Collective Movement Research Articles

Deformation-induced phase separation of active vesicles.

Many active materials, such as bacteria and cells, are deformable. Deformability significantly affects their collective behaviors and movements in complex environments. Here, we introduce a two-dimensional deformable active vesicle (DAV) model to emulate cell-like deformable active matter, wherein the deformability can be continuously adjusted. We find that changes in deformability can induce phase separation of DAVs. The system can transition between a homogeneous gas state, a coexistence of gas and liquid, and a coexistence of gas and solid. The occurrence of deformation-induced phase separation is accompanied by nonmonotonic changes in effective concentration, particle size and shape. Moreover, the degree of deformability also impacts the motility and stress within the dense phase following phase separation. Our results offer new insights into the role of deformability in the collective behavior of active matter.

Currículos e alfabetização: entre códigos, desvios e experimentação

ABSTRACT This text is an invitation to join a cartography held during a master’s degree research problematizing the macro policies of curriculum centralization and education regulation, which aim to standardize curricular movements in everyday school life. In the relationship between macro/micro policies, the text presents the statements of teachers and children in conversation networks about the curricular experiences produced amidst the hard lines of literacy policies. These flexible and escaping lines cross the school daily life, in movements that agency life processes, an open and susceptible map to question the effects that literacy, curricula, school and learning concepts can produce in educational processes. The text dialogues with Deleuze and Guattari to think education from an invention perspective and argue that, within the fissures of macro politics, it is possible to create curricular movements intertwined with art signs through experimentation as resistance to reproduction attempts. It concludes (always open to new experiments) that, in everyday school life, between forms and forces, there are life-affirming collective curricular movements in an exercise of thought that opens up to the new, the unthinkable, splitting postulates and inventing other ways of existing, with art.

Collective dynamics in active solids

After 25 years of research activity, the physics of collective motions -- flights of starlings, shoals of fish, micro-swimmers or artificial walkers -- is well understood. Here, we describe a new form of self-organization, emerging from the coupling between elasticity and activity: collective actuation, the solid counterpart of collective movements.

Terai Dalits’ Social Status in Nepal: Struggles and Aspirations

This study investigates the social status of Terai Dalits in Nepal, a marginalized community facing discrimination for centuries. The study aims to provide an in-depth understanding of the origin, social status, and identity of Terai Dalits. The research follows a qualitative design, relying on various sources including secondary documents, books, journals, and websites. It explores the historical perspectives and feelings of the people, focusing on abstract concepts and definitions. Descriptive and analytical methods are employed, adhering to APA 7th edition citation and referencing guidelines. Terai Dalits in Nepal endure precarious social status characterised by economic deprivation, social ostracisation, and untouchability discrimination. They lack land ownership, struggle for education, and face challenges in accessing government resources and services. Discrimination extends to gender disparities, with Dalit women experiencing greater marginalization. Lingering feudalistic practices in Terai society exacerbate their plight, perpetuating a cycle of inequality. Terai Dalits face multiple obstacles, including limited access to policymaking, linguistic divisions, and class exploitation by local elites. Discrimination from both the state and upper-caste individuals contributes to their social exclusion. Terai Dalits’ social status remains fragile, rooted in historical discrimination and cultural practices. To uplift their status, concerted efforts are required at local, regional, and national levels. Initiatives should aim to eradicate discrimination, promote education, and provide economic opportunities, ultimately fostering a more inclusive and equal society for Terai Dalits in Nepal. A collective liberation movement united across linguistic divisions, could be instrumental in achieving these goals and breaking the cycle of inequality.

Integrin-based adhesions promote cell-cell junction and cytoskeletal remodelling to drive embryonic wound healing.

Embryos repair wounds rapidly, with no inflammation or scarring. Embryonic wound healing is driven by the collective movement of the cells around the lesion. The cells adjacent to the wound polarize the cytoskeletal protein actin and the molecular motor non-muscle myosin II, which accumulate at the wound edge forming a supracellular cable around the wound. Adherens junction proteins, including E-cadherin, are internalized from the wound edge and localize to former tricellular junctions at the wound margin, in a process necessary for cytoskeletal polarity. We found that the cells adjacent to wounds in the Drosophila embryonic epidermis polarized Talin, a core component of cell-extracellular matrix (ECM) adhesions, which preferentially accumulated at the wound edge. Integrin knockdown and inhibition of integrin binding delayed wound closure and reduced actin polarization and dynamics around the wound. Additionally, disrupting integrins caused a defect in E-cadherin reinforcement at tricellular junctions along the wound edge, suggesting crosstalk between integrin-based and cadherin-based adhesions. Our results show that cell-ECM adhesion contributes to embryonic wound repair and reveal an interplay between cell-cell and cell-ECM adhesion in the collective cell movements that drive rapid wound healing.

"Giving back is typical African culture"

This article presents a collection of narrative examples on how a cohort of African graduates, who are beneficiaries of a scholarship from a global foundation, understand and practice giving back. The scholarship programme aims to cultivate and support a network of like-minded young leaders who are committed to giving back by providing training and mentorship that reinforces the core values of transformative leadership and a commitment to improving the lives of others. To investigate these ideas, the Human Sciences Research Council is tracking recent graduates of the scholarship programme using a longitudinal cohort study design consisting of a tracer study, annual qualitative interviews with scholarship alumni, and smaller collaborative enquiries. Beginning in 2019 and tracking alumni for a five-year period, the study involves alumni from seven study sites. Findings from the study show that alumni exhibit a strong sense of social consciousness including an alignment of their understanding and practices of give-back with deeply embedded African notions of give-back as a ‘ripple effect’, reciprocity and ubuntu. Alumni acknowledged that there was not only one way to give, indicating that they participated in give-back in relation to their capacity, usually beginning with contributions to the family. As they became more established in their careers, their sphere of give-back increased with their reach expanding to the broader community. A low proportion of alumni felt that they were making an impact on an institutional or systemic level. Findings also show the impactful position that university partners hold in fostering give-back engagement among students and their potential role in supporting alumni after graduation. The article argues that nurturing social consciousness in young people and an understanding of give-back as collective movement building can contribute to solving development and social justice problems in Africa.

TRPV6 Channel Is Involved in Pancreatic Ductal Adenocarcinoma Aggressiveness and Resistance to Chemotherapeutics.

Pancreatic ductal adenocarcinoma (PDAC) stands as a highly aggressive and lethal cancer, characterized by a grim prognosis and scarce treatment alternatives. Within this context, TRPV6, a calcium-permeable channel, emerges as a noteworthy candidate due to its overexpression in various cancers, capable of influencing the cell behavior in different cancer entities. Nonetheless, the exact expression pattern and functional significance of TRPV6 in the context of PDAC remains enigmatic. This study scrutinizes the expression of TRPV6 in tissue specimens obtained from 46 PDAC patients across distinct stages and grades. We manipulated TRPV6 expression (knockdown, overexpression) in the human PDAC cell lines Panc-1 and Capan-1. Subsequently, we analyzed its impact on multiple facets, encompassing Ca2+ influx, proliferation, apoptosis, migration, chemoresistance, and tumor growth, both in vitro and in vivo. Notably, the data indicate a direct correlation between TRPV6 expression levels, tumor stage, and grade, establishing a link between TRPV6 and PDAC proliferation in tissue samples. Decreasing TRPV6 expression via knockdown hampered Ca2+ influx, resulting in diminished proliferation and viability in both cell lines, and cell cycle progression in Panc-1. The knockdown simultaneously led to an increase in apoptotic rates and increased the susceptibility of cells to 5-FU and gemcitabine treatments. Moreover, it accelerated migration and promoted collective movement among Panc-1 cells. Conversely, TRPV6 overexpression yielded opposing outcomes in terms of proliferation in Panc-1 and Capan-1, and the migration of Panc-1 cells. Intriguingly, both TRPV6 knockdown and overexpression diminished the process of tumor formation in vivo. This intricate interplay suggests that PDAC aggressiveness relies on a fine-tuned TRPV6 expression, raising its profile as a putative therapeutic target.

Dielectric relaxations and the phenomena of glass transition in supercooled D-xylose aqueous mixtures

D-xylose aqueous solutions at various concentrations of water (0 ≤ x ≤ 40 %) were investigated using broadband dielectric spectroscopy and differential scanning calorimeter in the wide temperature range (150–300 K). Two resolvable relaxations were observed in all studied D-xylose aqueous solutions. The slower relaxation process (process-I) observed above the glass transition temperature (Tg), usually referred to as the structural relaxation process, is responsible for the collective movement of the D-xylose and water mixture. The faster one (process-II) observed below Tg is mainly related to the water molecular relaxation inside the D-xylose matrix. The temperature dependence of the average dielectric relaxation time and dielectric strength of both observed processes (I & II) were analyzed for all concentrations of water (x) in D-xylose. It was observed that the dielectric strength of process-II in the D-xylose water mixture increased sharply above critical concentration, x = 25 % shows moderate characteristics as compared to its isomers viz. D-ribose, D-arabinose and D-lyxose. Also the activation energies were found to be almost water content independent above critical concentration, x = 25 %. This suggests that this dynamic process was dominated by water-water interaction. Moreover, the Tg of bulk water was estimated at 133 ± 1 K and 138 ± 1.2 K from the extrapolation of DSC Tg and dielectric Tg, respectively of the D-xylose aqueous mixture using the Gordon-Taylor equation. This gives further support to the commonly accepted Tg value of bulk water.

Workability via Platform: A Legislative Proposal and a Collective Movement for Socio-Labor Civil Integration

Introduction: The legal integration of work via technological platforms (applications) in the Brazilian legal system. Contextualization/concept: Under the terms of articles 7 and 114 of the Constitution of the Federative Republic of Brazil of 1988, it is work and work relations that gain grammaticality and literality in the constitutional text, which inaugurate the concept of workability, when the tone of employment (industrial sector) would be giving way to work (services sector). Objective: The historical and normative broth induces a perspective of reflexivity in the midst of resisted change, which will impose on workers via the platform (as mostly urban workers) and labor institutions renewed forms of collective union political, legislative and organizational action, whether at a national or international level, to overcome obstacles that impede the effectiveness of constitutional labor standards. Methodology: The methodology follows comprehensive (Weberian) and extensive interpretative and constitutional historical analysis connected to excerpts from current reality, centered on the theoretical-normative method. Theoretical framework: For Weber (2000), legal norms have the function of disciplining and ordering actions and social relations, constituting maxims and, therefore, creating the conditions of administration and obedience of society's participants to the law. Conclusion: The duty to be constitutionally regulated inaugurated new labor precepts, which are still in resistance in the world of being, which imposes on actors and labor institutions the creation of a middle path suitable for the civil socio-labor integration of a new professional category of urban workers.

Watching the Interplay between Photoinduced Ultrafast Charge Dynamics and Nuclear Vibrations.

Here is presented the ultrafast hole-electron dynamics of photoinduced metal to ligand charge-transfer (MLCT) states in a Ru(II) complex, [Ru(dcbpy)2(NCS)2]4- (dcbpy = 4,4'-dicarboxy-2,2'-bipyridine), a photoactive molecule employed in dye sensitized solar cells. Via cutting-edge computational techniques, a tailored computational protocol is here presented and developed to provide a detailed analysis of the electronic manifold coupled with nuclear vibrations to better understand the nonradiative pathways and the resulting overall dye performances in light-harvesting processes (electron injection). Thus, the effects of different vibrational modes were investigated on both the electronic levels and charge transfer dynamics through a theoretical-computational approach. First, the linear response time-dependent density functional (LR-TDDFT) formalism was employed to characterize excitation energies and spacing among electronic levels (the electronic layouts). Then, to understand the ultrafast (femtosecond) charge dynamics on the molecular scale, we relied on the nonperturbative mean-field quantum electronic dynamics via real-time (RT-) TDDFT. Three vibrational modes were selected, representative for collective nuclear movements that can have a significant influence on the electronic structure: two involving NCS- ligands and one involving dcbpy ligands. As main results, we observed that such MLCT states, under vibrational distortions, are strongly affected and a faster interligand electron transfer mechanism is observed along with an increasing MLCT character of the adiabatic electronic states approaching closer in energy due to the vibrations. Such findings can help both in providing a molecular picture of multidimensional vibro-electronic spectroscopic techniques, used to characterize ultrafast coherent and noncoherent dynamics of complex systems, and to improve dye performances with particular attention to the study of energy or charge transport processes and vibronic couplings.

A strong quick-release biointerface in mussels mediated by serotonergic cilia-based adhesion.

The mussel byssus stem provides a strong and compact mechanically mismatched biointerface between living tissue and a nonliving biopolymer. Yet, in a poorly understood process, mussels can simply jettison their entire byssus, rebuilding a new one in just hours. We characterized the structure and composition of the byssus biointerface using histology, confocal Raman mapping, phase contrast-enhanced microcomputed tomography, and advanced electron microscopy, revealing a sophisticated junction consisting of abiotic biopolymer sheets interdigitated between living extracellular matrix. The sheet surfaces are in intimate adhesive contact with billions of motile epithelial cilia that control biointerface strength and stem release through their collective movement, which is regulated neurochemically. We posit that this may involve a complex sensory pathway by which sessile mussels respond to environmental stresses to release and relocate.

A chemo-mechanical model of endoderm movements driving elongation of the amniote hindgut.

Although mechanical and biochemical descriptions of development are each essential, integration of upstream morphogenic cues with downstream tissue mechanics remains understudied during vertebrate morphogenesis. Here, we developed a two-dimensional chemo-mechanical model to investigate how mechanical properties of the endoderm and transport properties of fibroblast growth factor (FGF) regulate avian hindgut morphogenesis in a coordinated manner. Posterior endoderm cells convert a gradient of FGF ligands into a contractile force gradient, leading to a force imbalance that drives collective cell movements that elongate the forming hindgut tube. We formulated a 2D reaction-diffusion-advection model describing the formation of an FGF protein gradient as a result of posterior displacement of cells transcribing unstable Fgf8 mRNA during axis elongation, coupled with translation, diffusion and degradation of FGF protein. The endoderm was modeled as an active viscous fluid that generates contractile stresses in proportion to FGF concentration. With parameter values constrained by experimental data, the model replicates key aspects of hindgut morphogenesis, suggests that graded isotropic contraction is sufficient to generate large anisotropic cell movements, and provides new insight into how chemo-mechanical coupling across the mesoderm and endoderm coordinates hindgut elongation with axis elongation.

The role of Wnt palmitoleylated loop conserved disulfide bonds in Wnt-frizzled complex structural dynamics: Insights from molecular dynamics simulations

Wnts are lipid-modified proteins rich in cysteine, regulating developmental processes, and are involved in various pathological conditions. Wnts structure resembles a hand, with a palmitoleylated thumb and an index finger-like domain interacting with frizzled (FZ) receptors. Previous research shows the palmitoleyl group and the disulfides importance in Wnt folding, secretion, and function, but the structural basis is not fully understood. Here, we utilized classical molecular dynamics simulation (800-ns in total) to investigate how the thumb palmitoleyl and its close conserved disulfides (183–190, 181–195) regulated Wnt-FZ interaction and structural dynamics. Using Steered molecular dynamics experiment followed by a relaxing procedure, we also explored if these disulfides are important in Wnt-FZ complex formation. According to our results, the palmitoleyl group contributes significantly to stabilize Wnt-FZ interaction, and the disulfides modulate this contribution. We also demonstrated that disulfide 183–190 regulates the Wnt thumb fluctuation, hydrogen bond network, and secondary structure. The DCCM analysis depicted disulfide 183–190 roles in regulating native-like collective movement in the palmitoleylated loop, which changed after this disulfide removal. The pulling-relaxing experiment showed that both the disulfides, and especially, the disulfide 183–190, are highly important for long-range salt-bridge interaction establishment between Wnt Lys182 and FZ Glu64, led palmitoleyl group appropriate positioning to FZ, suggested this disulfide essential role in Wnt-FZ complex formation. Together, our findings provide new insights to how thumb-positioned disulfides contribute to Wnt-FZ complex formation, structural dynamics, and stability, introducing disulfide 183–190 as a consequential element to target in drug design and development against Wnt signalling.

Emergence of diverse patterns driven by molecular motors in the motility assay.

Actomyosin contractility originating from interactions between F-actin and myosin motors in the actin cytoskeleton generates mechanical forces and drives a wide range of cellular processes including cell migration and cytokinesis. To probe the interactions between F-actin and myosin motors, the myosin motility assay has been popularly employed, which consists of myosin heads attached to a glass surface and F-actins gliding on the surface via interactions with the heads. Several experiments have shown that F-actins move in a collective fashion due to volume-exclusion effects between neighboring F-actins. Furthermore, Computational models have shown how changes in key parameters lead to diverse pattern formation in motility assay. However, in most of the computational models, myosin motors were implicitly considered by applying a constant propulsion force to filaments to reduce computational cost. This simplification limits the physiological relevance of the insights provided by the models and potentially leads to artifacts. In this study, we employed an agent-based computational model for the motility assay with explicit immobile motors interacting with filaments. We rigorously account for the kinetics of myosin motors including the force-velocity relationship for walking and the binding and unbinding behaviors. We probed the effects of the length, rigidity, and concentration of filaments and repulsive strength on collective movements and pattern formation. It was found that four distinct types of structures-homogeneous networks, flocks, bands, and rings-emerged as a result of collisions between gliding filaments. We further analyzed the frequency and morphology of these structures and the curvature, alignment, and rotational motions of filaments. Our study provides better insights into the origin and properties of patterns formed by gliding filaments beyond what was shown before.

Bioinspired self-assembled colloidal collectives drifting in three dimensions underwater.

Active matter systems feature a series of unique behaviors, including the emergence of collective self-assembly structures and collective migration. However, realizing collective entities formed by synthetic active matter in spaces without wall-bounded support makes it challenging to perform three-dimensional (3D) locomotion without dispersion. Inspired by the migration mechanism of plankton, we propose a bimodal actuation strategy in the artificial colloidal systems, i.e., combining magnetic and optical fields. The magnetic field triggers the self-assembly of magnetic colloidal particles to form a colloidal collective, maintaining numerous colloids as a dynamically stable entity. The optical field allows the colloidal collectives to generate convective flow through the photothermal effect, enabling them to use fluidic currents for 3D drifting. The collectives can perform 3D locomotion underwater, transit between the water-air interface, and have a controlled motion on the water surface. Our study provides insights into designing smart devices and materials, offering strategies for developing synthetic active matter capable of controllable collective movement in 3D space.

Unsettling the Conversation on Trans Rights

This article argues that trans rights are trapped within settler frameworks of gender and rights, therefore making them incompatible with and in opposition to Indigenous lifeways. Starting with the premise that engagement with the settler state is not benign, the authors argue that trans rights-based organizing diverts and thwarts the potential for solidarity work with Indigenous struggles for freedom and is inherently limited in its potential to secure Indigenous futurity. The authors hope that trans studies and collective struggles organized around gender embrace anti-colonial and anti-racist praxis to result in tangible and discursive outcomes to bolster Indigenous cultural continuity and land-based connections. The authors use this article to call for a collective movement toward gender self-determination that is sensitive and reflexive of settler colonialism and produces tangible decolonial actions that will benefit the lives of Indigenous Two-Spirit, trans, and nonbinary people and align with movements for Indigenous self-determination. Queer and trans settlers are urged to begin a process of accountability and to engage a decolonial praxis to support Indigenous decolonization in all its forms—fighting for land claims, defending water and land rights, and supporting the resurgence of Indigenous erotics and gender formations. To be truly decolonial we suggest that trans political organizing moves beyond the settler framework of rights and toward Indigenous solidarity in politics, practices, and shared struggles, foregrounding anti-colonial, anti-racist, and pro-Indigenous values.

Socio-spatially Segregated Experience of Urban Dalits and their Anti-caste Imagination: A Study of the Balmiki Community in Delhi, India

Over the last three decades, India has experienced rapid economic development and social and cultural transformation. Questions arise as to how minorities secure their livelihood and what strategies are being devised for the same. And, what vision of the future do they have in mind? In this article, I will focus on the Dalit community in North India. Fieldwork conducted on one such disadvantaged group, the urban Balmikis (known as the sweeper caste) in Delhi, is drawn upon to examine as a case study. Balmikis have a high rate of migration to urban areas, which is due to their historical background of being employed in the sanitation sector of municipalities and the Ministry of Railways since the colonial times. The name of the community, Balmiki, is derived from worshipping “Bhagwan Valmik,” a legendary saint and composer of Ramayana. It began to take root as a name with positive connotations among the sweeper caste in North India around the 1920s and 1930s. Because of this historical development, it is often accused of discrediting Dalits who dissent from Hindu values and for hindering Dalit solidarity. However, if one listens to the claims of the Balmikis, they do not necessarily consider themselves "Hindus”. For example, during my research, a frequent response to questions about religion was the statement, "We are forced to be Hindus”. In contrast, the words that immediately follow, "We are Balmikis," are restated. By focusing on the beliefs and ambiguity of self-identity of the Balmikis, this article attempts to examine their anti-caste imagination. It then poses the question as to how that imagination is intertwined with everyday experiences and collective grassroots movements.

Effects of Different Motion Parameters on the Interaction of Fish School Subsystems.

For a long time, fish school swimming has attracted a great deal of attention in biological systems, as fish schools can have complex hydrodynamic effects on individuals. This work adopted a non-iterative, immersed boundary-lattice Boltzmann method (IB-LBM). A numerical simulation of two-dimensional three-degree-of-freedom self-propelled fish, in side-by-side, staggered, and triangle formations, was conducted by adjusting spacing and motion parameters. A comprehensive analysis of individual speed gains and energy efficiencies in these formations was carried out. Furthermore, an analysis of the hydrodynamic characteristics of fish schools was performed, using instantaneous vorticity profiles and pressure fields. Certain studies have shown that passive interactions between individuals cannot always bring hydrodynamic benefits. The swimming efficiency of side-by-side formations in the same phase gradually increases as the distance decreases, but it also brings certain burdens to individuals when the phases are different. This paper also shows that the roles of passive interactions, spacing, and deflections affect fish school subsystems differently. When the low-pressure areas created by a wake vortex act on one side of an individual's body, the tail-end fish are good at gaining hydrodynamic benefits from it. This effect is not universal, and the degree to which individuals benefit from changes in exercise parameters varies. This study provides a theoretical basis for bioinspired robots, as well as providing certain insights into the mechanism of collective biological movement.

Energetics of collective movement in vertebrates.

The collective directional movement of animals occurs over both short distances and longer migrations, and is a critical aspect of feeding, reproduction and the ecology of many species. Despite the implications of collective motion for lifetime fitness, we know remarkably little about its energetics. It is commonly thought that collective animal motion saves energy: moving alone against fluid flow is expected to be more energetically expensive than moving in a group. Energetic conservation resulting from collective movement is most often inferred from kinematic metrics or from computational models. However, the direct measurement of total metabolic energy savings during collective motion compared with solitary movement over a range of speeds has yet to be documented. In particular, longer duration and higher speed collective motion must involve both aerobic and non-aerobic (high-energy phosphate stores and substrate-level phosphorylation) metabolic energy contributions, and yet no study to date has quantified both types of metabolic contribution in comparison to locomotion by solitary individuals. There are multiple challenging questions regarding the energetics of collective motion in aquatic, aerial and terrestrial environments that remain to be answered. We focus on aquatic locomotion as a model system to demonstrate that understanding the energetics and total cost of collective movement requires the integration of biomechanics, fluid dynamics and bioenergetics to unveil the hydrodynamic and physiological phenomena involved and their underlying mechanisms.

ECR Spotlight – Yangfan Zhang

ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology during our centenary year but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Yangfan Zhang is an author on ‘ Energetics of collective movement in vertebrates’, published in JEB. Yangfan is a Natural Sciences and Engineering Research Council of Canada (NSERC) post-doctoral research fellow in the lab of George V. Lauder at Harvard University, USA, investigating environmental effects on respiratory phenotype and the bioenergetics of specific locomotion gaits, to ultimately expand the potential of tracking field metabolic rate in fish in the light of ecology and evolution.