Molecular Dynamics of Polyisoprene/Polystyrene Oligomer Blends: The role of self-concentration and fluctuations on blend dynamics

The effect of self-concentration and intermolecular packing on the dynamics of polyisoprene (PI)/polystyrene (PS) blends is examined by extensive atomistic simulations. Direct information on local structure of the blend system allows a quantitative calculation of self- and effective composition terms at various length scales that are introduced to proposed models of blend dynamics. Through a detailed statistical analysis, the full distribution of relaxation times associated with reorienation of carbon-hydrogen bonds was extracted and compared to literature experimental data. A direct relation between relaxation times and local effective composition is found. Following an implementation of a model involving local composition as well as concentration fluctuations the relevant length scales characterizing the segmental dynamics of both components were critically examined. For PI the distribution of times becomes narrower for the system with the lowest PS content and then broadens as more PS is added. This is in contrast to the slow component (PS), where an extreme breadth is found for relaxation times in the 25/75 system prior to narrowing as we increase PI concentration. The chain dynamics was directly quantified by diffusion coefficients as well as the terminal (maximum) relaxation time of each component in the mixed state. Strong coupling between the friction coefficients of the two components was predicted that leads to very similar chain dynamics for PI and PS, particularly for high concentrations of PI. We anticipate this finding to the rather short oligomers (below the Rouse regime) studied here as well as to the rather similar size of PI and PS chains. The ratio of the terminal to the segmental relaxation time, τterm/τseg,c, presents a clear qualitative difference for the constituents: for PS the above ratio is almost independent of blend composition and very similar to the pure state. In contrast, for PI this ratio depends strongly on the composition of the blend; i.e. the terminal relaxation time of PI increases more than its segmental relaxation time, as the concentration of PS increases, resulting into a larger terminal/segmental ratio. We explain this disparity, based on the different length scales characterizing dynamics. The relevant length for the segmental dynamics of PI is about 0.4-0.6 nm, smaller than chain dimensions which are expected to characterize terminal dynamics, whereas for PS associated length scales are similar (about 0.7-1.0 nm) rendering a uniform change with mixing

Directed Search with Multiple Job Applications

We develop an equilibrium directed search model of the labor market where workers can simultaneously apply for multiple jobs. The main result is that all equilibria exhibit wage dispersion despite the fact that workers and firms are homogeneous. Wage dispersion is driven by the simultaneity of application choice. Risk-neutral workers apply for both ‘safe’ and ‘risky’ jobs. The former yield a high probability of a job offer, but for low pay, and act as a fallback option; the latter provide with higher potential payoff, but are harder to get. Furthermore, the density of posted wages is decreasing, consistent with stylized facts. Unlike most directed search models, the equilibria are not constrained efficient.

Use of Sodium–Glucose Cotransporter 2 (SGLT-2) Inhibitors Beyond Diabetes: On the Verge of a Paradigm Shift?

The sodium–glucose co-transporter 2 (SGLT2) inhibitors have proven effective in glycemia control in patients with type 2 diabetes (T2D) by increasing urinary glucose excretion. However, the beneficial effects of SGLT2 inhibition extend beyond glycemic control, with new studies demonstrating beneficial effects that lead to improved cardiovascular (CV) (cardioprotection) and renal outcomes (renoprotection) in patients with T2D. Pivotal CV outcomes trials have demonstrated a 27-35% reduction in heart failure (HF) hospitalizations in patients with T2D. Importantly, a variety of pleiotropic effects of these new agents have been identified that include, but are not limited to, anti-atherosclerotic, anti-inflammatory, and anti-oxidant effects, decreased vascular stiffness and improved endothelial function, weight loss, reduction in sympathetic activity and in cardiac arrhythmogenesis. Ongoing studies are investigating these actions in patients with and without diabetes. Such results, if positive, may lead to a paradigm shift in the management of CV, renal and even other diseases beyond diabetes. Rhythmos 2020;15(1):67-71

Hybrid Heart Failure Treatment

A case of refractory heart failure (HF) is presented in a 64-year-old gentleman with ischemic cardiomyopathy and severe left ventricular dysfunction, who availed himself of currently available hybrid HF treatment, like optimal medical treatment, electrical and interventional therapies comprising drugs, an implantable cardiac resynchronization therapy defibrillator (CRT-D) effected via alternate route (middle cardiac vein) for left ventricular lead placement combined with percutaneous mitral valve therapy (MitraClip) that prolonged his life to ~10 years. Rhythmos 2021; 16(1):99-101

Directed Search with Multiple Job Applications

We develop an equilibrium directed search model of the labor market where workers can simultaneously apply for multiple jobs. The main result is that all equilibria exhibit wage dispersion despite the fact that workers and firms are homogeneous. Wage dispersion is driven by the simultaneity of application choice. Risk-neutral workers apply for both ‘safe’ and ‘risky’ jobs. The former yield a high probability of a job offer, but for low pay, and act as a fallback option; the latter provide with higher potential payoff, but are harder to get. Furthermore, the density of posted wages is decreasing, consistent with stylized facts. Unlike most directed search models, the equilibria are not constrained efficient

Tracking Skin-Colored Objects in Real-Time

We present a methodology for tracking multiple skin-colored objects in a monocular image sequence. The proposed approach encompasses a collection of techniques that allow the modeling, detection and temporal association of skincolored objects across image sequences. A non-parametric model of skin color is employed. Skin-colored objects are detected with a Bayesian classifier that is bootstrapped with a small set of training data and refined through an off-line iterative training procedure. By using on-line adaptation of skin-color probabilities the classifier is able to cope with considerable illumination changes. Tracking over time is achieved by a novel technique that can handle multiple objects simultaneously. Tracked objects may move in complex trajectories, occlude each other in the field of view of a possibly moving camera and vary in number over time. A prototype implementation of the developed system operates on 320x240 live video in real time (28Hz), running on a conventional Pentium IV processor. Representative experimental results from the application of this prototype to image sequences are also presented. 1