Over-expressing the C3 photosynthesis cycle enzyme Sedoheptulose-1-7 Bisphosphatase improves photosynthetic carbon gain and yield under fully open air CO2fumigation (FACE)

Abstract Background Biochemical models predict that photosynthesis in C3 plants is most frequently limited by the slower of two processes, the maximum capacity of the enzyme Rubisco to carboxylate RuBP (Vc,max), or the regeneration of RuBP via electron transport (J). At current atmospheric [CO2] levels Rubisco is not saturated; consequently, elevating [CO2] increases the velocity of carboxylation and inhibits the competing oxygenation reaction which is also catalyzed by Rubisco. In the future, leaf photosynthesis (A) should be increasingly limited by RuBP regeneration, as [CO2] is predicted to exceed 550 ppm by 2050. The C3 cycle enzyme sedoheptulose-1,7 bisphosphatase (SBPase, EC 3.1.3.17) has been shown to exert strong metabolic control over RuBP regeneration at light saturation. Results We tested the hypothesis that tobacco transformed to overexpressing SBPase will exhibit greater stimulation of A than wild type (WT) tobacco when grown under field conditions at elevated [CO2] (585 ppm) under fully open air fumigation. Growth under elevated [CO2] stimulated instantaneous A and the diurnal photosynthetic integral (A') more in transformants than WT. There was evidence of photosynthetic acclimation to elevated [CO2] via downregulation of Vc,max in both WT and transformants. Nevertheless, greater carbon assimilation and electron transport rates (J and Jmax) for transformants led to greater yield increases than WT at elevated [CO2] compared to ambient grown plants. Conclusion These results provide proof of concept that increasing content and activity of a single photosynthesis enzyme can enhance carbon assimilation and yield of C3 crops grown at [CO2] expected by the middle of the 21st century. </jats:sec

A selected history of expectation bias in physics

The beliefs of physicists can bias their results towards their expectations in a number of ways. We survey a variety of historical cases of expectation bias in observations, experiments, and calculations.Comment: 6 pages, 2 figure

Evaluating Unpaid Time Contributions by Seniors: A Conceptual Framework

In the past, considerable research in gerontology has focused on services provided to seniors. Recently, however, there has a been a growing recognition of the contributions made by seniors to their families, communities and to society. Empirical estimates have been provided by researchers to show how much these contributions are worth in terms of savings in dollar amounts. A critical review of the literature identifies unresolved issues concerning which contributions to count and how to measure and value these contributions. As yet, no clear criteria exist that readily identify the distinction between volunteer activities and unpaid work, what specifically should be counted as an unpaid time contribution, how it should be quantified, and how this unit of contribution should be monetarily valued. The market replacement approach and the opportunity cost approach that are used to assign value to unpaid work often use very different wage rates or levels of income loss. This paper reviews the relevant literature and identifies important issues in evaluating unpaid time contribution of seniors. The authors propose a framework which addresses some of the methodological shortcomings identified in previous research and which provides a guide for future research in this area.seniors; valuing unpaid work

Modification to the Luminosity Distance Redshift Relation in Modified Gravity Theories

We derive an expression for the luminosity distance as a function of redshift for a flat Robertson-Walker spacetime perturbed by arbitrary scalar perturbations possibly produced by a modified gravity theory with two different scalar perturbation potentials. Measurements of the luminosity distance as function of redshift provide a constraint on a combination of the scalar potentials and so they can complement weak lensing and other measurements in trying to distinguish among the various alternative theories of gravity.Comment: 15 pages, we discuss in more detail how the luminosity distance expression can be used to differentiate among various theories of gravit

NEAR-SURFACE EFFECTS IN MODELLING OSCILLATIONS OF ETA BOO

Following the report of solar-like oscillations in the G0 V star eta Boo (Kjeldsen et al. 1995, AJ 109, 1313), a first attempt to model the observed frequencies was made by Christensen-Dalsgaard et al. (1995, ApJ Letters, in press). This attempt succeeded in reproducing the observed frequency separations, although there remained a difference of about 10 microHz between observed and computed frequencies. In those models, the near-surface region of the star was treated rather crudely. Here we consider more sophisticated models that include non-local mixing-length theory, turbulent pressure and nonadiabatic oscillations.Comment: uuencoded and compressed Postscript (2 pages, including figure); To appear in Proceedings of IAU Colloquium 155, "Astrophysical Applications of Stellar Pulsation", Cape Town, South Afric

Resource Competition on Integral Polymatroids

We study competitive resource allocation problems in which players distribute their demands integrally on a set of resources subject to player-specific submodular capacity constraints. Each player has to pay for each unit of demand a cost that is a nondecreasing and convex function of the total allocation of that resource. This general model of resource allocation generalizes both singleton congestion games with integer-splittable demands and matroid congestion games with player-specific costs. As our main result, we show that in such general resource allocation problems a pure Nash equilibrium is guaranteed to exist by giving a pseudo-polynomial algorithm computing a pure Nash equilibrium.Comment: 17 page