Association behavior of binary polymer mixtures under elongational flow

The influence of elongational flow on the association behavior of binary mixtures of functionalized polymers capable of forming single reversible orientationally dependent bonds, such as hydrogen bonds, is studied analytically. Applying a mean-field approach with an external potential representing the effect of the elongational flow, the orientation distribution functions for the dumbbell model and the freely jointed model of a polymer chain were obtained. Two opposite factors determine the association of “linear” diblock copolymerlike chains: the unfavorable extra stretching under flow of associated polymer chains and the favorable orientation of the chains (segments) along the flow direction. The former dominates and the fraction of associated “linear” chains decreases with increasing flow rate. For mixtures of polymers which are capable of forming associated T-chains, the association also decreases, however, more slowly, and this time due to unfavorable orientational effects. If the formation of associated linear and T-polymers as well as complex linear/T-polymers is possible, a strong preference for the formation of associated T-chains is found. At high flow rates any type of association becomes unfavorable

Measurement Properties and Implementation of a Checklist to Assess Leadership Skills during Interdisciplinary Rounds in the Intensive Care Unit

The implementation of interdisciplinary teams in the intensive care unit (ICU) has focused attention on leadership behavior. A daily recurrent situation in ICUs in which both leadership behavior and interdisciplinary teamwork are integrated concerns the interdisciplinary rounds (IDRs). Although IDRs are recommended to provide optimal interdisciplinary and patient-centered care, there are no checklists available for leading physicians. We tested the measurement properties and implementation of a checklist to assess the quality of leadership skills in interdisciplinary rounds. The measurement properties of the checklist, which included 10 essential quality indicators, were tested for interrater reliability and internal consistency and by factor analysis. The interrater reliability among 3 raters was good (κ, 0.85) and the internal consistency was acceptable (α, 0.74). Factor analysis showed all factor loadings on 1 domain (>0.65). The checklist was further implemented during videotaped IDRs which were led by senior physicians and in which 99 patients were discussed. Implementation of the checklist showed a wide range of “no” and “yes” scores among the senior physicians. These results may underline the need for such a checklist to ensure tasks are synchronized within the team

Proving Craig and Lyndon Interpolation Using Labelled Sequent Calculi

We have recently presented a general method of proving the fundamental logical properties of Craig and Lyndon Interpolation (IPs) by induction on derivations in a wide class of internal sequent calculi, including sequents, hypersequents, and nested sequents. Here we adapt the method to a more general external formalism of labelled sequents and provide sufficient criteria on the Kripke-frame characterization of a logic that guarantee the IPs. In particular, we show that classes of frames definable by quantifier-free Horn formulas correspond to logics with the IPs. These criteria capture the modal cube and the infinite family of transitive Geach logics

Strain-induced kinetics of intergrain defects as the mechanism of slow dynamics in the nonlinear resonant response of humid sandstone bars

A closed-form description is proposed to explain nonlinear and slow dynamics effects exhibited by sandstone bars in longitudinal resonance experiments. Along with the fast subsystem of longitudinal nonlinear displacements we examine the strain-dependent slow subsystem of broken intergrain and interlamina cohesive bonds. We show that even the simplest but phenomenologically correct modelling of their mutual feedback elucidates the main experimental findings typical for forced longitudinal oscillations of sandstone bars, namely, (i) hysteretic behavior of a resonance curve on both its up- and down-slopes, (ii) linear softening of resonant frequency with increase of driving level, and (iii) gradual recovery (increase) of resonant frequency at low dynamical strains after the sample was conditioned by high strains. In order to reproduce the highly nonlinear elastic features of sandstone grained structure a realistic non-perturbative form of strain potential energy was adopted. In our theory slow dynamics associated with the experimentally observed memory of peak strain history is attributed to strain-induced kinetic changes in concentration of ruptured inter-grain and inter-lamina cohesive bonds causing a net hysteretic effect on the elastic Young's modulus. Finally, we explain how enhancement of hysteretic phenomena originates from an increase in equilibrium concentration of ruptured cohesive bonds that are due to water saturation.Comment: 5 pages, 3 figure