Renormalization-Group Transformations Under Strong Mixing Conditions: Gibbsianness and Convergence of Renormalized Interactions

In this paper we study a renormalization-group map: the block averaging transformation applied to Gibbs measures relative to a class of finite-range lattice gases, when suitable strong mixing conditions are satisfied. Using a block decimation procedure, cluster expansion, and detailed comparison between statistical ensembles, we are able to prove Gibbsianness and convergence to a trivial (i.e., Gaussian and product) fixed point. Our results apply to the 2D standard Ising model at any temperature above the critical one and arbitrary magnetic field.     

Leaching potential of carbamates and their metabolites and comparison with triazines

This paper reports the results of a laboratory study aimed at defining the leaching potential of the following pesticides and respective metabolites belonging to the families of N-methylcarbamates and triazines: benfuracarb (BF), carbofuran (CF), 3-keto-carbofuran (3KC) and 3-hydroxy-carbofuran (3HC), atrazine (ATR), simazine (SIM), terbuthylazine (TER), deethylatrazine (DEA), deisopropylatrazine (DIA) and desethylterbuthylazine (DET).All tested compounds, but BF, are very mobile in soil. Triazines exhibited a relatively high persistence, especially DEA, with a DT₅₀ of 72 days. On the contrary, all the tested carbamates resulted easily degradable in soil with a partial exception represented by CF, with a DT₅₀ of 12 days.The GUS indices show high leaching potentials for all the tested triazines and CF. The GUS index of 3KC lies in the typical area of transient compounds; those of BF and 3HC clearly exhibited a non-leaching behaviour.In the leachate corresponding to the BF column, the parent compound was found at low concentration while its main metabolite, CF, reached much higher values. Also, when applied as parent compound, CF was determined at high values, whereas its metabolites 3KC and 3HC were never detected in the leachates. As to triazines, in the ATR column, the parent compound was found at high levels in the leachate, where DEA exhibited values more than 4 times higher than DIA. In the SIM column DIA reached levels 8-fold higher than those in the ATR column. TER occurred at levels close to that of ATR in the respective leachate; DET was found at high levels whereas DIA was not detectable.     

Hafnia sol-gel films synthesized from HfCl4: Changes of structure and properties with the firing temperature

Thin sol-gel hafnia films have been synthesised from HfCl₄, the synthesis has revealed to be a simple route to fabrication of hafnia films with high transparency in the UV-visible range. The films have been fired at different temperatures in air up to 1000°C and have been characterized by X-ray diffraction and Fourier transform infrared spectroscopy. Infrared absorption spectra of hafnia films have allowed to follow the formation of monoclinic crystalline phases together with XRD. Formation of monoclinic hafnia crystallites has been observed upon calcination at temperatures higher than 600°C, as shown by infrared spectroscopy and XRD. The optical transmission and the refractive index as a function of the temperature of firing have been characterized by UV-Visible spectroscopy and spectroscopic ellipsometry. The hafnia films, after firing at 600°C, had a refractive index of 1.92 with a thickness of around 70 nm.     

Zinc-induced switching of the nonlinear optical properties of a functionalized bis(styryl)benzene

A large variation of the nonlinear transmission properties of a cyclen-based bis(styryl)benzene can be induced by a small change of the linear absorption spectrum upon Zn2+ binding. This result has been interpreted in the frame of a sequential two-photon process in which one photon is absorbed from the ground state and one photon is absorbed from an excited state.     

A paramagnetic MRI-CEST agent responsive to lactate concentration

A paramagnetic Yb(III) complex bearing six exchangeable amide protons, [Yb(MBDO3AM)](3+), has been investigated with the aim of developing a MRI-CEST (chemical exchange saturation transfer) contrast agent responsive to the concentration of L-lactate. The complex binds the substrate quantitatively to yield [Yb(MBDO3AM)L-lactate](2+). The exchange between the free and the L-lactate-bound complex is slow on the NMR time scale, and the resonances of their corresponding amide protons are sufficiently separated (more than 10 ppm) to allow their selective irradiation. Therefore, the CEST properties of the two forms can be independently assessed. In turn, the resulting saturation transfer to the bulk water signal is dependent on the L-lactate concentration.     

Enantioselective recognition between chiral alpha-hydroxy-carboxylates and macrocyclic heptadentate lanthanide(III) chelates

Three novel heptacoordinated Ln(III) complexes (Ln = Gd and Yb) have been synthesized and investigated by (1)H NMR spectroscopy. These complexes contain two stereogenic centers, one associated with a deltadeltadeltadelta or lambdalambdalambdalambda conformation of the ethylenediamine moieties in the tetraazamacrocycle and the latter arises from the orientation (Delta or Lambda) of the coordinating arms. Evidence has been gained for the occurrence of a fast exchange between all the possible conformers. Upon addition of several (S)-alpha-hydroxy-carboxylate substrates, the formation of stable ternary adducts has been obtained. Their (1)H NMR spectra are consistent with the presence of two diastereoisomers differing in the conformation adopted by the macrocyclic ligand wrapping the lanthanide(III) ion. The interaction leading to the formation of the ternary complexes is enantioselective depending on the hydrophilicity of the alpha-hydroxy-carboxylate.     

Water proton spin-lattice relaxation behaviour in heterogeneous biological systems

The water proton spin-lattice relaxation rate has been measured for a condensed 50% deuterated erythrocyte water system. Nuclear relaxation data, obtained in non-selective and selective modes, indicate that cross relaxation between erythrocyte and water protons occurs. The observed selective relaxation enhancement is interpreted in terms of intermolecular nuclear interactions modulated by motions which satisfy the ω_oT_c > 1 condition. Selective relaxation rates are here proposed to be more sensitive to interface characteristics than the non-selective ones.     

On the rate of convergence to the normal law for solutions of the Burgers equation with singular initial data

We study the scaling limit of random fields which are the solutions of a nonlinear partial differential equation known as the Burgers equation, under stochastic initial condition. These are assumed to be a Gaussian process with long-range dependence. We present some results on the rate of convergence to the normal law.     

Composition of stochastic processes governed by higher-order parabolic and hyperbolic equations

We consider compositions of stochastic processes that are governed by higherorder partial differential equations. The processes studied include compositions of Brownian motions, stable-like processes with Brownian time, Brownian motion whose time is an integrated telegraph process, and an iterated integrated telegraph process. The governing higher-order equations that are obtained are shown to be either of the usual parabolic type or, as in the last example, of hyperbolic type.