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311.
Sbaraglia G Pitzurra L Moroni B Nocentini A Vitali M Poli G Miliani C Bistoni F 《Annali di chimica》2003,93(11):889-896
The microbial activity plays an important role in the biodegradative processes implied in stonework decay. In natural environments it is not possible to separate the damage produced by microorganisms from damage caused by physical and chemical agents. In vitro assays carried out with microbes isolated from weathered stones are required in order to understand the biological mechanisms involved in stone deterioration. We have described, as commented in the text, how fungal colonization observed on scaglia may be the result of the fine grain size of rock, whereas inhibition of growth on marble may depend on the surface characteristics of calcite grains after grinding. The extent of microbial growth clearly depends on the quantity of cations released in solution. However, fungal growth may, in turn, induce a decrease in pH, thus promoting mineral chemical attack. These observation points to selective action of fungal species in promoting weathering well evidenced by the presence of different extents of cations released in suspension from the same sample. Detailed studies are in progress in order to go into this question. 相似文献
312.
Darimont BD 《Chemistry & biology》2003,10(8):675-676
Recently developed approaches to generate drugs that regulate hormone-induced gene activation focus on modulating the interaction of nuclear receptors with coactivators. A study by Geistlinger and Guy demonstrates the feasibility of this approach and provides surprising evidence for specificity within the conserved nuclear receptor:coactivator interaction surface. 相似文献
313.
314.
We have obtained a large number of solutions to the aesthetic field equations. We discuss 19 solutions which appear to lead to bounded particle systems. One of the solutions is more complex (although only slightly) than the solution discussed in detail in Muraskin and Ring (1975). The solutions we have found have varied mathematical properties. 相似文献
315.
316.
Well-posedness for Optimization Problems with Constraints defined by Variational Inequalities having a unique solution 总被引:3,自引:0,他引:3
We introduce various notions of well-posedness for a family of variational inequalities and for an optimization problem with constraints defined by variational inequalities having a unique solution. Then, we give sufficient conditions for well-posedness of these problems and we present an application to an exact penalty method. 相似文献
317.
Elisa Perissutti Francesco Frecentese Ferdinando Fiorino Beatrice Severino Donatella Cirillo Vincenzo Santagada Giuseppe Caliendo 《Journal of heterocyclic chemistry》2007,44(4):815-819
1,3 Dipolar cycloaddition of Fmoc‐amino azides and acetylenic amides produces under solvent free irradiation a mixture of 1,4 or 1,5 substituted [1,2,3]‐triazoles. The presence of copper (I) iodide, plays a central role on regioselectivity. Four Fmoc‐amino azides characterized by different steric hindrance in side chains, and three different terminal alkynes, provided only the 1,4 substituted regioisomer under thermal microwave heating. Good yields, low consumption of organic solvents and short reaction times are the main aspects of our procedure. Reactions are compared to regioselective copper (I) catalysed solution synthesis performed at room temperature. 相似文献
318.
Bocca B Lamazza A Pino A De Masi E Iacomino M Mattei D Rahimi S Fiori E Schillaci A Alimonti A Forte G 《Rapid communications in mass spectrometry : RCM》2007,21(11):1776-1782
An analytical procedure applicable to restricted sample sizes was developed and applied to the analysis of 30 chemical elements in colorectal biopsies of healthy patients. Acidic microwave digestion processed =10 mg of tissue at 80 degrees C in 15-mL polystyrene liners. The digests were diluted to a volume of 2 mL with high-purity water and directly analyzed by sector field inductively coupled plasma mass spectrometry without further specimen handling. A careful selection of isotopes and instrumental resolution permitted the quantification in a single analytical sequence both of the elements present at parts per trillion and of those at parts per million. The accuracy calculated on BCR 184 ranged from 93.3-110%, the recoveries of the biopsy material was in the range 95.2-105%, the precision was <10%, and the blank levels were much below those expected in biopsy samples. The metal concentrations (on a dry-weight basis) in colorectal normal tissue showed a large range of variation: Ag, Au, Be, Bi, Co, Li, Sb, Tl, V, W and Zr were below 50 ng g(-1); As, Ba, Cd, Cr, Cs, Hg, Mo, Ni, Pb, Se and Sn were distributed from 100 to 500 ng g(-1); Al, Cu, Fe, Mn, Sr and Zn were from a few microg g(-1) to 100 microg g(-1); and Ca and Mg were at a level of 1000 microg g(-1). These data represent the first attempt to achieve an elemental profile in the colorectal mucosa of healthy patients as baseline level measurements for studies focused on the imbalance of chemical elements in diseased mucosa. 相似文献
319.
Andrew D. Wiersum Estelle Soubeyrand‐Lenoir Dr. Qingyuan Yang Dr. Beatrice Moulin Vincent Guillerm Dr. Mouna Ben Yahia Dr. Sandrine Bourrelly Dr. Alexandre Vimont Dr. Stuart Miller Dr. Christelle Vagner Prof. Marco Daturi Dr. Guillaume Clet Dr. Christian Serre Dr. Guillaume Maurin Dr. Philip L. Llewellyn 《化学:亚洲杂志》2011,6(12):3270-3280
In addition to its high thermal stability, repetitive hydration/dehydration tests have revealed that the porous zirconium terephthalate UiO‐66 switches reversibly between its dehydroxylated and hydroxylated versions. The structure of its dehydroxylated form has thus been elucidated by coupling molecular simulations and X‐ray powder diffraction data. Infrared measurements have shown that relatively weak acid sites are available while microcalorimetry combined with Monte Carlo simulations emphasize moderate interactions between the UiO‐66 surface and a wide range of guest molecules including CH4, CO, and CO2. These properties, in conjunction with its significant adsorption capacity, make UiO‐66 of interest for its further evaluation for CO2 recovery in industrial applications. This global approach suggests a strategy for the evaluation of metal–organic frameworks for gas‐based applications. 相似文献
320.
Fiorilli S Camarota B Garrone E Onida B 《Physical chemistry chemical physics : PCCP》2011,13(3):1201-1209
Proton-donor ability of carboxylic groups incorporated by co-condensation into SBA-15 and ethane-bridged periodic mesoporous organosilica (PMO) has been studied through IR spectroscopy by dosing ammonia, which forms reversibly COO(-) groups and NH(4)(+) ions. The related equilibrium constants, determined by elaboration of IR data, reveal a lower reactivity of -COOH groups at the surface of PMO than on SBA-15, when the two samples have been outgassed at the same temperature. This finding is interpreted in terms of different dielectric constants and intermolecular interactions engaged with the surface species. Carboxylic groups on ethane-bridged organosilica react with silanols upon thermal treatment at 473 K to form a mixed anhydride species Si-O-C(O)-, at variance with the same groups on SBA-15. 相似文献