On the route to mimic natural movements: synthesis and photophysical properties of a molecular arachnoid

The synthesis, photoswitchability and NIR emitting properties of a novel π-extended pyrene derivative, peripherally decorated with four azobenzenyl-ethynyl legs, are reported.     

Phenol transformation photosensitised by quinoid compounds

The phototransformation of phenol in aqueous solution was studied with different quinoid compounds, which are usually detected on atmospheric particulate matter: 2-ethylanthraquinone (EtAQ), benzanthracene-7,12-dione (BAD), 5,12-naphthacenequinone (NQ), 9,10-anthraquinone (AQ), and 2,6-dihydroxyanthraquinone (DAQ). All the studied quinones were able to sensitise the phototransformation of phenol. Under blue-light irradiation the approximated, polychromatic quantum yields for phenol photodegradation were in the order AQ > BAD > EtAQ > NQ > DAQ. Quantum mechanical calculations showed that AQ and DAQ have a very different spin distribution in the triplet state (largely located on the carbonyl oxygen and delocalised over the aromatic ring, respectively) that could account for the difference in reactivity. The spin distribution of EtAQ is similar to that of AQ. Under simulated sunlight, EtAQ induced the highest rate of phenol degradation. Radiation-excited EtAQ would oxidise both ground-state EtAQ and phenol; a kinetic model that excludes the ˙OH radical and singlet oxygen as reactive species is supported by the experimental data. Quinones were also able to oxidise nitrite to nitrogen dioxide, thereby inducing phenol nitration. Such a process is a potential source of nitrogen dioxide and nitrophenols in the atmospheric aerosols.     

Development of a microfluidics biosensor for agarose-bead immobilized Escherichia coli bioreporter cells for arsenite detection in aqueous samples

Contamination with arsenic is a recurring problem in both industrialized and developing countries. Drinking water supplies for large populations can have concentrations much higher than the permissible levels (for most European countries and the United States, 10 μg As per L; elsewhere, 50 μg As per L). Arsenic analysis requires high-end instruments, which are largely unavailable in developing countries. Bioassays based on genetically engineered bacteria have been proposed as suitable alternatives but such tests would profit from better standardization and direct incorporation into sensing devices. The goal of this work was to develop and test microfluidic devices in which bacterial bioreporters could be embedded, exposed and reporter signals detected, as a further step towards a complete miniaturized bacterial biosensor. The signal element in the biosensor is a nonpathogenic laboratory strain of Escherichia coli, which produces a variant of the green fluorescent protein after contact to arsenite and arsenate. E. coli bioreporter cells were encapsulated in agarose beads and incorporated into a microfluidic device where they were captured in 500 × 500 μm(2) cages and exposed to aqueous samples containing arsenic. Cell-beads frozen at -20 °C in the microfluidic chip retained inducibility for up to a month and arsenic samples with 10 or 50 μg L(-1) could be reproducibly discriminated from the blank. In the 0-50 μg L(-1) range and with an exposure time of 200 minutes, the rate of signal increase was linearly proportional to the arsenic concentration. The time needed to reliably and reproducibly detect a concentration of 50 μg L(-1) was 75-120 minutes, and 120-180 minutes for a concentration of 10 μg L(-1).     

On Elliptic Problems in Besov Spaces

Suppose that the distribution function of a standardized sum of independent identically distributed random variables tends to a stable law as n°. Some differences in moments and pseudomoments, inequalities of the BERRY-ESSEEN-Type and asymptotic expansions are characterized when the limit law is either normal or non-normal stable.     

Measurement of rotational diffusivity of rodlike molecules in amorphous polymer matrices by the dynamic kerr effect

Electrooptic (Kerr effect) relaxation experiments, designed to measure the rotational diffusivity of collagen (rodlike) molecules in aqueous poly(ethyleneoxide) (amorphous) semidilute solutions under various conditions have been performed. The experimental results have been compared with the predictions of a previously derived model giving the rotational diffusivity of dilute rods in semidilute amorphous polymer solutions as a function of rod length and amorphous polymer concentration. Excellent agreement is found between the predicted scaling D_r ～ ?L^?7 (D_r = rod rotational diffusivity, pi_p = polymer weight fraction, and L = rod length) and the experiments.     

Effects of temperature and thermo-mechanical couplings on material instabilities and strain localization of inelastic materials

A general framework for rate-independent, small-strain, thermoinelastic material behaviour is presented, which includes thermo-plasticity and -damage as particular cases. In this context, strain localization and the development of material instabilities are investigated to highlight the roles of thermal effects and thermomechanical couplings. During a loading process, it is shown that two conditions play the essential roles and correspond to the singularity of the isothermal and the adiabatic acoustic tensors. Under quasi-static conditions, strain localization (in a classical sense) may occur when either of these two conditions is met. It involves a jump in temperature rate in the latter case, whereas temperature rate remains continuous in the former, but a discontinuity in the spatial derivatives of the heat flux must occur. This is consistent with the condition of stationarity of acceleration waves, which are shown to be homothermal and propagate with a velocity related to the eigenvalues of the isothermal acoustic tensor. A linear perturbation analysis further clarifies the above findings. In particular, for a quasi-static path of an infinite medium, failure of positive definiteness of either of the acoustic tensors corresponds to bifurcations in wave-like modes of arbitrary wave-length and infinite rate of growth. Under dynamic conditions, unbounded growth of perturbations is associated only to the short wavelength regime and corresponds to divergence growth or flutter phenomena relative to the isothermal acoustic tensor.     

Solute-solvent interactions in dilute aqueous solution of some alkylureas and diazolidin-2-one

The integral heats of solution of urea, methylurea, 1,3 d$\text{i}$ methylurea, N,N,N′,N′ tetramethylurea, 1,3 diazolidin-2-one and N,N dimethyl 1,3 diazolidin-2-one have been measured at 298.15K.The results are interpreted qualitatively in terms of intercomponent molecular interaction and hydrophobic stabilisation of the water structure by the solute molecules.The obtained results indicate that the geometry, the number of hydrogen atoms and the number of alkyl groups have an important action on these two effects.A structural model between five water molecules bonded to 1,3 diazolidin-2-one is proposed by a diffractometric analysis on an aqueous solution 2 M of this compound.