Light-emitting diodes and half-cell electrodes in experimental recording of electroretinogram c-wave

A method of electroretinogram c-wave recording in the rat was developed that uses a contact lens electrode connected through a saline bridge with a silver-silver chloride half-cell. A cluster of light-emitting diodes, regulated by an electronic light-emitting diode stimulator, was used as a light source. The method enables recordings of c-waves of 0.4–1.6 mV amplitude as well as other electroretinogram components in narrow limits of variation. The two main sources of response variability are voltage shunting and eyeball protrusion.     

聚对苯乙炔（PPV）及其衍生物的研究进展

评价了ＰＰＶ系列衍生物的电学性质、非线性光学性质及其应用。     

发光二极管光固化灯和普通卤光灯对离体牙树脂固化微渗漏影响的研究

目的探讨牙科发光二极管光固化灯对离体牙备洞树脂充填固化后的边缘微渗漏的影响。方法离体磨牙73颗．随机分为实验组（MORITA^TM PENCURE，38颗牙）和对照组（3M^TM ESPE^TM Elipar^TM 2500，35颗牙），制备标准V类洞，隔湿、消毒，干燥后用可乐丽菲露AP-X复合树脂充填，用上述两种光源的固化灯固化，打磨抛光。经冷热循环处理后进行染色、剖开，用体视显微镜定量和扫描电镜定性观察并拍照。结果体视显微镜下实验组和对照组中没有产生微渗漏的牙齿均占大多数，而重度微渗漏均极少，两者均有较好的边缘封闭效果，差异无统计学意义，扫描电镜提示实验组边缘密合度要好于对照组。结论发光二极管光固化灯和普通卤光灯一样，都可以较好地固化可乐丽菲露AP-X复合树脂，而发光二极管光固化灯可能有更好的降低微渗漏的能力。     

Effects of Asymmetric Quantum Wells on the Structural and Optical Properties of InGaN-Based Light-Emitting Diodes

A metalorganic vapor phase epitaxy-grown InGaN/GaN multiple-quantum-well (MQW) with three graded-thickness wells (the first-grown well had the greatest width) near the n-GaN was used as the active layer of an LED. For LEDs with an asymmetric quantum well (AQW), high-resolution X-ray diffraction and transmission electron microscopic reveal that the modified MQWs with a reasonable crystalline quality were coherently strained on the underlying GaN epilayers without any relaxation. In addition, the slight increase of indium segregation in the LED with an AQW may be attributed to variations in indium contents experienced during epitaxial growth of the wide well-containing MQWs. By preventing the energetic electrons from accumulating at the topmost quantum well nearest the p-GaN, the presence of light intensity roll-off in the LED with an AQW is shifted to higher currents and the corresponding maximum light output power is increased with a ratio 7.9% higher than that of normal LEDs. Finally, similar emission wavelengths were observed in the electroluminescence spectra of both LEDs, suggesting that light emitted mostly from the top quantum wells (near the p-GaN) while the emissions from the AQW region were insignificant.     

Novel Highly Efficient Organophotocatalysts: Truxene–Acridine‐1,8‐diones as Photoinitiators of Polymerization

Truxene–acridine‐1,8‐dione derivatives ( Tr_AD ) are proposed as new photoinitiators of polymerization under very soft irradiation (by a household halogen lamp), as well as laser‐diode exposure at 405 nm. They exhibit a strong absorption around 380 nm. The Tr_AD /diphenyl iodonium salt/9‐vinylcarbazole combination is able to promote the ring‐opening polymerization of an epoxide, whereas the Tr_AD /alkyl halide/amine system is very efficient in initiating the radical photopolymerization of an acrylate. Excellent polymerization profiles are obtained. Acrylate/epoxide blends are also easily polymerized. These Tr_ADs in the three‐component systems behave as photocatalysts according to oxidative cycles. The mechanisms are discussed for the different multicomponent initiating systems.

     

Shedding light on a potential hazard: Dental light-curing units

BackgroundDental light-curing units (LCUs) are powerful sources of blue light that can cause soft-tissue burns and ocular damage. Although most ophthalmic research on the hazards of blue light pertains to low levels from personal electronic devices, computer monitors, and light-emitting diode light sources, the amount of blue light emitted from dental LCUs is much greater and may pose a “blue light hazard.”MethodsThe authors explain the potential risks of using dental LCUs, identify the agencies that provide guidelines designed to protect all workers from excessive exposure to blue light, discuss the selection of appropriate eye protection, and provide clinical tips to ensure eye safety when using LCUs.ResultsWhile current literature and regulatory standards regarding the safety of blue light is primarily based on animal studies, sufficient evidence exists to suggest that appropriate precautions should be taken when using dental curing lights. The authors found it difficult to find on the U.S. Food and Drug Administration database which curing lights had been cleared for use in the United States or Europe and could find no database that listed which brands of eyewear designed to protect against the blue light has been cleared for use. The authors conclude that more research is needed on the cumulative exposure to blue light in humans. Manufacturers of curing lights, government and regulatory agencies, employers, and dental personnel should collaborate to determine ocular risks from blue light exist in the dental setting, and recommend appropriate eye protection. Guidance on selection and proper use of eye protection should be readily accessible.Conclusions and Practical ImplicationsThe Centers for Disease Control and Prevention Guidelines for Infection Control in the Dental Health-Care Setting–2003 and the Occupational Safety and Health Administration Bloodborne Pathogen Standard do not include safety recommendations or regulations that are directly related to blue light exposure. However, there are additional Occupational Safety and Health Administration regulations that require employers to protect their employees from potentially injurious light radiation. Unfortunately, it is not readily evident that these regulations apply to the excessive exposure to blue light. Consequently employers and dental personnel may be unaware that these Occupational Safety and Health Administration regulations exist.     

Demonstration and evaluation of germicidal UV-LEDs for point-of-use water disinfection

Ultraviolet (UV) irradiation is a common disinfection option for water treatment in the developed world. There are a few systems installed in developing countries for point-of-use treatment, but the low-pressure mercury lamps currently used as the UV irradiation source have a number of sustainability issues including a fragile envelope, a lifetime of approximately one year, and they contain mercury. UV light emitting diodes (LEDs) may offer solutions to many of the sustainability issues presented by current UV systems. LEDs are small, efficient, have long lifetimes, and do not contain mercury. Germicidal UV LEDs emitting at 265 nm were evaluated for inactivation of E. coli in water and compared to conventional low-pressure UV lamps. Both systems provided an equivalent level of treatment. A UV-LED prototype was developed and evaluated as a proof-of-concept of this technology for a point-of-use disinfection option, and the economics of UV-LEDs were evaluated.