High quantum yield photoluminescence of new polyamides containing oligo‐PPV amino derivatives and related oligomers

The synthesis and the chemical physical characterization of new photoluminescent (PL) chromophores and polymers are reported. Chromophores (oligo‐PPV symmetric derivatives ending with amino groups) are strong blue emitters with a PL quantum yield of ～70% in dioxane solution. They have been used to prepare polyamides by reaction with aliphatic acyl dichlorides in which emitting and non emitting units are alternated. PL properties of the synthesized polyamides have been evaluated in solution and reveal a strong blue emission (PL quantum yield ～60%), To increase the solubility of these systems, oligomers have been purposely prepared and then characterized. They show a peculiar white emission when excited in DMF solution; to get insight into this interesting behavior, asymmetric monoacetylated chromophores have been prepared as model compounds for the chromophoric end groups of the polyamide chains. The emission spectra of these compounds reveal a broad excimeric yellow emission which is responsible, along with the blue emission of the inner chromophoric units, of the overall white emission of the oligomers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2677–2689, 2009     

On the Finiteness of Light Rays Between a Source and an Observer on Conformally Stationary Space-Times

We use a convexity condition to prove the finiteness of the number of light rays joining a pointlike source with a pointlike observer in a stationary relativistic spacetime. The result is extended to the case of conformally stationary metrics under suitable boundedness assumptions on the conformal factor. We discuss our hypotheses in some explicit examples of standard static and stationary Lorentzian manifolds.     

Rearrangement of 3,5-dicyano-1,4-dihydropyridines to densely functionalized cyclopentadienes

3,5-Dicyano-1,4-dihydropyridines underwent ring contraction to give functionalized cyclopentadienes upon treatment with trifluoroacetic anhydride.     

On Some Classical Methods to Improve Algebraic Curves and Surfaces

First, a modern presentation of the theory of the Halphen transform is given. This method associates to a plane projective curve C, once a general conic has been chosen, another birationally equivalent plane curve, whose singularities are simpler than those of C. Repeating, a curve is obtained whose only singularities are nodes. Next, it is studied how to apply this process to a family of plane curves. With this technique it is possible to transform a given family (with irreducible general member) into one where, generically, the curves are nodal. Finally, it is studied a similar process, called the Halphen–Picard transformation, for surfaces in three-space. By suitably reiterating this procedure, a surface can be transformed into a birationally equivalent one (in the same projective space), such that the sections with planes in a general pencil are, generically, nodal curves.     

Thermal decomposition of trifluoromethoxycarbonyl peroxy nitrate,CF3OC(O)O2NO2

The thermal decomposition of trifluoromethoxycarbonyl peroxy nitrate, CF₃OC(O)O₂NO₂, has been studied between 278 and 306 K at 270 mbar total pressure using He as a diluent gas. The pressure dependence of the reaction was also studied at 292 K between 1.2 and 270 mbar total pressure. The rate constant reaches its high‐pressure limit at 70 mbar. The first step of the decomposition leads to CF₃OC(O)O₂ and NO₂ formation, that is, CF₃OC(O)O₂NO₂ + M ? CF₃OC(O)O₂ + NO₂ + M (k₁, k_?1). Reaction (?1) was prevented by adding an excess of NO that reacts with the peroxy radical intermediate and leads to carbonyl fluoride (CF₂O), carbon dioxide (CO₂), nitrogen dioxide (NO₂), and small quantities of CF₃OC(O)O₂C(O)OCF₃. The kinetics of reaction (1) was determined by following the loss of CF₃OC(O)O₂NO₂ via IR spectroscopy. The temperature dependence of the decomposition follows the equation k₁(T) = 1.0 × 10¹⁶ e^{?((111±3)/(RT))} for the exponential term expressed in kJ mol^?1. The values obtained for the kinetic parameters such as k₁ at 298 K, the activation energy (E_a), and the preexponential factor (A) are compared with literature data for other acyl peroxy nitrates. The atmospheric thermal stability of CF₃OC(O)O₂NO₂ and its dependence with altitude is discussed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 831–838, 2008     

Entanglement and Non-Locality in Quantum Protocols with Identical Particles

We study the role of entanglement and non-locality in quantum protocols that make use of systems of identical particles. Unlike in the case of distinguishable particles, the notions of entanglement and non-locality for systems whose constituents cannot be distinguished and singly addressed are still debated. We clarify why the only approach that avoids incongruities and paradoxes is the one based on the second quantization formalism, whereby it is the entanglement of the modes that can be populated by the particles that really matters and not the particles themselves. Indeed, by means of a metrological and of a teleportation protocol, we show that inconsistencies arise in formulations that force entanglement and non-locality to be properties of the identical particles rather than of the modes they can occupy. The reason resides in the fact that orthogonal modes can always be addressed while identical particles cannot.     

New phosphorylating reagents for deoxyribonucleosides and oligonucleotides

New phosphorylating reagents 1 and 2 were prepared in three steps from 4-hydroxybenzaldehyde. They showed good efficiency in the solid phase synthesis of 5′-phosphate monoester nucleosides. End-phosphate DNA sequence synthesis demonstrated the efficiency of the new reagents (1 and 2) according to the general procedure of automated DNA synthesis. The oxidation of P(III) to P(V) and the removal of benzyl protecting groups were achieved in a single step by treatment with a 0.02 M I₂/pyridine/H₂O solution. Due to this one-pot treatment, it is possible to use the phosphorylating reagents (1 and 2) for the synthesis of base-sensitive ODNs. The reagents 1 and 2 are unique among phosphorylating reagents.     

Optimal Production of a <Emphasis Type="Italic">Rhodococcus erythropolis</Emphasis> ATCC 4277 Biocatalyst for Biodesulfurization and Biodenitrogenation Applications

Rhodococcus sp. has a broad catabolic diversity and unique enzymatic capabilities, and it is able to adapt under extreme conditions. Thereby, the production of this remarkable bacterium has a great biotechnological and industrial importance. In this sense, we sought to improve the R. erythropolis ATCC 4277 growth through a central composite design, by varying the components of nutrient medium (glucose, malt extract, yeast extract, CaCO₃), temperature, and agitation. It was found that the concentrations of glucose and malt extract are not statistically significant, being reduced of 4.0 and 10.0 g L^-1 to 2.0 and 5.0 g L^?1, respectively. The CaCO₃ concentration and temperature were also diminished of 2.0 to 1.16 g L^?1and 28 to 23.7 °C, respectively. Optimal growth conditions provided a 240% increase in final biomass concentration, an increment in specific growth rate, and a growth yield coefficient about five times greater. Application of the optimal conditions in biodesulfurization and biodenitrogenation processes showed that desulfurization capability is not associated with optimal growth conditions; however, it was achieved a 47% of nitrogen removal in the assay containing 10% (w/w) of heavy gas oil.

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Metastable flow in capillary tubes: An experimental evaluation

This work presents the results of an experimental study with pure refrigerants R-134a and R-600a and refrigerant–oil mixtures flowing through capillary tubes in order to analyse the metastable flow. A large number of experiments were carried out to verify the influence of several variables on the underpressure of vaporization, mainly the inlet subcooling, internal diameter and inlet pressure. Capillary tubes with internal diameter of 0.69 mm and 0.82 mm were tested for condensation temperatures between 40 °C and 50 °C and subcooling degrees between 3 °C and 12 °C. Measurements for oil concentrations of 1% and 3% were conducted and compared with those for pure refrigerant R-134a. The oil influence on the metastable flow was tested and the effect on the underpressure of vaporization is addressed for lower oil concentrations.