Heat current magnification in classical and quantum spin networks.

We investigate heat current magnification (CM) due to asymmetry in the number of spins in two-branched classical as well as quantum spin systems that are kept between two heat baths at different temperatures. We study the classical Ising-like spin models using Q2R and Creutz cellular automaton dynamics. We show that just the difference in the number of spins is not enough and some other source of asymmetry like unequal spin-spin interaction strengths in the upper and lower branches is required for heat CM.

Heat rectification by two qubits coupled with Dzyaloshinskii-Moriya interaction.

We investigate heat rectification in a two-qubit system coupled via the Dzyaloshinskii-Moriya (DM) interaction. We derive analytical expressions for heat currents and thermal rectification and provide possible physical mechanisms behind the observed results. We show that the anisotropy of DM interaction in itself is insufficient for heat rectification, and some other form of asymmetry is needed.

Moving towards "mobile warehouse": Last-mile logistics during COVID-19 and beyond.

Supply chains in general and last-mile logistics in particular, have been disrupted due to COVID-19. Though several innovative last-mile logistics solutions have been proposed in the past, they possess certain limitations, especially during COVID-19 motivating the need for an alternative last-mile logistics solution. We present a review of literature related to last-mile logistics and supply chain disruptions to identify the limitations of existing last-mile delivery practices during COVID-19.

Underdamped active Brownian heat engine.

Active Brownian engines rectify energy from reservoirs composed of self-propelling nonequilibrium molecules into work. We consider a class of such engines based on an underdamped Brownian particle trapped in a power-law potential. The energy they transform has thermodynamic properties of heat only if the nonequilibrium reservoir can be assigned a suitable effective temperature consistent with the second law and thus yielding an upper bound on the engine efficiency.

Rectification of twitching bacteria through narrow channels: A numerical simulations study.

Bacteria living on surfaces use different types of motility mechanisms to move on the surface in search of food or to form microcolonies. Twitching is one such form of motility employed by bacteria such as Neisseria gonorrhoeae, in which the polymeric extensions known as type IV pili mediate its movement. Pili extending from the cell body adhere to the surface and pull the bacteria by retraction.

Using queue to signal quality in primary care: The need for further empirical investigation.

In recent times, signalling quality via queues for generic services has received significant attention. However, the literature till date on primary care services has focussed on the optimal speed-quality trade-off to ensure higher service times and lower waiting times for the patients. Borrowing from the queue management literature on generic services, we aim to understand whether the hypothesis that queue is a signal of physician's quality is reasonable.

Twitching motility of bacteria with type-IV pili: Fractal walks, first passage time, and their consequences on microcolonies.

A human pathogen, Neisseria gonorrhoeae (NG), moves on surfaces by attaching and retracting polymeric structures called Type IV pili. The tug-of-war between the pili results in a two-dimensional stochastic motion called twitching motility. In this paper, with the help of real-time NG trajectories, we develop coarse-grained models for their description.

Two coupled, driven Ising spin systems working as an engine.

Miniaturized heat engines constitute a fascinating field of current research. Many theoretical and experimental studies are being conducted that involve colloidal particles in harmonic traps as well as bacterial baths acting like thermal baths. These systems are micron-sized and are subjected to large thermal fluctuations.

Bacterial twitching motility is coordinated by a two-dimensional tug-of-war with directional memory.

Type IV pili are ubiquitous bacterial motors that power surface motility. In peritrichously piliated species, it is unclear how multiple pili are coordinated to generate movement with directional persistence. Here we use a combined theoretical and experimental approach to test the hypothesis that multiple pili of Neisseria gonorrhoeae are coordinated through a tug-of-war.

Modeling stochastic gene expression in growing cells.

Gene expression is an inherently noisy process. Fluctuations arise at many points in the expression of a gene, as all the salient reactions such as transcription, translation, and mRNA degradation are stochastic processes. The fluctuations become important when the cellular copy numbers of the relevant molecules (mRNA or proteins) are low.

Energy current magnification in coupled oscillator loops.

Motivated by studies on current magnification in quantum mesoscopic systems, we consider sound and heat transmission in classical models of oscillator chains. A loop of coupled oscillators is connected to two leads through which one can either transmit monochromatic waves or white-noise signal from heat baths. We look for the possibility of current magnification in this system due to some asymmetry introduced between the two arms in the loop.

Cooling classical particles with a microcanonical Szilard engine.

The possibility of extracting energy from a system in a cyclic process is discussed. We present an explicit example where a system, initially prepared in a microcanonical state, is able to perform such an operation. The example is similar to the Szilard engine, but the microcanonical initial condition allows one to design a protocol where measurement is not necessary.

Driving particle current through narrow channels using a classical pump.

We study a symmetric exclusion process in which the hopping rates at two chosen adjacent sites vary periodically in time and have a relative phase difference. This mimics a colloidal suspension subjected to external time-dependent modulation of the local chemical potential. The two special sites act as a classical pump by generating an oscillatory current with a nonzero dc value whose direction depends on the applied phase difference.

Two simple models of classical heat pumps.

Motivated by recent studies of models of particle and heat quantum pumps, we study similar simple classical models and examine the possibility of heat pumping. Unlike many of the usual ratchet models of molecular engines, the models we study do not have particle transport. We consider a two-spin system and a coupled oscillator system which exchange heat with multiple heat reservoirs and which are acted upon by periodic forces.

Work distribution functions for hysteresis loops in a single-spin system.

We compute the distribution of the work done in driving a single Ising spin with a time-dependent magnetic field. Using Glauber dynamics we perform Monte Carlo simulations to find the work distributions at different driving rates. We find that in general the work distributions are broad with a significant probability for processes with negative dissipated work.

Patterns in abundance and diversity of faecally dispersed parasites of tiger in Tadoba National Park, central India.

Background: Importance of parasites in ecological and evolutionary interactions is being increasingly recognized. However, ecological data on parasites of important host species is still scanty. We analyze the patterns seen in the faecal parasites of tigers in the Tadoba National Park, India, and speculate on the factors and processes shaping the parasite community and the possible implications for tiger ecology.