The Clinical Landscape of Circulating Tumor DNA in Gastrointestinal Malignancies

Technologies for genomic analyses have revealed more details in cancer biology and have changed standard treatments for cancer, including the introduction of targeted gene-specific therapy. Currently, liquid biopsies are increasingly being utilized in clinical trials and research settings to analyze circulating tumor DNA (ctDNA) from peripheral blood. Several studies have shown the potential of ctDNA in the screening, prognostication, molecular profiling, and monitoring of gastrointestinal malignancies. Although limitations continue to exist in the use of ctDNA, such as method standardization, the sensitivity, concordance with tumor tissue, and regulatory issues, this field offers promising benefits for cancer treatment. A deeper understanding of tumor biology via ctDNA analyses and ctDNA-guided clinical trials will lead to the increasing use of ctDNA in clinical practice in the near future; this development will result in the improvement of outcomes among patients with gastrointestinal malignancies

Magnetoelectric switching of perpendicular exchange bias in Pt/Co/α-Cr₂O₃/Pt stacked films

We report the realization of magnetoelectric switching of the perpendicular exchange bias in Pt/Co/α-Cr₂O₃/Pt stacked films. The perpendicular exchange bias was switched isothermally by the simultaneous application of magnetic and electric fields. The threshold electric field required to switch the perpendicular exchange bias was found to be inversely proportional to the magnetic field, which confirmed the magnetoelectric mechanism of the process. The observed temperature dependence of the threshold electric field suggested that the energy barrier of the antiferromagnetic spin reversal was significantly lower than that assuming the coherent rotation. Pulse voltage measurements indicated that the antiferromagnetic domain propagation dominates the switching process. These results suggest an analogy of the electric-field-induced magnetization with a simple ferromagnet.Kentaro Toyoki, Yu Shiratsuchi, Atsushi Kobane, Chiharu Mitsumata, Yoshinori Kotani, Tetsuya Nakamura, and Ryoichi Nakatani, Appl. Phys. Lett. 106, 162404 (2015); https://doi.org/10.1063/1.4918940

Robust magnetic domain of Pt/Co/Au/Cr₂O₃/Pt stacked films with a perpendicular exchange bias

Magnetic domain pattern and magnetic domain wall motion are particularly important to understand the magnetization process. Here, we investigated the magnetization process of perpendicularly exchange-biased Pt/Co/Au/Cr₂O₃/Pt stacked films based on observations of the magnetic domain. In particular, in contrast to previous studies which use fully exchange-biased state, we used the bi-exchange-biased state. We found that the magnetic domain pattern at the remanent state was robust against magnetic-field cycling, which is relevant to the absence of the training effect. The magnetization process was followed by domain wall propagation in the increasing branch of the magnetization curve. In the decreasing branch, both nucleation of the reversed domain and domain wall propagation were involved. The former was accompanied by latency, suggesting that thermal activation played a significant role in the nucleation of the reversed domain.Yu Shiratsuchi, Saori Yoshida, Hiroaki Yoshida, Yoshinori Kotani, Kentaro Toyoki, Ryoichi Nakatani, Chiharu Mitsumata, and Tetsuya Nakamura, Journal of Applied Physics 127, 153902 (2020); https://doi.org/10.1063/5.0002240

Antiferromagnetic domain wall creep driven by magnetoelectric effect

We observed the magnetoelectric induced domain wall propagation in a Pt/Co/Au/Cr₂O₃/Pt stacked thin film based on magnetic domain observations using scanning soft X-ray magnetic circular dichroism microscopy. The antiferromagnetic (Cr₂O₃) domain wall velocity was estimated by a quasi-static approach using a pulsed voltage. At a pulse voltage amplitude of -12 V, corresponding to an electric field of -8.0 × 10²kV/cm, the domain wall velocity was very low, at 0.3 m/s. The domain wall velocity increased with increasing voltage amplitude, reaching 22 m/s at -20 V (-1.3 × 10³kV/cm). The change in the domain wall velocity with the applied voltage amplitude indicates the creep motion of the domain wall. Using a phenomenological model, we estimated the domain wall depinning energy, and found that the bulk and interface terms of the magnetic anisotropy affect the effective magnetic field to the same degree, suggesting that the magnetic domain wall motion may be controllable by the antiferromagnetic layer thickness.Yu Shiratsuchi, Hiroaki Yoshida, Yoshinori Kotani, Kentaro Toyoki, Thi Van Anh Nguyen, Tetsuya Nakamura, and Ryoichi Nakatani, APL Materials 6, 121104 (2018); https://doi.org/10.1063/1.5053928

Observation of the magnetoelectric reversal process of the antiferromagnetic domain

We investigated the switching process of the perpendicular exchange bias, which is driven by the magnetoelectric effect, by conducting magnetic domain observations using scanning soft X-ray magnetic circular dichroism microscopy. Isothermal and simultaneous application of magnetic and electric fields switches the perpendicular exchange bias polarity. The switching process proceeds by the nucleation and growth of reversed domains. The correspondence among the ferromagnetic/antiferromagnetic domains and exchange bias polarity indicates that interfacial antiferromagnetic spin/domain reversal is responsible for the magnetoelectric switching of the perpendicular exchange bias polarity.Yu Shiratsuchi, Shunsuke Watanabe, Hiroaki Yoshida, Noriaki Kishida, Ryoichi Nakatani, Yoshinori Kotani, Kentaro Toyoki, and Tetsuya Nakamura, Appl. Phys. Lett. 113, 242404 (2018); https://doi.org/10.1063/1.5053925

How Sensitive Are Our Eyes to Text Difficulty? : Application of Schema Fixation Curves to Japanese Text

This paper discusses the applicability of Schema Fixation Curves to the detection of changes in the behavior of eye movements in accordance with the readability of text. If the eyes are to respond to the degree of difficulty of the given task, we may say that the eyes are an output device of our cognitive activities. Our previous research led us to the notation of Schema Fixation and Schema Fixation Curves, a technique with which graphically analyze the cognitive load the subjects bear when they read texts. The results of our experiments based on this technique show that the eye movement records are a good clue to the detection of text difficulty or readability of texts. Conventionally, computer-calculated readability indices have been used to predict text readability, but the precision of the prediction may not necessarily be so high. This is because most of these indices use syntactic elements of text such as average sentence length and word length. Difficulty of texts arises from a variety of factors, such as the reader\u27s background knowledge of the passage, the range of vocabulary used in the text, syntactic and semantic ambiguities, etc. In this experiment, we used the Japanese language in order to focus on syntactic effect on readability. Japanese allows much freer syntactic structure than present-day English. For example, the natural, normal, and unstressed word order of English (from amongst the six logical possibilities, SVO, SOV, VSO, VOS, OSV, OVS) is SVO while various combinations are both possible and natural in Japanese. We changed the syntactic order of words in sentences and presented them to the subjects in order to examine the recorded eye movements, and found that different orders produced different levels of readability

Effect of Alcohol on the Cerebral Function Observed in Eye Movements during Tracking a Visual Target

In this study we especially associate eye movements in tracking a visual target with dysfunctions caused by symptoms of intoxication in both frontal and parietal lobes. Visual targets used in this study were of apparent movements and of periodical triangular wave form on display. Two moving patterns of a visual target were provided for the experiment One is designed so as to demand a perceptual task, and another for a cognitive task. Each subject carried out the tracking process under three conditions: of no-alcohol, of low and high concentrations. In the case of an intoxicated subject, the latency and the duration of saccade are more prolonged, the mean velocity is reduced, and the amplitude is enlarged, especially in the case of tracking a visual target with a moving pattern which requires a cognitive task. There is no difference between the two tasks on the neural network for setting up necessary parameters to start off a saccade, but the quality of eye tracking is definitely affected by high quantities of alcohol. This corroborates Terao\u27s hypothesis that the neural network can compensate for the damage only at one area in the brain, but does not cooperate well if damage exists in multiple areas of the brain

Simultaneous achievement of high perpendicular exchange bias and low coercivity by controlling ferromagnetic/antiferromagnetic interfacial magnetic anisotropy

This study investigates the influence of Pt and Au spacer layers on the perpendicular exchange bias field and coercivity of Pt/Co/(Pt or Au)/Cr₂O₃/Pt films. When using a Pt-spacer, the perpendicular exchange bias was highly degraded to less than 0.1 erg/cm², which was about half that of the Au-spacer system. The Au spacer also suppressed the enhancement in coercivity that usually occurs at around room temperature when using Pt. It is suggested that this difference in exchange bias field is due to in-plane interfacial magnetic anisotropy at the Pt/Cr₂O₃ interface, which cants the interfacial Cr spin from the surface normal and results in degradation in the perpendicular exchange bias.Yu Shiratsuchi, Wataru Kuroda, Thi Van Anh Nguyen, Yoshinori Kotani, Kentaro Toyoki, Tetsuya Nakamura, Motohiro Suzuki, Kohji Nakamura, and Ryoichi Nakatani, Journal of Applied Physics 121, 073902 (2017); https://doi.org/10.1063/1.4976568