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151.
Jaime Ortega Jorge San Martín Loredana Smaranda 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,188(4):969-993
In this paper, we use the Bloch wave method to study the asymptotic behavior of the solution of the Laplace equation in a
periodically perforated domain, under a non-homogeneous Neumann condition on the boundary of the holes, as the size of the
holes goes to zero more rapidly than the domain period. This method allows to prove that, when the hole size exceeds a given
threshold, the non-homogeneous boundary condition generates an additional term in the homogenized problem, commonly referred
to as “the strange term” in the literature. 相似文献
152.
Fabio Mazzotti Leonardo Di Donna Barbara Macchione Loredana Maiuolo Enzo Perri Giovanni Sindona 《Rapid communications in mass spectrometry : RCM》2009,23(10):1515-1518
Crop control is an important issue in both developed and developing countries. An environmentally friendly approach is represented by the so‐called Integrated Pest Management (IPM), whereby synthetic pesticides are only applied as a last resort, under the strict control of suitable experts. European and US regulatory authorities, such as the US EPA, are constantly assessing the risks of exposure to the organophosphate (OP) class of pesticides and, among these, specifically dimethoate. The use of dimethoate is still allowed in many crops, including olives, which once was based in the Mediterranean area but now is expanding rapidly throughout the world. An important aspect of IPM protocols is represented by the availability of reliable and sensitive methods to detect pesticides residues. This paper describes an isotope dilution dimethoate assay based on the application of electrospray ionization tandem mass spectrometry (ESI‐MS/MS) by means of a deuterium‐labeled internal standard. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
153.
Antonio Da Settimo Giampaolo Primofiore Anna Maria Marini Federico Da Settimo Concettina La Motta Silvia Salerno 《Journal of heterocyclic chemistry》1999,36(3):639-642
The preparation of two new heterocyclic ring systems, purinobenzodiazepine and purinobenzotriazocine derivatives by the condensation of 8-aminotheophylline or 8-hydrazinotheophylline with o-carboxybenzaldehyde or o-carboxyacetophenone is described. 相似文献
154.
Alejandra Salerno Monica E. Hedrera Isabel A. Perillo Norma B. D'Accorso Miriam Martins Alho 《Journal of heterocyclic chemistry》2000,37(1):57-62
The electron impact mass spectral fragmentation pathways for a series of 1,3‐di‐ and 1,2,3‐trisubstituted imidazolidines were investigated. The data show remarkable differences depending on the location and identity of substituents. The atypical 1,2,2,3‐tetrasubstituted imidazolidine, 2‐cyano‐1‐methyl‐3‐(p‐nitro‐phenyl)‐2‐phenylimidazolidine, was also investigated. 相似文献
155.
Marta L. Borges Loredana Latterini Fausto Elisei Palmira F. Silva Rui Borges Ralph S. Becker António L. Maçanita 《Photochemistry and photobiology》1998,67(2):184-191
The larger photobiological activity of visnagin (VI) versus khellin (KH) toward several living organisms, including fungi, viruses, yeasts and bacteria, induced a detailed investigation of the photophysical properties of these naturally occurring furanochromones, using laser-flash-photolysis, photoacoustic calorimetry and fluorescence (steady-state and time-resolved) techniques in solvents with different polarity and content of water, including micelles and vesicles. The results have shown that the magnitude of all the three rate constants out of S1 (radiative, kf; internal conversion, kic and intersystem crossing, kisc) for VI and KH strongly depend on the solvent, namely on its hydrogen bonding ability and polarity. The changes of kf and kisc are due to the solvent-assisted mixing and/or inversion of the two first singlet excited states (1n,π* and 1π,π*), while kic increases with a decrease of the So–S1 energy gap. As a consequence, the quantum yield of triplet formation (φT) strongly decreases from values of ?0.8 in dioxane to < 0.05 in water for both compounds. The magnitude of solvent polarity/hydrogen bonding ability required, at which the state order is inverted and φT starts to decrease, is greater for VI than for KH and consequently φT (VI) > φT (KH) over a broad range of water content including that appropriate to the environment of the compounds in a living system. These facts account for the larger photobiological activity of VI with respect to KH, regarding both the fungus Fusarium culmorum L. and the wild strain of Escherichia coli, studied by us. 相似文献
156.
Renato DalpozzoAntonio De Nino Loredana MaiuoloAntonio Procopio Monica NardiGiuseppe Bartoli Roberto Romeo 《Tetrahedron letters》2003,44(30):5621-5624
Cerium(III) triflate is a powerful catalyst for the acetylation of alcohols. The reaction works well for a large variety of simple and functionalized alcohols, without isomerisation of chiral centres. Changes of hydroxyl protective groups are possible in a one-pot procedure. The catalyst can be easily recycled. 相似文献
157.
Tanţa Spătaru Maria Marcu Loredana Preda Petre Osiceanu Jose Maria Calderon Moreno Nicolae Spătaru 《Journal of Solid State Electrochemistry》2011,15(6):1149-1157
Polytyramine (PTy) is shown to be a possible alternative to other conducting polymers as a support material for fuel cell
electrocatalysts such as platinum. In this work, a Pt–PTy composite was prepared via potentiodynamic deposition of polytyramine
on graphite substrate, followed by the electrochemical deposition of Pt nanoparticles. The material obtained by this straightforward
method exhibited, for platinum loadings as low as ca. 0.12 mg cm−2, a specific electrochemically active surface area of the electrocatalyst of ca. 54 m2 g−1, together with a good electrocatalytic activity for methanol oxidation in acidic media, thus ensuring better efficiency of
Pt utilization. The system Pt–PTy appears to be worthy of development for methanol fuel cell applications also because the
results suggested that, when deposited as small particles in a PTy matrix, platinum is less sensitive to fouling during CH3OH oxidation. 相似文献
158.
Adinolfi M Capasso D Di Gaetano S Iadonisi A Leone L Pastore A 《Organic & biomolecular chemistry》2011,9(18):6278-6283
Symmetrical glycosyl disulfides can be prepared within a few hours from per-O-acetylated precursors via a sequential approach entailing short reactions and no purification of any intermediate. The final thiolate-to-disulfide oxidation step is noticeably accelerated by low amounts of phenyl diselenide under air. Applicability of the strategy to non-saccharidic symmetrical alkyl disulfides has also been examined. A preliminary assay of the cytotoxic activity of symmetrical 1,1'- disulfides was performed on two human tumor cell lines, and a noteworthy activity was recorded for a range of these synthetic compounds. 相似文献
159.
Carotenoids are part of the human diet and a regular low-dose intake of these compounds from natural sources is normally preferred.
Carotenoid supplementation in various diseases, including cancer, was described to be useful, but evidence has been obtained
that high-dose supplementation of β-carotene may be unsafe, especially to smokers and asbestos-exposed workers, because of
a stastically detected increased cancer risk. The negative effect might be mediated by carotenoid breakdown products having
a high reactivity towards biomolecules. It has been suggested that these compounds originate from nonenzymatic cleavage of
carotenoids by oxidants liberated in large amounts by neutrophils that accumulate in various inflammatory diseases and, in
particular, in pulmonary disorders characterized by profound abnormalities in inflammatory pathways, such as those triggered
by tobacco smoking. Carotenoid breakdown products, in turn, may affect neutrophil response in different ways that depend on
the concentration that is reached by these products in the medium. In vitro studies show that nanomolar and micromolar concentrations of carotenoid derivatives stimulate superoxide production by neutrophils
activated by phorbol myristate acetate (PMA), while a slight inhibition is noticed with cells activated by the chemotactic
tripeptide N-formyl-Met-Leu-Phe (f-MLP). At higher concentrations, carotenoid breakdown products inhibit superoxide production
in the presence of both PMA and f-MLP.
相似文献
160.
Bartolo Gabriele Pierluigi Plastina Lucia Veltri Giuseppe Salerno 《Tetrahedron letters》2010,51(27):3565-1580
A simple and economical synthesis of substituted furans and pyrroles, by ligand-free CuCl2-catalyzed heterocyclodehydration of readily available 3-yne-1,2-diols and N-Boc- or N-tosyl-1-amino-3-yn-2-ols, respectively, is presented. Reactions are carried out in MeOH at 80-100 °C for 1-24 h and afford the corresponding heterocyclic derivatives in 53-99% isolated yields. 相似文献