Colour Constancy: Biologically-inspired Contrast Variant Pooling Mechanism

Pooling is a ubiquitous operation in image processing algorithms that allows for higher-level processes to collect relevant low-level features from a region of interest. Currently, max-pooling is one of the most commonly used operators in the computational literature. However, it can lack robustness to outliers due to the fact that it relies merely on the peak of a function. Pooling mechanisms are also present in the primate visual cortex where neurons of higher cortical areas pool signals from lower ones. The receptive fields of these neurons have been shown to vary according to the contrast by aggregating signals over a larger region in the presence of low contrast stimuli. We hypothesise that this contrast-variant-pooling mechanism can address some of the shortcomings of max-pooling. We modelled this contrast variation through a histogram clipping in which the percentage of pooled signal is inversely proportional to the local contrast of an image. We tested our hypothesis by applying it to the phenomenon of colour constancy where a number of popular algorithms utilise a max-pooling step (e.g. White-Patch, Grey-Edge and Double-Opponency). For each of these methods, we investigated the consequences of replacing their original max-pooling by the proposed contrast-variant-pooling. Our experiments on three colour constancy benchmark datasets suggest that previous results can significantly improve by adopting a contrast-variant-pooling mechanism

El mundo del trabajo indígena en Los Andes durante la colonia

El trabajo que presenté es un ensayo de opinión, cuyo referato se publica conjuntamente con mi respuesta. Resumen:¿Cómo lograron los conquistadores que la población indígena se incorporara a susempresas como fuerza de trabajo? ¿Cómo hicieron para que dejaran sus tierras y su producción y se fueran a trabajar a un emprendimiento ajeno? Éstas han sido preguntas clásicas de la historia social y también de la historiografía andina, aunque hayan sido planteadas con frecuencia con otras palabras. En este ensayo propongo hacer un recorrido, primero, por las principales respuestas que se articularon en torno a estos interrogantes, para después ponerlas en discusión a la luz de los nuevos avances que hubo y sigue habiendo en los estudios sobre esta región, en particular, algunos que están hoy en proceso. Si bien el ensayo se centra en Charcas, gran parte de la historiografía refiere a Andes Centrales: siempre que ha sido posible he distinguido ambos territorios, y si no fue posible, hablo de los AndesThis essay is structured around a classical question for both social historians and Andean historiography: How did the Spanish conquerors incorporate the indigenous population to their enterprises as labour force? The text begins with a summary of the answers given to this question, discussing them in the light of new developments in the studies of this region, including some that are now in process. My contribution focuses on two aspects developed at the end of the essay. On the one hand, the analytical decomposition of some of the key concepts proposed by the pioneers in Andean history what allows a reconsideration of some categories that we now know better thanks to new monographies. On the other hand, an emphasis is placed on chronology, specificity of different historical periods and specific situations and changes over time; all aspects that are sometimes discussed in those models, even if partially.Fil: Gil Montero, Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin

Indigenous recruitment mechanisms for silver mining. Lipez (South Bolivia) 17th century

Este artículo analiza el mundo del trabajo de una mina de plata del siglo XVII ubicada al sur de la actual Bolivia, llamada San Antonio del Nuevo Mundo. A partir de este análisis se busca comprender cuáles fueron los mecanismos a través de los cuales se logró satisfacer la demanda de mano de obra que tenían los mineros y otros españoles de este asiento minero. Entre las dos formas extremas, el trabajo forzado y el libre, hemos encontrado que en San Antonio había una combinación de variados mecanismos de atracción y de coacción. Además hemos visto que la influencia del principal centro minero –Potosí– fue muy significativa en aspectos tales como la migración, la presencia de trabajadores especializados y la adquisición de conocimiento.This article focuses on labour relations in a silver mine from the 17th century, located in present-day Bolivia, called San Antonio del Nuevo Mundo. The purpose of this analysis is to understand which were the mechanisms used to fulfil the workers needs that miners and other Spaniards had. Between forced and free labour we found different combinations of coaction and attraction in San Antonio. The influence of the main miner center which was Potosi was also very important in our region regarding migration, presence of skilled workers and adquisition of knowledge.Fil: Gil Montero, Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto Superior de Estudios Sociales; Argentina. Universidad Nacional de Tucumán; Argentin

TIME, to move forward? Comment on “a universal outcome measure for headache treatments, care-delivery systems and economic analysis”

The paper from Steiner et al. suggests that an outcome measure expressed in time units may be an adequate method to assess the impact of headache disorders, regardless of diagnosis or health care setting, proving useful for cost-benefit analysis and health policy definition. Using time lost to each attack – weighted by disability – may prove to be a reliable measure to establish the effectiveness of acute treatment, but if considering also the attack frequency it could evaluate the effects of preventive strategies. A measure such as the Headache Gauge, which translates the proportion of time lost to headache -related disability, has proven to be applicable also in routine clinical practice as well, and can be tested in clinical trials and populational analysis. There are practical limitations, such as disability assessment and the need for prospective data collection to avoid recall bias but it seems consensual that impairment related to primary headache disorders is primarily driven by the TIME stolen from the perfect health status.info:eu-repo/semantics/publishedVersio

Cognitive functions during migraine attacks

Tese de doutoramento, Medicina (Neurologia), Universidade de Lisboa, Faculdade de Medicina, 2015Background: Attack-related cognitive symptoms in migraine are frequent yet scarcely characterized and undervalued as contributors of disability. Conflicting evidence arose about an increased risk of cognitive decline in older migraine patients. Objectives: (1) to study the occurrence of cognitive symptoms in migraine attacks; (2) to evaluate objective evidence of cognitive dysfunction in migraine attacks and its neuronal correlates and (3) to study the effect of persisting migraine in cognitive function or cognitive decline in older adults. Methods: Occurrence of attack-related cognitive symptoms was detailed by systematic literature review and a cross-sectional clinical-based systematic survey; their relevance to disability was studied prospectively using headache diaries. An instrument (Mig-SCog) was developed, validated and tested to identify and quantify attack-related subjective cognitive symptoms. Cognitive function during attacks was evaluated by a systematic literature review and a clinical-based prospective two-period randomized cross-over study using an extensive neuropsychological battery. A briefer battery was tested in repeated applications in interictal patients and controls. Brain perfusion during attacks was studied with arterial spin labeling magnetic resonance imaging (ASL-MRI) and cortical response to a working memory task with blood-oxygen level dependent functional magnetic resonance imaging (BOLD-fMRI). A prospective controlled cross-sectional population-based study of neuropsychological performance of older adults with persisting migraine and non-migraine headache was followed by a 5 years re-evaluation of the same sample, to screen for cognitive decline. Results: Cognitive symptoms were the most frequent non-migraine defining symptoms reported in the prodromic(37%) and headache(38%) phases of migraine attacks in a systematic review of 28 series, with a total sample of 8392 patients. Cognitive symptoms are also present in the postdromic or resolution phase, although fatigue (71%) is reported more often. Of 165 patients prospectively surveyed, 87% reported an average of 2.5 attack-related symptoms, over two-thirds executive (attention, processing efficiency and speed). Cognitive symptoms were ranked prospectively by 34 migraine patients recording 229 attacks, being second only to pain in terms of intensity and attack-related disability. An instrument to quantify migraine attack-related symptoms was constructed from a set of 43 candidate items, using factor analysis. The reduced 9 item Mig-SCog is fast to apply covering executive functions and language, having good internal consistency (Cronbachs’ alpha 0.82) and reliability (Cohen’s kappa 0.55) and high correlation with external validity measures such as the 43-candidate item list (rho=0.69) and the Cognitive Failures Questionnaires(rho=0.61). The Mig-SCog presents negligible recall bias (no difference in scores obtained during an attack or while headache free) and Migraine patients score it higher for migraine higher for migraine (7.9±4.6) than for non-headache pain (2.3±2.9, p<0.0006) or pain free (1.6±2.4, p<0.0006). Comparing Mig-SCog scores in migraine and tension-type headache patients, those were higher for migraine in all scale items (p<0.0001) except those related to naming (8 and 9). The AUC of Mig-SCog score for the diagnosis of Migraine was 0.835 (95% CI of 0.763-0.906, p< 0.0001) reinforcing specificity for migraine. Ten studies of neuropsychological evaluation during migraine attacks are available in the literature, only half had data allowing comparison of cognitive performance within and outside attacks (encompassing 163 migraine patients). All these were able to demonstrate some type of impairment (most often executive) although some bias could not be excluded from their study design. In our sample of 24 patients which completed an extensive neuropsychological evaluation in these two conditions (attack and headache-free) controlling for the majority of relevant bias (in particular the practice effect), performance was worse during the attack in the majority of cognitive tests, in particular in word reading speed (p=0.013), verbal learning (p=0.01), short term verbal recall with (p=0.01) and without (p=0.013) semantic cueing and delayed recall with (p=0.003) and without (p=0.05) semantic cues. Another sample of 24 interictal migraine patients and 24 matched controls performed equally in a shorter battery focused on executive functions that was applied twice with a short interval (average 45 days) to test the practice effect of repeated evaluations that was demonstrated in all tests, being significant in Stroop Interference test (p=0.002, multiplicity corrected); a meaningful score change was determined for each raw test scores. We were unable to find any relevant brain perfusion nor brain activation differences evoked by a working memory task during a spontaneous migraine without aura attack of an average intensity of 6.8 on a 0-10 VAS scale and an average duration of 16 hours in a sample of 13 women, compared to being headache-free. Persistent migraine or headache after the age of 50 related to worse performance in some neuropsychological tests (attention and processing speed in migraine patients, n=61; sematic memory and memory retrieval in non-migraine headache, n=50) in a population sample of 478 individuals tested extensively. After 5 years, 275 (57.5%) of the same sample were screened for cognitive decline, that occurred in 14.9% of the sample. Neither migraine nor non-migraine headache influenced the odds of decline. Discussion: Attack-related cognitive symptoms are very frequent, mostly executive and contribute to disability, supporting that they should be addressed as endpoint in clinical trials of acute migraine treatments and included in disability assessments. An efficient way to assess attack-related subjective cognitive symptoms in clinical practice or research is now available – the Mig-SCog. Although migraine-related reversible cognitive dysfunction was demonstrated during attacks, no advances on potential brain mechanisms underlying these findings were made. Interest is focused to obtain more functional data, with studies of evoked activation paradigms, functional connectivity and combined imaging and neurophysiological studies. Although persisting headache in older adults seems to influence executive performance, these changes are most likely adaptive and do not seem to influence the process of brain degeneration and associated cognitive decline

Educational Use of Social Media in Primary and Childhood Education Degrees at a Virtual University

The use of social networks is part of people's daily lives, and university students, in their academic life, make particularly intense use of them on a daily basis for different purposes. This research analyses the nature, intensity, and type of educational use of these social media by childhood and primary pre-teachers who are pursuing their studies online in Spain. To this end, we designed and validated an ad hoc questionnaire, obtaining 268 valid responses to research the specific characteristics of students studying for degrees in early childhood education and primary education and a double degree in early childhood and primary education at a university that is exclusively online. The results show that participants habitually use a variety of social media, but they only use some of them for educational purposes. General social networks offer future teachers versatility, the possibility to develop and leverage social capital, and opportunities to connect formal, non-formal and informal settings. The most used networks were WhatsApp, YouTube and above all Facebook, a reasonably large percentage use Instagram or Pinterest, and, to a lesser extent, Skype, and a lightly under half have Twitter. With regards to how they are used for educational purposes, a majority of respondents reported using them to find classroom activities, new ideas and material that might be of use in their academic work. It was also found that students consumed more information than what they produced, such that social capital is not used in an optimal way. It is concluded that in a university that operates exclusively online, the use of social networks fulfils the function of covering affective and social needs in an optimal way

Analytical framework to discover churn rate insights

Employee turnover is a costly problem for any business. For every position left vacant, the time and cost associated with identifying, acquiring, and training the right person can lessen a businesses impact on revenue growth and brand expansion [1]. Employee retention becomes a crucial strategy for the company since it can reduce costs. To mitigate this problem, organizations must create strategy plans as a way to retain their employees. To create these strategies, in the first instance, there is a need to understand and evaluate the reasons employees leave the company. These reasons can be validated based on existing reasons, or by creating analyses of the organization's existing data regarding employees. The reasons an employee leaves the company can be classified into two events. The first can be initiated by the employee. In this case, it is a voluntary turnover. The second one is an involuntary turnover, characterized by the initiative of company. This dissertation includes the creation of a framework for the acknowledgement of the reasons for an employee to leave the company. The framework is created based on a real project of an organization and intends to demystify common misconceptions/premises, based on literature review, regarding the reasons for an employee turnover. It proposes to validate if the misconceptions apply to the business context and if they are true. Additionally, this framework also allows the study of the main reasons that lead to the decision to leave an organization (e.g. search for career progress) by suggesting some key variables for the application of these analyses to understand how they affect employee churn.A rotatividade de colaboradores é um problema que pode ter um enorme custo anual para qualquer empresa, monetário ou temporal. Quando um colaborador sai da empresa, pode exigir que essa vaga seja preenchida de imediato. Essa substituição resulta em uma nova contratação que custa tempo (recrutamento, aquisição, formações) e que pode diminuir o impacto de uma empresa no crescimento da receita e expansão. Neste sentido, a retenção dos colaboradores torna-se uma estratégia crucial para a empresa, uma vez que pode reduzir custos em larga escala. De forma a mitigar este problema, as organizações devem criar planos de estratégia para a retenção dos seus colaboradores. Para a criação destas estratégias, existe a necessidade em primeira instância de compreender e avaliar os motivos dos colaboradores a sair da empresa. Estes motivos podem ser validados com base na visualização/análises de dados históricos, existentes em uma organização referentes aos colaboradores. As razões de um colaborador sair da empresa, podem se classificar em dois eventos. Por vontade própria, neste caso rotatividade voluntária, ou rotatividade involuntária, caracterizado por ser iniciativa da empresa. Esta dissertação compreende a criação de uma framework para a análise dos motivos de saída de um colaborador de uma empresa. A framework proposta é criada com base em um projeto real de uma organização e, pretende desmistificar conceitos/premissas conhecidas, com base em revisão de literatura, referentes aos motivos de rotatividade dos colaboradores. Pretendendo validar se as premissas são aplicáveis ao contexto empresarial e se são verdadeiras. Adicionalmente a estas premissas, esta framework permite também estudar os principais motivos que levam à decisão de sair de uma organização (progressão de carreira) sugerindo algumas variáveis chave para a aplicação da framework

Educational Use of Social Media in Primary and Childhood Education Degrees at a Virtual University

The use of social networks is part of people's daily lives, and university students, in their academic life, make particularly intense use of them on a daily basis for different purposes. This research analyses the nature, intensity, and type of educational use of these social media by childhood and primary pre-teachers who are pursuing their studies online in Spain. To this end, we designed and validated an ad hoc questionnaire, obtaining 268 valid responses to research the specific characteristics of students studying for degrees in early childhood education and primary education and a double degree in early childhood and primary education at a university that is exclusively online. The results show that participants habitually use a variety of social media, but they only use some of them for educational purposes. General social networks offer future teachers versatility, the possibility to develop and leverage social capital, and opportunities to connect formal, non -formal and informal settings. The most used networks were WhatsApp, YouTube and above all Facebook, a reasonably large percentage use Instagram or Pinterest, and, to a lesser extent, Skype, and a lightly under half have Twitter. With regards to how they are used for educational purposes, a majority of respondents reported using them to find classroom activities, new ideas and material that might be of use in their academic work. It was also found that students consumed more information than what they produced, such that social capital is not used in an optimal way. It is concluded that in a university that operates exclusively online, the use of social networks fulfils the function of covering affective and social needs in an optimal way

Pre-service Teachers' Use of General Social Networking Sites Linked to Current Scenarios: Nature and Characteristics

Social networking sites form part of everyday life in classrooms at all educational levels. Within these, general social networking sites (GSNSs) offer pre-service teachers flexibility, versatility and the possibility of forming educational communities by connecting formal, non-formal and informal settings. This research analyses the nature, intensity, and type of pre-service teachers’ use of such for educational purposes in their initial training in order to detect the most important aspects for improvement. Possible factors shaping behaviour were gender, whether individuals belonged to universities operating online or in person, differences in the types of studies they were undertaking, and the time at which the questionnaire was administered, before or after the COVID-19 health crisis. To this end, we studied how much and with what aims these students use the most widely used GSNSs for educational purposes. To do so, we administered a questionnaire to a total of 812 students from 6 Spanish universities. The results show a preference for WhatsApp, YouTube, and Instagram. In addition, it was found that undergraduate students used them more intensively than postgraduate students. In the case of online universities, there was a greater need to cover affective and emotional aspects than in in-person universities. As in almost all areas, the situation caused by COVID-19 changed the way social networks were used. The findings also show that pre-service teachers consumed more information on social media than what they produced, which leads to a failure to fully exploit social capital and potential job or academic opportunities that could be generated through their own creations