Late Quaternary aggradation and incision in the headwaters of the Yangtze River, eastern Tibetan Plateau, China

River aggradation or incision at different spatial-temporal scales are governed by tectonics, climate change, and surface processes which all adjust the ratio of sediment load to transport capacity of a channel. But how the river responds to differential tectonic and extreme climate events in a catchment is still poorly understood. Here, we address this issue by reconstructing the distribution, ages, and sedimentary process of fluvial terraces in a tectonically active area and monsoonal environment in the headwaters of the Yangtze River in the eastern Tibetan Plateau, China. Field observations, topographic analyses, and optically stimulated luminescence dating reveal a remarkable fluvial aggradation, followed by terrace formations at elevations of 55-62 m (T7), 42-46 m (T6), 38 m (T5), 22-36 m (T4), 18 m (T3), 12-16 m (T2), and 2-6 m (T1) above the present floodplain. Gravelly fluvial accumulation more than 62 m thick has been dated prior to 24-19 ka. It is regarded as a response to cold climate during the last glacial maximum. Subsequently, the strong monsoon precipitation contributed to cycles of rapid incision and lateral erosion, expressed as cut-in-fill terraces. The correlation of terraces suggests that specific tectonic activity controls the spatial scale and geomorphic characteristics of the terraces, while climate fluctuations determine the valley filling, river incision and terrace formation. Debris and colluvial sediments are frequently interbedded in fluvial sediment sequences, illustrating the episodic, short-timescale blocking of the channel ca. 20 ka. This indicates the potential impact of extreme events on geomorphic evolution in rugged terrain

Fluvial or aeolian? Unravelling the origin of the silty clayey sediment cover of terraces in the Hanzhong Basin (Qinling Mountains, central China)

This study is focused on a silty clayey sedimentary sequence on a terrace in the intramontane Hanzhong Basin, located in the Qinling Mountains (QLM), central China. Traditionally, the QLM are considered to have blocked dust transport from northwest to southeast China. However, in recent years, geo-archaeological studies have documented loess-palaeosol sequences at numerous locations in and surrounding the QLM. In the loess deposits overlying the terraces of the Hanjiang River in the Hanzhong-, Ankang- and Yunxian basins, abundant artefacts, flakes, stone tools (e.g., scrapers and choppers) and cores are commonly found. The loess deposits have been deposited with lower sedimentation rates, and they are finer grained and more intensely weathered compared to the loess deposits on the Central Loess Plateau (CLP). The loess deposits overly coarse sandy and gravely fluvial deposits (terraces). Silty fluvial deposits are situated in between them. Discrimination between these two types of deposits could prove difficult because both deposits are fine grained (silt and clay) and can have similar grain size distribution characteristics. This is, however, crucial for palaeo-environmental interpretations during hominin occupation, understanding fluvial morphodynamics, and for pedostratigraphic correlation with the typical loess-palaeosol sequences on the CLP. The aim of this research is to determine and characterize the transition of the fluvial to aeolian depositional environment in a fine grained sequence, based on field observations, organic matter and carbonate content, grain size and shape analyses, mineral content (mica's) and end-member modelling of the grain size dataset. In addition, terrestrial cosmogenic nuclides (TCN) burial dating is used to determine the age of the basal, coarse grained fluvial deposits. The determined age, 0.6 ± 0.14 Ma, allows for a chronological correlation of the deposits to the loess-palaeosol sequence on the CLP independent from the pedostratigraphic correlation. This age also gives insight in terrace abandonment and the fluvial morphodynamics of the Hanjiang River. The result indicates a clear distinction between sediments deposited in a fluvial environment and those formed in an aeolian depositional environment. However, the aeolian (loess) deposits show some atypical characteristics. For example, the end-member model results show a coarsening in the five palaeosol layers. This is in contrast with the fine grained nature of palaeosols on the CLP. The coarsening observed in the studied palaeosol layers is interpreted as the result of local surface runoff processes, eroding fine sediment and/or depositing relatively coarse material during interglacial periods. Because of the known depth of the fluvial-aeolian transition and the absolute age of the TCN burial dated terrace deposits, pedostratigraphic correlation of the palaeosol layers with the Central Loess Plateau is possible. The oldest palaeosol is correlated with S5 (0.625–0.503 Ma). The transition from a fluvial to aeolian environment takes place in L6, between 0.625 and 0.693 Ma. This is consistent with the TCN age of 0.6 ± 0.14 Ma. This age also marks the abandonment of the terrace caused by incision of the Hanjiang River, which is possibly related to an uplift phase of the QLM

Fluvial terrace formation and its impacts on early human settlement in the Hanzhong basin, Qinling Mountains, central China

The Qinling Mountains (QLM) form the climatic boundary between the temperate north and subtropical south of China. Many important Paleolithic archaeological sites located on fluvial terraces in this area have been reported in recent decades. Abundant artifacts have been excavated in silt layers overlying fluvial gravels and coarse sands. These silt layers have thus far been interpreted as aeolian deposits. However, in principle they could also represent (in part) fluvial (floodplain) deposits, especially near the base of fine-grained sequences. Reconstruction of fluvial terrace formation is crucial for the correct interpretation of the environment of hominin occupation. In this paper, two sediment sequences from two Paleolithic sites, located on different terrace levels of the Hanjiang River in the Hanzhong basin, are studied mainly using grain-size and grain-shape analyses. In addition, grain-size distributions have been unraveled by applying end-member modelling to distinguish different sedimentary environments. The results show that three different units can be discriminated in each section. The lower unit, consisting of gravelly sand mixed with fine silt, is interpreted as shallow-channel-fill sediment deposited during the start of the transition from a channel to a floodplain environment. The middle unit comprises a fine-grained, gradually fining-upward sequence, representative a floodplain environment. At its base, it reflects a high-energy floodplain situation; at its top, the sequence is interpreted as a low-energy floodplain environment with aeolian input (settling in static water). The third, uppermost unit consists of aeolian loess interbedded with paleosol(s) and sediments that are interpreted as the results of episodic surface runoff. The gradual transition between the 3 units and the gradual fining upward trend of the middle unit indicates that there is no considerable age gap (no hiatus) between the fluvial- and aeolian sedimentary environments. Stone artifacts have been found in all 3 units, with difference abundance, indicating that both the aeolian and floodplain depositional environments provided favorable living conditions. For the floodplain environment, the resources of water and raw materials (fluvial gravels) for tool making may have offered fundamental resources for hominin settlement

Analysis of phosphorus forms in sediment cores from ephemeral ponds on Ardley Island, West Antarctica

The guano of penguins, other seabirds, and pinnipeds is an important source of phosphorus in the ecosystems of Antarctica. To study the vertical distribution of phosphorus in sediments influenced by penguins, we measured phosphorus forms in two sediment cores (G1 and Q2) from ephemeral ponds on Ardley Island. We also investigated the correlations between these phosphorus forms and physicochemical characteristics. Inorganic phosphorus was the main form of phosphorus in both cores. The vertical distribution patterns of phosphorus forms in G1 and Q2 differed, indicating different sedimentary sources. The G1 sediment profile was more influenced by penguin guano than the Q2 profile, and as a result sediments in the G1 core had higher total phosphorus, non-apatite inorganic phosphorus, and apatite phosphorus content. The findings from two ephemeral ponds on Ardley Island indicate that the contribution of penguin guano to organic matter in G1 core has increased in recent times, while Q2 showed a relatively larger contribution from mosses in ancient times, evident from the lithology and the vertical trend in organic matter

Mobile Guardian: A Novel Positioning and Monitoring System for Outdoor Special Users Based on GPS

Different to traditional vehicle positioning and navigation systems, requirements of positioning operations for individuals are always contingently, and it pays more attention to making navigation devices portable and easy to use. Bayed on GPS and GSM, a novel positioning and monitoring system for outdoor special users called Mobile Guardian is presented in this paper. Through analyzing the structure of GPS data, location-related information such as longitude and latitude of users can be extracted from GPS data stream. The GSM module which supported AT commands, is used to transmit these location data and telecommands between users and the monitoring center. And the technology for encapsulating and parsing XML spacial data is utilized fir Google Earth to display the detailed geographical information on the screen. Experiments show that the system is effective and could be popularized to family monitoring

Comparison of osteogenic capability of 3D-printed bioceramic scaffolds and granules with different porosities for clinical translation

Pore parameters, structural stability, and filler morphology of artificial implants are key factors influencing the process of bone tissue repair. However, the extent to which each of these factors contributes to bone formation in the preparation of porous bioceramics is currently unclear, with the two often being coupled. Herein, we prepared magnesium-doped wollastonite (Mg-CSi) scaffolds with 57% and 70% porosity (57-S and 70-S) via a 3D printing technique. Meanwhile, the bioceramic granules (57-G and 70-G) with curved pore topography (IWP) were prepared by physically disrupting the 57-S and 70-S scaffolds, respectively, and compared for in vivo osteogenesis at 4, 10, and 16 weeks. The pore parameters and the mechanical and biodegradable properties of different porous bioceramics were characterized systematically. The four groups of porous scaffolds and granules were then implanted into a rabbit femoral defect model to evaluate the osteogenic behavior in vivo. 2D/3D reconstruction and histological analysis showed that significant bone tissue production was visible in the central zone of porous granule groups at the early stage but bone tissue ingrowth was slower in the porous scaffold groups. The bone tissue regeneration and reconstruction capacity were stronger after 10 weeks, and the porous architecture of the 57-S scaffold was maintained stably at 16 weeks. These experimental results demonstrated that the structure-collapsed porous bioceramic is favorable for early-stage osteoconduction and that the 3D topological scaffolds may provide more structural stability for bone tissue growth for a long-term stage. These findings provide new ideas for the selection of different types of porous bioceramics for clinical bone repair

Differentiation and classification of bacterial endotoxins based on surface enhanced Raman scattering and advanced machine learning

Bacterial endotoxin, a major component of the Gram-negative bacterial outer membrane leaflet, is a lipopolysaccharide shed from bacteria during their growth and infection and can be utilized as a biomarker for bacterial detection. Here, the surface enhanced Raman scattering (SERS) spectra of eleven bacterial endotoxins with an average detection amount of 8.75 pg per measurement have been obtained based on silver nanorod array substrates, and the characteristic SERS peaks have been identified. With appropriate spectral pre-processing procedures, different classical machine learning algorithms, including support vector machine, k-nearest neighbor, random forest, etc., and a modified deep learning algorithm, RamanNet, have been applied to differentiate and classify these endotoxins. It has been found that most conventional machine learning algorithms can attain a differentiation accuracy of >99%, while RamanNet can achieve 100% accuracy. Such an approach has the potential for precise classification of endotoxins and could be used for rapid medical diagnoses and therapeutic decisions for pathogenic infections