Pharmaceutical pollution has emerged as a highly concerned issue due to its adverse effects. Elevated concentrations of pharmaceuticals in water should be regulated to satisfy the requirement for the ...provision of clean water. Metal-organic frameworks (MOFs) with high specific surface area, controllable porous structure, and facile modification can serve as promising adsorbents for the removal of pharmaceutical contaminants from water. In this review, a selected collection illustrating the reliable strategies and concepts to prepare the MOFs-based materials with superior water stability is described. In addition, recent progress on the adsorptive removal of pharmaceutical pollutant using burgeoning and functional MOFs is also summarized in terms of maximum capacity, equilibrium time, and regenerate ability. Meanwhile, to understand the adsorption mechanism, related interactions including coordination with unsaturated site, pore-filling effect, hydrogen bonding, electrostatic, and π-π stacking are further discussed. Finally, critical perspectives/assessment of future research emphasising on fabricating desirable MOFs and establishing structure-property relationships to facilitate capture performance are identified.
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•Metal−organic frameworks (MOFs) and their derivatives are attractive adsorbents for pharmaceuticals removal.•Strategies of design and preparation of water-stable MOFs are reviewed.•Recent advances in the utilization of MOFs and their derivatives for pharmaceuticals removal were described.•Critical future research perspectives in this field are provided.
The instability of the keyhole and bubble being captured by solidification interface are the main factors that affect the formation of porosity in laser welding of both aluminum alloy and steel. In ...laser welding of aluminum alloy, the more violent fluid flow behind the keyhole, the larger depth to width ratio can cause the keyhole more unstable, and susceptive to collapse that can be described as three necessary steps. The much larger solidification rate and longer escaping distance make the bubble easily captured by the solidification interface, and easily combined. All of these reasons contribute to the formation of larger number and size of porosity in laser welding of aluminum alloy. The numerical and experimental results are in good agreement.
•The droplet escape condition is established.•A three-dimensional numerical model is built to investigate spatter formation in laser welding of 5083 aluminum alloy.•The spatter formation mechanism ...and influence factors are analyzed.
The droplet escape condition is established, a three-dimensional numerical model is built to investigate the behavior of the weld pool in fiber laser welding of 5083 aluminum alloy, the shear stress caused by the metallic vapor flow that has great influence on spatter formation is considered. A high speed photography system is used to capture the transient images of the weld pool, the spatter formation is discussed. The numerical and experimental results show that the spatters generate mainly around the keyhole. Two factors are responsible for the spatter formation: the surface tension of the molten metal around the keyhole is low. The recoil pressure caused by evaporation and the shear stress caused by metallic vapor flow accelerate the upward moving melt around the keyhole. Increasing the welding speed and placing the nozzle at the trailing position can decrease the upward momentum of the molten metal around the keyhole, and stabilize the keyhole, which are help to suppress the formation of spatter.
Salinity is a major abiotic factor affecting plant growth and secondary metabolism. However, no information is available about its effects on
Briq., a traditional Chinese herb. Here, we investigated ...the changes of plant growth, antioxidant capacity, glandular trichome density, and volatile exudates of
exposed to salt stress (0, 25, 50, 75, 100 mM NaCl). Results showed that its dry biomass was reduced by salt treatments except 25 mM NaCl. Contents of antioxidants, including phenolics and flavonoids, increased at low (25 mM) or moderate (50 mM) levels, but declined at severe (75 and 100 mM) levels. On leaf surfaces, big peltate and small capitate glandular trichomes (GTs) were found. Salt treatments, especially at moderate and severe concentrations, enhanced the density of total GTs on both leaf sides. The most abundant compound in GT volatile exudates was pulegone. Under salinity, relative contents of this component and other monoterpenes decreased significantly; biosynthesis and accumulation of esters were enhanced, particularly sulfurous acid,2-ethylhexyl hexyl ester, which became the second major compound as salinity increased. In conclusion, salt stress significantly influenced the growth and secondary metabolism of S. tenuifolia, enabling us to study the changes of its pharmacological activities.
The keyhole behaviors were observed directly by laser welding experiment with quartz glass. Based on Fresnel absorption of laser beam and multi-reflection combined with volume of fluid (VOF) method, ...a three-dimensional mathematical model was established to study the role of welding speed on keyhole behaviors and keyhole-induced porosity formation in laser welding of aluminum alloy. The keyhole behaviors and weld pool fluid flow were discussed, and the result shows that, although the welding speed varies, the mechanism of keyhole collapse was similar. However, the keyhole stability at higher welding speed was improved due to reduced weld depth fluctuations, spatter number, keyhole depth to width ratio, and keyhole collapse frequency. Furthermore, the improved keyhole stability impeded the keyhole collapse, and the lower weld depth and solidification rate facilitated bubble escaping from the weld pool easily, which are the main factors for suppression of porosity at higher welding speed.
•Two mechanisms are responsible for keyhole-induced bubble formation.•The pressure balance equation is proposed to analyze the breaking of molten bridge by laser beam.•Large bubble and small bubble ...have high coalescence efficiency.
Laser welding experiment with the aid of glass, and numerical simulation are carried out to study the keyhole behavior and keyhole-induced bubble formation. Two mechanisms are responsible for keyhole-induced bubble formation. The first mechanism is the strong fluid flow inside the weld pool, and the capillary instability of the whole keyhole, causing the collapse between rear keyhole wall and front keyhole wall. This mechanism contributes to most of keyhole-induced bubble formation. The second mechanism is the instability of the rear keyhole wall caused by the increase absorption of laser energy reflected by the bulge at front keyhole wall. The breaking of molten bridge is analyzed based on static pressure balance. The molten bridge with large curvature and low temperature is difficult to be broken. Bubble coalescence can be clearly observed at the bottom of the weld pool. Large bubble and small bubble have high coalescence efficiency. The bubbles at keyhole bottom have more time to escape without broken by laser beam, and the bottom part of rear keyhole wall is more easily depressed, so bubbles are easily formed at the keyhole bottom.
MOF-derived zink and nitrogen co-doped porous carbon (ZNPC) was synthesized through the pyrolysis of MOF-5-NH
2
and used as a solid-phase microextraction (SPME) coating material. Coupled with gas ...chromatography-mass spectrometry (GC–MS), headspace SPME (HS-SPME) based on ZNPC was adopted for the determination of phenols in food samples. The co-existence of N and Zn in ZNPC endows the derived carbon superior hydrophilicity, which is highly beneficial for phenols capture. After optimizing the conditions of extraction and desorption, a sensitive analytical method was established with low limits of detections (LODs, 0.73–2.3 ng g
−1
) and wide linear ranges (5–5000 ng g
−1
). Both the intra-fiber repeatability (RSDs from 2.8–7.3%) and inter-fiber reproducibility (RSDs from 9.7–11.7%) were satisfactory. The established method was applied to phenol determination in beef jerky and duck neck with satisfactory recoveries of 81.2–120.4% and RSDs of 2.8–9.9%, which met well with the requirement of practical application.
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A three-dimensional (3D) transient numerical model is developed to simulate the keyhole dynamics, melt flow, and keyhole-induced porosity formation. The influence of the plate thickness on ...keyhole-induced porosity size and number is thoroughly investigated. The simulation results show that the average keyhole depth in plate thickness of 3, 6, and 10 mm is 2.07 mm, 1.89 mm, and 1.77 mm, respectively, and the value of keyhole depth reaching the quasi-steady state is 34 ms, 28 ms, and 14 ms, respectively. Compared to the thinner thickness plate, it is not easy to see the phenomenon of bubble amalgamation in the thickness of 10 mm under the parameter of low laser power and high welding speed. The less porosity in thicker plate laser welding is attributed to lower frequency of keyhole collapse, higher ratio of keyhole open after keyhole collapse to total keyhole collapse number, lower ratio of bubble number to total keyhole collapse number, higher ratio of bubble escape to the total bubbles number, and lower ratio of bubble amalgamation to the total.
Postharvest abnormal chilling injury (CI) behavior in papaya (Carica papaya L.) fruit is a rare phenomenon that may be associated with respiratory metabolism. This study thus aimed to investigate the ...impacts of storage temperatures (1 and 6 °C) on the respiratory metabolism of postharvest papaya and its impact on CI development. Results demonstrated that 1 °C storage reduced the activities of hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), citrate synthase (CS), and α-ketoglutarate dehydrogenase (α-KGDH) and regulated the expression of corresponding enzymes in the Embden–Meyerhof–Parnas (EMP) pathway and tricarboxylic acid (TCA) cycle compared with 6 °C storage, resulting in a lower respiration rate of the EMP-TCA pathway and mitigating the development of CI. Meanwhile, lower contents of nicotinamide adenine dinucleotide (hydrogen) (NAD(H)) were observed in papaya fruit stored at 1 °C. Notably, papaya fruit stored at 1 °C maintained higher activity and transcriptional levels of SDH and IDH during the whole storage period. These findings suggest that 1 °C storage reduced the respiration rate of the EMP-TCA pathway by reducing the expression level and activity of related enzymes, which is conducive to the reduction of respiration substrate consumption and finally alleviating the occurrence of CI.
Hybrid laser-MIG (metal inert gas) welding has not been extensively applied in welding of aluminium alloy with thickness more than 10 mm because of the existence of weld defects and low joint ...strength. In this study, an original hybrid laser-MIG welding plus MIG welding process was developed. Double-sided hybrid laser-MIG welding method was designed and applied to the welding of 30-mm-thick Al 5083 alloy. The process was then optimized by overlaying a MIG welding upon the weld. Analysis on the weld revealed that the overlaid MIG welding played multiple roles, including making up the bead formations, eliminating the keyhole-induced porosities as well as refining grains. Along the longitudinal direction of the weld, the grains became finer from two fringes to the middle, and the mechanical properties improved accordingly. Compared with MIG welding, the hybrid laser-MIG welding plus MIG welding process showed overwhelming superiorities over the MIG welding, which will be promising in industrial applications.
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