Tilapia fish-scale type I atelocollagen hydrogels with aligned fibril structures were fabricated under a strong magnetic field of 6 or 12 T using two different methods. In the first method, a ...solution of acid-soluble collagen was neutralized with phosphate buffer saline and maintained in the magnetic field at 28
°C for 3
h. Under these conditions fibrogenesis occurs, and a hydrogel is formed. The hydrogel was subsequently crosslinked with ethyl-dimethylcarbodiimide (EDC). In the second method, the hydrogels were formed as described above, but in the absence of an applied magnetic field. Only after being crosslinked with EDC were these gels exposed to the magnetic field (28
°C for 3
h). Both methods led to alignment of the collagen fibrils perpendicular to the magnetic direction, the extent of which depended on the duration of magnetic treatment. Even after EDC treatment, collagen fibrils can align, indicating that crosslinking has taken place within fibrils. Both sorts of aligned hydrogels exhibited similar rheological properties with higher storage and loss moduli than were observed with unoriented gels. The hydrogels treated at 6 T had the best rheological properties. The decrease in tangent angle phase delta indicated that the ratio of elasticity to viscosity was greater in the crosslinked than in the non-crosslinked hydrogels. Atomic force microscopy images showed that magnetic treatment had no effect on the nanostructure of collagen fibrils. Differential scanning calorimetry measurements indicated that collagen hydrogels with and without magnetic treatment had the same denaturation temperature, 48
°C, while EDC crosslinking increased the denaturation temperature to 62
°C.
Imaging properties of scanning confocal electron microscopy (SCEM) were studied by calculating simple model systems using the multislice method. A simple geometrical explanation was given, ...particularly for the difference between bright field (BF) and annular dark field (ADF) SCEM. It is demonstrated that the BF-SCEM image contrast consists of two features. One gradually changes over a wide defocus range and depends on the lateral size of the object. Another appears only near the focus and is independent of sample size. On the contrary, ADF-SCEM image contrast does not depend on the lateral size of the object. Therefore, the ADF-SCEM will provide more readily interpretable image contrast.
►Multislice based SCEM simulations demonstrate that BF-SCEM images have strong dependence on the lateral size of the object. ►The contrast dependence of BF-SCEM on the lateral size of the object is explained by a simple relation between
w and the illumination angle. ►In contrast to BF-SCEM, ADF-SCEM does not show much dependence on the lateral size because of the effect of ADF aperture in combination with the collector lens and detector aperture.
The imaging properties of bright field and annular dark field scanning confocal electron microscopy (BF-SCEM and ADF-SCEM) are discussed based on their point spread functions (PSFs) in comparison ...with multislice simulations. Although the PSFs of BF-SCEM and ADF-SCEM show similar hourglass shapes, their numerical distributions are quite different: BF-SCEM PSF is always positive and shows a center of symmetry whereas the ADF-SCEM PSF is complex and has Hermitian symmetry. These PSF properties explain the large elongation effect in BF-SCEM for laterally extended object and almost no-elongation in ADF-SCEM, illustrating the importance of the numerical analysis of PSFs. The Hermitian symmetry of the ADF-SCEM PSF results in an interesting “edge enhancement effect” at the interface. Simulation using the PSF and the multislice method verified this effect at GaAs surfaces and InAs interfaces embedded in GaAs. This unique feature of ADF-SCEM can potentially be useful for depth sectioning. It is also pointed out that a PSF imaging model cannot be applicable for BF-SCEM of a phase object, when the system is symmetric and aberration free.
► The properties of scanning confocal electron microscopy (SCEM) are discussed by PSF. ► The PSFs of BF- and ADF-SCEM show similar shapes, but values are quite different. ► This explains the large elongation effect in BF and no-elongation in ADF. ► The ADF-SCEM PSF shows “edge enhancement effect” that is useful for depth sectioning.
► SiC and/or toluene additives can enhance Jc of IMD processed MgB2 wire. ► SiC+toluene co-added MgB2 wire showed a Jc value of 50kA/cm2 at 10T and 4.2K. ► The amount of C substitution for B ...increased by the additives. ► Toluene addition reduces the grain size of IMD processed MgB2. ► C substitution for B and reduction of grain size are responsible for Jc enhancement.
The internal Mg diffusion (IMD) process produces a MgB2 layer with higher density than that achieved with the traditional Powder-in-tube (PIT) method; this makes the IMD process an attractive one for the fabrication of superconducting MgB2 wires with higher critical current densities (Jc). We have recently shown that co-addition of SiC and some liquid aromatic hydrocarbons (toluene and dimethylbenzene) can enhance the Jc of IMD-processed mono-core MgB2 wires. In the present contribution, we discuss the Jc of the IMD-processed mono-core MgB2 wires fabricated under different conditions, viz. with pure B powder, B powder with additive-like SiC or toluene, and B powder with SiC+toluene co-addition. The results from these samples indicated that the SiC+toluene co-addition gave the best Jc value, as in the previous results. The composition and microstructure suggested that carbon substitution for boron and reductions of grain size by SiC and/or toluene additives are responsible for the Jc enhancements of IMD-processed MgB2 wires.
An efficient, Bloch wave-based method is presented for simulation of high-resolution scanning confocal electron microscopy (SCEM) images. The latter are predicted to have coherent nature, i.e. to ...exhibit atomic contrast reversals depending on the lens defocus settings and sample thickness. The optimal defocus settings are suggested and the 3D imaging capabilities of SCEM are analyzed in detail. In particular, by monitoring average image intensity as a function of the probe focus depth, it should be possible to accurately measure the depth of a heavy-atom layer embedded in a light-element matrix.
This work investigates the evolution of microstructures and magnetic properties during isothermal annealing of Cu-Fe-Co alloys, using electron microscopy and superconducting quantum interference ...device (SQUID) magnetometry. Small coherent granular precipitates composed of iron and cobalt formed in the copper matrix in the early stage of precipitation. As annealing proceeded, the precipitates lost coherency to the matrix after reaching a size of 15–20 nm and twin-like structures were consecutively introduced in the particles. The SQUID measurements revealed that the magnetic properties of the specimens correlated with the microstructural evolution. The coercive force initially increased with annealing time but decreased after reaching a peak. Lorentz Microscopy suggested that the initial large increase of magnetization was invoked by a structural transition from fcc to B2 in the precipitates.
Electron beam induced deposition was performed using a Pt(PF
3
)
4
precursor gas. Self-standing nanowires were produced on the edge of a molybdenum film, followed by two post-deposition processes; ...electron beam irradiation at room temperature and heating at about 400 K in vacuum. The as-deposited nanowires were composed of an amorphous phase, of which the dominant composition was platinum but containing a small amount of phosphorus impurity. After irradiating with a 300 keV electron beam, the amorphous nanowires were transformed to crystalline ones. By heating, the as-deposited nanowires became single-crystal platinum with a large grain size and the phosphorus content disappeared.
Focused electron beam induced chemical vapor deposition was performed in a scanning electron microscope with a field emission gun using a precursor of iron carbonyl. Due to the longer deposition time ...and higher gas pressure than those of our previous electron beam-induced deposition method, a new type of deposition occurred. A large amount of nanosized crystals were produced around the focused beam irradiation point on a carbon substrate at room temperature. The nanocrystals were systematically characterized using transmission electron microscopy with electron energy loss spectroscopy (EELS), and were identified to be single crystals of α-Fe.
A nanometer-sized magnet (nano-magnet) was fabricated on the tip of a tungsten needle by electron-beam-induced deposition with Fe(CO)5 gas. The needle tip, which can be moved with a stepping motor ...and piezo-driver, was attached inside a specially designed TEM specimen holder. This nano-magnet on the piezo-driven tip is capable of making an approach to magnetic nanostructures formed on a substrate so that the nanometer-scale magnetic interaction could be studied. Electron holography observation of the magnetic field around the nano-magnet showed that the residual magnetic flux density Br of the nano-magnet was about 0.48 T.
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