Computer simulations of entropic cohesion in reversibly crosslinked polymers.

Reversibly crosslinked polymer networks - polymer networks that can undergo bond association and dissociation reactions - rearrange their structures while maintaining their overall integrity, thus resulting in unique properties such as self-healing, reprocessability, shape memory and adaptability. Here, we show that the introduction of crosslinks, whether reversible or permanent, directly impacts the equilibrium polymer density and hence the material's surface tension. For a limiting case where the bonds are the same size as the polymer chain bonds, simulations, Flory hypotheses and thermodynamic calculations show that the crosslinks induce an increased entropic cohesion in the liquid.

The effect of phlebotomy and placement of an intravenous catheter on plasma catecholamine and serum copeptin concentrations.

Objectives: Limited data are available on the hormonal response of children to venepuncture or intravenous cannulation (IVC). Catecholamines [epinephrine (E) and norepinephrine (NE)] have been traditionally recognized as stress hormones. Copeptin, the carboxyl-terminus of the arginine vasopressin (AVP) precursor peptide, is also a known marker for stressful stimuli, including myocardial infarction, critical illness, and sepsis.

Copeptin Stimulation by Combined Intravenous Arginine and Oral LevoDopa/Carbidopa in Healthy Short Children and Children with the Polyuria-Polydipsia Syndrome.

Introduction: Stimulated copeptin may provide an alternative to water deprivation testing (WDT) in the evaluation of polyuria-polydipsia syndrome (PPS). Though best studied, arginine stimulation alone produces a modest copeptin response in children. We investigated the effectiveness of the arginine + LevoDopa/Carbidopa stimulation test (ALD-ST) for copeptin.