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• Residual fracture toughness of corroded steel was determined. • Established empirical models to indicate relationships between corrosion degree and residual fracture toughness. • Revealed the mechanism of accelerated crack propagation and premature unstable fracture caused by corrosion. • Utilized calculated residual fracture toughness to predict fracture in corroded steel joints with macroscopic fatigue crack. Corroded steel structures show significant degradation in fracture behaviors. This research is aimed to investigate the degradation laws of corroded steel fracture toughness, and reveal the mechanism of accelerated crack propagation and premature unstable fracture caused by corrosion. The tensile tests of center notched corroded steel plates and numerical analysis were conducted. Research results show that the residual fracture toughness of corroded steel decreases as the uniform and pitting corrosion damage get worse. Empirical models were established to indicate relationships between corrosion degree and residual fracture toughness. The degraded fracture toughness and accelerated crack propagation can be attributed to the more intense crack tip field or increased driving force of crack propagation induced by corrosion. The calculated residual fracture toughness can be utilized to predict fracture in corroded steel joints with macroscopic fatigue crack. [ABSTRACT FROM AUTHOR]

To explore the geothermal system in the Gonghe basin located between Kunlun and Qinlin Orogen in northeast Tibetan Plateau, 310 Magnetotelluric (MT) sites were deployed in the basin. The MT sites have an average spacing of 1∼2 km and almost cover the whole basin with an area of ∼100 km by 100 km. We first analyzed the MT data using phase tensor analysis to qualitatively estimate the dimensionality of the subsurface resistivity structure and the resistivity anomalies. We then determined a 3D resistivity model from the surface to the depth of ∼50 km through a 3D MT inversion of MT data at the 272 sites with relatively higher quality. Overall, the inverted resistivity model fits the MT data very well. Our 3D resistivity model reveals significantly conductive anomalies at depths above ∼3 km, which are interpreted as widespread hot dry rocks or hydrothermal reservoirs. Furthermore, the 3D resistivity model shows pronounced low resistivity zones in the middle crust (∼15-35 km). These anomalies trend a NW-SE direction, consistent with the Kunlun Fault strike. Between the near-surface conductive zone and the middle crust conductive zone, lie several vertical narrow conductive zones, which are generally associated with hidden faults identified in the basin. Synthetic tests are used to validate the resolution of large low resistivity anomalies in the middle crust and the vertically elongated low resistivity anomalies in the model. These faults may serve as the channels for transporting heat from the heat source in the middle crust to the shallow zone around the depth of 3 km. Our 3D MT imaging results characterize for the first time the 3D distribution of the geothermal system in the Gonghe Basin. [ABSTRACT FROM AUTHOR]

The Gofar transform fault (GTF), 4°S on the East Pacific Rise, can generate M w 5.5–6 earthquakes quasiperiodically on some specific patches that are separated by stationary rupture barriers. Small earthquakes along strike show a clear spatial and temporal evolution. To better understand the cause of the observed behaviors of large and small earthquakes, we have determined high-resolution earthquake locations within a period of one year covering the 2008 M w 6.0 (M6) earthquake, as well as V p , V s , and V p / V s models along the westernmost segment of the GTF, using a well recorded ocean bottom seismograph dataset and a new V p / V s model consistency-constrained double-difference tomography method. Compared to the previous P-wave tomography study in this area, the use of a new automatic arrival picking algorithm significantly improves the accuracy of S-wave arrival times, thereby allowing for the inversion of V s and V p / V s models in addition to V p model. High-precision waveform cross-correlation differential times are also used. The tomographic V p / V s model reveals strong structural variations at multiple scales along the fault, which likely control the behaviors of large and small earthquakes. The M6 mainshock is generated within a specific ∼8-km-long fault patch composed of intact rocks. By contrast, multiple fluid-filled damaged zones on both sides of this asperity are imaged and have varying size which is suggested to be critical in their ability of stopping ∼M6 ruptures. High-resolution earthquake relocations and velocity models also indicate that the occurrence of small earthquakes is also correlated with structural variations. Combined with previous studies, our results further suggest that strong structural variations control the fault mechanics and earthquake behavior along the GTF. [ABSTRACT FROM AUTHOR]

For microseismic monitoring of hydraulic fracturing, microseismic migration can be used to image the fracture network with scattered microseismic waves. Compared with conventional microseismic location-based fracture characterization methods, microseismic migration can better constrain the stimulated reservoir volume regardless of the completeness of detected and located microseismic sources. However, the imaging results from microseismic migration may suffer from the contamination of other structures and thus the target fracture zones may not be illuminated properly. To solve this issue, in this study we propose a target-oriented staining algorithm for microseismic reverse-time migration. In the staining algorithm, the target area is first stained by constructing an imaginary velocity field and then a synchronized source wavefield only concerning the target structure is produced. As a result, a synchronized image from imaging with the synchronized source wavefield mainly contains the target structures. Synthetic tests based on a downhole microseismic monitoring system show that the target-oriented microseismic reverse-time migration method improves the illumination of target areas. [ABSTRACT FROM AUTHOR]

We have developed a new seismic tomography method, back azimuth constrained double-difference (DD) seismic tomography, which is suitable for downhole microseismic monitoring of hydraulic fracturing. The new method simultaneously locates microseismic events and determines three-dimensional (3D) Vp and Vs models for the fracturing zone using differential arrival times from pairs of events and event back azimuths in addition to absolute arrival times. Compared to the existing DD location and tomography method, our method incorporates back azimuth information to better constrain microseismic event locations in the case of poor spatial station coverage such as the linear downhole seismic array generally used for microseismic monitoring. By incorporating the relative arrival time and back azimuth information of events, the extended DD method can provide better relative event locations, and thus can better characterize the fracture distribution. In addition to microseismic locations, seismic velocity anomalies determined around the fracturing zone may also provide valuable information for fracture development. Due to the existence of fractures and fluids, the seismic velocity is expected to be lower in the fractured zone compared to the surrounding regions. Therefore the area of low seismic velocity anomaly may be used as a proxy for the stimulated reservoir volume. We have applied the new method to a downhole microseismic dataset from shale gas hydraulic fracturing. The microseismic events are more accurately relocated than the conventional grid search location method, and they are generally associated with low velocity anomalies. [ABSTRACT FROM AUTHOR]

For microseismic monitoring, in order to obtain accurate microseismic locations, a good estimation of the velocity model for the region covering the monitoring stations and microseismic sources is crucial. Perforation shots are generally used to estimate a velocity model suitable for microseismic location. However, the origin times of the perforation shots are generally not accurate. To mitigate the effect of inaccurate origin times of perforation shots on calibrating the velocity model, we propose to search for a velocity model fitting for station-pair differential arrival times instead of absolute arrival times from perforation shots. Another advantage of using station-pair differential arrival times is that waveform cross-correlation can be used to estimate more accurate differential times because of waveform similarity among stations for perforation shots. Due to high nonlinearity of the objective function for estimating one-dimensional velocity model, the differential evolution (DE) method for solving high-dimensional global optimization problems is utilized in the optimization. Compared to the grid-search method, the DE method is much more efficient. Synthetic tests based on a downhole microseismic monitoring system show the effectiveness of the proposed method to recover the velocity model. We also test our DE-based method by using perforation shots for a real microseismic monitoring project. Compared to the well sonic velocity model, station-pair differential arrival times are better fitted and perforation shots are also more accurately relocated with the calibrated velocity model. [ABSTRACT FROM AUTHOR]

It has been a challenge to accurately characterize fracture zones created by hydraulic fracturing from microseismic event locations. This is because generally detected events are not complete due to the associated low signal to noise ratio and some fracturing stages may not produce microseismic events even if fractures are well developed. As a result, spatial distribution of microseismic events may not well represent fractured zones by hydraulic fracturing. Here, we propose a new way to characterize the fractured zones by reverse time migration (RTM) of microseismic waveforms from some events. This is based on the fact that fractures filled with proppants and other fluids can act as strong scatterers for seismic waves. Therefore, for multi-stage hydraulic fracturing, recorded waveforms from microseismic events induced in a more recent stage may be scattered by fractured zones from previous stages. Through RTM of microseismic waveforms in the current stage, we can determine fractured zones created in previous stages by imaging area of strong scattering. We test the feasibility of this method using synthetic models with different configurations of microseismic event locations and borehole sensor positions for a 2D downhole microseismic monitoring system. Synthetic tests show that with a few events fractured zones can be directly imaged and thus the stimulated reservoir volume (SRV) can be estimated. Compared to the conventional location-based SRV estimation method, the proposed new method does not depend on the completeness of detected events and only a limited number of detected and located events are necessary for characterizing fracture distribution. For simplicity, the 2D model is used for illustrating the concept of microseismic RTM for imaging the fracture zone but the method can be adapted to real cases in the future. [ABSTRACT FROM AUTHOR]

The heavy fuel oils (HFOs) and crude oils are the main oil types in the marine oil spill accidents in China. It is usually a challenge to distinguish the HFOs from crude oils due to the highly similar physicochemical characteristics. In this paper, the distributions of phenanthrene (Phe), anthracene (Ant), methyl-phenanthrene (MP) and methyl-anthracene (MA) in hundreds of HFOs and crude oils samples which were collected from all over the world were characterized. Nine new diagnostic indexes, such as Ant/(Ant + Phe) and other eight diagnostic ratios based on the MP isomers and MA, were developed for effective distinguishing HFOs from crude oils. The histogram with normal fit plots, the double ratio plots and Bayes discriminant analysis (BDA) method were employed to illustrate the effectiveness of the new diagnostic indexes. BDA model based on nine new diagnostic indexes demonstrated high precision with discriminant ratio which lay between 93.92% and 99.32%. [ABSTRACT FROM AUTHOR]

We investigated the growth of cell protrusions from adherent HEK 293 cells and their capability to bridge cytophobic Teflon ® AF microgaps, establishing a critical length scale, beyond which cells cannot probe free space. For this purpose, we employed a photolithography-based surface fabrication strategy for producing micropatterned substrates composed of glass and the amorphous polymer Teflon ® AF. Cell protrusions growing from HEK 293 cells on these substrates were confined to extend on 2 μm wide glass lanes, intersected by Teflon ® AF microgaps of various lengths between 2 and 16 μm. After 24 hours of incubation, the frequency of cell protrusions crossing the gap was found to be strongly dependent on the gap size. Gaps which are greater than 4 μm were found to be increasingly difficult to cross. Cell extensions crossing the microgaps either appeared as nanosized connections, in approximately 30% of all observed cases, or as microsized connections. Molecular transport in the established cell-to-cell connection across the microgap was investigated by activation of TRPM8 ion channels followed by supply of Ca 2+ to one of the connected cells. The diffusion of the Ca 2+ ions was visualized by means of a cell-permeant pre-fluorescent dye. We observed both open- and closed-ended intercellular connections in both nano- and microsized cell protrusions. [ABSTRACT FROM AUTHOR]

Surface sediment samples from Bohai Bay and its adjacent river, China, were analyzed for aliphatic hydrocarbon, PAHs and biomarkers in order to determine the distribution, composition and source of organic matter in a coastal environment. Results suggested that the input of organic matter from anthropogenic activities has a more significant influence on its distribution than that from natural processes. Petroleum contamination, mainly from offshore oil exploration and discharge of pollutants from rivers, was the main source of n -alkanes. PAHs were mostly of pyrogenic origin; while some sites in Yellow River Estuary were derived mainly from the petrogenic sources. The toxic assessment suggested that the PAHs in surface sediments will not cause immediately adverse biological effects in sediments from Bohai Bay and its adjacent river, China. [ABSTRACT FROM AUTHOR]

Abstract: Lipid nanotubes interconnecting mammalian cells, sometimes referred to as tunneling nanotubes, have recently received increased attention, as their importance in intercellular transport and communication has been recognized. We present a set of microfabrication procedures for the deliberate formation of intercellular nanotube links between single mammalian cells, employing microneedle manipulation protocols, developed earlier for nanotube-vesicle networks. Cell-to-cell connections were established, and their effectiveness for intercellular transport of molecular cargo was demonstrated. We initiate transport of ions and fluorescein diphosphate, a prefluorescent enzyme substrate, between cells, and demonstrate the validity and effectiveness of artificially created nanotube connections for cell-to-cell communication. We thus provide a new experimental model for probing cell-to-cell communication, which we deem the foundation for man-made network architectures involving biological cells. This model can greatly facilitate fundamental studies of cell-to-cell communication modes, the exchange of cell constituents and components, and the dynamics of biochemical reactions in native network environments. [Copyright &y& Elsevier]

In order to study the fracture ductility of corroded steel plates under tension load, a series of tensile tests and numerical calculations on corroded steel plates were conducted. The results showed that corrosion damage would increase the speed of equivalent plastic strain growing at critical point, and decrease the equivalent plastic strain to fracture, thus degrade the nominal strain at fracture. The weakened and uneven cross-section along longitudinal direction caused by corrosion damage led to the strain concentration and accelerated growth of equivalent plastic strain. The corrosion pits increased the values of stress triaxiality and Lode stress parameter, thus degenerated the equivalent plastic strain to fracture. Based on the above results, the fracture locus of corroded steel plates in the nominal strain to fracture-corroded morphology space was established. [Display omitted] • The reasons which degraded the fracture strain of corroded plates were discussed. • The weakened cross-section accelerated the growth of equivalent plastic strain. • The sharp pits degraded the equivalent plastic strain to fracture. • The ductile fracture locus of corroded tensile plates was established. [ABSTRACT FROM AUTHOR]

• Finite element models with actual complex surface of corroded thin steel plates were established. • Ductile fracture toughness α and η of corroded thin steel plates was calculated. • Features of fracture initiation region affected by corrosion pits of corroded thin steel plates were summarized. • Distribution and evolution of fracture parameters in micromechanical models of corroded thin steel plates were represented. In order to investigate the fracture behaviors of corroded cold-formed thin steel plates, the tensile tests, surface scanning and numerical analysis considering actual corroded surface were conducted. The fracture toughness of corroded thin steel plates was back-calculated as α = 0.88 and η = 0.90. The features of fracture initiation region affected by corrosion pits were summarized as 4 types based on VGM and SMCS contour analysis. The distribution and evolution of fracture parameters (VGM, SMCS, plastic strain and triaxial stresses) in micromechanical models of corroded thin steel plates were represented. [ABSTRACT FROM AUTHOR]

Abstract: Ethnopharmacological relevance: Semen vaccariae, the seeds of Vaccaria Segatalis, is a famous traditional herb for the treatment of stranguria disease, e.g. benign prostatic hyperplasia (BPH). The present study investigated the effect of crude polysaccharide from Semen vaccariae (SVCP) on BPH in mice in order to further understand the efficacy substance of this medicinal plant. Materials and methods: Sixty healthy adult male Kunming mice were randomly divided into five groups with 12 mice for each group: sham-operated group, BPH model group; BPH model group treated with Pule''an at a dose of 1.20g/kg; BPH model group treated with SVCP at dose levels of 1.67g/kg and 0.42g/kg. The drugs were administered orally once a day consecutively for 12 days. The BPH in mice was created by subcutaneous injection of testosterone propionate for 5mg/(kgd) to the uncastrated mice once a day consecutively for 12 days. The inhibitory effects on BPH of SVCP were evaluated by prostatic index, testicular index and histopathologic examination. Results: Comparing with BPH model group, BPH mice fed with SVCP exhibited significant differences in both the prostatic index and testicular index. On the aspect of histopathology, the SVCP treated BPH mice exhibited similar histological aspects observed in the mice of sham group while the BPH mice exhibited typical features of prostate glandular hyperplasia. Conclusions: SVCP exhibited a significant inhibitory activity on BPH by reducing the prostatic index, testicular index, and ameliorating the pathomorphology. The results indicated that the polysaccharide should be the main efficacy substance of Semen vaccariae and may contribute, in a large part, to Semen vaccariae''s traditional medicinal use for the treatment of stranguria disease. [Copyright &y& Elsevier]

Owing to the semi-enclosed environment of the Bohai Sea, the ecological effects caused by an oil spill would be significant. A typical in- situ bioremediation engineering project for of oil-spilled marine sediments was performed in the Bohai Sea and a quantitative assessment of the ecological restoration was performed. The bioremediation efficiencies of n -alkane and PAHs in the sediment are 32.84 ± 21.66% and 50.42 ± 17.49% after 70 days of bioremediation, and 60.99 ± 10.14% and 68.01 ± 18.60% after 210 days, respectively. After 210 days of bioremediation, the degradation rates of two- to three ring PAHs and four-ring PAHs are 84.44 ± 23.03% and 26.62 ± 43.76%, respectively. In addition, the concentrations of the heavy metals first increased by 6.00% due to oil spill degradation and release, and then decreased by 72.60% with the degradation of oil caused by bioremediation or vertical migration. According to the continuous tracking monitoring, the composition of the microbial community in the restored area was similar to that in the control area and the clean area in Bohai Sea after 210 days of bioremediation. These results may provide some theoretical and scientific data to understand the degradation mechanism and assessing the ecological remediation efficiency for oil spills in open sea areas. • Removal efficiency of oil residue was higher than 60% after 210 days of bioremediation. • Heavy metal content first increased due to oil release, and then they were degraded. • Significant and satisfactory contamination bioremediation effects were achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • The damage pattern of the loaded rock exhibits end effects. • Tomography visualizes the damage evolution of the loaded rocks in a 3D manner. • Heterogeneity is explicitly considered when analyzing the damage evolution of the rock sample. • Kalman filter-based tomography can invert the rock damage evolution and simultaneously obtain the velocity model's uncertainty. Rock pillars in rock engineering are affected by the stress concentration, which is uneven and can lead to potential instability after loading disturbance. In this paper, considering the heterogeneity of the rock, time-dependent velocity tomography based on the Kalman filter system is adopted to invert the velocity evolution of the rock monitored via acoustic emission (AE) under diverse stresses. Furthermore, the tomography uncertainty is investigated to validate the experimental accuracy of the loaded rock. The experimental results show that Kalman filter-based tomography can characterize the damages of the loaded rock, which is influenced by the distance from the sample's end and heterogeneity of the rock. The rock damage and its growth rate increase when the loading increases or the cross section approaches the mid-waistline. The model uncertainty analysis demonstrates that the velocity tomography based on the Kalman filter has a high precision. Our study shows that for evaluating the stability of bearing rock pillars, we can simplify the rock pillar as a uniaxial loading rock and need to consider the rock's heterogeneity for understanding the damage distribution and evolution of the loaded rock. [ABSTRACT FROM AUTHOR]

The prevalent manual assembly process for satellites is marked by inefficiencies and a heightened risk of collision, thus limiting its scalability and potential for integration. To address these limitations, the adoption of industrial robots for an intelligent assembly mode has emerged as a promising alternative. Nonetheless, the implementation of an industrial robot satellite assembly system brings its own challenges, including low accuracy of the robot, large manufacturing errors of the satellite products and accumulated errors in the picking and placing process. As the main positioning feature, the detection of holes plays an important role in solving these problems. This paper introduces a novel binocular vision hole recognition system, coupled with an associated hole recognition algorithm, aiming at enhancing the detection accuracy of characteristic holes of satellite products. The proposed methodology includes the development of a confidence-based indicator to assess the quality of two-dimensional hole detection, and an iterative optimization of the fitting ellipse. Furthermore, a confidence-based neighborhood denoising two-stage fitting method is designed for accurate hole positioning. Experimental results validate the proposed methodology, showcasing a recognition accuracy of 0.060 mm and an assembly accuracy within 0.2 mm, thereby fulfilling the requirements of the industrial robot satellite assembly system. [Display omitted] • Address the measurement difficulties in the robotic satellite assembly systems. • Present an ellipse fitting method to improve the accuracy of ellipse fitting. • Propose a neighborhood denoising method to realize precise identification. • Establish a satellite assembly system with the recognition accuracy of 0.060 mm. [ABSTRACT FROM AUTHOR]

Abstract: We present three-dimensional (3D) seismic compressional wave velocity (V p), shear wave velocity (V s) and V p/V s models around the Longmen Shan fault, Sichuan, China region, using aftershocks associated with the 2008 Wenchuan Ms 8.0 earthquake. The velocity and ratio models are obtained using a new version of the double-difference seismic tomography code tomoDDPS (Zhang, 2003) to simultaneously solve for V p, V s, V p/V s and event locations. The data used in inversion include 73,013 P arrival times, 62,287 S arrival times and 61,823 S–P travel times recorded by 63 stations from both permanent and temporary networks in a region 400km northeast-southwest by 200km northwest-southeast. The velocity model shows structure heterogeneity both along and across the fault zone. Generally, the velocity model is consistent with the local geology, with older rocks having high velocity and younger rocks having low velocity. The Longmen Shan fault zone is a clear boundary in V p, V s and V p/V s ratio. Down to the depth around 15km, higher V p and V s and lower V p/V s ratio exist to the west of the fault, corresponding to the Songpan–Ganze Fold System, while lower V p and V s and higher V p/V s ratio exist to the east, corresponding to the Sichuan Basin. Along the fault zone, the velocity structure is generally consistent with various rupture slip models, with two high velocity bodies corresponding well to the two large slip patches. This shows the structure control on the slip distribution along the fault plane. [ABSTRACT FROM AUTHOR]

• Propose non-uniform corrosion damage parameter and profile-based extracted method. • Propose degradation law of monotonic/cyclic property with corrosion damage parameter. • Propose constitutive model for corroded steel under monotonic and cyclic loading. To study the hysteretic behavior of corroded steel under cyclic loading, corrosion morphology tests, monotonic tensile tests and cyclic loading tests were conducted on 7 groups of accelerated corrosion specimens and 10 groups of natural corrosion specimens. A new corrosion damage parameter D n for corrosion degree evaluation and mechanical properties prediction and an extracting method based on corrosion morphology were proposed. It was found that corrosion reduced the strength, ductility and hysteretic energy of steel, and the degradation law of monotonic/hysteretic performance with corrosion damage parameter D n was obtained. By analyzing the degradation laws of material parameters in classical combined hardening model with the corrosion degree and studying the relationship between the material parameters in monotonic and cyclic loading conditions, a plastic constitutive model of corroded steel was established. The simulated stress-strain curves of corroded steel were in good agreement with the experimental data, indicating that the proposed model successfully simulated the monotonic/cyclic loading performance of corroded steel. [ABSTRACT FROM AUTHOR]

Highlights • Zwitterionic sulfonated chitosan (SCS) was prepared and characterized. • Effect on antibiofilm formation of SCS against P. aeruginosa was studied. • SCS could significantly inhibit the biofilm formation and was dose-dependent. • SCS decreased the metabolic activity and exopolysaccharide secretion of biofilm. Abstract The exploitation of chitosan derivatives as safe and natural polymers against microorganisms has been reconsidered as an alternative to antibiotics and chemical preservatives. Herein, inhibition of bacterial adhesion and biofilm formation by anionic chitosan (sulfonated chitosan, SCS) and cationic chitosan (chitosan hydrochloride, WCS) against P. aeruginosa were investigated. The results showed SCS exhibited good antibacterial activity with 1 mg/mL MIC and 8 mg/mL MBC, while MIC and MBC of WCS were 1 mg/mL and 16 mg/mL, respectively. The metabolic activity and secretion of exopolysaccharide in biofilm of P. aeruginosa were significantly decreased after the treatment with SCS. Scanning electron microscopy and confocal laser scanning microscopy further demonstrated that SCS and WCS could significantly inhibit the biofilm formation in a concentration-dependent mode. Overall, these results suggest that WCS and SCS are useful to inhibit the biofilm formation of P. aeruginosa , and would be potential alternatives for the control of bacterial pathogens in food industry. [ABSTRACT FROM AUTHOR]