Random Classical Fidelity

We introduce a random perturbed version of the classical fidelity and we show that it converges with the same rate of decay of correlations, but not uniformly in the noise. This makes the classical fidelity unstable in the zero-noise limit.     

Liquid chromatography-tandem mass spectrometry for the identification of impurities in d-allethrin samples

A previous GC/MS study highlighting the impurity profile of the synthetic pesticide d-allethrin is extended here to validate and confirm the impurities identity through the development of soft ionisation HPLC-MS methods. To accomplish this, we developed a reverse phase LC-MS analysis in gradient elution with two distinct soft ionisation techniques, the atmospheric pressure ionisation with electrospray source (API-ESI) and the chemical ionisation (APCI). A single quadrupole and an ion trap, which allowed the simultaneous determination of the molecular masses and structural information of the impurities by acquisition of collisionally induced (CID) product ions spectrum and in-source fragmentation, were employed as analysers. Single quadrupole and ion trap analysers resulted perfectly matching in the d-allethrin impurity fragmentation patterns. All the main impurities over 0.1% identified by GC/MS were confirmed. Results indicate that the proposed HPLC/MS method was found appropriate to confirm the presence of impurities such as chrysolactone, chloro allethrin derivatives, allethrolone and chrysanthemic acid, excluding their formation under GC/MS strong ionisation condition.     

Detection of a stable nitroxide during chemical depolymerization of heparin

The use of low-molecular-weight heparins (LMWHs) has become common, since compared to unfractionated heparin (UFH), they have a much longer plasma half-life and lower incidence of side effects. LMWHs are derived from the depolymerization of UFH, obtained either chemically, physically or enzymatically. We employed electron spin resonance (ESR) spectroscopy to study the depolymerization of UFH by copper in the presence of hydrogen peroxide. A stable nitroxide radical was detected. This could be generated by the hydroxyl radical attack either to the N-SO⁻₃ group or to free amino groups present in the UFH preparation.     

Active Sites of Dermatan Sulfate for Heparin Cofactor II. Isolation of a Nonasaccharide Fragment Containing Four Disaccharide Sequences [α-l-Iduronic Acid 2-O-Sulfate (1,3)-β-d-N-Acetylgalactosamine 4-Sulfate]

Abstract

The active site of dermatan sulfate (DS) for heparin cofactor II (HCII) was isolated in a fragment obtained by periodate oxidation, borohydride reduction, mild acid hydrolysis, and SE- and SAX-chromatography of beef mucosal and pig skin DS preparations. Characterization by mass spectrometry, one- and two-dimensional NMR spectroscopy, and HPLC analysis of disaccharides, obtained by exhaustive digestion with chondroitinase-ABC, indicates that the fragment has the prevalent structure 1, GalNAc-4SO₃-[IdoA-2SO₃-GalNAc-4SO₃]₄-R, where R is CH(CH₂OH)CH(COO^?)-OH. 1, is the largest DS fragment thus far isolated containing IdoA2SO₃ as the only uronic acid. Its lower activity (30%) with respect to the parent polymeric DS is explainable by Tollefsen model, requiring longer polyanionic chains for formation of ternary complex with thrombin.     

Reversibility in Infinite Hamiltonian Systems with Conservative Noise

The set of stationary measures of an infinite Hamiltonian system with noise is investigated. The model consists of particles moving in with bounded velocities and subject to a noise that does not violate the classical laws of conservation, see [OVY]. Following [LO] we assume that the noise has also a finite radius of interaction, and prove that translation invariant stationary states of finite specific entropy are reversible with respect to the stochastic component of the evolution. Therefore the results of [LO] imply that such invariant measures are superpositions of Gibbs states. Received: 26 September 1996 / Accepted: 3 January 1997     

Exponential Decay of Correlations for Piecewise Cone Hyperbolic Contact Flows

We prove exponential decay of correlations for a realistic model of piecewise hyperbolic flows preserving a contact form, in dimension three. This is the first time exponential decay of correlations is proved for continuous-time dynamics with singularities on a manifold. Our proof combines the second author’s version (Liverani in Ann Math 159:1275–1312, 2004) of Dolgopyat’s estimates for contact flows and the first author’s work with Gouëzel (J Mod Dyn 4:91–137, 2010) on piecewise hyperbolic discrete-time dynamics.     

Ergodic Properties of a Model Related to Disordered Quantum Anharmonic Crystals

 We introduce a model suggested by disordered anharmonic quantum crystals. We then investigate in detail the ergodic properties exhibited by such a model. Received: 14 January 2002 / Accepted: 14 October 2002 Published online: 10 February 2003 Communicated by J. L. Lebowitz     

Ergodic Properties for a Quantum Nonlinear Dynamics

We present a quantum system composed of infinitely many particles, subject to a nonquadratic Hamiltonian, for which it is possible to investigate the long time behavior of the dynamics and its ergodic properties. We do so both for the KMS states and for a large class of locally normal invariant states, whose very existence is already of some interest.