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关键词： Image processing   Phase contrast   Phase measurement   Phase retrieval   Phase shift   Spatial light modulators  

摘要： Based on synchronous phase shift determination, we propose a differential phase measurement method for differential interference contrast (DIC) microscopy. An on-line phase shift measurement device is used to generate carrier interferograms and determine the phase shift of DIC images. Then the differential phase can be extracted with the least-squares phase-shifting algorithm. In addition to realizing on-line, dynamic, real-time, synchronous and high precision phase shift measurement, the proposed method also can reconstruct the phase of the specimen by using the phase-integral algorithm. The differential phase measurement method reveals obvious advantages in error compensation, anti-interference, and noise suppression. Both simulation analysis and experimental result demonstrate that using the proposed method, the accuracy of phase shift measurement is higher than 0.007 rad. Very accurate phase reconstructions were obtained with both polystyrene microspheres and human vascular endothelial. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Cryoelectron microscopy   Ion channels in the nervous system   Science   Humanities and Social Sciences   multidisciplinary  

摘要： Type A gamma-aminobutyric acid receptors (GABA(A)Rs) are pentameric ligand-gated chloride channels that mediate fast inhibitory signalling in neural circuits(1,2) and can be modulated by essential medicines including general anaesthetics and benzodiazepines(3). Human GABA(A)R subunits are encoded by 19 paralogous genes that can, in theory, give rise to 495,235 receptor types. However, the principles that govern the formation of pentamers, the permutational landscape of receptors that may emerge from a subunit set and the effect that this has on GABAergic signalling remain largely unknown. Here we use cryogenic electron microscopy to determine the structures of extrasynaptic GABA(A)Rs assembled from alpha 4, beta 3 and delta subunits, and their counterparts incorporating gamma 2 instead of delta subunits. In each case, we identified two receptor subtypes with distinct stoichiometries and arrangements, all four differing from those previously observed for synaptic, alpha 1-containing receptors(4-7). This, in turn, affects receptor responses to physiological and synthetic modulators by creating or eliminating ligand-binding sites at subunit interfaces. We provide structural and functional evidence that selected GABA(A)R arrangements can act as coincidence detectors, simultaneously responding to two neurotransmitters: GABA and histamine. Using assembly simulations and single-cell RNA sequencing data(8,9), we calculated the upper bounds for receptor diversity in recombinant systems and in vivo. We propose that differential assembly is a pervasive mechanism for regulating the physiology and pharmacology of GABA(A)Rs.

关键词： Lay date   Chlorophyll a   Breeding phenology   Egg-laying date   Seabirds   Time-series   Pytchoramphus aleuticus   Cerorhinca monocerata  

摘要： Many bird species use features of the physical environment to cue breeding activity. We show that for 2 species of Pacific auks (zooplanktivorous Cassin's auklet Ptychoramphus aleuticus and generalist rhinoceros auklet Cerorhinca monocerata), spatio-temporal variation in marine production indicators surrounding a major breeding colony in the northeast Pacific Ocean can cue laying date. By utilizing a multi-year phenological time series and a spatio-temporal sliding-window analysis spanning November up until median lay dates in spring, chlorophyll a (chl a) concentrations in the surface ocean around the colony strongly predicted lay date. However, the response to this cue differed between species by over 2 mo, as each species was exposed to different, sequential water-masses. We show that for Cassin's auklets, chl a levels at Triangle Island, British Columbia (Canada) in February, nearly 2 mo prior to actual laying, strongly correlated with lay date in April (average r = 0.83). At this time, the ocean environment around Triangle Island is dominated by water-masses from the south-southeast. However, for sympatric rhinoceros auklets, chl a along broad shelf-break areas in April prior to lay dates in May strongly correlated with lay date (average r = 0.76). Occurring after the spring transition, these water-masses flow primarily from the northwest. Consistent with other bird species, both auks appear to respond to information about food production, but at different spatio-temporal scales. We suggest that these different responses to environmental cues reflect species-specific differences in female migration behaviour, and an attempt by Cassin's auklets to bet-hedge against phenological mismatches.

摘要： Why do adolescents have a high propensity to engage in maladaptive behaviors? One explanation is that the adolescent nervous system is still undergoing maturation, and incomplete development of key brain regions results in poor behavioral regulation. Notably, the prefrontal cortex (PFC), a region

关键词： ODE   神经网络模型   正交多项式  

摘要： 本文研究神经网络模型对一类三阶常微分方程数值解的影响。首先,分析网络结构在神经网络模型求解常微分方程中的重要性,接着,探究单隐层前馈神经网络的网络隐层激活函数,选择几类正交多项式来消除隐层,构造不同类型的神经网络模型,利用极限习机(ELM)算法求解网络权值,最后利用数值实验模拟展示不同的神经网络模型形成的影响。

关键词： 函数   导数   零点   单调性  

摘要： 函数与导数一直是高考重要考点,导数应用的解答题也经常出现在最后一题压轴位置.2021年的新高考Ⅱ卷第22题依托含参的函数单调性和零点存在性问题,重点考查分类讨论、数形结合思想的应用,逻辑推理和数学抽象等核心素养的落实.第一问含参函数的求导和单调性分析,属于中档难度;第二问考查函数零点的存在性和唯一性,较难.