Probing Limits of Information Spread with Sequential Seeding

We consider here information spread which propagates with certain probability from nodes just activated to their not yet activated neighbors. Diffusion cascades can be triggered by activation of even a small set of nodes. Such activation is commonly performed in a single stage. A novel approach based on sequential seeding is analyzed here resulting in three fundamental contributions. First, we propose a coordinated execution of randomized choices to enable precise comparison of different algorithms in general. We apply it here when the newly activated nodes at each stage of spreading attempt to activate their neighbors. Then, we present a formal proof that sequential seeding delivers at least as large coverage as the single stage seeding does. Moreover, we also show that, under modest assumptions, sequential seeding achieves coverage provably better than the single stage based approach using the same number of seeds and node ranking. Finally, we present experimental results showing how single stage and sequential approaches on directed and undirected graphs compare to the well-known greedy approach to provide the objective measure of the sequential seeding benefits. Surprisingly, applying sequential seeding to a simple degree-based selection leads to higher coverage than achieved by the computationally expensive greedy approach currently considered to be the best heuristic

Social Networks through the Prism of Cognition

Human relations are driven by social events - people interact, exchange information, share knowledge and emotions, or gather news from mass media. These events leave traces in human memory. The initial strength of a trace depends on cognitive factors such as emotions or attention span. Each trace continuously weakens over time unless another related event activity strengthens it. Here, we introduce a novel Cognition-driven Social Network (CogSNet) model that accounts for cognitive aspects of social perception and explicitly represents human memory dynamics. For validation, we apply our model to NetSense data on social interactions among university students. The results show that CogSNet significantly improves quality of modeling of human interactions in social networks

Quasiquartet CEF ground state with possible quadrupolar ordering in the tetragonal compound YbRu2_{2}Ge2_{2}

e have investigated the magnetic properties of YbRu$_{2}$Ge$_{2}$ by means of magnetic susceptibility $\chi$(T), specific heat C(T) and electrical resistivity $\rho$(T) measurements performed on flux grown single crystals. The Curie-Weiss behavior of $\chi$(T) along the easy plane, the large magnetic entropy at low temperatures and the weak Kondo like increase in $\rho$(T) proves a stable trivalent Yb state. Anomalies in C(T), $\rho$(T) and $\chi$(T) at T$_{0}$ = 10.2 K, T$_{1}$ = 6.5 K and T$_{2}$ = 5.7 K evidence complex ordering phenomena, T$_{0}$ being larger than the highest Yb magnetic ordering temperature found up to now. The magnetic entropy just above T$_{0}$ amounts to almost Rln4, indicating that the crystal electric field (CEF) ground state is a quasiquartet instead of the expected doublet. The behavior at T$_{0}$ is rather unusual and suggest that this transition is related to quadrupolar ordering, being a consequence of the CEF quasiquartet ground state. The combination of a quasiquartet CEF ground state, a high ordering temperature, and the relevance of quadrupolar interactions makes YbRu$_{2}$Ge$_{2}$ a rather unique system among Yb based compounds.Comment: 11 pages, 5 figure, submitted to PRB rapi

APPLICATION OF ALLOMETRY FOR DETERMINATION OF STRENGTH PROFILE IN YOUNG FEMALE ATHLETES FROM DIFFERENT SPORTS

The goal of the study was to determine a strength profile in young female athletes practising different sports and to use allometry to evaluate muscular strength with respect to body mass. The study included 42 women who practised taekwondo (n = 10), weightlifting (n = 10), canoeing (n = 14) and speed skating (n = 8). Measurements of maximal muscle torques under static conditions in 10 groups of flexors and extensors of the elbow, shoulder, hip, knee and trunk were carried out. The MANCOVA procedure was employed to compare means between the groups. A logarithm of body mass was adopted as a covariate. Relationships between body mass and muscle torques in each muscle group were determined using a procedure of linear regression. The analysis of residuals was employed for the evaluation of maximal muscle torques. Mean values of logarithms of maximal muscle torques were significantly different for the representatives of individual sports and they depended on the logarithm of body mass. It was proposed to use a mean of residuals normalized for individual muscle groups as a synthetic strength index (mean of the strength profile). The women practising canoeing were characterized by the highest strength index. Its lowest values were obtained by weightlifting and taekwondo athletes. Differences in strength profiles in the tested athletes were attributed to the specific nature of their sports. It is suggested to use an allometric relationship scaled by body mass for strength assessment

Social media actions and interactions: The role of the Facebook and Twitter during the 2014 European Parliament elections in the 28 EU nations.

Most political parties across the democratic sphere have created their own spaces within social media. While ostensibly studies show that social media is being utilized by political parties to further their electoral goals, the uses of their social media profiles by visitors is largely beyond official control without devoting significant resources to moderation. This study will be the first to gather data that allows us to detect patterns of participation within and potentially across nations, but in particular within nations and across parties to determine the extent that visitors use social media to promote parties (through liking and sharing) or for entering comments on party posts or for entering into discussions with other visitors. We specifically seek to understand whether we can detect evidence of a political ecosystem in which visitors visit multiple party profiles, enter debates across differing profiles and so contribute to something that might resemble an informed and engaged public sphere

Discovering predictive variables when evolving cognitive models

A non-dominated sorting genetic algorithm is used to evolve models of learning from different theories for multiple tasks. Correlation analysis is performed to identify parameters which affect performance on specific tasks; these are the predictive variables. Mutation is biased so that changes to parameter values tend to preserve values within the population's current range. Experimental results show that optimal models are evolved, and also that uncovering predictive variables is beneficial in improving the rate of convergence

Modulation of Osteoblastic Cell Efferocytosis by Bone Marrow Macrophages

Apoptosis occurs at an extraordinary rate in the human body and the effective clearance of dead cells (efferocytosis) is necessary to maintain homeostasis and promote healing, yet the contribution and impact of this process in bone is unclear. Bone formation requires that bone marrow stromal cells (BMSCs) differentiate into osteoblasts which direct matrix formation and either become osteocytes, bone lining cells, or undergo apoptosis. A series of experiments were performed to identify the regulators and consequences of macrophage efferocytosis of apoptotic BMSCs (apBMSCs). Bone marrow derived macrophages treated with the anti‐inflammatory cytokine interleukin‐10 (IL‐10) exhibited increased efferocytosis of apBMSCs compared to vehicle treated macrophages. Additionally, IL‐10 increased anti‐inflammatory M2‐like macrophages (CD206+), and further enhanced efferocytosis within the CD206+ population. Stattic, an inhibitor of STAT3 phosphorylation, reduced the IL‐10‐mediated shift in M2 macrophage polarization and diminished IL‐10‐directed efferocytosis of apBMSCs by macrophages implicating the STAT3 signaling pathway. Cell culture supernatants and RNA from macrophages co‐cultured with apoptotic bone cells showed increased secretion of monocyte chemotactic protein 1/chemokine (C‐C motif) ligand 2 (MCP‐1/CCL2) and transforming growth factor beta 1 (TGF‐β1) and increased ccl2 gene expression. In conclusion, IL‐10 increases M2 macrophage polarization and enhances macrophage‐mediated engulfment of apBMSCs in a STAT3 phosphorylation‐dependent manner. After engulfment of apoptotic bone cells, macrophages secrete TGF‐β1 and MCP‐1/CCL2, factors which fuel the remodeling process. A better understanding of the role of macrophage efferocytosis as it relates to normal and abnormal bone turnover will provide vital information for future therapeutic approaches to treat bone related diseases. J. Cell. Biochem. 117: 2697–2706, 2016. © 2016 Wiley Periodicals, Inc.The process of efferocytosis (clearance of apoptotic cells) has been characterized in various tissues but the role of efferocytosis in the bone microenvironment is unclear. Bone marrow macrophage efferocytosis of apoptotic osteoblastic cells was enhanced by interleukin‐10 in a STAT‐3 dependent manner and resulted in increased production of TGF‐β1 and CCL‐2. The process of efferocytosis is likely important in bone remodeling and osseous wound healing.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134491/1/jcb25567.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134491/2/jcb25567_am.pd

The cryo-EM structure of a pannexin 1 reveals unique motifs for ion selection and inhibition

Pannexins are large-pore forming channels responsible for ATP release under a variety of physiological and pathological conditions. Although predicted to share similar membrane topology with other large-pore forming proteins such as connexins, innexins, and LRRC8, pannexins have minimal sequence similarity to these protein families. Here, we present the cryo-EM structure of a frog pannexin 1 (Panx1) channel at 3.0 A. We find that Panx1 protomers harbor four transmembrane helices similar in arrangement to other large-pore forming proteins but assemble as a heptameric channel with a unique constriction formed by Trp74 in the first extracellular loop. Mutating Trp74 or the nearby Arg75 disrupt ion selectivity whereas altering residues in the hydrophobic groove formed by the two extracellular loops abrogates channel inhibition by carbenoxolone. Our structural and functional study establishes the extracellular loops as important structural motifs for ion selectivity and channel inhibition in Panx1