Noise reduction of electron holography observations for a thin-foiled Nd-Fe-B specimen using the wavelet hidden Markov model.

In this study, we investigate the effectiveness of noise reduction in electron holography, based on the wavelet hidden Markov model (WHMM), which allows the reasonable separation of weak signals from noise. Electron holography observations from a Nd2Fe14B thin foil showed that the noise reduction method suppressed artificial phase discontinuities generated by phase retrieval. From the peak signal-to-noise ratio, it was seen that the impact of denoising was significant for observations with a narrow spacing of interference fringes, which is a key parameter for the spatial resolution of electron holography. These results provide essential information for improving the precision of electron holography studies.

Necl-1/CADM3 regulates cone synapse formation in the mouse retina.

In vertebrates, retinal neural circuitry for visual perception is organized in specific layers. The outer plexiform layer is the first synaptic region in the visual pathway, where photoreceptor synaptic terminals connect with bipolar and horizontal cell processes. However, molecular mechanisms underlying cone synapse formation to mediate OFF pathways remain unknown. This study reveals that Necl-1/CADM3 is localized at S- and S/M-opsin-containing cones and dendrites of type 4 OFF cone bipolar cells (CBCs). In Necl-1-/- mouse retina, synapses between cones and type 4 OFF CBCs were dislocated, horizontal cell distribution became abnormal, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors were dislocated. Necl-1-/- mice exhibited aberrant short-wavelength-light-elicited signal transmission from cones to OFF CBCs, which was rescued by AMPA receptor potentiator. Additionally, Necl-1-/- mice showed impaired optokinetic responses. These findings suggest that Necl-1 regulates cone synapse formation to mediate OFF cone pathways elicited by short-wavelength light in mouse retina.

High-precision charge analysis in a catalytic nanoparticle by electron holography.

The charge state of supported metal catalysts is the key to understanding the elementary processes involved in catalytic reactions. However, high-precision charge analysis of the metal catalysts at the atomic level is experimentally challenging. To address this critical challenge, high-sensitivity electron holography has recently been successfully applied for precisely measuring the elementary charges on individual platinum nanoparticles supported on a titanium dioxide surface. In this review, we introduce the latest advancements of high-precision charge analysis and discuss mechanisms of charge transfer at the metal-support interface. The development of charge measurements is entering a new era, and charge analyses under conditions closer to practical working environments, such as real-time, real-space, and reactive gas environments, are expected to be realized in near future.

Direct identification of the charge state in a single platinum nanoparticle on titanium oxide.

A goal in the characterization of supported metal catalysts is to achieve particle-by-particle analysis of the charge state strongly correlated with the catalytic activity. Here, we demonstrate the direct identification of the charge state of individual platinum nanoparticles (NPs) supported on titanium dioxide using ultrahigh sensitivity and precision electron holography. Sophisticated phase-shift analysis for the part of the NPs protruding into the vacuum visualized slight potential changes around individual platinum NPs. The analysis revealed the number (only one to six electrons) and sense (positive or negative) of the charge per platinum NP. The underlying mechanism of platinum charging is explained by the work function differences between platinum and titanium dioxide (depending on the orientation relationship and lattice distortion) and by first-principles calculations in terms of the charge transfer processes.

Accuracy improvement of phase estimation in electron holography using noise reduction methods.

We try to improve the limit of the phase estimation of the interference fringe at low electron dose levels in electron holography by a noise reduction method. In this paper, we focus on unsupervised approaches to apply it to electron beam-sensitive and unknown samples and describe an overview of denoising methods used widely in image processing, such as wiener filter, total variation denoising, nonlocal mean filters and wavelet thresholding. We compare the wavelet hidden Markov model (WHMM) denoising that we have studied so far with the other conventional noise reduction methods. We evaluate the denoise performance of each method using the peak signal-to-noise ratio between noise-free and the target holograms (noisy or denoised holograms) and the root mean-square error (RMSE) between the true phase of the fringe and the measured phase by the discrete Fourier transform phase estimator. We show the denoised holograms for simulation and experimental data by using each noise reduction method and then discuss evaluation indexes obtained from these denoised holograms. From experimental results, it can be seen that the WHMM denoising can reduce the RMSE of fringe phase to about 1/4.5 for noisy simulation holograms and it has stable and good performance for noise reduction of observed holograms with various image qualities.

Visual Target Strategies in Infantile Nystagmus Patients With Horizontal Jerk Waveform.

The aim of this study was to propose a new pathophysiological hypothesis for involuntary eye oscillation in infantile nystagmus (IN): patients with IN exhibit impaired gaze fixation, horizontal smooth pursuit and optokinetic nystagmus (OKN) and use saccadic eye movements for these underlying impairments. In order to induce saccades, they make enough angle between gaze and target by precedent exponential slow eye movements. IN consists of the alternate appearance of the saccade and the slow eye movements. Unlike most previous theories, IN is therefore considered a necessary strategy allowing for better vision and not an obstacle to clear vision. In five patients with IN, eye movements were analyzed during the smooth pursuit test, saccadic eye movement test, OKN test and vestibulo-ocular reflex (VOR) test. Their gaze fixation, horizontal smooth pursuit, OKN and the last half of the slow phase of VOR were impaired. The lines obtained by connection of the end eye positions of fast phase of nystagmus coincided with the trajectories of targets. The findings indicate that patients followed the target by the fast but not the slow phase of nystagmus, which supports our hypothesis. By setting the direction of slow phase of nystagmus opposite to the direction of the OKN stimulation, enough angle can be effectively made between the gaze and target for the induction of saccade. This is the mechanism of reversed OKN response. In darkness and when eyes are closed, IN weakens because there is no visual target and neither the saccade for catching up the target or slow phase for induction of the saccade is needed.

THz emission characteristics from p/n junctions with metal lines under non-bias conditions for LSI failure analysis.

We have investigated the characteristics of THz emissions from p/n junctions with metallic lines under non-bias conditions. The waveforms, spectra, and polarizations depend on the length and shape of the lines. This indicates that the transient photocurrents from p/n junctions flow into the metallic lines that emit THz waves and act as an antenna. We have successfully demonstrated the non-contact inspection of open defects of multi-layered interconnects in a large-scale integrated circuit using the laser THz emission microscope (LTEM). The p/n junctions connected to the defective interconnects can be identified by comparing the LTEM images of normal and defective circuits.

3D analysis of benign positional nystagmus due to cupulolithiasis in posterior semicircular canal.

CONCLUSIONS: The characteristic of both the vertical-torsional positional nystagmus with long time constant and its disappearance at the neutral head position could diagnose cupulolithiasis in posterior semicircular canal (PSCC) in the eight patients with the PSCC type of benign paroxysmal positional vertigo (P-BPPV). OBJECTIVE: The aim of the study was to diagnose cupulolithiasis in patients with P-BPPV. PATIENTS AND METHODS: We used three-dimensional rotation axis analysis of nystagmus of the vertical-torsional positional nystagmus in 111 patients with P-BPPV and evaluated its time constant. We then examined whether the vertical-torsional positional nystagmus with long time constant disappeared at the neutral head position where the axis of the heavy cupula of the affected PSCC is aligned with gravity. RESULTS: The first parameter showed a wide variation that could be divided into two groups: one lasting more than 40 s in 8 patients and another below 20 s in 103 patients. Since the time constant of the positional nystagmus induced by cupulolithiasis was much longer than that induced by canalolithiasis, this finding suggests that cupulolithiasis in the PSCC induced the vertical-torsional positional nystagmus with a long time constant in the group of eight patients. The vertical-torsional positional nystagmus disappeared in these patients at the neutral head position, where the axis of the cupula of affected PSCC aligned with gravity.