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81.
Fynbo HO Diget CA Bergmann UC Borge MJ Cederkäll J Dendooven P Fraile LM Franchoo S Fedosseev VN Fulton BR Huang W Huikari J Jeppesen HB Jokinen AS Jones P Jonson B Köster U Langanke K Meister M Nilsson T Nyman G Prezado Y Riisager K Rinta-Antila S Tengblad O Turrion M Wang Y Weissman L Wilhelmsen K Aystö J;ISOLDE Collaboration 《Nature》2005,433(7022):136-139
In the centres of stars where the temperature is high enough, three alpha-particles (helium nuclei) are able to combine to form 12C because of a resonant reaction leading to a nuclear excited state. (Stars with masses greater than approximately 0.5 times that of the Sun will at some point in their lives have a central temperature high enough for this reaction to proceed.) Although the reaction rate is of critical significance for determining elemental abundances in the Universe, and for determining the size of the iron core of a star just before it goes supernova, it has hitherto been insufficiently determined. Here we report a measurement of the inverse process, where a 12C nucleus decays to three alpha-particles. We find a dominant resonance at an energy of approximately 11 MeV, but do not confirm the presence of a resonance at 9.1 MeV (ref. 3). We show that interference between two resonances has important effects on our measured spectrum. Using these data, we calculate the triple-alpha rate for temperatures from 10(7) K to 10(10) K and find significant deviations from the standard rates. Our rate below approximately 5 x 10(7) K is higher than the previous standard, implying that the critical amounts of carbon that catalysed hydrogen burning in the first stars are produced twice as fast as previously believed. At temperatures above 10(9) K, our rate is much less, which modifies predicted nucleosynthesis in supernovae. 相似文献
82.
Entesarian M Matsson H Klar J Bergendal B Olson L Arakaki R Hayashi Y Ohuchi H Falahat B Bolstad AI Jonsson R Wahren-Herlenius M Dahl N 《Nature genetics》2005,37(2):125-127
Autosomal dominant aplasia of lacrimal and salivary glands (ALSG; OMIM 180920 and OMIM 103420) is a rare condition characterized by irritable eyes and dryness of the mouth. We mapped ALSG to 5p13.2-5q13.1, which coincides with the gene fibroblast growth factor 10 (FGF10). In two extended pedigrees, we identified heterozygous mutations in FGF10 in all individuals with ALSG. Fgf10(+/-) mice have a phenotype similar to ALSG, providing a model for this disorder. We suggest that haploinsufficiency for FGF10 during a crucial stage of development results in ALSG. 相似文献
83.
MYCN haploinsufficiency is associated with reduced brain size and intestinal atresias in Feingold syndrome 总被引:3,自引:0,他引:3
van Bokhoven H Celli J van Reeuwijk J Rinne T Glaudemans B van Beusekom E Rieu P Newbury-Ecob RA Chiang C Brunner HG 《Nature genetics》2005,37(5):465-467
Feingold syndrome is characterized by variable combinations of esophageal and duodenal atresias, microcephaly, learning disability, syndactyly and cardiac defect. We show here that heterozygous mutations in the gene MYCN are present in Feingold syndrome. All mutations are predicted to disrupt both the full-length protein and a new shortened MYCN isoform, suggesting that multiple aspects of early embryogenesis and postnatal brain growth in humans are tightly regulated by MYCN dosage. 相似文献
84.
Vega H Waisfisz Q Gordillo M Sakai N Yanagihara I Yamada M van Gosliga D Kayserili H Xu C Ozono K Jabs EW Inui K Joenje H 《Nature genetics》2005,37(5):468-470
Roberts syndrome is an autosomal recessive disorder characterized by craniofacial anomalies, tetraphocomelia and loss of cohesion at heterochromatic regions of centromeres and the Y chromosome. We identified mutations in a new human gene, ESCO2, associated with Roberts syndrome in 15 kindreds. The ESCO2 protein product is a member of a conserved protein family that is required for the establishment of sister chromatid cohesion during S phase and has putative acetyltransferase activity. 相似文献
85.
Diversity of arbuscular mycorrhizal fungi associated with desert ephemerals growing under and beyond the canopies of Tamarisk shrubs 总被引:3,自引:0,他引:3
SHI Zhaoyong ZHANG Liyun FENG Gu Chr stie Peter TIAN Changyan LI Xiaolin 《科学通报(英文版)》2006,51(A01):132-139
The arbuscular mycorrhizal (AM) fungal status of the four most common ephemeral plant species, Chorispora tenella (Pall.) DC., Ceratocephalus testiculatus (Crantz) Bess., Eremopyrum orientale (L.) Jaub et. Spash and Veronica campyIopoda Boiss growing in an area dominated by Tamarisk shrubs (Tamarix spp.) was investigated. Samples of the four ephemerals and their rhizosphere soils were collected from underneath and beyond the canopies of the Tamarisk shrubs. Plant mycorrhizal status and soil AM fungal spore densities and community structures were analyzed and compared under and beyond the shrub canopies. The mycorrhizal colonization rates of the ephemerals and spore densities in their corresponding rhizosphere soils were significantly lower under the shrub canopies than beyond. The number of AM fungal species under the shrubs (12) was also lower than beyond the canopies (19). When soil properties in the rhizospheres of the four ephemerals were examined, available N and P and total P, organic matter content, total salt content and electrical conductivity (EC) were all higher under the canopies than beyond. In contrast, soil available K and pH showed no such trend. A total of 21 AM fungal species were isolated from rhizosphere soils of the four ephemerals. Five belonged to Acaulospora, one to Archaeospora, thirteen to Glomus and two to Paraglomus. We conclude that the canopies of Tamarix spp. exerted some influence on the AM status of the ephemerals and on the AM fungal communities and some of the properties of their rhizosphere soils. 相似文献
86.
87.
Summary After injection of a high dose of 5-hydroxytryptamine into rats, the blood reveals a strong increase of the blood platelets and a definite decrease of the eosinophiles. The maxima of increase and decrease are in temporal accordance. 相似文献
88.
Hans Nachtsheim 《Cellular and molecular life sciences : CMLS》1954,10(8):317-326
Summary The mutation of homologous genes can produce the same changes in phenotype in different mammals, animals as well as human beings. In this way the same hereditary disease can arise in man and animal. This fact permits the study of human hereditary diseases in model experiments in animals under conditions impossible to be realized in man. How far the parallelism between human beings and animals can be taken and where the limits of this parallelism are, which are the problems of the comparative heredo-pathology in detail, and how these problems may be attacked, is demonstrated here in numerous examples.
Nach einem Vortrag in der Nederlandse Anthropogenetische Vereniging in Utrecht am 28. November 1953. 相似文献
Nach einem Vortrag in der Nederlandse Anthropogenetische Vereniging in Utrecht am 28. November 1953. 相似文献
89.
When Research and Practice Collide: The Role of Action Research When There Is a Conflict of Interest with Stakeholders 总被引:1,自引:0,他引:1
This article discusses problematic aspects of the role of the action researcher when working with multiple stakeholders on a complex research project concerning regional development. The case presented here deals with the improvement of the regional innovation system in a small region in the south of Norway. The project resulted in a conflict between stakeholders and the action research (AR) team. We claim that when working in a regional context, the role of the action researcher is set to be a collaborator in a context of power play; the ultimate stakeholders must be defined as the citizens in that region. Therefore, in some situations the action researcher must have a legitimatised right to abandon collaboration and present a critical voice in the public deliberation. Strategic power play and strategic action by stakeholders represent a clear threat to the soft approach of collaboration, reflectivity, and democratic dialogue that AR represents. The ultimate challenge and obligation of the action researcher is to improve democracy in society in a long-term perspective through representing a critical capacity in the public deliberation. 相似文献
90.
It has recently been shown that RNA interference can be induced in cultured mammalian cells by delivery of short interfering RNAs (siRNAs). Here we describe a method for efficient in vivo delivery of siRNAs to organs of postnatal mice and demonstrate effective and specific inhibition of transgene expression in a variety of organs. 相似文献