31 research outputs found
Multiscale Network Analysis for Financial Contagion
No full textContagion in financial markets has been one the most active areas of research, especially during the last decade and due to the major incidents during the Global Financial Crisis and the European Financial Crisis. However, two of the most important questions that remain after a financial crisis are what are the determinants of the crisis and how can we forecast an incident based on suitable indicators. The purpose of this study is twofold. First, to develop a measure of contagion based on the multiscale nature of the financial contagion. Second, to examine how financial contagion is spread in the US economy in different frequencies based on the proposed measure. We assert that important information on an upcoming crisis, not observed in the original data, may be revealed by performing a time-frequency analysis of the time-series and the cross-section of stock returns. We use wavelet analysis to decompose the returns and network analysis to compute various network characteristics related to contagion. Our proposed methodology allow us to: understand the short-, mid- and long-term connections of the network, bring out structures/relations that are not visible initially and mask the true connections between companies, study how the networks measures change over scale, and finally, examine the distribution of contagion at different time-horizons and scales
Carbon Carbon Bond Formation Via Enantioselective Multicatalysis: Book chapter in Comprehensive Chirality, 2nd edition 2023
No full textInternational audienceSince the last two decades, the development of multicatalytic transformations has seen a tremendous growth. The combination of two or more catalysts enables to take the best from different worlds to activate molecules in an orthogonal and complementary manner. These multicatalytic combinations offer unique opportunities for the discovery of new synthetic pathways notably in the enantioselective formation of carbon–carbon bonds, which are illustrated in this chapter. Based on different multicatalytic types such as synergistic activation or relay cascades, combination between two metal complexes, two organocatalysts, or finally metal- and organo-catalysis, provides a broad array of transformations of great synthetic utility. In these methods, the control of the stereochemistry on the new products by one or more catalysts, usually provides excellent levels of stereocontrol, making of multicatalysis an approach of choice for the creation of complex chiral scaffolds
Merging Iridium-Catalyzed Stereoselective Coupling from Alcohols with Organocatalytic Functionalization at the Aldehyde Oxidation Level
No full textInternational audienceWe report the selective merging between a Krische-type iridium-catalyzed CC coupling and an organocatalyzed oxa-Michael addition. Such a general strategy triggers the direct double functionalization of alcohols through a complex multicatalytic pathway merging the two catalytic cycles in one. The iridium catalyst dehydrogenates the alcohol to an aldehyde which is intercepted in an organocatalyzed functionalization. Meanwhile, the generated iridium hydride activates a pro-nucleophile to subsequently create the final chiral alcohol through a stereoselective CC coupling on the functionalized aldehyde. The disclosed multicatalytic reaction, fulfilling all the principles of redox economy, enables the stereoselective preparation of complex tetrahydropyrans, scaffolds present in numerous natural products and featuring up to three controlled stereogenic centers
Enantioselective Borrowing Hydrogen: A Modern Tool to Construct Enantioenriched Molecules
No full textInternational audienceIn the quest for the more rapid and eco‐compatible preparation of complex molecules from widely available ones, borrowing hydrogen is one of the most elegant manners to directly functionalize alcohols. Such catalytic cycles reduce the synthetic cost, and avoid waste and additional steps associated with adjusting the redox state for the functionalization of carbon chains. In this field, the last ten years have seen the development of general strategies to control the absolute stereochemistry of the created molecules. This enantiocontrol can arise from the three distinct steps of the catalytic cycle, namely the initial dehydrogenation, carbonyl functionalization or final hydrogen back‐transfer. This review presents the different enantioselective approaches developed according to these principles and highlights the great potential of these transformations, the current limitations and future challenges
Multicatalyse : combiner le meilleur de deux mondes pour une synthèse plus efficace
No full textNational audienceMulticatalysis, taking the best from two worlds Over the past fifteen years, the increasing application of multicatalyzed reactions has led to the discovery of more efficient transformations for the synthesis of complex molecules. These reactions can be based on a variety of principles, combining the best of different worlds, such as metal catalysis and organocatalysis.Depuis une quinzaine d'années, l'application croissante de réactions multicatalysées a permis la découverte de transformations plus efficaces pour la synthèse de molécules complexes. Ces réactions peuvent être basées sur différents principes, combinant notamment le meilleur de différents mondes tels que la catalyse métallique et l'organocatalyse
Merging Iridium-Catalyzed Stereoselective Coupling from Alcohols with Organocatalytic Functionalization at the Aldehyde Oxidation Level
No full textWe
report the selective merging between a Krische-type iridium-catalyzed
C–C coupling and an organocatalyzed oxa-Michael addition. Such
a general strategy triggers the direct double functionalization of
alcohols through a complex multicatalytic pathway, merging the two
catalytic cycles in one. The iridium catalyst dehydrogenates the alcohol
to an aldehyde, which is intercepted in an organocatalyzed functionalization.
Meanwhile, the generated iridium hydride activates a pro-nucleophile
to subsequently create the final chiral alcohol through stereoselective
C–C coupling on the functionalized aldehyde. The disclosed
multicatalytic reaction, fulfilling all of the principles of redox
economy, enables the stereoselective preparation of complex tetrahydropyrans,
scaffolds present in numerous natural products and featuring up to
three controlled stereogenic centers
Predicting the amount of air traffic demand regulations using machine learning
No full textDemand for air transportation is expected to continue growing. Within Europe one of the biggest impacts of this traffic growth, is an increase of air travel delay. As it happened during the summer of 2018, where demand from aircraft intending to enter an air sector was not complemented with capacity to safely accommodate it. Incentivised by this event, in this article the problem of predicting a class of measures for demand-capacity balancing, known as Air Traffic Flow and Capacity Management (ATFCM) regulations, is investigated. A Random Forest model was trained on public ATFCM notification messages to predict the amount of ATFCM regulations over different European air sectors for varying prediction horizons. In addition to the predictive model, in this paper a new way to estimate the maximum prediction horizon is proposed. Using the Hurst exponent, the time-scale at which random behaviour is initiated is found. Comparison of the proposed method with the prediction horizon obtained from the largest Lyapunov exponent indicates that the method is a valid technique for estimating the prediction horizon. By extending the prediction horizon of the model, it is found that the proposed method can reasonably estimate the prediction horizon above which prediction accuracy starts to degrade. Aerospace Engineerin
Palladium core superparamagnetic iron oxide nanoparticles for imaged – guided thermotherapy: comparison between synthesized and commercial nanoparticles
No full textHeat in thermal therapy can be produced by exposing superparamagnetic iron oxide nanoparticles (SPIONs) to alternating magnetic fields in order to treat cancer. In addition, Magnetic Resonance Imaging (MRI) uses SPIONs as T2 contrasts agents for diagnostic purposes. This attribute gives SPIONs potential to be used as theranostic agents in MRI – guided thermotherapy in order to visualize the concentration of the particles within the tumour and monitor the effect of the treatment. The performance of SPIONs as heating and contrast agents is highly dependent on their physical and magnetic properties. In this study, six different samples of palladium core superparamagnetic iron oxide nanoparticles (Pd – SPIONs), a formulation that has not been found in literature until today, synthesized at the Reactor Institute Delft were provided. The goal of this MSc Thesis was to determine the structural and magnetic particle parameters of Pd - SPIONs that were related with optimal heating and contrast enhancing performance in thermotherapy and MRI, respectively. For this purpose, all samples were fully characterized and their performances as heating and MRI contrast agents were investigated and compared along with commercial nanoparticles. In addition, MRI phantom and CT studies were performed using the commercial nanoparticles in order to determine whether quantification of different concentrations was possible.Biomedical Engineerin
Using a systematic mapping review to examine equine-assisted activities and therapies for people with mental health through an occupational therapy lens
No full text2017 Spring.Includes bibliographical references.Equine-assisted activities and therapies (EAAT) are one type of complementary and/or alternative treatment for persons with mental illness. Various approaches have been used to improve individual's self-esteem, self-efficacy, and overall health (Bizub, Joy, & Davidson, 2003; Burgon, 2003; Klontz, Bivens, Leinart, & Klontz, 2007). However, literature on the psychosocial benefits of EAAT is fragmented and often lacks rigor (Anestis, Anestis, Zawilinski, Hopkins, & Lilienfeld, 2014; Bachi, 2012). Moreover, occupational therapy is underrepresented in the literature despite its roots in mental health. Therefore, this study uses a systematic mapping review to ascertain theories, interventions, and outcomes within literature on EAAT specific to individuals with mental health concerns. Findings from the study were examined through the perspective of a conceptual framework specific to occupational therapy, the Model of Human Occupation, which consists of three subsystems: volition, habituation, and performance capacity. Specifically, this conceptual framework was used to identify how occupational therapy may address occupational performance deficits with horses and the equine environment. Current theories, interventions, and outcomes within the literature suggest horses and the equine environment may be used to improve aspects of volition, such as self-efficacy and self-esteem, habituation, and performance capacity. Occupational therapy using horses and the equine environment may be particularly well-suited for adolescents who have eating disorder or who have experienced abuse considering the high frequency at which this population is studied. In conclusion, there is great potential for occupational therapy to develop unique interventions that focus on occupational performance deficits using the equine environment
