The inherent plasticity and resiliency of fibroblasts make this cell type a conventional tool for basic research. But where do they come from, are all fibroblasts the same, and how do they function ...in disease? The first fibroblast lineages in mammalian development emerge from the ooze of primary mesenchyme during gastrulation. They are cells that efficiently create and negotiate the extracellular matrix of the mesoderm in order to migrate and meet their developmental fate. Mature fibroblasts in epithelial tissues live in the interstitial spaces between basement membranes that spatially delimit complex organ structures. While the function of resident fibroblasts in healthy tissues is largely conjecture, the accumulation of fibroblasts in pathologic lesions offers insight into biologic mechanisms that control their function; fibroblasts are poised to coordinate fibrogenesis in tissue injury, neoplasia, and aging. Here, we examine the developmental origin and plasticity of fibroblasts, their molecular and functional definitions, the epigenetic control underlying their identity and activation, and the evolution of their immune regulatory functions. These topics are reviewed through the lens of fate mapping using genetically engineered mouse models and from the perspective of single‐cell RNA sequencing. Recent observations suggest dynamic and heterogeneous functions for fibroblasts that underscore their complex molecular signatures and utility in injured tissues.
•An algebraic model is proposed for prediction of bypass and separation-induced transition.•The model only uses local variables.•Good results are obtained for transition in attached and separated ...boundary layers.•Good results are obtained for simulation of wake-induced transition.
An algebraic model using the intermittency concept is proposed for laminar to turbulent transition in attached and separated boundary layers. The model modifies the production terms of the k–ω RANS turbulence model by Wilcox. For attached flows, the model describes bypass transition by taking into account two main effects, which are damping of high-frequency disturbances by a laminar shear layer and breakdown of a near-wall laminar layer perturbed by streaks. For separated flow, the model describes breakdown of a laminar free shear layer. The proposed model is a modified and extended version of an earlier model by the authors for bypass transition only (Kubacki and Dick, Int. J. Heat and Fluid Flow, 58, 68–83, 2016).
The primary tuning of the model has been done with flat plate T3C flows of ERCOFTAC with steady approaching flow, relevant for bypass transition and separation-induced transition. Secondary tuning has been done with two cascades with steady approaching flow at high turbulence level, one with N3-60 (Re= 6×105) steam turbine stator vanes and one with V103 (Re= 1.385×105) compressor blades. Model validation has been done for steady approaching flows of the same cascades, but including a case with low level of free-stream turbulence, and for a cascade with T106A (Re= 1.6×105) gas turbine rotor blades for high and low levels of free-stream turbulence. Further validation has been done for flow perturbed by travelling wakes through a cascade of N3-60 vanes at high and low levels of background turbulence level. The transition model produces good results for all cases, both for bypass transition in attached boundary layer state and for transition in separated boundary layer state.
•Recent research on dielectric transition and ferroelectricity is overviewed.•Basic concepts and fundamentals of the two properties are introduced.•Structural changes during the phase transitions are ...discussed.
Structural phase transition in solid-state materials is an underlying factor for emergence and evolution of a number of important physical/chemical properties. In this review, we summarize recent achievements on two types of structural phase transition-associated properties, i.e., dielectric transition and ferroelectricity, in coordination compounds. The basic concepts and fundamentals of structural phase transition and the two properties are briefly introduced. This review aims to reveal the role of the structural phase transitions on bulk properties and afford a perspective on the connections among multiple topics of coordination chemistry from the structural phase transition viewpoint. It would be appealing to researchers in multidisciplinary fields such as coordination chemistry, crystal engineering, supramolecular chemistry, condensed matter physics, responsive materials and molecular machines.
Phase control plays an important role in the precise synthesis of inorganic materials, as the phase structure has a profound influence on properties such as conductivity and chemical stability. ...Phase-controlled preparation has been challenging for the metallic-phase group-VI transition metal dichalcogenides (the transition metals are Mo and W, and the chalcogens are S, Se and Te), which show better performance in electrocatalysis than their semiconducting counterparts. Here, we report the large-scale preparation of micrometre-sized metallic-phase 1T′-MoX2 (X = S, Se)-layered bulk crystals in high purity. We reveal that 1T′-MoS2 crystals feature a distorted octahedral coordination structure and are convertible to 2H-MoS2 following thermal annealing or laser irradiation. Electrochemical measurements show that the basal plane of 1T′-MoS2 is much more active than that of 2H-MoS2 for the electrocatalytic hydrogen evolution reaction in an acidic medium.
Metal-to-insulator transitions
driven by strong electronic correlations occur frequently in condensed matter systems, and are associated with remarkable collective phenomena in solids, including ...superconductivity and magnetism. Tuning and control of the transition holds the promise of low-power, ultrafast electronics
, but the relative roles of doping, chemistry, elastic strain and other applied fields have made systematic understanding of such transitions difficult. Here we show that existing data
on the tuning of metal-to-insulator transitions in perovskite transition-metal oxides through ionic size effects provides evidence of large systematic effects on the phase transition owing to dynamical fluctuations of the elastic strain, which have usually been neglected
. We illustrate this using a simple yet quantitative statistical mechanical calculation in a model that incorporates cooperative lattice distortions coupled to the electronic degrees of freedom. We reproduce the observed dependence of the transition temperature on the cation radius in the well studied manganite
and nickelate
materials. Because elastic couplings are generally strong, we anticipate that these conclusions will generalize to all metal-to-insulator transitions that couple to a change in lattice symmetry.
Inorganic perovskite ferroelectrics are widely used in nonvolatile memory elements, capacitors, and sensors because of their excellent ferroelectric and other properties. Organic ferroelectrics are ...desirable for their mechanical flexibility, low weight, environmentally friendly processing, and low processing temperatures. Although almost a century has passed since the first ferroelectric, Rochelle salt, was discovered, examples of highly desirable organic perovskite ferroelectrics are lacking. We found a family of metal-free organic perovskite ferroelectrics with the characteristic three-dimensional structure, among which MDABCO (
-methyl-
-diazabicyclo2.2.2octonium)-ammonium triiodide has a spontaneous polarization of 22 microcoulombs per square centimeter close to that of barium titanate (BTO), a high phase transition temperature of 448 kelvins (above that of BTO), and eight possible polarization directions. These attributes make it attractive for use in flexible devices, soft robotics, biomedical devices, and other applications.
Large‐area “in situ” transition‐metal substitution doping for chemical‐vapor‐deposited semiconducting transition‐metal‐dichalcogenide monolayers deposited on dielectric substrates is demonstrated. In ...this approach, the transition‐metal substitution is stable and preserves the monolayer's semiconducting nature, along with other attractive characteristics, including direct‐bandgap photoluminescence.
Transition‐metal‐mediated cleavage of C−C single bonds can enable entirely new retrosynthetic disconnections in the total synthesis of natural products. Given that C−C bond cleavage inherently alters ...the carbon framework of a compound, and that, under transition‐metal catalysis, the generated organometallic or radical intermediate is primed for further complexity‐building reactivity, C−C bond‐cleavage events have the potential to drastically and rapidly remodel skeletal frameworks. The recent acceleration of the use of transition‐metal‐mediated cleavage of C−C single bonds in total synthesis can be ascribed to a communal recognition of this fact. In this Review, we highlight ten selected total syntheses from 2014 to 2019 that illustrate how transition‐metal‐mediated cleavage of C−C single bonds at either the core or the periphery of synthetic intermediates can streamline synthetic efforts.
Rapid remodeling of skeletal frameworks can be achieved by transition‐metal‐mediated cleavage of C−C single bonds and enable new retrosynthetic disconnections. In this Review, ten total syntheses from 2014–2019 are highlighted that illustrate how transition‐metal‐mediated cleavage of C−C single bonds can streamline synthetic efforts.
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.
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