Are turbulent spheres suitable initial conditions for star-forming clouds?

To date, most numerical simulations of molecular clouds, and star formation within them, assume a uniform density sphere or box with an imposed turbulent velocity field. In this work, we select molecular clouds from galactic scale simulations as initial conditions, increase their resolution, and re-simulate them using the smoothed particle hydrodynamics code GADGET2. Our approach provides clouds with morphologies, internal structures and kinematics that constitute more consistent and realistic initial conditions for simulations of star formation. We perform comparisons between molecular clouds derived from a galactic simulation, and spheres of turbulent gas of similar dimensions, mass and velocity dispersion. We focus on properties of the clouds such as their density, velocity structure and star formation rate. We find that the inherited velocity structure of the galactic clouds has a significant impact on the star formation rate and evolution of the cloud. Our results indicate that, although we can follow the time evolution of star formation in any simulated cloud, capturing the entire history is difficult as we ignore any star formation that might have occurred before initialization. Overall, the turbulent spheres do not match the complexity of the galactic clouds

Thienylpyrrole azo dyes: synthesis, solvatochromic and electrochemical properties

The synthesis and the evaluation of solvatochromic and electrochemical properties of new donor-acceptor-substituted thienylpyrrole azo dyes 3 are described. These derivatives exhibit dramatic changes in both their electronic and redox properties in comparison with thienylpyrroles 1. In agreement with the solvatochromic and electrochemical studies of push-pull derivatives 3 the new compounds prepared, may find application in the manufacture of new materials with notable non-linear optical properties.Fundação para a Ciència e Tecnologia - POCTI/QUI/37816/2001

Synthesis of formyl-thienylpyrroles : versatile building blocks for NLO materials

Several formyl-substituted 1-alkyl(aryl)-2-(2´-thienyl)pyrroles 3-7 were synthesized by functionalization of the pyrrole or thiophene ring of thienylpyrroles 2 using different methods: Vilsmeier formylation or metalation followed by reaction with DMF.Fundação para a Ciência e Tecnologi

Donor-acceptor substituted thienylpyrrole azo dyes: synthesis, solvatochromic and electrochemical properties

The synthesis of thienyl- substituted pyrrole azo dyes and their UV-visible, solvatochromic and electrochemical properties are described. In agreement with the solvatochromic data and also with the electrochemical study the new donor-acceptor systems synthesized could have applications in NLO.Fundação para a Ciência e Tecnologia (FCT

Synthesis and UV-visible properties of thienyl- substituted pyrrole azo dyes

The synthesis of thienyl- substituted pyrrole azo dyes and their UV-visible properties are described.Fundação para a Ciência e Tecnologia. FEDER - POCTI/QUI/37816/2001.Thanks are due to Foundation for Science and Technology (Portugal) for financial support through IBQF (UM) and through FEDER, POCTI (ref. POCTI/QUI/37816/2001)

Unnatural benz-X-azolyl asparagine derivatives as novel fluorescent amino acids : synthesis and photophysical characterization

A family of new asparagine derivatives bearing benzothiazole and benzimidazole units, functionalised with electron donor or acceptor groups, were synthesized in good to excellent yields. The photophysical characterization of these new heterocyclic amino acids was performed by UV-visible absorption and fluorescence emission studies and revealed that the compounds displayed remarkably high fluorescence quantum yields and Stokes’ shifts, making them good candidates for application as fluorescent probes by incorporation into peptidic frameworks.Fundação para a Ciência e a Tecnologia (FCT

Litter Decomposition of Xaraes-Grass Pasture Subjected to Different Post-Grazing Residuals

Since fertilizers are used less extensively on Xaraes-grass (Brachiaria brizantha) pastures in Brazil because of costs, the main route of nitrogen (N) supply to plants is through nutrient recycling via litter decomposition. One of the strategies used to maintain the supply of N is to manage the pasture correctly by keeping it under grazing pressure so that the amount of recycled nutrients in the residue is sufficient to meet the pasture requirements (Jantalia et al.2006). Thus, the aim of this study was to evaluate different residual leaf area indices (RLAI) and determine which one provides the best restoration of pasture leaf area index and nutrient cycling

5´-alkoxy-2,2´-bithiophene azo dyes: a novel promising series of NLO chromophores

A series of bithienyl azo dyes has been prepared from their corresponding coupling components, 5-alkoxy-2,2´-bithiophenes. The solvatochromic behavior of the compounds was investigated. The hyperpolarizabilities β of derivatives 3-5 were measured using hyper-Rayleigh scattering and thermogravimetric analysis (TGA) was used to evaluate their thermal stability. The experimental results indicate that, good nonlinearity-thermal stability is well balanced for azo-bithiophene NLO-chromophores 3-5 making them good candidates for NLO applications.Fundação para a Ciência e Tecnologia

New fluorescent heterocyclic materials: Synthesis, solvatochromic and fluorescence properties

Thienyl- and bithienyl-1,3-benzothiazoles 1 and 2 were synthesised by reacting various formyl thienyl and bithienyl derivatives with o-aminobenzenethiol in moderate to excellent yields. Evaluation of the solvatochromic and fluorescence properties of these compounds was carried out. Due to their strong fluorescence and also the strong push-pull character, benzothiazole derivatives 1 and 2 can be used as potential NLO materials or as fluorescent markers.Fundação para a Ciência e Tecnologia (FCT

Synthesis and characterization of the thermal and the solvatochromic properties of heterocyclic azo dyes derived from 5-N,N-dialkylamino-2,2´-bithiophene couplers

A series of heterocyclic azo dyes was synthesized by diazotation of several substituted anilines and coupling with 5-N,N-dialkylamino-2,2´-bithiophenes to give 4-phenylazo-5-N,N-dialkylamino-2,2´-bithiophenes 4-7. This reaction contrasts with the behavior of 5-alkoxy-2,2´-bithiophenes towards aryldiazonium salts which gave 5-phenylazo-5-alkoxy-2,2´-bithiophenes. The thermal stability of the derivatives was evaluated using thermogravimetric analysis. The solvatochromic behaviour of the novel bithiophene azo dyes was investigated in several solvents of different polarity. The experimental results indicate that, the heterocyclic azo dyes 4-7 could be used as thermally stable solvatochromic probes.Fundação para a Ciência e a Tecnologia (FCT