Configuration Transition Research Articles

Competition between deformation and free volume quantified by 3D image analysis of red blood cell

Cells in living organisms are subjected to mechanical strains caused by external forces like overcrowding, resulting in strong deformations that affect cell function. We study the interplay between deformation and crowding of red blood cells (RBCs) in dispersions of nonabsorbing rod-like viruses. We identify a sequence of configurational transitions of RBC doublets, including configurations that can only be induced by long-ranged attraction: highly fluctuating T-shaped and face-to-face configurations at low, and doublets approaching a complete spherical configuration at high, rod concentrations. Complementary simulations are used to explore different energy contributions to deformation as well as the stability of RBC doublet configurations. Our advanced analysis of 3D reconstructed confocal images of RBC doublets quantifies the depletion interaction and the resulting deformation energy. Thus, we introduce a noninvasive, high-throughput platform that is generally applicable to investigate the mechanical response of biological cells to external forces and characterize their mechanical properties.

The CrBr3 monolayer: Two dimension sodium ion battery anode material to characterize state-of-charge by magnetism

Ion batteries always use the charge properties of electron to estimate the state-of-charge. In this work, we predict that CrBr3 monolayers can be used as anode materials for sodium ion batteries to characterize state-of-charge of corresponding ion batteries by magnetism. According to the first-principles calculations based on density functional theory, the available maximum Na storage capacity of CrBr3 monolayer can reach 795 mAh/g with the ultra-low open circuit voltage (∼0.02 V). Na ions have good diffusion properties in the CrBr3 monolayer, and the corresponding diffusion barrier is about to be 0.22 eV. There is a magnetic configuration transition in CrBr3 monolayer during charge/discharge, which arises from the change in the occupation of Cr-d orbitals. Our results shed a light to subsequently design and search for anode materials, suggesting that the magnetic properties of electrode materials could provide a new path to monitor the state-of-charge of ion battery.

Fragmentation dynamics of electron-impact double ionization of helium

We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 eV to 1 keV for comparative study. At the lowest excess energy, i.e., close to the double-ionization threshold, it is found that the projectile momentum is totally transferred to the recoil-ion while the residual energy is randomly partitioned among the three outgoing electrons, which are then most probably emitted with an equilateral triangle configuration. Our results agree well with experiments as compared with early quantum-mechanical calculation as well as classical simulation based on a two-dimensional Bohr’s model. Furthermore, by mapping the final momentum vectors event by event into a Dalitz plot, we unambiguously demonstrate that the ergodicity has been reached and thus confirm a long-term scenario conceived by Wannier. The time scale for such few-body thermalization, from the initial nonequilibrium state to the final microcanonical distribution, is only about 100 attoseconds. Finally, we predict that, with the increase of the excess energy, the dominant emission configuration undergoes a transition from equilateral triangle to T-shape and finally to a co-linear mode. The associated signatures of such configuration transition in the electron-ion joint momentum spectrum and triple-electron angular distribution are also demonstrated.

Final ion charge spectra upon cascade decay of inner-shell vacancies in atomic Au

Final ion charge spectra produced by the cascade de-excitations of 1s- to 5p 3/2-vacancies of the gold atom are calculated by direct construction and analysis of the cascade decay trees. The energies of multivacancy configurations arising in the course of the cascade development, and the partial widths of radiation and radiationless cascade transitions are calculated using the Pauli–Fock approximation. The energies of the cascade transitions are calculated as the differences of total Pauli–Fock energies of initial and final ionic configurations which allowed excluding energy-forbidden radiationless transitions in numerous multivacancy configurations. Partial widths of transitions are expressed in the form that allowed accounting for the effect of electron subshell populations on the transition widths. The partial widths of the transitions between the states of the overlapping initial and final state multiplets are corrected so as to exclude energy-forbidden transitions between the multiplet states. It is demonstrated that accurate accounting for possible forbiddance of transitions between cascade configurations and the exclusion of energy-forbidden term-to-term transitions between the multiplets’ states are crucial in deep-initial-vacancy cascade simulations.

First-principles prediction of configurational order-disorder phase transition in Mo2(Ti1−x V x )C2 MXene alloys

We investigated the thermodynamic stability of Mo2(Ti1−x V x )C2 MXenes (MTVCs), using the first-principles calculation based on density functional theory and cluster-expansion formalism. Our results suggest that Mo atoms prefer to substitute in the outer metal layers of MTVCs, and such occupying behavior is a crucial factor that determines the thermodynamic stability of MTVCs. On the other hand, Ti and V atoms residing in the inner metal layer of them are predicted to weakly interact with each other and their atomic configuration has a minimal impact on the stability of MTVCs. The transition temperatures between configurationally ordered and disordered phases of MTVCs have been predicted, and the possible existence of configurationally disordered MTVCs has also been discussed.

Single-nucleobase resolution of a surface energy transfer nanoruler for in situ measurement of aptamer binding at the receptor subunit level in living cells.

In situ identification of aptamer-binding targets on living cell membrane surfaces is of considerable interest, but a major challenge, specifically, when advancing recognition to the level of membrane receptor subunits. Here we propose a novel nanometal surface energy transfer (NSET) based nanoruler with a single-nucleobase resolution (SN-nanoruler), in which FAM-labeled aptamers and single-sized gold nanoparticle (GNP) antibody conjugates act as a donor and an acceptor. A single nucleobase resolution of the SN-nanoruler was experimentally illustrated by molecular size, orientation, quenching nature, and other dye-GNP pairs. The SN-nanoruler provides high reproducibility and precision for measuring molecule distance on living cell membranes at the nanometer level owing to only the use of single-sized antibody-capped GNPs. In situ identification of the aptamer binding site was advanced to the protein subunit level on the living cell membrane for the utilization of this SN-nanoruler. The results suggest that the proposed strategy is a solid step towards the wider application of optical-based rulers to observe the molecular structural configuration and dynamic transitions on the membrane surface of living cells.

A Wireless, Regeneratable Cocaine Sensing Scheme Enabled by Allosteric Regulation of pH Sensitive Aptamers.

A key challenge for achieving continuous biosensing with existing technologies is the poor reusability of the biorecognition interface due to the difficulty in the dissociation of analytes from the bioreceptors upon surface saturation. In this work, we introduce a regeneratable biosensing scheme enabled by allosteric regulation of a re-engineered pH sensitive anti-cocaine aptamer. The aptamer can regain its affinity with target analytes due to proton-promoted duplex-to-triplex transition in DNA configuration followed by the release of adsorbed analytes. A Pd/PdHx electrode placed next to the sensor can enable the pH regulation of the local chemical environment via electrochemical reactions. Demonstration of a "flower-shaped", stretchable, and inductively coupled electronic system with sensing and energy harvesting capabilities provides a promising route to designing wireless devices in biointegrated forms. These advances have the potential for future development of electronic sensing platforms with on-chip regeneration capability for continuous, quantitative, and real-time monitoring of chemical and biological markers.

A novel single phase La2CaZnO5:Dy3+ phosphor for potential applications in WLED's, latent fingerprint and cheiloscopy

Due to the distinctiveness and perseverance of the friction ridges in fingerprints (FPs), latent fingerprints (LFPs) and lip prints (LPs) are two most significant types of evidence at crime scene. Therefore, it is essential in forensic science to develop a reliable method to detect LFPs and LPs. Traditional detection methods still face a number of difficulties, such as limited sensitivity, low contrast, strong background, and complex processing stages. We proposed a method for visualization of LFPs and LPs by utilizing La2CaZnO5:Dy3+ (1–5 mol %) (LCZO: Dy) phosphor using a solution combustion method. The crystal structure, phase purity, particle morphology, photoluminescence (PL) properties of the resulting phosphors were then characterized in detail. SEM images suggested that the obtained phosphors are non-uniform shapes and agglomerated to big particles. The photophysical properties of Dy3+ doped phosphors are analyzed by exploiting their photoluminescence excitation (PLE) and emission profiles. The emission profiles of all the doped samples exhibit sharp emission lines centred at ∼481, 573, and 667 nm, which are ascribed to 4F9/2 → 6H15/2, 4F9/2 → 6H13/2, and 4F9/2 → 6H11/2 intra configurational transitions of Dy3+ ion, correspondingly. The optimum doping concentration of LCZO: Dy phosphor was 4 mol%, and the dominant factor of concentration quenching effect is the nearest-neighbor ions interaction. The chromaticity coordinates of International Committee LCZO: Dy were located in the yellow color area. In addition, LCZO: 4Dy phosphor can well visualize the LFP image and LP image. The levels 1–3 features of fingerprint and groove pattern of lip print can be easily recognised with high resolution and contrast. The experimental results showed La2CaZnO5:Dy3+ can be well applied to advanced forensic investigation.

Light Responsiveness and Assembly of Arylazopyrazole-Based Surfactants in Neat and Mixed CTAB Micelles.

The self-assembly of an arylazopyrazole-based photosurfactant (PS), based on cetyltrimethylammonium bromide (CTAB), and its mixed micelle formation with CTAB in aqueous solution was investigated by small angle neutron and X-ray scattering (SANS/SAXS) and UV-vis absorption spectroscopy. Upon UV light exposure, PS photoisomerizes from E-PS (trans) to Z-PS (cis), which transforms oblate ellipsoidal micelles into smaller, spherical micelles with larger shell thickness. Doping PS with CTAB resulted in mixed micelle formation at all stoichiometries and conditions investigated; employing selectively deuterated PS, a monotonic variation in scattering length density and dimensions of the micellar core and shell is observed for all contrasts. The concentration- and irradiance-dependence of the E to Z configurational transition was established in both neat and mixed micelles. A liposome dye release assay establishes the enhanced efficacy of photosurfactants at membrane disruption, with E-PS exhibiting a 4-fold and Z-PS a 10-fold increase in fluorescence signal with respect to pure CTAB. Our findings pave the way for external triggering and modulation of the wide range of CTAB-based biomedical and material applications.

Luminescence Thermometry - Crossing the Limits of Operating Range

Temperature is one of the fundamental thermodynamic parameters that affects and regulates the rate and nature of the chemical, physical and biological processes. A precise and accurate measurement of temperature is essential across a broad spectrum of areas, such as nanomedicine, electronics, aerospace, climate, food storage, etc. Therefore, there is a great variety of temperature sensors (which currently account for ≈80% of the worldwide sensor market), and their operating modes can be divided into two main groups: contact and noncontact techniques. However, in some specific cases, only non-contact systems may provide accurate information about temperature and its distribution over an area. These are as follows: harsh environments (for example inside turbines), fast-moving objects (gas jets), intense magnetic fields that prevent the use of metals or materials with free electric charges (NMR therapies) or when the size of the system to measure is smaller than 10 μm (cellular tracking or microelectronic circuits). One promising solution that can break through those limitations is luminescence thermometry (LT). LT is a non-contact and non-invasive spectroscopic technique based on the changes in a phosphor emission when temperature changes (e.g., the intensity of a band, relative intensities, band shapes, excited-state lifetimes, etc.).We shall present our original approach to use intra- and inter- configurational transitions of Pr3+ ion for accurate temperature reading with high relative sensitivity over an outstandingly wide range of temperatures. Studies were focused on Y2SiO5:0.05%Pr and its chemically modified version by a bandgap engineering approach (replacing Si with Ge). The addition of Ge to replace Si was expected to decrease the host bandgap – energetic separation of its valence and conduction bands. Consequently, we expected that the 5d→4f luminescence would be more susceptible to temperature quenching. This, in turn, allowed to control the range of temperatures within which the 5d→4f/4f→4f emission intensity ratio could be utilized for thermometry. Furthermore, possibilities to further improve such sensors will be discussed by widening the operating range of distinct thermometers.This presentation will show that luminescence thermometers working in unprecedented board operating range can be effectively constructed and managed. Further analysis of such an approach will be carefully discussed. This research was supported by the National Science Centre, Poland under grant #2020/37/N/ST5/02507 Figure 1

Satellite and hypersatellite structure of Mα1,2 x‐ray transitions in thorium excited by fast oxygen ions

AbstractThe high‐resolution spectra of thorium Mα1,2 (M5 → N6,7) and Mβ1 (M4 → N6) x‐ray lines induced by an impact of O ions with energy 376.0 MeV were measured using a von Hamos crystal spectrometer in order to study the x‐ray emission from multiple ionized atoms. The observed x‐rays have been interpreted in terms of the relativistic multiconfiguration Dirac‐Fock (MCDF) calculations performed for dominating vacancy configurations expected to contribute to the measured spectra. Due to the complexity of such calculations for selected multi‐vacancy configurations the simplified average <MCDF> model, combining the MCDF calculations and binomial distribution of vacancies has been used. The measured spectra clearly exhibit a rich structure of Mα1,2 x‐ray satellites of thorium, including the transitions from the multivacancy initial configurations M−1N−n as well as the hypersatellites corresponding to the transitions in complex multivacancy initial configurations M−mN−n (m,n ≤ 4). The present interpretation of the measured satellite/hypersatellite structure of Mα1,2 (M5 → N6,7) x‐ray transitions allows us to determine the ionization probabilities for the M‐ and N‐shell in central collisions. The measured ionization probabilities are compared with the theoretical predictions of the geometrical model (GM), and the semiclassical approximation (SCA) using both the Dirac hydrogenic and Dirac‐Hartree‐Fock selfconsistent wave functions.

From crumple conformation to gel configuration of reduced graphene oxide: The cation induction engineering

Spatial conformation of condensed state graphene is fundamentally important for its material properties, while its rational design or control is of great challenge. Herein, reduced graphene oxides with diverse crumple conformations are synthesized facilely and effectively by using electrostatic force from cation-oxidized functional group and cation-π interactions through NaCl/MgCl2/AlCl3 assisted hydrothermal reduction. A phase map for crumple conformation and gel configuration transitions of the reduced graphene oxides is established, where intramolecular effect of mono-valent cation and intermolecular effect of di-/tri-valent cations are captured and utilized to tune the crumple degree or gelation process. Desired material features, including specific surface area and surface functional groups, can be finely modulated via crumple conformation or cation interaction, and enable the reduced graphene oxides to present an outstanding rate capability of 68.8% and unparalleled areal capacitance of 98.0 μF/cm2 at 100 A/g in symmetric aqueous supercapacitors. This study broadens the topological behavior spectrum and stimulates the conformation engineering methodology of reduced graphene oxides, facilitating the development of novel graphene-based materials.

Electronic Spectroscopy of SmO in the 645 to 670 nm Range.

The associative ionization reaction Sm + O → SmO+ + e- is being investigated as an electron source that could transiently modify high-altitude electron densities via Sm vapor release. Electronic spectra have been obtained from tests where sounding rockets released Sm vapor, but the interpretation of these results has been hampered by the limited laboratory spectral data available for both SmO and SmO+. The present study extends the spectroscopic characterization of SmO in the 645-670 nm range, where the field data show the most prominent molecular emission features. Rotationally resolved excitation spectra, dispersed laser-induced fluorescence spectra, and fluorescence decay lifetimes are reported. The results are consistent with the assignment of a subset of the red-region bands to configurational transitions of the form Sm2+(4f56s)O2- ↔ Sm2+(4f55d)O2-. Analysis of the excited state hyperfine structure supports this configurational description.

Configurational entropy, transition rates, and optimal interactions for rapid folding in coarse-grained model proteins.

Under certain conditions, the dynamics of coarse-grained models of solvated proteins can be described using a Markov state model, which tracks the evolution of populations of configurations. The transition rates among states that appear in the Markov model can be determined by computing the relative entropy of states and their mean first passage times. In this paper, we present an adaptive method to evaluate the configurational entropy and the mean first passage times for linear chain models with discontinuous potentials. The approach is based on event-driven dynamical sampling in a massively parallel architecture. Using the fact that the transition rate matrix can be calculated for any choice of interaction energies at any temperature, it is demonstrated how each state's energy can be chosen such that the average time to transition between any two states is minimized. The methods are used to analyze the optimization of the folding process of two protein systems: the crambin protein and a model with frustration and misfolding. It is shown that the folding pathways for both systems are comprised of two regimes: first, the rapid establishment of local bonds, followed by the subsequent formation of more distant contacts. The state energies that lead to the most rapid folding encourage multiple pathways, and they either penalize folding pathways through kinetic traps by raising the energies of trapping states or establish an escape route from the trapping states by lowering free energy barriers to other states that rapidly reach the native state.

Square Lattice Formation in a Monodisperse Complex Plasma.

We present the first observations of a square lattice formation in a monodisperse complex plasma system, a configurational transition phenomenon that has long been an experimental challenge in the field. The experiments are conducted in a tabletop L-shaped dusty plasma experimental device in a dc glow discharge Argon plasma environment. By a careful control of the vertical potential confining the charged particles as well as the strength of the ion wake charge interactions with the dust particles, we are able to steer the system toward a crystalline phase that exhibits a square lattice configuration. The transition occurs when the vertical confinement strength is slightly reduced below a critical value leading to a buckling of the monodisperse hexagonal 2D dust crystal to form a narrowly separated bilayer state (a quasi-2D state). Some theoretical insights into the transition process are provided through molecular dynamics simulations carried out for the parameters relevant to our experiment.

Differential configurational complexity and phase transitions of the BPS solutions in the O(3)-sigma model

Using a spherically symmetric ansatz, we show that the Chern–Simons O(3)-sigma model with a logarithmic potential admits topological solutions. This result is quite interesting since the Gausson-type logarithmic potential only predicted topological solutions in (1+1)D models. To accomplish our goal, the Bogomol’nyi–Prasad–Sommerfield (BPS) method is used, to saturate the energy and obtain the BPS equations. Next, we show by the numerical method is the graphical results of the topological fields, as well as, the magnetic field behavior that generates a flux given by Φflux=−Q/κ and the energy density of the structures of vortices. On the other hand, we evaluate the measure of the differential configurational complexity (DCC) of the topological structures, by considering the energy density of the vortex. This analysis is important because it will provide us with information about the possible phase transitions associated with the localized structures and it shows that our model only supports one phase transition.

Switchable Multiplex Photoelectrochemical Immunoassay of Aβ42 and Aβ40 Based on a pH-Responsive i-Motif Probe and Pyrene-Based MOF Photocathode.

In accurately diagnosing Alzheimer's disease (AD) and distinguishing AD from other dementia, the concentration ratio of amyloid-beta 42 (Aβ42) to Aβ40 is more reliable than the concentration of Aβ42 alone. For the multiplex PEC assay, generating an independent photocurrent of multiple targets on a single interface is a great challenge. Herein, an i-motif-based switchable sensing approach is proposed to construct a pH-regulated multiplex PEC immunosensor for Aβ42 and Aβ40 by using Bi-TBAPy as an efficient photoactive cathode material. An independent photocurrent signal of Aβ42 and Aβ40 is produced through the regulation of the electron-transfer tunneling distance by a pH-dependent configuration transition of the i-motif DNA. In a 96-well plate, immunological recognition of Aβ42 (or Aβ40) coupled with an enzymatic catalytic reaction produces an acidic (or alkaline) lysis solution, which triggers the formation and unravelment of the i-motif structure. The above configuration transition regulates the distance between Au NPs labeled SH-DNA and Bi-TBAPy, leading to PEC signal switching. Smart integration of the pH-responsive switchable DNA probe with a high-efficiency photocathode enables the precise monitoring of Aβ42 and Aβ40 at a single interface in a wide detection range (10 fg/mL ∼ 1 μg/mL and 1 pg/mL ∼ 1 μg/mL) with detection limit of 4.5 fg/mL and 0.52 pg/mL, respectively. The proposed i-motif-based switchable sensing strategy paves a new avenue for a multiplex PEC assay on a single interface, showing great prospects in bioanalysis and early disease diagnosis.

Configurational entropy-induced phase transition in spinel LiMn2O4

The spinel-type LiMn2O4 is a promising candidate as cathode material for rechargeable Li-ion batteries due to its good thermal stability and safety. Experimentally, it is observed that in this compound there occur the structural phase transitions from cubic () to tetragonal (I41/amd) phase at slightly below room temperature. To understand the phase transition mechanism, we compare the Gibbs free energy between cubic phase and tetragonal phase by including the configurational entropy. Our results show that the configurational entropy contributes substantially to the stability of the cubic phase at room temperature due to the disordered Mn3+/Mn4+ distribution as well as the orientation of the Jahn–Teller elongation of the Mn3+O6 octahedron in the the spinel phase. Meanwhile, the phase transition temperature is predicted to be 267.8 K, which is comparable to the experimentally observed temperature. These results serve as a good complement to the experimental study, and are beneficial to the improving of the electrochemical performance of LiMn2O4 cathode.

Configuration of Magnetotail Current Sheet Prior to Magnetic Reconnection Onset

AbstractThe magnetotail current sheet configuration determines magnetic reconnection properties that control the substorm onset, one of the most energetic phenomena in the Earth’s magnetosphere. The quiet‐time current sheet is often approximated as a two‐dimensional (2D) magnetic field configuration balanced by isotropic plasma pressure gradients. However, reconnection onset is preceded by the current sheet thinning and the formation of a nearly one‐dimensional (1D) magnetic field configuration. In this study, using particle‐in‐cell simulations, we investigate the force balance of such thin current sheets when they are driven by plasma inflow. We demonstrate that the magnetic field configuration transitions from 2D to 1D thanks to the formation of plasma pressure nongyrotropy and reveal its origin in the nongyrotropic terms of the ion distributions. We show that substorm onset may be controlled by the instability and dynamics of such nongyrotropic current sheets, having properties much different from the most commonly investigated 2D isotropic configuration.

Supervised and unsupervised machine learning of structural phases of polymers adsorbed to nanowires.

We identify configurational phases and structural transitions in a polymer nanotube composite by means of machine learning. We employ various unsupervised dimensionality reduction methods, conventional neural networks, as well as the confusion method, an unsupervised neural-network-based approach. We find neural networks are able to reliably recognize all configurational phases that have been found previously in experiment and simulation. Furthermore, we locate the boundaries between configurational phases in a way that removes human intuition or bias. This could be done before only by relying on preconceived, ad hoc order parameters.