1,087 research outputs found
The Frisch Elasticity in the Mercosur Countries: A Pseudo-Panel Approach
This paper provides estimates for the Mercosur countries of the Frisch elasticity – i.e., the elasticity of substitution between worked hours and real wages holding constant the marginal utility of wealth. We find a strong heterogeneity, with estimated elasticities ranging from 12.8 in Argentina to -13.1 in Paraguay. Brazil and Uruguay are in between, both with negative values of -1.9 and -1.4, respectively. We argue that the existence of severe liquidity constraints is the main reason behind the negative estimates found in Brazil, Paraguay and Uruguay. The heterogeneity of these estimates is the outcome of differences in many relevant economic dimensions – ranging from sectorial specialization to welfare state provisions and labor market specificities – all of them crucially affecting the socioeconomic situation of individuals. The diversity of Frisch elasticities calls for the development of a cross-country (rather than a within-country) policy approach, since they crucially affect the dynamics of the business cycle and business cycle synchronization is a step prior to the design of macro-convergence policies in the Mercosur context.Frisch elasticity, labor supply, liquidity constraints, Mercosur, life-cycle models, pseudo-panel (synthetic panel)
Estimating hyperbolicity of chaotic bidimensional maps
We apply to bidimensional chaotic maps the numerical method proposed by
Ginelli et al. to approximate the associated Oseledets splitting, i.e. the set
of linear subspaces spanned by the so called covariant Lyapunov vectors (CLV)
and corresponding to the Lyapunov spectrum. These subspaces are the analog of
linearized invariant manifolds for non-periodic points, so the angles between
them can be used to quantify the degree of hyperbolicity of generic orbits;
however, being such splitting non invariant under smooth transformations of
phase space, it is interesting to investigate the properties of transversality
when coordinates change, e.g. to study it in distinct dynamical systems. To
illustrate this issue on the Chirikov-Taylor standard map we compare the
probability densities of transversality for two different coordinate systems;
these are connected by a linear transformation that deforms splitting angles
through phase space, changing also the probability density of almost-zero
angles although complete tangencies are in fact invariant. This is completely
due to the PDF transformation law and strongly suggests that any statistical
inference from such distributions must be generally taken with care.Comment: 14 pages, 23 figures (This paper is for the IJBC Special Issue edited
by Prof. Gregoire Nicolis, Prof. Marko Robnik, Dr. Vassilis Rothos and Dr.
Haris Skokos
Correlation decay and large deviations for mixed systems
We consider low--dimensional dynamical systems with a mixed phase space and
discuss the typical appearance of slow, polynomial decay of correlations: in
particular we emphasize how this mixing rate is related to large deviations
properties.Comment: 6 pages, 2 figures, submitted to publicatio
Transition metal catalyzed cyclizations and C-H couplings of heterocyclic scaffolds
This thesis work is consecrated to the study of transition metal-catalyzed C-H activation processes for
the synthesis or the functionalization of heterocycles. First, a new example of divergent catalysis was
developed, which involves the employment of palladium tetrakis complex for the hydroamination or Pt(II)
salts for the C-H hydroarylation reaction of O-propargyloxy anilines. The resulting benzopyranes are lately
employed through a three steps efficient synthesis for the preparation of pyrano[3,2-h]quinolins.
A new efficient version of Ru(0)-catalyzed carbonylative Murai reaction for the C3-H acylation was
investigated using bidentate or aromatic imines as directing group. The coupling with vinylsilanes or
styrenes was extended to a series of pentatomic heterocycles with moderate or excellent yields and the
reaxtion mechanism was clarified by DFT calculation.
Lastly, a totally new oxidant-free version of Ru(0)-catalyzed Fujiwara-Moritani reaction was studied.
The trimeric complex of Ru3(CO)12 was employed for the C3-alkenylation with acrylates or electronpoor
olefins with moderate or excellent yields. The reaction mechanism seems to proceed, after the activation
step and the olefin insertion, through a \uf062-elimination step followed by a reductive elimination of the metal
species formed.Ce travail de th\ue8se est consacr\ue9 \ue0 l'\ue9tude des processus d'activation C-H catalys\ue9s par les m\ue9taux de transition pour la synth\ue8se ou la fonctionnalisation d'h\ue9t\ue9rocycles. Tout d'abord, un nouvel exemple de catalyse divergente a \ue9t\ue9 d\ue9velopp\ue9, qui implique l'utilisation du complexe t\ue9trakis de palladium pour l'hydroamination ou des sels de Pt(II) pour la r\ue9action d'hydroarylation C-H des O-propargyloxy anilines. Les benzopyranes r\ue9sultants sont r\ue9cemment employ\ue9s \ue0 travers une synth\ue8se efficace en trois \ue9tapes pour la pr\ue9paration de pyrano [3,2-h] quinolines.Une nouvelle version efficace de la r\ue9action carbonylative de Murai catalys\ue9e par Ru(0) pour l'acylation C3-H a \ue9t\ue9 \ue9tudi\ue9e en utilisant des imines bident\ue9es ou aromatiques comme groupe directeur. Le couplage avec des vinylsilanes ou des styr\ue8nes a \ue9t\ue9 \ue9tendu \ue0 une s\ue9rie d'h\ue9t\ue9rocycles pentatomiques avec des rendements mod\ue9r\ue9s ou excellents et le m\ue9canisme de r\ue9extion a \ue9t\ue9 clarifi\ue9 par calcul DFT.Enfin, une toute nouvelle version sans oxydant de la r\ue9action Fujiwara-Moritani catalys\ue9e par Ru(0) a \ue9t\ue9 \ue9tudi\ue9e. Le complexe trim\ue9rique de Ru3(CO)12a \ue9t\ue9 utilis\ue9 pour l'alc\ue9nylation en C3 avec des acrylates ou des ol\ue9fines pauvres en \ue9lectrons avec des rendements mod\ue9r\ue9s ou excellents. Le m\ue9canisme de r\ue9action semble se d\ue9rouler, apr\ue8s l'\ue9tape d'activation et l'insertion d'ol\ue9fine, par une \ue9tape de \uf062-\ue9limination suivie d'une \ue9limination r\ue9ductrice de l'esp\ue8ce m\ue9tallique form\ue9e
Compressive Sensing for Dynamic XRF Scanning
X-Ray Fluorescence (XRF) scanning is a widespread technique of high
importance and impact since it provides chemical composition maps crucial for
several scientific investigations. There are continuous requirements for
larger, faster and highly resolved acquisitions in order to study complex
structures. Among the scientific applications that benefit from it, some of
them, such as wide scale brain imaging, are prohibitively difficult due to time
constraints. However, typically the overall XRF imaging performance is
improving through technological progress on XRF detectors and X-ray sources.
This paper suggests an additional approach where XRF scanning is performed in a
sparse way by skipping specific points or by varying dynamically acquisition
time or other scan settings in a conditional manner. This paves the way for
Compressive Sensing in XRF scans where data are acquired in a reduced manner
allowing for challenging experiments, currently not feasible with the
traditional scanning strategies. A series of different compressive sensing
strategies for dynamic scans are presented here. A proof of principle
experiment was performed at the TwinMic beamline of Elettra synchrotron. The
outcome demonstrates the potential of Compressive Sensing for dynamic scans,
suggesting its use in challenging scientific experiments while proposing a
technical solution for beamline acquisition software.Comment: 16 pages, 7 figures, 1 tabl
Wave-Shaped Round Functions and Primitive Groups
Round functions used as building blocks for iterated block ciphers, both in
the case of Substitution-Permutation Networks and Feistel Networks, are often
obtained as the composition of different layers which provide confusion and
diffusion, and key additions. The bijectivity of any encryption function,
crucial in order to make the decryption possible, is guaranteed by the use of
invertible layers or by the Feistel structure. In this work a new family of
ciphers, called wave ciphers, is introduced. In wave ciphers, round functions
feature wave functions, which are vectorial Boolean functions obtained as the
composition of non-invertible layers, where the confusion layer enlarges the
message which returns to its original size after the diffusion layer is
applied. This is motivated by the fact that relaxing the requirement that all
the layers are invertible allows to consider more functions which are optimal
with regard to non-linearity. In particular it allows to consider injective APN
S-boxes. In order to guarantee efficient decryption we propose to use wave
functions in Feistel Networks. With regard to security, the immunity from some
group-theoretical attacks is investigated. In particular, it is shown how to
avoid that the group generated by the round functions acts imprimitively, which
represent a serious flaw for the cipher
What memory binding functions is the hippocampus responsible for?
The role of the hippocampus in binding information in working memory (WM) is little understood. When complex experiences comprise associations between different pieces of information such as objects and locations (relational binding), the function of the hippocampus is required to hold them in WM (Mitchell et al., 2000; 2006; Piekema, 2006). However, recent evidence suggests that if the to-be-associated information leads to the formation of integrated objects such as coloured shapes (conjunctive binding), the hippocampus is less involved in holding temporary representations of these complex events in WM (Baddeley et al., 2010; Piekema, 2006). We investigated the relational and conjunctive binding hypotheses of the hippocampal functions in a patient with right hippocampal damage. The patient and controls were asked to study visual arrays of stimuli which consisted of shape-colour relations (shape-colour pairs) or shape-colour conjunctions (coloured shapes). After the study array, they were presented with a new screen consisting of one set of shapes (line drawings) and one set of colours. They were asked to reconstruct the bindings by selecting the shapes and their corresponding colours. As compared to healthy controls, the patient was impaired in holding relations of shapes and colours in WM whereas he could retain the conjunctions similarly to controls. These results lend support to the role of the hippocampus in supporting memory for inter-item associations but not memory for conjunctions of features which define objects' identity
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