It is shown that an improper regularization in the light-cone quantization of field theories can introduce a violation of rotational invariance as well as spurious divergences. Several methods are developed to avoid or cure these problems, as required for a consistent renormalization procedure of gauge theories. Based on these methods, the light-cone Hamiltonian for &E&+1 is constructed. Extens...

A fiber optic ultrasonic system is described which monitors the cure of an epoxy resin. Ultrasound is generated using a high-power optical fiber to deliver high-energy pulses of light to the prepared surface of an aluminum mold that contains the curing epoxy resin. The generated ultrasound is detected using a local fiber optic ultrasound sensor embedded in the curing epoxy resin. The system was...

AIM The purpose of this study was to investigate the effect of different temperatures on the efficacy of polymerization during the insertion of composite resin using different light curing units. METHODS AND MATERIALS A total of 45 disc-shaped specimens were fabricated from Z250 composite resin (3M/ESPE, St. Paul, MN, USA) with 15 each prepared at three different temperatures (refrigerated to...

Inadequate intensity of the polymerization light source can compromise the quality and longevity of dental composite restorations. In order to maintain optimal strength of polymerization devices, regular control of polymerization units is necessary. The aim of this study was to compare the accuracy of two radiometers in the measurement of light intensity of photopolymerization devices concernin...

OBJECTIVES Nowadays more and more newly introduced light sources (tungsten-halogen, compact fluorescent (CFL) and light-emitting diode (LED) lamps) are used in households. It is important to know whether their radiation poses any possible risk for human health or not. These light sources emit optical radiation not solely in the visible spectrum. Other bands emitted by these sources, i.e., ultra...