Electric-field-driven Non-volatile Multi-state Switching of Individual Skyrmions in a Multiferroic Heterostructure

Electrical manipulation of skyrmions attracts considerable attention for its rich physics and promising applications. To date, such a manipulation is realized mainly via spin-polarized current based on spin-transfer torque or spin-orbital torque effect. However, this scheme is energy-consuming and may produce massive Joule heating. To reduce energy dissipation and risk of heightened temperatures of skyrmion-based devices, an effective solution is to use electric field instead of current as stimulus. Here, we realize an electric-field manipulation of skyrmions in a nanostructured ferromagnetic/ferroelectrical heterostructure at room temperature via an inverse magneto-mechanical effect. Intriguingly, such a manipulation is non-volatile and exhibits a multi-state feature. Numerical simulations indicate that the electric-field manipulation of skyrmions originates from strain-mediated modification of effective magnetic anisotropy and Dzyaloshinskii-Moriya interaction. Our results open a direction for constructing low-energy-dissipation, non-volatile, and multi-state skyrmion-based spintronic devices.Comment: Accepted by Nature Communications 11, 3577 (2020

Impairment of cognitive function and synaptic plasticity associated with alteration of information flow in theta and gamma oscillations in melamine-treated rats.

Changes of neural oscillations at a variety of physiological rhythms are effectively associated with cognitive performance. The present study investigated whether the directional indices of neural information flow (NIF) could be used to symbolize the synaptic plasticity impairment in hippocampal CA3-CA1 network in a rat model of melamine. Male Wistar rats were employed while melamine was administered at a dose of 300 mg/kg/day for 4 weeks. Behavior was measured by the Morris water maze(MWM)test. Local field potentials (LFPs) were recorded before long-term potentiation (LTP) induction. Generalized partial directed coherence (gPDC) and phase-amplitude coupling conditional mutual information (PAC_CMI) were used to measure the unidirectional indices in both theta and low gamma oscillations (LG, ~ 30-50 Hz). Our results showed that melamine induced the cognition deficits consistent with the reduced LTP in CA1 area. Phase locking values (PLVs) showed that the synchronization between CA3 and CA1 in both theta and LG rhythms was reduced by melamine. In both theta and LG rhythms, unidirectional indices were significantly decreased in melamine treated rats while a similar variation trend was observed in LTP reduction, implying that the effects of melamine on cognitive impairment were possibly mediated via profound alterations of NIF on CA3-CA1 pathway in hippocampus. The results suggested that LFPs activities at these rhythms were most likely involved in determining the alterations of information flow in the hippocampal CA3-CA1 network, which might be associated with the alteration of synaptic transmission to some extent

The results of MWM.

<p>The results of MWM.</p

Lateral root elongation in maize is related to auxin synthesis and transportation mediated by N metabolism under a mixed NO3− and NH4+ supply

A mixed nitrate (NO3−) and ammonium (NH4+) supply can promote root growth in maize (Zea mays), however, the changes in root morphology and the related physiological mechanism under different N forms are still unclear. Here, maize seedlings were grown hydroponically with three N supplied in three different forms (NO3− only, 75/25 NO3−/NH4+ and NH4+ only). Compared with sole NO3− or NH4+, the mixed N supply increased the total root length of maize but did not affect the number of axial roots. The main reason was the increased total lateral root length, while the average lateral root (LR) length in each axle was only slightly increased. In addition, the average LR density of 2nd whorl crown root under mixed N was also increased. Compared with sole nitrate, mixed N could improve the N metabolism of roots (such as the N influx rate, nitrate reductase (NR) and glutamine synthase (GS)enzyme activities and total amino content of the roots). Experiments with exogenously added NR and GS inhibitors suggested that the increase in the average LR length under mixed N was related to the process of N assimilation, and whether the NR mediated NO synthesis participates in this process needs further exploration. Meanwhile, an investigation of the changes in root-shoot ratio and carbon (C) concentration showed that C transportation from shoots to roots may not be the key factor in mediating lateral root elongation, and the changes in the sugar concentration in roots further proved this conclusion. Furthermore, the synthesis and transportation of auxin in axial roots may play a key role in lateral root elongation, in which the expression of ZmPIN1B and ZmPIN9 may be involved in this pathway. This study preliminarily clarified the changes in root morphology and explored the possible physiological mechanism under a mixed N supply in maize, which may provide some theoretical basis for the cultivation of crop varieties with high N efficiency

The representative LFPs and the corresponding power spectra in CA3 and CA1 regions.

<p>A. Left: The original traces of LFPs in CA3 region from a Con rat (red line) and a Mel rat (blue line). Right: The corresponding power spectra distributing from 1 Hz to 50 Hz of the two rats. Arrows present some theta and gamma rhythms. The inserts show statistical results of relative power in theta and gamma rhythms in two groups. B. Left: The original traces of LFPs in CA1 region from a Con rat (red line) and a Mel rat (blue line). Right: The corresponding power spectrum distributing from 1 Hz to 50 Hz of the two rats. Arrows present some theta and gamma rhythms. The inserts show statistical results of relative power in theta and gamma rhythms in two groups. **p<0.01 comparison between Mel group and Con group.</p

MI analysis in CA3-CA1 network in Con and Mel groups.

<p>A & B. The modulation index as a function of analytic amplitude (30 to 70 Hz) and phase (1 to 20 Hz) in CA3, CA3-CA1 and CA1 in both Con and Mel groups. The higher MI value the stronger cross frequency coupling. C. Statistical MI data of phase-amplitude coupling between theta and gamma rhythms in hippocampal CA3-CA1 network. *P<0.05 for comparison between Con group and Mel group. D. Scatter plot of CA3 MI data vs. CA3-CA1 MI data for all normal and melamine-treated rats. E. Scatter plot of CA3-CA1 MI data vs. CA1 MI data for all normal and melamine-treated rats.</p

EMD-based PLV analysis between CA3 and CA1 in both Con group and Mel group.

<p>A. Examples of LFP-EMD in CA1 obtained from a normal rat. The first column illustrates the raw signals and IMFs and the second column shows the corresponding power spectra. B. The example of instantaneous phases of IMF4 (red) and band-filtered within 4 to 8 Hz (blue) signal. C. The EMD-based PLVs between CA3 and CA1 are significantly decreased in IMF4 and IMF1 in Mel group. Data represent mean ± SEM. *p<0.05 and **p<0.01 comparison between Mel group and Con group.</p

The LTP test in CA3-CA1 pathway.

<p>A. Low-frequency stimulation of Schaffer collaterals region for 20 min as the base line. The fEPSPs slope is plotted as a percentage change against the baseline before high-frequency titanic stimulation (HFS) indicated by arrows. Inset: reprehensive fEPSPs in Con group (left) and Mel group (right). B. Statistical results of fEPSPs in both Con group and Mel group. ***P<0.001 for comparison between Con group and Mel group.</p

Transcriptome raw data from maize (Zhengdan958) is uploaded to SRA database, SRA accession: PRJNA506798.

Transcriptome raw data from maize (Zhengdan958) is uploaded to SRA database, SRA accession: PRJNA506798

Metabolites in the shoot and root identified by LC-MS under sole nitrate, 75/25 nitrate and ammonium ratio supply, and sole ammonium supply in 12d for maize (Zhengdan 958) seedlings in hydroponic condition.

Metabolites in the shoot and root identified by LC-MS under sole nitrate, 75/25 nitrate and ammonium ratio supply, and sole ammonium supply in 12d for maize (Zhengdan 958) seedlings in hydroponic condition. Using the R (V3.3.2) XCMS package to identify peaks identification, peaks filtration, peaks alignment. In among, the main parameters are bw=5, ppm=15, peakwidth=c(10,120), mzwid=0.015, mzdiff=0.01, method=”centWave”. Obtain a data matrix including information such as“mass to charge ration, m/z”, retention time and intensity. In among, positive ion mode obtains 16068 precursor molecules and negative ion mode obtains 5259 precursor molecules for each N forms. The data was exported to excel for subsequent analysis. SCK, ST1 and ST2 indicate the metabolites in the shoot of sole nitrate supply, mixed N supply and sole ammonium supply in 12d, respectively. RCK, RT1 and RT2 indicate the metabolites in the root of sole nitrate supply, mixed N supply and sole ammonium supply in 12d, respectively