分类： 光学 >> 量子光学 提交时间： 2023-02-19
Shuiying Xiang
Yuechun Shi
Xingxing Guo
Yahui Zhang
Hongji Wang
Dianzhuang Zheng
Ziwei Song
Yanan Han
Shuang Gao
Shihao Zhao
Biling Gu
Hailing Wang
Xiaojun Zhu
Lianping Hou
Xiangfei Chen
Wanhua Zheng
Xiaohua Ma
Yue Hao
摘要： Photonic neuromorphic computing has emerged as a promising avenue toward building a low-latency and energy-efficient non-von-Neuman computing system. Photonic spiking neural network (PSNN) exploits brain-like spatiotemporal processing to realize high-performance neuromorphic computing. However, the nonlinear computation of PSNN remains a significant challenging. Here, we proposed and fabricated a photonic spiking neuron chip based on an integrated Fabry-P\'erot laser with a saturable absorber (FP-SA) for the first time. The nonlinear neuron-like dynamics including temporal integration, threshold and spike generation, refractory period, and cascadability were experimentally demonstrated, which offers an indispensable fundamental building block to construct the PSNN hardware. Furthermore, we proposed time-multiplexed spike encoding to realize functional PSNN far beyond the hardware integration scale limit. PSNNs with single/cascaded photonic spiking neurons were experimentally demonstrated to realize hardware-algorithm collaborative computing, showing capability in performing classification tasks with supervised learning algorithm, which paves the way for multi-layer PSNN for solving complex tasks.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Jing Wang
Nannan Han
Zheng-Dong Luo
Mingwen Zhang
Xiaoqing Chen
Yan Liu
Yue Hao
Jianlin Zhao
Xuetao Gan
摘要： Electrical tuning of second-order nonlinearity in optical materials is attractive to strengthen and expand the functionalities of nonlinear optical technologies, though its implementation remains elusive. Here, we report the electrically tunable second-order nonlinearity in atomically thin ReS2 flakes benefiting from their distorted 1T crystal structure and interlayer charge transfer. Enabled by the efficient electrostatic control of the few-atomic-layer ReS2, we show that second harmonic generation (SHG) can be induced in odd-number-layered ReS2 flakes which are centrosymmetric and thus without intrinsic SHG. Moreover, the SHG can be precisely modulated by the electric field, reversibly switching from almost zero to an amplitude more than one order of magnitude stronger than that of the monolayer MoS2. For the even-number-layered ReS2 flakes with the intrinsic SHG, the external electric field could be leveraged to enhance the SHG. We further perform the first-principles calculations which suggest that the modification of in-plane second-order hyperpolarizability by the redistributed interlayer-transferring charges in the distorted 1T crystal structure underlies the electrically tunable SHG in ReS2. With its active SHG tunability while using the facile electrostatic control, our work may further expand the nonlinear optoelectronic functions of two-dimensional materials for developing electrically controllable nonlinear optoelectronic devices.
分类： 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间： 2016-05-08
摘要： Small regulatory RNA (sRNA) that acts by an antisense mechanism is critical for gene regulation at the posttranscriptional level. Recently, an Hfq-dependent sRNA named MicM, which is related to the regulation of outer membrane protein, was verified as a novel antisense sRNA due to its catalytic mode of regulation. Here we propose a simple kinetic model for the enzyme-like regulation mode of sRNA and study in detail the noise properties of the target gene under various recycling rates of the regulator. We predict that the recycling rate of sRNA and other relative parameters have significant influence on the noise strength of target expression. In comparison with the stoichiometric regulatory mode, a lesser fluctuation of target expression was observed near the threshold at which the transcription rates of both sRNA and target mRNA equal each other. We also found that the new mode is better in terms of rapid response to external signals. However, it needs more time to achieve target recovery if the stimulating signal disappears. Additionally, the obtained time evolution results of the MicM-ybfM interaction system based on our model are consistent with previous experimental results, serving as experimental evidence to back up our theoretical analysis. (C) 2010 Elsevier Ltd. All rights reserved.
分类： 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间： 2016-05-08
摘要： Sequence-function relations for small RNA (sRNA)-mediated gene silencing were quantified for the sRNA RyhB and some of its mRNA targets in Escherichia coli. Numerous mutants of RyhB and its targets were generated and their in vivo functions characterized at various levels of target and RyhB expression. Although a core complementary region is required for repression by RyhB, variations in the complementary sequences of the core region gave rise to a continuum of repression strengths, correlated exponentially with the computed free energy of RyhB-target duplex formation. Moreover, sequence variations inthe linker region known to interact with the RNA chaperone Hfq also gave rise to a continuum of repression strengths, correlated exponentially with thecomputed energy cost of keeping the linker region open. These results support the applicability of the thermodynamic model in predicting sRNA-mRNA interaction and suggest that sequences at these locations may be used to fine-tune the degree of repression. Surprisingly, a truncated RyhB without the Hfq-binding region is found to repress multiple targets of the wild-type RyhB effectively, both in the presence and absence of Hfq, even though the former is required for the activity of wild-type RyhB itself. These findings challenge the commonly accepted model concerning the function of Hfq in gene silencing-bothin providing stability to the sRNAs and in catalyzing the target mRNAs to take on active conformations-and raise the intriguing question of why many endogenous sRNAs subject their functions to Hfq-dependences.
点击量
待评议
点击量
下载量
评论
