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151.
We prove an existence result for forced oscillations of delay differential equations on compact manifolds with nonzero Euler-Poincaré characteristic. When the period is smaller than the delay we need the asymptotic fixed point index theory for C1 maps due to Eells and Fournier, and Nussbaum. 相似文献
152.
Roberta Filippucci Patrizia Pucci Frédéric Robert 《Journal de Mathématiques Pures et Appliquées》2009,91(2):156-177
Using the Mountain-Pass Theorem of Ambrosetti and Rabinowitz we prove that admits a positive weak solution in of class , whenever , and . The technique is based on the existence of extremals of some Hardy–Sobolev type embeddings of independent interest. We also show that if is a weak solution in of , then when either , or and u is also of class . 相似文献
153.
154.
The extraction of silica from powdered glass cullet with an aqueous solution of sodium hydroxide has been proposed as an alternative to glass recycling aimed to the low temperature production of sodium silicates. The unextracted residue obtained after a counter current two-step extractive process at approximately 100 degrees C and room pressure is mainly made of calcium and sodium silicate and shows high porosity and a large surface area. We thought that it could be active as an agent for the removal of heavy metals from wastewater. In this paper the capacity of the unextracted residue of removing six metal ions (i.e., Cu2+, Ni2+, Zn2+, Cd2+, Pb2+ e Cr3+) was studied in a stirred batch reactor. The data obtained demonstrate that the removal of metal ions from wastewater is achieved with high capacity in a short time and their concentration is lowered under the legal limits without any appreciable influence from changes of physical and chemical conditions. Sodium and calcium ions take the place of heavy metals in water while pH keeps almost neutral. The exchange mechanism was identified. 相似文献
155.
Aflatoxin M1 determination in cheese by liquid chromatography-tandem mass spectrometry 总被引:1,自引:0,他引:1
Cavaliere C Foglia P Guarino C Marzioni F Nazzari M Samperi R Laganà A 《Journal of chromatography. A》2006,1135(2):135-141
A new method for determining aflatoxin M1 (AFM1) in cheese by liquid chromatography-tandem mass spectrometry has been developed. Two methodologies were compared for sample extraction. The first one involves sample extraction with dichloromethane for hard, aged cheese or acetone for fresh cheese and includes a preliminary matrix solid-phase dispersion-extraction step before solid-phase extraction (SPE) clean-up by a Carbograph-4 cartridge. The second method uses a water/methanol solution (90:10, v/v) extraction at 150 degrees C before clean-up. The average recoveries of AFM1 from samples spiked at levels of 0.25-0.45 microg/kg, were 81-92% and the precision (RSD) ranged from 3 to 7% with the first method, whilst the average recoveries were 79-84%, and RSD ranged from 7 to 15% for the second method. Due to different matrix effect, the quantification limits were 0.019-0.025 microg/kg in the first case and 0.048-0.143 microg/kg in the second one, depending on cheese typology. 相似文献
156.
Gaetano Corso Monica Gelzo Angela Chambery Valeria Severino Antimo Di Maro Filomena Schiano Lomoriello Oceania D'Apolito Antonio Dello Russo Patrizia Gargiulo Ciro Piccioli Paolo Arcari 《Journal of separation science》2012,35(21):2986-2993
Spectroscopic and MS techniques were used to characterize the pigments and the composition of polar and nonpolar binders of a stray wall painting fragment from Liternum (Italy) archaeological excavation. X‐ray fluorescence and diffraction analysis of the decorations indicated mainly the presence of calcite, quartz, hematite, cinnabar, and cuprorivaite. Infrared spectroscopy, GC coupled to flame‐ionization detector, and MS analysis of the polar and nonpolar components extracted from paint layers from three different color regions revealed the presence of free amino acids, sugars, and fatty acids. Interestingly, LC‐MS shotgun analysis of the red painting region showed the presence of αS1‐casein of buffalo origin. Compared to our previous results from Pompeii's wall paintings, even though the Liternum painting mixture contained also binders of animal origin, the data strongly suggest that in both cases a tempera painting technique was utilized. 相似文献
157.
Cordero C Zebelo SA Gnavi G Griglione A Bicchi C Maffei ME Rubiolo P 《Analytical and bioanalytical chemistry》2012,402(5):1941-1952
Headspace solid-phase microextraction (HS-SPME) comprehensive two-dimensional (2D) gas chromatography combined with quadrupole-mass
spectrometry (GC×GC-qMS) with dedicated comparative data elaboration was applied to separate chemical patterns arising from
the interaction between some Mentha species and the herbivore Chrysolina herbacea, also known as the mint bug. Upon feeding on different Mentha species (Mentha spicata L., Mentha × piperita L. and Mentha longifolia L.), C. herbacea produced frass (faeces) which were characterized by a typical volatile fraction. HS-SPME GC×GC-qMS analysis of the complex
volatile fraction of both mint leaf and C. herbacea frass was submitted to advanced fingerprinting analysis of 2D chromatographic data. 1,8-Cineole, found in the leaves of all
the Mentha species examined, was oxidized, and C. herbacea frass yielded high rates of several hydroxy-1,8-cineoles, including 2α-hydroxy-, 3α-hydroxy-, 3β-hydroxy- and 9-hydroxy-1,8-cineole.
Upon insect feeding, several unknown oxidized monoterpenes, a p-menthane diol and three unknown phenylpropanoids were also detected in the frass volatiles. In M. longifolia, the occurrence of the monoterpene piperitenone oxide was found to be toxic and associated with insect death. The results
of this work show that high throughput techniques such as HS-SPME and GC×GC-qMS fingerprint analysis are ideal tools to analyze
complex volatile matrices, and provide a sensitive method for the direct comparison and chemical visualization of plant and
insect emitted volatile components. 相似文献
158.
Struss AK Pasini P Flomenhoft D Shashidhar H Daunert S 《Analytical and bioanalytical chemistry》2012,402(10):3227-3236
Quorum sensing (QS) allows bacteria to communicate with one another by means of QS signaling molecules and control certain
behaviors in a group-based manner, including pathogenicity and biofilm formation. Bacterial gut microflora may play a role
in inflammatory bowel disease pathogenesis, and antibiotics are one of the available therapeutic options for Crohn’s disease.
In the present study, we employed genetically engineered bioluminescent bacterial whole-cell sensing systems as a tool to
evaluate the ability of antibiotics commonly employed in the treatment of chronic inflammatory conditions to interfere with
QS. We investigated the effect of ciprofloxacin, metronidazole, and tinidazole on quorum sensing. Several concentrations of
individual antibiotics were allowed to interact with two different types of bacterial sensing cells, in both the presence
and absence of a fixed concentration of N-acylhomoserine lactone (AHL) QS molecules. The antibiotic effect was then determined by monitoring the biosensor’s bioluminescence
response. Ciprofloxacin, metronidazole, and tinidazole exhibited a dose-dependent augmentation in the response of both bacterial
sensing systems, thus showing an AHL-like effect. Additionally, such an augmentation was observed, in both the presence and
absence of AHL. The data obtained indicate that ciprofloxacin, metronidazole, and tinidazole may interfere with bacterial
communication systems. The results suggest that these antibiotics, at the concentrations tested, may themselves act as bacterial
signaling molecules. The beneficial effect of these antibiotics in the treatment of intestinal inflammation may be due, at
least in part, to their effect on QS-related bacterial behavior in the gut. 相似文献
159.
Colombo M Sommaruga S Mazzucchelli S Polito L Verderio P Galeffi P Corsi F Tortora P Prosperi D 《Angewandte Chemie (International ed. in English)》2012,51(2):496-499
Particularly suitable: An N-terminal serine mutant of anti-HER2 scFv antibody was conjugated to polymer-coated magnetofluorescent nanoparticles by strain-promoted alkyne-nitrone cycloaddition. The resulting nanoparticles (see scheme) proved effective in targeting and labeling HER2-positive breast cancer cells. 相似文献
160.
Ciminiello P Dell'Aversano C Dello Iacovo E Fattorusso E Forino M Grauso L Tartaglione L Guerrini F Pezzolesi L Pistocchi R Vanucci S 《Journal of the American Chemical Society》2012,134(3):1869-1875
Since 2005, the benthic dinoflagellate Ostreopsis cf. ovata has bloomed across the Mediterranean basin, provoking serious toxic outbreaks. LC/MS studies have identified a number of palytoxin-like compounds, termed ovatoxins, along with trace amounts of putative palytoxin as the causative agents of the O. cf. ovata -related human sufferings. So far, any risk assessment for ovatoxins as well as establishment of their allowance levels in seafood has been prevented by the lack of pure toxins. The present paper reports on the isolation, NMR-based structural determination, and preliminary mouse lethality evaluation of ovatoxin-a, the major toxic compound contained in O. cf. ovata extracts. Availability of pure ovatoxin-a will open the double prospect of fully evaluating its toxicity and preparing reference standards to be employed in LC/MS quantitative analyses. Elucidation of ovatoxin-a's complex structure will ultimately herald the understanding of the molecular bases of ovatoxins bioactivity. 相似文献