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Elisa M Tartaglia, Nicolas Brunel
Electrophysiological recordings in cortex in vivo have revealed a rich variety of dynamical regimes ranging from irregular asynchronous states to a diversity of synchronized states, depending on species, anesthesia, and external stimulation. The average population firing rate in these states is typically low. We study analytically and numerically a network of sparsely connected excitatory and inhibitory integrate-and-fire neurons in the inhibition-dominated, low firing rate regime. For sufficiently high values of the external input, the network exhibits an asynchronous low firing frequency state (L)...
September 20, 2017: Scientific Reports
Michael Hopkins, John J Tyson, Béla Novák
The cell division cycle is the process by which eukaryotic cells replicate their chromosomes and partition them to two daughter cells. To maintain the integrity of the genome, proliferating cells must be able to block progression through the division cycle at key transition points (called 'checkpoints'), if there have been problems in the replication of the chromosomes or their biorientation on the mitotic spindle. These checkpoints are governed by protein-interaction networks, composed of phase-specific cell-cycle activators and inhibitors...
September 20, 2017: Molecular Biology of the Cell
August Romeo, Hans Supèr
We apply the competitive model of Loxley and Robinson (Phys Rev Lett 102:258701, 2009. doi: 10.1103/PhysRevLett.102.258701 ) to the study of a special case of visual rivalry. Three-peaked inputs with maxima at symmetrical locations are introduced, and the role of three-bump configurations is then considered. The model yields conditions for what can be interpreted as a bistable percept analogous to the one-dimensional version of a competition between the central and flanking parts of an image.
September 19, 2017: Biological Cybernetics
Dipali Kosey, Shailza Singh
Cutaneous leishmaniasis is the most common form of leishmaniasis, caused by Leishmania major and is spread by the bite of a sandfly .This species infects the macrophages and dendritic cells Due to multi-drug resistance, there is a need for a new therapeutic technique. Recently, a novel molecular motor of Leishmania, Myosin XXI, was classified and characterized. In addition, the drug resistance in this organism has been linked with the overexpression of ABC transporters. Systems biology aims to study the simulation and modeling of natural biological systems whereas synthetic biology deals with building novel and artificial biological parts and devices  Together they have contributed enormously to drug discovery, vaccine design and development, infectious disease detection and diagnostics...
2017: F1000Research
Zhiyong Yin, Hong Qi, Lili Liu, Zhen Jin
In most cell types, apoptosis occurs by the mitochondrial outer membrane permeability (MOMP)-mediated pathway, which is controlled by Bcl-2 family proteins (often referred to as Bcl-2 apoptotic switch). These proteins, which display a range of bioactivities, can be divided into four types: effectors, inhibitors, activators and sensitizers. Although the complex interactions among Bcl-2 family members have been studied intensively, a unifying hypothesis for the mechanism they use to regulate MOMP remains elusive...
September 15, 2017: Bio Systems
Chao Li, Zhongping Wang, Yan Lu, Xiaoqing Liu, Li Wang
Building electronic components made of individual molecules is a promising strategy for the miniaturization and integration of electronic devices. However, the practical realization of molecular devices and circuits for signal transmission and processing at room temperature has proven challenging. Here, we present room-temperature intermolecular signal transfer and processing using SnCl2Pc molecules on a Cu(100) surface. The in-plane orientations of the molecules are effectively coupled via intermolecular interaction and serve as the information carrier...
September 18, 2017: Nature Nanotechnology
Lukas H Hutter, Scott Rata, Helfrid Hochegger, Béla Novák
The transitions between phases of the cell cycle have evolved to be robust and switch-like, which ensures temporal separation of DNA replication, sister chromatid separation, and cell division. Mathematical models describing the biochemical interaction networks of cell cycle regulators attribute these properties to underlying bistable switches, which inherently generate robust, switch-like, and irreversible transitions between states. We have recently presented new mathematical models for two control systems that regulate crucial transitions in the cell cycle: mitotic entry and exit, (1) and the mitotic checkpoint...
September 13, 2017: Cell Cycle
Martin Börner, Laura Blömer, Marcus Kischel, Peter Richter, Georgeta Salvan, Dietrich R T Zahn, Pablo F Siles, Maria E N Fuentes, Carlos C B Bufon, Daniel Grimm, Oliver G Schmidt, Daniel Breite, Bernd Abel, Berthold Kersting
The chemisorption of magnetically bistable transition metal complexes on planar surfaces has recently attracted increased scientific interest due to its potential application in various fields, including molecular spintronics. In this work, the synthesis of mixed-ligand complexes of the type [Ni(II)2L(L')](ClO4), where L represents a 24-membered macrocyclic hexaazadithiophenolate ligand and L' is a ω-mercapto-carboxylato ligand (L' = HS(CH2)5CO2(-) (6), HS(CH2)10CO2(-) (7), or HS(C6H4)2CO2(-) (8)), and their ability to adsorb on gold surfaces is reported...
2017: Beilstein Journal of Nanotechnology
Brandon J Furlong, Michael J Katz
Dithienylethene-containing molecules have been examined due to their photoswitching capabilities. We have prepared a bistable, optically triggered, metal-organic framework (MOF) containing a dithienylethene moiety that was synthesized and characterized. The advantage of this material is that, unlike other dithienylethene-containing MOFs, the properties of the pore can be changed via an optical trigger without the potential risk of structural damage to the framework. We illustrate the application of this MOF to chemical separations...
September 14, 2017: Journal of the American Chemical Society
Nathan H Heller, Nicolas Davidenko
Motion processing is thought of as a hierarchical system composed of higher and lower order components. Past research has shown that these components can be dissociated using motion priming paradigms in which the lower order system produces negative priming while the higher order system produces positive priming. By manipulating various stimulus parameters, researchers have probed these two systems using bistable test stimuli that permit only two motion interpretations. Here we employ maximally ambiguous test stimuli composed of randomly refreshing pixels in a task that allows observers to report more than just two types of motion percepts...
January 1, 2017: Perception
Mahan Ghafari, Alireza Mashaghi
We study the impact of topology on the response of a transcriptional cascade with certain circuit topologies to a constant and time-varying input signal. We systematically analyze the response of the output to activating and repressing cascades. We identify two types of responses for a linear cascade, namely the "Decaying mode", where the input signal becomes exceedingly weaker as it propagates, and the "Bistable mode", where the input signal can either be amplified or die out in the pathway. We examine how the transition occurs from one mode to the other as we add coherent and/or incoherent feed-forward loops in an otherwise linear cascade...
September 20, 2017: Physical Chemistry Chemical Physics: PCCP
W Hamouche, C Maurini, S Vidoli, A Vincenti
We have designed and tested experimentally a morphing structure consisting of a neutrally stable thin cylindrical shell driven by a multi-parameter piezoelectric actuation. The shell is obtained by plastically deforming an initially flat copper disc, so as to induce large isotropic and almost uniform inelastic curvatures. Following the plastic deformation, in a perfectly isotropic system, the shell is theoretically neutrally stable, having a continuous set of stable cylindrical shapes corresponding to the rotation of the axis of maximal curvature...
August 2017: Proceedings. Mathematical, Physical, and Engineering Sciences
Niloufar Raeis-Hosseini, Junsuk Rho
Integration of phase-change materials (PCMs) into electrical/optical circuits has initiated extensive innovation for applications of metamaterials (MMs) including rewritable optical data storage, metasurfaces, and optoelectronic devices. PCMs have been studied deeply due to their reversible phase transition, high endurance, switching speed, and data retention. Germanium-antimony-tellurium (GST) is a PCM that has amorphous and crystalline phases with distinct properties, is bistable and nonvolatile, and undergoes a reliable and reproducible phase transition in response to an optical or electrical stimulus; GST may therefore have applications in tunable photonic devices and optoelectronic circuits...
September 6, 2017: Materials
P O Sepúlveda, E Carrasco, L F Tapia, M Ramos, F Cruz, P Conget, Q F B Olivares, I Cortínez
It is commonly assumed that loss of responsiveness and recovery of responsiveness occur at similar concentrations of propofol. However, the 'conscious' and 'anaesthetised' conditions produced by general anaesthetics may behave as two bistable states. We hypothesised that loss of responsiveness and recovery of responsiveness occur at different propofol concentrations. Propofol was administered to 19 healthy volunteers by effect-site target-controlled infusion using increasing and decreasing stable concentration steps of 7 min...
September 5, 2017: Anaesthesia
Chengzhe Tian, Szabolcs Semsey, Namiko Mitarai
Toxin-antitoxin (TA) loci are widespread in bacteria including important pathogenic species. Recent studies suggest that TA systems play a key role in persister formation. However, the persistence phenotype shows only weak dependence on the number of TA systems, i.e. they are functionally redundant. We use a mathematical model to investigate the interaction of multiple TA systems in the switching between growth and persistence. We explore two scenarios: (i) TA systems are bistable and each TA system experiences its own noise and (ii) the noise in the level of common stress signal (e...
August 21, 2017: Nucleic Acids Research
Sahand Jamal Rahi, Johannes Larsch, Kresti Pecani, Alexander Y Katsov, Nahal Mansouri, Krasimira Tsaneva-Atanasova, Eduardo D Sontag, Frederick R Cross
Biology emerges from interactions between molecules, which are challenging to elucidate with current techniques. An orthogonal approach is to probe for 'response signatures' that identify specific circuit motifs. For example, bistability, hysteresis, or irreversibility are used to detect positive feedback loops. For adapting systems, such signatures are not known. Only two circuit motifs generate adaptation: negative feedback loops (NFLs) and incoherent feed-forward loops (IFFLs). On the basis of computational testing and mathematical proofs, we propose differential signatures: in response to oscillatory stimulation, NFLs but not IFFLs show refractory-period stabilization (robustness to changes in stimulus duration) or period skipping...
August 28, 2017: Nature Methods
Albert S Y Wong, Wilhelm T S Huck
A new discipline of "systems chemistry" is emerging, which aims to capture the complexity observed in natural systems within a synthetic chemical framework. Living systems rely on complex networks of chemical reactions to control the concentration of molecules in space and time. Despite the enormous complexity in biological networks, it is possible to identify network motifs that lead to functional outputs such as bistability or oscillations. To truly understand how living systems function, we need a complete understanding of how chemical reaction networks (CRNs) create function...
2017: Beilstein Journal of Organic Chemistry
Yu-Yu Cheng, Andrew J Hirning, Krešimir Josić, Matthew R Bennett
Transcription factors and their target promoters are central to synthetic biology. By arranging these components into novel gene regulatory circuits, synthetic biologists have been able to create a wide variety of phenotypes, including bistable switches, oscillators, and logic gates. However, transcription factors (TFs) do not instantaneously regulate downstream targets. After the gene encoding a TF is turned on, the gene must first be transcribed, the transcripts must be translated, and sufficient TF must accumulate in order to bind operator sites of the target promoter...
September 5, 2017: ACS Synthetic Biology
Xia Wang, Kotaro Fujimaki, Geoffrey C Mitchell, Jungeun Sarah Kwon, Kimiko Della Croce, Chris Langsdorf, Hao Helen Zhang, Guang Yao
Reactivating quiescent cells to proliferate is critical to tissue repair and homoeostasis. Quiescence exit is highly noisy even for genetically identical cells under the same environmental conditions. Deregulation of quiescence exit is associated with many diseases, but cellular mechanisms underlying the noisy process of exiting quiescence are poorly understood. Here we show that the heterogeneity of quiescence exit reflects a memory of preceding cell growth at quiescence induction and immediate division history before quiescence entry, and that such a memory is reflected in cell size at a coarse scale...
August 22, 2017: Nature Communications
Stefano Giordano
The force-extension response of chains composed of bistable (or multistable) units strongly depends on the applied boundary conditions. As a matter of fact, isotensional conditions (soft devices) lead to a plateau-like response, whereas isometric conditions (hard devices) lead to a sawtooth-like pattern. We develop an equilibrium statistical mechanics methodology, based on the introduction of a set of discrete or spin variables, which is able to describe the thermal and mechanical properties of a folding and unfolding chain under arbitrary external conditions...
August 22, 2017: Soft Matter
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