Iron isotope behavior during fluid/rock interaction in K-feldspar alteration zone - A model for pyrite in gold deposits from the Jiaodong Peninsula, East China

NASA Astrophysics Data System (ADS)

Zhu, Zhi-Yong; Jiang, Shao-Yong; Mathur, Ryan; Cook, Nigel J.; Yang, Tao; Wang, Meng; Ma, Liang; Ciobanu, Cristiana L.

2018-02-01

Mechanisms for Fe isotope fractionation in hydrothermal mineral deposits and in zones of associated K-feldspar alteration remain poorly constrained. We have analyzed a suite of bulk samples consisting of granite displaying K-feldspar alteration, Precambrian metamorphic rocks, and pyrite from gold deposits of the Jiaodong Peninsula, East China, by multi-collector inductively-coupled plasma mass spectrometry. Pyrites from disseminated (J-type) ores show a δ56Fe variation from +0.01 to +0.64‰, overlapping with the signature of the host granites (+0.08 to +0.39‰). In contrast, pyrites from quartz veins (L-type ores) show a wide range of Fe-isotopic composition from -0.78 to +0.79‰. Negative values are never seen in the J-type pyrites. The Fe isotope signature of the host granite with K-feldspar alteration is significantly heavier than that of the bulk silicate Earth. The Fe isotopic compositions of Precambrian metamorphic rocks across the district display a narrow range between -0.16‰ and +0.19‰, which is similar to most terrestrial rocks. Concentrations of major and trace elements in bulk samples were also determined, so as to evaluate any correlation between Fe isotope composition and degree of alteration. We note that during progressive K-feldspar alteration to rocks containing >70 wt% SiO2, >75 ppm Rb, and <1.2 wt% total Fe2O3, the Fe isotope composition of the granite changes systematically. The Fe isotope signature becomes heavier as the degree of alteration increases. The extremely light Fe isotopic compositions in L-type gold deposits may be explained by Rayleigh fractionation during pyrite precipitation in an open fracture system. We note that the sulfur isotopic compositions of pyrite in the two types of ores are also different. Pyrite from J-type ores has a systematically 3.5‰-higher δ34S value (11.2‰) than those of pyrite from the L-type ores (7.7‰). There is, however, no correlation between Fe and S isotope signatures. The isotopic

Fate of process solution cyanide and nitrate at three nevada gold mines inferred from stable carbon and nitrogen isotope measurements

USGS Publications Warehouse

Johnson, C.A.; Grimes, D.J.; Rye, R.O.

2000-01-01

Stable isotope methods have been used to identify the mechanisms responsible for cyanide consumption at three heap-leach operations that process Carlin-type gold ores in Nevada, U.S.A. The reagent cyanide had ??15N values ranging from -5 to -2??? and ??13C values from -60 to -35???. The wide ??13C range reflects the use by different suppliers of isotopically distinct natural-gas feedstocks and indicates that isotopes may be useful in environmental studies where there is a need to trace cyanide sources. In heap-leach circuits displaying from 5 to 98% consumption of cyanide, barren-solution and pregnant-solution cyanide were isotopically indistinguishable. The similarity is inconsistent with cyanide loss predominantly by HCN offgassing (a process that in laboratory experiments caused substantial isotopic changes), but it is consistent with cyanide retention within the heaps as solids, a process that caused minimal isotopic changes in laboratory simulations, or with cyanide oxidation, which also appears to cause minimal changes. In many pregnant solutions cyanide was carried entirely as metal complexes, which is consistent with ferrocyanides having precipitated or cyanocomplexes having been adsorbed within the heaps. It is inferred that gaseous cyanide emissions from operations of this type are less important than has generally been thought and that the dissolution or desorption kinetics of solid species is an important control on cyanide elution when the spent heaps undergo rinsing. Nitrate, nitrite and ammonium had ??15N values of 1-16???. The data reflect isotopic fractionation during ammonia offgassing or denitrification of nitrate - particularly in reclaim ponds - but do not indicate the extent to which nitrate is derived from cyanide or from explosive residues. ?? The Institution of Mining and Metallurgy 2000.

Oxygen isotope exchange with quartz during pyrolysis of silver sulfate and silver nitrate.

PubMed

Schauer, Andrew J; Kunasek, Shelley A; Sofen, Eric D; Erbland, Joseph; Savarino, Joel; Johnson, Ben W; Amos, Helen M; Shaheen, Robina; Abaunza, Mariana; Jackson, Terri L; Thiemens, Mark H; Alexander, Becky

2012-09-30

Triple oxygen isotopes of sulfate and nitrate are useful metrics for the chemistry of their formation. Existing measurement methods, however, do not account for oxygen atom exchange with quartz during the thermal decomposition of sulfate. We present evidence for oxygen atom exchange, a simple modification to prevent exchange, and a correction for previous measurements. Silver sulfates and silver nitrates with excess (17)O were thermally decomposed in quartz and gold (for sulfate) and quartz and silver (for nitrate) sample containers to O(2) and byproducts in a modified Temperature Conversion/Elemental Analyzer (TC/EA). Helium carries O(2) through purification for isotope-ratio analysis of the three isotopes of oxygen in a Finnigan MAT253 isotope ratio mass spectrometer. The Δ(17)O results show clear oxygen atom exchange from non-zero (17)O-excess reference materials to zero (17)O-excess quartz cup sample containers. Quartz sample containers lower the Δ(17)O values of designer sulfate reference materials and USGS35 nitrate by 15% relative to gold or silver sample containers for quantities of 2-10 µmol O(2). Previous Δ(17)O measurements of sulfate that rely on pyrolysis in a quartz cup have been affected by oxygen exchange. These previous results can be corrected using a simple linear equation (Δ(17)O(gold) = Δ(17)O(quartz) * 1.14 + 0.06). Future pyrolysis of silver sulfate should be conducted in gold capsules or corrected to data obtained from gold capsules to avoid obtaining oxygen isotope exchange-affected data. Copyright © 2012 John Wiley & Sons, Ltd.

Gold(III) complexes in medicinal chemistry.

PubMed

Maia, Pedro Ivo da Silva; Deflon, Victor M; Abram, Ulrich

2014-09-01

A number of gold(III) compounds has been designed with the objective of overcoming the disadvantages associated with the platinum-based drugs for cancer treatment. Compounds of a remarkable structural manifold show significant antiproliferative effects in vitro against a number of cancer cells, including cisplatin resistant ones. The target of most of them is, unlike that of cisplatin, not the DNA. Although the mechanisms of action displayed by the gold compounds in biological media are still under investigation, many studies show evidence that the cellular targets are mitochondria-based. Recent advances in gold(III) medicinal chemistry also recommend such compounds for other pharmacological applications such as the treatment of viral or parasitic diseases. The radioactive isotopes (198)Au and (199)Au present potential in radiotherapy.

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

Isotopic studies of mariposite-bearing rocks from the south- central Mother Lode, California.

USGS Publications Warehouse

Kistler, R.W.; Dodge, F.C.W.; Silberman, M.L.

1983-01-01

Gold-bearing vein formation in the Mother Lode belt of the study area apparently occurred during the Early Cretaceous between 127 and 108 m.y. B.P. The hydrothermal fluids that carried the gold precipitated quartz and mariposite at approx 320oC, similar to the T of precipitation of gold-bearing quartz veins in the Allegheny district. The O- and H-isotopic composition calculated for the fluid indicate that it was similar to formation water or was metamorphic in origin. If the carbonate in the veins was in isotopic equilibrium with this same fluid, it apparently precipitated at a higher T of approx 400oC. The Sr in the carbonate is much less radiogenic than that in any known marine carbonate, but is similar in isotopic composition to that in metamorphosed mafic volcanic rocks of the general region. These mafic rocks could have been the source for the Sr in the hydrothermal veins. This observation supports the contention that the gold-mariposite-quartz-carbonate rocks were formed as an alteration product of serpentinite and other mafic igneous rocks.-A.P.

An Early Permian epithermal gold system in the Tulasu Basin in North Xinjiang, NW China: Constraints from in situ oxygen-sulfur isotopes and geochronology

NASA Astrophysics Data System (ADS)

Dong, Leilei; Wan, Bo; Deng, Chen; Cai, Keda; Xiao, Wenjiao

2018-03-01

The Axi and Jingxi-Yelmand gold deposits, being the largest gold deposits in the Chinese North Tianshan, NW China, are located ca. l0 km apart in the Tulasu Basin, and are hosted by the Late Devonian - Early Carboniferous Dahalajunshan Formation. In situ LA-ICP-MS titanium analyses on quartz from the Axi and Jingxi-Yelmand deposits are broadly identical. Accordingly, the calculated ore-forming temperatures by Ti-in-quartz thermometer give average temperatures of 279 °C and 294 °C, respectively. Results of in situ SIMS analyses of oxygen and sulfur isotopes on quartz and pyrite from these two deposits are similar. Temperature-corrected fluids of the Axi deposit have δ18O values of 2.6-8.1‰ and δ34S values of 0.8-2.4‰, whereas the fluids of the Jingxi-Yelmand deposit have δ18O of 6.4-8.9‰ and δ34S of -0.4 to 4.0‰. The oxygen and sulfur isotopes from the two deposits indicate a magmatic origin. LA-ICP-MS zircon U-Pb ages of Aqialehe Formation sandstone provided a lower limit for the mineralization timing of the Axi deposit (288 Ma). In situ SIMS U-Pb analyses on entrapped zircon (297 Ma) and newly recognized 284.5 Ma columnar rhyolite implies that the Jingxi-Yelmand deposit formed in the Early Permian. Based on the magmatic affinity of the ore fluids, similar age and ore-formation temperatures, we propose that the Axi and Jingxi-Yelmand deposits comprise an epithermal gold system, which was driven by the same Permian magma in the Tulasu Basin. The ore geological features together with our new results indicate that the Axi and Jingxi-Yelmand deposits are intermediate and high sulfidation type epithermal deposits, respectively.

Extreme variation of sulfur isotopic compositions in pyrite from the Qiuling sediment-hosted gold deposit, West Qinling orogen, central China: An in situ SIMS study with implications for the source of sulfur

USGS Publications Warehouse

Chen, Lei; Li, Xian-hua; Li, Jian-wei; Hofstra, Albert H.; Liu, Yu; Koenig, Alan E.

2015-01-01

High spatial resolution textural (scanning electron microscope (SEM)), chemical (electron microprobe (EMP)) and laser ablation-inductively coupled plasma-mass spec- trometry (LA-ICP-MS)), and sulfur isotopic (secondary ion mass spectrometry (SIMS)) analyses of pyrite from the Qiuling sediment-hosted gold deposit (232±4 Ma) in the West Qinling orogen, central China were conducted to distinguish pyrite types and gain insights into the source and evolution of sulfur in hydrothermal fluids. The results reveal an enormous variation (−27.1 to +69.6‰) in sulfur isotopic composition of pyrite deposited during three paragenetic stages. Pre-ore framboidal pyrite, which is characterized by low concentra- tions of As, Au, Cu, Co, and Ni, has negative δ34S values of −27.1 to −7.6‰ that are interpreted in terms of bacterial re- duction of marine sulfate during sedimentation and diagenesis of the Paleozoic carbonate and clastic sequences, the predom- inant lithologies in the deposit area, and the most important hosts of many sediment-hosted gold deposits throughout the West Qinling orogen. The ore-stage hydrothermal pyrite con- tains high concentrations of Au, As, Cu, Sb, Tl, and Bi and hasa relatively narrow range of positive δ34S values ranging from +8.1 to +15.2‰. The sulfur isotope data are comparable to those of ore pyrite from many Triassic orogenic gold deposits and Paleozoic sedimentary exhalative (SEDEX) Pb-Zn de- posits in the West Qinling orogen, both being hosted mainly in the Devonian sequence. This similarity indicates that sulfur, responsible for the auriferous pyrite at Qiuling, was largely derived from the metamorphic devolatization of Paleozoic marine sedimentary rocks. Post-ore-stage pyrite, which is sig- nificantly enriched in Co and Ni but depleted in Au and As, has unusually high δ34S values ranging from +37.4 to +69.6 ‰, that are interpreted to result from thermochemical reduc- tion of evaporite sulfates in underlying Cambrian sedimentary

Osmium isotope constraints on ore metal recycling in subduction zones

PubMed

McInnes; McBride; Evans; Lambert; Andrew

1999-10-15

Veined peridotite xenoliths from the mantle beneath the giant Ladolam gold deposit on Lihir Island, Papua New Guinea, are 2 to 800 times more enriched in copper, gold, platinum, and palladium than surrounding depleted arc mantle. Gold ores have osmium isotope compositions similar to those of the underlying subduction-modified mantle peridotite source region, indicating that the primary origin of the metals was the mantle. Because the mantle is relatively depleted in gold, copper, and palladium, tectonic processes that enhance the advective transport and concentration of these fluid soluble metals may be a prerequisite for generating porphyry-epithermal copper-gold deposits.

Accounting for cyanide and its degradation products at three Nevada gold mines; constraints from stable C- and N-isotopes

USGS Publications Warehouse

Johnson, C.A.; Grimes, D.J.; Rye, R.O.

1998-01-01

An understanding of the fate of cyanide (CN-) in mine process waters is important for addressing environmental concerns and for taking steps to minimize reagent costs. The utility of stable isotope methods in identifying cyanide loss pathways has been investigated in case studies at three Nevada gold mines. Freshly prepared barren solutions at the mines have cyanide d15N and d13C values averaging -4 ? and -36 ?, respectively, reflecting the nitrogen and carbon sources used by commercial manufacturers, air and natural gas methane. Pregnant solutions returning from ore heaps display small isotopic shifts to lower d15N and d13C values. The shifts are similar to those observed in laboratory experiments where cyanide was progressively precipitated as a cyanometallic compound, and are opposite in sign and much smaller in magnitude than the shifts observed in experiments where HCN was offgassed. Offgassing is inferred to be a minor cyanide loss mechanism in the heap leach operations at the three mines, and precipitation as cyanometallic compounds, and possibly coprecipitation with ferric oxides, is inferred to be an important loss mechanism. Isotopic analysis of dissolved inorganic carbon (DIC) shows that uptake of high d13C air CO2 has been important in many barren and pregnant solutions. However, DIC in reclaim pond waters at all three mines has low d13C values of -28 to -34 ? indicating cyanide breakdown either by hydrolysis or by other chemical pathways that break the C-N bond. Isotope mass balance calculations indicate that about 40 % of the DIC load in the ponds, at a minimum, was derived from cyanide breakdown. This level of cyanide hydrolysis accounts for 14-100 % of the dissolved inorganic nitrogen species present in the ponds. Overall, isotope data provide quantitative evidence that only minor amounts of cyanide are lost via offgassing and that significant amounts are destroyed via hydrolysis and related pathways. The data also highlight the possibility that

Lead Isotope Characteristics of the Mindyak Gold Deposit, Southern Urals: Evidence for the Source of Metals

NASA Astrophysics Data System (ADS)

Chugaev, A. V.; Znamensky, S. E.

2018-01-01

The isotopic composition of Pb in pyrite of the Mindyak orogenic gold deposit located in the Main Ural Fault Zone, the Southern Urals, has been studied by the high-precision MC-ICP-MS method. Orebodies at the deposit are composed of early pyrite and late polysulfide-carbonate-quartz mineral assemblages. The orebodies are localized in olistostrome with carbonaceous clayey-cherty cement. Pyrites from early and late mineral assemblages are close in Pb isotope ratios. For early pyrite 206Pb/204Pb = 18.250-18.336, 207Pb/204Pb = 15.645-15.653, 208Pb/204Pb = 38.179-38.461; while for late pyrite 206Pb/204Pb = 18.102-18.378, 207Pb/204Pb = 15.635-15.646, 208Pb/204Pb = 38.149-38.320. The model parameters μ2 (238U/204Pb = 9.91 ± 2), ω2 (232Th/204Pb = 38.5 ± 4), and 232Th/238U = 3.88 ± 3 indicate that an upper crustal Pb source played a leading role in ore formation. Carbonaceous shale as an olistostrome cement and syngenetic sulfide mineralization are considered to be the main Pb sources of both early and late mineral assemblages. An additional recept in apparently magmatic lead is suggested for the late veinlet mineralization. The involvement of lead from several sources in ore formation is consistent with the genetic model, which assumes a two-stage formation of orebodies at the Mindyak deposit.

Multistage deformation of Au-quartz veins (Laurieras, French Massif Central): evidence for late gold introduction from microstructural, isotopic and fluid inclusion studies

NASA Astrophysics Data System (ADS)

Essarraj, S.; Boiron, M.-C.; Cathelineau, M.; Fourcade, S.

2001-07-01

The relative chronology of fluid migration, quartz and Au-deposition in a silicified fault from the main Au-district (Laurieras, St Yrieix district) from northern French Massif Central has been determined from microstructural, fluid inclusion, isotopic and ore mineral evidences. Three main stages of fluid circulation, microfracturing and quartz crystallization, and ore deposition were distinguished on the basis of textural relationships and the pressure, temperature and composition of the palaeo-fluids: (1) a series of early fluid events was responsible for the localized drainage of retrograde metamorphic fluids along the main fault and the subsequent sealing by milky and microcrystalline quartz preceeded the main Au-ore stages. Early fluids were aqueous-carbonic, trapped under lithostatic to sublithostatic pressures at temperatures in the range 350-500°C. Subsequently, several types of microstructures were developed in the early quartz matrix. (2) NS microfractures filled by clear quartz, arsenopyrite and boulangerite (I) contain significant refractory gold concentrations. Clear quartz formed from aqueous-carbonic fluids of lower densities than those of the earlier fluids. Significant pressure drops, down to pressures around 55 MPa were responsible for a local immiscibility of the aqueous-carbonic fluids at temperatures of 340±20°C. (3) The main ore stage is characterized by the formation of dense sets of sub-vertical (EW) microfractures, healed fluid inclusion planes in quartz, and filled by ore minerals (native gold, galena and boulangerite II) when they crosscut earlier sulfides. The fluids are aqueous with low and decreasing salinity, and probable trapping temperatures around 230°C. Isotopic data, obtained on microfissured quartz, indicate these dilute aqueous fluids may be considered as meteoric waters that deeply infiltrated the crust. Late microfissuring of a mesothermal quartz vein, originally barren (only with pyrite and arsenopyrite), appears to be

Isotopic and geothermometric constraints on the structural and metamorphic evolution of Homestake gold deposit, Black Hills, South Dakota (USA)

NASA Astrophysics Data System (ADS)

Terry, M.; Dahl, P.; Frei, R.

2003-04-01

The Homestake Deposit, located in the northern Black Hills and host for 40 million ounces of gold, shows evidence for extensive remobilization of gold related to regional metamorphism deformation associated with the Early Proterozoic assembly of supercontinent Laurentia. Field and petrographic evidence for gold remobilization includes the occurrence of abundant quartz veins associated with selvages of chlorite-siderite-ankerite-pyrrhotite-arsenopyrite-gold in the Homestake Fm. The deposit is located on the western limb of a major anticlinorium that coincides with a vertical N-S-striking garnet isograd, and garnet-biotite geothermometry of metapelites sampled across the anticlinorium indicates a steep metamorphic field gradient of 150^oC/km (east side warmer). This gradient is mirrored by a pronounced fractionation of oxygen isotopes observed in the vein quartz, with δ18O ranging from 10 to 18 ppm. The isograd is parallel with a major N-S-striking shear zone, and kinematic indicators predominantly indicate oblique sinistral motion with east-side up. Garnet was separated from a subsurface sample of the Homestake Fm. collected from the nose of the so-called "main ledge" synform and subjected to Pb stepwise leaching (PbSL) to determine the age of garnet growth and thus metamorphism. PbSL analysis revealed a 207Pb/206Pb age of 1746 ± 10 Ma (± 2σ). Recent work in the southern Black Hills indicates that almandine does not contain sufficient Pb to be dated directly by this method; instead, the PbSL result represents the bulk age of abundant allanite inclusions observed in the garnet. Thus, 1746 Ma is interpreted as a maximum age of prograde garnet growth during regional thermotectonism. Mineral assemblages from selvages in Main Ledge indicate that mineralization occurred at or after peak metamorph, which indicates that 1746 Ma also represents a maximum age for gold remobilization. A minimum 1715 Ma age of these events is indicated by published ages of post

Carbon-oxygen isotopes and rare earth elements as an exploration vector for Carlin-type gold deposits: A case study of the Shuiyindong gold deposit, Guizhou Province, SW China

NASA Astrophysics Data System (ADS)

Tan, Qin-Ping; Xia, Yong; Wang, Xueqiu; Xie, Zhuo-Jun; Wei, Dong-Tian

2017-10-01

The Shuiyindong gold deposit is a deeply concealed strata-bound Carlin-type deposit in southwestern Guizhou Province, China. The deposit lies on the eastern limb of the Huijiabao anticline with ores mainly along the anticline axis and hosted in bioclastic limestone, containing calcite veins, of the Permian Longtan Formation units. In this study, we measured carbon and oxygen isotopic ratios and rare earth element (REE) concentrations of the host rocks and calcite veins along a profile across the Shuiyindong deposit. Orebodies in the upper unit of the Longtan Formation have higher δ18O values (20.6-22.4‰) and lower δ13C values (-3.7 to -0.5‰) than the country rocks (δ18O: 18.8-21.4‰; δ13C: -0.7 to 0.8‰). However, there are no obvious trends of δ18O and δ13C values from the country rocks to the orebodies in the middle unit of the Longtan Formation. The spatial distribution of the calcite veins displays distinct halos of δ13C and δ18O values and REE concentrations. Calcite veins along the anticlinal axis and major reverse fault are enriched in Middle REE (Sm, Eu, Gd, and Tb) and 18O and depleted in 13C. Surficial veining calcite-filled fractures/faults that connect to deep concealed strata-bound gold mineralization systems can be vectors toward deep ores in southwestern Guizhou Province, China.

The nature of the fluids associated with the Monte Rosa gold district, NW Alps, Italy

NASA Astrophysics Data System (ADS)

Lattanzi, P.

1990-12-01

Recent O-isotope and fluid inclusion studies have provided evidence on the nature of the fluids associated with the late-Alpine quartz-gold deposits of the Monte Rosa district. The most abundant inclusions in quartz from these deposits contain a low salinity aqueous fluid (about 2% to 10% wt. NaCl eq.), and a CO2 phase (usually less than 20% mol), in places with minor methane. CO2 densities and total homogenization temperatures vary widely throughout the district, reflecting diverse conditions of trapping (P = 1 to 3 kb, T = 300° to 450°C). At Miniera dei Cani, unmixing between CO2-rich and H2O-rich fluids possibly occurred. A second type of inclusion contains an aqueous brine without recognizable CO2, and is especially abundant at Val Toppa. O-isotope studies suggest that fluids were largely equilibrated in a metamorphic environment. It is concluded that the gold-related fluids in the district were mainly of a metamorphic nature; at Val Toppa, both isotopic and fluid inclusion data point to contributions of unexchanged meteoric waters. Mechanisms of gold transport and precipitation are less contrained. A possible model involves transport of gold as bisulfide complexes, and precipitation due to one or more of the following processes: decrease of sulfur activity due to precipitation of sulfides, wall-rock reaction, cooling/dilution, and/or fluid unmixing.

Sources of metals in the Porgera gold deposit, Papua New Guinea: Evidence from alteration, isotope, and noble metal geochemistry

NASA Astrophysics Data System (ADS)

Richards, Jeremy P.; McCulloch, Malcolm T.; Chappell, Bruce W.; Kerrich, Robert

1991-02-01

The Porgera gold deposit is spatially and temporally associated with the Late Miocene, mafic, alkalic, epizonal Porgera Intrusive Complex (PIC), located in the highlands of Papua New Guinea (PNG). The highlands region marks the site of a Tertiary age continent-island-arc collision zone, located on the northeastern edge of the Australasian craton. The PIC was emplaced within continental crust near the Lagaip Fault Zone, which represents an Oligocene suture between the craton and volcano-sedimentary rocks of the Sepik terrane. Magmatism at Porgera probably occurred in response to the Late Miocene elimination of an oceanic microplate, and subsequent Early Pliocene collision between the craton margin and an arc system located on the Bismarck Sea plate. Gold mineralization occurred within 1 Ma of the time of magmatism. Metasomatism accompanying early disseminated Au mineralization in igneous host rocks resulted in additions of K, Rb, Mn, S, and CO 2, and depletions of Fe, Mg, Ca, Na, Ba, and Sr; rare-earth and high-field-strength elements remained largely immobile. Pervasive development of illite-K-feldspar-quartz-carbonate alteration assemblages suggests alteration by mildly acidic, 200 to 350°C fluids, at high water/ rock ratios. Strontium and lead isotopic compositions of minerals from early base-metal sulphide veins associated with K-metasomatism, and later quartz-roscoelite veins carrying abundant free gold and tellurides, are remarkably uniform (e.g., 87Sr /86Sr = 0.70745 ± 0.00044 [n = 10] , 207Pb /204Pb = 15.603 ± 0.004 [n = 15] ). These compositions fall between those of unaltered igneous and sedimentary host rocks, and specifically sedimentary rocks from the Jurassic Om Formation which underlies the deposit (igneous rocks: 87Sr /86Sr ≈ 0.7035 , 207Pb /204Pb ≈ 15.560 ; Om Formation: 87Sr /86Sr |t~ 0.7153 , 207Pb /204Pb ≈ 15.636 ). It is therefore suggested that the hydrothermal fluids acquired their Sr and Pb isotopic signatures by interaction with, or

The Niassa Gold Belt, northern Mozambique - A segment of a continental-scale Pan-African gold-bearing structure?

NASA Astrophysics Data System (ADS)

Bjerkgard, T.; Stein, H. J.; Bingen, B.; Henderson, I. H. C.; Sandstad, J. S.; Moniz, A.

2009-01-01

The Niassa Gold Belt, in northernmost Mozambique, is hosted in the Txitonga Group, a Neoproterozoic rift sequence overlying Paleoproterozoic crust of the Congo-Tanzania Craton and deformed during the Pan-African Orogeny. The Txitonga Group is made up of greenschist-facies greywacke and schist and is characterized by bimodal, mainly mafic, magmatism. A zircon U-Pb age for a felsic volcanite dates deposition of the sequence at 714 ± 17 Ma. Gold is mined artisanally from alluvial deposits and primary chalcopyrite-pyrite-bearing quartz veins containing up to 19 ppm Au have been analyzed. In the Cagurué and M'Papa gold fields, dominantly N-S trending quartz veins, hosted in metagabbro and schist, are regarded as tension gashes related to regional strike-slip NE-SW-trending Pan-African shear zones. These gold deposits have been classified as mesozonal and metamorphic in origin. Re-Os isotopic data on sulfides suggest two periods of gold deposition for the Cagurué Gold Field. A coarse-crystalline pyrite-chalcopyrite assemblage yields an imprecise Pan-African age of 483 ± 72 Ma, dating deposition of the quartz veins. Remobilization of early-formed sulfides, particularly chalcopyrite, took place at 112 ± 14 Ma, during Lower Cretaceous Gondwana dispersal. The ˜483 Ma assemblage yields a chondritic initial 187Os/ 188Os ratio of 0.123 ± 0.058. This implies a juvenile source for the ore fluids, possibly involving the hosting Neoproterozoic metagabbro. The Niassa Gold Belt is situated at the eastern end of a SW-NE trending continental-scale lineament defined by the Mwembeshi Shear Zone and the southern end of a NW-SE trending lineament defined by the Rukwa Shear Zone. We offer a review of gold deposits in Zambia and Tanzania associated with these polyphase lineaments and speculate on their interrelation.

Re-Os, Sm-Nd, U-Pb, and stepwise lead leaching isotope systematics in shear-zone hosted gold mineralization: genetic tracing and age constraints of crustal hydrothermal activity

NASA Astrophysics Data System (ADS)

Frei, R.; Nägler, Th. F.; Schönberg, R.; Kramers, J. D.

1998-06-01

A combined Re-Os, Sm-Nd, U-Pb, and stepwise Pb leaching (PbSL) isotope study of hydrothermal (Mo-W)-bearing minerals and base metal sulfides from two adjacent shear zone hosted gold deposits (RAN, Kimberley) in the Harare-Shamva greenstone belt (Zimbabwe) constrain the timing of the mineralizing events to two periods. During an initial Late Archean event (2.60 Ga) a first molybdenite-scheelite bearing paragenesis was deposited in both shear zone systems, followed by a local reactivation of the shear systems during an Early Proterozoic (1.96 Ga) tectono-thermal overprint, during which base metal sulfides and most of the gold was (re-)deposited. While PbSL has revealed an open-system behavior of the U-Pb systematics in molybdenite and wolframite from the RAN mine, initial Archean Re-Os ages are still preserved implying that this system in these minerals was more resistant to the overprint. A similar retentivity could be shown for the Sm-Nd system in scheelite and powellite associated with the above ore minerals. Re-Os isotopic data from the Proterozoic mineralization in the Kimberley mine point to a recent gain of Re, most pronouncedly affecting Fe-rich sulfides such as pyrrhotite. A significant Re-loss in powellitic scheelite (an alteration phase of molybdenite-bearing scheelite), coupled with a marked loss of U in W-Mo ore minerals, complements the observation of a major Re uptake in Fe-sulfides during oxidizing conditions in a weathering environment. Pyrrhotite under these conditions behaves as an efficient Re-sink. Lead isotope signatures from PbSL residues of molybdenite, powellite, and quartz indicate a continental crustal source and/or contamination for the mineralizing fluid by interaction of the fluids with older sedimentary material as represented by the direct host country rocks. Our investigation reveals the potential of the Re-Os isotopic system applied to crustal hydrothermal ore minerals for genetic tracing and dating purposes. The simplified chemical

Paleoproterozoic high-sulfidation mineralization in the Tapajós gold province, Amazonian Craton, Brazil: geology, mineralogy, alunite argon age, and stable-isotope constraints

USGS Publications Warehouse

Juliani, Caetano; Rye, Robert O.; Nunes, Carmen M.D.; Snee, Lawrence W.; Correa, Rafael H.; Monteiro, Lena V.S.; Bettencourt, Jorge S.; Neumann, Rainer; Neto, Arnaldo A.

2005-01-01

The Brazilian Tapajós gold province contains the first evidence of high-sulfidation gold mineralization in the Amazonian Craton. The mineralization appears to be in large nested calderas. The Tapajós–Parima (or Ventuari–Tapajós) geological province consists of a metamorphic, igneous, and sedimentary sequence formed during a 2.10 to 1.87 Ga ocean−continent orogeny. The high-sulfidation mineralization with magmatic-hydrothermal alunite is related to hydrothermal breccias hosted in a rhyolitic volcanic ring complex that contains granitic stocks ranging in age from 1.89 to 1.87 Ga. Cone-shaped hydrothermal breccias, which flare upward, contain vuggy silica and have an overlying brecciated cap of massive silica; the deposits are located in the uppermost part of a ring-structure volcanic cone. Drill cores of one of the hydrothermal breccias contain alunite, natroalunite, pyrophyllite, andalusite, quartz, rutile, diaspore, woodhouseite–svanbergite, kaolinite, and pyrite along with inclusions of enargite–luzonite, chalcopyrite, bornite, and covellite. The siliceous core of this alteration center is surrounded by advanced argillic and argillic alteration zones that grade outward into large areas of propylitically altered rocks with sericitic alteration assemblages at depth. Several occurrences and generations of alunite are observed. Alunite is disseminated in the advanced argillic haloes that envelop massive and vuggy silica or that underlie the brecciated silica cap. Coarse-grained alunite also occurs in branching veins and locally is partly replaced by a later generation of fine-grained alunite. Silicified hydrothermal breccias associated with the alunite contain an estimated reserve of 30 tonnes of gold in rock that grades up to 4.5 g t−1 Au. Seven alunite samples gave 40Ar/39Ar ages of 1.869 to 1.846 Ga, with various degrees of apparent minor Ar loss. Stable isotopic data require a magmatic-hydrothermal origin for the alunite, typical for high

Gold deposits in the Xiaoqinling-Xiong'ershan region, Qinling mountains, central China

USGS Publications Warehouse

Mao, J.; Goldfarb, R.J.; Zhang, Z.; Xu, W.; Qiu, Yumin; Deng, J.

2002-01-01

The gold-rich Xiaoqinling-Xiong'ershan region in eastern Shaanxi and western Henan provinces, central China, lies about 30-50 km inland of the southern margin of the North China craton. More than 100 gold deposits and occurrences are concentrated in the Xiaoqinling (west), Xiaoshan (middle), and Xiong'ershan (east) areas. Late Archean gneiss of the Taihua Group, and Middle Proterozoic metavolcanic rocks of the Xiong'er Group are the main host rocks for the deposits. Mesozoic granitoids (ca. 178-104 Ma) are present in most gold districts, but deposits are typically hosted in the Precambrian basement rocks hundreds of meters to as far as 10 km from the intrusions and related hornfels zones. Deposits in the Xiaoqinling and Xiaoshan areas are best classified as orogenic gold deposits, with ores occurring in a number of distinct belts both in quartz veins and disseminated in altered metamorphic rocks. Alteration assemblages are dominated by quartz, sericite, pyrite, and carbonate minerals. The ore-forming fluids were low salinity, CO2-rich, and characterized by isotopically heavy ??18O. Four deposits (Dongchuang, Wenyu, Yangzhaiyu, and Dahu) in the Xiaoqinling area each contain resources of about 1 Moz Au. Some of the gold deposits in the Xiong'ershan area represent more shallowly emplaced tellurium-enriched orogenic systems, which include resources of approximately 1-1.5 Moz Au at Shanggong and Beiling (or Tantou). Others are epithermal deposits (e.g., Qiyugou and Dianfang) that are hosted in volcanic breccia pipes. Isotopic dates for all gold deposits, although often contradictory, generally cluster between 172-99 Ma and are coeval with emplacement of the post-kinematic granitoids. The gold deposits formed during a period of relaxation of far-field compressional stresses, clearly subsequent to the extensive Paleozoic-early Mesozoic accretion of are terranes and the Yangtze craton onto the southern margin of the North China craton. Hydrothermal and magmatic events

Geochemical and stable isotopic data on barren and mineralized drill core in the Devonian Popovich Formation, Screamer sector of the Betze-Post gold deposit, northern Carlin trend, Nevada

USGS Publications Warehouse

Christiansen, William D.; Hofstra, Albert H.; Zohar, Pamela B.; Tousignant, Gilles

2011-01-01

The Devonian Popovich Formation is the major host for Carlin-type gold deposits in the northern Carlin trend of Nevada. The Popovich is composed of gray to black, thin-bedded, calcareous to dolomitic mudstone and limestone deposited near the carbonate platform margin. Carlin-type gold deposits are Eocene, disseminated, auriferous pyrite deposits characterized by acid leaching, sulfidation, and silicification that are typically hosted in Paleozoic calcareous sedimentary rocks exposed in windows through siliceous sedimentary rocks of the Roberts Mountains allochthon. The Carlin trend currently is the largest gold producer in the United States. The Screamer ore zone is a tabular body on the periphery of the huge Betze-Post gold deposit. Screamer is a good place to study both the original lithogeochemistry of the Popovich Formation and the effects of subsequent alteration and mineralization because it is below the level of supergene oxidation, mostly outside the contact metamorphic aureole of the Jurassic Goldstrike stock, has small, high-grade ore zones along fractures and Jurassic dikes, and has intervening areas with lower grade mineralization and barren rock. In 1997, prior to mining at Screamer, drill core intervals from barren and mineralized Popovich Formation were selected for geochemical and stable isotope analysis. The 332, five-foot core samples analyzed are from five holes separated by as much as 2000 feet (600 meters). The samples extend from the base of the Wispy unit up through the Planar and Soft sediment deformation units into the lower part of the upper Mud unit of the Popovich Formation.

Metamorphism and gold mineralization in the Blue Ridge, Southernmost Appalachians

USGS Publications Warehouse

Stowell, H.H.; Lesher, C.M.; Green, N.L.; Sha, P.; Guthrie, G.M.; Sinha, A.K.

1996-01-01

Lode gold mineralization in the Blue Ridge of the southernmost Appalachians is hosted by metavolcanic rocks (e.g., Anna Howe mine, AL; Royal Vindicator mine, GA), metaplutonic rocks (e.g., Hog Mountain mine, AL), and metasedimentary rocks (e.g., Lowe, Tallapoosa, and Jones Vein mines, AL). Most gold occurs in synkinematic quartz ?? plagioclase ?? pyrite ?? pyrrhotite ?? chlorite veins localized along polydeformational faults that juxtapose rocks with significantly different peak metamorphic mineral assemblages. Mineralogy, chemistry, and O and H isotope studies suggest that the three types of host rocks have undergone differing amounts and types of alteration during mineralization. Limited wall-rock alteration in metavolcanic- and metasediment-hosted deposits, and relatively extensive wall-rock alteration in granitoid-hosted deposits, suggests that most deposits formed from fluids that were close to equilibrium with metavolcanic and metasedimentary rocks. Stable isotope compositions of the fluids calculated from vein minerals and vein selvages are consistent with a predominantly metasedimentary fluid source, but vary from deposit to deposit (-22 to -47??? ??D, 4-5??? ??18O, and 5-7??? ??34S at Anna Howe and Royal Vindicator; -48 to -50??? ??D, 9-13??? ??18O, and ca. 19??? ??34S at Lowe and Jones Vein; and -22 to -23??? ??D, 8-11??? ??18O, 9-10??? ??34S, and -6 ??13C at Hog Mountain). Silicate mineral thermobarometry of vein, vein selvage, and wall-rock mineral assemblages indicate that mineralization and regional metamorphism occured at greenschist to amphibolite facies (480?? ?? 75??C at Anna Howe, 535?? ?? 50??C at 6.4 ?? 1 kbars at Lowe, 530?? ?? 50??C at 6.9 ?? 1 kbars at Tallapoosa, and 460?? ?? 50??C at 5.5 ?? 1 kbars at Hog Mountain). Oxygen isotope fractionation between vein minerals and selvage minerals consistently records equilibration temperatures that are similar to or slightly lower than those estimated from silicate thermometry. Auriferous veins

An investigation of mercury sources in the Puyango-Tumbes River: Using stable Hg isotopes to characterize transboundary Hg pollution.

PubMed

Schudel, Gary; Miserendino, Rebecca Adler; Veiga, Marcello M; Velasquez-López, P Colon; Lees, Peter S J; Winland-Gaetz, Sean; Davée Guimarães, Jean Remy; Bergquist, Bridget A

2018-07-01

Mercury (Hg) concentrations and stable isotopes along with other trace metals were examined in environmental samples from Ecuador and Peru's shared Puyango-Tumbes River in order to determine the extent to which artisanal- and small-scale gold mining (ASGM) in Portovelo-Zaruma, Ecuador contributes to Hg pollution in the downstream aquatic ecosystem. Prior studies investigated the relationship between ASGM activities and downstream Hg pollution relying primarily on Hg concentration data. In this study, Hg isotopes revealed an isotopically heavy Hg signature with negligible mass independent fractionation (MIF) in downstream sediments, which was consistent with the signature observed in the ASGM source endmember. This signature was traced as far as ∼120 km downstream of Portovelo-Zaruma, demonstrating that Hg stable isotopes can be used as a tool to fingerprint and trace sources of Hg over vast distances in freshwater environments. The success of Hg isotopes as a source tracer in fresh waters is largely due to the particle-reactive nature of Hg. Furthermore, the magnitude and extent of downstream Hg, lead, copper and zinc contamination coupled with the Hg isotopes suggest that it is unlikely that the smaller artisanal-scale activities, which do not use cyanidation, are responsible for the pollution. More likely it is the scale of ores processed and the cyanide leaching, which can release other metals and enhance Hg transport, used during small-scale gold mining that is responsible. Thus, although artisanal- and small-scale gold mining occur in tandem in Portovelo-Zaruma, a distinction should be made between these two activities. Copyright © 2018 Elsevier Ltd. All rights reserved.

Late-Hercynian intrusion-related gold deposits: An integrated model on the Tighza polymetallic district, central Morocco

NASA Astrophysics Data System (ADS)

Éric, Marcoux; Khadija, Nerci; Yannick, Branquet; Claire, Ramboz; Gilles, Ruffet; Jean-Jacques, Peucat; Ross, Stevenson; Michel, Jébrak

2015-07-01

radiogenic isotope studies. Nd and Sr isotope compositions of scheelite and granites suggest the participation of a juvenile component while lead isotopes demonstrate a major participation of the basement. Both gold mineralization and zoning suggest that the system developed at the end of the magmatic activity, accompanying a major transition in magmatic fluid composition. The morphology of the gold-bearing mineralization is dependent of the permeability and the reactivity of host-rocks: focus circulation of fluids through pre-existing tectonic corridors, reactivated by late-Hercynian intrusions favor the formation of large W-type gold veins, while infiltration of fluid within reactive stratigraphic layers gives rise to skarn mineralization. A 40Ar/39Ar date (W1 north vein: 291.8 ± 0.3 Ma) indicates that hydrothermal circulation predates gold and tungsten deposition in open fractures as well as Mine granite emplacement. The W-Au mineralization preceded the onset of a large convective hydrothermal cell around the intrusion that led to the formation of the Pb-Ag-Zn mined veins. The Tighza polymetallic district displays numerous similarities with the R-IRG model that was defined in the American Cordillera, such as thermal and zonation patterns, carbonic hydrothermal fluids and chronology of intrusion and related deposits, but also provides new insight to the R-IRG model such as wide Au-quartz veins instead of sheeted Au-veins, oxidation state of the magma, and Sr-Nd isotopic data. These results establish a major magmatic contribution and discard a direct genetic relationship between gold mineralization and major neighboring Pb-Ag-Zn veins. A large number of classic Pb-Zn district of the Western Hercynides belong to the same clan.

The origin or the Archean Jardine iron formation-hosted lode gold deposit. Montana

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ping, Liu.

1992-06-09

While there is considerable controversy concerning the origin of greenstone-hosted lode gold deposits of Archean age, there is a general consensus that these deposits are epigenetic. By contrast, iron formation-hosted lode gold deposits of Archean or Proterozoic age are considered either epigenetic or syngenetic. At least three genetic models have been proposed for these gold deposits: a syngenetic model involving simultaneous deposition of gold and the iron formation; an epigenetic model involving a later introduction of gold, arsenic, and sulfur into the iron formation; and a multistage model involving primary concentration of gold during deposition of iron formation followed bymore » remobilization and reconcentration of gold during later events. The Jardine district is one of only three Archean lode gold districts in the United States that have reserves of greater than 300,000 ounces of gold. The other two are the South Pass-Atlantic City district, Wyoming, and the Ropes mine, Michigan. The fact that two of the three districts are in the Wyoming province suggests that the province might be an Archean gold province similar to Archean provinces in Canada. Placer gold was discovered near Jardine in 1866, and gold quartz veins were mined in the 1880's at Mineral Hill. Exploration by the Jardine Joint Venture has concentrated on the Jardine area, including Crevasse Mountain, where minor lode gold mineralization occurs in quartz-biotite schists. In order to complement previous geochemical, mineralogical, petrological and structural studies, the present study has concentrated on fluid inclusion, stable isotope, and electron microprobe studies with the intention of determining: (1) the source of the ore-forming fluids and gold, and (2) the genetic relationship between gold mineralization and iron formation, alteration and metamorphism.« less

The origin or the Archean Jardine iron formation-hosted lode gold deposit. Montana

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ping, Liu

1992-06-09

While there is considerable controversy concerning the origin of greenstone-hosted lode gold deposits of Archean age, there is a general consensus that these deposits are epigenetic. By contrast, iron formation-hosted lode gold deposits of Archean or Proterozoic age are considered either epigenetic or syngenetic. At least three genetic models have been proposed for these gold deposits: a syngenetic model involving simultaneous deposition of gold and the iron formation; an epigenetic model involving a later introduction of gold, arsenic, and sulfur into the iron formation; and a multistage model involving primary concentration of gold during deposition of iron formation followed bymore » remobilization and reconcentration of gold during later events. The Jardine district is one of only three Archean lode gold districts in the United States that have reserves of greater than 300,000 ounces of gold. The other two are the South Pass-Atlantic City district, Wyoming, and the Ropes mine, Michigan. The fact that two of the three districts are in the Wyoming province suggests that the province might be an Archean gold province similar to Archean provinces in Canada. Placer gold was discovered near Jardine in 1866, and gold quartz veins were mined in the 1880`s at Mineral Hill. Exploration by the Jardine Joint Venture has concentrated on the Jardine area, including Crevasse Mountain, where minor lode gold mineralization occurs in quartz-biotite schists. In order to complement previous geochemical, mineralogical, petrological and structural studies, the present study has concentrated on fluid inclusion, stable isotope, and electron microprobe studies with the intention of determining: (1) the source of the ore-forming fluids and gold, and (2) the genetic relationship between gold mineralization and iron formation, alteration and metamorphism.« less

Are modern geothermal waters in northwest Nevada forming epithermal gold deposits?

USGS Publications Warehouse

Breit, George N.; Hunt, Andrew G.; Wolf, Ruth E.; Koenig, Alan E.; Fifarek, Richard; Coolbaugh, Mark F.

2010-01-01

Hydrothermal systems currently are active near some gold deposits in northwestern Nevada. Possible links of these modern systems to gold mineralization were evaluated by chemically and isotopically analyzing water samples from the Brady, Dixie Valley, Humboldt House, San Emidio-Empire, Soda Lake, and Wabuska geothermal areas. In addition, quartz veins from Humboldt House and the adjacent Florida Canyon Mine were analyzed to compare ore and gangue phases with those predicted to form from proximal hydrothermal fluids.Nearly all water samples are alkali-chloride-type. Total dissolved solids range from 800 to 3900 mg/L, and pH varies from 5.6 to 7.8. Geochemical modeling with SOLVEQ, WATCH, and CHILLER predict the precipitation of silica in all systems during cooling. Anhydrite, calcite, barite, pyrite, base-metal sulfides, and alumino-silicates are variably saturated at calculated reservoir temperatures and also precipitate during boiling/cooling of some fluids. Measured dissolved gold concentrations are low (<0.2μg/L), but are generally consistent with contents predicted by equilibrium of sampled solutions with elemental gold at reservoir temperatures.  Although the modern geothermal waters can precipitate ore minerals, the low gold and other ore metal concentrations require very large fluid volumes to form a deposit of economic interest.

Bald Mountain gold mining district, Nevada: A Jurassic reduced intrusion-related gold system

USGS Publications Warehouse

Nutt, C.J.; Hofstra, A.H.

2007-01-01

The Bald Mountain mining district has produced about 2 million ounces (Moz) of An. Geologic mapping, field relationships, geochemical data, petrographic observations, fluid inclusion characteristics, and Pb, S, O, and H isotope data indicate that An mineralization was associated with a reduced Jurassic intrusion. Gold deposits are localized within and surrounding a Jurassic (159 Ma) quartz monzonite porphyry pluton and dike complex that intrudes Cambrian to Mississippian carbonate and clastic rocks. The pluton, associated dikes, and An mineralization were controlled by a crustal-scale northwest-trending structure named the Bida trend. Gold deposits are localized by fracture networks in the pluton and the contact metamorphic aureole, dike margins, high-angle faults, and certain strata or shale-limestone contacts in sedimentary rocks. Gold mineralization was accompanied by silicification and phyllic alteration, ??argillic alteration at shallow levels. Although An is typically present throughout, the system exhibits a classic concentric geochemical zonation pattern with Mo, W, Bi, and Cu near the center, Ag, Pb, and Zn at intermediate distances, and As and Sb peripheral to the intrusion. Near the center of the system, micron-sized native An occurs with base metal sulfides and sulfosalts. In peripheral deposits and in later stages of mineralization, Au is typically submicron in size and resides in pyrite or arsenopyrite. Electron microprobe and laser ablation ICP-MS analyses show that arsenopyrite, pyrite, and Bi sulfide minerals contain 10s to 1,000s of ppm Au. Ore-forming fluids were aqueous and carbonic at deep levels and episodically hypersaline at shallow levels due to boiling. The isotopic compositions of H and O in quartz and sericite and S and Pb in sulfides are indicative of magmatic ore fluids with sedimentary sulfur. Together, the evidence suggests that Au was introduced by reduced S-bearing magmatic fluids derived from a reduced intrusion. The reduced

Ore-fluid evolution at the Getchell Carlin-type gold deposit, Nevada, USA

USGS Publications Warehouse

Cline, J.S.; Hofstra, A.A.

2000-01-01

Minerals and fluid-inclusion populations were examined using petrography, microthermometry, quadrupole mass-spectrometer gas analyses and stable-isotope studies to characterize fluids responsible for gold mineralization at the Getchell Carlin-type gold deposit. The gold-ore assemblage at Getchell is superimposed on quartz-pyrite vein mineralization associated with a Late-Cretaceous granodiorite stock that intruded Lower-Paleozoic sedimentary rocks. The ore assemblage, of mid-Tertiary age, consists of disseminated arsenian pyrite that contains submicrometer gold, jasperoid quartz, and later fluorite and orpiment that fill fractures and vugs. Late ore-stage realgar and calcite enclose ore-stage minerals. Pre-ore quartz trapped fluids with a wide range of salinities (1 to 21 wt.% NaCl equivalent), gas compositions (H2O, CO2, and CH4), and temperatures (120 to >360??C). Oxygen- and hydrogen-isotope ratios indicate that pre-ore fluids likely had a magmatic source, and were associated with intrusion of the granodiorite stock and related dikes. Ore-stage jasperoid contains moderate salinity, aqueous fluid inclusions trapped at 180 to 220??C. Ore fluids contain minor CO2 and trace H2S that allowed the fluid to react with limestone host rocks and transport gold, respectively. Aqueous inclusions in fluorite indicate that fluid temperatures declined to ~175??C by the end of ore-stage mineralization. As the hydrothermal system collapsed, fluid temperatures declined to 155 to 115??C and realgar and calcite precipitated. Inclusion fluids in ore-stage minerals have high ??D(H2O) and ??18O(H2O) values that indicate that the fluid had a deep source, and had a metamorphic or magmatic origin, or both. Late ore-stage fluids extend to lower ??D(H2O) values, and have a wider range of ??18O(H2O) values suggesting dilution by variably exchanged meteoric waters. Results show that deeply sourced ore fluids rose along the Getchell fault system, where they dissolved carbonate wall rocks and

Native gold and gold-rich sulfide deposits in a submarine basaltic caldera, Higashi-Aogashima hydrothermal field, Izu-Ogasawara frontal arc, Japan

NASA Astrophysics Data System (ADS)

Iizasa, Kokichi; Asada, Akira; Mizuno, Katsunori; Katase, Fuyuki; Lee, Sangkyun; Kojima, Mitsuhiro; Ogawa, Nobuhiro

2018-04-01

Sulfide deposits with extremely high Au concentrations (up to 275 ppm; avg. 102 ppm, n = 15), high Au/Ag ratios (0.24, n = 15), and low Cu/(Cu + Zn) ratios (0.03, n = 15) were discovered in 2015 in active hydrothermal fields at a water depth of 760 m in a basalt-dominated submarine caldera in the Izu-Ogasawara frontal arc, Japan. Native gold grains occur in massive sulfide fragments, concretions, and metalliferous sediments from a sulfide mound (40 m across and 20 m high) with up to 30-m-high black smoker chimneys. Tiny native gold grains up to 14 μm in diameter are mainly present in sulfide fallouts from chimney orifices and plumes. Larger native gold grains up to 150 μm long occur mostly as discrete particles and/or with amorphous silica and sulfides. The larger gold grains are interpreted to represent direct precipitation from Au-bearing hydrothermal fluids circulating in and/or beneath the unconsolidated sulfide mound deposits. Sulfur isotope compositions from a limited number of sulfide separates (n = 4) range from 4.3 to 5.8‰ δ34S, similar to the quaternary volcanic rocks of the arc. Barite separates have values of 22.2 and 23.1‰, close to modern seawater values, and indicate probable seawater sulfate origin. The Cu, Zn, and Pb concentrations in bulk samples of sulfide-rich rocks are similar to those of volcanogenic massive sulfides formed in continental crustal environments. The gold is interpreted to have formed by low-temperature hydrothermal activity, perhaps genetically different from systems with documented magmatic contributions or from seafloor hydrothermal systems in other island arc settings. Its presence suggests that basalt-dominated submarine calderas situated on relatively thick continental crust in an intraoceanic arc setting such as the Higashi-Aogashima knoll caldera may be perspective for gold mineralization.

Spatial-temporal and genetic relationships between gold and antimony mineralization at gold-sulfide deposits of the Ob-Zaisan folded zone

NASA Astrophysics Data System (ADS)

Kalinin, Yu. A.; Naumov, E. A.; Borisenko, A. S.; Kovalev, K. R.; Antropova, A. I.

2015-05-01

The Ob-Zaisan folded zone is a fragment of a single structure composed of Paleozoic sedimentary and volcanogenic rocks (mainly black shale), which was formed at the margin of the Siberian continent and features a common set of magmatic complexes and mineral systems. However, there are some differences that determine the specific geological and metallogenic features of the Irtysh-Zaisan and Kolyvan-Tomsk fragments of the Ob-Zaisan folded zone. In the gold deposits of the West Kalba and Kolyvan-Tomsk auriferous belt, the main gold-sulfide mineralization is controlled by zones of shearing and dynamic metamorphism in carbonaceous carbonate-terrigenous rocks. This type of mineralization was formed in tectonic blocks in a compressional setting. Antimony mineralization is characterized by brecciated textures and the vein-like morphology of ore bodies, reflecting extensional tectonics. At some deposits (Zherek, Mirazh, Dalny), Sb mineralization is spatially separated from the main gold-sulfide ores and shows cross-cutting relations to the principal ore-controlling structures. In other gold deposits, stibnite is spatially associated with disseminated gold-sulfide ores and forms mineral assemblages with Ni, Co, Au, Pb, and Fe (Alimbet, Zhanan, Legostaevskoe, Semiluzhenskoe, and Kamenskoe deposits). This study reveals no direct correlation between Au and Sb in gold-sulfide ores of these deposits. SEM analysis indicated the absence of free gold in stibnite veins. However, atomic absorption and electron microprobe analysis indicated the presence of "invisible gold" from a few ppm to several tens of ppm in the stibnite. High gold contents in the gold-sulfide ores overprinted by antimony mineralization (Suzdalskoe, Zhanan, and Legostaevskoe deposits) can be explained by the processes of regeneration and redeposition. The results of microstructural observations, isotope geochronology, studies of mineral assemblages and fluid inclusions in the ores from gold deposits of the Ob

Disseminated gold-sulfide mineralization at the Zhaima deposit, eastern Kazakhstan

NASA Astrophysics Data System (ADS)

Kovalev, K. R.; Kuzmina, O. N.; Dyachkov, B. A.; Vladimirov, A. G.; Kalinin, Yu. A.; Naumov, E. A.; Kirillov, M. V.; Annikova, I. Yu.

2016-03-01

The Zhaima gold-sulfide deposit is located in the northwestern part of the West Kalba gold belt in eastern Kazakhstan. The mineralization is hosted in Lower Carboniferous volcanic and carbonate rocks formed under conditions of marginal-sea and island-arc volcanic activity. The paper considers the mineralogy and geochemistry of primary gold-sulfide ore and Au-bearing weathering crusts. Au-bearing arsenopyrite-pyrite mineralization formed during only one productive stage. Disseminated, stringer-disseminated, and massive rocks are enriched in Ti, Cr, V, Cu, and Ni, which correspond to the mafic profile of basement. The main ores minerals are represented by finely acicular arsenopyrite containing Au (up to few tens of ppm) and cubic and pentagonal dodecahedral pyrite with sporadic submicroscopic inclusions of native gold. The sulfur isotopic composition of sulfides is close to that of the meteoritic standard (δ34S =-0.2 to +0.2). The 40Ar/39Ar age of three sericite samples from ore veinlets corresponds to the Early Permian: 279 ± 3.3, 275.6 ± 2.9, and 272.2 ± 2.9 Ma. The mantle source of sulfur, ore geochemistry, and spatial compatibility of mineralization with basic dikes allow us to speak about the existence of deep fluid-magmatic systems apparently conjugate with the Tarim plume.

Greenstone-hosted lode-gold mineralization at Dungash mine, Eastern Desert, Egypt

NASA Astrophysics Data System (ADS)

Zoheir, Basem; Weihed, Pär

2014-11-01

The auriferous quartz ± carbonate veins at Dungash mine, central Eastern Desert of Egypt, are confined to ∼E-trending dilation zones within variably foliated/sheared metavolcanic/volcaniclastic rocks. The vein morphology and internal structures demonstrate formation concurrent with a dextral shear system. The latter is attributed to flexural displacement of folded, heterogeneous rock blocks through transpression increment, late in the Neoproterozoic deformation history of the area. Geochemistry of the host metavolcanic/metavolcaniclastic rocks from the mine area suggests derivation from a low-K, calc-alkaline magma in a subduction-related, volcanic arc setting. In addition, chemistry of disseminated Cr-spinels further constrain on the back-arc basin setting and low-grade metamorphism, typical of gold-hosting greenstone belts elsewhere. Mineralogy of the mineralized veins includes an early assemblage of arsenopyrite-As-pyrite-gersdorffite ± pyrrhotite, a transitional pyrite-Sb-arsenopyrite ± gersdorffite assemblage, and a late tetrahedrite-chalcopyrite-sphalerite-galena-gold assemblage. Based on arsenopyrite and chlorite geothermometers, formation of gold-sulfide mineralization occurred between ∼365 and 280 °C. LA-ICP-MS measurements indicate the presence of refractory Au in arsenian pyrite (up to 53 ppm) and Sb-bearing arsenopyrite (up to 974 ppm). Abundant free-milling gold associated with the late sulfide assemblage may have been mobilized and re-distributed by circulating, lower temperature ore fluids in the waning stages of the hydrothermal system. Based on the isotopic values of vein quartz and carbonate, the calculated average δ18OH2O values of the ore fluids are 5.0 ± 1.4‰ SMOW for quartz, and 3.3 ± 1.4‰ for vein carbonate. The measured carbonate δ13C values correspond to ore fluids with δ13CCO2 = -6.7 ± 0.7‰ PDB. These results suggest a mainly metamorphic source for ore fluids, in good agreement with the vein morphology, textures and

Granitoid-associated gold mineralization in Egypt: a case study from the Atalla mine

NASA Astrophysics Data System (ADS)

Zoheir, Basem; Deshesh, Fatma; Broman, Curt; Pitcairn, Iain; El-Metwally, Ahmed; Mashaal, Shabaan

2018-06-01

Gold-bearing sulfide-quartz veins cutting mainly through the Atalla monzogranite intrusion in the Eastern Desert of Egypt are controlled by subparallel NE-trending brittle shear zones. These veins are associated with pervasive sericite-altered, silicified, and ferruginated rocks. The hosting shear zones are presumed as high-order structures of the Najd-style faults in the Central Eastern Desert ( 615-585 Ma). Ore minerals include an early pyrite-arsenopyrite (±pyrrhotite) mineralization, partly replaced by a late pyrite-galena-sphalerite-chalcopyrite (±gold/electrum ± tetrahedrite ± hessite) assemblage. Gold occurs as small inclusions in pyrite and arsenopyrite, or more commonly as intergrowths with galena and sphalerite/tetrahedrite in microfractures. Arsenopyrite geothermometry suggests formation of the early Fe-As-sulfide mineralization at 380-340 °C, while conditions of deposition of the late base metal-gold assemblage are assumed to be below 300 °C. Rare hessite, electrum, and Bi-galena are associated with sphalerite and gold in the late assemblage. The early and late sulfide minerals show consistently a narrow range of δ34S ‰ (3.4-6.5) that overlaps with sulfur isotopic values in ophiolitic rocks. The Au-quartz veins are characterized by abundant CO2 and H2O ± CO2 ± NaCl inclusions, where three-dimensional clusters of inclusions show variable aqueous/carbonic proportions and broad range of total (bimodal) homogenization temperatures. Heterogeneous entrapment of immiscible fluids is interpreted to be caused by unmixing of an originally homogenous, low salinity ( 2 eq. mass % NaCl) aqueous-carbonic fluid, during transition from lithostatic to hydrostatic conditions. Gold deposition occurred generally under mesothermal conditions, i.e., 1.3 kbar and 280 °C, and continued during system cooling to < 200 °C and pressure decrease to 0.1 kbar. Based on the vein textures, sulfur isotope values, composition of ore fluids, and conditions of ore formation

Production of platinum radioisotopes at Brookhaven Linac Isotope Producer (BLIP)

DOE PAGES

Smith, Suzanne V.; Mccutchan, Elizabeth; Gurdal, Gulhan; ...

2017-09-13

The accelerator production of platinum isotopes was investigated at the Brookhaven Linac Isotope Producer (BLIP). In this paper high purity natural platinum foils were irradiated at 53.2, 65.7, 105.2, 151.9, 162.9 and 173.3 MeV. The irradiated foils were digested in aqua regia and then converted to their hydrochloride salt with concentrated hydrochloric acid before analyzing by gamma spectrometry periodically for at least 10 days post end of bombardment. A wide range of platinum (Pt), gold (Au) and iridiu m (Ir) isotopes were identified. Effective cross sections at BLIP for Pt-188, Pt-189, Pt-191 and Pt-195m were compared to literature and theoreticalmore » cross sections determined using Empire-3.2. The majority of the effective cross sections (<70 MeV) confirm those reported in the literature. While the absolute values of the theoretical cross sections were up to a factor of 3 lower, Empire 3.2 modeled thresholds and maxima correlated well with experimental values. Preliminary evaluation into a rapid separation of Pt isotopes from high levels of Ir and Au isotopes proved to be a promising approach for large scale production. In conclusion, this study demonstrated that with the use of isotopically enriched target material accelerator production of selected platinum isotopes is feasible over a wide proton energy range.« less

Production of platinum radioisotopes at Brookhaven Linac Isotope Producer (BLIP)

NASA Astrophysics Data System (ADS)

Smith, Suzanne V.; McCutchan, Elizabeth; Gürdal, Gülhan; Lister, Christopher; Muench, Lisa; Nino, Michael; Sonzogni, Alexandro; Herman, Michal; Nobre, Gustavo; Cullen, Chris; Chillery, Thomas; Chowdury, Partha; Harding, Robert

2017-09-01

The accelerator production of platinum isotopes was investigated at the Brookhaven Linac Isotope Producer (BLIP). In this study high purity natural platinum foils were irradiated at 53.2, 65.7, 105.2, 151.9, 162.9 and 173.3.MeV. The irradiated foils were digested in aqua regia and then converted to their hydrochloride salt with concentrated hydrochloric acid before analyzing by gamma spectrometry periodically for at least 10 days post end of bombardment. A wide range of platinum (Pt), gold (Au) and iridium (Ir) isotopes were identified. Effective cross sections at BLIP for Pt-188, Pt-189, Pt-191 and Pt-195m were compared to literature and theoretical cross sections determined using Empire-3.2. The majority of the effective cross sections (<70 MeV) confirm those reported in the literature. While the absolute values of the theoretical cross sections were up to a factor of 3 lower, Empire 3.2 modeled thresholds and maxima correlated well with experimental values. Preliminary evaluation into a rapid separation of Pt isotopes from high levels of Ir and Au isotopes proved to be a promising approach for large scale production. In conclusion, this study demonstrated that with the use of isotopically enriched target material accelerator production of selected platinum isotopes is feasible over a wide proton energy range.

Synthesis of gold structures by gold-binding peptide governed by concentration of gold ion and peptide.

PubMed

Kim, Jungok; Kim, Dong-Hun; Lee, Sylvia J; Rheem, Youngwoo; Myung, Nosang V; Hur, Hor-Gil

2016-08-01

Although biological synthesis methods for the production of gold structures by microorganisms, plant extracts, proteins, and peptide have recently been introduced, there have been few reports pertaining to controlling their size and morphology. The gold ion and peptide concentrations affected on the size and uniformity of gold plates by a gold-binding peptide Midas-11. The higher concentration of gold ions produced a larger size of gold structures reached 125.5 μm, but an increased amount of Midas-11 produced a smaller size of gold platelets and increased the yield percentage of polygonal gold particles rather than platelets. The mechanisms governing factors controlling the production of gold structures were primarily related to nucleation and growth. These results indicate that the synthesis of gold architectures can be controlled by newly isolated and substituted peptides under different reaction conditions.

Helium, neon, and argon composition of the solar wind as recorded in gold and other Genesis collector materials

NASA Astrophysics Data System (ADS)

Pepin, Robert O.; Schlutter, Dennis J.; Becker, Richard H.; Reisenfeld, Daniel B.

2012-07-01

We report compositions and fluxes of light noble gases in the solar wind (SW), extracted by stepped pyrolysis and amalgamation from gold collector materials carried on the Genesis Solar Wind Sample Return Mission. Results are compared with data from other laboratories on SW-He, Ne and Ar distributions implanted in Genesis aluminum, carbon, and silicon collectors and extracted by laser ablation. Corrections for mass-dependent losses (“backscatter”) of impinging SW ions due to scattering from the collector material are substantially larger for gold than for these lower atomic weight targets. We assess such losses by SRIM simulation calculations of SW backscatter from gold which are applied to the measurements to recover the composition of the incident SW. Averaged results of integrated stepped pyrolysis and single-step amalgamation measurements, with 1σ errors, are as follows: for SW-Ne and Ar isotope ratios (3He/4He was not measured), 20Ne/22Ne = 14.001 ± 0.042, 21Ne/22Ne = 0.03361 ± 0.00018, 36Ar/38Ar = 5.501 ± 0.014; for SW element ratios, 4He/20Ne = 641 ± 15, 20Ne/36Ar = 51.6 ± 0.5; and for SW fluxes in atoms cm-2 s-1 at the Genesis L1 station, 4He = 1.14 ± 0.04 × 107, 20Ne = 1.80 ± 0.06 × 104, 36Ar = 3.58 ± 0.11 × 102. Except for the 21Ne/22Ne and 20Ne/36Ar ratios, these values are in reasonable accord (within ∼1-3σ) with measurements on different collector materials reported by one or both of two other Genesis noble gas research groups. We further find, in three stepped pyrolysis experiments on gold foil, that He, Ne and Ar are released at increasing temperatures without elemental fractionation, in contrast to a pyrolytic extraction of a single non-gold collector (Al) where the release patterns point to mass-dependent thermal diffusion. The pyrolyzed gold foils exhibit enhancements, relative to sample totals, in 20Ne/22Ne and 21Ne/22Ne ratios evolved at low temperatures. The absence of elemental fractionation in pyrolytic release from gold

APPARATUS AND TECHNIC FOR THE ADMINISTRATION OF INTRACAVITARY RADIOACTIVE ISOTOPES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michaud, N.J.; Liegner, L.M.

1961-08-01

The method of administration of radioactive isotopes in the treatment of pleural effusions and ascites associated with cancer will vary according to the therapeutic technic. A procedure with a suitable apparatus that utilizes an economical and sterile disposable package is described. The radioactive isotope, whether colloidal chromic phosphate (P/sup 32/) or colloidal gold (Au/sup 198/), can be obtained in th e exact amount prescribed. The entire apparatus is assembled within a few minutes under sterile conditions. Before the hypodermic needles are inserted into the radioactive isotope vial, the air is removed from the tubing by the flow of saline inmore » each segment. Each section is then clamped. The shielded radioactive isotope is then placed on a table or stand and the rubber seal of the vial is swabbed with alcohol or iodine. The inflow needle is inserted just through the rubber stopper and the outflow needle is inserted to the bottom of the vial. This procedure is carried out without removing the vial from the lead container. (auth)« less

Magmatic-hydrothermal origin of the early Triassic Laodou lode gold deposit in the Xiahe-Hezuo district, West Qinling orogen, China: implications for gold metallogeny

NASA Astrophysics Data System (ADS)

Jin, Xiao-ye; Li, Jian-wei; Hofstra, Albert H.; Sui, Ji-xiang

2017-08-01

-sulfide-tourmaline veins have relatively homogeneous lead isotopic compositions, compatible with granitic intrusions in the district. The geochronological and isotopic data combined support a magmatic origin for the Laodou gold deposit, most likely formed from fluids exsolved from the Laodou quartz diorite porphyry or associated intrusive phases at deeper levels beneath the stock. Orogenic and Carlin-like gold deposits in the West Qinling orogen have been commonly thought to have formed from metamorphic fluids. This study, however, highlights the role of magmatic-derived fluids in the formation of lode gold deposits. Synthesis of geochronological, geological, and geochemical data on magmatic rocks and ore deposits in and surrounding the Xiahe-Hezuo district indicates that gold mineralization predominantly occurred within a subduction-related magmatic arc prior to collision between the Yangtze and North China cratons that produced the West Qinling orogen.

Gold Rush!

ERIC Educational Resources Information Center

Brahier, Daniel J.

1997-01-01

Describes a mathematical investigation of gold--how it is weighed, stored, used, and valued. For grades 3-4, children estimate the value of treasure chests filled with gold coins and explore the size and weight of gold bars. Children in grades 5-6 explore how gold is mined and used, and how the value of gold changes over time. (PVD)

Arkachan: A new gold-bismuth-siderite-sulfide type of deposits in the West Verkhoyansky tin district, Yakutia

NASA Astrophysics Data System (ADS)

Gamyanin, G. N.; Vikent'eva, O. V.; Prokof'ev, V. Yu.; Bortnikov, N. S.

2015-11-01

The formation sequence of orebodies, chemical composition of gangue and ore minerals, fluid inclusions, REE patterns, 40Ar/39Ar isotopic age, and relationships of stable isotopes (C, O, S) in minerals of the Arkachan gold-bismuth-siderite-sulfide deposit have been studied. The deposit has been localized in the Kuranakh Anticlinorium of the Verkhoyansky Fold-Nappe Belt at the intersection of the near-meridional Kygyltas and the NE-trending North Tirekhtyakh faults. The orebodies are extended (>2 km) and steeply dipping zones of veins and veinlets are hosted in Carbonaceous and Permian sandstones and siltstones deformed in anticlines and cut through by dikes pertaining to diorite-granodiorite-granite association. The deposit was formed during hydrothermal-metamorphic, productive main gold, silver-polymetallic, and silver-antimony stages. The orebodies are largely composed of quartz and siderite; arsenopyrite, pyrite, and pyrrhotite are widespread; bismuthinite, chalcopyrite, sphalerite, galena, and bismuth sulfosalts (gustavite, cosalite, matildite) are less abundant. The REE patterns of carbonates and quartz are characterized by a negative Eu anomaly. Three types of fluid inclusions (FI) in quartz and carbonates are distinguished: (I) liquid H2O + CO2 ± CH4 + NaCl, (II) gaseous CO2 ± CH4, and (III) aqueous salt solutions. The homogenization temperature and salinity of FI I vary from 385 to 280°C and 18.8 to 26.2 wt % NaCl equiv, respectively, whereas in FI III these parameters vary from 261 to 324°C and 3.7 to 9.5 wt % NaCl equiv. The pressure is estimated at 1830 to 1060 bar. The δ18O of quartz II associated with siderite I, native gold, and sulfosalts changes from +13.6 to 16.3‰(SMOW); δ18O and δ13C of siderite I related to gold-ore stage vary from +13.6 to +17.7‰ (SMOW) and from-6.0 to-3.0 (PDB). A wide range of δ34S from-5.7 to 16.0‰ (CDT) has been obtained for sulfides. The isotopic 40Ar/39Ar age of muscovite is 101.9 ± 1.4 Ma. The isotopic

Gold

USGS Publications Warehouse

Kirkemo, Harold; Newman, William L.; Ashley, Roger P.

1998-01-01

Through the ages, men and women have cherished gold, and many have had a compelling desire to amass great quantities of it -- so compelling a desire, in fact, that the frantic need to seek and hoard gold has been aptly named "gold fever." Gold was among the first metals to be mined because it commonly occurs in its native form -- that is, not combined with other elements -- because it is beautiful and imperishable, and because exquisite objects can be made from it.

Gold in minerals and the composition of native gold

USGS Publications Warehouse

Jones, Robert Sprague; Fleischer, Michael

1969-01-01

Gold occurs in nature mainly as the metal and as various alloys. It forms complete series of solid solutions with silver, copper, nickel, palladium, and platinum. In association with the platinum metals, gold occurs as free gold as well as in solid solution. The native elements contain the most gold, followed by the sulfide minerals. Several gold tellurides are known, but no gold selenides have been reported, and only one sulfide, the telluride-sulfide mineral nagyagite, is known. The nonmetallic minerals carry the least gold, and the light-colored minerals generally contain less gold than the dark minerals. Some conclusions in the literature are conflicting in regard to the relation of fineness of native gold to its position laterally and vertically within a lode, the nature of the country rocks, and the location and size of nuggets in a streambed, as well as to the variation of fineness within an individual nugget.

Derivatized gold clusters and antibody-gold cluster conjugates

DOEpatents

Hainfeld, James F.; Furuya, Frederic R.

1994-11-01

Antibody- or antibody fragment-gold cluster conjugates are shown wherein the conjugate size can be as small as 5.0 nm. Methods and reagents are disclosed in which antibodies, Fab' or F(ab').sub.2 fragments thereof are covalently bound to a stable cluster of gold atoms. The gold clusters may contain 6, 8, 9, 11, 13, 55 or 67 gold atoms in their inner core. The clusters may also contain radioactive gold. The antibody-cluster conjugates are useful in electron microscopy applications as well as in clinical applications that include imaging, diagnosis and therapy.

Production of stable isotope-labeled acyl-coenzyme A thioesters by yeast stable isotope labeling by essential nutrients in cell culture

PubMed Central

Snyder, Nathaniel W.; Tombline, Gregory; Worth, Andrew J.; Parry, Robert C.; Silvers, Jacob A.; Gillespie, Kevin P.; Basu, Sankha S.; Millen, Jonathan; Goldfarb, David S.; Blair, Ian A.

2015-01-01

Acyl-coenzyme A (CoA) thioesters are key metabolites in numerous anabolic and catabolic pathways, including fatty acid biosynthesis and β-oxidation, the Krebs cycle, and cholesterol and isoprenoid biosynthesis. Stable isotope dilution-based methodology is the gold standard for quantitative analyses by mass spectrometry. However, chemical synthesis of families of stable isotope labeled metabolites such as acyl-coenzyme A thioesters is impractical. Previously, we biosynthetically generated a library of stable isotope internal standard analogs of acyl-CoA thioesters by exploiting the essential requirement in mammals and insects for pantothenic acid (vitamin B5) as a metabolic precursor for the CoA backbone. By replacing pantothenic acid in the cell media with commercially available [13C3 15N1]-pantothenic acid, mammalian cells exclusively incorporated [13C3 15N1]-pantothenate into the biosynthesis of acyl-CoA and acyl-CoA thioesters. We have now developed a much more efficient method for generating stable isotope labeled CoA and acyl-CoAs from [13C3 15N1]-pantothenate using Stable Isotope Labeling by Essential nutrients in Cell culture (SILEC) in Pan6 deficient yeast cells. Efficiency and consistency of labeling were also increased, likely due to the stringently defined and reproducible conditions used for yeast culture. The yeast SILEC method greatly enhances the ease of use and accessibility of labeled CoA thioesters and also provides proof-of-concept for generating other labeled metabolites in yeast mutants. PMID:25572876

Derivatized gold clusters and antibody-gold cluster conjugates

DOEpatents

Hainfeld, J.F.; Furuya, F.R.

1994-11-01

Antibody- or antibody fragment-gold cluster conjugates are shown wherein the conjugate size can be as small as 5.0 nm. Methods and reagents are disclosed in which antibodies, Fab' or F(ab')[sub 2] fragments are covalently bound to a stable cluster of gold atoms. The gold clusters may contain 6, 8, 9, 11, 13, 55 or 67 gold atoms in their inner core. The clusters may also contain radioactive gold. The antibody-cluster conjugates are useful in electron microscopy applications as well as in clinical applications that include imaging, diagnosis and therapy. 7 figs.

Not All That Glitters is Gold: Gold Imitations in History.

PubMed

Karpenko, Vladimír

2007-07-01

When gold became considered as a precious metal for decorative purposes and later for coinage, attempts at producing imitations soon began to appear. There were two motives behind this activity: to make a metal that could pass as gold, and to quite openly imitate this precious metal for people who could not afford true gold. Imitation gold was produced by metallurgists, and later also by alchemists. This paper is about gold imitations that did not contain any precious metal. Gold-like alloys of silver are thus excluded. An attempt is further undertaken to classify into separate groups the various gold imitations that have appeared in different cultures throughout time, with an emphasis on brass as a typical imitation of gold.

Phage based green chemistry for gold ion reduction and gold retrieval.

PubMed

Setyawati, Magdiel I; Xie, Jianping; Leong, David T

2014-01-22

The gold mining industry has taken its toll on the environment, triggering the development of more environmentally benign processes to alleviate the waste load release. Here, we demonstrate the use of bacteriophages (phages) for biosorption and bioreduction of gold ions from aqueous solution, which potentially can be applied to remediate gold ions from gold mining waste effluent. Phage has shown a remarkably efficient sorption of gold ions with a maximum gold adsorption capacity of 571 mg gold/g dry weight phage. The product of this phage mediated process is gold nanocrystals with the size of 30-630 nm. Biosorption and bioreduction processes are mediated by the ionic and covalent interaction between gold ions and the reducing groups on the phage protein coat. The strategy offers a simple, ecofriendly and feasible option to recover of gold ions to form readily recoverable products of gold nanoparticles within 24 h.

31 CFR 100.4 - Gold coin and gold certificates in general.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 31 Money and Finance: Treasury 1 2011-07-01 2011-07-01 false Gold coin and gold certificates in... MONETARY OFFICES, DEPARTMENT OF THE TREASURY EXCHANGE OF PAPER CURRENCY AND COIN In General § 100.4 Gold coin and gold certificates in general. Gold coins, and gold certificates of the type issued before...

31 CFR 100.4 - Gold coin and gold certificates in general.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 31 Money and Finance: Treasury 1 2013-07-01 2013-07-01 false Gold coin and gold certificates in... MONETARY OFFICES, DEPARTMENT OF THE TREASURY EXCHANGE OF PAPER CURRENCY AND COIN In General § 100.4 Gold coin and gold certificates in general. Gold coins, and gold certificates of the type issued before...

31 CFR 100.4 - Gold coin and gold certificates in general.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 31 Money and Finance: Treasury 1 2012-07-01 2012-07-01 false Gold coin and gold certificates in... MONETARY OFFICES, DEPARTMENT OF THE TREASURY EXCHANGE OF PAPER CURRENCY AND COIN In General § 100.4 Gold coin and gold certificates in general. Gold coins, and gold certificates of the type issued before...

31 CFR 100.4 - Gold coin and gold certificates in general.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 31 Money and Finance: Treasury 1 2014-07-01 2014-07-01 false Gold coin and gold certificates in... MONETARY OFFICES, DEPARTMENT OF THE TREASURY EXCHANGE OF PAPER CURRENCY AND COIN In General § 100.4 Gold coin and gold certificates in general. Gold coins, and gold certificates of the type issued before...

31 CFR 100.4 - Gold coin and gold certificates in general.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Gold coin and gold certificates in... EXCHANGE OF PAPER CURRENCY AND COIN In General § 100.4 Gold coin and gold certificates in general. Gold coins, and gold certificates of the type issued before January 30, 1934, are exchangeable, as provided...

Gold and gold working in Late Bronze Age Northern Greece.

PubMed

Vavelidis, M; Andreou, S

2008-04-01

Numerous objects of gold displaying an impressive variety of types and manufacturing techniques are known from the Late Bronze Age (LBA) contexts of Mycenaean Greece, but very little is known about the origin and processing of gold during the second millennium B.C: . Ancient literature and recent research indicate that northern Greece is probably the richest gold-bearing region in Greece, and yet, very little evidence exists regarding the exploitation of its deposits and the production as well as use of gold in the area during prehistory. The unusual find of a group of small stone crucibles at the prehistoric settlement of Thessaloniki Toumba, one with visible traces of gold melting, proves local production and offers a rare opportunity to examine the process of on-site gold working. Furthermore, the comparison of the chemical composition of prehistoric artefacts from two settlements with those of gold deposits in their immediate areas supports the local extraction of gold and opens up the prospect for some of the Mycenaean gold to have originated in northern Greece. The scarcity of gold items in northern Greek LBA contexts may not represent the actual amount of gold produced and consumed, but could be a result of the local social attitudes towards the circulation and deposition of artefacts from precious metals.

Gold and gold working in Late Bronze Age Northern Greece

NASA Astrophysics Data System (ADS)

Vavelidis, M.; Andreou, S.

2008-04-01

Numerous objects of gold displaying an impressive variety of types and manufacturing techniques are known from the Late Bronze Age (LBA) contexts of Mycenaean Greece, but very little is known about the origin and processing of gold during the second millennium b.c. Ancient literature and recent research indicate that northern Greece is probably the richest gold-bearing region in Greece, and yet, very little evidence exists regarding the exploitation of its deposits and the production as well as use of gold in the area during prehistory. The unusual find of a group of small stone crucibles at the prehistoric settlement of Thessaloniki Toumba, one with visible traces of gold melting, proves local production and offers a rare opportunity to examine the process of on-site gold working. Furthermore, the comparison of the chemical composition of prehistoric artefacts from two settlements with those of gold deposits in their immediate areas supports the local extraction of gold and opens up the prospect for some of the Mycenaean gold to have originated in northern Greece. The scarcity of gold items in northern Greek LBA contexts may not represent the actual amount of gold produced and consumed, but could be a result of the local social attitudes towards the circulation and deposition of artefacts from precious metals.

Lead isotope compositions as guides to early gold mineralization: The North Amethyst vein system, Creede district, Colorado

USGS Publications Warehouse

Foley, Nora K.; Ayuso, Robert A.

1994-01-01

Pb isotope compositions from the late stage of the North Amethyst vein system and from the Bondholder and central and southern Creede mining districts are more radiogenic than the host volcanic rocks of the central cluster of the San Juan volcanic field. Our Pb isotope results indicate that early Au mineralization of the North Amethyst area may represent the product of an older and relatively local hydrothermal system distinct from that of the younger base metal and Ag mineralization found throughout the region. Fluids that deposited Au minerals may have derived their Pb isotope composition by a greater degree of interaction with shallow, relatively less radiogenic volcanic wall rocks. The younger, base metal and Ag-rich mineralization that overprints the Au mineralization in the North Amethyst area clearly has a more radiogenic isotopic signature, which implies that the later mineralization derived a greater component of its Pb from Proterozoic source rocks, or sediments derived from them.Paragenetically early sulfide-rich vein assemblages have the least radiogenic galenas and generally also have the highest Au contents. Thus, identification of paragenetically early vein assemblages with relatively unradiogenic Pb isotope compositions similar to those of the North Amethyst area provides an additional exploration tool for Au in the central San Juan Mountains area.

Oxygen, hydrogen, sulfur, and carbon isotopes in the Pea Ridge magnetite-apatite deposit, southeast Missouri, and sulfur isotope comparisons to other iron deposits in the region

USGS Publications Warehouse

Johnson, Craig A.; Day, Warren C.; Rye, Robert O.

2016-01-01

Oxygen, hydrogen, sulfur, and carbon isotopes have been analyzed in the Pea Ridge magnetite-apatite deposit, the largest historic producer among the known iron deposits in the southeast Missouri portion of the 1.5 to 1.3 Ga eastern granite-rhyolite province. The data were collected to investigate the sources of ore fluids, conditions of ore formation, and provenance of sulfur, and to improve the general understanding of the copper, gold, and rare earth element potential of iron deposits regionally. The δ18O values of Pea Ridge magnetite are 1.9 to 4.0‰, consistent with a model in which some magnetite crystallized from a melt and other magnetite—perhaps the majority—precipitated from an aqueous fluid of magmatic origin. The δ18O values of quartz, apatite, actinolite, K-feldspar, sulfates, and calcite are significantly higher, enough so as to indicate growth or equilibration under cooler conditions than magnetite and/or in the presence of a fluid that was not entirely magmatic. A variety of observations, including stable isotope observations, implicate a second fluid that may ultimately have been meteoric in origin and may have been modified by isotopic exchange with rocks or by evaporation during storage in lakes.Sulfur isotope analyses of sulfides from Pea Ridge and seven other mineral deposits in the region reveal two distinct populations that average 3 and 13‰. Two sulfur sources are implied. One was probably igneous melts or rocks belonging to the mafic- to intermediate-composition volcanic suite that is present at or near most of the iron deposits; the other was either melts or volcanic rocks that had degassed very extensively, or else volcanic lakes that had trapped rising magmatic gases. The higher δ34S values correspond to deposits or prospects where copper is noteworthy—the Central Dome portion of the Boss deposit, the Bourbon deposit, and the Vilander prospective area. The correspondence suggests that (1) sulfur either limited the deposition

LOCALIZATION OF GOLD IN MOUSE BRAIN IN RELATION TO GOLD THIOGLUCOSE OBESITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Debons, A.F.; Silver, L.; Cronkite, E.P.

1962-04-01

Administration of gold thioglucose led to the development of hyperphagia and obesity in mice; this confirmed findings by previous investigators. By employing neutron activation analysis and radioautography, it was observed that this syndrome was associated with focal accumulation of gold in the hypothalamus. Animals treated with gold thiomalate failed to show any hypothalamic Iocalization of gold radioautographically or any evidence of the syndrome of hyperphagla and obesity. In additlon, other foci of gold locallzation were found in gold thioglucose-treated but not in the gold thiomalate-treated animals. Gamma spectroscopy studies made possible quantitative measurements of the gold content ln the brainsmore » of both treated groups. Gold thioglucose-treated as well as gold thiomalate-treated animals had appreciable quantities of gold in the brain proper. Phosphorus-32 generated by neutron activation of the sulfur moiety of gold thioglucose proved to be insigniflcant in its contribution to the radioautographic flndings. Implication of the above findings for the glucostatic theory of appetite regulation is discussed. (auth)« less

Mechanisms of gold bioaccumulation by filamentous cyanobacteria from gold(III)-chloride complex.

PubMed

Lengke, Maggy F; Ravel, Bruce; Fleet, Michael E; Wanger, Gregory; Gordon, Robert A; Southam, Gordon

2006-10-15

The mechanisms of gold bioaccumulation by cyanobacteria (Plectonema boryanum UTEX 485) from gold(III)-chloride solutions have been studied at three gold concentrations (0.8,1.7, and 7.6 mM) at 25 degrees C, using both fixed-time laboratory and real-time synchrotron radiation absorption spectroscopy (XAS) experiments. Interaction of cyanobacteria with aqueous gold(III)-chloride initially promoted the precipitation of nanoparticles of amorphous gold(I)-sulfide at the cell walls, and finally deposited metallic gold in the form of octahedral (111) platelets (approximately 10 nm to 6 microm) near cell surfaces and in solutions. The XAS results confirm that the reduction mechanism of gold(III)-chloride to metallic gold by cyanobacteria involves the formation of an intermediate Au(I) species, gold(I)-sulfide.

Mercury stable isotope fractionation in a tropical ecosystem including human hair: New insights for an isotope balance

NASA Astrophysics Data System (ADS)

Laffont, Laure; Sonke, Jeroen; Maurice, Laurence; Behra, Philippe

2010-05-01

Mercury contamination is an environmental problem in the Amazon basin still relevant today as impacts on human health are poorly studied. In Bolivia, indigenous people have elevated methylmercury concentrations (between 2719 and 23701 ng.g-1) in their hair. This highly toxic molecule is formed after methylation of inorganic Hg released by chemical and physical weathering and from human activities. The aim of our study is to propose a first isotope balance in a Bolivian Amazon ecosystem, through variations in Hg isotopic compositions. The discovery of mass-independent fracionation (MIF) of odd-isotopes in our organic samples (fish and human hair) opened a new way of research in tracing the sources and the processes involved in the cycle of Hg. Four types of samples are studied: liquid Hg0 from gold mining, sediment samples, fish coming from the Beni River basin (from the main channel and an associated floodplain lake) and hair from gold miners and fish-eating native populations. Hg isotopic compositions were analyzed on a Thermo-Finnigan Neptune MC-ICP-MS at the LMTG after sample digestion by HCl/HNO3 or by H2O2/HNO3 for fish samples, at 120°C. The δ202Hg values (relative to NIST 3133) are signicantly different with respect to the external precision on UM-Almaden#2 of 0.18 ‰ (2σ, n = 42): -0.34 ± 0.02 ‰ for liquid mercury, between -1.33 and -0.81 ‰ for bottom and floodplain sediments (n=18), between -0.87 and 2.22 ‰ for miners hair (n=26), +1.29 ± 0.41 ‰ for native hair (n=13) and between -0.91 and -0.21 ‰ for fish samples (n=53). A large mass-independent isotope fractionation (MIF) was observed for odd isotope ratios in all hair samples and fish samples whereas weak anomalies were measured for sediment samples: - ∆199Hg anomaly: -0.12 to -0.04 ‰ for sediment, -0.22 to +0.63 ‰ for fish samples and +0.13 to +1.63 ‰ for hair - ∆201Hg anomaly: -0.12 to -0.02 ‰ for sediment, -0.21 to +0.43 ‰ for fish samples and +0.06 to +1.25 ‰ for hair

Geodynamic setting of mesothermal gold deposits: An association with accretionary tectonic regimes

NASA Astrophysics Data System (ADS)

Kerrich, Robert; Wyman, Derek

1990-09-01

Mesothermal gold provinces of Phanerozoic age are characteristically associated with regional structures along which allochthonous terranes have been accreted onto continental margins or arcs. A recurring sequence of transpressive deformation, uplift, late kinematic mineralization, and shoshonitic magmatism is consistent with thermal reequilibration of tectonically thickened crust. Mesothermal gold camps in the Superior province are spatially associated with large-scale structures that have been interpreted as zones of transpressive accretion of individual subprovinces or allochthonous terranes: these boundary structures are characterized by the sequence of significant horizontal shortening, uplift, late-kinematic mineralization, and shoshonitic lamprophyres and therefore may have the same geodynamic significance as Phanerozoic counterparts. In this model, thermal re-equilibration of underplated and subducted oceanic lithosphere and sediments in a transpressive regime, over time scales of 10 to 40 m.y., is a necessary precursor to gold mineralization. Hydrothermal fluids are released along boundary faults and their splays during uplift: the uniform temperature, low salinity and mole% CO2 signify uniform source conditions, whereas the variable O, C, Sr, and Pb isotopic compositions of fluids reflect lithological complexity of the source regions and conduits. Ou the basis of this model it is suggested that mesothermal lode gold deposits are the product of subduction-related crustal underplating and deep, late metamorphism, rather than magmatic or metamorphic events in the supracrustal rocks. Secular variations in the generation of Archean, Proterozoic, and Phanerozoic mesothermal Au provinces reflect the timing of collisional orogenies within terranes of these eras.

Gold and gold-iron oxide magnetic glyconanoparticles: synthesis, characterization and magnetic properties.

PubMed

de la Fuente, Jesús M; Alcántara, David; Eaton, Peter; Crespo, Patricia; Rojas, Teresa C; Fernandez, Asunción; Hernando, Antonio; Penadés, Soledad

2006-07-06

The preparation, characterization and the magnetic properties of gold and gold-iron oxide glyconanoparticles (GNPs) are described. Glyconanoparticles were prepared in a single step procedure in the presence of aqueous solution of thiol functionalized neoglycoconjugates and either gold salts or both gold and iron salts. Neoglycoconjugates of lactose and maltose disaccharides with different linkers were used. Iron-free gold or gold-iron oxide GNPs with controlled gold-iron ratios were obtained. The average core-size diameters are in the range of 1.5-2.5 nm. The GNPs are fully characterized by (1)H NMR spectrometry, transmission electron microscopy (TEM), and UV-vis and X-ray absorption (XAS) spectroscopies. Inductive plasma-atomic emission spectrometry (ICP) and elemental analysis gave the average number of neoglycoconjugates per cluster. The magnetic properties were measured in a SQUID magnetometer. The most remarkable results was the observation of a permanent magnetism up to room temperature in the iron-free gold GNPs, that was not present in the corresponding gold-iron oxide GNPs.

Extraction of Solar Wind Nitrogen and Noble Gases From the Genesis Gold Foil Collector

NASA Astrophysics Data System (ADS)

Schlutter, D. J.; Pepin, R. O.

2005-12-01

The Genesis gold foil is a bulk solar wind collector, integrating fluences from all three of the wind regimes. Pyrolytic extraction of small foil samples at Minnesota yielded He fluences, corrected for backscatter, in good agreement with measurements by on-board spacecraft instruments, and He/Ne elemental ratios close to those implanted in collector foils deployed on the lunar surface during the Apollo missions. Isotopic distributions of He, Ne and Ar are under study. Pyrolysis to temperatures above the gold melting point generates nitrogen blanks large enough to obscure the solar-wind nitrogen component. An alternative technique for nitrogen and noble gas extraction, by room-temperature amalgamation of the gold foil surface, will be discussed. Ne and Ar releases in preliminary tests of this technique on small foil samples were close to 100% of the amounts expected from the high-temperature pyrolysis yields, indicating that amalgamation quantitatively liberates gases from several hundred angstroms deep in the gold, beyond the implantation depth of most of the solar wind. Present work is focused on two problems currently interfering with accurate nitrogen measurements at the required picogram to sub-picogram levels: a higher than expected blank likely due to tiny air bubbles rolled into the gold sheet during fabrication, and the presence of a refractory hydrocarbon film on Genesis collector surfaces (the "brown stain") that, if left in place on the foil, shields the underlying gold from mercury attack. We have found, however, that the film is efficiently removed within tens of seconds by oxygen plasma ashing. Potential nitrogen contaminants introduced during the crash of the sample return canister are inert in amalgamation, and so are not hazards to the measurements.

Geology, geochemistry, and geochronology of the East Bay gold trend, Red Lake, Ontario, Canada

NASA Astrophysics Data System (ADS)

Gallagher, Shaun; Camacho, Alfredo; Fayek, Mostafa; Epp, Mark; Spell, Terry L.; Armstrong, Richard

2018-01-01

The Red Lake greenstone belt is situated in northwestern Ontario within the Uchi Subprovince, Superior Province. Most gold deposits therein are associated with major deformation corridors; the east-west oriented "Mine trend" hosts most of the large deposits and the northeast-southwest "East Bay trend" hosts several small deposits and showings. Gold along the East Bay trend typically occurs in quartz replacement veins that were emplaced into pre-existing quartz-carbonate veins. Gold can occur as free gold or along vein margins associated with pyrite and pyrrhotite. Most primary fluid inclusions, preserved in relatively undeformed portions of veins, are carbonaceous with lesser quantities of aqueous inclusions. The average homogenization temperature of aqueous fluids is 250 °C; however, the abundance of three-phase inclusions, variation in liquid-vapor ratios, and a wide range in homogenization temperatures indicate that immiscibility, effervescence, and fluid mixing are mechanisms associated with gold deposition. The age ( 2550 Ma) of alteration minerals in the Abino area is considerably younger (by 100 Myr) than alteration minerals in other deposits in the Red Lake district, indicating that the mineralizing fluid history was more protracted than previously thought. Along the East Bay trend, barren veins generally have lower δ18OVSMOW values (0.0 to 8.5‰) relative to auriferous veins (9.6 and 13.1‰). Consequently, the oxygen isotopic composition of quartz could be used as a vector for gold mineralization. The genetic model for the East Bay trend involves several stages of vein formation. Auriferous veins formed near the upper boundary of the mesozonal regime (depth of 5-6 km).

Origin of the transition voltage in gold-vacuum-gold atomic junctions.

PubMed

Wu, Kunlin; Bai, Meilin; Sanvito, Stefano; Hou, Shimin

2013-01-18

The origin and the distance dependence of the transition voltage of gold-vacuum-gold junctions are investigated by employing first-principles quantum transport simulations. Our calculations show that atomic protrusions always exist on the electrode surface of gold-vacuum-gold junctions fabricated using the mechanically controllable break junction (MCBJ) method. The transition voltage of these gold-vacuum-gold junctions with atomically sharp electrodes is determined by the local density of states (LDOS) of the apex gold atom on the electrode surface rather than by the vacuum barrier shape. More specifically, the absolute value of the transition voltage roughly equals the rising edge of the LDOS peak contributed by the 6p atomic orbitals of the gold atoms protruding from the electrode surface, whose local Fermi level is shifted downwards when a bias voltage is applied. Since the LDOS of the apex gold atom depends strongly on the exact shape of the electrode, the transition voltage is sensitive to the variation of the atomic configuration of the junction. For asymmetric junctions, the transition voltage may also change significantly depending on the bias polarity. Considering that the occurrence of the transition voltage requires the electrode distance to be larger than a critical value, the interaction between the two electrodes is actually rather weak. Consequently, the LDOS of the apex gold atom is mainly determined by its local atomic configuration and the transition voltage only depends weakly on the electrode distance as observed in the MCBJ experiments.

Fluorinated colloidal gold immunolabels for imaging select proteins in parallel with lipids using high-resolution secondary ion mass spectrometry

PubMed Central

Wilson, Robert L.; Frisz, Jessica F.; Hanafin, William P.; Carpenter, Kevin J.; Hutcheon, Ian D.; Weber, Peter K.; Kraft, Mary L.

2014-01-01

The local abundance of specific lipid species near a membrane protein is hypothesized to influence the protein’s activity. The ability to simultaneously image the distributions of specific protein and lipid species in the cell membrane would facilitate testing these hypotheses. Recent advances in imaging the distribution of cell membrane lipids with mass spectrometry have created the desire for membrane protein probes that can be simultaneously imaged with isotope labeled lipids. Such probes would enable conclusive tests of whether specific proteins co-localize with particular lipid species. Here, we describe the development of fluorine-functionalized colloidal gold immunolabels that facilitate the detection and imaging of specific proteins in parallel with lipids in the plasma membrane using high-resolution SIMS performed with a NanoSIMS. First, we developed a method to functionalize colloidal gold nanoparticles with a partially fluorinated mixed monolayer that permitted NanoSIMS detection and rendered the functionalized nanoparticles dispersible in aqueous buffer. Then, to allow for selective protein labeling, we attached the fluorinated colloidal gold nanoparticles to the nonbinding portion of antibodies. By combining these functionalized immunolabels with metabolic incorporation of stable isotopes, we demonstrate that influenza hemagglutinin and cellular lipids can be imaged in parallel using NanoSIMS. These labels enable a general approach to simultaneously imaging specific proteins and lipids with high sensitivity and lateral resolution, which may be used to evaluate predictions of protein co-localization with specific lipid species. PMID:22284327

Is It Real Gold?

ERIC Educational Resources Information Center

Harris, Harold H.

1999-01-01

Features acid tests for determining whether jewelry is "real" gold or simply gold-plated. Describes the carat system of denoting gold content and explains how alloys are used to create various shades of gold jewelry. Addresses the question of whether gold jewelry can turn a wearer's skin green by considering various oxidation reactions.…

Gold and isotopically enriched platinium targets for the production of radioactive beams of francium

NASA Astrophysics Data System (ADS)

Lipski, A. R.; Orozco, L. A.; Pearson, M. R.; Simsarian, J. E.; Sprouse, G. D.; Zhao, W. Z.

1999-12-01

Au and isotopically enriched Pt targets are discussed for the production of radioactive Fr beams. Target foils, serving also as ionizers, have to be heated in order to enhance the diffusion of atoms to the surface for further extraction and injection into the electrostatic transport system.

Gold paragenesis and chemistry at Batu Hijau, Indoneisa: implications for gold-rich porphyry copper deposits

NASA Astrophysics Data System (ADS)

Arif, J.; Baker, T.

2004-10-01

Gold is an important by-product in many porphyry-type deposits but the distribution and chemistry of gold in such systems remains poorly understood. Here we report the results of petrographic, electron microprobe, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and flotation test studies of gold and associated copper sulfides within a paragenetic framework from the world-class Batu Hijau (914 mt @ 0.53% Cu, 0.40 g/t Au) porphyry copper gold deposit, Indonesia. Unlike many other porphyry copper gold deposits, early copper minerals (bornite digenite chalcocite) are well preserved at Batu Hijau and the chalcopyrite pyrite overprint is less developed. Hence, it provides an excellent opportunity to study the entire gold paragenesis of the porphyry system. In 105 polished thin sections, 699 native gold grains were identified. Almost all of the native gold grains occurred either within quartz veins, attached to sulfide, or as free gold along quartz or silicate grain boundaries. The native gold grains are dominantly round in shape and mostly 1 12 μm in size. The majority of gold was deposited during the formation of early ‘A’ veins and is dominantly associated with bornite rather than chalcopyrite. The petrographic and LA-ICP-MS study results indicate that in bornite-rich ores gold mostly occurs within copper sulfide grains as invisible gold (i.e., within the sulfide structure) or as native gold grains. In chalcopyrite-rich ores gold mostly occurs as native gold grains with lesser invisible gold. Petrographic observations also indicate a higher proportion of free gold (native gold not attached to any sulfide) in chalcopyrite-rich ores compared to bornite rich ores. The pattern of free gold distribution appears to correlate with the flotation test data, where the average gold recovery value from chalcopyrite-rich ores is consistently lower than bornite-rich ores. Our data suggest that porphyry copper-gold deposits with chalcopyrite-rich ores

Enhancement of gold recovery using bioleaching from gold concentrate

NASA Astrophysics Data System (ADS)

Choi, S. H.; Cho, K. H.; Kim, B. J.; Choi, N. C.; Park, C. Y.

2012-04-01

The gold in refractory ores is encapsulated as fine particles (sometimes at a molecular level) in the crystal structure of the sulfide (typically pyrite with or without arsenopyrite) matrix. This makes it impossible to extract a significant amount of refractory gold by cyanidation since the cyanide solution cannot penetrate the pyrite/arsenopyrite crystals and dissolve gold particles, even after fine grinding. To effectively extract gold from these ores, an oxidative pretreatment is necessary to break down the sulfide matrix. The most popular methods of pretreatment include nitric acid oxidation, roasting, pressure oxidation and biological oxidation by microorganisms. This study investigated the bioleaching efficiency of Au concentrate under batch experimental conditions (adaptation cycles and chemical composition adaptation) using the indigenous acidophilic bacteria collected from gold mine leachate in Sunsin gold mine, Korea. We conducted the batch experiments at two different chemical composition (CuSO4 and ZnSO4), two different adaptation cycles 1'st (3 weeks) and 2'nd (6 weeks). The results showed that the pH in the bacteria inoculating sample decreased than initial condition and Eh increased. In the chemical composition adaptation case, the leached accumulation content of Fe and Pb was exhibited in CuSO4 adaptation bacteria sample more than in ZnSO4 adaptation bacteria samples, possibly due to pre-adaptation effect on chalcopyrite (CuFeS2) in gold concentrate. And after 21 days on the CuSO4 adaptation cycles case, content of Fe and Pb was appeared at 1'st adaptation bacteria sample(Fe - 1.82 and Pb - 25.81 times per control sample) lower than at 2'nd adaptation bacteria sample(Fe - 2.87 and Pb - 62.05 times per control sample). This study indicates that adaptation chemical composition and adaptation cycles can play an important role in bioleaching of gold concentrate in eco-/economic metallurgy process.

Effects of Burning Conditions to the Formation of Gold Layer Photograph and Gold Layer Hologram

NASA Astrophysics Data System (ADS)

Kuge, Ken'ichi; Takahashi, Ataru; Harada, Takahito; Doi, Keiji; Sakai, Tomoko

Burning stage from gold nanoparticles to gold layer in the formation process of gold-layer photograph using gold deposition development was investigated. The gelatin layer holding gold nanoparticles is carbonized at about 400°C and burned out until about 500°C. Because gold nanoparticles would be compressed only to vertical direction and then melt to form the gold layer, the gold-layer photograph still holds the high resolution. Gold nanoparaticles do not melt completely even at 900°C, and form continuous clusters of several hundred nm.

Influence of gold content on copper oxidation from silver-gold-copper alloys

NASA Astrophysics Data System (ADS)

Swinbourne, D. R.; Barbante, G. G.; Strahan, A.

1996-10-01

In the final stages of the smelting of copper anode slimes, a silver alloy, known as “doré,” is produced. Oxidation refining is used to remove copper since this element interferes with subsequent electroparting of the small amounts of gold and platinum group metals in the doré. The gold content of doré can be greatly increased by gold scrap additions and this may affect the minimum achievable copper content of doré. In this work, silver-gold-copper alloys were oxidized by injecting pure oxygen at 1100 °C in the absence of any slag cover. For the gold contents expected in practice, the equilibrium copper content of the doré did not increase significantly as the gold content increased. However, at the other extreme of composition, the equilibrium copper content was a very strong function of the silver content of the gold bullion. The activity coefficient of copper in silver-gold alloys was calculated and compared to those predicted from a ternary subregular solution model of the system Ag-Au-Cu. Satisfactory agreement was found.

Enrichment of Gold in Antimony Matte by Direct Smelting of Refractory Gold Concentrate

NASA Astrophysics Data System (ADS)

Yang, Tianzu; Xie, Boyi; Liu, Weifeng; Zhang, Duchao; Chen, Lin

2018-04-01

Conventional cyanidation technology achieves low gold recovery when used to process refractory gold concentrate. Based on the geochemical characteristics of gold deposit mineralization, a new method is proposed herein for gold enrichment in antimony matte by smelting of refractory gold concentrate. The effects of the FeO/SiO2 and CaO/SiO2 ratios, smelting temperature, and smelting time on the gold recovery were investigated in detail. The optimum conditions were determined to be FeO/SiO2 ratio of 1.2, CaO/SiO2 ratio of 0.4, smelting temperature of 1200°C, and smelting time of 45 min. The gold content in antimony matte and smelting slag was 96.68 and 1.13 g/t, respectively. The gold, antimony, and arsenic recovery was 97.72%, 26.89%, and 6.56%, respectively, with most of the antimony and arsenic volatilized into dust. Mineral liberation analyzer results showed that the antimony matte mainly consisted of FeS and FeO, with three phases, viz. FeAs, SbAs, and AuSb, embedded between them, indicating that gold was easily enriched with antimony and arsenic during smelting of refractory gold concentrate.

Enrichment of Gold in Antimony Matte by Direct Smelting of Refractory Gold Concentrate

NASA Astrophysics Data System (ADS)

Yang, Tianzu; Xie, Boyi; Liu, Weifeng; Zhang, Duchao; Chen, Lin

2018-06-01

Conventional cyanidation technology achieves low gold recovery when used to process refractory gold concentrate. Based on the geochemical characteristics of gold deposit mineralization, a new method is proposed herein for gold enrichment in antimony matte by smelting of refractory gold concentrate. The effects of the FeO/SiO2 and CaO/SiO2 ratios, smelting temperature, and smelting time on the gold recovery were investigated in detail. The optimum conditions were determined to be FeO/SiO2 ratio of 1.2, CaO/SiO2 ratio of 0.4, smelting temperature of 1200°C, and smelting time of 45 min. The gold content in antimony matte and smelting slag was 96.68 and 1.13 g/t, respectively. The gold, antimony, and arsenic recovery was 97.72%, 26.89%, and 6.56%, respectively, with most of the antimony and arsenic volatilized into dust. Mineral liberation analyzer results showed that the antimony matte mainly consisted of FeS and FeO, with three phases, viz. FeAs, SbAs, and AuSb, embedded between them, indicating that gold was easily enriched with antimony and arsenic during smelting of refractory gold concentrate.

Archaean lode gold deposits: the solute source problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kerrich, R.

1985-01-01

On a regional scale lode gold deposits typically occur throughout the entire spectrum of greenstone belt stratigraphy. In the Abitibi Belt lode deposits are sited at the base of the volcanic cycle (Noranda), at the boundary of two volcanic cycles (Timmins) and in the stratigraphically highest groups at Kirkland Lake and Bousquet. The gold deposits are preferentially disposed along major structures apparently demarking rift zones, where extension was accommodated by listric normal faults that subsequently acted as thrusts during compression. These major structures were also sites of emplacement of trondhjemite magmas, lamprophyres and potassic basalts. From previous work Abitibi Beltmore » volcanism spans 2725 to 2703 Ma, batholith emplacement 2675 to 2685 Ma (U-Pb on zircons), and the terminal Matachewan dyke swarm which transects all major structures is 2690 +/- 93 Ma. The lode deposits have age corrected /sup 87/Sr//sup 86/Sr initials of 0.7015 to 0.7025, as well as more radiogenic Pb and higher ..mu.. relative to contemporaneous mantle Sr and Pb isotope ratios. Tourmaline, scheelite, piemontite and apatites separated from 14 deposits all possess /sup 87/Sr//sup 86/Sr 0.7015 to 0.7025. These more radiogenic values contra-indicate a direct mantle source for Sr and Pb, but rather indicate that all mineralizing fluids carry contributions from a felsic crustal source having a significant production of Rb, U and Th radiogenic daughter nuclides as well as from komatiites and tholeiites. Gold, along with an array of lithophile elements including K, Rb, Pb, Li, Sr and CO/sub 2/ were distilled from this mixed source.« less

Rapid two-dimensional ALSOFAST-HSQC experiment for metabolomics and fluxomics studies: application to a 13C-enriched cancer cell model treated with gold nanoparticles.

PubMed

Schätzlein, Martina Palomino; Becker, Johanna; Schulze-Sünninghausen, David; Pineda-Lucena, Antonio; Herance, José Raul; Luy, Burkhard

2018-04-01

Isotope labeling enables the use of 13 C-based metabolomics techniques with strongly improved resolution for a better identification of relevant metabolites and tracing of metabolic fluxes in cell and animal models, as required in fluxomics studies. However, even at high NMR-active isotope abundance, the acquisition of one-dimensional 13 C and classical two-dimensional 1 H, 13 C-HSQC experiments remains time consuming. With the aim to provide a shorter, more efficient alternative, herein we explored the ALSOFAST-HSQC experiment with its rapid acquisition scheme for the analysis of 13 C-labeled metabolites in complex biological mixtures. As an initial step, the parameters of the pulse sequence were optimized to take into account the specific characteristics of the complex samples. We then applied the fast two-dimensional experiment to study the effect of different kinds of antioxidant gold nanoparticles on a HeLa cancer cell model grown on 13 C glucose-enriched medium. As a result, 1 H, 13 C-2D correlations could be obtained in a couple of seconds to few minutes, allowing a simple and reliable identification of various 13 C-enriched metabolites and the determination of specific variations between the different sample groups. Thus, it was possible to monitor glucose metabolism in the cell model and study the antioxidant effect of the coated gold nanoparticles in detail. Finally, with an experiment time of only half an hour, highly resolved 1 H, 13 C-HSQC spectra using the ALSOFAST-HSQC pulse sequence were acquired, revealing the isotope-position-patterns of the corresponding 13 C-nuclei from carbon multiplets. Graphical abstract Fast NMR applied to metabolomics and fluxomics studies with gold nanoparticles.

Trans-Atlantic slavery: isotopic evidence for forced migration to Barbados.

PubMed

Schroeder, Hannes; O'Connell, Tamsin C; Evans, Jane A; Shuler, Kristrina A; Hedges, Robert E M

2009-08-01

The question of the ultimate origin of African slaves is one of the most perplexing in the history of trans-Atlantic slavery. Here we present the results of a small, preliminary isotopic study that was conducted in order to determine the geographical origin of 25 enslaved Africans who were buried at the Newton plantation, Barbados, sometime between the late 17th and early 19th century. In order to gain a more nuanced understanding of the slaves' origin, we used a combination of carbon, nitrogen, oxygen, and strontium isotope analyses. Carbon and nitrogen isotope ratios were determined in bone and dentinal collagen; oxygen and strontium isotopes were measured in tooth enamel. Results suggest that the majority of individuals were born on the island, if not the estate itself. Seven individuals, however, yielded enamel oxygen and strontium ratios that are inconsistent with a Barbadian origin, which strongly suggests that we are dealing with first-generation captives who were brought to the island with the slave trade. This idea is also supported by the fact that their carbon and nitrogen stable isotope values differ markedly between their teeth and bones. These intra-skeletal shifts reflect major dietary changes that probably coincided with their enslavement and forced migration to Barbados. While it is impossible to determine their exact origins, the results clearly demonstrate that the slaves did not all grow up in the same part of Africa. Instead, the data seem to suggest that they originated from at least three different areas, possibly including the Gold Coast and the Senegambia.

Gold Leaching Characteristics and Intensification of a High S and As-Bearing Gold Concentrate

NASA Astrophysics Data System (ADS)

Yang, Yong-bin; Liu, Xiao-liang; Jiang, Tao; Li, Qian; Xu, Bin; Zhang, Yan

Some high sulfur and arsenic-bearing gold concentrate has a gold leaching rate less than 80% by oxidation roasting-pickling-cyanidation process. The characteristics and intensification of gold leaching were studied systemically. By combining chemical composition and phase analysis, the low gold leaching rate was found to lie in the capsulation of gold by iron-containing phases including iron oxides, arsenopyrite and pyrite. 96.66% of gold in the industrial leaching residue was capsulated and 95.88% of the capsulated turned out to be in the iron-containing phases. The results of laboratory pickling-cyanidation experiments on the calcine and industrial leaching residue presented further demonstration for the fact that gold capsulated in the iron-containing phases was hard to be leached. However, the gold cyanide leaching rate of calcine could be raised over 95% by a reduction roasting-pickling pretreatment which played such a significant role in exposing the capsulated gold that gold leaching was intensified remarkably.

Gold in placer deposits

USGS Publications Warehouse

Yeend, Warren; Shawe, Daniel R.; Wier, Kenneth L.

1989-01-01

Man most likely first obtained gold from placer deposits, more than 6,000 years ago. Placers account for more than two-thirds of the total world gold supply, and roughly half of that mined in the States of California, Alaska, Montana, and Idaho.Placer deposits result from weathering and release of gold from lode deposits, transportation of the gold, and concentration of the gold dominantly in stream gravels. Unless preserved by burial, a placer subsequently may be eroded, and either dispersed or reconcentrated.California has produced more than 40 million troy ounces of gold from placers, both modern and fossil (Tertiary). The source of the great bulk of the gold is numerous quartz veins and mineralized zones of the Mother Lode and related systems in the western Sierra Nevada region. The gold-bearing lodes were emplaced in Carboniferous and Jurassic metamorphic rocks intruded by small bodies of Jurassic and Cretaceous igneous rocks. Mineralization occurred probably in Late Cretaceous time. Significant amounts of placer gold also were mined along the Salmon and Trinity Rivers in northern California. Source of the gold is lode deposits in Paleozoic and Mesozoic metamorphic rocks that were intruded by Mesozoic igneous rocks.Alaska has produced roughly 21 million ounces of gold from placer deposits. Most (about 13 million ounces) has come from the interior region, including 7,600,000 ounces from the Fairbanks district and 1,300,000 ounces from the Iditarod district. Lode sources are believed to be mostly quartz veins in Precambrian or Paleozoic metamorphic rocks intruded by small igneous bodies near Fairbanks, and shear zones in Tertiary(?) quartz monzonite stocks at Iditarod. The Seward Peninsula has produced more than 6 million ounces of placer gold, including about 4,000,000 ounces from the Nome district. Most of the gold was derived from raised beach deposits. Source of the gold probably is Tertiary-mineralized faults and joints in metamorphic rocks of late

Association of gold with uraninite and pyrobitumen in the metavolcanic rock hosted hydrothermal Au-U mineralisation at Rompas, Peräpohja Schist Belt, northern Finland

NASA Astrophysics Data System (ADS)

Molnár, Ferenc; Oduro, Harry; Cook, Nick D. J.; Pohjolainen, Esa; Takács, Ágnes; O'Brien, Hugh; Pakkanen, Lassi; Johanson, Bo; Wirth, Richard

2016-06-01

-ordered graphite in calcsilicate veins. Mean random reflectance data for pyrobitumen indicate 270-340 °C maximum temperature of thermal maturation—this temperature range is also considered as the temperature of gold deposition. Results of multiple sulphur isotope analyses of organic material-, pyrite- and acid-volatile-bound sulphur show distinct ranges of δ34S values for SORG and SCRS in uraninite-pyrobitumen (from -6.99 to -3.55‰ and from -10.02 to -4.41‰, respectively) and uraninite-pyrobitumen-native gold mineral associations (from +1.36 to +6.87‰ and from +0.42 to +9.7‰, respectively). Δ33S data indicate local occurrence of nonmass-dependent sulphur isotope fractionation owing to interaction of fluids with organic material. Concentration of lead in uraninite is depleted along the gold mineral filled fractures whereas the uranogenic lead isotope contents of galena, altaite and hunchuite deposited in the same fractures are extremely high, suggesting that the dominant source of lead for the crystallisation of these minerals was the radiogenic lead content of uraninite. Taking into account this source of radiogenic lead, the calculated Pb-Pb model ages for the lead minerals are between 1.75 and 1.70 Ga. Sulphur and tellurium removal from the fluid by reaction with radiogenic lead released by uraninite appears to be an important mechanism in the strongly localised deposition of gold minerals. Scavenging of sulphur by pyrobitumen nodules from gold transporting fluids was an additional process triggering precipitation of gold. Carbon particles and organic functional groups in pyrobitumen probably acted as nucleation and adsorption centres for gold minerals.

Coal-oil gold agglomeration assisted flotation to recover gold from refractory ore

NASA Astrophysics Data System (ADS)

Otsuki, A.; Yue, C.

2017-07-01

This study aimed to investigate the applicability of coal-oil gold agglomeration (CGA) assisted flotation to recover gold from a refractory ore. The ore with the grade of 2-5 g/t was tested with the CGA-flotation process in six different size fractions from 38 to 300 urn using different collector types and dosages. In addition, the flotation without CGA was performed under the same condition for comparison. The results showed that the higher gold grade and recovery were achieved by applying the CGA-flotation, compared with the flotation without CGA. More than 20-60 times grade increase from the head grade was obtained with CGA-flotation. The elemental analysis of gold and sulphur explained their relationship with gold recovery. The results well indicated the applicability of CGA to upgrade the refractory gold ore.

Preparation of conductive gold nanowires in confined environment of gold-filled polymer nanotubes.

PubMed

Mitschang, Fabian; Langner, Markus; Vieker, Henning; Beyer, André; Greiner, Andreas

2015-02-01

Continuous conductive gold nanofibers are prepared via the "tubes by fiber templates" process. First, poly(l-lactide) (PLLA)-stabilized gold nanoparticles (AuNP) with over 60 wt% gold are synthesized and characterized, including gel permeation chromatography coupled with a diode array detector. Subsequent electrospinning of these AuNP with template PLLA results in composite nanofibers featuring a high gold content of 57 wt%. Highly homogeneous gold nanowires are obtained after chemical vapor deposition of 345 nm of poly(p-xylylene) (PPX) onto the composite fibers followed by pyrolysis of the polymers at 1050 °C. The corresponding heat-induced transition from continuous gold-loaded polymer tubes to smooth gold nanofibers is studied by transmission electron microscopy and helium ion microscopy using both secondary electrons and Rutherford backscattered ions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Distribution and composition of gold in porphyry gold systems: example from the Biely Vrch deposit, Slovakia

NASA Astrophysics Data System (ADS)

Koděra, Peter; Kozák, Jaroslav; Brčeková, Jana; Chovan, Martin; Lexa, Jaroslav; Jánošík, Michal; Biroň, Adrián; Uhlík, Peter; Bakos, František

2018-03-01

The Biely Vrch deposit in the Western Carpathians is assigned to the shallow, sulfide-poor porphyry gold deposit type and has an exceptionally low Cu/Au ratio. According to 3-D geochemical models, there is a limited spatial correlation between Au and Cu due to the primary introduction of gold by a salt melt and Cu by low-density vapor. Despite a rough spatial correlation of gold grades with quartz stockwork intensity, gold is hosted mostly by altered rock, exclusively in native form. Three main gold mineral assemblages were recognized here. In the deepest parts of the system, the K- and Ca-Na silicate gold assemblage is associated with minerals of high-temperature alteration (plagioclase, K-feldspar, actinolite), with gold grades and fineness depending on depth and potassium content of the host rock: K-silicate alteration hosts the lowest fineness gold ( 914), whereas Ca-Na silicate alteration has the highest ( 983). The intermediate argillic gold assemblage is the most widespread, with gold hosted mainly by chlorite, illite, smectite, and interstratified illite-chlorite-smectite minerals. The gold fineness is mostly variable (875-990) and inherited from the former gold mineral assemblages. The latest advanced argillic gold assemblage has its gold mostly in kaolinite. The extremely high fineness ( 994) results from gold remobilization by late-stage aqueous magmatic-hydrothermal fluids. Uncommon bonanza-grade appears where the earlier gold mineral assemblages were further enriched by this remobilized gold. Primary precipitation of gold occurred during ascent and cooling of salt melts at 450 to 309 °C, mostly during retrograde quartz solubility.

Silver, gold, and alloyed silver-gold nanoparticles: characterization and comparative cell-biologic action

NASA Astrophysics Data System (ADS)

Mahl, Dirk; Diendorf, Jörg; Ristig, Simon; Greulich, Christina; Li, Zi-An; Farle, Michael; Köller, Manfred; Epple, Matthias

2012-10-01

Silver, gold, and silver-gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly( N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15-25 nm), gold (5-6 nm), and silver-gold (50:50; 10-12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver-gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver-gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver-gold nanoparticles in the concentration range of 5-20 μg mL-1 induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8.

Gold deposits in metamorphic belts: Overview of current understanding, outstanding problems, future research, and exploration significance

USGS Publications Warehouse

Groves, D.I.; Goldfarb, R.J.; Robert, F.; Hart, C.J.R.

2003-01-01

Metamorphic belts are complex regions where accretion or collision has added to, or thickened, continental crust. Gold-rich deposits can be formed at all stages of orogen evolution, so that evolving metamorphic belts contain diverse gold deposit types that may be juxtaposed or overprint each other. This partly explains the high level of controversy on the origin of some deposit types, particularly those formed or overprinted/remobilized during the major compressional orogeny that shaped the final geometry of the hosting metamorphic belts. These include gold-dominated orogenic and intrusion-related deposits, but also particularly controversial gold deposits with atypical metal associations. There are a number of outstanding problems for all types of gold deposits in metamorphc belts. These include the following: (1) definitive classifications, (2) unequivocal recognition of fluid and metal sources, (3) understanding of fluid migration and focusing at all scales, (4) resolution of the precise role of granitoid magmatism, (5) precise gold-depositional mechanisms, particularly those producing high gold grades, and (6) understanding of the release of CO2-rich fluids from subducting slabs and subcreted oceanic crust and granitoid magmas at different crustal levels. Research needs to be better coordinated and more integrated, such that detailed fluid-inclusion, trace-element, and isotopic studies of both gold deposits and potential source rocks, using cutting-edge technology, are embedded in a firm geological framework at terrane to deposit scales. Ultimately, four-dimensional models need to be developed, involving high-quality, three-dimensional geological data combined with integrated chemical and fluid-flow modeling, to understand the total history of the hydrothermal systems involved. Such research, particularly that which can predict superior targets visible in data sets available to exploration companies before discovery, has obvious spin-offs for global- to deposit

GOLD PLATING PROCESS

DOEpatents

Seegmiller, R.

1957-08-01

An improved bath is reported for plating gold on other metals. The composition of the plating bath is as follows: Gold cyanide from about 15 to about 50 grams, potassium cyanide from about 70 to about 125 grams, and sulfonated castor oil from about 0.1 to about 10 cc. The gold plate produced from this bath is smooth, semi-hard, and nonporous.

Magmatic-vapor expansion and the formation of high-sulfidation gold deposits: Chemical controls on alteration and mineralization

USGS Publications Warehouse

Henley, R.W.; Berger, B.R.

2011-01-01

Large bulk-tonnage high-sulfidation gold deposits, such as Yanacocha, Peru, are the surface expression of structurally-controlled lode gold deposits, such as El Indio, Chile. Both formed in active andesite-dacite volcanic terranes. Fluid inclusion, stable isotope and geologic data show that lode deposits formed within 1500. m of the paleo-surface as a consequence of the expansion of low-salinity, low-density magmatic vapor with very limited, if any, groundwater mixing. They are characterized by an initial 'Sulfate' Stage of advanced argillic wallrock alteration ?? alunite commonly with intense silicification followed by a 'Sulfide' Stage - a succession of discrete sulfide-sulfosalt veins that may be ore grade in gold and silver. Fluid inclusions in quartz formed during wallrock alteration have homogenization temperatures between 100 and over 500 ??C and preserve a record of a vapor-rich environment. Recent data for El Indio and similar deposits show that at the commencement of the Sulfide Stage, 'condensation' of Cu-As-S sulfosalt melts with trace concentrations of Sb, Te, Bi, Ag and Au occurred at > 600 ??C following pyrite deposition. Euhedral quartz crystals were simultaneously deposited from the vapor phase during crystallization of the vapor-saturated melt occurs to Fe-tennantite with progressive non-equilibrium fractionation of heavy metals between melt-vapor and solid. Vugs containing a range of sulfides, sulfosalts and gold record the changing composition of the vapor. Published fluid inclusion and mineralogical data are reviewed in the context of geological relationships to establish boundary conditions through which to trace the expansion of magmatic vapor from source to surface and consequent alteration and mineralization. Initially heat loss from the vapor is high resulting in the formation of acid condensate permeating through the wallrock. This Sulfate Stage alteration effectively isolates the expansion of magmatic vapor in subsurface fracture arrays

Gold deposit styles and placer gold characterisation in northern and east-central Madagascar

USGS Publications Warehouse

Pitfield, Peter E. J; Styles, Michael T.; Taylor, Cliff D.; Key, Roger M.; Bauer,; Ralison, A

2009-01-01

Microchemical characterisation of bedrock and placer gold grains from six gold districts within the Archaean domains and intervening Neoproterozoic Anaboriana-Manampotsy belt of northern and east-central Madagascar show few opaque inclusions (e.g pyrrhotite, Bi tellurides) but wide range of Ag contents (40wt%). Some districts exhibit multiple source populations of grains. The ‘greenstone belt’ terranes have an orogenic gold signature locally with an intrusion-related to epithermal overprint. Proterozoic metasediments with felsic to ultramafic bodies yield dominantly intrusion-related gold. A high proportion of secondary gold (<0.5wt% Ag) is related to recycling of paleoplacers and erosion of post-Gondwana planation surfaces and indicates that some mesothermal gold systems were already partially to wholly removed by erosion by the PermoTriassic.

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.

Genetic links among fluid cycling, vein formation, regional deformation, and plutonism in the Juneau gold belt, southeastern Alaska

USGS Publications Warehouse

Miller, Lance D.; Goldfarb, Richard J.; Gehrels, George E.; Snee, Lawrence W.

1994-01-01

Gold-bearing quartz vein systems in the Juneau gold belt formed within a 160-km- long by 5- to 8-km-wide zone along the western margin of the Coast Mountains, Alaska. Vein systems are spatially associated with shear zones adjacent to terrane-bounding, mid-Cretaceous thrust faults. Analysis of vein orientations and sense of shear data define a stress configuration with greatest and least principal axes oriented subhorizontally with northeast-southwest trends and subverticaly, respectively. This local stress configuration is compatible with the far-field plate configuration during Eocene time. Isotopic ages of vein formation indicate that fluid cycling occurred between 56.5 and ≥52.8 Ma, and are consistent with a genetic link between veining and a change in plate motion in early Eocene time. Veining was also synchronous with the latter stages of rapid exhumation and voluminous plutonism immediately inboard of the gold belt. We propose a model in which interacting tectonic events facilitated fault-valve action and vein development along now-exhumed shear zones.

Gold Fever! Seattle Outfits the Klondike Gold Rush. Teaching with Historic Places.

ERIC Educational Resources Information Center

Blackburn, Marc K.

This lesson is based on the National Register of Historic Places registration file, "Pioneer Square Historic District," and other sources about Seattle (Washington) and the Klondike Gold Rush. The lesson helps students understand how Seattle exemplified the prosperity of the Klondike Gold Rush after 1897 when news of a gold strike in…

Petrogenesis of postcollisional magmatism at Scheelite Dome, Yukon, Canada: Evidence for a lithospheric mantle source for magmas associated with intrusion-related gold systems

USGS Publications Warehouse

Mair, John L.; Farmer, G. Lang; Groves, David I.; Hart, Craig J.R.; Goldfarb, Richard J.

2011-01-01

The type examples for the class of deposits termed intrusion-related gold systems occur in the Tombstone-Tungsten belt of Alaska and Yukon, on the eastern side of the Tintina gold province. In this part of the northern Cordillera, extensive mid-Cretaceous postcollisional plutonism took place following the accretion of exotic terranes to the continental margin. The most cratonward of the resulting plutonic belts comprises small isolated intrusive centers, with compositionally diverse, dominantly potassic rocks, as exemplified at Scheelite Dome, located in central Yukon. Similar to other spatially and temporally related intrusive centers, the Scheelite Dome intrusions are genetically associated with intrusion-related gold deposits. Intrusions have exceptional variability, ranging from volumetrically dominant clinopyroxene-bearing monzogranites, to calc-alkaline minettes and spessartites, with an intervening range of intermediate to felsic stocks and dikes, including leucominettes, quartz monzonites, quartz monzodiorites, and granodiorites. All rock types are potassic, are strongly enriched in LILEs and LREEs, and feature high LILE/HFSE ratios. Clinopyroxene is common to all rock types and ranges from salite in felsic rocks to high Mg augite and Cr-rich diopside in lamprophyres. Less common, calcic amphibole ranges from actinolitic hornblende to pargasite. The rocks have strongly radiogenic Sr (initial 87Sr/86Sr from 0.711-0.714) and Pb isotope ratios (206Pb/204Pb from 19.2-19.7), and negative initial εNd values (-8.06 to -11.26). Whole-rock major and trace element, radiogenic isotope, and mineralogical data suggest that the felsic to intermediate rocks were derived from mafic potassic magmas sourced from the lithospheric mantle via fractional crystallization and minor assimilation of metasedimentary crust. Mainly unmodified minettes and spessartites represent the most primitive and final phases emplaced. Metasomatic enrichments in the underlying lithospheric mantle

Mammalian sensitivity to elemental gold (Au?)

USGS Publications Warehouse

Eisler, R.

2004-01-01

There is increasing documentation of allergic contact dermatitis and other effects from gold jewelry, gold dental restorations, and gold implants. These effects were especially pronounced among females wearing body-piercing gold objects. One estimate of the prevalence of gold allergy worldwide is 13%, as judged by patch tests with monovalent organogold salts. Eczema of the head and neck was the most common response of individuals hypersensitive to gold, and sensitivity can last for at least several years. Ingestion of beverages containing flake gold can result in allergic-type reactions similar to those seen in gold-allergic individuals exposed to gold through dermal contact and other routes. Studies with small laboratory mammals and injected doses of colloidal gold showed increased body temperatures, accumulations in reticular cells, and dose enhancement in tumor therapy; gold implants were associated with tissue injuries. It is proposed that Au? toxicity to mammals is associated, in part, with formation of the more reactive Au+ and Au3+ species.

Gold grade distribution within an epithermal quartz vein system, Kestanelik, NW Turkey: implications for gold exploration

NASA Astrophysics Data System (ADS)

Gulyuz, Nilay; Shipton, Zoe; Gulyuz, Erhan; Lord, Richard; Kaymakci, Nuretdin; Kuscu, İlkay

2017-04-01

Vein-hosted gold deposits contribute a large part to the global gold production. Discovery of these deposits mainly include drilling of hundreds of holes, collecting thousands of soil and rock samples and some geophysical surveys which are expensive and time consuming. Understanding the structures hosting the veins and the variations in gold concentrations within the veins is crucial to constrain a more economic exploration program. The main aim of this study is to investigate the gold grade distribution in the mineralized quartz veins of a well exposed epithermal gold deposit hosted by Paleozoic schist and Eocene quartz-feldspar-hornblende porphyry in Lapseki, NW Turkey. We have constructed 3D architecture of the vein surfaces by mapping their outcrop geometries using a highly sensitive Trimble GPS, collecting detailed field data, well-logs and geochemistry data from 396 drill holes (255 diamond cut and 141 reverse circulation holes). Modelling was performed in MOVE Structural Modelling and Analysis software granted by Midland Valley's Academic Software Initiative, and GIS application softwares Global Mapper and Esri-ArcGIS. We envisaged that while fluid entering the conduit ascents, a sudden thickness increase in the conduit would lead to a drop in the fluid pressure causing boiling (the most dominant gold precipitation mechanism) and associated gold precipitation. Regression analysis was performed between the orthogonal thickness values and gold grades of each vein, and statistical analyses were performed to see if the gold is concentrated at specific structural positions along dip. Gold grades in the alteration zones were compared to those in the adjacent veins to understand the degree of mineralization in alteration zones. A possible correlation was also examined between the host rock type and the gold grades in the veins. These studies indicated that gold grades are elevated in the adjacent alteration zones where high gold grades exist in the veins. Schist

Mineral resource of the month: gold

USGS Publications Warehouse

George, Micheal W.

2009-01-01

The article presents information on the valuable mineral called gold. It states that early civilizations valued gold because of its scarcity, durability and characteristics yellow color. By the late 20th century, gold was used as an industrial metal because of its unique physicochemical properties. The U.S. has several productive deposits of gold, including placer, gold-quartz lode, epithermal and Carlin-type gold deposits.

Origin and significance of postore dissolution collapse breccias cemented with calcite and barite at the Meikle gold deposit, Northern Carlin trend, Nevada

USGS Publications Warehouse

Emsbo, P.; Hofstra, A.H.

2003-01-01

The final event in a complicated hydrothermal history at the Meikle gold deposit was gold deficient but caused extensive postore dissolution of carbonate, collapse brecciation, and precipitation of calcite and barite crystals in the resulting cavities. Although previously interpreted to be part of the Carlin-type hydrothermal system, crosscutting relationships and U-Th-Pb geochronology constrain this hydrothermal event to late Pliocene time (ca. 2 Ma), nearly 36 Ma after ore formation. Mineralogic, fluid inclusion, and stable isotope data indicate that postore hydrothermal fluids were reduced, H2S-rich, unevolved meteoric waters ((??18O = -17???) of low temperature (ca. 65??C). The ??18O values of barite and calcite indicate that these minerals were in isotopic equilibrium, requiring that barite SO4 was derived from the oxidation of reduced sulfur; however, preexisting sulfides in breccia cavities were not oxidized. The ??34S (15???) values of barite are higher than those of local bulk sulfide and supergene alunite indicating that SO4 was not derived from supergene oxidation of local sulfide minerals. The 15 per mil ??34S value suggests that the H2S in the fluids may have been leached from sulfur-rich organic matter in the local carbonaceous sedimentary rocks. A reduced H2S-rich fluid is also supported by the bright cathodoluminescence of calcite which indicates that it is Mn rich and Fe poor. Calcite has a narrow range of ??13C values (0.3-1.8???) that are indistinguishable from those of the host Bootstrap limestone, indicating that CO2 in the fluid was from dissolution of the local limestone. These data suggest that dissolution and brecciation of the Bootstrap limestone occurred where H2S-rich fluids encountered more oxidizing fluids and formed sulfuric acid (H2SO4). Intense fracturing in the mine area by previous structural and hydrothermal events probably provided conduits for the descent of oxidized surface water which mixed with the underlying H2S-rich waters

Occurrences of dendritic gold at the McLaughlin Mine hot-spring gold deposit

NASA Astrophysics Data System (ADS)

Sherlock, R. L.; Lehrman, N. J.

1995-06-01

Two styles of gold dendrites are variably developed at the McLaughlin Mine. The most abundant occurrence is hosted by amber-coloured hydrocarbon-rich opal. Silica likely precipitated from a boiling hydrothermal fluid and complexed with immiscible hydrocarbons forming an amorphous hydrocarbon-silica phase. This phase likely scavenged particulate gold by electrostatic attraction to the hydrocarbon-silica phase. The dendritic nature of the gold is secondary and is the result of dewatering of the amorphous hydrocarbon-silica phase and crystallization of gold into syneresis fractures. The second style of dendritic gold is hosted within vein swarms that focused large volumes of fluid flow. The dendrites occur along with hydrocarbon-rich silica at the upper contact of the vein margins which isolated the dendrites allowing sufficient time for them to grow. In a manner similar to the amber-coloured opal, the dendrites may have formed by scavenging particulate gold by electrostatic attraction to the hydrocarbon-silica phase.

Modeling of gold production in Malaysia

NASA Astrophysics Data System (ADS)

Muda, Nora; Ainuddeen, Nasihah Rasyiqah; Ismail, Hamizun; Umor, Mohd Rozi

2013-04-01

This study was conducted to identify the main factors that contribute to the gold production and hence determine the factors that affect to the development of the mining industry in Malaysia. An econometric approach was used by performing the cointegration analysis among the factors to determine the existence of long term relationship between the gold prices, the number of gold mines, the number of workers in gold mines and the gold production. The study continued with the Granger analysis to determine the relationship between factors and gold production. Results have found that there are long term relationship between price, gold production and number of employees. Granger causality analysis shows that there is only one way relationship between the number of employees with gold production in Malaysia and the number of gold mines in Malaysia.

A Non-Diazo Approach to α-Oxo Gold Carbenes via Gold-Catalyzed Alkyne Oxidation

PubMed Central

2015-01-01

For the past dozen years, homogeneous gold catalysis has evolved from a little known topic in organic synthesis to a fully blown research field of significant importance to synthetic practitioners, due to its novel reactivities and reaction modes. Cationic gold(I) complexes are powerful soft Lewis acids that can activate alkynes and allenes toward efficient attack by nucleophiles, leading to the generation of alkenyl gold intermediates. Some of the most versatile aspects of gold catalysis involve the generation of gold carbene intermediates, which occurs through the approach of an electrophile to the distal end of the alkenyl gold moiety, and their diverse transformations thereafter. On the other hand, α-oxo metal carbene/carbenoids are highly versatile intermediates in organic synthesis and can undergo various synthetically challenging yet highly valuable transformations such as C–H insertion, ylide formation, and cyclopropanation reactions. Metal-catalyzed dediazotizations of diazo carbonyl compounds are the principle and most reliable strategy to access them. Unfortunately, the substrates contain a highly energetic diazo moiety and are potentially explosive. Moreover, chemists need to use energetic reagents to prepare them, putting further constrains on operational safety. In this Account, we show that the unique access to the gold carbene species in homogeneous gold catalysis offers an opportunity to generate α-oxo gold carbenes if both nucleophile and electrophile are oxygen. Hence, this approach would enable readily available and safer alkynes to replace hazardous α-diazo carbonyl compounds as precursors in the realm of gold carbene chemistry. For the past several years, we have demonstrated that alkynes can indeed effectively serve as precursors to versatile α-oxo gold carbenes. In our initial study, we showed that a tethered sulfoxide can be a suitable oxidant, which in some cases leads to the formation of α-oxo gold carbene intermediates. The

A non-diazo approach to α-oxo gold carbenes via gold-catalyzed alkyne oxidation.

PubMed

Zhang, Liming

2014-03-18

For the past dozen years, homogeneous gold catalysis has evolved from a little known topic in organic synthesis to a fully blown research field of significant importance to synthetic practitioners, due to its novel reactivities and reaction modes. Cationic gold(I) complexes are powerful soft Lewis acids that can activate alkynes and allenes toward efficient attack by nucleophiles, leading to the generation of alkenyl gold intermediates. Some of the most versatile aspects of gold catalysis involve the generation of gold carbene intermediates, which occurs through the approach of an electrophile to the distal end of the alkenyl gold moiety, and their diverse transformations thereafter. On the other hand, α-oxo metal carbene/carbenoids are highly versatile intermediates in organic synthesis and can undergo various synthetically challenging yet highly valuable transformations such as C-H insertion, ylide formation, and cyclopropanation reactions. Metal-catalyzed dediazotizations of diazo carbonyl compounds are the principle and most reliable strategy to access them. Unfortunately, the substrates contain a highly energetic diazo moiety and are potentially explosive. Moreover, chemists need to use energetic reagents to prepare them, putting further constrains on operational safety. In this Account, we show that the unique access to the gold carbene species in homogeneous gold catalysis offers an opportunity to generate α-oxo gold carbenes if both nucleophile and electrophile are oxygen. Hence, this approach would enable readily available and safer alkynes to replace hazardous α-diazo carbonyl compounds as precursors in the realm of gold carbene chemistry. For the past several years, we have demonstrated that alkynes can indeed effectively serve as precursors to versatile α-oxo gold carbenes. In our initial study, we showed that a tethered sulfoxide can be a suitable oxidant, which in some cases leads to the formation of α-oxo gold carbene intermediates. The

Surface-stabilized gold nanocatalysts

DOEpatents

Dai, Sheng [Knoxville, TN; Yan, Wenfu [Oak Ridge, TN

2009-12-08

A surface-stabilized gold nanocatalyst includes a solid support having stabilizing surfaces for supporting gold nanoparticles, and a plurality of gold nanoparticles having an average particle size of less than 8 nm disposed on the stabilizing surfaces. The surface-stabilized gold nanocatalyst provides enhanced stability, such as at high temperature under oxygen containing environments. In one embodiment, the solid support is a multi-layer support comprising at least a first layer having a second layer providing the stabilizing surfaces disposed thereon, the first and second layer being chemically distinct.

Integrating a high-force optical trap with gold nanoposts and a robust gold-DNA bond.

PubMed

Paik, D Hern; Seol, Yeonee; Halsey, Wayne A; Perkins, Thomas T

2009-08-01

Gold-thiol chemistry is widely used in nanotechnology but has not been exploited in optical-trapping experiments due to laser-induced ablation of gold. We circumvented this problem by using an array of gold nanoposts (r = 50-250 nm, h approximately 20 nm) that allowed for quantitative optical-trapping assays without direct irradiation of the gold. DNA was covalently attached to the gold via dithiol phosphoramidite (DTPA). By using three DTPAs, the gold-DNA bond was not cleaved in the presence of excess thiolated compounds. This chemical robustness allowed us to reduce nonspecific sticking by passivating the unreacted gold with methoxy-(polyethylene glycol)-thiol. We routinely achieved single beads anchored to the nanoposts by single DNA molecules. We measured DNA's elasticity and its overstretching transition, demonstrating moderate- and high-force optical-trapping assays using gold-thiol chemistry. Force spectroscopy measurements were consistent with the rupture of the strepavidin-biotin bond between the bead and the DNA. This implied that the DNA remained anchored to the surface due to the strong gold-thiol bond. Consistent with this conclusion, we repeatedly reattached the trapped bead to the same individual DNA molecule. Thus, surface conjugation of biomolecules onto an array of gold nanostructures by chemically and mechanically robust bonds provides a unique way to carry out spatially controlled, repeatable measurements of single molecules.

Geological characteristics and ore-forming process of the gold deposits in the western Qinling region, China

NASA Astrophysics Data System (ADS)

Liu, Jiajun; Liu, Chonghao; Carranza, Emmanuel John M.; Li, Yujie; Mao, Zhihao; Wang, Jianping; Wang, Yinhong; Zhang, Jing; Zhai, Degao; Zhang, Huafeng; Shan, Liang; Zhu, Laimin; Lu, Rukui

2015-05-01

The western Qinling, belonging to the western part of the Qinling-Dabie-Sulu orogen between the North China Block and South China Block, is one of the most important gold regions in China. Isotopic dates suggest that the Mesozoic granitoids in the western Qinling region emplaced during the Middle-Late Triassic, and the deposits formed during the Late Triassic. Almost all gold deposits in the western Qinling region are classified as orogenic, Carlin-type, and Carlin-like gold deposits, and they are the products of Qinling Orogenesis caused by the final collision between the North China Block and the South China Block. The early subduction of the Mian-Lue oceanic crust and the latter collision between South Qinling Terrane and the South China Block along the Mian-Lue suture generated lithosphere-scale thermal anomalies to drive orogen-scale hydrothermal systems. The collision-related magmatism also provided heat source for regional ore-forming fluids in the Carlin-like gold deposits. Orogenic gold deposits such as Huachanggou, Liziyuan, and Baguamiao lie between the Shang-Dan and Mian-Lue sutures and are confined to WNW-trending brittle-ductile shear zones in Devonian and Carboniferous greenschist-facies metasedimentary rocks that were highly-deformed and regionally-metamorphosed. These deposits are typical orogenic gold deposits and formed within a Late Triassic age. The deposits show a close relationship between Au and Ag. Ores contain mainly microscopic gold, and minor electrum and visible gold, along with pyrite. The ore-forming fluids were main metamorphic fluids. Intensive tectonic movements caused by orogenesis created fluid-migrating channels for precipitation locations. Although some orogenic gold deposits occur adjacent to granitoids, mineralization is not synchronous with magmatism; that is, the granitoids have no genetic relations to orogenic gold deposits. As ore-forming fluids converged into dilated fractures during the extension stage of orogenesis

Testing ore deposit models using in situ U-Pb geochronology of hydrothermal monazite: Paleoproterozoic gold mineralization in northern Australia

NASA Astrophysics Data System (ADS)

Rasmussen, Birger; Sheppard, Stephen; Fletcher, Ian R.

2006-02-01

The inability to establish absolute ages for gold deposition in the Pine Creek orogen of northern Australia has led to conflicting ore deposit models, ranging from intrusion related, which predict that gold mineralization was synchronous with granite magmatism (ca. 1835 1820 Ma), to orogenic, which place ore deposition nearly 100 m.y. later. Here we present ion microprobe U-Pb geochronology for a mineralized quartz reef from Tom's Gully mine, Mount Bundey, Northern Territory, Australia, and nearby granitic rocks and associated contact aureoles. Isotopic dating of zircon and monazite indicates that intrusion and contact metamorphism occurred ca. 1825 Ma, whereas hydrothermal monazite from the auriferous quartz reef gives a mean 207Pb/206Pb age of 1780 ± 10 Ma, interpreted as the time of gold mineralization. Mineralization therefore postdated intrusion by ˜45 m.y. and preceded a postulated ca. 1740 1730 Ma cratonwide orogenic gold event by ˜50 m.y. Hence, neither the intrusion-related model nor the recently proposed orogenic model is applicable. Combined with a reevaluation of age data from the nearby Goodall gold deposit, our data suggest that mineralization coincides with, and may be related to, an episode of regional low-grade metamorphism, deformation, and fluid circulation (Shoobridge event). Our results demonstrate the importance of high-precision in situ geochronology and detailed petrography for deciphering age relationships in ore deposits, and of testing the veracity of models for ore formation.

Stable Te isotope fractionation in tellurium-bearing minerals from precious metal hydrothermal ore deposits

NASA Astrophysics Data System (ADS)

Fornadel, Andrew P.; Spry, Paul G.; Haghnegahdar, Mojhgan A.; Schauble, Edwin A.; Jackson, Simon E.; Mills, Stuart J.

2017-04-01

reduced vapor to a solid is necessary to form the common tellurides and native tellurium in ore-forming systems. Our data suggest that these sorts of reactions during mineralization may account for a ∼3‰ range of δ130/125Te values. Based on the data ranges for Te minerals from various ore deposits, the underpinning geologic processes responsible for mineralization seem to have primary control on the magnitude of fractionation, with tellurides in epithermal gold deposits showing a narrower range of isotope values than those in orogenic gold and volcanogenic massive sulfide deposits.

Rb-Sr, K-Ar, and stable isotope evidence for the ages and sources of fluid components of gold-bearing quartz veins in the northern Sierra Nevada foothills metamorphic belt, California

USGS Publications Warehouse

Böhlke, John Karl; Kistler, R. W.

1986-01-01

Gold-bearing quartz veins occur in and near major fault zones in deformed oceanic and island-arc rocks west of the main outcrop of the Sierra Nevada composite batholith. Veins typically occupy minor reverse faults that crosscut blueschist to amphibolite-grade metamorphic rocks whose metamorphic ages range from early Paleozoic to Jurassic. Vein micas and carbonate-quartz-mica assemblages that formed by hydrothermal metasomatism of ultramafic wall rocks in the Alleghany, Grass Valley, Washington, and Mother Lode districts yield concordant K-Ar and Rb-Sr ages. The dated veins are significantly younger than prograde metamorphism, penetrative deformation, and accretion of their host rocks to the continental margin. New and previously published mineralization ages from 13 localities in the Sierra foothills range from about 140 to 110 m.y. ago, with mean and median between 120 and 115 m.y. The age relations suggest that mineralizing fluids were set in motion by deep magmatic activity related to the resumption of east-dipping subduction along the western margin of North America following the Late Jurassic Nevadan collision event.CO 2 -bearing fluids responsible for metasomatism and much of the vein mica, carbonate, albite, and quartz deposition in several northern mines were isotopically heavy (delta 18 O [asymp] 8-14ppm; delta D between about -10 and -50ppm) and do not resemble seawater, magmatic, or meteoric waters. Metasomatic and vein-filling mica, dolomite, magnesite, and quartz in altered ultramafic rocks generally formed from fluids with similar Sr and O isotope ratios at a given locality. Consistent quartz-mica delta 18 O fractionations (delta 18 O (sub Q-M) = 4.5-4.9ppm) from various localities imply uniform equilibration temperatures, probably between 300 degrees and 350 degrees C. On a local (mine) scale, fluids responsible for both carbonate alteration of mafic and ultramafic wall rocks and albitic alteration of felsic and pelitic rocks had similar Sr isotope

Genetic Aspects of Gold Mineralization at Some Occurrences in the Eastern Desert of Egypt

NASA Astrophysics Data System (ADS)

Abd El Monsef, M.; Slobodník, M.; Salem, I. A.

2012-04-01

in each area and revealing the ore mineralogy and the ore textures, geochemical analyses (including rare earth elements) are to be used in order to determine the tectonic setting and magmatic evolution of the host intrusions, scanning electron microscope, microprobe analysis, stable isotopes and fluid inclusions will serve as a new part of this study in detection of the origin and the physico-chemical conditions (P-T condition) for the gold precipitation, Age dating of the host intrusion and mineralization will be based on K-Ar for dating potassium-bearing minerals in fresh host rocks and hydrothermal mineral phases.

Getting the Gold Treatment

NASA Technical Reports Server (NTRS)

2002-01-01

Epner Technology, Inc., worked with Goddard Space Center to apply gold coating to the Vegetation Canopy Lidar (VCL) mirror. This partnership resulted in new commercial applications for Epner's LaserGold(R) process in the automotive industry. Previously, the company did not have equipment large enough to handle the plating of the stainless steel panels cost effectively. Seeing a chance to renew this effort, Epner Technology and Goddard entered into an agreement by which NASA would fund the facility needed to do the gold-plating, and Epner Technology would cover all other costs as part of their internal research and development. The VCL mirror project proceeded successfully, fulfilling Goddard's needs and leaving Epner Technology with a new facility to provide LaserGold for the automotive industry. The new capability means increased power savings and improvements in both quality and production time for BMW Manufacturing Corporation of Spartanburg, South Carolina, and Cadillac of Detroit, Michigan, as well as other manufacturers who have implemented Epner Technology's LaserGold process. LaserGold(R) is a registered trademark of Epner Technology, Inc.

A porphyrin complex of Gold(I): (Phosphine)gold(I) azides as cation precursors

PubMed Central

Partyka, David V.; Robilotto, Thomas J.; Zeller, Matthias; Hunter, Allen D.; Gray, Thomas G.

2008-01-01

A silver- and Brönsted acid-free protocol for generating the (tricyclohexylphosphine)gold(I) cation from the corresponding azide complexes is disclosed. The gold(I) cations so liberated are trapped by complexation with octaethylporphyrin. The first structurally authenticated gold(I) porphyrin complex crystallizes with formula C72H112Au2F12N4P2Sb2, space group C2/c, a = 21.388 (4), b = 19.679 (4), c = 19.231 (3) Å; β = 111.030 (3)°. Solution spectroscopic studies indicate that the di-gold complex fragments on dissolution in organic solvents. Approximate density-functional theory calculations find an electrostatic origin for the binding of two gold(I) centers to the unprotonated nitrogen atoms, despite greater orbital density on the porphyrin meso carbons. PMID:18780788

A novel 'Gold on Gold' biosensing scheme for an on-fiber immunoassay

NASA Astrophysics Data System (ADS)

Punjabi, N.; Satija, J.; Mukherji, S.

2015-05-01

In this paper, we propose a novel „gold on gold‟ biosensing scheme for absorbance based fiber-optic biosensor. First, a self-assembled monolayer of gold nanoparticles is formed at the sensing region of the fiber-optic probe by incubating an amino-silanized probe in a colloidal gold solution. Thereafter, the receptor moieties, i.e. Human immunoglobulin G (HIgG) were immobilized by using standard alkanethiol and classic carbodiimide coupling chemistry. Finally, biosensing experiments were performed with different concentrations of gold nanoparticle-tagged analyte, i.e. Goat anti- Human immunoglobulin G (Nanogold-GaHIgG). The sensor response was observed to be more than five-fold compared to the control bioassay, in which the sensor matrix was devoid of gold nanoparticle film. Also, the response was found to be ~10 times higher compared to the FITC-tagged scheme and ~14.5 times better compared to untagged scheme. This novel scheme also demonstrated the potential in improving the limit of detection for the fiber-optic biosensors.

Stable isotope labeling by essential nutrients in cell culture for preparation of labeled coenzyme A and its thioesters.

PubMed

Basu, Sankha S; Mesaros, Clementina; Gelhaus, Stacy L; Blair, Ian A

2011-02-15

Stable isotope dilution mass spectrometry (MS) represents the gold standard for quantification of endogenously formed cellular metabolites. Although coenzyme A (CoA) and acyl-CoA thioester derivatives are central players in numerous metabolic pathways, the lack of a commercially available isotopically labeled CoA limits the development of rigorous MS-based methods. In this study, we adapted stable isotope labeling by amino acids in cell culture (SILAC) methodology to biosynthetically generate stable isotope labeled CoA and thioester analogues for use as internal standards in liquid chromatography/multiple reaction monitoring mass spectrometry (LC/MRM-MS) assays. This was accomplished by incubating murine hepatocytes (Hepa 1c1c7) in media in which pantothenate (a precursor of CoA) was replaced with [(13)C(3)(15)N(1)]-pantothenate. Efficient incorporation into various CoA species was optimized to >99% [(13)C(3)(15)N(1)]-pantothenate after three passages of the murine cells in culture. Charcoal-dextran-stripped fetal bovine serum (FBS) was found to be more efficient for serum supplementation than dialyzed or undialyzed FBS, due to lower contaminating unlabeled pantothenate content. Stable isotope labeled CoA species were extracted and utilized as internal standards for CoA thioester analysis in cell culture models. This methodology of stable isotope labeling by essential nutrients in cell culture (SILEC) can serve as a paradigm for using vitamins and other essential nutrients to generate stable isotope standards that cannot be readily synthesized.

Analysis of gold(I/III)-complexes by HPLC-ICP-MS demonstrates gold(III) stability in surface waters.

PubMed

Ta, Christine; Reith, Frank; Brugger, Joël; Pring, Allan; Lenehan, Claire E

2014-05-20

Understanding the form in which gold is transported in surface- and groundwaters underpins our understanding of gold dispersion and (bio)geochemical cycling. Yet, to date, there are no direct techniques capable of identifying the oxidation state and complexation of gold in natural waters. We present a reversed phase ion-pairing HPLC-ICP-MS method for the separation and determination of aqueous gold(III)-chloro-hydroxyl, gold(III)-bromo-hydroxyl, gold(I)-thiosulfate, and gold(I)-cyanide complexes. Detection limits for the gold species range from 0.05 to 0.30 μg L(-1). The [Au(CN)2](-) gold cyanide complex was detected in five of six waters from tailings and adjacent monitoring bores of working gold mines. Contrary to thermodynamic predictions, evidence was obtained for the existence of Au(III)-complexes in circumneutral, hypersaline waters of a natural lake overlying a gold deposit in Western Australia. This first direct evidence for the existence and stability of Au(III)-complexes in natural surface waters suggests that Au(III)-complexes may be important for the transport and biogeochemical cycling of gold in surface environments. Overall, these results show that near-μg L(-1) enrichments of Au in environmental waters result from metastable ligands (e.g., CN(-)) as well as kinetically controlled redox processes leading to the stability of highly soluble Au(III)-complexes.

Structural controls on Carlin-type gold mineralization in the gold bar district, Eureka County, Nevada

USGS Publications Warehouse

Yigit, O.; Nelson, E.P.; Hitzman, M.W.; Hofstra, A.H.

2003-01-01

The Gold Bar district in the southern Roberts Mountains, 48 km northwest of Eureka, Nevada, contains one main deposit (Gold Bar), five satellite deposits, and other resources. Approximately 0.5 Moz of gold have been recovered from a resource of 1,639,000 oz of gold in Carlin-type gold deposits in lower plate, miogeoclinal carbonate rocks below the Roberts Mountains thrust. Host rocks are unit 2 of the Upper Member of the Devonian Denay Formation and the Bartine Member of the McColley Canyon Formation. Spatial and temporal relations between structures and gold mineralization indicate that both pre-Tertiary and Tertiary structures were important controls on gold mineralization. Gold mineralization occurs primarily along high-angle Tertiary normal faults, some of which are reactivated reverse faults of Paleozoic or Mesozoic age. Most deposits are localized at the intersection of northwest- and northeast-striking faults. Alteration includes decalcification, and to a lesser extent, silicification along high-angle faults. Jasperoid (pervasive silicification), which formed along most faults and in some strata-bound zones, accounts for a small portion of the ore in every deposit. In the Gold Canyon deposit, a high-grade jasperoid pipe formed along a Tertiary normal fault which was localized along a zone of overturned fault-propagation folds and thrust faults of Paleozoic or Mesozoic age.

Study of thermochemical sulfate reduction mechanism using compound specific sulfur isotope analysis

NASA Astrophysics Data System (ADS)

Meshoulam, Alexander; Ellis, Geoffrey S.; Said Ahmad, Ward; Deev, Andrei; Sessions, Alex L.; Tang, Yongchun; Adkins, Jess F.; Liu, Jinzhong; Gilhooly, William P.; Aizenshtat, Zeev; Amrani, Alon

2016-09-01

The sulfur isotopic fractionation associated with the formation of organic sulfur compounds (OSCs) during thermochemical sulfate reduction (TSR) was studied using gold-tube pyrolysis experiments to simulate TSR. The reactants used included n-hexadecane (n-C16) as a model organic compound with sulfate, sulfite, or elemental sulfur as the sulfur source. At the end of each experiment, the S-isotopic composition and concentration of remaining sulfate, H2S, benzothiophene, dibenzothiophene, and 2-phenylthiophene (PT) were measured. The observed S-isotopic fractionations between sulfate and BT, DBT, and H2S in experimental simulations of TSR correlate well with a multi-stage model of the overall TSR process. Large kinetic isotope fractionations occur during the first, uncatalyzed stage of TSR, 12.4‰ for H2S and as much as 22.2‰ for BT. The fractionations decrease as the H2S concentration increases and the reaction enters the second, catalyzed stage. Once all of the oxidizable hydrocarbons have been consumed, sulfate reduction ceases and equilibrium partitioning then dictates the fractionation between H2S and sulfate (∼17‰). Experiments involving sparingly soluble CaSO4 show that during the second catalytic phase of TSR the rate of sulfate reduction exceeds that of sulfate dissolution. In this case, there is no apparent isotopic fractionation between source sulfate and generated H2S, as all of the available sulfate is effectively reduced at all reaction times. When CaSO4 is replaced with fully soluble Na2SO4, sulfate dissolution is no longer rate limiting and significant S-isotopic fractionation is observed. This supports the notion that CaSO4 dissolution can lead to the apparent lack of fractionation between H2S and sulfate produced by TSR in nature. The S-isotopic composition of individual OSCs record information related to geochemical reactions that cannot be discerned from the δ34S values obtained from bulk phases such as H2S, oil, and sulfate minerals, and

Sulfur, carbon, hydrogen, and oxygen isotope geochemistry of the Idaho cobalt belt

USGS Publications Warehouse

Johnson, Craig A.; Bookstrom, Arthur A.; Slack, John F.

2012-01-01

Cobalt-copper ± gold deposits of the Idaho cobalt belt, including the deposits of the Blackbird district, have been analyzed for their sulfur, carbon, hydrogen, and oxygen isotope compositions to improve the understanding of ore formation. Previous genetic hypotheses have ranged widely, linking the ores to the sedimentary or diagenetic history of the host Mesoproterozoic sedimentary rocks, to Mesoproterozoic or Cretaceous magmatism, or to metamorphic shearing. The δ34S values are nearly uniform throughout the Blackbird dis- trict, with a mean value for cobaltite (CoAsS, the main cobalt mineral) of 8.0 ± 0.4‰ (n = 19). The data suggest that (1) sulfur was derived at least partly from sedimentary sources, (2) redox reactions involving sulfur were probably unimportant for ore deposition, and (3) the sulfur was probably transported to sites of ore for- mation as H2S. Hydrogen and oxygen isotope compositions of the ore-forming fluid, which are calculated from analyses of biotite-rich wall rocks and tourmaline, do not uniquely identify the source of the fluid; plausible sources include formation waters, metamorphic waters, and mixtures of magmatic and isotopically heavy meteoric waters. The calculated compositions are a poor match for the modified seawaters that form vol- canogenic massive sulfide (VMS) deposits. Carbon and oxygen isotope compositions of siderite, a mineral that is widespread, although sparse, at Blackbird, suggest formation from mixtures of sedimentary organic carbon and magmatic-metamorphic carbon. The isotopic compositions of calcite in alkaline dike rocks of uncertain age are consistent with a magmatic origin. Several lines of evidence suggest that siderite postdated the emplacement of cobalt and copper, so its significance for the ore-forming event is uncertain. From the stable isotope perspective, the mineral deposits of the Idaho cobalt belt contrast with typical VMS and sedimentary exhalative deposits. They show characteristics of deposit

Gold grade variation and particle microchemistry in exploration pits of the Batouri gold district, SE Cameroon

NASA Astrophysics Data System (ADS)

Vishiti, A.; Suh, C. E.; Lehmann, B.; Egbe, J. A.; Shemang, E. M.

2015-11-01

The Batouri area hosts lode-gold mineralization under several-m-thick lateritic cover. Pitting to bed rock on a geochemical Au anomaly defined from previous reconnaissance soil sampling identified five horizons ranging from saprock at the base to laterite at the top. Analysis of bulk samples from each horizon by fire assay shows that most of the horizons are barren although 119 ppb and 48 ppb Au values were obtained from one laterite horizon and one saprolite horizon, respectively, from two separate pits. All the horizons were panned and particulate gold was also recovered only from these two horizons. The gold grains from both horizons are morphologically and compositionally indistinguishable with rare quartz, pyrite and galena inclusions. The grains have irregular, sub-rounded, bean to elongated shapes and they show a remarkable core-rim zonation. Electron microprobe analysis of the grains recorded high gold content in the rims (86.3-100 wt%) and along fissures within the grains (95.1-100 wt%). The cores are relatively Ag rich (11.8-14 wt% Ag) while the rims (0.63-13.7 wt% Ag, most of the values fall within the lower limit of this range) and fissures (0.03-5.02 wt% Ag) are poor in Ag. The low Ag concentration in the rims and along fissures is attributed to preferential leaching of Ag; a process recognized in gold grains and platiniferous alloys from alluvia. The core composition of the grains is similar to that of primary gold composition in the bedrock. These results show that gold in the soil is relic particulate gold derived from the primary source with no evidence of secondary gold precipitation in the weathering cycle. In all the pits no horizon was systematically enriched in gold suggesting there has been no chemical remobilization of gold in this environment. Rather the dispersion of gold here is in the particulate form. Therefore combining particulate gold features with assay data is relevant to exploration in such tropical environments.

Mineralogy, mineral chemistry, and paragenesis of gold, silver, and base-metal ores of the North Amethyst vein system, San Juan Mountains, Mineral County, Colorado

USGS Publications Warehouse

Foley, Nora K.; Caddey, Stanton W.; Byington, Craig B.; Vardiman, David M.

1993-01-01

Mineralogic, lead-isotopic, and fluid-inclusion characteristics of the younger association are similar to those of ores of the southern and central parts of the Creede mining district. In contrast, the gold and manganese-silicate assemblages of the older association are rare to absent in the southern and central parts of the district. The local and early occurrence of the manganese and gold assemblages may indicate that they formed in a small hydrothermal cell that predated the extensive hydrothermal system from which ores of the central and southern parts of the Creede district are proposed to have been deposited (Bethke, 1988). If similar early-stage cells were present in the southern and central parts of the district, they may have been replaced or overprinted by later assemblages, and they may remain to be discovered. In the latter case, mineral assemblages that formed at early stages in the paragenesis hold the most promise for gold exploration.

Automated system measuring triple oxygen and nitrogen isotope ratios in nitrate using the bacterial method and N2 O decomposition by microwave discharge.

PubMed

Hattori, Shohei; Savarino, Joel; Kamezaki, Kazuki; Ishino, Sakiko; Dyckmans, Jens; Fujinawa, Tamaki; Caillon, Nicolas; Barbero, Albane; Mukotaka, Arata; Toyoda, Sakae; Well, Reinhard; Yoshida, Naohiro

2016-12-30

Triple oxygen and nitrogen isotope ratios in nitrate are powerful tools for assessing atmospheric nitrate formation pathways and their contribution to ecosystems. N 2 O decomposition using microwave-induced plasma (MIP) has been used only for measurements of oxygen isotopes to date, but it is also possible to measure nitrogen isotopes during the same analytical run. The main improvements to a previous system are (i) an automated distribution system of nitrate to the bacterial medium, (ii) N 2 O separation by gas chromatography before N 2 O decomposition using the MIP, (iii) use of a corundum tube for microwave discharge, and (iv) development of an automated system for isotopic measurements. Three nitrate standards with sample sizes of 60, 80, 100, and 120 nmol were measured to investigate the sample size dependence of the isotope measurements. The δ 17 O, δ 18 O, and Δ 17 O values increased with increasing sample size, although the δ 15 N value showed no significant size dependency. Different calibration slopes and intercepts were obtained with different sample amounts. The slopes and intercepts for the regression lines in different sample amounts were dependent on sample size, indicating that the extent of oxygen exchange is also dependent on sample size. The sample-size-dependent slopes and intercepts were fitted using natural log (ln) regression curves, and the slopes and intercepts can be estimated to apply to any sample size corrections. When using 100 nmol samples, the standard deviations of residuals from the regression lines for this system were 0.5‰, 0.3‰, and 0.1‰, respectively, for the δ 18 O, Δ 17 O, and δ 15 N values, results that are not inferior to those from other systems using gold tube or gold wire. An automated system was developed to measure triple oxygen and nitrogen isotopes in nitrate using N 2 O decomposition by MIP. This system enables us to measure both triple oxygen and nitrogen isotopes in nitrate with comparable precision

Thermal stability of supported gold nanoparticles

NASA Astrophysics Data System (ADS)

Turba, Timothy Fredrick

Nanoparticle gold is of interest for a wide array of applications including catalysis, gas sensing, and light absorption for color filters and optical switches. Many of these applications are dependent upon the particles having sizes <5nm. In this paper, the thermal stability of nanoparticle gold is evaluated. Unsupported gold nanoparticles can grow (and in some cases double their size) even at room temperature. An important approach to stabilizing gold nanoparticles is through an interaction with a suitable substrate support material. Semiconductor substrates such as GaN are important supports for gold nanoparticles for applications such as sensors, but GaN does not provide a significant stabilizing effect at high temperatures. This paper covers a number of different substrate materials and in particular shows that for some substrates, such as SiO2, gold nanoparticles can be stable at temperatures up to 500°C, which is significantly above the Tammann temperature for bulk gold (395°C). In this dissertation, gold nanoparticles are shown to have complete stability on aluminum-supported silica nanosprings at 550°C in air. This stability window is one of the highest reported for nanoparticle gold and potentially enables a number of applications for this highly active catalyst. X-ray photoelectron spectroscopy measurements were performed before and after heating to 550°C to determine the nature of the interaction between gold and SiO2. A 1.2 eV drop in gold 4f binding energy after heating signified a shift to anionic gold particles (i.e., Au delta-) indicative of strong bonds to oxygen vacancies with neighboring Sidelta+ atoms. Heating in hydrogen at 550°C resulted in a binding energy decrease of 0.4 eV due to an increased fraction of particles with decreased coordination numbers (i.e., more atoms at edges and corners). Lastly, heating gold nanoparticles in an atmosphere of 10% relative humidity at 550°C resulted in apparent encapsulation of the gold.

Prospects of gold mineralization in the Gilgit-Baltistan Province of Pakistan

NASA Astrophysics Data System (ADS)

Shah, M. T.; Khan, S. D.; Tahirkheli, T.; Ahmad, L.; Miandad, S.; Rehman, A. U.; Ali, L.

2012-12-01

mainly pyrite and chalcopyrite with subordinate amount of bornite and tetrahedrite. Surface leaching of these phases to malachite, azurite and limonite is common. Quartz veining, silicification, carbonization and at places brecciation are the common features of these alteration zones. The concentrations of gold were found in the range of 3ppb to 112ppb, <5- 95ppb, 1ppb to 545ppb, 1ppb to 385 and 1ppb to 318ppb in the alteration zones of Golo Das, Bagrot valley, Shigri Bala, Machulu and Ranthak areas respectively. The barren rock samples have generally <5ppb gold. This is indicative of the multi-times enrichment of gold in the alteration zones. The sulfide mineralization along with gold in the alteration zones could be attributed to the hydrothermal/epithermal activity involving meteoric, igneous and or metamorphic fluid individually or mixture of these. The occurrence of dioritic intrusions (igneous fluid source) and the transitional dilated zones (metamorphic fluid source) on the major reactivated thrust fault (i.e., NSZ) in the vicinity of these alteration zones strengthen these observations. However, isotopic studies are underway to solve this problem. This study suggests that the alteration zones in the studied areas have the potential to be explored in detail for possible economical gold mineralization.

Native gold in Hawaiian alkalic magma

USGS Publications Warehouse

Sisson, T.W.

2003-01-01

Native gold found in fresh basanite glass from the early submarine phase of Kilauea volcano, Hawaii, may be the first documented case of the transport of gold as a distinct precious metal phase in a mantle-derived magma. The gold-bearing glass is a grain in bedded volcanic glass sandstone (Japan Marine Science and Technology Center (JAMSTEC) sample S508-R3) collected by the submersible Shinkai 6500 at 3879 m depth off Kilauea's south flank. Extensive outcrops there expose debris-flow breccias and sandstones containing submarine-erupted alkalic rock fragments and glasses from early Kilauea. Precipitation of an immiscible gold liquid resulted from resorption of magmatic sulfides during crystallization-differentiation, with consequent liberation of sulfide-hosted gold. Elevated whole-rock gold concentrations (to 36 ppb) for fresh lavas and clasts from early Kilauea further show that some magmas erupted at the beginning stages of Hawaiian shield volcanoes were distinctly gold rich, most likely owing to limited residual sulfide in their mantle source. Alkalic magmas at other ocean islands may also be gold rich, and oceanic hot-spot provinces may contain underappreciated gold resources.

Detailed energy distributions in laser-produced plasmas of solid gold and foam gold planar targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Yunsong; Department of Engineering Physics, Tsinghua University, Beijing 100084; Zhang, Lu

Foam gold was proposed to increase the laser to x-ray conversion efficiency due to its important applications. To understand the mechanism of x-ray enhancement, the detailed energy distributions and plasma profiles for laser-irradiated solid gold and foam gold targets were studied comparatively by hydrodynamic simulations using the code Multi-1D. It is confirmed that the radiation heat wave is subsonic for the normal solid gold target, while supersonic for the foam gold target. The shock wave, which is behind the supersonic radiation heat wave for the foam gold target, generates a plasma temperature gradient with high temperature near the shock wavemore » front to produce an additional net outward radiation for enhancement of the x-ray emission. Much larger inward plasma velocity is also driven by the shock wave as an initial plasma velocity for the laser deposition and electron thermal conduct zone, which decreases the expanding plasma kinetic energy loss and helps to increase the x-ray radiation.« less

41 CFR 101-45.002 - Gold.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 41 Public Contracts and Property Management 2 2014-07-01 2012-07-01 true Gold. 101-45.002 Section... PERSONAL PROPERTY § 101-45.002 Gold. (a) Gold will be sold in accordance with this section and part 102-38 of the Federal Management Regulation. (b) Sales of gold shall be processed to— (1) Use the sealed bid...

41 CFR 101-45.002 - Gold.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 41 Public Contracts and Property Management 2 2012-07-01 2012-07-01 false Gold. 101-45.002 Section... PERSONAL PROPERTY § 101-45.002 Gold. (a) Gold will be sold in accordance with this section and part 102-38 of the Federal Management Regulation. (b) Sales of gold shall be processed to— (1) Use the sealed bid...

41 CFR 101-45.002 - Gold.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 41 Public Contracts and Property Management 2 2011-07-01 2007-07-01 true Gold. 101-45.002 Section... PERSONAL PROPERTY § 101-45.002 Gold. (a) Gold will be sold in accordance with this section and part 102-38 of the Federal Management Regulation. (b) Sales of gold shall be processed to— (1) Use the sealed bid...

41 CFR 101-45.002 - Gold.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 41 Public Contracts and Property Management 2 2013-07-01 2012-07-01 true Gold. 101-45.002 Section... PERSONAL PROPERTY § 101-45.002 Gold. (a) Gold will be sold in accordance with this section and part 102-38 of the Federal Management Regulation. (b) Sales of gold shall be processed to— (1) Use the sealed bid...

41 CFR 101-45.002 - Gold.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 41 Public Contracts and Property Management 2 2010-07-01 2010-07-01 true Gold. 101-45.002 Section... PERSONAL PROPERTY § 101-45.002 Gold. (a) Gold will be sold in accordance with this section and part 102-38 of the Federal Management Regulation. (b) Sales of gold shall be processed to— (1) Use the sealed bid...

Gold metal liquid-like droplets.

PubMed

Smirnov, Evgeny; Scanlon, Micheál D; Momotenko, Dmitry; Vrubel, Heron; Méndez, Manuel A; Brevet, Pierre-Francois; Girault, Hubert H

2014-09-23

Simple methods to self-assemble coatings and films encompassing nanoparticles are highly desirable in many practical scenarios, yet scarcely any examples of simple, robust approaches to coat macroscopic droplets with continuous, thick (multilayer), reflective and stable liquid nanoparticle films exist. Here, we introduce a facile and rapid one-step route to form films of reflective liquid-like gold that encase macroscopic droplets, and we denote these as gold metal liquid-like droplets (MeLLDs). The present approach takes advantage of the inherent self-assembly of gold nanoparticles at liquid-liquid interfaces and the increase in rates of nanoparticle aggregate trapping at the interface during emulsification. The ease of displacement of the stabilizing citrate ligands by appropriate redox active molecules that act as a lubricating molecular glue is key. Specifically, the heterogeneous interaction of citrate stabilized aqueous gold nanoparticles with the lipophilic electron donor tetrathiafulvalene under emulsified conditions produces gold MeLLDs. This methodology relies exclusively on electrochemical reactions, i.e., the oxidation of tetrathiafulvalene to its radical cation by the gold nanoparticle, and electrostatic interactions between the radical cation and nanoparticles. The gold MeLLDs are reversibly deformable upon compression and decompression and kinetically stable for extended periods of time in excess of a year.

Gold Coating

NASA Technical Reports Server (NTRS)

1997-01-01

Epner Technology Inc. responded to a need from Goddard Space Flight Center for the ultimate in electroplated reflectivity needed for the Mars Global Surveyor Mars Orbiter Laser Altimeter (MOLA). Made of beryllium, the MOLA mirror was coated by Epner Technology Laser Gold process, specially improved for the project. Improved Laser Gold- coated reflectors have found use in an epitaxial reactor built for a large semiconductor manufacturer as well as the waveguide in Braun-Thermoscan tympanic thermometer and lasing cavities in various surgical instruments.

Origin of high-grade gold ore, source of ore fluid components, and genesis of the Meikle and neighboring Carlin-type deposits, Northern Carlin Trend, Nevada

USGS Publications Warehouse

Emsbo, P.; Hofstra, A.H.; Lauha, E.A.; Griffin, G.L.; Hutchinson, R.W.

2003-01-01

The Meikle mine exploits one of the world's highest grade Carlin-type gold deposits with reserves of ca. 220 t gold at an average grade of 24.7 g/t. Locally, gold grades exceed 400 g/t. Several geologic events converged at Meikle to create these spectacular gold grades. Prior to mineralization, a Devonian hydrothermal system altered the Bootstrap limestone to Fe-rich dolomite. Subsequently the rocks were brecciated by faulting and Late Jurassic intrusive activity. The resulting permeability focused flow of late Eocene Carlin-type ore fluids and allowed them to react with the Fe-rich dolomite. Fluid inclusion data and mineral assemblages indicate that these fluids were hot (ca. 220??C),of moderate salinity (400 g/t. Petrographic observations, geochemical data, and stable isotope results from the Meikle mine and other deposits at the Goldstrike mine place important constraints on genetic models for Meikle and other Carlin-type gold deposits on the northern Carlin trend. The ore fluids were meteoric water (??D = -135???, ??18O = -5???) that interacted with sedimentary rocks at a water/rock ratio of ca. 1 and temperatures of ca. 220??C. The absence of significant silicification suggests that there was little cooling of the ore fluids during mineralization. These two observations strongly suggest that ore fluids were not derived from deep sources but instead flowed parallel to isotherms. The gold was transported by H2S (??34S = 9???), which was derived from Paleozoic sedimentary rocks. The presence of auriferous sedimentary exhalative mineralization in the local stratigraphic sequence raises the possibility that preexisting concentrations of gold contributed to the Carlin-type deposits. Taken together our observations suggest that meteoric water evolved to become an ore fluid by shallow circulation through previously gold- and sulfur-enriched rocks. Carlin-type gold deposits formed where these fluids encountered permeable, reactive Fe-rich rocks.

Biorecovery of gold

USGS Publications Warehouse

Eisler, R.

2003-01-01

Recovery of ionic and metallic gold (Au) from a wide variety of solutions by selected species of bacteria, yeasts, fungi, algae, and higher plants is documented. Gold accumulations were up to 7.0 g/kg dry weight (DW) in various species of bacteria, 25.0 g/kg DW in freshwater algae, 84.0 g/kg DW in peat, and 100.0 g/kg DW in dried fungus mixed with keratinous material. Mechanisms of accumulation include oxidation, dissolution, reduction, leaching, and sorption. Uptake patterns are significantly modified by the physicochemical milieu. Crab exoskeletons accumulate up to 4.9 g Au/kg DW; however, gold accumulations in various tissues of living teleosts, decapod crustaceans, and bivalve molluscs are negligible.

Helium isotope data from the Goldfield epithermal system, Nevada: Evidence for volatile input from a primitive mantle source during ore formation

NASA Astrophysics Data System (ADS)

Hofstra, A. H.; Manning, A. H.

2013-12-01

Goldfield is the largest high sulfidation epithermal gold mining district in the United States with over 130 t of gold production and 23 sq. km. of argillic alteration (with alunite, pyrophyllite, or kaolinite). It formed at 20.0×0.5 Ma in an andesite to rhyolite volcanic field in the ancestral Cascades continental magmatic arc. Previous stable isotope studies of quartz, alunite, and sulfide minerals suggest that the gold ores formed in a magmatic vapor plume derived from a subjacent porphyry intrusion, which displaced and mixed with meteoric groundwater at shallow levels. The isotopic compositions of He, Ne, and Ar trapped in fluid inclusions in hydrothermal minerals (Cu-sulfides and sulfosalts, pyrite, quartz) were measured to further constrain volatile source and migration processes. Gases were released by thermal decrepitation at 300°C and analyzed using a high resolution static sector mass spectrometer. The isotopic compositions of Ne and Ar are typical of air-saturated water (ASW), indicating that the samples contain little nucleogenic Ne or radiogenic Ar derived from underlying old crustal sources. In contrast, He/Ne and He/Ar ratios are much greater than ASW, indicating that a component of He was produced in the subsurface. The wide range of He R/Ra values, 0.4 to 20, suggests that He was derived from both crustal and mantle sources. 4He/40Ar* and 4He/21Ne* systematics are characteristic of magma degassing. The highest R/Ra values (15-20) are well above those previously reported for modern volcanic rocks and geothermal fluids in subduction-related arcs. Such R/Ra values indicate a primitive mantle source, perhaps below the subducting slab. We hypothesize that the discharge of metal-laden fluids from the subjacent porphyry intrusion was influenced by the input of hot volatiles from mafic mantle-derived magmas. This scenario implies a magma column that remained open to the flux of volatiles over a considerable depth range, from the mantle to the shallow

Isotopic Biogeochemistry

NASA Technical Reports Server (NTRS)

Hayes, J. M.

1985-01-01

An overview is provided of the biogeochemical research. The funding, productivity, personnel and facilities are reviewed. Some of the technical areas covered are: carbon isotopic records; isotopic studies of banded iron formations; isotope effects in microbial systems; studies of organic compounds in ancient sediments; and development in isotopic geochemistry and analysis.

The IGY Gold History Preservation Program

NASA Astrophysics Data System (ADS)

Thompson, B. J.; Cliver, E. W.; Gentile, L. C.; Sigsbee, K. M.; Doel, R. E.

2006-05-01

An important part of the 2007 International Year activities will be preserving the history and memory of IGY 1957. The "IGY Gold" History initiative has several goals: 1) identifying and recognizing planners of and participants in the first IGY, 2) preserving memoirs, articles, photographs, and all items of historical significance for the IGY, 3) making these items available to historians, researchers, etc., 4) serving as a contact service for these activities, 5) spreading awareness of the history of geophysics, and 6) planning special events and "reunions." The IGY "Gold" Club identifies participants from the first IGY (gold symbolizing the 50th anniversary). "Gold club" participants will be rewarded with a special "IGY Gold Anniversary" certificate of recognition and a special commemorative "IGY Gold" lapel pin. Many IGY participants from around the globe have received IGY Gold Club awards, and many have submitted valuable historical material about the IGY activities. This is a joint program of the IHY, eGY, IPY, IYPE and IUGG.

The Hatu gold anomaly, Xinjiang-Uygur Autonomous Region, China - testing the hypothesis of aeolian transport of gold

USGS Publications Warehouse

Smith, D.B.; Theobald, P.K.; Shiquan, S.; Tianxiang, R.; Zhihui, H.

1993-01-01

In 1987, a cooperative project between the U.S. Geological Survey and the Institute of Geophysical and Geochemical Exploration was initiated to evaluate the origin of the Hatu gold anomaly. The anomaly is located in the Hatu mining district in the northwest corner of Xinjiang-Uygur Autonomous Region in northwest China. The climate is semiarid to arid and wind erosion predominates. A regional soil survey of the Hatu district, based on samples collected on a 200 by 500 m grid and composited prior to chemical analysis to a density of one sample per square km, delineated a series of south-southeast-trending Au anomalies. Anomalous Au values range from 5 ppb to more than 700 ppb. The Hatu anomaly, the most prominent of these anomalies, is more than 30 km long and about 5 km wide. The mining town of Hatu and the economic gold deposits of Qiqu 1 and Qiqu 2 are at the northern end of this anomaly. The axis of the Hatu anomaly cuts across mapped structure and stratigraphy in the district, but is parallel to the prevailing wind direction. This observation led to the hypothesis that the Hatu anomaly is the result of acolian dispersion of gold from the vicinity of Qiqu 1 and Qiqu 2. The alternative interpretation, that the anomalies reflected additional primary gold occurrences, was not consistent with existing information on the known occurrences and the geology. The investigation led to the identification of three types of gold in heavy-mineral concentrates derived from stream sediments that were collected along the axis of the Hatu anomaly: (1) free gold, (2) gold in pyrite, and (3) gold included in quartz. Gold in quartz was only observed within 2 km of Qiqu 1. The size of the gold particles and the number of gold particles in these samples did not decrease with distance from Qiqu 1 as would be expected from aeolian or fluvial dispersion from a point source. Instead, both the size and amount of gold increased significantly at a distance of 3.5 km from Qiqu 1 and this

Fluid inclusion and stable isotopes studies of epithermal gold-bearing veins in the SE Afar Rift (Djibouti)

NASA Astrophysics Data System (ADS)

Moussa, N.; Boiron, M. C.; Grassineau, N.; Fouquet, Y.; Le Gall, B.; Mohamed, J.

2015-12-01

The Afar rift results from the interaction of a number of actively-propagating tectono-magmatic axes. Recent field investigations in the SE Afar rift have emphasized the importance of hydrothermal system in rift-related volcanic complexes. Mineralization occur as gold-silver bearing veins and are associated with felsic volcanism. Late carbonate veins barren of sulfides and gold are common. The morphologies and textures of quartz show crustiform colloform banding, massive and breccias. Microthermometric measurements were made on quartz-hosted two phases (liquid + vapor) inclusions; mean homogenization temperature range from 150°C to 340°C and ice-melting temperatures range from -0.2° to 1.6°C indicating that inclusion solutions are dilute and contain 0.35 to 2.7 equivalent wt. % NaCl. Furthermore, δ18O and δ13C values from calcite range from 3.7 to 26.6 ‰ and -7.5 to 0.3‰, respectively. The presence of platy calcite and adularia indicate that boiling condition existed. This study shows that precious-metal deposition mainly occurred from hydrothermal fluids at 200°C at around 300 and 450 m below the present-day surface in a typical low-sulphidation epithermal environment.

SIMS chemical and isotopic analysis of impact features from LDEF experiments AO187-1 and AO187-2

NASA Technical Reports Server (NTRS)

Stadermann, Frank J.; Amari, Sachiko; Foote, John; Swan, Pat; Walker, Robert M.; Zinner, Ernst

1995-01-01

Previous secondary ion mass spectrometry (SIMS) studies of extended impact features from LDEF capture cell experiment AO187-2 showed that it is possible to distinguish natural and man-made particle impacts based on the chemical composition of projectile residues. The same measurement technique has now been applied to specially prepared gold target impacts from experiment AO187-1 in order to identify the origins of projectiles that left deposits too thin to be analyzed by conventional energy-dispersive x-ray (EDX) spectroscopy. The results indicate that SIMS may be the method of choice for the analysis of impact deposits on a variety of sample surfaces. SIMS was also used to determine the isotopic compositions of impact residues from several natural projectiles. Within the precision of the measurements all analyzed residues show isotopically normal compositions.

The extractive metallurgy of gold

NASA Astrophysics Data System (ADS)

Kongolo, K.; Mwema, M. D.

1998-12-01

Mössbauer spectroscopy has been successfully used in investigation of the gold compounds present in ores and the gold species which occur during the process metallurgy of this metal. This paper is a survey of the basic recovery methods and techniques used in extractive metallurgy of gold. Process fundamentals on mineral processing, ore leaching, zinc dust cementation, adsorption on activated carbon, electrowinning and refining are examined. The recovery of gold as a by-product of the copper industry is also described. Alternative processing methods are indicated in order to shed light on new interesting research topics where Mössbauer spectroscopy could be applied.

Geology, distribution, and classification of gold deposits in the western Qinling belt, central China

USGS Publications Warehouse

Mao, J.; Qiu, Yumin; Goldfarb, R.J.; Zhang, Z.; Garwin, S.; Fengshou, R.

2002-01-01

Gold deposits of the western Qinling belt occur within the western part of the Qinling-Dabie-Sulu orogen, which is located between the Precambrian North China and Yangtze cratons and east of the Songpan-Ganzi basin. The early Paleozoic to early Mesozoic orogen can be divided into northern, central, and southern zones, separated by the Shangdan and Lixian-Shanyang thrust fault systems. The northern zone consists of an early Paleozoic arc accreted to the North China craton by ca. 450 Ma. The central zone, which contains numerous orogenic gold deposits, is dominated by clastic rocks formed in a late Paleozoic basin between the converging cratonic blocks. The southern zone is characterized by the easternmost exposure of Triassic sedimentary rocks of the Songpan-Ganzi basin. These Early to Late Triassic turbidities, in part calcareous, of the immense Songpan-Ganzi basin also border the western Qinling belt to the west. Carlinlike gold deposits are abundant (1) along a westward extension of the southern zone defined by a window of early Paleozoic clastic rocks extending into the basin, and (2) within the easternmost margin of the basinal rocks to the south of the extension, and in adjacent cover rocks of the Yangtze craton. Triassic and Early Jurassic synkinematic granitoids are widespread across the western Qinling belt, as well as in the Songpan-Ganzi basin. Orogenic lode gold deposits along brittle-ductile shear zones occur within greenschist-facies, highly deformed, Devonian and younger clastic rocks of the central zone. Mainly coarse-grained gold, along with pyrite, pyrrhotite, arsenopyrite, and minor base metal sulfides, occur in networks of quartz veinlets, brecciated wall rock, and are dissminated in altered wall rock. Isotopic dates suggest that the deposits formed during the Late Triassic to Middle Jurassic as the leading edge of the Yangtze craton was thrust beneath rocks of the western Qinling belt. Many gold-bearing placers are distributed along the river

Quantitative Determination of Isotope Ratios from Experimental Isotopic Distributions

PubMed Central

Kaur, Parminder; O’Connor, Peter B.

2008-01-01

Isotope variability due to natural processes provides important information for studying a variety of complex natural phenomena from the origins of a particular sample to the traces of biochemical reaction mechanisms. These measurements require high-precision determination of isotope ratios of a particular element involved. Isotope Ratio Mass Spectrometers (IRMS) are widely employed tools for such a high-precision analysis, which have some limitations. This work aims at overcoming the limitations inherent to IRMS by estimating the elemental isotopic abundance from the experimental isotopic distribution. In particular, a computational method has been derived which allows the calculation of 13C/12C ratios from the whole isotopic distributions, given certain caveats, and these calculations are applied to several cases to demonstrate their utility. The limitations of the method in terms of the required number of ions and S/N ratio are discussed. For high-precision estimates of the isotope ratios, this method requires very precise measurement of the experimental isotopic distribution abundances, free from any artifacts introduced by noise, sample heterogeneity, or other experimental sources. PMID:17263354

Nature vs. nurture: gold perpetuates "stemness".

PubMed

Paul, Willi; Sharma, Chandra P; Deb, Kaushik Dilip

2011-01-01

Adult tissues contain quiescent reservoirs of multipotent somatic stem cells and pluripotent embryonic-like stem cells (ELSCs). Credited with regenerative properties gold is used across both -contemporary and -ancient medicines. Here, we show that gold exerted these effects by enhancing the pool of pluripotent ELSC while improving their stemness. We used hESCs as an in-vitro model to understand if gold could enhance self-renewal and pluripotency. Swarna-bhasma (SB), an ancient Indian gold microparticulate (41.1 nm), preparation, reduced spontaneous-differentiation, improved self-renewal, pluripotency and proliferation of hESCs. Colloidal gold-nanoparticles (GNP) (15.59 nm) were tested to confirm that the observations were attributable to nanoparticulate-gold. SB and GNP exposure: maintained -stemness, -karyotypic stability, enhanced pluripotency till day-12, increased average colony-sizes, and reduced the number of autonomously-derived differentiated FGFR1 positive fibroblast-niche-cells/colony. Particulate-gold induced upregulation of FGFR1 and IGF2 expression, and decrease in IGF1 secretion indicates IGF1/2 mediated support for enhanced pluripotency and self-renewal in hESCs.

Lichenoid dermatitis after consumption of gold-containing liquor.

PubMed

Russell, M A; Langley, M; Truett, A P; King, L E; Boyd, A S

1997-05-01

Medicinal gold has a well-known side effect profile that includes mucocutaneous eruptions. We describe three patients with a pruritic dermatitis that began after consumption of a gold-containing alcoholic beverage. Blood and urine gold levels, chemistry panels, hepatitis screens, skin biopsies, and patch tests were performed. The gold-containing liquor was analyzed for the presence and quantity of gold. The liquor consumed by all of the patients was a cinnamon schnapps with free-floating gold-colored flakes. Gold is present in the liquid portion of this liquor and in the solid flakes. Elevated levels of gold in the urine and blood were present in one patient 3 months after last drinking this beverage. Another patient had a positive patch test to gold sodium thiosulfate. All patients experienced improvement of their dermatitis after they stopped drinking the gold-containing liquor.

Hydrologic models of modern and fossil geothermal systems in the Great Basin: Genetic implications for epithermal Au-Ag and Carlin-type gold deposits

USGS Publications Warehouse

Person, M.; Banerjee, A.; Hofstra, A.; Sweetkind, D.; Gao, Y.

2008-01-01

The Great Basin region in the western United States contains active geothermal systems, large epithermal Au-Ag deposits, and world-class Carlin-type gold deposits. Temperature profiles, fluid inclusion studies, and isotopic evidence suggest that modern and fossil hydrothermal systems associated with gold mineralization share many common features, including the absence of a clear magmatic fluid source, discharge areas restricted to fault zones, and remarkably high temperatures (>200 ??C) at shallow depths (200-1500 m). While the plumbing of these systems varies, geochemical and isotopic data collected at the Dixie Valley and Beowawe geothermal systems suggest that fluid circulation along fault zones was relatively deep (>5 km) and comprised of relatively unexchanged Pleistocene meteoric water with small (<2.5%) shifts from the meteoric water line (MWL). Many fossil ore-forming systems were also dominated by meteoric water, but usually exhibit ??18O fluid-rock interactions with larger shifts of 5???-20??? from the MWL. Here we present a suite of two-dimensional regional (100 km) and local (40-50 km) scale hydrologic models that we have used to study the plumbing of modern and Tertiary hydrothermal systems of the Great Basin. Geologically and geophysically consistent cross sections were used to generate somewhat idealized hydrogeologic models for these systems that include the most important faults, aquifers, and confining units in their approximate configurations. Multiple constraints were used, including enthalpy, ??18O, silica compositions of fluids and/or rocks, groundwater residence times, fluid inclusion homogenization temperatures, and apatite fission track anomalies. Our results suggest that these hydrothermal systems were driven by natural thermal convection along anisotropic, subvertical faults connected in many cases at depth by permeable aquifers within favorable lithostratigraphic horizons. Those with minimal fluid ?? 18O shifts are restricted to high

Antibody-gold cluster conjugates

DOEpatents

Hainfeld, J.F.

1988-06-28

Antibody- or antibody fragment-gold cluster conjugates are shown wherein the conjugate size can be about 5.0 nm. Methods and reagents are disclosed in which antibodies or Fab' fragments thereof are covalently bound to a stable cluster of gold atoms. 2 figs.

Gold Nanoparticles Cytotoxicity

NASA Astrophysics Data System (ADS)

Mironava, Tatsiana

Over the last two decades gold nanoparticles (AuNPs) have been used for many scientific applications and have attracted attention due to the specific chemical, electronic and optical size dependent properties that make them very promising agents in many fields such as medicine, imagine techniques and electronics. More specifically, biocompatible gold nanoparticles have a huge potential for use as the contrast augmentation agent in X-ray Computed Tomography and Photo Acoustic Tomography for early tumor diagnostic as well these nanoparticles are extensively researched for enhancing the targeted cancer treatment effectiveness such as photo-thermal and radiotherapy. In most biomedical applications biocompatible gold nanoparticles are labeled with specific tumor or other pathology targeting antibodies and used for site specific drug delivery. However, even though gold nanoparticles poses very high level of anti cancer properties, the question of their cytotoxicity ones they are released in normal tissue has to be researched. Moreover, the huge amount of industrially produced gold nanoparticles raises the question of these particles being a health hazard, since the penetration is fairly easy for the "nano" size substances. This study focuses on the effect of AuNPs on a human skin tissue, since it is fall in both categories -- the side effects for biomedical applications and industrial workers and users' exposure during production and handling. Therefore, in the present project, gold nanoparticles stabilized with the biocompatible agent citric acid were generated and characterized by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). The cytotoxic effect of AuNPs release to healthy skin tissue was modeled on 3 different cell types: human keratinocytes, human dermal fibroblasts, and human adipose derived stromal (ADS) cells. The AuNPs localization inside the cell was found to be cell type dependent. Overall cytotoxicity was found to be dependent

Dating native gold by noble gas analyses

NASA Technical Reports Server (NTRS)

Niedermann, S.; Eugster, O.; Hofmann, B.; Thalmann, CH.; Reimold, W. U.

1993-01-01

Our recent work on He, Ne, and Ar in Alpine gold samples has demonstrated that gold is extremely retentive for He and could thus, in principle, be used for U/Th-He-4 dating. For vein-type gold from Brusson, Northern Italy, we derived a U/Th-He-4 age of 36 Ma, in agreement with the K-Ar formation age of associated muscovites and biotites. However, in placer gold from the Napf area, Central Switzerland, we observed large excesses of both He-4 and radiogenic Ar-40 (Ar-40 sub rad, defined as Ar-40-295.5-Ar-.36). The gas release systematics indicate two distinct noble gas components, one of which is released below about 800 C and the other one at the melting point of gold (1064 C). We now present results of He and Xe measurements in a 1 g placer gold sample from the river Kruempelgraben, as well as He and Ar data for Brusson vein-type gold and for gold from the Lily Gold Mine, South Africa. We calculate reasonable U/Th-He-4 as well as U-Xe ages based on those gases which are released at approximately 800 C. Probably the low-temperature components represent in-situ-produced radiogenic He and fission Xe, whereas the gases evolving when gold melts have been trapped during gold formation. Therefore, only the low-temperature components are relevant for dating purposes.

Fungal Biorecovery of Gold From E-waste.

PubMed

Bindschedler, Saskia; Vu Bouquet, Thi Quynh Trang; Job, Daniel; Joseph, Edith; Junier, Pilar

2017-01-01

Waste electric and electronic devices (e-waste) represent a source of valuable raw materials of great interest, and in the case of metals, e-waste might become a prized alternative source. Regarding gold, natural ores are difficult to mine due to their refractory nature and the richest ores have almost all been exploited. Additionally, some gold mining areas are present in geopolitically unstable regions. Finally, the gold mining industry produces toxic compounds, such as cyanides. As a result, the gold present in e-waste represents a nonnegligible resource (urban mining). Extraction methods of gold from natural ores (pyro- and hydrometallurgy) have been adapted to this particular type of matrix. However, to propose novel approaches with a lower environmental footprint, biotechnological methods using microorganisms are being developed (biometallurgy). These processes use the extensive metabolic potential of microbes (algae, bacteria, and fungi) to mobilize and immobilize gold from urban and industrial sources. In this review, we focus on the use of fungi for gold biomining. Fungi interact with gold by mobilizing it through mechanical attack as well as through biochemical leaching by the production of cyanides. Moreover, fungi are also able to release Au through the degradation of cyanide from aurocyanide complexes. Finally, fungi immobilize gold through biosorption, bioaccumulation, and biomineralization, in particular, as gold nanoparticles. Overall, the diversity of mechanisms of gold recycling using fungi combined with their filamentous lifestyle, which allows them to thrive in heterogeneous and solid environments such as e-waste, makes fungi an important bioresource to be harnessed for the biorecovery of gold. Copyright © 2017 Elsevier Inc. All rights reserved.

Immobilization of gold nanoparticles on cell culture surfaces for safe and enhanced gold nanoparticle-mediated laser transfection.

PubMed

Kalies, Stefan; Heinemann, Dag; Schomaker, Markus; Gentemann, Lara; Meyer, Heiko; Ripken, Tammo

2014-01-01

In comparison to standard transfection methods, gold nanoparticle-mediated laser transfection has proven to be a versatile alternative. This is based on its minor influence on cell viability and its high efficiency, especially for the delivery of small molecules like small interfering RNA. However, in order to transfer it to routine usage, a safety aspect is of major concern: The avoidance of nanoparticle uptake by the cells is desired. The immobilization of the gold nanoparticles on cell culture surfaces can address this issue. In this study, we achieved this by silanization of the appropriate surfaces and the binding of gold nanoparticles to them. Comparable perforation efficiencies to the previous approaches of gold nanoparticle-mediated laser transfection with free gold nanoparticles are demonstrated. The uptake of the immobilized particles by the cells is unlikely. Consequently, these investigations offer the possibility of bringing gold nanoparticle-mediated laser transfection closer to routine usage.

Enhanced chemiluminescence-based detection on gold substrate after electrografting of diazonium precursor-coated gold nanoparticles.

PubMed

Houmed Adabo, Ali; Zeggari, Rabah; Mohamed Saïd, Nasser; Bazzi, Rana; Elie-Caille, Céline; Marquette, Christophe; Martini, Matteo; Tillement, Olivier; Perriat, Pascal; Chaix, Carole; Boireau, Wilfrid; Roux, Stéphane

2016-04-01

Since it was demonstrated that nanostructured surfaces are more efficient for the detection based on the specific capture of analytes, there is a real need to develop strategies for grafting nanoparticles onto flat surfaces. Among the different routes for the functionalization of a surface, the reduction of diazonium salts appears very attractive for the covalent immobilization of nanoparticles because this method does not require a pre-treatment of the surface. For achieving this goal, gold nanoparticles coated by precursor of diazonium salts were synthesized by reduction of gold salt in presence of mercaptoaniline. These mercaptoaniline-coated gold nanoparticles (Au@MA) were successfully immobilized onto various conducting substrates (indium tin oxide (ITO), glassy carbon (GC) and gold electrodes with flat terraces) after addition of sodium nitrite at fixed potential. When applied onto the gold electrodes, such a grafting strategy led to an obvious enhancement of the luminescence of luminol used for the biodetection. Copyright © 2016 Elsevier Inc. All rights reserved.

XPS and NRA investigations during the fabrication of gold nanostructured functionalized screen-printed sensors for the detection of metallic pollutants

NASA Astrophysics Data System (ADS)

Jasmin, Jean-Philippe; Miserque, Frédéric; Dumas, Eddy; Vickridge, Ian; Ganem, Jean-Jacques; Cannizzo, Caroline; Chaussé, Annie

2017-03-01

An all covalent nanostructured lead sensor was built by the successive grafting of gold nanoparticles and carboxylic ligands at the surface of self-adhesive carbon screen-printed electrodes (SPEs). Surface analysis techniques were used in each step in order to investigate the structuration of this sensor. The self-adhesive surfaces were made from the electrochemical grafting of p-phenylenediamine at the surface of the SPEs via diazonium salts chemistry. The quantity of grafted aniline functions, estimated by Nuclear Reaction Analysis (NRA) performed with p-phenylenediamine labelled with 15N isotope, is in agreement with an almost complete coverage of the electrode surface. The subsequent diazotization of the aniline functions at the surface of the SPEs was performed; X-ray Photoelectron Spectroscopy (XPS) allowed us to consider a quantitative conversion of the aniline functions into diazonium moieties. The spontaneous grafting of gold nanoparticles on the as-obtained reactive surfaces ensures the nanostructuration of the material, and XPS studies showed that the covalent bonding of the gold nanoparticles at the surface of the SPEs induces a change both in the Au-4f (gold nanoparticles) and Cl-2p (carbon ink) core level signals. These unusual observations are explained by an interaction between the carbon ink constituting the substrate and the gold nanoparticles. Heavy and toxic metals are considered of major environmental concern because of their non-biodegradability. In a final step, the grafting of the carboxylic ligands at the surface of the SPEs and an accumulation step in the presence of lead(II) cations allowed us to evidence the interest of nanostructured materials as metallic pollutants sensors.

Gold(I) Carbenoids: On‐Demand Access to Gold(I) Carbenes in Solution

PubMed Central

Sarria Toro, Juan M.; García‐Morales, Cristina; Raducan, Mihai; Smirnova, Ekaterina S.

2017-01-01

Abstract Chloromethylgold(I) complexes of phosphine, phosphite, and N‐heterocyclic carbene ligands are easily synthesized by reaction of trimethylsilyldiazomethane with the corresponding gold chloride precursors. Activation of these gold(I) carbenoids with a variety of chloride scavengers promotes reactivity typical of metallocarbenes in solution, namely homocoupling to ethylene, olefin cyclopropanation, and Buchner ring expansion of benzene. PMID:28090747

Synthesis of camptothecin-loaded gold nanomaterials

NASA Astrophysics Data System (ADS)

Xing, Zhimin; Liu, Zhiguo; Zu, Yuangang; Fu, Yujie; Zhao, Chunjian; Zhao, Xiuhua; Meng, Ronghua; Tan, Shengnan

2010-04-01

Camptothecin-loaded gold nanomaterials have been synthesized by the sodium borohydride reduction method under a strong basic condition. The obtained gold nanomaterials have been characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV-vis absorption spectroscopy. The camptothecin-loaded gold colloidal solution was very stable and can be stored for more than two months at room temperature without obvious changes. The color of the colloidal solution can change from wine red to purple and blue during the acidifying process. It was revealed that the release of camptothecin and the aggregation of gold nanoparticles can be controlled by tuning the solution pH. The present study implied that the gold nanomaterials can be used as the potential carrier for CPT delivery.

Concentration of gold in natural waters

USGS Publications Warehouse

McHugh, J.B.

1988-01-01

The purpose of this paper is to investigate the amount of gold present in natural waters. One hundred and thirty-two natural water samples were collected from various sources and analyzed for gold by the latest techniques. Background values for gold in natural waters range from <0.001 to 0.005 ppb, and anomalous values range from 0.010 to 2.8 ppb. Waters collected from mineralized areas have a mean gold value of 0.101 ppb, whereas waters collected from unmineralized areas have a mean of 0.002 ppb. Some of the high gold values reported in the earlier literature were probably due to interferences by high salt content in the sample and/or lack of proper filter procedures. ?? 1988.

Gold and its relationship to neurological/glandular conditions.

PubMed

Richards, Douglas G; McMillin, David L; Mein, Eric A; Nelson, Carl D

2002-01-01

Despite increasing sales of gold supplements, and claims of benefits for neurological and glandular conditions, gold has received little attention in modern medical literature except as a drug for rheumatoid arthritis. Historically, however, gold had a reputation as a "nervine," a therapy for nervous disorders. A review of the historical literature shows gold in use during the 19th century for conditions including depression, epilepsy, migraine, and glandular problems such as amenorrhea and impotence. The most notable use of gold was in a treatment for alcoholism developed by Keeley (1897). In the modern medical literature, gold-containing medicines for rheumatoid arthritis are known to have occasional neurotoxic adverse effects. There are also a few studies suggesting a role for gold as a naturally occurring trace element in the reproductive glands. One small recent study demonstrated a possible positive effect of gold on cognitive ability. There is a need for more experimental and clinical research of the neuropharmacology and neurochemistry of gold, and for the exploration of gold's possible role as a trace element.

Methane clumped isotopes: Progress and potential for a new isotopic tracer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Douglas, Peter M. J.; Stolper, Daniel A.; Eiler, John M.

The isotopic composition of methane is of longstanding geochemical interest, with important implications for understanding hydrocarbon systems, atmospheric greenhouse gas concentrations, the global carbon cycle, and life in extreme environments. Recent analytical developments focusing on multiply substituted isotopologues (‘clumped isotopes’) are opening a potentially valuable new window into methane geochemistry. When methane forms in internal isotopic equilibrium, clumped isotopes can provide a direct record of formation temperature, making this property particularly valuable for identifying different methane origins. However, it has also become clear that in certain settings methane clumped isotope measurements record kinetic rather than equilibrium isotope effects. Here wemore » present a substantially expanded dataset of methane clumped isotope analyses, and provide a synthesis of the current interpretive framework for this parameter. We review different processes affecting methane clumped isotope compositions, describe the relationships between conventional isotope and clumped isotope data, and summarize the types of information that this measurement can provide in different Earth and planetary environments.« less

Gold - Old Drug with New Potentials.

PubMed

Faa, Gavino; Gerosa, Clara; Fanni, Daniela; Lachowicz, Joanna I; Nurchi, Valeria M

2018-01-01

Research into gold-based drugs for a range of human diseases has seen a revival in recent years. This article reviews the most important applications of gold products in different fields of human pathology. Au(I) and Au(III) compounds have been re-introduced in clinical practice for targeting the cellular components involved in the onset and progression of viral and parasitic diseases, rheumatoid arthritis and cancer. After some brief historical notes, this article takes into account the applications of gold compounds against Mycobacterium tuberculosis, and also in tuberculosis and in rheumatoid arthritis treatment. The use of gold containing drugs in the cure of cancer are then considered, with special emphasis to the use of nanoparticles and to the photo-thermal cancer therapy. The use of colloidal gold in diagnostics, introduced in the last decade is widely discussed. As a last point a survey on the adverse effects and on the toxicity of the various gold derivatives in use in medicine is presented. In this review, we described the surprisingly broad spectrum of possible uses of gold in diagnostics and in therapeutic approaches to multiple human diseases, ranging from degenerative to infectious diseases, and to cancer. In particular, gold nanoparticles appear as attractive elements in modern clinical medicine, combining high therapeutic properties, high selectivity in targeting cancer cells and low toxicity. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

The late cretaceous Donlin Creek gold deposit, Southwestern Alaska: Controls on epizonal ore formation

USGS Publications Warehouse

Goldfarb, R.J.; Ayuso, R.; Miller, M.L.; Ebert, S.W.; Marsh, E.E.; Petsel, S.A.; Miller, L.D.; Bradley, D.; Johnson, Chad; McClelland, W.

2004-01-01

-10 per mil, with the sulfur derived from diagenetic pyrite and organic matter within ihe flysch basin. A smaller group of ??34S measurements, which shows values as depleted as -27 per mil, suggests a different local sulfur reservoir in the basin for the later hydrothermal episode dominated by stibnite. Initial ENd of -8.7 to -3.1 and 87Sr/86Sr measurements of 0.706 to 0.709 for the ore-hosting dikes also indicate a crustal reservoir for some of the Late Cretaceous magmatism. Overlapping lead isotope data for these intrusive rocks and for sulfide minerals suggest a crustal contribution for the lead in both. Copper- and gold-bearing stockwork veinlets in hornfels occur at Dome, a prospect located at the northern end of the Donlin Creek deposit. These stockworks are cut by the younger auriferous gold veins that define the main Donlin Creek gold mineralization. Highly saline, gas-rich, heterogeneously trapped fluids deposited the stockworks at temperatures approximately 100??C hotter than those of the main gold-forming event at Donlin Creek. The genetic relationship of the Dome prospect to the main Donlin Creek gold resource is equivocal. The epizonal Donlin Creek deposit shows affinities to the gold systems interpreted by various workers as orogenic or intrusion related; it shows important differences from typical epithermal and Carlin-like deposits. The ore-forming fluids were derived by either broad-scale metamorphic devolatilization above rising mantle melts or exsolution from a magma that was dominated by a significant flysch melt component. ??2004 by Economic Geology.

Gold ink coating of thermocouple sheaths

DOEpatents

Ruhl, H. Kenneth

1992-01-01

A method is provided for applying a gold ink coating to a thermocouple sheath which includes the steps of electropolishing and oxidizing the surface of the thermocouple sheath, then dipping the sheath into liquid gold ink, and finally heat curing the coating. The gold coating applied in this manner is highly reflective and does not degrade when used for an extended period of time in an environment having a temperature over 1000.degree. F. Depending on the application, a portion of the gold coating covering the tip of the thermocouple sheath is removed by abrasion.

Directed assembly of gold nanowires on silicon via reorganization and simultaneous fusion of randomly distributed gold nanoparticles.

PubMed

Reinhardt, Hendrik M; Bücker, Kerstin; Hampp, Norbert A

2015-05-04

Laser-induced reorganization and simultaneous fusion of nanoparticles is introduced as a versatile concept for pattern formation on surfaces. The process takes advantage of a phenomenon called laser-induced periodic surface structures (LIPSS) which originates from periodically alternating photonic fringe patterns in the near-field of solids. Associated photonic fringe patterns are shown to reorganize randomly distributed gold nanoparticles on a silicon wafer into periodic gold nanostructures. Concomitant melting due to optical heating facilitates the formation of continuous structures such as periodic gold nanowire arrays. Generated patterns can be converted into secondary structures using directed assembly or self-organization. This includes for example the rotation of gold nanowire arrays by arbitrary angles or their fragmentation into arrays of aligned gold nanoparticles.

Lithologic controls on mineralization at the Lagunas Norte high-sulfidation epithermal gold deposit, northern Peru

NASA Astrophysics Data System (ADS)

Cerpa, Luis M.; Bissig, Thomas; Kyser, Kurt; McEwan, Craig; Macassi, Arturo; Rios, Hugo W.

2013-06-01

, auriferous pyrite, and enargite. Alteration and mineralization in the breccias were controlled by permeability, which depends on the type and composition of the matrix, cement, and clast abundance. Coarse alunite from the main mineralization stage in textural equilibrium with pyrite and enargite has δ34S values of 24.8-29.4 ‰ and {δ^{18 }}{{O}_{{S{{O}_4}}}} values of 6.8-13.9 ‰, consistent with H2S as the dominant sulfur species in the mostly magmatic fluid and constraining the fluid composition to low pH (0-2) and log fO2 of -28 to -30. Alunite-pyrite sulfur isotope thermometry records temperatures of 190-260 °C; the highest temperatures corresponding to samples from near the diatremes. Alunite of the third hydrothermal stage has been dated by 40Ar/39Ar at 17.0 ± 0.22 Ma. The fourth hydrothermal stage introduced only modest amounts of gold and is characterized by the presence of massive alunite-pyrite in fractures, whereas barite, drusy quartz, and native sulfur were deposited in the volcanic rocks. The {δ^{18 }}{{O}_{{S{{O}_4}}}} values of stage IV alunite vary between 11.5 and 11.7 ‰ and indicate that the fluid was magmatic, an interpretation also supported by the isotopic composition of barite (δ34S = 27.1 to 33.8 ‰ and {δ^{18 }}{{O}_{{S{{O}_4}}}} = 8.1 to 12.7 ‰). The Δ34Spy-alu isotope thermometry records temperatures of 210 to 280 °C with the highest values concentrated around the Josefa diatreme. The Lagunas Norte deposit was oxidized to a depth of about 80 m below the current surface making exploitation by heap leach methods viable.

Diazonium-derived aryl films on gold nanoparticles: evidence for a carbon-gold covalent bond.

PubMed

Laurentius, Lars; Stoyanov, Stanislav R; Gusarov, Sergey; Kovalenko, Andriy; Du, Rongbing; Lopinski, Gregory P; McDermott, Mark T

2011-05-24

Tailoring the surface chemistry of metallic nanoparticles is generally a key step for their use in a wide range of applications. There are few examples of organic films covalently bound to metal nanoparticles. We demonstrate here that aryl films are formed on gold nanoparticles from the spontaneous reduction of diazonium salts. The structure and the bonding of the film is probed with surface-enhanced Raman scattering (SERS). Extinction spectroscopy and SERS show that a nitrobenzene film forms on gold nanoparticles from the corresponding diazonium salt. Comparison of the SERS spectrum with spectra computed from density functional theory models reveals a band characteristic of a Au-C stretch. The observation of this stretch is direct evidence of a covalent bond. A similar band is observed in high-resolution electron energy loss spectra of nitrobenzene layers on planar gold. The bonding of these types of films through a covalent interaction on gold is consistent with their enhanced stability observed in other studies. These findings provide motivation for the use of diazonium-derived films on gold and other metals in applications where high stability and/or strong adsorbate-substrate coupling are required.

New insights into the extraction of invisible gold in a low-grade high-sulfur Carlin-type gold concentrate by bio-pretreatment

NASA Astrophysics Data System (ADS)

Qiu, Xiao-bin; Wen, Jian-kang; Huang, Song-tao; Yang, Hong-ying; Liu, Mei-lin; Wu, Biao

2017-10-01

To extract gold from a low-grade (13.43 g/t) and high-sulfur (39.94wt% sulfide sulfur) Carlin-type gold concentrate from the Nibao deposit, Guizhou, a bio-pretreatment followed by carbon-in-pulp (CIP) cyanide leaching process was used. Various methods were used to detect the low-grade gold in the concentrate; however, only time-of-flight secondary-ion mass spectrometry (TOF-SIMS) was successful. With bio-pretreatment, the gold recovery rate increased by approximately 70.16% compared with that obtained by direct cyanide leaching of the concentrate. Various attempts were made to increase the final gold recovery rate. However, approximately 20wt% of the gold was non-extractable. To determine the nature of this non-extractable gold, mineralogy liberation analysis (MLA), formation of secondary product during the bio-pretreatment, and the preg-robbing capacity of the carbonaceous matter in the ore were investigated. The results indicated that at least four factors affected the gold recovery rate: gold occurrence, tight junctions of gold-bearing pyrite with gangue minerals, jarosite coating of the ore, and the carbonaceous matter content.

The gold rush 1925-35.

PubMed Central

Keers, R Y

1980-01-01

Although from the time of Koch onwards there had been desultory experiments with a variety of gold preparations in the management of pulmonary tuberculosis, gold as a recognised and accepted treatment did not emerge until 1925. In that year Holger Mollgaard of Copenhagen introduced sanocrysin, a double thiosulphate of gold and sodium, with which he had conducted an extensive series of animal experiments. The results of these were considered to justify its use in clinical practice and two physicians, Secher and Faber, undeterred by its toxicity, reported enthusiastically in its favour. Other Danish physicians followed but, alarmed by violent reactions, modified the dosage, an example followed by British workers. Encouraging results continued to be reported although each series contained a significant proportion of failures, and toxicity remained high. The first properly planned and fully controlled clinical trial took place in the United States and produced a report which was wholly adverse and which sounded the death knell of gold therapy throughout America. Until 1934-35 gold was used extensively in Europe but thereafter there was a sudden and largely universal cessation of interest and within a few years gold, introduced with such éclat and carrying so many high hopes, had vanished from the therapy of tuberculosis even though, at that point, no better alternative was available. PMID:6791290

Sensitive flotation-spectrophotometric determination of gold, based on the gold(I)-iodide-methylene blue system.

PubMed

Marczenko, Z; Jankowski, K

1985-04-01

The gold(I)-iodide-Methylene Blue (MB) system is suitable for flotation separation and spectrophotometric determination of gold. Under the optimum conditions [(MB(+))(AuI(2)(-))].3[(MB(+))(I(3)(-))] is formed, and floated with cyclohexane. The product is dissolved in methanol and its absorbance measured. The molar absorptivity is 3.4 x 10(5)1.mole(-1).cm(-1) at 655 nm. The proposed method is more than three times as sensitive as the Rhodamine B method. Pt, Pd, Ag and Hg interfere seriously, and Ir, Rh, Bi and Cd to a smaller extent. Preliminary separation of gold by precipitation with tellurium as a collector is recommended. The method has been applied to determination of gold traces (about 1 x 10(-4)%) in a copper sample.

Petrology, zircon U-Pb ages, geochemistry and Sr-Nd-Hf isotopes of the Late Paleozoic gold-bearing magmatic rocks (porphyry intrusions) in Jiamante area, Northwest Tianshan: Implications for petrogenesis and mineralization

NASA Astrophysics Data System (ADS)

Zhang, Tongliang; Cai, Keda; Wang, Xiangsong

2017-04-01

A series of Cu-Au-Mo deposits distributed from east to west in the Northwestern Tianshan Orogenic Belt (NTOB), which is located in the northwestern China. The tectonic settings and associated geodynamic processes of these deposits have been disputed. This paper presents whole-rock geochemical data, in-situ U-Th-Pb ages and Sr-Nd-Hf isotopic composition for granite porphyry and quartz porphyry in the Jiamante gold deposit from the Yelimodun Basin, in the NTOB. These two type representative high potassium granitic intrusions have the LA-ICP-MS zircon U-Pb ages of 350.8±4 Ma, 351.7±3 Ma and 350.4±5 Ma, 353.9±2.5 Ma, interpreted as the crystallization ages. High contents of SiO2 ( 71.1-75.2wt.%), K2O (4.96-6.33 wt.%), Al2O3 (12.45-14.35 wt.%) and low contents of Fe2O3T (1.47-3.25 wt.%), MgO (0.3-0.5 wt.% ), and CaO (0.49-1.29wt.%), High ASI (Alumina Saturation Index, Al2O3/(CaO+Na2O+K2O)=1.37-1.80 molecular ratios) can be found in these rocks. These porphyries are enriched in both large ion lithophile and light rare earth elements, but deplet in high field strength elements and are characterized by moderately negative Eu anomalies (Eu/Eu*=0.27-0.66) and strong depletion in Ba, Nb,Ti and Sr elements. These two porphyries have negative and positive zircon ɛHf(t) (-11.6 to +6.7) values, low Mg# ratios (21.85-35.51wt%), and low Cr (3.24ppm -11.35ppm) and Ni (1.88ppm-13.41ppm) contents. The regional geological and geochemical characteristics of the Early Carboniferous rocks in the Northwestern Tianshan show that peraluminous granitoids, with hybrid Sr-Nd-Hf isotopic signatures, suggesting that their parental magmas could be derived from the subduction of Paleo-Junggar Ocean beneath the Yili Block and the sediments from the Yili Block. In combination with the compositions of the volcanic rocks and basic lavas in the region in the Early Carboniferous, we suggest that the Jiamante peraluminous granitic porphyries and quartz porphyries were generated by the interaction

Bats, cyanide, and gold mining

USGS Publications Warehouse

Clark, Donald R.

1991-01-01

Although the boom days of prospectors and gold nuggets are long gone, modern technology enables gold to continue to be extracted from ore. Unfortunately, the extraction method has often been disastrous for bats and other wildlife, an issue I first became aware of in early 1989. Phone calls from Drs. Merlin Tuttle and Elizabeth Pierson, a BCI member and bat researcher from Berkeley, California, alerted me that bats were dying from apparent cyanide poisoning at gold mines in the western United States.

Precipitation of lamellar gold nanocrystals in molten polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palomba, M.; Carotenuto, G., E-mail: giancaro@unina.it

Non-aggregated lamellar gold crystals with regular shape (triangles, squares, pentagons, etc.) have been produced by thermal decomposition of gold chloride (AuCl) molecules in molten amorphous polymers (polystyrene and poly(methyl methacrylate)). Such covalent inorganic gold salt is high soluble into non-polar polymers and it thermally decomposes at temperatures compatible with the polymer thermal stability, producing gold atoms and chlorine radicals. At the end of the gold precipitation process, the polymer matrix resulted chemically modified because of the partial cross-linking process due to the gold atom formation reaction.

Porphyry-Style Petropavlovskoe Gold Deposit, the Polar Urals: Geological Position, Mineralogy, and Formation Conditions

NASA Astrophysics Data System (ADS)

Vikentyev, I. V.; Mansurov, R. Kh.; Ivanova, Yu. N.; Tyukova, E. E.; Sobolev, I. D.; Abramova, V. D.; Vykhristenko, R. I.; Trofimov, A. P.; Khubanov, V. B.; Groznova, E. O.; Dvurechenskaya, S. S.; Kryazhev, S. G.

2017-11-01

Geological and structural conditions of localization, hydrothermal metasomatic alteration, and mineralization of the Petropavlovskoe gold deposit (Novogodnenskoe ore field) situated in the northern part of the Lesser Ural volcanic-plutonic belt, which is a constituent of the Middle Paleozoic island-arc system of the Polar Urals, are discussed. The porphyritic diorite bodies pertaining to the late phase of the intrusive Sob Complex play an ore-controlling role. The large-volume orebodies are related to the upper parts of these intrusions. Two types of stringer-disseminated ores have been revealed: (1) predominant gold-sulfide and (2) superimposed low-sulfide-gold-quartz ore markedly enriched in Au. Taken together, they make up complicated flattened isometric orebodies transitory to linear stockworks. The gold potential of the deposit is controlled by pyrite-(chlorite)-albite metasomatic rock of the main productive stage, which mainly develops in a volcanic-sedimentary sequence especially close to the contacts with porphyritic diorite. The relationships between intrusive and subvolcanic bodies and dating of individual zircon crystals corroborate a multistage evolution of the ore field, which predetermines its complex hydrothermal history. Magmatic activity of mature island-arc plagiogranite of the Sob Complex and monzonite of the Kongor Complex initiated development of skarn and beresite alterations accompanied by crystallization of hydrothermal sulfides. In the Early Devonian, due to emplacement of the Sob Complex at a depth of approximately 2 km, skarn magnetite ore with subordinate sulfides was formed. At the onset of the Middle Devonian, the large-volume gold porphyry Au-Ag-Te-W ± Mo,Cu stockworks related to quartz diorite porphyry—the final phase of the Sob Complex— were formed. In the Late Devonian, a part of sulfide mineralization was redistributed with the formation of linear low-sulfide quartz vein zones. Isotopic geochemical study has shown that the

Establishment of gold-quartz standard GQS-1

USGS Publications Warehouse

Millard, Hugh T.; Marinenko, John; McLane, John E.

1969-01-01

A homogeneous gold-quartz standard, GQS-1, was prepared from a heterogeneous gold-bearing quartz by chemical treatment. The concentration of gold in GQS-1 was determined by both instrumental neutron activation analysis and radioisotope dilution analysis to be 2.61?0.10 parts per million. Analysis of 10 samples of the standard by both instrumental neutron activation analysis and radioisotope dilution analysis failed to reveal heterogeneity within the standard. The precision of the analytical methods, expressed as standard error, was approximately 0.1 part per million. The analytical data were also used to estimate the average size of gold particles. The chemical treatment apparently reduced the average diameter of the gold particles by at least an order of magnitude and increased the concentration of gold grains by a factor of at least 4,000.

Genetic environment of germanium-bearing gold-silver vein ores from the Wolyu mine, Republic of Korea

NASA Astrophysics Data System (ADS)

Yun, Seong-Taek; So, Chil-Sup; Choi, Sang-Hoon; Shelton, Kevin L.; Koo, Ja-Hak

1993-04-01

The Wolyu mine is one of the largest vein-type gold-silver-bearing epithermal systems in the Youngdong district and is the first gold-silver deposit in Korea found to contain significant germanium, in the form of argyrodite (Ag8GeS6). Mineralized veins (78.9 ± 1.2 Ma) crosscutting Late Cretaceous hostrock tuff and quartz porphyry (81.5 ± 1.8 Ma) consist of three stages of quartz and carbonates, the first of which contains pyrite, basemetal sulfides and Au-Ag-minerals. Stage I Au-Ag-Ge-mineralized veins show a systematic variation of mineral assemblage with time: (1) quartz + pyrite; (2) quartz + pyrite + sphalerite + electrum + argentite; (3) carbonate + quartz + sphalerite + electrum + argentite; (4) carbonate + native silver + argentite + Ag-sulfosalts + argyrodite + sphalerite. Calculated values of temperature and sulfur activity are: assemblage (1), 360-280°C and 10-7-10-10; (2), 280-210°C and 10-10-10-14; (3), 210-180°C and 10-14-10-16; (4), 180-155°C and 10-17-10-18. These data, the frequent association of gold with sulfides, and the abundance of pyrite in alteration zones indicate that decreasing sulfur activity and cooling were important in triggering gold deposition. Hydrogen and oxygen isotope compositions of ore fluids display a systematic variation with increasing time. Within the main Ag-Au-Ge mineralization, δD and δ 18O values decrease with the transition from quartz to carbonate deposition (from -78 and -2.8% to -90 and -8.7%., respectively), indicating increasing involvement (mixing) of less evolved meteoric water which resulted in progressive cooling and dilution of ore fluids in the shallow (≈ 370 600 m) Wolyu epithermal system.

Cosmogenic 3He in detrital gold

NASA Astrophysics Data System (ADS)

Stuart, Finlay; Yakubovich, Olga; Caracedo, Ana; Nesterenok, Alexander

2017-04-01

Since the measurement of cosmogenic He in an alluvial diamond by McConville and Reynolds (1996) the application of cosmogenic noble gases to individual detrital grains to quantify surface processes has not been vigorously pursued. The likely low rate of diffusion of cosmogenic He in native metals, and their resistance to weathering and disintegration during erosion and transport, makes them a potential record of long-term Earth surface processes. In an effort to assess the extent that detrital refractory metals record the exposure history during transport and storage we have undertaken a reconnaissance study of the He isotope composition in 18 grains (2-200 mg) of native gold, copper, silver, and PtPd, Pt3Fe and OsIr alloys from alluvial placer deposits from around the world. 4He is dominantly the result of U and Th decay within the grains, or decay of 190Pt in the Pt-rich alloys. 3He is measurable in 13 grains, concentrations range up to 2.7E+6 atoms/g. 3He/4He are always in excess of the crustal radiogenic ratio, up to 306 Ra. Although nucleogenic 3He produced by (n,α) reactions on 6Li, and 3He from trapped hydrothermal fluids, are present, the majority of the 3He is cosmogenic in origin. Using newly calculated cosmogenic 3He production rates in heavy metals, and a determination of the effect of implantation based on the stopping distances of spallogenic 3He and 3H, the grains have 3Hecos concentrations that are equivalent to 0.35 to 1.5 Ma exposure at Earth's surface. In a study of detrital gold grains from several sites in Scotland we have found that 10 % have 3He concentrations that are significantly in excess of that generated since the Last Glacial Maximum. These studies demonstrate that, with refinement, cosmogenic 3He in refractory detrital minerals can be used to quantify sediment transport and storage on the 1-10 Ma timescale. P. McConville & J.H. Reynolds (1989). Geochim. Cosmochim. Acta, 53, 2365-75.

Laser isotope separation of erbium and other isotopes

DOEpatents

Haynam, Christopher A.; Worden, Earl F.

1995-01-01

Laser isotope separation is accomplished using at least two photoionization pathways of an isotope simultaneously, where each pathway comprises two or more transition steps. This separation method has been applied to the selective photoionization of erbium isotopes, particularly for the enrichment of .sup.167 Er. The hyperfine structure of .sup.167 Er was used to find two three-step photoionization pathways having a common upper energy level.

Glucose Measurement: Time for a Gold Standard

PubMed Central

Hagvik, Joakim

2007-01-01

There is no internationally recognized reference method for the measurement of blood glucose. The Centers for Disease Control and Prevention (CDC) highlighted the need for standardization some years ago when a project was started. The project objectives were to (1) investigate whether there are significant differences in calibration levels among currently used glucose monitors for home use and (2) develop a reference method for glucose determination. A first study confirmed the assumption that currently used home-use monitors differ significantly and that standardization is necessary in order to minimize variability and to improve patient care. As a reference method, CDC recommended a method based on isotope dilution gas chromatography–mass spectrometry, an assay that has received support from clinical chemists worldwide. CDC initiated a preliminary study to establish the suitability of this method, but then the project came to a halt. It is hoped that CDC, with support from the industry, as well as academic and professional organizations such as the American Association for Clinical Chemistry and International Federation of Clinical Chemistry and Laboratory Medicine, will be able to finalize the project and develop the long-awaited and much needed “gold standard” for glucose measurement. PMID:19888402

Gel Electrophoresis of Gold-DNA Nanoconjugates

DOE PAGES

Pellegrino, T.; Sperling, R. A.; Alivisatos, A. P.; ...

2007-01-01

Gold-DNA conjugates were investigated in detail by a comprehensive gel electrophoresis study based on 1200 gels. A controlled number of single-stranded DNA of different length was attached specifically via thiol-Au bonds to phosphine-stabilized colloidal gold nanoparticles. Alternatively, the surface of the gold particles was saturated with single stranded DNA of different length either specifically via thiol-Au bonds or by nonspecific adsorption. From the experimentally determined electrophoretic mobilities, estimates for the effective diameters of the gold-DNA conjugates were derived by applying two different data treatment approaches. The first method is based on making a calibration curve for the relation between effectivemore » diameters and mobilities with gold nanoparticles of known diameter. The second method is based on Ferguson analysis which uses gold nanoparticles of known diameter as reference database. Our study shows that effective diameters derived from gel electrophoresis measurements are affected with a high error bar as the determined values strongly depend on the method of evaluation, though relative changes in size upon binding of molecules can be detected with high precision. Furthermore, in this study, the specific attachment of DNA via gold-thiol bonds to Au nanoparticles is compared to nonspecific adsorption of DNA. Also, the maximum number of DNA molecules that can be bound per particle was determined.« less

Plastic deformation in nanoscale gold single crystals and open-celled nanoporous gold

NASA Astrophysics Data System (ADS)

Lee, Dongyun; Wei, Xiaoding; Zhao, Manhong; Chen, Xi; Jun, Seong C.; Hone, James; Kysar, Jeffrey W.

2007-01-01

The results of two sets of experiments to measure the elastic-plastic behaviour of gold at the nanometre length scale are reported. One set of experiments was on free-standing nanoscale single crystals of gold, and the other was on free-standing nanoscale specimens of open-celled nanoporous gold. Both types of specimens were fabricated from commercially available leaf which was either pure Au or a Au/Ag alloy following by dealloying of the Ag. Mechanical testing specimens of a 'dog-bone' shape were fabricated from the leaf using standard lithographic procedures after the leaf had been glued onto a silicon wafer. The thickness of the gauge portion of the specimens was about 100 nm, the width between 250 nm and 300 nm and the length 7 µm. The specimens were mechanically loaded with a nanoindenter (MTS) at the approximate midpoint of the gauge length. The resulting force-displacement curve of the single crystal gold was serrated and it was evident that slip localization occurred on individual slip systems; however, the early stages of the plastic deformation occurred in a non-localized manner. The results of detailed finite element analyses of the specimen suggest that the critical resolved shear stress of the gold single crystal was as high as 135 MPa which would lead to a maximum uniaxial stress of about 500 MPa after several per cent strain. The behaviour of the nanoporous gold was substantially different. It exhibited an apparent elastic behaviour until the point where it failed in an apparently brittle manner, although it is assumed that plastic deformation occurred in the ligaments prior to failure. The average elastic stiffness of three specimens was measured to be Enp = 8.8 GPa and the stress at ultimate failure averaged 190 MPa for the three specimens tested. Scaling arguments suggest that the stress in the individual ligaments could approach the theoretical shear strength. Presented at the IUTAM Symposium on Plasticity at the Micron Scale, Technical

Biophysical characterization of gold nanoparticles-loaded liposomes.

PubMed

Mady, Mohsen Mahmoud; Fathy, Mohamed Mahmoud; Youssef, Tareq; Khalil, Wafaa Mohamed

2012-10-01

Gold nanoparticles were prepared and loaded into the bilayer of dipalmitoylphosphatidylcholine (DPPC) liposomes, named as gold-loaded liposomes. Biophysical characterization of gold-loaded liposomes was studied by transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy as well as turbidity and rheological measurements. FTIR measurements showed that gold nanoparticles made significant changes in the frequency of the CH(2) stretching bands, revealing that gold nanoparticles increased the number of gauche conformers and create a conformational change within the acyl chains of phospholipids. The transmission electron micrographs (TEM) revealed that gold nanoparticles were loaded in the liposomal bilayer. The zeta potential of DPPC liposomes had a more negative value after incorporating of Au NPs into liposomal membranes. Turbidity studies revealed that the loading of gold nanoparticles into DPPC liposomes results in shifting the temperature of the main phase transition to a lower value. The membrane fluidity of DPPC bilayer was increased by loading the gold nanoparticles as shown from rheological measurements. Knowledge gained in this study may open the door to pursuing liposomes as a viable strategy for Au NPs delivery in many diagnostic and therapeutic applications. Copyright © 2011 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Functionalization of gold nanoparticles as antidiabetic nanomaterial

NASA Astrophysics Data System (ADS)

Venkatachalam, M.; Govindaraju, K.; Mohamed Sadiq, A.; Tamilselvan, S.; Ganesh Kumar, V.; Singaravelu, G.

2013-12-01

In the present investigation, functionalization of gold nanoparticles synthesized using propanoic acid 2-(3-acetoxy-4,4,14-trimethylandrost-8-en-17-yl) (PAT) an active biocomponent isolated from Cassia auriculata is studied in detail. On reaction of PAT with aqueous HAuCl4, rapid formation of stable gold nanoparticles was achieved. Formation of gold nanoparticles was confirmed by UV-vis spectroscopy, XRD, GC-MS, FTIR, TEM and SEM with EDAX. Gold nanoparticles mostly were monodisperse, spherical in shape and ranged in size 12-41 nm. Gold nanoparticles synthesised using PAT was administered to alloxan (150 mg/kg body weight) induced diabetic male albino rats at different doses (0.25, 0.5, 0.75 and 1.0 mg/kg body weight) for 28 days. Plasma glucose level, cholesterol and triglyceride were significantly (p < 0.001) reduced in experimental animals treated with gold nanoparticles at dosage of 0.5 mg/kg body weight and plasma insulin increased significantly. The newly genre green gold nanoparticles exhibit remarkable protein tyrosine phosphatase 1B inhibitory activity.

Gold and Iron-Gold Nanoparticles for Intracellular Tracking and in Vivo Medical Applicatons

NASA Astrophysics Data System (ADS)

Fu, Wei

2005-03-01

We have fabricated Au and Fe-Au nanoparticles for potential use in ex vivo experiments such as intracellular tracking, as well as a variety of in vivo medical applications. In order to improve their targeting potential, circulation time and flexibility, gold NPs were surface modified using a hetero-bifunctional poly(ethylene glycol) (PEG, MW 1,500) spacers. A coumarin-PEG-gold NP complex was formed and cell viability studies and optical fluorescence experiments were carried out demonstrating the use of these surface-modified gold NPs for drug delivery, gene therapy and cell trafficking experiments. Fe-Au nanoparticles were also fabricated and show significant contrast enhancement in MRI studies through a substantial reduction of the T2 relaxation time.

[Biosynthesis of gold nanoparticles by Azospirillum brasilense].

PubMed

Kupriashina, M A; Vetchinkina, E P; Burov, A M; Ponomareva, E G; Nikitina, V E

2014-01-01

Plant-associated nitrogen-fixing soil bacteria Azospirillum brasilense were shown to reduce the gold of chloroauric acid to elemental gold, resulting in formation of gold nanoparicles. Extracellular phenoloxidizing enzymes (laccases and Mn peroxidases) were shown to participate in reduction of Au+3 (HAuCl4) to Au(0). Transmission electron microscopy revealed accumulation of colloidal gold nanoparticles of diverse shape in the culture liquid of A. brasilense strains Sp245 and Sp7. The size of the electron-dense nanospheres was 5 to 50 nm, and the size of nanoprisms varied from 5 to 300 nm. The tentative mechanism responsible for formation of gold nanoparticles is discussed.

Facile preparation of gold nanocages and hollow gold nanospheres via solvent thermal treatment and their surface plasmon resonance and photothermal properties.

PubMed

Wang, Haifei; Han, Jing; Lu, Wensheng; Zhang, Jianping; Li, Jinru; Jiang, Long

2015-02-15

Although template etching method is one of the most common ways of preparation of hollow gold nanostructures, this approach still requires further improvements to avoid the collapse of gold shells after the cores were removed. In this work, an improved template etching method, with which hollow gold nanostructure is fabricated by etching Polystyrene (PS) cores from PS@Au core-shell nanospheres with solvent thermal treatment in N,N-Dimethylformamide (DMF), is demonstrated. When PS cores were removed by a thermal treatment process, gold nanoshells reconstruct and the collapse of the nanoshells is avoided. Gold nanocages and hollow gold nanospheres are easily obtained from the various structures of PS@Au core-shell nanospheres. These hollow nanostructures represent special near infrared (NIR) optical property and photothermal property. Compared with hollow gold nanospheres, the gold nanocages show higher temperature increase at the same particle concentration. Copyright © 2014 Elsevier Inc. All rights reserved.

Laser isotope separation of erbium and other isotopes

DOEpatents

Haynam, C.A.; Worden, E.F.

1995-08-22

Laser isotope separation is accomplished using at least two photoionization pathways of an isotope simultaneously, where each pathway comprises two or more transition steps. This separation method has been applied to the selective photoionization of erbium isotopes, particularly for the enrichment of {sup 167}Er. The hyperfine structure of {sup 167}Er was used to find two three-step photoionization pathways having a common upper energy level. 3 figs.

Site-specific biomolecule labeling with gold clusters.

PubMed

Ackerson, Christopher J; Powell, Richard D; Hainfeld, James F

2010-01-01

Site-specific labeling of biomolecules in vitro with gold clusters can enhance the information content of electron cryomicroscopy experiments. This chapter provides a practical overview of well-established techniques for forming biomolecule/gold cluster conjugates. Three bioconjugation chemistries are covered: linker-mediated bioconjugation, direct gold-biomolecule bonding, and coordination-mediated bonding of nickel(II) nitrilotriacetic acid (NTA)-derivatized gold clusters to polyhistidine (His)-tagged proteins. Copyright © 2010 Elsevier Inc. All rights reserved.

Raman scattering method and apparatus for measuring isotope ratios and isotopic abundances

DOEpatents

Harney, Robert C.; Bloom, Stewart D.

1978-01-01

Raman scattering is used to measure isotope ratios and/or isotopic abundances. A beam of quasi-monochromatic photons is directed onto the sample to be analyzed, and the resulting Raman-scattered photons are detected and counted for each isotopic species of interest. These photon counts are treated mathematically to yield the desired isotope ratios or isotopic abundances.

Protein targets for anticancer gold compounds: mechanistic inferences.

PubMed

Gabbiani, Chiara; Messori, Luigi

2011-12-01

Gold compounds form an interesting class of antiproliferative agents of potential pharmacological use in cancer treatment. Indeed, a number of gold compounds, either gold(III) or gold(I), were recently described and characterised that manifested remarkable cytotoxic properties in vitro against cultured cancer cells; for some of them encouraging in vivo results were also reported toward a few relevant animal models of cancer. The molecular mechanisms through which gold compounds exert their biological effects are still largely unknown and the subject of intense investigations. Recent studies point out that the modes of action of cytotoxic gold compounds are essentially DNA-independent and cisplatin-unrelated, relying -most likely- on gold interactions with a variety of protein targets. Notably, a few cellular proteins playing relevant functional roles were proposed to represent effective targets for cytotoxic gold compounds but these hypotheses need adequate validation. The state of the art of this research area and the perspectives for future studies are herein critically analysed and discussed.

Molecular Simulations of The Formation of Gold-Molecule-Gold Junctions

NASA Astrophysics Data System (ADS)

Wang, Huachuan

2013-03-01

We perform classical molecular simulations by combining grand canonical Monte Carlo (GCMC) sampling with molecular dynamics (MD) simulation to explore the dynamic gold nanojunctions in a Alkenedithiol (ADT) solvent. With the aid of a simple driving-spring model, which can reasonably represent the long-range elasticity of the gold electrode, the spring forces are obtained during the dynamic stretching procedure. A specific multi-time-scale double reversible reference system propagator (double-RESPA) algorithm has been designed for the metal-organic complex in MD simulations to identify the detailed metal-molecule bonding geometry at metal-molecule-metal interface. We investigate the variations of bonding sites of ADT molecules on gold nanojunctions at Au (111) surface at a constant chemical potential. Simulation results show that an Au-ADT-Au interface is formed on Au nanojunctions, bond-breaking intersection is at 1-1 bond of the monatomic chain of the cross-section, instead of at the Au-S bond. Breaking force is around 1.5 nN. These are consistent with the experimental measurements.

Gold deposits of the Carolina Slate Belt, southeastern United States--Age and origin of the major gold producers

USGS Publications Warehouse

Foley, Nora K.; Ayuso, Robert A.

2012-01-01

Gold- and iron sulfide-bearing deposits of the southeastern United States have distinctive mineralogical and geochemical features that provide a basis for constructing models of ore genesis for exploration and assessment of gold resources. The largest (historic) deposits, in approximate million ounces of gold (Moz Au), include those in the Haile (~ 4.2 Moz Au), Ridgeway (~1.5 Moz Au), Brewer (~0.25 Moz Au), and Barite Hill (0.6 Moz Au) mines. Host rocks are Late Proterozoic to early Paleozoic (~553 million years old) metaigneous and metasedimentary rocks of the Carolina Slate Belt that share a geologic affinity with the classic Avalonian tectonic zone. The inferred syngenetic and epithermal-subvolcanic quartz-porphyry settings occur stratigraphically between sequences of metavolcanic rocks of the Persimmon Fork and Uwharrie Formations and overlying volcanic and epiclastic rocks of the Tillery and Richtex Formations (and regional equivalents). The Carolina Slate Belt is highly prospective for many types of gold ore hosted within quartz-sericite-pyrite altered volcanic rocks, juvenile metasedimentary rocks, and in associated shear zones. For example, sheared and deformed auriferous volcanogenic massive sulfide deposits at Barite Hill, South Carolina, and in the Gold Hill trend, North Carolina, are hosted primarily by laminated mudstone and felsic volcanic to volcaniclastic rocks. The high-sulfidation epithermal style of gold mineralization at Brewer and low-sulfidation gold ores of the Champion pit at Haile occur in breccias associated with subvolcanic quartz porphyry and within crystal-rich tuffs, ash flows, and subvolcanic rhyolite. The Ridgeway and Haile deposits are primarily epithermal replacements and feeder zones within (now) metamorphosed crystal-rich tuffs, volcaniclastic sediments, and siltstones originally deposited in a marine volcanic-arc basinal setting. Recent discoveries in the region include (1) extensions of known deposits, such as at Haile where

Statistical clumped isotope signatures

PubMed Central

Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.

2016-01-01

High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

How to find gold and gems: Introduction to gemology in school

NASA Astrophysics Data System (ADS)

Bauer, Gregory

2016-04-01

Gemology is a part of geosciences usually not taught in French schools or universities, only in some private professional training centers. Teachers and students have often knowledge coming only from their non-professional activities; nevertheless a lot of jobs are linked to gemology. In our high school we propose optional education for students in 2nd class (about 16 years old) in that they can discover gemology and mine linked jobs. We study gemstones and how they are categorized with their crystal structure, specific gravity, hardness, and optical properties. We study chemical composition, accumulation processes and deposit identification in their geological context. We use spectroscopic and isotopic analysis of cut gemstones to understand the atomic structure and identify its origin, which is also a factor in valuing a gemstone. Our region is also rich in gold and silver so we see in our program precious metals deposit processes too.

Geology and geochemistry of Carlin-type gold deposits in China

USGS Publications Warehouse

Rui-Zhong, H.; Wen-Chao, S.; Xian-Wu, B.; Guang-Zhi, T.; Hofstra, A.H.

2002-01-01

mineral assemblages, residence of gold, geochemical signatures, paragenetic sequence, and fluid inclusions are remarkably similar, which indicates that the deposits formed from low salinity, moderately acidic, CO2 and H2S-rich in the crust similar processes at relatively shallow levels in the crust (<5 km). However, the deposits in China are associated with large Hg, Sb, As, U, and Tl deposits, which may reflect higher background abundances of these elements. Stable isotopic data suggest meteoric water evolved to become ore fluids through interactions with sedimentary rocks, although contributions of volatiles or metals from deeper levels are present in some deposits in Nevada. In both countries, the deposits appear to have formed in an area of high paleothermal gradients after a change in stress regime during the later phases of orogenic activity.

Gold in the hills: patterns of placer gold accumulation under dynamic tectonic and climatic conditions

NASA Astrophysics Data System (ADS)

Roy, Sam; Upton, Phaedra; Craw, Dave

2018-01-01

Formation of placer accumulations in fluvial environments requires 103-106 or even greater times concentration of heavy minerals. For this to occur, regular sediment supply from erosion of adjacent topography is required, the river should remain within a single course for an extended period of time and the material must be reworked such that a high proportion of the sediment is removed while a high proportion of the heavy minerals remains. We use numerical modeling, constrained by observations of circum-Pacific placer gold deposits, to explore processes occurring in evolving river systems in dynamic tectonic environments. A fluvial erosion/transport model is used to determine the mobility of placer gold under variable uplift rate, storm intensity, and rock mass strength conditions. Gold concentration is calculated from hydraulic and bedload grain size conditions. Model results suggest that optimal gold concentration occurs in river channels that frequently approach a threshold between detachment-limited and transport-limited hydraulic conditions. Such a condition enables the accumulation of gold particles within the framework of a residual gravel lag. An increase in transport capacity, which can be triggered by faster uplift rates, more resistant bedrock, or higher intensity storm events, will strip all bedload from the channel. Conversely, a reduction in transport capacity, triggered by a reduction in uplift rate, bedrock resistance, or storm intensity, will lead to a greater accumulation of a majority of sediments and a net decrease in gold concentration. For our model parameter range, the optimal conditions for placer gold concentration are met by 103 times difference in strength between bedrock and fault, uplift rates between 1 and 5 mm a-1, and moderate storm intensities. Fault damage networks are shown to be a critical factor for high Au concentrations and should be a target for exploration.

Growth process and anticancer properties of gold nanorods.

PubMed

Zhang, Junyan; Wang, Mian; Webster, Thomas J

2017-09-01

Gold nanoparticles have been of great interest because of their unique optical properties, facile synthesis and conjugation. Among various shapes of gold nanoparticles, gold nanorods have been widely studied. They can be conjugated with different molecules for biomedical applications, such as tumor imaging and therapy. However, few researchers have studied the antitumor properties of bare gold nanorods. In this study, unfunctionalized gold nanorods were synthesized and tested on breast tumor cells. Results showed that the aspect ratio of gold nanorods could be easily influenced by both reaction time and the amount of silver nitrate in the growth solution. A new growth process is proposed here based on the UV-Vis spectra and TEM images of gold nanorods at different reaction times. More importantly, cell studies showed that within a certain concentration range, the gold nanorods can selectively kill tumor cells while having limited or little influence on healthy mammalian (dermal fibroblast) cells. Thus, this study shows promise for the use of bare gold nanorods for further study alone or in combination with photothermal treatment. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2616-2621, 2017. © 2017 Wiley Periodicals, Inc.

Tailoring surface plasmon resonance and dipole cavity plasmon modes of scattering cross section spectra on the single solid-gold/gold-shell nanorod

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chou Chau, Yuan-Fong, E-mail: chou.fong@ubd.edu.bn; Lim, Chee Ming; Kumara, N. T. R. N.

Tunable surface plasmon resonance (SPR) and dipole cavity plasmon modes of the scattering cross section (SCS) spectra on the single solid-gold/gold-shell nanorod have been numerically investigated by using the finite element method. Various effects, such as the influence of SCS spectra under x- and y-polarizations on the surface of the single solid-gold/gold-shell nanorod, are discussed in detail. With the single gold-shell nanorod, one can independently tune the relative SCS spectrum width by controlling the rod length and rod diameter, and the surface scattering by varying the shell thickness and polarization direction, as well as the dipole peak energy. These behaviorsmore » are consistent with the properties of localized SPRs and offer a way to optically control and produce selected emission wavelengths from the single solid-gold/gold-shell nanorod. The electric field and magnetic distributions provide us a qualitative idea of the geometrical properties of the single solid-gold/gold-shell nanorod on plasmon resonance.« less

Tailoring surface plasmon resonance and dipole cavity plasmon modes of scattering cross section spectra on the single solid-gold/gold-shell nanorod

NASA Astrophysics Data System (ADS)

Chou Chau, Yuan-Fong; Lim, Chee Ming; Lee, Chuanyo; Huang, Hung Ji; Lin, Chun-Ting; Kumara, N. T. R. N.; Yoong, Voo Nyuk; Chiang, Hai-Pang

2016-09-01

Tunable surface plasmon resonance (SPR) and dipole cavity plasmon modes of the scattering cross section (SCS) spectra on the single solid-gold/gold-shell nanorod have been numerically investigated by using the finite element method. Various effects, such as the influence of SCS spectra under x- and y-polarizations on the surface of the single solid-gold/gold-shell nanorod, are discussed in detail. With the single gold-shell nanorod, one can independently tune the relative SCS spectrum width by controlling the rod length and rod diameter, and the surface scattering by varying the shell thickness and polarization direction, as well as the dipole peak energy. These behaviors are consistent with the properties of localized SPRs and offer a way to optically control and produce selected emission wavelengths from the single solid-gold/gold-shell nanorod. The electric field and magnetic distributions provide us a qualitative idea of the geometrical properties of the single solid-gold/gold-shell nanorod on plasmon resonance.

The tungsten isotopic composition of the Earth's mantle before the terminal bombardment.

PubMed

Willbold, Matthias; Elliott, Tim; Moorbath, Stephen

2011-09-07

Many precious, 'iron-loving' metals, such as gold, are surprisingly abundant in the accessible parts of the Earth, given the efficiency with which core formation should have removed them to the planet's deep interior. One explanation of their over-abundance is a 'late veneer'--a flux of meteorites added to the Earth after core formation as a 'terminal' bombardment that culminated in the cratering of the Moon. Some 3.8 billion-year-old rocks from Isua, Greenland, are derived from sources that retain an isotopic memory of events pre-dating this cataclysmic meteorite shower. These Isua samples thus provide a window on the composition of the Earth before such a late veneer and allow a direct test of its importance in modifying the composition of the planet. Using high-precision (less than 6 parts per million, 2 standard deviations) tungsten isotope analyses of these rocks, here we show that they have a isotopic tungsten ratio (182)W/(184)W that is significantly higher (about 13 parts per million) than modern terrestrial samples. This finding is in good agreement with the expected influence of a late veneer. We also show that alternative interpretations, such as partial remixing of a deep-mantle reservoir formed in the Hadean eon (more than four billion years ago) or core-mantle interaction, do not explain the W isotope data well. The decrease in mantle (182)W/(184)W occurs during the Archean eon (about four to three billion years ago), potentially on the same timescale as a notable decrease in (142)Nd/(144)Nd (refs 3 and 6). We speculate that both observations can be explained if late meteorite bombardment triggered the onset of the current style of mantle convection.

Gold leaf counter electrodes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Shimada, Kazuhiro; Toyoda, Takeshi

2018-03-01

In this study, a gold leaf 100 nm thin film is used as the counter electrode in dye-sensitized solar cells. The traditional method of hammering gold foil to obtain a thin gold leaf, which requires only small amounts of gold, was employed. The gold leaf was then attached to the substrate using an adhesive to produce the gold electrode. The proposed approach for fabricating counter electrodes is demonstrated to be facile and cost-effective, as opposed to existing techniques. Compared with electrodes prepared with gold foil and sputtered gold, the gold leaf counter electrode demonstrates higher catalytic activity with a cobalt-complex electrolyte and higher cell efficiency. The origin of the improved performance was investigated by surface morphology examination (scanning electron microscopy), various electrochemical analyses (cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy), and crystalline analysis (X-ray diffractometry).

Hydrofluorination of Alkynes Catalysed by Gold Bifluorides.

PubMed

Nahra, Fady; Patrick, Scott R; Bello, Davide; Brill, Marcel; Obled, Alan; Cordes, David B; Slawin, Alexandra M Z; O'Hagan, David; Nolan, Steven P

2015-01-01

We report the synthesis of nine new N -heterocyclic carbene gold bifluoride complexes starting from the corresponding N -heterocyclic carbene gold hydroxides. A new methodology to access N,N' -bis(2,6-diisopropylphenyl)imidazol-2-ylidene gold(I) fluoride starting from N,N' -bis(2,6-diisopropylphenyl)imidazol-2-ylidene gold(I) hydroxide and readily available potassium bifluoride is also reported. These gold bifluorides were shown to be efficient catalysts in the hydrofluorination of symmetrical and unsymmetrical alkynes, thus affording fluorinated stilbene analogues and fluorovinyl thioethers in good to excellent yields with high stereo- and regioselectivity. The method is exploited further to access a fluorinated combretastatin analogue selectively in two steps starting from commercially available reagents.

Gold, currencies and market efficiency

NASA Astrophysics Data System (ADS)

Kristoufek, Ladislav; Vosvrda, Miloslav

2016-05-01

Gold and currency markets form a unique pair with specific interactions and dynamics. We focus on the efficiency ranking of gold markets with respect to the currency of purchase. By utilizing the Efficiency Index (EI) based on fractal dimension, approximate entropy and long-term memory on a wide portfolio of 142 gold price series for different currencies, we construct the efficiency ranking based on the extended EI methodology we provide. Rather unexpected results are uncovered as the gold prices in major currencies lay among the least efficient ones whereas very minor currencies are among the most efficient ones. We argue that such counterintuitive results can be partly attributed to a unique period of examination (2011-2014) characteristic by quantitative easing and rather unorthodox monetary policies together with the investigated illegal collusion of major foreign exchange market participants, as well as some other factors discussed in some detail.

Gold-Decorated Supraspheres of Block Copolymer Micelles

NASA Astrophysics Data System (ADS)

Kim, M. P.; Kang, D. J.; Kannon, A. G.; Jung, D.-W.; Yi, G. R.; Kim, B. J.

2012-02-01

Gold-decorated supraspheres displaying various surface morphologies were prepared by infiltration of gold precursor into polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) supraspheres under acidic condition. The supraspheres were fabricated by emulsifying PS-b-P2VP polymer solution into surfactant solution. Selective swelling of P2VP in the suprasphere by gold precursor under acidic condition resulted in the formation of gold-decorated supraspheres with various surface structures. As evidenced by TEM and SEM images, dot pattern was formed in the case of smaller supraspheres than 800 nm; whereas fingerprint-like pattern was observed in larger supraspheres than 800 nm. Gold nanoparticles were located inside P2VP domains near the surface of prepared supraspheres as confirmed by TEM. The optical property of the supraspheres was characterized using UV-vis absorption spectroscopy and the maximum absorption peak at around 580 nm was observed, which means that gold nanoparticles densely packed into P2VP domain on the suprasphere. Our approach to prepare gold-decorated supraspheres can be extended to other metallic particles such as iron oxide or platinum nanoparticles, and those precursors can be also selectively incorporated into the P2VP domain.

Gold/silver/gold trilayer films on nanostructured polycarbonate substrates for direct and label-free nanoplasmonic biosensing.

PubMed

López-Muñoz, Gerardo A; Estévez, M-Carmen; Vázquez-García, Marc; Berenguel-Alonso, Miguel; Alonso-Chamarro, Julián; Homs-Corbera, Antoni; Lechuga, Laura M

2018-05-01

Ultrasmooth gold/silver/gold trilayer nanostructured plasmonic sensors were obtained using commercial Blu-ray optical discs as nanoslits-based flexible polymer substrates. A thin gold film was used as an adhesion and nucleation layer to improve the chemical stability and reduce the surface roughness of the overlying silver film, without increasing ohmic plasmon losses. The structures were physically and optically characterized and compared with nanostructures of single gold layer. Ultrasmooth and chemically stable trilayer nanostructures with a surface roughness <0.5 nm were obtained following a simple and reproducible fabrication process. They showed a figure of merit (FOM) value up to 69.2 RIU -1 which is significantly higher (more than 95%) than the gold monolayer counterpart. Their potential for biosensing was demonstrated by employing the trilayer sensor for the direct and refractometric (label-free) detection of C-reactive protein (CRP) biomarker in undiluted urine achieving a Limit of Detection (LOD) in the pM order. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical Assay of Gold-Plating Solutions

NASA Technical Reports Server (NTRS)

Chiodo, R.

1982-01-01

Gold content of plating solution is assayed by simple method that required only ordinary electrochemical laboratory equipment and materials. Technique involves electrodeposition of gold from solution onto electrode, the weight gain of which is measured. Suitable fast assay methods are economically and practically necessary in electronics and decorative-plating industries. If gold content in plating bath is too low, poor plating may result, with consequent economic loss to user.

[Theragnostic approaches using gold nanorods and near infrared light].

PubMed

Niidome, Takuro; Shiotani, Atsushi; Akiyama, Yasuyuki; Ohga, Akira; Nose, Keisuke; Pissuwan, Dakrong; Niidome, Yasuro

2010-12-01

Gold nanoparticles have unique optical properties such as surface-plasmon and photothermal effects. Such properties have resulted in gold nanoparticles having several clinical applications. Gold nanorods (which are rod-shaped gold nanoparticles) show a surface plasmon band in the near-infrared region. They have therefore been proposed as contrast agents for bioimaging, or as heating devices for photothermal therapy. Polyethylene glycol-modified gold nanorods systemically administrated into mice can be detected with integrating sphere, and the stability of the gold nanorods in blood flow evaluated. After intravenous injection of gold nanorods followed by near-infrared laser irradiation, significant tumor damage triggered by the photothermal effect was observed. To deliver gold nanorods to the target tissue, thermosensitive polymer gel-coated gold nanorods were prepared. After intravenous injection of the gel-modified gold nanorods and irradiation of the tumor, a larger amount of gold was detected in the irradiated tumor than in the non-irradiated tumor. This effect is due to the hydrophobic interaction between the cellular membrane or the extracellular matrix and the gel surfaces induced by the photothermal effect. Furthermore, the photothermal effect enhanced the permeability of the stratum corneum of the skin. As a result of treatment of the skin with ovalbumin and gold nanorods followed by near-infrared light irradiation, a significant amount of protein was detected in the skin. The gold nanorods therefore showed several functions as a photothermal nanodevice for bioimaging, thermal therapy, and a drug delivery system.

Cross-correlations and influence in world gold markets

NASA Astrophysics Data System (ADS)

Lin, Min; Wang, Gang-Jin; Xie, Chi; Stanley, H. Eugene

2018-01-01

Using the detrended cross-correlation analysis (DCCA) coefficient and the detrended partial cross-correlation analysis (DPCCA) coefficient, we investigate cross-correlations and net cross-correlations among five major world gold markets (London, New York, Shanghai, Tokyo, and Mumbai) at different time scales. We propose multiscale influence measures for examining the influence of individual markets on other markets and on the entire system. We find (i) that the cross-correlations, net cross-correlations, and net influences among the five gold markets vary across time scales, (ii) that the cross-market correlation between London and New York at each time scale is intense and inherent, meaning that the influence of other gold markets on the London-New York market is negligible, (iii) that the remaining cross-market correlations (i.e., those other than London-New York) are greatly affected by other gold markets, and (iv) that the London gold market significantly affects the other four gold markets and dominates the world-wide gold market. Our multiscale findings give market participants and market regulators new information on cross-market linkages in the world-wide gold market.

Gold nanoprobes for theranostics

PubMed Central

Panchapakesan, Balaji; Book-Newell, Brittany; Sethu, Palaniappan; Rao, Madhusudhana; Irudayaraj, Joseph

2011-01-01

Gold nanoprobes have become attractive diagnostic and therapeutic agents in medicine and life sciences research owing to their reproducible synthesis with atomic level precision, unique physical and chemical properties, versatility of their morphologies, flexibility in functionalization, ease of targeting, efficiency in drug delivery and opportunities for multimodal therapy. This review highlights some of the recent advances and the potential for gold nanoprobes in theranostics. PMID:22122586

The effect of 3 torque delivery systems on gold screw preload at the gold cylinder-abutment screw joint.

PubMed

Tan, Keson B; Nicholls, Jack I

2002-01-01

This study measured the gold screw preload at the gold cylinder-abutment screw joint interface obtained by 3 torque delivery systems. Using a precalibrated, strain-gauged standard abutment as the load cell, 3 torque delivery systems tested were shown to have significant differences in gold screw preload when a gold cylinder was attached. Mean preloads measured were 291.2 N for hand torque drivers set at 10 Ncm, 340.3 N for electronic torque controllers at low setting/10 Ncm, 384.4 N for electronic torque controllers at high setting/10 Ncm; and 140.8 N for hand-tightening with a prosthetic slot screwdriver. Significant differences in screw preload were also found between operators using a hand torque driver. Hand-tightening delivered insufficient preload and cannot be recommended for final gold screw tightening. Different electronic torque controller units set at 10 Ncm induced mean gold screw preloads that ranged from 264.1 N to as high as 501.2 N. Electronic torque controllers should be regularly recalibrated to ensure optimal output.

Preparation, characterization, and optical properties of gold, silver, and gold-silver alloy nanoshells having silica cores.

PubMed

Kim, Jun-Hyun; Bryan, William W; Lee, T Randall

2008-10-07

This report describes the structural and optical properties of a series of spherical shell/core nanoparticles in which the shell is comprised of a thin layer of gold, silver, or gold-silver alloy, and the core is comprised of a monodispersed silica nanoparticle. The silica core particles were prepared using the Stöber method, functionalized with terminal amine groups, and then seeded with small gold nanoparticles (approximately 2 nm in diameter). The gold-seeded silica particles were coated with a layer of gold, silver, or gold-silver alloy via solution-phase reduction of an appropriate metal ion or mixture of metal ions. The size, morphology, and elemental composition of the composite nanoparticles were characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The optical properties of the nanoparticles were analyzed by UV-vis spectroscopy, which showed strong absorptions ranging from 400 nm into the near-IR region, where the position of the plasmon band reflected not only the thickness of the metal shell, but also the nature of the metal comprising the shell. Importantly, the results demonstrate a new strategy for tuning the position of the plasmon resonance without having to vary the core diameter or the shell thickness.

Structure and reactivity of a mononuclear gold(II) complex

NASA Astrophysics Data System (ADS)

Preiß, Sebastian; Förster, Christoph; Otto, Sven; Bauer, Matthias; Müller, Patrick; Hinderberger, Dariush; Hashemi Haeri, Haleh; Carella, Luca; Heinze, Katja

2017-12-01

Mononuclear gold(II) complexes are very rare labile species. Transient gold(II) species have been suggested in homogeneous catalysis and in medical applications, but their geometric and electronic structures have remained essentially unexplored: even fundamental data, such as the ionic radius of gold(II), are unknown. Now, an unprecedentedly stable neutral gold(II) complex of a porphyrin derivative has been isolated, and its structural and spectroscopic features determined. The gold atom adopts a 2+2 coordination mode in between those of gold(III) (four-coordinate square planar) and gold(I) (two-coordinate linear), owing to a second-order Jahn-Teller distortion enabled by the relativistically lowered 6s orbital of gold. The reactivity of this gold(II) complex towards dioxygen, nitrosobenzene and acids is discussed. This study provides insight on the ionic radius of gold(II), and allows it to be placed within the homologous series of nd9 Cu/Ag/Au divalent ions and the 5d8/9/10 Pt/Au/Hg 'relativistic' triad in the periodic table.

ISOTOPE CONVERSION DEVICE

DOEpatents

Wigner, E.P.; Young, G.J.; Ohlinger, L.A.

1957-12-01

This patent relates to nuclear reactors of tbe type utilizing a liquid fuel and designed to convert a non-thermally fissionable isotope to a thermally fissionable isotope by neutron absorption. A tank containing a reactive composition of a thermally fissionable isotope dispersed in a liquid moderator is disposed within an outer tank containing a slurry of a non-thermally fissionable isotope convertible to a thermally fissionable isotope by neutron absorption. A control rod is used to control the chain reaction in the reactive composition and means are provided for circulating and cooling the reactive composition and slurry in separate circuits.

Synthesis, characterization, cytotoxic and antitubercular activities of new gold(I) and gold(III) complexes containing ligands derived from carbohydrates.

PubMed

Chaves, Joana Darc Souza; Damasceno, Jaqueline Lopes; Paula, Marcela Cristina Ferreira; de Oliveira, Pollyanna Francielli; Azevedo, Gustavo Chevitarese; Matos, Renato Camargo; Lourenço, Maria Cristina S; Tavares, Denise Crispim; Silva, Heveline; Fontes, Ana Paula Soares; de Almeida, Mauro Vieira

2015-10-01

Novel gold(I) and gold(III) complexes containing derivatives of D-galactose, D-ribose and D-glucono-1,5-lactone as ligands were synthesized and characterized by IR, (1)H, and (13)C NMR, high resolution mass spectra and cyclic voltammetry. The compounds were evaluated in vitro for their cytotoxicity against three types of tumor cells: cervical carcinoma (HeLa) breast adenocarcinoma (MCF-7) and glioblastoma (MO59J) and one non-tumor cell line: human lung fibroblasts (GM07492A). Their antitubercular activity was evaluated as well expressed as the minimum inhibitory concentration (MIC90) in μg/mL. In general, the gold(I) complexes were more active than gold(III) complexes, for example, the gold(I) complex (1) was about 8.8 times and 7.6 times more cytotoxic than gold(III) complex (8) in MO59J and MCF-7 cells, respectively. Ribose and alkyl phosphine derivative complexes were more active than galactose and aryl phosphine complexes. The presence of a thiazolidine ring did not improve the cytotoxicity. The study of the cytotoxic activity revealed effective antitumor activities for the gold(I) complexes, being more active than cisplatin in all the tested tumor cell lines. Gold(I) compounds (1), (2), (3), (4) and (6) exhibited relevant antitubercular activity even when compared with first line drugs such as rifampicin.

Colloidal-gold electrosensor measuring device

DOEpatents

Wegner, S.; Harpold, M.A.; McCaffrey, T.M.; Morris, S.E.; Wojciechowski, M.; Zhao, J.; Henkens, R.W.; Naser, N.; O`Daly, J.P.

1995-11-21

The present invention provides a new device for use in measuring lead levels in biological and environmental samples. Using square wave coulometry and colloidal gold particles impregnated on carbon electrodes, the present invention provides a rapid, reliable, portable and inexpensive means of detecting low lead levels. The colloidal gold modified electrodes have microelectrode array characteristics and produce significantly higher stripping detection signals for lead than are produced at bulk gold electrode surfaces. The method is effective in determining levels of lead down to at least 5 {micro}g/dL in blood samples as small as 10 {micro}L. 9 figs.

Colloidal-gold electrosensor measuring device

DOEpatents

Wegner, Steven; Harpold, Michael A.; McCaffrey, Terence M.; Morris, Susan E.; Wojciechowski, Marek; Zhao, Junguo; Henkens, Robert W.; Naser, Najih; O'Daly, John P.

1995-01-01

The present invention provides a new device for use in measuring lead levels in biological and environmental samples. Using square wave coulometry and colloidal gold particles impregnated on carbon electrodes, the present invention provides a rapid, reliable, portable and inexpensive means of detecting low lead levels. The colloidal gold modified electrodes have microelectrode array characteristics and produce significantly higher stripping detection signals for lead than are produced at bulk gold electrode surfaces. The method is effective in determining levels of lead down to at least 5 .mu.g/dL in blood samples as small as 10 .mu.L.

Redbed-type gold mineralisation, Kupferschiefer, south-west Poland

NASA Astrophysics Data System (ADS)

Piestrzyński, Adam; Pieczonka, Jadwiga; Głuszek, Adam

2002-06-01

A new type of gold mineralisation containing minor amounts of platinum and palladium has been found proximal to the secondary redox interface located below the Cu-Ag Kupferschiefer orebody of the Polkowice-Sieroszowice mine in the south-western part of the Lubin-Sieroszowice district, Poland. This deposit can be classified as redbed-type gold. Our study shows that gold, platinum and palladium occur in secondary red-coloured sections of the basal Zechstein sedimentary rocks and in the uppermost Weissliegendes sandstone. Noble metal mineralisation occurs within an average interval of 0.22 m, which lies directly below the copper ores. The average grade of the horizon is 2.25 ppm Au, 0.138 ppm Pt and 0.082 ppm Pd with a metal content of several tens of tonnes of gold. A transition zone has been recognised between the gold-bearing horizon and the copper deposit. This transition zone is characterised by the presence of low grades of copper (<0.2 wt%) and elevated gold contents (>0.5 ppm). Native gold accompanied by electrum, mercury-bearing gold, haematite, covellite, chalcocite, bornite and chalcopyrite has been identified in the gold-bearing horizon. In some sections, Pd-arsenides, tetra-auricupride, Co-arsenides, clausthalite, tennantite, digenite, yarrowite, spionkopite and galena have also been noted.

Mercury contamination from historical gold mining in California

USGS Publications Warehouse

Alpers, Charles N.; Hunerlach, Michael P.; May, Jason T.; Hothem, Roger L.

2005-01-01

Mercury contamination from historical gold mines represents a potential risk to human health and the environment. This fact sheet provides background information on the use of mercury in historical gold mining and processing operations in California, with emphasis on historical hydraulic mining areas. It also describes results of recent USGS projects that address the potential risks associated with mercury contamination. Miners used mercury (quicksilver) to recover gold throughout the western United States. Gold deposits were either hardrock (lode, gold-quartz veins) or placer (alluvial, unconsolidated gravels). Underground methods (adits and shafts) were used to mine hardrock gold deposits. Hydraulic, drift, or dredging methods were used to mine the placer gold deposits. Mercury was used to enhance gold recovery in all the various types of mining operations; historical records indicate that more mercury was used and lost at hydraulic mines than at other types of mines. On the basis of USGS studies and other recent work, a better understanding is emerging of mercury distribution, ongoing transport, transformation processes, and the extent of biological uptake in areas affected by historical gold mining. This information has been used extensively by federal, state, and local agencies responsible for resource management and public health in California.

Increased cellular uptake of peptide-modified PEGylated gold nanoparticles.

PubMed

He, Bo; Yang, Dan; Qin, Mengmeng; Zhang, Yuan; He, Bing; Dai, Wenbing; Wang, Xueqing; Zhang, Qiang; Zhang, Hua; Yin, Changcheng

2017-12-09

Gold nanoparticles are promising drug delivery vehicles for nucleic acids, small molecules, and proteins, allowing various modifications on the particle surface. However, the instability and low bioavailability of gold nanoparticles compromise their clinical application. Here, we functionalized gold nanoparticles with CPP fragments (CALNNPFVYLI, CALRRRRRRRR) through sulfhydryl PEG to increase their stability and bioavailability. The resulting gold nanoparticles were characterized with transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-visible spectrometry and X-ray photoelectron spectroscopy (XPS), and the stability in biological solutions was evaluated. Comparing to PEGylated gold nanoparticles, CPP (CALNNPFVYLI, CALRRRRRRRR)-modified gold nanoparticles showed 46 folds increase in cellular uptake in A549 and B16 cell lines, as evidenced by the inductively coupled plasma atomic emission spectroscopy (ICP-AES). The interactions between gold nanoparticles and liposomes indicated CPP-modified gold nanoparticles bind to cell membrane more effectively than PEGylated gold nanoparticles. Surface plasmon resonance (SPR) was used to measure interactions between nanoparticles and the membrane. TEM and uptake inhibitor experiments indicated that the cellular entry of gold nanoparticles was mediated by clathrin and macropinocytosis. Other energy independent endocytosis pathways were also identified. Our work revealed a new strategy to modify gold nanoparticles with CPP and illustrated the cellular uptake pathway of CPP-modified gold nanoparticles. Copyright © 2017 Elsevier Inc. All rights reserved.

Stable-isotope geochemistry of the Pierina high-sulfidation Au-Ag deposit, Peru: Influence of hydrodynamics on SO42--H2S sulfur isotopic exchange in magmatic-steam and steam-heated environments

USGS Publications Warehouse

Fifarek, R.H.; Rye, R.O.

2005-01-01

environment was unusually slow, which provided sufficient time for the uptake of groundwater and partial to complete SO42--H2S isotopic exchange. The slow steam velocities were likely related to the dispersal of the steam column as it entered the tuffs and possibly to intermediate exsolution rates from magmatic brine. The low ??D values may also partly reflect continuous degassing of the mineralizing magma. Similarly, data for steam-heated alunite (??34S=12.3??? to 27.2???; ??18OSO4=11.7??? to 13.0???; ??18OOH=6.6??? to 9.4???; ??D=-59??? to -42???) are unusual and indicate a strong magmatic influence, relatively high temperatures (140 to 180 ??C, based on ??18 OSO4-OH fractionations), and partial to complete sulfur isotopic exchange between steam-heated sulfate and H2S. Restricted lithologically controlled fluid flow in the host tuffs allowed magmatic condensate to supplant meteoric groundwater at the water table and create the high-temperature low-pH conditions that permitted unusually rapid SO42--H2S isotopic equilibration (50-300 days) and (or) long sulfate residence times for this environment. Late void-filling barite (??34S=7.4??? to 29.7???; ??18OSO4=-0.4??? to 15.1???) and later void-filling goethite (??18O=-11.8??? to 0.2???) document a transition from magmatic condensate to dominantly meteoric water in steam-heated fluids during cooling and collapse of the hydrothermal system. These steam-heated fluids oxidized the top ???300 m of the deposit by leaching sulfides, redistributing metals, and precipitating barite??acanthite??gold and goethite-hematite ??gold. Steam-heated oxidation, rather than weathering, was critical to forming the orebody in that it not only released encapsulated gold but likely enriched the deposit to ore-grade Au concentrations. ?? 2004 Elsevier B.V. All rights reserved.

Constraints on the composition of ore fluids and implications for mineralising events at the Cleo gold deposit, Eastern Goldfields Province, Western Australia

USGS Publications Warehouse

Brown, S.M.; Johnson, C.A.; Watling, R.J.; Premo, W.R.

2003-01-01

The Cleo gold deposit, 55 km south of Laverton in the Eastern Goldfields Province of Western Australia, is characterised by banded iron-formation (BIF)-hosted ore zones in the gently dipping Sunrise Shear Zone and high-grade vein-hosted ore in the Western Lodes. There is evidence that gold mineralisation in the Western Lodes (which occurred at ca 2655 Ma) post-dates the majority of displacement along the Sunrise Shear Zone, but it remains uncertain if the ore in both structures formed simultaneously or separately. Overall, the Pb, Nd, Sr, C. O and S isotopic compositions of ore-related minerals from both the Western Lodes and ore zones in the Sunrise Shear Zone are similar. Early low-salinity aqueous-carbonic fluids and late high-salinity fluids with similar characteristics are trapped in inclusions in quartz veins from both the Sunrise Shear Zone and the Western Lodes. The early CO2, CO2-H2O, and H2O- dominant inclusions are interpreted as being related to ore formation, and to have formed from a single low-salinity aqueous-carbonic fluid as a result of intermittent fluid immiscibility. Homogenisation temperatures indicate that these inclusions were trapped at approximately 280??C and at approximately 4 km depth, in the deeper epizonal range. Differences between the ore zones are detected in the trace-element composition of gold samples, with gold from the Sunrise Shear Zone enriched in Ni, Pb, Sn, Te and Zn, and depleted In As, Bi, Cd, Cu and Sb, relative to gold from the Western Lodes. Although there are differences in gold composition between the Sunrise Shear Zone and Western Lodes, and hence the metal content of ore fluids may have varied slightly between the different ore zones, no other systematic fluid or solute differences are detected between the ore zones. Given the fact that the ore fluids in each zone have very similar bulk properties, the considerable differences in gold grade, sulfide mineral abundance, and ore textures between the two ore zones

Electron linac for medical isotope production with improved energy efficiency and isotope recovery

DOEpatents

Noonan, John; Walters, Dean; Virgo, Matt; Lewellen, John

2015-09-08

A method and isotope linac system are provided for producing radio-isotopes and for recovering isotopes. The isotope linac is an energy recovery linac (ERL) with an electron beam being transmitted through an isotope-producing target. The electron beam energy is recollected and re-injected into an accelerating structure. The ERL provides improved efficiency with reduced power requirements and provides improved thermal management of an isotope target and an electron-to-x-ray converter.

Pulling monatomic gold wires with single molecules: an Ab initio simulation.

PubMed

Krüger, Daniel; Fuchs, Harald; Rousseau, Roger; Marx, Dominik; Parrinello, Michele

2002-10-28

Car-Parrinello molecular dynamics simulations demonstrate that pulling a single thiolate molecule anchored on a stepped gold surface does not preferentially break the sulfur-gold chemical bond. Instead, it is found that this process leads to the formation of a monoatomic gold nanowire, followed by breaking a gold-gold bond with a rupture force of about 1.2 nN. The simulations also indicate that previous single-molecule thiolate-gold and gold-gold rupture experiments both probe the same phenomenon, namely, the breaking of a gold-gold bond within a gold nanowire.

Subchronic inhalation toxicity of gold nanoparticles

PubMed Central

2011-01-01

Background Gold nanoparticles are widely used in consumer products, including cosmetics, food packaging, beverages, toothpaste, automobiles, and lubricants. With this increase in consumer products containing gold nanoparticles, the potential for worker exposure to gold nanoparticles will also increase. Only a few studies have produced data on the in vivo toxicology of gold nanoparticles, meaning that the absorption, distribution, metabolism, and excretion (ADME) of gold nanoparticles remain unclear. Results The toxicity of gold nanoparticles was studied in Sprague Dawley rats by inhalation. Seven-week-old rats, weighing approximately 200 g (males) and 145 g (females), were divided into 4 groups (10 rats in each group): fresh-air control, low-dose (2.36 × 104 particle/cm3, 0.04 μg/m3), middle-dose (2.36 × 105 particle/cm3, 0.38 μg/m3), and high-dose (1.85 × 106 particle/cm3, 20.02 μg/m3). The animals were exposed to gold nanoparticles (average diameter 4-5 nm) for 6 hours/day, 5 days/week, for 90-days in a whole-body inhalation chamber. In addition to mortality and clinical observations, body weight, food consumption, and lung function were recorded weekly. At the end of the study, the rats were subjected to a full necropsy, blood samples were collected for hematology and clinical chemistry tests, and organ weights were measured. Cellular differential counts and cytotoxicity measurements, such as albumin, lactate dehydrogenase (LDH), and total protein were also monitored in a cellular bronchoalveolar lavage (BAL) fluid. Among lung function test measurements, tidal volume and minute volume showed a tendency to decrease comparing control and dose groups during the 90-days of exposure. Although no statistically significant differences were found in cellular differential counts, histopathologic examination showed minimal alveoli, an inflammatory infiltrate with a mixed cell type, and increased macrophages in the high-dose rats. Tissue distribution of gold

Formation of a paleothermal anomaly and disseminated gold deposits associated with the Bingham Canyon porphyry Cu-Au-Mo system, Utah

USGS Publications Warehouse

Cunningham, C.G.; Austin, G.W.; Naeser, C.W.; Rye, R.O.; Ballantyne, G.H.; Stamm, R.G.; Barker, C.E.

2004-01-01

the quartzite with circulating meteoric water related to the Bingham Canyon porphyry system. The ??18O and ??13C values of limestone vary with respect to degree of recrystallization and proximity to open fractures. Recrystallized limestone at the Melco and Barneys Canyon gold deposits has the highest ??18O values (about 30???), whereas limestone adjacent to the porphyry copper deposit has the lowest values (about 10???). The high ??18O values for the recrystallized limestone at Barneys Canyon and Melco strongly suggest that mineralization was related to low temperature fluids with exceptionally high ??18OH2O values such as could be derived from water in a crater lake of an active volcano. The age of formation of the gold deposits has been interpreted to range from Jurassic to Eocene. The mineralized rocks at the Barneys Canyon and Melco deposits are likely the same age as the geochemically similar deposits that are present in north-striking, late faults that cut the Bingham Canyon porphyry. The patterns of apatite and zircon fission-track data, conodont color alteration indices, solid bitumen reflectivity, stable isotope data, and mineral zoning are consistent with the gold deposits being genetically related to formation of the 37 Ma Bingham porphyry deposit. We interpret the disseminated gold mineralization to be related to collapse of the Bingham Canyon hydrothermal system in which isotopically heavy, oxidizing, acidic waters, possibly from an internally draining acidic crater lake, mixed with and were entrained into reduced gold-bearing meteoric water fluids in the collapsing main-stage hydrothermal system. Most of this fluid mixing and cooling was probably located close to the hydrologic interface between the sedimentary basement rocks and overlying volcanic rocks. ??2004 by Economic Geology.

Gold-Collar Workers. ERIC Digest.

ERIC Educational Resources Information Center

Wonacott, Michael E.

The gold-collar worker has problem-solving abilities, creativity, talent, and intelligence; performs non-repetitive and complex work difficult to evaluate; and prefers self management. Gold-collar information technology workers learn continually from experience; recognize the synergy of teams; can demonstrate leadership; and are strategic thinkers…

Nanoporous Gold for Enzyme Immobilization.

PubMed

Stine, Keith J; Jefferson, Kenise; Shulga, Olga V

2017-01-01

Nanoporous gold (NPG) is a material of emerging interest for immobilization of biomolecules, especially enzymes. The material provides a high surface area form of gold that is suitable for physisorption or for covalent modification by self-assembled monolayers. The material can be used as a high surface area electrode and with immobilized enzymes can be used for amperometric detection schemes. NPG can be prepared in a variety of formats from alloys containing between 20 and 50 % atomic composition of gold and less noble element(s) by dealloying procedures. Materials resembling NPG can be prepared by hydrothermal and electrodeposition methods. Related high surface area gold structures have been prepared using templating approaches. Covalent enzyme immobilization can be achieved by first forming a self-assembled monolayer on NPG bearing a terminal reactive functional group followed by conjugation to the enzyme through amide linkages to lysine residues. Enzymes can also be entrapped by physisorption or immobilized by electrostatic interactions.

Zircon U-Pb ages and Hf isotope data from the Kukuluma Terrain of the Geita Greenstone Belt, Tanzania Craton: Implications for stratigraphy, crustal growth and timing of gold mineralization

NASA Astrophysics Data System (ADS)

Kwelwa, S. D.; Sanislav, I. V.; Dirks, P. H. G. M.; Blenkinsop, T.; Kolling, S. L.

2018-03-01

The Geita Greenstone Belt is a late Archean greenstone belt located in the Tanzania Craton, trending approximately E-W and can be subdivided into three NW-SE trending terrains: the Kukuluma Terrain to the east, the Central Terrain in the middle and the Nyamullilima Terrain in the west. The Kukuluma Terrain, forms a NW-SE trending zone of complexly deformed sediments, intruded by the Kukuluma Intrusive Complex which, contains an early-syntectonic diorite-monzonite suite and a late-syntectonic granodiorite suite. Three gold deposits (Matandani, Kukuluma and Area 3W) are found along the contact between the Kukuluma Intrusive Complex and the sediments. A crystal tuff layer from the Kukuluma deposits returned an age of 2717 ± 12 Ma which can be used to constrain maximum sedimentation age in the area. Two granodiorite dykes from the same deposit and a small granodiorite intrusion found along a road cut yielded zircon ages of 2667 ± 17 Ma, 2661 ± 16 Ma and 2663 ± 11 Ma respectively. One mineralized granodiorite dyke from the Matandani deposit has an age of 2651 ± 14 Ma which can be used to constrain the maximum age of the gold mineralization in the area. The 2717 Ma crystal tuff has zircon grains with suprachondritic 176Hf/177Hf ratios (0.28108-0.28111 at 2717 Ma) and positive (+1.6 to +2.6) εHf values indicating derivation from juvenile mafic crust. Two of the granodiorite samples have suprachondritic 176Hf/177Hf ratios (avg. 0.28106 and 0.28107 at 2663 and 2651 Ma respectively) and nearly chondritic εHf values (avg. -0.5 and -0.3 respectively). The other two granodiorite samples have chondritic 176Hf/177Hf ratios (avg. 0.28104 and 0.28103 at 2667 and 2661 Ma respectively) and slightly negative εHf values (avg. -1.1 and -1.5 respectively). The new zircon age and isotope data suggest that the igneous activity in the Kukuluma Terrain involves a significant juvenile component and occurred within the 2720 to 2620 Ma period which, is the main period of crustal growth

δ15N values of atmospheric N species simultaneously collected using sector-based samplers distant from sources - Isotopic inheritance and fractionation

NASA Astrophysics Data System (ADS)

Savard, Martine M.; Cole, Amanda; Smirnoff, Anna; Vet, Robert

2017-08-01

The nitrogen isotope ratios (δ15N) of atmospheric N species are commonly suggested as indicators of N emission sources. Therefore, numerous research studies have developed analytical methodologies and characterized primary (gases) and secondary emission products (mostly precipitation and aerosols) from various emitters. These previous studies have generally collected either reduced or oxidized N forms, and sampled them separately prior to determining their δ15N values. Distinctive isotopic signals have been reported for emissions from various sources, and seasonality of the δ15N values has been frequently attributed to shifts in relative contributions from sources with different isotopic signals. However, theoretical concepts suggest that temperature effects on isotopic fractionation may also affect the δ15N values of atmospheric reaction products. Here we use a sector-based multi-stage filter system to simultaneously collect seven reduced and oxidized N species downwind from five different source types in Alberta, Canada. We report δ15N values obtained with a state-of-the-art gold-furnace pre-concentrator online with an isotope ratio mass spectrometer (IRMS) to provide representative results even for oxidized-N forms. We find that equilibrium isotope effects and their temperature dependence play significant roles in determining the δ15N values of the secondary emission products. In the end, seasonal δ15N changes here are mainly caused by temperature effects on fractionation, and the δ15N values of only two N species from one source type can be retained as potential fingerprints of emissions.

Detection of squamous carcinoma cells using gold nanoparticles

NASA Astrophysics Data System (ADS)

Dai, Wei-Yun; Lee, Sze-tsen; Hsu, Yih-Chih

2015-03-01

The goal of this study is to use gold nanoparticle as a diagnostic agent to detect human squamous carcinoma cells. Gold nanoparticles were synthesized and the gold nanoparticle size was 34.3 ± 6.2 nm. Based on the over-expression of epidermal growth factor receptor (EGFR) biomarkers in squamous carcinoma cells, we hypothesized that EGFR could be a feasible biomarker with a target moiety for detection. We further modified polyclonal antibodies of EGFR on the surface of gold nanoparticles. We found selected squamous carcinoma cells can be selectively detected using EGFR antibody-modified gold nanoparticles via receptor-mediated endocytosis. Cell death was also examined to determine the survival status of squamous carcinoma cells with respect to gold nanoparticle treatment and EGFR polyclonal antibody modification.

Precipitation of gold by the reaction of aqueous gold(III)-chloride with cyanobacteria at 25-80{degrees}C, studied by x-ray absorption spectroscopy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lengke, M. F.; Ravel, B.; Fleet, M. E.

2007-10-01

The mechanisms of gold precipitation by the interaction of cyanobacteria (Plectonema boryanum UTEX 485) and gold(III) chloride aqueous solutions (7.6 mmol/L final gold) have been studied at 25, 60, and 80 C, using both laboratory and real-time synchrotron radiation absorption spectroscopy experiments. Addition of aqueous gold(III) chloride to the cyanobacterial culture initially promoted the precipitation of amorphous gold(I) sulfide at the cell walls and finally caused the formation of octahedral (111) platelets (<1 to 6 {micro}m) of gold metal near cell surfaces and in solutions. X-ray absorption spectroscopy results confirmed that the reduction mechanism of gold(III) chloride to elemental goldmore » by cyanobacteria involves the formation of an intermediate Au(I) species, gold(I) sulfide, with sulfur originating from cyanobacterial proteins, presumably cysteine or methionine. Although the bioreduction of gold(III) chloride to gold(I) sulfide was relatively rapid at all temperatures, the reaction rate increased with the increase in temperature. At the completion of the experiments, elemental gold was the major species present at all temperatures.« less

Antifungal activity of gold nanoparticles prepared by solvothermal method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmad, Tokeer, E-mail: tahmad3@jmi.ac.in; Wani, Irshad A.; Lone, Irfan H.

2013-01-15

Graphical abstract: Gold nanoparticles (7 and 15 nm) of very high surface area (329 and 269 m{sup 2}/g) have been successfully synthesized through solvothermal method by using tin chloride and sodium borohydride as reducing agents. As-prepared gold nanoparticles shows very excellent antifungal activity against Candida isolates and activity increases with decrease in the particle size. Display Omitted Highlights: ► Effect of reducing agents on the morphology of gold nanoparticles. ► Highly uniform and monodisperse gold nanoparticles (7 nm). ► Highest surface area of gold nanoparticles (329 m{sup 2/}g). ► Excellent antifungal activity of gold nanoparticles against Candida strains. -- Abstract:more » Gold nanoparticles have been successfully synthesized by solvothermal method using SnCl{sub 2} and NaBH{sub 4} as reducing agents. X-ray diffraction studies show highly crystalline and monophasic nature of the gold nanoparticles with face centred cubic structure. The transmission electron microscopic studies show the formation of nearly spherical gold nanoparticles of average size of 15 nm using SnCl{sub 2}, however, NaBH{sub 4} produced highly uniform, monodispersed and spherical gold nanoparticles of average grain size of 7 nm. A high surface area of 329 m{sup 2}/g for 7 nm and 269 m{sup 2}/g for 15 nm gold nanoparticles was observed. UV–vis studies assert the excitations over the visible region due to transverse and longitudinal surface plasmon modes. The gold nanoparticles exhibit excellent size dependant antifungal activity and greater biocidal action against Candida isolates for 7 nm sized gold nanoparticles restricting the transmembrane H{sup +} efflux of the Candida species than 15 nm sized gold nanoparticles.« less

Orogenic gold and geologic time: A global synthesis

USGS Publications Warehouse

Goldfarb, R.J.; Groves, D.I.; Gardoll, S.

2001-01-01

Orogenic gold deposits have formed over more than 3 billion years of Earth's history, episodically during the Middle Archean to younger Precambrian, and continuously throughout the Phanerozoic. This class of gold deposit is characteristically associated with deformed and metamorphosed mid-crustal blocks, particularly in spatial association with major crustal structures. A consistent spatial and temporal association with granitoids of a variety of compositions indicates that melts and fluids were both inherent products of thermal events during orogenesis. Including placer accumulations, which are commonly intimately associated with this mineral deposit type, recognized production and resources from economic Phanerozoic orogenic-gold deposits are estimated at just over one billion ounces gold. Exclusive of the still-controversial Witwatersrand ores, known Precambrian gold concentrations are about half this amount. The recent increased applicability of global paleo-reconstructions, coupled with improved geochronology from most of the world's major gold camps, allows for an improved understanding of the distribution pattern of orogenic gold in space and time.

Reconnaissance guidelines for gold exploration in Central Alaska

USGS Publications Warehouse

Light, T.D.; Moll, S.H.; Bie, S.W.; Lee, G.K.

1993-01-01

Distribution of more than 300 gold-bearing samples from the Livengood (Tolovana) and parts of the Fairbanks and Rampart mining districts in central Alaska, USA, indicate that the concentration of gold in placers is spatially related both to structural features and to Late Cretaceous and (or) Tertiary felsic plutons. The regional consistency of these spatial relationships is demonstrated by proximity analysis using a Geographic Information System (GIS), and suggests a genetic association between faults, felsic plutons, and gold occurrences. The local presence of gold within several of the plutons indicates that these are the source of some of the gold. In addition, some gold occurs proximal to faults where plutons are not present, suggesting that some of the gold was also derived from the country rock. We envision a model whereby weakly mineralized solutions, thermally driven by latent plutonic heat, were enriched by circulation through clastic units that may have had a naturally elevated gold background. The resultant enriched solutions were channeled and reconcentrated along or adjacent to large-scale fault systems. Future exploration to define individual target areas should be directed toward areas where Late Cretaceous and (or) Tertiary felsic plutons occur near major faults. ?? 1993.

Thiosulfate leaching of gold from waste mobile phones.

PubMed

Ha, Vinh Hung; Lee, Jae-chun; Jeong, Jinki; Hai, Huynh Trung; Jha, Manis K

2010-06-15

The present communication deals with the leaching of gold from the printed circuit boards (PCBs) of waste mobile phones using an effective and less hazardous system, i.e., a copper-ammonia-thiosulfate solution, as an alternative to the conventional and toxic cyanide leaching of gold. The influence of thiosulfate, ammonia and copper sulfate concentrations on the leaching of gold from PCBs of waste mobile phones was investigated. Gold extraction was found to be enhanced with solutions containing 15-20 mM cupric, 0.1-0.14 M thiosulfate, and 0.2-0.3 M ammonia. Similar trends were obtained for the leaching of gold from two different types of scraps and PCBs of waste mobile phones. From the scrap samples, 98% of the gold was leached out using a solution containing 20 mM copper, 0.12 M thiosulfate and 0.2 M ammonia. Similarly, the leaching of gold from the PCBs samples was also found to be good, but it was lower than that of scrap samples in similar experimental conditions. In this case, only 90% of the gold was leached, even with a contact time of 10h. The obtained data will be useful for the development of processes for the recycling of gold from waste mobile phones. Copyright 2010 Elsevier B.V. All rights reserved.

Gold absorbing film for a composite bolometer

NASA Technical Reports Server (NTRS)

Dragovan, M.; Moseley, S. H.

1984-01-01

The principles governing the design of metal films are reviewed, with attention also given to the choice of metals. A description is then given of the characteristics of a bolometer with a gold absorbing film. It is demonstrated that gold is effective as an absorbing film for a millimeter bolometer operated at 1.5 K. At 1.5 K, gold is significantly better than bismuth since gold has a lower heat capacity for the absorbing film. At 0.3 K, gold and bismuth are both suitable. It is pointed out that at temperatures below 0.3 K, a superconducting absorbing film can have a heat capacity low enough not to dominate the heat capacity of the detector; for this reason, it may give better performance than a nonsuperconducting absorbing film.

A Placer-Gold Evaluation Exercise.

ERIC Educational Resources Information Center

Tunley, A. Tom

1984-01-01

A laboratory exercise allowing students to use drillhole data to simulate the process of locating a placer gold paystreak is presented. As part of the activity students arithmetically compute the value of their gold, mining costs, and personal profits or losses, and decide on development plans for the claim. (BC)

Bottom-up formation of robust gold carbide

PubMed Central

Westenfelder, Benedikt; Biskupek, Johannes; Meyer, Jannik C.; Kurasch, Simon; Lin, Xiaohang; Scholz, Ferdinand; Gross, Axel; Kaiser, Ute

2015-01-01

A new phenomenon of structural reorganization is discovered and characterized for a gold-carbon system by in-situ atomic-resolution imaging at temperatures up to 1300 K. Here, a graphene sheet serves in three ways, as a quasi transparent substrate for aberration-corrected high-resolution transmission electron microscopy, as an in-situ heater, and as carbon supplier. The sheet has been decorated with gold nanoislands beforehand. During electron irradiation at 80 kV and at elevated temperatures, the accumulation of gold atoms has been observed on defective graphene sites or edges as well as at the facets of gold nanocrystals. Both resulted in clustering, forming unusual crystalline structures. Their lattice parameters and surface termination differ significantly from standard gold nanocrystals. The experimental data, supported by electron energy loss spectroscopy and density-functional theory calculations, suggests that isolated gold and carbon atoms form – under conditions of heat and electron irradiation – a novel type of compound crystal, Au-C in zincblende structure. The novel material is metastable, but surprisingly robust, even under annealing condition. PMID:25772348

Formation of neutral and charged gold carbonyls on highly facetted gold nanostructures

NASA Astrophysics Data System (ADS)

Chau, Thoi-Dai; Visart de Bocarmé, Thierry; Kruse, Norbert; Wang, Richard L. C.; Kreuzer, Hans Jürgen

2003-12-01

We show that gold mono- and di-carbonyls are formed on gold field emitter tips during interaction with carbon monoxide gas at room temperature and in the presence of high electrostatic fields. The experiments are done in a time-of-flight atom probe to obtain mass spectra. The yield of monocarbonyl cations is about twice that of di-carbonyl ions. Density functional theory calculations are reported that explain the field stabilization of adsorbed carbonyls and the desorption yield of their cations.

Hydrous pyrolysis of crude oil in gold-plated reactors

USGS Publications Warehouse

Curiale, J.A.; Lundegard, P.D.; Kharaka, Y.K.

1992-01-01

Crude oils from Iraq and California have been pyrolyzed under hydrous conditions at 200 and 300??C for time periods up to 210 days, in gold-plated reactors. Elemental (vanadium, nickel), stable isotopic (carbon), and molecular (n-alkanes, acyclic isoprenoids, steranes, terpanes and aromatic steroid hydrocarbons) analyses were made on the original and pyrolyzed oils. Various conventional crude oil maturity parameters, including 20S/(20S + 20R)-24-ethylcholestane ratios and the side-chain-length distribution of aliphatic and aromatic steroidal hydrocarbons, were measured in an effort to assess the modification of molecular maturity parameters in clay-free settings, similar to those encountered in "clean" reservoirs. Concentrations of vanadium and nickel in the Iraq oil decrease significantly and the V/(V + Ni) ratio decreases slightly, with increasing pyrolysis time/temperature. Whole oil carbon isotope ratios remain fairly constant during pyrolysis, as do hopane/sterane ratios and carbon number distribution of 5??(H),14??(H),17??(H),20R steranes. These latter three parameters are considered maturity-invariant. The ratios of short side-chain components to long side-chain components of the regular steranes [C21/(C21 + C29R)] and the triaromatic steroid hydrocarbons [C21/(C21 + C28)] vary systematically with increasing pyrolysis time, indicating that these parameters may be useful as molecular maturity parameters for crude oils in clay-free reservoir rocks. In addition, decreases in bisnorhopane/hopane ratio with increasing pyrolysis time, in a clay-free and kerogen-free environment, suggest that the distribution of these compounds is controlled by either differential thermal stabilities or preferential release from a higher-molecular weight portion of the oil. ?? 1992.

Isotope separation by photochromatography

DOEpatents

Suslick, Kenneth S.

1977-01-01

An isotope separation method which comprises physically adsorbing an isotopically mixed molecular species on an adsorptive surface and irradiating the adsorbed molecules with radiation of a predetermined wavelength which will selectively excite a desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thereby separate them from the unexcited undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes.

Highly active thermally stable nanoporous gold catalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biener, Juergen; Wittstock, Arne; Biener, Monika M.

In one embodiment, a system includes a nanoporous gold structure and a plurality of oxide particles deposited on the nanoporous gold structure; the oxide particles are characterized by a crystalline phase. In another embodiment, a method includes depositing oxide nanoparticles on a nanoporous gold support to form an active structure and functionalizing the deposited oxide nanoparticles.

Local density variation of gold nanoparticles in aquatic environments

NASA Astrophysics Data System (ADS)

Hosseinzadeh, F.; Shirazian, F.; Shahsavari, R.; Khoei, A. R.

2016-10-01

Gold (Au) nanoparticles are widely used in diagnosing cancer, imaging, and identification of therapeutic methods due to their particular quantum characteristics. This research presents different types of aqueous models and potentials used in TIP3P, to study the effect of the particle size and density of Au clusters in aquatic environments; so it can be useful to facilitate future investigation of the interaction of proteins with Au nanoparticles. The EAM potential is used to model the structure of gold clusters. It is observed that in the systems with identical gold/water density and different cluster radii, gold particles are distributed in aqueous environment almost identically. Thus, Au particles have identical local densities, and the root mean square displacement (RMSD) increases with a constant slope. However in systems with constant cluster radii and different gold/water densities, Au particle dispersion increases with density; as a result, the local density decreases and the RMSD increases with a larger slope. In such systems, the larger densities result in more blunted second peaks in gold-gold radial distribution functions, owing to more intermixing of the clusters and less FCC crystalline features at longer range, a mechanism that is mediated by the competing effects of gold-water and gold-gold interactions.

Iron isotope fractionation among magnetite, pyrrhotite, chalcopyrite, rhyolite melt and aqueous fluid at magmatic-hydrothermal conditions

NASA Astrophysics Data System (ADS)

Bilenker, L. D.; Simon, A.; Lundstrom, C.; Gajos, N.

2012-12-01

Fractionation of non-traditional stable isotopes (NTSI) such as Fe in magmatic systems is a relatively understudied subject. The fractionation of Fe stable isotopes has been quantified in some natural igneous samples, but there is a paucity of experimental data that could provide further insight into the causative processes of the observed fractionation. Substantial experimental work has been performed at higher temperatures pertaining to the formation of chondrites and the Earth's core, but only a handful of studies have addressed crustal rocks. To fill this knowledge gap, we performed isothermal, isobaric experiments containing mineral (e.g., magnetite, Fe-sulfides) and fluid, or mineral, rhyolite melt, and fluid assemblages to quantify equilibrium fractionation factors (α). These data, to our knowledge, are the first data that quantify the effect of a fluid phase on iron isotope fractionation at conditions appropriate for evolving magmatic systems. Charges were run inside gold capsules held in a René-41 cold seal vessel, and heated to 400, 600, or 800°C at 150 MPa for mineral-fluid, and 800°C and 100 MPa for mineral-melt-fluid runs. Use of the René vessel fixed the fO2 at the NNO buffer, an oxidation state consistent with arc magmas. The isotopic compositions of the starting and quenched phases were obtained by using a Multi-Collector Plasma Mass Spectrometer (MC-ICP-MS). Equilibrium was assessed by performing time-series runs and the three-isotope method, used only once before in a similar Fe isotope study. Correlation between Fe isotope mass and oxidation state is also being explored. Magnetite-fluid results indicate enrichment of heavy Fe isotopes in the mineral relative to the fluid, consistent with measurements of felsic igneous rocks. Magnetite-melt-fluid relationships are also consistent with measurements of natural samples. In the latter assemblage, over the course of the run, the rhyolite melt becomes heavy relative to the fluid while magnetite

Isotope separation by photochromatography

DOEpatents

Suslick, K.S.

1975-10-03

A photochromatographic method for isotope separation is described. An isotopically mixed molecular species is adsorbed on an adsorptive surface, and the adsorbed molecules are irradiated with radiation of a predetermined wavelength which will selectively excite desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thus separate them from the undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes. (BLM)

Effects of dissolucytotic gold ions on recovering brain lesions.

PubMed

Danscher, Gorm; Larsen, Agnete

2010-04-01

Recent experimental research has shown that metallic gold releases charged gold atoms when placed intracerebrally and that the liberated gold ions affect inflammation in the brain. The observations suggest that metallic gold can be used as a safe suppressor of inflammation in the central nervous system.

Synthetic isotope mixtures for the calibration of isotope amount ratio measurements of carbon

NASA Astrophysics Data System (ADS)

Russe, K.; Valkiers, S.; Taylor, P. D. P.

2004-07-01

Synthetic isotope mixtures for the calibration of carbon isotope amount ratio measurements have been prepared by mixing carbon tetrafluoride highly enriched in 13C with carbon tetrafluoride depleted in 13C. Mixing procedures based on volumetry and gravimetry are described. The mixtures served as primary measurement standards for the calibration of isotope amount ratio measurements of the Isotopic Reference Materials PEF1, NBS22 and USGS24. Thus SI-traceable measurements of absolute carbon isotope amount ratios have been performed for the first time without any hypothesis needed for a correction of oxygen isotope abundances, such as is the case for measurements on carbon dioxide. As a result, "absolute" carbon isotope amount ratios determined via carbon tetrafluoride have smaller uncertainties than those published for carbon dioxide. From the measurements of the Reference Materials concerned, the absolute carbon isotope amount ratio of Vienna Pee Dee Belemnite (VPDB)--the hypothetical material upon which the scale for relative carbon isotope ratio measurements is based--was calculated to be R13(VPDB) = (11 101 +/- 16) × 10-6.

Method for separating isotopes

DOEpatents

Jepson, B.E.

1975-10-21

Isotopes are separated by contacting a feed solution containing the isotopes with a cyclic polyether wherein a complex of one isotope is formed with the cyclic polyether, the cyclic polyether complex is extracted from the feed solution, and the isotope is thereafter separated from the cyclic polyether.

Malaria in gold-mining areas in Colombia

PubMed Central

Castellanos, Angélica; Chaparro-Narváez, Pablo; Morales-Plaza, Cristhian David; Alzate, Alberto; Padilla, Julio; Arévalo, Myriam; Herrera, Sócrates

2016-01-01

Gold-mining may play an important role in the maintenance of malaria worldwide. Gold-mining, mostly illegal, has significantly expanded in Colombia during the last decade in areas with limited health care and disease prevention. We report a descriptive study that was carried out to determine the malaria prevalence in gold-mining areas of Colombia, using data from the public health surveillance system (National Health Institute) during the period 2010-2013. Gold-mining was more prevalent in the departments of Antioquia, Córdoba, Bolívar, Chocó, Nariño, Cauca, and Valle, which contributed 89.3% (270,753 cases) of the national malaria incidence from 2010-2013 and 31.6% of malaria cases were from mining areas. Mining regions, such as El Bagre, Zaragoza, and Segovia, in Antioquia, Puerto Libertador and Montelíbano, in Córdoba, and Buenaventura, in Valle del Cauca, were the most endemic areas. The annual parasite index (API) correlated with gold production (R2 0.82, p < 0.0001); for every 100 kg of gold produced, the API increased by 0.54 cases per 1,000 inhabitants. Lack of malaria control activities, together with high migration and proliferation of mosquito breeding sites, contribute to malaria in gold-mining regions. Specific control activities must be introduced to control this significant source of malaria in Colombia. PMID:26814645

Malaria in gold-mining areas in Colombia.

PubMed

Castellanos, Angélica; Chaparro-Narváez, Pablo; Morales-Plaza, Cristhian David; Alzate, Alberto; Padilla, Julio; Arévalo, Myriam; Herrera, Sócrates

2016-01-01

Gold-mining may play an important role in the maintenance of malaria worldwide. Gold-mining, mostly illegal, has significantly expanded in Colombia during the last decade in areas with limited health care and disease prevention. We report a descriptive study that was carried out to determine the malaria prevalence in gold-mining areas of Colombia, using data from the public health surveillance system (National Health Institute) during the period 2010-2013. Gold-mining was more prevalent in the departments of Antioquia, Córdoba, Bolívar, Chocó, Nariño, Cauca, and Valle, which contributed 89.3% (270,753 cases) of the national malaria incidence from 2010-2013 and 31.6% of malaria cases were from mining areas. Mining regions, such as El Bagre, Zaragoza, and Segovia, in Antioquia, Puerto Libertador and Montelíbano, in Córdoba, and Buenaventura, in Valle del Cauca, were the most endemic areas. The annual parasite index (API) correlated with gold production (R2 0.82, p < 0.0001); for every 100 kg of gold produced, the API increased by 0.54 cases per 1,000 inhabitants. Lack of malaria control activities, together with high migration and proliferation of mosquito breeding sites, contribute to malaria in gold-mining regions. Specific control activities must be introduced to control this significant source of malaria in Colombia.

Microbial synthesis of Flower-shaped gold nanoparticles.

PubMed

Singh, Priyanka; Kim, Yeon Ju; Wang, Chao; Mathiyalagan, Ramya; Yang, Deok Chun

2016-09-01

The shape of nanoparticles has been recognized as an important attribute that determines their applicability in various fields. The flower shape (F-shape) has been considered and is being focused on, because of its enhanced properties when compared to the properties of the spherical shape. The present study proposed the microbial synthesis of F-shaped gold nanoparticles within 48 h using the Bhargavaea indica DC1 strain. The F-shaped gold nanoparticles were synthesized extracellularly by the reduction of auric acid in the culture supernatant of B. indica DC1. The shape, size, purity, and crystalline nature of F-shaped gold nanoparticles were revealed by various instrumental techniques including UV-Vis, FE-TEM, EDX, elemental mapping, XRD, and DLS. The UV-Vis absorbance showed a maximum peak at 536 nm. FE-TEM revealed the F-shaped structure of nanoparticles. The EDX peak obtained at 2.3 keV indicated the purity. The peaks obtained on XRD analysis corresponded to the crystalline nature of the gold nanoparticles. In addition, the results of elemental mapping indicated the maximum distribution of gold elements in the nanoproduct obtained. Particle size analysis revealed that the average diameter of the F-shaped gold nanoparticles was 106 nm, with a polydispersity index (PDI) of 0.178. Thus, the methodology developed for the synthesis of F-shaped gold nanoparticles is completely green and economical.

Mercury Stable Isotopic Composition of Monomethylmercury in Estuarine Sediments and Pure Cultures of Mercury Methylating Bacteria

NASA Astrophysics Data System (ADS)

Janssen, S.; Johnson, M. W.; Barkay, T.; Blum, J. D.; Reinfelder, J. R.

2014-12-01

Tracking monomethylmercury (MeHg) from its source in soils and sediments through various environmental compartments and transformations is critical to understanding its accumulation in aquatic and terrestrial food webs. Advances in the field of mercury (Hg) stable isotopes have allowed for the tracking of discrete Hg sources and the examination of photochemical and bacterial transformations. Despite analytical advances, measuring the Hg stable isotopic signature of MeHg in environmental samples or laboratory experiments remains challenging due to difficulties in the quantitative separation of MeHg from complex matrices with high concentrations of inorganic Hg. To address these challenges, we have developed a MeHg isolation method for sediments and bacterial cultures which involves separation by gas chromatography. The MeHg eluting from the GC is passed through a pyrolysis column and purged onto a gold amalgam trap which is then desorbed into a final oxidizing solution. A MeHg reference standard carried through our separation process retained its isotopic composition within 0.02 ‰ for δ202Hg, and for native estuarine sediments, MeHg recoveries were 80% to 100%. For sediment samples from the Hackensack and Passaic Rivers (New Jersey, USA), δ202Hg values for MeHg varied from -1.2 to +0.58 ‰ (relative to SRM 3133) and for individual samples were significantly different from that of total Hg (-0.38 ± 0.06 ‰). No mass independent fractionation was observed in MeHg or total Hg from these sediments. Pure cultures of Geobacter sulfurreducens, grown under fermentative conditions showed preferential enrichment of lighter isotopes (lower δ202Hg) during Hg methylation. The Hg stable isotope signatures of MeHg in sediments and laboratory methylation experiments will be discussed in the context of the formation and degradation of MeHg in the environment and the bioaccumulation of MeHg in estuarine food webs.

Effects of mother lode-type gold mineralization on 187Os/188Os and platinum group element concentrations in peridotite: Alleghany District, California

USGS Publications Warehouse

Walker, R.J.; Böhlke, J.K.; McDonough, W.F.; Li, Ji

2007-01-01

Osmium isotope compositions and concentrations of Re, platinum group elements (PGE), and Au were determined for host peridotites (serpentinites and barzburgites) and hydrothermally altered ultramafic wall rocks associated with Mother Lode-type hydrothermal gold-quartz vein mineralization in the Alleghany district, California. The host peridotites have Os isotope compositions and Re, PGE, and Au abundances typical of the upper mantle at their presumed formation age during the late Proterozoic or early Paleozoic. The hydrothermally altered rocks have highly variable initial Os isotope compositions with ??os, values (% deviation of 187OS/188OS from the chondritic average calculated for the approx. 120 Ma time of mineralization) ranging from -1.4 to -8.3. The lowest Os isotope compositions are consistent with Re depletion of a chondritic source (e.g., the upper mantle) at ca. 1.6 Ga. Most of the altered samples are enriched in Au and have depleted and fractionated abundances of Re and PGE relative to their precursor peridotites. Geoehemical characteristics of the altered samples suggest that Re and some PGE were variably removed from the ultramafic rocks during the mineralization event. In addition to Re, the Pt and Pd abundances of the most intensely altered rocks appear to have been most affected by mineralization. The 187Os-depleted isotopic compositions of some altered rocks are interpreted to be a result of preferential 187Os loss via destruction of Re-rich phases during the event. For these rocks, Os evidently is not a useful tracer of the mineralizing fluids. The results do, however, provide evidence for differential mobility of these elements, and mobility of 187Os relative to the initial bulk Os isotope composition during hydrothermal metasomatic alteration of ultramafic rocks. ?? 2007 Society of Economic Geologists, Inc.

Photochemical isotope separation

DOEpatents

Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Greiner, Norman R.; Boyer, Keith

1987-01-01

A process for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium.

Laser isotope separation

DOEpatents

Robinson, C.P.; Reed, J.J.; Cotter, T.P.; Boyer, K.; Greiner, N.R.

1975-11-26

A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light is described. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.

Laser isotope separation

DOEpatents

Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Boyer, Keith; Greiner, Norman R.

1988-01-01

A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.

Photochemical isotope separation

DOEpatents

Robinson, C.P.; Jensen, R.J.; Cotter, T.P.; Greiner, N.R.; Boyer, K.

1987-04-28

A process is described for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium. 8 figs.

Gold nanoparticles for photoacoustic imaging

PubMed Central

Li, Wanwan; Chen, Xiaoyuan

2015-01-01

Photoacoustic (PA) imaging is a biomedical imaging modality that provides functional information regarding the cellular and molecular signatures of tissue by using endogenous and exogenous contrast agents. There has been tremendous effort devoted to the development of PA imaging agents, and gold nanoparticles as exogenous contrast agents have great potential for PA imaging due to their inherent and geometrically induced optical properties. The gold-based nanoparticles that are most commonly employed for PA imaging include spheres, rods, shells, prisms, cages, stars and vesicles. This article provides an overview of the current state of research in utilizing these gold nanomaterials for PA imaging of cancer, atherosclerotic plaques, brain function and image-guided therapy. PMID:25600972

Gold nanoparticles deposited on glass: physicochemical characterization and cytocompatibility

PubMed Central

2013-01-01

Properties of gold films sputtered under different conditions onto borosilicate glass substrate were studied. Mean thickness of sputtered gold film was measured by gravimetry, and film contact angle was determined by goniometry. Surface morphology was examined by atomic force microscopy, and electrical sheet resistance was determined by two-point technique. The samples were seeded with rat vascular smooth muscle cells, and their adhesion and proliferation were studied. Gold depositions lead to dramatical changes in the surface morphology and roughness in comparison to pristine substrate. For sputtered gold structures, the rapid decline of the sheet resistance appears on structures deposited for the times above 100 s. The thickness of deposited gold nanoparticles/layer is an increasing function of sputtering time and current. AFM images prove the creation of separated gold islands in the initial deposition phase and a continuous gold coverage for longer deposition times. Gold deposition has a positive effect on the proliferation of vascular smooth muscle cells. Largest number of cells was observed on sample sputtered with gold for 20 s and at the discharge current of 40 mA. This sample exhibits lowest contact angle, low relative roughness, and only mild increase of electrical conductivity. PMID:23705782

Gold deposits of the northern margin of the North China craton: Multiple late Paleozoic-Mesozoic mineralizing events

USGS Publications Warehouse

Hart, C.J.R.; Goldfarb, R.J.; Qiu, Yumin; Snee, L.; Miller, L.D.; Miller, M.L.

2002-01-01

The northern margin of the North China craton is well-endowed with lode gold deposits hosting a resource of approximately 900 tonnes (t) of gold. The ???1,500-km-long region is characterized by east-trending blocks of metamorphosed Archean and Proterozoic strata that were episodically uplifted during Variscan, Indosinian, and Yanshanian deformational and magmatic events. At least 12 gold deposits from the Daqinshan, Yan-Liao (includes the Zhangjiakou, Yanshan, and Chifeng gold districts), and Changbaishan gold provinces contain resources of 20-100 t Au each. Most deposits are hosted in uplifted blocks of Precambrian metamorphic rocks, although felsic Paleozoic and Mesozoic plutons are typically proximal and host ???30% of the deposits. The lodes are characterized by sulfide-poor quartz veins in brittle structures with low base metal values and high Au:Ag ratios. Although phyllic alteration is most common, intensive alkali feldspar metasomatism characterizes the Wulashan, Dongping, and Zhongshangou deposits, but is apparently coeval with Variscan alkalic magmatism only at Wulashan. Stepwise 40Ar-39Ar geochronology on 16 samples from gangue and alteration phases, combined with unpublished SHRIMP U-Pb dates on associated granitoids, suggest that gold mineralizing events occured during Variscan, Indosinian, and Yanshanian orogenies at circa 350, 250, 200, 180, 150, and 129 Ma. However, widespread Permo-Triassic (???250 Ma) and Early Jurassic (???180 Ma) thermal events caused variable resetting of most of the white mica and K-feldspar argon spectra, as well as previously reported K-Ar determinations. Compiled and new stable isotope and fluid inclusion data show that most ??18O values for ore-stage veins range from 8 to 14???, indicating a fluid in equilibrium with the Precambrian metamorphic basement rocks; ??D values from fluid inclysions range widely from -64 to -154???, which is indicative of a local meteoric component in some veins; and highly variable ??34S data

The La Unión Au ± Cu prospect, Camagüey District, Cuba: fluid inclusion and stable isotope evidence for ore-forming processes

NASA Astrophysics Data System (ADS)

Santana, Miriela María Ulloa; Moura, Márcia Abrahão; Olivo, Gema R.; Botelho, Nilson Francisquini; Kyser, T. Kurtis; Bühn, Bernhard

2011-01-01

The Camagüey district, Cuba, is known for its epithermal precious metal deposits in a Cretaceous volcanic arc setting. Recently, the La Unión prospect was discovered in the southern part of the district, containing gold and minor copper mineralization interpreted as porphyry type. Mineralization is hosted in a 73.0 ± 1.5 Ma calc-alkaline I-type oxidized porphyry quartz diorite intrusive within volcanic and volcaniclastic rocks of the early Cretaceous Guáimaro Formation. The porphyry is affected by propylitic alteration and crosscut by a network of quartz and carbonate veinlets and veins. Chlorite, epidote, sericite, quartz, and pyrite are the main minerals in the early veins which are cut by late carbonate and zeolite veins. Late barite pseudomorphously replaces pyrite. Gold is associated with pyrite as disseminations in the altered quartz diorite and in the veins, occurring as inclusions or filling fractures in pyrite with 4 g/t Au in bulk samples, and up to 900 ppm Au in in pyrite. Fluid inclusion and oxygen isotope data are consistent with a H2O-NaCl-(KCl) mineralizing fluid, derived from the quartz diorite magma, and trapped at least at 425°C and 1.2 kbar. This primary fluid unmixed into two fluid phases, a hypersaline aqueous fluid and a low-salinity vapor-rich fluid. Boiling during cooling may have played an important role in metal precipitation. Pyrite δ34S values for the La Unión prospect range between 0.71‰ and 1.31‰, consistent with a homogeneous magmatic sulfur source. The fluids in equilibrium with the mineralized rocks have estimated δ18O values from 8‰ to 11.8‰, calculated for a temperature range of 480-505°C. The tectonic environment of the La Unión prospect, its high gold and low copper contents, the physical-chemical characteristics of the mineralizing fluids and the isotopic signature of the alteration minerals and fluids indicate that the La Unión gold mineralization is similar to the porphyry gold type, even though the ore

Isotope reference materials

USGS Publications Warehouse

Coplen, Tyler B.

2010-01-01

Measurement of the same isotopically homogeneous sample by any laboratory worldwide should yield the same isotopic composition within analytical uncertainty. International distribution of light element isotopic reference materials by the International Atomic Energy Agency and the U.S. National Institute of Standards and Technology enable laboratories to achieve this goal.

Gold-nickel-titanium brazing alloy

DOEpatents

Mizuhara, Howard

1995-01-03

A brazing alloy in accordance with this invention has the following composition, by weight: 91 to 99 gold, 0.5 to 7% nickel; 0.10 to 2% titanium. Alternatively, with palladium present, the composition is as follows, by weight: 83 to 96% gold; 3 to 10% palladium; 0.5 to 5% nickel; 0.10 to 2% titanium.

Gold-nickel-titanium brazing alloy

DOEpatents

Mizuhara, Howard

1990-07-03

A brazing alloy in accordance with this invention has the following composition, by weight: 91 to 99% gold, 0.5 to 7% nickel; 0.10 to 2% titanium. Alternatively, with palladium present, the composition is as follows, by weight: 83 to 96% gold; 3 to 10% palladium; 0.5 to 5% nickel; 0.10 to 2% titanium.

Combination of Mass Signal Amplification and Isotope-Labeled Alkanethiols for the Multiplexed Detection of miRNAs.

PubMed

Kang, Hyunook; Hong, Seol-Hye; Sung, Jiha; Yeo, Woon-Seok

2017-08-04

We report a fast and sensitive method for the multiplexed detection of miRNAs by combining mass signal amplification and isotope-labeled signal reporter molecules. In our strategy, target miRNAs are captured specifically by immobilized DNAs on gold nanoparticles (AuNPs), which carry a large number of small molecules, called amplification tags (Am-tags), as the reporter for the detection of target miRNAs. For multiplexed detection, we designed and synthesized four Am-tags containing 0, 4, 8, 12 isotopes so that they had same molecular properties but different molecular weights. By observing the mass signals of the Am-tags on AuNPs decorated along with different probe DNAs, four types of miRNAs in a sample could be easily discriminated, and the relative amounts of these miRNAs could be quantified. The practicability of our strategy was further verified by measuring the expression levels of two miRNAs in HUVECs in response to different CuSO 4 concentrations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study on Sumbawa gold recovery using centrifuge

NASA Astrophysics Data System (ADS)

Ferdana, A. D.; Petrus, H. T. B. M.; Bendiyasa, I. M.; Prijambada, I. D.; Hamada, F.; Sachiko, T.

2018-01-01

The Artisanal Small Gold Mining in Sumbawa has been processing gold with mercury (Hg), which poses a serious threat to the mining and global environment. One method of gold processing that does not use mercury is by gravity method. Before processing the ore first performed an analysis of Mineragraphy and analysis of compound with XRD. Mineragraphy results show that gold is associated with chalcopyrite and covelite and is a single particle (native) on size 58.8 μm, 117 μm up to 294 μm. characterization with XRD shows that the Sumbawa Gold Ore is composed of quartz, pyrite, pyroxene, and sericite compounds. Sentrifugation is one of separation equipment of gravity method to increase concentrate based on difference of specific gravity. The optimum concentration result is influenced by several variables, such as water flow rate and particle size. In this present research, the range of flow rate is 5 lpm and 10 lpm, the particle size - 100 + 200 mesh and -200 +300 mesh. Gold concentration in concentrate is measured by EDX. The result shows that the optimum condition is obtained at a separation with flow rate 5 lpm and a particle size of -100 + 200 mesh.

Acoustic vibrations of single suspended gold nanostructures

NASA Astrophysics Data System (ADS)

Major, Todd A.

The acoustic vibrations for single gold nanowires and gold plates were studied using time-resolved ultrafast transient absorption. The objective of this work was to remove the contribution of the supporting substrate from the damping of the acoustic vibrations of the metal nano-objects. This was achieved by suspending the nano-objects across trenches created by photolithography and reactive ion etching. Transient absorption measurements for single suspended gold nanowires were initially completed in air and water environments. The acoustic vibrations for gold nanowires over the trench in air last typically for several nanoseconds, whereas gold nanowires in water are damped more quickly. Continuum mechanics models suggest that the acoustic impedance mismatch between air and water dominates the damping rate. Later transient absorption studies on single suspended gold nanowires were completed in glycerol and ethylene glycol environments. However, our continuum mechanical model suggests nearly complete damping in glycerol due to its high viscosity, but similar damping rates are seen between the two liquids. The continuum mechanics model thus incorrectly addresses high viscosity effects on the lifetimes of the acoustic vibrations, and more complicated viscoelastic interactions occur for the higher viscosity liquids. (Abstract shortened by UMI.).

Recent Developments in Australian Gold Extraction.

ERIC Educational Resources Information Center

Thiele, Rodney B.

1995-01-01

Describes new technologies that have greatly improved the extraction efficiency of gold ore, including: altering plant layout to promote efficiency, engaging Filiblast forced oxidation and bioxidation systems, and updating the electrowinning procedure at the gold recovery stage. (JRH)

The Complete Reconfiguration of Dendritic Gold

NASA Astrophysics Data System (ADS)

Paneru, Govind; Flanders, Bret

2014-03-01

Reconfigurability-by-design is an important strategy in modern materials science, as materials with this capability could potentially be used to confer hydrophobic, lipophobic, or anti-corrosive character to substrates in a regenerative manner. The present work extends the directed electrochemical nanowire assembly (DENA) methodology, which is a technique that employs alternating voltages to grow single crystalline metallic nanowires and nano-dendrites from simple salt solutions, to enable the complete dissolution of macroscopic arrays of metallic dendrites following their growth. Our main finding is that structural reconfiguration of dendritic gold is induced by changes in the MHz-level frequencies of voltages that are applied to the dendrites. Cyclic voltammetry and micro-Raman spectroscopy have been used to show that dendritic gold grows and dissolves by the same chemical mechanisms as bulk gold. Hence, the redox chemistry that occurs at the crystal-solution interface is no different than the established electrochemistry of gold. What differs in this process and allows for reconfiguration to occur is the diffusive behavior of the gold chloride molecules in the solution adjacent to the interface. We will present a simple model that captures the physics of this behavior.

Gold Nanoparticle Microwave Synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krantz, Kelsie E.; Christian, Jonathan H.; Coopersmith, Kaitlin

At the nanometer scale, numerous compounds display different properties than those found in bulk material that can prove useful in areas such as medicinal chemistry. Gold nanoparticles, for example, display promise in newly developed hyperthermia therapies for cancer treatment. Currently, gold nanoparticle synthesis is performed via the hot injection technique which has large variability in final particle size and a longer reaction time. One underdeveloped area by which these particles could be produced is through microwave synthesis. To initiate heating, microwaves agitate polar molecules creating a vibration that gives off the heat energy needed. Previous studies have used microwaves formore » gold nanoparticle synthesis; however, polar solvents were used that partially absorbed incident microwaves, leading to partial thermal heating of the sample rather than taking full advantage of the microwave to solely heat the gold nanoparticle precursors in a non-polar solution. Through this project, microwaves were utilized as the sole heat source, and non-polar solvents were used to explore the effects of microwave heating only as pertains to the precursor material. Our findings show that the use of non-polar solvents allows for more rapid heating as compared to polar solvents, and a reduction in reaction time from 10 minutes to 1 minute; this maximizes the efficiency of the reaction, and allows for reproducibility in the size/shape of the fabricated nanoparticles.« less

16 CFR 23.4 - Misrepresentation as to gold content.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 16 Commercial Practices 1 2014-01-01 2014-01-01 false Misrepresentation as to gold content. 23.4... JEWELRY, PRECIOUS METALS, AND PEWTER INDUSTRIES § 23.4 Misrepresentation as to gold content. (a) It is unfair or deceptive to misrepresent the presence of gold or gold alloy in an industry product, or the...

16 CFR 23.4 - Misrepresentation as to gold content.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 16 Commercial Practices 1 2011-01-01 2011-01-01 false Misrepresentation as to gold content. 23.4... JEWELRY, PRECIOUS METALS, AND PEWTER INDUSTRIES § 23.4 Misrepresentation as to gold content. (a) It is unfair or deceptive to misrepresent the presence of gold or gold alloy in an industry product, or the...

A Comparative XAFS Study of Gold-thiolate Nanoparticles and Nanoclusters

NASA Astrophysics Data System (ADS)

Chevrier, D. M.; Chatt, A.; Sham, T. K.; Zhang, P.

2013-04-01

Tiopronin-capped gold nanoparticles and gold nanoclusters of sizes 3.0 and 1.5 nm, respectively, were investigated with XAFS at the gold L3-edge. The specific EXAFS fitting procedure is discussed for obtaining reliable fit parameters for each system. The difficulties and challenges faced when analysing EXAFS data for gold nanoparticles and nanoclusters are also mentioned. Fitting results for gold nanoparticles reveal a small amount of surface Au-thiolate interactions with a large Au-Au metal core. For gold nanoclusters, only a one-shell fit was obtainable. Instead of Au-Au metal core, long-range interactions are expected for gold nanoclusters. Tiopronin-capped gold nanoclusters are proposed to be polymeric in nature, which helps explain the observed red luminescence.

Site-Specific Biomolecule Labeling with Gold Clusters

PubMed Central

Ackerson, Christopher J.; Powell, Richard D.; Hainfeld, James F.

2013-01-01

Site-specific labeling of biomolecules in vitro with gold clusters can enhance the information content of electron cryomicroscopy experiments. This chapter provides a practical overview of well-established techniques for forming biomolecule/gold cluster conjugates. Three bioconjugation chemistries are covered: Linker-mediated bioconjugation, direct gold–biomolecule bonding, and coordination-mediated bonding of nickel(II) nitrilotriacetic acid (NTA)-derivatized gold clusters to polyhistidine (His)-tagged proteins. PMID:20887859

Beneficiation of the gold bearing ore by gravity and flotation

NASA Astrophysics Data System (ADS)

Gül, Alim; Kangal, Olgaç; Sirkeci, Ayhan A.; Önal, Güven

2012-02-01

Gold concentration usually consists of gravity separation, flotation, cyanidation, or the combination of these processes. The choice among these processes depends on the mineralogical characterization and gold content of the ore. Recently, the recovery of gold using gravity methods has gained attention because of low cost and environmentally friendly operations. In this study, gold pre-concentrates were produced by the stepwise gravity separation and flotation techniques. The Knelson concentrator and conventional flotation were employed for the recovery of gold. Gold bearing ore samples were taken from Gümüşhane Region, northern east part of Turkey. As a result of stepwise Knelson concentration experiments, a gold concentrate assaying around 620 g/t is produced with 41.4wt% recovery. On the other hand, a gold concentrate about 82 g/t is obtained with 89.9wt% recovery from a gold ore assaying 6 g/t Au by direct flotation.

33 CFR 13.01-10 - Gold and silver bars.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and one...

33 CFR 13.01-10 - Gold and silver bars.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and one...

33 CFR 13.01-10 - Gold and silver bars.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and one...

33 CFR 13.01-10 - Gold and silver bars.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and one...

33 CFR 13.01-10 - Gold and silver bars.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and one...

Inhibition of HIV Fusion with Multivalent Gold Nanoparticles

PubMed Central

Bowman, Mary-Catherine; Ballard, T. Eric; Ackerson, Christopher J.; Feldheim, Daniel L.; Margolis, David M.; Melander, Christian

2010-01-01

The design and synthesis of a multivalent gold nanoparticle therapeutic is presented. SDC-1721, a fragment of the potent HIV inhibitor TAK-779, was synthesized and conjugated to 2.0 nm diameter gold nanoparticles. Free SDC-1721 had no inhibitory effect on HIV infection; however, the (SDC-1721)-gold nanoparticle conjugates displayed activity comparable to that of TAK-779. This result suggests that multivalent presentation of small molecules on gold nanoparticle surfaces can convert inactive drugs into potent therapeutics. PMID:18473457

16 CFR 23.4 - Misrepresentation as to gold content.

Code of Federal Regulations, 2010 CFR

2010-01-01

... JEWELRY, PRECIOUS METALS, AND PEWTER INDUSTRIES § 23.4 Misrepresentation as to gold content. (a) It is... covered with a base metal (such as nickel), which is covered with a thin wash of gold, unless there is a disclosure that the primary gold coating is covered with a base metal, which is gold washed. (7) Use of the...

16 CFR 23.4 - Misrepresentation as to gold content.

Code of Federal Regulations, 2013 CFR

2013-01-01

... JEWELRY, PRECIOUS METALS, AND PEWTER INDUSTRIES § 23.4 Misrepresentation as to gold content. (a) It is... covered with a base metal (such as nickel), which is covered with a thin wash of gold, unless there is a disclosure that the primary gold coating is covered with a base metal, which is gold washed. (7) Use of the...

16 CFR 23.4 - Misrepresentation as to gold content.

Code of Federal Regulations, 2012 CFR

2012-01-01

... JEWELRY, PRECIOUS METALS, AND PEWTER INDUSTRIES § 23.4 Misrepresentation as to gold content. (a) It is... covered with a base metal (such as nickel), which is covered with a thin wash of gold, unless there is a disclosure that the primary gold coating is covered with a base metal, which is gold washed. (7) Use of the...

50 CFR 665.169 - Gold coral harvest moratorium.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Gold coral harvest moratorium. 665.169... Fisheries § 665.169 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

50 CFR 665.169 - Gold coral harvest moratorium.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Gold coral harvest moratorium. 665.169... Fisheries § 665.169 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

50 CFR 665.469 - Gold coral harvest moratorium.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Gold coral harvest moratorium. 665.469... Archipelago Fisheries § 665.469 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

50 CFR 665.270 - Gold coral harvest moratorium.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Gold coral harvest moratorium. 665.270... Fisheries § 665.270 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

50 CFR 665.169 - Gold coral harvest moratorium.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Gold coral harvest moratorium. 665.169... Fisheries § 665.169 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

50 CFR 665.469 - Gold coral harvest moratorium.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Gold coral harvest moratorium. 665.469... Archipelago Fisheries § 665.469 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

50 CFR 665.270 - Gold coral harvest moratorium.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Gold coral harvest moratorium. 665.270... Fisheries § 665.270 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

50 CFR 665.469 - Gold coral harvest moratorium.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Gold coral harvest moratorium. 665.469... Archipelago Fisheries § 665.469 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

50 CFR 665.270 - Gold coral harvest moratorium.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Gold coral harvest moratorium. 665.270... Fisheries § 665.270 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

Engineered Gold Nanoparticles and Plant Adaptation Potential

NASA Astrophysics Data System (ADS)

Siddiqi, Khwaja Salahuddin; Husen, Azamal

2016-09-01

Use of metal nanoparticles in biological system has recently been recognised although little is known about their possible effects on plant growth and development. Nanoparticles accumulation, translocation, growth response and stress modulation in plant system is not well understood. Plants exposed to gold and gold nanoparticles have been demonstrated to exhibit both positive and negative effects. Their growth and yield vary from species to species. Cytoxicity of engineered gold nanoparticles depends on the concentration, particle size and shape. They exhibit increase in vegetative growth and yield of fruit/seed at lower concentration and decrease them at higher concentration. Studies have shown that the gold nanoparticles exposure has improved free radical scavenging potential and antioxidant enzymatic activities and alter micro RNAs expression that regulate different morphological, physiological and metabolic processes in plants. These modulations lead to improved plant growth and yields. Prior to the use of gold nanoparticles, it has been suggested that its cost may be calculated to see if it is economically feasible.

Simple Fabrication of Gold Nanobelts and Patterns

PubMed Central

Zhang, Renyun; Hummelgård, Magnus; Olin, Håkan

2012-01-01

Gold nanobelts are of interest in several areas; however, there are only few methods available to produce these belts. We report here on a simple evaporation induced self-assembly (EISA) method to produce porous gold nanobelts with dimensions that scale across nanometer (thickness ∼80 nm) and micrometer (width ∼20 µm), to decimeter (length ∼0.15 m). The gold nanobelts are well packed on the beaker wall and can be easily made to float on the surface of the solution for depositing onto other substrates. Microscopy showed that gold nanobelts had a different structure on the two sides of the belt; the density of gold nanowires on one side was greater than on the other side. Electrical measurements showed that these nanobelts were sensitive to compressive or tensile forces, indicating a potential use as a strain sensor. The patterned nanobelts were further used as a template to grow ZnO nanowires for potential use in applications such as piezo-electronics. PMID:22291962

The interaction of gold with gallium arsenide

NASA Technical Reports Server (NTRS)

Weizer, Victor G.; Fatemi, Navid S.

1988-01-01

Gold and gold-based alloys, commonly used as solar-cell contact materials, are known to react readily with gallium arsenide. Experiments designed to identify the mechanisms involved in these GaAs-metal interactions have yielded several interesting results. It is shown that the reaction of GaAs with gold takes place via a dissociative diffusion process. It is shown further that the GaAs-metal reaction rate is controlled to a very great extent by the condition of the free surface of the contact metal, an interesting example of which is the previously unexplained increase in the reaction rate that has been observed for samples annealed in a vacuum environment as compared to those annealed in a gaseous ambient. A number of other hard-to-explain observations, such as the low-temperature formation of voids in the gold lattice and crystallite growth on the gold surface, are also explained by invoking this mechanism.

Extreme 34S depletions in ZnS at the Mike gold deposit, Carlin Trend, Nevada: Evidence for bacteriogenic supergene sphalerite

USGS Publications Warehouse

Bawden, T.M.; Einaudi, M.T.; Bostick, B.C.; Meibom, A.; Wooden, J.; Norby, J.W.; Orobona, M.J.T.; Chamberlain, C.P.

2003-01-01

We identified submicrometer-sized framboidal sphalerite (ZnS) below the base of supergene oxidation in a Carlin-type gold deposit of Eocene age in Nevada, United States, where the framboidal sphalerite forms a blanket-like body containing >400,000 metric tons of zinc. Framboidal sphalerite <0.1 ??m in diameter, formed in the early Miocene, ranges from <0.1 to 0.35 mol% FeS; the ??34S values range from -25??? to -70???, the lowest values measured in a marine or terrestrial environment. These S isotope data demonstrate the involvement of sulfate-reducing bacteria and provide the first documentation that sphalerite can form significant supergene sulfide-enrichment blankets.

Crack injection in silver gold alloys

NASA Astrophysics Data System (ADS)

Chen, Xiying

Stress corrosion cracking (SCC) is a materials degradation phenomena resulting from a combination of stress and a corrosive environment. Among the alphabet soup of proposed mechanism of SCC the most important are film-rupture, film-induced cleavage and hydrogen embrittlement. This work examines various aspects of film-induced cleavage in gold alloys for which the operation of hydrogen embrittlement processes can be strictly ruled out on thermodynamic grounds. This is so because in such alloys SCC occurs under electrochemical conditions within which water is stable to hydrogen gas evolution. The alloy system examined in this work is AgAu since the corrosion processes in this system occur by a dealloying mechanism that results in the formation of nanoporous gold. The physics behind the dealloying process as well as the resulting formation of nanoporous gold is today well understood. Two important aspects of the film-induced cleavage mechanism are examined in this work: dynamic fracture in monolithic nanoporous gold and crack injection. In crack injection there is a finite thickness dealloyed layer formed on a AgAu alloy sample and the question of whether or not a crack that nucleates within this layer can travel for some finite distance into the un-corroded parent phase alloy is addressed. Dynamic fracture tests were performed on single edge-notched monolithic nanoporous gold samples as well as "infinite strip" sample configurations for which the stress intensity remains constant over a significant portion of the crack length. High-speed photography was used to measure the crack velocity. In the dynamic fracture experiments cracks were observed to travel at speeds as large as 270 m/s corresponding to about 68% of the Raleigh wave velocity. Crack injection experiments were performed on single crystal Ag77Au23, polycrystalline Ag72Au28 and pure gold, all of which had thin nanoporous gold layers on the surface of samples. Through-thickness fracture was seen in both the

Synthesis of fullerene@gold core-shell nanostructures.

PubMed

Ren, Yupeng; Paira, Priyankar; Nayak, Tapas Ranjan; Ang, Wee Han; Pastorin, Giorgia

2011-07-21

A "direct encapsulation" method was developed for the synthesis of highly stable water-soluble fullerene@gold core-shell nanostructures, with gold nanoshells showing either closed or porous morphology. This gold nano-shell coating formed a "nano-oven", capable of decomposing encapsulated fullerene molecules rapidly when irradiated by laser. We envisaged this being a useful tool for chemical reactions as well as a novel scaffold for nano-material synthesis.

Classification of Chronic Obstructive Pulmonary Disease (COPD) according to the new Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2017: Comparison with GOLD 2011.

PubMed

Marçôa, Raquel; Rodrigues, Daniela Marta; Dias, Margarida; Ladeira, Inês; Vaz, Ana Paula; Lima, Ricardo; Guimarães, Miguel

2018-02-01

Chronic Obstructive Pulmonary Disease (COPD) is a major cause of morbidity and mortality worldwide. The Global Initiative for Chronic Obstructive Lung Disease (GOLD) project has been working to improve awareness, prevention and management of this disease. The aim of this study is to evaluate how COPD patients are reclassified by the 2017 GOLD system (versus GOLD 2011), to calculate the level of agreement between these two classifications in allocation to categories and to compare the performance of each classification to predict future exacerbations. Two-hundred COPD patients (>40 years, post bronchodilator forced expiratory volume in one second/forced vital capacity<0.7) followed in pulmonology consultation were recruited into this prospective multicentric study. Approximately half of the patients classified as GOLD D [2011] changed to GOLD B [2017]. The extent of agreement between GOLD 2011 and GOLD 2017 was moderate (Cohen's Kappa = 0.511; p < 0.001) and the ability to predict exacerbations was similar (69.7% and 67.6%, respectively). GOLD B [2017] exacerbated 17% more than GOLD B [2011] and had a lower percent predicted post bronchodilator forced expiratory volume in one second (FEV1). GOLD B [2017] turned to be the predominant category, more heterogeneous and with a higher risk of exacerbation versus GOLD B [2011]. Physicians should be cautious in assessing the GOLD B [2017] patients. The assessment of patients should always be personalized. More studies are needed to evaluate the impact of the 2017 reclassification in predicting outcomes such as future exacerbations and mortality.

Quantum sized gold nanoclusters with atomic precision.

PubMed

Qian, Huifeng; Zhu, Manzhou; Wu, Zhikun; Jin, Rongchao

2012-09-18

Gold nanoparticles typically have a metallic core, and the electronic conduction band consists of quasicontinuous energy levels (i.e. spacing δ ≪ k(B)T, where k(B)T is the thermal energy at temperature T (typically room temperature) and k(B) is the Boltzmann constant). Electrons in the conduction band roam throughout the metal core, and light can collectively excite these electrons to give rise to plasmonic responses. This plasmon resonance accounts for the beautiful ruby-red color of colloidal gold first observed by Faraday back in 1857. On the other hand, when gold nanoparticles become extremely small (<2 nm in diameter), significant quantization occurs to the conduction band. These quantum-sized nanoparticles constitute a new class of nanomaterial and have received much attention in recent years. To differentiate quantum-sized nanoparticles from conventional plasmonic gold nanoparticles, researchers often refer to the ultrasmall nanoparticles as nanoclusters. In this Account, we chose several typical sizes of gold nanoclusters, including Au(25)(SR)(18), Au(38)(SR)(24), Au(102)(SR)(44), and Au(144)(SR)(60), to illustrate the novel properties of metal nanoclusters imparted by quantum size effects. In the nanocluster size regime, many of the physical and chemical properties of gold nanoparticles are fundamentally altered. Gold nanoclusters have discrete electronic energy levels as opposed to the continuous band in plasmonic nanoparticles. Quantum-sized nanoparticles also show multiple optical absorption peaks in the optical spectrum versus a single surface plasmon resonance (SPR) peak at 520 nm for spherical gold nanocrystals. Although larger nanocrystals show an fcc structure, nanoclusters often have non-fcc atomic packing structures. Nanoclusters also have unique fluorescent, chiral, and magnetic properties. Due to the strong quantum confinement effect, adding or removing one gold atom significantly changes the structure and the electronic and optical

50 CFR 665.669 - Gold coral harvest moratorium.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Gold coral harvest moratorium. 665.669... Island Area Fisheries § 665.669 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

50 CFR 665.669 - Gold coral harvest moratorium.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Gold coral harvest moratorium. 665.669... Island Area Fisheries § 665.669 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

50 CFR 665.669 - Gold coral harvest moratorium.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Gold coral harvest moratorium. 665.669... Island Area Fisheries § 665.669 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2013. ...

Simulation of spectral properties of bundlelike gold nanorods

NASA Astrophysics Data System (ADS)

Ozaki, Ryotaro; Nagao, Yoshiki; Kadowaki, Kazunori; Kuwahara, Yutaka

2016-03-01

Metal nanoparticles have become increasingly important in fields such as electronics, photonics, and biotechnology. In particular, anisotropic gold nanoparticles, such as gold nanorods, exhibit unique properties owing to their anisotropy. Optical properties of isolated gold nanorods and dimers of gold nanorods have been investigated from both experimental and theoretical points of view. We have reported a method for three-dimensional assembly of anisotropic gold nanoparticles by two-phase transfer in which the morphologies of the assemblies can be controlled by the aspect ratio of nanorods. In this study, we numerically calculate extinction spectra to investigate the plasmonic properties of bundlelike assemblies by the finite-element method. Their plasmonic properties depend on not only the three orthogonal directions but also the alignment of the nanorod assembly.

Polypeptide-Based Gold Nanoshells for Photothermal Therapy.

PubMed

Mayle, Kristine M; Dern, Kathryn R; Wong, Vincent K; Sung, Shijun; Ding, Ke; Rodriguez, April R; Taylor, Zachary; Zhou, Z Hong; Grundfest, Warren S; Deming, Timothy J; Kamei, Daniel T

2017-02-01

Targeted killing of cancer cells by engineered nanoparticles holds great promise for noninvasive photothermal therapy applications. We present the design and generation of a novel class of gold nanoshells with cores composed of self-assembled block copolypeptide vesicles with photothermal properties. Specifically, poly(L-lysine) 60 - block-poly(L-leucine) 20 (K 60 L 20 ) block copolypeptide vesicles coated with a thin layer of gold demonstrate enhanced absorption of light due to surface plasmon resonance (SPR) in the near-infrared range. We show that the polypeptide-based K 60 L 20 gold nanoshells have low toxicity in the absence of laser exposure, significant heat generation upon exposure to near-infrared light, and, as a result, localized cytotoxicity within the region of laser irradiation in vitro. To gain a better understanding of our gold nanoshells in the context of photothermal therapy, we developed a comprehensive mathematical model for heat transfer and experimentally validated this model by predicting the temperature as a function of time and position in our experimental setup. This model can be used to predict which parameters of our gold nanoshells can be manipulated to improve heat generation for tumor destruction. To our knowledge, our results represent the first ever use of block copolypeptide vesicles as the core material of gold nanoshells.

ICT: isotope correction toolbox.

PubMed

Jungreuthmayer, Christian; Neubauer, Stefan; Mairinger, Teresa; Zanghellini, Jürgen; Hann, Stephan

2016-01-01

Isotope tracer experiments are an invaluable technique to analyze and study the metabolism of biological systems. However, isotope labeling experiments are often affected by naturally abundant isotopes especially in cases where mass spectrometric methods make use of derivatization. The correction of these additive interferences--in particular for complex isotopic systems--is numerically challenging and still an emerging field of research. When positional information is generated via collision-induced dissociation, even more complex calculations for isotopic interference correction are necessary. So far, no freely available tools can handle tandem mass spectrometry data. We present isotope correction toolbox, a program that corrects tandem mass isotopomer data from tandem mass spectrometry experiments. Isotope correction toolbox is written in the multi-platform programming language Perl and, therefore, can be used on all commonly available computer platforms. Source code and documentation can be freely obtained under the Artistic License or the GNU General Public License from: https://github.com/jungreuc/isotope_correction_toolbox/ {christian.jungreuthmayer@boku.ac.at,juergen.zanghellini@boku.ac.at} Supplementary data are available at Bioinformatics online. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Gold-coated nanoparticles for use in biotechnology applications

DOEpatents

Berning, Douglas E [Los Alamos, NM; Kraus, Jr., Robert H.; Atcher, Robert W [Los Alamos, NM; Schmidt, Jurgen G [Los Alamos, NM

2009-07-07

A process of preparing gold-coated magnetic nanoparticles is disclosed and includes forming a suspension of magnetic nanoparticles within a suitable liquid, adding an amount of a reducible gold compound and a reducing agent to the suspension, and, maintaining the suspension for time sufficient to form gold-coated magnetic nanoparticles.

47 CFR 3.46 - Use of gold francs.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 1 2014-10-01 2014-10-01 false Use of gold francs. 3.46 Section 3.46... AUTHORITIES IN MARITIME AND MARITIME MOBILE-SATELLITE RADIO SERVICES Settlement Operations § 3.46 Use of gold francs. An accounting authority must accept accounts presented to it from foreign administrations in gold...

47 CFR 3.46 - Use of gold francs.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 1 2013-10-01 2013-10-01 false Use of gold francs. 3.46 Section 3.46... AUTHORITIES IN MARITIME AND MARITIME MOBILE-SATELLITE RADIO SERVICES Settlement Operations § 3.46 Use of gold francs. An accounting authority must accept accounts presented to it from foreign administrations in gold...

21 CFR 872.3580 - Preformed gold denture tooth.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Preformed gold denture tooth. 872.3580 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3580 Preformed gold denture tooth. (a) Identification. A preformed gold denture tooth is a device composed of austenitic alloys or alloys containing 75...

21 CFR 872.3580 - Preformed gold denture tooth.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Preformed gold denture tooth. 872.3580 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3580 Preformed gold denture tooth. (a) Identification. A preformed gold denture tooth is a device composed of austenitic alloys or alloys containing 75...

47 CFR 3.46 - Use of gold francs.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false Use of gold francs. 3.46 Section 3.46... AUTHORITIES IN MARITIME AND MARITIME MOBILE-SATELLITE RADIO SERVICES Settlement Operations § 3.46 Use of gold francs. An accounting authority must accept accounts presented to it from foreign administrations in gold...

21 CFR 872.3580 - Preformed gold denture tooth.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Preformed gold denture tooth. 872.3580 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3580 Preformed gold denture tooth. (a) Identification. A preformed gold denture tooth is a device composed of austenitic alloys or alloys containing 75...

21 CFR 872.3580 - Preformed gold denture tooth.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Preformed gold denture tooth. 872.3580 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3580 Preformed gold denture tooth. (a) Identification. A preformed gold denture tooth is a device composed of austenitic alloys or alloys containing 75...

47 CFR 3.46 - Use of gold francs.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false Use of gold francs. 3.46 Section 3.46... AUTHORITIES IN MARITIME AND MARITIME MOBILE-SATELLITE RADIO SERVICES Settlement Operations § 3.46 Use of gold francs. An accounting authority must accept accounts presented to it from foreign administrations in gold...

47 CFR 3.46 - Use of gold francs.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 1 2012-10-01 2012-10-01 false Use of gold francs. 3.46 Section 3.46... AUTHORITIES IN MARITIME AND MARITIME MOBILE-SATELLITE RADIO SERVICES Settlement Operations § 3.46 Use of gold francs. An accounting authority must accept accounts presented to it from foreign administrations in gold...

21 CFR 872.3580 - Preformed gold denture tooth.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Preformed gold denture tooth. 872.3580 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3580 Preformed gold denture tooth. (a) Identification. A preformed gold denture tooth is a device composed of austenitic alloys or alloys containing 75...

Gold-coated nanoparticles for use in biotechnology applications

DOEpatents

Berning, Douglas E [Los Alamos, NM; Kraus, Jr., Robert H.; Atcher, Robert W [Los Alamos, NM; Schmidt, Jurgen G [Los Alamos, NM

2007-06-05

A process of preparing gold-coated magnetic nanoparticles is disclosed and includes forming a suspension of magnetic nanoparticles within a suitable liquid, adding an amount of a reducible gold compound and a reducing agent to the suspension, and, maintaining the suspension for time sufficient to form gold-coated magnetic nanoparticles.

Gastrointestinal bioavailability of 2.0 nm diameter gold nanoparticles.

PubMed

Smith, Candice A; Simpson, Carrie A; Kim, Ganghyeok; Carter, Carly J; Feldheim, Daniel L

2013-05-28

The use of gold nanoparticles as imaging agents and therapeutic delivery systems is growing rapidly. However, a significant limitation of gold nanoparticles currently is their low absorption efficiencies in the gastrointestinal (GI) tract following oral administration. In an attempt to identify ligands that facilitate gold nanoparticle absorption in the GI tract, we have studied the oral bioavailability of 2.0 nm diameter gold nanoparticles modified with the small molecules p-mercaptobenzoic acid and glutathione, and polyethylene glycols (PEG) of different lengths and charge (neutral and anionic). We show that GI absorption of gold nanoparticles modified with the small molecules tested was undetectable. However, the absorption of PEGs depended upon PEG length, with the shortest PEG studied yielding gold nanoparticle absorptions that are orders-of-magnitude larger than observed previously. As the oral route is the most convenient one for administering drugs and diagnostic reagents, these results suggest that short-chain PEGs may be useful in the design of gold nanoparticles for the diagnosis and treatment of disease.

Gold Pennies.

ERIC Educational Resources Information Center

Dominic, Sheryl

1995-01-01

Describes an approach to a demonstration of the Golden Penny Experiment for high school students in which the teacher assumes the disguise of an alchemist and invites the students to devise ways of determining whether the penny has really turned to gold. (DDR)

Radiofrequency Heating Pathways for Gold Nanoparticles

PubMed Central

Collins, C. B.; McCoy, R. S.; Ackerson, B. J.; Collins, G. J.

2015-01-01

This feature article reviews the thermal dissipation of nanoscopic gold under radiofrequency (RF) irradiation. It also presents previously unpublished data addressing obscure aspects of this phenomenon. While applications in biology motivated initial investigation of RF heating of gold nanoparticles, recent controversy concerning whether thermal effects can be attributed to nanoscopic gold highlight the need to understand the involved mechanism or mechanisms of heating. Both the nature of the particle and the nature of the RF field influence heating. Aspects of nanoparticle chemistry and physics, including the hydrodynamic diameter of the particle, the oxidation state and related magnetism of the core, and the chemical nature of the ligand shell may all strongly influence to what extent a nanoparticle heats in an RF field. Aspects of RF include: power, frequency and antenna designs that emphasize relative strength of magnetic or electric fields, and also influence the extent to which a gold nanoparticle heats in RF. These nanoparticle and RF properties are analysed in the context of three heating mechanisms proposed to explain gold nanoparticle heating in an RF field. This article also makes a critical analysis of the existing literature in the context of the nanoparticle preparations, RF structure, and suggested mechanisms in previously reported experiments. PMID:24962620

Intracellular Cadmium Isotope Fractionation

NASA Astrophysics Data System (ADS)

Horner, T. J.; Lee, R. B.; Henderson, G. M.; Rickaby, R. E.

2011-12-01

Recent stable isotope studies into the biological utilization of transition metals (e.g. Cu, Fe, Zn, Cd) suggest several stepwise cellular processes can fractionate isotopes in both culture and nature. However, the determination of fractionation factors is often unsatisfactory, as significant variability can exist - even between different organisms with the same cellular functions. Thus, it has not been possible to adequately understand the source and mechanisms of metal isotopic fractionation. In order to address this problem, we investigated the biological fractionation of Cd isotopes within genetically-modified bacteria (E. coli). There is currently only one known biological use or requirement of Cd, a Cd/Zn carbonic anhydrase (CdCA, from the marine diatom T. weissfloggii), which we introduce into the E. coli genome. We have also developed a cleaning procedure that allows for the treating of bacteria so as to study the isotopic composition of different cellular components. We find that whole cells always exhibit a preference for uptake of the lighter isotopes of Cd. Notably, whole cells appear to have a similar Cd isotopic composition regardless of the expression of CdCA within the E. coli. However, isotopic fractionation can occur within the genetically modified E. coli during Cd use, such that Cd bound in CdCA can display a distinct isotopic composition compared to the cell as a whole. Thus, the externally observed fractionation is independent of the internal uses of Cd, with the largest Cd isotope fractionation occurring during cross-membrane transport. A general implication of these experiments is that trace metal isotopic fractionation most likely reflects metal transport into biological cells (either actively or passively), rather than relating to expression of specific physiological function and genetic expression of different metalloenzymes.

A carbon isotope mass balance for an anoxic marine sediment: Isotopic signatures of diagenesis

NASA Technical Reports Server (NTRS)

Boehme, Susan E.

1993-01-01

A carbon isotope mass balance was determined for the sediments of Cape Lookout Bight, NC to constrain the carbon budgets published previously. The diffusive, ebullitive and burial fluxes of sigma CO2 and CH4, as well as the carbon isotope signatures of these fluxes, were measured. The flux-weighted isotopic signature of the remineralized carbon (-18.9 plus or minus 2.7 per mil) agreed with the isotopic composition of the remineralized organic carbon determined from the particulate organic carbon (POC) delta(C-13) profiles (-19.2 plus or minus 0.2), verifying the flux and isotopic signature estimates. The measured delta(C-13) values of the sigma CO2 and CH4 diffusive fluxes were significantly different from those calculated from porewater gradients. The differences appear to be influenced by methane oxidation at the sediment-water interface, although other potential processes cannot be excluded. The isotope mass balance provides important information concerning the locations of potential diagenetic isotope effects. Specifically, the absence of downcore change in the delta(C-13) value of the POC fraction and the identical isotopic composition of the POC and the products of remineralization indicate that no isotopic fractionation is expressed during the initial breakdown of the POC, despite its isotopically heterogeneous composition.

Extracellular mycosynthesis of gold nanoparticles using Fusarium solani

NASA Astrophysics Data System (ADS)

Gopinath, K.; Arumugam, A.

2014-08-01

The development of eco-friendly methods for the synthesis of nanomaterial shape and size is an important area of research in the field of nanotechnology. The present investigation deals with the extracellular rapid biosynthesis of gold nanoparticles using Fusarium solani culture filtrate. The UV-vis spectra of the fungal culture filtrate medium containing gold ion showed peak at 527 nm corresponding to the plasmon absorbance of gold nanoparticles. FTIR spectra provide an evidence for the presence of heterocyclic compound in the culture filtrate, which increases the stability of the synthesized gold nanoparticles. The X-ray analysis respects the Bragg's law and confirmed the crystalline nature of the gold nanoparticles. AFM analysis showed the results of particle sizes (41 nm). Transmission electron microscopy (TEM) showed that the gold nanoparticles are spherical in shape with the size range from 20 to 50 nm. The use of F. solani will offer several advantages since it is considered as a non-human pathogenic organism. The fungus F. solani has a fast growth rate, rapid capacity of metallic ions reduction, NPs stabilization and facile and economical biomass handling. Extracellular biosynthesis of gold nanoparticles could be highly advantageous from the point of view of synthesis in large quantities, time consumption, eco-friendly, non-toxic and easy downstream processing.

50 CFR 665.469 - Gold coral harvest moratorium.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Gold coral harvest moratorium. 665.469... Archipelago Fisheries § 665.469 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2018. [78 FR 32182, May 29, 2013] ...

50 CFR 665.270 - Gold coral harvest moratorium.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Gold coral harvest moratorium. 665.270... Fisheries § 665.270 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2018. [78 FR 32182, May 29, 2013] ...

50 CFR 665.469 - Gold coral harvest moratorium.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Gold coral harvest moratorium. 665.469... Archipelago Fisheries § 665.469 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2018. [78 FR 32182, May 29, 2013] ...

50 CFR 665.270 - Gold coral harvest moratorium.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Gold coral harvest moratorium. 665.270... Fisheries § 665.270 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2018. [78 FR 32182, May 29, 2013] ...

50 CFR 665.169 - Gold coral harvest moratorium.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Gold coral harvest moratorium. 665.169... Fisheries § 665.169 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2018. [78 FR 32182, May 29, 2013] ...

50 CFR 665.169 - Gold coral harvest moratorium.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Gold coral harvest moratorium. 665.169... Fisheries § 665.169 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2018. [78 FR 32182, May 29, 2013] ...

Alteration, oxygen isotope, and fluid inclusion study of the Meishan iron oxide-apatite deposit, SE China

NASA Astrophysics Data System (ADS)

Yu, Jinjie; Che, Linrui; Wang, Tiezhu

2015-10-01

‰ and -123 and -111 ‰, respectively. These values suggest late-stage input of a shallow-sourced, isotopically light meteoric fluid at the temperature of pyrite and gold deposition. The fluid inclusion and stable isotope data indicate a cooling magmatic-hydrothermal system that progressed from isotopically heavy to isotopically depleted fluids as it cooled. Such fluid evolution is comparable with those of other Kiruna-type deposits worldwide.

GOLD NANOPARTICLES: A REVIVAL IN PRECIOUS METAL ADMINISTRATION TO PATIENTS

PubMed Central

Thakor, AS; Jokerst, J; Zaveleta, C; Massoud, TF; Gambhir, SS

2011-01-01

Gold has been used as a therapeutic agent to treat a wide variety of rheumatic diseases including psoriatic arthritis, juvenile arthritis and discoid lupus erythematosus. Although the use of gold has been largely superseded by newer drugs, gold nanoparticles are being used effectively in laboratory based clinical diagnostic methods whilst concurrently showing great promise in vivo either as a diagnostic imaging agent or a therapeutic agent. For these reasons, gold nanoparticles are therefore well placed to enter mainstream clinical practice in the near future. Hence, the present review summarizes the chemistry, pharmacokinetics, bio-distribution, metabolism and toxicity of bulk gold in humans based on decades of clinical observation and experiments in which gold was used to treat patients with rheumatoid arthritis. The beneficial attributes of gold nanoparticles, such as their ease of synthesis, functionalization and shape control are also highlighted demonstrating why gold nanoparticles are an attractive target for further development and optimization. The importance of controlling the size and shape of gold nanoparticles to minimize any potential toxic side effects is also discussed. PMID:21846107

Geological and geochemical implications of the genesis of the Qolqoleh orogenic gold mineralisation, Kurdistan Province (Iran)

NASA Astrophysics Data System (ADS)

Taghipour, Batoul; Ahmadnejad, Farhad

2015-03-01

�C and Tm from -11 to -16°C. Type III three-phase carbonic-liquid inclusions (liquid water-liquid CO2-vapour CO2) with Th of 345-385°C. The mean values of the density of ore-forming fluids, pressure and depth of mineralisation have been calculated to be 0.79-0.96 gr/cm3, 2 kbar and 7 km, respectively. The δ18Owater and δD values of the gold-bearing quartz-sulphide veins vary from 7.2‰ to 8‰ and -40.24‰ to -35.28‰, respectively, which are indicative of an isotopically heavy crustal fluid and likely little involvement of meteoric fluid. The δ18Owater values of the quartz-calcite veins have a range of -5.31‰ to -3.35‰, and the δD values of -95.65‰ to -75.31‰, which are clearly lower than those of early-stage quartz-sulphide-gold veins, and are close to the meteoric water line. Based on comparisons of the D-O isotopic systematics, the Qolqoleh ore-mineralising fluids originated from metamorphic devolatilisation of Cretaceous volcano-sedimentary piles. Devolatilisation of these units occurred either synchronously with, or postdates, the development of penetrative (ductile) structures such as shear zones and during overprinting brittle deformation

Propulsion of gold nanoparticles with surface plasmon polaritons: evidence of enhanced optical force from near-field coupling between gold particle and gold film.

PubMed

Wang, Kai; Schonbrun, Ethan; Crozier, Kenneth B

2009-07-01

We experimentally demonstrate the enhanced propulsion of gold nanoparticles by surface plasmon polaritons (SPPs). Three dimensional finite difference time domain (FDTD) simulations indicate considerably enhanced optical forces due to the field enhancement provided by SPPs and the near-field coupling between the gold particles and the film. This coupling is an important part of the enhanced propulsion phenomenon. Finally, the measured optical force is compared with that predicted by FDTD simulations and proven to be reasonable.

A new route to gold nanoflowers

NASA Astrophysics Data System (ADS)

Liebig, Ferenc; Henning, Ricky; Sarhan, Radwan M.; Prietzel, Claudia; Bargheer, Matias; Koetz, Joachim

2018-05-01

Catanionic vesicles spontaneously formed by mixing the anionic surfactant bis(2-ethylhexyl) sulfosuccinate sodium salt with the cationic surfactant cetyltrimethylammonium bromide were used as a reducing medium to produce gold clusters, which are embedded and well-ordered into the template phase. The gold clusters can be used as seeds in the growth process that follows by adding ascorbic acid as a mild reducing component. When the ascorbic acid was added very slowly in an ice bath round-edged gold nanoflowers were produced. When the same experiments were performed at room temperature in the presence of Ag+ ions, sharp-edged nanoflowers could be synthesized. The mechanism of nanoparticle formation can be understood to be a non-diffusion-limited Ostwald ripening process of preordered gold nanoparticles embedded in catanionic vesicle fragments. Surface-enhanced Raman scattering experiments show an excellent enhancement factor of 1.7 · 105 for the nanoflowers deposited on a silicon wafer.

Gold Nanoparticle Hyperthermia Reduces Radiotherapy Dose

PubMed Central

Lin, Lynn; Slatkin, Daniel N.; Dilmanian, F. Avraham; Vadas, Timothy M.; Smilowitz, Henry M.

2014-01-01

Gold nanoparticles can absorb near infrared light, resulting in heating and ablation of tumors. Gold nanoparticles have also been used for enhancing the dose of X-rays in tumors during radiotherapy. The combination of hyperthermia and radiotherapy is synergistic, importantly allowing a reduction in X-ray dose with improved therapeutic results. Here we intratumorally infused small 15 nm gold nanoparticles engineered to be transformed from infrared-transparent to infrared-absorptive by the tumor, which were then heated by infrared followed by X-ray treatment. Synergy was studied using a very radioresistant subcutaneous squamous cell carcinoma (SCCVII) in mice. It was found that the dose required to control 50% of the tumors, normally 55 Gy, could be reduced to <15 Gy (a factor of >3.7). Gold nanoparticles therefore provide a method to combine hyperthermia and radiotherapy to drastically reduce the X-ray radiation needed, thus sparing normal tissue, reducing the side effects, and making radiotherapy more effective. PMID:24990355

Cripple Creek and other alkaline-related gold deposits in the Southern Rocky Mountains, USA: Influence of regional tectonics

USGS Publications Warehouse

Kelley, K.D.; Ludington, S.

2002-01-01

Alkaline-related epithermal vein, breccia, disseminated, skarn, and porphyry gold deposits form a belt in the southern Rocky Mountains along the eastern edge of the North American Cordillera. Alkaline igneous rocks and associated hydrothermal deposits formed at two times. The first was during the Laramide orogeny (about 70-40 Ma), with deposits restricted spatially to the Colorado mineral belt (CMB). Other alkaline igneous rocks and associated gold deposits formed later, during the transition from a compressional to an extensional regime (about 35-27 Ma). These younger rocks and associated deposits are more widespread, following the Rocky Mountain front southward, from Cripple Creek in Colorado through New Mexico. All of these deposits are on the eastern margin of the Cordillera, with voluminous calc-alkaline rocks to the west. The largest deposits in the belt include Cripple Creek and those in the CMB. The most important factor in the formation of all of the gold deposits was the near-surface emplacement of relatively oxidized volatile-rich alkaline magmas. Strontium and lead isotope compositions suggest that the source of the magmas was subduction-modified subcontinental lithosphere. However, Cripple Creek alkaline rocks and older Laramide alkaline rocks in the CMB that were emplaced through hydrously altered LREE-enriched rocks of the Colorado (Yavapai) province have 208Pb/204Pb ratios that suggest these magmas assimilated and mixed with significant amounts of lower crust. The anomalously hot, thick, and light crust beneath Colorado may have been a catalyst for large-scale transfer of volatiles and crustal melting. Increased dissolved H2O (and CO2, F, Cl) of these magmas may have resulted in more productive gold deposits due to more efficient magmatic-hydrothermal systems. High volatile contents may also have promoted Te and V enrichment, explaining the presence of fluorite, roscoelite (vanadium-rich mica) and tellurides in the CMB deposits and Cripple Creek as

The chemistry of gold as an anion.

PubMed

Jansen, Martin

2008-09-01

Due to relativistic and classical shell structure effects, the 6s orbital of gold is significantly contracted and energetically stabilized. This is reflected by a strikingly high electron affinity, and a distinct tendency to adopt negatively polarized valence states. This tutorial review focuses on the chemistry of gold as an anion, displaying the integral ionic charge number of 1-. Two synthetic approaches to compounds containing monoatomic gold anions have become available: (1) reacting elemental gold with molten caesium and an oxide, e.g. Cs2O; (2) metathesis reactions involving Au- dissolved in liquid ammonia. Both procedures have proven to be rather versatile. Aurides synthesized along these routes are surveyed, in particular with respect to their structures and bonding properties.

Aqueous Black Colloids of Reticular Nanostructured Gold

NASA Astrophysics Data System (ADS)

Stanca, S. E.; Fritzsche, W.; Dellith, J.; Froehlich, F.; Undisz, A.; Deckert, V.; Krafft, C.; Popp, J.

2015-01-01

Since ancient times, noble gold has continuously contributed to several aspects of life from medicine to electronics. It perpetually reveals its new features. We report the finding of a unique form of gold, reticular nanostructured gold (RNG), as an aqueous black colloid, for which we present a one-step synthesis. The reticules consist of gold crystals that interconnect to form compact strands. RNG exhibits high conductivity and low reflection, and these features, coupled with the high specific surface area of the material, could prove valuable for applications in electronics and catalysis. Due to high absorption throughout the visible and infrared domain, RNG has the potential to be applied in the construction of sensitive solar cells or as a substrate for Raman spectroscopy.

Gold recovery from low concentrations using nanoporous silica adsorbent

NASA Astrophysics Data System (ADS)

Aledresse, Adil

The development of high capacity adsorbents with uniform porosity denoted 5%MP-HMS (5% Mercaptopropyl-Hexagonal Mesoporous Structure) to extract gold from noncyanide solutions is presented. The preliminary studies from laboratory simulated noncyanide gold solutions show that the adsorption capacities of these materials are among the highest reported. The high adsorption saturation level of these materials, up to 1.9 mmol/g (37% of the adsorbent weight) from gold chloride solutions (potassium tetrachloroaurate) and 2.9 mmol/g (57% of the adsorbent weight) from gold bromide solutions (potassium tetrabromoaurate) at pH = 2, is a noteworthy feature of these materials. This gold loading from [AuC4]- and [AuBr4 ]- solutions corresponds to a relative Au:S molar ratio of 2.5:1 and 3.8:1, respectively. These rates are significantly higher than the usual 1:1 (Au:S) ratio expected for metal ion binding with the material. The additional gold ions loaded have been spontaneously reduced to metallic gold in the mesoporous material. Experimental studies indicated high maximum adsorptions of gold as high as 99.9% recovery. Another promising attribute of these materials is their favourable adsorption kinetics. The MP-HMS reaches equilibrium (saturation) in less than 1 minute of exposure in gold bromide and less than 10 minutes in gold chloride. The MP-HMS materials adsorption is significantly improved by agitation and the adsorption capacity of Au (III) ions increases with the decrease in pH. The recovery of adsorbed gold and the regeneration of spent adsorbent were investigated for MP-HMS adsorbent. The regenerated adsorbent (MP-HMS) maintained its adsorption capacity even after repeated use and all the gold was successfully recovered from the spent adsorbent. For the fist time, a promising adsorbent system has been found that is capable of effectively concentrating gold thiosulphate complexes, whereas conventional carbon-inpulp (CIP) and carbon-in-leach (CIL) systems fail. The

Geomorphological control of gold distribution and gold particle evolution in glacial and fluvioglacial placers of the Ancocala-Ananea basin - Southeastern Andes of Peru

NASA Astrophysics Data System (ADS)

Hérail, Gérard; Fornari, Michel; Rouhier, Michel

1989-10-01

Gold placers are formed as a result of surficial processes but glacial and fluvioglacial systems are generally considered to be unfavourable for placer genesis. Nevertheless, some important glacial and fluvioglacial placers have been discovered and are currently being exploited in the Andes of Peru and Bolivia. In the Plio-Pleistocene Ananea-Ancocala basin (4300-4900 m above sea-level), the gold content of the various formations indicates that only glacial and fluvioglacial sediments related to the Ancocala and Chaquiminas Glaciations (middle and upper Pleistocene) contain gold in any notable quantity. Local concentrations of economic interest occur only where a glacier has cut through a primary mineralized zone. Glacial erosion of dispersed primary mineralizations does not produce high-content placers of the kind found in fluviatile environments. Gold distribution in tills is more irregular than in fluviatile sediments and no marked enrichment at bedrock occurs. The transition from a glacial to a fluvioglacial environment is characterized by an increase in gold content due to a relative concentration of the biggest gold flakes and by the appearance of a gold distribution pattern similar to that found in a fluviatile environment. During their transport by glacial and fluvioglacial processes, gold particles acquire specific features; the size and morphology of a gold flake population are determined by the sedimentological and geomorphological environment in which the flakes are carried.

50 CFR 665.669 - Gold coral harvest moratorium.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Gold coral harvest moratorium. 665.669... Island Area Fisheries § 665.669 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2018. [78 FR 32182, May 29, 2013] ...

50 CFR 665.669 - Gold coral harvest moratorium.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Gold coral harvest moratorium. 665.669... Island Area Fisheries § 665.669 Gold coral harvest moratorium. Fishing for, taking, or retaining any gold coral in any precious coral permit area is prohibited through June 30, 2018. [78 FR 32182, May 29, 2013] ...

Application of U-Th-Pb phosphate geochronology to young orogenic gold deposits: New age constraints on the formation of the Grass Valley gold district, Sierra Foothills province, California

USGS Publications Warehouse

Taylor, Ryan D.; Goldfarb, Richard J.; Monecke, Thomas; Fletcher, Ian R.; Cosca, Michael A.; Kelly, Nigel M.

2015-01-01

The Grass Valley orogenic gold district in the Sierra Nevada foothills province, central California, the largest historic gold producer of the North American Cordillera, comprises both steeply dipping east-west (E-W) veins located along lithologic contacts in accreted ca. 300 and 200 Ma oceanic rocks and shallowly dipping north-south (N-S) veins hosted by the Grass Valley granodiorite; the latter have yielded about 70 percent of the 13 million ounces of historic lode gold production in the district. The oceanic host rocks were accreted to the western margin of North America between 200 and 170 Ma, metamorphosed to greenschist and amphibolite facies, and uplifted between 175 and 160 Ma. Large-scale magmatism in the Sierra Nevada occurred between 170-140 Ma and 120-80 Ma, with the Grass Valley granodiorite being emplaced during the older episode of magmatism. Uranium-lead isotopic dating of hydrothermal xenotime yielded the first absolute age of 162±5 Ma for the economically more significant N-S veins. The vein-hosted xenotime, as well as associated monazite, are unequivocally of hydrothermal origin as indicated by textural and chemical characteristics, including grain shape, lack of truncated growth banding, lack of a Eu anomaly, and low U and Th concentrations. Furthermore, the crack-seal texture of the veins, with abundant wallrock slivers, suggests their formation as a result of episodic fluid flow possibly related to reoccurring seismic events, rather than a period of fluid exsolution from an evolving magma. The N-S veins are temporally distinct from a younger 153-151 Ma gold event that was previously reported for the E-W veins. Overlapping U-Pb zircon (159.9±2.2 Ma) and 40Ar/39Ar biotite and hornblende (159.7±0.6 to 161.9±1.4 Ma) ages and geothermobarometric calculations indicate that the Grass Valley granodiorite was emplaced at ca. 160 Ma at elevated temperatures (~800°C) within approximately 3 km of the paleosurface and rapidly cooled to the ambient

A grand unified model for liganded gold clusters

NASA Astrophysics Data System (ADS)

Xu, Wen Wu; Zhu, Beien; Zeng, Xiao Cheng; Gao, Yi

2016-12-01

A grand unified model (GUM) is developed to achieve fundamental understanding of rich structures of all 71 liganded gold clusters reported to date. Inspired by the quark model by which composite particles (for example, protons and neutrons) are formed by combining three quarks (or flavours), here gold atoms are assigned three `flavours' (namely, bottom, middle and top) to represent three possible valence states. The `composite particles' in GUM are categorized into two groups: variants of triangular elementary block Au3(2e) and tetrahedral elementary block Au4(2e), all satisfying the duet rule (2e) of the valence shell, akin to the octet rule in general chemistry. The elementary blocks, when packed together, form the cores of liganded gold clusters. With the GUM, structures of 71 liganded gold clusters and their growth mechanism can be deciphered altogether. Although GUM is a predictive heuristic and may not be necessarily reflective of the actual electronic structure, several highly stable liganded gold clusters are predicted, thereby offering GUM-guided synthesis of liganded gold clusters by design.

A grand unified model for liganded gold clusters

PubMed Central

Xu, Wen Wu; Zhu, Beien; Zeng, Xiao Cheng; Gao, Yi

2016-01-01

A grand unified model (GUM) is developed to achieve fundamental understanding of rich structures of all 71 liganded gold clusters reported to date. Inspired by the quark model by which composite particles (for example, protons and neutrons) are formed by combining three quarks (or flavours), here gold atoms are assigned three ‘flavours' (namely, bottom, middle and top) to represent three possible valence states. The ‘composite particles' in GUM are categorized into two groups: variants of triangular elementary block Au3(2e) and tetrahedral elementary block Au4(2e), all satisfying the duet rule (2e) of the valence shell, akin to the octet rule in general chemistry. The elementary blocks, when packed together, form the cores of liganded gold clusters. With the GUM, structures of 71 liganded gold clusters and their growth mechanism can be deciphered altogether. Although GUM is a predictive heuristic and may not be necessarily reflective of the actual electronic structure, several highly stable liganded gold clusters are predicted, thereby offering GUM-guided synthesis of liganded gold clusters by design. PMID:27910848

When the value of gold is zero.

PubMed

Chase, J Geoffrey; Moeller, Knut; Shaw, Geoffrey M; Schranz, Christoph; Chiew, Yeong Shiong; Desaive, Thomas

2014-06-27

This manuscript presents the concerns around the increasingly common problem of not having readily available or useful "gold standard" measurements. This issue is particularly important in critical care where many measurements used in decision making are surrogates of what we would truly wish to use. However, the question is broad, important and applicable in many other areas.In particular, a gold standard measurement often exists, but is not clinically (or ethically in some cases) feasible. The question is how does one even begin to develop new measurements or surrogates if one has no gold standard to compare with?We raise this issue concisely with a specific example from mechanical ventilation, a core bread and butter therapy in critical care that is also a leading cause of length of stay and cost of care. Our proposed solution centers around a hierarchical validation approach that we believe would ameliorate ethics issues around radiation exposure that make current gold standard measures clinically infeasible, and thus provide a pathway to create a (new) gold standard.

Isotope pattern deconvolution as rising tool for isotope tracer studies in environmental research

NASA Astrophysics Data System (ADS)

Irrgeher, Johanna; Zitek, Andreas; Prohaska, Thomas

2014-05-01

During the last decade stable isotope tracers have emerged as versatile tool in ecological research. Besides 'intrinsic' isotope tracers caused by the natural variation of isotopes, the intentional introduction of 'extrinsic' enriched stable isotope tracers into biological systems has gained significant interest. Hereby the induced change in the natural isotopic composition of an element allows amongst others for studying the fate and fluxes of metals, trace elements and species in organisms or provides an intrinsic marker or tag of particular biological samples. Due to the shoreless potential of this methodology, the number of publications dealing with applications of isotope (double) spikes as tracers to address research questions in 'real world systems' is constantly increasing. However, some isotope systems like the natural Sr isotopic system, although potentially very powerful for this type of application, are still rarely used, mainly because their adequate measurement/determination poses major analytical challenges; as e.g. Sr is available in significant amounts in natural samples. In addition, biological systems underlie complex processes such as metabolism, adsorption/desorption or oxidation/reduction. As a consequence, classic evaluation approaches such as the isotope dilution mass spectrometry equation are often not applicable because of the unknown amount of tracer finally present in the sample. Isotope pattern deconvolution (IPD), based on multiple linear regression, serves as simplified alternative data processing strategy to double spike isotope dilution calculations. The outstanding advantage of this mathematical tool lies in the possibility of deconvolving the isotope pattern in a spiked sample without knowing the quantities of enriched isotope tracer being incorporated into the natural sample matrix as well as the degree of impurities and species-interconversion (e.g. from sample preparation). Here, the potential of IPD for environmental tracer

Meteoritic Sulfur Isotopic Analysis

NASA Technical Reports Server (NTRS)

Thiemens, Mark H.

1996-01-01

Funds were requested to continue our program in meteoritic sulfur isotopic analysis. We have recently detected a potential nucleosynthetic sulfur isotopic anomaly. We will search for potential carriers. The documentation of bulk systematics and the possible relation to nebular chemistry and oxygen isotopes will be explored. Analytical techniques for delta(sup 33), delta(sup 34)S, delta(sup 36)S isotopic analysis were improved. Analysis of sub milligram samples is now possible. A possible relation between sulfur isotopes and oxygen was detected, with similar group systematics noted, particularly in the case of aubrites, ureilites and entstatite chondrites. A possible nucleosynthetic excess S-33 has been noted in bulk ureilites and an oldhamite separate from Norton County. High energy proton (approximately 1 GeV) bombardments of iron foils were done to experimentally determine S-33, S-36 spallogenic yields for quantitation of isotopic measurements in iron meteorites. Techniques for measurement of mineral separates were perfected and an analysis program initiated. The systematic behavior of bulk sulfur isotopes will continue to be explored.

Geostatistical Approach to Estimating the Gold Ore Characteristics and Gold Reserves: A Case Study Daksa Area, Quang Nam Province, Viet Nam

NASA Astrophysics Data System (ADS)

Luan Truong, Xuan; Luong Le, Van; Quang Truong, Xuan

2015-04-01

Daksa gold deposit is the biggest gold deposits in Vietnam. The Daksa geological structure complicated, distributed mainly metamorphosed sedimentary NuiVu formation (PR3-?1nv2). The sulfide gold ore bodies distributed in quartz schist, quartz - biotite related to faut and distribution wing anticline. The gold ore bodies form circuits, network circuits, circuits lenses; fill the cup surface layer of the developing northeast - southwest; is the less than or west longitude north - SE. The results show that, Au and accompanying elements (Ag, Pb and Zn) have correlated pretty closely. All of its consistent with the logarithmic distribution standard, in accordance with the law of distribution of content mineral rare. The structure functions have nugget effect and spherical models with show that Au and accompanying elements special variation are changes. Au contents shown local anisotropy, no clearly anisotropy (K=1,17) and weakly anisotropy (K=1,4). Intensity mineralization of the ore bodies are quite high with demand spherical conversion coefficient ranging from 0.49 to 0.75 and from 0.66 to 0.97 (for other body). With nugget effects, ore bodies shown that it is consistent with mineralization in the ore bodies study, ore erasable, micro vein, infilling fractures in quartz vein. All of variogram presents local anisotropy, indicated gold mineralization at study area has least two-mineralization stages, consistent with the analysis of mineralography samples. By the results of the structure function study, the authors present the system optimization for exploration deposit and used to evaluate gold reserves by Ordinary Kriging. High accuracy of Kriging estimation results are expressed in the minimum Kriging variance, by compare the results calculated by some other methods (such as distance inverse weighting method, ..) and specially compare to the results of a some blocks have been exploited. Key words: Geostat and gold deposits VN. Daksa and gold mineralization. Geostat

Cytogenetic evaluation of gold nanorods using Allium cepa test.

PubMed

Rajeshwari, A; Roy, Barsha; Chandrasekaran, Natarajan; Mukherjee, Amitava

2016-12-01

The current study reveals the impact of gold nanorods (NRs) capped with CTAB (cetyltrimethylammonium bromide) or PEG (polyethylene glycol) on Allium cepa. The morphology and surface charge of CTAB- and PEG-capped gold NRs were characterized by electron microscopic and zeta potential analyses. The chromosomal aberrations like clumped chromosome, chromosomal break, chromosomal bridge, diagonal anaphase, disturbed metaphase, laggard chromosome, and sticky chromosome were observed in the root tip cells exposed to different concentrations (0.1, 1, and 10 μg/mL) of CTAB- and PEG-capped gold NRs. We found that both CTAB- and PEG-capped gold NRs were able to induce toxicity in the plant system after 4-h interaction. At a maximum concentration of 10 μg/mL, the mitotic index reduction induced by CTAB-capped gold NRs was 40-fold higher than that induced by PEG-capped gold NRs. The toxicity of gold NRs was further confirmed by lipid peroxidation and oxidative stress analyses. The unbound CTAB also contributed to the toxicity in root tip cells, while PEG alone shows less toxicity to the cells. The vehicle control CTAB contributed to the toxic effects in root tip cells, while PEG alone did not show any toxicity to the cells. The results revealed that even though both the particles have adverse effects on A. cepa, there was a significant difference in the mitotic index and oxidative stress generation in root cells exposed to CTAB-capped gold NRs. Thus, this study concludes that the surface polymerization of gold NRs by PEG can reduce the toxicity of CTAB-capped gold NRs. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Interaction of β-Sheet Folds with a Gold Surface

PubMed Central

Hoefling, Martin; Monti, Susanna; Corni, Stefano; Gottschalk, Kay Eberhard

2011-01-01

The adsorption of proteins on inorganic surfaces is of fundamental biological importance. Further, biomedical and nanotechnological applications increasingly use interfaces between inorganic material and polypeptides. Yet, the underlying adsorption mechanism of polypeptides on surfaces is not well understood and experimentally difficult to analyze. Therefore, we investigate here the interactions of polypeptides with a gold(111) surface using computational molecular dynamics (MD) simulations with a polarizable gold model in explicit water. Our focus in this paper is the investigation of the interaction of polypeptides with β-sheet folds. First, we concentrate on a β-sheet forming model peptide. Second, we investigate the interactions of two domains with high β-sheet content of the biologically important extracellular matrix protein fibronectin (FN). We find that adsorption occurs in a stepwise mechanism both for the model peptide and the protein. The positively charged amino acid Arg facilitates the initial contact formation between protein and gold surface. Our results suggest that an effective gold-binding surface patch is overall uncharged, but contains Arg for contact initiation. The polypeptides do not unfold on the gold surface within the simulation time. However, for the two FN domains, the relative domain-domain orientation changes. The observation of a very fast and strong adsorption indicates that in a biological matrix, no bare gold surfaces will be present. Hence, the bioactivity of gold surfaces (like bare gold nanoparticles) will critically depend on the history of particle administration and the proteins present during initial contact between gold and biological material. Further, gold particles may act as seeds for protein aggregation. Structural re-organization and protein aggregation are potentially of immunological importance. PMID:21687744

Interaction of β-sheet folds with a gold surface.

PubMed

Hoefling, Martin; Monti, Susanna; Corni, Stefano; Gottschalk, Kay Eberhard

2011-01-01

The adsorption of proteins on inorganic surfaces is of fundamental biological importance. Further, biomedical and nanotechnological applications increasingly use interfaces between inorganic material and polypeptides. Yet, the underlying adsorption mechanism of polypeptides on surfaces is not well understood and experimentally difficult to analyze. Therefore, we investigate here the interactions of polypeptides with a gold(111) surface using computational molecular dynamics (MD) simulations with a polarizable gold model in explicit water. Our focus in this paper is the investigation of the interaction of polypeptides with β-sheet folds. First, we concentrate on a β-sheet forming model peptide. Second, we investigate the interactions of two domains with high β-sheet content of the biologically important extracellular matrix protein fibronectin (FN). We find that adsorption occurs in a stepwise mechanism both for the model peptide and the protein. The positively charged amino acid Arg facilitates the initial contact formation between protein and gold surface. Our results suggest that an effective gold-binding surface patch is overall uncharged, but contains Arg for contact initiation. The polypeptides do not unfold on the gold surface within the simulation time. However, for the two FN domains, the relative domain-domain orientation changes. The observation of a very fast and strong adsorption indicates that in a biological matrix, no bare gold surfaces will be present. Hence, the bioactivity of gold surfaces (like bare gold nanoparticles) will critically depend on the history of particle administration and the proteins present during initial contact between gold and biological material. Further, gold particles may act as seeds for protein aggregation. Structural re-organization and protein aggregation are potentially of immunological importance.

Designing Hollow Nano Gold Golf Balls

PubMed Central

2015-01-01

Hollow/porous nanoparticles, including nanocarriers, nanoshells, and mesoporous materials have applications in catalysis, photonics, biosensing, and delivery of theranostic agents. Using a hierarchical template synthesis scheme, we have synthesized a nanocarrier mimicking a golf ball, consisting of (i) solid silica core with a pitted gold surface and (ii) a hollow/porous gold shell without silica. The template consisted of 100 nm polystyrene beads attached to a larger silica core. Selective gold plating of the core followed by removal of the polystyrene beads produced a golf ball-like nanostructure with 100 nm pits. Dissolution of the silica core produced a hollow/porous golf ball-like nanostructure. PMID:24937196

Peptide-functionalized iron oxide magnetic nanoparticle for gold mining

NASA Astrophysics Data System (ADS)

Shen, Wei-Zheng; Cetinel, Sibel; Sharma, Kumakshi; Borujeny, Elham Rafie; Montemagno, Carlo

2017-02-01

Here, we present our work on preparing a novel nanomaterial composed of inorganic binding peptides and magnetic nanoparticles for inorganic mining. Two previously selected and well-characterized gold-binding peptides from cell surface display, AuBP1 and AuBP2, were exploited. This nanomaterial (AuBP-MNP) was designed to fulfill the following two significant functions: the surface conjugated gold-binding peptide will recognize and selectively bind to gold, while the magnetic nano-sized core will respond and migrate according to the applied external magnetic field. This will allow the smart nanomaterial to mine an individual material (gold) from a pool of mixture, without excessive solvent extraction, filtration, and concentration steps. The working efficiency of AuBP-MNP was determined by showing a dramatic reduction of gold nanoparticle colloid concentration, monitored by spectroscopy. The binding kinetics of AuBP-MNP onto the gold surface was determined using surface plasmon resonance (SPR) spectroscopy, which exhibits around 100 times higher binding kinetics than peptides alone. The binding capacity of AuBP-MNP was demonstrated by a bench-top mining test with gold microparticles.

Recovery of Silver and Gold from Copper Anode Slimes

NASA Astrophysics Data System (ADS)

Chen, Ailiang; Peng, Zhiwei; Hwang, Jiann-Yang; Ma, Yutian; Liu, Xuheng; Chen, Xingyu

2015-02-01

Copper anode slimes, produced from copper electrolytic refining, are important industrial by-products containing several valuable metals, particularly silver and gold. This article provides a comprehensive overview of the development of the extraction processes for recovering silver and gold from conventional copper anode slimes. Existing processes, namely pyrometallurgical processes, hydrometallurgical processes, and hybrid processes involving the combination of pyrometallurgical and hydrometallurgical technologies, are discussed based in part on a review of the form and characteristics of silver and gold in copper anode slimes. The recovery of silver and gold in pyrometallurgical processes is influenced in part by the slag and matte/metal chemistry and related characteristics, whereas the extraction of these metals in hydrometallurgical processes depends on the leaching reagents used to break the structure of the silver- and gold-bearing phases, such as selenides. By taking advantage of both pyrometallurgical and hydrometallurgical techniques, high extraction yields of silver and gold can be obtained using such combined approaches that appear promising for efficient extraction of silver and gold from copper anode slimes.

Platinum isotopes in iron meteorites: Galactic cosmic ray effects and nucleosynthetic homogeneity in the p-process isotope 190Pt and the other platinum isotopes

NASA Astrophysics Data System (ADS)

Hunt, Alison C.; Ek, Mattias; Schönbächler, Maria

2017-11-01

Platinum isotopes are sensitive to the effects of galactic cosmic rays (GCR), which can alter isotope ratios and mask nucleosynthetic isotope variations. Platinum also features one p-process isotope, 190Pt, which is very low abundance and therefore challenging to analyse. Platinum-190 is relevant for early solar-system chronology because of its decay to 186Os. Here, we present new Pt isotope data for five iron meteorite groups (IAB, IIAB, IID, IIIAB and IVA), including high-precision measurements of 190Pt for the IAB, IIAB and IIIAB irons, determined by multi-collector ICPMS. New data are in good agreement with previous studies and display correlations between different Pt isotopes. The slopes of these correlations are well-reproduced by the available GCR models. We report Pt isotope ratios for the IID meteorite Carbo that are consistently higher than the predicted effects from the GCR model. This suggests that the model predictions do not fully account for all the GCR effects on Pt isotopes, but also that the pre-atmospheric radii and exposure times calculated for Carbo may be incorrect. Despite this, the good agreement of relative effects in Pt isotopes with the predicted GCR trends confirms that Pt isotopes are a useful in-situ neutron dosimeter. Once GCR effects are accounted for, our new dataset reveals s- and r-process homogeneity between the iron meteorite groups studied here and the Earth. New 190Pt data for the IAB, IIAB and IIIAB iron meteorites indicate the absence of GCR effects and homogeneity in the p-process isotope between these groups and the Earth. This corresponds well with results from other heavy p-process isotopes and suggests their homogenous distribution in the inner solar system, although it does not exclude that potential p-process isotope variations are too diluted to be currently detectable.

Sesquicentennial: Gold Rush to Golden Statehood.

ERIC Educational Resources Information Center

Sabato, George

1998-01-01

Provides an annotated bibliography of educational resources that can be used to support instructional units on the Gold Rush or the sesquicentennial of California's statehood. The materials include workbooks, videos, teacher's guides, monographs, and magazines. Offers a brief history of the Gold Rush and a set of relevant discussion questions.…

Naked Gold Nanoparticles and hot Electrons in Water.

PubMed

Ghandi, Khashayar; Wang, Furong; Landry, Cody; Mostafavi, Mehran

2018-05-08

The ionizing radiation in aqueous solutions of gold nanoparticles, stabilized by electrostatic non-covalent intermolecular forces and steric interactions, with antimicrobial compounds, are investigated with picosecond pulse radiolysis techniques. Upon pulse radiolysis of an aqueous solution containing very low concentrations of gold nanoparticles with naked surfaces available in water (not obstructed by chemical bonds), a change to Cerenkov spectrum over a large range of wavelengths are observed and pre-solvated electrons are captured by gold nanoparticles exclusively (not by ionic liquid surfactants used to stabilize the nanoparticles). The solvated electrons are also found to decay rapidly compared with the decay kinetics in water. These very fast reactions with electrons in water could provide an enhanced oxidizing zone around gold nanoparticles and this could be the reason for radio sensitizing behavior of gold nanoparticles in radiation therapy.

Radicals are required for thiol etching of gold particles

PubMed Central

Dreier, Timothy A.

2016-01-01

Etching of gold with excess thiol ligand is used in both synthesis and analysis of gold particles. Mechanistically, the process of etching gold with excess thiol is opaque. Previous studies have obliquely considered the role of oxygen in thiolate etching of gold. Herein, we show that oxygen or a radical initator is a necessary component for efficient etching of gold by thiolates. Attenuation of the etching process by radical scavengers in the presence of oxygen, and the restoration of activity by radical initiators under inert atmosphere, strongly implicate the oxygen radical. These data led us to propose an atomistic mechanism in which the oxygen radical initiates the etching process. PMID:26089294

Gold placers of the historical Fortymile River region, Alaska

USGS Publications Warehouse

Yeend, Warren E.

1996-01-01

The Fortymile River region in east-central Alaska has a long and colorful history as the site of the first major gold discovery in interior Alaska. Placer gold has been mined in the region nearly every year since its original discovery in 1886. Total gold production is approximately 500,000 troy ounces. Although many of the rich deposits have been mined, there still exist areas that contain gold. Areas of mined and unmined gold-bearing creek and terrace gravels are outlined on the accompanying geologic map. The early history of the Fortymile area centered on the small frontier settlement of Fortymile City located at the junction of the Fortymile and Yukon Rivers in Canadian territory. This was the supply and jumping-off point for prospectors who worked their way into Alaska up the Fortymile River and found gold on many of its tributaries. Hand mining, both underground and surface, using sluice boxes and (or) rockers were the earliest methods; later, hydraulicking, dredging, and draglining methods were used. More recently, bulldozers and elevated trammels have been used, as well as very portable floating suction dredges. The rich mining lore of the area is closely associated with events of the nearby world-famous Klondike District. Bedrock and placer geology and mining history of individual gold-rich creeks are herein updated. The Fortymile area, which is part of the Yukon-Tanana Upland, contains quartzite, schist, gneiss, amphibolite, marble, serpentinite, and granite overlain by basalt, sandstone, conglomerate, shale, tuff, and coal; overlying these rocks are several deposits of varying ages consisting of gold-bearing gravel and colluvium. The close spatial association of creeks containing placer gold and the gneiss, schist, amphibolite, and marble unit strongly suggests this metamorphic unit is the gold source. High terrace gravels record a time from the late Tertiary to early Pleistocene when the ancestral Fortymile River and its major tributaries, the North and

Direct electrodeposition of porous gold nanowire arrays for biosensing applications.

PubMed

Zhang, Xinyi; Li, Dan; Bourgeois, Laure; Wang, Huanting; Webley, Paul A

2009-02-02

Nanochannel alumina templates are used as templates for fabrication of porous gold nanowire arrays by a direct electrodeposition method. After modification with glucose oxidase, a porous gold nanowire-array electrode is shown to be an excellent electrochemical biosensor for the detection of glucose. The picture shows an SEM image of a nanowire array after removal of the alumina template by acid dissolution. We report the fabrication of porous gold nanowire arrays by means of a one-step electrodeposition method utilizing nanochannel alumina templates. The microstructure of gold nanowires depends strongly on the current density. The formation of porous gold nanowires is attributed to disperse crystallization under conditions of low nucleation rate. Interfacial electron transport through the porous gold nanowires is studied by electrochemical impedance spectroscopy. Cyclic voltammetric studies on the porous gold nanowire arrays reveal a low-potential electrocatalytic response towards hydrogen peroxide. The properties of the glucose oxidase modified porous gold nanowire array electrode are elucidated and compared with those of nonporous enzyme electrodes. The glucose oxidase modified porous gold nanowire-array electrode is shown to be an excellent electrochemical biosensor for the detection of glucose.

Characterization of protein-bound gold in rat urine following aurothiomalate administration and of rat and human albumin-gold-thiomalate.

PubMed

Shaw, C F; Schaeffer-Memmel, N; Krawczak, D

1986-03-01

The metabolites of gold in the urine of rats given the antiarthritic drug aurothiomalate were investigated by gel permeation chromatography, electrophoresis, and chemical studies. Following a single dose of aurtothiomalate, the excreted gold was protein-bound in the high-molecular-weight (greater than or equal to 150,000 dalton) and serum albumin fractions. Electrophoresis confirmed the presence of albumin, but showed that the other proteins present differ from those in normal or in vitro aurothiomalate-incubated rat sera. The pattern of the proteins establishes that the proteinuria was of the glomerular type. The alterations in the gold distribution produced by incubation of the urine with the low-molecular-weight thiol penicillamine and with exogenously added aurothiomalate indicated the existence of a labile equilibrium of gold among protein binding sites in the urine. Incubation of rat and human sera and commercially prepared serum albumins with aurothiomalate increased the electrophoretic mobility of the albumin. The significance of this change in electrophoretic mobility with respect to two models of gold binding by serum albumin is discussed.

Genesis of the Sb-W-Au deposits at Ixtahuacan, Guatemala: evidence from fluid inclusions and stable isotopes

NASA Astrophysics Data System (ADS)

Guillemette, N.; Williams-Jones, A. E.

1993-06-01

The Ixtahuacan Sb-W deposits are hosted by upper Pennsylvanian to Permian metasedimentary rocks of the central Cordillera of Guatemala. The deposits consist of gold-bearing arsenopyrite, stibnite and scheelite. Arsenopyrite and scheelite are early in the paragenesis, occurring as disseminations in pyritiferous black shale/sandstone and in argillaceous limestone, respectively. Some stibnite is disseminated, but the bulk of the stibnite occurs as massive stratabound lenses in black shales and in quartz-ankerite veins and breccias, locally containing scheelite. Microthermometric measurements on fluid inclusions in quartz and scheelite point to a low temperature (160 190°C) and low to moderate salinity (5 15 wt% NaCl eq.) aqueous ore fluid. Abundant vapour-rich inclusions suggest that the fluid boiled. Carbon dioxide was produced locally as a result of interaction of the aqueous fluid with the argillaceous limestone. Bulk leaching experiments and SEM-EDS analyses of decrepitated fluid inclusion residues indicate that the ore-bearing solution was NaCl-dominated. The δ18O values of quartz, ankerite and scheelite from mineralized veins range from 19.7 to 20.5‰, 18.1 to 20.0‰ and 7.0 to 8.4‰ respectively. The average temperature calculated from quartz-scheelite oxygen isotopic fractionation is 170°C. The oxygen isotopic composition of the fluid, interpreted to have been in equilibrium with these minerals, ranged from 5.7 to 7.6‰, and is considered to represent an evolved meteoric water. Diagenetic or syngenetic pyrite has a sulphur isotopic composition of 0.5±0.3‰ which is consistent with bacterial reduction of sulphate. The δ34S values of arsenopyrite and stibnite range from -2.8 to 2.0‰ and -2.7 to -2.3‰ respectively, and are though to reflect sulphur derived from pyrite. The Ixtahuacan deposits are interpreted to have formed at low temperature (<200°C) and a depth of a few hundred metres from a low fO2 (10-49-10-57), high pH (7 8) fluid. Arsenic was

Geochemistry, geochronology, mineralogy, and geology suggest sources of and controls on mineral systems in the southern Toquima Range, Nye County, Nevada; with geochemistry maps of gold, silver, mercury, arsenic, antimony, zinc, copper, lead, molybdenum, bismuth, iron, titanium, vanadium, cobalt, beryllium, boron, fluorine, and sulfur; and with a section on lead associations, mineralogy and paragenesis, and isotopes

USGS Publications Warehouse

Shawe, Daniel R.; Hoffman, James D.; Doe, Bruce R.; Foord, Eugene E.; Stein, Holly J.; Ayuso, Robert A.

2003-01-01

Geochemistry maps showing the distribution and abundance of 18 elements in about 1,400 rock samples, both mineralized and unmineralized, from the southern Toquima Range, Nev., indicate major structural and lithologic controls on mineralization, and suggest sources of the elements. Radiometric age data, lead mineralogy and paragenesis data, and lead-isotope data supplement the geochemical and geologic data, providing further insight into timing, sources, and controls on mineralization. Major zones of mineralization are centered on structural margins of calderas and principal northwest-striking fault zones, as at Round Mountain, Manhattan, and Jefferson mining districts, and on intersections of low-angle and steep structures, as at Belmont mining district. Paleozoic sedimentary rocks, mostly limestones (at Manhattan, Jefferson, and Belmont districts), and porous Oligocene ash-flow tuffs (at Round Mountain district) host the major deposits, although all rock types have been mineralized as evidenced by numerous prospects throughout the area. Principal mineral systems are gold-silver at Round Mountain where about 7 million ounces of gold and more than 4 million ounces of silver has been produced; gold at Gold Hill in the west part of the Manhattan district where about a half million ounces of gold has been produced; gold-mercury-arsenic-antimony in the east (White Caps) part of the Manhattan district where a few hundred thousand ounces of gold has been produced; and silver-lead-antimony at Belmont where more than 150,000 ounces of silver has been produced. Lesser amounts of gold and silver have been produced from the Jefferson district and from scattered mines elsewhere in the southern Toquima Range. A small amount of tungsten was produced from mines in the granite of the Round Mountain pluton exposed east of Round Mountain, and small amounts of arsenic, antimony, and mercury have been produced elsewhere in the southern Toquima Range. All elements show unique

A gold nanoparticle-based immunochromatographic assay: the influence of nanoparticulate size.

PubMed

Lou, Sha; Ye, Jia-ying; Li, Ke-qiang; Wu, Aiguo

2012-03-07

Four different sized gold nanoparticles (14 nm, 16 nm, 35 nm and 38 nm) were prepared to conjugate an antibody for a gold nanoparticle-based immunochromatographic assay which has many applications in both basic research and clinical diagnosis. This study focuses on the conjugation efficiency of the antibody with different sized gold nanoparticles. The effect of factors such as pH value and concentration of antibody has been quantificationally discussed using spectra methods after adding 1 wt% NaCl which induced gold nanoparticle aggregation. It was found that different sized gold nanoparticles had different conjugation efficiencies under different pH values and concentrations of antibody. Among the four sized gold nanoparticles, the 16 nm gold nanoparticles have the minimum requirement for antibody concentrations to avoid aggregation comparing to other sized gold nanoparticles but are less sensitive for detecting the real sample compared to the 38 nm gold nanoparticles. Consequently, different sized gold nanoparticles should be labeled with antibody under optimal pH value and optimal concentrations of antibody. It will be helpful for the application of antibody-labeled gold nanoparticles in the fields of clinic diagnosis, environmental analysis and so on in future.

Enhancement of radiation effect on cancer cells by gold-pHLIP

PubMed Central

Antosh, Michael P.; Wijesinghe, Dayanjali D.; Shrestha, Samana; Lanou, Robert; Huang, Yun Hu; Hasselbacher, Thomas; Fox, David; Neretti, Nicola; Sun, Shouheng; Katenka, Natallia; Cooper, Leon N; Andreev, Oleg A.; Reshetnyak, Yana K.

2015-01-01

Previous research has shown that gold nanoparticles can increase the effectiveness of radiation on cancer cells. Improved radiation effectiveness would allow lower radiation doses given to patients, reducing adverse effects; alternatively, it would provide more cancer killing at current radiation doses. Damage from radiation and gold nanoparticles depends in part on the Auger effect, which is very localized; thus, it is important to place the gold nanoparticles on or in the cancer cells. In this work, we use the pH-sensitive, tumor-targeting agent, pH Low-Insertion Peptide (pHLIP), to tether 1.4-nm gold nanoparticles to cancer cells. We find that the conjugation of pHLIP to gold nanoparticles increases gold uptake in cells compared with gold nanoparticles without pHLIP, with the nanoparticles distributed mostly on the cellular membranes. We further find that gold nanoparticles conjugated to pHLIP produce a statistically significant decrease in cell survival with radiation compared with cells without gold nanoparticles and cells with gold alone. In the context of our previous findings demonstrating efficient pHLIP-mediated delivery of gold nanoparticles to tumors, the obtained results serve as a foundation for further preclinical evaluation of dose enhancement. PMID:25870296

Contributions to the gold metallogeny of northern Nevada

USGS Publications Warehouse

Tosdal, Richard M.

1998-01-01

Nevada is one of the Earth's premier gold producing regions, accounting for approximately 64 percent of the U.S and nine percent of the world total. The impact of these mines on nearby local economies and on our national balance of payments is profound, and will continue well into the next century. Of principal importance in this region are giant sedimentary-rock-hosted (Carlin-type) deposits. These are some of the world's largest deposits, but yet are poorly understood. Other sedimentary-rock hosted deposits in the region, the distal-disseminated Ag-Au type, are genetically related to shallow plutonic complexes. Hot-spring gold-silver systems associated with Tertiary volcanic rocks represent a third type of precious metal deposit in northern Nevada. These deposits, despite being generally smaller than sedimentary-rock-hosted gold deposits, are also important gold-silver resources. Aspects about the geologic and metallogenic setting of gold-silver deposits in northern Nevada are addressed in the twenty-two chapters that compose this volume. The volume is organized along four themes: (1) crustal structure; (2) Carlin-type deposits; (3) pluton-related gold-silver deposits near Battle Mountain; and (4) hot-spring gold-silver deposits. This Open-File Report, the result of ongoing geologic and mineral-resource investigations, provides a basis for mineral exploration, for land-use planning decisions, and for environmental questions in northern Nevada.

33 CFR 13.01-25 - Description of Gold Lifesaving Medal.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Description of Gold Lifesaving... SECURITY GENERAL DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-25 Description of Gold Lifesaving Medal. (a) The Gold Lifesaving Medal is 99.9...

In situ measurement of gold nanoparticle production

NASA Astrophysics Data System (ADS)

Affandi, Mohd Syafiq; Bidin, Noriah; Abdullah, Mundzir; Aziz, Muhammad Safuan Abd.; Al-Azawi, Mohammed; Nugroho, Waskito

2015-01-01

The closeness of the experimental and theoretical values enables the development of an in situ characterization technique to monitor and analyze the production of gold nanoparticles (NPs), overcoming the use of high-end and expensive instrumentation. Gold NPs below the radius size of 10 nm were successfully synthesized in accordance with a few working parameters of pulse laser ablation in a liquid technique. In this report, the size, shape, concentration, and aggregation properties of gold NPs were estimated by the Mie-Gans model based on a reliable and interactive real-time absorption spectroscopy. The major features can be an important means toward determination of efficient process measures, productivity of gold NPs generated, and efficiency of the mass ablation rate. The accuracy in the measurement is confirmed via transmission electron microscopy analysis.

Biotin-streptavidin-induced aggregation of gold nanorods: tuning rod-rod orientation.

PubMed

Gole, Anand; Murphy, Catherine J

2005-11-08

We report herein biotin-streptavidin-mediated aggregation studies of long gold nanorods. We have previously demonstrated end-to-end linkages of gold nanorods driven by the biotin-streptavidin interaction (Caswell et al. J. Am. Chem. Soc. 2003, 125, 13914). In that report, the specific binding of biotin disulfide to the gold nanorod edges was achieved due to the preferred binding of thiol molecules to the Au[111] surface (gold nanorod ends) as opposed to the gold nanorod side faces. This led to the end-end linkage of gold nanorods upon subsequent addition of streptavidin. In this report we demonstrate a simple procedure to biotinylate the entire gold nanorod surface and subsequently form a 3-D assembly by addition of streptavidin. Gold nanorods were synthesized by the three-step seeding protocol documented in our previous articles. The surface of gold nanorods was further modified by a layer of a weak polyelectrolyte, poly(acrylic acid), PAA. A biotin molecule which has an amine group at one end (biotin-PEO-amine) was anchored to the carboxylic acid group of the polyelectrolyte using the well-known carbodiimide chemistry. This process biotinylates the entire gold nanorod surface. Addition of streptavidin further leads to aggregation of gold nanorods. A closer look at the aggregates reveals a preferential side-to-side assembly of gold nanorods. The gold nanorods were characterized at each stage by UV-vis spectroscopy, light scattering, and transmission electron microscopy (TEM) measurements.

Electrochemically controlled iron isotope fractionation

NASA Astrophysics Data System (ADS)

Black, Jay R.; Young, Edward D.; Kavner, Abby

2010-02-01

Variations in the stable isotope abundances of transition metals have been observed in the geologic record and trying to understand and reconstruct the physical/environmental conditions that produced these signatures is an area of active research. It is clear that changes in oxidation state lead to large fractionations of the stable isotopes of many transition metals such as iron, suggesting that transition metal stable isotope signatures could be used as a paleo-redox proxy. However, the factors contributing to these observed stable isotope variations are poorly understood. Here we investigate how the kinetics of iron redox electrochemistry generates isotope fractionation. Through a combination of electrodeposition experiments and modeling of electrochemical processes including mass-transport, we show that electron transfer reactions are the cause of a large isotope separation, while mass transport-limited supply of reactant to the electrode attenuates the observed isotopic fractionation. Furthermore, the stable isotope composition of electroplated transition metals can be tuned in the laboratory by controlling parameters such as solution chemistry, reaction overpotential, and solution convection. These methods are potentially useful for generating isotopically-marked metal surfaces for tracking and forensic purposes. In addition, our studies will help interpret stable isotope data in terms of identifying underlying electron transfer processes in laboratory and natural samples.

Geochemistry of placer gold, Koyukuk-Chandalar mining district, Alaska

USGS Publications Warehouse

Mosier, E.L.; Cathrall, J.B.; Antweiler, J.C.; Tripp, R.B.

1989-01-01

The Koyukuk-Chandalar mining district of the Brooks Range mineral belt in north-central Alaska contains numerous placer gold deposits but few known lode gold sources. Gold grains, collected from 46 placer localities and 6 lode gold sites in the district, were analyzed for Ag and 37 trace elements utilizing direct current-arc optical emission spectroscopy. When possible, several measurements were made on each sample and averaged. Gold content was calculated by the summation of the 38 elements determined and subtracting from 100. The objectives of our study were to characterize the deposits by defining the type and number of distinct geochemical characteristics for the Au, to determine relationships of Au in placer deposits to possible lode sources (placer and lode), to identify possible primary sources of placer gold, and to study processes of placer formation. Interpretation of results emphasize that the Au grains are almost invariably ternary (Au-Ag-Cu) alloys. The average Cu content is 0.040% and the average Ag content and fineness [(Au/Au+Ag)??1,000] are 10.5% and 893 parts per thousand, respectively, for the 46 placer localities. Six geochemically distinct types of placer gold can be identified in the Koyukuk-Chandalar mining district based on Ag and Cu values. One type with an average Ag content of 21.2%, an average Cu content of 0.007%, and 786 average fineness is found only in the eastern part of the district. Placer gold grains that have an average Ag content of 6.0%, an average Cu content of 0.276%, and 940 average fineness were found in the western part of the district. Four intermediate types generally occur in order across the district. Variations in the chemistry of the placer gold can be related to variable depositional environments at the primary gold sources. Placer gold geochemistry is important in determining the origin and depositional environment of the primary Au sources and could add to the knowledge of the thermal history of the southcentral

Chemically functionalized gold nanoparticles: Synthesis, characterization, and applications

NASA Astrophysics Data System (ADS)

Daniel, Weston Lewis

This thesis focuses on the development and application of gold nanoparticle based detection systems and biomimetic structures. Each class of modified nanoparticle has properties that are defined by its chemical moieties that interface with solution and the gold nanoparticle core. In Chapter 2, a comparison of the biomolecular composition and binding properties of various preparations of antibody oligonucleotide gold nanoparticle conjugates is presented. These constructs differed significantly in terms of their structure and binding properties. Chapter 3 reports the use of electroless gold deposition as a light scattering signal enhancer in a multiplexed, microarray-based scanometric immunoassay using the gold nanoparticle probes evaluated in Chapter 2. The use of gold development results in greater signal enhancement than the typical silver development, and multiple rounds of metal development were found to increase the resulting signal compared to one development. Chapter 4 describes an amplified scanometric detection method for human telomerase activity. Gold nanoparticles functionalized with specific oligonucleotide sequences can efficiently capture telomerase enzymes and subsequently be elongated. Both the elongated and unmodified oligonucleotide sequences are simultaneously measured. At low telomerase concentrations, elongated strands cannot be detected, but the unmodified sequences, which come from the same probe particles, can be detected because their concentration is higher, providing a novel form of amplification. Chapter 5 reports the development of a novel colorimetric nitrite and nitrate ion assay based upon gold nanoparticle probes functionalized with Griess reaction reagents. This assay takes advantage of the distance-dependent plasmonic properties of the gold nanoparticles and the ability of nitrite ion to facilitate the cross coupling of novel nanoparticle probes. The assay works on the concept of a kinetic end point and can be triggered at the EPA

Refractory concentrate gold leaching: Cyanide vs. bromine

NASA Astrophysics Data System (ADS)

Dadgar, Ahmad

1989-12-01

Gold extraction, recovery and economics for two refractory concentrates were investigated using cyanide and bromine reagents. Gold extractions for cyanide leaching (24-48 hours) and bromine leaching (six hours) were the same and ranged from 94 to 96%. Gold recoveries from bromine pregnant solutions using carbon adsorption, ion exchange, solvent extraction, and zinc and aluminum precipitation methods were better than 99.9%. A preliminary economic analysis indicates that chemical costs for cyanidation and bromine process are 11.70 and 11.60 respectively, per tonne of calcine processed.

Use of Soybean Lecithin in Shape Controlled Synthesis of Gold Nanoparticles

NASA Astrophysics Data System (ADS)

Ayres, Benjamin Robert

The work presented in this dissertation is a composite of experiments in the growth of gold nanoparticles with specific optical properties of interest. The goal is to synthesize these gold nanoparticles using soybean extract for not only shape control, but for propensity as a biocompatible delivery system. The optical properties of these nanoparticles has found great application in coloring glass during the Roman empire and, over the centuries, has grown into its own research field in applications of nanoparticulate materials. Many of the current functions include use in biological systems as biosensors and therapeutic applications, thus making biocompatibility a necessity. Current use of cetyltrimethylammonium bromide leads to rod-shaped gold nanoparticles, however, the stability of these gold nanoparticles does not endure for extended periods of time in aqueous media. In my research, two important components were found to be necessary for stable, anisotropic growth of gold nanoparticles. In the first experiments, it was found that bromide played a key role in shape control. Bromide exchange on the gold atoms led to specific packing of the growing crystals, allowing for two-dimensional growth of gold nanoparticles. It was also discerned that soybean lecithin contained ligands that blocked specific gold facets leading to prismatic gold nanoparticle growth. These gold nanoprisms give a near infrared plasmon absorption similar to that of rod-shaped gold nanoparticles. These gold nanoprisms are discovered to be extremely stable in aqueous media and remain soluble for extended periods of time, far longer than that of gold nanoparticles grown using cetyltrimethylammonium bromide. Since soy lecithin has a plethora of compounds present, it became necessary to discover which compound was responsible for the shape control of the gold nanoprisms in order to optimize the synthesis and allow for a maximum yield of the gold nanoprisms. Many of these components were identified

Time series analysis of gold production in Malaysia

NASA Astrophysics Data System (ADS)

Muda, Nora; Hoon, Lee Yuen

2012-05-01

Gold is a soft, malleable, bright yellow metallic element and unaffected by air or most reagents. It is highly valued as an asset or investment commodity and is extensively used in jewellery, industrial application, dentistry and medical applications. In Malaysia, gold mining is limited in several areas such as Pahang, Kelantan, Terengganu, Johor and Sarawak. The main purpose of this case study is to obtain a suitable model for the production of gold in Malaysia. The model can also be used to predict the data of Malaysia's gold production in the future. Box-Jenkins time series method was used to perform time series analysis with the following steps: identification, estimation, diagnostic checking and forecasting. In addition, the accuracy of prediction is tested using mean absolute percentage error (MAPE). From the analysis, the ARIMA (3,1,1) model was found to be the best fitted model with MAPE equals to 3.704%, indicating the prediction is very accurate. Hence, this model can be used for forecasting. This study is expected to help the private and public sectors to understand the gold production scenario and later plan the gold mining activities in Malaysia.

Antibacterial properties and mechanisms of gold-silver nanocages

NASA Astrophysics Data System (ADS)

Wang, Yulan; Wan, Jiangshan; Miron, Richard J.; Zhao, Yanbin; Zhang, Yufeng

2016-05-01

Despite the number of antibiotics used in routine clinical practice, bacterial infections continue to be one of the most important challenges faced in humans. The main concerns arise from the continuing emergence of antibiotic-resistant bacteria and the difficulties faced with the pharmaceutical development of new antibiotics. Thus, advancements in the avenue of novel antibacterial agents are essential. In this study, gold (Au) was combined with silver (Ag), a well-known antibacterial material, to form silver nanoparticles producing a gold-silver alloy structure with hollow interiors and porous walls (gold-silver nanocage). This novel material was promising in antibacterial applications due to its better biocompatibility than Ag nanoparticles, potential in photothermal effects and drug delivery ability. The gold-silver nanocage was then tested for its antibacterial properties and the mechanism involved leading to its antibacterial properties. This study confirms that this novel gold-silver nanocage has broad-spectrum antibacterial properties exerting its effects through the destruction of the cell membrane, production of reactive oxygen species (ROS) and induction of cell apoptosis. Therefore, we introduce a novel gold-silver nanocage that serves as a potential nanocarrier for the future delivery of antibiotics.

Carbon isotope ratios and isotopic correlations between components in fruit juices

NASA Astrophysics Data System (ADS)

Wierzchnicki, Ryszard

2013-04-01

Nowadays food products are defined by geographical origin, method of production and by some regulations concerning terms of their authenticity. Important data for confirm the authenticity of product are providing by isotopic methods of food control. The method checks crucial criteria which characterize the authenticity of inspected product. The European Union Regulations clearly show the tendency for application of the isotopic methods for food authenticity control (wine, honey, juice). The aim of the legislation steps is the protection of European market from possibility of the commercial frauds. Method of isotope ratio mass spectrometry is very effective tool for the use distinguishably the food products of various geographical origin. The basic problem for identification of the sample origin is the lack of databases of isotopic composition of components and information about the correlations of the data. The subject of the work was study the isotopic correlations existing between components of fruits. The chemical and instrumental methods of separation: water, sugars, organic acids and pulp from fruit were implemented. IRMS technique was used to measure isotopic composition of samples. The final results for original samples of fruits (apple, strawberry etc.) will be presented and discussed. Acknowledgement: This work was supported by the Polish Ministry of Science and Higher Education under grant NR12-0043-10/2010.

Chemisorbed monolayers of corannulene penta-thioethers on gold.

PubMed

Angelova, Polina; Solel, Ephrath; Parvari, Galit; Turchanin, Andrey; Botoshansky, Mark; Gölzhäuser, Armin; Keinan, Ehud

2013-02-19

Penta(tert-butylthio)corannulene and penta(4-dimethylaminophenylthio)corannulene form highly stable monolayers on gold surfaces, as indicated by X-ray photoelectron spectroscopy (XPS). Formation of these homogeneous monolayers involves multivalent coordination of the five sulfur atoms to gold with the peripheral alkyl or aryl substituents pointing away from the surface. No dissociation of C-S bonds upon binding could be observed at room temperature. Yet, the XPS experiments reveal strong chemical bonding between the thioether groups and gold. Temperature-dependent XPS study shows that the thermal stability of the monolayers is higher than the typical stability of self-assembled monolayers (SAMs) of thiolates on gold.

Measurement of isotope abundance variations in nature by gravimetric spiking isotope dilution analysis (GS-IDA).

PubMed

Chew, Gina; Walczyk, Thomas

2013-04-02

Subtle variations in the isotopic composition of elements carry unique information about physical and chemical processes in nature and are now exploited widely in diverse areas of research. Reliable measurement of natural isotope abundance variations is among the biggest challenges in inorganic mass spectrometry as they are highly sensitive to methodological bias. For decades, double spiking of the sample with a mix of two stable isotopes has been considered the reference technique for measuring such variations both by multicollector-inductively coupled plasma mass spectrometry (MC-ICPMS) and multicollector-thermal ionization mass spectrometry (MC-TIMS). However, this technique can only be applied to elements having at least four stable isotopes. Here we present a novel approach that requires measurement of three isotope signals only and which is more robust than the conventional double spiking technique. This became possible by gravimetric mixing of the sample with an isotopic spike in different proportions and by applying principles of isotope dilution for data analysis (GS-IDA). The potential and principle use of the technique is demonstrated for Mg in human urine using MC-TIMS for isotopic analysis. Mg is an element inaccessible to double spiking methods as it consists of three stable isotopes only and shows great potential for metabolically induced isotope effects waiting to be explored.

Photonuclear Production of Medical Isotopes

NASA Astrophysics Data System (ADS)

Weinandt, Nick

2011-10-01

Every year, more than 20 million people in the United States receive a nuclear medicine procedure. Many of the isotopes needed for these procedures are under-produced. Suppliers of the isotopes are usually located outside the United States, which presents a problem when the desired isotopes have short half-lives. Linear accelerators were investigated as a possible method of meeting isotope demand. Linear accelerators are cheaper, safer, and have lower decommissioning costs compared to nuclear reactors. By using (γ,p) reactions, the desired isotope can be separated from the target material due to the different chemical nature of each isotope. Isotopes investigated were Cu-67, In-111, and Lu-111. Using the results the photon flux Monte Carlo simulations, the expected activity of isotopes can be calculated. After samples were irradiated, a high purity germanium detector and signal processing apparatus were used to count the samples. The activity at the time of irradiation stop was then calculated. The uses of medical isotopes will also be presented. Thanks to Idaho State University, the Idaho Accelerator Center, and the National Science Foundation for supporting the research.

Analyses of gold artifacts from Slovenia

NASA Astrophysics Data System (ADS)

Šmit, Ž.; Budnar, M.; Pelicon, P.; Zorko, B.; Knific, T.; Istenič, J.; Trampuž-Orel, N.; Demortier, G.

2000-03-01

The method of particle-induced X-ray emission (PIXE) was used for the study of two gold archaeological finds: a Norico-Pannonian brooch, presumably a votive item, and a pair of earrings and a ring from a Slavic female grave. The analysis was performed by an external proton millibeam and aimed to identify the manufacturing techniques. The brooch, including the spring, was made of a rather pure 98% gold. This may indicate that the brooch was produced for votive purposes, as a more flexible spring would suit an object to be worn. The Slavic ring was made of a different alloy than the earrings; moreover, its inhomogeneous alloy reveals the exploitation of local gold sources.

Stable oxygen and hydrogen isotopes of brines - comparing isotope ratio mass spectrometry and isotope ratio infrared spectroscopy

NASA Astrophysics Data System (ADS)

Ahrens, Christian; Koeniger, Paul; van Geldern, Robert; Stadler, Susanne

2013-04-01

Today's standard analytical methods for high precision stable isotope analysis of fluids are gas-water equilibration and high temperature pyrolysis coupled to isotope ratio mass spectrometers (IRMS). In recent years, relatively new laser-based analytical instruments entered the market that are said to allow high isotope precision data on nearly every media. This optical technique is referred to as isotope ratio infrared spectroscopy (IRIS). The objective of this study is to evaluate the capability of this new instrument type for highly saline solutions and a comparison of the analytical results with traditional IRMS analysis. It has been shown for the equilibration method that the presence of salts influences the measured isotope values depending on the salt concentration (see Lécuyer et al, 2009; Martineau, 2012). This so-called 'isotope salt effect' depends on the salt type and salt concentration. These factors change the activity in the fluid and therefore shift the isotope ratios measured by the equilibration method. Consequently, correction factors have to be applied to these analytical data. Direct conversion techniques like pyrolysis or the new laser instruments allow the measurement of the water molecule from the sample directly and should therefore not suffer from the salt effect, i.e. no corrections of raw values are necessary. However, due to high salt concentrations this might cause technical problems with the analytical hardware and may require labor-intensive sample preparation (e.g. vacuum distillation). This study evaluates the salt isotope effect for the IRMS equilibration technique (Thermo Gasbench II coupled to Delta Plus XP) and the laser-based IRIS instruments with liquid injection (Picarro L2120-i). Synthetic salt solutions (NaCl, KCl, CaCl2, MgCl2, MgSO4, CaSO4) and natural brines collected from the Stassfurt Salt Anticline (Germany; Stadler et al., 2012) were analysed with both techniques. Salt concentrations ranged from seawater salinity

Synthesis and catalytic activity of the metastable phase of gold phosphide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernando, Deshani; Nigro, Toni A.E.; Dyer, I.D.

Recently, transition metal phosphides have found new applications as catalysts for the hydrogen evolution reaction that has generated an impetus to synthesize these materials at the nanoscale. In this work, Au{sub 2}P{sub 3} was synthesized utilizing the high temperature decomposition of tri-n-octylphosphine as a source of elemental phosphorous. Gold nanorods were used as morphological templates with the aim of controlling the shape and size of the resulting gold phosphide particles. We demonstrate that the surface capping ligand of the gold nanoparticle precursors can influence the purity and extent to which the gold phosphide phase will form. Gold nanorods functionalized withmore » 1-dodecanethiol undergo digestive ripening to produce discrete spherical particles that exhibit reduced reactivity towards phosphorous, resulting in low yields of the gold phosphide. In contrast, gold phosphide was obtained as a phase pure product when cetyltrimethylammonium bromide functionalized gold nanorods are used instead. The Au{sub 2}P{sub 3} nanoparticles exhibited higher activity than polycrystalline gold towards the hydrogen evolution reaction. - Graphical abstract: Au{sub 2}P{sub 3} was synthesized utilizing the high temperature decomposition of tri-n-octylphosphine as a source of elemental phosphorous and gold nanoparticles as reactants. We demonstrate that the surface capping ligand of the gold nanoparticle precursors influence the purity and extent to which the Au{sub 2}P{sub 3} phase will form. Gold nanorods functionalized with 1-dodecanethiol undergo digestive ripening to produce discrete spherical particles that exhibit reduced reactivity towards phosphorous, resulting in low yields of the gold phosphide. In contrast, gold phosphide was obtained as a phase pure product when cetyltrimethylammonium bromide functionalized gold nanoparticles are used instead. The Au{sub 2}P{sub 3} nanoparticles exhibited higher activity than polycrystalline gold towards the hydrogen

HYDROGEN ISOTOPE TARGETS

DOEpatents

Ashley, R.W.

1958-08-12

The design of targets for use in the investigation of nuclear reactions of hydrogen isotopes by bombardment with accelerated particles is described. The target con struction eomprises a backing disc of a metal selected from the group consisting of molybdenunn and tungsten, a eoating of condensed titaniunn on the dise, and a hydrogen isotope selected from the group consisting of deuterium and tritium absorbed in the coatiag. The proeess for preparing these hydrogen isotope targets is described.

Gold and other metals in big sagebrush (Artemisia tridentata Nutt.) as an exploration tool, Gold Run District, Humboldt County, Nevada

USGS Publications Warehouse

Erdman, J.A.; Cookro, T.M.; O'Leary, R. M.; Harms, T.F.

1988-01-01

Big sagebrush - a cold-desert species that dominates the terrain over large parts of western United States - was sampled along several traverses that crossed thermally metamorphosed limestone, phyllitic shale, and schist of the Middle and Upper Cambrian Preble Formation that host skarn-, disseminated gold and silver-, and hot springs gold-type mineral occurrences. Patterns of detectable levels of gold (8 to 28 ppb or ng g-1) in ash of new growth were consistent with areas affected by known or suspected gold mineralization. Soils collected along one of the traverses where a selenium-indicator plant was common contained no gold above background levels of 2ppb, but were consistently high in As, Sb, and Zn, and several samples were unusually high in Se (maximum 11 ppm or ??g g-1). Sagebrush along this traverse contained Li at levels above norms for this species. We also found a puzzling geochemical anomaly at a site basinward from active hot springs along a range-front fault scarp. Sagebrush at this site contained a trace of gold and an unusually high concentration of Cd (13 ppm) and the soil had anomalous concentrations of Cd and Bi (3.2 and 6 ppm, respectively). The source of this anomaly could be either metal-rich waters from an irrigation ditch or leakage along a buried fault. Despite the limited nature of the study, we conclude that gold in sagebrush could be a cost-effective guide to drilling locations in areas where the geology seems favorable for disseminated and vein precious metals. ?? 1988.

Using mineralogy to optimize gold recovery by direct cyanidation

NASA Astrophysics Data System (ADS)

Venter, D.; Chryssoulis, S. L.; Mulpeter, T.

2004-08-01

The complete and accurate gold deportments of direct cyanide leach residues provide a clear picture of the occurrence of unrecovered gold and identify causes for poor extraction. Based on the independent measurement of each form and carrier of unleached gold, opportunities for recovery optimization can be assessed more accurately by providing meaningful targets and can help identify the means to achieve such targets. In ten of 14 leach plants surveyed, 23% of the unrecovered gold could be extracted without finer grinding.

Recovering gold from thiosulfate leach pulps via ion exchange

NASA Astrophysics Data System (ADS)

Nicol, Michael J.; O'Malley, Glen

2002-10-01

Increasing environmental and occupational safety concerns about the use of cyanide in gold processing has increased interest in more acceptable alternative lixiviants, the most promising of which is thiosulfate. However, the thiosulfate process lacks a proven inpulp method of recovering the dissolved gold because activated carbon is not effective for the absorption of the gold-thiosulfate complex. This paper describes work aimed at evaluating the effectiveness of commercially available anion exchange resins for the recovery of gold from thiosulfate leach liquors and pulps.

The graphene-gold interface and its implications for nanoelectronics.

PubMed

Sundaram, Ravi S; Steiner, Mathias; Chiu, Hsin-Ying; Engel, Michael; Bol, Ageeth A; Krupke, Ralph; Burghard, Marko; Kern, Klaus; Avouris, Phaedon

2011-09-14

We combine optical microspectroscopy and electronic measurements to study how gold deposition affects the physical properties of graphene. We find that the electronic structure, the electron-phonon coupling, and the doping level in gold-plated graphene are largely preserved. The transfer lengths for electrons and holes at the graphene-gold contact have values as high as 1.6 μm. However, the interfacial coupling of graphene and gold causes local temperature drops of up to 500 K in operating electronic devices.

Electrically Conductive Polyimide Films Containing Gold Surface

NASA Technical Reports Server (NTRS)

Caplan, Maggie L.; Stoakley, Diane M.; St. Clair, Anne K.

1994-01-01

Polyimide films exhibiting high thermo-oxidative stability and including electrically conductive surface layers containing gold made by casting process. Many variations of basic process conditions, ingredients, and sequence of operations possible, and not all resulting versions of process yield electrically conductive films. Gold-containing layer formed on film surface during cure. These metallic gold-containing polyimides used in film and coating applications requiring electrical conductivity, high reflectivity, exceptional thermal stability, and/or mechanical integrity. They also find commercial potential in areas ranging from thin films for satellite antennas to decorative coatings and packaging.

Oxygen and carbon isotope disequilibria in Galapagos corals: isotopic thermometry and calcification physiology

DOE Office of Scientific and Technical Information (OSTI.GOV)

McConnaughey, T.A.

1986-01-01

Biological carbonate skeletons are built largely from carbon dioxide, which reacts to form carbonate ion within thin extracellular solutions. The light isotopes of carbon and oxygen react faster than the heavy isotopes, depleting the resulting carbonate ions in /sup 13/C and /sup 18/O. Calcium carbonate precipitation occurs sufficiently fast that the skeleton remains out of isotopic equilibrium with surrounding fluids. This explanation for isotopic disequilibrium in biological carbonates was partially simulated in vitro, producing results similar to those seen in non-photosynthetic corals. Photosynthetic corals have higher /sup 13/C//sup 12/C ratios due to the preferential removal of /sup 12/C (as organicmore » carbon) from the reservoir of dissolved inorganic carbon. The oxygen isotopic variations in corals can be used to reconstruct past sea surface temperatures to an accuracy of about 0.5/sup 0/C. The carbon isotopic content of photosynthetic corals provides an indication of cloudiness. Using isotopic data from Galapagos corals, it was possible to construct proxy histories of the El Nino phenomenon. The physiology of skeletogenesis appears to be surprisingly similar in calcium carbonate, calcium phosphate, and silica precipitating systems.« less

The shape of Au8: gold leaf or gold nugget?

NASA Astrophysics Data System (ADS)

Serapian, Stefano A.; Bearpark, Michael J.; Bresme, Fernando

2013-06-01

The size at which nonplanar isomers of neutral, pristine gold nanoclusters become energetically favored over planar ones is still debated amongst theoreticians and experimentalists. Spectroscopy confirms planarity is preferred at sizes up to Au7, however, starting with Au8, the uncertainty remains for larger nanoclusters. Au8 computational studies have had different outcomes: the planar D4h ``cloverleaf'' isomer competes with the nonplanar Td, C2v and D2d ``nugget'' isomers for greatest energetic stability. We here examine the 2D vs. 3D preference in Au8 by presenting our own B2PLYP, MP2 and CCSD(T) calculations on these isomers: these methods afford a better treatment of long-range correlation, which is at the root of gold's characteristic aurophilicity. We then use findings from these high-accuracy computations to evaluate two less expensive DFT approaches, applicable to much larger nanoclusters: alongside the standard functional PBE, we consider M06-L (highly parametrized to incorporate long-range dispersive interactions). We find that increasing basis set size within the B2PLYP framework has a greater destabilizing effect on the nuggets than it has on the Au8 cloverleaf. Our CCSD(T) and B2PLYP predictions, replicated by DFT-PBE, all identify the cloverleaf as the most stable isomer; MP2 and DFT-M06-L show overestimation of aurophilicity, and favor, respectively, the nonplanar D2d and Td nuggets in its stead. We conclude that PBE, which more closely reproduces CCSD(T) findings, may be a better candidate density functional for the simulation of gold nanoclusters in this context.The size at which nonplanar isomers of neutral, pristine gold nanoclusters become energetically favored over planar ones is still debated amongst theoreticians and experimentalists. Spectroscopy confirms planarity is preferred at sizes up to Au7, however, starting with Au8, the uncertainty remains for larger nanoclusters. Au8 computational studies have had different outcomes: the planar D4

Calcium Isotope Analysis by Mass Spectrometry

NASA Astrophysics Data System (ADS)

Boulyga, S.; Richter, S.

2010-12-01

The variations in the isotopic composition of calcium caused by fractionation in heterogeneous systems and by nuclear reactions can provide insight into numerous biological, geological, and cosmic processes, and therefore isotopic analysis finds a wide spectrum of applications in cosmo- and geochemistry, paleoclimatic, nutritional, and biomedical studies. The measurement of calcium isotopic abundances in natural samples has challenged the analysts for more than three decades. Practically all Ca isotopes suffer from significant isobaric interferences, whereas low-abundant isotopes can be particularly affected by neighboring major isotopes. The extent of natural variations of stable isotopes appears to be relatively limited, and highly precise techniques are required to resolve isotopic effects. Isotope fractionation during sample preparation and measurements and instrumental mass bias can significantly exceed small isotope abundance variations in samples, which have to be investigated. Not surprisingly, a TIMS procedure developed by Russell et al. (Russell et al., 1978. Geochim Cosmochim Acta 42: 1075-1090) for Ca isotope measurements was considered as revolutionary for isotopic measurements in general, and that approach is used nowadays (with small modifications) for practically all isotopic systems and with different mass spectrometric techniques. Nevertheless, despite several decades of calcium research and corresponding development of mass spectrometers, the available precision and accuracy is still not always sufficient to achieve the challenging goals. This presentation discusses figures of merits of presently used analytical methods and instrumentation, and attempts to critically assess their limitations. Additionally, the availability of Ca isotope reference materials will be discussed.

Potential of Chilopsis Linearis for Gold Phytomining: Using XAS to Determine Gold Reduction And Nanoparticle Formation Within Plant Tissues

DOE Office of Scientific and Technical Information (OSTI.GOV)

E, Rodriguez; Parsons, J.G.; Peralta-Videa, J.R.

This study reports on the capability of the desert plant Chilopsis linearis (Cav.) Sweet (desert willow) to uptake gold (Au) from gold-enriched media at different plant-growth stages. Plants were exposed to 20, 40, 80, 160, and 320 mg Au L{sup -1} in agar-based growing media for 13, 18, 23, and 35 d. The Au content and oxidation state of Au in the plants were determined using an inductively coupled plasma/optical emission spectrometer (ICP/OES) and X-ray absorption spectroscopy (XAS), respectively. Gold concentrations ranging from 20 to 80 mg Au L{sup -1} did not significantly affect Chilopsis linearis plant growth. The concentrationmore » of gold in the plants increased as the age of the plant increased. The Au concentrations in leaves for the 20, 40, 80, and 160 mg Au L{sup -1} treatments were 32, 60, 62, and 179 mg Au kg{sup -1} dry weight mass, respectively, demonstrating the gold uptake capability of desert willow. The XAS data indicated that desert willow produced gold nanoparticles within plant tissues. Plants exposed to 160 mg Au L{sup -1} formed nanoparticles that averaged approximately 8, 35, and 18 in root, stem, and leaves, respectively. It was observed that the average size of the Au nanoparticles formed by the plants is related to the total Au concentration in tissues and their location in the plant.« less

Therapeutic gold, silver, and platinum nanoparticles.

PubMed

Yamada, Miko; Foote, Matthew; Prow, Tarl W

2015-01-01

There are an abundance of nanoparticle technologies being developed for use as part of therapeutic strategies. This review focuses on a narrow class of metal nanoparticles that have therapeutic potential that is a consequence of elemental composition and size. The most widely known of these are gold nanoshells that have been developed over the last two decades for photothermal ablation in superficial cancers. The therapeutic effect is the outcome of the thickness and diameter of the gold shell that enables fine tuning of the plasmon resonance. When these metal nanoparticles are exposed to the relevant wavelength of light, their temperature rapidly increases. This in turn induces a localized photothermal ablation that kills the surrounding tumor tissue. Similarly, gold nanoparticles have been developed to enhance radiotherapy. The high-Z nature of gold dramatically increases the photoelectric cross-section. Thus, the photoelectric effects are significantly increased. The outcome of these interactions is enhanced tumor killing with lower doses of radiation, all while sparing tissue without gold nanoparticles. Silver nanoparticles have been used for their wound healing properties in addition to enhancing the tumor-killing effects of anticancer drugs. Finally, platinum nanoparticles are thought to serve as a reservoir for platinum ions that can induce DNA damage in cancer cells. The future is bright with the path to clinical trials is largely cleared for some of the less complex therapeutic metal nanoparticle systems. © 2014 The Authors. WIREs Nanomedicine and Nanobiotechnology published by Wiley Periodicals, Inc.

Gold Nanoparticle Labels Amplify Ellipsometric Signals

NASA Technical Reports Server (NTRS)

Venkatasubbarao, Srivatsa

2008-01-01

The ellipsometric method reported in the immediately preceding article was developed in conjunction with a method of using gold nanoparticles as labels on biomolecules that one seeks to detect. The purpose of the labeling is to exploit the optical properties of the gold nanoparticles in order to amplify the measurable ellipsometric effects and thereby to enable ultrasensitive detection of the labeled biomolecules without need to develop more-complex ellipsometric instrumentation. The colorimetric, polarization, light-scattering, and other optical properties of nanoparticles depend on their sizes and shapes. In the present method, these size-and-shape-dependent properties are used to magnify the polarization of scattered light and the diattenuation and retardance of signals derived from ellipsometry. The size-and-shape-dependent optical properties of the nanoparticles make it possible to interrogate the nanoparticles by use of light of various wavelengths, as appropriate, to optimally detect particles of a specific type at high sensitivity. Hence, by incorporating gold nanoparticles bound to biomolecules as primary or secondary labels, the performance of ellipsometry as a means of detecting the biomolecules can be improved. The use of gold nanoparticles as labels in ellipsometry has been found to afford sensitivity that equals or exceeds the sensitivity achieved by use of fluorescence-based methods. Potential applications for ellipsometric detection of gold nanoparticle-labeled biomolecules include monitoring molecules of interest in biological samples, in-vitro diagnostics, process monitoring, general environmental monitoring, and detection of biohazards.

GOFC-GOLD :: Global Observation of Forest and Land Cover Dynamics

Science.gov Websites

Validation: Recommendations for Evaluation and Accuracy Assessment of Global Land Cover Maps, A. Strahler et GOFC-GOLD-38: Report of the GOFC-GOLD/CEOS Workshop on Land Cover Change Accuracy Assessment as part of al., March 2006 860 kb GOFC-GOLD-24: A Revised Strategy for GOFC-GOLD, J.R. Townshend and M.A. Brady

The isotopic effects of electron transfer: an explanation for Fe isotope fractionation in nature

NASA Astrophysics Data System (ADS)

Kavner, A.; Shahar, A.; Bonet, F.; Simon, J. I.; Young, E.

2004-12-01

Recent developments in mass spectrometry techniques have created opportunities to examine the partitioning behavior of stable isotopes of transition metals with a focus on application to iron isotopes. Iron oxidizing and reducing bacteria have been shown to cause isotope fractionations similar in magnitude to those observed in sedimentary environments and it is believed that biological activity is responsible for the most significant Fe isotope fractionation in natural settings. Debate over the use of Fe isotopes as a biological marker resulted from subsequent measurements of fractionations in a variety of abiotic systems. The accumulated evidence, in both biotic and abiotic systems, points to a connection between redox processes and Fe isotope fractionation, however the exact mechanism for isotope fractionation is not yet well understood. Here, we present both a newly-developed theory based on chemical kinetics and preliminary experimental results that quantitatively delineate the relationship between driving force in a charge transfer reaction and resulting Fe isotope fractionation. The theory, based on R. Marcus's chemical kinetics theory for electron transfer (Ann. Rev. Phys. Chem. 15 (1964), 155), predicts that fractionation increases linearly with driving force with a proportionality related to two factors: the difference between isotopic equilibrium exchange of products and reactants, and the reorganization energy along the reaction coordinate. The theoretical predictions were confirmed by measurements of isotopic fractionation associated with electroplating iron metal from a ferrous chloride solution. Isotope fractionation of Fe electroplated under potentiostatic conditions was measured as a function of applied electrochemical potential. As plating voltage was varied from -50 mV to -2.0 V, the isotopic signature of the electroplated iron became depleted in heavy Fe, with δ 56Fe values ranging from -0.106(±0.01) to -2.290(±±0.006)‰ , and corresponding

Observation of enhanced infrared absorption in silicon supersaturated with gold by pulsed laser melting of nanometer-thick gold films

NASA Astrophysics Data System (ADS)

Chow, Philippe K.; Yang, Wenjie; Hudspeth, Quentin; Lim, Shao Qi; Williams, Jim S.; Warrender, Jeffrey M.

2018-04-01

We demonstrate that pulsed laser melting (PLM) of thin 1, 5, and 10 nm-thick vapor-deposited gold layers on silicon enhances its room-temperature sub-band gap infrared absorption, as in the case of ion-implanted and PLM-treated silicon. The former approach offers reduced fabrication complexity and avoids implantation-induced lattice damage compared to ion implantation and pulsed laser melting, while exhibiting comparable optical absorptance. We additionally observed strong broadband absorptance enhancement in PLM samples made using 5- and 10-nm-thick gold layers. Raman spectroscopy and Rutherford backscattering analysis indicate that such an enhancement could be explained by absorption by a metastable, disordered and gold-rich surface layer. The sheet resistance and the diode electrical characteristics further elucidate the role of gold-supersaturation in silicon, revealing the promise for future silicon-based infrared device applications.

Radicals Are Required for Thiol Etching of Gold Particles.

PubMed

Dreier, Timothy A; Ackerson, Christopher J

2015-08-03

Etching of gold with an excess of thiol ligand is used in both synthesis and analysis of gold particles. Mechanistically, the process of etching gold with excess thiol is unclear. Previous studies have obliquely considered the role of oxygen in thiolate etching of gold. Herein, we show that oxygen or a radical initiator is a necessary component for efficient etching of gold by thiolates. Attenuation of the etching process by radical scavengers in the presence of oxygen, and the restoration of activity by radical initiators under inert atmosphere, strongly implicate the oxygen radical. These data led us to propose an atomistic mechanism in which the oxygen radical initiates the etching process. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Metal precursor induced shape controlled synthesis of gold nanostructures

NASA Astrophysics Data System (ADS)

Verma, Manoj; Kathy, Annu Dahiya; Kumar, P. Senthil

2018-05-01

Anisotropic gold nanoparticles have excellent properties which enables them to utilize in exciting applications in plasmonics as well as in nanophotonics, catalysis etc. In this report we have synthesized/tune shape of gold nanoparticles by utilizing in situ polymer halide interaction. Our quest for achieving shape control of gold nanoparticles succeeded even under ambient conditions by utilizing the mild but effective reducing power of versatile polymer, polyvinyl pyrrolidone(PVP) on different precursor more specifically on Hydrochloroauric acid and Potassiumbromoauric acid. The significant shape dependent optical plasmonic signature agrees in excellent manner with TEM observations as shown below. Moreover, as prepared gold nanocrystals having different morphology were studied with XRD measurements and a beautiful conclusion was drawn between crystallographic facets and shapes of gold nanoparticles.

Altered biodistribution of Ga-67 by intramuscular gold salts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moult, R.G.; Bekerman, C.

1989-11-01

The authors observed a deviation from the normal scintigraphic pattern of Ga-67 citrate biodistribution. An 8-year-old black girl with juvenile rheumatoid arthritis, who had been treated with intramuscular injections of gold salts, had a Ga-67 study as part of her workup. The study demonstrated no hepatic uptake, but showed elevated skeletal and renal activity. This characteristic biodistribution of Ga-67 may be due to inhibition of lysosomal enzymes by gold and/or to accumulation of gold in lysosomes. To study these possibilities, the authors reviewed the mechanisms of Ga-67 localization and gold metabolism. Alteration of the Ga-67 citrate scintigraphic pattern due tomore » earlier treatment with gold salts has not been reported previously.« less

Lithogeochemistry of Carlin-type gold mineralization in the Gold Bar district, Battle Mountain-Eureka trend, Nevada

USGS Publications Warehouse

Yigit, O.; Hofstra, A.H.

2003-01-01

The Gold Bar district contains five Carlin-type gold deposits and four resources for a combined gold endowment of 1.6 M oz [50 t]. The gold deposits are hosted in Devonian carbonate rocks below parautochthonous and allochthonous Paleozoic siliciclastic rocks emplaced during the Early Mississippian Antler orogeny. The district is in the Battle Mountain-Eureka trend, a long-lived structural feature that localized intrusions and ore deposits of different types and ages. The whole-rock geochemistry of four different mineralized and unmineralized Devonian carbonate rock units (two favorable and two unfavorable) were determined and interpreted in the context of the regional geology. A combination of basic statistics, R-mode factor analysis, isocon plots, and alteration diagrams were utilized to (1) identify favorable geochemical attributes of the host rocks, (2) characterize alteration and associated element enrichments and depletions, and (3) identify the mechanism of gold precipitation. This approach also led to the recognition of other types of alteration and mineralization in host rocks previously thought to be solely affected by Carlin-type mineralization. Unit 2 of the Upper Member of the Denay Formation, with the highest Al2O3, Fe2O3 and SiO2 contents and the lowest CaO content, is the most favorable host rock. Based on the high regression coefficients of data arrays on X-Y plots that project toward the origin, Al2O3 and TiO2 were immobile and K2O and Fe2O3 were relatively immobile during alteration and mineralization. Specific element associations identified by factor analysis are also prominent on isocon diagrams that compare the composition of fresh and altered equivalents of the same rock units. The most prominent associations are: Au, As, Sb, SiO2, TI, -CaO and -LOI, the main gold mineralizing event and related silicification and decalcification; Cd, Zn, Ag, P, Ni and Tl, an early base metal event; and MgO, early dolomitization. Alteration diagrams

Perchlorate isotope forensics

USGS Publications Warehouse

Böhlke, J.K.; Sturchio, N.C.; Gu, B.; Horita, J.; Brown, G.M.; Jackson, W.A.; Batista, J.; Hatzinger, P.B.

2005-01-01

Perchlorate has been detected recently in a variety of soils, waters, plants, and food products at levels that may be detrimental to human health. These discoveries have generated considerable interest in perchlorate source identification. In this study, comprehensive stable isotope analyses ( 37Cl/35Cl and 18O/17O/ 16O) of perchlorate from known synthetic and natural sources reveal systematic differences in isotopic characteristics that are related to the formation mechanisms. In addition, isotopic analyses of perchlorate extracted from groundwater and surface water demonstrate the feasibility of identifying perchlorate sources in contaminated environments on the basis of this technique. Both natural and synthetic sources of perchlorate have been identified in water samples from some perchlorate occurrences in the United States by the isotopic method. ?? 2005 American Chemical Society.

Method for aqueous gold thiosulfate extraction using copper-cyanide pretreated carbon adsorption

DOEpatents

Young, Courtney; Melashvili, Mariam; Gow, Nicholas V

2013-08-06

A gold thiosulfate leaching process uses carbon to remove gold from the leach liquor. The activated carbon is pretreated with copper cyanide. A copper (on the carbon) to gold (in solution) ratio of at least 1.5 optimizes gold recovery from solution. To recover the gold from the carbon, conventional elution technology works but is dependent on the copper to gold ratio on the carbon.

Synthesis and catalytic activity of the metastable phase of gold phosphide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernando, Deshani; Nigro, Toni A. E.; Dyer, I. D.

Recently, transition metal phosphides have found new applications as catalysts for the hydrogen evolution reaction that has generated an impetus to synthesize these materials at the nanoscale. In this work, Au2P3 was synthesized utilizing the high temperature decomposition of tri-n-octylphosphine as a source of elemental phosphorous. Gold nanorods were used as morphological templates with the aim of controlling the shape and size of the resulting gold phosphide particles. We demonstrate that the surface capping ligand of the gold nanoparticle precursors can influence the purity and extent to which the gold phosphide phase will form. Gold nanorods functionalized with 1-dodecanethiol undergomore » digestive ripening to produce discrete spherical particles that exhibit reduced reactivity towards phosphorous, resulting in low yields of the gold phosphide. In contrast, gold phosphide was obtained as a phase pure product when cetyltrimethylammonium bromide functionalized gold nanorods are used instead. The Au2P3 nanoparticles exhibited higher activity than polycrystalline gold towards the hydrogen evolution reaction.« less

Characteristics of pulse gold vapor laser outlined

NASA Astrophysics Data System (ADS)

1981-09-01

Several dozen laser oscillating spectra lines were found within the very broad spectral wavelengths from infrared to ultraviolet. Laser studies of gold vapor were carried out and a pulsed laser of gold atoms of an operating wavelength of 6278 angstroms was obtained.

Morphology-selective synthesis of polyhedral gold nanoparticles: what factors control the size and morphology of gold nanoparticles in a wet-chemical process.

PubMed

Lee, Jong-Hee; Kamada, Kai; Enomoto, Naoya; Hojo, Junichi

2007-12-15

Polyhedral gold nanoparticles below 100 nm in size were fabricated by continuously delivered HAuCl(4) and PVP starting solutions into l-ascorbic acid aqueous solution in the presence of gold seeds, and under addition of sodium hydroxide (NaOH). By continuously delivered PVP and HAuCl(4) starting solutions in the presence of gold seed, the size and shape of polyhedral gold were achieved in relatively good uniformity (particle size distribution=65-95 nm). Morphological evolution was also attempted using different growth rates of crystal facets with increasing reaction temperature, and selective adsorption of PVP.

Gold deposits and occurrences of the Greater Caucasus, Georgia Republic: Their genesis and prospecting criteria

USGS Publications Warehouse

Kekelia, S.A.; Kekelia, M.A.; Kuloshvili, S.I.; Sadradze, N.G.; Gagnidze, N.E.; Yaroshevich, V.Z.; Asatiani, G.G.; Doebrich, J.L.; Goldfarb, R.J.; Marsh, E.E.

2008-01-01

trapping pressures of 0.2 to 0.5??kbar. Ore-forming fluids, with approximately 5 to 20??mol% non-aqueous gas, evolved from N2-dominant to CO2-dominant during evolution of the hydrothermal system. ??34S values of + 1 to + 4??? for ore-related sulfides at Zopkhito are consistent with a sedimentary rock source for the sulfur, and ??18O quartz measurements of 16 to 21??? are consistent with either a magmatic or metamorphic fluid. More than 60 gold-bearing lodes and placers in the Svaneti district occur along the thrust between the Southern Slope and Main Zones. Lode gold potential was first recognized in the historic placer district in the 1980s, with many auriferous quartz veins cutting Middle Jurassic igneous rocks. Brecciated veins in the 18??t Au Lukhra deposit cut a small granodioritic to dioritic stock; the latter intrudes Devonian schist immediately north of the thrust. Presently, there are three recognized ore zones in the deposit, with the most significant occurring over an area 140??m in length and 12??m-wide, with typical grades of 7 to 9??g/t Au. Reconnaissance fluid-inclusion studies of ore samples from the Lukhra deposit indicate minimum trapping temperatures of 220????C. Measurements of ??18Oquartz of about 10??? suggest buffering of isotopic composition by the igneous host rocks.

The history of gold therapy for tuberculosis.

PubMed

Benedek, Thomas G

2004-01-01

This is a historical study of the popularization of a medical therapy contrary to pertinent experimental findings. Presumably this circumstance reflects the desperation about tuberculosis: highly prevalent, highly fatal, and lacking any etiologically directed therapy. Gold compounds were introduced, based initially on the reputation of Robert Koch, who had found gold cyanide effective against M. tuberculosis in cultures, but not in experimentally infected animals. Treatment of pulmonary tuberculosis with these compounds was popularized, particularly by Danish physicians, in the mid-1920s, despite consistently negative experimental results, based on Paul Ehrlich's theories of antimicrobial drug effects. Difficulties in the design of interpretable clinical studies were soon recognized but also generally ignored, thus permitting data to be interpreted as favorable to antituberculous gold therapy. Eventually toxicity was considered to outweigh the alleged therapeutic benefit of all gold compounds. This resulted in their discard shortly before the introduction of streptomycin therapy.

Gold Nanoparticle Conjugation Enhances the Antiacanthamoebic Effects of Chlorhexidine

PubMed Central

Aqeel, Yousuf; Siddiqui, Ruqaiyyah; Anwar, Ayaz; Shah, Muhammad Raza

2015-01-01

Acanthamoeba keratitis is a serious infection with blinding consequences and often associated with contact lens wear. Early diagnosis, followed by aggressive topical application of drugs, is a prerequisite in successful treatment, but even then prognosis remains poor. Several drugs have shown promise, including chlorhexidine gluconate; however, host cell toxicity at physiologically relevant concentrations remains a challenge. Nanoparticles, subcolloidal structures ranging in size from 10 to 100 nm, are effective drug carriers for enhancing drug potency. The overall aim of the present study was to determine whether conjugation with gold nanoparticles enhances the antiacanthamoebic potential of chlorhexidine. Gold-conjugated chlorhexidine nanoparticles were synthesized. Briefly, gold solution was mixed with chlorhexidine and reduced by adding sodium borohydride, resulting in an intense deep red color, indicative of colloidal gold-conjugated chlorhexidine nanoparticles. The synthesis was confirmed using UV-visible spectrophotometry that shows a plasmon resonance peak of 500 to 550 nm, indicative of gold nanoparticles. Further characterization using matrix-assisted laser desorption ionization-mass spectrometry showed a gold-conjugated chlorhexidine complex at m/z 699 ranging in size from 20 to 100 nm, as determined using atomic force microscopy. To determine the amoebicidal and amoebistatic effects, amoebae were incubated with gold-conjugated chlorhexidine nanoparticles. For controls, amoebae also were incubated with gold and silver nanoparticles alone, chlorhexidine alone, neomycin-conjugated nanoparticles, and neomycin alone. The findings showed that gold-conjugated chlorhexidine nanoparticles exhibited significant amoebicidal and amoebistatic effects at 5 μM. Amoebicidal effects were observed by parasite viability testing using a Trypan blue exclusion assay and flow-cytometric analysis using propidium iodide, while amoebistatic effects were observed using growth

Plasmonic Horizon in Gold Nanosponges.

PubMed

Vidal, Cynthia; Sivun, Dmitry; Ziegler, Johannes; Wang, Dong; Schaaf, Peter; Hrelescu, Calin; Klar, Thomas A

2018-02-14

An electromagnetic wave impinging on a gold nanosponge coherently excites many electromagnetic hot-spots inside the nanosponge, yielding a polarization-dependent scattering spectrum. In contrast, a hole, recombining with an electron, can locally excite plasmonic hot-spots only within a horizon given by the lifetime of localized plasmons and the speed carrying the information that a plasmon has been created. This horizon is about 57 nm, decreasing with increasing size of the nanosponge. Consequently, photoluminescence from large gold nanosponges appears unpolarized.

Polyaspartic acid functionalized gold nanoparticles for tumor targeted doxorubicin delivery.

PubMed

Khandekar, Sameera V; Kulkarni, M G; Devarajan, Padma V

2014-01-01

In this paper, we present polyaspartic acid, a biodegradable polymer as a reducing and functionalizing agent for the synthesis of doxorubicin loaded gold nanoparticles by a green process. Gold nanoparticles were stable to electrolytes and pH. Secondary amino groups of polyaspartic acid enabled reduction of gold chloride to form gold nanoparticles of size 55 +/-10 nm, with face centered cubic crystalline structure as confirmed by UV, TEM, SAED and XRD studies. Cationic doxorubicin was readily loaded onto anionic polyaspartic acid gold nanoparticles by ionic complexation. Fluorescence studies confirmed doxorubicin loading while FTIR spectra confirmed ionic complexation. Doxorubicin loading onto polyaspartic acid gold nanoparticles was studied at doxorubicin/polyaspartic acid molar ratios 1:10 to 1:1. As the molar ratio tended to unity, although loading up to 60% was achieved, colloidal instability resulted and is attributed to effective covering of negative charges of polyaspartic acid. Stable doxorubicin loaded polyaspartic acid gold nanoparticles of 105 +/- 15.1 nm with doxorubicin loading of 23.85% w/w and zeta potential value of -28 +/- 0.77 mV were obtained at doxorubicin/polyaspartic acid molar ratio 1:10. Higher doxorubicin release rate from the doxorubicin loaded polyaspartic acid gold nanoparticles in an acid medium (i.e., pH 5.5) as compared to that in pH 7.4 and deionized water is a desirable characteristic for tumor targeted delivery. Enhanced cytotoxicity and 3 fold higher uptake of doxorubicin loaded polyaspartic acid gold nanoparticles as compared to doxorubicin solution were seen in MCF-7 breast cancer cells while polyaspartic acid gold nanoparticles revealed no cytotoxicity confirming safety. Prominent regression in tumor size in-vivo in fibrosarcoma tumor induced mouse model was observed upto 59 days with doxorubicin loaded polyaspartic acid gold nanoparticles while doxorubicin solution treated mice showed regrowth beyond 23rd day. Moreover, a

Micrometeorite penetration effects in gold foil

NASA Technical Reports Server (NTRS)

Hallgren, D. S.; Radigan, W.; Hemenway, C. L.

1976-01-01

Penetration structures revealed by a Skylab experiment dealing with exposure of single and double layers of 500-800 A thick gold foil to micrometeorites are examined. Examination of all double-layered gold foils revealed that particles producing holes of any type greater than 5 microns in diameter in the first foil break up into many fragments which in turn produce many more holes in the second foil. Evidence of an original particle is not found on any stainless steel plate below the foils, except in one instance. A precise relationship between the size of the event and the mass of the particle producing it could not be determined due to the extreme morphological variety in penetration effects. Fluxes from gold foil and crater experiments are briefly discussed.

The isotopic effects of electron transfer: An explanation for Fe isotope fractionation in nature

NASA Astrophysics Data System (ADS)

Kavner, Abby; Bonet, François; Shahar, Anat; Simon, Justin; Young, Edward

2005-06-01

Isotope fractionation of electroplated Fe was measured as a function of applied electrochemical potential. As plating voltage was varied from -0.9 V to 2.0 V, the isotopic signature of the electroplated iron became depleted in heavy Fe, with δ 56Fe values (relative to IRMM-14) ranging from -0.18(±0.02) to -2.290(±0.006) ‰, and corresponding δ 57Fe values of -0.247(±0.014) and -3.354(±0.019) ‰. This study demonstrates that there is a voltage-dependent isotope fractionation associated with the reduction of iron. We show that Marcus's theory for the kinetics of electron transfer can be extended to include the isotope effects of electron transfer, and that the extended theory accounts for the voltage dependence of Fe isotope fractionation. The magnitude of the electrochemically-induced fractionation is similar to that of Fe reduction by certain bacteria, suggesting that similar electrochemical processes may be responsible for biogeochemical Fe isotope effects. Charge transfer is a fundamental physicochemical process involving Fe as well as other transition metals with multiple isotopes. Partitioning of isotopes among elements with varying redox states holds promise as a tool in a wide range of the Earth and environmental sciences, biology, and industry.