Kinetics and mechanisms of substitution of the axial and equatorial ligands in an iron(II) macrocyclic heme model complex

The complex [Fe(imox) (Nmim)₂], where imox is a planar bis(iminooxime) macrocyclic ligand and Nmim=N-methyl imidazole, undergoes substitution reactions in the presence of 2,2′bipyridine (bipy), leading to a series of intermediate mixed complexes. The forward and reverse rate constants for the substitution of the Nmim ligand by water are k₁ = 0.23 s^?1 and k_?1=62 M^?1s^?1, respectively. The binding of a bipy to the [Fe(imox) (Nmim) (H₂O)]⁺ complex proceeds according to k₂ = 4.7×10^?2 M^?1 s^?1 and k_?2 = 3.6 × 10^?4 s^?1, yielding [Fe(imox) (bipy) (Nmim)]⁺, which eliminates Nmim according to k₃ = 1.6 × 10^?4 s^?1. Further substitution in the [Fe(imox) (bipy)]⁺ complex with bipy takes place very slowly leading to the [Fe(imox) (bipy)₂]⁺ and [Fe(bipy)₃]²⁺ complexes. © 1993 John Wiley & Sons, Inc.     

A Variational Theory for Light Rays in Stably Causal Lorentzian Manifolds: Regularity and Multiplicity Results

This paper is dedicated to the study of light rays joining an event p with a timelike curve γ in a light–convex subset &\Lambda; of a stably causal Lorentzian manifold . We set up a functional framework, defined intrinsically, consisting of a family of manifolds and a positive functional Q defined on them. The critical points of Q on approach, as , the lightlike, future pointing geodesics joining p and γ. We prove some regularity results, including the C ¹–regularity of , the C ²–regularity of Q on and the C ²–regularity of its critical points. Using them, we develop a Ljusternik–Schnirelman theory for light rays, obtaining some multiplicity results, depending on the topology of the space of all lightlike curves joining p and γ. Received: 9 April 1996 / Accepted: 27 December 1996     

On a class of stochastic differential equations used in quantum optics

Stochastic differential equations for processes with values in Hilbert spaces are now largely used in the quantum theory of open systems. In this work we present a class of such equations and discuss their main properties; moreover, we explain how they are derived from purely quantum mechanical models, where the dynamics is represented by a unitary evolution in a Hilbert space, and how they are related to the theory of continual measurements. An essential tool is an isomorphism between the bosonic Fock space and the Wiener space, which allows to connect certain quantum objects with probabilistic ones.     

Global existence for a class of generalized systems for irreversible phase changes

A nonlinear evolution system is investigated. It can describe a wide class of phase transition phenomena, including irreversible phase changes. The nonlinearities are of various kind and two maximal monotone graphs appear in the phase relaxation equation. An existence result is established for the related Cauchy-Neumann problem by using regularization, truncation, and monotonicity techniques.     

On the number of solutions of some ordinary periodic boundary value problems by their geometrical properties

Summary We describe the geometrical properties of some ordinary nonlinear differential equations, and we obtain multiplicity results of solutions by the study of the behaviour of our operator near certain singular points.Work supported by M.P.I. and G.N.A.F.A.     

Material stability restrictions on the response function in finite elasticity

This paper is concerned with the problem of findinga priori constitutive inequalities in finite elasticity. It is required here that the response function of a general elastic material be such as to render a strong localization of Hadamard's inequality valid in every infinitesimal deformation superimposed on every finite deformation of a certain class. The consequences of this assumption are illustrated by means of some examples.     

Chromatographic quantitation using fractions of the peak areas

Quantitative chromatographic analysis is liable to errors due to peak asymmetry because the uncertainty in the detected position of the end of the peak tail decreases the reliability of the computed peak area. This dependence may be a severe drawback whenever peaks of different areas must be compared, as in the case of calibration curves. A new approach to overcome the uncertainties of area calculation due to peak asymmetry is reported in this paper. The approach consists of calculating only the area included between the start and the maximum of the chromatographic peak. Simulated and experimental chromatographic data were used in this study. Both the peak start-to-peak maximum area (SMA) and the start-to-end or total area (TA) were calculated and the quantitative results were compared. Within the scope of this work it is concluded that the SMA yields calibration curves that are more linear and have intercepts closer to zero than the calibration curves obtained using the TA.     

Synthesis of new 3,5-diarylisoxazolidines by cycloaddition of oxaziridines and alkenes

This article reports a novel process of cycloaddition of C-aryloxaziridines with a variety of alkenes to afford stable, five-membered heterocycles 13–24. The steric hindrance of the tert-butyl group on the nitrogen atom of the oxaziridine is responsible for the high stereoselectivity of the cycloaddition reaction.