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Alice E. Fischer 《武汉大学学报:自然科学英文版》2001,6(1-2):83-99
Computers have changed nearly every aspect of life in this world. Invented roughly fifty years ago, they now form the infrastructure on which government, business, and global communications rest. As our reliance on computers increases, so does the number and complexity of the applications and the number and quality of trained professionals that will be needed to support further progress. The United States already faces personnel shortages in some computer-related jobs, including university teaching. In the face of this evident and increasing need, we must think clearly about out expectations for computing professionals of all sorts and the way they are trained. In the forty years that I have been in the field, the focus in industry has changed from programming to software development. A gulf is growing between the skills that students build at a university and the needs of industry. This paper examines the nature and extent of the problem and suggests a variety of ways to address it. 相似文献
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Although grand-design spiral galaxies are relatively common in the local Universe, only one has been spectroscopically confirmed to lie at redshift z?>?2 (HDFX 28; z = 2.011); and it may prove to be a major merger that simply resembles a spiral in projection. The rarity of spirals has been explained as a result of disks being dynamically 'hot' at z?>?2 (refs 2-5), which may instead favour the formation of commonly observed clumpy structures. Alternatively, current instrumentation may simply not be sensitive enough to detect spiral structures comparable to those in the modern Universe. At z?2, the velocity dispersion of disks decreases, and spiral galaxies are more numerous by z?≈?1 (refs 7, 13-15). Here we report observations of the grand-design spiral galaxy Q2343-BX442 at z = 2.18. Spectroscopy of ionized gas shows that the disk is dynamically hot, implying an uncertain origin for the spiral structure. The kinematics of the galaxy are consistent with a thick disk undergoing a minor merger, which can drive the formation of short-lived spiral structure. A duty cycle of <100?Myr for such tidally induced spiral structure in a hot massive disk is consistent with its rarity. 相似文献
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We captured >2000 Crawford’s gray shrews ( Notiosorex crawfordi ) in a riparian forest mainly consisting of cottonwoods ( Populus deltoides ) along the Rio Grande in central New Mexico. Little has been published about abundance and habitat of Crawford’s gray shrew throughout its distributional range. During 7 summers, we captured shrews in pitfall traps at 13 study sites in Bernalillo, Valencia, and Socorro counties. Capture rates of shrews were greatest in August and September, and we did not detect a response of shrews to restoration treatments that removed nonnative plants from riparian forests. Results from our study indicate that (1) Crawford’s gray shrews are more abundant in riparian habitats than historically presumed and (2) pitfall traps with drift fences are an effective means to capture shrews. 相似文献
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Cortina C Palomo-Ponce S Iglesias M Fernández-Masip JL Vivancos A Whissell G Humà M Peiró N Gallego L Jonkheer S Davy A Lloreta J Sancho E Batlle E 《Nature genetics》2007,39(11):1376-1383
The genes encoding tyrosine kinase receptors EphB2 and EphB3 are beta-catenin and Tcf4 target genes in colorectal cancer (CRC) and in normal intestinal cells. In the intestinal epithelium, EphB signaling controls the positioning of cell types along the crypt-villus axis. In CRC, EphB activity suppresses tumor progression beyond the earliest stages. Here we show that EphB receptors compartmentalize the expansion of CRC cells through a mechanism dependent on E-cadherin-mediated adhesion. We demonstrate that EphB-mediated compartmentalization restricts the spreading of EphB-expressing tumor cells into ephrin-B1-positive territories in vitro and in vivo. Our results indicate that CRC cells must silence EphB expression to avoid repulsive interactions imposed by normal ephrin-B1-expressing intestinal cells at the onset of tumorigenesis. 相似文献
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Delous M Baala L Salomon R Laclef C Vierkotten J Tory K Golzio C Lacoste T Besse L Ozilou C Moutkine I Hellman NE Anselme I Silbermann F Vesque C Gerhardt C Rattenberry E Wolf MT Gubler MC Martinovic J Encha-Razavi F Boddaert N Gonzales M Macher MA Nivet H Champion G Berthélémé JP Niaudet P McDonald F Hildebrandt F Johnson CA Vekemans M Antignac C Rüther U Schneider-Maunoury S Attié-Bitach T Saunier S 《Nature genetics》2007,39(7):875-881
Cerebello-oculo-renal syndrome (CORS), also called Joubert syndrome type B, and Meckel (MKS) syndrome belong to the group of developmental autosomal recessive disorders that are associated with primary cilium dysfunction. Using SNP mapping, we identified missense and truncating mutations in RPGRIP1L (KIAA1005) in both CORS and MKS, and we show that inactivation of the mouse ortholog Rpgrip1l (Ftm) recapitulates the cerebral, renal and hepatic defects of CORS and MKS. In addition, we show that RPGRIP1L colocalizes at the basal body and centrosomes with the protein products of both NPHP6 and NPHP4, known genes associated with MKS, CORS and nephronophthisis (a related renal disorder and ciliopathy). In addition, the RPGRIP1L missense mutations found in CORS individuals diminishes the interaction between RPGRIP1L and nephrocystin-4. Our findings show that mutations in RPGRIP1L can cause the multiorgan phenotypic abnormalities found in CORS or MKS, which therefore represent a continuum of the same underlying disorder. 相似文献
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de Pontual L Yao E Callier P Faivre L Drouin V Cariou S Van Haeringen A Geneviève D Goldenberg A Oufadem M Manouvrier S Munnich A Vidigal JA Vekemans M Lyonnet S Henrion-Caude A Ventura A Amiel J 《Nature genetics》2011,43(10):1026-1030
MicroRNAs (miRNAs) are key regulators of gene expression in animals and plants. Studies in a variety of model organisms show that miRNAs modulate developmental processes. To our knowledge, the only hereditary condition known to be caused by a miRNA is a form of adult-onset non-syndromic deafness, and no miRNA mutation has yet been found to be responsible for any developmental defect in humans. Here we report the identification of germline hemizygous deletions of MIR17HG, encoding the miR-17~92 polycistronic miRNA cluster, in individuals with microcephaly, short stature and digital abnormalities. We demonstrate that haploinsufficiency of miR-17~92 is responsible for these developmental abnormalities by showing that mice harboring targeted deletion of the miR-17~92 cluster phenocopy several key features of the affected humans. These findings identify a regulatory function for miR-17~92 in growth and skeletal development and represent the first example of an miRNA gene responsible for a syndromic developmental defect in humans. 相似文献
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The genome of the mesopolyploid crop species Brassica rapa 总被引:21,自引:0,他引:21
Wang X Wang H Wang J Sun R Wu J Liu S Bai Y Mun JH Bancroft I Cheng F Huang S Li X Hua W Wang J Wang X Freeling M Pires JC Paterson AH Chalhoub B Wang B Hayward A Sharpe AG Park BS Weisshaar B Liu B Li B Liu B Tong C Song C Duran C Peng C Geng C Koh C Lin C Edwards D Mu D Shen D Soumpourou E Li F Fraser F Conant G Lassalle G King GJ Bonnema G Tang H Wang H Belcram H Zhou H Hirakawa H Abe H Guo H Wang H Jin H Parkin IA Batley J Kim JS Just J Li J Xu J Deng J Kim JA Li J Yu J Meng J Wang J Min J 《Nature genetics》2011,43(10):1035-1039
We report the annotation and analysis of the draft genome sequence of Brassica rapa accession Chiifu-401-42, a Chinese cabbage. We modeled 41,174 protein coding genes in the B. rapa genome, which has undergone genome triplication. We used Arabidopsis thaliana as an outgroup for investigating the consequences of genome triplication, such as structural and functional evolution. The extent of gene loss (fractionation) among triplicated genome segments varies, with one of the three copies consistently retaining a disproportionately large fraction of the genes expected to have been present in its ancestor. Variation in the number of members of gene families present in the genome may contribute to the remarkable morphological plasticity of Brassica species. The B. rapa genome sequence provides an important resource for studying the evolution of polyploid genomes and underpins the genetic improvement of Brassica oil and vegetable crops. 相似文献
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