Evidence accumulation and change rate inference in dynamic environments

In a constantly changing world, animals must account for environmental volatility when making decisions. To appropriately discount older, irrelevant information, they need to learn the rate at which the environment changes. We develop an ideal observer model capable of inferring the present state of the environment along with its rate of change. Key to this computation is an update of the posterior probability of all possible changepoint counts. This computation can be challenging, as the number of possibilities grows rapidly with time. However, we show how the computations can be simplified in the continuum limit by a moment closure approximation. The resulting low-dimensional system can be used to infer the environmental state and change rate with accuracy comparable to the ideal observer. The approximate computations can be performed by a neural network model via a rate-correlation based plasticity rule. We thus show how optimal observers accumulate evidence in changing environments, and map this computation to reduced models which perform inference using plausible neural mechanisms.Comment: 43 pages, 8 figures, in pres

A Sinorhizobium meliloti-specific N-acyl homoserine lactone quorum-sensing signal increases nodule numbers in Medicago truncatula independent of autoregulation

N-acyl homoserine lactones (AHLs) act as quorum sensing signals that regulate cell-density dependent behaviors in many gram-negative bacteria, in particular those important for plant-microbe interactions. AHLs can also be recognized by plants, and this may influence their interactions with bacteria. Here we tested whether the exposure to AHLs affects the nodule-forming symbiosis between legume hosts and rhizobia. We treated roots of the model legume, Medicago truncatula, with a range of AHLs either from its specific symbiont, Sinorhizobium meliloti, or from the potential pathogens, Pseudomonas aeruginosa and Agrobacterium vitis. We found increased numbers of nodules formed on root systems treated with the S. meliloti-specific AHL, 3-oxo-C14-homoserine lactone, at a concentration of 1 μM, while the other AHLs did not result in significant changes to nodule numbers. We did not find any evidence for altered nodule invasion by the rhizobia. Quantification of flavonoids that could act as nod gene inducers in S. meliloti did not show any correlation with increased nodule numbers. The effects of AHLs were specific for an increase in nodule numbers, but not lateral root numbers or root length. Increased nodule numbers following 3-oxo-C14-homoserine lactone treatment were under control of autoregulation of nodulation and were still observed in the autoregulation mutant, sunn4 (super numeric nodules4). However, increases in nodule numbers by 3-oxo-C14-homoserine lactone were not found in the ethylene-insensitive sickle mutant. A comparison between M. truncatula with M. sativa (alfalfa) and Trifolium repens (white clover) showed that the observed effects of AHLs on nodule numbers were specific to M. truncatula, despite M. sativa nodulating with the same symbiont. We conclude that plant perception of the S. meliloti-specific 3-oxo-C14-homoserine lactone influences nodule numbers in M. truncatula via an ethylene-dependent, but autoregulation-independent mechanism

Diseño de una estrategia de evaluación virtual para prácticas de laboratorio en Ingeniería

En este trabajo se presenta una experiencia de dos años en la implementación de una estrategia de evaluación a distancia de prácticas de laboratorio de Máquinas Eléctricas. Se diseñó la estrategia con diferentes instrumentos abarcando las instancias tradicionales de evaluación para este tipo de prácticas experimentales. Se implementaron además instancias tutoriales a través de foros y correcciones progresivas de los trabajos que los estudiantes realizan a través del campus. Se describen tanto los problemas que se presentaron como los resultados para el aprendizaje. Se analiza la factibilidad de extender esta experiencia a otras asignaturas de carreras de Ingeniería que incorporen prácticas de laboratorio.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Diseño de una estrategia de evaluación virtual para prácticas de laboratorio en Ingeniería

En este trabajo se presenta una experiencia de dos años en la implementación de una estrategia de evaluación a distancia de prácticas de laboratorio de Máquinas Eléctricas. Se diseñó la estrategia con diferentes instrumentos abarcando las instancias tradicionales de evaluación para este tipo de prácticas experimentales. Se implementaron además instancias tutoriales a través de foros y correcciones progresivas de los trabajos que los estudiantes realizan a través del campus. Se describen tanto los problemas que se presentaron como los resultados para el aprendizaje. Se analiza la factibilidad de extender esta experiencia a otras asignaturas de carreras de Ingeniería que incorporen prácticas de laboratorio.Sociedad Argentina de Informática e Investigación Operativa (SADIO

A perspective on the pathway to a scalable quantum internet using rare-earth ions

The ultimate realization of a global quantum internet will require advances in scalable technologies capable of generating, storing, and manipulating quantum information. The essential devices that will perform these tasks in a quantum network are quantum repeaters, which will enable the long-range distribution of entanglement between distant network nodes. In this perspective, we provide an overview of the primary functions of a quantum repeater and discuss progress that has been made toward the development of repeaters with rare-earth ion doped materials while noting challenges that are being faced as the technologies mature. We give particular attention to erbium, which is well suited for networking applications. Finally, we provide a discussion of near-term benchmarks that can further guide rare-earth ion platforms for impact in near-term quantum networks

Comparison Between the Material Improvement of the Megarok and San José Quarries, Applying the AASTHO Standards

Comparative analyzes were carried out between the materials of the Magarok and San José quarries, taking into account AASTHO standards with the objective of being used as a base / sub-base in the pavement structure. The asphalt emulsion material was stabilized to increase the strength and give the material sub-base and / or base characteristics, with a suitable mixing design, obtaining results with suitable characteristics to be used in the pavement structure composed of a 65 % Asphalt AC 20; 34.30% water and 0.70% ASFIER 121 emulsions, with good resistance to the stability of the materials

Growth rate, scrotal circumference, sperm characteristics, and sexual behavior of mixed-breed goat bucks fed three leguminous trees

Aim of study: To investigate the effect of feeding foliage of leguminous trees on growth rate, semen characteristics, and sexual behavior of bucks. Area of study: Northeastern Mexico (23°44' N, 99°8' W). Material and methods: Twenty-two young goat bucks were randomly allocated to one of four treatment groups: 33% alfalfa hay (dry matter basis), 33%; Acacia farnesiana; Leucaena leucocephala; or Prosopis laevigata foliage (n=4 for alfalfa; n=6 for the rest of groups). Main results: Average daily gain (ADG) did not differ between bucks fed alfalfa, A. farnesiana, or L. leucocephala (120 ± 26, 134 ± 37, and 103 ± 29 g/d, respectively), but ADG of bucks offered P. laevigata was the lowest (72 ± 8 g; p<0.05). Bucks fed alfalfa had the highest feed efficiency (6.59 ± 1.25 kg of feed consumed/kg of gain; p<0.05) and bucks offered leguminous trees had the lowest (average 9.85 ± 2.3). Bucks offered alfalfa, and A. farnesiana had increased (p<0.05) scrotal circumference (26.6 ± 0.4 and 25.8 ± 1.5 cm) than bucks fed L. leucocephala, or P. laevigata (24.3 ± 1.2 and 24.1 ± 2.0 cm). Mean ejaculate volume was two-fold higher in alfalfa-fed bucks than all other dietary treatments. Sexual behavior did not differ among bucks fed the different legumes. Research highlights: Foliage of both A. farnesiana and L. leucocephala could totally replace alfalfa hay for rearing growing goat bucks in confinement without affecting daily weight gain, most semen characteristics, and copulation ability. P. laevigata reduced body weight and reproductive function

Ballast Treated with Asphalt Emulsion, Megarok and San Jose. AASTHO Standards

In the research work, the results obtained at the laboratory level of the lending material (ballast) treated with asphalt emulsion from the quarries "Megarok and San José" are compared, applying the AASTHO standards. The quarries are located in the Picoazá-La Sequita parish of the Portoviejo canton. Samples from both quarries were evaluated in the laboratory and it was possible to carry out tests of natural humidity, Atterberg, granulometric, compaction, and soil bearing capacity (CBR). Based on the results obtained, they were compared by disclosing which of the quarries meets the appropriate conditions within the construction standards and techniques, in order to stabilize the material with asphalt emulsion; in addition to comparing it with the specifications of the AASTHO standards and the MTOP standard. The result was that the materials extracted from the quarries do not meet the technical specifications; but when mixed with the asphalt emulsion, the Megarok material fulfills as type A base

Conception rate of artificially inseminated holstein cows affected by cloudy vaginal mucus, under intense heat conditions.

The objective of this work was to obtain prevalence estimates of cloudy vaginal mucus in artificially inseminated Holstein cows raised under intense heat, in order to assess the effect of meteorological conditions on its occurrence during estrus and to determine its effect on conception rate. In a first study, an association was established between the occurrence of cloudy vaginal mucus during estrus and the conception rate of inseminated cows (18,620 services), raised under intense heat (mean annual temperature of 22°C), at highly technified farms, in the arid region of northern Mexico. In a second study, data from these large dairy operations were used to assess the effect of meteorological conditions throughout the year on the occurrence of cloudy vaginal mucus during artificial insemination (76,899 estruses). The overall rate of estruses with cloudy vaginal mucus was 21.4% (16,470/76,899; 95% confidence interval = 21.1?21.7%). The conception rate of cows with clean vaginal mucus was higher than that of cows with abnormal mucus (30.6 vs. 22%). Prevalence of estruses with cloudy vaginal mucus was strongly dependent on high ambient temperature and markedly higher in May and June. Acceptable conception rates in high milk-yielding Holstein cows can only be obtained with cows showing clear and translucid mucus at artificial insemination.Título em português: Taxa de concepção de vacas Holandesas inseminadas artificialmente e afetadas por muco vaginal turvo, sob condições de intenso calor