Spin-polarized electron beam is provided by a laser-driven electron gun using a semiconductor photocathode with a negative electron affinity surface. Nagoya University group of Prof. Nakanishi had realized a high polarization of 92 % with a quantum efficiency of 0.5 %, pico-second pulse beam, and a high reduced-brightness of 10⁷ A/m².sr.V by using the electron source. The R&D of polarized electron source is taken account of a complex of optical property of semiconductor, transport process in solid, surface physics and beam physics. In this paper, we describe the generation process of spin-polarized electron beam and the characteristics, and also mention a development of a novel transmission electron microscope (TEM) as an application research of the spin-polarized electron source. We have constructed a spin-polarized transmission electron microscope (SP-TEM) by mounting a polarized electron source on an ordinal TEM. TEM images and electron energy loss spectrum have been acquired in the SP-TEM. Moreover the energy spread of the spin-polarized electron beam is below 0.3 eV without any monochromater. In the end of this paper, we would like to mention about the first step of application and a future plan of the SP-TEM as a novel method of electron microscope.

Low energy electron microscopy (LEEM) and photo-emission electron microscopy (PEEM) have been widely paid attention to because of their dynamic and versatile observation. However the magnetic contrast cannot be easily obtained with the dynamic mode so far due to the low brightness and spin-polarization of the electron gun.  We describe the detailed development results on high brightness, highly spin-polarized and long life time electron gun with novel ideas which are the back-side illumination of the laser beam, the strained super lattice for the photocathode and XHV including novel design of the electron optics. After the development, we achieved dynamic observation of the magnetic domain contrast (20ms/frame) and the detailed experimental results of [CoNi₂]_y multi-layers on W(110) have been obtained, which could be important for spintronics materials.

A spin-polarized scanning electron microscope (spin SEM) is a unique method for observing the magnetic domain structures in high resolution. It uses the phenomenon where the spin-polarization vector of secondary electrons emitted from ferromagnetic material is related to the magnetization vector at the originating point of the secondary electrons on the material. The spin polarization of the secondary electrons is detected by the spin polarimeter, which is a key component of spin SEM. The spin polarimeter is based on the Mott scattering, and all three spin polarization components can be analyzed by functioning the spin manipulator with the spin polarimeter.

Spin SEM has several advantages besides the high resolution, such as no limitation for sample thickness and flatness, magnetization information independent from the sample surface topography, and quantitative analysis of the magnetization vectors in three dimensions. In this paper, the principle of spin SEM and the spin polarimeter are explained and spin SEM data of HDD recording medium are introduced. At the end, the observation of the magnetic domains on Co crystal up to 500°C is shown.

Spin-polarized scanning tunneling microscopy (SP-STM) shows surface electronic spin and quantum structures of nano materials, such as single atoms, single molecules, nano-clusters, with a resolution of atomic scale. With a combination of SP-STM spectroscopy mode we can directly observe the electronic spin band structures near the Fermi energy (±3 eV) of nano materials, and therefore this technique is one of the most powerful tools for development of new nano spintronics devices.

Melanosomes are tissue-specific organelles that synthesize and store “black” melanins in pigment cells. Melanosomes are visible even under a primitive light microscope, and by taking advantage of this nature they have been studied for more than 150 years. In the long history of the melanosome research, many protocols of isolation and purification of melanosomes have been established, and recent analyses of human or mouse hereditary diseases with hypopigmentation have revealed a variety of molecules that are necessary for proper functions of melanosomes. Here, we describe basic features of melanosomes and provide a historical overview of the molecular mechanisms of biogenesis, maturation, and transport of melanosomes in mammalian melanocytes.

The immunohistochemistry is an essential technique to make an exact pathological diagnosis. It is used with careful morphological assessment and provides various useful informations for the pathologists. In this article, the representative antibodies are introduced, including various epithelial, hematopoietic, mesenchymal, neural/neuroendocrine markers, and the promising markers for identification of appropriate patients for molecular targeting therapies.

In the present paper, we start with a general introduction of electron vortex beam and show our latest results of the production, propagation and interference of electron vortex beams.  We inserted fork-shaped gratings and spiral zone plates, which were nano-fabricated by an FIB instrument, to the illumination lens system of transmission electron microscopes and observed a formation of electron vortex beam with a few nanometers in diameter on the specimen position. Electron vortex beams with a large orbital angular momentum of ℓ=±90ћ were successfully produced by the spiral zone plate. The propagation features show a fairly good agreement with a simulation based on the Fresnel propagation theory. We also performed an interference experiment between two electron vortex beams, and found out that the two electron vortex beams are interfered irrespective of their orbital angular momentum. This result shows that orbital angular momentum of electron, unlike spin angular momentum, is not a simultaneously measurable observable with position and linear momentum.

In natural environments, bacteria are exposed to various stress conditions, such as starvation or low temperature. To survive under harmful conditions, non-spore-forming gram-negative bacteria are known to undergo an active adaptation program. Vibrio cholerae is the causative agent of cholera and can shift to a rugose colony morphology from its normal translucent smooth colony morphology in response to environmental stress. The rugose strains produce an amorphous exopolysaccharide (EPS) and promote biofilm formation. The rugose strains also exhibit resistance to oxidative and osmotic stress.

V. cholerae can enter the VNC (viable but nonculturable) state after exposure to adverse environmental conditions. A cell considered to be in a VNC state if it is metabolically active while being incapable of undergoing the sustained cellular division required to form a colony on media that are regularly used in standard or recommended procedures for bacterial enumeration. VNC state of V. cholerae cells can be resuscitated when inoculated onto an agar medium amended with catalase or nonenzyme peroxide-degrading compound such as sodium pyruvate.

Phase variation of colony morphology, subsequent biofilm formation and the entering into VNC state might be the starvation-survival response of V. cholerae.

Mycobacterium tuberculosis, causative agent of tuberculosis, has specific morphological characteristics such as acid-fastness, cord-formation of the colonies and the inhibition of phagosome-lysosome fusion in the infected host phagocytes. Although many of these findings have been obtained by light microscopic observation, the mechanisms underlying these characteristics remain unclear. In this lecture, TEM and SEM observation data of these specific characteristics in mycobacterial cells and colonies are shown, which may initiate the interest of mycobacteriology and general microbiology.

Direct electron detector (DED) cameras using CMOS image sensor are developed and used as an imaging media in transmission electron microscope (TEM). Since images recorded in DED show higher spatial resolution and better signal to noise ratio than those in CCD, it is applied to low dose imaging, especially for cryo-electron microscopy. The fast readout speed of DED is also used to a time-lapse recording and a specimen drift correction. In this article, we describe the principle and the performance of DED, and introduce the recent applications.

In cryogenic transmission electron microscopy (TEM), the specimen is exposed to high vacuum, low temperature, and a high-energy electron probe beam. Such an environment can be considered to mimic outer space under cosmic ray irradiation. To investigate the structures and structural transition of ice in outer space under cosmic rays irradiation, the structural transformation of ice under electron beam irradiation was observed in situ by cryogenic TEM. Here we briefly review the experimental results.

To reveal atomic dynamics directly, we have developed Ultrafast Electron Diffraction system using Relativistic electrons. The homemade rf-photocathode allows both the high brightness sufficient for single shot experiments and the high time resolution for monitoring real time atomic motions. The system has electromagnetic lenses as for a transmission electron microscope that keep the system compact and rich in optical configurations. We also introduced the homemade electron detection method that was capable of recording diffraction patterns precisely and detecting their subtle changes sufficient to monitor atomic motions.