147 research outputs found
A Geometric Morphometric Approach to the Quantification of Population Variation in Sub-Saharan African Crania
No full textWe report here on new data examining cranial variation in 18 modern human sub-Saharan African populations. Previously, we investigated variation within southern Africa; we now extend our analyses to include a series of Central, East, and West African crania, to further knowledge of the relationships between, and variation and regional morphological patterning in, those populations. The sample comprises 377 male individuals; the three-dimensional coordinates of 96 landmarks are analyzed using Procrustes-based methods. Interpopulation variation is examined by calculating shape distances between groups, which are compared using resampling statistics and parametric tests. Phenotypic variance, as a proxy for genetic variance, is measured and compared across populations. Principal components and cluster analyses are employed to explore relationships between the populations. Shape differences are visualized using three-dimensional rendered models. Observed disparity patterns imply a mix of differences and similarities across populations, with no apparent support for genetic bottlenecks, which is likely a consequence of migrations that may have influenced differences in cranial form; supporting data are found in recent molecular studies. The Pygmy sample had the most distinctive cranial morphology; characteristically small in size with marked prognathism. These features characterized, although less strongly, the neighboring Bateke, and are possibly related to similar selective pressures in conjunction with interbreeding. Small cranial size is also involved in the considerable distinctiveness of the San and Khoikhoi. The statistical procedures applied in this study afford a powerful and robust means of quantifying and visualizing the magnitude and pattern of cranial variation between sub-Saharan African populations. Am. J. Hum. Biol. 22:23-35, 2010. (C) 2009 Wiley-Liss, Inc
Mandibular morphology as an indicator of human subadult age: geometric morphometric approaches
No full textMethods for skeletal identification have a long history in physical and forensic anthropology. Recent literature demonstrates that new methods are constantly being developed, concurrent with refinements to those already commonly employed. The present study concerns the application of geometric morphometrics to assess the potential of mandibular morphology as a developmental marker for estimating age at death in subadult human skeletal remains. The sample comprises 79 known age and sex subadult individuals of South African Bantu and African American origin; 38 bilateral three-dimensional landmarks were designed and acquired using a portable digitizer. Linear regression was used to predict age using the multivariate descriptors of mandible size and shape based on configurations of three-dimensional landmarks. Our results show that the mandible can be used to predict age in the subadult skeleton with accuracy comparable to standards based on the dentition (standard error rates are between +/- 13 and +/- 3.0 years). These results closely parallel our previous study using the linear measurement of ramus height, but suggest that geometric morphometrics may be slightly more accurate when adolescents are included in the sample
Policies, Guidelines, And Services For The Developmentally Disabled Student At Oxnard College.
No full textA current issue in the California Community Colleges is that of serving the developmentally disabled learner. Developmentally disabled students are an extremely heterogeneous group ranging from individuals who are intellectually gifted but who have severe physical impairments to those who are severely mentally retarded but who are physically perfectly sound. The purposes of this study were: (1) to determine the California Community Colleges\u27 policies on serving the developmentally disabled adult and lo identify the federal and state statutes regulating the community colleges serving the developmentally disabled adult; (2) to determine what programs and related services are offered for the developmentally disabled adult at the California Community Colleges; (3) to identify what criteria are utilized by special education offices for determining a developmentally disabled adult\u27s eligibility for their program(s); and (4) to develop a series of policies, guidelines, educational services, and related services for the developmentally disabled learner at Oxnard College and a plan for implementing and evaluating the program. Two survey questionnaires were developed as part of this study. The mail-in questionnaire was sent to each of the California Community Colleges. Upon receipt of the questionnaire, each institution identified as having an established developmentally disabled program was asked to complete the survey questionnaire as well as respond to a telephone survey. Their educational materials were also requested. Upon completing all telephone interviews and receiving all requested documents from the participating colleges, the data were tabulated and analyzed by utilizing content analysis, measures of central tendency, frequency distribution, and percentage. The findings revealed that: (a) twenty-five percent of the 106 California Community Colleges had established on-campus programs for students with developmental disabilities; (b) mandatory assessment and program placement were provided in over seventy percent of the colleges for this student population; (c) the most widely utilized services by the colleges in their programs for students with developmental disabilities were special classes, counseling, and physical education; (d) the range in student enrollment was noted from thirteen students to over 1,200 students; and (e) sixty-eight percent of the colleges surveyed had conducted forma l evaluations of their programs. It was concluded that: (a) programs for students with developmental disabilities on the California Community College campuses, for the most part, are still nonexistent; (b) not all of the colleges perceive a need to offer services to students with developmental disabilities; (c) developmentally disabled adults were appropriate community college students; (d) special education personnel have not been providing inservice training on a regular basis with any consistency to regular college faculty and staff; and (e) there are few available resources for developing programs for this student population on community college campuses. Recommendations were that: (a) results of the study be shared with appropriate administrators at Oxnard College for program implementation purposes; (b) the study should be used as a justification for the budget expense request for program implementation; ( c) additional funding sources be explored by appropriate Oxnard College administration; and (d) the Oxnard College special education department developmental disabilities specialist should provide an inservice training program for all Oxnard College administrators, faculty, and staff prior to the program\u27s implementation and on an ongoing basis thereafter
Concordance of traditional osteometric and volume rendered MSCT interlandmark cranial measurements
No full textThe statistical quantification of error and uncertainty is inherently intertwined with ascertaining the admissibility of forensic evidence in a court of law. In the forensic anthropological discipline, the robustness of any given standard should not only be evaluated according to its stated error, but the accuracy and precision of the raw data (measurements) from which they are derived. In the absence of Australian contemporary documented skeletal collections, medical scans (e.g. multislice computed tomography – MSCT) offer a source of contemporary population-specific data for the formulation of skeletal standards. As the acquisition of morphometric data from clinical MSCT scans is still relatively novel, the purpose of this study is to assess validity of the raw data that is being used to formulate Australian forensic standards.Six human crania were subjected to clinical MSCT at a slice thickness of 0.9mm. Each cranium and its corresponding volume rendered three-dimensional MSCT image were measured multiple times. Whether differences between MSCT and dry bone interlandmark measurements are negligible is statistically quantified; intra- and inter-observer measurement error is also assessed. We found that traditional bone measurements are more precise than their MSCT counterparts, although overall differences between the two data acquisition methods are negligible compared to sample variance. Cranial variation accounted on average for more than 20x the variance explained by MSCT vs. bone measurements. Similarly, although differences between operators were sometimes significant compared to intra-operator variance, they were negligible when compared to sample variance, which was on average 12x larger than that due to inter-operator differences
MODELING THE EFFECT OF SPATIAL EXTERNALITIES ON INVASIVE SPECIES MANAGEMENT
No full textChanges in production conditions associated with biological invasions can be complex. As a result, modeling invasive species management decisions can be difficult. Modeling these decisions is further compounded by externalities associated with spatial relationships among growers. In order to calculate optimal management decisions, an accurate bioeconomic model of the feedback between grower decisions and the new biological interactions created by an invasive species population is needed. In this paper, a bioeconomic model is used to explicitly analyze how externalities caused by spatial relationships among agricultural producers affect optimal invasive species management decisions. The example of the coordinated greenhouse whitefly management in the Oxnard, CA, area is discussed. This is an interesting example because of the complex cycle of host crops used by the whitefly and the effect this cycle has on the optimal whitefly management decisions for strawberry growers. Three research objectives achieved in this paper include first, using the model to assess how the spatial relationship among growers affects incentives for regional invasive pest management. Second, analyze whether current policies could be adjusted to substitute for coordination among growers. Third, the use of the bioeconomic model to identify factors for this specific case that affect whether or not growers may voluntarily coordinate their management decisions. We find that spatial relationships among growers affect the need for coordination in the strawberry/whitefly case. Whitefly migrations across host crop fields require growers to manage the whitefly on a regional basis in order to maximize strawberry producer welfare. The results also indicate that the amount of effort needed to achieve coordination required is limited; the only requirement is that information related to field management be shared among growers of whitefly host crops. The results from the bioeconomic model describe the biological and economic feedback of the grower's decision which allows policymakers to identify the willingness of producers to coordinate at various times of year. In the Oxnard strawberry/whitefly case, for example, growers will not find it optimal to adjust their application timing for a second immigration of adult greenhouse whiteflies when they occur near the end of the season, such as in May or June, but will for earlier points in the season. Three policy implications of the results from the strawberry/whitefly case are also discussed in the paper. First, adjustments to current policies regulating whitefly management do not remove the need for coordination among growers to them. Also, it was found that current policies do not, by themselves, generate the need for coordination. Finally, the results show it is not always necessary to create a central agency for regional invasive species management.Invasive species, strawberry, greenhouse whitefly, externality, optimal management, Research Methods/ Statistical Methods,
A response to unfounded criticisms of Burkey and Obeng (2004) made by the IIHS (2005)
No full textAbstract: The Insurance Institute for Highway Safety mailed an essay written by Richard Retting and Sergey Kyrychenko (IIHS, 2005) to many universities and individuals where they accused my coauthor and me of being Junk Scientists. This has become a typical pattern for the IIHS, attacking every study that fails to find a benefit of Red Light Cameras, but never criticizing work that supports their beliefs. In this paper I defend my work against their claims, and pose the question: Who are the real junk scientists?Red Light Camera; Intersection Safety;
MODELING THE EFFECT OF SPATIAL EXTERNALITIES ON INVASIVE SPECIES MANAGEMENT
No full textChanges in production conditions associated with biological invasions can be complex. As a result, modeling invasive species management decisions can be difficult. Modeling these decisions is further compounded by externalities associated with spatial relationships among growers. In order to calculate optimal management decisions, an accurate bioeconomic model of the feedback between grower decisions and the new biological interactions created by an invasive species population is needed. In this paper, a bioeconomic model is used to explicitly analyze how externalities caused by spatial relationships among agricultural producers affect optimal invasive species management decisions. The example of the coordinated greenhouse whitefly management in the Oxnard, CA, area is discussed. This is an interesting example because of the complex cycle of host crops used by the whitefly and the effect this cycle has on the optimal whitefly management decisions for strawberry growers. Three research objectives achieved in this paper include first, using the model to assess how the spatial relationship among growers affects incentives for regional invasive pest management. Second, analyze whether current policies could be adjusted to substitute for coordination among growers. Third, the use of the bioeconomic model to identify factors for this specific case that affect whether or not growers may voluntarily coordinate their management decisions. I find that spatial relationships among growers affect the need for coordination in the strawberry/whitefly case. Whitefly migrations across host crop fields require growers to manage the whitefly on a regional basis in order to maximize strawberry producer welfare. The results also indicate that the amount of effort needed to achieve coordination required is limited; the only requirement is that information related to field management be shared among growers of whitefly host crops. The results from the bioeconomic model describe the biological and economic feedback of the growers decision which allows policymakers to identify the willingness of producers to coordinate at various times of year. In the Oxnard strawberry/whitefly case, for example, growers will not find it optimal to adjust their application timing for a second immigration of adult greenhouse whiteflies when they occur near the end of the season, such as in May or June, but will for earlier points in the season. Three policy implications of the results from the strawberry/whitefly case are also discussed in the paper. First, adjustments to current policies regulating whitefly management do not remove the need for coordination among growers to them. Also, it was found that current policies do not, by themselves, generate the need for coordination. Finally, the results show it is not always necessary to create a central agency for regional invasive species management.Invasive species, strawberry, greenhouse whitefly, externality, optimal management., Resource /Energy Economics and Policy,
Caminantes del Mayab: construcción de identidades entre migrantes de Telchac Pueblo, Yucatán/Oxnard, Ventura, California
No full textTesis para optar por el grado de maestría en Antropología Social</p
Anatomies and lifestyles, morphometrics and niche metrics: Tools for studying primate evolution
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