au Cu nanorods

    NASA Astrophysics Data System (ADS)

    Azarian, A.; Iraji zad, A.; Dolati, A.; Ghorbani, M.

    2008-10-01

    Two-segmented gold-copper nanorods were electrodeposited inside the pores of polycarbonate track-etched membranes from two separate solutions. The PCT membranes were dissolved in dichloromethane (CH2Cl2) and the solvent was replaced by methanol solution. Optical absorption spectra of two-segmented Au-Cu nanorods dispersed in methanol showed two peaks which were related to the transverse mode of copper and the longitudinal mode of gold. By increasing the length of the gold segment, when the total length of both metals was fixed at 1 µm, the copper and gold peaks shifted to the blue and red wavelengths, respectively. We observed that the wavelengths of the extinction peaks are not in good agreement with the expected value obtained from calculations using the nominal dielectric constant of the medium. Therefore, we suggest the effective medium dielectric constant (ɛmeff) for Cu and Au segments by comparing the experimental data and calculation results. The values of ɛmeff decrease by increasing the gold length.

  7. Large extrinsic spin Hall effect in Au-Cu alloys by extensive atomic disorder scattering

    NASA Astrophysics Data System (ADS)

    Zou, L. K.; Wang, S. H.; Zhang, Y.; Sun, J. R.; Cai, J. W.; Kang, S. S.

    2016-01-01

    Spin Hall angle, which denotes the conversion efficiency between spin and charge current, is a key parameter in the pure spin current phenomenon. The search for materials with large spin Hall angle is indeed important for scientific interest and potential application in spintronics. Here the large enhanced spin Hall effect (SHE) of Au-Cu alloy is reported by investigating the spin Seebeck effect, spin Hall anomalous Hall effect, and spin Hall magnetoresistance of the Y3F e5O12 (YIG)/A uxC u1 -x hybrid structure over the full composition. At the near equiatomic Au-Cu composition with maximum atomic disorder scattering, the spin Hall angle of the Au-Cu alloy increases by two to three times together with a moderate spin diffusion length in comparison with Au. The longitudinal spin Seebeck voltage and the spin Hall magnetoresistance ratio also increase by two to three times. More importantly, no evidence of anomalous Hall effect is observed in all YIG/Au-Cu samples, in contrast to the cases of other giant SHE materials Pt(Pd), Ta, and W. This behavior makes Au-Cu free from any suspicion of the magnetic proximity effect involved in the hybrid structure, and thus the Au-Cu alloy can be an ideal material for pure spin current study.

  8. Au@Cu(II)-MOF: Highly Efficient Bifunctional Heterogeneous Catalyst for Successive Oxidation-Condensation Reactions.

    PubMed

    Wang, Jing-Si; Jin, Fa-Zheng; Ma, Hui-Chao; Li, Xiao-Bo; Liu, Ming-Yang; Kan, Jing-Lan; Chen, Gong-Jun; Dong, Yu-Bin

    2016-07-01

    A new composite Au@Cu(II)-MOF catalyst has been synthesized via solution impregnation and full characterized by HRTEM, SEM-EDS, XRD, gas adsorption-desorption, XPS, and ICP analysis. It has been shown here that the Cu(II)-framework can be a useful platform to stabilize and support gold nanoparticles (Au NPs). The obtained Au@Cu(II)-MOF exhibits a bifunctional catalytic behavior and is able to promote selective aerobic benzyl alcohol oxidation-Knoevenagel condensation in a stepwise way. PMID:27322613

  9. Size Control and Growth Process Study of Au@Cu2O Particles

    NASA Astrophysics Data System (ADS)

    Wang, Yuyuan; Zheng, Min; Liu, Shengnan; Wang, Zuoshan

    2016-09-01

    Au@Cu2O cuboctahedron with gold triangular nanoplate core and Cu2O shell was synthesized by a chemical method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) tests demonstrated that the as-synthesis samples were consisted of gold triangular nanoplate core and Cu2O shell, and both of them were in good crystallization. The effective size control of the particles could be realized by controlling the amount of Au cores added in the synthetic process and Au@Cu2O particles with different shell thickness could be synthesized. The decrease of Cu2O shell thickness had a great difference in the optical performance, including blue shift of the resonant peaks and enhanced absorption intensity. The growth process from rough sheet structure to cuboctahedron was also explored. The results of photocatalytic degradation experiment showed that Au@Cu2O particles showed much better photocatalytic performance than that of pure Cu2O. The improved photocatalytic property of the Au@Cu2O particles was attributed to the comprehensive effect of the enhanced visible-light absorption and high separation rate of electron-hole pairs.

  10. Size Control and Growth Process Study of Au@Cu2O Particles.

    PubMed

    Wang, Yuyuan; Zheng, Min; Liu, Shengnan; Wang, Zuoshan

    2016-12-01

    Au@Cu2O cuboctahedron with gold triangular nanoplate core and Cu2O shell was synthesized by a chemical method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) tests demonstrated that the as-synthesis samples were consisted of gold triangular nanoplate core and Cu2O shell, and both of them were in good crystallization. The effective size control of the particles could be realized by controlling the amount of Au cores added in the synthetic process and Au@Cu2O particles with different shell thickness could be synthesized. The decrease of Cu2O shell thickness had a great difference in the optical performance, including blue shift of the resonant peaks and enhanced absorption intensity. The growth process from rough sheet structure to cuboctahedron was also explored. The results of photocatalytic degradation experiment showed that Au@Cu2O particles showed much better photocatalytic performance than that of pure Cu2O. The improved photocatalytic property of the Au@Cu2O particles was attributed to the comprehensive effect of the enhanced visible-light absorption and high separation rate of electron-hole pairs. PMID:27613067

  11. Reverse telescoping in distal skarns at Campiglia Marittima (Italy)

    NASA Astrophysics Data System (ADS)

    Vezzoni, Simone; Dini, Andrea; Rocchi, Sergio

    2014-05-01

    Skarn deposits commonly results from the metasomatic alteration of a rock, usually carbonate-rich, by infiltration of hydrothermal fluids. Most carbonate-hosted skarn deposits show a direct spatial relationship with magmatic intrusions and an intimate relationship with porphyry copper deposits. Their primary mineralogical and geochemical features indicate metasomatism by high-temperature magmatic fluids. Conversely, many distal Pb-Zn-Ag skarns pose an important challenge because there is no apparent association with magmatic intrusions and external, meteoric and/or basinal fluids should become increasingly dominant with increasing distance from the igneous source. Nevertheless recent investigation of distal skarn deposits indicates that ore-forming fluids match the composition of proximal magmatic fluids in granitoid-related mineral deposits. Besides that metal producer (Pb, Zn, Ag, Cu, Fe, W, Sn), skarn deposits can be key to understanding fluid dynamics at the periphery of magmatic-hydrothermal systems, unraveling pathways to hidden ore deposits (e.g porphyry copper). In this scenario, research on distal skarns opens new perspectives for deep mineral exploration and/or modeling of intrusion centered geothermal systems, because they should represent the outer limit of the hydrothermal system dominated by magmatic aqueous fluids. Here we present exceptional evidences from a distal Pb-Zn-Ag skarn deposit in Campiglia Marittima, Italy, where the magma, after having released the metasomatic fluids, fled up chasing its own fluid stream and invading large pockets of the newly formed skarn bodies at shallower level. Detailed underground mapping and petrologic data indicate that, after the formation of a typical distal Pb-Zn-Ag skarn, the intrusion of the parent magma produced prograde reactions in the skarn silicates, mobilization of the Pb-Zn-Ag sulfides and precipitation of a new Cu-Fe sulfide assemblage. This is a very unusual case of reverse telescoping during which

  12. Detection of H2O2 at the nanomolar level by electrode modified with ultrathin AuCu nanowires.

    PubMed

    Wang, Ning; Han, Yu; Xu, Ying; Gao, Caizhen; Cao, Xia

    2015-01-01

    Bimetallic AuCu nanowires (AuCuNWs) are synthesized via a facile water solution method at room temperature. Enhanced electrocatalytic activity is observed toward the oxidation of H2O2, which makes the AuCu nanowire, along with its unique catalytic properties, intriguing bifunctional mechanism, and surface atomic construction, a promising platform for the amplification of interfacing signal. A highly sensitive H2O2 biosensor is thus developed on the base of the as-prepared AuCuNW catalyst. A very low real determination limit (2.0 nM) was reached, and a linear range as wide as 5 orders of magnitude was demonstrated. In addition, a trace amount of H2O2, which was released from Raw 264.7 cells, was selectively detected, hinting at the possible applications for real-time quantitative detection of H2O2 in a biological environment. PMID:25418032

  13. Synthesis and Characterization of Au@Cu Core-Shell Nanoparticles

    NASA Astrophysics Data System (ADS)

    Khanal, Subarna; Velazquez-Salazar, Jesus; Yacaman, Miguel Jose

    2011-10-01

    The synthesis of bimetallic nanoparticles has become so important in present times due to its diverse applications of nanotechnology. Particularly most of the bimetallic nanoparticles are focused to use in catalysis, plasmonic, magnetic, sensors, and many other applications. In Au/Cu case, the bulk Au and Cu are soluble at all compositions. But the structure of Au/Cu nanoparticles depends on the preparation methods. The structure might be the core shell, alloys or other morphology. Au- Cu core-shell nanocrystals were prepared using a two-step polyol reduction method. First, Au core seeds were prepared by reducing HAuCl4. 4H2O in ethylene glycol (EG) using oil-bath heating in the presence of polyvinylpyrrolidone (PVP) as a polymer surfactant. Then Cu shells were overgrown on Au core seeds by reducing Cu2(OAc)4 in EG with PVP again using oil-bath heating. The morphology is studied by STEM HITACHI S-5500.The resultant crystal structures were characterized using TEM, high-resolution (HR)-TEM and the STEM were using for the study of micro analysis.

  14. Catalytic degradation of dye molecules and in situ SERS monitoring by peroxidase-like Au/CuS composite

    NASA Astrophysics Data System (ADS)

    Cai, Qian; Lu, Shunkai; Liao, Fan; Li, Yanqing; Ma, Shuzhen; Shao, Mingwang

    2014-06-01

    In this paper, Au/CuS composites were fabricated by a two-step method based on a facile solvothermal approach combined with the in situ reduction. It was demonstrated that the Au/CuS composite not only exhibited excellent peroxidase-like catalytic activity in the oxidation of the typical peroxidases (o-phenylenediamine and diaminobenzidine), but also showed promising SERS performance with remarkable sensitivity and high reproducibility. Based on these properties, the bi-functional Au/CuS composite was employed both as a catalyst for degrading a pollutant (Rhodamine 6G) and a SERS substrate for real-time monitoring of the degradation process quantitatively.In this paper, Au/CuS composites were fabricated by a two-step method based on a facile solvothermal approach combined with the in situ reduction. It was demonstrated that the Au/CuS composite not only exhibited excellent peroxidase-like catalytic activity in the oxidation of the typical peroxidases (o-phenylenediamine and diaminobenzidine), but also showed promising SERS performance with remarkable sensitivity and high reproducibility. Based on these properties, the bi-functional Au/CuS composite was employed both as a catalyst for degrading a pollutant (Rhodamine 6G) and a SERS substrate for real-time monitoring of the degradation process quantitatively. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01751j

  15. Hulsite from Sengendera skarn deposit, Miyazaki, Japan

    NASA Astrophysics Data System (ADS)

    Ogoshi, Yukikazu; Minakawa, Tetsuo; Hamane, Daisuke

    Hulsite, Sn bearing Fe borate, was found from the Sengendera skarn deposit which formed by high temperature pneumatolytic metasomatism derived from intrusion of the Okueyama granite mass. It occurred as radiating aggregate of acicular and columnar crystals up to 1 cm, associated closely with magnetite, diopside and tremolite-actinolite, and rarely occurred as chemical sector zone within vonsenite crystals. It is black in color and opaque zones with metallic luster. Cleavages is not distinct. Color of reflection is gray. Monoclinic cell dimensions are a=10.695(4), b=3.102(1), c=5.431(1) Å, β=94.21(3)°. The empirical formula of hulsite from Sengendera skarn deposit is (Fe1.5132+Mg0.459Mn0.023)Σ1.995(Fe0.7923+ Sn0.204Al0.002)Σ0.998B1.015O5, and range of Sn content is 9.06 to 11.88 wt%. The average Sn content of vonsenite, an Fe-borate, from Sengendera mine is 1.40 wt%. Hulsite domain within vonsenite crystals was probably formed at lower temperature on account of high Sn content more than 4 wt% SnO2.

  16. Theoretical study of AuCu nanoalloys adsorbed on MgO(001)

    NASA Astrophysics Data System (ADS)

    Cerbelaud, M.; Barcaro, G.; Fortunelli, A.; Ferrando, R.

    2012-06-01

    The structures of AuCu clusters adsorbed on the (001) face of MgO are searched for by a two-step methodology. In a first step, the relevant structural motifs are singled out by global optimization searches within an atomistic model. In a second step, the lowest energy structures of each motif are relaxed by density-functional calculations. Three different sizes (30, 40 and 50 atoms) are considered. For each size, three compositions are analyzed. For size 30, a competition between fcc pyramids and a new motif (the daisy structure) is found. For 40 and 50 atoms, icosahedral fragments prevail. The results are discussed in connection with experimental data related to clusters of larger sizes.

  17. NANOCRYSTALLINE GROWTH AND GRAIN-SIZE EFFECTS IN AU-CU ELECTRODEPOSITS

    SciTech Connect

    Jankowski, A F; Saw, C K; Harper, J F; Vallier, R F; Ferreira, J L; Hayes, J P

    2005-02-25

    The processing-structure-property relationship is investigated for electrodeposited foils of the gold-copper alloy system. A model is presented that relates the deposition process parameters to the nanocrystalline grain size. An activation energy of 1.52 eV {center_dot} atom{sup -1} for growth is determined for a long pulse (>10 msec) mode, and is 0.16 eV {center_dot} atom{sup -1} for short pulses (<5 msec). The affect of nanocrystalline grain size on the mechanical properties is assessed using indentation measurements. A Hall-Petch type variation of the Vickers microhardness with nanocrystalline grain size (>6 nm) is observed for Au-Cu samples with 1-12 wt.% Cu as tested in cross-section. The hardness increases three-fold from a rule-of-mixtures value <1 GPa to a maximum of 2.9 GPa.

  18. Solidification of Au-Cu-Si alloys investigated by a combinatorial approach

    SciTech Connect

    Ding Shiyan; Schroers, Jan; Gregoire, John; Vlassak, Joost J.

    2012-06-01

    Composition libraries of Au-Cu-Si films comprising 800 composition patches were fabricated through co-sputtering deposition from elemental targets. The gold composition varies between 47% (compositions are in atomic percentage) and 81%, copper between 8% and 40%, and silicon between 6% and 36% within the library. We designed and used a high-throughput optical characterization method to detect melting and solidification based on changes in the film's contrast; further microscopy characterization reveals the microstructure. This approach reveals the composition dependence of the nucleation temperature and primary phase, which allows us to draw conclusions about glass forming ability and to identify bulk metallic glass forming compositions. Our solidification results suggest that the best glass forming composition coincides with the composition at which a transition from one primary phase to another occurs. We show that in general this transition is not at the eutectic composition but at the lowest nucleation temperature.

  19. High performance Au-Cu alloy for enhanced visible-light water splitting driven by coinage metals.

    PubMed

    Liu, Mingyang; Zhou, Wei; Wang, Ting; Wang, Defa; Liu, Lequan; Ye, Jinhua

    2016-03-28

    A Au-Cu alloy strategy is, for the first time, demonstrated to be effective in enhancing visible-light photocatalytic H2 evolution via promoting metal interband transitions. Au3Cu/SrTiO3, in which oxidation of Cu was successfully restrained, showed the highest visible-light H2 evolution activity.

  20. High performance Au-Cu alloy for enhanced visible-light water splitting driven by coinage metals.

    PubMed

    Liu, Mingyang; Zhou, Wei; Wang, Ting; Wang, Defa; Liu, Lequan; Ye, Jinhua

    2016-03-28

    A Au-Cu alloy strategy is, for the first time, demonstrated to be effective in enhancing visible-light photocatalytic H2 evolution via promoting metal interband transitions. Au3Cu/SrTiO3, in which oxidation of Cu was successfully restrained, showed the highest visible-light H2 evolution activity. PMID:26952932

  1. A Facile One-Pot Synthesis of Au/Cu2O Nanocomposites for Nonenzymatic Detection of Hydrogen Peroxide

    NASA Astrophysics Data System (ADS)

    Chen, Ting; Tian, Liangliang; Chen, Yuan; Liu, Bitao; Zhang, Jin

    2015-06-01

    Au/Cu2O nanocomposites were successfully synthesized by a facile one-pot redox reaction without additional reducing agent under room temperature. The morphologies and structures of the as-prepared products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The electrocatalytic performance of Au/Cu2O nanocomposites towards hydrogen peroxide was evaluated by cyclic voltammetry (CV) and chronoamperometry (CA). The prepared Au/Cu2O nanocomposite electrode showed a wide linear range from 25 to 11.2 mM ( R = 0.9989) with a low detection limit of 1.05 μM ( S/ N = 3) and high sensitivity of 292.89 mA mM-1 cm-2. The enhanced performance for H2O2 detection can be attributed to the introduction of Au and the synergistic effect between Au and Cu2O. It is demonstrated that the Au/Cu2O nanocomposites material could be a promising candidate for H2O2 detection.

  2. Photocatalytic reduction of triclosan on Au-Cu2O nanowire arrays as plasmonic photocatalysts under visible light irradiation.

    PubMed

    Niu, Junfeng; Dai, Yunrong; Yin, Lifeng; Shang, Jianying; Crittenden, John C

    2015-07-14

    Triclosan (TCS) is a potential threat to the environment and human health. Photocatalysis can be used to degrade TCS, but the photocatalytic efficiency is usually limited by the photoabsorptivity and photostability of the photocatalyst. In addition, some toxic by-products might also be generated during photocatalytic processes. In this study, we prepared Au-coated Cu2O nanowire arrays (Au-Cu2O NWAs) by beam sputtering Au onto Cu2O nanowires grown from a Cu foil. We found that photocatalytic degradation of TCS under visible light (420 nm < λ < 780 nm) irradiation and Au-Cu2O NWAs had several advantages. Au-Cu2O NWAs had good photoabsorptivity, high photostability (negligible activity loss after 16 runs), excellent photocatalytic activity (47.6 times faster than that of Cu2O), and low yield of dichlorodibenzo-dioxins/dichlorohydroxydibenzofurans. The degradation intermediates were identified as chlorophenoxyphenol, phenoxyphenol, chlorophenol, catechol, phenol, benzoquinone, and lower volatile acids. We developed the degradation pathway of TCS which follows electron reduction and then oxidation by reactive oxygen species. The mechanism was developed and strengthened using the radical trapping and other measurements. The unusual mechanism and photostability of Au-Cu2O NWAs were attributed to the Au/Cu2O/Cu "sandwich"-like structure. This structure yields a sustained and steady internal electric field, raises the conduction band of Cu2O, reinforces the reductive activity of the photo-generated electrons, and eliminates the photo-generated holes that are responsible for the photo-etching of Cu2O.

  3. Synthesis and photocatalytic properties of multi-morphological AuCu3-ZnO hybrid nanocrystals

    NASA Astrophysics Data System (ADS)

    Zeng, Deqian; Chen, Yuanzhi; Peng, Jian; Xie, Qingshui; Peng, Dong-Liang

    2015-10-01

    Noble metal-semiconductor hybrid nanocrystals represent an important class of materials for many potential applications, especially for photocatalysis. The utilization of transition metals to form alloys with noble metals can not only reduce the preparation costs, but may also offer tunable optical and catalytic properties for a broader range of applications. In this study, we report on the solution synthesis of AuCu3-ZnO hybrid nanocrystals with three interesting morphologies, including urchin-like, flower-like and multipod-like nanocrystals. In the synthetic strategy, Au-Cu bimetallic alloy seeds formed in situ are used to induce the heteroepitaxial growth of ZnO nanocrystals on the surface of bimetallic alloy cores; thus different types of morphologies can be achieved by controlling the reaction conditions. Through high-resolution transmission electron microscopy observations, well-defined interfaces between ZnO and AuCu3 are observed, which indicate that ZnO has a (0001) orientation and prefers to grow on AuCu3 {111} facets. The as-prepared hybrid nanocrystals demonstrate morphology- and composition-dependent surface plasmon resonance (SPR) absorption bands. In addition, much higher photocatalytic efficiency than pure ZnO nanocrystals is observed for the hybrid nanocrystals in the degradation of methylene blue. In particular, the multipod-like AuCu3-ZnO hybrid nanocrystals show the highest catalytic performance, as well as more than three times higher photocurrent density than the pure ZnO sample. The reported synthetic strategy provides a facile route to the effective combination of a plasmonic alloy with semiconductor components at the nanoscale in a controlled manner.

  4. Pt skin on AuCu intermetallic substrate: a strategy to maximize Pt utilization for fuel cells.

    PubMed

    Wang, Gongwei; Huang, Bing; Xiao, Li; Ren, Zhandong; Chen, Hao; Wang, Deli; Abruña, Héctor D; Lu, Juntao; Zhuang, Lin

    2014-07-01

    The dependence on Pt catalysts has been a major issue of proton-exchange membrane (PEM) fuel cells. Strategies to maximize the Pt utilization in catalysts include two main approaches: to put Pt atoms only at the catalyst surface and to further enhance the surface-specific catalytic activity (SA) of Pt. Thus far there has been no practical design that combines these two features into one single catalyst. Here we report a combined computational and experimental study on the design and implementation of Pt-skin catalysts with significantly improved SA toward the oxygen reduction reaction (ORR). Through screening, using density functional theory (DFT) calculations, a Pt-skin structure on AuCu(111) substrate, consisting of 1.5 monolayers of Pt, is found to have an appropriately weakened oxygen affinity, in comparison to that on Pt(111), which would be ideal for ORR catalysis. Such a structure is then realized by substituting the Cu atoms in three surface layers of AuCu intermetallic nanoparticles (AuCu iNPs) with Pt. The resulting Pt-skinned catalyst (denoted as Pt(S)AuCu iNPs) has been characterized in depth using synchrotron XRD, XPS, HRTEM, and HAADF-STEM/EDX, such that the Pt-skin structure is unambiguously identified. The thickness of the Pt skin was determined to be less than two atomic layers. Finally the catalytic activity of Pt(S)AuCu iNPs toward the ORR was measured via rotating disk electrode (RDE) voltammetry through which it was established that the SA was more than 2 times that of a commercial Pt/C catalyst. Taking into account the ultralow Pt loading in Pt(S)AuCu iNPs, the mass-specific catalytic activity (MA) was determined to be 0.56 A/mg(Pt)@0.9 V, a value that is well beyond the DOE 2017 target for ORR catalysts (0.44 A/mg(Pt)@0.9 V). These findings provide a strategic design and a realizable approach to high-performance and Pt-efficient catalysts for fuel cells.

  5. Mineralogy, geochemistry, and evolution of the Mivehrood skarn and the associated pluton, northwest Iran

    NASA Astrophysics Data System (ADS)

    Alirezaei, Saeed; Einali, Morteza; Jones, Peter; Hassanpour, Shohreh; Arjmandzadeh, Reza

    2016-04-01

    An Upper Miocene (9.12 ± 0.19 Ma; biotite 40Ar/39Ar) shallow pluton and numerous dykes and sills of felsic-intermediate compositions intruded the Upper Cretaceous, flysch-type sediments in the Mivehrood area, northwest Iran. The intrusions caused extensive thermal metamorphism and metasomatism, leading to the formation of hornfels and skarn. A massive skarn, 1-10 m thick, immediate to the intrusive contact, is bordered by a banded skarn, 100-400 m thick, that grades outward into hornfels and original sediments. The Mivehrood pluton is characterized by steep REE pattern, high Al2O3 (14.64-16.4 wt%) and Sr (380-786 ppm), and low MgO (1.3-3.4 wt%), Y (4.8-10.7 ppm), and Yb (0.35-0.95 ppm), characteristics typical of high-silica adakites. Skarn formation started with thermal metamorphism, followed by anhydrous prograde and hydrous retrograde stages. Prograde and retrograde mineral assemblages are developed in both skarns, represented by garnet-clinopyroxene-wollastonite and epidote-actinolite-scapolite-chlorite, respectively. Granditic F-bearing garnet dominates clinopyroxene in both skarns. The banded skarn contains minor scapolite of marialite composition. The calc-silicate mineral assemblages and the mineral chemistry allow the Mivehrood skarn to be classified as a calcic, oxidized skarn. Mass balance assessments suggest that Fe, Si, and S were significantly enriched, and Na, LILEs, and LREEs were strongly depleted, in the massive skarn. In the banded skarn, Na, K, Si, and S were enriched. Significant dehydration and carbon degassing occurred in both skarns. Stockworks, veins, and replacement bodies of pyrite ± chalcopyrite locally occur in the pluton and the dykes and in the skarns. The δ34SCDT values for the sulfides fall in a narrow range around 0.0 ‰, suggesting a magmatic source for sulfur and possibly the hydrothermal water and solutes involved in the skarn formation.

  6. Isotope geochemistry and fluid inclusion study of skarns from Vesuvius

    USGS Publications Warehouse

    Gilg, H.A.; Lima, A.; Somma, R.; Belkin, H.E.; de Vivo, B.; Ayuso, R.A.

    2001-01-01

    We present new mineral chemistry, fluid inclusion, stable carbon and oxygen, as well as Pb, Sr, and Nd isotope data of Ca-Mg-silicate-rich ejecta (skarns) and associated cognate and xenolithic nodules from the Mt. Somma-Vesuvius volcanic complex, Italy. The typically zoned skarn ejecta consist mainly of diopsidic and hedenbergitic, sometimes "fassaitic" clinopyroxene, Mg-rich and Ti-poor phlogopite, F-bearing vesuvianite, wollastonite, gehlenite, meionite, forsterite, clinohumite, anorthite and Mg-poor calcite with accessory apatite, spinell, magnetite, perovskite, baddeleyite, and various REE-, U-, Th-, Zr- and Ti-rich minerals. Four major types of fluid inclusions were observed in wollastonite, vesuvianite, gehlenite, clinopyroxene and calcite: a) primary silicate melt inclusions (THOM = 1000-1050??C), b) CO2 ?? H2S-rich fluid inclusions (THOM = 20-31.3??C into the vapor phase), c) multiphase aqueous brine inclusions (THOM = 720-820??C) with mainly sylvite and halite daughter minerals, and d) complex chloride-carbonate-sulfate-fluoride-silicate-bearing saline-melt inclusions (THOM = 870-890??C). The last inclusion type shows evidence for immiscibility between several fluids (silicate melt - aqueous chloride-rich liquid - carbonate/sulfate melt?) during heating and cooling below 870??C. There is no evidence for fluid circulation below 700??C and participation of externally derived meteoric fluids in skarn formation. Skarns have considerably variable 206Pb/204Pb (19.047-19.202), 207Pb/204Pb (15.655-15.670), and 208Pb/204Pb (38.915-39.069) and relatively low 143Nd/144Nd (0.51211-0.51244) ratios. The carbon and oxygen isotope compositions of skarn calcites (??13CV-PDB = -5.4 to -1.1???; ??18OV-SMOW = 11.7 to 16.4???) indicate formation from a 18O- and 13C-enriched fluid. The isotope composition of skarns and the presence of silicate melt inclusion-bearing wollastonite nodules suggests assimilation of carbonate wall rocks by the alkaline magma at moderate depths (< 5

  7. Subaqueous environment and volcanic evolution of the Late Cretaceous Chelopech Au-Cu epithermal deposit, Bulgaria

    NASA Astrophysics Data System (ADS)

    Chambefort, Isabelle; Moritz, Robert

    2014-12-01

    A detailed field and petrographic study constrains the volcanic evolution and environment setting of the volcano-sedimentary-hosted Chelopech Cu-Au epithermal deposit, Bulgaria. Magmatic activity and associated high-sulfidation epithermal mineralization occurred at about 91 Ma in the Panagyurishte ore district of the Eastern European Banat-Timok-Srednogorie metallogenic belt. Volcanic and hydrothermal activity took place in a complex subaqueous setting, resulting in the intercalation of quartz sandstone with andesitic volcanic and volcaniclastic breccia. There are also hypabyssal andesite intrusion, phreatomagmatic breccia and interbeds of pyroclastic, oolithic and bioclastic rocks. The presence of altered cerebroid ooid-bearing sedimentary units characteristic of salty environment is in accordance with a lagoon environment predating the mineralization at Chelopech. Four principal stages of evolution for the Chelopech district are proposed based on field and petrographic observations. Initial volcanism occurred in a lake or in a coastal, shallow lagoon environment above crystalline basement. The Chelopech "phreatomagmatic" breccia and subsurface andesites were emplaced at this time. Subsequent hydrothermal activity produced the different hydrothermal breccia types, advanced argillic and quartz-phyllic alteration, and Au-Cu vein and replacement mineralization. The end of volcanism and hydrothermal activity was associated with opening of a pull-apart basin that covered the Chelopech environment with a sedimentary flysch. Tertiary compression faulting juxtaposed various rocks and tilted the ore deposit during the Alpine orogeny.

  8. Au-Cu{sub 2}O core-shell nanowire photovoltaics

    SciTech Connect

    Oener, S. Z.; Mann, S. A.; Sciacca, B.; Sfiligoj, C.; Hoang, J.; Garnett, E. C.

    2015-01-12

    Semiconductor nanowires are among the most promising candidates for next generation photovoltaics. This is due to their outstanding optical and electrical properties which provide large optical cross sections while simultaneously decoupling the photon absorption and charge carrier extraction length scales. These effects relax the requirements for both the minority carrier diffusion length and the amount of semiconductor needed. Metal-semiconductor core-shell nanowires have previously been predicted to show even better optical absorption than solid semiconductor nanowires and offer the additional advantage of a local metal core contact. Here, we fabricate and analyze such a geometry using a single Au-Cu{sub 2}O core-shell nanowire photovoltaic cell as a model system. Spatially resolved photocurrent maps reveal that although the minority carrier diffusion length in the Cu{sub 2}O shell is less than 1 μm, the radial contact geometry with the incorporated metal electrode still allows for photogenerated carrier collection along an entire nanowire. Current-voltage measurements yield an open-circuit voltage of 600 mV under laser illumination and a dark diode turn-on voltage of 1 V. This study suggests the metal-semiconductor core-shell nanowire concept could be extended to low-cost, large-scale photovoltaic devices, utilizing for example, metal nanowire electrode grids coated with epitaxially grown semiconductor shells.

  9. Core/shell Au/CuPt nanoparticles and their dual electrocatalysis for both reduction and oxidation reactions.

    PubMed

    Sun, Xiaolian; Li, Dongguo; Ding, Yong; Zhu, Wenlei; Guo, Shaojun; Wang, Zhong Lin; Sun, Shouheng

    2014-04-16

    We report a facile synthesis of monodisperse core/shell 5/1.5 nm Au/CuPt nanoparticles by coreduction of platinum acetylacetonate and copper acetylacetonate in the presence of 5 nm Au nanoparticles. The CuPt alloy effect and core/shell interactions make these Au/CuPt nanoparticles a promising catalyst for both oxygen reduction reaction and methanol oxidation reaction in 0.1 M HClO4 solution. Their specific (mass) reduction and oxidation activities reach 2.72 mA/cm(2) (1500 mA/mg Pt) at 0.9 V and 0.755 mA/cm(2) (441 mA/mg Pt) at 0.8 V (vs reversible hydrogen electrode), respectively. Our studies show that the existence of the Au nanoparticle core not only minimizes the Pt usage but also improves the stability of the Au/CuPt catalyst for fuel cell reactions. The results suggest that the core/shell design is indeed effective for optimizing nanoparticle catalysis. The same concept may be extended to other multimetallic nanoparticle systems, making it possible to tune nanoparticle catalysis for many different chemical reactions.

  10. Effect of Au nanorods on potential barrier modulation in morphologically controlled Au@Cu2O core-shell nanoreactors for gas sensor applications.

    PubMed

    Majhi, Sanjit Manohar; Rai, Prabhakar; Raj, Sudarsan; Chon, Bum-Soo; Park, Kyung-Kuen; Yu, Yeon-Tae

    2014-05-28

    In this work, Au@Cu2O core-shell nanoparticles (NPs) were synthesized by simple solution route and applied for CO sensing applications. Au@Cu2O core-shell NPs were formed by the deposition of 30-60 nm Cu2O shell layer on Au nanorods (NRs) having 10-15 nm width and 40-60 nm length. The morphology of Au@Cu2O core-shell NPs was tuned from brick to spherical shape by tuning the pH of the solution. In the absence of Au NRs, cubelike Cu2O NPs having ∼200 nm diameters were formed. The sensor having Au@Cu2O core-shell layer exhibited higher CO sensitivity compared to bare Cu2O NPs layer. Tuning of morphology of Au@Cu2O core-shell NPs from brick to spherical shape significantly lowered the air resistance. Transition from p- to n-type response was observed for all devices below 150 °C. It was demonstrated that performance of sensor depends not only on the electronic sensitization of Au NRs but also on the morphology of the Au@Cu2O core-shell NPs.

  11. An Experimental Study of Transient Liquid Phase Bonding of the Ternary Ag-Au-Cu System Using Differential Scanning Calorimetry

    NASA Astrophysics Data System (ADS)

    Kuntz, M. L.; Panton, B.; Wasiur-Rahman, S.; Zhou, Y.; Corbin, S. F.

    2013-08-01

    An experimental approach using differential scanning calorimetry (DSC) has been applied to quantify the solid/liquid interface kinetics during the isothermal solidification stage of transient liquid phase (TLP) bonding in an Ag-Au-Cu ternary alloy solid/liquid diffusion couple. Eutectic Ag-Au-Cu foil interlayers were coupled with pure Ag base metal to study the effects of two solutes on interface motion. Experimental effects involving baseline shift and primary solidification contribute to a systematic underestimation of the fraction of liquid remaining. A temperature program has been used to quantify and correct these effects. The experimental results show a linear relationship between the interface position and the square root of the isothermal hold time. The shifting tie line composition at the interface has been shown to affect the DSC results; however, the impact on the calculated interface kinetics has been shown to be minimal in this case. This work has increased the knowledge of isothermal solidification in ternary alloy systems and developed accurate experimental methods to characterize these processes, which is valuable for designing TLP bonding schedules.

  12. Nanocatalyst superior to Pt for oxygen reduction reactions: the case of core/shell Ag(Au)/CuPd nanoparticles.

    PubMed

    Guo, Shaojun; Zhang, Xu; Zhu, Wenlei; He, Kai; Su, Dong; Mendoza-Garcia, Adriana; Ho, Sally Fae; Lu, Gang; Sun, Shouheng

    2014-10-22

    Controlling the electronic structure and surface strain of a nanoparticle catalyst has become an important strategy to tune and to optimize its catalytic efficiency for a chemical reaction. Using density functional theory (DFT) calculations, we predicted that core/shell M/CuPd (M = Ag, Au) NPs with a 0.8 or 1.2 nm CuPd2 shell have similar but optimal surface strain and composition and may surpass Pt in catalyzing oxygen reduction reactions. We synthesized monodisperse M/CuPd NPs by the coreduction of palladium acetylacetonate and copper acetylacetonate in the presence of Ag (or Au) nanoparticles with controlled shell thicknesses of 0.4, 0.75, and 1.1 nm and CuPd compositions and evaluated their catalysis for the oxygen reduction reaction in 0.1 M KOH solution. As predicted, our Ag/Cu37Pd63 and Au/Cu40Pd60 catalysts with 0.75 and 1.1 nm shells were more efficient catalysts than the commercial Pt catalyst (Fuel Cells Store), with their mass activity reaching 0.20 A/mg of noble metal at -0.1 V vs Ag/AgCl (4 M KCl); this was over 3 times higher than that (0.06 A/mg Pt) from the commercial Pt. These Ag(Au)/CuPd nanoparticles are promising non-Pt catalysts for oxygen reduction reactions. PMID:25279704

  13. Proposed power-function N-body potential for the fcc structured metals Ag, Au, Cu, Ni, Pd, and Pt

    SciTech Connect

    Li, J. H.; Kong, Y.; Guo, H. B.; Liang, S. H.; Liu, B. X.

    2007-09-01

    We propose, for the fcc structured Ag, Au, Cu, Ni, Pd, and Pt metals, an N-body potential with a simple power-function form, which significantly simplifies the fitting procedure and computation. The proposed potentials are able to correctly reproduce the lattice constants, cohesion energies, elastic constants, relative stabilities of different structures, formation energies of vacancy, and surface energies. In addition, the thermal properties, such as melting points and heat capacities, etc., are also satisfactorily determined from the proposed potentials. Moreover, the proposed potential is applied to calculate the trigonal and tetragonal paths between the fcc and bcc structures, and the calculated paths match well with those obtained from the first principles calculations.

  14. Spin Polarization of Mg-23 in Mg-24 + Au, Cu and Al Collisions at 91 A MeV

    NASA Technical Reports Server (NTRS)

    Matsuta, K.; Fukuda, S.; Izumikawa, T.; Tanigaki, M.; Fukuda, M.; Nakazato, M.; Mihara, M.; Onishi, T.; Yamaguchi, T.; Miyake, T.

    1994-01-01

    Spin polarization of beta-emitting fragment Mg-23(I(sup pi) = 3/2(sup +), T(sub 1/2 = l1.3 s) produced through the projectile fragmentation process in Mg-24 + Au, Cu and Al collisions has been observed at 91 AMeV. General trend in the observed momentum dependence of polarization is reproduced well qualitatively by a simple fragmentation model based on the participant-spectator picture, for heavy and light targets. However the polarization behavior differs from this model in tern of zero crossing momentum, which become prominent in the case of Cu target, where the polarization is not monotone function of the fragment momentum.

  15. Comparison of the Activity and the Stability in CO Oxidation of Au-Cu Catalysts Supported on TiO2 in Anatase or Rutile Phase.

    PubMed

    Zanella, Rodolfo; Bokhimi, Xim; Maturano, Viridiana; Morales, Antonio

    2015-09-01

    Au-Cu catalysts supported on anatase or rutile phases were prepared by deposition-precipitation method. The titania polymorph used as the support determined the catalytic behavior. For the Au-Cu/rutile catalysts, the metallic phase had smaller dimensions than for the Au-Cu/anatase catalysts. The catalysts supported on anatase, however, were more active and stable than those supported on rutile. A systematic study of the catalytic activity for CO oxidation as a function of the temperature of activation and the aging time was performed. The catalytic properties were correlated with the properties of the catalysts analyzed with X-ray powder diffraction, refinement of the crystalline structures with the Rietveld method, and transmission electron microscopy. When the support was anatase, a pretreatment at 400 degrees C in air led to the most active catalysts, whereas when the support was rutile, a pretreatment between 200 and 300 degrees C in air led to the most active catalysts; activation under hydrogen generated less active catalysts. The Au-Cu catalysts activated in air were more active for the oxidation of CO than the respective monometallic gold catalysts, indicating a promoting effect between gold and copper to catalyze this reaction.

  16. Hollow Au-Cu2O Core-Shell Nanoparticles with Geometry-Dependent Optical Properties as Efficient Plasmonic Photocatalysts under Visible Light.

    PubMed

    Lu, Biao; Liu, Aiping; Wu, Huaping; Shen, Qiuping; Zhao, Tingyu; Wang, Jianshan

    2016-03-29

    Hollow Au-Cu2O core-shell nanoparticles were synthesized by using hollow gold nanoparticles (HGNs) as the plasmon-tailorable cores to direct epitaxial growth of Cu2O nanoshells. The effective geometry control of hollow Au-Cu2O core-shell nanoparticles was achieved through adjusting the HGN core sizes, Cu2O shell thicknesses, and morphologies related to structure-directing agents. The morphology-dependent plasmonic band red-shifts across the visible and near-infrared spectral regions were observed from experimental extinction spectra and theoretical simulation based on the finite-difference time-domain method. Moreover, the hollow Au-Cu2O core-shell nanoparticles with synergistic optical properties exhibited higher photocatalytic performance in the photodegradation of methyl orange when compared to pristine Cu2O and solid Au-Cu2O core-shell nanoparticles under visible-light irradiation due to the efficient photoinduced charge separation, which could mainly be attributed to the Schottky barrier and plasmon-induced resonant energy transfer. Such optical tunability achieved through the hollow cores and structure-directed shells is of benefit to the performance optimization of metal-semiconductor nanoparticles for photonic, electronic, and photocatalytic applications. PMID:26954100

  17. New experimental evidences of Au-Cu2S core-shell nanoparticles and atomic resolution imaging by aberration-corrected STEM

    NASA Astrophysics Data System (ADS)

    Khanal, Subarna; Casillas, Gilberto; Bhattarai, Nabraj; Velazquez-Salazar, J. Jesus; Yacaman, Miguel Jose

    2013-03-01

    Au-Cu2S core-shell nanoparticles present different properties than their monometallic counterparts, opening a wide range of possibilities for different applications. Au-Cu2S core-shell nanostructures have raised interest for their many applications in photoelectronic, sensing, catalysis and so on. Au and Au-Cu2S core-shell nanoparticles were prepared by using a modified polyol method. First Au seeds were prepared by reducing HAuCl4.xH2O in ethylene glycol (EG) in the presence of poly(vinylpyrrolidone) (PVP) as a polymer surfactant. Then Cu2S shells were overgrown on Au core seeds by reducing CuSO4 in EG with PVP. The morphology and structural characteristics of Au and Au-Cu2S nanostructures were studied in detail using scanning electron microcopy HITACHI S-5500 and high resolution transmission electron microscope (HRTEM), a resolution 0.19 nm. Moreover, the Cs-corrected scanning transmission electron microscopy (Cs-corrected STEM) technique allowed us to probe the structure at the atomic level of these nanoparticles revealing new structural information. We determined the structure of the four main polyhedral morphologies obtained in the synthesis: decahedral, icosahedral, triangular plates, and rods. This project was supported by grants from the National Center for Research Resources (5 G12RR013646-12) and the National Institute on Minority Health and Health Disparities (G12MD007591).

  18. Garnetization as a ground preparation process for copper mineralization: evidence from the Mazraeh skarn deposit, Iran

    NASA Astrophysics Data System (ADS)

    Karimzadeh Somarin, Alireza

    2010-03-01

    The Mazraeh Cu-Fe skarn deposit, NW Iran is the result of the intrusion of an Oligocene-Miocene granitic pluton into Cretaceous calcareous rocks. The pluton ranges in composition from monzonite to quartz monzonite, monzogranite, tonalite and granodiorite with I-type, calc-alkaline, and weakly peraluminous characteristics. The Mazraeh pluton was emplaced in a volcanic arc setting in an active continental margin at a depth of ~8 km. Pyroxene skarn, garnet skarn, and epidote skarn zones were formed during the intrusive phase. The garnet skarn developed as exoskarn and endoskarn from the calcareous wall rocks and the pluton, respectively, prior to mineralization. Garnet skarn from the exoskarn zone is identified by relict layering inherited from the precursor calcareous lithologies. Mass balance calculation of garnet skarn in the endoskarn zone indicates that hydrothermal fluids originating from the cooling magma introduced Si, Fe, Mn, Ca, Mg, P, Ag, Cu, Zn, La, Pb, Cd, Mo, and Y. The main mass loss in the garnet skarn was due to destruction of feldspars in the Mazraeh plutonic rocks and leaching of K2O and Na2O. Released Ca has been fixed in the andraditic garnet. Garnetization of the Mazraeh pluton was accompanied by mass and volume increase. The magnitude of these changes depends mainly on the degree of alteration and composition of the precursor. The brittle behavior of the endoskarn zone was increased due to formation of massive garnet which subsequently fractured. These fractures not only facilitated movement of hydrothermal fluids but also provided new locations for Cu mineralization. Therefore locating strongly garnetized zones may be a vector to ore in skarn deposits.

  19. Using bond-length-dependent transferable force constants to predict vibrational entropies in Au-Cu, Au-Pd, and Cu-Pd alloys

    NASA Astrophysics Data System (ADS)

    Wu, Eric J.; Ceder, Gerbrand; van de Walle, Axel

    2003-04-01

    A model is tested to rapidly evaluate the vibrational properties of alloys with site disorder. It is shown that length-dependent transferable force constants exist and can be used to accurately predict the vibrational entropy of substitutionally ordered and disordered structures in Au-Cu, Au-Pd, and Cu-Pd. For each relevant force constant, a length-dependent function is determined and fitted to force constants obtained from first-principles pseudopotential calculations. We show that these transferable force constants can accurately predict vibrational entropies of L12-ordered and disordered phases in Cu3Au, Au3Pd, Pd3Au, Cu3Pd, and Pd3Au. In addition, we calculate the vibrational entropy difference between L12-ordered and disordered phases of Au3Cu and Cu3Pt.

  20. Modeling of Disordered Binary Alloys Under Thermal Forcing: Effect of Nanocrystallite Dissociation on Thermal Expansion of AuCu3

    NASA Astrophysics Data System (ADS)

    Kim, Y. W.; Cress, R. P.

    2016-11-01

    Disordered binary alloys are modeled as a randomly close-packed assembly of nanocrystallites intermixed with randomly positioned atoms, i.e., glassy-state matter. The nanocrystallite size distribution is measured in a simulated macroscopic medium in two dimensions. We have also defined, and measured, the degree of crystallinity as the probability of a particle being a member of nanocrystallites. Both the distribution function and the degree of crystallinity are found to be determined by alloy composition. When heated, the nanocrystallites become smaller in size due to increasing thermal fluctuation. We have modeled this phenomenon as a case of thermal dissociation by means of the law of mass action. The crystallite size distribution function is computed for AuCu3 as a function of temperature by solving some 12 000 coupled algebraic equations for the alloy. The results show that linear thermal expansion of the specimen has contributions from the temperature dependence of the degree of crystallinity, in addition to respective thermal expansions of the nanocrystallites and glassy-state matter.

  1. Cu2O and Au/Cu2O Particles: Surface Properties and Applications in Glucose Sensing

    PubMed Central

    Won, Yu-Ho; Stanciu, Lia A.

    2012-01-01

    In this work we investigated the surface and facet-dependent catalytic properties of metal oxide particles as well as noble metal/metal oxide heterogeneous structures, with cuprous oxide (Cu2O) and Au/Cu2O being selected as model systems. As an example of application, we explored the potential of these materials in developing electrocatalytic devices. Cu2O particles were synthesized in various shapes, then used for testing their morphology-dependent electrochemical properties applied to the detection of glucose. While we did not attempt to obtain the best detection limit reported to date, the octahedral and hexapod Cu2O particles showed reasonable detection limits of 0.51 and 0.60 mM, respectively, which are physiologically relevant concentrations. However, detection limit seems to be less affected by particle shapes than sensitivity. Heterogeneous systems where Au NPs were deposited on the surface of Cu2O particles were also tested with similar results in terms of the effect of surface orientation. PMID:23201983

  2. Understanding the Composition and Reactivity of Au/Cu Electrocatalyst Nanoparticles in Solution Using Highly Accurate Reactive Potentials

    NASA Astrophysics Data System (ADS)

    Artrith, Nongnuch; Kolpak, Alexie

    2014-03-01

    The shape, size, and composition of catalyst nanoparticles can have a significant influence on their catalytic activity. Understanding such structure-reactivity relationships is crucial for the optimization of industrial catalysts and the design of novel catalysts with enhanced properties. In this work, we investigate the equilibrium shape and surface structure/composition of Au/Cu nanoparticles in solution, which have recently been shown to be stable and efficient catalysts for CO2 reduction. Using a combination of density functional theory calculations and large-scale Monte-Carlo and molecular dynamics simulations with reactive atomistic potentials, we determine how the nanoparticle shape, surface structure, and surface stoichiometry (i.e., fraction of Au at the surface relative to overall composition), evolve as a function of varying catalytic conditions. We discuss the effects of these changes on the surface electronic structure and binding energies of CO2, H2, and CH3OH. Our results emphasize the important relationships between catalytic environment (e.g., solvent effects), catalyst structure, and catalytic activity. We thank the Schlumberger Foundation Faculty for the Future for financial support. Computing time at XSEDE and NERSC clusters are gratefully acknowledged.

  3. Au nanocrystal-directed growth of Au-Cu(2)O core-shell heterostructures with precise morphological control.

    PubMed

    Kuo, Chun-Hong; Hua, Tzu-En; Huang, Michael H

    2009-12-16

    Formation of metal-semiconductor core-shell heterostructures with precise morphological control of both components remains challenging. Heterojunctions, rather than core-shell structures, were typically produced for metal-semiconductor composites. Furthermore, growth of semiconductor shells with systematic shape evolution using the same metal particle cores can also present a significant challenge. Here, we have synthesized Au-Cu(2)O core-shell heterostructures using gold nanoplates, nanorods, octahedra, and highly faceted nanoparticles as the structure-directing cores for the overgrowth of Cu(2)O shells by a facile aqueous solution approach. The gold nanoparticle cores guide the growth of Cu(2)O shells with morphological and orientation control. Systematic shape evolution of the shells can be easily achieved by simply adjusting the volume of reductant added. For example, truncated cubic to octahedral Cu(2)O shells were produced from octahedral gold nanocrystal cores. Unusual truncated stellated icosahedral and star column structures have also been synthesized. The heterostructures were found to be formed via an unusual hollow-shell-refilled growth mechanism not reported before. The approach has potential toward the preparation of other complex Cu(2)O structures with well-defined facets. PMID:19919066

  4. Au@Cu2O stellated polytope with core-shelled nanostructure for high-performance adsorption and visible-light-driven photodegradation of cationic and anionic dyes.

    PubMed

    Wu, Xueqing; Cai, Jiabai; Li, Shunxing; Zheng, Fengying; Lai, Zhanghua; Zhu, Licong; Chen, Tanju

    2016-05-01

    Au nanoparticles were covered by Cu2O nanoparticles shell and then Au@Cu2O stellated polytope was synthesized by a facile aqueous solution approach. The samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction patterns, X-ray photoelectron spectroscopy, Brunner-Emmet-Teller measurements, and Ultraviolet-visible spectroscopy analysis. With good aqueous dispersibility, surface positive charge, and high chemisorption capacity, Au@Cu2O could be used for anionic dyes removal. Compared with Degussa P25-TiO2, the adsorption of anionic dyes (acid violet 43 or methyl blue, 5.0 mg L(-1)) onto Au@Cu2O was increased by 90.12% and 50.8%, respectively. The photodegradation activity of methyl orange and methyl violet were in the declining order: Au@Cu2O>Cu2O-Au nanocomposites>Cu2O>P25-TiO2. The synergistic effect of coupling Au core with Cu2O shell on the dyes photodegradation was observed. The photoexcited electrons from Cu2O conduction band could be captured by Au nanoparticles, resulting in an improved electron-hole separation. Moreover, a Schottky barrier was assumed to form at the Cu2O-Au interface and Au NPs as electron sink could reduce the recombination of photoinduced electrons and holes, facilitating the photocatalytic interface reaction. The geometry of core-shell and stellated polytope is effective in the design of Cu2O-Au nanocomposites for adsorption and photocatalysis. PMID:26874979

  5. New insights into the mixing of gold and copper in a nanoparticle from a structural study of Au-Cu nanoalloys synthesized via a wet chemistry method and pulsed laser deposition.

    PubMed

    Prunier, Hélène; Nelayah, Jaysen; Ricolleau, Christian; Wang, Guillaume; Nowak, Sophie; Lamic-Humblot, Anne-Félicie; Alloyeau, Damien

    2015-11-14

    Gold-copper nanoparticles (Au-Cu NPs) were elaborated by both chemical (polyol reduction method) and physical (laser deposition) routes. The size, composition and crystal structure of these bimetallic nanoalloys were then characterized by aberration corrected transmission electron microscopy (TEM). Using a one-pot polyol method, Au-Cu nanocubes (NCs) with nominal compositions Au3Cu and AuCu3 were synthesized. The size and composition of the NCs were tuned by varying the amount and the ratio of Au(iii) and Cu(ii) ions used as metallic precursors in the reaction. While the particle shape and size were well-controlled, single particle X-ray spectroscopy showed that, irrespective of the targeted compositions, the Cu content in all NCs was about 11-12 at%, i.e. in both samples, the real composition was different from the nominal one. This was ascribed to an incomplete alloying of the two constituent metals of the alloy in the cubes due to different reduction kinetics of the two metallic precursors. To shed light on the alloying of gold and copper at the nanoscale, Au-Cu NPs with targeted compositions Au3Cu and AuCu3 were deposited on amorphous carbon by laser ablation of two monometallic sources, and their structural properties were studied by TEM. These studies show that Au-Cu nanoalloys were synthesized in both samples and that the complete mixing of Au and Cu atoms achieved with this synthesis technique led to the production of Au-Cu NPs with well-controlled compositions. These results constitute a first but major step towards a complete understanding of the details of kinetics and thermodynamics determining the mixing of gold and copper atoms at the nanoscale. Such an understanding is essential for producing Au-Cu bimetallic nanoalloys with well-defined structural properties via wet chemical synthesis.

  6. Thermodynamic properties and equations of state for Ag, Al, Au, Cu and MgO using a lattice vibrational method

    NASA Astrophysics Data System (ADS)

    Jacobs, M.; Schmid-Fetzer, R.

    2012-04-01

    A prerequisite for the determination of pressure in static high pressure measurements, such as in diamond anvil cells is the availability of accurate equations of state for reference materials. These materials serve as luminescence gauges or as X-ray gauges and equations of state for these materials serve as secondary pressure scales. Recently, successful progress has been made in the development of consistency between static, dynamic shock-wave and ultrasonic measurements of equations of state (e.g. Dewaele et al. Phys. Rev. B70, 094112, 2004, Dorogokupets and Oganov, Doklady Earth Sciences, 410, 1091-1095, 2006, Holzapfel, High Pressure Research 30, 372-394, 2010) allowing testing models to arrive at consistent thermodynamic descriptions for X-ray gauges. Apart from applications of metallic elements in high-pressure work, thermodynamic properties of metallic elements are also of mandatory interest in the field of metallurgy for studying phase equilibria of alloys, kinetics of phase transformation and diffusion related problems, requiring accurate thermodynamic properties in the low pressure regime. Our aim is to develop a thermodynamic data base for metallic alloy systems containing Ag, Al, Au, Cu, Fe, Ni, Pt, from which volume properties in P-T space can be predicted when it is coupled to vibrational models. This mandates the description of metallic elements as a first step aiming not only at consistency in the pressure scales for the elements, but also at accurate representations of thermodynamic properties in the low pressure regime commonly addressed in metallurgical applications. In previous works (e.g. Jacobs and de Jong, Geochim. Cosmochim. Acta, 71, 3630-3655, 2007, Jacobs and van den Berg, Phys. Earth Planet. Inter., 186, 36-48, 2011) it was demonstrated that a lattice vibrational framework based on Kieffer's model for the vibrational density of states, is suitable to construct a thermodynamic database for Earth mantle materials. Such a database aims at

  7. Conductance and spin-filter effects of oxygen-incorporated Au, Cu, and Fe single-atom chains

    SciTech Connect

    Zheng, Xiaolong; Xie, Yi-Qun Ye, Xiang; Ke, San-Huang

    2015-01-28

    We studied the spin-polarized electron transport in oxygen-incorporated Au, Cu, and Fe single-atom chains (SACs) by first-principles calculations. We first investigated the mechanism responsible for the low conductance (<1G{sub 0}) of the Au and Cu SACs in an oxygen environment reported in recent experiments. We found that for the Au SACs, the low conductance plateau around 0.6G{sub 0} can be attributed to a distorted chain doped with a single oxygen atom, while the 0.1G{sub 0} conductance comes from a linear chain incorporated with an oxygen molecule and is caused by an antibonding state formed by oxygen's occupied frontier orbital with d{sub z} orbitals of adjacent Au atoms. For the Cu SACs, the conductance about 0.3G{sub 0} is ascribed to a special configuration that contains Cu and O atoms in an alternating sequence. This exhibits an even-odd conductance oscillation with an amplitude of ∼0.1G{sub 0}. In contrast, for the alternating Fe-O SACs, conductance overall decreases with an increase in O atoms and it approaches nearly zero for the chain with more than four O atoms. While the Cu-O SACs behave as perfect spin filters for one spin channel due to the half metallic nature, the Fe-O SACs can serve as perfect spin filters for two spin channels depending on the polarity of the applied gate voltage.

  8. Slab melting and the origin of gold in Au and Au-Cu deposits: geochemical clues from recent adakites.

    NASA Astrophysics Data System (ADS)

    Polve, M.; Maury, R.; Joron, J. L.

    2003-04-01

    Understanding the genetic processes responsible for the common occurrence of Au and Au-Cu deposits in subduction environments is a fairly "hot" question nowadays, as it is clear that most subduction-related magmatic rocks are barren. Studies of space and time relationships between magmatic intrusions, hydrothermal episodes and Au deposits have shown that, very often, Au deposits are associated with adakitic intrusions (Thieblemont et al, 1997, Sajona and Maury, 1998). Adakites are here understood as being generated by melting of the subducting oceanic crust. This study aims to check wether or not magmas derived from melted oceanic crust do contain significantly more Au than regular calc-alkaline magmas by measuring directly Au concentrations in fresh (and barren) adakites and equivalent calc-alkaline andesites. There is a lack of reliable data on Au content in unaltered adakites and andesites, because Au analyses are generally done on hydrothermalized rocks in connection with Au deposits and also because old measurements may give overestimated Au contents, due to technical limitations. Therefore we compiled recent literature data on gold contents of fresh calc-alkaline rocks, and measured Au on a selection of 40 well studied and dated adakites from different localities (Philippines, Baja California). Analyses have been performed either by INAA or by ICP-MS after Au extraction with aqua regia, following the method described by Terashima (1988). Preliminary results show that, for equivalent Si02 contents, adakites are systematically enriched in Au compared to regular dacites, even if regional trends also exist. Moreover, Au seems to behave as an incompatible element in adakitic magmas, whereas in calc-alkaline dacites it is controlled by sulfide crystallization. Our data suggest that, not excluding any other processes related to the hydrothermal phase in the deposit generation, adakites may indeed represent the source of Au, a possible explanation for the adakite

  9. Mineral zoning and gold occurrence in the Fortuna skarn mine, Nambija district, Ecuador

    NASA Astrophysics Data System (ADS)

    Markowski, Agnès; Vallance, Jean; Chiaradia, Massimo; Fontboté, Lluìs

    2006-07-01

    The Fortuna oxidized gold skarn deposit is located in the northern part of the Nambija gold district, southern Ecuador. It has been subdivided into four mineralized sites, covering a distance of 1 km, which are named from north to south: Cuerpo 3, Mine 1, Mine 2, and Southern Sector. Massive skarn bodies occur in K-Na metasomatized volcanic and volcaniclastic rocks of the Triassic Piuntza unit. They appear to result from selective replacement of volcaniclastic rocks. Very minor presence of bioclast relicts suggests the presence of subordinate limestone. Endoskarn type alteration with development of Na-rich plagioclase, K-feldspar, epidote, actinolite, anhedral pyroxene, and titanite affects a quartz-diorite porphyritic intrusion which crops out below the skarn bodies in Mine 2 and the Southern Sector. Endoskarn alteration in the intrusion grades into a K-feldspar ± biotite ± magnetite assemblage (K-alteration), suggesting that skarn formation is directly related to the quartz-diorite porphyritic intrusion, the latter being probably emplaced between 141 and 146 Ma. The massive skarn bodies were subdivided into a dominant brown garnet skarn, a distal green pyroxene-epidote skarn, and two quartz-rich varieties, a blue-green garnet skarn and light green pyroxene-garnet skarn, which occur as patches and small bodies within the former skarn types. The proximal massive brown garnet skarn zone is centered on two 060° trending faults in Mine 2, where the highest gold grades (5-10 g/t) were observed. It grades into a distal green pyroxene-epidote skarn zone to the North (Cuerpo 3). Granditic garnet shows iron enrichment from the proximal to the distal zone. Diopsidic pyroxene exhibits iron and manganese enrichment from proximal to distal zones. The retrograde stage is weakly developed and consists mainly of mineral phases filling centimeter-wide veins, vugs, and interstices between garnet and pyroxene grains. The main filling mineral is quartz, followed by K

  10. Contact metamorphism in the Los Santos W skarn (NW Spain)

    NASA Astrophysics Data System (ADS)

    Timón, S. M.; Moro, M. C.; Cembranos, M. L.; Fernández, A.; Crespo, J. L.

    2007-05-01

    The intrusion of the Lower Permian Los Santos-Valdelacasa granitoids in the Los Santos area caused contact metamorphism of Later Vendian-Lower Cambrian metasediments. High grade mineral assemblages are confined to a 7 km wide contact aureole. Contact metamorphism was accompanied by intense metasomatism and development of skarns, and it generated the following mineral assemblages: diopside, forsterite, phlogopite (±clintonite) and humites and spinel-bearing assemblages or diopside, grossular, vesuvianite ± wollastonite in the marbles, depending on the bulk rock composition. Cordierite, K-feldspar, andalusite and, locally, sillimanite appear in the metapelitic rocks. Mineral assemblages of marbles and hornfelses indicate pressure conditions ranging from 0.2 to 0.25 GPa and maximum temperatures between 630 and 640 °C. 13C and 18O depletions in calcite marbles are consistent with hydrothermal fluid-rock interaction during metamorphism. Calcites are depleted in both 18O (δ18O = 12.74‰) and 13C (δ13C = -5.47‰) relative to dolomite of unmetamorphosed dolostone (δ18O = 20.79‰ and δ13C = -1.52‰). The δ13C variation can be interpreted in terms of Rayleigh distillation during continuous CO2 fluid removal from the carbonates. The δ18O values reflect hydrothermal exchange with an externally derived fluid. Microthermometric analyses of fluid inclusions from vesuvianite indicate that the fluid was water dominated with minor contents of CO2 (±CH4 ± N2) suggesting a metamorphic origin. Fluorine-bearing minerals such as chondrodite, norbergite and F-rich phlogopite indicate that contact metamorphism was accompanied by fluorine metasomatism. Metasomatism was more intense in the inner-central portion of the contact aureole, where access to fluids was extensive. The irregular geometry of the contact with small aplitic intrusives between the metasediments and the Variscan granitoids probably served as pathways for fluid circulation.

  11. REE, trace elements, Sr, Pb, C, and O isotopes in a zoned skarn ore deposit

    SciTech Connect

    Langmuir, C.; LeHuray, A.; Fairbanks, R.; Meinert, L.

    1985-01-01

    The Groundhog skarn in the Central Mining District, New Mexico, is zoned along its >2km length adjacent to a dike swarm which trends NE toward the Santa Rita porphyry Cu deposit. Isotopes and trace elements in whole rocks and mineral separates from skarn and adjacent carbonate allow the study of the source of the metals and the systematics of trace element behavior in a skarn system. (1) /sup 87/Sr//sup 86/Sr ratios are uniform (.7083 +/- 1) in the carbonate host, but they range up to .714 in hydrothermal calcite and pyx from the skarn, values distinct from both Santa Rita (.706) and carbonate. (2) delta/sup 18/O (SMOW) in carbonate ranges from (+6.3 -+ 23) and is correlated positively with delta/sup 13/C (-5.6-+2.4) and negatively with /sup 87/Sr//sup 86/Sr. Several trace elements also correlate with delta/sup 18/O. (3) Pb isotopes in galenas lie on the regression line for southwestern New Mexico Proterozoic crust. PbS from the skarn closest to Santa Rita has isotope ratios identical to PbS from the Santa Rita pit. (4) Most of the REE are not in gar or pyx. REE abundances are <1X chondrites after HC1 leaches, but in unleached samples can be >20X chondrites. All pyx separates have deep negative Ce and very deep Eu anomalies. Sr isotopes show that neither Santa Rita magma nor carbonate is the sole source of Sr. Pb isotopes are consistent with a Santa Rita source. The Ce anomaly suggests a seawater source for the REE. The data show that many of the metals in the skarn are not derived from the Santa Rita porphyry, and suggest that different elements may be derived from different source rocks.

  12. Fe isotope behaviours during sulfide-dominated skarn-type mineralisation

    NASA Astrophysics Data System (ADS)

    Wang, Yue; Zhu, Xiang-kun; Cheng, Yanbo

    2015-05-01

    Fe isotope compositions of mineral separates and bulk samples from Dongguashan and Fenghuangshan skarn type Cu-Fe deposits in Tongling District, Middle-Lower Yangtze Valley Cu-Fe-Au-Mo polymetallic belt have been investigated. Differences in δ57Fe values exist in co-precipitated bornite-chalcopyrite and pyrite-chalcopyrite mineral pairs. The bornite is enriched in light iron isotopes relative to coexisting chalcopyrite, whereas pyrite samples show a tendency of heavy isotopes enrichment relative to chalcopyrite. Moreover, the δ57Fe values of endoskarn and the earliest formed Fe-mineral phase magnetite of the three deposits investigated in Tongling district are consistently lower relative to ore-related igneous rocks, suggesting Fe isotopic fractionation occurs during fluid exsolution and exsolved fluid is enriched in light Fe isotopes relative to the stock. Furthermore, spatial and temporal variations in δ57Fe values within single mineral phases are observed, suggesting iron isotopic fractionation occurs between mineral and fluid phases as a result of precipitation of Fe-bearing minerals during fluid evolution. Overall, according to Fe isotope compositions of three representative skarn deposits formed under the same geological setting in Tongling district, this study indicates that Fe isotopes have the potential to unraveling ore-forming processes, as well as constraining the metal sources of skarn deposits. Combining with results of previous studies, a protocol for using Fe isotopes to trace skarn-type metallogeny is proposed.

  13. Fluids in distal Zn-Pb-Ag skarns: Evidence from El Mochito, Honduras

    NASA Astrophysics Data System (ADS)

    Samson, I. M.; Williams-Jones, A. E.; Ault, K.; Gagnon, J. E.; Fryer, B. J.

    2009-05-01

    Zn-Pb-Ag mantos, chimneys, and skarns represent a spectrum of carbonate-hosted sulfide mineral deposits that have been collectively termed carbonate replacement deposits. Most such deposits cannot be related to plutons and, particularly for distal skarns, the role of magmatic versus other fluids (basinal brines and meteoric waters) has been uncertain. The El Mochito Zn-Pb-Ag deposit, Honduras, is an example of a large distal skarn, and comprises mantos and chimneys hosted mainly by limestones of the Early Cretaceous Tepemechin Formation. Previous isotopic studies indicate a magmatic source for the S and Pb and involvement of both magmatic and meteoric fluids in ore formation. The ore is hosted by garnet, magnetite, and pyroxene skarns, which developed sequentially from grandite- to andradite- to magnetite- and hedenbergite- rich skarns. Sphalerite and argentiferous galena occur interstitially to, or replace, the skarn minerals, with Fe- poor sphalerite (S1) principally associated with garnet skarn and Fe-rich (S2) sphalerite associated with pyroxene. Data from primary fluid inclusions show that the salinity of the mineralizing fluids decreased from ˜10-18 wt. % during the formation of garnet skarn and S1 sphalerite to ˜2-13 wt. % during pyroxene skarn formation and S2 sphalerite precipitation. Early, high-salinity fluids (˜33 wt. %) are represented by rare halite-saturated inclusions in garnet. Temperature increased from ˜ 365°C to ˜ 365°C from garnet/S1 sphalerite to pyroxene/S2 sphalerite, assuming a pressure of 500 bars. GC analyses indicate that the total concentrations of COv(2), CH4, and N2 were < 1 mole %. LA-ICPMS analyses were conducted mainly on inclusions in grandite and S1 sphalerite. The principal dissolved elements in the inclusions are Ca and Na, followed by K and Mn. The ore metals, Zn, Pb, and Ag, are present in high concentrations, with median values of 6000, 900, and 50 ppm, respectively. Element concentrations in fluid inclusions hosted

  14. 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

  15. Tunable thermodynamic stability of Au-CuPt core-shell trimetallic nanoparticles by controlling the alloy composition: insights from atomistic simulations.

    PubMed

    Huang, Rao; Shao, Gui-Fang; Wen, Yu-Hua; Sun, Shi-Gang

    2014-11-01

    A microscopic understanding of the thermal stability of metallic core-shell nanoparticles is of importance for their synthesis and ultimately application in catalysis. In this article, molecular dynamics simulations have been employed to investigate the thermodynamic evolution of Au-CuPt core-shell trimetallic nanoparticles with various Cu/Pt ratios during heating processes. Our results show that the thermodynamic stability of these nanoparticles is remarkably enhanced upon rising Pt compositions in the CuPt shell. The melting of all the nanoparticles initiates at surface and gradually spreads into the core. Due to the lattice mismatch among Au, Cu and Pt, stacking faults have been observed in the shell and their numbers are associated with the Cu/Pt ratios. With the increasing temperature, they have reduced continuously for the Cu-dominated shell while more stacking faults have been produced for the Pt-dominated shell because of the significantly different thermal expansion coefficients of the three metals. Beyond the overall melting, all nanoparticles transform into a trimetallic mixing alloy coated by an Au-dominated surface. This work provides a fundamental perspective on the thermodynamic behaviors of trimetallic, even multimetallic, nanoparticles at the atomistic level, indicating that controlling the alloy composition is an effective strategy to realize tunable thermal stability of metallic nanocatalysts. PMID:25234428

  16. Production of ω mesons in p + p, d + Au, Cu + Cu, and Au + Au collisions at sNN=200 GeV

    NASA Astrophysics Data System (ADS)

    Adare, A.; Afanasiev, S.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Al-Bataineh, H.; Al-Jamel, A.; Alexander, J.; Angerami, A.; Aoki, K.; Apadula, N.; Aphecetche, L.; Aramaki, Y.; Armendariz, R.; Aronson, S. H.; Asai, J.; Atomssa, E. T.; Averbeck, R.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Baksay, G.; Baksay, L.; Baldisseri, A.; Barish, K. N.; Barnes, P. D.; Bassalleck, B.; Basye, A. T.; Bathe, S.; Batsouli, S.; Baublis, V.; Bauer, F.; Baumann, C.; Bazilevsky, A.; Belikov, S.; Belmont, R.; Bennett, R.; Berdnikov, A.; Berdnikov, Y.; Bhom, J. H.; Bickley, A. A.; Bjorndal, M. T.; Blau, D. S.; Boissevain, J. G.; Bok, J. S.; Borel, H.; Boyle, K.; Brooks, M. L.; Brown, D. S.; Bucher, D.; Buesching, H.; Bumazhnov, V.; Bunce, G.; Burward-Hoy, J. M.; Butsyk, S.; Camacho, C. M.; Campbell, S.; Caringi, A.; Chai, J.-S.; Chang, B. S.; Charvet, J.-L.; Chen, C.-H.; Chernichenko, S.; Chi, C. Y.; Chiba, J.; Chiu, M.; Choi, I. J.; Choi, J. B.; Choudhury, R. K.; Christiansen, P.; Chujo, T.; Chung, P.; Churyn, A.; Chvala, O.; Cianciolo, V.; Citron, Z.; Cleven, C. R.; Cobigo, Y.; Cole, B. A.; Comets, M. P.; Conesa Del Valle, Z.; Connors, M.; Constantin, P.; Csanád, M.; Csörgő, T.; Dahms, T.; Dairaku, S.; Danchev, I.; Das, K.; Datta, A.; David, G.; Dayananda, M. K.; Deaton, M. B.; Dehmelt, K.; Delagrange, H.; Denisov, A.; D'Enterria, D.; Deshpande, A.; Desmond, E. J.; Dharmawardane, K. V.; Dietzsch, O.; Dion, A.; Donadelli, M.; Drachenberg, J. L.; Drapier, O.; Drees, A.; Drees, K. A.; Dubey, A. K.; Durham, J. M.; Durum, A.; Dutta, D.; Dzhordzhadze, V.; D'Orazio, L.; Edwards, S.; Efremenko, Y. V.; Egdemir, J.; Ellinghaus, F.; Emam, W. S.; Engelmore, T.; Enokizono, A.; En'yo, H.; Espagnon, B.; Esumi, S.; Eyser, K. O.; Fadem, B.; Fields, D. E.; Finger, M.; Finger, M., Jr.; Fleuret, F.; Fokin, S. L.; Forestier, B.; Fraenkel, Z.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fujiwara, K.; Fukao, Y.; Fung, S.-Y.; Fusayasu, T.; Gadrat, S.; Garishvili, I.; Gastineau, F.; Germain, M.; Glenn, A.; Gong, H.; Gonin, M.; Gosset, J.; Goto, Y.; Granier de Cassagnac, R.; Grau, N.; Greene, S. V.; Grim, G.; Grosse Perdekamp, M.; Gunji, T.; Gustafsson, H.-Å.; Hachiya, T.; Hadj Henni, A.; Haegemann, C.; Haggerty, J. S.; Hagiwara, M. N.; Hahn, K. I.; Hamagaki, H.; Hamblen, J.; Han, R.; Hanks, J.; Harada, H.; Hartouni, E. P.; Haruna, K.; Harvey, M.; Haslum, E.; Hasuko, K.; Hayano, R.; He, X.; Heffner, M.; Hemmick, T. K.; Hester, T.; Heuser, J. M.; Hiejima, H.; Hill, J. C.; Hobbs, R.; Hohlmann, M.; Holmes, M.; Holzmann, W.; Homma, K.; Hong, B.; Horaguchi, T.; Hornback, D.; Huang, S.; Hur, M. G.; Ichihara, T.; Ichimiya, R.; Ide, J.; Iinuma, H.; Ikeda, Y.; Imai, K.; Inaba, M.; Inoue, Y.; Isenhower, D.; Isenhower, L.; Ishihara, M.; Isobe, T.; Issah, M.; Isupov, A.; Ivanischev, D.; Iwanaga, Y.; Jacak, B. V.; Jia, J.; Jiang, X.; Jin, J.; Jinnouchi, O.; Johnson, B. M.; Jones, T.; Joo, K. S.; Jouan, D.; Jumper, D. S.; Kajihara, F.; Kametani, S.; Kamihara, N.; Kamin, J.; Kaneta, M.; Kang, J. H.; Kanou, H.; Kapustinsky, J.; Karatsu, K.; Kasai, M.; Kawagishi, T.; Kawall, D.; Kawashima, M.; Kazantsev, A. V.; Kelly, S.; Kempel, T.; Khanzadeev, A.; Kijima, K. M.; Kikuchi, J.; Kim, A.; Kim, B. I.; Kim, D. H.; Kim, D. J.; Kim, E.; Kim, E. J.; Kim, S. H.; Kim, Y.-J.; Kim, Y.-S.; Kim, Y. J.; Kinney, E.; Kiriluk, K.; Kiss, Á.; Kistenev, E.; Kiyomichi, A.; Klay, J.; Klein-Boesing, C.; Kochenda, L.; Kochetkov, V.; Komkov, B.; Konno, M.; Koster, J.; Kotchetkov, D.; Kozlov, A.; Král, A.; Kravitz, A.; Kroon, P. J.; Kubart, J.; Kunde, G. J.; Kurihara, N.; Kurita, K.; Kurosawa, M.; Kweon, M. J.; Kwon, Y.; Kyle, G. S.; Lacey, R.; Lai, Y. S.; Lajoie, J. G.; Lebedev, A.; Le Bornec, Y.; Leckey, S.; Lee, D. M.; Lee, J.; Lee, K.; Lee, K. B.; Lee, K. S.; Lee, M. K.; Lee, T.; Leitch, M. J.; Leite, M. A. L.; Leitner, E.; Lenzi, B.; Li, X.; Li, X. H.; Lichtenwalner, P.; Liebing, P.; Lim, H.; Linden Levy, L. A.; Liška, T.; Litvinenko, A.; Liu, H.; Liu, M. X.; Love, B.; Luechtenborg, R.; Lynch, D.; Maguire, C. F.; Makdisi, Y. I.; Malakhov, A.; Malik, M. D.; Manko, V. I.; Mannel, E.; Mao, Y.; Mašek, L.; Masui, H.; Matathias, F.; McCain, M. C.; McCumber, M.; McGaughey, P. L.; Means, N.; Meredith, B.; Miake, Y.; Mibe, T.; Mignerey, A. C.; Mikeš, P.; Miki, K.; Miller, T. E.; Milov, A.; Mioduszewski, S.; Mishra, G. C.; Mishra, M.; Mitchell, J. T.; Mitrovski, M.; Mohanty, A. K.; Moon, H. J.; Morino, Y.; Morreale, A.; Morrison, D. P.; Moss, J. M.; Moukhanova, T. V.; Mukhopadhyay, D.; Murakami, T.; Murata, J.; Nagamiya, S.; Nagata, Y.; Nagle, J. L.; Naglis, M.; Nagy, M. I.; Nakagawa, I.; Nakamiya, Y.; Nakamura, K. R.; Nakamura, T.; Nakano, K.; Nam, S.; Newby, J.; Nguyen, M.; Nihashi, M.; Norman, B. E.; Nouicer, R.; Nyanin, A. S.; Nystrand, J.; Oakley, C.; O'Brien, E.; Oda, S. X.; Ogilvie, C. A.; Ohnishi, H.; Ojha, I. D.; Oka, M.; Okada, K.; Omiwade, O. O.; Onuki, Y.; Oskarsson, A.; Otterlund, I.; Ouchida, M.; Ozawa, K.; Pak, R.; Pal, D.; Palounek, A. P. T.; Pantuev, V.; Papavassiliou, V.; Park, I. H.; Park, J.; Park, S. K.; Park, W. J.; Pate, S. F.; Pei, H.; Peng, J.-C.; Pereira, H.; Peresedov, V.; Peressounko, D. Yu.; Petti, R.; Pinkenburg, C.; Pisani, R. P.; Proissl, M.; Purschke, M. L.; Purwar, A. K.; Qu, H.; Rak, J.; Rakotozafindrabe, A.; Ravinovich, I.; Read, K. F.; Rembeczki, S.; Reuter, M.; Reygers, K.; Riabov, V.; Riabov, Y.; Richardson, E.; Roach, D.; Roche, G.; Rolnick, S. D.; Romana, A.; Rosati, M.; Rosen, C. A.; Rosendahl, S. S. E.; Rosnet, P.; Rukoyatkin, P.; Ružička, P.; Rykov, V. L.; Ryu, S. S.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sakai, S.; Sakashita, K.; Sakata, H.; Samsonov, V.; Sano, S.; Sato, H. D.; Sato, S.; Sato, T.; Sawada, S.; Sedgwick, K.; Seele, J.; Seidl, R.; Semenov, A. Yu.; Semenov, V.; Seto, R.; Sharma, D.; Shea, T. K.; Shein, I.; Shevel, A.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shohjoh, T.; Shoji, K.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Silvestre, C.; Sim, K. S.; Singh, B. K.; Singh, C. P.; Singh, V.; Skutnik, S.; Slunečka, M.; Smith, W. C.; Soldatov, A.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Sourikova, I. V.; Sparks, N. A.; Staley, F.; Stankus, P. W.; Stenlund, E.; Stepanov, M.; Ster, A.; Stoll, S. P.; Sugitate, T.; Suire, C.; Sukhanov, A.; Sullivan, J. P.; Sziklai, J.; Tabaru, T.; Takagi, S.; Takagui, E. M.; Taketani, A.; Tanabe, R.; Tanaka, K. H.; Tanaka, Y.; Taneja, S.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tarján, P.; Themann, H.; Thomas, D.; Thomas, T. L.; Togawa, M.; Toia, A.; Tojo, J.; Tomášek, L.; Torii, H.; Towell, R. S.; Tram, V.-N.; Tserruya, I.; Tsuchimoto, Y.; Tuli, S. K.; Tydesjö, H.; Tyurin, N.; Vale, C.; Valle, H.; van Hecke, H. W.; Vazquez-Zambrano, E.; Veicht, A.; Velkovska, J.; Vértesi, R.; Vinogradov, A. A.; Virius, M.; Vrba, V.; Vznuzdaev, E.; Wagner, M.; Walker, D.; Wang, X. R.; Watanabe, D.; Watanabe, K.; Watanabe, Y.; Wei, F.; Wei, R.; Wessels, J.; White, S. N.; Willis, N.; Winter, D.; Wood, J. P.; Woody, C. L.; Wright, R. M.; Wysocki, M.; Xie, W.; Yamaguchi, Y. L.; Yamaura, K.; Yang, R.; Yanovich, A.; Yasin, Z.; Ying, J.; Yokkaichi, S.; You, Z.; Young, G. R.; Younus, I.; Yushmanov, I. E.; Zajc, W. A.; Zaudtke, O.; Zhang, C.; Zhou, S.; Zimányi, J.; Zolin, L.

    2011-10-01

    The PHENIX experiment at the Relativistic Heavy Ion Collider has measured ω meson production via leptonic and hadronic decay channels in p+p, d+Au, Cu+Cu, and Au+Au collisions at sNN = 200 GeV. The invariant transverse momentum spectra measured in different decay modes give consistent results. Measurements in the hadronic decay channel in Cu+Cu and Au+Au collisions show that ω production has a suppression pattern at high transverse momentum, similar to that of π0 and η in central collisions, but no suppression is observed in peripheral collisions. The nuclear modification factors, RAA, are consistent in Cu+Cu and Au+Au collisions at similar numbers of participant nucleons.

  17. First-principles study of Au-Cu alloy surface changes induced by gas adsorption of CO, NO, or O2.

    PubMed

    Dhifallah, Marwa; Dhouib, Adnene; Aldulaijan, Sarah; D I Renzo, Francesco; Guesmi, Hazar

    2016-07-14

    The surface composition of bimetallics can be strongly altered by adsorbing molecules where the metal with the strongest interaction with the adsorbate segregates into the surface. To investigate the effect of reactive gas on the surface composition of Au-Cu alloy, we examined by means of density functional theory to study the segregation behavior of copper in gold matrices. The adsorption mechanisms of CO, NO, and O2 gas molecules on gold, copper, and gold-copper low index (111), (100), and (110) surfaces were analyzed from energetic and electronic points of view. Our results show a strong segregation of Cu toward the (110) surface in the presence of all adsorbed molecules. Interestingly, the Cu segregation toward the (111) and (100) surface could occur only in the presence of CO and at a lower extent in the presence of NO. The analysis of the electronic structure highlights the different binding characters of adsorbates inducing the Cu segregation. PMID:27421421

  18. Au plasmonics in a WS{sub 2}-Au-CuInS{sub 2} photocatalyst for significantly enhanced hydrogen generation

    SciTech Connect

    Cheng, Zhongzhou; Wang, Zhenxing E-mail: hej@nanoctr.cn; Shifa, Tofik Ahmed; Wang, Fengmei; Zhan, Xueying; Xu, Kai; He, Jun E-mail: hej@nanoctr.cn; Liu, Quanlin

    2015-11-30

    Promoting the activities of photocatalysts is still the critical challenge in H{sub 2} generation area. Here, a Au plasmon enhanced photocatalyst of WS{sub 2}-Au-CuInS{sub 2} is developed by inserting Au nanoparticles between WS{sub 2} nanotubes and CuInS{sub 2} (CIS) nanoparticles. Due to the localized surface plasmonic resonance properties from Au nanoparticles, WS{sub 2}-Au-CIS shows the best performance as compared to Au-CIS, CIS, WS{sub 2}-CIS, CIS-Au, WS{sub 2}-Au, and WS{sub 2}-CIS-Au. The surface plasmonic resonance effects dramatically intensify the absorption of visible light and help to inject hot electrons into the semiconductors. Our findings open up an efficient method to optimize the type-II structures for photocatalytic water splitting.

  19. First-principles study of Au-Cu alloy surface changes induced by gas adsorption of CO, NO, or O2

    NASA Astrophysics Data System (ADS)

    Dhifallah, Marwa; Dhouib, Adnene; Aldulaijan, Sarah; D. I. Renzo, Francesco; Guesmi, Hazar

    2016-07-01

    The surface composition of bimetallics can be strongly altered by adsorbing molecules where the metal with the strongest interaction with the adsorbate segregates into the surface. To investigate the effect of reactive gas on the surface composition of Au-Cu alloy, we examined by means of density functional theory to study the segregation behavior of copper in gold matrices. The adsorption mechanisms of CO, NO, and O2 gas molecules on gold, copper, and gold-copper low index (111), (100), and (110) surfaces were analyzed from energetic and electronic points of view. Our results show a strong segregation of Cu toward the (110) surface in the presence of all adsorbed molecules. Interestingly, the Cu segregation toward the (111) and (100) surface could occur only in the presence of CO and at a lower extent in the presence of NO. The analysis of the electronic structure highlights the different binding characters of adsorbates inducing the Cu segregation.

  20. Manganiferous pyroxenes and pyroxenoids from three Pb-Zn-Cu skarn deposits

    NASA Astrophysics Data System (ADS)

    Abrecht, Jürgen

    1985-05-01

    Samples from the Pb-Zn-Cu skarns of M. Ci-villina (Italy), Valle del Temperino (Italy), and Empire Mine (New Mexico, USA) have been analysed for their pyroxenes and pyroxenoids. The samples were collected immediately adjacent to the marble-skarn replacement front. All contain manganiferous pyroxenoids and manganeserich Ca-pyroxenes. The pyroxenes from each deposit form distinct groups of compositions within the diopside-hedenbergite-johannsenite triangle, with no apparent miscibility gap. Diopside contents usually are below 15 mole percent. Fibrous bustamite occurs as monomineralic zones in the Empire and in the Temperino deposit. Although rhodonite may be a primary phase in some samples from the Empire Mine, it is commonly of secondary origin in the Empire Mine and in the Civillina deposit. Its formation from manganiferous clinopyroxenes is either due to increasing Mn activity in the hydrothermal skarn solution or to higher X(CO2) in the vapour phase. When rhodonite is formed within clinopyroxenes as submicroscopic lamellae that eventually replace the whole host crystal, resulting compositions lie in the miscibility gap between rhodonite and bustamite. Textural relations indicate the replacement reaction: johannsenite + CO2 = rhodonite + calcite + quartz. Equilibrium temperatures for this reaction have been calculated by using estimated thermochemical data for johannsenite, giving a T(eq)=385° C for X(CO2)=0.1 at P(tot)= 1 kbar. Taking into consideration the reduced activity of Mn in rhodonite and of Ca in calcite, both buffered by the johannsenite, the temperature is increased for about 15° C at X(CO2)=0.01. At lower temperatures, where johannsenite is stable, the X(CO2) is confined to values below 0.01. Despite the mineralogical similarities of the three deposits differences in the development of the manganiferous skarns can be depicted.

  1. Mineralogical composition of Oravita calcic skarns as a function of the high-temperature contact

    NASA Astrophysics Data System (ADS)

    Ghinet, Cristina; Marincea, Stefan; Dumitras, Delia

    2014-05-01

    Insignificant in terms of mineralization, the skarns of Oravita are scientifically interested because of their mineralogical associations. The higher crystallinity and good natural conditions (they are generally barren) are two characteristics of this rocks that can provide the ideally system to understand the behavior of the mineralogical components in certain conditions of temperature and pressure, but also for the hydrated carbonate phases whose forming understanding may be useful in the applied mineralogy. The occurrence of skarns from Oraviţa includes, as representative species, gehlenite, calcic garnet, monticellite, ellestadite-(OH), vesuvianite, that means in the geochemically terms CaO - SiO2 - H2O - Al2O3 system, usually described as C-S-H-A phases by the cement researches, difficult to study because of the small dimensions of the compounds crystals. The inner skarn zone is dominated by the presence of the gehlenite, an aluminum calcium silicate whose formation involves, as conditions, high temperature (~ 750oC) and low pressure (up to 1kbar). Typically, it is associated with monticellite, ellestadite-(OH), wollastonite 2M, diopside and calcic garnets. As it is expected, the intensity of the contact metamorphism decreases from the innermost to the outermost parts of the aureole, reflected in the chemical activity of the cations that participated at the chemical reactions. In this respect, the observed garnets are zoned, being characterized by a peripheral rich in Al, while the centers of the crystals are characterized by a high content of Fe and Ti. The replacement of gehlenite with vesuvianite along the metasomtatic front, a process that was observed at the optical microscope, indicates the existence of late stage metasomatic mineral phases. The presence of the vesuvianite, frequently including partially chloritized clintonite slides, and its main associated minerals as wollastonite 2M and calcium garnet with an andradite composition, points out the

  2. Mechanical Architecture and Engineering of PAZ Instrument

    NASA Astrophysics Data System (ADS)

    Bautista Juzgado, Victor

    2012-07-01

    PAZ is a highly flexible X-Band Synthetic Aperture Radar satellite devoted to global Earth Observation. It fulfills the strategic needs of the Spanish Government within the National Earth Observation Program. This satellite will be capable of providing high quality SAR images up to very high resolution (e.g. meter and sub- meter). Its flexibility lies on the various instrument modes (Stripmap, ScanSAR, Sporlight...) with a wide number of configurations, both in left and right-looking scanning. The S/C will cover the Earth with a mean revisit time of 1 day taking around 200000 images per day over an area above 300000km2. In the frame of this program, EADS CASA Espacio (ECE) stands as satellite prime contractor as well as responsible for the design and development of the SAR instrument, also called Front End. This paper describes the mechanical architecture, driving requirements, analyses, tests and main challenges found during the Front End development at ECE from the structural point of view.

  3. Slicing-independent RISC activation requires the argonaute PAZ domain.

    PubMed

    Gu, Shuo; Jin, Lan; Huang, Yong; Zhang, Feijie; Kay, Mark A

    2012-08-21

    Small RNAs regulate genetic networks through a ribonucleoprotein complex called the RNA-induced silencing complex (RISC), which, in mammals, contains at its center one of four Argonaute proteins (Ago1-Ago4). A key regulatory event in the RNA interference (RNAi) and microRNA (miRNA) pathways is Ago loading, wherein double-stranded small-RNA duplexes are incorporated into RISC (pre-RISC) and then become single-stranded (mature RISC), a process that is not well understood. The Agos contain an evolutionarily conserved PAZ (Piwi/Argonaute/Zwille) domain whose primary function is to bind the 3' end of small RNAs. We created multiple PAZ-domain-disrupted mutant Ago proteins and studied their biochemical properties and biological functionality in cells. We found that the PAZ domain is dispensable for Ago loading of slicing-competent RISC. In contrast, in the absence of slicer activity or slicer-substrate duplex RNAs, PAZ-disrupted Agos bound duplex small interfering RNAs, but were unable to unwind or eject the passenger strand and form functional RISC complexes. We have discovered that the highly conserved PAZ domain plays an important role in RISC activation, providing new mechanistic insights into how miRNAs regulate genes, as well as new insights for future design of miRNA- and RNAi-based therapeutics.

  4. Fluids drainage along detachments: the West Cycladic Detachment System and synkinematic skarns on Serifos Island (Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Ducoux, Maxime; Jolivet, Laurent; Arbaret, Laurent; Branquet, Yannick; Rabillard, Aurélien

    2014-05-01

    Back-arc extension in the Aegean Sea has been accommodated by several large-scale detachments such as the West Cycladic Detachment System (WCDS) in the Oligocene and Miocene. The WCDS is associated on Serifos island (Cyclades) with a synkinematic granodioritic intrusion. Serifos is also well known for its skarn deposit and a rich mineralogy as well as colder Fe-Ba ore deposits that were exploited until 1963. The geometrical and kinematic relations between the detachments and ore bodies have so far been little studied. Different types of skarn can be observed (1) massive garnet endoskarns, (2) garnet-pyroxene endoskarns in the granodiorite, (3) garnet-pyroxene cracks exoskarns, (4) brecciated pyroxene +/- ilvaite skarn within the Meghàlo Livadhi and Kavos Kiklopas detachments. Fields observations show that the formation of the skarn is intimately associated with the detachments and the deformation of the intrusion in the footwall. Endo and exo-skarn deposits formed before, during and after the ductile and brittle structures resulting from the activity of the WCDS. They are represented by echelon veins, veins with antithetic shear and boudinaged veins wrapped within sheath folds, with a shearing movement top SSW or SW compatible with the regional tectonics, deformation in host-rock and the emplacement of the syn-tectonic granodioritic intrusion. Skarnified breccias formed within the two main detachments attesting for the intense circulation of fluids at a certain distance from the main intrusion. These skarn parageneses were deposited by hydrothermal fluids associated with the intrusion, mixed with meteoric or oceanic fluids forming at the regional level of pyroxene. The two detachments acted as preferential crustal-scale drains during footwall exhumation. This example illustrates the potential of detachments to channelize large amount of fluids in the crust during extension.

  5. 78 FR 3027 - Notice of Temporary Closures of Public Lands in La Paz County, AZ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-15

    ...-10-05] Notice of Temporary Closures of Public Lands in La Paz County, AZ AGENCY: Bureau of Land... Lake Havasu Field Office in La Paz County, Arizona. This action is being taken to help ensure public... the La Paz County Emergency Medical Services and Fire, the Arizona Department of Public Safety, or...

  6. 76 FR 5398 - Notice of Temporary Closure of Selected Public Lands in La Paz County, AZ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-31

    ...-330-07-02] Notice of Temporary Closure of Selected Public Lands in La Paz County, AZ AGENCY: Bureau of... its administration in La Paz County, Arizona. This action is being taken to protect persons, property... under the guidance of the La Paz County Emergency Medical Services and Fire, or the Arizona...

  7. Fluid inclusions and U/Pb dating of the El Pilote Fluorite skarn occurrence: Metallogenic implications

    NASA Astrophysics Data System (ADS)

    Levresse, Gilles; Tritlla, Jordi; Solorio-Munguía, Jose Gregorio; Valencia, Victor; Linares, Porfirio Julio Pinto

    2011-05-01

    The "El Pilote" deposit, located in the Coahuila State (NE Mexico), is a small fluorite-bearing calcic skarn we dated at 28.4 ± 0.4 Ma (U/Pb). Fluid inclusion studies, performed on fluorite, indicate the occurrence of hot, hypersaline fluids, trapped during the prograde stage. The retrograde fluids present progressively lower temperatures and salinities. All this fluid data depicts a coherent scenario where early magmatic-dominated fluids were progressively mixed up with low-temperature, low-salinity meteoric fluids whose predominance indicates the waning of the hydrothermal system.

  8. Dal'negosrk skarn deposit, Sikhote-Alin: Stages and sources of matter for borosilicate ores

    NASA Astrophysics Data System (ADS)

    Karas', O. A.; Ratkin, V. V.

    2014-04-01

    The danburite orebody at the northeastern wall of the open pit of the Dal'negorsk borosilicate deposit is studied. The comparative mineralogical-, isotopic-, and thermobarogeochemical analyses of danburite from the Levoberezhnyi area and datolite of the late skarn stage from the Tsentral'nyi open pit confirms that danburite is a result of the early borosilicate stage of formation of the deposit. Combined with previously published data, it is concluded that marine sedimentary rocks or Early Cretaceous arkose sandstones from the matrix of the Taukhin accretionary prism could be the source of boron.

  9. Oxygen Isotope Zoning in Skarn Garnets: Evidence for Spatial and Temporal Fluid Source Variability in the Sierra Nevada and Mojave

    NASA Astrophysics Data System (ADS)

    Gevedon, M. L.; Ryan-Davis, J.; Lackey, J. S.; Barnes, J.; Kitajima, K.; Valley, J. W.

    2014-12-01

    Skarns provide insight to the depth, longevity, and dominant fluid regime associated with Sierra Nevada plutonism and Mesozoic magmatism in the Mojave National Preserve, which represent different spatial and temporal exposures of the Mesozoic arc. Skarns from these regions may serve as proxies for intricacies in the fluid source, and have the potential to resolve magmatic flare-ups and relative depths of emplacement. Both laser fluorination (LF) and secondary ion mass spectrometry (SIMS) δ18O analyses of garnet from multiple Mojave (Lucerne valley) skarns indicate a strong, early influence of meteoric fluid despite the presence of relatively deep plutonism. LF data from individual whole garnets and garnet chips broken during sample preparation reveal variation from +4.2‰ to -8.8‰ (n = 24), with an average of approximately -4.0‰. The large spread in these LF data suggest that (A) δ18O reflects an average of varying δ18O (fluid) compositions spanning multiple garnet growth oscillations; or (B) multiple generations of garnets exist within individual skarns, the growth of each coinciding with changes in the hydrothermal source and composition. SIMS analysis of two individual Mojave skarn garnets with oscillatory zoning (seen in backscatter electron images) reveal crystal cores with δ18O values of -9.6‰, internal variations of -9.4‰ to -3.3‰, and crystal rims of -2.2‰ and -2.9‰ (precision ±0.3; 2σ). In general, δ18O values negatively correlate with andradite compositions, with high andradite zones having lower δ18O values ([AND + CaTi] compositions range from 100 to 73). Similar analyses (both SIMS and LF) of garnets from Sierra Nevadan skarns (Tungsten Hills region) show variation in δ18O values with LF data ranging from 5.4‰ to 6.2‰ (n = 8), with an average of 5.7‰, and an additional 2.7‰ value obtained from a garnet interior. SIMS data show δ18O compositional variation from 4.0‰ to 5.9‰. Data across the two Tungsten Hills garnets

  10. Iron mobility during synmetamorphic alteration in the Selwyn Range area, NW Queensland: implications for the origin of ironstone-hosted Au-Cu deposits

    NASA Astrophysics Data System (ADS)

    Williams, P. J.

    1994-07-01

    The Proterozoic metamorphic rocks of the Selwyn Range area in western Queensland contain a variety of styles of Au + Cu deposit including some (e.g. Selwyn mine and Osborne prospect) that are spatially associated with magnetite-rich ironstones. The area is characterized by extensive alkali-(chloride) metasomatism that occurred during the later stages of regional metamorphism. Existing experimental data indicate that hot saline fluids will dissolve and transport iron as they move through temperature/pressure gradients in the vicinity of the amphibolite-greenschist facies transition and predict that circulation cells will move iron and concentrate it in relatively cool, dilute and/or oxidized parts of such systems. New geological mapping coupled with geochemical data from the amphibolite facies zone of the Selwyn Range area suggest such processes occurred on a large scale and that large masses of Fe were mobilized, particularly in association with Na-metasomatism of biotite-bearing metasediments and high Fe-tholeiitic dolerites. Field and textural features of ironstones and other Fe-rich lithologies demonstrate that some of them at least formed by replacement of other rocks during metamorphism and deformation. Mineralization localized within such iron stones must itself be epigenetic.

  11. Skarn formation and trace elements in garnet and associated minerals from Zhibula copper deposit, Gangdese Belt, southern Tibet

    NASA Astrophysics Data System (ADS)

    Xu, Jing; Ciobanu, Cristiana L.; Cook, Nigel J.; Zheng, Youye; Sun, Xiang; Wade, Benjamin P.

    2016-10-01

    Trace element concentrations in garnet and associated minerals from the mid-Miocene Zhibula Cu skarn, Gangdese Belt, Tibet reflect a diversity of local environments, evolving fluid parameters and partitioning with coexisting minerals. Exoskarn occurs as massive but narrow intervals within a Lower Jurassic volcano-sedimentary sequence containing limestone, the main skarn protolith. Endoskarn is present at the contact with mid-Miocene granodiorite dikes. Prograde skarn associations are garnet-dominant but also include diopside-dominant pyroxene in variable amounts. Garnet compositions in exoskarn change from andradite (And)- to grossular (Gr)-dominant from the massive intervals to bands/lenses within marble/tuff, but not in endoskarn. In both cases however, associations at the protolith contact include anorthite and wollastonite, both indicative of skarnoid or distal (relative to fluid source) skarn formation. Exoskarns also contain vesuvianite. Retrograde clinozoisite, actinolite and chlorite replace pre-existing skarn minerals. Garnet displays brecciation and replacement by Al-richer garnet. Depending on partitioning among coexisting minerals, chondrite-normalised REY (REE + Y) fractionation trends for garnet depict endo- to exoskarn diversity, the dominance of And- vs. Gr-rich garnet (in turn related to proximal-to-distal relationship to fluid source), as well as prograde-to-retrograde evolution in the same sample. A strong variation in Eu-anomaly, from positive to negative, in And-dominant garnet can be correlated with variation in salinity of ore-forming fluids, concordant with published fluid inclusion data. Trends depicted by And- and Gr-dominant garnets are consistent with published data from skarns elsewhere, in which the dominant substitution mechanism for REY is YAG-type. Zhibula garnets are enriched in a range of trace elements less commonly reported, including W, Sn, and As, but also Mo (as high as 730 ppm), an element seldom analysed for in silicates

  12. Mineralogical and sulfur isotopic evidence for the incursion of evaporites in the Jinshandian skarn Fe deposit, Edong district, Eastern China

    NASA Astrophysics Data System (ADS)

    Zhu, Qiaoqiao; Xie, Guiqing; Mao, Jingwen; Li, Wei; Li, Yanhe; Wang, Jian; Zhang, Ping

    2015-12-01

    Evaporites have played important role in the formation of diverse metallic ore deposits, especially in the case of magmatic-hydrothermal deposits. However, the relationship between evaporites and skarn Fe deposit remains poorly constrained. In this contribution, we present new sulfur isotope data of pyrite, as well as the composition of halogen-rich minerals (scapolite and amphibole) in the Jinshandian skarn Fe deposit. The data are used to evaluate the evidence for incursion of evaporites in the skarn Fe deposit. The δ34S values for pyrite from the early and late retrograde stage range from +17.4‰ to +18.7‰ (n = 4) and +16.4‰ to +19.4‰ (n = 13), respectively. Both these values are markedly heavier than the common δ34S values of sulfides from magmatic-hydrothermal fluid, indicating that sulfur in the Jinshandian ore-forming system was mostly derived from evaporites. Compared to the amphibole from endoskarn, the scapolite and amphibole from exoskarn show high Cl content up to 4.04% and 3.01%, respectively, suggesting that the hydrothermal fluid with high NaCl content was probably derived from evaporites. The amphiboles from endoskarn are more enriched in F which is probably of magmatic in origin. The data presented in our study suggest that the hydrothermal system of the Jinshandian skarn Fe deposit probably experienced significant incursion of evaporites before or during the late prograde stage.

  13. Fluid inclusion and H-O isotope evidence for immiscibility during mineralization of the Yinan Au-Cu-Fe deposit, Shandong, China

    NASA Astrophysics Data System (ADS)

    Zhang, Y. M.; Gu, X. X.; Liu, L.; Dong, S. Y.; Li, K.; Li, B. H.; Lv, P. R.

    2011-07-01

    The fluid inclusion and H-O isotope studies have provided the evidences for the source of ore-forming fluids, and helped to recognize two types of immiscibility and their relationships with mineralization. Hydrogen and oxygen isotopic geochemistry shows that the earlier ore-forming fluids during the anhydrous skarn stage (I) and the hydrous skarn-magnetite stage (II) were mainly derived from magmatic water, while the later fluids during the quartz-sulfide stage (III) and the carbonate stage (IV) were mainly from magmatic water mixed with small amounts of meteoric water. Various types of fluid inclusions, including abundant vapor- or liquid-rich two-phase aqueous inclusions, daughter minerals-bearing multiphase inclusions, CO 2-H 2O inclusions, and less abundant liquid inclusions, vapor inclusions and melt inclusions, are present in hydrothermal minerals of different stages. The liquid-vapor fluid inclusions are mainly composed of H 2O, with significant amounts of CO 2 and a small amount of CH 4. In the opaque-bearing fluid inclusions, the hematite and fahlore (tetrahedrite) were identified. The homogenization temperature of the aqueous fluid inclusions decreases from Stage I (520-410 °C), through Stage II (430-340 °C) and III (250-190 °C), to Stage IV (190-130 °C). The coexistence of melt inclusions with simultaneously trapped vapor- or liquid-rich two-phase aqueous inclusions and daughter minerals-bearing multiphase inclusions in garnet, diopside and epidote of Stages I and II suggests an immiscibility between silicate melt and hydrothermal fluid. It is an effective mechanism on scavenging and transporting ore-forming components from magmas. The aqueous fluid inclusions with various vapor/liquid ratios (from <10% to >65%) commonly coexist with simultaneously trapped liquid inclusions, vapor inclusions, daughter minerals-bearing multiphase inclusions and CO 2-H 2O inclusions in the quartz of Stage III, and the different kinds of the fluid inclusions have

  14. Tuning RNA Interference by Enhancing siRNA/PAZ Recognition.

    PubMed

    Gaglione, Maria; Potenza, Nicoletta; Di Fabio, Giovanni; Romanucci, Valeria; Mosca, Nicola; Russo, Aniello; Novellino, Ettore; Cosconati, Sandro; Messere, Anna

    2013-01-10

    Chemically modified siRNAs were synthesized to enhance the corresponding silencing activities. The introduced modifications endowed siRNAs with high silencing effect, long RNAi persistence, and better serum resistance. Theoretical data allowed us to correlate the observed siRNAs interfering performance with the peculiar interactions with PAZ.

  15. Rare earths and other trace elements in minerals from skarn assemblages, Hillside iron oxide-copper-gold deposit, Yorke Peninsula, South Australia

    NASA Astrophysics Data System (ADS)

    Ismail, Roniza; Ciobanu, Cristiana L.; Cook, Nigel J.; Teale, Graham S.; Giles, David; Mumm, Andreas Schmidt; Wade, Benjamin

    2014-01-01

    The Hillside Cu-(Au) deposit, Yorke Peninsula, South Australia, is a recently-discovered ore system within the 1.6 Ga World-class Olympic iron oxide-copper-gold (IOCG) Province. The deposit is characterized by a skarn-style alteration zone. Analyses of feldspar, calcite, skarn minerals (garnet, pyroxene, clinozoisite and actinolite) and accessories (titanite, apatite and allanite), and grain-scale element mapping by laser-ablation inductively-coupled plasma mass spectrometry are used to assess the distributions of rare earth element (REE), incompatible and ore-forming elements in host rocks, prograde and retrograde skarn.

  16. Saltwater ecotoxicology of Ag, Au, CuO, TiO2, ZnO and C60 engineered nanoparticles: An overview.

    PubMed

    Minetto, D; Volpi Ghirardini, A; Libralato, G

    2016-01-01

    This review paper examined 529 papers reporting experimental nanoecotoxicological original data. Only 126 papers referred to saltwater environments (water column and sediment) including a huge variety of species (n=51), their relative endpoints and engineered nanoparticles (ENPs) (n=38). We tried to provide a synthetic overview of the ecotoxicological effects of ENPs from existing data, refining papers on the basis of cross-cutting selection criteria and supporting a "mind the gap" approach stressing on missing data for hazard and risk assessment. After a codified selection procedure, attention was paid to Ag, Au, CuO, TiO2, ZnO and C60 ENPs, evidencing and comparing the observed nanoecotoxicity range of effect. Several criticisms were evidenced: i) some model organisms are overexploited like microalgae and molluscs compared to annelids, echinoderms and fish; ii) underexploited model organisms: mainly bacteria and fish; iii) exposure scenario variability: high species-specific and ENP scenarios including organism life stage and way of administration/spiking of toxicants; iv) scarce comparability between results due to exposure scenario variability; v) micro- and mesocosms substantially unexplored; vi) mixture effects: few examples are available only for ENPs and traditional pollutants; mixtures of ENPs have not been investigated yet; vii) effects of ions and ENPs: nAg, nCuO and nZnO toxicity aetiology is still a matter of discussion; viii) size and morphology effects of ENPs: scarcely investigated, justified and understood. Toxicity results evidenced that: nAu>nZnO>nAg>nCuO>nTiO2>C60. PMID:27107224

  17. [Distribution characteristics and risk assessment of heavy metals in farming domestic muscovy duck originated from Au/Cu mining and smelting activites].

    PubMed

    Hang, Xiao-Shuai; Liang, Bin; Wang, Wen-Lin; Wang, Xia; Li, Wei-Xin

    2012-09-01

    To investigate the impacts of mining and spilling activities on domestic fowl raising, ten muscovy duck (Cairna moschata) samples were collected in 2010 from farms in different villages located at the banks of the river originated from an Au/Cu mine. Concentrations of Cu, Hg and As in muscle, liver and blood of the muscovy duck samples were determined. According to relative national standards of China, the health safety of heavy metals in muscovy duck was evaluated. The results indicated that content of Cu was higher than those of Hg and As in the same tissue of the duck. The average content (17.20 mg x kg(-1)) of Cu in liver of the duck was higher than those in other tissues, but the concentrations of Hg and As had no significant difference among three tissues of the duck. There was no significant spatial distribution pattern of Cu, Hg and As in three tissues of the duck samples collected from the farms in different villages located at the banks of the river, indicating no significant impacts of mining and spilling activities on the ducks samples. The contents of Cu, Hg and As in the tissues of the duck samples fell in normal level ranges, and the ducks didn't show abnormal physical symptoms. According to the tolerance limits of heavy metals in foods of China, Cu in livers of the duck samples exceeded the standard by 100%, and the highest value of Cu in the liver was 1.74 times higher than its maximum allowable concentration in foods. Moreover, Hg contents in some muscle, blood and liver tissues of the duck samples were relatively high.

  18. On the mechanisms of cation injection in conducting bridge memories: The case of HfO2 in contact with noble metal anodes (Au, Cu, Ag)

    NASA Astrophysics Data System (ADS)

    Saadi, M.; Gonon, P.; Vallée, C.; Mannequin, C.; Grampeix, H.; Jalaguier, E.; Jomni, F.; Bsiesy, A.

    2016-03-01

    Resistance switching is studied in HfO2 as a function of the anode metal (Au, Cu, and Ag) in view of its application to resistive memories (resistive random access memories, RRAM). Current-voltage (I-V) and current-time (I-t) characteristics are presented. For Au anodes, resistance transition is controlled by oxygen vacancies (oxygen-based resistive random access memory, OxRRAM). For Ag anodes, resistance switching is governed by cation injection (Conducting Bridge random access memory, CBRAM). Cu anodes lead to an intermediate case. I-t experiments are shown to be a valuable tool to distinguish between OxRRAM and CBRAM behaviors. A model is proposed to explain the high-to-low resistance transition in CBRAMs. The model is based on the theory of low-temperature oxidation of metals (Cabrera-Mott theory). Upon electron injection, oxygen vacancies and oxygen ions are generated in the oxide. Oxygen ions are drifted to the anode, and an interfacial oxide is formed at the HfO2/anode interface. If oxygen ion mobility is low in the interfacial oxide, a negative space charge builds-up at the HfO2/oxide interface. This negative space charge is the source of a strong electric field across the interfacial oxide thickness, which pulls out cations from the anode (CBRAM case). Inversely, if oxygen ions migration through the interfacial oxide is important (or if the anode does not oxidize such as Au), bulk oxygen vacancies govern resistance transition (OxRRAM case).

  19. Mechanism of Coupled Folding and Binding in the siRNA-PAZ Complex.

    PubMed

    Chen, Hai-Feng

    2008-08-01

    The PAZ domain plays a key role in gene silencing pathway. The PAZ domain binds with siRNAs to form the multimeric RNA-induced silencing complex (RISC). RISC identifies mRNAs homologous to the siRNAs and promotes their degradation. It was found that binding with siRNA significantly enhances apo-PAZ folding. However, the mechanism by which folding is coupled to binding is poorly understood. Thus, the coupling relationship between binding and folding is very important for understanding the function of gene silencing. We have performed molecular dynamics (MD) of both bound and apo-PAZ to study the coupling mechanism between binding and folding in the siRNA-PAZ complex. Room-temperature MD simulations suggest that both PAZ and siRNA become more rigid and stable upon siRNA binding. Kinetic analysis of high-temperature MD simulations shows that both bound and apo-PAZ unfold via a two-state process. The unfolding pathways are different between bound and apo-PAZ: the order of helix III and helices I & II unfolding is switched. Furthermore, transition probability was used to determine the transition state ensemble for both bound and apo-PAZ. It was found that the transition state of bound PAZ is more compact than that of apo-PAZ. The predicted Φ-values suggest that the Φ-values of helix III and sheets of β3-β7 for bound PAZ are more native-like than those of apo-PAZ upon the binding of siRNA. The results can help us to understand the mechanism of gene silencing.

  20. Hydrothermal Zircon U-Pb Dating for Early Cretaceous Iron Skarn Mineralization in the Handan-Xingtai District, North China Craton

    NASA Astrophysics Data System (ADS)

    Deng, X., Sr.; Li, J. W., Sr.; Wen, G., Sr.

    2015-12-01

    The Handan-Xingtai district in the North China craton (NCC) is one of the most important concentrations of iron skarn deposits in China. The iron mineralization occurs predominantly along contact zones between early Cretaceous intrusions and Middle Ordovician marine carbonates. We present textural features and LA-ICP-MS U-Pb dating results of hydrothermal zircon to constrain on the time of iron mineralization. Zircon grains from mineralized skarns are subhedral crystals and euhedral tetragonal bipyramids, which are closely intergrown with skarn minerals. They contain abundant inclusions of skarn minerals and daughter mineral-rich (mostly magnetite, halite, and sylvite) fluid inclusions, and have variable Th (518-17477 ppm) and U (109-25610 ppm) contents, with Th/U ratios of 0.01-5.23. These features indicate their hydrothermal origin. The hydrothermal zircon grains from 5 deposits yield concordant U-Pb ages ranging from 133.6 ± 0.9 to 128.5 ± 1.4 Ma (2σ). These ages are consistent with U-Pb ages (134.1 ± 1.2 to 128.5 ± 0.9 Ma; 2σ) of magmatic zircon grains, confirming the reliability of hydrothermal zircon U-Pb ages. Our new geochronological data indicate that iron mineralization and associated magmatism in the Handan-Xingtai district occurred mainly at the ca. 137-133 and 131-128 Ma intervals. These iron skarn deposits represent as the only known giant Mesozoic iron skarn province in a cratonic block on the Earth. Their formation time coincided with lithospheric thinning or destruction of the NCC, strongly suggesting a causal link between the two processes. Our work provides a valuable approach to date iron skarn mineralization by using U-Pb geochronology of hydrothermal zircon and highlights its potential for similar studies. Keywords: Hydrothermal zircon; LA-ICPMS; U-Pb geochronology, iron skarn deposits; North China craton

  1. AmeriFlux MX-Lpa La Paz

    DOE Data Explorer

    Oechel, Walter [San Diego State University

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site MX-Lpa La Paz. Site Description - As evident by some very large Cardon (5-7 meters), according to Coyle and Roberts, 1975, extent vegetation has likely been around at least 200 years. Until about 15 years ago from 1996, site was used for livestock production and selective firewood extraction. However, when I look over the fence where there has been livestock activity, not much difference

  2. Sulfur isotope study of the Velardeña skarn (Zn-Pb), Durango, Mexico

    NASA Astrophysics Data System (ADS)

    Jimenez, A.

    2012-04-01

    Sulfur isotope study of the Velardeña skarn (Zn-Pb), Durango, Mexico Abigail Jimenez-Franco1*, Pura Alfonso Abella2, Carles Canet3, Eduardo González-Partida4 1 Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de México, Ciudad Universitaria, Delegación Coyoacán, 04510 México D.F., Mexico 2 Departament d'Enginyeria Minera i Recursos Naturals, Universitat Politècnica de Catalunya, Av de Les Bases de Manresa 61-73, 08242 Manresa. 3Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Delegación Coyoacán, 04510 México D.F., Mexico 4Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, Boulevard Juriquilla 3001, 76230 Santiago de Querétaro, Qro., Mexico The Velardeña mining district is located in north-eastern part of the state of Durango, in northern of Mexico. The ore deposit is a lead-zinc, garnet-rich skarn developed at the contact between granite porphyry dikes (Eocene) and well-laminated limestones with interbedded chert (Albian-Cenomanian). A study of sulfur isotopes has been carried out in various sulfide minerals of the ores of Velardeña, in order to: (a) constrain the possible sources of sulfur and, therefore, better understand the sulfide mineralizing processes, and (b) to estimate the temperature of the ore-forming stage of the skarn. Sulfur isotope analyses were performed in 21 pure fractions of sulfide minerals of the ore mineralization (pyrite, chalcopyrite, sphalerite and galena). The mineral separation was performed using a series of sieves, and the purity of the samples was verified under a binocular microscope. Isotopic analyses were done on a Finnigan MAT Delta C flow elemental analyzer coupled to a TC-EA, according with the method of Giesemann et al. (1974). The δ34S values of the analyzed sulfides range mostly between -0.6 and +2.6 ‰ (relative to the CDT standard). These values are indicative of a magmatic source of sulfur. A single analysis falls

  3. Geochronology and petrogenesis of Miocene granitic intrusions related to the Zhibula Cu skarn deposit in the Gangdese belt, southern Tibet

    NASA Astrophysics Data System (ADS)

    Xu, Jing; Zheng, You-ye; Sun, Xiang; Shen, Ya-hui

    2016-04-01

    The Zhibula Cu skarn deposit (19.5 Mt ore @ 1.64%), near the Qulong porphyry Cu-Mo deposit, is located in the Gangdese porphyry copper belt in southern Tibet. The deposit is a typical metasomatic skarn that is related to the interaction of magmatic-hydrothermal fluids and calcareous host rocks. Stratiform skarn orebodies are mainly distributed in the contact between tuff and marble in the lower part of the Jurassic Yeba Formation. Endoskarn zonations for an outward trend are observed in the granodiorite, which grade from a fresh granodiorite to a weakly chlorite-altered granodiorite, a green diopside-bearing granodiorite, and a dark red-brown garnet-bearing granodiorite. The Zhibula granodiorite and monzogranite have similar secondary ion mass spectrometry (SIMS) zircon U-Pb ages of 16.9 ± 0.3 Ma and 17.0 ± 0.2 Ma, respectively. They exhibit different fractional crystallization from granodiorite (SiO2 = 64.8-69.3 wt.%) to monzogranite (SiO2 = 72.3-76.8 wt.%). Both the granodiorite and monzogranite are characterized by high Al2O3 (12.6-16.7 wt.%) and K2O (1.5-5.5 wt.%) contents, high Sr/Y (35-151) and La/Yb (19-48) ratios, and variable MgO (0.16-3.91) and Mg# (31-61) values. They display features of enrichment in large ion lithophile elements (LILEs, e.g., Rb, Ba, Sr, and K), depletion in high field strength elements (HFSEs, e.g., Nb, Ta, Ti, and P), and moderate negative Eu anomalies (δEu = 0.58-0.98). They show restricted in situ zircon Hf isotopic compositions (+6.7 to +8.8; only one sample is +4.5) and consistent δ18O values (+6.0‰ to +6.6‰). The geochemical data indicated that the Miocene Zhibula granitic intrusions formed by the magma that were characterized by high Sr/Y ratios and were derived from the partial melting of the thickened juvenile lower crust, which may have been metasomatized by the slab melts during subduction of the Neo-Tethyan oceanic crust and were induced by the convective removal of the thickened lithosphere. In addition, the

  4. Krasnotur'insk Skarn copper ore field, Northern Urals: The U-Pb age of ore-controlling diorites and their place in the regional metallogeny

    NASA Astrophysics Data System (ADS)

    Grabezhev, A. I.; Ronkin, Yu. L.; Puchkov, V. N.; Gerdes, A.; Rovnushkin, M. Yu.

    2014-06-01

    The Krasnotur'insk skarn copper ore field known from the theoretical works of Academician K.S. Korzhinskii is located in the western part of the Tagil volcanic zone (in the area of the town of Krasnotur'insk). The ore field is composed of layered Devonian (Emsian) volcanosedimentary rocks intruded by small plutons of quartz diorites, diorites, and gabbrodiorites. Widespread pre-ore and intra-ore dikes of similar composition control the abundance of the andradite skarns formed after limestones and the magnetitesulfide and sulfide ore bodies formed after skarns. The LA-ICP-MS U-Pb concordant age of zircon from the quartz diorite of the Vasil'evsko-Moskalevskii pluton calculated by 16 analyses (16 crystals) is 407.7 ± 1.6 Ma (MSWD = 1.5). Taking into account the geological and petrogeochemical similarity of diorites of small plutons and intra-ore dikes, it is assumed that this age corresponds to the period of formation of the ore-magmatic system of the Krasnotur'insk skarn copper ore field. It was probably formed somewhat earlier than the Auerbakh montzonitic pluton and the accompanying skarn magnetite deposits in the south.

  5. Large slope failures in the La Paz basin, Bolivian Andes

    NASA Astrophysics Data System (ADS)

    Roberts, N. J.; Hermanns, R. L.; Rabus, B.; Guzmán, M. A.; Minaya, E.; Clague, J. J.

    2014-12-01

    The La Paz basin in the eastern Bolivian Andes has been a hotspot for large-scale, deep-seated gravitational slope deformation during the Holocene. In less than 2 Ma, a network of steep-sided valleys up to 800 m deep formed in sediments of the Altiplano Plateau and underlying basement rocks. We characterize the distribution, extent, mechanisms, and modern activity of large-scale failures within this landscape using optical image interpretation, existing geologic maps, synthetic RADAR interferometry (InSAR), and field investigation. Deposits of nearly 20 landslides larger than 100 Mm3 occur within the basin. Most failures have occurred in weakly lithified Late Miocene to Pliocene sedimentary rocks and include earth flows, translational and rotational landslides, and plug flows. Failures in underlying tectonized Paleozoic sedimentary rocks include bedding-parallel rockslides. The largest failure is the 3 km3 Achcocalla earth flow (ca. 11 ka BP), which ran out ~20 km. Other dated events span the period from the early Holocene to nearly the Colonial historic period. InSAR results show that many large slope failures, including the Achocalla earth flow, are currently moving at rates of a few centimeters to a few decimeters per year. Rapid deposition, shallow burial, and rapid incision of the basin fills produced steep slopes in weak geologic materials that, coupled with groundwater discharge from the valley walls, are the primary controls on instability. In contrast, the Altiplano surface has changed little in 2 Ma and the adjacent slopes of the Cordilleran Real, although steep, are relatively stable. Of the over 100 landslides that have occurred in the city of La Paz since the early twentieth century, most are at the margins of large, deep-seated prehistoric failures, and two of the most damaging historic landslides (Hanko-Hanko, 1582; Pampahasi, 2011) were large-scale reactivations of previously failed slopes. Improved understanding of large, deep-seated landslides in

  6. Status of the lidar station at La Paz - Bolivia

    NASA Astrophysics Data System (ADS)

    Zaratti, Francesco; Forno, Ricardo N.; Calderon, Fernando

    2010-05-01

    The current status of the LIDAR station at La Paz is discussed, including the technical difficulties of operating an Alexandrite system at this high altitude location. Advances related to the reconditioning of this system, especially those related to the new laser system, are also discussed. In addition, the goals and perspectives of the Atmospheric Physics Laboratory, part of the Universidad Mayor de San Andrés, are described in the context of the new instrument and the new initiatives recently undertaken with the help of the international scientific community.

  7. Stable isotope studies of metasomatic Ca-Fe-Al-Si skarns and associated metamorphic and igneous rocks, Osgood Mountains, Nevada

    USGS Publications Warehouse

    Taylor, B.E.; O'Neil, J.R.

    1977-01-01

    Garnet-pyroxene skarns were formed 90 m.y. B.P. in the Osgood Mountains at or near contacts of grandiorite with calcareous rocks of the Cambrian Preble Formation. The metasomatic replacement followed contact metamorphic recrystallization of the Preble. The sources, temperature, and variation in H2O/CO2 ratios of the metasomatic fluid are interpreted from 269 analyses of oxygen, carbon, hydrogen, and sulfur isotopes in whole rocks, minerals and inclusion fluids. Skarns formed in three mineralogical stages. Oxygen isotope data indicate that temperatures during the crystallization of garnet, pyroxene and wollastonite (Stage I) were least 550 ?? C, and that the metasomatic fluid had an {Mathematical expression} ??? 0.035 in the massive skarns, and ??? 0.12 in vein skarns up to 3 cm thick. Pore fluids in isotopic equilibrium with garnet in calc-silicate metamorphic rocks, on the other hand, had {Mathematical expression} ??? 0.15. The metasomatic fluids of Stage I were derived primarily from the crystallizing magma. The isotopic composition of magmatic water was ??18O =+9.0, ??D= -30 to -45. Oxygen isotope temperatures of greater than 620 ?? C were determined for the granodiorite. Isotopic and chemical equilibria between mineral surfaces and the metasomatic fluid were approached simultaneously in parts of the skarn several meters or more apart, while isotopic and chemical disequilibria (i.e. zoning) have been preserved between 20 to 40 ??m-thick zones in grandite garnet. More Fe-, or andradite-rich garnet crystallized in more H2O-rich C-O-H fluids ( {Mathematical expression} ??? 0.01) than present with grossularite-rich garnet ( {Mathematical expression}??? 0.035). Stage II was marked by the replacement of garnet and pyroxene by quartz, amphibole, plagioclase, epidote, magnetite, and calcite. Many of the replacement reactions took place over a relatively narrow range in temperature (480-550 ?? C), as indicated by 18O fractionations between quartz and amphibole. Meteoric

  8. [Study on Mineralogical Characteristics of Quartz and Calcite from Feieling Skarn-Type Pb-Zn Deposit in Southwest Margin of Yunkai Massif].

    PubMed

    Zeng, Chang-yu; Zhao, Ming-zhen; Li, Hong-zhong; Niu, Jia; Zhang, Jie-tang; He, Jun-guo; Zhou, Yong-zhang; Yang, Zhi-jun

    2015-09-01

    The Feieling Pb-Zn deposit of skarn-type is located the in Southwest margin of Yunkai massif, China. This ore deposit can be divided into wall rock near ore, concealed rock mass, endoskarn, exoskarn and orebody. The Raman and FTIR spectrum are conducted to study the mineralogical characteristics of quartz and calcite from five types of rocks from Feieling skarn-type deposit. The analysis shows that the quartz included in the near ore wall rock, endoskarn and exoskarn, comparing with recrystallized quartz of concealed rock mass, has a tend to change into low symmetry quartz in varying degrees. The crystalinity and order degree of quartz from near ore wall rock to concealed rock mass and to endoskarn are becoming higher, but that of quartz from different exoskarn samples display no regular. The origin or the quartz microstructure changes may be related to the multi-stage evolution of skarn mineralization process. The quartz, included in near ore wall rock, endoskarn and exoskarn, become easier to recrystallize and adjust microstructure under the influence of the multi-stage hydrothermal and temperature effect. In anyone sample, the earlier crystalline calcite, showing subhedral-euhedral crystal, display higher crystalinity and order degree. On the contrary, the later crystalline calcite, showing xenomorphic crystal, display lower crystalinity and order degree. Calcite crystal of exoskarn rock contains some silica impurity, while endoskarn and orebody rock is pure. The purity of calcite crystal may relate to Multi-stage evolution of skarn mineralization process. At the early and late skarn stage, active silica-containing fluid is easier to join into calcite, which is under higher temperature environments. On the contrary, at the late quartz-surfide stage, the later crystalized calcite displays higher purity, which is under lower temperature environments. Therefore, spectral characteristics of quartz and calcite reflect multi-stage evolution of skarn mineralization

  9. [Study on Mineralogical Characteristics of Quartz and Calcite from Feieling Skarn-Type Pb-Zn Deposit in Southwest Margin of Yunkai Massif].

    PubMed

    Zeng, Chang-yu; Zhao, Ming-zhen; Li, Hong-zhong; Niu, Jia; Zhang, Jie-tang; He, Jun-guo; Zhou, Yong-zhang; Yang, Zhi-jun

    2015-09-01

    The Feieling Pb-Zn deposit of skarn-type is located the in Southwest margin of Yunkai massif, China. This ore deposit can be divided into wall rock near ore, concealed rock mass, endoskarn, exoskarn and orebody. The Raman and FTIR spectrum are conducted to study the mineralogical characteristics of quartz and calcite from five types of rocks from Feieling skarn-type deposit. The analysis shows that the quartz included in the near ore wall rock, endoskarn and exoskarn, comparing with recrystallized quartz of concealed rock mass, has a tend to change into low symmetry quartz in varying degrees. The crystalinity and order degree of quartz from near ore wall rock to concealed rock mass and to endoskarn are becoming higher, but that of quartz from different exoskarn samples display no regular. The origin or the quartz microstructure changes may be related to the multi-stage evolution of skarn mineralization process. The quartz, included in near ore wall rock, endoskarn and exoskarn, become easier to recrystallize and adjust microstructure under the influence of the multi-stage hydrothermal and temperature effect. In anyone sample, the earlier crystalline calcite, showing subhedral-euhedral crystal, display higher crystalinity and order degree. On the contrary, the later crystalline calcite, showing xenomorphic crystal, display lower crystalinity and order degree. Calcite crystal of exoskarn rock contains some silica impurity, while endoskarn and orebody rock is pure. The purity of calcite crystal may relate to Multi-stage evolution of skarn mineralization process. At the early and late skarn stage, active silica-containing fluid is easier to join into calcite, which is under higher temperature environments. On the contrary, at the late quartz-surfide stage, the later crystalized calcite displays higher purity, which is under lower temperature environments. Therefore, spectral characteristics of quartz and calcite reflect multi-stage evolution of skarn mineralization

  10. Geological, geochronological, and mineralogical constraints on the genesis of the Chengchao skarn Fe deposit, Edong ore district, Middle-Lower Yangtze River Valley metallogenic belt, eastern China

    NASA Astrophysics Data System (ADS)

    Yao, Lei; Xie, Guiqing; Mao, Jingwen; Lü, Zhicheng; Zhao, Caisheng; Zheng, Xianwei; Ding, Ning

    2015-04-01

    The Edong ore district is located within the westernmost Middle-Lower Yangtze River Valley metallogenic belt (MLYRB), and hosts the largest concentration of skarn Fe deposits in China, although the origin of these deposits remains controversial. The Chengchao deposit is the largest skarn Fe deposit so far discovered within the MLYRB, and provides a good opportunity to address the debate surrounding the origin of these skarn Fe deposits. Here, we present geological, geochronological, and mineralogical data from the Chengchao skarn deposit and associated intrusions, and discuss the relationships between granitoids and mineralization in the Chengchao deposit. The NW-SE-striking orebodies in the study area have porphyritic quartz monzonite and/or granite footwalls, and Triassic marble or diorite hangingwalls, indicating a spatial relationship between these intrusions and Fe mineralization. Zircon U-Pb data from the granite, porphyritic quartz monzonite, diorite, and porphyritic diabase dike within the deposit show ages of 129 ± 1, 128 ± 1, 140 ± 1, and 126 ± 1 Ma, respectively. These ages and the previously reported ages on the timing of mineralization suggest that the porphyritic quartz monzonite and granite are coeval with the formation of the skarn Fe deposit. Our data confirm that the granitic rocks are temporally associated with Fe mineralization. The prograde substage of skarn development is characterized by two stages of andradite (Adr98-38Grs61-2Prp2-0Sps1-0Alm1-0) and diopside (Di95-61Hd37-5Jo3-0), including an early stage of garnet and pyroxene formation that is genetically associated with the mineralization. The early stage garnets are more andradite-rich (Adr98-50Grs49-2Prp1-0Sps1-0Alm0) than the late veinlet garnets characterized by intermediate grandite compositions (Adr67-37Grs61-31Prp2-0Sps1-0Alm1-0). The early stage pyroxenes (Di95-74Hd26-5Jo1-0) are compositionally distinct from the late stage pyroxenes (Di84-61Hd37-16Jo3-0). Compositional

  11. The large Bystrinskoe Cu-Au-Fe deposit (Eastern Trans-Baikal Region): Russia's first example of a skarn-porphyry ore-forming system related to adakite

    NASA Astrophysics Data System (ADS)

    Kovalenker, V. A.; Abramov, S. S.; Kiseleva, G. D.; Krylova, T. L.; Yazykova, Yu. I.; Bortnikov, N. S.

    2016-06-01

    The Bystrinskoe skarn-porphyry Cu-Au-Fe deposit (Eastern Trans-Baikal Region) is confined to skarn zones, which were formed along the contact of granitoids referred to the Shakhtama intrusive complex (J2-3), with terrigenous-carbonate sedimentary rocks. Commercial (Cu-Au-Fe ± W, Mo) mineralization was formed due to the regional postcollision development involving the intrusion of porphyritic granitoids, the derivatives of oxidized adakite highly magnesian magmas enriched in water, sulfur, and metals, which could develop under melting of garnet-bearing amphibolite in the mafic lower crustal arc.

  12. Iron mineralization and associated skarn development around southern contact of the Eğrigöz pluton (northern Menderes Massif-Turkey)

    NASA Astrophysics Data System (ADS)

    Uǧurcan, Okşan Gökçen; Oyman, Tolga

    2016-11-01

    The Eğrigöz pluton is located in the northern portion of the Menderes Massif, which is the largest known metamorphic core complex that is also characterized by large-scale extension. Kalkan and Karaağıl skarn deposits are located on the southern border of the Eğrigöz Pluton, whereas Katrandağ mineralization developed along the roof pendant. Skarnization in these three areas is associated with the peraluminous, I-type, calc-alkaline, high-K calc-alkaline Eğrigöz Pluton. Geochemical characteristics of the pluton indicate that it was generated in a continental arc setting. Kalkan, Karaağıl, and Katrandağ skarns are hosted in marble bands in two-mica gneiss of the Kalkan Formation, a locally dolomitic and clay-bearing limestone of the Arıkaya Formation and locally dolomitised limestone of the Balıkbaşı Formation, respectively. Skarn development occurred sequentially in two stages, prograde and retrograde. In Kalkan skarn, prograde stage is characterized by clinopyroxene (Di56-73 Hd26-43 Joh1-2), garnet (Adr45-69 Grs30-52 Alm0-1.4 Sps0.7-2.3), amphibole, and magnetite, whereas retrograde stage is dominated by epidote, amphibole, chlorite, quartz, and calcite. In Karaağıl, both calcic and magnesian skarn association occurred as a result of local variations in dolomite content in Arıkaya Formation. The prograde assemblage of magnesian skarn is composed chiefly of spinel, amphibole and olivine. These mineral assemblages were, partially or fully, altered to serpentine, talc, and chlorite during retrograde alteration. Mesh textures of the serpentine indicates that the serpentine was altered from olivine. Olivine was completely destroyed during retrograde alteration without relict grains remaining. Calcic skarn paragenesis include garnet (Grs36-80Adr20-62Alm0-2.2Sps0.2-2.6), clinopyroxene (Di81-92 Hd7-19 Jo0-1), and plagioclase, that belongs to the earlier stage, and amphibole of the retrograde stage. High grossular end member of the garnet probably

  13. Small pulmonary arteries in some natives of La Paz, Bolivia.

    PubMed Central

    Heath, D; Smith, P; Rios Dalenz, J; Williams, D; Harris, P

    1981-01-01

    A histological study was made of the small pulmonary blood vessels in pieces of lung obtained at necropsy from 19 long-term residents of La Paz, Bolivia (3800 m). There was variation in the response of the pulmonary vasculature of these subjects to the chronic hypoxia of high altitude. The most characteristic finding, seen in seven of the 16 cases beyond infancy, was distal extension of vascular smooth muscle into pulmonary arterioles as small as 20 micrometer in diameter. Medial hypertrophy of the muscular pulmonary arteries occurred in only three of these seven subjects. Intimal fibrosis was seen in eight of the 19 cases and was ascribed to age; such fibrotic proliferation may affect the reversibility of hypoxic pulmonary hypertension and associated vascular changes in highlanders. Images PMID:7314035

  14. Large-scale metal zoning in a late-Precambrian skarn-type mineralization, Wadi Kid, SE Sinai, Egypt

    NASA Astrophysics Data System (ADS)

    Helmy, H. M.; Shalaby, I. M.; Abdel Rahman, H. B.

    2014-02-01

    A Precambrian skarn-type mineralization is recently discovered in the Wadi Kid area in southeast Sinai, Egypt. Two sulfide ore types define large scale metal zoning; Cu-Zn-Co in calc-silicate rocks and Zn-Pb-As-Ag in metapelites. The sulfides and host rocks underwent amphibolite facies metamorphism (2.1-4.2 kbar and 500-620 °C). Dating by the chemical Th-U-total Pb isochrone method yields an Th-Pb isochrone age of 660 ± 25 Ma for metamorphic monazite from metapelites. Overall structural and textural relationships of silicate and sulfide minerals favor syn-tectonic formation during granitoids emplacement in a continental margin setting. Large-scale metal zoning reflects variable distances from the causative pluton(s). The Wadi Kid area is highly prospective for Cu, Zn, Pb and Ag mineralization.

  15. GIS database model for development of mining information system for the Skarn/Porphyry type ore deposit

    NASA Astrophysics Data System (ADS)

    Roh, T.; Choi, Y.; Park, H.

    2009-12-01

    This study presents a prototype of GIS database model for development of mining information system for the Skarn/Porphyry type ore deposit. Database table was established for the analysis of collected datum from mining activity and geological investigation of mine development. Also structure and property of geological/mining information elements composing each table were defined and specified. For each mine, mine shaft, line and point, independent ID code were assigened. Database is also designed to keep the graphic data of Stereophotogrammetry from mining working face and of geophysical and boring investigation. After combining existing mine map and digital elevation map, sample data was inputed to the database. Finally, database system model that can be used for additional development of mining information system was constructed in this study.

  16. Multistage amphiboles from the Galinge iron skarn deposit in Qiman Tagh, western China: evidence of igneous rocks replacement

    NASA Astrophysics Data System (ADS)

    Yu, M.; Feng, C.-Y.; Zhu, Y.-F.; Mao, J.-W.; Zhao, Y.-M.; Li, D.-X.

    2016-08-01

    Amphiboles from the Galinge skarn deposit, the largest iron (Fe) polymetallic skarn deposit in the Qiman Tagh metallogenic belt (western China), were formed by multistage fluid-rock interactions. Mineral analysis of the various amphiboles suggest that they were formed by the replacement of mafic to intermediate igneous rocks. The two alteration phases have formed three generations of compositionally distinct amphiboles: Amp-I: Ferro-edenitic hornblende (FE); Amp-II: Deep bluish-green magnesian-hastingsite (MH); Amp-III: Light greenish-beige ferro-actinolite (FA). The Amp-I preserves the primary igneous amphibole composition, and was subsequently replaced by Amp-II. The amphibole Cl content markedly increases from the FE (0.176 - 0.582 wt.%) to the MH (0.894 - 3.161 wt.%), and abruptly drops in the FA (0.017 - 0.039 wt.%). The Cl-rich MH contains the lowest concentration of Si [5.64 - 6.28 atoms per formula unit (apfu)], and the highest (K + Na) values (0.72 - 1.06 apfu) in the amphibole A-site with a high K/(K + Na) of 0.491 to 0.429. Both Mg and Fe contents of the MH and FA vary widely, possibly due to the interactions of magma-derived hydrothermal fluids with the basaltic / andesitic host rocks. Formation of the Cl-rich MH may have been associated with the early high-temperature and high-saline hydrothermal fluids, meanwhile the Cl-poor FA may have formed from later low-temperature and low-saline hydrothermal fluids. The MH plays an important role for consuming Cl carried by hydrothermal fluids. The Cl-rich fluids may have mobilized some elements, such as Fe, Al, Mg, Ca and Ti from the host rocks. Considerable amounts of Ti, Al, Mg and Fe were incorporated into the sphene and Fe-Ti oxides that coexist with the MH.

  17. Near-side azimuthal and pseudorapidity correlations using neutral strange baryons and mesons in d +Au , Cu + Cu, and Au + Au collisions at √{sN N}=200 GeV

    NASA Astrophysics Data System (ADS)

    Abelev, B.; Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Barnby, L. S.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bombara, M.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chatterjee, A.; Chattopadhyay, S.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; di Ruzza, B.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Eppley, G.; Esha, R.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Gaillard, L.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Hamad, A. I.; Hamed, A.; Haque, R.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, T.; Huang, B.; Huang, X.; Huang, H. Z.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Jentsch, A.; Jia, J.; Jiang, K.; Jones, P. G.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z. H.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Kochenda, L.; Koetke, D. D.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kumar, L.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, C.; Li, Y.; Li, W.; Li, X.; Li, X.; Lin, T.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, S.; Luo, X.; Ma, L.; Ma, R.; Ma, G. L.; Ma, Y. G.; Magdy, N.; Majka, R.; Manion, A.; Margetis, S.; Markert, C.; Matis, H. S.; McDonald, D.; McKinzie, S.; Meehan, K.; Mei, J. C.; Miller, Z. W.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nattrass, C.; Nasim, Md.; Nayak, T. K.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Ray, R. L.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, B.; Sharma, A.; Sharma, M. K.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stepanov, M.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Summa, B.; Sun, Y.; Sun, Z.; Sun, X. M.; Surrow, B.; Svirida, D. N.; Tang, Z.; Tang, A. H.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Varma, R.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, H.; Wang, Y.; Wang, G.; Wang, Y.; Wang, J. S.; Wang, F.; Webb, G.; Webb, J. C.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xin, K.; Xu, Y. F.; Xu, Q. H.; Xu, N.; Xu, J.; Xu, H.; Xu, Z.; Yang, Y.; Yang, Q.; Yang, S.; Yang, Y.; Yang, Y.; Yang, C.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, S.; Zhang, X. P.; Zhang, Y.; Zhang, S.; Zhang, J. B.; Zhang, J.; Zhang, J.; Zhang, Z.; Zhao, J.; Zhong, C.; Zhou, L.; Zhu, X.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

    2016-07-01

    We present measurements of the near side of triggered di-hadron correlations using neutral strange baryons (Λ ,Λ ¯) and mesons (KS0) at intermediate transverse momentum (3 < pT <6 GeV /c ) to look for possible flavor and baryon-meson dependence. This study is performed in d +Au , Cu+Cu, and Au+Au collisions at √{sN N}=200 GeV measured by the STAR experiment at RHIC. The near-side di-hadron correlation contains two structures, a peak which is narrow in azimuth and pseudorapidity consistent with correlations from jet fragmentation, and a correlation in azimuth which is broad in pseudorapidity. The particle composition of the jet-like correlation is determined using identified associated particles. The dependence of the conditional yield of the jet-like correlation on the trigger particle momentum, associated particle momentum, and centrality for correlations with unidentified trigger particles are presented. The neutral strange particle composition in jet-like correlations with unidentified charged particle triggers is not well described by PYTHIA. However, the yield of unidentified particles in jet-like correlations with neutral strange particle triggers is described reasonably well by the same model.

  18. Centrality, Rapidity And Transverse-Momentum Dependence of Cold Nuclear Matter Effects on J/Psi Production in D Au, Cu Cu And Au Au Collisions at S(NN)**(1/2)

    SciTech Connect

    Ferreiro, E.G.; Fleuret, F.; Lansberg, J.P.; Rakotozafindrabe, A.; /SPhN, DAPNIA, Saclay

    2011-11-11

    We have carried out a wide study of Cold Nuclear Matter (CNM) effects on J/{Psi} = production in dAu, CuCu and AuAu collisions at {radical}s{sub NN} = 200 GeV. We have studied the effects of three different gluon-shadowing parameterizations, using the usual simplified kinematics for which the momentum of the gluon recoiling against the J/{Psi} is neglected as well as an exact kinematics for a 2 {yields} 2 process, namely g + g {yields} J/{psi} + g as expected from LO pQCD. We have shown that the rapidity distribution of the nuclear modification factor R{sub dAu}, and particularly its anti-shadowing peak, is systematically shifted toward larger rapidities in the 2 {yields} 2 kinematics, irrespective of which shadowing parameterization is used. In turn, we have noted differences in the effective final-state nuclear absorption needed to fit the PHENIX dAu data. Taking advantage of our implementation of a 2 {yields} 2 kinematics, we have also computed the transverse momentum dependence of the nuclear modification factor, which cannot be predicted with the usual simplified kinematics. All the corresponding observables have been computed for CuCu and AuAu collisions and compared to the PHENIX and STAR data. Finally, we have extracted the effective nuclear absorption from the recent measurements of RCP in dAu collisions by the PHENIX collaboration.

  19. Charged-particle multiplicity and pseudorapidity distributionsmeasured with the PHOBOS detector in Au+Au, Cu+Cu, d+Au, and p+p collisions at ultra-relativistic energies.

    SciTech Connect

    Alver, B.; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Wuosmaa, A.

    2011-01-01

    Pseudorapidity distributions of charged particles emitted in Au+Au, Cu+Cu, d+Au, and p+p collisions over a wide energy range have been measured using the PHOBOS detector at the BNL Relativistic Heavy-Ion Collider (RHIC). The centrality dependence of both the charged particle distributions and the multiplicity at midrapidity were measured. Pseudorapidity distributions of charged particles emitted with |{eta}| < 5.4, which account for between 95% and 99% of the total charged-particle emission associated with collision participants, are presented for different collision centralities. Both the midrapidity density dN{sub ch}/d{eta} and the total charged-particle multiplicity N{sub ch} are found to factorize into a product of independent functions of collision energy, {radical}s{sub NN}, and centrality given in terms of the number of nucleons participating in the collision, N{sub part}. The total charged particle multiplicity, observed in these experiments and those at lower energies, assumes a linear dependence of (lns{sub NN}){sup 2} over the full range of collision energy of {radical}s{sub NN} = 2.7-200 GeV.

  20. Charged-particle multiplicity and pseudorapidity distributions measured with the PHOBOS detector in Au+Au, Cu+Cu, d+Au, and p+p collisions at ultrarelativistic energies

    SciTech Connect

    Alver, B.; Ballintijn, M.; Busza, W.; Decowski, M. P.; Gulbrandsen, K.; Henderson, C.; Kane, J. L.; Katzy, J.; Kulinich, P.; Li, W.; Loizides, C.; Pernegger, H.; Reed, C.; Roland, C.; Roland, G.; Rosenberg, L.; Sarin, P.; Steadman, S. G.; Stephans, G. S. F.; Vale, C.

    2011-02-15

    Pseudorapidity distributions of charged particles emitted in Au+Au, Cu+Cu, d+Au, and p+p collisions over a wide energy range have been measured using the PHOBOS detector at the BNL Relativistic Heavy-Ion Collider (RHIC). The centrality dependence of both the charged particle distributions and the multiplicity at midrapidity were measured. Pseudorapidity distributions of charged particles emitted with |{eta}|<5.4, which account for between 95% and 99% of the total charged-particle emission associated with collision participants, are presented for different collision centralities. Both the midrapidity density dN{sub ch}/d{eta} and the total charged-particle multiplicity N{sub ch} are found to factorize into a product of independent functions of collision energy, {radical}(s{sub N{sub N}}), and centrality given in terms of the number of nucleons participating in the collision, N{sub part}. The total charged particle multiplicity, observed in these experiments and those at lower energies, assumes a linear dependence of (lns{sub N{sub N}}){sup 2} over the full range of collision energy of {radical}(s{sub N{sub N}})=2.7-200 GeV.

  1. 75 FR 2133 - Construction and Operation of the Quartzsite Solar Energy Project, La Paz County, AZ (DOE/EIS-0440)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-14

    ... Area Power Administration Construction and Operation of the Quartzsite Solar Energy Project, La Paz..., intends to prepare an environmental impact statement (EIS) for the proposed Quartzsite Solar Energy Project (Project) in La Paz County, near Quartzsite, Arizona. Quartzsite Solar Energy, LLC (QSE)...

  2. Zircon U-Pb geochronology of the basement rocks and dioritic intrusion associated with the Fushan skarn iron deposit, southern Taihang Mountains, China

    NASA Astrophysics Data System (ADS)

    Shen, Jun-Feng; Li, Sheng-Rong; Santosh, M.; Dong, Guo-Chen; Wang, Yan-Juan; Liu, Hai-Ming; Peng, Zi-Dong; Zhang, Zhao-Yu

    2015-12-01

    The Fushan iron ores, located in the southern part of the Taihang Mountains (TM) within the Trans-North China Orogen, is among the medium-sized skarn iron deposits in China. In this paper we report U-Pb age data on zircon grains from the magmatic intrusion related with the skarn formation and from the Neoarchean metamorphic basement in the area. The results show that the dioritic intrusion which generated the skarn mineralization was emplaced at 128.8 ± 1.9 Ma. Zircon grains from the basement rocks and xenoliths, as well as inherited zircon in the dioritic intrusion show Neoarchean to Paleoproterozoic ages, corresponding to similar ages reported from elsewhere in the North China Craton. Our results and those from previous studies suggest that the continental lower crust was the major source of Mesozoic magmatism and associated ore mineralization. The Mesozoic magmatism and metallogeny in the Fushan region correlate with the peak of lithospheric destruction of the North China Craton.

  3. Feasibility study for La Paz Hydroelectric Power Plant Project. Export trade information

    SciTech Connect

    Not Available

    1991-12-01

    A feasibility study for a hydroelectric project is defined as an investigation whose purpose is to determine whether any reasonable acceptable design for a project is technically viable. Alternatives of site development are studied and various solutions for civil works and equipment sizing are evaluated. When alternatives are considered technically viable they are then evaluated for financial viability. The purpose of the study is to evaluate the viability of the La Paz Hydroelectric Project. The La Paz Feasibility Study discusses: Site Characteristics and Existing Facilities; Hydrology and Sedimentation; Alternatives and Development; Hydraulics; Project Energy Output; Environmental, Social and Institutional Impacts; Project Cost Analysis; Market Considerations; Economics; Financial Analysis; and Project Implementation.

  4. AIDS and hemophilia: experience in the La Paz Hemophilia Center.

    PubMed

    Magallón Martínez, M; Ortega, F; Pinilla, J

    1992-01-01

    435 hemophiliacs are usually being attended in the La Paz hemophilia Center (Madrid, Spain). 257 (59%) of these patients have been infected by the human immunodeficiency virus (HIV-1) because of human plasma derivate substitution therapy. The infection has been more frequent among the severely affected patients and among the most treated patients. 82% of the infected patients are between 14 and 40 years old. By December 1991, 95 (37%) of 257 seropositive patients have developed full-blown AIDS. The most frequent opportunistic infection they had suffered was esophageal candidiasis. Looking for an evolution marker, we can point that the patients older than 35 years with CD4 levels below 200/mm3 had the worst prognosis. There was no difference in the evolution among the patients aged below 17 and those aged between 17 and 35 years. The amount of concentrate used between 1980 and 1984 did not hold any relation to the evolution. 49 patients (51%) of the 95 suffering from AIDS had died by December 1991. The evolution to the death was unrelated to the patient age, CD4 lymphocyte levels, and amount of substitution therapy. In our opinion, the most valuable marker could be the kind of opportunistic infection or tumor the patient suffers from. Finally, Retrovir has demonstrated to be useful in increasing the survival rate of the patients, but after 36 months of treatment, only 33% of those AIDS patients who began taking it remained alive. Retrovir was also used in asymptomatic patients, and during an average period of time of 15 months, a lesser bone marrow toxicity and a stabilization in CD4 lymphocyte levels could be observed, but this was unable to modify the disease progression in those patients who presented circulating p24 antigen.

  5. The Beiminghe skarn iron deposit, eastern China: Geochronology, isotope geochemistry and implications for the destruction of the North China Craton

    NASA Astrophysics Data System (ADS)

    Shen, Jun-Feng; Santosh, M.; Li, Sheng-Rong; Zhang, Hua-Feng; Yin, Na; Dong, Guo-Cheng; Wang, Yan-Juan; Ma, Guang-Gang; Yu, Hong-Jun

    2013-01-01

    The Beiminghe (BMH) iron ore in the southern part of the Taihang Mountain (TM), Hebei province, is one of the largest skarn iron deposits in China. Here we report phlogopite 40Ar-39Ar and zircon U-Pb age data, as well as sulfur, lead, and He-Ar isotope geochemistry of pyrite from the ores and skarnitized rocks in the deposit in an attempt to constrain the timing and mechanism of formation of the mineralization. The phlogopite 40Ar-39Ar and LA-ICP-MS zircon U-Pb data show markedly consistent ages constraining the timing of ore formation as 136-137 Ma. The presence of several inherited zircons with late Archean or Paleoproterozoic ages indicates the participation of the basement rocks during the ore-forming process. The δ34S values of pyrite from the ores range from 12.2 to 16.5‰, with 206Pb/204Pb = 17.84-18.79, 207Pb/204Pb = 15.46-15.62, and 208Pb/204Pb = 37.93-39.75, suggesting that continental crust is the major contributor. This is further confirmed by the He-Ar isotope data (3He/4He = 0.0648-0.1886 Ra, mean 0.1237Ra; 40Ar/36Ar = 311.7-22909.4; and 40Ar*/4He = 0.036-0.421). The Mesozoic magmatism and metallogeny in the BMH correlate well with the peak event of lithospheric thinning and destruction of the North China Craton during this process, the early Precambrian lower crustal rocks in the region were re-melted through underplating of mantle magmas, leading to the formation of the Beiminghe monzodioritic pluton. Minor mantle input occurred during the evolution of the monzodiorite magma, which scavenged the ore-forming materials from the lower crust. Interaction of the magmas and fluids with the surrounding rocks resulted in the formation of the Beiminghe skarn iron deposits. The magmatism and metallogeny in the Taihang Mountain are signatures of the extensive craton destruction and lithospheric thinning in the eastern part of the North China Craton during Mesozoic, probably associated with Pacific slab subduction.

  6. The As-contaminated Elqui river basin: a long lasting perspective (1975-1995) covering the initiation and development of Au-Cu-As mining in the high Andes of northern Chile.

    PubMed

    Oyarzun, R; Guevara, S; Oyarzún, J; Lillo, J; Maturana, H; Higueras, P

    2006-10-01

    The Elqui watershed (northern Chile) constitutes a highly contaminated river system, with arsenic exceeding by up to three orders of magnitude the average for river waters. There are three main reasons that explain this contamination: (1) the regional geology and hydrothermal (mineralizing) processes that developed in this realm during Miocene time; (2) the later unroofing-erosion-oxidation-leaching of As-Cu rich sulfide ores, a process that have been taking place for at least 10,000 years; and last but not least (3) mining activities at the high-altitude (>4000 m above sea level) Au-Cu-As El Indio mine, from the late 1970s onwards. The El Indio mineral deposit hosted large veins of massive sulfides, including the important presence of enargite (Cu(3)AsS(4)). The continuous natural erosion of these veins and their host rocks (also rich in As and Cu) during Holocene time, led to important and widespread metal dispersion along the river system. During the studied pre mining period (1975-1977), the high altitude river Toro waters already showed very large As concentrations (0.36-0.52 mg l(-1)). The initiation of full scale mining at El Indio (1980 onwards) led to an increase of these values, reaching a concentration of 1.51 mg l(-1) As in 1995. During the same year other rivers of the watershed reached peak As concentrations of 0.33 (Turbio) and 0.11 mg l(-1) (Elqui). These figures largely exceed the USEPA regulations for drinking water (0.01 mg l(-1) As), and about 10% of the total As data from the river Elqui (and 70% from the river Turbio) are above the maximum level allowed by the Chilean law for irrigation water (0.1 mg l(-1) As).

  7. The As-contaminated Elqui river basin: a long lasting perspective (1975-1995) covering the initiation and development of Au-Cu-As mining in the high Andes of northern Chile.

    PubMed

    Oyarzun, R; Guevara, S; Oyarzún, J; Lillo, J; Maturana, H; Higueras, P

    2006-10-01

    The Elqui watershed (northern Chile) constitutes a highly contaminated river system, with arsenic exceeding by up to three orders of magnitude the average for river waters. There are three main reasons that explain this contamination: (1) the regional geology and hydrothermal (mineralizing) processes that developed in this realm during Miocene time; (2) the later unroofing-erosion-oxidation-leaching of As-Cu rich sulfide ores, a process that have been taking place for at least 10,000 years; and last but not least (3) mining activities at the high-altitude (>4000 m above sea level) Au-Cu-As El Indio mine, from the late 1970s onwards. The El Indio mineral deposit hosted large veins of massive sulfides, including the important presence of enargite (Cu(3)AsS(4)). The continuous natural erosion of these veins and their host rocks (also rich in As and Cu) during Holocene time, led to important and widespread metal dispersion along the river system. During the studied pre mining period (1975-1977), the high altitude river Toro waters already showed very large As concentrations (0.36-0.52 mg l(-1)). The initiation of full scale mining at El Indio (1980 onwards) led to an increase of these values, reaching a concentration of 1.51 mg l(-1) As in 1995. During the same year other rivers of the watershed reached peak As concentrations of 0.33 (Turbio) and 0.11 mg l(-1) (Elqui). These figures largely exceed the USEPA regulations for drinking water (0.01 mg l(-1) As), and about 10% of the total As data from the river Elqui (and 70% from the river Turbio) are above the maximum level allowed by the Chilean law for irrigation water (0.1 mg l(-1) As). PMID:16752201

  8. Geochemistry of rare earth elements in the Baba Ali magnetite skarn deposit, western Iran - a key to determine conditions of mineralisation

    NASA Astrophysics Data System (ADS)

    Zamanian, Hassan; Radmard, Kaikosrov

    2016-03-01

    The Baba Ali skarn deposit, situated 39 km to the northwest of Hamadan (Iran), is the result of a syenitic pluton that intruded and metamorphosed the diorite host rock. Rare earth element (REE) values in the quartz syenite and diorite range between 35.4 and 560 ppm. Although the distribution pattern of REEs is more and less flat and smooth, light REEs (LREEs) in general show higher concentrations than heavy REEs (HREEs) in different lithounits. The skarn zone reveals the highest REE-enriched pattern, while the ore zone shows the maximum depletion pattern. A comparison of the concentration variations of LREEs (La-Nd), middle REEs (MREEs; Sm-Ho) and HREEs (Er-Lu) of the ore zone samples to the other zones elucidates two important points for the distribution of REEs: 1) the distribution patterns of LREEs and MREEs show a distinct depletion in the ore zone while representing a great enrichment in the skarn facies neighbouring the ore body border and decreasing towards the altered diorite host rock; 2) HREEs show the same pattern, but in the exoskarn do not reveal any distinct increase as observed for LREEs and MREEs. The ratio of La/Y in the Baba Ali skarn ranges from 0.37 to 2.89. The ore zone has the highest La/Y ratio. In this regard the skarn zones exhibit two distinctive portions: 1) one that has La/Y >1 beingadjacent to the ore body and; 2) another one with La/Y < 1 neighbouring altered diorite. Accordingly, the Baba Ali profile, from the quartz syenite to the middle part of the exoskarn, demonstrates chiefly alkaline conditions of formation, with a gradual change to acidic towards the altered diorite host rocks. Utilising three parameters, Ce/Ce*, Eu/Eu* and (Pr/Yb)n, in different minerals implies that the hydrothermal fluids responsible for epidote and garnet were mostly of magmatic origin and for magnetite, actinolite and phlogopite these were of magmatic origin with low REE concentration or meteoric water involved.

  9. Role of evaporitic sulfates in iron skarn mineralization: a fluid inclusion and sulfur isotope study from the Xishimen deposit, Handan-Xingtai district, North China Craton

    NASA Astrophysics Data System (ADS)

    Wen, Guang; Bi, Shi-Jian; Li, Jian-Wei

    2016-08-01

    The Xishimen iron skarn deposit in the Handan-Xingtai district, North China Craton, contains 256 Mt @ 43 % Fe (up to 65 %). The mineralization is dominated by massive magnetite ore along the contact zone between the early Cretaceous Xishimen diorite stock and middle Ordovician dolomite and dolomitic limestones with numerous intercalations of evaporitic beds. Minor lenticular magnetite-dominated bodies also occur in the carbonate rocks proximal to the diorite stock. Hydrothermal alteration is characterized by extensive albitization within the diorite stock and extreme development of magnesian skarn along the contact zone consisting of diopside, forsterite, serpentine, tremolite, phlogopite, and talc. Magmatic quartz and amphibole from the diorite and hydrothermal diopside from the skarns contain abundant primary or pseudosecondary fluid inclusions, most of which have multiple daughter minerals dominated by halite, sylvite, and opaque phases. Scanning electron microscopy (SEM) and laser Raman spectrometry confirm that pyrrhotite is the predominant opaque phase in most fluid inclusions, in both the magmatic and skarn minerals. These fluid inclusions have total homogenization temperatures of 416-620 °C and calculated salinities of 42.4-74.5 wt% NaCl equiv. The fluid inclusion data thus document a high-temperature, high-salinity, ferrous iron-rich, reducing fluid exsolved from a cooling magma likely represented by the Xishimen diorite stock. Pyrite from the iron ore has δ34S values ranging from 14.0 to 18.6 ‰, which are significantly higher than typical magmatic values (δ34S = 0 ± 5 ‰). The sulfur isotope data thus indicate an external source for the sulfur, most likely from the evaporitic beds in the Ordovician carbonate sequences that have δ34S values of 24 to 29 ‰. We suggest that sulfates from the evaporitic beds have played a critically important role by oxidizing ferrous iron in the magmatic-hydrothermal fluid, leading to precipitation of massive

  10. Stable isotope (C, O, H) characteristics and genesis of the Tazheran brucite marbles and skarns, Olkhon region, Russia

    NASA Astrophysics Data System (ADS)

    Doroshkevich, Anna; Sklyarov, Eugene; Starikova, Anastasia; Vasiliev, Vladimir; Ripp, German; Izbrodin, Ivan; Posokhov, Viktor

    2016-10-01

    Stable isotope compositions are examined for brucite marble and Mg-skarn that occur in the southern part of the Tazheran massif, Olkhon region, Russia. Brucite marble exhibits a narrow range in δ18O of +23.3 to +26.2 ‰ and shows carbon isotope depletion of -1.9 to -4.4 ‰) as compared with the country dolomite isotope compositions (+2.0 to +2.4 ‰) which is explained by both decarbonation processes and participation of fluids depleted in 13C. The emplacement of brucite marble was accompanied by the formation of endo- and exoskarn at the contact between syenite and brucite marble. δ18O profiles across the contact show a typical decrease towards the syenite side interpreted as the result of fluid/rock interaction and influx of magmatic fluids. Finally, we discuss the mechanisms of brucite marble emplacement and consider three possible ways of producing these rocks: (1) injection of dolomite with subsequent transformation to periclase marble and then to brucite marble; (2) injection of periclase marble with a following replacement of periclase by brucite or injection of brucite marble; (3) crustal water-rich carbonate melt. We favor models 2 and 3 and discuss their strengths and weaknesses.

  11. Feasibility Study of EO SARs as Opportunity Illuminators in Passive Radars: PAZ-Based Case Study.

    PubMed

    Bárcena-Humanes, Jose-Luis; Gómez-Hoyo, Pedro-José; Jarabo-Amores, Maria-Pilar; Mata-Moya, David; Del-Rey-Maestre, Nerea

    2015-01-01

    Passive radars exploit the signal transmitted by other systems, known as opportunity illuminators (OIs), instead of using their own transmitter. Due to its almost total invulnerability to natural disasters or physical attacks, satellite OIs are of special interest. In this line, a feasibility study of Earth Observation Synthetic Aperture Radar (EO SAR) systems as OIs is carried out taking into consideration signal waveform, availability, bistatic geometry, instrumented coverage area and incident power density. A case study based on the use of PAZ, the first Spanish EO SAR, is presented. PAZ transmitted waveform, operation modes, orbit characteristics and antenna and transmitter parameters are analyzed to estimate potential coverages and resolutions. The study concludes that, due to its working in on-demand operating mode, passive radars based on PAZ-type illuminators can be proposed as complementing tools during the sensor commissioning phase, for system maintenance and for improving its performance by providing additional information about the area of interest and/or increasing the data updating speed, exploiting other sensors during the time PAZ is not available. PMID:26593921

  12. Response to Marie Paz Morales' "Influence of Culture and Language Sensitive Physics on Science Attitude Achievement"

    ERIC Educational Resources Information Center

    Cole, Mikel Walker

    2015-01-01

    This response to Marie Paz Morales' "Influence of culture and language sensitive physics on science attitude achievement" explores the ideas of culturally responsive pedagogy and critical literacy to examine some implications for culturally responsive science instruction implicit in the original manuscript. [For "Influence of…

  13. Feasibility Study of EO SARs as Opportunity Illuminators in Passive Radars: PAZ-Based Case Study

    PubMed Central

    Bárcena-Humanes, Jose-Luis; Gómez-Hoyo, Pedro-José; Jarabo-Amores, Maria-Pilar; Mata-Moya, David; De-Rey-Maestre, Nerea

    2015-01-01

    Passive radars exploit the signal transmitted by other systems, known as opportunity illuminators (OIs), instead of using their own transmitter. Due to its almost total invulnerability to natural disasters or physical attacks, satellite OIs are of special interest. In this line, a feasibility study of Earth Observation Synthetic Aperture Radar (EO SAR) systems as OIs is carried out taking into consideration signal waveform, availability, bistatic geometry, instrumented coverage area and incident power density. A case study based on the use of PAZ, the first Spanish EO SAR, is presented. PAZ transmitted waveform, operation modes, orbit characteristics and antenna and transmitter parameters are analyzed to estimate potential coverages and resolutions. The study concludes that, due to its working in on-demand operating mode, passive radars based on PAZ-type illuminators can be proposed as complementing tools during the sensor commissioning phase, for system maintenance and for improving its performance by providing additional information about the area of interest and/or increasing the data updating speed, exploiting other sensors during the time PAZ is not available. PMID:26593921

  14. Feasibility Study of EO SARs as Opportunity Illuminators in Passive Radars: PAZ-Based Case Study.

    PubMed

    Bárcena-Humanes, Jose-Luis; Gómez-Hoyo, Pedro-José; Jarabo-Amores, Maria-Pilar; Mata-Moya, David; Del-Rey-Maestre, Nerea

    2015-11-17

    Passive radars exploit the signal transmitted by other systems, known as opportunity illuminators (OIs), instead of using their own transmitter. Due to its almost total invulnerability to natural disasters or physical attacks, satellite OIs are of special interest. In this line, a feasibility study of Earth Observation Synthetic Aperture Radar (EO SAR) systems as OIs is carried out taking into consideration signal waveform, availability, bistatic geometry, instrumented coverage area and incident power density. A case study based on the use of PAZ, the first Spanish EO SAR, is presented. PAZ transmitted waveform, operation modes, orbit characteristics and antenna and transmitter parameters are analyzed to estimate potential coverages and resolutions. The study concludes that, due to its working in on-demand operating mode, passive radars based on PAZ-type illuminators can be proposed as complementing tools during the sensor commissioning phase, for system maintenance and for improving its performance by providing additional information about the area of interest and/or increasing the data updating speed, exploiting other sensors during the time PAZ is not available.

  15. Transformative Peace Education with Teachers: Lessons from "Juegos De Paz" in Rural Colombia

    ERIC Educational Resources Information Center

    Diazgranados, Silvia; Noonan, James; Brion-Meisels, Steven; Saldarriaga, Lina; Daza, Berta C.; Chávez, Minerva; Antonellis, Irene

    2014-01-01

    Effective peace education helps to create a transformation in the knowledge, skills, dispositions, and relationships of its students. Drawing on their experiences training teachers as part of "Juegos de Paz," an education for peace program that received support from the Colombian National Program for Citizenship Competencies, the authors…

  16. Ideology in the Works of Octavio Paz and Jose Carlos Mariategui: The Pre-Columbian Case

    ERIC Educational Resources Information Center

    Espinosa, Paul

    1976-01-01

    The paper discusses how the two prominent Latin American writers approach the historical material of their national pasts, Mexico and Peru, and attempt to use that material for the creation of a national ideology. In confronting the future with a new national identity, Mariategui's myth of agrarian communism and Paz's version of invisible history…

  17. Adolescents' Expectations for Higher Education in Bogota, Colombia, and La Paz, Bolivia

    ERIC Educational Resources Information Center

    Forste, Renata; Heaton, Tim B.; Haas, David W.

    2004-01-01

    Drawing on status attainment models, the authors examine the effects of family, peer, and school factors on expectations to graduate from a university for a sample of high school students in Bogota, Colombia, and La Paz, Bolivia. The expansion of higher education in these countries has followed different strategies. In Bolivia, the policy has been…

  18. Correlates of Adolescent Pregnancy in La Paz, Bolivia: Findings from a Quantitative-Qualitative Study.

    ERIC Educational Resources Information Center

    Lipovsek, Varja; Karim, Ali Mehryar; Gutierrez, Emily Zielinski; Magnani, Robert J.; Gomez, Maria del Carmen Castro

    2002-01-01

    Study explores why some female adolescents in La Paz, Bolivia, become pregnant while others in similar circumstances avoid early pregnancy. Results reveal that girls who had experienced a pregnancy were less likely to have reported affectionate and supportive parents, more likely to have reported fighting in their home, and exhibited lower levels…

  19. Response to Marie Paz Morales' ``Influence of culture and language sensitive physics on science attitude achievement''

    NASA Astrophysics Data System (ADS)

    Cole, Mikel Walker

    2015-12-01

    This response to Marie Paz Morales' "Influence of culture and language sensitive physics on science attitude achievement" explores the ideas of culturally responsive pedagogy and critical literacy to examine some implications for culturally responsive science instruction implicit in the original manuscript.

  20. Recognition of 2'-O-methylated 3'-end of piRNA by the PAZ domain of a Piwi protein.

    PubMed

    Simon, Bernd; Kirkpatrick, John P; Eckhardt, Stephanie; Reuter, Michael; Rocha, Elsa A; Andrade-Navarro, Miguel A; Sehr, Peter; Pillai, Ramesh S; Carlomagno, Teresa

    2011-02-01

    Piwi proteins are germline-specific Argonautes that associate with small RNAs called Piwi-interacting RNAs (piRNAs), and together with these RNAs are implicated in transposon silencing. The PAZ domain of Argonaute proteins recognizes the 3'-end of the RNA, which in the case of piRNAs is invariably modified with a 2'-O-methyl group. Here, we present the solution structure of the PAZ domain from the mouse Piwi protein, MIWI, in complex with an 8-mer piRNA mimic. The methyl group is positioned in a hydrophobic cavity made of conserved amino acids from strand β7 and helix α3, where it is contacted by the side chain of methionine-382. Our structure is similar to that of Ago-PAZ, but subtle differences illustrate how the PAZ domain has evolved to accommodate distinct 3' ends from a variety of RNA substrates.

  1. Geochemistry and petrology of the indium-bearing polymetallic skarn ores at Pitkäranta, Ladoga Karelia, Russia

    NASA Astrophysics Data System (ADS)

    Valkama, M.; Sundblad, K.; Cook, N. J.; Ivashchenko, V. I.

    2016-08-01

    The historic mining district of Pitkäranta in the Ladoga region, Fennoscandian Shield, was exploited for Fe, Cu, Zn, Pb, Sn and Ag in the nineteenth to twentieth centuries. The Pitkäranta region is dominated by Palaeoproterozoic supracrustal rocks, which, together with gneissic Archaean dome structures, constitute an allochthonous terrane complex that amalgamated to the Archaean continent during the Svecokarelian orogeny at 1.9-1.8 Ga. This crustal complex was intruded by 1.8 Ga Late orogenic granites, 1.54 Ga anorogenic rapakivi granites and 1.45 Ga dolerites. The polymetallic skarn ores of Pitkäranta extend over a 25-km-long zone in Palaeoproterozoic supracrustal rocks and formed from hydrothermal solutions, which emanated from the anorogenic rapakivi granites and reacted with marble layers. Four major ore types are recognised after the dominating metal: Fe, Cu, Sn and Zn, respectively. These types are not restricted to individual mines or mine fields but represent end members in zonation patterns within each ore body. Pitkäranta was the second discovery site in the world for indium but has been without modern documentation for more than 75 years. The indium contents in the ores are up to 600 ppm, in most cases sphalerite-hosted. The only roquesite-bearing sample in this study had an indium grade of 291 ppm and an In/Zn ratio of 51 (close to the criteria for the limiting conditions for creating an In-rich mineral). The Pitkäranta ores have a potential for future small-scale exploitation, but all such plans are hampered by high contents if Bi, Cd and As.

  2. Genesis of the Datuanshan stratabound skarn Cu(-Mo) deposit, Middle-Lower Yangtze Valley, Eastern China: constraints from geology, Re-Os geochronology, mineralogy, and sulfur isotopes

    NASA Astrophysics Data System (ADS)

    Cao, Yi; Gao, Fuping; Du, Yangsong; Du, Yilun; Pang, Zhenshan

    2016-07-01

    Stratabound deposits are the most abundant and economically significant ore type in the Middle-Lower Yangtze River Valley, one of the most important metallogenic belts in China. The Datuanshan deposit is one of the largest and most representative stratabound Cu(-Mo) deposits in the Tongling district of the Middle-Lower Yangtze River metallogenic belt. All the orebodies of the Datuanshan deposit occur around Mesozoic quartz monzodiorite and are tabular or semi-tabular bodies along bedding-parallel faults within upper Permian to Lower Triassic strata. However, discordant and crosscutting relationships (e.g., the host rocks crosscut by skarn- and quartz-sulfide veins, with alteration halos around the veins) have also been found, especially along the skarn-host contact and orebody-host contact, indicating that skarnitization and mineralization postdated the deposition of the host sediments. The skarn consists mainly of prograde garnet and pyroxene and retrograde alteration assemblages of amphibole, epidote, and chlorite, as well as quartz and sulfides. Electron microprobe analyses show that the garnets and pyroxenes are grossular-andradite and hedenbergite-diopside series, respectively, and all samples plot in the field of typical skarn copper deposits worldwide. Molybdenite samples from stratiform copper ores yield Re-Os model ages of 138.2-139.9 Ma with a weighted mean age of 139.2 ± 0.9 Ma. This is reasonably consistent with the ages of the stratiform Mo ores (138.0-140.8 Ma) and genetically related quartz monzodiorite (135.2-139.3 Ma) in the Datuanshan deposit, indicating that the stratiform Cu and Mo mineralization was contemporaneous with emplacement of the quartz monzodiorite magmas in the Early Cretaceous. Fifteen δ34S values for sulfides range from -1.8 to +4.7 ‰, with a mean of 0.5 ‰, indicating that the sulfur was derived mainly from a magmatic source. Moreover, the sulfur isotope values of the ores are consistent with those of Mesozoic intermediate

  3. Bioenergetics and gene silencing approaches for unraveling nucleotide recognition by the human EIF2C2/Ago2 PAZ domain.

    PubMed

    Kandeel, Mahmoud; Al-Taher, Abdullah; Nakashima, Remi; Sakaguchi, Tomoya; Kandeel, Ali; Nagaya, Yuki; Kitamura, Yoshiaki; Kitade, Yukio

    2014-01-01

    Gene silencing and RNA interference are major cellular processes that control gene expression via the cleavage of target mRNA. Eukaryotic translation initiation factor 2C2 (EIF2C2, Argonaute protein 2, Ago2) is considered to be the major player of RNAi as it is the core component of RISC complexes. While a considerable amount of research has focused on RNA interference and its associated mechanisms, the nature and mechanisms of nucleotide recognition by the PAZ domain of EIF2C2/Ago2 have not yet been characterized. Here, we demonstrate that the EIF2C2/Ago2 PAZ domain has an inherent lack of binding to adenine nucleotides, a feature that highlights the poor binding of 3'-adenylated RNAs with the PAZ domain as well as the selective high trimming of the 3'-ends of miRNA containing adenine nucleotides. We further show that the PAZ domain selectively binds all ribonucleotides (except adenosine), whereas it poorly recognizes deoxyribonucleotides. In this context, the modification of dTMP to its ribonucleotide analogue gave a drastic improvement of binding enthalpy and, hence, binding affinity. Additionally, higher in vivo gene silencing efficacy was correlated with the stronger PAZ domain binders. These findings provide new insights into the nature of the interactions of the EIF2C2/Ago2 PAZ domain.

  4. Bioenergetics and gene silencing approaches for unraveling nucleotide recognition by the human EIF2C2/Ago2 PAZ domain.

    PubMed

    Kandeel, Mahmoud; Al-Taher, Abdullah; Nakashima, Remi; Sakaguchi, Tomoya; Kandeel, Ali; Nagaya, Yuki; Kitamura, Yoshiaki; Kitade, Yukio

    2014-01-01

    Gene silencing and RNA interference are major cellular processes that control gene expression via the cleavage of target mRNA. Eukaryotic translation initiation factor 2C2 (EIF2C2, Argonaute protein 2, Ago2) is considered to be the major player of RNAi as it is the core component of RISC complexes. While a considerable amount of research has focused on RNA interference and its associated mechanisms, the nature and mechanisms of nucleotide recognition by the PAZ domain of EIF2C2/Ago2 have not yet been characterized. Here, we demonstrate that the EIF2C2/Ago2 PAZ domain has an inherent lack of binding to adenine nucleotides, a feature that highlights the poor binding of 3'-adenylated RNAs with the PAZ domain as well as the selective high trimming of the 3'-ends of miRNA containing adenine nucleotides. We further show that the PAZ domain selectively binds all ribonucleotides (except adenosine), whereas it poorly recognizes deoxyribonucleotides. In this context, the modification of dTMP to its ribonucleotide analogue gave a drastic improvement of binding enthalpy and, hence, binding affinity. Additionally, higher in vivo gene silencing efficacy was correlated with the stronger PAZ domain binders. These findings provide new insights into the nature of the interactions of the EIF2C2/Ago2 PAZ domain. PMID:24788663

  5. [Polyplacophoran communities (Mollusca: Polyplacophora) at Bahia de La Paz, Baja California Sur, México].

    PubMed

    García Ríos, Cedar I; Alvarez Ruiz, Migdalia

    2007-03-01

    Eight species of polyplacophorans have been reported from La Bahia de la Paz, Baja California Sur, Mexico. We add Lepidochitona beanii, Chaetopleura lurida, Stenoplax limaciformis, S. mariposa, Lepidozona clathrata, L. serrata and Acanthochitona arragonites, increasing the known number of species to 15. Ordination analysis of five chiton communities at the site suggests a correlation of wave exposure to species composition and diversity: communities with intermediate wave exposure have more species (richness) and higher diversity (Shannon's index).

  6. [Polyplacophoran communities (Mollusca: Polyplacophora) at Bahia de La Paz, Baja California Sur, México].

    PubMed

    García Ríos, Cedar I; Alvarez Ruiz, Migdalia

    2007-03-01

    Eight species of polyplacophorans have been reported from La Bahia de la Paz, Baja California Sur, Mexico. We add Lepidochitona beanii, Chaetopleura lurida, Stenoplax limaciformis, S. mariposa, Lepidozona clathrata, L. serrata and Acanthochitona arragonites, increasing the known number of species to 15. Ordination analysis of five chiton communities at the site suggests a correlation of wave exposure to species composition and diversity: communities with intermediate wave exposure have more species (richness) and higher diversity (Shannon's index). PMID:18457125

  7. Determining the Gruneisen coefficient for liquids using the PAZ-scan technique

    NASA Astrophysics Data System (ADS)

    Dantiste, Olivier A.

    Measurement of Gruneisen coefficient is utterly important in developing efficient molecular photoacoustic (PA) contrast agents. It is one of the two parameters that describes how efficient a molecule is in transforming optical energy into sound, the other being absorption coefficient. Using the PAZ-scan technique, the Gruneisen coefficient was obtained for various samples and the values are compared with standard techniques. In a PAZ-scan, the sample is translated through the path of a focused laser beam in small steps while the generated PA signal is recorded. The incident intensity is optimum at the focal point and decreases gradually on either side of the focus. As such, the absorption and the PA signal varies according to the sample properties. Therefore at positions away from the focal point, the incident intensities are weak and the PA signal varies linearly with intensity. A plot of the PA signal versus the intensity is used to obtain the Gruneisen coefficient. Using this technique, the Gruneisen coefficients for crystal violet in two different solvents, food coloring dyes that are dissolved in water were determined. Results show that the linear part of the PAZ-scan can be used to determine the Gruneisen coefficient for liquids.

  8. Geochemical and fluid zonation in the skarn environment at the tomboy-minnie gold deposits, Lander County, Nevada

    USGS Publications Warehouse

    Theodore, T.G.; Howe, S.S.; Blake, D.W.; Wotruba, P.R.

    1986-01-01

    The Tomboy-Minnie gold deposits are related to the middle Tertiary porphyry copper system centered at Copper Canyon. Gold-silver ores in the deposits occur mostly in a pyrrhotite- and pyrite-rich basal 30-m-thick sequence of altered calcareous conglomerate belonging to the Middle Pennsylvanian Battle Formation. The entire mineralized system contained at least 3.3 million troy oz gold before large-scale mining operations began. Alteration in the Tomboy-Minnie deposits includes actinolite- and chlorite-dominant assemblages, in marked contrast to the skarn, potassic, and phyllic assemblages characterizing the copper-gold-silver deposits of the system. Introduction of gold occurred penecontemporaneously with replacement of early diopside-alteration assemblages by actinolite and chlorite. Metals are zoned strongly in the Copper Canyon system: the West and East ore bodies occur in a copper-gold-silver zone that is followed outward by a gold-silver zone which includes the Tomboy deposit and in turn, is succeeded by a lead-zinc-silver zone. Locations of drill holes that have Au/Ag assay ratios of ??? 1 clearly outline the Tomboy-Minnie deposits within an area of rocks with Au/Ag ratios of ??? 0.5. Fluid-inclusion studies suggest wide variations in temperature and chemistry prevailed in the fluids associated with mineralization at the Tomboy. Early fluids associated with diopsidequartz assemblages probably were dominantly CaCl2-rich brines and were boiling at temperatures higher than 500??C. These fluids were progressively enriched in sodium and potassium over time, and during the hydrosilicate stages, temperatures probably ranged from 320 to 500??C at the time actinolite formed, and from 220 to 320??C at the time chlorite was dominant. Sulfur isotopic data suggest that sulfur, mostly from a magmatic or deep-seated crustal source, was transported by hydrothermal fluids as aqueous H2S with a ?? 34S of about 4 ?? 1??? to the West, East, and Tomboy deposits. ?? 1986.

  9. In silico molecular docking analysis of the human Argonaute 2 PAZ domain reveals insights into RNA interference.

    PubMed

    Kandeel, Mahmoud; Kitade, Yukio

    2013-07-01

    RNA interference (RNAi) is a critical cellular pathway activated by double stranded RNA and regulates the gene expression of target mRNA. During RNAi, the 3' end of siRNA binds with the PAZ domain, followed by release and rebinding in a cyclic manner, which deemed essential for proper gene silencing. Recently, we provided the forces underlying the recognition of small interfering RNA by PAZ in a computational study based on the structure of Drosophila Argonaute 2 (Ago2) PAZ domain. We have now reanalyzed these data within the view of the new available structures from human Argonauts. While the parameters of weak binding are correlated with higher (RNAi) in the Drosophila model, a different profile is predicted with the human Ago2 PAZ domain. On the basis of the human Ago2 PAZ models, the indicators of stronger binding as the total binding energy and the free energy were associated with better RNAi efficacy. This discrepancy might be attributable to differences in the binding site topology and the difference in the conformation of the bound nucleotides.

  10. Boron and strontium isotope compositions of groundwater from the La Paz arid coastal aquifer, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Mahlknecht, Jürgen; Rosner, Martin; Meixner, Anette

    2016-04-01

    In groundwater studies boron and strontium isotopic compositions can be used to identify natural and anthropogenic sources as well as processes related to groundwater recharge, flow and mixing. The La Paz arid costal aquifer in Baja California Sur, Mexico, is the most important source of drinking and irrigation water for La Paz area and suffers from anthropogenic contamination and intensive exploitation of the aquifer causing seawater intrusion and general groundwater abatement. The relatively un-radiogenic 87Sr/86Sr isotope ratios of the La Paz groundwater range in a narrow field between 0.7054 and 0.7062. In contrast to strontium the boron isotope composition displays a large variability between +27 and +55 permil d11B. The relatively low 87Sr/86Sr ratios of the La Paz groundwater highlight a significant contribution of strontium derived from local terrestrial sediments and igneous rocks with known 87Sr/86Sr ratios between 0.705 and 0.7035. The large variability of d11B values indicate that multiple sources and processes determine the boron isotope composition of La Paz groundwater. Rainwater (high d11B), seawater (~+40 permil) due to seawater intrusions, wastewater (low to medium d11B) and boron derived from the local geology (low to medium d11B) explain most of the observed groundwater d11B variability. However, d11B values higher than modern seawater point to significant boron isotope fractionation by preferential absorption of 10B onto clay minerals during the evolution of some groundwater samples. Due to low boron concentrations in rainwater a significant contribution of 11B-rich rainwater (>+40 permil) on the La Paz groundwater is unlikely.

  11. Modern carbonate sediments and environments of the LaPaz region, Baja California Sur, Mexico

    SciTech Connect

    Halfar, J.; Ingle, J.C. Jr.; Cruz-Orozco, R.; Godinez-Orta, L.

    1996-12-31

    The Gulf of California represents one of the most productive and unique marginal seas in the world. The mouth of the Gulf captures warm equatorial water while annual wind patterns assure major upwelling of nutrient-rich water leading to a rich marine biota. These conditions have created a wide array of tropical through warm temperate carbonate environments. The most unusual of these environments is located in the La Paz region of Baja California Sur where tropical-subtropical water temperatures and low rainfall have allowed growth of corals, calcareous red algae, and other shelled invertebrates to form a carbonate bank environment. Sampling and mapping transacts in shallow bays north of La Paz and on the adjacent Espiritu Santo island have revealed a full spectrum of subenvironments including mangrove bordered, terrigenous mud dominated coastal zones, which grade into carbonate tidal flats. In addition, single coral heads as well as incipient reef structures constructed by Porites and Pocillopora coral are present in deeper water areas. Coralline red algae, which are increasingly utilized for paleoenvironmental reconstructions, grow in high abundance on coral debris and in soft sediments and turn out to be main contributors to the La Paz carbonates. Analysis of siliciclastic admixtures, grain size and organic carbon content allow a classification of distinct environments. These data are supplemented by an evaluation of benthic foraminiferal zonations and the varying abundance of biogenic constituents. This Baja California Sur carbonate environment holds special relevance for the interpretation of analogous Neogene and Paleogene paleoenvironments marking major paleoclimatic and paleoceanographic events along the Pacific Coast of North America.

  12. Modern carbonate sediments and environments of the LaPaz region, Baja California Sur, Mexico

    SciTech Connect

    Halfar, J.; Ingle, J.C. Jr. ); Cruz-Orozco, R. ); Godinez-Orta, L. )

    1996-01-01

    The Gulf of California represents one of the most productive and unique marginal seas in the world. The mouth of the Gulf captures warm equatorial water while annual wind patterns assure major upwelling of nutrient-rich water leading to a rich marine biota. These conditions have created a wide array of tropical through warm temperate carbonate environments. The most unusual of these environments is located in the La Paz region of Baja California Sur where tropical-subtropical water temperatures and low rainfall have allowed growth of corals, calcareous red algae, and other shelled invertebrates to form a carbonate bank environment. Sampling and mapping transacts in shallow bays north of La Paz and on the adjacent Espiritu Santo island have revealed a full spectrum of subenvironments including mangrove bordered, terrigenous mud dominated coastal zones, which grade into carbonate tidal flats. In addition, single coral heads as well as incipient reef structures constructed by Porites and Pocillopora coral are present in deeper water areas. Coralline red algae, which are increasingly utilized for paleoenvironmental reconstructions, grow in high abundance on coral debris and in soft sediments and turn out to be main contributors to the La Paz carbonates. Analysis of siliciclastic admixtures, grain size and organic carbon content allow a classification of distinct environments. These data are supplemented by an evaluation of benthic foraminiferal zonations and the varying abundance of biogenic constituents. This Baja California Sur carbonate environment holds special relevance for the interpretation of analogous Neogene and Paleogene paleoenvironments marking major paleoclimatic and paleoceanographic events along the Pacific Coast of North America.

  13. Atmospheric and precipitation sounding with polarimetric radio-occultations aboard PAZ LEO

    NASA Astrophysics Data System (ADS)

    Padulles, Ramon; Cardellach, Estel; Tomás, Sergio; Oliveras, Santi; Rius, Antonio; de la Torre, Manuel; Turk, Joseph; Ao, Chi; Kursinski, Robert; Shreiner, Bill; Ector, Dave; Cucurull, Lidia; Wickert, Jens

    2015-04-01

    The Radio Occultation and Heavy Precipitation experiment aboard the PAZ Low Earth Orbiter (ROHP-PAZ) is a mission of opportunity: The Spanish Ministry of Science and Innovation (MICINN) approved in 2009 a proposal to include a polarimetric Global Navigation Satellite System (GNSS) Radio-Occultation (RO) payload on board of the Spanish Earth Observation satellite PAZ. This will be a new technique that has never been tested before, that aims to improve the knowledge of the precipitation through simultaneous thermodynamic and vertical rain profiles. The concept is similar to that used in some polarimetric weather radars: to measure the differential phase shift between the two polarimetric antennas, although here we will use the forward scattering geometry instead of the backscattering.The depolarization effect increases as the propagation line aligns with the plane of the drops' flattening (nominally perpendicular to the local gravity, i.e., parallel to the local horizon). The RO signals cross the lower troposphere tangentially, i.e., along the local horizon, which should maximize the depolarization effect. The satellite launch is scheduled for March 2015, and it will be followed by a 6-month commissioning phase period and has an expected life of 7 years, with a goal of 10 years. A sensitivity analysis have been performed, showing that we should be able to detect the 90% of all the events with along-ray averaged rain rate higher than 5 mm/h. Also, a ground field campaign has been conducted prior to the launch of the satellite. Results from the campaign also show a good correlation between phase shifts increases and heavy rain events. We will present here the status of the mission, which will have been launched few weeks before the EGU, together with some preliminary data analysis from both the actual satellite data and the prior-to-launch work.

  14. Geochronology and fluid inclusion study of the Yinjiagou porphyry-skarn Mo-Cu-pyrite deposit in the East Qinling orogenic belt, China

    NASA Astrophysics Data System (ADS)

    Wu, Guang; Chen, Yuchuan; Li, Zongyan; Liu, Jun; Yang, Xinsheng; Qiao, Cuijie

    2014-01-01

    The Yinjiagou Mo-Cu-pyrite deposit of Henan Province is located in the Huaxiong block on the southern margin of the North China craton. It differs from other Mo deposits in the East Qingling area because of its large pyrite resource and complex associated elements. The deposit's mineralization process can be divided into skarn, sulfide, and supergene episodes with five stages, marking formation of magnetite in the skarn episode, quartz-molybdenite, quartz-calcite-pyrite-chalcopyrite-bornite-sphalerite, and calcite-galena-sphalerite in the sulfide episode, and chalcedony-limonite in the supergene episode. Re-Os and 40Ar-39Ar dating indicates that both the skarn-type and porphyry-type orebodies of the Yinjiagou deposit formed approximately 143 Ma ago during the Early Cretaceous. Four types of fluid inclusions (FIs) have been distinguished in quartz phenocryst, various quartz veins, and calcite vein. Based on petrographic observations and microthermometric criteria the FIs include liquid-rich, gas-rich, H2O-CO2, and daughter mineral-bearing inclusions. The homogenization temperature of FIs in quartz phenocrysts of K-feldspar granite porphyry ranges from 341 °C to >550 °C, and the salinity is 0.4-44.0 wt% NaCl eqv. The homogenization temperature of FIs in quartz-molybdenite veins is 382-416 °C, and the salinity is 3.6-40.8 wt% NaCl eqv. The homogenization temperature of FIs in quartz-calcite-pyrite-chalcopyrite-bornite-sphalerite ranges from 318 °C to 436 °C, and the salinity is 5.6-42.4 wt% NaCl eqv. The homogenization temperature of FIs in quartz-molybdenite stockworks is in a range of 321-411 °C, and the salinity is 6.3-16.4 wt% NaCl eqv. The homogenization temperature of FIs in quartz-sericite-pyrite is in a range of 326-419 °C, and the salinity is 4.7-49.4 wt% NaCl eqv. The ore-forming fluids of the Yinjiagou deposit are mainly high-temperature, high-salinity fluids, generally with affinities to an H2O-NaCl-KCl ± CO2 system. The δ18OH2O values of ore

  15. Mineral inclusions and SHRIMP U-Pb dating of zircons from the Alamas nephrite and granodiorite: Implications for the genesis of a magnesian skarn deposit

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Zhang, Rongqing; Zhang, Zhiyu; Shi, Guanghai; Zhang, Qichao; Abuduwayiti, Maituohuti; Liu, Jianhui

    2015-01-01

    Extending approximately 1300 km and located in the Western Kunlun Mountains, the Hetian nephrite belt is the largest nephrite belt in the world and contains approximately 11 major deposits and more than 20 orebodies including the Alamas deposit. Hetian nephrite deposits can be classified as Mg-skarn deposits with Precambrian dolomitic marble host rock and green, green-white and white nephrite zones are distributed gradually in the zone of a granodiorite pluton. The green nephrite is mainly predominately composed of tremolite with generally minor to trace constituents of diopside, grossularitic garnet, actinolite and other minerals. Also green nephrite has higher content of TFe2O3, than green-white and white nephrites have. We subdivided the zircons from the green nephrites into four types, depending on their internal textures, mineral inclusions, and SHRIMP U-Pb ages. Type I zircons are round instead of idiomorphic in shape and lack obvious zoning. Type II and IV zircons have broad, clear oscillatory zoning and are hypidiomorphic or idiomorphic in shape; they contain inclusions of diopside, tremolite, chlorite and calcite. Most Type III zircons are narrow rims (< 10 μm) surrounding Type II and Type I zircons with highly luminous brightness and no zoning. Both Type I and Type II zircons have individual ages of 411 to 445 Ma and Type IV zircons have younger ages (388 to 406 Ma). Among the concordant ages, 425.7 ± 5.8 Ma and 420.0 ± 9.9 Ma for the QYZr1 and QYZr2 are consistent within error, with the 418.5 ± 2.8 Ma of the Alamas granodiorite formation age and the maximum age of the Alamas nephrite deposit. The partially recrystallization of zircons during skarn formation possibly lead to some younger individual ages (406.5 to 308 Ma). In the Western Kunlun Mountain, both Buya granite and Alamas grandiorite are high Ba-Sr granites and crystallized in Western Kunlun Orogen. The Buya granite formed at about 430 Ma in a post-orogenic tectonic environment. Considering

  16. Genetic relationship of high-Mg dioritic pluton to iron mineralization: A case study from the Jinling skarn-type iron deposit in the North China Craton

    NASA Astrophysics Data System (ADS)

    Jin, Ziliang; Zhang, Zhaochong; Hou, Tong; Santosh, M.; Han, Liu

    2015-12-01

    The Jinling complex is spatially and temporally associated with the Jinling skarn-type iron deposit. The complex is composed of biotite diorite, hornblende diorite, monzonite and quartz diorite. U-Pb dating of zircons from the biotite diorite and monzonite using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) yields ages of 126 ± 1.9 Ma and 128 ± 1.4 Ma, respectively. The unaltered rocks in the complex are characterized by variable contents of SiO2 (54.6-65.3 wt.%), MgO (2.7-9.2 wt.%), total FeO (3.5-8.8 wt.%), Na2O + K2O (5.2-8.9 wt.%), high Mg# values (73-88), Cr (103-452 ppm) and Ni (49-212 ppm) contents. The altered monzonite has lower MgO (2.1-3.7 wt.%), total FeO (1.2-2.6 wt.%) and higher Na2O + K2O (8.5-9.9 wt.%) contents. The initial (87Sr/86Sr)t ranges from 0.70450 to 0.70555 and εNd(t) shows a range of -3.0 to -8.0. The geochemical characteristics suggest that the primary magma witnessed the interaction between the partial melts of relatively oxidized delaminated ancient crust and mantle peridotite. Fractional crystallization and crustal contamination during the magmatic ascent and emplacement are also indicated. The Jinling skarn-type Fe deposit is of hydrothermal origin and the Fe enrichment can be ascribed to multiple factors. The delaminated ancient crustal source contributed to the high oxygen fugacity of the primary magma. Two-stage Fe-enrichment process involving fractional crystallization of the primary magma giving rise to high Cl and Fe contents in the magmatic hydrothermal fluid and later Fe-leaching process, accounts for the high-grade ore bodies.

  17. Effect of Mining Activities in Biotic Communities of Villa de la Paz, San Luis Potosi, Mexico

    PubMed Central

    Espinosa-Reyes, Guillermo; González-Mille, Donaji J.; Ilizaliturri-Hernández, César A.; Mejía-Saavedra, Jesús; Cilia-López, V. Gabriela; Costilla-Salazar, Rogelio; Díaz-Barriga, Fernando

    2014-01-01

    Mining is one of the most important industrial activities worldwide. During its different stages numerous impacts are generated to the environment. The activities in the region have generated a great amount of mining residues, which have caused severe pollution and health effects in both human population and biotic components. The aim of this paper was to assess the impact of mining activities on biotic communities within the district of Villa de la Paz. The results showed that the concentrations of As and Pb in soil were higher than the national regulations for urban or agricultural areas. The bioavailability of these metals was certified by the presence of them in the roots of species of plants and in kidneys and livers of wild rodents. In regard to the community analysis, the sites that were located close to the mining district of Villa de la Paz registered a lower biological diversity, in both plants and wild rodents, aside from showing a change in the species composition of plant communities. The results of this study are evidence of the impact of mining on biotic communities, and the need to take into account the wildlife in the assessment of contaminated sites. PMID:24592381

  18. Structurally controlled porosity evolution and production, La Paz Field, Maracaibo basin, Venezuela

    SciTech Connect

    Nelson, R.A.; Moldovanyi, E.P.; Matcek, C.C.

    1996-08-01

    La Paz Field is a large inversion structure, partially uplifted in the late Eocene and later inverted in the Mio-Pliocene. Fracture distributions, initial rates, cumulative production, pressure declines and trends in formation water chemistry suggest the reservoir is compartmentalized and that reservoir quality and reserves are controlled by the position of current strike-slip faults and by the geometry of the earlier Eocene block uplift. Within the area of Eocene uplift, production levels are high and drainage areas overlap substantially. This suggests highly elliptical to linear drainage along faults, higher than anticipated matrix storage, or likely a combination of the two. Diagenetic microporosity may be an important component in matrix storage, and may be due to water-rock interactions within the Eocene uplifted block. Initial and cumulative production, formation water chemistry, and lower than anticipated baseline fracture intensity in cores support the concept that in La Paz Field rate and reserves are dependent on the interaction of planar zones of intense fracturing along faults and secondary porosity (macro & micro) in the matrix. In fields like this, reserves may be optimally developed by judicious selection of well locations and well paths.

  19. Atmospheric polarimetric effects on GNSS Radio Occultations: the ROHP-PAZ field campaign

    NASA Astrophysics Data System (ADS)

    Padullés, R.; Cardellach, E.; de la Torre Juárez, M.; Tomás, S.; Turk, F. J.; Oliveras, S.; Ao, C. O.; Rius, A.

    2015-07-01

    This study describes the first experimental observations showing that hydrometeors induce polarimetric signatures in Global Navigation Satellite System (GNSS) signals. This evidence is relevant to the PAZ Low Earth Orbiter, which will test the concept and applications of polarimetric GNSS Radio Occultation (RO) (i.e. ROs obtained with a two-polarization antenna). A ground field campaign was carried out in preparation for PAZ to verify the theoretical sensitivity studies about this concept (Cardellach et al., 2015). The main aim of the campaign is to identify and understand the factors that might affect the polarimetric GNSS observables. Studied for the first time, GNSS signals measured with two polarimetric antennas (H, horizontal and V, vertical) are shown to discriminate heavy rain events, by comparing the measured phase difference between the H and V phase delays (Δ Φ) in different weather scenarios. The measured phase difference indicates higher dispersion under rain conditions. When individual events are examined, significant increases of Δ Φ occur when the radio signals cross rain cells. Moreover, the amplitude of such signal is much higher than the theoretical prediction for precipitation; thus other sources of polarimetric signatures have been explored and identified. Modelling of other hydrometeors like melting particles and ice crystals have been proposed to explain the obtained measurements, with good agreement in more than 90 % of the cases.

  20. Atmospheric polarimetric effects on GNSS radio occultations: the ROHP-PAZ field campaign

    NASA Astrophysics Data System (ADS)

    Padullés, R.; Cardellach, E.; de la Torre Juárez, M.; Tomás, S.; Turk, F. J.; Oliveras, S.; Ao, C. O.; Rius, A.

    2016-01-01

    This study describes the first experimental observations showing that hydrometeors induce polarimetric signatures in global navigation satellite system (GNSS) signals. This evidence is relevant to the PAZ low Earth orbiter, which will test the concept and applications of polarimetric GNSS radio occultation (RO) (i.e. ROs obtained with a dual-polarization antenna). A ground field campaign was carried out in preparation for PAZ to verify the theoretical sensitivity studies on this concept (Cardellach et al., 2015). The main aim of the campaign is to identify and understand the factors that might affect the polarimetric GNSS observables. Studied for the first time, GNSS signals measured with two polarimetric antennas (H, horizontal, and V, vertical) are shown to discriminate between heavy rain events by comparing the measured phase difference between the H and V phase delays (ΔΦ) in different weather scenarios. The measured phase difference indicates higher dispersion under rain conditions. When individual events are examined, significant increases in ΔΦ occur when the radio signals cross rain cells. Moreover, the amplitude of such a signal is much higher than the theoretical prediction for precipitation; thus, other sources of polarimetric signatures have been explored and identified. Modelling of other hydrometeors, such as melting particles and ice crystals, have been proposed to explain the obtained measurements, with good agreement in more than 90 % of the cases.

  1. A phosphate-binding pocket within the platform-PAZ-connector helix cassette of human Dicer.

    PubMed

    Tian, Yuan; Simanshu, Dhirendra K; Ma, Jin-Biao; Park, Jong-Eun; Heo, Inha; Kim, V Narry; Patel, Dinshaw J

    2014-02-20

    We have solved two families of crystal structures of the human Dicer "platform-PAZ-connector helix" cassette in complex with small interfering RNAs (siRNAs). The structures possess two adjacently positioned pockets: a 2 nt 3'-overhang-binding pocket within the PAZ domain (3' pocket) and a phosphate-binding pocket within the platform domain (phosphate pocket). One family of complexes contains a knob-like α-helical protrusion, designated "hDicer-specific helix," that separates the two pockets and orients the bound siRNA away from the surface of Dicer, which could be indicative of a product release/transfer state. In the second complex, the helical protrusion is melted/disordered and the bound siRNA is aligned toward the surface of Dicer, suggestive of a cleavage-competent state. These structures allow us to propose that the transition from the cleavage-competent to the postulated product release/transfer state may involve release of the 5'-phosphate from the phosphate pocket while retaining the 3' overhang in the 3' pocket.

  2. Inorganic phosphate blocks binding of pre-miRNA to Dicer-2 via its PAZ domain.

    PubMed

    Fukunaga, Ryuya; Colpan, Cansu; Han, Bo W; Zamore, Phillip D

    2014-02-18

    In Drosophila, Dicer-1 produces microRNAs (miRNAs) from pre-miRNAs, whereas Dicer-2 generates small interfering RNAs from long double-stranded RNA (dsRNA), a process that requires ATP hydrolysis. We previously showed that inorganic phosphate inhibits Dicer-2 cleavage of pre-miRNAs, but not long dsRNAs. Here, we report that phosphate-dependent substrate discrimination by Dicer-2 reflects dsRNA substrate length. Efficient processing by Dicer-2 of short dsRNA requires a 5' terminal phosphate and a two-nucleotide, 3' overhang, but does not require ATP. Phosphate inhibits cleavage of such short substrates. In contrast, cleavage of longer dsRNA requires ATP but no specific end structure: phosphate does not inhibit cleavage of these substrates. Mutation of a pair of conserved arginine residues in the Dicer-2 PAZ domain blocked cleavage of short, but not long, dsRNA. We propose that inorganic phosphate occupies a PAZ domain pocket required to bind the 5' terminal phosphate of short substrates, blocking their use and restricting pre-miRNA processing in flies to Dicer-1. Our study helps explain how a small molecule can alter the substrate specificity of a nucleic acid processing enzyme.

  3. Uranium-series ages of marine terraces, La Paz Peninsula, Baja California Sur, Mexico

    USGS Publications Warehouse

    Sirkin, L.; Szabo, B. J.; Padilla, G.A.; Pedrin, S.A.; Diaz, E.R.

    1990-01-01

    Uranium-series dating of coral samples from raised marine terrace deposits between 1.5 and 10 m above sea level in the La Paz Peninsula area, Baja California Sur, yielded ages between 123 ka and 138 ka that are in agreement with previously reported results. The stratigraphy and ages of marine units near the El Coyote Arroyo indicate the presence of two high stands of the sea during the last interglacial or oxygen isotope substage 5e at about 140 ka and 123 ka. Accepting 5 m for the sea level during the last interglacial transgression, we calculate average uplift rates for the marine terraces of about ???70 mm/ka and 40 mm/ka. These slow rates of uplift indicate a relative stability of the La Paz peninsula area for the past 140 000 years. In contrast, areas of Baja California affected by major faultf experienced higher rates of uplift. Rockwell et al. (1987) reported vertical uplift rates of 180 to 300 mm/ka at Punta Banda within the Aqua Blanea fault zone in northern Baja California. ?? 1990 Springer-Verlag.

  4. Effect of mining activities in biotic communities of Villa de la Paz, San Luis Potosi, Mexico.

    PubMed

    Espinosa-Reyes, Guillermo; González-Mille, Donaji J; Ilizaliturri-Hernández, César A; Mejía-Saavedra, Jesús; Cilia-López, V Gabriela; Costilla-Salazar, Rogelio; Díaz-Barriga, Fernando

    2014-01-01

    Mining is one of the most important industrial activities worldwide. During its different stages numerous impacts are generated to the environment. The activities in the region have generated a great amount of mining residues, which have caused severe pollution and health effects in both human population and biotic components. The aim of this paper was to assess the impact of mining activities on biotic communities within the district of Villa de la Paz. The results showed that the concentrations of As and Pb in soil were higher than the national regulations for urban or agricultural areas. The bioavailability of these metals was certified by the presence of them in the roots of species of plants and in kidneys and livers of wild rodents. In regard to the community analysis, the sites that were located close to the mining district of Villa de la Paz registered a lower biological diversity, in both plants and wild rodents, aside from showing a change in the species composition of plant communities. The results of this study are evidence of the impact of mining on biotic communities, and the need to take into account the wildlife in the assessment of contaminated sites.

  5. PAZ6 Cells Constitute a Representative Model for Human Brown Pre-Adipocytes

    PubMed Central

    Kazantzis, Melissa; Takahashi, Virginia; Hinkle, Jessica; Kota, Smitha; Zilberfarb, Vladimir; Issad, Tarik; Abdelkarim, Mouaadh; Chouchane, Lotfi

    2012-01-01

    The role of brown adipose tissue (BAT) in human metabolism and its potential as an anti-obesity target organ have recently received much renewed attention. Following radiological detection of substantial amounts of BAT in adults by several independent research groups, an increasing number of studies are now dedicated to uncover BAT’s genetic, developmental, and environmental determinants. In contrast to murine BAT, human BAT is not present as a single major fat depot in a well-defined location. The distribution of BAT in several areas in the body significantly limits its availability to research. A human brown adipocyte cell line is therefore critical in broadening the options available to researchers in the field. The human BAT-cell line PAZ6 was created to address such a need and has been well characterized by several research groups around the world. In the present review, we discuss their findings and propose potential applications of the PAZ6 cells in addressing the relevant questions in the BAT field, namely for future use in therapeutic applications. PMID:22649407

  6. Polarimetric mountain based radio-occultation for rain detection: The ROHP-PAZ ground campaign

    NASA Astrophysics Data System (ADS)

    Padulles, Ramon; Cardellach, Estel; Tomas, Sergio; de la Torre, Manuel; Turk, Joe

    2014-05-01

    The Radio Occultation and Heavy Precipitation experiment aboard the PAZ Low Earth Orbiter (ROHP-PAZ) is a mission of opportunity: The Spanish Ministry of Science and Innovation (MICINN) approved in 2009 a proposal to include a polarimetric Global Navigation Satellite System (GNSS) Radio-Occultation (RO) payload on board of the Spanish Earth Observation satellite PAZ. This will be a new technique that has never been tested before, that aims to improve the knowledge of precipitation through simultaneous thermodynamic and vertical rain profiles. Prior to the launch of the satellite, expected for 2014, a ground experimental campaign is being conducted with the goal of starting the process of identifying and understanding all the factors that might affect the polarimetric RO observables. The campaign is being carried out at the top of Puig Sesolles, a 1667m peak in the Natural Park of Montseny (41º46'24 N, 2º26'17 E), 50 km N-NE from Barcelona, with clear views over the horizon to the South (East to West) direction, an area in which intense precipitation events tend to occur a few times per year. The campaign uses a ICE-CSIC/IEEC's GOLD-RTR open-loop receiver initially designed for collecting GNSS signals reflected off the sea surface. The receiver has been adjusted to track occulting GNSS radio-links. A double polarization (H and V) GNSS antenna has been designed and manufactured by the Polytechnic University of Barcelona (UPC) team for this particular ground-based experiment. The antenna is a phase-array made of 7 elements, each of them being a square patch built using a Rogers 4003 substrate, and symmetrically fed by four probes. It provides a pattern of 12.9 dB peak gain, 45 degrees half-power beam-width, and <-35 dB cross-polar isolation at the peak (better than -30 dB in the main lobe). The preliminary results show that not only precipitation, but also other factors are affecting the GNSS signal, wich means that the polarimetric signal is richer than expected

  7. SHRIMP U-Pb and Ar-Ar geochronology of major porphyry and skarn Cu deposits in the Balkhash Metallogenic Belt, Central Asia, and geological implications

    NASA Astrophysics Data System (ADS)

    Chen, Xuanhua; Seitmuratova, Eleonora; Wang, Zhihong; Chen, Zhengle; Han, Shuqin; Li, Yong; Yang, Yi; Ye, Baoying; Shi, Wei

    2014-01-01

    The Balkhash Metallogenic Belt (BMB) in Kazakhstan, Central Asia, with the occurrence of the super-large Kounrad and Aktogai, the large Borly porphyry Cu-Mo deposits, and the large Sayak skarn polymetallic ore-field, is one of the central regions of the Paleozoic Central Asian metallogenic domain and orogenic belt. In this study, newly obtained SHRIMP zircon U-Pb ages of nine samples and 40Ar/39Ar ages of six mineral samples (inclding hornblende, biotite and K-feldspar) give more detailed constraints on the timing of the granitic intrusions and their metallogeny. Porphyritic monzonite granite and tonalite porphyry from the Kounrad deposit yield U-Pb zircon SHRIMP ages of 327.3 ± 2.1 Ma and 308.7 ± 2.2 Ma, respectively. Quartz diorite and porphyritic granodiorite from the Aktogai deposit yield U-Pb SHRIMP ages of 335.7 ± 1.3 Ma and 327.5 ± 1.9 Ma, respectively. Porphyritic granodiorite and granodiorite from the Borly deposit yield U-Pb SHRIMP ages of 316.3 ± 0.8 Ma and 305 ± 3 Ma, respectively. Diorite, granodiorite, and monzonite from the Sayak ore-field yield U-Pb SHRIMP ages of 335 ± 2 Ma, 308 ± 10 Ma, and 297 ± 3 Ma, respectively. Hornblende, biotite, and K-feldspar from the Aktogai deposit yield 40Ar/39Ar cooling ages of 310.6 Ma, 271.5 Ma, and 274.9 Ma, respectively. Hornblende, biotite, and K-feldspar from the Sayak ore-field yield 40Ar/39Ar cooling ages of 287.3 ± 2.8 Ma, 307.9 ± 1.8 Ma, and 249.8 ± 1.6 Ma, respectively. The new ages constrain the timing of Late Paleozoic felsic magmatism to ˜336 to ˜297 Ma. Skarn mineralization in the Sayak ore-field formed at ˜335 and ˜308 Ma. Porphyry Cu-Mo mineralization in the Kounrad deposit and the Aktogai deposit formed at ˜327 Ma, and in the Borly deposit at ˜316 Ma. The Late Paleozoic regional cooling in the temperature range of ˜600 °C to ˜150 °C occurred from ˜307 to ˜257 Ma.

  8. Mineral resources of the New Water Mountains Wilderness Study Area, La Paz County, Arizona

    SciTech Connect

    Sherrod, D.R.; Smith, D.B.; Koch, R.D.; Hanna, W.F.; Pitkin, J.A.; Lane, M.E.

    1989-01-01

    The New Water Mountains Wilderness Study Area, situated in La Paz County, west-central Arizona, locally has a moderate resource potential for gold and silver from replacement-type deposits occurring in Paleozoic marble in the western and north-central parts of the area, and a low resource potential for copper, lead, zinc, and manganese localized in fault zones that cut Tertiary volcanic rocks near the eastern edge of the range. Resource potential is low for geothermal energy or oil and gas. There is an unknown resource potential for lime, which could be developed from Paleozoic marble in the north-central part of the area. Sand and gravel occur in the area, but these materials are abundant closer to markets in the region.

  9. A new species of Psychrophrynella (Anura: Craugastoridae) from the Cordillera Real, Department La Paz, Bolivia.

    PubMed

    De La Riva, Ignacio; Burrowes, Patricia A

    2014-11-26

    We describe a new species of Psychrophrynella from a single locality in the Cordillera Real, in the Andes of Department of La Paz, Bolivia. Psychrophrynella teqta sp. nov. is highly variable in color pattern and differs from the species geographically closer mostly by presenting yellow or red blotches, usually absent in other species. In addition, the new species differs from all species in the genus because the males have a pulsed call. Males of this species show parental care, and the high number of eggs per nest suggest that perhaps more than one clutch might be attended by a single male. As other species in the genus, the new species is infected by Batrachochytrium dendrobatidis, and thus, a conservation threat is already present upon its discovery.

  10. U-Pb, Re-Os, and 40Ar/39Ar geochronology of the Nambija Au-skarn and Pangui porphyry Cu deposits, Ecuador: implications for the Jurassic metallogenic belt of the Northern Andes

    NASA Astrophysics Data System (ADS)

    Chiaradia, Massimo; Vallance, Jean; Fontboté, Lluis; Stein, Holly; Schaltegger, Urs; Coder, Joshua; Richards, Jeremy; Villeneuve, Mike; Gendall, Ian

    2009-05-01

    New U-Pb, Re-Os, and 40Ar/39Ar dates are presented for magmatic and hydrothermal mineral phases in skarn- and porphyry-related ores from the Nambija and Pangui districts of the Subandean zone, southeastern Ecuador. Nambija has been one of the main gold-producing centers of Ecuador since the 1980s due to exceptionally high-grade ores (average 15 g/t, but frequently up to 300 g/t Au). Pangui is a recently discovered porphyry Cu-Mo district. The geology of the Subandean zone in southeastern Ecuador is dominated by the I-type, subduction-related, Jurassic Zamora batholith, which intrudes Triassic volcanosedimentary rocks. The Zamora batholith is in turn cut by porphyritic stocks, which are commonly associated with skarn formation and/or porphyry-style mineralization. High precision U-Pb and Re-Os ages for porphyritic stocks (U-Pb, zircon), associated prograde skarn (U-Pb, hydrothermal titanite), and retrograde stage skarn (Re-Os, molybdenite from veins postdating gold deposition) of the Nambija district are all indistinguishable from each other within error (145 Ma) and indicate a Late Jurassic age for the gold mineralization. Previously, gold mineralization at Nambija was considered to be Early Tertiary based on K-Ar ages obtained on various hydrothermal minerals. The new Jurassic age for the Nambija district is slightly younger than the 40Ar/39Ar and Re-Os ages for magmatic-hydrothermal minerals from the Pangui district, which range between 157 and 152 Ma. Mineralization at Nambija and Pangui is associated with porphyritic stocks that represent the last known episodes of a long-lived Jurassic arc magmatism (˜190 to 145 Ma). A Jurassic age for mineralization at Nambija and Pangui suggests that the Northern Andean Jurassic metallogenic belt, which starts in Colombia at 3° N, extends down to 5° S in Ecuador. It also adds a new mineralization style (Au-skarn) to the metal endowment of this belt.

  11. Laparoscopic radical prostatectomy training for residents: Hospital Universitario La Paz model

    PubMed Central

    Gregorio, Sergio Alonso y; Molina, Susana Sánchez; Gómez, Angel Tabernero; Ledo, Jesús Cisneros; Sebastián, Jesús Díez; Barthel, Jesús Javier de la Peña

    2014-01-01

    Introduction In the last decade, we have seen the advance of laparoscopic surgery in urology. All laparoscopic procedures in our department are performed by staff members and are assisted by a single resident, ensuring resident training in laparoscopic surgery. The aim of this study is to evaluate the results of the Hospital La Paz training program for residents in the field of laparoscopic surgery. Material and methods We have done a retrospective review of LRP performed by the residents in our department. We also evaluated different variables. Descriptive statistical analysis was done and the results were compared with the descriptive analysis of the initial series of our department. Results We reviewed 82 patients, with an average age of 61.6 years. Most cases were pT1c at diagnosis. Average surgical time was 288 minutes, with a transfusion rate of 9.7% and a intra and postoperative complication rates of 1.2% and 7.3%. The mean hospital stay was 3.3 days. Histological results of this series are: 76.8% of pT2 and 23.2% of pT3. The biochemical relapse rate is 15.8%. Global surgical margin rate is 20.7%. The global continence rate is 52.4%. Conclusions The outcomes of LRP performed by residents are similar to the ones reported in the initial series of our department. The fact that 84.6% of the residents formed in this period actually belong to different laparoscopic units supports the success of La Paz Hospital training model. PMID:25247081

  12. Seasonal Cycle of the Near-Surface Diurnal Wind Field Over the Bay of La Paz, Mexico

    NASA Astrophysics Data System (ADS)

    Turrent, Cuauhtémoc; Zaitsev, Oleg

    2014-05-01

    The results of numerical simulations of the troposphere over the Bay of La Paz, calculated for the months of January, April, July and October during the period 2006-2010 with the Weather Research and Forecast (WRF v3.5) regional model, are used to describe the seasonal features of the diurnal cycle of planetary boundary-layer winds. Two distinct near-surface diurnal flows with strong seasonal variability were identified: (1) a nocturnal and matutinal breeze directed from the subtropical Pacific Ocean, over the Baja California peninsula and the Bay of La Paz, into the Gulf of California that is associated with the regional sea-surface temperature difference between those two major water bodies; and (2) a mid to late afternoon onshore sea-breeze related to the peninsula's daily cycle of insolation heating that evolves with counter-clockwise rotation over the Bay of La Paz. The model results reveal the interaction over Baja California of opposing afternoon sea-breeze fronts that originate from the subtropical Pacific Ocean and the Gulf of California, with a convergence line forming over the peaks of the peninsula's topography and the associated presence of a closed vertical circulation cell over the Bay of La Paz and the adjacent Gulf. The collision of the opposing sea-breeze fronts over the narrow peninsula drives convection that is relatively weak due to the reduced heat source and only appears to produce precipitation sporadically. The spatial structure of the sea-breeze fronts over the Bay of La Paz region is complex due to shoreline curvature and nearby topographic features. A comparison of the numerical results with available meteorological near-surface observations indicates that the modelling methodology adequately reproduced the observed features of the seasonal variability of the local planetary boundary-layer diurnal wind cycle and confirms that the low-level atmospheric circulation over the Bay of La Paz is dominated by kinetic energy in the diurnal band

  13. Trace Elements in the Marine Sediments of the La Paz Lagoon, Baja California Peninsula, Mexico: Pollution Status in 2013.

    PubMed

    Pérez-Tribouillier, Habacuc; Shumilin, Evgueni; Rodríguez-Figueroa, Griselda Margarita

    2015-07-01

    To determine the actual concentrations of trace elements in surface sediments from the La Paz Lagoon, as well as their associations and possible origins, 91 sediment samples were analyzed for more than 50 elements using a combination of ICP-MS and ICP-AES. The results of a principal component analysis are used to distinguish four associative groups within the elements. Natural enrichment of As, Cd and U occurs due to the supply of weathered phosphorites from the El Cien formation located to the north-west of the lagoon. Sediment quality indices for potentially toxic trace elements do not show any probable impact on the biota of the lagoon. Only the concentrations of As in 30 % of the stations and Cu in 20 % of them exceed related effect range low levels. The highest concentration of Pb (36.8 mg kg(-1)) was measured in the sediments near the City of La Paz.

  14. First Report of Widespread Wild Populations of Triatoma infestans (Reduviidae, Triatominae) in the Valleys of La Paz, Bolivia

    PubMed Central

    Buitrago, Rosio; Waleckx, Etienne; Bosseno, Marie-France; Zoveda, Faustine; Vidaurre, Pablo; Salas, Renata; Mamani, Elio; Noireau, François; Brenière, Simone Frédérique

    2010-01-01

    Wild populations of Triatoma infestans, the main vector of Chagas disease in the Southern Cone countries, may be involved in reinfestation of human dwellings, limiting the success of vector-control campaigns in Bolivia. Knowledge of the distribution of these populations remains incomplete. We report here the detection of T. infestans wild populations in large areas in the department of La Paz, Bolivia. Among 18 sylvatic areas investigated, 17 were positive with T. infestans specimens. The infection rate of captured T. infestans with Trypanosoma cruzi was 85.7% in adult specimens. These results expand the geographical distribution of wild populations of T. infestans; it may be distributed throughout the Inter-Andean Dry Forest eco-region of Bolivia. The current information allows us to propose the hypothesis that a sylvatic origin of the reinfestation is located in the valleys of La Paz. PMID:20348501

  15. Geochronology of the Hongniu-Hongshan porphyry and skarn Cu deposit, northwestern Yunnan province, China: Implications for mineralization of the Zhongdian arc

    NASA Astrophysics Data System (ADS)

    Peng, Hui-juan; Mao, Jing-wen; Pei, Rong-fu; Zhang, Chang-qing; Tian, Guang; Zhou, Yunman; Li, Jianxin; Hou, Lin

    2014-01-01

    The Hongniu-Hongshan porphyry and skarn copper deposit is located in the Triassic Zhongdian island arc, northwestern Yunnan province, China. Single-zircon laser ablation inductively coupled plasma mass spectrometry U-Pb dating suggests that the diorite porphyry and the quartz monzonite porphyry in the deposit area formed at 200 Ma and 77 Ma, respectively. A Re-Os isotopic date of molybdenite from the ore is 78.9 Ma, which indicates that in addition to the known Triassic Cu-(Au) porphyry systems, a Late Cretaceous porphyry Cu-Mo mineralization event also exists in the Zhongdian arc. The quartz monzonite porphyry shows characteristics of a magnetite series intrusion, with a high concentration of Al, K, Rb, Ba, and Pb, low amount of Ta, Ti, Y, and Yb, and a high ratio of Sr/Y (average 26.42). The Cretaceous porphyry also shows a strong fractionation between light and heavy rare earth elements (average (La/Yb)N 37.9), which is similar to those of the Triassic subduction-related diorite porphyry in the Hongniu-Hongshan deposit and the porphyry hosting the Pulang copper deposit. However, in contrast to the older intrusions, the quartz monzonite porphyry contains higher concentrations of large ion lithophile elements and Co, and lesser Sr and Zr. Therefore, whereas the Triassic porphyry Cu-(Au) mineralization is related to slab subduction slab in an arc setting, the quartz monzonite porphyry in the Hongniu-Hongshan deposit formed by the remelting of the residual oceanic slab combined with contributions from subduction-modified arc lithosphere and continental crust, which provided the metals for the Late Cretaceous mineralization.

  16. Rainfall Effects on Marine Paleoproductivity in La Paz Bay, Mexico through the Middle and Late Holocene

    NASA Astrophysics Data System (ADS)

    Ricaurte-villota, C.; Gonzalez-Yajimovich, O.

    2012-12-01

    The effect of rainfall on the paleoproductivity of Bahía de la Paz, Mexico, based on geochemical proxies of mass accumulation rates of biogenic silica, organic carbon and carbonates (paleoproductivity), and terrigenous content and titanium (rainfall) was reconstructed from two cores (NH01-15MC1b and NH01-15GC3) recovered from Alfonso Basin. The records indicate that marine productivity in the middle and late Holocene (last 5.8 ky) decreased synchronically with a decrease in rainfall throughout the region. The records also indicate greater variability between 5.5 and 2.7 ky. Periods of less rainfall correspond to a decrease of organic carbon and biogenic opal, probably caused by less fertilization in the photic zone due to a possible weakening of the cyclonic gyre that has been documented within the bay. The gyre provides nutrients from intermediate depths to the surface layer during periods of warmer temperatures. More carbonate content during times of less productivity could indicate less dissolution (changes in preservation). This is because a lower organic carbon flux results in less dissolution of CaCO3 since this lowers the oxygen demand to degrade the carbon. However, periods of higher carbonate content also coincide with epochs of more rainfall, which could indicate a more tropical influence.

  17. Lower Gila South Resource Management Plan, La Paz, Maricopa, Pima, Pinal and Yuma Counties, Arizona

    SciTech Connect

    Not Available

    1985-08-01

    Implementation of a resource management plan is proposed for 2.0 million surface acres and 1.9 million acres of subsurface minerals in the Lower Gila South resource area, located in La Paz, Maricopa, Pima, Pinal, and Yuma counties, Arizona. The preferred alternative would involve range land improvements consisting of construction of 47 miles of fence, 10 reservoirs and 7 wells. Portions of the New Water Mountains, Eagletail Mountains, Woosley Peak, and Table Top Mountains wilderness study areas (WSAs), totaling 190,391 acres, would be designated as wilderness. The remaining portions of these WSAs and eight other WSAs, totaling 431,540 acres, would not be recommended for wilderness designation and would revert to multiple-use management. Approximately 72,123 acres of isolated land parcels would be made available for sale or exchange, approximately 36,845 acres of nonpublic lands would be acquired, 112,160 acres of state and private mineral estate would be acquired, and 23,645 acres of federal minerals would be disposed of to facilitate management. Ten utility corridors would be designated. Mineral access and off-road vehicle use would be restricted on the lands proposed for wilderness designation.

  18. Morphological changes in the pituitary-adrenocortical axis in natives of La Paz

    NASA Astrophysics Data System (ADS)

    Gosney, John; Heath, Donald; Williams, David; Rios-Dalenz, Jaime

    1991-03-01

    Increased activity of the hypothalamic-pituitary-adrenocortical axis is part of the response to the stress of initial exposure to hypoxia, but there is evidence to suggest that it persists after homeostatic stability has been regained and acclimatization achieved. The adrenal glands of five lifelong residents of La Paz, Bolivia, who had lived at altitudes in the range 3600 3800 m, were significantly larger than those in age-matched controls from sea level (15.3g vs 10.4g; P<0.001) and appeared hyperplastic. The pituitary glands of the highlanders were not significantly different in size from those of the controls (0.67 g vs 0.51 g), but contained larger populations of corticotrophs expressed in terms of the total cell population of their anterior lobes (25.6% vs 19.4%; P<0.001). In conjunction with other studies of this endocrine axis in man and animals exposed to a hypoxic environment, these data suggest that greater amounts of adrenocorticotrophic hormone (ACTH) are required to maintain normal adrenocortical function under such circumstances, probably as a result of hypoxic inhibition of adrenocortical sensitivity to stimulation. Physiological hyperplasia of the adrenal cortex may be common in people living at high altitude.

  19. Risk perception, risk management and vulnerability to landslides in the hill slopes in the city of La Paz, Bolivia. A preliminary statement.

    PubMed

    Nathan, Fabien

    2008-09-01

    The article begins by describing the difficult living conditions of many people in the hill slopes (laderas) of La Paz, Bolivia, demonstrating that they are exposed to a combination of natural and social hazards. It shows that residents, community leaders and city planners tend to underestimate or deny risk, with important consequences for risk management, such as a failure to raise risk awareness. The article then proposes some hypotheses to explain risk perceptions in La Paz, discarding the usual single-approach interpretations and suggesting instead more nuanced theoretical explanations to account for why people build their homes in such hazardous environments.

  20. Relative inactivity during the last 140,000 years of a portion of the La Paz fault, southern Baja California Sur, Mexico

    USGS Publications Warehouse

    Szabo, B. J.; Hausback, B.P.; Smith, Joe T.

    1990-01-01

    Uranium-series dating of corals overlying the undeformed Punta Coyote gravels indicates that the underlying La Paz fault zone has been relatively inactive in this part of the Baja California peninsula during the last 140,000 years, and possibly for a significantly longer period. However, Holocene seismic activities along extensions of the fault zone north of Cabo San Lucas suggest potential seismic hazards for the city of La Paz (population 200,000), which lies about 6 km from the fault. ?? 1990 Springer-Verlag New York Inc.

  1. Precipitation measurements with GNSS polarimetric Radio Occultations: Status of the ROHP-PAZ mission and anticipated retrievals

    NASA Astrophysics Data System (ADS)

    Padullés, Ramon; Cardellach, Estel; de la Torre Juárez, Manuel; Tomás, Sergio; Turk, F. Joseph; Ao, Chi O.; Rius, Toni; Oliveras, Santi

    2016-04-01

    The upcoming ROHP-PAZ (Radio Occultations and Heavy Precipitation experiment aboard the spanish PAZ satellite) mission aims to detect, for the first time, precipitation using Global Navigation Satellite System Radio Occultations (GNSS-RO). The electromagnetic signals coming from the GNSS satellites travel tangentially through the atmosphere and will be collected in the PAZ Low Earth Orbiter at two polarizations (vertical and horizontal). This sounding-like technique of the atmosphere will measure all the atmospheric phenomena that are inducing depolarization effects, in addition to all the thermodynamic profiles that standard RO are nowadays providing. The main contributors to depolarization in the troposphere are known to be the hydrometeors, both rain drops from heavy precipitation events and horizontally oriented ice particles in the top of clouds. Their effects on the GNSS signals were predicted in Cardellach et. al. 2015 (IEEE Trans. Geosci. Remote Sens.), and measured in the ROHP-PAZ field campaign Padullés et. al. 2016 (Atmos. Chem. Phys.). Prior to the launch, a complete characterization of all the possible effects, including hydrometeors but also taking into account other elements was needed. To do so, actual data from the COSMIC - FORMOSAT 3 mission (Radio Occultation events) have been collocated with the TRMM, GPM and CloudSat missions (precipitation and clouds missions). Thousands of events have been analyzed, in terms of SNR and phase delays. For the same events, the effect of hydrometeors has been simulated as well as the most known ionospheric effects, such as Faraday Rotation and Cotton-Mouton effects. And finally, the predicted noise, actual measurements of the antenna pattern and some tolerance in the purity of the emitted signal have been included. This has resulted in an extensive data base that is key in the understanding of the upcoming actual data, as well as for the characterization of all the unpredicted effects. We will discuss here the

  2. Petrogenesis of the Zhangmatun gabbro in the Ji'nan complex, North China Craton: Implications for skarn-type iron mineralization

    NASA Astrophysics Data System (ADS)

    Xie, Qiuhong; Zhang, Zhaochong; Hou, Tong; Santosh, M.; Jin, Ziliang; Han, Liu; Cheng, Zhiguo

    2015-12-01

    The Zhangmatun gabbro is part of the Ji'nan complex in the North China Craton. It is spatially and temporally associated with the Zhangmatun skarn-type high-grade iron deposit. U-Pb dating of zircons from the Zhangmatun gabbro yielded an age of 130.2 ± 1.8 Ma, indicating the emplacement time as Early Cretaceous. The Zhangmatun gabbro displays porphyritic texture with plagioclase and clinopyroxene as the major phenocryst phases, together with minor biotite, hornblende, and magnetite. The rocks show a restricted range of SiO2 (50.1-52.7 wt.%) and Al2O3 (14.7-16.0 wt.%), low TiO2 (0.69-0.86 wt.%), relatively variable FeOT (2.87-8.62 wt.%), high MgO (6.50-8.01 wt.%) and Na2O (3.36-5.13 wt.%). The gabbro is also characterized by marked enrichment of LREEs and other LILEs (e.g., Rb, Sr and Ba), and strong depletion in HFSEs (e.g., Nb, Ta, Ti, Zr and Hf), similar to arc-related magma. The plagioclase and clinopyroxene from the Ji'nan gabbro, Zhangmatun gabbro, as well as Yaoshan and Huashan gabbroic diorite exhibit higher oxygen isotopes than those of the primitive mantle, indicating involvement of crustal materials. The similarity in geology, geochronology and petrology of these rocks suggests that they are co-magmatic. The parent magma of the Zhangmatun gabbro was produced by partial melting of amphibole-bearing spinel lherzolite in the upper mantle which has been modified by the lower crustal materials beneath the North China Craton. In combination with the Sr-Nd isotopic compositions of the Zhangmatun gabbro, we recognize EMI-type mantle source beneath the Ji'nan area. Moreover, the relatively high values as well as the relatively large variation of εHf(t) (-9.1 to +1.8) imply that asthenospheric material was also involved in the mantle-derived melt. The formation of iron concentration in the hydrothermal fluids is attributed to the exsolution of Fe-rich magmatic fluids and leaching from the solidified Zhangmatun gabbro at the retrograde alteration stage.

  3. The Riviera Deposit: Endo-skarn and Vein-hosted W-MO-REE Mineralization in I-type Granites of the Cape Granite Suite, South Africa

    NASA Astrophysics Data System (ADS)

    Rozendaal, A.; Moyen, J.

    2009-05-01

    The blind Riviera deposit is located in the western Cape Province and was discovered by stream sediment sampling in the mid 1970's. Resources total 46 million metric tons assaying 0,216 per cent tungsten and 200 parts per million molybdenum, a marginal grade that has prohibited development into an open cast mine. Mineralization is mainly hosted by granitoids of the Riviera Pluton which intruded the regionally metamorphosed volcano-sedimentary Malmesbury Group. These granitoids form part of the Cape Granite Suite, a series of batholiths and plutons with S-, I- and A-type characteristics. The composite Riviera Pluton comprises a suite of metaluminous to slightly peraluminous granitoids. The rocks least affected by hydrothermal alteration are granodioritic to adamelitic in composition whereas the more altered host rocks include quartz-monzonite, granite and quartz syenite. As a whole the suite is subalkaline to K-calcalkaline and conforms to the characteristics of I-type granites. The pluton was emplaced into a dome-shaped interference structure, late in the Neoproterozoic Saldanian orogenic cycle. Alteration, particularly prevalent in the roof or cupola of the pluton, occurs as zones of pervasive sericitization, argillization, silicification and potassic alteration. Their spatial and temporal relationship is complex and indicates several superimposed alteration events. Wall rocks display limited alteration and have acted as an impermeable cap. The cross-cutting granitoid intrusions produced wall rock xenoliths of various dimensions consisting mainly of meta-carbonates displaying various stages of digestion. Economic concentrations of scheelite are spatially linked to these assimilations, particularly proximal to the wall rock contact. The occurrence of diagnostic minerals such as vesuvianite, hornblende, hedenbergite, grandite garnets define a typical endo-skarn association. Accessory minerals include pyrite, pyrrhotite, chalcopyrite, sphalerite and the LREE enriched

  4. Structural and binding study of modified siRNAs with the Argonaute 2 PAZ domain by NMR spectroscopy.

    PubMed

    Maiti, Mohitosh; Nauwelaerts, Koen; Lescrinier, Eveline; Herdewijn, Piet

    2011-02-01

    By using high-resolution NMR spectroscopy, the structures of a natural short interfering RNA (siRNA) and of several altritol nucleic acid (ANA)-modified siRNAs were determined. The interaction of modified siRNAs with the PAZ domain of the Argonaute 2 protein of Drosophila melanogaster was also studied. The structures show that the modified siRNA duplexes (ANA/RNA) adopt a geometry very similar to the naturally occurring A-type siRNA duplex. All ribose residues, except for the 3' overhang, show 3'-endo conformation. The six-membered altritol sugar in ANA occurs in a chair conformation with the nucleobase in an axial position. In all siRNA duplexes, two overhanging nucleotides at the 3' end enhance the stability of the first neighboring base pair by a stacking interaction. The first overhanging nucleotide has a rather fixed position, whereas the second overhanging nucleotide shows larger flexibility. NMR binding studies of the PAZ domain with ANA-modified siRNAs demonstrate that modifications in the double-stranded region of the antisense strand have some small effects on the binding affinity as compared with the unmodified siRNA. Modification of the 3' overhang with thymidine (dTdT) residues shows a sixfold increase in the binding affinity compared with the unmodified siRNA (relative binding affinity of 17% compared with dTdT-modified overhang), whereas modification of the 3' overhang with ANA largely decreases the binding affinity.

  5. Structural Basis for piRNA 2-O-methylated 3-end Recognition by Piwi PAZ (Piwi/Argonaute/Awille) Domains

    SciTech Connect

    Y Tian; D Simanshu; J Ma; D Patel

    2011-12-31

    Argonaute and Piwi proteins are key players in the RNA silencing pathway, with the former interacting with micro-RNAs (miRNAs) and siRNAs, whereas the latter targets piwi-interacting RNAs (piRNAs) that are 2'-O-methylated (2'-OCH{sub 3}) at their 3' ends. Germline-specific piRNAs and Piwi proteins play a critical role in genome defense against transposable elements, thereby protecting the genome against transposon-induced defects in gametogenesis and fertility. Humans contain four Piwi family proteins designated Hiwi1, Hiwi2, Hiwi3, and Hili. We report on the structures of Hili-PAZ (Piwi/Argonaute/Zwille) domain in the free state and Hiwi1 PAZ domain bound to self-complementary 14-mer RNAs (12-bp + 2-nt overhang) containing 2'-OCH{sub 3} and 2'-OH at their 3' ends. These structures explain the molecular basis underlying accommodation of the 2'-OCH{sub 3} group within a preformed Hiwi1 PAZ domain binding pocket, whose hydrophobic characteristics account for the preferential binding of 2'-OCH{sub 3} over 2'-OH 3' ends. These results contrast with the more restricted binding pocket for the human Ago1 PAZ domain, which exhibits a reverse order, with preferential binding of 2'-OH over 2'-OCH{sub 3} 3' ends.

  6. Impacts of glacier shrinkage on water resources of La Paz city, Bolivia (16°S) over the last four decades

    NASA Astrophysics Data System (ADS)

    Soruco, Alvaro; Vincent, Christian; Rabatel, Antoine; Francou, Bernard; Thibert, Emmanuel; Sicart, Jean-Emmanuel; Condom, Thomas

    2014-05-01

    Under tropical conditions, water discharge from glaciers is crucial for water resources in the dry season, as it is the case for La Paz, Bolivia (16°S). In the current study, the glacier water supply of La Paz city has been assessed at annual and seasonal time-scale for the first time thanks to the mass balance analysis of 70 glaciers located within the drainage basins of La Paz between 1963 and 2006. The ice melting has contributed to about 15% of the water resources of the city at an annual scale, 14% in the humid season and 27% in the dry season. Despite the loss of about the half of the glaciers areas during this period, the runoff at La Paz did not change significantly. It reveals that ice melting rise compensated the surface areas decrease. Contrary, assuming that glaciers disappear in the future and precipitation does not change in the catchment areas, the runoff should diminish by about 12% at annual scale, 9% during the humid season and 24% during the dry season.

  7. Structural basis for piRNA 2'-O-methylated 3'-end recognition by Piwi PAZ (Piwi/Argonaute/Zwille) domains.

    PubMed

    Tian, Yuan; Simanshu, Dhirendra K; Ma, Jin-Biao; Patel, Dinshaw J

    2011-01-18

    Argonaute and Piwi proteins are key players in the RNA silencing pathway, with the former interacting with micro-RNAs (miRNAs) and siRNAs, whereas the latter targets piwi-interacting RNAs (piRNAs) that are 2'-O-methylated (2(')-OCH(3)) at their 3' ends. Germline-specific piRNAs and Piwi proteins play a critical role in genome defense against transposable elements, thereby protecting the genome against transposon-induced defects in gametogenesis and fertility. Humans contain four Piwi family proteins designated Hiwi1, Hiwi2, Hiwi3, and Hili. We report on the structures of Hili-PAZ (Piwi/Argonaute/Zwille) domain in the free state and Hiwi1 PAZ domain bound to self-complementary 14-mer RNAs (12-bp + 2-nt overhang) containing 2(')-OCH(3) and 2'-OH at their 3' ends. These structures explain the molecular basis underlying accommodation of the 2(')-OCH(3) group within a preformed Hiwi1 PAZ domain binding pocket, whose hydrophobic characteristics account for the preferential binding of 2(')-OCH(3) over 2'-OH 3' ends. These results contrast with the more restricted binding pocket for the human Ago1 PAZ domain, which exhibits a reverse order, with preferential binding of 2'-OH over 2(')-OCH(3) 3' ends.

  8. Lunar meteorite LaPaz Icefield 04841: Petrology, texture, and impact-shock effects of a low-Ti mare basalt

    NASA Astrophysics Data System (ADS)

    Hill, E.; Taylor, L. A.; Floss, C.; Liu, Y.

    2009-03-01

    Found during the 2004 U.S. Antarctic Search for Meteorites season, LaPaz Icefield (LAP) 04841 represents an addition to the LaPaz lunar basalts suite and brings the total mass collected to 1.93 kg. The presence of FeNi grains, troilite, and the anorthositic composition of plagioclase are evidence for the lunar origin of this meteorite. Pyroxene and olivine Mn/Fe values plot along the trend set for lunar basalts. Analyses of chromite grains provide a V/(Al + Cr) ratio of 1.33 ± 13, translating to an fO2 one log unit below the IW buffer, in accordance with previous fO2 estimates for lunar basalts. Application of the Zr-cooling speedometer, for ilmenite and ulvöspinel pairs, gives a cooling rate of 5.2 °C/day, matching previous estimates of cooling rates for the LaPaz lunar meteorites and Apollo mare basalts. Mineral modes and chemistries, as well as trace-element patterns, provide compelling evidence for pairing of this meteorite to others in the LaPaz lunar basalt suite.

  9. U-Pb geochronology, geochemistry, and H-O-S-Pb isotopic compositions of the Leqingla and Xin'gaguo skarn Pb-Zn polymetallic deposits, Tibet, China

    NASA Astrophysics Data System (ADS)

    Wang, Liqiang; Cheng, Wenbin; Tang, Juxing; Kang, Haoran; Zhang, Yan; Li, Zhuang

    2016-01-01

    The Leqingla and Xin'gaguo deposits are two representative skarn Pb-Zn polymetallic deposits of the Gangdese Pb-Zn polymetallic belt, Tibet, China. LA-ICP-MS zircon U-Pb dating of the mineralization-related biotite granites from both the Leqingla and Xin'gaguo deposits yielded weighted mean ages of 60.8 Ma and 56.5 Ma, respectively, which can be inferred as their mineralization ages. The Leqingla biotite granite is characterized by high Al2O3, total Fe, Na2O, and low K2O. In comparison, the Xin'gaguo biotite granite is characterized by relative higher K2O but lower Al2O3, total Fe, and Na2O. Geochemical and mineralogical characteristics indicate that the Leqingla and Xin'gaguo biotite granites are calc-alkaline I-type granite and High K calc-alkaline I-type granite, respectively. Both the Leqingla and Xin'gaguo biotite granites are enrichment in LREE and LILEs and depletion in HFSEs, and they were formed at the India-Asia collision stage. δ18O and δD values for the Leqingla and Xin'gaguo deposits are -8.8‰ to 5.3‰ and -140.4‰ to -90.1‰, -4.5‰ to 7.0‰ and -117.3‰ to -81.0‰, respectively, indicating magma fluids mixed with meteoric water in ore-forming fluids. δ34S values (-11.6‰ to -0.3‰) of ore sulfides from the Leqingla deposit show characteristics of biogenetic sulfur isotope compositions, suggesting sulfur for the Leqingla deposit were sourced from wall rocks of the Mengla and Luobadui Formation, which are rich in organic materials. δ34S values of ore sulfides from the Xin'gaguo deposits show bimodal distribution (-5.0‰ to -1.6‰ and 1.6-2.1‰), indicating sulfur in the Xin'gaguo deposit were derived from both wall rocks and magma. In the Leqingla deposit, most ore sulfides have the similar Pb isotopic compositions with that of the mineralization-related biotite granite, suggesting the biotite granite supplied most of the ore-forming metals. Pb isotopic compositions of ore sulfides and Hf isotopic compositions of biotite granite show

  10. Archean high-Mg monzodiorite-syenite, epidote skarn, and biotite-sericite gold lodes in the Granny Smith-Wallaby district, Australia: U-Pb and Re-Os chronometry of two intrusion-related hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Mueller, Andreas G.; Hall, Gregory C.; Nemchin, Alexander A.; Stein, Holly J.; Creaser, Robert A.; Mason, Douglas R.

    2008-03-01

    The Granny Smith (37 t Au production) and Wallaby deposits (38 t out of a 180 t Au resource) are located northeast of Kalgoorlie, in 2.7 Ga greenstones of the Eastern Goldfields Province, the youngest orogenic belt of the Yilgarn craton, Western Australia. At Granny Smith, a zoned monzodiorite-granodiorite stock, dated by a concordant titanite-zircon U-Pb age of 2,665 ± 3 Ma, cuts across east-dipping thrust faults. The stock is fractured but not displaced and sets a minimum age for large-scale (1 km) thrust faulting (D2), regional folding (D1), and dynamothermal metamorphism in the mining district. The local gold-pyrite mineralization, controlled by fractured fault zones, is younger than 2,665 ± 3 Ma. In augite-hornblende monzodiorite, alteration progressed from a hematite-stained alkali feldspar-quartz-calcite assemblage and quartz-molybdenite-pyrite veins to a late reduced sericite-dolomite-albite assemblage. Gold-related monazite and xenotime define a U-Pb age of 2,660 ± 5 Ma, and molybdenite from veins a Re-Os isochron age of 2,661 ± 6 Ma, indicating that mineralization took place shortly after the emplacement of the main stock, perhaps coincident with the intrusion of late alkali granite dikes. At Wallaby, a NE-trending swarm of porphyry dikes comprising augite monzonite, monzodiorite, and minor kersantite intrudes folded and thrust-faulted molasse. The conglomerate and the dikes are overprinted by barren (<0.01 g/t Au) anhydrite-bearing epidote-actinolite-calcite skarn, forming a 600-m-wide and >1,600-m-long replacement pipe, which is intruded by a younger ring dike of syenite porphyry pervasively altered to muscovite + calcite + pyrite. Skarn and syenite are cut by pink biotite-calcite veins, containing magnetite + pyrite and subeconomic gold-silver mineralization (Au/Ag = 0.2). The veins are associated with red biotite-sericite-calcite-albite alteration in adjacent monzonite dikes. Structural relations and the concordant titanite U-Pb age of the skarn

  11. The environmental hazard caused by smelter slags from the Sta. Maria de la Paz mining district in Mexico.

    PubMed

    Manz, M; Castro, L J

    1997-01-01

    The noxious potential of metallurgical tailings from the Ag/Pb/Zn/Cu mining district of Sta. María de la Paz (Mexico) is ascertained via the chemical characterization of slag material. Batch experiments using various extraction solutions (e.g. natural rainwater, water rich in humic substances, ammonium nitrate solution) revealed information on the dissolution behaviour of the elements Fe, Mn, Ni, Cu, Zn, As, Ba and Pb from slag with respect of grain size (slag material screened under 2 mm and analytically fine fraction) and elution time (2, 7.5, 24 and 240 h). An initial ecotoxicological assessment of the results is made and the environmental danger caused by large volumes of slag tailings is discussed.

  12. Middle-late Holocene climate variability in La Paz Basin, southern Gulf of California

    NASA Astrophysics Data System (ADS)

    Gómez-Lizárraga, L. E.; Perez-Cruz, L. L.; Fucugauchi, J. U.

    2013-12-01

    Sediments from DIPAL III-K47 core collected at 830 m depth in the western slope within the oxygen minimum zone of La Paz Basin, southern Gulf of California provide a detailed record of paleoceanography and paleoclimatology for the tropical Pacific on centennial time scales for the past 7300 years. The sedimentary sequence is compose of hemipelagic sediments and is laminated throughout its entire length (145 cm). According to the preliminary age model based on radiocarbon AMS dates, core covers the period from ca 7300 to 1000 cal yr BP. The estimated sedimentation rates are between 0.20 and 0.29 mm/yr. Radiolarian assemblages, geochemical (major and trace elements Al, Ba, Ca, K, Si Ti, Zr and Zr/Al and Ba/Al ratios) and magnetic susceptibility are used as proxies of variations of oceanic circulation patterns, paleoproductivity, aeolian activity and precipitation. Eighty-two intervals were sampled for radiolarians and the core was sampled at 1-cm intervals to produce records of major and trace elements. Factor Analysis of the radiolarian abundances counted in sediments samples identified three assemblages. The first one (Arachnocorallium calvata, Lithomelissa setosa, Lithomelissa thoracites and Peridium longispinum) suggests winter-spring like conditions (cold and dry), Gulf of California Water persistence and a relative increase in productivity that might become from the east-to-west upwelling gradient. The second radiolarian assemblage (Tetrapyle octacantha group and Phorticium pylonium group) was interpreted as stratification of the column water and the incursion of warm, oligotrophic Tropical Surface Water that remind summer-fall like conditions. The third assemblage (Clathrocircus stapedius, Phorticium pylonium group, Lithomelissa pentacantha, Phormacantha hystrix, Phormospyris stabilis scaphipes, Lithomelissa thoracites, Pseudocubus obeliscus, Druppatractus irregularis and Druppatractus variabilis), suggests a mix water column that favors the organic carbon

  13. The ROHP-PAZ mission and the polarimetric and non-polarimetric effects of rain and other fozen hydrometeors on GNSS Radio-Occultation signals.

    NASA Astrophysics Data System (ADS)

    De La Torre Juarez, M.; Padulles, R.; Cardellach, E.; Tomás, S.; Turk, J.; Ao, C. O.; Oliveras, S.; Rius, A.

    2015-12-01

    The Radio Occultation and Heavy Precipitation experiment aboard the PAZ Low Earth Orbiter (ROHP-PAZ) will test, for the first time, the new polarimetric radio occultation (RO) concept. This is a mission of opportunity: The Spanish Ministry of Science and Innovation (MICINN) approved in 2009 a proposal to include a polarimetric Global Navigation Satellite System (GNSS) RO payload on board of the Spanish Earth Observation satellite PAZ. The launch of the satellite is scheduled for October 2015, and it will be followed by a 6-month commissioning phase period and has an expected life of 7 years, with a goal of 10 years.The concept is similar to that used in some polarimetric weather radars: to measure the differential phase shift between the two polarimetric components of the received signal, although in this case we will use the forward scattering geometry instead of the backscattering one. It will allow us to retrieve precipitation and other hydrometeors information, and simultaneous thermodynamic vertical profiles which will help to the understanding of the thermodynamic processes beyond heavy rain events. A sensitivity analysis has been performed, showing that the rain-induced effect is above PAZ detectability threshold in 90% of the events with along-ray averaged rain rate higher than 5 mm/h. Also, a ground field campaign has been conducted prior to the launch of the satellite. The measurements from the campaign have shown the first experimental evidences that precipitation and frozen hydrometeors induce a noticeable effect into the polarimetric RO observables. We will present here the actual status of the mission and the results from the field campaign. We will also discuss the results of the theoretical study of the thermodynamics and the effects of rain and frozen hydrometeors into standard and polarimetric RO, based on a large collocation exercise of COSMIC and TerrasSar-X with TRMM, GPM and CloudSat.

  14. Dovyrenite Ca6Zr[Si2O7]2(OH)4 - A New Mineral from Skarned Carbonate Xenoliths in Basic-Ultrabasic Rocks of the Ioko-Dovyren Massif, Northern Baikal Region, Russia

    NASA Astrophysics Data System (ADS)

    Galuskin, Evgeny V.; Pertsev, Nikolai N.; Armbruster, Thomas; Kadiyski, Milen; Zadov, Aleksander E.; Galuskina, Irina O.; Dzierżanowski, Piotr; Wrzalik, Roman; Kislov, Evgeny V.

    2007-01-01

    Dovyrenite, simplified formula Ca6Zr[Si2O7]2(OH)4, occurs as an accessory mineral in vein skarns developed in carbonate xenoliths in subvolcanic layered plagiodunite-troctolite series in the Ioko-Dovyren Massif of Proterozoic age, Northern Baikal Region, Buryatia, Russia. Dovyrenite is a late mineral of altered pyroxene and melilite-monticellite skarns. Associated minerals are Zr-bearing phases: fassaitic pyroxene, perovskite and hydrogarnets; and also monticellite, vesuvianite, diopside, foshagite, brucite, calzirtite, tazheranite, baghdadite, apatite, calcite, native bismuth, sphalerite, selenian galena, clausthalite, safflorite, rammelsbergite, pyrrhotite, pentlandite, valleriite, laitakarite, nickeline, nickel-skutterudite. The average structure of dovyrenite is orthorhombic, space group Pnnm, with subcell parameters A = 5.666(16) Å, B = 18.844(5) Å, C = 3.728(11) Å, V = 398.0(2) Å3 and Z = 1. Dovyrenite shows a new type of modular structure with stacking of the tobermorite-like and the rosenbuschite-like layers parallel to (010). Single-crystal structural data point to an incompletely occupied Ca(2) site from the rosenbuschite module which is confirmed by microprobe analyses: ZrO2 16.47, SiO2 32.83, TiO2 0.14, HfO2 0.16, Cr2O3 0.01, CaO 43.87, FeO 0.25, MgO 0.13, MnO 0.02, Nb2O3 0.03; total 99.38 wt% with calculated H2O. The empirical formula is (Ca5.73Fe0.03Mg0.02)σ5.78(Zr0.98Hf0.01Ti0.01)σ1Si4(O13.56OH0.44)σ14(OH)4. The presence of two types of OH group in the dovyrenite structure is corroborated by FTIR and Raman spectroscopy. Dovyrenite is an optically positive biaxial mineral: α 1.659(2), β 1.660(2); γ 1.676(2); 2Vz 30(5)° (measured), 28° (calculated). The coexistence of monticellite, foshagite and dovyrenite points to a narrow interval of crystallization 560-630°C under subvolcanic conditions (P < 108 Pa).

  15. Bloom of Cochlodinium polykrikoides (Dinophyceae: Gymnodiniales) in Bahía de La Paz, Gulf of California.

    PubMed

    Gárate-Lizárraga, Ismael

    2013-02-15

    As part of a continuing toxic microalgae monitoring program, phytoplankton samples were collected on 16-17 August 2012 at several sampling sites in the southern part of the Bahía de La Paz. A bloom of the dinoflagellate Cochlodinium polykrikoides was detected. Abundance of C. polykrikoides ranged from 73 to 276×10(3) cells L(-1) on the first day to 980-1425×10(3) cells L(-1) on the second day. Study of live specimens showed great variation in cell size and form, mainly as single cells or chains of two cells. Live cells were 30-47 μm long and 20-35 μm wide (n=30). Seawater temperature during the bloom was 29-30°C. Low densities of Cochlodinium convolutum, Cochlodinium helicoides, and Cochlodinium shuettii were also found in the samples of the bloom event. These high densities of C. polykrikoides did not lead to fish die-offs in the bay. PMID:23290658

  16. [Evolution of salaries and the price of food and domestic fuels in the city of La Paz (1975-1985)].

    PubMed

    Laure, J

    1987-03-01

    An analysis was performed on the variations of the food purchasing power of the average industry wage during the period comprised between 1975 and 1984 (increase of 7%), and of the minimum wage between November 1982 and August 1985 (decline of 73%). Development of retail prices in La Paz, for the main food groups, beverages and fuels, was analyzed over the same periods. Variations in work time, paid at average industry wage or at minimum wage, needed to acquire such foodstuffs, beverages or fuels, were also carefully studied. Similarly, development of the cost of calories and proteins was examined. Trends in accessibility of calories and proteins are described. Between 1975 and 1984 these included: a progressive decline in the number of foods that are sources of "cheap" or "very cheap" calories; the same trend was observed with regard to foods which are sources of "cheap" or "very cheap" proteins: A decline in their number and even the disappearance of any source of "very cheap" proteins, and an ever-increasing dependence on agro-industry and foreign imports (notably wheat). Finally, some proposals are made for the purpose of contributing to the establishment of food and nutrition planning. In particular, suggestion is made to automatically reevaluate the minimum wage on the basis of monetary inflation, in order to maintain at least the food purchasing power of the minimum wage. Maintaining this purchasing power greatly determines the nutritional status of the wage-earning population which purchases the most essential foodstuffs.

  17. Differential distribution of diatoms and dinoflagellates in a cyclonic eddy confined in the Bay of La Paz, Gulf of California

    NASA Astrophysics Data System (ADS)

    Coria-Monter, Erik; Monreal-Gómez, María. Adela; Salas-de-León, David Alberto; Aldeco-Ramírez, Javier; Merino-Ibarra, Martín.

    2014-09-01

    The differential distribution of diatoms and dinoflagellates in the Bay of La Paz, Gulf of California, Mexico, was analyzed in summer of 2009, when a cyclonic eddy confined in the bay dominated the circulation. An uplift of the nutricline in the eddy drove high concentrations of nutrients to the euphotic layer. A differential phytoplankton distribution was observed to be associated with the eddy: there was an abundance of dinoflagellates close to the center of the cyclonic eddy, whereas diatoms were more abundant at the periphery. A significant inverse correlation (R = -0.62, p < 0.002) was found between the temperature at 25 m depth and the dinoflagellates abundance. Based on the temporal evolution of chlorophyll measured by MODIS satellite images, and a conceptual model proposed for the lifecycle of eddies, the cyclonic eddy may have been an old decaying structure. The effect of the cyclonic eddy on the phytoplankton distribution in this small semienclosed region was apparently similar to that found in larger eddies in the open ocean, but this is the first time such a differential distribution has been found associated to a confined eddy.

  18. High Resolution Simulations of a Severe Hail Storm and Flooding Event over La Paz city with WRF

    NASA Astrophysics Data System (ADS)

    Zamuriano, Marcelo; Brönnimann, Stefan

    2016-04-01

    On February 19, 2002 a very local hail storm and a flash flood episode occurred in La Paz city, Bolivia. About 40 millimeters of precipitation in over an hour was observed, it was the strongest rainfall registered until that date. This event caused at least 69 causalities and important damages to the city's infrastructure, being considered as an exceptional natural disaster. It is thought that the vertical humid air motion driven by the high surface temperatures and topographical forcing is the responsible of such event, nevertheless a formal study about the atmospheric features leading to this episode has not been done yet. In order to overcome this issue, a series of high resolution numerical experiments with the WRF-ARW model is conducted using two global datasets: GFS and ECMWF. Several micro-physics schemes are used in a four-nested domain configuration with 2 kilometers as finest resolution, giving more details about the effects topography on this event. Overall, high-resolution simulations improves the spatial distribution of rainfall and represents better the local atmospheric circulation leading to this extreme event.

  19. Yuma District Resource Management Plan, Yuma, La Paz, and Mohave Counties, Arizona and San Bernardino, Riverside and Imperial Counties, California

    SciTech Connect

    Not Available

    1985-08-01

    Implementation of a resource management plan is proposed for 1.2 million acres within the 2.7-million-acre Yuma District, located in Yuma, La Paz, and Mohave counties, Arizona and San Bernardino, Riverside, and Imperial counties, California. Under the preferred alternative, wildlife habitat would be a priority consideration on approximately 247,740 acre, and nine special management areas would be designated. A portion of the Cactus Plain and the Chemehuevi/Needles wilderness study areas would be recommended for wilderness designation. Two areas totaling 31,360 acres would be designated as special management areas, and another six areas totaling 155,705 acres would be managed to protect their natural values. Livestock grazing would be authorized at 3998 animal unit months on four allotments. Approximately 55,490 acres of federal lands would be available for disposal and 31,220 acres would be acquired. Nine utility corridors and nine communication sites would be designated. Existing recreational facilities would be maintained, with additional facilities provided when warranted. Along Parker Strip, only floodproofed day-use facilities would be allowed within the 100-year flood plain. Off-road vehicle (ORV) use designations would be made on 640 acres and ORV use in the remainder of the district would be limited to existing roads and trails. Continuous occupancy of mobile home sites would be restricted to one five-month period in a single year. Permanent residential use would be phased out.

  20. Computational analysis of siRNA recognition by the Ago2 PAZ domain and identification of the determinants of RNA-induced gene silencing.

    PubMed

    Kandeel, Mahmoud; Kitade, Yukio

    2013-01-01

    RNA interference (RNAi) is a highly specialized process of protein-siRNA interaction that results in the regulation of gene expression and cleavage of target mRNA. The PAZ domain of the Argonaute proteins binds to the 3' end of siRNA, and during RNAi the attaching end of the siRNA switches between binding and release from its binding pocket. This biphasic interaction of the 3' end of siRNA with the PAZ domain is essential for RNAi activity; however, it remains unclear whether stronger or weaker binding with PAZ domain will facilitate or hinder the overall RNAi process. Here we report the correlation between the binding of modified siRNA 3' overhang analogues and their in vivo RNAi efficacy. We found that higher RNAi efficacy was associated with the parameters of lower Ki value, lower total intermolecular energy, lower free energy, higher hydrogen bonding, smaller total surface of interaction and fewer van der Waals interactions. Electrostatic interaction was a minor contributor to compounds recognition, underscoring the presence of phosphate groups in the modified analogues. Thus, compounds with lower binding affinity are associated with better gene silencing. Lower binding strength along with the smaller interaction surface, higher hydrogen bonding and fewer van der Waals interactions were among the markers for favorable RNAi activity. Within the measured parameters, the interaction surface, van der Waals interactions and inhibition constant showed a statistically significant correlation with measured RNAi efficacy. The considerations provided in this report will be helpful in the design of new compounds with better gene silencing ability.

  1. An ethnobotanical survey of medicinal plants commercialized in the markets of La Paz and El Alto, Bolivia.

    PubMed

    Macía, Manuel J; García, Emilia; Vidaurre, Prem Jai

    2005-02-28

    An ethnobotanical study of medicinal plants marketed in La Paz and El Alto cities in the Bolivian Andes, reported medicinal information for about 129 species, belonging to 55 vascular plant families and one uncertain lichen family. The most important family was Asteraceae with 22 species, followed by Fabaceae s.l. with 11, and Solanaceae with eight. More than 90 general medicinal indications were recorded to treat a wide range of illnesses and ailments. The highest number of species and applications were reported for digestive system disorders (stomach ailments and liver problems), musculoskeletal body system (rheumatism and the complex of contusions, luxations, sprains, and swellings), kidney and other urological problems, and gynecological disorders. Some medicinal species had magic connotations, e.g. for cleaning and protection against ailments, to bring good luck, or for Andean offerings to Pachamama, 'Mother Nature'. In some indications, the separation between medicinal and magic plants was very narrow. Most remedies were prepared from a single species, however some applications were always prepared with a mixture of plants, e.g. for abortion, and the complex of luxations and swellings. The part of the plant most frequently used was the aerial part (29.3%) and the leaves (20.7%). The remedies were mainly prepared as a decoction (47.5%) and an infusion (28.6%). Most of species were native from Bolivia, but an important 36.4% of them were introduced from different origins. There exists a high informant consensus for species and their medicinal indications. The present urban phytotherapy represents a medicinal alternative to treat main health problems and remains closer to the cultural and social context of this society. PMID:15707774

  2. Blood lead concentrations in wild birds from a polluted mining region at Villa de La Paz, San Luis Potosi, Mexico.

    PubMed

    Chapa-Vargas, Leonardo; Mejia-Saavedra, Jose J; Monzalvo-Santos, Karina; Puebla-Olivares, Fernando

    2010-01-01

    This investigation was undertaken to determine the concentrations of lead in bird blood samples from a mining region in central Mexico and to compare concentrations among several different feeding guilds. The study took place in the Mexican state of San Luis Potosi in a region known as "Villa de la Paz." This is one of the most intensely exploited mining regions in central Mexico and has been actively mined for over four centuries. Lead concentrations from bird blood samples taken from four polluted sites were significantly higher than those from a control, unpolluted site (F = 6.3, P < 0.0002). Similarly, mean blood lead concentrations in birds from a highly polluted site were higher than those from a site that has intermediate pollution levels (P < 0.05). In addition, samples from insectivorous birds had significantly lower lead concentrations compared to granivores, frugivores-insectivores, and omnivores (F = 4.86, P = 0.004), and a large proportion of all individuals had blood lead concentrations indicative of low, sub-lethal toxic effects. Finally, in two polluted sites, remarkably small numbers of insectivore-frugivores, and granivores were trapped, and in one polluted site a large number of insectivores was trapped (X(2) = 29.9, P = 0.03), and no differences in proportions of migrants and non-migrants were found among sampling sites (X(2) = 0.6, P = 0.96). To date, it has not been determined to what extent constant exposure to these levels of pollution can influence health at the individual level, lifespan, and, therefore, population demography of birds from this region.

  3. Suppression of RNA silencing by Flock house virus B2 protein is mediated through its interaction with the PAZ domain of Dicer.

    PubMed

    Singh, Gatikrushna; Popli, Sonam; Hari, Yukti; Malhotra, Pawan; Mukherjee, Sunil; Bhatnagar, Raj K

    2009-06-01

    RNA silencing is a conserved pathway that functions as an antiviral mechanism. The majority of viruses encode silencing suppressors that interfere with siRNA- and miRNA-guided silencing pathways. The insect flock house virus B2 protein (FHVB2) functions as an RNAi silencing suppressor that inhibits siRNA biogenesis. Here, we describe the generation of a GFP silent sensor line (Sf21) and a GFP sensor line expressing FHVB2 to study RNAi suppression mechanisms. Overexpression of FHVB2 resulted in suppression of GFP-RNAi and resumption of GFP expression. Protein fractionation studies with FHVB2-transfected cells showed that FHVB2 associates with a high-molecular-weight complex of Dicer and dsRNA/siRNAs. Yeast two-hybrid and pulldown assays revealed an interaction between FHVB2 and Drosophila Dicer proteins that appeared to involve PAZ domains. To map the FHVB2 domains interacting with Dicer, we used a 17-residue C-terminal deletion mutant. RNAi suppression was reversed in cells transfected with the FHVB2 mutant as revealed by loss of GFP. Additional yeast two-hybrid and in vitro pulldown assays confirmed that the C-terminal region of FHVB2 was involved in the interaction with the PAZ domains of Dicers. These results thus reveal a novel interaction between FHVB2 and Dicer that leads to suppression of siRNA biogenesis.

  4. Conceptualization of groundwater flow of a coastal arid aquifer using isotopic and chemical tools: La Paz, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Tamez-Melendez, Carol; Hernández-Antonio, Arturo; Mahlknecht, Jürgen

    2016-04-01

    Groundwater from the La Paz coastal aquifer in Baja California Sur, Mexico, is the main source of drinking water for the local population. Due to its proximity to the coast, sea water intrusion is the main factor of salinization of groundwater. Other geochemical processes also affect the quality of the aquifer threating its vulnerability. Forty-seven samples were analyzed for ion chemistry and isotopes. A hierarchical cluster analysis was performed for a better interpretation resulting in three main groups and proved for geographical correspondence. Deuterium and d18O ranged from -82 to -52.1 and from -11.6 to -7 permil, respectively, showing that the main recharge originates in the Sierra el Novillo, flowing toward SE-NW direction and in accordance to deuterium excess (d) high evaporation effects (d>10‰) are mostly in the middle portion of the study area and in El Centenario due to high kinetic isotope fractioning related to elevated temperatures. Hydrogeochemistry analyses demonstrated salinization mainly due to sea water intrusion and in second instance due water-rock interaction, where enrichment of Na+ (ranges from 35.7 to 1089 mg/L-1) was present in some samples probably due to weathering of silicates and/or cation exchange in soils with Ca2+ (27.7 to 658 mg/L-1) at clay-surfaces. High concentrations of NO3-2 (ranges from 1.4 to 48.8 mg/L-1), Cl- (ranges from 54.4 to 2960 mg/L-1) and Na+ show that anthropogenic input is mainly coming from an agricultural area (El Centenario-Chametla) where heavy groundwater extractions are made for irrigational purposes, lowering the groundwater table up to 10 m and consequently promoting upconing and salinity concentrations (NaCl). Carbon-13 and radiocarbon ranged from -12.3 to -9.1‰ and from 29.5 to 100.4 pmC, respectively. Distribution of ages (up to ~5000 years) indicates two flow trends (E-W and SE-NW).

  5. Time-series measurements of settling particulate matter in Alfonso Basin, La Paz Bay, southwestern Gulf of California

    NASA Astrophysics Data System (ADS)

    Silverberg, Norman; Aguirre-Bahena, Fernando; Mucci, Alfonso

    2014-08-01

    More than 200 sediment trap samples were collected at 310 or 360 m depth during 2002-2009 from the center of the 410 m-deep Alfonso Basin in La Paz Bay, an arid, subtropical embayment of the southern Gulf of California. Sample splits were analyzed for total mass flux (TMF), particulate organic carbon (POC), inorganic carbon (CaCO3) and opal (biogenic silica BioSi). The lithogenic (Litho) and biogenic fluxes (Biogen), but especially the particulate organic matter (POM) and CaCO3, fluxes are relatively high compared with those recorded in a number of other coastal basins at depths less than ~500 m. The average yearly Litho fluxes (mean of 133±158 g m-2 yr-1) are well correlated with the frequency of strong wind gusts and reflect the relative proximity of the mooring to shore and the importance of eolian transport. The sedimentation patterns are influenced by monsoonal shifts-cool temperatures and strong northerly winds in late fall and winter sustain a well-mixed deep surface layer and high lithogenic fluxes, whereas progressive heating and relatively weak southerlies in summer and fall lead to a shallower, more-stratified surface layer with lower nutrient levels, limited productivity and generally low particulate fluxes. There is considerable interannual variability in the size of the various fluxes. This is likely related to a number of regional and internal factors whose timing, intensity and interactions remain to be resolved. Although there is an inverse relationship between SST and satellite-derived net primary production (NPP) estimates, no correlation was found between NPP and the POC, CaCO3 and BioSi fluxes (r2<0.05 and p>0.05). Significant correlations (p<0.001) do exist, however, between the POC flux and the total mineral flux as well as with the CaCO3, Litho and BioSi fluxes (r=0.86, 0.82, 0.79 and 0.69, respectively). As suggested by the ballast ratio hypothesis, the strength of these correlations follows the relative density of the individual ballast

  6. Mineralogy, Petrology and Oxygen Fugacity of the LaPaz Icefield Lunar Basaltic Meteorites and the Origin of Evolved Lunar Basalts

    NASA Technical Reports Server (NTRS)

    Collins, S. J.; Righter, K.; Brandon, A. D.

    2005-01-01

    LAP 02205 is a 1.2 kg lunar mare basalt meteorite found in the Lap Paz ice field of Antarctica in 2002 [1]. Four similar meteorites were also found within the same region [1] and all five have a combined mass of 1.9 kg (LAP 02224, LAP 02226, LAP 02436 and LAP 03632, hereafter called the LAP meteorites). The LAP meteorites all contain a similar texture, mineral assemblage, and composition. A lunar origin for these samples comes from O isotopic data for LAP 02205 [1], Fe/Mn ratios of pyroxenes [1-5], and the presence of distinct lunar mineralogy such as Fe metal and baddeleyite. The LAP meteorites may represent an area of the Moon, which has never been sampled by Apollo missions, or by other lunar meteorites. The data from this study will be used to compare the LAP meteorites to Apollo mare basalts and lunar basaltic meteorites, and will ultimately help to constrain their origin.

  7. [Complete process of implantation of a nutritional risk screening system in the University Hospital La Paz, Madrid].

    PubMed

    Gómez-Candela, Carmen; Serrano Labajos, Ruth; García-Vazquez, Natalia; Valero Pérez, Marlhyn; Morato Martínez, Marina; Santurino Fontecha, Cristina; González Madroño, Ana; Palma-Milla, Samara

    2013-11-01

    La malnutrición asociada a la enfermedad (MAE) está presente en un porcentaje muy elevado de los pacientes que ingresan en los hospitales y su repercusión es diversa y de mucha trascendencia. Objetivo. Desde la Unidad de Nutrición del Hospital Universitario la Paz, en colaboración con todos los miembros de la Comisión de Nutrición, nos planteamos implantar algún método de cribado en nuestro centro, que permitiese abarcar al mayor número posible de pacientes. Resultados. Debido al gran tamaño de nuestro centro, con cerca de 1500 camas, unido a una escasez de recursos humanos en nuestra unidad, optamos por utilizar el sistema de cribado CONUT (Control Nutricional) 100 % automático y basado en parámetros analíticos, muy fácil de manejar, de bajo coste y cuya validez está confirmada, adaptándolo a nuestras necesidades. El método recoge información de las bases de datos del servicio de Admisión (filiación, edad, fecha) y del Laboratorio (albúmina, colesterol, linfocitos totales) y genera, en el informe de resultados de los análisis clínicos, la información sobre la alerta de riesgo nutricional de cada paciente, así como las recomendaciones nutricionales a seguir en función del riesgo detectado en cada caso. Para llegar su implantación se llevaron a cabo diferentes evaluaciones que nos permitieron conocer previamente la carga extra de trabajo que podría generar su implantación y nuestra capacidad para asumirlas, así como numerosas actividades formativas encaminadas a que los médicos y profesionales sanitarios del hospital asumieran cada vez más responsabilidades en el proceso del tratamiento nutricional de sus pacientes. Este sistema de cribado funciona desde Junio del año 2010 y detecta riesgo de desnutrición en el 32 % de los pacientes evaluados. En general, sólo en los casos en los que la alerta corresponde a una situación de Alto riesgo nutricional, hecho que se da aproximadamente en el 10 % del total, se requirió la intervenci

  8. Garnets in porphyry-skarn systems: A LA-ICP-MS, fluid inclusion, and stable isotope study of garnets from the Hongniu-Hongshan copper deposit, Zhongdian area, NW Yunnan Province, China

    NASA Astrophysics Data System (ADS)

    Peng, Hui-juan; Zhang, Chang-qing; Mao, Jing-wen; Santosh, M.; Zhou, Yun-man; Hou, Lin

    2015-05-01

    The Late Cretaceous Hongniu-Hongshan porphyry-skarn copper deposit is located in the Zhongdian area of northwestern Yunnan Province, China. Garnets from the deposit have compositions that range from Adr14Grs86 to almost pure andradite (Adr98Grs2) and display two different styles of zoning. The garnets are predominantly of magmatic-hydrothermal origin, as is evidenced by their 18Ofluid (5.4-6.9‰) and low Dfluid (-142‰ to -100‰) values, both of which likely result from late-stage magmatic open-system degassing. Three generations of garnet have been identified in this deposit: (1) Al-rich garnets (Grt I; Adr22-57Grs78-43) are anisotropic, have sector dodecahedral twinning, are slightly enriched in light rare earth elements (LREEs) compared with the heavy rare earth elements (HREEs), have negative or negligible Eu anomalies, and contain high concentrations of F. Fluid inclusions within these Al-rich garnets generally have salinities of 12-39 wt.% NaCl eq. and have liquid-vapor homogenization temperatures (Th) of 272-331 °C. The Grt I are most likely associated with low- to medium-salinity fluids that were generated by the contraction of an ascending vapor phase and that formed during diffusive metasomatism caused by pore fluids equilibrating with the host rocks at low W/R (water/rock) ratios. These garnets formed as a result of the high F activity of the system, which increased the solubility of Al within the magmato-hydrothermal fluids in the system. (2) Fe-rich garnets (Adr75-98Grs25-2) have trapezohedral faces, and are both anisotropic with oscillatory zoning and isotropic. These second-generation Fe-rich garnets (Grt II) have high ΣREE concentrations, are LREE-enriched and HREE-depleted, and generally have positive but variable Eu anomalies. All of the Fe-rich garnets contain high-salinity fluid inclusions with multiple daughter minerals with salinities of 33-80 wt.% NaCl eq. Some of them show higher temperatures of halite dissolution (465-591 °C) than

  9. Antioxidant enzymes and heavy metal levels in tissues of the black chocolate clam Megapitaria squalida in Bahía de La Paz, Mexico.

    PubMed

    Cantú-Medellín, Nadiezhda; Olguín-Monroy, Norma O; Méndez-Rodríguez, Lía C; Zenteno-Savín, Tania

    2009-01-01

    The black chocolate clam Megapitaria squalida is a commercially important bivalve along the Pacific coast of Mexico and is used as a bioindicator in environmental health studies. Previous studies of Bahía de La Paz indicated significant differences in heavy metal content among localities in this clam. To identify areas affected by heavy metal pollution, lipid peroxidation (TBARS) levels and activity of superoxide dismutase (SOD) and glutathione S-transferase (GST) were measured in muscle, gonad, and digestive gland tissue and correlated with heavy metal levels of clams from six localities along the shore of the bay. Significant differences in TBARS levels and antioxidant enzyme activity were found among these tissues at all localities. Such differences are ascribed to the physiology of each organ. Higher levels of TBARS were found in areas with higher cadmium content. SOD activity in muscle correlated positively with cadmium, lead, and iron in areas with a higher content of those elements. This study suggests that TBARS levels and SOD and GST activity are affected by biotic and abiotic factors and have potential as indicators of heavy metal contamination.

  10. D-Isonucleotide (isoNA) incorporation around cleavage site of passenger strand promotes the vibration of Ago2-PAZ domain and enhances in vitro potency of siRNA.

    PubMed

    Huang, Ye; Tian, Miao; Zhang, Yichao; Sheng, Gang; Chen, Zhuo; Ma, Yuan; Chen, Yue; Peng, Yihong; Zhao, Yi-Lei; Wang, Yanli; Zhang, Lihe; Yang, Zhenjun

    2015-11-28

    It has been demonstrated that passenger strand cleavage is important for the activation of RNA-induced silencing complex (RISC), which is a crucial step for siRNA-mediated gene silencing. Herein, we report that isonucleotide (isoNA) modification around the cleavage site of the passenger strand would affect the in vitro potency of modified siRNAs by altering the motion pattern of the Ago2-PAZ domain. According to western blotting, q-PCR and antiviral test results, we proved that D-isonucleotide (isoNA) modification at the position 8 of the passenger strand (siMek1-S08D), which is adjacent to the cleavage site, markedly improved the in vitro potency of the modified siRNA, whereas siRNAs with D-isoNA incorporation at position 9 (siMek1-S09D) or L-isoNA incorporation at positions 8 and 9 (siMek1-S08L, siMek1-S09L) displayed lower activity compared to native siRNA. Kinetics evaluation of passenger strand cleavage induced by T. thermophilus Ago (Tt-Ago) showed that D-isoNA modification at position 8 of the passenger strand had no significant influence on the cleavage rate, but L-isoNA modification at position 8 slowed the cleavage rate markedly. Moreover, the results of molecular dynamics simulations showed that D-isoNA modification at position 8 affected the open-close motion of the PAZ domain in the Ago/siRNA complex, which may promote the loading of RISC and release of a passenger strand cleavage product, and consequently accelerate the activation of RISC and enhance silencing activity. However, D-isoNA modification at position 9 or L-isoNA modification at position 8 or 9 exerted opposite influences on the motion of the Ago-PAZ domain.

  11. A Rb-Sr and Sm-Nd Isotope Geochronology and Trace Element Study of Lunar Meteorite LaPaz Icefield 02205

    NASA Technical Reports Server (NTRS)

    Rankenburg, K.; Brandon, A. D.; Norman, M. D.

    2007-01-01

    Rubidium-strontium and samarium-neodymium isotopes of lunar meteorite LaPaz Icefield (LAP) 02205 are consistent with derivation of the parent magma from a source region similar to that which produced the Apollo 12 low-Ti olivine basalts followed by mixing of the magma with small amounts (1 to 2 wt%) of trace element-enriched material similar to lunar KREEP-rich sample SaU 169. The crystallization age of LAP 02205 is most precisely dated by an internal Rb-Sr isochron of 2991+/-14 Ma, with an initial Sr-87/Sr-88 at the time of crystallization of 0.699836+/-0.000010. Leachable REE-rich phosphate phases of LAP 02205 do not plot on a Sm-Nd mineral isochron, indicating contamination or open system behavior of the phosphates. Excluding anomalous phases from the calculation of a Sm-Nd isochron yields a crystallization age of 2992+/-85 (initial Epsilon Nd-143 = +2.9+/-0.8) that is within error of the Rb-Sr age, and in agreement with other independent age determinations for LAP 02205 from Ar-Ar and U-Pb methods. The calculated Sm-147/Nd-144 source ratios for LAP 02205, various Apollo 12 and 15 basalts, and samples with strong affinities to KREEP (SaU 169, NWA 773, 15386) are uncorrelated with their crystallization ages. This finding does not support the involvement of a common KREEP component as a heat source for lunar melting events that occurred after crystallization of the lunar magma ocean.

  12. Local structure of disordered Au-Cu and Au-Ag alloys

    NASA Astrophysics Data System (ADS)

    Frenkel, A. I.; Machavariani, V. Sh.; Rubshtein, A.; Rosenberg, Yu.; Voronel, A.; Stern, E. A.

    2000-10-01

    X-ray-absorption fine structure (XAFS) and x-ray-diffraction (XRD) measurements of disordered alloys AuxCu1-x and Au0.5Ag0.5 prepared by melt spinning were performed. In the Au0.5Ag0.5 alloy, no significant local deviations of the atoms from the average fcc lattice were detected while in AuxCu1-x alloys, significant deviations of atoms from the average fcc lattice were found. Mean-square vibrations of the Cu-Cu distances revealed by the XAFS in AuxCu1-x alloys indicate the weakening of contact between Cu atoms in the dilute limit. Our computer simulation for AuxCu1-x clusters of 105 atoms reproduces the main features of both the XAFS and XRD data.

  13. Crystalline monolayer surface of liquid Au-Cu-Si-Ag-Pd: Metallic glass former

    SciTech Connect

    Mechler, S; Yahel, E; Pershan, P S; Meron, M; Lin, B

    2012-02-06

    It is demonstrated by means of x-ray synchrotron reflectivity and diffraction that the surface of the liquid phase of the bulk metallic glass forming alloy Au49Cu26.9Si16.3Ag5.5Pd2.3 consists of a two-dimensional crystalline monolayer phase for temperatures of up to about 50 K above the eutectic temperature. The present alloy as well as glass forming Au82Si18 and Au-Si-Ge alloys containing small amounts of Ge are the only metallic liquids to exhibit surface freezing well above the melting temperature. This suggests that the phenomena of surface freezing in metallic liquids and glass forming ability are related and probably governed by similar physical properties.

  14. Origin of epithermal Ag-Au-Cu-Pb-Zn mineralization in Guanajuato, Mexico

    NASA Astrophysics Data System (ADS)

    Mango, Helen; Arehart, Greg; Oreskes, Naomi; Zantop, Half

    2014-01-01

    The Guanajuato epithermal district is one of the largest silver producers in Mexico. Mineralization occurs along three main vein systems trending dominantly northwest-southeast: the central Veta Madre, the La Luz system to the northwest, and the Sierra system to the east. Mineralization consists dominantly of silver sulfides and sulfosalts, base metal sulfides (mostly chalcopyrite, galena, sphalerite, and pyrite), and electrum. There is a broad zonation of metal distribution, with up to 10 % Cu+Pb+Zn in the deeper mines along the northern and central portions of the Veta Madre. Ore occurs in banded veins and breccias and as stockworks, with gangue composed dominantly of quartz and calcite. Host rocks are Mesozoic sedimentary and intrusive igneous rocks and Tertiary volcanic rocks. Most fluid inclusion homogenization temperatures are between 200 and 300 °C, with salinities below 4 wt.% NaCl equivalent. Fluid temperature and salinity decreased with time, from 290 to 240 °C and from 2.5 to 1.1 wt.% NaCl equivalent. Relatively constant fluid inclusion liquid-to-vapor ratios and a trend of decreasing salinity with decreasing temperature and with increasing time suggest dilution of the hydrothermal solutions. However, evidence of boiling (such as quartz and calcite textures and the presence of adularia) is noted along the Veta Madre, particularly at higher elevations. Fluid inclusion and mineralogical evidence for boiling of metal-bearing solutions is found in gold-rich portions of the eastern Sierra system; this part of the system is interpreted as the least eroded part of the district. Oxygen, carbon, and sulfur isotope analysis of host rocks, ore, and gangue minerals and fluid inclusion contents indicate a hydrothermal fluid, with an initial magmatic component that mixed over time with infiltrating meteoric water and underwent exchange with host rocks. Mineral deposition was a result of decreasing activities of sulfur and oxygen, decreasing temperature, increasing pH, and, in places, boiling.

  15. Plasmon Modes Induced by Anisotropic Gap Opening in Au@Cu2 O Nanorods.

    PubMed

    Zhang, Shouren; Jiang, Ruibin; Guo, Yanzhen; Yang, Baocheng; Chen, Xiao-Lan; Wang, Jianfang; Zhao, Yufen

    2016-08-01

    Integration of semiconductors with noble metals to form heteronanostructures can give rise to many interesting plasmonic and electronic properties. A number of such heteronanostructures have been demonstrated comprising noble metals and n-type semiconductors, such as TiO2 , ZnO, SnO2 , Fe3 O4 , and CuO. In contrast, reports on heteronanostructures made of noble metals and p-type semiconductors are scarce. Cu2 O is an unintentional p-type semiconductor with unique properties. Here, the uniform coating of Cu2 O on two types of Au nanorods and systematic studies of the plasmonic properties of the resultant core-shell heteronanostructures are reported. One type of Au nanorods is prepared by seed-mediated growth, and the other is obtained by oxidation of the as-prepared Au nanorods. The (Au nanorod)@Cu2 O nanostructures produced from the as-prepared nanorods exhibit two transverse plasmon peaks, whereas those derived from the oxidized nanorods display only one transverse plasmon peak. Through electrodynamic simulations the additional transverse plasmon peak is found to originate from a discontinuous gap formed at the side of the as-prepared nanorods. The existence of the gap is verified and its formation mechanism is unraveled with additional experiments. The results will be useful for designing metal-semiconductor heteronanostructures with desired plasmonic properties and therefore also for exploring plasmon-enhanced applications in photocatalysis, solar-energy harvesting, and biotechnologies.

  16. Plasmon Modes Induced by Anisotropic Gap Opening in Au@Cu2 O Nanorods.

    PubMed

    Zhang, Shouren; Jiang, Ruibin; Guo, Yanzhen; Yang, Baocheng; Chen, Xiao-Lan; Wang, Jianfang; Zhao, Yufen

    2016-08-01

    Integration of semiconductors with noble metals to form heteronanostructures can give rise to many interesting plasmonic and electronic properties. A number of such heteronanostructures have been demonstrated comprising noble metals and n-type semiconductors, such as TiO2 , ZnO, SnO2 , Fe3 O4 , and CuO. In contrast, reports on heteronanostructures made of noble metals and p-type semiconductors are scarce. Cu2 O is an unintentional p-type semiconductor with unique properties. Here, the uniform coating of Cu2 O on two types of Au nanorods and systematic studies of the plasmonic properties of the resultant core-shell heteronanostructures are reported. One type of Au nanorods is prepared by seed-mediated growth, and the other is obtained by oxidation of the as-prepared Au nanorods. The (Au nanorod)@Cu2 O nanostructures produced from the as-prepared nanorods exhibit two transverse plasmon peaks, whereas those derived from the oxidized nanorods display only one transverse plasmon peak. Through electrodynamic simulations the additional transverse plasmon peak is found to originate from a discontinuous gap formed at the side of the as-prepared nanorods. The existence of the gap is verified and its formation mechanism is unraveled with additional experiments. The results will be useful for designing metal-semiconductor heteronanostructures with desired plasmonic properties and therefore also for exploring plasmon-enhanced applications in photocatalysis, solar-energy harvesting, and biotechnologies. PMID:27374920

  17. The impact of hurricanes on sedimenting particulate matter in the semi-arid Bahía de La Paz, Gulf of California

    NASA Astrophysics Data System (ADS)

    Silverberg, Norman; Shumilin, Evgueni; Aguirre-Bahena, Fernando; Rodríguez-Castañeda, Ana Patricia; Sapozhnikov, Dmitry

    2007-11-01

    From 2002 through 2004, time-series sediment trap samples were collected from a depth of 410 m in Cuenca Alfonso, Bahía de La Paz, on the SW coast of the Gulf of California. The instrument recorded the impact of the local passage of hurricanes "Ignacio" (24-26 August) and "Marty" (21-23 September) in 2003. These two events accounted for 82% of the total rainfall measured in 2003, equivalent to the annual average precipitation in years without hurricanes. Mean total mass fluxes (TMFs) of 2.88 and 3.58 g m -2 d -1 were measured during the week of each hurricane as well as the following week. This may have been enough to produce a lamina in the underlying sediment with characteristics peculiar to such events. The terrigenous component was particularly abundant, with notably higher concentrations of Fe, Sc, Co and Cs and REEs. In contrast, TMFs throughout 2002-2004 (excluding the hurricane periods) averaged only 0.73 g m -2 d -1 and had a larger marine biogenic component. The extraordinary elemental fluxes during the 29 days of hurricane-influenced sedimentation represented a great proportion of the totals over an entire "normal" year: Co (67.8%) >Sc (62.6) >Fe (59.6) >Cs (53.4)>Lu (51.5)>La (51.3)>Yb (51.0)>Ce (49.5) >Tb (48.4) >Sm (44.7)>Cr (36.5) >Ca (31.0)>Eu (25.4%). The terrigenous fraction was calculated using (a) TMF minus the sum of CaCO 3, biogenic silica and organic matter and (b) the ratio of Sc in the trap samples to the average in the Earth's crust. The latter was consistently smaller, but the two methods offered similar results following hurricanes (78% vs. 63% , respectively). For normal sedimentation, however, the difference method yielded values twice as large as the Sc method (58% vs. 30%) This suggests that the mineralogy of the terrigenous fraction may also vary, with unsorted dessert soil being carried to sea by the powerful flash floods associated with hurricanes. Eolian supply of particles, particularly Sc-free quartz grains, possibly from

  18. Impact of urban contamination of the La Paz River basin on thermotolerant coliform density and occurrence of multiple antibiotic resistant enteric pathogens in river water, irrigated soil and fresh vegetables.

    PubMed

    Poma, Violeta; Mamani, Nataniel; Iñiguez, Volga

    2016-01-01

    La Paz River in Andean highlands is heavily polluted with urban run-off and further contaminates agricultural lowlands and downstream waters at the Amazon watershed. Agricultural produce at this region is the main source of vegetables for the major Andean cities of La Paz and El Alto. We conducted a 1 year study, to evaluate microbial quality parameters and occurrence of multiple enteropathogenic bacteria (Enterohemorrhagic E. coli-EHEC, Enteroinvasive E. coli or Shigella-EIEC/Shigella, Enteroaggregative E. coli-EAEC, Enteropathogenic E. coli-EPEC Enterotoxigenic E. coli-ETEC and Salmonella) and its resistance to 11 antibiotics. Four sampling locations were selected: a fresh mountain water reservoir (un-impacted, site 1) and downstream sites receiving wastewater discharges (impacted, sites 2-4). River water (sites 1-4, N = 48), and soil and vegetable samples (site 3, N = 24) were collected during dry (April-September) and rainy seasons (October-March). Throughout the study, thermotolerant coliform density values at impacted sites greatly exceeded the guidelines for recreational and agricultural water uses. Seasonal differences were found for thermotolerant coliform density during dry season in water samples nearby a populated and hospital compound area. In contrast to the un-impacted site, where none of the tested enteropathogens were found, 100 % of surface water, 83 % of soil and 67 % of vegetable samples at impacted sites, were contaminated with at least one enteropathogen, being ETEC and Salmonella the most frequently found. ETEC isolates displayed different patterns of toxin genes among sites. The occurrence of enteropathogens was associated with the thermotolerant coliform density. At impacted sites, multiple enteropathogens were frequently found during rainy season. Among isolated enteropathogens, 50 % were resistant to at least two antibiotics, with resistance to ampicillin, nalidixic acid, trimethoprim-sulfamethoxazole and tetracycline commonly

  19. Impact of urban contamination of the La Paz River basin on thermotolerant coliform density and occurrence of multiple antibiotic resistant enteric pathogens in river water, irrigated soil and fresh vegetables.

    PubMed

    Poma, Violeta; Mamani, Nataniel; Iñiguez, Volga

    2016-01-01

    La Paz River in Andean highlands is heavily polluted with urban run-off and further contaminates agricultural lowlands and downstream waters at the Amazon watershed. Agricultural produce at this region is the main source of vegetables for the major Andean cities of La Paz and El Alto. We conducted a 1 year study, to evaluate microbial quality parameters and occurrence of multiple enteropathogenic bacteria (Enterohemorrhagic E. coli-EHEC, Enteroinvasive E. coli or Shigella-EIEC/Shigella, Enteroaggregative E. coli-EAEC, Enteropathogenic E. coli-EPEC Enterotoxigenic E. coli-ETEC and Salmonella) and its resistance to 11 antibiotics. Four sampling locations were selected: a fresh mountain water reservoir (un-impacted, site 1) and downstream sites receiving wastewater discharges (impacted, sites 2-4). River water (sites 1-4, N = 48), and soil and vegetable samples (site 3, N = 24) were collected during dry (April-September) and rainy seasons (October-March). Throughout the study, thermotolerant coliform density values at impacted sites greatly exceeded the guidelines for recreational and agricultural water uses. Seasonal differences were found for thermotolerant coliform density during dry season in water samples nearby a populated and hospital compound area. In contrast to the un-impacted site, where none of the tested enteropathogens were found, 100 % of surface water, 83 % of soil and 67 % of vegetable samples at impacted sites, were contaminated with at least one enteropathogen, being ETEC and Salmonella the most frequently found. ETEC isolates displayed different patterns of toxin genes among sites. The occurrence of enteropathogens was associated with the thermotolerant coliform density. At impacted sites, multiple enteropathogens were frequently found during rainy season. Among isolated enteropathogens, 50 % were resistant to at least two antibiotics, with resistance to ampicillin, nalidixic acid, trimethoprim-sulfamethoxazole and tetracycline commonly

  20. Detection of Fracture Patterns Within the Southern Portion of a Residential Complex (Tepozanes), Los Reyes-La Paz County (Edo. de Mexico)

    NASA Astrophysics Data System (ADS)

    Chavez, R. E.; Arango, C.; Tejero, A.; Cifuentes, G.; Hernandez, E.

    2008-12-01

    Most of the urban zone within the Valley of Mexico is built on top of the sediments of the ancient lakes of Chalco, Xochimilco, Mexico, Texcoco, Xaltocan and Zumpango. The sediments that cover this great valley are mainly composed by highly saturated clay-sandy materials; which offer a weak resistance to the constructions built on top. In addition, the increasing need of water supply for the population living in the valley (~22 million inhabitants) has weakened the main groundwater aquifers. This has lead to a differentiated subsidence and collapse of buildings, habitation units and roads. These effects put in a serious risk the inhabitants and the infrastructure of the city. As an example, we present a case of an area located in a densely populated zone, within a low-income residential complex denominated Tepozanes. This is located in the Los Reyes-La Paz County (Mexico State), towards the southeastern portion of the Valley of Mexico. The area is geologically limited by the Chimalhuacan Hill to the N, by the Santa Catarina volcanic range to the S. The previously mentioned effects are evident in the constructions of some buildings, where an exposed fracture is found in the NE-SW direction. This feature is affecting the structure of one of them in the residential complex, where the fracture runs underneath. A geophysical study was proposed to characterize the subsoil and to define the fracturing patterns in the zone. The electrical resistivity tomography (ETR) method employing the capacitive and galvanic modes was used to define the fracturing patters and the position at depth of the saturated layers, which might affect the Residential buildings. As a complement, GPR (Ground Penetrating Radar) profiles were carried out on the same profiles to correlate the information obtained from the ETR capacitive method which has a better resolution in the shallower zone. The computed results show that the buildings foundations were set on top of a high resistivity layer (~1000

  1. The GNSS polarimetric radio-occultation technique to sense precipitation events: a new concept to be tested aboard PAZ Low Earth Satellite

    NASA Astrophysics Data System (ADS)

    Tomás, Sergio; Oliveras, Santi; Cardellach, Estel; Rius, Antonio

    2013-04-01

    The Radio Occultation and Heavy Precipitation (ROHP) experiment, to be conducted aboard the Spanish PAZ satellite, consists of a radio occultation (RO) mission provided with dual-polarization capabilities. The research with polarimetric RO data has the goal of assessing the capabilities and limitations of this technique to infer profiles of heavy precipitation. The technique aims to provide vertical profiles of precipitation simultaneously to the vertical profiles of thermodynamic parameters (standard RO products) perfectly collocated both in space and time. If successful, the polarimetric RO will represent the first technique able to provide these complementary information on precipitation. This is a relevant input for studies on heavy and violent rainfall events, which being poorly represented by the current-generation of Numerical Weather Prediction and General Circulation Models appear to be difficult to forecast on all time-scales. The Low Earth Orbiter hosting this experiment, to be launched in 2013, will orbit at 500 km altitude in a near-Polar orbit. The Radio Occulation payload includes a RO GNSS receiver and a dual polarization (H/V) limb oriented antenna to capture the signals of setting GNSS transmitters. NOAA and UCAR participate in the ground-segment of the radiometric experiment to enable near-real time dissemination of the level-1 standard RO products. The space-based GNSS RO technique scans the atmosphere vertically at fine resolution (close to 300 meter in the troposphere) by precisely measure the delay between a GNSS transmitter and a GNSS receiver aboard a Low Earth Orbiter, when the former is setting below or rising above the Earth limb. The standard, thermodynamical, products are extracted from the excess delay induced by the atmosphere at different layers. This presentation will not focus on this well-established application, but a novel concept using polarimetry to also retrieve rain information. The precipitation-measurement principle is

  2. Temporal variations of C, N, δ13C, and δ15N in organic matter collected by a sediment trap at Cuenca Alfonso, Bahía de La Paz, SW Gulf of California

    NASA Astrophysics Data System (ADS)

    Aguiñiga, Sergio; Sanchez, Alberto; Silverberg, Norman

    2010-09-01

    To monitor the composition and the vertical flux of particulate matter from the sea surface, a sediment trap was moored in Cuenca Alfonso, Bahía de La Paz, a zone of high productivity in the southwestern Gulf of California. Carbonate-free samples from 2002 to 2005 were analyzed for C org, N, δ13C, and δ15N. The results show seasonal and interannual variability, with the δ13C and δ15N values larger in spring and summer than in fall and winter. The C:N ratio and δ13C increased by 1.5 units from 2002 to 2003-2005, suggesting a change in the supply of organic matter and-or the use or preferential degradation of N org. There was no interannual variation in δ15N. The occasional high δ15N values suggest that physical mechanisms, such as the shoaling and advection into the bay of 15N-rich subsurface equatorial water, occur over short time periods. The latter is presumed to be related to the periodic development of a significant cyclonic gyre in the southern Gulf.

  3. Sulfur isotope and trace element systematics of zoned pyrite crystals from the El Indio Au-Cu-Ag deposit, Chile

    NASA Astrophysics Data System (ADS)

    Tanner, Dominique; Henley, Richard W.; Mavrogenes, John A.; Holden, Peter

    2016-04-01

    We present a comparative study between early, massive pyrite preceding (Cu-Ag) sulfosalt mineralization in high-temperature feeder zones (`early pyrite') and late pyrite that formed during silicic alteration associated with Au deposition (`late pyrite') at the El Indio high-sulfidation Au-Ag-Cu deposit, Chile. We use coupled in situ sulfur isotope and trace element analyses to chronologically assess geochemical variations across growth zones in these pyrite crystals. Early pyrite that formed in high-temperature feeder zones shows intricate oscillatory zonation of Cu, with individual laminae containing up to 1.15 wt% Cu and trace Co, As, Bi, Ni, Zn, Se, Ag, Sb, Te, Au, Pb and Bi. Late pyrite formed after (Cu-Ag) sulfosalt mineralization. It contains up to 1.14 wt% As with trace Cu, Zn, Pb, V, Mn, Co, Ni, Ge, Se, Ag, Sb, Te, Pb and Bi, as well as colloform Cu-rich growth bands containing vugs toward the outer edges of some crystals. Plotting the trace element data in chronological order (i.e., from core to rim) revealed that Co and Ni were the only elements to consistently co-vary across growth zones. Other trace elements were coupled in specific growth zones, but did not consistently co-vary across any individual crystal. The δ34S of early pyrite crystals in high-temperature feeder zones range from -3.19 to 1.88 ‰ (±0.5 ‰), consistent with sublimation directly from a high-temperature magmatic vapor phase. Late pyrite crystals are distinctly more enriched in δ34S than early pyrite (δ34S = 0.05-4.77 ‰, ±0.5 ‰), as a consequence of deposition from a liquid phase at lower temperatures. It is unclear whether the late pyrite was deposited from a small volume of liquid condensate, or a larger volume of hydrothermal fluid. Both types of pyrite exhibit intracrystalline δ34S variation, with a range of up to 3.31 ‰ recorded in an early pyrite crystal and up to 4.48 ‰ in a late pyrite crystal. Variations in δ34Spyrite at El Indio did not correspond with changes in trace element geochemistry. The lack of correlation between trace elements and δ34S, as well as the abundance of microscale mineral inclusions and vugs in El Indio pyrite indicate that the trace element content of pyrite at El Indio is largely controlled by nanoscale, syn-depositional mineral inclusions. Co and Ni were the only elements partitioned within the crystal structure of pyrite. Cu-rich oscillatory zones in early pyrite likely formed by nanoscale inclusions of Cu-rich sulfosalts or chalcopyrite, evidence of deposition from a fluid cyclically saturated in ore metals. This process may be restricted to polymetallic high-sulfidation-like deposits.

  4. Effect of Au Content on Thermal Stability and Mechanical Properties of Au-Cu-Ag-Si Bulk Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Guo, H.; Zhang, W.; Chen, M. W.; Saotome, Y.; Fukuhara, M.; Inoue, A.

    2011-06-01

    The thermal stability, glass-forming ability (GFA), and mechanical and electrical properties of Au-based Au x Si17Cu75.5- x Ag7.5 ( x = 40 to 75.5 at. pct) metallic glasses were investigated. The glass transition temperature ( T g ) and crystallization temperature ( T x ) decreased with increasing Au content. The ultralow T g values below 373 K (100 °C) were obtained for alloys with x = 55 to 75.5. The alloys with x = 45 to 70 exhibited a high stabilization of supercooled liquid and a high GFA, and the supercooled liquid region and critical sample diameter for glass formation were in the range of 31 K to 50 K and 2 to 5 mm, respectively. The compressive fracture strength ( σ c,f ), Young's modulus ( E), and Vicker's hardness ( H v ) of the bulk metallic glasses (BMGs) decreased with increasing Au content. A linear correlation between Au concentration and the characteristic temperature, i.e., T g and T x , and mechanical properties, i.e., σ c,f , E, and H v , as well as electrical resistivity can be found in the BMGs, which will be helpful for the composition design of the desirable Au-based BMGs with tunable physical properties.

  5. Petrology, geochemistry and U-Pb geochronology of magmatic rocks from the high-sulfidation epithermal Au-Cu Chelopech deposit, Srednogorie zone, Bulgaria

    NASA Astrophysics Data System (ADS)

    Chambefort, Isabelle; Moritz, Robert; von Quadt, Albrecht

    2007-10-01

    The Chelopech deposit is one of the largest European gold deposits and is located 60 km east of Sofia, within the northern part of the Panagyurishte mineral district. It lies within the Banat-Srednegorie metallogenic belt, which extends from Romania through Serbia to Bulgaria. The magmatic rocks define a typical calc-alkaline suite. The magmatic rocks surrounding the Chelopech deposit have been affected by propylitic, quartz-sericite, and advanced argillic alteration, but the igneous textures have been preserved. Alteration processes have resulted in leaching of Na2O, CaO, P2O5, and Sr and enrichment in K2O and Rb. Trace element variation diagrams are typical of subduction-related volcanism, with negative anomalies in high field strength elements (HFSE) and light element, lithophile elements. HFSE and rare earth elements were relatively immobile during the hydrothermal alteration related to ore formation. Based on immobile element classification diagrams, the magmatic rocks are andesitic to dacitic in compositions. Single zircon grains, from three different magmatic rocks spanning the time of the Chelopech magmatism, were dated by high-precision U-Pb geochronology. Zircons of an altered andesitic body, which has been thrust over the deposit, yield a concordant 206Pb/238U age of 92.21 ± 0.21 Ma. This age is interpreted as the crystallization age and the maximum age for magmatism at Chelopech. Zircon analyses of a dacitic dome-like body, which crops out to the north of the Chelopech deposit, give a mean 206Pb/238U age of 91.95 ± 0.28 Ma. Zircons of the andesitic hypabyssal body hosting the high-sulfidation mineralization and overprinted by hydrothermal alteration give a concordant 206Pb/238U age of 91.45 ± 0.15 Ma. This age is interpreted as the intrusion age of the andesite and as the maximum age of the Chelopech epithermal high-sulfidation deposit. 176Hf/177Hf isotope ratios of zircons from the Chelopech magmatic rocks, together with published data on the Chelopech area and the about 92-Ma-old Elatsite porphyry-Cu deposit, suggest two different magma sources in the Chelopech-Elatsite magmatic area. Magmatic rocks associated with the Elatsite porphyry-Cu deposit and the dacitic dome-like body north of Chelopech are characterized by zircons with ɛHfT90 values of ˜5, which suggest an important input of mantle-derived magma. Some zircons display lower ɛHfT90 values, as low as -6, and correlate with increasing 206Pb/238U ages up to about 350 Ma, suggesting assimilation of basement rocks during magmatism. In contrast, zircon grains in andesitic rocks from Chelopech are characterized by homogeneous 176Hf/177Hf isotope ratios with ɛHfT90 values of ˜1 and suggest a homogeneous mixed crust-mantle magma source. We conclude that the Elatsite porphyry-Cu and the Chelopech high-sulfidation epithermal deposits were formed within a very short time span and could be partly contemporaneous. However, they are related to two distinct upper crustal magmatic reservoirs, and they cannot be considered as a genetically paired porphyry-Cu and high-sulfidation epithermal related to a single magmatic-hydrothermal system centered on the same intrusion.

  6. Surface effects on the mechanical elongation of AuCu nanowires: De-alloying and the formation of mixed suspended atomic chains

    SciTech Connect

    Lagos, M. J.; Autreto, P. A. S.; Galvao, D. S. Ugarte, D.; Bettini, J.; Sato, F.; Dantas, S. O.

    2015-03-07

    We report here an atomistic study of the mechanical deformation of Au{sub x}Cu{sub (1−x)} atomic-size wires (nanowires (NWs)) by means of high resolution transmission electron microscopy experiments. Molecular dynamics simulations were also carried out in order to obtain deeper insights on the dynamical properties of stretched NWs. The mechanical properties are significantly dependent on the chemical composition that evolves in time at the junction; some structures exhibit a remarkable de-alloying behavior. Also, our results represent the first experimental realization of mixed linear atomic chains (LACs) among transition and noble metals; in particular, surface energies induce chemical gradients on NW surfaces that can be exploited to control the relative LAC compositions (different number of gold and copper atoms). The implications of these results for nanocatalysis and spin transport of one-atom-thick metal wires are addressed.

  7. Discriminant diagrams for iron oxide trace element fingerprinting of mineral deposit types

    NASA Astrophysics Data System (ADS)

    Dupuis, Céline; Beaudoin, Georges

    2011-04-01

    Magnetite and hematite are common minerals in a range of mineral deposit types. These minerals form partial to complete solid solutions with magnetite, chromite, and spinel series, and ulvospinel as a result of divalent, trivalent, and tetravalent cation substitutions. Electron microprobe analyses of minor and trace elements in magnetite and hematite from a range of mineral deposit types (iron oxide-copper-gold (IOCG), Kiruna apatite-magnetite, banded iron formation (BIF), porphyry Cu, Fe-Cu skarn, Fe-Ti, V, Cr, Ni-Cu-PGE, Cu-Zn-Pb volcanogenic massive sulfide (VMS) and Archean Au-Cu porphyry and Opemiska Cu veins) show compositional differences that can be related to deposit types, and are used to construct discriminant diagrams that separate different styles of mineralization. The Ni + Cr vs. Si + Mg diagram can be used to isolate Ni-Cu-PGE, and Cr deposits from other deposit types. Similarly, the Al/(Zn + Ca) vs. Cu/(Si + Ca) diagram can be used to separate Cu-Zn-Pb VMS deposits from other deposit types. Samples plotting outside the Ni-Cu-PGE and Cu-Zn-Pb VMS fields are discriminated using the Ni/(Cr + Mn) vs. Ti + V or Ca + Al + Mn vs. Ti + V diagrams that discriminate for IOCG, Kiruna, porphyry Cu, BIF, skarn, Fe-Ti, and V deposits.

  8. Radio-Occultation and Heavy Precipitation aboard the PAZ orbiter (ROHP-PAZ) and its Ground-Based campaign

    NASA Astrophysics Data System (ADS)

    De La Torre Juarez, M.; Padulles, R.; Cardellach, E.; Tomás, S.; Turk, J.; Ao, C. O.

    2014-12-01

    For the first time ever, GNSS Radio Occultastion measurements will be taken at two polarizations, to exploit the potential capabilities of polarimetric radio occultation for detecting and quantifying heavy precipitation events and other de-polarizing atmospheric effects (e.g. cloud ice). We report the results on discriminating rain from a mountain top experiment set up to identify and understand the factors that affect the polarimetric RO signal by collecting heavy rain together with free-rain data.

  9. Characteristics and genesis of mineral deposits in East Ujimqin Banner, western segment of the Great Xing'an Mountains, NE China

    NASA Astrophysics Data System (ADS)

    Zhang, Wanyi; Nie, Fengjun; Liu, Shuwen; Zuo, Liyan; Yao, Xiaofeng; Jia, Delong; Liu, Jiangtao

    2015-01-01

    The East Ujimqin Banner, located in the western segment of the Great Xing'an Mountains, NE China, has undergone a long and multi-stage tectonic evolution, which has resulted in significant Fe-Ag-Pb-Zn-Au-Cu-Mo deposits. There are two main types of mineralization: vein and skarn types. The Jilinbaolige and Aerhada vein deposits, and the Chagan Obo and Chaobuleng skarn-type deposits are four typical deposits in this area. The vein deposits mainly occur as veins with hydrothermal alteration in fractures within pre-mineralization clastic rocks and felsic volcanic rocks. The skarn-type deposits always show a temporal and spatial relationship with Mesozoic granite intruded into Paleozoic limestone. The sulfur isotope data from the sulfides in these four deposits have a very narrow range (+1‰ to +8‰), suggesting that most were derived from magma. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios range from 17.949 to 18.529, 15.370 to 15.691 and 37.653 to 38.460 respectively, indicating that the metals derive mainly from the mantle source. In the diagrams 207Pb/204Pb vs. 206Pb/204Pb and 208Pb/204Pb vs. 206Pb/204Pb, the points of lead isotope of the sulfide ores are very near or coincide to the K-feldspar, indicating that the ore-forming materials sources have the genetic relationship. It seems that there are four key factors controlling the mineralization styles in this district: the tectonic setting, magmatic activity, wall rocks, and structures. The superposition of multi-stage tectonism from a Mesozoic extensional setting on a Paleozoic subduction setting provided a remobilization and enrichment mechanism for the ore-forming elements. The magmatic activities were sources of metals and fluids, and drove them to the mineralization sites. The wall rocks are key factors for mineralization styles. When metal-bearing fluid flows into clastic rocks and felsic volcanic rocks, the mineralization is mainly vein type, and mineralization in limestone is mainly skarn type. NE

  10. Pseudosinhalite: discovery of the hydrous MgAl-borate as a new mineral in the Tayozhnoye, Siberia, skarn deposit

    NASA Astrophysics Data System (ADS)

    Schreyer, W.; Pertsev, N. N.; Medenbach, O.; Burchard, M.; Dettmar, D.

    After its initial synthesis as the new compound Mg2Al3B2O9(OH) (Daniels et al. 1997) pseudosinhalite has now been discovered as a new mineral. It occurs, together with hydrotalcite, as a replacement product of sinhalite, MgAlBO4, in an impure marble of the contact metasomatic iron boron deposit of Tayozhnoye in the Aldan Shield of Siberia. Its chemical composition determined by electron microprobe is (wt%): Al2O3 46.88; MgO 25.12; FeO 1.99; B2O3 (calculated) 21.75; H2O (calculated) 2.81 giving a total of 98.55 and leading to the empirical formula (Mg2.00 Fe2+0.09)Σ=2.09 Al2.94 B2O9(OH). The small deviation from the ideal stoichiometry with (Mg+Fe2+):Al≠2:3 may be caused by either solid solution towards, or submicroscopic interlayering with lamellae of, the structurally similar mineral sinhalite. The underlying substitution involving also B and H would be (Mg+Fe)+B=Al+2H. Pseudosinhalite is monoclinic, space group P21/c, with a=7.49(1), b=4.33(1), c=9.85(2) Å β=110.7(1)° V=299(1) Å3 Z=2. Calculated density is 3.508g/cm3. Pseudosinhalite is colourless with white streak and has a vitreous lustre. It is transparent; no fluorescence was detected. There is no cleavage and parting; fractures are concoidal. Optical constants could not be measured properly due to polysynthetic microtwinning, but α<1.72<γ. For synthetic pseudosinhalite α=1.691(1) β=1.713(1) γ=1.730(1) Δ=0.039 2V=80°. The temperature of pseudosinhalite formation was below about 400°C at low pressures and with a hydrous, CO2-bearing fluid participating in the reaction.

  11. H/L chondrite LaPaz Icefield 031047 - A feather of Icarus?

    SciTech Connect

    Wittmann, Axel; Friedrich, Jon M; Troiano, Julianne; Macke, Robert J; Britt, Daniel T; Swidle, Timothy D; Weirich, John R; Rumble, III, Douglas; Lasue, Jeremie; King, David A

    2011-10-28

    Antarctic meteorite LAP 031047 is an ordinary chondrite composed of loosely consolidated chondritic fragments. Its petrography, oxygen isotopic composition and geochemical inventory are ambiguous and indicate an intermediate character between H and L chondrites. Petrographic indicators suggest LAP 031047 suffered a shock metamorphic overprint below ~10 GPa, which did not destroy its unusually high porosity of ~27 vol%. Metallographic textures in LAP 031047 indicate heating above ~700 °C and subsequent cooling, which caused massive transformation of taenite to kamacite. The depletion of thermally labile trace elements, the crystallization of chondritic glass to microcrystalline plagioclase of unusual composition, and the occurrence of coarsely crystallized chondrule fragments is further evidence for post-metamorphic heating to ~700-750 °C. However, this heating event had a transient character because olivine and low-Ca pyroxene did not equilibrate. Nearly complete degassing up to very high temperatures is indicated by the thorough resetting of LAP 031047's Ar-Ar reservoir ~100 ± 55 Ma ago. A noble gas cosmic-ray exposure age indicates it was reduced to a meter-size fragment at <0.5 Ma. In light of the fact that shock heating cannot account for the thermal history of LAP 031047 in its entirety, we test the hypothesis that this meteorite belonged to the near-surface of an Aten or Apollo asteroid that underwent heating during orbital passages close to the Sun.

  12. Research amateur astronomy; Proceedings of the Symposium, La Paz, Mexico, July 7-12, 1991

    NASA Technical Reports Server (NTRS)

    Edberg, Stephen J. (Editor)

    1992-01-01

    The present volume on amateur astronomy deals with solar observations; planet, asteroid, and comet studies; photometry; education and communication; and history and sociology. Particular attention is given to the observation of the 1984 annular eclipse in Mexico, amateur solar astronomy in Germany, the Ashen Light of Venus, dust clouds on Mars in 1990, and the importance of comets Encke and Machholz. Also discussed are a UBVRI and occultation photometry acquisition and reduction software package for PC-based observatories, a Skyweek weekly newsletter on astronomy and spaceflight, and the Hubble Space Telescope and the Goddard High Resolution Spectrograph.

  13. Is There Room for Octavio Paz in the Spanish for Business Class?

    ERIC Educational Resources Information Center

    Gomez, Rafael

    This paper examines ways that Hispanic culture can be dealt with in Spanish as a foreign language for business. First, rationales for teaching culture are offered, ranging from the abstract observation that knowledge of culture is a required part of a humanistic education, to the more pragmatic need of businesses for representatives who are fluent…

  14. Mineral resources of Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona

    SciTech Connect

    Tosdal, R.M.; Eppinger, R.G.; Erdman, J.A.; Hanna, W.F.; Pitkin, J.A.; Blank, H.R. Jr.; O'Leary, R.M.; Watterson, J.R. ); Kreidler, T.J. )

    1990-01-01

    This paper reports on geologic, geochemical, and geophysical studies in the Cactus Plain and East Cactus Plain Wilderness Study Areas outlined in areas with moderate to high potential for gold, silver, copper, lead, zinc, barite, fluorite, manganese, and sand suitable for foundry, fracturing, and abrasive uses and low resource potential for beryllium, uranium and bentonitic clays.

  15. Alteration of Sulphides in the Rumuruti Chondrite La Paz Icefield (LAP) 031275

    NASA Astrophysics Data System (ADS)

    Steer, E. D.; Treiman, A. H.

    2014-09-01

    Pyrrhotite in LAP 03175 (R5) has altered to a fine-grained mineral mixture. New data (optical, chemical, and Raman) suggest the mixture includes violarite and tochilinite, but not (as suggested earlier) graphite, hematite, and/or jarosite.

  16. Efficiency in Universities: The La Paz Papers. Studies on Education; Vol. 4.

    ERIC Educational Resources Information Center

    Lumsden, Keith

    Most universities have been organized as non-profit public or private institutions. Their objectives have not been clearly defined nor has their behavior been well understood. In practice, the management of universities is carried out by administrators who depend largely on government funding and/or private donations. They are subject to various…

  17. Mineral resources of the Eagletail Mountains Wilderness Study Area, La Paz, Maricopa, and Yuma counties, Arizona

    SciTech Connect

    Miller, R.J.; Gvay, F.; Hassemer, J.R.; Hanna, W.F.; Pitkin, J.A.; Hornberger, M.L.; Jones, S.L. ); Lane, M.E. )

    1989-01-01

    The Eagletail Mountains Wilderness Study Area is located in southwestern Arizona. There are no identified resources in this study area. An area near and extending into the northwest corner of this study area has a moderate potential for gold, silver, lead, zinc, and copper; a surrounding area has a low potential for these same commodities. An area northeast of Cemetery Ridge and extending along the southern boundary of this study area has a low potential for gold, silver, lead, zinc, copper, manganese, barium, and molybdenum. Along Cemetery Ridge, which crosses the southern boundary of this study area, is an area with a moderate potential for gold and lead and a low potential for gold, barium, copper, manganese, molybdenum, and zinc.

  18. Reflection seismic investigations in the Dannemora area, central Sweden: Insights into the geometry of polyphase deformation zones and magnetite-skarn deposits

    NASA Astrophysics Data System (ADS)

    Malehmir, Alireza; Dahlin, Peter; Lundberg, Emil; Juhlin, Christopher; SjöStröM, HâKan; HöGdahl, Karin

    2011-11-01

    The Bergslagen region is one of the most ore prospective districts in Sweden. Presented here are results from two nearly 25 km long reflection seismic profiles crossing this region in the Dannemora mining area. The interpretations are constrained by seismic wave velocity measurements on a series of rock samples, cross-dip analysis, prestack time migration, and swath 3-D imaging, as well as by other available geophysical and geological observations. A series of major fault zones is imaged by the seismic data, as is a large mafic intrusion. However, the most prominent feature is a package of east-dipping reflectors found east of the Dannemora area that extend down to at least 3 km depth. This package is associated with a polyphase, ductile-brittle deformation zone with the latest ductile movement showing east-side-up or reverse kinematics. Its total vertical displacement is estimated to be in the order of 2.5 km. Also clearly imaged in the seismic data is a steeply dipping reflector near the Dannemora mine that extends down to a depth of at least 2.2 km. The geological nature of this reflector is not known, but it could represent either a fluid-bearing fault zone or a deep-seated iron deposit, making it an important target for further detailed geophysical and geological investigations.

  19. Mineralogical and geochemical behavior of mill tailing material produced from lead-zinc skarn mineralization, Hanover, Grant County, New Mexico, USA

    NASA Astrophysics Data System (ADS)

    Walder, I. F.; Chavez, W. X.

    1995-07-01

    Mineral extraction and processing, especially metal mining, produces crushed and milled waste; such material, exposed to weathering, poses the potential threat of environmental contamination. In this study, mill tailings from inactive Pb-Zn mines in New Mexico, southwest USA, have been examined for their potential environmental impacts by means of detailed mineralogical and geochemical characterization. The principal ore minerals remaining in the tailings material are sphalerite, chalcopyrite, and very minor galena, smithsonite, and cerrusite, accompanied by the gangue minerals pyrite, pyrrhotite, magnetite, hematite, garnet, pyroxene, quartz, and calcite. White precipitate occurring on tailings surfaces is composed of gypsum and hydrated magnesium sulfates. Pyrite is mostly unaltered or shows only micron-scale rims of oxidation (goethite/hematite) in some surface samples. This iron oxide rim on pyrite is the only indication of weathering-derived minerals found by microscopy. There are variations in element concentrations with depth that reflect primary variations through time as the tailings ponds were filled. Cadmium and Zn concentrations increase with depth and Ag and Pb are low for the uppermost core samples, while Cu, Ni, and Co concentrations are generally high for the uppermost core samples. These elemental distributions indicate that little or no leaching has taken place since emplacement of the tailings because no accumulation or enrichment of these metals is observed in Hanover tailings, even in reducing portions of tailings piles. Element concentrations of surface samples surrounding the tailings reflect underlying mineralized zones rather than tailings-derived soil contamination. We observed no successive decreasing metal concentrations in prevalent wind directions away from the tailings. Stream sediment samples from Hanover Creek have somewhat elevated Zn, Cd, and Pb concentrations in areas that receive sediments from erosion of the tailings. However, input from tributaries downstream of the ponds appears to be principal source of heavy metals in Hanover Creek. The results of this study indicate that there is low risk for groundwater heavy-metal contamination from Hanover tailings. Tailings material do not show significant geochemical oxidation/alteration or metal leaching with depth. Our studies indicate that neutralizing minerals present in the tailings are sufficient to keep the tailings material chemically stable. Geochemically, however, tailings materials are being eroded and may pose a threat to Hanover Creek via siltation.

  20. Undiscovered Locatable Mineral Resources in the Bay Resource Management Plan Area, Southwestern Alaska: A Probabilistic Assessment

    USGS Publications Warehouse

    Schmidt, J.M.; Light, T.D.; Drew, L.J.; Wilson, F.H.; Miller, M.L.; Saltus, R.W.

    2007-01-01

    The Bay Resource Management Plan (RMP) area in southwestern Alaska, north and northeast of Bristol Bay contains significant potential for undiscovered locatable mineral resources of base and precious metals, in addition to metallic mineral deposits that are already known. A quantitative probabilistic assessment has identified 24 tracts of land that are permissive for 17 mineral deposit model types likely to be explored for within the next 15 years in this region. Commodities we discuss in this report that have potential to occur in the Bay RMP area are Ag, Au, Cr, Cu, Fe, Hg, Mo, Pb, Sn, W, Zn, and platinum-group elements. Geoscience data for the region are sufficient to make quantitative estimates of the number of undiscovered deposits only for porphyry copper, epithermal vein, copper skarn, iron skarn, hot-spring mercury, placer gold, and placer platinum-deposit models. A description of a group of shallow- to intermediate-level intrusion-related gold deposits is combined with grade and tonnage data from 13 deposits of this type to provide a quantitative estimate of undiscovered deposits of this new type. We estimate that significant resources of Ag, Au, Cu, Fe, Hg, Mo, Pb, and Pt occur in the Bay Resource Management Plan area in these deposit types. At the 10th percentile probability level, the Bay RMP area is estimated to contain 10,067 metric tons silver, 1,485 metric tons gold, 12.66 million metric tons copper, 560 million metric tons iron, 8,100 metric tons mercury, 500,000 metric tons molybdenum, 150 metric tons lead, and 17 metric tons of platinum in undiscovered deposits of the eight quantified deposit types. At the 90th percentile probability level, the Bay RMP area is estimated to contain 89 metric tons silver, 14 metric tons gold, 911,215 metric tons copper, 330,000 metric tons iron, 1 metric ton mercury, 8,600 metric tons molybdenum and 1 metric ton platinum in undiscovered deposits of the eight deposit types. Other commodities, which may occur in the

  1. Mineralogical and Geochemical Characterization of the Kimmeria Intrusion-Related Deposit, Xanthi, NE Greece

    NASA Astrophysics Data System (ADS)

    Theodoridou, Stella; Melfos, Vasilios; Voudouris, Panagiotis; Miskovic, Aleksandar

    2016-04-01

    Although intrusion-related systems have not been previously recognized in the European segment of the Tethyan Metallogenic Belt, the Rhodope metallogenic province of SE Balkan peninsula hosts numerous such occurrences. The Kimmeria hydrothermal system incorporates two styles of ore mineralization: i) a massive Au-bearing magnetite-pyrrhotite skarn and ii) a Mo-Cu-Bi-W quartz vein-hosted mineralization, both of which are related to the Oligocene Xanthi pluton (25.5±1.2 to 30±1 My, K-Ar in hornblende and biotite). The Xanthi pluton, consisting of I-type gabbros, monzonites and amphibole-biotite granodiorites, intrudes the basement gneisses, mica schists, amphibolites and marbles of the Southern Rhodope Core Complex; a dome that has gradually exhumed from Paleocene/mid Eocene to Miocene (starting between 65 and >42 to 10 My). The Xanthi pluton emplacement and the magmatically derived hydrothermal fluid circulation were controlled by two major regional structures: the low-angle Kavala-Xanthi-Komotini detachment fault and the Nestos thrust fault. The Kimmeria Au-Cu-Fe skarn mineralization features a well-preserved aureole at the contact between the granodiorite and the surrounding marbles. It consists of two paragenetic stages comprising magnetite and pyrrhotite-rich assemblages. Alteration minerals comprise chlorite and sericite. Bulk chemical analyses of the skarn mineralization revealed relatively high concentration of Cu (1 wt.%), Pb (288 ppm) and Zn (0.74 wt.%). The mineralization is also enriched in As (< 75.8 ppm), W (< 82.1 ppm), Bi (<10.1 ppm), Sb (<331.9 ppm), Ag (< 15.9 ppm), and Sn (< 50 ppm). Te and Au are found in low concentrations of less than 2 ppm and 0.4 ppm, respectively. The Kimmeria Mo-Cu-Bi-W vein-type mineralization comprises a system of cross-cutting and sheeted quartz veins within the granodiorite, with pyrite, chalcopyrite and molybdenite as dominant sulfides. Minor sphalerite, tetrahedrite-tennantite, galena and rutile are also present

  2. New enthalpies determination and in situ X-ray diffraction observations of order/disorder transitions in Au[sub 0. 5]Cu[sub 0. 5

    SciTech Connect

    Feutelais, Y.; Legendre, B. . Faculte de Pharmacie); Guymont, M. . Lab. de Metallurgie Structurale)

    1999-06-22

    Differential scanning calorimetry (DSC) and in situ X-ray diffraction experiments on stoichiometric AuCu are reported. Enthalpy peaks of successive transitions AuCu I (L1[sub 0]) [r arrow] AuCu II and AuCu II [r arrow] disorder (Al) are observed, and their integration leads to [Delta]H values of 2.5 and 9.4 J/g, respectively. These successive transitions are well seen in in situ diffraction. Each transformation is spread over a temperature range, and it is shown that the transition AuCu I (L1[sub 0]) [r arrow] AuCu II starts at a temperature as low as 350 C. Some kinetic studies were performed. The long-range order parameter evolution against time is estimated for the ordering at 300 C into L1[sub 0] from quenched disordered AuCu. The AuCu I (L1[sub 0]) [r arrow] AuCu II was also studied from a kinetic point of view, using the intensities of characteristic lines. Various results are compared with previously reported observations and discussed.

  3. Cuerpo de Paz Manual de Sistema de Programacion y Capacitacion (Peace Corps Programming and Training System Manual): T0063.

    ERIC Educational Resources Information Center

    Peace Corps, Washington, DC.

    This Spanish version of the Peace Corps Programming and Training System Manual is designed to help field staff members of the Peace Corps train volunteers. Its task descriptions, guidelines, examples, and definitions are intended to be practical and informative rather than restrictive. The manual is divided into six major sections: (1)…

  4. Where Does It Take You? Using the Poetry of Paz, Pacheco, Guitierrez, Blanco, and Deltoro as Models.

    ERIC Educational Resources Information Center

    Nye, Naomi Shihab

    1997-01-01

    Notes the importance of noticing details and the precious, weird little details of neighborhoods. Uses poetry by Latin American poets to teach children and adults how to write their own poetry. Starts with basic techniques--talking, reading, discussing, and notetaking. (PA)

  5. The Short Cosmic-Ray Exposure Age of the LaPaz Icefield 10018/10060 Howardites

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Nishiizumi, K.; Caffee, M. W.

    2016-08-01

    Cosmogenic radionuclides indicate a CRE age of ~1.3 Myr for the LAP 10018/10060 howardites. This short CRE age is best explained by ejection of the two howardites from one of the vestoids that is near a resonance zone or in an Earth-crossing orbit.

  6. Preservation of GEMS and Presolar Silicates in an Ultracarbonaceous Clast in LaPaz Icefield 02342 (CR)

    NASA Astrophysics Data System (ADS)

    Stroud, R. M.; Nittler, L. R.; Moyano-Cambero, C. E.; Trigo-Rodriguez, J. M.; Davidson, J.; De Gregorio, B. T.; Alexander, C. M. O'D.

    2016-08-01

    STEM, XANES and NanoSIMS analyses of a C-rich clast in LAP 20343 (CR) reveal similarities to ultracarbonaceous Antarctic micrometeorites and IDPs, including abundant GEMS and presolar silicates, likely preserved by pervasive organic matter.

  7. Oxygen reduction of several gold alloys in 1-molar potassium hydroxide

    NASA Technical Reports Server (NTRS)

    Miller, R. O.

    1975-01-01

    With rotated disk-and-ring equipment, polarograms and other electrochemical measurements were made of oxygen reduction in 1-molar potassium hydroxide on an equiatomic gold-copper (Au-Cu) alloy and a Au-Cu alloy doped with either indium (In) or cobalt (Co) and on Au doped with either nickel (Ni) or platinum (Pt). The results were compared with those for pure Au and pure Pt. The two-electron reaction dominated on all Au alloys as it did on Au. The polarographic results at lower polarization potentials were compared, assuming exclusively a two-step reduction. A qualified ranking of cathodic electrocatalytic activity on the freshly polished reduced disks was indicated: anodized Au Au-Cu-In Au-Cu Au-Cu-Co is equivalent or equal to Au-Pt Au-Ni. Aging in distilled water improved the electrocatalytic efficiency of Au-Cu-Co, Au-Cu, and (to a lesser extent) Au-Cu-In.

  8. Synthesis and characterization in AuCu–Si nanostructures

    SciTech Connect

    Novelo, T.E.; Amézaga-Madrid, P.; Maldonado, R.D.; Oliva, A.I.; Alonzo-Medina, G.M.

    2015-03-15

    Au/Cu bilayers with different Au:Cu concentrations (25:75, 50:50 and 75:25 at.%) were deposited on Si(100) substrates by thermal evaporation. The thicknesses of all Au/Cu bilayers were 150 nm. The alloys were prepared by thermal diffusion into a vacuum oven with argon atmosphere at 690 K during 1 h. X-ray diffraction analysis revealed different phases of AuCu and CuSi alloys in the samples after annealing process. CuSi alloys were mainly obtained for 25:75 at.% samples, meanwhile the AuCuII phase dominates for samples prepared with 50:50 at.%. Additionally, the Au:Cu alloys with 75:25 at.%, produce Au{sub 2}Cu{sub 3} and Au{sub 3}Cu phases. The formed alloys were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) to study the morphology and the elemental concentration of the formed alloys. - Highlights: • AuCu/Si alloy thin films were prepared by thermal diffusion. • Alloys prepared with 50 at.% of Au produce the AuCuII phase. • Alloys prepared with 75 at.% of Au produce Au{sub 3}Cu and Au{sub 2}Cu{sub 3} phases. • All alloys present diffusion of Si and Cu through the CuSi alloy formation.

  9. Source and redox controls on metallogenic variations in intrusion-related ore systems, Tombstone-Tungsten Belt, Yukon Territory, Canada

    USGS Publications Warehouse

    Hart, C.J.R.; Mair, J.L.; Goldfarb, R.J.; Groves, D.I.

    2004-01-01

    The Tombstone, Mayo and Tungsten plutonic suites of granitic intrusions, collectively termed the Tombstone-Tungsten Belt, form three geographically, mineralogically, geochemically and metallogenically distinct plutonic suites. The granites (sensu lato) intruded the ancient North American continental margin of the northern Canadian Cordillera as part of a single magmatic episode in the mid-Cretaceous (96-90 Ma). The Tombstone Suite is alkalic, variably fractionated, slightly oxidised, contains magnetite and titanite, and has primary, but no xenocrystic, zircon. The Mayo Suite is sub-alkalic, metaluminous to weakly peraluminous, fractionated, but with early felsic and late mafic phases, moderately reduced with titanite dominant, and has xenocrystic zircon. The Tungsten Suite is peraluminous, entirely felsic, more highly fractionated, reduced with ilmenite dominant, and has abundant xenocrystic zircon. Each suite has a distinctive petrogenesis. The Tombstone Suite was derived from an enriched, previously depleted lithospheric mantle, the Tungsten Suite is from the continental crust including, but not dominated by, carbonaceous pelitic rocks, and the Mayo Suite is from a similar sedimentary crustal source, but is mixed with a distinct mafic component from an enriched mantle source. Each suite has a distinctive metallogeny that is related to the source and redox characteristics of the magma. The Tombstone Suite has a Au-Cu-Bi association that is characteristic of most oxidised and alkalic magmas, but also has associated, and enigmatic, U-Th-F mineralisation. The reduced Tungsten Suite intrusions are characterised by world-class tungsten skarn deposits with less significant Cu, Zn, Sn and Mo anomalies. The Mayo Suite intrusions are characteristically gold-enriched, with associated As, Bi, Te and W associations. All suites also have associated, but distal and lower temperature Ag-Pb-and Sb-rich mineral occurrences. Although processes such as fractionation, volatile

  10. Source and redox controls on metallogenic variations in intrusion-related ore systems, Tombstone-Tungsten Belt, Yukon Territory, Canada

    USGS Publications Warehouse

    Hart, C.J.R.; Mair, J.L.; Goldfarb, R.J.; Groves, D.I.

    2004-01-01

    The Tombstone, Mayo and Tungsten plutonic suites of granitic intrusions, collectively termed the Tombstone-Tungsten Belt, form three geographically, mineralogically, geochemically and metallogenically distinct plutonic suites. The granites (sensu lato) intruded the ancient North American continental margin of the northern Canadian Cordillera as part of a single magmatic episode in the mid-Cretaceous (96-90 Ma). The Tombstone Suite is alkalic, variably fractionated, slightly oxidised, contains magnetite and titanite, and has primary, but no xenocrystic, zircon. The Mayo Suite is sub-alkalic, metaluminous to weakly peraluminous, fractionated, but with early felsic and late mafic phases, moderately reduced with titanite dominant, and has xenocrystic zircon. The Tungsten Suite is peraluminous, entirely felsic, more highly fractionated, reduced with ilmenite dominant, and has abundant xenocrystic zircon. Each suite has a distinctive petrogenesis. The Tombstone Suite was derived from an enriched, previously depleted lithospheric mantle, the Tungsten Suite is from the continental crust including, but not dominated by, carbonaceous pelitic rocks, and the Mayo Suite is from a similar sedimentary crustal source, but is mixed with a distinct mafic component from an enriched mantle source. Each suite has a distinctive metallogeny that is related to the source and redox characteristics of the magma. The Tombstone Suite has a Au-Cu-Bi association that is characteristic of most oxidised and alkalic magmas, but also has associated, and enigmatic, U-Th-F mineralisation. The reduced Tungsten Suite intrusions are characterised by world-class tungsten skarn deposits with less significant Cu, Zn, Sn and Mo anomalies. The Mayo Suite intrusions are characteristically gold-enriched, with associated As, Bi, Te and W associations. All suites also have associated, but distal and lower temperature Ag-Pb- and Sb-rich mineral occurrences. Although processes such as fractionation, volatile

  11. Newly discovered Jurassic skarnfields in the Ecuadorian Andes

    NASA Astrophysics Data System (ADS)

    Litherland, M.; Fortey, N. J.; Beddoe-Stephens, B.

    1992-08-01

    A series of calcic magnetite skarn klippen in the north of the Cordillera Real are interpreted as erosional relics of a great skarn sheet, over 150 km long, formed by thrusting of island-arc type sediments and volcanics over the Jurassic Azafran batholith during an accretion event. The skarns are contrasted petrographically and compositionally with those of the Nambija field in the south of the Cordillera, which probably relates to the same chain of batholiths. However, the Nambija skarns are autochthonous and rich in gold, with Au:Ag ratios in the region of 20:1, whereas those to the north are allochthonous and relatively barren.

  12. Geologic map of the west half of the Blythe 30' by 60' quadrangle, Riverside County, California and La Paz County, Arizona

    USGS Publications Warehouse

    Stone, Paul

    2006-01-01

    The Blythe 30' by 60' quadrangle is located along the Colorado River between southeastern California and western Arizona. This map depicts the geology of the west half of the Blythe quadrangle, which is mostly in California. The map area is a desert terrain consisting of mountain ranges surrounded by extensive alluvial fans and plains, including the flood plain of the Colorado River which covers the easternmost part of the area. Mountainous parts of the area, including the Big Maria, Little Maria, Riverside, McCoy, and Mule Mountains, consist of structurally complex rocks that range in age from Proterozoic to Miocene. Proterozoic gneiss and granite are overlain by Paleozoic to Early Jurassic metasedimentary rocks (mostly marble, quartzite, and schist) that are lithostratigraphically similar to coeval formations of the Colorado Plateau region to the east. The Paleozoic to Jurassic strata were deposited on the tectonically stable North American craton. These rocks are overlain by metamorphosed Jurassic volcanic rocks and are intruded by Jurassic plutonic rocks that represent part of a regionally extensive, northwest-trending magmatic arc. The overlying McCoy Mountains Formation, a very thick sequence of weakly metamorphosed sandstone and conglomerate of Jurassic(?) and Cretaceous age, accumulated in a rapidly subsiding depositional basin south of an east-trending belt of deformation and east of the north-trending Cretaceous Cordilleran magmatic arc. The McCoy Mountains Formation and older rocks were deformed, metamorphosed, and locally intruded by plutonic rocks in the Late Cretaceous. In Oligocene(?) to Miocene time, sedimentary and minor volcanic deposits accumulated locally, and the area was deformed by faulting. Tertiary rocks and their Proterozoic basement in the Riverside and northeastern Big Maria Mountains are in the upper plate of a low-angle normal (detachment) fault that lies within a region of major Early to Middle Miocene crustal extension. Surficial deposits of the flanking alluvial fans and plains range in age from late Miocene to Holocene. Among the oldest of these deposits are limestone and fine-grained clastic sediments of the late Miocene and (or) Pliocene Bouse Formation, which is commonly interpreted to represent an estuary or marine embayment connected to the proto-Gulf of California. Most of the surficial deposits younger than the Bouse Formation are composed of alluvium either derived from local mountain ranges or transported into the area by the Colorado River. Large parts of the area, particularly near the northern margin, are covered by eolian sand, and small parts are covered by playa sediments.

  13. [Knowledge on drugs phenomenon by students and faculty from the Medical School at Universidad Mayor de San Andrés, La Paz, Bolivia].

    PubMed

    Navia-Bueno, Maria del Pilar; Farah-Bravo, Jacqueline; Yaksic-Feraudy, Nina; Philco-Lima, Patrícia; Takayanagui, Angela Maria Magosso

    2011-06-01

    The goal of this study was to identify the degree of knowledge of students and health educators on licit and illicit drugs, related to the type, classification, action, mechanisms damages, consequences and adverse effects, besides use and consumption. A cross-sectional methodological design was used, with a sample of 172 students, professors and residents in medicine and nursing at Universidad Mayor de San Andrés (UMSA), Bolivia. The results reveal weak knowledge on the classification of psychotropic substances according to structure, chemical property and effects for health, highlighting significant difference with knowledge on licit and illicit drugs use, with high percentages. In conclusion, there is lack of knowledge in all groups studied on licit and illicit drugs regarding the consequences and adverse effects. This confirms the need to improve teaching on this content in health schools.

  14. 77 FR 62413 - Establishment of the C[eacute]sar E. Ch[aacute]vez National Monument

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-12

    ... Paz (Our Lady Queen of Peace) (La Paz), is recognized for its historic significance to C sar Estrada... of October, in the year of our Lord two thousand twelve, and of the Independence of the United...

  15. Sulfur's Effect on Iron Concentration in Chloride-Bearing, Aqueous, Hydrothermal-Magmatic Fluids

    NASA Astrophysics Data System (ADS)

    Simon, A. C.; Candela, P. A.; Piccoli, P. M.

    2002-05-01

    Characterizing the physico-chemical properties of fluids responsible for Fe transport in crustal environments is fundamental to our understanding of large-scale magmatic-hydrothermal transport properties responsible for the production of Fe skarns, magnetite-rich Au- and Cu-porphyry deposits and metamorphic assemblages which have experienced significant introduction or removal of iron. The interest in Fe transport is driven by questions such as: 1) What fluid properties facilitate the formation of magnetite-rich, Cornwall-type skarn deposits?; and 2) How does Fe concentration in an exsolved magmatic volatile phase (MVP) affect the transport of other metals, such as Au, Cu? Previous studies in S-free systems have shown that iron is transported as FeCl2 in the MVP (Boctor et al., 1980), Fe concentration is a function of HCl concentration in the MVP (Chou and Eugster, 1977), Fe concentration experiences order of magnitude increases as a function of proximity to the NaCl-H2O critical point (Simon et al., 2001), and Fe moderates chloride partitioning between a co-existing silicate melt and MVP which can affect the transport properties for other Cl-complexed metals (Simon, et al., 2000). In S-free assemblages these results suggest a simple model wherein FeCl2 is the primary complex responsible for Fe transport and magnetite precipitation occurs as a function of changes in fluid pressure, temperature and hydrogen fugacity. As of yet, no systematic study of sulfur's effect on aqueous iron concentrations in the magmatic-hydrothermal environment has been performed. Therefore, we carried out a set of experiments to determine the effect of sulfur on iron concentration in chloride-bearing magmatic-hydrothermal fluids. Santa Eulalia pyrrhotite (Fe0.904S), a synthetic haplogranitic minimum melt (100 MPa) and an aqueous phase (molar K:Na=1.2 and K:H=10) were reacted in Au capsules in cold-seal René vessels, using water as the pressure medium, at T=800\\degC, log f_{O2} ~NNO, P

  16. Charged particle multiplicity studies with PHOBOS.

    SciTech Connect

    Alver, B.; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Physics; Massachusetts Inst. of Tech.; BNL

    2008-01-01

    Summary and conclusion: (1) Multiplicity - PHOBOS have performed complete charged particle multiplicity measurements for Au+Au, Cu+Cu, d+Au, and p+p collisions, System size dependence, and 'Complete' pseudorapidity distributions; 'Universality' compared to elementary e+e- collisions; and (2) Midrapidity multiplicity - Factorization of centrality and energy dependencies; (3) Limiting fragmentation - extended longitudinal scaling - Seen for Au+Au, Cu+Cu, and d+Au, Also observed in flow observables; (4) Total charged particle multiplicity - N{sub ch}/N{sub part} constant with centrality, (5) Future - Finish up many analysis and reviews.

  17. Fluid inclusion geobarometry from ejected Mt. Somma-Vesuvius nodules.

    USGS Publications Warehouse

    Belkin, H.E.; de Vivo, B.; Roedder, E.; Cortini, M.

    1985-01-01

    The results of a microthermometric study of fluid inclusions from seven cumulate and three 'skarn' nodules collected from the pyroclastics of three non-Plinian eruptive episodes are presented. -J.A.Z.

  18. Comment by J.P. Figueiredo, & Hoorn, C. on 'Late Miocene sedimentary environments in south-western Amazonia (Solimões Formation; Brazil)' by Martin Gross, Werner E. Piller, Maria Ines Ramos, Jackson Douglas da Silva Paz

    NASA Astrophysics Data System (ADS)

    Figueiredo, Jorge Jesus Picanço

    2012-04-01

    In their paper Gross et al., 2011 present an excellent description of a series of outcrops from the Eirunepe region in western Amazonia (Brazil). The authors interpret these sediments as relics of a Late Miocene anastomosing fluvial system and conclude that the paleogeography of the entire western Amazon region must have been characterized by this environmental setting. They also imply that therefore a long-lived lake system - or megawetland - never existed. We contend this assumption for some reasons, amongst them, the most important are: (1) this is an inconsistent overgeneralized conclusion; (2) The authors make references to previous scientific works we published which we consider incorrect, and therefore can mislead their readers.

  19. Synthesis of small interfering RNAs containing acetal-type nucleoside analogs at their 3'-ends and analysis of their silencing activity and their ability to bind to the Argonaute2 PAZ domain.

    PubMed

    Inada, Natsumi; Nakamoto, Kosuke; Yokogawa, Takashi; Ueno, Yoshihito

    2015-10-20

    In this study, we aimed to create small interfering RNAs (siRNAs) with increased silencing activities and nuclease resistance properties. Therefore, we designed and synthesized five types of siRNA containing acetal-type nucleoside analogs at their 3'-dangling ends. We found that the siRNA containing 1-O-(2,2,2-trifluoroethyl)-β-D-ribofuranose at the 3'-dangling end was the most potent among the synthesized siRNAs and showed more resistance to nucleolytic degradation by a 3' exonuclease than a natural RNA did. Thus, modification of siRNAs by addition of 1-O-(2,2,2-trifluoroethyl)-β-D-ribofuranose may hold promise as a means of improving the silencing activity and nuclease resistance of siRNAs.

  20. Microstructural Evolution and Mechanical Properties in (AuSn)eut-Cu Interconnections

    NASA Astrophysics Data System (ADS)

    Dong, Hongqun; Vuorinen, Vesa; Laurila, Tomi; Paulasto-Kröckel, Mervi

    2016-06-01

    The interfacial reactions between the widely employed solder Au-20wt.%Sn and the common contact metallizations (e.g. Ni, Cu and Pt) are normally complex and not well determined. In order to identify the proper contactor for Au-20wt.%Sn solder, the present study focuses on (1) rationalizing the interfacial reaction mechanisms of Au-20wt.%Sn|Cu as well as (2) measuring the mechanical properties of individual intermetallics formed at the interface. The evolution of interfacial reaction products were rationalized by using the experimental results in combination with the calculated Au-Cu-Sn phase diagram information. It was found that the growth of the AuCu interfacial intermetallic layer was diffusion-controlled. The diffusion path of Au-20wt.%Sn|Cu at 150°C was proposed. The hardness and indentation modulus of the interfacial reaction products were measured using nanoindentation tests. The results revealed a significant influence of the Cu solubility on the mechanical properties of (Au,Cu)Sn and (Au,Cu)5Sn, i.e. their hardness and contact modulus increased with the increase in the amount of Cu. Furthermore, results obtained here for the Au-20wt.%Sn|Cu joints were compared to those from Au-20wt.%Sn|Ni in order to assess the similarities and differences between these widely used interconnection metallization systems.

  1. Microstructural Evolution and Mechanical Properties in (AuSn)eut-Cu Interconnections

    NASA Astrophysics Data System (ADS)

    Dong, Hongqun; Vuorinen, Vesa; Laurila, Tomi; Paulasto-Kröckel, Mervi

    2016-10-01

    The interfacial reactions between the widely employed solder Au-20wt.%Sn and the common contact metallizations (e.g. Ni, Cu and Pt) are normally complex and not well determined. In order to identify the proper contactor for Au-20wt.%Sn solder, the present study focuses on (1) rationalizing the interfacial reaction mechanisms of Au-20wt.%Sn|Cu as well as (2) measuring the mechanical properties of individual intermetallics formed at the interface. The evolution of interfacial reaction products were rationalized by using the experimental results in combination with the calculated Au-Cu-Sn phase diagram information. It was found that the growth of the AuCu interfacial intermetallic layer was diffusion-controlled. The diffusion path of Au-20wt.%Sn|Cu at 150°C was proposed. The hardness and indentation modulus of the interfacial reaction products were measured using nanoindentation tests. The results revealed a significant influence of the Cu solubility on the mechanical properties of (Au,Cu)Sn and (Au,Cu)5Sn, i.e. their hardness and contact modulus increased with the increase in the amount of Cu. Furthermore, results obtained here for the Au-20wt.%Sn|Cu joints were compared to those from Au-20wt.%Sn|Ni in order to assess the similarities and differences between these widely used interconnection metallization systems.

  2. Antiviral Activity of Gold/Copper Sulfide Core/Shell Nanoparticles against Human Norovirus Virus-Like Particles

    PubMed Central

    Broglie, Jessica Jenkins; Alston, Brittny; Yang, Chang; Ma, Lun; Adcock, Audrey F.; Chen, Wei; Yang, Liju

    2015-01-01

    Human norovirus is a leading cause of acute gastroenteritis worldwide in a plethora of residential and commercial settings, including restaurants, schools, and hospitals. Methods for easily detecting the virus and for treating and preventing infection are critical to stopping norovirus outbreaks, and inactivation via nanoparticles (NPs) is a more universal and attractive alternative to other physical and chemical approaches. Using norovirus GI.1 (Norwalk) virus-like particles (VLPs) as a model viral system, this study characterized the antiviral activity of Au/CuS core/shell nanoparticles (NPs) against GI.1 VLPs for the rapid inactivation of HuNoV. Inactivation of VLPs (GI.1) by Au/CuS NPs evaluated using an absorbance-based ELISA indicated that treatment with 0.083 μM NPs for 10 min inactivated ~50% VLPs in a 0.37 μg/ml VLP solution and 0.83 μM NPs for 10 min completely inactivated the VLPs. Increasing nanoparticle concentration and/or VLP-NP contact time significantly increased the virucidal efficacy of Au/CuS NPs. Changes to the VLP particle morphology, size, and capsid protein were characterized using dynamic light scattering, transmission electron microscopy, and Western blot analysis. The strategy reported here provides the first reported proof-of-concept Au/CuS NPs-based virucide for rapidly inactivating human norovirus. PMID:26474396

  3. The effects of social anxiety on alcohol and cigarette use across adolescence: Results from a longitudinal twin study in Finland.

    PubMed

    Savage, Jeanne E; Kaprio, Jaakko; Korhonen, Tellervo; Pulkkinen, Lea; Rose, Richard J; Verhulst, Brad; Dick, Danielle M

    2016-06-01

    Conflicting reports exist on the direction of the relationship between social anxiety (SA) and alcohol/cigarette use (AU/CU) and alcohol/nicotine dependence (AD/ND), with both positive and negative associations reported. A prospective, longitudinal sample of Finnish twins (n = 1,906) was used to test potential explanations for these discrepancies. Specifically, this study used peer, parent, and teacher ratings of SA, and a clinical interview screening item for social anxiety disorder (SAD-Sc) to examine associations between SA and AU/CU and AD/ND from early adolescence into young adulthood. Peer-rated SA was negatively associated with AU, CU, and AD from age 14 through age 22, implying a protective effect (β = -0.01 to -.03). Teacher- and parent-rated SA associations were in the same directions but weaker or nonsignificant, indicating that aspects of SA that are recognizable by peers may be most relevant to AU/CU. Self-reported SAD-Sc was also negatively associated with AU, but positively associated with AD symptoms in young adulthood (β = 0.38). Our findings partially support the existence of different associations between SA and AU versus AD, but only in the context of SAD-Sc rather than trait SA. Neither trait SA nor SAD-Sc significantly predicted ND symptoms, although SAD-Sc was associated with both cigarette abstinence and daily smoking. These findings suggest that adolescent SA is modestly associated with lower AU/CU, although there may be some individuals with more severe SA who develop alcohol problems later in life. There was little evidence of a common underlying liability contributing to both SA and alcohol/cigarette use. (PsycINFO Database Record PMID:27322804

  4. Controlled Dealloying of Alloy Nanoparticles toward Optimization of Electrocatalysis on Spongy Metallic Nanoframes.

    PubMed

    Li, Guangfang Grace; Villarreal, Esteban; Zhang, Qingfeng; Zheng, Tingting; Zhu, Jun-Jie; Wang, Hui

    2016-09-14

    Atomic-level understanding of the structural transformations of multimetallic nanoparticles triggered by external stimuli is of vital importance to the enhancement of our capabilities to fine-tailor the key structural parameters and thereby to precisely tune the properties of the nanoparticles. Here, we show that, upon thermal annealing in a reducing atmosphere, Au@Cu2O core-shell nanoparticles transform into Au-Cu alloy nanoparticles with tunable compositional stoichiometries that are predetermined by the relative core and shell dimensions of their parental core-shell nanoparticle precursors. The Au-Cu alloy nanoparticles exhibit distinct dealloying behaviors that are dependent upon their Cu/Au stoichiometric ratios. For Au-Cu alloy nanoparticles with Cu atomic fractions above the parting limit, nanoporosity-evolving percolation dealloying occurs upon exposure of the alloy nanoparticles to appropriate chemical etchants, resulting in the formation of particulate spongy nanoframes with solid/void bicontinuous morphology composed of hierarchically interconnected nanoligaments. The nanoporosity evolution during percolation dealloying is synergistically guided by two intertwining structural rearrangement processes, ligament domain coarsening driven by thermodynamics and framework expansion driven by Kirkendall effects, both of which can be maneuvered by controlling the Cu leaching rates during the percolation dealloying. The dealloyed nanoframes possess large open surface areas accessible by the reactant molecules and high abundance of catalytically active undercoordinated atoms on the ligament surfaces, two unique structural features highly desirable for high-performance electrocatalysis. Using the room temperature electro-oxidation of methanol as a model reaction, we further demonstrate that, through controlled percolation dealloying of Au-Cu alloy nanoparticles, both the electrochemically active surface areas and the specific activity of the dealloyed metallic

  5. 76 FR 70125 - Notice of Availability of the Draft Environmental Impact Statement for the Proposed Solar Reserve...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-10

    ... Proposed Solar Reserve LLC Quartzsite Solar Energy Project, La Paz County, AZ (DOE/EIS--0440) and the... Solar Energy Project (Project), in La Paz County, Arizona, and the proposed amendment to the Yuma Field... Administration, P.O. Box 281213, Lakewood, CO 80228-8213 or ] sent by email to...

  6. 40 CFR 81.303 - Arizona.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... citations affecting § 81.303 see the List of CFR Sections Affected which appears in the Finding Aids section... Apache County Cochise County Coconino County Gila County Graham County Greenlee County La Paz County... La Paz County Maricopa County (part) area outside of Phoenix Mohave County Navajo County Pima...

  7. 75 FR 68942 - Karnal Bunt; Regulated Areas in Arizona, California, and Texas

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-10

    ... FR 8091-8097, Docket No. 02-056-2), we removed soil from the list of regulated articles. In that rule... Young Counties, TX, portions of Riverside County, CA, and certain areas in La Paz, Maricopa, and Pinal... quarantined areas in Sec. 301.89-3(g) by removing certain areas in La Paz County, AZ; two fields in...

  8. Mexican-American Cultural Assumptions and Implications.

    ERIC Educational Resources Information Center

    Carranza, E. Lou

    The search for presuppositions of a people's thought is not new. Octavio Paz and Samuel Ramos have both attempted to describe the assumptions underlying the Mexican character. Paz described Mexicans as private, defensive, and stoic, characteristics taken to the extreme in the "pachuco." Ramos, on the other hand, described Mexicans as being…

  9. Spectral-induced polarization characteristics of rocks from Shinyemi deposit in Northeastern South Korea

    NASA Astrophysics Data System (ADS)

    Park, Samgyu; Shin, Seung Wook; Son, Jeong-Sul; Kim, Changryol

    2016-04-01

    Contact metasomatism between carbonate and igneous rocks leads to the formation of skarn deposits, and ore minerals are abundant. Geophysical methods that visualize the distributions of physical properties have been utilized to determine lithological boundaries in ore deposits. In particular, spectral-induced polarization (SIP) is the most effective of those methods for mineral exploration because it can obtain not only the boundaries but also the abundance and grain size of ore minerals. It is crucial to characterize the SIP responses of in situ rocks for a more realistic interpretation. Thus, typical rocks composed of igneous rock, skarn rock, skarn ore, and carbonate rock were sampled from drilling cores in the Shinyemi deposit, which is one of the well-known skarn deposits in Northeastern South Korea. The purpose of this study was to characterize the SIP responses of rocks by laboratory measurements. The characterization was performed by evaluating spectra and IP parameters. The IP properties were acquired from equivalent circuit analysis using a circuit model based on the electrochemical theory, and the analysis results of this circuit model were relatively well fit compared with those of the traditional Dias and Cole-Cole models. The frequency responses below 100 Hz in the spectra and the chargeability values of the skarn rocks and ores containing magnetite were relatively strong and high, respectively, compared with those of non-mineralized igneous and carbonate rocks. Therefore, it is considered that these characteristics are dependent on the abundance of magnetite. In case of the skarn ores with high magnetite content, the resistivity values were significantly low and the relaxation time values were influenced by the grain size of magnetite. On the other hand, it is considered that the DC resistivity and the relaxation time values of the igneous and carbonate rocks are slightly related to the porosity and the grade of hydrothermal alteration, respectively.

  10. Geologic map of the Ahankashan-Rakhna basin, Badghis, Ghor, and Herat Provinces, Afghanistan, modified from the 1974 original map compilation of Y.I. Shcherbina and others

    USGS Publications Warehouse

    Tucker, Robert D.; Stettner, Will R.; Masonic, Linda M.; Bogdanow, Anya K.

    2014-01-01

    The Ahankashan and Rakhna prospect area is one of several gold and copper deposits within west-central Afghanistan. Here, various felsic to intermediate igneous porphyries intrude Lower Triassic to lower Paleogene sedimentary rocks, producing mineral and ore-bearing zones related to hydrothermal alteration, skarns, silicification, and crushing (brecciation). Mineralized skarns contain assemblages such as magnetite, magnetite-hematite, epidote-hematite, and epidote-garnet, as well as disseminations of chalcopyrite, covellite, chalcocite, cuprite, malachite, and azurite. Gold mineralization is mainly associated with zones of crushing along faults, and with small silicified igneous veins within granite and quartz porphyry.

  11. Mineral resources and resource potential map of the Pyramid Peak Roadless Area, Riverside County, California

    USGS Publications Warehouse

    Calzia, J.P.

    1988-01-01

    Geologic and geochemical data indicate that the study area has high resource potential for marble, and moderate resource potential for epithermal gold deposits and tungsten skarns. The Desert Divide Group and the Palm Canyon Complex contain large resources of marble quarried for Portland cement and for construction applications. Gold occurs in quartz veins and pegmatites in the Desert Divide Group and the Penrod Quartz Monzonite. Skarns in the Desert Divide Group contain scheelite and anomalous concentrations of arsenic and beryllium. Thin layers of tremolite asbestos along low-angle thrust faults occur outside of the study area.

  12. Metallic-mineral assessment of the Aban Al Ahmar quadrangle, sheet 25F, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Kamilli, Robert J.; Arnold, Mark A.; Cole, James C.; Kleinkopf, M. Dean; Lee, Keenan; Miller, William R.; Raines, Gary L.; ,; ,

    1990-01-01

    Comprehensive detailed interdisciplinary study assesses the metallic-mineral-resource potential in the Aban Al Ahmar Quadrangle of the Kingdom of Saudi Arabia, located in the eastern margin of the northeastern Arabian Shield, utilizing techniques of geophysics, geologic mapping, remote sensing and geochemistry. The landscape of the study area is characterized by isolated mountain groups, inselbergs, and local tracts of dissected hills separated by broad, low-relief peneplain. Topics covered include mining and exploration history; geological setting; interpretation of geophysical anomalies; limonitic hydrothermally altered and mineralized rocks; geochemical interpretation; mineral resource potential; skarn deposiits associated with intermediate igneous rocks; gold deposits; tin/tungsten skarn deposits; etc. 

  13. Effect of gold on keV x-ray emission yield from laser produced plasma of gold-copper mix-Z targets

    SciTech Connect

    Arora, V.; Chakera, J. A.; Naik, P. A.; Kumbhare, S. R.; Gupta, P. D.; Gupta, N. K.

    2006-08-01

    The effect of gold on keV x-ray emission from gold-copper (Au-Cu) mix-Z plasma has been experimentally studied. The intensity of the copper L-shell line radiation ({lambda}{approx}7.8-10.9 A) as well as the integrated keV x-ray yield were observed to decrease sharply with increasing atomic fraction of gold in the mix-Z target. The decrease was observed to be by a factor of {approx}2.1 for 0.12 atomic fraction of gold in the Au-Cu mix-Z target with respect to the pure copper target. The results can be explained from physical consideration of the high value of free-bound opacity of gold in the spectral region of the L-shell emission of copper ions and downconversion of the absorbed keV line radiation.

  14. Recent Developments in High-Temperature Shape Memory Thin Films

    NASA Astrophysics Data System (ADS)

    Motemani, Y.; Buenconsejo, P. J. S.; Ludwig, A.

    2015-11-01

    High-temperature shape memory alloy (HTSMA) thin films are candidates for development of microactuators with operating temperatures exceeding 100 °C. This article reviews recent advances and developments in the field of HTSMA thin films during the past decade, with focus on the systems Ti-Ni-X (X = Hf, Zr, Pd, Pt and Au), Ti-Ta, and Au-Cu-Al. These actuator films offer a wide range of transformation temperatures, thermal hysteresis, and recoverable strains suitable for high-temperature applications. Promising alloy compositions in the systems Ti-Ni-Hf, Ti-Ni-Pd, Ti-Ni-Au, and Au-Cu-Al are highlighted for further upscaling and development. The remaining challenges as well as prospects for development of HTSMA thin films are also discussed.

  15. Rational design of binder-free noble metal/metal oxide arrays with nanocauliflower structure for wide linear range nonenzymatic glucose detection.

    PubMed

    Li, Zhenzhen; Xin, Yanmei; Zhang, Zhonghai; Wu, Hongjun; Wang, Peng

    2015-01-01

    One-dimensional nanocomposites of metal-oxide and noble metal were expected to present superior performance for nonenzymatic glucose detection due to its good conductivity and high catalytic activity inherited from noble metal and metal oxide respectively. As a proof of concept, we synthesized gold and copper oxide (Au/CuO) composite with unique one-dimensional nanocauliflowers structure. Due to the nature of the synthesis method, no any foreign binder was needed in keeping either Au or CuO in place. To the best of our knowledge, this is the first attempt in combining metal oxide and noble metal in a binder-free style for fabricating nonenzymatic glucose sensor. The Au/CuO nanocauliflowers with large electrochemical active surface and high electrolyte contact area would promise a wide linear range and high sensitive detection of glucose with good stability and reproducibility due to its good electrical conductivity of Au and high electrocatalytic activity of CuO.

  16. Antimicrobial effects of gold/copper sulphide (Gold/Copper monosulfide) core/shell nanoparticles on Bacillus anthracis spores and cells

    NASA Astrophysics Data System (ADS)

    Addae, Ebenezer

    Bacillus anthracis is a gram positive, rod shaped and spore forming bacteria. It causes anthrax, a deadly human and animal disease that can kill its victims in three days. The spores of B. anthracis can survive extreme environmental conditions for decades and germinate when exposed to proper conditions. Due to its potential as a bio-weapon, effective disinfectants that pose less harm to the environment and animals are urgently needed. Metal nanoparticles have the potential of killing microbial cells and spores. We present here the effect of Gold/Copper Sulphide core/shell (Au/CuS) nanoparticles on B. anthracis cells and spores. The results indicated that the continuous presence of 0.83 microM during the spore growth in nutrient medium completely inhibited spore outgrowth. Au/CuS nanoparticles at concentration of 4.15 μM completely inactivated B. anthracis cells (x 107) after 30 min of pre-treatment in any of the three buffers including water, PBS, and nutrient broth. However, the same and even higher concentrations of nanoparticles produce no significant spore (x 105) killing after 24 h of pre-treatment. SEM imaging, EDS analysis, and DNA extrusion experiments revealed that nanoparticles damaged the cell membrane causing DNA and cytosolic content efflux and eventually cell death. The study demonstrated the strong antimicrobial activity of Au/CuS nanoparticles to B. anthracis cells and revealed that Au/CuS NPs showed more effective inactivation effect against the cells than they did against the spores.

  17. A phasin with extra talents: a polyhydroxyalkanoate granule-associated protein has chaperone activity.

    PubMed

    Mezzina, Mariela P; Wetzler, Diana E; de Almeida, Alejandra; Dinjaski, Nina; Prieto, M Auxiliadora; Pettinari, Maria Julia

    2015-05-01

    Phasins are proteins associated to intracellular polyhydroxyalkanoate granules that affect polymer accumulation and the number and size of the granules. Previous work demonstrated that a phasin from Azotobacter sp FA-8 (PhaPAz ) had an unexpected growth-promoting and stress-protecting effect in Escherichia coli, suggesting it could have chaperone-like activities. In this work, in vitro and in vivo experiments were performed in order to investigate this possibility. PhaPAz was shown to prevent in vitro thermal aggregation of the model protein citrate synthase and to facilitate the refolding process of this enzyme after chemical denaturation. Microscopy techniques were used to analyse the subcellular localization of PhaPAz in E. coli strains and to study the role of PhaPAz in in vivo protein folding and aggregation. PhaPAz was shown to colocalize with inclusion bodies of PD, a protein that aggregates when overexpressed. A reduction in the number of inclusion bodies of PD was observed when it was coexpressed with PhaPAz or with the known chaperone GroELS. These results demonstrate that PhaPAz has chaperone-like functions both in vitro and in vivo in E. coli recombinants, and suggests that phasins could have a general protective role in natural polyhydroxyalkanoate producers.

  18. Ratiometric ultrasensitive electrochemical immunosensor based on redox substrate and immunoprobe

    PubMed Central

    Tang, Zhongxue; Ma, Zhanfang

    2016-01-01

    In this work, we presented a ratiometric electrochemical immunosensor based on redox substrate and immunoprobe. Carboxymethyl cellulose-Au-Pb2+ (CMC-Au-Pb2+) and carbon-Au-Cu2+ (C-Au-Cu2+) nanocomposites were firstly synthesized and implemented as redox substrate and immunoprobe with strong current signals at −0.45 V and 0.15 V, respectively. Human immunoglobulin G (IgG) was used as a model analyte to examine the analytical performance of the proposed method. The current signals of CMC-Au-Pb2+ (Isubstrate) and C-Au-Cu2+ (Iprobe) were monitored. The effect of redox substrate and immunoprobe behaved as a better linear relationship between Iprobe/Isubstrate and Lg CIgG (ng mL−1). By measuring the signal ratio Iprobe/Isubstrate, the sandwich immunosensor for IgG exhibited a wide linear range from 1 fg mL−1 to 100 ng mL−1, which was two orders of magnitude higher than other previous works. The limit of detection reached 0.26 fg mL−1. Furthermore, for human serum samples, the results from this method were consistent with those of the enzyme linked immunosorbent assay (ELISA), demonstrating that the proposed immunoassay was of great potential in clinical diagnosis. PMID:27739493

  19. Ratiometric ultrasensitive electrochemical immunosensor based on redox substrate and immunoprobe

    NASA Astrophysics Data System (ADS)

    Tang, Zhongxue; Ma, Zhanfang

    2016-10-01

    In this work, we presented a ratiometric electrochemical immunosensor based on redox substrate and immunoprobe. Carboxymethyl cellulose-Au-Pb2+ (CMC-Au-Pb2+) and carbon-Au-Cu2+ (C-Au-Cu2+) nanocomposites were firstly synthesized and implemented as redox substrate and immunoprobe with strong current signals at ‑0.45 V and 0.15 V, respectively. Human immunoglobulin G (IgG) was used as a model analyte to examine the analytical performance of the proposed method. The current signals of CMC-Au-Pb2+ (Isubstrate) and C-Au-Cu2+ (Iprobe) were monitored. The effect of redox substrate and immunoprobe behaved as a better linear relationship between Iprobe/Isubstrate and Lg CIgG (ng mL‑1). By measuring the signal ratio Iprobe/Isubstrate, the sandwich immunosensor for IgG exhibited a wide linear range from 1 fg mL‑1 to 100 ng mL‑1, which was two orders of magnitude higher than other previous works. The limit of detection reached 0.26 fg mL‑1. Furthermore, for human serum samples, the results from this method were consistent with those of the enzyme linked immunosorbent assay (ELISA), demonstrating that the proposed immunoassay was of great potential in clinical diagnosis.

  20. Precipitation Behavior of Thermo-Mechanically Treated Ti50Ni20Au20Cu10 High-Temperature Shape-Memory Alloy

    NASA Astrophysics Data System (ADS)

    Kayani, Saif Haider; Imran Khan, M.; Khalid, Fazal Ahmad; Kim, Hee Young; Miyazaki, Shuichi

    2016-03-01

    In the present work, precipitation behavior of TiNiAuCu-based high-temperature shape-memory alloys is studied. Two alloys with compositions Ti50Ni30Au20 and Ti50Ni20Au20Cu10 were prepared. After 30 % cold rolling, both alloys were then annealed at different temperatures. Formation of Cu-rich TiAuCu and Ti-rich Ti3Au precipitates was observed in Ti50Ni20Au20Cu10 alloy when annealed at different temperatures after cold deformation. It was noticed that prior cold deformation has significant effect on the precipitation behavior. A similar kind of precipitation behavior has been previously reported in TiNiPdCu alloys. Both TiAuCu and Ti3Au type precipitates were found to be deficient in Ni content which causes an increase in Ni content of the matrix and a small decrease in transformation temperatures of the Ti50Ni20Au20Cu10 alloy.

  1. Beyond entropy: magnetic forces induce formation of quasicrystalline structure in binary nanocrystal superlattices.

    PubMed

    Yang, Zhijie; Wei, Jingjing; Bonville, Pierre; Pileni, Marie-Paule

    2015-04-01

    Here, it is shown that binary superlattices of Co/Ag nanocrystals with the same size, surface coating, differing by their type of crystallinity are governed by Co-Co magnetic interactions. By using 9 nm amorphous-phase Co nanocrystals and 4 nm polycrystalline Ag nanocrystals at 25 °C, triangle-shaped NaCl-type binary nanocrystal superlattices are produced driven by the entropic force, maximizing the packing density. By contrast, using ferromagnetic 9 nm single domain (hcp) Co nanocrystals instead of amorphous-phase Co, dodecagonal quasicrystalline order is obtained, together with less-packed phases such as the CoAg13 (NaZn13-type), CoAg (AuCu-type), and CoAg3 (AuCu3-type) structures. On increasing temperature to 65 °C, 9 nm hcp Co nanocrystals become superparamagnetic, and the system yields the CoAg3 (AuCu3-type) and CoAg2 (AlB2-type) structures, as observed with 9 nm amorphous Co nanocrystals. Furthermore, by decreasing the Co nanocrystal size from 9 to 7 nm, stable AlB2-type binary nanocrystal superlattices are produced, which remain independent of the crystallinity of Co nanocrystals with the superparamagnetic state. PMID:25785302

  2. Nonlinear scattering studies of carbon black suspensions using photoacoustic Z-scan technique

    NASA Astrophysics Data System (ADS)

    Kislyakov, Ivan M.; Yelleswarapu, Chandra S.

    2013-10-01

    Nonlinear scattering properties of carbon black suspensions (CBS) are studied using nanosecond photoacoustic (PA) and optical z-scan techniques. When the laser is operated in multi-pulse mode, no nonlinear behavior is observed in PAZ-scans. However, in the single-pulse mode, we observed the nonlinear scattering in both PAZ and optical z- scans. Our results are in agreement with the well-known bleaching effect in CBS and demonstrate the importance of pulse repetition frequency for studying nonlinear scattering using photoacoustics. The effective nonlinear extinction coefficients of CBS were determined, and we found that PAZ-scan data are more sensitive and offer information on higher nonlinearities.

  3. Contact metamorphism by an ophiolite peridotite from neyriz, iran.

    PubMed

    Hall, R

    1980-06-13

    Ophiolites are conventionally regarded as fragments of former oceanic lithosphere. Mineralogical and field evidence indicates that peridotite of the Neyriz ophiolite was intruded at high temperature into folded crystalline limestones, forming skarns. This excludes the formation of the ophiolite at a mid-ocean ridge but is consistent with its origin by intrusion during continental rifting. PMID:17830810

  4. The role of ophiolite in metallogeny of the Sikhote-Alin region

    NASA Astrophysics Data System (ADS)

    Kazachenko, V. T.; Perevoznikova, E. V.; Lavrik, S. N.; Skosareva, N. V.

    2012-06-01

    Metalliferous sediments of the Triassic siliceous formation of the Sikhote-Alin (manganese-silicate rocks and cherts with dispersed rhodochrosite, silicate-magnetite ores, and jasper) and skarns of the Dalnegorsk and Olginsk ore districts were initially the wash away products (Late Anisian-end of the Triassic) of the lateritic weathering crust on ophiolite in the islands. Manganese, iron, and other metals were deposited in the sediments of both lagoons (present-day, skarns) and island water areas (manganese-silicate and siliceousrhodochrosite rocks, silicate-magnetite ores, and jasper). Skarns contain boric and polymetallic ores thus indicating the occurrence of both shallow (periodically drying up) and quite deep (with hydrogen sulfide contamination zones) lagoons. Lead was deposited in protoliths of the skarn deposits in lagoons from the beginning of the Carboniferous to the beginning of the Late Anisian (initial island submergence). Tin, tin-leadzinc (with Ag), and silver-lead-zinc (with Sn and Au) vein deposits (Late Cretaceous-Paleogene) of the Taukha and Zhuravlevka Terrains contain lead deposited in the sediments flanking the islands of water areas with the hydrogen sulfide contamination zones, in the Carboniferous-Permian and Triassic metalliferous sediments.

  5. Contact metamorphism by an ophiolite peridotite from neyriz, iran.

    PubMed

    Hall, R

    1980-06-13

    Ophiolites are conventionally regarded as fragments of former oceanic lithosphere. Mineralogical and field evidence indicates that peridotite of the Neyriz ophiolite was intruded at high temperature into folded crystalline limestones, forming skarns. This excludes the formation of the ophiolite at a mid-ocean ridge but is consistent with its origin by intrusion during continental rifting.

  6. Selective hydrogenation of butadiene over TiO2 supported copper, gold and gold-copper catalysts prepared by deposition-precipitation.

    PubMed

    Delannoy, Laurent; Thrimurthulu, Gode; Reddy, Padigapati S; Méthivier, Christophe; Nelayah, Jaysen; Reddy, Benjaram M; Ricolleau, Christian; Louis, Catherine

    2014-12-28

    Oxide supported copper and gold catalysts are active for the selective hydrogenation of polyunsaturated hydrocarbons but their low activity compared to palladium catalysts and the deactivation of copper catalysts limit their use. There are only a very limited number of studies concerned with the use of bimetallic Au-Cu catalysts for selective hydrogenation reactions and the aim of this work was to prepare TiO2-supported monometallic Au and Cu and bimetallic AuCu (Cu/Au atomic ratio of 1 and 3) catalysts and to evaluate their catalytic performance in the selective hydrogenation of butadiene. Small gold, copper and gold-copper nanoparticles (average particle size < 2 nm) were obtained on TiO2 using the preparation method of deposition-precipitation with urea followed by reduction under H2 at 300 °C. Very small clusters were observed for Cu/TiO2 (∼1 nm) which might result from O2 induced copper redispersion, as also supported by the XPS analyses. The alloying of copper with gold was found to inhibit its redispersion and also limits its reoxidation, as attested by XPS. The bimetallic character of the AuCu nanoparticles was confirmed by XPS and EDX-HAADF. Cu/TiO2 was initially more active than Au/TiO2 in the selective hydrogenation of butadiene at 75 °C but it deactivated rapidly during the first hours of reaction whereas the gold catalyst was very stable up to 20 hours of reaction. The bimetallic AuCu/TiO2 catalysts displayed an activation period during the first hours of the reaction, which was very pronounced for the sample containing a higher Cu/Au atomic ratio. This initial gain in activity was tentatively assigned to copper segregation at the surface of the bimetallic nanoparticles, induced by the reactants. When the AuCu/TiO2 catalysts were pre-exposed to air at 75 °C before butadiene hydrogenation, surface copper segregation occurred, leading to higher initial activity and the suppression of the activation period. Under the same conditions, Cu/TiO2 totally

  7. Rare earth element metasomatism in hydrothermal systems: The Willsboro-Lewis wollastonite ores, New York, USA

    USGS Publications Warehouse

    Whitney, P.R.; Olmsted, J.F.

    1998-01-01

    Wollastonite ores and garnet-pyroxene skarns in the Willsboro-Lewis district, New York, USA were formed in a complex hydrothermal system associated with the emplacement of a large anorthosite pluton. Contact-metamorphic marbles were replaced by wollastonite, garnet, and clinopyroxene during infiltration metasomatism involving large volumes of water of chiefly meteoric origin. Rare earth elements (REE) in these rocks show large departures from the protolith REE distribution, indicative of substantial REE mobility. Three types of chondrite-normalized REE distribution patterns are present. The most common, found in ores and skarns containing andradite-rich garnet, is convex-up in the light REE (LREE) with a maximum at Pr and a positive Eu anomaly. Europium anomalies and Pr/Yb ratios are correlated with X(Ad) in garnet. This pattern (type C) results from uptake of REE from hydrothermal fluids by growing crystals of calcsilicate minerals, principally andradite, with amounts of LREE controlled by the difference in ionic radius between Ca++ and REE3+ in garnet X sites. The Eu anomaly results either from prior interaction of the fluids with plagioclase-rich, Eu-positive anorthositic rocks in and near the ore zone, or by enrichment of divalent Eu on growth surfaces of garnet followed by entrapment, or both. Relative enrichment in heavy REE (type H) occurs in ores and skarn where calcsilicates, including grossularitic garnet, in contact-metamorphic marble have been concentrated by dissolution of calcite. In most cases a negative Eu anomaly is inherited from the marble protolith. Skarns containing titanite and apatite exhibit high total REE, relative light REE enrichment, and negative Eu anomalies (type L). These appear to be intrusive igneous rocks (ferrodiorites or anorthositic gabbros) that have been converted to skarn by Ca metasomatism. REE, sequestered in titanite, apatite, and garnet, preserve the approximate REE distribution pattern of the igneous protolith. Post

  8. 75 FR 15453 - Arizona; Major Disaster and Related Determinations

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-29

    ... as adversely affected by this major disaster: Apache, Coconino, Gila, Greenlee, La Paz, Mohave... Apache, Tohono O'odham Nation, and White Mountain Apache Tribe for Public Assistance. All counties...

  9. 78 FR 53492 - California Disaster #CA-00208 Declaration of Economic Injury

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-29

    ... Number 59002) Dated: August 19, 2013. Karen G. Mills, Administrator. [FR Doc. 2013-21154 Filed 08/28/2013..., Orange, San Bernardino, San Diego. Arizona: La Paz. The Interest Rates are: Percent Businesses And...

  10. 7 CFR 301.89-3 - Regulated areas.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... § 301.89-3, see the List of CFR Sections Affected, which appears in the Finding Aids section of the... Protection and Quarantine, 4700 River Road Unit 98, Riverdale, MD 20737-1236): Arizona La Paz...

  11. 2. Lake Havasu on left, Colorado River on right below ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Lake Havasu on left, Colorado River on right below Parker Dam; View southeast from TV Hill above Whitsett Pump Plant. - Parker Dam, Spanning Colorado River between AZ & CA, Parker, La Paz County, AZ

  12. 4. Aerial view of Whitsett intake (lower right), Parker Dam ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. Aerial view of Whitsett intake (lower right), Parker Dam and village (left), Gene Wash Reservoir, Gene Pump Plant and village (right). - Parker Dam, Spanning Colorado River between AZ & CA, Parker, La Paz County, AZ

  13. Upward flow of magmatic fluids from the Old Woman granodiorite, Old Woman Mountains southeastern California

    NASA Astrophysics Data System (ADS)

    Morrison, Jean; Hoisch, Thomas D.

    1994-05-01

    Isotopic compositions, mineral equilibrium, and field relations at the contact between the midcrustal Cretaceous Old Woman granodiorite and Paleozoic carbonates indicate that water-rich, silica-saturated magmatic fluids were transported upward, away from the pluton, across an impermeable 30- to 40-m thick marble which caps the granodiorite, to higher structural levels along a complex network of hydrologically induced fractures. Within the fractures, fluids reacted to form symmetrical radiating splays of wollastonite with minor amounts of diopside, vesuvianite, and quartz. In many cases, pegmatites are found in the center of these calc-silicate skarns. Cross-cutting pegmatites and wollastonite veins in the aureole indicate that during late stages of crystallization of the granodiorite there were multiple episodes of fluid expulsion. Above the marble layer at higher structural levels, magmatic fluids flowed both laterally and vertically, interacting with lithologies in a more pervasive manner. Values of delta O-18 for calcite in the vein skarns average 11.8% and pegmatite whole rock silicate delta O-18 values average 9.4%. Thus oxygen isotopic compositions are consistent with a magmatic origin for the skarn-forming fluids. Away from the vein skarns, values of delta O-18 for the capping marble range from 18.7 to 22.1% (avg. = 21%) and values of delta C-13 range from -3.8 to -3.0% (avg. = -3.4%). The high delta O-18 values provide evidence that the marble largely retained its premetamorphic isotopic composition, indicating that fluids from the granodiorite did not flow pervasively across the unit. Lithologies at higher structural levels show evidence of more pervasive interaction with magmatic fluids: forsterite-bearing calc-silicates have delta O-18 values down to 11.8% and coarse-grained vesuvianite- and wollastonite-bearing skarns have delta O-18 values of approximately 13%.

  14. Seminario Regional para el Desarrollo de Materiales Educativos para la Paz (San Jose, Costa Rica, 27-31 de octubre de 1986). Informe Final (Regional Seminar for the Development of Educational Materials on the Theme of Peace--San Jose, Costa Rica, October 27-31, 1986. Final Report).

    ERIC Educational Resources Information Center

    United Nations Educational, Scientific, and Cultural Organization, Santiago (Chile). Regional Office for Education in Latin America and the Caribbean.

    In conjunction with United Nations Educational, Scientific, and Cultural Organization's 40th anniversary, 1986 was named the International Year of Peace. During 1986, UNESCO selected the theme "peace" as an education project to be undertaken in Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, Ecuador, Guatemala, Honduras, Mexico, and…

  15. Electropolymerized hydrophobic polyazulene as solid-contacts in potassium-selective electrodes.

    PubMed

    He, Ning; Gyurcsányi, Róbert E; Lindfors, Tom

    2016-05-10

    Electropolymerized hydrophobic polyazulene (PAz) based solid-state potassium ion-selective electrodes (SC-ISEs) have been characterized in terms of their suitability for clinical application. Polarization of the PAz solid contact before applying the plasticised poly(vinyl chloride) based K(+)-selective membrane was implemented as a convenient approach to address the general problem of the irreproducible standard potential (E(0)) of SC-ISEs. Using this method, the E(0) reproducibility among different electrodes was, in the worst case, ±7.9 mV (n = 4). The effectiveness of the redox buffer-free approach presented here in stabilizing E(0) is strengthened by the absence of light, oxygen and carbon dioxide sensitivity of the PAz SC-ISEs. No evidence was found for the formation of an aqueous layer for the PAz-based SC-ISEs. Thus the hydrophobic carbon structure of PAz having a water contact angle of 98 ± 11°, which is slightly higher than that for graphene, can apparently efficiently counteract the aqueous layer formation. In terms of the specific application, the PAz solid contact ISEs were found to show a remarkably good potential stability at their first contact with an aqueous sample. We also confirmed that the PAz-based SC-ISEs can be used for the accurate determination of the K(+) concentration in serum solutions. Overall, the PAz solid contact shows significant advantages as compared to the state-of-the-art of electrically conducting polymer based SC-ISEs. PMID:27052267

  16. Concept of the exhumed partial annealing (retention) zone in thermochronology: An appraisal

    NASA Astrophysics Data System (ADS)

    Fitzgerald, P. G.

    2013-12-01

    The concept of an exhumed partial annealing zone (PAZ) in fission track (FT) thermochronology has been a widely used and successful interpretative tool since the 1980s. This 1D-interpretative approach is typically applied to samples collected over significant relief, with best results if the sampling is undertaken in steep short-wavelength topography and samples collected parallel to topography (perpendicular to curved isotherms), and for samples following a vertical exhumation path. While annealing of fission tracks occurs even at low ambient temperatures the PAZ is defined as the zone between where tracks are annealed 'geologically' instantaneously and where the rate of annealing slows dramatically; between ~60 and ~110°C for tracks in apatite depending on composition. The shape and average slope of a PAZ varies depending on the paleogeothermal gradient and its stability, and the length of time over which a PAZ forms. PAZs and partial retention zones (PRZ) are now known for different minerals for various techniques. Single grain age dispersion can be significantly magnified in a PAZ/PRZ depending on composition, grain size, [eU], radiation damage and zoning for the FT and (U-Th)/He methods. An exhumed PAZ/PRZ may be revealed in an age-elevation ('vertical') profile when, following a period of uplift/exhumation, the form of the PAZ/PRZ is retained with a 'sharp' convex inflexion (the 'break in slope') marking the base of the exhumed PAZ/PRZ with reset samples structurally beneath. The break in slope represents a minimal age for the transition from 'relative thermal stability' to rapid cooling, as the rock column has to cool through the PAZ/PRZ, with the underestimate greater if the change in cooling rate is not significant. The base of an exhumed PAZ/PRZ is a curve, but we approximate it with straight lines, with less precision with fewer samples. The break in slope may not be distinguishable if the cooling/exhumation was long ago and/or of low magnitude. The

  17. Luminescent Mechanochromism in a Gold(I)-Copper(I) N-Heterocyclic Carbene Complex.

    PubMed

    Chen, Kelly; Nenzel, Michelle M; Brown, Thomas M; Catalano, Vincent J

    2015-07-20

    The silver(I) species [Ag(benzim(CH2py)2)2]PF6 (1) was prepared by refluxing the ligand precursor [H(benzim(CH2py)2)2]PF6 with Ag2O and aqueous sodium hydroxide in dichloromethane. Simple transmetalation of 1 with tetrahydrothiophenegold(I) chloride forms the gold(I) analogue [Au(benzim(CH2py)2)2]PF6 (2). The addition of 2 equiv of [Cu(NCCH3)4]PF6 to 2 in acetonitrile produces a blue-luminescent, trimetallic complex, [AuCu2(benzim(CH2py)2)2(NCCH3)4](PF6)3·2CH3CN (3·2CH3CN). When blue-luminescent 3·2CH3CN is exposed to air, the complex loses four acetonitrile molecules, and the emission of the desolvated complex (4) appears aquamarine. Crystallization of 4 from different solvents produces the complexes [AuCu2(benzim(CH2py)2)2](PF6)3 (5) and [AuCu2(benzim(CH2py)2)2(NCCH2CH3)2](PF6)3 (6). Upon grinding, both 3·2CH3CN and 4 exhibit mechanochromic transformations to a yellow-luminescent powder (ground-4). The reversible mechanochromic transformation of 3·2CH3CN to ground-4 is a crystalline-to-amorphous conversion accompanied by partial desolvation. The luminescent mechanochromism of 4 to ground-4 is an "amorphous-to-amorphous" process and does not require solvent loss. In addition to their mechanochromic properties, both 3·2CH3CN and 4 exhibit luminescent thermochromism through desolvation to form a weak luminescent powder (7). PMID:26155017

  18. A liquid drop model for embedded atom method cluster energies

    NASA Technical Reports Server (NTRS)

    Finley, C. W.; Abel, P. B.; Ferrante, J.

    1996-01-01

    Minimum energy configurations for homonuclear clusters containing from two to twenty-two atoms of six metals, Ag, Au, Cu, Ni, Pd, and Pt have been calculated using the Embedded Atom Method (EAM). The average energy per atom as a function of cluster size has been fit to a liquid drop model, giving estimates of the surface and curvature energies. The liquid drop model gives a good representation of the relationship between average energy and cluster size. As a test the resulting surface energies are compared to EAM surface energy calculations for various low-index crystal faces with reasonable agreement.

  19. High-pT Identified Hadron Production in Au+Au and Cu+Cu Collisions at RHIC-PHENIX

    SciTech Connect

    Konno, M.; Awes, Terry C; Batsouli, Sotiria; Cianciolo, Vince; Efremenko, Yuri; Read Jr, Kenneth F; Silvermyr, David O; Sorensen, Soren P; Stankus, Paul W; Young, Glenn R; Zhang, Chun; PHENIX, Collaboration

    2007-01-01

    Particle-type dependences of hadron yield suppression/enhancement patterns, especially its difference between mesons and baryons, at intermediate p{sub T} (2-5 GeV/c) is one of the findings in heavy ion collisions at RHIC. A systematic study of identified hadron production was performed in Au+Au/Cu+Cu collisions at {radical}s{sub NN} = 62.4/200 GeV, to investigate the possible origins of this difference. In this paper, we show particle ratios, nuclear modification factors and their scaling properties.

  20. Understanding Anharmonicity in fcc Materials: From its Origin to ab initio Strategies beyond the Quasiharmonic Approximation.

    PubMed

    Glensk, A; Grabowski, B; Hickel, T; Neugebauer, J

    2015-05-15

    We derive the Gibbs energy including the anharmonic contribution due to phonon-phonon interactions for an extensive set of unary fcc metals (Al, Ag, Au, Cu, Ir, Ni, Pb, Pd, Pt, Rh) by combining density-functional-theory (DFT) calculations with efficient statistical sampling approaches. We show that the anharmonicity of the macroscopic system can be traced back to the anharmonicity in local pairwise interactions. Using this insight, we derive and benchmark a highly efficient approach which allows the computation of anharmonic contributions using a few T=0 K DFT calculations only.

  1. Magnetron co-sputtering system for coating ICF targets

    SciTech Connect

    Hsieh, E.J.; Meyer, S.F.; Halsey, W.G.; Jameson, G.T.; Wittmayer, F.J.

    1981-12-09

    Fabrication of Inertial Confinement Fusion (ICF) targets requires deposition of various types of coatings on microspheres. The mechanical strength, and surface finish of the coatings are of concern in ICF experiments. The tensile strength of coatings can be controlled through grain refinement, selective doping and alloy formation. We have constructed a magnetron co-sputtering system to produce variable density profile coatings with high tensile strength on microspheres. The preliminary data on the properties of a Au-Cu binary alloy system by SEM and STEM analysis is presented.

  2. Luminescent Copper(I) Halide Butterfly Dimers Coordinated to [Au(CH3imCH2py)2]BF4 and [Au(CH3imCH2quin)2]BF4

    SciTech Connect

    Catalano, V.; Moore, A; Shearer, J; Kim, J

    2009-01-01

    The coordination chemistry of copper(I) halides to the homoleptic, N-heterocyclic carbene Au(I) complexes [Au(CH{sub 3}imCH{sub 2}quin){sub 2}]BF{sub 4} and [Au(CH{sub 3}imCH{sub 2}py){sub 2}]BF{sub 4} was explored. The reaction of CuX (X = Cl, Br, I) with either [Au(CH{sub 3}imCH{sub 2}quin){sub 2}]BF{sub 4} or [Au(CH{sub 3}imCH{sub 2}py){sub 2}]BF{sub 4} produces trimetallic complexes containing Cu{sub 2}X{sub 2}-butterfly copper clusters coordinated to the two imine moieties. The triangular arrangement of the metals places the gold(I) center in close proximity ({approx}2.5-2.6 {angstrom}) to the centroid of the Cu-Cu vector. The Cu-Cu separations vary as a function of bridging halide with the shortest Cu-Cu separations of {approx}2.5 {angstrom} found in the iodo-complexes and the longest separations of 2.9 {angstrom} found in the bridging chloride complexes. In all six complexes the Au-Cu separations range from {approx}2.8 to 3.0 {angstrom}. In the absence of halides, the dimetallic complex [AuCu(CH{sub 3}imCH{sub 2}py){sub 2}(NCCH{sub 3}){sub 2}](BF{sub 4}){sub 2}, containing a long Au-Cu distance of {approx}4.72 {angstrom} is formed. Additionally, as the byproduct of the reaction of CuBr with [Au(CH{sub 3}imCH{sub 2}quin){sub 2}]BF{sub 4} the deep-red, dimetallic compound, AuCuBr{sub 2}(CH{sub 3}imCH{sub 2}quin){sub 2}, was isolated in very low yield. All of these complexes were studied by NMR spectroscopy, mass spectrometry, and the copper containing species were additionally characterized by X-ray crystallography. In solution the copper centers dissociate from the gold complexes, but as shown by XANES and EXAFS spectroscopy, at low temperature the Cu-Cu linkage is broken, and the individual copper(I) halides reposition themselves to opposite sides of the gold complex while remaining coordinated to one imine moiety. In the solid state all of the complexes are photoluminescent, though the nature of the excited state was not determined.

  3. Solubility of hydrogen in metals and its effect of pore-formation and embrittlement. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Shahani, H. R.

    1984-01-01

    The effect of alloying elements on hydrogen solubility were determined by evaluating solubility equations and interaction coefficients. The solubility of dry hydrogen at one atmosphere was investigated in liquid aluminum, Al-Ti, Al-Si, Al-Fe, liquid gold, Au-Cu, and Au-Pd. The design of rapid heating and high pressure casting furnaces used in meta foam experiments is discussed as well as the mechanism of precipitation of pores in melts, and the effect of hydrogen on the shrinkage porosity of Al-Cu and Al-Si alloys. Hydrogen embrittlement in iron base alloys is also examined.

  4. Influence of strain aging on the strain-rate sensitivity of the flow stress

    SciTech Connect

    Schwarz, R.B.

    1982-01-01

    Previously published studies on the deformation kinetics of several fcc alloys, i.e. single crystals of Al-0.7% Mg, polycrystals of AlMg, Inconel 600, Inconel X750, NiCo, AuCu, and FeC, are cited, and two models are proposed to explain the reported observations. The calculations suggest that excess vacancies play an important role in the dynamic strain aging of the alloys and that an intermediate thermal annealing process should remove the vacancies. (BLM)

  5. Empirical relation between surface tension and density for some pure liquid metals

    NASA Astrophysics Data System (ADS)

    Ceotto, D.

    2015-12-01

    A new investigation is conducted on the experimental values of surface tension and density for some common pure liquid metals. Using the most recent and accredited data a new relation is found between these values for Au, Cu, Sn, Al, Pb, In, Bi, Ni, Co, Fe, Ba, Na, Nd, Ga, and Sb. The proportion constant has then been calculated giving an accuracy R2 equal to about 0.98. The equation proposed finds agreement with other theoretical models present in literature; it can be used by engineers in many industrial fields to predict the variables but also to simulate macroscopic processes involving liquid metals.

  6. Synthesis and Shape Control of Copper Tin Sulphide Nanocrystals and Formation of Gold-Copper Tin Sulphide Hybrid Nanostructures

    NASA Astrophysics Data System (ADS)

    Kruszynska, Marta; Parisi, Jürgen; Kolny-Olesiak, Joanna

    2014-09-01

    Hexagonal prismatic Cu3SnS4 nanoparticles and nanorods were synthesized by a hot-injection procedure. Changing the reaction conditions leads to the formation of different shapes. When oleylamine is used as a solvent, hexagonal prismatic particles are obtained, while a reaction in octadecene results in the formation of nanorods. The growth process of copper tin sulphide starts with the formation of djurleite copper sulphide seeds. Their reaction with Sn4+ ions leads to the formation of Cu3SnS4. These Cu3SnS4 nanocrystals form Au-Cu3SnS4 hybrid nanostructures by reaction with gold seeds

  7. Nuclear modification factors at forward rapidity in Au Au and Cu Cu collisions at \\sqrt{s_NN} = 62.4 GeV

    NASA Astrophysics Data System (ADS)

    Larsen, Truls Martin; BRAHMS Collaboration

    2007-08-01

    Data from Au Au, Cu Cu and p p collisions at \\sqrt{s_NN}=62.4 GeV have been collected by the BRAHMS experiment from pseudorapidity η = 0 3.1. Nuclear modification factors, RAA at forward rapidity, with pT up to ~2 GeV/c, which corresponds to more than half of the kinematical limit, are presented together with results from midrapidity for Au Au and Cu Cu collisions. They will also be shown as a function of centrality.

  8. Exploration criteria for mineral target mapping based on 3D geological modeling in the Taebaek mineralized belt in Korea

    NASA Astrophysics Data System (ADS)

    Oh, H. J.; Kihm, Y. H.; Cho, S. J.

    2015-12-01

    We constructed a three-dimensional (3D) geological model based on a 1:50,000-scaled geologic map and determined the exploration criteria for skarn deposit target mapping in the Taebaek mineralized belt. All available geological and geophysical data were compiled in a 3D computing environment using GOCAD software. Twenty-four stratigraphic horizons and more than 100 fault surfaces are defined in the 3D geological model. The primary geological criteria for skarn mineralization in the Taebaek mineralized belt included the presence of an NE-oriented strike-slip fault, key stratigraphic horizons, and a high magnetic susceptibility anomaly based on 3D inversion of magnetic data. The 3D geological criteria were extracted from the 3D geological model for skarn deposit target mapping in the belt. The distance values of the three criteria (NE strike-slip fault, limestone horizon, and area of high magnetic susceptibility) were divided into four classes based on cutoff values determined by experts. The weight values for all of the geological criteria and the score value for each class of the distance criteria were also estimated based on expert knowledge. The weights and scores of geological criteria derived from expert knowledge serve as useful guides for target mapping in the Taebaek mineralized belt.

  9. Polyazomethine as a component of solar cells-theoretical and optical study

    NASA Astrophysics Data System (ADS)

    Korona, K. P.; Korona, T.; Rutkowska-Zbik, D.; Grankowska-Ciechanowicz, S.; Iwan, A.; Kamińska, M.

    2015-11-01

    A recently synthesized 25Th-cardo polyazomethine (PAZ) and its photocurrent generating junction with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) have been examined as possible materials for construction of new-generation solar cells. Properties of a 25Th-cardo/PCBM system, where PAZ and PCBM act as donor and acceptor materials, respectively, have been studied theoretically by time-dependent density-functional theory (TD-DFT) and experimentally by means of optical absorption, photocurrent spectroscopy (PCS), and time-resolved luminescence (TRPL). Theoretical calculations show that highest occupied molecular orbital (HOMO) energy levels of PAZ and PCBM are almost equal (values of -6.01 and -5.98 eV were obtained with the B3LYP functional and the def2-TZVP orbital basis for PAZ and PCBM, respectively), what suggests a possibility of charge transfer in both directions for this system. The shape of the calculated absorption spectrum is in a qualitative agreement with the experiment. The PCS measurements of the new material show that the external quantum efficiency is the highest (about 0.3%) in the near UV range. The TRPL studies reveal a fast decay of a Langevin type (in picosecond range) of the PAZ-related photoluminescence, which accelerates in presence of PCBM, probably due to the charge transfer to PCBM. In addition, our measurements document a usually neglected process of the hole transfer from a donor to an acceptor. A leakage of holes from PAZ to PCBM is supported by a small energy difference of the HOMO energies, as predicted by theory.

  10. Rational design of binder-free noble metal/metal oxide arrays with nanocauliflower structure for wide linear range nonenzymatic glucose detection.

    PubMed

    Li, Zhenzhen; Xin, Yanmei; Zhang, Zhonghai; Wu, Hongjun; Wang, Peng

    2015-01-01

    One-dimensional nanocomposites of metal-oxide and noble metal were expected to present superior performance for nonenzymatic glucose detection due to its good conductivity and high catalytic activity inherited from noble metal and metal oxide respectively. As a proof of concept, we synthesized gold and copper oxide (Au/CuO) composite with unique one-dimensional nanocauliflowers structure. Due to the nature of the synthesis method, no any foreign binder was needed in keeping either Au or CuO in place. To the best of our knowledge, this is the first attempt in combining metal oxide and noble metal in a binder-free style for fabricating nonenzymatic glucose sensor. The Au/CuO nanocauliflowers with large electrochemical active surface and high electrolyte contact area would promise a wide linear range and high sensitive detection of glucose with good stability and reproducibility due to its good electrical conductivity of Au and high electrocatalytic activity of CuO. PMID:26068705

  11. Rational design of binder-free noble metal/metal oxide arrays with nanocauliflower structure for wide linear range nonenzymatic glucose detection

    PubMed Central

    Li, Zhenzhen; Xin, Yanmei; Zhang, Zhonghai; Wu, Hongjun; Wang, Peng

    2015-01-01

    One-dimensional nanocomposites of metal-oxide and noble metal were expected to present superior performance for nonenzymatic glucose detection due to its good conductivity and high catalytic activity inherited from noble metal and metal oxide respectively. As a proof of concept, we synthesized gold and copper oxide (Au/CuO) composite with unique one-dimensional nanocauliflowers structure. Due to the nature of the synthesis method, no any foreign binder was needed in keeping either Au or CuO in place. To the best of our knowledge, this is the first attempt in combining metal oxide and noble metal in a binder-free style for fabricating nonenzymatic glucose sensor. The Au/CuO nanocauliflowers with large electrochemical active surface and high electrolyte contact area would promise a wide linear range and high sensitive detection of glucose with good stability and reproducibility due to its good electrical conductivity of Au and high electrocatalytic activity of CuO. PMID:26068705

  12. Low energy electron elastic reflection from solid surfaces

    NASA Astrophysics Data System (ADS)

    Starý, Vladimír.; Zemek, Josef

    2004-09-01

    Using our Monte-Carlo (MC) code, we calculated the ratio of the coefficients of elastic reflection of electrons from Si, SiO 2 and Au to those of Cu and Al in the electron energy range 0.2-1.0 and 1.5 keV (Au-Cu), respectively. The electron scattering was simulated by a single scattering model. For the MC calculations, we compared the elastic differential cross-sections calculated using a static field approximation with relativistic partial wave analysis on either the Thomas-Fermi-Dirac potential of free atoms (TFD model) or the Hartree-Fock-Wigner-Seitz (muffin-tin) potential of atoms in the solid state (HFWS model). The MC data were compared with the experimental values. For both models, reasonably good agreement for Si-Cu and SiO 2-Cu systems was found. In the Au-Cu system, better agreement was achieved using the TFD model. The addition of C in a surface interaction layer of 2-5 nm improves the agreement between simulated and experimental values for the Si-Al and Si-SiO 2 systems.

  13. Hydrogen-induced atomic rearrangement in MgPd{sub 3}

    SciTech Connect

    Kohlmann, H. . E-mail: h.kohlmann@mx.uni-saarland.de; Renaudin, G.; Yvon, K.; Wannek, C.; Harbrecht, B.

    2005-04-15

    The hydrogenation behavior of MgPd{sub 3} has been studied by in situ X-ray powder diffraction and by neutron powder diffraction. At room temperature and p {approx}500kPa hydrogen pressure its structure is capable of incorporating up to one hydrogen atom per formula unit ({alpha}-MgPd{sub 3}H{sub {approx}}{sub 1}), thereby retaining a tetragonal ZrAl{sub 3}-type metal atom arrangement. Upon heating to 750K in a hydrogen atmosphere of 610kPa it transforms into a cubic modification with AuCu{sub 3}-type metal atom arrangement ({beta}-MgPd{sub 3}H{sub {approx}}{sub 0.7}). Neutron diffraction on the deuteride reveals an anion deficient anti-perovskite-type structure ({beta}-MgPd{sub 3}D{sub 0.67}, a=398.200(7)pm) in which octahedral sites surrounded exclusively by palladium atoms are occupied by deuterium. Complete removal of hydrogen (480K, 1Pa) stabilizes a new binary modification ({beta}-MgPd{sub 3}, a=391.78(2)pm) crystallizing with a primitive cubic AuCu{sub 3}-type structure. Mechanical treatment (grinding) transforms both {alpha} and {beta} modifications of MgPd{sub 3} into a cubic face-centered solid solution Mg{sub 0.25}Pd{sub 0.75} showing a random distribution of magnesium and palladium atoms.

  14. Investigation of the Phase Equilibria of Sn-Cu-Au Ternary and Ag-Sn-Cu-Au Quaternary Systems and Interfacial Reactions in Sn-Cu/Au Couples

    NASA Astrophysics Data System (ADS)

    Yen, Yee-Wen; Jao, Chien-Chung; Hsiao, Hsien-Ming; Lin, Chung-Yung; Lee, Chiapyng

    2007-02-01

    The phase equilibria of the Sn-Cu-Au ternary, Ag-Sn-Cu-Au quaternary systems and interfacial reactions between Sn-Cu alloys and Au were experimentally investigated at specific temperatures in this study. The experimental results indicated that there existed three ternary intermetallic compounds (IMCs) and a complete solid solubility between AuSn and Cu6Sn5 phases in the Sn-Cu-Au ternary system at 200°C. No quaternary IMC was found in the isoplethal section of the Ag-Sn-Cu-Au quaternary system. Three IMCs, AuSn, AuSn2, and AuSn4, were found in all couples. The same three IMCs and (Au,Cu)Sn/(Cu,Au)6Sn5 phases were found in all Sn-Cu/Au couples. The thickness of these reaction layers increased with increasing temperature and time. The mechanism of IMC growth can be described by using the parabolic law. In addition, when the reaction time was extended and the Cu content of the alloy was increased, the AuSn4 phase disappeared gradually. The (Au, Cu)Sn and (Cu,Au)6Sn5 layers played roles as diffusion barriers against Sn in Sn-Cu/Au reaction couple systems.

  15. Composition-Structure-Property Relations in Au35-68Cu49-15Al16-17 Shape Memory Thin Films

    NASA Astrophysics Data System (ADS)

    Buenconsejo, Pio John S.; Pfetzing-Micklich, Janine; Paulus, Michael; Sternemann, Christian; Ludwig, Alfred

    2016-03-01

    The phase transformation behaviour, structure and mechanical properties of Au35-68Cu49-15Al16-17 thin film shape memory alloys (SMA) have been investigated, with emphasis on the effects of Au content. The results revealed the underlying composition-structure-property relations. The thermal transformation hysteresis (Δ T) is wide (~55 K) for thin films with Au <50 at.%, while it is narrow (~15 K) for thin films with Au >50 at.%. This behaviour is correlated with the change in lattice constant of β-(Au-Cu-Al) (a β ), suggesting a structural origin on the Δ T behaviour. The mechanical properties, such as hardness and elastic modulus, varied in the range of 2-4 and 70-120 GPa, respectively. The optimum Au composition range for tuning the functional property is between 43 and 55 at.% Au, where the least amount of non-transforming phases form and Δ T can be tailored between 55 K (43 at.% Au) and 17 K (55 at.% Au). This is important for the development and practical application of Au-Cu-Al based thin film SMA.

  16. Dependence on temperature and energy of the heteroepitaxy of small metallic nanoclusters.

    PubMed

    Jiménez-Sáez, J C; Pérez-Martín, A M C; Jiménez-Rodríguez, J J

    2011-10-01

    Deposition at different energies and temperatures of small metallic nanoclusters on metallic substrates is studied by molecular-dynamics simulations. Small-, Co/Cu(001), and large-misfit, Cu/Au(001) and Au/Cu(001), systems are considered. The rise in temperature improves the epitaxial order, although its effect is smaller in large-misfit systems. Thus, by increasing this parameter, non-epitaxial clusters can turn their structure into epitaxial in the case of Co/Cu(001), into aligned in Cu/Au(001), and into layered in Au/Cu(001). Therefore, the characteristics of the alignment are determined by the properties of the material. In addition, the influence of the initial structure is more marked in Co and Cu clusters, since they can reproduce locally other phases. Epitaxy can also be improved if the deposition energy is increased, although the deposited cluster loses its original shape progressively. Its effect is different depending mainly on the degree of misfit. An increase in energy (of up to 0.75 eV/atom) produces similar effects, but more noticeable, as a rise in temperature.

  17. Mesozoic magmatism and metallogeny in the Chizhou area, Middle-Lower Yangtze Valley, SE China: Constrained by petrochemistry, geochemistry and geochronology

    NASA Astrophysics Data System (ADS)

    Song, Guoxue; Qin, Kezhang; Li, Guangming; Evans, Noreen J.; Li, Xianhua

    2014-09-01

    The Chizhou area, southeast China, hosts extensive W-Mo-Pb-Zn and Cu-Au deposits but remains relatively unstudied. A wide range of Mesozoic magmatic intrusives were analyzed (whole-rock geochemistry, Sr-Nd isotopes, zircon U-Pb dating, and zircon Lu-Hf isotopes) in order to elucidate their genesis, relationship to W-Mo-Pb-Zn-Cu-Au mineralization, and the tectonic setting of emplacement. Zircon U-Pb geochronology yielded a range of ages (147-110 Ma) encompassing three magmatic episodes; 147-135 Ma, 130-120 Ma, and 115-110 Ma. This work marks the first time the youngest episode has been identified. The oldest episode resulted in the formation of small granite porphyries, always associated with skarn-porphyry type W-Mo-Pb-Zn-Cu-Au deposits under an extensional setting. The 130-120 Ma and 115-110 Ma intrusives were the products of enhanced N-S extension with no associated mineralization. A comparative study reveals two types of magmatism-mineralization systems: acid magmatic rocks in the Chizhou area related to skarn-porphyry type W-Mo-Pb-Zn-Cu-Au deposits and intermediate-acid magmatic rocks in the Tongling area related to skarn-porphyry type Cu-Au-Fe-S deposits. Whole-rock Sr-Nd isotopes, zircon Lu-Hf isotopes, and inherited zircon U-Pb ages suggest that the lower crust and meso-neoproterozoic Shangxi group rocks were the main sources of magmatic rocks and related W-Mo-Pb-Zn-Cu-Au deposits. A genetic model for Mesozoic magmatism-skarn-porphyry type W-Mo-Pb-Zn-Cu-Au mineralization involves partial melting of the lower crust, mixing with the re-melted products of Meso-neoproterozoic Shangxi group rocks, and assimilation/fractional crystallization process. Results from this study suggest that there is great potential for the discovery of more and larger skarn-porphyry type W-Mo deposits in the transitional W-Mo-Pb-Zn metallogenic belt.

  18. [Anatomopathological behavior of gallbladder cancer. Frequency and importance of precancerous epithelial lesions of gallbladder cancer].

    PubMed

    Trujillo, C; Olaechea de Careaga, B; Uría, J L; Villagómez, G; Antelo, J

    1986-01-01

    Surgical and autopsy materials were analyzed in a period of six years at La Paz, Bolivia "Bolivian Japanese Gastroenterological Institute" (Instituto de Gastroenterología Boliviano Japonés de La Paz, Bolivia), searching for macro and microscopic appearance of gallbladder cancer. Adenocarcinoma with infiltrative growth was the most frequent finding. Cholecystitis and Cholelithiasis were present in all the cases of gallbladder cancer. Epithelial lesions such hyperplasia, atypical hyperplasia and carcinoma in situ were frequent findings in the surrounding mucosa of invasive gallbladder carcinoma and not so frequent in benign gallbladder lesions. Group V of Nevin classification was common in our cases.

  19. Drug education in bolivian schools: A feasibility study for cross-cultural application of a preventive curricular unit

    NASA Astrophysics Data System (ADS)

    Gonzalez, Gerardo M.; Moreno, Veronica Kaune

    1995-11-01

    The purpose of this study was to test the feasibility of adapting and implementing in La Paz, Bolivia a drug education course originally developed for use in the middle schools in the United States. On the basis of teacher and student evaluations, it was concluded that the unit is a viable, culturally relevant and effective method of drug education in the public and private schools in La Paz. Implications for the prevention of other health-related problems and for implementation of a demandreduction strategy to prevent drug abuse throughout the Americas are discussed.

  20. Geology and Mineral Resources of the East Mojave National Scenic Area, San Bernardino County, California

    USGS Publications Warehouse

    Theodore, Ted G.

    2007-01-01

    resources in the EMNSA only to currently known types of deposits and to regionally representative tonnages for such deposits would undoubtedly yield small estimates for volumes of many metals that might be exploited. Metals from most newly discovered, base- and ferrous-metal deposits of the types presently known in the EMNSA probably would be insignificant from the standpoint of national needs. For example, copper from a newly discovered skarn deposit in the EMNSA would have roughly a 25 percent chance of being in excess of approximately 10,000 tonnes contained Cu, if the grade-and-tonnage distribution curves of Jones and Menzie (1986b) for copper skarns are applicable to copper skarn in the EMNSA. Most copper in the United States is produced in the Southwest from much larger open-pit operations than those associated with the typical copper skarn; the former operations exploit large-tonnage porphyry-type systems. Historically, the EMNSA has been the site of minor production of many metals from a large number of sites. Since 1985, however, a small number of sites in the EMNSA whose gold production and reserves are much greater than that of the preceding discoveries have been developed (see U.S. Bureau of Mines, 1990a). Nonetheless, widespread distribution of numerous types of deposits (including copper skarn, lead-zinc skarn, tin-tungsten skarn, polymetallic vein, gold-silver quartz-pyrite vein, low-fluorine porphyry molybdenum, gold breccia pipe, and volcanic-hosted gold) that are petrogenetically associated with igneous rock in many parts of the EMNSA is indicative of a metallogenic environment that may be the site of future discoveries of mineral-deposit types that are not now recognized by the exploration community. The science, art, and, yes, even luck of exploration procedures continually evolve, and this evolution is one of the most important aspects of currently employed methods of exploration (Bailly, 1981; Hutchinson and Grauch, 1991).

  1. Noble metal based plasmonic nanomaterials and their application for bio-imaging and photothermal therapy

    NASA Astrophysics Data System (ADS)

    Zhu, Dewei

    (Cu 2-xS) NCs as a template for preparing gold sulfide (Au2S) NCs and intermediate Cu2-xS-Au2S heterostructures by cation exchange. In chapter two, we demonstrate the use of Au-Cu2-xSe nano-dimers for high contrast multimodal imaging in vitro and in vivo. Their broad LSPR absorbance and scattering enables both dark-field optical imaging and photoacoustic (PA) imaging with different light sources. The clinical relevance of these new PA contrast agents was demonstrated through deep tissue visualization of a sentinel lymph node (SLN) in a rat. Imaging through layers of chicken breast tissue at total imaging depths needed for human SLN imaging was achieved. Further, the kinetics of these NCs in the rat circulatory system were monitored in vivo. A widely available and relatively low cost Nd:YAG laser source(1064 nm) was used for all PA imaging experiments, which is an additional benefit for easy commercialization and clinical translation. Thus, these unique Au-Cu2-xSe heterodimer NPs provide a promising optical contrast agent for deep tissue imaging by PAT, as well as a new material system for fundamental studies of plasmonic interactions. In chapter three, we study the potential of both Au-Cu 2-xSe NCs and multi-branched Au NCs for use in photothermal therapy (PTT). Upon illumination with a 980 nm laser beam, the Au-Cu2-xSe nanocrystals produce significant photothermal heating, exhibiting a photothermal transduction efficiency of 32%, which is comparable to that of Au nanorods and nanoparticles (10nm). The multi-branched Au NCs exhibited a photothermal transduction efficiency of 60%, significantly higher than other materials tested in this study. In vitro photothermal heating of either Au-Cu2-xSe nanocrystals or multi-branched Au nanocrystals in the presence of human cervical cancer cells caused effective cell ablation after 10 min laser irradiation at 1.34 W/cm2. Cell viability assays demonstrate that the two classes of nanocrystals are biocompatible at doses needed for

  2. 75 FR 14643 - Arizona Disaster #AZ-00011

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-26

    ... disaster: Primary Counties: Apache, Coconino, Gila, Greenlee, La Paz, Mohave, Navajo, Yavapai, and the Gila River Indian Community, Hopi Tribe, Navajo Nation, San Carlos Apache, Tohono O'odham Nation, and White Mountain Apache Tribe. The Interest Rates are: Percent For Physical Damage: Non-Profit Organizations...

  3. Synopsis of the genus Neoeutrypanus Monné, 1977 (Coleoptera, Cerambycidae, Lamiinae), with the description of two new species.

    PubMed

    Botero, Juan Pablo; Monné, Miguel A

    2015-01-01

    Two new species of Neoeutrypanus Monné, 1977 are described: N. llanero sp. nov. from Colombia (Meta Department), and N. dentatus sp. nov. from Bolivia (La Paz Department). A key to species of Neoeutrypanus is provided and new distributional data for N. decorus (Bates, 1881) and N. mutilatus (Germar, 1824) are given.

  4. Implant-supported fixed dental prostheses with CAD/CAM-fabricated porcelain crown and zirconia-based framework.

    PubMed

    Takaba, Masayuki; Tanaka, Shinpei; Ishiura, Yuichi; Baba, Kazuyoshi

    2013-07-01

    Recently, fixed dental prostheses (FDPs) with a hybrid structure of CAD/CAM porcelain crowns adhered to a CAD/CAM zirconia framework (PAZ) have been developed. The aim of this report was to describe the clinical application of a newly developed implant-supported FDP fabrication system, which uses PAZ, and to evaluate the outcome after a maximum application period of 36 months. Implants were placed in three patients with edentulous areas in either the maxilla or mandible. After the implant fixtures had successfully integrated with bone, gold-platinum alloy or zirconia custom abutments were first fabricated. Zirconia framework wax-up was performed on the custom abutments, and the CAD/CAM zirconia framework was prepared using the CAD/CAM system. Next, wax-up was performed on working models for porcelain crown fabrication, and CAD/CAM porcelain crowns were fabricated. The CAD/CAM zirconia frameworks and CAD/CAM porcelain crowns were bonded using adhesive resin cement, and the PAZ was cemented. Cementation of the implant superstructure improved the esthetics and masticatory efficiency in all patients. No undesirable outcomes, such as superstructure chipping, stomatognathic dysfunction, or periimplant bone resorption, were observed in any of the patients. PAZ may be a potential solution for ceramic-related clinical problems such as chipping and fracture and associated complicated repair procedures in implant-supported FDPs.

  5. 3 CFR 8884 - Proclamation 8884 of October 8, 2012. Establishment of the César E. Chávez National Monument

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... national monuments, and to reserve as a part thereof parcels of land, the limits of which in all cases... have expressed support for establishing a unit of the National Park System at La Paz; Whereas the... hereby proclaim, set apart, and reserve as the César E. Chávez National Monument (monument) the...

  6. In Galápagos … and Uncomfortable with Evolution

    ERIC Educational Resources Information Center

    Cotner, Sehoya; Graczyk, Hannah; Rodríguez Garcia, José Luis; Moore, Randy

    2016-01-01

    In June 2013, the third World Evolution Summit convened on San Cristóbal, hosting scientists from around the world (Paz-y-Miño-C and Espinosa 2013)--neither the first nor likely the last gathering of biologists on these remote islands. Clearly, both locals and an international audience perceive Galápagos as figuring prominently in discourse about…

  7. Larval description of Copitarsia incommoda (Walker) (Lepidoptera: Noctuidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The last-instar larva of Copitarsia incommoda (Walker) is described for the first time. Specimens in this study were reared from quinoa (Chenopodium quinoa Willd., Chenopodiaceae), Bolivia, La Paz, 4 km S Viacha, Quipaquipani, 3880 m. The larva of Copitarsia incommoda is compared with larvae of Copi...

  8. 77 FR 12873 - Notice of Segregation of Public Lands in the State of Arizona Associated With the Proposed...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-02

    ... the Proposed Quartzsite Solar Energy Project, La Paz County, AZ AGENCY: Bureau of Land Management... made in connection with the BLM's processing of a right-of-way (ROW) application for Quartzsite Solar Energy, LLC's Quartzsite Solar Energy Project (Proposed Project). This segregation covers approximately...

  9. Arizona Public Library Statistics, 1998-1999.

    ERIC Educational Resources Information Center

    Arizona State Dept. of Library, Archives and Public Records, Phoenix.

    The "Arizona Public Library Statistics, 1998-1999" is compiled from information supplied by the state's public libraries. The document is divided according to the following county groups: Apache, Cochise; Coconino, Gila; Graham, Greenlee, La Paz; Maricopa; Mohave, Navajo; Pima, Pinal; Santa Cruz, Yavapai; and Yuma. Within each of these sections,…

  10. Arizona Public Library Statistics, 1996-1997.

    ERIC Educational Resources Information Center

    Arizona State Dept. of Library, Archives and Public Records, Phoenix.

    This document is a compilation of information supplied by Arizona public libraries. Data is arranged by a separate index divider for each of these county groups: Apache, Cochise, and Coconino; Gila, Graham, Greenlee, and La Paz; Maricopa and Mohave; Navajo, Pima, and Pinal; and Santa Cruz, Yavapai, and Yuma. Each section contains tables of the…

  11. Relationship Between Orthographic-Motor Integration And Computer Use For The Production Of Creative And Well-Structured Written Text

    ERIC Educational Resources Information Center

    Christensen, Carol A.

    2004-01-01

    Background: Orthographic-motor integration refers to the way in which orthographic knowledge is integrated with fine-motor demands of handwriting. A strong relationship has shown to exist between orthographic-motor integration and students' ability to produce creative and well-structured written text (De La Paz & Graham, 1995). This relationship…

  12. 77 FR 71702 - Final Flood Elevation Determinations

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-04

    ... 12866 of September 30, 1993, Regulatory Planning and Review, 58 FR 51735. ] Executive Order 13132... et seq.; Reorganization Plan No. 3 of 1978, 3 CFR, 1978 Comp., p. 329; E.O. 12127, 44 FR 19367, 3 CFR... Mascaras confluence. Approximately 100 feet +7338 upstream of Camino Del Norte. Arroyo De La Paz At...

  13. The Shape of Things to Come: CEMSE and the Reinvention of Bolivian Public Education.

    ERIC Educational Resources Information Center

    Healy, Kevin

    1994-01-01

    Since 1986, the Centro de Multiservicios Educativos (multiservice educational center) in urban La Paz (Bolivia) has increased educational opportunities of low-income students attending public schools. The center offers a variety of services including vocational programs, legal assistance, health programs, counseling programs, science labs, and…

  14. American Cooperative Schools in Bolivia. The Ball State Report.

    ERIC Educational Resources Information Center

    Dunworth, John

    Four American Cooperative Schools in Bolivia are surveyed in this document in connection with a project to provide inservice development in the form of graduate courses, workshops, and consultantships. The four schools were 1) the American Cooperative School in La Paz, serving children of all nationalities from prekindergarten through grade 12…

  15. Listening to the Third Voices of Pangasinan Students: Designing and Enacting Culturally Sensitive Curriculum

    ERIC Educational Resources Information Center

    Wilder, Phillip

    2015-01-01

    This response builds upon Marie Paz Morales' "Influence of culture and language sensitive physics on science attitude achievement" by exploring how an expanded understanding of the ubiquitous nature of adolescent literacy practices and identities challenge traditional notions of "in school" and "out of school"…

  16. Gender Analysis in Agriculture in Luribay Valley, Bolivia.

    ERIC Educational Resources Information Center

    Garcia-Pabon, Jose Luis

    A study focused on gender issues in Luribay, an isolated Andean region that shelters small, resource-limited farmers in the province of La Paz, Bolivia. Gender analysis was used as a tool for the planning and implementation of development programs. The research was carried out during June, July, and August 1993. A literature review focused on…

  17. Arizona Public Library Statistics. 1994-1995.

    ERIC Educational Resources Information Center

    Arizona State Dept. of Library and Archives, Phoenix.

    The statistics in this document were provided by Arizona public libraries for 1994-95. The counties are grouped as follows: Apache, Cochise,and Coconino; Gila, Graham, Greenlee, and La Paz; Maricopa and Mohave; Navajo, Pima, and Pinal; and Santa Cruz, Yavapai, and Yuma. The following data is presented in table form for each of the five groups: (1)…

  18. Arizona Public Library Statistics, 2000-2001.

    ERIC Educational Resources Information Center

    Elliott, Jan, Comp.

    These statistics were compiled from information supplied by Arizona's public libraries. The document is divided according to the following county groups: Apache, Cochise; Coconino, Gila; Graham, Greenlee, La Paz; Maricopa; Mohave, Navajo; Pima, Pinal; Santa Cruz, Yavapai; and Yuma. Statistics are presented on the following: general information;…

  19. Arizona Public Library Statistics, 1999-2000.

    ERIC Educational Resources Information Center

    Arizona State Dept. of Library, Archives and Public Records, Phoenix.

    These statistics were compiled from information supplied by Arizona's public libraries. The document is divided according to the following county groups: Apache, Cochise; Coconino, Gila; Graham, Greenlee, La Paz; Maricopa; Mohave, Navajo; Pima, Pinal; Santa Cruz, Yavapai; Yuma. Statistics are presented on the following: general information;…

  20. Prevalence of infection with Toxoplasma gondii in landrace and mixed breed pigs slaughtered in Baja California Sur state, Mexico

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Purpose We performed a cross-sectional study to determine the seroprevalence of Toxoplasma gondii infection in 308 domestic pigs slaughtered in La Paz, Baja California Sur State, Mexico using the modified agglutination test (MAT, cut off 1:25). Results Forty (13%) of the 308 pigs were seropositive ...

  1. Adolescents at Risk: Depression, Low Academic Performance, Violence, and Alcohol Increase Bolivian Teenagers' Risk of Attempted Suicide

    ERIC Educational Resources Information Center

    Dearden, Kirk A.; De La Cruz, Natalie G.; Crookston, Benjamin T.; Novilla, M. Lelinneth B.; Clark, Matthew

    2005-01-01

    This paper describes the prevalence of depression and suicidal tendencies as well as risk factors for attempted suicide among students in Bolivia. Adolescents 13-18 years old (182 females, 394 males) from randomly selected schools in La Paz completed the Youth Risk Behavior Survey. Frequencies and logistic regression were used to identify…

  2. Arizona Public Library Statistics, 1995-1996.

    ERIC Educational Resources Information Center

    Arizona State Dept. of Library, Archives and Public Records, Phoenix.

    The statistics in this document were provided by Arizona public libraries for 1995-96. The counties are grouped as follows: Apache, Cochise, and Coconino; Gila, Graham, Greenlee, and La Paz; Maricopa and Mohave; Navajo, Pima, and Pinal; and Santa Cruz, Yavapai, and Yuma. The following data is presented in table form for each of the five groups:…

  3. Source Interpretation: Teaching Students with and without LD to Read and Write Historically

    ERIC Educational Resources Information Center

    De La Paz, Susan; Morales, Petra; Winston, Philip M.

    2007-01-01

    We review domain-specific teaching approaches for students with learning disabilities in social studies, then present De La Paz's 2005 historical reasoning strategy so that readers understand the rationale for and have information on each stage of instruction. Next, we highlight the role of self-regulation for the reasoning process. We then turn…

  4. Lecciones de Aymara (Lessons in Aymara).

    ERIC Educational Resources Information Center

    Instituto de Idiomas Padres de Maryknoll, Cochabamba (Bolivia).

    This two-volume audiolingual course in Aymara for Spanish speakers is based on the variety of Aymara spoken in La Paz. The Aymara appears in phonetic transcription; all other material (introduction, directions, notes, and explanations) appear in Spanish. Lesson units in Volume I begin with a dialogue introducing the basic sentence patterns for the…

  5. CREADS, a Teacher Training Course on ESD in Costa Rica

    ERIC Educational Resources Information Center

    Jimenez-Elizondo, Alicia

    2010-01-01

    After the Costa Rican government signed a commitment to implement the UN Decade of Education for Sustainable Development (DESD), the challenge was how to put the commitment into action. Fortunately, an opportunity presented itself with an initiative called Peace with Nature (Iniciativa Paz con la Naturaleza-IPN), under which a teacher training…

  6. Central America's "Peace Parks" and Regional Conflict Resolution.

    ERIC Educational Resources Information Center

    Weed, Timothy J.

    1994-01-01

    Examines the development of transborder conservation zones, known as "peace parks," in terms of their potential importance as proving grounds for international cooperation and sustainable development, and then in their role as symbols and outright manifestations of the peace process. Includes case studies of La Amistad Biosphere Reserve, Si-a-Paz,…

  7. 76 FR 76972 - Environmental Impacts Statements; Notice of Availability

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-09

    ..., Implementation, Right-of-Way Application to the BLM, La Paz County, AZ, Comment Period Ends: 02/10/2012, Contact: Liana Reilly (720) 962-7253. Revision to FR Notice 11/10/2011: Extending Comment from 02/08/2012 to...

  8. Antarctic Meteorite Newsletter, Volume 28, Number 2

    NASA Technical Reports Server (NTRS)

    Righter, Kevin (Editor); Satterwhite, Cecilia (Editor)

    2005-01-01

    This newsletter contains classifications for 274 new meteorites from the 2003 and 2004 ANtarctic Search for METeorites (ANSMET) collections. They include samples from the Cumulus Hills, Larkman Nunatak, LaPaz Ice Field, MacAlpine Hills, Dominion Range, Miller Range, Roberts Massif, and Sandford Cliffs. Tables are provided of the newly classified Antarctic meteorites, meteorites classified by type, and tentative pairings petrographic descriptions.

  9. 16. Parker Dam, only top fourth of dam visible, at ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    16. Parker Dam, only top fourth of dam visible, at 320' high, Parker Dam is one of the highest in the world. Much of this height is because dam penetrates well below river bottom to fasten to bedrock. - Parker Dam, Spanning Colorado River between AZ & CA, Parker, La Paz County, AZ

  10. Photocopy of photograph (original print located in Archivo General de ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of photograph (original print located in Archivo General de Puerto Rico, San Juan, PR). CAISSON GATE GENERAL PLANS Dwg. 38-SJ-29 - Graving Dock, Caisson Gate, Southern end of Central Street bounded by Villaverde and La Paz Streets, Miramar, San Juan Municipio, PR

  11. Photocopy of photograph (original print located in Archivo General de ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of photograph (original print located in Archivo General de Puerto Rico, San Juan, PR). CAISSON GATE FABRICATION PHOTO DATED 1-9-40 - Graving Dock, Caisson Gate, Southern end of Central Street bounded by Villaverde and La Paz Streets, Miramar, San Juan Municipio, PR

  12. Photocopy of photograph (original print located in Archivo General de ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of photograph (original print located in Archivo General de Puerto Rico, San Juan, PR). CAISSON GATE FABRICATION PHOTO DATED APRIL 6, 1941 - Graving Dock, Caisson Gate, Southern end of Central Street bounded by Villaverde and La Paz Streets, Miramar, San Juan Municipio, PR

  13. Photocopy of photograph (original print located in Archivo General de ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of photograph (original print located in Archivo General de Puerto Rico, San Juan, PR). PHYSICAL SETTING VIEW TO SOUTHWEST DATED 12-2-40 - Graving Dock, Caisson Gate, Southern end of Central Street bounded by Villaverde and La Paz Streets, Miramar, San Juan Municipio, PR

  14. Photocopy of photograph (original print located in Archivo General de ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of photograph (original print located in Archivo General de Puerto Rico, San Juan, PR). GENERAL PLAN ELEVATION SHOWING GENERAL DETAILS - Graving Dock, Caisson Gate, Southern end of Central Street bounded by Villaverde and La Paz Streets, Miramar, San Juan Municipio, PR

  15. A first case of cutaneous leishmaniasis due to Leishmania (Viannia) lainsoni in Bolivia.

    PubMed

    Martinez, E; Le Pont, F; Mollinedo, S; Cupolillo, E

    2001-01-01

    We present the first known case of cutaneous leishmaniasis due to Leishmania (Viannia) lainsoni detected in Bolivia. The parasite was isolated from a young girl living in the subtropical region of Carrasco (900-1000 m above sea level, Caranavi Province, Department of La Paz, Bolivia). The parasite identification was confirmed by multilocus enzyme electrophoresis. PMID:11579876

  16. "From la Malinche and Menchu to Modern-Day "Mayas": Women Forging Paths through the Maze of Higher Education"

    ERIC Educational Resources Information Center

    Hall, Vickie A.

    2010-01-01

    "Beneath the rule of men entirely great, the pen is mightier than the sword." Bulwer-Lytton recognized this strength years ago, and its truth continues to ring true in the works of authors: Tzvetan Todorov, Octavio Paz, Carlos Fuentes, Rigoberta Menchu, and Deborah Tannen. Language is a centuries-old weapon wielded in the struggle against…

  17. Application of the theory of martensite crystallography to displacive phase transformations in substitutional nonferrous alloys

    NASA Astrophysics Data System (ADS)

    Muddle, B. C.; Nie, J. F.; Hugo, G. R.

    1994-09-01

    It has been demonstrated that the theory of martensite crystallography is capable of accounting successfully for the form and crystallography of a range of plate- or lath-shaped transformation products, even when the formation of the product phase involves significant substitutional diffusion. These transformations include the precipitation of metastable hexagonal γ’ (Ag2Al) plates in disordered face-centered cubic (fcc) solid-solution Al-Ag alloys, the formation of ordered AuCu II plates from disordered fcc solid solution in equiatomic Au-Cu alloys, and the formation of metastable 9R α 1, plates in ordered (B2) Cu-Zn and Ag-Cd alloys. The application of the theory to these transformations is reviewed critically and the features common to them identified. It is confirmed that, in all three transformations, the product phase produces relief at a free surface consistent with an invariant plane-strain shape change and that the transformations are thus properly described as displacive. The agreement between experimental observations and theoretical predictions of the transformation crystallography is in all cases excellent. It is proposed that successful application of the theory implies a growth mechanism in which the coherent or semicoherent, planar interface between parent and product phases maintains its structural identity during migration and that growth proceeds atom by atom in a manner consistent with the maintenance of a correspondence of lattice sites. In the case of the coherent, planar interfaces associated with γ’ precipitate plates in Al-Ag alloys, there is direct experimental evidence that this is accomplished by the motion of transformation dislocations across the coherent broad faces of the precipitate plates; the transformation dislocations define steps that are two atom layers in height normal to the habit plane and have a Burgers vector at least approximately equivalent to an (α/6)(112) Shockley partial dislocation in the parent fcc

  18. Mineralogical and fluid inclusion constraints on the evolution of the Plaka intrusion-related ore system, Lavrion, Greece

    NASA Astrophysics Data System (ADS)

    Voudouris, P.; Melfos, V.; Spry, P. G.; Bonsall, T.; Tarkian, M.; Economou-Eliopoulos, M.

    2008-05-01

    The intrusion-centered, polymetallic Plaka ore system, Lavrion, Greece, is genetically related to the emplacement of a Miocene biotite ± hornblende granodioritic body and granodiorite porphyry dikes/sills within metamorphic Mesozoic rocks of the Attic-Cycladic Crystalline Belt. The ore system includes porphyry, breccia-type, skarn, skarn-free carbonate replacement and vein-type ores enriched in Mo, W, Pb, Zn, Cu, As, Sb, Bi and Ag. Early pyrite-molybdenite (±chalcopyrite ± pyrrhotite) mineralization was deposited in multidirectional and sheeted quartz veins within the silicically and sericitically altered granodiorite intrusive. The emplacement of granodiorite porphyry dikes/sills was followed by the introduction of base metal sulphides during hydrothermal brecciation of the porphyritic rocks. Skarn- and skarn-free carbonate replacement ores developed contemporaneously with these magmatic-hydrothermal events and are characterized by the presence of pyrrhotite, pyrite, Fe-rich sphalerite and Bi-Ag-rich galena. A late Pb-As-Sb-Cu-Ag-rich banded vein (Filoni 80) is composed of pyrrhotite, chalcopyrite, arsenopyrite, sphalerite (both Fe-rich and Fe-poor), löllingite, argentian tetrahedrite, bournonite, pyrargyrite, miargyrite, native arsenic, semseyite, heteromorphite, veenite, falkmanite and fluorite, quartz and siderite. The ore mineralogy of the Plaka deposit is generally consistent with reducing and low sulphidation fluid conditions during metal deposition. Fluid inclusion data indicate that molybdenite deposition was associated with boiling between 270 and 360 °C and at a pressure of 50-200 bars, corresponding to a depth of approximately 1 km. Dilution of a saline fluid by mixing with less saline water resulted in the formation of a moderately saline (14-18 wt% NaCl equiv.), low-temperature (190-220 °C) fluid and the precipitation of sulphides and sulphosalts in the Filoni 80 vein. The evolution from early porphyry-style mineralization to the later vein ores

  19. U-Pb zircon geochronology of Mesoproterozoic postorogenic rocks and implications for post-Ottawan magmatism and metallogenesis, New Jersey Highlands and contiguous areas, USA

    USGS Publications Warehouse

    Volkert, R.A.; Zartman, R.E.; Moore, P.B.

    2005-01-01

    Postorogenic rocks are widespread in Grenville terranes of the north-central Appalachians where they form small, discordant, largely pegmatitic felsic intrusive bodies, veins, and dikes, and also metasomatic calcic skarns that are unfoliated and postdate the regional 1090 to 1030 Ma upper amphibolite- to granulite-facies metamorphism related to the Grenville (Ottawan) Orogeny. Zircons from magmatic and nonmagmatic rocks from northern New Jersey and southern New York were dated to provide information on the regional tectonomagmatic and metallogenic history following Ottawan orogenesis. We obtained U-Th-Pb zircon ages of 1004 ?? 3 Ma for pegmatite associated with the 1020 ?? 4 Ma Mount Eve Granite near Big Island, New York, 986 ?? 4 Ma for unfoliated, discordant pegmatite that intrudes supracrustal marble at the Buckwheat open cut, Franklin, New Jersey, ???990 Ma for a silicate-borate skarn layer in the Franklin Marble at Rudeville, New Jersey, and 940 ?? 2 Ma for a calc-silicate skarn layer at Lower Twin Lake, New York. This new data, together with previously published ages of 1020 ?? 4 to 965 ?? 10 Ma for postorogenic rocks from New Jersey and southern New York, provide evidence of magmatic activity that lasted for up to 60 Ma past the peak of high-grade metamorphism. Postorogenic magmatism was almost exclusively felsic and involved relatively small volumes of metaluminous to mildly peraluminous melt that fractionated from an A-type granite parent source. Field relationships suggest the melts were emplaced along lithosphere-scale fault zones in the Highlands that were undergoing extension and that emplacement followed orogenic collapse by least 30 Ma. Postorogenic felsic intrusions correspond to the niobium-yttrium-fluorine (NYF) class of pegmatites of C??erny?? (1992a). Geochronologic data provide a temporal constraint on late-stage hydrothermal activity and a metallogenic event in New Jersey at ???990 to 940 Ma that mineralized pegmatites with subeconomic to

  20. Fluid inclusion and stable isotope data for the Pea Ridge Fe-REE orebody, Missouri

    SciTech Connect

    Sidder, G.B.; Day, W.C.; Rye, R.O. )

    1993-03-01

    New fluid-inclusion and stable-isotope data define the character of the mineralizing fluids that formed the iron and rare-earth-element ore deposit at the Pea Ridge Mine, southeast Missouri. These fluids were very hot and highly saline brines that may have been magmatically derived. Early, pre-magnetite ore skarn alteration of the host rhyolitic tuff took place at temperatures greater than 420 C and possibly as high as 680 C based upon calculated temperatures of quartz-magnetite pairs. Halite homogenization of three- or more phase (liquid + vapor + salts) fluid inclusions in quartz indicates that the skarn-forming fluid had a temperature of about 460 C to > 530 C and a salinity of about 45 to 57 equivalent weight percent NaCl. Analyses of [delta][sup 18]O in quartz from the skarn zone average about 14.5[per thousand], compared to a value of about 13.0[per thousand] for quartz in the host rhyolite. Average [delta][sup 34]S values for pyrite of about 2.3[per thousand] in the skarn zone may reflect a magmatic source. Magnetite ore was deposited at temperatures between about 340 C and 530 C from a fluid with a salinity between about 54 and 60 equivalent weight percent NaCl. The large apparent range of temperatures indicated by both fluid-inclusion and stable-isotope data within each zone may be due to contamination by quartz from multiple stages of quartz deposition. Also, the assumed isotopic equilibrium between some mineral pairs may be incorrect. Moreover, fluid inclusions are relatively rare in all ore and alteration zones except the silicified zone, and only a few inclusions are clearly primary in origin. Nonetheless, the predominance of high temperatures and high salinities in all of the mineralized and altered zones supports the interpretation that Pea ridge is a magmatic hydrothermal deposit. This magmatic hydrothermal model is also supported by paragenetic relations defined by geologic mapping and geochemical modeling of major-, minor-, and trace-element data.

  1. Mineral resources potential map of the South Sierra Wilderness and the South Sierra Roadless Area, Inyo and Tulare counties, California

    USGS Publications Warehouse

    Diggles, Michael F.

    1987-01-01

    There are five areas with mineral resource potential and one area with geothermal energy potential in the South Sierra Wilderness and the South Sierra Roadless Area. The area south of Summit Meadows and the area south of Hogback Creek have moderate resource potential for tungsten and molybdenum in small skarn deposits. The area between Summit meadow and Hogback Creek and the area from south of Jackass Meadows to northwest of Granite Knob have low mineral resource potential for tungsten and molybdenum. The area south of and including Walker Creek has low mineral resource potential for lead and zinc. The area including and surrounding Monache Mountain has high geothermal energy resource potential.

  2. Colorado quartz: occurrence and discovery

    USGS Publications Warehouse

    Kile, D.E.; Modreski, P.J.; Kile, D.L.

    1991-01-01

    The many varieties and associations of quartz found throughout the state rank it as one of the premier worldwide localities for that species. This paper briefly outlines the historical importance of the mineral, the mining history and the geological setting before discussing the varieties of quartz present, its crystallography and the geological enviroments in which it is found. The latter include volcanic rocks and near surface igneous rocks; pegmatites; metamorphic and plutonic rocks; hydrothermal veins; skarns and sedimentary deposits. Details of the localities and mode of occurrence of smoky quartz, amethyst, milky quartz, rock crystal, rose quartz, citrine, agate and jasper are then given. -S.J.Stone

  3. EAST PART OF THE RAYMOND PEAK ROADLESS AREA, CALIFORNIA.

    USGS Publications Warehouse

    John, David A.; Federspiel, Frank E.

    1984-01-01

    The east part of the Raymond Peak Roadless Area, Alpine County, California encompasses about 58 sq mi along the crest and eastern slope of the Sierra Nevada. Based on a mineral survey there are demonstrated silver-gold resources at five properties within a large area of probable silver-gold potential in the east part of the area. A small area with probable mineral-resource potential for skarn-type tungsten resources occurs at the north end of the roadless area. The geologic setting precludes the presence of fossil fuels and no other energy resources were identified in the study.

  4. Metal-residence sites in mine tailings in the Magdalena District, New Mexico, USA

    SciTech Connect

    Larocque, A.C.L.; Chapin, C.E.; Laughlin, A.W.; Hickmott, D.

    1996-05-01

    Mineralization in the Kelly Mining Camp is hosted by the Mississippian Kelly Limestone and comprises Zn-Pb skarn, replacement, and vein deposits related to Tertiary intrusive activity. The ore consists of primary (hypogene) sulfide mineralization which has been oxidized near surface to form secondary (supergene) mineralization. A zone of secondary sulfide-enrichment separates the sulfide and oxide ores. Mine tailings in the camp contain primary sulfide, oxide and gangue minerals, secondary (supergene) minerals formed during weathering of the primary ore, and tertiary minerals formed by alteration of hypogene and supergene assemblages after deposition in the tailings impoundment.

  5. Eagle Mountain Mine: geology of the former Kaiser Steel Operation in Riverside County, California

    USGS Publications Warehouse

    Force, Eric R.

    2001-01-01

    Iron ore replaces a variety of host rocks along the two unconformities, forming massive to globular bodies, and its mineralogy correlates with deuteric alteration features, not anhydrous skarn. Its pyrite contains as much as 3% cobalt. Iron was only one of five elements that showed mobility in this region on a scale that suggests basic crustal processes. The others in probable order of flux magnitude are silica, magnesium, sodium, and potassium, to form regionally distributed “vitreous quartzite”, dolomite, and secondary feldspars, respectively.

  6. Estimating gold-ore mineralization potential within Topolninsk ore field (Gorny Altai)

    NASA Astrophysics Data System (ADS)

    Timkin, T.; Voroshilov, V.; Askanakova, O.; Cherkasova, T.; Chernyshov, A.; Korotchenko, T.

    2015-11-01

    Based on the results of ore and near-ore metasomatite composition analysis, the factors and indicators of gold-ore mineralization potential were proposed. Integration of the obtained data made it possible to outline magmatic, structural, and lithological factors, as well as direct and indirect indicators of gold-ore mineralization. Applying multidimensional analysis inherent to geochemical data, the spatial structure was investigated, as well as the potential mineralization was identified. Based on the developed and newly-identified mineralization, small (up to medium-sized) mineable gold-ore deposits in skarns characterized by complex geological setting was identified.

  7. Study of structural, electronic and elastic properties of RPd{sub 3} (R = Lu and Sc) compounds

    SciTech Connect

    Thakur, Veena Pagare, Gitanjali Chouhan, S. S.; Sanyal, S. P.

    2014-04-24

    The structural, electronic and elastic properties of nonmagnetic RPd{sub 3} (R = Lu and Sc) compounds, which crystallize in AuCu{sub 3}-type structure, are studied using first principles density functional theory based on full potential linearized augmented plane wave (FP-LAPW) method. The calculations are carried out within the PBE-GGA and WC-GGA for the exchange correlation potential. Our calculated ground state properties such as lattice constant (a0), bulk modulus (B) and its pressure derivative (B’) are in good agreement with the experimental results. We first time predict the elastic constants for these compounds using different approximations of GGA. These RPd{sup 3} compounds are found to be ductile in nature in accordance with Pugh’s criteria. The computed electronic band structures and density of states show metallic character of these compounds.

  8. Effects of postdeposition treatments on surfaces of CdTe/CdS solar cells

    NASA Astrophysics Data System (ADS)

    Pookpanratana, S.; Liu, X.; Paudel, N. R.; Weinhardt, L.; Bär, M.; Zhang, Y.; Ranasinghe, A.; Khan, F.; Blum, M.; Yang, W.; Compaan, A. D.; Heske, C.

    2010-10-01

    Soft x-ray spectroscopy has been used to follow the effects of postdeposition steps (CdCl2 activation and back contact treatment) on surfaces and interfaces in CdTe-based superstrate solar cells. We find that the CdCl2 activation drives sulfur atoms from the CdS layer toward the back contact but not to its surface. Using atomic force microscopy, we find that both treatments strongly influence the morphology of the Au/Cu back contact. The spectroscopic results, in contrast, suggest that CdCl2 activation exhibits a larger impact on the surface composition and chemical structure of the interfaces involved in CdTe solar cells.

  9. Determination of Trace Concentration in TMD Detectors using PGAA

    NASA Astrophysics Data System (ADS)

    Tomandl, I.; Viererbl, L.; Kudějová, P.; Lahodová, Z.; Klupák, V.; Fikrle, M.

    2015-05-01

    Transmutation detectors could be alternative to the traditional activation detector method for neutron fluence dosimetry at power nuclear reactors. This new method require an isotopically highly-sensitive, non-destructive in sense of compactness as well as isotopic content, precise and standardly used analytical method for trace concentration determination. The capability of Prompt Gamma-ray Activation Analysis (PGAA) for determination of trace concentrations of transmuted stable nuclides in the metallic foils of Ni, Au, Cu and Nb, which were irradiated for 21 days in the reactor core at the LVR-15 research reactor in Řež, is reported. The PGAA measurements of these activation foils were performed at the PGAA facility at Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRMII) in Garching.

  10. Advanced electron microscopy characterization of multimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Khanal, Subarna Raj

    Research in noble metal nanoparticles has led to exciting progress in a versatile array of applications. For the purpose of better tailoring of nanoparticles activities and understanding the correlation between their structures and properties, control over the composition, shape, size and architecture of bimetallic and multimetallic nanomaterials plays an important role on revealing their new or enhanced functions for potentials application. Advance electron microscopy techniques were used to provide atomic scale insights into the structure-properties of different materials: PtPd, Au-Au3Cu, Cu-Pt, AgPd/Pt and AuCu/Pt nanoparticles. The objective of this work is to understand the physical and chemical properties of nanomaterials and describe synthesis, characterization, surface properties and growth mechanism of various bimetallic and multimetallic nanoparticles. The findings have provided us with novel and significant insights into the physical and chemical properties of noble metal nanoparticles. Different synthesis routes allowed us to synthesize bimetallic: Pt-Pd, Au-Au3Cu, Cu-Pt and trimetallic: AgPd/Pt, AuCu/Pt, core-shell and alloyed nanoparticles with monodispersed sizes, controlled shapes and tunable surface properties. For example, we have synthesized the polyhedral PtPd core-shell nanoparticles with octahedral, decahedral, and triangular plates. Decahedral PtPd core-shell structures are novel morphologies for this system. For the first time we fabricated that the Au core and Au3Cu alloyed shell nanoparticles passivated with CuS2 surface layers and characterized by Cs-corrected scanning transmission electron microscopy. The analysis of the high-resolution micrographs reveals that these nanoparticles have decahedral structure with shell periodicity, and that each of the particles is composed by Au core and Au3Cu ordered superlattice alloyed shell surrounded by CuS 2 surface layer. Additionally, we have described both experimental and theoretical methods of

  11. Thermodynamic properties of liquid Au–Cu–Sn alloys determined from electromotive force measurements

    PubMed Central

    Guo, Zhongnan; Hindler, Michael; Yuan, Wenxia; Mikula, Adolf

    2011-01-01

    The thermodynamic properties of the ternary Au–Cu–Sn system were determined with the electromotive force (EMF) method using a liquid electrolyte. Three different cross-sections with constant Au:Cu ratios of 3:1, 1:1, and 1:3 were applied to measure the thermodynamic properties of the ternary system in the temperature range between the liquidus temperature of the alloys and 1023 K. The partial free energies of Sn in liquid Au–Cu–Sn alloys were obtained from EMF data. The integral Gibbs free energy and the integral enthalpy at 900 K were calculated by Gibbs–Duhem integration. The ternary interaction parameters were evaluated using the Redlich–Kister–Muggianu polynomial. PMID:22039311

  12. First-principles study of electronic and elastic properties of LuAl3

    NASA Astrophysics Data System (ADS)

    Shukla, Pushplata; Shrivastava, Deepika; Sanyal, Sankar P.

    2016-05-01

    A systematic theoretical study of electronic structure of rare earth intermetallic LuAl3 has been carried out using full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT) within the generalized gradient approximation(GGA) for exchange and correlation potential. The ground state properties such as lattice constant (ao), bulk modulus (B) and pressure derivative of bulk modulus (Bˈ) were evaluated. LuAl3 has the cubic AuCu3 type crystal structure. The electronic properties of this compound have been analyzed quantatively from band structure and DOS. It is clear from band structure that this compound is metallic in nature. The calculated elastic constants infer that this compound is mechanically stable.

  13. Gold based bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Schroers, Jan; Lohwongwatana, Boonrat; Johnson, William L.; Peker, Atakan

    2005-08-01

    Gold-based bulk metallic glass alloys based on Au-Cu-Si are introduced. The alloys exhibit a gold content comparable to 18-karat gold. They show very low liquidus temperature, large supercooled liquid region, and good processibility. The maximum casting thickness exceeds 5mm in the best glassformer. Au49Ag5.5Pd2.3Cu26.9Si16.3 has a liquidus temperature of 644K, a glass transition temperature of 401K, and a supercooled liquid region of 58K. The Vickers hardness of the alloys in this system is ˜350Hv, twice that of conventional 18-karat crystalline gold alloys. This combination of properties makes the alloys attractive for many applications including electronic, medical, dental, surface coating, and jewelry.

  14. A new bimetallic plasmonic photocatalyst consisting of gold(core)-copper(shell) nanoparticle and titanium(IV) oxide support

    SciTech Connect

    Sato, Yuichi; Naya, Shin-ichi; Tada, Hiroaki

    2015-10-01

    Ultrathin Cu layers (∼2 atomic layers) have been selectively formed on the Au surfaces of Au nanoparticle-loaded rutile TiO{sub 2} (Au@Cu/TiO{sub 2}) by a deposition precipitation-photodeposition technique. Cyclic voltammetry and photochronopotentiometry measurements indicate that the reaction proceeds via the underpotential deposition. The ultrathin Cu shell drastically increases the activity of Au/TiO{sub 2} for the selective oxidation of amines to the corresponding aldehydes under visible-light irradiation (λ > 430 nm). Photochronoamperometry measurements strongly suggest that the striking Cu shell effect stems from the enhancement of the charge separation in the localized surface plasmon resonance-excited Au/TiO{sub 2}.

  15. Atomic Diffusion within Individual Gold Nanocrystal

    PubMed Central

    Xiong, Gang; Clark, Jesse N.; Nicklin, Chris; Rawle, Jonathan; Robinson, Ian K.

    2014-01-01

    Due to their excess surface free energy and structural instabilities, nanoparticles exhibit interesting physical and chemical properties. There has been an ever-growing interest in investigating these properties, driven by the desire to further miniaturize electronic devices, develop new functional materials and catalysts. Here, the intriguing question of how diffusion evolves in a single nanoparticle is investigated by measuring the spatial and temporal variations of the diffracted coherent X-ray intensity during copper diffusion into a gold nanocrystal. Dislocation loops formed from the insertion of single layer of extra atoms between neighbouring gold host lattice planes are detected. Au-Cu alloy channels are found to penetrate the nanocrystal due to the differential diffusion rate along different directions. With the advent of higher brilliance sources and free-electron-lasers, Bragg Coherent X-ray Diffraction Imaging can play an important role in unveiling atomic behaviours in three dimensions for nanomaterials during various fundamental processes. PMID:25341377

  16. Quantum transport effects in copper(II) phthalocyanine sandwiched between gold nanoelectrodes.

    PubMed

    Tada, Tomofumi; Hamayama, Shinya; Kondo, Masakazu; Yoshizawa, Kazunari

    2005-06-30

    The electrical transmission of copper(II) phthalocyanine (CuPc) sandwiched between gold nanoelectrodes is studied on the basis of the Green function formalism coupled with the Gaussian-broadening technique. In the Au-CuPc-Au junction, broadened density of states (DOS) of the Au chains is defined as continuous DOS of electrodes to calculate the Green function of the electrodes. Two peaks of the transmission function found in the vicinity of the Fermi level are analyzed in terms of molecular orbitals (MOs). A convenient procedure to analyze MO contribution to a transmission peak is proposed. It is found that (I) symmetry-matched interactions between CuPc and the gold nanoelectrodes are important to the enhancement of the transmission function and (II) the nanoelectrodes have almost no effect on the electronic states of CuPc.

  17. Single-source precursors for alloyed gold-silver nanocrystals - a molecular metallurgy approach.

    PubMed

    Zopes, David; Hegemann, Corinna; Schläfer, Johannes; Tyrra, Wieland; Mathur, Sanjay

    2015-04-20

    Multiple silver(I)-aurates(I) have been prepared by salt metathesis reactions that act as efficient single-source precursors to colloidal gold silver alloys with the highest possible atom economy in the chemical synthesis of nanostructures. The CF3 group present on the Au cation acts as an in situ reducing agent and can be converted into CO ligands by simple hydrolysis. This ligand-mediated activation and subsequent decomposition of metal-organic precursors impose a molecular control over the nucleation process, producing homogeneously alloyed (Ag-Au) nanoparticles with an atomic Au:Ag ratio of 1:1. The concept also works for the Au-Cu system and acts as a pointer to replace Au (Ag) with less expensive (Cu) metals.

  18. Current-induced spin polarization on metal surfaces probed by spin-polarized positron beam

    PubMed Central

    Zhang, H. J.; Yamamoto, S.; Fukaya, Y.; Maekawa, M.; Li, H.; Kawasuso, A.; Seki, T.; Saitoh, E.; Takanashi, K.

    2014-01-01

    Current-induced spin polarization (CISP) on the outermost surfaces of Au, Cu, Pt, Pd, Ta, and W nanoscaled films were studied using a spin-polarized positron beam. The Au and Cu surfaces showed no significant CISP. In contrast, the Pt, Pd, Ta, and W films exhibited large CISP (3~15% per input charge current of 105 A/cm2) and the CISP of Ta and W were opposite to those of Pt and Pd. The sign of the CISP obeys the same rule in spin Hall effect suggesting that the spin-orbit coupling is mainly responsible for the CISP. The magnitude of the CISP is explained by the Rashba-Edelstein mechanism rather than the diffusive spin Hall effect. This settles a controversy, that which of these two mechanisms dominates the large CISP on metal surfaces. PMID:24776781

  19. Wetting of metals and glasses on Mo

    SciTech Connect

    Saiz, Eduardo; Tomsia, Antoni P.; Saiz, Eduardo; Lopez-Esteban, Sonia; Benhassine, Mehdi; de Coninck, Joel; Rauch, Nicole; Ruehle, Manfred

    2008-01-08

    The wetting of low melting point metals and Si-Ca-Al-Ti-O glasses on molybdenum has been investigated. The selected metals (Au, Cu, Ag) form a simple eutectic with Mo. Metal spreading occurs under nonreactive conditions without interdiffusion or ridge formation. The metals exhibit low (non-zero) contact angles on Mo but this requires temperatures higher than 1100 C in reducing atmospheres in order to eliminate a layer of adsorbed impurities on the molybdenum surface. By controlling the oxygen activity in the furnace, glass spreading can take place under reactive or nonreactive conditions. We have found that in the glass/Mo system the contact angle does not decrease under reactive conditions. In all cases, adsorption from the liquid seems to accelerate the diffusivity on the free molybdenum surface.

  20. High Pressure Transport Studies of NdIn3

    NASA Astrophysics Data System (ADS)

    Purcell, Kenneth; Graf, David; Ebihara, Takao

    2015-03-01

    NdIn3 is a cubic antiferromagnetic metal that orders with a Neel temperature of 5.9 K and belongs to a family of rare earth intermetallic compounds RIn3 that have a cubic AuCu3-type crystal structure. At 0.5 K and the magnetic field applied in 100 direction, NdIn3 exhibits metamagnetic transitions at 7.8 T and 8.9 T before entering a field induced paramagnetic state at 11.1 T. We report high pressure transport studies of single crystal NdIn3 and the effect that pressure has on the Neel temperature, critical field, and metamagnetic transitions observed in the magnetoresistance. Comparisons to the behavior of the pressure induced superconductor CeIn3 will be discussed.

  1. Insensitivity of tunneling anisotropic magnetoresistance to non-magnetic electrodes

    SciTech Connect

    Wang, Y. Y.; Song, C. Wang, G. Y.; Zeng, F.; Pan, F.

    2013-11-11

    Ferromagnetic electrodes play a crucial role in magnetoresistance effect and spin injection, whereas the essential features of non-magnetic metal electrodes in spintronics are commonly ignored except for their electrical conductivity. Here, we verify that the room-temperature tunneling anisotropic magnetoresistance (TAMR) behavior in antiferromagnet-based [Pt/Co]/IrMn/AlO{sub x}/metal (metal = Pt, Au, Cu, Al) junctions is insensitive to the top metal electrodes. Similar out-of-plane signals are detected for different electrodes, in contrast to the varied shapes of in-plane TAMR curves which are most likely attributed to the differences in the multidomain structure of the magnetic electrode. This would add a different dimension to spintronics.

  2. Servohydraulic methods for mechanical testing in the Sub-Hopkinson rate regime up to strain rates of 500 1/s.

    SciTech Connect

    Crenshaw, Thomas B.; Boyce, Brad Lee

    2005-10-01

    Tensile and compressive stress-strain experiments on metals at strain rates in the range of 1-1000 1/s are relevant to many applications such as gravity-dropped munitions and airplane accidents. While conventional test methods cover strain rates up to {approx}10 s{sup -1} and split-Hopkinson and other techniques cover strain rates in excess of {approx}1000 s{sup -1}, there are no well defined techniques for the intermediate or ''Sub-Hopkinson'' strain-rate regime. The current work outlines many of the challenges in testing in the Sub-Hopkinson regime, and establishes methods for addressing these challenges. The resulting technique for obtaining intermediate rate stress-strain data is demonstrated in tension on a high-strength, high-toughness steel alloy (Hytuf) that could be a candidate alloy for earth penetrating munitions and in compression on a Au-Cu braze alloy.

  3. Chemical ordering in magnetic FePd/Pd(001) epitaxial thin films induced by annealing

    SciTech Connect

    Halley, D.; Bayle-Guillemaud, P.; Arenal, R.; Marty, A.; Samson, Y.; Gilles, B.

    2004-11-01

    Chemically disordered FePd epitaxial layers are grown at room temperature by molecular beam epitaxy on a Pd(001) buffer layer and then annealed in order to induce the chemically ordered L1{sub 0} (AuCu I) structure. Contrary to what is observed in the case of ordering during growth above room temperature, the ordered structure appears here with the three possible variants of the L1{sub 0} phase. The ratio of the three different variant volumes is set by the residual epitaxial strain in the layer before annealing. It thus explains that for long annealing times, the long-range order parameter associated with the L1{sub 0} variant with c along the (100) growth direction saturates at a value close to 0.65, and never reaches unity. Magnetic consequences of the ordering are studied.

  4. Wheel Abrasion Experiment Metals Selection for Mars Pathfinder Mission

    NASA Technical Reports Server (NTRS)

    Hepp, Aloysius F.; Fatemi, Navid S.; Wilt, David M.; Ferguson, Dale C.; Hoffman, Richard; Hill, Maria M.; Kaloyeros, Alain E.

    1996-01-01

    A series of metals was examined for suitability for the Wheel Abrasion Experiment, one of ten microrover experiments of the Mars Pathfinder Mission. The seven candidate metals were: Ag, Al, Au, Cu, Ni, Pt, and W. Thin films of candidate metals from 0.1 to 1.0 micrometer thick were deposited on black anodized aluminum coupons by e-beam and resistive evaporation and chemical vapor deposition. Optical, corrosion, abrasion, and adhesion criteria were used to select Al, Ni, and Pt. A description is given of the deposition and testing of thin films, followed by a presentation of experimental data and a brief discussion of follow-on testing and flight qualification.

  5. Solid Inclusions in Au-nuggets, genesis and derivation from alkaline rocks of the Guli Massif, Northern Siberia

    NASA Astrophysics Data System (ADS)

    Dvorani, Sami N.

    2016-04-01

    A total of 112 Au-nuggets, collected from alluvial placer deposits of the Ingarinda River from the Guli massif, located in northem Siberia, Russia, were investigated. The Guli massif consists of a huge dunite-clinopyroxenite complex (the largest complex in the world), an alkaline to highly alkaline rock suite (melilite, nephelinite, ijolite) enveloping the dunite and carbonatite intrusions, associated with disseminated schlieren type chromitite and Au-Ag, Pt placer deposits. The nuggets are characterized by various sizes and shapes and show chemical compositions Au, Au-Ag and AuCu, typical for a derivate of carbon-atites and/or ultramafic complexes. A great variety of oxide, silicate, REE-minerals, carbonate and sulphide inclusions have been detected in the nuggets, which are identical in mineralogy and chemical composition to mineral constituents of the alkaline to highly alkaline rock suite surrounding the Guli dunite core complex thus, considered as the source for Au-nuggets.

  6. Automated Tracking of Nanometer-Scale Feature Evolution Using an STM

    NASA Astrophysics Data System (ADS)

    Lake, Russell; Dean, Adam; Maheswaranathan, Niru; Sosolik, Chad

    2007-03-01

    Time-resolved measurements of vacancy pits and adatom islands on monatomic metallic surfaces (e.g. Ag(111) [1]) have provided valuable insight into the underlying atomic diffusion processes that drive dynamics at nanometer length scales. Utilizing our variable temperature scanning tunneling microscope or STM, we are extending this probing method to more complex systems, such as the AuCu and NiAl alloys. To increase the rate of successful data acquisition for these measurements, we have developed automated tracking routines that allow for the continuous monitoring of evolving surface features with minimal operator involvement. Post-acquisition image analysis is further enhanced utilizing feature detection algorithms. Current proof-of-concept results spanning several hours of acquisition time on single crystal metal surfaces are presented. [1] K. Morgenstern et al., Phys. Rev. B 63, 045412 (2001).

  7. Automated Tracking of Nanometer-Scale Feature Evolution Using an STM

    NASA Astrophysics Data System (ADS)

    Lake, Russell; Dean, Adam; Maheswaranathan, Niru; Sosolik, Chad

    2006-11-01

    Time-resolved measurements of vacancy pits and adatom islands on monatomic metallic surfaces (e.g. Ag(111) [1]) have provided valuable insight into the underlying atomic diffusion processes that drive dynamics at nanometer length scales. Utilizing our variable temperature scanning tunneling microscope or STM, we are extending this probing method to more complex systems, such as the AuCu and NiAl alloys. To increase the rate of successful data acquisition for these measurements, we have developed automated tracking routines that allow for the continuous monitoring of evolving surface features with minimal operator involvement. Post-acquisition image analysis is further enhanced utilizing feature detection algorithms. Current proof-of-concept results spanning several hours of acquisition time on single crystal metal surfaces are presented. [1] K. Morgenstern et al., Phys. Rev. B 63, 045412 (2001).

  8. Atomic Diffusion within Individual Gold Nanocrystal

    NASA Astrophysics Data System (ADS)

    Xiong, Gang; Clark, Jesse N.; Nicklin, Chris; Rawle, Jonathan; Robinson, Ian K.

    2014-10-01

    Due to their excess surface free energy and structural instabilities, nanoparticles exhibit interesting physical and chemical properties. There has been an ever-growing interest in investigating these properties, driven by the desire to further miniaturize electronic devices, develop new functional materials and catalysts. Here, the intriguing question of how diffusion evolves in a single nanoparticle is investigated by measuring the spatial and temporal variations of the diffracted coherent X-ray intensity during copper diffusion into a gold nanocrystal. Dislocation loops formed from the insertion of single layer of extra atoms between neighbouring gold host lattice planes are detected. Au-Cu alloy channels are found to penetrate the nanocrystal due to the differential diffusion rate along different directions. With the advent of higher brilliance sources and free-electron-lasers, Bragg Coherent X-ray Diffraction Imaging can play an important role in unveiling atomic behaviours in three dimensions for nanomaterials during various fundamental processes.

  9. [Environmental and biological monitoring of subjects occupationally exposed to precious metals (gold lost-wax casting)].

    PubMed

    Minoia, C; Oppezzo, M C; Pozzoli, L; Catenacci, G; Capodaglio, E

    1985-01-01

    Environmental monitoring during lost wax casting in jewelry handicrafts was performed for gold, silver, zinc and copper by means of personal samplers and ICP-AAS techniques were used for determining airborne metals. Personal sampling was prolonged for a working week by continuous monitoring during 8 hours shifts, replacing the membrane filter every 2 hours, in 6 workers; in the same workers urine samples were collected during the week and levels of Au, Ag, Zn and Cu were measured by ETA-AAS. During casting process Ag air concentrations ranged 0.27-0.6 mg/m3 while mean levels of Au, Cu, and Zn were 0.028 0.030 and 0.056 mg/m3 respectively. Urinary excretion of Ag (I) determined by solvent extraction and separation by liquid anion exchanger proved very high, after 24-36 h from the casting processes.

  10. Reconnaissance Study of Water Quality in the Mining-Affected Aries River Basin, Romania

    USGS Publications Warehouse

    Friedel, Michael J.; Tindall, James A.; Sardan, Daniel; Fey, David L.; Poputa, G.L.

    2008-01-01

    The Aries River basin of western Romania has been subject to mining activities as far back as Roman times. Present mining activities are associated with the extraction and processing of various metals including Au, Cu, Pb, and Zn. To understand the effects of these mining activities on the environment, this study focused on three objectives: (1) establish a baseline set of physical parameters, and water- and sediment-associated concentrations of metals in river-valley floors and floodplains; (2) establish a baseline set of physical and chemical measurements of pore water and sediment in tailings; and (3) provide training in sediment and water sampling to personnel in the National Agency for Mineral Resources and the Rosia Poieni Mine. This report summarizes basin findings of physical parameters and chemistry (sediment and water), and ancillary data collected during the low-flow synoptic sampling of May 2006.

  11. A method for measuring tissue-equivalent dose using a pin diode and activation foil in epithermal neutron beams with EN < 100 keV.

    PubMed

    Carolan, Martin G; Rosenfeld, Anatoly B

    2006-01-01

    Silicon (Si) pin diodes can be used for neutron dosimetry by observing the change in forward bias voltage caused by neutron induced displacement damage in the diode junction. Pin diode energy response depends on Si displacement damage KERMA (K(Si)). It is hypothesised that tissue-equivalent (TE) neutron dose could be expressed as a linear combination of K(Si) and foil activation terms. Monte Carlo simulations (MCNP) of parallel monoenergetic neutron beams incident on a cylindrical TE phantom were used to calculate TE dose, K(Si) and Au, Cu and Mn foil activations along the central axis of the phantom. For spectra with neutron energies <100 keV, it is possible to estimate the TE kerma based on silicon damage kerma and Cu or Mn foil measurements. More accurate estimates are possible for spectra where the maximum neutron energy does not exceed 30 keV. PMID:16644975

  12. Structural defect induced peak splitting in gold-copper bimetallic nanorods during growth by single particle spectroscopy.

    PubMed

    Thota, Sravan; Chen, Shutang; Zhou, Yadong; Zhang, Yong; Zou, Shengli; Zhao, Jing

    2015-09-21

    A single particle level study of bimetallic nanoparticle growth provides valuable information that is usually hidden in ensemble measurements, helping to improve the understanding of a reaction mechanism and overcome the synthetic challenges. In this study, we use single particle spectroscopy to monitor the changes in the scattering spectra of Au-Cu alloy nanorods during growth. We found that the unique features of the single particle scattering spectra were due to atomic level geometric defects in the nanorods. Electrodynamics simulations have demonstrated that small structural defects of a few atomic layers split the scattering peaks, giving rise to higher order modes, which do not exist in defect-free rods of similar geometry. The study shows that single particle scattering technique is as sensitive as high-resolution electron microscopy in revealing atomic level structural defects. PMID:26268683

  13. Lattice-mismatch-induced twinning for seeded growth of anisotropic nanostructures.

    PubMed

    Wang, Zhenni; Chen, Zhengzheng; Zhang, Hui; Zhang, Zhaorui; Wu, Haijun; Jin, Mingshang; Wu, Chao; Yang, Deren; Yin, Yadong

    2015-03-24

    Synthesis of anisotropic nanostructures from materials with isotropic crystal structures often requires the use of seeds containing twin planes to break the crystalline symmetry and promote the preferential anisotropic growth. Controlling twinning in seeds is therefore critically important for high-yield synthesis of many anisotropic nanostructures. Here, we demonstrate a unique strategy to induce twinning in metal nanostructures for anisotropic growth by taking advantage of the large lattice mismatch between two metals. By using Au-Cu as an example, we show, both theoretically and experimentally, that deposition of Cu to the surface of single-crystalline Au seeds can build up strain energy, which effectively induces the formation of twin planes. Subsequent seeded growth allows the production of Cu nanorods with high shape anisotropy that is unachievable without the use of Au seeds. This work provides an effective strategy for the preparation of anisotropic metal nanostructures. PMID:25744113

  14. Synthesis of metallic nanoparticles through X-ray radiolysis using synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Akinobu; Okada, Ikuo; Fukuoka, Takao; Sakurai, Ikuya; Utsumi, Yuichi

    2016-05-01

    The potential to fabricate metallic nanoparticles directly on silicon substrates from liquid solutions is ideal for three-dimensional lithography systems, drug delivery materials, and sensing applications. Here, we report the successful synthesis of Au, Cu, and Fe nanoparticles from the corresponding liquid solutions [gold(I) trisodium disulphite, copper(II) sulfate, and potassium ferricyanide] by synchrotron (SR) X-ray irradiation. The deposition of gold nanoparticles in the gold(I) trisodium disulphite solution was performed by monochromatic X-ray exposure from synchrotron radiation. The use of ethanol as an additive enabled the nucleation and growth of Cu particles, while no Cu particles were produced in the copper sulfate solution without ethanol with polychromatic SR X-ray irradiation. Fe particles were generated by direct polychromatic SR X-ray irradiation. These results demonstrate the behavior of three-dimensional printers, enabling us to build composite material structures with metallic and plastic materials.

  15. Metal nanoparticles and IR laser applications in medicine for biotissue ablation and welding

    NASA Astrophysics Data System (ADS)

    Lalayan, A. A.; Israelyan, S. S.

    2016-05-01

    We report the possibility of laser welding and ablation of biotissue by using metal and hybrid metal nanoparticles (NPs) and infrared laser irradiation spectrally located far from plasmon resonances. A nanosecond YAG:Nd laser of wavelength 1064 nm has been used for synthesis of metal NPs. The Ag, Au, Cu, Ti and Ni, as well as Au–Ag and Au–Cu hybrid metal colloidal NPs were formed in a liquid medium. The diagnostic technique of second harmonic generation (SHG) has been applied to determine the biotissue ablation area after IR laser irradiation. The effectiveness of biotissue ablation was 4–5 times larger in the case of a tissue sample colored with metal NPs than for an uncolored sample. IR laser welding has been demonstrated for deep-located biotissue layers colored by metal NPs.

  16. Evaluation of performance of three different hybrid mesoporous solids based on silica for preconcentration purposes in analytical chemistry: From the study of sorption features to the determination of elements of group IB.

    PubMed

    Kim, Manuela Leticia; Tudino, Mabel Beatríz

    2010-08-15

    Several studies involving the physicochemical interaction of three silica based hybrid mesoporous materials with metal ions of the group IB have been performed in order to employ them for preconcentration purposes in the determination of traces of Cu(II), Ag(I) and Au(III). The three solids were obtained from mesoporous silica functionalized with 3-aminopropyl (APS), 3-mercaptopropyl (MPS) and N-[2-aminoethyl]-3-aminopropyl (NN) groups, respectively. Adsorption capacities for Au, Cu and Ag were calculated using Langmuir's isotherm model and then, the optimal values for the retention of each element onto each one of the solids were found. Physicochemical data obtained under thermodynamic equilibrium and under kinetic conditions - imposed by flow through experiments - allowed the design of simple analytical methodologies where the solids were employed as fillings of microcolumns held in continuous systems coupled on-line to an atomic absorption spectrometry. In order to control the interaction between the filling and the analyte at short times (flow through conditions) and thus, its effect on the analytical signal and the presence of interferences, the initial adsorption velocities were calculated using the pseudo second order model. All these experiments allowed the comparison of the solids in terms of their analytical behaviour at the moment of facing the determination of the three elements. Under optimized conditions mainly given by the features of the filling, the analytical methodologies developed in this work showed excellent performances with limits of detection of 0.14, 0.02 and 0.025 microg L(-1) and RSD % values of 3.4, 2.7 and 3.1 for Au, Cu and Ag, respectively. A full discussion of the main findings on the interaction metal ions/fillings will be provided. The analytical results for the determination of the three metals will be also presented.

  17. A Theoretical Study of Methanol Synthesis from CO(2) Hydrogenation on Metal-doped Cu(111) Surfaces

    SciTech Connect

    Liu P.; Yang, Y.; White, M.G.

    2012-01-12

    Density functional theory (DFT) calculations and Kinetic Monte Carlo (KMC) simulations were employed to investigate the methanol synthesis reaction from CO{sub 2} hydrogenation (CO{sub 2} + 3H{sub 2} {yields} CH{sub 3}OH + H{sub 2}O) on metal-doped Cu(111) surfaces. Both the formate pathway and the reverse water-gas shift (RWGS) reaction followed by a CO hydrogenation pathway (RWGS + CO-Hydro) were considered in the study. Our calculations showed that the overall methanol yield increased in the sequence: Au/Cu(111) < Cu(111) < Pd/Cu(111) < Rh/Cu(111) < Pt/Cu(111) < Ni/Cu(111). On Au/Cu(111) and Cu(111), the formate pathway dominates the methanol production. Doping Au does not help the methanol synthesis on Cu(111). Pd, Rh, Pt, and Ni are able to promote the methanol production on Cu(111), where the conversion via the RWGS + CO-Hydro pathway is much faster than that via the formate pathway. Further kinetic analysis revealed that the methanol yield on Cu(111) was controlled by three factors: the dioxomethylene hydrogenation barrier, the CO binding energy, and the CO hydrogenation barrier. Accordingly, two possible descriptors are identified which can be used to describe the catalytic activity of Cu-based catalysts toward methanol synthesis. One is the activation barrier of dioxomethylene hydrogenation, and the other is the CO binding energy. An ideal Cu-based catalyst for the methanol synthesis via CO{sub 2} hydrogenation should be able to hydrogenate dioxomethylene easily and bond CO moderately, being strong enough to favor the desired CO hydrogenation rather than CO desorption but weak enough to prevent CO poisoning. In this way, the methanol production via both the formate and the RWGS + CO-Hydro pathways can be facilitated.

  18. Structural defect induced peak splitting in gold-copper bimetallic nanorods during growth by single particle spectroscopy

    NASA Astrophysics Data System (ADS)

    Thota, Sravan; Chen, Shutang; Zhou, Yadong; Zhang, Yong; Zou, Shengli; Zhao, Jing

    2015-08-01

    A single particle level study of bimetallic nanoparticle growth provides valuable information that is usually hidden in ensemble measurements, helping to improve the understanding of a reaction mechanism and overcome the synthetic challenges. In this study, we use single particle spectroscopy to monitor the changes in the scattering spectra of Au-Cu alloy nanorods during growth. We found that the unique features of the single particle scattering spectra were due to atomic level geometric defects in the nanorods. Electrodynamics simulations have demonstrated that small structural defects of a few atomic layers split the scattering peaks, giving rise to higher order modes, which do not exist in defect-free rods of similar geometry. The study shows that single particle scattering technique is as sensitive as high-resolution electron microscopy in revealing atomic level structural defects.A single particle level study of bimetallic nanoparticle growth provides valuable information that is usually hidden in ensemble measurements, helping to improve the understanding of a reaction mechanism and overcome the synthetic challenges. In this study, we use single particle spectroscopy to monitor the changes in the scattering spectra of Au-Cu alloy nanorods during growth. We found that the unique features of the single particle scattering spectra were due to atomic level geometric defects in the nanorods. Electrodynamics simulations have demonstrated that small structural defects of a few atomic layers split the scattering peaks, giving rise to higher order modes, which do not exist in defect-free rods of similar geometry. The study shows that single particle scattering technique is as sensitive as high-resolution electron microscopy in revealing atomic level structural defects. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03979g

  19. Double-layer mode of acid intrusive rocks from Xiuwacu Porphyry Mo deposit, Northwestern Yunnan SW China: U-Pb geochronology evidence

    NASA Astrophysics Data System (ADS)

    Yu, Haijun; Li, Wenchang

    2016-04-01

    Recent research infer that, the south-north extension of the Xiuwacu-Tongchanggou acidic intrusive belt along the Geza island arc have been developed of intense molybdenum-mutimetallic mineralization(Li et al., 2012, 2013; Yu et al., 2015). The northern section of this intrusive belt exposed widly and occur much monzonitic granite, biotite-granite, granodiorite, biotite-monzogranite; while in southern section, intrusions are cocealed. The Tongchanggou district in south section have been obtained large breakthrough of porphyry-skarn type molybdenum-multimetallic deposits exploration recent years(Yu et al., 2014), the Mo-W mineral resources also increased year after year in north section of the belt. The Mo-mineral resouree potential of porphyry-skarn type Mo-mutimetallic deposits in whole area are tremendous. Xiuwacu Porphyry molybdenum deposit was explored in Geza island arc, and widespread Biotite granite and monzonitic granite that is closely related to mineralization. We have understood poorly about this ore deposit for the harsh geographical circumstance, through, some referential result in chronology have accumulated, it still lack of systematic lithogeochemical study and reliable chronology data about intrusions. We yield biotite granite and monzonitic zircons U-Pb ages(200.93±0.65Ma, 83.57±0.32Ma, respectively) of Xiuwacu. There are two periods of intermediate-acid intrusive rocks of Xiuwacu area. Indosinian Biotite granite and Yanshanian monzonitic granite were formed as superposition phenomenon.

  20. Mapping hydrothermal alteration using aircraft VNIR scanners at the Rosemont porphyry copper deposit. [Visible-Near Infrared

    NASA Technical Reports Server (NTRS)

    Sadowski, R. M.; Abrams, M. J.

    1983-01-01

    Two Visible-Near Infrared (VNIR) scanners, the NS-001 and the M2S, were flown over the Rosemont porphyry copper deposit as part of the NASA/JPL/GEOSAT test site program. This program was established to determine the feasibility and limitations of mapping hydrothermal alteration with multispectral scanners. Data from the NS-001 at 0.83 and 2.2 microns were used to identify Fe(3+) and OH enriched outcrops. These areas were then correlated with three alteration assemblages. The first correlation, hematite-epidote, was the most obvious and appeared as a strong ferric iron signature associated with hematite stained Cretaceous arkoses and andesites. The second correlation, qtz-sericite, showed a combined ferric-hydroxyl signature for a phyllicly altered quartz monzonite. The third correlation, skarn, was identified only after a review of calc-silicate mineral VNIR spectra. Altered limestones that outcrop west of the deposit have a similar ferric iron-hydroxyl signature as the quartz-sericite altered quartz monzonite. This skarn signature has been interpreted to indicate the presence of andradite, hydro-grossularite and idocrase. Data from the second scanner, M2S, was used to search for variation in ferric iron mineral type. Resulting imagery data indicated that hematite was the dominant ferric iron mineral present in the Rosemont area.

  1. Calc-silicate alteration and sulfide mineralization, San Martin mine, Zacatecas, Mexico

    SciTech Connect

    Rubin, J.N.; Kyle, J.R.; Olivares, R.

    1985-01-01

    The San Martin skarn deposit was formed by intrusion of the 46 Ma Cerro de la Gloria quartz monzonite stock into the Middle Cretaceous Cuesta del Cura limestone. Ensuing hydrothermal alteration produced a metamorphic aureole consisting of calc-silicate minerals and economic concentrations of Cu, Zn, and Ag. Ore bodies are centered around several large veins that roughly parallel the intrusive contact; mineralized endoskarn is locally developed. Cu and Ag decrease with increasing distance from the intrusive contact, and correlate inversely with Pb and Zn horizontally. Cu, Zn, Pb, and Fe increase with depth. Initial metasomatism produced andraditic garnet with lesser hedenbergitic clinopyroxene, along with substantial intercrystalline pore space which was subsequently filled with sulfides. Lower temperature calc-silicates include wollastonite, epidote, chlorite, and tremolite. Metallic minerals show a paragenetic sequence of early arsenopyrite, molybdenite, pyrrhotite, bornite, and chalcopyrite; intermediate sphalerite, chalcopyrite, tetrahedrite, and galena; and late native silver, pyrite, and stibnite. Fluorite, calcite, and minor quartz postdate prograde skarn development. Hydrothermal fluid circulation was controlled by pre-intrusion Laramide deformation and probably was enhanced by intrusion-related fracturing. The intrusive contact and the veins represent the major channels for fluid migration, with local controls affected by layers of impermeable shale and chert. Fluid inclusion data suggest that early mineralizing fluids were dominantly magmatic, with the meteoric component increasing with time.

  2. Late paleozoic base and precious metal deposits, East Tianshan, Xinjiang, China: Characteristics and geodynamic setting

    USGS Publications Warehouse

    Mao, J.; Goldfarb, R.J.; Wang, Y.; Hart, C.J.; Wang, Z.; Yang, J.

    2005-01-01

    The East Tianshan is a remote Gobi area located in eastern Xinjiang, northwestern China. In the past several years, a number of gold, porphyry copper, and Fe(-Cu) and Cu-Ag-Pb-Zn skarn deposits have been discovered there and are attracting exploration interest. The East Tianshan is located between the Junggar block to the north and early Paleozoic terranes of the Middle Tianshan to the south. It is part of a Hercynian orogen with three distinct E-W-trending tectonic belts: the Devonian-Early Carboniferous Tousuquan-Dananhu island arc on the north and the Carboniferous Aqishan - Yamansu rift basin to the south, which are separated by rocks of the Kanggurtag shear zone. The porphyry deposits, dated at 322 Ma, are related to the late evolutionary stages of a subduction-related oceanic or continental margin arc. In contrast, the skarn, gold, and magmatic Ni-Cu deposits are associated with post-collisional tectonics at ca. 290-270 Ma. These Late Carboniferous - Early Permian deposits are associated with large-scale emplacement and eruption of magmas possibly caused by lithosphere delamination and rifting within the East Tianshan.

  3. Marano volcanic rocks, East Azarbaijan Province, Iran, and associated Fe mineralisation

    NASA Astrophysics Data System (ADS)

    Karimzadeh Somarin, A.

    2004-10-01

    There are two main types of economic iron ore deposits in Iran: (1) magmatic segregation deposits and (2) skarns. Most of the hydrothermal iron deposits in Iran, except for the skarns, are uneconomic. One of these uneconomic hydrothermal deposits is the Marano Fe deposit, located in East Azarbaijan Province (NW Iran). This deposit is considered to have been formed by an epithermal style of mineralisation related to a volcanic-dome. There are 5 volcanic domes in the Marano area, ranging in composition from dacite to rhyolite. The volcanic rocks show geochemical evidence of fractionation of biotite, hornblende, magnetite, apatite and feldspars. The Marano volcanic domes crystallised from an I-type magma, formed in a volcanic arc setting. Fe mineralisation has occurred around one of these Marano domes (MA dome) in which the igneous rocks contain more biotite and hornblende and are less fractionated than in the other domes. The main Fe oxide, hematite, occurs as veins and disseminations in sedimentary wall rocks. Alteration of the minerals in the host rocks suggests aS2<10-9.5, aO2>10-34.2 and pH<5.5. The small size and shallow-level of emplacement of magma, together with the absence of extensive hydrothermally altered zones, shows that the hydrothermal system was not voluminous enough to form an economic iron deposit.

  4. Trioctahedral micas in xenolithic ejecta from recent volcanism of the Somma-Vesuvius (Italy): Crystal chemistry and genetic inferences

    NASA Astrophysics Data System (ADS)

    Balassone, Giuseppina; Scordari, Fernando; Lacalamita, Maria; Schingaro, Emanuela; Mormone, Angela; Piochi, Monica; Petti, Carmela; Mondillo, Nicola

    2013-02-01

    This study reports the first crystal chemical database resulting from a detailed structural investigation of trioctahedral micas found in xenolithic ejecta produced during the AD 1631, 1872 and 1944 eruptions, three explosive episodes of recent volcanic period of Vesuvius volcano (Southern Italy). Three xenolith types were selected: metamorphic/metasomatic skarns, pyrometamorphic/hydrothermally altered nodules and mafic cumulates. They are related to different magma chemistry and effusive styles: from sub-plinian and most evolved (AD 1631 eruption) to violent strombolian with medium evolution degree (AD 1872 eruption) to vulcanian-effusive, least evolved (AD 1944 eruption) event, respectively. Both xenoliths and micas were investigated employing multiple techniques: the xenoliths were characterized by X-ray fluorescence, inductively-coupled plasma-mass spectrometry, optical microscopy, X-ray powder diffraction, and quantitative energy-dispersive microanalysis; the micas were studied by electron probe microanalysis and single crystal X-ray diffraction. The mica-bearing xenoliths show variable texture and mineralogical assemblage, clearly related to their different origin. Based on the major oxide chemistry, only one xenolithic sample falls in the skarn compositional field from the Somma-Vesuvius literature, some fall close to the skarns and cumulate fields, others plot close to the syenite/foidolite/essexite field. A subgroup of the selected ejecta does not fall or approach any of the compositional fields. Trace and rare earth element patterns show some petrological affinity between studied xenoliths and erupted magmas with typical Eu, Ta and Nb negative anomalies. Strongly depleted patterns were detected for the 1631 metamorphic/metasomatic skarns xenoliths. Three distinct mica groups were distinguished: 1) Mg-, Al-rich, low Ti-bearing, low to moderate F-bearing varieties (1631 xenolith), 2) Al-moderate, F- and Mg-rich, Ti-, Fe-poor varieties (1872 xenolith), and 3

  5. Crystallization and preliminary X-ray diffraction analysis of a complex between the electron-transfer partners hexameric Cu-containing nitrite reductase and pseudoazurin.

    PubMed

    Hira, Daisuke; Nojiri, Masaki; Suzuki, Shinnichiro

    2009-02-01

    The complex between Cu-containing nitrite reductase (HdNIR) and its electron-donor protein pseudoazurin (HdPAz) from Hyphomicrobium denitrificans has been crystallized. The crystals were obtained from a mixture of the two proteins using the hanging-drop vapour-diffusion method in the presence of polyethylene glycol (PEG) and 2-methyl-2,4-pentanediol (MPD) as precipitants. SDS-PAGE analysis demonstrated that the crystals contained both proteins. The X-ray diffraction experiment was carried out at SPring-8 and diffraction data were collected to 3.3 A resolution. The crystals were tetragonal (space group P4(1)2(1)2), with unit-cell parameters a = b = 130.39, c = 505.55 A. Preliminary analysis indicated that there was one HdNIR and at least two HdPAz molecules in the asymmetric unit of the crystal. PMID:19193999

  6. Source interpretation: teaching students with and without LD to read and write historically.

    PubMed

    De La Paz, Susan; Morales, Petra; Winston, Philip M

    2007-01-01

    We review domain-specific teaching approaches for students with learning disabilities in social studies, then present De La Paz's 2005 historical reasoning strategy so that readers understand the rationale for and have information on each stage of instruction. Next, we highlight the role of self-regulation for the reasoning process. We then turn to describing the role of each teacher (Morales as the social studies educator and Winston as the special educator), first as they collaborate with De La Paz and each other, then as Morales works alone, 1 year later. Implications are given for changes in teaching. The topic of women's suffrage is used throughout the article to highlight the teaching approach and to present student work. PMID:17380988

  7. Pollen-based paleoenvironmental and paleoclimatic change at Lake Ohrid (SE Europe) during the past 500 ka

    NASA Astrophysics Data System (ADS)

    Sadori, L.; Koutsodendris, A.; Masi, A.; Bertini, A.; Combourieu-Nebout, N.; Francke, A.; Kouli, K.; Joannin, S.; Mercuri, A. M.; Panagiotopoulos, K.; Peyron, O.; Torri, P.; Wagner, B.; Zanchetta, G.; Donders, T. H.

    2015-09-01

    Lake Ohrid is located at the border between FYROM and Albania and formed during the latest phases of Alpine orogenesis. It is the deepest, the largest and the oldest tectonic lake in Europe. To better understand the paleoclimatic and paleoenvironmental evolution of Lake Ohrid a deep drilling was carried out in 2013 within the framework of the Scientific Collaboration on Past Speciation Conditions (SCOPSCO) project that was funded by the International Continental Drilling Program (ICDP). Preliminary results indicate that lacustrine sedimentation of Lake Ohrid started between 1.2 and 1.9 Ma ago. Here we present new pollen data (selected percentage and concentration taxa/groups) of the uppermost ~200 m of the 569 m-long DEEP core drilled in the depocenter of Lake Ohrid. The study is the fruit of a cooperative work carried out in several European palynological laboratories. The age model is based on nine tephra layers and on tuning of biogeochemical proxy data to orbital parameters and to the global benthic isotope stack LR04. According to the age model the studied sequence covers the last ~500 000 years at a millennial-scale resolution (~1.6 ka) and record the major vegetation and climate changes that occurred during the last 12 (13 only pro parte) marine isotope stages (MIS). Our results indicate that there is a general good correspondence between forested/non-forested periods and glacial/interglacial cycles of marine isotope stratigraphy. Our record shows a progressive change from cooler and wetter to warmer and dryer interglacial conditions. This shift is visible also in glacial vegetation. The interglacial phase corresponding to MIS11 (pollen assemblage zone, PAZ OD-12, 488-455 ka BP and OD-19, 367-328 ka BP) is dominated by montane trees such as conifers. The two younger interglacial periods, MIS5 (PAZ OD-3, 126-70 ka BP) and MIS1 (PAZ OD-1, 12 ka BP to present) are marked by dominance of mesophilous elements such as deciduous and semi-deciduous oaks. Moreover

  8. APP Is a Context-Sensitive Regulator of the Hippocampal Presynaptic Active Zone.

    PubMed

    Laßek, Melanie; Weingarten, Jens; Wegner, Martin; Mueller, Benjamin F; Rohmer, Marion; Baeumlisberger, Dominic; Arrey, Tabiwang N; Hick, Meike; Ackermann, Jörg; Acker-Palmer, Amparo; Koch, Ina; Müller, Ulrike; Karas, Michael; Volknandt, Walter

    2016-04-01

    The hallmarks of Alzheimer's disease (AD) are characterized by cognitive decline and behavioral changes. The most prominent brain region affected by the progression of AD is the hippocampal formation. The pathogenesis involves a successive loss of hippocampal neurons accompanied by a decline in learning and memory consolidation mainly attributed to an accumulation of senile plaques. The amyloid precursor protein (APP) has been identified as precursor of Aβ-peptides, the main constituents of senile plaques. Until now, little is known about the physiological function of APP within the central nervous system. The allocation of APP to the proteome of the highly dynamic presynaptic active zone (PAZ) highlights APP as a yet unknown player in neuronal communication and signaling. In this study, we analyze the impact of APP deletion on the hippocampal PAZ proteome. The native hippocampal PAZ derived from APP mouse mutants (APP-KOs and NexCreAPP/APLP2-cDKOs) was isolated by subcellular fractionation and immunopurification. Subsequently, an isobaric labeling was performed using TMT6 for protein identification and quantification by high-resolution mass spectrometry. We combine bioinformatics tools and biochemical approaches to address the proteomics dataset and to understand the role of individual proteins. The impact of APP deletion on the hippocampal PAZ proteome was visualized by creating protein-protein interaction (PPI) networks that incorporated APP into the synaptic vesicle cycle, cytoskeletal organization, and calcium-homeostasis. The combination of subcellular fractionation, immunopurification, proteomic analysis, and bioinformatics allowed us to identify APP as structural and functional regulator in a context-sensitive manner within the hippocampal active zone network. PMID:27092780

  9. APP Is a Context-Sensitive Regulator of the Hippocampal Presynaptic Active Zone

    PubMed Central

    Mueller, Benjamin F.; Rohmer, Marion; Baeumlisberger, Dominic; Arrey, Tabiwang N.; Hick, Meike; Ackermann, Jörg; Acker-Palmer, Amparo; Koch, Ina; Müller, Ulrike; Karas, Michael; Volknandt, Walter

    2016-01-01

    The hallmarks of Alzheimer’s disease (AD) are characterized by cognitive decline and behavioral changes. The most prominent brain region affected by the progression of AD is the hippocampal formation. The pathogenesis involves a successive loss of hippocampal neurons accompanied by a decline in learning and memory consolidation mainly attributed to an accumulation of senile plaques. The amyloid precursor protein (APP) has been identified as precursor of Aβ-peptides, the main constituents of senile plaques. Until now, little is known about the physiological function of APP within the central nervous system. The allocation of APP to the proteome of the highly dynamic presynaptic active zone (PAZ) highlights APP as a yet unknown player in neuronal communication and signaling. In this study, we analyze the impact of APP deletion on the hippocampal PAZ proteome. The native hippocampal PAZ derived from APP mouse mutants (APP-KOs and NexCreAPP/APLP2-cDKOs) was isolated by subcellular fractionation and immunopurification. Subsequently, an isobaric labeling was performed using TMT6 for protein identification and quantification by high-resolution mass spectrometry. We combine bioinformatics tools and biochemical approaches to address the proteomics dataset and to understand the role of individual proteins. The impact of APP deletion on the hippocampal PAZ proteome was visualized by creating protein-protein interaction (PPI) networks that incorporated APP into the synaptic vesicle cycle, cytoskeletal organization, and calcium-homeostasis. The combination of subcellular fractionation, immunopurification, proteomic analysis, and bioinformatics allowed us to identify APP as structural and functional regulator in a context-sensitive manner within the hippocampal active zone network. PMID:27092780

  10. First record of a louse fly, Stilbometopa impressa (Bigot), and new host for Microlynchia pusilla (Speiser) (Hippoboscidae) from the Cape Region, Baja California Sur, México.

    PubMed

    Llinas, J; Jiménez, M L

    1996-04-01

    Nine of thirty California quail (Callipepla californica achrustera) captured in autumn of 1992, 17 km west of La Paz, Baja California Sur, México, were parasitized by louse flies. We identified eight Microlynchia pusilla and three Stilbometopa impressa from 30 quails in the ratio of 2.75:1. These are the first records of S. impressa for Cape Region and the first time either fly has been reported from the California quail in Baja California Sur. PMID:8722274

  11. Dye-sensitized solar cell from polyaniline-ZnS nanotubes and its characterization through impedance spectroscopy.

    PubMed

    Shit, Arnab; Chatterjee, Shreyam; Nandi, Arun K

    2014-10-01

    Polyaniline (PANI)-zinc sulphide (ZnS) nanocomposites (PAZs) are synthesized by polymerizing aniline in the presence of acetic acid with different concentrations of ZnS nanoparticles (NPs). FESEM and TEM images indicate the nanotube morphology of PANI and ZnS NPs remain adhered to the nanotube surface, but at higher ZnS concentration the nanotube morphology is lost. UV-vis spectra indicate PANI is in the doped state and the doping increases with an increase in ZnS concentration. Fluorescence intensity passes through a minimum with ZnS content and the dc-conductivity of the composites gradually increases with an increase in ZnS NP concentration. The I-V plot of PAZ composites indicates that the photocurrent is higher than that of the dark current at each voltage, and the device exhibits reversible turning "on" and "off" by switching the white light illumination "on" and "off". Dye-sensitized solar cells fabricated with PAZ composites display a reasonably higher power conversion efficiency (η = 3.38%) than pure ZnS NPs. An attempt is made to shed light on the operating mechanism of the DSSC from the impedance data using a Cole-Cole plot by drawing an equivalent circuit illustrating the different electronic and ionic transport processes within the cell.

  12. Atomic resolution structure of pseudoazurin from the methylotrophic denitrifying bacterium Hyphomicrobium denitrificans: structural insights into its spectroscopic properties.

    PubMed

    Hira, Daisuke; Nojiri, Masaki; Suzuki, Shinnichiro

    2009-01-01

    The crystal structure of native pseudoazurin (HdPAz) from the methylotrophic denitrifying bacterium Hyphomicrobium denitrificans has been determined at a resolution of 1.18 A. After refinement with SHELX employing anisotropic displacement parameters and riding H atoms, R(work) and R(free) were 0.135 and 0.169, respectively. Visualization of the anisotropic displacement parameters as thermal ellipsoids provided insight into the atomic motion within the perturbed type 1 Cu site. The asymmetric unit includes three HdPAz molecules which are tightly packed by head-to-head cupredoxin dimer formation. The shape of the Cu-atom ellipsoid implies significant vibrational motion diagonal to the equatorial xy plane defined by the three ligands (two His and one Cys). The geometric parameters of the type 1 Cu site in the HdPAz structure differ unambiguously from those of other pseudoazurins. It is demonstrated that their structural aspects are consistent with the unique visible absorption spectrum. PMID:19153470

  13. Preliminary results from two intensive campaigns characterizing urban aerosols at two high altitude cities in the Tropical Andes

    NASA Astrophysics Data System (ADS)

    Andrade, M. F.; Wiedensohler, A.; Velarde, F.; Moreno, I.; Weinhold, K.; Avila, F.

    2013-05-01

    Preliminary results from a short campaign carried out between September and December of 2012 at the cities of El Alto (16°30'36.09"S; 68°11'55.31"W; 4040 masl) and La Paz (16°30'13.83"S; 68° 7'45.56"W; 3580 masl), Bolivia are presented on this work. Particle size distribution was measured using a Mobility Particle Size Spectrometer (Reference of the World Calibration Center for Aerosol Physics) whereas concentration of black carbon was measured using a Multi Angle Absorption Photometer (MAAP). In addition meteorological parameters as well as CO concentration were collected on both locations. In the case of El Alto, the instruments were located within the International Airport of the city at approximately 300 m from the main and only landing strip and at least 1.5 km away from the main roads. On the other hand, in the case of La Paz, the instruments were set up at the Planetarium of University Mayor de San Andres. The building is located besides a road with heavy traffic. Because the two cities are part of the same metropolitan area (the sites were located 7.5 km apart), the cars and trucks produce a similar signature and therefore both background and non-background urban aerosols were sampled during the campaign. In addition, an interesting case was registered at La Paz where a day with practically no vehicular traffic was studied.

  14. Noble metal based plasmonic nanomaterials and their application for bio-imaging and photothermal therapy

    NASA Astrophysics Data System (ADS)

    Zhu, Dewei

    (Cu 2-xS) NCs as a template for preparing gold sulfide (Au2S) NCs and intermediate Cu2-xS-Au2S heterostructures by cation exchange. In chapter two, we demonstrate the use of Au-Cu2-xSe nano-dimers for high contrast multimodal imaging in vitro and in vivo. Their broad LSPR absorbance and scattering enables both dark-field optical imaging and photoacoustic (PA) imaging with different light sources. The clinical relevance of these new PA contrast agents was demonstrated through deep tissue visualization of a sentinel lymph node (SLN) in a rat. Imaging through layers of chicken breast tissue at total imaging depths needed for human SLN imaging was achieved. Further, the kinetics of these NCs in the rat circulatory system were monitored in vivo. A widely available and relatively low cost Nd:YAG laser source(1064 nm) was used for all PA imaging experiments, which is an additional benefit for easy commercialization and clinical translation. Thus, these unique Au-Cu2-xSe heterodimer NPs provide a promising optical contrast agent for deep tissue imaging by PAT, as well as a new material system for fundamental studies of plasmonic interactions. In chapter three, we study the potential of both Au-Cu 2-xSe NCs and multi-branched Au NCs for use in photothermal therapy (PTT). Upon illumination with a 980 nm laser beam, the Au-Cu2-xSe nanocrystals produce significant photothermal heating, exhibiting a photothermal transduction efficiency of 32%, which is comparable to that of Au nanorods and nanoparticles (10nm). The multi-branched Au NCs exhibited a photothermal transduction efficiency of 60%, significantly higher than other materials tested in this study. In vitro photothermal heating of either Au-Cu2-xSe nanocrystals or multi-branched Au nanocrystals in the presence of human cervical cancer cells caused effective cell ablation after 10 min laser irradiation at 1.34 W/cm2. Cell viability assays demonstrate that the two classes of nanocrystals are biocompatible at doses needed for

  15. Effects of altitude versus economic status on birth weight and body shape at birth.

    PubMed

    Giussani, D A; Phillips, P S; Anstee, S; Barker, D J

    2001-04-01

    The compelling evidence linking small size at birth with later cardiovascular disease has renewed and amplified a clinical and scientific interest in the determinants of fetal growth. Although the effects of maternal nutrition on fetal growth have been extensively studied, comparatively little is known about the effects of maternofetal hypoxia. This study tested the hypothesis that in highland regions, high altitude rather than maternal economic status is associated with reduced and altered fetal growth by investigating the effects of high altitude versus economic status on birth weight and body shape at birth in Bolivia. Bolivia is geographically and socioeconomically unique. It contains several highland (>3500 m above sea level) and lowland (<500 m) cities that are inhabited by very economically divergent populations. Birth weight, body length, and head circumference were compared between a high- (n = 100) and low- (n = 100) income region of La Paz (3649 m; largest high-altitude city) and a high- (n = 100) and low- (n = 100) income region of Santa Cruz (437 m; largest low-altitude city). In addition, the frequency distribution across the continuum of birth weights was plotted for babies born from high- and low-income families in La Paz and Santa Cruz. Mean birth weights were lower in babies from La Paz than in babies from Santa Cruz in both high- and low-income groups. The cumulative frequency curve across all compiled birth weights was shifted to the left in babies from La Paz compared with those from Santa Cruz, regardless of economic status. The frequency of low birth weight (<2500 g) was higher in babies from La Paz than from Santa Cruz in both high- and low-income groups. In addition, at high altitude but not at low altitude, high income was associated with an increase in the head circumference:birth weight ratio. These findings suggest that high altitude rather than economic status is associated with low birth weight and altered body shape at birth in

  16. Porphyry Cu indicator minerals in till as an exploration tool: Example from the giant pebble porphyry Cu-Au-Mo deposit, Alaska, USA

    USGS Publications Warehouse

    Kelley, Karen D.; Eppinger, Robert G.; Lang, J.; Smith, Steven M.; Fey, David L.

    2011-01-01

    Porphyry Cu indicator minerals are mineral species in clastic sediments that indicate the presence of mineralization and hydrothermal alteration associated with porphyry Cu and associated skarn deposits. Porphyry Cu indicator minerals recovered from shallow till samples near the giant Pebble Cu-Au-Mo porphyry deposit in SW Alaska, USA, include apatite, andradite garnet, Mn-epidote, visible gold, jarosite, pyrite, and cinnabar. Sulphide minerals other than pyrite are absent from till, most likely due to the oxidation of the till. The distribution of till samples with abundant apatite and cinnabar suggest sources other than the Pebble deposit. With three exceptions, all till samples up-ice of the Pebble deposit contain 40grains/10kg) are in close proximity to smaller porphyry and skarn occurrences in the region. The distribution of Mn-epidote closely mimics the distribution of garnet in the till samples and further supports the interpretation that these minerals most likely reflect skarns associated with the porphyry deposits. All but two till samples, including those up-ice from the deposit, contain some gold grains. However, tills immediately west and down-ice of Pebble contain more abundant gold grains, and the overall number of grains decreases in the down-ice direction. Furthermore, all samples in the immediate vicinity of Pebble contain more than 65% pristine and modified grains compared to mostly re-shaped grains in distal samples. The pristine gold in till reflects short transport distances and/or liberation of gold during in-situ weathering of transported chalcopyrite grains. Jarosite is also abundant (1-2 500 grains/10kg) in samples adjacent to and up to 7 km down-ice from the deposit. Most jarosite grains are rounded and preliminary Ar/Ar dates suggest the jarosite formed prior to glaciation and it implies that a supergene cap existed over Pebble West. Assuming this interpretation is accurate, it suggests a shallow level of erosion of the Pebble deposit by

  17. Genesis of the Bangbule Pb-Zn-Cu polymetallic deposit in Tibet, western China: Evidence from zircon U-Pb geochronology and S-Pb isotopes

    NASA Astrophysics Data System (ADS)

    Kan, Tian; Zheng, Youye; Gao, Shunbao

    2016-04-01

    The Banbule Pb-Zn-Cu skarn deposit is located in the Longger-Gongbujiangda volcanic magma arc in the Gangdese-Nyainqentanglha Plate. It is the only lead-zinc polymetallic deposit discovered in the westernmost Nyainqentanglha metallogenic belt. The measured and indicated resources include 0.9 Mt of Pb+Zn (4.77% Pb and 4.74% Zn, respectively), 6499 t of Cu, and 178 t of Ag (18.75g/t Ag). The orebodies mainly occur as lenses, veins and irregular shapes in the contact zone between the quartz-porphyry and limestone of the Upper Permian Xiala Formation, or in the boundaries between limestone and sandstone. Pb-Zn-Cu mineralization in the Banbule deposit is closely associated with skarns. The ore minerals are dominated by galena, sphalerite, chalcopyrite, bornite, and magnetite, with subordinate pyrite, malachite, and azurite. The gangue minerals are mainly garnet, actinolite, diopside, quartz, and calcite. The ore-related quartz-porphyry displays LA-ICP-MS zircon U-Pb age of 77.31±0.74 Ma. The δ34S values of sulfides define a narrow range of -0.8 to 4.7‰ indicating a magmatic source for the ore-forming materials. Lead isotopic systematics yield 206Pb/204Pb of 18.698 to 18.752, 207Pb/204Pb of 15.696 to 15.760, and 208Pb/204Pb of 39.097 to 39.320. The data points are constrained around the growth curves of upper crust and orogenic belt according to the tectonic discrimination diagrams. The calculated Δβ - Δγ values plot within the magmatic field according to the discrimination diagram of Zhu et al. (1995). The S-Pb isotopic data suggest that Bangbule is a typical skarn deposit, and the Pb-Zn-Cu mineralization is genetically related to the quartz-porphyry in the mining district. The discovery of the Bangbule deposit indicates that there is metallogenic potential in the westernmost Nyainqentanglha belt, which is of great importance for the exploration work in this area.

  18. Genesis of the Bangbule Pb-Zn-Cu polymetallic deposit in Tibet, western China: Evidence from zircon U-Pb geochronology and S-Pb isotopes

    NASA Astrophysics Data System (ADS)

    Kan, Tian; Zheng, Youye; Gao, Shunbao

    2016-04-01

    The Banbule Pb-Zn-Cu skarn deposit is located in the Longger-Gongbujiangda volcanic magma arc in the Gangdese-Nyainqentanglha Plate. It is the only lead-zinc polymetallic deposit discovered in the westernmost Nyainqentanglha metallogenic belt. The measured and indicated resources include 0.9 Mt of Pb+Zn (4.77% Pb and 4.74% Zn, respectively), 6499 t of Cu, and 178 t of Ag (18.75g/t Ag). The orebodies mainly occur as lenses, veins and irregular shapes in the contact zone between the quartz-porphyry and limestone of the Upper Permian Xiala Formation, or in the boundaries between limestone and sandstone. Pb-Zn-Cu mineralization in the Banbule deposit is closely associated with skarns. The ore minerals are dominated by galena, sphalerite, chalcopyrite, bornite, and magnetite, with subordinate pyrite, malachite, and azurite. The gangue minerals are mainly garnet, actinolite, diopside, quartz, and calcite. The ore-related quartz-porphyry displays LA-ICP-MS zircon U-Pb age of 77.31±0.74 Ma. The δ34S values of sulfides define a narrow range of -0.8 to 4.7‰ indicating a magmatic source for the ore-forming materials. Lead isotopic systematics yield 206Pb/204Pb of 18.698 to 18.752, 207Pb/204Pb of 15.696 to 15.760, and 208Pb/204Pb of 39.097 to 39.320. The data points are constrained around the growth curves of upper crust and orogenic belt according to the tectonic discrimination diagrams. The calculated Δβ ‑ Δγ values plot within the magmatic field according to the discrimination diagram of Zhu et al. (1995). The S-Pb isotopic data suggest that Bangbule is a typical skarn deposit, and the Pb-Zn-Cu mineralization is genetically related to the quartz-porphyry in the mining district. The discovery of the Bangbule deposit indicates that there is metallogenic potential in the westernmost Nyainqentanglha belt, which is of great importance for the exploration work in this area.

  19. New constraints on the release of noble gases during in vacuo crushing and application to scapolite Br-Cl-I and 40Ar/ 39Ar age determinations

    NASA Astrophysics Data System (ADS)

    Kendrick, M. A.; Phillips, D.

    2009-10-01

    The release of irradiation-produced noble gas isotopes ( 38Ar Cl, 80Kr Br, 128Xe I and 39Ar K) during in vacuo crushing scapolite has been investigated and is compared to quartz. Three thousand crushing strokes released ˜98% of fluid inclusion-hosted noble gas from quartz. In comparison, 3000 crushing strokes released only ˜4% of the lattice-hosted 38Ar Cl from a scapolite gem. In vacuo crushing released lattice Ar preferentially relative to lattice Kr or Xe and prolonged crushing released ˜88% of the lattice-hosted noble gas in 96,000 crushing strokes. We suggest fast diffusion pathways generated by crushing are an important noble gas release mechanism and we demonstrate two applications of prolonged in vacuo crushing on irradiated scapolite. Firstly, scapolite molar Br/Cl and I/Cl values are shown to vary over a similar range as crustal fluids. The Cl-rich scapolite gem from Hunza, Pakistan has Br/Cl of 0.5-0.6 × 10 -3 and I/Cl values of 0.3-2 × 10 -6, that are similar to fluids that have dissolved evaporites. In contrast, three out of four skarn-related scapolites from the Canadian Grenville Province have molar Br/Cl values of 1.5-2.4 × 10 -3, and I/Cl values of 11-24 × 10 -6, that are broadly consistent with skarn formation by magmatic fluids. The fourth Grenvillian scapolite, with only 0.02 wt% Cl, has an exceptionally elevated molar Br/Cl value of up to ˜54 × 10 -3 and I/Cl of 284 × 10 -6. It is unclear if these values reflect the composition of fluids formed during metamorphism or preferential incorporation of Br and I in Cl-poor meionitic scapolite. Secondly, the Grenvillian scapolites give plateau ages of between 830 Ma and 400 Ma. The oldest ages post-date regional skarn formation by ˜200 Myr, but are similar to feldspar cooling ages in the Province. The age variation in these samples is attributed to a combination of factors including variable thermal history and the presence of mineral sub-grains in some of the samples. These sub

  20. El Ventorrillo, a paleostructure of Popocatépetl volcano: insights from geochronology and geochemistry

    NASA Astrophysics Data System (ADS)

    Sosa-Ceballos, G.; Macías, J. L.; García-Tenorio, F.; Layer, P.; Schaaf, P.; Solís-Pichardo, G.; Arce, J. L.

    2015-10-01

    Volcán Popocatépetl (México) was constructed over the remains of a volcanic paleostructure. Based on fieldwork, 40Ar/39Ar dating, U-Pb dating, and geochemistry, we have determined the age, chemistry, and location of this paleostructure and named it El Ventorrillo. Most remnants of El Ventorrillo are covered by deposits from subsequent activity of Popocatépetl, except for the El Abanico scarp and the Barranca de Nexpayantla, where the stratigraphy of El Ventorrillo eruptive products can be investigated. Inception of volcanism at El Ventorrillo occurred at 331 ± 10 ka with emission of the Nexpayantla andesitic lavas, and continued with extrusion of the Yoloxochitl (267 ± 31 ka) and microwave (227 ± 6 ka) domes. Intrusion of dikes occurred at 298 ± 94 and 230 ± 3 ka. Activity at El Ventorrillo continued with the emission of lavas that built the El Abanico scarp (193 ± 29 to 96 ± 8 ka) and continued until the Tutti Frutti eruption destroyed the cone 14.1 kyr ago. El Ventorrillo magmas produced rocks divided into two mineralogical groups. The first group contains biotite-amphibole-rich rocks and the second group consists of biotite-amphibole-free lavas. The rocks that contain biotite and amphibole are older than 198 ± 13 ka, whereas the rocks with no hydrous phases are younger than 227 ± 6 ka and contain skarn and granodiorite xenoliths. We interpret the change to an anhydrous mineral assemblage and the occurrence of skarn and granodiorite xenoliths as evidence for the formation of a new, shallower reservoir. A granodiorite xenolith was chosen for 40Ar/39Ar dating and U-Pb zircon analyses. The U-Pb method yielded an age of 540 ± 110 ka and the 40Ar/39Ar an age of 109 ± 24 ka. These ages are interpreted to indicate granodiorite crystallization (540 ± 110 ka), which metamorphosed the calcareous basement beneath Popocatépetl into skarn and an influx of magma (109 ± 24 ka) that reheated the granodiorite. Major and trace elements, Sr, Nd, and Pb isotopic

  1. The Palaeoproterozoic Kristineberg VMS deposit, Skellefte district, northern Sweden, part I: geology

    NASA Astrophysics Data System (ADS)

    Årebäck, Hans; Barrett, Timothy J.; Abrahamsson, Stig; Fagerström, Pia

    2005-12-01

    The Kristineberg volcanic-hosted massive sulphide (VMS) deposit, located in the westernmost part of the Palaeoproterozoic Skellefte district, northern Sweden, has yielded 22.4 Mt of ore, grading 1.0% Cu, 3.64% Zn, 0.24% Pb, 1.24 g/t Au, 36 g/t Ag and 25.9% S, since the mine opened in 1941, and is the largest past and present VMS mine in the district. The deposit is hosted in a thick pile of felsic to intermediate and minor mafic metavolcanic rocks of the Skellefte Group, which forms the lowest stratigraphic unit in the district and hosts more than 85 known massive sulphide deposits. The Kristineberg deposit is situated lower in the Skellefte Group than most other deposits. It comprises three main ore zones: (1) massive sulphide lenses of the A-ore (historically the main ore), having a strike length of about 1,400 m, and extending from surface to about 1,200 m depth, (2) massive sulphide lenses of the B-ore, situated 100-150 m structurally above the A-ore, and extending from surface to about 1,000 m depth, (3) the recently discovered Einarsson zone, which occurs in the vicinity of the B-ore at about 1,000 m depth, and consists mainly of Au-Cu-rich veins and heavily disseminated sulphides, together with massive sulphide lenses. On a regional scale the Kristineberg deposit is flanked by two major felsic rock units: massive rhyolite A to the south and the mine porphyry to the north. The three main ore zones lie within a schistose, deformed and metamorphosed package of hydrothermally altered, dominantly felsic volcanic rocks, which contain varying proportions of quartz, muscovite, chlorite, phlogopite, pyrite, cordierite and andalusite. The strongest alteration occurs within 5-10 m of the ore lenses. Stratigraphic younging within the mine area is uncertain as primary bedding and volcanic textures are absent due to strong alteration, and tectonic folding and shearing. In the vicinity of the ore lenses, hydrothermal alteration has produced both Mg-rich assemblages (Mg

  2. Geochemical constraints on the genesis of the Scheelite dome intrusion-related gold deposit, Tombstone gold belt, Yukon, Canada

    USGS Publications Warehouse

    Mair, J.L.; Goldfarb, R.J.; Johnson, C.A.; Hart, C.J.R.; Marsh, E.E.

    2006-01-01

    The Scheelite dome intrusion-related gold deposit, western Selwyn basin, Yukon, is hosted in hornfelsed metasedimentary strata that lie adjacent to the exposed apices of a monzogranite to quartz monzonite plutonic complex of the mid-Cretaceous Tombstone-Tungsten magmatic belt, Tintina gold province, Alaska and Yukon. A variety of mineralization styles occur throughout a 10- ?? 3-km east-trending corridor and include reduced Au- and W-rich skarns, Au, W- and Ag-Pb-Zn-Sb-rich quartz tension-vein arrays, and multiphase fault veins and isolated zones of Au-rich sericite-carbonate altered rock. Integrated U-Pb SHRIMP data for magmatic zircon and Ar-Ar data for magmatic and hydrotbermal biotite indicate that gold mineralization occurred within 1 to 2 m.y. of magma emplacement. Fluid inclusion, oxygen isotope, and arsenopyrite geothermometry data indicate that hydrothermal minerals formed at depths of 6 to 9 km over a temperature range from 550??C. High-temperature Au-rich skarns formed at >400??C, whereas vein-hosted mineralization formed at 280?? to 380??C. In skarns, Au is strongly associated with enrichments of Bi, Te, W, and As, whereas a variety of Au-rich veins occur, with Asrich (type 1), and Te- and W-rich (type 2) end members. Silver-Pb-Zn-Sb veins are typically Au poor and represent the latest and lowest temperature phase in the hydrothermal paragenesis. The fluid inclusion data indicate that all mineralization styles were formed from low-salinity (???4 wt % NaCl equiv) aqueous-carbonic fluids, consistent with the composition of fluid inclusions within infilled miarolitic cavities in the intrusive rocks. However, the nonaqueous fluid was predominantly CH4 in skarn, CO2 in Au-Te and Au-W veins, and a fluid with roughly equal amounts Of CO2, CH4, and N2 in Au-As and Ag-Pb-Zn-Sb veins. Oxygen isotope data are consistent with a mineralizing fluid of predominantly magmatic origin that was variably modified to more positive ??18O values during interaction with 18O

  3. Petrology of greenstones in southern Wyoming Province

    NASA Astrophysics Data System (ADS)

    Takeuchi, Y.; Yuasa, T.; Ogasawara, Y.

    2006-12-01

    generally grade into pelitic rocks. All the greenstones were metamorphosed under a condition of amphibolite and no relic of protolith minerals are preserved. Ring structures suggesting pillow lavas (core, 20- 30 cm x 30-50 cm; rim, 1.0-3.0 cm wide) occur in fine-grained mafic greenstones. Skarn (several cm to several tens cm in scale) occurs only near these ring structures and cuts the greenstones. This skarn is cut by granite intrusions. Both the South Pass area and the southern Wind River Canyon area are possibly regarded as upper part of Archean oceanic crust. The South Pass greenstones were regionally metamorphosed under low-grade (lower greenschist facies). Amphibolite facies greenstones were formed by thermal effects by the granitic batholith. The southern Wind River Canyon greenstones were subjected to amphibolite facies regional metamorphism and no thermal effect by the granites was observed. Archean skarn occurs only in the southern Wind River Canyon area. What did make these differences between Archean greenstones in the South Pass area and the southern Wind River Canyon area? Comparisons of greenstones between these two areas are significant for the formation of the Archean greenstones and the formation of Archean skarn in these areas.

  4. Ore Mineralogy Features of Hayriye and Arapdede Mineralizations in (Inegol-Bursa) Area

    NASA Astrophysics Data System (ADS)

    Sendir, Hüseyin; Kocatürk, Hüseyin; Cesur, Duru; Toygar, Özlem

    2016-04-01

    Western Anatolia (Turkey) experienced widespread Cenozoic magmatism after the collision between the Sakarya and Anatolide-Tauride continental blocks in the pre-middle Eocene. The widespread magmatic activity in NW Anatolia postdates this continental collisional event in the region. The following magmatic episode during the Oligocene and Early Miocene is known to have produced the widespread granitic plutons. Many skarn mineralization associated with plutons formed in the region (such as Hayriye and Arapdede Mineralizations). The Paleozoic aged Devlez Metabasite is the oldest unit of the study area. This unit includes amphibolite, glaucophane-lawsonite schist, muscovite schists. The unit has widely spread in area. This units are overlain unconformably by the Geyiktepe Marbles. Paleocene aged Domaniç granitoidic intrusives cut other rock series and located as a batholite. Magmatic units present porphyric and holocrystalline textures. Granitoidic intrusions are represented by tonalite, tonalite porphyr, granodiorite, granodiorite porphyr, granite, diorite, diorite porphyries. The Domaniç granitoid intruded in to the metamorphides during Paleocene and caused formations of skarn zones and related Cu-Pb-Zn mineralizations along the contacts. Mineralizations are known in the locations named as Arapdede and Hayriye. The mineralizations occur along the metamorphites - plutonics contact, in the pockets and fractures extending towards marble. The thickness of the mineralized bodies can reach up to 1 -2 m. Primary minerals are galenite, magnetite, pyrite, chalcopyrite and sphalerite at Hayriye mineralizations and sphalerite, galenite, chalcopyrite and pyrite minerals at the Arapdede mineralizations. This study supported by ESOGU BAP (201115031) Keywords: Ore mineralogy, mineralization, Cu-Pb-Zn deposits, Inegöl (Bursa).

  5. Fold Structures in the tectono-metamorphic Evolution of the Serifos MCC

    NASA Astrophysics Data System (ADS)

    Iglseder, C.; Grasemann, B.; Petrakakis, K.; Zamolyi, A.; Rambousek, C.

    2003-04-01

    The Attic-Cycladic belt is part of the Alpine orogen in the eastern Mediterranean. It is located SE of the Greek mainland and trends parallel to the Hellenic volcanic arc. Since the Miocene, the whole area of the southern Aegean is characterized by a roughly NS oriented extensional regime partly accommodated by crustal low-angle normal faults. Some of the islands in the eastern Cyclades (Naxos, Paros, Ios) have been suggested to represent metamorphic core complex (MCC) indicating an asymmetric extension partly to the N and to the S (e.g. Lister et al. 1984). These MCCs are characterized by intertectonic granodioritic intrusions, which are subsequently deformed asymmetrically by the main detachment, resulting in a discordant contact on one side and a mylonitized contact on the other side of the intrusion. This work focuses on the discordant northern contact of the granodiorite of a newly found MCC on western Cycladic Serifos island. The granodiorite intruded a series of metabasites, orthogneisses and marbles that shows a complex folding pattern. Whereas the southern granodiorite contact has been overprinted by the main detachment under greenschist-facies conditions, the northern contact cross-cuts mylonitized orthogneisses, skarn-bearing amphibolites and marbles that partly record earlier contact metamorphism, Ca-Fe-Mg skarn formation and shearing. Because the shear sense indicators in these rocks record the same kinematic frame as the one observed in the greenschist-facies detachment in the south, it is proposed that the deformation recorded in the mylonitic rocks at the northern contact belongs to an earlier stage of the same MCC formation. Lister, G. S., Banga, G. &Feenstra, A (1984). Geology 12, 221-225.

  6. The Luanchuan Mo-W-Pb-Zn-Ag magmatic-hydrothermal system in the East Qinling metallogenic belt, China: Constrains on metallogenesis from C-H-O-S-Pb isotope compositions and Rb-Sr isochron ages

    NASA Astrophysics Data System (ADS)

    Cao, Hua-Wen; Zhang, Shou-Ting; Santosh, M.; Zheng, Luo; Tang, Li; Li, Dong; Zhang, Xu-Huang; Zhang, Yun-Hui

    2015-11-01

    The Luanchuan Mo-W-Pb-Zn-Ag polymetallic ore district is located in the East Qinling metallogenic belt on the southern margin of the North China Craton. Two ore fields (Nannihu and Yuku) are recognized in the district, and three types of deposits are identified from the two ore fields as follows: (1) the 6 proximal porphyry-skarn type Mo-W deposits occurring at the inner contact zone of the granite porphyries, (2) the 3 middle skarn-hydrothermal type Zn deposits, and (3) the 8 distal hydrothermal type Pb-Zn-Ag deposits at the periphery of the porphyry. We present C-H-O isotope compositions of hydrothermal quartz and calcite, S-Pb isotope compositions of sulfide minerals, and sphalerite Rb-Sr isochron ages from the 17 deposits. The geochemical and geochronological data from the two ore fields all show systematic temporal and spatial variation, and primarily lead to the following inferences. (1) The temperatures and salinities of the ore-forming fluids decreased during mineralization. The ore-forming fluids gradually evolved from magmatic water to mixed magmatic-meteoric water. (2) The metallogenic components were primarily derived from igneous rocks, with increasing proportions of the materials from the ore-bearing rocks. (3) The mineralization ages of these deposits are close (147-136 Ma), which correspond to the emplacement of the granite intrusions. (4) The three types of deposits and the ore-related late Mesozoic intrusives constitute a unified magmatic-hydrothermal-mineralization system. Finally, we also suggest exploration strategies for the Luanchuan ore district.

  7. Summary of the Ahankashan Area of Interest

    USGS Publications Warehouse

    Drew, Lawrence J.; Sutphin, David M.; Mars, John C.; Bogdanow, Anya K.

    2015-09-15

    This report summarizes and interprets results of the work in the Ahankashan Area of Interest in northwestern Afghanistan and four study areas—the Ahankashan Prospect Area, Syahsang-Kushkak, Taghab-Soni, and Zakak-e ‘Olya—delineated for their potential undiscovered mineral occurrences with specific emphasis on porphyry copper and related occurrence types. The Area of Interest is underlain by rocks of three different geologic domains that cross from east to west—the Band-e-Bayan Block/Central Pamirs Domain in the south, the Hindu Kush Domain in the Paropamisus Mountains, and the Afghan Turkestan Domain in the north. The domains are sutured remnants of Tethyan tectonic elements. Interpretation of the geologic maps indicates the presence of thrust faults, strike-slip faults, and granitic intrusions emplaced in ground prepared by faulting. Thrust faulting was followed by strike-slip faulting and then followed by magmatic intrusions. Advanced Spaceborne Thermal Emission and Reflection Radiometer data were used to map minerals that have been altered by hydrothermal fluids typically associated with mineralization to delineate new potential occurrences of copper, gold, and silver. Propylitic-, argillic-, and phyllic-altered intrusive rocks are found in the area, as well as very minor amounts of hydrothermal silica-rich rocks. This area of interest is vastly underexplored and contains only seven known mineral occurrences, of which the Ahankashan copper (gold) skarn occurrence is the best known. Gold has been found in stream sediments near the Ahankashan skarn, in the Taghab-Soni study area, and possibly other parts of the Area of Interest, suggesting potential for at least small-scale placer occurrences.

  8. Temperature and emissivity separation and mineral mapping based on airborne TASI hyperspectral thermal infrared data

    NASA Astrophysics Data System (ADS)

    Cui, Jing; Yan, Bokun; Dong, Xinfeng; Zhang, Shimin; Zhang, Jingfa; Tian, Feng; Wang, Runsheng

    2015-08-01

    Thermal infrared remote sensing (8-12 μm) (TIR) has great potential for geologic remote sensing studies. TIR has been successfully used for terrestrial and planetary geologic studies to map surface materials. However, the complexity of the physics and the lack of hyperspectral data make the studies under-investigated. A new generation of commercial hyperspectral infrared sensors, known as Thermal Airborne Spectrographic Imager (TASI), was used for image analysis and mineral mapping in this study. In this paper, a combined method integrating normalized emissivity method (NEM), ratio algorithm (RATIO) and maximum-minimum apparent emissivity difference (MMD), being applied in multispectral data, has been modified and used to determine whether this method is suitable for retrieving emissivity from TASI hyperspectral data. MODTRAN 4 has been used for the atmospheric correction. The retrieved emissivity spectra matched well with the field measured spectra except for bands 1, 2, and 32. Quartz, calcite, diopside/hedenbergite, hornblende and microcline have been mapped by the emissivity image. Mineral mapping results agree with the dominant minerals identified by laboratory X-ray powder diffraction and spectroscopic analyses of field samples. Both of the results indicated that the atmospheric correction method and the combined temperature-emissivitiy method are suitable for TASI image. Carbonate skarnization was first found in the study area by the spatial extent of diopside. Chemical analyses of the skarn samples determined that the Au content was 0.32-1.74 g/t, with an average Au content of 0.73 g/t. This information provides an important resource for prospecting for skarn type gold deposits. It is also suggested that TASI is suitable for prospect and deposit scale exploration.

  9. Microthermometric and stable isotopic (O and H) characteristics of fluid inclusions in the porphyry related Çöpler (İliç - Erzincan) gold deposit, central eastern Turkey

    NASA Astrophysics Data System (ADS)

    Canbaz, Oktay; Gökce, Ahmet

    2014-06-01

    The Çöpler gold deposit occurs within the stockwork of quartz hosted by the Çöpler granitoid (Eosen) and by surrounding metasediments of Keban metamorphic (Late Paleozoic - Early Mesozoic) and the Munzur limestones (Late Carboniferous - Early Cretaceous). Native gold accompanied by small amounts of chalcopyrite, pyrite, magnetite, maghemite, hematite, fahlerz, marcasite, bornite, galena, sphalerite, specular hematite, goethite, lepidochrosite and bravoitic pyrite within the stockwork ore veinlets. In addition, epidote (pistazite - zoisite), garnet, scapolite, chlorite, tremolite/actinolite, muscovite and opaque minerals were determined within the veinlets occurred in skarn zones. The study of fluid inclusions in quartz veinlets showed that the hydrothermal fluids contain CaCl2, MgCl2 and NaCl and the salinities of the two phases (L+V) inclusions range from 1.7 to 20.6% NaCl equivalent. Salinity values up to 44% were determined within the halite bearing three phases inclusions. Their homogenization temperature values have a wide range from 145.0 to 380.0°C, indicative of catathermal/hypothermal to epithermal conditions. The δ 18O and δD values of the fluid inclusion waters from the Çöpler granitoid correspond to those assigned to Primary Magmatic Water, those from the metasediments of Keban metamorphics fall outside of the Primary Magmatic and are within the Metamorphic Water field. A sample from a quartz vein within the skarn zone hosted by the Munzur limestones has a particularly low δD value. The results suggest that fluids derived from the granitoids were mixed with those derived from the metasediments of Keban metamorphics and the the Munzur limestones and resulting in quartz veinlets in these lithologies and the formation of stockwork ores. In view of the occurrence, the features described and processes envisaged for this study area may be applicable in similar settings.

  10. Metallogenic events and tectonic setting of the Duobaoshan ore field in Heilongjiang Province, NE China

    NASA Astrophysics Data System (ADS)

    Hao, Yu-Jie; Ren, Yun-Sheng; Duan, Ming-Xin; Tong, Kuang-Yin; Chen, Cong; Yang, Qun; Li, Chao

    2015-01-01

    The Duobaoshan ore field, a major center of metal production in Northeast China, is located in the northeast of the Xing'an-Mongolia Orogenic Belt (the eastern part of the Central Asian Orogenic Belt) and within the northern Greater Xing'an Mountains. Several types of ore deposits are mined in the Duobaoshan region, including the Duobaoshan and Tongshan porphyry copper-molybdenum deposits, the Sankuanggou skarn iron-copper deposit, and the Zhengguang epithermal gold deposit. Zircon grains from the Tongshan granodiorite and porphyritic granite yield laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb weighted mean ages of 475.9 ± 0.8 Ma and 230.9 ± 0.9 Ma to 240.7 ± 0.8 Ma, respectively. The Re-Os isochron age of molybdenites from the Tongshan deposit is 473 ± 4 Ma. Because both field observations and petrographic analysis identified disseminated chalcopyrite, pyrite, and malachite in the porphyritic granite, the isotope dating indicates that the Tongshan deposit underwent at least two magmatic-mineralization events, during the Ordovician and the Triassic. Zircon grains from the metallogenic granodiorite of the Sankuanggou skarn deposit yield an age of 176.1 ± 0.3 Ma, and Re-Os dating of molybdenite gives an age of 173 ± 6 Ma, indicating a Jurassic event. Based on previous research and the new geochemical analysis presented in this study, it is inferred that the magmatism and mineralization of the Sankuanggou deposit were associated with the subduction of the Paleo-Pacific Plate. The Duobaoshan region has therefore experienced at least three major magmatic and mineralization events, during the Ordovician (470-480 Ma), the Triassic (230-240 Ma), and the Early Jurassic (170-180 Ma).

  11. Porphyry Cu-Au and associated polymetallic Fe-Cu-Au deposits in the Beiya Area, western Yunnan Province, south China

    USGS Publications Warehouse

    Xu, X.-W.; Cai, X.-P.; Xiao, Q.-B.; Peters, S.G.

    2007-01-01

    The Alkaline porphyries in the Beiya area are located east of the Jinshajiang suture, as part of a Cenozoic alkali-rich porphyry belt in western Yunnan. The main rock types include quartz-albite porphyry, quartz-K-feldspar porphyry and biotite-K-feldspar porphyry. These porphyries are characterised by high alkalinity [(K2O + Na2O)% > 10%], high silica (SiO2% > 65%), high Sr (> 400??ppm) and 87Sr/86Sr (> 0.706)] ratio and were intruded at 65.5??Ma, between 25.5 to 32.5??Ma, and about 3.8??Ma, respectively. There are five main types of mineral deposits in the Beiya area: (1) porphyry Cu-Au deposits, (2) magmatic Fe-Au deposits, (3) sedimentary polymetallic deposits, (4) polymetallic skarn deposits, and (5) palaeoplacers associated with karsts. The porphyry Cu-Au and polymetallic skarn deposits are associated with quartz-albite porphyry bodies. The Fe-Au and polymetallic sedimentary deposits are part of an ore-forming system that produced considerable Au in the Beiya area, and are characterised by low concentrations of La, Ti, and Co, and high concentrations of Y, Yb, and Sc. The Cenozoic porphyries in western Yunnan display increased alkalinity away from the Triassic Jinshajiang suture. Distribution of both the porphyries and sedimentary deposits in the Beiya area are interpreted to be related to partial melting in a disjointed region between upper mantle lithosphere of the Yangtze Plate and Gondwana continent, and lie within a shear zone between buried Palaeo-Tethyan oceanic lithosphere and upper mantle lithosphere, caused by the subduction and collision of India and Asia. ?? 2006 Elsevier B.V. All rights reserved.

  12. Methods of the international study on soccer at altitude 3600 m (ISA3600)

    PubMed Central

    Gore, Christopher J; Aughey, Robert J; Bourdon, Pitre C; Garvican-Lewis, Laura A; Soria, Rudy; Claros, Jesus C Jimenez; Sargent, Charli; Roach, Gregory D; Buchheit, Martin; Simpson, Ben M; Hammond, Kristal; Kley, Marlen; Wachsmuth, Nadine; Pepper, Mark; Edwards, Alistair; Cuenca, Douglas; Vidmar, Tony; Spielvogel, Hilde; Schmidt, Walter F

    2013-01-01

    Background We describe here the 3-year process underpinning a multinational collaboration to investigate soccer played at high altitude—La Paz, Bolivia (3600 m). There were two main aims: first, to quantify the extent to which running performance would be altered at 3600 m compared with near sea level; and second, to characterise the time course of acclimatisation of running performance and underlying physiology to training and playing at 3600 m. In addition, this project was able to measure the physiological changes and the effect on running performance of altitude-adapted soccer players from 3600 m playing at low altitude. Methods A U20 Bolivian team (‘The Strongest’ from La Paz, n=19) played a series of five games against a U17 team from sea level in Australia (The Joeys, n=20). 2 games were played near sea level (Santa Cruz 430 m) over 5 days and then three games were played in La Paz over the next 12 days. Measures were (1) game and training running performance—including global positioning system (GPS) data on distance travelled and velocity of movement; (2) blood—including haemoglobin mass, blood volume, blood gases and acid–base status; (3) acclimatisation—including resting heart rate variability, perceived altitude sickness, as well as heart rate and perceived exertion responses to a submaximal running test; and (4) sleep patterns. Conclusions Pivotal to the success of the project were the strong professional networks of the collaborators, with most exceeding 10 years, the links of several of the researchers to soccer federations, as well as the interest and support of the two head coaches. PMID:24282214

  13. Magnetic and Structural Properties of Ultra-Thin Cobalt Films

    NASA Astrophysics Data System (ADS)

    Wiedmann, Michael Helmut

    In situ polar Kerr effect measurements have been used to study the magnetic anisotropy of Au(111)/Co/X, Pd(111)/Co/X, Cu(111)/Co/X, and Pd(100)/Co/X sandwiches, where X is the nonmagnetic metal Ag, Au, Cu, Ir, and Pd or the insulator MgO. The films were grown by molecular beam epitaxy (MBE). For the metals, we found that the magnitude of the Co/X perpendicular interface anisotropy is strongly peaked at ~1 atomic layer (1.5-2.5 A) coverage. To investigate structural influences on the anisotropy, we have used reflection high energy diffraction (RHEED) and low energy electron diffraction (LEED) to measure changes resulting from overlayer coverage. Analysis of digitized RHEED images captured every ~ 1 A during metal overlayer coverage shows no abrupt change of the in-plane lattice constant. We have also investigated the out-of-plane lattice spacing as a function of nonmagnetic metal coverage by measuring LEED I-V curves along the (0,0) rod. In the case of Cu, where the LEED behavior is nearly kinematic, we see no evidence of any abrupt structural changes at ~1 atomic layer coverage. These results suggest the observed peak in magnetic anisotropy is not structural in origin. The influence of an insulating overlayer, MgO, on the perpendicular magnetic properties was also investigated.

  14. Core-level shifts in fcc random alloys: A first-principles approach

    NASA Astrophysics Data System (ADS)

    Olovsson, W.; Göransson, C.; Pourovskii, L. V.; Johansson, B.; Abrikosov, I. A.

    2005-08-01

    First-principles theoretical calculations of the core-level binding-energy shift (CLS) for eight binary face-centered-cubic (fcc) disordered alloys, CuPd, AgPd, CuNi, NiPd, CuAu, PdAu, CuPt, and NiPt, are carried out within density-functional theory (DFT) using the coherent potential approximation. The shifts of the Cu and Ni 2p3/2 , Ag and Pd 3d5/2 , and Pt and Au 4f7/2 core levels are calculated according to the complete screening picture, which includes both initial-state (core-electron energy eigenvalue) and final-state (core-hole screening) effects in the same scheme. The results are compared with available experimental data, and the agreement is shown to be good. The CLSs are analyzed in terms of initial- and final-state effects. We also compare the complete screening picture with the CLS obtained by the transition-state method, and find very good agreement between these two alternative approaches for the calculations within the DFT. In addition the sensitivity of the CLS to relativistic and magnetic effects is studied.

  15. An Experimental Review on Heavy-Flavor v 2 in Heavy-Ion Collision

    DOE PAGES

    Nasim, Md.; Esha, Roli; Huang, Huan Zhong

    2016-01-01

    For overmore » a decade now, the primary purpose of relativistic heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC) has been to study the properties of QCD matter under extreme conditions—high temperature and high density. The heavy-ion experiments at both RHIC and LHC have recorded a wealth of data in p+p, p+Pb, d+Au, Cu+Cu, Cu+Au, Au+Au, Pb+Pb, and U+U collisions at energies ranging from s N N = 7.7  GeV to 7 TeV. Heavy quarks are considered good probe to study the QCD matter created in relativistic collisions due to their very large mass and other unique properties. A precise measurement of various properties of heavy-flavor hadrons provides an insight into the fundamental properties of the hot and dense medium created in these nucleus-nucleus collisions, such as transport coefficient and thermalization and hadronization mechanisms. The main focus of this paper is to present a review on the measurements of azimuthal anisotropy of heavy-flavor hadrons and to outline the scientific opportunities in this sector due to future detector upgrade. We will mainly discuss the elliptic flow of open charmed meson ( D -meson), J / ψ , and leptons from heavy-flavor decay at RHIC and LHC energy.« less

  16. Magneto-optic superlattice thin films: Fabrication, structural and magnetic characterization

    NASA Technical Reports Server (NTRS)

    Falco, C. M.; Engel, B. N.; Vanleeuwen, R. A.; Yu, J.

    1993-01-01

    During this quarter studies were extended to determine the electronic contribution to the perpendicular interface anisotropy in Co-based multilayers. Using in situ Kerr effect measurements, the influences of different transition metals (TM = Ag, Au, Cu, and Pd) on the magnetic properties of single-crystal Co films grown on Pd (111) and Au (111) surfaces are investigated. Last quarter the discovery of a large peak in the perpendicular anisotropy when approximately one monolayer of Cu or Ag is deposited on the Co surface was reported. We now have added a computer-controlled stepper-motor drive to our MBE sample transfer mechanism. The motor allows us to move the sample at a constant velocity from behind a shutter during deposition. The film, therefore, is deposited as a wedge with a linear variation of thickness across the substrate. In this way, a continuous range of coverage on a single sample is studied. The stepper motor also provides the necessary control for precisely positioning the sample in the laser beam for Kerr effect measurements at the different coverages.

  17. Search for microremnants of the Tunguska Cosmic Body

    NASA Astrophysics Data System (ADS)

    Longo, G.; Serra, R.; Cecchini, S.; Galli, M.

    1994-02-01

    A new method is used here to obtain experimental data on the nature and composition of the Tunguska Cosmic Body. The leading hypothesis of the method is that in the forest conifers which have survived the Tunguska catastrophe, the fluid resin present at the moment of the event could have acted as a trap for airborne particles, as happens in amber. The growth rings of trees can give information on the age of the resin and therefore on the time when the particulate was trapped in it. With a scanning electron microscope, a total of 7163 particles were found in resin samples from Tunguska branches and from two control trees. The time distributions of the particles in the years 1885-1930 show clear abundance peaks centered on 1908. This makes it possible to conclude that the presence of Fe, Ca, Al, Si, Au, Cu, S, Zn, Cr, Ba, Ti, Ni, C and O in the particles observed is related to the Tunguska event and that these elements are probable constituents of the Tunguska Cosmic Body. This result is compatible with recent calculations showing that the Tunguska body can be a normal density meteorite.

  18. Fe-Ni composition dependence of magnetic anisotropy in artificially fabricated L1 0-ordered FeNi films.

    PubMed

    Kojima, Takayuki; Ogiwara, Misako; Mizuguchi, Masaki; Kotsugi, Masato; Koganezawa, Tomoyuki; Ohtsuki, Takumi; Tashiro, Taka-Yuki; Takanashi, Koki

    2014-02-12

    We prepared L10-ordered FeNi alloy films by alternate deposition of Fe and Ni monatomic layers, and investigated their magnetic anisotropy. We employed a non-ferromagnetic Au-Cu-Ni buffer layer with a flat surface and good lattice matching to L10-FeNi. An L10-FeNi film grown on Au6Cu51Ni43 showed a large uniaxial magnetic anisotropy energy (Ku = 7.0 × 10(6) erg cm(-)3). Ku monotonically increased with the long-range order parameter (S) of the L10 phase. We investigated the Fe-Ni composition dependence by alternating the deposition of Fe 1 − x and Ni 1 + x monatomic layers (− 0.4 < x < 0.4). Saturation magnetization (Ms) and Ku showed maxima (Ms = 1470 emu cm(-3), Ku = 9.3 × 10(6) erg cm(-3)) for Fe60Ni40 (x = -0.2) while S showed a maximum at the stoichiometric composition (x = 0). The change in the ratio of lattice parameters (c/a) was small for all compositions. We found that enrichment of Fe is very effective to enhance Ku. The large Ms and Ku of Fe60Ni40 indicate that Fe-rich L10-FeNi is promising as a rare-earth-free permanent magnet. PMID:24469082

  19. Fabrication and characterization of SnO2/ZnO gas sensors for detecting toluene gas.

    PubMed

    Min, Byung-Sam; Park, Young-Ho; Lee, Chang-Seop

    2014-11-01

    This study investigates the use of SnO2, ZnO, Ag, Au, Cu, In, Pd, Ru and carbon black to improve the sensitivity of a gas sensor for detecting toluene gas. Metal-SnO2/ZnO thick films were screen-printed onto Al2O3 substrates with platinum electrodes. The physico-chemical properties of the sensor materials were characterized using SEM/EDS, XRD, and BET analyses. Measuring the electrical resistance of each sensor as a function of the gas concentration determined the sensing characteristics. The sensors were tested using toluene, benzene, xylene, ethanol, methanol, ammonia and trimethylamine vapors with concentrations of 1-2000 ppm. The gas sensing properties of metal-SnO2/ZnO thick films depended on the content and variety of metals and the content of carbon black. The optimum condition of sensor material for toluene gas detection is operation temperature 300 degrees C and when metal catalyst Cu and carbon black were added. The best sensitivity and selectivity for toluene gas at 300 degrees C resulted from doping with 5 wt.% carbon black, 1 wt.% Cu and 20 wt.% ZnO to SnO2.

  20. Photovoltaic enhancement due to surface-plasmon assisted visible-light absorption at the inartificial surface of lead zirconate-titanate film.

    PubMed

    Zheng, Fengang; Zhang, Peng; Wang, Xiaofeng; Huang, Wen; Zhang, Jinxing; Shen, Mingrong; Dong, Wen; Fang, Liang; Bai, Yongbin; Shen, Xiaoqing; Sun, Hua; Hao, Jianhua

    2014-03-01

    PZT film of 300 nm thickness was deposited on tin indium oxide (ITO) coated quartz by a sol-gel method. Four metal electrodes, such as Pt, Au, Cu and Ag, were used as top electrodes deposited on the same PZT film by sputtering at room temperature. In ITO-PZT-Ag and ITO-PZT-Au structures, the visible light (400-700 nm) can be absorbed partially by a PZT film, and the maximum efficiency of photoelectric conversion of the ITO-PZT-Ag structure was enhanced to 0.42% (100 mW cm(-2), AM 1.5G), which is about 15 times higher than that of the ITO-PZT-Pt structure. Numerical simulations show that the natural random roughness of polycrystalline-PZT-metal interface can offer a possibility of coupling between the incident photons and SPs at the metal surface. The coincidence between the calculated SP properties and the measured EQE spectra reveals the SP origin of the photovoltaic enhancement in these ITO-PZT-metal structures, and the improved photocurrent output is caused by the enhanced optical absorption in the PZT region near the metal surface, rather than by the direct charge-transfer process between two materials. PMID:24477668

  1. Bifunctional Interface of Au and Cu for Improved CO2 Electroreduction.

    PubMed

    Back, Seoin; Kim, Jun-Hyuk; Kim, Yong-Tae; Jung, Yousung

    2016-09-01

    Gold is known currently as the most active single-element electrocatalyst for CO2 electroreduction reaction to CO. In this work, we combine Au with a second metal element, Cu, to reduce the amount of precious metal content by increasing the surface-to-mass ratio and to achieve comparable activity to Au-based catalysts. In particular, we demonstrate that the introduction of a Au-Cu bifunctional "interface" is more beneficial than a simple and conventional homogeneous alloying of Au and Cu in stabilizing the key intermediate species, *COOH. The main advantages of the proposed metal-metal bifunctional interfacial catalyst over the bimetallic alloys include that (1) utilization of active materials is improved, and (2) intrinsic properties of metals are less affected in bifunctional catalysts than in alloys, which can then facilitate a rational bifunctional design. These results demonstrate for the first time the importance of metal-metal interfaces and morphology, rather than the simple mixing of the two metals homogeneously, for enhanced catalytic synergies. PMID:27526778

  2. "High specific activity" radiotracers for metallo-toxicological studies: cyclotron and nuclear reactor production, radiochemical separation and "quality control": platinum, iridium, gold, copper and gallium.

    PubMed

    Bonardi, Mauro; Groppi, Flavia; Birattari, Claudio; Arginelli, Dolores

    2002-09-01

    Very High Specific Activity RadioNuclides, HSARN, are a powerful tool to label a wide variety of chemical elements and compounds present in the biosphere in ultra-trace amounts. Medium and high Z radionuclides, can be produced by irradiation in light-ions accelerator and sometimes nuclear reactor. If the nuclear reaction product has atomic number different from irradiated target, it is possible separating the radioactive nuclide from irradiated target, without addition of isotopic carrier. These kinds of radionuclides are named No Carrier Added, NCA, and their specific activity is very high and can reach values close to the theoretical Carrier Free one. The true specific activity must be determined by use of very sensitive radioanalytical techniques. If a low isotopic dilution factor is obtained, these radiotracers are used to label inorganic species and complexes of elements, which are presently introduced into the echo-systems by human activities. New production methods for NCA Pt, Ir, Au, Cu and Ga radiotracers are presented, with some details on radiochemistry and quality controls.

  3. Synthesis of gold nano-wire and nano-dumbbell shaped colloids and AuC60 nano-clusters

    NASA Astrophysics Data System (ADS)

    Landon, Preston B.; Jarvis, Brandon C.; Gilleland, Cody L.; Renfro, Tim; Gutierrez, Jose; Synowczynski, Jennifer; Hirsch, Samuel G.; Glosser, Robert

    2005-08-01

    A technique for the fabrication of colloidal gold nano-wire and nano-dumbbell shaped particles using carbon nanotubes and rod shaped viruses as templates is described. The gold (Au) encapsulation process was accomplished by the precipitation of gold chloride from aqueous solutions. When this process was conducted in the presence of hydroxylated C60, small pieces of phase-separated composites of AuC60 appeared to have formed. These nano-clusters may turn out to be large noble metal analogs of the alkali metal fullerides with the smallest geometrically possible Au aggregate consisting of 55 gold atoms. The existence of noble metal fullerene composites has been previously theorized. The alkali metal fullerides are examples of phase separated solids and have exhibited superconductivity with temperatures as high 33K. The mechanism required for the binding energy between C60 and gold has been observed to exist between C60 and many of the mirror metals (Al, Ag, Au, Cu, Ni). This binding energy is a charge transfer from the metal Fermi level into the C60 LUMO. If this bonding energy, is greater than the metals coagulation energy an Au/C60 size terminated mechanism during the formation of the gold aggregates by the adhesion of C60 to the surface is energetically favorable.

  4. Effect of different metallic nano-inclusions (Ag, Al, Au and Cu) and gain assistance for isotropic left-handed photonic material in blue light region

    NASA Astrophysics Data System (ADS)

    Rajput, M.; Sinha, R. K.; Varshney, S. K.

    2013-07-01

    A gain assisted Double Negative-Metallo-Semiconductor Photonic Crystal (DN-MSPC) for blue light with effect of different plasmonic (Al, Ag, Au, Cu) nanorod inclusions is presented. Effect of different metal nanocomposites and inverted host matrix, on dispersion and transmission properties of the designed DN-MSPC is demonstrated. Negative real values of both permeability (μ) and permittivity (ɛ) with extremely low imaginary values in the visible region are obtained by applying coupled dipole approximation for different nanocomposites. It is shown that index matching to the incident medium and compensated losses due to the gain assistance lead to the light amplification in the designed structure. A comparison of dispersion properties and left-handed resonance for different plasmonic nanocomposites of a similar shape and geometry shows permittivity-dependent dispersion and resonant properties. Fabrication tolerance with effect of change in plasmonic nanorod radius by ±10% is also analyzed. Furthermore, the sensitivity of the left-handed transmission to index changes of the host material (i.e., refractive index sensitivity) and highest left-handed transmission efficiency (>99%) is also investigated for biosensing application.

  5. Development of high-efficiency, thin-film CdTe solar cells. Final subcontract report, 1 February 1992--30 November 1995

    SciTech Connect

    Rohatgi, A.; Chou, H.C.; Kamra, S.; Bhat, A.

    1996-01-01

    This report describes work performed by the Georgia Institute of Technology (GIT) to bring the polycrystalline CdTe cell efficiency a step closer to the practically achievable efficiency of 18% through fundamental understanding of detects and loss mechanisms, the role of chemical and heat treatments, and investigation of now process techniques. The objective was addressed by a combination of in-depth characterization, modeling, materials growth, device fabrication, and `transport analyses of Au/Cu/CdTe/CdS/SnO {sub 2} glass front-wall heterojunction solar cells. GiT attempted to understand the loss mechanism(s) in each layer and interface by a step-by-step investigation of this multilayer cell structure. The first step was to understand, quantify, and reduce the reflectance and photocurrent loss in polycrystalline CdTe solar calls. The second step involved the investigation of detects and loss mechanisms associated with the CdTe layer and the CdTe/CdS interface. The third stop was to investigate the effect of chemical and heat treatments on CdTe films and cells. The fourth step was to achieve a better and reliable contact to CdTe solar cells by improving the fundamental understanding. Of the effects of Cu on cell efficiency. Finally, the research involved the investigation of the effect of crystallinity and grain boundaries on Cu incorporation in the CdTe films, including the fabrication of CdTe solar calls with larger CdTe grain size.

  6. A Systematic Investigation of p-Nitrophenol Reduction by Bimetallic Dendrimer Encapsulated Nanoparticles

    PubMed Central

    2013-01-01

    We demonstrate that the reduction of p-nitrophenol to p-aminophenol by NaBH4 is catalyzed by both monometallic and bimetallic nanoparticles (NPs). We also demonstrate a straightforward and precise method for the synthesis of bimetallic nanoparticles using poly(amido)amine dendrimers. The resulting dendrimer encapsulated nanoparticles (DENs) are monodisperse, and the size distribution does not vary with different elemental combinations. Random alloys of Pt/Cu, Pd/Cu, Pd/Au, Pt/Au, and Au/Cu DENs were synthesized and evaluated as catalysts for p-nitrophenol reduction. These combinations are chosen in order to selectively tune the binding energy of the p-nitrophenol adsorbate to the nanoparticle surface. Following the Brønsted–Evans–Polanyi (BEP) relation, we show that the binding energy can reasonably predict the reaction rates of p-nitrophenol reduction. We demonstrate that the measured reaction rate constants of the bimetallic DENs is not always a simple average of the properties of the constituent metals. In particular, DENs containing metals with similar lattice constants produce a binding energy close to the average of the two constituents, whereas DENs containing metals with a lattice mismatch show a bimodal distribution of binding energies. Overall, in this work we present a uniform method for synthesizing pure and bimetallic DENs and demonstrate that their catalytic properties are dependent on the adsorbate’s binding energy. PMID:23616909

  7. Accumulation and phytotoxicity of engineered nanoparticles to Cucurbita pepo.

    PubMed

    Hawthorne, Joseph; Musante, Craig; Sinha, Saion K; White, Jason C

    2012-04-01

    The effect of bulk and engineered nanoparticle (NP) Ag, Au, Cu, Si, and C at 250 and 750 mg/L on zucchini biomass, transpiration, and element content was determined. The pH of bulk and NP solutions prior to plant growth frequently differed. Nanoparticle Cu solution pH was significantly higher than bulk Cu, whereas for Ag and C, the NPs had significantly lower pH. Plants were unaffected by Au, regardless of particle size or concentration. NP Ag reduced plant biomass and transpiration by 49-91% compared to equivalent bulk Ag. NP Si at 750 mg/L reduced plant growth and transpiration by 30-51% relative to bulk Si. Bulk and NP Cu were phytotoxic but much of the effect was alleviated by humic acid. The shoot Ag and Cu content did not differ based on particle size or concentration. The accumulation of bulk Au was greater than the NP, but humic acid increased the accumulation of NP and bulk Au by 5.6-fold and 80%, respectively. The uptake of NP Si was 5.6-6.5-fold greater than observed with the bulk element. These findings show that the NPs may have unique phytotoxicity or accumulation patterns and that solution properties can significantly impact particle fate and effects. PMID:22567722

  8. Screening plasmonic materials using pyramidal gratings

    PubMed Central

    Gao, Hanwei; Henzie, Joel; Lee, Min Hyung; Odom, Teri W.

    2008-01-01

    Surface plasmon polaritons (SPPs) are responsible for exotic optical phenomena, including negative refraction, surface enhanced Raman scattering, and nanoscale focusing of light. Although many materials support SPPs, the choice of metal for most applications has been based on traditional plasmonic materials (Ag, Au) because there have been no side-by-side comparisons of the different materials on well-defined, nanostructured surfaces. Here, we report a platform that not only enabled rapid screening of a wide range of metals under different excitation conditions and dielectric environments, but also identified new and unexpected materials for biosensing applications. Nanopyramidal gratings were used to generate plasmon dispersion diagrams for Al, Ag, Au, Cu, and Pd. Surprisingly, the SPP coupling efficiencies of Cu and Al exceeded widely used plasmonic materials under certain excitation conditions. Furthermore, grazing angle excitation led to the highest refractive index sensitivities (figure of merit >85) reported at optical frequencies because of extremely narrow SPP resonances (full-width-at-half-minimum <6 nm or 7 meV). Finally, our screening process revealed that Ag, with the highest sensitivity, was not necessarily the preferred material for detecting molecules. We discovered that Au and even Pd, a weak plasmonic material, showed comparable index shifts on formation of a protein monolayer. PMID:19074259

  9. SERS activity with tenfold detection limit optimization on a type of nanoporous AAO-based complex multilayer substrate.

    PubMed

    Sui, Chaofan; Wang, Kaige; Wang, Shuang; Ren, Junying; Bai, Xiaohong; Bai, Jintao

    2016-03-21

    Most of SERS applications are constricted by heterogeneous hotspots and aggregates of nanostructure, which result in low sensitivity and poor reproducibility of characteristic signals. This work intends to introduce SERS properties of a type of SERS-active substrate, Au-CuCl2-AAO, which is innovatively developed on a porous anodic alumina oxide (AAO) template. Spectral measuring results of Rhodamine 6G (R6G) on this substrate optimized by controlling morphology and gold thickness showed that enhancement factor (2.30 × 10(7)) and detection limit (10(-10) M) were both improved and represented better performance than its template AAO. Homogenous hot spots across the region of interest were achieved by scanning SERS intensity distribution for the band at 1505 cm(-1) in 5 × 5 μm(2) area. Furthermore, the promising SERS activity of the flower-patterned substrate was theoretically explained through simulation of the electromagnetic field distribution. In addition, this SERS substrate is proposed for applications within the field of chemical and biochemical analyses. PMID:26911325

  10. Density functional theory study of mercury adsorption on metal surfaces

    SciTech Connect

    Steckel, J.A.

    2008-01-01

    Density functional theory _DFT_ calculations are used to characterize the interaction of mercury with copper, nickel, palladium, platinum, silver, and gold surfaces. Mercury binds relatively strongly to all the metal surfaces studied, with binding energies up to _1 eV for Pt and Pd. DFT calculations underestimate the energy of adsorption with respect to available experimental data. Plane-wave DFT results using the local density approximation and the Perdew-Wang 1991 and Perdew-Burke-Ernzerhof parametrizations of the generalized gradient approximation indicate that binding of mercury at hollow sites is preferred over binding at top orbridge sites. The interaction with mercury in order of increasing reactivity over the six metals studied is Ag_Au_Cu_Ni_Pt_Pd. Binding is stronger on the _001_ faces of the metal surfaces, where mercury issituated in fourfold hollow sites as opposed to the threefold hollow sites on _111_ faces. In general, mercury adsorption leads to decreases in the work function; adsorbate-induced work function changes are particularly dramatic on Pt.

  11. Density functional theory study of mercury adsorption on metal surfaces

    SciTech Connect

    Steckel, Janice A.

    2008-03-10

    Density functional theory (DFT) calculations are used to characterize the interaction of mercury with copper, nickel, palladium, platinum, silver, and gold surfaces. Mercury binds relatively strongly to all the metal surfaces studied, with binding energies up to ~1eV for Pt and Pd. DFT calculations underestimate the energy of adsorption with respect to available experimental data. Plane-wave DFT results using the local density approximation and the Perdew-Wang 1991 and Perdew-Burke-Ernzerhof parametrizations of the generalized gradient approximation indicate that binding of mercury at hollow sites is preferred over binding at top or bridge sites. The interaction with mercury in order of increasing reactivity over the six metals studied is Ag<Au

  12. Excess Entropy Scaling Law for Diffusivity in Liquid Metals.

    PubMed

    Jakse, N; Pasturel, A

    2016-01-01

    Understanding how dynamic properties depend on the structure and thermodynamics in liquids is a long-standing open problem in condensed matter physics. A very simple approach is based on the Dzugutov contribution developed on model fluids in which a universal (i.e. species-independent) connection relates the pair excess entropy of a liquid to its reduced diffusion coefficient. However its application to "real" liquids still remains uncertain due to the ability of a hard sphere (HS) reference fluid used in reducing parameters to describe complex interactions that occur in these liquids. Here we use ab initio molecular dynamics simulations to calculate both structural and dynamic properties at different temperatures for a wide series of liquid metals including Al, Au, Cu, Li, Ni, Ta, Ti, Zn as well as liquid Si and B. From this analysis, we demonstrate that the Dzugutov scheme can be applied successfully if a self-consistent method to determine the packing fraction of the hard sphere reference fluid is used as well as the Carnahan-Starling approach to express the excess entropy. PMID:26862002

  13. Excess Entropy Scaling Law for Diffusivity in Liquid Metals

    PubMed Central

    Jakse, N.; Pasturel, A.

    2016-01-01

    Understanding how dynamic properties depend on the structure and thermodynamics in liquids is a long-standing open problem in condensed matter physics. A very simple approach is based on the Dzugutov contribution developed on model fluids in which a universal (i.e. species-independent) connection relates the pair excess entropy of a liquid to its reduced diffusion coefficient. However its application to “real” liquids still remains uncertain due to the ability of a hard sphere (HS) reference fluid used in reducing parameters to describe complex interactions that occur in these liquids. Here we use ab initio molecular dynamics simulations to calculate both structural and dynamic properties at different temperatures for a wide series of liquid metals including Al, Au, Cu, Li, Ni, Ta, Ti, Zn as well as liquid Si and B. From this analysis, we demonstrate that the Dzugutov scheme can be applied successfully if a self-consistent method to determine the packing fraction of the hard sphere reference fluid is used as well as the Carnahan-Starling approach to express the excess entropy. PMID:26862002

  14. Influence of anisotropic elasticity on the mechanical properties of fivefold twinned nanowires

    NASA Astrophysics Data System (ADS)

    Niekiel, Florian; Spiecker, Erdmann; Bitzek, Erik

    2015-11-01

    Previous atomistic simulations and experiments have shown an increased Young's modulus and yield strength of fivefold twinned (FT) face-centered cubic metal nanowires (NWs) when compared to single crystalline (SC) NWs of the same orientation. Here we report the results of atomistic simulations of SC and FT Ag, Al, Au, Cu and Ni NWs with diameters between 2 and 50 nm under tension and compression. The simulations show that the differences in Young's modulus between SC and FT NWs are correlated with the elastic anisotropy of the metal, with Al showing a decreased Young's modulus. We develop a simple analytical model based on disclination theory and constraint anisotropic elasticity to explain the trend in the difference of Young's modulus between SC and FT NWs. Taking into account the role of surface stresses and the elastic properties of twin boundaries allows to account for the observed size effect in Young's modulus. The model furthermore explains the different relative yield strengths in tension and compression as well as the material and loading dependent failure mechanisms in FTNWs.

  15. Structures of 38-atom gold-platinum nanoalloy clusters

    SciTech Connect

    Ong, Yee Pin; Yoon, Tiem Leong; Lim, Thong Leng

    2015-04-24

    Bimetallic nanoclusters, such as gold-platinum nanoclusters, are nanomaterials promising wide range of applications. We perform a numerical study of 38-atom gold-platinum nanoalloy clusters, Au{sub n}Pt{sub 38−n} (0 ≤ n ≤ 38), to elucidate the geometrical structures of these clusters. The lowest-energy structures of these bimetallic nanoclusters at the semi-empirical level are obtained via a global-minimum search algorithm known as parallel tempering multi-canonical basin hopping plus genetic algorithm (PTMBHGA), in which empirical Gupta many-body potential is used to describe the inter-atomic interactions among the constituent atoms. The structures of gold-platinum nanoalloy clusters are predicted to be core-shell segregated nanoclusters. Gold atoms are observed to preferentially occupy the surface of the clusters, while platinum atoms tend to occupy the core due to the slightly smaller atomic radius of platinum as compared to gold’s. The evolution of the geometrical structure of 38-atom Au-Pt clusters displays striking similarity with that of 38-atom Au-Cu nanoalloy clusters as reported in the literature.

  16. Fabrication and characterization of SnO2/ZnO gas sensors for detecting toluene gas.

    PubMed

    Min, Byung-Sam; Park, Young-Ho; Lee, Chang-Seop

    2014-11-01

    This study investigates the use of SnO2, ZnO, Ag, Au, Cu, In, Pd, Ru and carbon black to improve the sensitivity of a gas sensor for detecting toluene gas. Metal-SnO2/ZnO thick films were screen-printed onto Al2O3 substrates with platinum electrodes. The physico-chemical properties of the sensor materials were characterized using SEM/EDS, XRD, and BET analyses. Measuring the electrical resistance of each sensor as a function of the gas concentration determined the sensing characteristics. The sensors were tested using toluene, benzene, xylene, ethanol, methanol, ammonia and trimethylamine vapors with concentrations of 1-2000 ppm. The gas sensing properties of metal-SnO2/ZnO thick films depended on the content and variety of metals and the content of carbon black. The optimum condition of sensor material for toluene gas detection is operation temperature 300 degrees C and when metal catalyst Cu and carbon black were added. The best sensitivity and selectivity for toluene gas at 300 degrees C resulted from doping with 5 wt.% carbon black, 1 wt.% Cu and 20 wt.% ZnO to SnO2. PMID:25958552

  17. Progress and Challenges in Transfer of Large‐Area Graphene Films

    PubMed Central

    Chen, Yi; Gong, Xiao‐Lei

    2016-01-01

    Graphene, the thinnest, strongest, and stiffest material with exceptional thermal conductivity and electron mobility, has increasingly received world‐wide attention in the past few years. These unique properties may lead to novel or improved technologies to address the pressing global challenges in many applications including transparent conducting electrodes, field effect transistors, flexible touch screen, single‐molecule gas detection, desalination, DNA sequencing, osmotic energy production, etc. To realize these applications, it is necessary to transfer graphene films from growth substrate to target substrate with large‐area, clean, and low defect surface, which are crucial to the performances of large‐area graphene devices. This critical review assesses the recent development in transferring large‐area graphene grown on Fe, Ru, Co, Ir, Ni, Pt, Au, Cu, and some nonmetal substrates by using various synthesized methods. Among them, the transfers of the most attention kinds of graphene synthesized on Cu and SiC substrates are discussed emphatically. The advances and the main challenges of each wet and dry transfer method for obtaining the transferred graphene film with large‐area, clean, and low defect surface are also reviewed. Finally, the article concludes the most promising methods and the further prospects of graphene transfer. PMID:27812479

  18. Time-resolved X-ray Absorption Spectroscopy for Electron Transport Study in Warm Dense Gold

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Won; Bae, Leejin; Engelhorn, Kyle; Heimann, Philip; Ping, Yuan; Barbrel, Ben; Fernandez, Amalia; Beckwith, Martha Anne; Cho, Byoung-Ick; GIST Team; IBS Team; LBNL Collaboration; SLAC Collaboration; LLNL Collaboration

    2015-11-01

    The warm dense Matter represents states of which the temperature is comparable to Fermi energy and ions are strongly coupled. One of the experimental techniques to create such state in the laboratory condition is the isochoric heating of thin metal foil with femtosecond laser pulses. This concept largely relies on the ballistic transport of electrons near the Fermi-level, which were mainly studied for the metals in ambient conditions. However, they were barely investigated in warm dense conditions. We present a time-resolved x-ray absorption spectroscopy measured for the Au/Cu dual layered sample. The front Au layer was isochorically heated with a femtosecond laser pulse, and the x-ray absorption changes around L-edge of Cu, which was attached on the backside of Au, was measured with a picosecond resolution. Time delays between the heating of the `front surface' of Au layer and the alternation of x-ray spectrum of Cu attached on the `rear surface' of Au indicate the energetic electron transport mechanism through Au in the warm dense conditions. IBS (IBS-R012-D1) and the NRF (No. 2013R1A1A1007084) of Korea.

  19. Spectroscopic and structural studies of energetically efficient transport in nanocontacts to NiSi nanowires

    NASA Astrophysics Data System (ADS)

    Stein, A.; Farhat, I. A. H.; Lacevic, N.; Bazuhair, S. K.; Azhar, S. S.; Isakovic, A. F.

    Understanding correlations between mechanical, thermal, structural and electronic transport properties of different nanocontact geometries to nanowires, such as Au/Cu-NiSi-Si, remain one of the major goals of nanodevices reliability and scalability research. Aiming to clarify the failure modes and processes that affect the energy efficiency of transport and switching in constrained nanocontact geometries, such as end contacts, we conducted the structural, spectroscopic, and noise correlation studies. We show how the spatial (in)homogeneity at and in the near vicinity of the interface affects the transport performance of the nanojunctions. Mobile Ni clusters are identified at the nanojunction interface via Raman spectromicroscopy and their influence on charge transport is analyzed. We also show that the noise correlation spectra and micro-X-ray stress-strain studies in the nanojunctions are effictive tools in predicting the energy efficiency of the nanojunctions. A computational study of the interfacial properties of metal/Ni-Si via DFT and MD simulations is implemented. Work supported by Mubadala-SRC # 2011-KJ-2190. A part of the work done at BNL-CFN, supported by DOE. A part of the work done at Cornell Univ.CFN and CCMR, supported by the NSF.

  20. Interfacial Electrode-Driven Enhancement of the Switching Parameters of a Copper Oxide-Based Resistive Random-Access Memory Device

    NASA Astrophysics Data System (ADS)

    Sangani, L. D. Varma; Kumar, Ch. Ravi; Krishna, M. Ghanashyam

    2016-01-01

    The characteristics of an Au/Cu x O/Au bipolar resistive random-access memory device are reported. It is demonstrated that switching parameters of this device structure can be enhanced by introducing an interfacial Al layer between the Au top electrode and the Cu x O-based dielectric layer. The set and reset voltages are, respectively, between -2.5 V to -6.0 V and +1.2 V to +3.0 V for the Al-based device. In contrast, the range of values are -0.5 V to -2.5 V and +0.5 V to +1.5 V for the set and reset voltages in the absence of Al. The Al-based device has a higher low resistance state value of 5-6 KΩ as compared to the 0.3-0.5 KΩ for the Au-based device, which leads to a 12 times lower power dissipation factor and lower reset current of 370 μA. Endurance studies carried out over 50 switching cycles show less than 2% variation in both the low resistance and high resistance values. The conduction is ohmic at low values of bias and non-ohmic at higher bias voltage which shows that the enhanced behaviour is a result of the formation of an insulating aluminum oxide layer at the Al-Cu x O interface.

  1. The Agan epithermal gold-silver deposit and prospects for the discovery of high-sulfidation mineralization in northeast Russia

    NASA Astrophysics Data System (ADS)

    Volkov, A. V.; Savva, N. E.; Sidorov, A. A.; Kolova, E. E.; Chizhova, I. A.; Alekseev, V. Yu.

    2015-01-01

    The Arman volcanotectonic depression (VTD) containing the Agan deposit is distinguished as the most promising area for the discovery of high-sulfidation (HS) epithermal Au deposit during prospecting in the Central Okhotsk ore district of the Okhotsk-Chukotka volcanogenic belt (OChVB). Studies reveal that the volcanic rocks of the Agan deposit strongly differ from those of the reference HS-type epithermal deposits. It was found that quartz-alunite metasomatites in the ore field are characterized by low Au content and Sn content two orders of magnitude higher than those of Cu and Mo. The pair-correlation coefficients are K cor (Au-Sn) = 0.73 and K cor(Au-Cu) = 0.22. The ore bodies of the Agan deposit do not contain enargite and luzonite—the main indicator minerals for Au productive HS-type mineralization; porous ("vuggy") quartz is weakly manifested. In terms of the mineral complex, the epithermal mineralization revealed in the metasomatites of the deposit is close to the intermediate sulfidation type. At the same time, this mineralization, in many of its features, is similar to the mineralization developed in siliceous and quartz-alunite lithocaps, which are formed above degassing intrusions. In this setting, HS-type ore-bearing fluids either are not formed in the system or do not reach epithermal depths.

  2. Charge transfer on the metallic atom-pair bond, and the crystal structures adopted by intermetallic compounds.

    PubMed

    Rajasekharan, T; Seshubai, V

    2012-01-01

    It has been argued in our recent papers that the heat of formation of intermetallic compounds is mostly concentrated in the nearest neighbor unlike atom-pair bonds, and that the positive term in Miedema's equation is associated with charge transfer on the bond to maintain electroneutrality. In this paper, taking examples of some well populated crystal-structure types such as MgCu(2), AsNa(3), AuCu(3), MoSi(2) and SiCr(3) types, the effect of such charge transfer on the crystal structures adopted by intermetallic compounds is examined. It is shown that the correlation between the observed size changes of atoms on alloying and their electronegativity differences is supportive of the idea of charge transfer between atoms. It is argued that the electronegativity and valence differences need to be of the required magnitude and direction to alter, through charge transfer, the elemental radius ratios R(A)/R(B) to the internal radius ratios r(A)/r(B) allowed by the structure types. Since the size change of atoms on alloying is highly correlated to how different R(A)/R(B) is from the ideal radius ratio for a structure type, the lattice parameters of intermetallic compounds can be predicted with excellent accuracy knowing R(A)/R(B). A practical application of the approach developed in our recent papers to superalloy design is presented. PMID:22186292

  3. Correct Expressions of Enthalpy of Mixing and Excess Entropy from MIVM and Their Simplified Forms

    NASA Astrophysics Data System (ADS)

    Tao, Dong-Ping

    2016-02-01

    In this work, the author pointed out that empirically to compare the molecular interaction volume model (MIVM) with thermodynamic definition of excess Gibbs energy would result in the incorrect expressions of enthalpy of mixing and excess entropy. The correct expressions of molar and partial molar enthalpies of mixing and excess entropies from the MIVM are consistent thermodynamically and are suggested for replacing their past incorrect ones. The simplification of Z i = Z = 10 is verified to be feasible by the average errors of fitting in the binary liquid alloys M-P (M = Cr, Fe, and Mn) and of predicting in the ternary liquid alloys Fe-Cr-P and Fe-Mn-P by using two coordination numbers of phosphorus Z P = 3.04 and Z P = 8.96. Further, their simplified forms are proposed for predicting easily thermodynamic properties of a multicomponent liquid system and are preliminarily tested to be coordinated mutually in the binary liquid alloys Au-Cu, Cd-Zn, Ca-Zn, and Ni-Pb.

  4. Interfacial properties of stanene-metal contacts

    NASA Astrophysics Data System (ADS)

    Guo, Ying; Pan, Feng; Ye, Meng; Wang, Yangyang; Pan, Yuanyuan; Zhang, Xiuying; Li, Jingzhen; Zhang, Han; Lu, Jing

    2016-09-01

    Recently, two-dimensional buckled honeycomb stanene has been manufactured by molecular beam epitaxy growth. Free-standing stanene is predicted to have a sizable opened band gap of 100 meV at the Dirac point due to spin-orbit coupling (SOC), resulting in many fascinating properties such as quantum spin Hall effect, quantum anomalous Hall effect, and quantum valley Hall effect. In the first time, we systematically study the interfacial properties of stanene-metal interfaces (metals = Ag, Au, Cu, Al, Pd, Pt, Ir, and Ni) by using ab initio electronic structure calculations considering the SOC effects. The honeycomb structure of stanene is preserved on the metal supports, but the buckling height is changed. The buckling of stanene on the Au, Al, Ag, and Cu metal supports is higher than that of free-standing stanene. By contrast, a planar graphene-like structure is stabilized for stanene on the Ir, Pd, Pt, and Ni metal supports. The band structure of stanene is destroyed on all the metal supports, accompanied by a metallization of stanene because the covalent bonds between stanene and the metal supports are formed and the structure of stanene is distorted. Besides, no tunneling barrier exists between stanene and the metal supports. Therefore, stanene and the eight metals form a good vertical Ohmic contact.

  5. Calculations of Auger intensity versus beam position for a sample with layers perpendicular to its surface

    NASA Astrophysics Data System (ADS)

    Zommer, L.; Jablonski, A.

    2010-07-01

    Recent advances in nanotechnology are a driving force for the improvement of lateral resolution in advanced analytical techniques such as scanning electron microscopy or scanning Auger microscopy (SAM). Special samples with multilayers which are perpendicular to their surface are presently proposed for testing the lateral resolution, as discussed in recent works of Senoner et al (2004 Surf. Interface Anal. 36 1423). The relevant experiment needs a theoretical description based on recent progress in the theory. Monte Carlo simulations of electron trajectories make possible an accurate description of the considered system. We selected exemplary samples, with layers perpendicular to the surface. The layer materials are elemental solids with high, medium and low atomic numbers, i.e. Au|Cu|Au and Au|Si|Au. For these systems calculations of the Auger current versus beam position were performed. We found that, for a system with layers consisting of elements of considerably different atomic numbers, the relation can have an unexpected extreme. This observation can be important in analysis of SAM pictures.

  6. New Insights into the Structure of Multimetallic Nanoparticles and their Advanced Characterization

    NASA Astrophysics Data System (ADS)

    Khanal, Subarna; Bhattarai, Nabraj; Velázquez-Salazar, Jesus; Guisbiers, Gregory; Jose-Yacaman, Miguel

    2015-03-01

    Noble multimetallic nanoparticles have led to exciting progress in a versatile array of applications. For the purpose of better tailoring of nanoparticles activities and understanding the correlation between their structures and properties, control over the composition, shape, size and architecture of bimetallic and multimetallic nanomaterials plays an important role on revealing their new or enhanced functions for potentials application. Advance electron microscopy techniques were used to provide atomic scale insights into the structure-properties of different materials: Pt-Pd, Au-Au3Cu, Cu-Pt, AgPd-Pt and AuCu/Pt nanoparticles. These multimetallic nanoparticles have raised interest for their various applications in fuel cells, ethanol and methanol oxidation reactions, hydrogen storage, and so on. The nanostructures were analyzed by transmission electron microscopy (TEM) and by aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM), in combination with high angle annular dark field (HAADF), bright field (BF), energy dispersive X-ray spectroscopy (EDS), and electron energy loss spectroscopy (EELS) detectors. These techniques allowed us to probe the structure at the atomic level of the nanoparticles revealing new structural information and elemental composition of the nanoparticles.

  7. The stabilities, electronic structures and elastic properties of Rb—As systems

    NASA Astrophysics Data System (ADS)

    Havva Bogaz, Ozisik; Kemal, Colakoglu; Engin, Deligoz; Haci, Ozisik

    2012-04-01

    The structural, electronic and elastic properties of Rb—As systems (RbAs in NaP, LiAs and AuCu structures, RbAs2 in the MgCu2 structure, Rb3As in Na3As, Cu3P and Li3Bi structures, and Rb5As4 in the A5B4 structure) are investigated with the generalized gradient approximation in the frame of density functional theory. The lattice parameters, cohesive energies, formation energies, bulk moduli and the first derivatives of the bulk moduli (to fit Murnaghan's equation of state) of the considered structures are calculated and reasonable agreement is obtained. In addition, the phase transition pressures are also predicted. The electronic band structures, the partial densities of states corresponding to the band structures and the charge density distributions are presented and analysed. The second-order elastic constants based on the stress-strain method and other related quantities such as Young's modulus, the shear modulus, Poisson's ratio, sound velocities, the Debye temperature and shear anisotropy factors are also estimated.

  8. Mechanisms and Morphology Evolution in Dealloying

    SciTech Connect

    Chen, Q; Sieradzki, K

    2013-03-08

    Historically, dealloying, the selective dissolution of elemental components from an alloy, has been studied most intensively for binary noble-metal alloys such as Ag-Au, Cu-Au and Zn-Cu. There have been three primacy "mechanisms" proposed to explain ambient temperature dealloying in such systems: "simultaneous" dissolution of both components/redeposition of the more-noble constituent, lattice diffusion-supported by a di-vacancy mechanism of the more reactive component to the alloy/electrolyte interface and percolation dissolution. Here, we briefly discuss each of these mechanisms and the corresponding dealloyed morphology. In order to examine the connection between a mechanism and morphology we examined dealloying of Mg from Mg-Cd alloys under conditions for which vacancy-mediated lattice diffusion occurs at significant rates. Depending on alloy composition and dealloying rate, we observed either "negative" dendrites or bi-continuous structures, each of which is directly associated with the operation of a particular mechanism. Our findings should be useful to researchers employing dealloying to obtain particular types nanostructured features for a variety of applications. (C) 2013 The Electrochemical Society. All rights reserved.

  9. Detailed investigation on the possibility of nanoparticles of various metal elements for surface-assisted laser desorption/ionization mass spectrometry.

    PubMed

    Yonezawa, Tetsu; Kawasaki, Hideya; Tarui, Akira; Watanabe, Takehiro; Arakawa, Ryuichi; Shimada, Toshihiro; Mafuné, Fumitaka

    2009-03-01

    In this paper, we describe systematic detailed considerations of the feasibility of using various metal nanoparticles for organic-matrix-free surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). In order to avoid the influence of organic molecules on the nanoparticles, stabilizer-free bare nanoparticles of Ag, Au, Cu and Pt were prepared by laser ablation. Although all metal nanoparticles absorbed N(2) laser light (337 nm) energy, the performance of desorption/ionization of a representative peptide, angiotensin I, strongly depended on the metal element. Citrate buffer was used as a proton source; it reduced the amount of alkali cation adducts present. Then, protonated molecules of analytes predominated in the mass spectra when Au and Pt nanoparticles were used. Pt nanoparticles showed the highest performance in SALDI-MS, owing to their smaller heat conductivity and higher melting temperature. The selective desorption of a cationic surfactant with longer alkyl chains and a peptide with methionine was also observed. PMID:19276588

  10. Gold-copper nano-alloy, "Tumbaga", in the era of nano: phase diagram and segregation.

    PubMed

    Guisbiers, Grégory; Mejia-Rosales, Sergio; Khanal, Subarna; Ruiz-Zepeda, Francisco; Whetten, Robert L; José-Yacaman, Miguel

    2014-11-12

    Gold-copper (Au-Cu) phases were employed already by pre-Columbian civilizations, essentially in decorative arts, whereas nowadays, they emerge in nanotechnology as an important catalyst. The knowledge of the phase diagram is critical to understanding the performance of a material. However, experimental determination of nanophase diagrams is rare because calorimetry remains quite challenging at the nanoscale; theoretical investigations, therefore, are welcomed. Using nanothermodynamics, this paper presents the phase diagrams of various polyhedral nanoparticles (tetrahedron, cube, octahedron, decahedron, dodecahedron, rhombic dodecahedron, truncated octahedron, cuboctahedron, and icosahedron) at sizes 4 and 10 nm. One finds, for all the shapes investigated, that the congruent melting point of these nanoparticles is shifted with respect to both size and composition (copper enrichment). Segregation reveals a gold enrichment at the surface, leading to a kind of core-shell structure, reminiscent of the historical artifacts. Finally, the most stable structures were determined to be the dodecahedron, truncated octahedron, and icosahedron with a Cu-rich core/Au-rich surface. The results of the thermodynamic approach are compared and supported by molecular-dynamics simulations and by electron-microscopy (EDX) observations. PMID:25338111

  11. Accumulation and phytotoxicity of engineered nanoparticles to Cucurbita pepo.

    PubMed

    Hawthorne, Joseph; Musante, Craig; Sinha, Saion K; White, Jason C

    2012-04-01

    The effect of bulk and engineered nanoparticle (NP) Ag, Au, Cu, Si, and C at 250 and 750 mg/L on zucchini biomass, transpiration, and element content was determined. The pH of bulk and NP solutions prior to plant growth frequently differed. Nanoparticle Cu solution pH was significantly higher than bulk Cu, whereas for Ag and C, the NPs had significantly lower pH. Plants were unaffected by Au, regardless of particle size or concentration. NP Ag reduced plant biomass and transpiration by 49-91% compared to equivalent bulk Ag. NP Si at 750 mg/L reduced plant growth and transpiration by 30-51% relative to bulk Si. Bulk and NP Cu were phytotoxic but much of the effect was alleviated by humic acid. The shoot Ag and Cu content did not differ based on particle size or concentration. The accumulation of bulk Au was greater than the NP, but humic acid increased the accumulation of NP and bulk Au by 5.6-fold and 80%, respectively. The uptake of NP Si was 5.6-6.5-fold greater than observed with the bulk element. These findings show that the NPs may have unique phytotoxicity or accumulation patterns and that solution properties can significantly impact particle fate and effects.

  12. Method to remove ammonia using a proton-conducting ceramic membrane

    DOEpatents

    Balachandran, Uthamalinga; Bose, Arun C

    2003-10-07

    An apparatus and method for decomposing NH.sub.3. A fluid containing NH.sub.3 is passed in contact with a tubular membrane that is a homogeneous mixture of a ceramic and a first metal, with the ceramic being selected from one or more of a cerate having the formula of M'Ce.sub.1-x M".sub.3-.delta., zirconates having the formula M'Zr.sub.1-x M"O.sub.3-.delta., stannates having the formula M'Sn.sub.1-x M'O.sub.3-.delta., where M' is a group IIA metal, M" is a dopant metal of one or more of Ca, Y, Yb, In, Nd, Gd or mixtures thereof and .delta. is a variable depending on the concentration of dopant and is in the range of from 0.001 to 0.5, the first metal is a group VIII or group IB element selected from the group consisting of Pt, Ag, Pd, Fe, Co, Cr, Mn, V, Ni, Au, Cu, Rh, Ru and mixtures thereof. The tubular membrane has a catalytic metal on the side thereof in contact with the fluid containing NH.sub.3 which is effective to cause NH.sub.3 to decompose to N.sub.2 and H.sub.2. When the H.sub.2 contacts the membrane H.sup.+ ions are formed which pass through the membrane driving the NH.sub.3 decomposition toward completion.

  13. Gold and silver in PGE-Cu-Ni and PGE ores of the Noril'sk deposits, Russia

    NASA Astrophysics Data System (ADS)

    Sluzhenikin, Sergey F.; Mokhov, Andrey V.

    2015-04-01

    Gold and silver contents in Noril'sk ore are controlled by the amount of sulphides and bulk Cu grade. Relative concentrations, re-calculated to 100 % sulphide, depend on type of ore: they are higher for disseminated ore than for massive ore and are the highest for low-sulphide platinum ore. Gold occurs mainly as high-fineness Au-Ag alloy in pyrrhotite-rich ore, whereas silver enters chalcopyrite mainly as solid solution. Increase in Cu grade correlates with an increase in the concentration of silver in chalcopyrite. Gold and silver form discrete minerals such as Au-Cu alloys, Au-Ag alloys, tellurides, sulphides, selenides, sulphobismuthides, Ag and Ag-Pd chlorides in Cu-rich ores; they also enter the structures of complex platinum-group minerals. The Au-Ag mineralisation is related to the post-magmatic hydrothermal stage under temperature conditions of 350-50 °C. Silver entered crystallizing chalcopyrite in solid solution in the late-magmatic stage, while all of the gold and the remainder of the silver and some platinum-group elements were transported predominantly as chloride and hydrosulphide complexes in hydrothermal fluids.

  14. Direct Observations of Rapid Diffusion of Cu in Au Thin Films using In-Situ X-ray Diffraction

    SciTech Connect

    Elmer, J W; Palmer, T A; Specht, E D

    2005-11-28

    In-situ x-ray diffraction was performed while annealing thin-film Au/Cu binary diffusion couples to directly observe diffusion at elevated temperatures. The temperature dependence of the interdiffusion coefficient was determined from isothermal measurements at 700 C, 800 C, and 900 C, where Cu and Au form a disordered continuous face centered cubic solid solution. Large differences in the lattice parameters of Au and Cu allowed the initial diffraction peaks to be easily identified, and later tracked as they merged into one diffraction peak with increased diffusion time. Initial diffusion kinetics were studied by measuring the time required for the Cu to diffuse through the Au thin film of known thickness. The activation energy for interdiffusion was measured to be 65.4 kJ/mole during this initial stage, which is approximately 0.4x that for bulk diffusion and 0.8x that for grain boundary diffusion. The low activation energy is attributed to the high density of columnar grain boundaries combined with other defects in the sputter deposited thin film coatings. As interdiffusion continues, the two layers homogenize with an activation energy of 111 kJ/mole during the latter stages of diffusion. This higher activation energy falls between the reported values for grain boundary and bulk diffusion, and may be related to grain growth occurring at these temperatures which accounts for the decreasing importance of grain boundaries on diffusion.

  15. Phase transitions in femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Povarnitsyn, Mikhail E.; Khishchenko, Konstantin V.; Levashov, Pavel R.

    2009-03-01

    In this study we simulate an interaction of femtosecond laser pulses (100 fs, 800 nm, 0.1-10 J/cm 2) with metal targets of Al, Au, Cu, and Ni. For analysis of laser-induced phase transitions, melting and shock waves propagation as well as material decomposition we use an Eulerian hydrocode in conjunction with a thermodynamically complete two-temperature equation of state with stable and metastable phases. Isochoric heating, material evaporation from the free surface of the target and fast propagation of the melting and shock waves are observed. On rarefaction the liquid phase becomes metastable and its lifetime is estimated using the theory of homogeneous nucleation. Mechanical spallation of the target material at high strain rates is also possible as a result of void growth and confluence. In our simulation several ablation mechanisms are taken into account but the main issue of the material is found to originate from the metastable liquid state. It can be decomposed either into a liquid-gas mixture in the vicinity of the critical point, or into droplets at high strain rates and negative pressure. The simulation results are in agreement with available experimental findings.

  16. Corrosion investigation of fire-gilded bronze involving high surface resolution spectroscopic imaging

    NASA Astrophysics Data System (ADS)

    Masi, G.; Chiavari, C.; Avila, J.; Esvan, J.; Raffo, S.; Bignozzi, M. C.; Asensio, M. C.; Robbiola, L.; Martini, C.

    2016-03-01

    Gilded bronzes are often affected by severe corrosion, due to defects in the Au layer and Au/Cu alloy galvanic coupling, stimulated by large cathodic area of the gilded layer. Galvanic corrosion, triggered by gilding defects, leads to products growth at the Au/bronze interface, inducing blistering or break-up of the Au layer. In this context, fire-gilded bronze replicas prepared by ancient methods (use of spreadable Au-Hg paste) was specifically characterised by compiling complementary spectroscopic and imaging information before/after accelerated ageing with synthetic rain. Fire-gilded bronze samples were chemically imaged in cross-section at nano-metric scale (<200 nm) using high energy and lateral resolution synchrotron radiation photoemission (HR-SRPES) of core levels and valence band after conventional characterisation of the samples by Glow Discharge optical Emission Spectroscopy (GD-OES) and conventional X-ray photoelectron spectroscopy (XPS). We have found a net surface enrichment in Zn and Sn after fire-gilding and presence of metallic Hg, Pb and Cu within the Au layer. Moreover, the composition distribution of the elements together with their oxidation has been determined. It was also revealed that metallic phases including Hg and Pb remain in the gilding after corrosion. Moreover, selective dissolution of Zn and Cu occurs in the crater due to galvanic coupling, which locally induces relative Sn species enrichment (decuprification). The feasibility advantages and disadvantages of chemical imaging using HR-SRPES to study artworks have been investigated on representative replicas.

  17. Fe-Ni composition dependence of magnetic anisotropy in artificially fabricated L1 0-ordered FeNi films.

    PubMed

    Kojima, Takayuki; Ogiwara, Misako; Mizuguchi, Masaki; Kotsugi, Masato; Koganezawa, Tomoyuki; Ohtsuki, Takumi; Tashiro, Taka-Yuki; Takanashi, Koki

    2014-02-12

    We prepared L10-ordered FeNi alloy films by alternate deposition of Fe and Ni monatomic layers, and investigated their magnetic anisotropy. We employed a non-ferromagnetic Au-Cu-Ni buffer layer with a flat surface and good lattice matching to L10-FeNi. An L10-FeNi film grown on Au6Cu51Ni43 showed a large uniaxial magnetic anisotropy energy (Ku = 7.0 × 10(6) erg cm(-)3). Ku monotonically increased with the long-range order parameter (S) of the L10 phase. We investigated the Fe-Ni composition dependence by alternating the deposition of Fe 1 − x and Ni 1 + x monatomic layers (− 0.4 < x < 0.4). Saturation magnetization (Ms) and Ku showed maxima (Ms = 1470 emu cm(-3), Ku = 9.3 × 10(6) erg cm(-3)) for Fe60Ni40 (x = -0.2) while S showed a maximum at the stoichiometric composition (x = 0). The change in the ratio of lattice parameters (c/a) was small for all compositions. We found that enrichment of Fe is very effective to enhance Ku. The large Ms and Ku of Fe60Ni40 indicate that Fe-rich L10-FeNi is promising as a rare-earth-free permanent magnet.

  18. Interfacial properties of stanene–metal contacts

    NASA Astrophysics Data System (ADS)

    Guo, Ying; Pan, Feng; Ye, Meng; Wang, Yangyang; Pan, Yuanyuan; Zhang, Xiuying; Li, Jingzhen; Zhang, Han; Lu, Jing

    2016-09-01

    Recently, two-dimensional buckled honeycomb stanene has been manufactured by molecular beam epitaxy growth. Free-standing stanene is predicted to have a sizable opened band gap of 100 meV at the Dirac point due to spin–orbit coupling (SOC), resulting in many fascinating properties such as quantum spin Hall effect, quantum anomalous Hall effect, and quantum valley Hall effect. In the first time, we systematically study the interfacial properties of stanene–metal interfaces (metals = Ag, Au, Cu, Al, Pd, Pt, Ir, and Ni) by using ab initio electronic structure calculations considering the SOC effects. The honeycomb structure of stanene is preserved on the metal supports, but the buckling height is changed. The buckling of stanene on the Au, Al, Ag, and Cu metal supports is higher than that of free-standing stanene. By contrast, a planar graphene-like structure is stabilized for stanene on the Ir, Pd, Pt, and Ni metal supports. The band structure of stanene is destroyed on all the metal supports, accompanied by a metallization of stanene because the covalent bonds between stanene and the metal supports are formed and the structure of stanene is distorted. Besides, no tunneling barrier exists between stanene and the metal supports. Therefore, stanene and the eight metals form a good vertical Ohmic contact.

  19. Gold-copper nano-alloy, "Tumbaga", in the era of nano: phase diagram and segregation.

    PubMed

    Guisbiers, Grégory; Mejia-Rosales, Sergio; Khanal, Subarna; Ruiz-Zepeda, Francisco; Whetten, Robert L; José-Yacaman, Miguel

    2014-11-12

    Gold-copper (Au-Cu) phases were employed already by pre-Columbian civilizations, essentially in decorative arts, whereas nowadays, they emerge in nanotechnology as an important catalyst. The knowledge of the phase diagram is critical to understanding the performance of a material. However, experimental determination of nanophase diagrams is rare because calorimetry remains quite challenging at the nanoscale; theoretical investigations, therefore, are welcomed. Using nanothermodynamics, this paper presents the phase diagrams of various polyhedral nanoparticles (tetrahedron, cube, octahedron, decahedron, dodecahedron, rhombic dodecahedron, truncated octahedron, cuboctahedron, and icosahedron) at sizes 4 and 10 nm. One finds, for all the shapes investigated, that the congruent melting point of these nanoparticles is shifted with respect to both size and composition (copper enrichment). Segregation reveals a gold enrichment at the surface, leading to a kind of core-shell structure, reminiscent of the historical artifacts. Finally, the most stable structures were determined to be the dodecahedron, truncated octahedron, and icosahedron with a Cu-rich core/Au-rich surface. The results of the thermodynamic approach are compared and supported by molecular-dynamics simulations and by electron-microscopy (EDX) observations.

  20. Highly Facet-Dependent Photocatalytic Properties of Cu2 O Crystals Established through the Formation of Au-Decorated Cu2 O Heterostructures.

    PubMed

    Yuan, Guo-Zhi; Hsia, Chi-Fu; Lin, Zhen-Wen; Chiang, Chieh; Chiang, Yun-Wei; Huang, Michael H

    2016-08-22

    This work confirms the presence of a large facet-dependent photocatalytic activity of Cu2 O crystals through sparse deposition of gold particles on Cu2 O cubes, octahedra, and rhombic dodecahedra. Au-decorated Cu2 O rhombic dodecahedra and octahedra showed greatly enhanced photodegradation rates of methyl orange resulting from a better separation of the photogenerated electrons and holes, with the rhombic dodecahedra giving the best efficiency. Au-Cu2 O core-shell rhombic dodecahedra also displayed a better photocatalytic activity than pristine rhombic dodecahedra. However, Au-deposited Cu2 O cubes, pristine cubes, and Au-deposited small nanocubes bound by entirely {100} facets are all photocatalytically inactive. X-ray photoelectron spectra (XPS) showed identical copper peak positions for these Au-decorated crystals. Remarkably, electron paramagnetic resonance (EPR) measurements indicated a higher production of hydroxyl radicals for the photoirradiated Cu2 O rhombic dodecahedra than for the octahedra, but no radicals were produced from photoirradiated Cu2 O cubes. The Cu2 O {100} face may present a high energy barrier through its large band edge bending and/or electrostatic repulsion, preventing charge carriers from reaching to this surface. The conventional photocatalysis model fails in this case. The facet-dependent photocatalytic differences should be observable in other semiconductor systems whenever a photoinduced charge-transfer process occurs across an interface. PMID:27470656

  1. Evidence from meimechites and other low-degree mantle melts for redox controls on mantle-crust fractionation of platinum-group elements

    PubMed Central

    Mungall, James E.; Hanley, Jacob J.; Arndt, Nicholas T.; Debecdelievre, Anne

    2006-01-01

    Understanding of the geochemistry of the chalcophile elements [i.e., Os, Ir, Ru, Pt, Pd (platinum-group elements), and Au, Cu, Ni] has been informed for at least 20 years by the common assumption that when crust-forming partial melts are extracted from the upper mantle, sulfide liquid in the restite sequesters chalcophile elements until the extent of partial melting exceeds ≈25% and all of the sulfide has been dissolved in silicate melt [Hamlyn, P. R. & Keays, R. R. (1985) Geochim. Cosmochim. Acta 49, 1797–1811]. Here we document very high, unfractionated, chalcophile element concentrations in small-degree partial melts from the mantle that cannot be reconciled with the canonical residual sulfide assumption. We show that the observed high, unfractionated platinum-group element concentrations in small-degree partial melts can be attained if the melting takes place at moderately high oxygen fugacity, which will reduce the amount of sulfide due to the formation of sulfate and will also destabilize residual monosulfide solid solution by driving sulfide melts into the spinel-liquid divariant field. Magmas formed at high oxygen fugacity by small degrees of mantle melting can be important agents for the transfer of chalcophile elements from the upper mantle to the crust and may be progenitors of significant ore deposits of Pt, Pd, and Au. PMID:16908861

  2. A new species of Websterinereis from the Gulf of California and redescription of Websterinereis foli (Fauvel, 1930) (Annelida, Nereididae)

    PubMed Central

    de León-González, Jesús Angel; Balart, Eduardo F.

    2016-01-01

    Abstract A new species of Websterinereis Pettibone, 1971, Websterinereis pettiboneae sp. n. is described from La Paz Bay, Gulf of California, Mexico. This species is similar to Websterinereis foli (Fauvel, 1930) in the neuropodial falcigers shape, but can be separated by the tentacular cirri length, notopodial prechaetal lobe shape, and the size of the notopodial dorsal and ventral ligules on posterior parapodia. Websterinereis foli is redescribed based upon type material. Additional observations on the inter-annual density variation of Websterinereis pettiboneae sp. n. during a four-year study are also provided. A key to all species of Websterinereis is included.

  3. [Elevated gastric lesions].

    PubMed

    de Careaga, B; Villagómez, G; Pabón, J; Calderón, O; Elío, D; Pérez, J; Martínez, M; Patiño, F; Ponce, R; Lora, J

    1986-01-01

    Elevated gastric lesions, represent an important group among gastric pathology. To establish its incidence in our experience, we studied the endoscopic reports of two important hospitals in La Paz city: Instituto de Gastroenterología Boliviano Japonés and Hospital Obrero No. 1. In order to make a good endoscopic diagnosis among different elevated lesions we use some parameters like: location, shape, size, diameter, surface of the lesion and surrounding mucosa and characteristics of the falls. 10.472 endoscopic reports were reviewed, 497 elevated gastric lesions were found, 475 corresponded to mucosal lesions (352 benign lesions and 123 malignant lesions), 11 to submucosal and 11 extragastric lesions.

  4. LOBIN: E-textile and wireless-sensor-network-based platform for healthcare monitoring in future hospital environments.

    PubMed

    López, Gregorio; Custodio, Víctor; Moreno, José Ignacio

    2010-11-01

    This paper describes a novel healthcare IT platform developed under the LOBIN project, which allows monitoring several physiological parameters, such as ECG, heart rate, body temperature, etc., and tracking the location of a group of patients within hospital environments. The combination of e-textile and wireless sensor networks provides an efficient way to support noninvasive and pervasive services demanded by future healthcare environments. This paper presents the architecture, system deployment as well as validation results from both laboratory tests and a pilot scheme developed with real users in collaboration with the Cardiology Unit at La Paz Hospital, Madrid, Spain. PMID:20643610

  5. Bolivia: rural electrification. Project impact evaluation report No. 16

    SciTech Connect

    Butler, E.; Poe, K.M.; Tendler, J.

    1980-12-01

    Two rural electrification systems initiated in Bolivia in 1973 and 1974 are the subject of this report. By 1979, all distribution networks were completed, except in the La Paz region. Power was supplied to 42,000 consumers and was used primarily for residential lighting. Although demand outpaced supply, consumption per household was lower than projected, and irrigation and industrial use was negligible. The preponderant positive impact of the projects was social. Household lighting improved the physical quality of life for 7% of Bolivia's rural population.

  6. Lake Titicaca, Peru and Bolivia, South America

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Lake Titicaca, high in the Andean Altiplano of South America, is on the border between Peru and Bolivia (15.5S, 70.0W). At an altitude of 12,500 ft, an area of 3,206 sq. mi. and a depth of about 900 ft., it is the world's highest navigable fresh water lake. La Paz, the capital city of Bolivia, may be seen near the center left of the image on the eastern downslope side of the mountains. 3,206 sq mi (8,303 sqkm), 12,

  7. Petrography of Lunar Meteorite LAP 02205, a New Low-Ti Basalt Possibly Launch Paired with NWA 032

    NASA Technical Reports Server (NTRS)

    Jolliff, B. L.; Zeigler, R. A.; Korotev, R. L.

    2004-01-01

    Lunar meteorite LAP 02205 is a 1.23 kg basalt collected during the 2002 field season in the La- Paz ice field, Antarctica [1]. We present a petrographic description including mineral modes and compositions, and the major-element composition of the bulk meteorite. LAP 02205 is an Fe-rich, moderately low-Ti mare basalt that is similar in composition, mineralogy, and mineral chemistry to the NWA 032 basaltic lunar meteorite. LAP 02205 is yet another of the moderately low- Ti basaltic meteorites that are underrepresented among Apollo and Luna samples but that appear from remote sensing to be the most common basalt type on the Moon.

  8. Transmission of phage by glassy-winged sharpshooters, a vector of Xylella fastidiosa

    PubMed Central

    Bhowmick, Tushar Suvra; Das, Mayukh; Heinz, Kevin M.; Krauter, Peter C.; Gonzalez, Carlos F.

    2016-01-01

    ABSTRACT Xylella fastidiosa subsp. fastidiosa (Xff) is the causal agent of Pierce's Disease (PD) of grapevines and is vectored by the glassy-winged sharpshooter (GWSS, Homalodisca vitripennis). Previously we have reported the development of a bacteriophage (phage) based biocontrol system for PD, but no information on insect transmission of phages has been reported. Here we communicate that laboratory reared GWSSs fed on cowpea plants (Vigna unguiculata subsp. unguiculata) harboring the virulent phage Paz were able to uptake of phage efficiently when the phage was present in high concentration, but were inefficient in transfer to plants. PMID:27738554

  9. VizieR Online Data Catalog: M33 HII regions SED (Relano+, 2013)

    NASA Astrophysics Data System (ADS)

    Relano, M.; Verley, S.; Perez, I.; Kramer, C.; Calzetti, D.; Xilouris, E. M.; Boquien, M.; Abreu-Vicente, J.; Combes, F.; Israel, F.; Tabatabaei, F. S.; Braine, J.; Buchbender, C.; Gonzalez, M.; Gratier, P.; Lord, S.; Mookerjea, B.; Quintana-Lacaci, G.; van der Werf, P.

    2013-09-01

    To investigate the continuum UV emission of M 33, we used the data from GALEX, in particular the data distributed by de Paz et al. (2007, Cat. J/ApJS/173/185). To trace the ionised gas, we used the narrow-line Hα image of M 33 obtained by Greenawalt (1998, Ph.D. Thesis, New Mexico state University). Dust emission can be investigated through the mid-IR (MIR) and FIR data of M 33 obtained with the Spitzer Infrared Array Camera (IRAC) and Multiband Imaging Photometer (MIPS). (3 data files).

  10. A new species of arboreal toad (Anura : Bufonidae : Chaunus) from Madidi National Park, Bolivia

    USGS Publications Warehouse

    Padial, J.M.; Reichle, S.; McDiarmid, R.; De la Riva, I.

    2006-01-01

    A new arboreal species of the Chaunus veraguensis group is described for the humid montane forest of Madidi National Park, in northern Bolivia. The new species differs from other species in the group by the combination small size, long and slender extremities, webbed hands, conspicuous tympanic membrane, well developed parotoid glands, absence of large glands on dorsum and extremities, nuptial excrescences of males composed of pungent spines on dorsal surface of thumb, greenish-brown coloration on dorsum with red warts in life, and green iris. It is only known from two nearby localities in the Serran Eslabon, Department La Paz. An operational key for species in the C. veraguensis group is provided.

  11. A monoclinic form of dendocarbin A: a borderline case of one-dimensional isostructural polymorphism.

    PubMed

    Paz, Cristian; Burgos, Viviana; Suarez, Sebastián; Baggio, Ricardo

    2015-04-01

    The title compound, dendocarbin A [systematic name: (1R,5aS,9aS,9bR)-1-hydroxy-6,6,9a-trimethyldodecahydronaphtho[1,2-c]furan-3-one], C15H22O3, is a sesquiterpene lactone isolated from Drimys winteri var chilensis. The monoclinic phase described herein displays an identical molecular structure to the orthorhombic phase that we reported previously [Paz Robles et al. (2014). Acta Cryst. C70, 1007-1010], while varying significantly in chain pitch, and can thus be considered as a borderline case of one-dimensional isostructural polymorphism.

  12. A new species of Websterinereis from the Gulf of California and redescription of Websterinereis foli (Fauvel, 1930) (Annelida, Nereididae)

    PubMed Central

    de León-González, Jesús Angel; Balart, Eduardo F.

    2016-01-01

    Abstract A new species of Websterinereis Pettibone, 1971, Websterinereis pettiboneae sp. n. is described from La Paz Bay, Gulf of California, Mexico. This species is similar to Websterinereis foli (Fauvel, 1930) in the neuropodial falcigers shape, but can be separated by the tentacular cirri length, notopodial prechaetal lobe shape, and the size of the notopodial dorsal and ventral ligules on posterior parapodia. Websterinereis foli is redescribed based upon type material. Additional observations on the inter-annual density variation of Websterinereis pettiboneae sp. n. during a four-year study are also provided. A key to all species of Websterinereis is included. PMID:27667930

  13. Earth observations - STS-7

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Earth observations - STS-7. North part of Western Australia province, Dampier Land, Fitzroy and Lennard Rivers and the Buccaneer Archipelago (35792); Lake Titicaca, on the Peru-Bolivia border. The Bolivian capital city La Paz is also visible (35793); Denham Sound and Shark Bay in Western Australia are easily recognizable (35794); The Mona Loa Volcano, on the island of Hawaii can be seen in this view. A close look reveals lava flows from the active volcano (35795); Africa; Namibia, Grandberg and Cape Cross, Atlantic Ocean as photographed from the Challenger (35796); View of Venezuela, Aruba, Curacao, and Peninsula de Paraguana (35797).

  14. 2p2 Team News

    NASA Astrophysics Data System (ADS)

    Jones, H.

    2000-06-01

    The 2p2 Team continued towards the implementation at the 2.2-m of the same BOB (Broker for Observation Blocks) observing interface as seen at other ESO telescopes. This requires an interface to be written between the existing BOB software and the non-VLT compatible control software for the Wide-Field Imager (WFI) and 2.2-m. Cristian Urrutia, Tatiana Paz and Eduardo Robledo are heading its development. With this software in place, observers can use the VLT Phase 2 Proposal Preparation System (P2PP) for definition of their exposures, whether they are for Visitor or Service Mode.

  15. A new species of Websterinereis from the Gulf of California and redescription of Websterinereis foli (Fauvel, 1930) (Annelida, Nereididae).

    PubMed

    de León-González, Jesús Angel; Balart, Eduardo F

    2016-01-01

    A new species of Websterinereis Pettibone, 1971, Websterinereis pettiboneae sp. n. is described from La Paz Bay, Gulf of California, Mexico. This species is similar to Websterinereis foli (Fauvel, 1930) in the neuropodial falcigers shape, but can be separated by the tentacular cirri length, notopodial prechaetal lobe shape, and the size of the notopodial dorsal and ventral ligules on posterior parapodia. Websterinereis foli is redescribed based upon type material. Additional observations on the inter-annual density variation of Websterinereis pettiboneae sp. n. during a four-year study are also provided. A key to all species of Websterinereis is included. PMID:27667930

  16. The Northern Bolivian Altiplano: a region highly endemic for human fascioliasis.

    PubMed

    Mas-Coma, S; Anglés, R; Esteban, J G; Bargues, M D; Buchon, P; Franken, M; Strauss, W

    1999-06-01

    The worldwide importance of human infection by Fasciola hepatica has been recognized in recent years. The endemic region between Lake Titicaca and the valley of La Paz, Bolivia, at 3800-4100 m altitude, presents the highest prevalences and intensities recorded. Large geographical studies involving Lymnaea truncatula snails (malacological, physico-chemical, and botanic studies of 59, 28 and 30 water bodies, respectively, inhabited by lymnaeids; environmental mean temperature studies covering a 40-year period), livestock (5491 cattle) and human coprological surveys (2723 subjects, 2521 of whom were school children) were conducted during 1991-97 to establish the boundaries and distributional characteristics of this endemic Northern Altiplano region. The endemic area covers part of the Los Andes, Ingavi, Omasuyos and Murillo provinces of the La Paz Department. The human endemic zone is stable, isolated and apparently fixed in its present outline, the boundaries being marked by geographical, climatic and soil-water chemical characteristics. The parasite distribution is irregular in the endemic area, the transmission foci being patchily distributed and linked to the presence of appropriate water bodies. Prevalences in school children are related to snail population distribution and extent. Altiplanic lymnaeids mainly inhabit permanent water bodies, which enables parasite transmission during the whole year. A confluence of several factors mitigates the negative effects of the high altitude.

  17. Why Bolivians are talking about gender roles.

    PubMed

    Eschen, A

    1998-01-01

    The first hospital to offer no-scalpel vasectomy services in La Paz, Bolivia, introduced its program in 1996. However, over the course of 2 years, only 1 vasectomy was performed. Vasectomy services in La Paz are underutilized due to inadequate counseling, outreach, and use of educational materials. While the national health and population policy mandates the provision of comprehensive reproductive health care for both men and women, Bolivian men rarely seek health care services of any kind because most services are designed mainly for women and children. The only services offered to men are urology related, which focus upon screening for STDs, and workplace-related services, such as for factory workers and miners. Nongovernmental organizations (NGO) are exploring how to increase men's involvement in health care and family planning services. Men need to be made aware of gender issues related to reproductive and sexual health. The Centro de Investigacion Social Tecnologia Apropriada y Capacitacion (CISTAC), a Bolivian NGO which focuses upon research and training in health and social issues, plans to use research, training, and information dissemination to broaden the male role and identity in Bolivia, which will also affect men's access to and receipt of health care services. Toward that end, CISTAC and AVSC co-sponsored a workshop to teach health care program managers about the relationship between gender issues and men's involvement in reproductive health care.

  18. AN UPDATED ULTRAVIOLET CATALOG OF GALEX NEARBY GALAXIES

    SciTech Connect

    Bai, Yu; Zou, Hu; Liu, JiFeng; Wang, Song E-mail: zouhu@nao.cas.cn E-mail: songw@nao.cas.cn

    2015-09-15

    The ultraviolet (UV) catalog of nearby galaxies compiled by Gil de Paz et al. presents the integrated photometry and surface brightness profiles for 1034 nearby galaxies observed by GALEX. We provide an updated catalog of 4138 nearby galaxies based on the latest Genral Release (GR6/GR7) of GALEX. These galaxies are selected from HyperLeda with apparent diameters larger than 1′. From the surface brightness profiles accurately measured using the deep NUV and FUV images, we have calculated the asymptotic magnitudes, aperture (D25) magnitudes, colors, structural parameters (effective radii and concentration indices), luminosities, and effective surface brightness for these galaxies. Archival optical and infrared photometry from HyperLeda, 2MASS, and IRAS are also integrated into the catalog. Our parameter measurements and some analyses are consistent with those of Paz et al. The (FUV − K) color provides a good criterion to distinguish between early- and late-type galaxies, which can be improved further using the concentration indices. The IRX–β relation is reformulated with our UV-selected nearby galaxies.

  19. Coordinated Activities of Human Dicer Domains in Regulatory RNA Processing

    PubMed Central

    Ma, Enbo; Zhou, Kaihong; Kidwell, Mary Anne; Doudna, Jennifer A.

    2012-01-01

    Summary The conserved ribonuclease Dicer generates microRNAs and short interfering RNAs that guide gene silencing in eukaryotes. The specific contributions of human Dicer's structural domains to RNA product length and substrate preference are incompletely understood, due in part to the difficulties of Dicer purification. Here we show that active forms of human Dicer can be assembled from recombinant polypeptides expressed in bacteria. Using this system, we find that three distinct modes of RNA recognition give rise to Dicer's fidelity and product length specificity. The first involves anchoring one end of a dsRNA helix within the PAZ domain, which can assemble in trans with Dicer's catalytic domains to reconstitute an accurate but non-substrate-selective dicing activity. The second entails non-specific RNA binding by the double-stranded RNA binding domain (dsRBD), an interaction that is essential for substrate recruitment in the absence of the PAZ domain. The third mode of recognition involves hairpin RNA loop recognition by the helicase domain, which ensures efficient processing of specific substrates. These results reveal distinct interactions of each Dicer domain with different RNA structural features, and provide a facile system for investigating the molecular mechanisms of human miRNA biogenesis. PMID:22727743

  20. Kuramoto model with uniformly spaced frequencies: Finite-N asymptotics of the locking threshold.

    PubMed

    Ottino-Löffler, Bertrand; Strogatz, Steven H

    2016-06-01

    We study phase locking in the Kuramoto model of coupled oscillators in the special case where the number of oscillators, N, is large but finite, and the oscillators' natural frequencies are evenly spaced on a given interval. In this case, stable phase-locked solutions are known to exist if and only if the frequency interval is narrower than a certain critical width, called the locking threshold. For infinite N, the exact value of the locking threshold was calculated 30 years ago; however, the leading corrections to it for finite N have remained unsolved analytically. Here we derive an asymptotic formula for the locking threshold when N≫1. The leading correction to the infinite-N result scales like either N^{-3/2} or N^{-1}, depending on whether the frequencies are evenly spaced according to a midpoint rule or an end-point rule. These scaling laws agree with numerical results obtained by Pazó [D. Pazó, Phys. Rev. E 72, 046211 (2005)PLEEE81539-375510.1103/PhysRevE.72.046211]. Moreover, our analysis yields the exact prefactors in the scaling laws, which also match the numerics. PMID:27415267

  1. Image Based Characterization of Formal and Informal Neighborhoods in an Urban Landscape

    SciTech Connect

    Graesser, Jordan B; Cheriyadat, Anil M; Vatsavai, Raju; Chandola, Varun; Bright, Eddie A

    2012-01-01

    The high rate of global urbanization has resulted in a rapid increase in informal settlements, which can be de ned as unplanned, unauthorized, and/or unstructured housing. Techniques for ef ciently mapping these settlement boundaries can bene t various decision making bodies. From a remote sensing perspective, informal settlements share unique spatial characteristics that distinguish them from other types of structures (e.g., industrial, commercial, and formal residential). These spatial characteristics are often captured in high spatial resolution satellite imagery. We analyzed the role of spatial, structural, and contextual features (e.g., GLCM, Histogram of Oriented Gradients, Line Support Regions, Lacunarity) for urban neighborhood mapping, and computed several low-level image features at multiple scales to characterize local neighborhoods. The decision parameters to classify formal-, informal-, and non-settlement classes were learned under Decision Trees and a supervised classi cation framework. Experiments were conducted on high-resolution satellite imagery from the CitySphere collection, and four different cities (i.e., Caracas, Kabul, Kandahar, and La Paz) with varying spatial characteristics were represented. Overall accuracy ranged from 85% in La Paz, Bolivia, to 92% in Kandahar, Afghanistan. While the disparities between formal and informal neighborhoods varied greatly, many of the image statistics tested proved robust.

  2. Efficient method for fast simulation of scanning tunneling microscopy with a tip effect.

    PubMed

    Zhang, Ruiqi; Hu, Zhenpeng; Li, Bin; Yang, Jinlong

    2014-10-01

    On the basis of Bardeen's perturbation theory on electron tunneling and inspired by Paz et al.'s study, a new expression for the tunneling current between the scanning tunneling microscopy (STM) tip and sample has been obtained, and it provides us with an efficient method to simulate STM images. The method can be implemented in any code of first-principles computing software, which offers the wave functions of the tip and sample, calculated independently at the same footing, as input. By calculating the integral with fast Fourier transform (FFT), simulating the STM image of a given sample surface by a database of different tips on a PC turns out to be not a time-consuming work. Compared with Paz et al.'s method, our method abandons the application of the vacuum Green function and possesses better computing efficiency, fewer parameters, and more reasonable simulated results especially at lower computing cost. Simple tip-sample systems, such as H-H and Pd2-Ag2, are taken as benchmarks to test our method. The topographic images of a CO molecule adsorbed on a Cu(111) surface obtained by using a tungsten tip and a CO-terminated tip are also simulated, and the simulated results are in good agreement with the experimental ones. PMID:24708199

  3. Reproductive parameters of the Pacific angel shark Squatina californica (Selachii: Squatinidae).

    PubMed

    Romero-Caicedo, A F; Galván-Magaña, F; Hernández-Herrera, A; Carrera-Fernández, M

    2016-04-01

    Reproductive characteristics of the Pacific angel shark, Squatina californica, were evaluated from 420 specimens obtained from the artisanal fishery in La Paz Bay, Gulf of California, Mexico. Females (99 cm, 6000 g) were larger than males (95 cm, 5000 g) in terms of both total length (L(T)) and body mass (M(T)). The overall sex ratio was significantly different from the expected 1:1, suggesting sexual segregation of mature individuals in La Paz Bay. Males had developed reproductive organs and calcified claspers from 72 cm L(T); the median size at maturity (LT50 ) was 75.6 cm. In females, only the left ovary was functional and mature ovarian follicles were present from 77 cm L(T); the estimated LT50 was 77.7 cm. For the 10 gravid females sampled, uterine fecundity was between two and 10 embryos. Mature, non-gravid females with small and large ovarian follicles appeared simultaneously with gravid females with follicles that did not exceed 1.9 cm diameter.

  4. Reproductive parameters of the Pacific angel shark Squatina californica (Selachii: Squatinidae).

    PubMed

    Romero-Caicedo, A F; Galván-Magaña, F; Hernández-Herrera, A; Carrera-Fernández, M

    2016-04-01

    Reproductive characteristics of the Pacific angel shark, Squatina californica, were evaluated from 420 specimens obtained from the artisanal fishery in La Paz Bay, Gulf of California, Mexico. Females (99 cm, 6000 g) were larger than males (95 cm, 5000 g) in terms of both total length (L(T)) and body mass (M(T)). The overall sex ratio was significantly different from the expected 1:1, suggesting sexual segregation of mature individuals in La Paz Bay. Males had developed reproductive organs and calcified claspers from 72 cm L(T); the median size at maturity (LT50 ) was 75.6 cm. In females, only the left ovary was functional and mature ovarian follicles were present from 77 cm L(T); the estimated LT50 was 77.7 cm. For the 10 gravid females sampled, uterine fecundity was between two and 10 embryos. Mature, non-gravid females with small and large ovarian follicles appeared simultaneously with gravid females with follicles that did not exceed 1.9 cm diameter. PMID:26931737

  5. VizieR Online Data Catalog: Updated catalog of GALEX nearby galaxies (Bai+, 2015)

    NASA Astrophysics Data System (ADS)

    Bai, Y.; Zou, H.; Liu, J.; Wang, S.

    2015-10-01

    The ultraviolet (UV) catalog of nearby galaxies compiled by Gil de Paz et al. (2007, J/ApJS/173/185) presents the integrated photometry and surface brightness profiles for 1034 nearby galaxies observed by GALEX. We provide an updated catalog of 4138 nearby galaxies based on the latest General Release (GR6/GR7) of GALEX. These galaxies are selected from HyperLeda with apparent diameters larger than 1'. From the surface brightness profiles accurately measured using the deep NUV and FUV images, we have calculated the asymptotic magnitudes, aperture (D25) magnitudes, colors, structural parameters (effective radii and concentration indices), luminosities, and effective surface brightness for these galaxies. Archival optical and infrared photometry from HyperLeda, 2MASS, and IRAS are also integrated into the catalog. Our parameter measurements and some analyses are consistent with those of Paz et al. The (FUV-K) color provides a good criterion to distinguish between early- and late-type galaxies, which can be improved further using the concentration indices. The IRX-β relation is reformulated with our UV-selected nearby galaxies. (3 data files).

  6. An Updated Ultraviolet Catalog of GALEX Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Bai, Yu; Zou, Hu; Liu, JiFeng; Wang, Song

    2015-09-01

    The ultraviolet (UV) catalog of nearby galaxies compiled by Gil de Paz et al. presents the integrated photometry and surface brightness profiles for 1034 nearby galaxies observed by GALEX. We provide an updated catalog of 4138 nearby galaxies based on the latest Genral Release (GR6/GR7) of GALEX. These galaxies are selected from HyperLeda with apparent diameters larger than 1‧. From the surface brightness profiles accurately measured using the deep NUV and FUV images, we have calculated the asymptotic magnitudes, aperture (D25) magnitudes, colors, structural parameters (effective radii and concentration indices), luminosities, and effective surface brightness for these galaxies. Archival optical and infrared photometry from HyperLeda, 2MASS, and IRAS are also integrated into the catalog. Our parameter measurements and some analyses are consistent with those of Paz et al. The (FUV - K) color provides a good criterion to distinguish between early- and late-type galaxies, which can be improved further using the concentration indices. The IRX-β relation is reformulated with our UV-selected nearby galaxies.

  7. Kuramoto model with uniformly spaced frequencies: Finite-N asymptotics of the locking threshold

    NASA Astrophysics Data System (ADS)

    Ottino-Löffler, Bertrand; Strogatz, Steven H.

    2016-06-01

    We study phase locking in the Kuramoto model of coupled oscillators in the special case where the number of oscillators, N , is large but finite, and the oscillators' natural frequencies are evenly spaced on a given interval. In this case, stable phase-locked solutions are known to exist if and only if the frequency interval is narrower than a certain critical width, called the locking threshold. For infinite N , the exact value of the locking threshold was calculated 30 years ago; however, the leading corrections to it for finite N have remained unsolved analytically. Here we derive an asymptotic formula for the locking threshold when N ≫1 . The leading correction to the infinite-N result scales like either N-3 /2 or N-1, depending on whether the frequencies are evenly spaced according to a midpoint rule or an end-point rule. These scaling laws agree with numerical results obtained by Pazó [D. Pazó, Phys. Rev. E 72, 046211 (2005), 10.1103/PhysRevE.72.046211]. Moreover, our analysis yields the exact prefactors in the scaling laws, which also match the numerics.

  8. Structural studies on Laz, a promiscuous anticancer Neisserial protein

    PubMed Central

    Hashimoto, Wataru; Ochiai, Akihito; Hong, Chang Soo; Murata, Kousaku; Chakrabarty, Ananda M

    2015-01-01

    Azurin and Laz (lipidated azurin) are 2 bacterial proteins with anticancer, anti-viral and anti-parasitic activities. Azurin, isolated from the bacterium Pseudomonas aeruginosa, termed Paz, demonstrates anticancer activity against a range of cancers but not against brain tumors. In contrast, Laz is produced by members of Gonococci/Meningococci, including Neisseria meningitides which can cross the blood-brain barrier to infect brain meninges. It has been previously reported that Laz has an additional 39 amino acid moiety, called an H.8 epitope, in the N-terminal part of the azurin moiety that allows Laz to cross the entry barrier to brain tumors such as glioblastomas. Exactly, how the H.8 epitope helps the azurin moiety of Laz to cross the entry barriers to attack glioblastoma cells is unknown. In this paper, we describe the structural features of the H.8 moiety in Laz using X-ray crystallography and demonstrate that while the azurin moiety of Laz adopts a β-sandwich fold with 2 β-sheets arranged in the Greek key motif, the H.8 epitope was present as a disordered structure outside the Greek key motif. Structures of Paz and H.8 epitope-deficient Laz are well superimposed. The structural flexibility of the H.8 motif in Laz explains the extracellular location of Laz in Neisseria where it can bind the key components of brain tumor cells to disrupt their tight junctions and allow entry of Laz inside the tumors to exert cytotoxicity. PMID:25714335

  9. Origin of Bolivian Quechua Amerindians: their relationship with other American Indians and Asians according to HLA genes.

    PubMed

    Martinez-Laso, Jorge; Siles, Nancy; Moscoso, Juan; Zamora, Jorge; Serrano-Vela, Juan I; R-A-Cachafeiro, Juan I; Castro, Maria J; Serrano-Rios, Manuel; Arnaiz-Villena, Antonio

    2006-01-01

    The Incas were Quechua-speaking people who settled down near Cuzco (Peru). They had an empire ranging from Ecuador to Chile, when Spanish conquerors seized their kingdom around 1532 AD. Nowadays, Quechua-speaking people inhabits Colombia, Ecuador, Bolivia, Peru and Argentina; however, Quechua language was imposed by both Incas and Spaniards to many non-Quechua speaking communities. We have taken a sample of Quechuan Bolivian blood donors from La Paz (Titicaca Lake region) where Inca-Quechuas themselves believed that came from. This group was compared with 6892 individuals from 68 different world populations regarding HLA/DNA allele frequencies distribution. Genetic distances, dendrograms and correspondence analyses were carried out in order to establish relationships among populations. The main conclusions are: (1) DRB1 and -DQB1 haplotypes shared with Asians are found in Quechuas and are not observed in other (Mesoamerican) Amerindians. (2) Aymara-speaking people from the same Titicaca Lake (La Paz) area shows close genetic distances with Quechuas in one dimension results (genetic distances); however, their HLA gene frequency distribution differs according to Neighbor-Joining (NJ) trees and correspondence analysis (multidimensional and more reliable analyses). Also, the common high frequency Asian and Athabascan HLA-DRB1*0901 allele is found in Quechuas in a significant frequency. Quechuas are clearly included within the Amerindian group.

  10. Mount Chacaltaya Regional GAW Station in the Central Andes

    NASA Astrophysics Data System (ADS)

    Zaratti, Francesco; Forno, Ricardo N.; Lolli, Simone

    2010-05-01

    The Mount Chacaltaya Laboratory (MCL), located 30 km from the city of La Paz , at 5300 m asl, is well known as a cosmic ray laboratory that made important contributions to the Elementary Particles Physics in the 40's and 50's of the last century. Since its beginnings, the MCL has also hosted instruments and experiments devoted to atmospheric research and health studies at high altitude locations. In addition, the Chacaltaya glacier has attracted the interest of worldwide climatologists, due to its dramatic retreat. In fact, this glacier does not exist almost anymore. Recently, the Atmospheric Physics Laboratory (LFA-UMSA) has begun to take permanent and field measurements of some relevant atmospheric parameters at MCL, such as carbon dioxide, aerosols and ultraviolet irradiance. In this work we show some characteristics that made Chacaltaya a Regional GAW Station (CHC), recently nominated by WMO. In addition we show some pioneering steps of this project, supported by research institutes from France, Italy, Switzerland and USA. Finally, thanks to the vigorous co-operation of the Raman lidar group at Goddard Space Flight Center, a new YAG Laser is being installed, to be operated together with the "old" Alexandrite Lidar in the study of aerosols at La Paz.

  11. Mangrove health in an arid environment encroached by urban development--a case study.

    PubMed

    Holguin, Gina; Gonzalez-Zamorano, Patricia; de-Bashan, Luz E; Mendoza, Renato; Amador, Edgar; Bashan, Yoav

    2006-06-15

    Urban development will soon encroach upon several protected and largely unspoiled arid climate mangroves ecosystems located along the lagoon called Ensenada de La Paz in Baja California Sur, Mexico. Many of these mangroves are located on a large sandbar that separates the lagoon on the south side from Bahía de La Paz to the north. A general evaluation of the current status of these mangroves was conducted to establish biological and physicochemical indicators of the health of these mangroves to serve as a natural or predevelopment baseline in future management. The following parameters were measured in the feeding channels of the mangroves and at the mouth of the channels: vegetation coverage, species and health, and levels of dissolved oxygen, pH, salinity, total nitrogen, ammonium, nitrates and nitrites, phosphorus ions, and organic matter in sediments and seawater. The microbiological elements that were studied included aerobic bacteria, N2-fixing bacteria, inorganic phosphate solubilizers, coliform, and phytoplankton diversity. Bird populations were counted, with special attention to migratory and resident birds and protected and endangered species. A comprehensive analysis of all the elements indicated that the health of the sandbar mangrove populations is good despite the proximity of a modest urban center. It also demonstrated that several biological and physicochemical parameters used in this study, including the birds, can serve as indicators of mangrove health and as a baseline for future management of mangroves in regions with arid climates.

  12. Holocene late Pleistocene non-tropical carbonate sediments and tectonic history of the western rift basin margin of the southern Gulf of California

    NASA Astrophysics Data System (ADS)

    Halfar, Jochen; Godinez-Orta, Lucio; Goodfriend, Glenn A.; Mucciarone, David A.; Ingle, James C.; Holden, Peter

    2001-10-01

    Using high-resolution seismic reflection profiling and dating of (1) shallow marine vibracores and (2) sediments collected from uplifted marine terraces we reconstruct the tectonic history and sediment accumulation patterns of Holocene to late Pleistocene warm-temperate to subtropical carbonates in the southern Gulf of California, Mexico. The study was conducted in the vicinity of La Paz where carbonates form along the fault bounded narrow western shelf of the tectonically active Gulf of California rift basin. The non-tropical nature of the setting is responsible for (1) poor cementation of the bioclastic carbonates, and (2) a composition which is dominated by rhodoliths (coralline red algae), corals and mollusks. Unrimmed carbonate flats forming in small pocket bays and a rhodolith bioherm, which has a surface area of more than 20 km 2 and is up to 16 m thick, constitute the major carbonate factories. Holocene carbonate accumulation rates were deduced from seismic and core data and are highest on the rhodolith bioherm (260 cm/ka) and in subtidal zones of pocket bays (210 cm/ka), and lowest on the inner and middle shelf (100 cm/ka). Taken together, rates of carbonate accumulation are intermediate in magnitude between higher rates recorded in fully tropical carbonate settings and lower rates typical of cool-water carbonates. Seismic reflection profiles demonstrate that Isla Espiritu Santo in the center of the study area is a west dipping fault block, which is tectonically influenced by two distinct faults, the La Paz and Espiritu Santo faults. The latter fault accommodates at least 700 m of east-side down normal offset, and forms a steep eastern escarpment leading into the La Paz slope basin. Some of the sediments produced in the shallow carbonate factories of the narrow La Paz shelf are transported across this escarpment and are redeposited in the slope basin at a water depth of 750 m. Uranium-series dates of marine terraces exposed on Isla Espiritu Santo indicate

  13. Ore genesis of the Weibao lead-zinc district, Eastern Kunlun Orogen, China: constrains from ore geology, fluid inclusion and isotope geochemistry

    NASA Astrophysics Data System (ADS)

    Fang, Jing; Chen, Huayong; Zhang, Li; Zheng, Yi; Li, Dengfeng; Wang, Chengming; Shen, Dengliang

    2015-07-01

    The Weibao lead-zinc district, composed by two deposits named the East Weibao deposit and the West Weibao deposit, respectively, is located in the Qimantagh area, Eastern Kunlun Orogen. Although both controlled by skarn alternation and experienced similar mineralization processes, the East Weibao deposit is dominated by massive ores, while the West Weibao deposit is characterized by banded ores. The ore-forming processes of both the deposits can be divided into four stages including prograde skarn stage, retrograde skarn stage, sulfide stage and carbonate stage. Three types of fluid inclusions, i.e., pure CO2 fluid inclusion (PC-type), CO2-bearing fluid inclusion (C-type) and aqueous types (W-type), have been identified in quartz, calcite and sphalerite from different stages. Noteworthily, only sulfide stage of the East Weibao deposit contains carbonic fluid inclusions, whereas only aqueous fluid inclusions were observed in sulfide stage of the West Weibao deposit. The CO2-rich and aqueous-type fluid inclusions in sulfide stage of the East Weibao deposit were homogenized at temperatures between 263 and 424 °C, concentrating at 360-400 °C, with salinities ranging between 3.2 and 13.6 wt% NaCl eqv.; the W-type fluid inclusions in sulfide stage of the West Weibao deposit were homogenized at temperatures between 228 and 381 °C, concentrating at 280-340 °C, with salinities between 1.6 and 9.0 wt% NaCl eqv.; and the aqueous-type fluid inclusions in carbonate stage in both deposits were homogenized at temperatures between 115 and 336 °C, concentrating at 200-240 °C, with salinities between 0.2 and 5.9 wt% NaCl eqv. The ore-forming fluid in sulfide stage at the East Weibao deposit yielded calculated and δ18D values of 4.2 to 5.6 and -88 to -83 ‰, respectively. The results are 8.8 to 10.8, -99 to -92 ‰ for the sulfide stage at the West Weibao deposit and -1.0 to -0.2, -50 to -45 ‰ for carbonate stages in both deposits. The lead isotopic ratios of sulfide

  14. Post-intrusive south directed Deformation of the Serifos metamorhic Core Complex (western Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Rambousek, C.; Grasemann, B.; Petrakakis, K.; Zamolyi, A.; Iglseder, C.

    2003-04-01

    The Attic - Cycladic belt is part of the Alpine orogen in the eastern Mediterranean. It is located SE of the Greek mainland and trends parallel to the Hellenic volcanic arc. Since the Miocene the whole area of the southern Aegean region is characterized by a NS oriented extensional regime partly accommodated by crustal low-angle normal faults. Some of the islands in the eastern Cyclades (Naxos, Paros, Ios) have been suggested to represent metamorphic core complex (MCC) indicating an asymmetric extension partly to the N and to the S (e.g. Lister et al. 1984). This work focuses on the S directed detachment of a newly found MCC on Serifos, in the western Cyclades. The SE part of the island is dominated by an undeformed Hornbelende-Biotite granodiorite pluton in the core, which becomes with increasing intensity foliated towards higher structural levels transforming into S-dipping low-temperature mylonitic to ultra-mylonitic rocks with abundant SSW-directed kinematic indicators (scc´ fabrics, sigma- and delta-clasts, flanking fold structures and mica-fish). This zone forms the main detachment of the Serifos MCC. The northern contact of the granodiorite is mainly intrusive cross cutting amphibolite facies highly deformed marbles, metabasic and metapelitic rocks with typical Ca-Fe-Mg skarns (Salemink, 1985). On the peninsular in the SE most part of Serifos (E of Livadi) statically recristallized mylonitic marbles and amphibolite grade metabasic and metapelitic rocks with the typical Ca-Fe-Mg skarns occur in the hanging wall of the main detachment zone. These characteristic lithologies also occur as mega boudins (several tens of meters long) in the main detachment zone and are lithologically similar to the host rocks in the north of the intrusion. There, these rocks are structurally in the footwall of the main detachment and therefore a minimum dip-slip 6 km can be estimated for the post-intrusive deformation. Geochronological cooling ages of the granodiorite using

  15. Nature, diversity of deposit types and metallogenic relations of South China

    USGS Publications Warehouse

    Zaw, K.; Peters, S.G.; Cromie, P.; Burrett, C.; Hou, Z.

    2007-01-01

    The South China Region is rich in mineral resources and has a wide diversity of deposit types. The region has undergone multiple tectonic and magmatic events and related metallogenic processes throughout the earth history. These tectonic and metallogenic processes were responsible for the formation of the diverse styles of base and precious metal deposits in South China making it one of the resource-rich regions in the world. During the Proterozoic, the South China Craton was characterised by rifting of continental margin before eruption of submarine volcanics and development of platform carbonate rocks, and the formation of VHMS, stratabound copper and MVT deposits. The Phanerozoic metallogeny of South China was related to opening and closing of the Tethyan Ocean involving multiple orogenies by subduction, back-arc rifting, arc-continent collision and post-collisional extension during the Indosinian (Triassic), Yanshanian (Jurassic to Cretaceous) and Himalayan (Tertiary) Orogenies. The Late Palaeozoic was a productive metallogenic period for South China resulting from break-up and rifting of Gondwana. Significant stratabound base and precious metal deposits were formed during the Devonian and Carboniferous (e.g., Fankou and Dabaoshan deposits). These Late Palaeozoic SEDEX-style deposits have been often overprinted by skarn systems associated with Yanshanian magmatism (e.g., Chengmenshan, Dongguashan and Qixiashan). A number of Late Palaeozoic to Early Mesozoic VHMS deposits also developed in the Sanjiang fold belt in the western part of South China (e.g., Laochang and Gacun). South China has significant sedimentary rock-hosted Carlin-like deposits, which occur in the Devonian- to Triassic-aged accretionary wedge or rift basins at the margin of the South China Craton. They are present in a region at the junction of Yunnan, Guizhou, and Guangxi Provinces called the 'Southern Golden Triangle', and are also present in NW Sichuan, Gansu and Shaanxi, in an area known as

  16. Neogene Uplift and Exhumation of Plutonic Bodies in the Beni Bou Ifrour Massif (Nador, northeastern Morocco)

    NASA Astrophysics Data System (ADS)

    Lebret, Noëmie; Jolivet, Laurent; Branquet, Yannick; Bourdier, Jean-Louis; Jolivet, Marc; Marcoux, Eric

    2013-04-01

    In Neogene times, the whole Mediterranean Sea was the center of an intense magmatic activity. This post-collisional magmatism produced a large amount of volcanic edifices through the Alpine belts, together with some intrusives. These plutonic bodies can be associated with skarn-type mineralization, well-known in Elba Island or Serifos Island (Cyclades), where they are generally exhumed by detachment faults. In Morocco, the plutons hosted by the Beni Bou Ifrour massif are connected to the biggest skarn-type iron concentrations of the country (production > 60 Mt, reserves ≈ 25 Mt). The purpose of this work is to explain the late uplift of this massif and subsequent exhumation of the intrusives. As a final product of the Africa-Eurasia plate convergence since ca. 70 Ma, the Rif Mountains constitute the westernmost segment of the Mediterranean Alpine belts. In the oriental part of this range, volcanic summits and Paleozoic to Mesozoic massifs outcrop in the surrounding Mio-Pliocene plains. The Beni Bou Ifrour massif, in the Nador province, consists in a dome-shaped folded Mesozoic series (Domerian to Barremian) affected by a slight epizonal regional metamorphism (ca. 14-12 Ma), dislocated by Neogene NE-SW faults and eventually sealed by upper Miocene transgressive sediments. The hosted intrusives (7.58 ± 0.03 Ma; Duggen et al., 2005) are the plutonic equivalents to the potassic calc-alkaline lavas (andesites mainly) from the surrounding "satellite" volcanic massifs. They turn out to stand in higher topographic position than the younger shoshonitic lavas of the neighboring Gourougou stratovolcano (6.12 ± 0.01 Ma; Duggen et al., 2005). Previous studies have attributed this uplift to the action of normal faults (pull-apart basins; Guillemin & Houzay, 1982), thrusting (Kerchaoui, 1985; 1995) or even of a caldeira resurgence (El Bakkali, 1995). To discriminate against those exhumation mechanisms, field work has been performed, coming along with new cross-sections to

  17. Late Paleozoic tectonic evolution and concentrated mineralization in Balkhash and West Junggar, western part of the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Dong, Shuwen; Chen, Xuanhua; Chen, Zhengle

    2016-04-01

    The Central Asia Orogenic Belt (CAOB) is an important area with significant growth of the crust and metallogeny in the Late Paleozoic. The Balkhash-Junggar tectono-metallogenic belt consists of the Balkhash, the West Junggar, and the East Junggar tectono-metallogenic belts in western part of the Central Asian Orogenic Belt (CAOB). According to the structural geological relationship, the East Junggar, the West Junggar, and the Balkhash belts are considered to be once a continuous E-W-trending tectono-metallogenic belt in Late Carboniferous. The West Junggar belt is featured with NE-trending left-lateral strike-slip faulting tectonic system (WJTS), while the left-lateral strike-slip faults are E-W-trending in the Balkhash belt. The WJTS consists of the Darabut, the Mayile, and the Baerluke faults, and the blocks among them. All these left-lateral strike-slip faults are forming due to the transition of tectonic settings from syn-collisional orogeny to post-collisional extension during the closure of the ocean (the Junggar Sea) in Late Carboniferous, with significant intrusion of batholiths and crust growth occurred in this period. These faults are truncated by the right-lateral strike-slip faults, such as the Chingiz-Junggar fault, and the Central Balkhash fault in Mesozoic. The Balkhash-Junggar tectono-metallogenic belt is important for the occurrence of many well-known super-large and large porphyry Cu-Mo deposits (such as the Kounrad, the Aktogai, the Borly, and the Baogutu deposits), large skarn Cu deposits (in the Sayak ore-filed), large rare metal deposits (such as the East Kounrad, the Zhanet, and the Akshatau deposits), and large gold deposits (such as the Hatu deposit). Zircon U-Pb ages, Re-Os isotopic dating of molybdenites, 40Ar/39Ar thermochronology of hornblendes, muscovites, biotites, and K-feldspars, and zircon and apatite fission track (FT) and (U-Th)/He dating and thermal history modeling, provide a multidisciplinary approach to constrain the whole

  18. Mesozoic Magmatism and Base-Metal Mineralization in the Fortymile Mining District, Eastern Alaska - Initial Results of Petrographic, Geochemical, and Isotopic Studies in the Mount Veta Area

    USGS Publications Warehouse

    Dusel-Bacon, Cynthia; Slack, John F.; Aleinikoff, John N.; Mortensen, James K.

    2009-01-01

    -bearing Zn skarn. Cu-Zn-Pb-Ag-Au showings at the Oscar pros-pect occur in marble-hosted magnetite and pyrrhotite skarn that is spatially related to the stocks, dikes, and sills of the Early Jurassic syenite of Mount Veta. Mineralized rocks at the Eva Creek Ag-Zn-Pb-Cu prospect are within 1.5 km of the Mount Veta pluton, which is epidotized and locally altered along its contact with metamorphosed country rock east of the prospect. We report five new sulfide Pb-isotopic analyses from the LWM, Oscar, and Eva Creek prospects and compare these sulfide Pb-isotopic ratios with those for sulfides from nearby deposits and prospects in the Yukon-Tanana Upland and with feldspar Pb-isotopic ratios for Mesozoic plutons in the region. Disparities between the Pb-isotopic ratios for sulfides and igneous feldspars are consistent with a carbonate-replacement model for both the LWM and Eva Creek prospects. The presence in the Fortymile district of base-metal sulfides within both calc-silicate-rich skarns and the calc-silicate-free carbonate replacement deposits may reflect multistage mineralization by magmatic-hydrothermal systems during the emplacement of two or more magmatically unrelated igneous intrusions. Alternatively, all of the mineralized occurrences could be products of one regionally zoned system that formed during the intrusion of a single pluton. In addition to the likely origin of some of the base-metal occurrences by intrusion-related hydrothermal fluids, proximity of the LWM prospect to the northeast-striking, high-angle Kechumstuk Fault suggests that fluid flow along the fault also played an important role during carbonate-replacement mineralization.

  19. 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

  20. Magmatism and polymetallic mineralization in southwestern Qinzhou-Hangzhou metallogenic belt, South China

    NASA Astrophysics Data System (ADS)

    Huang, Xudong; Lu, Jianjun; Wang, Rucheng; Ma, Dongsheng

    2016-04-01

    As Neoproterozoic suture zone between the Yangtze Block and Cathaysia Block, Qinzhou-Hangzhou metallogenic belt is one of the 21 key metallogenic belts in China. Intensive multiple-aged felsic magmatism and related polymetallic mineralization take place in this belt. Although Neoproterozoic, Paleozoic, Triassic granites and associated deposits have been found in southwestern Qinzhou-Hangzhou metallogenic belt, Middle-Late Jurassic (150-165 Ma) magmatism and related mineralization is of the most importance. Three major kinds of Middle-Late Jurassic granitoids have been distinguished. (Cu)-Pb-Zn-bearing granitoids are slightly differentiated, calc-alkaline and metaluminous dioritic to granodioritic rocks. Sn-(W)-bearing granites contain dark microgranular enclaves and have high contents of REE and HFSE, suggesting affinities of aluminous A-type (A2) granites. W-bearing granites are highly differentiated and peraluminous rocks. (Cu)-Pb-Zn-bearing granitoids have ɛNd(t) values of -11 ˜ -4 and ɛHf(t) values of -12 ˜ -7, corresponding to TDMC(Nd) from 1.4 to 1.8 Ga and TDMC(Hf) from 1.6 to 2.0 Ga, respectively. The ɛNd(t) values of W-bearing granites vary from -11 to -8 with TDMC(Nd) of 1.6 ˜ 1.9 Ga and ɛHf(t) values change from -16 to -7 with TDMC(Hf) of 1.5 ˜ 2.0 Ga. Compared with (Cu)-Pb-Zn-bearing granitoids and W-bearing granites, the Sn-(W)-bearing granites have higher ɛNd(t) (-8 ˜ -2) and ɛHf(t) (-8 ˜ -2) values and younger TDMC(Nd) (1.1 ˜ 1.6 Ga) and TDMC(Hf) (1.2 ˜ 1.8 Ga) values, showing a more juvenile isotopic character. Sn-(W)-bearing granites originate from partial melting of granulitized lower crust involved with some mantle-derived materials. W-bearing granites are derived from partial melting of crust. (Cu)-Pb-Zn-bearing granitoids are also derived from crust but may be influenced by more mantle-derived materials. For (Cu)-Pb-Zn deposits, skarn and carbonate replacement are the most important mineralization types. Cu ore bodies mainly