منابع مشابه
What limits meiotic crossovers?
Meiotic crossovers are points of exchange between homologous chromosomes that create genetic diversity in gametes. However, the number of crossovers (COs) is tightly constrained. At the lower limit, there is at least one CO per pair of homologous chromosomes per meiosis, and this “obligate” CO is essential for the balanced distribution of chromosomes in the gametes. At the upper end, the number...
متن کاملWhat Limits Social Spending?
The forces that are most likely to set the ultimate limits on social spending as a share of GDP are not those usually imagined. The deadweight costs of such spending, and the taxes behind them, fail to show the predicted upward spiral. The experience of 1960–1981 shows a major role for shifts in relative age-group sizes, but with an approaching sunset to the effect of aging on social-spending p...
متن کاملWhat limits simultaneous discrimination accuracy?
Discrimination accuracy decreases when viewers simultaneously monitor two perceptually distinct stimulus components for changes in a common property, e.g. contrast [Magnussen & Greenlee (1997). Journal of Experimental Psychology: Human Perception and Performance, 23, 1603-1616; Olzak & Wickens (1997). Perception, 26, 1101-1120]. We ask whether the limitation is in monitoring two components or i...
متن کاملReaction front formation in contaminant plumes.
The formation of successive fronts in contaminated groundwater plumes by subsoil bacterial action is a commonly accepted feature of their propagation, but it is not obviously clear from a mathematical standpoint quite how such fronts are formed or propagate. In this paper we show that these can be explained by combining classical reaction-diffusion theory involving just two reactants (oxidant a...
متن کاملBioconvection and front formation of Paramecium tetraurelia.
We have investigated the bioconvection of Paramecium tetraurelia in high-density suspensions made by centrifugal concentration. When a suspension is kept at rest in a Hele-Shaw cell, a crowded front of paramecia is formed in the vicinity of the bottom and it propagates gradually toward the water-air interface. Fluid convection occurs under this front, and it is driven persistently by the upward...
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ژورنال
عنوان ژورنال: Nature
سال: 1985
ISSN: 0028-0836,1476-4687
DOI: 10.1038/315099a0