One-Pot Conversion of Alkenes into Oxazolines and Oxazolidin-2-Ones Promoted by Diphenyl Diselenide

Abstract: Abstract. Oxazolines or oxazolidin-2-ones are produced from the reaction of diphenyl diselenide, ammonium persulfate and trifluoromethanesulfonic acid with alkenes in the presence of MeCN/H₂O, NH₂CN/H₂O or NH₂CO₂Et.     

Synthesis of dimeric phenylethanoids isolated from olive oil mill wastewaters

Two dimeric phenylethanoids isolated from olive oil mill wastewaters have been synthesized from cathecol, tyrosol and 3,4-dihydroxyphenylacetic acid.     

Iridoid glucosides from Viburnum chinshanense

The phytochemical study of the aerial parts of Viburnum chinshanense Graebn., a species growing in Western and Central China, led to the isolation of six iridoid glucosides: the novel 10,2'-diacetylpatrinoside, 1, and the known 2'-acetyldihydropenstemide, 2'-trans- p-coumaroyl-dihydropenstemide, 2'-acetylpatrinoside, decapetaloside, and patrinoside. In addition, amentoflavone and rosarin were also isolated.     

A minimax theorem in the presence of unbounded Palais-Smale sequences

In a reflexive Banach space we consider a family of functionals that may admit unbounded Palais-Smale sequences. Under some structural conditions we provide a suitable Deformation Lemma that is obtained by modifying the classical pseudo-gradient flow. This leads to a variant of the minimax principle in the Lusternik-Schnirelman Theory.     

Terahertz spectroscopy applied to the analysis of artists’ materials

Terahertz (THz) spectroscopy and imaging have been actively studied in these decades. THz waves (0.1–10 THz) are non-invasive, can penetrate opaque materials, and can be used to obtain fingerprint spectra whose characteristics depend upon molecular and intermolecular behavior. Unlike the mid-infrared region, no commercial spectral library is available for the THz region. Consequently, a spectral database of artists’ materials was developed in order to include THz spectroscopy among conservation science techniques. Most pigments and some synthetic polymers have characteristic fingerprint spectra in the THz region. With this technique most of these materials used in paintings can be identified alone or as paint, a combination of pigments and binders. Although the meaning of the spectral features has so far not been fully explained, previous studies on optical materials suggest that phonon absorption and the behavior of hydrogen bonds contribute to their spectral features. Examples of THz spectra of various art materials are discussed on the basis of measurements obtained using a conventional Fourier transform system.     

Cluster formation in opinion dynamics: a qualitative analysis

In this paper we formulate a discrete version of the bounded confidence model (Deffuant et al. in Adv Complex Syst 3:87–98, 2000; Weisbuch et al. in Complexity 7:55–63, 2002), which is representable as a family of ordinary differential equation systems. Then, we analytically study these systems. We establish the existence of equilibria which correspond to opinion profiles displaying a finite number of isolated clusters. We prove the asymptotic stability of some of these equilibria and show that they represent the asymptotic trend of the solutions of the systems under consideration. For a particular case, we also characterize the initial profiles that lead to different cluster configurations.     

Investigation of anomalous very fast decay regimes in homogeneous isotropic turbulence

The emergence of anomalous fast decay regimes in homogeneous isotropic turbulence (HIT) decay is investigated via both theoretical analysis and eddy-damped quasi-normal Markovian simulations. The work provides new insight about a fundamental issue playing a role in HIT decay, namely the influence of non-standard shapes of the energy spectrum, in particular in the large energetic scale region. A detailed analysis of the kinetic energy spectrum E(k) and the non-linear energy transfer T(k) shows that anomalous decay regimes are associated with the relaxation of initial energy spectra which exhibit a bump at energetic scales. This feature induces an increase in the energy cascade rate, toward solutions with a smooth shape at the spectrum peak. Present results match observations reported in wind-tunnel experiments dealing with turbulence decay in the wake of grids and bluff bodies, including scaling laws for the dissipation parameter C_?. They also indicate that the ratio between the initial eddy turnover time and the advection time determines of how fast anomalous regimes relax toward classical turbulence free-decay. This parameter should be used for consistent data comparison and it opens perspectives for the control of multiscale effects in industrial applications.