Generalizing the transition from amplitude to oscillation death in coupled oscillators

Peer reviewedPublisher PD

Robustness and timing of cellular differentiation through population-based symmetry breaking

During mammalian development, cell types expressing mutually exclusive genetic markers are differentiated from a multilineage primed state. These observations have invoked single-cell multistability view as the dynamical basis of differentiation. However, the robust regulative nature of mammalian development is not captured therein. Considering the well-established role of cell-cell communication in this process, we propose a fundamentally different dynamical treatment in which cellular identities emerge and are maintained on population level, as a novel unique solution of the coupled system. Subcritical system’s organization here enables symmetry-breaking to be triggered by cell number increase in a timed, self-organized manner. Robust cell type proportions are thereby an inherent feature of the resulting inhomogeneous solution. This framework is generic, as exemplified for early embryogenesis and neurogenesis cases. Distinct from mechanisms that rely on pre-existing asymmetries, we thus demonstrate that robustness and accuracy necessarily emerge from the cooperative behaviour of growing cell populations during development

Trilingual aligned corpus – current state and new applications

Trilingual aligned corpus – current state and new applications This article describes current state of a trilingual parallel corpus consisted of texts in two Slavic (Bulgarian and Polish) and one Baltic language (Lithuanian). The corpus contains original literary texts (fiction, novels, and short stories) in one of the three languages with translations to the other two, and texts in other languages translated into Bulgarian, Polish, and Lithuanian. A part of the texts are aligned at the sentence level. The authors propose a semantic annotation of verbs appearing in these aligned texts that will facilitate contrastive studies of natural languages. A theoretical background for the proposed semantic annotation is briefly also discussed

Restoration of rhythmicity in diffusively coupled dynamical networks

We acknowledge financial support from the National Natural Science Foundation of China (No. 11202082, No. 61203235, No. 11371367 and No. 11271290), the Fundamental Research Funds for the Central Universities of China under Grant No. 2014QT005, IRTG1740(DFG-FAPESP), and SERB-DST Fast Track scheme for young scientist under Grant No. ST/FTP/PS-119/2013, NSF CHE-0955555 and Grant No. 229171/2013-3 (CNPq).Peer reviewedPublisher PD

Cells use molecular working memory to navigate inchanging chemoattractant fields

In order to migrate over large distances, cells within tissues and organisms rely on sensing local gradient cues which are irregular, conflicting, and changing over time and space. The mechanism how they generate persistent directional migration when signals are disrupted, while still remaining adaptive to signal's localization changes remain unknown. Here we find that single cells utilize a molecular mechanism akin to a working memory to satisfy these two opposing demands. We derive theoretically that this is characteristic for receptor networks maintained away from steady states. Time-resolved live-cell imaging of Epidermal growth factor receptor (EGFR) phosphorylation dynamics shows that cells transiently memorize position of encountered signals via slow-escaping remnant of the polarized signaling state, a dynamical 'ghost', driving memory-guided persistent directional migration. The metastability of this state further enables migrational adaptation when encountering new signals. We thus identify basic mechanism of real-time computations underlying cellular navigation in changing chemoattractant fields

Presentation of the verbs in Bulgarian-Polish electronic dictionary

Presentation of the verbs in Bulgarian-Polish electronic dictionary This paper briefly discusses the presentation of the verbs in the first electronic Bulgarian-Polish dictionary that is currently being developed under a bilateral collaboration between IMI-BAS and ISS-PAS. Special attention is given to the digital entry classifiers that describe Bulgarian and Polish verbs. Problems related to the correspondence between natural language phenomena and their presentations are discussed. Some examples illustrate the different types of dictionary entries for verbs

Definiteness-indefiniteness category and logical quantification

Definiteness-indefiniteness category and logical quantificationThis work has been written within the “Logic and Language” project, realized under a cooperation agreement between the Institute of Slavic Studies of the Polish Academy of Sciences and the Institute of Bulgarian Language of the Bulgarian Academy of Sciences. The publication of a many-volume Bulgarian Polish Grammar (12 monographs), and of a Polish-Bulgarian Contrastive Grammar, from now on: Synthesis, is completed. Theories of mathematical logic are satisfied in perfect way in a natural language, which is shown by our understanding of the semantic definiteness / indefiniteness category as a system of scope-based quantification notions. A natural language complements and modifies logical theories. For example, understanding of the definiteness / indefiniteness category as a sentence category follows from the language material, especially in article languages. In such languages, quantification of the predicate is a necessary prerequisite for interpretation. Also introduction of the notions of strong and weak quantification meanings is motivated, for example, by the need to distinguish between the meanings of expressions like Pol. pewien x, jakiś x / Bulg. njakoj x, njakakyv x on the nominal phrase level, and by understanding of the ambiguity of quantification expressions like Bulg. vinagi, ponjakoga / Pol. zawsze, czasami. The fact of treating the definiteness / indefiniteness category as a sentence category expands understanding of the incomplete quantification notion also with respect to the verbal phrase, rather than, as in Ajdukiewicz’s approach, with respect to the nominal phrase only. Similarly, a proper name in a natural language is not a unique name, like in mathematical logic, but requires additional unique quantification. A network-based description of time is the first attempt at this type of description in the subject literature. In the present article, I stress that fact that quantification of states and events understood as in Petri net theory reveals the dependence between the aspectual and temporal meanings of verb, and proves that the information on time and aspect need not be dealt with separately

Timing cellular decision making under noise via cell-cell communication

Many cellular processes require decision making mechanisms, which must act reliably even in the unavoidable presence of substantial amounts of noise. However, the multistable genetic switches that underlie most decision-making processes are dominated by fluctuations that can induce random jumps between alternative cellular states. Here we show, via theoretical modeling of a population of noise-driven bistable genetic switches, that reliable timing of decision-making processes can be accomplished for large enough population sizes, as long as cells are globally coupled by chemical means. In the light of these results, we conjecture that cell proliferation, in the presence of cell-cell communication, could provide a mechanism for reliable decision making in the presence of noise, by triggering cellular transitions only when the whole cell population reaches a certain size. In other words, the summation performed by the cell population would average out the noise and reduce its detrimental impact