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51.
Abe S Mukai T Hirata N Barnouin-Jha OS Cheng AF Demura H Gaskell RW Hashimoto T Hiraoka K Honda T Kubota T Matsuoka M Mizuno T Nakamura R Scheeres DJ Yoshikawa M 《Science (New York, N.Y.)》2006,312(5778):1344-1347
The ranging instrument aboard the Hayabusa spacecraft measured the surface topography of asteroid 25143 Itokawa and its mass. A typical rough area is similar in roughness to debris located on the interior wall of a large crater on asteroid 433 Eros, which suggests a surface structure on Itokawa similar to crater ejecta on Eros. The mass of Itokawa was estimated as (3.58 +/- 0.18) x 10(10) kilograms, implying a bulk density of (1.95 +/- 0.14) grams per cubic centimeter for a volume of (1.84 +/- 0.09) x 10(7) cubic meters and a bulk porosity of approximately 40%, which is similar to that of angular sands, when assuming an LL (low iron chondritic) meteorite composition. Combined with surface observations, these data indicate that Itokawa is the first subkilometer-sized small asteroid showing a rubble-pile body rather than a solid monolithic asteroid. 相似文献
52.
Navarro L Dunoyer P Jay F Arnold B Dharmasiri N Estelle M Voinnet O Jones JD 《Science (New York, N.Y.)》2006,312(5772):436-439
Plants and animals activate defenses after perceiving pathogen-associated molecular patterns (PAMPs) such as bacterial flagellin. In Arabidopsis, perception of flagellin increases resistance to the bacterium Pseudomonas syringae, although the molecular mechanisms involved remain elusive. Here, we show that a flagellin-derived peptide induces a plant microRNA (miRNA) that negatively regulates messenger RNAs for the F-box auxin receptors TIR1, AFB2, and AFB3. Repression of auxin signaling restricts P. syringae growth, implicating auxin in disease susceptibility and miRNA-mediated suppression of auxin signaling in resistance. 相似文献
53.
Vian MA Tomao V Coulomb PO Lacombe JM Dangles O 《Journal of agricultural and food chemistry》2006,54(15):5230-5235
The anthocyanin composition of Syrah grapes harvested at different stages of ripening and produced using organic or conventional agriculture was studied. Samples of grapes were collected from veraison to full maturity in each plot, and the content in nine anthocyanins was determined by high-performance liquid chromatography with diode array detection. The total content in anthocyanins during ripening of the conventionally grown grapes was significantly higher compared to that found in the organic production. The accumulation of anthocyanins reached a maximum 28 days after veraison (in agreement with high temperature) and then decreased until harvest. In all samples, grapes from the conventional agriculture presented higher proportions of delphinidin, petunidin, malvidin, and acylated malvidin glucosides compared to grapes from organic agriculture. In contrast with other comparative studies of organically and conventionally grown plants, the results demonstrated a higher content in anthocyanins in conventionally grown grapes. 相似文献
54.
Bengochea P Christiaens O Amor F Viñuela E Rougé P Medina P Smagghe G 《Pest management science》2012,68(7):976-985
BACKGROUND: The moulting accelerating compounds (MACs) or ecdysteroid agonists represent a selective group of insecticides acting upon binding to the ecdysteroid receptor (EcR) and leading to lethal premature moulting in larval stages and aborted reproduction in adults. Psyttalia concolor Szèpl. is a useful parasitic wasp attacking important tephritid pests such as the medfly and olive fruit fly. RESULTS: Contact and oral exposure in the laboratory of female parasitic wasps to the dibenzoylhydrazine‐based methoxyfenozide, tebufenozide and RH‐5849 did not provoke negative effects. No mortality and no reduction in beneficial capacity were observed. The ligand‐binding domain (LBD) of the EcR of P. concolor was sequenced, and a homology protein model was constructed which confirmed a cavity structure with 12 α‐helices, harbouring the natural insect moulting hormone 20‐hydroxyecdysone. However, a steric clash occurred for the MAC insecticides owing to a restricted extent of the ligand‐binding cavity of the PcLBD‐EcR, while they did dock well in that of susceptible insects. CONCLUSIONS: The insect toxicity assays demonstrated that MACs are selective for P. concolor. The modelling/docking experiments are indications that these insecticides do not bind with the LBD‐EcR of P. concolor and support the theory that they show no biological effects in the parasitic wasp. These data may help in explaining the compatible use of MACs together with parasitic wasps in IPM programmes. Copyright © 2012 Society of Chemical Industry 相似文献
55.
Zuber MT Smith DE Phillips RJ Solomon SC Neumann GA Hauck SA Peale SJ Barnouin OS Head JW Johnson CL Lemoine FG Mazarico E Sun X Torrence MH Freed AM Klimczak C Margot JL Oberst J Perry ME McNutt RL Balcerski JA Michel N Talpe MJ Yang D 《Science (New York, N.Y.)》2012,336(6078):217-220
Laser altimetry by the MESSENGER spacecraft has yielded a topographic model of the northern hemisphere of Mercury. The dynamic range of elevations is considerably smaller than those of Mars or the Moon. The most prominent feature is an extensive lowland at high northern latitudes that hosts the volcanic northern plains. Within this lowland is a broad topographic rise that experienced uplift after plains emplacement. The interior of the 1500-km-diameter Caloris impact basin has been modified so that part of the basin floor now stands higher than the rim. The elevated portion of the floor of Caloris appears to be part of a quasi-linear rise that extends for approximately half the planetary circumference at mid-latitudes. Collectively, these features imply that long-wavelength changes to Mercury's topography occurred after the earliest phases of the planet's geological history. 相似文献
56.
Thaunat O Granja AG Barral P Filby A Montaner B Collinson L Martinez-Martin N Harwood NE Bruckbauer A Batista FD 《Science (New York, N.Y.)》2012,335(6067):475-479
During the activation of humoral immune responses, B cells acquire antigen for subsequent presentation to cognate T cells. Here we show that after mouse B cells accumulate antigen, it is maintained in a polarized distribution for extended periods in vivo. Using high-throughput imaging flow cytometry, we observed that this polarization is preserved during B cell division, promoting asymmetric antigen segregation among progeny. Antigen inheritance correlates with the ability of progeny to activate T cells: Daughter cells receiving larger antigen stores exhibit a prolonged capacity to present antigen, which renders them more effective in competing for T cell help. The generation of progeny with differential capacities for antigen presentation may have implications for somatic hypermutation and class switching during affinity maturation and as B cells commit to effector cell fates. 相似文献
57.
Scientific interest in the cognitive underpinnings of religious belief has grown in recent years. However, to date, little experimental research has focused on the cognitive processes that may promote religious disbelief. The present studies apply a dual-process model of cognitive processing to this problem, testing the hypothesis that analytic processing promotes religious disbelief. Individual differences in the tendency to analytically override initially flawed intuitions in reasoning were associated with increased religious disbelief. Four additional experiments provided evidence of causation, as subtle manipulations known to trigger analytic processing also encouraged religious disbelief. Combined, these studies indicate that analytic processing is one factor (presumably among several) that promotes religious disbelief. Although these findings do not speak directly to conversations about the inherent rationality, value, or truth of religious beliefs, they illuminate one cognitive factor that may influence such discussions. 相似文献
58.
A yearling Irish Cob stallion was presented to De Morette Equine clinic for severe acute abdominal pain, nonresponsive to analgesics and sedatives. Rectal palpation and a limited transabdominal ultrasonographic examination led to the presumptive diagnosis of a strangulated obstruction of the small intestine. The painful behaviour of the pony did not allow conservative treatment and surgical exploration was denied by the owners for financial considerations. On necropsy, a large cystic mature teratoma was adhered to the ventral body wall, the mesenteric root, omentum and intestines. Teratomas are rare in man and animals, and an extragonadal intraperitoneal location has not previously been reported in the equine species. 相似文献
59.
Friardi Ismed Françoise Lohézic-Le Dévéhat Olivier Delalande Sourisak Sinbandhit Amri Bakhtiar Joël Boustie 《Fitoterapia》2012
The diphenyl ether, lobarin (1) (syn. lobariol carboxylic acid) related to lobaric acid was isolated for the first time as a natural product along with five known compounds from Stereocaulon halei, a fruticose lichen collected in Indonesia. The structure of lobarin was elucidated by spectroscopic data analysis and its most stable conformers were determined by molecular mechanic dynamic calculations. A marked superoxide anion scavenging was found for compound 1 while no cytotoxicity on the B16 murine melanoma and HaCaT human keratinocyte cell lines was observed. 相似文献
60.
Olivier Taugourdeau Jean Dauzat Sébastien Griffon Sylvie Sabatier Yves Caraglio Daniel Barthélémy 《Annals of Forest Science》2012,69(6):713-721