The impact of alcohol and drug use on employment: A labor market study using the National Longitudinal Survey of Youth

The purpose of this study was, first, to estimate of the impact of alcohol and drug use on the employment status of men and women, and second, to examine whether a history of past use, as opposed to current use, adversely affects the propensity to be employed. Using data from the National Longitudinal Survey of Youth we conducted a cross-sectional and a longitudinal analysis with logistic regression estimation to model the probability that a person was employed in 1992. In addition to usual regressors, interactions between substance use measures, between substance use measures and human capital variables, and between substance use measures and race dummies were included in the equation. The longitudinal analysis utilized a conditional likelihood method based on employment data in 1992 and 1988 and included the difference between 1992 regressors and their 1988 counterparts. A comparison was made between the prediction accuracy of the logit choice model, linear discriminant analysis, k-nearest neighbor analysis, and three modern classification methods that are used extensively in the area of machine learning. Results showed that the logit model performs relatively well in classifying individuals into employed and unemployed categories based on individual attributes. Results of the cross-sectional and longitudinal analysis were mixed, but not inconsistent with our prior expectations that use of alcohol or drug has a negative impact on a person's propensity to be employed. Cross-sectional results show a clear negative impact of past substance use on a person's employment probability among all demographic groups examined (by gender: all persons, blacks, Hispanics, families with income below the poverty line, and high users of alcohol or drugs). However, when current and past use are considered together, only women seem to experience negative impacts. The results of the longitudinal analysis are less clear, although they do indicate that negative impacts are associated with the interaction between substance use measures and human capital variables. Limitations of the study are pointed out and suggestions are made for future research.

On the relationship between mass and diameter distributions in tree communities

It has been suggested that frequency distributions of individual tree masses in natural stands are characterized by power-law distributions with exponents near -3/4, and that therefore tree communities exhibit energetic equivalence among size classes. Because the mass of trees is not measured directly, but estimated from diameter, this supposition is based on the fact that the observed distribution of tree diameters is approximately characterized by a power-law with an exponent -2. Here we show that diameter distributions of this form are not equivalent to mass distributions with exponents of -3/4, but actually to mass distributions with exponents of -11/8. We discuss the implications of this result for the metabolic theory of ecology and for understanding energetic equivalence and the processes structuring tree communities

Baraminology: A Young-Earth Creation Biosystematic Method

Walter ReMine \u27s (1) discontinuity systematics can be used as a basis for a biological classification system either within creation or evolution theory. Such a model-neutral methodology can be more efficiently utilized within any given theory of life by supplementing it with model-dependent membership criteria. Discontinuity systematics supplemented with young-earth creation model-dependent membership criteria is here called baraminology. Four young-earth creation model-dependent membership criteria are here suggested -- one based on Scripture, another based upon molecular similarity studies, a third based on cladistically-defined frequency of homoplasy, and a fourth based on flood-generated diversity bottlenecks. This paper also attempts to relate the empirically-defined holobaramins, monobaramins, apobaramins, and polybaramins of baraminology and discontinuity systematics to Biblical, creationist, and evolutionist thought. The original, created group of individuals capable of reproduction is a theoretical construct, here called an archaebaramin. Frank Marsh\u27s term baramin is considered the created \u27kind\u27 (or \u27Biblical kind\u27), and is here redefined as the archaebaramin and all its descendants. Baramins are apobaraminic groups, and may be holobaraminic in most, if not all, cases. Microevolutionary processes, including speciation occur within the baramin. Extra- and interbaraminic evolution is considered impossible. Baraminology is an easily employed and extremely powerful biosystematic method. Baraminology is the most efficient method of classifying life available to the young-earth creation biologist. It will allow the collection of an abundance of heretofore unrecognizable data in favor of a creation model, and serve as an empirical foundation upon which to construct a creationist reclassification of life

Measuring Future Time Perspective across Adulthood: Development and Evaluation of a Brief Multidimensional Questionnaire.

PURPOSE OF THE STUDY: Despite calls for the consideration of future time perspective (FTP) as a multidimensional construct, mostly unidimensional measurement instruments have been used. This study had two objectives: (a) to develop a brief multidimensional questionnaire for assessing FTP in adulthood and evaluate its psychometric properties; and (b) to examine age associations and age-group differences of the dimensions of FTP. DESIGN AND METHODS: Data were collected from 625 community-residing adults between the ages of 18 and 93, representing young, middle-aged, and older adults. The psychometric evaluation involved exploratory factor analyses (EFA) and confirmatory FA (CFA), reliability and validity analyses, and measurement invariance testing. Zero-order and partial correlations were used to examine the association of the dimensions of FTP with age, and multivariate analysis of variance was used to examine age-group differences. RESULTS: EFA and CFA supported a three-factor solution: Future as Open, Future as Limited, and Future as Ambiguous. Metric measurement invariance for this factor structure was confirmed across the three age groups. Reliability and validity analyses provided evidence of sound psychometric properties of the brief questionnaire. Age was negatively associated with Future as Open and positively associated with Future as Limited. Young adults exhibited significantly greater ambiguity toward the future than middle-aged or older adults. IMPLICATIONS: This study provides evidence in support of the psychometric properties of a new brief multidimensional FTP scale. It also provides evidence for a pattern of age associations and age-group differences consistent with life-span developmental theory

Master of Science

thesisThe curious pattern of metabolic rate scaling with mass to the ¾ power has been observed across organisms and has eluded biologists for nearly a century. Metabolic scaling in trees has recently attracted attention as scientists try to model ecosystem dynamics of the hydrologic cycle and the carbon cycle. In this study, we attempt to gain greater understanding about the mechanical and hydraulic principles that govern vascular networks, how water transport through these networks scale with tree size, and how water use relates to growth rates in functionally diverse ring-porous Quercus gambelii and diffuse-porous Acer grandidentatum. We parameterized a numeric network model with species-specific vascular and structural characters to predict water use and growth rate scaling with tree size. The network model currently is confined to optimal water supply. To better understand water use and growth rate patterns during variable season conditions, we measured whole-tree sapflow, conductance and growth rates over one growing season in these two species. The numeric network model did exceptionally well at predicting species-specific scaling of water use and growth rates with tree size. In addition, it accurately predicted relative water use per species. Comparison of these two sympatric species over the growing season suggested that ring-porous Q. gambelii has relatively stable (isohydric) water use patterns and similar growth rates to diffuse-porous A. grandidentatum which has more flexible water use strategy leading to variable growth rates. These two species are able to be co-dominant in this region due to unique water use niches and vasculature. The accuracy of the numeric model predictions tested here suggest that scaling models such as these could be valuable in making ecohydrological predictions enabling the prediction of water use and growth rates with tree size and scaling this up to the stand and ecosystem level. We hope this work infusing hydraulic and mechanical constraints driving water use and growth rates of individuals within and between species contributes to better understanding of processes that effect predictions of ecosystem challenges under global change

Allometric scaling and metabolic ecology of microorganisms and major evolutionary transitions

My dissertation centers around investigating big-picture questions related to understanding the consequences of metabolism and energetics on the evolution, ecology, and physiology of life. The evolutionary transitions from prokaryotes to unicellular eukaryotes to multicellular organisms were accompanied by major innovations in metabolic design. In my first chapter, I show that the scaling of metabolic rate, population growth rate, and production efficiency with body size have changed across these transitions. Metabolic rate scales with body mass superlinearly in prokaryotes, linearly in protists, and sublinearly in metazoans, so Kleibers 3/4 power scaling law does not apply universally across organisms. This means that major changes in metabolic processes during the early evolution of life overcame existing physical constraints, exploited new opportunities, and imposed new constraints on organism physiology. Surface areas of physiological structures of organisms impose fundamental constraints on metabolic rate. In my second chapter, I demonstrate that organisms have a variety of options for increasing the scaling of the area of their metabolic surfaces with body sizes. I develop models and examples illustrating the role of cell membrane elaborations, mitochondria, vacuoles, vesicles, inclusions, and shape-shifting in the architectural design, evolution, and ecology of unicellular microbes. I demonstrate how these surface-area scaling adaptations have played important roles in the evolution of major biological designs of cells and the physiological ecology of organisms. In my third and final chapter, I integrate and synthesize findings from the previous two chapters with important developments in geochemistry, microbiology, and astrobiology in order to identify the fundamental physical and biological dimensions that characterize a metabolic theory of ecology of microorganisms. These dimensions are thermodynamics, chemical kinetics, physiological harshness, cell size, and levels of biological organization. I show how addressing these dimensions can inform understanding of the physical and biological factors governing the metabolic rate, growth rate, and geographic distribution of cells. I propose a unifying theory to understand how the major ecological and evolutionary transitions that led to increases in levels of organization of life, such as endosymbiosis, multicellularity, eusociality, and multi-domain complexes, influences the metabolism and growth and the metabolic scaling of these complexes