The Effect of Imbalanced Carrier Transport on the Efficiency Droop in GaInN-Based Blue and Green Light-Emitting Diodes

The effect of strongly-imbalanced carrier concentration and mobility on efficiency droop is studied by comparing the onset voltage of high injection, the onset current density of the droop, and the magnitude of the droop, as well as their temperature dependence, of GaInN-based blue and green light-emitting diodes (LEDs). An n-to-p asymmetry factor is defined as sigma(n)/sigma(p), and was found to be 17.1 for blue LEDs and 50.1 for green LEDs. Green LEDs, when compared to blue LEDs, were shown to enter the high-injection regime at a lower voltage, which is attributed to their less favorable p-type transport characteristics. Green LEDs, with lower hole concentration and mobility, have a lower onset current density of the efficiency droop and a higher magnitude of the efficiency droop when compared to blue LEDs. The experimental results are in quantitative agreement with the imbalanced carrier transport causing the efficiency droop, thus providing guidance for alleviating the phenomenon of efficiency droop.114sciescopu

Point Mutation of Hoxd12 in Mice

Purpose: Genes of the HoxD cluster play a major role in vertebrate limb development, and changes that modify the Hoxd12 locus affect other genes also, suggesting that HoxD function is coordinated by a control mechanism involving multiple genes during limb morphogenesis. In this study, mutant phenotypes were produced by treatment of mice with chemical mutagen, N-ethyl-N-nitrosourea (ENU). We analyzed mutant mice exhibiting the specific microdactyly phenotype and examined the genes affected. Materials and Methods: We focused on phenotype characteristics including size, bone formation, and digit morphology of ENU-induced microdactyly mice. The expressions of several molecules were analyzed by genome-wide screening and quantitative real-time PCR to define the affected genes. Results: We report on limb phenotypes of an ENU-induced A-to-C mutation in the Hoxd12 gene, resulting in alanine-to-serine conversion. Microdactyly mice exhibited growth defects in the zeugopod and autopod, shortening of digits, a missing tip of digit I, limb growth affected, and dramatic increases in the expressions of Fgf4 and Lmx1b. However, the expression level of Shh was not changed Hoxd12 point mutated mice. Conclusion: These results suggest that point mutation rather than the entire deletion of Hoxd12, such as in knockout and transgenic mice, causes the abnormal limb phenotype in microdactyly mice. The precise nature of the spectrum of differences requires further investigation.link_to_subscribed_fulltex

Optical repumping of triplet PP-states enhances magneto-optical trapping of ytterbium atoms

Radiative decay from the excited $^1P_1$ state to metastable $^3P_2$ and $^3P_0$ states is expected to limit attainable trapped atomic population in a magneto-optic trap of ytterbium (Yb) atoms. In experiments we have carried out with optical repumping of $^3P_{0,2}$ states to $^3P_1$, we observe enhancement of trapped atoms yield in the excited $^1P_1$ state. The individual decay rate to each metastable state is measured and the results show an excellent agreement with the theoretical values.Comment: 5 pages, 5 figure

Energy bandgap variation in oblique angle-deposited indium tin oxide

Indium tin oxide (ITO) thin films deposited using the oblique angle deposition (OAD) technique exhibit a strong correlation between structural and optical properties, especially the optical bandgap energy. The microstructural properties of ITO thin films are strongly influenced by the tilt angle used during the OAD process. When changing the tilt angle, the refractive index, porosity, and optical bandgap energy of ITO films also change due to the existence of a preferential growth direction at the interface between ITO and the substrate. Experiments reveal that the ITO film's optical bandgap varies from 3.98 eV (at normal incident deposition) to 3.87 eV (at a 60 tilt angle). 2-10 OAD is generally associated with physical vapor deposition of thin films (prepared through, e.g., electron-beam or thermal evaporation), in which the material vapor flux arrives at the substrate surface at an oblique angle. Tilted and columnar nanostructures are the most typical morphological characteristics of OAD thin films. 1, Deposition of ITO films on soda lime glass and silicon substrates was conducted with an E-beam evaporation system using an ITO source composed of 90 wt. % In 2 O 3 and 10 wt. % SnO 2 . Prior to the deposition, all substrates were sequentially cleaned in acetone, isopropyl alcohol, and deionized water and dried under nitrogen flow. The apparatus used in our OAD process has a sample stage (onto which the substrate was loaded), allowing for control of the polarangle as well as azimuthal rotation. The distance between the substrate and evaporation source material was approximately 50 cm. The sample stage was positioned at a fixed polar angle so that the substrate had a certain tilt angle (deposition angle) with respect to the vapor-flux direction. The chamber was evacuated to a pressure less than 1.0 Â 10 À6 Torr, and substrates were held at room temperature. During the deposition, the deposition rate was held steady at 0.2 nm/s, as measured by a quartz crystal monitor inside the chamber. The low growth rate on the substrate at higher deposition angles 11 was compensated by increasing the deposition time to keep the same film thickness for all samples. The ITO films unloaded from the E-beam evaporation system were annealed in O 2 at 550 C for 1 min in a rapid thermal annealing system in order to compensate a deficiency of oxygen in the films. Optical transmittance measurements of the ITO thin films were performed using non-polarized light at normal incidence in the wavelength range of 280-780 nm using a JASCO UV-VIS spectrophotometer. The refractive index (n) was measured using a spectroscopic ellipsometry system, in which absorption is neglected during fitting. A film thickness was measured first by ellipsometry, and then confirmed by a scanning electron microscope (SEM, Hitachi S-4300). The porosity and optical bandgap energy values of the ITO thin films were calculated using theoretical models developed by Poxson et al. 11 and Tauc, 13 respectively. The morphological features of the films were examined using an optical microscope and SEM. Several regions on the sample surface were investigated in order to produce representative images. Furthermore, the crystallographic structure of the ITO thin films was examined by X-ray diffraction (XRD) using the nickel-filtered Ka emission of copper. Figures 1(a) and 1(b) show optical microscope images of the ITO films deposited on (a) silicon (Si) and (b) glass substrates at tilt angles ranging from 0 to 60 . A color difference of the ITO thin films is clearly evident, which can result from a variation in thickness and/or refractive index. In this case, because the thicknesses of all films are the same (about 210 nm), the variation in refractive index is the cause for the color variation. It is well known that the refractive index of a a

Prognostic Value of Postoperative CEA Clearance in Rectal Cancer Patients with High Preoperative CEA Levels

PURPOSE: We determined the prognostic value of carcinoembryonic antigen (CEA) clearance after tumor resection with serial evaluation of postoperative CEA levels in rectal cancer. METHODS: Between 1994 and 2004, we retrospectively reviewed 122 patients with rectal cancer whose serum CEA levels were measured on the preoperative day and postoperative days 7 and 30. Patients with preoperative CEA levels <5.0 ng/ml were excluded. An exponential trend line was drawn using the three CEA values. Patients were categorized into three groups based on R(2) values calculated through trend line, which indicates the correlation coefficient between exponential graph and measured CEA values: exponential decrease group (group 1: 0.9 < R(2) < or = 1.0), nearly exponential decrease group (group 2: 0.5 < R(2) < or = 0.9), and randomized clearance group (group 3: 0.5 < or = R(2)). We then analyzed the CEA clearance pattern as a prognostic indicator. RESULTS: With a median follow-up of 57 months, the 5-year overall survival was 62.3% vs. 48.1% vs. 25% and the 5-year disease-free survival was 58.6% vs. 52.7% vs. 25% among groups 1, 2, and 3 (P = 0.014, P = 0.027, respectively) in patients with stage III rectal cancer. For those with stage II rectal cancer, the 5-year overall survival rate of group 1 was significantly better than groups 2 and 3 (88.8% vs. 74.1%, respectively, P = 0.021). CONCLUSIONS: the postoperative pattern of CEA clearance is a useful prognostic determinant in patients with rectal cancer. Patients with a randomized pattern of CEA clearance after tumor resection should be regarded as having the possibility of a persistent CEA source and may require consideration of intensive follow-up or adjuvant therapy.ope

The association between vitamin D supplementation and the long-term prognosis of differentiated thyroid cancer patients: a retrospective observational cohort study with propensity score matching

ObjectiveBenefits of vitamin D in various cancers have been reported, but its effects on differentiated thyroid cancer (DTC) have not been established. We aimed to analyze the effect of vitamin D supplementation on the prognosis of DTC.MethodsA retrospective observational cohort study was conducted on 9,739 DTC patients who underwent thyroidectomy from January 1997 to December 2016. Mortality was classified as all-cause, cancer-related, or thyroid cancer-related. Patients were divided into the “VD group” (supplemented with vitamin D) and the “control group” (without vitamin D supplementation). Propensity score matching was performed in a 1:1 ratio according to age, sex, tumor size, extrathyroidal extension (ETE), and lymph node metastasis (LNM) status, and 3,238 patients were assigned to each group. Kaplan-Meier curves, log-rank test and Cox proportional hazards regression analysis were performed.ResultsThe follow-up period was 10.7 ± 4.2 years. Clinicopathological variables between two groups were similar except for all-cause (p&lt;0.001) and total cancer death (p=0.001). From the Kaplan−Meier curve and log-rank test, “VD group” had significantly favorable all-cause (p&lt;0.001) and total cancer mortality (p=0.003), but similar thyroid cancer mortality (p=0.23). In Cox regression, vitamin D intake reduced the risk of all-cause (hazard ratio [HR], 0.617, p=0.001) and total cancer mortality (HR, 0.668, p=0.016) but had no effect on thyroid cancer mortality.Discussion/conclusionVitamin D supplementation was positively associated with all-cause and total cancer mortality in DTC and might be a modifiable prognostic factor for improved survival. Further research will be needed to clarify the effect of vitamin D supplementation on DTC

Imaging Findings of Castleman's Disease Localized in the Axilla: A Case Report

Castleman's disease is a rare benign lymphoproliferative disorder of uncertain origin which most commonly involves the mediastinum but rarely affects the axilla. We report a case of localized Castleman's disease involving the axillary lymph node. Mammography revealed a well-defined, homogeneously dense ovoid mass, 3 cm in size, in the left axilla, while gray-scale ultrasonography (US) demonstrated a well-defined, uniformly hypoechoic ovoid mass with good through transmission. Peripheral hypervascularity was observed at power Dopper US, and early rapid homogeneous enhancement at contrast-enhanced dynamic CT

Development of a Rating System for Digestive System Impairments: Korean Academy of Medical Sciences Guideline

A systematic and effective welfare system for people with digestive system impairments is required. In Korea, an objective and scientific rating guideline does not exist to judge the digestive system impairments. Whether the impairments exist or not and the degree of it need to be examined. Thus, with these considerations we need a scientific rating guideline for digestive system impairments to fit our cultural and social background. In 2007, a research team, for the development of rating impairment guidelines, was organized under the supervision of Korean Academy of Medical Sciences. The rating guidelines for digestive system impairments was classified into upper and lower gastrointestinal tracts impairments and liver impairment. We developed objective rating guidelines for the upper gastrointestinal tract, the impairment generated after surgery for the stomach, duodenum, esophagus, and for the lower gastrointestinal tract, the impairment generated after construction and surgery for colon, rectum, anus, and intestinal stomas. We tried to make the rating impairment guidelines to include science, objectivity, convenience, rationality, and actuality. We especially emphasized objectivity as the most important value. We worked to make it easy and convenient to use for both the subjects who received the impairment ratings and the doctors who will give the ratings