Prospects brighten for electron accelerator     

Crawford M 《Science (New York, N.Y.)》1985,228(4696):161

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Condor agreement reached     

Crawford M 《Science (New York, N.Y.)》1985,229(4719):1248

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Gene Mapping Japan's Number One Crop     

Crawford R 《Science (New York, N.Y.)》1991,252(5013):1611

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Hot fusion: a meltdown in political support     

Crawford M 《Science (New York, N.Y.)》1990,247(4950):1534-1535

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Japanes Wire for U.S. SSC Magnets?     

Crawford MH 《Science (New York, N.Y.)》1989,246(4934):1117

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Superconductors: is Japan ahead?     

Crawford M 《Science (New York, N.Y.)》1988,241(4862):152-153

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Ordered and dynamic assembly of single spliceosomes     

Hoskins AA  Friedman LJ  Gallagher SS  Crawford DJ  Anderson EG  Wombacher R  Ramirez N  Cornish VW  Gelles J  Moore MJ 《Science (New York, N.Y.)》2011,331(6022):1289-1295

The spliceosome is the complex macromolecular machine responsible for removing introns from precursors to messenger RNAs (pre-mRNAs). We combined yeast genetic engineering, chemical biology, and multiwavelength fluorescence microscopy to follow assembly of single spliceosomes in real time in whole-cell extracts. We find that individual spliceosomal subcomplexes associate with pre-mRNA sequentially via an ordered pathway to yield functional spliceosomes and that association of every subcomplex is reversible. Further, early subcomplex binding events do not fully commit a pre-mRNA to splicing; rather, commitment increases as assembly proceeds. These findings have important implications for the regulation of alternative splicing. This experimental strategy should prove widely useful for mechanistic analysis of other macromolecular machines in environments approaching the complexity of living cells.  相似文献   

Oxygen Isotope Effect and Structural Phase Transitions in La2CuO4-Based Superconductors     

Crawford MK  Farneth WE  McCarronn EM  Harlow RL  Moudden AH 《Science (New York, N.Y.)》1990,250(4986):1390-1394

The oxygen isotope effect on the superconducting transition temperature (alpha(o)) varies as a function of x in La2-xSrxCuO(4) and La2-xBaxCuO(4), with the maximum alpha(o) values (alpha(o) >/= 0.5) found for x near 0.12. This unusual x dependence implies that the isotope effect is influenced by proximity to the Abma --> P4(2)/ncm structural phase transition in these systems. Synchrotron x-ray difaction measurements reveal little change in lattice parameters or orthorhombicity due to isotope exchange in strontium-doped materials where alpha(o) > 0.5, eliminating static structural distortion as a cause of the large isotope effects. The anomalous behavior of alpha(o) in both strontium- and barium-doped materials, in combination with the previously discovered Abma --> P4(2)/ncm structural phase-transition in La(1.88)B(0.12)CuO(4), suggests that an electronic contribution to the lattice instability is present and maximizes at approximately 1/8 hole per copper atom. These observations indicate a dose connection between hole doping of the Cu-O sheets, tilting instabilities of the CuO(6) octahedra, and superconductivity in La(2)CuO(4)-based superconductors.  相似文献   

Clinical outcome following pneumonectomy for management of chronic pyothorax in four cats     

Crawford AH  Halfacree ZJ  Lee KC  Brockman DJ 《Journal of Feline Medicine and Surgery》2011,13(10):762-767

Pneumonectomy is the resection of all lung lobes from one side of the thorax. The clinical findings, treatment and outcome of four cases of feline chronic pyothorax managed with exploratory thoracotomy and pneumonectomy are reported. All cases were initially medically managed with thoracic drain placement and antibiosis. However, resolution was not achieved with medical therapy and diagnostic imaging findings consistent with an area of abscessation or marked lung lobe consolidation were identified, supporting a decision for surgical management. Surgical exploration was performed via median sternotomy and, on the basis of gross inspection, non-functional lung was removed. A left-sided pneumonectomy was performed in three cats and a right-sided pneumonectomy in one. All cases survived to discharge and an excellent quality of life was reported on long-term follow-up. Pneumonectomy appears to be well tolerated in the cat.  相似文献   

Significance of earthworms in stimulating soil microbial activity   总被引：9，自引：0，他引：9  

F. Binet  L. Fayolle  M. Pussard  J. J. Crawford  S. J. Traina  O. H. Tuovinen 《Biology and Fertility of Soils》1998,27(1):79-84

 The stimulatory effect of earthworms (Lumbricus terrestris L.) on soil microbial activity was studied under microcosm-controlled conditions. The hypothesis was tested that microbial stimulation observed in the presence of a soil invertebrate would be due to the utilization of additional nutritive substances (secretion and excretion products) that it provides. Changes in microbial activity were monitored by measuring simultaneously CO₂ release and protozoan population density. The increase in CO₂ released in the presence of earthworms was found to result from both earthworm respiration and enhanced microbial respiration. The stimulation of microbial activity was confirmed by a significant increase in protozoan population density, which was 3–19 times greater in the presence of earthworms. The respiratory rate of L. terrestris was estimated to be 53 μl O₂ g^–1 h^–1. Earthworm respiration significantly correlated with individual earthworm weight, but there was no correlation between the increase in microbial respiration and earthworm weight. This finding does not support the hypothesis given above that enhanced microbial respiration is due to utilization of earthworm excreta. A new hypothesis that relationships between microbial activity and earthworms are not based on trophic links alone but also on catalytic mechanisms is proposed and discussed. Received: 26 August 1997  相似文献