1,880 research outputs found
A connexin30 mutation rescues hearing and reveals roles for gap junctions in cochlear amplification and micromechanics
Get PDFAbstractAccelerated age-related hearing loss disrupts high-frequency hearing in inbred CD-1 mice. The p.Ala88Val (A88V) mutation in the gene coding for the gap-junction protein connexin30 (Cx30) protects the cochlear basal turn of adult CD-1Cx30A88V/A88V mice from degeneration and rescues hearing. Here we report that the passive compliance of the cochlear partition and active frequency tuning of the basilar membrane are enhanced in the cochleae of CD-1Cx30A88V/A88V compared to CBA/J mice with sensitive high-frequency hearing, suggesting that gap junctions contribute to passive cochlear mechanics and energy distribution in the active cochlea. Surprisingly, the endocochlear potential that drives mechanoelectrical transduction currents in outer hair cells and hence cochlear amplification is greatly reduced in CD-1Cx30A88V/A88V mice. Yet, the saturating amplitudes of cochlear microphonic potentials in CD-1Cx30A88V/A88V and CBA/J mice are comparable. Although not conclusive, these results are compatible with the proposal that transmembrane potentials, determined mainly by extracellular potentials, drive somatic electromotility of outer hair cells.</jats:p
Modified protein expression in the tectorial membrane of the cochlea reveals roles for the striated sheet matrix
Get PDFThe tectorial membrane (TM) of the mammalian cochlea is a complex extracellular matrix which, in response to acoustic stimulation, displaces the hair bundles of outer hair cells (OHCs), thereby initiating sensory transduction and amplification. Here, using TM segments from the basal, high-frequency region of the cochleae of genetically modified mice (including models of human hereditary deafness) with missing or modified TM proteins, we demonstrate that frequency-dependent stiffening is associated with the striated sheet matrix (SSM). Frequency-dependent stiffening largely disappeared in all three TM mutations studied where the SSM was absent either entirely or at least from the stiffest part of the TM overlying the OHCs. In all three TM mutations, dissipation of energy is decreased at low (<8 kHz) and increased at high (>8 kHz) stimulus frequencies. The SSM is composed of polypeptides carrying fixed charges, and electrostatic interaction between them may account for frequency-dependent stiffness changes in the material properties of the TM. Through comparison with previous in vivo measurements, it is proposed that implementation of frequency-dependent stiffening of the TM in the OHC attachment region facilitates interaction among tones, backward transmission of energy, and amplification in the cochlea
Multi-Agent Reinforcement Learning using Centralized Critics in Collaborative Environments
No full textAgents trained through single-agent reinforcement learning methods such as self-play can provide a good level of performance in multi-agent settings and even in fully cooperative environments. However, most of the time, training multiple agents together using single-agent self-play yields poor results as each agent tries to learn how to perform their task while their teammates are also learning. Thus, training models to reach an optimal behaviour in such situations becomes a challenging, if not impossible issue to overcome. One possible solution to deal with this problem is to facilitate a centralized training process in which the policies of all agents are evaluated by a centralized critic that has access to the observations and actions of all the agents in the environment. By using this approach, the environment becomes stationary and the agents learn in a similar way to using a single-agent algorithm in settings where only one agent needs to be trained. In this paper, we test whether by using a multi-agent reinforcement learning algorithm with centralized critics, as opposed to single-agent ones, we would obtain an agent that generalizes better to new partners in a collaborative environment such as Overcooked, where coordination is critical for good performance. The results display a similar performance between the two algorithms when evaluated through self-play and slightly better or worse results when paired with the human model, representing a mediocre agent, depending on the map. Thus, the multi-agent, centralized critics algorithm used in this study did not train agents that generalize better to new partners. However, the training metrics clearly indicate that the centralized critics method makes the agents learn and converge twice as fast as its single-agent version.https://github.com/andrei-07/rp-overcooked-centralized-critics Link to GitHub repositoryCSE3000 Research ProjectComputer Science and Engineerin
Andrei Tarkovsky:
No full textThe author studies the originality of the film language of Andrei Tarkovsky, one of the great filmmakers of the twentieth century. For this purpose he considers the symbolic, poetic, technical and mystical elements of Tarkovsky’s seven films. Beyond the standard critics, he builds an unitary language for the interpretation of a work reputedly tight.El autor estudia la originalidad del lenguaje cinematográfico de Andrei Tarkovsky, uno de los grandes directores de cine del siglo XX. Para este propósito considera los aspectos simbólicos, poéticos, técnicos y místicos de sus siete películas. Desecha el formato de ficha crítica y construye un lenguaje unitario para la interpretación de una obra reputada como hermética
Frequency-dependent properties of the tectorial membrane facilitate energy transmission and amplification in the cochlea
No full textThe remarkable sensitivity, frequency selectivity, and dynamic range of the mammalian cochlea relies on longitudinal transmission of minuscule amounts of energy as passive, pressure-driven, basilar membrane (BM) traveling waves. These waves are actively amplified at frequency-specific locations by a mechanism that involves interaction between the BM and another extracellular matrix, the tectorial membrane (TM). From mechanical measurements of isolated segments of the TM, we made the important new (to our knowledge) discovery that the stiffness of the TM is reduced when it is mechanically stimulated at physiologically relevant magnitudes and at frequencies below their frequency place in the cochlea. The reduction in stiffness functionally uncouples the TM from the organ of Corti, thereby minimizing energy losses during passive traveling-wave propagation. Stiffening and decreased viscosity of the TM at high stimulus frequencies can potentially facilitate active amplification, especially in the high-frequency, basal turn, where energy loss due to internal friction within the TM is less than in the apex. This prediction is confirmed by neural recordings from several frequency regions of the cochlea.<br/
História e Documentário no Cinema de Andrei Tarkóvski
No full textIn the article, the author discuses the Cinematic history and documentary of Andrei Tarkóvski
Andrei Tarkovsky:: devolver a la naturaleza sus enigmas
Get PDFThe author studies the originality of the film language of Andrei Tarkovsky, one of the great filmmakers of the twentieth century. For this purpose he considers the symbolic, poetic, technical and mystical elements of Tarkovsky’s seven films. Beyond the standard critics, he builds an unitary language for the interpretation of a work reputedly tight.El autor estudia la originalidad del lenguaje cinematográfico de Andrei Tarkovsky, uno de los grandes directores de cine del siglo XX. Para este propósito considera los aspectos simbólicos, poéticos, técnicos y místicos de sus siete películas. Desecha el formato de ficha crítica y construye un lenguaje unitario para la interpretación de una obra reputada como hermética
Fotografia ca apropiere și distanțare la Andrei Codrescu / Photography as distance and nearness to Andrei Codrescu
No full textThe present study is part of a PhD thesis titled “Space in Andrei Codrescu’s prose – between reality and imaginary”, analysing the religious space, the virtual space, the photo studio, the American space and the library, as reflected in the above mentioned writer’s prose. The chapter dedicated to the photo studio depicts the manner in which the professional environment of the writer’s parents and close relatives influence the perception of the Self and of the Other, passing from the hypostasis of photographed subject to that of photographer “withtheeyes”, starting from the postmodern statement: “I am a camera”. Our study presents the travel literature of the author, “Ay, Cuba!” and “Prof pe drum” (Road Scholar), the last one also an autobiographical volume, illustrated by photos as a completion of the text. We also discuss the transformation of Road Scholar into a documentary, well received by the critics. The second part of our study presents the text written by Andrei Codrescu for several photobooks, as Walker Evans’ “Cuba” and “Signs”, David Graham’s “Land of the free: What makes Americans different” and others. If, in thefirst part of the study, Andrei Codrescu needs the production of a photo camera to deepen the understanding of the words, we discover him in the second part as a verbalising agent helping the rounding and the guiding of a Weltanschauung for other viewers, the public of the images from the photo books
Andrei Sakharov: quarks and the structure of matter
No full textIn 1980, the Cold War was in full bloom. The Soviet father of the hydrogen bomb and Nobel Peace Laureate turned dissident physicist, Andrei Sakharov, had been exiled to Gorki by the Soviet authorities. Called senile and under heavy Soviet censorship, Sakharov had a hard time communicating with the outside world. Around this time, the author, Harry Lipkin, came into contact with Sakharov's scientific work. What followed was a remarkable adventure in which both scientists fought the Soviet censors, smuggling postcards and manuscripts into and out of the Soviet Union while trying to further scientific progress. Against a backdrop of politics, suppression, and genius, Andrei Sakharov, Quarks and the Structure of Matter details the search for the basic building blocks of matter, the path to understanding the forces that bind them together, and how scientific knowledge is learned, communicated and passed from one group of investigators to another.In 1980, the Cold War was in full bloom. The Soviet father of the hydrogen bomb and Nobel Peace Laureate turned dissident physicist, Andrei Sakharov, had been exiled to Gorki by the Soviet authorities. Called "senile" and under heavy Soviet censorship, Sakharov had a hard time communicating his latest scientific results to readers outside of Gorki. Some smuggled results reached the author, Harry Lipkin, who then realized that he and Sakharov were both pioneers in a new revolution on our understanding the structure of matter. The particle physics community had resisted their revelation that th
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