Search results for "PERT"
showing 10 items of 7689 documents
The Calderón problem for the fractional Schrödinger equation
2020
We show global uniqueness in an inverse problem for the fractional Schr\"odinger equation: an unknown potential in a bounded domain is uniquely determined by exterior measurements of solutions. We also show global uniqueness in the partial data problem where the measurements are taken in arbitrary open, possibly disjoint, subsets of the exterior. The results apply in any dimension $\geq 2$ and are based on a strong approximation property of the fractional equation that extends earlier work. This special feature of the nonlocal equation renders the analysis of related inverse problems radically different from the traditional Calder\'on problem.
El puzle de Aronson (Jigsaw) como técnica para la lectura y análisis de textos científicos en las aulas universitarias
2015
El aprendizaje cooperativo nos permite, entre otras cosas, a través de sus distintas técnicas incrementar la motivación del alumnado, su rendimiento académico y mejorar las relaciones sociales en el aula. En este artículo vamos a desarrollar una experiencia educativa, realizada con alumnado del Máster de Formación del Profesorado durante varios cursos académicos, donde ponemos en práctica la técnica del Puzle de Aronson (Jigsaw) para la lectura y análisis de textos científicos.
Proton coupled electron transfer of ubiquinone Q2 incorporated in a self-assembled monolayer.
2011
We present a complete study of the reduction of ubiquinone Q(2) (UQ(2)) in simpler aqueous medium, over a pH range of 2.5 to 12.5. The short isoprenic chain ubiquinones (UQ(2)) were incorporated in a self-assembled monolayer. Under these conditions, the global 2e(-) electrochemical reaction can be described on the basis of a nine-member square scheme. The thermodynamic constants of the system were determined. The global 2e(-) process is controlled by the uptake of the second electron. The elementary electrochemical rate constants obtained by fitting of the experimental rate constant were k(s4) = 1.5 s(-1) for QH˙(+)(2)↔ QH(2), k(s5) = 1.5 s(-1) for QH˙↔ QH(-) and k(s6) = 1 s(-1) for Q˙(-)↔ …
Synthesis and characterization of acetazolamide complexes of Ni(II), Cd(II), Hg(II), and Ag(I)
1989
The preparation and characterization of K2Ni2(Acm)3·5H2O, Cd(Acm)·32 H2O, Hg(Acm)·12H2O, Ag2(Acm), and Ag2(Acm)(NH3) complexes are described. The spectral properties suggest that Acm interacts with the metal ions through the doubly deprotonated form as observed in the [Cu(Acm)(NH3)2(OH2)]2·2H2O complex, whose crystalline structure has been previously reported. The crystal field parameters of the Ni(II) complex indicate an octahedral environment for the metal ion in the solid and its aqueous, DMSO, and DMF solutions. UV spectra of all the Acm complexes until now synthesized are discussed.
Effect of Large Changes in Temperature and Pressure on the Thermodynamic Properties of Micellization and on the Distribution Constant of a Polar Solu…
1996
Density measurements of pentanol (PentOH)−dodecyltrimethylammonium bromide (DTAB)−water mixtures as functions of both alcohol and surfactant (mS) concentrations were carried out at 0.1 MPa from 45 to 75 °C and at 19 MPa from 25 to 130 °C. The standard (infinite dilution) partial molar volumes and expansibilities of DTAB in water and the corresponding properties in the micellar phase were calculated from the experimental data. As far as PentOH in DTAB micellar solutions is concerned, with the exception of the standard partial molar volume (V°R) data at 130 °C and 19 MPa, all the V°R vs mS trends are monotonic curves with mS. The data of V°R as a function of mS were treated by means of an equ…
Aqueous nonionic copolymer-functionalized laponite clay. A thermodynamic and spectrophotometric study to characterize its behavior toward an organic …
2006
The affinity of functionalized Laponite clay toward an organic material in the aqueous phase was explored. Functionalization was performed by using triblock copolymers based on ethylene oxide (EO) and propylene oxide (PO) units that are EO(11)PO(16)EO(11) (L35) and PO(8)EO(23)PO(8) (10R5). Phenol (PhOH) was chosen as organic compound, which represents a contaminant prototype. To this purpose, densities and enthalpies of mixing as well as PhOH UV-absorption spectra were determined. The enthalpy and the spectrophotometry revealed PhOH-Laponite interactions whereas the volume did not. It emerged that the area occupied by PhOH on the Laponite surface is equal to that computed from the partial m…
Partial molar volumes of cobalt(II) chloride in ethanol + water at 298.15 K
1996
Densities of ethanol + water + cobalt(II) chloride mixtures have been measured with an oscillating-tube densimeter over a large range of concentrations of salt, at 298.15 K. From these densities, apparent molar volumes of the electrolyte in these mixtures have been calculated, and partial molar volumes at infinite dilution have been evaluated, at different concentrations of alcohol in the solvent.
Thermodynamics of Solubilization of Pentanol in Sodium Dodecyl Sulfate-Dodecyldimethylamine Oxide Mixed Micelles
1994
Abstract Heat capacity and density measurements of pentanol (PeOH)-sodium dodecyl sulfate (NaDS)-dodecyldimethylamine oxide-water mixtures were carried out at 0.03 m PeOH as a function of the total surfactants concentration (mc) at different ratios (XNaDS). From experimental data, the apparent molar volumes (VΦ,R) and heat capacities (CΦ,R) of PeOH in the surfactants mixture solutions were calculated. As a general feature, at a given mixture composition, VΦ,R increases monotonically with mt as observed in pure surfactants. In the cases of XNaDS = 0.1 and 0.3, VΦ,R drops at about 0.1 and 0.15 mt respectively. The decreasing CΦ,R VS mt curve shows peculiarities which were ascribed to the pres…
Apparent molar volumes of lithium nitrate in 1-propanol + water in the temperature range from 288.15 to 318.15 K
2002
Abstract Densities of 1-propanol+water+lithium chloride mixtures have been measured with an oscillating-tube densimeter over a large range of concentrations of the salt and 1-propanol at 288.15, 298.15, 308.15, and 318.15 K. From these densities, apparent molar volumes of lithium chloride in 1-propanol+water mixtures have been calculated for each temperature, and apparent molar volumes at infinite dilution have been evaluated. An empirical correlation for partial molar volumes of lithium chloride in 1-propanol+water mixtures with solvent composition and temperature has been derived.
Structural Characterization of Zirconia Nanoparticles Prepared by Microwave-Hydrothermal Synthesis
2009
Nanocrystalline zirconia powders have been prepared by microwave-hydrothermal synthesis starting from aqueous solution of ZrOCl2·8H2O. Results of investigations on the aqueous suspension stability of the washed zirconia nanopowders by dynamic light scattering showed that the suspension, constituted by superaggregates of nanoparticles (131 ± 10 nm), was stable up to 15 days. Nanopowders were investigated by means of transmission electron microscopy and small angle x-ray scattering measurements which proved that the zirconia nanopowder is constituted by small primary nanoparticles of ca. 8 nm that agglomerate forming bigger aggregates of 50 ± 1 nm.