13,277 research outputs found

    Identification of Hindbrain Neural Substrates for Motor Initiation in the hatchling Xenopus laevis Tadpole

    Get PDF
    Animal survival profoundly depends on the ability to detect stimuli in the environment, process them and respond accordingly. In this respect, motor responses to a sensory stimulation evolved into a variety of coordinated movements, which involve the control of brain centres over spinal locomotor circuits. The hatchling Xenopus tadpole, even in its embryonic stage, is able to detect external sensory information and to swim away if the stimulus is considered noxious. To do so, the tadpole relies on well-known ascending sensory pathway, which carries the sensory information to the brain. When the stimulus is strong enough, descending interneurons are activated, leading to the excitation of spinal CPG neurons, which causes the undulatory movement of swimming. However, the activation of descending interneurons that marks the initiation of motor response appears after a long delay from the sensory stimulation. Furthermore, the long-latency response is variable in time, as observed in the slow-summating excitation measured in descending interneurons. These two features, i.e. long-latency and variability, cannot be explained by the firing time and pattern of the ascending sensory pathway of the Xenopus tadpole. Therefore, a novel neuronal population has been proposed to lie in the hindbrain of the tadpole, and being able to 'hold' the sensory information, thus accounting for the long and variable delay of swim initiation. In this work, the role of the hindbrain in the maintenance of the long and variable response to trunk skin stimulation is investigated in the Xenopustadpole at developmental stage 37/38. A multifaceted approach has been used to unravel the neuronal mechanisms underlying the delayed motor response, including behavioural experiments, electrophysiology analysis of fictive swimming, hindbrain extracellular recordings and imaging experiments. Two novel neuronal populations have been identified in the tadpole's hindbrain, which exhibit activation patterns compatible with the role of delaying the excitation of the spinal locomotor circuit. Future work on cellular properties and synaptic connections of these newly discovered populations might shed light on the mechanism of descending control active at embryonic stage. Identifying supraspinal neuronal populations in an embryonic organism could aid in understanding mechanisms of descending motor control in more complex vertebrates

    Balancing the urban stomach: public health, food selling and consumption in London, c. 1558-1640

    Get PDF
    Until recently, public health histories have been predominantly shaped by medical and scientific perspectives, to the neglect of their wider social, economic and political contexts. These medically-minded studies have tended to present broad, sweeping narratives of health policy's explicit successes or failures, often focusing on extraordinary periods of epidemic disease viewed from a national context. This approach is problematic, particularly in studies of public health practice prior to 1800. Before the rise of modern scientific medicine, public health policies were more often influenced by shared social, cultural, economic and religious values which favoured maintaining hierarchy, stability and concern for 'the common good'. These values have frequently been overlooked by modern researchers. This has yielded pessimistic assessments of contemporary sanitation, implying that local authorities did not care about or prioritise the health of populations. Overly medicalised perspectives have further restricted historians' investigation and use of source material, their interpretation of multifaceted and sometimes contested cultural practices such as fasting, and their examination of habitual - and not just extraordinary - health actions. These perspectives have encouraged a focus on reactive - rather than preventative - measures. This thesis contributes to a growing body of research that expands our restrictive understandings of pre-modern public health. It focuses on how public health practices were regulated, monitored and expanded in later Tudor and early Stuart London, with a particular focus on consumption and food-selling. Acknowledging the fundamental public health value of maintaining urban foodways, it investigates how contemporaries sought to manage consumption, food production waste, and vending practices in the early modern City's wards and parishes. It delineates the practical and political distinctions between food and medicine, broadly investigates the activities, reputations of and correlations between London's guild and itinerant food vendors and licensed and irregular medical practitioners, traces the directions in which different kinds of public health policy filtered up or down, and explores how policies were enacted at a national and local level. Finally, it compares and contrasts habitual and extraordinary public health regulations, with a particular focus on how perceptions of and actual food shortages, paired with the omnipresent threat of disease, impacted broader aspects of civic life

    The Lived Experiences of Yoga Practice for Female Survivors of Child Sexual Abuse: An Interpretative Phenomenological Analysis

    Get PDF
    Childhood sexual abuse (CSA) permeates all aspects of personhood including the body. There is a surge in the interest in reviewing yoga’s potential usefulness for trauma survivors in clinical trials. However, very little research focuses on women’s perspectives who experienced CSA and have subsequently practised yoga in community settings. This study investigated six women’s lived experiences of yoga practice, mainly focusing on the helpful and unhelpful aspects of yoga that mediated their recovery. Adult women survivors with experience of movement-based yoga in a group setting for at least eight weeks in the last year were recruited. Data were collected using individual, face-to-face, and semi-structured interviews. The transcribed data were analysed using Interpretative phenomenological analysis (IPA) underpinned by constructivist ontology, phenomenological epistemology, and feminist axiology. Three emergent themes were identified- “Coming to yoga”, “Process of becoming” and “Reclaiming life”. Women’s narratives in this study illustrated that they found yoga a useful and resilience-building resource in their journey of healing. With consistent and frequent practice, they reported feeling more present, self-aware, and compassionate towards themselves. Teacher’s qualities such as fostering safety, choice and holistic focus were identified as significant mediating factors that aided this journey, whereas crowded, mixed-gender, and posture-focused practice presented challenges for some respondents. This study has the potential to help Counselling psychologists (CoP), therapists, psychologists, mental health practitioners, yoga teachers, and health professionals involved in the care of the CSA survivors in implementing an evidence-based and holistic approach that facilitates self-directed recovery of CSA survivors. Further research is needed to establish if the benefits and challenges of different aspects of practice apply to the diverse population and its potential usefulness in various phases of recovery. Also, find ways to standardize the yoga practice considering variations in the approach to ensure safe and ethical practice

    Bank managers in Jordan: a study of motivation, job satisfaction and comparative organizational practices

    Get PDF
    This thesis is an attempt to fill a gap in research in the area of motivation and job satisfaction in the Jordanian/Arab managerial context. It is basically built on a representative sample of 266 Jordanian managers taken from 21 Jordanian/Arab and Western (Anglo-American) banks in Jordan. The thesis is an exploratory and comparative organizational behaviour and management study. It implements two instruments of investigation, a standardized questionnair and in-depth interviews. The major findings of the thesis that Jordanian bank managers' patterns of motivation and job satisfaction and their interpretation of the 'higher goals of the job' (for example, autonomy) are similar to Western managers'. The assessmentf about 20 related factors on bank managers' motivation and job satisfaction reveal that different demographic and social and other organizational factors contribute to the significant impact on bank managers' motivation and job satisfaction. However, the significant impact of job related factors is more noticeable compared with other factors. The thesis, with consideration to the recommendation and the implications of relevant research, extends the study beyond managers' attitudes and includes relevant managerial practices and systems. It also attemps to reflect on the interaction of the organization within the wider environment. The comparison of the managerial practices and systems (for example, delegation of authority) and other organizational variables (for example, specialization) relevant to bank managers' motivation and job satisfaction reveal that major and significant differences are found between Western (Anglo-American) and Jordanian/Arab banks. It also reveals that the type of managerial practices and systems in the Jordanian/Arab banks is, by and large, traditional and less bureaucratic compared with the managerial practices in Western (Anglo-American) banks. The thesis addresses the main managerial implications Jordanian/Arab banks could consider when designing their motivational and job satisfaction systems. In an attempt to interpret the traditional managerial practices in the Jordanian/Arab banks, pertinent factors are discussed. These relate to particular factors of the Jordanian/Arab banks and to specific cultural and social factors in the Jordanian/Arab societies

    Interactive query expansion for professional search applications

    Get PDF
    Knowledge workers (such as healthcare information professionals, patent agents and recruitment professionals) undertake work tasks where search forms a core part of their duties. In these instances, the search task is often complex and time-consuming and requires specialist expert knowledge to formulate accurate search strategies. Interactive features such as query expansion can play a key role in supporting these tasks. However, generating query suggestions within a professional search context requires that consideration be given to the specialist, structured nature of the search strategies they employ. In this paper, we investigate a variety of query expansion methods applied to a collection of Boolean search strategies used in a variety of real-world professional search tasks. The results demonstrate the utility of context-free distributional language models and the value of using linguistic cues to optimise the balance between precision and recall

    Shedding light on dark matter through 21 cm cosmology and reionization constraints

    Get PDF
    Durante las últimas décadas, nuestra comprensión del universo ha alcanzado un nivel remarcable, pudiendo probar predicciones cosmológicas con una precisión asombrosa. Las observaciones de los fotones del Fondo Cósmico de Microondas, junto con los estudios de catálogos galaxias, nos proporcionan una comprensión profunda de la geometría, los componentes y la cronología del cosmos. No obstante, la naturaleza de la Materia Oscura aún se desconoce. La composición, masa e interacciones de las partículas de Materia Oscura presentan uno de los enigmas más intrigantes de la cosmología actual. En esta tesis doctoral se estudian diferentes candidatos a Materia Oscura que pueden dejar un impacto en el proceso de formación de estructuras y en la evolución del Medio Intergaláctico. El análisis del estado de ionización del Medio Intergaláctico, su impacto en el Fondo Cósmico de Microondas y la señal cosmológica corrida al rojo de 21 cm, pueden proporcionar información reveladora sobre las propiedades de la Materia Oscura. Esta tesis está organizada en tres partes. La Parte I está dedicada a una amplia introducción a los fundamentos que describen los temas considerados. Los conceptos básicos del paradigma cosmológico estándar, el universo Lambda-CDM, y un esbozo de la cronología cósmica se presentan en el Capítulo 1. El Capítulo 2 repasa el progreso histórico de las evidencias de la Materia Oscura, seguido de una discusión sobre el estado y la cuestiones del paradigma de la Materia Oscura Fría. Posteriormente se examinan dos escenarios alternativos de Materia Oscura no estándar: Materia Oscura Templada, con partículas con masas del orden del keV, y Materia Oscura Interactiva, donde las partículas de Materia Oscura interactúan a través de la dispersión elástica con fotones. Los efectos físicos, las motivaciones y las restricciones actuales de estos escenarios se estudian en detalle. El Capítulo 3 considera los Agujeros Negros Primordiales como otro candidato de Materia Oscura, repasando su mecanismo de formación, propiedades físicas y límites actuales en su abundancia. Se discuten ampliamente dos efectos principales: el acrecimiento de materia circundante y el incremento de las fluctuaciones a pequeña escala debido al ruido de Poisson, los cuales podrían dejar un impacto observacional en el Medio Intergaláctico. Los fundamentos de la señal cosmológica de 21 cm se revisan en el Capítulo 4, proporcionando las principales derivaciones a partir de un tratamiento de transferencia radiativa, resumiendo los procesos principales que pueden excitar y desexcitar átomos a través de la transición hiperfina en el hidrógeno, y discutiendo los detalles de sus fluctuaciones espaciales a través del espectro de potencias. También se examinan los diferentes métodos de observación por interferometría y experimentos de una única antena, el estado experimental actual y las perspectivas para la detección de la señal de 21 cm con futuros interferómetros. Finalmente, el Capítulo 5 está dedicado al tratamiento del Medio Intergaláctico y la evolución de su estado térmico y de ionización. Se discute el estudio de la Reionización en marcos globales y no homogéneos, así como los límites actuales sobre la evolución de la fracción ionizada por diferentes métodos. Se examinan los canales de enfriamiento y calentamiento relevantes en el medio neutro, junto con la evolución del flujo Lyman-alfa, finalizando con un bosquejo de las diferentes fases evolutivas del universo que se pueden estudiar mediante el estudio de la línea de 21 cm. La Parte II incluye siete artículos científicos originales publicados durante el desarrollo del doctorado, que constituyen el trabajo principal de esta tesis. Finalmente, la Parte III contiene un resumen de los principales resultados en castellano.During the last decades, our understanding of the universe has reached a remarkable level, being able to test cosmological predictions with an astonishing precision. Observations of relic photons of the Cosmic Microwave Background, together with galaxy surveys, provide us with a deep comprehension of the geometry, components and chronology of the cosmos. Nonetheless, the nature of the Dark Matter still remains unknown. The composition, mass and interactions of Dark Matter particles present one of the most intriguing conundrums in current cosmology. In this doctoral thesis, signatures of Dark Matter candidates which can leave an impact on the process of formation of structures and on the evolution of the Intergalactic Medium are studied. The analysis of the state of ionization of the Intergalactic Medium, its impact on the Cosmic Microwave Background, and the 21 cm redshifted cosmological signal, can provide insightful information regarding the properties of the Dark Matter. This thesis is organized in three parts. Part I is devoted to a broad introduction to the fundamentals describing the state of the art of the topics considered. The basics of the standard cosmological paradigm, the Lambda-CDM universe, and a sketch of the cosmic timeline is presented in Chapter 1. Chapter 2 overviews the historical progress of evidences of Dark Matter, followed by a discussion of the status and small-scale issues of the Cold Dark Matter paradigm. Two alternative non-standard Dark Matter scenarios are then examined: Warm Dark Matter, whose particles with masses of the order of keV present free streaming, and Interacting Dark Matter, where Dark Matter particles interact via elastic scattering with photons, producing collisional damping. The physical effects, motivations and current constraints of these Dark Matter scenarios are studied in detail. Chapter 3 considers Primordial Black Holes as another Dark Matter candidate, overviewing their formation mechanism, physical properties and current constraints on their abundance. Two main effects are widely discussed: accretion of surrounding matter and the enhancement of small-scale fluctuations due to the Poisson shot noise, both of which could leave an observational impact in the Intergalactic Medium. The fundamentals of the 21 cm cosmological signal are reviewed in Chapter 4, providing the main derivations from a radiative transfer treatment, summarizing the main processes which can excite and de-excite atoms via the hyperfine transition in Hydrogen, and discussing the details of its spatial fluctuations via the power spectrum. The different observational tests by interferometry and single-dish experiments, current experimental status and prospects for the detection of the 21 cm signal with future interferometers are also examined. Finally, Chapter 5 is dedicated to the treatment of the Intergalactic Medium and the evolution of its ionization and thermal state. The study of Reionization in global and inhomogeneous frameworks are discussed, as well as the current bounds on the evolution of the ionized fraction by different probes. The relevant cooling and heating channels in the neutral medium, together with the evolution of the Lyman-alpha flux are examined, finishing with a sketch of the different evolutionary phases of the universe that can be traced by studying the 21 cm line. Part II includes seven original scientific articles published during the development of the PhD, which constitute the main work of this thesis. Finally, Part III contains a summary of the main results in Spanish
    corecore