Defect formation is a common problem in selective laser melting （SLM）. This paper provides a review of defect formation mechanisms in SLM. It sum- marizes the recent research outcomes on defect ...findings and classification, analyzes formation mechanisms of the common defects, such as porosities, incomplete fusion holes, and cracks. The paper discusses the effect of the process parameters on defect formation and the impact of defect formation on the mechanical properties of a fabri- cated part. Based on the discussion, the paper proposes strategies for defect suppression and control in SLM.
Polarized detection has been brought into operation for optics applications in the visible band. Meanwhile, an advanced requirement in short-wave near-infrared (SW-NIR) (700–1100 nm) is proposed. ...Typical IV–VI chalcogenides2D GeSe with anisotropic layered orthorhombic structure and narrow 1.1–1.2 eV band gappotentially meets the demand. Here we report the unusual angle dependences of Raman spectra on high-quality GeSe crystals. The polarization-resolved absorption spectra (400–950 nm) and polarization-sensitive photodetectors (532, 638, and 808 nm) both exhibited well-reproducible cycles, distinct anisotropic features, and typical absorption ratios α y /α x ≈ 1.09 at 532 nm, 1.26 at 638 nm, and 3.02 at 808 nm (the dichroic ratio I py/I px ≈ 1.09 at 532 nm, 1.44 at 638 nm, 2.16 at 808 nm). Obviously, the polarized measurement for GeSe showed superior anisotropic response at around 808 nm within the SW-NIR band. Besides, the two testing methods have demonstrated the superior reliability for each other. For the layer dependence of linear dichroism, the GeSe samples with different thicknesses measured under both 638 and 808 nm lasers identify that the best results can be achieved at a moderate thickness about 8–16 nm. Overall, few-layer GeSe has capacity with the integrated SW-NIR optical applications for polarization detection.
The great potential of bioelectrochemical systems (BESs) in pollution control combined with energy recovery has attracted increasing attention. Classified by their functions in the BES, ...microorganisms including degraders, electricigens, and element cycle-related microbes play key roles in pollutant degradation and electricity generation, and the functions of these microbes are affected by various environmental and operating conditions. This review systematically summarizes the effects of crucial conditions on the efficiency of the process of contaminant removal combined with electricity generation in BESs, with particular focus on the pH, temperature, conductivity, substrates, inoculums, magnetic field and reactor design parameters, such as architecture, electrode material, and electrode potential. The aim of this review is to help reveal the microbial functions during the bioelectrochemical remediation of environmental media and to optimize the system by determining the appropriate conditions for functional microorganisms, thus better promoting the transition of BESs from the laboratory to actual applications.
The great potential of bioelectrochemical systems (BESs) in pollution control combined with energy recovery has attracted increasing attention.
Plant growth promoting rhizobacteria (PGPR) provide an effective and environmentally sustainable method to protect crops against pathogens. The spore-forming Bacilli are attractive PGPR due to their ...ease of storage and application. Here, we characterized two rhizosphere-associated Bacillus velezensis isolates (Y6 and F7) that possess strong antagonistic activity against Ralstonia solanacearum and Fusarium oxysporum under both laboratory and greenhouse conditions. We identified three lipopeptide (LP) compounds (surfactin, iturin and fengycin) as responsible for the antimicrobial activity of these two strains. We further dissected the contribution of LPs to various biological processes important for rhizosphere colonization. Although either iturin or fengycin is sufficient for antibacterial activity, cell motility and biofilm formation, only iturin plays a primary role in defense against the fungal pathogen F. oxysporum. Additionally, we found that LP production is significantly stimulated during interaction with R. solanacearum. These results demonstrate the different roles of LPs in the biology of B. velezensis and highlight the potential of these two isolates as biocontrol agents against phytopathogens.
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•The novel adsorbent was synthesized by functionalizing Zr-MOF with bisthiourea.•The maximum adsorption capacity of Au(III) reached up to 680.20 mg/g at pH 2.•The UiO-66-BTU exhibited ...excellent reusability and selectivity for Au(III).•The reduction of Au(III) to high-purity Au(0) was a dominant recovery mechanism.•Faster formation kinetics and bigger size of Au(0) were achieved by UiO-66-BTU membrane.
The design and synthesis of efficient adsorbents for recovery of precious metal from secondary resources are of great environmental and economic significance. In present study, an efficient and redox-active adsorbent (UiO-66-BTU) was fabricated by modifying Zr-MOF (Zirconium-based Metal Organic Framework) with bisthiourea for gold recovery in aqueous solution. It is indicated that Au(III) adsorbing onto UiO-66-BTU is an irreversible, favorable chemisorption process conformed to D-R model and pseudo-second-order model. The UiO-66-BTU showed significant adsorption ability (680.20 mg/g at pH 2.0) and high selectivity towards Au(III) in presence of various mixed ions in actual wastewater, which were mainly attributed to the Lewis soft–soft interaction, ion-exchange/electrostatic interactions, and redox reaction between Au(III) and S-containing functional groups. Notably, we demonstrated that the reduction of Au(III) to metallic gold as a dominant recovery mechanism involving the in situ confined nucleation, fusion and growth of AuNPs to branched Au precipitation, with Au(0) accounted for approximately 80% for the recycling products. Furthermore, the UiO-66-BTU membrane achieved similar high adsorption capacity and the membrane surface remains active to efficiently recovered metallic particles with an excellent repeatability at eight cycles of adsorption. The reduced Au particles formed isolated clusters with bigger size and regular hexagonal shape. Consequently, UiO-66-BTU has great potential for gold recycling in industrial practice.
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•Anionic, cationic, zwitterionic, and neutral PFASs had different environmental fates.•RCFs of PFASs for plants grown in soil were not significantly correlated with logKow.•Plants ...with fewer Casparian strip had higher TF values, such as carrots and radishes.•The transport process/pathway of PFASs was plant species-specific.
Per- and polyfluoroalkyl substances (PFASs) are ubiquitous in the environment but pose potential risks to ecosystems and human health. The soil–plant system plays an important role in the bioaccumulation of PFASs. Because most PFASs in the natural environment are anionic and amphiphilic (both lipophilic and hydrophilic), their sorption and accumulation behaviors differ from those of neutral organic and common ionic compounds. In this review, we discuss processes affecting the availability of PFASs in soil after analyzing the potential mechanisms underlying the sorption and uptake of PFASs in the soil–plant system. We also summarize the current knowledge on root uptake and translocation of PFASs in plants. We found that the root concentration factor of PFASs for plants grown in soil was not significantly correlated with hydrophobicity, whereas the translocation factor was significantly and negatively correlated with PFAS hydrophobicity regardless of whether plants were grown hydroponically or in soil. Further research on the cationic, neutral, and zwitterionic forms of diverse PFASs is urgently needed to comprehensively understand the environmental fates of PFASs in the soil–plant system. Additional research directions are suggested, including the development of more accurate models and techniques to evaluate the bioavailability of PFASs, the effects of root exudates and rhizosphere microbiota on the bioavailability and plant uptake of PFASs, and the roles of different plant organelles, lipids, and proteins in the accumulation of PFASs by plants.
In present study, the feasibility of applying a natural adsorbent with Fe3+ modification (Fe3+-modified argillaceous limestone, FAL) on the competitive adsorption of heavy metals (i.e., Cd2+, Pb2+ ...and Ni2+) was evaluated. The current results revealed an efficient adsorption on Cd2+, Pb2+ and Ni2+ in mono-metal system. Further experiments demonstrated a high selectivity of Pb2+ during the competitive adsorption of Cd2+, Pb2+ and Ni2+. The adsorption selectivity of the metal ions followed the order of Pb ≫ Cd > Ni. In addition, both pH and ionic strength are important factors affecting the metal adsorptions. It is interestingly that various NOMs (i.e., humic acid (HA) and glycine (Gly)) exerted different effects on the adsorption behaviors, probably due to the different affinities for Pb2+, Cd2+ and Ni2+ and the redistribution of newly-formed metal-DOM complexes. X-ray photoelectron spectroscopy (XPS) analysis together with X-ray diffraction (XRD) and energy dispersive spectrometer (EDS) analysis revealed that the metal adsorptions were mainly regulated via the synergistic mechanisms of ion exchange by Na+, Ca2+, and Al3+, precipitation to form CdCO3 and Pb2(OH)2(CO3)2, as well as complexes of FAL-OPb and FAL-ONi by hydroxyl groups on the surface of FAL. The application of FAL would be a promising option in leading to an efficient heavy metal removal.
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•Fe3+-modified argillaceous limestone showed effective adsorption of Cd2+/Pb2+/Ni2+.•The adsorption selectivity of the metals followed the order of Pb ≫ Cd > Ni.•Both pH and ionic strength played key roles in metal adsorption.•Humic acid and glycine exerted distinct effects on adsorption behaviors of metals.•Mechanisms of metal adsorption were ion exchange, precipitation and complexation.
The real-time reverse transcription-polymerase chain reaction (RT-PCR) detection of viral RNA from sputum or nasopharyngeal swab had a relatively low positive rate in the early stage of coronavirus ...disease 2019 (COVID-19). Meanwhile, the manifestations of COVID-19 as seen through computed tomography (CT) imaging show individual characteristics that differ from those of other types of viral pneumonia such as influenza-A viral pneumonia (IAVP). This study aimed to establish an early screening model to distinguish COVID-19 from IAVP and healthy cases through pulmonary CT images using deep learning techniques. A total of 618 CT samples were collected: 219 samples from 110 patients with COVID-19 (mean age 50 years; 63 (57.3%) male patients); 224 samples from 224 patients with IAVP (mean age 61 years; 156 (69.6%) male patients); and 175 samples from 175 healthy cases (mean age 39 years; 97 (55.4%) male patients). All CT samples were contributed from three COVID-19-designated hospitals in Zhejiang Province, China. First, the candidate infection regions were segmented out from the pulmonary CT image set using a 3D deep learning model. These separated images were then categorized into the COVID-19, IAVP, and irrelevant to infection (ITI) groups, together with the corresponding confidence scores, using a location-attention classification model. Finally, the infection type and overall confidence score for each CT case were calculated using the Noisy-OR Bayesian function. The experimental result of the benchmark dataset showed that the overall accuracy rate was 86.7% in terms of all the CT cases taken together. The deep learning models established in this study were effective for the early screening of COVID-19 patients and were demonstrated to be a promising supplementary diagnostic method for frontline clinical doctors.
In the environment, simultaneous presence of arsenic (As) of different oxidation states is common, which hampers our understanding of As behavior. In the current study, the pH dependency of arsenite ...(As(III)) and arsenate (As(V)) adsorption to goethite under the influence of calcium (Ca2+) (as a major cation) and phosphate (PO43−) (as a major anion) was studied, and the reliability of the CD-MUSIC model prediction was tested. The results show that the presence of the major ions led in general to a weaker and more complicated pH dependency of As adsorption. Calcium promoted As(V) adsorption especially at high pH, which can reverse the direction of the pH dependency. The presence of Ca2+ can even decrease As(III) adsorption when As(V) and/or PO43− are present. Phosphate competed strongly with both As(III) and As(V) in their adsorption, especially at intermediate and low pH. In the multi-component system, As(III) adsorbs weaker than As(V) over the environmental relevant pH range, therefore it is often the dominant As species in solution and soluble As(III) concentration generally decreases with increasing pH. In the same pH range, As(V) adsorption shows a complicated pH dependency. Soluble As(V) reaches a minimum around pH 6 at high concentration of major bivalent cations (e.g. Ca2+), whereas soluble As(V) will decrease with pH at low bivalent cation concentrations. The experimental results can be reliably predicted and explained with the CD-MUSIC model. The outcome of this study can provide understanding needed in the risk assessment and remediation of As contaminated soils and water.
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•Ca2+ and PO43− reduce the increasing trend with pH of As(III) adsorption.•Ca2+ may decrease As(III) adsorption when As(V) and/or PO43− are present.•As(III) dominated soluble As shows a weak decreasing trend with pH.•Soluble As with As(V) or both As(III) and As(V) shows a minimum around pH 6.•CD-MUSIC model successfully predicted As adsorption in multi-component system.
Strategies for reducing cadmium (Cd) content in polluted farmland soils are currently limited. A type of composite with nanoparticles incorporated into a hydrogel have been developed to efficiently ...remove heavy metals from sewage, but their application in soils faces challenges, such as organic hydrogel degradation due to oxygen exposure and slow Cd2+ release from soil constituents. To overcome these challenges, a composite with superior stability for long-term application in soil is required. In this study, ferrous sulfide (FeS) nanoparticle@lignin hydrogel composites were developed. The lignin-based hydrogels inherited lignin’s natural mechanical and environmental stability and the FeS nanoparticles efficiently adsorbed Cd2+ and enhanced Cd2+ desorption from soils by producing H+. The high sorption capacity (833.3 g kg−1) of the composite was attributed to four proposed mechanisms, including cadmium sulfide (CdS) precipitation via chemical reaction (84.06%), lignin complexation (13.19%), hydrogel swelling (0.61%), and nanoparticle sorption (2.15%). In addition, Fe2+ displaced from the composite was gradually oxidized to form solid iron oxide hydroxide, which increased Cd2+ sorption. The composite significantly reduced the total, surfactant-soluble, and fixed Cd in heavily and lightly polluted paddy soils by 22.4–49.6%, 13.5–68.6%, and 40.1–16.6%, respectively, in 7 days.
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•The synthesized nFeS@lh reduced soil total and stable Cd by 16.6–49.6% in 7 days.•Lignin hydrogel realized the efficient dispersion and recovery of FeS nanoparticles.•The nFeS@lh had a high Cd sorption capacity (833.3 g kg−1) and mechanical strength.•The relative contributions of four sorption mechanisms were quantitively evaluated.
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