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991.
992.
Tyers M Brown E Andrews DW Bergeron JJ Boone C Bremner R Bussey HA Cross JC Davies JE Desjardins M Dick JE Dumont DJ Durocher D Ellison MJ Golding GB Gray MW Harrington LA Hieter PA Johnston G Kelvin DJ McCarry BE Michnick SW Ouellette F Pearlman RE Penn LJ Pelletier J Rachubinski RA Rennie PS Rotin D Rottapel R Sadowski I Sicheri F Siminovitch L Sonenberg N Siu KW Tremblay ML Winegarden N Wozniak RW Wright GD Woodgett JR 《Science (New York, N.Y.)》2005,308(5730):1867
993.
Cirak F Cisternas JE Cuitiño AM Ertl G Holmes P Kevrekidis IG Ortiz M Rotermund HH Schunack M Wolff J 《Science (New York, N.Y.)》2003,300(5627):1932-1936
Because of the small thermal capacity of ultrathin ( approximately 200 nanometers) metal single crystals, it is possible to explore the coupling of catalytic and thermal action at low pressures. We analyzed a chemothermomechanical instability in this regime, in which catalytic reaction kinetics interact with heat transfer and mechanical buckling to create oscillations. These interacting components are separated and explored through experimentation, mathematical modeling, and scientific computation, and an explanation of the phenomenon emerges from their synthesis. 相似文献
994.
Vekua A Lordkipanidze D Rightmire GP Agusti J Ferring R Maisuradze G Mouskhelishvili A Nioradze M De Leon MP Tappen M Tvalchrelidze M Zollikofer C 《Science (New York, N.Y.)》2002,297(5578):85-89
Another hominid skull has been recovered at Dmanisi (Republic of Georgia) from the same strata in which hominid remains have been reported previously. The Dmanisi site dated to approximately 1.75 million years ago has now produced craniofacial portions of several hominid individuals, along with many well-preserved animal fossils and quantities of stone artifacts. Although there are certain anatomical differences among the Dmanisi specimens, the hominids do not clearly represent more than one taxon. We assign the new skull provisionally to Homo erectus (=ergaster). The Dmanisi specimens are the most primitive and small-brained fossils to be grouped with this species or any taxon linked unequivocally with genus Homo and also the ones most similar to the presumed habilis-like stem. We suggest that the ancestors of the Dmanisi population dispersed from Africa before the emergence of humans identified broadly with the H. erectus grade. 相似文献
995.
Gilbert MT Jenkins DL Götherstrom A Naveran N Sanchez JJ Hofreiter M Thomsen PF Binladen J Higham TF Yohe RM Parr R Cummings LS Willerslev E 《Science (New York, N.Y.)》2008,320(5877):786-789
The timing of the first human migration into the Americas and its relation to the appearance of the Clovis technological complex in North America at about 11,000 to 10,800 radiocarbon years before the present (14C years B.P.) remains contentious. We establish that humans were present at Paisley 5 Mile Point Caves, in south-central Oregon, by 12,300 14C years B.P., through the recovery of human mitochondrial DNA (mtDNA) from coprolites, directly dated by accelerator mass spectrometry. The mtDNA corresponds to Native American founding haplogroups A2 and B2. The dates of the coprolites are >1000 14C years earlier than currently accepted dates for the Clovis complex. 相似文献
996.
The fossil record of early feathers has relied on carbonized compressions that lack fine structural detail. Specimens in amber are preserved in greater detail, but they are rare. Late Cretaceous coal-rich strata from western Canada provide the richest and most diverse Mesozoic feather assemblage yet reported from amber. The fossils include primitive structures closely matching the protofeathers of nonavian dinosaurs, offering new insights into their structure and function. Additional derived morphologies confirm that plumage specialized for flight and underwater diving had evolved in Late Cretaceous birds. Because amber preserves feather structure and pigmentation in unmatched detail, these fossils provide novel insights regarding feather evolution. 相似文献
997.
998.
Summary The use of transgenic plants in breeding makes it possible to utilise a wide variety of novel genes from unrelated plants, microbes and animals. Because of the diversity of genes that have now become available for modifying crop plants, it is agreed internationally that there should be a risk assessment before transgenic plants are grown outside the laboratory or glasshouse. Various aspects are considered in a risk assessment including any non-target effects of the transgene, changes in plant persistence and invasiveness, and the possibility of movement of the transgenes to wild populations by cross pollination. It is generally argued that the need for risk assessment and regulation should be determined by an analysis of certain products of transformation, rather than a risk assessment being required for all plants modified by the process of transformation. A possible consequence of considering the product only, however, could be that some of the products of conventional breeding may need to be assessed by the risk assessment procedures developed for transgenic plants. There are discussions with interest groups on the use of transgenic plants in the environment and in food products. It is likely that some form of labelling will be required for certain foods containing ethically-sensitive genes. There is little doubt that transgenic plants will make a significant contribution to agriculture in the coming decades. Developments in the patenting of genes, release regulations, food labelling, consumer reaction etc., will influence the rate of progress and should be considered in the strategic planning of plant breeding programmes. 相似文献
999.
1000.
Development of AFLP and derived CAPS markers for root-knot nematode resistance in cotton 总被引:3,自引:0,他引:3
Resistance to root-knot nematode (Meloidogyne incognita) is determined by a single major gene rkn1 in Gossypium hirsutum Acala NemX cotton. Bulked segregant analysis (BSA) combined with amplified fragment length polymorphism (AFLP) was used to identify molecular markers linked to rkn1. DNA pools from homozygous susceptible (S) and resistant (R) bulks of an F2:3 originating from the intraspecific cross NemX × SJ-2 were screened with 128 EcoR1/Mse1 primer combinations. Putative AFLP markers were then screened with 60 F2:7 RIL plants and four AFLP markers were found linked to rkn1. The linkage of AFLP markers to rkn1 was also confirmed in a F2 population. The closest AFLP marker was converted to a cleaved amplified polymorphic sequence (CAPS) marker (designated GHACC1) by aligning the sequences from both susceptible and resistant parents. GHACC1 linkage to rkn1 was confirmed in the F2 (1R:3S), F2:7 RIL (1R:1S) and the backcross population SJ-2 × F1 (NemX × SJ-2) (1 heterozygous: 1 homozygous). The four AFLP markers, GHACC1 plus two SSR markers (CIR316 and BNL1231) linked to rkn1 from previous work were mapped to intervals of 2.6–14.2 cM from the rkn1 locus, and the genomic region around rkn1 was spanned to about 28.2 cM in the F2:7 population. The PCR-based GHACC1 and CIR316 markers were tested on 21 nematode resistant and susceptible cotton breeding lines and cultivars. GHACC1 was suitable for nematode resistance screening within G.␣hirsutum, but not G. barbadense, whereas CIR316 was useful in both species, indicating their␣potential for utilization in marker-assisted selection. 相似文献