A stochastic model for the evolution of the web allowing link deletion

Recently several authors have proposed stochastic evolutionary models for the growth of the web graph and other networks that give rise to power-law distributions. These models are based on the notion of preferential attachment leading to the ``rich get richer'' phenomenon. We present a generalisation of the basic model by allowing deletion of individual links and show that it also gives rise to a power-law distribution. We derive the mean-field equations for this stochastic model and show that by examining a snapshot of the distribution at the steady state of the model, we are able to tell whether any link deletion has taken place and estimate the link deletion probability. Our model enables us to gain some insight into the distribution of inlinks in the web graph, in particular it suggests a power-law exponent of approximately 2.15 rather than the widely published exponent of 2.1

The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modelling and analysed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM) project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD) have been used together with c-axis orientations using an optical technique (Fabric Analyser). Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighbouring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modelling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be used to identify grain dissection in natural microstructures

Gross N-cycling rates in ephemeral wetlands

Non-Peer ReviewedEphemeral wetlands or depressions in hummocky landscapes have high levels of C, N, and soil moisture, often leading to high nutrient cycling activity. However, measuring soil nitrate and ammonium pools is typically a poor indication of N-cycling activity or of the soil N that is available for other processes such as N2O emissions. This study used stable 15N isotope dilution techniques in cultivated and uncultivated ephemeral wetlands in central Saskatchewan to quantify land use effects on gross mineralization and nitrification rates. In-field incubation experiments were repeated in early May, mid-June and late July. There was a clear land use effect on inorganic soil N levels, with significantly less NH4+ and more NO3- in the cultivated wetland soils. However, the rates of NH4+ mineralization and NO3 - nitrification were similar for both land uses, indicating similar substrate availability but different N-consuming processes. Both N pools turned over in as little as 1-2 d, highlighting the ineffectuality of measuring inorganic N pools as a predictor for N availability in these soils

Quantifying changes in biomass and soil organic carbon after abandonment of croplands in Saskatchewan

Non-Peer Reviewe

Variability of ammonium and nitrate in disturbed and undisturbed forest soils

Non-Peer ReviewedThe spatial distribution of NH4+- and N03--N in forest soils, as affected by site disturbance, was studied at the landscape-scale. A sampling grid, consisting of 169 points, was established at an undisturbed site located in Prince Albert National Park. Additional grids, consisting of 36 and 49 sampling points, were established at a burned and a clear-cut site, respectively. Similar levels of inorganic-N at the undisturbed and disturbed sites suggests that management practices had little effect on the availability of inorganic-N. Similarly, the spatial distribution of inorganic-N was not related to landform element complexes, suggesting that hydrologic processes were not the primary factor controlling the distribution of inorganic-N at the scale studied. The occurrence of NH4+ -N as the dominant inorganic-N form suggests that nitrification was strictly limited in these forest soils. This contrasts agricultural soils in which nitrification often proceeds swiftly in the presence of NH4+-N

UCF PEGASUS PLANS- 3rd Grade - Maps and Regions of the United States of America

Designed by pre-service teachers, this fifteen-day Social Studies unit covers 3rd grade Florida Social Studies Sunshine State Standards and Florida B.E.S.T. Standards while incorporating Universal Design for Learning strategies, English Language strategies, and opportunities for students to engage with educational technology in various capacities. This unit is complete with a daily Instructional Guide for teachers, turnkey student-facing materials, lists of or links to any necessary resources not created by the authors, and a post-assessment. During this unit, students will explore maps and their key elements through songs and fun activities. Students will also be exploring the United States of America and its 5 regions by exploring each region and its unique features with songs, books, and interactive activities

Novel Phosphorylation Sites in the S. cerevisiae Cdc13 Protein Reveal New Targets for Telomere Length Regulation

The S. cerevisiae Cdc13 is a multifunctional protein with key roles in regulation of telomerase, telomere end protection, and conventional telomere replication, all of which are cell cycle-regulated processes. Given that phosphorylation is a key mechanism for regulating protein function, we identified sites of phosphorylation using nano liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS). We also determined phosphorylation abundance on both wild type (WT) and a telomerase deficient form of Cdc13, encoded by the cdc13-2 allele, in both G1 phase cells, when telomerase is not active, and G2/M phase cells, when it is. We identified 21 sites of in vivo phosphorylation, of which only five had been reported previously. In contrast, phosphorylation of two in vitro targets of the ATM-like Tel1 kinase, S249 and S255, was not detected. This result helps resolve conflicting data on the importance of phosphorylation of these residues in telomerase recruitment. multiple residues showed differences in their cell cycle pattern of modification. For example, phosphorylation of S314 was significantly higher in the G2/M compared to the G1 phase and in WT versus mutant Cdc13, and a S314D mutation negatively affected telomere length. Our findings provide new targets in a key telomerase regulatory protein for modulation of telomere dynamics. [Image: see text

American Thyroid Association Guide to Investigating Thyroid Hormone Economy and Action in Rodent and Cell Models

Background: An in-depth understanding of the fundamental principles that regulate thyroid hormone homeostasis is critical for the development of new diagnostic and treatment ap-proaches for patients with thyroid disease. Summary: Important clinical practices in use today for the treatment of patients with hypothy-roidism, hyperthyroidism, or thyroid cancer, are the result of laboratory discoveries made by scientists investigating the most basic aspects of thyroid structure and molecular biology. In this document, a panel of experts commissioned by the American Thyroid Association makes a se-ries of recommendations related to the study of thyroid hormone economy and action. These recommendations are intended to promote standardization of study design, which should in turn increase the comparability and reproducibility of experimental findings. Conclusions: It is expected that adherence to these recommendations by investigators in the field will facilitate progress towards a better understanding of the thyroid gland and thyroid hormone dependent processes