Sequential primed kinases create a damage-responsive phosphodegron on Eco1.

Sister-chromatid cohesion is established during S phase when Eco1 acetylates cohesin. In budding yeast, Eco1 activity falls after S phase due to Cdk1-dependent phosphorylation, which triggers ubiquitination by SCF(Cdc4). We show here that Eco1 degradation requires the sequential actions of Cdk1 and two additional kinases, Cdc7-Dbf4 and the GSK-3 homolog Mck1. These kinases recognize motifs primed by previous phosphorylation, resulting in an ordered sequence of three phosphorylation events on Eco1. Only the latter two phosphorylation sites are spaced correctly to bind Cdc4, resulting in strict discrimination between phosphates added by Cdk1 and by Cdc7. Inhibition of Cdc7 by the DNA damage response prevents Eco1 destruction, allowing establishment of cohesion after S phase. This elaborate regulatory system, involving three independent kinases and stringent substrate selection by a ubiquitin ligase, enables robust control of cohesion establishment during normal growth and after stress

Detecting nonlinearity in run-up on a natural beach

International audienceNatural geophysical timeseries bear the signature of a number of complex, possibly inseparable, and generally unknown combination of linear, stable non-linear and chaotic processes. Quantifying the relative contribution of, in particular, the non-linear components will allow improved modelling and prediction of natural systems, or at least define some limitations on predictability. However, difficulties arise; for example, in cases where the series are naturally cyclic (e.g. water waves), it is most unclear how this cyclic behaviour impacts on the techniques commonly used to detect the nonlinear behaviour in other fields. Here a non-linear autoregressive forecasting technique which has had success in demonstrating nonlinearity in non-cyclical geophysical timeseries, is applied to a timeseries generated by videoing the waterline on a natural beach (run-up), which has some irregular oscillatory behaviour that is in part induced by the incoming wave field. In such cases, the deterministic shape of each run-up cycle has a strong influence on forecasting results, causing questionable results at small (within a cycle) prediction distances. However, the technique can clearly differentiate between random surrogate series and natural timeseries at larger prediction distances (greater than one cycle). Therefore it was possible to clearly identify nonlinearity in the relationship between observed run-up cycles in that a local autoregressive model was more adept at predicting run-up cycles than a global one. Results suggest that despite forcing from waves impacting on the beach, each run-up cycle evolves somewhat independently, depending on a non-linear interaction with previous run-up cycles. More generally, a key outcome of the study is that oscillatory data provide a similar challenge to differentiating chaotic signals from correlated noise in that the deterministic shape causes an additional source of autocorrelation which in turn influences the predictability at small forecasting distances

The Vegetation of Three Sphagnum-dominated Basin-type Bogs in Northeastern Ohio

Author Institution: Division of Natural Sciences, Cuyahoga Community College and Department of Biological Sciences, Kent State UniversityVegetation and selected ground water characteristics were examined for three closely proximate basin-type bogs in northeastern Ohio. These peatlands exhibit zonation, with a low shrub zone dominated by Chamaedaphne calyculata (Frequency-Presence Index [FPI] 4433) and Decodon verticillatus (FPI 5400) adjacent to and invading the open water. A tall shrub zone, extending aproximately 5 to 10 m to the exterior of the low shrub zone, is dominated by Vaccinium corymbosum (FPI 5533), Gaylussacia baccata (FPI 3133), andNemopanthus mucronatus (FPI 2200). Extending for the next 5 -10 m is a tree zone, dominated by Larix laricina (FPI 800), Betula alieghaniensis (FPI 198), andNyssa sylvatica (FPI 77). Sphagnum recurvum (sensu lato) (FPI 6500) forms a more or less continuous mat throughout the bogs. The vegetation of the three peatlands is similar, with similarity indices (c) ranging from 0.59 to 0.67. Based on pH, conductivity and Ca and Mg ion concentrations, these peatlands are semi-ombrotrophic to weakly minerotrophic. These communities, located near the glacial boundary, represent northern peatlands at the southern edge of glaciation

Edge-weighting of gene expression graphs

In recent years, considerable research efforts have been directed to micro-array technologies and their role in providing simultaneous information on expression profiles for thousands of genes. These data, when subjected to clustering and classification procedures, can assist in identifying patterns and providing insight on biological processes. To understand the properties of complex gene expression datasets, graphical representations can be used. Intuitively, the data can be represented in terms of a bipartite graph, with weighted edges corresponding to gene-sample node couples in the dataset. Biologically meaningful subgraphs can be sought, but performance can be influenced both by the search algorithm, and, by the graph-weighting scheme and both merit rigorous investigation. In this paper, we focus on edge-weighting schemes for bipartite graphical representation of gene expression. Two novel methods are presented: the first is based on empirical evidence; the second on a geometric distribution. The schemes are compared for several real datasets, assessing efficiency of performance based on four essential properties: robustness to noise and missing values, discrimination, parameter influence on scheme efficiency and reusability. Recommendations and limitations are briefly discussed

Regrowth-related defect formation and evolution in 1 MeV amorphized (001) Ge

Geimplanted with 1MeV Si⁺ at a dose of 1×10¹⁵cm⁻² creates a buried amorphous layer that, upon regrowth, exhibits several forms of defects–end-of-range (EOR), regrowth-related, and clamshell defects. Unlike Si, no planar {311} defects are observed. The minimal EOR defects are small dotlike defects and are very unstable, dissolving between 450 and 550°C. This is in contrast to Si, where the EOR defects are very stable. The amorphous layer results in both regrowth-related defects and clamshell defects, which were more stable than the EOR damage.This work is supported by Semiconductor Research Corporation Contract No. 00057787

The X-ray surface brightness distribution from diffuse gas

We use simulations to predict the X-ray surface brightness distribution arising from hot, cosmologically distributed diffuse gas. The distribution is computed for two bands: 0.5-2 keV and 0.1-0.4 keV, using a cosmological-constant dominated cosmology that fits many other observations. We examine a number of numerical issues such as resolution, simulation volume and pixel size and show that the predicted mean background is sensitive to resolution such that higher resolution systematically increases the mean predicted background. Although this means that we can compute only lower bounds to the predicted level, these bounds are already quite restrictive. Since the observed extra-galactic X-ray background is mostly accounted for by compact sources, the amount of the observed background attributable to diffuse gas is tightly constrained. We show that without physical processes in addition to those included in the simulations (such as radiative cooling or non-gravitational heating), both bands exceed observational limits. In order to examine the effect of non-gravitational heating we explore a simple modeling of energy injection and show that substantial amounts of heating are required (i.e. 5 keV per particle when averaged over all baryons). Finally, we also compute the distribution of surface brightness on the sky and show that it has a well-resolved characteristic shape. This shape is substantially modified by non-gravitational heating and can be used as a probe of such energy injection.Comment: 11 pages, 11 figures, submitted to Ap

Clinical Social Workers, Gender, and Perceptions of Political Participation

Political participation to create social change is considered a professional and ethical imperative for social workers. Although researchers have examined overall political participation by social workers, little is known about how clinical social workers participate and the broader societal factors that influence their political participation. A critical phenomenological methodology was used with a sample of 23 clinical social workers from New England states to (1) identify how socio-political forces influenced their political activity; and, (2) understand how the concept of power affected individuals’ level of engagement or inclination toward the political process. This article describes one of the study’s major findings. Female participants described themselves as unqualified and/or unknowledgeable in the political sphere, with low levels of ambition and confidence to engage in political processes. Many female participants also described the challenges of achieving a work-life balance between their careers and traditional gender-based roles with little time left for political engagement. Social work education and policy advocacy can affect change that will increase the internal and external efficacy of social workers and create a policy environment that allows more options for all social workers in balancing the demands of professional and personal lives