Search

In this study, the effect of quantum barrier thickness in the multi-quantum wells active region on electrical and optical properties of nitride-based light emitting diodes (LEDs) were investigated and demonstrated. The forward voltage decreased as the thickness of quantum barrier decreased owing to the reduction of series resistance. The external quantum efficiency (EQE) and droop effect can be effectively improved by decreasing the barrier thickness which was attributed to the enhancement of the holes injection and uniform distribution in the active region. However, if barrier was too thin, it would get the opposite effect due to the influence of electron overflow. Regarding the hot/cold factor, the thinner quantum barrier of LEDs achieved a better performance. The reason is that the thicker quantum barrier with poor holes distribution resulted in the holes accumulation of a few MQWs near the p-side layer was more easily influenced by thermal effect and escaped from the QWs. [ABSTRACT FROM AUTHOR]

Abstract: Radiobiological models are used in modern radiotherapy to evaluate the biological effects of different treatment plans or modalities. A radiobiological model typically converts a physical quantity (e.g. absorbed dose) to a biological quantity (e.g. cell survival fraction). Currently, the linear-quadratic model (LQM) is the most widely used model. Since it is a deterministic model, the LQM naturally ignores the uncertainties arising from the stochastic randomness of energy depositions along radiation tracks and the inherent unpredictable nature of biological systems. Recently, many studies have revealed the detailed spatial and temporal distributions of DNA damages, e.g. the DNA double strand breaks (DSBs), along various types of radiation tracks traversing a cell nucleus. Studies have also been conducted to unravel the biological pathways that involve in how cells and tissues process DNA damages. As such, the author proposes to start developing a new multi-scale radiobiological model based on the “bottom-up” approach. The model includes a Monte Carlo procedure to treat the stochastic randomness of radiation-induced DNA damages, and it also includes the relevant intercellular and intracellular pathways to allow the DNA damages to evolve into higher-order biological endpoints, e.g. chromosome aberrations, cell death, or tumorigenesis. Because of its stochastic nature, the new model inherently addresses the uncertainty issue being ignored by LQM. More importantly perhaps is that the model opens a new way to study radiation effects that involve biological pathways, and therefore, may have a profound impact on radiotherapy in the future. [Copyright &y& Elsevier]

Purpose: The aim of this study was to retrospectively observe and analyze the long-term treatment outcomes for a total of 952 esophageal cancer patients who were treated with 252Cf neutron brachytherapy (NBT) in combination with external beam radiotherapy (EBRT). Methods and Materials: From November 2001 to March 2012, 952 patients with esophageal cancer underwent NBT in combination with EBRT. The patient numbers distributed over various cancer Stages I, IIA, IIB, III, and IVA were 9, 290, 51, 579, and 23, respectively. The total radiation dose to the reference point via NBT was 8-25 Gy-eq in three to five fractions with one fraction/week. The total dose via EBRT was 40-60 Gy delivered over a period of 5-6 weeks with normal fractionation. Results: The overall median survival time was 20.3 months. The 1-, 3-, and 5-year survival rates were 67.1%, 36.3%, and 26.6%, respectively. These results compare favorably with the results obtained from conventional high-dose rate in combination with EBRT. Although a majority of the patients (860 or 90.3%) developed Grades 1 and 2 esophagitis during treatment, the symptoms were effectively relieved after the application of antacid and surface anesthesia. Conclusions: The clinical data show that NBT in combination with EBRT produced favorable local control and long-term survival rates for patients with esophageal cancer and that the side effects are tolerable. As such, we conclude that this dual-modality method is an effective and safe way for treating esophageal cancer. [ABSTRACT FROM AUTHOR]

Abstract: We present a dynamical theory of nonlinear absorption and propagation of a laser pulse train that contains 20 subpulses with an individual pulse width of 100ps. It is shown that the accumulative nonlinearity and the reverse saturation absorption play important roles in the optical limiting performance and pulse shaping. When the incident field is not too strong, the population transfer reveals a slow response process, and the periodic sequence of short light pulses can be regarded as a continuous long pulse. The general theory is applied to fullerence , which is a popular reverse saturable absorption material and a good limiter because of its larger excited-state absorption cross-section compared with that of the ground state. The propagation of the front subpulses is mainly affected by the linear transition between the ground state and the first excited singlet state, while the latter subpulses are attenuated by the excited-state absorption. Moreover, these two different kinds of absorption mechanisms result in different radial distributions for different subpulses. The pulse propagation is studied by solving numerically the coupled rate equations and the propagation equation of the optical pulse intensity, using experimental parameters as input. We suggest a new method to measure the lifetime of the triplet state. [Copyright &y& Elsevier]

Fourteen microsatellite markers with a coverage of 63.5 cM on bovine chromosome 6 were selected, and 26 sire families with 2,260 daughters were analyzed for mapping quantitative trait loci (QTL) affecting 5 milk production traits in a Chinese Holstein population. In the analyses across 26 families and within the largest significant families with a one-QTL model fitted, a QTL near BMS470 was detected that affected fat yield at the 5% experiment-wide significance level. When a 2-QTL model was fitted in the across-family analysis, it was found that there might exist 2 QTL affecting the 3 yield traits, although the exact or empirical thresholds for the significance testing were unknown. In all analyses, the results for milk yield and protein yield were generally consistent, which might have resulted from the same genetic background for milk and protein yield. [ABSTRACT FROM AUTHOR]