Over the past several decades, evolution models for both the PSP and the SCS have been established reasonably. For example, the time of the NNW oriented seafloor spreading of the SCS along the South China Block was calibrated to begin at 33 Ma and cease at 15 Ma, respectively, during which the east subbasin (33-15 Ma) formed first and the southwest subbasin (23.6-16 Ma) formed later (

The impact of central Asian aridification on the low latitude North Pacific Ocean since the late Miocene remains unclear. To address this question, we systematically studied an abyssal manganese nodule from the northwestern Pacific Ocean, which is expected to be sensitive to eolian dust sourced from central Asia. Geochemical variations and the fossilized remains of magnetotactic bacteria within the studied nodule manifest two prominent Asian aridification events at ∼8–7 Ma and 3.6–0 Ma. These results suggest that central Asian aridification impacted both primary productivity and abyssal microbial activity in the NW Pacific Ocean via eolian dust inputs. In contrast to the Pliocene aridification event, the late Miocene event was associated with a primary productivity bloom that is not evident in coeval global primary productivity records, which indicates that the ∼8–7 Asian aridification event was likely due to NE Tibetan Plateau uplift rather than to global cooling.

BACKGROUND Insect‐associated Streptomyces is a valuable resource for development of compounds with antibacterial potential. However, relatively little is known of the secondary metabolites produced by termite‐associated Streptomyces. RESULTS Here, seven compounds including o‐acetaminophenol (1), phenazine‐1,6‐dicarboxylic acid (2), phenylacetic acid (3), phenazinolin D (4), izumiphenazine A (5), izumiphenazine B (6) and phenazinolin E (7) were obtained from the fermentation broth of a termite‐associated Streptomyces showdoensis BYF17, which was isolated from the body surfaces of Odontotermes formosanus. Two additional novel derivative compounds (6a and 6b) were synthesized via acetylation and methylation, respectively. The structures of these compounds were elucidated by spectroscopic analyses. The antibacterial bioassay showed that compound 6a displayed strong inhibitory effects against Pseudomonas syringae pv. actinidiae (Psa), with a zone of inhibition (ZOI) diameter of 20.6 mm, which was comparable to that of positive gentamicin sulfate with a ZOI value of 25.6 mm. Furthermore, the Day 5 curative activities of both compounds 6 and 6a against kiwifruit bacterial canker were 71.5%, which was higher than those of referred oxine‐copper (55.0%) and ethylicin (46.8%) at a concentration of 200 μg mL−1. In addition, the mechanism analysis based on scanning electron microscopic observation revealed that both compounds 6 and 6a destroyed the integrity of the Psa cell membrane. CONCLUSION The results of biological tests showed that these bioactive compounds exhibit potent antimicrobial activities, which have the potential to be developed into new antibacterial agents. © 2023 Society of Chemical Industry.

No abstract

Hematite concentration is an important climatic proxy for environmental (climatic) studies of soils and sediments. However, the accurate quantification of naturally occurring hematite has always been a difficult question, especially for those areas with lower hematite concentrations. Diffuse reflectance spectroscopy (DRS) is an effective method for hematite identification and quantification with lower detection limits. In this study, we synthesized a set of samples with well-determined concentrations to explore the exact detectable range of hematite and propose the most effective transfer function between the DRS proxy and hematite concentration. In addition, natural sediments from Inland Asia and the Western Pacific Ocean were used to further test the feasibility of the new transfer function. Results show that the lowest DRS detection limit for hematite could reach ~0.00078%, but is affected by the natural matrix. We also find that the second derivative of the Kubelka–Munk (K–M) function is monotonically correlated with the hematite concentration (0.00078%–100%), but ambiguities exist for the first derivative. Therefore, the second derivative of the K–M function is highly suggested for the hematite quantification, especially when concentration exhibits a wide range of variations. This study provides important references for the application of hematite proxy and promotes the popularization and development of the DRS method.

The South China Sea (SCS) is the largest marginal sea of the western Pacific Ocean, and is an ideal location for reconstructing past environmental changes in southeast Asia in response to climate change. The northern SCS is

Magnetic surveys have been widely used in archaeological field investigations. However, conventional survey methods are often restricted by complicated field conditions and ambiguities in data interpretation. In this study, a novel magnetic survey system was designed for pre-archaeological investigation (preliminary survey prior to the archaeological excavation) based on a modified quadrotor unmanned aerial vehicle (UAV) and was successfully applied to an archaeological area with a complex landform in Huizhou, China. Results show that the target anomaly identified by UAV aeromagnetic survey corresponds well to the location of a potential archaeological site. Subsequent soil analyses further confirm the archaeological value of UAV aeromagnetic results and provide strong constraints on the interpretation of target anomalies. This study demonstrates that the newly proposed UAV aeromagnetic system can adapt to the various field conditions with the advantages of flexibility and efficiency, which has great potential for future archaeological investigations.

No abstract