We studied the physicochemical characteristics and mycobiota associated to five key historic documents from Costa Rica, including the Independence Act of Costa Rica from 1821. We used nondestructive techniques (i.e.
View Article and Find Full Text PDFThe formalism of the Lorenz-Mie (LM) theory is used to estimate the contributions of radiation being scattered into the detector acceptance angle of spectrophotometers (with or without an integrating sphere) to the apparent direct transmittance and specular reflectance measurements. These contributions are subtracted from the measurements before doing the inversion to obtain the spectral variation of the scattering and absorption (S&A) coefficients of optically particulate liquid samples, decoupling the contribution to extinction from these two mechanisms. The method is applied to transmittance spectra of Pickering emulsions of dodecane oil (DO) and DO micelles with saturated dissolved Nile red dye, stabilized with anatase ( ) in water.
View Article and Find Full Text PDFSpectrochim Acta A Mol Biomol Spectrosc
February 2022
Direct (photo)electrochemical production of non-fossil fuels from water and CO requires water-oxidation catalysis at near-neutral pH in the presence of appropriate anions that serve as proton acceptors. We investigate the largely enigmatic structural role of anions in water oxidation for the prominent cobalt-phosphate catalyst (CoCat), an amorphous and hydrated oxide material. Co([(P/As)O])·8HO served, in conjunction with phosphate-arsenate exchange, as a synthetic model system.
View Article and Find Full Text PDFIs water oxidation catalyzed at the surface or within the bulk volume of solid oxide materials? This question is addressed for cobalt phosphate catalysts deposited on inert electrodes, namely crystallites of pakhomovskyite (Co3(PO4)2⋅8 H2O, Pak) and phosphate-containing Co oxide (CoCat). X-ray spectroscopy reveals that oxidizing potentials transform the crystalline Pak slowly (5-8 h) but completely into the amorphous CoCat. Electrochemical analysis supports high-TOF surface activity in Pak, whereas its amorphization results in dominating volume activity of the thereby formed CoCat material.
View Article and Find Full Text PDFThe adjuvanticity of aluminum hydroxide and calcium phosphate on the antibody response in mice towards the venom of the snake Bothrops asper was studied. It was found that, in vitro, most of the venom proteins are similarly adsorbed by both mineral salts, with the exception of some basic phospholipases A2, which are better adsorbed by calcium phosphate. After injection, the adjuvants promoted a slow release of the venom, as judged by the lack of acute toxicity when lethal doses of venom were administered to mice.
View Article and Find Full Text PDFThis combined experimental (STM, XPS) and molecular dynamics simulation study highlights the complex and subtle interplay of solvent effects and surface interactions on the 2-D self-assembly pattern of a Schiff-base macrocycle containing catechol moieties at the liquid-solid interface. STM imaging reveals a hexagonal ordering of the macrocycles at the n-tetradecane/Au(111) interface, compatible with a desorption of the lateral chains of the macrocycle. Interestingly, all the triangular-shaped macrocycles are oriented in the same direction, avoiding a close-packed structure.
View Article and Find Full Text PDFFluorine-nitrogen metathesis in the reaction of a cyclic iminoalane with titanocene fluorides results in unexpected cage compounds. Treatment of one of these compounds with diethyl ether leads to 1, which contains a titanium-nitrogen double bond stabilized intramolecularly by fluorine.
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