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International audience; Tropospheric NO2 column retrievals from the Global Ozone Monitoring Experiment (GOME) satellite spectrometer are used to quantify the source strength and 3-D distribution of lightning produced nitrogen oxides (NOx=NO+NO2). A sharp increase of NO2 is observed at convective cloud tops with increasing cloud top height, consistent with a power-law behaviour with power 5±2. Convective production of clouds with the same cloud height are found to produce NO2 with a ratio 1.6/1 for continents compared to oceans. This relation between cloud properties and NO2 is used to construct a 10:30 local time global lightning NO2 production map for 1997. An extensive statistical comparison is conducted to investigate the capability of the TM3 chemistry transport model to reproduce observed patterns of lightning NO2 in time and space. This comparison uses the averaging kernel to relate modelled profiles of NO2 to observed NO2 columns. It exploits a masking scheme to minimise the interference of other NOx sources on the observed total columns. Simulations are performed with two lightning parameterizations, one relating convective preciptation (CP scheme) to lightning flash distributions, and the other relating the fifth power of the cloud top height (H5 scheme) to lightning distributions. The satellite-retrieved NO2 fields show significant correlations with the simulated lightning contribution to the NO2 concentrations for both parameterizations. Over tropical continents modelled lightning NO2 shows remarkable quantitative agreement with observations. Over the oceans however, the two model lightning parameterizations overestimate the retrieved NO2 attributed to lightning. Possible explanations for these overestimations are discussed. The ratio between satellite-retrieved NO2 and modelled lightning NO2 is used to rescale the original modelled lightning NOx production. Eight estimates of the lightning NOx production in 1997 are obtained from spatial and temporal correlation methods, from cloud-free and cloud-covered observations, and from two different lightning parameterizations. Accounting for a wide variety of random and possible systematic errors, we estimate the global NOx production from lightning to be in the range 1.1?6.4 Tg N in 1997.

Properties of organic electronic materials in solid-state are determined as individual molecules and molecular assembly. It is essential to optimize conjugated materials to control performance of molecular assembly that constitute electronic devices such as light-emitting diodes and solar cells, and is fundamental for technical applications in nanoelectronics.Here supermolecular structure of block copolymers with .PI.-conjugated block and unconjugated block were studied.Oligo-fluolene series and chiral oligomers in solid state were studied. The material adjusting conditions such as solvent evaporation rate and properties of base material widely affected molecular association. Morphologies of thin- walled polymers were observed by AFM, and it shows that conjugated molecule surface can be organized over length scale from several nm to several .MU.m. Sensitivity of supermolecular organization is controlled by weak force such as .PI.-bond interaction.

The self-assembly of alpha,alpha'-linked sexithiophenes with chiral and achiral penta(ethylene glycol) chains attached at the alpha-positions of the terminal rings, that is, 2,2':5',2'':5'',2''':5''',2'''':5'''',2'''''-sexithiophene-5,5'''''-dicarboxylic acid-2S)-2-methyl-3,6,9,12,15-pentaoxahexadecyl ester (1) and 2,2':5',2'':5'',2''':5'''',2''''':5''''',2'''''-sexithiophene-5,5'''''-dicarboxylic acid-3,6,9,12,15-pentaoxahexadecyl ester (2), respectively is described. Analysis of the UV/vis, fluorescence, circular dichroism, and circular polarization of luminescence spectroscopic data shows that these compounds form chiral aggregates in polar solvents and in the solid state. In n-butanol aggregation occurs at temperatures below 30 degrees C, while above this threshold temperature the aggregates break up without an intermediate disordered state of aggregation, and the compounds are molecularly dissolved. The "melting temperature" of the aggregates depends on the concentration of sexithiophene, indicating that the optical changes observed are a result of intermolecular processes. Mass spectrometric measurements reveal that 1 and 2 can form mixed aggregates. Analysis of the optical spectra reveals that in these mixed aggregates, chiral 1 molecules act as "sergeants" to direct the packing of the "soldiers" 2, illustrating cooperativity within the columns. In water, the same type of chiral aggregates are formed as in n-butanol below 30 degrees C; however, these aggregates are still present, but the chirality is lost above 30 degrees C. In spin-coated films of 1 chiral aggregates are present. AFM studies show that 1 self-organizes into chiral fiberlike structures in the solid state. Furthermore both 1 and 2 display thermotropic liquid crystalline behavior between 180 and 200 degrees C.

We present a combined experimental and theoretical investigation of the photophysical properties of four π-conjugated oligomers with varying chemical constitutions. Three of these contain alkoxy-substituted p-phenylene vinylene/ethynylene units with a phenylene, anthracene, or p-dialkoxyphenylene moiety as the central aromatic ring; the fourth oligomer contains only p-dialkoxyphenylene vinylene units. The electronic structure and optical properties are investigated by combining UV�vis, fluorescence, and electrochemical techniques with quantum-chemical semiempirical calculations. The simulated absorption spectra are in excellent agreement with the experimental data and illustrate the role of the central aromatic ring on the nature of the lowest excited state. Chem. Mater.

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Generations of two dendrimers based on poly(propylenimine) with CN and palmitoyl terminal groups was studied by translational diffusion and viscometric methods. The (D-3[eta])(-1) values obtained were compared with the calculated molecular weights. By comparing the volumes of these dendrimers with those of the previously studied lacto-poly(propylene) dendrimers, the volumes occupied by the terminal groups in hybrid dendrimers were estimated

Cooperative interactions are responsible for the organization of a variety of biol. polymers, but only recently has this behavior been explored in synthetic chain mols. This presentation will describe the study of two series of chiral phenylene ethynylene oligomers, bearing either polar or non-polar side chains. Under solvent conditions that are specific to the type of side chain, both oligomers can adopt helical conformations in soln. A single stereocenter in each side chain is capable of imparting a twist sense bias to the folded conformation indicating that there are highly cooperative interactions between the side chains. The bias has been studied as a function of chain length, solvent quality and temp. [on SciFinder (R)]

Poly[3,4-bis(3-methylbutylthio)thienylenevinylene] and poly[3,4-bis-(S)-(2-methylbutylthio)thienylenevinylene] were synthesized using McMurry coupling. The mesoscopic ordering of the polymers were investigated through optical techniques, in particular the introduction of chiral enantiomerically pure side chains induces the formation of chiral aggregates both in soln. and in the solid state. Mobility measurements for possible applications in FET will also be presented

The solid-state photophysical properties of semiconducting polymers result from the interplay between the intrinsic features of the polymer chains and interchain interactions. Exciton coupling, which in principle can be estimated from circular dichroism (CD) spectra, is one of the major interchain interactions affecting the optical properties of semiconducting polymers. Here the authors present a combined experimental and theoretical investigation of the chiroptical properties of oligothiophenes. The results confirm that the CD spectrum provides an independent estimate of the exciton coupling.