Voltammetric probe of milk samples by using a platinum microelectrode

Milk is a complex heterogeneous fluid containing many components in several states of dispersion. When used as a bulk solvent for studying electrochemical processes of some of the electroactive species present, it displayed mainly aqueous solution properties. With microelectrodes (25 μm in diameter) some typical constituents can be detected and the reproducibility of the processes studied was found to be satisfactory, with relative standard deviations (r.s.d.s.) lower than 2%, whereas measurements with conventional-sized platinum electrode (3 mm in diameter) gave r.s.d.s, of about 10%. Moreover, because of enhanced mass transport associated with the smallest electrodes, it was possible to diagnose the formation of precipitates of calcium phosphates on the electrode surface, as a consequence of a CEC electrode process at ?0.920 V vs. SCE, involving protons released by H₂PO^?₄, HPO^2?₄ formed in the electrode reaction and Ca²⁺. The reduction of acidic groups from casein, the oxidation of ascorbate and oxygen effects were also studied.     

On the ab initio calculation of a pairing gap in atomic nuclei

The role of an effective mass in the ab initio BCS equation for a pairing gap in atomic nuclei has been analyzed.     

Partially carboxymethylated cotton dust waste for sorption of textile wastewater coloured with the cationic dye Basic Blue 41 as a model: synthesis,regeneration and biodegradability

The removal of residual dyes in coloured textile wastewaters is mandatory, and a significant portion of the dyes used are cationic. Textile factories mainly process cotton yarns, and 8 % of this virgin feedstock is lost as cotton dust waste (CDW). Using factorial experimental design, this dust was derivatised with monochloroacetic acid (MCAA) to produce a partially carboxymethylated cellulose (CM^?-CDW) with NaOH, MCAA and isopropanol for the retention of Basic Blue 41 dye (BB 41) (column and batch), and biodegradability was investigated. The dye retention efficiency was examined with additional experiments varying the initial concentration, contact time and addition of salts. Heteronuclear multiple bonding correlation-nuclear magnetic resonance confirmed the covalent insertion of CM^? groups in the cellulosic fibres. The selected matrix provided a dye sorption of 58.33 (column) and 64.50 mg/g (batch). The Langmuir isotherm was a good fit to the sorption data. The efficiency of uptake of BB 41 was predominantly dictated by the concentration of alkali in the matrix synthesis. Biodegradability by cellulases was similar when using uncharged and dye-charged matrices. The latter were fully regenerated by washing in dilute acid. Retention was proportional to the initial dye concentration and the contact time required to reach equilibrium, which was longer for higher dye concentrations. The addition of 10 mmol/l NaCl decreased BB 41 retention by 50 %. Therefore, CM^?-CDW proved effective for the removal of the cationic dye BB 41 and thus represents an important alternative in the treatment of coloured textile effluents.     

Phase diagram of strongly correlated Fermi systems

Phase transitions caused by the redistribution of quasiparticle occupation numbers n(p) in homogeneous Fermi systems with particle repulsion are analyzed. The phase diagram of a strongly correlated Fermi system, when drawn in the coordinates “density ρ-dimensionless coupling constant η,” resembles a Washington pie for a rather broad class of interactions. Its upper part is “filled” with Fermi condensate, and the bottom part is filled with normal Fermi liquid. Both parts are separated by a narrow interlayer of Lifshitz phase with a multiply connected Fermi surface.     

Excited states of linear polyenes in the SCF–RPA method

In the framework of the PPP Hamiltonian, we have studied the low-lying spectra of all trans linear polyenes with the dielectirc function method. It is shown that higher order processes, not included in the RPA scheme as local field correction (LFC) and self-energy (SE) effects can be introduced in a effective way by a suitable parametrization of the residual coulomb interaction. This parametrization is fixed along the polyene series both for singlet and triplet states, at variance with previous RPA calculations. Comparison with the most refined CI calculations, as well as with the experimental findings shows very good agreement. Furthermore, chain length and geometry dependence of the electron–electron correlation is briefly discussed.     

Pyrolysis/gas chromatography/mass spectrometry in the analysis of glycated poly-L-lysine

Pyrolysis/gas chromatography/mass specfrometry was applied to the study of products arising from the interaction between glucose and poly-L -lysine. The comparison of pyrograms of control poly-L -lysine and glycated poly-L -lysine led to the identification of six different compounds, four of which were furan derivatives that can be considered as markers for advanced glycation processes.     

The role of superfluidity in the structure of the neutron star inner crust

A self-consistent quantum approach to describe the inner crust structure of neutron stars is developed, within the Wigner–Seitz approximation. It is based on the generalized energy functional method involving explicitly neutron and proton pairing correlations. The energy functional is constructed by matching the realistic phenomenological functional by Fayans et al. for describing the nuclear-type cluster in the center of the Wigner–Seitz cell with the one calculated microscopically for neutron matter. It is shown that the neutron and proton superfluidity influences significantly the ground state structure of the inner crust.     

The local potential approximation for the Brueckner G-matrix and a simple model of the scalar-isoscalar Landau-Migdal amplitude

The Brueckner G-matrix for a slab of nuclear matter is analyzed in the singlet ^1S and triplet ³ S + ³ D channels. The complete Hilbert space is split into two domains, the model subspace S₀, in which the two-particle propagator is calculated explicitly, and the complementary one, S', in which the local potential approximation is used. This kind of local approximation was previously found to be quite accurate for the ^1S pairing problem. A set of model spaces S ₀(E ₀) with different values of the energy E₀ is considered, E₀ being the upper limit for the single-particle energies of the states belonging to S₀. The independence of the G-matrix on E₀ is assumed as a criterion for the validity of the local potential approximation. It turns out that such an independence holds within few percents for E ₀ = 10-20 MeV, for both channels under consideration. The G-matrix within the local potential approximation is used for justifying a simple microscopic model for the coordinate-dependent scalar-isoscalar component f (r) of the Landau-Migdal amplitude in terms of the free T-matrix. Received: 2 November 2001 / Accepted: 4 January 2002     

A new solution to the Anderson-Newns Hamiltonian of chemisorption

A new solution to the Anderson-Newns Hamiltonian of chemisorption is proposed by using the Green-function formalism and an adequate approximation to the adatom self-energy. The method has been checked in simple models. Our results give both the quasi-particle spectrum and the chemisorption energy with a high accuracy better than 99.9%.