Molecular piezoelectrics are highly desirable for their easy and environment-friendly processing, light weight, low processing temperature, and mechanical flexibility. However, although 136 years ...have passed since the discovery in 1880 of the piezoelectric effect, molecular piezoelectrics with a piezoelectric coefficient
comparable with piezoceramics such as barium titanate (BTO; ~190 picocoulombs per newton) have not been found. We show that trimethylchloromethyl ammonium trichloromanganese(II), an organic-inorganic perovskite ferroelectric crystal processed from aqueous solution, has a large
of 185 picocoulombs per newton and a high phase-transition temperature of 406 kelvin (K) (16 K above that of BTO). This makes it a competitive candidate for medical, micromechanical, and biomechanical applications.
Phase transitions connect different states of matter and are often concomitant with the spontaneous breaking of symmetries. An important category of phase transitions is mobility transitions, among ...which is the well known Anderson localization
, where increasing the randomness induces a metal-insulator transition. The introduction of topology in condensed-matter physics
lead to the discovery of topological phase transitions and materials as topological insulators
. Phase transitions in the symmetry of non-Hermitian systems describe the transition to on-average conserved energy
and new topological phases
. Bulk conductivity, topology and non-Hermitian symmetry breaking seemingly emerge from different physics and, thus, may appear as separable phenomena. However, in non-Hermitian quasicrystals, such transitions can be mutually interlinked by forming a triple phase transition
. Here we report the experimental observation of a triple phase transition, where changing a single parameter simultaneously gives rise to a localization (metal-insulator), a topological and parity-time symmetry-breaking (energy) phase transition. The physics is manifested in a temporally driven (Floquet) dissipative quasicrystal. We implement our ideas via photonic quantum walks in coupled optical fibre loops
. Our study highlights the intertwinement of topology, symmetry breaking and mobility phase transitions in non-Hermitian quasicrystalline synthetic matter. Our results may be applied in phase-change devices, in which the bulk and edge transport and the energy or particle exchange with the environment can be predicted and controlled.
How a cell changes from one stable phenotype to another one is a fundamental problem in developmental and cell biology. Mathematically, a stable phenotype corresponds to a stable attractor in a ...generally multi-dimensional state space, which needs to be destabilized so the cell relaxes to a new attractor. Two basic mechanisms for destabilizing a stable fixed point, pitchfork and saddle-node bifurcations, have been extensively studied theoretically; however, direct experimental investigation at the single-cell level remains scarce. Here, we performed live cell imaging studies and analyses in the framework of dynamical systems theories on epithelial-to-mesenchymal transition (EMT). While some mechanistic details remain controversial, EMT is a cell phenotypic transition (CPT) process central to development and pathology. Through time-lapse imaging we recorded single cell trajectories of human A549/Vim-RFP cells undergoing EMT induced by different concentrations of exogenous TGF-β in a multi-dimensional cell feature space. The trajectories clustered into two distinct groups, indicating that the transition dynamics proceeds through parallel paths. We then reconstructed the reaction coordinates and the corresponding quasi-potentials from the trajectories. The potentials revealed a plausible mechanism for the emergence of the two paths where the original stable epithelial attractor collides with two saddle points sequentially with increased TGF-β concentration, and relaxes to a new one. Functionally, the directional saddle-node bifurcation ensures a CPT proceeds towards a specific cell type, as a mechanistic realization of the canalization idea proposed by Waddington.
The metal–insulator transition (MIT) in correlated materials is a novel phenomenon that accompanies a large change in resistivity, often many orders of magnitude. It is important in its own right but ...its switching behavior in resistivity can be useful for device applications. From the material physics point of view, the starting point of the research on the MIT should be to understand the microscopic mechanism. Here, an overview of recent efforts to unravel the microscopic mechanisms for various types of MITs in correlated materials is provided. Research has focused on transition metal oxides (TMOs), but transition metal chalcogenides have also been studied. Along the way, a new class of MIT materials is discovered, the so‐called relativistic Mott insulators in 5d TMOs. Distortions in the MO6 (M = transition metal) octahedron are found to have a large and peculiar effect on the band structure in an orbital dependent way, possibly paving a way to the orbital selective Mott transition. In the final section, the character of the materials suitable for applications is summarized, followed by a brief discussion of some of the efforts to control MITs in correlated materials, including a dynamical approach using light.
The metal–insulator transition (MIT) is one of the most fascinating phenomena observed in correlated materials, with its switching behavior under various environmental perturbations leading to high potential for novel devices. The microscopic mechanisms of MITs in various correlated materials discovered through spectroscopic investigations are reviewed. Possible ways to control MITs in correlated materials are also discussed based on the findings.
It is well-known that upon lithiation, both crystalline and amorphous Si transform to an armorphous Li x Si phase, which subsequently crystallizes to a (Li, Si) crystalline compound, either Li15Si4 ...or Li22Si5. Presently, the detailed atomistic mechanism of this phase transformation and the degradation process in nanostructured Si are not fully understood. Here, we report the phase transformation characteristic and microstructural evolution of a specially designed amorphous silicon (a-Si) coated carbon nanofiber (CNF) composite during the charge/discharge process using in situ transmission electron microscopy and density function theory molecular dynamic calculation. We found the crystallization of Li15Si4 from amorphous Li x Si is a spontaneous, congruent phase transition process without phase separation or large-scale atomic motion, which is drastically different from what is expected from a classic nucleation and growth process. The a-Si layer is strongly bonded to the CNF and no spallation or cracking is observed during the early stages of cyclic charge/discharge. Reversible volume expansion/contraction upon charge/discharge is fully accommodated along the radial direction. However, with progressive cycling, damage in the form of surface roughness was gradually accumulated on the coating layer, which is believed to be the mechanism for the eventual capacity fade of the composite anode during long-term charge/discharge cycling.
Monolayer transition metal dichalcogenide (TMD) alloys with tunable direct band gaps have promising applications in nanoelectronics and optoelectronics. The composition-dependent band gaps of ...ternary, quaternary and quinary monolayer TMD alloys have been systematically studied combining density functional theory and machine learning models in the present study. The excellent agreement between the DFT-calculated band gaps and the ML-predicted values for the training, validation and test datasets demonstrates the accuracy of our machine learning based on a neural network model. It is found that the band gap bowing parameter is closely related to the difference between the band gaps of the endpoint material compositions of the monolayer TMD alloy and increases with increasing band gap difference. The band gap bowing effects of monolayer TMD alloys obtained by mixing different transition metals are attributed to the conduction band minimum positions, while those of monolayer TMD alloys obtained by mixing different chalcogen atoms are dominated by the valence band maximum positions. This study shows that monolayer TMD alloys with tunable direct band gaps can provide new opportunities for band gap engineering, as well as electronic and optoelectronic applications.
The kagome lattice of transition metal atoms provides an exciting platform to study electronic correlations in the presence of geometric frustration and nontrivial band topology1-18, which continues ...to bear surprises. Here, using spectroscopic imaging scanning tunnelling microscopy, we discover a temperature-dependent cascade of different symmetry-broken electronic states in a new kagome superconductor, CsV3Sb5. We reveal, at a temperature far above the superconducting transition temperature Tc ~ 2.5 K, a tri-directional charge order with a 2a0 period that breaks the translation symmetry of the lattice. As the system is cooled down towards Tc, we observe a prominent V-shaped spectral gap opening at the Fermi level and an additional breaking of the six-fold rotational symmetry, which persists through the superconducting transition. This rotational symmetry breaking is observed as the emergence of an additional 4a0 unidirectional charge order and strongly anisotropic scattering in differential conductance maps. The latter can be directly attributed to the orbital-selective renormalization of the vanadium kagome bands. Our experiments reveal a complex landscape of electronic states that can coexist on a kagome lattice, and highlight intriguing parallels to high-Tc superconductors and twisted bilayer graphene.
Aim and objective
To critically review contemporary transition theories to determine how they apply to the newly qualified graduate registered nurse programmes.
Background
Graduate nurse transition ...to employment is the time of significant change which has resulted in high attrition rates. Graduates are often challenged by their expectation of nursing practice and the reality of the role. The transition from hospital‐based training to university‐based training has resulted in the need for primary employment to commence with graduate/orientation/internship programmes to help support new graduates transition into clinical practice. One transition model, Duchscher's stages of transition theory, utilised three former theories to develop a final model.
Design
A narrative critical literature review.
Method
The theories selected for the review were Kramer's reality shock theory, Benner's novice to expert theory, Bridges transition theory and Duchscher's stages of transition theory.
Conclusion
Duchscher's stages of transition theory reflects the experiences of registered nursing transition into the workforce directly from university. The application of the theory is effective to guide understanding of the current challenges that new graduate nurse's experience today. There is a need for new graduates to complete their university degree as advanced beginners in order to decrease the experience of transition shock and keep pace with rapidly changing demands of the clinical environment. This may be achieved by increasing ward‐based simulation in university education. A theoretical framework can provide a deep understanding of the various stages and processes of transition and enable development of successful programmes.
Relevance to clinical practice
Both universities and hospitals need to adapt their current practice to align with the needs of new graduates due to large student numbers and ongoing systematic advancements to decrease the attrition rate.
Highlights • Sorafenib resistance of advanced HCC has raised global concern and understanding the underlying mechanism is in urgent need. • Several growth factors and signaling pathways involved in ...EMT and MET play a pivotal role in sorafenib resistance. • CSCs and CSC-like cells associate with sorafenib resistance with great likelihood. • Biological processes related to tumor microenvironment demonstrate potential correlation with sorafenib resistance.
Developing extra safety encryption technologies to prevent information leakage and combat fakes is in high demand but is challenging. Herein, we propose a “double lock” strategy based on both lower ...critical solution temperature (LCST) and upper critical solution temperature (UCST) polymer hydrogels for information camouflage and multilevel encryption. Two types of hydrogels were synthesized by the method of random copolymerization. The number of −CO−NH2 groups in the network structure of the hydrogels changed the enthalpic or entropic thermo‐responsive hydrogels, and ultimately precisely controlled their phase transition temperature. The crosslink density of the polymer hydrogels governs the diffusion kinetics, resulting in a difference in the time for their color change. The combination of multiple LCST and UCST hydrogels in one label realized information encryption and dynamic information identification in the dimensions of both time and temperature. This work is highly interesting for the fields of information encryption, anti‐counterfeiting, and smart responsive materials.
A double lock encryption strategy with both temperature and time as keys and excellent comprehensive capabilities has been established via a combination of lower critical and upper critical solution temperature (LCST and UCST) thermosensitive polymer hydrogels, of which the phase transition temperature and time can be arbitrarily tailored by changing the contents of monomer and crosslinker in their networks. This strategy provides powerful double insurances for confidential information.
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