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M. Navarrete A. Gaudry L. Cabrera T. Martínez 《Journal of Radioanalytical and Nuclear Chemistry》2002,251(2):297-298
The retention of iodine traces (ppb) was investigated in small activated carbon filters (50 mg) from solution at a yielding rate exclusively determined by pH. Retention is approximately 100% at pH values of 4–6, while no retention of iodine traces occurs after filtering them through an activated carbon filter from very acidic and basic solutions (pH values of 1 and 11, respectively) with 0% yielding rate. Since activated carbon is a very pure material, this procedure may be an alternative method of the activation analysis of iodine traces in foodstuffs, because the half-life of 128I, formed by (n,g) reaction, is only 25 minutes. It does not allow either the sample to be placed readily in solution or the radioisotope to be separated after irradiation with the purpose of attaining maximal accuracy and sensitivity in this type of analysis. 相似文献
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An in situ method of bonding monolithic rods clad in poly-ether-ether-ketone (PEEK) based on polyhydrogenosiloxane is described. The hydrogenosiloxanes provide good solubility for the substances used in the silanization reaction in aromatic hydrocarbon solvents (non-aggressive to PEEK). The reaction of the Si-H bond with silanol groups produces hydrogen as a non-aggressive byproduct to the environment. This hydrogenosiloxane method is illustrated in the synthesis of monomeric and polymeric acceptor-bonded, monolithic phases. The use of these new bonded monolithic rods for the separation of PAHs in normal phase LC is described. 相似文献
46.
Cotes S. M. Cabrera A. F. Damonte L. C. Mercader R. C. Desimoni J. 《Hyperfine Interactions》2002,141(1-4):409-414
Hyperfine Interactions - We have studied the dependence on the milling time of the amounts of metastable fcc and hcp phases produced by ball milling on Fe-13.7 wt% Mn alloys by Mössbauer... 相似文献
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This study investigates the vertical localization of single complex tones (monads) and simultaneous complex tone pairs (dyads), especially as it is affected by their fundamental frequency and source elevation. Two complex tone timbres are considered: one consisting of five low-order harmonics, and the other of all odd harmonics (a square wave). Sound sources were at -15, 0, 15, and 30 deg from the horizontal plane at ear height. For eight subjects, this source array was in the median plane, and for a further nine subjects, it was directly to the subject's left (lateral plane). The subjects localized the angle of the auditory image(s) of one or two complex tones around the vertical plane containing the sound sources. Mean responses for the five-harmonic complex tones show a systematic effect (referred to as Pratt's effect) of fundamental frequency on vertical localization--whereby high-frequency complex tones are localized to positions higher than low-frequency complex tones for equivalent source positions. For the square wave, the sound-source position dominates localization, although some effect of fundamental frequency is evident for median plane sources. 相似文献
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María Pérez-SánchezÁlvaro Cortés Cabrera Héctor García-MartínJ. Vicent Sinisterra José I. GarcíaMaría J. Hernáiz 《Tetrahedron》2011,67(40):7708-7712
A noticeably increase in activity, keeping total regioselectivity was found in the synthetic behaviour of Escherichia coli β-galactosidase in glycerol-based solvents using a 1:7 molar ratio of donor (pNP-β-Gal): acceptor (GlcNAc). Yields of up to 97% of β(1→6) with different solvents were found. These reactions take place without noticeable hydrolytic activity and with total regioselectivity, representing a considerable improvement over the use of aqueous buffer or conventional organic solvents. There is a clear dependence of the catalytic results on the solvent structure, which is analysed in terms of polarity and hydrophobicity. 相似文献
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Sodium orthonitrate (Na3NO4) is an unusual phase containing the first example of isolated tetrahedrally bonded NO43− groups. This compound was obtained originally by heating together mixtures of Na2O and NaNO3 for periods extending up to >14 days in evacuated chambers. Considering the negative volume change between reactants and products, it was inferred that a high-pressure synthesis route might favor the formation of the Na3NO4 compound. We found that the recovered sample is likely to be a high-pressure polymorph, containing NO43− groups as evidenced by Raman spectroscopy. The high-pressure behavior of Na3NO4 was studied using Raman spectroscopy and synchrotron X-ray diffraction in a diamond anvil cell above 60 GPa. We found no evidence for major structural transformations, even following laser heating experiments carried out at high pressure, although broadening of the Raman peaks could indicate the onset of disordering at higher pressure. 相似文献
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Comini LR Montoya SC Páez PL Argüello GA Albesa I Cabrera JL 《Journal of photochemistry and photobiology. B, Biology》2011,102(2):108-114
Photosensitizing anthraquinones isolated from Heterophyllaea pustulata Hook f. (Rubiaceae), namely soranjidiol, rubiadin, damnacanthal and 5,5'-bisoranjidiol, showed antibacterial activity (bacteriostatic/bactericide) on Staphylococcus aureus. The mechanism of action seems to involve an increase in the levels of superoxide anion (O(2)(·-)) and/or singlet molecular oxygen ((1)O(2)). Moreover, the effect of actinic irradiation as a boosting agent for the production of both reactive species of oxygen as well as its influence on antibacterial activity was assessed. The routine susceptibility assay (minimum inhibitory concentration determination) was carried out by means of the broth macrodilution method. Bactericide activity was determined counting the colony-forming units per milliliter (cfu/mL) in plate. The O(2)(·-) production was determined by means of an indirect photobiological assay (Nitroblue Tetrazolium test), and the production of (1)O(2) was followed using an indirect steady-state method, with methionine as the (1)O(2) chemical quencher. 相似文献