Effects of experimental floods on periphyton and stream metabolism below a high dam in the Swiss Alps (River Spöl)

We investigated the effects of an experimental flood regime on periphyton and stream metabolism downstream of a large reservoir. Three floods took place in summer of 2000 and 2001 and two floods in summer of 2002. Residual flow in the River Spöl was <2.5 m3s-1. The experimental floods lasted 9 to 11 hours with peak flows ranging from 12 to 55 m3s-1. Periphyton was collected in the River Spöl (impact site) and in a reference stream in 1999 (pre-flood) and before and after each flood from 2000 to 2002. We measured ecosystem metabolism with the single station diel oxygen method a few days before and after floods in the River Spöl. Floods temporarily reduced periphyton biomass, but the disturbance impact and recovery patterns were not uniform among floods, thus resulting in high inter-annual variation in seasonal biomass patterns. The average periphyton biomass in the River Spöl even increased after a transient reduction in 2000. A principal component analysis indicated a persistent shift in the structure of the diatom community at the impact site. The floods reduced gross primary production and to minor extent ecosystem respiration, resulting in a transient decline in the P/R ratio. However, ecosystem metabolism recovered relatively fast. The new flow regime increased ecosystem dynamics, but it may take several years until the autotrophic energy base becomes adapted to the new and more dynamic flow regim

Average distance in growing trees

Two kinds of evolving trees are considered here: the exponential trees, where subsequent nodes are linked to old nodes without any preference, and the Barab\'asi--Albert scale-free networks, where the probability of linking to a node is proportional to the number of its pre-existing links. In both cases, new nodes are linked to $m=1$ nodes. Average node-node distance $d$ is calculated numerically in evolving trees as dependent on the number of nodes $N$. The results for $N$ not less than a thousand are averaged over a thousand of growing trees. The results on the mean node-node distance $d$ for large $N$ can be approximated by $d=2\ln(N)+c_1$ for the exponential trees, and $d=\ln(N)+c_2$ for the scale-free trees, where the $c_i$ are constant. We derive also iterative equations for $d$ and its dispersion for the exponential trees. The simulation and the analytical approach give the same results.Comment: 6 pages, 3 figures, Int. J. Mod. Phys. C14 (2003) - in prin

New algorithm for the computation of the partition function for the Ising model on a square lattice

A new and efficient algorithm is presented for the calculation of the partition function in the $S=\pm 1$ Ising model. As an example, we use the algorithm to obtain the thermal dependence of the magnetic spin susceptibility of an Ising antiferromagnet for a $8\times 8$ square lattice with open boundary conditions. The results agree qualitatively with the prediction of the Monte Carlo simulations and with experimental data and they are better than the mean field approach results. For the $8\times 8$ lattice, the algorithm reduces the computation time by nine orders of magnitude.Comment: 7 pages, 3 figures, to appear in Int. J. Mod. Phys.

Biology of the freshwater diatom Didymosphenia : a review

Features of the colonial diatom Didymosphenia are reviewed, especially D. geminata. Although there is a long record of its occurrence in north temperate regions, mass growths have been reported much more widely in recent years. Contrary to some statements in the literature, there are also reliable older records for the southern hemisphere, though the first report of mass growth was in New Zealand in 2004. The annual cycle of morphological changes in D. geminata in northern England, and probably elsewhere, includes a winter period when motile cells are attached to the substratum followed by spring when stalks start to develop. These raise cells into the water column and provide a site for phosphatase activity. Environmental factors associated with success include absence of extreme floods, high light, pH above neutral and nutrient chemistry. D. geminata often, but not always, occurs in waters where the N:P ratio is high for much of the year, but the key factor is the ratio of organic to inorganic phosphate. D. geminata thrives where organic P is predominant and the overall P concentration is low enough for organic P to be an important P source. It is unknown whether organic N can be used. Environmental changes increasing the relative importance of organic P are likely to favour D. geminata. Likely examples are increased N:P due to atmospheric N deposition and changes in form and seasonality of P release from organic-rich soils due to climatic warming. The nutrient chemistry of deep water released from dams to rivers also needs investigation. To what extent are genetic changes occurring in response to environmental changes and are new ecotypes spreading round the world? In spite of many adverse reports about D. geminata, such as detached mats blocking water pipes, there is still doubt about the extent to which it causes problems, particularly for fish. There have been few adverse effects on migratory salmonids in Europe and North America, but at least one report of harm to a brown trout population in USA. In New Zealand, it has caused serious problems for water sports, although it remains open to question how much adverse effect it has had on fish populations. If the presence of microcystins in or associated with D. geminata, as indicated recently for two populations, proves to be widespread and at sufficiently high concentration, their possible accumulation in fish requires study. Where control is required, this could be achieved by enhancing the ratio of inorganic to organic phosphate in the water early in the growth season. Practical ways to achieve this are suggested

The Cosmos of a Public Sector Township: Democracy as an Intellectual Culture

The public sector plays an important role in responding to the rights of citizens and evolving norms of social interest (Qu 2015). Qu argues that the nature of public enterprise is never final and there is a constant negotiation between the private and the public emergence of life and rights. One such space where the tension between the private and the public manifests itself is the public sector township or the residential colony in India. The sociality of hierarchy in public sector organizations manifest itself in the public sector township and may nurture everyday aspirations, angsts and divides. The officer lives in a bigger hone, in a bungalow, and the clerk lives in a smaller home, many times with a larger family. [excerpt

Epigenetic reprogramming at estrogen-receptor binding sites alters 3D chromatin landscape in endocrine-resistant breast cancer

Endocrine therapy resistance frequently develops in estrogen receptor positive (ER+) breast cancer, but the underlying molecular mechanisms are largely unknown. Here, we show that 3-dimensional (3D) chromatin interactions both within and between topologically associating domains (TADs) frequently change in ER+ endocrine-resistant breast cancer cells and that the differential interactions are enriched for resistance-associated genetic variants at CTCF-bound anchors. Ectopic chromatin interactions are preferentially enriched at active enhancers and promoters and ER binding sites, and are associated with altered expression of ER-regulated genes, consistent with dynamic remodelling of ER pathways accompanying the development of endocrine resistance. We observe that loss of 3D chromatin interactions often occurs coincidently with hypermethylation and loss of ER binding. Alterations in active A and inactive B chromosomal compartments are also associated with decreased ER binding and atypical interactions and gene expression. Together, our results suggest that 3D epigenome remodelling is a key mechanism underlying endocrine resistance in ER+ breast cancer