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81.
In this work, the analysis the response to vibrations of a small building equipped with an electromechanical vibration absorber is investigated. In the first part, the case of harmonic excitation with constant or time dependent frequencies is considered, and in the second part, the case of random earthquakes, respectively. The cross correlation functions and the mean square displacements are calculated for the structure when it is equipped with an electromechanical vibration absorber. The stochastic process which characterizes the earth movements is coupled to the cnoidal method, which delivers the analytical solutions of the nonlinear problem. The interaction between the structure and the energy source is analyzed via the Sommerfeld effect inside the resonance region. The resonance capture and the vibration reduction are displayed by the time history responses of the displacement and angular velocities above the resonance. 相似文献
82.
Angel Leiva Csar Saldías Caterina Quezada Alejandro Toro-Labb Francisco J. Espinoza-Beltrn Marcela Urzúa Ligia Gargallo Deodato Radic 《European Polymer Journal》2009,45(11):3035-3042
Block copolymers have been extensively used in the synthesis of many types of nanoparticles, where generally are considered as stabilizer and protective agent. In this work a double function of the biodegradable triblock copolymer poly(N-vinyl-2-pyrrolidone)-b-poly(ε-caprolactone)-b-poly(N-vinyl-2-pyrrolidone), (PVP–PCL–PVP) in the gold nanoparticle-copolymer synthesis is reported.Gold-copolymer composed nanoparticles were synthesized using the triblock copolymer (PVP–PCL–PVP) and potassium tetrachloro aurate (III), both in aqueous solution. The copolymer work as both, reductant and stabilizer agent. The obtained nanoparticles were characterized by FT-IR, dynamic light scattering (DLS), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The shape and the size of the obtained nanoparticles are dependent on the copolymer/salt of gold concentration ratio used in the synthesis.To complement the experimental results about the copolymer role in the nanoparticles synthesis, computational tools were used to characterize the reactivity of the reactant species. 相似文献
83.
Sarah C. W. S. E. Franco de Oliveira Alexandre D. Zucoloto Carolina D. R. de Oliveira Edna M. M. Hernandez Ligia V. G. Fruchtengarten Tiago F. de Oliveira Mauricio Yonamine 《Journal of mass spectrometry : JMS》2019,54(7):ii-ii
A fast and simple approach to overcome challenges in emergency toxicological analysis, using ultra‐high performance liquid chromatography–tandem mass spectrometry (UHPLC‐MS/MS) has been developed, for the detection of analytes in blood and urine samples from the following drug classes: analgesics, benzodiazepines, antidepressants, anticonvulsants, drugs of abuse, and pesticides. These substances are relevant in the context of emergency toxicology in Brazil. The sample preparation procedure was relatively easy and fast to perform. The method was fully validated giving limits of in the range of 0.5 and 20 ng mL?1 for blood and urine samples. The intraday and interday precision and accuracy were considered adequate for all analytes once the relative standard deviation (RSD) (%) was lower than 20% for quality control (QC) low and lower than 15% for CQ medium and high. The developed method was successfully applied to 320 real samples collected at the Poison Control Center of São Paulo, and 89.1% have shown to be positive for some of the analytes. This confirms its applicability and importance to emergency toxicological analysis, and it could be very useful in both fields of clinical and forensic toxicology. 相似文献
84.
John Nicolson Low Antonio Quesada Luís M. N. B. F. Santos B. Schröder Ligia R. Gomes 《Journal of chemical crystallography》2009,39(10):747-752
Abstract The crystal structure of 2-thoiphenecarboxamide is described. The compound crystallizes in the orthorhombic Pna21 space group with unit cell parameters a = 10.044 (3) ?, b = 14.203 (4) ? and c = 15.941 (3) ?; V = 2,274.1 (10) ?3. The asymmetric unit contains four independent molecules which are linked by N–H···O hydrogen bonds. The asymmetric unit
at (x, y, z) is connected with another one, produced by the a-glide plane at 0.75 along the b-axis, that lies at (x + 0.5, −y + 1.5, z) by two N–H···O hydrogen bonds and by a C–H···O weak hydrogen bond to form a one-dimensional tube. Adjacent tubes are linked
by C–H···pi interactions to form a three-dimensional framework.
Graphical Abstract The crystal structure of 2-thiophenecarboxamide, contains four crystallographically independent molecular components in the
asymmetric unit linked by four N–H···O hydrogen bonds and a weak C–H···O hydrogen bond and form a one-dimensional tube.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
85.
Ligia Todan Cristian Andronescu Dumitru Mircea Vuluga Daniela C. Culita Maria Zaharescu 《Journal of Thermal Analysis and Calorimetry》2013,114(1):91-99
Phosphosilicate glasses are of great interest in important fields, such as optical active systems, energy generating systems, humidity sensors, and as materials for biomedical applications. Many studies were accomplished to establish the influence of different reaction parameters on the evolution and final structure of sol–gel prepared phosphosilicate gels. In the present work, we studied the thermal behavior of the silicophosphate gels obtained starting with different phosphorous precursors, the influence of these precursors on the composition and structure of the resultant gels, and their evolution with thermal treatment. By Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and thermodifferential analysis (DTA/TG), and Differential Scanning calorimetry coupled with Mass Spectrometry (DSC-MS), it was established that the type of the precursors essentially influences the composition and structure and consequently the thermal behavior of the obtained gels. In the case of triethylphosphate precursor, all used methods of investigation have shown that the ester is trapped in the silica matrix and it is eliminated during the thermal treatment. Triethylphosphite partially hydrolizes and reacts with the silica network during post-preparation thermal treatment. Only in the case of H3PO4, an interaction with TEOS takes place and leads to Si–O–P bond formation. By thermal treatment, the gels with different composition and structure lead to materials with different properties. 相似文献
86.
Maria Zaharescu Maria Crisan Luminita Predoana Mariuca Gartner Dana Cristea Stefania Degeratu Elena Manea 《Journal of Sol-Gel Science and Technology》2004,32(1-3):173-177
In the present work, the influence of substituted Si-alkoxides on the structural and optical properties of films obtained in the SiO2-TiO2 system was studied. Methyltriethoxysilane (MTEOS) and 3-(tri-methoxysilyl)propyl methacrylate (TSPM) were used as SiO2 sources and Ti(OBu)4 was used as TiO2 source. Acetylacetone was added to the Ti(OBu)4 as chelating agent and the synthesis was carried out in acid medium. The films were deposited on oxidized Si-wafers by spin-coating. The films were characterized by XRD, spectro-ellipsometry (SE), and atomic force microscopy (AFM). The results obtained have shown that in the case of hybrid films the desired thickness could be obtained in a single deposition step. The thickness of the films and the optical properties are controlled by the bulkiness of the organic substitute bounded to Si. Among other optical applications, the potential use of such films as optical waveguides is proposed. 相似文献
87.
Paula V.S. Rizzo Ligia A. Boarin Ingridhy O.M. Freitas Roberto S. Gomes Adilson Beatriz Andrelson W. Rinaldi Nelson Luís C. Domingues 《Tetrahedron letters》2014
This Letter introduces a new, cheap and green protocol for the thio-Michael reaction. Here we applied three free enzymes such as lipase from pancreas porcine, chymosin and papain and an immobilized one: the Liposyme®. The reactions were executed at room temperature and resulted in the thio-Michael adduct in good or excellent yields. The protocol describes the use of EtOH as solvent and a less percentage of enzymes, which is in concordance with the green chemistry topics, so we can mention that chymosin and papain were used as biocatalyst in an organic reaction for the first time in this Letter. 相似文献
88.
A two-dimensional finite difference lattice Boltzmann model for two-component fluid systems is introduced. Phase separaton
is achieved using an appropriate expression of the bulk free energy. Flux limiter techniques are used to improve the numberical
accuracy of this model. 相似文献
89.
Dorina Strugaru Eleonora Trif V. Cristea Gabriela Gheorghe R. Russu 《Radiation Physics and Chemistry》1995,45(6):917-922
The EPR spectroscopy has been used to study the interaction of vanadium pentoxide with H-ZSM-5 zeolite, supplied by ICITPR-Ploiesti, Romania, occurring at the calcination of the mixture at temperatures from 100 to 1000°C, in air, followed by evacuation at 20°C, as well as for those rehydrated at room temperature. The EPR method is also used to follow the thermal stability of the investigated zeolite, the framework alteration and the nature of VO2+ complexes formed during solid phase reaction. At least two types VO2+ centres were identified in H-ZSM-5 zeolite. One of them being ascribed to dehydrated VO2+ complexes in cationic sites, with C4v ligand field symmetry and the second one corresponding to the hydrated complex with a square bipyramidal symmetry, D4h. Increasing covalent character, for the in-plane σ-bond and increasing ionic character for the out-of-plane π bond, have been found on rehydrated samples. For a low content of oxide ( 5% wt V2O5) in a mixture the thermal stability, T = 1070°C, of the zeolite phase is not affected by the presence of the reaction products. 相似文献
90.