X-ray study of ferroic octupole order producing anomalous Hall effect

放射光でついに見えた磁気オクタポール --熱を電気に変える新たな担い手--. 京都大学プレスリリース. 2021-09-27.Recently found anomalous Hall, Nernst, magnetooptical Kerr, and spin Hall effects in the antiferromagnets Mn₃X (X = Sn, Ge) are attracting much attention for spintronics and energy harvesting. Since these materials are antiferromagnets, the origin of these functionalities is expected to be different from that of conventional ferromagnets. Here, we report the observation of ferroic order of magnetic octupole in Mn₃Sn by X-ray magnetic circular dichroism, which is only predicted theoretically so far. The observed signals are clearly decoupled with the behaviors of uniform magnetization, indicating that the present X-ray magnetic circular dichroism is not arising from the conventional magnetization. We have found that the appearance of this anomalous signal coincides with the time reversal symmetry broken cluster magnetic octupole order. Our study demonstrates that the exotic material functionalities are closely related to the multipole order, which can produce unconventional cross correlation functionalities

Gustatory Imagery Reveals Functional Connectivity from the Prefrontal to Insular Cortices Traced with Magnetoencephalography

Our experience and prejudice concerning food play an important role in modulating gustatory information processing; gustatory memory stored in the central nervous system influences gustatory information arising from the peripheral nervous system. We have elucidated the mechanism of the 'top-down" modulation of taste perception in humans using functional magnetic resonance imaging (fMRI) and demonstrated that gustatory imagery is mediated by the prefrontal (PFC) and insular cortices (IC). However, the temporal order of activation of these brain regions during gustatory imagery is still an open issue. To explore the source of "top-down" signals during gustatory imagery tasks, we analyzed the temporal activation patterns of activated regions in the cerebral cortex using another non-invasive brain imaging technique, magnetoencephalography (MEG). Gustatory imagery tasks were presented by words (Letter G-V) or pictures (Picture G-V) of foods/beverages, and participants were requested to recall their taste. In the Letter G-V session, 7/9 (77.8%) participants showed activation in the IC with a latency of 401.7 +/- 34.7 ms (n = 7) from the onset of word exhibition. In 5/7 (71.4%) participants who exhibited IC activation, the PFC was activated prior to the IC at a latency of 315.2 +/- 56.5 ms (n = 5), which was significantly shorter than the latency to the IC activation. In the Picture G-V session, the IC was activated in 6/9 (66.7%) participants, and only 1/9 (11.1%) participants showed activation in the PFC. There was no significant dominance between the right and left IC or PFC during gustatory imagery. These results support those from our previous fMRI study in that the Letter G-V session rather than the Picture G-V session effectively activates the PFC and IC and strengthen the hypothesis that the PFC mediates "top-down" control of retrieving gustatory information from the storage of long-term memories and in turn activates the IC

Reduced responsiveness is an essential feature of chronic fatigue syndrome: A fMRI study

BACKGROUND: Although the neural mechanism of chronic fatigue syndrome has been investigated by a number of researchers, it remains poorly understood. METHODS: Using functional magnetic resonance imaging, we studied brain responsiveness in 6 male chronic fatigue syndrome patients and in 7 age-matched male healthy volunteers. Responsiveness of auditory cortices to transient, short-lived, noise reduction was measured while subjects performed a fatigue-inducing continual visual search task. RESULTS: Responsiveness of the task-dependent brain regions was decreased after the fatigue-inducing task in the normal and chronic fatigue syndrome subjects and the decrement of the responsiveness was equivalent between the 2 groups. In contrast, during the fatigue-inducing period, although responsiveness of auditory cortices remained constant in the normal subjects, it was attenuated in the chronic fatigue syndrome patients. In addition, the rate of this attenuation was positively correlated with the subjective sensation of fatigue as measured using a fatigue visual analogue scale, immediately before the magnetic resonance imaging session. CONCLUSION: Chronic fatigue syndrome may be characterised by attenuation of the responsiveness to stimuli not directly related to the fatigue-inducing task

Evolutionary Game Theory-Based Evaluation of P2P File-Sharing Systems in Heterogeneous Environments

Peer-to-Peer (P2P) file sharing is one of key technologies for achieving attractive P2P multimedia social networking. In P2P file-sharing systems, file availability is improved by cooperative users who cache and share files. Note that file caching carries costs such as storage consumption and processing load. In addition, users have different degrees of cooperativity in file caching and they are in different surrounding environments arising from the topological structure of P2P networks. With evolutionary game theory, this paper evaluates the performance of P2P file sharing systems in such heterogeneous environments. Using micro-macro dynamics, we analyze the impact of the heterogeneity of user selfishness on the file availability and system stability. Further, through simulation experiments with agent-based dynamics, we reveal how other aspects, for example, synchronization among nodes and topological structure, affect the system performance. Both analytical and simulation results show that the environmental heterogeneity contributes to the file availability and system stability

Application of a Persistent Heparin Treatment Inhibits the Malignant Potential of Oral Squamous Carcinoma Cells Induced by Tumor Cell-Derived Exosomes

<div><p>Exosomes are 30–100 nm-sized membranous vesicles, secreted from a variety of cell types into their surrounding extracellular space. Various exosome components including lipids, proteins, and nucleic acids are transferred to recipient cells and affect their function and activity. Numerous studies have showed that tumor cell-derived exosomes play important roles in tumor growth and progression. However, the effect of exosomes released from oral squamous cell carcinoma (OSCC) into the tumor microenvironment remains unclear. In the present study, we isolated exosomes from OSCC cells and investigated the influence of OSCC cell-derived exosomes on the tumor cell behavior associated with tumor development. We demonstrated that OSCC cell-derived exosomes were taken up by OSCC cells themselves and significantly promoted proliferation, migration, and invasion through the activation of the PI3K/Akt, MAPK/ERK, and JNK-1/2 pathways <i>in vitro</i>. These effects of OSCC cell-derived exosomes were obviously attenuated by treatment with PI3K, ERK-1/2, and JNK-1/2 pharmacological inhibitors. Furthermore, the growth rate of tumor xenografts implanted into nude mice was promoted by treatment with OSCC cell-derived exosomes. The uptake of exosomes by OSCC cells and subsequent tumor progression was abrogated in the presence of heparin. Taken together, these data suggest that OSCC cell-derived exosomes might be a novel therapeutic target and the use of heparin to inhibit the uptake of OSCC-derived exosomes by OSCC cells may be useful for treatment.</p></div

Effects of OSCC cell-derived exosomes on the activation of signal transduction proteins.

<p>(A) The phosphorylation of kinases in whole cell lysate from OSC-3 and OSC-4 cells in the presence or absence of 100 μg exosomes was analyzed by Proteome Profiler™ Human Phospho-Kinase Array Kit. The five representative molecules, which were about 50% more hyperphosphorylated in the treated cells than in the control cells are shown in the right panel. (B) Time course of the expression of p-Akt, p-ERK, and p-JNK induced by exosomes in OSCC cells. Cells were exposed to 100 μg exosomes for the indicated periods and total cell lysate was subjected to western blotting analysis.</p

Effects of heparin on OSCC cell-derived exosome-induced tumor growth in xenograft models.

<p>BALB/c nude mice were treated as described in Materials and Methods. Tumor volume of OSC-4 cells xenografted to the back of mice was estimated for 27 days. (A) Tumor size was measured and calculated every 3 days. (B) Tumor weight at euthanasia for control and exosome-treated mice. The values are presented as the mean ± SD; n = 8 for each group. *p < 0.05 against control tumor by Mann-Whitney’s U-test. Hepa means heparin, and Sali means saline.</p

Effects of heparin on cellular internalization of OSCC cell-derived exosomes into OSCC cells.

<p>OSC-4 cells were pretreated with 10 μg/mL heparin for 1 h and then cultured in the presence of 100 μg of PKH26 (red)-labeled exosomes from OSC-4 cells for 1, 4, 8, and 16 h and analyzed by confocal microscopy. Nuclei were stained with DAPI (blue).</p

Effects of OSCC cell-derived exosomes on tumor growth in a xenograft model.

<p>BALB/c nude mice were treated as described in Materials and Methods. Tumor volume of OSC-4 cells xenografted to the back of the mice was estimated for 27 days. (A) Photographs of OSC-4 tumor-bearing mice were taken at euthanasia. (B) Tumor size was measured and calculated every 3 days. (C) Tumor weight at euthanasia for control and exosome-treated mice. The values are presented as the mean ± SD; n = 8 for each group. *p < 0.05 against control tumor by Mann-Whitney’s U-test.</p