Metal halide perovskites (MHPs) have numerous advantages as light emitters such as high photoluminescence quantum efficiency with a direct bandgap, very narrow emission linewidth, high charge‐carrier ...mobility, low energetic disorder, solution processability, simple color tuning, and low material cost. Based on these advantages, MHPs have recently shown unprecedented radical progress (maximum current efficiency from 0.3 to 42.9 cd A−1) in the field of light‐emitting diodes. However, perovskite light‐emitting diodes (PeLEDs) suffer from intrinsic instability of MHP materials and instability arising from the operation of the PeLEDs. Recently, many researchers have devoted efforts to overcome these instabilities. Here, the origins of the instability in PeLEDs are reviewed by categorizing it into two types: instability of (i) the MHP materials and (ii) the constituent layers and interfaces in PeLED devices. Then, the strategies to improve the stability of MHP materials and PeLEDs are critically reviewed, such as A‐site cation engineering, Ruddlesden–Popper phase, suppression of ion migration with additives and blocking layers, fabrication of uniform bulk polycrystalline MHP layers, and fabrication of stable MHP nanoparticles. Based on this review of recent advances, future research directions and an outlook of PeLEDs for display applications are suggested.
Recent progress in understanding the origins of the low stability of metal halide perovskite (MHP) materials and light‐emitting diodes (PeLEDs) is reviewed. Various strategies to overcome the low stability are discussed with a special focus on the MHP material stability and operational stability of the PeLEDs. Future research directions to improve the stability are also suggested.
Ruddlesden–Popper phase (RP‐phase) perovskites that consist of 2D perovskite slabs interleaved with bulky organic ammonium (OA) are favorable for light‐emitting diodes (LEDs). The critical limitation ...of LED applications is that the insulating OA arranged in a preferred orientation limits charge transport. Therefore, the ideal solution is to achieve a randomly connected structure that can improve charge transport without hampering the confinement of the electron–hole pair. Here, a structurally modulated RP‐phase metal halide perovskite (MHP), (PEA)2(CH3NH3)m−1PbmBr3m+1 is introduced to make the randomly oriented RP‐phase unit and ensure good connection between them by applying modified nanocrystal pinning, which leads to an increase in the efficiency of perovskite LEDs (PeLEDs). The randomly connected RP‐phase MHP forces contact between inorganic layers and thereby yields efficient charge transport and radiative recombination. Combined with an optimal dimensionality, (PEA)2(CH3NH3)2Pb3Br10, the structurally modulated RP‐phase MHP exhibits increased photoluminescence quantum efficiency, from 0.35% to 30.3%, and their PeLEDs show a 2,018 times higher current efficiency (20.18 cd A−1) than in the 2D PeLED (0.01 cd A−1) and 673 times than in the 3D PeLED (0.03 cd A−1) using the same film formation process. This approach provides insight on how to solve the limitation of RP‐phase MHP for efficient PeLEDs.
Ruddlesden–Popper phase (RP‐phase) perovskites are promising materials for optoelectronic devices. Efficient RP‐phase perovskite light‐emitting diodes (PeLEDs) are developed by introducing a structurally modulated RP‐phase metal halide perovskite (MHP) emitter to increase the charge transport ability without hampering the confinement of the electron–hole pair. This approach provides insight on how to solve the limitation of RP‐phase MHP for efficient PeLEDs.
Conventional organic light‐emitting devices without an encapsulation layer are susceptible to degradation when exposed to air, so realization of air‐stable intrinsically‐stretchable display is a ...great challenge because the protection of the devices against penetration of moisture and oxygen is even more difficult under stretching. An air‐stable intrinsically‐stretchable display that is composed of an intrinsically‐stretchable electroluminescent device (SELD) integrated with a stretchable color‐conversion layer (SCCL) that contains perovskite nanocrystals (PeNCs) is proposed. PeNCs normally decay when exposed to air, but they become resistant to this decay when dispersed in a stretchable elastomer matrix; this change is a result of a compatibility between capping ligands and the elastomer matrix. Counterintuitively, the moisture can efficiently passivate surface defects of PeNCs, to yield significant increases in both photoluminescence intensity and lifetime. A display that can be stretched up to 180% is demonstrated; it is composed of an air‐stable SCCL that down‐converts the SELD’s blue emission and reemits it as green. The work elucidates the basis of moisture‐assisted surface passivation of PeNCs and provides a promising strategy to improve the quantum efficiency of PeNCs with the aid of moisture, which allows PeNCs to be applied for air‐stable stretchable displays.
An air‐stable stretchable display consisting of an intrinsically stretchable electroluminescent device and perovskite nanocrystal (PeNCs) stretchable color conversion layer is proposed. Surprisingly, the increase in photoluminescence intensity of PeNCs in the water is proved to be caused by the surface passivation of moisture, which overcomes the water instability of perovskite materials.
The relationship between trade and environmental quality is a major controversial issue. The paper intends to provide robust evidence and new insights into the discussion. Specifically, it examines ...the effect of trade on carbon dioxide emissions (CO2) systematically in a North-North, North-South, South-North, and South-South context. It employs a panel data instrumental-variable quantile approach to control for endogeneity and account for potential (quantile) parameter heterogeneity. Some important results emerge. First, trade with the North increases CO2 emissions whereas trade with the South mitigates CO2 emissions with a relatively larger effect for less polluted host countries. Second, for advanced countries, their trade with the South or the North leads to a reduction in CO2 emissions, the effect that seems relatively stronger for less polluted advanced countries. Third, for developing countries, their trade with the North worsens CO2 emissions whereas their trade with the South mitigates CO2 emissions with a larger effect for less polluted developing countries. Last, the environmental Kuznets hypothesis is also detected across quantiles for the full sample and both developing and advanced countries subsamples. The findings suggest that trade benefits the advanced countries but could hurt the developing countries when trade with high-income trading partners occurs, in terms of CO2 emissions.
•Study trade and CO2 emissions in a North-North, North-South, South-North and South-South setting•North's trade with South or North mitigates CO2 emissions with larger effects for less polluted North countries.•South-North trade worsens South's CO2 emissions across quantiles.•South-South trade mitigates CO2 emissions with larger effects for less polluted South countries.•The environmental Kuznets hypothesis is also detected across quantiles.
Scope
Kefir consumption inhibits the development of obesity and non‐alcoholic fatty liver disease (NALFD) in mice fed 60% high‐fat diet (HFD). To identify the key contributor of this effect, we ...isolated lactic acid bacteria (LAB) from kefir and examined their anti‐obesity properties from in vitro screening and in vivo validation.
Methods and results
Thirteen kefir LAB isolates were subjected to survivability test using artificial gastrointestinal environment and cholesterol‐reducing assay. Lactobacillus kefiri DH5 showed 100% survivability in gastrointestinal environments and reduced 51.6% of cholesterol; thus, this strain was selected for in vivo experiment. Compared to the HFD‐saline group, the HFD‐DH5 group showed significantly lower body weight (34.68 versus 31.10 g; p < 0.001), epididymal adipose tissue weight (1.39 versus 1.05 g; p < 0.001), blood triglyceride (38.2 versus 31.0 mg/dL; p < 0.01) and LDL‐cholesterol levels (19.4 versus 15.7 mg/dL; p < 0.01). In addition, L. kefiri DH5 administration significantly modulated gut microbiota of HFD‐fed mice. The hepatic steatosis was significantly milder (Lesion score, 2.1 versus 1.2; p < 0.001) and adipocyte diameter was significantly smaller (65.1 versus 42.2 μm; p < 0.001) in the HFD‐DH5 group. L. kefiri DH5 upregulated PPAR‐α, FABP4, and CPT1 expression in the epididymal adipose tissues (2.29‐, 1.77‐, and 2.05‐fold change, respectively), suggesting a reduction in adiposity by stimulating fatty acid oxidation.
Conclusion
L. kefiri DH5 exerts anti‐obesity effects by direct reduction of cholesterol in the lumen and upregulation of PPAR‐α gene in adipose tissues.
The proposed dual mechanism underlying the anti‐obesity and anti‐non‐alcoholic fatty liver disease (NAFLD) effects of L. kefiri DH5 in high‐fat diet (HFD)‐fed mice was explored. A large proportion of the orally administered L. kefiri DH5 remains active and viable in the gastrointestinal tract and exerts potent anti‐obesity effects in HFD‐fed mice via a dual mechanism: (i) direct reduction of excessive cholesterol in the lumen to decrease overall fat influx, and (ii) upregulation of genes encoding PPAR‐α, CPT1, and FABP4 in adipose tissue to increase fatty acid oxidation.
Laser-assisted machining involves machining a workpiece after softening it with laser-emitted heat. Compared with conventional machining, laser assisted milling is a green manufacturing method, ...because it saves energy by reducing the cutting force. This paper examines cutting force and preheating temperature prediction for laser-assisted milling. Inconel 718 and AISI 1045 steel are employed in the experiments. The absorptivity of Inconel 718 was determined by conducting preheating experiments using a high power diode laser. Equations for determining cutting force and preheating temperature in laser-assisted milling are proposed using statistical analysis and regression analysis. The proposed equations are verified experimentally under a wide range of machining conditions. The cutting force and preheating temperature are measured using a tool dynamometer and a pyrometer, respectively. The results of this study can be applied to similar type of thermally assisted machining.
Kefir is a natural complex fermented milk product containing more than 50 species of probiotic bacteria and yeast, and has been demonstrated to have multiple properties conferring health benefits, ...including antiobesity, anti-hepatic steatosis, antioxidative, antiallergenic, antitumor, anti-inflammatory, cholesterol-lowering, constipation-alleviating, and antimicrobial properties. To better understand the underlying mechanisms of these benefits, we here review research on the effect of kefir (and kefir microorganisms) consumption to modulate the host gut microbiota. Owing to its excellent gastrointestinal resistance and colonization ability and wide ranges of microbial interaction, kefir has shown significant and wide-spectrum modulatory effects on the host gut microbiota. In particular, as a bacteria- and yeast-containing food, kefir can modulate both the gut microbiota and mycobiota. Since the association of this modulation with health benefit has only been addressed in a small number of recent studies thus far, further studies are needed to determine the precise mechanisms of the beneficial effects of kefir in relation to the modulation of the gut microbiota and mycobiota. Gaining this insight will surely help to take full advantage of this unique probiotic food.
Kefir is fermented milk produced by co-cultures of lactic and acetic acid bacteria and yeast that are encapsulated by an exopolysaccharide (EPS) called kefiran. Probiotic kefir provides many ...benefits, including antimicrobial effects against many pathogens. The mechanisms underlying these effects, however, are not yet completely understood. In this study, a total of 22 strains of lactic acid bacteria (LAB), including eight strains of Lactobacillus kefiranofaciens, two strains of Lactobacillus kefiri, seven strains of Lactococcus lactis, and five strains of Leuconostoc mesenteroides, were isolated from kefir and classified by 16S ribosomal RNA gene sequencing. The ability of each strain to produce EPS was determined, and Lactobacillus kefiranofaciens DN1 was found to have the highest EPS yield among all isolates. Lactobacillus kefiranofaciens DN1 produced EPS, using glucose and lactose, and EPS yield rose to 2.2 g/L in modified MRS broth (60 g/L glucose). The antimicrobial activities of the EPS produced by Lactobacillus kefiranofaciens DN1 (EPS_DN1) against Listeria monocytogenes and Salmonella Enteritidis were assessed by growth curve analysis. We found that EPS_DN1 at a concentration of at least 1% was able to exert bactericidal effects against both pathogens. Notably, results of high-performance size-exclusion chromatography (HPSEC) analysis indicated that EPS_DN1 was not kefiran, the major EPS of kefir grains, suggesting that EPS_DN1 represents a novel bioactive compound in kefir.
•A new exopolysaccharide (EPS), EPS_DN1, was isolated from kefir-derived bacteria.•Lactobacillus kefiranofaciens DN1 was the best EPS producer among 22 kefir isolates.•Lb. kefiranofaciens DN1 produced EPS_DN1 in glucose concentration-dependent manner.•EPS_DN1 exerted bactericidal effects against S. Enteritidis and L. monocytogenes.•EPS_DN1 is a heteropolysaccharide composed of five kinds of monosaccharide.
Due to its regulation of CDK1/2 phosphorylation, WEE1 plays essentially roles in the regulations of G2/M checkpoint and DNA damage response (DDR). WEE1 inhibition can increase genomic instability by ...inducing replication stress and G2/M checkpoint inactivation, which result in increased cellular sensitivity to DNA damaging agents. We considered an increase in genomic instability induced by WEE1 inhibition might be used to augment the effects of drugs targeting DNA repair protein. Typically, PARP inhibitors are effective in germline BRCA 1/2 mutated breast and ovarian cancer, but their applicabilities in triple-negative breast cancer (TNBC) are limited. This study was conducted to investigate the anti-tumor effects of the WEE1 inhibitor, AZD1775, and the mechanism responsible for its potentiation of sensitivity to olaparib (a PARP inhibitor) via the modulation of DDR in TNBC cells. Our results suggest that AZD1775 could be used to broaden the application range of olaparib in TNBC and provide a rationale for a clinical trial of combined olaparib and AZD1775 therapy.
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