排序方式: 共有83条查询结果,搜索用时 109 毫秒
61.
Julien Malherbe Fanny Claverie Aitor Alvarez Beatriz Fernandez Rosario Pereiro John L. Molloy 《Analytica chimica acta》2013
Quantitative analysis using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) remains challenging primarily due to the lack of appropriate reference materials available for the wide variety of samples of interest and to elemental fractionation effects. Isotopic dilution mass spectrometry (IDMS) is becoming the methodology of choice to address these issues because the different isotopes of an element represent near-perfect internal standards. In this work, we investigated the lithium borate fusion of powdered solid samples, including soils, sediments, rock mine waste and a meteorite, as a strategy to homogenously distribute, i.e. equilibrate the elements and the added isotopically enriched standards. A comparison of this methodology using two pulsed laser ablation systems (ArF* excimer and Nd:YAG) with different wavelengths as well as two ICP-MS instruments (quadrupole and double-focusing sector field) was performed. Emphasis was put on using standard equipment to show the potential of the proposed strategy for its application in routine laboratories. Cr, Zn, Ba, Sr and Pb were successfully determined by LA-ICP-IDMS in six Standard Reference Materials (SRMs) representing different matrices of environmental interest. Experimental results showed the SRM fused glasses exhibited a low level of heterogeneity (intra- and inter-sample) for both natural abundance and isotopically enriched samples (RSD <3%, n = 3, 1σ). A good agreement between experimental results and the certified values was also observed. 相似文献
62.
63.
While many types of bacteria have been engineered to produce an optical output in response to given analytes in a culture,
their use for extensive, in situ monitoring of distinct chemical species in soil is hampered by a dearth of practicable spreading
schemes. In this work, we report and validate a comprehensive system for the long-term preservation of Pseudomonas putida cells genetically designed for biosensing benzene, toluene, ethylbenzene, and xylenes (BTEX) in soil, along with a procedure
to formulate, spread, and vigorously activate such bacteria at the desired site and occasion. To this end, various known lyoprotectants
were tested for promoting the long-term maintenance of biosensor cells with quite variable outcomes. While a formulation of
inositol and maltodextrines was optimal for preservation of freeze-dried BTEX-sensing bacteria, adsorption of P. putida cells to corncob powder (an abundant residue of the corn industry) endowed the resulting material with a lasting viability
at ambient conditions. In any case, the thereby preserved bacterial biomass acquired physical and mechanical properties adequate
for formulating the biosensor agent in water-soluble but otherwise hard dry gelatine capsules with a long shelf life. When
such capsules were spread in a soil microcosm and subsequently liquefied with water or high humidity, the released microorganisms
formed spots that gave an intense luminiscent signal upon exposure to effectors of the sensor circuit implanted in the chromosome
of the P. putida strain. We argue that the procedures described here can facilitate implementation of wide-area biological detection strategies
for revealing the location of toxic or perilous chemicals. 相似文献
64.
Aitor Carretero Zacarías León Juan Carlos García-Cañaveras Ángela Zaragoza María José Gómez-Lechón María Teresa Donato Agustín Lahoz 《Analytical and bioanalytical chemistry》2014,406(22):5465-5476
Multiple analytical methods are required to comprehensively assess oxidative homeostasis and specific damage to macromolecules. Our aim was to develop a straightforward strategy for the fast assessment of global oxidative status and specific damage to DNA, proteins, and lipids. To this end, an analytical method, based on ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-MS/MS), was developed and validated for the quantification of 16 oxidative stress (OS) biomarkers. Some of these markers were unstable; thus, an easy sample treatment procedure, including fractionation and derivatization, was set up. The method was validated according to Food and Drug Administration (FDA) guidelines, and it provided good results in terms of intra- and inter-day precision (≤17.2 and 16 %, respectively), accuracy (relative error measurement between ?16.6 and 19.8 %), and linearity (R 2?>?0.994). The approach was applied to determine the oxidative insult provoked to cultured rat hepatocytes by cumene hydroperoxide and to analyze the liver and serum samples from patients diagnosed with nonalcoholic steatohepatitis. In both studies, significant differences were found if compared to the corresponding control groups; interestingly, ophthalmic acid was shown as an OS biomarker in both models for the first time. A key advantage of the novel approach in comparison with former multi-method approaches is that now a single method is applied to assess the 16 OS biomarkers. Its comprehensive capacity to profile oxidative homeostasis and damage in both in vitro and clinical samples has been illustrated, which indicates that the proposed approach is a good choice to evaluate whether OS is involved in physiological signals, diseases, or toxic events and to what extent. 相似文献
65.
Sabatier Jocelyn Oustaloup Alain Iturricha Aitor Garcia Lanusse Patrick 《Nonlinear dynamics》2002,29(1-4):363-385
The principles of CRONE control, a frequency-domain robust control designmethodology based on fractional differentiation, are presented.Continuous time-variant plants with asymptotically constant coefficientsare analysed in the frequency domain, through their representation usingtime-variant frequency responses. A stability theorem for feedbacksystems including time-variant plants with asymptotically constantcoefficients is proposed. Finally, CRONE control is extended to robustcontrol of these plants. 相似文献
66.
Palomo C Oiarbide M Landa A González-Rego MC García JM González A Odriozola JM Martín-Pastor M Linden A 《Journal of the American Chemical Society》2002,124(29):8637-8643
A new type of sugar-amino acid hybrid, which is comprised of a sugar unit (gluco-, galacto-, or mannopyranose) linked through a C-glycosidic linkage to the beta-position of an alpha-unsubstituted beta-amino acid unit, is presented. It is hypothesized that these new compounds, or the oligomeric peptides derived therefrom, might possess the structural features of beta-amino acid oligomers and the chemical and enzymatic resistance of C-glycosides to hydrolysis. The synthetic strategy is based on a new Mannich-type reaction between a chiral acetate enolate equivalent and alpha-amido sulfones derived from the corresponding sugar-C-glycoside aldehydes. While the sugar-C-glycoside aldehyde partner is prepared from well-established transformations on known sugar precursors, the lithium enolate derived from (1R)-endo-2-acetylisoborneol 3 is employed as the key element. This Mannich approach proceeds with essentially perfect diasteromeric control leading to the new beta-amino carbonyl adducts in good yields. Further, cleavage of the camphor auxiliary is smoothly performed by oxidative treatment with ammonium cerium nitrate (CAN). Complementarily, direct peptide-type coupling of the beta-amino carbonyl Mannich adducts with an alpha- or beta-amino acid residue and subsequent CAN-promoted detachment of the auxiliary yields dipeptide fragments bearing a sugar-containing aliphatic side chain and is a process that can be iterated. A preliminary conformational study based on the combination of experimental NMR data and molecular mechanics and molecular dynamics (MD) of one particular adduct is also provided. 相似文献
67.
Larrañaga A Mesa JL Pizarro JL Lezama L Chapman JP Arriortua MI Rojo T 《Dalton transactions (Cambridge, England : 2003)》2005,(9):1727-1733
Two new manganese(II) selenite polymorphs with formula Mn(SeO3) have been synthesised using supercritical hydrothermal conditions. The crystal structure of both compounds (1) and (2) has been solved from single-crystal X-ray diffraction data. The structures consist of a three-dimensional framework formed by MnO6 octahedra and (SeO3)2- selenite anions with trigonal pyramidal geometry. Compound (1) shows chains of elongated, corner-sharing MnO6 octahedra. These chains are linked alternately by Mn2O10 dimers of edge-sharing octahedra. Conversely, compound (2) exhibits MnO6 octahedra sharing edges with three further octahedra, giving rise to a complex three-dimensional framework. The IR spectra show the characteristic bands of the selenite anion. Studies of luminescence and diffuse reflectance spectroscopy, performed at 6 K and at room temperature, respectively, have been carried out for both compounds. The Dq and Racah parameters are Dq= 830, B= 500 and C= 3790 cm(-1) for (1) and Dq= 795, B= 520 and C= 3785 cm(-1) for (2). The EPR spectra of both compounds are isotropic with a g-value of 1.99(1), which remains unchanged with variation in temperature. Magnetic measurements indicate the presence of antiferromagnetic couplings as the major interactions in both phases, but with compound (2) exhibiting at low temperature a canting of antiferromagnetically aligned spins. The estimated J-exchange parameters are J/k=-2.2 and -1.93 for (1) and (2), respectively, with J'= -0.87 and -0.55 K. 相似文献
68.
Gual A Axet MR Philippot K Chaudret B Denicourt-Nowicki A Roucoux A Castillon S Claver C 《Chemical communications (Cambridge, England)》2008,(24):2759-2761
Ruthenium nanoparticles (RuNPs) were prepared through the hydrogenation of [Ru(COD)(COT)] (COD = 1,5-cyclooctadiene, COT = 1,3,5-cyclooctatriene) in the presence of diphosphites derived from carbohydrates as stabilizing agents, and interestingly, structural modifications of the diphosphite backbone were found to influence nanoparticle size and dispersity, as well as their catalytic activity in arene hydrogenation. 相似文献
69.
Elena Guinea Asier Salicio-Paz Aitor Iriarte Hans-Jürgen Grande Estíbaliz Medina Eva García-Lecina 《ChemistryOpen》2019,8(8):1094-1099
Aluminum electrodeposition can be carried out from several ionic liquid electrolyte formulations. Nevertheless, this plating process has not been industrialized so far because of the durability of the electrolytes and because the Al coatings obtained are non-fully homogeneous in terms of coating morphology and thickness distribution. In this work we electrodeposited Al coatings from a 3-butyl-1-ethylimidazolium tetrachloroaluminate electrolyte additivated with increasing concentrations of a new cost-effective additive: light aromatic naphtha solvent. Firstly, electrolytes were characterized by cyclic voltammetry, where changes in the electrochemistry of the process were identified. Then, surface characterization showed that Al coatings morphology turned out to be smoother, more homogeneous and more compact with increasing additive concentration. Furthermore, the process was scaled up to flat plates of 18 cm2 area and also on 25 cm2 parts designed with straight corners to demonstrate both the optimization of the electrolytic bath performance and its throwing power enhancement. 相似文献
70.
Martín Barquero Dolores Martín González Cándido Sánchez-Ortega Juana Vandeyar Morgan 《Aequationes Mathematicae》2021,95(5):841-865
Aequationes mathematicae - We take a categorical approach to describe ternary derivations and ternary automorphisms of triangular algebras. New classes of automorphisms and derivations of... 相似文献