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Aromatic main chain polyesters with perpendicularly attached nonlinear optical chromophores embedded in long alkoxy side chains are synthesized starting from 4,7-dihydroxy-2-(dicyanomethylene)-1,3-benzodithiolane. The polymers were characterized by DSC, XRD and polarized optical microscopy. Nonlinear optical properties of models of the chromophore subunits were investigated separately by electric field induced second harmonic generation (EFISH) and electrooptical absorption measurement (EOAM). Electric poling of the polymers was successfully applied to thin films of the polymer to induce the noncentrosymmetry required for second-order nonlinearity. Characterization of electrooptical properties of the poled polymer films was accomplished by the method of attenuated total reflection

[(18)F]Fluoroethylcholine has been recently introduced as a promising (18)F-labelled analogue of [(11)C]choline which had been previously described as a tracer for metabolic cancer imaging with positron emission tomography (PET). Due to the practical advantages of using the longer-lived radioisotope (18)F (t(1/2)=110 min), offering the opportunity of a more widespread clinical application, we established a reliable, fully automated synthesis for its production using a modified, commercially available module. [(18)F]Fluoroethylcholine was prepared from N,N-dimethylaminoethanol by iodide catalyzed alkylation with 1-[(18)F]fluoro-2-tosylethane as alkylating agent, resulting in a total radiochemical yield of 30+/-6% after a synthesis time of 50 min. The specific activity of [(18)F]fluoroethylcholine was >55 GBq/micromol and the radiochemical purity 95-99%.

In most organic photorefractive systems discrete components are assigned for each function, i.e., a photochemical charge generating species, a transport media, a nonlinear chromophore and, in some cases, even trapping species. All these components are mixed with, attached to, or otherwise constitute some kind of polymer binder that may also contain plasticizers to control the glass transition temperature. These systems are obviously complex mixtures that may sometimes suffer from heterogeneity, phase separation, and resulting poor linear optical properties due to scattering and other fluctuations. A general goal then is to design compositions that contain a minimum number of discrete components and this can be accomplished by designing molecules which are multifunctional and perform more than one of the requisite tasks. It is even possible to eliminate the polymer altogether and form high optical quality monomeric molecular glasses from specially modified chromophores. It turns out that glass formation in organic monomers is really not that uncommon. However, the optimization of monomer glasses to enhance the temperature range and stability of the glass phase entails understanding and control of the appropriate structure features such as hydrogen bonding and conformational flexibility. For photorefractive applications highly birefringent chromophores in the pyridone and methylenedihydropyridine families were identified and by appropriate structure modifications were converted to highly stable glasses. The characterization of the electronic and structural properties of these of these materials and other related chromophores to provide useful photorefractive media is being actively pursued.

Cristallisation dans P4/nmm avec a=4,696, c=7,559, Z=2; affinement jusqu'a R=0,0223. La structure est caracterisee par des couches de tetraedres ∞ 2 [NaS − 4/4 ], separees par des couches doubles de Rb, pour former une geometrie de type PbFCl

Using a distillation method for the separation of18F-fluoride from aqueous18F-solutions obtained after cyclotron irradiation of a water target by means of the16O(3He, p)18F reaction, the radiohalogen could be generated as a highly reactive species for nucleophilic substitution reactions. Thus, with the starting compounds 1,3,4,6-tetra-O-acetyl-2-O-trifluoromethanesulfonyl-β-D-mannopyranose and 1,2:5,6-di-O-isopropylidene-3-O-trifluoromethanesulfonyl-α-D-allofuranose18F-2-deoxy-2-fluoro-D-glucose (2-18FDG) and18F-3-deoxy-3-fluoro-D-glucose (3-18FDG) could be synthesized with radiochemical yields of 71.6% and 85.9%, respectively. Including purification by HPLC, the total preparation time was 70 min, yielding the glucose derivatives in a no-carrier-added state. Specific activities coold be calculated to be greater than 103 Ci/mmol.