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Computational Management Science - High levels of correlation among financial assets and extreme losses are typical during crises. In such situations, investing in few assets might be a better... 相似文献
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Margherita Porcelli Francesco Rinaldi 《Computational Optimization and Applications》2014,59(3):565-589
The problem of finding sparse solutions to underdetermined systems of linear equations is very common in many fields as e.g. signal/image processing and statistics. A standard tool for dealing with sparse recovery is the \(\ell _1\) -regularized least-squares approach that has recently attracted the attention of many researchers. In this paper, we describe a new version of the two-block nonlinear constrained Gauss–Seidel algorithm for solving \(\ell _1\) -regularized least-squares that at each step of the iteration process fixes some variables to zero according to a simple active-set strategy. We prove the global convergence of the new algorithm and we show its efficiency reporting the results of some preliminary numerical experiments. 相似文献
95.
Margherita Brindisi Sandra Gemma Gloria Alfano Giridhar Kshirsagar Ettore Novellino Giuseppe Campiani Stefania Butini 《Tetrahedron letters》2013
We developed a novel and convenient stereoselective path for the preparation of pyrrolo-1,5-benzoxazepinones (PBOs). This innovative route envisaged the employment of (−)-menthol as convenient chiral auxiliary and a key SNAr for the stereoselective preparation of a tertiary aryl–alkyl ether. As a further advancement, we exploited this newly conceived synthetic route for the preparation of 2-substituted PBO analogues to either undergo biological evaluation themselves or give access to a variety of further functionalization options. 相似文献
96.
Dr. Simone Di Motta Dr. Tommaso Avellini Dr. Serena Silvi Prof. Margherita Venturi Dr. Xiang Ma Prof. He Tian Prof. Alberto Credi Prof. Fabrizia Negri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(9):3131-3138
The photophysical properties of a multicomponent [1]rotaxane bearing a β‐cyclodextrin ring covalently connected to an axle comprising an azobenzene photoisomerisable moiety and a naphthalimide‐type fluorescent stopper are investigated by a combined experimental and computational study. The absorption and fluorescence spectra, and particularly the induced circular dichroism (ICD) signal, are determined. The latter shows a sign relation that cannot be rationalised in terms of the simple general rules commonly employed to analyse the ICD spectra of achiral guests encircled by chiral hosts. To assist the interpretation of experimental results, DFT and time‐dependent (TD) DFT calculations are performed to explore the availability of low‐energy conformations and to model their spectroscopic response. Molecular dynamics simulations performed in water show the interconversion of a number of conformers, the contribution of which to the ICD signal is in agreement with the observation. 相似文献
97.
Alberto Credi Steven J. Langford Anna Prodi J. Fraser Stoddart Margherita Venturi 《Supramolecular chemistry》2013,25(2):303-311
Abstract The spectroscopic and electrochemical properties of two cyclophanes containing one and, respectively, two 2,7-diazapyrenium electron-acceptor units, and of their [2]catenanes with macrocycles containing two dioxybenzene or dioxynaphthalene electrondonor units have been investigated. The absorption spectra of the catenanes show weak and broad bands in the visible region, assigned to charge-transfer (CT) interactions. The very strong and structured fluorescence (298 K) and the structured fluorescence and phosphorescence (77 K) of the diazapyrenium unit are maintained in the two cyclophanes, but they are no longer present in the [2]catenanes, presumably because of a quenching process caused by the lower energy CT excited states. Each diazapyrenium unit undergoes two distinct reduction processes - only the first one of which is fully reversible - that are hardly affected at all when the diazapyrenium units are incorporated in a cyclophane. In the [2]catenanes, the CT interaction displaces the reduction processes of the diazapyrenium units toward more negative potentials. The results obtained for the diazapyrenium and previously investigated 4,4′-bipyridinium salts, selected cyclophane derivatives, and some [2]catenanes obtained by interlocking the cyclophanes with macrocycles containing two dioxyaromatic electron-donor units are compared and discussed. 相似文献
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Marianna Carbone M. Letizia Ciavatta Gianluca De Rinaldis Francesco CastelluccioErnesto Mollo Margherita Gavagnin 《Tetrahedron》2014
The re-investigation of the Mediterranean opisthobranch Thuridilla hopei resulted in the isolation and chemical characterization of three novel nor-diterpene aldehydes, nor-thuridillonals 2–4, structurally related to co-occurring already reported thuridillins. Analogous with the thuridillins, the new molecules were thought to derive from the same dietary precursor epoxylactone 1. 相似文献
100.
Fabio Mastrogiovanni Loredana Basiricò Umberto Bernabucci Margherita Campo Annalisa Romani 《Natural product research》2020,34(10):1465-1469
AbstractPomegranate peel extracts (PPE) were tested for the first time on BME-UV1, a valid cellular model to study the bovine mammary epithelial metabolism, to evaluate the effects on the oxidative stress and inflammatory status. Based on the statistical analysis of MTT data, PPE at 0.1, 1.0 and 10?μg/mL resulted not cytotoxic after 24?h, 48?h and 7 days of treatment. At the same concentrations, PPE induced a reduction of ROS production elicited by the addition of hydrogen peroxide or lipopolysaccharide evidencing an antioxidant effect confirmed also by a decrease of malondialdehyde. At 10?μg/mL, PPE reduced pro-inflammatory cytokines expressions showing an anti-inflammatory effect on BME-UV1 treated with lipopolysaccharide. Although in vivo experiments are necessary, the results of this study are promising for future applications of PPE as feed supplement for dairy cattle, in particular around calving, when the animals are more subject to oxidative stress and inflammatory diseases. 相似文献