Dynamic Motifs Research Articles

Flexible multitask computation in recurrent networks utilizes shared dynamical motifs

Flexible computation is a hallmark of intelligent behavior. However, little is known about how neural networks contextually reconfigure for different computations. In the present work, we identified an algorithmic neural substrate for modular computation through the study of multitasking artificial recurrent neural networks. Dynamical systems analyses revealed learned computational strategies mirroring the modular subtask structure of the training task set. Dynamical motifs, which are recurring patterns of neural activity that implement specific computations through dynamics, such as attractors, decision boundaries and rotations, were reused across tasks. For example, tasks requiring memory of a continuous circular variable repurposed the same ring attractor. We showed that dynamical motifs were implemented by clusters of units when the unit activation function was restricted to be positive. Cluster lesions caused modular performance deficits. Motifs were reconfigured for fast transfer learning after an initial phase of learning. This work establishes dynamical motifs as a fundamental unit of compositional computation, intermediate between neuron and network. As whole-brain studies simultaneously record activity from multiple specialized systems, the dynamical motif framework will guide questions about specialization and generalization.

Reprocessable, Highly Transparent Ionic Conductive Elastomers Based on β-Amino Ester Chemistry for Sensing Devices.

Ionic conductive elastomers (ICEs) exhibit a compelling combination of ionic conductivity and elastic properties, rendering them excellent candidates for stretchable electronics, particularly in applications like sensing devices. Despite their appeal, a significant challenge lies in the reprocessing of ICEs without compromising their performance. To address this issue, we propose a strategy that leverages covalent adaptable networks (CANs) for the preparation of ICEs. Specifically, β-amino ester bonds as dynamic motifs are incorporated into a poly(ethylene oxide) network containing lithium bis(trifluoromethane) sulfonimide (LiTFSI) salt. LiTFSI-containing β-amino ester networks (LBAEs) exhibit superb transparency (94%), thermal stability (>280 °C), and modest conductivity (0.00576 mS·cm-1 at 20 °C), and some LBAEs maintain operational capability across a wide temperature range (-20 to 100 °C). By regulating the lithium salt content, the mechanical properties, conductivities, and viscoelastic behaviors can be tailored. Benefiting from these features, LBAEs have been successfully applied in sensing devices for monitoring human motion (e.g., finger bending, swallowing, and clenching). Notably, even after four reprocessing cycles, LBAEs demonstrate structural integrity and maintain their operational capability. This novel approach represents a promising solution to the reprocessing challenges associated with flexible conductive devices, demonstrating the successful integration of CANs and ICEs.

High voltage, toughness and improved interfacial ion deposition through a dual-crosslinked and self-healable hydrogel electrolyte for green zinc-ion batteries

The inconsistent zinc stripping/deposition leading to low durability of zinc anodes is a fundamental obstacle for the practical application of zinc-based aqueous batteries. Hence, the self-healing capability of flexible batteries is crucial for enhancing their durability and dependability during routine operation, as it allows them to withstand various deformations. Through composite strengthening and dynamic coordination complexation, we have developed a dual-crosslinked and natural polymer-based self-healing hydrogel electrolyte (sodium carboxymethyl cellulose/sodium alginate-Zn2+, denoted as CMC/SA-Zn2+) for flexible Zn-MnO2 batteries. The metal coordination interactions of carboxyl groups with Zn2+ as the dynamic motif are contributed to excellent mechanical and electrochemical properties, as well as fast self-healing ability for the CMC/SA-Zn2+ hydrogel electrolyte. Moreover, the improved compatibility of the electrode and electrolyte at their interfaces results in considerably more meticulous Zn deposition. Subsequently, a reversible plating/stripping performance is observed in a symmetric cell for a duration of 2000 h. After applying this self-healing and tough electrolyte to the flexible Zn-MnO2 battery, it is constructed with a high capacity of 218 mAh/g and a high coulombic efficiency close to 100 %. Additionally, the flexible batteries exhibit exceptional resilience and can recover their electrochemical performance even after enduring multiple mechanical damages, highlighting their potential use in wearable electronics.

Stimuli‐responsive fluorescent hydrogels: Strategies and applications

AbstractStimuli‐responsive fluorescent hydrogels are three‐dimensional networked polymeric materials with tunable luminescence and dynamic properties, which play an important role as a water‐rich soft material in the fields of information encryption, bionic actuation, bioimaging, environmental monitoring, and luminescent materials. Compared with conventional hydrogels, their unique luminescent properties allow the visualization of microscopic dynamics within the polymer network. By rational inclusion of dynamic motifs, such as photoswitches, AIEgens, lanthanide complexes, and host–guest complexes, these materials are endowed with tunability of emission, shape, and phase in time and space in response to environmental effectors. In this review, we summarize the fabrication strategies that are mainly used by recently reported stimuli‐responsive fluorescent hydrogels and the applications of these materials.

Transient Structural Dynamics of Glycogen Phosphorylase from Nonequilibrium Hydrogen/Deuterium-Exchange Mass Spectrometry.

It remains a major challenge to ascertain the specific structurally dynamic changes that underpin protein functional switching. There is a growing need in molecular biology and drug discovery to complement structural models with the ability to determine the dynamic structural changes that occur as these proteins are regulated and function. The archetypal allosteric enzyme glycogen phosphorylase is a clinical target of great interest to treat type II diabetes and metastatic cancers. Here, we developed a time-resolved nonequilibrium millisecond hydrogen/deuterium-exchange mass spectrometry (HDX-MS) approach capable of precisely locating dynamic structural changes during allosteric activation and inhibition of glycogen phosphorylase. We resolved obligate transient changes in the localized structure that are absent when directly comparing active/inactive states of the enzyme and show that they are common to allosteric activation by AMP and inhibition by caffeine, operating at different sites. This indicates that opposing allosteric regulation by inhibitor and activator ligands is mediated by pathways that intersect with a common structurally dynamic motif. This mass spectrometry approach uniquely stands to discover local transient structural dynamics and could be used broadly to identify features that influence the structural transitions of proteins.

A Versatile Comonomer Additive for Radically Recyclable Vinyl‐derived Polymers

AbstractRadically‐formed, vinyl‐derived polymers account for over 30 % of polymer production. Connected through stable carbon‐carbon bonds, these materials are notoriously challenging to chemically recycle. Herein, we report universal copolymerization of a cyclic allyl sulfide (CAS) additive with multiple monomers under free‐radical conditions, to introduce main‐chain dynamic motifs. Backbone allyl sulfides undergo post‐polymerization radical rearrangement via addition‐fragmentation‐transfer (AFT) that fosters both chain scission and extension. Scission is selectively induced through allyl sulfide exchange with small molecule thiyl radicals, resulting in oligomers as low as 14 % of the initial molar mass. Crucially, oligomers retain allyl sulfide end groups, enabling their extension with monomer under radical conditions. Extended, i.e., recycled, product molar mass is tunable through the ratio of monomer to oligomer, and can surpass that of the initial copolymer. Two scission‐extension cycles are demonstrated in copolymers with methyl methacrylate and styrene without escalation in dispersity. In illustration of forming higher‐value products, i.e., upcycling, we synthesized block copolymers through the extension of oligomers with a different vinyl monomer. Collectively, our approach to chemical recycling is unparalleled in its ability to 1) function in a variety of vinyl‐derived polymers, 2) complete radical closed‐loop cycling, and 3) upcycle waste material.

A Versatile Comonomer Additive for Radically Recyclable Vinyl-derived Polymers.

Radically-formed, vinyl-derived polymers account for over 30 % of polymer production. Connected through stable carbon-carbon bonds, these materials are notoriously challenging to chemically recycle. Herein, we report universal copolymerization of a cyclic allyl sulfide (CAS) additive with multiple monomers under free-radical conditions, to introduce main-chain dynamic motifs. Backbone allyl sulfides undergo post-polymerization radical rearrangement via addition-fragmentation-transfer (AFT) that fosters both chain scission and extension. Scission is selectively induced through allyl sulfide exchange with small molecule thiyl radicals, resulting in oligomers as low as 14 % of the initial molar mass. Crucially, oligomers retain allyl sulfide end groups, enabling their extension with monomer under radical conditions. Extended, i.e., recycled, product molar mass is tunable through the ratio of monomer to oligomer, and can surpass that of the initial copolymer. Two scission-extension cycles are demonstrated in copolymers with methyl methacrylate and styrene without escalation in dispersity. In illustration of forming higher-value products, i.e., upcycling, we synthesized block copolymers through the extension of oligomers with a different vinyl monomer. Collectively, our approach to chemical recycling is unparalleled in its ability to 1) function in a variety of vinyl-derived polymers, 2) complete radical closed-loop cycling, and 3) upcycle waste material.

Benzene Tetraamide: A Covalent Supramolecular Dual Motif in Dynamic Covalent Polymer Networks.

In dynamic polyamide networks, 1,2,4,5-benzene tetraamide (B4A) units act simultaneously as a dynamic covalent cross-linker and as supramolecular stacking motif. This results in materials with a rubbery plateau modulus that is about 20 times higher than that of a corresponding reference network in which the supramolecular interaction is suppressed. In branched polyamides with the same B4A dynamic motif, hydrogen bonding and stacking lead to strong and reversible supramolecular networks, whereas a branched polyamide with the nonstacking reference linker is a viscous liquid under the same conditions. Wide-angle X-ray scattering and variable-temperature infrared experiments confirm that covalent cross-linking and stacking cooperatively contribute to the dynamics of the network. Stress relaxation in the reference network is dominated by a single mode related to the dynamic covalent chemistry, whereas relaxation in the B4A network has additional modes assigned to the stacking dynamics.

Conformational Dynamics of the D53-D3-D14 Complex in Strigolactone Signaling.

Strigolactones (SLs) play fundamental roles in regulating plant architecture, which is a major factor determining crop yield. The perception and signal transduction of SLs require the formation of a complex containing the receptor DWARF14 (D14), an F-box protein D3 and a transcriptional regulator D53 in an SL-dependent manner. Structural and biochemical analyses of D14 and its orthologues DAD2 and AtD14, D3, and the complexes of ASK1-D3-AtD14 and D3CTH-D14 have made great contributions to understanding the mechanisms of SL perception. However, structural analyses of D53 and the D53-D3-D14 holo-complex are challenging, and the biochemical mechanism underlying complex assembly remains poorly understood. Here, we found that apo-D53 was rather flexible and reconstituted the holo-complex containing D53, SKP1, D3, and D14 with rac-GR24. The cryo-EM structure of SKP1-D3-D14 in the presence of D53 was analyzed and superimposed on the crystal structure of ASK1-D3-AtD14 without D53. No large conformational rearrangement was observed but a 9 Å rotation appeared between D14 and AtD14. Using hydrogen-deuterium exchange monitored by mass spectrometry, we analyzed dynamic motifs of D14, D3 and D53 in the D53-SKP1-D3-D14 complex assembly process and further identified two potential interfaces in D53 that are located in the N and D2 domains, respectively. Together, our results uncovered the dynamic conformational changes and built a model of the holo-complex D53-SKP1-D3-D14, offering valuable information for the biochemical and genetic mechanisms of SL perception and signal transduction.

Robust Inversion of Time-Resolved Data via Forward-Optimization in a Trajectory Basis.

An inversion method for time-resolved data from ultrafast experiments is introduced, based on forward-optimization in a trajectory basis. The method is applied to experimental data from X-ray scattering of the photochemical ring-opening reaction of 1,3-cyclohexadiene and electron diffraction of the photodissociation of CS2. In each case, inversion yields a model that reproduces the experimental data, identifies the main dynamic motifs, and agrees with independent experimental observations. Notably, the method explicitly accounts for continuity constraints and is robust even for noisy data.

Expressive architectures enhance interpretability of dynamics-based neural population models.

Artificial neural networks that can recover latent dynamics from recorded neural activity may provide a powerful avenue for identifying and interpreting the dynamical motifs underlying biological computation. Given that neural variance alone does not uniquely determine a latent dynamical system, interpretable architectures should prioritize accurate and low-dimensional latent dynamics. In this work, we evaluated the performance of sequential autoencoders (SAEs) in recovering latent chaotic attractors from simulated neural datasets. We found that SAEs with widely-used recurrent neural network (RNN)-based dynamics were unable to infer accurate firing rates at the true latent state dimensionality, and that larger RNNs relied upon dynamical features not present in the data. On the other hand, SAEs with neural ordinary differential equation (NODE)-based dynamics inferred accurate rates at the true latent state dimensionality, while also recovering latent trajectories and fixed point structure. Ablations reveal that this is mainly because NODEs (1) allow use of higher-capacity multi-layer perceptrons (MLPs) to model the vector field and (2) predict the derivative rather than the next state. Decoupling the capacity of the dynamics model from its latent dimensionality enables NODEs to learn the requisite low-D dynamics where RNN cells fail. Additionally, the fact that the NODE predicts derivatives imposes a useful autoregressive prior on the latent states. The suboptimal interpretability of widely-used RNN-based dynamics may motivate substitution for alternative architectures, such as NODE, that enable learning of accurate dynamics in low-dimensional latent spaces.

Ionogel electrolyte with dynamic metal-ligand interactions enabled self-healable supercapacitor with high energy density

Flexible semisolid supercapacitors (FSCs) are a kind of essential energy supplies for fast-developed wearable devices. However, the widely reported FSCs use hydrogel electrolytes, dramatically limiting the improvement of the energy density and working potential. Using ionogel electrolytes can solve these problems, but tolerating destruction is still a challenge. Herein, an ionogel electrolyte with good flexibility, high mechanical strength, wide potential window, and fast self-healing feature is designed to assemble the FSCs, solving the above problems simultaneously. The metal-ligand interaction of P(VI-co-VmimBF4) with Zn2+ as the dynamic motif is introduced in the ionogel electrolyte, which not only leads to good flexibility and high mechanical strength of 0.58 MPa, but also endows the fast self-healing ability. Benefitting from the good ionic conductivity of 0.36 mS/cm and wide potential window of 3.2 V of the electrolyte, the assembled FSCs with a covalent organic framework/reduced graphene oxide electrodes achieve a high energy density of 46 Wh/kg. No capacitance deterioration appears for the assembled supercapacitor in bending, and 85% of the original capacitance can be retained for the healed device from two cut pieces. This work provides a way to design a high-performance gel electrolyte for assembling flexible and healable energy storage devices.

Dynamic-Covalent Crosslinking of Benzenetricarboxamide-Phenylboronate Conjugates.

In an effort to augment the function of supramolecular biomaterials, recent efforts have explored the creation of hybrid materials that couple supramolecular and covalent components. Here, the benzenetricarboxamide (BTA) supramolecular polymer motif is modified to present a phenylboronic acid (PBA) in order to promote the crosslinking of 1D BTA stacks by PBA-diol dynamic-covalent bonds through the addition of a multi-arm diol-bearing crosslinker. Interestingly, the combination of these two motifs serves to frustrate the resulting assembly process, yielding hydrogels with worse mechanical properties than those prepared without the multi-arm diol crosslinker. Both systems with and without the crosslinker do, however, respond to the presence of a physiological level of glucose with a reduction in their mechanical integrity; repulsive electrostatic interactions in the BTA stacks occur in both cases upon glucose binding, with added competition from glucose with PBA-diol bonds amplifying glucose response in the hybrid material. Accordingly, the present results point to an unexpected outcome of reduced hydrogel mechanics, yet increased glucose response, when two disparate dynamic motifs of BTA supramolecular polymerization and PBA-diol crosslinking are combined, offering a vision for future preparation of glucose-responsive supramolecular biomaterials.

Mechanical switching of a comblike dual dynamic polymer network

Hydrogels are polymer networks swollen in water and, therefore, suitable for biomedical applications. For this purpose, hydrogels have to mimic the functionality and mechanics of natural tissues. In drug delivery, for example, the diffusion is crucial and can be controlled through targeted variation of the network mesh-size. In tissue engineering, on the other side, the mechanics plays a fundamental role and can be strengthened through the use of two interpenetrated polymer networks, realizing a double network, or with two dynamic motifs anchored in one common network, realizing a dual dynamic network (DDN). However, current knowledge encompasses mainly nonlinear rheological characterization of these networks. We intend to fill this gap and provide a systematic linear rheological study. To realize this strategy, we combine two supramolecular motifs in a common network, thereby realizing a comblike DDN with the ability to change the building blocks on demand. In our DDN, a tetra-poly(ethylene) glycol (pEG) (the first building block) is functionalized on each arm with two dynamic motifs: terpyridine capable of undergoing metal-complexation with different divalent metal ions, and a thermo-responsive unit consisting of poly(N-isopropylacrylamide) (pNIPAAm) (the second building block) that is capable of undergoing temperature-dependent nano-phase-separation. In particular, we change the molar mass of the tetra-pEG-terpyridine and the pNIPAAm grafted chains. In addition, we investigate two different metal ions that form complexes with the terpyridine. With this platform, we tune the elastic properties on demand, and we systematically study the structure–property relationships with oscillatory shear rheology in the linear regime.

ЗНАЧЕННЯ ПРИКРАС В УКРАЇНСЬКІЙ КУЛЬТУРІ: ВІД НАЙДАВНІШИХ ЧАСІВ ДО ВОЄННИХ РЕАЛІЙ СЬОГОДЕННЯ

The aim of the article is to describe the significance of jewelry in Ukrainian culture at various stages of human development. The research focuses on the study of the semantics of the elements of human body decoration and clothing, their features and functional differences over the centuries. Attention is focused on the fact that Ukrainian jewelry is a special and very ancient type of decorative and applied art. His images, convenient utilitarian forms and dynamic motifs of the ornament contain symbols of nature, historical motifs, peculiarities of everyday life and worldview of the Ukrainian people. The original decorations were body tattoos and various amulets. The art of body decoration was known already in ancient times. The history of jewelry originates from the sources of human history. The need to decorate the body is clearly expressed in primitive peoples, even more than the need for clothes. Since ancient times, decorations performed other important tasks in parallel with the aesthetic function. First: they were a charm, an amulet, a talisman. Secondly: they fastened, fixed clothes, shoes, belts, decorated hair. Each era created its own jewelry not only from the point of view of style, but also from the point of view of material, technique and method of processing. The art of the most ancient times incorporates various functions: ritual-magical, practicalcognitive, symbolic-communicative. Peculiarities of ancient culture are syncretism, the absence of a clear boundary between the artistic and life-practical spheres of human activity. Syncretism is also expressed in the absence of a clear genre-species structure. In the study, an attempt was made to analyze the importance of jewelry in the life of modern Ukrainians, to trace the change in priorities of Ukrainians in peacetime and wartime.

Preparation of Poly(thiol-urethane) Covalent Adaptable Networks Based on Multiple-Types Dynamic Motifs.

To solve the issue of polymeric materials recycling, developing intrinsic self-healing materials containing dynamic bonds has attracted many researchers' highly concerning. However, the tradeoff between their mechanical strength and stretchability always does not avoid. Herein, to surmount the above tradeoff, metal-ligand (Cu2+ -S) interactions are introduced into the cross-linking polythiourethane covalent adaptable networks (PTU CANs) with three kinds of dynamic motifs (thiourethane, disulfide, and hydrogen bonds). When the molar ratio of Cu2+ to S is 6.37%, the break strength (9.41 ± 0.34MPa)and Young's modulus (26.02 ± 0.55MPa)of the metal-ligand coordination complex PTU (Cu2+ -PTU-3) dramatically increase, whereas the peak strain almost does not decline (454.44 ± 3.95%).To conduct the repairing, Cu2+ -PTU-3 is further confirmed excellent repairing capability. Therefore, these new PTU CANs have significant potential for the new self-healing materials.

Illuminating the Imperceptible, Researching Mina'i Ceramics with Digital Imaging Techniques.

Mina’i ceramics dating to the late 12th and early 13th century made in the Kashan region of Iran represent a novel period of overglaze enamelling technology in ceramic history. New colours were used to produce stylistically attractive and dynamic polychrome motifs. Due to their archaeological context, and popularity in the art market since the mid-20th century, these objects often have complex conditions involving reconstruction and overpainting. The aesthetic and technological significance of these pieces warrants further study, but in practice, removing restorations can lead to structural destabilisation, requiring time-consuming and potentially unplanned for conservation treatment. To determine if it is possible to gain useful information from the study of these artworks without disturbing existing restorations, a group of objects were drawn from the Sarikhani and Ashmolean Museum of Art and Archaeology collections. The objective of this project was twofold, first to assess the merits of the imaging techniques for understanding condition, and second to propose a protocol for imaging with the aim of encouraging collaborative projects with international partners. The techniques used in this study include digital photography under visible and ultraviolet light, infrared reflectography, and radiography. The results show that important information invisible to the naked eye can be obtained about the decorative surfaces, using ultraviolet light and infrared reflectography. Digital radiography proved to be equally effective when studying the condition of the ceramic body. The results of this project were used to produce guidance on these techniques as a collaborative documentation package for the study of Mina’i ceramics.

Multi-layered scenario of the novel “Earth” by Mikhail Elizarov

This article discusses the novel “Earth” by the contemporary Russian writer Mikhail Elizarov. The plot of the novel develops in the context of philosophical views of the writer with postmodernist idea of thanatological concept of the world. The goal consist in analysis of the plot through organizing power of the “motifs” and their modifications. The relevance of this research lies in the fact that this article is first to carry out the motivic analysis of multi-layered scenario of the novel “Earth”. The author explores the thanatological motif that forms the plot of the novel and correlates with other motifs, such as anthropological, philosophical, maturing, romantic, and procedural criminal. The following conclusions were made:  1) The work “Earth” demonstrates the genre characteristics of the novel and balances on the border between realism and deconstruction, The conducted motivic analysis proves the presence of static and dynamic motifs. The theme of hallucinogenic narrative resembles life, death, and fate. 2) The motifs in the novel “Earth” are intertwined, overlaying and complementing each other. The author believes that the key motif is thanatological motif, which manifests on several levels and interlaces with the characters of the novel in most episodes. This motif forms the plot and theme, as well as other philosophical, anthropological, maturing, romantic, and procedural criminal motifs in the novel. 3)  The lyrical motif of the novel “Earth” is the romantic motif. The epic motif is the duel between two Krotyshevs brothers. Dramatic motif is both, thanatological and philosophical motifs, which describes senescence and brevity of life. Motif of maturing along with anthropological motif are considered as individual motif.

Inosine Substitutions in RNA Activate Latent G-Quadruplexes.

It is well-accepted that gene expression is heavily influenced by RNA structure. For instance, stem-loops and G-quadruplexes (rG4s) are dynamic motifs in mRNAs that influence gene expression. Adenosine-to-inosine (A-to-I) editing is a common chemical modification of RNA which introduces a nucleobase that is iso-structural with guanine, thereby changing RNA base-pairing properties. Here, we provide biophysical, chemical, and biological evidence that A-to-I exchange can activate latent rG4s by filling incomplete G-quartets with inosine. We demonstrate the formation of inosine-containing rG4s (GI-quadruplexes) in vitro and verify their activity in cells. GI-quadruplexes adopt parallel topologies, stabilized by potassium ions. They exhibit moderately reduced thermal stability compared to conventional G-quadruplexes. To study inosine-induced structural changes in a naturally occurring RNA, we use a synthetic approach that enables site-specific inosine incorporation in long RNAs. In summary, RNA GI-quadruplexes are a previously unrecognized structural motif that may contribute to the regulation of gene expression in vivo.

Recyclable crosslinked elastomer based on dynamic dithioacetals

Recent progress in introducing elegant dynamic covalent bonds into covalently crosslinked networks enabled the trade-offs between chemical crosslinking and recycling. Thus far, continuous efforts are made to exploit new dynamic chemistries to address the constrains of intricate preparation procedures and need of catalyst additives in creating dynamic covalent networks. In this work, we report an industrially feasible process to prepare catalyst-free malleable elastomers by engineering dithioacetals as the dynamic motifs into a commercial diene rubber. Specifically, a dithioacetal-containing diacid (BTA) is synthesized and used as a novel crosslinker for epoxidized natural rubber (ENR), by which dynamic dithioacetals are introduced into the elastomeric networks. Small molecule model study shows that dithioacetal exchange can be conducted at elevated temperature without catalyst. In the BTA crosslinked ENR, the thermoactivated dithioacetal exchange reactions can alter its network topologies in an associative pathway and confer it with remarkable reprocessability. The mechanical properties and relaxation rate of the networks can be readily manipulated by varying the dithioacetal concentration.