Weak ties: Subtle role of information diffusion in online social networks

As a social media, online social networks play a vital role in the social information diffusion. However, due to its unique complexity, the mechanism of the diffusion in online social networks is different from the ones in other types of networks and remains unclear to us. Meanwhile, few works have been done to reveal the coupled dynamics of both the structure and the diffusion of online social networks. To this end, in this paper, we propose a model to investigate how the structure is coupled with the diffusion in online social networks from the view of weak ties. Through numerical experiments on large-scale online social networks, we find that in contrast to some previous research results, selecting weak ties preferentially to republish cannot make the information diffuse quickly, while random selection can achieve this goal. However, when we remove the weak ties gradually, the coverage of the information will drop sharply even in the case of random selection. We also give a reasonable explanation for this by extra analysis and experiments. Finally, we conclude that weak ties play a subtle role in the information diffusion in online social networks. On one hand, they act as bridges to connect isolated local communities together and break through the local trapping of the information. On the other hand, selecting them as preferential paths to republish cannot help the information spread further in the network. As a result, weak ties might be of use in the control of the virus spread and the private information diffusion in real-world applications.Comment: Final version published in PR

A Comparison of Sociodemographic Correlates of Cigarette, Alcohol, and Energy Drink Consumption among High School Students in the United States, 2010-2015

OBJECTIVE: Despite growing awareness about the harmful physiological effects of energy drinks, especially among young people, there is little regulation governing the marketing and sale of these products to adolescents. Thus, in contrast to substances such as cigarettes and alcohol, energy drinks are readily available to adolescents, and widely consumed. It is not known if the easy availability of energy drinks has the effect of increasing usage of these substances among adolescents, and reducing sociodemographic differences in the consumption of energy drinks. In this study, we use pooled data (2010-2015) from the nationally representative Monitoring the Future survey (n=43,283), to compare consumption of energy drinks with other substance use, and to compare the sociodemographic correlates of energy drink consumption among high school students (10th and 12th grade) with those of cigarette and alcohol consumption. METHODS: Covariate-adjusted estimates for prevalence of consumption of energy drinks, cigarettes, and alcohol for each of different sociodemographic strata were obtained via logistic regression analysis. Additional analyses examined the extent to which socioeconomic disparities in prevalence of consumption of energy drinks are predicated by cigarette smoking and alcohol use. RESULTS: While the patterning of differences in energy drink use by sex, grade, race and parental education (as a measure of socioeconomic status) were similar to those seen in cigarette smoking and ever-use of alcohol, the magnitude of differences across subgroups varied across these behaviors. Racial/ethnic, socioeconomic and age differences were smaller in the case of energy drink use compared to alcohol or cigarette use. Gender differences were larger than in the case of cigarette smoking. In all cases, energy drink use were higher among students who were current users of alcohol or cigarettes, but there was little evidence that sociodemographic variables were differentially associated with energy drink use within these strata. CONCLUSIONS: Ready availability of energy drinks has resulted in elevated use of these products relative to cigarette smoking and alcohol, and some narrowing of socioeconomic differentials in use. Regardless of socioeconomic status, use of energy drinks is higher among current users of cigarettes and / or alcohol

Superfluid-insulator transitions of two-species Bosons in an optical lattice

We consider a realization of the two-species bosonic Hubbard model with variable interspecies interaction and hopping strength. We analyze the superfluid-insulator (SI) transition for the relevant parameter regimes and compute the ground state phase diagram for odd filling at commensurate densities. We find that in contrast to the even commensurate filling case, the superfluid-insulator transition occurs with (a) simultaneous onset of superfluidity of both species or (b) coexistence of Mott insulating state of one species and superfluidity of the other or, in the case of unit filling, (c) complete depopulation of one species. The superfluid-insulator transition can be first order in a large region of the phase diagram. We develop a variational mean-field method which takes into account the effect of second order quantum fluctuations on the superfluid-insulator transition and corroborate the mean-field phase diagram using a quantum Monte Carlo study.Comment: 12 pages, 11 figure

Origin of 21+2_1^+ Excitation Energy Dependence on Valence Nucleon Numbers

It has been shown recently that a simple formula in terms of the valence nucleon numbers and the mass number can describe the essential trends of excitation energies of the first $2^+$ states in even-even nuclei. By evaluating the first order energy shift due to the zero-range residual interaction, we find that the factor which reflects the effective particle number participating in the interaction from the Fermi orbit governs the main dependence of the first $2^+$ excitation energy on the valence nucleon numbers.Comment: 9 pages, 5 figure

Superfluid-insulator transition of the Josephson junction array model with commensurate frustration

We have studied the rationally frustrated Josephson-junction array model in the square lattice through Monte Carlo simulations of $(2+1)$D XY-model. For frustration $f=1/4$, the model at zero temperature shows a continuous superfluid-insulator transition. From the measurement of the correlation function and the superfluid stiffness, we obtain the dynamical critical exponent $z=1.0$ and the correlation length critical exponent $\nu=0.4 \pm 0.05$. While the dynamical critical exponent is the same as that for cases $f=0$, 1/2, and 1/3, the correlation length critical exponent is surprisingly quite different. When $f=1/5$, we have the nature of a first-order transition.Comment: RevTex 4, to appear in PR

Revisiting the project management knowledge framework: Rebalancing the framework to include transformation projects

Purpose This paper highlights that extant project management (PM) bodies of knowledge have not fully addressed organisational transformation enabled by information systems projects. The purpose of this paper is to examine the transformation context in the PM disciplines. The authors argue that the execution-oriented PM bodies of knowledge are limited, as they place too much emphasis on the delivery outputs by the supplier rather than the achievement of beneficial outcomes by the project owner. Design/methodology/approach As a conceptual paper, this paper reviews extant PM bodies of knowledge, life cycle models, the context of organisational transformation and benefits realisation, and the distinction between a project owner’s and the project supplier’s capabilities. Findings A new PM knowledge framework is provided as an advanced research frame for future works by enhancing Peter Morris’ Management of Projects framework by employing the conceptual lens of Winch’s Three Domains of Project Organising model. Originality/value The advanced model emphasises the necessity of distinguishing a project owner’s and a supplier’s PM capability and knowledge to achieve successful IS-enabled organisational transformation. Through this effort to resolve the fragmentation and specialisation problems in PM disciplines, the model can be used as a theoretical groundwork for the advancement of PM research

Systemic control of immune cell development by integrated carbon dioxide and hypoxia chemosensation in Drosophila.

Drosophila hemocytes are akin to mammalian myeloid blood cells that function in stress and innate immune-related responses. A multi-potent progenitor population responds to local signals and to systemic stress by expanding the number of functional blood cells. Here we show mechanisms that demonstrate an integration of environmental carbon dioxide (CO2) and oxygen (O2) inputs that initiate a cascade of signaling events, involving multiple organs, as a stress response when the levels of these two important respiratory gases fall below a threshold. The CO2 and hypoxia-sensing neurons interact at the synaptic level in the brain sending a systemic signal via the fat body to modulate differentiation of a specific class of immune cells. Our findings establish a link between environmental gas sensation and myeloid cell development in Drosophila. A similar relationship exists in humans, but the underlying mechanisms remain to be established

Who Contributes to the Knowledge Sharing Economy?

Information sharing dynamics of social networks rely on a small set of influencers to effectively reach a large audience. Our recent results and observations demonstrate that the shape and identity of this elite, especially those contributing \emph{original} content, is difficult to predict. Information acquisition is often cited as an example of a public good. However, this emerging and powerful theory has yet to provably offer qualitative insights on how specialization of users into active and passive participants occurs. This paper bridges, for the first time, the theory of public goods and the analysis of diffusion in social media. We introduce a non-linear model of \emph{perishable} public goods, leveraging new observations about sharing of media sources. The primary contribution of this work is to show that \emph{shelf time}, which characterizes the rate at which content get renewed, is a critical factor in audience participation. Our model proves a fundamental \emph{dichotomy} in information diffusion: While short-lived content has simple and predictable diffusion, long-lived content has complex specialization. This occurs even when all information seekers are \emph{ex ante} identical and could be a contributing factor to the difficulty of predicting social network participation and evolution.Comment: 15 pages in ACM Conference on Online Social Networks 201

Phase Transitions in the Two-Dimensional XY Model with Random Phases: a Monte Carlo Study

We study the two-dimensional XY model with quenched random phases by Monte Carlo simulation and finite-size scaling analysis. We determine the phase diagram of the model and study its critical behavior as a function of disorder and temperature. If the strength of the randomness is less than a critical value, $\sigma_{c}$, the system has a Kosterlitz-Thouless (KT) phase transition from the paramagnetic phase to a state with quasi-long-range order. Our data suggest that the latter exists down to T=0 in contradiction with theories that predict the appearance of a low-temperature reentrant phase. At the critical disorder $T_{KT}\rightarrow 0$ and for $\sigma > \sigma_{c}$ there is no quasi-ordered phase. At zero temperature there is a phase transition between two different glassy states at $\sigma_{c}$. The functional dependence of the correlation length on $\sigma$ suggests that this transition corresponds to the disorder-driven unbinding of vortex pairs.Comment: LaTex file and 18 figure