Evidence from claw geometry indicating arboreal habits of archaeopteryx

The Late Jurassic Archaeopteryx has been thought to have been a feathered predator adapted to running that represented a terrestrial stage in the evolution of true birds from coelurosaurian dinosaurs. Examination of claw geometry, however, shows that (i) modern ground- and tree-dwelling birds can be distinguished on the basis of claw curvature, in that greater claw arcs characterize tree-dwellers and trunk-climbers, and (ii) the claws of the pes (hind foot) and manus (front hand) of Archaeopteryx exhibit degrees of curvature typical of perching and trunk-climbing birds, respectively. On this basis, Archaeopteryx appears to have been a perching bird, not a cursorial predator.     

A cellular automation model of excitable media including curvature and dispersion

Excitable media are spatially distributed systems characterized by their ability to propagate signals undamped over long distances. Wave propagation in excitable media has been modeled extensively both by continuous partial differential equations and by discrete cellular automata. Cellular automata are desirable because of their intuitive appeal and efficient digital implementation, but until now they have not served as reliable models because they have lacked two essential properties of excitable media. First, traveling waves show dispersion, that is, the speed of wave propagation into a recovering region depends on the time elapsed since the preceding wave passed through that region. Second, wave speed depends on wave front curvature: curved waves travel with normal velocities noticeably different from the plane-wave velocity. These deficiencies of cellular automation models are remedied by revising the classical rules of the excitation and recovery processes. The revised model shows curvature and dispersion effects comparable to those of continuous models, it predicts rotating spiral wave solutions in quantitative accord with the theory of continuous excitable media, and it is parameterized so that the spatial step size of the automation can be adjusted for finer resolution of traveling waves.     

Stress and fold localization in thin elastic membranes

Thin elastic membranes supported on a much softer elastic solid or a fluid deviate from their flat geometries upon compression. We demonstrate that periodic wrinkling is only one possible solution for such strained membranes. Folds, which involve highly localized curvature, appear whenever the membrane is compressed beyond a third of its initial wrinkle wavelength. Eventually the surface transforms into a symmetry-broken state with flat regions of membrane coexisting with locally folded points, reminiscent of a crumpled, unsupported membrane. We provide general scaling laws for the wrinkled and folded states and proved the transition with numerical and experimental supported membranes. Our work provides insight into the interfacial stability of such diverse systems as biological membranes such as lung surfactant and nanoparticle thin films.     

Spray aiming in bombardier beetles: jet deflection by the coanda effect

Bombardier beetles of the carabid subfamily Paussinae have a pair of flanges, diagnostic for the group, that project outward from the sides of the body. Behind each flange is a gland opening, from which the beetles discharge a hot, quinone-containing secretion when disturbed. The flanges are curved and grooved and serve as launching guides for anteriorly aimed ejections of secretion. Jets of fluid, on emergence from the gland openings, follow the curvature of the flanges and are thereby bent sharply in their trajectory and directed forward. The phenomenon is illustrative of the Coanda effect, widely applicable in engineering and responsible for the familiar tendency of liquids to curve around spouts and down the front of containers when being poured.     

A Laboratory Model for Convection in Earth's Core Driven by a Thermally Heterogeneous Mantle

Thermal convection experiments in a rapidly rotating hemispherical shell suggest a model in which the convection in Earth's liquid outer core is controlled by a thermally heterogeneous mantle. Experiments show that heterogeneous boundary heating induces an eastward flow in the core, which, at a sufficiently large magnitude, develops into a large-scale spiral with a sharp front. The front separates the warm and cold regions in the core and includes a narrow jet flowing from the core-mantle boundary to the inner-core boundary. The existence of this front in the core may explain the Pacific quiet zone in the secular variation of the geomagnetic field and the longitudinally heterogeneous structure of the solid inner core.     

西藏东南部边缘地区昆虫多样性的特点

根据西藏东南部边缘地区:墨脱、察隅和米林三县的204科昆虫,分别统计了这三个地区昆虫属和种的数量,其中墨脱昆虫922属、1433种,大大超过西藏已知昆虫的1/3,察隅319属、446种,米林119属、152种;列出了每个地区的珍奇昆虫和特有物种;总结了这些地区物种多样性的种种特点。首先,这些地区昆虫区系的主要组成属于亚热带、热带的区系性质,它们的起源和演化与东洋区的昆虫区系密切相关;第二,这些地区的生态环境复杂,昆虫种类非常丰富,物种的分化十分活跃;第三,这三个地区的特有物种都十分富庶,作为县级行政单位,这种现象在其它地区是非常少见的;第四,这里还保存了众多的古老类群和珍稀物种。     

子宫颈冷刀锥切术与LEEP锥切术在宫颈上皮内瘤变诊治中临床价值对比分析

目的探讨子宫颈冷刀锥切术和LEEP锥切术在子宫颈上皮内瘤变诊治中的临床意义。方法比较患者子宫颈冷刀锥切与宫颈LEEP锥切术后结果与术前多点病理活检结果符合率并比较治疗效果。结果子宫颈冷刀锥切病理与术前多点病理活检结果完全符合者有70例(81.4%);有差异者16例(18.6%),其中7例术前多点活检为CINⅡ和CINⅢ,而锥切为CINⅢ和微小早期浸润癌。子宫颈LEEP锥切术病理与术前多点病理活检结果完全符合者有45例(75%);有差异者15例(25%),其中5例术前多点活检为CINⅡ和CINⅢ,而锥切为微小早期浸润癌。65例为CINⅢ或以上,常伴有累及宫颈管腺体;同时累及2个象限例57例,伴有HPV感染132例;切缘病变残留率分别是CINⅡ(3.2%)和CINⅢ(8.1%)。结论在子宫颈上皮内瘤变的诊治中,子宫颈冷刀锥切在完整切除病变、低残留方面占有优势,而LEEP锥切术省时、简单、安全、价廉。     

基于逆向工程的汽车车身前翼子板重建技术

逆向工程技术是一项具有广泛应用前景的高新技术,可以迅速、精确、方便地获得实物模型的三维数据及模型,为产品设计提供了先进的产品开发、设计及制造的途径。以车身前翼子板为例,利用非接触式三维扫描仪获得车身的点云文件,利用geomagic-studio软件对点云进行曲率和点距取样,得到计算机能够处理的点云数据,将点云文件进行降噪等处理,生成曲面,对曲面进行光顺等一系列的处理,获得B级曲面。     

263例宫颈上皮内瘤变的临床特征及阴道镜检查的诊断意义

目的 总结宫颈上皮内瘤变(CIN)的临床特征及阴道镜检查的诊断意义.方法 回顾性分析263例CIN患者的临床病理资料.结果 全部病例中30～49岁者占80.6%,CIN无典型临床特征.阴道镜图像以醋酸白上皮最多见,醋酸白上皮的厚薄与CIN分级有关(P＜0.01).阴道镜检诊断CIN的敏感性、特异性分别为87.1%、59...     

基于Maxent模型的长林小蠹的全球及中国适生区预测

  目的  长林小蠹是一种重要的林木检疫性害虫，对智利、新西兰等多国松树造成严重危害，并随林木进口入侵我国山东，对我国林业安全造成威胁。根据长林小蠹的已知分布，对其全球和中国范围内的适生区范围进行准确预测，明确该虫在我国潜在的分布区范围，为相关部门提供理论参考，有助于采取科学高效的监测和防治措施，降低潜在的生态和经济损失。  方法  利用Maxent物种分布模型，通过筛选生物气候变量和优化模型参数构建拟合优度和复杂度综合表现最佳的模型，进而应用于长林小蠹在全球和中国范围内的适生区的预测。利用ArcGIS软件对预测结果进行可视化处理和面积统计，并利用模型的结果对影响长林小蠹定殖的主要环境因素进行分析。  结果  相较默认参数下的模型，参数优化后的模型精度明显提高，平均AUC值达到0.964 6。同时，模型预测结果显示:长林小蠹在全球的适生区主要位于欧洲、北美洲东部和西部沿海、亚洲东部、南美洲东南部、非洲最南端以及大洋洲的东南沿海。其中高度适生区、中度适生区和低度适生区的面积分别占比1.21%、1.92%和3.95%。中国范围内该虫的适生区主要位于中部和南部，其南界至中国台湾，北界至辽宁大连。其中高度适生区、中度适生区和低度适生区的面积分别占比0.28%、5.00%和13.43%。在所有生物环境变量中，贡献率最为显著的为最干季降水量、最冷月份的最低温度、温度季节性、最热月份的最高温度、年降水量。贡献率分别为37.9%、25.4%、12.7%、7.0%和6.6%。  结论  已有长林小蠹发生的区域外，美国东南部和西北部、阿根廷东部、巴西的南部和中国大部的适生区尚未有长林小蠹的捕获记录，被入侵风险较高。长林小蠹在中国的适生区主要以中度和低度适生区为主，几乎囊括了中国中部和南部所有的省份，其中，山东省和江苏省的沿海地带及其周边地带、中国西部局地和中国中南部局地的适生性相对较高。由此我们建议在国内开展长林小蠹的普查及防控工作，严防其扩散蔓延；同时加强入境口岸的各项检疫措施。      

Deep human genealogies reveal a selective advantage to be on an expanding wave front

Since their origin, human populations have colonized the whole planet, but the demographic processes governing range expansions are mostly unknown. We analyzed the genealogy of more than one million individuals resulting from a range expansion in Quebec between 1686 and 1960 and reconstructed the spatial dynamics of the expansion. We find that a majority of the present Saguenay Lac-Saint-Jean population can be traced back to ancestors having lived directly on or close to the wave front. Ancestors located on the front contributed significantly more to the current gene pool than those from the range core, likely due to a 20% larger effective fertility of women on the wave front. This fitness component is heritable on the wave front and not in the core, implying that this life-history trait evolves during range expansions.     

Isolation and Characterization of NBS-LRR Class Resistance Homologous Gene from Wheat

One resistance gene analog fragment named RGA-CIN14 was isolated from TcLr19 wheat,which contains kinase-2,kinase-3a,and the GLPL motif of the NBS-spanning region,using degenerated primers according to the nucleotide binding site (NBS) conserved domain.Based on the RGA-CIN14,a full-length cDNA,CIN14,which was 2 987 bp encoding 880 amino acids,was obtained by using the method of the rapid amplification cDNA ends (RACE).Bioinformatics analysis showed that the deduced amino acids of CIN14 protein consisted of a NB-ARC conserved domain and many leucine-rich repeats (LRR) domains.The phylogenetic tree analysis indicated a considerable identity of the protein encoded by CIN14 with that of wheat leaf rust resistance gene Lr1,but a lower similarity with Lr21.The expression profile of the CIN14 gene detected by semi-quantitative RT-PCR showed that the CIN14 gene was not induced by Puccinia triticina and it was a constitutive gene with low abundance in the wheat leaf tissue.The resistance homology sequence was successfully obtained,which provides the shortcut for cloning of the resistance gene in TcLrl9 wheat.     

自由曲面的高斯曲率计算方法

针对用定义方法计算各种不同类型表达方式曲面的高斯曲率中存在的问题 ,提出了一种利用局部插值计算曲面点的高斯曲率的方法 ,该方法具有明确的几何意义 ,适用于各种不同表达方式的自由曲面。     

Andesitic Volcanism and Seismicity around the Pacific

Circum-Pacific andesites, with associated basalts and dacites, are erupted from linear island arcs and marginal continental ranges whose ocean-side borders coincide approximately with the continent-side boundaries of belts of shallow seismicity that parallel adjacent trenches. The lines of active volcanoes stand above elongate subcrustal regions delineated by the intersection of inclined Benioff seismic zones and the subhorizontal Gutenberg low-velocity zone. Close correlation between content of potash in erupted lavas and vertical depth to the Benioff zone suggests that andesitic volcanism has its origins in the mantle where magmas are generated by events associated with earthquakes of intermediate focal depth.     

湖南省丘陵山区苎麻气候资源分析

分析比较了湖南丘陵山区与湖区平原的苎麻气候资源特点和分布规律,探讨了在丘陵山区发展苎麻生产的有利气候条件。结果表明,在丘陵山区,苎麻优质高产所需的光热水风等气候要素大部分都比湖区优越。     

基于行业减排的森林碳汇需求空间测度与分类

  目的   对全国28个省级行政区域和深圳市的森林碳汇需求空间进行分类,就提升各类地区未来的森林碳汇需求空间提出针对性建议,为科学设计碳汇政策以及差异化开发森林碳汇需求空间提供客观依据。   方法   以全国28个省级行政区域和深圳市为样本地区,收集整理2008?2017年《统计年鉴》中工业行业的投入产出数据,运用方向性距离函数模型测算各地区工业行业碳边际减排成本,并采用需求空间模型,对全国28个省级行政区域和深圳市10 a的森林碳汇需求空间进行测度,对求得的需求空间数据进行聚类分析和判别分析。   结果   各样本地区的碳边际减排成本和森林碳汇需求空间数据均存在一定的地区性波动。3类地区碳边际减排成本与森林碳汇需求空间的皮尔逊相关系数为0.999,呈显著正相关。聚类结果发现:1、2、3类地区的碳边际减排成本平均值分别为1.59、1.18、0.51万元·t?1;1、2、3类地区森林碳汇需求空间平均值分别为571.91、374.93、174.15万t·a?1。最终判别方程发现:2011、2014年的需求空间数据对地区分类的影响最为显著。   结论   整体来看,分类结果与中国东中西部地区的经济发展水平大致吻合。政策情景模拟显示:差异化开发森林碳汇需求空间要将超排处罚率作为第1、2类地区的重要切入点,同时优化配额发放模式;第3类地区以鼓励引导为主。表6参16     

广义Riesz平均的交换子

讨论了一类Ｒｉｅｓｚ平均与ＢＭＯ函数生成的交换子的Ｌ＾ｐ有界性问题。得到的结果表明在超曲面的高斯曲率不为零的条件下，与经典的Ｂｏｃｈｍｅｒ－Ｒｉｅｓｚ平均有相类似的结果。     

干旱半干旱地区边际地种植能源作物的资源环境问题探讨

为减少对进口石油的依赖及应对燃烧化石能源造成的空气污染和温室气体排放问题,世界各国争相发展生物质能源产业。针对利用能源植物带来的粮价上涨和粮食安全问题,适应人多耕地少的国情,我国制定了"不与民争粮,不与粮争地"生物质能源的发展原则。许多学者提出利用边际性土地种植能源作物。多数边际性土地过于零散,不利于能源作物大规模种植和收获、运输,人们把注意力集中到草原及荒草地。干旱和半干旱地区天然降水不能满足植物旺盛生长的水分需求。大规模集约化种植一年生能源作物,主要依靠灌溉,消耗大量的水资源,同"与民争粮,与粮争地"一样威胁粮食安全,同时还可能会造成生物多样性丧失、植被破坏、土地沙化、土壤次生盐渍化等环境和生态问题,影响草原畜牧业发展,使牧民生活无靠,与现有的《草原法》等法律、法规相悖,且无异于"问题搬家"。本研究通过分析能源作物,特别是在干旱和半干旱区规模化、集约化种植,对资源、生态环境的影响,依据国家相关法律法规,提出了干旱和半干旱地区边际土地能源作物规模化种植准入政策建议,以期为生物质能源产业的健康可持续发展提供依据。     

The arctic mirage and the early north atlantic

The arctic mirage is a phenomenon that is common in higher latitudes. It occurs under conditions of pronounced temperature inversion, which impart to the air a refractive capability that may equal or exceed the curvature of the earth. Manifestations of the arctic mirage, though largely forgotten in modern times, are described in the earliest accounts of North Atlantic discovery. This interdisciplinary investigation, combining historical induction with scientific observation and analysis, has suggested a new interpretation of historical events. We believe that information gleaned from these mirages was vital to Norse navigation and exploration in the North Atlantic. We further contend that the mirage may furnish a logical basis for the pervasive ancient and medieval concept of the flat or saucer-shaped world.