Cellular functions are fundamentally regulated by intracellular temperature, which influences biochemical reactions inside a cell. Despite the important contributions to biological and medical applications that it would offer, intracellular temperature mapping has not been achieved. Here we demonstrate the first intracellular temperature mapping based on a fluorescent polymeric thermometer and fluorescence lifetime imaging microscopy. The spatial and temperature resolutions of our thermometry were at the diffraction limited level (200 nm) and 0.18–0.58 °C. The intracellular temperature distribution we observed indicated that the nucleus and centrosome of a COS7 cell, both showed a significantly higher temperature than the cytoplasm and that the temperature gap between the nucleus and the cytoplasm differed depending on the cell cycle. The heat production from mitochondria was also observed as a proximal local temperature increase. These results showed that our new intracellular thermometry could determine an intrinsic relationship between the temperature and organelle function. Intracellular temperature mapping has not previously been achieved. Now, a fluorescent polymeric thermometer has been developed that can be used in combination with fluorescence-lifetime imaging microscopy to allow thermometry with spatial and temperature resolutions of 200 nm and 0.18–0.58 ° C.
We report an imaging method, termed Fourier ptychographic microscopy (FPM), which iteratively stitches together a number of variably illuminated, low-resolution intensity images in Fourier space to produce a wide-field, high-resolution complex sample image. By adopting a wavefront correction strategy, the FPM method can also correct for aberrations and digitally extend a microscope's depth of focus beyond the physical limitations of its optics.As a demonstration, we built a microscope prototype with a half-pitch resolution of 0.78 µm, a field of view of ∼120 mm2 and a resolution-invariant depth of focus of 0.3 mm (characterized at 632 nm). Gigapixel colour images of histology slides verify successful FPM operation. The reported imaging procedure transforms the general challenge of high-throughput, high-resolution microscopy from one that is coupled to the physical limitations of the system's optics to one that is solvable through computation. A wide-field, high-resolution imaging scheme that offers enhanced depth of field is demonstrated. The approach relies on stitching together time-multiplexed images in Fourier space.
Abstract Volume electron microscopy (vEM) has become a widely adopted technique for acquiring three-dimensional structural information of biological specimens. In addition to the traditional use of transmission electron microscopy, recent advances in the resolution of scanning electron microscopy (SEM) made it suitable for vEM application. Currently, various types of SEM with different advantages have been utilized. For selecting the appropriate type of SEM to obtain optimal vEM images for the purpose of individual research, it is important to understand the physics underlying each SEM technology. This article aims to explain the physics for signal electron generation, various objective lens configurations and detection systems, employed in SEM to enhance high-resolution imaging and improve signal detection conditions.
Specimen reconstitution technology is important for the in-service safety of reactor pressure vessels (RPVs) in nuclear power plants. To verify the feasibility of electron beam welding for the restructured specimens, the electron beam welding to restructure the 16MND5, 10Cr12Ni3Mo2VN, and X6NiCrTiMoVB 25-15-2 Charpy impact specimens for three kinds of steels was adopted, the microstructure and mechanical properties of the restructured specimens were characterized, and the Vickers hardness and impact toughness of the specimens were tested by non-destructive flaw detection, optical microscopy, and scanning electron microscopy. The results show that the microstructure of these three steels in weld zone is relatively dense, and no obvious crack defects occur. The welding quality of 10Cr12Ni3Mo2VN restructured specimens is the best, and the mechanical properties are relatively close to those of the original specimens, demonstrating that the electron beam welding has the good application potential of reconstitution in nuclear power field.
YANG Hongwei, WANG Haifeng, YANG Jun, PU Renbin, YANG Can, JIN Chen
In order to enhance the long-term protective performance of water-based epoxy coatings，benzotriazole (BTAH) corrosion inhibitor was incorporated into hollow cerium oxide (CeO2) nanocontainers，resulting in the preparation of BTAH＠CeO2-doped epoxy coatings.The surface morphology，chemical composition and corrosion resistance of the epoxy/BTAH＠CeO2 composite coating were characterized using scanning electron microscopy (SEM)，X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS).The results showed that the loading amount of BTAH inhibitor in the CeO2 nanocontainers was 24.7%.The BTAH inhibitor was able to be rapidly released from the CeO2 nanocontainers，with a release amount reaching 92.6%after 8 h.The BTAH＠CeO2 particles were uniformly dispersed in the water-based epoxy resin and effectively filled the microscopic voids inside the coating.Electrochemical impedance testing results after corrosion in a 3.5%NaCl solution for 1 h indicated that the coating resistance of the epoxy/BTAH＠CeO2 composite coating was 16.7 times higher than that of pure epoxy coatings.After immersion in a 3.5%(mass fraction) NaCl solution for 30 d，the polarization resistance loss rate of the epoxy/BTAH＠CeO2 composite coating was only 10.6%compared to 1 h of immersion，demonstrating excellent long-term protective performance.
Materials of engineering and construction. Mechanics of materials, Technology
[Purposes] Because of the high charging overpotential and lagging electrochemical reaction kinetics caused by the low electronic conductivity of Li2O2 in Li-O2 batteries, it is important to develop cathode catalysts with high activity. [Methods] By coating nitrogen-doped molybdenum disulfide ultra-thin nanosheets on the surface of nitrogen-doped carbon nanotubes, the N-MoS2/N-CNTs composite was prepared through hydrothermal method combined with ammonia annealing method. The morphology, surface element state, and Li-O2 battery electrochemical performance of N-MoS2/N-CNTs were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical tests. [Results] The cathode obtains high initial charge/discharge capacity (7909/10015 mAh g-1), low charging overpotential, and high catalytic activity. Moreover, the performance of Li-O2 battery is further improved at large O2 mass transfer area. According to electrochemical reaction engineering, it is proposed that the possible initial discharge reaction interface is electrode/Li2O2 interface, and the charging reaction interface is electrode/electrolyte/Li2O2 interface. Three overpotential theories are used to explain the capacity and rate performance improvement mechanism of N-MoS2/N-CNTs cathode Li-O2 batteries, which is the decrease of electrochemical reaction overpotential (ηR) providing more space for the increase of concentration overpotential (ηC).
Chemical engineering, Materials of engineering and construction. Mechanics of materials
Anastasiia Kudriavtseva, Stefan Jarić, Nikita Nekrasov
et al.
Graphene-based materials are actively being investigated as sensing elements for the detection of different analytes. Both graphene grown by chemical vapor deposition (CVD) and graphene oxide (GO) produced by the modified Hummers’ method are actively used in the development of biosensors. The production costs of CVD graphene- and GO-based sensors are similar; however, the question remains regarding the most efficient graphene-based material for the construction of point-of-care diagnostic devices. To this end, in this work, we compare CVD graphene aptasensors with the aptasensors based on reduced GO (rGO) for their capabilities in the detection of NT-proBNP, which serves as the gold standard biomarker for heart failure. Both types of aptasensors were developed using commercial gold interdigitated electrodes (IDEs) with either CVD graphene or GO formed on top as a channel of liquid-gated field-effect transistor (FET), yielding GFET and rGO-FET sensors, respectively. The functional properties of the two types of aptasensors were compared. Both demonstrate good dynamic range from 10 fg/mL to 100 pg/mL. The limit of detection for NT-proBNP in artificial saliva was 100 fg/mL and 1 pg/mL for rGO-FET- and GFET-based aptasensors, respectively. While CVD GFET demonstrates less variations in parameters, higher sensitivity was demonstrated by the rGO-FET due to its higher roughness and larger bandgap. The demonstrated low cost and scalability of technology for both types of graphene-based aptasensors may be applicable for the development of different graphene-based biosensors for rapid, stable, on-site, and highly sensitive detection of diverse biochemical markers.