2,986 research outputs found

    Characterisation of porous solids using small-angle scattering and NMR cryoporometry

    Get PDF
    The characteristics of several porous systems have been studied by the use of small-angle neutron scattering [SANS] and nuclear magnetic resonance [NMR] techniques. The measurements reveal different characteristics for sol-gel silicas, activated carbons and ordered mesoporous silicas of the MCM and SBA type. Good agreement is obtained between gas adsorption measurements and the NMR and SANS results for pore sizes above 10 nm. Recent measurements of the water/ice phase transformation in SBA silicas by neutron diffraction are also presented and indicate a complex relationship that will require more detailed treatment in terms of the possible effects of microporosity in the silica substrate. The complementarity of the different methods is emphasised and there is brief discussion of issues related to possible future developments

    Cultivation of embryos of Drosophyllum lusitanicum link-an insectivorous plant

    Get PDF
    There has been growing interest in recent years in the understanding of nutrition and flowering of insectivorous angiosperms in axenic cultures. This note reports our preliminary results on the cultivation of seeds and embroys of Drosophyllum lusitanicum Link. The seed is pyramidal in shape and has a thick, black seed coat. The mature embryo is small and fully organized. The bulk of the seed is occupied by the cellular, starchy endosperm. Modified White's medium containing 2% sucrose and solidified with 0.8% agar but without IAA served as the basal medium (WB). Mature seeds were surface sterilized with chlorine water and planted on WB as well as on WB + 500 mg/1 each of beef extract, casein hydrolysate and yeast extract separately

    Pressure-tuning of the electron-phonon coupling: the insulator to metal transition in manganites

    Get PDF
    A comprehensive understanding of the physical origin of the unique magnetic and transport properties of A_(1-x)A'^xMnO_3 manganites (A = trivalent rare-earth and A' = divalent alkali-earth metal) is still far from being achieved. The complexity of these systems arises from the interplay among several competing interactions of comparable strength. Recently the electron-phonon coupling, triggered by a Jahn-Teller distortion of the MnO_6 octahedra, has been recognised to play an essential role in the insulator to metal transition and in the closely related colossal magneto-resistance. The pressure tuning of the octahedral distortion gives a unique possibility to separate the basic interactions and, at least in principle, to follow the progressive transformation of a manganite from an intermediate towards a weak electron-phonon coupling regime. Using a diamond anvil cell, temperature and pressure-dependent infrared absorption spectra of La_(0.75)Ca_(0.25)MnO_3 have been collected and, from the spectral weight analysis, the pressure dependence of the insulator to metal transition temperature T_IM has been determined for the first time up to 11.2 GPa. The T_IM(P) curve we proposed to model the present data revealed a universality character in accounting for the whole class of intermediate coupling compounds. This property can be exploited to distinguish the intermediate from the weak coupling compounds pointing out the fundamental differences between the two coupling regimes.Comment: 8 pages, 4 figure

    Resonance raman characterization of the forms of ground-state 8-substituted 7-hydroxyquinoline caged acetate compounds in aqueous solutions

    Get PDF
    Monday Poster Session: Resonance Raman in Biological and Chemical Systems (MP22) - Poster Number: 0978-substituted 7-hydroxyquinolines, like 8-chloro-7-hydroxyquinoline (CHQ) and 8-cyano-7-hydroxyquinoline (CyHQ), are able to be useful for 1PE and 2PE and their acetate acids CHQ−OAc and CyHQ−OAc were also able to undergo photolysis reactions in neutral aqueous buffer solutions. To examine the substituent effect on the relative populations of the forms of the ground state species of 8-substituted 7-hydroxyquinolines, ultraviolet absorption and resonance Raman spectroscopy experiments were done for CHQ–OAc and CyHQ–OAc in differnt solutions.postprintThe 22nd International Conference on Raman Spectroscopy (ICORS 2010), Boston, MA., 8-13 August 2010
    corecore