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Time-resolved X-ray photoelectron spectroscopy (TR-XPS) is used in a simulation study to monitor the excited state intramolecular proton transfer between oxygen and nitrogen atoms in 2-(iminomethyl)phenol. Real-time monitoring of the chemical bond breaking and forming processes is obtained through the time evolution of excitedstate chemical shifts. By employing individual atomic probes of the proton donor and acceptor atoms, we predict distinct signals with opposite chemical shifts of the donor and acceptor groups during proton transfer. Details of the ultrafast bond breaking and forming dynamics are revealed by extending the classical electron spectroscopy chemical analysis to real time. Through a comparison with simulated time-resolved photoelectron spectroscopy at the valence level, the distinct advantage of TR-XPS is demonstrated thanks to its atom specificity. [ABSTRACT FROM AUTHOR]

Heterotrimeric G proteins can be regulated by posttranslational modifications, including ubiquitylation. KCTD5, a pentameric substrate receptor protein consisting of an N-terminal BTB domain and a C-terminal domain, engages CUL3 to form the central scaffold of a cullin-RING E3 ligase complex (CRL3KCTD5) that ubiquitylates Gβγ and reduces Gβγ protein levels in cells. The cryo-EM structure of a 5:5:5 KCTD5/CUL3NTD/Gβ1γ2 assembly reveals a highly dynamic complex with rotations of over 60° between the KCTD5BTB/CUL3NTD and KCTD5CTD/Gβγ moieties of the structure. CRL3KCTD5 engages the E3 ligase ARIH1 to ubiquitylate Gβγ in an E3-E3 superassembly, and extension of the structure to include full-length CUL3 with RBX1 and an ARIH1~ubiquitin conjugate reveals that some conformational states position the ARIH1~ubiquitin thioester bond to within 10 Å of lysine-23 of Gβ and likely represent priming complexes. Most previously described CRL/substrate structures have consisted of monovalent complexes and have involved flexible peptide substrates. The structure of the KCTD5/CUL3NTD/Gβγ complex shows that the oligomerization of a substrate receptor can generate a polyvalent E3 ligase complex and that the internal dynamics of the substrate receptor can position a structured target for ubiquitylation in a CRL3 complex. [ABSTRACT FROM AUTHOR]

The substituent effects on cooperativity between pnicogen and halogen bonds in ternary complexes involving pyrimidine with substituents X in the 5-position (X = CN, NC, CF3, Br, Cl, F, H, CH3, C(CH3)3, NH2, N(CH3)2), H2FP, and ClF are investigated using theoretical calculations at the MP2/aug-cc-pVDZ level. The reduced density gradient (RDG) analysis indicates that the halogen and pnicogen interactions clearly stand out as attractive interactions. The calculated synergetic energies in ternary complexes are positive, which demonstrates the antagonist effect of pnicogen and halogen interactions upon each other. According to geometrical parameters, binding energies, molecular electrostatic potentials (MEPs), and the results of natural bond orbital (NBO), atoms in molecules (AIM), and nuclear magnetic resonance (NMR) analyses, pnicogen and halogen bonds are weakened in the ternary complexes where two pnicogen and halogen bonds coexist. The results indicate reduced electron density values, second-order perturbation energies, charge transfer values, and two-bonded spin–spin coupling constants for both pnicogen and halogen bonds in the ternary complex as compared to the isolated binary systems. Also, the results show that substituent effects on cooperativity between N...P pnicogen and N...Cl halogen bonds in considered system can be expressed by Hammett constants. [ABSTRACT FROM AUTHOR]

We assessed volatility transmissions that occurred (inter and intra) commodities of metals and energy from October 16, 1998 to October 17, 2018. With a total of 5220 price observations for each commodity, we estimate spillover indexes. We measure such transmissions among twelve commodities and computed the parcels of shock's effects in each pairwise of assets. We also compute how much of these volatilities transmissions was absorbed by each asset in these markets. And using complex network statistics metrics, we describe statistically and graphically these transmissions. Our results pointed that total connectivity is 53% and, through the network analysis, we realize that the greatest interactions occur involving oil and nickel and gold and silver. We confirm the findings of Arouri, et al. (2013) that most precious metals can be a good hedge option in stock portfolios and other assets, especially when there are crises or increased uncertainties in international financial markets. Indeed, we also attested to the conclusion of Papenfuß et al. (2021) that the value of metals was what, among the factors analyzed by them, had a relevant negative effect on the pricing and forecasting. We believe that these evidence are useful for the literatures of financial networks and metallic/energetic commodity markets; as well for investors, risk managers, fund managers, policy makers and metals and energy's producers and buyers. [ABSTRACT FROM AUTHOR]

The diffusion processes during the contact melting at the boundary of explosively welded VT1-0 titanium with CuNi19 (melchior) and CuNi45 (constantan) alloy composites were studied. Heat treatment of composites led to the formation of the interaction zone at the joint boundary. The interaction zone in VT1-0 + CuNi19 consists of TiCuNi and αTi + Ti2Cu(Ni) continuous layers as well as a mixture of TiNi(Cu) + TiCu(Ni) + Ti2Cu(Ni) intermetallics. It has been shown that an increase in the nickel content in the case of VT1-0 + CuNi45 composite leads to a decrease in the temperature of contact melting, a change in its mechanism, an increase in the titanium content in the interaction zone, and the appearance of additional Ti2Ni(Cu) intermetallic in its composition. [ABSTRACT FROM AUTHOR]

Herein, we report four new chiral 1,4,7‐triazacyclononane (TACN) derivatives and their corresponding nickel(II) chloride complexes. All TACN ligands are bearing one chiral N‐substituent and two alkyl (methyl or tert‐butyl) N‐substituents, and we have developed a new synthetic method for the dimethyl‐substituted TACN derivative, in order to prevent the rotational isomers that hinder the cyclization reaction. The nickel complexes change their coordination geometry significantly depending on the steric bulk of the N‐alkyl substituents, from a dinuclear tris(μ‐chloro)dinickel complex to mononuclear Ni‐dichloride and Ni‐chloride complexes. These complexes were then employed in the alkyl‐alkyl Kumada cross‐coupling reaction and revealed that the more sterically hindered ligands produced more homocoupled product rather than the cross‐coupled product, while the mononuclear Ni‐dichloride complex exhibited significantly lower catalytic activity. These chiral complexes were also employed in enantioconvergent cross‐coupling reactions as well, to afford significant enantioenrichment. Overall, the least sterically hindered Ni complex yields the best yields in the alkyl‐alkyl Kumada cross‐coupling reaction among the four complexes investigated, as well as the highest enantioselectivity. [ABSTRACT FROM AUTHOR]

We study integer-valued matrices with bounded determinants. Such matrices appear in the theory of integer programs (IPs) with bounded determinants. For example, an IP can be solved in strongly polynomial time if the constraint matrix is bimodular: that is, the determinants are bounded in absolute value by two. Determinants are also used to bound the ℓ 1 distance between IP solutions and solutions of its linear relaxation. One of the first to quantify the complexity of IPs with bounded determinants was Heller, who identified the maximum number of differing columns in a totally unimodular matrix. Each extension of Heller's bound to general determinants has been superpolynomial in the determinants or the number of equations. We provide the first column bound that is polynomial in both values. For integer programs with box constraints, our result gives the first ℓ 1 distance bound that is polynomial in the determinants and the number of equations. Our result can also be used to derive a bound on the height of Graver basis elements that is polynomial in the determinants and the number of equations. Furthermore, we show a tight bound on the number of differing columns in a bimodular matrix; this is the first tight bound since Heller. Our analysis reveals combinatorial properties of bimodular IPs that may be of independent interest. Funding: J. Lee was supported in part by the Office of Naval Research [Grant N00014-21-1-2135] and the Air Force Office of Scientific Research [Grant FA9550-19-1-0175]. J. Paat was supported by a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant [Grant RGPIN-2021-02475]. [ABSTRACT FROM AUTHOR]

The potential applications of nanowires in thermal management and thermoelectric energy conversion have sparked extensive research on thermal transport in various nanowires. Nickel nanowires, with their unique properties and promising applications, have been extensively studied. However, the influence of size, particularly the impact of kink structures, on the thermal transport behavior in nickel nanowires remains unclear. In this paper, we employed electron-beam lithography and liftoff techniques to fabricate suspended nickel nanowires with varying sizes and kinks to experimentally investigate the size and kink effect on the thermal conductivity. The experimental results revealed that the thermal transport behavior of nickel nanowires is significantly influenced by both size and kink effects. Notably, as the nanowire size decreases, the thermal conductivity also decreases. Furthermore, we discovered that the thermal conductivity can be adjusted by altering the number and angle of kinks. Increasing the number of kinks from 18 to 36 resulted in a significant decrease in thermal conductivity. In contrast, as the kink angle decreased from 157° to 90°, the thermal conductivity also decreased. However, intriguingly, when the kink angle was further decreased from 90° to 43°, the thermal conductivity increases. This non-monotonic change in thermal conductivity with the kink angle provides an interesting insight into the intricate behavior of heat carriers in kinked nickel nanowires. Additionally, we found that varying the alloy elements can profoundly alter the thermal conductivity of nanowires with kinks. These results offer valuable insights into the behaviors of heat carriers, including electrons and phonons, during heat transfer in nickel nanowires. [ABSTRACT FROM AUTHOR]

This paper explores the variation pattern of nickel futures prices using the daily closing levels of the nickel futures price index of the London Futures Exchange and the Shanghai Futures Exchange. The data coarse-graining method is employed to transform the continuous time series data of price index changes into symbols {P, N, M}, which are slid through continuous windows to form the modalities of price index linkage fluctuations. By treating the modalities as nodes and the transformations between them as edges, a weighted directed complex network is constructed to represent the linked volatility of the LME and SHFE nickel futures indices time series. The complex network is applied to analyse the network characteristics and obtain the inner pattern of the linked fluctuations. The results show that the complex network of time series linked volatility of the LME and SHFE nickel futures indices exhibits a power-law nature, with closely linked subgroups formed within it. And the mode transitions within these subgroups follow certain patterns. This paper also identifies core positioned modes and important intermediate modes that reflect the dynamics of nickel prices in reality. The method presented in this paper may be extended to related fields and has good applicability. [ABSTRACT FROM AUTHOR]

The facile synthesis of large size borophene is highly desirable, especially in reserving green energy by borophene-based Li-ion batteries (LIBs). In this study, an easy method of synthesizing a series of nickel foam (NF) deposited with borophene sheets without the use of catalysts is reported via an improved chemical vapor deposition (CVD) process. During the CVD process, the B2O2 vapor was moved to the heated nickel foam and converted into Ni3B and crystalline B under an H2 atmosphere. Numerous micron-sized lamellar borophene with thicknesses of less than 2 nm were deposited on the surface of the nickel foam, and the borophene sheets displayed ultrathin and transparency. Deep microstructural analysis revealed the crystalline nature of pure B in the as-obtained borophene sheets, and the β12-phase is dominant. The β12-borophene holds great potential for designing high-capacity anode material for LIBs. When the nickel foam-supported borophene sheets were directly used as a self-supporting binder-free anode material for LIBs, the NF framework not only hindered the aggregation of borophene sheets and alleviated the strain change during the lithiation/delithiation process but also provided a three-dimensional highway conductive network for fast electron transport. The fabricated electrodes exhibit superior lithium storage capacity and cyclic stability than blank NF electrodes. However, the results suggest that this is still far lower than the theoretical lithium storage capacity of the boron anode. The kinetics analysis combined with density functional theory calculations demonstrated that slow electron and ion transportation in the electrodes is attributed to the existence of the Ni3B phase and deactivated borophene. This study may provide vital guidance for designing high-performance borophene-based LIBs. [ABSTRACT FROM AUTHOR]

• We describe a model of optimal consumer-merchant exchange of cash payments. • Diary data are used to quantify the burden of exchanging currency notes and coins. • The model and data are used to analyze the effects of eliminating the one-penny coin. • Penny elimination would reduce the burden of exchanging cash. • Penny elimination would result in little or no inflationary consequences. • Elimination of the penny and the nickel would not reduce this burden relative to penny elimination only. This article quantifies the burden of exchanging currency notes and coins using a model of optimal consumer-merchant exchange of cash payments and consumer payment choice diary data. The model is then applied to analyze a policy debate whether to eliminate the penny coin from circulation. We find that penny elimination would reduce the burden of exchanging cash and will not have any significant inflationary consequences caused by price rounding. Surprisingly, a removal of both the penny and nickel coins from circulation would slightly increase (not decrease) the burden relative to penny elimination only. [ABSTRACT FROM AUTHOR]

Olivine, one of the most abundant silicates on earth, thermodynamically captures CO2 in relevant amounts during its dissolution. Upscaling the use of this mineral as a replacement for sand or gravel may contribute to reduce concentrations of greenhouse gasses in the atmosphere. However, the reliable quantification of weathering rates and prognoses for effects of various environmental conditions on weathering are lacking. This currently inhibits the monitoring, reporting and verification of CO2 capture and hampers the exploitation of the carbon dioxide removal economy. A mineral dissolution model was developed, and olivine weathering rates were directly coupled to particle sizes of the ground mineral. A particle size-dependent calculation approach, based on the shrinking core model, showed faster weathering rates as compared to a single-size, monodisperse approach. This provided a better underpinning of the prediction of the overall weathering and, consequently, the sequestration rate of CO2. Weathering of olivine releases nickel, which is incorporated in the mineral. The dissolution model was coupled to advanced biotic ligand models (BLM) for nickel in order to assess potential chronic ecotoxicological risks upon release in the environment. Predicted no-effect concentrations for nickel showed that both the release of Mg and the increase of pH following olivine weathering significantly lowers nickel ecotoxicity. [ABSTRACT FROM AUTHOR]

Along time, many minted coins were withdrawn from circulation, being replaced with new ones. The returned obsolete metal coins were melted in order to use the alloy for other purpose. Between the withdrawing and melting, some of the metal coins were cancelled by destruction of the original shape and dimension, using some adequate tools. The paper presents some aspects about the cancelling method used on the Romanian old nickel coins. In the first part of the paper, the introductive aspects about the used cancelling methods are presented; also, there are presented some examples. In the paper second part, the simplified 3D model computed for the cancelling dies, respectively the coin, are presented. Then, there are introduced the assembled models, corresponding to each cancelling case, which consist by the obverse and reverse cancelling dies, having the coin inside them. For the each model, the finite element analysis is realized and is achieved for different initial conditions. The final part of the paper presents the analysis results and also the conclusions. [ABSTRACT FROM AUTHOR]

Microbial electrolysis cell can utilize biocathode attached to methanogens to reduce CO2 to methane.A conductive nickel-based polyvinylidene fluoride（Ni-PVDF） composite hollow fiber membrane was prepared by electroless nickel plating.The Ni-PVDF hollow fiber membrane was assembled into a membrane module electrode, which served as the biocathode of the microbial electrolysis cell for methane production.The H2 produced by the hydrogen evolution reaction catalyzed by the cathode nickel layer and CO2 were utilized by the hydrogenotrophic methanogens to produce methane through indirect electron transfer.The results showed that the cumulative methane production（2 176.24 mmol/（L·m²)) of the direct CO2 transport system using the Ni-PVDF hollow fiber membrane module cathode was much greater than that of the indirect CO2 transport system with the membrane module only acting as the cathode（613.94 mmol/（L·m²)) after the system run stably.The high specific surface area of the membrane module cathode and the direct CO2 transmission of the cathode greatly reduce the gas-liquid mass transfer resistance, thus ensuring the high methane production of the direct CO2 transmission system. [ABSTRACT FROM AUTHOR]

A multi-physics model has been developed to investigate the molybdenum and nickel distribution in large-scale Ti-0.3 wt.% Mo-0.8 wt.% Ni slab ingots obtained by electron beam cold hearth melting. Numerical methods are pivotal in revealing the distribution trends of molybdenum and nickel in slab ingot in different casting conditions. The distribution of molybdenum slightly changed between 0.28 and 0.32 wt.% in the solidified ingot. However, the sharp change in the nickel distribution (between 0.73 and 1.53 wt.%) was caused by the fluid velocity decrease along the flow direction, resulting from a weakened vortexing effect. Additionally, the increase of the casting speed or pouring temperature led to a deeper molten pool and evident vortexing effect. A potential relationship indicates the decrease of nickel segregation degree at higher pouring temperatures, or the casting speed decrease within the research scope. [ABSTRACT FROM AUTHOR]

The formation of carbon–carbon bonds from prebiotic precursors such as carbon dioxide represents the foundation of all primordial life processes. In extant organisms, this reaction is carried out by the carbon monoxide dehydrogenase (CODH)/acetyl coenzyme A synthase (ACS) enzyme, which performs the cornerstone reaction in the ancient Wood–Ljungdahl metabolic pathway to synthesize the key biological metabolite, acetylCoA. Despite its significance, a fundamental understanding of this transformation is lacking, hampering efforts to harness analogous chemistry. To address these knowledge gaps, we have designed an artificial metalloenzyme within the azurin protein scaffold as a structural, functional, and mechanistic model of ACS. We demonstrate the intermediacy of the NiI species and requirement for ordered substrate binding in the bioorganometallic carbon–carbon bond-forming reaction from the one-carbon ACS substrates. The electronic and geometric structures of the nickel-acetyl intermediate have been characterized using time-resolved optical, electron paramagnetic resonance, and X-ray absorption spectroscopy in conjunction with quantum chemical calculations. Moreover, we demonstrate that the nickel-acetyl species is chemically competent for selective acyl transfer upon thiol addition to biosynthesize an activated thioester. Drawing an analogy to the native enzyme, a mechanism for thioester generation by this ACS model has been proposed. The fundamental insight into the enzymatic process provided by this rudimentary ACS model has implications for the evolution of primitive ACS-like proteins. Ultimately, these findings offer strategies for development of highly active catalysts for sustainable generation of liquid fuels from one-carbon substrates, with potential for broad applications across diverse fields ranging from energy storage to environmental remediation. [ABSTRACT FROM AUTHOR]

The association between two intrinsically disordered proteins (IDPs) may produce a fuzzy complex characterized by a high binding affinity, similar to that found in the ultrastable complexes formed between two well-structured proteins. Here, using coarsegrained simulations, we quantified the biophysical forces driving the formation of such fuzzy complexes. We found that the high-affinity complex formed between the highly and oppositely charged H1 and ProTα proteins is sensitive to electrostatic interactions. We investigated 52 variants of the complex by swapping charges between the two oppositely charged proteins to produce sequences whose negatively or positively charged residue content was more homogeneous or heterogenous (i.e., polyelectrolytic or polyampholytic, having higher or lower absolute net charges, respectively) than the wild type. We also changed the distributions of oppositely charged residues within each participating sequence to produce variants in which the charges were segregated or well mixed. Both types of changes significantly affect binding affinity in fuzzy complexes, which is governed by both enthalpy and entropy. The formation of H1-ProTa is supported by an increase in configurational entropy and by entropy due to counterion release. The latter can be twice as large as the former, illustrating the dominance of counterion entropy in modulating the binding thermodynamics. Complexes formed between proteins with greater absolute net charges are more stable, both enthalpically and entropically, indicating that enthalpy and entropy have a mutually reinforcing effect. The sensitivity of the thermodynamics of the complex to net charge and the charge pattern within each of the binding constituents may provide a means to achieve binding specificity between IDPs. [ABSTRACT FROM AUTHOR]

• β-NiAl phase precipitates in a novel high Ru-containing Ni-SC. • Ru element is found to be obviously biased in β-NiAl phase. • The partition of Ru assists nucleation of β-NiAl phase during solidification. • Studies based on the solidification path of experimental alloy were carried out. The precipitation of β-NiAl phase in a high Ru-containing Ni-based single crystal superalloys was investigated. The β-NiAl phase is mainly distributed in the interdendritic region of the as-cast structure. And it was found parts of Ru elements were polarized in β-NiAl phase as the existence of strong bonds between Ru atoms and Al atoms. In addition, the solidification path of the experimental alloy passes through the region of the L → L 1 + γ → L 2 + γ + β-NiAl → L 3 + γ + β-NiAl + precipitated γ′ → γ + β-NiAl + precipitated γ′ + γ/γ′ eutectics. It provides experimental data and theoretical guidance for the composition design of the novel Ru-containing high-generation Ni-SCs. [ABSTRACT FROM AUTHOR]

• The added interlayer can decrease the width of the diffusion zone near the interface. • The formation tendency of Laves phase can be decrease by added interlayer. • The added interlayer can promote the formation of Ni 2 (Cr,Mo). • The strength of the plate adding nickel interlayer increased by 35 % to 341 MPa. The brittle Laves phase forming on the interfaces of nickel-based composite plate has evident effect on its application. For the purpose of decreasing the formation of brittle phase and improving mechanical performance, X65/IN625 composite plates were synthesized using vacuum hot pressing under varying conditions. The investigation was focused on understanding the bonding properties and interfacial microstructure of these composites. The results show that the optimal process is 30 min holding time, 30 MPa pressure and 1050 °C heating temperature. It is worth noting that after the addition of nickel and invar alloy interlayers to the composite plate, the interface bonding strength of the composite plate is significantly improved by approximately 35 % (341 MPa) and 17 % (305 MPa), respectively, compared to plates without interlayer. This is because the addition of nickel and invar alloy layer can decrease the width of the diffusion zone near the interface and effectively inhibit the diffusion of Fe element, thereby reducing the formation tendency of Laves phase, and promoting the formation of Ni 2 (Cr,Mo). [ABSTRACT FROM AUTHOR]

Nickel ferrite (NiFe 2 O 4) nanostructures (NSs) were synthesized via a low-cost and reproducible co-precipitation method. The as-synthesized material was annealed at different temperatures to investigate electrochemical performances for oxygen reduction reaction (ORR) and energy storage capacity. The X-ray diffraction (XRD) pattern confirmed the cubic structure of NiFe 2 O 4 (NF) NSs. The decreased agglomeration and increased particle size were observed by field effect scanning electron microscopy (FE-SEM) with annealing temperature. The presence of Ni–O and Fe–O bonds at tetrahedral and octahedral sites was confirmed by Fourier transform infrared (FTIR) spectroscopy. The electrochemical analysis studied using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) demonstrated that the NF NSs annealed at 900 °C exhibited impressive electrochemical activity with a specific capacitance of ∼136 F/g, outperforming samples synthesized at lower temperatures. Moreover, the electrode material displayed excellent long-term stability over 3000 cycles for ORR activity. The remarkable electrochemical performance of NF NSs at higher annealing temperatures highlights their potential for future energy storage and conversion devices. [Display omitted] • The NiFe 2 O 4 NPs were successfully synthesized by using a simple and economical co-precipitation method. • The cubic nature of the NF NPs was confirmed by XRD and HR-TEM analysis. • The NF annealed at 900 °C showing the highest capacitance of 136 F/g. • The NF NPs having excellent long-term stability over 3000 cycles. [ABSTRACT FROM AUTHOR]

Metal mobilization event was linked to shear-associated granodiorite magmatism. [Display omitted] • Um Samiuki volcanogenic massive sulfide deposit in Egypt's South Eastern Desert. • Zircon U-Pb and sulfide Re-Os dating reveal the genetic link with the host rocks. • Ore-hosted stratum formed ∼700 Ma, and a crosscutting granodiorite at 624 Ma. • Sulfide minerals show high Re-Os ratios and crustal isotope signature. • Ductile shearing formed discrete sulfide masses, followed by intermittent brittle deformation. • Ag-mineral inclusions in galena and solid solution in sulfides contribute to Ag budget. The Um Samiuki deposit in the South Eastern Desert of Egypt is a Kuroko-type volcanogenic massive sulfide deposit associated with arc-related bimodal volcanic rocks. SIMS U-Pb zircon ages of the host metavolcanic rocks and a crosscutting granodiorite intrusion are integrated with Re-Os isotopes of ore sulfides, allowing the determination of the genetic relationships between sulfide mineralization and host rocks to be determined. Zircon U-Pb dating reveals that the ore-hosted stratum of banded tuffs formed at ∼700.0 ± 7.3 Ma, whereas the granodiorite yielded a concordia age of 624.0±8.5 Ma. Sulfide mineral separates (pyrite, sphalerite, chalcopyrite) and sulfide mixtures from the massive ores have significantly high radiogenic Re-Os concentrations and ratios. Regression of seven 187Re/188Os-187Os/188Os data points with the corresponding uncertainty correlation values yields a 624±46 Ma age (2σ, MSWD = 0.56), with an initial 187Os/188Os ratio of 3.58±0.7, thereby pinpointing a distinctive crustal isotope signature. Evolution towards textural equilibrium by recrystallization, as revealed by grain growth and annealing textures in the ores, suggests that ductile shearing and penetrative deformation of the host metavolcanic/metavolcaniclastic rocks led to the formation of discrete sulfide disseminations and masses. Deformed, rolled and rotated pyrites in veins and tension gashes with or without quartz evidently suggests an intermittently rejuvenated brittle deformation regime superimposed on the early ductile deformation textures. Pyrite, galena, chalcopyrite, and sphalerite contain elevated Ag contents between 5 and 812 ppm. Two pyrite generations can be distinguished with the earlier one (Py1) having the highest Ag contents of all sulfides. Silver was released during replacement of Py1 by a late assemblage (Py2-galena-chalcopyrite-sphalerite) with some Ag incorporated into the late sulfides but most Ag was released and retained in discrete Ag minerals like cerveilleite, hessite and acanthite. Time-resolved analyses of LA-ICP-MS data reveal the presence of micron-scale Ag-bearing inclusions in galena while other base metal sulfides also contribute a notable part to the Ag budget of Um Samiuki ore. The new geochronological data integrated with results of the microscopic and microanalytical analyses of the sulfide phases provide an updated insight into a metal mobilization event in the Um Samiuki volcanogenic massive sulfides, roughly coincided with shear-associated granodiorite magmatism. [ABSTRACT FROM AUTHOR]

The paper is devoted to the experimental and theoretical studies of self-sustained oscillations and wave phenomena during CO oxidation on Ni foil. A new type of spatial structures arising due to the redox processes of the catalyst and observed under isothermal conditions at atmospheric pressure were studied. A 3D distributed mathematical model was constructed, which describes the color change and the propagation of kinetic waves of nickel oxidation–reduction in a flow-through reactor. The main reason for the wave phenomena and their propagation during CO oxidation on nickel was shown to be the presence of an oxygen concentration gradient in the flow-through reactor due to the effect of mass transfer on the reaction rate. [ABSTRACT FROM AUTHOR]

A rotating disk method is used to investigate the dissolution rate of metallic iron, nickel, and their alloys in nitric acid media. Discs 2 cm in diameter made of nickel grade N1 and Armco iron, as well as two samples with an Ni:Fe ratio of 15:85 and 50:50 are used. The effect of temperature, initial nitric acid concentration, disk rotation rate, and process duration on specimen dissolution rate are investigated. The rate is determined by the amount of dissolved metal per unit of time from a disk unit surface. Regression analysis is used to describe the effect of nitric acid concentration on specimen dissolution rate. It is found that the dissolution rate of iron metal is up to 20–60 times faster than nickel metal dissolution rate. The effect of HNO3 temperature and initial concentration when dissolving Ni and Fe alloys in nitric acid is investigated. With an increase in temperature from 303 to 353 K ([HNO3] = 0.2 M, Ni:Fe = 50:50) the amount of dissolved Fe and Ni increases by a factor of 8–9. Dissolution of Ni:Fe alloy (15:85) under the same conditions results in an increase in dissolved iron by a factor of four. An increase in nickel concentration in solution occurs within 30 minutes, after which the concentration does not change. In experiments with Ni:Fe alloy = 50:50 the amount of dissolved Fe is 1.8–2.3 times greater than the amount of dissolved Ni depending on the initial acidity. [ABSTRACT FROM AUTHOR]