Spontaneous beating and synchronization of extensile active filament.

We simulate a semi-flexible active filament that exhibits spontaneous oscillations on clamping and show self-propulsion when left free. The activity on the filament relies on the nano-dimers distributed at regular intervals along the chain. With an emphasis on the spontaneous beating of a clamped filament, we demonstrate that the two competing forces necessary for oscillation are the elastic forces due to polymer rigidity and the active forces due to chemical activity. In addition, we also study the synchronization of two extensile filaments and the role played by non-local hydrodynamic interactions. We observe a phase lock scenario between the filaments during their synchronous motion.

Ring closure dynamics for a chemically active polymer.

The principles that underlie the motion of colloidal particles in concentration gradients and the propulsion of chemically-powered synthetic nanomotors are used to design active polymer chains. The active chains contain catalytic and noncatalytic monomers, or beads, at the ends or elsewhere along the polymer chain. A chemical reaction at the catalytic bead produces a self-generated concentration gradient and the noncatalytic bead responds to this gradient by a diffusiophoretic mechanism that causes these two beads to move towards each other. Because of this chemotactic response, the dynamical properties of these active polymer chains are very different from their inactive counterparts. In particular, we show that ring closure and loop formation are much more rapid than those for inactive chains, which rely primarily on diffusion to bring distant portions of the chain in close proximity. The mechanism presented in this paper can be extended to other chemical systems which rely on diffusion to bring reagents into contact for reactions to occur. This study suggests the possibility that synthetic systems could make use of chemically-powered active motion or chemotaxis to effectively carry out complex transport tasks in reaction dynamics, much like those that molecular motors perform in biological systems.

Readiness to Provide Antenatal Corticosteroids for Threatened Preterm Birth in Public Health Facilities in Northern India.

INTRODUCTION: In 2014, the Government of India (GOI) released operational guidelines on the use of antenatal corticosteroids (ACS) in preterm labor. However, without ensuring the quality of childbirth and newborn care at facilities, the use of ACS in low- and middle-income countries is potentially harmful. This study assessed the readiness to provide ACS at primary and secondary care public health facilities in northern India. METHODS: A cross-sectional study was conducted in 37 public health facilities in 2 districts of Haryana, India. Facility processes and program implementation for ACS delivery were assessed using pretested study tools developed from the World Health Organization (WHO) quality of care standards and WHO guidelines for threatened preterm birth. RESULTS: Key gaps in public health facilities' process of care to provide ACS for threatened preterm birth were identified, particularly concerning evidence-based practices, competent workforce, and actionable health information system. Emphasis on accurate gestational age estimation, quality of childbirth care, and quality of preterm care were inadequate. Shortage of trained staff was widespread, and a disconnect was found between knowledge and attitudes regarding ACS use. ACS administration was provided only at district or subdistrict hospitals, and these facilities did not uniformly record ACS-specific indicators. All levels lacked a comprehensive protocol and job aids for identifying and managing threatened preterm birth. CONCLUSIONS: ACS operational guidelines were not widely disseminated or uniformly implemented. Facilities require strengthened supervision and standardization of threatened preterm birth care. Facilities need greater readiness to meet required conditions for ACS use. Increasing uptake of a single intervention without supporting it with adequate quality of maternal and newborn care will jeopardize improvement in preterm birth outcomes. We recommend updating and expanding the existing GOI ACS operational guidelines to include specific actions for the safe and effective use of ACS in line with recent scientific evidence.

Coarse-grained simulations of an active filament propelled by a self-generated solute gradient.

A self-propelling semiflexible filament exhibits a variety of dynamical states depending on the flexibility and activity of the filament. Here we investigate the dynamics of such an active filament using a bead-spring model with the explicit hydrodynamic interactions. The activity in the filament is incorporated by inserting chemically active dimers at regular intervals along the chain. The chemical reactions at the catalytic bead of the dimer produces a self-generated concentration gradient and gives sufficient fuel to exhibit self-propulsion for the filament. Depending upon the rigidity and the configuration, the polymeric filament exhibits three distinct types of spontaneous motion, namely, rotational, snaking, and translational motion. The self-propulsion velocity of the filament for various rigidity and sizes has been calculated, and the factors affecting the propulsion are identified.