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1.
An amperometric biosensor for the determination of l-lysine based on l-lysine-α-oxidase immobilized by co-crosslinking on a platinum electrode previously modified by an overoxidized polypyrrole film is described. The optimization of experimental parameters, such as pH and flow rate, permitted to minimize significantly substrate interferences even using a low specific, commercial enzyme. The relevant biases introduced in the measurement of lysine were just about 1% for l-arginine, l-histidine and l-ornithine, roughly 4% for l-phenylalanine and l-tyrosine. The developed approach allowed linear lysine responses from 0.02 mM up to 2 mM with a sensitivity of 41 nA/(mM × mm2) and a detection limit of 4 μM (S/N = 3). No appreciable loss in lysine sensitivity was observed up to about 40 days. Allowing polypyrrole layer to remove interference from electroactive compounds, the present method revealed suitable to detect l-lysine in a pharmaceutical and cheese sample, showing a good agreement with the expected values. 相似文献
2.
G.M.N. Costa T. Dias M. Cardoso Y. Guerrieri F.L.P. Pessoa S.A.B. Vieira de Melo M. Embiruu 《Fluid Phase Equilibria》2008,267(2):140-149
A large number of equations of state and activity coefficient models capable of describing phase equilibria in polymer solutions are available today, but only a few of these models have been applied to different systems. It is therefore useful to investigate the performance of existing thermodynamic models for complex polymer solutions which have not yet been widely studied. The present work studies the application of several activity coefficient models [P.J. Flory, Principles of Polymer Chemistry, Cornell University Press, New York, NY, 1953; T. Oishi, J.M. Prausnitz, Estimation of solvent activities in polymer solutions using a group-contribution method, Ind. Eng. Chem. Process Design Dev. 17 (1978) 333; H.S. Elbro, A. Fredenslund, P. Rasmussen, A new simple equation for the prediction of solvent activities in polymer solutions, Macromolecules 23 (1990) 4707; G.M. Kontogeorgis, A. Fredenslund, D. Tassios, Simple activity coefficient model for the prediction of solvent activities in polymer solutions, Ind. Eng. Chem. Res. 32 (1993) 362; C. Chen, A segment-based local composition model for the Gibbs energy of polymer solutions, Fluid Phase Equilib. 83 (1993) 301; A. Vetere, Rules for predicting vapor–liquid equilibria of amorphous polymer solutions using a modified Flory–Huggins equation, Fluid Phase Equilib. 97 (1994) 43; C. Qian, S.J. Mumby, B.E. Eichinger, Phase diagrams of binary polymer solutions and blends, Macromolecules 24 (1991) 1655; Y.C. Bae, J.J. Shim, D.S. Soane, J.M. Prausnitz, Representation of vapor–liquid and liquid–liquid equilibria for binary systems containing polymers: applicability of an extended Flory–Huggins equation, J. Appl. Polym. Sci. 47 (1993) 1193; G. Bogdanic, J. Vidal, A segmental interaction model for liquid–liquid equilibrium calculations for polymer solutions, Fluid Phase Equilibria 173 (2000) 241] and activity coefficient from equations of state [F. Chen, A. Fredenslund, P. Rasmussen, Group-contribution Flory equation of state for vapor–liquid equilibria en mixtures with polymers, Ind. Eng. Chem. Res. 29 (1990) 875; M.S. High, R.P. Danner, Application of the group contribution lattice—fluids EOS to polymer solutions, AIChE J. 36 (1990) 1625]. The evaluation of these models was carried out both at infinite dilution and at finite concentrations and the results compared to experimental data. Furthermore, liquid–liquid equilibrium predictions for binary polymer solutions using six activity coefficient models are compared in this work. The parameters were estimated for all the models to achieve the best possible representation of the reported experimental equilibrium behavior. 相似文献
3.
Liquid chromatography with on-line anodic amperometric detection is used after a liquid/solid extraction step for the determination of the anticancer drug 5-fluorouracil added to blood serum. A detection limit of 15 ng ml?1 can be achieved. The anodic electrochemical behaviour of the drug at a mercury electrode, which is the basis of the detection principle, is also described. Anodic amperometric detection at a mercury electrode is compared with detection at a glassy carbon electrode in terms of sensitivity, linearity and selectivity. 相似文献
4.
Guerrieri F Maccone L Wong FN Shapiro JH Tisa S Zappa F 《Physical review letters》2010,105(16):163602
The Rayleigh diffraction bound sets the minimum separation for two point objects to be distinguishable in a conventional imaging system. We demonstrate sub-Rayleigh resolution by scanning a focused beam--in an arbitrary, object-covering pattern that is unknown to the imager--and using N-photon photodetection implemented with a single-photon avalanche detector array. Experiments show resolution improvement by a factor ~(N-N(max))(?) beyond the Rayleigh bound, where N(max) is the maximum average detected photon number in the image, in good agreement with theory. 相似文献
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6.
S. Santucci S. Guerrieri M. Passacantando P. Picozzi F. Fam N. Nardi F. Basile 《Journal of Non》2001,280(1-3):54-58
Silicon oxide has been grown by rapid thermal processing. The growth rate, in the range of very thin films (<10 nm), has been studied as a function of the oxidation temperature. Combined films composed by conventional thermal silicon oxide growth over SiO2 passivation layer deposited by rapid thermal processing onto Si(1 0 0) substrates have been used as gate oxide of p-channel metal-oxide semiconductor (p-MOS) transistors of dynamic random access memory (DRAM). The effect of rapid thermal annealing treatments on these films has also been experimented. Improvements in the electrical performances of transistors have been observed. 相似文献
7.
Georg Reichel Martin Balleer Hans Storck Borsetti Guerrieri Braakman Kwakman Verbraak Coe Courtis Friend Hogstroem Hazlehurst Heinicke Heubeck Johnsen Aabakken Kaiser Kolehmainen Kühle Lyon Myers Scarpa Schaetzle Vaucher Smith Tanskanen Thomas Wylie Nikolaus Müller 《Bl?tter der DGVFM》1972,10(4):561-577
8.
A comprehensive account is given of the behavior of the eigenvalues of Mathieu's equation as functions of the complex variable q. The convergence of their small-q expansions is limited by an infinite sequence of rings of branch points of square-root type at which adjacent eigenvalues of the same type become equal. New asymptotic formulae are derived that account for how and where the eigenvalues become equal. Known asymptotic series for the eigenvalues apply beyond the rings of branch points; we show how they can now be identified with specific eigenvalues. 相似文献
9.
Guerrieri Anna 《代数通讯》2013,41(12):4447-4460
Let (R,m) be a local ring and Ian ideal of R. In this work we find conditions on Ithat allow us to describe simple relations among depth R(It), depth grI(R), depth S(I) and depth S(I/I 2). These relations are useful also from a practical point, of view since it is usually difficult to evaluate depth grI(R) and depth S(I/I 2) even with the help of a computer. Furthermore we study the class of ideals that satisfy one of the required conditions and we show that ideals generated by quadratic sequences are in this class 相似文献
10.
D. Centonze A. Guerrieri C. Malitesta F. Palmisano P. G. Zambonin 《Fresenius' Journal of Analytical Chemistry》1992,342(9):729-733
Summary An amperometric glucose sensor is described; it is based on glucose oxidase immobilized in an overoxidized non-conducting polypyrrole membrane. The overoxidation process of polypyrrole produces a permselective, antifouling membrane capable of rejecting ascorbate, urate, acetaminophen and cysteine, as well as proteins and other surface active components typically present in serum. The amperometric assay of glucose in serum correlates well with an established routine procedure based on an enzymatic-colorimetric method. 相似文献