Convert widespread paraelectric perovskite to ferroelectrics

While nature provides a plethora of perovskite materials, only a few exhibits large ferroelectricity and possibly multiferroicity. The majority of perovskite materials have the non-polar CaTiO$_3$(CTO)structure, limiting the scope of their applications. Based on effective Hamiltonian model as well as first-principles calculations, we propose a general thin-film design method to stabilize the functional BiFeO$_3$(BFO)-type structure, which is a common metastable structure in widespread CaTiO$_3$-type perovskite oxides. It is found that the improper antiferroelectricity in CTO-type perovskite and ferroelectricity in BFO-type perovskite have distinct dependences on mechanical and electric boundary conditions, both of which involve oxygen octahedral rotation and tilt. The above difference can be used to stabilize the highly polar BFO-type structure in many CTO-type perovskite materials

Nonlinear Dynamics of a PI Hydroturbine Governing System with Double Delays

A PI hydroturbine governing system with saturation and double delays is generated in small perturbation. The nonlinear dynamic behavior of the system is investigated. More precisely, at first, we analyze the stability and Hopf bifurcation of the PI hydroturbine governing system with double delays under the four different cases. Corresponding stability theorem and Hopf bifurcation theorem of the system are obtained at equilibrium points. And then the stability of periodic solution and the direction of the Hopf bifurcation are illustrated by using the normal form method and center manifold theorem. We find out that the stability and direction of the Hopf bifurcation are determined by three parameters. The results have great realistic significance to guarantee the power system frequency stability and improve the stability of the hydropower system. At last, some numerical examples are given to verify the correctness of the theoretical results

Light irradiation induced brittle-to-ductile and ductile-to-brittle transition in inorganic semiconductors

The intrinsic brittleness of inorganic semiconductors prevents them from extended engineering applications under extreme conditions of high temperature and pressure, making it essential to improve their ductility. Here, we applied the constrained density functional theory to examine the relationship between plastic deformation and photonic excitation in sphalerite ZnS and related II-IV semiconductors. We find that ZnS transforms from a dislocation dominated deformation mode in the ground state to a twin dominated deformation mode with bandgap electronic excitations, leading to brittle failure under light illumination. This agrees very well with recent mechanical experiments on single crystal ZnS. More interesting, we predict that the ZnTe and CdTe display the opposite mechanical behavior compared to ZnS, exhibiting ductility close to metallic level with bandgap illumination, but typical brittle failure in the dark state. Our results provide a general approach to design more shapeable and tougher semiconductor devices by controlling exposure to electronic excitation

ETHYLENE-INSENSITIVE5 Encodes a 5\u27→3\u27 Exoribonuclease Required for Regulation of the EIN3-Targeting F-Box Proteins EDF1⁄2

Ethylene is a gaseous plant growth regulator that controls a multitude of developmental and stress responses. Recently, the levels of Arabidopsis EIN3 protein, a key transcription factor mediating ethylene-regulated gene expression, have been demonstrated to increase in response to the presence of ethylene gas. Furthermore, in the absence of ethylene, EIN3 is quickly degraded through a ubiquitin/proteasome pathway mediated by two F-box proteins, EBF1 and EBF2. Here we report the identification of ETHYLENE-INSENSITIVE5 as the 5′→3′ exoribonuclease XRN4. Specifically, we demonstrate that EIN5 is a component of the ethylene signal transduction cascade acting downstream of CTR1 that is required for ethylene-mediated gene expression changes. Furthermore, we find that the ethylene insensitivity of ein5 mutant plants is a consequence of the over-accumulation of EBF1 and EBF2 mRNAs resulting in the under-accumulation of EIN3 even in the presence of ethylene gas. Together, our results suggest that the role of EIN5 in ethylene perception is to antagonize the negative feedback regulation on EIN3 by promoting EBF1 and EBF2 mRNA decay, which consequently allows the accumulation of EIN3 protein to trigger the ethylene response

Altered fluvial patterns in North China indicate rapid climate change linked to the Permian-Triassic mass extinction

The causes of the severest crisis in the history of life around the Permian-Triassic boundary (PTB) remain controversial. Here we report that the latest Permian alluvial plains in Shanxi, North China, went through a rapid transition from meandering rivers to braided rivers and aeolian systems. Soil carbonate carbon isotope (δ13C), oxygen isotope (δ18O), and geochemical signatures of weathering intensity reveal a consistent pattern of deteriorating environments (cool, arid, and anoxic conditions) and climate fluctuations across the PTB. The synchronous ecological collapse is confirmed by a dramatic reduction or disappearance of dominant plants, tetrapods and invertebrates and a bloom of microbially-induced sedimentary structures. A similar rapid switch in fluvial style is seen worldwide (e.g. Karoo Basin, Russia, Australia) in terrestrial boundary sequences, all of which may be considered against a background of global marine regression. The synchronous global expansion of alluvial fans and high-energy braided streams is a response to abrupt climate change associated with aridity, hypoxia, acid rain, and mass wasting. Where neighbouring uplands were not uplifting or basins subsiding, alluvial fans are absent, but in these areas the climate change is evidenced by the disruption of pedogenesis

Hyperosmolarity evokes histamine release from ileum mucosa by stimulating a cholinergic pathway.

editorial reviewedChanges in extracellular osmolarity lead to alteration in cellular volume. In the study, we examined the effects of hyperosmolarity on short-circuit currents (Isc) in the rat ileum using the Ussing chamber technique. Mucosal exposure to 20 mM glucose evoked a decrease of ISC in the rat ileum, which was antagonized by the stretch-activated channel blocker GdCl3, TTX and atropine, respectively. In contrast, it was not blocked by phlorizin, a Na+-glucose cotransporter SGLT1 inhibitor. Furthermore, the unabsorbed substances, such as sucrose, lactulose or urea, also induced a decrease of ISC in rat ileum. ELISA results revealed that 20 mM glucose stimulated the release of histamine from rat ileum mucosa, which was attenuated by TTX. In addition, the glucose-induced ISC was depressed by pyrilamine, a histamine H1 receptor blocker (H1 antagonist) whereas it was not affected by ranitidine (H2 antagonist), clobenpropit (H3 antagonists) or JNJ7777120 (H4 antagonist), respectively. The ion substitution experiments suggest that the changes of Na+ and HCO3- ion flux underlie the glucose-induced ISC. In conclusion, osmotic stimulus decreased the basal ISC of rat ileum by evoking histamine release from ileum mucosa. The changes of Na+ and HCO3- ion transport are involved in the glucose-evoked decrease of basal ISC

The plasticity of mesenchymal stem cells in regulating surface HLA-I

Summary A low surface expression level of human leukocyte antigen class I(HLA-I) ensures the mesenchymal stem cells’(MSCs) escape from the allogeneic recipients’ immunological surveillance. Here, we discovered that both transcriptional and synthesis levels of HLA-I in MSCs increased continuously after IFN-γ treatment, while interestingly, their surface HLA-I expression was downregulated after reaching an HLA-I surface expression peak. Microarray data indicated the post-transcriptional process plays an important role in downregulation of surface HLA-I. Further studies identified that IFN-γ-treated MSCs accelerated HLA-I endocytosis through a Clathrin–independent Dynamin-dependent endocytosis pathway. Furthermore, the cells which have self-downregulated surface HLA-I expression elicit a weaker immune response than they previously could. Thus, uncovering the plasticity of MSCs in the regulation of HLA-I surface expression would reveal insights into the membrane-transportation events leading to the maintenance of low surface HLA-I expression, providing more evidence for selecting and optimizing low immunogenic MSCs to improve the therapeutic efficiency.Peer reviewe

Generation of Trophoblast Stem Cells from Rabbit Embryonic Stem Cells with BMP4

Trophoblast stem (TS) cells are ideal models to investigate trophectoderm differentiation and placental development. Herein, we describe the derivation of rabbit trophoblast stem cells from embryonic stem (ES) cells. Rabbit ES cells generated in our laboratory were induced to differentiate in the presence of BMP4 and TS-like cell colonies were isolated and expanded. These cells expressed the molecular markers of mouse TS cells, were able to invade, give rise to derivatives of TS cells, and chimerize placental tissues when injected into blastocysts. The rabbit TS-like cells maintained self-renewal in culture medium with serum but without growth factors or feeder cells, whilst their proliferation and identity were compromised by inhibitors of FGFs and TGF-β receptors. Taken together, our study demonstrated the derivation of rabbit TS cells and suggested the essential roles of FGF and TGF-β signalings in maintenance of rabbit TS cell self-renewal