[en] The authors describe an aptamer based assay for the food mycotoxin ochratoxin A (OTA). It is based on the use of exonuclease III (Exo III) which assists in signal amplification, and of single-walled carbon nanohorns (SWCNHs) which act as quenchers of fluorescence. The detection scheme employs a hairpin probe (HP) and a signal probe (SP) labeled with carboxyfluorescein (FAM) at its 5′-end. The fluorescence of intact SPs (best measured at excitation/emission wavelengths of 495/518 nm) is quenched by SWCNHs. The HP contains the OTA-specific aptamer sequence and is partially complementary to the SP. After addition of OTA, the aptamer binds OTA and thus exposes a single-stranded sequence that can hybridize with the SP. Exo III digests the SP to liberate the free fluorophore labels. The damaged SPs no longer are adsorbed by the SWCNHs so that fluorescence is no longer quenched. The method has a detection range that is linear from 10 nM to 1000 nM (with a correlation coefficient of 0.997). The limit of detection (LOD), calculated on the basis of a signal to noise ratio of 3, is 4.2 nM. The procedure was validated by the quantitation of OTA in spiked real samples and were found to be free of interference by the sample matrix. Recoveries ranged from 93.8 to 113.0% in beer and from 92.0 to115.9% in red wine. .

[en] This study describes an aptamer based assay for the mycotoxin ochratoxin A (OTA). The method is based on the use of an OTA-specific aptamer, exonuclease (Exo) III, SYBR Gold as a fluorescent probe, and a complementary strand that specifically combines with the aptamer. In the presence of OTA, the aptamer and OTA hybridize, thereby resulting in the formation of ssDNA, which is not digested by Exo III. Intense fluorescence is observed after addition of SYBR Gold (best measured at excitation/emission wavelengths of 495/540 nm). Fluorescence increases linearly with the log of the OTA concentration in the range from 8 to 1000 ng·mL⁻¹. The detection limit is 4.7 ng·mL⁻¹. The assay was applied to the determination of OTA in diluted [2%(v/v)] red wine, and recoveries and RSDs ranged between 93.5% and 113.8%, and between 3.2% and 5.7%, respectively. .

[en] Highlights: • Good mechanical properties was achieved in a novel ultralight Mg-2.76Li–3Al-2.6Zn-0.39Y alloy. • Bimodal microstructures during multidirectional forging (MDF) of this alloy were discovered and elucidated. • Intense mechanically shearing fragmentation and incomplete DRX are deformation mechanism of MDF. • A criterion of judging the occurrence of the Portevin–Le Chatelier effect was proposed and verified. • The contributions of different strengthening mechanisms to tensile yield strength were estimated. A novel Mg-2.76Li–3Al-2.6Zn-0.39Y alloy was prepared by multidirectional forging (MDF) and rolling (R) to improve strength and ductility, and its microstructural evolution and mechanical properties were investigated by an optical microscope, X-ray diffraction (XRD), transmission electron microscope (TEM), and tensile tester. After MDFR, the ultimate tensile strength was 275 ± 8 MPa, the yield strength was 207 ± 7 MPa, and the elongation was 29% at a grain size of 6.8 ± 1.1 μm. The specific modulus of this alloy was 30.04 MN m kg⁻¹, and the specific strength was 183.58 kN m kg⁻¹. Microstructural examination of decreased-temperature MDF revealed the presence of a bimodal microstructure, which is favorable for the enhancement of both strength and ductility. The deformation mechanisms of MDF are intense mechanically shearing fragmentation and incomplete dynamic recrystallization. XRD analysis revealed that the present alloy consists of α(Mg) phase, and Al₂Y, Mg₁₇(Al,Zn)₁₂, Mg₂Y, and AlLi intermetallic compounds. TEM analysis confirmed the existence of Mg₁₇(Al,Zn)₁₂ compound and dislocation wall and pile-up. Portevin–Le Chatelier (PLC) effect or serrated flow was discovered in this alloy. The relationship between the break-away stress and the experimental stress was proposed as a criterion for judging the occurrence of the PLC effect. The estimated stress is consistent with the experimental stress. The contributions of different strengthening mechanisms to tensile yield strength were estimated. The estimated tensile yield strength is in good agreement with the experimental tensile yield strength.

[en] Ba₂FeMoO₆ has been reported to exhibit a ferromagnetic to a paramagnetic transition with a Curie temperature above room temperature, and thus it is a potential material for spintronics. These exciting properties are related, at least in part, to combined structural and magnetic instabilities. A conventional analysis of lattice parameter data from the present study and literature in terms of spontaneous strain shows that the magnetic ordering is accompanied by a significant volume strain, which implies a strong coupling behavior of magneto-elastic properties in Ba₂FeMoO₆. In addition, to address the correlation between anti-site defects (ASD) and magnetic properties, we have carried out a comparative study of six cubic Ba₂FeMoO₆ polycrystals with different degrees of ASD. The correlations among the Curie temperature, low-temperature saturation magnetism, and ASD are discussed in detail using a combination of diffraction and magnetic measurements. This systematic study, especially the strain analysis, of Ba₂FeMoO₆ will facilitate its potential applications in the field of spin electronics and thin film engineering. (paper)

[en] In this paper, a facile and controllable method for in-situ synthesis of the magnetic carbon nanotubes nanocomposites (Fe/CNTs) in water-ethylene glycol (EG) mixed solvents is reported by the deposition–precipitation method following annealing. The effect of water/EG ratio on the physico-chemical properties of magnetic Fe/CNTs is investigated by X-ray diffraction, transmission electron microscope, scanning electron microscopy, thermogravimetric analysis and physical property measurement system. The results indicate that the iron particle size distribution and grain size can be well-tuned by adjusting the water/EG ratio. With the variation of EG fraction in the mixed solvent, the nucleation, growth and crystallization of magnetic iron oxides with a controllable morphologies and particle sizes attached on the exterior surface of CNTs can be achieved. The as-prepared Fe/CNTs nanocomposites display superparamagnetic property at room temperature and the water/EG ratio determines the magnetization of the sample. Possible formation mechanism for magnetic Fe/CNTs is proposed based on the characterization results. - Highlights: • In-situ synthesis of monodisperse magnetic Fe/CNTs nanocomposites was reported. • Water/EG ratio determined the dispersion and distribution of magnetic particles. • The as-prepared Fe/CNTs nanocomposites were superparamagnetic at room temperature. • Formation mechanism for magnetic Fe/CNTs was proposed.