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Here we describe a functional magnetic resonance imaging study of humans engaged in memory search during a free recall task. Patterns of cortical activity associated with the study of three categories of pictures (faces, locations, and objects) were identified by a pattern-classification algorithm. The algorithm was used to track the reappearance of these activity patterns during the recall period. The reappearance of a given category's activity pattern correlates with verbal recalls made from that category and precedes the recall event by several seconds. This result is consistent with the hypothesis that category-specific activity is cueing the memory system to retrieve studied items. 相似文献
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采用广东省土地利用规划图和各自然保护区总体规划资料,在GIS软件ARCGIS8.0和MAPGIS支持下提取广东省省级以上森林生态系统自然保护区的空间资料,对区域水平上广东省省级以上森林生态系统自然保护区空间分布格局进行了研究。结果表明,目前广东省已建立自然保护区在区域空间水平上表现为随机分布,但保护区间连接度较差;保护区之间的隔离程度表现出显著的差别,基本可以区分为3个类别,其中空间隔离最大的保护区有9个,占已建立保护区的28%。因此,在广东省自然保护区建设过程中,应做好选点工作,增加自然保护区的空间连接度。 相似文献
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Visual instruction of the neural map of auditory space in the developing optic tectum 总被引:1,自引:0,他引:1
Neural maps of visual and auditory space are aligned in the adult optic tectum. In barn owls, this alignment of sensory maps was found to be controlled during ontogeny by visual instruction of the auditory spatial tuning of neurons. Large adaptive changes in auditory spatial tuning were induced by raising owls with displacing prisms mounted in spectacle frames in front of the eyes; neurons became tuned to sound source locations corresponding to their optically displaced, rather than their normal, visual receptive field locations. The results demonstrate that visual experience during development calibrates the tectal auditory space map in a site-specific manner, dictating its topography and alignment with the visual space map. 相似文献
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Brandon MP Bogaard AR Libby CP Connerney MA Gupta K Hasselmo ME 《Science (New York, N.Y.)》2011,332(6029):595-599
Grid cells recorded in the medial entorhinal cortex of freely moving rats exhibit firing at regular spatial locations and temporal modulation with theta rhythm oscillations (4 to 11 hertz). We analyzed grid cell spatial coding during reduction of network theta rhythm oscillations caused by medial septum (MS) inactivation with muscimol. During MS inactivation, grid cells lost their spatial periodicity, whereas head-direction cells maintained their selectivity. Conjunctive grid-by-head-direction cells lost grid cell spatial periodicity but retained head-direction specificity. All cells showed reduced rhythmicity in autocorrelations and cross-correlations. This supports the hypothesis that spatial coding by grid cells requires theta oscillations, and dissociates the mechanisms underlying the generation of entorhinal grid cell periodicity and head-direction selectivity. 相似文献
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【目的】研究R软件在植物种群分布格局中的应用,为分析植物种群分布格局的繁杂数据提供一种新方法。【方法】基于西双版纳20ha热带季节雨林动态监测样地的野外调查数据,以绒毛番龙眼、网脉肉托果、玉蕊树种为例,应用R软件绘制其树种空间分布图,并分析树种种群分布格局及种间关系。【结果】网脉肉托果在样地空间分布中为集群分布,而在空间分布格局中分析,在尺度0-2m为集群分布,在12~15m为随机分布;网脉肉托果和玉蕊两个树种在空间分布图中为交错分布,重叠区域不大,进行种间关系分析,两个物种在尺度0~5m无明显相关,在5~30m为负相关。【结论】R软件能够根据研究需要实现物种空间分布图的绘制、种群分布格局分析及物种相关性分析,值得推广。 相似文献
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乡村色彩具有强烈的地域化特征,是乡村文化与景观风貌的重要外显形式。基于近年国内外文献的梳理,将乡村色彩分为自然色彩、人工色彩、人文色彩三大类,阐述了乡村色彩的自然和文化属性,总结了乡村色彩在量化提取、感知评价、规划调控等方面的研究进展、技术方法和操作流程,综述了乡村色彩在乡村文化保护与传承、乡村景观规划与改造、乡村旅游规划与开发等方面的实践应用,并对研究趋势进行了分析和展望,提出未来应重视乡村人文色谱体系、乡村色彩感知评价研究,推动新一代技术的运用,加强色彩规划管控的科学性和参与性。 相似文献
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运用地学统计学的方法,建立了烟草普通花叶病(TMV)在东西、南北2个方向上的半变异函数模型,研究了TMV在空间大尺度上的分布格局。结果表明,在东西和南北2个方向上该病害的分布模型均为线性有基台模型,在调查范围内其空间格局为聚集型;在东西、南北2个方向上的空间依赖范围分别为29.953 4和47.813 8 km,其空间变异度分别为95.71%和80.05%,说明其具有较强的空间相关性。通过Kriging插值法得出的等值线图,可清晰地看出其空间聚集模式。 相似文献
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Pierre Auger Collaboration Abraham J Abreu P Aglietta M Aguirre C Allard D Allekotte I Allen J Allison P Alvarez C Alvarez-Muñiz J Ambrosio M Anchordoqui L Andringa S Anzalone A Aramo C Argirò S Arisaka K Armengaud E Arneodo F Arqueros F Asch T Asorey H Assis P Atulugama BS Aublin J Ave M Avila G Bäcker T Badagnani D Barbosa AF Barnhill D Barroso SL Bauleo P Beatty J Beau T Becker BR Becker KH Bellido JA Benzvi S Berat C Bergmann T Bernardini P Bertou X Biermann PL Billoir P Blanch-Bigas O 《Science (New York, N.Y.)》2007,318(5852):938-943
Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 x 10(19) electron volts and the positions of active galactic nuclei (AGN) lying within approximately 75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these cosmic rays with at least a 99% confidence level from a prescribed a priori test. The correlation we observed is compatible with the hypothesis that the highest-energy particles originate from nearby extragalactic sources whose flux has not been substantially reduced by interaction with the cosmic background radiation. AGN or objects having a similar spatial distribution are possible sources. 相似文献
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人为草原火及其影响因素的空间分布格局与相关关系研究对于草原火发生、草原火管理等研究具有重要的意义.应用Ripley''s K函数对呼伦贝尔草原1976-1996年间发生的人为草原火进行了空间统计分析,确定人为草原火空间分布在年内主要发生月份和年际间均呈聚集分布;应用Kernel密度函数对人为草原火及其影响因素居民点、道路和农田的空间分布密度进行了研究,结果表明呼伦贝尔草原人为火分布广泛,热点区域主体在123.05-124.82°E、48.25-50.21°N之间;居民点、农田空间分布密度的热点区域主要分布在东部和中部地区,道路的分布密度较农田和居民点分布更加均匀.人为草原火空间分布密度与居民点、道路和农田的空间分布密度呈显著性正相关,其Pearson相关系数依次为0.448、0.236、0.602 (P<0.001),火源因素(居民点、道路、农田)的空间分布格局是呼伦贝尔草原人为火空间分布格局的主要影响因素. 相似文献
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林木竞争指数空间格局的地统计学分析 总被引:2,自引:0,他引:2
运用地统计学原理和方法,分析了天然次生林中林木竞争指数分布的空间变异特征,计算了竞争指数的变异函数、分维数,并用Kriging方法对竞争指数进行了插值,结果表明:竞争指数的半方差函数可拟合为指数模型,在空间中呈聚集分布;竞争指数的空间异质性较大,且空间变异的大小与尺度大小密切相关。分维数的分析证明,林木个体属性在小尺度上的空间变异不可忽视。 相似文献
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贵港市土地利用空间格局分析 总被引:1,自引:0,他引:1
分析了贵港市及其县(市、区)的土地利用现状和空间布局,并运用多种数学模型对贵港市及其县(市、区)的土地利用的数量结构和空间格局进行分析,找出了各地区的土地利用存在的差异,这种差异与其所处的地理位置、地形地貌、经济水平及历史文化等密切相关。 相似文献
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以江南乡村居民的空间感知为研究对象,通过问卷调查了解村民的乡村意象,基于不同性别、年龄以及学历进行乡村意象感知差异分析,并从认知地图的角度出发,对不同群体的差异进行分析。寻求具有本土特色的乡村意象要素进行合理的保护,保留并挖掘乡村文化特色,树立鲜明的乡村意象,为乡村的开发与规划提供借鉴和参考,唤起人们情感上的共鸣,产生对乡村生活的向往与归属。 相似文献
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Optimised Spatial Sampling Scheme for Soil Electriclal Conductivity Based on Variance Quad-Tree (VQT) Method 总被引:1,自引:0,他引:1
The acquisition of precise soil data representative of the entire survey area,is a critical issue for many treatments such as irrigation or fertilization in precision agriculture.The aim of this study was to investigate the spatial variability of soil bulk electrical conductivity(ECb)in a coastal saline field and design an optimized spatial sampling scheme of ECb based on a sampling design algorithm,the variance quad-tree(VQT)method.Soil ECb data were collected from the field at 20m interval in a regular grid scheme.The smooth contour map of the whole field was obtained by ordinary kriging interpolation,VQT algorithm was then used to split the smooth contour map into strata of different number desired,the sampling locations can be selected within each stratum in subsequent sampling.The result indicated that the probability of choosing representative sampling sites was increased significantly by using VQT method with the sampling number being greatly reduced compared to grid sampling design while retaining the same prediction accuracy.The advantage of the VQT method is that this scheme samples sparsely in fields where the spatial variability is relatively uniform and more intensive where the variability is large.Thus the sampling efficiency can be improved,hence facilitate an assessment methodology that can be applied in a rapid,practical and cost-effective manner. 相似文献
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由耕地、林地、草地、湿地及水域共同构成的绿色空间有利于提升城市生态环境,维护生物多样性和社会经济的可持续发展,理清福建省绿色空间的景观结构组成以及空间配置演变情况对构建生态屏障、打造全国生态示范省具有重要意义。以福建省绿色空间为对象,分析其景观格局在2000-2020年的演变,并采用地理加权回归(geographically weighted regression,GWR)构建回归模型,分析福建省绿色空间景观格局演变的影响因素及其空间差异性。结果表明:1)2000-2020年,整体绿色空间景观格局的时空变化特征较明显。福建省整体绿色空间破碎化程度上升,总体连通性降低和多样性降低。空间分布上,整体绿色格局破碎化、连通性和多样性变化随着空间位置不同而变化。2)GWR模型在空间位置层面对不同时期的绿色空间格局演变影响因素的解释优于普通最小二乘法(ordinary least squares,OLS)模型。GWR模型结果表明,社会经济影响因素对绿色空间景观格局破碎化、连通性、多样性的影响以负相关为主,且具有较显著的空间差异。自然因素中,地形、温度、降水对绿色空间景观格局的影响也具空间差异。分析揭示了福建省绿色空间景观格局的时空演变特征,并在空间层面上量化影响因素对绿色空间景观格局的影响特征,有助于进一步优化福建省绿色空间格局并构建福建省生态安全格局。 相似文献
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Rubin VC 《Science (New York, N.Y.)》1980,209(4452):64-71
Our perception of the universe has been altered by recent discoveries in astronomy, discoveries of new objects and of new phenomena, coming from a wide range of observing techniques. By 1990 astronomers expect to know more about the distribution of mass in the universe, the physics of energetic sources, and the intricate interconnections of astrophysical processes on a variety of spatial and temporal scales. 相似文献
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基于巢湖流域土壤类型图,使用ArcGIS 10.1和Fragstats 4.2,并选择5个景观格局指数,研究了巢湖流域景观格局指数随空间粒度的变化趋势,并且计算了变异系数。结果表明:巢湖流域土壤类型图最适合进行景观格局分析的空间尺度范围在30~60 m。 相似文献
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态势标绘指在地图背景上标绘各种具有空间特征的事、物的分布状态或行动部署.给出了态势标绘系统中实现各种标绘符号算法的关键技术,提出并实现了基于SuperMap Object.NET的二三维一体化态势标绘系统的集成应用,并将成果成功应用于黑龙江省森林防火电子沙盘指挥系统中,有效提高了系统态势标绘的表现效果. 相似文献