A generalized model for predicting different morphologies of bacterial swarming on a porous solid surface.

In this study, we develop a comprehensive two-phase model to analyze the dynamics of bacterial swarming on porous substrates. The two distinct phases under consideration are the cell and aqueous phases. We use the thin-film approximation, as the characteristic height of the swarm is significantly lower than its characteristic radius.

Engineering advancements in microfluidic systems for enhanced mixing at low Reynolds numbers.

Mixing within micro- and millichannels is a pivotal element across various applications, ranging from chemical synthesis to biomedical diagnostics and environmental monitoring. The inherent low Reynolds number flow in these channels often results in a parabolic velocity profile, leading to a broad residence time distribution. Achieving efficient mixing at such small scales presents unique challenges and opportunities.

Detection of azadirachtin from neem kernels using a paper-based sandwich sensor.

In this work, a microfluidic paper-based analytical device (μPAD) was developed to detect the biopesticide azadirachtin (Aza) through a colorimetric assay. High precision estimation of Aza is classically carried out using high performance liquid chromatography (HPLC), which requires highly skilled personnel. Acidified vanillin is a commonly used colorimetric indicator in thin layer chromatography for detection of various phytochemicals.

Green Approach for the Simultaneous Synthesis and Separation of Gold Nanoparticles.

Gold nanoparticles (AuNPs) have diagnostic and therapeutic applications as they are biocompatible and can be surface-functionalized. The use of organic solvents in the synthesis of AuNPs hampers their applications in the medicinal field. The large-scale production of nanoparticles requires their simultaneous synthesis and separation.

Adsorption of Triclosan on Nylon 66 Membrane: Preconcentration and Ultrasensitive Colorimetric Detection.

In this work, adsorption of triclosan (TCS) on nylon 66 membrane is explored to develop a preconcentration and sensing platform. Nylon 66 membrane exhibits superior sorption ability even for trace amounts of TCS (10 μg/L). Investigating the surface adsorption chemistry by XPS analysis revealed the formation of a hydrogen bond between the hydroxyl group of TCS and the amide group of nylon 66.

Continuous protein refolding and purification by two-stage periodic counter-current chromatography.

Matrix-assisted refolding (MAR) has been used as an alternative to conventional dilution-based refolding to improve recovery and reduce specific buffer consumption. Size exclusion chromatography (SEC) has been extensively used for MAR because of its ability to load and refold proteins at high concentrations. However, the SEC-based batch MAR processes have the disadvantages of requiring longer columns for better separation and product dilution due to a high column-to-sample volume ratio.

Adsorptive preconcentration integrated with colorimetry for ultra-sensitive detection of lead and copper.

This work proposes a novel detection method for the ultra-sensitive colorimetric determination of lead and copper in complex water matrix. The method integrates signal amplification with analytical sensing, achieved by adsorptive preconcentration and a colorimetric assay. We report for the first time a strategic application of batch adsorption as a preconcentration method and colorimetry performed directly on the adsorbent surface enriched with metal.

Adsorptive colorimetric determination of chromium(VI) ions at ultratrace levels using amine functionalized mesoporous silica.

There is an urgent need for a rapid, affordable and sensitive analytical method for periodic monitoring of heavy metals in water bodies. Herein, we report for the first time a versatile method for ultratrace level metal detection based on colorimetric sensing. The method integrates preconcentration using a nanomaterial with a colorimetric assay performed directly on the metal-enriched nanomaterial surface.

Continuous refolding of L-asparaginase inclusion bodies using periodic counter-current chromatography.

Chromatography-based refolding is emerging as a promising alternative to dilution-refolding of solubilized inclusion bodies (IBs). The advantages of this matrix-assisted refolding (MAR) lie in its ability to reduce aggregate formation, leading to better recovery of active protein, and enabling refolding at higher protein concentration. However, batch chromatography has the disadvantage of ineffective solvent utilization, under-utilization of resin, and low throughput.

Semi-batch and continuous production of Pickering emulsion direct contact steam condensation.

We propose a versatile strategy for the production of highly stable water in oil Pickering emulsion by direct contact condensation of steam. In contrast to conventional methods that use mechanical energy for creating drops, the condensation of steam brought in contact with a non-aqueous colloidal dispersion is exploited to produce Pickering emulsions in two modes of operation, namely, semi-batch and continuous. As steam that comes in contact with oil condenses into water drops, the particles adsorb to the interface and thus arrest drop-drop coalescence.

Self-propulsion in 2D confinement: phoretic and hydrodynamic interactions.

Chemically active Janus particles generate tangential concentration gradients along their surface for self-propulsion. Although this is well studied in unbounded domains, the analysis in biologically relevant environments such as confinement is scarce. In this work, we study the motion of a Janus sphere in weak confinement.

A Network Architecture for Bidirectional Neurovascular Coupling in Rat Whisker Barrel Cortex.

Neurovascular coupling is typically considered as a master-slave relationship between the neurons and the cerebral vessels: the neurons demand energy which the vessels supply in the form of glucose and oxygen. In the recent past, both theoretical and experimental studies have suggested that the neurovascular coupling is a bidirectional system, a loop that includes a feedback signal from the vessels influencing neural firing and plasticity. An integrated model of bidirectionally connected neural network and the vascular network is hence required to understand the relationship between the informational and metabolic aspects of neural dynamics.

Sensitive and selective determination of triclosan using visual spectroscopy.

Triclosan is a commonly used biocide effective against bacterial and fungal infections. However, its overuse in pharmaceutical and personal care products has resulted in its abundance in the natural environment. The detection of triclosan by visual spectroscopy can be carried out using the azo-coupling reaction of diazonium complexes.

Modeling Temperature-Dependent Sex Determination in Oviparous Species Using a Dynamical Systems Approach.

In many oviparous species, the incubation temperature of the egg determines the sex of the offspring. This is known as temperature-dependent sex determination (TSD). The probability of the hatched offspring being male or female varies across the incubation temperature range.

Fabrication of laser printed microfluidic paper-based analytical devices (LP-µPADs) for point-of-care applications.

Microfluidic paper-based analytical devices (µPADs) have provided a breakthrough in portable and low-cost point-of-care diagnostics. Despite their significant scope, the complexity of fabrication and reliance on expensive and sophisticated tools, have limited their outreach and possibility of commercialization. Herein, we report for the first time, a facile method to fabricate µPADs using a commonly available laser printer which drastically reduces the cost and complexity of fabrication.

Removal of trace hexavalent chromium from aqueous solutions by ion foam fractionation.

Ion foam fractionation is a green and cost-effective technology where separation of molecules exploits the difference in surface affinity. In this work, a batch ion foam fractionation system was designed and optimized for the separation of trace hexavalent chromium (Cr(VI)) from aqueous solutions. The effect of surfactant head groups (collectors) on the adsorption dynamics was analyzed.

Effect of soluble surfactants on the stability of stratified flows through soft-gel-coated walls.

The effect of a soluble surfactant on the linear stability of layered two-phase Poiseuille flows through soft-gel-coated parallel walls is studied in this paper. The focus is on determining the effect of the elastohydrodynamic coupling between the fluids and the soft-gel layers on the various flow instabilities. The fluids are assumed Newtonian and incompressible, while the soft gels are modeled as linear viscoelastic solids.

Linear stability of layered two-phase flows through parallel soft-gel-coated walls.

The linear stability of layered two-phase Poiseuille flows through soft-gel-coated parallel walls is studied in this work. The focus is on determining the effect of the elastohydrodynamic coupling between the fluids and the soft-gel layers on the different instabilities observed in flows between parallel plates. The fluids are assumed Newtonian and incompressible, while the soft gels are modeled as linear viscoelastic solids.

Numerical study of enhanced mixing in pressure-driven flows in microchannels using a spatially periodic electric field.

We propose an innovative mechanism for enhancing mixing in steady pressure driven flow of an electrolytic solution in a straight rectangular microchannel. A transverse electric field is used to generate an electroosmotic flow across the cross-section. The resulting flow field consists of a pair of helical vortices that transport fluid elements along the channel.

Synthesis and characterization of chitosan-TiO:Cu nanocomposite and their enhanced antimicrobial activity with visible light.

In the present investigation, novel strategy for the preparation of hybrid nanocomposite containing organic polymer (Chitosan) and inorganic (TiO:Cu) nanoparticles (NPs) has been developed and demonstrated its biomedical application. The sol-gel and ultra-sonication method assisted for the preparation of uniformly distributed Chitosan-TiO:Cu (CS-CT) nanocomposite. The structural properties of prepared CS-CT nanocomposite were studied by XRD and FTIR techniques.

Understanding the shape of ant craters: a continuum model.

The disposal of soil grains by ants, during excavation of their nest, results in the formation of axisymmetric craters around the nest entrance. We give a simple explanation for the shape of these biological constructs based on basic processes underlying grain transport and grain dropping. We propose that the tendency of an ant to drop a grain, in its next step, keeps increasing as it carries the grain farther away from the nest.

A holistic approach combining factor analysis, positive matrix factorization, and chemical mass balance applied to receptor modeling.

Rapid urbanization and population growth resulted in severe deterioration of air quality in most of the major cities in India. Therefore, it is essential to ascertain the contribution of various sources of air pollution to enable us to determine effective control policies. The present work focuses on the holistic approach of combining factor analysis (FA), positive matrix factorization (PMF), and chemical mass balance (CMB) for receptor modeling in order to identify the sources and their contributions in air quality studies.

Variation of spatial and temporal characteristics of reactive flow in a periodically driven cavity: gelation of sodium acrylate.

A reactive flow, the gelation of sodium acrylate (SA), was carried out in a cuboidal cavity with the top surface undergoing sinusoidal periodic motion. The instantaneous two-dimensional planar velocity fields during gelation were obtained using particle image velocimetry. The experiments were carried out with different plate velocities and different amounts of accelerator (TEMED).

Viscous fingering in a horizontal flow through a porous medium induced by chemical reactions under isothermal and adiabatic conditions.

In this work we analyze the viscous fingering instability induced by an autocatalytic chemical reaction in a liquid flowing horizontally through a porous medium. We have analyzed the behavior of the system for isothermal as well as adiabatic conditions. The kinetics of the reaction is chosen so that the rate depends on the concentration of only a single species.