The extension and convergence of mean curvature flow in higher codimension

In this paper, we first investigate the integral curvature condition to extend the mean curvature flow of submanifolds in a Riemannian manifold with codimension $d\geq1$, which generalizes the extension theorem for the mean curvature flow of hypersurfaces due to Le-\v{S}e\v{s}um \cite{LS} and the authors \cite{XYZ1,XYZ2}. Using the extension theorem, we prove two convergence theorems for the mean curvature flow of closed submanifolds in ${R}^{n+d}$ under suitable integral curvature conditions.Comment: 29 page

Basic psychological need satisfaction and aggressive behavior: the role of negative affect and its gender difference

Background Basic psychological need satisfaction (BPNS) is a significant factor in a person’s development, especially for adolescents, and the failure to satisfy these basic needs may contribute to individuals’ aggressive behavior. However, it is still unclear about the underlying mechanism by which BPNS is negatively associated with aggressive behavior. This study aimed to explore the relationship between BPNS and aggressive behavior in Chinese adolescents, with a focus on the mediating role of negative affect and its gender differences. Method A sample of 1,064 junior high school students from three schools in China were selected randomly for the cross-sectional survey. The revised Need Satisfaction Scale, the Positive and Negative Affect Schedule, and Youth’s Self-Report were used to measure BPNS, affect, and aggressive behavior. The proposed model was examined by the structural equation modeling test and multi-group comparison analysis. Results The results showed that BPNS was negatively linked with adolescents’ aggressive behavior, and this effect was mediated by negative affect. Moreover, multigroup analysis demonstrated that there existed a stronger negative association between BPNS and negative affect in female group. Also, the mediating effect of negative affect in the model was greater for girls. Conclusions Our findings highlighted the importance of BPNS in adolescents’ social behavior (i.e., aggressive behavior), and reveal disparate patterns in how BPNS affects aggressive behavior in girls as compared to boys

U-Th age distribution of coral fragments from multiple rubble ridges within the Frankland Islands, Great Barrier Reef: implications for past storminess history

Prograded coral rubble ridges have been widely used as archives for reconstructing long-term storm or storminess history. Chronologies of ridge systems in previous studies are often based on a limited number of low-resolution radiocarbon or optically-stimulated luminescence (OSL) ages per ridge (usually only one age per ridge), which carry intrinsic age uncertainties and make interpretation of storm histories problematic. To test the fidelity of storm ridges as palaeo-storm archives, we used high-precision U-Th dating to examine whether different samples from a single ridge are temporally constrained. We surveyed three transects of ridge systems from two continental islands (Normanby Island and High Island) within the Frankland Islands, Great Barrier Reef (GBR), and obtained 96 U-Th dates from coral rubble samples collected from within and between different ridges. Our results revealed significant differences in age ranges between the two islands. The steeper and more defined rubble ridges present on Normanby Island revealed that the majority of U-Th ages (over 60%) from a single ridge clustered within a narrow age range (~100 years). By contrast, the lower and less defined ridges on High Island, which were more likely formed during both storm and non-storm high-energy events, revealed significant scatter in age distribution (>>200 years) with no notable clustering. The narrower age ranges obtained from the steeper and more defined rubble ridges suggest that previous approaches of using either limited samples from a single ridge or low-precision dating methods to establish chronologies are generally valid at centennial to millennial timescales, although caution must be taken to use such approaches for storm history reconstruction on shorter timescales (e.g. decadal). The correlation between U-Th mortality ages of coral rubble and historical stormy periods highlights the possibility of using coral rubble age distribution from rubble ridges to reconstruct the long-term regional storminess history. U-Th age distribution of all dated coral rubble samples, combined with previously published storm-transported coral block data from the same region, revealed at least six relatively stormy periods in the past 500 years in the Frankland Islands region: 1570-1590, 1760-1780, 1800-1830, 1860-1880, 1940-1960, 1980-2010 CE. Wavelet power analysis of the relative probability of U-Th age distribution indicates that the Pacific Decadal Oscillation (PDO) and El Nino-Southern Oscillation (ENSO) may be partially responsible for the long-term variability in stormines

A new technology of basin fluid geochronology: In-situ U-Pb dating of calcite

Basin fluid is the most active geological agent in sedimentary basins, having a close relationship with the generation, migration and accumulation of hydrocarbon resources. Accurate determination of fluid flow history has been a challenging and frontier research topic. In general, the previous studies of basin fluids mainly rely on the analysis of fluid inclusions, which is difficult to successfully reconstruct the events of basin fluids. More seriously, this method is unable to determine the timing of fluid flow events. Authigenic calcite is the direct product of basin fluids. Thus, accurate dating of authigenic calcite provides a new approach to determine the history of fluid flow events. In the field of calcite geochronology, the most widely used dating method was the isotope dilution U-Pb dating approach. However, this approach is time-consuming, and has a low success rate. In recent years, laser ablation technology has greatly facilitated U-Pb dating of accessory minerals (including calcite) because of its high spatial resolution and rapid data acquisition. It has been confirmed that the newly-developed in-situ U-Pb dating method is able to accurately determine the age of calcite with U content less than 10×10 . This method has successfully reconstructed the history of fluid flow events in the sedimentary basins, suggesting that it has a good application prospect in the field of basin fluid geochronology. In the future, it can be expected that the application of in-situ U-Pb dating of calcite together with C-O isotope and rare earth element analysis will be a significant development direction in the field of basin fluid studies. It is worth noting that the determination of stage of authigenic calcite through systematic microscopic identification and diagenetic observation is the premise of application success