Spatial frequency-based correction of the spherical aberration in living brain imaging.

Optical errors, including spherical aberrations, hinder high-resolution imaging of biological samples due to biochemical components and physical properties. We developed the Deep-C microscope system to achieve aberration-free images, employing a motorized correction collar and contrast-based calculations. However, current contrast-maximization techniques, such as the Brenner gradient method, inadequately assess specific frequency bands. The Peak-C method addresses this issue, but its arbitrary neighbor selection and susceptibility to the noise limit its effectiveness. In this paper, we emphasize the importance of a broad spatial frequency range for accurate spherical aberration correction and propose Peak-F. This spatial frequency-based system utilizes a fast Fourier transform as a bandpass filter. This approach overcomes Peak-C's limitations and comprehensively covers the low-frequency domain of image spatial frequencies.

Cell stimulation by focused electron beam of atmospheric SEM.

Cell stimulation has been performed with a focused electron beam. To protect the live cells from the vacuum environment of the electron beam, the beam irradiated the ambient cells via a thin film. In this way, the cells were electrically stimulated with nanometre resolution in a non-contact process. The response of calcium ion concentration in a single HeLa cell after electron beam irradiation was examined. This technique has the potential to stimulate single ion channels, granules, and organelles.