Indian Institute of Science Education and Research, Mohali

We study directed transport in a two-dimensional suspension of repulsively interacting colloids driven by a stochastic asymmetric piecewise-linear flashing ratchet using large-scale molecular dynamics simulations. The driving frequency and the ratchet asymmetry offer two independent ways of controlling the particle current, but they affect the suspension differently. At fixed asymmetry, the current shows a resonance with ratcheting frequency that is set by the collective relaxation dynamics of the interacting particles. The resulting increase in transport is accompanied by structural reorganization and by changes in the population of topological defects, showing density-dependent hexatic and solid-like states, with larger currents generally associated with weaker ordering.By contrast, at fixed frequency, changing the ratchet asymmetry mainly alters the strength of the directed bias and can significantly enhance the current while leaving the hexatic order largely unchanged. Near the equilibrium hexatic-melting regime, this makes it possible to generate substantial directed currents without strongly disrupting sixfold orientational order. These results show that frequency tuning couples transport to structural reorganization, whereas asymmetry tuning primarily controls transport leaving the structure largely unaltered, providing distinct and complementary routes for manipulating transport and order in driven colloidal suspensions.

Abstract Recent observations from the DESI survey have reignited the debate on the true nature of dark energy, challenging the standard model of cosmology. The results suggest a preference for dynamical dark energy rather than a constant. Several recent analyses of DESI data indicate that the universe’s expansion may not be accelerating in the way suggested by supernova based cosmology. Motivated by these studies, we investigated a tachyon type scalar field $$\phi $$ ϕ as a model for dark energy, assuming an exponential potential for the field and performed parameter estimation using MCMC techniques. Such a model offers solutions that have $$w\sim -1$$ w ∼ - 1 and are decelerating without requiring a phantom like equation of state (EoS). The present day value of EoS parameter is treated as a free parameter. However, for the reference model, we fix its present value to $$-1$$ - 1 . The analysis is carried out using Pantheon+ and BAO measurements from DESI. The results show that both types of datasets consistently predict a turnaround in the EoS, regardless of whether $$w_{\phi 0}$$ w ϕ 0 is treated as a free parameter or fixed to $$-1$$ - 1 . The corresponding deceleration parameter also exhibits a future turnaround for both datasets when $$w_{\phi 0}$$ w ϕ 0 is free. However, in the reference model with $$w_{\phi 0}=-1$$ w ϕ 0 = - 1 , the deceleration parameter instead approaches $$-1$$ - 1 asymptotically. A model comparison shows that the Pantheon+ dataset favors free $$w_{\phi 0}$$ w ϕ 0 , while BAO observations prefer $$w_{\phi 0} = -1$$ w ϕ 0 = - 1 . This indicates a disagreement in the future evolution predicted by the two datasets within the tachyon dark energy model.

We present an efficient one-pot transformation for the synthesis of unprecedented classes of cyclopropyl-fused allocolchicinoids through the discovery of a new reactivity pattern of sulfoxonium ylides. This hybrid strategy rationally manipulates the nucleophilic character of sulfur ylides to achieve the regio- and stereoselective construction of structurally intriguing allocolchicinoids bearing multiple stereocenters. Notably, this methodology represents the first general approach to sp3-rich dibenzocycloheptanes, including enantiomerically enriched variants. Furthermore, we have demonstrated the synthetic utility of this protocol in preparing various advanced intermediates pertinent to natural product synthesis and medicinal chemistry. Comprehensive biological studies have identified a potent analogue that disrupts microtubule organization and dynamics, leading to mitotic arrest and the consequent attenuation of influenza A virus infection.

Variational quantum algorithms are emerging as promising candidates for near-term practical applications of quantum information processors in the field of quantum chemistry. We implement a variational quantum deflation algorithm to calculate the excited-state energy of the H _2 molecule and experimentally demonstrate it on an NMR quantum simulator. We also develop a simulation of the energy calculation of the H _2 molecule using only a single qubit and verify the results on the same NMR quantum simulator. Our experimental results demonstrate that a single NMR qubit suffices to calculate the molecular energies of the H _2 molecule to the desired accuracy.

Ultrasmall bimetallic coinage nanoclusters are attractive platforms for drug delivery and chemical sensing because their electronic structure can be tuned by composition and surface functionalization. Here we use DFT, NCIs, and MD to examine how 2-(3-methylureido)acetic acid (MUA) binds to coinage clusters X6 and X4Y2 (X, Y = Ag, Au, Cu, Ni). Three binding motifs are considered, with the cluster approaching to the C--O (MUA1), COOH (MUA2), or NH site (MUA3). For all metals, adsorption is exothermic and strongest when cluster interacts with the carbonyl oxygen, with particularly large binding energies for Ni- and Au-containing systems such as Ag4Ni2MUA1, Cu4Ni2-MUA1 and Cu4Au2-MUA1. Changes in the frontier gap and the calculated recovery times point to composition-dependent conductivity and desorption kinetics, suggesting that these clusters can operate as reusable drug carriers and SERS-active sensing platforms. MD simulation on (111) metal slabs support clusterlevel results and confirm robust MUA adsorption at room temperature.