Configuration Transition Research Articles

A switched model predictive control with parametric weights-based mode transition strategy for a novel parallel hybrid electric vehicle

In a novel parallel hybrid electric vehicle (HEV) configuration, the transition from pure electric mode to hybrid mode encompasses critical operations such as engine startup, coordinated control of motor and engine torque, and engagement of the clutch. Addressing the intricate challenges associated with enhancing speed tracking performance during and after mode transition, mitigating jerk during mode transition, and minimizing mode transition time, this paper conducts a meticulous analysis of the vehicle configuration and mode transition process. The mode transition process is systematically delineated into four stages, with each stage characterized by the establishment of dynamic models. Subsequently, a mode transition strategy is proposed, leveraging switched model predictive control with parametric weights (SMPC-PW). This controller framework includes the design of two model predictive controllers (MPC) tailored for two pivotal stages, the formulation of a parametric weights pattern based on pre-transition acceleration, and the development of a stage switching strategy to ensure seamless switches between controllers. The efficacy of the proposed strategy is validated through co-simulations in the Simulink and GT-Power environment. The fine-tuning of MPC parameters is grounded in multiple sets of prediction horizons and sampling time simulation results. In comparison to strategies based on MPC and PID under various acceleration scenarios, the SMPC-PW strategy consistently maintains acceleration control below 10 m/s3. It not only achieves superior speed tracking during and after mode transition but also reduces mode switch time by 0.1 s-0.3 s. These compelling results unequivocally demonstrate that the proposed mode transition strategy significantly elevates the quality of mode transition for this specific parallel HEV configuration.

Visualization of azobenzene mesogens trans-cis isomerization through structural color of photonic crystal

Azobenzene, a representative photoresponsive liquid crystal, has extensive applications in fields such as bionic robotics, actuators, artificial muscles, motors, and various functional devices. Photoisomerization (trans-cis isomerization) is the most important mechanism for its photoresponse. Currently, the isomerization of azobenzene mesogens can be measured through UV–vis absorption spectra, NMR techniques or transient grating methods. Visualization of the trans-cis isomerization of azobenzene mesogens still remains a challenge. In this study, a linear relationship is observed between the absorption intensity of azobenzene mesogens and the stopband shift of azobenzene inverse opals (AZOIOs) films during the isomerization process. This phenomenon can be used to determine the isomerization degree of azobenzene mesogens through the switching of the stopband of the AZOIOs film, enabling the visualization of the azobenzene mesogens’s configuration transition. The results of this study are highly significant for the design and fabrication of novel azobenzene devices.

The chromatin accessibility landscape of mouse oocytes during configuration transition.

The transition of chromatin configuration in mammalian oocytes from a non-surrounded nucleolus (NSN) to a surrounded nucleolus (SN) is critical for acquiring the developmental competence. However, the genomic and epigenomic features underlying this process remain poorly understood. In the present study, we first establish the chromatin accessibility landscape of mouse oocytes from NSN to SN stage. Through the integrative analysis of multi-omics, we find that the establishment of DNA methylation in oocytes is independent of the dynamics of chromatin accessibility. In contrast, histone H3K4me3 status is closely associated with the dynamics of accessible regions during configuration transition. Furthermore, by focusing on the actively transcribed genes in NSN and SN oocytes, we discover that chromatin accessibility coupled with histone methylation (H3K4me3 and H3K27me3) participates in the transcriptional control during phase transition. In sum, our data provide a comprehensive resource for probing configuration transition in oocytes, and offer insights into the mechanisms determining chromatin dynamics and oocyte quality.

Effector Binding Sequentially Alters KRAS Dimerization on the Membrane: New Insights Into RAS-Mediated RAF Activation.

RAS proteins are peripheral membrane GTPases that activate multiple downstream effectors for cell proliferation and differentiation. The formation of a signaling RAS-RAF complex at the plasma membrane is implicated in a quarter of all human cancers; however, the underlying mechanism remains unclear. In this work, nanodisc platforms and paramagnetic relaxation enhancement (PRE) analyses to determine the structure of a hetero-tetrameric complex comprising KRAS and the RAS-binding domain (RBD) and cysteine-rich domain (CRD) of activated RAF1 are employed. The binding of the RBD or RBD-CRD differentially alters the dimerization modes of KRAS on both anionic and neutral membranes, validated by interface-specific mutagenesis. Notably, the RBD binding allosterically generated two distinct KRAS dimer interfaces in equilibrium, favored by KRAS free and in complex with the RBD-CRD, respectively. Additional interactions of the CRD with both KRAS protomers are mutually cooperative to stabilize a new dimer configuration of KRAS bound to the RBD-CRD. The RAF binding sequentially alters KRAS dimerization, providing new insights into RAF activation, including a configurational transition of the KRAS dimer to provide an interaction site for the CRD and release the autoinhibited RAF complex. These methods are applicable to many other signaling protein complexes on the membrane.

Structural evolution, electronic and optical properties of praseodymium doped silicon cluster PrSin0/- (n = 10–20): A theoretical investigation

The rare earth dope d nano-cluster can be a building block for the next-generation photo-electrical industry, so the imminent discovery of novel, suitable nano-functional material is urgent. Praseodymium element as a wonderful dopant, bestow a novel photoelectrochemical properties for nanomaterials especially for semiconductor, derived from its unfulfilled 4f electrons configuration and active electronic transitions between 4f to 4f and 4f to 5d. In view of this, the neutral and anionic clusters of PrSin0/- with a medium size of n = 10–20 are comprehensively investigated by the quantum chemistry method of mPW2PLYP associated with the global searching potential energy surface techniques. The geometry evolution in medium size for PrSin can be attributed to three stages of replaced (n = 10–12), linked (n = 13–19), and cage (n = 20) structure. For PrSin-, two evolution phases are obviously observed by linked (n = 10–19) and cage (n = 20) structure. The PES spectra of the anionic most stable cluster and several degeneracy structures are simulated to identify the ground state structure. Each cluster of AEA, charge transfer, and VDE values are all calculated. Combined with binding energy, HOMO-LUMO gap, molecular orbital analysis, and a series of optical properties estimated, including simulated UV–vis, IR, and Raman spectra, excitation behavior shows PrSi20- has not only prominent stability but also has a proper range of lighting absorption, higher electron-hole recombination, possible as a functional material for optoelectronic devices.

Tracking the extensive three-dimensional motion of single ions by an engineered point-spread function

Three-dimensional (3D) imaging of individual atoms is a critical tool for discovering new physical phenomena and developing new technologies in microscopic systems. However, the current single-atom-resolved 3D imaging methods are limited to static circumstances or a shallow detection range. Here, we demonstrate a generic dynamic 3D imaging method to track the extensive motion of single ions by exploiting the engineered point-spread function (PSF). We show that the image of a single ion can be engineered into a helical PSF, thus enabling single-snapshot acquisition of the position information of the ion in the trap. A preliminary application of this technique is demonstrated by recording the 3D motion trajectory of a single trapped ion and reconstructing the 3D dynamical configuration transition between the zig and zag structures of a 5-ion crystal. This work opens the path for studies on single-atom-resolved dynamics in both trapped-ion and neutral-atom systems.

Pappus phenotypes and flight performance across evolutionary history in the daisy family.

Diversity in pappus shapes and size in Asteraceae suggests an adaptive response to dispersion challenges adjusting diaspores to optimal phenotypic configurations. Here, by analysing the relationship among pappus-cypsela size relationships, flight performance and pappus types in an evolutionary context, we evaluate the role of natural selection acting on the evolution of diaspore configuration at a macro-ecological scale in the daisy family. To link pappus-cypsela size relationships with flight performance we collected published data on these traits from 82 species. This allowed us to translate morphometric traits in flight performance for 150 species represented in a fully resolved backbone phylogeny of the daisy family. Through ancestral reconstructions and evolutionary model selection, we assessed whether flight performance was associated with and constrained by different pappus types. Additionally, we evaluated, through phylogenetic regressions, whether species with different pappus types exhibited evolutionary allometric pappus-cypsela size relationships. The setose pappus type had the highest flight performances and represented the most probable ancestral state in the family. Stepwise changes in pappus types independently led from setose to multiple instances of pappus loss with associated reduction in flight performance. Flight performance evolution was best modelled as constrained by five adaptive regimes represented by specific pappus types which correspond to specific optimal diaspore configurations that are distinct in pappus-cypsela allometric relationships. Evolutionary modelling suggests natural selection as the main factor of diaspore configuration changes which proceeded towards five optima, often overcoming constraints imposed by allometric relationships and favouring evolution in certain directions. With the perspective that natural selection is the main process driving the observed patterns, various biotic and abiotic are suggested as principal drivers of transitions in diaspore configurations along space and time in the daisy family history. The results also allow discussion of evolutionary changes in a historical context.

Investigation into the DNA's conformations and their conversions from the phase transition theory

The functions and transformation mechanisms of nucleic acids in their various states are of great importance in physiology and pathology. Based on the Landau model, this study reveals the mechanism of the existence of chirality and the transformation rules between different chiral conformations by studying the Duffing oscillation response of the local gauge potential on the DNA chain. The research results show that normal chiral DNA and DNA configuration transition behaviors exhibit regular nonlinear periodic oscillations. Moreover, the gauge potential value approaches zero at the B-Z junction site, which may add a criterion for detecting Z-forming sites. In addition, external force and damping play a key role in the chiral gauge potential of nucleic acids, and they can influence, regulate and even control the configuration transition of nucleic acids. Finally, we verified the rationality of our theory by combining x-ray crystal diffraction data of multiple configurations of DNA. This study provides new insights into the behavior and function of chiral DNA in organisms, and provides new possibilities for regulating DNA conformational transition in the future.

MIB2 Functions in Oocyte Meiosis by Modulating Chromatin Configuration

Chromatin configuration serves as a principal indicator of GV (germinal vesicle)-stage oocyte quality. However, the underlying mechanisms governing the chromatin configuration transition from NSN (non-surrounded nucleolus) to SN (surrounded nucleolus) remain unclear. In this study, by conducting a quantitative proteomic analysis, we identified an increased expression of the MIB2 (MIB E3 ubiquitin protein ligase 2) protein in SN oocytes. Specific depletion of MIB2 in SN oocytes not only leads to severe disruption of the meiotic apparatus and a higher incidence of aneuploidy but also adversely affects meiotic maturation and early embryo development. Notably, overexpression of MIB2 in NSN oocytes facilitates the chromatin configuration transition. Meantime, we observed that forced expression of MIB2 in NSN oocytes significantly mitigates spindle/chromosome disorganization and aneuploidy. In summary, our results suggest that chromatin configuration transition regulated by MIB2 is crucial for oocytes to acquire developmental competence.

Thermodynamic cost for precision of general counting observables.

We analytically derive universal bounds that describe the tradeoff between thermodynamic cost and precision in a sequence of events related to some internal changes of an otherwise hidden physical system. The precision is quantified by the fluctuations in either the number of events counted over time or the waiting times between successive events. Our results are valid for the same broad class of nonequilibrium driven systems considered by the thermodynamic uncertainty relation, but they extend to both time-symmetric and asymmetric observables. We show how optimal precision saturating the bounds can be achieved. For waiting-time fluctuations of asymmetric observables, a phase transition in the optimal configuration arises, where higher precision can be achieved by combining several signals.

Effects of chain-chain interaction on the configuration of short-chain alkanethiol self-assembled monolayers on a metal surface.

Surface-specific sum frequency generation vibrational spectroscopy is applied to study the molecular configuration of short-chain n-alkanethiol self-assembled monolayers (SAMs with n = 2-6) on the Au surface. For monolayers with n≥ 3, the alkanethiols are upright-oriented, with the CH3 tilt angle varying between ∼33° and ∼46° in clear even-odd dependency. The ethanethiol monolayer (n = 2) is, however, found to exhibit a distinct lying-down configuration with a larger methyl tilt angle (67°-79°) and a smaller CH2 tilt angle (56°-68°). Such a unique configurational transition from n = 2 to n≥ 3 discloses the steric effect owing to chain-chain interaction among neighboring molecules. Through density functional theory calculations, the transition is further confirmed to be energetically favorable for thiols on a defective reconstructed Au(111) surface but not on the pristine one. Our study highlights the roles of the chain-chain interaction and the substrate surface atomic structure when organizing SAMs, offering a strategic pathway for exploiting their applications.

The role of SRPK1-mediated phosphorylation of SR proteins in the chromatin configuration transition of mouse germinal vesicle oocytes.

Meiotic resumption in mammalian oocytes involves nucleus and organelle structural changes, notably chromatin configuration transitioning from non-surrounding nucleolus (NSN) to surrounding nucleolus (SN) in germinal vesicle (GV) oocytes. Our study found that nuclear speckles, a subnuclear structure mainly composed of serine-arginine (SR) proteins, changed from a diffuse spotted distribution in mouse NSN oocytes to an aggregation pattern in SN oocytes. We further discovered that SRPK1, an enzyme phosphorylating SR proteins, co-localized with NS at SN stage and NSN oocytes failed to convert into SN oocytes after inhibiting the activity of SRPK1. Furthermore, the typical structure of chromatin ring around the nucleolus in SN oocytes collapsed after inhibitor treatment. To explore the underlying mechanism, phosphorylated SR proteins were confirmed to be associated with chromatin by salt extraction experiment, and in situ DNase I assay showed that the accessibility of chromatin enhanced in SN oocytes with SRPK1 inhibited, accompanied by decreased repressive modification on histone and abnormal recurrence of transcriptional signal. In conclusion, our results indicated that SRPK1-regulated phosphorylation on SR proteins was involved in the NSN to SN transition and played an important role in maintaining the condensation nucleus of SN oocytes via interacting with chromatin.

Studying the Collective Functional Response of a Receptor in Alchemical Ligand Binding Free Energy Simulations with Accelerated Solvation Layer Dynamics.

Ligand binding free energy simulations (LB-FES) that involve sampling of protein functional conformations have been longstanding challenges in research on molecular recognition. Particularly, modeling of the conformational transition pathway and design of the heuristic biasing mechanism are severe bottlenecks for the existing enhanced configurational sampling (ECS) methods. Inspired by the key role of hydration in regulating conformational dynamics of macromolecules, this report proposes a novel ECS approach that facilitates binding-associated structural dynamics by accelerated hydration transitions in combination with the λ-exchange of free energy perturbation (FEP). Two challenging protein-ligand binding processes involving large configurational transitions of the receptor are studied, with hydration transitions at binding sites accelerated by Hamiltonian-simulated annealing of the hydration layer. Without the need for pathway analysis or ad hoc barrier flattening potential, LB-FES were performed with FEP/λ-exchange molecular dynamics simulation at a minor overhead for annealing of the hydration layer. The LB-FES studies showed that the accelerated rehydration significantly enhances the collective conformational transitions of the receptor, and convergence of binding affinity calculations is obtained at a sweet-spot simulation time scale. Alchemical LB-FES with the proposed ECS strategy is free from the effort of trial and error for the setup and realizes efficient on-the-fly sampling for the collective functional response of the receptor and bound water and therefore presents a practical approach to high-throughput screening in drug discovery.

Magneto‐Responsive Bistable Structures with Rate‐Dependent Actuation Modes

AbstractStructural instabilities can be used to provide rapid responses activated by mechanical force or displacement thresholds. The emergence of responsive materials has opened the door for adapting such structural instabilities to actuators that will abruptly deform guided by external stimuli. However, fast configurational transitions between equilibrium states imply important viscoelastic roles at the material level that inevitably scale up to the structural level. A comprehensive understanding of viscoelastic effects is provided on bistable structural transitions combining a new experimental perspective and a thorough modeling analysis. The insights from these results are here translated to magneto‐responsive bistable structures offering a route‐map to design effective actuation conditions. The bistable transition functionally depends on the combination of magnetic field amplitude and application rate. The understanding of the viscoelastic and magneto‐mechanical coupling provides efficient actuation via temporal magnetic pulses, removing the need of generating continued magnetic fields. Finally, these insights are combined to develop a responsive structure whose transient and steady bistable transitions can be modulated by the application rate of external magnetic stimuli.

A bistable honeycomb mechanical metamaterial with transformable Poisson's ratio and tunable vibration isolation properties

With the increasing demand for vibration-isolation structures with tunable and multifunctional properties driven by the rapid development of complex engineering applications, metamaterials have emerged as promising candidates for this purpose owing to their extraordinary properties derived from their unique structural configurations. Owing to their unique deformation mechanisms, negative Poisson's ratio structures have been extensively studied in terms of vibration isolation and energy absorption; however, research on their performance tunability remains lacking. This paper describes a bistable honeycomb mechanical metamaterial (BHMM) consisting of cosine-shaped beams, which exhibits transformable Poisson's ratio and tunable vibration isolation properties. The proposed structure exhibited bistable properties, i.e., undergoing a configuration transition under external forces and retaining its existing configuration after the loading was removed. Furthermore, the two stable configurations exhibited distinctive elastic vibration characteristics, allowing the manipulation of elastic wave propagation on a subwavelength scale via local resonant mechanisms. Overall, this study presents a design methodology for multi-performance tunable metamaterials that satisfy the demands of the external environment. For example, the tunable vibration-isolation property of metamaterial makes it intriguing safety protection structures during crash events.

Giant electric field-induced second harmonic generation in polar skyrmions

Electric field-induced second harmonic generation allows electrically controlling nonlinear light-matter interactions crucial for emerging integrated photonics applications. Despite its wide presence in materials, the figures-of-merit of electric field-induced second harmonic generation are yet to be elevated to enable novel device functionalities. Here, we show that the polar skyrmions, a topological phase spontaneously formed in PbTiO3/SrTiO3 ferroelectric superlattices, exhibit a high comprehensive electric field-induced second harmonic generation performance. The second-order nonlinear susceptibility and modulation depth, measured under non-resonant 800 nm excitation, reach ~54.2 pm V−1 and ~664% V−1, respectively, and high response bandwidth (higher than 10 MHz), wide operating temperature range (up to ~400 K) and good fatigue resistance (>1010 cycles) are also demonstrated. Through combined in-situ experiments and phase-field simulations, we establish the microscopic links between the exotic polarization configuration and field-induced transition paths of the skyrmions and their electric field-induced second harmonic generation response. Our study not only presents a highly competitive thin-film material ready for constructing on-chip devices, but opens up new avenues of utilizing topological polar structures in the fields of photonics and optoelectronics.

Defect-guided self-tearing in graphene

The two-dimensional to three-dimensional configuration transition through self-tearing promises the engineering and promising applications of graphene. However, it is challenging to control the tearing path on demand through common thermal and interfacial treatments. In this manuscript, a defect-guided self-tearing technique is proposed to generate wider, longer, and even curved and serrated configurations, which is impossible for defect-free graphene. The underlying tearing mechanisms regarding the advancing displacement are disclosed through molecular dynamics simulations and theoretical model. This study provides a useful guidance to the implementation of complex and functional three-dimensional graphene structures.

Janus MXene nanosheets with a strain-induced reversible magnetic state transition for storing information without electricity.

The application of strain induces a transition in the ground-state magnetic configuration of Janus TiVC MXene from A-AFM to FM. A new system and method of solid-state disk information storage without electricity is developed based on the as-discovered reversible magnetic state transition in TiVC, which can achieve efficient storage of information in extremely harsh conditions.

Trans-IV restriction: a new configuration for metal bis-cyclam complexes as potent CXCR4 inhibitors.

The chemokine receptor CXCR4 is implicated in multiple diseases including inflammatory disorders, cancer growth and metastasis, and HIV/AIDS. CXCR4 targeting has been evaluated in treating cancer metastasis and therapy resistance. Cyclam derivatives, most notably AMD3100 (Plerixafor™), are a common motif in small molecule CXCR4 antagonists. However, AMD3100 has not been shown to be effective in cancer treatment as an individual agent. Configurational restriction and transition metal complex formation increases receptor binding affinity and residence time. In the present study, we have synthesized novel trans-IV locked cyclam-based CXCR4 inhibitors, a previously unexploited configuration, and demonstrated their higher affinity for CXCR4 binding and CXCL12-mediated signaling inhibition compared to AMD3100. These results pave the way for even more potent CXCR4 inhibitors that may provide significant efficacy in cancer therapy.

Experimental observation of two-dimensional phase in compressed FeF2

Iron difluoride (FeF2) has attracted considerable attention for its physical characteristics and practical applications, and its compression behaviors usually play a key role in the in-depth understanding of this compound. Since its high-pressure crystal structure evolution determining a more profound comprehension remains disputable, we carried out extensive experiments to focus on the pressure-induced structural phase transitions of FeF2. Through in situ high-pressure synchrotron x-ray diffraction measurements, we not only confirmed a reported high-pressure orthorhombic Pbca phase at 11 GPa but also identified an interesting two-dimensional structure with hexagonal close packed symmetry (P-3m1) that appears above 25 GPa at room temperature. Furthermore, the spontaneous strain fitting and electronic transport measurements suggest that its ambient rutile-type structure (P42/mnm) evolves into an orthorhombic structure (Pnnm) through a second-order phase transition at 5 GPa. These experimental results elaborate on the pressure-induced phase transitions of FeF2 on the order of P42/mnm → Pnnm → Pbca → P-3m1, shedding light on a rare three-dimensional to two-dimensional configuration transition in difluorides.