In Situ Transmission Electron Microscopy Study of Bubble Behavior Near the Surface of Ice Crystals by Using a Liquid Cell With a Peltier Cooling Holder.

Liquid cell transmission electron microscopy (LC-TEM) is a unique technique that permits in situ observations of various phenomena in liquids with high spatial and temporal resolutions. One difficulty with this technique is the control of the environmental conditions in the observation area. Control of the temperature ranging from room temperature to minus several tens of degrees Celsius, is desirable for controlling the supersaturation in various materials and for observing crystallization more easily. We have developed a cooling transmission electron microscopy specimen holder that uses Peltier devices, and we have combined it with a liquid cell to realize accurate temperature control in LC-TEM. We evaluated this system by using water as a specimen. Motionless bubbles, shown to be voids containing pressurized gas, formed in the specimen sometime after the temperature had reached -12°C. An electron diffraction pattern showed that the specimen turned into ice Ih after the formation of these bubbles, confirming that our system works properly and can induce crystallization. In addition, we analyzed the behavior of bubbles formed in the ice Ih, and we discussed the formation of these bubbles and their internal pressure.

Novel -75°C SEM cooling stage: application for martensitic transformation in steel.

Microstructural changes during the martensitic transformation from face-centred cubic (FCC) to body-centred cubic (BCC) in an Fe-31Ni alloy were observed by scanning electron microscopy (SEM) with a newly developed Peltier stage available at temperatures to -75°C. Electron channelling contrast imaging (ECCI) was utilized for the in situ observation during cooling. Electron backscatter diffraction analysis at ambient temperature (20°C) after the transformation was performed for the crystallographic characterization. A uniform dislocation slip in the FCC matrix associated with the transformation was detected at -57°C. Gradual growth of a BCC martensite was recognized upon cooling from -57°C to -63°C.

Diagnostic Value of Serum Procalcitonin in Patients with Convulsion in Emergency Department, an Observational Study.

Procalcitonin (PCT), a widely used biomarker for bacterial infections, is sometimes measured in convulsion patients to distinguish bacterial infections including bacterial meningitis. However, serum PCT elevation is reported in several other conditions. This study assessed the diagnostic value of serum PCT concentrations in convulsion patients. This study examined a convulsion group: patients admitted to our critical care center during April 2018 through September 2019 via the emergency department presenting with convulsions. Randomly sampled patients admitted without convulsions were categorized as a non-convulsion group. Serum PCT analysis was performed with consideration of whether or not the patient had an infection. Diagnostic values of serum PCT for bacterial infection were evaluated for convulsion and non-convulsion patients using the positive likelihood ratio of PCT. This study found 84 patients as eligible for the convulsion group; 1:2 matched 168 control patients were selected as non-convulsion group members. The positive likelihood ratio for bacterial infection was found to be significantly lower in the convulsion group than in the control group (1.94 vs. 2.65) when setting the positive cut-off for PCT as 0.5 ng/mL. Convulsion patients had a higher PCT value. The positive likelihood ratio for patients without bacterial infection was lower.

Chemoradiation therapy for oesophageal cancer with airway stenosis under mechanical ventilation with light sedation using dexmedetomidine alone.

For malignant tumours, treatment is rarely indicated in cases requiring mechanical ventilation management because such intensive care would engender a decrease in performance status. However, light sedation using dexmedetomidine might enable chemoradiation while accommodating activities of daily living. We experienced two cases of fatal tracheal invasion and airway stenosis of stage Ⅳ oesophageal cancer that were treated with chemoradiation or radiation under mechanical ventilation (one case was differential lung ventilation.) with dexmedetomidine alone and rehabilitation was performed under a ventilator. Early mobilisation by light sedation with dexmedetomidine can inhibit performance status decline attributable to mechanical ventilation. Bridging tracheal intubation with light sedation by dexmedetomidine for temporary chemoradiation therapy to reduce tumour volume might present a good alternative for patients with malignant tumour.

Electron tomography imaging methods with diffraction contrast for materials research.

Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) enable the visualization of three-dimensional (3D) microstructures ranging from atomic to micrometer scales using 3D reconstruction techniques based on computed tomography algorithms. This 3D microscopy method is called electron tomography (ET) and has been utilized in the fields of materials science and engineering for more than two decades. Although atomic resolution is one of the current topics in ET research, the development and deployment of intermediate-resolution (non-atomic-resolution) ET imaging methods have garnered considerable attention from researchers. This research trend is probably not irrelevant due to the fact that the spatial resolution and functionality of 3D imaging methods of scanning electron microscopy (SEM) and X-ray microscopy have come to overlap with those of ET. In other words, there may be multiple ways to carry out 3D visualization using different microscopy methods for nanometer-scale objects in materials. From the above standpoint, this review paper aims to (i) describe the current status and issues of intermediate-resolution ET with regard to enhancing the effectiveness of TEM/STEM imaging and (ii) discuss promising applications of state-of-the-art intermediate-resolution ET for materials research with a particular focus on diffraction contrast ET for crystalline microstructures (superlattice domains and dislocations) including a demonstration of in situ dislocation tomography.

Development of a three-dimensional tomography holder for in situ tensile deformation for soft materials.

An in situ straining holder capable of tensile deformation and high-angle tilt for electron tomography was developed for polymeric materials. The holder has a dedicated sample cartridge, on which a variety of polymeric materials, such as microtomed thin sections of bulk specimens and solvent-cast thin films, can be mounted. Fine, stable control of the deformation process with nanoscale magnification was achieved. The holder allows large tensile deformation (≃800 µm) with a large field of view (800 × 200 µm before the deformation), and a high tilt angle (±75°) during in situ observations. With the large tensile deformation, the strain on the specimen can be as large as 26, at least one order of magnitude larger than the holder's predecessor. We expect that meso- and microscopic insights into the dynamic mechanical deformation and fracture processes of polymeric materials can be obtained by combining the holder with a transmission electron microscope equipped with an energy filter. The filter allows zero-loss imaging to improve the resolution and image contrast for thick specimens. We used this technique to study the deformation process in a silica nanoparticle-filled isoprene rubber.

Three-dimensional visualization of dislocations in a ferromagnetic material by magnetic-field-free electron tomography.

In conventional transmission electron microscopy, specimens to be observed are placed in between the objective lens pole piece and therefore exposed to a strong magnetic field about 2 T. For a ferromagnetic specimen, magnetization of the specimen causes isotropic and anisotropic defocusing, deflection of the electron beam as well as deformation of the specimen, which all become more severe when the specimen tilted. Therefore electron tomography on a ferromagnetic crystalline specimen is highly challenging because tilt-series data sets must be acquired without changing the excitation condition of a specific diffraction spot. In this study, a scanning transmission electron microscopy (STEM) tomography method without magnetizing a ferromagnetic specimen has been developed for three-dimensional (3D) visualization of dislocations in α-Fe, which is a typical ferromagnetic material. Magnetic-field-free environment down to 0.38 ± 0.07 mT at the specimen position is realized by demagnetizing the objective lens pole piece of a commercial STEM instrument. By using a spherical aberration corrector with the magnetic-field-free environment, an "aberration corrected Low-Mag STEM mode" with no objective lens field reaches a convergence semi angle ∼1 mrad and a spatial resolution ∼5 nm, and shows an adequate performance of imaging dislocations under a two-beam excitation condition for a low-index diffracted beam. The illumination condition for the aberration corrected Low-Mag STEM mode gives no overlap between the direct beam disk (spot) and neighboring diffraction disks. An electron channeling contrast imaging technique, in which an annular detector was located at a doughnut area between the direct beam and the neighboring diffracted beams, was effectively employed with the aberration corrected Low-Mag STEM mode to keep image intensity high enough even at large specimen-tilt angles. The resultant tomographic observation visualized 3D dislocation arrangements and active slip planes in a deformed α-Fe specimen.

3D visualization of TiO2 nanocrystals in mesoporous nanocomposite using energy filtered transmission electron microscopy tomography.

IntroductionMesoporous silica, SBA-15, is one of the best candidate for the supporting material of catalytic nanoparticles because of its relative large and controllable pore size and large specific surface area [1]. So far, various nanoparticles, such as Au, Pt and Pd, have been introduced into the pore for catalytic application [2]. The size of nanoparticles supported inside SBA-15 is restricted by that of the pore, and they are usually ranging from 2 nm and 50 nm in space.It is necessary to anchor the nanoparticles within pores to avoid segregation / sintering of them. However, it is difficult to anchor them within pores in the case of use of deposition-precipitation method due to extreme low iso-electric point (IEP) of silica (∼2). Therefore, TiO2 nanocrystals (IEP 6-8) were then introduced to anchor AuNPs [3].In this study, EFTEM tomography was applied to examine the effectiveness of TiO2 for AuNPs. Materials and methodAu/TiO2-SBA-15 was embedded into epoxy resin for electron microscopy and microtomed to about 30 nm thickness. EFTEM-tomography was operated at 120 kV and using Ti-L ionization edge via three-window method. Prior to EFTEM, STEM-HAADF tomography was also carried out for visualizing AuNPs and for comparison. Result and discussionFigure 1 shows 3D-volume of AuNPs and TiO2 nanocrystals from EFTEM-tomography. TiO2 nanocrystals in the porous material were successfully visualized using EFTEM -tomography, and local relationship between AuNPs and TiO2 nanocrystals were revealed. A large number of TiO2 nanocrystals were randomly distributed in the SBA-15. It was found that most AuNPs were directly on the exposed TiO2 nanocrystals. It implies that TiO2 nanocrystals were exposed on the surface of the pore and anchored AuNPs inside the pores.jmicro;63/suppl_1/i27/DFU081F1F1DFU081F1Fig. 1.3D volume of AuNPs and TiO2 nanocrystals.

Microstructural analysis of Au/TiO2-SBA-15 nanocomposite.

Properties of gold nanoparticles (AuNPs) are very different from bulk gold, in particular, highly dispersed AuNPs exhibit high catalytic activities on metal oxide supports. Catalytic activities of AuNPs are strongly dependent on: (i) size and morphology; (ii) synthesis methods; (iii) nature of the support; (iv) interaction between AuNPs and the support; and (v) oxidation state of AuNPs in the synthesized catalysts. A goal is to maintain the size and to prohibit aggregation of AuNPs, since aggregations deteriorate catalytic activities. Some strong interactions are therefore required between AuNPs and their supports to prevent the movement of AuNPs. SBA-15 is a promising material for the support of AuNPs since it has ordered two-dimensional hexagonal pore channels, uniform pore size ranging from 5 to 30 nm, narrow pore size distribution, thick amorphous walls ranging from 3 to 6 nm, and high surface area. In this study, SBA-15, TiO2-SBA-15 and TiO2-SBA-15-AuNP nanocomposites were synthesized by the sol-gel method and microstructural characterizations were carried out by both X-ray diffraction analysis and electron microscopy.