基于AutoCAD环境前处理接口程序的开发     

霍俊芳 《内蒙古农业大学学报(自然科学版)》2003,24(2):92-95

本文通过分析传统的结构数据处理方法的缺陷，提出了基于AutoCAD环境下的前处理模式的开发；详细研究了Auto CAD的DXF文件结构，叙述了如何运用嵌套于AutoCAD内部的AutoLISP语言来读取、处理AutoCAD图形文件，进而生成计算程序所需要的数据文件；最后总结了前处理的主要工作。  相似文献   

Asteroid landing     

Guth JH  Alfvén H  Arrhenius G 《Science (New York, N.Y.)》1970,170(3965):1431-1432

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Structure of Nup58/45 suggests flexible nuclear pore diameter by intermolecular sliding     

Melcák I  Hoelz A  Blobel G 《Science (New York, N.Y.)》2007,315(5819):1729-1732

The nucleoporins Nup58 and Nup45 are part of the central transport channel of the nuclear pore complex, which is thought to have a flexible diameter. In the crystal structure of an alpha-helical region of mammalian Nup58/45, we identified distinct tetramers, each consisting of two antiparallel hairpin dimers. The intradimeric interface is hydrophobic, whereas dimer-dimer association occurs through large hydrophilic residues. These residues are laterally displaced in various tetramer conformations, which suggests an intermolecular sliding by 11 angstroms. We propose that circumferential sliding plays a role in adjusting the diameter of the central transport channel.  相似文献   

Wind as a long-distance dispersal vehicle in the Southern Hemisphere     

Muñoz J  Felicísimo AM  Cabezas F  Burgaz AR  Martínez I 《Science (New York, N.Y.)》2004,304(5674):1144-1147

Anisotropic (direction-dependent) long-distance dispersal (LDD) by wind has been invoked to explain the strong floristic affinities shared among landmasses in the Southern Hemisphere. Its contribution has not yet been systematically tested because of the previous lack of global data on winds. We used global winds coverage from the National Aeronautics and Space Administration SeaWinds scatterometer to test whether floristic similarities of Southern Hemisphere moss, liverwort, lichen, and pteridophyte floras conform better with (i) the anisotropic LDD hypothesis, which predicts that connection by "wind highways" increases floristic similarities, or (ii) a direction-independent LDD hypothesis, which predicts that floristic similarities among sites increase with geographic proximity. We found a stronger correlation of floristic similarities with wind connectivity than with geographic proximities, which supports the idea that wind is a dispersal vehicle for many organisms in the Southern Hemisphere.  相似文献   

Chemical transformations in individual ultrasmall biomimetic containers     

Chiu DT  Wilson CF  Ryttsén F  Strömberg A  Farre C  Karlsson A  Nordholm S  Gaggar A  Modi BP  Moscho A  Garza-López RA  Orwar O  Zare RN 《Science (New York, N.Y.)》1999,283(5409):1892-1895

Individual phospholipid vesicles, 1 to 5 micrometers in diameter, containing a single reagent or a complete reaction system, were immobilized with an infrared laser optical trap or by adhesion to modified borosilicate glass surfaces. Chemical transformations were initiated either by electroporation or by electrofusion, in each case through application of a short (10-microsecond), intense (20 to 50 kilovolts per centimeter) electric pulse delivered across ultramicroelectrodes. Product formation was monitored by far-field laser fluorescence microscopy. The ultrasmall characteristic of this reaction volume led to rapid diffusional mixing that permits the study of fast chemical kinetics. This technique is also well suited for the study of reaction dynamics of biological molecules within lipid-enclosed nanoenvironments that mimic cell membranes.  相似文献   

Chromosomal localization of muscle nicotinic acetylcholine receptor genes in the mouse   总被引：9，自引：0，他引：9  

O Heidmann  A Buonanno  B Geoffroy  B Robert  J L Guénet  J P Merlie  J P Changeux 《Science (New York, N.Y.)》1986,234(4778):866-868

The chromosomal localization of the genes encoding the four subunits of muscle nicotinic receptor was determined by analyzing restriction fragment length polymorphisms between two mouse species Mus musculus domesticus (DBA/2) and Mus spretus (SPE). Analysis of the progeny of the interspecies mouse backcross (DBA/2 X SPE) X DBA/2 showed that the alpha-subunit gene cosegregates with the alpha-cardiac actin gene on chromosome 17, that the beta-subunit gene is located on chromosome 11, and that the gamma- and delta-subunit genes cosegregate and are located on chromosome 1.  相似文献   

Comment on "Preserved feedforward but impaired top-down processes in the vegetative state"     

King JR  Bekinschtein T  Dehaene S 《Science (New York, N.Y.)》2011,334(6060):1203; author reply 1203

Boly et al. (Reports, 13 May 2011, p. 858) investigated cortical connectivity patterns in patients suffering from a disorder of consciousness, using electroencephalography in an auditory oddball paradigm. We point to several inconsistencies in their data, including a failure to replicate the classical mismatch negativity. Data quality, source reconstruction, and statistics would need to be improved to support their conclusions.  相似文献   

Forests of the past: a window to future changes     

Petit RJ  Hu FS  Dick CW 《Science (New York, N.Y.)》2008,320(5882):1450-1452

The study of past forest change provides a necessary historical context for evaluating the outcome of human-induced climate change and biological invasions. Retrospective analyses based on fossil and genetic data greatly advance our understanding of tree colonization, adaptation, and extinction in response to past climatic change. For instance, these analyses reveal cryptic refugia near or north of continental ice sheets, leading to reevaluation of postglacial tree migration rates. Species extinctions appear to have occurred primarily during periods of high climatic variability. Transoceanic dispersal and colonization in the tropics were widespread at geological time scales, inconsistent with the idea that tropical forests are particularly resistant to biological invasions.  相似文献   

Revisiting the taxonomic impediment     

de Carvalho MR  Bockmann FA  Amorim DS  de Vivo M  de Toledo-Piza M  Menezes NA  de Figueiredo JL  Castro RM  Gill AC  McEachran JD  Compagno LJ  Schelly RC  Britz R  Lundberg JG  Vari RP  Nelson G 《Science (New York, N.Y.)》2005,307(5708):353

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Infectious behavior in a parasitoid     

Varaldi J  Fouillet P  Ravallec M  López-Ferber M  Boulétreau M  Fleury F 《Science (New York, N.Y.)》2003,302(5652):1930

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