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Ítem Acceso Abierto 2do Congreso Argentino de Técnicas Neutrónicas(Comisión Nacional de Energía Atómica (Argentina), 2019) Santisteban, Javier; Suarez, Federico; Robinson, Robert; Signorelli, Javier; Juárez, Gabriel; Fasano, Yanina; Fernández Bordin, Santiago; Silvi, Luca; Gojiman, Dafne; Swainson, Ian; Robledo, J.; Carbonio, Raúl; Granado, Eduardo; Malamud, Florencia; Novas, Fernando; Schweickardt, Josefina; Hussey, Daniel; Santa Cruz, Gustavo; Portu, Agustina; Campo, Javier; Comisión Nacional de Energía Atómica (Argentina). Laboratorio Argentino de Haces de Neutrones.Bienvenidos al 2do Congreso Argentino de Técnicas Neutrónicas, que esperamos se convierta nuevamente en un espacio entre la comunidad de usuarios, los desarrolladores de instrumentos, los expertos internacionales y los actores políticos relevantes. El Congreso ha sido organizado por la Comisión Nacional de Energía Atómica (CNEA) y la Secretaría de Gobierno de Ciencia, Tecnología e Innovación Productiva de la Nación en el marco del desarrollo del Laboratorio Argentino de Haces de Neutrones (LAHN). Este laboratorio ofrecerá a la comunidad científica-tecnológica un conjunto de instrumentos de clase mundial, que harán uso de los haces de neutrones fríos y térmicos de alta intensidad provenientes del nuevo reactor RA-10, en construcción en el Centro Atómico Ezeiza, y con su puesta en marcha prevista para fines del año 2022. Durante el congreso tendremos la oportunidad de visitarlo y apreciar el estado de avance y la magnitud de este proyecto nacional. Uno de los pilares fundamentales para el éxito del LAHN, es el desarrollo de una comunidad de usuarios amplia, multidisciplinar, organizada, capacitada y comprometida con el laboratorio. Con ese espíritu organizamos este congreso, para que entre todos los actores involucrados podamos dar forma y contribuir al diseño, desarrollo y construcción de los distintos aspectos que definirán LAHN. El 1er Congreso de Técnicas Neutrónicas y su Taller satélite de "Instrumentos para la Fase II del LAHN", realizados en el año 2017, resultaron sumamente fructíferos y permitieron definir el plantel de instrumentos demandados por la comunidad científica. En esta nueva edición, tendremos la oportunidad de interactuar con investigadores nacionales e internacionales expertos en aquellas áreas identificadas en los casos científicos, a quienes hemos convocado a fin de favorecer nuevas colaboraciones que ayuden a incoporar las técnicas neutrónicas en nuestras investigaciones. Por otro lado, conoceremos los avances que han realizado los diferentes grupos de trabajo del LAHN para que, al momento del inicio de operaciones, dispongamos de un conjunto de instrumentos que dé respuesta a las demandas expresadas en los casos científicos. Esperamos que disfruten del Programa Científico y que tengan la oportunidad de conocer y reecontrar amigos, colegas y nuevos colabroadores, haciendo de TN|2019 un encuentro estimulante y memorable.Ítem Acceso Abierto 3D-2D dimensional crossover in YBa2Cu3O7 films(American Physical Society, 1993-11-08) Gao, Z.X.; Osquiguil, E.; Maenhoudt, M.; Wuyts, B.; Libbrecht, S.; Bruynseraede, Y.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasWe show that, in fully oxidized YBa2Cu3O7 c-axis oriented films, the changes induced in the angular and field dependence of the magnetoresistivity ρab by increasing the temperature towards Tc are similar to those caused by a lowering in oxygen content. This remarkable behavior can be interpreted as due to a crossover from a three-dimensional to a two-dimensional system as T approaches Tc. Moreover, our critical current data mimic the behavior observed by Qi Li et al. in YBa2Cu3O7/(PrxY1−x)Ba2Cu3O7 multilayers, suggesting the possibility that chain planes are superconducting.Ítem Acceso Abierto 4D Printing: The Development of Responsive Materials Using 3D-Printing Technology(MDPI, 07-12-2023) Antezana, Pablo Edmundo; Municoy, Sofia; Ostapchuk, Gabriel; Catalano, Paolo Nicolás; Hardy, John G.; Evelson, Pablo A.; Orive, Gorka; Desimone, Martin FedericoAdditive manufacturing, widely known as 3D printing, has revolutionized the production of biomaterials. While conventional 3D-printed structures are perceived as static, 4D printing introduces the ability to fabricate materials capable of self-transforming their configuration or function over time in response to external stimuli such as temperature, light, or electric field. This transformative technology has garnered significant attention in the field of biomedical engineering due to its potential to address limitations associated with traditional therapies. Here, we delve into an in-depth review of 4D-printing systems, exploring their diverse biomedical applications and meticulously evaluating their advantages and disadvantages. We emphasize the novelty of this review paper by highlighting the latest advancements and emerging trends in 4D-printing technology, particularly in the context of biomedical applications.Ítem Acceso Abierto A comparison between volume and electronic concentration effects in Ce transformations(IOP Publishing, 1994-00-00) Sereni, J.G.; Kappler, J.P.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasThe crossover from magnetic to non-magnetic ground states in Ce compounds is analysed within the competition between the on-site and inter-site interactions proposed by Doniach. The comparison of the evolution of the ordering temperature, as a function of pressure and alloying, was performed in more than twenty Ce systems. This systematic shows that volume (Delta V) and electronic concentration (Delta Z) effects, as the driving forces for such a transformation, present different characteristics. The maximum in the ordering temperature (T0), predicted by the model, is only observed under Delta V effects (induced by alloying or by pressure) and not under Delta Z variations. This study leads to the conclusion that the maximum in T0 cannot be considered intrinsic to a complete magnetic to non-magnetic transformation, but rather is a consequence of the Ce-Ce spacing decrease, before the wavefunction overlap turns on the hybridization mechanism.Ítem Acceso Abierto A corpus analysis of rubato in Bach's C major prelude, WTC I(Royal Northern College of Music, 2015) Benadon, Fernando; Zanette, Damian HoracioWe examined microtiming properties in a corpus of 48 recorded performances of J.S. Bach's C Major Prelude from The Well Tempered Clavier, Book I. Drawing on the results of a listening experiment and from wavelet analysis, we derived a quantitative measure of rubato 'depth' that was used to assess timing trends across performances. In addition to highlighting important structural moments in the Prelude, rubato was used to bring melodic elements into relief as well as to generate grouping segmentations that may contradict the Prelude's inherent phrase structure. We then applied the statistical method of principal components analysis (PCA) to examine timing contours specific to individual performers. Repetitively consistent microrhythmic patterns, which we qualified as groove-like, differed from non-consistent and non-repetitive timing inflections, which we qualified as rubatoSlike.Ítem Acceso Abierto A quantitative experiment on the fountain effect in superfluid helium(IOP Publishing, 2017-08-17) Amigó, M.L.; Herrera, T.; Neñer, L.; Peralta Gavensky, L.; Turco, F.; Luzuriaga, J.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasSuperfluid helium, a state of matter existing at low temperatures, shows many remarkable properties. One example is the so called fountain effect, where a heater can produce a jet of helium. This converts heat into mechanical motion; a machine with no moving parts, but working only below 2 K. Allen and Jones first demonstrated the effect in 1938, but their work was basically qualitative. We now present data of a quantitative version of the experiment. We have measured the heat supplied, the temperature and the height of the jet produced. We also develop equations, based on the two-fluid model of superfluid helium, that give a satisfactory fit to the data. The experiment has been performed by advanced undergraduate students in our home institution, and illustrates in a vivid way some of the striking properties of the superfluid state.Ítem Acceso Abierto A single channel capillary microviscometer(Springer, 2013-03-12) Morhell, N.; Pastoriza, H.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasWe have developed a microviscometer analyzing the fluid dynamics in a single channel glass microfluidic chip with a closed end. The device is able to test sample volumes of a few microliters by inserting one drop in the inlet. The fluid enters the channel driven by capillary pressure and an optical sensor registers the motion. The equation that describes the fluid dynamics is function of the channel geometry, atmospheric pressure, fluid viscosity, and capillary pressure. Knowing the first two, the last parameters can be obtained as fitting parameters from the meniscus position as a function of time plot. We have successfully tested Newtonian fluids with different viscosities and capillary pressure.Ítem Acceso Abierto A spatially extended model to assess the role of landscape structure on the pollination service of Apis mellifera(Board, 2020) Joseph, Julien; Santibáñez, Fernanda; Laguna, María Fabiana; Abramson, Guillermo; Kuperman, Marcelo Néstor; Garibaldi, Lucas AlejandroApis mellifera plays a crucial role as pollinator of the majority of crops linked to food production and thus its presence is currently fundamental to our health and survival. The composition and configuration of the landscape in which Apis mellifera lives will likely determine the well-being of the hives and the pollination service that their members can provide to the crops. Here we present a spatially explicit model that predicts the spatial distribution of visits by Apis mellifera to crops, by simulating daily trips of honey bees, the demographical dynamic of each hive and their honey production. This model goes beyond existing approaches by including 1) a flower resource affected by the feedback interaction between nectar extraction, pollination, blossoming and repeated visits, 2) a pollinators dynamic that allows competition through short term resource depletion, 3) a probabilistic approach of the foraging behavior, modeling the fact that the pollinators have only partial knowledge of the resource on their surroundings, and 4) the specific and systematic foraging behavior and strategies of Apis mellifera at the moment of choosing foraging sites, as opposed to those adopted by solitary and wild pollinators. With a balance between simplicity and realism we show the importance of keeping a minimal fraction of natural habitat in an agricultural landscape. We also evaluate the effects of the landscape’s structure on pollination, and demonstrate that there exists an optimal size of natural habitat patches that maximizes the pollination service for a fixed fraction of natural habitat.Ítem Acceso Abierto A watchmaker's precision at high-pressure reveals CeCu 2 Si 2 and CeAu 2 Si 2 p-T phase diagrams(IOP Publishing, 2017-00-00) Giriat, G.; Scheerer, G.W.; Ren, Z.; Pedrazzini, P.; Lapertot, G.; Jaccard, D.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasNearly forty years after the discovery of the first heavy fermion (HF) superconductor, CeCu 2 Si2 ,1 high-pressure (HP) investigations continue to provide information on the above and also enable the discovery of new Ce-based HF superconductors.Ítem Acceso Abierto Analysis of motion of solid hydrogen tracer particles in oscillating superfluid flows(IOP Publishing, 2014-00-00) Zemma, E.; Luzuriaga, J.; Babuin, S.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasWe have developed a relatively simple cryostat which allows us to image turbulent flows in superfluid helium at temperatures below 2 K, using frozen H2 particles. We analyze the statistics of the velocities of these solid tracers, which follow the turbulent flow generated by oscillating bodies. We have also studied one of the oscillators working in air at room temperature, and traced the flow with solid talcum particles for comparison. Images were recorded by a digital camera at 240 frames per second, while frequencies of the oscillators are between 20 to 45 Hz. The flow is characterized by a modified Reynolds number Reδ based on the viscous penetration depth δ. Software in a dedicated particle tracking velocimetry code allows us to compute the trajectories and velocities of tens of thousands of particles. We have obtained the number of particles for equally spaced intervals of the velocity modulus. For the oscillators in the superfluid, the probability of finding particles at higher velocities has an exponential decay. Within our resolution the statistics in the superfluid for oscillating objects with sharp borders is largely independent of Reδ, while the logarithmic decay at low velocities seems faster than for high velocities for rounded objects. On the other hand, for data taken in air the result is closer to a classical Gaussian distribution of velocities.Ítem Acceso Abierto Analysis of the role of the low threshold currents IT and Ih in intrinsic delta oscillations of thalamocortical neurons(Frontiers Media S.A., 2015-05-07) Amarillo Gomez, Yimy; Mato, German; Nadal, MarcelaThalamocortical neurons are involved in the generation and maintenance of brain rhythms associated with global functional states. The repetitive burst firing of TC neurons at delta frequencies (1-4 Hz) has been linked to the oscillations recorded during deep sleep and during episodes of absence seizures. To get insight into the biophysical properties that are the basis for intrinsic delta oscillations in these neurons, we performed a bifurcation analysis of a minimal conductance-based thalamocortical neuron model including only the IT channel and the sodium and potassium leak channels. This analysis unveils the dynamics of repetitive burst firing of TC neurons, and describes how the interplay between the amplifying variable mT and the recovering variable hT of the calcium channel IT is sufficient to generate low threshold oscillations in the delta band. We also explored the role of the hyperpolarization activated cationic current Ih in this reduced model and determine that, albeit not required, Ih amplifies and stabilizes the oscillation.Ítem Acceso Abierto Angular variation of pinning near the irreversibility temperature in single crystal Y Ba2Cu3O7−δ with splayed columnar defects(Elsevier, 1998-08-01) Herbsommer, J.A.; Luzuriaga, J.; Civale, L.; Nieva, G.; Pasquini, G.; Lanza, H.; Levy, P.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasWe have studied vortex pinning through ac susceptibility measurements in single crystals of YBCO with columnar defects (CDs). The CDs have 0°, 10° and 20° splay angle and average direction 10° off the c-axis. By studying the angular variation we can compensate for the anisotropy and effects of twins, etc. Using a simple expression we can obtain the angular spread when the field direction is outside the splay angle. An increase of pinning when the field direction is inside the angle defined by the CDs can be attributed to vortex entanglement due to the splay and the suppression of the sliding of double kinks.Ítem Acceso Abierto Anisotropic response of the moving vortex lattice in superconducting Mo(1-x)Gex amorphous films(Elsevier, 2012-03-00) Dolz, M.I.; Shalóm, D.E.; Pastoriza, H.; López, D.O.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasWe have performed magnetic susceptibility measurements in Mo1−xGex amorphous thin films biased with an electrical current using anisotropic coils. We tested the symmetry of the vortex response changing the relative orientation between the bias current and the susceptibility coils. We found a region in the DC current–temperature phase diagram where the dynamical vortex structures behave anisotropically. In this region the shielding capability of the superconducting currents measured by the susceptibility coils is less effective along the direction of vortex motion compared to the transverse direction. This anisotropic response is found in the same region where the peak effect in the critical current is developed. On rising temperature the isotropic behavior is recovered.Ítem Acceso Abierto Annealing disorder and photoinduced order of oxygen chains in detwinned YBa2Cu3O6.65 single crystals probed by Raman scattering(American Physical Society, 2000-02-01) Fainstein, A.; Maiorov, B.; Guimpel, J.; Nieva, G.; Osquiguil, E.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasRaman scattering in detwinned YBa2Cu3O6.65 single crystals is studied as a function of photoexcitation and annealing. Copper-oxygen chain-related forbidden Raman bands that are known to strongly bleach with illumination at low temperatures, increase their intensity with chain fragmentation induced by annealing at high temperature. This contrasting behavior proves the conjunction of short Cu-O fragments into longer chains on photoexcitation. We interpret the Raman modes as due to vibrations at the end of CuO chain fragments and Cu-O-Cu monomers, and use their evolution with illumination and annealing as anisotropic sensitive markers of oxygen reordering processes. The identification of the “forbidden” Raman bands is discussed in the context of our results and recent literature in the subject. We also present absorption measurements performed on GdBa2Cu3Ox thin films with varying oxygen content. These experiments show that the 2.2-eV absorption and the chain-related Raman peaks have different dependencies with oxygen content and illumination, ruling out an explanation that suggests that the Raman intensity reduction of these modes is due to a photobleaching of intermediate defect states. These results highlight the potentialities of Raman scattering for oxygen dynamics studies and demonstrate the presence of photoinduced oxygen ordering in these high-Tc superconductor compounds.Ítem Acceso Abierto Annealing effects on the sound velocity and internal friction in the superconducting and normal states of the Cu30Zr70 amorphous alloy(American Physical Society, 1988-05-01) Esquinazi, P.; Luzuriaga, J.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasBy means of the vibrating-reed technique we have measured the evolution upon low-temperature annealing of the internal friction Q−1 and sound velocity v of the Cu30Zr70 amorphous alloy between 0.1 and 10 K. With an applied magnetic field of 5.6 T we measured also the normal-state behavior of both properties. Upon annealing, the internal friction and the slope of the logarithmic temperature dependence of v in the superconducting state decrease, in agreement with the standard tunneling model. Our results indicate that with thermal treatments, the coupling constant between tunneling systems (TS’s) and phonons decreases, and the density of states of the TS remains constant or decreases, at most 25%, in the fully relaxed state, which is in agreement with published specific-heat results in these materials. From our data we conclude that the coupling constant between the TS and phonons should be very sensitive to the relaxed state of the disordered structure. The sound-velocity behavior strongly indicates that relaxation processes up to 10 K involve the interaction with the TS. A well-defined change of slope in v at the superconducting critical temperature Tc is observed in the as-quenched and the first relaxed state, which cannot be explained with the standard tunneling model and the Korringa-like relaxation rate between the TS and electrons. Several features observed in the superconducting and normal states lead to the conclusion that the TS-electron interaction problem remains unsolved.Ítem Acceso Abierto Anomalies in the internal friction and sound velocity in the high-temperature superconductor La1.8Sr0.2CuO4(American Physical Society, 1987-08-01) Esquinazi, P.; Luzuriaga, J.; Durán, C.; Esparza, D.A.; D'Ovidio, C.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasThe internal friction Q−1 and the Young's-modulus sound velocity vE have been measured in La1.8Sr0.2CuO4 using the vibrating-reed technique. Measurements were performed at a frequency of 700 Hz at temperatures between 0.2 and 100 K. A drastic change of slope in the internal friction versus temperature curve is observed at T=44 K just above the superconducting transition temperature Tc=40 K. A plateau in Q−1 is observed between 44 and 5 K. The sound velocity shows a decrease with decreasing temperature between 100 and 20 K and remains almost constant between 2 and 0.2 K.Ítem Acceso Abierto Anomalous Behavior of Hc3/Hc2 near Tc for Sn-In and In-Bi Alloy Systems(American Physical Society, 1970-10-01) Maloney, M.D.; de la Cruz, F.; Cardona, M.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasPreviously reported measurements of the ratio Hc3Hc2 for tin-rich Sn-In alloys and indium-rich In-Bi alloys have been extended in further detail, and include variations in foil thickness (6 - 300 μ). The anomalous behavior in the ratio very near Tc is found to be dependent on foil thickness. Each alloy system is characterized by a certain thickness, above which Hc3Hc2 decreases markedly as Tc is approached, and below which the opposite behavior takes place. The results can be interpreted qualitatively in terms of a sandwich model in which the strength of the pairing interaction is depressed in a layer at the surface of the sample. For the thickest samples (most nearly "semi-infinite"), there is good quantitative agreement with the recent theory of this proximity effect given by Fink and Presson.Ítem Acceso Abierto Anomalous behavior of superconducting samples with a fixed number of vortices(American Physical Society, 1987-09-01) Civale, L.; de la Cruz, F.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasWe report an anomalous reversible temperature dependence of the magnetization of amorphous type-II superconductors. The experimental results were obtained studying the vortex pinning in samples with very low vortex concentration. The anomaly is shown to be a consequence of the lack of flux quantization in finite samples.Ítem Acceso Abierto Anomalous behaviour of X-ray absorption observed on the highly correlated cerium nitride (CeN) compound(EDP Sciences, 1991-10-00) Kappler, J.P.; Beaurepaire, E.; Krill, G.; Sereni, J.G.; Godart, C.; Olcese, G.L.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasIn this study, we present recent X-ray Absorption Spectroscopy (XAS) results obtained on highly pure cerium nitride (CeN) compounds. CeN is the "archetype" of the strongly mixed-valent (MV) cerium compounds, where the ground state properties are governed by strong hybridization effects between the 4f and the conduction electrons. We will show that, in clear contradistinction with earlier results, the L]]], ]] absorption edges of cerium in CEN do not exhibit the two contributions usually observed in strong MV systems. Indeed, in all cases only one single white line is observed. This anomalous behaviour is related with similar results obtained recently on in-situ prepared CeN studied by both L]]], ]] absorption and Ce 2p X-ray photoemission (XPS). The possible influence of the presence of p conduction states to explain this anomalous behaviour is addressed.Ítem Acceso Abierto Anomalous reduction in the long-time flux creep relaxation in superconducting Ca10(Pt4As8)((Fe1−x Ptx )2As2)5 (x ≈ 0.05) single crystals(IOP Publishing, 2018-05-11) Haberkorn, N.; Huang, Silu; Jin, R.; Gerencia Física. Departamento Materia Condensada. División Bajas TemperaturasWe report the vortex dynamics of superconducting a Ca10(Pt4As8)((Fe1−xPtx)2As2)5 (x ≈ 0.05) single crystal with Tc = 26 K investigated by performing magnetic measurements. The field dependence of the magnetization displays a second peak (SPM), typically related to a crossover between elastic and plastic vortex relaxation in a weak pinning scenario. Long-time flux creep relaxation measurements for fields smaller that of the SPM show that the vortex dynamics can be separated in two different regions. For magnetic fields smaller than the lower end of the SPM, glassy relaxation (with a characteristic glassy exponent μ) is observed. For magnetic fields between the lower end and the SPM, the flux creep rate decreases systematically to values below to the ones predicted by the collective theory. This effect can be understood by considering a stable vortex lattice configuration. As the field position of the SPM can be adjusted by modifying the quenched potential, our results suggest that extremely low flux creep relaxation rate may be tuned in many other superconducting materials.