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161.
Supernova 1987A, the first naked-eye supernova observed since Kepler's supernova in 1604, defies a number of theoretical expectations. Its anomalies have long been attributed to a merger between two massive stars that occurred some 20,000 years before the explosion, but so far there has been no conclusive proof that this merger took place. Here, we present three-dimensional hydrodynamical simulations of the mass ejection associated with such a merger and the subsequent evolution of the ejecta, and we show that this accurately reproduces the properties of the triple-ring nebula surrounding the supernova. 相似文献
162.
The spatial organization of the microtubule cytoskeleton is thought to be directed by steady-state activity gradients of diffusible regulatory molecules. We visualized such intracellular gradients by monitoring the interaction between tubulin and a regulator of microtubule dynamics, stathmin, using a fluorescence resonance energy transfer (FRET) biosensor. These gradients were observed both during interphase in motile membrane protrusions and during mitosis around chromosomes, which suggests that a similar mechanism may contribute to the creation of polarized microtubule structures. These interaction patterns are likely to reflect phosphorylation of stathmin in these areas. 相似文献
163.
Endothelial interleukin-8: a novel inhibitor of leukocyte-endothelial interactions 总被引:45,自引:0,他引:45
M A Gimbrone M S Obin A F Brock E A Luis P E Hass C A Hébert Y K Yip D W Leung D G Lowe W J Kohr 《Science (New York, N.Y.)》1989,246(4937):1601-1603
Certain inflammatory stimuli render cultured human vascular endothelial cells hyperadhesive for neutrophils. This state is transient and reversible, in part because activated endothelial cells secrete a leukocyte adhesion inhibitor (LAI). LAI was identified as endothelial interleukin-8 (IL-8), the predominant species of which is an extended amino-terminal IL-8 variant. At nanomolar concentrations, purified endothelial IL-8 and recombinant human IL-8 inhibit neutrophil adhesion to cytokine-activated endothelial monolayers and protect these monolayers from neutrophil-mediated damage. These findings suggest that endothelial-derived IL-8 may function to attenuate inflammatory events at the interface between vessel wall and blood. 相似文献
164.
An integrated genomic analysis of human glioblastoma multiforme 总被引:1,自引:0,他引:1
Parsons DW Jones S Zhang X Lin JC Leary RJ Angenendt P Mankoo P Carter H Siu IM Gallia GL Olivi A McLendon R Rasheed BA Keir S Nikolskaya T Nikolsky Y Busam DA Tekleab H Diaz LA Hartigan J Smith DR Strausberg RL Marie SK Shinjo SM Yan H Riggins GJ Bigner DD Karchin R Papadopoulos N Parmigiani G Vogelstein B Velculescu VE Kinzler KW 《Science (New York, N.Y.)》2008,321(5897):1807-1812
Glioblastoma multiforme (GBM) is the most common and lethal type of brain cancer. To identify the genetic alterations in GBMs, we sequenced 20,661 protein coding genes, determined the presence of amplifications and deletions using high-density oligonucleotide arrays, and performed gene expression analyses using next-generation sequencing technologies in 22 human tumor samples. This comprehensive analysis led to the discovery of a variety of genes that were not known to be altered in GBMs. Most notably, we found recurrent mutations in the active site of isocitrate dehydrogenase 1 (IDH1) in 12% of GBM patients. Mutations in IDH1 occurred in a large fraction of young patients and in most patients with secondary GBMs and were associated with an increase in overall survival. These studies demonstrate the value of unbiased genomic analyses in the characterization of human brain cancer and identify a potentially useful genetic alteration for the classification and targeted therapy of GBMs. 相似文献
165.
- Human translocations of non-native aquatic species are a global conservation challenge. Aquarists and anglers are two hobbyist groups whose practices are particularly likely to translocate non-native aquatic species, especially fish.
- This article aims to stipulate a change of perspective among these hobbyists, who – by acting simultaneously as anglers and aquarists – establish novel pathways for non-native fish.
- This study showed that: (i) 51 of 226 respondents to a questionnaire act simultaneously as anglers and aquarists; (ii) 53 of 237 non-native fish species in the European Union are used for both angling and aquarium hobbies; and (iii) hobbyists write online reports on the catch and exchange of a particularly invasive fish, the round goby (Neogobius melanostomus).
- This combination of knowledge on how hobbyists use non-native fish and the ecological impacts of round goby demonstrates how the impact of an invasive species can be influenced by the combined behaviours of anglers and aquarists.
- We suggest that future research in aquatic conservation should move beyond considering the commercial aquarium trade and angling as separate pathways for translocating non-native fish, and instead consider these hobbyist groups as interconnected.
166.
Elisabeth Lutz Philipp Emanuel Hirsch Karen Bussmann Joschka Wiegleb Hans‐Peter Jermann Roxane Muller Patricia Burkhardt‐Holm Irene Adrian‐Kalchhauser 《水产资源保护:海洋与淡水生态系统》2020,30(8):1566-1577
- Conservation of riverine fish often aims to improve access to spawning grounds and restore longitudinal connectivity by removing migration barriers, and involves substantial investments. However, these investments also enable non‐native predators to invade upstream into spawning areas and potentially adversely affect the recruitment of threatened freshwater fish through egg or fry predation.
- Detecting egg predation is often challenging. Visual inspections of fish gut contents may underestimate predation of soft materials such as eggs and fry, which limits the discovery of predators preying upon these life‐stages. DNA‐based detection assays may offer a more sensitive tool to assess predation of soft materials.
- A conservation issue was confirmed by developing and applying a species‐specific DNA‐based detection assay: invasive round goby (Neogobius melanostomus) prey on the eggs or fry of the threatened common nase (Chondrostoma nasus) in Switzerland.
- DNA‐based detection assays were also developed for five other valuable native fish species, including endangered salmonid and cyprinid river spawners. The applicability of the assays was confirmed in a series of laboratory and field feeding experiments involving eggs and fish tissue. In addition, this work provides a guiding framework for conservation managers regarding the use and applicability of different DNA‐based detection approaches for gut content analysis.
- The results of this study could inform local conservation measures – such as temporary reductions in the density of round goby at spawning sites prior to spawning – and demonstrate how targeted application of species‐specific molecular markers may advance freshwater fish management.
167.
168.
Soil rheology characterises the flow behaviour of soils at the particle-particle to aggregate scale. Amplitude sweep tests (ASTs) are often the method of choice for parameterizing soil flow properties, such as the shear strain values at the end of the linear viscoelastic range (i.e., the deformation is mainly elastic) and at the yield point (i.e., elastic equals plastic deformation). Samples from seven soil profiles and five soil depths of Chernozems, collected in the Maidanetske study area, clo... 相似文献
169.
170.
Manuel Carrillo Christina Siebe Philipp Dalkmann Jan Siemens 《Journal of Soils and Sediments》2016,16(9):2186-2194