The loader complex Scc2/4 forms co-condensates with DNA as loading sites for cohesin

The genome is organized by diverse packaging mechanisms like nucleosome formation, loop extrusion and phase separation, which all compact DNA in a dynamic manner. Phase separation additionally drives protein recruitment to condensed DNA sites and thus regulates gene transcription. The cohesin complex is a key player in chromosomal organization that extrudes loops to connect distant regions of the genome and ensures sister chromatid cohesion after S-phase. For stable loading onto the DNA and for activation, cohesin requires the loading complex Scc2/4. As the precise loading mechanism remains unclear, we investigated whether phase separation might be the initializer of the cohesin recruitment process. We found that, in absence of cohesin, budding yeast Scc2/4 forms phase separated co-condensates with DNA, which comprise liquid-like properties shown by droplet shape, fusion ability and reversibility. We reveal in DNA curtain and optical tweezer experiments that these condensates are built by DNA bridging and bending through Scc2/4. Importantly, Scc2/4-mediated condensates recruit cohesin efficiently and increase the stability of the cohesin complex. We conclude that phase separation properties of Scc2/4 enhance cohesin loading by molecular crowding, which might then provide a starting point for the recruitment of additional factors and proteins.

A Rapid Method for the determination of Dehydrated alcohol (Ethanol) content in Clobetasol propionate foam by Non-polar Capillary Gas chromatography

Clobeatsol propionate foam is a topical class 1 corticosteroid used to treat itching and inflammatory arthritis on the skin occurred by allergic reactions, psoriasis and eczema. In the pharmaceutical aerosol products, Dehydrated alcohol (Ethanol) is the primary ingredient and its concentration level in the formulation composition plays a significant role in the regulation of aerosol rate, droplet shape and particle size. It can also act as solubilizer for active pharmaceutical ingredient, topical disinfectant and skin permeation enhancer. Hence accurate assay of Ethanol is a crucial quality control component. A simple and rapid gas chromatography method was developed to quantify Ethanol content in Clobetasol propionate foam drug product using fused silica glass tube non-polar capillary column (HP-5, 30 m, 0.53 mm, 1.5 µm). Ethanol in the sample was diluted with methanol after adding suitable amount of internal standard, the isopropyl alcohol solution.The developed method is precise, linear and accurate in the range of 5 mg/mL to 15 mg/mL of nominal concentration of ethanol i.e. 10 mg/mL . The presented method has an advantage of a very quick gas chromatographic separation (less than 16 min) and therefore is highly suitable for in-process and stability analysis of Ethanol content in Clobetasol propionate foam drug product.

Active droploids

Active matter comprises self-driven units, such as bacteria and synthetic microswimmers, that can spontaneously form complex patterns and assemble into functional microdevices. These processes are possible thanks to the out-of-equilibrium nature of active-matter systems, fueled by a one-way free-energy flow from the environment into the system. Here, we take the next step in the evolution of active matter by realizing a two-way coupling between active particles and their environment, where active particles act back on the environment giving rise to the formation of superstructures. In experiments and simulations we observe that, under light-illumination, colloidal particles and their near-critical environment create mutually-coupled co-evolving structures. These structures unify in the form of active superstructures featuring a droplet shape and a colloidal engine inducing self-propulsion. We call them active droploids—a portmanteau of droplet and colloids. Our results provide a pathway to create active superstructures through environmental feedback.

Simulation of jet printing of solder paste for surface mounted technology

Purpose The purpose of this study is to propose a novel simulation framework and show that it captures the main effects of the deposition process, such as droplet shape, volume and speed. Design/methodology/approach In the framework, the time-dependent flow and the fluid-structure interaction between the suspension, the moving piston and the deflection of the jetting head is simulated. The system is modelled as a two-phase system with the surrounding air being one phase and the dense suspension the other. The non-Newtonian suspension is modelled as a mixed single phase with properties determined from material testing. The simulations were performed with two coupled in-house solvers developed at Fraunhofer-Chalmers Centre; IBOFlow, a multiphase flow solver; and LaStFEM, a large strain FEM solver. Experimental deposition was performed with a commercial jet printer and quantitative measurements were made with optical profilometry. Findings Jetting behaviour was shown to be affected by not only piston motion, fluid rheology and head deformation but also the viscous energy loss in the jetting head nozzle. The simulation results were compared to experimental data obtained from an industrial jetting head and found to match characteristic lengths, speed and volume within ca 10%. Research limitations/implications The simulations are based on a rheological description using the Carreau model that does not include a time-dependent relaxation of the fluid. This modelling approach limits the descriptive nature of the deposit after impact on the substrate. The simulation also adopts a continuum approach to the suspension, which will not accurately model the break-off of the droplet filament under the characteristic diameter of the particles in the suspension. Practical implications The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and minimised product development duration. Social implications The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and therefore an improvement from a sustainability perspective. The ability to plan deposition strategies virtually will also enable a decrease in consumables at manufacturers which will in turn decrease their carbon foot print. Originality/value While basic fluid dynamic simulations have been performed to simulate flow through nozzles, the ability to include both fluid-structure interaction and multiphase capability together with a more accurate rheological description of the suspension and with a substrate for surface mount applications has not been published to the knowledge of the authors.

Chemical Design of Self-Propelled Janus Droplets

<p>The study of active colloidal microswimmers with tunable phoretic and self-organizational behaviors is important for understanding out-of-equilibrium systems and the design of functional, adaptive matter. Solubilizing, self-propelling droplets have emerged as a rich chemical platform for exploration of active behaviors, but isotropic droplets rely on spontaneous symmetry breaking to sustain motion. The introduction of permanent asymmetry, e.g. in the form of a biphasic Janus droplet, has not been explored previously as a comprehensive design strategy for active droplets, despite the widespread use of Janus structures in motile solid particles. Here, we uncover the chemomechanical framework underlying the self-propulsion of active, biphasic Janus oil droplets solubilizing in aqueous surfactant. We elucidate how droplet propulsion is influenced by the degree of oil mixing, droplet shape, and oil solubilization rates for a range of oil combinations. A key finding is that for droplets containing both a mobile (solubilizing) and non-mobile oil, the degree of partitioning of the mobile oil across the Janus droplets’ oil-oil interface plays a pivotal role in determining the droplet speed and swimming direction. As a result, we observe propulsion speeds of Janus droplets more than an order-of-magnitude faster than chasing pairs of single emulsion droplets which lack an oil-oil interface. In addition, spatiotemporal control over droplet swimming speed and orientation is demonstrated through the application of local thermal gradients applied via induced via joule heading and laser spot illumination. We also explore the interactions between collections of Janus droplets including the spontaneous formation of multi-droplet spinning clusters that rotate predictably based on symmetry. Our findings provide key insights as to how the chemistry and structure of multiphase fluids can be harnessed to design microswimmers with programmable active and collective behaviors.</p><br>

Chemical Design of Self-Propelled Janus Droplets

<p>The study of active colloidal microswimmers with tunable phoretic and self-organizational behaviors is important for understanding out-of-equilibrium systems and the design of functional, adaptive matter. Solubilizing, self-propelling droplets have emerged as a rich chemical platform for exploration of active behaviors, but isotropic droplets rely on spontaneous symmetry breaking to sustain motion. The introduction of permanent asymmetry, e.g. in the form of a biphasic Janus droplet, has not been explored previously as a comprehensive design strategy for active droplets, despite the widespread use of Janus structures in motile solid particles. Here, we uncover the chemomechanical framework underlying the self-propulsion of active, biphasic Janus oil droplets solubilizing in aqueous surfactant. We elucidate how droplet propulsion is influenced by the degree of oil mixing, droplet shape, and oil solubilization rates for a range of oil combinations. A key finding is that for droplets containing both a mobile (solubilizing) and non-mobile oil, the degree of partitioning of the mobile oil across the Janus droplets’ oil-oil interface plays a pivotal role in determining the droplet speed and swimming direction. As a result, we observe propulsion speeds of Janus droplets more than an order-of-magnitude faster than chasing pairs of single emulsion droplets which lack an oil-oil interface. In addition, spatiotemporal control over droplet swimming speed and orientation is demonstrated through the application of local thermal gradients applied via induced via joule heading and laser spot illumination. We also explore the interactions between collections of Janus droplets including the spontaneous formation of multi-droplet spinning clusters that rotate predictably based on symmetry. Our findings provide key insights as to how the chemistry and structure of multiphase fluids can be harnessed to design microswimmers with programmable active and collective behaviors.</p><br>

Numerical Treatment of the Interface in Two Phase Flows Using a Compressible Framework in OpenFOAM: Demonstration on a High Velocity Droplet Impact Case

The ability to accurately predict the dynamics of fast moving and deforming interfaces is of interest to a number of applications including ink printing, drug delivery and fuel injection. In the current work we present a new compressible framework within OpenFOAM which incorporates mitigation strategies for the well known issue of spurious currents. The framework incorporates the compressible algebraic Volume-of-Fluid (VoF) method with additional interfacial treatment techniques including volume fraction smoothing and sharpening (for the calculation of the interface geometries and surface tension force, respectively) as well as filtering of the capillary forces. The framework is tested against different benchmarks: A 2D stationary droplet, a high velocity impact droplet case (500 m/s impact velocity) against a dry substrate and, with the same impact conditions, against a liquid film. For the 2D static droplet case, our results are consistent with what is observed in the literature when these strategies are implemented within incompressible frameworks. For the high impact droplet cases we find that accounting for both compressibility and correct representation of the interface is very important in numerical simulations, since pressure waves develop and propagate within the droplet interacting with the interface. While the implemented strategies do not alter the dynamics of the impact and the droplet shape, they have a considerable effect on the lamella formation. Our numerical method, although currently implemented for droplet cases, can also be used for any fast moving interface with or without considering the impact on a surface.