试论银心说及其应用

本文以天地人统一现论述了人类认识宇宙历史的发展，包括从地心说到日心说，又从日心说到银心说等，把银心作为我们所在星系－－银河系的中心去观察分析包括太阳系演化在内的各种有关天象的见解，称为银心说，几是研究长时间尺度的天象，必然涉及太空范围，就更应当使用银心说。本文应用银心说着重研究了近６亿年来地球上所多次发生的各类全巨变事件的银河旋臂成因，接着又从银河系的高度对太阳系的形成，地球水的来源和地生命的起原     

以色列暗物质研究取得进展

“暗物质”是一种不可见的物质，是构成宇宙绝大多数物体的原素，它非常神秘，因为目前不仅没人知道它的构成，而且在有些星系中还难觅其踪。在今天的英国《自然》杂志上，以色列希伯来大学的研究人员公布了他们的最新研究发现，即在那些看起来似乎不含”暗物质”的星系中，“暗物质”其实也依然存在。     

VLBI软件相关处理机研究进展及其在深空探测中的应用

甚长基线干涉测量（VLBI）是重要的射电天文技术，具有极高的空间分辨率，是国际上广泛采用的深空探测器高精度测量手段，相关处理机则是VLBI数据预处理的核心设备.由于VLBI观测数据的相关处理具有数据密集和计算密集的双重特点，目前绝大多数均由专用的大规模高速硬件相关处理机承担.随着通用计算机性能的迅猛发展，基于通用商用计算机的VLBI软件相关处理机的研究逐渐得到重视，并发展迅速，成为VLBI技术领域新的研究热点.软件相关处理机具有制造价低、复制容易、升级简便等特点，有可能在不久的将来，以深空探测领域为切入点，得以普遍应用，并且在常规天文数据相关处理中替代现有的硬件相关处理机。     

基于文献计量的天文学科发展态势分析

本文基于2014-2019年天文学领域发表的8.2万篇论文进行文献计量,从产出规模、学科布局、学术影响等角度分析我国天文学科的发展现状.从论文产出规模看,我国天文学科以第一作者统计全球排名第二位;在过去5年论文量增幅远高于世界平均水平.从学科布局看,我国在太阳物理领域学术产出比较活跃;星系宇宙学、恒星银河系科学产出稳定...     

法国和瑞士科学家观测到迄今最遥远星系

借助设在南美洲智利的欧洲ESO天文望远镜,法国与瑞士科学家最近发现了一个距地球132亿多光年的星系。据有关媒体称,这是迄今人类观测到的最遥远的星系。据《欧洲天体物理与天文学》杂志近日报道,法国科研中心与瑞士日内瓦大学的科学家借助“引力透镜效应”,在阿贝尔1835星系团中观测到了这个名为IR1916的星系。根据爱因斯坦的广义相对论,所谓“引力透镜效应”,就是当光在星系、星系团、黑洞等具有巨大引力的天体附近通过时,光会像通过凸透镜一样发生弯曲。根据变化了的光线在光谱红外波段呈现的不规则程度,也就是红移值,可以推算出发光星…     

"哈勃"望远镜拍到宇宙最深处景观照片

美国宇航局前些时候说,“哈勃”太空望远镜新拍到了迄今可见宇宙最深处景观的照片,这张具有历史意义的照片中可能包含着宇宙诞生后不久产生的最早的星系。科学界普遍认为,宇宙诞生于距今约137亿年前的“大爆炸”。在“大爆炸”后的3亿年间,宇宙处于黑暗和冷寂状态,随后第一批恒星以及星系开始产生。“哈勃”新拍下的照片捕获到的正是宇宙中首批星系所发出的光芒。美国宇航局在公布新照片时称,该照片是根据“哈勃”望远镜两台相机的拍摄结果合成的,共包含约1万个星系。从照片上看,这些星系仿佛散落在黑天鹅绒上的宝石。照片覆盖的太空区域相…     

基于中美基金项目数据的深度学习领域研究热点对比分析

与传统研究成果类型不同，基金项目数据中蕴含的潜在情报更具有战略性和前瞻性。本文使用文本挖掘方法，对中美深度学习领域基金项目数据进行挖掘与分析，从资助强度、发展态势、主题聚类及热度演化角度进行分析，对比中美深度学习领域研究热点的异同及热点演化情况。研究发现，中美深度学习领域基金项目数量自2010年后呈上升趋势，发展势头较好，且两国均出台相关政策支持该领域发展。但中美两国在研究的侧重方向上有所不同，美国侧重深度学习基础理论、算法研究，中国在深度学习更关注应用层面的落地情况。在应用层面上，美国更重视生物医学、经济领域、图像识别领域及硬件设备应用，中国不仅重视生物医学领域、同时使用深度学习相关算法对地学领域、多媒体领域的数据应用较多。新兴研究方向上，对深度学习硬件设备及应用方向成为美国的近年来研究热点方向，而中国较新的研究热点方向在于将深度学习应用到生物信息领域。未来我国应加大科研经费的投入，支持人工智能领域的自主创新发展；发挥在地学领域应用、图像和计算机视觉、多媒体领域、以及中医领域应用的科技布局优势，形成成果转化新生态；应关注和加强对理论算法的研究，提高技术实力并掌握科技主动权；对软硬件及...     

基于专利分析的煤炭清洁高效转化技术发展态势分析

实现碳达峰碳中和目标要求加快推进能源绿色低碳转型与创新发展。本文围绕煤炭清洁高效转化技术及相关能源政策，从专利分布、技术来源地、领先专利申请人等方面分析了相关专利的整体发展趋势。专利布局情况分析结果表明，我国是煤炭清洁高效转化技术领域专利的主要研发力量和目标市场国家；中国煤炭清洁高效转化技术各领域的专利技术构成揭示了我国当前的重点研究领域；结合煤炭转化利用领域近年获得国家科技进步奖的项目中具有自主知识产权的关键核心技术来深入分析专利布局情况。在此基础上，提出煤炭转化关键专利技术应向生产力转化，抓住“一带一路”机遇以提升我国现代煤化工产业国际竞争力。     

基于文献计量的人脸识别技术研究进展与趋势分析

基于1991年以来全球人脸识别领域的研究论文和专利数据,对人脸识别技术的时间发展趋势、被引频次、产出国、研究机构等进行分析,并绘制引文编年图对演化路径进行解读。研究表明:中国和美国是目前世界上人脸识别研究领域综合实力最强的两个国家。美国在人脸识别的历史发展中起到了关键性作用;中国人脸识别研究整体水平已经进入世界先进行列,但整体学术影响力和科研质量有待进一步提高。从演化路径来看,人脸识别的技术演进经过了传统算法和深度学习算法两个阶段,后者是目前的主流算法。未来,提高在非理想环境下的人脸辨识度将是人脸识别研究的重点。     

悖论中的爆炸

以一种的的视角对大爆炸宇宙提出质疑从空间膨胀特性的分析入手而导出大爆炸理论与其赖以存在的基本证据之间深刻而又难以克服的矛盾性，基于提出了几条定理和结论，推导出几科遍及大爆炸理论与其基础证据中的悖论，诸如可测空间膨胀渤论，星系红移与宇宙起源论，哈毂定律与大爆炸悖论，此力与哈勃定律悖论等等。通过对上述悖论的分析，提出星系红移产生于一种非多普勒效应的新机制的可能性。并对其他的理论要点作了简要的分析。     

Pepsinogens, progastricsins, and prochymosins: structure, function, evolution, and development

Five types of zymogens of pepsins, gastric digestive proteinases, are known: pepsinogens A, B, and F, progastricsin, and prochymosin. The amino acid and/or nucleotide sequences of more than 50 pepsinogens other than pepsinogen B have been determined to date. Phylogenetic analyses based on these sequences indicate that progastricsin diverged first followed by prochymosin, and that pepsinogens A and F are most closely related. Tertiary structures, clarified by X-ray crystallography, are commonly bilobal with a large active-site cleft between the lobes. Two aspartates in the center of the cleft, Asp32 and Asp215, function as catalytic residues, and thus pepsinogens are classified as aspartic proteinases. Conversion of pepsinogens to pepsins proceeds autocatalytically at acidic pH by two different pathways, a one-step pathway to release the intact activation segment directly, and a stepwise pathway through a pseudopepsin(s). The active-site cleft is large enough to accommodate at least seven residues of a substrate, thus forming S₄ through S₃′ subsites. Hydrophobic and aromatic amino acids are preferred at the P₁ and P₁′ positions. Interactions at additional subsites are important in some cases, for example with cleavage of κ-casein by chymosin. Two potent naturally occurring inhibitors are known: pepstatin, a pentapeptide from Streptomyces, and a unique proteinous inhibitor from Ascaris. Pepsinogen genes comprise nine exons and may be multiple, especially for pepsinogen A. The latter and progastricsin predominate in adult animals, while pepsinogen F and prochymosin are the main forms in the fetus/infant. The switching of gene expression from fetal/infant to adult-type pepsinogens during postnatal development is noteworthy, being regulated by several factors, including steroid hormones. Received 25 May 2001; received after revision 27 August 2001; accepted 30 August 2001     

Bile Acids: Chemistry, Pathochemistry, Biology, Pathobiology, and Therapeutics

Bile acids and bile alcohols in the form of their conjugates are amphipathic end products of cholesterol metabolism with multiple physiological functions. The great variety of bile acids and bile alcohols that are present in vertebrates are tabulated. Bile salts have an enterohepatic circulation resulting from efficient vectorial transport of bile salts through the hepatocyte and the ileal enterocyte; such transport leads to the accumulation of a pool of bile salts that cycles between the liver and intestine. Bile salt anions promote lipid absorption, enhance tryptic cleavage of dietary proteins, and have antimicrobial effects. Bile salts are signaling molecules, activating nuclear receptors in the hepatocyte and ileal enterocyte, as well as an increasing number of G-protein coupled receptors. Bile acids are used therapeutically to correct deficiency states, to decrease the cholesterol saturation of bile, or to decrease the cytotoxicity of retained bile acids in cholestatic liver disease.     

Immunofluorescent localization of collagen types I,III, IV,V, fibronectin,laminin, entactin,and heparan sulphate proteoglycan in human immature placenta

The distribution of eight components of the extracellular matrix in immature human placenta was studied by an indirect immunofluorescence method with monospecific antibodies. In the stroma of the term chorionic villi, collagen types I, III, IV, V, and fibronectin formed a mesh of fibers and conglomerates. Heparan sulphate proteoglycan formed multiple conglomerates, whereas laminin comprised small, scanty, discrete granules. Collagen type IV, laminin, entactin, and heparan sulphate proteoglycan were confined to the basement membrane of the trophoblast. Sometimes, only collagen type IV was identified in fetal vascular basement membrane.     

Phylogeography of crossbills, bullfinches, grosbeaks, and rosefinches

Mitochondrial cytochrome b (cyt b) from 24 Carduelini species including crossbills, bullfinches, grosbeaks, rosefinches, and other related, but not conclusively classified species, was sequenced. These sequences were also compared with all the available sequences from the genera Carduelis, Serinus, and Passer. Phylogenetic analyses consistently gave the same groups of finches and the calculated divergence times suggest that speciation of the studied species occurred between 14 and 3 million years ago (Miocene-Pliocene), appearing before the Passer, Carduelis, and Serinus genera. Pleistocene glaciations may have been important in sub-speciation. Crossbills are integrated within the genus Carduelis, and within redpolls; the common crossbill shows subspeciation with Loxia japonica in the Pleistocene epoch. Pinicola enucleator groups together with bullfinches and is probably the ancestor of the group. Hawfinch is only distantly related to the studied groups, and might either represent an isolated genus or be related to the New World genus Hesperiphona. The grosbeak genera Eophona and Mycerobas are clearly sister groups, and species belonging to the former might have given rise to Mycerobas species. The isolated (in classification) Uragus sibiricus and Haematospiza sipahi are included within the genus Carpodacus (rosefinches); Carpodacus nipalensis is outside the genus Carpodacus in the molecular analyses and might be an isolated species or related to the genus Montifringilla.     

Forecasting technique familiarity,satisfaction, usage,and application

A ten-year retrospective study of Mentzer and Cox (1984) was undertaken to answer the question 'Have sales forecasting practices changed over the past ten years?' A mail survey of 207 forecasting executives was employed to investigate this important question. Findings revealed both discrepancies and similarities between today's sales forecasting practices and those of ten years ago. One particular finding indicated greater reliance on and satisfaction with quantitative forecasting techniques today versus ten years ago. Another indicated that forecasting accuracy has not improved over the past ten years, even though the familiarity and usage of various sophisticated sales forecasting techniques have increased. Future research and managerial implications are discussed based on these and other findings.