The correlation between electric field emission phenomenon and Schottky contact reverse bias characteristics in nanostructured systems

Two different morphologies of nanotextured molybdenum oxide were deposited by thermal evaporation. By measuring their field emission (FE) properties, an enhancement factor was extracted. Subsequently, these films were coated with a thin layer of Pt to form Schottky contacts. The current-voltage (I-V) characteristics showed low magnitude reverse breakdown voltages, which we attributed to the localized electric field enhancement. An enhancement factor was obtained from the I-V curves. We will show that the enhancement factor extracted from the I-V curves is in good agreement with the enhancement factor extracted from the FE measurements.

Reverse biased Schottky contact hydrogen sensors based on Pt∕nanostructured ZnO∕SiC

Pt/nanostructured ZnO/SiC Schottky contact devices were fabricated and characterized for hydrogen gas sensing. These devices were investigated in reverse bias due to greater sensitivity, which attributes to the application of nanostructured ZnO. The current-voltage (I-V) characteristics of these devices were measured in different hydrogen concentrations. Effective change in the barrier height for 1% hydrogen was calculated as 27.06 meV at 620°C. The dynamic response of the sensors was also investigated and a voltage shift of 325 mV was recorded at 620°C during exposure to 1% hydrogen in synthetic air.

Non-contact ACL injuries : association with clegg soil impact test values for sports fields, soil moisture and prevailing weather

Introduction: There is a recognised relationship between dry weather conditions and increased risk of anterior cruciate ligament (ACL) injury. Previous studies have identified 28 day evaporation as an important weather-based predictor of non-contact ACL injuries in professional Australian Football League matches. The mechanism of non-contact injury to the ACL is believed to increased traction and impact forces between footwear and playing surface. Ground hardness and the amount and quality of grass are factors that would most likely influence this and are inturn, related to the soil moisture content and prevailing weather conditions. This paper explores the relationship between soil moisture content, preceding weather conditions and the Clegg Soil Impact Test (CSIT) which is an internationally recognised standard measure of ground hardness for sports fields. Methodology: The 2.25 kg Clegg Soil Impact Test and a pair of 12 cm soil moisture probes were used to measure ground hardness and percentage moisture content. Five football fields were surveyed at 13 prescribed sites just before seven football matches from October 2008 to January 2009 (an FC Women’s WLeague team). Weather conditions recorded at the nearest weather station were obtained from the Bureau of Meteorology website and total rainfall less evaporation was calculated for 7 and 28 days prior to each match. All non-contact injuries occurring during match play and their location on the field were recorded. Results/conclusions: Ground hardness varied between CSIT 5 and 17 (x10G) (8 is considered a good value for sports fields). Variations within fields were typically greatest in the centre and goal areas. Soil moisture ranged from 3 to 40% with some fields requiring twice the moisture content of others to maintain similar CSIT values. There was a non-linear, negative relationship for ground hardness versus moisture content and a linear relationship with weather (R2, of 0.30 and 0.34, respectively). Three non-contact ACL injuries occurred during the season. Two of these were associated with hard and variable ground conditions.

Molecular dynamics study of ‘contact epitaxy’ in Ag clusters supported on a copper (001) surface

In this paper, the formation of heteroepitaxial interfacial layers was investigated by molecular dynamics simulation of soft silver particles landing on the (001) surface of single-crystal copper. In our simulations, the clusters Ag13, Ag55, Ag147 and Ag688 were chosen as projectiles. A small cluster will rearrange into an f.c.c. structure when it is supported on the substrate, due to the large value of its surface/volume ratio. Contact epitaxy appeared in large clusters. The characteristic structure of an epitaxial layer in large silver cluster shows the 〈111〉 direction to be the preferential orientation of heteroepitaxial layers on the surface because of the lattice mismatch between the cluster and the substrate. This was confirmed by studying soft landing events in other systems (Au/Cu and Al/Ni).

Energy efficient virtual machine placement in data centers

Electricity cost has become a major expense for running data centers and server consolidation using virtualization technology has been used as an important technology to improve the energy efficiency of data centers. In this research, a genetic algorithm and a simulation-annealing algorithm are proposed for the static virtual machine placement problem that considers the energy consumption in both the servers and the communication network, and a trading algorithm is proposed for dynamic virtual machine placement. Experimental results have shown that the proposed methods are more energy efficient than existing solutions.

Through-focus performance with multifocal contact lenses : effect of binocularity, pupil diameter and inherent ocular aberrations

Purpose to evaluate the effects of the wearer’s pupil size and spherical aberration on visual performance with centre-near, aspheric multifocal contact lenses (MFCLs). The advantage of binocular over monocular vision was also investigated. Methods Twelve young volunteers, with an average age of 27±5 years, participated in the study. LogMAR Visual Acuity (VA) was measured under cycloplegia for a range of defocus levels (from +3.0 to -3.0D, in 0.5D steps) with no correction and with three aspheric MFCLs (Air Optix Aqua Multifocal, Ciba Vision, Duluth, GA, US) with a centre-near design, providing correction for “Low”, “Med” and “High” near demands. Measurements were performed for all combinations of the following conditions: i) artificial pupils of 6mm and 3mm diameter, ii) binocular and monocular (dominant eye) vision. Depth-of-focus (DOF) was calculated from the VA vs. defocus curves. Ocular aberrations under cycloplegia were measured using iTrace. Results VA at -3.0D defocus (simulating near performance) was statistically higher for the 3mm than for the 6mm pupil (p=0.006), and for binocular rather than for monocular vision (p<0.001). Similarly, DOF was better for the 3mm pupil (p=0.002) and for binocular viewing conditions (p<0.001, ANOVA). Both VA at –3.0D defocus and DOF increased as the “addition” of the MFCL correction increased. Finally, with the centre-near MFCLs a linear correlation was found between VA at –3.0D defocus and the wearer’s ocular spherical aberration (R2=0.20 p<0.001 for 6mm data), with the eyes exhibiting the higher positive spherical aberration experiencing lower VAs. By contrast, no correlation was found between VA and spherical aberration at 0.00D defocus (distance vision). Conclusions Both near VA and depth-of-focus improve with these MFCLs, with the effects being more pronounced for small pupils and binocular than for monocular vision. Coupling of the wearer’s ocular spherical aberration with the aberration profiles provided by MFCLs affects their functionality.

The impact of community health professional contact postpartum on breastfeeding at 3 months : a cross-sectional retrospective study

This study investigated the effect of any health professional contact and the types of contact new mothers received in the first 10 days post-discharge on breastfeeding rates at 3 months. This cross-sectional retrospective self-report survey was distributed to women who birthed in Queensland, Australia between 1st February and 31st May 2010 at 4–5 months postpartum. Data were collected on pregnancy, birth, postpartum care and infant feeding. Logistic regression was used to assess the relationship between health professional contact and breastfeeding at 3 months. Data were analysed by birthing facility sector because of significant differences between sectors in health professional contact. The study cohort consisted of 6,852 women. Women in the public sector were more likely to be visited at home than women birthing in the private sector. Any health professional contact (AOR 1.65 99 % CI 0.98–2.76 public sector, AOR 0.78 99 % CI 0.59–1.03 private sector) and home visits (AOR 1.50 99 % CI 0.89–2.54 public sector, AOR 0.80 99 % CI 0.46–1.39 private sector) were not associated with breastfeeding at 3 months in either sector. A telephone call (AOR 2.07 99 % CI 1.06–4.03) or visit to a general practitioner (GP) (AOR 1.83 99 % CI 1.04–3.21) increased the odds of breastfeeding in public sector women. Health professional contact or home visiting in the first 10 days post-discharge did not have a significant impact on breastfeeding rates at 3 months. Post-discharge telephone contact for all women and opportunities for self-initiated clinic visits for women assessed to be at higher risk of ceasing breastfeeding may be the most effective care.

Hexagon platinum Schottky contact with ZnO thin film for hydrogen sensing

This paper reports on the study of the effect on adding total peripheries and sharp edges to the Schottky contact as a hydrogen sensor. Schottky contact was successfully designed and fabricated as hexagon-shape. The contact was integrated together with zinc oxide thin film and tested towards 1% hydrogen gas. Simulations of the design were conducted using COMSOL Multiphysics to observe the electric field characteristic at the contact layer. The simulation results show higher electric field induced at sharp edges with 4.18×104 V/m. Current-voltage characteristic shows 0.27 V voltage shift at 40 μA biased current.

Power profiles of multifocal contact lenses and their interpretation

Purpose Many contact lens (CL) manufacturers produce simultaneous-image lenses in which power varies either smoothly or discontinuously with zonal radius. We present in vitro measurements of some recent CLs and discuss how power profiles might be approximated in terms of nominal distance corrections, near additions, and on-eye visual performance. Methods Fully hydrated soft, simultaneous-image CLs from four manufacturers (Air Optix AQUA, Alcon; PureVision multifocal, Bausch & Lomb; Acuvue OASYS for Presbyopia, Vistakon; Biofinity multifocal- ‘‘D’’ design, Cooper Vision) were measured with a Phase focus Lens Profiler (Phase Focus Ltd., Sheffield,UK) in a wet cell and powerswere corrected to powers in air. All lenses had zero labeled power for distance. Results Sagittal power profiles revealed that the ‘‘low’’ add PureVision and Air Optix lenses exhibit smooth (parabolic) profiles, corresponding to negative spherical aberration. The ‘‘mid’’ and ‘‘high’’ add PureVision and Air Optix lenses have biaspheric designs, leading to different rates of power change for the central and peripheral portions. All OASYS lenses display a series of concentric zones, separated by abrupt discontinuities; individual profiles can be constrained between two parabolically decreasing curves, each giving a valid description of the power changes over alternate annular zones. Biofinity lenses have constant power over the central circular region of radius 1.5 mm, followed by an annular zone where the power increases approximately linearly, the gradient increasing with the add power, and finally an outer zone showing a slow, linear increase in power with a gradient being almost independent of the add power. Conclusions The variation in power across the simultaneous-image lenses produces enhanced depth of focus. The throughfocusnature of the image, which influences the ‘‘best focus’’ (distance correction) and the reading addition, will vary with several factors, including lens centration, the wearer’s pupil diameter, and ocular aberrations, particularly spherical aberration; visual performance with some designs may show greater sensitivity to these factors.

Non-contact laser-scanning confocal microscopy of the human cornea in vivo

PURPOSE To investigate the utility of using non-contact laser-scanning confocal microscopy (NC-LSCM), compared with the more conventional contact laser-scanning confocal microscopy (C-LSCM), for examining corneal substructures in vivo. METHODS An attempt was made to capture representative images from the tear film and all layers of the cornea of a healthy, 35 year old female, using both NC-LSCM and C-LSCM, on separate days. RESULTS Using NC-LSCM, good quality images were obtained of the tear film, stroma, and a section of endothelium, but the corneal depth of the images of these various substructures could not be ascertained. Using C-LSCM, good quality, full-field images were obtained of the epithelium, subbasal nerve plexus, stroma, and endothelium, and the corneal depth of each of the captured images could be ascertained. CONCLUSIONS NC-LSCM may find general use for clinical examination of the tear film, stroma and endothelium, with the caveat that the depth of stromal images cannot be determined when using this technique. This technique also facilitates image capture of oblique sections of multiple corneal layers. The inability to clearly and consistently image thin corneal substructures - such as the tear film, subbasal nerve plexus and endothelium - is a key limitation of NC-LSCM.

An international survey of daily disposable contact lens prescribing

Purpose The aim was to determine the extent of daily disposable contact lens prescribing worldwide and to characterise the associated demographics and fitting patterns. Methods Up to 1,000 survey forms were sent to contact lens fitters in up to 40 countries between January and March every year for five consecutive years (2007 to 2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Survey data collected since 1996 were also analysed for seven nations to assess daily disposable lens fitting trends since that time. Results Data were collected in relation to 97,289 soft lens fits, of which 23,445 (24.1 per cent) were with daily disposable lenses and 73,170 (75.9 per cent) were with reusable lenses. Daily disposable lens prescribing ranged from 0.6 per cent of all soft lenses in Nepal to 66.2 per cent in Qatar. Compared with reusable lens fittings, daily disposable lens fittings can be characterised as follows: older age (30.0 ± 12.5 versus 29.3 ± 12.3 years for reusable lenses); males are over-represented; a greater proportion of new fits versus refits; 85.9 per cent hydrogel; lower proportion of toric and presbyopia designs and a higher proportion of part-time wear. There has been a continuous increase in daily disposable lens prescribing between 1996 and 2011. The proportion of daily disposable lens fits (as a function of all soft lens fits) is positively related to the gross domestic product at purchasing power parity per capita (r2 = 0.55, F = 46.8, p < 0.0001). Conclusions The greater convenience and other benefits of daily disposable lenses have resulted in this modality capturing significant market share. The contact lens field appears to be heading toward a true single-use-only, disposable lens market.

2. Contact lens care and ocular surface homeostasis

Moderator Opening The early focus of contact lens wear and ocular health was on oxygen delivery. However, as we learn more about how the eye works, and investigate how the contact lens interacts with the cornea, the role of the tear film has risen in prominence. A healthy tear film is critical for normal ocular homeostasis, and abnormalities of the tear film are the primary cause of dry eye. In order to improve patient eye health and comfort during lens wear, we need to further elucidate the relationship among contact lenses, contact lens solutions, the tear film, and the corneal epithelium, and find ways to maintain homeostasis of the ocular surface. In this section, we review the latest data and opinions on this complex relationship between contact lenses and lens care solutions

Ocular surface health with contact lens wear

Eye care practitioners (ECPs) would tend to agree that wearing contact lenses increases the risk for infection, but millions of patients are still fitted with lenses every year because ECPs feel that the risk is manageable and that their patients' eye health can be protected. The Fusarium and Acanthamoeba keratitis outbreaks of years past were a wake-up call to manufacturers, ECPs, and regulatory agencies that risk cannot be managed without diligence, and that the complex relationship between contact lens materials, contact lens solutions, and compliance needs to be better understood in order to optimize the efficacy of contact lens care and improve care guidelines.

International survey of rigid contact lens fitting

Purpose To determine the extent of rigid contact lens fitting worldwide and to characterize the associated demographics and fitting patterns. Methods Survey forms were sent to contact lens fitters in up to 40 countries between January and March every year for five consecutive years (2007 to 2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Survey data collected between 1996 and 2011 were also analyzed to assess rigid lens fitting trends in seven nations during this period. Results Data were obtained for 12,230 rigid and 100,670 soft lens fits between 2007 and 2011. Overall, rigid lenses represented 10.8% of all contact lens fits, ranging from 0.2% in Lithuania to 37% in Malaysia. Compared with soft lens fits, rigid lens fits can be characterized as follows: older age (rigid, 37.3 ± 15.0 years; soft, 29.8 ± 12.4 years); fewer spherical and toric fits; more bifocal/multifocal fits; less frequent replacement (rigid, 7%; soft, 85%); and less part-time wear (rigid, 4%; soft, 10%). High-Dk (contact lens oxygen permeability) (36%) and mid-Dk (42%) materials are predominantly used for rigid lens fitting. Orthokeratology represents 11.5% of rigid contact lens fits. There has been a steady decline in rigid lens fitting between 1996 and 2011. Conclusions Rigid contact lens prescribing is in decline but still represents approximately 10% of all contact lenses fitted worldwide. It is likely that rigid lenses will remain as a viable, albeit increasingly specialized, form of vision correction.

An international survey of toric contact lens prescribing

Objectives To characterize toric contact lens prescribing worldwide. Methods Up to 1,000 survey forms were sent to contact lens fitters in up to 39 countries between January and March every year for 5 consecutive years (2007–2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Only data for toric and spherical soft lens fits were analyzed. Survey data collected since 1996 were also analyzed for 7 nations to assess toric lens fitting trends since that time. Results Data were collected in relation to 21,150 toric fits (25%) and 62,150 spherical fits (75%). Toric prescribing ranged from 6% of lenses in Russia to 48% in Portugal. Compared with spherical fittings, toric fittings can be characterized as follows: older age (29.8 ± 11.4 years vs. 27.6 ± 10.8 years for spherical lenses); men are overrepresented (38% vs. 34%); greater proportion of new fits (39% vs. 32%); use of silicone hydrogel lenses (49% vs. 39%); and lower proportion of daily disposable lenses (14% vs. 28%). There has been a continuous increase in toric lens prescribing between 1996 and 2011. The proportion of toric lens fits was positively related to the gross domestic product at purchasing power parity per capita for year 2011 (r2 = 0.21; P=0.004). Conclusions At the present time, in the majority of countries surveyed, toric soft contact lens prescribing falls short of that required to correct clinically significant astigmatism (≥0.75 diopters) in all lens wearers.