Precious Metals Research Articles

Effective oxygen evolution of NCF@CoNiO2 with one-dimensional core-shell structure synthesized by induced effect of polymer nanofibers

The non-noble bimetallic oxides have recently received more and more attention in electrocatalytic oxygen evolution reaction (OER) because of their potential to replace traditional precious metal catalysts, but the low activity and stability limit their wide application. Herein, the bimetallic oxide CoNiO2 layers are decorated on the nitrogen-doped carbon nanofibers (NCF) through in situ grown of Ni(Co) bimetal organic frameworks (Ni(Co)-MOFs) on polyacrylonitrile nanofibers and subsequent pyrolysis process, so that a new NCF@CoNiO2 electrocatalyst with one-dimensional (1D) core-shell structure is synthesized by structural induced effect of polyacrylonitrile nanofibers. Importantly, the unique interconnected network formed in the 1D NCF@CoNiO2 electrocatalyst effectively improves electron mobility and mass transport capacity, thus exhibiting the glorious OER activity and long-term stability in alkaline solutions. As a result, the optimal NCF@CoNiO2-7 electrocatalyst requires an overpotential of 518 mV for OER at the current density of 100 mA cm−2, which is obvious lower than that of RuO2 (633 mV) and CoNiO2/C-7 as a contrast sample (569 mV), respectively. This work opens up a new path for structural control of 1D bimetallic oxides to improve OER activity and stability.

Valorization of lithium containing slags from pyrometallurgical recycling route of spent lithium-ion batteries: The enrichment of γ-LiAlO2 phase from thermodynamic controlled and modified slags

Pyro-metallurgical processing technology is widely used in the spent lithium-ion batteries recycling to recover valuable metals such as cobalt, nickel and copper, while lithium primarily remains in the slag. The effective valorization of slag, especially lithium recovery, constitutes a significant issue in contemporary pyrometallurgical processes due to the paucity of studies. This paper proposes a novel perspective by defining slag as an aggregate of engineered artificial minerals. Thus, not only the parameters of the beneficiation process can be studied to optimize the separation efficiency during treatment, but also the slag can be re-designed to optimize the carrier minerals of target elements and gangue mineral composition in the initial step with thermodynamic tools. In this paper, the engineering of artificial minerals (EnAM) method was applied to the slag design of the Li2O-CaO-Al2O3-SiO2-MnO system, and an initial attempt was made to apply EnAM method to the flotation study. A flotation study on enrichment effect of the target phase γ-LiAlO2 from thermodynamic controlled slags is conducted.

A Study on the Construction of Brand Storytelling and the Emotional Connection of Generation Z

This study explores the characteristics and effects of Chow Tai Fook’s (CTF) brand storytelling, as well as the current situation and trend of Generation Z’s (Gen Z) emotional connection to the brand. The results show that CTF’s brand storytelling is unique and able to attract the attention of Gen Z. Gen Z has high awareness and emotional connection to CTF, and most of them highly recognize the importance of the background of the brand story. In terms of willingness to buy, a significant proportion of respondents believe that brand storytelling is one of the reasons why they buy jewelry and precious metal products, and that brand storytelling and creation are more appealing to consumers than simple sales pitches. Emotional resonance, uniqueness, quality assurance and social responsibility, and lifestyle leadership were all seen as important factors in terms of brand cultural characteristics. As for story construction, compelling plot construction and authentic and believable content presentation are the most significant attractions for Gen Z consumers, while all other aspects have significant impacts as well.

A Two-Step Leaching Process Using Thiourea for the Recovery of Precious Metals from Waste Printed Circuit Boards

The development of efficient recovery methods for waste printed circuit boards (WPCBs) not only tackles the environmental risks of disposal but also promotes the conservation of resources within the electronics industry. This study proposes a two-step leaching approach for recovering metals from WPCBs. Initially, transition metals are leached using nitric acid, followed by the recovery of precious metals with thiourea in the second stage. In the first stage, dissolution rates exceeding 90 wt% were achieved for transition metals, including Cu, Fe, Ni, Pb, and Sn. In this stage, the dissolution of precious metals (i.e., Au and Pd) was insignificant. In the second stage, the effect of four parameters was investigated, including the impact of temperature, concentrations of ferric ions, sulfuric media, and thiourea on the recovery of Au and Pd. Precise control over sulfate concentration played a vital role in achieving maximum Au recovery. The optimal acid concentration was 0.2 M, resulting in a recovery rate of ~50 wt%. Ferric ion concentration positively affects Au recovery, whereas, in extracting Pd, optimal conditions imposed the absence of ferric ions. Thiourea concentration positively impacted Au and Pd recovery rates, peaking at 49 wt% for Au at 1 M and 44 wt% for Pd at 1.5 M. Prolonged leaching resulted in declining Au recovery rates, indicating a decrease in reagent concentration. Temperature variation yielded similar outcomes, with 50 °C resulting in peak recovery rates of 53 wt% for Au and 54 wt% for Pd. Metal dissolution kinetics during leaching were analyzed using pseudo-first-order and pseudo-second-order models. The second-order model proved suitable for transition metals in the first stage, while only for Au and Pd in the second stage (with R2 = 0.99).

Application of (U-Th)/He hematite geochronology to the Çaldağ lateritic Ni-Co deposit, Western Anatolia: Implications for multi-stage weathering events during interglacial periods/segments

Lateritic Ni-Co deposits are supergene deposits that develop due to intense weathering of the underlying ultramafic parent rocks and/or their serpentinized equivalents under tropical to sub-tropical climatic conditions. These deposits provide not only important sources of valuable metals such as iron, aluminium, nickel, and cobalt, but they also provide a proxy for paleoclimatic conditions. In this regard, geochronological studies on these deposits are critical to determine the timing of the paleoclimatic conditions, which is important for a better understanding of the paleoclimate at regional scale and for identification of favourable weathering periods that can be targeted in the exploration of undiscovered lateritic deposits in a region. In this contribution, we report hematite (U-Th)/He geochronology results from a well-preserved Çaldağ lateritic Ni-Co deposit in Western Türkiye. We sampled the different parts of the lateritic profile from the different laterite zones at the Çaldağ deposit and carried out analyses of polished thin section to determine and identify the phases of hematite formation and primary hematite formed during primary lateritization. Then, we applied scanning electron microscopy (SEM) analysis and TESCAN Integrated Mineral Analyser (TIMA) mineral mapping to identify the suitable areas on primary hematites for subsequent (U-Th)/He dating.Primary hematites are detected at the base of the lateritic profiles (transition between the limonite zone and altered serpentinite) that are only in-situ parts of the laterites exposed in two different pits in the deposit. The obtained (U-Th)/He dates of ca. 502, 206, 178, and 63 ka correspond to the interglacial periods. The three youngest (U-Th)/He dates (206, 178, and 63 ka) from the weathering front of the hematite pit become younger towards the deeper parts of the profile in the direction of weathering. The ages indicate the weathering processes should have lasted until the Quaternary with some interruptions during interglacial periods/segments, despite the fact that the main intensive lateralization period is thought to be during the Middle Eocene.This study presents the first hematite (U-Th)/He dating of lateritic Ni-Co deposits and demonstrates the reliable use of this method after a careful selection of hematite samples. Our results suggest that, in contrast to the short-living lateritization model for lateritic Ni-Co deposits, they may have a multi-stage weathering history throughout their long-lasting development. In addition, the study showed that it has huge potential for the dating of lateritization and weathering processes that are related to paleoclimatic events. Finally, knowledge of the favourable paleoclimatic periods of chemical weathering in a region may help in determining the potential areas for ultramafic exposures for discovering new lateritic deposits.

Short-Wave Infrared Light-Emitting Diodes Using Colloidal CuInS2 Quantum Dots with ZnI2 Dual-Passivation.

Short-wave infrared (SWIR) light-emitting diodes (LEDs) have emerged as promising technologies for diverse applications such as optical communication, biomedical imaging, surveillance, and machine vision. Colloidal quantum dots (QDs) are particularly attractive for SWIR LEDs due to their solution processability, compatibility with flexible substrates, and tunable absorption and luminescence. However, the presence of toxic elements or precious metals in most SWIR-emitting QDs poses health, environmental, and cost challenges. In this context, CuInS2 (CIS) QDs are known for low toxicity, cost-effective fabrication, and SWIR-light emitting capability. However, CIS QDs have not yet been directly utilized to fabricate SWIR LEDs to date, which is due to low particle stability, inefficient charge carrier recombination, and significantly blue-shifted luminescence after integrating into LED devices. To address challenges, we propose a dual-passivation strategy using ZnI2 as a chemical additive to enhance both the optical property of plain CIS QDs and charge carrier recombination upon LED device implementation. The resulting CIS-QD-based LEDs exhibit a stable SWIR electroluminescence (EL) peak (over 1000 nm) with a high EL radiance and a record external quantum efficiency in the SWIR region. Our study represents a significant step forward in SWIR-QLED technology, offering a pathway for the development of high-performance, low-cost, and nontoxic SWIR light sources.

Functional Living Materials for Virus Disinfection Based on Engineered Bacillus subtilis Biofilm by Displaying Viral Affinity Peptides and Expressing Protease

AbstractGlobal pandemics caused by pathogenic viruses have highlighted the need to develop effective and sustainable materials to defend against these viruses. However, most commercial viral disinfection materials rely on precious metals, which are toxic. In this study, an engineered living material based on Bacillus subtilis biofilms is presented that can effectively remove Influenza A virus and SARS‐CoV‐2 from water. First, B. subtilis biofilm is used to display the H1N1 and H5N1 specific binding peptide C40 and SARS‐CoV‐2 specific binding peptide SBP1; thus, the biofilm materials has outstanding efficacy against H1N1, H5N1, and SARS‐CoV‐2 pseudovirus from water. In addition to capturing the virus, these biofilm materials can also inactivate the virus by secreting alkaline protease AprE, which effectively degrades the viral proteins at temperatures of 4, 16, 25, and 37 °C. Furthermore, to constrain bacterial growth and prevent the leakage of genetically modified organisms, a suicide genetic circuit using the quorum‐sensing system ComQXPA to control Lytc expression is constructed, leading to bacterial lysis. Overall, this study demonstrates a novel, effective, and sustainably engineered living material for preventing viral transmission. This material provides a safeguard for public health and promotes environmentally friendly governance.

Earth‐Abundant Nickel‐Catalyzed Asymmetric Hydrogenation†

Comprehensive SummaryTransition metal‐catalyzed asymmetric hydrogenation is an efficient and direct synthetic method to access chiral compounds, which features simplicity, easy working‐up process, and high atomic economy. It typically relies on precious transition metal catalytic systems, including ruthenium, rhodium, iridium and palladium, which always face the difficulties of limited resources, high cost, and environmental contamination. Therefore, great efforts were made to apply earth‐abundant, low (non‐)toxic, and environmentally friendly transition metals, such as iron, cobalt, nickel and copper, to the asymmetric hydrogenation in the past decades, and some considerable breakthroughs have been obtained. In this review, we mainly summarized some recent research progress of nickel‐catalyzed asymmetric hydrogenation of prochiral unsaturated molecules, including olefins, imines and ketones. And continuous development of chiral nickel catalytic systems and the application of them into challenging asymmetric hydrogenation is prospected in the future. Key ScientistsTransition metal‐catalyzed asymmetric hydrogenation has been regarded as an important and direct approach to access chiral molecules. The first example of homogeneous catalytic asymmetric hydrogenation was developed by Knowles and Horner in 1968, respectively. In 1971, Kagan developed privileged chiral DIOP ligand for asymmetric hydrogenation. Halpern and Brown made deep studies on the Rh‐catalyzed asymmetric hydrogenation in 1977, respectively. Noyori developed a powerful and privileged chiral BINAP ligand in 1980. Owing to Knowles and Noyori's great contribution in the field of catalytic asymmetric hydrogenation, they were awarded the Nobel Prize in Chemistry in 2001. In 1984, Ohkubo developed pioneering earth‐abundant transition metal Ni‐catalyzed asymmetric hydrogenation of ethyl α‐methylcrotonate. A great many scientists made tremendous contribution to the development of chiral privileged ligands, such as, Bosnich, Kumada, Giongo, Takaya, Miyashima, Achiwa, Burk, Pflaltz, Chan, X. Zhang, Imamoto, Zhou, Genet, Sannicolo, Ding, Hoge, W. Zhang, Z. Zhang, Tang, these ligands owned wide application in the catalytic asymmetric hydrogenation. In addition, Zhou, Fan made deep investigation on the asymmetric hydrogenation of challenging aromatic heterocyclic compounds. Owing to the great importance of the development of the asymmetric (transfer) hydrogenation promoted by cheap transition metal catalytic systems, some researchers, such as Hamada, Gao, J. S. Zhou, Chirik, X. Zhang, Y.‐G. Zhou, W. Zhang, Lv, Dong, Fu, Deng, and Hou, made great efforts to the development of earth‐abundant nickel‐catalyzed asymmetric hydrogenation of prochiral unsaturated molecules, including olefins, imines and ketones. In addition, there are some other scientists that have also made great contribution to the development of catalytic asymmetric hydrogenation and Ni‐catalyzed asymmetric transformation, with too limited space to list all of them.

Paired Electrolysis Enables Reductive Heck Coupling of Unactivated (Hetero)Aryl Halides and Alkenes.

The formation of carbon-carbon (C-C) bonds is a cornerstone of organic synthesis. Among various methods to construct Csp2-Csp3 bonds, the reductive Heck reaction between (hetero)aryl halides and alkenes stands out due to its potential efficiency and broad substrate availability. However, traditional reductive Heck reactions are limited by the use of precious metal catalysts and/or limited aryl halide and alkene compatibility. Here, we present an electrochemically mediated, metal- and catalyst-free reductive Heck reaction that tolerates both unactivated (hetero)aryl halides and diverse alkenes such as vinyl boronates and silanes. Detailed electrochemical and deuterium-labeling studies support that this transformation likely proceeds through a paired electrolysis pathway, in which acid generated by the oxidation of N,N-diisopropylethylamine (DIPEA) at the anode intercepts an alkyl carbanion formed after radical-polar crossover at the cathode. As such, this approach offers a sustainable method for the construction of Csp2-Csp3 bonds from (hetero)aryl halides and alkenes, paving the way for the development of other electrochemically mediated olefin difunctionalization reactions.

Device design of efficient HTL-free all carbon-based perovskite solar cell

Perovskite solar cells (PSCs) are a very promising photovoltaic technology, however, the cost issue of their precious metal back electrodes needs to be addressed. Carbon-electrode-based perovskite solar cells (C-PSCs) have attracted considerable attention for their superior stability, high economic efficiency, and eco-friendliness. However, compared to other types of PSCs, there is still significant potential for improving the power conversion efficiency (PCE) of C-PSCs. Moreover, if the transparent front electrode and transport layer can also be replaced by stable carbon materials to form the all-carbon-based PSCs (AC-PSCs), it will further promote their practical applications. This work proposes four types of C-PSCs (including two AC-PSCs) and conducts simulation with the SCAPS-1D program. For the four structures, the device with FASnI3 absorber layer always has better performance, and the structure of graphene/C60/FASnI3/carbon (Cell 4) attained the highest PCE of 31.62%. The optimal parameters for each layer are also determined through the simulation work. This work will promote the development of all-carbon-based perovskite solar cells.

Paired Electrolysis Enables Reductive Heck Coupling of Unactivated (Hetero)Aryl Halides and Alkenes

AbstractThe formation of carbon‐carbon (C−C) bonds is a cornerstone of organic synthesis. Among various methods to construct Csp2−Csp3 bonds, the reductive Heck reaction between (hetero)aryl halides and alkenes stands out due to its potential efficiency and broad substrate availability. However, traditional reductive Heck reactions are limited by the use of precious metal catalysts and/or limited aryl halide and alkene compatibility. Here, we present an electrochemically mediated, metal‐ and catalyst‐free reductive Heck reaction that tolerates both unactivated (hetero)aryl halides and diverse alkenes such as vinyl boronates and silanes. Detailed electrochemical and deuterium‐labeling studies support that this transformation likely proceeds through a paired electrolysis pathway, in which acid generated by the oxidation of N,N‐diisopropylethylamine (DIPEA) at the anode intercepts an alkyl carbanion formed after radical‐polar crossover at the cathode. As such, this approach offers a sustainable method for the construction of Csp2−Csp3 bonds from (hetero)aryl halides and alkenes, paving the way for the development of other electrochemically mediated olefin difunctionalization reactions.

Efficient and selective recovery of Mo and V from spent hydrodesulfurization catalysts via oxidation roasting followed by Na2CO3 and NaOH leaching

Spent hydrodesulfurization (HDS) catalysts containing large amounts of valuable metals, such as Mo and V, are hazardous solid wastes but also valuable secondary resources. However, the current recovery process suffers from the difficulty of balancing the leaching efficiency of Mo and V and their selectivity over Al. This work focused on the effect of phase transformation during roasting operation on the leaching behavior Mo, V, and Al and adopted an oxidation roasting followed by mixed alkali of Na2CO3 and NaOH leaching process to recover Mo and V from spent HDS catalysts. The results indicated that the phase transformation of Mo, V, and Al species during oxidation roasting process played a crucial role in achieving efficient leaching of Mo and V, as well as reducing leaching efficiency of Al. This transformation involved the change in Mo and V species changed from low valent compounds to high valent oxides, and Al2O3 from γ-phase to θ- and α-phases. In addition, efficient and selective leaching of 99.3% Mo and 97.8% V was realized, with only 0.03% Al being dissolved, by roasting the spent catalysts at 700 °C for 2 h and then leaching with a mixed solution of 1.2 mol/L Na2CO3 and 1.6 mol/L NaOH. The efficient and selective leaching of Mo and V can significantly reduce the burden of subsequent separation and purification, which provided an important prerequisite for the development of a new process for the recovery of Mo and V from HDS spent catalysts in alkaline systems.

Ultrasound-assisted enhanced leaching of lithium and fluoride compounds from waste cathode carbon: Comprehensive recovery and leaching mechanism

Due to the rapid development of the aluminum industry, waste cathode carbon, as a hazardous solid waste, is inevitably generated during the production process of the aluminum electrolysis industry. Improper treatment of waste cathode carbon will inevitably result in significant environmental damage, affecting both flora and fauna. Therefore, ultrasound-assisted leaching was employed to extract the waste cathode carbon, using a sodium hydroxide solution as the leaching medium to recover valuable metals and electrolytes, thereby mitigating environmental risks and reclaiming resources. Optimal conditions for ultrasonic-assisted alkali leaching were determined through a single-factor experiment: a leaching temperature of 70 °C, a liquid-solid ratio of 7:1, a leaching time of 50 min, an alkali concentration of 100 g/L, and ultrasonic power of 250 W. Under these conditions, the fluoride leaching efficiency reached 89.17 %, and the lithium ion leaching efficiency was 86.33 %. Comparative analyses between traditional leaching methods and the optimized experiments revealed that the advantages of ultrasonic action and cyclic leaching contributed to an increase of 5.28 % in the fluoride leaching efficiency and 11 % in the lithium ion leaching efficiency. Furthermore, ultrasonic-assisted leaching significantly reduces the leaching time to 50 min while achieving a higher rate of impurity removal.

The first isotopic evidence of Early Iron Age lead ore exploitation in the Silesian‐Krakow upland, Poland: a provenance study of Lusatian culture lead ornaments

AbstractThe Bronze and Early Iron Ages witnessed a significant increase in trade relations driven by the search for valuable metals. This paper presents new insights into the use of galena from the Silesia and Krakow Upland region in southern Poland, known as the ‘Olkusz ore deposits’, within the context of metal ores in prehistoric Europe. Eleven lead‐based ornaments from Lusatian Urnfield Culture cemeteries were examined using lead isotope analysis. The majority of these ornaments were found to be made from local ore, which provides evidence for the early exploitation of Olkusz lead deposits dating back 1,000 years earlier than previously known from archaeological artefacts.

Comparing the hedge and safe haven properties of individual commodities for China and United States equity sectors

PurposeThe purpose of this paper is to scrutinize the safe haven benefits of 13 individual commodities for the USA and Chinese equity sectors during the financial turmoil period. Therefore, sectoral investors in the USA and China could invest in those specific commodities that provide stable returns during the health crisis and financial turmoil periods.Design/methodology/approachThe daily data spans from February 1, 2015, to July 28, 2022. The present study applies several different approaches to analyzing the data set. The author apply the cross-quantilogram (C.Q) methodology to capture the lead-lag bivariate quantile interdependence between two stationary time series variables during the bearish, bullish and normal periods. Then the study used the hedging effectiveness (HE) and conditional diversification benefits (CDB) approaches to capture the hedging and diversification benefits of commodity classes and individual commodities.FindingsThe noteworthy findings of the quantilogram methodology reveal that livestock and agriculture commodities serve as better refuges as compared to the precious metals and energy index in both countries. On average, precious metals failed to serve as safe haven investments for the USA and Chinese equity market sectors. All energy commodities except soybean oil had strong comovements with China and the US equity sectors during bearish, bullish and normal periods. Lean hogs, fiddler cattle and live cattle are perfect hedging assets for both countries due to the presence of blue color at normal and bullish periods in all C.Q heat-maps. The HE table depicts that commodity indices and individual commodities failed to serve as hedging assets for the Chinese equity sectors. But commodities are semistrong hedging assets for the US equity sectors and the S&P 500 due to the average HE values being 0.7 and above. The CDB values depict that precious metals provide diversification benefits in both equity markets.Practical implicationsThe present study results have important implications for equity sector investors of the USA and China in suggesting particular commodity during the financial turmoil period. During the bearish market condition, risk averse equity sector investors can invest in livestock commodities and agriculture commodities, due to their relatively stable returns. In addition, policymakers can use the analysis insights to formulate policy tools and monitoring mechanisms, effectively mitigating the unfavorable effects arising from asymmetric dependence between commodities and equity sectors during the upper tail, middle and lower tail. Policymakers can suggest equity investors to invest in which commodity during extreme conditions.Originality/valueThe current study has the following points of originality. First, to the best of the author’s knowledge, this is the first study to investigate the individual commodities’ roles as safe havens taken from all four major commodity classes. More importantly, it is also noticeable that the safe haven abilities of commodities are usually tested for the stock market, but the equity sectors are ignored. Therefore, the present study used both stock market and sectoral indices data.

Electrodeposition of Nickel–Molybdenum–Phosphide on copper foam electrode for efficient hydrogen evolution reaction

In the quest for efficient and cost-effective catalysts to drive the hydrogen evolution reaction (HER) in electrochemical water splitting, copper foam (CuF) is a favorable candidate for electrode coating. Precious metal catalysts like Pt/C dominate the field but must be improved because of their high cost and scarcity. Therefore, we have synthesized and evaluated a sequence of nickel-originated electrocatalysts (Ni, NiMo, NiP, and NiMoP) with the electrodeposition of CuF to facilitate substantial improvements in HER performance. Herein, the Ni–Mo–P ternary system, owing to its desirable electronic structure and catalytic mechanism, contributes to enhancing the thermodynamics and kinetics of the HER. Performance analysis reveals that all studied catalysts follow the order of Ni/CuF > NiMo/CuF > NiP/CuF > NiMoP/CuF regarding both the Tafel slope and overpotential. Hence, the top performer, NiMoP/CuF, exhibits tremendous thermodynamics with an η10 = 159 mV and Tafel slope kinetics of 126.66 mV·dec⁻1 at 1.0 M KOH in water splitting. Overall, this report presents a well-capable way of optimizing the electrocatalytic function and stability of CuF-electro-coated catalysts for the HER. This research opens new avenues for cost-effective, stable, and efficient HER catalysts, showcasing the potential of NiMoP/CuF in advancing sustainable hydrogen production technologies.

Analysis of membrane fouling during microfiltration of copper sulfide precipitates

Membrane filtration, particularly MF-UF, has previously been assessed as an attractive process for clarifying and recovering valuable metals from metal sulfide precipitation. Previous results of the high transmembrane flux achieved have shown to be promising. However, those studies were primarily focused on demonstrating the method’s feasibility and estimating its performance under different operational conditions. Based on that, this study represents a significant advancement in the field, assessing the fouling behavior and its impact on process performance during the microfiltration of metal sulfide precipitates. Different operational conditions were evaluated using commercial microfiltration membranes operating in batch and continuous regimes, varying Cu concentration in the feed solution (200 and 1800 mg/L), and cross-flow velocities (0.2 – 0.16 m/s). Batch recirculation tests had over 80 % better flux results than the long-term continuous-mode operation tests, mainly due to a progressive decline in the membrane flux observed at longer operation times.Moreover, the cross-flow velocity evaluation indicated that elevated tangential flow rates might result in a decline in the performance of particles with high aggregation behavior. Analyses with modified Hermia’s models and with SEM-EDX image characterizations demonstrated that cake filtration represents the primary fouling mechanism in this process under long-term operation. The present study offers crucial insights that will inform the further development of MF for the treatment of metal sulfide precipitates.

Leveraging Deep Learning for Time-Series Extrinsic Regression in Predicting the Photometric Metallicity of Fundamental-Mode RR Lyrae Stars.

Astronomy is entering an unprecedented era of big-data science, driven by missions like the ESA's Gaia telescope, which aims to map the Milky Way in three dimensions. Gaia's vast dataset presents a monumental challenge for traditional analysis methods. The sheer scale of this data exceeds the capabilities of manual exploration, necessitating the utilization of advanced computational techniques. In response to this challenge, we developed a novel approach leveraging deep learning to estimate the metallicity of fundamental mode (ab-type) RR Lyrae stars from their light curves in the Gaia optical G-band. Our study explores applying deep-learning techniques, particularly advanced neural-network architectures, in predicting photometric metallicity from time-series data. Our deep-learning models demonstrated notable predictive performance, with a low mean absolute error (MAE) of 0.0565, the root mean square error (RMSE) of 0.0765, and a high R2 regression performance of 0.9401, measured by cross-validation. The weighted mean absolute error (wMAE) is 0.0563, while the weighted root mean square error (wRMSE) is 0.0763. These results showcase the effectiveness of our approach in accurately estimating metallicity values. Our work underscores the importance of deep learning in astronomical research, particularly with large datasets from missions like Gaia. By harnessing the power of deep-learning methods, we can provide precision in analyzing vast datasets, contributing to more precise and comprehensive insights into complex astronomical phenomena.

Wine – The Favourite Beverage of Serbian Medieval Rulers and Nobility

Wine, as the most noble and beloved drink of the Middle Ages, was primarily consumed in the courts of Serbian medieval rulers and nobility. During the early decades of the 14th century, Serbian rulers and nobles imported wine from the coastal cities of Zeta, which were under Serbian rule and where viticulture was the main agricultural production. The nobility from Serbian lands gravitating towards the Adriatic Coast (Trebinje and Hum) during the 14th and 15th centuries imported wine from the region of Dubrovnik, which represented the largest producer of this drink on the eastern coast of the Adriatic Sea. By the first decades of the 15th century, viticulture had reached a higher level of development even in the inner Serbian regions, especially in the vicinity of urban settlements, enabling rulers and nobility to have access to larger quantities of domestic wine. During visits and stays in Dubrovnik, Serbian rulers and regional lords were often honored with generous amounts of wine. This drink was almost invariably present at rulers’ and nobility’s banquets, organized for various occasions, but also as a form of everyday socializing and entertainment, where toasts were raised with glasses of wine in hand. The military dignitaires and soldiers also consumed wine during military campaigns. It is assumed that various types of red wine were more commonly consumed, among which the well-known kratošija from the Budva area and tamjanika from the Dubrovnik region, the latter also being cultivated as a white variety. White wine was considered more luxurious, such as trebbiano wine from Dubrovnik, wine from the Itailian town of Ortona, as well as the particulary esteemed malvasia, which Serbian and Bosnian rulers imported from Dubrovnik and Venice in the late 14th and the first half of the 15th century. In the summer months, wine was consumed chilled with ice, while during winter, pure wine was consumed. At the ruler’s court, a servant or cupbearer was responsible for the wine, referred to during the period of the Serbian Empire (1346–1371), as enohijar, a term of Greek origin. The person overseeing the servant and other courtiers in the ruler’s court held the title of grand servant, which was granted to members of the most prestigious noble families. Large quantities of wine were stored in fortresses near the ruler’s court or in special cellars called vinice or pivnice. Rulers and nobles’ tableware for pouring and drinking wine was made from precious metals, mostly silver. For pouring wine, vessels known as bokal, bardak, imbrik, kondir, možul, and others were used, with the goblet, glass and cup being especially favored among the wine glasses.

Oxygen-enriched Fe-N-C electrocatalyst for efficient oxygen reduction reaction

The cathode's oxygen reduction reaction (ORR) plays a crucial role in a variety of fuel cells. Developing affordable and efficient non-precious electrocatalysts for the ORR poses a major hurdle in the realm of electrochemical energy technologies. This work presents a transition metal-based catalyst, Fe-ONC, in which Fe is loaded in an oxygen-enriched nitrogen-doped carbon (NC) material. Oxygen enrichment of the catalyst was achieved by a pre-oxidation strategy. The XPS analysis reveals that Fe-ONC exhibits a higher abundance of oxidized species. The Fe of Fe-ONC exists in the form of Fe3O4 particles and Fe-Nx, respectively, which are uniformly distributed in the NC. The even spread of iron sites and the plentiful presence of oxygen-rich species are key factors in the superior ORR efficiency of Fe-ONC. Fe-ONC's half-wave potential (E1/2) in an alkaline environment (0.1 M KOH) stands at 0.891 V, markedly surpassing the standard commercial Pt/C value (0.840 V). Additionally, Fe-ONC demonstrated enhanced longevity and resistance to ethanol in comparison to commercially available Pt/C. Fe-ONC's outstanding efficacy highlights its potential as an alternative to precious metal catalysts. The document outlines a plan for creating ORR catalytic materials that are sustainable, economical, and efficient.