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561.
562.
Between 6 and 10 months of age, the infant's ability to discriminate among native speech sounds improves, whereas the same ability to discriminate among foreign speech sounds decreases. Our study aimed to determine whether this perceptual narrowing is unique to language or might also apply to face processing. We tested discrimination of human and monkey faces by 6-month-olds, 9-month-olds, and adults, using the visual paired-comparison procedure. Only the youngest group showed discrimination between individuals of both species; older infants and adults only showed evidence of discrimination of their own species. These results suggest that the "perceptual narrowing" phenomenon may represent a more general change in neural networks involved in early cognition. 相似文献
563.
The collared lemming in the high-Arctic tundra in Greenland is preyed upon by four species of predators that show marked differences in the numbers of lemmings each consumes and in the dependence of their dynamics on lemming density. A predator prey model based on the field-estimated predator responses robustly predicts 4-year periodicity in lemming dynamics, in agreement with long-term empirical data. There is no indication in the field that food or space limits lemming population growth, nor is there need in the model to consider those factors. The cyclic dynamics are driven by a 1-year delay in the numerical response of the stoat and stabilized by strongly density-dependent predation by the arctic fox, the snowy owl, and the long-tailed skua. 相似文献
564.
Renaud G Lazzari R Revenant C Barbier A Noblet M Ulrich O Leroy F Jupille J Borensztein Y Henry CR Deville JP Scheurer F Mane-Mane J Fruchart O 《Science (New York, N.Y.)》2003,300(5624):1416-1419
One challenge in the production of nanometer-sized objects with given properties is to control their growth at a macroscopic scale in situ and in real time. A dedicated ultrahigh-vacuum grazing-incidence small-angle x-ray scattering setup has been developed, yielding high sensitivity and dynamics. Its capabilities to derive the average particle shape and size and the film growth mode and ordering and to probe both surfaces and buried interfaces are illustrated for two prototypical cases: the model catalyst Pd/MgO(100) and the self-organized Co/Au(111) system. A wide range of technologically important systems can potentially be investigated in various gaseous environments. 相似文献
565.
Hanotte O Bradley DG Ochieng JW Verjee Y Hill EW Rege JE 《Science (New York, N.Y.)》2002,296(5566):336-339
The genetic history of African cattle pastoralism is controversial and poorly understood. We reveal the genetic signatures of its origins, secondary movements, and differentiation through the study of 15 microsatellite loci in 50 indigenous cattle breeds spanning the present cattle distribution in Africa. The earliest cattle originated within the African continent, but Near East and European genetic influences are also identified. The initial expansion of African Bos taurus was likely from a single region of origin. It reached the southern part of the continent by following an eastern route rather than a western one. The B. indicus genetic influence shows a major entry point through the Horn and the East Coast of Africa and two modes of introgression into the continent. 相似文献
566.
The response of the ocean redox state to the rise of atmospheric oxygen about 2.3 billion years ago (Ga) is a matter of controversy. Here we provide iron isotope evidence that the change in the ocean iron cycle occurred at the same time as the change in the atmospheric redox state. Variable and negative iron isotope values in pyrites older than about 2.3 Ga suggest that an iron-rich global ocean was strongly affected by the deposition of iron oxides. Between 2.3 and 1.8 Ga, positive iron isotope values of pyrite likely reflect an increase in the precipitation of iron sulfides relative to iron oxides in a redox stratified ocean. 相似文献
567.
Peters D Demes B Krause DW Labarbera M Rieppel O 《Science (New York, N.Y.)》2005,308(5725):1112-3; author reply 1112-3
568.
G. Gianquinto J. P. Goffart M. Olivier G. Guarda M. Colauzzi L. Dalla Costa G. Delle Vedove J. Vos D. K. L. Mackerron 《Potato Research》2004,47(1-2):35-80
Summary Fifteen experiments were carried out in different sites of Italy, Belgium, Scotland and The Netherlands from 1995 to 1999
to study the possible use of chlorophyll meter to assess the nitrogen status and to guide nitrogen fertilization of the potato
crop. The results are gathered here and reviewed together with available information in literature.
The paper deals with measuring principles of chlorophyll meter; relation between chlorophyll meter readings and analytical
measurements of chlorophyll, analytical measurements of nitrogen, crop nitrogen content, tuber yield, and physiological processes
in leaves; variations in chlorophyll meter readings related to nitrogen supply, potato cultivar, crop management, and sampling
methods; use of chlorophyll meter readings for decision making in the management of supplemental nitrogen fertilization (assessment
of chlorophyll meter critical threshold, plant response to addition of supplementary N). 相似文献
569.
Galland S Mora N Abert-Vian M Rakotomanomana N Dangles O 《Journal of agricultural and food chemistry》2007,55(18):7573-7579
This work describes the chemical synthesis of O-aryl-beta-D-glucosides and 1-O-beta-D-glucosyl esters of hydroxycinnamic acids. In particular, O-aryl-beta-D-glucosides were efficiently prepared via a simple diastereoselective glycosylation procedure using phase transfer conditions. Despite the lability of its ester linkage, 1-O-beta-D-caffeoylglucose could also be obtained using a Lewis acid catalyzed glycosylation step and a set of protective groups that can be removed under neutral conditions. Hydroxycinnamic acid O-aryl-beta-D-glucosides were then quantitatively investigated for their affinity for the naturally occurring anthocyanin malvin (pigment). Formation of the pi-stacking molecular complexes (copigmentation) was characterized in terms of binding constants and enthalpy and entropy changes. The glucosyl moiety did not significantly alter these thermodynamic parameters, in line with a binding process solely involving the polyphenolic nuclei. 相似文献
570.
Benoit Marçais Olivier Caël 《European journal of plant pathology / European Foundation for Plant Pathology》2000,106(3):227-232
Collybia fusipes is the cause of a root rot of Quercus petraea (sessile oak), Q. robur (pedunculate oak) and Q. rubra (red oak). This parasite is often reported to cause problems in stands of red oaks and field evidence suggests that this North American oak species is more susceptible than the two European oak species. Young saplings of the three oak species and of chestnut, Castanea sativa, in the glasshouse, and also mature sessile and red oaks growing in the same stand were inoculated with C. fusipes to compare their susceptibility. Red oak, both as young seedlings and mature trees, was more susceptible to C. fusipes than sessile oak. Chestnut seedlings were as susceptible as sessile oak. Susceptibility of pedunculate oak seedlings was intermediate between red oak and sessile oak. In one experiment this species was significantly less susceptible than red oak, and in the other it was as susceptible. 相似文献