Properties of quantum Markovian master equations

In this paper we give an essentially self-contained account of some general structural properties of the dynamics of quantum open Markovian systems. We review some recent results regarding the problem of the classification of quantum Markovian master equations and the limiting conditions under which the dynamical evolution of a quantum open system obeys an exact semigroup law (weak coupling limit and singular coupling limit). We discuss a general form of quantum detailed balance and its relation to thermal relaxation and to microreversibility.     

Linear kinematical groups

We prove a theorem which states that in an (n+1)-dimensional space-time (n3) the only linear kinematical groups which are compatible with the isotropy of space are the Lorentz and Galilei groups. The special casesn=1 andn=2 are also briefly discussed.On leave of absence from Instituto di Fisica dell' Universitá, Milano, Italy. A. v. Humboldt fellow.     

Extreme affine transformations

We classify the extreme points of the compact convex set of affine maps of IR ⁿ which map into itself the closed unit ball. This work is a preliminary step towards solving the problem of finding the extreme points of the compact convex set of affine maps of theN×N density matrices (dynamical maps of anN-level system) and forn=3 furnishes the solution of the problem in the simplest case of a two-level system.The bulk of this work was performed while the first author was visiting the Center for Particle Theory of the University of Texas at Austin under the partial support of the U.S.A.E.C. under contract ORO-(40-1) 3992. A travel grant under the Fulbright-Hays program is acknowledged.     

113Cd NMR and fluorescence studies of multiple binding mechanisms of Cd(II) by the Suwannee River fulvic acid

The binding of Cd (II) by the fulvic acid from a Suwannee River (FA) was investigated at various pH values and reactants ratios by 113Cd NMR and fluorescence spectroscopy. The NMR results provided evidences that the FA-Cd interactions occur through a variety of binding modes and mechanisms. Different kinds of organically bound Cd-species were detected in the 1.8-10.8 pH range depending on the FA/Cd ratios. Labile complexes (amenable to Cd-aminoacidic and Cd-hydroxy interactions or outer-sphere complexes) were observed at low pH and FA/Cd levels while stronger interactions (of carboxylate-type or inner-sphere complexation) took place as the pH and/or the FA concentration were increased. At pH ca. 6 insoluble FA-Cd adducts were primarily produced but, at relatively large FA concentration, only soluble complexes, stable in the whole pH 1.8-10.8 range, were formed. A complementary analysis, by fluorescence spectroscopy, provided clear evidences of FA-Cd association/aggregation phenomena. While no noticeable effects occurred with soluble samples, the formation of insoluble adducts led to significant enhancements of the emission fluorescence spectra. Although other explanations could not be excluded, this result was accounted for by modifications of the optical properties of the ligand itself due to sedimentation of the heavier components. Fluorescence enhancement was also observed on samples before the effective precipitation and interpreted as spectroscopic evidence of the onset of aggregation phenomena.     

Measurements of the fine structure of laser intensity correlations near threshold

The correlation function of the intensity fluctuations of a single mode laser in the threshold region has been measured with a fast digital correlator. The various exponential components have been separated for the first time, by exploiting the nonlinear characteristics of the correlator. The results are in quantitative agreement with the theoretical predictions.     

Quantum chemical study of the geometries and stabilities of the two valence-tautomers of C2H2F+

Non-empirical SCF-MO molecular wavefunctions were computed for the two limiting structures of C₂H₂F⁺ with full geometry optimization using double-zeta quality atomic orbital basis sets. The bridged structure (fluorenium ion) was found to be an energy maximum (transition state) about 31 kcal/mole higher than the open structure (fluoro-vinyl cation). The latter, contrary to the unsubstituted vinyl cation, is slightly (4.5 °) bent away from fluorine at the electron deficient centre.     

Markov dilations and quantum detailed balance

We construct quantum stochastic processes whose multi-time correlation functions, with suitable time ordering, can be obtained from a quantum dynamical semigroup. We prove that such a process defines a stationary Markov dilation of the associated semigroup if and only if (up to technicalities) the semigroup satisfies the quantum detailed balance condition with respect to its stationary state.     

Investigating the interactions of hyaluronan derivatives with biomolecules. The use of diffusional NMR techniques

[Chemical structure: see text] The interactions between a biomaterial and biomolecules present in body fluids often determine the fate of the biomaterial. This paper presents a study on hyaluronan (HA)-containing materials (in soluble or colloidal form) that focuses on their interactions with lipids and proteins and for the first time uses PFG NMR as an analytical technique for probing these events. The interactions of HA-based polymers with phospholipids (DPPC and DPPG liposomes) are shown to depend both on charge and hydrophobicity factors. Despite the difference in behavior between albumin (substantially non-adhesive) and fibrinogen (adhesive), the interactions of the polymers with proteins do not seem to be based on hydrophobic effects but on surface polar interactions.     

Influence of the substituent on selective photocatalytic oxidation of aromatic compounds in aqueous TiO2 suspensions

Experimental results are reported showing that the photocatalytic oxidation of aromatic compounds containing an electron-donor group (EDG) gives rise mainly to ortho- and para-monohydroxy derivatives while in the presence of an electron-withdrawing group (EWG) all the monohydroxy derivatives are obtained.     

Quantum private queries

We propose a cheat sensitive quantum protocol to perform a private search on a classical database which is efficient in terms of communication complexity. It allows a user to retrieve an item from the database provider without revealing which item he or she retrieved: if the provider tries to obtain information on the query, the person querying the database can find it out. The protocol ensures also perfect data privacy of the database: the information that the user can retrieve in a single query is bounded and does not depend on the size of the database. With respect to the known (quantum and classical) strategies for private information retrieval, our protocol displays an exponential reduction in communication complexity and in running-time computational complexity.