Spike timing and synaptic plasticity in the premotor pathway of birdsong

The neural circuits of birdsong appear to utilize specific time delays in their operation. In particular, the anterior forebrain pathway (AFP) is implicated in an approximately 40- to 50- ms time delay, ΔT, playing a role in the relative timing of premotor signals from the nucleus HVc to the nucleus robust nucleus of the archistratium (RA) and control/learning signals from the nucleus lateral magnocellular nucleus of the anterior neostratium (lMAN) to RA. Using a biophysical model of synaptic plasticity based on experiments on mammalian hippocampal and neocortical pyramidal neurons, we propose an understanding of this ≈ 40- to 50- ms delay. The biophysical model describes the influence of Ca2+ influx into the postsynaptic RA cells through NMDA and AMPA receptors and the induction of LTP and LTD through complex metabolic pathways. The delay, ΔT, between HVc → RA premotor signals and lMAN → RA control/learning signals plays an essential role in determining if synaptic plasticity is induced by signaling from each pathway into RA. If ΔT is substantially larger than 40 ms, no plasticity is induced. If ΔT is much less than 40 ms, only potentiation is expected. If ΔT≈ 40 ms, the sign of synaptic plasticity is sensitive to ΔT. Our results suggest that changes in ΔT may influence learning and maintenance of birdsong. We investigate the robustness of this result to noise and to the removal of the Ca2+ contribution from lMAN → RA NMDA receptors. © Springer-Verlag 2004.Fil: Abarbanel, Henry D. I.. University of California at San Diego; Estados UnidosFil: Gibb, Leif. University of California at San Diego; Estados UnidosFil: Mindlin, Bernardo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Rabinovich, M.I.. University of California at San Diego; Estados UnidosFil: Talathi, Sachin. University of California at San Diego; Estados Unido

Rendimiento y eficiencia de distintas técnicas de control en un calefón eléctrico

El calentamiento de agua en el sector residencial ecuatoriano se ha convertido en un espacio de investigación y desarrollo, debido al intento de mitigar el gasto corriente de las personas y a la vez contribuir de manera activa a los procesos de eficiencia energética que van tomando fuerza en el país. En el presente documento se muestra un análisis comparativo entre diferentes maneras de controlar la temperatura del agua para un sistema residencial utilizando un calentador eléctrico; se analizó la respuesta de un conversor AC/AC de control de fase directa que permite retrasar el ángulo de disparo de la onda de corriente alterna y la respuesta del control ON/OFF que activa o desactiva el calentador durante un número preestablecido de semiciclos de corriente alterna. Para las pruebas se instaló un prototipo de calentador eléctrico con un serpentín de 14 metros a base de resistencias eléctricas; con las respuestas de temperatura que se generan de cada conversor se procedió a identificar la función de transferencia de cada sistema ya que ambos difieren en su técnica de transmisión de calor y a la vez en su modelo matemático. Posteriormente se procedió a sintonizar un controlador PID para cada sistema, obteniendo buenos resultados de respuesta de temperatura en ambos casos, pero solo uno resultó eficiente en ahorro energético.// Water heating in the Ecuadorian residential sector has become a space for research and development, due to the attempt to mitigate the current spending of people and at the same time contribute actively to the energy efficiency processes that are gaining strength in the country. This document shows a comparative analysis between different ways of controlling the water temperature for a residential system using an electric heater; the response of a direct phase control AC / AC converter was analyzed, which allows to delay the firing angle of the AC wave and the response of the ON / OFF control that activates or deactivates the heater during a pre-established number of half-cycles of current alternating, for the tests a prototype of electric heater was implemented with a coil of 14 meters based on electrical resistances, with the temperature responses that are generated from each converter, we proceeded to identify the transfer function of each system since both differ in its heat transmission technique and at the same time in its mathematical model, a PID controller was then tuned for each system, obtaining good results of temperature response in both cases but only one was efficient in energy saving

Vegetation response to invasive Tamarix control in southwestern U.S. rivers: a collaborative study including 416 sites

Most studies assessing vegetation response following control of invasive Tamarix trees along southwestern U.S. rivers have been small in scale (e.g., river reach), or at a regional scale but with poor spatial-temporal replication, and most have not included testing the effects of a now widely used biological control. We monitored plant composition following Tamarix control along hydrologic, soil, and climatic gradients in 244 treated and 172 reference sites across six U.S. states. This represents the largest comprehensive assessment to date on the vegetation response to the four most common Tamarix control treatments. Biocontrol by a defoliating beetle (treatment 1) reduced the abundance of Tamarix less than active removal by mechanically using hand and chain-saws (2), heavy machinery (3) or burning (4). Tamarix abundance also decreased with lower temperatures, higher precipitation, and follow-up treatments for Tamarix resprouting. Native cover generally increased over time in active Tamarix removal sites, however, the increases observed were small and was not consistently increased by active revegetation. Overall, native cover was correlated to permanent stream flow, lower grazing pressure, lower soil salinity and temperatures, and higher precipitation. Species diversity also increased where Tamarix was removed. However, Tamarix treatments, especially those generating the highest disturbance (burning and heavy machinery), also often promoted secondary invasions of exotic forbs. The abundance of hydrophytic species was much lower in treated than in reference sites, suggesting that management of southwestern U.S. rivers has focused too much on weed control, overlooking restoration of fluvial processes that provide habitat for hydrophytic and floodplain vegetation. These results can help inform future management of Tamarix-infested rivers to restore hydrogeomorphic processes, increase native biodiversity and reduce abundance of noxious species

No More Active Galactic Nuclei in Clumpy Disks Than in Smooth Galaxies at z~2 in CANDELS / 3D-HST

We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to investigate if active galactic nuclei (AGNs) are preferentially fueled by violent disk instabilities funneling gas into galaxy centers at 1.3<z<2.4. We select galaxies undergoing gravitational instabilities using the number of clumps and degree of patchiness as proxies. The CANDELS visual classification system is used to identify 44 clumpy disk galaxies, along with mass-matched comparison samples of smooth and intermediate morphology galaxies. We note that, despite being being mass-matched and having similar star formation rates, the smoother galaxies tend to be smaller disks with more prominent bulges compared to the clumpy galaxies. The lack of smooth extended disks is probably a general feature of the z~2 galaxy population, and means we cannot directly compare with the clumpy and smooth extended disks observed at lower redshift. We find that z~2 clumpy galaxies have slightly enhanced AGN fractions selected by integrated line ratios (in the mass-excitation method), but the spatially resolved line ratios indicate this is likely due to extended phenomena rather than nuclear AGNs. Meanwhile the X-ray data show that clumpy, smooth, and intermediate galaxies have nearly indistinguishable AGN fractions derived from both individual detections and stacked non-detections. The data demonstrate that AGN fueling modes at z~1.85 - whether violent disk instabilities or secular processes - are as efficient in smooth galaxies as they are in clumpy galaxies.Comment: ApJ accepted. 17 pages, 17 figure

Diel activity patterns of two distinct populations of Aedes aegypti in Miami, FL and Brownsville, TX

The diel biting activity of Aedes (Stegomyia) aegypti (L) populations was extensively investigated in the early 1900s to gain more information on the biology of Ae. aegypti, and this information was used to devise effective approaches to controlling populations of this species and protect the human population from widespread arbovirus outbreaks. However, few contemporary studies are available regarding the diel activity patterns of Ae. aegypti. To assess the diel activity patterns of Ae. aegypti in southern Florida and Texas, we conducted 96-h uninterrupted mosquito collections once each month from May through November 2019 in Miami, Florida, and Brownsville, Texas, using BG-Sentinel 2 Traps. The overall diel activity pattern in both cities was bimodal with morning and evening peak activity between 7:00 and 8:00 and between 19:00 and 20:00. There were significant daily, monthly, seasonal, and site-specific differences in activity patterns, but these differences did not affect the overall peak activity times. These differences suggest daily, monthly, seasonal, and site-specific variations in human exposure to Ae. aegypti. Our observations can be used in planning and executing Ae. aegypti vector control activities in southern Florida and southern Texas, specifically those targeting the adult mosquito populations