27th Colloquium of Systems Science
Winter Semester 2020/21
The colloquium takes place only in the winter semester on Wednesdays from 16:15 to 18:00. The 27th colloquium will become a virtual event due to the Covid-19 pandemic.
The link for attendees is available through the announcement in Stud.IP. Speakers will receive it by e-mail.
28 Oct 2020
Prof. Dr. Christiane Zarfl, Environmental Systems Analysis, Center for Applied Geoscience, Eberhard Karls University of Tübingen:
Assessing pollutant turnover in rivers by integrating field sampling, chemical and toxicity analysis, and mathematical modelling.
04 Nov 2020
Dr. Peter Viebahn, Wuppertal Institute, Research Unit Sectors and Technologies (Lecture in the context of the habilitation procedure with separate announcement and invitation):
Methoden der Technikbewertung - Status und Forschungsbedarf am Beispiel von Modellbildung und Simulation, eindimensionalen Bewertungsverfahren und multikriterieller Bewertung.
11 Nov 2020
Prof. Dr. Andreas Beyer, Institute of Genetics, CECAD Research Center, University of Cologne:
Systems biology approaches towards high-throughput single cell data.
18 Nov 2020
Dr. Volker Berding, The German Federal Environmental Foundation, Osnabrück:
Funding circular economy.
25 Nov 2020
Dr. Ivo Siekmann, Department of Applied Mathematics, Liverpool John Moores University, United Kingdom:
Listening to the whispers within our cells - Mathematical modelling of calcium dynamics.
02 Dec 2020
Prof. Dr. Jamie Linton, GEOLAB – Géographie Physique et Environnementale, Université de Limoges, France:
Nature, people, and the Water Framework Directive.
09 Dec 2020
Prof. Dr. Lena Partzsch, Chair of Development Politics, University of Passau:
Alternatives to multilateralism: New forms of social and environmental governance.
16 Dec 2020
Dr. Andrew Morozov, Department of Mathematics, University of Leicester, United Kingdom:
Long transients in ecology and social sciences: Models and data.
13 Jan 2021
Prof. Dr. Natalia Mantilla Beniers, Facultad de Ciencias, Universidad Nacional Autónoma de México:
Ecology and epidemiology of some human infections.
20 Jan 2021
Prof. Dr. Sergei V. Petrovskii, Department of Mathematics, University of Leicester, United Kingdom:
Population dynamics under climate change: catastrophes, extinctions, and long transients.
27 Jan 2021
Prof. Dr. Sheona Shackleton, Deputy Director, African Climate and Development Initiative, University of Cape Town, South Africa:
Challenges for climate change adaptation in Sub-Saharan Africa.
03 Feb 2021
Prof. Dr. Andreas Lange, Universität Hamburg, Faculty of Business, Economics and Social Sciences; Volkswirtschaftslehre:
On the role of intrinsic motivation in market settings.
Abstracts of Presentations
28 Oct 2020
Prof. Dr. Christiane Zarfl, Environmental Systems Analysis, Center for Applied Geoscience, Eberhard Karls University of Tübingen
Assessing pollutant turnover in rivers by integrating field sampling, chemical and toxicity analysis, and mathematical modelling
Water quality in rivers is affected by pollutant emissions from agricultural and urban areas under different weather and, thus, discharge conditions. Rivers collect water, sediment, and solute fluxes of their entire catchment and thus integrate the input of compounds into the catchment and their transformations therein. They also reflect temporal and spatial dynamics within the catchment as the resulting mixtures of compounds in river water and sediments vary in space and time. Transformation processes in the field are not well understood with results from lab experiments being hardly transferable to environmental conditions. The aim of the study, in the frame of the CRC “CAMPOS – Catchments as Reactors”, was to identify dominant input sources of organic pollutants into the Ammer River and its tributaries, in the vicinity of Tübingen, Germany, and dominant attenuation processes and their driving factors along the main river by analysing chemical and toxicological profiles. We integrated field sampling of the main river Ammer, its tributaries and headwaters with chemical target and non-target analysis as well as with toxicity analysis with cell-based bioassays and evaluated the available data with process-based model approaches. First screenings provided a chemical pollutant inventory of over one hundred target chemicals in the low ng L-1 concentration range, among them pesticides (herbicides, fungicides and insecticides) and their metabolites, pharmaceuticals, industrial and household chemicals. Chemicals associated with agricultural activities such as pest control were found both in the main stem and in the tributaries. Under base flow conditions, the chemical and toxicological pollutant profile in the Ammer main stem was dominated by inputs via wastewater treatment plants (WWTPs). Lagrangian sampling along a selected river stretch downstream of the WWTP allowed quantification of attenuation processes of target compounds selected as representatives for different transformation pathways like photo- and biodegradation. Sampling campaigns following moderate to strong rain events indicated different pollutant mass flux dynamics related to the pollutant source (urban vs. agriculture) and particle-associated pollutant mobilization. Next steps will focus on urban in comparison to agricultural areas as pollutant source and further analyse the pollutant emissions and dynamics following rain events of different strength.
04 Nov 2020
Dr. Peter Viebahn, Wuppertal Institute, Research Unit Sectors and Technologies
Methoden der Technikbewertung - Status und Forschungsbedarf am Beispiel von Modellbildung und Simulation, eindimensionalen Bewertungsverfahren und multikriterieller Bewertung
In der Energiesystemanalyse existiert eine Vielzahl von Methoden, die alleinstehend oder auch miteinander kombiniert eingesetzt werden. Die jeweilige Auswahl hängt von der Fragestellung und dem Untersuchungsgegenstand ab – sei es die Entwicklung eines Energiesystems als ganzes und der in sie eingebetteten Technologien (z. B. über Langfrist-Energieszenarien) oder die vergleichende Bewertung mehrerer Technologien (z. B. mittels einer multikriteriellen Bewertung). Durch das immer komplexer werdende Energiesystem mit Hunderten von Stellschrauben, die zunehmende Anzahl von Akteuren sowie die Fragestellungen im Hinblick auf der Ausrichtung des Energiesystems am globalen Klimaziel und generell einer nachhaltigen Entwicklung steigen auch die Anforderungen an die Bewertungsmethoden. In dem Vortrag werden eine Reihe von Methoden sowie Forschungsbedarf zu deren Weiterentwicklung und Anpassung vorgestellt.
11 Nov 2020
Prof. Dr. Andreas Beyer, Institute of Genetics, CECAD Research Center, University of Cologne
Systems biology approaches towards high-throughput single cell data
Gene regulatory networks are a centerpiece of modern systems biology. However, it remains unclear to what extent gene regulatory relationships are invariant across tissues and cell types. Here, we show that a substantial fraction of transcriptional regulatory relationships is tissue- and cell-type invariant. We trained a network using bulk expression data from 1,376 cancer cell lines and validated its performance on 17,382 samples from 30 different healthy tissues. Subsequently, we used that network to inform the imputation of missing values ('dropouts') in single-cell RNA-sequencing data. Using this network-based approach significantly outperformed existing methods for dropout imputation. Additionally, we tested a baseline approach, where we imputed missing values using the sample-wide average expression of a gene. Unexpectedly, up to 48% of the genes were better predicted using this baseline approach, suggesting negligible cell-to-cell variation of expression levels for many genes. Our work shows that there is no single best imputation method; rather, the best method depends on gene-specific features, such as expression level and expression variation across cells. We thus implemented an R-package called ADImpute that automatically determines the best imputation method for each gene in a dataset.
This work reveals an unexpected robustness of transcriptional regulatory relationships, it demonstrates the benefits of integrating systems biology approaches with single-cell data, and it presents a new paradigm for gene-adaptive dropout imputation.
18 Nov 2020
Dr. Volker Berding, The German Federal Environmental Foundation, Osnabrück
Funding circular economy
The German Federal Environmental Foundation (Deutsche Bundesstiftung Umwelt - DBU) funds innovative, exemplary and solution-oriented projects for the protection of the environment, with special consideration of small and medium-sized enterprises. The funding activities focus on environmental technology and research, nature conservation, environmental communication and protection of cultural assets. Funded projects should achieve sustainable effects in practice, give impulses and lead to a “multiplier effect”. It is the objective of the DBU to contribute to the solution of current environmental problems, in particular, which result from unsustainable business practices and lifestyles.
Dealing with the earth's natural resources is a key issue for humanity. Regardless of whether it is energy, land or raw materials, the use of natural resources already exceeds the earth's ability to regenerate. We are observing a growing global extraction of raw materials. At the same time, the diversity of elements and substances in products (e.g. in composite materials) is rapidly increasing, making it more difficult to retrieve them. In addition, the demand for raw materials for important future fields such as energy system transformation, digitization and e-mobility is considerably higher than the current demand for some elements. For this reason, the careful and efficient use of resources is a key competence of future generations. There is currently much discussion about a paradigm shift in the logic of value creation that represents an alternative to the conventional linear "take - make - waste"; the concept of a circular economy promises a solution.
I will outline the main approaches to a circular economy and give practical examples from our funding activities.
25 Nov 2020
Dr. Ivo Siekmann, Department of Applied Mathematics, Liverpool John Moores University
Listening to the whispers within our cells - Mathematical modelling of calcium dynamics
The dynamics of calcium concentrations in living cells has strong similarities with the electrical activity in the brain. Whereas local calcium spikes that vanish as quickly as they appear resemble the firing of neurons, the regular oscillations of calcium concentration across the whole cell remind us of the patterns seen in electroencephalograms (EEGs).
Similar to how neurons communicate with each other and broadcast signals across our body using electrical currents, signals within cells are transmitted via calcium signals. Calcium signals are generated by ion channels which, by opening and closing stochastically, release calcium from internal stores into the cell. Although each individual ion channel is stochastic, cells nevertheless behave deterministically – one of the most striking examples is the heartbeat which is reliably generated approximately every second for a whole lifetime. However, as difficult as it has been to relate the stochastic firing of individual neurons to the global electrical activity of the brain, it remains challenging to understand how calcium signals across the whole cell depend on the properties of individual ion channels.
In my talk I will explain how calcium dynamics can be modelled mathematically and how models can be parameterised with experimental data. I will also tell you of some of the discoveries that my collaborators and I made along the way.
02 Dec 2020
Prof. Dr. Jamie Linton, GEOLAB – Géographie Physique et Environnementale, Université de Limoges
Nature, people, and the Water Framework Directive
In my talk, I will argue that in many cases the failure to reach the implementation goals of the Water Framework Directive (WFD) is not due to a lack of political will or to implementation deficits; rather, it is due to a fundamental conceptual problem. In a recent paper co-written with Tobias Krueger, we describe this problem in terms of an "ontological fallacy" that is built into the directive. This ontological fallacy is founded on a radical conceptual separation of nature from human society, one which Bruno Latour identified over 25 years ago as the "modern Constitution". In my talk, I will describe some of the research in political ecology that has contributed to this argument, drawing from examples in France and in the UK.
09 Dec 2020
Prof. Dr. Lena Partzsch, Chair of Development Politics, University of Passau
Alternatives to multilateralism: New forms of social and environmental governance
Globalization has lost its shine. While the worldwide integration of markets has drained political control from individual nation-states, multilateralism has proven unsuccessful in coordinating states' responses to global challenges. In this lecture, Lena Partzsch describes alternatives to multilateralism, offering analyses and case studies of emerging—alternative—forms of private, public, and hybrid social and environmental regulation. She presents her case study research on cotton/textile supply chains and voluntary (private) certification in Ethiopia; public supply-chain regulation of “conflict resources” from the Democratic Republic of the Congo; and hybrid governance of palm oil production in Indonesia. Partzsch finds that there is a new entanglement of public and private regulation. This entanglement fails to address social and environmental considerations in mainstream markets. Only in exceptional cases do alternative forms of regulation overcome the power asymmetries between actors in the consuming countries of the Global North and those in the producing countries of the Global South. While the paradigm of free trade fades, we must continue to develop viable alternatives in order to pursue collective norms of environmental sustainability and social justice.
Partzsch, L. (2020) Alternatives to Multilateralism: New Forms of Social and Environmental Governance, MIT Press, Cambridge, MA, mitpress.mit.edu/books/alternatives-multilateralism
16 Dec 2020
Dr. Andrew Morozov, Department of Mathematics, University of Leicester
Long transients in ecology and social sciences: Models and data
Traditionally, the main focus in modelling in ecology as well as in social sciences was on asymptotic states of considered systems: such states are mathematically defined as attractors. However, many models and empirical observations demonstrate transient behaviour that may persist over very long time periods, followed by rapid changes in dynamics. Obviously, in this situation focusing solely on the long-term behaviour of systems would be misleading. Correspondingly, a big new challenge for computational and empirical biological as well social sciences is to understand the implications of transient dynamics, especially of long transients. For example, transients can provide an alternative explanation for observed regime shifts and population collapse that does not depend on underlying environmental changes. Although the importance of transients is now being gradually recognised, the current area of research seems to be in its infancy both in terms of lack of systematic studies and developing appropriate research techniques. Here, by using both empirical examples and model systems (both deterministic and stochastic), I will comprehensively review the current knowledge of transient dynamics, showing that hitherto idiosyncratic and individual patterns can be classified into a coherent framework, with important general lessons and directions for future study. I will argue that we need to include the possibility of long transient scenarios in ecosystems management and experimental design. Finally, as an insightful example, I will show how transient-based framework can be applied to modelling social unrests.
13 Jan 2021
Prof. Dr. Natalia Mantilla Beniers, Facultad de Ciencias, Universidad Nacional Autónoma de México
Ecology and epidemiology of some human infections
The human and economic importance of infectious diseases through history has led to their frequent and often accurate recording in many populations around the World. After the formulation of the germ theory, mathematical models were posed to reflect transmission and gave insights into the conditions that enable invasion and persistence of disease in a population. Disease records have challenged model predictions, leading to change hypotheses and inspiring new theories. Population ecology constitutes a lesser known influence that has both informed and benefited from epidemiological studies. In this talk I shall discuss the spatiotemporal patterns of sympatric acute infections of childhood, as well as chronic diseases as enabled by mathematical and ecological tools.
20 Jan 2021
Prof. Dr. Sergei V. Petrovskii, Department of Mathematics, University of Leicester
Population dynamics under climate change: catastrophes, extinctions, and long transients
The effect of climate change on population dynamics is widely recognised, usually with many adverse effects, often resulting in species extinctions and biodiversity loss. Population dynamics can also have feedback on the climate; however, this issue remains poorly understood. In my talk, I will focus on the effect that the global warming can have on plankton, in particular, on phytoplankton ability to produce oxygen. It is estimated that more than one half of the total atmospheric oxygen is produced in the oceans due to the photosynthetic activity of phytoplankton. Any significant decrease in the net oxygen production by phytoplankton is therefore likely to result in the depletion of atmospheric oxygen and in a mass mortality of animals and humans. However, the rate of oxygen production depends on water temperature and hence can be affected by the global warming. I address this issue theoretically by considering a novel model of a coupled plankton-oxygen dynamics where the rate of oxygen production changes with time to account for the ocean warming . I first prove that the model, albeit being simple or “conceptual”, provides an upper bound for a class of complex realistic models of ocean (bio)dynamics [2,3]. I then show that, when the temperature rises sufficiently high, a regime shift happens: the sustainable oxygen production becomes impossible and the system’s dynamics leads to plankton extinction and oxygen depletion. I also consider a scenario when, after a certain period of increase, the temperature is set on a new higher yet apparently safe value, i.e. before the oxygen depletion disaster happens. I show that in this case the system dynamics may exhibit a long-term quasi-sustainable dynamics that can still result in the regime shift but only after a considerable delay: the phenomenon known as long transient dynamics . Finally, I will argue that this catastrophe of the global oxygen depletion might have been the factor that resulted in a few mass extinctions in the Earth geological past.
- Sekerci Y, Petrovskii SV. (2015) Mathematical modelling of plankton-oxygen dynamics under the climate change. Bull. Math. Biol. 77, 2325-2353.
- Petrovskii SV, Sekerci Y, Venturino E. (2017) Regime shifts and ecological catastrophes in a model of plankton-oxygen dynamics under the climate change. J. Theor. Biol. 424, 91-109.
- Sekerci Y, Petrovskii SV. (2018) Global warming can lead to depletion of oxygen by disrupting phytoplankton photosynthesis: a mathematical modelling approach. Geosciences 8, 201.
- Hastings A, Abbott KC, Cuddington K, Francis T, Gellner G, Lai YC, Morozov A, Petrovskii SV, Scranton K, Zeeman ML. (2018) Transient phenomena in ecology. Science 361, eaat6412.
27 Jan 2021
Prof. Dr. Sheona Shackleton, Deputy Director, African Climate and Development Initiative, University of Cape Town
Challenges for climate change adaptation in Sub-Saharan Africa
Sub-Saharan Africa (SSA) represents one of the most vulnerable regions globally to climate change. Persistent poverty and socioeconomic inequality, low levels of development, high dependence on climate-sensitive livelihood sectors, limited economic capacity, and countless governance and institutional challenges have led to low adaptive capacity and a significant adaptation deficit. New risks from climate change, that are intensifying each year, include warming and drying, more intense and prolonged droughts, and more floods. These changes have major impacts on agriculture, fisheries, ecosystems and food security across the region, and feed back into livelihood security and the development system, undermining progress in dealing with poverty and low levels of human development. The COVID 19 pandemic, as an intersecting crisis, has further thwarted progress as African countries try to recover from the economic and other impacts of this disease. Given this context, there is an urgent need for adaptation on the African continent. But realizing adaptation action is not without it challenges, nor is it transpiring fast enough to keep up with the dramatic changes we are observing. Thus, it is important to ask: What is blocking progress? What are the challenges to adaptation action? To advance climate change adaptation, and to facilitate the planning and implementation of socially-just adaptation strategies that target the most vulnerable, deeper consideration of the factors that impede adaptation is required. In response, scholars have increasingly identified barriers to adaptation in the literature, but literature and evidence from developing countries remains limited, especially in relation to underlying causes of vulnerability and low adaptive capacity. In this talk, I will explore some of the challenges to both autonomous and facilitated adaptation (that is fair and equitable) and suggest ways forward drawing on several studies and reviews I have been involved in recent years, as well as some of the latest literature and state-of-the-art reports.
03 Feb 2021
Prof. Dr. Andreas Lange, Universität Hamburg, Faculty of Business, Economics and Social Sciences; Volkswirtschaftslehre
On the role of intrinsic motivation in market settings
The voluntary provision of public goods is present in many market settings. Many give to charity. Consumers care for green- or social dimensions of the products they consume. Investors may focus on ESG investments, firms may provide products with green or socially responsible products that go beyond regulatory requirements. This presentation combines theoretical and empirical studies to address reasons for such activities in market settings. Intrinsic motivations for quality choice have largely been overlooked in economic models, yet they are highly relevant in the real world. Going beyond the typical reasons of price discrimination and product differentiation, we study a rich model to understand how intrinsic motivation among entrepreneurs affects the structure and evolution of markets. Non-profit motives for quality interact with consumer preferences. We generate novel insights on the role of intrinsically motivated entrepreneurs in discovering latent consumer preferences for quality-preferences that might otherwise go unnoticed in the absence of these agents. We further investigate how these markets respond to policies, such as quality standards, subsidies, and taxes. These policies directly impact quality choice by changing marginal incentives for quality, but we reveal that they can have additional impacts on market structure by altering incentives for innovation and product differentiation. These insights are complemented by experimental findings on motivations for linking selling private goods with public good provision. Studying a prosocial ultimatum game where a proposer can suggest a split between himself, the responder and a charitable donation, we vary the enforceability of the donation pledge as well as the availability of alternative donation channels. Doing so, we demonstrate that prosocial characteristics of sold products tend to be used as strategic device, thereby exposing the provision of public goods to exploitation, i.e. cheating, by free-riders.