A derivation of the optimal answer-copying index and some applications

Multiple-choice exams are frequently used as an efficient and objective method to assess learning but they are more vulnerable to answer-copying than tests based on open questions. Several statistical tests (known as indices in the literature) have been proposed to detect cheating; however, to the best of our knowledge they all lack mathematical support that guarantees optimality in any sense. We partially fill this void by deriving the uniform most powerful (UMP) under the assumption that the response distribution is known. In practice, however, we must estimate a behavioral model that yields a response distribution for each question. We calculate the empirical type-I and type-II error rates for several indices that assume different behavioral models using simulations based on real data from twelve nationwide multiple-choice exams taken by 5th and 9th graders in Colombia. We find that the index with the highest power among those studied, subject to the restriction of preserving the type-I error, is one based on the work of Wollack (1997) and Linden and Sotaridona (2006) and is superior to the indices studied and developed by Wesolowsky (2000) and Frary, Tideman, and Watts (1977). We compare the results of applying this index to all 12 exams and find that examination rooms with stricter proctoring have a lower level of copying. Finally, a Bonferroni correction to control for the false positive rate is proposed to detect massive cheating

BIOLOGY AND MANAGEMENT OF THE BED BUG, Cimex lectularius L. (HETEROPTERA: CIMICIDAE)

The near absence of bed bugs from human dwellings for fifty or more years has left us with limited knowledge of its biology and few answers to eliminate populations. I explored a diverse set of objectives to answer key questions concerning bed bug biology and control. Major objectives were studies of circadian rhythmicity, pyrethroid resistance, sublethal effects of insecticides, synergism of pyrethroids, and evaluation of a pyrrole insecticides, chlorfenapyr. Additional studies included persistence of Borrelia in bed bugs after ingestion, and aggregation factors from feces. In the absence of host stimuli, insects were much more active in the dark than in the light. Nocturnal activity was periodical under continuous light conditions, which indicates that locomotion is endogenously generated by a circadian clock. Circadian rhythm was entrained to reverse dark-light regimes. Short–term starved adults moved more frequently than long-starved adults. These results suggest that starved bugs reduce locomotor activity as a strategy to conserve metabolic reserves. Pyrethroid resistance in C. lectularius was documented for the first time. Extremely high levels of resistance to deltamethrin and λ-cyhalothrin, was detected in populations collected in Kentucky and Ohio. The resistance ratios reported are among the highest documented in any arthropod. Evaluations of more than 20 populations from across the United States indicate that resistance to pyrethroid insecticides is widespread. Bed bugs avoided resting on surfaces treated with deltamethrin but not with chlorfenapyr. Video recordings of bed bugs showed that insects increased their activity when they contacted sublethal doses of deltamethrin. However, harborages treated with a deltamethrin remained attractive. A nearby heat source overcame avoidance to deltamethrin. The P450 inhibitor piperonyl butoxide (PBO) enhanced toxicity of deltamethrin to resistant bed bugs. However, the residual resistance after PBO treatment indicated that other resistance mechanisms are involved. The effectiveness of combining PBO with pyrethroids varied among populations, which indicates that this synergist is not a comprehensive solution to pyrethroid resistance. Chlorfenapyr was effective against pyrethroid resistant strains. While it does not cause quick knockdown, long residual activity and no avoidance behavior to dry residues appears to make this insecticide a useful tool for bed bug control

Depression-related difficulties disengaging from negative faces are associated with sustained attention to negative feedback during social evaluation and predict stress recovery

The present study aimed to clarify: 1) the presence of depression-related attention bias related to a social stressor, 2) its association with depression-related attention biases as measured under standard conditions, and 3) their association with impaired stress recovery in depression. A sample of 39 participants reporting a broad range of depression levels completed a standard eye-tracking paradigm in which they had to engage/disengage their gaze with/from emotional faces. Participants then underwent a stress induction (i.e., giving a speech), in which their eye movements to false emotional feedback were measured, and stress reactivity and recovery were assessed. Depression level was associated with longer times to engage/disengage attention with/from negative faces under standard conditions and with sustained attention to negative feedback during the speech. These depression-related biases were associated and mediated the association between depression level and self-reported stress recovery, predicting lower recovery from stress after giving the speech

Associations between Social Support Dimensions and Resilience Factors and Pathways of Influence in Depression and Anxiety Rates in Young adults

Emerging adulthood is an important developmental period, associated to mental health risk. Resilience research points to both social and personal protective factors against development of psychopathology, but there is paucity with their comprehensive study in young adults. This study provides and initial integrative approach to model multiple dimensions of perceived social support (i.e., from family, friends, significant others) and personal factor of trait resilience (i.e., coping and persistence during stress, tolerance to negative affect, positive appraisals, trust) and their hypothesized contributions to reducing depression and anxiety rates. The study was conducted with a sample of 500 Spanish emerging adults (18 to 29 years old). Regression analyses and multiple mediation models were performed to test our hypotheses. Results showed that social support from family was the dimension with the highest strength relating individual differences in resilience. Furthermore, analyses supported a differential mediating role of specific resilience factors (coping and persistence during stress, tolerance to negative affect, positive appraisals, trust) in partially accounting for the association between higher social support from family and lower depression and anxiety levels in young adults. These results may inform new programs of mental health during emerging adulthood via the promotion of different sources of social support and their related resilience pathways contributing to low emotional symptomatology at this stage of development

Evaluación de los factores que inciden en el rendimiento de las llantas de los vehiculos montacargas de la empresa embotelladora nacional S.A en el período de Enero a Julio del 2015

El presente trabajo sobre la evaluación de los factores que inciden en el rendimiento de las llantas de los vehículos montacargas tiene como finalidad adquirir un cierto grado de conocimiento acerca de rendimiento de llantas y generar un sistema de control ante las condiciones de trabajo ya que actualmente uno de los mayores problemas que tiene ENSA es el mal rendimiento que presenta las llantas de los vehículos montacargas, logrando mantener el mejor bienestar físico de los colaboradores. Esta investigación está orientada en un tipo de enfoque mixto ya que se utilizó el cualitativo porque se explican los factores que inciden en el rendimiento de llantas y el cuantitativo porque se tomaron datos de los vehículos montacargas analizados, teniendo un carácter descriptivo ya que en ella se señalan las causas del fenómeno estudiado contando con una población de 18 vehículos montacargas de los cuales se tomó una muestra de 9 vehículos que operan en las dos áreas estudiadas (agencia Managua y centro de distribución). Fue necesario para nuestro trabajo utilizar el cuestionario, la observación directa y las entrevistas no estructuradas para tener un conocimiento más exacto de la situación técnica de las llantas. Las superficies donde operan los vehículos montacargas se encuentran en muy mal estado, lo cual es el factor que más incide en el rendimiento de llantas, así como la mala operacionalización de los vehículos incide en el desgaste temprano de las llantas. Los factores que inciden en el rendimiento de llantas son: condiciones de superficie, operación de los vehículos, actividades de mantenimiento, cargas levantadas y transportadas. Por el estudio realizado lo más recomendable es hacer un plan de mantenimiento en relación a las llantas de estos vehículos y así obtener menores costos de operación en las mismas

Crecimiento económico en el cono sur de América. Dos Perspectivas: una estructuralista y otra Institucionalista (1870-2010)

En este trabajo se da cuenta del crecimiento económico, y la diferencia con un país rico, de cinco países de América del Sur entre 1870 y 2010. Argentina, Brasil, Chile, Paraguay y Uruguay son analizados a partir de la teoría estructuralista v ista desde la trayectoria de la CEPAL y de la teoría institucionalista vista desde el campo de la ciencia política. El relato se concentra en la evolución de los países y se utiliza un método comparado que tiene como antesala la revisión histórica de documentos y textos para la recopilación de datos, el abordaje técnico es multidisciplinario y da cuenta de la situación de los países que se contrastarán entre sí y con respecto a EEUU. El problema principal que se analiza en este trabajo se relaciona con el subdesarrollo económico que se observa en los países analizados y con las notorias carencias que han mostrado éstos países para superar esta situación y converger hacia los niveles de desarrollo económico y social que se observan en el mundo desarrollado. La pregunta central que la investigación aborda para brindar una respuesta tentativa consiste en saber: ¿Cuáles son las causas del crecimiento económico que ha caracterizado a la región del Cono Sur de América, identificando el papel que han desempeñado algunas dimensiones institucionales y aspectos claves de la estructura económica de los países? Por lo tanto, a partir de diferentes enfoques teóricos se construye un único marco conceptual que pretende dar cuenta de variables explicativas que surgen de disciplinas diferentes y se combinan a tales efectos. El resultado final del trabajo vincula dimensiones propias de la política y características estructurales de los países que en conjunto explican el escaso crecimiento económico de los países del cono sur en estudio. En la dimensión política - institucional, la permanencia de la democracia en el tiempo incide en forma directa sobre él crecimiento económico y los partidos y sistemas de partidos pueden visualizarse como variables antecedentes de la permanencia de la democracia en los países, a su vez, el clientelismo también actúa como una dimensión de incidencia directa. Y en el caso del estructuralismo, la escasa productividad del trabajo y la alta desigualdad de ingresos se visualizan como los factores principa les que combinados a las dimensiones institucionales conforman el “paquete causal” del escaso crecimiento para dichos países.The aim of this work is to explain the economic development of five countries in South America between 1870 and 2010 and their difference compared to a rich country. Argentina, Brazil, Chile, Paraguay and Uruguay are analyzed using both the structuralist theory taking the CEPAL trajectory into account and the Institutionalist theory seen from the scene of the political science. The narration centers on the evolution of the countries mentioned; it is used a method of comparison which has the historic revision of texts and documents for data collecting as an anteroom; it has a multidisciplinary approach and it accounts for the countires situations that are compared to one another and to EEUU. The principal problem that is analysed in this thesis is linked to economic underdevelopment that can be found in the countries studied and the notorius limitations they have shown to overcame this situation and converge towards the levels of economic and social development that are observed in the underdeveloped world. The main question that the research addresses to provide a tentative response consists of knowing what are the causes of the economic growth that have characterized the southern cone region of America identifying the role played by some institutional dimensions and the key aspects of the economic structure of the countries? So from different theoretical approaches a unique conceptual framework is elaborated to account for the explanatory variables that arise from different disciplines and are combined for this purpose. The final result of the research links the specific dimensions of the politics and the structural characteristics of the southern cone countries studied. In the institutional - political dimension, the permanence of democracy over time has a direct impact on economic growth and the political parties and party systems can be visualized as background variables of the permanence of democracy in the countries, at the same time, the political clientelism acts as a dimension of direct incidence. In the case of structuralism, low labor productivity and high income inequality are seen as primary factors that combined with the structural dimensions make up the low growth package for these countries

La tecnología y los países en desarrollo

Las potencias - Los EE.UU. y la U.R.S.S. - Y los países industrializados avanzan, ampliando la brecha económica, mientras los países en desarrollo, en particular los NPI, incrementan su capacidad tecnológica, mediante la adecuada combinación de sus recursos. Los políticos internacionales en financiación, comercio y tecnología determinan la división mundial entre países pobres y ricos