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Bistability

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https://www.readbyqxmd.com/read/28342717/slow-chromatin-dynamics-allow-polycomb-target-genes-to-filter-fluctuations-in-transcription-factor-activity
#1
Scott Berry, Caroline Dean, Martin Howard
Genes targeted by Polycomb repressive complex 2 (PRC2) are regulated in cis by chromatin modifications and also in trans by diffusible regulators such as transcription factors. Here, we introduce a mathematical model in which transcription directly antagonizes Polycomb silencing, thereby linking these cis- and trans-regulatory inputs to gene expression. The model is parameterized by recent experimental data showing that PRC2-mediated repressive chromatin modifications accumulate extremely slowly. The model generates self-perpetuating, bistable active and repressed chromatin states that persist through DNA replication, thereby ensuring high-fidelity transmission of the current chromatin state...
March 21, 2017: Cell Systems
https://www.readbyqxmd.com/read/28332670/high-temperature-structural-phase-transition-coupled-with-dielectric-switching-in-an-organic-inorganic-hybrid-crystal-nh3-ch2-2br-3cdbr5
#2
Hai-Peng Chen, Zhong-Xia Wang, Cheng Chen, Yang Lu, Zi Yin, Xiao-Fen Sun, Da-Wei Fu
Molecular bistable switches (electrical switches "ON" and "OFF") represent a class of highly desirable intelligent materials due to their sensitive switchable responses, simple and environmentally friendly processing, light weight, and mechanical flexibility. In particular, these switches above room temperature with potential practical application are rarely reported. In this work, a new zigzag chained organic-inorganic hybrid compound [NH3(CH2)2Br]3CdBr5 (1), which displays rapidly sensitive dielectric switching reversibility and remarkable switching antifatigue, has been successfully synthesized...
March 23, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28323019/comparison-of-perceptual-properties-of-auditory-streaming-between-spectral-and-amplitude-modulation-domains
#3
Shimpei Yamagishi, Sho Otsuka, Shigeto Furukawa, Makio Kashino
The two-tone sequence (ABA_), which comprises two different sounds (A and B) and a silent gap, has been used to investigate how the auditory system organizes sequential sounds depending on various stimulus conditions or brain states. Auditory streaming can be evoked by differences not only in the tone frequency ("spectral cue": ΔFTONE, TONE condition) but also in the amplitude modulation rate ("AM cue": ΔFAM, AM condition). The aim of the present study was to explore the relationship between the perceptual properties of auditory streaming for the TONE and AM conditions...
March 17, 2017: Hearing Research
https://www.readbyqxmd.com/read/28317845/dna-damage-during-s-phase-mediates-the-proliferation-quiescence-decision-in-the-subsequent-g1-via-p21-expression
#4
Alexis R Barr, Samuel Cooper, Frank S Heldt, Francesca Butera, Henriette Stoy, Jörg Mansfeld, Béla Novák, Chris Bakal
Following DNA damage caused by exogenous sources, such as ionizing radiation, the tumour suppressor p53 mediates cell cycle arrest via expression of the CDK inhibitor, p21. However, the role of p21 in maintaining genomic stability in the absence of exogenous DNA-damaging agents is unclear. Here, using live single-cell measurements of p21 protein in proliferating cultures, we show that naturally occurring DNA damage incurred over S-phase causes p53-dependent accumulation of p21 during mother G2- and daughter G1-phases...
March 20, 2017: Nature Communications
https://www.readbyqxmd.com/read/28301094/binocular-rivalry-in-children-on-the-autism-spectrum
#5
Themelis Karaminis, Claudia Lunghi, Louise Neil, David Burr, Elizabeth Pellicano
When different images are presented to the eyes, the brain is faced with ambiguity, causing perceptual bistability: visual perception continuously alternates between the monocular images, a phenomenon called binocular rivalry. Many models of rivalry suggest that its temporal dynamics depend on mutual inhibition among neurons representing competing images. These models predict that rivalry should be different in autism, which has been proposed to present an atypical ratio of excitation and inhibition [the E/I imbalance hypothesis; Rubenstein & Merzenich, 2003]...
March 16, 2017: Autism Research: Official Journal of the International Society for Autism Research
https://www.readbyqxmd.com/read/28290506/high-binding-affinity-of-repressor-iolr-avoids-costs-of-untimely-induction-of-myo-inositol-utilization-by-salmonella-typhimurium
#6
Jessica Hellinckx, Ralf Heermann, Angela Felsl, Thilo M Fuchs
Growth of Salmonella enterica serovar Typhimurium strain 14028 with myo-inositol (MI) is characterized by a bistable phenotype that manifests with an extraordinarily long (34 h) and variable lag phase. When cells were pre-grown in minimal medium with MI, however, the lag phase shortened drastically to eight hours, and to six hours in the absence of the regulator IolR. To unravel the molecular mechanism behind this phenomenon, we investigated this repressor in more detail. Flow cytometry analysis of the iolR promoter at a single cell level demonstrated bistability of its transcriptional activation...
March 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28286945/controlled-sol-gel-transitions-by-actuating-molecular-machine-based-supramolecular-polymers
#7
Antoine Goujon, Giacomo Mariani, Thomas Lang, Emilie Moulin, Michel Rawiso, Eric Buhler, Nicolas Giuseppone
The implementation of artificial molecular machines in polymer science is an important objective that challenges chemists and physicists in order to access an entirely new class of smart materials. To design such systems, the amplification of a mechanical actuation from the nanoscale up to a macroscopic response in the bulk material is a central issue. In this article we show that bistable [c2]daisy chain rotaxanes (i.e. molecular muscles) can be linked into main-chain Upy-based supramolecular polymers. We then reveal by an in depth quantitative study that the pH actuation of the mechanically active rotaxane at the nanoscale influences the physical reticulation of the polymer chains by changing the supramolecular behavior of the Upy units...
March 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28281748/pegylated-perylenemonoimide-dithienylethene-for-super-resolution-imaging-of-liposomes
#8
Jun-Xia Liu, Bo Xin, Chong Li, Nuo-Hua Xie, Wen-Liang Gong, Zhen-Li Huang, Ming-Qiang Zhu
We have designed and synthesized an amphiphilic photoswitchable fluorophore, PEGylated perylenemonoimide-dithienylethene (PEG-PMI-DTE), which exhibits evident bistable photochromism, fluorescence switching and fatigue resistance. The fine nanostructures of liposomes can be observed directly under super-resolution fluorescent microscopy by aid of the amphiphilic photoswitchable fluorophore as a staining agent, with an optical resolution of 30 nm.
March 10, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28280580/organization-of-biogeochemical-nitrogen-pathways-with-switch-like-adjustment-in-fluctuating-soil-redox-conditions
#9
Sanjay Lamba, Soumen Bera, Mubasher Rashid, Alexander B Medvinsky, Gui-Quan Sun, Claudia Acquisti, Amit Chakraborty, Bai-Lian Li
Nitrogen is cycled throughout ecosystems by a suite of biogeochemical processes. The high complexity of the nitrogen cycle resides in an intricate interplay between reversible biochemical pathways alternatively and specifically activated in response to diverse environmental cues. Despite aggressive research, how the fundamental nitrogen biochemical processes are assembled and maintained in fluctuating soil redox conditions remains elusive. Here, we address this question using a kinetic modelling approach coupled with dynamical systems theory and microbial genomics...
January 2017: Royal Society Open Science
https://www.readbyqxmd.com/read/28277519/reading-and-writing-single-atom-magnets
#10
Fabian D Natterer, Kai Yang, William Paul, Philip Willke, Taeyoung Choi, Thomas Greber, Andreas J Heinrich, Christopher P Lutz
The single-atom bit represents the ultimate limit of the classical approach to high-density magnetic storage media. So far, the smallest individually addressable bistable magnetic bits have consisted of 3-12 atoms. Long magnetic relaxation times have been demonstrated for single lanthanide atoms in molecular magnets, for lanthanides diluted in bulk crystals, and recently for ensembles of holmium (Ho) atoms supported on magnesium oxide (MgO). These experiments suggest a path towards data storage at the atomic limit, but the way in which individual magnetic centres are accessed remains unclear...
March 8, 2017: Nature
https://www.readbyqxmd.com/read/28273072/bistable-front-dynamics-in-a-contractile-medium-travelling-wave-fronts-and-cortical-advection-define-stable-zones-of-rhoa-signaling-at-epithelial-adherens-junctions
#11
Rashmi Priya, Guillermo A Gomez, Srikanth Budnar, Bipul R Acharya, Andras Czirok, Alpha S Yap, Zoltan Neufeld
Mechanical coherence of cell layers is essential for epithelia to function as tissue barriers and to control active tissue dynamics during morphogenesis. RhoA signaling at adherens junctions plays a key role in this process by coupling cadherin-based cell-cell adhesion together with actomyosin contractility. Here we propose and analyze a mathematical model representing core interactions involved in the spatial localization of junctional RhoA signaling. We demonstrate how the interplay between biochemical signaling through positive feedback, combined with diffusion on the cell membrane and mechanical forces generated in the cortex, can determine the spatial distribution of RhoA signaling at cell-cell junctions...
March 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28271230/attention-or-instruction-do-sustained-attentional-abilities-really-differ-between-high-and-low-hypnotisable-persons
#12
Jean-Rémy Martin, Jérôme Sackur, Zoltan Dienes
Previous research has suggested that highly hypnotisable participants ('highs') are more sensitive to the bistability of ambiguous figures-as evidenced by reporting more perspective changes of a Necker cube-than low hypnotisable participants ('lows'). This finding has been interpreted as supporting the hypothesis that highs have more efficient sustained attentional abilities than lows. However, the higher report of perspective changes in highs in comparison to lows may reflect the implementation of different expectation-based strategies as a result of differently constructed demand characteristics according to one's level of hypnotisability...
March 7, 2017: Psychological Research
https://www.readbyqxmd.com/read/28249391/multicluster-oscillation-death-and-chimeralike-states-in-globally-coupled-josephson-junctions
#13
Arindam Mishra, Suman Saha, Prodyot K Roy, Tomasz Kapitaniak, Syamal K Dana
We observe the multiclustered oscillation death and chimeralike states in an array of Josephson junctions under a combination of self-repulsive and cross-attractive mean-field interaction when each isolated junction is in a bistable state, a coexisting fixed point and an oscillatory state. We locate the parameter landscape of the multiclustered oscillation death and chimeralike states. Alternatively, a purely repulsive mean-field interaction in an array of all oscillatory junctions produces chimeralike states with signatures of metastability in the incoherent subpopulation of junctions...
February 2017: Chaos
https://www.readbyqxmd.com/read/28249390/a-wind-powered-one-way-bistable-medium-with-parity-effects
#14
Tessa Rosenberger, Graham Schattgen, Matthew King-Smith, Prakrit Shrestha, Katsuo J Maxted, John F Lindner
We describe the design, construction, and dynamics of low-cost mechanical arrays of 3D-printed bistable elements whose shapes interact with wind to couple them one-way. Unlike earlier hydromechanical unidirectional arrays, our aeromechanical one-way arrays are simpler, easier to study, and exhibit a broader range of phenomena. Solitary waves or solitons propagate in one direction at speeds proportional to wind speeds. Periodic boundaries enable solitons to annihilate in pairs in arrays with an even number of elements...
February 2017: Chaos
https://www.readbyqxmd.com/read/28246663/steady-state-statistical-correlations-predict-bistability-in-reaction-motifs
#15
Suchana Chakravarty, Debashis Barik
Various cellular decision making processes are regulated by bistable switches that take graded input signals and convert them to binary all-or-none responses. Traditionally, a bistable switch generated by a positive feedback loop is characterized either by a hysteretic signal response curve with two distinct signaling thresholds or by characterizing the bimodality of the response distribution in the bistable region. To identify the intrinsic bistability of a feedback regulated network, here we propose that bistability can be determined by correlating higher order moments and cumulants (≥2) of the joint steady state distributions of two components connected in a positive feedback loop...
March 1, 2017: Molecular BioSystems
https://www.readbyqxmd.com/read/28245235/the-role-of-the-hes1-crosstalk-hub-in-notch-wnt-interactions-of-the-intestinal-crypt
#16
Sophie K Kay, Heather A Harrington, Sarah Shepherd, Keith Brennan, Trevor Dale, James M Osborne, David J Gavaghan, Helen M Byrne
The Notch pathway plays a vital role in determining whether cells in the intestinal epithelium adopt a secretory or an absorptive phenotype. Cell fate specification is coordinated via Notch's interaction with the canonical Wnt pathway. Here, we propose a new mathematical model of the Notch and Wnt pathways, in which the Hes1 promoter acts as a hub for pathway crosstalk. Computational simulations of the model can assist in understanding how healthy intestinal tissue is maintained, and predict the likely consequences of biochemical knockouts upon cell fate selection processes...
February 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28229148/uniform-and-janus-like-nanoparticles-in-contact-with-vesicles-energy-landscapes-and-curvature-induced-forces
#17
Jaime Agudo-Canalejo, Reinhard Lipowsky
Biological membranes and lipid vesicles often display complex shapes with non-uniform membrane curvature. When adhesive nanoparticles with chemically uniform surfaces come into contact with such membranes, they exhibit four different engulfment regimes as recently shown by a systematic stability analysis. Depending on the local curvature of the membrane, the particles either remain free, become partially or completely engulfed by the membrane, or display bistability between free and completely engulfed states...
February 23, 2017: Soft Matter
https://www.readbyqxmd.com/read/28219776/deactivation-in-the-posterior-mid-cingulate-cortex-reflects-perceptual-transitions-during-binocular-rivalry-evidence-from-simultaneous-eeg-fmri
#18
Abhrajeet V Roy, Keith W Jamison, Sheng He, Stephen A Engel, Bin He
Binocular rivalry is a phenomenon in which perception spontaneously shifts between two different images that are dichoptically presented to the viewer. By elucidating the cortical networks responsible for these stochastic fluctuations in perception, we can potentially learn much about the neural correlates of visual awareness. We obtained concurrent EEG-fMRI data for a group of 20 healthy human subjects during the continuous presentation of dichoptic visual stimuli. The two eyes' images were tagged with different temporal frequencies so that eye specific steady-state visual evoked potential (SSVEP) signals could be extracted from the EEG data for direct comparison with changes in fMRI BOLD activity associated with binocular rivalry...
February 20, 2017: NeuroImage
https://www.readbyqxmd.com/read/28213682/mathematical-modelling-of-cytokines-mmps-and-fibronectin-fragments-in-osteoarthritic-cartilage
#19
Michelle Baker, Bindi S Brook, Markus R Owen
Osteoarthritis (OA) is a degenerative disease which causes pain and stiffness in joints. OA progresses through excessive degradation of joint cartilage, eventually leading to significant joint degeneration and loss of function. Cytokines, a group of cell signalling proteins, present in raised concentrations in OA joints, can be classified into pro-inflammatory and anti-inflammatory groups. They mediate cartilage degradation through several mechanisms, primarily the up-regulation of matrix metalloproteinases (MMPs), a group of collagen-degrading enzymes...
February 17, 2017: Journal of Mathematical Biology
https://www.readbyqxmd.com/read/28208479/self-tuning-bistable-parametric-feedback-oscillator-near-optimal-amplitude-maximization-without-model-information
#20
David J Braun, Andrius Sutas, Sethu Vijayakumar
Theory predicts that parametrically excited oscillators, tuned to operate under resonant condition, are capable of large-amplitude oscillation useful in diverse applications, such as signal amplification, communication, and analog computation. However, due to amplitude saturation caused by nonlinearity, lack of robustness to model uncertainty, and limited sensitivity to parameter modulation, these oscillators require fine-tuning and strong modulation to generate robust large-amplitude oscillation. Here we present a principle of self-tuning parametric feedback excitation that alleviates the above-mentioned limitations...
January 2017: Physical Review. E
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