In this work, phosphorus-doped graphene quantum dots (P-GQDs) with a high phosphorus doping content (>7 at%) are synthesized via an electrochemical approach. Sodium phytate (C
H
Na
O
P
), a green ...food antioxidant additive, is used as the electrolyte for providing both a phosphorus source and an electrolysis environment. The obtained P-GQDs exhibit excellent scavenging activity of free radicals, such as hydroxyl radicals (˙OH) and 2,2-diphenyl-1-picrylhydrazyl (DPPH). Combined with Raman, FT-IR, and XPS spectral analyses, the reason for high phosphorus content and the mechanism of free radical scavenging of P-GQDs are investigated in our work.
Sea-level fluctuations exert a major influence on deep-water depositional processes through changing sediment supply and oceanographic processes. By utilizing the bathymetric map and six piston cores ...(P1 and P5–P9) from the two major canyon systems (i.e., Pearl River Canyon (PRC) and Shenhu Submarine Canyon Group (SSCG)) within the Baiyun Sag, northern South China Sea (SCS), this study investigated the deep-water depositional responses to the sea-level fluctuations in the past 30 kyr, during which the last glacial maximum (LGM) shelf edge remained farther (>60 km) seawards of the contemporary shoreline and had water depths greater than 120 m. In the past 30 kyr, the Baiyun Sag was dominated by mixed sedimentary processes involving in both turbidity and bottom currents. Coarse-grained turbidites were mostly deposited at the upper-middle segments of the slope channel within the PRC and the canyon heads of the SSCG from the LGM to the middle deglacial stage (ca. 11.5 ka); while the fine-grained contourites were continuously and widely deposited within the Baiyun Sag. It is noted that the contourites show fining- and coarsening-upwards trends before and after 6.7 ka, respectively.
The turbidity currents in the past 30 kyr were mainly triggered by oceanographic processes (i.e., contour currents and internal waves) within the Baiyun Sag. Internal waves exerted greater effects on the occurrences of turbidity currents flowing within the canyons of the SSCG. The near-seafloor intensities of contour currents and internal waves around the shelf edge weakened with sea level rising. Internal waves were responsible for triggering high-frequency turbidity currents to deposit the multiple thin-bedded turbidites at the slope canyon heads of the SSCG. The fining-upwards trend of the contourites during the period of 29.5–6.7 ka was mainly attributed to the decreasing sediment supply from the Pearl River with sea level rising, whereas the coarsening-upwards trend in the past 6.7 kyr was resulted from the circulation intensification, in response to the reopening of all straits around the SCS. This study provides a new insight into the significance of varying oceanographic processes for deep-water deposition in response to sea-level fluctuations on sediment-starved continental margin with wide shelf.
•The Baiyun Sag is affected by both turbidite and contourite processes.•Oceanographic processes are crucial for gravity-flow generation on sediment-starved margin.•Deep-sea deposition is response to varying hydrologic regimes with sea-level fluctuations.
Epithelial tight junctions are compromised in gastrointestinal disease. Processes that contribute to the resulting barrier loss include endocytic occludin removal from the tight junction and reduced ...occludin expression. Nevertheless, the relatively-normal basal phenotype of occludin knockout (KO) mice has been taken as evidence that occludin does not contribute to gastrointestinal barrier function. We asked whether stress could unmask occludin functions within intestinal epithelia.
Wildtype (WT), universal and intestinal epithelial-specific occludin KO, and villin-EGFP-occludin transgenic mice as well as WT and occludin knockdown (KD) Caco-2BBe cell monolayers were challenged with DSS, TNBS, staurosporine, 5-FU, or TNF. Occludin and caspase-3 expression were assessed in patient biopsies.
Intestinal epithelial occludin loss limited severity of DSS- and TNBS-induced colitis due to epithelial resistance to apoptosis; activation of both intrinsic and extrinsic apoptotic pathways was blocked in occludin KO epithelia. Promoter analysis revealed that occludin enhances CASP3 transcription and, conversely, that occludin downregulation reduces caspase-3 expression. Analysis of biopsies from Crohn’s disease and ulcerative colitis patients and normal controls demonstrated that disease-associated occludin downregulation was accompanied by and correlated with reduced caspase-3 expression. In vitro, cytokine-induced occludin downregulation resulted in reduced caspase-3 expression and resistance to intrinsic and extrinsic pathway apoptosis, demonstrating an overall protective effect of inflammation-induced occludin loss.
The tight junction protein occludin regulates apoptosis by enhancing caspase-3 transcription. These data suggest that reduced epithelial caspase-3 expression downstream of occludin downregulation is a previously-unappreciated anti-apoptotic process that contributes to mucosal homeostasis in inflammatory conditions.
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Toxic element-free Zr-based bulk metallic glasses (BMGs) with a property combination of high glass-forming ability, ultrahigh strength and large room-temperature plasticity are useful as surgical ...devices materials. In the present work, the critical glass formation size (dmax), thermal glass stability and room-temperature mechanical properties of a series of Zr56.25Al18.75(Co1-xCux)25 (x = 0, 0.125, 0.25, 0.375, 0.5, at.%) alloys have been investigated. The Zr56.25Al18.75Co18.75Cu6.25 (x = 0.25) BMG alloy is found to combine a centimeter scale dmax with ultrahigh strength (σy = 2.05 GPa), high Young's modulus (E = 92.4 GPa) and large room-temperature plasticity (ɛP = 3.5%). Comparison of the property combination of various biomedical Zr-based BMGs suggests that the Zr56.25Al18.75Co18.75Cu6.25 BMG can be a promising surgical devices material. The thermal and mechanical stabilities of these BMG alloys are qualitatively understood with the electron concentration and split d-band electronic structure stabilization mechanisms.
•Zr56.25Al18.75Co18.75Cu6.25 BMG exhibits large GFA, high strength and plasticity.•Split d-band affects the thermal and mechanical stabilities of ZrAlCoCu BMGs.•Zr56.25Al18.75Co18.75Cu6.25 BMG is a promising surgical devices material.
Intercell interference management has become a critical issue for future cellular mobile systems. Coordinated multipoint transmission/reception, or CoMP, is an effective way of managing intercell ...interference, and has been regarded as a key technology of LTE-Advanced. This article first provides an overview of downlink CoMP techniques specified in 3GPP LTE Rel-11, which mainly focuses on transmission schemes, channel state information reporting, interference measurement, and reference signal design. Then uplink CoMP is discussed in brief as most of the coordination gain can be achieved by implementation with little standardization support. Evaluation results are provided to show the efficiency of CoMP. The challenges as well as possible solutions for future CoMP standardization are also discussed.
A review of 127 shelf-margin accretion segments from 24 margins worldwide suggests that sediment flux can be low or high, that shelf accommodation can be low, medium, or high, and that climatic ...conditions can be Icehouse or Greenhouse. The interplay of these three variables yields four main Greenhouse margins and six main Icehouse margins, and thus has a fundamental control on shelf-margin architectural styles, providing new tools for predicting internal architecture of deep-water systems.
In Greenhouse settings, there is commonly a strong supply drive (because of higher temperatures, more variable precipitation and higher sediment discharge), but only modest shelf accommodation (because of low-frequency and low-amplitude eustatic sea-level changes). Low shelf accommodation is able to deliver significant volumes of sand sourced from either low or high sediment supply areas to deep-water environments, and residence time for deltas at Greenhouse margins is likely to be relatively long because of the low amplitude of Greenhouse sea-level changes. Medium accommodation, in contrast, may overwhelm any low sediment supply, but could be partly overwhelmed by high sediment supply, which, in turn, can inhibit fans or encourage highstand fans.
In Icehouse settings, there is a strong, cross-shelf accommodation drive created by high-frequency and high-amplitude eustatic sea-level changes, thus causing significant and frequently repeated transits of river mouths and deltas across the shelf. Sandy basin-floor fans created by low accommodation are predicted with either high or low sediment flux. Both medium and high accommodation can be volumetrically overwhelmed by high sediment supply, which, in turn, cause greater volumes of sediment storage on the shelf, resulting in volumetrically less significant highstand or transgressive submarine fans. However, a low supply may barely allow deltas to reach the shelf edge, causing the deep-water areas to be dominantly muddy.
In order to improve the robustness and positioning accuracy of the matched field processing (MFP) in underwater acoustic systems, we propose a conditional probability constraint matched field ...processing (MFP-CPC) algorithm in this paper, which protects the main-lobe and suppresses the side-lobe to the AMFP by the constraint parameters, such as the posterior probability density of source locations obtained by Bayesian criterion under the assumption of white Gaussian noise. Under such constraint, the proposed MFP-CPC algorithm not only has the same merit of a high resolution as AMFP but also improves the robustness. To evaluate the algorithm, the simulated and experimental data in an uncertain shallow ocean environment is used. From the results, MFP-CPC is robust to the moored source, as well as the moving source. In addition, the localization and tracking performances of using the proposed algorithm are consistent with the trajectory of the moving source.
Continental margins usually display along-strike morphological variation, with diverse underlying controls around the world. Based on 3D seismic data from the Baiyun Sag, northern South China Sea, ...this work provides a new case study to understand the combined controls on along-strike morphological variation over short strike distances. The northern slope of the Baiyun sag was characterized by a gently dipping ramp at the beginning of the Quaternary, and the Quaternary along-strike morphological variation in this area is mainly displayed in the deltas, submarine canyons and contourite depositional system. The deltas were featured by lobate form and mainly distributed at the western area, with shoreline parallel and oblique to the ramp strike in the west and east, respectively. The scales of the deltas and the associated submarine canyons decreased towards the east. The eastern plastered contourite drifts have a greater areal extent than those in the west, and the former are terraced. The Quaternary slope evolution took place in three stages (stage 1–3), of which the time intervals are ca. 2.6 - ca. 1.6 Ma, ca. 1.6 - ca. 0.14 Ma and ca. 0.14–0 Ma, respectively. The slope was characterized by a gentle ramp, deltas and contourites from stage 1–3 respectively.
The along-strike morphological variation of the northern slope of the Baiyun Sag was predominantly influenced by the interplays between the deltas, pre-existing morphology, and oceanographic regimes. The localization of the lobate-form deltas with respect to the pre-existing submarine canyons on the ramp exerted a great influence on the along-strike variation of these canyons within stage 2. The interplay between the delta morphology (i.e., delta position and delta-front gradients) and the oceanographic regimes (i.e. contour currents and internal waves) controlled the along-strike variation in contourite processes during the stage 3. This study provides a new insight into the combination of controls responsible for along-strike morphological variation of post-rift continental margins evolving from a ramp. The underlying depositional processes revealed by this study would be helpful for understanding the lateral variability of sequence architectures and the deep-water sands deposition, which are important basis for guiding future deep-water hydrocarbon exploration on such continental margins elsewhere.
●The northern slope of the Baiyun Sag displays along-strike morphological variability●Lobate-form delta localization influences the along-strike variation of canyons●Interplay between delta morphology and oceanographic regimes influences contourite processes
Noise suppression capacity in multiple-input multiple-output (MIMO) sonar signal processing is derived under the assumption of white Gaussian noise. However, underwater noise mainly includes white ...Gaussian noise and colored noise. There exists a certain correlation between the noise signals received by each MIMO sonar array element. The performance of traditional direction-of-arrival (DOA) estimation methods decreases obviously in complex marine noise. In this paper, we propose a marine environment noise suppression method for MIMO applied to multiple targets' DOA estimation. The noise field can be decomposed into a symmetric noise component and an asymmetric noise component. We use the covariance matrix imaginary component to pre-estimate the signal sources, then use the dimension reduction transformation to reconstruct the real component of the covariance matrix. The Toeplitz technique is utilized to reduce the correlation of the reconstructed covariance matrix. Thus, the subspace decomposition-based techniques such as multiple signal classification (MUSIC) can be used for multiple targets' DOA estimation. To reduce the computational complexity of the methods, search-free direction-finding techniques such as the estimation of signal parameters via rotational invariance techniques (ESPRIT) can be utilized. As a result, the proposed methods can achieve better direction-finding performance in the condition of limited snapshots with lower computational cost. The corresponding Cramer-Rao bound (CRB) is deduced and the signal-to-noise ratio (SNR) gain obtained by dimension reduction processing is discussed. Simulation results also show the superiority of the proposed method over the existing methods.
•High Mg-content AlSiMg1.4 alloy was fabricated by selective laser melting.•YS and UTS of SLMed AlSiMg1.4 alloy reached 341 ± 14 MPa and 518 ± 6 MPa, respectively.•The strength of alloy are much ...higher than most known SLM fabricated Al-Si-Mg alloys.•The new strengthening mechanism was mentioned in the paper.
A high Mg-content AlSiMg1.4 alloy was designed for selective laser melting (SLM) processing. The SLMed AlSiMg1.4 alloy exhibits a high yield strength of 341±14 MPa and a high ultimate tensile strength of 518±6 MPa, along with a total elongation of 7.1±0.4%. The composition profile in the α-Al matrix of the alloy manifests in-phase concentration fluctuations of Mg and Si. The presence of high density Mg-Si atomic clusters as strong obstacles to dislocation gliding is suggested to provide an additional strengthening mechanism for the SLMed Al-Si-Mg alloy.
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