The penetrance and characteristics of contact lens wear in Australia

Background A population-based, cross-sectional telephone survey was conducted to estimate the penetrance and characteristics of contact lens wear in Australia. Methods Based on postcode distribution, 42,749 households around Australia were randomly selected from the national electronic telephone directory. During calls, the number of individuals and contact lens wearers in each household aged between 15 and 64 years was ascertained. Contact lens wearers were interviewed using a structured questionnaire, to determine details of demographics, lens type, mode of lens wear and hygienic habits. Contact lens wear characteristics and habits were compared by lens type and mode of use. Results Of the 32,405 households contacted, 19,171 (59.2 per cent) agreed to participate. The penetrance of contact lens wear during the study period was 5.01 per cent (95% CI: 4.78-5.24). The mean age of lens wearers was 36.5 ± 18.3 years and 63.4 per cent were female. There were significant differences in the habits and characteristics of lens wearers depending on their lens type and mode of use. Conclusions The penetrance of contact lens wear concurs with market estimates and equates to approximately 680,000 contact lens wearers aged between 15 and 64 years in Australia. This is the most detailed and extensive population-based survey of contact lens wearers ever conducted. The discrepancies found between the characteristics of lens wearers surveyed in this study compared to those in previous studies of contact lens practitioners highlights the importance of study design. These results may be applied to other regions with similar health-care and regulatory systems.

Task modeling for collaborative authoring

Motivation ?Task analysis for designing modern collaborative work needs a more fine grained approach. Especially in a complex task domain, like collaborative scientific authoring, when there is a single overall goal that can only be accomplished only by collaboration between multiple roles, each requiring its own expertise. We analyzed and re-considered roles, activities, and objects for design for complex collaboration contexts. Our main focus is on a generic approach to design for multiple roles and subtasks in a domain with a shared overall goal, which requires a detailed approach. Collaborative authoring is our current example. This research is incremental: an existing task analysis approach (GTA) is reconsidered by applying it to a case of complex collaboration. Our analysis shows that designing for collaboration indeed requires a refined approach to task modeling: GTA, in future, will need to consider tasks at the lowest level that can be delegated or mandates. These tasks need to be analyzed and redesigned in more in detail, along with the relevant task object.

Associations between individual and workplace risk factors for self-reported neck pain and disability among female office workers

A cross-sectional survey of female office workers (n=333) was undertaken to determine the level of neck pain and disability (Neck Disability Index—NDI) and to explore the relationship between individual and workplace risk factors with the NDI score and the presence of pain. Workers reported nil (32%), mild (53%), moderate (14%) and severe (1%) neck pain. There were more risk factors associated with the NDI score than the presence of neck pain. The presence of neck pain was associated with a history of neck trauma (OR: 4.8), using a graduated lens (OR: 4.6), and negative affectivity (OR: 2.7) in the multiple regression model. Factors associated with higher NDI score were using the computer mouse for more than 6 h per day, higher negative affectivity, older age and an uncomfortable workstation. These results suggest that measuring the level of neck pain and disability rather than just the presence of neck pain provides more specific directives for the prevention and management of this disorder.

Organizational factors impacting on patient satisfaction : a cross sectional examination of service climate and linkages to nurses' effort and performance

Background Patient satisfaction is influenced by the setting in which patients are treated and the employees providing care. However, to date, limited research has explained how health care organizations or nurses influence patient satisfaction. Objectives The purpose of this study was to test the model that service climate would increase the effort and performance of nursing groups and, in turn, increase patient satisfaction. Method This study incorporated data from 156 nurses, 28 supervisors, and 171 patients. A cross-sectional design was utilized to examine the relationship between service climate, nurse effort, nurse performance and patient satisfaction. Structural equation modeling was conducted to test the proposed relationships. Results Service climate was associated with the effort that nurses directed towards technical care and extra-role behaviors. In turn, the effort that nurses exerted predicted their performance, as rated by their supervisors. Finally, task performance was a significant predictor of patient satisfaction. Conclusions This study suggests that both hospital management and nurses play a role in promoting patient satisfaction. By focusing on creating a climate for service, health care managers can improve nursing performance and patient satisfaction with care.

Mitigation of distorted and unbalanced stator voltage of stand-alone doubly fed induction generators using repetitive control technique

Unbalanced or non-linear loads result in distorted stator currents and electromagnetic torque pulsations in stand-alone doubly fed induction generators (DFIGs). This study proposes the use of a proportional-integral repetitive control (PIRC) scheme so as to mitigate the levels of harmonic and unbalance at the stator terminals of the DFIG. The PIRC is structurally simpler and requires much less computation than existing methods. Analysis of the PIRC operation and the methodology to determine the control parameters is included. Simulation study as well as laboratory test measurements demonstrate clearly the effectiveness of the proposed PIRC control scheme.

Mode matching pursuit for estimating dominant modes in bulk power grid

This study presents a general approach to identify dominant oscillation modes in bulk power system by using wide-area measurement system. To automatically identify the dominant modes without artificial participation, spectral characteristic of power system oscillation mode is applied to distinguish electromechanical oscillation modes which are calculated by stochastic subspace method, and a proposed mode matching pursuit is adopted to discriminate the dominant modes from the trivial modes, then stepwise-refinement scheme is developed to remove outliers of the dominant modes and the highly accurate dominant modes of identification are obtained. The method is implemented on the dominant modes of China Southern Power Grid which is one of the largest AC/DC paralleling grids in the world. Simulation data and field-measurement data are used to demonstrate high accuracy and better robustness of the dominant modes identification approach.

Evaluation of a community-based intervention to promote physical activity in youth : lessons from active winners

Purpose To test the effects of a community-based physical activity intervention designed to increase physical activity and to conduct an extensive process evaluation of the intervention. Design Quasi-experimental. Setting Two rural communities in South Carolina. One community received the intervention, and the other served as the comparison. Subjects Public school students who were in fifth grade at the start of the study (558 at baseline) were eligible to participate. A total of 436 students participated over the course of the study. Intervention The intervention included after-school and summer physical activity programs and home, school, and community components designed to increase physical activity in youth. The intervention took place over an 18-month period. Measures. Students reported after-school physical activity at three data collection points (prior to, during, and following the intervention) using the Previous Day Physical Activity Recall (PDPAR). They also completed a questionnaire designed to measure hypothesized psychosocial and environmental determinants of physical activity behavior The process evaluation used meeting records, documentation of program activities, interviews, focus groups, and heart rate monitoring to evaluate the planning and implementation of the intervention. Results There were no significant differences in the physical activity variables and few significant differences in the psychosocial variables between the intervention and comparison groups. The process evaluation indicated that the after-school and summer physical activity component of the intervention was implemented as planned, but because of resource and time limitations, the home, school, and community components were not implemented as planned. Conclusions The intervention did not have a significant effect on physical activity in the target population of children in the intervention community. This outcome is similar to that reported in other studies of community-based physical activity intervention.

Bit-stream-based space vector modulators

Bit-stream-based control, which uses one bit wide signals to control power electronics applications, is a new approach for controller design in power electronic systems. This study presents a novel family of three-phase space vector modulators, which are based on the bit-stream technique and suitable for three-phase inverter systems. Each of the proposed modulators simultaneously converts a two-phase reference to the three-phase domain and reduces switching frequencies to reasonable levels. The modulators do not require carrier oscillators, trigonometric functions or, in some cases, sector detectors. A complete three-phase modulator can be implemented in as few as 102 logic elements. The performance of the proposed modulators is compared through simulation and experimental testing of a 6 kW, three-phase DC-to-AC inverter. Subject to limits on the modulation index, the proposed modulators deliver spread-spectrum output currents with total harmonic distortion comparable to a standard carrier-based space vector pulse width modulator.

Cascade multilevel static synchronous compensator configuration for wind farms

Modulation and control of a cascade multilevel static synchronous compensator (STATCOM) configuration to improve the quality of voltage generated by wind power systems are presented. The proposed STATCOM configuration needs only four dc-link capacitors and 24 switches to synthesise nine-level operation. In addition to that, switching losses are further reduced by splitting the voltage source inverter of the STATCOM into two units called the `bulk inverter` and the `conditioning inverter`. The high-power bulk inverter is operated at low frequency whereas the low-power conditioning inverter is operated at high frequency to suppress harmonics produced by the bulk inverter. Fluctuations at the point of common coupling voltage, caused by sudden wind changes, are suppressed by controlling reactive power of the STATCOM. Simulation and experimental results are presented to verify the efficacy of the proposed modulation and control techniques used in the STATCOM.

Five-level Z-source diode-clamped inverter

This study proposes a five-level Z-source diode-clamped inverter designed with two intermediate Z-source networks connected between the dc input sources and rear-end inverter circuitry. By partially shorting the Z-source networks, new operating states not previously reported for two-level Z-source inverter are introduced here for operating the proposed inverter with voltage buck-boost energy conversion ability and five-level phase voltage switching. These characteristic features are in fact always ensured at the inverter terminal output by simply adopting a properly designed carrier modulation scheme, which always inserts two partial shoot-through states per half carrier cycle for smooth balanced operation. Theoretical findings and practical issues identified are eventually verified by constructing a scaled down laboratory prototype for testing.

Objectively measured physical activity behavior in children attending a half day preschool program

Obesity rates are increasing in children of all ages, and reduced physical activity (PA) is a likely contributor to this trend. Little is known about the physical activity behavior of preschool-age children, or about the influence of preschool attendance on physical activity. Purpose The purpose of this study was to quantify the physical activity levels of children attending a center-based half-day preschool program. Methods Forty-two 3-to-5-year old children (Mean age = 4.0 ± 0.7, 54.8% Male, Mean BMI = 16.5 ± 5.5, Mean BMI %tile = 52.1 ± 33.5) from four class groups (two morning and two afternoon), wore an Actigraph 7164 accelerometer for the entire halfday program (including classroom learning experiences, snack and recess time) 2 times per week, for 10 weeks (20 activity monitoring records in total). Activity counts for each 5-sec interval were uploaded to a customized data reduction program to determine total counts, minutes of moderate PA (MPA) (3–5.9 METs), and minutes of vigorous PA (VPA) (> = 6 METs) per session. Counts were categorized as either MPA or VPA using the cutpoints developed by Sirard and colleagues (2001). Results Across the four 2.5 hour programs, the average MPA, VPA and total counts (× 103) were 12.4 ± 3.1 minutes, 18.3 ± 4.6 minutes, and 171.1 ± 29.7 counts, respectively. Thus, on average, children accumulated just over 12 minutes of moderateto-vigorous PA per hour of program attendance. The PA variables did not differ significantly by gender, weight status, or time of day. There were, however, significant age differences, with 3-year-olds exhibiting significantly less PA than their 4- and 5-year-old counterparts. Conclusions These results suggest that young children are relatively lowactive while attending preschool. Accordingly, interventions to increase movement opportunities during the preschool day are warranted.

Taxonomic resolution and quantification of freshwater macroinvertebrate samples from an Australian dryland river : The benefits and costs of using species abundance data

In studies using macroinvertebrates as indicators for monitoring rivers and streams, species level identifications in comparison with lower resolution identifications can have greater information content and result in more reliable site classifications and better capacity to discriminate between sites, yet many such programmes identify specimens to the resolution of family rather than species. This is often because it is cheaper to obtain family level data than species level data. Choice of appropriate taxonomic resolution is a compromise between the cost of obtaining data at high taxonomic resolutions and the loss of information at lower resolutions. Optimum taxonomic resolution should be determined by the information required to address programme objectives. Costs saved in identifying macroinvertebrates to family level may not be justified if family level data can not give the answers required and expending the extra cost to obtain species level data may not be warranted if cheaper family level data retains sufficient information to meet objectives. We investigated the influence of taxonomic resolution and sample quantification (abundance vs. presence/absence) on the representation of aquatic macroinvertebrate species assemblage patterns and species richness estimates. The study was conducted in a physically harsh dryland river system (Condamine-Balonne River system, located in south-western Queensland, Australia), characterised by low macroinvertebrate diversity. Our 29 study sites covered a wide geographic range and a diversity of lotic conditions and this was reflected by differences between sites in macroinvertebrate assemblage composition and richness. The usefulness of expending the extra cost necessary to identify macroinvertebrates to species was quantified via the benefits this higher resolution data offered in its capacity to discriminate between sites and give accurate estimates of site species richness. We found that very little information (<6%) was lost by identifying taxa to family (or genus), as opposed to species, and that quantifying the abundance of taxa provided greater resolution for pattern interpretation than simply noting their presence/absence. Species richness was very well represented by genus, family and order richness, so that each of these could be used as surrogates of species richness if, for example, surveying to identify diversity hot-spots. It is suggested that sharing of common ecological responses among species within higher taxonomic units is the most plausible mechanism for the results. Based on a cost/benefit analysis, family level abundance data is recommended as the best resolution for resolving patterns in macroinvertebrate assemblages in this system. The relevance of these findings are discussed in the context of other low diversity, harsh, dryland river systems.

Clinical faculty : major contributors to the education of new CRNAs - Part 2

This study examines the important contributions of clinical faculty toward the education of the future workforce of Certified Registered Nurse Anesthetists (CRNAs). Differences in workload, work activities and income among clinical faculty, academic faculty and nonfaculty are examined. This is Part 2 of a 2-part column. Part 1, published in the April 2008 AANA Journal discussed salaries, recruitment, and retention of CRNA faculty.

Controlling current and voltage type interfaces in power-hardware-in-the-loop simulations

The usual practice to study a large power system is through digital computer simulation. However, the impact of large scale use of small distributed generators on a power network cannot be evaluated strictly by simulation since many of these components cannot be accurately modelled. Moreover, the network complexity makes the task of practical testing on a physical network nearly impossible. This study discusses the paradigm of interfacing a real-time simulation of a power system to real-life hardware devices. This type of splitting a network into two parts and running a real-time simulation with a physical system in parallel is usually termed as power-hardware-in-the-loop (PHIL) simulation. The hardware part is driven by a voltage source converter that amplifies the signals of the simulator. In this paper, the effects of suitable control strategy on the performance of PHIL and the associated stability aspects are analysed in detail. The analyses are validated through several experimental tests using an real-time digital simulator.