scholarly journals Contrasting Fluids in the Svetlinsk Gold-Telluride Hydrothermal System, South Urals

Minerals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 37 ◽  
Author(s):  
Olga Vikent’eva ◽  
Vsevolod Prokofiev ◽  
Andrey Borovikov ◽  
Sergey Kryazhev ◽  
Elena Groznova ◽  
...  
Keyword(s):  
Hydrothermal System ◽  
Magmatic Fluid ◽  
South Urals ◽  
Multiple Sources ◽  
Forming Process ◽  
Ore Formation ◽  
Gold Telluride ◽  
Icp Ms ◽  
Wide Range ◽  
Late Stages

The large gold-telluride Svetlinsk deposit (~135 t Au) is considered to be a nontraditional one in the Urals and its origin is debated. A specific feature of the deposit is the abundance of various tellurides, such as tellurides of Fe, Ni, Pb, Sb, Bi, Ag, and Au. The new data of microthermometry, Raman spectroscopy, LA-ICP-MS, and crush-leach analysis (gas and ion chromatography, ICP-MS) for fluid inclusions as well as O-isotope data for quartz were obtained for the construction of PTX parameters of ore-formation and fluid sources in the deposit. Mineralisation was formed at a wide range of temperature and pressure (200–400 °C, 1–4 kbar) and from contrasting fluids with multiple sources. At the early stages, the magmatic fluid evolved during its ascent and phase separation and the fluid derived from the host rock decarbonation and dehydration were involved in the hydrothermal system. In addition, mantle-derived fluid might be involved in the ore-forming process during gold-telluride precipitation as well as heated meteoric waters during the late stages. Early fluids were rich in H2S, S0, and CH4, while the Au-Te mineralisation was formed from N2-rich fluid.

scholarly journals Influence of Genetic Processes on Geochemistry of Fe-oxy-hydroxides in Supergene Zn Non-Sulfide Deposits

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 602
Author(s):  
Licia Santoro ◽  
Francesco Putzolu ◽  
Nicola Mondillo ◽  
Maria Boni ◽  
Richard Herrington
Keyword(s):  
Trace Element ◽  
Trace Element Composition ◽  
Sulfide Ores ◽  
Critical Metals ◽  
Ore Formation ◽  
Sulfide Deposits ◽  
Icp Ms ◽  
Wide Range ◽  
Significant Enrichment ◽  
Specific Association

In supergene Zn non-sulfide deposits, the Fe-oxy-hydroxides (FeO/OH) are mainly concentrated in the residual zones (gossan) on top of the oxidized ore bodies, although they can also be found throughout the whole weathering profile coexisting with the primary and secondary ore assemblages. Fe-oxy-hydroxides are rarely pure as they form in systems where a wide range of metals, most of them of economic importance (e.g., Zn, Pb, Co, REE, Sc, Ga, Ge, V, etc.), freely circulate and can be “captured” under specific conditions. Although their occurrence can be widespread, and they have a potential to scavenge and accumulate critical metals, FeO/OH are considered gangue phases during the existing processing routes of Zn non-sulfide ores. Moreover, very little is known about the role of the deposit type on the geochemistry of FeO/OH formed in a specific association. Therefore, this paper provides a comprehensive assessment of the trace element footprint of FeO/OH from a number of Zn non-sulfide deposits, in order to define parameters controlling the metals’ enrichment process in the mineral phase. To achieve this, we selected FeO/OH-bearing mineralized samples from four supergene Zn non-sulfide ores in diverse settings, namely Hakkari (Turkey), Jabali (Yemen), Cristal (Peru) and Kabwe (Zambia). The petrography of FeO/OH was investigated by means of scanning electron microscope energy dispersive analysis (SEM-EDS), while the trace element composition was assessed using laser ablation-ICP-MS (LA-ICP-MS). Statistical analyses performed on LA-ICP-MS data defined several interelement associations, which can be ascribed to the different nature of the studied deposits, the dominant ore-formation process and subsequent evolution of the deposits and the environmental conditions under which FeO/OH phases were formed. Based on our results, the main new inferences are: (A) Zinc, Si, Pb, Ga and Ge enrichment in FeO/OH is favored in ores where the direct replacement of sulfides is the dominant process and/or where the pyrite is abundant (e.g., Cristal and Hakkari). (B) When the dissolution of the host-rock is a key process during the supergene ore formation (i.e., Jabali), the buffering toward basic pH of the solutions favors the uptake in FeO/OH of elements leached from the host carbonate rock (i.e., Mn), whilst restricting the uptake of elements derived from the dissolution of sulfides (i.e., Zn, Pb, Ga and Ge), as well as silica. (C) The input of exotic phases can produce significant enrichment in “unconventional” metals in FeO/OH (i.e., Cr and Co at Kabwe; Y at Cristal) depending on whether the optimal pH-Eh conditions are attained. (D) In the Kabwe deposit, FeO/OH records heterogeneous geochemical conditions within the system: where locally basic conditions prevailed during the alteration process, the V and U concentration in FeO/OH is favored; yet conversely, more acidic weathering produced Zn- and Si-bearing FeO/OH.

scholarly journals Comparison of Modified Mohr–Coulomb Model and Bai–Wierzbicki Model for Constructing 3D Ductile Fracture Envelope of AA6063

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Jianye Gao ◽  
Tao He ◽  
Yuanming Huo ◽  
Miao Song ◽  
Tingting Yao ◽  
...  
Keyword(s):  
Ductile Fracture ◽  
Fracture Criterion ◽  
Fracture Strain ◽  
Stress Triaxiality ◽  
Ductile Fracture Criterion ◽  
Forming Process ◽  
Tension Tests ◽  
Wide Range ◽  
Round Bar ◽  
Fracture Envelope

AbstractDuctile fracture of metal often occurs in the plastic forming process of parts. The establishment of ductile fracture criterion can effectively guide the selection of process parameters and avoid ductile fracture of parts during machining. The 3D ductile fracture envelope of AA6063-T6 was developed to predict and prevent its fracture. Smooth round bar tension tests were performed to characterize the flow stress, and a series of experiments were conducted to characterize the ductile fracture firstly, such as notched round bar tension tests, compression tests and torsion tests. These tests cover a wide range of stress triaxiality (ST) and Lode parameter (LP) to calibrate the ductile fracture criterion. Plasticity modeling was performed, and the predicted results were compared with corresponding experimental data to verify the plasticity model after these experiments. Then the relationship between ductile fracture strain and ST with LP was constructed using the modified Mohr–Coulomb (MMC) model and Bai-Wierzbicki (BW) model to develop the 3D ductile fracture envelope. Finally, two ductile damage models were proposed based on the 3D fracture envelope of AA6063. Through the comparison of the two models, it was found that BW model had better fitting effect, and the sum of squares of residual error of BW model was 0.9901. The two models had relatively large errors in predicting the fracture strain of SRB tensile test and torsion test, but both of the predicting error of both two models were within the acceptable range of 15%. In the process of finite element simulation, the evolution process of ductile fracture can be well simulated by the two models. However, BW model can predict the location of fracture more accurately than MMC model.

scholarly journals The Survival of Haloferax mediterranei under Stressful Conditions

2021 ◽  
Vol 9 (2) ◽  
pp. 336
Author(s):  
Laura Matarredona ◽  
Mónica Camacho ◽  
Basilio Zafrilla ◽  
Gloria Bravo-Barrales ◽  
Julia Esclapez ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Sea Water ◽  
Industrial Applications ◽  
Growth Responses ◽  
Haloferax Mediterranei ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Wide Range ◽  
High Metal ◽  
Plasma Mass Spectrometry

Haloarchaea can survive and thrive under exposure to a wide range of extreme environmental factors, which represents a potential interest to biotechnology. Growth responses to different stressful conditions were examined in the haloarchaeon Haloferax mediterranei R4. It has been demonstrated that this halophilic archaeon is able to grow between 10 and 32.5% (w/v) of sea water, at 32–52 °C, although it is expected to grow in temperatures lower than 32 °C, and between 5.75 and 8.75 of pH. Moreover, it can also grow under high metal concentrations (nickel, lithium, cobalt, arsenic), which are toxic to most living beings, making it a promising candidate for future biotechnological purposes and industrial applications. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis quantified the intracellular ion concentrations of these four metals in Hfx. mediterranei, concluding that this haloarchaeon can accumulate Li+, Co2+, As5+, and Ni2+ within the cell. This paper is the first report on Hfx. mediterranei in which multiple stress conditions have been studied to explore the mechanism of stress resistance. It constitutes the most detailed study in Haloarchaea, and, as a consequence, new biotechnological and industrial applications have emerged.

Nickel-Catalyzed Electronically-Reversed Enantioselective Hydrocarbofunctionalizations of Acrylamides

Synlett ◽  
2021 ◽  
Author(s):  
Lou Shi ◽  
Wei Shu
Keyword(s):  
Nickel Catalyst ◽  
Functional Group ◽  
Optically Active ◽  
Forming Process ◽  
Carbon Bond ◽  
Bond Forming ◽  
Synthetic Strategy ◽  
Carbon Carbon Bond ◽  
Wide Range ◽  
Simple Protocol

Asymmetric hydrocarbofunctionalizations of alkenes has emerged as an efficient synthetic strategy for accessing optically active molecules via carbon-carbon bond-forming process from readily available alkenes and carbo-electrophiles. Herein, we present a summary of the efforts from our group to control the regio- and enantioselectivity of hydrocarbofunctionalizations of electron-deficient alkenes with a nickel catalyst and chiral bisoxazolidine ligand. The reaction undergoes electron-reversed hydrocarbofunctionalizations acrylamides with excellent enantioselectivity. This operationally simple protocol enables the asymmetric hydroalkylation, hydrobenzylation and hydropropargylation of acrylamides. This reaction is useful for preparing a wide range of α-branched chiral amides with broad functional group tolerance.

Measurement and Calculation of Elastic Properties in Low Carbon Steel Sheet

2005 ◽  
Vol 495-497 ◽  
pp. 1591-1596 ◽  
Author(s):  
Vladimir Luzin ◽  
S. Banovic ◽  
Thomas Gnäupel-Herold ◽  
Henry Prask ◽  
R.E. Ricker
Keyword(s):  
Carbon Steel ◽  
Elastic Property ◽  
Elastic Properties ◽  
Steel Sheet ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Forming Process ◽  
Element Analysis ◽  
Wide Range ◽  
Carbon Steel Sheet

Low carbon steel (usually in sheet form) has found a wide range of applications in industry due to its high formability. The inner and outer panels of a car body are good examples of such an implementation. While low carbon steel has been used in this application for many decades, a reliable predictive capability of the forming process and “springback” has still not been achieved. NIST has been involved in addressing this and other formability problems for several years. In this paper, texture produced by the in-plane straining and its relationship to springback is reported. Low carbon steel sheet was examined in the as-received condition and after balanced biaxial straining to 25%. This was performed using the Marciniak in-plane stretching test. Both experimental measurements and numerical calculations have been utilized to evaluate anisotropy and evolution of the elastic properties during forming. We employ several techniques for elastic property measurements (dynamic mechanical analysis, static four point bending, mechanical resonance frequency measurements), and several calculation schemes (orientation distribution function averaging, finite element analysis) which are based on texture measurements (neutron diffraction, electron back scattering diffraction). The following objectives are pursued: a) To test a range of different experimental techniques for elastic property measurements in sheet metals; b) To validate numerical calculation methods of the elastic properties by experiments; c) To evaluate elastic property changes (and texture development) during biaxial straining. On the basis of the investigation, recommendations are made for the evaluation of elastic properties in textured sheet metal.

The Research on the Mechanical Property of CBF/PP Composite Board

2010 ◽  
Vol 150-151 ◽  
pp. 1063-1067
Author(s):  
Fei Fei Zhu ◽  
Zhi Li Zhong ◽  
Zong Fu Guo
Keyword(s):  
Mechanical Property ◽  
Polypropylene Fiber ◽  
Basalt Fiber ◽  
Variance Analysis ◽  
Forming Process ◽  
Composite Board ◽  
Actual Application ◽  
Wide Range ◽  
Significant Difference ◽  
The Difference

The three composite boards which were made of continuous basalt fiber (CBF) and polypropylene fiber (PP) in different fiber ratios were researched on this paper. The manufacturing forming process included blending, carding, web formation, laminating and compression molding orderly. The tension and bending properties were investigated experimentally, and then dual variance analysis was used to show the significant difference of the mechanical property in the transverse and longitudinal orientation as well the appreciable impact of different fiber ratios to the mechanical property. The results show that the difference of the tension and blending strength in the same direction, among composite boards in different fiber proportions, is about 1~10Mpa; the difference in the same fiber proportion, between transverse and longitudinal, vary within a wide range from 10Mpa to 30Mpa. The results of variance analysis have also proved the conclusion, the difference between transverse and longitudinal is more significant than the difference among different fiber proportions. In the similar study, the significance hadn’t been seen sufficiently, so this paper provides reference to the actual application of the composite board.

Memories of Tiananmen

2021 ◽  
Author(s):  
Francis Lee ◽  
Joseph Man Chan
Keyword(s):  
Hong Kong ◽  
Collective Memory ◽  
Digital Media ◽  
Political Communication ◽  
Civil Liberties ◽  
Significant Degree ◽  
Historical Period ◽  
Multiple Sources ◽  
News Reports ◽  
Wide Range

This book analyzes how collective memory regarding the 1989 Beijing student movement and the Tiananmen crackdown was produced, contested, sustained, and transformed in Hong Kong between 1989 and 2019. Drawing on data gathered through multiple sources such as news reports, digital media content, vigil onsite surveys, population surveys, and in-depth interviews with activists, rally participants, and other stakeholders, it identifies six key processes in the dynamics of social remembering: memory formation, memory mobilization, memory institutionalization, intergenerational transfer, memory repair, and memory balkanization. Memories of Tiananmen demonstrates how a socially dominant collective memory, even one the state finds politically irritable, can be generated and maintained through constant negotiation and efforts by a wide range of actors. While the book mainly focuses on the interplay between political changes and Tiananmen commemoration in the historical period within which the society enjoyed a significant degree of civil liberties, it also discusses how the trajectory of the collective memory may take a drastic turn as Hong Kong's autonomy is abridged. The book promises to be a key reference for anyone interested in collective memory studies, social movement research, political communication, and China and Hong Kong studies.

scholarly journals Lutetium oxide analysis by direct arc atomic emission spectrometry

2021 ◽  
Vol 25 (2) ◽  
pp. 70-83
Author(s):  
E. S. Koshel ◽  
◽  
A. A. Arkhipenko ◽  
V. B. Baranovskaya ◽  
◽  
...  
Keyword(s):  
Atomic Emission ◽  
Emission Spectrometry ◽  
Experimental Conditions ◽  
Impurity Composition ◽  
Operating Modes ◽  
Lutetium Oxide ◽  
Icp Ms ◽  
Wide Range ◽  
Sample Dissolution ◽  
Dc Arc

The requirements for the composition of initial oxides for the lutetium orthosilicate crystals are quite stringent: the content of the basic substance Lu2O3 is 99.999 wt%. Critical are coloring impurities: Fe, Ni, Cr, Co, Cu, V, Mn, the content of each should be no more than 0.0005 - 0.0010 wt%, Pr, Nd, Sm, Er, Tb, Yb no more than 0.0005 wt% for each one. It is also necessary to control the content of Al, As, Bi, Cd, Mg, Mo, Pb, Sb, Si, Sn, Ti, Zn, Y, La, Ce, Sc, Eu, Gd, Dy, Ho, Tm. To determine the impurity composition of lutetium oxide, one of the promising methods of analysis is direct arc atomic emission spectroscopy (DC Arc). The advantages of this method are the determination of the chemical composition without sample dissolution, a wide range of concentrations (10-6 - 10-1% wt%), a large number of determined elements. To realize the potential analytical capabilities of the method, the experimental conditions were studied: the interelectrode distance, the shape and size of graphite electrodes, the ratio of Lu2O3 to the spectral buffer, the type of carriers and operating modes of the generator. For most elements, the limits of determination are n ∙ 10-6 - n ∙ 10-4 wt%, that is significantly lower than in the current methods of DC Arc. The trueness of results is controlled by ICP-MS. The complex application of new approaches and modern capabilities of spectral equipment made it possible to develop a method with improved metrological characteristics.

scholarly journals Comparison and evaluation of statistical error models for scRNA-seq

2021 ◽  
Author(s):  
Saket Choudhary ◽  
Rahul Satija
Keyword(s):  
Linear Models ◽  
Negative Binomial ◽  
Statistical Error ◽  
Rna Seq ◽  
Multiple Sources ◽  
Error Models ◽  
Wide Range ◽  
Data Driven Approach ◽  
Downstream Analysis ◽  
Experimental Processing

Heterogeneity in single-cell RNA-seq (scRNA-seq) data is driven by multiple sources, including biological variation in cellular state as well as technical variation introduced during experimental processing. Deconvolving these effects is a key challenge for preprocessing workflows. Recent work has demonstrated the importance and utility of count models for scRNA-seq analysis, but there is a lack of consensus on which statistical distributions and parameter settings are appropriate. Here, we analyze 58 scRNA-seq datasets that span a wide range of technologies, systems, and sequencing depths in order to evaluate the performance of different error models. We find that while a Poisson error model appears appropriate for sparse datasets, we observe clear evidence of overdispersion for genes with sufficient sequencing depth in all biological systems, necessitating the use of a negative binomial model. Moreover, we find that the degree of overdispersion varies widely across datasets, systems, and gene abundances, and argues for a data-driven approach for parameter estimation. Based on these analyses, we provide a set of recommendations for modeling variation in scRNA-seq data, particularly when using generalized linear models or likelihood-based approaches for preprocessing and downstream analysis.

scholarly journals PHYSICAL-CHEMICAL FORMATION CONDITIONS OF URANIUM-TITANIUM-METAGEL MINERALIZATION AT THE GOLD-URANIUM ELKON DEPOSIT

2017 ◽  
pp. 52-57 ◽  
Author(s):  
M. M. Komarova ◽  
VL. B. Komarov ◽  
A. P. Aleshin ◽  
T. L. Krylova
Keyword(s):  
Crystalline Form ◽  
Fluid Regime ◽  
Ore Formation ◽  
Physical Chemical ◽  
Wide Range ◽  
Moderate Salinity ◽  
Formation Conditions ◽  
Carbonate Composition ◽  
Main Factor

A wide range of the temperatures of hydrothermal fluid regime (430-103 °C) has been revealed in the result of microthermometric study of the fluid inclusions in the minerals of pre-ore and post-ore stages developed at the Elkon deposit. Average temperatures, as well as the temperature variation are similar for both pre-ore and post-ore stages. It allows sure determination of temperatures of uranium ore formation as 400-120 °C. Fluids possessed Na-chloride, rarely Na-chloride-carbonate composition and moderate salinity (6-16 wt. % · NaCl equiv.). The wide range of tem-peratures confirms an assumption made before that various temperatures were the reason of formation of uranium mineralization both in the form of predominantly amorphous phase (U-Ti-metagel), as well as the rarely crystalline form (brannerite). Abrupt temperature decrease was apparently the main factor of the ore precipitation.

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