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Rapid detection of a threat or its symbol (e.g., fearful face), whether visible or invisible, is critical for human survival. This function is suggested to be enabled by a subcortical pathway to the amygdala independent of the cortex. However, conclusive electrophysiological evidence in humans is scarce. Here, we explored whether the amygdala can rapidly encode invisible fearful faces. We recorded intracranial electroencephalogram (iEEG) responses in the human (both sexes) amygdala to faces with fearful, happy, and neutral emotions rendered invisible by backward masking. We found that a short-latency intracranial event-related potential (iERP) in the amygdala, beginning 88 ms post-stimulus onset, was preferentially evoked by invisible fearful faces relative to invisible happy or neutral faces. The rapid iERP exhibited selectivity to the low spatial frequency (LSF) component of the fearful faces. Time-frequency iEEG analyses further identified a rapid amygdala response preferentially for LSF fearful faces at the low γ frequency band, beginning 45 ms post-stimulus onset. In contrast, these rapid responses to invisible fearful faces were absent in cortical regions, including early visual areas, the fusiform gyrus, and the parahippocampal gyrus. These findings provide direct evidence for the existence of a subcortical pathway specific for rapid fear detection in the amygdala and demonstrate that the subcortical pathway can function without conscious awareness and under minimal influence from cortical areas.SIGNIFICANCE STATEMENT:Automatic detection of biologically relevant stimuli, such as threats or dangers, has remarkable survival value. Here we provide direct intracranial electrophysiological evidence that the human amygdala preferentially responds to fearful faces at a rapid speed, despite that the faces are invisible. This rapid, fear-selective response is restricted to faces containing low spatial frequency information transmitted by magnocellular neurons and does not appear in cortical regions. These results support the existence of a rapid subcortical pathway independent of cortical pathways to the human amygdala.

Abstract-Single-loop current control is an attractive scheme for the LCL-type grid-connected inverter due to its simplicity and low cost. However, conventional single-loop control schemes, which command either the inverter current or the grid current, are subject to the specific resonance frequency regions. The weighted average current control, which splits the filter capacitor into two parts (in form of an LCCL filter) and commands the current flowing between these two parts, is independent of the resonance frequency, but on the other hand, it is limited by the poor sensitivity to the grid impedance variation and weak stability in the grid current. These limitations are comprehensively explained in this paper and then addressed by identifying that the single-loop weighted average current control is equivalent to the dual-loop grid current control with an inherent capacitor current active damping. By tuning the capacitor split proportion as a second degree of freedom, an optimal damping performance that is robust to the grid impedance variation can be naturally achieved using only the inherent damping. Thus, no extra damping is required, and the single-loop structure with only one current sensing turns to be adequate. Moreover, for convenience of practical implementation, an improved LCCL filter configuration is proposed to allow the use of two equal nominal capacitances for the split capacitors. Finally, experiments are performed to verify the effectiveness of the proposed method.

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In this work, different contents of CNTs were introduced into an immiscible poly(L-lactide)/ethylene-covinyl acetate (PLLA/EVA) blend that exhibited a sea-island structure to further demonstrate the toughening probability of CNTs on the immiscible polymer blends. The fracture toughness was evaluated through impact measurements. The impact-fractured surface morphologies as well as the morphological changes of the blend induced by adding CNTs were characterized using scanning electron microscope. Furthermore, rheological properties and glass transition behaviors of samples were comparatively investigated to better understand the toughening mechanisms. The results demonstrated that although the presence of CNTs resulted in the formation of EVA particles with irregular shape and simultaneously increased diameters and matrix ligament thickness, which were usually thought to be unfavorable for the improvement of fracture toughness according to the Wu's toughening mechanism, the blend composites still exhibited largely enhanced fracture toughness compared with the binary blend, and the impact strength increased gradually with increasing content of CNTs. The plastic deformation ability of PLLA matrix during the fracture process was greatly enhanced, especially when CNTs formed the physical network structure. Further results demonstrated that the glass transition behavior of EVA particles was greatly influenced by CNTs. Then, the toughening mechanism was proposed on the basis of the morphological changes of EVA particles, the formation of CNT physical network structure and the glass transition behavior of EVA. The other mechanical properties were also measured and analyzed. This work further demonstrated the toughening effect of CNTs on the immiscible polymer blends, and the methodology can be widely adopted in industry application.

Through improving the interaction and forming an occlusion structure, significantly improved ductility is achieved by adding PMMA into a PLLA/PVDF blend.

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