Evidence for an additive inhibitory component of contrast adaptation

The latency of visual responses generally decreases as contrast increases. Recording in the lateral geniculate nucleus (LGN), we find that response latency increases with increasing contrast in ON cells for some visual stimuli. We propose that this surprising latency trend can be explained if ON cells rest further from threshold at higher contrasts. Indeed, while contrast changes caused a combination of multiplicative gain change and additive shift in LGN cells, the additive shift predominated in ON cells. Modeling results supported this theory: the ON cell latency trend was found when the distance-to-threshold shifted with contrast, but not when distance-to-threshold was fixed across contrasts. In the model, latency also increases as surround-to-center ratios increase, which has been shown to occur at higher contrasts. We propose that higher-contrast full-field stimuli can evoke more surround inhibition, shifting the potential further from spiking threshold and thereby increasing response latency

SNUS-2.5, a Multimoment Analysis of Road Demand, Accidents and their Severity in Germany, 1968 – 1989

The present article presents an improved and refined version of the SNUS-1 model (GAUDRY and BLUM 1993) documented only in French. The greatest difficulty faced in the development of the model did not have to do with structure – the multilevel structure is straightforward – but with the specification of the employment activity variable, due to the specifics of the German economy,and with the proper formulation of the role of vehicle stocks in the road demand models. Moreover,we consider the following aspects to be special in the context of an analysis of Germany: • there exist no general speed limits on motorways, i.e. about 70% allow unlimited speed today,and in the Sixties, when our analysis starts, this share was even higher; • the country is large compared with other regions were the DRAG-methodology is employed, and it possesses high car ownership levels and an important car industry that sees the German infrastructure as an appropriate testing ground; • Germany is poly-central, its infrastructure resembles a grid, whereas France’s is almost a huband-spoke system, as compared for instance to Norway’s line; • unification is not yet included because of lagging data availability and, thus, problems to compensate for the structural break in data series.Classification-JEL:

Improved Complexity Bounds for Counting Points on Hyperelliptic Curves

We present a probabilistic Las Vegas algorithm for computing the local zeta function of a hyperelliptic curve of genus $g$ defined over $\mathbb{F}_q$. It is based on the approaches by Schoof and Pila combined with a modeling of the $\ell$-torsion by structured polynomial systems. Our main result improves on previously known complexity bounds by showing that there exists a constant $c>0$ such that, for any fixed $g$, this algorithm has expected time and space complexity $O((\log q)^{cg})$ as $q$ grows and the characteristic is large enough.Comment: To appear in Foundations of Computational Mathematic

Tie Turning Box-Cox including Quadratic Forms in Regression

In a regression model where a Box-Cox transformation is used on a positive independent variable X which appears only once in the equation, the effect of X on the dependent variable Y is either strictly increasing or decreasing over the whole range of X , since the transformation is a monotonic function of X , increasing or decreasing depending on the Box-Cox parameter ë. This paper considers the case where the variable X appears twice in the regression with two different Box-Cox parameters 1 ë and 2 ë , to allow a turning point in Y which can be a maximum or minimum. First and second-order conditions for the critical point are derived. This general specification includes as a special case the quadratic form in X where 1 ë and 2 ë are set equal to 1 and 2, respectively. If, instead of using the Box-Cox transformations, one uses simple powers of X , this form is equivalent to the Box-Cox form except that neither 1 ë nor 2 ë can be equal to zero, since in this case 1 ë X or 2 ë X reduces to a constant of value 1.Box-Cox Transformation, Quadratic Form, Asymmetric U-shaped Forms, Regression. Classification-JEL :

Fast genus 2 arithmetic based on Theta functions

descriptionInternational audienceIn 1986, D. V. Chudnovsky and G. V. Chudnovsky proposed to use formulae coming from Theta functions for the arithmetic in Jacobians of genus 2 curves. We follow this idea and derive fast formulae for the scalar multiplication in the Kummer surface associated to a genus 2 curve, using a Montgomery ladder. Our formulae can be used to design very efficient genus 2 cryptosystems that should be faster than elliptic curve cryptosystems in some hardware configurations

Evergreening: A Common Practice to Protect New Drugs

Exclusivity periods serve as an incentive for pharmaceutical companies to engage in the costly and risky activities underlying drug discovery and development. Patents offer one form of exclusivity. Other exclusivities are awarded upon receiving specific types of approvals from the Food and Drug Administration. Here, I present data related to the exclusivity periods associated with all new-drug applications approved between 2000 and 2010. Recently approved drugs have fewer exclusivity periods. The duration between a drug’s approval and the expiration of its final exclusivity period is also shorter for recently approved drugs. This data suggests that companies frequently engage in evergreening strategies, through which exclusivity periods are gradually accrued beyond drugs’ approval date. Thus, companies’ total exclusivity time periods may be extended. Though later-granted exclusivity periods may be of more limited scope than earlier obtained exclusivities, they may nonetheless increase total drug-associated profits. The potential widespread occurrence of evergreening suggests that this exclusivity-extending opportunity itself contributes to the incentives that justify pharmaceutical companies’ new-drug investments

Un aperçu de DRAG, un modèle de sécurité routière compréhensif

Nous faisons un résumé surtout qualitatif de DRAG, un modèle explicatif de la Demande Routière, des Accidents et de leur Gravité. Nous montrons le caractère compréhensif du modèle, en ce qui a trait à sa structure, aux catégories de facteurs explicatifs prises en compte et aux méthodes d’estimation des paramètres utilisées. Nous soulignons en particulier comment la structure même de DRAG permet de décomposer la contribution de chaque facteur explicatif de l’insécurité routière entre des effets sur l’exposition au risque, sur la fréquence et sur la gravité des accidents — et comment on peut ainsi étudier la présence de substitution entre les diverses dimensions du risque de conduite. Nous donnons une idée de l’application et des résultats obtenus pour le Québec et faisons mention de travaux européens en cours inscrits dans la foulée de DRAG.We provide a primarily qualitative summary of the DRAG model of the Demand for Road use, Accidents and their Gravity. We show the comprehensive nature of the model in terms of structure, categories of factors taken into account and parameter estimation technique used. We note in particular how the very structure of the DRAG model makes it possible to decompose the impact of each explanatory factor on exposure risk, as well as on accident frequency and severity—thus making it possible to detect the presence of substitution among the different dimensions of driving risk. We give an idea of the application and results obtained for the Province of Quebec and mention the emergence of a European network of DRAG-inspired modeling efforts

Index calculus for abelian varieties of small dimension and the elliptic curve discrete logarithm problem

International audienceWe propose an index calculus algorithm for the discrete logarithm problem on general abelian varieties of small dimension. The main difference with the previous approaches is that we do not make use of any embedding into the Jacobian of a well-suited curve. We apply this algorithm to the Weil restriction of elliptic curves and hyperelliptic curves over small degree extension fields. In particular, our attack can solve an elliptic curve discrete logarithm problem defined over GF(q^3) in heuristic asymptotic running time O~(q^(4/3)); and an elliptic problem over GF(q^4) or a genus 2 problem over GF(q^2) in heuristic asymptotic running time O~(q^(3/2))