Through first‐principles calculations, it is found that two lattice‐matched halide double‐perovskites, Cs2NaBiBr6 and Cs2AgBiBr6, have a type‐I band alignment and can form highly miscible alloys in ...which the disordering makes the bandgaps become direct and activates the direct transition from the valence to conduction band edge, leading to a strong optical absorption and high radiative recombination rate. The bandgaps of the alloys are tunable in a wide range of 1.93–3.24 eV, while the lattice constants remain unchanged. This advantage inspires the design of a coherent crystalline matrix based on Cs2(Na,Ag)BiBr6 alloys, in which the Ag‐rich and narrower‐bandgap regions are embedded in the Na‐rich and wide‐bandgap region with lattice‐matched and coherent interfaces. The type‐I band alignment drives the photogenerated excitons into the narrower‐bandgap Ag‐rich regions, so the regions become light‐emitting centers with a high photoluminescence quantum yield (PLQY). The bandgaps of the Ag‐rich regions are tunable, so the color of emitted light can be adjusted, making a broadband emission possible. Such kind of coherent crystalline matrix with high‐PLQY and broadband emission can also be fabricated based on the alloys of other lattice‐matched halide double‐perovskites, demonstrating the flexibility of band structure engineering in the coherent heterostructures of various halide double‐perovskites.
Through embedding narrower‐bandgap alloys in wide‐bandgap alloys, a coherent crystalline matrix based on the alloys of two lattice‐matched halide double‐perovskites, such as Cs2(Na,Ag)BiBr6 alloys, are fabricated and a high photoluminescence quantum yield and broadband light emission are achieved, which demonstrates the flexibility of band structure engineering in coherent heterostructures of various halide double‐perovskites.
Pancreatic ductal adenocarcinoma (PDA) is the most lethal of common human malignancies, with no truly effective therapies for advanced disease. Preclinical studies have suggested a therapeutic ...benefit of targeting the Hedgehog (Hh) signaling pathway, which is activated throughout the course of PDA progression by expression of Hh ligands in the neoplastic epithelium and paracrine response in the stromal fibroblasts. Clinical trials to test this possibility, however, have yielded disappointing results. To further investigate the role of Hh signaling in the formation of PDA and its precursor lesion, pancreatic intraepithelial neoplasia (PanIN), we examined the effects of genetic or pharmacologic inhibition of Hh pathway activity in three distinct genetically engineered mouse models and found that Hh pathway inhibition accelerates rather than delays progression of oncogenic Kras-driven disease. Notably, pharmacologic inhibition of Hh pathway activity affected the balance between epithelial and stromal elements, suppressing stromal desmoplasia but also causing accelerated growth of the PanIN epithelium. In striking contrast, pathway activation using a small molecule agonist caused stromal hyperplasia and reduced epithelial proliferation. These results indicate that stromal response to Hh signaling is protective against PDA and that pharmacologic activation of pathway response can slow tumorigenesis. Our results provide evidence for a restraining role of stroma in PDA progression, suggesting an explanation for the failure of Hh inhibitors in clinical trials and pointing to the possibility of a novel type of therapeutic intervention.
Phase engineering by strain in 2D semiconductors is of great importance for a variety of applications. Here, a study of the strain‐induced ferroelectric (FE) transition in bismuth oxyselenide ...(Bi2O2Se) films, a high‐performance (HP) semiconductor for next‐generation electronics, is presented. Bi2O2Se is not FE at ambient pressure. At a loading force of ≳400 nN, the piezoelectric force responses exhibit butterfly loops in magnitude and 180° phase switching. By carefully ruling out extrinsic factors, these features are attributed to a transition to the FE phase. The transition is further supported by the appearance of a sharp peak in optical second‐harmonic generation under uniaxial strain. In general, solids with paraelectrics at ambient pressure and FE under strain are rare. The FE transition is discussed using first‐principles calculations and theoretical simulations. The switching of FE polarization acts as a knob for Schottky barrier engineering at contacts and serves as the basis for a memristor with a huge on/off current ratio of 106. This work adds a new degree of freedom to HP electronic/optoelectronic semiconductors, and the integration of FE and HP semiconductivity paves the way for many exciting functionalities, including HP neuromorphic computing and bulk piezophotovoltaics.
In a high‐performance semiconductor Bi2O2Se, a strain‐induced ferroelectric transition is demonstrated by the appearance of butterfly loops and 180° phase switching in the piezoelectric force microscopy measurements, together with the evolution of optical second‐harmonic generation. Materials with paraelectrics at ambient pressure and ferroelectrics under strain are rare.
Mulitipe stoichiometric ratio of two-dimensional (2D) transition metal dichalcogenides (TMDCs) attracted considerable interest for their unique chemical and physical properties. Here we developed a ...chemical vapor deposition (CVD) method to controllably synthesize ultrathin NiS and NiS
2
nanoplates. By tuning the growth temperature and the amounts of the sulfur powder, 2D non-layered NiS and NiS
2
nanoplates can be selectively prepared with the thickness of 2.0 and 7.0 nm, respectively. X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterization reveal that the 2D NiS and NiS
2
nanoplates are high-quality single crystals in the hexagonal and cubic phase, respectively. Electrical transport studies show that electrical conductivities of the 2D NiS and NiS
2
nanoplates are as high as 4.6 × 10
5
and 6.3 × 10
5
S·m
−1
, respectively. The electrical results demonstrate that the synthesized metallic NiS and NiS
2
could serve as good electrodes in 2D electronics.
PURPOSE OF REVIEWAcute anemic stress induces a physiological response that includes the rapid development of new erythrocytes. This process is referred to as stress erythropoiesis, which is distinct ...from steady state erythropoiesis. Much of what we know about stress erythropoiesis comes from the analysis of murine models. In this review, we will discuss our current understanding of the mechanisms that regulate stress erythropoiesis in mice and discuss outstanding questions in the field.
RECENT FINDINGSStress erythropoiesis occurs in the murine spleen, fetal liver and adult liver. The signals that regulate this process are Hedgehog, bone morphogenetic protein 4 (BMP4), stem cell factor and hypoxia. Recent findings show that stress erythropoiesis utilizes a population of erythroid-restricted self-renewing stress progenitors. Although the BMP4-dependent stress erythropoiesis pathway was first characterized during the recovery from acute anemia, analysis of a mouse model of chronic anemia demonstrated that activation of the BMP4-dependent stress erythropoiesis pathway provides compensatory erythropoiesis in response to chronic anemia as well.
SUMMARYThe BMP4-dependent stress erythropoiesis pathway plays a key role in the recovery from acute anemia and new data show that this pathway compensates for ineffective steady state erythropoiesis in a murine model of chronic anemia. The identification of a self-renewing population of stress erythroid progenitors in mice suggests that therapeutic manipulation of this pathway may be useful for the treatment of human anemia. However, the development of new therapies will await the characterization of an analogous pathway in humans.
Tissue hypoxia induces a systemic response designed to increase oxygen delivery to tissues. One component of this response is increased erythropoiesis. Steady-state erythropoiesis is primarily ...homeostatic, producing new erythrocytes to replace old erythrocytes removed from circulation by the spleen. In response to anemia, the situation is different. New erythrocytes must be rapidly made to increase hemoglobin levels. At these times, stress erythropoiesis predominates. Stress erythropoiesis is best characterized in the mouse, where it is extramedullary and utilizes progenitors and signals that are distinct from steady-state erythropoiesis. In this report, we use an in vitro culture system that recapitulates the in vivo development of stress erythroid progenitors. We identify cell-surface markers that delineate a series of stress erythroid progenitors with increasing maturity. In addition, we use this in vitro culture system to expand human stress erythroid progenitor cells that express analogous cell-surface markers. Consistent with previous suggestions that human stress erythropoiesis is similar to fetal erythropoiesis, we demonstrate that human stress erythroid progenitors express fetal hemoglobin upon differentiation. These data demonstrate that similar to murine bone marrow, human bone marrow contains cells that can generate BMP4-dependent stress erythroid burst-forming units when cultured under stress erythropoiesis conditions.
•Murine stress erythroid progenitors develop through a series of progenitors that express CD34, CD133, Kit, and Sca1.•Human stress erythroid progenitors can be expanded using the same culture system and are predisposed to express γ-globin.
The small field‐of‐view (FOV) limits the range of vision in various detecting/imaging devices from biological microscopes to commercial cameras and military radar. To date, imaging with FOV over 90° ...has been realized with fish‐eye lenses, catadioptric lens, and rotating cameras. However, these devices suffer from inherent imaging distortion and require multiple bulky elements. Inspired by compound eyes found in nature, here a small‐size (84 μm), distortion‐free, wide‐FOV imaging system is presented via an advanced 3D artificial eye architecture. The 3D artificial eye structure is accomplished by exploiting an effective optical strategy — high‐speed voxel‐modulation laser scanning (HVLS). The eye features a hexagonal shape, high fill factor (FF) (100%), large numerical aperture (NA) (0.4), ultralow surface roughness (2.5 nm) and aspherical profile, which provides high uniformity optics (error < ±6%) and constant resolution (FWHM = 1.7 ± 0.1 μm) in all directions. Quantitative measurement shows the eye reduces imaging distortion by two/three times under 30°/45° incidence, compared with a single lens. The distortion‐free FOV can be controlled from 30° to 90°.
A small‐size (84 μm), distortion‐free, wide‐field‐of‐view (FOV) 3D artificial eye architecture is reported by exploiting an effective optical strategy — high‐speed voxel‐modulation laser scanning (HVLS). The eye features a hexagonal shape, high fill factor (FF) (100%), large numerical aperture (NA) (0.4), ultralow surface roughness (2.5 nm) and aspherical profile. The eye reduces imaging distortion by two/three times under 30°/45° incidence, compared with a single lens.
Rice leaves with anisotropic sliding properties have the ability to directionally control the movement of water microdroplets. However, the realization of artificial anisotropic sliding biosurfaces ...has remained challenging. It is found, by a systematic investigation, that the height of 200‐μm‐width groove arrays on rice leaves reaches up to 45 μm, far greater than the smaller microgrooves that are widely adopted for the study of anisotropic wetting. A new model based on three‐level microstructures (macro/micro/nano) is developed to interpret the anisotropic sliding behavior. Moreover, artificial rice leaves with different macrogrooves are demonstrated by combining micro/nanostructures and macrogrooves, which are prepared by photolithography, PDMS imprinting, and micro/nanostructure coating. Sliding‐angle measurement further prove that the third‐level macrogroove arrays are the determining factor for anisotropic sliding. Finally, a new testing method, curvature‐assisted droplet oscillation (CADO), is developed to quantitatively reveal the anisotropic dynamic behavior of biomimetic rice‐leaf‐like surfaces.
A new model to interpret the anisotropic sliding behavior of the rice leaf is proposed based on three‐level microstructures (macrogrooves, micropapilla, and nanostructures). The three‐level hierarchical surfaces were reproduced by combining photolithography, PDMS imprinting, and micro/nanostructure coating, and a new method was developed, named curvature‐assisted droplet oscillation (CADO), to quantitatively characterize the weak frictional interaction between the liquid droplet and the structured surface.
Summary
Despite the great interest in identifying protein–protein interactions (PPIs) in biological systems, only a few attempts have been made at large‐scale PPI screening in planta. Unlike ...biochemical assays, bimolecular fluorescence complementation allows visualization of transient and weak PPIs in vivo at subcellular resolution. However, when the non‐fluorescent fragments are highly expressed, spontaneous and irreversible self‐assembly of the split halves can easily generate false positives. The recently developed tripartite split‐GFP system was shown to be a reliable PPI reporter in mammalian and yeast cells. In this study, we adapted this methodology, in combination with the β‐estradiol‐inducible expression cassette, for the detection of membrane PPIs in planta. Using a transient expression assay by agroinfiltration of Nicotiana benthamiana leaves, we demonstrate the utility of the tripartite split‐GFP association in plant cells and affirm that the tripartite split‐GFP system yields no spurious background signal even with abundant fusion proteins readily accessible to the compartments of interaction. By validating a few of the Arabidopsis PPIs, including the membrane PPIs implicated in phosphate homeostasis, we proved the fidelity of this assay for detection of PPIs in various cellular compartments in planta. Moreover, the technique combining the tripartite split‐GFP association and dual‐intein‐mediated cleavage of polyprotein precursor is feasible in stably transformed Arabidopsis plants. Our results provide a proof‐of‐concept implementation of the tripartite split‐GFP system as a potential tool for membrane PPI screens in planta.
Significance Statement
We demonstrate that the inducible tripartite split‐GFP system with small‐size tags (19–20 amino acids) yields no spurious background signal in plant cells even with abundant fusion proteins readily accessible to the compartments of interaction, thus providing advantages over conventional bimolecular fluorescence complementation for detecting membrane protein–protein interactions (PPIs). Furthermore, the dual‐intein‐based coordinated tripartite split‐GFP tool promises the opportunity to perform large‐scale membrane PPI screens in planta.
Precise tuning of surface wettability – by means of curvature‐driven reversible switching from the pinned to the roll‐down superhydrophobic state (see figure) – is reported for for the first time. ...The adhesion force and sliding behaviors of superhydrophobic poly(dimethylsiloxane) (PDMS) pillar arrays show strong dependence on surface curvature. Alteration of the curvature of the surface allows a water droplet to be easily adjusted from the “ pinned” to the “roll‐down” state, which provides the possibility of precise, in situ control of the movements of water droplets.
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