67 research outputs found
Liquid crystal films on curved surfaces: An entropic sampling study
The confining effect of a spherical substrate inducing anchoring (normal to
the surface) of rod-like liquid crystal molecules contained in a thin film
spread over it has been investigated with regard to possible changes in the
nature of the isotropic-to-nematic phase transition as the sample is cooled.
The focus of these Monte Carlo simulations is to study the competing effects of
the homeotropic anchoring due to the surface inducing orientational ordering in
the radial direction and the inherent uniaxial order promoted by the
intermolecular interactions. By adopting entropic sampling procedure, we could
investigate this transition with a high temperature precision, and we studied
the effect of the surface anchoring strength on the phase diagram for a
specifically chosen geometry. We find that there is a threshold anchoring
strength of the surface below which uniaxial nematic phase results, and above
which the isotropic fluid cools to a radially ordered nematic phase, besides of
course expected changes in the phase transition temperature with the anchoring
strength. In the vicinity of the threshold anchoring strength we observe a
bistable region between these two structures, clearly brought out by the
characteristics of the corresponding microstates constituting the entropic
ensemble.Comment: 14 pages, 5 figure
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Hypoxia sensing requires H<sub>2</sub>S-dependent persulfidation of olfactory receptor 78
Oxygen (O2) sensing by the carotid body is critical for maintaining cardiorespiratory homeostasis during hypoxia. Hydrogen sulfide (H2S) signaling is implicated in carotid body activation by low O2. Here, we show that persulfidation of olfactory receptor 78 (Olfr78) by H2S is an integral component of carotid body activation by hypoxia. Hypoxia and H2S increased persulfidation in carotid body glomus cells and persulfidated cysteine240 in Olfr78 protein in heterologous system. Olfr78 mutants manifest impaired carotid body sensory nerve, glomus cell, and breathing responses to H2S and hypoxia. Glomus cells are positive for GOlf, adenylate cyclase 3 (Adcy3) and cyclic nucleotide–gated channel alpha 2 (Cnga2), key molecules of odorant receptor signaling. Adcy3 or Cnga2 mutants exhibited impaired carotid body and glomus cell responses to H2S and breathing responses to hypoxia. These results suggest that H2S through redox modification of Olfr78 participates in carotid body activation by hypoxia to regulate breathing
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Construction of Electrochemical Sensor Based on Praseodymium Hexacyanoferrate Modified Graphite Electrode and Its Application for Cysteine Determination
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