Search

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. [ABSTRACT FROM AUTHOR]

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−2 and 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. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the influence of the TEGa flow on the optical and structural properties of InGaN/GaN multiple quantum wells (MQWs) with an indium composition around 20%. The samples with five-pairs InGaN/GaN MQWs were grown on sapphire substrates by metalorganic chemical vapor deposition. Photoluminescence spectra at 8K showed that the MQWs grown with a low amount of TEGa flow gave a strong single peak and a higher emission energy. High-resolution X-ray diffraction measurements showed a deterioration of the InGaN/GaN interfaces in the sample grown with the large TEGa flow. The luminescence thermal quenching characteristics suggested that more structural defects acting as non-radiative recombination centers formed in the MQWs when the TEGa flow increased. The results indicate that decreasing the TEGa flow help to build up a new growth balance during the growth of InGaN wells, leading to less structural defects, more homogeneous indium distribution and the abrupt MQWs interfaces. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Digital light processing (DLP) has emerged as a highly promising 3D printing technology, which is due to its ability to fabricate components and structures with low cost and high precision. The DLP is, therefore, applicable in a wide range of fields. The phenomenon of light-scattering plays a dominant role in the DLP manufacturing process, but the specific impact of ceramic particles on the distribution of incident light remains unclear. The present study has, therefore, focused on studying the effect of ceramic particles on light-scattering by performing extensive theoretical finite element simulations. The aim was then to improve the curing quality of the DLP 3D printing process. More specifically, spherically shaped particles with a uniform distribution, lower duty ratios, or materials with lower refractive indices were necessary conditions for enhancing the printing precision due to the mitigated lateral light scattering effects. The overall results of this study have provided valuable guidance for the control of the light-induced curing in the 3D printing process of ceramics, thereby facilitating advancements in ceramic-based fabrication techniques. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The luminescence properties of InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with different quantum-well (QW) thicknesses were investigated. It is found that with decreasing the QW thicknesses, the integrated intensities of the photoluminescence (PL) and electroluminescence (EL) peaks demonstrate a contrary changing trend. The PL results show that the luminescence efficiency is improved by using thinner QWs. However, in the EL process, such a positive effect is counteracted by the low carrier injection efficiency in the thin QW LEDs, and consequently leads to a lower light output. Based on our experimental results, it is inferred that the tunneling leakage current associated with dislocations should be responsible for the low carrier-injection efficiency and the observed weaker EL integrated intensity of the LEDs with thin QWs. [ABSTRACT FROM AUTHOR]

An advanced three-dimensional electrothermal-coupled simulation model basing on finite-element method numerical simulation is developed to study the electrical and thermal properties of chip-level high-power GaN-based light-emitting diodes (LEDs). The current spreading, heat generation, and transfer in the device are comprehensively considered in this model. The current-spreading effect of the transparent current-spreading layer and the thermal performance of LEDs with interdigitated-electrodes are investigated. The simulation results prove that the temperature distribution in the active layer is strongly affected by the electrode pattern. The obvious heat accumulation in LEDs with conventional interdigitated-electrode patterns can be seen both in the simulated results and the infrared measured results. The heat transfer efficiency can be improved by using a symmetry electrode pattern design. The thermal management of the bump configurations in flip-chip LEDs is also studied. A more reasonable and thermal effective bump configuration is presented, and the simulated results show that a lower average temperature and more uniform heat distribution in the chips can be obtained. [ABSTRACT FROM AUTHOR]

• Proposed a bone substitution development strategy for craniomaxillofacial bone regeneration by inhibiting the upper soft tissue proliferation. • Unveiled the role of an effective immune target spot, dectin-1, to regulate cranial soft and hard tissue repair. • discovered the biological effects of nano zirconia with on dectin-1 to control the immune microenvironment. • Developed a HA/nano zirconia scaffold targeted at dectin-1 and regulating soft tissue invasion. • optimized the falling-down-type DLP printing system for HA/nano zirconia 3D scaffolds with different ratios. One major challenge of craniomaxillofacial bone regeneration is the direct contact of subcutaneous fibrous tissue towards bone regenerative region, which results in fast fibroblast invasion and suppression of bone regeneration. Dectin-1, a pattern recognition receptor expressed on activated macrophages, is crucial for directing fibrous invasion. Targeting Dectin-1 and its downstream signaling cascade could be an effective strategy to resist "craniomaxillofacial soft tissue invasion". Nano zirconia can shelter the essential amino acids of Dectin-1 and was reported to deactivate the inflammation signals. Herein, we succeeded in incorporating nano zirconia into high-resolution 3D hydroxyapatite (HA) scaffolds via modified digital light processing (DLP) technique system. The incorporation of nano zirconia can endow high-resolution HA scaffolds with the capacity of regulating the key structure of extracellular C-type lectin-like domain (CTLD) of dectin-1, proved by computational simulation. This results in inhibiting the dectin-1/syk axis and pro-soft tissue proliferation cytokines production. In vivo experiments further validated the effects of HA/nano zirconia resisting craniomaxillofacial soft tissue invasion and promoting bone regeneration. Our work practices the concept of "soft tissue invasion resisting capacity" via targeting in manipulating dectin-1, which succeeds in attenuating fibrous invasion and craniomaxillofacial bone regeneration. The "soft tissue invasion resisting capacity" could become a valuable biological paradigm of craniomaxillofacial bone biomaterials. [ABSTRACT FROM AUTHOR]

• Ultrathin VSe 2 nanosheets with thickness less than 5 nm are prepared by liquid phase exfoliation. • Two-dimensional metallic layered VSe 2 exhibits saturable absorption properties. • Single- and Dual-wavelength mode-locked fiber lasers are realized using VSe 2 -based saturable absorber, respectively. Vanadium selenide (VSe 2) is a special two-dimensional (2D) transition metal dichalcogenide (TMD) material with metallic properties similar to graphene, which has been proved to have saturable absorption properties and used in mode-locked fiber lasers. As an excellent saturable absorber (SA) material, VSe 2 has advantage of ultrafast carrier recovery time and broadband optical response range. However, the potential application of VSe 2 in the field of ultrafast photonics has not been fully developed so far. In this work, the as-prepared VSe 2 nanosheets were deposited on tapered fiber by optical deposition to obtain VSe 2 SA. By inserting VSe 2 SA into an Er-doped fiber laser, the mode-locked pulses with a central wavelength of 1574.4 nm can be obtained. The pulse width of the laser is measured to be ∼680 fs which is narrowest in the reported VSe 2 SA-based lasers. In addition, the unique dual-wavelength mode-locked pulse is also obtained by further adjusting intracavity dispersion and polarization. This kind of dual-wavelength pulse is valuable in high order harmonic generation enhancement, terahertz wave generation, dense wavelength division multiplexing, dual-frequency comb and other applications. Our results show that metallic VSe 2 is of great potential value in ultrafast fiber laser. [ABSTRACT FROM AUTHOR]

[Display omitted] Linear piezoelectric materials offer new opportunities for next-generation multifunctional micro/nano systems on chip aside from ferroelectrics. However, the advantage of quantitative pressure sensing of linear piezoelectric materials over ferroelectrics has not been demonstrated, while the thermal stability of linear piezoelectric zinc oxide (ZnO) is yet to be evaluated. In this work, pressure sensors based on linear piezoelectric undoped ZnO and ferroelectric vanadium doped ZnO (V-ZnO) films are studied side by side. Both films possess similar fiber textures oriented along the polar ZnO [0 0 2] direction, yet each of the V-ZnO grains consists of strip-like domains observed by SEM. Applying triangular-wave pressures, the linear piezoelectric ZnO sensor generates triangular-wave voltage signals that are one-to-one linearly correlated to the applied pressure, showing decisive advantages for quantitative pressure sensing compared to the 'sail-like' voltage signals of the ferroelectric V-ZnO sensor that is many-to-one correlated to the applied pressure. Superior thermal stability is demonstrated in the linear piezoelectric ZnO sensor showing stable pressure sensing properties up to 450 °C compared to the degraded sensing properties of the ferroelectric V-ZnO sensor at 150 °C. The thermally stable piezoelectric sensors for quantitative pressure sensing based on linear piezoelectric ZnO films serve as candidates for high-performance multifunctional micro/nano systems. [ABSTRACT FROM AUTHOR]

Carbazole oxime ester exhibited good absorption in visible light region, all of co-initiator had absorption below 350 nm. Multi-component OXE/ION/co-initiator photoinitiator systems exhibited excellent polymerization efficiency, and double-bond conversions in this type of system were higher than those in two-component systems. Synergism between OXEs and co-initiator were experimentally studied. • Two new arylaminocarbazole oxime esters (OXE1 and OXE2) with visible absorption were successfully synthesized. • Obtaining a series of multi-component oxime esters photoinitiating systems with high performance. • Synergism between OXEs and co-initiators were experimentally studied. • The thermodynamic feasibility and the photopolymerization kinetics further proved the synergistic effect of multi-component initiators. To broaden the application of oxime ester and obtain a photoinitiating system with high performance in visible light photopolymerization, we prepared the two arylaminocarbazole oxime ester (CZ–OXE), OXE1 and OXE2, with visible absorption. The multicomponent initiation systems of OXE as one of the components were evaluated in visible photopolymerization. Synergism between OXEs and diaryliodonium salt (ION), N-vinylcarbazole (NVK), ethyl 4-dimethylamino benzoate (EDB), and triphenylphosphine (TPP) were experimentally studied via steady state photolysis and fluorescence quenching. The thermodynamic feasibility for electron transfer reaction in photoinitiating systems was confirmed by cyclic voltammetry experiments. Electron spin resonance techniques proved the production of active species in the systems. Polymerization experiments under a 405 nm light source showed that the two-component initiation system OXEs/ION was more efficient than the one-component initiator OXEs. Similarly, three-component OXEs/ION/co-initiator photoinitiating systems are more efficient than OXEs/ION systems. [ABSTRACT FROM AUTHOR]

Due to the high refractive index of nitrides, encapsulation is necessary to improve the light extraction efficiency for GaN-based light-emitting diodes (LEDs). Traditional thermal-curing encapsulant needs to be heated for several minutes to form a dome-shaped lens, which is time-consuming. In this paper, we have developed a novel kind of silicon-based ultraviolet (UV)-curing encapsulant, for which only 20 s of near-UV (NUV) light radiation at room temperature is needed. The composition of the encapsulants is optimized to enhance light extraction ability. For 392-nm NUV LEDs packaged by this UV-curing encapsulant, the light output power is enhanced by 10.0%. Moreover, the LEDs packaged by UV-curing and thermal-curing encapsulant presented similar stability and reliability after 480 h of the aging test under a high driving current of 200 mA. This paper demonstrates the potential of silicon-based UV-curing encapsulants for the package of NUV, blue and white LEDs, which is time- and cost-effective for the LED industry. [ABSTRACT FROM AUTHOR]

The function and performance of textured polycrystalline thin films are closely related to their microstructures. However, the corresponding growth mechanisms remain unclear, which brings obstacles to the effective engineering of the films' properties. In this work, textured nanocrystalline Indium Oxide (nc-In 2 O 3 ) thin films are prepared and the growth mechanism is explored. Texture morphology within or beyond the prediction of Wulff's theorem and van der Drift's growth mechanism are both observed. The orientation of the textured film changes from (100)-preferred in quasi-equilibrium growth conditions to (111)-preferred in non-equilibrium growth conditions. From a microscopic perspective of adatoms' diffusion, different growth modes for the growth of the textured In 2 O 3 thin films is classified and a quantitative growth zone model is developed. According to the zone model, the morphology and orientation of the films could be successfully designed and controlled by changing growth conditions. [ABSTRACT FROM AUTHOR]

A nonvolatile memory (NVM) based on an amorphous-indium–gallium–zinc oxide (a-IGZO) thin-film transistor (TFT) with defect-engineered gate insulator was demonstrated. The gate insulator was a blocking alumina/storage alumina/tunneling alumina stack structure, which was simply assembled in a single atomic layer deposition step. The memory device showed a positive shift of threshold voltage as large as 14.4 V after +20 V, 1 s programming. In contrast, the memory erasing was not sensitive to negative gate voltage in the dark. Once programmed, the memory can only be light erased. Furthermore, the light combined with a negative bias improved the erasing speed effectively. In addition, a 10-year memory window as large as 7.5 V was extrapolated at room temperature with a charge loss of 34.7%. Based on the observation of blisters in the storage alumina layer after high temperature annealing, Fourier transform infrared spectroscopy measurement and first-principles calculations, the high electron storage capacity can be attributed to the deep defect levels in the storage alumina layer, which were originated from hydrogen impurity. This a-IGZO TFT charge trapping NVM with high performance and simple process is a candidate device for the application of fully functional transparent system on panel. [ABSTRACT FROM AUTHOR]

In this study, the resistive switching performance of amorphous indium–gallium–zinc oxide (a-IGZO) resistive switching random-access memory (ReRAM) was improved by inserting a thin silicon oxide layer between silver (Ag) top electrode and a-IGZO resistive switching layer. Compared with the single a-IGZO layer structure, the SiO 2 /a-IGZO bi-layer structure exhibits the higher On/Off resistance ratio larger than 10 3 , and the lower operation power using a smaller SET compliance current. In addition, good endurance and excellent retention characteristics were achieved. Furthermore, multilevel resistance states are obtained through adjusting SET compliance current and RESET stop voltage, which shows a promise for high-performance nonvolatile multilevel memory application. [ABSTRACT FROM AUTHOR]

In this study, various InO thin films were grown on c-plane sapphire substrates by metal-organic chemical vapor deposition via changing the growth parameters. The structural and electrical properties of the films were investigated by employing the X-ray diffraction (XRD), scanning electron microscopy, conductive atomic force microscopy (CAFM), and Hall Effect measurement. Results revealed that the investigated InO thin films are bcc phase poly-crystalline with preferred orientation along the [100] or [111] direction. Moreover, the existence of two types of grains with different conductivities in the investigated InO thin films was confirmed by CAFM measurement. Interestingly, a positive correlation was found between carrier concentrations and (222)/(400) XRD diffraction peak intensity ratios of the investigated InO thin films. The mechanism of the positive correlation was explained by the difference in impurities concentrations between the two types of grains with the difference crystalline orientations. [ABSTRACT FROM AUTHOR]

Abstract: We report the effect of periodic Si-delta-doping on the yellow luminescence (YL) and stress evolution in n-GaN epilayers. Photoluminescence measurements indicated that the YL component could be effectively suppressed with increasing dopant flow rate or decreasing period length. X-ray diffraction, transmission electron microscopy and secondary ion mass spectroscopy measurements revealed that the variations of dislocation density and carbon concentration are not the responsible mechanisms for the of YL emissions. The reduction of Ga vacancy related defects seems to be the probable reason for the YL suppression by Si-delta-doping. Moreover, Raman spectroscopy showed no obvious stress variation among these samples with different equivalent electron concentration. These observed features are entirely different from those reported for uniformly Si-doped GaN. [Copyright &y& Elsevier]

Hole transport control and carrier injection improvement have been demonstrated in the InGaN/GaN light-emitting diodes (LEDs) with step-stage multiple-quantum-well (MQW) structure and Si-doped hole-blocking barriers. Single-wavelength emission was obtained under electrical pumping in these LEDs by utilizing hole-blocking effect. The light emission around 450 nm showed a substantial increase compared with the reference sample with single or step-stage indium-content MQWs. The droop behavior and wavelength stability were also improved significantly. These improvements were attributed to the enhanced carrier injection to the active region due to the alleviation of the quantum-confined Stark effect and the effective hole-blocking effect of the Si-doped barriers. [ABSTRACT FROM AUTHOR]

A design strategy is proposed to optimize the structure of photonic crystal (PC) slabs in order to achieve high reflection on its interface. A broad band (Δλ/λ > 19%) and ultrahigh (>95%) reflection spectrum can be realized for one-dimensional (1D) and two-dimensional (2D) PC slabs. Tolerance analysis of design parameters reveals distinct merits for different PC structures: as to maintain high reflection, 1D PC slabs show better structural tolerance, while 2D PC ones have a much greater tolerance for the material parameter. Such a difference may provide a criterion for the design of PCs-assist mirror structure in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Abstract: The influence of growth pressure on the properties of p-GaN grown by metal-organic chemical vapor deposition method was investigated. The p-GaN layers were grown at low temperature under growth pressures ranging from 100 to 400mbar. We find that higher growth pressure leads to lower Mg incorporation in the p-GaN layer and results in high resistivity of p-GaN grown at 400mbar. By optimizing the Cp2Mg/TMGa ratio, however, low sheet resistivity can be achieved for p-GaN grown at 100–300mbar. The p-GaN grown at 300mbar using optimal Cp2Mg/TMGa ratio of 1.3% shows the highest hole concentration of 5.0×1017 cm−3 and the consequent minimum sheet resistivity of 2.6×104 Ω/sq. The superior electrical properties are ascribed to the reduction of compensation effect for the layer grown under the high growth pressure. [Copyright &y& Elsevier]

We report significantly improved electrostatic discharge (ESD) properties of InGaN/GaN-based light-emitting diodes (LEDs) with inserting Si-delta-doped layers between multiple quantum wells and n-cladding layer. The ESD endurance voltage increased from -1200 V to -4000 V with the insertion of delta-doped layers. The mechanism of the enhanced ESD properties was then investigated. According to capacitance-voltage results, the factor of capacitance modulation was ruled out. However, infrared microscopy image proved better current spreading in the LEDs with delta-doped layers. In addition, current-voltage, photoluminescence, and atomic force microscope measurements demonstrated substantial quality improvements. These two reasons were considered as the dominant mechanisms of the enhanced ESD properties. [ABSTRACT FROM AUTHOR]

Finding novel photoinitiators with photobleaching properties suitable for long-wavelength LED light sources is important for their potential use in the photocuring ceramic suspensions containing acrylate resin. Two D-π-A-π-D conjugated benzylidene ketones with visible light absorption (TPAK and CZK) were synthesized and evaluated as photoinitiators in the photocuring of acrylate resin and ceramic suspension under blue (460 nm)/green (520 nm) LED sources. Results showed that the two photoinitiators have high photoinitiating activity and can effectively produce thick-layer curing in acrylate resin and ceramic suspension due to their quick photobleaching properties under 460 nm and 520 nm LED light sources. The curing depth of the ceramic suspensions was measured as a function of the concentration of TPAK and CZK and the energy level of the LED light source. Jacob's equation was used to determine the critical energy E c and depth sensitivity D p of every suspension with different concentrations of benzylidene ketones. Image 1 • Novel photoinitiators with photobleaching properties were found. • They showed novel activity in the photocuring of ceramic suspension under blue/green LED. • Deep curing was obtained by using these photoinitiators. [ABSTRACT FROM AUTHOR]

GaN-based light emitting diodes (LEDs) with shallow triangular quantum wells (TQW) structure were proposed and investigated. LEDs with shallow TQW demonstrated a lower turn-on voltage and 80% higher lighting efficiency at 20 mA than devices without the shallow QW structure. A more stable emission wavelength and a lower ideality factor were achieved with the proposed structure. X-ray reciprocal space mapping revealed a partial strain relaxation in active region due to the insertion of the TQW structure. The improved performance is ascribed to the weakening of the polarization field in the MQW active region induced by the TQW structure. [ABSTRACT FROM AUTHOR]

We report the anomalous mobility properties of Si-delta-doped GaN with periodically doping profile. Samples with different delta-doping periods or with varied Si source flow were investigated. It is found that for the short delta-doping-period (<26.5 nm) samples, the Hall mobility increases with decreasing electron concentration; while for the longer-doping-period samples, the situation is just the opposite. To interpret this observation, a two-layer model has been built up for long-period samples based on secondary ion mass spectroscopy measurements. The fitting results using this model are well consistent with the experimental data. [ABSTRACT FROM AUTHOR]