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101.
In this article we present the first results obtained for nanostructured γ-Ni20Zn80 alloy prepared by a thermo-mechanical (TM) process developed in our laboratory. The process uses the energy stored in the defect structure, generated via mechanical milling of the nickel, to accelerate the reaction in the solid state, allowing a more rapid alloy formation. The process presents several advantages, when compared with techniques currently used for the production of this class of materials. The X-ray diffraction pattern for the alloy produced by the TM process is compared with that measured for the same alloy, produced by the mechanical alloying technique. The results show that the TM process holds the potential to become a valuable alternative method for the production of nanostructured materials. 相似文献
102.
Time and temperature induced phase transformation in L‐isoleucine hydrochloride monohydrated crystal
Ricardo S. Ferreira Júnior Geanso M. Moura Andreia C. Pereira Paulo R. da Silva Ribeiro Luzeli M. da Silva Adenilson O. dos Santos 《Crystal Research and Technology》2016,51(12):738-741
Semi organic crystals have been intensively studied aiming applications in nonlinear optical (NLO). Such applicability requires crystals with both high quality and thermal stability, which make the full characterization of this material a topic issue. In this paper, single crystals of L‐isoleucine hydrochloride monohydrated (L‐Ile.H2O.HCl) was synthesized by slow evaporation technique and characterized by thermal analysis and X‐ray diffraction (XRD) measurements. XRD results at 298 K showed that the sample crystallize with the orthorhombic structure, and the lattice parameters obtained by Rietveld refinement were a = 5.873(3) Å, b = 24.814(4) Å, and c = 6.873(5) Å. Thermal analysis measurements shows four decomposition stages between 328 ‐480 K which were associated with loss of water by desolvation, loss crystallization water and decomposition of L‐Ile.HCl. XRD measurements as a function of temperature up to 428 K show an irreversible phase transformation. This transformation was obtained after 32 hours keeping the L‐Ile.HCl.H2O sample at 413 K. The analysis shows that phase transformation occurs due to water and chlorine losses without destroy the amino acid carbon chain and in the end of transformation only the precursor amino acid remains. L‐Ile.HCl.H2O present low thermal stability and the phase transformation is time and temperature dependent. 相似文献
103.
Carla F. C. Ruschel Marcelo C. A. Marcelo Francisco P. dos Santos Marco F. Ferrão 《Analytical letters》2017,50(11):1767-1777
Automotive fuel adulteration is an old and significant problem. One common type of fuel adulteration is the addition of diesel to gasoline. Unsupervised models were developed through hierarchical cluster and principal component analysis models. Supervised models through partial least square discriminant analysis using 1H nuclear magnetic resonance spectra as the input were used to classify samples as adulterated or unadulterated. Quantitative models were developed using partial least squares to determine the gasoline and diesel concentrations in the samples. This set contained samples composed of pure gasoline and anhydrous ethanol reproducing commercial gasoline and other samples treated with diesel. Hierarchical cluster and principal component analysis did not distinguish between adulterated and unadulterated samples except for the most adulterated materials. However, partial least square discriminant analysis classified 100% of the samples correctly. The partial least square algorithm provided excellent regression models for the gasoline and diesel content. The determination coefficient was 0.9920 for both models, whereas the root mean square error of cross-validation and root mean square error of prediction for the diesel model were 2.32 and 1.42%, respectively, and 2.40 and 1.38% for the gasoline model. 相似文献
104.
Sidney Xavier dos Santos Éder T. G. Cavalheiro Christopher M. A. Brett 《Electroanalysis》2010,22(23):2776-2783
A new composite electrode based on multiwall carbon nanotubes (MWCNT) and silicone‐rubber (SR) was developed and applied to the determination of propranolol in pharmaceutical formulations. The effect of using MWCNT/graphite mixtures in different proportions was also investigated. Cyclic voltammetry and electrochemical impedance spectroscopy were used for electrochemical characterization of different electrode compositions. Propranolol was determined using MWCNT/SR 70 % (m/m) electrodes with linear dynamic ranges up to 7.0 µmol L?1 by differential pulse and up to 5.4 µmol L?1 by square wave voltammetry, with LODs of 0.12 and 0.078 µmol L?1, respectively. Analysis of commercial samples agreed with that obtained by the official spectrophotometric method. The electrode is mechanically robust and presented reproducible results and a long useful life. 相似文献
105.
Éder José dos Santos Amanda Beatriz Herrmann Charyane Satie Sato Tatiane Andrade Maranhão Adilson José Curtius 《Microchemical Journal》2010,96(1):27-216
Mercury and lead were determined in an extraction solution applied to compact fluorescent lamps by axial view inductively coupled plasma optical emission spectrometry (ICP OES). The solution contained 50% v/v HNO3 and 10% v/v H2O2. The compact fluorescent lamps were treated by removing the socket and breaking the rest of the lamp inside the solution, followed by placing the mixture in an ultrasonic bath for 1 h. The mixture was filtrated in a coarse paper filter and the resulting extraction slurry was analyzed. The determination of Pb in the slurry required calibration by the analyte addition technique, while for Hg, external calibration was adequate. The quantification limits (10 s, n = 7), for Hg (194.164 nm) and Pb (220.353 nm) were, respectively, 10 and 30 µg per lamp. Analysis of spiked samples demonstrated reasonable accuracy of the method, with recoveries in the range from 99 to 120% for Hg and from 91 to 107% for Pb. Fifteen analyzed samples showed Hg masses per lamp in the range from 1.6 to 27 mg, and six samples were above the limit allowed by the European Community that is 5 mg per compact lamp. The values for Pb were between 0.07 and 0.75 mg per lamp. By filtrating the slurry in a membrane filter, and analyzing the resulting solution, it was found that all Hg was extracted to the liquid phase of the slurry, while a fraction of about 40% m/v of Pb is retained in the solid particles. The lamp cover glass, after extraction of the phosphor layer, was also analyzed for Hg and Pb. The concentration of Hg in the glass is quite low; however, the Pb content is high. 相似文献
106.
Danielle da Silveira dos Santos Anna Carolina Camelo Kelly Cristina Pedro Rodrigues Luís Cláudio Carlos Nei Pereira Jr. 《Applied biochemistry and biotechnology》2010,161(1-8):93-105
Considerable efforts have been made to utilize agricultural and forest residues as biomass feedstock for the production of second-generation bioethanol as an alternative fuel. Fermentation utilizing strains of Zymomonas mobilis and the use of simultaneous saccharification and fermentation (SSF) process has been proposed. Statistical experimental design was used to optimize the conditions of SSF, evaluating solid content, enzymatic load, and cell concentration. The optimum conditions were found to be solid content (30%), enzymatic load (25 filter paper units/g), and cell concentration (4 g/L), resulting in a maximum ethanol concentration of 60 g/L and a volumetric productivity of 1.5 g L?1?h?1. 相似文献
107.
Denise Tofanello Gimenes Wallans Torres Pio dos Santos Rodrigo Alejandro Abarza Munoz Eduardo Mathias Richter 《Electrochemistry communications》2010,12(2):216-218
In this work, we describe for the first time the use of the internal standard method in flow injection analysis (FIA) with amperometric detection. The method is based on the application of sequential potential pulses to the working electrode in an electrochemical flow cell. The sequence of potential pulses is selected in such a way that the analyte and internal standard compound are detected and monitored individually and independently at the same working electrode. This approach compensates for random errors associated with variations of flow rate, injection volume, ionic strength difference between standards and samples, and accidental insertion or formation of air bubbles in the carrier stream. In addition, this method can overcome the major drawback of amperometric detection using solid electrodes, which is gradual electrode passivation. To illustrate the potential of this method, the flow-injection amperometric detection of uric acid using [Fe(CN)6]3? as an internal standard (IS) is presented as an example. 相似文献
108.
Marcelo Kobelnik Douglas Lopes Cassimiro Clóvis Augusto Ribeiro Diógenes dos Santos Dias Marisa Spirandeli Crespi 《Journal of Thermal Analysis and Calorimetry》2010,102(3):1167-1173
Two ONNO type naphtaldehyde derivative Schiff base compounds were reduced and two symmetric phenol-amine ligands containing
naphthalene groups were obtained; bis-N,N′[(2-hydroxy-1-naphtyl) methyl]-1,3-propanediamine (NAFLH) and bis-N,N′[(2-hydroxy-1-naphtyl) methyl]-2,2′-dimetyhyl-1,3-propanediamine (NAFLDMH). Homotrinuclear Ni(II) complexes of these ligands were prepared. The solid-state molecular structures of representative
nickel complex of NAFLDMH were determined using single crystal X-ray diffraction analysis. The terminal Ni(II) ions were found to be situated in between
the donor atoms of the organic ligand. The central Ni(II) ion was observed to be bonded via two different μ-bridges. The phenolic
oxygens and carboxylate ion were seen to form two different μ-bridges. TG analysis proved that the compounds have different
thermal characteristics than those cited in literature. The complexes showed extreme exothermic degradation reactions in inert
atmosphere. The complexes are ruptured with a two stepped exothermic reaction which appears huge heat over 300 °C. The heat
appeared in O2 atmosphere is observed to be higher than the heat appeared in inert atmosphere. Revealed heat is observed to be higher than
the conventional explosive materials. 相似文献
109.
Rodrigo S. Corrêa Marcelo H. dos Santos Tanus J. Nagem Javier Ellena 《Structural chemistry》2010,21(3):555-563
Oxygenated xanthones have been extensively investigated over the years, but there are few reports concerning their crystal
structure. Our chemical investigations of Brazilian plants resulted in the isolation of four natural products named 1-hydroxyxanthone
(I), 1-hydroxy-7-methoxyxanthone (II), 1,5-dihydroxy-3-methoxyxanthone (III), and 1,7-dihydroxy-3,8-dimethoxyxanthone (IV).
The structures of these compounds were established on the basis of single crystal X-ray diffraction. The xanthone nucleus
conformation is essentially planar with the substituents adopting the orientations less sterically hindered. In addition,
classical intermolecular hydrogen bonds (O–H···O) present in III and IV give rise to infinite ribbons. However, the xanthone
I does not present any intermolecular hydrogen bonds, meanwhile the xanthone II presents only a non-classical one (C–H···O).
The crystal packing of all xanthone structures is also stabilized by π–π interactions. The fingerprint plots, derived from
the Hirshfeld surfaces, exhibited significant features of each crystal structures. 相似文献
110.
Koen Sandra Alberto dos Santos Pereira Gerd Vanhoenacker Frank David Pat Sandra 《Journal of chromatography. A》2010,1217(25):4087-4099
A lipidomics strategy, combining high resolution reversed-phase liquid chromatography (RPLC) with high resolution quadrupole time-of-flight mass spectrometry (QqTOF), is described. The method has carefully been assessed in both a qualitative and a quantitative fashion utilizing human blood plasma. The inherent low technical variability associated with the lipidomics method allows to measure 65% of the features with an intensity RSD value below 10%. Blood plasma lipid spike-in experiments demonstrate that relative concentration differences smaller than 25% can readily be revealed by means of a t-test. Utilizing an advanced identification strategy, it is shown that the detected features mainly originate from (lyso-)phospholipids, sphingolipids, mono-, di- and triacylglycerols and cholesterol esters. The high resolution offered by the up-front RPLC step further allows to discriminate various isomeric species associated with the different lipid classes. The added value of utilizing a Jetstream electrospray ionization (ESI) source over a regular ESI source in lipidomics is for the first time demonstrated. In addition, the application of ultra high performance LC (UHPLC) up to 1200 bar to extend the peak capacity or increase productivity is discussed. 相似文献