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Search Results: 1 - 10 of 401197 matches for " M. Sisti "
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Learning to Learn: Theta Oscillations Predict New Learning, which Enhances Related Learning and Neurogenesis
Miriam S. Nokia, Helene M. Sisti, Monica R. Choksi, Tracey J. Shors
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031375
Abstract: Animals in the natural world continuously encounter learning experiences of varying degrees of novelty. New neurons in the hippocampus are especially responsive to learning associations between novel events and more cells survive if a novel and challenging task is learned. One might wonder whether new neurons would be rescued from death upon each new learning experience or whether there is an internal control system that limits the number of cells that are retained as a function of learning. In this experiment, it was hypothesized that learning a task that was similar in content to one already learned previously would not increase cell survival. We further hypothesized that in situations in which the cells are rescued hippocampal theta oscillations (3–12 Hz) would be involved and perhaps necessary for increasing cell survival. Both hypotheses were disproved. Adult male Sprague-Dawley rats were trained on two similar hippocampus-dependent tasks, trace and very-long delay eyeblink conditioning, while recording hippocampal local-field potentials. Cells that were generated after training on the first task were labeled with bromodeoxyuridine and quantified after training on both tasks had ceased. Spontaneous theta activity predicted performance on the first task and the conditioned stimulus induced a theta-band response early in learning the first task. As expected, performance on the first task correlated with performance on the second task. However, theta activity did not increase during training on the second task, even though more cells were present in animals that had learned. Therefore, as long as learning occurs, relatively small changes in the environment are sufficient to increase the number of surviving neurons in the adult hippocampus and they can do so in the absence of an increase in theta activity. In conclusion, these data argue against an upper limit on the number of neurons that can be rescued from death by learning.
Low doses of intravenous epinephrine for refractory sustained monomorphic ventricular tachycardia
Aimé Bonny,Antonio De Sisti,Manlio F Márquez,Richard Megbemado
World Journal of Cardiology , 2012, DOI: 10.4330/wjc.v4.i10.296
Abstract: We report three cases of sustained monomorphic ventricular tachycardia (VT) in the setting of coronary artery disease, resistant to beta-blockers in two patients and to amiodarone in all, successfully terminated by low doses of intravenous (IV) epinephrine. VT was the first manifestation of coronary artery disease in one patient, whereas the other two patients had a previous history of myocardial infarction and were recipients of an implantable cardioverter-defibrillator (ICD). One of these two patients experienced an arrhythmic storm. All had hemodynamic instability at the time of epinephrine administration. A single slow administration of IV epinephrine (0.5 to 1 mg administered over 30 to 60 s) restored sinus rhythm after 30-90 s with only minor side effects. In the ICD patient with recurrent VT and several cardioversions due to transformation of VT to ventricular fibrillation, epinephrine injection led to the avoidance of further shocks. Although potentially harmful, low doses of IV epinephrine used alone or in combination with beta-blocker treatment and electrical cardioversion may be an alternative effective therapy for sustained monomorphic VT refractory to amiodarone. The role of epinephrine in the termination of VT should be studied further, especially in patients pre-treated with amiodarone in combination with beta-blockers.
Investigation of peak shapes in the MIBETA experiment calibrations
E. Ferri,S. Kraft-Bermuth,A. Monfardini,A. Nucciotti,D. Schaeffer,M. Sisti
Physics , 2012, DOI: 10.1140/epja/i2012-12131-5
Abstract: In calorimetric neutrino mass experiments, where the shape of a beta decay spectrum has to be precisely measured, the understanding of the detector response function is a fundamental issue. In the MIBETA neutrino mass experiment, the X-ray lines measured with external sources did not have Gaussian shapes, but exhibited a pronounced shoulder towards lower energies. If this shoulder were a general feature of the detector response function, it would distort the beta decay spectrum and thus mimic a non-zero neutrino mass. An investigation was performed to understand the origin of the shoulder and its potential influence on the beta spectrum. First, the peaks were fitted with an analytic function in order to determine quantitatively the amount of events contributing to the shoulder, also depending on the energy of the calibration X-rays. In a second step, Montecarlo simulations were performed to reproduce the experimental spectrum and to understand the origin of its shape. We conclude that at least part of the observed shoulder can be attributed to a surface effect.
Trabajo y rehabilitación psicosocial: una perspectiva histórica.
Giuseppe Cardemore,Elvio Sisti
Revista de la Asociación Espa?ola de Neuropsiquiatría , 1997,
Abstract: Sin resumen.
Los caminos en el folklore del noroeste argentino: Geografía cultural
Ramón Alberto Sisti
Invenio , 2004,
Abstract: La cultura se manifiesta a través de los individuos a quienes es transmitida, como una herencia social que pasa de una generación a otra, bajo distintas y diversas modalidades. En la década de los cincuenta del siglo XX, se produce un movimiento jerarquizador del folklore argentino en la poesía de numerosos autores que intentan dar cuenta de una realidad social enmarcada en las distintas geografías del territorio nacional y que va a encontrar eco en la interpretación vocal de numerosos conjuntos modernizadores. Atahualpa Yupanqui es uno de los principales referentes de esa movida cultural en el folklore del noroeste argentino. La lectura de su libro Aires Indios , publicado en 1954, decidió la elección del tema de este trabajo, que se encuadra en la necesidad de la revalorización de elementos culturales que hacen a la identidad nacional, o por lo menos regional, en este mundo de desdibujamiento globalizador. En la producción poética de Atahualpa Yupanqui es notoria la significación que otorga al papel de los caminos en relación con la cotidianeidad multifacética del hombre que ve transcurrir su vida en un paisaje singular. Como poeta hacedor de canciones jerarquiza la producción de la época con letras de indudable valor estético, llenas de metáforas e imágenes deslumbrantes, como cuando nos dice he andado caminos de claridad y de sombras, de dichas y penas, de paz y de luchas
Cambios y riesgos geopolíticos en América del Sur
Ramón Sisti
Invenio , 2005,
Abstract: Los países que integran América del Sur están atravesando por una serie de conflictos y tensiones que obedecen a diversas problemáticas que se constituyen en obstáculos para enfrentar los cambios necesarios y urgentes requeridos por sus pueblos. Se plantea que las democracias de América Latina y la del Sur en particular, padecerán nuevas formas de crisis que acentuarán las brechas sociales y económicas entre sus poblaciones y que se ampliará la existente entre la región y los países más desarrollados
El abra del negro pintado un problema de desconexión territorial
Ramón Alberto Sisti
Invenio , 2001,
Abstract: Las tendencias globalizadoras, paradójicamente o no, permiten la emergencia deuna multiplicidad de regiones y subregiones que jerarquizan a las ciudades o poblaciones decierta importancia como centros o nodos de creciente participación en los campos culturales,políticos, económicos y sociales de sus espacios de influencia directa o indirecta. Este trabajotrata acerca de un proyecto de reestructuración espacial regional para superar un problema dedesconexión territorial entre dos áreas situadas a corta distancia relativa y cuya accesibilidad seve interrumpida por una cadena orográfica
Effects of concavity on the motion of a body immersed in a Vlasov gas
F. Sisti,C. Ricciuti
Mathematics , 2014, DOI: 10.1137/140954003
Abstract: We consider a body immersed in a perfect gas, moving under the action of a constant force $E$ along the $ x $ axis . We assume the gas to be described by the mean-field approximation and interacting elastically with the body. Such a dynamic was studied in previous papers In these studies the asymptotic trend showed no sensitivity whatsoever to the shape of the object moving through the gas. In this work we investigate how a simple concavity in the shape of the body can affect its asymptotic behavior; we thus consider the case of hollow cylinder in three dimensions or a box-like body in two dimensions. We study the approach of the body velocity $V (t) $ to the limiting velocity $V_{\infty} $ and prove that, under suitable smallness assumptions, the approach to equilibrium is $| V_{\infty}-V(t)| \approx C t^{-3} $ both in two or three dimensions, being $C$ a positive constant. This approach is not exponential, as typical in friction problems, and even slower than for the simple disk and the convex body in $ \mathbb{R}^2 $ or $ \mathbb{R}^3 $.
Discrimination between Nuclear Recoils and Electron Recoils by Simultaneous Detection of Phonons and Scintillation Light
P. Meunier,M. Bravin,M. Bruckmayer,S. Giordano,M. Loidl,O. Meier,F. Proebst,W. Seidel,M. Sisti,L. Stodolsky,S. Uchaikin,L. Zerle
Physics , 1999, DOI: 10.1063/1.124685
Abstract: We have developed a detector, consisting of a cryogenic calorimeter with a scintillating crystal as absorber, and a second calorimeter for the detection of the scintillation light, both operated at 12 mK. Using a CaWO4 crystal with a mass of 6g as scintillating absorber, we have achieved a discrimination of nuclear recoils against electron recoils with a suppression factor of 99.7% at energies above 15 keV. This novel method will be applied for background rejection in the CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) experiment looking for dark matter Weakly Interacting Massive Particles (WIMPs).
Testing Multiple Coordination Constraints with a Novel Bimanual Visuomotor Task
Helene M. Sisti, Monique Geurts, René Clerckx, Jolien Gooijers, James P. Coxon, Marcus H. Heitger, Karen Caeyenberghs, Iseult A. M. Beets, Leen Serbruyns, Stephan P. Swinnen
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0023619
Abstract: The acquisition of a new bimanual skill depends on several motor coordination constraints. To date, coordination constraints have often been tested relatively independently of one another, particularly with respect to isofrequency and multifrequency rhythms. Here, we used a new paradigm to test the interaction of multiple coordination constraints. Coordination constraints that were tested included temporal complexity, directionality, muscle grouping, and hand dominance. Twenty-two healthy young adults performed a bimanual dial rotation task that required left and right hand coordination to track a moving target on a computer monitor. Two groups were compared, either with or without four days of practice with augmented visual feedback. Four directional patterns were tested such that both hands moved either rightward (clockwise), leftward (counterclockwise), inward or outward relative to each other. Seven frequency ratios (3:1, 2:1, 3:2, 1:1, 2:3. 1:2, 1:3) between the left and right hand were introduced. As expected, isofrequency patterns (1:1) were performed more successfully than multifrequency patterns (non 1:1). In addition, performance was more accurate when participants were required to move faster with the dominant right hand (1:3, 1:2 and 2:3) than with the non-dominant left hand (3:1, 2:1, 3:2). Interestingly, performance deteriorated as the relative angular velocity between the two hands increased, regardless of whether the required frequency ratio was an integer or non-integer. This contrasted with previous finger tapping research where the integer ratios generally led to less error than the non-integer ratios. We suggest that this is due to the different movement topologies that are required of each paradigm. Overall, we found that this visuomotor task was useful for testing the interaction of multiple coordination constraints as well as the release from these constraints with practice in the presence of augmented visual feedback.
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