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Item type:Publication, Development of global temperature and pH calibrations based on bacterial 3-hydroxy fatty acids in soils(Copernicus Publications, 2020-11-24)Abstract. 3-hydroxy fatty acids (3-OH FAs) with 10 to 18 C atoms are membrane lipids mainly produced by Gram-negative bacteria. They have been recently proposed as temperature and pH proxies in terrestrial settings. Nevertheless, the existing correlations between pH/temperature and indices derived from 3-OH FA distribution (RIAN, RAN15 and RAN17) are based on a small soil dataset (ca. 70 samples) and only applicable regionally. The aim of this study was to investigate the applicability of 3-OH FAs as mean annual air temperature (MAAT) and pH proxies at the global level. This was achieved using an extended soil dataset of 168 topsoils distributed worldwide, covering a wide range of temperatures (5 °C to 30 °C) and pH (3 to 8). The response of 3-OH FAs to temperature and pH was compared to that of established branched GDGT-based proxies (MBT'5Me/CBT). Strong linear relationships between 3-OH FA-derived indices (RAN15, RAN17 and RIAN) and MAAT/pH could only be obtained locally, for some of the individual transects. This suggests that these indices cannot be used as paleoproxies at the global scale using simple linear regression models, in contrast with the MBT'5Me and CBT. However, strong global correlations between 3-OH FA relative abundances and MAAT/pH were shown by using other algorithms (multiple linear regression, k-NN and random forest models). The applicability of the k-NN and random forest models for paleotemperature reconstruction was tested and compared with the MAAT record from a Chinese speleothem. The calibration based on the random forest model appeared to be the most robust. It showed similar trends with previously available records and highlighted known climatic events poorly visible when using local 3-OH FA calibrations. Altogether, these results demonstrate the potential of 3-OH FAs as paleoproxies in terrestrial settings. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Dissolution kinetics and solubilities of copper sulfides in cyanide and hydrogen peroxide leaching: applications to increase selective extractions(Elsevier, 2021-11-01)Accurate quantification of secondary and primary sulfide minerals is fundamental for resource evaluation, ore processing, and long-term sustainability of mining operations. In addition to visual mapping and automated mineral quantification, chemical analysis can also be harnessed to characterize the mineralogy of ore deposits. By evaluating the conditions in which certain minerals can be selectively dissolved from others, a chemical evaluation could provide geochemical speciation data of low-abundance minerals, such as copper/iron sulfides present in low-grade copper ores. The selective dissolution of copper sulfide minerals is, however, understudied. Here, we evaluate the use of potential selective dissolution conditions to differentiate supergene copper sulfides from hypogene copper sulfides. By characterizing the dissolution kinetics of chalcocite, covellite, bornite, enargite, chalcopyrite, and pyrite concentrates, we found that alkaline cyanidation (and not hydrogen peroxide or acid leaching in the presence of oxidizing agents) selectively dissolves supergene copper sulfides, which can be applied in a sequential extraction scheme to estimate the sulfide mineralogy of tailings samples. Cyanide completely dissolved chalcocite and covellite within 5–15 min, whereas dissolution in acid oxidative media only partially dissolved copper sulfides. Pyrite, chalcopyrite, enargite, and bornite under 0.5% KCN leaching (1 mg/mL) for 10 min showed approximately 1, 10, 30, and 40% of copper recovery, respectively. Cyanide leaching applied in sequential extractions of porphyry copper tailings samples from the Piuquenes impoundment, La Andina, Chile, improved the selective dissolution of secondary sulfides compared to a previously proposed hydrogen peroxide dissolution method, thus allowing their differentiation from primary sulfide minerals. The selective leaching of supergene sulfides by cyanidation provides a cheap and efficient method to estimate the copper sulfide mineralogy in copper ores, facilitating the sustainability and resource evaluation of mining operations. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Comparative study of anion removal using adsorbents prepared from a homoionic clay(Elsevier, 2021-05-01)The adsorption capacity of adsorbent materials (organophilic clays) prepared from a homoionic clay was compared for the removal of nitrates and nitrites present in aqueous solution in batch systems at room temperature.The organophilic clays were obtained by replacing the exchange cations present in the precursor clays with quaternary ammonium cations. For this purpose, two precursor clays were used, a natural clay (FS) and the same clay exchanged with sodium (CP) and two ammonium cations with different structure: hexadecyltrimethylammonium (HDTMA) and benzyltriethylammonium (BTEA) with amounts equivalent to 1.5, 2.5 and 4.0 cation exchange capacity (C.E.C.). Ion exchange is important to obtain a good affinity between organoclay and anionic contaminants. The clays were characterized by XRD, FTIR and SEM-EDX. The maximum adsorption capacities of the CP-HDTMA-4.0 clay for nitrate and nitrite ion were 7.23 and 0.65 mg g−1, respectively, indicating that the organophilic clay obtained from the homoionic clay with 4 C.E.C. ion exchange and the surfactant HDTMA had significant effects on the adsorption of nitrate and nitrite ions. Finally, the possible mechanisms and implications of the results for the use of these organophilic clays as adsorbent materials for the removal of the ions under study are discussed. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Detektion und Visualisierung der Pflanzen-Pathogen-Response durch Nah-Infrarot-fluoreszente Polyphenolsensoren(Wiley, 2021-10-06)Pflanzen nutzen Sekundärmetabolite, wie Polyphenole, zur chemischen Verteidigung gegenüber Pathogenen und Herbivoren. Trotz ihrer wichtigen Rolle bei der Reaktion von Pflanzen auf Pathogene bleibt die Detektion von Polyphenolen in komplexen Pflanzengeweben eine Herausforderung. Hier berichten wir vom Aufbau molekularer Sensoren zur Visualisierung pflanzlicher Polyphenole, basierend auf Nah‐Infrarot (NIR)‐fluoreszenten Kohlenstoff‐Nanoröhren (SWCNTs). Dabei identifizierten wir Oberflächenmodifikationen mit Polyethylenglycol‐Phospholipiden, die (6,5)‐SWCNTs sensitiv (Kd=90 nM) gegenüber pflanzlichen Polyphenolen machen und die Emission (ca. 1000 nm) quenchen und bathochrom (bis zu 20 nm) verschieben. Diese Sensoren detektieren Unterschiede im Gesamtphenolgehalt nach Herbivor‐ oder Pathogenstimulus im Nutzpflanzensystem und in Blattextrakten. Ferner erlauben sie die Bildgebung der Pathogen‐induzierten Polyphenolausschüttung (24 h). Dieser Ansatz ermöglicht die In‐situ‐Visualisierung und Charakterisierung der chemischen Pflanzenverteidigung in Echtzeit und ebnet den Weg zur Phänotyp‐basierten Optimierung der Polyphenolsekretion. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Development of global temperature and pH calibrations based on bacterial 3-hydroxy fatty acids in soils(Copernicus GmbH, 2021-07-01)Gram-negative bacteria produce specific membrane lipids, i.e. 3-hydroxy fatty acids with 10 to 18 C atoms. They have been recently proposed as temperature and pH proxies in terrestrial settings. Nevertheless, the existing correlations between pH or temperature and indices derived from 3-OH FA distribution are based on a small soil dataset (ca. 70 samples) and only applicable regionally. The aim of this study was to investigate the applicability of 3-OH FAs as mean annual air temperature (MAAT) and pH proxies at the global level. This was achieved using an extended soil dataset of 168 topsoils distributed worldwide, covering a wide range of temperatures (5 to 30 ∘C) and pH (3 to 8). The response of 3-OH FAs to temperature and pH was compared to that of established branched glycerol dialkyl glycerol tetraether (GDGT)-based proxies (MBT'5Me/CBT). Strong linear relationships between 3-OH-FA-derived indices (RAN15, RAN17 and RIAN) and MAAT or pH could only be obtained locally for some of the individual transects. This suggests that these indices cannot be used as palaeoproxies at the global scale using simple linear regression models, in contrast with the MBT'5Me and CBT. However, strong global correlations between 3-OH FA relative abundances and MAAT or pH were shown by using other algorithms (multiple linear regression, k-NN and random forest models). The applicability of the three aforementioned models for palaeotemperature reconstruction was tested and compared with the MAAT record from a Chinese speleothem. The calibration based on the random forest model appeared to be the most robust. It generally showed similar trends with previously available records and highlighted known climatic events poorly visible when using local 3-OH FA calibrations. Altogether, these results demonstrate the potential of 3-OH FAs as palaeoproxies in terrestrial settings. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Combined H-N cross-polarization and carbonyl detection NMR spectroscopy allow to record high-resolution, high-sensitivity spectra of alpha-synuclein in bacterial cells(Springer Science+Business Media, 2022-10-30)Studies of intrinsically disordered proteins (IDPs) under physiological conditions by conventional NMR methods based on proton detection are severely limited by fast proton amide solvent exchange. Carbon detection has been proposed as a solution to the exchange problem but is hampered by low sensitivity. Here, we present a protocol combining proton–nitrogen cross-polarization and carbonyl detection to record high-resolution and high-sensitivity NMR spectra of IDPs under physiological conditions. The protocol describes a step-by-step method to register high-quality N-CO correlation spectrum of alpha-synuclein in E.coli bacterial cells at 37 °C. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Frontispiz: Detektion und Visualisierung der Pflanzen‐Pathogen‐Response durch Nah‐Infrarot‐fluoreszente Polyphenolsensoren(Wiley, 2022-01-05)Biosensoren Molekulare Sensoren für die Bildgebung von Polyphenol in Pflanzen basierend auf nahinfrarotfluoreszierenden einwandigen Kohlenstoffnanoröhren werden von Sebastian Kruss et al. in ihrem Forschungsartikel (e202108373) vorgestellt. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, The role of skin-contact time and heads fraction on Pisco terpene content(2025-07-01)Pisco is a traditional Peruvian spirit, and Muscat of Alexandria (“Italia”) is amongst the main grape varieties used to produce it. Pisco production is mainly artisanal and varies widely across regions and producers; more information is needed on the impact of different operations on its composition. This study demonstrated the effect of changes in skin-contact duration and the amount of “head fraction” discarded on terpene content to guide producers during Pisco manufacturing.2 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Steady State Free Precession NMR without Fourier Transform: Redefining the Capabilities of <sup>19</sup>F NMR as a Discovery Tool(Wiley, 2025-01-28)The 2024 Zurich perfluorinated compounds (PFCs) summit reiterated the urgent need for non‐selective analytical approaches for PFC detection. 19 F NMR holds great potential, however, sensitivity limitations lead to long analysis times and/or the possibility of not detecting low concentration species. Steady State Free Precession (SSFP) NMR collects the signal in a steady state regime, allowing 100's of acquisitions in the timespan of a single traditional NMR scan. Unfortunately, data truncation from SSFP leads to artifacts and spectral broadening with Fourier transform, hindering interpretation. When non‐Fourier based time‐domain analysis is used, namely, complete reduction to amplitude frequency tables (CRAFT), limitations of SSFP are eliminated while sensitivity gains are retained. This work introduces the combined approach, then applies it for the measurement of PFCs in environmental and biological samples. In all cases, the approach reduces analysis time from many hours to minutes and/or greatly increases the range of compounds detected. For example, when PFOA was spiked into human blood, the detection limit improved ~50‐fold vs standard NMR, while in a standard mixture, the approach detected compounds missed by LC‐MS/MS. The technique can be adapted to any nucleus providing a facile approach to reduce experiment time and improve sensitivity of NMR in general.4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Regeneration of Deteriorated Internal Combustion Engine Components used in Thermal Power Plants(2025-01-30)The generation of electric power through internal combustion engines plays an important role in the world economy. Exhaust cases and valves are critical engine components and are subjected to high pressures and temperatures. The additive remanufacturing technology of mechanical components that have reached the end of their useful life due to wear, through the L-DED laser directed energy deposition method, proves to be an effective method to obtain spare parts with similar or even superior characteristics to a new part, extending the product life cycle in the circular economy. The process consists of obtaining 3D models through reverse engineering, additive remanufacturing by L-DED and final machining. It was determined through the study that this methodology can be successfully applied to the exhaust boxes and valves of internal combustion engines for electric generation. The results obtained have shown that this remanufacturing method is an effective solution for the recovery of exhaust boxes and valves that have completed their useful life and can be applied to other engine elements, reducing the cost of the spare part compared to a new one and bringing with it important environmental benefits. In reference to the remanufacturing time, it has been determined that the application of the L-DED process in the exhaust boxes and valves is 3943 and 3677 s respectively. In addition to this time, the time used in the initial preparation and final machining must be added; however, the time is substantially less than the manufacturing of a new spare part, which brings with it an increase in the availability of these spare parts to perform scheduled maintenance in the engines for power generation, contributing to improve the efficiency of the national electric system.2