Comment on "A well-preserved Archaeopteryx specimen with theropod features"

On the basis of new information from the 10th specimen of Archaeopteryx, Mayr et al. (Reports, 2 December 2005, p. 1483) suggested that birds, or avian flight, originated twice. We investigate the statistical support for this phylogenetic hypothesis and show that it is no better supported by available morphological character data than the hypothesis of a single avian origin.     

Archaeopteryx: notice of a "new" specimen

A fourth specimen of Archaeopteryx (cf. lithographica), the oldest known fossil bird, was recently found in the collections of the Teyler Museum in the Netherlands. Unique preservation of the horny sheaths of the manus claws provides new evidence that may be relevant to the question of the origins of avian flight. Tentative interpretation suggests a cursorial rather than arboreal origin.     

A crested theropod dinosaur from antarctica

Jurassic fossil vertebrates collected from the Falla Formation in the Central Transantarctic Mountains included a partial skull and postcranial elements of a crested theropod, Cryolophosaurus ellioti gen. nov. sp. nov. The theropod bears some resemblance to the large tetanurans of the Middle to Late Jurassic but also has primitive ceratosaurian features. Elements from a prosauropod, teeth from scavenging theropods, a pterosaur humerus, and a tritylodont molar were also recovered. The presence of this fauna suggests that a mild climate existed at high paleolatitude in this area of Gondwana during the Early Jurassic.     

A theropod dinosaur embryo and the affinities of the flaming cliffs dinosaur eggs

An embryonic skeleton of a nonavian theropod dinosaur was found preserved in an egg from Upper Cretaceous rocks in the Gobi Desert of Mongolia. Cranial features identify the embryo as a member of Oviraptoridae. Two embryo-sized skulls of dromaeosaurids, similar to that of Velociraptor, were also recovered in the nest. The eggshell microstructure is similar to that of ratite birds and is of a type common in the Djadokhta Formation at the Flaming Cliffs (Bayn Dzak). Discovery of a nest of such eggs at the Flaming Cliffs in 1923, beneath the Oviraptor philoceratops holotype, suggests that this dinosaur may have been a brooding adult.     

肝内胆管细胞癌的CT特征与病理对照研究

目的;观察肝内胆和细胞癌的ＣＴ特征及其病理基础。方法：１３例经病理证实的肝内胆管细胞癌均行ＣＴ平扫及增强扫描,其中部分病例加做ＣＴ延迟扫描,１３例肝内胆管细胞癌均行病理切片观察。结果：１３例ＣＴ表面低密度,伴肝内胆管扩张６例,合并肝内胆管结石４例;增强扫描呈线样强化５例,网络样强化４例,结节状强化２例,无明显强化２例。     

一种使用多特征的鱼类图像检索方法

为解决数量巨大、特征复杂的鱼类图像难以用单个特征准确描述,以至于给鱼类图像检索带来困难的问题,提出了一种基于多特征的鱼类图像检索方法——MFFIR,并针对鱼类图像的特点设计了由颜色直方图、特征矩和Gabor特征构成多维特征向量。在此基础上,采用MFFIR法通过计算多维特征向量的特征相关性,实现了鱼类图像的匹配与检索。为验证此方法的有效性,使用QUT_fish_data数据集和DLOU_fish_data数据集进行了仿真实验,实验结果表明,MFFIR法具有较好的准确率和较强的鲁棒性。     

一种使用多特征的鱼类图像检索方法

为解决数量巨大、特征复杂的鱼类图像难以用单个特征准确描述,以至于给鱼类图像检索带来困难的问题,提出了一种基于多特征的鱼类图像检索方法——MFFIR,并针对鱼类图像的特点设计了由颜色直方图、特征矩和Gabor特征构成多维特征向量。在此基础上,采用MFFIR法通过计算多维特征向量的特征相关性,实现了鱼类图像的匹配与检索。为验证此方法的有效性,使用"QUT_fish_data"数据集和"DLOU_fish_data"数据集进行了仿真实验,实验结果表明,MFFIR法具有较好的准确率和较强的鲁棒性。     

用主成分法进行林分及相关因子光谱特征研究

以1997年底、1998年初广东省12景美国LANDSAT TM数据为信息源,以地理信息系统(GIS)为平台,马尾松林、杉木林、桉树林、软阔叶林、硬阔叶林、其他阔叶林、针叶混交林、针阔混交林为研究对象,通过主成分分析,探讨TM光谱值及其比值项对林分及其相关因子的解释作用．结果表明,第4主分量均反映与林分蓄积有关的平均树高、平均胸径、龄组、郁闭度等信息,大部分林分的第1、2、3主分量均由波段光谱值及其比值项来反映其信息,其他主分量表示的信息因林分而异．     

A portrait of Alzheimer secretases--new features and familiar faces

The amyloid beta-peptide (Abeta) is a principal component of the cerebral plaques found in the brains of patients with Alzeheimer's disease (AD). This insoluble 40- to 42-amino acid peptide is formed by the cleavage of the Abeta precursor protein (APP). The three proteases that cleave APP, alpha-, beta-, and gamma-secretases, have been implicated in the etiology of AD. beta-Secretase is a membrane-anchored protein with clear homology to soluble aspartyl proteases, and alpha-secretase displays characteristics of certain membrane-tethered metalloproteases. gamma-Secretase is apparently an oligomeric complex that includes the presenilins, which may be the catalytic component of this protease. Identification of the alpha-, beta-, and gamma-secretases provides potential targets for designing new drugs to treat AD.     

A sublimation model for martian south polar ice features

In their pioneering work, Leighton and Murray argued that the Mars atmosphere, which at present is 95% carbon dioxide, is controlled by vapor equilibrium with a much larger polar reservoir of solid carbon dioxide. Here we argue that the polar reservoir is small and cannot function as a long-term buffer to the more massive atmosphere. Our work is based on modeling of the circular depressions commonly found on the south polar cap. We argue that a carbon dioxide ice layer about 8 meters thick is being etched away to reveal water ice underneath. This is consistent with thermal infrared data from the Mars Odyssey mission.     

基于多运动特征的森林火灾烟雾图像识别算法

为甄别林火烟雾与大气云雾,提出了基于多种运动特征判据的视频烟雾图像检测算法。首先利用烟雾自身 的光学动态特征———光流方向性、相关性、扩散性,分别对连续帧包含烟云的可疑区域进行图像特征标志判别;再 经数据融合算法有效区分林火烟雾与大气云雾,克服了依靠单一图像特征检测烟雾的不足。结果表明,光流方向 性、相关性、扩散性判别相结合的识别算法能提高森林火灾视频图像的有效识别率。      

13例肠系膜淋巴管瘤CT分析

目的：探讨肠系膜淋巴管瘤(ML)的CT表现及其分型。方法：经病理证实的ML13例，男7例，女6例，平均34岁。8例做常规CT扫描，5例做螺旋CT扫描，层厚10mm。结果：10例起源于小肠系膜，3例起源于结肠系膜。单房型囊肿3例，多发或多房囊肿10例，囊壁菲薄，光滑，囊内密度均匀，增强扫描如有囊壁及分隔有明显强化是其特点。成年型：囊肿形状较规则，分叶明显，类似扩张的结肠；幼儿型：囊肿形状欠规则，分叶及分隔不规则。结论：肠系膜淋巴管瘤好发于小肠系膜，无年龄特异性，CT表现为单房或多房性(多发性)囊肿，多呈壁薄分叶状多房性囊肿，增强扫描多数病变囊壁及分隔有明显强化。     

A ground-based hyperspectral imaging system for characterizing vegetation spectral features

A cropping system is usually characterized by continuous spatio-temporal vegetation variability. Vegetation variability can be detected by changes in several vegetation parameters defined according to purpose. Estimation of these vegetation parameters has been made possible by calculating various vegetation indices (VIs), usually by ratioing, differencing, ratioing differences and sums, or by forming linear combinations of spectral band data. Spectrometers or sensors have been used to acquire visible and infrared spectral properties of vegetation. This paper presents a ground-based hyperspectral imaging system for characterizing vegetation spectral features. The hyperspectral sensor used was a ground-based line sensor, ImSpector (V10-12-102), with a nominal spectral resolution of 1.5–2 nm and a wavelength range of 360–1010 nm. A graphical user interface (GUI) was developed in a MATLAB environment to aid in processing and analysis of acquired multidimensional spectral image data. Issues that arise when applying the imaging system to a particular field include acquiring hyperspectral images, selecting appropriate vegetation features or VIs, and quantifying the selected vegetation features or indices with the GUI developed. Vegetation features extracted by the proposed imaging system contribute not only to monitoring vegetation variability in crop systems, but also provide a potential source of relevant variables that can be used to estimate various vegetation parameters. A study that was set up to investigate the alternate bearing phenomenon of citrus trees illustrates the basic elements of the proposed approach.     

一种基于混合纹理特征的木板材表面缺陷检测方法

利用计算机视觉技术检测木板材表面缺陷。提出了一种基于混合纹理特征的表面缺陷检测算法,能准确、鲁棒地检测出木板材表面图像中是否有缺陷。首先,分别使用灰度共生矩阵方法、Gabor滤波方法和几何不变矩方法提取了10个优化后的图像纹理及尺度、平移、旋转不变特征;然后,对特征向量进行有效组合;最后,基于融合后的混合纹理特征向量,应用BP人工神经网络对样本集进行训练和检测。实验表明,该方法能准确地对木板材表面缺陷进行检测,平均检测成功率达96.2%。     

具有归属感的校园物质文化环境特性探究

校园是教书育人的圣地。为了营造具有归属感的校园物质文化环境,结合实际工作经验对校园环境特性进行分析,认为校园物质文化环境具有功能完善性、信息传达性、社会同步性、艺术多样性和文化特色性等特点。     

银川地区景天科多肉花卉新品种形态特征与栽培管理初报

景天科多肉花卉种类繁多、色彩丰富、形态各异、适应性强.以银川地区广泛应用的景天科多肉花卉为研究对象,开展其品种调查、收集和生长习性研究,探索多肉花卉在银川地区的种植与养护方法.     

Biologic features of HIV-1 that correlate with virulence in the host

Individuals infected with the human immunodeficiency virus type 1 (HIV-1) may be asymptomatic or have AIDS-related complex or the acquired immuno deficiency syndrome (AIDS). Little is known about the factors that influence progression of infection to AIDS. In this study of isolates of HIV-1 obtained at intervals during the infection of four individuals, the development of disease was found to be correlated with the emergence of HIV-1 variants that were more cytopathic in vitro as the disease progressed and that replicated more efficiently in a wide variety of different human cells. The biologic properties of HIV-1 in vitro thus appear to reflect its virulence in the host. Further studies of such sequentially isolated viruses may lead to the identification of viral genes that govern pathogenesis.     

跨境电子商务的商务英语语言特点与翻译问题研究

现阶段,随着全球一体化的深入发展和各国经济文化交往的日益密切,跨境电子商务的发展也取得了长足的进步。翻译是各国贸易往来之间重要的桥梁与纽带,在国际商务的交流与发展方面跨境电子商务英语的翻译发挥着不可替代的作用,承担着信息交流的重要作用,然而不可否认的是,近年来在跨境电子商务不断发展的背景下,商务英语的翻译却存在着一些问题,这在很大程度上阻碍了跨境电子商务的顺利发展。本文以跨境电子商务的商务英语语言特点与翻译问题为切入点,深入分析跨境电子商务英语的主要特征,并在此基础上提出了几条跨境电子商务英语的翻译技巧,希望对于促进跨境电子商务的商务英语翻译技能的提高有一定的积极影响。