Astronomical forcing on the development of depositional sequences has been of particular interest to researchers in recent years. To investigate the forming mechanism of depositional sequences in the ...Middle Permian Maokou Formation, outcrop sequence stratigraphic analysis and cyclostratigraphic analysis were conducted on one outcrop section and one drilling well in South China. Up to ninety-two meter-scale 6th-order parasequences, thirty-one 5th-order parasequences, eight 4th-order parasequences and two 3rd-order sequences were recognized based on vertical facies changes and stratal stacking patterns. Astronomical cycles (i.e., eccentricity, obliquity and precession) were detected by spectral analysis. An ∼3.1 Myr temporal framework and a high-resolution sedimentation rate curve were constructed by cyclostratigraphic analysis. The similar ratios of average thickness for the high-frequency sequences and the spectral periodicities suggest an astronomical forcing origin for the parasequences. The 4th-, 5th-, and 6th-order high-frequency parasequences correlate well with long eccentricity, short eccentricity and obliquity cycles, respectively. The durations of local and global 3rd-order sea-level sequences match the s4-s3 obliquity modulation cycles. Our results suggest that tectonic and autocyclic processes did not exert a major influence on the development of depositional sequences and that in the Middle Permian Maokou Formation the development of 3rd-order sequences and 4th-, 5th- and 6th-order parasequences was controlled by orbitally-driven glacio-eustatic sea-level changes. The coevolution trends in obliquity power, sea-level change and sedimentation rate hold important implications for stratigraphic correlation and sequence stratigraphic subdivision on a regional scale.
•Constructing a high-resolution time scale to constrain the relative role of tectonic processes, stochastic processes, autocyclic processes and eustatic sea level change on 3rd order sequences development.•Confirming the formation of 3rd order sequence and high-frequency paraseqeunces (i.e. 4th, 5th and 6th order) were all controlled by obliquity driven glacio-eustatic sea level change in Middle Permian Maokou Formation.•Using high-resolution sedimentation rate curve to implement stratigraphic correlation and sequence stratigraphic division in a regional scale.
Benthic foraminifera are significant indicators of habitat changes and are useful for paleoenvironmental reconstruction. During the Permian period, the variation in species, individual sizes, and ...morphological characteristics of the different assemblages, such as the fusulinids, is a clue to paleoecological and paleoenvironmental interpretations. The eastern part of the Sichuan Basin, located near the equator in the middle Permian, Guadalupian period, was precipitated by thick beds of marine carbonate rocks with numerous benthic foraminifera. In this study, we record the species and calculate the frequency of benthic foraminifera from 445 thin sections of Guadalupian (Maokou Formation) marine carbonate rocks. Seven types of benthic foraminiferal biofacies are recognized and associated with five sedimentary microfacies in the Erya and Huilongchang sections, eastern Sichuan area. During the early Guadalupian period, small uniserial nodosariids and Endothyrida dominated the benthic foraminiferal assemblages; in the middle Guadalupian period, species of Miliolida, Ammodiscidae, and uniserial nodosariids were common; however, the species of Fusulinida, such as Schwagerina sp. and Verbeekina sp., were abundant in the late Guadalupian period. The associated sedimentary microfacies indicates a shallow open platform to marginal platform. In our study area, the early Guadalupian was deposited in an open platform to grain shoals. This was followed by gradual shallowing as the sedimentary environment shifted to marginal shallow shoals from the middle to late Guadalupian period until the paleoweathering abruptly terminated the deposition at the end of the Guadalupian period.
•The ecological significance of Benthic foraminifera combined with microfacies in the Middle Permian Guadalupian period.•Reconstruction of the sedimentary model to explore paleoenvironmental changes in the upper Yangtze platform.•The water depth decreased gradually during the Guadalupian.•The paleoweathering abruptly terminated the well-oxygenated and nutrient-rich environment of the late Guadalupian period.
Compressive sensing (CS) has been recently and enthusiastically promoted as a joint sampling and compression approach. The advantages of CS over conventional signal compression techniques are ...architectural: the CS encoder is made signal independent and computationally inexpensive by shifting the bulk of system complexity to the decoder. While these properties of CS allow signal acquisition and communication in some severely resource-deprived conditions that render conventional sampling and coding impossible, they are accompanied by rather disappointing rate-distortion performance. In this paper, we propose a novel coding technique that rectifies, to a certain extent, the problem of poor compression performance of CS and, at the same time, maintains the simplicity and universality of the current CS encoder design. The main innovation is a scheme of progressive fixed-rate scalar quantization with binning that enables the CS decoder to exploit hidden correlations between CS measurements, which was overlooked in the existing literature. Experimental results are presented to demonstrate the efficacy of the new CS coding technique. Encouragingly, on some test images, the new CS technique matches or even slightly outperforms JPEG.
Understanding and controlling the growth of the vital Li2O2 product, which is associated with intrinsic property of cathode surface, is essential to design effective cathode catalysts in Li-O2 ...batteries. Herein we establish the correlation between the Li2O2 growth model and the O2 adsorbability on cathode surface that determines the pathway of the first electron transfer to O2. The weak O2 adsorbability drives the solution growth model to form Li2O2 toroid, while the strong one drives the surface growth model to thin film. Based on this mechanism, we select the N-doped carbon nanocages as cathode to realize a simultaneous large discharge capacity and low charge overpotential by forming copious thin-film Li2O2, deriving from its high specific surface area and enhanced O2 adsorbability due to N-doping. Our study demonstrates an effective strategy to design advanced cathode catalysts in Li–O2 batteries and potentially other metal-air batteries.
The correlation between the Li2O2 growth mechanism and the O2 adsorbability on cathode surface is established, and a strategy to design advanced cathode catalysts of Li-O2 batteries is demonstrated accordingly. Display omitted
•The correlation between Li2O2 growth mechanism and O2 adsorbability is established.•A strategy to realize a simultaneous large capacity and low overpotential is demonstrated.•The dominant role of the carbon additive on the discharge performance is revealed.
Polycomb group (PcG) proteins play important roles in maintaining the silent state of HOX genes. Recent studies have implicated histone methylation in long-term gene silencing. However, a connection ...between PcG-mediated gene silencing and histone methylation has not been established. Here we report the purification and characterization of an EED-EZH2 complex, the human counterpart of the Drosophila ESC-E(Z) complex. We demonstrate that the complex specifically methylates nucleosomal histone H3 at lysine 27 (H3-K27). Using chromatin immunoprecipitation assays, we show that H3-K27 methylation colocalizes with, and is dependent on, E(Z) binding at an Ultrabithorax (Ubx) Polycomb response element (PRE), and that this methylation correlates with Ubx repression. Methylation on H3-K27 facilitates binding of Polycomb (PC), a component of the PRC1 complex, to histone H3 amino-terminal tail. Thus, these studies establish a link between histone methylation and PcG-mediated gene silencing.
By taking the blasting excavation of a deeply buried karst tunnel in the North Tianshan Mountains in China as research objects, the damage induced by blasting excavation and seepage characteristics ...of deep rock under high seepage pressure was investigated. The COMSOL Multiphysics® software was adopted to establish a simulation model for the blasting excavation of a deeply buried tunnel. By embedding the stress-damage-seepage multifield coupled constitutive relationship, the mechanism of the influences of factors including blasting load, geostress, and hydraulic pressure of karst caves on the blasting excavation-induced damage to, and seepage characteristic of, the surrounding rocks of the tunnel. The results indicate that blasting excavation in the karst tunnel triggers the damage of surrounding rocks, which consists of blasting-induced damage and unloading damage. The time-history curve of the variable for surrounding rock damage rises and consequently tends to a constant value. With the increases in blasting load, geostress, and hydraulic pressure of karst caves, the degree of damage to surrounding rocks is intensified; an increase in geostress will weaken the effect of blasting-induced damage to rock while increasing rock damage arising from unloading. Meanwhile, the degree of damage to the surrounding rock can affect the seepage velocity of water in the surrounding rock to a certain extent. A strong damage and seepage coupled effect occur in the blasting excavation process of the karst tunnel. The such coupled effect is strengthened little by little with the increases in the degree of surrounding rock damage and hydraulic pressures. The results are expected to provide theoretical guidance for hazard prevention and control of blasting excavation in karst tunnels under high geostress conditions.
Large-scale sedimentary Mg-phyllosilicate occurrences have rarely been reported in deep marine successions worldwide, with few studies reporting the natural transformation of sepiolite into talc, ...although published laboratory experiments have proven the existence of this mineral transformation at high temperature. Mg-phyllosilicates occur extensively in the Middle Permian deep marine successions in South China. To investigate the genesis of these extensive occurrences, we conducted integrated studies including field trips, thin section observation, filed emission scanning electron microscope (FE-SEM), vitrinite reflectance (Ro), X-ray diffraction mineralogy (XRD), and trace element and rare earth element (REE) concentration analysis.
The XRD patterns suggested that in the west of our study zone, talc was the major species of Mg-phyllosilicates with aliettite and Mg-smectite being minor species, while in the east of our study zone, sepiolite was the major species of Mg-phyllosilicates. Mg-smectite was dominant in the intermediate zone. Ro values serve as a proxy for the maximum paleogeothermal temperature coupled with the differential distribution of these Mg-phyllosilicates. The distribution zones of talc, Mg-smectite and sepiolite correspond to distinct ranges of Ro < 1.0%, Ro = 1.0–1.2% and Ro > 1.2%, respectively. This pattern indicates that the maximum paleogeothermal temperature is the controlling factor for natural transformation between Mg-phyllosilicates. Moreover, there are lower transformation temperatures from sepiolite to Mg-smectite (approximately 140 °C) and from Mg-smectite to talc (approximately 155 °C) under natural conditions than revealed in labs. Regarding the cause of original Mg-phyllosilicate deposition, analyses of trace element and rare earth element concentrations reveal that a diffuse Si-rich hydrothermal vent fluid contributed to the elevated Si content in seawater and that the upwelling current extended the Mg-phyllosilicate deposition areas from the deep basin onto the carbonate ramp in the Middle Permian in South China. Hence, favorable seawater conditions for Mg-phyllosilicate deposition occurred in the deep basin and carbonate ramp in the Middle Permian in South China.
•More extensive distribution of Mg-phyllosilicates than previous expectation is reported.•Maximum paleogeothermal temperatures control the transformation among Mg-phyllosilicates.•Sepiolite is the precursor phase of Mg-smectite and talc.•Sepiolite precipitated in the deep ramp and basin.•The elevated Si content in seawater resulted from the mixing of diffuse hydrothermal fluids.
In this report, a few-layer molybdenum disulfide (MoS2) shell was coated on core multiwalled carbon nanotube (CNT) by a facile solvothermal method. The morphology and high crystallinity of this ...structure were demonstrated and verified by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). After being integrated into a planar device, the CNT–MoS2 core–shell structure exhibits clear photoresponse and a wide response range upon laser illumination. In addition, the device shows a bias-dependent and position-sensitive photocurrent effect. Further experiments show that larger photocurrent was obtained under laser illumination with longer wavelength. Both the photocurrent and response speed are enhanced when the device is placed under vacuum condition. The simple material synthesis and device fabrication method used in this work may provide a practical strategy for low-cost and large-scale optical applications.
Based on the lattice Boltzmann Method (LBM), a new moving boundary treatment is proposed by studying the influence of the moving boundary in a low-speed incompressible fluid. Simulating flow past a ...static cylinder, flow past a moving cylinder, and flow in a curved moving pipe shows that the LBM has high reliability and stability with moving boundary conditions. In order to reduce parallel computing time and take full advantage of the characteristics of the model, the solid grids are allocated according to the number of computing cores. Two parallel speedup ratios were tested, keeping the overall task volume unchanged to increase the number of cores and keeping the single-core task volume unchanged. In the first speedup ratio, the efficiency of the flow field calculation at 112 cores reached more than 80%. The second speedup ratio indicated that the proportion of communication in the program was tiny and suitable for large-scale parallel computing. The study of the moving boundary problem can effectively help solve the fluid-structure coupling problem. Due to the particularity of the model, it can be used to simulate the fluid-structure coupling problem of blood vessel flow effectively.
This study investigated the characteristics and genesis of reservoirs in the 2nd and 4th members of Sinian Dengying Formation in northern Sichuan and its surrounding areas, on the basis of outcrop, ...drilling cores and thin section observation and geochemical analysis. The reservoirs of 2nd member are distributed in the middle part of the stratum. The reservoir quality is controlled by supergene karst and the distribution of mound-shoal complex. The bedded elongated isolated algal framework solution-cave and the residual “grape-lace” cave, which are partially filled with multi-stage dolosparite, constituted the main reservoir space of the 2nd member. There is no asphalt distribution in the pores. The pore connectivity is poor, and the porosity and permeability of the reservoir is relatively low. The reservoirs of 4th member were distributed in the upper and top part of the stratum. The reservoir quality is controlled by burial dissolution and the distribution of mound-shoal complex. The bedded algal framework solution-pores or caves, intercrystalline pores and intercrystalline dissolved pores constituted the main reservoir space of the 4th member. It's partially filled with asphalt and quartz, without any dolosparite fillings in the pores and caves. The pore connectivity is good. Most of the 4th member reservoirs had medium-low porosity and low permeability, and, locally, medium-high porosity and medium permeability. Affected by the development of mound-shoal complex and heterogeneous dissolution, the platform margin along Ningqiang, Guangyuan, Jiange and Langzhong is the most favorable region for reservoir development. Deep buried Dengying Formation in the guangyuan and langzhong areas should be the most important hydrocarbon target for the future exploration.
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