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The physical state of embryonic tissues emerges from non-equilibrium, collective interactions among constituent cells. Cellular jamming, rigidity transitions and characteristics of glassy dynamics have all been observed in multicellular systems, but it is unclear how cells control these emergent tissue states and transitions, including tissue fluidization. Combining computational and experimental methods, here we show that tissue fluidization in posterior zebrafish tissues is controlled by the stochastic dynamics of tensions at cell–cell contacts. We develop a computational framework that connects cell behaviour to embryonic tissue dynamics, accounting for the presence of extracellular spaces, complex cell shapes and cortical tension dynamics. We predict that tissues are maximally rigid at the structural transition between confluent and non-confluent states, with actively generated tension fluctuations controlling stress relaxation and tissue fluidization. By directly measuring strain and stress relaxation, as well as the dynamics of cell rearrangements, in elongating posterior zebrafish tissues, we show that tension fluctuations drive active cell rearrangements that fluidize the tissue. These results highlight a key role of non-equilibrium tension dynamics in developmental processes.A computational framework draws analogy with foams to offer a comprehensive picture of how cell behaviours influence fluidization in embryonic tissues, highlighting the role of tension fluctuations in regulating tissue rigidity.

Tissue, cell, and nucleus morphology change during tumor progression. In 2D confluent cell cultures, different tissue states, such as fluid (unjammed) and solid (jammed), are correlated with cell shapes. These results do not have to apply a priori to three dimensions. Cancer cell motility requires and corresponds to a fluidization of the tumor tissue on the bulk level. Here, we investigate bulk tissue fluidity in 3D and determine how it correlates with cell and nucleus shape. In patient samples of mamma and cervix carcinoma, we find areas where cells can move or are immobile. We compare 3D cell spheroids composed of cells from a cancerous and a noncancerous cell line. Through bulk mechanical spheroid-fusion experiments and single live-cell tracking, we show that the cancerous sample is fluidized by active cells moving through the tissue. The healthy, epithelial sample with immobile cells behaves more solidlike. 3D segmentations of the samples show that the degree of tissue fluidity correlates with elongated cell and nucleus shapes. This correlation links cell shapes to cell motility and bulk mechanical behavior. We find two active states of matter in solid tumors: an amorphous glasslike state with characteristics of 3D cell jamming and a disordered fluid state. Individual cell and nucleus shape may serve as a marker for metastatic potential to foster personalized cancer treatment.

The collective behaviour of cells in epithelial tissues is dependent on their mechanical properties. However, the contribution of tissue mechanics to wound healing in vivo remains poorly understood. Here, we investigate the relationship between tissue mechanics and wound healing in live Drosophila wing imaginal discs and show that by tuning epithelial cell junctional tension, we can systematically alter the rate of wound healing. Coincident with the contraction of an actomyosin purse string, we observe cells flowing past each other at the wound edge by intercalating, reminiscent of molecules in a fluid, resulting in seamless wound closure. Using a cell-based physical model, we predict that a reduction in junctional tension fluidizes the tissue through an increase in intercalation rate and corresponding reduction in bulk viscosity, in the manner of an unjamming transition. The resultant fluidization of the tissue accelerates wound healing. Accordingly, when we experimentally reduce tissue tension in wing discs, the intercalation rate increases and wounds repair in less time.

The manufacturing of polystyrene around the globe has escalated in the past years due to its huge applications in various areas. The perpetual market needs of polystyrene led the polystyrene wastes accretion in the landfill causing environmental deterioration. The soaring need for polystyrene also led to the exhaustion of petroleum, a non-renewable energy source, as polystyrene is a petroleum-derived product. Researchers from around the world have discovered a few techniques to take care of the polystyrene scraps, namely recycling and energy recovery techniques. Nevertheless, there are demerits involved with recycling techniques, such as they call for huge labor expenses in the separation process and cause water pollution, thereby decreasing the process sustainability. Owing to these demerits, the researchers have focused their attention on the energy recovery technique. Since petroleum is the main ingredient of polystyrene synthesis, the restoration of liquid oil from polystyrene via the pyrolysis method is a promising technique as the recovered oil has greater calorific value as compared to commercially available fuel. The present paper surveys the pyrolysis technique for polystyrene and the important process parameters that control the end product, like oil, gas, and char. The chief process parameters that are discussed in this review paper include the type of reactors, temperature, residence time, pressure, catalyst types, type of fluidizing gases, and their flow rate. A more recent technique of utilizing a solvent to perform pyrolysis and the effect of various process conditions on the product yield have been discussed. Apart from this, various outlooks to optimize the liquid oil recovery from polystyrene are also reviewed.

Plasticity of cancer invasion and metastasis depends on the ability of cancer cells to switch between collective and single-cell dissemination, controlled by cadherin-mediated cell–cell junctions. In clinical samples, E-cadherin-expressing and -deficient tumours both invade collectively and metastasize equally, implicating additional mechanisms controlling cell–cell cooperation and individualization. Here, using spatially defined organotypic culture, intravital microscopy of mammary tumours in mice and in silico modelling, we identify cell density regulation by three-dimensional tissue boundaries to physically control collective movement irrespective of the composition and stability of cell–cell junctions. Deregulation of adherens junctions by downregulation of E-cadherin and p120-catenin resulted in a transition from coordinated to uncoordinated collective movement along extracellular boundaries, whereas single-cell escape depended on locally free tissue space. These results indicate that cadherins and extracellular matrix confinement cooperate to determine unjamming transitions and stepwise epithelial fluidization towards, ultimately, cell individualization.Ilina et al. investigate the balance between cell adhesion and matrix density on patterns of collective breast cancer cell invasion using three-dimensional models of the extracellular matrix, in vivo imaging and in silico modelling

With the expansion of the scale of zinc smelting enterprises and the progress of new equipment and technology, 152 m 2 fluidized roasting furnace has been developed and applied to industrial production, with a single unit capacity of 150,000 to 170,000 tons of electrolytic zinc per year. This paper analyzes and introduces an engineering example of zinc concentrate treatment by a dual-series fluidized roasting furnace. The project was designed by China ENFI Engineering Corporation and put into operation in Hunan province of China in 2018. This paper firstly describes the process flow and main equipment of the preparation system, roasting furnace system, waste heat utilization system, dust collection system from a design perspective. Then, based on production practice, it analyzes and compares aspects such as furnace operation, actual production data, major technical and economic indicators, and the characteristics and optimization of the roasting system equipment. Finally, it is concluded that the dual-series large-scale fluidized roasting furnace has stable production, good product quality, less investment, and fewer labor requirements, which brings good economic benefits to the enterprise. Its operational experience has accumulated parameters and experience for the development of larger roasting furnaces in the future.

It has long been proposed that phase-separated compartments can provide a basis for the formation of cellular precursors in prebiotic environments. However, we know very little about the properties of coacervates formed from simple peptides, their compatibility with ribozymes or their functional significance. Here we assess the conditions under which functional ribozymes form coacervates with simple peptides. We find coacervation to be most robust when transitioning from long homopeptides to shorter, more pre-biologically plausible heteropeptides. We mechanistically show that these RNA–peptide coacervates display peptide-dependent material properties and cofactor concentrations. We find that the interspacing of cationic and neutral amino acids increases RNA mobility, and we use isothermal calorimetry to reveal sequence-dependent Mg 2+ partitioning, two critical factors that together enable ribozyme activity. Our results establish how peptides of limited length, homogeneity and charge density facilitate the compartmentalization of active ribozymes into non-gelating, magnesium-rich coacervates, a scenario that could be applicable to cellular precursors with peptide-dependent functional phenotypes. Phase-separated compartments have long been proposed as precursors to cellular life. Now, it has been shown that RNA–peptide protocells are more robust when formed using shorter (rather than longer) peptides, and that peptide sequence determines the functional materials properties of these compartments.

During wound repair, branching morphogenesis and carcinoma dissemination, cellular rearrangements are fostered by a solid-to-liquid transition, known as unjamming. The biomolecular machinery behind unjamming and its pathophysiological relevance remain, however, unclear. Here, we study unjamming in a variety of normal and tumorigenic epithelial two-dimensional (2D) and 3D collectives. Biologically, the increased level of the small GTPase RAB5A sparks unjamming by promoting non-clathrin-dependent internalization of epidermal growth factor receptor that leads to hyperactivation of the kinase ERK1/2 and phosphorylation of the actin nucleator WAVE2. This cascade triggers collective motility effects with striking biophysical consequences. Specifically, unjamming in tumour spheroids is accompanied by persistent and coordinated rotations that progressively remodel the extracellular matrix, while simultaneously fluidizing cells at the periphery. This concurrent action results in collective invasion, supporting the concept that the endo-ERK1/2 pathway is a physicochemical switch to initiate collective invasion and dissemination of otherwise jammed carcinoma.

Ranging from subcellular organelle biogenesis to embryo development, the formation of self-organized structures is a hallmark of living systems. Whereas the emergence of ordered spatial patterns in biology is often driven by intricate chemical signalling that coordinates cellular behaviour and differentiation 1 – 4 , purely physical interactions can drive the formation of regular biological patterns such as crystalline vortex arrays in suspensions of spermatozoa 5 and bacteria 6 . Here we discovered a new route to self-organized pattern formation driven by physical interactions, which creates large-scale regular spatial structures with multiscale ordering. Specifically we found that dense bacterial living matter spontaneously developed a lattice of mesoscale, fast-spinning vortices; these vortices each consisted of around 10 4 –10 5  motile bacterial cells and were arranged in space at greater than centimetre scale and with apparent hexagonal order, whereas individual cells in the vortices moved in coordinated directions with strong polar and vortical order. Single-cell tracking and numerical simulations suggest that the phenomenon is enabled by self-enhanced mobility in the system—that is, the speed of individual cells increasing with cell-generated collective stresses at a given cell density. Stress-induced mobility enhancement and fluidization is prevalent in dense living matter at various scales of length 7 – 9 . Our findings demonstrate that self-enhanced mobility offers a simple physical mechanism for pattern formation in living systems and, more generally, in other active matter systems 10 near the boundary of fluid- and solid-like behaviours 11 – 17 . We demonstrate that self-enhanced mobility offers a simple physical mechanism for pattern formation in living systems and, more generally, in other active matter systems near the boundary of fluid- and solid-like behaviours.

Collective behaviour in dense assemblies of self-propelled active particles occurs in a wide range of biological phenomena, including the dynamical transitions of cellular and subcellular biological assemblies such as the cytoskeleton and the cell nucleus. Here, motivated by observations of mechanically induced changes in the dynamics of such systems and the apparent role of confinement geometry, we show that the fluidization transition broadly resembles yielding in amorphous solids, which is consistent with recent suggestions. More specifically, however, we find that a detailed analogy holds with the yielding transition under cyclic shear deformation, for large but finite persistence times. The fluidization transition is accompanied by driving-induced annealing, strong dependence on the initial state of the system, a divergence of timescales to reach steady states and a discontinuous onset of diffusive motion. We also observe a striking dependence of transition on persistence times and on the nature of confinement. Collectively, our results have implications for biological assemblies in confined geometries, including epigenetic cell-state transitions. Assemblies of active particles display a range of dynamical phenomena. Simulations now show that the transition of an assembly of active particles from a jammed to a fluidized state is similar to the process of mechanical yielding seen in amorphous solids.