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Bilayer graphene (BLG) is intriguing for its unique properties and potential applications in electronics, photonics, and mechanics. However, the chemical vapor deposition synthesis of large-area high-quality bilayer graphene on Cu is suffering from a low growth rate and limited bilayer coverage. Herein, we demonstrate the fast synthesis of meter-sized bilayer graphene film on commercial polycrystalline Cu foils by introducing trace CO2 during high-temperature growth. Continuous bilayer graphene with a high ratio of AB-stacking structure can be obtained within 20 min, which exhibits enhanced mechanical strength, uniform transmittance, and low sheet resistance in large area. Moreover, 96 and 100% AB-stacking structures were achieved in bilayer graphene grown on single-crystal Cu(111) foil and ultraflat single-crystal Cu(111)/sapphire substrates, respectively. The AB-stacking bilayer graphene exhibits tunable bandgap and performs well in photodetection. This work provides important insights into the growth mechanism and the mass production of large-area high-quality BLG on Cu.

$\mathrm{Fe_{n=4,5}GeTe_2}$ exhibits quasi-two-dimensional properties as a promising candidate for a near-room-temperature ferromagnet, which has attracted great interest. In this work, we notice that the crystal lattice of $\mathrm{Fe_{n=4,5}GeTe_2}$ can be approximately regarded as being stacked by three bipartite crystal lattices. By combining the model Hamiltonians of bipartite crystal lattices and first-principles calculations, we investigate the electronic structure and the magnetism of $\mathrm{Fe_{n=4,5}GeTe_2}$. We conclude that flat bands near the Fermi level originate from the bipartite crystal lattices and that these flat bands are expected to lead to the itinerant ferromagnetism in $\mathrm{Fe_{n=4,5}GeTe_2}$. Interestingly, we also find that the magnetic moment of the Fe5 atom in $\mathrm{Fe_5 Ge Te_2}$ is distinct from the other Fe atoms and is sensitive to the Coulomb interaction $U$ and external pressure. These findings may be helpful to understand the exotic magnetic behavior of $\mathrm{Fe_{n=4,5} Ge Te_2}$., Comment: 9 pages, 8 figures

Federated learning (FL) enables multiple clients to collaboratively train deep learning models while considering sensitive local datasets' privacy. However, adversaries can manipulate datasets and upload models by injecting triggers for federated backdoor attacks (FBA). Existing defense strategies against FBA consider specific and limited attacker models, and a sufficient amount of noise to be injected only mitigates rather than eliminates FBA. To address these deficiencies, we introduce a Flexible Federated Backdoor Defense Framework (Fedward) to ensure the elimination of adversarial backdoors. We decompose FBA into various attacks, and design amplified magnitude sparsification (AmGrad) and adaptive OPTICS clustering (AutoOPTICS) to address each attack. Meanwhile, Fedward uses the adaptive clipping method by regarding the number of samples in the benign group as constraints on the boundary. This ensures that Fedward can maintain the performance for the Non-IID scenario. We conduct experimental evaluations over three benchmark datasets and thoroughly compare them to state-of-the-art studies. The results demonstrate the promising defense performance from Fedward, moderately improved by 33% $\sim$ 75 in clustering defense methods, and 96.98%, 90.74%, and 89.8% for Non-IID to the utmost extent for the average FBA success rate over MNIST, FMNIST, and CIFAR10, respectively., Comment: Accepted by IEEE ICME 2023

The building block of in-memory computing with spintronic devices is mainly based on the magnetic tunnel junction with perpendicular interfacial anisotropy (p-MTJ). The resulting asymmetric write and read-out operations impose challenges in downscaling and direct cascadability of p-MTJ devices. Here, we propose that a new symmetric write and read-out mechanism can be realized in perpendicular-anisotropy spin-orbit (PASO) quantum materials based on Fe3GeTe2 and WTe2. We demonstrate that field-free and deterministic reversal of the perpendicular magnetization can be achieved by employing unconventional charge to z-spin conversion. The resulting magnetic state can be readily probed with its intrinsic inverse process, i.e., z-spin to charge conversion. Using the PASO quantum material as a fundamental building block, we implement the functionally complete set of logic-in-memory operations and a more complex nonvolatile half-adder logic function. Our work highlights the potential of PASO quantum materials for the development of scalable energy-efficient and ultrafast spintronic computing., Accepted by Science Advances

Machine learning promotes the continuous development of signal processing in various fields, including network traffic monitoring, EEG classification, face identification, and many more. However, massive user data collected for training deep learning models raises privacy concerns and increases the difficulty of manually adjusting the network structure. To address these issues, we propose a privacy-preserving neural architecture search (PP-NAS) framework based on secure multi-party computation to protect users' data and the model's parameters/hyper-parameters. PP-NAS outsources the NAS task to two non-colluding cloud servers for making full advantage of mixed protocols design. Complement to the existing PP machine learning frameworks, we redesign the secure ReLU and Max-pooling garbled circuits for significantly better efficiency ($3 \sim 436$ times speed-up). We develop a new alternative to approximate the Softmax function over secret shares, which bypasses the limitation of approximating exponential operations in Softmax while improving accuracy. Extensive analyses and experiments demonstrate PP-NAS's superiority in security, efficiency, and accuracy., Accepted by IEEE ISCC 2022

This study aimed to investigate the probiotic potential of lactic acid bacteria (LAB) strains isolated from De'ang pickled tea, a traditional food consumed by the De'ang nationality of Yunnan, China. Twenty-six LAB strains isolated from De'ang pickled tea were subjected to identification based on 16S rRNA gene sequence analysis. Twenty-four belonged to Lactobacillus plantarum, one belonged to Enterococcus casseliflavus, and one belonged to Lactobacillus acidophilus. Eighteen out of 26 LAB strains which showed a higher capability to tolerate simulated gastrointestinal juices were chosen to further evaluate their probiotic properties. Varied adhesive abilities and auto-aggregative capacities of selected LAB strains were dependent on species and even strains. All tested LAB strains were resistant to kanamycin, streptomycin, gentamycin, and vancomycin and sensitive to tetracycline and chloramphenicol. Ten out of the 18 strains are resistant to ampicillin, and the remaining strains are sensitive to ampicillin; 4 out of the 18 strains showed resistance to erythromycin. Compared to reference strain Lactobacillus rhamnosus strain GG, these LAB strains had a greater or comparative antimicrobial activity against Salmonella typhimurium or Escherichia coli. In contrast, eight out of the 18 strains suppressed growth of Shigella flexneri. Two L. plantarum strains, ST and STDA10, not only exhibited good probiotic properties but also showed a good ability of scavenging DPPH and ABTS+. This study suggests that L. plantarum ST and STDA10 could be used as potential probiotics applied in functional foods.

A new adsorbent cinchoine loaded resin (CCR) was prepared with cinchonine loaded on cation exchange resin. ICP-AES was used to study CCR's adsorption properties to Mo(VI) and V(VI). It was found that the adsorption rate was more than 90% in pH (3∼6); and 0.6 mol/L HCl could elute Mo and V quantitatively from CCR. The static adsorption capacities are 8.3 mg/g and 9.9 mg/g for Mo and V, respectively. The interference of some ions were also investigated. The proposed method has been applied to determine Mo and V in standard reference samples with s8543172 results.

A 6% (m/v) slurry of polytetrafluoroethylene (PTFE) in 4% HNO 3 was used as a chemical modifier for direct determination of trace cadmium in solid biological samples by slurry sampling electrothermal atomic absorption spectrometry (ETAAS). Because of the presence of PTFE, an ashing temperature of 800°C was attained with no loss of cadmium within 50 s. In this case, the main coexisting components in solid biological samples did not interfere with the cadmium determination. The process of cadmium vaporization and atomization with PTFE/HNO 3 is discussed. Under the optimum conditions, the calibration graph was linear from 1 to 10 ng ml −1 with relative standard deviations of 1.9% for 10 ng ml −1 and 7.8% for 1 ng ml −1 Cd ( n =5). The detection limit and characteristic mass were 0.12 and 0.85 pg of Cd, respectively. The contents of cadmium in some solid biological reference materials were determined by the proposed method with aqueous calibration, and no chemical pretreatment was necessary. The determined values were in good agreement with the certified values.

A novel method for the direct determination of trace Co and Ni in SiO 2 powder by slurry sampling ETAAS was developed. At high temperature of the graphite furnace, a PTFE slurry in HNO 3 was used as a fluorinating reagent to convert the silica matrix into high-volatility fluoride, which was subsequently evaporated by selective vaporization prior to the atomization of analytes. In this case, the severe interference of the matrix on the vaporization and atomization of analytes was reduced significantly, and chemical attack of the excess of silica matrix on the graphite tube was also minimized. The proposed method was successfully applied to the determination of trace Co and Ni in SiO 2 powder with aqueous calibration and minimum chemical pre-treatment. For the direct analysis of high purity SiO 2 powder, the detect limits of Co and Ni were 18.8 and 35.0 ng g –1 , respectively. The analysis of NIES CRM2 Pond Sediment confirmed the reliability of the approach.

The chemical modification of polytetrafluoroethylene (PTFE) slurry in electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) and in electrothermal atomic absorption spectrometry (ETAAS) was investigated and compared systematically. For both cases, the graphite furnace can be used as a chemical reactor in which the fluorinating reagent PTFE can convert the oxides of analytes into their volatile fluorides at high temperature. However, different influences resulting from fluorination in ETV-ICP-AES and ETAAS were observed owing to different functions of the graphite furnace in the two techniques. The formation of fluoride enhanced the emission signals of the refractory elements Mo, Cr and Yb significantly in ETV-ICP-AES, but only improved the sensitivity of Cr in ETAAS. In both ETV-ICP-AES and ETAAS, the addition of PTFE increased the maximum ashing temperature of volatile analyte cadmium. Moreover, PTFE can obviously reduce or remove the matrix interference and particle size effects of solid samples; this advantage is a benefit in the analysis of complicated samples, especially for the direct analysis of solid samples.

Using poly(tetrafluoroethylene) (PTFE) slurry as a chemical modifier, the process of vaporization and atomization of Cr in a graphite furnace for electrothermal atomic absorption spectrometry was investigated. It was shown that PTFE could react with Cr to form chromium fluoride and suppressed the formation of refractory metal carbides. The addition of PTFE clearly enhanced the analytical sensitivity of Cr and significantly reduced the interferences of a 103–104-fold excess of matrix elements. The detection limit (DL) and characteristic mass (mch) of the conventional method are 9.6 and 24.5 pg (Cr), respectively, whereas with PTFE the best DL and mch values of the proposed method are 2.73 and 10.0 pg (Cr), respectively. The calibration graph is linear in the range 5–80 ng ml–1 (Cr) with RSDs of 1.1–6.6%. The method was applied to the determination of trace amounts of Cr in surface water and copper chloride samples. The Cr recoveries from the samples were 96.4–103.7%.