Quantitative evaluation on 3D fetus morphology via X-ray grating based imaging technique

Synchrotron-based X-ray phase sensitive micro-tomography techniques enable to visualize detailed three-dimensional (3D) insight into nondestructive inner-structure of biomedical samples. Different phase sensitive mechanisms have been employed for discrimination of tissue's tiny density variations in biomedical research. We effectively visualized and analyzed the phase-contrast experimental results of X-ray grating-based imaging, based on grating interferometry with phase stepping, by using transgenic mouse fetus. We quantitatively measured and evaluated the contrast-to-noise ratio or the mass density resolution, spatial resolution, radiation dose, and figure of merit of X-ray grating-based imaging technique in biomedical research respectively. Moreover, the complex coherent degrees of light source were duly taken into account in the analysis of spatial resolution. In addition, the mass density distribution of soft biomedical specimens can be estimated using our presented method preliminarily. For most soft tissue and organ observation, this work provides explicit guidelines to help future synchrotron users obtain the quantitative image information, suitable for their specific biomedical research.     

Experimental investigation of phase relations in Al-Co-Y ternary system

Phase relations in the Al-Co-Y ternary system at 1173 K have been established by means of scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD) techniques. Isothermal section at 1173 K of this system was constructed, which consists of 27 three-phase regions and 50 two-phase regions (27wider+23line). The ternary compound τ₅-AlCo₂Y₂ has been confirmed to exist and the crystal structure has been preliminarily analyzed with pattern indexing method as well. The intermetallic phase Co₂Y, Co₃Y, Co₇Y₂, Co₅Y, Co₁₇Y_2, Al₂Y, τ₄-AlCoY and τ₅-AlCo₂Y₂ were expressed as the formula of Al_xCo_2−xY, Al_xCo_3−xY, Al_xCo_7−xY₂, Al_xCo_5−xY, Al_xCo_17−xY₂, Al_2−xCo_xY, Al_1+xCo_1−xY and Al_1−xCo_2+xY₂, respectively.     

A numerical study of plasticity induced crack closure under plane strain conditions

The level of plasticity induced crack closure (PICC) is greatly affected by stress state. Under plane strain conditions, however, the level and even the existence of PICC still are controversial. The objective here is to study the influence of the main numerical parameters on plane strain PICC, namely the total crack propagation, the number of load cycles between crack increments, the finite element mesh and the parameter used to quantify PICC. The PICC predictions were included in a parallel numerical study of crack propagation, in order to quantify the impact of plane strain values on fatigue life. The results indicate that literature may be overestimating plane strain PICC due to incorrect numerical parameters. The number of load cycles usually considered is unrealistically small, and its increase was found to vanish crack closure, particularly for kinematic hardening. This effect was linked to the ratcheting effect observed at the crack tip. The total crack increment, Δa, must be large enough to obtain stabilized PICC values, but this may imply a huge numerical effort particularly for 3D models. The size of crack tip plastic zone may be overestimated in literature, which means that the meshes used may be too large. Additionally, the crack propagation study showed that the plane strain PICC has usually a dominant effect on fatigue life, and plane stress PICC is only relevant for relatively thin geometries.     

Internal elemental imaging by scanning X-ray fluorescence microtomography at the hard X-ray microprobe beamline of the SSRF: Preliminary experimental results

Synchrotron-based X-ray micro-fluorescence (μ-SXRF) is a non-destructive analytical technique and has been widely used to detect and quantify the elemental composition of samples in their natural state. To determine the internal elemental distributions within samples, X-ray fluorescence microtomography has been developed based on the hard X-ray microprobe at beamline BL15U1 of the Shanghai Synchrotron Radiation Facility (SSRF) in Shanghai, China. This technique was applied to image the cross-sectional distributions of multiple elements within a single human hair, and its validity was evaluated by comparing the results with the elemental maps of a thin hair section obtained using the well-established μ-SXRF mapping method. Elemental images of S, Ca, Mn, Fe, Cu, and Zn within a virtual slice of the hair were reconstructed after the tomographic measurements. The tomographic images of heavy elements like Fe, Cu, and Zn were found to be in good agreement with the corresponding μ-SXRF maps. Light elements, such as S, however, represented different patterns due to non-negligible self-absorption in the sample, and sophisticated correction algorithms accounting for such effects are required for obtaining qualitatively and quantitatively more accurate images. Compared to μ-SXRF mapping, X-ray fluorescence microtomography reduces the sample preparation requirements and has been demonstrated in this work as being a more ideal and effective imaging modality to non-destructively mapping out the internal distribution of heavy elements within samples at the micrometer scale at the SSRF.     

Synthesis and characterization of robust zero valent iron/mesoporous carbon composites and their applications in arsenic removal

Nanoscale zero valent iron particles (nZVI) have been developed by in situ reduction of Fe³⁺ ions onto a mesoporous type of carbon matrix – Starch-Derived Mesoporous Carbonaceous Material previously reported and marketed commercially as “Starbon”. The obtained nZVI/Starbon hybrid material exhibits homogeneous distribution of nZVI (10–20 nm) within the carbon matrix, surface area of 141 m²/g and a total iron loading of 1 mmol per gram of the composite, in accordance with transmission electron microscopy (TEM), X-ray diffraction (XRD), N₂ adsorption–desorption measurements, Infrared (IR)/Raman spectroscopy and Thermal gravimetric (TG)/Differential Thermal analysis (DTA). Electron Paramagnetic Resonance (EPR) and proton binding measurements show that the nanoparticles have a core–shell structure with iron(III) oxide/hydroxide shell due to partial air-oxidation of nZVI and the composite exhibits four different types of proton binding groups. Most importantly, the nZVI/Starbon hybrid has been tested as absorbent for As(III) removal showing a total removal of 358 μmol (26.8 mg) of As(III) per gram of the composite at pH = 7. We also discuss the principal role of surface OH groups of iron oxide in arsenic uptake and the crucial effect of pH on removal efficiency.     

Nitrogen-doped graphene supported Pd@PdO core-shell clusters for C-C coupling reactions

The introduction of nitrogen significantly decreases the metal particle size and improves the performance of metal-based graphene-supported catalysts. In this work, the density functional theory is used to understand the interaction between nitrogen-doped graphene and Pd@PdO clusters. Experiments show that small size Pd@PdO clusters （1-2 nm） can be grown uniformly on nitrogen-doped graphene sheets by a facile oxidation-reduction method. The nanoscale interaction relationship between nitrogen-doped graphene and Pd@PdO clusters is investigated through X-ray photoelectron spectroscopy （XPS） and X-ray absorption spectra （XAS）. The composite catalysts are applied in Suzuki-Miyaura reactions giving high yields and good structural stability. These results have potential impact in design and optimization of future high performance catalyst materials for cross coupling reactions.     

Suppressing Kinetic Aggregation of Non-Fullerene Acceptor via Versatile Alloy States Enables High-Efficiency and Stable Ternary Polymer Solar Cells

Despite considerable advances devoted to improving the operational stability of organic solar cells (OSCs), the metastable morphology degradation remains a challenging obstacle for their practical application. Herein, the stabilizing function of the alloy states in the photoactive layer from the perspective of controlling the aggregation characteristics of non-fullerene acceptors (NFAs), is revealed. The alloy-like model is adopted separately into host donor and acceptor materials of the state-of-the-art binary PM6:BTP-4Cl blend with the self-stable polymer acceptor PDI-2T and small molecule donor DRCN5T as the third components, delivering the simultaneously enhanced photovoltaic efficiency and storage stability. In such ternary systems, two separate arguments can rationalize their operating principles: (1) the acceptor alloys strengthen the conformational rigidity of BTP-4Cl molecules to restrain the intramolecular vibrations for rapid relaxation of high-energy excited states to stabilize BTP-4Cl acceptor. (2) The donor alloys optimize the fibril network microstructure of PM6 polymer to restrict the kinetic diffusion and aggregation of BTP-4Cl molecules. According to the superior morphological stability, non-radiative defect trapping coefficients can be drastically reduced without forming the long-lived, trapped charge species in ternary blends. The results highlight the novel protective mechanisms of engineering the alloy-like composites for reinforcing the long-term stability of NFA-based ternary OSCs.     

Gd induced the variations of anti-site defect and magnetism in the double perovskite oxides Sr2FeMoO6

Crystal structure, magnetic and transport properties of Sr_2−xGd_xFeMoO₆ (0 ≤ x ≤ 0.25) are investigated. The anti-site defect in this series can be adjusted by rare-earth element of Gd. Gd³⁺ replace for Sr²⁺ results in the increase of anti-site defect due to the differences in valence and size between Gd³⁺ and Sr²⁺. The moment of Gd³⁺ may be in canted structure. The effective moment of Gd³⁺ is about 1.5 μ_B/Gd³⁺, which is anti-parallel to that of Fe³⁺. The moment of Gd³⁺, Fe³⁺, and Mo⁵⁺/Mo⁴⁺ interact each other, and play important roles on transport and magnetic properties.     

Sorption properties of biofilms

The distribution and fate of pollutants in biological wastewater treatment is highly influenced by sorption processes. Biofilms can provide a sink for dissolved matter with extracelluar polymeric substances (EPS), cell walls, cell membranes, and cytoplasm serving as sorption sites. These sites display different sorption properties, preferences, and capacities. The distribution of organic pollutants such as BTX or heavy metals such as cadmium and zinc in biofilms could be investigated by fractionating the biomass. Therefore, an EPS extraction method with a crown ether was used which allowed the detection of organic and inorganic substances in the different fractions. After extraction, more than 60% of BTX could be localized in the EPS In contrast to organic substances, more than 80% of the total content of cadmium and zinc was found in the cellular fraction.