Elevated-Temperature Space Charge Characteristics and Trapping Mechanism of Cross-Linked Polyethylene Modified by UV-Initiated Grafting MAH.

Space charge characteristics of cross-linked polyethylene (XLPE) at elevated temperatures have been evidently improved by the graft modifications with ultraviolet (UV) initiation technique, which can be efficiently utilized in industrial cable manufactures. Maleic anhydride (MAH) of representative cyclic anhydride has been successfully grafted onto polyethylene molecules through UV irradiation process. Thermal stimulation currents and space charge characteristics at the elevated temperatures are coordinately analyzed to elucidate the trapping behavior of blocking charge injection and impeding carrier transport which is caused by grafting MAH. It is also verified from the first-principles calculations that the bound states as charge carrier traps can be introduced by grafting MAH onto polyethylene molecules. Compared with pure XLPE, the remarkably suppressed space charge accumulations at high temperatures have been achieved in XLPE-g-MAH. The polar groups on the grafted MAH can provide deep traps in XLPE-g-MAH, which will increase charge injection barrier by forming a charged layer of Coulomb-potential screening near electrodes and simultaneously reduce the electrical mobility of charge carriers by trap-carrier scattering, resulting in an appreciable suppression of space charge accumulations inside material. The exact consistence of experimental results with the quantum mechanics calculations demonstrates a promising routine for the modification strategy of grafting polar molecules with UV initiation technique in the development of high-voltage DC cable materials.

Transparent organic light-emitting diodes with balanced white emission by minimizing waveguide and surface plasmonic loss.

It is challenging in realizing high-performance transparent organic light-emitting diodes (OLEDs) with symmetrical light emission to both sides. Herein, an efficient transparent OLED with highly balanced white emission to both sides is demonstrated by integrating quasi-periodic nanostructures into the organic emitter and the metal-dielectric composite top electrode, which can simultaneously suppressing waveguide and surface plasmonic loss. The power efficiency and external quantum efficiency are raised to 83.5 lm W-1 and 38.8%, respectively, along with a bi-directional luminance ratio of 1.26. The proposed scheme provides a facile route for extending application scope of transparent OLEDs for future transparent displays and lightings.

Light outcoupling enhanced flexible organic light-emitting diodes.

Flexible organic light-emitting diodes (OLEDs) are emerging as a leading technology for rollable and foldable display applications. For the development of high-performance flexible OLEDs on plastic substrate, we report a transparent nanocomposite electrode with superior mechanical, electrical, and optical properties, which is realized by integrating the nanoimprinted quasi-random photonic structures into the ultrathin metal/dielectric stack to collectively optimize the electrical conduction and light outcoupling capabilities. The resulting flexible OLEDs with green emission yield the enhanced device efficiency, reaching the maximum external quantum efficiency of 43.7% and luminous efficiency of 154.9 cd/A, respectively.

Significantly Improved Electrical Properties of Crosslinked Polyethylene Modified by UV-Initiated Grafting MAH.

Direct current (DC) electrical performances of crosslinked polyethylene (XLPE) have been evidently improved by developing graft modification technique with ultraviolet (UV) photon-initiation. Maleic anhydride (MAH) molecules with characteristic cyclic anhydride were successfully grafted to polyethylene molecules under UV irradiation, which can be efficiently realized in industrial cable production. The complying laws of electrical current varying with electric field and the Weibull statistics of dielectric breakdown strength at altered temperature for cable operation were analyzed to study the underlying mechanism of improving electrical insulation performances. Compared with pure XLPE, the appreciably decreased electrical conductivity and enhanced breakdown strength were achieved in XLPE-graft-MAH. The critical electric fields of the electrical conduction altering from ohm conductance to trap-limited mechanism significantly decrease with the increased testing temperature, which, however, can be remarkably raised by grafting MAH. At elevated temperatures, the dominant carrier transport mechanism of pure XLPE alters from Poole-Frenkel effect to Schottky injection, while and XLPE-graft-MAH materials persist in the electrical conductance dominated by Poole-Frenkel effect. The polar group of grafted MAH renders deep traps for charge carriers in XLPE-graft-MAH, and accordingly elevate the charge injection barrier and reduce charge mobility, resulting in the suppression of DC electrical conductance and the remarkable amelioration of insulation strength. The well agreement of experimental results with the quantum mechanics calculations suggests a prospective strategy of UV initiation for polar-molecule-grafting modification in the development of high-voltage DC cable materials.

Enhanced Insulation Performances of Crosslinked Polyethylene Modified by Chemically Grafting Chloroacetic Acid Allyl Ester.

Modified crosslinked polyethylene (XLPE) with appreciably enhanced DC electrical insulation properties has been developed by chemical modification of grafting chloroacetic acid allyl ester (CAAE), exploring the trapping mechanism of charge transport inhibition. The bound state traps deriving from grafted molecule are analyzed by first-principles calculations, in combination with the electrical DC conductivity and dielectric breakdown strength experiments to study the underlying mechanism of improving the electrical insulation properties. In contrast to pure XLPE, the XLPE-graft-CAAE represents significantly suppressed space charge accumulation, increased breakdown strength, and reduced conductivity. The substantial deep traps are generated in XLPE-graft-CAAE molecules by polar group of grafted CAAE and accordingly decrease charge mobility and raise charge injection barrier, consequently suppressing space charge accumulation and charge carrier transport. The well agreement of experiments and quantum mechanics calculations suggests a prospective material modification strategy for achieving high-voltage polymer dielectric materials without nanotechnology difficulties as for nanodielectrics.

Efficient Color-Stable Inverted White Organic Light-Emitting Diodes with Outcoupling-Enhanced ZnO Layer.

Inverted organic light-emitting diode (OLED) has attracted extensive attention due to the demand in active-matrix OLED display panels as its geometry enables the direct connection with n-channel transistor backplane on the substrate. One key challenge of high-performance inverted OLED is an efficient electron-injection layer with superior electrical and optical properties to match the indium tin oxide cathode on substrate. We here propose a synergistic electron-injection architecture using surface modification of ZnO layer to simultaneously promote electron injection into organic emitter and enhance out-coupling of waveguided light. An efficient inverted white OLED is realized by introducing the nanoimprinted aperiodic nanostructure of ZnO for broadband and angle-independent light out-coupling and inserting an n-type doped interlayer for energy level tuning and injection barrier lowering. As a result, the optimized inverted white OLEDs have an external quantum efficiency of 42.4% and a power efficiency of 85.4 lm W1-, which are accompanied by the superiority of angular color stability over the visible wavelength range. Our results may inspire a promising approach to fabricate high-efficiency inverted OLEDs for large-scale display panels.

Switching Hole and Electron Transports of Molecules on Metal Oxides by Energy Level Alignment Tuning.

Charge transport at organic/inorganic hybrid contacts significantly affects the performance of organic optoelectronic devices because the unfavorable energy level offsets at these interfaces can hinder charge injection or extraction due to large barrier heights. Herein, we report a technologically relevant method to functionalize a traditional hole-transport layer of solution-processed nickel oxide (NiOx) with various interlayers. The photoemission spectroscopy measurements reveal the continuous tuning of the NiOx substrate work function ranging from 2.5 to 6.6 eV, enabling the alignment transition of energy levels between the Schottky-Mott limit and Fermi level pinning at the organic/composite NiOx interface. As a result, switching hole and electron transport for the active organic material on the composite NiOx layer is achieved due to the controlled carrier injection/extraction barriers. The experimental findings indicate that tuning the work function of metal oxides with optimum energy level offsets can facilitate the charge transport at organic/electrode contacts.

Microcavity-Free Broadband Light Outcoupling Enhancement in Flexible Organic Light-Emitting Diodes with Nanostructured Transparent Metal-Dielectric Composite Electrodes.

Flexible organic light-emitting diodes (OLEDs) hold great promise for future bendable display and curved lighting applications. One key challenge of high-performance flexible OLEDs is to develop new flexible transparent conductive electrodes with superior mechanical, electrical, and optical properties. Herein, an effective nanostructured metal/dielectric composite electrode on a plastic substrate is reported by combining a quasi-random outcoupling structure for broadband and angle-independent light outcoupling of white emission with an ultrathin metal alloy film for optimum optical transparency, electrical conduction, and mechanical flexibility. The microcavity effect and surface plasmonic loss can be remarkably reduced in white flexible OLEDs, resulting in a substantial increase in the external quantum efficiency and power efficiency to 47.2% and 112.4 lm W(-1).

Developmental toxicity of doxorubicin hydrochloride in embryo-larval stages of zebrafish.

Doxorubicin hydrochloride is widely used to treat various types of cancers. Its therapeutic and side effects are well documented. However, the developmental toxicity of doxorubicin has not been previously described. Lethal and sublethal effects on embryo-larval stages of zebrafish in a study of the developmental toxicity of doxorubicin were observed. Zebrafish embryos were exposed to different concentrations (0-100 mg/L) of doxorubicin between 4 and 120 h post fertilization, and zebrafish larvae were exposed to different concentrations (0-200 mg/L) of doxorubicin for 96 h. The markers about the development toxicity of doxorubicin in zebrafish were observed under a stereomicroscope. Higher doxorubicin concentrations mainly caused acute lethal effects, and lower doxorubicin concentrations mainly caused sublethal effects, such as multiple malformations in embryos and larvae. Moreover, with the increase of doxorubicin concentration, the malformation rate increased. The heart rate of embryos was accelerated at lower concentrations of doxorubicin (≤ 10 mg/L) and decelerated at higher concentrations (≥ 25 mg/L). The hatching rate and body length were inhibited at higher concentrations of doxorubicin (≥ 25 mg/L).In conclusion, doxorubicin has serious developmental toxicity and this raises a concern for developmental effects of doxorubicin in clinical practice.

[Effect of dendritic cells on expansion and function of autologous natural killer cells in vitro].

The objective of this study was to investigate the effect of dendritic cells (DCs) on expansion and function of autologous natural killer (NK) cells and its mechanism in vitro. NK cells were expanded from peripheral blood mononuclear cells (PBMNCs) of healthy volunteers in stem cell growth medium (SCGM) supplemented with rhIL-2 (control group) in 24-well culture plates at 37 degrees C in a humidified CO(2)-containing atmosphere. NK cells were cultured with autologous DCs in the ratio of 5 to 1 (group 5:1) or 1 to 1 (group 1:1) from day 10 after expansion. Total cells of every group were counted and the expression of CD3, CD16/56 on the surface of NK cells was assayed by flow cytometry on days 7, 14 and 21 to calculate the expansion of NK cells. Cytotoxicity of expanded NK cells against K562 cells was assayed by MTT method. TNF-alpha and IL-12p70 were detected in culture supernatants by sandwich ELISA. The results indicated that the expansion and cytotoxicity of NK cells were improved after mixed with autologous DCs. Furthermore, when DCs were mixed with NK cells, the ratio of DCs to NK cells was higher, the expansion and cytotoxicity NK cells were higher. On day 14, the expansion multiple in control, group 5:1 and group 1:1 were 16.26 +/- 1.58, 29.25 +/- 4.01 and 21.23 +/- 2.91 respectively. The expansion multiple of group 5:1 was much higher than that of the other two groups (p < 0.05). The expressions of CD3(-), CD56/16(+) on surface of NK cells in control, group 5:1, group 1:1 were (34.8 +/- 5.1)%, (64.6 +/- 7.8)% and (50.6 +/- 8.7)% respectively and that of group 5:1 was the highest (p < 0.05). The cytotoxicities against K562 cells in control, group 5:1 and group 1:1 were (63.7 +/- 3.8)%, (87.4 +/- 6.8)% and (75.4 +/- 6.3)% respectively. The cytotoxicity of group 5:1 was higher than that in the other two groups also (p < 0.05). TNF-alpha and IL-12p70 levels in culture supernatants when DCs and NK cells were mixed in the ratio of 5 to 1 were much higher than those in culture supernatants of DCs and NK cells alone or in culture supernatants when DCs and NK cells were mixed in the ratio of 1 to 1 (p < 0.05). It is concluded that the expansion and cytotoxicity of NK cells can be improved by DCs and it depended on the mixed ratio of DCs to NK cells. The elevated expansion of NK cells by DCs bears relation to IL-12 produced by DCs. The enhanced cytotoxicity of NK cells is associated with TNF-alpha secreted by NK cells.

[Study on rapid generation of dendritic cells from K562 cell line induced by A23187 alone].

OBJECTIVE: To explore a simple, rapid and efficient way to generate dendritic cells from leukemic cells. METHODS: K562 cells were cultured with calcium ionosphere A23187 alone, A23187 plus GM-CSF, or a DC differentiation cocktail consisting of GM-CSF, IL-4 and TNF-alpha, respectively. The expression of surface markers of induced DCs was analyzed by flow cytometry. The K562-DCs stimulating the proliferation of allo-genetic naive T cells and inducing cytotoxicity of T cells were determined by MTT assay. RESULTS: Microscopic examination revealed that under all the three culture conditions, K562 cells became displaying DC morphology. At 72 hours in the two culture systems containing A23187, there were higher proportions of cells with dendritic morphology [(69.5 +/- 17.2)% and (73.1 +/- 13.9)%, respectively] than that in the cocktail system [(28.5 +/- 12.3)%] (P < 0.05). And the same did when cultured for 7 days [(69.5 +/- 17.2)%, (73.1 +/- 13.9)% respectively vs (51.2 +/- 10.7)%, P < 0.05]. In the 7-day cultures, the percentage of CD1a expressing cells was lower [(8.2 +/- 2.3)% and (10.3 +/- 5.1)% vs (17.2 +/- 1.6)%, respectively] while the CD83 expressing cells was higher [(85.6 +/- 8.8)% and (82.4 +/- 9.1)% vs (77.4 +/- 12.9)%, respectively] compared with that in the cocktail system (P < 0.05). No significant difference was found in the allogeneic T cell proliferation response and induced T cell cytotoxicity between A23187 containing and cocktail groups (P > 0.05). CONCLUSIONS: A23187 treatment is a simple, rapid and efficient in vitro strategy for inducing dendritic cell from leukemic cells.

[Expression of nm23-H(1) mRNA in Bone Marrow Cells from Patients with Myelodysplastic Syndrome and Its Clinical Implication]

The purpose of this investigation was to explore the expression of nm23-H(1) gene in patients with myelodysplastic syndrome (MDS) and evaluate the relationship between nm23-H(1) expression and therapeutic outcomes. Semi-quantitative RT-PCR was used to detect the expression of nm23-H(1) mRNA in marrow mononuclear cells from 28 MDS patients and 15 normal subjects. nm23-H(1)/GAPDH ratio >/= 0.5 was believed to a positive case. The expression of nm23-H(1) was positive in 24 of 28 MDS patients, and the average level was 0.89 +/- 0.56. nm23-H(1) mRNA was negative in normal controls. The overexpression of nm23-H(1) mRNA in MDS patients could predict outcome of treatment and prognosis for MDR patients.