Статті в журналах: "Precious opal"

1

Bellacera, Carole. "The Precious Opal." Appalachian Heritage 18, no. 4 (1990): 56–58. http://dx.doi.org/10.1353/aph.1990.0029.

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2

Bootkul, Duangkhae, and Sawet Intarasiri. "Development of Glass-Ceramics from Soda Lime Silica Glass Waste by Direct Sintering Method for Opal Imitation." Key Engineering Materials 751 (August 2017): 397–402. http://dx.doi.org/10.4028/www.scientific.net/kem.751.397.

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Natural opal, an amorphous, hydrous form of silica (SiO2-n-H2O), has been one of the favored precious gemstones for many centuries. Though beautiful, opal is very fragile and is damaged quite easily. Thus, opals of all varieties have been synthesized experimentally and commercially. The objective of this project was to synthesize and to compare crystalline opals. In this work, the development of powder sintered glass ceramics process based on soda lime silica glass waste with metal oxide powder enable jewelry applications. The substantial viscous flow of the glass led to dense products for rapid treatments at relatively low temperatures (900–1,000°C), whereas glass/metal powder interactions resulted in the formation of color agent crystals, provide enhancing optical properties. Several techniques were applied for characterization of the ingots. The chemical analysis was performed by Energy Dispersive X-ray Fluorescence (ED-XRF). The mineralogical compositions of the samples were determined by X-ray diffraction analysis. Raman spectroscopy was applied for optical characterization. The results were compared with a natural common opal. The present investigation demonstrated that the common opal with both color and colorless appearance can be synthesized by the technique, as the crystalline phase of opal structure was identified by XRD measurement. There is a great potential for such materials with novel functionalities for artificial gemstone application, i.e. opal forming.

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3

Ejigu, Assamen Ayalew, Desalegn Gezahegn Ketemu, Sisay Awoke Endalew, and Wudu Yimer Assen. "Characterization of Natural Precious Opal Using Modern Spectroscopic Techniques in Ethiopia: The Case from Delanta, South Wollo." Journal of Spectroscopy 2022 (August 24, 2022): 1–8. http://dx.doi.org/10.1155/2022/3194151.

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The purpose of this study was to conduct characterization of the Delanta natural opals obtained from different mining sites. Characteristics of opals mined from different geological locality were examined. Six opal samples were collected from the main mining sites found in different localities from Delanta district and characterized using Fourier infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and inductively coupled plasma optical emission spectroscopy characterization techniques. The scanning electron microscope micrographs showed that all the samples have relatively semi-ordered (semi-crystalline) structural surface morphologies composed of tiny spherical particles. The performed X-ray diffraction analysis showed that the samples have main peaks at 20.0°, 21.72°, 36.9°, 44.0°, and 56.85° with 2 θ values between 10° and 60°. The five diffraction peaks are characteristic peak positions of opal-CT. The Fourier infrared spectroscopy data indicated that the prominent absorption bands for cristobalite at 620 and 520 cm−1 were absent from the spectrum. Instead, three bands in the low frequency region centered at 470, 791, and 1100 cm−1 were observed because of the absorptions of the silicate framework (Si-O) vibrations. red−1−1 Moreover,spectra feature of molecular water and silanol (Si-OH) groups with broadabsorption band centered around 3447 cm-1 andthe O-H stretching vibration of watermolecules and water bending vibration withan absorption band centered around 1634 cm-1were observed.. These values were consistently comparable with literature data. The inductively coupled plasma optical emission spectroscopy analysis showed that four main impurities (>500 parts per million) were Ca (∼1,750–4,730 parts per million), Al (∼1,990–4,319 parts per million, K (∼1,670–3,895 parts per million), and Na (∼595–3,723 parts per million). In general, this study revealed that all opal samples taken from six mining sites in Delanta district were found to be opal-CT as per the results of X-ray diffraction and Fourier infrared spectroscopy investigations.

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4

Guo, Ying, Zhi Xuan Dai, and Hong Juan Sun. "The Correlation between Play-of-Color Effect and SiO₂ Cavities Size of Australian Blue Opal." Key Engineering Materials 492 (September 2011): 366–69. http://dx.doi.org/10.4028/www.scientific.net/kem.492.366.

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Its play-of-color effect of Australian opal makes it unique and much more precious than any other gemstones in the world. More than 50 Australian opals were chosen to conduct the experiments, including boulder and black opals with blue-green to blue-purple color. Spectropotometer Color i5 was used to analyze the color of opal samples with CIE L*a*b* uniform color space. Dominant wavelength was put into comparison with hue angle. SEM and AFM were the main means to analyze the internal structure of opal samples, and the diameter and size of cavities of SiO2 were measured and discussed. It is revealed that the hue angle of blue-purple opal is 302.15° with 449nm as its dominant wavelength, and so the size of SiO2 cavities in the sample is about 155.32nm; the hue angle of blue opals is between (256°, 286°) with the dominant wavelength between (471nm, 485nm), and so their size of SiO2 cavities is between (154.35nm, 182.54nm); the hue angle of blue-green opal is between (183°, 213°) with the dominant wavelength between (489nm, 500nm) and so their size of SiO2 cavities is between (172.95nm, 193.66nm). Besides, the diameter and size of SiO2 cavities were analyzed against the dominant wavelength, hue angle, lightness, and saturation to reveal their correlation. It is indicated that the diameter and size of SiO2 cavities are in positive correlation with the dominant wavelength, but negative correlation with the hue angle. As the diameter and size of SiO2 cavities grow, the dominant wavelength increases but the hue angle decreases. Also they are in positive correlation with lightness but their correlation with saturation was not discovered.

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5

Stewart, A. M., Lewis T. Chadderton, and Brian R. Senior. "Self-assembly in the growth of precious opal." Journal of Crystal Growth 312, no. 3 (January 2010): 391–96. http://dx.doi.org/10.1016/j.jcrysgro.2009.09.042.

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6

Potapov, V. V., and D. V. Kamashev. "Synthesis of precious opal in a hydrothermal solution." Glass Physics and Chemistry 32, no. 1 (January 2006): 89–98. http://dx.doi.org/10.1134/s1087659606010123.

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7

Palgutová, Silvia, and Ľubomír Štrba. "Geoheritage of the Precious Opal Bearing Zone in Libanka Mining District (Slovakia) and Its Geotourism and Geoeducation Potential." Land 11, no. 12 (December 14, 2022): 2293. http://dx.doi.org/10.3390/land11122293.

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The northern part of the Slanské Vrchy Mountains, in Slovakia, within the territory of Dubnik Opal Mines, is considered to be the historical source of opal, including the opal known to the Romans. Dubnik precious opal mineralization originating from post-magmatic hydrothermal fluids based on its values should be recognized as an area of global importance. Geological processes that are connected to Neogene volcanic activity took place in the territory of the Dubnik Opal Mines and resulted in the formation of various geological products and processes represented by polymetallic mineral formation, opal formation, antimonite formation, and mineralization of the supergene stage, as well as the stratovolcano rock environment, which are of geoheritage significance. Remnants of intensive mining activity that took place during the past 2000 years provide opportunities for visitors to explore, study, and appreciate this unique geological heritage of international importance. However, geo-interpretation aimed at the general public (the largest group of potential visitors from sustainable geotourism development) and research on (geo)tourism and/or geoheritage for tourism purposes, as discussed in this paper, are lacking.

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8

Dickson, B. L. "Which water formed Australian sediment-hosted precious and potch opal?" Australian Journal of Earth Sciences 66, no. 5 (March 24, 2019): 645–55. http://dx.doi.org/10.1080/08120099.2019.1572032.

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9

Chauviré, Boris, Benjamin Rondeau, Francesco Mazzero, and Dereje Ayalew. "The Precious Opal Deposit At Wegel Tena, Ethiopia: FormationViaSuccessive Pedogenesis Events." Canadian Mineralogist 55, no. 4 (July 2017): 701–23. http://dx.doi.org/10.3749/canmin.1700010.

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10

Pewkliang, B., A. Pring, and J. Brugger. "THE FORMATION OF PRECIOUS OPAL: CLUES FROM THE OPALIZATION OF BONE." Canadian Mineralogist 46, no. 1 (February 1, 2008): 139–49. http://dx.doi.org/10.3749/canmin.46.1.139.

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11

Taksavasu, Tadsuda, Thomas Monecke, and T. Reynolds. "Textural Characteristics of Noncrystalline Silica in Sinters and Quartz Veins: Implications for the Formation of Bonanza Veins in Low-Sulfidation Epithermal Deposits." Minerals 8, no. 8 (August 2, 2018): 331. http://dx.doi.org/10.3390/min8080331.

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Silica sinters forming at the Wairakei geothermal power plant in New Zealand are composed of noncrystalline opal-A that deposited rapidly from cooling geothermal liquids flashed to atmosphere. The sinter is laminated with alternating layers of variably compacted silicified filamentous microbes encased by chains of fused silica microspheres. Microscopic inspection of bonanza quartz vein samples from the Buckskin National low-sulfidation epithermal precious metal deposit in Nevada showed that colloform bands in these veins exhibit relic microsphere textures similar to those observed in the silica sinters from the Wairakei power plant. The textural similarity suggests that the colloform bands were originally composed of noncrystalline opal-A that subsequently recrystallized to quartz. The colloform bands contain dendrites of electrum and naumannite that must have grown in a yielding matrix of silica microspheres deposited at the same time as the ore minerals, implying that the noncrystalline silica exhibited a gel-like behavior. Quartz bands having other textural characteristics in the crustiform veins lack ore minerals. This suggests that ore deposition and the formation of the colloform bands originally composed of compacted microspheres of noncrystalline silica are genetically linked and that ore deposition within the bonanza veins was only episodic. Supersaturation of silica and precious metals leading to the formation of the colloform bands may have occurred in response to transient flashing of the hydrothermal liquids. Flashing of geothermal liquids may thus represent a key mechanism in the formation of bonanza precious metal grades in low-sulfidation epithermal deposits.

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12

Temerov, Filipp, Bright Ankudze, and Jarkko J. Saarinen. "TiO2 inverse opal structures with facile decoration of precious metal nanoparticles for enhanced photocatalytic activity." Materials Chemistry and Physics 242 (February 2020): 122471. http://dx.doi.org/10.1016/j.matchemphys.2019.122471.

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13

Rey, P. F. "Remarks on the age of precious opal in central Australia: reply to comment by Bruce Dickson." Australian Journal of Earth Sciences 60, no. 8 (December 2013): 835–38. http://dx.doi.org/10.1080/08120099.2013.870229.

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14

Kaczan, Wojciech, Jan Kudełko, and Herbert Wirth. "Szklary nickel deposit — a review and introduction to attempts in hydrometallurgical processing." Mineral Economics 34, no. 2 (May 12, 2021): 315–22. http://dx.doi.org/10.1007/s13563-021-00269-0.

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AbstractSzklary Massif is situated about 60 km from Wrocław (southwestern Poland) and around 7 km from Ząbkowice Śląskie. The history of raw materials in this region started in the fifteenth century with the discovery of precious minerals like chrysoprase, chalcedony, and opal. The exploitation of nickel ore in this region started in the nineteenth century and was conducted with few stops until 1983. The remaining 17.21 mln mg of ore with 125,000 mg of nickel might be a chance to satisfy rising demand for raw materials used to develop electromobility. One of the crucial aspects regarding possible investment is the processing of ore. The pilot tests show the efficient use of heap leaching. The authors provide the future project in Szklary within the framework of circular economy.

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15

Smallwood, A., P. S. Thomas, A. S. Ray, and P. Šimon. "Application of a Fickian model of diffusion to the dehydration of graded specimens of a precious Australian sedimentary opal derived from Coober Pedy." Journal of Thermal Analysis and Calorimetry 97, no. 2 (June 10, 2009): 685–88. http://dx.doi.org/10.1007/s10973-009-0076-6.

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16

Hoskins, Andrew, Shekerah Primus, Mary Yazdani, Kimberley Gutierrez, Benjamin Foret, Fabien Bernard, and Rémi Dangla. "Abstract 2932: The 6-color naica® system: a digital PCR platform and workflow for high multiplex genetic detection and analysis." Cancer Research 82, no. 12_Supplement (June 15, 2022): 2932. http://dx.doi.org/10.1158/1538-7445.am2022-2932.

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Abstract There are several molecular platforms routinely used to investigate genomic material. Quantitative polymerase chain reaction (qPCR) is ubiquitously used because of the ease of use and the precision however, it does not offer high multiplexing. While digital PCR (dPCR) is known for increased precision and sensitivity, most digital PCR platforms provide the same level of multiplexing as qPCR. Next-generation sequencing (NGS) is less precise than qPCR or dPCR and but has the highest multiplexing capability of the three technologies. Conventional digital PCR systems have been limited by the number of instruments required to conduct the workflow, time-to-result compared to qPCR, and level of multiplexing as compared to next-generation sequencing (NGS). Crystal Digital PCR™ and the naica system is a next-generation digital PCR platform that simplifies the number of instruments in the workflow, speeds up the time of results to less than 3 hours, and increases the number of detection colors to 6 spectrally distinct channels. By using a combination of dual-labelled fluorescent probes, multiplexed digital PCR provides a simple solution that makes it possible to use less of a precious sample when faced with limited quantity without sacrificing sensitivity. The naica system workflow utilizes microfluidic consumables, such as the Sapphire chip for high sensitivity applications, and the Opal chip for higher throughput studies. All reagents including primers and probes, master mix, and sample are inputted into the chips in one single loading step. Chips are transferred to the Geode instrument, where the sample is partitioned into a 2D-monolayer of droplet crystals and where all targets are amplified. After the PCR program has been completed, the same chips are then loaded into the Prism6 imager which detects all targets across 6 fluorescent channels and outputs an image of all droplets in a sample. Finally, Crystal Miner analysis software can be used to analyze and decipher the quantifications and expression of all targets in the assay. The 6-color naica system allows for high multiplex detection of targets previously unattainable by conventional digital PCR systems. With this advent, genomic scientists have an additional platform in the molecular toolbox that supports seamless assay development of oncology biomarker assays for gene expression, rare target detection, and liquid biopsy applications. Citation Format: Andrew Hoskins, Shekerah Primus, Mary Yazdani, Kimberley Gutierrez, Benjamin Foret, Fabien Bernard, Rémi Dangla. The 6-color naica® system: a digital PCR platform and workflow for high multiplex genetic detection and analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2932.

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17

Vysotskiy, S. V., A. V. Ignatiev, A. G. Khlestunova, T. A. Velivetskaya, and A. S. Okrugin. "Peculiarities of the oxygen isotope ratio in precious opals." Russian Journal of Pacific Geology 7, no. 6 (November 2013): 427–30. http://dx.doi.org/10.1134/s1819714013060079.

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18

McOrist, G. D., and A. Smallwood. "Trace elements in precious and common opals using neutron activation analysis." Journal of Radioanalytical and Nuclear Chemistry 223, no. 1-2 (September 1997): 9–15. http://dx.doi.org/10.1007/bf02223356.

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19

Vysotskiy, S. V., N. G. Galkin, A. V. Barkar, E. A. Chusovitin, and A. A. Karabtsov. "Hydrothermal precious opals of the Raduzhnoe deposit, north Primorye: The nature of the opalescence." Russian Journal of Pacific Geology 4, no. 4 (August 2010): 347–54. http://dx.doi.org/10.1134/s1819714010040068.

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20

Povarennykh, M. Yu, A. V. Knot’ko, E. N. Matvienko, P. Yu Plechov, A. A. Burmistrov, and V. L. Luksha. "Peculiarities of the irisation in precious opals in view of their mosaic–cluster (frustumation) inner fabric." Doklady Earth Sciences 467, no. 2 (April 2016): 415–17. http://dx.doi.org/10.1134/s1028334x1604022x.

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21

Chauviré, Boris, Benjamin Rondeau, Anne Alexandre, Sarah Chamard-Bois, Carole La, and Francesco Mazzero. "Pedogenic origin of precious opals from Wegel Tena (Ethiopia): Evidence from trace elements and oxygen isotopes." Applied Geochemistry 101 (February 2019): 127–39. http://dx.doi.org/10.1016/j.apgeochem.2018.12.028.

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22

Warren, Graeme. "Mesolithic Montology." Open Archaeology 8, no. 1 (January 1, 2022): 132–44. http://dx.doi.org/10.1515/opar-2022-0227.

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Abstract This article focuses on the Mesolithic occupation of mountain environments in Europe. The montane Mesolithic is a important aspect of the Mesolithic as a whole, but neither its significance nor its potential is fully recognised. Evidence also suggests that we have not communicated this to the wider interdisciplinary community of mountain researchers – a field sometimes known as montology – which is dominated by models of human behaviour in mountains drawn from agricultural examples. Leading publications in the latter field have suggested that human use of mountains can be understood as structured by three key themes: resources, valuable minerals and precious stones, and the cultural importance of mountains. These themes are used to review the Mesolithic record.

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23

Tsunekawa, S., Yu A. Barnakov, V. V. Poborchii, S. M. Samoilovich, A. Kasuya, and Y. Nishina. "Characterization of precious opals: AFM and SEM observations, photonic band gap, and incorporation of CdS nano-particles." Microporous Materials 8, no. 5-6 (March 1997): 275–82. http://dx.doi.org/10.1016/s0927-6513(96)00089-2.

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24

Squitieri, Andrea, Silvia Amicone, Ada Dinckal, Mark Altaweel, Shira Gur-Arieh, Jens Rohde, Jean-Jacques Herr, Sophie Pietsch, and Christopher Miller. "A Multi-Method Study of a Chalcolithic Kiln in the Bora Plain (Iraqi Kurdistan): The Evidence From Excavation, Micromorphological and Pyrotechnological Analyses." Open Archaeology 8, no. 1 (January 1, 2022): 853–72. http://dx.doi.org/10.1515/opar-2022-0265.

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Abstract Pyrotechnology has always been a core topic in the archaeological debate concerning phases of deep cultural transformations, such as the Chalcolithic period in the Near East (c. 6000–3500 BC). However, previous studies on pyrotechnological installations, such as pottery kilns, pertaining to this period, have often been mainly descriptive, with a limited use of archaeometric investigations. This work presents a multi-method investigation of a Chalcolithic kiln recently discovered in the Bora Plain (part of the larger Peshdar Plain, in Iraqi Kurdistan), which combines stratigraphic analysis, pyrotechnological, micromorphological, and micro-remains analyses. Since this kiln represents the first Chalcolithic architectural feature excavated in the Bora Plain, this work offers precious insights into the pyrotechnology of the period, which is still relatively poorly understood, through the reconstruction of the kiln’s use and abandonment processes. The analytical outputs can be used to compare with other Near East kilns from the Chalcolithic and later periods.

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25

Estrada Alvarez, Silvia Adriana, Isabella Guger, Jana Febbraro, Ayse Turak, Hong-Ru Lin, Yolanda Salinas, and Oliver Brüggemann. "Synthesis and Spatial Order Characterization of Controlled Silica Particle Sizes Organized as Photonic Crystals Arrays." Materials 15, no. 17 (August 25, 2022): 5864. http://dx.doi.org/10.3390/ma15175864.

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The natural occurrence of precious opals, consisting of highly organized silica particles, has prompted interest in the synthesis and formation of these structures. Previous research has shown that a highly organized photonic crystal (PhC) array is only possible when it is based on a low polydispersity index (PDI) sample of particles. In this study, a solvent-only variation method is used to synthesize different sizes of silica particles (SiPs) by following the traditional sol-gel Stöber approach. The controlled rate of the addition of the reagents promoted the homogeneity of the nucleation and growth of the spherical silica particles, which in turn yielded a low PDI. The opalescent PhC were obtained via self-assembly of these particles using a solvent evaporation method. Analysis of the spatial statistics, using Voronoi tessellations, pair correlation functions, and bond order analysis showed that the successfully formed arrays showed a high degree of quasi-hexagonal (hexatic) organization, with both global and local order. Highly organized PhC show potential for developing future materials with tunable structural reflective properties, such as solar cells, sensing materials, and coatings, among others.

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Oliver, Roger Clive, Muhali Olaide Jimoh, and Charles Petrus Laubscher. "Germination ecology of three Asteraceae annuals Arctotis hirsuta, Oncosiphon suffruticosum, and Cotula duckittiae in the winter-rainfall region of South Africa: A review." Open Agriculture 7, no. 1 (January 1, 2022): 656–67. http://dx.doi.org/10.1515/opag-2022-0115.

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Abstract Asteraceae annuals from South Africa’s winter-rainfall region often exhibit poor germination, and it is a challenge to establish a garden display using fresh seeds from the wild. Arctotis hirsuta (Harv.) Beauvard is a popular ornamental, Oncosiphon suffruticosum (L. Bolus) K. Bremer & Humphries is important in traditional medicine, and Cotula duckittiae (L. Bolus) K. Bremer & Humphries has a vulnerable (VU) status on the red list of South African plants. C. duckittiae is teetering on the brink of extinction in a few localities on severely threatened ecosystems due to continued pressure on land for housing developments and invasive aliens. At present, there is no knowledge of O. suffruticosum being cultivated exclusively for its healing properties. The successful cultivation of this species may allow it to fulfil not only a more acute medicinal role in society but also in the economy to create precious job opportunities. The potential to develop or improve certain plant breeding lines of A. hirsuta commercially, besides just normal wild forms of these species at the Kirstenbosch National Botanical Garden, is huge. This, in addition to the ongoing pressure exerted on wild populations of C. duckittiae, warrants investigations into aspects of germination ecology of this VU species of the West Coast.

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Schiffman, Marlene. "Sources for Central and Eastern European Jewish History: The Louis Lewin Collection at Yeshiva University." Judaica Librarianship 11, no. 1 (January 1, 2003): 7–26. http://dx.doi.org/10.14263/2330-2976.1122.

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The Louis Lewin Collection of archival materials in the Rare Book Room of Yeshiva University comprises some 400 boxes of historical records on the Jews in Poland, Germany, and the Czech Republic. Lewin (1868–1941) was a rabbi and Jewish historian in Poland between the Wars and a proponent of the Wissenschaft des Judentums, “Science of Judaism,” movement in Jewish scholarship. The documents Lewin collected are of great historical value for their description of Jewish life in Europe, the history of Judaism, and Hebrew language and literature. While some records are original documents, others were copied by hand by Lewin from non-Jewish repositories in state or municipal archives. Not only are these documents precious for their historical value, but they are unique survivors of the devastation of World War II. Most of the records of these communities in Poland and Germany were obliterated, and the communities themselves disappeared. All that now exists are the copies that Louis Lewin preserved. Most items in this unique collection have been cataloged, and the rest are being worked on. The catalog records can be found in the Yeshiva University Library OPAC and on RLIN.

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Manrique-Ortega, Mayra Dafne, Pieterjan Claes, Valentina Aguilar-Melo, Malinalli Wong-Rueda, José Luis Ruvalcaba-Sil, Edgar Casanova-González, Emiliano Melgar, and Reyna Solis. "Non-Invasive Characterization of Stone Artifacts from the Great Temple of Tenochtitlan, Mexico." MRS Proceedings 1656 (January 13, 2015): 293–307. http://dx.doi.org/10.1557/opl.2015.2.

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ABSTRACTThe Museum of the Great Temple of Tenochtitlan in Mexico City holds a collection of several thousands of polished stone artifacts that were excavated and identified as temple offerings. These can stratigraphically be related to the sequential construction stages (II-VII) of the ceremonial area of the Aztec capital from the foundation of the city in 1325 to 1521, when the Spaniards conquered the city. A non-destructive investigation of the elemental and chemical composition of these archaeological artifacts helps us to understand the provenance of these pieces, their use and the specific mineralogical choice for these artifacts as well as more information regarding trade routes relevant to the development of the Aztec empire. A mineralogical analysis of, in total, 450 stone artifacts was carried out using infrared spectroscopy (FTIR) and X-ray Fluorescence (XRF). From this, eighty-five pieces were selected according to their excavation location, either in the Great Temple itself or in the surrounding buildings, as well as to represent the different construction stages of the area (this is part of a World Heritage Site). The resulting mineralogical and chemical information was related to possible mineral resources that were controlled and used as the empire expanded. Artifacts made from high-status semi-precious minerals, like jadeite and turquoise, are found to be concentrated in the central buildings and in the Great Temple itself, but also in the later construction periods of the area.

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Cerecedo, E., V. Rodríguez, P. D. Andrade, E. Salinas, J. Hernández, and A. Arenas. "Chemical Characterization of a Mineral Deposit of Economic Interest." MRS Proceedings 1766 (2015): 115–22. http://dx.doi.org/10.1557/opl.2015.418.

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ABSTRACTChemical and structural characterization of four representative samples of an ore deposit located in the eastern of Hidalgo State was carried out. According with the results, it could be appreciate some areas showing silicified zones with abundant amounts of disseminated pyrites that are part of a rock unit from early Jurassic consisting in inter - bedded black shales and sandstones. Thus, the contents of base metal were greater than 30 ppm Zn and 9 ppm Cu. Chemical analysis of rock gave the following results; 82 ppm of Ba, 1.64 % Wt. Fe, 0.08 % Wt. Ti, 40.8 % Wt. Si, 20 ppm of Ce, 2.2 ppm Co, 30 ppm Cr, 2.7 ppm Cs, 0.9 ppm Er, 2.5 ppm Ga, 1.6 ppm Gd , 1.5 ppm Ge, 9 ppm La, 71 ppm Li, 104 ppm Mn, 10 ppm Nd , 17 ppm Rb, 2 ppm Se, 9 ppm Sr, 10 ppm Ta, 6 ppm Te, 28 ppm V, 9 ppm Y, and 0.7 ppm Yb, among others. Finally, the values found for precious metals, were; Au < 0.02 ppm, Pd <0.05 ppm, Pt <0.05 ppm. It was inferred that the low content of base metals in outcrop studied, are due to the alteration of the black shales. According to these results, we can consider a stratiform – type mineralization of Pb-Zn which could be prospective for SEDEX – Type deposit. By means of XRD, it was possible to identify; pyrite, chalcopyrite, pyrrhotite, and minor amounts of sphalerite and Co -Ni arsenide.

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Heinsch, MaryFran, Pamela B. Vandiver, Kyra Lyublyanovics, Alice M. Choyke, Chandra Reedy, Perry Tourtellotte, and Claudia Chang. "Ceramics at the Emergence of the Silk Road: A Case of Village Potters from Southeastern Kazakhstan during the Late Iron Age." MRS Proceedings 1656 (November 5, 2015): 251–81. http://dx.doi.org/10.1557/opl.2015.841.

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ABSTRACTBetween the fourth century B.C. and second century A.D., changes in climate, culture and commerce converged to extend networks of influence and intensify social stratification in communities situated along the Silk Road. The horse-riding nomads and agro-pastoralists of what is now Southeastern Kazakhstan were important actors in the unfolding of these events. The settlements and kurgan burials of the Saka and Wusun could be found dotting the alluvial fans north of the Tien Shan Mountains just a short time before Alexander the Great founded outposts in the Ferghana Valley and Chinese emissaries formalized relations with their periphery. In other words, the appearance of Iron Age Saka-Wusun sites anticipated the formation of the Silk Road’s northern branch and subsequently helped mediate long-distance relationships connecting East and West. Historical accounts appear to confirm the presence of the Saka and Wusun in this role, but there is much that remains unknown regarding relationships both within and across their communities. Typological variability in their material culture has fed speculation concerning their position within trade networks, but there has been very little in the way of materials analysis to test the validity of these assumptions.The ceramics recovered at Tuzusai near Almaty provide an excellent opportunity for examination of the impacts and implications of extended regional contacts throughout the region. Although no Persian or Chinese ceramic imports were identified, an extensive vocabulary of pot forms was locally produced. However, the pottery, particularly pitchers, drinking cups and bowls, and, especially with bright red surface decoration, is found in elaborate burial kurgans. The pottery is coarse, perhaps better called a “rock body” than a clay body, as very little clay is present. The frequency of sherds from the excavation (over 1000) and from surface survey is very low (e.g. 3 surface sherds for one-half days effort) compared with excavations in Southwest Asia or China. Rims are unusually worn. Thus, we suggest pottery was precious and high status, but difficult to make. A local survey of clay resources produced meager results. Tests showed that the finest sediments had perhaps 3% clay-sized particles. Among the adobe houses at Tuzusai is evidence of courtyard work areas for pottery production with fired remains of a possible firing pit or kiln and bone potting tools. Other courtyards were areas for dairying and spinning and some copper alloy and iron metal working. Our aim was to establish the life history, production sequences, status and uses of the pottery. Given our current understanding of local production resources and the technical difficulty associated with the production of thin walled forms using these materials, we suggest that these ceramics were high-status goods, many used in feasting activities, and valued not solely for their function in feasting activities, but for the labor and skill required to produce them. Study of the ceramics, clay sources, production methods, and decoration suggests greater social permeability of Saka-Wusun communities than was previously proposed and allows us to understand the formative dynamics of village along the Silk Road.

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31

Pacheco, Emily Barbosa Alves, Dyovana Sena Martins, and Marina Pereira Rocha. "Atividade antibacteriana in vitro de extratos etanólicos e aquosos de Schinus terebinthifolia (aroeira-vermelha) e Cymbopogon nardus (citronela) frente à Staphylococus epidermidis e Staphylococus aureus." Brazilian Journal of Health Review 5, no. 6 (December 19, 2022): 24872–88. http://dx.doi.org/10.34119/bjhrv5n6-236.

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A resistência bacteriana (RAM) é considerada um grave problema de saúde pública mundial, e tem ocasionado a dificuldade de tratamento de diferentes patologias microbiológicas. Segundo a Organização Pan-Americana da Saúde (OPAS) em 2021, a pandemia desencadeada pelo novo Sars-CoV tipo 2 elevou os índices de resistências microbiana, relacionado a intensa atividade hospitalar e uso de antimicrobianos, além da elevação no período de internação. A fim de buscar novas formas terapêuticas que rompam com a elevação de RAM, a busca por novos agentes terapêuticos a partir de plantas medicinais vem se tornando promissora. Dessa forma, dentre as plantas conhecidas com ação medicinal para o tratamento de doenças infecciosas, têm-se Schinus terebinthifolia (aroeira-vermelha) e Cymbopogon nardus (citronela) que possuem poucos dados na literatura sobre sua química e avaliação da atividade antibacteriana. Portanto, o presente trabalho visa avaliar o potencial inibitório dos extratos etanólicos e aquosos de S. terebinthinfolia e C. Nardus frente à S. aureus e S. epidermidis. Os extratos etanólicos e aquosos foram obtidos das folhas (citronela e aroeira-vermelha) e cascas (aroeira-vermelha). As concentrações estudadas foram de 1mg/mL, 0,5mg/mL e 0,25mg/mL para S.epidermidis e 5mg/mL, 1mg/mL e 0,5mg/mL para S. aureus. Não foi observada a inibição por nenhum dos extratos sejam folhas ou cascas para S. epidermidis. Por outro lado, para o patógeno S. aureus foi observado a inibição pelo extrato etanólico das folhas de aroeira-vermelha na contração de 1,0 mg/mL (halo inibibitório de 7mm) e em 5,0 mg/mL (halo de 9mm). Cabe ressaltar que o estudo demonstra que as espécies vegetais investigadas podem contribuir com a descoberta e desenvolvimento de novas terapias antimicrobianas. Entretanto, suas composições químicas detalhadas e suas atividades microbianas devem ser melhor exploradas para que se obtenha informações precisas sobre as espécies abordadas.

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Monecke, Thomas, T. James Reynolds, Tadsuda Taksavasu, Erik R. Tharalson, Lauren R. Zeeck, Mario Guzman, Garrett Gissler, and Ross Sherlock. "Natural growth of gold dendrites within silica gels." Geology, January 3, 2023. http://dx.doi.org/10.1130/g48927.1.

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High-grade ores in low-sulfidation epithermal precious metal deposits include banded quartz veins that contain gold dendrites. The processes by which dendrite growth takes place have been subject to debate for decades, especially given that these deposits are known to form from dilute thermal liquids that contain only trace amounts of gold. It is shown here that growth of gold dendrites in epithermal veins at the McLaughlin deposit in California (western USA) originally took place within bands of gel-like noncrystalline silica. The gel provided a framework for the delicate dendrites to form. The high permeability of the gel allowed the diffusion and advection of gold from the thermal liquids flowing across the top of the silica layers to the sites of crystal growth within the gel. Over time, the gel hardened to form opal-AG. This silica phase is thermodynamically unstable and recrystallized to quartz that has a distinct mosaic texture.

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Nishimura, Shun, Nao Yoshida, and Kohki Ebitani. "Bimetallic PdCu Nanoparticle Catalyst Supported on Hydrotalcite for Selective Aerobic Oxidation of Benzyl Alcohol." MRS Proceedings 1760 (2015). http://dx.doi.org/10.1557/opl.2015.58.

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ABSTRACTTo decrease the amount of precious metal usage for Pd-catalyzed aerobic alcohol oxidation, various amount of Cu-contained Pd bimetallic nanoparticle-supported solid base hydrotalcite catalyst (PdxCuy-PVP/HTs) were prepared and applied for aerobic benzyl alcohol oxidation. It was found that the addition of Cu atoms into Pd in the range of 0-40% provided a similar or a little superior activity to that of Pd100-PVP catalyst, whereas a large quantity of co-existence Cu (>40%) gradually decreased their activity of the catalyst. The aerobic benzyl alcohol oxidation over Pd80Cu20-PVP/HT served 77% yield and 95% selectivity towards benzaldehyde at 313 K for 5 h in toluene under O2 flow. X-ray adsorption spectroscopy (XAS) studies and scanning transmission electron microscopy-high angle annuar dark field (STEM-HAADF) with energy dispersive X-ray spectroscopy (EDS) analyses suggested that Cu atoms doping into Pd(0) NP influenced not only localized nanostructure but also oxidation state around Pd atoms. We suggested that substitution of precious metal with small amount of transition metals such as Cu lead to geometric/electronic changes in active sites would be one of nice strategies for reducing the cost for the catalyst in the oxidation process.

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34

Tian, Shipeng, Shaojun Liu, Feng Gao, Min Fan, and Jianguang Ren. "Preparation and Assessment of Superhydrophobic Organic-Inorganic Hybrid Coatings for Conservation of Yungang Grottoes." MRS Proceedings 1319 (2011). http://dx.doi.org/10.1557/opl.2011.736.

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ABSTRACTYungang Grottoes in Shanxi, China, which represent outstanding example of Chinese outdoor immovable stone artifacts, are precious world cultural heritage. In the present study, the preparation and assessment of superhydrophobic hybrid coatings with photocatalytic activity on the sandstone substrate collected from Yungang were explored preliminarily. The protection efficiency of coating is investigated by measuring the water-stone contact angles, water vapor permeability, water absorption, and resistance to acid and salt corrosion. Results show that the superhydrophobic organic-inorganic hybrid coatings with photocatalytic and self-cleaning properties are highly suitable for the conservation of stone monuments.

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Barone, Germana, Paolo Mazzoleni, Danilo Bersani, and Simona Raneri. "Portable XRF: A Tool for the Study of Corundum Gems." Open Archaeology 3, no. 1 (September 26, 2017). http://dx.doi.org/10.1515/opar-2017-0011.

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AbstractOrigin of gemstones is a key aspect not only in gemological field but also in Cultural Heritage studies, for the correct evaluation of precious artifacts. The studies on gems require the application of non-invasive and non-destructive methods; among them, portable spectroscopic techniques has been demonstrated as powerful tools, providing a fingerprint of gems for origin and provenance determination. In this study, portable XRF spectroscopy has been applied to test the potential of the technique for the origin determination of corundum gems. The obtained results allowed distinguishing natural and synthetic rubies and sapphires.

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36

Taki, Yuya, Zhenquan Tan, Satoshi Ohara, Takashi Itoh, Yoshiaki Nakano, Katsushi Fujii, and Masakazu Sugiyama. "Synthesis of CaMn2O4-related electrocatalyst for oxygen evolution electrode of water-splitting." MRS Proceedings 1640 (2014). http://dx.doi.org/10.1557/opl.2014.406.

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ABSTRACTWater-splitting by using electric power produced by solar cells is promising system to produce hydrogen without fossil fuels. Oxygen evolving catalyst is, however, major problem to prevent using this system widely because precious materials are used in the catalyst. Considering from the photosynthesis II of plants, the compound of Ca-Mn-O is one of the candidates for the oxygen evolving catalyst. In this study, the synthesis condition and the oxygen evolving electrocatalytic activity of CaMn2O4•xH2O are investigated. The overpotential at 0.1 mA/cm2 was 0.28 V when using the electrode of carbon paste and CaMn2O4•H2O with the weight ratio of 3:1.

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Mondal, Sujit K., Jason Rugolo, and Michael J. Aziz. "Alloy Oxide Electrocatalysts for Regenerative Hydrogen-Halogen Fuel Cell." MRS Proceedings 1311 (2011). http://dx.doi.org/10.1557/opl.2011.108.

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ABSTRACTStable, catalytically active, and inexpensive halogen electrodes are essential for the success of the regenerative hydrogen-halogen fuel cell as a competitive means of large-scale electricity storage. We report the synthesis and electrochemical testing of two novel electrode materials — ruthenium-cobalt and ruthenium-manganese alloy oxides. These alloys were fabricated by wet chemical synthesis methods as a coating on a titanium metal substrate and tested for chloride and bromide oxidation and for chlorine and bromine reduction. These alloy oxides exhibit high catalytic potency and good electrical conductivity good stability, while having a significantly reduced precious metal composition compared to commercial chloride oxidation electrodes made of the oxide of a ruthenium-titanium alloy. We tested alloys with Ru content as low as 1% that maintained good electrochemical activity. Stability tests indicate immeasurably small mass loss.

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Watteaux, Magali. "The Road Network in the Longue Durée: A Reading Key of the History of Territories." Open Archaeology 3, no. 1 (August 28, 2017). http://dx.doi.org/10.1515/opar-2017-0009.

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AbstractThe historical study of routes has long remained confined to the great Roman roads, to the modern royal roads and to the medieval pilgrimage routes. For fifteen years, the French school of Archaeogeography has revisited this research field in great depth, following the first intuitions of the archaeologist Eric Vion. The innovative idea ‒ at least because it leads to a questioning of our methods ‒ is to consider the current road network as the starting point of the analysis. It is the true object of research for the historianarchaeologist because it represents a solid legacy whose logic one must unravel. Because this story is closely integrated with urban, political and economic matters, the study of this inherited road network represents a precious reading key to understanding the history of the territories in the longue durée. In the frame of this paper, we propose to recall these methodological advances and to present a case study in Brittany, around the small town of Chateaugiron. By this example, we want to show that the archaeogeographical analysis and interpretation offer a scientific narrative based on the paradigms of complexity and resilience to contemporary societies in charge of our territories.

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Celano, U., T. Conard, T. Hantschel, and W. Vandervorst. "Probing the metal gate high k interactions by backside XPS and C-AFM." MRS Proceedings 1336 (2011). http://dx.doi.org/10.1557/opl.2011.1125.

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ABSTRACTThe metal gate high k interaction is one of the dominant processes influencing the electrical performance (Vt, charge accumulation,..) of advanced gate stacks. These interactions are influenced by the entire thermal budget and the presence of reactive elements (on top/ within the material gate) such that relevant measurements can only be performed after a full processing cycle and on a complete gate stack.In such cases the relevant metal gate high k interface is a buried interface located below the metal gate (+ Si cap) and is not accessible for standard characterization methods like x-ray photoemission spectroscopy (XPS) due the limited escape depth of the photoelectrons. Moreover the presence of a conductive metal gate prevents the application of techniques such as conductive atomic force microscopy (C-AFM), to probe the local distribution of the defects, trapping sites and local degradation upon stressing. XPS in combination with layer removal steps like ion beam sputtering will destroy the bonding information and is thus not applicable. Chemical etching of the metal gate stack prior to the XPS measurements requires an extremely precious control of the etching in order to stop 1-2 nm before the high k metal interface.As an alternative we have developed a backside removal approach, that allows us to investigate using techniques such as XPS and C-AFM, the metal gate high k interface.

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Walton, Richard I., Kripasindhu Sardar, Helen Y. Playford, Deena R. Modeshia, Richard J. Darton, Janet Fisher, and David Thompsett. "Controlled Hydrothermal Synthesis of Complex Mixed Oxides Using Solution Redox Chemistry." MRS Proceedings 1309 (2011). http://dx.doi.org/10.1557/opl.2011.198.

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ABSTRACTWe present the results of a study of the solvothermal synthesis of mixed-metal cerium-containing oxides all prepared from CeCl3.7H2O at less than 250 ºC in single step reactions. The use of NaBiO3 in the presence of aqueous NaOH yields fluorite solid solutions Ce1-xBixO2-x/2 (x ≤ 0.6), whereas the use of either H2O2 or NaBrO3 as oxidant in the presence of TiF3 yields a Ce(IV) pyrochlore (Na0.33Ce0.67)2Ti2O7. With replacement of a fraction of the Ti reagent by Sn(IV) acetate, tin doping is possible in the pyrochlore. The materials have all been assessed for their use in catalysis by performing temperature programmed reduction (TPR) experiments under dilute hydrogen flow. The cerium-bismuth oxides show large and apparently reversible hydrogen uptake, but in situ powder X-ray diffraction shows that this is accompanied by phase separation into bismuth metal and CeO2 that occurs over 5 or more TPR cycles. In contrast, the cerium (IV) titanate pyrochlore shows reversible reduction at low temperature (150 ºC, after an activation step), which gives the material potential use as a precious metal support for catalysis: such as in the water-gas-shift reaction. Although Sn doping lowers the onset of reduction of the pyrochlore, consistent with an expanded lattice, the materials suffer from collapse to give SnO.

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