Collective phenomenon in active systems with multichannel perception

Active matter systems show remarkable self-organization across different scales, from micron-size bacteria to meter-size birds. Examples extend beyond biological systems such as flocks of birds, animal herds, and bacterial biofilms, to artificial systems like active colloids and swarms of microrobots. The global patterns and structures often occur purely based on local interactions among neighbors. Emergent properties and functions go beyond what individual components can achieve on their own. Some important features of such systems are active non-equilibrium behavior, non-reciprocal interactions, information processing, and self-steering. In our model of intelligent active Brownian particles (iABPs), information about the position and orientation of neighboring particles obtained through directed visual and isotropic perception, respectively, is used to adjust the propulsion direction. We start with the role of visual perception, where an iABP can sense the instantaneous position of neighboring iABPs within a vision cone (VC) and vision range. Several non-equilibrium structures like motile worms, worm-aggregate coexistence, aggregates, dilute-gas, and compact or dispersed cluster phases are obtained, depending on the system parameters. The maneuverability due to visual signal, activity, density, vision angle, and vision range determine the location and extent of these phases in the phase diagram. The analysis of the particle’s mean-square displacement shows ABP-like dynamics for dilute systems and the worm phase. We then delve into the interplay of visual perception and alignment interactions. The maneuverability due to visual signal and polar alignment determines the selforganization. Various non-equilibrium dynamical aggregates – like motile worm-like swarms and milling, and compact or dispersed clusters – are obtained. Strong polar alignment favors elongated worm-like swarms, which show super-diffusive motion over a much longer time range than individual ABPs. These swarms also show highly polarised and persistent motion. The behavior of particles for changing maneuverability and vision angle is very similar, and we can capture it by effective maneuverability. Higher maneuverability favors the formation of compact clusters. Milling rings, where swarms bite their own tail, emerge for balanced polar to visual maneuverability, intermediate activity, and vision angles. The study of binary mixtures of iABPs interacting with visual perception shows several intriguing patterns such as dimeric, tetrameric, multimeric phase, hopping, prey-predator behavior, and honeycomb lattice structures. The structures obtained depend on the sign and magnitude of visual maneuverability, activity, vision angles, vision range, and the number of these two types of particles. For opposite attractive and similar repulsive interaction of particles, i.e., particles of type-A are mutually attracted to particles of type-B but repelled by other particles of type-A (similarly for type-B), at nearly the same density, we observe an interesting behavior where an unpaired particle (known as a hopper) shuttles between pairs composed of particles from both types. As the density increases, the average hopping distance covered by these particles decreases. When particles of type-A are attracted to particles of type-B, while particles of type-B simultaneously repel particles of type-A, an intriguing dynamic similar to a prey-predator relationship emerges between the two types. Both the fraction of time spent by prey (type-B) in the vicinity of a predator (type-A), as well as the prey distribution around a predator, indicates focused vision angle \pi/4 and higher steering maneuverability of the predator towards prey is highly effective for the predator to reach prey. We also investigate systems where type-B particles steer toward each other, while type-A particles tend to steer away from other type-B as well as type-A particles; which display the formation of honeycombtype lattices. The average size of the cluster within the honeycomb lattice structure depends upon the vision range and the structure becomes more distinct as the vision range increases. Finally, we consider assembles of actively avoiding particles having visual clues. This model mimics some features of pedestrian behaviors like interpersonal distancing in a dense crowd. A high value of maneuverability ! and a low value of activity Pe favors interpersonal distancing for high vision angles, where the average minimum distance scales Pe^3/2/\Gamma. Also, the average distance to the nearest particles decreases with number density. A higher activity leads to less exposure time where two particles are in close vicinity. For a more focused vision and beyond certain maneuverability, we obtain band-like aggregates that move ballistically over a long time and show highly persistent motion. In summary, our results help to understand the collective behavior of cognitive self-propelled particles, like animal herds, swarming bacteria, and non-reciprocally interacting prey-predator systems like fish schools, and provide new insights for the design of micro-robotic swarms. Our model can also be employed to study pedestrian behavior in semi-dense crowds

Collective behavior of self-steering active particles with velocity alignment and visual perception

The formation and dynamics of swarms is widespread in living systems, from bacterial biofilms to schools of fish and flocks of birds. We study this emergent collective behavior via agent-based simulations in a model of active Brownian particles with visual-perception-based steering and alignment interactions. The dynamics, shape, and internal structure of the emergent aggregates, clusters, and swarms of these intelligent active Brownian particles are determined by the maneuverabilities Ω_{v} and Ω_{a}, quantifying the steering based on the visual signal and polar alignment, respectively, the propulsion velocity, characterized by the Péclet number Pe, the vision angle θ, and the orientational noise. Various nonequilibrium dynamical aggregates—like motile wormlike swarms and milling, and close-packed or dispersed clusters—are obtained. Small vision angles imply the formation of small clusters, while large vision angles lead to more complex clusters. In particular, a strong polar-alignment maneuverability Ω_{a} favors elongated wormlike swarms, which display superdiffusive motion over a much longer time range than individual ABPs, whereas a strong vision-based maneuverability Ω_{v} favors compact, nearly immobile aggregates. Swarm trajectories show long persistent directed motion, interrupted by sharp turns. Milling rings, where a wormlike swarm bites its own tail, emerge for an intermediate regime of Pe and vision angles. Our results offer insights into the behavior of animal swarms and provide design criteria for swarming microbots

Synergistic anticandidal activity of pure polyphenol curcumin I in combination with azoles and polyenes generates reactive oxygen species leading to apoptosis

We have shown previously that pure polyphenol curcumin I (CUR-I) shows antifungal activity against Candida species. By employing the chequerboard method, filter disc and time-kill assays, in the present study we demonstrate that CUR-I at non-antifungal concentration interacts synergistically with azoles and polyenes. For this, pure polyphenol CUR-I was tested for synergy with five azole and two polyene drugs -fluconazole (FLC), miconazole, ketoconazole (KTC), itraconazole (ITR), voriconazole (VRC), nystatin (NYS) and amphotericin B (AMB) - against 21 clinical isolates of Candida albicans with reduced antifungal sensitivity, as well as a drug-sensitive laboratory strain. Notably, there was a 10-35-fold drop in the MIC80 values of the drugs when CUR-I was used in combination with azoles and polyenes, with fractional inhibitory concentration index (FICI) values ranging between 0.09 and 0.5. Interestingly, the synergistic effect of CUR-I with FLC and AMB was associated with the accumulation of reactive oxygen species, which could be reversed by the addition of an antioxidant such as ascorbic acid. Furthermore, the combination of CUR-I and FLC/AMB triggered apoptosis that could also be reversed by ascorbic acid. We provide the first evidence that pure CUR-I in combination with azoles and polyenes represents a novel therapeutic strategy to improve the activity of common antifungals

Prioritization of Socio-Ecological Indicators for Adaptation Action in Pauri District of Western Himalaya

Socio-ecological systems have increasingly faced climate-change impacts, which have adversely affected the lives and property of inhabitants. The present study aims to prioritize adaptation actions along an altitudinal gradient (1801 m asl (Zone C)) in Pauri District, Uttarakhand. A cross-sectional survey research design was employed to prioritize adaptation action from 545 randomly selected households in 91 villages. A multi-disciplinary bottom-up indicator-based approach was applied to identify and normalize sectoral indicators, and PCA was used to prioritize sectoral indicators. Adaptation actions were designed with prioritized sectoral indicators along the altitude and stakeholder consultations. The prioritized indicators varied along the altitudinal gradient, and more than 50% of the indicators for the same sector were different along an altitudinal gradient. Sectoral adaptation planning along the altitude is pertinent in the mountain because they contribute to adaptation planning differently. Additionally, the mainstreaming of adaptation strategies with national and regional development measures is also required. Finally, cross-sectoral resource management that combines users, planners, scientists, and policymakers should be formulated along the altitude within the district. These findings contribute to minimizing the gap between policy/program fabrication and local requirements. The evidence-based valuable knowledge for decision-makers could enable Himalayan communities to adapt to the impacts of climate change effectively. Adaptation planning is also critical for designing adaptation projects for the Green Climate Fund, Adaptation Fund, and funds from multilateral and bilateral agencies. It will facilitate Nationally Determined Contributions, which aims to adapt better to climate change by enhancing investments in development programs in vulnerable sectors

Pharmaceutical compounds in drinking water

Pharmaceutical products and their wastes play a major role in the degradation of environment. These drugs have positive as well as negative consequences on different environmental components including biota in different ways. Many types of pharmaceutical substances have been detected with significant concentrations through various advanced instrumental techniques in surface water, subsurface water, ground water, domestic waste water, municipal waste water and industrial effluents. The central as well as state governments in India are providing supports by creating excise duty free zones to promote the pharmaceutical manufacturers for their production. As a result, pharmaceutical companies are producing different types of pharmaceutical products at large scale and also producing complex non-biodegradable toxic wastes byproducts and releasing untreated or partially treated wastes in the environment in absence of strong regulations. These waste pollutants are contaminating all types of drinking water sources. The present paper focuses on water quality pollution by pharmaceutical pollutants, their occurrences, nature, metabolites and their fate in the environment