Ozone interaction with conjugated polymers—I. Polyacetylene

Free-standing films of cis- and trans-rich polyacetylene (PA) obtained on a Rh(I) catalyst, were treated with ozonized oxygen (O₃ 1% by weight on average). The initial superficial charge-transfer complex formed between ozone and the polyene chain and the subsequent ozone accelerated cis-trans isomerization were studied by electronic and FT-IR spectroscopies. A peculiar mechanism of interaction between ozone and polyenic chain was proposed, and cation radicals were observed on the ozone doped surfaces of PA. Ozone treatment of PA films creates a superficial oxidized barrier that prevents subsequent thermo-oxidative destruction of the bulk portion of PA film. This treatment could be a way of protecting PA from degradative oxidation.     

Memory loss process and non-Gibbsian equilibrium solutions of master equations

The phonon dynamics of a harmonic oscillator coupled to a steady reservoir is studied. In the Markovian limit, the equilibrium is reached through a progressive loss of memory process which involves the moments of the initial distribution. The relationship to the non-Markovian equations of motion and its resolvent poles is settled. As a particular model of the coupling mechanism is adopted, the possibility of non-Gibbsian equilibrium distribution arises, which is analyzed focusing upon the dependence of various parameters of the system on an effective equilibrium temperature.     

Multielement analysis of a municipal landfill leachate with total reflection X-ray fluorescence (TXRF). A comparison with ICP-OES analytical results

A complete analysis of a landfill leachate coming from a landfill site of several years old was performed with a total reflection X-ray fluorescence (TXRF) spectrometer in comparison with an inductively coupled plasma optical emission spectroscopy (ICP-OES). The results of the two analytical techniques are compared and advantages and drawbacks emphasized. The TXRF analytical technique appears a reliable, economic, rapid and simpler technique for the everyday monitoring of the composition of the landfill leachate before the purification treatment and after the treatment to check the quality of the resulting purified water. The TXRF and the ICP-OES analytical techniques were also employed in the analysis of three groundwater samples.     

Free vibrations of an uncertain energy pumping system

The aim of this paper is to study the energy pumping (the irreversible energy transfer from one structure, linear, to another structure, nonlinear) robustness considering the uncertainties of the parameters of a two DOF mass-spring-damper, composed of two subsystems, coupled by a linear spring: one linear subsystem, the primary structure, and one nonlinear subsystem, the so-called NES (nonlinear energy sink). Three parameters of the system will be considered as uncertain: the nonlinear stiffness and the two dampers. Random variables are associated to the uncertain parameters and probability density functions are constructed for the random variables applying the Maximum Entropy Principle. A sensitivity analysis is then performed, considering different levels of dispersion, and conclusions are obtained about the influence of the uncertain parameters in the robustness of the system.     

Synthesis and chemical structure of natural rubber adduct with SO2 and study of the thermal stability

Natural rubber (NR, cis-1,4-polyisoprene) was reacted in solution with SO₂ at room temperature in different solvents (tetrahydrofuran, CHCl₃, CH₂Cl₂ and tetralin). The reaction product consisted of an adduct between NR and SO₂. The chemical structure of the adduct was studied by FT-IR spectroscopy, by thermogravimetry coupled with FT-IR (TGA-FT-IR), by differential thermal analysis (DTA) and by derivative thermogravimetry (DTG). The maximum SO₂ uptake from NR was 21% as determined by TGA. The TGA of the NR-SO₂ shows that the adduct decomposes in two steps initially releasing SO₂ at lower temperature and then decomposing at higher temperature like common NR. It is proposed that the chemical structure of the NR-SO₂ adduct consists of SO₂ molecules added to the double bonds of the isoprene units forming a sulfone derivative with three-membered rings known as thiirane-1,1-dioxide. On heating the thiirane ring decomposes releasing SO₂ in an extrusion reaction giving back the NR macromolecule.The possible potential applications of the NR-SO₂ adduct which is cheap and easy to prepare are outlined.     

Non-Markovian quantal Brownian motion model

A non-Markovian version of the quantal Brownian motion model is given. The integrodifferential equations of motion are solved, establishing the analytic form of the resolvent poles and analyzing their properties. An explicit investigation of the poles at zero temperature is performed. In this frame a rule can be found that relates the relevant poles of the non-Markovian resolvent to the eigenvalues of the associated Markovian generator of the motion.     

Radiolysis and radioracemization of RNA ribonucleosides: implications for the origins of life

The RNA nucleosides, namely adenosine, cytidine, guanosine and uridine were γ-radioyzed in solid state and in vacuo at room temperature to a total dose of 3.2 MGy. Through electronic absorption spectroscopy, differential scanning calorimetry and through polarimetry and optical rotatory dispersion spectroscopy, it was found that the purine-based nucleosides (adenosine and guanosine) show a much higher radiolysis resistance than the pyrimidine-based nucleosides (cytidine and uridine). In an astrochemical/astrobiological context, these results may explain why purine nucleobases are found in practically all carbonaceous chondrite meteorites while the pyrimidine nucleobases are absent or below the detection limits of the current analytical techniques. In the hypothesis that both purines and pyrimidines nucleobases were present in certain bodies at the beginning of the solar system 4.6?×?10⁹ years ago, the radiolysis due to radionuclides decay has destroyed more easily and completely the pyrimidine bases due to their much lower radiolysis resistance than the purine bases.     

Synthesis of 3-(2-chloro-5-nitroanilino and 4-nitroanilino)-1-(2,4,6-trichlorophenyl)-2-pyrazolin-5-ones

A new synthesis of 3-anilino-1-aryl-2-pyrazolin-5-ones in which the pyrazolinone ring is built via N? N bond formation is described. 2-Cyano-2′,4′,6′-trichloroacetanilide 1 was converted to imino ether hydrochloride 2 which was reacted with anilines in methanol to produce N-arylimino ether 3a,b. Reaction of these N-arylimino ethers with hydroxylamine gave N-arylamidoximes 4a,b . An 1,2,4-oxadiazol-5-one 6a was prepared from the N-arylamidoxime 4a and subjected to base-induced rearrangement. The desired 3-anilino-pyrazolinone 7a was obtained only in a very low yield. However, O-acetylation of the N-arylamidoximes 4a,b followed by acid-catalyzed ring closure and rearrangement in the presence of excess acetic anhydride gave a mixture of N-acetylanilinopyrazolinones (e.g. 10 ) and 4-acetyloxy-3-N-acetylanilinopyrazoles (e.g. 12 ) which upon acid hydrolysis afforded the 3-anilinopyrazolinones 7a,b in better yield.