Divisive Normalization from Wilson-Cowan Dynamics

Divisive Normalization and the Wilson-Cowan equations are influential models of neural interaction and saturation [Carandini and Heeger Nat.Rev.Neurosci. 2012; Wilson and Cowan Kybernetik 1973]. However, they have not been analytically related yet. In this work we show that Divisive Normalization can be obtained from the Wilson-Cowan model. Specifically, assuming that Divisive Normalization is the steady state solution of the Wilson-Cowan differential equation, we find that the kernel that controls neural interactions in Divisive Normalization depends on the Wilson-Cowan kernel but also has a signal-dependent contribution. A standard stability analysis of a Wilson-Cowan model with the parameters obtained from our relation shows that the Divisive Normalization solution is a stable node. This stability demonstrates the consistency of our steady state assumption, and is in line with the straightforward use of Divisive Normalization with time-varying stimuli. The proposed theory provides a physiological foundation (a relation to a dynamical network with fixed wiring among neurons) for the functional suggestions that have been done on the need of signal-dependent Divisive Normalization [e.g. in Coen-Cagli et al., PLoS Comp.Biol. 2012]. Moreover, this theory explains the modifications that had to be introduced ad-hoc in Gaussian kernels of Divisive Normalization in [Martinez et al. Front. Neurosci. 2019] to reproduce contrast responses. The proposed relation implies that the Wilson-Cowan dynamics also reproduces visual masking and subjective image distortion metrics, which up to now had been mainly explained via Divisive Normalization. Finally, this relation allows to apply to Divisive Normalization the methods which up to now had been developed for dynamical systems such as Wilson-Cowan networks

Un modelo de demanda de trabajo con expectativas de output aplicado a la industria española

El propósito de este trabajo es contrastar dos métodos de estimación aplicados en diversos trabajos realizados en colaboración con J.J. Dolado a los datos del sector industrial español. En la primera sección se expone la estructura analítica tomada de Dolado y Malo de Molina (1985 b). En la segunda sección se expone una breve descripción de la evolución del empleo y de las variables explicativas en el sector industrial español, asi como de los resultados alcanzados en estimaciones econométricas anteriores (Dolado y Malo de Molina, 1983 y 1985 a). En la tercera sección se incluyen los resultados econométricos de este ejercicio, y, finalmente se incluye una breve sección de conclusiones

Atrazine and Alachlor Adsorption Characteristics to Benchmark Soil Series in Eastern South Dakota

Corn, grain sorghum, and soybean are grown on about six million acres in eastern South Dakota each year. Two herbicides used routinely for weed control are atrazine(6-chloro-N-ethyl-N’-(1-methylethyl)-1,3,5-triazine-2,4-diamine) in corn and grain sorghum and alachlor (2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide) in all three crops. Six benchmark soil series that include a majority of the cropped acres treated with these herbicides are the Egan, Moody, Nora, and Brandt silty clay loams, and Clarno and Enet loams. Batch adsorption studies determined atrazine and alachlor binding characteristics to these soils and aids in assessing the amount of herbicide available for movement. These data also provide a basis for future use and management decisions for these and other related herbicides in similar soils. Soils from three horizons (A, B, and C) for each soil type were treated with atrazine or alachlor at four herbicide concentrations. Atrazine and alachlor sorption partition coefficients differed most in A horizon soils and ranged from 2.16 to 5.35 µmol1-1/n L1/nKg-1 for atrazine and 1.95 to 5.78 µmol1-1/n L1/nKg-1 for alachlor. Atrazine binding to A horizon soils ranked as Brandt \u3eEgan = Moody \u3e Enet = Clarno \u3e Nora. Alachlor binding to A horizon soils ranked as Brandt \u3eMoody \u3e Nora \u3e Enet \u3e Clarno. B and C horizon soils had lower binding for both herbicides; the sorption partition coefficient for atrazine ranged from 0.12 to 1.9 µmol1-1/n L1/nKg-1 while alachlor ranged from 0.43 to 1.64 µmol1-1/n L1/nKg-1. These data indicate that some soil types would be more susceptible to herbicide leaching than others. Once the herbicide moves through the A horizon, it may move rapidly through the lower soil profile (because of the decrease in binding capacity), and therefore, increase the vulnerability of the aquifer to contamination. Best management practices for these herbicides are being investigated to limit their movement through soil

Bird flight behavior, collision risk and mitigation options at high-speed railway viaducts

High-speed railway (HSR) networks are rapidly expanding and are predicted to continue to grow over coming decades. However, there is scant knowledge of their environmental impacts. Their possible effects on bird mortality, particularly at viaducts, gives especial cause for concern. This work presents the results of a nine-month monitoring of bird activity in the vicinity of three HSR viaducts in Central Spain. The study focused on the effects of the infrastructure regarding bird frequentation of the site and on bird flight activity in the danger zone for collision with passing trains. The findings show (i) that bird communities may differ markedly between sites and (ii) that bird activity increases near the railway together with changes in relative species abundances. Furthermore, (iii) birds show a significant tendency to avoid flying across the danger zone, but (iv) all kinds of birds are at a real risk of collisions with trains at viaducts. The greatest danger is at viaduct extremes rather than in their central section, particularly during gusts of wind and for small or medium-sized birds. It also appears that relatively low viaducts might pose greater risk. In practical terms, these results (i) emphasise the need for thorough prior prospection of bird species present, and their flight patterns, where new viaducts are to be built, (ii) show that there is a real risk of bird collisions with trains at viaducts, which should be mitigated, with particular attention due to viaduct extremes and areas where their height is not much above the surrounding vegetation and (iii) strongly indicate the need to minimise viaduct features that may attract birds to them, for example as potential nest sitesThis study is derived from research into the ecology and mortality of birds at highspeed railways done under project EU LIFE+ Impacto Cero (LIFE 12 BIO/ES/000660). JEM and JH form part of the REMEDINAL TE-CM research network, funded by the Comunidad de Madrid (P2018/ EMT-4338). Comments by two anonymous reviewers improved the final tex

Point-by-point inscription of apodized fiber Bragg gratings

We demonstrate apodized fiber Bragg gratings inscribed with a point-by-point technique. We tailor the grating phase and coupling amplitude through precise control over the longitudinal and transverse position of each laser-inscribed modification. This method of apodization is facilitated by the highly-localized, high-contrast modifications generated by focussed IR femtosecond laser inscription. Our technique provides a simple method for the design and implementation of point-by-point fiber Bragg gratings with complex apodization profiles.Comment: 6 pages, 4 figures, article in revie

Scientists' warning to humanity for long-term planetary thinking on biodiversity and humankind preservation, a cosmic perspective

We are all made of stars,? the song claims. Indeed, as Carl Sagan said, we are made of star stuff. But we often forget the message of unity ingrained in such reality. The typical narrow short-term perspective characterizing human planning, combined with self-interest, frequently leads to a tragedy of the commons where the very same resources essential for survival or prosperity are compromised or destroyed (Hardin 1968). Such selfish exploitation of common goods sits at the base of many current global problems, including the depletion of natural resources, accelerated climate change, and the loss of biodiversity. Fortunately, there is an increasing awareness of the importance of the natural environment, and an emerging paradigm shift is attempting to ameliorate the negative consequences of global problems for our children and subsequent generations. However, most if not all current plans are somehow shortsighted. For example, the Sustainable Development Goals adopted by the United Nations in 2015 set their targets for the year 2030. The United Nations Climate Change Conferences of the Parties implicitly or explicitly set their purposes for one or a few generations. The question is whether short-term goals and vision will be enough?or even adequate?to ensure the preservation of most life forms, including humanity, into the distant future. Although short-term targets are essential to trigger the necessary immediate action, shouldn't biodiversity preservation thinking and planning occur on a much longer time frame? If so, what is the appropriate time frame

100% RAG: Syracuse School of Architecture, Student Newspaper, Volume 1, Number 3

100% RAG: Syracuse School of Architecture, Student Newspaper, Volume 1, Number 3. Student newsletter from student contributors of Syracuse School of Architecture in 1976