Search results for "FÍSICA"
showing 10 items of 4992 documents
A quantum mechanics-molecular mechanics study of dissociative electron transfer : The methylchloride radical anion in aqueous solution
2002
The dissociative electron transfer reaction CH3Cl+e−→CH3•+Cl− in aqueous solution is studied by using a QM/MM method. In this work the quantum subsystem (a methylchloride molecule plus an electron) is described using density functional theory while the solvent (300 water molecules) is described using the TIP3P classical potential. By means of molecular dynamics simulations and the thermodynamic integration technique we obtained the potential of mean force (PMF) for the carbon–chlorine bond dissociation of the neutral and radical anion species. Combining these two free energy curves we found a quadratic dependence of the activation free energy on the reaction free energy in agreement with Ma…
BIOMECHANICAL FACTORS TO BE TAKEN INTO ACCOUNT TO PREVENT INJURIES AND IMPROVE SPORTING PERFORMANCE ON ARTIFICIAL TURF
2009
This article reviews existing knowledge concerning the epidemiology, instruments and regulatory criteria currently used to evaluate artificial turf soccer pitches. Recent years have seen tremendous growth in the use of artificial turf as a playing surface for sports (rugby, soccer, American football…) and the problems traditionally associated with artificial turf and its relationship with a higher percentage of injuries seem to be disappearing. The contribution of biomechanics to the development of new techniques and instruments for analysing the properties and characteristics of grass pitches has contributed towards close collaboration with the regulatory bodies of different sporting organ…
Qüestions sòcio-científiques i debats per a millorar l'argumentació en classes de Física i Química
2017
En aquesta investigació s’estudia l’ús de les qüestions sòcio-científiques i els debats per a millorar l’argumentació a les classes de Física i Química. Els problemes que s’aborden al llarg de l’estudi són: Quines habilitats argumentatives en ciència tenen els alumnes d’ESO i Batxillerat? En quina mesura l’ensenyament tradicional de la Física i Química potencia l’habilitat argumentativa dels alumnes? Pot la realització de debats sòcio-científics millorar aquesta habilitat? Per a donar resposta a les dos primeres preguntes a manera de diagnòstic es proposa la següent primera hipòtesi: Els alumnes de Secundària tenen un baix nivell d’habilitat argumentativa perquè l’argumentació és un procedi…
Quaestiones super Metaphysicam Aristotelis
Sign.: a8, b-g6, h8 L. gòt. - 3 mides. - 2 col. - 68 lín. - Inic. grav. - Min. p. inic. - Registre. - Llegendes de foli. - Filigr.: balança encerclada
Francisci Vicomercati mediolanensis, in quatuor libros Aristotelis, meteorologicarum commentarii et eorundem librorum e greco in latinum per eundem c…
1565
Sig. *4, A-Z6, AA4 Els grav. xil., quasi tots figures geomètriques. - Retrat xil. d'Aristòtil a la port. i al colofó. - Capitals grav. - Frisos Text a dos col. - Reclams. - Errates de pag. De la p. 95 passa a la 94, de la 114 a la 107
A theory ofnonverticaltriplet energy transfer in terms of accurate potential energy surfaces: The transfer reaction from π,π* triplet donors to 1,3,5…
2004
Triplet energy transfer (TET) from aromatic donors to 1,3,5,7-cyclooctatetraene (COT) is an extreme case of "nonvertical" behavior, where the transfer rate for low-energy donors is considerably faster than that predicted for a thermally activated (Arrhenius) process. To explain the anomalous TET of COT and other molecules, a new theoretical model based on transition state theory for nonadiabatic processes is proposed here, which makes use of the adiabatic potential energy surfaces (PES) of reactants and products, as computed from high-level quantum mechanical methods, and a nonadiabatic transfer rate constant. It is shown that the rate of transfer depends on a geometrical distortion paramet…
Current‐voltage curves of bipolar membranes
1992
Bipolar membranes consist of a layered ion‐exchange structure composed of a cation selective membrane joined to an anion selective membrane. They are analogous to semiconductor p‐n devices as both of them present current‐voltage curves exhibiting similar rectification properties. In this article, we present some current‐voltage curves obtained for different bipolar membranes at several temperatures. The results can be interpreted in terms of a simple model for ion transport and field‐enhanced water dissociation previously developed. The mechanism responsible for water splitting is assumed to be a catalytic proton transfer reaction between the charged groups and the water at the membrane int…
Artes marciales japonesas: prácticas corporales representativas de su identidad cultural
2011
La implantación y difusión de las artes marciales japonesas en Occidente supuso la importación de prácticas socioculturales privadas de las premisas de su contexto de origen. ¿Cómo afrontar estas prácticas que son ajenas a nuestra identidad cultural? Una interpretación estricta exige entenderlas como prácticas corporales con una idiosincrasia cultural, caracterizadas por incorporar una experiencia vivencial en la que el cuerpo ocupa un lugar preeminente. Su enseñanza y aprendizaje se establecen a través de un sistema triangular integrado por una esencia espiritual, una forma técnica y una estructura física (sin-gi-tai), que se inserta en un proceso singular (shu-ha-ri).
Effect of the high-level trigger for detecting long-lived particles at LHCb.
2022
Long-lived particles (LLPs) show up in many extensions of the Standard Model, but they are challenging to search for with current detectors, due to their very displaced vertices. This study evaluated the ability of the trigger algorithms used in the Large Hadron Collider beauty (LHCb) experiment to detect long-lived particles and attempted to adapt them to enhance the sensitivity of this experiment to undiscovered long-lived particles. A model with a Higgs portal to a dark sector is tested, and the sensitivity reach is discussed. In the LHCb tracking system, the farthest tracking station from the collision point is the scintillating fiber tracker, the SciFi detector. One of the challenges i…
Beta Decay Studies of Neutron Rich Nuclei Using Total Absorption Gamma-ray Spectroscopy and Delayed Neutron Measurements
2010
International audience; A complete characterisation of the β-decay of neutron-rich nuclei can be obtained from the measurement of β-delayed gamma rays and, whenever the process is energetically possible, β-delayed neutrons. The accurate determination of the β-intensity distribution and the β-delayed neutron emission probability is of great relevance in the fields of reactor technology and nuclear astrophysics. A programme for combined measurements using the total absorption gamma-ray spectroscopy technique and both neutron counters and neutron time-of-flight spectrometers is presented.