Suchergebnisse

Subjective image quality databases are a major source of raw data on how the visual system works in naturalistic environments. These databases describe the sensitivity of many observers to a wide range of distortions of different nature and intensity seen on top of a variety of natural images. Data of this kind seems to open a number of possibilities for the vision scientist to check the models in realistic scenarios. However, while these natural databases are great benchmarks for models developed in some other way (e.g., by using the well-controlled artificial stimuli of traditional psychophysics), they should be carefully used when trying to fit vision models. Given the high dimensionality of the image space, it is very likely that some basic phenomena are under-represented in the database. Therefore, a model fitted on these large-scale natural databases will not reproduce these under-represented basic phenomena that could otherwise be easily illustrated with well selected artificial stimuli. In this work we study a specific example of the above statement. A standard corticalmodel using wavelets and divisive normalization tuned to reproduce subjective opinion on a large image quality dataset fails to reproduce basic cross-masking. Here we outline a solution for this problem by using artificial stimuli and by proposing a modification that makes the model easier to tune. Then, we show that the modified model is still competitive in the large-scale database. Our simulations with these artificial stimuli show that when using steerable wavelets, the conventional unit norm Gaussian kernels in divisive normalization should be multiplied by high-pass filters to reproduce basic trends in masking. Basic visual phenomena may be misrepresented in large natural image datasets but this can be solved with model-interpretable stimuli. This is an additional argument in praise of artifice in line with Rust and Movshon (2005). ; This work was partially funded by the Spanish and EU FEDER fund through the MINECO/FEDER/EU grants TIN2015-71537- P and DPI2017-89867-C2-2-R; and by the European Union's Horizon 2020 research and innovation programme under grant agreement number 761544 (project HDR4EU) and under grant agreement number 780470 (project SAUCE).

Precise navigation with GPS buoys has actually a number of scientist applications in the Earth sciences. The work presented is focussed in the application of the kinematic GPS buoys positioning for sea level monitoring and ocean surveying, oriented to the absolute calibration of space-borne radar altimeters at local scale. The application of the GPS buoys technology for these purposes requires centimeter accuracy in the estimation of the sea surface heights. A discussion of the differential kinematic strategies with short baselines (less than 50km) applied to the positioning of buoys in the open sea is presented. The data analyzed corresponds to several GPS buoy campaigns conducted in the Spanish North-Western Mediterranean Sea in March 1999 and in July 2000 offshore the Begur Cape. These experiences, performing the absolute calibration of the TOPEX side-B altimeter, had been developed in the frame of a project founded by the Spanish government, CICYT (Comision Interministerial de Ciencia Y Tecnologia), as a National Coordinated R+D project in space research (ref. ESP97- 1816-004). The aim of these campaigns was a previous training for the absolute calibration of both the future RA-2 altimeter on-board the ENVISAT satellite (ESA) and the INDEX POSEIDON-2 solid state altimeter on-board the JASON-1 satellite (NASA/CNES) in the Spanish territory. Apart to calibrate radar sensors on-board, the GPS buoys technology is applied to validate other geophysical data derived from the altimeter measurements as the significant wave height. Also a potential use of these kind of buoys to state a reference absolute sea surface at regional scales is discussed. The mapping of the sea surface with GPS buoys can be a useful tool for the estimation of biases and drifts for any altimeter mission that traverses the studied area. For this purpose, it is needed a combination of both the GPS buoys observations and the long-term measurements of a tide gauge placed nearby that region. An overview of the results of the last two year calibration campaigns will be presented as well as the future scientist guidelines in the topic. ; Peer Reviewed ; Postprint (published version)

In this study, we recorded single unit activity from rat auditory cortex while the animals performed an interval-discrimination task. The animals had to decide whether two auditory stimuli were separated by either 150 or 300 ms, and go to the left or right nose poke accordingly. Spontaneous firing in between auditory responses was compared in the attentive versus non-attentive brain states. We describe the firing rate modulation detected during intervals while there was no auditory stimulation. Nearly 18% of neurons (n = 14) showed a prominent neuronal discharge during the interstimulus interval, in the form of an upward or downward ramp towards the second auditory stimulus. These patterns of spontaneous activity were often modulated in the attentive versus passive trials. Modulation of the spontaneous firing rate during the task was observed not only between auditory stimuli, but also in the interval preceding the stimulus. These slow modulatory components could be locally generated or the result of a top-down influence originated in higher associative association areas. Such a neuronal discharge may be related to the computation of the interval time and contribute to the perception of the auditory stimulus. ; Supported by a grant from the Ministerio de Ciencia e Innovación/n(BFU2008-01371/BFI) to MVS–V. MM–G and GD were supported/nby the European Union grant BRAINSCALES, by the Spanish/nResearch Project SAF2010-16085 and by the CONSOLIDERINGENIO/n2010 Programme CSD2007-00012, and EU FP7/2007-/n2013 under grant agreement 214728-2.

Population confinements have been one of the most widely adopted non-pharmaceutical interventions (NPIs) implemented by governments across the globe to help contain the spread of the SARS-CoV-2 virus. While confinement measures have been proven to be effective to reduce the number of infections, they entail significant economic and social costs. Thus, different policy makers and social groups have exhibited varying levels of acceptance of this type of measures. In this context, understanding the factors that determine the willingness of individuals to be confined during a pandemic is of paramount importance, particularly, to policy and decision-makers. In this paper, we study the factors that influence the unwillingness to be confined during the COVID-19 pandemic by the means of a large-scale, online population survey deployed in Spain. We perform two types of analyses (logistic regression and automatic pattern discovery) and consider socio-demographic, economic and psychological factors, together with the 14-day cumulative incidence per 100,000 inhabitants. Our analysis of 109,515 answers to the survey covers data spanning over a 5-month time period to shed light on the impact of the passage of time. We find evidence of pandemic fatigue as the percentage of those who report an unwillingness to be in confinement increases over time; we identify significant gender differences, with women being generally less likely than men to be able to sustain long-term confinement of at least 6 months; we uncover that the psychological impact was the most important factor to determine the willingness to be in confinement at the beginning of the pandemic, to be replaced by the economic impact as the most important variable towards the end of our period of study. Our results highlight the need to design gender and age specific public policies, to implement psychological and economic support programs and to address the evident pandemic fatigue as the success of potential future confinements will depend on the population's willingness to comply with them.

The three Begur experiments have been conducted on March, 16-19, 1999, which was the first altimeter calibration ever developed in Spain and the first Alt-B altimeter calibration made in the Mediterranean Sea; on July, 4-7, 2000, and on August, 25-28, 2002. Direct absolute altimeter calibration, estimating the TOPEX Alt-B bias, was made from direct overflights using GPS buoys. This method does not require any modelling of geoid and tidal error. Other main objective of the campaigns was to map with GPS buoys the Mean Sea Surface, MSS, along an ascending T/P groundtrack about 15-20 km from the coast, using coastal tide gauge measurements. This method requires geographical mapping of geoid and ocean tides which reduces the accuracy of the bias estimate by a factor of two. Indirect absolute altimeter calibration is possible for any satellite crossing the MSS, with the only requirement that tide gauges are operational during the overflight. In the framework of the JASON-1 CNES/NASA mission, a campaign was conducted on June 9-17, 2003, in the Absolute Calibration Site of the Island of Ibiza. The objective was to determine the local marine geoid slope under the ascending (187) and descending (248) Jason-1 ground tracks, in order to allow a better extrapolation of the open-ocean altimetric data with on-shore tide gauge locations, and thereby improve the overall precision of the calibration process. We present preliminary results on Jason-1 altimeter calibration using the derived marine geoid: from this analysis the altimeter bias is estimated to be 120 ± 5 mm. ; These campaigns have been supported by the Spanish Government, Comisión Interministerial de Ciencia y Tecnología CICYT R+D Projects in Space Research Ref.: ESP97-1816-CO4 and ESP2001-4534-PE. GPS (SANB) and tide gauge data from Ibiza and San Antonio were obtained also within the framework of the ESEAS-RI EU project under contract EVR1-CT-2002-40025. ; Peer reviewed