The uncoupling limit of identical Hopf bifurcations with an application to perceptual bistability

We study the dynamics arising when two identical oscillators are coupled near a Hopf bifurcation where we assume a parameter $\epsilon$ uncouples the system at $\epsilon=0$. Using a normal form for $N=2$ identical systems undergoing Hopf bifurcation, we explore the dynamical properties. Matching the normal form coefficients to a coupled Wilson-Cowan oscillator network gives an understanding of different types of behaviour that arise in a model of perceptual bistability. Notably, we find bistability between in-phase and anti-phase solutions that demonstrates the feasibility for synchronisation to act as the mechanism by which periodic inputs can be segregated (rather than via strong inhibitory coupling, as in existing models). Using numerical continuation we confirm our theoretical analysis for small coupling strength and explore the bifurcation diagrams for large coupling strength, where the normal form approximation breaks down

Dietary and Nutritional Support in Gastrointestinal Diseases of the Upper Gastrointestinal Tract (I): Esophagus

The esophagus is the centerpiece of the digestive system of individuals and plays an essential role in transporting swallowed nutrients to the stomach. Diseases of the esophagus can alter this mechanism either by causing anatomical damage that obstructs the lumen of the organ (e.g., peptic, or eosinophilic stricture) or by generating severe motility disorders that impair the progression of the alimentary bolus (e.g., severe dysphagia of neurological origin or achalasia). In all cases, nutrient assimilation may be compromised. In some cases (e.g., ingestion of corrosive agents), a hypercatabolic state is generated, which increases resting energy expenditure. This manuscript reviews current clinical guidelines on the dietary and nutritional management of esophageal disorders such as severe oropharyngeal dysphagia, achalasia, eosinophilic esophagitis, lesions by caustics, and gastroesophageal reflux disease and its complications (Barrett’s esophagus and adenocarcinoma). The importance of nutritional support in improving outcomes is also highlighted

Conformally related massless fields in dS, AdS and Minkowski spaces

In this paper we write down the equation for a scalar conformally coupled field simultaneously for de Sitter (dS), anti-de Sitter (AdS) and Minkowski spacetime in d-dimensions. The curvature dependence appears in a very simple way through a conformal factor. As a consequence the process of curvature free limit, including wave functions limit and two-points functions, turns to be a straightforward issue. We determine a set of modes, that we call de Sitter plane waves, which become ordinary plane waves when the curvature vanishes.Comment: 7 pages, 1 figur

Wick ordering for coherent state quantization in 1+1 de Sitter space

We show that the coherent state quantization of massive particles in 1+1 de Sitter space exhibits an ordering property: There exist some classical observables $A$ and $A^*$ such that $O_{A^{*p}}O_{A^q}=O_{A^{*p} A^q}$ $p, q \in \Z$, where $O_A$ is the quantum observable corresponding to the classical observable $A$.Comment: Accepted in Phys. Lett.

Dynamic force spectroscopy of DNA hairpins. II. Irreversibility and dissipation

We investigate irreversibility and dissipation in single molecules that cooperatively fold/unfold in a two state manner under the action of mechanical force. We apply path thermodynamics to derive analytical expressions for the average dissipated work and the average hopping number in two state systems. It is shown how these quantities only depend on two parameters that characterize the folding/unfolding kinetics of the molecule: the fragility and the coexistence hopping rate. The latter has to be rescaled to take into account the appropriate experimental setup. Finally we carry out pulling experiments with optical tweezers in a specifically designed DNA hairpin that shows two-state cooperative folding. We then use these experimental results to validate our theoretical predictions.Comment: 28 pages, 12 figure

Repo-Man/protein phosphatase 1 SUMOylation mediates binding to lamin A and serine 22 dephosphorylation

© 2022 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License. http://creativecommons.org/licenses/by/4.0/Lamin A phosphorylation/de-phosphorylation is an important process during cells division as it allows for nuclear envelope (NE) disassembly at mitotic entry and its re-assembly during mitotic exit. Several kinases have been identified as responsible for these phosphorylations, but no protein phosphatase has been implicated in their reversal. One of the mitotic phosphosites in lamin A responsible for its dynamic behaviour is serine 22 (S22) which is de-phosphorylated during mitotic exit. Recent evidence has also linked the nuclear pool of lamin A S22ph in interphase to gene expression regulation. Previous work suggested that the phosphatase responsible for lamin A S22 de-phosphorylation is chromatin bound and interacts with lamin A via SUMO-SIM motives. We have previously reported that Repo-Man/protein phosphatase 1 (PP1) is a chromatin-associated phosphatase that regulates NE reformation. Here we propose that Repo-Man/PP1 phosphatase mediates lamin A S22 de-phosphorylation. We indeed show that depletion of Repo-Man leads to NE defects, causes hyperphosphorylation of lamin A S22 that can be rescued by a wild-type but not a SUMOylation-deficient mutant. Lamin A and Repo-Man interact in vivo and in vitro, and the interaction is mediated by SUMOylation. Moreover, the localization of Repo-Man/PP1 to the chromatin is essential for lamin A S22 de-phosphorylation.Peer reviewedFinal Published versio