Effect of La and Sc Co-Addition on the Mechanical Properties and Thermal Conductivity of As-Cast Al-4.8% Cu Alloys

The effects of La and La+Sc addition on mechanical properties and thermal conductivity of Al-4.8Cu alloy were comprehensively studied. The as-cast samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and first-principles methods. The results reveal that the grain morphology of Al-4.8Cu alloy changes from dendrite to fine equiaxed grain with La, La+Sc addition. The average grain size of Al-Cu-La (Al-4.8Cu-0.4La) and Al-Cu-La-Sc (Al-4.8Cu-0.4La-0.4Sc) decreased by 37.2% (70.36 μm) and 63.3% (119.64 μm) respectively compared with Al-Cu (Al-4.8Cu). Al-Cu-La has the highest elongation among the three which is 34.4% (2.65%) higher than Al-Cu. Al-Cu-La-Sc has the highest ultimate tensile strength and yield strength which are 55.1% (80.9 MPa) and 65.2% (62.1 MPa) higher than Al-Cu, respectively. The thermal conductivity of Al-Cu-La and Al-Cu-La-Sc is 10.0% (18.797 W·m−1·k−1) and 6.5% (12.178 W·m−1·k−1) higher than Al-Cu alloy respectively. Compared with Al-Cu, Al-Cu-La has less shrinkage and porosity, the presence of Al4La and AlCu3 contribute a lot to the decrease of specific heat capacity and the increase of plasticity and toughness. The porosity of Al-Cu-La-Sc does not significantly decrease compared with Al-Cu-La, the presence of Al3Sc and AlCuSc bring about the increase of specific heat capacity and brittleness.

Co-Addition of Mg2Si and Graphene for Synergistically Improving the Hydrogen Storage Properties of Mg−Li Alloy

Mg−Li alloy possesses a high hydrogen capacity. However, the hydrogenation and dehydrogenation performances are still far from practical application. In this work, Mg2Si (MS) and graphene (G) were employed together to synergistically improve the hydrogen storage properties of Mg−Li alloy. The structures of the samples were studied by XRD and SEM methods. The hydrogen storage performances of the samples were studied by nonisothermal and isothermal hydrogenation and dehydrogenation, thermal analysis, respectively. It is shown that the onset dehydrogenation temperature of Mg−Li alloy was synergistically reduced from 360°C to 310°C after co-addition of Mg2Si and graphene. At a constant temperature of 325°C, the Mg−Li−MS−G composite can release 2.7 wt.% of hydrogen within 2 h, while only 0.2 wt.% of hydrogen is released for the undoped Mg−Li alloy. The hydrogenation activation energy of the Mg−Li−MS−G composite was calculated to be 86.5 kJ mol−1. Microstructure and hydrogen storage properties studies show that graphene can act as a grinding aid during the ball milling process, which leads to a smaller particle size for the composites. This work demonstrates that coaddition of Mg2Si and graphene can synergistically improve the hydrogen storage properties of Mg−Si alloy and offers an insight into the role of graphene in the Mg−Li−MS−G composite.

Induced effect of Ca2+ and Al3+ on chaetominine synthesis by Aspergillus fumigatus CY018 under submerged fermentation

Chaetominine (CHA), an alkaloid with biological activity produced by Aspergillus fumigatus CY018, has strong anticancer activity against the human leukemia cell. However, its further research for pharmacokinetics is limited by CHA production in submerged fermentation, which is a problem urgently awaiting solutions by effective biological strategies. In this work, Ca2+ and Al3+ exhibited a strong promoting effect on CHA production after multiple metal ions screening. Then, the concentration of Ca2+ and Al3+ and the addition time was optimized. The suitable conditions were 0.5 mM Ca2+ and 0.5 mM Al3+ at 120 h, in which the CHA production reached 58.5 and 49.45 mg/L with optimized condition of Ca2+ and Al3+ respectively. The intermediate metabolites, such as DAHP, chorismate and tryptophan, were increased obviously with addition of Ca2+ and Al3+. The activities of key enzymes of DAHPs, AroAs and TrpCs in CHA biosynthesis pathway were improved by 3.58-, 3.60- and 3.34-folds respectively. Meanwhile, the transcription levels of laeA, dahp, cs, and trpC were upregulated by 3.22-, 12.65-, 5.58- and 6.99-fold respectively by addition of Ca2+ and Al3+. Additionally, the fermentation strategy was successfully scaled up to 5 L reactor, in which CHA production could attain 75.6 mg/L at 336 h. This work demonstrated that Ca2+ and Al3+ co-addition was an effective strategy for increasing CHA production, and the information obtained might be useful to the further improvement of CHA fermentation on large scale.

Effect of Co-Addition of Ag and Cu on Mechanical Properties of Sn–5Sb Lead-Free Solder

Sn–Sb lead-free solders are considered to substitute the tin–lead solders due to their great mechanical properties. At room temperature, the mechanical properties of Ni/Au/Sn–5Sb/Au/Ni and Ni/Au/Sn–5Sb–0.3Ag–0.05Cu/Au/Ni linear solder joints were investigated by nanoindentation experiments at different loads. The results showed that the Sn–Sb intermetallic compound (IMC) was distributed in the β-Sn matrix in Ni/Au/Sn–5Sb/Au/Ni solder joints. Co-addition of Cu and Ag resulted in the formation of the rod-shaped Cu6Sn5 and the fine granular Ag3Sn IMCs. At the same load and loading/unloading rate, the indentation depth and residual indentation morphologies of Ni/Au/Sn–5Sb–0.3Ag–0.05Cu/Au/Ni solder joints were smaller than those of Ni/Au/Sn–5Sb/Au/Ni solder joints. The hardness of the two kinds of solder joints decreased with the increase in load, while the Young’s modulus was independent of load. In addition, compared to the Ni/Au/Sn–5Sb/Au/Ni solder joints, the hardness, Young’s modulus and stress exponents of Ni/Au/Sn–5Sb–0.3Ag–0.05Cu/Au/Ni solder joints achieved an improvement due to the co-addition of Ag and Cu.

Structural and Functional Impairments of Reconstituted High-Density Lipoprotein by Incorporation of Recombinant β-Amyloid42

Beta (β)-amyloid (Aβ) is a causative protein of Alzheimer’s disease (AD). In the pathogenesis of AD, the apolipoprotein (apo) A-I and high-density lipoprotein (HDL) metabolism is essential for the clearance of Aβ. In this study, recombinant Aβ42 was expressed and purified via the pET-30a expression vector and E.coli production system to elucidate the physiological effects of Aβ on HDL metabolism. The recombinant human Aβ protein (51 aa) was purified to at least 95% purity and characterized in either the lipid-free and lipid-bound states with apoA-I. Aβ was incorporated into the reconstituted HDL (rHDL) (molar ratio 95:5:1, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC):cholesterol:apoA-I) with various apoA-I:Aβ ratios from 1:0 to 1:0.5, 1:1 and 1:2. With an increasing molar ratio of Aβ, the α-helicity of apoA-I was decreased from 62% to 36% with a red shift of the Trp wavelength maximum fluorescence from 337 to 340 nm in apoA-I. The glycation reaction of apoA-I was accelerated further by the addition of Aβ. The treatment of fructose and Aβ caused more multimerization of apoA-I in the lipid-free state and in HDL. The phospholipid-binding ability of apoA-I was impaired severely by the addition of Aβ in a dose-dependent manner. The phagocytosis of LDL into macrophages was accelerated more by the presence of Aβ with the production of more oxidized species. Aβ severely impaired tissue regeneration, and a microinjection of Aβ enhanced embryotoxicity. In conclusion, the beneficial functions of apoA-I and HDL were severely impaired by the addition of Aβ via its detrimental effect on secondary structure. The impairment of HDL functionality occurred more synergistically by means of the co-addition of fructose and Aβ.