Synthesis and characterization of a series of PAEs containing DPP units in the main chain are described. of the polymers was in the range 10 800–111 900. The polymers formed a deep blue solution in chloroform with absorption maxima between 589 and 645 nm and optical band gaps ranging from 1.61 to 1.74 eV. When excited at the absorption maxima, the polymer solutions showed red fluorescence with emission maxima between 656 and 676 nm. The polymers exhibited quasi‐reversible oxidation process with HOMO energy levels between ?5.60 and ?6.17 eV. EL properties of three polymers were investigated with device configuration ITO/PEDOT:PSS/Polymer/LiF/Al. When appropriate bias voltage was applied, a red EL with a maximum brightness of 17.5–24 cd · m?2 could observe from the devices.
A novel nitrogen‐containing electroluminescent copolymer, PQV‐alt‐MOPPV has been designed and synthesized by Wittig‐Horner polymerization. Structure, thermal stability, and optical and electrochemical properties of the resulting copolymer were characterized by FT‐IR, 1H NMR, elemental analysis, GPC, DSC, TGA, UV‐vis, PL, EL, and CV. The copolymer possesses excellent solubility in common organic solvents and good thermal stability. The absorption maxima of the copolymer in solution and a thin film are 490 and 516 nm, and the photoluminescence maxima in solution and thin film are 571 and 629 nm, respectively. The PLED (ITO/PEDOT: PSS (40 nm)/PQV‐alt‐MOPPV (80 nm)/Ca (30 nm)/Al (150 nm) shows a very pure red light emission with maximum peaks around 618 nm.
Lack of irradiance-beam profile uniformity across the emission area of light-curing units (LCUs) may result in suboptimal properties of composite restorations. The authors’ objective for this study was to assess the variation in local cure of 1 composite at 3 different LCU emission area locations cured with 3 different LCUs by means of testing the degree of conversion (DC) and microflexural strength.
Methods
The authors fabricated dual-photoinitiator composite specimens (n = 5), which were cured using either a quartz-tungsten-halogen, a multiple-emission peak, or a single-emission peak light-emitting diode LCU. The specimen’s top surfaces received irradiation from either the center, 1.5 millimeters straight to the left of the center, or 1.5 mm straight to the right of the center of the LCU emission area. The authors measured irradiance and DC on top and bottom specimen surfaces using a spectrometer and attenuated total reflection–Fourier transform infrared spectroscopy, respectively. The authors performed micro 3-point bend tests using a universal mechanical testing machine. They used multifactorial analysis of variance (α = 0.05).
Results
The irradiance ranged from 452 through 946 milliwatts per square centimeter, and DC ranged from 49.7% through 65.8% on top surfaces. Microflexural strength ranged from 313 through 458 megapascals.
Conclusions
The authors did not find correlations among the LCU irradiance-beam profile of the 3 emission area locations and the investigated material properties, although they found variations in the measured properties.
Practical Implications
The irradiance-beam profile from the different LCUs explored did not have a major influence on the DC and microflexural strength for the investigated composite. 相似文献
A study of the organic semiconductor F8TBT is presented, directly comparing a conventional form (F8TBT‐out) with a form with varied alkyl side‐chain position (F8TBT‐in), in terms of optical properties and device performance in light‐emitting‐diodes (LEDs). Computational simulations of the side‐chain position with respect to the TBT unit reveal geometrical differences between F8TBT‐out and F8TBT‐in. π–π conjugation on the backbone of F8TBT‐in is interrupted by a distortion of the benzothiadiazole ring, leading to a blue‐shift of the absorption spectrum and increased photoluminescence quantum efficiency. Both conventional and hybrid LEDs demonstrate that devices with F8TBT‐in show improved performance, as compared to F8TBT‐out, illustrating how tuning the optoelectronic properties of conjugated polymers by varying the placement of side chains has an important role in device optimization.
BackgroundDespite the accuracy of intraoral scanners (IOSs) in producing single-unit scans and the possibility of generating complete dentures digitally, little is known about their feasibility and accuracy in digitizing edentulous jaws. The purpose of this in vitro investigation was to evaluate the feasibility and accuracy of digitizing edentulous jaw models with IOSs.MethodsThe authors used an industrial laser scanner (reference scanner) and four IOSs to digitize two representative edentulous jaw models. They loaded the data sets obtained into three-dimensional evaluation software, superimposed the data sets and compared them for accuracy. The authors used a one-way analysis of variance to compute differences within groups (precision), as well as to compare values with those of the reference scanner (trueness) (statistical significance, P < .05).Results. Mean trueness values ranged from 44.1 to 591.8 micrometers. Data analysis yielded statistically significant differences in trueness between all scanners (P < .05). Mean precision values ranged from 21.6 to 698.0 μm. The study results showed statistically significant differences in precision between all scanners (P < .05), except for the CEREC AC Bluecam (Sirona, Bensheim, Germany) and the Zfx IntraScan (manufactured by MHT Italy, Negrar, Italy/ MHT Optic Research, Niederhasli, Switzerland; distributed by Zfx, Dachau, Germany) (P > .05).ConclusionsDigitizing edentulous jaw models with the use of IOSs appears to be feasible, although the accuracy of the scanners differs significantly. The results of this study showed that only one scanner was sufficiently accurate to warrant further intraoral investigations. Further enhancements are necessary to recommend these IOSs for this particular indication.Practical Implications. On the basis of the results of this study, the authors cannot recommend these four IOSs for digitization of edentulous jaws in vivo. 相似文献
BackgroundThe authors conducted a study to examine the irradiance from light-curing units (LCUs) used in dental offices in Jordan.MethodsTwo of the authors visited 295 private dental offices (15 percent) in Jordan and collected the following information about the LCUs: age, type (quartz-tungsten-halogen or light-emitting diode), date of last maintenance, type of maintenance, last date of use, number of times used during the day, availability of a radiometer, exposure time for each resin-based composite increment, size of light-curing tips and presence of resin-based composite on the tips. The authors used a radiometer to measure the irradiance from the LCUs. They used linear regression with stepwise correlation for the statistical analysis. The authors set the minimum acceptable irradiance at 300 milliwatts/square centimeter.ResultsThe mean irradiance of the 295 LCUs examined was 361 mW/cm2, and 136 LCUs (46.1 percent) delivered an irradiance of less than 300 mW/cm2. The unit's age, type and presence of resin-based composite on the light-curing tips had a significant effect on the irradiance (P ≤ .001).ConclusionsOnly 37 of the 141 quartz-tungsten-halogen units (26.2 percent) and 122 of the 154 light-emitting diode units (79.2 percent) delivered at least 300 mW/cm2. Resin contamination on the light-curing tips had a significant effect on the irradiance delivered. The irradiance from the LCUs decreased with use.Practical ImplicationsThe irradiance from many of the units in this study was less than 300 mW/cm2, which may affect the quality of resin-based composite restorations. Dentists should monitor the performance of the LCUs in their offices weekly. 相似文献
Fluorene‐based single‐chain copolymers with a white light emitter consisting of a blue and an orange chromophore have been synthesized and their photophysical and electroluminescent properties are investigated. The experimental results suggest that only a relatively small fraction of the orange‐emitting units incorporated into the fluorene is needed to achieve efficient white light emission by controlled incomplete energy transfer. A device from a copolymer with 0.02% DDQ content showed the highest external quantum efficiency of 2.64% with a luminance efficiency of 4.06 cd · A?1 with CIE coordinates (0.28, 0.24). The EL emissions are extremely stable over a wide range of current densities.
方法：大鼠视网膜血管内皮细胞随机分为三组：正常对照组、高糖模型组、高糖模型发光二极管照射组,高糖模型发光二极管组的细胞在造模48h后开始采用发光二极管对培养箱中的细胞进行照射。MTT细胞凋亡实验检测各组细胞凋亡率; 激光共聚焦显微镜观察各组视网膜血管内皮细胞胞内钙离子变化; Western blot 法检测各组磷酸化丝氨酸-苏氨酸激酶(P-AKT)蛋白表达。
To define the efficacy and safety of narrowband ultraviolet A1 (UVA1) for the treatment of dermal fibrosis in bleomycin-induced mouse model of scleroderma.
Materials and methods
42 DBA/2 strain mice were included in the study: healthy mice and mice with established scleroderma, treated with high or medium dose of UVA1. Non-treated groups served as control. The equipment emitting 365 ± 5 nm UVA1 radiation was used in the study. The average cumulative doses were 1200 J/cm2 for high and 600 J/cm2 for medium dose course. Histological analysis was performed for the evaluation of the dermal thickness and mast cells density. The expressions of p53 and Ki-67 proteins were assessed by immunohistochemical analyses.
Results
Skin thickness of mice with scleroderma, treated with high and medium dose of UVA1, were lower (272.9 ± 113.2 μm and 394 ± 125.9 μm, respectively) in comparison to the dermal thickness of non-treated animals (599 ± 55.7 μm). The dermal mast cells count in mice with scleroderma was reduced after high and medium dose treatment to 11 ± 1.7 and 13 ± 2.2, respectively, as compared to that in non-treated mice (23 ± 3.0). No significant upregulation of p53 nor Ki-67 proteins was observed in the skin of healthy mice and mice with scleroderma after high- and medium-dose of UVA1.
Conclusions
The results of this study indicate that 365 nm UVA1 with the cumulative doses of 1200 J/cm2 and 600 J/cm2 is safe and effective for the dermal fibrosis treatment. 相似文献
