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MJ Thompson J Toomre ER Anderson HM Antia G Berthomieu D Burtonclay SM Chitre J Christensen-Dalsgaard T Corbard M DeRosa CR Genovese DO Gough DA Haber JW Harvey F Hill R Howe SG Korzennik AG Kosovichev JW Leibacher FP Pijpers J Provost EJ Rhodes J Schou T Sekii PB Stark PR Wilson 《Science (New York, N.Y.)》1996,272(5266):1300-1305
Splitting of the sun's global oscillation frequencies by large-scale flows can be used to investigate how rotation varies with radius and latitude within the solar interior. The nearly uninterrupted observations by the Global Oscillation Network Group (GONG) yield oscillation power spectra with high duty cycles and high signal-to-noise ratios. Frequency splittings derived from GONG observations confirm that the variation of rotation rate with latitude seen at the surface carries through much of the convection zone, at the base of which is an adjustment layer leading to latitudinally independent rotation at greater depths. A distinctive shear layer just below the surface is discernible at low to mid-latitudes. 相似文献
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J Santiago‐Moreno C Castaño A Toledano‐Díaz MC Esteso A López‐Sebastián SG Dávila JL Campo 《Reproduction in domestic animals》2014,49(1):134-139
It is well known that when a hen mates with multiple roosters, it is the sperm of the last male that usually fertilizes most of the eggs (‘last male precedence’). Sperm quality varies between males within a breed, but also between breeds, and thus, sperm competitiveness after mating may depend on the breeds of the roosters involved. The aim of the present work was to identify differences in sperm competitiveness between breeds, especially with respect to motility. A multibreed mating model was used. Blue Andaluza (BA) and Black Castellana (BC) hens left for 21 days with BA and BC roosters, respectively, were then left with Black‐barred Andaluza (Bb) roosters for another 21 days (experimental groups hBA‐rBC‐rBb and hBC‐rBA‐rBb). Bb roosters (as the second breed replacing the first) fertilized the majority of eggs in both the hBC‐rBA‐rBb and hBA‐rBC‐rBb groups. The percentage of offspring sired by BA roosters (8.0%) was higher (p < 0.05) than the percentage of chicks sired by BC roosters (2.1%). The fertility of the BC hens in the hBC‐rBA‐rBb group was higher (p < 0.01) than that of the BA hens in the hBA‐rBC‐rBb group. No difference in sperm concentration was seen between the breeds. Within the rapid sperm subpopulation (sperm velocity, >50 μm/s), Bb sperm showed a higher straight‐line velocity (VSL) and average path velocity (VAP) (p < 0.05) than BC sperm. The VSL and VAP values for Bb and BA sperm were similar. In conclusion, the present results show that the sperm of the BA breed, traditionally regarded as of moderate fertility, compensates for this drawback via sperm movement characteristics that afford it an advantage in competition scenarios involving males of other breeds. The VSL and VAP of the rapid sperm subpopulation may play the most important role in securing last male precedence. 相似文献
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Contrasting canopy and fibrous root damage on Swingle citrumelo caused by ‘Candidatus Liberibacter asiaticus’ and Phytophthora nicotianae 
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下载免费PDF全文 Huanglongbing (HLB), associated with the phloem‐limited bacterium ‘Candidatus Liberibacter asiaticus’ (Las), is devastating trees in citrus orchards of Florida. Additionally, Phytophthora nicotianae, omnipresent in citrus soils, causes root rot that reduces water and nutrient uptake by fibrous roots. To investigate fibrous root damage and replacement and canopy size in relation to infection of fibrous roots by Las and P. nicotianae, rootstock seedlings of Swingle citrumelo (Citrus paradisi × Poncirus trifoliata) were inoculated with Las or P. nicotianae in two greenhouse pot trials. Phytophthora nicotianae caused root damage within 5 weeks post‐inoculation, which led to greater reduction of canopy size than for Las‐infected seedlings by the end of the experiment. Las increased accumulation of fibrous root biomass at 5 weeks post‐root trimming (wpt) in the 2014 trial and at 11 wpt in the 2015 trial. New root length was not consistently increased by Las. Reduced total leaf area of symptomless Las‐infected seedlings compared to noninoculated controls might be due to the combined effect of altered carbohydrate allocation between shoots and roots and altered leaf morphology. 相似文献
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Chondrules are millimeter-sized rounded igneous rocks within chondritic meteorites. Their textures and fractionated mineral chemistries suggest that they formed by repeated, localized, brief (minutes to hours) melting of cold aggregates of mineral dust in the protoplanetary nebula. Astrophysical models of chondrule formation have been unable to explain the petrologically diverse nature of chondrites. However, a nebular shock wave model for chondrule formation agrees with many of the observed petrologic and geochemical properties of chondrules and shows how particles within the nebula are sorted by size and how rims around chondrules are formed. It also explains the volatile-rich nature of chondrule rims and the chondrite matrix. 相似文献
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On 15 September,2010,a Pechora Pipit Anthus gustavi Swinhoe was found in the Hami prefecture(41°13’N and 93°29’E,1,143 m a.s.l.),Xinjiang,during the period of a comprehensive scientific survey in Lop Nur region.The bird,which was photographed,is a new avian record for Xinjiang.The pipit reproduces in northern Eurasia,mainly in wide meadows and low hills,and can be found in open forests and nearby residential areas in the process of on migration.The species is an insectivore and is a rare migrant or vagrant in Xinjiang.The geographical distribution,character,habitat,ecological habit and subspecies of the Pechora Pipit were discussed in this paper. 相似文献
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AIMS: To study the adhesion properties of a biotype 4, serotype O:3 (human pathogenic) strain of Yersinia enterocolitica and to determine if adhesion in vitro and colonisation in vivo can be prevented by competition with a biotype 1A, serotype O:6,30 (non-pathogenic) strain. To study interaction between Y. enterocolitica biotype 4, serotype O:3 and cultured epithelial cells using the synthetic tripeptide arginine-glycine-aspartic acid (RGD). METHODS: The human intestinal epithelial (HEp-2) cell line was used for in vitro studies. Inocula of Y. enterocolitica biotype 4, serotype O:3 radiolabelled using tritium were incubated with HEp-2 cells and RGD tripeptide, or with Y. enterocolitica biotype 1A, serotype O:6,30 sequentially or concurrently, then washed and lysed, and radioactivity measured to determine the effect of RGD on adhesion, and competitive exclusion of pathogenic by non-pathogenic bacteria. For in vivo studies, two groups of 5-week-old piglets (n=5/group) were sequentially inoculated orally with 5x109 colony forming units (cfu) of either a non-pathogenic biotype 1A, serotype O:6,30 strain of Y. enterocolitica followed by a pathogenic biotype 4, serotype O:3 strain, or vice versa. Pigs were monitored for carriage of strains using bacterial culture and a multiplex polymerase chain reaction (PCR). RESULTS: The RGD tripeptide significantly inhibited adherence of the pathogenic Y. enterocolitica strain to cultured epithelial cells, suggesting that adhesion involved the RGD tripeptide sequence. The non-pathogenic biotype 1A, serotype O:6,30 strain of Y. enterocolitica prevented adhesion of the pathogenic strain to cells in vitro when allowed to adhere first. Pathogenic Y. enterocolitica was consistently isolated from rectal swabs from 80-100% of pigs on all sampling occasions but not from oral swabs after 14 days in pigs first inoculated with the non- pathogenic strain or at 26 days in pigs first inoculated with the pathogenic strain. CONCLUSIONS: A non-pathogenic strain of Y. enterocolitica reduced adhesion of a human pathogenic strain in vitro but not in vivo. 相似文献
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F Hill PB Stark RT Stebbins ER Anderson HM Antia TM Brown TL Duvall DA Haber JW Harvey DH Hathaway R Howe RP Hubbard HP Jones JR Kennedy SG Korzennik AG Kosovichev JW Leibacher KG Libbrecht JA Pintar EJ Rhodes J Schou MJ Thompson S Tomczyk CG Toner R Toussaint WE Williams 《Science (New York, N.Y.)》1996,272(5266):1292-1296
The Global Oscillation Network Group (GONG) project estimates the frequencies, amplitudes, and linewidths of more than 250,000 acoustic resonances of the sun from data sets lasting 36 days. The frequency resolution of a single data set is 0.321 microhertz. For frequencies averaged over the azimuthal order m, the median formal error is 0.044 microhertz, and the associated median fractional error is 1.6 x 10(-5). For a 3-year data set, the fractional error is expected to be 3 x 10(-6). The GONG m-averaged frequency measurements differ from other helioseismic data sets by 0.03 to 0.08 microhertz. The differences arise from a combination of systematic errors, random errors, and possible changes in solar structure. 相似文献