Ordering kinetics and steady states of XY-model with ferromagnetic and nematic interaction.

Previous studies on the generalized XY model have concentrated on the equilibrium phase diagram and the equilibrium nature of distinct phases under varying parameter conditions. We direct our attention towards examining the system's evolution towards equilibrium states across different parameter values, specifically by varying the relative strengths of ferromagnetic and nematic interactions. We study the kinetics of the system, using the temporal annihilation of defects at varying temperatures and its impact on the coarsening behavior of the system. For both pure polar and pure nematic systems, we observe temperature-dependent decay of the exponent, leading to a decelerated growth of domains within the system. At parameter values where both ferromagnetic and nematic interactions are simultaneously present, we show a phase diagram highlighting three low-temperature phases-polar, nematic, and coexistence-along- side a high-temperature disordered phase. Our study provides valuable insights into the complex interplay of interactions, offering a comprehensive understanding of the system's behavior during its evolution towards equilibrium.

Synchronized rotations of active particles on chemical substrates.

Many microorganisms use chemical 'signaling' - a quintessential self-organizing strategy in non-equilibrium - that can induce spontaneous aggregation and coordinated motion. Using synthetic signaling as a design principle, we construct a minimal model of active Brownian particles (ABPs) having soft repulsive interactions on a chemically quenched patterned substrate. The interplay between chemo-phoretic interactions and activity is numerically investigated for a proposed variant of the Keller-Segel model for chemotaxis. Such competition not only results in a chemo-motility-induced phase-separated state, but also results in a new cohesive clustering phase with synchronized rotations. Our results suggest that rotational order can emerge in systems by virtue of activity and repulsive interactions alone without an explicit alignment interaction. These rotations can also be exploited by designing mechanical devices that can generate reorienting torques using active particles.

Prenatal air pollution exposure in relation to the telomere-mitochondrial axis of aging at birth: A systematic review.

BACKGROUND: Telomere length (TL) and mitochondrial DNA (mtDNA) are central markers of vital biological mechanisms, including cellular aging. Prenatal air pollution exposure may impact molecular markers of aging leading to adverse health effects. OBJECTIVE: To perform a systematic review on human population-based studies investigating the association between prenatal air pollution exposure and TL or mtDNA content at birth. METHODOLOGY: Searches were undertaken on PubMed and Web of Science until July 2023. The framework of the review was based on the PRISMA-P guidelines. RESULTS: Nineteen studies studied prenatal air pollution and TL or mtDNA content at birth. Studies investigating TL or mtDNA content measured at any other time or did not evaluate prenatal air pollution were excluded. Twelve studies (including 4381 participants with study sample range: 97 to 743 participants) investigated newborn TL and eight studies (including 3081 participants with study sample range: 120 to 743 participants) investigated mtDNA content at birth. Seven studies focused on particulate matter (PM2.5) exposure and newborn TL of which all, except two, showed an inverse association in at least one of the gestational trimesters. Of the eight studies on mtDNA content, four focused on PM2.5 air pollution with two of them reporting an inverse association. For PM2.5 exposure, observations on trimester-specific effects were inconsistent. Current literature showing associations with other prenatal air pollutants (including nitrogen oxides, sulfur dioxide, carbon monoxide and ozone) is inconsistent. CONCLUSION: This review provides initial evidence that prenatal PM2.5 exposure impacts the telomere-mitochondrial axis of aging at birth. The current evidence did not reveal harmonious observations for trimester-specific associations nor showed consistent effects of other air pollutants. Future studies should elucidate the specific contribution of prenatal exposure to pollutants other than PM in relation to TL and mtDNA content at birth, and the potential later life health consequences.

Phase separation of passive particles in active liquids.

The transport properties of colloidal particles in active liquids have been studied extensively. It has led to a deeper understanding of the interactions between passive and active particles. However, the phase behavior of colloidal particles in active media has received little attention. Here, we present a combined experimental and numerical investigation of passive colloids dispersed in suspensions of active particles. Our study reveals dynamic clustering of colloids in active media due to an interplay of activity and attractive effective potential between the colloids. The strength of the effective potential is set by the size ratio of passive particles to the active ones. As the relative size of the passive particles increases, the effective potential becomes stronger and the average size of the clusters grows. The simulations reveal a macroscopic phase separation at sufficiently large size ratios. We will discuss the effect of density fluctuations of active particles on the nature of effective interactions between passive ones.

Current reversal in polar flock at order-disorder interface.

We studied a system of polar self-propelled particles (SPPs) on a thin rectangular channel designed into three regions of order-disorder-order. The division of the three regions is made on the basis of the noise SPPs experience in the respective regions. The noise in the two wide regions is chosen lower than the critical noise of order-disorder transition and noise in the middle region or interface is higher than the critical noise. This makes the geometry of the system analogous to the Josephson junction (JJ) in solid-state physics. Keeping all other parameters fixed, we study the properties of the moving SPPs in the bulk as well as along the interface for different widths of the junction. On increasing interface width, the system shows an order-to-disorder transition from coherent moving SPPs in the whole system to the interrupted current for large interface width. Surprisingly, inside the interface, we observed the current reversal for intermediate widths of the interface. Such current reversal is due to the strong randomness present inside the interface, which makes the wall of the interface reflecting. Hence, our study gives new interesting collective properties of SPPs at the interface which can be useful to design switching devices using active agents.

Ordering through learning in two-dimensional Ising spins.

We study two-dimensional Ising spins, evolving through reinforcement learning using their state, action, and reward. The state of a spin is defined by whether it is in the majority or minority with its nearest neighbors. The spin updates its state using an ε-greedy algorithm. The parameter ε plays a role equivalent to the temperature in the Ising model. We find a phase transition from long-ranged ordered to a disordered state as we tune ε from small to large values. In analogy with the phase transition in the Ising model, we calculate the critical ε and the three critical exponents ß, Î³, ν of magnetization, susceptibility, and correlation length, respectively. A hyperscaling relation dν=2ß+γ is obtained between the three exponents. The system is studied for different learning rates. The exponents approach the exact values for a two-dimensional Ising model for lower learning rates.

Active nematic gel with quenched disorder.

With quenched disorder, we introduce two-dimensional active nematics suspended in an incompressible fluid. We write the coarse-grained hydrodynamic equations of motion for slow variables, viz. density, orientation, and flow fields. The quenched disorder is introduced such that it interacts with the local orientation at every point with some strength. Disorder strength is tuned from zero to large values. We numerically study the defect dynamics and system kinetics and find that the finite disorder slows the ordering. The presence of fluid induces large fluctuation in the orientation field, further disturbing the ordering. The large fluctuation in the orientation field due to the fluid is so dominant that it reduces the effect of the quenched disorder. We have also found that the disorder effect is almost the same for both the contractile and extensile nature of active stresses in the system. This study can help to understand the impact of quenched disorder on the ordering kinetics of active gels with nematic interaction among the constituent objects.

Effective single component description of steady state structures of passive particles in an active bath.

We model a binary mixture of passive and active Brownian particles in two dimensions using the effective interaction between passive particles in the active bath. The activity of active particles and the size ratio of two types of particles are the two control parameters in the system. The effective interaction is calculated from the average force on two particles generated by the active particles. The effective interaction can be attractive or repulsive, depending on the system parameters. The passive particles form four distinct structural orders for different system parameters, viz., homogeneous structures, disordered cluster, ordered cluster, and crystalline structure. The change in structure is dictated by the change in nature of the effective interaction. We further confirm the four structures using a full microscopic simulation of active and passive mixture. Our study is useful to understand the different collective behavior in non-equilibrium systems.

A Prospective Study to Assess the Outcome of Motivational Interviewing Among Male Students of Haryana, India: A Strive Towards Smoking Cessation in the Youth.

Background The brown plague is a classic example of the modern-day epidemic.Motivational interviewing has been found to increase smokers' readiness to quit, attempts to quit, and reduce smoking levels.Thus, this study, attempts to find out the prevalence of smoking and assess the impact of motivational interviewing on male smoker students (18-30 years). Methodology The study was conducted among the male students of educational institutes in Maharishi Markandeshwar University in Haryana. A cross-sectional study to estimate the prevalence of smoking was carried out. With motivational interviewing of the smokers a prospective cohort study was conducted following the smokers for six months. The probability proportionate to size (PPS) sampling method was applied to recruit 830 participants in the study. A self-designed, semi-structured proforma was used to collect data on smoking behavior, level of dependence, and level of motivation to quit. A modified Fagerstrom questionnaire was used to assess the nicotine dependence level. The motivation to quit smoking was measured by the 10 point scale of Contemplation Ladder, Prochaska, and DiClemente transtheoretical model was used to categorize smokers into stages of readiness to change. Statistical analysis was done using SPSS version 16.0 (IBM Inc., Armonk, New York). Results The prevalence of smoking was 20.4%. Following motivational interview on the first contact, more than half of the current smokers (66.2%) had high motivation which further increased to 88.13% on the third visit at six months (p < 0.001). Likewise, at first contact, 47% had low nicotine dependence; this increased to 52.5 % at two weeks, and finally, at six months, 53.4% had low nicotine dependence. But this finding was statistically insignificant (p=0.23). It was noted that 21 (16.5%) smokers out of 127 quit smoking. A high degree of motivation, support from family and friends, and a low degree of nicotine dependence were identified as significant independent predictors for smoking cessation. Conclusion A satisfying proportion of smokers could attain a high level of motivation for quitting smoking, but less than one-fourth of the current smokers were able to abstain from smoking at the end of the study period. However, the impact of motivational interviewing was not very promising and calls for multi-pronged approach for discouraging smoking.

Activity-driven phase separation and ordering kinetics of passive particles.

The steady state and phase ordering kinetics in a pure active Brownian particle system are studied in recent years. In binary mixture of active and passive Brownian particles passive particles are used as probe to understand the properties of active medium. In our present study, we study the mixture of passive and active Brownian particles. Here, we aim to understand the steady state and kinetics of small passive particles in the mixture. In our system, the passive particles are small in size and large in number, whereas ABPs are large in size and small in number. The system is studied on a two-dimensional substrate using overdamped Langevin dynamic simulation. The steady state and kinetics of passive particles are studied for various size and activity of active particles. Passive particles are purely athermal in nature and have dynamics only due to bigger ABPs. For small size ratio and activity, the passive particles remain homogeneous in the system, whereas on increasing size ratio and activity they form periodic hexagonal close pack (HCP) spanning clusters in the system. We have also studied the kinetics of growing passive particle clusters. The mass of the largest cluster shows a much slower growth kinetics in contrast to conserved growth kinetics in ABP system. Our study provides an understanding of steady state and kinetics of passive particles in the presence of bigger active particles. The mixture can be thought of as effect of big microorganism moving in passive medium.

Convalescent plasma therapy in COVID-19 and discharge status: A systematic review.

OBJECTIVE: Covid19 has emerged as a greatest threat of the decade worldwide. At present there is no certain treatment for treating coronavirus diseases, while some antiviral drugs (Remdesivir , Lopinavir and Ritonavir) are under investigation. Many countries including India have adopted the convalescent plasma therapy in the treatment of moderate to severely ill patients. Despite the treatment being given ,there are no such evidences on the utility and efficacy of convalescent plasma. Hence this study tries to find out the impact on the discharge status from hospital of the patients receiving the very therapy. DESIGN: Systematic review and meta analysis. SETTING: An extensive search was made, following PRISMA guidelines on online databases such as Pubmed, Google scholar and Science direct. Studies those fulfilled the inclusion and exclusion criteria ,were included and reviewed and analyzed for a common outcome(discharge status). PARTICIPANTS: A total of 6 eligible studies were analyzed qualitatively and quantitatively which included three case control, two case series and one case report. RESULTS: The overall pooled discharge rate from the above studies was 75.7% after the CP therapy. When analyzed for relative risk , it showed CP therapy having a lower risk of staying in hospital (not getting discharged) when compared to Standard therapy ,overall RR (relative risk) being 0.946. CONCLUSION: Our study shows that there is always a higher rate of discharge and low risk of prolonged hospital stay in those patients who receive plasma therapy. CP therapy being a low cost and easy to administer therapy with very less adverse events, requires more focus on further research as it has a potential to become an ideal effective treatment option for COVID-19.

Polar swimmers induce several phases in active nematics.

Swimming bacteria in passive nematics in the form of lyotropic liquid crystals are defined as a new class of active matter known as living liquid crystals in recent studies. It has also been shown that liquid crystal solutions are promising candidates for trapping and detecting bacteria. We ask the question, can a similar class of matter be designed for background nematics which are also active? Hence, we developed a minimal model for the mixture of polar particles in active nematics. It is found that the active nematics in such a mixture are highly sensitive to the presence of polar particles and show the formation of large scale higher order structures for a relatively low polar particle density. Upon increasing the density of polar particles, different phases of active nematics are found and it is observed that the system shows two phase transitions. The first phase transition is a first order transition from quasi-long-ranged ordered active nematics to disordered active nematics with larger scale structures. On further increasing density of polar particles, the system transitions to a third phase, where polar particles form large, mutually aligned clusters. These clusters sweep the whole system and enforce local order in the nematics. The current study can be helpful for detecting the presence of very low densities of polar swimmers in active nematics and can be used to design and control different structures in active nematics.

Effect of polydispersity on the dynamics of active Brownian particles.

We numerically study the dynamics and the phases of self-propelled disk-shaped particles of different sizes with soft repulsive potential in two dimensions. Size diversity is introduced by the polydispersity index (PDI) ε, which is the width of the uniform distribution of the particle's radius. The self-propulsion speed of the particles controls the activity v. We observe enhanced dynamics for large size diversity among the particles. We calculate the effective diffusion coefficient D_{eff} in the steady state. The system exhibits four distinct phases, jammed phase with small D_{eff} for small activity and liquid phase with enhanced D_{eff} for large activity. The number fluctuation is larger and smaller than the equilibrium limit in the liquid and jammed phases, respectively. Further, the jammed phase is of two types: solid jammed and liquid jammed for small and large PDI. Whereas the liquid phase is called motility induced phase separation (MIPS) liquid for small PDI and for large PDI, we find enhanced diffusivity and call it the pure liquid phase. The system is studied for three packing densities ϕ, and the response of the system for polydispersity is the same for all ϕ's. Our study can help understand the behavior of cells of various sizes in a tissue, artificial self-driven granular particles, or living organisms of different sizes in a dense environment.

Ordering kinetics in the active model B.

We undertake a detailed numerical study of the Active Model B proposed by Wittkowski et al., [Nature Commun. 5, 4351 (2014)]2041-172310.1038/ncomms5351. We find that the introduction of activity has a drastic effect on the ordering kinetics. First, the domain growth law shows a crossover from the usual Lifshitz-Slyozov growth law for phase separation (L∼t^{1/3}, where t is the time) to a novel growth law (L∼t^{1/4}) at late times. Second, the equal-time correlation function of the density field exhibits dynamical scaling for a given activity strength λ, but the scaling function depends on λ.

Dynamics of a collection of active particles on a two-dimensional periodic undulated surface.

We study the dynamics of circular disk-shaped active particles on a two-dimensional periodic undulated surface. Each particle has an internal energy mechanism which is modeled by an active friction force and it is controlled by an activity parameter [Formula: see text]. It acts as negative friction if the speed of the particle is smaller than [Formula: see text] and normal friction otherwise. Surface undulation is modeled by the periodic undulation of fixed amplitude and wavelength. The dynamics of the particle is studied for different activities and surface undulations (SU). Three types of particle dynamic is observed on varying activity and SU: confined, early time subdiffusion to diffusion and super diffusion to late time diffusion. An effective equilibrium is established by showing the Green-Kubo relation between the effective diffusivity and the velocity auto-correlation function for all activities and small SU.

Active nematics with quenched disorder.

We introduce a two-dimensional active nematic with quenched disorder. We write the coarse-grained hydrodynamic equations of motion for slow variables, viz. density and orientation. Disorder strength is tuned from zero to large values. Results from the numerical solution of equations of motion as well as the calculation of two-point orientation correlation function using linear approximation shows that the ordered steady state follows a disorder dependent crossover from quasi-long-range order to short-range order. Such crossover is due to the pinning of ±1/2 topological defects in the presence of finite disorder, which breaks the system in uncorrelated domains. Finite disorder slows the dynamics of +1/2 defect, and it leads to slower growth dynamics. The two-point correlation functions for the density and orientation fields show good dynamic scaling but no static scaling for the different disorder strengths. Our findings can motivate experimentalists to verify the results and find applications in living and artificial apolar systems in the presence of a quenched disorder.

Speed inhomogeneity accelerates information transfer in polar flock.

A collection of self-propelled particles (SPPs) shows coherent motion and exhibits a true long-range-ordered state in two dimensions. Various studies show that the presence of spatial inhomogeneities can destroy the usual long-range ordering in the system. However, the effects of inhomogeneity due to the intrinsic properties of the particles are barely addressed. In this paper we consider a collection of polar SPPs moving at inhomogeneous speed (IS) on a two-dimensional substrate, which can arise due to varying physical strengths of the individual particles. To our surprise, the IS not only preserves the usual long-range ordering present in homogeneous speed models but also induces faster ordering in the system. Furthermore, the response of the flock to an external perturbation is also faster, compared to the Vicsek-like model systems, due to the frequent update of neighbors of each SPP in the presence of the IS. Therefore, our study shows that an IS can promote information transfer in a moving flock.

Nonquenched rotators ease flocking and memorize it.

We introduce a minimal model for a two-dimensional polar flock with nonquenched rotators and show that the rotators make the usual macroscopic long-range order of the flock more robust than the clean system. The rotators memorize the flock-information which helps in establishing the robustness. Moreover, the memory of the rotators assists in probing the moving flock. We also formulate a hydrodynamic framework for the microscopic model that makes our study comprehensive. Using linearized hydrodynamics, it is shown that the presence of such nonquenched heterogeneities increases the sound speeds of the flock. The enhanced sound speeds lead to faster convection of information and consequently the robust ordering in the system. We argue that similar nonquenched heterogeneities may be useful in monitoring and controlling large crowds.

Immunization coverage among children aged 12-23 months: A cross sectional study in low performing blocks of Bihar, India.

INTRODUCTION: Immunization is one of the most cost-effective measures in public health to date, preventing at an approximately 2 to 3 million fatalities in young children every year. As per recent World Health Organisation (WHO) bulletin, these lifesaving vaccines have been successfully averted around 20 million premature deaths and 500 million disease cases. Inspite of this progress the routine vaccine coverage is slow to rise as challenges still live for the underserved, inaccessible and vulnerable children. It is therefore essential to evaluate the coverage of immunization at periodic intervals and to take the required measures to enhance the vaccination status in the State Bihar. AIMS AND OBJECTIVE: This study aims to find out the vaccination coverage in different Blocks of study area. MATERIAL AND METHODS: The study was community based cross sectional study which was conducted between January to March 2019 in the selected villages of 59 low performing blocks of Bihar. The study subjects were all the children aged 12-23 month old from selected low performing blocks of the Bihar. Results-Corrected FIC of the study was 90.85%. Close to nine percent (8.8%) children thou have started vaccination could not able to complete it. Rest of the beneficiaries are completely left out. The most common reason for incomplete immunization was unavailability of child on the day of vaccination followed by sickness of the child. CONCLUSION: The overall Immunization coverage of Bihar is less than the National Immunization coverage as per NFHS-4. This study shows higher rate of immunization as far as Corrected Immunization Coverage is concerned.

Enhanced dynamics of active Brownian particles in periodic obstacle arrays and corrugated channels.

We study the motion of an active Brownian particle (ABP) using the overdamped Langevin dynamics on a two-dimensional substrate with periodic array of obstacles and in a quasi-one-dimensional corrugated channel comprised of periodically arrayed obstacles. The periodic arrangement of the obstacles enhances the persistent motion of the ABP in comparison to its motion in the free space. Persistent motion increases with the activity of the ABP. We note that the periodic arrangement induces directionality in ABP motion at late time, and it increases with the size of the obstacles. We also note that the ABP exhibits a super-diffusive dynamics in the corrugated channel. The transport property is independent of the shape of the channel; rather it depends on the packing fraction of the obstacles in the system. However, the ABP shows the usual diffusive dynamics in the quasi-one-dimensional channel with flat boundary.