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Halide perovskite nanocrystals are at the forefront of materials research due to their remarkable optoelectronic properties and versatile applications. While their lattice structure and optical properties have been extensively investigated for the structure–property correlation, their lattice dynamics, the physical link between the lattice structure and optoelectronic properties, has been much less visited. We report the evolution of structural dynamics of a series of cesium lead halide perovskite nanocrystals whose size and morphology are systematically varied by synthesis temperature. Low-frequency Raman spectroscopy uncovers the nanocrystals' structural dynamics, including a relaxational spectral continuum from ligand librations and a phonon spectrum evolving with nanocrystal size. As the size of nanocrystals increases, their phonon spectrum becomes more intense, and their spectral weights redistribute with new first- and second-order modes being activated. The linewidth of the observed phonon modes generally broadens as the nanocrystal grows larger, an interesting deviation from the established phonon confinement model. We suggest that strong confinement and truncation of the lattice and ligands anchoring on the surface might lead to pinning of the lattice dynamics at nanoscale. These findings offer new insights into the bulk–nano-transition in halide perovskite soft semiconductors. [ABSTRACT FROM AUTHOR]

Cooperativity is essential for the proper functioning of numerous proteins by allosteric interactions. Hemoglobin from Scapharca inaequivalvis (HbI) is a homodimeric protein that can serve as a minimal unit for studying cooperativity. We investigated the structural changes in HbI after carbon monoxide dissociation using time-resolved resonance Raman spectroscopy and observed structural rearrangements in the Fe–proximal histidine bond, the position of the heme in the pocket, and the hydrogen bonds between heme and interfacial water upon ligand dissociation. Some of the spectral changes were different from those observed for human adult hemoglobin due to differences in subunit assembly and quaternary changes. The structural rearrangements were similar for the singly and doubly dissociated species but occurred at different rates. The rates of the observed rearrangements indicated that they occurred synchronously with subunit rotation and are influenced by intersubunit coupling, which underlies the positive cooperativity of HbI. [ABSTRACT FROM AUTHOR]

Pinning particles at the equilibrium configuration of the liquid is expected not to affect the structure and any property that depends on the structure while slowing down the dynamics. This leads to a breakdown of the structure dynamics correlation. Here, we calculate two structural quantities: the pair excess entropy, S2, and the mean field caging potential, the inverse of which is our structural order parameter (SOP). We show that when the pinned particles are treated the same way as the mobile particles, both S2 and SOP of the mobile particles remain the same as those of the unpinned system, and the structure dynamics correlation decreases with an increase in pinning density, "c." However, when we treat the pinned particles as a different species, even if we consider that the structure does not change, the expression of S2 and SOP changes. The microscopic expressions show that the interaction between a pinned particle and a mobile particle affects S2 and SOP more than the interaction between two mobile particles. We show that a similar effect is also present in the calculation of the excess entropy and is the primary reason for the well-known vanishing of the configurational entropy at high temperatures. We further show that, contrary to the common belief, the pinning process does change the structure. When these two effects are considered, both S2 and SOP decrease with an increase in "c," and the correlation between the structural parameters and the dynamics continues even for higher values of "c." [ABSTRACT FROM AUTHOR]

Revived attention in black phosphorus (bP) has been tremendous in the past decade. While many photoinitiated experiments have been conducted, a cross-examination of bP's photocarrier and structural dynamics is still lacking. In this article, we provide such analysis by examining time-resolved data acquired using optical transient reflectivity and reflection ultrafast electron diffraction, two complementary methods under the same experimental conditions. At elevated excitation fluences, we find that more than 90% of the photoinjected carriers are annihilated within the first picosecond (ps) and transfer their energy to phonons in a nonthermal, anisotropic fashion. Electronically, the remaining carrier density around the band edges induces a significant interaction that leads to an interlayer lattice contraction in a few ps but soon diminishes as a result of the continuing loss of carriers. Structurally, phonon–phonon scattering redistributes the energy in the lattice and results in the generation of out-of-plane coherent acoustic phonons and thermal lattice expansion. Their onset times at ∼6 ps are found to be in good agreement. Later, a thermalized quasi-equilibrium state is reached following a period of about 40–50 ps. Hence, we propose a picture with five temporal regimes for bP's photodynamics. [ABSTRACT FROM AUTHOR]

The photochemical dynamics of the acetic acid and trifluoro-acetic acid dimers in hexane are studied using time-resolved infrared absorption spectroscopy and ab initio electronic structure calculations. The different hydrogen bond strengths of the two systems lead to changes in the character of the accessed excited states and in the timescales of the initial structural rearrangement that define the early time dynamics following UV excitation. The much stronger hydrogen bonding in the acetic acid dimer stabilizes the system against dissociation. Ground state recovery is mediated by a structural buckling around the hydrogen bond itself with no evidence for excited state proton transfer processes that are usually considered to drive ultrafast relaxation processes in hydrogen bonded systems. The buckling of the ring leads to relaxation through two conical intersections and the eventual reformation of the electronic and vibrational ground states on a few picosecond timescale. In trifluoro-acetic acid, the weaker hydrogen bonding interaction means that the dimer dissociates under similar irradiation conditions. The surrounding solvent cage restricts the full separation of the monomer components, meaning that the dimer is reformed and returns to the ground state structure via a similar buckled structure but over a much longer, ∼100 ps, timescale. [ABSTRACT FROM AUTHOR]

We present the simulation of the photochemical dynamics of cyclobutanone induced by the excitation of the 3 s Rydberg state. For this purpose, we apply the complete active space self-consistent field method together with the spin–orbit multireference configuration interaction singles treatment, combined with the trajectory surface hopping for the inclusion of nonadiabatic effects. The simulations were performed in the spin-adiabatic representation, including nine electronic states derived from three singlet and two triplet spin-diabatic states. Our simulations reproduce the two previously observed primary dissociation channels: the C2 pathway yielding C2H4 + CH2CO and the C3 pathway producing c-C3H6 + CO. In addition, two secondary products, CH2 + CO from the C2 pathway and C3H6 from the C3 pathway, both of them previously reported, are also observed in our simulation. We determine the ratio of the C3:C2 products to be about 2.8. Our findings show that most of the trajectories reach their electronic ground state within 200 fs, with dissociation events finished after 300 fs. We also identify the minimum energy conical intersections that are responsible for the relaxation and provide an analysis of the photochemical reaction mechanism based on multidimensional scaling. Furthermore, we demonstrate a minimal impact of triplet states on the photodissociation mechanism within the observed timescale. In order to provide a direct link to experiments, we simulate the gas phase ultrafast electron diffraction patterns and connect their features to the underlying structural dynamics. [ABSTRACT FROM AUTHOR]

Binary mixtures of water with lower alcohols display non-linear phase behaviors upon mixing, which are attributed to potential cluster formation at the molecular level. Unravelling such elusive structures requires investigation of hydrogen-bonding sub-nanosecond dynamics. We employ high-resolution neutron time-of-flight spectroscopy with polarization analysis in combination with selective deuteration to study the concentration-dependent structural dynamics in the water rich part of the phase diagram of water–ethanol mixtures. This method enables simultaneous access to atomic correlations in space and time and allows us to separate spatially incoherent scattering probing self-diffusion of the ethanol fraction from the coherent scattering probing collective diffusion of the water network as a whole. Our observations indicate an enhanced rigidity of the hydrogen bond network at the mesoscopic length scale compared to the molecular scale as the ethanol fraction increases, which is consistent with the hypothesis of clusters. [ABSTRACT FROM AUTHOR]

Highly acidic protic ionic liquids (PILs) are promising materials for potential electrochemical applications due to their high proton conductivity and excellent thermal stability. Still, little is known about the correlation between charge transport and structural dynamics as well as the proton transport mechanism despite the large body of literature on this topic. Here, we have examined the charge transport and structural dynamics by employing broadband dielectric spectroscopy in two highly acidic PILs in their supercooled liquid and glassy states, which included the same anion [TfO]− and different cations, [Tau]+ vs [Ahs]+. Unlike many other ionic liquids, the conductivity relaxation time τe of two studied PILs is substantially faster than the structural relaxation time τα. The decoupling behavior between charge transport and structural dynamics of two materials, which is manifested by a decoupling index Rτ, varies between 0.3 and 2.3 over the temperature range above Tg. Moreover, "Walden" plots of the molar conductivity vs the viscosity qualify both compounds as "Super ILs." All findings support the physical picture of large, polar, and orientationally correlated ion clusters, where the slow α-relaxation can be identified as structural relaxation associated with cooperative reorientations of the cluster macrodipole. In contrast, the shortest timescale for diffusive charge transport, τe, is 1–2 decades shorter than τα, implying that proton hopping is triggered by "single particle" (ions or ion pair) rotations and jumps on a sub-length scale of the cluster size, a dynamics being present even in the glassy state as indicated by a strong β-relaxation. These results demonstrate the practicality of employing highly acidic PILs in electrochemical fields. [ABSTRACT FROM AUTHOR]

Physical aging is the process of a system evolving toward a new equilibrium, and thus the response to a change in external parameters such as temperature T, pressure p, or static electric field E. Using a static electric field has been shown to access physical aging above the glass transition temperature Tg, in the regime of milliseconds or faster, but the relation to its temperature jump counterpart has not been investigated to date. This work compares temperature and field induced physical aging in the limit of small perturbations for supercooled tributyl phosphate. It is found that both structural recovery dynamics are very similar, and that they match the collective reorientational dynamics as observed by dielectric relaxation. The results facilitate expanding the range of aging experiments to well above Tg, where a comparison with structural relaxation in equilibrium is straightforward, thus improving models of structural recovery and physical aging. [ABSTRACT FROM AUTHOR]

Site-selective probing of iodine 4d orbitals at 13.1 nm was used to characterize the photolysis of CH2I2 and CH2BrI initiated at 202.5 nm. Time-dependent fragment ion momenta were recorded using Coulomb explosion imaging mass spectrometry and used to determine the structural dynamics of the dissociating molecules. Correlations between these fragment momenta, as well as the onset times of electron transfer reactions between them, indicate that each molecule can undergo neutral three-body photolysis. For CH2I2, the structural evolution of the neutral molecule was simultaneously characterized along the C–I and I–C–I coordinates, demonstrating the sensitivity of these measurements to nuclear motion along multiple degrees of freedom. [ABSTRACT FROM AUTHOR]

The collective density–density and hydrostatic pressure–pressure correlations of glass-forming liquids are spatiotemporally mapped out using molecular dynamics simulations. It is shown that the sharp rise of structural relaxation time below the Arrhenius temperature coincides with the emergence of slow, nonhydrodynamic collective dynamics on mesoscopic scales. The observed long-range, nonhydrodynamic mode is independent of wave numbers and closely coupled to the local structural dynamics. Below the Arrhenius temperature, it dominates the slow collective dynamics on length scales immediately beyond the first structural peak in contrast to the well-known behavior at high temperatures. These results highlight a key connection between the qualitative change in mesoscopic two-point collective dynamics and the dynamic crossover phenomenon. [ABSTRACT FROM AUTHOR]

Using electric fields to initiate the process of physical aging has facilitated measurements of structural recovery dynamics on the time scale of milliseconds. This, however, complicates the interesting comparison with aging processes due to a temperature jump, as these are significantly slower. This study takes a step toward comparing the results of field and temperature perturbations by providing data on field-induced structural recovery of vinyl ethylene carbonate at two different time scales: 1.0 ms at 181 K and 33 s at 169 K, i.e., 4.5 decades apart. It is found that structural recovery is a factor of two slower than structural relaxation in equilibrium, with the latter determined via dielectric relaxation in the limit of linear response. The relation between recovery and relaxation dynamics remains temperature invariant across the present experimental range. [ABSTRACT FROM AUTHOR]

Boron phosphide (BP) is a (super)hard semiconductor constituted of light elements, which is promising for high demand applications at extreme conditions. The behavior of BP at high temperatures and pressures is of special interest but is also poorly understood because both experimental and conventional ab initio methods are restricted to studying refractory covalent materials. The use of machine learning interatomic potentials is a revolutionary trend that gives a unique opportunity for high-temperature study of materials with ab initio accuracy. We develop a deep machine learning potential (DP) for accurate atomistic simulations of the solid and liquid phases of BP as well as their transformations near the melting line. Our DP provides quantitative agreement with experimental and ab initio molecular dynamics data for structural and dynamic properties. DP-based simulations reveal that at ambient pressure, a tetrahedrally bonded cubic BP crystal melts into an open structure consisting of two interpenetrating sub-networks of boron and phosphorous with different structures. Structure transformations of BP melt under compressing are reflected by the evolution of low-pressure tetrahedral coordination to high-pressure octahedral coordination. The main contributions to structural changes at low pressures are made by the evolution of medium-range order in the B-subnetwork and, at high pressures, by the change of short-range order in the P-subnetwork. Such transformations exhibit an anomalous behavior of structural characteristics in the range of 12–15 GPa. DP-based simulations reveal that the Tm(P) curve develops a maximum at P ≈ 13 GPa, whereas experimental studies provide two separate branches of the melting curve, which demonstrate the opposite behavior. Analysis of the results obtained raises open issues in developing machine learning potentials for covalent materials and stimulates further experimental and theoretical studies of melting behavior in BP. [ABSTRACT FROM AUTHOR]

Inferring transient molecular structural dynamics from diffraction data is an ambiguous task that often requires different approximation methods. In this paper, we present an attempt to tackle this problem using machine learning. Although most recent applications of machine learning for the analysis of diffraction images apply only a single neural network to an experimental dataset and train it on the task of prediction, our approach utilizes an additional generator network trained on both synthetic and experimental data. Our network converts experimental data into idealized diffraction patterns from which information is extracted via a convolutional neural network trained on synthetic data only. We validate this approach on ultrafast electron diffraction data of bismuth samples undergoing thermalization upon excitation via 800 nm laser pulses. The network was able to predict transient temperatures with a deviation of less than 6% from analytically estimated values. Notably, this performance was achieved on a dataset of 408 images only. We believe that employing this network in experimental settings where high volumes of visual data are collected, such as beam lines, could provide insights into the structural dynamics of different samples. [ABSTRACT FROM AUTHOR]

AgPd nanoalloys often undergo structural evolution during catalytic reactions; the mechanism underlying such restructuring remains largely unknown due to the use of oversimplified interatomic potentials in simulations. Herein, a deep-learning potential is developed for AgPd nanoalloys based on a multiscale dataset spanning from nanoclusters to bulk configurations, exhibits precise predictions of mechanical properties and formation energies with near-density functional theory accuracy, calculates the surface energies closer to experimental values compared to those obtained by Gupta potentials, and is applied to investigate the shape reconstruction of single-crystalline AgPd nanoalloys from cuboctahedron (Oh) to icosahedron (Ih) geometries. The Oh to Ih shape restructuring is thermodynamically favorable and occurs at 11 and 92 ps for Pd55@Ag254 and Ag147@Pd162 nanoalloys, respectively. During the shape reconstruction of Pd@Ag nanoalloys, concurrent surface restructuring of the (100) facet and internal multi-twinned phase change are observed with collaborative displacive characters. The presence of vacancies can influence the final product and reconstructing rate of Pd@Ag core–shell nanoalloys. The Ag outward diffusion on Ag@Pd nanoalloys is more pronounced in Ih geometry compared to Oh geometry and can be further accelerated by the Oh to Ih deformation. The deformation of single-crystalline Pd@Ag nanoalloys is characterized by a displacive transformation involving the collaborative displacement of a large number of atoms, distinguishing it from the diffusion-coupled transformation of Ag@Pd nanoalloys. [ABSTRACT FROM AUTHOR]

Tunable piezoelectric metasurfaces have been proposed as a means of adaptively steering incident elastic waves for various applications in vibration mitigation and control. Bonding piezoelectric material to thin structures introduces electromechanical coupling, enabling structural dynamics to be altered via tunable electric shunts connected across each unit cell. For example, by carefully calibrating the inductive shunts, it is possible to implement the discrete phase shifts necessary for gradient-based waveguiding behaviors. However, experimental validations of localized phase shifting are challenging due to the narrow bandgap of local resonators, resulting in poor transmission of incident waves and high sensitivity to transient noise. These factors, in combination with the difficulties in experimental circuitry synthesis, can lead to significant variability of data acquired within the bandgap operating region. This paper presents a systematic approach for extracting localized phase shifts by taking advantage of the inherent correlation between the incident and transmitted wavefronts. During this procedure, matched filtering greatly reduces noise in the transmitted signal when operating in or near bandgap frequencies. Experimental results demonstrate phase shifts as large as −170° within the locally resonant bandgap, with an average 28% reduction in error relative to a direct time domain measurement of phase, enabling effective comparison of the dispersive behavior with corresponding analytical and finite element models. In addition to demonstrating the tunable waveguide characteristics of a piezoelectric metasurface, this technique can easily be extended to validate localized phase shifting of other elastic waveguiding metasurfaces. [ABSTRACT FROM AUTHOR]

A novel method combining the maximum entropy principle, the Bayesian-inference of ensembles approach, and the optimization of empirical forward models is presented. Here, we focus on the Karplus parameters for RNA systems, which relate the dihedral angles of γ, β, and the dihedrals in the sugar ring to the corresponding 3J-coupling signal between coupling protons. Extensive molecular simulations are performed on a set of RNA tetramers and hexamers and combined with available nucleic-magnetic-resonance data. Within the new framework, the sampled structural dynamics can be reweighted to match experimental data while the error arising from inaccuracies in the forward models can be corrected simultaneously and consequently does not leak into the reweighted ensemble. Carefully crafted cross-validation procedure and regularization terms enable obtaining transferable Karplus parameters. Our approach identifies the optimal regularization strength and new sets of Karplus parameters balancing good agreement between simulations and experiments with minimal changes to the original ensemble. [ABSTRACT FROM AUTHOR]

The vibration of different structural members is highly dependent on the external forces and environment they are moving in it. The stiffness and mass properties of the structure are the main factors in determining the frequency responses. However, situations commonly occur in which the structures are exposed to perpetual external loading conditions. In the present study, a novel model for investigating the effects of friction between structure and substrate is proposed and applied in small-scale cylindrical structures. In this regard, nanocomposite materials made of epoxy and reinforced by graphene oxide particles in an axial direction are used as the main material of the cylinder. The classical formulation of elasticity for anisotropic materials in a polar coordinate system is derived and presented. Moreover, the homogeneous properties of the nanocomposite are evaluated using Halpin–Tsai formulation. The core idea of the current study is to develop and present a new concept of the frictional substrate to incorporate friction forces into consideration along with visco-elastic reactions. Both finite element and analytical solutions are provided to examine the effects of different parameters on the vibrational behavior of the structure. The results of the study are presented using graphs for a detailed presentation of the effects of different parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] Ultraviolet B (UVB) radiation can compromise the functionality of the skin barrier through various mechanisms. We hypothesize that UVB induce photochemical alterations in the components of the outermost layer of the skin, known as the stratum corneum (SC), and modulate its antioxidative defense mechanisms. Catalase is a well-known antioxidative enzyme found in the SC where it acts to scavenge reactive oxygen species. However, a detailed characterization of acute UVB exposure on the activity of native catalase in the SC is lacking. Moreover, the effects of UVB irradiation on the molecular dynamics and organization of the SC keratin and lipid components remain unclear. Thus, the aim of this work is to characterize consequences of UVB exposure on the structural and antioxidative properties of catalase, as well as on the molecular and global properties of the SC matrix surrounding the enzyme. The effect of UVB irradiation on the catalase function is investigated by chronoamperometry with a skin covered oxygen electrode, which probes the activity of native catalase in the SC matrix. Circular dichroism is used to explore changes of the catalase secondary structure, and gel electrophoresis is used to detect fragmentation of the enzyme following the UVB exposure. UVB induced alterations of the SC molecular dynamics and structural features of the SC barrier, as well as its water sorption behavior, are investigated by a complementary set of techniques, including natural abundance 13C polarization transfer solid-state NMR, wide-angle X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and dynamic vapor sorption microbalance. The findings show that UVB exposure impairs the antioxidative function of catalase by deactivating both native catalase in the SC matrix and lyophilized catalase. However, UVB radiation does not alter the secondary structure of the catalase nor induce any observable enzyme fragmentation, which otherwise could explain deactivation of its function. NMR measurements on SC samples show a subtle increase in the molecular mobility of the terminal segments of the SC lipids, accompanied by a decrease in the mobility of lipid chain trans-gauche conformers after high doses of UVB exposure. At the same time, the NMR data suggest increased rigidity of the polypeptide backbone of the keratin filaments, while the molecular mobility of amino acid residues in random coil domains of keratin remain unaffected by UVB irradiation. The FTIR data show a consistent decrease in absorbance associated with lipid bond vibrations, relative to the main protein bands. Collectively, the NMR and FTIR data suggest a small modification in the composition of fluid and solid phases of the SC lipid and protein components after UVB exposure, unrelated to the hydration capacity of the SC tissue. To conclude, UVB deactivation of catalase is anticipated to elevate oxidative stress of the SC, which, when coupled with subtle changes in the molecular characteristics of the SC, may compromise the overall skin health and elevate the likelihood of developing skin disorders. [ABSTRACT FROM AUTHOR]

Glulam timber is gaining popularity as a structural element due to its cost-effectiveness, strength, and environmental benefits. However, being an organic material, it is susceptible to degradation. Therefore, nondestructive testing (NDT) methods are essential for assessing its structural health. In this study, two NDT approaches, ultrasound-based and modal updating, were used to predict the static bending modulus of elasticity (MOE) in Pinus Sylvestris and Spruce species. The results demonstrated that the modal updating and linear regression models outperformed the ultrasound technique in accurately determining the static MOE. Additionally, considering the influence of knots improved the accuracy of ultrasound predictions. [ABSTRACT FROM AUTHOR]

The Dengue virus (DENV) is the most significant arthropod-borne viral pathogen in humans with 400 million infections annually. DENV comprises four distinct serotypes (DENV-1 to -4) which complicates vaccine development. Any of the four serotypes can cause clinical illness but with distinctive infection dynamics. Variations in sequences identified within the four genomes induce structural differences in crucial RNA motifs that were suggested to be correlated to the degree of pathogenicity among DENV-1 to -4. In particular, the RNA Stem-loop A (SLA) at the 5′-end of the genome, acts as a key regulator of the viral replication cycle by interacting with the viral NS5 polymerase to initiate the minus-strand viral RNA synthesis and later to methylate and cap the synthesized RNA. The molecular details of this interaction remain not fully described. Here, we report the solution secondary structures of SLA from DENV-1 to -4. Our results highlight that the four SLA exhibit structural and dynamic differences. Secondly, to determine whether SLA RNA contains serotype-specific determinants for the recognition by the viral NS5 protein, we investigated interactions between SLA from DENV -1 to -4 and DENV2 NS5 using combined biophysical approaches. Our results show that NS5 from DENV2 is able to bind SLA from other serotypes, but that other viral or host factors may be necessary to stabilize the complex and promote the catalytically active state of the NS5. By contrast, we show that a serotype-specific binding is driven by specific interactions involving conformational changes within the SLA RNA. • SLA RNA from DENV-1 to -4 exhibit structural and dynamics differences. • First NMR description of viral NS5 polymerase binding to SLA RNA. • Binding of NS5 to serotype-specific SLA induces structural rearrangement. • Binding of NS5 to a non-serotype-specific SLA occurs through different mechanisms. [ABSTRACT FROM AUTHOR]

• Excitatory synapses are destabilized in EAE. • Unstable excitatory inputs occur closer to one another in EAE. • Unstable excitatory inputs are distributed across the dendritic tree in EAE. • With super-resolution imaging a small proportion of excitatory synapses are lost. Synapses are lost on a massive scale in the brain and spinal cord of people living with multiple sclerosis (PwMS), and this synaptic loss extends far beyond demyelinating lesions. Post-mortem studies show the long-term consequences of multiple sclerosis (MS) on synapses but do not inform on the early impacts of neuroinflammation on synapses that subsequently lead to synapse loss. How excitatory circuit inputs are altered across the dendritic tree of individual neurons under neuroinflammatory stress is not well understood. Here, we directly assessed the structural dynamics of labeled excitatory synapses in experimental autoimmune encephalomyelitis (EAE) as a model of immune-mediated cortical neuronal damage. We used in vivo two-photon imaging and a synthetic tissue-hydrogel super-resolution imaging technique to reveal the dynamics of excitatory synapses, map their location across the dendritic tree of individual neurons, and examine neurons at super-resolution for synaptic loss. We found that excitatory synapses are destabilized but not lost from dendritic spines in EAE, starting with the earliest imaging session before symptom onset. This led to changes in excitatory circuit inputs to individual cells. In EAE, stable synapses are replaced by synapses that appear or disappear across the imaging sessions or repeatedly change at the same location. These unstable excitatory inputs occur closer to one another in EAE than in healthy controls and are distributed across the dendritic tree. When imaged at super-resolution, we found that a small proportion of dendritic protrusions lost their presynapse and/or postsynapse. Our finding of diffuse destabilizing effects of neuroinflammation on excitatory synapses across cortical neurons may have significant functional consequences since normal dendritic spine dynamics and clustering are essential for learning and memory. [ABSTRACT FROM AUTHOR]

At present, the dynamic studies of cylindrical shells are mostly limited to free- and forced vibration, the transient response of which is very limited. It is worth noting that no one has conducted research on the transient response of cylindrical shells with rotating speed and initial geometrical imperfection. Based on this fact, the present article is dedicated to discussing the transient response of rotating carbon nanotubes reinforced composite cylindrical shells with initial geometrical imperfection for the first time. Firstly, four distribution patterns of carbon nanotubes are taken into consideration, in which the material properties are calculated with the help of the mixing rule. Subsequently, considering the effect of initial geometric imperfection, the dynamic model is built according to Love's thin shell theory. Then, the motion equation of the shell is derived based on the Hamilton principle. Assuming three different boundary conditions, the Galerkin principle is applied to reduce the dimensionality of the motion equation, which leads to a nonlinear equation containing central radial displacement, pulse load, and time. Simultaneously, two comparative analyses are developed to confirm the validity of this article, and the results indicate that there is no significant difference between the current results and existing literature. By summarizing the characteristics of four pulse loads, the blast load is determined for numerical analysis. Finally, the Runge–Kutta method is employed to acquire the transient response with various influence factors. The current research provides theoretical guidance for structural design and vibration reduction of the spacecrafts subjected to pulse loads. [ABSTRACT FROM AUTHOR]

The optimal local truncation error method (OLTEM) with unfitted Cartesian meshes recently developed for the scalar wave and heat equations for heterogeneous materials is extended to a more complex case of a system of the elastodynamics PDEs. Compact 9-point stencils (similar to those for linear finite elements) are used for OLTEM. Compared to our previous results, a new approach is used for the calculation of the right-hand side of the stencil equations due to body forces. It significantly simplifies the analytical derivations of OLTEM for time-dependent problems. There are no unknowns on interfaces between different materials; the structure of the global semi-discrete equations for OLTEM is the same for homogeneous and heterogeneous materials. For the first time we have also developed OLTEM with the diagonal mass matrix. In contrast to many known approaches with some ad-hoc calculations of the diagonal mass matrix, OLTEM offers a rigorous approach which is a particular case of OLTEM with the non-diagonal mass matrix. Another novelty of the article is a new post-processing procedure for the accurate calculations of stresses. It includes the same compact 9-point stencils as those in basic computations and uses the accelerations and the displacements at the grid points along with the PDEs for the stress calculations. OLTEM yields accurate numerical results for heterogeneous materials with big contrasts in the material properties of different components. Numerical experiments for elastic heterogeneous materials show: a) at the same number of degrees of freedom (dof), OLTEM with unfitted Cartesian meshes is more accurate than linear finite elements with similar stencils and conformed meshes; at the engineering accuracy of 0.1 % for the displacements, OLTEM reduces the number of dof by more than 20 times; at the engineering accuracy of 0.1 % for the stresses, OLTEM with the new post-processing procedure reduces the number of dof by more than 104 times compared to linear finite elements; b) at the same number of dof, OLTEM with unfitted Cartesian meshes is even more computationally efficient than high-order finite elements with much wider stencils and conformed meshes. This will lead to a huge reduction in the computation time for elastodynamics problems solved by OLTEM and will allow the direct computations of some complex wave propagation and structural dynamics problems for heterogeneous materials without the scale separation. [ABSTRACT FROM AUTHOR]

In this study, the electrochemical performance of Na 3 MnTi(PO 4) 3 material has been improved through cation/anion-dual regulation. This dual regulation provides a strategy for phosphate materials as an advanced cathode for sodium-ion batteries. [Display omitted] Na 3 MnTi(PO 4) 3 (NMTP) emerges as a promising cathode material with high-performance for sodium-ion batteries (SIBs). Nevertheless, its development has been limited by several challenges, including poor electronic conductivity, the Mn3+ Jahn-Teller effect, and the presence of a Na+/Mn2+ cation mixture. To address these issues, we have developed a cation/anion-dual regulation strategy to activate the redox reactions involving manganese, thereby significantly enhancing the performance of NMTP. This strategy simultaneously enhances the structural dynamics and facilitates rapid ion transport at high rates by inducing the formation of sodium vacancy. The combined effects of these modifications lead to a substantial improvement in specific capacity (79.1 mAh/g), outstanding high-rate capabilities (35.9 mAh/g at 10C), and an ultralong cycle life (only 0.040 % capacity attenuation per cycle over 250 cycles at 1C for Na 3.34 Mn 1.2 Ti 0.8 (PO 3.98 F 0.02) 3) when used as a cathode material in SIBs. Furthermore, its performance in full cell demonstrates impressive rate capability (44.4 mAh/g at 5C) and exceptional cycling stability (with only 0.116 % capacity decay per cycle after 150 cycles at 1C), suggesting its potential for practical applications. This work presents a dual regulation strategy targeting different sites, offering a significant advancement in the development of NASICON phosphate cathodes for SIBs. [ABSTRACT FROM AUTHOR]

On October 18, 2019, Chile experienced the most important social upheaval since the country regained democracy in the late 1980s. The "Social Outbreak" surprised economic and political elites and seemed paradoxical to the international community who had often praised Chile as a model of successful development. In this paper, we used structural-demographic theory to analyze the interaction between the overproduction of elites and the stagnation in the relative income of the population as the underlying structural cause of Chilean political instability. This theory was able to predict the three most significant instances of political tension in the recent history of Chile: the crisis of the late 1960s that culminated in the coup d'état of 1973, popular mobilizations during the 1980s, and the recent student mobilizations and social upheaval. Our results suggest that, at least during the period 1938–2019, Chilean sociopolitical dynamics is determined by the same structural drivers. [ABSTRACT FROM AUTHOR]

Transthyretin (TTR), also known as prealbumin, is a highly conserved protein found in several vertebrate species. Dissociation of TTR tetramer followed by aggregation and misfolding of the monomers causes genesis of insoluble amyloid fibrils, which might systematically lead to peripheral and/or autonomic neuropathy and other systemic manifestations. Structural insights into the conformational landscape of TTR monomers upon mutation are useful for understanding amyloid aggregation. In this study, we used all-atom molecular dynamics (MD) simulations to investigate the role of V30M mutation on the structure of TTR monomer. The MD simulations of the wild-type and V30M TTR monomeric showed that the V30M mutation leads to dissociation of one of the edge strands, strand C, from the core of the monomer and forms an ensemble of partially unfolded conformations. These changes can be linked to disruption in the inter-strand hydrogen bonding and the secondary structure of the monomeric state. Moreover, non-covalent interactions in the E–F loop region, which is important for aggregation propensity of TTR, are also perturbed. Overall, the MD simulations provide comparative structural insights into the dynamics of wild-type and V30M TTR monomers. [ABSTRACT FROM AUTHOR]

The series tuned inerter dampers (STID) with distributed inerters are proposed in this paper to suppress seismic response for ground motion excited structures with broadband characteristics. In order to reveal the mechanism of the STID for vibration mitigation, the dimensionless displacement objective function of a single degree of freedom structure equipped with an STID under random Gaussian white noise base excitations is thereupon derived. Based on the principle of the reasonable distribution of inertance, the analytical optimal design parameters of STID are obtained under constraint for total inerter-mass ratio. The vibration mitigation performance of the STID is evaluated and further compared with the tuned inerter damper (TID), tuned mass damper (TMD) and typical series dampers using same mass ratio or inerter-mass ratio when structure is subjected to harmonic and random excitation. Results demonstrate that the performance of structural vibration control and broadband characteristics of STID outperform both the TMD and TID. On the condition of same inerter-mass ratio, the deformation enhancement of damping element can be further increased compared with TID because of dual-tuning effect of series inerters. The higher vibration control performance of STID is realized by using very small nominal damping ratio compared with the TMD and TID. Meanwhile, there exist two grounded inerters in STID compared to other series dampers, and both two subsystems are not affected by base random acceleration excitation which also brings STID a wider VSB and better seismic response mitigation effect. Substantially, due to STID is a type of dual-grounded inerter-based device, for force and base acceleration excited main system, the optimal expressions are identical. Hence, STID can adapt to more complex practical engineering and random and diverse excitations. Hence, the STID can be deemed to be a broadband, high effectiveness and high-performance inerter system. Meanwhile, considering low damping, lightweight and flexible install of STID, it is easier for implementation in practical engineering. [ABSTRACT FROM AUTHOR]

Resonance of multi-degree-of-freedom system or structure is a basic and important concept in structural vibration theory, but it lacks a complete and rigorous definition. In order to establish an accurate concept of structural resonance, based on the concept of single-degree-of-freedom system resonance and modal orthogonality, this paper discusses the necessary conditions of system resonance by analyzing the displacement response of multi-degree-of-freedom vibration system, that is, while ensuring that the vibration frequency of the system (a certain natural frequency) is equal to the excitation frequency, its displacement response should also present the corresponding modal shape. An example of simply supported beam is used to illustrate its rationality. At the same time, the theoretical method of pure modal resonance of multi-degree-of-freedom system is given by rational allocation of excitation force. The pure modal resonance of multi-degree-of-freedom system or structure can be realized, which can be used to accurately identify the modal parameters of the structure. It is of great theoretical significance and engineering application value to discriminate the concept of multi-degree-of-freedom system or structure resonance. [ABSTRACT FROM AUTHOR]

Inhomogeneous damping distribution leads to the occurrence of complex modes of structures. Complex modes' vibration and acoustic radiation characteristics are different from real modes. This paper studies the complex modal characteristics of inhomogeneously damped plates for forced vibration. We used the state space method to obtain the complex eigenvalues and eigenvectors of the vibration system and calculated the relationship between modal coordinates and frequency under unit force. The results show that the absolute values of the modal coordinates of two conjugate complex eigenvectors are different, and the structure's vibration is dominated by the eigenvectors corresponding to eigenvalues with positive imaginary parts near natural frequencies. When investigating the structural sound radiation in the vibration mode space, each mode's acoustic radiation is not independent but coupled with each other. The influence of the coupling between complex modes on the calculation results of the acoustic radiation power of the plate is studied in this paper. The results show that the coupling effect between modes cannot be ignored when calculating the acoustic radiation power based on complex modes. Finally, the error of calculating acoustic power using the decoupling approximation instead of the complex mode method is analyzed. [ABSTRACT FROM AUTHOR]

The automotive industry has transitioned from internal combustion engine (ICE) vehicles to electric vehicles (EVs) in recent years. Also essential to the development of the next generation are the enhancement of engine performance and production of lightweight vehicle bodies. Through this method, it is possible to increase vehicle output. However, as the vehicle's excitation strength increases, structural noise and vibrations caused by the engine increase. Intelligent structure-based active mounting systems are widely used in the automotive industry to reduce vibration and noise. It can continuously control the dynamic characteristics of the mount system, enabling real-time control of active mounting systems. When determining the position of the active mounting system, it must be installed in the most efficient position possible. Therefore, the purpose of this study is to determine the optimal placement criteria for an active mounting system consisting of a piezoelectric actuator and a rubber grommet. The lumped parameter model is used to model the plate structure with two hybrid mounting systems based on the source–path–receiver structure. In addition, the forces of two active mounts are calculated using static and dynamic approaches. When the calculated force on the hybrid mount system is relatively low, the location with the greatest vibration reduction can be determined, and this location can be regarded as the optimal location for the active mounting system. In addition, a feasibility test is conducted to validate the proposed criteria and validate the static and dynamic results. The findings indicate that the optimal location for the active engine mounting system can be determined. [ABSTRACT FROM AUTHOR]

Due to the three-dimensional non-axisymmetric shape of the volute, its interaction with the impeller increases the internal flow field complexity and instability of the marine centrifugal pump, representing the main reason for pump body vibration and hydraulic noise. First, the basic principle of fluid machinery noise calculation was explained based on the Lighthill acoustic analogy method and Curle's theory. Then, the fluid pressure pulsation and flow characteristics of centrifugal pumps were analyzed using the Fluent software, after which the Actran software was used to examine the flow-induced vibration noise properties. The results showed that the clearance size significantly impacted the pump head, while the peak value of the flow-induced vibration response was mainly twice the blade frequency. Although a larger ring clearance increased the structural vibration, it had little impact on the sound pressure level changes in the external sound field. The results provided a new method for the structural optimization and low-noise design of marine centrifugal pumps. [ABSTRACT FROM AUTHOR]

Based on nanoarchitectonics and molecular dynamics simulations, we investigate the structural properties and diffusion pathway of Na atoms in sodium trisilicate over a wide temperature range. The structural and dynamics properties are analyzed through the radial distribution function (RDF), the Voronoi Si- and O-polyhedrons, the cluster function fCL(r), and the sets of fastest (SFA) and slowest atoms (SSA). The results indicate that Na atoms are not placed in Si-polyhedrons and bridging oxygen (BO) polyhedrons; instead, Na atoms are mainly placed in non-bridging oxygen (NBO) polyhedrons and free oxygen (FO) polyhedrons. Here BO, NBO, and FO represent O bonded with two, one, and no Si atoms, respectively. The simulation shows that O atoms in sodium trisilicate undergo numerous transformations: NBF0 ↔ NBF1, NBF1 ↔ NBF2, and BO0 ↔ BO1, where NBF is NBO or FO. The dynamics in sodium trisilicate are mainly distributed by the hopping and cooperative motion of Na atoms. We suppose that the diffusion pathway of Na atoms is realized via hopping Na atoms alone in BO-polyhedrons and the cooperative motion of a group of Na atoms in NBO- and FO-polyhedrons. [ABSTRACT FROM AUTHOR]

This paper presents the design, modeling, and characterizing tests of an assembled freely pendulum-type active tuned mass damper (AP-ATMD) for structural vibration control, highlighting its unique features such as noncontact force transmission, nonextra stiffness, and damping members. This device can operate passively as a tuned mass damper (TMD) with optimal tuning when environmental disturbances are minimal, or it can engage efficiently in active control when significant disturbances are present. The AP-ATMD mainly consists of a robust suspension system, an arc-shaped mass block with permanent magnets (PMs), and an arc-shaped electromagnetic motor. Notably, both the electromagnetic motor and the mass block have identical curvatures. A laboratory prototype of the AP-ATMD was designed and fabricated for the purpose of characterizing tests. Furthermore, an electromechanical model based on the Bouc–Wen hysteresis loop was developed to accurately characterize the active force behavior generated by the device. The parameters of this model were identified through a series of characterizing tests of the prototype AP-ATMD under harmonic excitations, and subsequently were validated under random excitation. The results confirmed the efficacy of the proposed electromechanical model in precisely capturing the active force behavior across a wide array of operational conditions. Finally, a numerical simulation of a 3-story frame with the AP-ATMD installed was conducted. The outcomes of the simulation highlighted the AP-ATMD's ability to reduce structural responses significantly. Moreover, the system employing the proposed electromechanical model outperformed a linear model, demonstrating a superior reduction in structural response. [ABSTRACT FROM AUTHOR]

Ubiquitin-specific protease 14 (USP14), one of the three major proteasome-associated deubiquitinating enzymes (DUBs), is known to be activated by the AKT-mediated phosphorylation at Ser432. Thereby, AKT can regulate global protein degradation by controlling the ubiquitin-proteasome system (UPS). However, the exact molecular mechanism of USP14 activation by AKT phosphorylation at the atomic level remains unknown. By performing the molecular dynamics (MD) simulation of the USP14 catalytic domain at three different states (inactive, active, and USP14-ubiquitin complex), we characterized the change in structural dynamics by phosphorylation. We observed that the Ser432 phosphorylation induced substantial conformational changes of USP14 in the blocking loop (BL) region to fold it from an open loop into a β-sheet, which is critical for USP14 activation. Furthermore, phosphorylation also increased the frequency of critical hydrogen bonding and salt bridge interactions between USP14 and ubiquitin, which is essential for DUB activity. Structural dynamics insights from this study pinpoint the important local conformational landscape of USP14 by the phosphorylation event, which would be critical for understanding USP14-mediated proteasome regulation and designing future therapeutics. [ABSTRACT FROM AUTHOR]

Analogous electrical networks were previously derived from the Euler–Bernoulli and Kirchhoff–Love theories to represent beams and plates, respectively, for use in multimodal structural vibration damping. However, these networks do not account for shear deformations or rotary inertia, which can result in suboptimal vibration damping performance when used on moderately thick beams and plates. In this paper, we investigate the incorporation of shear deformation and rotary inertia using Timoshenko–Ehrenfest beam theory and Mindlin–Reissner plate theory to develop improved electrical networks that can more accurately represent thick beams and plates. Our findings suggest that the inclusion of shear deformation and rotary inertia can significantly improve the frequency coherence of the electrical networks and multimodal vibration damping for thicker structures. The electrical analogs presented here are of use for various applications, especially to conveniently design complex circuit topologies in fields spanning from vibration attenuation to energy harvesting. [ABSTRACT FROM AUTHOR]

The article presents Luigi Pasinetti's theoretical system by foregrounding (i) the multiple forms of interdependence between specialised production activities, and the representations of economic structure associated with each form of interdependence (e.g., horizontal vs. vertical); (ii) the coordination requirements imposed on interdependent activities by the need to achieve systemic goals such as full employment and full utilization of production capacity; (iii) the bounded open-endedness of the proportions between activities that satisfy such requirements; (iv) the distinction between the coordination requirements imposed by economic structure and the contextual conditions that may or may not make it possible to satisfy those requirements; and hence (v) the different socio-political and institutional arrangements that may be compatible with different systemic objectives. In this light, the essay introduces a collection of articles published in Structural Change and Economic Dynamics that explores the interfaces between Pasinetti's work and multiple lines of research in economics. [ABSTRACT FROM AUTHOR]

• Pasinetti's Natural Economic System gives an important reference to the analysis of the structural changes in a growing economy. • The natural rate of profit is given by the rate of profit to the wage (r w) in our Sraffian aggregate model. • The pure labour theory of value is compatible with the positive rate of profit in the aggregates. • The standard productivity index gives the base to combine the changes in sectoral labour productivities, the average productivity, income distribution, and commodity prices. Pasinetti's (1981) natural economic system is a central idea of Pasinetti's structural economic dynamics, which explains various features of a growing economy, focusing on an evolving structure of commodity prices, an evolving structure of production, and the time pass of the wage rate and the rate of profit (Pasinetti, 1981 , p.128). It exhibits three core properties: first, the sum of the growth rate of the quantity of labour and the growth rate of demand or the growth rate of labour productivity determines the rate of profit (the natural rate of profit). Second, under a 'positive' natural rate of profit, the quantity of labour commanded by a commodity equals the quantity of labour embodied in the commodity (a pure labour theory of value). Finally, equal rewards should be paid for equal amounts of homogenous labour (the basic principle of equal rewards). These core properties were examined, using our Sraffian discrete-time models corresponding to the three cases. The first model explains the simple case of a growing economy with no technical change and an invariant composition of demand. The second model treats the difference between the actual net product and the standard net product, assuming no technical change and an invariant composition of demand. The third model explains the occurrence of technical progress in a growing economy. The validity of three core properties of the natural economic system in Pasinetti (1981) is examined by three Sraffian models. [ABSTRACT FROM AUTHOR]

High diversity and differential evolution profiles have been observed for DD34E/ Tc1 transposons; several families originating from these groups, such as DD34E/ ZB , DD34E/ SB , DD35E/ TR , DD36E/ IC, and DD38E/ IT , have been well defined. Even though Frisky , Tiang , Tsessebe, and Topi transposons have been identified in Anopheles gambiae , their taxonomic distribution and phylogenetic relationship in nature remain largely unknown. The evolutionary profiles of Frisky , Tiang , Tsessebe , and Topi homology transposons were investigated in the current study. In total, 254 homology transposons of Frisky , Tiang , Hob , Tsessebe, and Topi were obtained in 200 species by data mining. The phylogenetic tree revealed that these transposons were classified into five main clades (Frisky , Tiang , Hob , Tsessebe , and Topi) forming a monophyletic clade with 98% bootstrap support, belonging to the DD34E/ Tc1 group, and named as Skipper (SK). SK transposons show a wide distribution in animals; however, differential taxonomic distribution patterns were observed for the subfamilies of Frisky , Tiang , Hob , Tsessebe, and Topi ; extensive invasion of Frisky in animals was found, whereas Tiang , Hob , Tsessebe, and Topi were mainly detected in Diptera. SK elements share a similar structural organization and display high sequence identities across subfamilies. Evolutionary dynamics and structural analysis revealed that SK s in some species, such as Bombyx mori , Lordiphosa magnipectinata , Carassius gibelio , Triplophysa dalaica , and Silurus glanis , have recently evolved and present as intact copies, indicating that SK s in these genomes may be active. Together, these observations improve our understanding of the diversity of DD34E/ Tc1 transposons and their impacts on genome evolution in animals. [ABSTRACT FROM AUTHOR]

Due to the considerable complexity of meshfree approximants, there still lacks a rational theoretical estimate on the frequency accuracy of lumped mass meshfree methods. In this study, a detailed theoretical analysis is presented for the lumped mass Galerkin meshfree formulation with particular reference to the frequency accuracy. The proposed accuracy analysis is quite general and is fully based upon the reproducing or consistency conditions of meshfree shape functions and their gradients. The theoretical findings reveal that there exists an important and interesting odd/even basis degree discrepancy feature for the frequency accuracy, i.e., (p + 2)th and (p + 1)th order accurate frequencies are attained by the lumped mass Galerkin meshfree formulation using even and odd degrees of basis functions, where p is the degree of basis function employed in the meshfree shape function construction. Furthermore, it is found that interpolatory meshfree shape functions are capable of not only circumventing the non-physical modes arising from the lumped mass Galerkin meshfree formulation using the standard non-interpolatory shape functions, but also elevating the frequency accuracy for meshfree structural vibration analysis. Numerical examples well replicate the theoretical frequency accuracy analysis results for lumped mass Galerkin meshfree methods. [ABSTRACT FROM AUTHOR]

The boundary performance of direct-acting pressure valves (DAPV) is significantly impacted by surging in small opening situations. This paper illustrates the causes of vibration of DAPVs under small opening conditions from the viewpoints of statics and dynamics. This paper studies a pressure valve using several techniques. These include studying the structural dynamics of the pressure valve using experimental and modal analysis methods, simulating the pressure valve vibration process using flow-solid-control coupling simulation methods, and studying the internal jet characteristics of the pressure valve using non-constant flow field simulation analysis methods. Based on the conclusions drawn from the above methods, several possible effective vibration damping methods are proposed to improve the performance of DAPVs under low flow conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Explores different approaches for expressing, purifying, and labeling GPCRs both in vitro and in live cell environments. • Discusses specific sample preparation methods for single-molecule fluorescence microscopy. • Examines the unique challenges involved in each stage of sample preparation for single-molecule GPCR experiments. • Highlights recent applications of single-molecule TIRF microscopy in investigating different classes of human GPCRs. G protein-coupled receptors (GPCRs) are membrane proteins that transmit specific external stimuli into cells by changing their conformation. This conformational change allows them to couple and activate G-proteins to initiate signal transduction. A critical challenge in studying and inferring these structural dynamics arises from the complexity of the cellular environment, including the presence of various endogenous factors. Due to the recent advances in cell-expression systems, membrane-protein purification techniques, and labeling approaches, it is now possible to study the structural dynamics of GPCRs at a single-molecule level both in vitro and in live cells. In this review, we discuss state-of-the-art techniques and strategies for expressing, purifying, and labeling GPCRs in the context of single-molecule research. We also highlight four recent studies that demonstrate the applications of single-molecule microscopy in revealing the dynamics of GPCRs. These techniques are also useful as complementary methods to verify the results obtained from other structural biology tools like cryo-electron microscopy and x-ray crystallography. [ABSTRACT FROM AUTHOR]

This article is about a modification of Verlet's time integration method. First, a one-step version of the basic scheme is described. Subsequently, a diagonal matrix is introduced in the scheme to improve the behavior of Verlet's method with respect to period elongation. The generic coefficient of this diagonal matrix is defined by referring to the frequency which locally dominates the structural dynamics of the correlated unknown. Since the computation of these coefficients is algorithmic, the method presented does not involve the adjustment of any parameter. Furthermore, the presented modification does not alter the excellent amplitude decay and stability characteristics of the original method. As a result, a second order one-step explicit time integration scheme with desirable accuracy and stability properties is obtained. Several numerical examples for nonlinear problems are conducted to show the ability of the presented method to reduce unwanted period distortion. Computational algorithms can automate repetitive design tasks, saving designers time and effort. In this sense, these computational tools provide designers with detailed data insights that can guide decision-making processes. Once implemented, algorithms become effective and useful tools for increasing productivity and creating more robust designs. However, the reliability of the results is a prerequisite for the success of these approaches. In the context of the dynamic behavior of structures, the present work improves a preexisting computational tool to reproduce the motion of the system under study. Practical engineering applications for linear and nonlinear dynamic analysis can then be addressed by introducing data rigor into the design. Starting from appropriate mathematical models for the analyzed structures, the presented algorithm provides an accurate description of the resulting displacements and stresses. All this through a calculation effort comparable to that of the previous method. As demonstrated by the tests carried out, the simulation for the control of suspension systems as well as the seismic response to earthquake excitation on buildings can represent applicative implications in the engineering field. [ABSTRACT FROM AUTHOR]

Living objects are able to consume chemical energy and process information independently from others. However, living objects can coordinate to form ordered groups such as schools of fish. This work considers these complex groups as living materials and presents imaging-based experiments of laboratory schools of fish to understand how activity, which is a non-equilibrium feature, affects the structure and dynamics of a group. We use spatial confinement to control the motion and structure of fish within quasi-2D shoals of fish and use image analysis techniques to make quantitative observations of the structures, their spatial heterogeneity, and their temporal fluctuations. Furthermore, we utilize Monte Carlo simulations to replicate the experimentally observed data which provides insight into the effective interactions between fish and confirms the presence of a confinement-based behavioral preference transition. In addition, unlike in short-range interacting systems, here structural heterogeneity and dynamic activities are positively correlated as a result of complex interplay between spatial arrangement and behavioral dynamics in fish collectives. [ABSTRACT FROM AUTHOR]

Advancements in machining technology demand higher speeds and precision, necessitating improved control systems in equipment like CNC machine tools. Due to lead errors, structural vibrations, and thermal deformation, commercial CNC controllers commonly use rotary encoders in the motor side to close the position loop, aiming to prevent insufficient stability and premature wear and damage of components. This paper introduces a multivariable iterative learning control (MILC) method tailored for flexible feed drive systems, focusing on enhancing dynamic positioning accuracy. The MILC employs error data from both the motor and table sides, enhancing precision by injecting compensation commands into both the reference trajectory and control command through a norm-optimization process. This method effectively mitigates conflicts between feedback control (FBC) and traditional iterative learning control (ILC) in flexible structures, achieving smaller tracking errors in the table side. The performance and efficacy of the MILC system are experimentally validated on an industrial biaxial CNC machine tool, demonstrating its potential for precision control in modern machining equipment. [ABSTRACT FROM AUTHOR]

Accelerometers are commonly used to measure vibrations for condition monitoring in mechanical and civil structures; however, their high cost and point-based measurement approach present practical limitations. With rapid advancements in computer vision and deep learning, research into tracking the motion of individual pixels with vision cameras has increased. The recently developed CoTracker, a transformer-based model, has demonstrated excellence in motion tracking, yet its performance in measuring structural vibrations has not been fully explored. This paper investigates the efficacy of the CoTracker model in extracting full-field structural vibrations using cameras. It is initially applied to capture the dense point movements in video sequences of a cantilever beam recorded using a high-speed camera. Subsequently, modal analysis using delay-embedding dynamic mode decomposition (DMD) is conducted to extract modal parameters including natural frequencies, damping ratios, and mode shapes. The results, benchmarked against those from a reference accelerometer and the Finite Element Method (FEM) result, demonstrate CoTracker's high potential for general applicability in structural vibration measurements. [ABSTRACT FROM AUTHOR]

Maintaining lipid asymmetry across membrane leaflets is critical for functions like vesicular traffic and organelle homeostasis. However, a lack of molecular‐level understanding of the mechanisms underlying membrane fission and fusion processes in synthetic systems precludes their development as artificial analogs. Here, we report asymmetry induction of a bilayer membrane formed by an extended π‐conjugated molecule with oxyalkylene side chains bearing terminal tertiary amine moieties (BA1) in water. Autogenous protonation of the tertiary amines in the periphery of the bilayer by water induces anisotropic curvature, resulting in membrane fission to form vesicles and can be monitored using time‐dependent spectroscopy and microscopy. Interestingly, upon loss of the induced asymmetry by extensive protonation using an organic acid restored bilayer membrane. The mechanism leading to the compositional asymmetry in the leaflet and curvature induction in the membrane is validated by density functional theory (DFT) calculations. Studies extended to control molecules having changes in hydrophilic (BA2) and hydrophobic (BA3) segments provide insight into the delicate nature of molecular scale interactions in the dynamic transformation of supramolecular structures. The synergic effect of hydrophobic interaction and the hydrated state of BA1 aggregates provide dynamicity and unusual stability. Our study unveils mechanistic insight into the dynamic transformation of bilayer membranes into vesicles. [ABSTRACT FROM AUTHOR]

Organic piezochromic materials that manifest pressure‐stimuli‐responses are important in various fields such as data storage and anticounterfeiting. The manipulation of piezofluorochromic behaviors for these materials is promising but remains a great challenge. Herein, a non‐luminous components regulated strategy is developed and organic molecular cages (OMCs), a burgeoning class of crystalline organic materials with structural dynamics, are first explored for the design of piezofluorochromic materials with tunable luminescence. A series of OMCs based on aggregation‐induced emission (AIE) chromophores, termed Cage 1–3, are synthesized and their piezofluorochromic behaviors are investigated by diamond anvil cell technique. Due to the sufficient voids between its flexible chromophores offered by the OMC structure, Cage 1 exhibits thermofluorochromic and piezofluorochromic properties. Moreover, the piezofluorochromic performance of this OMC could be further promoted by replacing its non‐luminous components with improved flexibilities, and a remarkable luminescence peak shift by 150 nm together with a response sensitivity of 13.8 nm GPa−1 was achieved upon hydrostatic compression. The cage structure plays a vital role in facilitating efficient and reversible piezofluorochromic behaviors. This study has shed light on the rational design and exploitation of OMCs as an exceptional platform to accomplish customizable piezofluorochromic behaviors and enlarge their potential applications in pressure‐based luminescence. [ABSTRACT FROM AUTHOR]

Maintaining lipid asymmetry across membrane leaflets is critical for functions like vesicular traffic and organelle homeostasis. However, a lack of molecular‐level understanding of the mechanisms underlying membrane fission and fusion processes in synthetic systems precludes their development as artificial analogs. Here, we report asymmetry induction of a bilayer membrane formed by an extended π‐conjugated molecule with oxyalkylene side chains bearing terminal tertiary amine moieties (BA1) in water. Autogenous protonation of the tertiary amines in the periphery of the bilayer by water induces anisotropic curvature, resulting in membrane fission to form vesicles and can be monitored using time‐dependent spectroscopy and microscopy. Interestingly, upon loss of the induced asymmetry by extensive protonation using an organic acid restored bilayer membrane. The mechanism leading to the compositional asymmetry in the leaflet and curvature induction in the membrane is validated by density functional theory (DFT) calculations. Studies extended to control molecules having changes in hydrophilic (BA2) and hydrophobic (BA3) segments provide insight into the delicate nature of molecular scale interactions in the dynamic transformation of supramolecular structures. The synergic effect of hydrophobic interaction and the hydrated state of BA1 aggregates provide dynamicity and unusual stability. Our study unveils mechanistic insight into the dynamic transformation of bilayer membranes into vesicles. [ABSTRACT FROM AUTHOR]

Organic piezochromic materials that manifest pressure‐stimuli‐responses are important in various fields such as data storage and anticounterfeiting. The manipulation of piezofluorochromic behaviors for these materials is promising but remains a great challenge. Herein, a non‐luminous components regulated strategy is developed and organic molecular cages (OMCs), a burgeoning class of crystalline organic materials with structural dynamics, are first explored for the design of piezofluorochromic materials with tunable luminescence. A series of OMCs based on aggregation‐induced emission (AIE) chromophores, termed Cage 1–3, are synthesized and their piezofluorochromic behaviors are investigated by diamond anvil cell technique. Due to the sufficient voids between its flexible chromophores offered by the OMC structure, Cage 1 exhibits thermofluorochromic and piezofluorochromic properties. Moreover, the piezofluorochromic performance of this OMC could be further promoted by replacing its non‐luminous components with improved flexibilities, and a remarkable luminescence peak shift by 150 nm together with a response sensitivity of 13.8 nm GPa−1 was achieved upon hydrostatic compression. The cage structure plays a vital role in facilitating efficient and reversible piezofluorochromic behaviors. This study has shed light on the rational design and exploitation of OMCs as an exceptional platform to accomplish customizable piezofluorochromic behaviors and enlarge their potential applications in pressure‐based luminescence. [ABSTRACT FROM AUTHOR]