Generalized Contact Bundles

In this Note, we propose a line bundle approach to odd-dimensional analogues of generalized complex structures. This new approach has three main advantages: (1) it encompasses all existing ones; (2) it elucidates the geometric meaning of the integrability condition for generalized contact structures; (3) in light of new results on multiplicative forms and Spencer operators, it allows a simple interpretation of the defining equations of a generalized contact structure in terms of Lie algebroids and Lie groupoids.Comment: Short Note: 8 pages. Minor revisions. Published in C. R. Math. Comments welcome

The Dynamic Properties of Alternative Assumptions on Price Adjustment in New Keynesian Models

This paper presents a classification of the different new Phillips curves existing in the literature as a set of choices based on three assumptions: the choice of the structure of price adjustments (Calvo or Taylor), the presence of backward indexation, and the type of price contracts (fixed prices or predetermined prices). The paper suggests study of the dynamic properties of each specification, following different monetary shocks on the growth rate of the money stock. We develop the analytical form of the price dynamics, and we display graphics for the responses of prices, output, and inflation. We show that the choice made for each of the three assumptions has a strong influence on the dynamic properties. Notably, the choice of the price structure, while often considered as unimportant, is indeed the most influential choice concerning the dynamic responses of output and inflation.New Keynesian Phillips Curves, Taylor Price Rule, Calvo Price Rule, Fixed Prices, Predetermined Prices, Disinflation policy.

Booms petroliers et basculements du rapport de force

Chaque boom et chaque crise des prix pétroliers marquent le basculement du rapport de force au profit de l’un des acteurs de l’économie pétrolière (pays producteurs, pays consommateurs et multinationales pétrolières). Le principal enjeu de ces basculements réside dans la prise ou la perte de contrôle du marché pétrolier par les acteurs. Chacun d’eux ne cherche qu’à instaurer la politique de prix satisfaisant les objectifs inhérents aux stratégies économiques nationales, aux relations internationales ou même s’accaparer de la part la plus importante du surplus pétrolier.Mots-clefsBoom pétrolier, crise pétrolière, rapport de force, prix dub pétrole.Code Jel : Q33, Q41, Q4

Locally-adapted convolution-based super-resolution of irregularly-sampled ocean remote sensing data

Super-resolution is a classical problem in image processing, with numerous applications to remote sensing image enhancement. Here, we address the super-resolution of irregularly-sampled remote sensing images. Using an optimal interpolation as the low-resolution reconstruction, we explore locally-adapted multimodal convolutional models and investigate different dictionary-based decompositions, namely based on principal component analysis (PCA), sparse priors and non-negativity constraints. We consider an application to the reconstruction of sea surface height (SSH) fields from two information sources, along-track altimeter data and sea surface temperature (SST) data. The reported experiments demonstrate the relevance of the proposed model, especially locally-adapted parametrizations with non-negativity constraints, to outperform optimally-interpolated reconstructions.Comment: 4 pages, 3 figure

PtCl₂-Catalyzed Rearrangement of Methylenecyclopropanes

Alkylidenecyclopropanes readily convert into cyclobutene derivatives on treatment with catalytic amounts of PtCl2. The reaction is strongly accelerated when performed under an atmosphere of CO (1 atm). The resulting cyclobutenes are isolated in good to excellent yields for substrates bearing aliphatic as well as aromatic substituents R on their olefinic site. If the substituent R, however, is a very electron-rich arene, the cyclobutenes initially formed react further to give dimeric products with a previously unknown 1,2,2a,7a-tetrahydrospiro[cyclobuta[a]indene-7,1‘-cyclobutane skeleton. A mechanism accounting for these experimental observations as well as for a deuterium-labeling experiment is proposed which implies reactive intermediates at the nonclassical cation/carbene interface. Furthermore it is shown that the PtCl2-catalyzed cyclobutene formation can be geared with subsequent ring-opening/ring-closing metathesis (ROM/RCM) events. Finally, a convenient “one pot” method for the preparation of the alkylidenecyclopropane substrates used in this study is presented, which is based on a modified Julia−Kocienski olefination of aldehydes with readily available 1-tert-butyl-1H-tetrazol-5-yl-cyclopropyl sulfone under Barbier conditions

A Rhodium-Catalyzed C−H Activation/Cycloisomerization Tandem

A reaction cascade comprising a rhodium-catalyzed C−H activation, a subsequent hydrometalation of an alkylidene cyclopropane in vicinity, regioselective C−C bond activation of the flanking cyclopropane ring, followed by reductive elimination of the resulting metallacycle, opens a new entry into functionalized cycloheptene derivatives. This crossover of C−H activation and higher order cycloaddition has been performed in two different formats, either using alkylidenecyclopropanes with a lateral vinylpyridine moiety or with a pending aldehyde group as the trigger. The reaction tolerates various functional groups, leaves chiral centers α to the reacting sites unaffected, and proceeds with excellent stereoselectivity. Labeling experiments support the proposed mechanism explaining the observed net cycloisomerization process