Search results for " física"
showing 10 items of 920 documents
Facultat de Física i Optometria
2008
La Universitat de València t'obri les seues portes. En les seues Facultats i Escoles Universitàries descobriràs una àmplia oferta d'estudis, equipament docent d'última tecnologia, instal·lacions esportives i culturals i una completa xarxa de biblioteques. Tot el que necessites per a accedir a una formació integral que garantisca el teu futur professional.
Spatial modulation of the electromagnetic energy transfer by excitation of graphene waveguide surface plasmons
2019
We theoretically study the electromagnetic energy transfer between donor and acceptor molecules near a graphene waveguide (WG). The surface plasmons (SPs) supported by the structure provide decay channels which lead to an improvement in the energy transfer rate when the donor and acceptor are localized on the same side or even on opposite sides of the WG. The modification of the energy transfer rate compared to its value in absence of the WG are calculated by deforming the integration path into a suitable path in the complex plane. Our results show that this modification is dramatically enhanced when the symmetric and antisymmetric SPs are excited. Notable effects on the spatial dependence …
Electrochemical performance of activated screen printed carbon electrodes for hydrogen peroxide and phenol derivatives sensing
2019
Screen-printed carbon electrodes (SPCEs) are widely used for the electroanalysis of a plethora of organic and inorganic compounds. These devices offer unique properties to address electroanalytical chemistry challenges and can successfully compete in numerous aspects with conventional carbon-based electrodes. However, heterogeneous kinetics on SPCEs surfaces is comparatively sluggish, which is why the electrochemical activation of inks is sometimes required to improve electron transfer rates and to enhance sensing performance. In this work, SPCEs were subjected to different electrochemical activation methods and the response to H2O2 electroanalysis was used as a testing probe. Changes in to…
Trimesic acid on Cu in ethanol: Potential-dependent transition from 2-D adsorbate to 3-D metal-organic framework
2017
We report the potential-dependent interactions of trimesic acid with Cu surfaces in EtOH. CV experiments and electrochemical surface-enhanced Raman spectroscopy show the presence of an adsorbed trimesic acid layer on Cu at potentials lower than 0 V vs Cu. The BTC coverage increases as the potential increases, reaching a maximum at 0 V. Based on molecular dynamics simulations, we report adsorption geometries and possible structures of the organic adlayer. We find that, depending on the crystal facet, trimesic acid adsorbs either flat or with one or two of the carboxyl groups facing the metal surface. At higher coverages, a multi-layer forms that is composed mostly of flat-lying trimesic acid…
Prevenció de la malaltia d'Alzheimer en etapes primerenques i mitjanes de la vida
2015
La malaltia d'Alzheimer és la causa més freqüent de demència a l'edat adulta. A més, la seua incidència s'incrementa fortament amb l'edat i, és per això, que la seua prevalença està augmentant en tot el món degut a l'augment a l'expectativa de vida. Clínicament es caracteritza per un dèficit cognitiu progressiu i irreversible i alteracions de la conducta que afecten a la memòria i altres dominis cognitius, a la capacitat d'aprenentatge, activitats de la vida diària i, en últim terme, a la qualitat de vida. Donat que el tractament farmacèutic disponible actualment solament pot millorar moderadament els símptomes, la modificació de factors de risc a etapes primerenques i mitjanes de la vida é…
Juegos de niñas y juegos de niños: Estudio sobre la representación del juego infantil a través del dibujo
2016
Resumen:El objetivo del estudio consistió en describir la forma en que niños y niñas de primer ciclo de educación primaria representan el juego infantil a través del dibujo. La recolección de datos se realizó en dos sesiones separadas por una semana, acompañada de narraciones orales de los participantes para cada dibujo. Una vez transcritas las entrevistas se codificaron las categorías más importantes a saber: Tipo de juego, dominio de actividad física, edad, género, dimensión social y lugar. Los dibujos de niños representan actividades deportivas y competitivas en espacios al aire libre en compañía de niños. Por el contrario, los dibujos de niñas representan actividades sedentarias o de ba…
Donnan phenomena in membranes with charge due to ion adsorption. Effects of the interaction between adsorbed charged groups
1993
A physical model for the modified Donnan phenomenon associated with ion adsorption on localized membrane sites is presented. This model accounts for the dependence of the concentration of adsorbed ions on electrolyte concentration and pH as it is influenced by the electrostatic interaction between adsorbed ions. The equilibrium thermodynamic concepts employed are based on the Donnan formalism for the ion equilibria between membrane and solution, and the Bragg–Williams approximation for an adsorption isotherm that incorported interaction between adsorbed ions. Our results include the concentration of charged groups in the membrane, the pH of the membrane phase solution, and the Donnan potent…
A CI study of the CuCO and CuCO+ complexes
1987
MO CI calculations are carried out using an optimal space of valence virtual MOs obtained by means of a projection technique, as a linear combination of the AOs which are more occupied in the molecular Fock space. Localization of the occupied MOs and nonvalence virtual MOs is also achieved. The overall procedure is proven to be quite advantageous and well suited to obtain potential energy curves which keep the same physical meaning along the range of distances studied. Using a slightly better than double‐zeta quality basis set, a valence CAS‐CI, and selected CI wave function by the CIPSI algorithm have revealed a possible weak van der Waals interaction for the 2Σ+ state of CuCO, which remai…
Large-scale calculations of excitation energies in coupled cluster theory: The singlet excited states of benzene
1996
Algorithms for calculating singlet excitation energies in the coupled cluster singles and doubles (CCSD) model are discussed and an implementation of an atomic-integral direct algorithm is presented. Each excitation energy is calculated at a cost comparable to that of the CCSD ground-state energy. Singlet excitation energies are calculated for benzene using up to 432 basis functions. Basis-set effects of the order of 0.2 eV are observed when the basis is increased from augmented polarized valence double-zeta (aug-cc-pVDZ) to augmented polarized valence triple-zeta (aug-cc-pVTZ) quality. The correlation problem is examined by performing calculations in the hierarchy of coupled cluster models…
Excited states of the water molecule: Analysis of the valence and Rydberg character
2008
The excited states of the water molecule have been analyzed by using the extended quantum-chemical multistate CASPT2 method, namely, MS-CASPT2, in conjunction with large one-electron basis sets of atomic natural orbital type. The study includes 13 singlet and triplet excited states, both valence and 3s-, 3p-, and 3d-members of the Rydberg series converging to the lowest ionization potential and the 3s- and 3p-Rydberg members converging to the second low-lying state of the cation, 1 math. The research has been focused on the analysis of the valence or Rydberg character of the low-lying states. The computation of the 1 math state of water at different geometries indicates that it has a predom…