79 research outputs found
Quantum multifractality as a probe of phase space in the Dicke model
We study the multifractal behavior of coherent states projected in the energy
eigenbasis of the spin-boson Dicke Hamiltonian, a paradigmatic model describing
the collective interaction between a single bosonic mode and a set of two-level
systems. By examining the linear approximation and parabolic correction to the
mass exponents, we find ergodic and multifractal coherent states and show that
they reflect details of the structure of the classical phase space, including
chaos, regularity, and features of localization. The analysis of
multifractality stands as a sensitive tool to detect changes and structures in
phase space, complementary to classical tools to investigate it. We also
address the difficulties involved in the multifractal analyses of systems with
unbounded Hilbert spacesComment: 14 pages, 7 figure
Association among Obesity-Related Anthropometric Phenotypes: Analyzing Genetic and Environmental Contribution
Exenatide regulates pancreatic islet integrity and insulin sensitivity in the nonhuman primate baboon Papio hamadryas.
The glucagon-like peptide-1 receptor agonist exenatide improves glycemic control by several and not completely understood mechanisms. Herein, we examined the effects of chronic intravenous exenatide infusion on insulin sensitivity, β cell and α cell function and relative volumes, and islet cell apoptosis and replication in nondiabetic nonhuman primates (baboons). At baseline, baboons received a 2-step hyperglycemic clamp followed by an l-arginine bolus (HC/A). After HC/A, baboons underwent a partial pancreatectomy (tail removal) and received a continuous exenatide (n = 12) or saline (n = 12) infusion for 13 weeks. At the end of treatment, HC/A was repeated, and the remnant pancreas (head-body) was harvested. Insulin sensitivity increased dramatically after exenatide treatment and was accompanied by a decrease in insulin and C-peptide secretion, while the insulin secretion/insulin resistance (disposition) index increased by about 2-fold. β, α, and δ cell relative volumes in exenatide-treated baboons were significantly increased compared with saline-treated controls, primarily as the result of increased islet cell replication. Features of cellular stress and secretory dysfunction were present in islets of saline-treated baboons and absent in islets of exenatide-treated baboons. In conclusion, chronic administration of exenatide exerts proliferative and cytoprotective effects on β, α, and δ cells and produces a robust increase in insulin sensitivity in nonhuman primates
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