645 research outputs found
On Universality in Human Correspondence Activity
Identifying and modeling patterns of human activity has important
ramifications in applications ranging from predicting disease spread to
optimizing resource allocation. Because of its relevance and availability,
written correspondence provides a powerful proxy for studying human activity.
One school of thought is that human correspondence is driven by responses to
received correspondence, a view that requires distinct response mechanism to
explain e-mail and letter correspondence observations. Here, we demonstrate
that, like e-mail correspondence, the letter correspondence patterns of 16
writers, performers, politicians, and scientists are well-described by the
circadian cycle, task repetition and changing communication needs. We confirm
the universality of these mechanisms by properly rescaling letter and e-mail
correspondence statistics to reveal their underlying similarity.Comment: 17 pages, 3 figures, 1 tabl
Scaling laws of human interaction activity
Even though people in our contemporary, technological society are depending
on communication, our understanding of the underlying laws of human
communicational behavior continues to be poorly understood. Here we investigate
the communication patterns in two social Internet communities in search of
statistical laws in human interaction activity. This research reveals that
human communication networks dynamically follow scaling laws that may also
explain the observed trends in economic growth. Specifically, we identify a
generalized version of Gibrat's law of social activity expressed as a scaling
law between the fluctuations in the number of messages sent by members and
their level of activity. Gibrat's law has been essential in understanding
economic growth patterns, yet without an underlying general principle for its
origin. We attribute this scaling law to long-term correlation patterns in
human activity, which surprisingly span from days to the entire period of the
available data of more than one year. Further, we provide a mathematical
framework that relates the generalized version of Gibrat's law to the long-term
correlated dynamics, which suggests that the same underlying mechanism could be
the source of Gibrat's law in economics, ranging from large firms, research and
development expenditures, gross domestic product of countries, to city
population growth. These findings are also of importance for designing
communication networks and for the understanding of the dynamics of social
systems in which communication plays a role, such as economic markets and
political systems.Comment: 20+7 pages, 4+2 figure
Persistence and Uncertainty in the Academic Career
Understanding how institutional changes within academia may affect the
overall potential of science requires a better quantitative representation of
how careers evolve over time. Since knowledge spillovers, cumulative advantage,
competition, and collaboration are distinctive features of the academic
profession, both the employment relationship and the procedures for assigning
recognition and allocating funding should be designed to account for these
factors. We study the annual production n_{i}(t) of a given scientist i by
analyzing longitudinal career data for 200 leading scientists and 100 assistant
professors from the physics community. We compare our results with 21,156
sports careers. Our empirical analysis of individual productivity dynamics
shows that (i) there are increasing returns for the top individuals within the
competitive cohort, and that (ii) the distribution of production growth is a
leptokurtic "tent-shaped" distribution that is remarkably symmetric. Our
methodology is general, and we speculate that similar features appear in other
disciplines where academic publication is essential and collaboration is a key
feature. We introduce a model of proportional growth which reproduces these two
observations, and additionally accounts for the significantly right-skewed
distributions of career longevity and achievement in science. Using this
theoretical model, we show that short-term contracts can amplify the effects of
competition and uncertainty making careers more vulnerable to early
termination, not necessarily due to lack of individual talent and persistence,
but because of random negative production shocks. We show that fluctuations in
scientific production are quantitatively related to a scientist's collaboration
radius and team efficiency.Comment: 29 pages total: 8 main manuscript + 4 figs, 21 SI text + fig
Microdynamics in stationary complex networks
Many complex systems, including networks, are not static but can display
strong fluctuations at various time scales. Characterizing the dynamics in
complex networks is thus of the utmost importance in the understanding of these
networks and of the dynamical processes taking place on them. In this article,
we study the example of the US airport network in the time period 1990-2000. We
show that even if the statistical distributions of most indicators are
stationary, an intense activity takes place at the local (`microscopic') level,
with many disappearing/appearing connections (links) between airports. We find
that connections have a very broad distribution of lifetimes, and we introduce
a set of metrics to characterize the links' dynamics. We observe in particular
that the links which disappear have essentially the same properties as the ones
which appear, and that links which connect airports with very different traffic
are very volatile. Motivated by this empirical study, we propose a model of
dynamical networks, inspired from previous studies on firm growth, which
reproduces most of the empirical observations both for the stationary
statistical distributions and for the dynamical properties.Comment: 8 pages, 7 figure
Sense-it: A Smartphone Toolkit for Citizen Inquiry Learning
We describe a toolkit for Android smartphones and tablets that enables a user to access all the sensors available on the device. Data from individual sensors can be viewed as dynamic graphs. Output from one or more sensors can be recorded to a spreadsheet, with the sampling rate set by the learner. As a tool for inquiry learning, the sensors can be linked to ‘missions’ on the nQuire-it website, allowing learners to sample and share data for collaborative crowd-sourced investigations.
Four nQuire-it missions have employed the sensor toolkit for investigating environmental noise, sunlight levels, air pressure and rainfall, and the speed of lifts (elevators). These four investigations represent a variety of methods to initiate, orchestrate and conclude inquiry science learning. Two of the missions are in the context of a study to develop a community of inquiry around weather and meteorology. The others are intended to engage members of the public in practical science activities. Analysis of the missions and the associated online discussions reveals that the Sense-it toolkit can be adopted for practical and engaging science investigations, though the issue of calibrating sensors on personal devices needs to be addressed
Mediating boundaries between knowledge and knowing: ICT and R4D praxis
Research for development (R4D) praxis (theory-informed practical action) can be underpinned by the use of Information and Communication Technologies (ICTs) which, it is claimed, provide opportunities for knowledge working and sharing. Such a framing implicitly or explicitly constructs a boundary around knowledge as reified, or commodified – or at least able to be stabilized for a period of time (first order knowledge). In contrast ‘third-generation knowledge’ emphasizes the social nature of learning and knowledge-making; this reframes knowledge as a negotiated social practice, thus constructing a different system boundary. This paper offers critical reflections on the use of a wiki as a data repository and mediating technical platform as part of innovating in R4D praxis. A sustainable social learning process was sought that fostered an emergent community of practice among biophysical and social researchers acting for the first time as R4D co-researchers. Over time the technologically mediated element of the learning system was judged to have failed. This inquiry asks: How can learning system design cultivate learning opportunities and respond to learning challenges in an online environment to support R4D practice? Confining critical reflection to the online learning experience alone ignores the wider context in which knowledge work took place; therefore the institutional setting is also considered
Fostering 21st Century Skill Development by Engaging Students in Authentic Game Design Projects in a High School Computer Programming Class
This study used technology-rich ethnography (TRE) to examine the use of game development in a high school computer programming class for the development of 21st century skills. High school students created games for elementary school students while obtaining formative feedback from their younger clients. Our experience suggests that in the teaching of computer science in high schools, the development of games that include common game features such as dynamic feedback systems, backstory, levels, cheats, and compelling graphics challenges students and engages them in learning. Incorporating real client feedback is also useful for improving their work and connecting it to the “real” world. This article reports findings from the second year of a research project with a high school computer programming class. The authors argue that such approaches that leverage video games, design, programming, authenticity, and cooperation mobilize multiple 21st century skills that must be nurtured among contemporary young people so that they may grow to be part of a productive citizenry.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
A Poissonian explanation for heavy-tails in e-mail communication
Patterns of deliberate human activity and behavior are of utmost importance
in areas as diverse as disease spread, resource allocation, and emergency
response. Because of its widespread availability and use, e-mail correspondence
provides an attractive proxy for studying human activity. Recently, it was
reported that the probability density for the inter-event time between
consecutively sent e-mails decays asymptotically as , with
. The slower than exponential decay of the inter-event time
distribution suggests that deliberate human activity is inherently
non-Poissonian. Here, we demonstrate that the approximate power-law scaling of
the inter-event time distribution is a consequence of circadian and weekly
cycles of human activity. We propose a cascading non-homogeneous Poisson
process which explicitly integrates these periodic patterns in activity with an
individual's tendency to continue participating in an activity. Using standard
statistical techniques, we show that our model is consistent with the empirical
data. Our findings may also provide insight into the origins of heavy-tailed
distributions in other complex systems.Comment: 9 pages, 5 figure
Sandpile model on an optimized scale-free network on Euclidean space
Deterministic sandpile models are studied on a cost optimized
Barab\'asi-Albert (BA) scale-free network whose nodes are the sites of a square
lattice. For the optimized BA network, the sandpile model has the same critical
behaviour as the BTW sandpile, whereas for the un-optimized BA network the
critical behaviour is mean-field like.Comment: Five pages, four figure
Dispensability of Escherichia coli's latent pathways
Gene-knockout experiments on single-cell organisms have established that
expression of a substantial fraction of genes is not needed for optimal growth.
This problem acquired a new dimension with the recent discovery that
environmental and genetic perturbations of the bacterium Escherichia coli are
followed by the temporary activation of a large number of latent metabolic
pathways, which suggests the hypothesis that temporarily activated reactions
impact growth and hence facilitate adaptation in the presence of perturbations.
Here we test this hypothesis computationally and find, surprisingly, that the
availability of latent pathways consistently offers no growth advantage, and
tends in fact to inhibit growth after genetic perturbations. This is shown to
be true even for latent pathways with a known function in alternate conditions,
thus extending the significance of this adverse effect beyond apparently
nonessential genes. These findings raise the possibility that latent pathway
activation is in fact derivative of another, potentially suboptimal, adaptive
response
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