Can we consider the policy instruments as cyclical substitutes? Some Empirical Evidence

The main objective of this article is to study how central banks and fiscal authorities interact when they conduct the economic policy. Specially, it seems very helpful to specify if this two policymakers act under complementary or substitutability strategy. Our methodology is based on a simple model of policy-mix that is estimated by panel data method. Our main results show that for seven OECD countries and during the period 1975-1997, the two policy instruments seem to be complementary. Moreover, even if the central banks become more and more independent during this period, the estimates underline that the reaction functions of central banks depend on output and the governments have continued to care about inflation rate.monetary policy, fiscal policy, policy coordination, public debt

Machine Assisted Analysis of Vowel Length Contrasts in Wolof

Growing digital archives and improving algorithms for automatic analysis of text and speech create new research opportunities for fundamental research in phonetics. Such empirical approaches allow statistical evaluation of a much larger set of hypothesis about phonetic variation and its conditioning factors (among them geographical / dialectal variants). This paper illustrates this vision and proposes to challenge automatic methods for the analysis of a not easily observable phenomenon: vowel length contrast. We focus on Wolof, an under-resourced language from Sub-Saharan Africa. In particular, we propose multiple features to make a fine evaluation of the degree of length contrast under different factors such as: read vs semi spontaneous speech ; standard vs dialectal Wolof. Our measures made fully automatically on more than 20k vowel tokens show that our proposed features can highlight different degrees of contrast for each vowel considered. We notably show that contrast is weaker in semi-spontaneous speech and in a non standard semi-spontaneous dialect.Comment: Accepted to Interspeech 201

Testing convex hypotheses on the mean of a Gaussian vector. Application to testing qualitative hypotheses on a regression function

In this paper we propose a general methodology, based on multiple testing, for testing that the mean of a Gaussian vector in R^n belongs to a convex set. We show that the test achieves its nominal level, and characterize a class of vectors over which the tests achieve a prescribed power. In the functional regression model this general methodology is applied to test some qualitative hypotheses on the regression function. For example, we test that the regression function is positive, increasing, convex, or more generally, satisfies a differential inequality. Uniform separation rates over classes of smooth functions are established and a comparison with other results in the literature is provided. A simulation study evaluates some of the procedures for testing monotonicity.Comment: Published at http://dx.doi.org/10.1214/009053604000000896 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Mobilisation de connaissances antérieures lors de la préparation d'une leçon de mathématiques par des jeunes professeurs stagiaires

International audienceDans ce texte nous avons choisi d'analyser comment des professeurs débutants préparent leurs séances de classe, ce qui constitue pour nous une tâche dans laquelle ils doivent mobiliser diverses connaissances ou savoir faire qu'ils ont pu acquérir dans divers lieux et à certains moments. Nous avons analysé ce corpus en utilisant la théorie de l'activité et l'approche anthropologique du didactique afin de comparer les types d'analyses qu'ils induisent et les résultats et interprétations auxquels ils conduisent. Ainsi, nous souhaitons apporter des éléments de réflexion théorique sur la question de la mobilisation de diverses connaissances, en repartant des courants qui traitent classiquement du transfert de connaissances, puis en élargissant à deux autres approches qui apportent des points de vue différents dans une perspective d'étude du transfert en situation non expérimentale

Ruminal bacterial community change in response to diet-induced variation of ruminal trans-10 fatty acids

Trans fatty acids (FA) are produced during the biohydrogenation of linoleic acid in the rumen. Because of their health‐promoting properties, trans‐11 isomers, which are usually the most abundant biohydrogenation intermediates, are most desirable (1). However, in high yielding dairy cows, when high concentrate diets containing fat are fed to cows, a shift from trans‐11 to trans‐10 FA can occur, therefore, trans‐10 isomers can become the predominant biohydrogenation intermediates, inducing milk fat depression in dairy cows(2) and having possible detrimental effects on human health(3). The aim of this work was to study the bacterial community dynamics in response to diet‐induced trans‐10 FA shift

Double walled carbon nanotube/polymer composites via in-situ nitroxide mediated polymerisation of amphiphilic block copolymers

Because of their unique physical, chemical, and structural properties, carbon nanotubes (CNT) are playing an increasingly important role in the development of new engineering materials [1]. Across many different applications, CNT/polymer composites have been extensively studied [2] S.B. Sinnot and R. Andrews, Carbon nanotubes: synthesis, properties, and applications, Crit Rev Solid State Mater Sci 26 (2001), pp. 145–249.[2]. The key problem for CNT/polymer composite elaboration is the dispersion, compatibilization, and stabilization of the CNT in the polymer matrix. To solve this problem, a structure with di-block copolymers, one with a good affinity to CNT (monomer M1), the other being the matrix (monomer M2), is proposed in this study, as shown on the two steps mechanism of Fig. 1

Temperature and duration of heating of sunflower oil affect ruminal biohydrogenation of linoleic acid in vitro

Sunflower oil heated at 110 or 150°C for 1, 3, or 6 h was incubated with ruminal content in order to investigate the effects of temperature and duration of heating of oil on the ruminal biohydrogenation of linoleic acid in vitro. When increased, these 2 parameters acted together to decrease the disappearance of linoleic acid in the media by inhibiting the isomerization of linoleic acid, which led to a decrease in conjugated linoleic acids and trans-C18:1 production. Nevertheless, trans-10 isomer production increased with heating temperature, suggesting an activation of Δ9-isomerization, whereas trans-11 isomer production decreased, traducing an inhibition of Δ12-isomerization. The amount of peroxides generated during heating was correlated with the proportions of biohydrogenation intermediates so that they might explain, at least in part, the observed effects. The effects of heating temperature and duration on ruminal bacteria community was assessed using capillary electrophoresis single-strand conformation polymorphism. Ruminal bacterial population significantly differed according to heating temperature, but was not affected by heating duration. Heating of fat affected ruminal biohydrogenation, at least in part because of oxidative products generated during heating, by altering enzymatic reactions and bacterial population

Random changes in the heifer rumen in bacterial community structure,physico-chemical and fermentation parameters, and in vitro fiber degradation

The variability over time of several main ruminal characteristics was studied in heifers over 15 consecutive weeks. Three heifers were assigned to a low-fiber diet (27% NDF) and three to a high-fiber diet (44% NDF). The physico-chemical (pH and redox potential) and fermentation(volatile fatty acids and ammonia contents) parameters were determined on 1 day per week for 15 consecutive weeks. On the same days the bacterial community structure was studied using a molecular fingerprint technique and the ruminal fiber degradation was studied by in vitro incubation of a withdrawn ruminal content sample. Numerous random changes were observed from week to week for all physico-chemical and fermentative parameters and in vitro fiber degradation. The redox potential was the only parameter to show a significant interaction between diet and week. Except for the ammonia content, the amplitudes of fluctuations observed were higher for the low-fiber diet. The bacterial community structure did not differ between diets or weeks. The in vitro fiber degradation was similar for both diets, with numerous random changes throughout the study. The findings of this study indicated that most of the parameters of the ruminal ecosystem had time-related changes with random fluctuations around a mean value which reflect an unstable equilibrium. This conclusion was valid for both low- and high-fiber diets

Speed perturbation and vowel duration modeling for ASR in Hausa and Wolof languages

International audienceAutomatic Speech Recognition (ASR) for (under-resourced) Sub-Saharan African languages faces several challenges: small amount of transcribed speech, written language normalization issues, few text resources available for language modeling, as well as specific features (tones, morphology, etc.) that need to be taken into account seriously to optimize ASR performance. This paper tries to address some of the above challenges through the development of ASR systems for two Sub-Saharan African languages: Hausa and Wolof. First, we investigate data augmentation technique (through speed perturbation) to overcome the lack of resources. Secondly, the main contribution is our attempt to model vowel length contrast existing in both languages. For reproducible experiments, the ASR systems developed for Hausa and Wolof are made available to the research community on github. To our knowledge, the Wolof ASR system presented in this paper is the first large vocabulary continuous speech recognition system ever developed for this language

New effective neighborhoods for the permutation flow shop problem

We propose an extension of the Taillard's implementation, which allows to remove efficiently the less well inserted jobs in a permutation. We describe then six new neighborhoods for the permutation flow shop problem. Computational results show clearly that at least three of them are better than the insertion move. Their application into a simple metaheuristic is very effective, since a new upper bound has been found for a hard Taillard's instance