基于时间调制的相控阵技术研究进展

基于单边带时间调制技术的新型相控阵具有精度高、成本低、宽带宽和可重构等诸多优点,在精确制导和移动通信等军民领域具有巨大的应用潜力,是当前的研究热点.本文全面回顾了时间调制相控阵的发展历程,介绍了在提升效率、抑制边带和抑制副瓣等方面的最新研究进展,展示了互补金属氧化物半导体(complementary metal-oxide semiconductor,CMOS)工艺时间调制相控阵芯片等工程化研究成果.本文不仅对时间调制相控阵的进一步发展具有参考价值,而且可为其军事、航天和新一代无线通信等前沿领域的推广应用起到推动作用.

Review of Related Studies on Eco-city Theory

This paper reviews the birth and development of eco-city research by means of historical analysis and literature search. It elaborates the concepts,connotations and principles of scholars both at home and abroad. By comparing the research and practice differences between domestic and foreign eco-city construction,it reviews the various indicators and research progress applied in the current eco-city construction in foreign countries. It systematically sorts out the characteristics of eco-city construction practice in China and points out the main problems in the construction of China's eco-city.

A new neural-network-based method for structural damage identification in single-layer reticulated shells

Single-layer reticulated shells(SLRSs)find widespread application in the roofs of crucial public structures,such as gymnasiums and exhibition center.In this paper,a new neural-network-based method for structural damage identification in SLRSs is proposed.First,a damage vector index,NDL,that is related only to the damage localization,is proposed for SLRSs,and a damage data set is constructed from NDL data.On the basis of visualization of the NDL damage data set,the structural damaged region locations are identified using convolutional neural networks(CNNs).By cross-dividing the damaged region locations and using parallel CNNs for each regional location,the damaged region locations can be quickly and efficiently identified and the undamaged region locations can be eliminated.Second,a damage vector index,DS,that is related to the damage location and damage degree,is proposed for SLRSs.Based on the damaged region identified previously,a fully connected neural network(FCNN)is constructed to identify the location and damage degree of members.The effectiveness and reliability of the proposed method are verified by considering a numerical case of a spherical SLRS.The calculation results showed that the proposed method can quickly eliminate candidate locations of potential damaged region locations and precisely determine the location and damage degree of members.

“Sentinel or accomplice”:gut microbiota and microglia crosstalk in disorders of gut-brain interaction

Abnormal brain-gut interaction is considered the core pathological mechanism behind the disorders of gut-brain interaction(DGBI),in which the intestinal microbiota plays an important role.Microglia are the“sentinels”of the central nervous system(CNS),which participate in tissue damage caused by traumatic brain injury,resist central infection and participate in neurogenesis,and are involved in the occurrence of various neurological diseases.With in-depth research on DGBI,we could find an interaction between the intestinal microbiota and microglia and that they are jointly involved in the occurrence of DGBI,especially in individuals with comorbidities of mental disorders,such as irritable bowel syndrome(IBS).This bidirectional regulation of microbiota and microglia provides a new direction for the treatment of DGBI.In this review,we focus on the role and underlying mechanism of the interaction between gut microbiota and microglia in DGBI,especially IBS,and the corresponding clinical application prospects and highlight its potential to treat DGBI in individuals with psychiatric comorbidities.

Carbonate-induced enhancement of phenols degradation in CuS/peroxymonosulfate system: A clear correlation between this enhancement and electronic effects of phenols substituents

This study investigated the enhancement effects of dissolved carbonates on the peroxymonosulfate-based advanced oxidation process with CuS as a catalyst.It was found that the added CO_(3)^(2−)increased both the catalytic activity and the stability of the catalyst.Under optimized reaction conditions in the presence of CO_(3)^(2−),the degradation removal of 4-methylphenol(4-MP)within 2 min reached 100%,and this was maintained in consecutivemulti-cycle experiments.The degradation rate constant of 4-MP was 2.159 min^(−1),being 685%greater than that in the absence of CO_(3)^(2−)(0.315 min−1).The comparison of dominated active species and 4-MP degradation pathways in both CO_(3)^(2−)-free and CO_(3)^(2−)-containing systems suggested thatmore CO_(3)·^(−)/^(1)O_(2) was produced in the case of CO_(3)^(2−)deducing an electron transfer medium,which tending to react with electron-richmoieties.Meanwhile,Characterization by X-ray photoelectron spectroscopic and cyclic voltammetrymeasurement verified CO_(3)^(2−)enabled the effective reduction of Cu^(2+)to Cu^(+).By investigating the degradation of 11 phenolics with different substituents,the dependence of degradation kinetic rate constant of the phenolics on their chemical structures indicated that there was a good linear relationship between the Hammett constantsσp of the aromatic phenolics and the logarithm of k in the CO_(3)^(2−)-containing system.This work provides a new strategy for efficient removal of electron-rich moieties under the driving of carbonate being widely present in actual water bodies.

四川卧龙国家级自然保护区多空间尺度下绿尾虹雉的生境选择

动物的生境选择具有空间尺度依赖性,在不同空间尺度上影响生境选择的环境因素有所不同。研究不同空间尺度下动物生境选择的关键影响因子及其季节性变化,对于全面了解物种的生境资源需求和开展生境保护具有重要意义。绿尾虹雉(Lophophoruslhuysii)是中国特有的高山雉类,国家一级重点保护野生动物,具有极高的保护价值。然而,目前尚未对其不同尺度和时期的生境选择进行过探究。本研究于2019年10月至2020年10月,在四川卧龙国家级自然保护区的羊角湾、魏家沟和文扎都3个区域共布设15条样线、303个样方,并结合红外相机监测(176个红外相机位点),对保护区内绿尾虹雉种群的生境利用状况进行了调查,使用主成分分析和逻辑斯蒂回归模型分别从景观和微生境两个尺度对繁殖期(3-8月)和非繁殖期(9月至翌年2月)的生境选择模式进行了分析。结果显示,在景观尺度上,在繁殖期和非繁殖期都显著偏好海拔较高(3,700-4,300 m)、坡度较小(27°-33°)、靠近阳坡、草甸和流石滩比例较高而森林和灌丛比例较低的生境。在微生境尺度上,绿尾虹雉在繁殖期显著偏好岩石盖度较高的生境;而非繁殖期则显著偏好草本盖度较高、灌木盖度和落叶盖度较低的生境。研究表明,绿尾虹雉在景观和微生境尺度上均对生境有明显的选择性,并且其微生境选择还存在季节性变化,反映了该物种在生活史不同阶段具有不同的资源需求。本研究丰富了绿尾虹雉的基础生态学信息,为卧龙及其他自然保护区绿尾虹雉的生境管理和种群保护工作提供了参考。

四川卧龙国家级自然保护区三种高山同域鸡形目鸟类的时空生态位比较

高海拔山区气候条件恶劣,资源匮乏,探究同域分布的近缘物种如何利用有限的资源以实现稳定共存,对于了解高山生态系统生物多样性格局的形成和维持机制具有重要意义。鸡形目鸟类飞行能力弱,属于典型的地栖物种,生态位空间相对狭窄,可能面临更高的种间竞争压力。本研究旨在比较几种同域分布的鸡形目鸟类的时空生态位,为了解高山生态系统同域物种的共存机制提供新的研究案例。2020年4-9月,研究人员在四川卧龙国家级自然保护区海拔3,300-4,200m的高山区域进行了野外调查,通过样线法和样方法对鸡形目鸟类群落优势物种绿尾虹雉(Lophophorus lhuysii)、雉鹑(Tetraophasis obscurus)和雪鹑(Lerwalerwa)繁殖期的微生境进行调查,使用红外相机对其活动节律进行监测,并运用核密度估计法从微生境利用和日活动节律两个生态维度进行了种间生态位比较。结果显示,雪鹑在微生境利用和日活动节律上均与其他两个物种存在显著差异。绿尾虹雉与雉鹑在微生境的利用上具有相似偏好;但绿尾虹雉的早活动高峰晚于雉鹑,晚活动高峰早于雉鹑,表现出显著的种间日活动节律差异;然而,整合两个维度后,绿尾虹雉和雉鹑的整体生态位仍然高度重叠,没有显著分化。本研究表明高山鸡形目物种间的生态位分化体现于多个不同的生态维度,并且不同物种之间的分化方式有所差异。在空间和时间生态位上的显著分化使雪鹑与同域物种间的竞争压力相对较小,有利于其实现稳定共存。而绿尾虹雉与雉鹑的整体生态位高度重叠,建议进一步对其食性开展研究,探讨营养生态位上的潜在种间分化。

下一代益生菌的研究进展

肠道菌群与疾病关系的研究进展揭示和推动了肠道微生态疗法的发展, 其中益生菌是目前最为广泛使用的干预手段。疾病相关关键菌株的发现为下一代益生菌的开发提供了重要基础。目前下一代益生菌主要应用方向为代谢性疾病、炎症性肠病和肿瘤等, 其安全性、定殖能力与厌氧特性是开发过程中需要重点考虑的问题, 对其益生机制的研究有助于实现临床转化。

Increased Expression of Colonic Mucosal Melatonin in Patients with Irritable Bowel Syndrome Correlated with Gut Dysbiosis

Dysregulation of the gut microbiota/gut hormone axis contributes to the pathogenesis of irritable bowel syndrome(IBS).Melatonin plays a beneficial role in gut motility and immunity.However,altered expression of local mucosal melatonin in IBS and its relationship with the gut microbiota remain unclear.Therefore,we aimed to detect the colonic melatonin levels and microbiota profiles in patients with diarrhea-predominant IBS(IBS-D)and explore their relationship in germ-free(GF)rats and BON-1 cells.Thirty-two IBS-D patients and twenty-eight healthy controls(HCs)were recruited.Fecal specimens from IBS-D patients and HCs were separately transplanted into GF rats by gavage.The levels of colon mucosal melatonin were assessed by immunohistochemical methods,and fecal microbiota communities were analyzed using 16S rDNA sequencing.The effect of butyrate on melatonin synthesis in BON-1 cells was evaluated by ELISA.Melatonin levels were significantly increased and negatively correlated with visceral hypersensitivity in IBS-D patients.GF rats inoculated with fecal microbiota from IBS-D patients had high colonic melatonin levels.Butyrate-producing Clostridium cluster XIVa species,such as Roseburia species and Lachnospira species,were positively related to colonic mucosal melatonin expression.Butyrate significantly increased melatonin secretion in BON-1 cells.Increased melatonin expression may be an adaptive protective mechanism in the development of IBS-D.Moreover,some Clostridium cluster XIVa species could increase melatonin expression via butyrate production.Modulation of the gut hormone/gut microbiota axis offers a promising target of interest for IBS in the future.

Probing interlayer interactions in WSe2-graphene heterostructures by ultralow-frequency Raman spectroscopy

Interlayer interactions at the heterointerfaces of van der Waals heterostructures (vdWHs), which consist of vertically stacked two-dimensional materials, play important roles in determining their properties. The interlayer interactions are tunable from noncoupling to strong coupling by controlling the twist angle between adjacent layers. However, the influence of stacking sequence and individual component thickness on the properties of vdWHs has rarely been explored. In this work, the influence of the stacking sequence of WSe2 and graphene in vdWHs of graphene-on-WSe2 (graphene/WSe2) or WSe2-on-graphene (WSe2/graphene), as well as their thickness, on their interlayer interaction was systematically investigated by ultralow-frequency (ULF) Raman spectroscopy. A series of ULF breathing modes of WSe2 nanosheets in these vdWHs were observed with frequencies highly dependent on graphene thickness. Interestingly, the ULF breathing modes of WSe2 red-shifted in graphene/WSe2 and WSe2/graphene configurations, and the amount of shift in the former was much larger than that in the latter. In contrast, no obvious ULF shift was observed by varying the twist angle between WSe2 and graphene. This indicates that the interlayer interaction is more sensitive to the stacking sequence compared with the twist angle. The results provide alternative approaches to modulate the interlayer interaction of vdWHs and, thus, tune their optical and optoelectronic properties.

二维有机分子吸附层对过渡金属硫化物纳米薄片超低波拉曼光谱的影响（英文）

在二维材料下表面与衬底之间的受限空间中,物理吸附物如水分子和有机分子等可形成二维吸附层.然而,这类吸附层如何影响其上层二维材料的性能尚未被探究.本文中,我们结合原子力显微镜、开尔文力显微镜以及超低波拉曼光谱仪来探究有机分子吸附层对其上的少层二硫化钼及二硒化钨纳米薄片性质的影响.随吸附层厚度增加,纳米薄片的超低波呼吸模式拉曼峰发生红移、红移和蓝移共存以及仅有蓝移的现象.此外,纳米薄片的掺杂程度也逐渐增强.理解有机分子吸附层与二维材料下表面之间的相互作用,有望对二维材料性质的调节提供帮助.

Mixed-method study on medicinal herb collection in relation to wildlife conservation:the case of giant pandas in China

Medicinal herb collection has historical and cultural roots in many rural communities in developing countries.Areas where herb collection occurs may overlap with biodiversity hotspots and crucial habitat of endangered and threatened species.However,impacts of such practices on wildlife are unknown and possibly underestimat­ed,perhaps due to the elusive nature of such activities.We examined this phenomenon in Wolong Nature Re­serve,China,a protected area in the South-Central China biodiversity hotspot that also supports a community of Tibetan,Qiang and Han people who use herb collection as a supplementary source of livelihood.We adopted a participatory approach in which we engaged local people in outlining spatial and temporal dynamics of medici­nal herb collection practices.We found that the overall spatial extent of herb collection increased in the past two decades.We then overlaid herb collection maps with localities of giant panda(Ailuropoda melanoleuca)feces collected over two time points in the reserve.Using a Bayesian parameter estimation,we found evidence for de­clined giant panda occurrence in the areas most recently impacted by emerging medicinal herb collection.Our methodology demonstrates the potential power of integrating participatory approaches with quantitative meth­ods for processes like herb collection that may be difficult to examine empirically.We discuss future directions for improving explanatory power and addressing uncertainty in this type of mixed-method,interdisciplinary re­search.This work has implications for future attempts to understand whether and how prevalent but subtle hu­man activities may affect wildlife conservation.