Growth rates, seed size, and physiology: do small-seeded species really grow faster?

Relative growth rate (RGR) is currently the most commonly used method for measuring and comparing species' intrinsic growth potential. Comparative studies have, for example, revealed that small-seeded species have higher RGR, leading to the common belief that small-seeded species possess physiological adaptations for rapid growth that would allow them to outgrow large-seeded species, given sufficient time. We show that, because RGR declines as individual plants grow, it is heavily biased by initial size and does not measure the size-corrected growth potential that determines the outcome of competition in the long-term. We develop a daily growth model that includes a simple mechanistic representation of aboveground and belowground growth and its dependency on plant size and environmental factors. Intrinsic growth potential is encapsulated by the size-independent growth coefficient, G. We parameterized the model using repeated-harvest data from 1724 plants of nine species growing in contrasting nutrient and temperature regimes. Using information-theoretic criteria, we found evidence for interspecific differences in only three of nine model parameters: G, aboveground allocation, and frost damage. With other parameters shared between species, the model accurately reproduced above- and belowground biomass trajectories for all nine species in each set of environmental conditions. In contrast to conventional wisdom, the relationship between G and seed size was positive, despite a strong negative correlation between seed size and average RGR, meaning that large-seeded rather than small-seeded species have higher size-corrected growth potential. Further, we found a significant positive correlation between G and frost damage that, according to simulations, causes rank reversals in final biomass under daily temperature changes of +/- 5 degrees C. We recommend the wider use of this new kind of plant growth analysis as a better way of understanding underlying differences in species' physiology; but we recognize that RGR is still a useful metric if considering the potential rate of population increase in empty habitats.     

Accounting for the effects of buoyancy on the turbulent scalar fluxes

Environmental Fluid Mechanics - The paper reports on the development of an explicit, algebraic model for the turbulent scalar fluxes which properly reflects the dependence of these fluxes on the...     

Simulation of information propagation in real-life primate networks: longevity, fecundity, fidelity

In many vertebrate species, we find temporally stable traditions of socially learned behaviors. The social structure of animal populations is highly diverse and it has been proposed that differences in the social organization influence the patterns of information propagation. Here, we provide results of a simulation study of information propagation on real-life social networks of 70 primate groups comprising 30 different species. We found that models that include the social structure of a group differ significantly from those that assume random associations of individuals. Information spreads slower in the structured groups than in the well-mixed groups. While we found only a minor effect on the path lengths of the transmission chains, robustness against information extinction was strongly influenced by the group structure. Interestingly, robustness against information loss was not correlated with propagation speed but could be predicted reasonably well by relative strength assortativity—a structural network metric. In those groups where highly pro-social individuals preferentially interact with other pro-social individuals, information was more likely to be lost. Our results show that incorporating group structure in any social propagation model significantly alters predictions for spreading patterns, speed, and robustness of information.     

Elektronen-Energieverlust-Spektroskopie (FELS) als Methode zur Lokalisierung von Antigenen und anderen Substanzen in Zellen und Geweben

The localization of antigens and other substances in cells and tissues by electron microscopy is usually performed by immunohistochemical techniques employing labelled conventional or monoclonal antibodies. For the ultrastructural localization of the antibodies, they are coupled to electron-dense labels like gold or ferritin. Here, we demonstrate a novel method to localize antigens in cells, tissues, and on other supports. By electron energy loss spectroscopy (EELS) it is possible to directly analyze the distribution of antigens, metabolites or other substances without the use of labelled antibodies: as an example we demonstrate the distribution of the immunomodulator lipopeptide in B lymphocytes and macrophages. EELS represents a novel, sensitive, and generally applicable method for the detection and localization of antigens and other substances in biology and medicine.     

Visualizing different uranium oxidation states during the surface alteration of uraninite and uranium tetrachloride

Low-temperature alteration reactions on uranium phases may lead to the mobilization of uranium and thereby poses a potential threat to humans living close to uranium-contaminated sites. In this study, the surface alteration of uraninite (UO₂) and uranium tetrachloride (UCl₄) in air atmosphere was studied by confocal laser scanning microscopy (CLSM) and laser-induced fluorescence spectroscopy using an excitation wavelength of 408 nm. It was found that within minutes the oxidation state on the surface of the uraninite and the uranium tetrachloride changed. During the surface alteration process U(IV) atoms on the uraninite and uranium tetrachloride surface became stepwise oxidized by a one-electron step at first to U(V) and then further to U(VI). These observed changes in the oxidation states of the uraninite surface were microscopically visualized and spectroscopically identified on the basis of their fluorescence emission signal. A fluorescence signal in the wavelength range of 415–475 nm was indicative for metastable uranium(V), and a fluorescence signal in the range of 480–560 nm was identified as uranium(VI). In addition, the oxidation process of tetravalent uranium in aqueous solution at pH 0.3 was visualized by CLSM and U(V) was fluorescence spectroscopically identified. The combination of microscopy and fluorescence spectroscopy provided a very convincing visualization of the brief presence of U(V) as a metastable reaction intermediate and of the simultaneous coexistence of the three states U(IV), U(V), and U(VI). These results have a significant importance for fundamental uranium redox chemistry and should contribute to a better understanding of the geochemical behavior of uranium in nature. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Urine concentrations of selected trace metals in a cohort of Irish adults

Environmental Science and Pollution Research - Human biomonitoring studies are of increasing importance in regulatory toxicology; however, there is a paucity of human biomonitoring data for the...