Human behavior displays hierarchical structure: simple actions cohere into subtask sequences, which work together to accomplish overall task goals. Although the neural substrates of such hierarchy ...have been the target of increasing research, they remain poorly understood. We propose that the computations supporting hierarchical behavior may relate to those in hierarchical reinforcement learning (HRL), a machine-learning framework that extends reinforcement-learning mechanisms into hierarchical domains. To test this, we leveraged a distinctive prediction arising from HRL. In ordinary reinforcement learning, reward prediction errors are computed when there is an unanticipated change in the prospects for accomplishing overall task goals. HRL entails that prediction errors should also occur in relation to task subgoals. In three neuroimaging studies we observed neural responses consistent with such subgoal-related reward prediction errors, within structures previously implicated in reinforcement learning. The results reported support the relevance of HRL to the neural processes underlying hierarchical behavior.
► In hierarchical tasks, temporal-difference prediction errors occur with subgoals ► These signals are clearest in cingulate and insular cortices ► Subgoal PEs may also occur in amygdala, habenula, and nucleus accumbens ► Subgoal PEs may represent a neural signature of hierarchical reinforcement learning
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The function of midcingulate cortex (MCC) remains elusive despite decades of investigation and debate. Complicating matters, individual MCC neurons respond to highly diverse task-related events, and ...MCC activation is reported in most human neuroimaging studies employing a wide variety of task manipulations. Here we investigate this issue by applying a model-based cognitive neuroscience approach involving neural network simulations, functional magnetic resonance imaging, and representational similarity analysis. We demonstrate that human MCC encodes distributed, dynamically evolving representations of extended, goal-directed action sequences. These representations are uniquely sensitive to the stage and identity of each sequence, indicating that MCC sustains contextual information necessary for discriminating between task states. These results suggest that standard univariate approaches for analyzing MCC function overlook the major portion of task-related information encoded by this brain area and point to promising new avenues for investigation.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Context. The prediction of stellar occultations by trans-Neptunian objects (TNOs) and Centaurs is a difficult challenge that requires accuracy both in the occulted star position and in the object ...ephemeris. Until now, the most used method of prediction, involving dozens of TNOs/Centaurs, has been to consider a constant offset for the right ascension and for the declination with respect to a reference ephemeris, usually the latest public version. This offset is determined as the difference between the most recent observations of the TNO/Centaur and the reference ephemeris. This method can be successfully applied when the offset remains constant with time, i.e. when the orbit is stable enough. In this case, the prediction even holds for occultations that occur several days after the last observations. Aims. This paper presents an alternative method of prediction, based on a new accurate orbit determination procedure, which uses all the available positions of the TNO from the Minor Planet Center database, as well as sets of new astrometric positions from unpublished observations. Methods. Orbits were determined through a numerical integration procedure called NIMA, in which we developed a specific weighting scheme that considers the individual precision of the observation, the number of observations performed during one night by the same observatory, and the presence of systematic errors in the positions. Results. The NIMA method was applied to 51 selected TNOs and Centaurs. For this purpose, we performed about 2900 new observations in several observatories (European South Observatory, Observatório Pico dos Dias, Pic du Midi, etc.) during the 2007–2014 period. Using NIMA, we succeed in predicting the stellar occultations of 10 TNOs and 3 Centaurs between July 2013 and February 2015. By comparing the NIMA and Jet Propulsion Laboratory (JPL) ephemerides, we highlight the variation in the offset between them with time, by showing that, generally, the constant offset hypothesis is not valid, even for short time scales of a few weeks. Giving examples, we show that the constant offset method cannot accurately predict 6 out of the 13 observed positive occultations that have been successfully predicted by NIMA. The results indicate that NIMA is capable of efficiently refining the orbits of these bodies. Finally, we show that the astrometric positions given by positive occultations can help to refine the orbit of the TNO and, consequently, the future predictions. We also provide unpublished observations of the 51 selected TNOs and their ephemeris in a usable format by the SPICE library.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
SORA: Stellar occultation reduction and analysis Gomes-Júnior, A R; Morgado, B E; Benedetti-Rossi, G ...
Monthly notices of the Royal Astronomical Society,
02/2022, Volume:
511, Issue:
1
Journal Article
Peer reviewed
Open access
ABSTRACT
The stellar occultation technique provides competitive accuracy in determining the sizes, shapes, astrometry, etc., of the occulting body, comparable to in-situ observations by spacecraft. ...With the increase in the number of known Solar system objects expected from the LSST, the highly precise astrometric catalogs, such as Gaia, and the improvement of ephemerides, occultations observations will become more common with a higher number of chords in each observation. In the context of the Big Data era, we developed sora, an open-source python library to reduce and analyse stellar occultation data efficiently. It includes routines from predicting such events up to the determination of Solar system bodies’ sizes, shapes, and positions.
A flow-based method for the spectrophotometric determination of chromium (VI) in recreational waters with different salinities was developed. Chromium can occur in the environment in different ...oxidation states with different related physiological properties. With regard to chromium, the speciation is particularly important, as the hexavalent chromium is considered to be carcinogenic. To achieve that purpose, the use of the diphenylcarbazide (DPC) selective colored reaction with the hexavalent chromium was the chosen strategy. The main objective was to develop a direct and simple spectrophotometric method that could cope with the analysis of different types of environmental waters, within different salinity ranges (fresh to marine waters). The potential interference of metal ions, that can usually be present in environmental waters, was assessed and no significant interferences were observed (<10%). For a complete Cr(VI) determination (three replicas) cycle, the corresponding reagents consumption was 75 µg of DPC, 9 mg of ethanol and 54 mg of sulfuric acid. Each cycle takes about 5 min, including the system clean-up. The limit of detection was 6.9 and 12.2 µg L−1 for waters with low and high salt content, respectively. The method was applied for the quantification of chromium (VI) in both fresh and marine water, and the results were in agreement with the reference procedure.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•System developed for performance evaluation and optimization of a hydropower plant.•Detailed modeling of hydropower production function, using sensors data.•A comparative analysis of two methods for ...the determination of turbined outflow.•Real-time optimization of the dispatch, seeking to use the water efficiently.
This paper describes a system for the performance evaluation and energy optimization of the real-time operation at Itá Hydropower Plant, which is located in southern Brazil. Using data collected from sensors and meters, several variables of the units are precisely calculated, such as turbined outflows, heads, losses and efficiencies. The unit turbined outflow, which is the most challenging and important parameter for real-time operation, is calculated using an ultrasonic flow meter and a Hill diagram. Additionally, the system performs a real-time optimization in which the dispatch aims to use the water efficiently. In predominant hydropower systems, as in Brazil, this computational tool is very useful for the efficient use of hydro resources, for which every tenth of a percentage increase in the energy conversion efficiency is welcome. The benefits detailed in this paper can also be achieved in other plants, particularly if there are a large number of units with distinct operating characteristics.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A bi-parametric sequential injection method for the determination of copper(II) and zinc(II) when present together in aqueous samples was developed. This was achieved by using a non-specific ...colorimetric reagent (4-(2-pyridylazo)resorcinol, PAR) together with two ion-exchange polymeric materials to discriminate between the two metal ions. A polymer inclusion membrane (PIM) and a chelating resin (Chelex 100) were the chosen materials to retain zinc(II) and copper(II), respectively. The influence of the flow system parameters, such as composition of the reagent solutions, flow rates and standard/sample volume, on the method sensitivity were studied. The interference of several common metal ions was assessed, and no significant interferences were observed (<10% signal deviation). The limits of detection were 3.1 and 5.6 µg L
for copper(II) and zinc(II), respectively; the dynamic working range was from 10 to 40 µg L
for both analytes. The newly developed sequential injection analysis (SIA) system was applied to natural waters and soil leachates, and the results were in agreement with those obtained with the reference procedure.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A REVIEW AND TEST OF SHORELINE EXTRACTION TECHNIQUES Angelini, R.; Angelats, E.; Luzi, G. ...
International archives of the photogrammetry, remote sensing and spatial information sciences.,
05/2023, Volume:
XLVIII-1/W1-2023
Journal Article, Conference Proceeding
Peer reviewed
Open access
Shoreline represents the boundary between land and sea, and its accurate extraction is of utmost importance because of the economic and ecological value of coastal areas. Nowadays, satellite remote ...sensing is widely used for monitoring the natural environment. Indeed, satellite remote sensing data are cost-effective and periodically available over large areas at a relatively high spatial resolution. Hence, the automatic shoreline extraction from satellite images is a fundamental task for coastal monitoring and management. Shoreline extraction methods are usually applied to satellite remote sensing data. The goal of this study is to compare the performance of different shoreline extraction methods, such as thresholding and more complex classification approaches, such as Random Forest (RF), Minimum Distance (MD), Maximum Likelihood (ML) and K-means, using both optical and radar images. The considered case study area is the shallow basin of the Orbetello Lagoon and one of its ayre called Feniglia. The data supplier is the Copernicus program, which, through the Sentinel-1 and Sentinel-2 missions, provides medium-resolution, open-access products. The accuracy of the obtained results from both methodologies is checked by validating the extracted shoreline using an aerial orthomosaic and, subsequently, a manually extracted shoreline. A preliminary accuracy assessment was performed for image classification, focusing on extracting four classes: water, soil, urban, and forest, using manual segmentation as a reference. In terms of deviation from the reference shoreline, the results obtained through the analysed methodologies achieved an accuracy of 3.75 m, less than half of the pixel size of the Sentinel-1 and Sentinel-2 used products.
ABSTRACT
Recording a stellar occultation is one powerful method that gives direct information about the physical properties of the occulting Solar system object. In order to obtain reliable and ...accurate results, simultaneous observations from different locations across-track of the projected path are of great importance. However, organizing all the observing stations, aggregating, and analysing the data is time-consuming and not that easy. We have developed a web portal named Occultation Portal (OP) to manage all those occultation observation campaigns from a central server. With this portal, the instrumental and observational information of all observers participating in a stellar occultation campaign and the concerned data are archived systematically in a standard format. The researchers can then visualize the archived data on an event basis. The investigators can also extract the light curve for each data set with the added reduction pipeline to the portal base. This paper describes in detail the portal structure and the developed features.
Following genome sequencing of crop plants, one of the main challenges today is determining the function of all the predicted genes. When gene validation approaches are used for woody species, the ...main obstacle is the low recovery rate of transgenic plants from elite or commercial cultivars. Embryogenic calli have frequently been the target tissue for transformation, but the difficulty in producing or maintaining embryogenic tissues is one of the main problems encountered in genetic transformation of many woody plants, including Coffea arabica.
We identified the conditions required for successful long-term proliferation of embryogenic cultures in C. arabica and designed a highly efficient and reliable Agrobacterium tumefaciens-mediated transformation method based on these conditions. The transformation protocol with LBA1119 harboring pBin 35S GFP was established by evaluating the effect of different parameters on transformation efficiency by GFP detection. Using embryogenic callus cultures, co-cultivation with LBA1119 OD600 = 0.6 for five days at 20 °C enabled reproducible transformation. The maintenance conditions for the embryogenic callus cultures, particularly a high auxin to cytokinin ratio, the age of the culture (optimum for 7-10 months of proliferation) and the use of a yellow callus phenotype, were the most important factors for achieving highly efficient transformation (> 90%). At the histological level, successful transformation was related to the number of proembryogenic masses present. All the selected plants were proved to be transformed by PCR and Southern blot hybridization.
Most progress in increasing transformation efficiency in coffee has been achieved by optimizing the production conditions of embryogenic cultures used as target tissues for transformation. This is the first time that a strong positive effect of the age of the culture on transformation efficiency was demonstrated. Our results make Agrobacterium-mediated transformation of embryogenic cultures a viable and useful tool both for coffee breeding and for the functional analysis of agronomically important genes.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
