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A diffusion model for phloem swelling and contraction is proposed in which the rate of water movement changes markedly with moisture content. Good agreement between the actual swelling of the phloem of cotton stems and that predicted by the model was obtained. This result implies that water moves more readily into the phloem when it becomes wetter. This(More)
In the past, relations of diffusive resistance to stomatal geometry have concerned circular pores or pores that are replaced by equivalent circles of the same area. We calculated the resistance for general shapes that include the realistic slit. The resistance comprises two terms. The first is an outer resistance that depends only on ventilation and leaf(More)
expecting that more and richer people will demand more from the land, cultivating wider fields, logging more forests, and pressing nature, comes naturally. the past half-century of disciplined and dematerializing demand and more intense and efficient land use encourage a rational hope that humanity's pressure will not overwhelm nature. Beginning with the(More)
Amid widespread reports of deforestation, some nations have nevertheless experienced transitions from deforestation to reforestation. In a causal relationship, the Forest Identity relates the carbon sequestered in forests to the changing variables of national or regional forest area, growing stock density per area, biomass per growing stock volume, and(More)
_________________________________________________ Vernon W. Ruttan is Regents Professor in the Department of Applied Economics and in the Department of Economics at the University of Minnesota. This paper draws on two earlier papers (Ruttan, 1998; in press). I am indebted to Donald N. Duvick, Nicholas Kalaitzandonakes, John M. Reilly, C. Ford Runge, W. Burt(More)
Learning actors' leverage for change along the journey to sustainability requires quantifying the component forces of environmental impact and integrating them. Population, income, consumers' behavior, and producers' efficiency jointly force impact. Here, we renovate the "IPAT Identity" to identify actors with the forces. Forcing impact I are P for(More)
This paper demonstrates a capability to use a developed embedded sensor suite to consistently track the position, motion behavior, and orientation of a canine. Quantifying and recording canine position and motion in real time provides a useful mechanism for objective analysis of canine trials and missions. We provide a detailed description of the sensor(More)