Nitrogen doped-ZnO/n-GaN heterojunctions

Nitrogen-doped ZnO nanorods were prepared by electrodeposition using two different Zn precursors (zinc nitrate and zinc acetate), while all other growth conditions (dopant precursor, concentration, growth temperature, and bias) were identical. We have shown that the precursor used affects the properties of the ZnO nanorods, and that the presence of rectifying properties in n-GaN/N:ZnO heterojunctions is strongly related to the use of nitrate precursor for ZnO growth. The difference in the properties of ZnO obtained from two precursors is attributed to the differences in native defect and impurity concentrations, which could affect the electronic properties of the samples. © 2011 American Institute of Physics.published_or_final_versio

Solution-based growth of ZnO nanorods for light-emitting devices: Hydrothermal vs. electrodeposition

ZnO nanorods have been grown by two inexpensive, solution-based, low-temperature methods: hydrothermal growth and electrodeposition. Heterojunction n-ZnO nanorods/p-GaN light-emitting diodes have been studied for different nanorod growth methods and different preparation of the seed layer. We demonstrate that both the nanorod properties and the device performance are strongly dependent on the growth method and seed layer. All the devices exhibit light emission under both forward and reverse bias, and the emission spectra can be tuned by ZnO nanorod deposition conditions. Electrodeposition of rods or a seed layer results in yellow emission, while conventional hydrothermal growth results in violet emission. © The Author(s) 2010. This article is published with open access at Springerlink.com.published_or_final_versionSpringer Open Choice, 01 Dec 201

Plasma treatment of p-GaN/n-ZnO nanorod light-emitting diodes

Conference vol. 8987 entitled: Oxide-based Materials and Devices VZinc oxide (ZnO) is a material of great interest for short-wavelength optoelectronic applications due to its wide band gap (3.37 eV) and high exciton binding energy (60 meV). Due to the difficulty in stable p-type doping of ZnO, other p-type materials such as gallium nitride (GaN) have been used to form heterojunctions with ZnO. p-GaN/n-ZnO heterojunction devices, in particular light-emitting diodes (LED) have been extensively studied. There was a huge variety of electronic properties and emission colors on the reported devices. It is due to the different energy alignment at the interface caused by different properties of the GaN layer and ZnO counterpart in the junction. Attempts have been made on modifying the heterojunction by various methods, such as introducing a dielectric interlayer and post-growth surface treatment, and changing the growth methods of ZnO. In this study, heterojunction LED devices with p-GaN and ZnO nanorods array are demonstrated. The ZnO nanorods were grown by a solution method. The ZnO nanorods were exposed to different kinds of plasma treatments (such as nitrogen and oxygen) after the growth. It was found that the treatment could cause significant change on the optical properties of the ZnO nanorods, as well as the electronic properties and light emissions of the resultant LED devices. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.Link_to_subscribed_fulltex

From Cleanroom to Desktop: Emerging Micro-Nanofabrication Technology for Biomedical Applications

This review is motivated by the growing demand for low-cost, easy-to-use, compact-size yet powerful micro-nanofabrication technology to address emerging challenges of fundamental biology and translational medicine in regular laboratory settings. Recent advancements in the field benefit considerably from rapidly expanding material selections, ranging from inorganics to organics and from nanoparticles to self-assembled molecules. Meanwhile a great number of novel methodologies, employing off-the-shelf consumer electronics, intriguing interfacial phenomena, bottom-up self-assembly principles, etc., have been implemented to transit micro-nanofabrication from a cleanroom environment to a desktop setup. Furthermore, the latest application of micro-nanofabrication to emerging biomedical research will be presented in detail, which includes point-of-care diagnostics, on-chip cell culture as well as bio-manipulation. While significant progresses have been made in the rapidly growing field, both apparent and unrevealed roadblocks will need to be addressed in the future. We conclude this review by offering our perspectives on the current technical challenges and future research opportunities

Aspirin as an antifungal lock therapy agent

Poster Session - Microbiology/Immunology II: abstract no. 177Journal of Dental Research, 2011, Special Issue B, p. 177Candida biofilms on central venous catheters are one of the commonest nosocomial fungal bloodstream infections. Antifungal lock solutions have been shown to be effective in salvaging indwelling catheters in patients requiring intravenous therapy. Objectives: To determine the activity of aspirin as a lock solution against four Candida biofilms on silicone catheter sections. Methods: Biofilms of Candida albicans, Candida glabrata, Candida krusei and Candida tropicalis were formed on silicone catheters in vitro. The catheters were exposed to lock therapy with aspirin at concentrations of 5 mg/ml – 45 mg/ml, for 2, 4 and 24 hr. Untreated biofilms served as controls. The catheters were then removed and quantified by culture and XTT assays. Results: Significant reduction in CFU counts (approaching 100%) was detected as early as 2 hr in C. albicans biofilms treated with 40 mg/ml aspirin, whereas the same level of reduction was only obtained at 45 mg/ml aspirin, locked for 4 hr in C. glabrata and C. tropicalis (p < 0.05). However, C. krusei only showed 50 % reduction of XTT activities at concentration of 45 mg/ml aspirin, locked for 24 hr. Conclusion: Our results showed that catheter-lock solution of aspirin may be used to salvage catheters infected with C. albicans, C. glabrata, C. tropicalis , but not C. krusei.link_to_OA_fulltextThe 25th IADR-SEA Division Annual Scientific Meeting, Singapore, 28-30 October 2011

Stereoscopic Technique for Conversion of Radiographic Guide into Implant Surgical Guide

Purpose: The aim of this study was to develop and evaluate a new stereoscopic technique for conversion of radiographic guide into surgical guide for dental implant placement. Materials and Methods: Ten partially dentate patients requiring 18 implants for tooth replacement were recruited. Radiographic guides were modified with the addition of index rods for double computed tomography scanning. Implant positions were planned with implant planning software, and the stereoscopic angulations were measured. The radiographic guides were converted into surgical guides using either a generic bench drill (Group A, n=9) or a milling machine (Group B, n=9). Stereolithographic surgical guides were also made for three patients (Group S, n=5). Differences between the planned and actual angulations were tested by pair-sample t-test. Difference of mean angle deviation among groups was tested by Brown-Forsythe test. Differences were considered significant if p<.05. Results: Eighteen implant sites were successfully treated with the converted surgical guides. The mean angle deviation of Group A (1.3±0.6°) was significantly greater than Group S (0.4±0.6°), while no differences were found between Group B (0.9±0.3°) and Group S. The linear error was greatest in Group A with 1.5mm at the head and 1.8mm at the apex of the implant. Conclusions: The use of this new stereoscopic technique appears to be an acceptable alternative method for converting radiographic guide into surgical guide. © 2011 Wiley Periodicals, Inc.link_to_subscribed_fulltex

An energy-based failure criterion for delamination initiation in electronic packaging

The significance of interfacial delamination as a crucial failure mechanism in electronic packaging has been documented in many papers. A number of failure criteria have been used to solve the problems with a pre-crack at the interface. However, in real electronic packages, the size and location of the cracks or/and delamination cannot be predicted. It is not easy to use the traditional fracture criteria to deal with more complicated 3D delamination problems. The epoxy molding compound (EMC)/copper leadframe interface was selected in this study. A series of button shear tests were conducted to evaluate the interfacial adhesion between the EMC and copper. In each test, the failure load acting on the EMC of the button shear sample was measured at different shear angles and a finite element model was used to evaluate the stresses at the EMC/copper interface. In this paper, an energy-based failure criterion is proposed using both the interfacial distortional and hydrostatic strain energy densities as two failure parameters. Stresses were extracted from the numerical simulation in order to calculate the interfacial distortional strain energy density, U-d, and the interfacial hydrostatic strain energy density, U-h, related, respectively, to the shear and tensile modes. U-d and U-h were averaged within a selected region of the finite element model where it exhibits high interfacial strain energy density values

Efficacy of aromatherapy (Lavandula angustifolia) as an intervention for agitated behaviours in Chinese older persons with dementia: A cross-over randomized trial

Background: Agitated behaviours among persons with dementia are distressing to both patients and their caregivers. As pharmacological interventions may be limited by their potentially adverse effects, the use of complementary therapies for treatment of agitation has become more popular and aromatherapy is the fastest growing one. Objectives: This study investigates the effectiveness of lavandula angustifolia (lavender) in treating agitated behaviours of demented people in Hong Kong. Methods: It was a cross-over randomized trial. Seventy Chinese older adults with dementia were recruited; half were randomly assigned to the active group (lavender inhalation) for three weeks and then switched to control group (sunflower inhalation) for another three weeks; the other half did the opposite. Clinical response was evaluated using the Chinese versions of Cohen-Mansfield Agitation Inventory (CCMAI) and Neuropsychiatric Inventory (CNPI). Results: The mean CCMAI total scores decreased from 24.68 to 17.77(t = 10.79, df = 69, p < 0.001). The CNPI scores changed from 63.17 (SD = 17.81) to 58.77 (SD = 16.74) (t = 14.59, df = 69, p < 0.001) after receiving Treatment A (Lavandula Angustifolia). There were no period and sequential effects noted. Conclusion: In summary, lavender is effective as an adjunctive therapy in alleviating agitated behaviours in Chinese patients with dementia. In a patient population particularly vulnerable to side effects of psychotropic medications, aromatherapy using lavender may offer an alternative option. Copyright © 2007 John Wiley & Sons, Ltd.link_to_subscribed_fulltex

Energy based failure criterion for interfacial delamination

Plastic integrated circuit packages can fail due to delamination between the interfaces of the different materials. The adhesion properties across the interface of the epoxy encapsulant and the substrate are important to package reliability. The button shear test is one of the standard tests carried out to evaluate the interfacial adhesion material properties. This paper presents a method to derive a criterion for interfacial delamination using the result of the button shear test. A series of button shear tests was conducted to evaluate the adhesion properties of Epoxy Molding Compounds (EMCs) on copper substrate. In each of the tests, the critical load acting on the EMC of the button shear sample was measured at different shear heights and a finite element model was used to evaluate the stresses at the interface between the mold compound and the copper substrate. The distortional and hydrostatic strain energy densities across the interface were also calculated. The test was also applied to a range of EMC materials. The distortional energy was found to have a linear relationship with the square of the fracture load and the EMC's Young's Modulus. The hydrostatic energy was also found to have a similar but marginally different relationship with those terms. The result of the energy densities across the interface at different shear heights was also reviewed. Based on these observations, a delamination criterion was developed which includes the ratio of the distortional and hydrostatic energy density. The delamination criterion is to be tested on packages under thermal loading