Data_Sheet_1_Brain-inspired Predictive Coding Improves the Performance of Machine Challenging Tasks.PDF

Backpropagation has been regarded as the most favorable algorithm for training artificial neural networks. However, it has been criticized for its biological implausibility because its learning mechanism contradicts the human brain. Although backpropagation has achieved super-human performance in various machine learning applications, it often shows limited performance in specific tasks. We collectively referred to such tasks as machine-challenging tasks (MCTs) and aimed to investigate methods to enhance machine learning for MCTs. Specifically, we start with a natural question: Can a learning mechanism that mimics the human brain lead to the improvement of MCT performances? We hypothesized that a learning mechanism replicating the human brain is effective for tasks where machine intelligence is difficult. Multiple experiments corresponding to specific types of MCTs where machine intelligence has room to improve performance were performed using predictive coding, a more biologically plausible learning algorithm than backpropagation. This study regarded incremental learning, long-tailed, and few-shot recognition as representative MCTs. With extensive experiments, we examined the effectiveness of predictive coding that robustly outperformed backpropagation-trained networks for the MCTs. We demonstrated that predictive coding-based incremental learning alleviates the effect of catastrophic forgetting. Next, predictive coding-based learning mitigates the classification bias in long-tailed recognition. Finally, we verified that the network trained with predictive coding could correctly predict corresponding targets with few samples. We analyzed the experimental result by drawing analogies between the properties of predictive coding networks and those of the human brain and discussing the potential of predictive coding networks in general machine learning.</p

Epitaxially Constrained Hexagonal Ferroelectricity and Canted Triangular Spin Order in LuFeO₃ Thin Films

Epitaxially Constrained Hexagonal Ferroelectricity and Canted Triangular Spin Order in LuFeO₃ Thin Film

Plasmonic Nanosnowmen with a Conductive Junction as Highly Tunable Nanoantenna Structures and Sensitive, Quantitative and Multiplexable Surface-Enhanced Raman Scattering Probes

The precise design and synthesis of plasmonic nanostructures allow us to manipulate, enhance, and utilize the optical characteristics of metallic materials. Although many multimeric structures (e.g., dimers) with interparticle nanogap have been heavily studied, the plasmonic nanostructures with a conductive junction have not been well studied mostly because of the lack of the reliable synthetic methods that can reproducibly and precisely generate a large number of the plasmonic nanostructures with a controllable conductive nanojunction. Here, we formed various asymmetric Au–Ag head–body nanosnowman structures with a highly controllable conductive nanojunction and studied their plasmon modes that cover from visible to near-infrared range, electromagnetic field enhancement, and surface-enhanced Raman scattering (SERS) properties. It was shown that change in the plasmonic neck region between Au head and Ag body nanoparticles and symmetry breaking using different sizes and compositions within a structure can readily and controllably introduce various plasmon modes and change the electromagnetic field inside and around a nanosnowman structure. The charge-transfer and capacitive coupling plasmon modes at low frequencies are tunable in the snowman structure, and subtle change in the conductive junction area of the nanosnowman dramatically affects the resulting electromagnetic field and optical signal. The relationships between the electromagnetic field distribution and enhancement in the snowman structure, excitation laser wavelength, and Raman dye were also studied, and it was found that the strongest electromagnetic field was observed in the crevice area on the junction and synthesizing a thinner and sharper neck junction is critical to generate the stronger electromagnetic field in the crevice area and to obtain the charge-transfer mode-based near-infrared signal. We have further shown that highly reproducible SERS signals can be generated from these nanosnowman structures with a linear dependence on particle concentration (5 fM to 1 pM) and the SERS-enhancement factor values of >10⁸ can be obtained with the aid of the resonance effect in SERS. Finally, a wide range of LSPR bands with high tunability along with high structural reproducibility and high synthetic yield make the nanosnowman structures as very good candidates for practically useful multiple-wavelength-compatible, quantitative and sensitive SERS probes, and highly tunable nanoantenna structures

Single-Molecule and Single-Particle-Based Correlation Studies between Localized Surface Plasmons of Dimeric Nanostructures with ∼1 nm Gap and Surface-Enhanced Raman Scattering

Understanding the detailed electromagnetic field distribution inside a plasmonically coupled nanostructure, especially for structures with ∼1 nm plasmonic gap, is the fundamental basis for the control and use of the strong optical properties of plasmonic nanostructures. Using a multistep AFM tip-matching strategy that enables us to gain the optical spectra with the optimal signal-to-noise ratio as well as high reliability in correlation measurement between localized surface plasmon (LSP) and surface-enhanced Raman scattering (SERS), the coupled longitudinal dipolar and high-order multipolar LSPs were detected within a dimeric structure, where a single Raman dye is located via a single-DNA hybridization between two differently sized Au–Ag core–shell particles. On the basis of the characterization of each LSP component, the distinct phase differences, attributed to different quantities of the excited quadrupolar LSPs, between the transverse and longitudinal regimes were observed for the first time. By assessing the relative ratio of dipolar and quadrupolar LSPs, we found that these LSPs of the dimer with ∼1 nm gap were simultaneously excited, and large longitudinal bonding dipolar LSP/longitudinal bonding quadrupolar LSP value is required to generate high SERS signal intensity. Interestingly, a minor population of the examined dimers exhibited strong SERS intensities along not only the dimer axis but also the direction that arises from the interaction between the coupled transverse dipolar and longitudinal bonding quadrupolar LSPs. Overall, our high-precision correlation measurement strategy with a plasmonic heterodimer with ∼1 nm gap allows for the observation of the characteristic spectral features with the optimal signal-to-noise ratio and the subpopulation of plasmonic dimers with a distinct SERS behavior, hidden by a majority of dimer population, and the method and results can be useful in understanding the whole distribution of SERS enhancement factor values and designing plasmonic nanoantenna structures

Four-States Multiferroic Memory Embodied Using Mn-Doped BaTiO₃ Nanorods

Multiferroics that show simultaneous ferroic responses have received a great deal of attention by virtue of their potential for enabling new device paradigms. Here, we demonstrate a high-density four-states multiferroic memory using vertically aligned Mn-doped BaTiO₃ nanorods prepared by applying the dip-pen nanolithography technique. In the present nanorods array, the polarization (<b>P</b>) switching by an external electric field does not influence the magnetization (<b>M</b>) of the nanorod owing to a negligible degree of the <b>P</b>–<b>M</b> cross-coupling. Similarly, the magnetic-field-induced <b>M</b> switching is unaffected by the ferroelectric polarization. On the basis of these, we are able to implement a four-states nonvolatile multiferroic memory, namely, (+P,+M), (+P,–M) ,(−P,+M), and (−P,–M) with the reliability in the <b>P</b> and <b>M</b> switching. Thus, the present work makes an important step toward the practical realization of multistate ferroic memories

An Atomic Insight into the Confusion on the Activity of Fe₃O₄ Nanoparticles as Peroxidase Mimetics and Their Comparison with Horseradish Peroxidase

Although Fe3O4 nanoparticles were early reported to outperform horseradish peroxidase (HRP), recent studies suggested that this material bears a very poor activity instead. Here, we resolve this disagreement by reviewing the definition of descriptors used and provide an atomic view into the origin of Fe3O4 nanoparticles as peroxidase mimetics. The redox between H2O2 and Fe(II) sites on the Fe3O4 surface was identified as the key step to producing OH radicals for the oxidation of colorimetric substrates. This mechanism involving free radicals is distinct from that of HRP oxidizing substrates with a radical retained on its Fe-porphyrin ring. Surprisingly, the distribution and chemical state of Fe species were found to be very different on single- and polycrystalline Fe3O4 nanoparticles with the latter bearing not only a higher Fe(II)/Fe(III) ratio but also a more reactive Fe(II) species at surface grain boundaries. This accounts for the unexpected gap in the catalytic constant (kcat) observed for this material in the literature

Effect of adipose-derived stem cells (ASCs) on airway hyperresponsiveness (AHR) and inflammatory cells in the bronchoalveolar lavage fluid (BALF).

<p>ASCs significantly decreased AHR and the number of total inflammatory cells and eosinophils in asthmatic mice. Treatment with the PGE2 inhibitor or TGF-β neutralizing Ab eliminated the reduction in AHR (A, C) and total cell and eosinophil counts (B, D) induced by ASC treatment. Data are expressed as the mean ± SEM of four independent experiments each performed in triplicate. *,†,§,¶,††,ǁǁ,***,††† <i>p</i><0.001, ‡ <i>p =</i> 0.032, ǁ <i>p</i> = 0.045, ** <i>p</i> = 0.027, ‡‡ <i>p</i> = 0.032, §§ <i>p</i> = 0.005, ¶¶ <i>p</i> = 0.005.</p

Effect of adipose-derived stem cells (ASCs) on cytokine levels in the bronchoalveolar lavage fluid.

<p>IL-4, IL-5, and IL-13 were significantly higher in the OVA group than PBS group. ASC treatment significantly decreased IL-4, IL-5, and IL-13 but increased IL-10 and TGF—β in asthmatic mice. However, the PGE2 inhibitor (A) or TGF-β neutralizing Ab (B) eliminated these immunomodulatory effects of ASCs. Data are expressed as the mean ± SEM of four independent experiments each performed in triplicate. *,§,ǁ,¶,_**, §§§,§§§§, ¶¶¶¶¶ <i>p</i><0.001, †,_******<i>p</i> = 0.007, ‡ <i>p</i> = 0.027, ††,¶¶¶ <i>p</i> = 0.028, ‡‡ <i>p =</i> 0.030, §§ <i>p =</i> 0.010, ǁǁ <i>p</i> = 0.022, ¶¶ <i>p</i> = 0.032, ***,‡‡‡ <i>p</i> = 0.038, ††† <i>p =</i> 0.049, ǁǁǁ,†††† <i>p</i> = 0.003, ****,‡‡‡‡ <i>p =</i> 0.004, ǁǁǁǁǁ <i>p =</i> 0.026, ¶¶¶¶ <i>p</i> = 0.029, ***** <i>p</i> = 0.006, ††††† <i>p</i> = 0.012, ‡‡‡‡‡ <i>p</i> = 0.036, §§§§§ <i>p =</i> 0.042, ǁǁǁǁǁ <i>p =</i> 0.046.</p

The experimental protocol.

<p>(A) Mice were sensitized on days 0, 1, 7, and 8 by intraperitoneal injection of ovalbumin (OVA) and challenged intranasally on days 14, 15, 21, and 22. Purified adipose-derived stem cells (ASCs; 1 × 10⁶) were injected via the tail vein on days 12, 13, 19, and 20. PGE2 and TGF-β were blocked by intraperitoneal injection of a PGE2 inhibitor or anti-TGF-β-Ab on days 13, 14, 15, 16, 17, 20, 21, 22, and 23. (B) The mice were divided into five treatment groups.</p

Effects of adipose-derived stem cells (ASCs) on T cells in the lung draining lymph nodes.

<p>The CD4⁺ T cells were initially gated and the percentage of IFN-γ⁺, IL-4⁺, IL-10⁺, and CD25⁺ Foxp3⁺ T cells subsequently analyzed. When treating asthmatic mice with PGE2 inhibitor (A) or TGF-β neutralizing Abs (B), blocking of PGE2 and TGF-β prevented the increases in Foxp3⁺CD25⁺, IL-10⁺, and IFN-γ⁺ T cell populations and the decrease in the IL-4⁺ T cell population in the OVA+ASC group.</p