Comparison of subjective and objective methods to determine the retinal arterio-venous ratio using fundus photography

Purpose: To assess the inter and intra observer variability of subjective grading of the retinal arterio-venous ratio (AVR) using a visual grading and to compare the subjectively derived grades to an objective method using a semi-automated computer program. Methods: Following intraocular pressure and blood pressure measurements all subjects underwent dilated fundus photography. 86 monochromatic retinal images with the optic nerve head centred (52 healthy volunteers) were obtained using a Zeiss FF450+ fundus camera. Arterio-venous ratios (AVR), central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) were calculated on three separate occasions by one single observer semi-automatically using the software VesselMap (ImedosSystems, Jena, Germany). Following the automated grading, three examiners graded the AVR visually on three separate occasions in order to assess their agreement. Results: Reproducibility of the semi-automatic parameters was excellent (ICCs: 0.97 (CRAE); 0.985 (CRVE) and 0.952 (AVR)). However, visual grading of AVR showed inter grader differences as well as discrepancies between subjectively derived and objectively calculated AVR (all p < 0.000001). Conclusion: Grader education and experience leads to inter-grader differences but more importantly, subjective grading is not capable to pick up subtle differences across healthy individuals and does not represent true AVR when compared with an objective assessment method. Technology advancements mean we no longer rely on opthalmoscopic evaluation but can capture and store fundus images with retinal cameras, enabling us to measure vessel calibre more accurately compared to visual estimation; hence it should be integrated in optometric practise for improved accuracy and reliability of clinical assessments of retinal vessel calibres. © 2014 Spanish General Council of Optometry.

A Statistical Approach for Multilingual Document Clustering and Topic Extraction from Clusters

2000 Mathematics Subject Classification: 62H30

Evaluating techniques to improve visual performance with and assessment of premium intraocular lenses

Premium Intraocular Lenses (IOLs) such as toric IOLs, multifocal IOLs (MIOLs) and accommodating IOLs (AIOLs) can provide better refractive and visual outcomes compared to standard monofocal designs, leading to greater levels of post-operative spectacle independence. The principal theme of this thesis relates to the development of new assessment techniques that can help to improve future premium IOL design. IOLs designed to correct astigmatism form the focus of the first part of the thesis. A novel toric IOL design was devised to decrease the effect of toric rotation on patient visual acuity, but found to have neither a beneficial or detrimental impact on visual acuity retention. IOL tilt, like rotation, may curtail visual performance; however current IOL tilt measurement techniques require the use of specialist equipment not readily available in most ophthalmological clinics. Thus a new idea that applied Pythagoras’s theory to digital images of IOL optic symmetricality in order to calculate tilt was proposed, and shown to be both accurate and highly repeatable. A literature review revealed little information on the relationship between IOL tilt, decentration and rotation and so this was examined. A poor correlation between these factors was found, indicating they occur independently of each other. Next, presbyopia correcting IOLs were investigated. The light distribution of different MIOLs and an AIOL was assessed using perimetry, to establish whether this could be used to inform optimal IOL design. Anticipated differences in threshold sensitivity between IOLs were not however found, thus perimetry was concluded to be ineffective in mapping retinal projection of blur. The observed difference between subjective and objective measures of accommodation, arising from the influence of pseudoaccommodative factors, was explored next to establish how much additional objective power would be required to restore the eye’s focus with AIOLs. Blur tolerance was found to be the key contributor to the ocular depth of focus, with an approximate dioptric influence of 0.60D. Our understanding of MIOLs may be limited by the need for subjective defocus curves, which are lengthy and do not permit important additional measures to be undertaken. The use of aberrometry to provide faster objective defocus curves was examined. Although subjective and objective measures related well, the peaks of the MIOL defocus curve profile were not evident with objective prediction of acuity, indicating a need for further refinement of visual quality metrics based on ocular aberrations. The experiments detailed in the thesis evaluate methods to improve visual performance with toric IOLs. They also investigate new techniques to allow more rapid post-operative assessment of premium IOLs, which could allow greater insights to be obtained into several aspects of visual quality, in order to optimise future IOL design and ultimately enhance patient satisfaction.

International stock portfolio selection and performance measures recognizing higher moments of return distributions

Since the seminal works of Markowitz (1952), Sharpe (1964), and Lintner (1965), numerous studies on portfolio selection and performance measure have been based upon the mean-variance framework. However, several researchers (e.g., Arditti (1967, and 1971), Samuelson (1970), and Rubinstein (1973)) argue that the higher moments cannot be neglected unless there is reason to believe that: (i) the asset returns are normally distributed and the investor's utility function is quadratic, or (ii) the empirical evidence demonstrates that higher moments are irrelevant to the investor's decision. Based on the same argument, this dissertation investigates the impact of higher moments of return distributions on three issues concerning the 14 international stock markets.^ First, the portfolio selection with skewness is determined using: the Polynomial Goal Programming in which investor preferences for skewness can be incorporated. The empirical findings suggest that the return distributions of international stock markets are not normally distributed, and that the incorporation of skewness into an investor's portfolio decision causes a major change in the construction of his optimal portfolio. The evidence also indicates that an investor will trade expected return of the portfolio for skewness. Moreover, when short sales are allowed, investors are better off as they attain higher expected return and skewness simultaneously.^ Second, the performance of international stock markets are evaluated using two types of performance measures: (i) the two-moment performance measures of Sharpe (1966), and Treynor (1965), and (ii) the higher-moment performance measures of Prakash and Bear (1986), and Stephens and Proffitt (1991). The empirical evidence indicates that higher moments of return distributions are significant and relevant to the investor's decision. Thus, the higher moment performance measures should be more appropriate to evaluate the performances of international stock markets. The evidence also indicates that various measures provide a vastly different performance ranking of the markets, albeit in the same direction.^ Finally, the inter-temporal stability of the international stock markets is investigated using the Parhizgari and Prakash (1989) algorithm for the Sen and Puri (1968) test which accounts for non-normality of return distributions. The empirical finding indicates that there is strong evidence to support the stability in international stock market movements. However, when the Anderson test which assumes normality of return distributions is employed, the stability in the correlation structure is rejected. This suggests that the non-normality of the return distribution is an important factor that cannot be ignored in the investigation of inter-temporal stability of international stock markets. ^

Development of risk based treatability and engineering measures for reducing exposure to lead contaminated media in the Miami inner city, Florida

A major consequence of contamination at the local level’s population as it relates to environmental health and environmental engineering is childhood lead poisoning. Environmental contamination is one of the pressing environmental concerns facing the world today. Current approaches often focus on large contaminated industrial size sites that are designated by regulatory agencies for site remediation. Prior to this study, there were no known published studies conducted at the local and smaller scale, such as neighborhoods, where often much of the contamination is present to remediate. An environmental health study of local lead-poisoning data in Liberty City, Little Haiti and eastern Little Havana in Miami-Dade County, Florida accounted for a disproportionately high number of the county’s reported childhood lead poisoning cases. An engineering system was developed and designed for a comprehensive risk management methodology that is distinctively applicable to the geographical and environmental conditions of Miami-Dade County, Florida. Furthermore, a scientific approach for interpreting environmental health concerns, while involving detailed environmental engineering control measures and methods for site remediation in contained media was developed for implementation. Test samples were obtained from residents and sites in those specific communities in Miami-Dade County, Florida (Gasana and Chamorro 2002). Currently lead does not have an Oral Assessment, Inhalation Assessment, and Oral Slope Factor; variables that are required to run a quantitative risk assessment. However, various institutional controls from federal agencies’ standards and regulation for contaminated lead in media yield adequate maximum concentration limits (MCLs). For this study an MCL of .0015 (mg/L) was used. A risk management approach concerning contaminated media involving lead demonstrates that the linkage of environmental health and environmental engineering can yield a feasible solution.

An Examination of Qualitative Empirical Studies at the AHRD from 1999-2003: Method, Rationale for Method, Data Collection, Sampling Strategies, and Integrity Measures

The paper examines the nature of qualitative empirical studies published in the AHRD proceedings from 1999-2003 and discusses findings on method, rationale for method, data collection, sampling strategies, and integrity measures.

Algorithms for Geometric Matching, Clustering, and Covering

With the popularization of GPS-enabled devices such as mobile phones, location data are becoming available at an unprecedented scale. The locations may be collected from many different sources such as vehicles moving around a city, user check-ins in social networks, and geo-tagged micro-blogging photos or messages. Besides the longitude and latitude, each location record may also have a timestamp and additional information such as the name of the location. Time-ordered sequences of these locations form trajectories, which together contain useful high-level information about people's movement patterns.

The first part of this thesis focuses on a few geometric problems motivated by the matching and clustering of trajectories. We first give a new algorithm for computing a matching between a pair of curves under existing models such as dynamic time warping (DTW). The algorithm is more efficient than standard dynamic programming algorithms both theoretically and practically. We then propose a new matching model for trajectories that avoids the drawbacks of existing models. For trajectory clustering, we present an algorithm that computes clusters of subtrajectories, which correspond to common movement patterns. We also consider trajectories of check-ins, and propose a statistical generative model, which identifies check-in clusters as well as the transition patterns between the clusters.

The second part of the thesis considers the problem of covering shortest paths in a road network, motivated by an EV charging station placement problem. More specifically, a subset of vertices in the road network are selected to place charging stations so that every shortest path contains enough charging stations and can be traveled by an EV without draining the battery. We first introduce a general technique for the geometric set cover problem. This technique leads to near-linear-time approximation algorithms, which are the state-of-the-art algorithms for this problem in either running time or approximation ratio. We then use this technique to develop a near-linear-time algorithm for this

shortest-path cover problem.

Extracting Patterns from Educational Traces via Clustering and Associated Quality Metrics

Clustering algorithms, pattern mining techniques and associated quality metrics emerged as reliable methods for modeling learners’ performance, comprehension and interaction in given educational scenarios. The specificity of available data such as missing values, extreme values or outliers, creates a challenge to extract significant user models from an educational perspective. In this paper we introduce a pattern detection mechanism with-in our data analytics tool based on k-means clustering and on SSE, silhouette, Dunn index and Xi-Beni index quality metrics. Experiments performed on a dataset obtained from our online e-learning platform show that the extracted interaction patterns were representative in classifying learners. Furthermore, the performed monitoring activities created a strong basis for generating automatic feedback to learners in terms of their course participation, while relying on their previous performance. In addition, our analysis introduces automatic triggers that highlight learners who will potentially fail the course, enabling tutors to take timely actions.

Transportation of Children in Ground Ambulances: Professionals' Knowledge and Safety Measures

Background: The transport of children in ground ambulances is a rarely studied topic worldwide. The ambulance vehicle is a unique and complex environment with particular challenges for the safe, correct and effective transportation of patients. Unlike the well developed and readily available guidelines on the safe transportation of a child in motor vehicles, there is a lack on consistent specifications for transporting children in ambulances. Nurses are called daily to transfer children to hospitals or other care centers, so safe transport practices should be a major concern. Purpose: to know which are the safety precautions and specific measures used in the transport of children in ground ambulances by nurses and firefighters and to identify what knowledge these professionals had about safe modes of children transportation in ground ambulances. Methods: In this context, an exploratory - descriptive study and quantitative analysis was conducted. A questionnaire was completed by 135 nurses and firefighters / ambulance crew based on 4 possible children transport scenarios proposed by the NHTSA (National Highway Traffic Safety Administration) and covered 5 different children´s age groups (new born children, 1 to 12 months; 1 to 3 years old; 4 to 7 years old and 8 to 12 years old). Results: The main results showed a variety of safety measures used by the professionals and a significant difference between their actual mode of transportation and the mode they consider to be the ideal considering security goals. In addition, findings showed that achieved scores related to what ambulance crews do in the considered scenarios reflect mostly satisfactory levels of transportation rather than optimum levels of safety, according to NHTSA recommendations. Variables as gender, educational qualifications, occupational group and local where professionals work seem to influence the transport options. Female professionals and nurses from pediatric units appear to do a safer transportation of children in ground ambulances than other professionals. Conclusion: Several professionals refereed unawareness of the safest transportation options for children in ambulances and did not to know the existence of specific recommendations for this type of transportation. The dispersion of the results suggests the need for investment in professional training and further regulation for this type of transportation.

Fishers’ perception on livelihood strategies, adaptation and mitigation measures to cope with changes in climate variables around Lake Wamala, Uganda

Fisheries support livelihoods but are threatened by climate variability and change which intensified since the 1970s. This study used quantitative and qualitative methods to determine the extent to which fishers around Lake Wamala in Uganda were copying with perceived changes in climate variables and the impacts on their livelihoods, to generate knowledge to enable the fishers increase resilience and sustain their livelihoods. Fishers were aware of changes in climate manifested by unpredictable seasons, floods and droughts. Fishing was the main livelihood activity. The African catfish had replaced Nile tilapia as the dominant fish species. There was damage and loss of gear, boats, landing sites and lives, and changes in fish catches and sizes, income and fish consumption during the perceived floods and droughts. The fishers adapted to the changes through increasing time on fishing grounds and changing target species and fishing gears but innovative ones diversified to high value crops and livestock which increased their income beyond what was earned from fishing thus acting as an incentive for some of them to quit fishing. Diversification to non-fishery activities as a form of adaptation was enhanced by membership to social groups, weekly fishing days, fishing experience and age of fishers but its benefits were not equally shared among men and women. Mitigation measures included planting trees, mulching gardens and protecting wetlands. Adaptation and mitigation measures were constrained by limited credit, awareness and land. The required interventions included improving access to credit, irrigation facilities and appropriate planting materials and raising awareness. The study showed that the fishers were aware of changes in climatic variables and the impacts on their livelihoods. There were also adaptation and mitigation measures practiced by the fishers which if promoted and their constraints addressed, could increase resilience of fishers to climatic change and sustain their livelihoods.

An examination of the dynamic validities of cognitive ability and personality measures with performance

Prior research shows that both cognitive ability (Schmidt & Hunter, 1998) and personality measures (Poropat, 2009; Hough & Furnham, 2003) are valid predictors of job performance. The dynamic nature of the relationships between cognitive ability and personality measures with performance over time spent on the job is less understood and thus this paper explores their relationships. Although there is much research to suggest that the predictive relationship between cognitive ability and performance decreases over years of tenure (e.g., Hulin, Henry, & Noon, 1990), other research suggests that the relationship between cognitive ability and performance will increase over time (Kolz, McFarland, & Silverman, 1988). In regard to personality, this study provides a critical test of two competing theories. The first position holds that the validity of personality degrades over time. Support for this position comes from the “ubiquitous” nature of the simplex pattern in individual differences (Humphreys, 1985). It follows that personality validities should perform like cognitive ability in this respect, and thus decline over time. In contrast to this viewpoint, the alternative position contends that the predictive relationship between personality variables and performance increases over time, with the correlation becoming larger in magnitude and more positive in direction over years of tenure. The results of this study support the latter position; personality validities predicted long term performance outcomes.

Transportation of Children in Ground Ambulances: Professionals' Knowledge and Safety Measures

Background: The transport of children in ground ambulances is a rarely studied topic worldwide. The ambulance vehicle is a unique and complex environment with particular challenges for the safe, correct and effective transportation of patients. Unlike the well developed and readily available guidelines on the safe transportation of a child in motor vehicles, there is a lack on consistent specifications for transporting children in ambulances. Nurses are called daily to transfer children to hospitals or other care centers, so safe transport practices should be a major concern. Purpose: to know which are the safety precautions and specific measures used in the transport of children in ground ambulances by nurses and firefighters and to identify what knowledge these professionals had about safe modes of children transportation in ground ambulances. Methods: In this context, an exploratory - descriptive study and quantitative analysis was conducted. A questionnaire was completed by 135 nurses and firefighters / ambulance crew based on 4 possible children transport scenarios proposed by the NHTSA (National Highway Traffic Safety Administration) and covered 5 different children´s age groups (new born children, 1 to 12 months; 1 to 3 years old; 4 to 7 years old and 8 to 12 years old). Results: The main results showed a variety of safety measures used by the professionals and a significant difference between their actual mode of transportation and the mode they consider to be the ideal considering security goals. In addition, findings showed that achieved scores related to what ambulance crews do in the considered scenarios reflect mostly satisfactory levels of transportation rather than optimum levels of safety, according to NHTSA recommendations. Variables as gender, educational qualifications, occupational group and local where professionals work seem to influence the transport options. Female professionals and nurses from pediatric units appear to do a safer transportation of children in ground ambulances than other professionals. Conclusion: Several professionals refereed unawareness of the safest transportation options for children in ambulances and did not to know the existence of specific recommendations for this type of transportation. The dispersion of the results suggests the need for investment in professional training and further regulation for this type of transportation.

Transportation of Children In Ground Ambulances: Professionals' Knowledge and Safety Measures.

Summary The transport of children in ground ambulances is a rarely studied topic worldwide. The ambulance vehicle is a unique environment with particular challenges for the safe, correct and effective transportation of patients. Unlike the well developed and available guidelines on the transportation of children in motor vehicles, there is a lack on specifications for transporting children in ambulances. Nurses are called daily to transfer children to hospitals or other care centres, so safe transport practices should be a major concern. Methods An exploratory - descriptive study and quantitative analysis was conducted. The safety measures used by the professionals in the transportation of children in ambulances were analysed based on the NHTSA (National Highway Traffic Safety Administration) recommendations. A questionnaire was applied to 135 nurses and firefighters/crew of Portuguese ambulances using 4 possible transport situations and covering 5 paediatric age groups. Results There are a variety of safety measures used by professionals and a significant difference between actual mode of transportation and the mode they consider to be the ideal. In addition, findings showed that scores related to what ambulance crews do in these scenarios reflect most satisfactory levels of transportation rather than the optimum levels, according to NHTSA recommendations. Variables as gender, educational qualifications, occupational group and local where professionals work seem to influence the transport options. Female professionals and pediatric nurses do a safer transportation of children in ambulances than other professionals. Conclusion The results suggest the need for investment in professional training and further regulation for this type of transportation.

Relationships between residual intake and gain, performance, feeding behavior and body measures in Brahman young bulls

2016

Assessing the state of Nephrops norvegicus and management measures in the Central Adriatic Sea

Nephrops norvegicus is a sedentary bottom-dwelling crustacean that represents one of the main commercial species exploited in the Adriatic Sea (Central Mediterranean). An evaluation of the status of this important resource is thus extremely important in order to manage it in a sustainable way. The evaluation of N. norvegicus is complicated by several issues, mainly: (i) the complex biology and behaviour of the species itself, (ii) the presence of subpopulations with different biological traits within the same stock unit. Relevant concentration of N.norvegicus occurs within the Pomo/Jabuka Pits area which is characterised by peculiar oceanographic and geophysical conditions. This area represented for a long time an important fishing ground shared by Italian and Croatian fleets and recently a Fishery Restricted Area (FRA) was established there. The aim of the present study is to perform for the first time an evaluation of the status of the N.norvegicus subpopulation inhabiting the Pomo/Jabuka Pits also accounting for the possible effects on it of the management measures. To achieve this, the principal fisheryindependent and fishery-dependent dataset available for the study area were firstly analysed and then treated. Data collected by the CNR-IRBIM of Ancona through both indirect (“UWTV”) and direct (trawling) methods were refined by means of a revision of the time series and related biases, and a modelling approach accounting for environmental and fishery effects, respectively. Commercial data for both Italy and Croatia were treated in order to obtain landings and length distributions for the Pomo area only; an historical reconstruction of data starting from 1970 was carried out for both countries. The obtained information was used as input for a Bayesian length-based stock assessment model developed through the CASAL software; the flexibility of this model is recommended for N.norvegicus and similar species allowing to deal with sex- and fleet-based integrated assessment method