Semi-Classical Analysis of a Dirac Equation Without Adiabatic Decoupling

We study adiabatic decoupling for Dirac equation with some scaling which yields that the mass appears with a coefficient where is the semi-classical parameter and > 0. Therefore, the system presents an avoided crossing. The scale = 1/2 is critical: adiabatic decoupling holds for (0,1/2) while for 1/2, there is energy transfer at leading order between the two modes. We describe this transfer in terms of two-scale Wigner measures by means of Landau-Zener formula which takes into account the change of polarization of the measures after the crossing.     

Structural and magnetic properties of carboxylato-bridged manganese(II) complexes involving tetradentate ligands: discrete complex and 1D polymers. Dependence of J on the nature of the carboxylato bridge

The crystal structure of an inorganic linear polymer consisting of Mn(II) and an N-centered tripodal ligand N,N-bis(2-(6-methyl)pyridylmethyl)glycinate is presented (1, C(16)H(20)N(3)O(3)F(6)P(1)Mn(1), a = 9.993(2) A, b = 13.285(3) A, c = 16.040(3) A, orthorhombic, Pnam, Z = 4). The polymeric structure is ensured by carboxylato ligands connecting two Mn(II) in a rather rare syn-anti geometry. The magnetic properties of this infinite chain have been investigated, together with the magnetic properties of a dimeric Mn(II) compound (3) from a closely related ligand [N,N-bis[(1-methylimidazol-2-yl)-methyl)glycinate] involving an unusual bis(monatomic-carboxylato) bridge. The inorganic polymer 1 shows a pseudo-2D magnetic structure, with a major interaction pathway along the chain (J/k = -0.172 +/- 0.005 K) and an interchain minor one (zJ'/k = -0.006 +/- 0.004 K). These properties are reminiscent of those from a closely related previously reported inorganic Mn(II) polymer (2 obtained from manganese(II) and N,N-(2-pyridylmethyl)((1-methylimidazol-2-yl)methyl)glycinate). The dimer 3 shows a small antiferromagnetic coupling of J/k = -0.693 +/- 0.016 K. To address the influence of the carboxylato bridging mode on the magnetic properties, these complexes are compared to a series of compounds involving carboxylato bridges of several geometries between Mn(II) ions. Carboxylato bridges induce usually antiferromagnetic coupling, with the magnitude of the interaction (/J/) increasing with the number of bridges. The J value is dependent on the bridging mode. The syn-syn bridge is an efficient pathway, even by comparison with the monatomic [(mu-eta(1)-carboxylato)] bridge.     

Synthesis, characterization and dioxygen reactivity of copper(I) complexes with glycoligands

A new family of copper(I) complexes with "glycoligands" containing a central saccharide scaffold, with 2-picolyl ether groups or 2-picolylamine or N-imidazolylamine groups, has been prepared and characterized. For this purpose, the following tetradentate ligands have been synthesized: methyl 2,3-di-O-(2-picolyl)-alpha-D-lyxofuranoside (L1), 1,5-anhydro-2-deoxy-3,4-di-O-(2-picolyl)-d-galactitol (L2), 5-(amino-N-(2-salicyl))-5-deoxy-1,2-O-isopropylidene-3-O-(2-picolyl)-alpha-D-xylofuranose (L3), and 5-(amino-N-(2-salicyl))-5-deoxy-1,2-O-isopropylidene-3-O-(methylimidazol-2-yl)-alpha-D-xylofuranose (L4). The ligands and the complexes were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopies, ESI mass spectrometry, and cyclic voltammetry. Collaterally with the experimental work, HF-DFT(B3LYP/6-31G*) computations were performed to obtain additional structural information. The Cu(I) complexes are found to be pentacoordinated. The redox properties and the O2-reactivity of the Cu(I)Ln complexes have been studied. Reactions of Cu(I) complexes with dioxygen in ethanol yield stable Cu(II) complexes as confirmed by UV-visible spectrophotometry and EPR spectroscopy.     

Synthesis of a novel amphiphilic GdPCTA-[12] derivative as a potential micellar MRI contrast agent

A novel amphiphilic contrast agent, a GdPCTA-[12] derivative containing a dodecyl chain as lipophilic moiety, has been prepared. A convergent synthetic route from commercially available diethylene triamine and 3-hydroxypyridine is described. The target amphiphilic gadolinium complex was obtained in nine steps in 22% overall yield. Physicochemical properties and relaxivity measurements of this new contrast agent are described.     

Refined inequalities on graded Lie groups

We construct a Littlewood–Paley decomposition associated to a Rockland operator on graded Lie groups, which allows us to deduce refined Gagliardo–Nirenberg, Sobolev and Hardy inequalities.     

Nonlinear Coherent States and Ehrenfest Time for Schrödinger Equation

We consider the propagation of wave packets for the nonlinear Schrödinger equation, in the semi-classical limit. We establish the existence of a critical size for the initial data, in terms of the Planck constant: if the initial data are too small, the nonlinearity is negligible up to the Ehrenfest time. If the initial data have the critical size, then at leading order the wave function propagates like a coherent state whose envelope is given by a nonlinear equation, up to a time of the same order as the Ehrenfest time. We also prove a nonlinear superposition principle for these nonlinear wave packets.     

Liquid–liquid extraction of actinides,lanthanides, and fission products by use of ionic liquids: from discovery to understanding

Liquid–liquid extraction of actinides and lanthanides by use of ionic liquids is reviewed, considering, first, phenomenological aspects, then looking more deeply at the various mechanisms. Future trends in this developing field are presented.     

Divergent Synthesis of Molecular Winch Prototypes

We report the synthesis of conceptually new prototypes of molecular winches with the ultimate aim to investigate the work performed by a single ruthenium-based molecular motor anchored on a surface by probing its ability to pull a load upon electrically-driven directional rotation. According to a technomimetic design, the motor was embedded in a winch structure, with a long flexible polyethylene glycol chain terminated by an azide hook to connect a variety of molecular loads. The structure of the motor was first derivatized by means of two sequential cross-coupling reactions involving a penta(4-halogenophenyl)cyclopentadienyl hydrotris(indazolyl)borate ruthenium(II) precursor and the resulting benzylamine derivative was next exploited as key intermediate in the divergent synthesis of a family of nanowinch prototypes. A one-pot method involving sequential peptide coupling and Cu-catalyzed azide-alkyne cycloaddition was developed to yield four loaded nanowinches, with load fragments encompassing triptycene, fullerene and porphyrin moieties.     

Phytochemical Characterization of Chamomile (Matricaria recutita L.) Roots and Evaluation of Their Antioxidant and Antibacterial Potential

Matricaria recutita L., German chamomile, is one of the most widely used medicinal plants, whose efficacy has been proven in numerous studies. However, its roots have attracted only little interest so far, since mainly above-ground plant parts are used for medicinal purposes. To broaden the knowledge of chamomile roots, a profound phytochemical characterization was performed along with a bioactivity screening of corresponding root extracts. While volatile constituents such as chamomillol and polyynes were detected using GC-MS, HPLC-MSⁿ analyses revealed the occurrence of four coumarin glycosides, more than ten phenolic acid esters and five glyceroglycolipids. Furthermore, the antioxidant activity of the extracts was evaluated. Polar extracts revealed IC₅₀ values ranging from 13 to 57 µg/mL in the DPPH radical scavenging assay, which is in the same range as reported for chamomile flower extracts. In addition, superoxide radical scavenging potential and mild antibacterial effects against S. aureus und B. subtilis were demonstrated. Moreover, to assess interspecies variation in chamomile roots, extracts of M. recutita were compared to those of M. discoidea DC. Interestingly, the latter revealed stronger antioxidant activity. The presented results aim at the valorization of chamomile roots, previously discarded as by-product of chamomile flower production, as a sustainable source of bioactive phytochemicals.     

Von den vielen Verfahren zum Nachweis von kleinsten Mengen Formaldehyd

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