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排序方式: 共有618条查询结果,搜索用时 546 毫秒
111.
César IC Byrro RM de Santana E Silva Cardoso FF Mundim IM de Souza Teixeira L Rezende KR da Silva EP Gomes SA de Sousa VA Bonfim RR Pianetti GA 《Biomedical chromatography : BMC》2012,26(7):851-856
A rapid method for the quantification of glucosamine in human plasma using high‐performance liquid chromatography coupled to tandem mass spectrometry was developed and validated. The sample preparation includes a simple deproteinization step, using d ‐[1‐13C] glucosamine hydrochloride as an internal standard. Chromatographic separation was performed on an ACE Ciano column using isocratic elution with acetonitrile and aqueous 2 mm ammonium acetate containing 0.025% formic acid (80:20). Selected reaction monitoring was performed using the transitions m/z 180.1 → m/z 72.1 and m/z 181.0 → m/z 74.6 to quantify glucosamine and internal standard, respectively. The method was validated and proved to be linear, accurate and precise over the range 50–5000 ng/mL of glucosamine. Recovery rates higher than 90% were obtained for both glucosamine and internal standard. No matrix effect was detected in the samples. The validated method was successfully applied to a pharmacokinetic study after oral administration of a powder for oral solution formulation containing glucosamine sulfate. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
112.
Gouveia CA Oliveira A Pinho S Vasconcelos C Carvalho F Moreira RF Dinis-Oliveira RJ 《Biomedical chromatography : BMC》2012,26(8):1041-1047
The development of analytical techniques that enable the use of hair as an alternative matrix for the analysis of drugs of abuse is useful for confirming the exposure in a larger time window (weeks to months, depending on the length of the hair shaft). In the present study a methodology aimed at the simultaneous quantification of cocaine and morphine in human hair was developed and validated. After decontamination, hair samples (20?mg) were incubated with a mixture of methanol/hydrochloric acid (2:1) at 65?°C overnight (~16?h) in order to extract the drugs of the matrix. Purification was performed by solid-phase extraction using mixed-mode extraction cartridges. After derivatization with N-methyl-N-(trimethylsilyl) trifluoroacetamide, blank, standards and samples were analyzed by gas chromatography/electron impact-mass spectrometry (GC-EI/MS). The method proved to be selective, as there were no interferences of endogenous compounds with the same retention time as cocaine, morphine and ethylmorphine (internal standard). The regression analysis for both analytes showed linearity in the range 0.25-10.00?ng/mg with correlation coefficients ranging from 0.9989 to 0.9991. The coefficients of variation oscillated between 0.83 and 14.60%. The limits of detection were 0.01 and 0.02?ng/mg, and the limits of quantification were 0.03 and 0.06?ng/mg for cocaine and morphine, respectively. The proposed GC-EI/MS method provided an accurate and simple assay with adequate precision and recovery for the quantification of cocaine and morphine in hair samples. The proof of applicability was performed in hair samples obtained from drug addicts enrolled in a Regional Detoxification Treatment Center. The importance of hair samples is highlighted, since positives results were obtained when urine immunoassay analyses were negative. Copyright ? 2012 John Wiley & Sons, Ltd. 相似文献
113.
Martins MA Rossatto M Prola LD Pizzuti L Moreira DN Campos PT Frizzo CP Zanatta N Bonacorso HG 《Ultrasonics sonochemistry》2012,19(2):227-231
The synthesis of 14 novel N-propargylic β-enaminones from the reaction of β-alkoxy vinyltrihalomethyl[carboxyethyl] ketones [R3C(O)CHC(R1)OMe, where R3 = CF3, CCl3, CO2Et and R1 = Me, Et, Pr, Bu, i-Pent, CH2CH2CO2Me] with propargyl amines [R2NHCH2CCH, where R2 = Pr, PhCH2] is reported. Yields, solvents and reaction times needed for reaction completion, by microwave irradiation (MW), conventional thermal heating (TH) and under ultrasound irradiation (US) are compared. The best results were obtained under US irradiation in good to excellent yields (70-93%). 相似文献
114.
García-Flores AF Moreira AF Kaneko UF Ardito FM Terashita H Orlando MT Gopalakrishnan J Ramesha K Granado E 《Physical review letters》2012,108(17):177202
A remarkable hardening (~30 cm(-1)) of the normal mode of vibration associated with the symmetric stretching of the oxygen octahedra for the Ba(2)FeReO(6) and Sr(2)CrReO(6) double perovskites is observed below the corresponding magnetic ordering temperatures. The very large magnitude of this effect and its absence for the antisymmetric stretching mode provide evidence against a conventional spin-phonon coupling mechanism. Our observations are consistent with a collective excitation formed by the combination of the vibrational mode with oscillations of Fe or Cr 3d and Re 5d occupations and spin magnitudes. 相似文献
115.
In this paper we use a Renormalization Group (RG) method to study the long-time asymptotics of nonlinear diffusion equations with time-dependent diffusion coefficients and nonlinearities which are marginal (or critical) with respect to the RG operator. These equations describe the time evolution of the average concentration of a passive scalar being advected by a random velocity field. We prove that, besides the expected diffusive behavior, there is an extra logarithmic correction which is the imprint of the critical nonlinearity. 相似文献
116.
Letícia P. Ferreira Andrei N. Moreira Thaís Delazare Geiza. Esperandio Oliveira Fernando Gomes Souza Jr. 《Macromolecular Symposia》2012,319(1):210-221
Summary: The petroleum has become our most important source of energy since the mid-1950s. It is due to its high energy density, easy transportability and relative abundance. However, along extraction, storage or transportation of oil, spill accidents may happen. This kind of accident causes severe impacts on the environment, being directly responsible for the destruction of the marine life, which affects the fishing and even tourism industries. Main goal of this work is related to the use of renewable sources aiming to obtain “absorbent green materials”. These materials were synthesized by a typical phenolic resin polycondensation route using cashew nut shell liquid (CNSL) as main phenolic compound. Focused on keep the green characteristic of the materials, furfuraldehyde from hemicellulose was used as aldehyde and the reaction was catalyzed using a small amount of sulfuric acid. Resins were characterized using Optical Microscopy, Scanning Electron Microscopy, Infrared Spectroscopy with Fourier Transformed (FTIR) and density tests. In addition, contraction of the oil spilled was studied in presence of resins. Obtained results demonstrated that synthesized resins present a good chemical similarity with oil, which produces a good interaction among resins and oil, making easy the contraction of the oil spot on the water and, consequently, the removal process of oil spilled on water. 相似文献
117.
Anderson N. Mendes Isabela Hubber Mônica Siqueira Gleyce Moreno Barbosa Davyson de Lima Moreira Carla Holandino José Carlos Pinto Marcio Nele 《Macromolecular Symposia》2012,319(1):34-40
Summary: This work aimed to produce poly(methyl methacrylate) nanoparticles for use in drug encapsulation. The polymer nanoparticles were produced using miniemulsion polymerization technique. Monomer miniemulsion showed moderate stability and polymer average particle size was about 90 nm. PMMA nanoparticles were tested for toxicity in human leukemic cell strain K562 and they did not show any adverse effect on cell viability. Therefore, poly(methyl methacrylate) nanoparticles are suitable to encapsulate antitumor agents. 相似文献
118.
Mayron César O. Moreira Marcus Ritt Alysson M. Costa Antonio A. Chaves 《Journal of Heuristics》2012,18(3):505-524
We propose simple heuristics for the assembly line worker assignment and balancing problem. This problem typically occurs
in assembly lines in sheltered work centers for the disabled. Different from the well-known simple assembly line balancing
problem, the task execution times vary according to the assigned worker. We develop a constructive heuristic framework based
on task and worker priority rules defining the order in which the tasks and workers should be assigned to the workstations.
We present a number of such rules and compare their performance across three possible uses: as a stand-alone method, as an
initial solution generator for meta-heuristics, and as a decoder for a hybrid genetic algorithm. Our results show that the
heuristics are fast, they obtain good results as a stand-alone method and are efficient when used as a initial solution generator
or as a solution decoder within more elaborate approaches. 相似文献
119.
We consider a trade policy model, where the costs of the home firm are private information but can be signaled through the output levels of the firm to a foreign competitor and a home policymaker. We compute the separating equilibrium and the Bayesian Nash equilibrium, and we compare the subsidies, firms' expected profits and home government's welfare in both equilibria, for different values of the own price effect parameter. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
120.
Natlia Aniceto Vanda Marques Joana D. Amaral Patrícia A. Serra Rui Moreira Cecília M. P. Rodrigues Rita C. Guedes 《Molecules (Basel, Switzerland)》2022,27(15)
Necroptosis has emerged as an exciting target in oncological, inflammatory, neurodegenerative, and autoimmune diseases, in addition to acute ischemic injuries. It is known to play a role in innate immune response, as well as in antiviral cellular response. Here we devised a concerted in silico and experimental framework to identify novel RIPK1 inhibitors, a key necroptosis factor. We propose the first in silico model for the prediction of new RIPK1 inhibitor scaffolds by combining docking and machine learning methodologies. Through the data analysis of patterns in docking results, we derived two rules, where rule #1 consisted of a four-residue signature filter, and rule #2 consisted of a six-residue similarity filter based on docking calculations. These were used in consensus with a machine learning QSAR model from data collated from ChEMBL, the literature, in patents, and from PubChem data. The models allowed for good prediction of actives of >90, 92, and 96.4% precision, respectively. As a proof-of-concept, we selected 50 compounds from the ChemBridge database, using a consensus of both molecular docking and machine learning methods, and tested them in a phenotypic necroptosis assay and a biochemical RIPK1 inhibition assay. A total of 7 of the 47 tested compounds demonstrated around 20–25% inhibition of RIPK1’s kinase activity but, more importantly, these compounds were discovered to occupy new areas of chemical space. Although no strong actives were found, they could be candidates for further optimization, particularly because they have new scaffolds. In conclusion, this screening method may prove valuable for future screening efforts as it allows for the exploration of new areas of the chemical space in a very fast and inexpensive manner, therefore providing efficient starting points amenable to further hit-optimization campaigns. 相似文献