High efficiency long pulse FIR Raman conversion in ammonia

Generally the quantum efficiency of FIR Raman generation in molecular gases is below the theoretical value. This disagreement is particularly evident in Raman scattering from pulsed sources with short pulse length, when the vibrational saturation limits the power conversion. Other nonlinear processes can overcome this saturation, but they require a very intense pump power for too short a time to use the FIR radiation in high sensitive experiments with heterodyne detection. This is the case, for instance, of RFWM. In this work we describe the experimental conditions to achieve a high efficiency 90 micron Raman conversion in ammonia, with both short and long pulses.     

Natural products for human health: an historical overview of the drug discovery approaches

Natural products (NPs) are secondary metabolites produced and used by organisms for defending or adapting purposes. These molecules were naturally selected during thousands of years to improve the specificity and cover a very wide range of functions, depending on the origin, the habitat and the specific activity carried out in the organism of origin. Due to these intrinsic features, NPs have been used as healing agents since thousands of years and still today continue to be the most important source of new potential therapeutic preparations.The purpose of this review is to provide information about the historical evolution of the NPs investigation methods, focusing attention on the relative benefit/problems emerged after the improvement of the scientific investigations about them, especially over the last two centuries. Taken together, the reported information lead to the central role of NPs in the future of drug development for human needs.     

Fragmentation sous l'Impact Electronique de Diamino-4,5 Triazoles-1,2,4 et d'Amino-4 Mercapto-5 Triazoles-1,2,4

The mass spectra of several 4-amino 1,2,4-triazoles with an amino, methylamino, mercapto or methylmercapto group in position 5 are reported and analysed. Five different fragmentation pathways of the molecular ion are observed in the heterocylic ring but the amino group in position 4 also involves some other specific cleavages.     

Étude de la tautomérie des halogéno-triazoles-1,2,4 par determination expérimentale et théorique de leurs moments dipolaires

The dipole moments of sixteen 3(5)-halogeno-triazoles have been measured in dioxane at 25 ° C. Experimental dipole moments have been compared with those calculated by two semi-empirical methods CNDO/2 and PCILO, and with those computed vectorially. An energetic approach is also given.It is shown, in _N-unsubstituted 1,2,4-triazoles (for which three tautomeric forms, A, B and C are possible) that the predominating tautomer has a proton on the N1 atom and the electron-accepting substituent on the C3 atom.The effect of the introduction of an electron-accepting or donating substituent in position 3 and 5 of the triazole ring is discussed.     

Halloysite nanotubes/pluronic nanocomposites for waterlogged archeological wood: thermal stability and X-ray microtomography

Journal of Thermal Analysis and Calorimetry - Filling a polymer with halloysite nanotubes is considered a promising strategy to generate nanocomposites with tailored physicochemical properties. We...