ORCID Profile
0000-0001-8786-6429
Current Organisation
University of Canterbury
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Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 02-2012
Publisher: AIP Publishing
Date: 28-12-2018
DOI: 10.1063/1.5054355
Abstract: Size-controlled ZnO nanowires were grown by eclipse pulsed laser deposition using Au colloids and ultra-small (sub 2 nm) Au101 and Au9 clusters as catalysts, tethered to c-plane sapphire substrates using aminopropyltrimethoxysilane (APTMS). A strong correlation was observed between ZnO nanowire tip diameter and Au catalyst size, with no apparent lower limit to the size of Au nanoparticles able to catalyze nanowire growth. All ZnO nanowires produced intense ultraviolet photoluminescence with almost no visible defect band emission that is commonly observed in ZnO-based materials, including nanowires. A correlation was also observed between the quality of the ultraviolet photoluminescence (in terms of decreasing exciton line widths and surface-related emission) and decreasing ZnO nanowire diameter, with the highest quality emission obtained using Au9 atomically precise cluster catalysts, used here as catalysts for ZnO growth for the first time.
Publisher: American Chemical Society (ACS)
Date: 25-04-2023
Publisher: American Physical Society (APS)
Date: 19-02-2010
Publisher: American Physical Society (APS)
Date: 13-07-2020
Publisher: AIP Publishing
Date: 10-12-2012
DOI: 10.1063/1.4769899
Abstract: We report on the properties of metal-semiconductor-field-effect-transistors (MESFETs) on ZnO films grown using the filtered cathodic vacuum arc (FCVA) technique. FCVA ZnO films deposited on a-plane sapphire at 200 °C showed good structural and electrical properties that improved further on annealing at 800 °C in oxygen, due to the formation of larger grains with lower inter-grain transport barriers. MESFETs with silver oxide and iridium oxide Schottky gates on these annealed films showed excellent long-term stability with low ideality factors (& .3), low gate leakage, and channel mobilities up to 50 cm2/Vs that were unchanged with both age and stress testing.
Publisher: JMIR Publications Inc.
Date: 19-12-2017
Abstract: kin cancer is the most prevalent cancer in Australia. Skin cancer prevention programs aim to reduce sun exposure and increase sun protection behaviors. Effectiveness is usually assessed through self-report. t was the aim of this study to test the acceptance and validity of a newly developed ultraviolet radiation (UVR) exposure app, designed to reduce the data collection burden to research participants. Physical activity data was collected because a strong focus on sun avoidance may result in unhealthy reductions in physical activity. This paper provides lessons learned from collecting data from participants using paper diaries, a mobile app, dosimeters, and accelerometers for measuring end-points of UVR exposure and physical activity. wo participant groups were recruited through social and traditional media c aigns 1) Group A—UVR Diaries and 2) Group B—Physical Activity. In Group A, nineteen participants wore an UVR dosimeter wristwatch (University of Canterbury, New Zealand) when outside for 7 days. They also recorded their sun exposure and physical activity levels using both 1) the UVR diary app and 2) a paper UVR diary. In Group B, 55 participants wore an accelerometer (Actigraph, Pensacola, FL, USA) for 14 days and completed the UVR diary app. Data from the UVR diary app were compared with UVR dosimeter wristwatch, accelerometer, and paper UVR diary data. Cohen kappa coefficient score was used to determine if there was agreement between categorical variables for different UVR data collection methods and Spearman rank correlation coefficient was used to determine agreement between continuous accelerometer data and app-collected self-report physical activity. he mean age of participants in Groups A (n=19) and B (n=55) was 29.3 and 25.4 years, and 63% (12/19) and 75% (41/55) were females, respectively. Self-reported sun exposure data in the UVR app correlated highly with UVR dosimetry (κ=0.83, 95% CI 0.64-1.00, P .001). Correlation between self-reported UVR app and accelerometer-collected moderate to vigorous physical activity data was low (ρ=0.23, P=.10), while agreement for low-intensity physical activity was significantly different (ρ=-0.49, P .001). Seventy-nine percent of participants preferred the app over the paper diary for daily self-report of UVR exposure and physical activity. his feasibility study highlights self-report using an UVR app can reliably collect personal UVR exposure, but further improvements are required before the app can also be used to collect physical activity data.
Publisher: IEEE
Date: 12-2010
Publisher: IEEE
Date: 03-2011
Publisher: Elsevier BV
Date: 02-2022
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2020
Publisher: Elsevier BV
Date: 08-2012
Publisher: Elsevier BV
Date: 08-2012
Publisher: Wiley
Date: 18-09-2012
DOI: 10.1111/J.1751-1097.2012.01221.X
Abstract: Self-reported sun exposure is commonly used in research, but how well this represents actual sun exposure is poorly understood. From February to July 2011, a volunteer s le (n = 47) of older adults (≥45 years) in Canberra, Australia, answered brief questions on time outdoors (weekdays and weekends) and natural skin color. They subsequently maintained a sun diary and wore an ultraviolet radiation (UVR) digital dosimeter for 7 days. Melanin density was estimated using reflectance spectrophotometry lifetime sun damage was assessed using silicone casts of the back of the hand and serum 25-hydroxyvitamin D (25(OH)D) concentration was assayed. Questionnaire-reported time outdoors correlated significantly with diary-recorded time outdoors (Spearman correlation r(s) = 0.66 95% CI 0.46, 0.80 P < 0.001) and UVR dosimeter dose (r(s ) = 0.46 95% CI 0.18, 0.68 P = 0.003), but not 25(OH)D concentration (r(s) = 0.24 95% CI -0.05, 0.50 P = 0.10). Questionnaire-reported untanned skin color correlated significantly with measured melanin density at the inner upper arm (r(s) = 0.49 95% CI 0.24, 0.68 P < 0.001). In a multiple linear regression model, statistically significant predictors of 25(OH)D concentration were self-reported frequency of physical activity, skin color and recent osteoporosis treatment (R(2) = 0.54). In this study, brief questionnaire items provided valid rankings of sun exposure and skin color, and enabled the development of a predictive model for 25(OH)D concentration.
Publisher: JMIR Publications Inc.
Date: 17-04-2018
DOI: 10.2196/RESPROT.9695
Publisher: Wiley
Date: 17-05-0005
Abstract: Nanotechnology has delivered an amazing range of new materials such as nanowires, tubes, ribbons, belts, cages, flowers, and sheets. However, these are usually circular, cylindrical, or hexagonal in nature, while nanostructures with square geometries are comparatively rare. Here, a highly scalable method is reported for producing vertically aligned Sb‐doped SnO 2 nanotubes with perfectly‐square geometries on Au nanoparticle covered m ‐plane sapphire using mist chemical vapor deposition. Their inclination can be varied using r ‐ and a ‐plane sapphire, while unaligned square nanotubes of the same high structural quality can be grown on silicon and quartz. X‐ray diffraction measurements and transmission electron microscopy show that they adopt the rutile structure growing in the [001] direction with (110) sidewalls, while synchrotron X‐ray photoelectron spectroscopy reveals the presence of an unusually strong and thermally resilient 2D surface electron gas. This is created by donor‐like states produced by the hydroxylation of the surface and is sustained at temperatures above 400 °C by the formation of in‐plane oxygen vacancies. This persistent high surface electron density is expected to prove useful in gas sensing and catalytic applications of these remarkable structures. To illustrate their device potential, square SnO 2 nanotube Schottky diodes and field effect transistors with excellent performance characteristics are fabricated.
Publisher: American Chemical Society (ACS)
Date: 15-12-2021
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.JID.2018.12.025
Abstract: Animal and human studies show that exposure to solar-simulated UVR is immunomodulatory. Human studies that used natural sun exposure and controlled for confounding are rare. We immunized 217 healthy adults (age range = 18-40 years) with a T-cell-dependent antigen, keyhole limpet hemocyanin, and measured personal clothing-adjusted UVR exposure (for 5 days before and after immunization), lifetime cumulative UVR exposure, serum 25-hydroxyvitamin D concentration at immunization, and potential confounding factors. We tested cellular and humoral immune responses in relation to UVR exposure. The delayed-type hypersensitivity response to keyhole limpet hemocyanin recall challenge was lower in in iduals with higher personal clothing-adjusted UVR exposure on the day before immunization (P = 0.015) and during intervals spanning the day before to 2-3 days after immunization. There was an incremental increase in T helper type 17 cells (as a proportion of CD4
Publisher: Springer Science and Business Media LLC
Date: 30-06-2020
DOI: 10.1186/S13063-020-04351-W
Abstract: The Melanoma Genomics Managing Your Risk Study is a randomised controlled trial that aims to evaluate the efficacy of providing information on personal genomic risk of melanoma in reducing ultraviolet radiation (UV) exposure, stratified by traditional risk group (low or high phenotypic risk) in the general population. The primary outcome is objectively measured total daily Standard Erythemal Doses at 12 months. Secondary outcomes include UV exposure at specific time periods, self-reported sun protection and skin-examination behaviours, psychosocial outcomes, and ethical considerations surrounding offering genomic testing at a population level. A within-trial and modelled economic evaluation will be undertaken from an Australian health system perspective to assess the cost-effectiveness of the intervention. To publish the pre-determined statistical analysis plan (SAP) before database lock and the start of analysis. This SAP describes the data synthesis, analysis principles and statistical procedures for analysing the outcomes from this trial. The SAP was approved after closure of recruitment and before completion of patient follow-up. It outlines the planned primary analyses and a range of subgroup and sensitivity analyses. Health economic outcomes are not included in this plan but will be analysed separately. The SAP will be adhered to for the final data analysis of this trial to avoid potential analysis bias that may arise from knowledge of the outcome data. This SAP is consistent with best practice and should enable transparent reporting. This SAP has been developed for the Melanoma Genomics Managing Your Risk Study and will be followed to ensure high-quality standards of internal validity and to minimise analysis bias. Prospectively registered with the Australian New Zealand Clinical Trials Registry, ID: ACTR N12617000691347 . Registered on 15 May 2017.
Publisher: AIP Publishing
Date: 07-03-2011
DOI: 10.1063/1.3562308
Abstract: Significant polarity-related effects were observed in the near-surface atomic composition and valence band electronic structure of ZnO single crystals, investigated by x-ray photoemission spectroscopy using both Al Kα (1486.6 eV) and synchrotron radiation (150 to 1486 eV). In particular, photoemission from the lowest binding energy valence band states was found to be significantly more intense on the Zn-polar face compared to the O-polar face. This is a consistent effect that can be used as a simple, nondestructive indicator of crystallographic polarity in ZnO and other wurtzite semiconductors.
Publisher: Wiley
Date: 2016
DOI: 10.1111/PHP.12551
No related grants have been discovered for Martin Allen.