High Thermal Performance Ultraviolet (368 nm) AlGaN-Based Flip-Chip LEDs with an Optimized Structure.

In this study, we have fabricated a 368 nm LED with an epitaxial Indium Tin Oxide (ITO) contact layer. We analyze the thermal performance of the flip-chip LED with a symmetric electrode and metal reflective layer, applying ANSYS to build a coupled electro-thermal finite element model (FEM) of the temperature distribution in the multiple quantum wells (MQWs). We compare our system with the traditional Au-bump flip-chip LED and a flip-chip LED with a Distributed Bragg Reflector (DBR) layer. The simulation results have shown that the flip-chip LED with a metal reflective layer and symmetric electrode exhibits better heat dissipation performance, particularly at high input power. The influence of the insulating layer on the LED chip junction temperature is also examined. The simulation data establish an effect due to the thermal conductivity of the insulating layer in terms of heat dissipation, but this effect is negligible at an insulation layer thickness ≤1 µm.

Phosphorylation of adducin-1 by TPX2 promotes interpolar microtubule homeostasis and precise chromosome segregation in mouse oocytes.

BACKGROUND: ADD1 (adducin-1) and TPX2 (targeting protein for Xklp2) are centrosomal proteins and regulate mitotic spindle assembly. Mammalian oocytes that segregate homologous chromosomes in Meiosis I and sister chromatids in Meiosis II with a spindle lacking centrosomes are more prone to chromosome segregation errors than in mitosis. However, the regulatory mechanisms of oocyte spindle assembly and the functions of ADD1 and TPX2 in this process remain elusive. RESULT: We found that the expression levels and localization of ADD1, S726 phosphorylated ADD1 (p-ADD1), and TPX2 proteins exhibited spindle assembly-dependent dynamic changes during mouse oocyte meiosis. Taxol treatment, which stabilizes the microtubule polymer and protects it from disassembly, made the signals of ADD1, p-ADD1, and TPX2 present in the microtubule organizing centers of small asters and spindles. Knockdown of approximately 60% of ADD1 protein levels destabilized interpolar microtubules in the meiotic spindle, resulting in aberrant chromosome alignment, reduced first polar body extrusion, and increased aneuploidy in metaphase II oocytes, but did not affect K-fiber homeostasis and the expression and localization of TPX2. Strikingly, TPX2 deficiency caused increased protein content of ADD1, but decreased expression and detachment of p-ADD1 from the spindle, thereby arresting mouse oocytes at the metaphase I stage with collapsed spindles. CONCLUSION: Phosphorylation of ADD1 at S726 by TPX2 mediates acentriolar spindle assembly and precise chromosome segregation in mouse oocytes.

Temperature-Dependent Optical Properties of Perovskite Quantum Dots with Mixed-A-Cations.

In this work, metal halide perovskite quantum dots (QDs) with Formamidinium (FA) and Cs mixed cations were fabricated using a solution-processed method at room temperature. By controlling Cs doping ratios in a precursor, the optical properties of mixed-cation perovskite QDs were systematically studied. With the increase in Cs ion doping, the photoluminescence (PL) spectra of perovskite QDs were blueshifted, which was mainly due to the smaller radius of Cs ions than those of FA. Temperature-dependent PL spectra were conducted on mixed-cation perovskite QDs. As the temperature gradually increased from 4 K to 300 K, PL peaks were blue shifted, and full-width at half maximum (FWHM) was widened, which was directly related to lattice thermal expansion and the carrier-photon coupling effect under temperature variation. At the same time, excess Cs ion doping had a prominent influence on optical properties at low temperatures, which was mainly due to the introduction of detrimental defects in perovskite crystals. Therefore, it is particularly important to control doping concentration in the preparation of high-quality perovskite QDs and efficient photoelectric devices.

Properties of mesoporous hybrid perovskite nanocrystals and its application in light-emitting diodes.

We fabricated mesoporous perovskite nanocrystal for the first time, and investigated its optical properties and application in light-emitting diodes (LEDs). The transformation of mesoporous structure can be ascribed to the decomposition of nanocrystals under dilution condition, which results in the blueshift of luminescence. The mesoporous nanocrystals under proper dilution may achieve improved perovskite LEDs, with maximum luminance and current efficiency of 23370 cd m-2and 6.7 cd A-1, respectively. This work provide an avenue to the optical engineering of perovskite nanocrystals, and demonstrate that perovskite concentration is one of key factors for realizing efficient LEDs.

Transcriptomic analysis of ovarian signaling at the emergence of the embryo from obligate diapause in the American mink (Neovison vison).

Mink embryonic diapause occurs when embryos, at the blastocyst stage, enter a state of a reversible arrest in development and metabolism. Some ovarian factors are required because ovariectomy leads to prevention of implantation in mink. Mechanisms regulating this process, however, remain largely unknown. To explore ovarian modifications associated with emergence of embryonic diapause in mink, there was comparison of transcriptomes after embryonic activation to when there was embryonic diapause using RNA-sequencing. A library of 655 differentially expressed genes (DEGs) of all assembled 33,656 genes was generated. Among these, 558 genes were annotated with 106 genes being expressed to a greater extent in ovaries during embryonic diapause, whereas 452 genes were more abundantly expressed in ovaries after embryonic activation. The major categories of genes with differential transcript abundances include metabolic pathways, metabolism of tryptophan, tyrosine and vitamin B6, oxidoreductase activity, calcium signaling pathway, steroid biosynthesis and lysosome. The APOE and APOA1 hub genes identified through the protein-protein interaction (PPI) analysis have important functions in cholesterol transport and steroidogenesis. Transcript abundances associated with 39 genes were investigated using RT-qPCR procedures to confirm RNA-sequencing data. Of 29 mRNA transcripts, 26 were validated using RNA-sequencing, whereas three of ten indistinguishable genes determined using RNA-sequencing were confirmed. Most of these verified DEGs are involved in the prolactin signaling pathway, formation of functional corpora lutea, and steroid synthesis, suggesting these biological processes are implicated in embryonic reactivation. Overall, results provide new insights into ovarian signaling at the time of emergence of the blastocyst from diapause in mink.

Study on the optimization of the deposition rate of planetary GaN-MOCVD films based on CFD simulation and the corresponding surface model.

Metal-organic chemical vapour deposition (MOCVD) is a key technique for fabricating GaN thin film structures for light-emitting and semiconductor laser diodes. Film uniformity is an important index to measure equipment performance and chip processes. This paper introduces a method to improve the quality of thin films by optimizing the rotation speed of different substrates of a model consisting of a planetary with seven 6-inch wafers for the planetary GaN-MOCVD. A numerical solution to the transient state at low pressure is obtained using computational fluid dynamics. To evaluate the role of the different zone speeds on the growth uniformity, single factor analysis is introduced. The results show that the growth rate and uniformity are strongly related to the rotational speed. Next, a response surface model was constructed by using the variables and the corresponding simulation results. The optimized combination of the matching of different speeds is also proposed as a useful reference for applications in industry, obtained by a response surface model and genetic algorithm with a balance between the growth rate and the growth uniformity. This method can save time, and the optimization can obtain the most uniform and highest thin film quality.