1,380 research outputs found

    Income Mobility in the United States

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    This study makes use of the National Longitudinal Survey of Youth (NLSY) in order to examine the relationship between the standard of living one experiences as a youth and their income as an adult. Human capital theory, as well as previous empirical research in economics suggests that as standard of living as a youth increases, future income as an adult should increase as well. The 1979 cohort as well as the 1997 cohort of the NLSY were studied in order to provide insight into how the relationship in question has changed over time. I hypothesize that as standard of living as a youth increases, so too will income as an adult. Furthermore I hypothesize that the level of income mobility will be greater for the 1979 cohort than the 1997 cohort. An extended treatment of this topic was awarded University Honors and may be found in the Department of Economics Honors Projects collection

    Imine catalyst stability

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    Chapter 1 presents a review of the background and current research regarding Schiff-base olefin polymerization catalysts, with special reference to the salicylaldimine species. An attempt is made to review trends within the current literature. Chapter 2 describes the synthesis and polymerization properties of tetradentate ligands with a bibenzyl backbone at titanium and zirconium centres, prepared with the intent of sterically hindering a 1,2-Migratory Insertion into the ligand imine functionality. A custom-built polymerization reactor was used to determine the stability of the catalytic systems. Steric protection is moderately successful in enhancing the stability of these systems. Chapter 3 reports the synthesis and detailed polymerization behaviour of a series of group 4 catalysts based on salicyloxazoline ligands, which should be resistant to 1,2-Migratory Insertion. Comparisons are made between polymerization under different conditions, including using High-Throughput methodology to screen catalysts under a range of differing conditions rapidly. Such systems are extremely active for polymerization of ethene, but demonstrate limited stability at elevated temperature. Chapter 4 presents our investigations into the polymerization behaviour of salicyloxazoline catalysts containing a para-methoxy substituent on the phenoxy donor unit. This substituent significantly enhances the stability of the catalysts at elevated temperature. Chapter 5 explores the nature of the active species in polymerizations with group 4 salicyloxazoline species. Alkyl cations of such species are generated from metal alkyl species with borate activators, and also from metal chloride species with MAO. We conclude that the primary deactivation mechanism is loss of ligand to aluminium co-catalyst, and that the methoxy substituent prevents this. A computational approach (DFT) is also applied, to examine the catalytic pathways which may be available to various stereoisomers of the catalyst. Chapter 6 details the experimental procedures used during this work

    Modeling Expert Opinions on Food Healthiness: A Nutrition Metric

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    Background Research over the last several decades indicates the failure of existing nutritional labels to substantially improve the healthiness of consumers' food and beverage choices. The difficulty for policy-makers is to encapsulate a wide body of scientific knowledge in a labeling scheme that is comprehensible to the average shopper. Here, we describe our method of developing a nutrition metric to fill this void. Methods We asked leading nutrition experts to rate the healthiness of 205 sample foods and beverages, and after verifying the similarity of their responses, we generated a model that calculates the expected average healthiness rating that experts would give to any other product based on its nutrient content. Results The form of the model is a linear regression that places weights on 12 nutritional components (total fat, saturated fat, cholesterol, sodium, total carbohydrate, dietary fiber, sugars, protein, vitamin A, vitamin C, calcium, and iron) to predict the average healthiness rating that experts would give to any food or beverage. We provide sample predictions for other items in our database. Conclusions Major benefits of the model include its basis in expert judgment, its straightforward application, the flexibility of transforming its output ratings to any linear scale, and its ease of interpretation. This metric serves the purpose of distilling expert knowledge into a form usable by consumers so that they are empowered to make healthier decisions.

    Risk of root intrusion by tree and shrub species into sewer pipes in Swedish urban areas

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    Blockages in sewer pipes caused by roots are very common and several tree and shrub species are reported to be particularly likely to cause root intrusion. This study examined the relative ability of roots of different species to intrude into urban sewer pipes. Data on root-intruded pipes and the woody plants surrounding these pipes were collected from two Swedish cities, Malmö and Skövde. Plant material, location data and closed-circuit television (CCTV) inspections on root-intruded pipes with a total length of 33.7 km, containing 2180 different points of root intrusion, were examined. An inventory of 4107 woody plants was compiled. The results showed that broad-leaved trees dominated as a cause of root intrusion, but that conifers and a number of shrubs, e.g. the genera Ligustrum, Spiraea and Syringa, were also likely to have caused root intrusion. Malus floribunda Van Houtte was found to have the highest mean share of root intrusions per estimated number of pipe joints when all joints and all root intrusions within a 10 m radius from trees were calculated (0.694, maximum number of intrusions per joint 1.0), while Populus canadensis ‘Robusta’ Moench had the second highest, with 0.456 intrusions per estimated joint. However, other Malus and Populus species and cultivars had a much lower mean share of root intrusions. Most species seemed capable of causing root intrusion, and not only species of the genera Populus and Salix that were previously seen as the species most likely to cause damage to stormwater and sewer systems. There were differences in the frequency of joint intrusion by roots of different species, but the reasons for these differences were not identified and further research in the area is needed

    Imine catalyst stability

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    Chapter 1 presents a review of the background and current research regarding Schiff-base olefin polymerization catalysts, with special reference to the salicylaldimine species. An attempt is made to review trends within the current literature. Chapter 2 describes the synthesis and polymerization properties of tetradentate ligands with a bibenzyl backbone at titanium and zirconium centres, prepared with the intent of sterically hindering a 1,2-Migratory Insertion into the ligand imine functionality. A custom-built polymerization reactor was used to determine the stability of the catalytic systems. Steric protection is moderately successful in enhancing the stability of these systems. Chapter 3 reports the synthesis and detailed polymerization behaviour of a series of group 4 catalysts based on salicyloxazoline ligands, which should be resistant to 1,2-Migratory Insertion. Comparisons are made between polymerization under different conditions, including using High-Throughput methodology to screen catalysts under a range of differing conditions rapidly. Such systems are extremely active for polymerization of ethene, but demonstrate limited stability at elevated temperature. Chapter 4 presents our investigations into the polymerization behaviour of salicyloxazoline catalysts containing a para-methoxy substituent on the phenoxy donor unit. This substituent significantly enhances the stability of the catalysts at elevated temperature. Chapter 5 explores the nature of the active species in polymerizations with group 4 salicyloxazoline species. Alkyl cations of such species are generated from metal alkyl species with borate activators, and also from metal chloride species with MAO. We conclude that the primary deactivation mechanism is loss of ligand to aluminium co-catalyst, and that the methoxy substituent prevents this. A computational approach (DFT) is also applied, to examine the catalytic pathways which may be available to various stereoisomers of the catalyst. Chapter 6 details the experimental procedures used during this work.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    A Film Analysis of Motor Pattern Development of Educable Mentally Retarded Children.

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    The purpose of the study was to compare the standing long jump, place kick, overarm throw and striking patterns of educable mentally retarded children to the mature patterns of highly skilled individuals. It was also the purpose of this study to determine if these same motor patterns were inherent in educable mentally retarded subjects and to determine if these patterns would emerge naturally in a goal-centered teaching-learning environment. Eleven educable mentally retarded children between the ages of five and eight years were selected to participate in the study. The children participated in a one week (fifteen minutes per day) orientation program so that they could become familiar with working with the investigator and his assistant, and accustomed to performing before the camera. During this time the children participated in motor activities not related to the motor patterns investigated. The first filming session, during which the initial motor patterns were recorded, was held the first day of the treatment period. The second filming session was held on the twentieth and final day of the treatment period. During each day of the treatment period, each subject performed the standing long jump, overarm throw, place kick and striking patterns ten times. Two university students were utilized to establish, on film, the mature patterns used in this study. One subject, a place kicker for the varsity football team, served as the model for the mature place kick pattern. The second subject, a member of the varsity baseball team, served as the model for the mature standing long jump, overarm throw and striking patterns. Once the motor patterns of the mentally retarded subjects and the mature patterns were recorded on film, they were viewed and analyzed, and tracings were made. For each of the four motor patterns, the standing long jump, place kick, overarm throw and striking, the final motor patterns of the mentally retarded subjects were compared to the mature motor patterns. The initial motor patterns of the mentally retarded subjects were also compared to their final motor patterns in order to determine pattern changes. All comparisons were based on the involvement of body parts, the sequence of movements, the timing of movements and the range of movements during the various phases of each skill. The findings of the study indicated that the standing long jump, overarm throw, place kick and striking patterns of the educable mentally retarded subjects between five and eight years old, to some extent, resemble the patterns of mature performers. However, in reference to the involvement of body parts, the sequence of movements, the timing of movements and the range of movements, the patterns of the mentally retarded subjects were immature and were executed in an inefficient manner. Although changes in the standing long jump, overarm throw, place kick and striking patterns of the mentally retarded subjects were noticeable, they were not perceived to be improvement. This is indicative that either the mentally retarded subjects were not aware of the changes they were making, or that they were unable to determine which of the changes would improve their skill performances

    Sylvester Normalizing Flows for Variational Inference

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    Variational inference relies on flexible approximate posterior distributions. Normalizing flows provide a general recipe to construct flexible variational posteriors. We introduce Sylvester normalizing flows, which can be seen as a generalization of planar flows. Sylvester normalizing flows remove the well-known single-unit bottleneck from planar flows, making a single transformation much more flexible. We compare the performance of Sylvester normalizing flows against planar flows and inverse autoregressive flows and demonstrate that they compare favorably on several datasets.Comment: Published at UAI 2018, 12 pages, 3 figures, code at: https://github.com/riannevdberg/sylvester-flow

    Evaluation of the economic impact of California's Tobacco Control Program: a dynamic model approach

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    ObjectiveTo evaluate the long-term net economic impact of the California Tobacco Control Program.MethodsThis study developed a series of dynamic models of smoking-caused mortality, morbidity, health status and healthcare expenditures. The models were used to evaluate the impact of the tobacco control programme. Outcomes of interest in the evaluation include net healthcare expenditures saved, years of life saved, years of treating smoking-related diseases averted and the total economic value of net healthcare savings and life saved by the programme. These outcomes are evaluated to 2079. Due to data limitations, the evaluations are conducted only for men.ResultsThe California Tobacco Control Program resulted in over 700,000 person-years of life saved and over 150,000 person-years of treatment averted for the 14.7 million male California residents alive in 1990. The value of net healthcare savings and years of life saved resulting from the programme was 22billionor22 billion or 107 billion in 1990 dollars, depending on how a year of life is discounted. If women were included, the impact would likely be much greater.ConclusionsThe benefits of California's Tobacco Control Program are substantial and will continue to accrue for many years. Although the programme has resulted in increased longevity and additional healthcare resources for some, this impact is more than outweighed by the value of the additional years of life. Modelling the programme's impact in a dynamic framework makes it possible to evaluate the multiple impacts that the programme has on life, health and medical expenditures

    The History of Urological Care and Training at Thomas Jefferson University

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    The Department of Urology at Thomas Jefferson University and Thomas Jefferson University Hospital is generally acknowledged as the oldest formal Department of Urology in the US, formally designated as the Department of Genitourinary Surgery in 1904. The Department has been under the direction of 8 chairmen and has trained over 144 residents and 25 fellows with over 200 Jefferson Medical College graduates specializing in urology. Thomas Jefferson University was originally founded as Jefferson Medical College in 1824. Dr. George McClelland petitioned Jefferson College at Cannonsburg (now Washington and Jefferson College) to add a medical school to their institution. While technically part of Jefferson College in western Pennsylvania, Jefferson Medical College was to be located in Philadelphia under the direction of the medical faculty. By 1838, Jefferson Medical College gained its own charter and was no longer affiliated with Jefferson College. As a proprietary school, the faculty administrated and managed all the finances of the school. This included the sale of “tickets” to attend lectures. An infirmary to treat the poor was established in 1825. This dispensary to treat indigent patients under student observation was the first instituted by any medical school in the United States. Eventually, all medical schools in the United States adopted Jefferson’s example of combining lectures with practical patient experience. In 1969 Thomas Jefferson University was established that incorporated Jefferson Medical College, the College of Allied Health Sciences, the College of Graduate Studies and the Jefferson Medical College Hospital
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