High-resolution carbon isotope stratigraphy of the Lower and Middle Ordovician succession of the Yangtze Platform, China

Variation in the relative abundance of the stable carbon isotopes has been widely used to correlate Ordovician marine successions over the past two decades. To date, only a few of studies of Ordovician carbon chemostratigraphy have been conducted in South China. Most of the previous studies in this field have focused on specific time intervals and/or events in the Middle and Upper Ordovician. The Lower and Middle Ordovician of the Yangtze Platform is typically represented by a sedimentary succession dominated by carbonate rocks, which is ideal for studying the carbon chemostratigraphy. Three sections spanning the Nantsinkuan/Lunshan, Fenhsiang, Hunghuayuan, and Dawan/Zitai formations, corresponding to the TremadocianâDapingian in age, have been sampled for high-resolution δ13C chemostratigraphy. Our new δ13C data reveal five tie-points with the potential for global correlation: (1) a positive δ13C excursion in the lower Nantsinkuan Formation within the Tremadocian Rossodus manitouensis Zone; (2) an excursion with two peaks roughly within the late Tremadocian Paltodus âdeltiferâ Zone; (3) a positive δ13C shift in the lower Hunghuayuan Formation, within the early Floian Serratognathus diversus Zone; (4) a gradual positive δ13C shift in the late Floian, ranging from the uppermost S. diversus Zone to the basal Oepikodus evae Zone; (5) a minor negative shift in the lower Dawan/Zitai Formation, within the early Dapingian Baltoniodus triangularis Zone. These excursions are herein used for correlation of the Yangtze Platform strata with successions from South China, North China, the Argentine Precordillera, North America and Baltica. From a palaeogeographical perspective, the Gudongkou, Xiangshuidong and Daling sections represent depositional environments along an inner to outer ramp profile. The δ13C data from these sections show successively heavier (higher) δ13C values with increasing depositional depth, which can be interpreted as due to remineralization of organic carbon within the carbonate rocks formed in the shallow-water environment

Data from: Katian (Late Ordovician) trilobites of the North Qilian Mountains and their palaeogeographical implications for the Proto-Tethys Archipelagic Ocean (PTAO)

<p class="MsoNormal"><span>Trilobites from the middle Koumenzi Formation (Katian, Upper Ordovician) of the North Qilian Mountains, Menyuan, northeastern Qinghai Province are systematically documented for the first time. The fauna consists of five families, seven genera and seven species, amongst which one is new (</span><em><span>Remopleurides</span> <span>zhangi</span> </em><span>sp. nov.), showing a close relationship to those of the Kazakh terranes (such as Chu-Ili terrane, Chingiz-Tarbagatai area and KNNTS (Karatau-Naryn and North-Tien Shan Microcontinents)), North China and Laurentia palaeoplates during the Katian (Late Ordovician). The cluster and Non-metric Multidimensional Scaling analyses of the Middle<span class="fontstyle01">–Late Ordovician (</span>late Darriwilian<span class="fontstyle01">–</span>Katian<span class="fontstyle01">) trilobite faunas with 299 genera or subgenera from 46 horizons of 37 areas, provide valuable information for the palaeogeographical reconstruction of the </span>Proto-Tethys Archipelagic Ocean (PTAO) of this interval. The Qilian terrane and adjacent areas are essential components of the PTAO, some of which include the Qilian terrane (QT), the North Qilian Mountains area (NQ), the Altun faulted terrane (AFT), the Hexi Corridor area (HX) and the East Qinling terrane (EQT). Their relative positions within the PTAO are inferred by the palaeobiogeography of trilobite faunas. Based on further discussions on the spatiotemporal distribution of those faunas<span class="fontstyle01">, the </span></span><em><span>Pliomerina</span></em><span> and/or </span><em><span>Sinocybele</span> </em><span>Province of the Middle<span class="fontstyle01">–Late Ordovician (</span>late Darriwilian<span class="fontstyle01">–</span>Katian<span class="fontstyle01">) age is defined as a trilobite faunal province of the PTAO. </span>Moreover, a distinct faunal subprovince, essentially comprised of the South China Palaeoplate and its neighbours (e.g. Tarim, Annamia, Sibuma, East Qinling, Turkestan-Alai and probably Talesh), might be surrounded by the equatorial cold-water tongue.</span></p><p>Funding provided by: Chinese Academy of Sciences<br>Crossref Funder Registry ID: https://ror.org/034t30j35<br>Award Number: XDB26000000</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: https://ror.org/01h0zpd94<br>Award Number: 41972011</p><p>Funding provided by: State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS)*<br>Crossref Funder Registry ID: <br>Award Number: 213123</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: https://ror.org/01h0zpd94<br>Award Number: 41972015</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: https://ror.org/01h0zpd94<br>Award Number: 42072005</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: https://ror.org/01h0zpd94<br>Award Number: 42072007</p><p>Funding provided by: National Natural Science Foundation of China<br>Crossref Funder Registry ID: https://ror.org/01h0zpd94<br>Award Number: 42102130</p&gt

Recovery of Metals from Acid Mine Drainage by Bioelectrochemical System Inoculated with a Novel Exoelectrogen, Pseudomonas sp. E8

Acid mine drainage (AMD) is a typical source of environmental pollution ascribing to its characteristics of high acidity and heavy metal content. Currently, most strategies for AMD treatment merely focus on metal removal rather than metal recovery. However, bioelectrochemical system (BES) is a promising technology to simultaneously remove and recover metal ions from AMD. In this study, both cupric ion and cadmium ion in simulated AMD were effectively recovered by BES inoculated with a novel exoelectrogen, Pseudomonas sp. E8, that was first isolated from the anodic electroactive biofilm of a microbial fuel cell (MFC) in this study. Pseudomonas sp. E8 is a facultative anaerobic bacterium with a rod shape, 0.43–0.47 μm wide, and 1.10–1.30 μm long. Pseudomonas sp. E8 can agglomerate on the anode surface to form a biofilm in the single-chamber MFC using diluted Luria-Bertani (LB) medium as an energy substrate. A single-chamber MFC containing the electroactive Pseudomonas sp. E8 biofilms has a maximum output voltage of 191 mV and a maximum power density of 70.40 mW/m2, which is much higher than those obtained by most other exoelectrogenic strains in the genus of Pseudomonas. Almost all the Cu2+ (99.95% ± 0.09%) and Cd2+ (99.86% ± 0.04%) in simulated AMD were selectively recovered by a microbial fuel cell (MFC) and a microbial electrolysis cell (MEC). After the treatment with BES, the high concentrations of Cu2+(184.78 mg/L), Cd2+(132.25 mg/L), and total iron (49.87 mg/L) in simulated AMD were decreased to 0.02, 0.19, and 0 mg/L, respectively. Scanning electron micrograph (SEM), energy dispersive X-ray spectrometry (EDXS) and X-ray diffraction (XRD) analysis indicate that the Cu2+ and Cd2+ in simulated AMD were selectively recovered by microbial electrochemical reduction as Cu0 (together with trace amounts of Cu2O) or Cd0 on the cathode surface. Collectively, data suggest that Pseudomonas sp. E8 has great potential for AMD treatment and metal recovery

Silicon Nitride Bioceramics Sintered by Microwave Exhibit Excellent Mechanical Properties, Cytocompatibility <i>In Vitro</i>, and Anti-Bacterial Properties

Silicon nitride is a bioceramic with great potential, and multiple studies have demonstrated its biocompatibility and antibacterial properties. In this study, silicon nitride was prepared by a microwave sintering technique that was different from common production methods. SEM and pore distribution analysis revealed the microstructure of microwave-sintered silicon nitride with obvious pores. Mechanical performance analysis shows that microwave sintering can improve the mechanical properties of silicon nitride. The CCK-8 method was used to demonstrate that microwave-sintered silicon nitride has no cytotoxicity and good cytocompatibility. From SEM and CLSM observations, it was observed that there was good adhesion and cross-linking of cells during microwave-sintered silicon nitride, and the morphology of the cytoskeleton was good. Microwave-sintered silicon nitride has been proven to be non-cytotoxic. In addition, the antibacterial ability of microwave-sintered silicon nitride against Staphylococcus aureus and Escherichia coli was tested, proving that it has a good antibacterial ability similar to the silicon nitride prepared by commonly used processes. Compared with silicon nitride prepared by gas pressure sintering technology, microwave-sintered silicon nitride has excellent performance in mechanical properties, cell compatibility, and antibacterial properties. This indicates its enormous potential as a substitute material for manufacturing bone implants

The record of early Silurian climate changes from South China and Baltica based on integrated conodont biostratigraphy and isotope chemostratigraphy

New conodont and stable isotope data are presented from the classical Baizitian section in the Yanbian County of Sichuan Province, South China. The Telychian to Sheinwoodian strata were sampled and studied for carbon isotope stratigraphy and conodont biostratigraphy. The paired δ13Ccarb and δ13Corg data reveal a pronounced positive excursion, the Manitowoc carbon isotope excursion (Manitowoc CIE, ‘Manitowoc Excursion’) spanning the upper Pterospathodus eopennatus Zone and the lower Pterospathodus amorphognathoides amorphognathoides Superzone, with an increase of ca. 2‰ in δ13Ccarb and ca. 5‰ in δ13Corg. Well-bracketed by conodont biostratigraphy, the Manitowoc CIE is an essential tie-point for correlation between the Baizitian succession and the Telychian strata of Baltica and Laurentia. Our new δ13Ccarb and δ13Corg data imply that the carbon isotope excursion previously recognized as the ‘Ireviken Excursion’ (Early Sheinwoodian Carbon Isotope Excursion) at Baizitian should be revised as being the Manitowoc CIE. The Δ13C data presented in this study further suggest a slight concurrent drop of atmospheric CO2, and thus add evidence for a perturbation of the global carbon cycle during the middle Telychian. Based on the combined information from the conodont apatite oxygen isotope records from Estonia and the significant stratigraphic gaps recognized at the Baizitian section, we propose that the latter stratigraphic gaps should correlate with the Telychian Valgu and the early Sheinwoodian glaciation

Purification, Characterization, and Ferrous Oxidation Kinetics of Iron Oxidase from <i>Acidithiobacillus ferridurans</i>

Iron oxidase was proposed to be the initial electron acceptor from the ferrous ion in the iron oxidation of the Acidithiobacillus genus for metal bioextraction; however, its most fundamental property of direct ferrous oxidation kinetics remains undetermined due to the confusion of reaction monitor method. Here, a recombinant iron oxidase from Acidithiobacillus ferridurans Riv11 was constructed, expressed, purified, characterized, and further used to investigate the kinetics and mechanism of ferrous oxidation. This protein is more stable in an acid solution than in a neutral solution. An infrared characteristic peak around 1050 cm−1 of the [Fe4S4] cluster was identified. The [Fe4S4] cluster does not affect the secondary structure of protein, but plays an important role in the stability of protein and strongly absorbs the intrinsic fluorescence of protein, resulting in a great loss of the fluorescence emission. The protein has far more absorbance than those of the iron ions in solution in the visible region; therefore, the maximum difference absorbance around 500 nm between the oxidized and reduced states of protein can be used to monitor the reaction of ferrous oxidation. Accordingly, the kinetic rate constant of the reaction was determined. Bioinformatics analysis and molecular simulation further revealed the underlying molecular mechanism that ferrous ions approach the protein at the edge of a large hydrophobic surface patch nearest to the [Fe4S4] cluster from a direction far from all positively charged residues, which enough enables an efficient electron transfer