Anastassia defends her PhD: Urban Data Science for Sustainable Mobility

Big congratulations to Dr. Anastassia Vybornova – she defended her thesis yesterday, on Urban Data Science for Sustainable Mobility! 🥳 🎓 This makes Anastassia the first PhD student who did their whole PhD journey at NERDS – about which we are especially proud, besides her brilliant scientific accomplishments.

Supervisor: Michael Szell
Committee: Luca Rossi, Malene Freudendal-Pedersen, Robin Lovelace

Read her thesis here: https://en.itu.dk/Research/PhD-Programme/PhD-Defences/PhD-Defences-2025/March/Anastassia-Vybornova

The thesis spans 8 papers that advance Urban Data Science, exploring how this emerging field can ethically support human mobility that is both environmentally and socially sustainable, through the two lenses of Data and Networks.

In her research she develops algorithms and pipelines for multi-purpose spatial network simplification, for data quality assessment and planning of bicycle networks and low-traffic neighborhoods, showcasing applications to various cities. Further, she outlines pathways for incorporating data ethics into computational approaches to spatial manifestations of social inequalities. Lastly, she investigates the impact of transportation infrastructure on social connections in cities, quantitatively corroborating that urban highways are barriers to social ties. Stemming from various interdisciplinary collaborations, the results of this thesis cover multiple conceptual levels of Urban Data Science, from open source software development and data quality assessment to transportation network planning and the intersection of social and spatial networks. Through these efforts, this thesis advances the emerging field of Urban Data Science, showcasing the field’s potential to make human mobility more sustainable.

With her PhD completed, Anastassia starts a postdoc position at SODAS with Roberta Sinatra, retaining a visiting affiliation at NERDS. Anastassia has been both a professional and social cornerstone of NERDS, so we are lucky we will keep seeing her around. 💜

Update April 4th 2025: The defense and time in Copenhagen made a lasting impact on our external examiner: https://www.robinlovelace.net/post/copenhagenize/

Call for PhD and Postdocs: Using data science to improve epidemic preparedness

We are looking for PhDs and Postdocs to join Jonas Juul improving inference, forecasting, and mitigation in future pandemics. The application deadline is May 1st and you can apply here.

The project (funded by the Novo Nordisk Foundation) will improve epidemic preparedness in several ways, for example:

  • By studying a unique data set of hundreds of thousands of COVID-19 genomes. Studying these nation-scale data in combination with the Danish collection of registers, we hope to understand the details of COVID-19 propagation and mitigation impact in Denmark.
  • By quantifying the effectiveness and efficiency of mitigation strategies analytically and numerically, we will get a better understanding of how mitigation strategies should adapt as an epidemic unfolds,
  • By improving the statistical foundation for the projection of epidemic case numbers we hope to save lives and money when the next pandemic hits.

The positions come with attractive opportunities for conference participation, travel, etc., and Copenhagen offers a world-class research community in network science, epidemiology, and data science.

Interested in large-scale data analysis, applied statistics, and/or analytical methods for studying epidemics in networks? Read more and apply here: https://candidate.hr-manager.net/ApplicationInit.aspx?cid=119&ProjectId=181783&DepartmentId=3439&MediaId=1282  and feel free to reach out to Jonas Juul if you have any questions (deadline May 1st 2025)

The NERDS group is a down-to-earth and fun place to be. Copenhagen is often named as the best city in the world to live in, and for good reasons. It’s world-renowned for food, beer, art, music, architecture, the Scandinavian “hygge”, and much more. In Denmark, parental leave is generous, and child-care is excellent and cheap.

New NERDS paper on highway barriers to social ties

This week we are on fire and have yet another big paper out, long time in the making, led by Luca Maria Aiello with multi-NERDS involvement, just published in PNAS: Urban highways are barriers to social ties, by L.M. Aiello, A. Vybornova, S. Juhász, M. Szell, and E. Bokányi.

Highways are physical barriers that cut opportunities for social connections, but the magnitude of this effect has not been quantified. Such quantitative evidence would enable policy-makers to prioritize interventions that reconnect urban communities—an urgent need in many US cities. We relate urban highways in the 50 largest US cities with massive, geolocated online social network data to quantify the decrease in social connectivity associated with highways. We find that this barrier effect is strong in all 50 cities, and particularly prominent over shorter distances. We also confirm this effect for highways that are historically associated with racial segregation. Our research demonstrates with high granularity the long-lasting impact of decades-old infrastructure on society and provides tools for evidence-based remedies.

New NERDS paper on academic mentorship

We have a big paper out today, long time in the making, led by Yanmeng Xin, our long-term PhD student visitor in 2021-2023, co-authored by Roberta Sinatra, just published in Nature Human Behavior: Academic mentees thrive in big groups, but survive in small groups, by Y. Xing, Y Ma, Y. Fan, R. Sinatra, and A. Zeng.

The main message of the paper is intriguing: If you “grow up” in a big research group, and if you survive, you will have high success. At the same time, in a big group it is also harder to survive, especially if your mentor is very productive. So what is then good mentorship, and what is a good group to be?

Interestingly, at NERDS we are a fairly big research group, but with several mentors who are by themselves not too busy, so we combine the best of both worlds 😁 In fact, this paper itself is another one in a long series of success stories where a visitor accomplished something great while staying at our ✨🦄 ~enchanted NERDS grounds~ 🧚‍♂️✨ in Copenhagen. (“NERDS is one of the best places I have ever stayed.”)

Mentoring is a key component of scientific achievements, contributing to overall measures of career success for mentees and mentors. Within the scientific community, possessing a large research group is often perceived as an indicator of exceptional mentorship and high-quality research. However, such large, competitive groups may also escalate dropout rates, particularly among early-career researchers. Overly high dropout rates of young researchers may lead to severe postdoc shortage and loss of top-tier academics in contemporary academia. In this context, we collect longitudinal genealogical data on mentor-mentee relations and their publication, and analyze the influence of a mentor’s group size on the future academic longevity and performance of their mentees. Our findings indicate that mentees trained in larger groups tend to exhibit superior academic performance compared to those from smaller groups, provided they remain in academia post-graduation. However, we also observe two surprising patterns: Academic survival rate is significantly lower for (1) mentees from larger groups, and for (2) mentees with more productive mentors. The trend is verified in institutions of different prestige. These findings highlight a negative correlation between a mentor’s success and the academic survival rate of their mentees, prompting a rethinking of effective mentorship and offering actionable insights for career advancement.

NERDS at the Bridging Approaches in Science of Science Workshop in Munich

Last week, NERDS made their mark at the Bridging Approaches in Science of Science workshop in Munich! 🥨 The event, organized by the European Network for the Science of Science, brought together researchers from diverse backgrounds to discuss new methodologies and perspectives in the field.

Claudia Acciai presented her work on misinformation spreading and perception among scientists, sparking insightful discussions. Elisabetta Salvai and Jacob Aarup Dalsgaard also attended, engaging with the community and exchanging ideas. 🔬

The workshop was a fantastic opportunity to connect with researchers across disciplines, gather feedback on ongoing work, and explore potential collaborations. With such an inspiring exchange of ideas, we are excited to keep building bridges in the science of science community, and we are looking forward to gathering together soon at the ICSSI conference in Copenhagen!

Jonas wins Novo Nordisk Data Science Investigator Grant!

As reported today on ITU’s frontpage, our newest NERDS faculty member, Jonas Juul, has just won a Novo Nordisk Foundation Data Science Investigator grant of DKK 6.5 million (~EUR 870,000) for a project to improve statistical methods for predicting outbreaks of infections. Congratulations Jonas, we are so happy for you and your great start at NERDS/ITU! 🥳

The project InForM: Inference, Forecasting, and Mitigation of future pandemics runs for five years. It is a collaboration between the IT University of Copenhagen, Statistics Denmark and The State Serum Institute, where Jonas has already collaborated successfully.

It consists of three different parts. The first part is about improving statistical methods that are used for predicting how diseases spread, the second part is looking into which methods for prevention and control of disease are more efficient in what situations, and the third part is about figuring out how COVID-19 spread during the pandemic. Read more in the ITU news.

Winning such a prestigious grant as an assistant Professor is in itself an achievement, but we as NERDS are even more so happy for finally convincing also Novo Nordisk Foundation as the last “missing” major Danish grant agency to fund us. We applaud Novo for their decision – Jonas’ excellent health-related know-how is turning into a boost for epidemiological research in Denmark.

Jonas’ InForM project will soon open calls for PhDs/Postdocs.. stay tuned!

The Atlas for the Aspiring Network Scientist v2

NERDS member Michele Coscia has updated his textbook for the Network Analysis and Advanced Network Science classes he teaches at ITU. This “Atlas for the Aspiring Network Scientist”, has now reached version 2.0, and 916 pages, and is available for anyone to read for free: https://arxiv.org/abs/2101.00863

Website: https://www.networkatlas.eu/

The new edition has a much improved coverage on graph neural networks, network data uncertainty, and background knowledge in statistics, machine learning, probability theory, and linear algebra.

Even version 2.0 has big margins for improvements. Please contact Michele with any comments.

Find a more detailed explanation of The Atlas for the Aspiring Network Scientist on Michele’s page: https://www.michelecoscia.com/?p=2393.

Two new NERDS papers published: Gamestop, Copenhagen bike lanes

We have two new publications out, one on the Gamestop short squeeze by Reddit users, and one on bicycle network design with use case Copenhagen:

  1. The dynamics of the Reddit collective action leading to the GameStop short squeeze, by A. Desiderio, L.M. Aiello, G. Cimini & L. Alessandretti , published in npj complexity

    In early 2021, the stock prices of GameStop, AMC, Nokia, and BlackBerry experienced dramatic increases, triggered by short-squeeze operations that have been largely attributed to Reddit’s retail investors. Here we shed light on the extent and timing of Reddit users’ influence on the GameStop short squeeze. Using statistical analysis tools with high temporal resolution, we find that increasing Reddit discussions anticipated high trading volumes. This effect emerged abruptly a few weeks before the event but waned once the community gained widespread visibility through Twitter. Meanwhile, the collective investment of the community, quantified through posts of individual positions, closely mirrored the market capitalization of the stock. This evidence suggests a coordinated action of users in developing a shared financial strategy through social media—targeting GameStop first and other stocks afterward. Overall, our results provide novel insights into the role of Reddit users in the dynamics of the GameStop short squeeze.
  2. Cohesive urban bicycle infrastructure design through optimal transport routing in multilayer networks, by A. Lonardi, M. Szell and C. De Bacco, published in Journal of the Royal Society Interface

    Bicycle infrastructure networks must meet the needs of cyclists to position cycling as a viable transportation choice in cities. In particular, protected infrastructure should be planned cohesively for the whole city and spacious enough to accommodate all cyclists safely and prevent cyclist congestion—a common problem in cycling cities like Copenhagen. Here, we devise an adaptive method for optimal bicycle network design and for evaluating congestion criticalities on bicycle paths. The method goes beyond static network measures, using computationally efficient adaptation rules inspired by optimal transport on the dynamically updating multilayer network of roads and protected bicycle lanes. Street capacities and cyclist flows reciprocally control each other to optimally accommodate cyclists on streets with one control parameter that dictates the preference of bicycle infrastructure over roads. Applying our method to Copenhagen confirms that the city’s bicycle network is generally well-developed. However, we are able to identify the network’s bottlenecks, and we find, at a finer scale, disparities in network accessibility and criticalities between different neighbourhoods. Our model and results are generalizable beyond this particular case study to serve as a scalable and versatile tool for aiding urban planners in designing cycling-friendly cities.

PhD Open Call 2025

The ITU-wide PhD Open Call 2025, deadline Feb 24th, is now open!  If your research overlaps with ours and you are interested, get in touch!

Either reach out directly to one of us, or use the student contact form on our students page, where you can also get inspiration for potential research projects. Most professors at NERDS are currently open to PhD supervision and have good ideas for possible PhD projects, so don’t hesitate to reach out. One of our past PhD students, Anastassia, has joined us previously through this call.

In Denmark, PhD students are employees, where both salary and working conditions are excellent. The NERDS group is a down-to-earth and fun place to be. Copenhagen is often named as the best city in the world to live in, and for good reasons. It’s world-renowned for food, beer, art, music, architecture, the Scandinavian “hygge”, and much more. In Denmark, parental leave is generous, and child-care is excellent and cheap.