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Bonding between plasma-facing materials (PFMs) and heat sinks is an important factor for the performance of plasma-facing components (PFCs) in the tokamak device; in some specific applications, graphite is adopted as the plasma-facing material and CuCrZr as the heatsink. Bonding of graphite and CuCrZr is a critical and difficult process due to the poor wettability of graphite and wide gap of material properties between graphite and CuCrZr, to which should be paid more attention. Herein, brazing processes were developed to achieve the bonding of CuCrZr and graphite, and a layer of oxygen-free copper (OFC) was placed between graphite tiles and CuCrZr heat sinks as a stress-buffer layer. Three types of brazing fillers including Ti powder with AgCu foil, AgCuTi paste and AgCuTi foil were used to achieve the bonding of CuCrZr and graphite. Samples were tested by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and shear strength experiment; the results showed that these three types of fillers can achieve the bonding of CuCrZr and graphite. In addition, one-step brazing and multi-step brazing were both developed to achieve the bonding of graphite/OFC/CuCrZr, and the mock-ups were manufactured and endured cyclic high heat loads in the high heat flux (HHF) tests. In conclusion, the simplified one step brazing process including types of fillers, brazing temperature and brazing sequence was determined, which provides a promising premise method for the heat transfer structure design of PFCs.

Algae are an entry point for mercury (Hg) into the food web. Bioconcentration of Hg by algae is crucial for its biogeochemical cycling and environmental risk. Herein, considering the cell heterogeneity, we investigated the bioconcentration of coexisting isotope-labeled inorganic (199IHg) and methyl Hg (201MeHg) by six typical freshwater and marine algae using dual-mass single-cell inductively coupled plasma mass spectrometry (scICP-MS). First, a universal pretreatment procedure for the scICP-MS analysis of algae was developed. Using the proposed method, the intra- and interspecies heterogeneities and the kinetics of Hg bioconcentration by algae were revealed at the single-cell level. The heterogeneity in the cellular Hg contents is largely related to cell size. The bioconcentration process reached a dynamic equilibrium involving influx/adsorption and efflux/desorption within hours. Algal density is a key factor affecting the distribution of Hg between algae and ambient water. Cellular Hg contents were negatively correlated with algal density, whereas the volume concentration factors almost remained constant. Accordingly, we developed a model based on single-cell analysis that well describes the density-driven effects of Hg bioconcentration by algae. From a novel single-cell perspective, the findings improve our understanding of algal bioconcentration governed by various biological and environmental factors.

Hg(I) may control Hg redox kinetics; however, its metastable nature hinders analysis. Herein, the stability of Hg(I) during standard preparation and analysis was studied. Gravimetric analysis showed that Hg(I) was stable in its stock solution (1000 mg L–1), yet completely disproportionated when its dilute solution (10 μg L–1) was analyzed using liquid chromatography (LC)-ICPMS. The Hg(I) dimer can form through an energetically favorable comproportionation between Hg(0) and Hg(II), as supported by density functional theory calculation and traced by the rapid isotope exchange between 199Hg(0)aqand 202Hg(II). However, the separation of Hg(0) and Hg(II) (e.g., LC process) triggered its further disproportionation. Polypropylene container, increasing headspace, decreasing pH, and increasing dissolved oxygen significantly enhanced the disproportionation or redox transformations of Hg(I). Thus, using a glass container without headspace and maintaining a slightly alkaline solution are recommended for the dilute Hg(I) stabilization. Notably, we detected elevated concentrations of Hg(I) (4.4–6.1 μg L–1) in creek waters from a heavily Hg-polluted area, accounting for 54–70% of total dissolved Hg. We also verified the reductive formation of Hg(I) in Hg(II)-spiked environmental water samples, where Hg(I) can stably exist in aquatic environments for at least 24 h, especially in seawater. These findings provide mechanistic insights into the transformation of Hg(I), which are indicative of its further environmental identification.

Computer architecture simulators are widely used to explore new architectures, e.g., the gem5 simulator. However, gem5 has significant performance errors that may lead to misleading research results. Researchers typically reduce errors with the target machine by manual calibration methods, which are time-consuming and require significant expertise. This paper presents gem5Tune, a parameter auto-tuning framework for the gem5 simulator to reduce errors. Applying black-box optimization (BBO) methods, recommended for TPE-based Bayesian optimization, gem5Tune minimizes the error between gem5 and the target machine within a limited number of iterations. Three optimization methods, instruction calibration, sensitivity analysis, and dynamic pruning, are proposed to accelerate the error convergence. Experimental results show that compared to the manual calibration method, gem5Tune significantly reduces performance errors between gem5 and three modern ARM servers by more than 10% (13.83%, 10.86%, and 25.22%, respectively) for SPEC CPU benchmarks. It also scales effectively to PARSEC and SPLASH-2x benchmarks and reduces the errors of architectural events.

Microbial reduction plays a crucial role in Hg redox and the global cycle. Although intracellular Hg(II) reduction mediated by MerA protein is well documented, it is still unclear whether or how bacteria reduce Hg(II) extracellularly without its internalization. Herein, for the first time, we discovered the extracellular reduction of Hg(II) by a widely distributed aerobic marine bacterium Alteromonassp. KD01 through a superoxide-dependent mechanism. The generation of superoxide by Alteromonassp. KD01 was determined using 3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide and methyl cypridina luciferin analogue as probes via UV–vis and chemiluminescence detection, respectively. The results demonstrated that Hg(II) reduction was inhibited by superoxide scavengers (superoxide dismutase (SOD) and Cu(NO3)2) or inhibitors of reduced nicotinamide adenine dinucleotide (NADH) oxidoreductases. In contrast, the addition of NADH significantly improved superoxide generation and, in turn, Hg(II) reduction. Direct evidence of superoxide-mediated Hg(II) reduction was provided by the addition of superoxide using KO2in deionized water and seawater. Moreover, we observed that even superoxide at an environmental concentration of 9.6 ± 0.5 nM from Alteromonassp. KD01 (5.4 × 106cells mL–1) was capable of significantly reducing Hg(II). Our findings provide a greater understanding of Hg(II) reduction by superoxide from heterotrophic bacteria and eukaryotic phytoplankton in diverse aerobic environments, including surface water, sediment, and soil.

Natural organic matter (NOM) exhibits a distinctive electron-donating capacity (EDC) that serves a pivotal role in the redox reactions of contaminants and minerals through the transformation of electron-donating phenolic moieties. However, the ambiguity of the molecular transformation pathways (MTPs) that engender the EDC during NOM oxidation remains a significant issue. Here, MTPs that contribute to EDC were investigated by identifying the oxidized products of phenolic model compounds and NOM samples in direct or mediated electrochemical oxidation (DEO or MEO, respectively) using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). It was found that the oxidation of newly formed phenolic-OH (ArOH) and the oxidative coupling reaction of the phenoxy radical are the main MTPs that directly contribute to EDC, in addition to the transformation of hydroquinones to quinones. Notably, the oxidative coupling reaction of ArOH contributed at least 22–42% to the EDC. Ferulic acid-like structures can also directly contribute to EDC by incorporating H2O into their acrylic substituents. Furthermore, the opening of C rings can indirectly attenuate the EDC through structural alterations in the electron-donating process of NOM. Decarboxylation can either weaken or enhance the EDC depending on the structure of the phenolic moieties in NOM. These findings suggest that the EDC of NOM is a comprehensive result of multiple NOM MTPs, involving not only ArOH oxidation but also the addition of H2O to olefinic bonds and bond-breaking reactions. Our work provides molecular evidence that aids in the comprehension of the multiple EDC-associated transformation pathways of NOM.

Mercury sulfide nanoparticles (HgSNPs), which occur widely in oxic and anoxic environments, can be microbially converted to highly toxic methylmercury or volatile elemental mercury, but it remains challenging to assess their bioavailability. In this study, an Escherichia coli-based whole-cell fluorescent biosensor was developed to explore the bioavailability and microbial activation process of HgSNPs. Results show that HgSNPs(3.17 ± 0.96 nm) trigger a sharp increase in fluorescence intensity of the biosensor, with signal responses almost equal to that of ionic Hg (Hg(II)) within 10 h, indicating high bioavailability of HgSNP. The intracellular total Hg (THg) of cells exposed to HgSNPs(200 μg L–1) was 3.52–8.59-folds higher than that of cells exposed to Hg(II) (200 μg L–1), suggesting that intracellular HgSNPswere only partially dissolved. Speciation analysis using size-exclusion chromatography (SEC)–inductively coupled plasma mass spectrometry (ICP-MS) revealed that the bacterial filtrate was not responsible for HgSNPdissolution, suggesting that HgSNPsentered cells in nanoparticle form. Combined with fluorescence intensity and intracellular THg analysis, the intracellular HgSNPdissolution ratio was estimated at 22–29%. Overall, our findings highlight the rapid internalization and high intracellular dissolution ratio of HgSNPsby E. coli, and intracellular THg combined with biosensors could provide innovative tools to explore the microbial uptake and dissolution of HgSNPs.

Radiotherapy is one of the cornerstone of the glioblastoma treatment paradigm. However, the resistance of tumor cells to radiation results in poor survival. The mechanism of radioresistance has not been fully elucidated. This study aimed to screen the differential expressed genes related with radiosensitivity. The differentially expressed genes were screened based on RNA sequencing in 15 pairs of primary and recurrent glioblastoma that have undergone radiotherapy. Candidate genes were validated in 226 primary and 134 recurrent glioblastoma (GBM) obtained from the Chinese Glioma Genome Atlas (CGGA) database. RNA and protein expression were verified by Quantitative Real-time PCR (qPCR) and western blot in irradiated GBM cell lines. The candidate gene was investigated to explore the relationship between mRNA levels and clinical characteristics in the CGGA and The Cancer Genome Atlas dataset. Kaplan–Meier survival analysis and Cox regression analysis were used for survival analysis. Gene ontology and KEGG pathway analysis were used for bioinformatics analysis. Four genes (TMEM59L, Gelsolin, ZBTB7Aand ATX) were screened. TMEM59Lexpression was significantly elevated in recurrent glioblastoma and lower in normal brain tissue. We selected TMEM59Las the target gene for further study. The increasing of TMEM59Lexpression induced by radiation was confirmed by mRNA and western blot in irradiated GBM cell. Further investigation revealed that high expression of TMEM59Lwas enriched in IDHmutant and MGMT methylated gliomas and associated with a better prognosis. Gene ontology and KEGG pathway analysis revealed that TMEM59Lwas closely related to the DNA damage repair and oxidative stress respond process. We speculated that the high expression of TMEM59Lmight enhance radiotherapy sensitivity by increasing ROS-induced DNA damage and inhibiting DNA damage repair process.

The multiscale micro‐nano pores in coal can result in the ultra‐low permeability of coal, which restricts the efficiency of gas extraction. It is difficult for the conventional seepage‐enhancement measures to affect the nanoscale pores within the coal matrix. Thermal stimulation can reach deep into the micro‐nano pores within coal matrix to improve the permeability. Therefore, it is important to study the diffusivity and permeability of the multiscale micro‐nano pores at different temperatures. In this study, the experiments of diffusion‐seepage measured by the methods of GRI (Gas Research Institution) and steady‐state were conducted using a cylindrical coal at different temperatures and pressures. The experimental results show that the apparent diffusion coefficient of cylindrical coal is not constant but variable dynamically; and the classical diffusion model fails to describe the full‐time process of gas flow accurately. On this basis, a model of multiscale dynamic apparent diffusion‐seepage that can accurately describe the full‐time flow process was proposed. As is observed, the apparent permeability attenuates dynamically with time without stress loading, and the initial apparent permeability and the attenuation coefficient increase monotonically with the rise of temperature. Under the stress constraint, the steady‐state permeability increases after a decrease as the temperature rises, displaying a “U‐shaped” pattern. Without stress constraint, the increasing temperature causes the exterior multiscale pores to expand outward by different degrees so as to increase permeability, while the interior micro‐nano pores show three inward and outward expansion mechanisms. Under stress constraint, at low temperature and high effective stress, the increasing temperature causes pores to expand inward and the permeability decreases accordingly. When temperature continues to increase, coal expands outward because the effective stress is counteracted by the thermal stress, leading to an increase in permeability. This study is of significance for thermal gas extraction engineering. The multiscale micro‐nano pores in coal cause the ultra‐low permeability of coal, which restricts the gas extraction efficiency. The conventional seepage‐enhancement measures are difficult to affect the nanoscale pores within the coal matrix. Thermal stimulation can reach deep into the micro‐nano pores within coal matrix to improve the permeability. Therefore, it is important to study the diffusivity and permeability of the multiscale micro‐nano pores at different temperatures. This paper presents multiscale dynamic permeabilityIn this paper, we propose the mechanism of inward and outward expansionThis paper presents the permeability at different temperatures This paper presents multiscale dynamic permeability In this paper, we propose the mechanism of inward and outward expansion This paper presents the permeability at different temperatures

Mercury sulfide nanoparticles (HgSNP), as natural metal-containing nanoparticles, are the dominant Hg species in anoxic zones. Although the microbial Hg methylation of HgSNPhas been previously reported, the importance of this process in Hg methylation has yet to be clarified due to the lack of knowledge on the internalization and transformation of HgSNP. Here, we investigated the internalization and transformation of HgSNPin microbial methylator Geobacter sulfurreducensPCA through total Hg analysis and different Hg species quantification in medium and cytoplasm. We found that the microbial uptake of HgSNP, via a passive diffusion pathway, was significantly higher than that of the Hg2+-dissolved organic matter (Hg2+-DOM) complex. Internalized HgSNPwere dissolved to Hg2+in cytoplasm with a maximal dissolution of 41%, suggesting a “Trojan horse” mechanism. The intracellular Hg2+from HgSNPexposure at the initial stage (8 h) was higher than that in Hg2+-DOM group, which led to higher methylation of HgSNP. Furthermore, no differences in methylmercury (MeHg) production from HgSNPwere observed between the hgcABgene knockout (ΔhgcAB) and wild-type strains, suggesting that HgSNPmethylation may occur through HgcAB-independent pathways. Considering the possibility of a broad range of hgcAB-lacking microbes serving as methylators for HgSNPand the ubiquity of HgSNPin anoxic environments, this study highlights the importance of HgSNPinternalization and methylation in MeHg production and demonstrates the necessity of understanding the assimilation and transformation of nutrient and toxic metal nanoparticles in general.

The driving conditions of urban consecutive signalized intersections are one of the main research scenarios for vehicle speed trajectory optimization, and typical for bus driving, where frequent acceleration and deceleration before and after the intersection can intensify the energy consumption of the bus. Prior research has predictive cruise controlled under Intelligent Transportation System, which is not feasible to directly communicate with controllers’ units of Intelligent Connected Vehicles. Besides, the effect of queue dissipation is a topic that has received less attention in recent related work. Therefore, this paper proposes a vehicle-cloud hierarchical architecture based on Cloud Control System at first, under which a predictive cruise control for urban buses is deployed. Given the impact of intersection queue length and dissipation time on vehicle driving, a queue dissipation time estimation model based on shockwave theory is proposed to predict changes in intersection traffic state. The queue dissipation time equivalent to the extension of the red-light window is reflected in the constraints of the Receding Distance Horizon Dynamic Programming (RDHDP) algorithm for solving the optimal control problem. Eventually, comparison simulations, a segment of realistic trip between adjacent stops, are presented. The results show that the proposed method saves 44.94%–56.74% of energy consumption and at least 26.8s of waiting time compared to human drivers, and 22.72%–41.27% of energy consumption compared to vehicle with the Intelligent Vehicle Infrastructure Cooperative Systems.

The self-assembly of surface-order structures based on the surface wrinkling of stiff film-compliant substrate structures (SFCS) is potentially useful in the fabrication of functional devices, the manufacture of superhydrophobic or self-cleaning surfaces, and so on. Due to the influence of the intrinsic characteristic length (g), the surface wrinkling behavior of SFCS at the micro scale is different from that at the macro scale. In this work, based on the strain gradient theory, a trans-scale surface wrinkling model for SFCS is established. First, the effectiveness of this model is verified by previous experiments. Then, based on the model and dimensional analysis, the effect of gon the surface wrinkling behavior is investigated, and the scaling relationship of surface wrinkling of SFCS at different scales is analyzed. The results show that the influence of gcannot be neglected when the film thickness decreases to the one comparable to g. At the micro scale, gwill lead to the increase of the critical wrinkling wavelength and load. In addition, the scaling relationship of surface wrinkling at the micro scale will not follow the traditional one. Our study explains the underlying mechanism of the dissimilarity of surface wrinkling behaviors of SFCS at different scales and lays a theoretical foundation for the precise control of surface-order structures.

Mobile edge computing (MEC) is a cloud server running at the edge of a mobile network, which can effectively reduce network communication delay. However, due to the numerous edge servers and devices in the MEC, there may be multiple servers and devices that can provide services to the same user simultaneously. This paper proposes a userside adaptive user service deployment algorithm ASD (Adaptive Service Deployment) based on reinforcement learning algorithms. Without relying on complex system information, it can master only a few tasks and users. In the case of attributes, perform effective service deployment decisions, analyze and redefine the key parameters of existing algorithms, and dynamically adjust strategies according to task types and available node types to optimize user experience delay. Experiments show that the ASD algorithm can implement user-side decision-making for service deployment. While effectively improving parameter settings in the traditional Multi-Armed Bandit algorithm, it can reduce user-perceived delay and enhance service quality compared with other strategies.

Coal is a porous medium with pores that vary in size from nanometer to millimeter, which entails multiscale characteristics in space and time that influence coal permeability. The current steady-state method used to measure coal permeability cannot reflect these multiscale characteristics and often results in an insufficient understanding of the ultralow coal permeability. To reveal the multiscale flow mechanism of methane in coal, a cylindrical coal sample is used to conduct the unsteady diffusion-seepage experiment using CH4/He under triaxial stress condition and a dynamic attenuation of the apparent diffusion coefficient is experimentally observed. Based on the characteristic of the coal pore structure, a mathematical model of the multiscale pores in series is proposed and then validated experimentally using mercury injection. The flow of methane in multiscale pores is revealed as a step-by-step mechanism of gas outflow from interior pores to surface pores. As the number of the connected pore series increases, the equivalent pore radius decreases and the equivalent permeability is determined by the minimum pore radius. Furthermore, a dynamic apparent diffusion model is proposed to describe the full-time unsteady flow of methane in the multiscale pores. Finally, a permeability model that accounts for multiscale pores in series is built to reflect the influence of flow regime, stress, and pore pressure. The research results show that the micro–nanopore radius and number of connected pore series are vital for determining coal permeability. A larger pore radius ratio indicates a greater permeability attenuation. As pore radius decreases, the gas flow regime gradually changes from continuous flow to slip flow, transition flow, and finally to Knudsen flow. This explains the ultralow coal permeability as well as the fast reduction of coalbed gas production and concentration.

Redox-active quinone and nonquinone moieties represent the electron exchange capacity (EEC) of natural organic matter (NOM), playing an important role in the electron transfer link of microbes and transformation of contaminants/metal minerals. However, the corresponding transformation of quinone/phenol and their respective influence on the EECs during reduction and reoxidation remain poorly characterized. Besides, it is still controversial whether nonquinones donate or accept electrons. Herein, we demonstrated that reoxidation of NOM after reduction can form new phenolic/quinone moieties, thus increasing the EEC. The assessment for the EEC, including the electron-donating capacity (EDC) and electron-accepting capacity (EAC), of nonquinones reflects the contribution of sulfur-containing moieties with considerable EDCs and EACs. In contrast, nitrogen-containing moieties donate negligible electrons even at Eh= +0.73 V. The contributions of both thiol and amine moieties to the EEC are greatly affected by adjacent functional groups. Meanwhile, aldehydes/ketones did not display an EAC during the electron transfer process of NOM. Furthermore, substantially increased EDC at Ehfrom +0.61 to +0.73 V could not be fully explained using thiol and phenolic moieties, suggesting the contribution of unknown moieties with high oxidation potential. The overall findings suggest that the roles of new quinones/phenol (derived from the addition of oxygen to condensed aromatic/lignin-like components) during redox dynamic cycling and thiol species should be considered in assessing the electron transfer processes of NOM.

Particle-bound mercury (HgP), ubiquitously present in aquatic environments, can be methylated into highly toxic methylmercury, but it remains challenging to assess its bioavailability. In this study, we developed anEscherichia coli-based whole-cell biosensor to probe the microbial uptake of inorganic Hg(II) and assess the bioavailability of HgPsorbed on natural and model particles. This biosensor can quantitatively distinguish the contribution of dissolved Hg(II) and HgPto intracellular Hg. Results showed that the microbial uptake of HgPwas ubiquitous in the environment, as evidenced by the bioavailability of sorbed-Hg(II) onto particulate matter and model particles (Fe2O3, Fe3O4, Al2O3, and SiO2). In both oxic and anoxic environments, HgPwas an important Hg(II) source for microbial uptake, with enhanced bioavailability under anoxic conditions. The composition of particles significantly affected the microbial uptake of HgP, with higher bioavailability being observed for Fe2O3and lower for Al2O3particles. The bioavailability of HgPvaried also with the size of particles. In addition, coating with humic substances and model organic compound (cysteine) on Fe2O3particles decreased the bioavailability of HgP. Overall, our findings highlight the role of HgPin Hg biogeochemical cycling and shed light on the enhanced Hg-methylation in settling particles and sediments in aquatic environments.

An optimal framework for dual-clutch coordinating starting is presented to balance the friction work of two clutches. Based on the dual-clutch coordinating starting dynamics model, optimal equation is formulated in which the weighting of the friction work, square of the jerk, and square of the control variables are considered as the optimisation objectives, and the engine torque and clutch-torque change rate are considered as the control variables. The Legendre pseudospectral method is suitable to be used to solve complex nonlinear problems and it is adopted for transforming the optimal control problem into a nonlinear programming problem, and the sequential quadratic programming method is employed for solving the integral term constraint problem with a state variable. Using a dual-clutch transmission car as prototype, optimal trajectories for starting in different working conditions are obtained. Experiments performed on a dual-clutch coordinating starting bench test verify the effectiveness of proposed optimal control strategy.

When mining high-rank coals with strong adsorption and weak desorption, the fully mechanized mining face of a thick coal seam under full-seam mining may encounter broken coal, surrounding rock and instantaneous release of large amounts of gas into the mining space from adjacent coal seams due to mining stress relief, which is extremely likely to cause gas overrun accidents at the working face. At present, the major gas control method adopted to solve this problem is the directional drainage of the fractured zone in the mining area through a roof extraction roadway (RER). However, the drainage effect is closely related to its horizontal distance from the return airway and its vertical distance from the coal seam roof. Based on the analysis of fracture characteristics in different areas of the overlying strata above the gob, this paper elaborates the extraction mechanism of RER, and employs three methods: RER at different positions, directional long borehole on roof (RDLB) at different horizontal and vertical positions, and numerical simulation of the stress release effect of the overlying rock, to investigate the gas drainage effect in mining area. A method to determine the best drainage location in the gob based on the stress release ratio of the overlying rock is proposed. The results show that either RERs or RDLBs work to conduct directional drainage in the mining area; the best position is 25 m from the return airway of the mining face horizontally and 50–55 m from the coal seam roof vertically. The research methods provide insight for later studies concerning highly gassy mines and coal and gas outburst mines. Moreover, the research results serve as guidance for other mines with similar mining conditions.

Air leakage around the in-seam borehole leads to a poor quality of gas extracted, thus gas outburst danger is difficult to eliminate but also may cause other disasters, such as coal spontaneous combustion and gas explosion. Moreover, the low concentration gas discharged into the atmosphere always possesses an intense greenhouse effect. To investigate multiphase and multifield coupling problem of gas extraction, a dual medium coupling model was developed in this study to describe the gas–air mixture flow by considering the influences of matrix shrinkage and effective stress on coal permeability. And the coupling model was calculated by the 3D numerical simulation and presented an ideal matching result with the field data. Then, the key factors affecting the gas extraction quality were also investigated with the model. It was found that the gas concentration elevated with the increase in the sealing length and borehole diameter, and reduced with the augmentation of extraction negative pressure and coal permeability. Therefore, we developed an improved sealing technology, which can fully seal the various fractures around the borehole for improving gas extraction. The field test indicated that the gas concentration by this improved sealing technology was 1.91 times that of the traditional sealing method, and still maintained a relatively high extraction level in the subsequent extraction stage with a superior application effect. The results of this work can help in optimizing the borehole sealing technology for improving gas extraction quality, which is of great significance to CBM exploitation and utilization, reduce greenhouse gas emission and ensure safe mining.

Redox transformation of mercury (Hg) is critical for Hg exchange at the air–sea interface and it can also affect the methylation of Hg in marine environments. However, the contributions of microalgae and aerobic bacteria in oxic seawater to Hg2+reduction are largely unknown. Here, we studied the reduction of Hg2+mediated by microalgae and aerobic bacteria in surface marine water and microalgae cultures under dark and sunlight conditions. The comparable reduction rates of Hg2+with and without light suggest that dark reduction by biological processes is as important as photochemical reduction in the tested surface marine water and microalgae cultures. The contributions of microalgae, associated free-living aerobic bacteria, and extracellular substances to dark reduction were distinguished and quantified in 7 model microalgae cultures, demonstrating that the associated aerobic bacteria are directly involved in dark Hg2+reduction. The aerobic bacteria in the microalgae cultures were isolated and a rapid dark reduction of Hg2+followed by a decrease of Hg0was observed. The reduction of Hg2+and re-oxidation of Hg0were demonstrated in aerobic bacteria Alteromonasspp. using double isotope tracing (199Hg2+and 201Hg0). These findings highlight the importance of algae-associated aerobic bacteria in Hg transformation in oxic marine water.

Energy management of the fuel cell hybrid electric vehicles (FCHEVs) is vital with respect to improving FCHEV's performance and durability. Radau Pseudospectral method (RPM)-based optimal control of energy management of FCHEV is proposed to optimise the fuel cell's lifetime by means of reducing its performance degradation. To utilise the RPM, both state and control variables are approximated by global interpolation polynomials, and differential equations of state variables are approximated by the derivatives of interpolation polynomials. Accordingly, the optimal control problem is transformed into nonlinear problem to be solved. The fuel cell's performance degradation is selected as objective function. The optimal results in NEDC show that battery with larger capacity is more beneficial than smaller one for reducing the fuel cell's performance degradation, with the total time of large load change of the fuel cell reducing. The RPM is also an effective way to optimise other objectives to energy management.

Exploitation of deep-lying coal resources, an inevitable result of the conflict between the depletion of shallow coal resources and the enormous demand for energy, is subject to safety accidents caused by increased risks of coal and gas outbursts. Factors such as low gas extraction efficiency resulted from poor air permeability of coal seams, failure of extracting methane in coal mine and low utilization rate of the methane extracted from coal mine not only cause serious greenhouse effect, but also waste a lot of energy and fuel. Recent innovations have seen that the new elements of three zone linkage based on the joint mining of coal and gas is used to ensure the safety of workers and achieve the maximum energy comprehensive utilization. Sihe coalfield represents a particularly challenging mining environment for applying this practice. Due to the high risk of coal seam outburst, mining disturbance will not only cause coal and gas outburst and cause casualties, gas emissions will also cause serious greenhouse effect and energy waste. Sihe coalfield has formed a green coal mining mode of low-carbon and environmental protection, which provides attractive experience and lessons for the application of other coal mines at home and abroad. This approach achieves multiple benefits: large-scale extraction and utilization of CBM resources, safe and efficient production of coal areas, and reduction in greenhouse methane emissions. The successful application of this method to Sihe coalfield provides a new way of gas management for other coal mines with similar geological conditions. In view of the extreme nature of Sihe minefield, it will be easier to implement in other coal mines.

To maintain the high-efficiency production of fully mechanized working face under the condition of highly mechanized mining and guarantee the security operations during mining process at high gassy outburst-prone mines, in most cases, the gas control methods adopted include: burying pipes in the gob, gas extraction at the stress relief zone, roof borehole with common drilling rig (RBCDR), roof borehole with directional drilling rig (RBDDR), and roof extraction roadway (RER), etc. The above method solves the gas emission problem in the mining area to some extent during the mining face. In recent years, the most popular method to deal with great depth and high gas content is RER. However, with this method, there are several adverse impacts: the work amount and investment for the roadway are large; the construction period is long; the gangue generated will cause serious pollution to the ecological environment; so on and so forth. Therefore, an integrated drainage technique of super large diameter borehole on roof (SDBR) has been proposed to replace traditional method of RER. With this technique, the directional rig with the largest power in China has been applied to make roof borehole with one-time drilling and multiple enlarged borehole diameter. Meanwhile, it can achieve the replacing effect of RER by supporting special hole-protective device. This technique has three major advantages as follows. First, while guaranteeing efficient drainage, the construction period can be shortened and the investment can be greatly reduced. Second, it can replace RER and avoid the risks in construction, transportation and outburst caused by gangue. Third, the effect of mining in the soft thick coal seam with low permeability can be ensured in a highly mechanized way. This technique can achieve simple construction process, low costs, and satisfactory outcome. Owning universal applicability, it can be widely applied in high gas and outburst mines.

Coal seam gas content is frequently measured in quantity during underground coal mining operation and coalbed methane (CBM) exploration as a significant basic parameter. Due to the calculation error of lost gas and residual gas in the direct method, the efficiency and accuracy of the current methods are not inadequate to the large area multi-point measurement of coal seam gas content. This paper firstly deduces a simplified theoretical dynamic model for calculating lost gas based on gas dynamic diffusion theory. Secondly, the effects of various factors on gas dynamic diffusion from coal particle are experimentally studied. And sampling procedure of representative coal particle is improved. Thirdly, a new estimation method of residual gas content based on excess adsorption and competitive adsorption theory is proposed. The results showed that the maximum error of calculating the losing gas content by using the new simplified model is only 4%. Considering the influence of particle size on gas diffusion law, the particle size of the collected coal sample is below 0.25 mm, which improves the measurement speed and reflects the safety representativeness of the sample. The determination time of gas content reduced from 36 to 3 h/piece. Moreover, the absolute error is 0.15–0.50 m3/t, and the relative error is within 5%. A new engineering method for determining the coal seam gas content is developed according to the above research.

There are many problems within drilling in soft and broken coal seams, such as borehole collapse, borehole air leakage, CO Toxic gas generated during borehole construction, coal dust pollution to the working environment and other hazards. The efficiency of coal seam gas drainage can be seriously affected by the above problems. To solve these problems, an integrated drilling, protection and sealing (IDPS) technology is proposed for borehole construction. Four major technologies are integrated: the high-purity nitrogen as slag discharge medium is used for the long-distance drilling; the integrated screen pipe inserting technology is adopted to achieve the purpose of borehole protection in the whole drilling process; the new airbag grouting technology guarantees high-quality borehole sealing; and the dust collection device is utilized to realize safe and clean operation environment. The new technology proposed in this study have the following five advantages in such as: long-distance drilling in soft coal seams, borehole protection in the whole drilling process, high-quality borehole sealing, a dust-free and safe operation environment, and efficient gas drainage. The application of IDPS technology in Hudi Coal Mine shows that the problems such as difficult borehole formation, poor gas drainage effect and coal seam outburst risk in soft and broken outburst coal seam can be effectively solved. Meanwhile, the IDPS technology proposed in this study provides scientific guidance for gas drainage in soft and broken coal seam.

Three donor–acceptor–donor molecular emitters have been designed by taking triphenylamine or N-phenylcarbazole as the donor and maleimide or phenyl maleimide as the acceptor, in which the highest occupied molecular orbital interaction between two donor units is maximized via the acceptor bridge. This is envisaged to enable both strong fluorescence radiation and fast exoergic reverse intersystem crossing via the second triplet state. Detailed photophysical characterization and theoretical calculations confirm that all the compounds have large oscillator strengths and short delayed fluorescence lifetimes of ∼0.2 μs. The fabricated organic light-emitting diodes (OLEDs) give red emission above 600 nm, luminance exceeding 6000 cd m–2, and external quantum efficiencies (EQEs) of over 6%. In particular, the best device shows an emission at 645 nm and a maximum EQE of 10.4%. Moreover, the EQEs remain above 3% at 1000 cd m–2for all the emitters. This work provides an effective method to develop organic emitters for highly efficient OLEDs with low-efficiency roll-off.

This paper aims to improve the accuracy and applicability of gas diffusion mathematical models from coal particles. Firstly, a new constitutive model for gas diffusion from coal particles with tri-disperse pore structure is constructed by considering the difference in characteristics between soft coal and hard coal. The analytical solution is then derived, that is, the quantitative relationship between gas diffusion rate (Qt/Q∞) and diffusion time (t). The pore structure parameters of soft coal and hard coal from Juji coal mine are determined. Gas diffusion rules are numerically calculated and investigated by physical simulation methods. Lastly, the applicability of this model is verified. The results show that the homogeneous model only applies to the gas diffusion process of hard coal during the initial 10min. The calculation results from this model and the physical experimental results of soft coal and hard coal are nearly identical during the initial 30min.

Complexes with low-molecular-weight thiols are crucial species of methylmercury (MeHg) excreted by anaerobic Hg-methylating microbes, notably, MeHg–cysteine (MeHg–Cys). As MeHg–Cys diffuses into surface water, it would undergo a ligand exchange process with dissolved organic matter (DOM) under nonsulfidic conditions, inevitably altering MeHg speciation and bioavailability to phytoplankton. In this study, we investigated the competitive binding kinetics between MeHg–Cys and Suwannee River natural organic matter, and their influence on the adsorption and uptake of MeHg by the cyanobacterium, Synechocystissp. PCC6803. Liquid chromatography-inductively coupled plasma mass spectrometry was employed to monitor the kinetics processes involving competition of DOM with Cys for MeHg binding, which revealed that competitive binding kinetics were dictated by the abundance of thiol moieties in DOM. Thiol concentrations of 0.97 and 49.34 μmol of thiol (g C)−1resulted in competitive binding rate constant (kvalues) of 0.30 and 3.47 h–1, respectively. Furthermore, the time-dependent competitive binding of DOM toward MeHg–Cys significantly inhibited MeHg adsorption and uptake by cyanobacteria, an effect that was amplified by an increased thiol abundance in DOM. These findings offer valuable insights into the kinetic characteristics of MeHg’s fate and transport, as well as their impact on bioconcentration in aquatic organisms within natural aquatic ecosystems.

Graphical Abstract:

Bromophenols occur naturally and are used globally as man-made additives in various industrial products. They are decomposition products of many emerging organic pollutants, such as tetrabromobisphenol A, polybrominated dibenzo-p-dioxin (PBDD), polybrominated diphenyl ethers (PBDE), and others. To characterize their biotransformation pathways, bromophenol congener 2,4,6-tribromophenol, being used most frequently in the synthesis of brominated flame retardants and having the greatest environmental abundance, was selected to hydroponically expose rice plants. After exposure for 5 days, 99.2% of 2,4,6-tribromophenol was metabolized by rice. Because of the lack of relative reference standards, an effective screening strategy was used to screen for potential metabolites that were further qualitatively identified by gas and liquid chromatography combined with high-resolution mass spectrometry. Forty transformation products were confirmed or tentatively identified at different confidence levels, including 9 phase I and 31 phase II metabolites. A large number of metabolites (39) were found in rice root, and 10 of them could be translocated and detected in rice stems or leaves. Many transformation pathways were proposed, including debromination, hydroxylation, methylation, coupling reactions, sulfation, and glycosylation. It was remarkable that a total of seven hydrophobic, persistent, and toxic OH-PBDEs and PBDD/Fs were found, indicating the biotic dimeric reactions of 2,4,6-tribromophenol that occurred in the rice plants. These results improve our understanding of the transformation and environmental fates of bromophenols, and they indicate new potential sources for OH-PBDEs and PBDD/Fs in the environment, especially in food chains.

Objective To compare the clinical efficacy of cyclophosphamide (CTX) and cyclosporine A (CSA) in initial treatment of children with steroid-resistant nephrotic syndrome (SRNS).Methods Prospectively maintained databases were reviewed to retrospectively compare two cohorts with SRNS that received peroral administration of 2 to 2.5 mg/kg/d CTX for 3 to 6 months or 1 to 5 mg/kg/d CSA for 2 years until the primary analysis cut-off date during 2007 to 2011. The time to first on-study relapse of SRNS was the primary endpoint. The effective rate was the second endpoint.Results A total of 127 children with SRNS were included (CTX-treated cohort: n = 62; CSA-treated cohort: n = 65), with a mean 5-year follow-up. CTX-treated children showed a significantly delayed time to first on-study relapse of SRNS compared with CSA-treated children (hazard ratio 0.66, 95% confidence interval 0.32–1.75). The relapse rate (rate/year) in CTX-treated children (1.1 ± 0.1) at the 24-month follow-up was significantly higher than that with CSA (0.4 ± 0.2). This difference persisted until the final follow-up.Conclusions CSA is associated with a significantly lower relapse rate and significantly higher effective rate compared with CTX, especially in children with minimal change disease.

Systematic understanding and real-time feedback capability for x-ray free electron laser (FEL) accelerator and optical components are critical for scientific experiments and instrument performance. Single-shot wavefront sensing enables characterization of the intensity and local electric field distribution at the sample plane, something that is important for understanding scientific experiments such as nonlinear studies. It can also provide feedback for alignment and tuning of the FEL beam and instrumentation optics, leading to optimal instrument performance and greater operational efficiency. A robust, sensitive, and accurate single-shot wavefront sensor for x-ray FEL beams using single grating Talbot interferometry has been developed. Experiments performed at the Linac Coherent Light Source (LCLS) demonstrate 3σ sensitivity and accuracy, both better than λ/100, and retrieval of hard x-ray (λ=0.13  nm, E=9.5  keV) wavefronts in 3D. Exhibiting high performance from both unfocused and focused beams, the same setup can be used to systematically study the wavefront from the FEL output, beam transport optics, and endstation focusing optics. This technique can be extended for use with softer and harder x rays with modified grating configurations.

Cemented carbide tools are often used for milling operations that cause high thermal and mechanical process loads, e.g. machining processes for titanium alloys. However, the disposal of those tools after one life cycle would significantly reduce their resource efficiency. Therefore, regrinding operations are crucial in order to recycle worn tools and ensure an economical as well as resource efficient manufacturing process. The main challenges during regrinding are the precise quantification of present defects and the subsequent determination of the grinding allowance. As it is, a worker performs both tasks using his individual estimations. Consequently, the estimated grinding allowance is often too low or too high. This either decreases the lifetime of the reground tools due to remaining defects or reduces the resource efficiency since more material than necessary is removed. This paper investigates the determination of the grinding allowance and the environmental impact of regrinding operations on the life cycle of the investigated tools. It is shown that about 12.5% percent of the worn tools are being unnecessarily disposed of. Furthermore, the resource efficiency of tools with small breakouts might be increased by 20% if the recommended allowance strategy is utilized. The tool wear of the grinding tools is also taken into consideration in order to further increase the resource efficiency of the whole life cycle, including milling tool and grinding wheel. The results show that small grain sizes and low grain concentrations are not suitable for efficient regrinding processes since higher wear and consequently higher geometrical inaccuracies of the reground tools occur.

Global mobile video traffic is predicted to grow explosively in the near future and high-definition (HD) video streaming applications are increasingly prevailing over the mobile Internet. To optimize the transmission performance of HD video streaming applications over the heterogeneous wireless access networks, multipath video streaming that exploits the multihoming features of mobile devices is proposed as a potential solution. However, the delivery of HD video has much higher bitrate and more stringent delay constraint than other services. It is thus challenging to transfer HD video through wireless networks. Conventionally, multipath video streaming is optimized by the video distortions or other network-level quality-of-service parameters, which do not correlate well with the human visual perceptions. To address this problem, we first propose a novel quality-of-experience (QoE) prediction model to prefer the QoE values of different rate allocation scenarios over heterogeneous wireless access networks. Then, the rate allocation problem over heterogeneous wireless networks is formulated as a nonlinear optimization problem of maximizing the perceived video quality at the receiver. A relaxing function called penalty function is exploited to transform the rate allocation problem into an unconstrained optimizing problem and the pattern search method is adopted to obtain the close-to-optimal solution in each rate allocation session. The extensive simulation results show that our proposal significantly improves the QoE in terms of mean opinion score compared with the reference schemes.

For a novel seamless 2-speed transmission specially equipped in the electric vehicles, the optimal coordinating control problem of the motor and the friction clutch with complex constraints on both the state and control variables during the overlapping shifts is investigated in this article. First, the shift principle and the dynamic models of the overlapping shifts between the friction clutch and the one-way clutch are analyzed. Next, the parameters for evaluating the shift quality are analyzed. The jerks in process and at the key moments (speed synchronization moments of the friction clutch or the one-way clutch) are distinguished and selected as the constraints and the objective function’s terminal items, respectively. Finally, an integral optimal coordinating controller is proposed to optimize the shift trajectories and improve the overlapping shift quality. The linear feed-forward coordinating control strategy is used in the torque phase to regulate the motor torque with the engaging or disengaging process of the friction clutch to maintain the jerk within the permissible range, and the optimal control strategy based on the principle of the minimum is used to optimize the shift trajectories with complex constraints on both the control and state variables in the inertia phase. The effectiveness of the proposed optimal coordinating controller on addressing the coordinating control problem of the motor and the friction clutch during the overlapping shifts and establishing a solid foundation for the application of the seamless 2-speed transmission in electric vehicles have been verified by the simulation and experimental test-bench results.

Plant-based milk is considered a healthy and environmentally sustainable option. In order to solve the physical and chemical instability problem of most plant milk and increase the chance of consumer acceptance of the flavor, this experiment used soybean as raw material, fructo-oligosaccharides (FOS) as prebiotics, and added kombucha for fermentation. The microbial composition, functional components, antioxidant capacity, physicochemical properties and flavor relationship of fermented soy milk at different fermentation times (up to 96 h) were studied by high-throughput sequencing, laser confocal scanning imaging, and gas chromatography−mass spectrometry. According to the results, the synbiotic interaction of FOS and kombucha consortium promoted the growth of yeast and lactic acid bacteria in soy milk. The ideal fermentation time was 84 h. At this time, fermented soy milk added with FOS displayed increased β-glucosidase activity (by 68.10 mU/mL), isoflavones mainly represented by genistein content (by 612.41%), and DPPH radical scavenging activity (by 25.02%). Furthermore, the addition of FOS intensified the sour taste of the 84 h-fermented soy milk. The content of hexanal was reduced, while favorable flavor substances, such as citric acid and linalool, were also produced. Soymilk fermented with kombucha and FOS provides an opportunity to explore the physical and chemical characteristics and the mechanism of flavor formation in multi-strain co-fermentation systems and to develop commercial plant-based fermentation products.

A heptagonal isomerized bithiophene imide (iBTI) acceptor has been effectively synthesized on a gram scale. Its series of β-, α′,β-, α,α′-, α,α′,β-, and α,α′,β,β′-substituted derivatives can be obtained by controlling brominated sites. Single-crystal analyses indicate that the torsion angle of the imide backbone depends on the number and rigidity of β-substituted groups. Furthermore, the helical chirality of tetrasubstituted and [7]helicene-like derivatives based on iBTI shows great promise for the construction of chiral semiconductor materials.

An extraordinarily high degree of spatial coherence from a high average power tabletop 46.9 nm laser was observed in two-pinhole interference experiments. Refractive anti-guiding and gain guiding along a capillary discharge-produced plasma column causes a rapid increase of the spatial coherence with amplifier length. Full spatial coherence was approached with a 36 cm long plasma of very high axial uniformity and a length to diameter ratio exceeding 1000:1.

In-situ immobilization is a fast soil remediation method that can recover the value of As-contaminated land quickly. Hydrous zirconium oxide was reported for its efficient arsenic adsorption properties in wastewater treatment, but has not been reported in soil remediation with As contamination. Herein, hydrous zirconium oxide modified biochar (BC-Zr) was synthesized along with hydrous ferric oxide modified biochar (BC-Fe) and hydrous titanium oxide modified biochar (BC-Ti). After comparing their As(III)/As(V) adsorption performance under diverse conditions, BC-Zr showed superior As-immobilization potential in both simulated water and real soil leachate environment. To evaluate its performance in soil remediation, pot experiments were conducted in real As-contaminated agricultural soil using cowpea (Vigna unguiculataL.) as an indicator plant. Although all these modified BC could improve the growth of cowpea, the shoot biomass treated by BC-Zr increased by 115.8% than CK, while the As concentration in the stem and leaves decreased by 30.8% and 42.6%, respectively. Interestingly, BC-Zr promoted the root nodule system of cowpea in real As-contaminated soil while BC-Fe and BC-Ti failed. The observation of improved root nodule symbiotic system is significant for further development of soil remediation using in-situ remediation technology. This first successful trial of Zr-based soil amendment indicates the superior As-immobilization property of hydrous zirconium oxide in in-situ remediation of As-contaminated soil, implying the great potential applications of BC-Zr in soil remediation.

This paper presents a wheeled wall-climbing robot with the ability to climb concrete, brick walls using circular arrays of miniature spines located around the wheel. The robot consists of two driving wheels and a flexible tail, just like letter “T”, so it is called Tbot. The simple and effective structure of Tbot enables it to be steerable and to transition from horizontal to vertical surfaces rapidly and stably. Inspired by the structure and mechanics of the tarsal chain in the Serica orientalisMotschulsky, a compliant spine mechanism was developed. With the bio-inspired compliant spine mechanism, the climbing performance of Tbot was improved. It could climb on 100° (10° past vertical) brick walls at a speed of 10 cm·s−1. A mechanical model is also presented to analyze the forces acting on spine during a climbing cycle as well as load share between multi-spines. The simulation and experiment results show that the mechanical model is suitable and useful in the optimum design of Tbot.

Continuous progress in flexible electronics is bringing more convenience and comfort to human lives. In this field, interconnection and novel display applications are acknowledged as important future directions. However, it is a huge scientific and technical challenge to develop intrinsically flexible displays due to the limited size and shape of the display panel. To address this conundrum, it is crucial to develop intrinsically flexible electrode materials, semiconductor materials and dielectric materials, as well as the relevant flexible transistor drivers and display panels. In this review, we focus on the recent progress in this field from seven aspects: background and concept, intrinsically flexible electrode materials, intrinsically flexible organic semiconductors and dielectric materials for organic thin film transistors (OTFTs), intrinsically flexible organic emissive semiconductors for electroluminescent devices, and OTFT-driven electroluminescent devices for intrinsically flexible displays. Finally, some suggestions and prospects for the future development of intrinsically flexible displays are proposed.This review introduces the concept, key materials and device structure design of intrinsically flexible displays, and proposes some potential solutions to current concerns and future development.

A theoretical analysis and an experimental study are presented on the phase-matching condition of noncollinearly pumped optical parametric oscillators (OPO’s) based on a noncritical phase-matching potassium titanyl phosphate (KTP) OPO. It is shown that noncollinearly pumped, double-pass, singly resonant optical parametric oscillators maintain the advantage of round-trip parametric gain in a collinear pump, since in this case the two generated signal waves are coherent, which results in high conversion efficiency and low pump threshold. With this KTP OPO we achieved 31% energy conversion efficiency from a 1064-nm pump wave to 1572-nm eye-safe output. In addition, because the incident pump beam is not perpendicular to the OPO cavity mirrors and consequently no reflected beam flows back into the pump source, we can avoid employing optical isolators.

The instability of hydrothermal liquefaction (HTL) biocrude has impeded the broader utilization of fuel and chemical feedstock. In this paper, we investigated the storage stability of biocrude produced from HTL of microalgae. The biocrude showed good stability in phase homogeneity and water content, whereas the viscosity and average molecular weight increased by 48.4 and 41.9%, respectively, after storing for 12 months. Thermogravimetric analysis (TGA) and asphaltene content analysis indicated more high-boiling-point fraction, and asphaltene fraction appeared in biocrude during storage. Further elemental analysis and increased total acid numbers (TANs) demonstrated that oxidization acidic-compound-forming reactions occurred, and the gas chromatography–mass spectrometry (GC–MS) results evidenced this guess. However, the mechanism of biocrude storage instability still needs further analysis. The current biocrude assuredly requires stabilization refining for future applications.

For the most complex artificial chlorinated environmental contaminants, much less is known for medium-chain CPs than short-chain CPs. In this research, the spatial distributions of MCCPs and SCCPs in farmland soil and maize leaves near a CP production facility were found marginally influenced by seasonal winds. The levels of ∑MCCPs and ∑SCCPs were in the ranges of <1.51–188 and 5.41–381 ng/g dw for soils; and 77.6–52930 and 119–61999 ng/g dw for maize leaf, respectively. Bioaccumulation and tissue distributions of the CPs within maize plants were specifically analyzed. Most of the CPs were contained in the tissues directly exposed to airborne CPs. Though the estimated risk of CPs to humans through ingestion of kernels appears to be minimal, the edible safety of MCCPs in maize plants for cattle was nearly in the designated range of adverse effects. To our knowledge, this is the first report on bioaccumulation of CPs in mature maize plants, especially in the parts eaten by humans and domestic animals. It provides a baseline reference to the edible risks of CPs in agricultural food plants and alerts us to the problematic environmental behavior of MCCPs, a probable future replacement for SCCPs commercially.

Injection seeding of solid-target soft x-ray laser amplifiers with high harmonic pulses is shown to dramatically improve the far-field laser beam profile and reduce the beam divergence. Measurements and two-dimensional simulations for a 13.9nm nickel-like Ag amplifier show that the amplified beam divergence depends strongly on the seed and can therefore be controlled by selecting the divergence of the seed. The near-field beam size of both the seeded and unseeded lasers is shown to be determined by the size of the gain region and the divergence of the amplified beams.

An experimental method is presented to experimentally measure and control the carrier-envelope-phase (CEP)-dependent pulse-energy contrast of isolated attosecond pulses. By scanning the CEP and measuring the photoelectron spectrum produced by the combined action of the attosecond pulses and the high-harmonic driving laser pulses at zero relative time delay, one can extract the pulse-energy ratio between the main attosecond pulse and its neighboring satellite pulses arriving in preceding or subsequent half-cycles of the driver pulse. Moreover, this method allows fast and efficient in situ retrieval of the optimal CEP for high-contrast isolated attosecond pulse generation.