The topology of a discussion: the #occupy case

We analyse a large sample of the Twitter activity developed around the social movement 'Occupy Wall Street' to study the complex interactions between the human communication activity and the semantic content of a discussion. We use a network approach based on the analysis of the bipartite graph @Users-#Hashtags and of its projections: the 'semantic network', whose nodes are hashtags, and the 'users interest network', whose nodes are users In the first instance, we find out that discussion topics (#hashtags) present a high heterogeneity, with the distinct role of the communication hubs where most the 'opinion traffic' passes through. In the second case, the self-organization process of users activity leads to the emergence of two classes of communicators: the 'professionals' and the 'amateurs'. Moreover the network presents a strong community structure, based on the differentiation of the semantic topics, and a high level of structural robustness when a certain set of topics are censored and/or accounts are removed. Analysing the characteristics the @Users-#Hashtags network we can distinguish three phases of the discussion about the movement. Each phase corresponds to specific moment of the movement: from declaration of intent, organisation and development and the final phase of political reactions. Each phase is characterised by the presence of specific #hashtags in the discussion. Keywords: Twitter, Network analysisComment: 13 pages, 9 figure

Portraits of Complex Networks

We propose a method for characterizing large complex networks by introducing a new matrix structure, unique for a given network, which encodes structural information; provides useful visualization, even for very large networks; and allows for rigorous statistical comparison between networks. Dynamic processes such as percolation can be visualized using animations. Applications to graph theory are discussed, as are generalizations to weighted networks, real-world network similarity testing, and applicability to the graph isomorphism problem.Comment: 6 pages, 9 figure

Geometric and dynamic perspectives on phase-coherent and noncoherent chaos

Statistically distinguishing between phase-coherent and noncoherent chaotic dynamics from time series is a contemporary problem in nonlinear sciences. In this work, we propose different measures based on recurrence properties of recorded trajectories, which characterize the underlying systems from both geometric and dynamic viewpoints. The potentials of the individual measures for discriminating phase-coherent and noncoherent chaotic oscillations are discussed. A detailed numerical analysis is performed for the chaotic R\"ossler system, which displays both types of chaos as one control parameter is varied, and the Mackey-Glass system as an example of a time-delay system with noncoherent chaos. Our results demonstrate that especially geometric measures from recurrence network analysis are well suited for tracing transitions between spiral- and screw-type chaos, a common route from phase-coherent to noncoherent chaos also found in other nonlinear oscillators. A detailed explanation of the observed behavior in terms of attractor geometry is given.Comment: 12 pages, 13 figure

A meta-analysis of state-of-the-art electoral prediction from Twitter data

Electoral prediction from Twitter data is an appealing research topic. It seems relatively straightforward and the prevailing view is overly optimistic. This is problematic because while simple approaches are assumed to be good enough, core problems are not addressed. Thus, this paper aims to (1) provide a balanced and critical review of the state of the art; (2) cast light on the presume predictive power of Twitter data; and (3) depict a roadmap to push forward the field. Hence, a scheme to characterize Twitter prediction methods is proposed. It covers every aspect from data collection to performance evaluation, through data processing and vote inference. Using that scheme, prior research is analyzed and organized to explain the main approaches taken up to date but also their weaknesses. This is the first meta-analysis of the whole body of research regarding electoral prediction from Twitter data. It reveals that its presumed predictive power regarding electoral prediction has been rather exaggerated: although social media may provide a glimpse on electoral outcomes current research does not provide strong evidence to support it can replace traditional polls. Finally, future lines of research along with a set of requirements they must fulfill are provided.Comment: 19 pages, 3 table

The Insulin-Like Growth Factor System in the Long-Lived Naked Mole-Rat.

Naked mole-rats (Heterocephalus glaber) (NMRs) are the longest living rodents known. They show negligible senescence, and are resistant to cancers and certain damaging effects associated with aging. The insulin-like growth factors (IGFs) have pluripotent actions, influencing growth processes in virtually every system of the body. They are established contributors to the aging process, confirmed by the demonstration that decreased IGF signaling results in life-extending effects in a variety of species. The IGFs are likewise involved in progression of cancers by mediating survival signals in malignant cells. This report presents a full characterization of the IGF system in the NMR: ligands, receptors, IGF binding proteins (IGFBPs), and IGFBP proteases. A particular emphasis was placed on the IGFBP protease, pregnancy-associated plasma protein-A (PAPP-A), shown to be an important lifespan modulator in mice. Comparisons of IGF-related genes in the NMR with human and murine sequences indicated no major differences in essential parts of the IGF system, including PAPP-A. The protease was shown to possess an intact active site despite the report of a contradictory genome sequence. Furthermore, PAPP-A was expressed and translated in NMRs cells and retained IGF-dependent proteolytic activity towards IGFBP-4 and IGF-independent activity towards IGFBP-5. However, experimental data suggest differential regulatory mechanisms for PAPP-A expression in NMRs than those described in humans and mice. This overall description of the IGF system in the NMR represents an initial step towards elucidating the complex molecular mechanisms underlying longevity, and how these animals have evolved to ensure a delayed and healthy aging process

Structural and Electronic Properties of Small Neutral (MgO)n Clusters

Ab initio Perturbed Ion (PI) calculations are reported for neutral stoichiometric (MgO)n clusters (n<14). An extensive number of isomer structures was identified and studied. For the isomers of (MgO)n (n<8) clusters, a full geometrical relaxation was considered. Correlation corrections were included for all cluster sizes using the Coulomb-Hartree-Fock (CHF) model proposed by Clementi. The results obtained compare favorably to the experimental data and other previous theoretical studies. Inclusion of correlaiotn is crucial in order to achieve a good description of these systems. We find an important number of new isomers which allows us to interpret the experimental magic numbers without the assumption of structures based on (MgO)3 subunits. Finally, as an electronic property, the variations in the cluster ionization potential with the cluster size were studied and related to the structural isomer properties.Comment: 24 pages, LaTeX, 7 figures in GIF format. Accepted for publication in Phys. Rev.

Trends in Pharmacotherapy for Bladder Dysfunction among Children in the United States, 2000 to 2013

Bladder-related issues such as nocturnal enuresis and incontinence have long been a part of general pediatric practice. Increasingly, clinicians are prescribing medications directed at a variety of types of bladder dysfunction, but no prior population-based data exist. We used MarketScan health care claims data on 32 074 638 insured children to estimate utilization patterns by age, sex, year, and geographic region in the United States from 2000 to 2013, and to assess related diagnosis codes. Approximately 1 in 500 children filled an antimuscarinic prescription. The most common prescriptions were for oxybutynin (78%) and tolterodine (17%). Rates were highest at ages 6 to 10 years (65/100 000 person-months), 31% higher for girls versus boys, peaked in 2011 (44/100 000 person-months), and were highest in the Midwest (59/100 000 person-months). Seventy-three percent of children with prescriptions had diagnosis codes for genitourinary symptoms, and 13% had codes for congenital anomalies. Research is needed regarding the comparative effectiveness and safety of these drugs in children

Impact of New Medications and $4 Generic Programs on Overactive Bladder Treatment among Older Adults in the United States, 2000-2015

Background: Despite several new medications being Food and Drug Administration-Approved for overactive bladder (OAB) and new prescription drug payment programs, there are limited population-based data regarding OAB medication use among older adults. Objectives: To examine: (1) impacts of new medications and 4 generic programs on time trends for OAB-related medication dispensing for older adults in the United States; (2) differences by age and sex; and (3) temporal changes in OAB-related medication payments. Methods: Using Truven Health Analytics' Medicare Supplemental Database (2000-2015), we analyzed OAB-related medication claims for 9,477,061 Medigap beneficiaries age 65-104. We estimated dispensing rates (per 1000 person-months), assessed dispensing trends using interrupted time-series methods, compared dispensing rates by age and sex, and summarized payment trends. Results: From 2000 to 2015, 771,609 individuals filled 13,863,998 OAB-related prescriptions. During 2000-2007, 3 new extended-release medications became available (tolterodine, darifenacin, solifenacin), leading to increases in overall OAB-related dispensing rates by 19.1 (99% confidence interval, 17.0-21.2), a 92% increase since 2000; overall rates remained stable during 2008-2015. By 2015, the most common medications were oxybutynin (38%), solifenacin (20%), tolterodine (19%), and mirabegron (12%). Dispensing rates peaked at age 90 (rate, 53.4; 99% confidence interval, 53.1-53.7). Women had higher rates than men at all ages (average rate women-rate men, 22.0). The gap between upper and lower percentiles of medication payments widened between 2008-2015; by 2015, 25% of reimbursed dispensed prescriptions had total payments exceeding 250. Conclusions: Medication-specific dispensing rates for OAB changed when new alternatives became available. Recent changes in utilization and cost of OAB medications have implications for clinical guidelines, pharmacoepidemiologic studies, and payment policies

Inference with interference between units in an fMRI experiment of motor inhibition

An experimental unit is an opportunity to randomly apply or withhold a treatment. There is interference between units if the application of the treatment to one unit may also affect other units. In cognitive neuroscience, a common form of experiment presents a sequence of stimuli or requests for cognitive activity at random to each experimental subject and measures biological aspects of brain activity that follow these requests. Each subject is then many experimental units, and interference between units within an experimental subject is likely, in part because the stimuli follow one another quickly and in part because human subjects learn or become experienced or primed or bored as the experiment proceeds. We use a recent fMRI experiment concerned with the inhibition of motor activity to illustrate and further develop recently proposed methodology for inference in the presence of interference. A simulation evaluates the power of competing procedures.Comment: Published by Journal of the American Statistical Association at http://www.tandfonline.com/doi/full/10.1080/01621459.2012.655954 . R package cin (Causal Inference for Neuroscience) implementing the proposed method is freely available on CRAN at https://CRAN.R-project.org/package=ci