The effect of carrier-induced change on the optical properties of AlGaAs-GaAs intermixed quantum wells

The carrier-induced effects in the change of absorption and refractive index on the AlGaAs-GaAs intermixing modified quantum wells (QW's) have been investigated theoretically. Band-filling, bandgap shrinkage, and free-carrier absorption have been included for various carrier concentrations. The Schrodinger and the Poisson equations have been considered self-consistently. The polarized absorption coefficients are calculated using the Kane k·p method for a four band model and followed by the Kramers-Kranig transformation to obtain the refractive index change. The results obtained show a more enhanced bandgap renormalization and change of absorption, but a reduced change in refractive index for the larger intermixing extents. It is important to know the carrier-induced optical parameter changes the intermixed QW's because of their recent interests in photonics.published_or_final_versio

Designing an external efficieny of over 30% for light emittingdiode

In designing high intensity LED's, substantial increase in efficiency can be achieved with the use of a textured surface, which is characterized by its external quantum efficiency and radiation pattern. We have found that the randomness of the inclined facade surfaces contributes substantially to the enhanced efficiency substantially. Such efficiency is strongly dependent upon the textured surface layer's thickness and its distance to the active layer of the diode. To attain the maximum efficiency, an optimal range for these parameters is required.published_or_final_versio

Optimization of Textured-surface Light Emitting Diode

We present an analysis of the efficiency and radiation pattern of the textured-surface LED by tracing the light rays that emits from the active layer. Through simulation, we discover that the efficiency depends on the thickness of the textured layer and its separation distance from the active layer. By carefully choosing these two parameters, maximum efficiency an be achieved. The radiation pattern of a texture-surface LED is found to be different from the flat-surfaced LED in that the textured surface has a wider angular spread.published_or_final_versio

In-house human immunodeficiency virus-1 genotype resistance testing to determine highly active antiretroviral therapy resistance mutations in Hong Kong

Objective To determine the frequency of highly active antiretroviral therapy resistance mutations in the viral pol gene of human immunodeficiency virus-1 (HIV-1) genotypes that circulate in Hong Kong, by means of an in-house HIV-1 genotyping system. Design Retrospective study. Setting Two HIV clinics in Hong Kong. Patients A modified in-house genotyping resistance test was used to sequence the partial pol gene in 1165 plasma samples from 965 patients. The performance of our test was cross-compared with the US Food and Drug Administration-approved ViroSeq HIV-1 genotyping system. The results of genotyping were submitted to the Stanford HIV-1 drug resistance database for analysis. Results The cost-effective in-house genotypic resistance test (US$40) demonstrated comparable performance to the US Food and Drug Administration-approved ViroSeq system. The detection limit of this in-house genotypic resistance test could reach 400 copies/mL for both HIV-1 subtype B and CRF01_AE, which were the predominant genotypes in Hong Kong. Drug resistance mutations were detected only in post-treatment samples from treatment-failure patients. However, there was no significant difference in the frequency of drug resistance mutations between subtype B and CRF01_AE. Conclusion Our cost-effective in-house genotypic resistance test detected no significant difference in drug resistance-related mutations frequencies between HIV-1 subtype B and CRF01_AE in Hong Kong. A drug resistance-related mutations database for different HIV-1 genotypes should be established in Hong Kong to augment guidance for HIV treatment.published_or_final_versio

Motor neuron disease in Hong Kong Chinese: Epidemiology and clinical picture

This study documents the clinical features, incidence and prevalence of motor neuron disease (MND) in Hong Kong Chinese. Patients with MND who were alive between 1989 and 1992 were recruited by retrieval of medical records from the four major hospitals in Hong Kong, and by referral of neurologists, neurosurgeons and medical consultants. Mortality statistics was provided by the Census and Statistics Department. A total of 84 cases were identified with a male preponderance of 1.98:1. The average annual period incidence was 0.31/100,000 and the point prevalence on December 31, 1992, was 0.95/100,000. The mean age at onset was 55.5 years (range 19-81) with a peak observed from 55 to 65 years. The clinical features are similar to other reported series of MND. The incidence and mortality of MND in Hong Kong are therefore lower than the worldwide figures of 2.0/100,000 and 1.5/100,000, respectively.published_or_final_versio

Recent advances in unveiling active sites in molybdenum sulfide-based electrocatalysts for the hydrogen evolution reaction

Hydrogen has received significant attention as a promising future energy carrier due to its high energy density and environmentally friendly nature. In particular, the electrocatalytic generation of hydrogen fuel is highly desirable to replace current fossil fuel-dependent hydrogen production methods. However, to achieve widespread implementation of electrocatalytic hydrogen production technology, the development of highly active and durable electrocatalysts based on Earth-abundant elements is of prime importance. In this context, nanostructured molybdenum sulfides (MoS x ) have received a great deal of attention as promising alternatives to precious metal-based catalysts. In this focus review, we summarize recent efforts towards identification of the active sites in MoS x -based electrocatalysts for the hydrogen evolution reaction (HER). We also discuss recent synthetic strategies for the engineering of catalyst structures to achieve high active site densities. Finally, we suggest ongoing and future research challenges in the design of advanced MoS x -based HER electrocatalysts

Can a Mediterranean diet reduce the effects of lipodystrophy syndrome in people living with HIV? A pilot randomised controlled trial

BACKGROUND: HIV and highly active antiretroviral therapies have been associated with changes in individuals' lipid profiles and fat distribution (lipodystrophy). A pilot study was conducted for a randomised controlled trial to evaluate whether lipodystrophy in HIV patients can be controlled by adopting the low-fat and low-cholesterol diet or the modified Mediterranean diet. METHODS: Forty-eight HIV patients were randomised into two diet groups. Thirty-six (75%) completed the 1-year pilot study with regular dietetic consultations, during which time lipid levels, weight, body mass index and fat distribution were recorded. Differences between and within groups were determined. RESULTS: Undesirable body fat changes in the low-fat diet group included decreases in tricep skinfold (from 19.9 mm to 15.4 mm (P = 0.03)), hip circumference (from 93.6 cm to 91.7 cm (P = 0.01)) but a significant increase in waist-to-hip ratio (from 0.87 to 0.89 (P = 0.003)). Serum cholesterol increased significantly in the Mediterranean diet group at 9 and 12 months (from 4.6 to 5.06 mmol L(-1) (P = 0.03) and 5.12 mmol L(-1) (P = 0.01)) with no obvious change in the low-fat diet group. Serum triglyceride levels remained the same in the Mediterranean diet group, whereas it increased from 1.9 to 3.22 mmol L(-1) (P = 0.07) in the low-fat diet group. CONCLUSIONS: A Mediterranean diet seems to have an advantage over the low-fat diet in maintaining serum triglyceride levels and avoiding lipodystrophy, but this advantage was offset by a rise in cholesterol level. Several procedural and methodological issues were identified which must be rectified before a similar large-scale trial taking place.link_to_OA_fulltex

Potential Use of the Adenosine Triphosphate Cell Viability Assay in Endometrial Cancer

Objective: Adenosine triphosphate cell viability assay (ATP-CVA) was used previously to evaluate chemotherapy in uterine cancer cell lines. In this study, we have performed the ATP-CVA on endometrial cancer patients to study the feasibility of using ATP-CVA in endometrial cancer to determine the intrinsic chemosensitivity of the cytotoxic drugs. Methods: Thirty-three patients with endometrial adenocarcinoma who presented for a staging operation were recruited. Endometrial cancer samples were obtained at the time of operation. In vitro ATP-CVA and chemosensitivity testing was performed using cisplatin, carboplatin, paclitaxel, etoposide, doxorubicin, 4-epidoxorubicin, and topotecan. Results: Thirty-two of the 33 endometrial cancer samples were evaluable for SF50 (survival fraction at 50% of the peak plasma concentration [PPC]) using ATP-CVA. The median SF50 of carboplatin (0.33) was significantly less than the median SF50 of cisplatin (0.71), topotecan (0.93), paclitaxel (0.68), doxorubicin (1.0), etoposide (0.70), or 4-epidoxorubicin (0.88) (Wilcoxon signed rank test, P <.001). Conclusion: This study showed the feasibility of using the ATP-CVA in endometrial cancer to determine the intrinsic chemosensitivity of cytotoxic drugs. © 2006 Society for Gynecologic Investigation.link_to_subscribed_fulltex

An analytical two-dimensional model for circular spreading-resistance temperature sensor based on thin silicon film

An analytical two-dimensional model is developed to explain the minority-carrier exclusion effect in circular spreading-resistance temperature (SRT) sensor fabricated on thin silicon film. The model can be used to show the relation between minority-carrier exclusion length and maximum operating temperature of the sensor under different bias currents and different doping levels. Comparison is made between the proposed model and the conventional one-dimensional model used for similar sensors with rectangular shape. Experimental results show that the new model is more accurate than the one-dimensional model for predicting the characteristics of the circular SRT sensor. © 2004 Elsevier Ltd. All rights reserved.link_to_subscribed_fulltex