On the heterogeneous character of water's amorphous polymorphism

In this letter we report {\it in situ} small--angle neutron scattering results on the high--density (HDA) and low-density amorphous (LDA) ice structures and on intermediate structures as found during the temperature induced transformation of HDA into LDA. We show that the small--angle signal is characterised by two $Q$ regimes featuring different properties ($Q$ is the modulus of the scattering vector defined as $Q = 4\pi\sin{(\Theta)}/\lambda_{\rm i}$ with $\Theta$ being half the scattering angle and $\lambda_{\rm i}$ the incident neutron wavelength). The very low--$Q$ regime ($< 5\times 10^{-2}$ \AA $^{-1}$) is dominated by a Porod--limit scattering. Its intensity reduces in the course of the HDA to LDA transformation following a kinetics reminiscent of that observed in wide--angle diffraction experiments. The small--angle neutron scattering formfactor in the intermediate regime of $5 \times 10^{-2} < Q < 0.5$ \AA$^{-1}$ HDA and LDA features a rather flat plateau. However, the HDA signal shows an ascending intensity towards smaller $Q$ marking this amorphous structure as heterogeneous. When following the HDA to LDA transition the formfactor shows a pronounced transient excess in intensity marking all intermediate structures as strongly heterogeneous on a length scale of some nano--meters

Eigenvalue Separation in Some Random Matrix Models

The eigenvalue density for members of the Gaussian orthogonal and unitary ensembles follows the Wigner semi-circle law. If the Gaussian entries are all shifted by a constant amount c/Sqrt(2N), where N is the size of the matrix, in the large N limit a single eigenvalue will separate from the support of the Wigner semi-circle provided c > 1. In this study, using an asymptotic analysis of the secular equation for the eigenvalue condition, we compare this effect to analogous effects occurring in general variance Wishart matrices and matrices from the shifted mean chiral ensemble. We undertake an analogous comparative study of eigenvalue separation properties when the size of the matrices are fixed and c goes to infinity, and higher rank analogues of this setting. This is done using exact expressions for eigenvalue probability densities in terms of generalized hypergeometric functions, and using the interpretation of the latter as a Green function in the Dyson Brownian motion model. For the shifted mean Gaussian unitary ensemble and its analogues an alternative approach is to use exact expressions for the correlation functions in terms of classical orthogonal polynomials and associated multiple generalizations. By using these exact expressions to compute and plot the eigenvalue density, illustrations of the various eigenvalue separation effects are obtained.Comment: 25 pages, 9 figures include

Clustering in complex networks. II. Percolation properties

The percolation properties of clustered networks are analyzed in detail. In the case of weak clustering, we present an analytical approach that allows to find the critical threshold and the size of the giant component. Numerical simulations confirm the accuracy of our results. In more general terms, we show that weak clustering hinders the onset of the giant component whereas strong clustering favors its appearance. This is a direct consequence of the differences in the $k$-core structure of the networks, which are found to be totally different depending on the level of clustering. An empirical analysis of a real social network confirms our predictions.Comment: Updated reference lis

Heteroclinic Chaos, Chaotic Itinerancy and Neutral Attractors in Symmetrical Replicator Equations with Mutations

A replicator equation with mutation processes is numerically studied. Without any mutations, two characteristics of the replicator dynamics are known: an exponential divergence of the dominance period, and hierarchical orderings of the attractors. A mutation introduces some new aspects: the emergence of structurally stable attractors, and chaotic itinerant behavior. In addition, it is reported that a neutral attractor can exist in the mutataion rate -> +0 region.Comment: 4 pages, 9 figure

Species Abundance Patterns in Complex Evolutionary Dynamics

An analytic theory of species abundance patterns (SAPs) in biological networks is presented. The theory is based on multispecies replicator dynamics equivalent to the Lotka-Volterra equation, with diverse interspecies interactions. Various SAPs observed in nature are derived from a single parameter. The abundance distribution is formed like a widely observed left-skewed lognormal distribution. As the model has a general form, the result can be applied to similar patterns in other complex biological networks, e.g. gene expression.Comment: 4 pages, 3 figures. Physical Review Letters, in pres

Overcoming the barriers to implementing urban road user charging schemes

Urban road user charging offers the potential to achieve significant improvements in urban transport, but is notoriously difficult to implement. Cities need guidance on the range of factors to be considered in planning and implementing such schemes. This paper summarises the results of a 3 year programme which has collated evidence on the issues of most concern to cities. A state of the art report has provided evidence on 14 themes, ranging from objectives and design to implementation and evaluation. A set of 16 case studies has reviewed experience in design and implementation across Europe. The paper summarises their findings, provides references to more detailed information, presents the resulting policy recommendations to European, national and local government, and outlines the areas in which further research is needed

Optimising the analysis of transcript data using high density oligonucleotide arrays and genomic DNA-based probe selection

Background: Affymetrix GeneChip arrays are widely used for transcriptomic studies in a diverse range of species. Each gene is represented on a GeneChip array by a probe-set, consisting of up to 16 probe-pairs. Signal intensities across probe-pairs within a probe-set vary in part due to different physical hybridisation characteristics of individual probes with their target labelled transcripts. We have previously developed a technique to study the transcriptomes of heterologous species based on hybridising genomic DNA (gDNA) to a GeneChip array designed for a different species, and subsequently using only those probes with good homology. Results: Here we have investigated the effects of hybridising homologous species gDNA to study the transcriptomes of species for which the arrays have been designed. Genomic DNA from Arabidopsis thaliana and rice (Oryza sativa) were hybridised to the Affymetrix Arabidopsis ATH1 and Rice Genome GeneChip arrays respectively. Probe selection based on gDNA hybridisation intensity increased the number of genes identified as significantly differentially expressed in two published studies of Arabidopsis development, and optimised the analysis of technical replicates obtained from pooled samples of RNA from rice. Conclusion: This mixed physical and bioinformatics approach can be used to optimise estimates of gene expression when using GeneChip arrays

Self-consistent simulation of quantum wires defined by local oxidation of Ga[Al]As heterostructures

We calculate the electronic width of quantum wires as a function of their lithographic width in analogy to experiments performed on nanostructures defined by local oxidation of Ga[Al]As heterostructures. Two--dimensional simulations of two parallel oxide lines on top of a Ga[Al]As heterostructure defining a quantum wire are carried out in the framework of Density Functional Theory in the Local Density Approximation and are found to be in agreement with measurements. Quantitative assessment of the influence of various experimental uncertainties is given. The most influential parameter turns out to be the oxide line depth, followed by its exact shape and the effect of background doping (in decreasing order).Comment: 5 pages, 6 figures; revised figures, clarified tex

Effect of various combinations of trellis, pruning, and rootstock on vigorous Sultana vines

The combined effects of three trellis, three pruning, and three rootstock treatments were tested on vigorous Sultana vines (Vitis vinifera L.) growing in a lighttextured, nematode- and phylloxera-free, virgin soil of the Australian Murray Valley.Vines on Salt Creek rootstock outyielded vines on 1613 C rootstock or on their own roots by about 40 per cent during the first four cropping seasons after planting, which preceded the experiment, and by about 30 per cent during the four seasons of the experiment, because they had more and larger bunches.A wide, high trellis with two cane-wires 1.2 m apart and 1.5 m above ground level, a narrow, high trellis (0.3 m X 1.5 m) and a narrow, low trellis (0.3 m X 1.0 m) were compared. On the wide trellis, the foliage canopy was divided naturally into two halves. In the season following the trellis conversion, vines on the wide trellis yielded slightly better than those on either of the narrow trellises, possibly because there was less mould damage. In the subsequent seasons, the wide trellis was much more productive. lt produced 40 to 50 per cent more crop because the vines had more bunches with more berries per bunch, while the concentration of sugar or acids remained unaltered. The amount of pruning wood was also somewhat greater. For the three pruning treatments, vines were given 126, 196, or 266 nodes (i. e. 9, 14, or 19 canes of 14 nodes each). In the later years of the experiment, the lightest pruning level could not be maintained on the narrow trellis, and pruning weight tended to become smaller. Yield increased disproportionately with increasing nodenumber; a two-fold increase in the number of nodes led to only a 20 per cent increase in yield.There were few interactions between the trellis, pruning, and rootstock treatments. The beneficial effects of wide trellis, Salt Creek rootstock and of light pruning, at least up to the level of 196 nodes per vine, tended to be additive. Thus lightly pruned Sultana vines on Salt Creek rootstock grown on a wide trellis with split canopy produced twice as much fruit as the conventionally treated Sultana, i. e. an own-rooted vine with 126 nodes grown on a narrow, low trellis.lt is concluded that Sultanas benefit from wide trellis through an effect on bud fruitfulness which leacls to more berries per vine, and through better photosynthetic activity which allows f4ll maturation of this increased crop potential. The economic implications of using wicle trellises and Salt Creek rootstock are discussed.Der Einfluß verschiedener Kombinationen von Drahtrahmen, Rebschnitt und Unterlage auf starkwüchsige Sultana-RebenDer vereinte Einfluß von drei Drahtrahmen-Typen und drei Schnittarten auf wurzelechte Sultana-Reben und auf Sultana, gepfropft auf den Unterlagen Salt Creek und 1613 C, die in einem leichten, Nematoden- und Phylloxerafreien Urboden des australischen Murray-Bewässerungsgebietes wuchsen, wurde untersucht. Alle Resultate wurden der Varianzanalyse unterworfen.In den ersten vier Ertragsjahren nach der Pflanzung, die dem Versuch vorausgingen, war der Ertrag von Sultana auf Salt Creek um 40°/o höher als derjenige von wurzelechten oder auf 1613 C gepfropften Reben. In den folgenden vier Versuchsjahren betrug dieser Unterschied etwa 30°/o. Mehr und größere Trauben waren der Grund hierfür.Die drei Drahtrahmen hatten die folgenden Dimensionen: Ein weiter, hoher Rahmen mit zwei Drähten, die mit 1,2 m Abstand 1,5 m über dem Boden angebracht waren; ein enger, hoher Rahmen (0,3 m X 1,5 m) und ein enger, niedriger Rahmen (0,3 m X 1,0 m) mit einem weiteren Draht für das Blattwerk. Am weiten Drahtrahmen teilte sich das Blattwerk spontan in zwei Hälften. In der ersten Vegetationsperiode nach dem Erstellen der Drahtrahmen war der Ertrag am weiten Rahmen etwas besser, vermutlich wegen des geringeren Fäulnisbefalles. In den folgenden drei Vegetationsperioden brachten die Reben am weiten Drahtrahmen um 40 bis 50°/o höhere Erträge, da mehr und größere Trauben vorhanden waren, während Beerengröße, Zucker- und Säuregehalt unverändert blieben. Auch das Gewicht des Schnittholzes war etwas größer. Die Reben wurden zu 9, 14 oder 19 Tragruten von je 14 Knospen, demnach zu 126, 196 oder 266 Knospen, geschnitten. Am engen Drahtrahmen konnte man die höchste Knospenzahl in den letzten Jahren des Versuches nicht erhalten, und auch das Triebgewicht wurde kleiner. Im allgemeinen hatte die Verdopplung der Knospenzahl nur einen 20prozentigen Anstieg im Ertrag zur Folge.Wechselwirkungen zwischen den Behandlungsarten Drahtrahmen, Schnitt und Unterlage kamen nur vereinzelt vor. Die vorteilhaften Einflüsse von weitem Drahtrahmen, Salt Creek-Unterlage und von höheren Knospenzahlen, wenigstens bis zu 196 Knospen je Rebe, waren additiv. Infolgedessen war der Ertrag der zu 196 Knospen geschnittenen Sultana auf Salt Creek und auf weitem Rahmen zweimal so groß wie derjenige der wurzelechten Sultana auf engem Rahmen mit 126 Knospen.Es wird geschlossen, daß Sultanaknospen am weiten Drahtrahmen fruchtbarer sind und daß folglich im nächsten Jahr die Reben mehr Traubenbeeren tragen, die überdies durch Verbesserung der Photosynthese völlig ausreifen können. Die ökonomischen Verhältnisse für den Gebrauch von weiten Drahtrahmen werden diskutiert