Graphical modelling for brain connectivity via partial coherence

Spectral and coherence methodologies are ubiquitous for the analysis of multiple time series. Partial coherence analysis may be used to try to determine graphical models for brain functional connectivity. The outcome of such an analysis may be considerably influenced by factors such as the degree of spectral smoothing, line and interference removal, matrix inversion stabilization and the suppression of effects caused by side-lobe leakage, the combination of results from different epochs and people, and multiple hypothesis testing. This paper examines each of these steps in turn and provides a possible path which produces relatively ‘clean’ connectivity plots. In particular we show how spectral matrix diagonal up-weighting can simultaneously stabilize spectral matrix inversion and reduce effects caused by side-lobe leakage, and use the stepdown multiple hypothesis test procedure to help formulate an interaction strength.

Primary health care management in Nigeria

This research sets out to assess if the PHC system in rural Nigeria is effective by testing the research hypothesis: `PHC can be effective if and only if the Health Care Delivery System matches the attitudes and expectations of the Community'. The field surveys to accomplish this task were carried out in IBO, YORUBA, and HAUSA rural communities. A variety of techniques have been used as Research Methodology and these include questionnaires, interviews and personal observations of events in the rural community. This thesis embraces three main parts. Part I traces the socio-cultural aspects of PHC in rural Nigeria, describes PHC management activities in Nigeria and the practical problems inherent in the system. Part II describes various theoretical and practical research techniques used for the study and concentrates on the field work programme, data analysis and the research hypothesis-testing. Part III focusses on general strategies to improve PHC system in Nigeria to make it more effective. The research contributions to knowledge and the summary of main conclusions of the study are highlighted in this part also. Based on testing and exploring the research hypothesis as stated above, some conclusions have been arrived at, which suggested that PHC in rural Nigeria is ineffective as revealed in people's low opinions of the system and dissatisfaction with PHC services. Many people had expressed the view that they could not obtain health care services in time, at a cost they could afford and in a manner acceptable to them. Following the conclusions, some alternative ways to implement PHC programmes in rural Nigeria have been put forward to improve and make the Nigerian PHC system more effective.

When do incentives work in channels of distribution?

The incentive dilemma refers to a situation in which incentives are offered but do not work as intended. The authors suggest that, in an interorganizational context, whether a principal-provided incentive works is a function of how it is evaluated by an agent: for its contribution to the agent's bottom line (instrumental evaluation) and for the extent it is strategically aligned with the agent's direction (congruence evaluation). To further understand when incentives work, the influence of two key contextual variables-industry volatility and dependence-are examined. A field study featuring 57 semi-structured depth interviews and 386 responses from twin surveys in the information technology and brewing industries provide data for hypothesis testing. When and whether incentives work is demonstrated by certain conditions under which the agent's evaluation of an incentive has positive or negative effects on its compliance and active representation. Further, some outcomes are reversed in the high volatility condition. © 2013 Academy of Marketing Science.

Stability of multi-agent systems

This work attempts to shed light to the fundamental concepts behind the stability of Multi-Agent Systems. We view the system as a discrete time Markov chain with a potentially unknown transitional probability distribution. The system will be considered to be stable when its state has converged to an equilibrium distribution. Faced with the non-trivial task of establishing the convergence to such a distribution, we propose a hypothesis testing approach according to which we test whether the convergence of a particular system metric has occurred. We describe some artificial multi-agent ecosystems that were developed and we present results based on these systems which confirm that this approach qualitatively agrees with our intuition.

New business histories! Plurality in business history research methods

We agree with de Jong et al.'s argument that business historians should make their methods more explicit and welcome a more general debate about the most appropriate methods for business historical research. But rather than advocating one ‘new business history’, we argue that contemporary debates about methodology in business history need greater appreciation for the diversity of approaches that have developed in the last decade. And while the hypothesis-testing framework prevalent in the mainstream social sciences favoured by de Jong et al. should have its place among these methodologies, we identify a number of additional streams of research that can legitimately claim to have contributed novel methodological insights by broadening the range of interpretative and qualitative approaches to business history. Thus, we reject privileging a single method, whatever it may be, and argue instead in favour of recognising the plurality of methods being developed and used by business historians – both within their own field and as a basis for interactions with others.

Suboptimal Multistage Nonparametric Hypotheses Test

2000 Mathematics Subject Classification: 62L10, 62L15.

Suboptimal Nonparametric Hypotheses Discriminating from Small Dependent Observations

2000 Mathematics Subject Classification: 62L10.

The influence of body size on the ecology of coastal fish predators in the Bahamas

Body size is a fundamental structural characteristic of organisms, determining critical life history and physiological traits, and influencing population dynamics, community structure, and ecosystem function. For my dissertation, I focused on effects of body size on habitat use and diet of important coastal fish predators, as well as their influence on faunal communities in Bahamian wetlands. First, using acoustic telemetry and stable isotope analysis, I identified high variability in movement patterns and habitat use among individuals within a gray snapper (Lutjanus griseus) and schoolmaster snapper (L. apodus) population. This intrapopulation variation was not explained by body size, but by individual behavior in habitat use. Isotope values differed between individuals that moved further distances and individuals that stayed close to their home sites, suggesting movement differences were related to specific patterns of foraging behavior. Subsequently, while investigating diet of schoolmaster snapper over a two-year period using stomach content and stable isotope analyses, I also found intrapopulation diet variation, mostly explained by differences in size class, individual behavior and temporal variability. I then developed a hypothesis-testing framework examining intrapopulation niche variation between size classes using stable isotopes. This framework can serve as baseline to categorize taxonomic or functional groupings into specific niche shift scenarios, as well as to help elucidate underlying mechanisms causing niche shifts in certain size classes. Finally, I examined the effect of different-sized fish predators on epifaunal community structure in shallow seagrass beds using exclusion experiments at two spatial scales. Overall, I found that predator effects were rather weak, with predator size and spatial scale having no impact on the community. Yet, I also found some evidence of strong interactions on particular common snapper prey. As Bahamian wetlands are increasingly threatened by human activities (e.g., overexploitation, habitat degradation), an enhanced knowledge of the ecology of organisms inhabiting these systems is crucial for developing appropriate conservation and management strategies. My dissertation research contributed to this effort by providing critical information about the resource use of important Bahamian fish predators, as well as their effect on faunal seagrass communities.

The relationships between elementary school principals' emotional intelligence, leadership style and school culture

The role of the principal in school settings and the principal's perceived effect on student achievement have frequently been considered vital factors in school reform. The relationships between emotional intelligence, leadership style and school culture have been widely studied. The literature reveals agreement among scholars regarding the principal's vital role in developing and fostering a positive school culture. The purpose of this study was to explore the relationships between elementary school principals' emotional intelligence, leadership style and school culture. ^ The researcher implemented a non-experimental ex post facto research design to investigate four specific research hypotheses. Utilizing the Qualtrics Survey Software, 57 elementary school principals within a large urban school district in southeast Florida completed the Emotional Quotient Inventory (EQ-i), and 850 of their faculty members completed the Multifactor Leadership Questionnaire (MLQ Form 5X). Faculty responses to the school district's School Climate Survey retrieved from the district's web site were used as the measure of school culture. ^ Linear regression analyses revealed significant positive associations between emotional intelligence and the following leadership measures: Idealized Influence-Attributes (β = .23, p = < .05), Idealized Influence-Behaviors (β = .34, p = < .01), Inspirational Motivation (β = .39, p = < .01) and Contingent Reward (β = .33, p = < .01). Hierarchical regression analyses revealed positive associations between school culture and both transformational and transactional leadership measures, and negative associations between school culture and passive-avoidant leadership measures. Significant positive associations were found between school culture and the principals' emotional intelligence over and above leadership style. Hierarchical linear regressions to test the statistical hypothesis developed to account for alternative explanations revealed significant associations between leadership style and school culture over and above school grade. ^ These results suggest that emotional intelligence merits consideration in the development of leadership theory. Practical implications include suggestions that principals employ both transformational and transactional leadership strategies, and focus on developing their level of emotional intelligence. The associations between emotional intelligence, transformational leadership, Contingent Reward and school culture found in this study validate the role of the principal as the leader of school reform.^

Avaliação e correções de testes de hipóteses em modelos de sobrevivência com fração de cura

Survival models deals with the modelling of time to event data. In certain situations, a share of the population can no longer be subjected to the event occurrence. In this context, the cure fraction models emerged. Among the models that incorporate a fraction of cured one of the most known is the promotion time model. In the present study we discuss hypothesis testing in the promotion time model with Weibull distribution for the failure times of susceptible individuals. Hypothesis testing in this model may be performed based on likelihood ratio, gradient, score or Wald statistics. The critical values are obtained from asymptotic approximations, which may result in size distortions in nite sample sizes. This study proposes bootstrap corrections to the aforementioned tests and Bartlett bootstrap to the likelihood ratio statistic in Weibull promotion time model. Using Monte Carlo simulations we compared the nite sample performances of the proposed corrections in contrast with the usual tests. The numerical evidence favors the proposed corrected tests. At the end of the work an empirical application is presented.

Optimal selection of autoregressive model coefficients for early damage detectability with an application to wind turbine blades

Piotr Omenzetter and Simon Hoell's work within the Lloyd's Register Foundation Centre for Safety and Reliability Engineering at the University of Aberdeen is supported by Lloyd’s Register Foundation. The Foundation helps to protect life and property by supporting engineering-related education, public engagement and the application of research.

Optimal selection of autoregressive model coefficients for early damage detectability with an application to wind turbine blades

Piotr Omenzetter and Simon Hoell's work within the Lloyd's Register Foundation Centre for Safety and Reliability Engineering at the University of Aberdeen is supported by Lloyd’s Register Foundation. The Foundation helps to protect life and property by supporting engineering-related education, public engagement and the application of research.

Maternal-Fetal Attachment and Health Behaviors among Women with HIV/AIDS

Background: Mothers with HIV often face personal and environmental risks for poor maternal health behaviors and infant neglect, even when HIV transmission to the infant was prevented. Maternal-fetal attachment (MFA), the pre-birth relationship of a woman with her fetus, may be the precursor to maternal caregiving. Using the strengths perspective in social work, which embeds MFA within a socio-ecological conceptual framework, it is hypothesized that high levels of maternal-fetal attachment may protect mothers and infants against poor maternal health behaviors. Objective: To assess whether MFA together with history of substance use, living marital status, planned pregnancy status, and timing of HIV diagnosis predict three desirable maternal health behaviors (pregnancy care, adherence to prenatal antiretroviral therapy–ART, and infant’s screening clinic care) among pregnant women with HIV/AIDS. Method: Prospective observation and hypothesis-testing multivariate analyses. Over 17 consecutive months, all eligible English- or Spanish-speaking pregnant women with HIV ( n = 110) were approached in the principal obstetric and screening clinics in Miami-Dade County, Florida at 24 weeks’ gestation; 82 agreed to enroll. During three data collection periods from enrollment until 16 weeks after childbirth (range: 16 to 32 weeks), participants reported on socio-demographic and predictor variables, MFA, and pregnancy care. Measures of adherence to ART and infant care were extracted from medical records. Findings: Sociodemographic, pregnancy, and HIV disease characteristics in this sample suggest changes in the makeup of HIV-infected pregnant women parallel to the evolution of the HIV epidemic in the USA over the past two decades. The MFA model predicted maternal health behaviors for pregnancy care (R2 = .37), with MFA, marital living status, and planned pregnancy status independently contributing ( = .50, = .28, = .23, respectively). It did not predict adherence to ART medication or infant care. Relevance: These findings provide the first focused evidence of the protective role of MFA against poor maternal health behaviors among pregnant women with HIV, in the presence of adverse life circumstances. Social desirability biases in some self-report measures may limit the findings. Suggestions are made for orienting future inquiry on maternal health behaviors during childbirth toward relationship and protection.

Communication-efficient decentralized sequential detection

The problem of decentralized sequential detection is studied in this thesis, where local sensors are memoryless, receive independent observations, and no feedback from the fusion center. In addition to traditional criteria of detection delay and error probability, we introduce a new constraint: the number of communications between local sensors and the fusion center. This metric is able to reflect both the cost of establishing communication links as well as overall energy consumption over time. A new formulation for communication-efficient decentralized sequential detection is proposed where the overall detection delay is minimized with constraints on both error probabilities and the communication cost. Two types of problems are investigated based on the communication-efficient formulation: decentralized hypothesis testing and decentralized change detection. In the former case, an asymptotically person-by-person optimum detection framework is developed, where the fusion center performs a sequential probability ratio test based on dependent observations. The proposed algorithm utilizes not only reported statistics from local sensors, but also the reporting times. The asymptotically relative efficiency of proposed algorithm with respect to the centralized strategy is expressed in closed form. When the probabilities of false alarm and missed detection are close to one another, a reduced-complexity algorithm is proposed based on a Poisson arrival approximation. In addition, decentralized change detection with a communication cost constraint is also investigated. A person-by-person optimum change detection algorithm is proposed, where transmissions of sensing reports are modeled as a Poisson process. The optimum threshold value is obtained through dynamic programming. An alternative method with a simpler fusion rule is also proposed, where the threshold values in the algorithm are determined by a combination of sequential detection analysis and constrained optimization. In both decentralized hypothesis testing and change detection problems, tradeoffs in parameter choices are investigated through Monte Carlo simulations.

Aprendizaje basado en problemas, ABP : una propuesta para transformar la enseñanza-aprendizaje de las aplicaciones de la trigonometría en la solución de triángulos en el grado 10º

El estudio tuvo como propósito determinar la efectividad relativa del ABP, comparado con el método tradicional para desarrollar habilidades de resolución de problemas en el aprendizaje de las aplicaciones de la solución de triángulos en el grado 10º de la Institución Educativa El Progreso, de El Carmen de Viboral, Antioquia. La enseñanza-aprendizaje de las matemáticas sustentadas con la estrategia didáctica Aprendizaje Basado en Problemas permite a los estudiantes y docentes aproximarse al conocimiento de una manera similar a como lo hacen los científicos; el primer paso es una situación de duda, perplejidad del estudiante provocada por la Situación Problema planteada por el docente, el segundo un momento de “sugerencias” en las que la mente salta hacia adelante en busca de una posible solución (Dewey, 1933, p. 102). El tercer paso “intelectualización” de la dificultad que se ha percibido para convertirlo en un problema que debe solucionarse (Dewey, 1933, p. 103). La cuarta es “la idea conductora o hipótesis”, las cuales se basan en la formulación de explicaciones sugeridas o soluciones posibles (Dewey, 1933, p. 104). El quinto paso sería el “razonamiento”, consiste en la elaboración racional de una idea que se va desarrollando de acuerdo a las habilidades de cada persona (Dewey, 1933, p. 105). El paso final es la “comprobación de hipótesis” en situaciones reales. Este proceso se evidenció a través de cuatro Situaciones-Problema enfocadas desde un contexto auténtico “la remodelación del parque principal de El Carmen de Viboral” con el objetivo de motivar a los estudiantes para el aprendizaje de algunos conceptos matemáticos y el desarrollo de habilidades de resolución de problemas. La metodología de la investigación fue un diseño cuasi-experimental con grupo experimental compuesto por 38 estudiantes del grado 10º2 y grupo control con 37 estudiantes del grado 10º1. Se empleó como técnica de recolección de la información una prueba pre-test antes del tratamiento y una prueba post-test que se aplicó después del tratamiento a ambos grupos; se aplicó también una escala de satisfacción de los estudiantes con la metodología tradicional en ambos grupos y una escala de satisfacción con la estrategia didáctica ABP sólo al grupo experimental; la observación directa, y el portafolio que evidenciaba todas las construcciones de los estudiantes. La aplicación de la estrategia didáctica experimental se aplicó durante 4 meses, con una intensidad horaria de cuatro horas semanales, tiempo durante el cual se implementaron las cuatro Situaciones-Problema. Se concluyó entre otros aspectos que el 86,5% de los estudiantes encuentran las clases de matemáticas como interesantes, contextualizadas, aplicables y significativas, mientras que antes del tratamiento sólo el 44,4% se encontraba satisfecho con las clases de matemáticas, con una diferencia en cambio de actitud de 42,1% frente a las clases de matemáticas con la metodología tradicional. En el análisis comparativo de adquisición de competencias específicas se demuestra que el grupo experimental demostró ser matemáticamente más competente con respecto al grupo control en todas las competencias evaluadas: capacidad de modelación, inductiva, comunicativa y habilidad procedimental. Además, el proyecto de investigación tuvo un valor agregado: 10 estudiantes tuvieron la oportunidad de conocer más sobre su cultura ceramista mediante el diseño y construcción de mosaicos que los ofreció la casa de la cultura en forma gratuita.