Origin and evolution of osmoregulatory mechanisms in blue-green algae as a function of metabolic and structural complexity: Reflections of precambrian paleobiology

Twenty-four of the twenty-nine cyanobacteria proposed for culture were successfully cultured. Betaines are discussed

Classifying general nonlinear force laws in cell-based models via the continuum limit

though discrete cell-based frameworks are now commonly used to simulate a whole range of biological phenomena, it is typically not obvious how the numerous different types of model are related to one another, nor which one is most appropriate in a given context. Here we demonstrate how individual cell movement on the discrete scale modeled using nonlinear force laws can be described by nonlinear diffusion coefficients on the continuum scale. A general relationship between nonlinear force laws and their respective diffusion coefficients is derived in one spatial dimension and, subsequently, a range of particular examples is considered. For each case excellent agreement is observed between numerical solutions of the discrete and corresponding continuum models. Three case studies are considered in which we demonstrate how the derived nonlinear diffusion coefficients can be used to (a) relate different discrete models of cell behavior; (b) derive discrete, intercell force laws from previously posed diffusion coefficients, and (c) describe aggregative behavior in discrete simulations

Theory of commensurable magnetic structures in holmium

The tendency for the period of the helically ordered moments in holmium to lock into values which are commensurable with the lattice is studied theoretically as a function of temperature and magnetic field. The commensurable effects are derived in the mean-field approximation from numerical calculations of the free energy of various commensurable structures, and the results are compared with the extensive experimental evidence collected during the last ten years on the magnetic structures in holmium. In general the stability of the different commensurable structures is found to be in accord with the experiments, except for the tau=5/18 structure observed a few degrees below T_N in a b-axis field. The trigonal coupling recently detected in holmium is found to be the interaction required to explain the increased stability of the tau=1/5 structure around 42 K, and of the tau=1/4 structure around 96 K, when a field is applied along the c-axis.Comment: REVTEX, 31 pages, 7 postscript figure

Lieb's Theorem and Maximum Entropy Condensates

The maximum entropy steady states which form upon Floquet heating of the ground state of the Hubbard model on unbalanced bi-partite lattices are shown to possess uniform finite off-diagonal long-range order in the thermodynamic limit. For repulsive interactions the induced order corresponds to the formation of a spin-wave condensate, whilst for attractive interactions it instead corresponds to the formation of a superconducting, $\eta$-paired condensate. This creation of a `hot' condensate can occur on any periodically driven unbalanced lattice where the relevant SU(2) symmetry is preserved. Our results provide an understanding of how strong driving can expose order which has been suppressed by the lattice geometry - independent of any microscopic parameters. We discuss the implications of this for recent experiments observing emergent superconductivity in solid-state photoexcited compounds.Comment: 5 pages, 2 figures, comments are welcom

What is the impact of a peer counselling approach to help vulnerable children during lunchtimes?

There are many forms of peer support and collaboration projects and they are becoming increasingly popular throughout the world in both secondary and primary school. Peer counselling is individualised and palliative and this study examines the impact of four trained Year 5 and Year 6 counsellors on four Year 4 and Year 5 vulnerable, marginalised children with an extremely low sociometric status, who would become the focus group. The aim of the study was to increase prosocial interactions of the focus group. Sociometric testing was used before the project in order to identify the focus group and counsellors. Sociometric testing was used after the project to assess the impact of the intervention. Behavioural observations and questionnaires were also used to provide variable support for the projects effectiveness. Although two of the focus group left before the end of the project, the outcome was that positive interactions with peer counsellors and other children in the playground during lunchtimes very gradually increased. One child of the two remaining had a higher social status at the end of the project. Peer counselling proved a very useful model for a healthier world outside the classroom and a useful supplement to existing pastoral and inclusive strategies

Inter-annual tropical Pacific climate variability in an isotope-enabled CGCM: implications for interpreting coral stable oxygen isotope records of ENSO

Water isotope-enabled coupled atmosphere/ocean climate models allow for exploration of the relative contributions to coral stable oxygen isotope (δ<sup>18</sup>O<sub>coral</sub>) variability arising from Sea Surface Temperature (SST) and the isotopic composition of seawater (δ<sup>18</sup>O<sub>sw</sub>). The unforced behaviour of the isotope-enabled HadCM3 Coupled General Circulation Model affirms that the extent to which inter-annual δ<sup>18</sup>O<sub>sw</sub> variability contributes to that in model δ<sup>18</sup>O<sub>coral</sub> is strongly spatially dependent, ranging from being negligible in the eastern equatorial Pacific to accounting for 50% of δ<sup>18</sup>O<sub>coral</sub> variance in parts of the western Pacific. In these latter cases, a significant component of the inter-annual δ<sup>18</sup>O<sub>sw</sub> variability is correlated to that in SST, meaning that local calibrations of the effective local δ<sup>18</sup>O<sub>coral</sub>–SST relationships are likely to be essential. Furthermore, the relationship between δ<sup>18</sup>O<sub>sw</sub> and SST in the central and western equatorial Pacific is non-linear, such that the interpretation of model δ<sup>18</sup>O<sub>coral</sub> in the context of a linear dependence on SST alone may lead to overestimation (by up to 20%) of the SST anomalies associated with large El-Niño events. Intra-model evaluation of a salinity-based pseudo-coral approach shows that such an approach captures the first-order features of the model δ<sup>18</sup>O<sub>sw</sub> behaviour. However, the utility of the pseudo-corals is limited by the extent of spatial variability seen within the modelled slopes of the temporal salinity–δ<sup>18</sup>O<sub>sw</sub> relationship

Fertilizer Impact on Groundwater in Utah

Water quality has become the focal point of many decisions involving crop production. Crop production depends on specific inputs including fertilizer application. Without proper fertilization a farmer cannot achieve maximum economic returns. Crop yields in Utah have been increased over 50% by nitrogen fertilizer application alone. However, increasing nitrogen application beyond that needed for optimum economic return does more harm than good. This is especially true when groundwater concerns are ressed

A hairy situation: Plant species in warm, sunny places are more likely to have pubescent leaves

Aim: Leaf pubescence has several important roles, including regulating heat balance, reducing damage from UV radiation, minimizing water loss and reducing herbivory. Each of these functions could affect a plant's ability to tolerate the biotic and abiotic stresses encountered in different parts of the world. However, we know remarkably little about large scale biogeographic patterns in leaf pubescence. Our aims were: (a) to determine whether a higher proportion of species have pubescence at sites where it is hot, dry and solar radiation is high, and (b) to quantify the latitudinal gradient in pubescence. Location: Australia. Taxon: Vascular land plants. Methods: We compiled data on the presence/absence of pubescence on mature photosynthetic organs for 4,183 species, spanning 107 families. We combined these data with over 1.9 million species occurrence records from the Atlas of Living Australia to calculate the proportion of species with pubescence in 3,261 grid cells spanning the Australian continent. Results: The proportion of pubescent species was most closely related to solar radiation (R2 = 0.33), followed by maximum temperature in the warmest month (R2 = 0.30). Mean annual precipitation was very weakly related to pubescence (R2 = 0.01). We found a significant negative relationship between latitude and pubescence (R2 = 0.19), with the average percentage of species with pubescence dropping from 46% at 10° S to 35% at 44° S. This cross-species relationship remained significant after accounting for phylogenetic relationships between species. We found that a quadratic model explained more variation in pubescence across latitudes than did a linear model. The quadratic model shows a peak in the proportion of pubescent species at 19° S (within the tropics). Main conclusions: Our findings are consistent with the idea that leaf pubescence may have a protective function in areas with high solar radiation and high temperatures. Our data are also consistent with the idea that species towards the tropics should be better defended than are species at higher latitudes