The zebrafish has the potential to regenerate many of its tissues. In this study, we examined caudal fin regeneration in zebrafish that received repeated injuries (fin amputation) at different ages. In zebrafish that received repeated injuries, the potential for caudal fin regeneration, such as tissue growth and the expression of regeneration marker genes (msxb, fgf20a, bmp2b), did not decline in comparison to zebrafish that received only one amputation surgery. The process of initial fin regeneration (e.g., tissue outgrowth and the expression of regeneration marker genes at 7 days post-amputation) did not seem to correlate with age. However, slight differences in fin outgrowth were observed between young and old animals when examined in the late regeneration stages (e.g., 20 and 30 days post-amputation). Together, the data suggest that zebrafish has unlimited regenerative potential in the injured caudal fin. Developmental Dynamics 240:1271-1277,

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Ferroelectric (FE) size effects against the scaling law were reported recently in ultrathin group-IV monochalcogenides, and extrinsic effects (e.g. defects and lattice strains) were often resorted to. Via first-principles based finite-temperature (T ) simulations, we reveal that these abnormalities are intrinsic to their unusual symmetry breaking from bulk to thin film. Changes of the electronic structures result in different order parameters characterizing the FE phase transition in bulk and in thin films, and invalidation of the scaling law. Beyond the scaling law Tc limit, this mechanism can help predicting materials promising for room-T ultrathin FE devices of broad interest.Miniaturized ferroelectric (FE) device of continued demand in portable consumer electronics poses prerequisite understandings of a fundamental question, i.e. the nature of FE size effects [1][2][3][4][5][6]. Finite size scaling (FSS) theory, as the conventional wisdom, predicts that the Curie temperature T c for the paraelectric (PE) to FE phase transitions decreases when scaling down to finite sizes [7-9], following:where T c (d) and T c (∞) are the T c of the film of thickness d and bulk, respectively [10]. The T c s of different sizes are related via the character length ξ 0 and the universal critical exponent λ. As FSS theory shown predictive in perovskite compounds and a variety of FEs [1,[11][12][13], T c (d) being lower in ultrathin films was believed heretofore as an essential limit in realizing room temperature (T ) ultrathin FE devices of broad interest [2, 11]. Recent studies on group-IV monochalcogenides, however, opened the door for realization of room T ultrathin FE devices beyond the FSS theory prediction [14][15][16][17][18][19]. The experiment by K. Chang et al. showed that in one unit-cell (1UC) SnTe film the Curie temperature (T 1UC c ) is 270 K [14], enhanced from the bulk value (T bulk c ) of 98 K [20]. Parallel to this, Fei et al. predicted robust ferroelectricity in analogous monolayer group-IV monochalcogenides MX (M = Ge, Sn; X = S, Se) via the Landau-Ginzburg type effective Hamiltonian method [15]. Wu and Zeng showed MX's multiferroelectricity, where the polarization valley switching by using stress or electric field enables designing room-T nonvolatile memory [16,21]. Nevertheless, large extrinsic effects claimed in these studies such as lower free carrier density [14,17,22,23], lattice strains [18,24,25], etc. render the intrinsic size effect of ferroelectricity unimportant, thereby hindering further investigation and search-ing for other promising materials.In this letter, we address two issues: i) reveal the nature of intrinsic FE size effects in these materials and analyze their relation with the FSS theory; ii) propose an easy-to-use criteria for potential low-dimensional FE materials with T c higher than their high-dimensional correspondences. SnTe and BaTiO 3 (BTO), two paradigmatic FE materials whose scaling behaviors show remarkable difference, are discussed in details. Based on the firstprinciples expl...

Recent discoveries of dynamic ice VII and superionic ice highlight the importance of ionic diffusions in discriminating high-pressure (P) water phases. The rare event nature and the chemical bond breaking associated with these diffusions, however, make extensive simulations of these processes unpractical to ab initio and inappropriate for force field based methods. Using a first-principles neural network potential, we performed a theoretical study of water at 5–70 GPa and 300–3000 K. Long-time dynamics of protons and oxygens were found indispensable in discriminating several subtle states of water, characterized by proton’s and oxygen ion’s diffusion coefficients and the distribution of proton’s displacements. Within dynamic ice VII, two types of proton transfer mechanisms, i.e., translational and rotational transfers, were identified to discriminate this region further into dynamic ice VII T and dynamic ice VII R. The triple point between ice VII, superionic ice (SI), and liquid exists because the loosening of the bcc oxygen skeleton is prevented by the decrease of interatomic distances at high P’s. The melting of ice VII above ∼40 GPa can be understood as a process of two individual steps: the melting of protons and the retarded melting of oxygens, responsible for the forming of SI. The boundary of the dynamic ice VII and SI lies on the continuation line ice VII’s melting curve at low P’s. Based on these, a detailed phase diagram is given, which may shed light on studies of water under P’s in a wide range of interdisciplinary sciences.

Optical tracking and biocompatibility study of nanoparticles (NPs) have received lots of attention in nano-research areas. In this paper, PDMAEMA-b-poly(PEGMA)-b-PDMAEMA-fluorescein (DED-F) NPs were synthesized by encapsulating hydrophobic fluorescein in an amphiphilic triblock copolymer DED. DED possessed gene transfection functions as our previous work demonstrated and the encapsulated fluorescein guaranteed the bioimaging capability of DED-F NPs. The bioimaging and biocompatibility assessments were conducted in vitro using PC12 cells and in vivo through the model organism zebrafish. The results demonstrated that DED-F NPs could be internalized by cells without changing the electrophysiological conditions of ion channels on cell membranes. Moreover, the absorption, distribution, metabolism and excretion of DED-F NPs in early developmental zebrafish indicated that these NPs could serve as biocompatible imaging agents in in vivo studies. Scheme 1 A schematic illustration showing the synthesis of DED-F NPs by an emulsification-solvent evaporation technique.