Random sequential adsorption and diffusion of dimers and k-mers on a square lattice

We have performed extensive simulations of random sequential adsorption and diffusion of $k$-mers, up to $k=5$ in two dimensions with particular attention to the case $k=2$. We focus on the behavior of the coverage and of vacancy dynamics as a function of time. We observe that for $k=2,3$ a complete coverage of the lattice is never reached, because of the existence of frozen configurations that prevent isolated vacancies in the lattice to join. From this result we argue that complete coverage is never attained for any value of $k$. The long time behavior of the coverage is not mean field and nonanalytic, with $t^{-1/2}$ as leading term. Long time coverage regimes are independent of the initial conditions while strongly depend on the diffusion probability and deposition rate and, in particular, different values of these parameters lead to different final values of the coverage. The geometrical complexity of these systems is also highlighted through an investigation of the vacancy population dynamics.Comment: 9 pages, 9 figures, to be published in the Journal of Chemical Physic

Protist predation can favour cooperation within bacterial species

Here, we studied how protist predation affects cooperation in the opportunistic pathogen bacterium Pseudomonas aeruginosa, which uses quorum sensing (QS) cell-to-cell signalling to regulate the production of public goods. By competing wild-type bacteria with QS mutants (cheats), we show that a functioning QS system confers an elevated resistance to predation. Surprisingly, cheats were unable to exploit this resistance in the presence of cooperators, which suggests that resistance does not appear to result from activation of QS-regulated public goods. Instead, elevated resistance of wild-type bacteria was related to the ability to form more predation-resistant biofilms. This could be explained by the expression of QS-regulated resistance traits in densely populated biofilms and floating cell aggregations, or alternatively, by a pleiotropic cost of cheating where less resistant cheats are selectively removed from biofilms. These results show that trophic interactions among species can maintain cooperation within species, and have further implications for P. aeruginosa virulence in environmental reservoirs by potentially enriching the cooperative and highly infective strains with functional QS system

Evolution models with extremal dynamics

AbstractThe random-neighbor version of the Bak-Sneppen biological evolution model is reproduced, along with an analogous model of random replicators, the latter eventually experiencing topology changes. In the absence of topology changes, both types of models self-organize to a critical state. Species extinctions in the replicator system degenerates the self-organization to a random walk, as does vanishing of species interaction for the BS-model. A replicator model with speciation is introduced, experiencing dramatic topology changes. It produces a variety of features, but self-organizes to a possibly critical state only in a few special cases. Speciation-extinction dynamics interfering with self-organization, biological macroevolution probably is not a self-organized critical system

Evaluating and designing language learning games for minority languages:focus on Karelian language

Abstract. There are plenty of language learning applications found for smartphone on Google Play store, but only a few of them are for minority language learning, particularly for Karelian language as none of the most popular applications have it listed as an option. Luckily there are few found on the web, but they have their limitations. Both analysing and evaluating them in this study provide a good starting point for designing and developing games further so that one day someone who wants to learn Karelian language can find number of language learning games to choose from. The options for designs would go from having serious borderline gamified applications for language learning to more educational games where effortless learning would be one of the key aspects and having fun is highlighted. The games do not need to be strictly on either mobile or PC, but with the current situation of covid-19 restrictions, the need for digital-based learning games is apparent. Literature review gives good aspects as to why it is important to do language learning games and as to what aspects should be considered when doing one. The studies on gamification bring forward the usefulness of individual game mechanics that otherwise would not be so carefully thought about when designing games. Giving users achievements and stars as a form of rewards when they succeed makes them stay more motivated when interacting with the game. Design science research provides good set of guidelines for artefact construction phase, where different kind of concepts are first presented based on the cognitive walkthrough and evaluation phases. In addition to the games that are constructed, a set of design recommendations for further game development are formed to answer the question of what aspects need to be taken into account when developing games for minority language learning. Most of the aspects in the design recommendations are user experience related themes, since the usability aspect of the prototyped games is not on the level that it should be yet

Improvement of steel ladle lid circulation and lifetime

Abstract. For an energy-intensive field of industry, such as steelmaking, temperature control in steel production is essential. As one of the methods to improve energy efficiency in SSAB Raahe’s steel plant production, they introduced lids for their steel ladles to prevent heat losses during transportation. However, even though the lids have been in use for years, their actual properties have not been properly studied. The aim of this work is to clarify current steel ladle lid lifetime, chart areas for development and improve condition monitoring methods. As a fundamental study, this thesis mainly presents the current situation and does not aim for major structural improvement. The essential part of this work is to develop methods to monitor the condition of steel ladle lids and record necessary information throughout lid lifetimes. In the experimental part of this work, the condition of the lining was monitored to create a model of refractory wear for the steel ladle lids. Based on the observations during the trial and theoretical studies, the sources of the most common defects were investigated. The results show that the lids endure the process conditions decently but there is still room for improvement

Single qubit dephasing in the many-body localization phase transition

Abstract. We are interested in a model for quantum computer that consists of superconducting qubits, transmons. These transmons are known to experience decoherence which causes unwanted dynamics in their quantum state. In this thesis, one form of decoherence experienced by the transmon, dephasing, is studied. The goal of this research is to differentiate the thermalization phase from the many-body localization phase in a transmon chain by studying dephasing of a single transmon. This phase transition is measured by simulating an array of transmons using the Bose–Hubbard model and calculating the dephasing rate R2 that a single transmon experiences. The many-body localization is shown to have significantly reduced dephasing rates compared to the rates observed at the thermalization phase in three different cases with varying ratio between the interaction strength and the hopping rate U/J = 2, 3.5 and 5. From these results we see that the phase transition is seen when the disorder strength is in the range of W/J = 10−15 on all three cases. An interesting future outlook could be to study the deeper features of the phase transition by examining the the effect of spin-echo pulses on the transmon dephasing

Empirical observations of the yield of logs from trees of the boreal region

The yield of sawlogs and plywood logs from boreal trees is discussed. First, taper curves are used to compute geometric (maximal) sawlog and plywood log contents. Then, a quality reduction is implemented, according to previously published models. Finally, the outcome is verified using empirical observations. Regarding spruce trees, the different estimates of sawlog content agree. In the case of birch and pine trees, the estimates differ. The sawlog and plywood log yield from large trees is greater than prognosticated, probably due to missing over-aged trees in the empirical data. The yield of sawlogs and plywood logs from small trees is smaller than prognosticated, most of the empirical data originating from thinnings with a focus on the quality of the remaining trees. The sawlog content of individual trees from clearcutting displays a skew distribution around the expected value. The distribution in thinning trunks shows a binary component, with a large proportion of trees with zero sawlog content

Microeconomics of nitrogen fertilization in boreal carbon forestry

Nitrogen fertilization of boreal forests is investigated in terms of microeconomics, as a tool for carbon sequestration. The effects of nitrogen fertilization's timing on the return rate on capital and the expected value of the timber stock are investigated within a set of semi-fertile, spruce-dominated boreal stands, using an inventory-based growth model. Early fertilization tends to shorten rotations, reducing timber stock and carbon storage. The same applies to fertilization after the second thinning. Fertilization applied ten years before stand maturity is profitable and increases the timber stock, but the latter effect is small. Fertilization of mature stands, extending any rotation by ten years, effectively increases the carbon stock. Profitability varies but is increased by fertilization, instead of merely extending the rotation.Comment: 16 pages, 9 Figure

Somatostatin agonist pasireotide inhibits exercise stimulated growth in the male Siberian hamster (Phodopus sungorus)

R.Dumbell was supported by a University of Aberdeen PhD studentship and a research visit grant awarded by the British Society of Neuroendocrinology. Further support was provided by the Scottish Government Rural and Environment Science and Analytical Services Division (Barrett and the German Research Foundation (DFG; STE 331/8-1; Steinlechner lab). We are grateful for technical assistance from Dana Wilson at RINH and Siegried Hiliken at UVMH, and thank Dr Claus-Dieter Mayer of Biomathematics & Statistics Scotland for valuable advice on statistical analysis.Peer reviewedPostprin

Interaction-induced current-reversals in driven lattices

We demonstrate that long-range interactions can cause, as time evolves, consecutive reversals of directed currents for dilute ensembles of particles in driven lattices. These current-reversals are based on a general mechanism which leads to an interaction-induced accumulation of particles in the regular regions of the underlying single-particle phase space and to a synchronized single-particle motion as well as an enhanced efficiency of Hamiltonian ratchets.Comment: 5 pages, 5 figure