36,721 research outputs found
What is the importance of sperm subpopulations?
.The study of sperm subpopulations spans three decades. The origin, meaning, and practical significance, however, are less clear. Current technology for assessing sperm morphology (CASA-Morph) and motility (CASA-Mot) has enabled the accurate evaluation of these features, and there are many options for data classification. Subpopulations could occur as a result of the stage of development of each spermatozoon in the subpopulation. Spermatogenesis might contribute to the production of these subpopulations. Insights from evolutionary biology and recent molecular research are indicative of the diversity among male gametes that could occur from unequal sharing of transcripts and other elements through cytoplasmic bridges between spermatids. Sperm cohorts exiting the gonads would contain different RNA and protein contents, affecting the spermatozoon physiology and associations with the surrounding environmental milieu. Subsequently, these differences could affect how spermatozoa interact with the environmental milieu (maturation, mixing with seminal plasma, and interacting with the environmental milieu, or female genital tract and female gamete). The emergence of sperm subpopulations as an outcome of evolution, related to the reproductive strategies of the species, genital tract structures, and copulatory and fertilization processes. This kind of approach in determining the importance of sperm subpopulations in fertilization capacity should have a practical impact for conducting reproductive technologies, inspiring and enabling new ways for the more efficient use of spermatozoa in the medical, animal breeding, and conservation fields. This manuscript is a contribution to the Special Issue in memory of Dr. Duane GarnerS
Identification of Hindbrain Neural Substrates for Motor Initiation in the hatchling Xenopus laevis Tadpole
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
Dynamic and Static Cognitive Deficits in Schizophrenia and Bipolar Disorder After the First Episode
Abstract Few studies have comprehensively examined the profile of cognitive functioning in first episode psychosis patients throughout the lifespan, and from first episode to chronic stage. We assessed functioning in general and specific cognitive functions, comparing both schizophrenia (N = 64) and bipolar I (N = 19) patients to controls (N = 103). Participants were from a population-based, case-control study of first episode psychosis patients, who were followed prospectively up to 10 years post first admission. A cognitive battery was administered at baseline and follow-up. By combining longitudinal and cross-sectional data, we were able to examine the cognitive profile of patients and controls throughout the entire age range of our sample (16â65). Schizophrenia patients exhibited widespread declines in IQ, executive function, visual memory, language ability, and verbal knowledge. However, the ages at which these declines occurred differed between functions. Deficits in verbal memory, working memory, processing speed, and visuospatial ability, on the other hand, were present at the first episode, and remained relatively static thereafter. Bipolar I patients also showed declines in IQ, verbal knowledge, and language ability, albeit at different ages to schizophrenia patients and only in verbal functions. Deficits on measures of verbal memory, processing speed, and executive function remained relatively static. Thus, both schizophrenia and bipolar I patients experienced cognitive decline in general and specific functions after the first episode, but the age at which these declines occurred differed between disorder and function. Cognitive remediation efforts may be most fruitful when targeting individual functions during specific time periods throughout adulthood
Strung pieces: on the aesthetics of television fiction series
As layered and long works, television fiction series have aesthetic properties that are built over time, bit by bit. This thesis develops a group of concepts that enable the study of these properties, It argues that a series is made of strung pieces, a system of related elements. The text begins by considering this sequential form within the fields of film and television. This opening chapter defines the object and methodology of research, arguing for a non-essentialist distinction between cinema and television and against the adequacy of textual and contextual analyses as approaches to the aesthetics of these shows. It proposes instead that these programmes should be described as televisual works that can be scrutinised through aesthetic analysis. The next chapters propose a sequence of interrelated concepts. The second chapter contends that series are composed of building blocks that can be either units into which series are divided or motifs that unify series and are dispersed across their pans. These blocks are patterned according to four kinds of relations or principles of composition. Repetition and variation are treated in tandem in the third chapter because of their close connection, given that variation emerges from established repetition. Exception and progression are also discussed together in the fourth chapter since they both require a long view of these serial works. The former, in order to be recognised as a deviation from the patterns of repetition and variation. The latter, In order to be understood in Its many dimensions as the series advances. Each of these concepts is further detailed with additional distinctions between types of units, motifs, repetitions, variations, and exceptions, using illustrative examples from numerous shows. In contrast, the section on progression uses a single series as case study, CarnivĂ le (2003-05), because this is the overarching principle that encompasses all the others. The conclusion considers the findings of the research and suggests avenues for their application
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Constraints on a potential aerial biosphere on Venus: II. Ultraviolet radiation
Despite the harsh conditions in the atmosphere of Venus, the possibility for an aerial habitable zone exists. A thermal habitable zone is predicted to exist at an altitude range of 62 to 48âŻkm, above which temperatures drop below the lower thermal limit of cell growth and below which temperatures exceed the evaporation temperature. Many biocidal factors must be considered for the complete definition of an aerial habitable zone; in this study we consider the constraint specifically from the perspective of biocidal solar ultraviolet (UV) intensity in the atmosphere. We simulated the penetration of solar ultraviolet and visible light through the atmosphere using a radiative transfer model, to determine the spectral environment (and thus the UV biocidal effect) as a function of altitude in the atmosphere of Venus. At the top of the thermal aerial habitable zone (62âŻkm) the incoming solar irradiance creates a severely challenging UV environment, with extremophiles such as Deinococcus radiodurans expected to be able to endure these UV conditions for approximately 80âŻs. At an altitude of around 59âŻkm the biologically-weighted UV irradiance drops below that calculated for the Archean Earth, and continues to fall with decreasing altitude until at 54âŻkm it is less than that found currently at the surface of Earth. Crucially, longer wavelength photosynthetically active light continues to penetrate to these altitudes and below, resulting in a solar radiation environment in the venusian atmosphere below around 54âŻkm that screens biologically-damaging UV radiation yet permits the process of photosynthesis. Whilst not claiming to suggest the existence of an aerial habitable zone in general, by considering thermal conditions, ionising radiation and the UV flux environment of the venusian cloud deck alone, we define a potential habitable zone that extends from 59âŻkm to 48âŻkm. This region should form the focus of future remote and in situ astrobiological investigations of Venus
Facial expression recognition and intensity estimation.
Doctoral Degree. University of KwaZulu-Natal, Durban.Facial Expression is one of the profound non-verbal channels through which human emotion state is inferred from the deformation or movement of face components when facial muscles are activated. Facial Expression Recognition (FER) is one of the relevant research fields in Computer Vision (CV) and Human-Computer Interraction (HCI). Its application is not limited to: robotics, game, medical, education, security and marketing. FER consists of a wealth of information. Categorising the information into primary emotion states only limit its performance. This thesis considers investigating an approach that simultaneously predicts the emotional state of facial expression images and the corresponding degree of intensity. The task also extends to resolving FER ambiguous nature and annotation inconsistencies with a label distribution learning method that considers correlation among data. We first proposed a multi-label approach for FER and its intensity estimation using advanced machine learning techniques. According to our findings, this approach has not been considered for emotion and intensity estimation in the field before. The approach used problem transformation to present FER as a multilabel task, such that every facial expression image has unique emotion information alongside the corresponding degree of intensity at which the emotion is displayed. A Convolutional Neural Network (CNN) with a sigmoid function at the final layer is the classifier for the model. The model termed ML-CNN (Multilabel Convolutional Neural Network) successfully achieve concurrent prediction of emotion and intensity estimation. ML-CNN prediction is challenged with overfitting and intraclass and interclass variations. We employ Visual Geometric Graphics-16 (VGG-16) pretrained network to resolve the overfitting challenge and the aggregation of island loss and binary cross-entropy loss to minimise the effect of intraclass and interclass variations. The enhanced ML-CNN model shows promising results and outstanding performance than other standard multilabel algorithms. Finally, we approach data annotation inconsistency and ambiguity in FER data using isomap manifold learning with Graph Convolutional Networks (GCN). The GCN uses the distance along the isomap manifold as the edge weight, which appropriately models the similarity between adjacent nodes for emotion predictions. The proposed method produces a promising result in comparison with the state-of-the-art methods.Author's List of Publication is on page xi of this thesis
Lecture Notes on Quantum Field Theory I
El documento ha sido corregido por el Servicio de PolĂtica LinguĂstica de la Universidad de Valencia.Material docente preparado para la asignatura TeorĂa CuĂĄntica de Campos en el Master de FĂsica Avanzada.These lectures notes are based on the material covered in the course on Quantum Field Theory I in the Master in Advanced Physics at the University of Valencia, delivered in the years 2017-2021
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Using Digital Storytelling in Science: Meaning Making with Students aged 10-12 years old
Meaning making is an essential aspect of learning as a process of interpreting and negotiating information while sharing it with others. One way of meaning making is through (digital) storytelling. The process of creating and telling a story depends on how one can see their understanding of something come together and make sense and it is considered a (socio) constructivist strategy of learning. The purpose and contribution of this research are to explore how digital storytelling may support engagement in meaning-making as students externalise their understanding of the science topic of matter. To this aim, two digital storytelling activities were constructed â SEeDS (Sequencing of Events enabling Digital Storytelling) and Narration. The two activities included the same content but differed in structure. SEeDS presented the story scenes in an order that was not predefined and Narration in a predefined order. Both activities derived elements from the theoretical concept of Tricky Topics and Stumbling Blocks (SBs). This research was informed by the theory of Problem-based learning.
Participants were sixty-one Greek primary students aged 10-12 years old and twenty-two English secondary students aged 11-12 years old. Half students worked through the SEeDS activity and the rest through the Narration activity. Students worked cooperatively in small teams to implement the two activities. A systematic analysis of the collected data was conducted using qualitative methods. Findings revealed that the two activities had supported the Greek and English students in externalising their understanding of many scientific concepts included in the topic of matter, while it identified gaps in their prior knowledge. The two activities have also facilitated the instinctive use of exploratory talk over the other two types (cumulative and disputational talk) that can often be found in peer talk in science learning. Finally, the two activities appeared to have engaged students in the two contexts, as they allowed them to own the story creation whilst working independently. Finally, the Greek and English students viewed the SEeDS activity as challenging, making it hard to complete and at times tiring and confusing, and the Narration activity as easy to implement, giving students the opportunity to mainly focus on inventing the story plot.
This research makes a valuable contribution to the literature on making meaning in science, offering new insights about the use of problem-based stories supported by mobile technology. The findings provide opportunities to further explore the practical application of problem-based digital storytelling activities, which are hard thinking and challenging, across different age groups and cultural contexts. There is a need for teaching practices to be based on socio-constructivist learning approaches that focus on studentsâ thinking, not performance. Therefore, the implications of this research are relevant to a number of educational contexts and levels
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Anomalous psychedelic experiences: at the neurochemical juncture of the humanistic and parapsychological
This paper explores the nature of psychedelically-induced anomalous experiences for what they reveal regarding the nature of 'expanded consciousness' and its implications for humanistic and transpersonal psychology, parapsychology and the psychology and underlying neuroscience of such experiences. Taking a multidisciplinary approach this essay reviews the nature of ten transpersonal or parapsychological experiences that commonly occur spontaneously and in relation to the use of psychedelic substances, namely synaesthesia, extra-dimensional percepts, out-of-body experiences, near-death experiences, entity encounters, alien abduction, sleep paralysis, interspecies communication, possession, and psi (telepathy, precognition, and clairvoyance and psychokinesis)
Magnetized accretion disks around compact objects
Los recientes avances observacionales logrados por la colaboracioĚn LIGO-Virgo- KAGRA â con las primeras detecciones histoĚricas de ondas gravitacionales de fusiones de sistemas binarios de objetos compactos â junto con la colaboracioĚn Event Horizon Telescope - con la imagen del agujero negro supermasivo que reside en el centro de la galaxia M87 - han brindado una oportunidad sin precedentes para investigar la fiĚsica de la gravedad en el regimen de campo intenso e incluso analizar la TeoriĚa General de la Relatividad de Einstein en esta situacioĚn tan extrema. En esta tesis se discute un caso particular de sistema astrofiĚsico relativista que suele considerarse como el ejemplo paradigmaĚtico de sistema en el reĚgimen de campo intenso â un agujero negro rodeado de un disco grueso de acrecioĚn (o toro). Se presentan nuevas prescripciones para construir datos iniciales de discos de acrecioĚn magnetizados alrededor de objetos compactos, extendiendo el estado actual del tema en varias direcciones, a saber, acomodando diferentes configuraciones de campo magneĚtico, distribuciones de momento angular, y tipos de espacio-tiempo (incluyendo agujeros negros de Kerr, agujeros negros con pelo escalar y agujeros negros de Yukawa) sobre los que evoluciona el fluido. Los resultados obtenidos en esta tesis nos proporcionan valiosa informacioĚn sobre los efectos que tiene anĚadir diferentes fenoĚmenos fiĚsicos en las propiedades morfoloĚgicas y fiĚsicas del sistema. AdemaĚs, los resultados de esta investigacioĚn tambieĚn proporcionan una amplia muestra de datos iniciales de dominio puĚblico para que puedan ser usados en simulaciones evolutivas del sistema toro de acrecioĚn-agujero negro, gobernado por las ecuaciones de la magnetohidrodinaĚmica relativista .The recent observational breakthroughs accomplished by the LIGO-Virgo-KAGRA Collaboration â with the historical first detections of gravitational waves from mergers of compact binaries â and by the Event Horizon Telescope Collaboration â with the image of the supermassive black hole lurking in the centre of the M87 galaxy â have provided an unprecedented opportunity to investigate the physics of strong gravity and to even test Einsteinâs General Theory of Relativity in such a extreme situation. This thesis discusses one particular relativistic astrophysical system which is often invoked as a paradigmatic example of such strong-gravity realm â a black hole surrounded by a geometrically thick accretion disk (or torus). New prescriptions to build initial data of magnetized accretion disks around compact objects are presented, extending the current state-of-the-art in several directions, namely accommodating diverse magnetic field configurations, angular momentum distributions, and types of spacetimes (including Kerr black holes, black holes with scalar hair, and Yukawa black holes) where the fluid evolves. The results reported in this thesis provide insight on the eff ects that adding diff erent physics has in the systemâs morphological and physical properties. In addition, this research o ers large new samples of open-source initial data to conduct time-dependent general-relativistic, magneto-hydrodynamical simulations of black hole-torus systems
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