14 resultados para Linear discriminant function

em Digital Commons at Florida International University


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This study investigated the factors considered by forensic examiners when evaluating sexually violent predators (SVP) for civil commitment under Florida's “Jimmy Ryce Act.” The project was funded by a pre-doctoral research grant awarded by the Association for the Treatment of Sexual Abusers (ATSA). ^ This study proposed two specific research questions. First, what is the direct relationship between actuarial risk assessment scores and recommendations for sex offender civil commitment? Second, which other variables are likely to influence SVP commitment decisions, and to what degree? The purpose of the study was to determine if risk assessment practices are evidence-based, and whether offenders selected for commitment meet statutory criteria. ^ The purposive sample of 450 SVPs was drawn from the population of sex offenders evaluated for civil commitment in Florida between July 1, 2000 and June 30, 2001. Data were extracted from SVP evaluations provided by the Florida Department of Children and Families. Using multivariate logistic regression, this correlational research design examined the relationship between the dependent variable, commitment decision, and several sets of independent variables. The independent variables were derived from a review of the literature, and were grouped conceptually according to their degree of correlation with sex offense recidivism. Independent variables included diagnoses, actuarial risk assessment scores, empirically validated static and dynamic risk factors, consensus based risk factors, evaluator characteristics, and demographics. This study investigated the degree to which the identified variables predicted civil commitment decisions. ^ Logistic regression results revealed that the statistically significant predictors of recommendations for sex offender civil commitment were actuarial risk assessment scores, diagnoses of Pedophilia and Paraphilia NOS, psychopathy, younger age of victim, and non-minority race. Discriminant function analysis confirmed that these variables correctly predicted commitment decisions in 90% of cases. ^ It appears that civil commitment evaluators in Florida used empirically-based assessment procedures, and did not make decisions that were heavily influenced by extraneous factors. SVPs recommended for commitment consistently met the criteria set forth by the U.S. Supreme Court in Hendricks v. Kansas (1997): they suffered from a mental abnormality predisposing them to sexual violence, and risk assessment determined that they were likely to reoffend. ^

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The spatial and temporal distribution of modern diatom assemblages in surface sediments, on the most dominant macrophytes, and in the water column at 96 locations in Florida Bay, Biscayne Bay and adjacent regions were examined in order to develop paleoenvironmental prediction models for this region. Analyses of these distributions revealed distinct temporal and spatial differences in assemblages among the locations. The differences among diatom assemblages living on subaquatic vegetation and sediments, and in the water column were significant. Because concentrations of salts, total phosphorus (WTP), total nitrogen (WTN) and total organic carbon (WTOC) are partly controlled by water management in this region, diatom-based models were produced to assess these variables. Discriminant function analyses showed that diatoms can also be successfully used to reconstruct changes in the abundance of diatom assemblages typical for different habitats and life habits. ^ To interpret paleoenvironmental changes, changes in salinity, WTN, WTP and WTOC were inferred from diatoms preserved in sediment cores collected along environmental gradients in Florida Bay (4 cores) and from nearshore and offshore locations in Biscayne Bay (3 cores). The reconstructions showed that water quality conditions in these estuaries have been fluctuating for thousands of years due to natural processes and sea-level changes, but almost synchronized shifts in diatom assemblages occurred in the mid-1960’s at all coring locations (except Ninemile Bank and Bob Allen Bank in Florida Bay). These alterations correspond to the major construction of numerous water management structures on the mainland. Additionally, all the coring sites (except Card Sound Bank, Biscayne Bay and Trout Cove, Florida Bay) showed decreasing salinity and fluctuations in nutrient levels in the last two decades that correspond to increased rainfall in the 1990’s and increased freshwater discharge to the bays, a result of increased freshwater deliveries to the Everglades by South Florida Water Management District in the 1980’s and 1990’s. Reconstructions of the abundance of diatom assemblages typical for different habitats and life habits revealed multiple sources of diatoms to the coring locations and that epiphytic assemblages in both bays increased in abundance since the early 1990’s. ^

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Road pricing has emerged as an effective means of managing road traffic demand while simultaneously raising additional revenues to transportation agencies. Research on the factors that govern travel decisions has shown that user preferences may be a function of the demographic characteristics of the individuals and the perceived trip attributes. However, it is not clear what are the actual trip attributes considered in the travel decision- making process, how these attributes are perceived by travelers, and how the set of trip attributes change as a function of the time of the day or from day to day. In this study, operational Intelligent Transportation Systems (ITS) archives are mined and the aggregated preferences for a priced system are extracted at a fine time aggregation level for an extended number of days. The resulting information is related to corresponding time-varying trip attributes such as travel time, travel time reliability, charged toll, and other parameters. The time-varying user preferences and trip attributes are linked together by means of a binary choice model (Logit) with a linear utility function on trip attributes. The trip attributes weights in the utility function are then dynamically estimated for each time of day by means of an adaptive, limited-memory discrete Kalman filter (ALMF). The relationship between traveler choices and travel time is assessed using different rules to capture the logic that best represents the traveler perception and the effect of the real-time information on the observed preferences. The impact of travel time reliability on traveler choices is investigated considering its multiple definitions. It can be concluded based on the results that using the ALMF algorithm allows a robust estimation of time-varying weights in the utility function at fine time aggregation levels. The high correlations among the trip attributes severely constrain the simultaneous estimation of their weights in the utility function. Despite the data limitations, it is found that, the ALMF algorithm can provide stable estimates of the choice parameters for some periods of the day. Finally, it is found that the daily variation of the user sensitivities for different periods of the day resembles a well-defined normal distribution.

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Historic changes in water-use management in the Florida Everglades have caused the quantity of freshwater inflow to Florida Bay to decline by approximately 60% while altering its timing and spatial distribution. Two consequences have been (1) increased salinity throughout the bay, including occurrences of hypersalinity, coupled with a decrease in salinity variability, and (2) change in benthic habitat structure. Restoration goals have been proposed to return the salinity climates (salinity and its variability) of Florida Bay to more estuarine conditions through changes in upstream water management, thereby returning seagrass species cover to a more historic state. To assess the potential for meeting those goals, we used two modeling approaches and long-term monitoring data. First, we applied the hydrological mass balance model FATHOM to predict salinity climate changes in sub-basins throughout the bay in response to a broad range of freshwater inflow from the Everglades. Second, because seagrass species exhibit different sensitivities to salinity climates, we used the FATHOM-modeled salinity climates as input to a statistical discriminant function model that associates eight seagrass community types with water quality variables including salinity, salinity variability, total organic carbon, total phosphorus, nitrate, and ammonium, as well as sediment depth and light reaching the benthos. Salinity climates in the western sub-basins bordering the Gulf of Mexico were insensitive to even the largest (5-fold) modeled increases in freshwater inflow. However, the north, northeastern, and eastern sub-basins were highly sensitive to freshwater inflow and responded to comparatively small increases with decreased salinity and increased salinity variability. The discriminant function model predicted increased occurrences ofHalodule wrightii communities and decreased occurrences of Thalassia testudinum communities in response to the more estuarine salinity climates. The shift in community composition represents a return to the historically observed state and suggests that restoration goals for Florida Bay can be achieved through restoration of freshwater inflow from the Everglades.

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Annual mean salinity, light availability, and sediment depth to bedrock structured the submerged aquatic vegetation (SAV) communities in subtropical mangrove-lined estuaries. Three distinct SAV communities (i.e., Chara group, Halodule group, and Low SAV coverage group) were identified along the Everglades–Florida Bay ecotone and related to water quality using a discriminant function model that predicted the type of plant community at a given site from salinity, light availability, and sediment depth to bedrock. Mean salinity alone was able to correctly classify 78% of the sites and reliably separated the Chara group from the Halodule group. The addition of light availability and sediment depth to bedrock increased model accuracy to 90% and further distinguished the Chara group from the Halodule group. Light availability was uniquely valuable in separating the Chara group from the Low SAV coverage group. Regression analyses identified significant relationships between phosphorus concentration, phytoplankton abundance, and light availability and suggest that a decline in water transparency, associated with increasing salinity, may have also contributed to the historical decline of Chara communities in the region. This investigation applies relationships between environmental variables and SAV distribution and provides a case study into the application of these general principals to ecosystem management.

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Extensive data sets on water quality and seagrass distributions in Florida Bay have been assembled under complementary, but independent, monitoring programs. This paper presents the landscape-scale results from these monitoring programs and outlines a method for exploring the relationships between two such data sets. Seagrass species occurrence and abundance data were used to define eight benthic habitat classes from 677 sampling locations in Florida Bay. Water quality data from 28 monitoring stations spread across the Bay were used to construct a discriminant function model that assigned a probability of a given benthic habitat class occurring for a given combination of water quality variables. Mean salinity, salinity variability, the amount of light reaching the benthos, sediment depth, and mean nutrient concentrations were important predictor variables in the discriminant function model. Using a cross-validated classification scheme, this discriminant function identified the most likely benthic habitat type as the actual habitat type in most cases. The model predicted that the distribution of benthic habitat types in Florida Bay would likely change if water quality and water delivery were changed by human engineering of freshwater discharge from the Everglades. Specifically, an increase in the seasonal delivery of freshwater to Florida Bay should cause an expansion of seagrass beds dominated by Ruppia maritima and Halodule wrightii at the expense of the Thalassia testudinum-dominated community that now occurs in northeast Florida Bay. These statistical techniques should prove useful for predicting landscape-scale changes in community composition in diverse systems where communities are in quasi-equilibrium with environmental drivers.

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Eating disorders can lead to a negative impact on students' academic growth, nutrition and can cause death (Claude-Pierre, 1997; Manley, Rickson, & Standeven, 2000; Romeo, 1996). Early intervention by referring students to professional counseling might help counter these negative consequences. The teacher is in the position to assist students by providing health information, identifying those with problems, and intervening for a variety of dysfunctions that may include the eating disorders called anorexia nervosa and bulimia nervosa (Myers-Clark & Christopher, 2000). However teachers are in a difficult position to know when to address student concerns and judge what action to take (Ransley, 1999). Teachers' engagement seems crucial (Smolak, Harris, Levine, & Shisslak, 2001) since eating disorders are being identified in younger children. The purpose of this study was to examine (a) the relationships of the theoretical constructs, attitude, subjective norm, and perceived behavioral control of the theory of planned behavior as predictors of behavioral intention (Ajzen & Fishbein, 1980) of middle school teachers to identify and refer suspected anorexia nervosa (AN) and/or bulimia nervosa (BN) students for professional help; and (b) the actual behavior of middle school teachers who reported having ever referred a student suspected of having AN and BN and those teachers who reported not having made such a referral. One hundred fourteen middle school teachers in Broward County, Florida volunteered to participate in the ex post facto research. Data were collected from a questionnaire. Multiple regression analysis revealed that the constructs of subjective norm (perception of what others think about one's performance of behavior combined with motivation to comply) and perceived behavioral control (perception regarding the extent of the difficulty of performing the behavior) were predictive of teachers' intent (likelihood of engaging in a behavior) to refer. However, the analysis revealed that attitude (overall positive or negative feeling with respect to performing the behavior) was not predictive of teachers' intent. Discriminant function analysis revealed that both intent and perceived behavioral control were predictive of group membership, either having referred a student suspected of having an eating disorder for counseling or not having made such a referral. Attitude and subjective norm were not predictive of group membership.

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This study examined relationships among variables in the Pre-International Baccalaureate (Pre-IB) Program admissions criteria and the Pre-IB Program course grades to discriminate between recipient and non recipient groups of the International Baccalaureate (IB) Diploma award. The study involved a multiracial sample of 142 IB Diploma graduates between the years 1992 and 1996 from one IB magnet school. The IB school is located within an urban high school of a predominantly Black student enrollment. A discriminant function analysis found that the highest correlations between predictors and the discriminant function were 9th- and 10th-grade mathematics and 10th-grade science course grades. Ninth-grade course grades of science, 9th-grade and 10th-grade course grades of English, foreign language, and social studies, and 7th-grade Iowa Tests of Basic Skills (ITBS) Reading Comprehension scores were also highly correlated to the discriminant function. The ITBS Battery and subscores of Vocabulary, Total Language, Total Work-Study, and Total Mathematics subscores in seventh grade and a grade point average from language arts, social studies, science, and mathematics in seventh grade were not highly correlated to the discriminant function. Recommendations were presented in the areas of curriculum and instruction, guidance services, student mentoring, and decision-making processes which would parallel the IB examination procedure and thereby enhance the alignment of the IB Program enabling more students to become recipients of the IB Diploma award. ^

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This study documented differences between substance using adolescent participants who either completed or dropped out of a brief motivational intervention. Therapeutic alliance, working alliance and patient involvement were used to describe differences in treatment process ratings in a sample of majority Latino males who either (a) completed a adolescent substance abuse intervention called Alcohol Treatment Targeting Adolescents In Need (ATTAIN) or (b) dropped out after the first or second Guided Self-Change therapy session. Fifteen-minute segments were copied from the midpoint of previously recorded audio-tapes of Guided Self-Change therapy sessions. Raters were trained to a criterion level of interrater reliability for both the Working Alliance Inventory-Short and Vanderbilt Psychotherapy Process Scale. Correlations among Working Alliance Inventory- Short and Vanderbilt Psychotherapy Process Scale subscales reflected a general similarity in the assignment of ratings to client-therapist dyads. Findings underscore why these concepts are often used interchangeably in the treatment process literature. The Vanderbilt Psychotherapy Process Scale patient participation subscale demonstrated substantial empirical differentiation from overall therapeutic alliance. Discriminant function analysis demonstrated the Working Alliance Inventory-Short goal subscale and the Vanderbilt Psychotherapy Process Scale patient participation and therapist warmth and friendliness subscales as successful classifiers of groups of mostly Latino youth based on completion status. Follow-up logistic regression analyses confirmed major findings and successfully predicted group membership. Treatment process constructs can be used as clinical tools to identify participants who may be susceptible to dropping out of treatment services. Further investigation of treatment process may enhance understanding of the influence of alliance between clients and Guided Self-Change therapists. Investigating the role of treatment process as a critical component of brief motivational interventions for substance-using adolescents will inform both practitioners and researchers regarding the effectiveness of community-based substance abuse interventions for adolescents.

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The elemental analysis of soil is useful in forensic and environmental sciences. Methods were developed and optimized for two laser-based multi-element analysis techniques: laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and laser-induced breakdown spectroscopy (LIBS). This work represents the first use of a 266 nm laser for forensic soil analysis by LIBS. Sample preparation methods were developed and optimized for a variety of sample types, including pellets for large bulk soil specimens (470 mg) and sediment-laden filters (47 mg), and tape-mounting for small transfer evidence specimens (10 mg). Analytical performance for sediment filter pellets and tape-mounted soils was similar to that achieved with bulk pellets. An inter-laboratory comparison exercise was designed to evaluate the performance of the LA-ICP-MS and LIBS methods, as well as for micro X-ray fluorescence (μXRF), across multiple laboratories. Limits of detection (LODs) were 0.01-23 ppm for LA-ICP-MS, 0.25-574 ppm for LIBS, 16-4400 ppm for μXRF, and well below the levels normally seen in soils. Good intra-laboratory precision (≤ 6 % relative standard deviation (RSD) for LA-ICP-MS; ≤ 8 % for μXRF; ≤ 17 % for LIBS) and inter-laboratory precision (≤ 19 % for LA-ICP-MS; ≤ 25 % for μXRF) were achieved for most elements, which is encouraging for a first inter-laboratory exercise. While LIBS generally has higher LODs and RSDs than LA-ICP-MS, both were capable of generating good quality multi-element data sufficient for discrimination purposes. Multivariate methods using principal components analysis (PCA) and linear discriminant analysis (LDA) were developed for discriminations of soils from different sources. Specimens from different sites that were indistinguishable by color alone were discriminated by elemental analysis. Correct classification rates of 94.5 % or better were achieved in a simulated forensic discrimination of three similar sites for both LIBS and LA-ICP-MS. Results for tape-mounted specimens were nearly identical to those achieved with pellets. Methods were tested on soils from USA, Canada and Tanzania. Within-site heterogeneity was site-specific. Elemental differences were greatest for specimens separated by large distances, even within the same lithology. Elemental profiles can be used to discriminate soils from different locations and narrow down locations even when mineralogy is similar.

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The elemental analysis of soil is useful in forensic and environmental sciences. Methods were developed and optimized for two laser-based multi-element analysis techniques: laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and laser-induced breakdown spectroscopy (LIBS). This work represents the first use of a 266 nm laser for forensic soil analysis by LIBS. Sample preparation methods were developed and optimized for a variety of sample types, including pellets for large bulk soil specimens (470 mg) and sediment-laden filters (47 mg), and tape-mounting for small transfer evidence specimens (10 mg). Analytical performance for sediment filter pellets and tape-mounted soils was similar to that achieved with bulk pellets. An inter-laboratory comparison exercise was designed to evaluate the performance of the LA-ICP-MS and LIBS methods, as well as for micro X-ray fluorescence (μXRF), across multiple laboratories. Limits of detection (LODs) were 0.01-23 ppm for LA-ICP-MS, 0.25-574 ppm for LIBS, 16-4400 ppm for µXRF, and well below the levels normally seen in soils. Good intra-laboratory precision (≤ 6 % relative standard deviation (RSD) for LA-ICP-MS; ≤ 8 % for µXRF; ≤ 17 % for LIBS) and inter-laboratory precision (≤ 19 % for LA-ICP-MS; ≤ 25 % for µXRF) were achieved for most elements, which is encouraging for a first inter-laboratory exercise. While LIBS generally has higher LODs and RSDs than LA-ICP-MS, both were capable of generating good quality multi-element data sufficient for discrimination purposes. Multivariate methods using principal components analysis (PCA) and linear discriminant analysis (LDA) were developed for discriminations of soils from different sources. Specimens from different sites that were indistinguishable by color alone were discriminated by elemental analysis. Correct classification rates of 94.5 % or better were achieved in a simulated forensic discrimination of three similar sites for both LIBS and LA-ICP-MS. Results for tape-mounted specimens were nearly identical to those achieved with pellets. Methods were tested on soils from USA, Canada and Tanzania. Within-site heterogeneity was site-specific. Elemental differences were greatest for specimens separated by large distances, even within the same lithology. Elemental profiles can be used to discriminate soils from different locations and narrow down locations even when mineralogy is similar.

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This study is to theoretically investigate shockwave and microbubble formation due to laser absorption by microparticles and nanoparticles. The initial motivation for this research was to understand the underlying physical mechanisms responsible for laser damage to the retina, as well as the predict threshold levels for damage for laser pulses with of progressively shorter durations. The strongest absorbers in the retina are micron size melanosomes, and their absorption of laser light causes them to accrue very high energy density. I theoretically investigate how this absorbed energy is transferred to the surrounding medium. For a wide range of conditions I calculate shockwave generation and bubble growth as a function of the three parameters; fluence, pulse duration and pulse shape. In order to develop a rigorous physical treatment, the governing equations for the behavior of an absorber and for the surrounding medium are derived. Shockwave theory is investigated and the conclusion is that a shock pressure explanation is likely to be the underlying physical cause of retinal damage at threshold fluences for sub-nanosecond pulses. The same effects are also expected for non-biological micro and nano absorbers. ^

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Interpersonal conflicts have the potential for detrimental consequences if not managed successfully. Understanding the factors that contribute to conflict resolution has implications for interpersonal relationships and the workplace. Researchers have suggested that personality plays an important and predictable role in conflict resolution behaviors (Chanin & Schneer, 1984; Kilmann & Thomas, 1975; Mills, Robey & Smith, 1985). However, other investigators have contended that contextual factors are important contributors in triggering the behavioral responses (Shoda & Mischel, 2000; Mischel & Shoda, 1995). The purpose of this study was to investigate the relationships among personality types, demographic characteristics and contextual factors on the conflict resolution behaviors reported by graduate occupational therapy students (n = 125). ^ The study design was correlational. The Myers Briggs Type Indicator (MBTI) and the Thomas-Kilmann (MODE) Instrument were used to establish the personality types and the context independent conflict resolution behaviors respectively. The effects of contextual factors of task vs. relationship and power were measured with the Conflict Case Scenarios Questionnaire (CCSQ). One-way ANOVA and linear regression procedures were used to test the relationships between personality types and demographic characteristics with the context independent conflict behaviors. Chi-Square procedures of the personality types by contextual conditions ascertained the effects of contexts in modifying the resolution modes. Descriptive statistics established a profile of the sample. ^ The results of the hypotheses tests revealed significant relationships between the personality types of feeling-thinking and sensing-intuition with the conflict resolution behaviors. The contextual attributes of task vs. relationship orientation and of peer vs. supervisor relationships were shown to modify the conflict behaviors. Furthermore, demographic characteristics of age, gender, GPA and educational background were shown to have an effect on the conflict resolution behaviors. The knowledge gained has implications for students' training, specifically understanding their styles and use of effective conflict resolution strategies. It also contributes to the knowledge on management approaches and interpersonal competencies and how this might facilitate the students' transition to the clinical role. ^

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Background: Diabetes and diabetes-related complications are major causes of morbidity and mortality in the United States. Depressive symptoms and perceived stress have been identified as possible risk factors for beta cell dysfunction and diabetes. The purpose of this study was to assess associations between depression symptoms and perceived stress with beta cell function between African and Haitian Americans with and without type 2 diabetes. Participants and Methods: Informed consent and data were available for 462 participants (231 African Americans and 231 Haitian Americans) for this cross-sectional study. A demographic questionnaire developed by the Primary Investigator was used to collect information regarding age, gender, smoking, and ethnicity. Diabetes status was determined by self-report and confirmed by fasting blood glucose. Anthropometrics (weight, and height and waist circumference) and vital signs (blood pressure) were taken. Blood samples were drawn after 8 10 hours over-night fasting to measure lipid panel, fasting plasma glucose and serum insulin concentrations. The homeostatic model assessment, version 2 (HOMA2) computer model was used to calculate beta cell function. Depression was assessed using the Beck Depression Inventory-II (BDI-II) and stress levels were assessed using the Perceived Stress Scale (PSS). Results: Moderate to severe depressive symptoms were more likely for persons with diabetes (p = 0.030). There were no differences in perceived stress between ethnicity and diabetes status (p = 0.283). General linear models for participants with and without type 2 diabetes using beta cell function as the dependent variable showed no association with depressive symptoms and perceived stress; however, Haitian Americans had significantly lower beta cell function than African Americans both with and without diabetes and adjusting for age, gender, waist circumference and smoking. Further research is needed to compare these risk factors in other race/ethnic groups.