It’s of great challenge to address for heavy metal-contaminated soil. Once the farmland is contaminated with heavy metals, the microbial ecology of the plant rhizosphere will change, which in turn ...impacts crop productivity and quality. However, few studies have explored the effects of heavy metals on plant rhizosphere microbes in farmland and the role that plant cultivation plays in such a phytoremediation practice. In this study, the impacts of comfrey (Symphytum officinale L.) cultivation and the stresses of cadmium/zinc (Cd/Zn) on rhizosphere soil microflora were examined. Microbial DNA was collected from soils to evaluate the prevalence of bacteria and fungi communities in rhizosphere soils. High-throughput 16 S rRNA sequencing was used to determine the diversity of the bacterial and fungal communities. The results showed that growing comfrey on polluted soils reduced the levels of Cd and Zn from the vertical profile. Both the comfrey growth and Cd/Zn stresses affected the community of rhizosphere microorganisms (bacteria or fungi). Additionally, the analysis of PCoA and NMDS indicated that the cultivation of comfrey significantly changed the bacterial composition and structure of unpolluted soil. Comfrey cultivation in polluted and unpolluted soils did not result in much variance in the fungi’s species composition, but the fungal compositions of the two-type soils were noticeably different. This work provided a better understanding of the impacts of Cd/Zn stresses and comfrey cultivation on rhizosphere microbial community, as well as new insight into phytoremediation of heavy metal-contaminated soils.
•Growing comfrey reduced the levels of Cd and Zn from the vertical profile.•Comfrey cultivation and Cd/Zn stresses affected the microbial community.•The study further enhanced the role of plant rhizosphere in phytoextraction process.
This paper presents the background, scientific objectives, experimental design, and preliminary achievements of the Third Tibetan Plateau (TP) Atmospheric Scientific Experiment (TIPEX-III) for 8–10 ...years. It began in 2013 and has expanded plateau-scale observation networks by adding observation stations in data-scarce areas; executed integrated observation missions for the land surface, planetary boundary layer, cloud–precipitation, and troposphere–stratosphere exchange processes by coordinating ground-based, air-based, and satellite facilities; and achieved noticeable progress in data applications. A new estimation gives a smaller bulk transfer coefficient of surface sensible heat over the TP, which results in a reduction of the possibly overestimated heat intensity found in previous studies. Summer cloud–precipitation microphysical characteristics and cloud radiative effects over the TP are distinguished from those over the downstream plains. Warm rain processes play important roles in the development of cloud and precipitation over the TP. The lower-tropospheric ozone maximum over the northeastern TP is attributed to the regional photochemistry and long-range ozone transports, and the heterogeneous chemical processes of depleting ozone near the tropopause might not be a dominant mechanism for the summer upper-tropospheric–lower-stratospheric ozone valley over the southeastern TP. The TP thermodynamic function not only affects the local atmospheric water maintenance and the downstream precipitation and haze events but also modifies extratropical atmospheric teleconnections like the Asia–Pacific Oscillation, subtropical anticyclones over the North Pacific and Atlantic, and temperature and precipitation over Africa, Asia, and North America. These findings provide new insights into understanding land–atmosphere coupled processes over the TP and their effects, improving model parameterization schemes, and enhancing weather and climate forecast skills.
Biotreatment of high load hydrogen sulfide (H2S) can lead to rapid acidification of a bioreactor, which greatly challenges the application of bio-desulfurization technology. In this study, the ...bio-desulfurization performance was improved by enriching acidophilic mixotrophic sulfur-oxidizing bacteria (SOB) by adding organics under extremely acidic conditions (pH < 1.0). A biotrickling filter (BTF) for the removal of H2S was established and operated under pH < 1.0 for 420 days. In the autotrophic period, the maximum H2S elimination capacity (ECmax-H2S) was 135.8 g/m3/h with biofilm mass remaining within 11.1 g/L-BTF. The autotrophic SOB bacterium Acidithiobacillus was dominant (62.1 %). When glucose was added to the BTF system, ECmax-H2S increased by 272 % to 464.3 g/m3/h as biofilm mass increased to 22.3 g/L-BTF. The acidophilic mixotrophic SOB bacteria Mycobacterium (78.4 %) and Alicyclobacillus (20.7 %) were enriched while Acidithiobacillus was gradually eliminated (<0.1 %). Furthermore, the major sulfur metabolism pathways were identified to explore the desulfurization mechanism under extremely acidic conditions. To maintain optimal desulfurization performance and avoid biofilm overgrowth in the BTF system, biofilm mass should be maintained within 20–22 g/L-BTF. This can be achieved by adding 1.0 g/L-BTF glucose every 20 days under a load rate of H2S in 50–90 g/m3/h and a trickling liquid velocity of 1.8 m/h. Extremely acidic conditions eliminated non-aciduric microorganisms so that the addition of organics can increase the abundance of acidophilic mixotrophic SOB (>99 %), thus offering a novel strategy for enhancing H2S removal.
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•Adding organics under extreme acidity is a new strategy for increasing SOB biomass.•Mixotrophic SOB (>99 %) was enriched while autotrophic SOB was eliminated.•Enrichment of mixotrophic SOB enhanced the EC-H2S by 272 % to 464.3 g/m3/h.•The desulfurization performance of BTF was optimal with biofilm mass at 22 g/L-BTF.•The major metabolism pathways of sulfur under extreme acidity were first revealed.
Radiotherapy is the main treatment strategy for nasopharyngeal carcinoma. A major factor affecting radiotherapy outcome is the accuracy of target delineation. Target delineation is time-consuming, ...and the results can vary depending on the experience of the oncologist. Using deep learning methods to automate target delineation may increase its efficiency. We used a modified deep learning model called U-Net to automatically segment and delineate tumor targets in patients with nasopharyngeal carcinoma. Patients were randomly divided into a training set (302 patients), validation set (100 patients), and test set (100 patients). The U-Net model was trained using labeled computed tomography images from the training set. The U-Net was able to delineate nasopharyngeal carcinoma tumors with an overall dice similarity coefficient of 65.86% for lymph nodes and 74.00% for primary tumor, with respective Hausdorff distances of 32.10 and 12.85 mm. Delineation accuracy decreased with increasing cancer stage. Automatic delineation took approximately 2.6 hours, compared to 3 hours, using an entirely manual procedure. Deep learning models can therefore improve accuracy, consistency, and efficiency of target delineation in T stage, but additional physician input may be required for lymph nodes.
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•A novel mode coupling mechanism applicable to robotic milling is developed.•The feedback between dynamic milling forces and vibrations is modeled.•The low-frequency chatter is ...efficiently predicted.
The low-frequency chatter (LFC) of the robot body during milling severely constrains the machining efficiency. Taking the classical mode coupling mechanism as the underlying foundation, previous studies have developed various stability models to predict the LFC in robotic milling. However, the classical mode coupling mechanism has recently been proven to be applicable only to operations such as threading and boring, showing significant deviations in robotic milling. In response, this paper proposes a novel vibration feedback-based mode coupling (VF-MC) mechanism applicable to robotic milling based on robotic modal directionality, which describes the coupling and feedback process of modal vibration among multiple modes through dynamic cutting forces. The feedback process is modeled considering the time delay effect. The LFC can be judged by the trend of the amplitudes of the feedback vibrations. The effectiveness and efficiency of the VF-MC model for predicting the LFC are verified by comparing with the milling experiment results and the traditional mode coupling chatter model. Furthermore, the dynamical conditions for the LFC are investigated based on the VF-MC mechanism with the experimental evidence. The core contribution of this paper is to quantitatively reveal the feedback mechanism of low-frequency self-excited vibration among modes in robotic milling, and further develop the VF-MC model to efficiently predict the LFC. The code for the VF-MC model is available at https://github.com/Dr-JwWu/VF-MC__A-chatter-model-for-robotic-milling.
The application of carbon-based materials (CBMs) for heavy metal polluted soil remediation has gained growing interest due to their versatile properties and excellent remediation performance. ...Although the progresses on applications of CBMs in removing heavy metal from aqueous solution and their corresponding mechanisms were well known, comprehensive review on applications of CBMs in heavy metal polluted soil remediation were less identified. Therefore, this review provided insights into advanced progresses on utilization of typical CBMs including biochar, activated carbon, graphene, graphene oxide, carbon nanotubes, and carbon black for heavy metal polluted soil remediation. The mechanisms of CBM remediation of heavy metals in soil were summarized, mainly including physical adsorption, precipitation, complexation, electrostatic interaction, and cationic-π coordination. The key factors affecting the remediation effect include soil pH, organic matter, minerals, microorganisms, coexisting ions, moisture, and material size. Disadvantages of CBMs were also included, such as: potential health risks, high cost, and difficulty in achieving co-passivation of anions and cations. This work will contribute to our understanding of current research advances, challenges, and opportunities for CBMs remediation of heavy metal-contaminated soils.
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•Progresses and prospects on carbon-based materials for metal(loid)s polluted soil remediation were discussed.•Fully introduced the key factors affecting the passivation of soil heavy metals by carbon-based materials•Interactions between carbon-based materials and heavy metals in soil condition were summarized.
Self‐rectifying memristor has no need for selector devices, but possesses the one‐way transmission behaviour and multi‐level non‐volatile memory characteristics, which makes it a promising candidate ...for electronic synapse. In this letter, the authors propose a novel self‐rectifying memristor based on a Pt/Hf0.5Zr0.5O2/TiN structure. The devices show large memory window (104) and high rectifying ratio (104), which can block the sneak current in a passive crossbar array without any additional hardware overhead. Moreover, the devices demonstrate excellent multi‐level states modulation capability, low power consumption, high endurance and long retention. The final benchmark demonstrates that the proposed Pt/Hf0.5Zr0.5O2/TiN self‐rectifying memristor is a promising candidate for electronic synapse application.
Different from other memristors, the self‐rectifying memristors possess the similar one‐way transmission characteristic as biological synapses, making these devices better to mimic the synaptic plasticity. In this letter, the authors propose a novel self‐rectifying memristor based on the Pt/Hf0.5Zr0.5O2/TiN structure. The device shows competitive advantages, large memory window (104) and high rectifying ratio (104).
The bio-treatment of methanethiol (MT) and dimethyl sulfide (DMS), the most common sulfur compounds in odorous gas, is difficult due to the inhibition of DMS degradation by MT. This article ...investigated the treatment of MT and DMS odorous gas using a single-stage biotrickling filter (BTF) packed with polyurethane foam cubes that were inoculated with activated sludge from a sewage treatment plant operating an anaerobic/aerobic/oxic (AAO) process. The BTF system lasted for 161 days (with 9 days to startup) under an empty gas residence time of 39 s. The elimination capacities for MT and DMS were 85.2 g/m3/h (removal efficiency = 96.6%) and 6.4 g/m3/h (removal efficiency = 95.0%), respectively, and the maximal elimination capacities of MT and DMS were 119.7 g/m3/h and 7.3 g/m3/h, respectively. The optimal parameters were as follows: empty bed retention time, 39 s; pH, 6.1; recirculation medium flow rate, ≥1.2 m3/m2/h; temperature, 29–36 °C; and SO42− concentration, < 2.0 g-SO42-/L. Microbial community analysis revealed that spatial differentiation between MT-degrading bacteria and DMS-degrading bacteria enable the single-stage BTF can simultaneously remove MT and DMS. The activated sludge of AAO process can be used as the inoculation sludge to treating MT and DMS gas, which provides an important reference for the industrial application of treating odorous gas containing MT and DMS.
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•The single-stage BTF system obtained the ECMT of 85.2 g/m3/h (RE = 96.6%) and the ECDMS of 6.4 g/m3/h (RE = 95.0%).•The optimal value of the key parameters of the BTF system were as follows: EBRT = 39 s; pH = 6.1.•The startup time of the BTF system can be as short as 9 days.•DMS-degrading bacteria (Bacillus and Hyphomicrobium) are mainly distributed in the top of BTF.
It is well known that organic acids (OAs) could affect the flavour of fruit juices and beverages. However, the molecular mechanism of aroma release is still unclear. In this study, the effects of ...citric acid (CA), L-(-)-malic acid (MA) and L-lactic acid (LA) on the release of six selected esters and their sensory perception were investigated by means of HS-GC-MS analyses and odour detection threshold determination, respectively. Meanwhile, the density functional theory (DFT) calculation was employed to explore the interaction modes between esters and OAs. HS-GC-MS analyses showed that the concentration and the type of OAs regulated the release of esters. The results were basically consistent with the detection threshold change of those esters. The DFT calculation suggested that the main intermolecular interaction was hydrogen bonds, and several esters could form a ternary ring structure with OAs through hydrogen bonds. The interactions can induce the different release behaviours of esters in OAs water solution. The number of carboxyl functional groups in OAs and the spatial conformation of esters appeared to influence the magnitude of the interaction. The above results demonstrated the mechanism of OAs affecting the release of esters and indicated a possible flavour control way by using different OAs and OA concentrations.
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