Evolutionary game theory in growing populations

Existing theoretical models of evolution focus on the relative fitness advantages of different mutants in a population while the dynamic behavior of the population size is mostly left unconsidered. We here present a generic stochastic model which combines the growth dynamics of the population and its internal evolution. Our model thereby accounts for the fact that both evolutionary and growth dynamics are based on individual reproduction events and hence are highly coupled and stochastic in nature. We exemplify our approach by studying the dilemma of cooperation in growing populations and show that genuinely stochastic events can ease the dilemma by leading to a transient but robust increase in cooperationComment: 4 pages, 2 figures and 2 pages supplementary informatio

Assembly and use of new task rules in fronto-parietal cortex

Severe capacity limits, closely associated with fluid intelligence, arise in learning and use of new task rules. We used fMRI to investigate these limits in a series of multirule tasks involving different stimuli, rules, and response keys. Data were analyzed both during presentation of instructions and during later task execution. Between tasks, we manipulated the number of rules specified in task instructions, and within tasks, we manipulated the number of rules operative in each trial block. Replicating previous results, rule failures were strongly predicted by fluid intelligence and increased with the number of operative rules. In fMRI data, analyses of the instruction period showed that the bilateral inferior frontal sulcus, intraparietal sulcus, and presupplementary motor area were phasically active with presentation of each new rule. In a broader range of frontal and parietal regions, baseline activity gradually increased as successive rules were instructed. During task performance, we observed contrasting fronto-parietal patterns of sustained (block-related) and transient (trial-related) activity. Block, but not trial, activity showed effects of task complexity. We suggest that, as a new task is learned, a fronto-parietal representation of relevant rules and facts is assembled for future control of behavior. Capacity limits in learning and executing new rules, and their association with fluid intelligence, may be mediated by this load-sensitive fronto-parietal network

Combined antiproliferative activity of imatinib mesylate (STI-571) with radiation or cisplatin in vitro

Little is known about the interaction of novel anticancer drugs with other treatment modalities. The aim of this study was to examine the effect of combining imatinib mesylate (STI-571) with radiation or cisplatin on the survival of two human solid tumor cell lines – SKNMC cells derived from Ewing sarcoma and breast cancer MCF-7 cells. Methods: Cell proliferation was determined using the sulphorodamine B cytotoxicity assay. Cell cycle analysis was performed with flow cytometry. Apoptosis was determined using a commercial cell death ELISA plus kit. Phosphorylated AKT, which has been suggested to be involved in radiation resistance, was detected by Western blot analysis. Results: Exposure of SKNMC cells to STI-571 resulted in a dose-dependent antiproliferative effect and a decrease in phosphorylated AKT expression. There was no evidence of apoptosis. The combination of STI-571 with radiation or cisplatin had an additive antiproliferative effect in SKNMC cells (60% reduction in cell number). A similar effect was observed in human MCF-7 breast cancer cells. Conclusion: STI-571 improves the outcome of cisplatin or irradiation treatment in vitro. AKT pathway may play a role in the additive effect of STI-571 and irradiation.Цель: оценить антипролиферативный эффект иматиниба (STI-571) в комбинации с облучением или цисплатиной по отношению к двум клеточным линиям – клеткам линии SKNMC, полученным из саркомы Эвинга, и клеткам рака молочной железы человека линии MCF-7. Методы: для оценки пролиферации клеток применяли метод анализа цитотоксичности с использованием сульфородамина B. Для анализа распределения клеток по фазам клеточного цикла применяли метод проточной цитометрии, апоптоза – с применением коммерческого набора для проведения ИФА. Уровень фосфорилированной киназы АКТ, предположительно связанной с радиорезистентностью, определяли методом Вестерн-блот анализа. Результаты: инкубация клеток SKNMC STI-571 приводила к дозозависимому антипролиферативному эффекту и снижению фосфорилирования AKT, но не апоптозу клеток. Комбинированное применение STI-571 и обления или цисплатины оказывало дополнительное антипролиферативное воздействие на клетки линии SKNMC (60% уменьшения количества клеток). Аналогичные эффекты отмечали на клетках линии MCF-7. Выводы: обработка опухолевых клеток STI-571 усиливает эффект обления и цисплатины in, причем таковой может быть опосредован сигнальным каскадом AK

Observation of Quantum Effects in sub Kelvin Cold Reactions

There has been a long-standing quest to observe chemical reactions at low temperatures where reaction rates and pathways are governed by quantum mechanical effects. So far this field of Quantum Chemistry has been dominated by theory. The difficulty has been to realize in the laboratory low enough collisional velocities between neutral reactants, so that the quantum wave nature could be observed. We report here the first realization of merged neutral supersonic beams, and the observation of clear quantum effects in the resulting reactions. We observe orbiting resonances in the Penning ionization reaction of argon and molecular hydrogen with metastable helium leading to a sharp increase in the absolute reaction rate in the energy range corresponding to a few degrees kelvin down to 10 mK. Our method is widely applicable to many canonical chemical reactions, and will enable a breakthrough in the experimental study of Quantum Chemistry

Seasonal shifts in bacterial community responses to phytoplankton-derived dissolved organic matter in the Western Antarctic Peninsula

© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Microbiology 8 (2017): 2117, doi:10.3389/fmicb.2017.02117.Bacterial consumption of dissolved organic matter (DOM) drives much of the movement of carbon through the oceanic food web and the global carbon cycle. Understanding complex interactions between bacteria and marine DOM remains an important challenge. We tested the hypothesis that bacterial growth and community succession would respond differently to DOM additions due to seasonal changes in phytoplankton abundance in the environment. Four mesocosm experiments were conducted that spanned the spring transitional period (August–December 2013) in surface waters of the Western Antarctic Peninsula (WAP). Each mesocosm consisted of nearshore surface seawater (50 L) incubated in the laboratory for 10 days. The addition of DOM, in the form of cell-free exudates extracted from Thalassiosira weissflogii diatom cultures led to changes in bacterial abundance, production, and community composition. The timing of each mesocosm experiment (i.e., late winter vs. late spring) influenced the magnitude and direction of bacterial changes. For example, the same DOM treatment applied at different times during the season resulted in different levels of bacterial production and different bacterial community composition. There was a mid-season shift from Collwelliaceae to Polaribacter having the greatest relative abundance after incubation. This shift corresponded to a modest but significant increase in the initial relative abundance of Polaribacter in the nearshore seawater used to set up experiments. This finding supports a new hypothesis that starting community composition, through priority effects, influenced the trajectory of community succession in response to DOM addition. As strong inter-annual variability and long-term climate change may shift the timing of WAP phytoplankton blooms, and the corresponding production of DOM exudates, this study suggests a mechanism by which different seasonal successional patterns in bacterial communities could occur.CL was partially funded by the Graduate School and the Department of Ecology and Evolutionary Biology at Brown University and the Brown University-Marine Biological Laboratory Joint Graduate Program. This material is based upon work supported by the National Science Foundation under Grant Nos. ANT-1142114 to LA-Z, OPP-0823101 and PLR-1440435 to HD, and ANT-1141993 to JR. The Gordon and Betty Moore Foundation grant 1711 supported work by DR

Synaesthesia: a distinct entity that is an emergent feature of adaptive neurocognitive differences

In this article, I argue that synaesthesia is not on a continuum with neurotypical cognition. Synaesthesia is special: its phenomenology is different; it has distinct causal mechanisms; and is likely to be associated with a distinct neurocognitive profile. However, not all synaesthetes are the same, and there are quantifiable differences between them. In particular, the number of types of synaesthesia that a person possesses is a hitherto underappreciated variable that predicts cognitive differences along a number of dimensions (mental imagery, sensory sensitivity, attention to detail). Together with enhanced memory, this may constitute a common core of abilities that may go some way to explaining why synaesthesia might have evolved. I argue that the direct benefits of synaesthesia are generally limited (i.e. the synaesthetic associations do not convey novel information about the world) but, nevertheless, synaesthesia may develop due to other adaptive functions (e.g. perceptual ability, memory) that necessitate changes to design features of the brain. The article concludes by suggesting that synaesthesia forces us to reconsider what we mean by a ‘normal’ mind/brain. There may be multiple ‘normal’ neurodevelopmental trajectories that can sculpt very different ways of experiencing the world, of which synaesthesia is but one. This article is part of a discussion meeting issue ‘Bridging senses: novel insights from synaesthesia’

The simulation of action disorganisation in complex activities of daily living

Action selection in everyday goal-directed tasks of moderate complexity is known to be subject to breakdown following extensive frontal brain injury. A model of action selection in such tasks is presented and used to explore three hypotheses concerning the origins of action disorganisation: that it is a consequence of reduced top-down excitation within a hierarchical action schema network coupled with increased bottom-up triggering of schemas from environmental sources, that it is a more general disturbance of schema activation modelled by excessive noise in the schema network, and that it results from a general disturbance of the triggering of schemas by object representations. Results suggest that the action disorganisation syndrome is best accounted for by a general disturbance to schema activation, while altering the balance between top-down and bottom-up activation provides an account of a related disorder - utilisation behaviour. It is further suggested that ideational apraxia (which may result from lesions to left temporoparietal areas and which has similar behavioural consequences to action disorganisation syndrome on tasks of moderate complexity) is a consequence of a generalised disturbance of the triggering of schemas by object representations. Several predictions regarding differences between action disorganisation syndrome and ideational apraxia that follow from this interpretation are detailed