The number and size of nations revisited: Endogenous border formation with non-uniform population distributions

The endogenous border formation model of Alesina and Spolaore (1997) has received a lot of attention in the economics community. One of its central messages is that in a democratic world in equilibrium there is an ineciently large number of nation states. However, this result is obtained under very specic assumptions like a uniform population distribution and no population mobility. In this paper, I generalize the model of Alesina and Spolaore allowing for population distributions other than the uniform distribution. Since this generalization is accompanied by the loss of tractability in closed form, I calculate the equilibria by means of numerical computation. It turns out that the above-mentioned central result is highly sensitive to the choice of population distribution and that the model shows four different regimes depending on the chosen distribution. Furthermore, the behaviour implied by the Alesina and Spolaore model with uniform population distribution is the exception, not the rule.Size of Nations; Endogenous Border Formation; Computational Economics

Replication of the Demographic Prisoner’s Dilemma

This paper documents our efforts in replicating Epstein’s (1998) demographic prisoner’s dilemma model. While, qualitatively speaking, our replicated model resembles the results of the original model reasonably well, statistical testing reveals that in quantitative terms our endeavor was only partially successful. This fact hints towards some unstated assumptions regarding the original model. Confronted with a number of ambiguous descriptions of model features we introduce a method for systematically generating a large number of model replications and testing for their equivalence to the original model. With the help of this approach we show that the original model was probably based on a number of dubious assumptions. Finally we conduct a number of statistical tests with respect to the influence of certain design choices like the method of updating, the timing of events and the randomization of the activation order. The results of these tests highlight the importance of an explicit documentation of design choices and especially of the timing of events.Demographic, Prisoner’s Dilemma, Replication, Simulation, Complex Adaptive Systems, Social Science Models

Prospects and Pitfalls of Statistical Testing: Insights from Replicating the Demographic Prisoner's Dilemma

This paper documents our efforts (and troubles) in replicating Epstein's (1998) demographic prisoner's dilemma model. Confronted with a number of ambiguous descriptions of model features we introduce a method for systematically generating a large number of model replications and testing for their equivalence to the original model. While, qualitatively speaking, a number of our replicated models resemble the results of the original model reasonably well, statistical testing reveals that in quantitative terms our endeavor was only partially successful. This fact hints towards some unstated assumptions regarding the original model. Finally we conduct a number of statistical tests with respect to the influence of certain design choices like the method of updating, the timing of events and the randomization of the activation order. The results of these tests highlight the importance of an explicit documentation of design choices and especially of the timing of events. A central lesson learned from this exercise is that the power of statistical replication analysis is to a large degree determined by the available data.Agent-Based Model, Verification, Comparative Computational Methodology, Prisoners Dilemma, Replication, Demographic Prisoners Dilemma

An Agent-Based Model of Institutional Life-Cycles

We use an agent-based model to investigate the interdependent dynamics between individual agency and emergent socioeconomic structure, leading to institutional change in a generic way. Our model simulates the emergence and exit of institutional units, understood as generic governed social structures. We show how endogenized trust and exogenously given leader authority influences institutional change, i.e., diversity in institutional life-cycles. It turns out that these governed institutions (de)structure in cyclical patterns dependent on the overall evolution of trust in the artificial society, while at the same time, influencing this evolution by supporting social learning. Simulation results indicate three scenarios of institutional life-cycles. Institutions may, (1) build up very fast and freeze the artificial society in a stable but fearful pattern (ordered system); (2) exist only for a short time, leading to a very trusty society (highly fluctuating system); and (3) structure in cyclical patterns over time and support social learning due to cumulative causation of societal trust (complex system)

Ammonia-Oxidizing Archaea in Marine Cold-Water Sponges

Thaumarchaea (Archaea) kommen in vielen terrestrischen und marinen Lebensräumen vor und sind oftmals mit marinen Schwämmen assoziiert. Basierend auf Metagenom- und Kultivierungsstudien hat sich gezeigt, dass viele (wenn nicht sogar alle) Thaumarchaea die Fähigkeit besitzen, mittels dem Enzym Ammoniummonooxygenase (AMO), Ammonium zu oxidieren. In dieser Studie untersuchen wir die Aktivität und Diversität der Thaumarchaea in Kaltwasserschwämmen aus Norwegen. Durch die Kombination von quantitativ-physiologischen und molekularen Analysen und die Messungen von Produktion und Verbrauch bestimmter Stickstoffverbindungen in Inkubationsexperimenten wurde Nitrifikation in Geodia barretti, Phakellia ventilabrum, Antho dichotoma und Tentorium semisuberites nachgewiesen und quantifiziert. Zugleich konnte mittels quantitativer PCR und fluoreszenter in situ Hybridisierung eine hohe Anzahl an AMO-kodierenden Archaea (bis zu 6*108 archaeale amoA Genkopien pro µg Nukleinsäure) detektiert werden. Im Schwamm G. barretti wurden zum ersten Mal Raten von Denitrifikation und anaerober Ammoniumoxidation nachgewiesen und somit wurde gezeigt, dass der gesamten Stickstoffkreislauf in marinen Schwämmen ablaufen kann. Um die Diversität und Funktion der aktiven Archaea (und Bakterien) in G. barretti genauer zu untersuchen, haben wir den “Doppel-RNS” Metatranskriptomik Ansatz angewandt, wobei revers-transkribierte RNS direkt sequenziert und anschließend bioinformatisch ausgewertet wurde. Von den ca. 260.000 RNS-tags der Pyrosequenzierung, waren etwa 110.000 von der kleinen Untereinheit der ribosomalen RNS, woraus ein detailliertes taxonomisches Profil von den drei Domänen des Lebens des Schwammsystems erstellt wurde. Innerhalb der transkribierten mRNS-tags haben wir eine große Anzahl an archaealen Genen identifiziert, die wahrscheinlich in den Transport und die Oxidation von Ammonium involviert sind. Einige dieser hoch transkribierten Gene sind in thaumarchaealen Genomen konserviert, aber deren eventueller Beitrag in Ammoniumoxidation war bisher noch nicht bekannt. Aus den Messungen von Nitrifikationsraten, zusammen mit hoher Transkription von amoA Genen in mehreren Schwammarten aus der mesopelagischen Zone des Nordatlantiks, schließen wir eine Schlüsselrolle der Archaea für den Stickstoffmetabolismus mariner Schwämme.Thaumarchaeota have been discovered not only in a diverse range of moderate terrestrial and marine habitats but also as frequent inhabitants of marine sponges. Based on metagenomic and cultivation studies, it has become evident over the past years that some (or all) thaumarchaea have the capability of oxidizing ammonia using the enzyme ammonia monooxygenase (Amo), a homologue of the well-known bacterial counterpart. Here we explore the activity and diversity of Thaumarchaeota in marine cold-water sponges of the Northern hemisphere (Norway) by combining quantitative physiological data and molecular analyses. By monitoring the production and consumption of nitrogen compounds in defined incubation experiments we have demonstrated and quantified nitrification in Geodia barretti, Phakellia ventilabrum, Tentorium semisuberites and Antho dichotoma. In parallel, large numbers of Amo-encoding archaea were detected by quantitative PCR (up to 6*108 archaeal amoA gene copies per µg of nucleic acids) and fluorescence in situ hybridisation, with bacterial amoA genes mostly being under the detection limit. We report denitrification and anammox rates in the sponge Geodia barretti beside nitrification activity by employing stable isotope labelling techniques, thus closing the nitrogen cycle in a marine sponge for the first time. We also identified the potential microbial lineages that are responsible for the activities. To obtain insights into the in situ diversity and function of active microbes in Geodia barretti we employed the “double-RNA” approach, which involved analysis of reverse-transcribed total RNA. Of the approximately 260,000 RNA-tags obtained by pyrosequencing, we assigned ≈110,000 tags to small subunit rRNA and derived a detailed community profile of all three domains of life. Around 50% of all 16S rRNA-tags were assembled and phylogeny of the abundant taxa was performed and compared to sequences of a 16S rRNA clone library of the same cDNA. Within the expressed sequence tags (mRNA), we identified a large number of archaeal genes that are potentially involved in transport and oxidation of ammonia. Some of these highly expressed genes are conserved in thaumarchaeal genomes but their potential function in ammonia oxidation was not previously recognized. From our studies we infer a key role for archaea in the nitrogen metabolism in marine sponges

Die Kraft des Taktischen

Diese Arbeit wirft einen genauen Blick auf die sogenannte Julikrise, die 1870 zum Ausbruch des Deutsch-Französischen Kriegs führte. Anders als die meisten Studien zum Thema konzentriert sie sich nicht auf das politisch-strategische Interesse der beiden Regierungen an einem Krieg. Im Mittelpunkt stehen vielmehr die taktischen Fehler, die auf beiden Seiten begangen wurden. Sie waren für den Kriegsausbruch von entscheidender Bedeutung, da sie am Ende der Krise zu einer Situation führten, in der sowohl Paris als auch Berlin keine andere Möglichkeit sahen, als die diplomatische Auseinandersetzung auf die Spitze zu treiben. Im Fall der französischen Regierung ist diese Feststellung nicht neu; im Fall der preußischen dagegen ist sie eine Seltenheit. Auch Bismarck, so die zentrale These dieser Arbeit, wurde am Ende zum Gefangenen seiner eigenen taktischen Fehler.This thesis takes a close look at the so-called July crisis, which in 1870 led to the outbreak of the Franco-Prussian War. Unlike most studies on the subject, it focuses not on the political-strategic interests of the two governments in going to war. Rather, the tactical errors committed by both sides are at the centre of attention. They were crucial for the outbreak of the war, because they led to a situation at the end of the crisis in which both Paris and Berlin saw only the option of taking the diplomatic quarrel to extremes. In the case of the French government this finding is not new; in the case of Prussia, however, it is a rarity. Bismarck, too, in the end, according to the central thesis of this work, became a prisoner of his own tactical mistakes

Halorubrum chaoviator sp. nov., a haloarchaeon isolated from sea salt in Baja California, Mexico, Western Australia and Naxos, Greece

hree halophilic isolates, strains Halo-G*T, AUS-1 and Naxos II, were compared. Halo-G* was isolated from an evaporitic salt crystal from Baja California, Mexico, whereas AUS-1 and Naxos II were isolated from salt pools in Western Australia and the Greek island of Naxos, respectively. Halo-G*T had been exposed previously to conditions of outer space and survived 2 weeks on the Biopan facility. Chemotaxonomic and molecular comparisons suggested high similarity between the three strains. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that the strains clustered with Halorubrum species, showing sequence similarities of 99.2–97.1 %. The DNA–DNA hybridization values of strain Halo-G*T and strains AUS-1 and Naxos II are 73 and 75 %, respectively, indicating that they constitute a single species. The DNA relatedness between strain Halo-G*T and the type strains of 13 closely related species of the genus Halorubrum ranged from 39 to 2 %, suggesting that the three isolates constitute a different genospecies. The G+C content of the DNA of the three strains was 65.5–66.5 mol%. All three strains contained C20C20 derivatives of diethers of phosphatidylglycerol, phosphatidylglyceromethylphosphate and phosphatidylglycerolsulfate, together with a sulfated glycolipid. On the basis of these results, a novel species that includes the three strains is proposed, with the name Halorubrum chaoviator sp. nov. The type strain is strain Halo-G*T (=DSM 19316T =NCIMB 14426T =ATCC BAA-1602T)

The number and size of nations revisited: Endogenous border formation with non-uniform population distributions

The endogenous border formation model of Alesina and Spolaore (1997) has received a lot of attention in the economics community. One of its central messages is that in a democratic world in equilibrium there is an ineciently large number of nation states. However, this result is obtained under very specic assumptions like a uniform population distribution and no population mobility. In this paper, I generalize the model of Alesina and Spolaore allowing for population distributions other than the uniform distribution. Since this generalization is accompanied by the loss of tractability in closed form, I calculate the equilibria by means of numerical computation. It turns out that the above-mentioned central result is highly sensitive to the choice of population distribution and that the model shows four different regimes depending on the chosen distribution. Furthermore, the behaviour implied by the Alesina and Spolaore model with uniform population distribution is the exception, not the rule

Replication of the Demographic Prisoner’s Dilemma

This paper documents our efforts in replicating Epstein’s (1998) demographic prisoner’s dilemma model. While, qualitatively speaking, our replicated model resembles the results of the original model reasonably well, statistical testing reveals that in quantitative terms our endeavor was only partially successful. This fact hints towards some unstated assumptions regarding the original model. Confronted with a number of ambiguous descriptions of model features we introduce a method for systematically generating a large number of model replications and testing for their equivalence to the original model. With the help of this approach we show that the original model was probably based on a number of dubious assumptions. Finally we conduct a number of statistical tests with respect to the influence of certain design choices like the method of updating, the timing of events and the randomization of the activation order. The results of these tests highlight the importance of an explicit documentation of design choices and especially of the timing of events