Investigation of Microstructure, Oxides, Cracks, and Mechanical Properties of Ti-4Al-2V Joints Prepared Using Underwater Wet Laser Welding.

Developing advanced underwater welding technology for titanium, which is the key structural material for underwater applications, is of great significance for the design, fabrication, and maintenance of submarine equipment. In this study, in order to investigate the underwater welding microstructure and mechanical properties of Ti-4Al-2V alloy, underwater wet laser welding was conducted on Ti-4Al-2V alloy using varying laser power. The microstructure and properties of the welding joints were characterized and analyzed. The microstructure of the heat-affected zone and fusion zone in the welding joints are not significantly different from those of welding in air, but a mixed oxide layer composed of Al2O3 and TiO2 is formed on the surface of the fusion zone. Due to internal stress, a large number of cracks initiate on the oxide layer and propagate to the joints. In the 4 kW and 5 kW joints, a penetrating crack formed due to the excessive accumulation of internal stress breaking up the α phase. The mechanical properties of the joints are significantly affected by the laser power. The tensile strength of the 3 kW and 4 kW joints is comparable to that of the base metal, which is about 600 MPa, while the 5 kW joint shows brittle fracture with no plastic deformation and 228 MPa strength. This research lays a solid foundation for understanding the underwater wet laser welding behavior of titanium alloys.

Water-soluble chitosan-g-PMAm (PMAA)-Bodipy probes prepared by RAFT methods for the detection of Fe3+ ion.

It is a challenge to achieve the fully water-soluble chitosan. In this work, water-soluble chitosan-based probes were obtained by the following steps: boron-dipyrrolemethene (BODIPY)-OH was synthesized, and then BODIPY-OH was halogenated to BODIPY-Br. Afterwards, BODIPY-Br reacted with carbon disulfide and mercaptopropionic acid to obtain BODIPY-disulfide. BODIPY-disulfide was introduced to chitosan via amidation reaction to obtain fluorescent chitosan-thioester (CS-CTA); it is employed as the macro-initiator. Methacrylamide (MAm) was grafted onto chitosan fluorescent thioester through reversible addition-fragmentation chain transfer (RAFT) polymerization method. Thus, a water-soluble macromolecular probe (CS-g-PMAm) with chitosan as the main chain and PMAm as long-branched chains was obtained. It greatly improved the solubility in pure water. The thermal stability was reduced slightly, and the stickiness was greatly reduced and the samples displayed the characteristics of liquid. CS-g-PMAm could detect Fe3+ in pure water. By the same method, CS-g-PMAA (CS-g-Polymethylacrylic acid) was synthesized and investigated as well.

Co-amorphous formulation of dipyridamole with p-hydroxybenzoic acid: Underlying molecular mechanisms, physical stability, dissolution behavior and pharmacokinetic study.

Coamorphization has been proven to be an effective approach to improve bioavailability of poorly soluble active pharmaceutical ingredients (APIs) by virtue of solubilization, and also contributes to overcome limitation of physical stability associated with amorphous drug alone. In current work, a co-amorphous formulation of dipyridamole (DPM), a poor solubility drug, with p-hydroxybenzoic acid (HBA) was prepared and investigated. At a molar ratio of 1:2, DPM and HBA were melted result in the formation of a binary co-amorphous system. The DPM-HBA co-amorphous was structurally characterized by powder X-ray diffraction (PXRD), temperature modulated differential scanning calorimetry (mDSC), high performance liquid chromatography (HPLC) and solution state 1H nuclear magnetic resonance (1H NMR). The molecular mechanisms in the co-amorphous were further analysed via Fourier-transform infrared (FTIR) and Raman spectroscopies, as well as density functional theory (DFT) calculation. All the results consistently revealed the presence of hydrogen bonding interactions between -OH of DPM and -COOH on HBA. Accelerated test and glass transition kinetics showed excellent physical stability of DPM-HBA co-amorphous compared with amorphous DPM along with glass transition temperatures (Tg). The phase-solubility study indicated that complexation occurred between DPM and HBA in solution, which contributed to the solubility and dissolution enhancement of DPM in co-amorphous system. Pharmacokinetic study of co-amorphous DPM-HBA in mouse plasma revealed that the DPM exhibited 1.78-fold and 2.64-fold improvement in AUC0­∞ value compared with crystalline and amorphous DPM, respectively. This current study revealed coamorphization is an effective approach for DPM to improve the solubility and biopharmaceutical performance.

Electrochemiluminescence resonance energy transfer system between ruthenium-based nanosheets and CdS quantum dots for detection of chlorogenic acid.

A new strategy is proposed for ultrasensitive detection of chlorogenic acid (CGA) by fabricating an electrochemiluminescence resonance energy transfer (ECL-RET) sensing platform. The novel system designed by introducing ruthenium-based 2D metal-organic framework nanosheets (Ru@Zn-MOF) as ECL acceptor and L-cysteine capped CdS quantum dots (L-CdS QDs) as ECL donor, exhibited good ECL response. The possible mechanism of the modified electrode surface reaction was discussed. Modifying of the electrode surface by application of L-CdS QDs directly on ultrathin MOF nanosheets greatly shortened the electron-transfer distance and reduce energy loss, therefore significantly improving the ECL efficiency. The prepared sensor demonstrated good stability and highly selective detection of the target molecule. Under optimal conditions, the constructed sensor for the detection of CGA exhibited a wide linear range from 1.0 × 10-10 to 1.0 × 10-4 mol·L-1 and a low detection limit of 3.2 × 10-11 mol·L-1 with a correction coefficient of 0.995. The recovery for spiked samples was calculated to be 94.4-109% and the RSD was 1.07-1.72% in real samples. The obtained sensor is considered to be a promising platform for CGA detection. Electrochemiluminescence resonance energy transfer (ECL-RET) sensing platform is used for the detection for chlorogenic acid.

Facile method to synthesize fluorescent chitosan hydrogels for selective detection and adsorption of Hg2+/Hg.

Fluorescent chitosan-based hydrogel for the selective detection and adsorption of Hg2+/Hg+ in aqueous environment was prepared through three-step synthesis strategy. NO2-Boron-dipyrrolemethene (BODIPY) was prepared firstly, and then the -NO2 group was reduced to -NH2 group. Finally, the NH2-BODIPY was introduced to chitosan by Schiff base formation reaction through bi-aldehyde. Eventually, fluorescent chitosan hydrogel was obtained. The as-prepared fluorescent hydrogel probe could detect Hg2+/Hg+ through PET mechanism with the detection limit of 0.3 µM. The recognition site which combines Hg2+/Hg+ is CN, it is just formed in the reaction with chitosan and the amino group on BODIPY. Adsorption capacity of the fluorescent hydrogel is 121 mg·g-1, which is almost seven times of the original chitosan. The isotherm and kinetics of Hg2+/Hg+ removal follows Langmuir isotherm and pseudo-second order kinetics, respectively. Besides, a series of fluorescent hydrogels were prepared to compare the elasticity, hydropHilicity, fluorescence intensity and adsorption capacity.

Investigation on Microstructure and Properties of Duplex Stainless Steel Welds by Underwater Laser Welding with Different Shielding Gas.

Taking S32101 duplex stainless steel as the research object, underwater laser wire filling welding technology was used for U-groove filling welding. The influence of different shielding gas compositions on the ferrite content, microstructure, mechanical properties and pitting corrosion resistance was studied by simulating a water depth of 15 m in the hyperbaric chamber. The results show that, under the same process parameters, the size and proportion of austenite in the weld when using pure nitrogen as the shielding gas are larger than those protected by other shielding gases. In a mixed shielding gas, the increase in nitrogen content has little effect on the strength and toughness of the weld. Regardless of the shielding gas used, the base metal was the weakest part of the weld. At the same time, intermetallic inclusions have an adverse effect on the impact toughness of the weld. The pitting corrosion resistance of the welds depends on the Cr2N content in the heat-affected zone. The precipitation and enrichment of Cr2N causes local chromium deficiency, which is the main factor for the weak pitting corrosion ability of the heat-affected zone. Pure nitrogen protection has a better corrosion resistance than other gas protection.

Microstructure and Corrosion Resistance of Underwater Laser Cladded Duplex Stainless Steel Coating after Underwater Laser Remelting Processing.

Combined with the technologies of underwater local dry laser cladding (ULDLC) and underwater local dry laser remelting (ULDLR), a duplex stainless steel (DSS) coating has been made in an underwater environment. The phase composition, microstructure, chemical components and electrochemical corrosion resistance was studied. The results show that after underwater laser remelting, the phase composition of DSS coating remains unchanged and the phase transformation from Widmanstätten austenite + intragranular austenite + (211) ferrite to (110) ferrite occurred. The ULDLR process can improve the corrosion resistance of the underwater local dry laser cladded coating. The corrosion resistance of remelted coating at 3 kW is the best, the corrosion resistance of remelted coating at 1kW and 5kW is similar and the corrosion resistance of (110) ferrite phase is better than grain boundary austenite phase. The ULDLC + ULDLR process can meet the requirements of efficient underwater maintenance, forming quality control and corrosion resistance. It can also be used to repair the surface of S32101 duplex stainless steel in underwater environment.

Chitosan based macromolecular probes for the selective detection and removal of Fe3+ ion.

Chitosan has been widely used due to its biodegradable, cost-effective and environmentally friendly properties. Modification of chitosan attracts much attention as promising methods to detect and remove organic and inorganic pollutants. In this work, chitosan-based macromolecular probes were designed and synthesized. The probes can detect Fe3+ in the presence of other metal ions. The detection mechanism is investigated as well. The probe's fluorescence quenching upon the addition of Fe3+ ion could be ascribed to the complexation between the electron-deficient ion Fe3+ and "C=N" (electron-rich group) of fluorescent chitosan probes. What's more, the obtained fluorescent macromolecular probes can be used for the removal of Fe3+ in solution. The probes could adsorb the Fe3+ in solution and the removal efficiency can reach as high as 62.0% while the removal efficiency of original chitosan is only 16.0%. The probes have good selective detection for Fe3+ and the detection limit reaches 1.2 µM.

Spectroscopic Methodology and Molecular Docking Studies on Changes in Binding Interaction of Felodipine with Bovine Serum Albumin Induced by Cocrystallization with ß-Resorcylic Acid.

In the present study, a novel cocrystal of felodipine (FEL) and ß-resorcylic acid (ßRA) was developed. We specially focused on the change of binding pattern with bovine serum albumin (BSA) induced by cocrystallization of FEL with ßRA. The solid characterizations and density functional theory (DFT) simulation verified that FEL-ßRA cocrystal formed in equimolar ratio (1 : 1 M ratio) through C=O…H-O hydrogen bond between C=O group in FEL and O-H group in ßRA. The binding interactions between FEL-ßRA system and BSA were studied using fluorescence spectral and molecular docking methods. Two guest molecule systems, including a physical mixture of FEL and ßRA and FEL-ßRA cocrystal were performed binding to BSA in molecular docking. According to the Kb and binding energy, the supramolecular form of FEL-ßRA system was retained during binding to BSA. Molecular docking simulation suggested that FEL and its cocrystal inserted into the subdomain IIIA (site II') of BSA. The interactions between FEL and BSA including hydrogen bonding with ASN390 residue and intermolecular hydrophobic interactions with LEU429 and LEU452 residues. However, the size of supramolecular FEL-ßRA better matched that of active cavity of BSA; the cocrystal is closely bound to BSA through hydrogen bonding with ASN390 residue and intermolecular hydrophobic interactions with LEU429, VAL432, LEU452 and ILE387 residues. This change on binding affinity of FEL to BSA induced by cocrystallization with ßRA provided theoretical basis to evaluate the transportation, distribution and metabolism of cocrystal drug.

Effect of Heat Treatment on Microstructure and Tribocorrosion Performance of Laser Cladding Ni-65 WC Coating.

The Ni-65wt%WC cladding layers were prepared on the surface of Q235 using laser cladding technology, in which the effect of heat treatment on microstructure and tribocorrosion performance was investigated. The results showed that the coating is mainly consisted of Ni, WC, and W2C, and a significant diffusion phenomenon is formed between the interfaces of WC/Ni matrix, benefited for the improvement of bonding layer between WC/Ni-based matrixes. Meanwhile, the crystallization of WC particles after heat treatment was more obvious than untreatment; the Ni matrix grain size was also grown remarkable, leading to the lower hardness and weaker plastic deformation resistance of Ni-65wt%WC coating. And the erosion results showed that the wear rate of coating gradually decreased with heat treatment temperature increasing, while brittle WC was not suitable for high impact wear conditions. Furthermore, with the increase of heat treatment temperature, the reciprocating wear performance showed that the friction coefficient and wear rate of Ni-65wt%WC coating decreased. And the friction coefficient and wear rate of the coating (700°C) in 3.5% NaCl solution were 0.15 and 4.82 × 10-8 mm3·N-1·m-1, respectively. Therefore, the comprehensive comparison showed that Ni-65WC coating had better performance in low impact reciprocating testing under corrosion environment, and heat treatment was helpful to further improve the tribocorrosion performance of laser cladding Ni-65wt%WC coating.

Characterizations and Assays of α-Glucosidase Inhibition Activity on Gallic Acid Cocrystals: Can the Cocrystals be Defined as a New Chemical Entity During Binding with the α-Glucosidase?

Cocrystallization with co-former (CCF) has proved to be a powerful approach to improve the solubility and even bioavailability of poorly water-soluble active pharmaceutical ingredients (APIs). However, it is still uncertain whether a cocrystal would exert the pharmacological activity in the form of a new chemical entity, an API-CCF supramolecule. In the present study, gallic acid (GA)-glutaric acid and GA-succinimide cocrystals were screened. The solubility, dissolution rate and oral bioavailability of the two cocrystals were evaluated. As expected, AUCs of GA-glutaric acid and GA-succinimide cocrystals were 1.86-fold and 2.60-fold higher than that of single GA, respectively. Moreover, experimental evaluations on α-glucosidase inhibition activity in vitro and theoretical simulations were used to detect whether the two cocrystals would be recognized as a new chemical entity during binding with α-glucosidase, a target protein in hypoglycemic mechanisms. The enzyme activity evaluation results showed that both GA and glutaric acid displayed α-glucosidase inhibition activity, and GA-glutaric acid cocrystals showed strengthened α-glucosidase inhibition activity at a moderate concentration, which is attributed to synergism of the two components. Molecular docking displayed that the GA-glutaric acid complex deeply entered the active cavity of the α-glucosidase in the form of a supramolecule, which made the guest-enzyme binding configuration more stable. For the GA and succinimide system, succinimide showed no enzyme inhibition activity, however, the GA-succinimide complex presented slightly higher α-glucosidase inhibition activity than that of GA. Molecular docking simulation indicated that the guest molecules entering the active cavity of the α-glucosidase were free GA and succinimide, not the GA-succinimide supramolecule.

Trace metals, organic carbon and nutrients in the Beidagang Wetland Nature Reserve, northern China.

This study aimed to determine sediment contamination in the Beidagang Wetland Nature Reserve to describe atmospheric deposition of trace metals. We analyzed Hg, Cd, Pb, TOC, TN, TP, δ13C, and δ15N, and studied their variations in surface sediments and in the vertical profiles of sediment cores collected from the reserve. Evaluation of environmental trace metal contamination using sediment quality guidelines and geochemical background values indicated that the risk of metal pollution in the reserve sediments was relatively low. Concentrations of Hg, Cd, and Pb in the sediments were much lower than concentrations in sediment samples from Bohai Bay and polluted rivers in Tianjin. Enrichment factors indicate that samples are moderately contaminated with Hg, Cd, and Pb; whereas the geo-accumulation index results classify the sediments as uncontaminated to moderately contaminated with Hg, Cd, and Pb. The distribution patterns of trace metal concentrations in the three core samples were uniform. δ13C and δ15N were used to track the sources of TOC and TN in sediments. Results show that TOC mainly originated from the residue and decaying matter of aquatic plants (e.g., algae, reeds, and Typha), while TN was derived from soil N and elevated atmospheric N deposition. Because domestic and industrial waste is not discharged into the Beidagang Wetland Nature Reserve, trace metals found in sediments mainly originate from atmospheric deposition. The results provide baseline data for analysis of trace metal accumulation in Beijing-Tianjin-Hebei, a region subject to atmospheric deposition in northern China.

[Effect of Rutin on Liver Function and Morphology in Type 1 Diabetes Mice Induced by Streptozotocin].

OBJECTIVE: To investigate the effect of Rutin on the function and morphology of liver in type 1 diabetes mice induced by streptozotocin (STZ). METHODS: Type 1 diabetic mice model was established with the treatment of STZ by a 5 d intraperitoneal administration to male Kunming mice. Normal group had 12 mice without treatment of STZ,the mice with DM after STZ treated were randomly divided into DM group,low-dose (50 mg/kg) Rutin group and high-dose (100 mg/kg) Rutin group,each group had 12 mice. The mice in normal and DM group were given sodium carboxymethyl cellulose (10 mg/kg). Each mice was given above drugs by intragastric administration for 8 weeks. Postprandial random blood glucose was measured at 4 weeks and 8 weeks and the levels of alanine aminotransferase (ALT),aspartate aminotransferase (AST),lactate dehydrogenase (LDH),total protein (TP) and albumin (ALB) in serum were detected by automatic biochemical analyzer after 8 weeks. The morphology of liver was observed by HE and Masson staining. The ultrastructure of liver tissue was observed by electron microscope. RESULTS: After a continuous small-dose injection of STZ,the success rate of diabetes model mice were up to 98%. The blood glucose of the model group was significantly increased (P<0.01),and the levels of ALT,AST and LDH in serum were significantly higher,and TP and ALB were lower than those in normal group (P<0.05,P<0.01). Compared to the DM group,the levels of blood glucose were lower (P<0.05) at 4 weeks and 8 weeks,the contents of ALT,AST and LDH were significantly decreased,and TP and ALB were improved in both Rutin dose group. High-dose group performed more obvious (P<0.05,P<0.01). Morphological observation showed the tissue morphology of Rutin treatment group were improved obviously,and the effect was more significant in high-dose Rutin group. CONCLUSION: Rutin may improve the liver function and reduce the damage of liver tissue in STZ-induced type 1 diabetic mice.

Mobility and contamination assessment of mercury in coal fly ash, atmospheric deposition, and soil collected from Tianjin, China.

Samples of class F coal fly ash (levels I, II, and III), slag, coal, atmospheric deposition, and soils collected from Tianjin, China, were analyzed using U.S. Environmental Protection Agency (U.S. EPA) Method 3052 and a sequential extraction procedure, to investigate the pollution status and mobility of Hg. The results showed that total mercury (HgT) concentrations were higher in level I fly ash (0.304 µg/g) than in level II and level III fly ash and slag (0.142, 0.147, and 0.052 µg/g, respectively). Total Hg in the atmospheric deposition was higher during the heating season (0.264 µg/g) than the nonheating season (0.135 µg/g). Total Hg contents were higher in suburban area soils than in rural and agricultural areas. High HgT concentrations in suburban area soils may be a result of the deposition of Hg associated with particles emitted from coal-fired power plants. Mercury in fly ash primarily existed as elemental Hg, which accounted for 90.1, 85.3, and 90.6% of HgT in levels I, II, and III fly ash, respectively. Mercury in the deposition existed primarily as sulfide Hg, which accounted for 73.8% (heating season) and 74.1% (nonheating season) of HgT. However, Hg in soils existed primarily as sulfide Hg, organo-chelated Hg and elemental Hg, which accounted for 37.8 to 50.0%, 31.7 to 41.8%, and 13.0 to 23.9% of HgT, respectively. The percentage of elemental Hg in HgT occurred in the order fly ash > atmospheric deposition > soils, whereas organo-chelated Hg and sulfide Hg occurred in the opposite order. The present approach can provide a window for understanding and tracing the source of Hg in the environment in Tianjin and the risk associated with Hg bioaccessibility.