General Behaviour of Bianchi VI0 Solutions with an Exponential-Potential Scalar Field

The solutions to the Einstein-Klein-Gordon equations without a cosmological constant are investigated for an exponential potential in a Bianchi VI₀ metric. There exists a two-parameter family of solutions which have a power-law inflationary behaviour when the exponent of the potential, k, satisfies k² < 2. In addition, there exists a two-parameter family of singular solutions for all k² values. A simple anisotropic exact solution is found to be stable when 2 < k².     

Simultaneous determination of iron and ruthenium by preconcentration on sulfopropyl sephadex cation exchanger

A new method for the simultaneous determination of iron and ruthenium at ultra-trace levels is proposed. The method is based on the formation of the iron and ruthenium complexes with 2,4,6-tri-(2-pyridil)-1,3,5-triazine (TPTZ) in the presence of hydroxylamine hydrochloride and buffer CH₂ClCOOH/CH₂ClCOONa (pH=3.0). The formation of the complexes and their retention on a cationic resin SP-Sephadex C25 were integrated in one step at 90 °C, with stirring for 90 min. Under these conditions a high preconcentration level was achieved for both analytes. The complexes retained on the solid phase were evaluated by second derivative spectrophotometry. The selected analytical wavelengths were 539.7 and 553.3 nm for the determination of ruthenium and iron, respectively, by using the zero crossing approach. The detection and quantification limits were 0.54 ng ml⁻¹ and 1.79 ng ml⁻¹ for ruthenium and 0.41 ng ml⁻¹ and 1.38 ng ml⁻¹ for iron. The proposed method was applied to the determination of both analytes in synthetic mixtures.     

A thermodynamic study of two anionic amphiphilic penicillins in aqueous solution by ultrasound speed measurements

The critical concentrations of sodium cloxacillin and sodium dicloxacillin penicillins in aqueous solution were determined over the temperature range 288.15–313.15 K by a method based on deconvolution into Gaussians of the second derivative of the measured ultrasound velocity. The mass action model was used to calculate the thermodynamic standard quantities: free Gibbs energy, enthalpy and entropy of aggregate formation. The results are discussed in terms of the structure of the drug aggregates.     

Thermodynamic study on supramolecular complex formation of theophylline derivates with a synthetic receptor

Thermodynamic parameters for the supramolecular complex formation of macrobicyclophane with several theophylline dimers are reported. Solvation of guests plays an important role in the supramolecular complex formation. A good correlation between ΔG and guest solubility is obtained in different CHCl₃/CH₂Cl₂ proportions.     

Experimental Investigation of Transmission Properties and All-Optical Label Swapping of Orthogonal IM/FSK Labeled Signals

Optically labeled IM/FSK signal saretran smitte dover 50km of SMF under different compensation schemes.All-opticallabel swapping based on MZ-SOA and EAM is presented. Transmission followed by label swapping shows a 2dB overall power penalty.     

Connected components in the space of composition operators on<Emphasis Type="Italic">H∞</Emphasis> functions of many variables

LetE be a complex Banach space with open unit ballB _e. The structure of the space of composition operators on the Banach algebra H∞, of bounded analytic functions onB _e with the uniform topology, is studied. We prove that the composition operators arising from mappings whose range lies strictly insideB _e form a path connected component. WhenE is a Hilbert space or aC _o(X)- space, the path connected components are shown to be the open balls of radius 2. The research of this author was supported by grant number SAB1999-0214 from the Ministerio de Educación, Cultura y Deporte during his stay at the Universidad de Valencia. The research of this author was partially supported DGES(Spain) pr. 96-0758. The research of this author was partially supported by Magnus Ehrnrooths stiftelse.     

Hybrid Sol-Gel Coatings Produced from TEOS and γ-MPS

Hybrids sols from tetraetoxysilane (TEOS) and 3-(methacryloxypropyl) trimethoxysilane (-MPS) were prepared in acid medium for different TEOS/-MPS ratios and were modified by the addition of a colloidal silica suspension. The stability of the different sols was evaluated by viscosity measurements; the sols showed a Newtonian behaviour and the ageing effect was negligible even after two months from their preparation. Coatings were obtained by dipping at different withdrawal rates and heat-treated between 150 and 250°C. Transparent coatings with thickness higher than 4 m were reached for most of the studied compositions. The surface microhardness of coatings for each composition and thermal treatment was evaluated by the pencil hardness test. The thermal stability was followed by simultaneous thermogravimetric and differential thermal analysis (TGA-DTA) determining the limit temperatures at which the coatings can be treated without losingits hybrid character. A structural analysis was made by deconvolution of Fourier transformed infrared spectra (FTIR) of self-supported films observing the influence of the organic groups on the silica network.     

PREPARATION OF Ru/Al2O3 CATALYSTS FROM RuCl3

Increasing reduction time increases ruthenium reduction, but even after 6 h, ruthenium is not completely reduced and chlorine is not completely eliminated in Ru/Al₂O₃ prepared from RuCl₃.     

A simple synthesis of γ-aminoacids

The addition of dianions of carboxylic acids to bromoacetonitrile, leads, in good yields, to the corresponding γ-cyanoacids that give γ-aminoacids on hydrogenation. This two-step methodology improves the results previously described.