Using Text Similarity to Detect Social Interactions not Captured by Formal Reply Mechanisms

In modeling social interaction online, it is important to understand when people are reacting to each other. Many systems have explicit indicators of replies, such as threading in discussion forums or replies and retweets in Twitter. However, it is likely these explicit indicators capture only part of people's reactions to each other, thus, computational social science approaches that use them to infer relationships or influence are likely to miss the mark. This paper explores the problem of detecting non-explicit responses, presenting a new approach that uses tf-idf similarity between a user's own tweets and recent tweets by people they follow. Based on a month's worth of posting data from 449 ego networks in Twitter, this method demonstrates that it is likely that at least 11% of reactions are not captured by the explicit reply and retweet mechanisms. Further, these uncaptured reactions are not evenly distributed between users: some users, who create replies and retweets without using the official interface mechanisms, are much more responsive to followees than they appear. This suggests that detecting non-explicit responses is an important consideration in mitigating biases and building more accurate models when using these markers to study social interaction and information diffusion.Comment: A final version of this work was published in the 2015 IEEE 11th International Conference on e-Science (e-Science

Characterizing weak chaos in nonintegrable Hamiltonian systems: the fundamental role of stickiness and initial conditions

Weak chaos in high-dimensional conservative systems can be characterized through sticky effect induced by invariant structures on chaotic trajectories. Suitable quantities for this characterization are the higher cummulants of the finite time Lyapunov exponents (FTLEs) distribution. They gather the {\it whole} phase space relevant dynamics in {\it one} quantity and give informations about ordered and random states. This is analyzed here for discrete Hamiltonian systems with local and global couplings. It is also shown that FTLEs plotted {\it versus} initial condition (IC) and the nonlinear parameter is essential to understand the fundamental role of ICs in the dynamics of weakly chaotic Hamiltonian systems.Comment: 7 pages, 6 figures, submitted for publicatio

Supplier reputation and price premium: the case of groundnuts in Rotterdam

Firm’s reputation depends on the quality of its goods and its reliability as a supplier. This may explain observed price differences between commodities from different origins but with the same observable characteristics. We analyse data for the Rotterdam market and use hedonic price analysis to show the existence of a price premium that favours the US over other origins. As secondary information points out exporter reliability as one explanation we formalise the relationship between reliability and price premiums in a theoretical model and analyse its implications.firm reputation, supplier reliability, price differences, groundnuts trade, hedonic analysis, country of origin, Demand and Price Analysis, Crop Production/Industries,

Farmland Control Decisions under Different Intertemporal Risk Behavioral Constructs

Simulation-optimization techniques are employed to analyze changes in farmland control arrangements as a result of using different constructs of intertemporal risk behavior. Risk behavior based on constant absolute risk aversion (CARA) and constant relative risk aversion (CRRA) mean-standard deviation functions are used to achieve this objective. Specfically, a multi-period programming framework for a representative grain farm is developed to explore farmland control decisions under these two behavioral assumptions. Our results suggest that the use of a CRRA behavioral construct in analyzing farmland control decisions produce predictions that are more consistent with observed farm behavior.Farm Management,

DOES THE EXISTENCE OF MARKET POWER AFFECT MARKETING LOAN PROGRAMS?

The paper analyzes the effects that a demand with oligopsonistic power may have on the operation of a marketing loan program (especially on the program cost). We measure these effects using a model for the US peanut market where evidence indicates that the demand is highly concentrated. Our results show that the USDA strategy of keeping a repayment rate above the market-clearing price set by the demand is not a sustainable strategy, since the demand can follow a hand-to-mouth strategy, postponing its purchases of peanuts, letting USDA accumulate stocks and forcing it to reduce the price.Agricultural Finance,

Motivation as a predictor of dental students’ affective and behavioral outcomes: Does the quality of motivation matter?

Since the motivation to study and engage in academic activities plays a key role in students’ learning experience and well-being, gaining a better understanding of dental students’ motivations can help educators implement interventions to support students’ optimal motivations. The aim of this study, grounded in self-determination theory, was to determine the predictive role of different types of motivation (autonomous motivation, controlled motivation, and amotivation) in the affective and behavioral outcomes of dental students. Amotivation is the absence of drive to pursue an activity due to a failure to establish relationships between activity and behavior; controlled motivation involves behaving under external pressure or demands; and autonomous motivation is an internalized behavior with a full sense of volition, interest, choice, and self-determination. A cross-sectional correlational study was conducted in 2016, in which 924 students (90.2% response rate) from years one to six agreed to participate, granting permission to access their current GPAs and completing four self-reported questionnaires on academic motivation, study strategies, vitality, and self-esteem. The results showed that self-determined motivation (i.e., autonomous over controlled motivation) was positively associated with vitality, self-esteem, and deep study strategies and negatively associated with surface study strategies. The contrary results were found for amotivation. In the motivational model, deep study strategies showed a positive association with students’ academic performance. Contrary results were found for surface study strategies. This study extends understanding of the differentiation of motivation based on its quality types and suggests that being motivated does not necessarily lead to positive educational outcomes. Autonomous motivation, in contrast to controlled motivation and amotivation, should be supported to benefit students with regard to their approaches to learning and well-being since it can promote students’ vitality, self-esteem, deep over surface study strategies, and enhanced academic performance

Vacuum stability with spontaneous violation of lepton number

The vacuum of the Standard Model is known to be unstable for the measured values of the top and Higgs masses. Here we show how vacuum stability can be achieved naturally if lepton number is violated spontaneously at the TeV scale. More precise Higgs measurements in the next LHC run should provide a crucial test of our symmetry breaking scenario. In addition, these schemes typically lead to enhanced rates for processes involving lepton flavour violation .Comment: 9 pages, 4+2 figures; some references added, some textual modifications: 2 figures added, appendices added. Results unchanged. Matches published versio