Poetics of Interplay and Interferences of Potentiodynamic Sweeps and Peaks in Electrocatalysis for Oxygen Electrode Reactions

Strong irreversible adsorptive monolayer growth of the surface (Pt=O→1), out of the reversible primary (Pt−OH→0) oxides, imposes typical highly pronounced reaction polarization, and that way prevents, at least partially, the reversible electrocatalytic properties and behavior of even all plain and non-interactive supported noble metals (Pt, Pt/C) for oxygen electrode reactions, within closed loop of potentiodynamic spectra between hydrogen and oxygen evolving limits. Substantially quite another type of assembly afford nanostructured hyper-d-electronic-metals (Pt,Au,Ru), interactive grafted upon hypo-d-(f)-oxide supports, in particular of mixed and higher alter-valence values (W,Mo,Ta,Nb), well and for longer known in heterogeneous catalysis as SMSI (Strong Metal-Support Interaction, the ones of strongest in the entire chemistry). The most promising being Magneli phases (MPs, TinO(2n−1), or Ti4O7 in average, and as the optimum in catalytic activity), which arise after simple thermal recrystallization (pure entropy change contribution) yield effect, out of anatase and/or rutile titania (TiO2). The main accompanying achievements of substantial significance then have been: (i) Prevailing percentage in spontaneous adsorptive dissociation of molecular water upon hypo-d-(f)-oxide surfaces, or the corresponding latent storage and spillover of the yielding primary oxides (Pt−OH); (ii) Extra high stability MPs, (Plate type electrodes of MPs are straightforward employed in industrial chlorate cell production, and/or Li-batteries); (iii) Spontaneously adsorptive dissociated water molecules (or, hydroxide ions), then undergo membrane type ionic transfer all along hypo-d-(f)-oxide supports, until approaching catalytic metal surface, when the latter takes the prevailing amount of electron charge, and that way creates the primary oxide dipole species (Pt−OH); (iv) these undergo spillover by repulsion upon metallic, hypo-d-(f)-oxide and even over the suboxide MPs surfaces; (v) while the Magneli phases themselves feature a rather high n-type electron conductivity (up to and even above 1,000 S/cm). The wetness impact factor and effect have been introduced as the lowest threshold level associated with the Pt−OH (Au−OH), bellow which there is no (electro)catalytic oxidation reaction taking place, such as the CO tolerance. The overall result of the present study has then been the development and achievement of the reversible electrocatalysts for the oxygen electrode reactions (ORR, OER), primarily for L&MT PEMFCs. This work is licensed under a Creative Commons Attribution 4.0 International License

Level Crossing Rate of Macrodiversity System in the Presence of Multipath Fading and Shadowing

Macrodiversity system including macrodiversity SC receiver and two microdiversity SC receivers is considered in this paper. Received signal experiences, simultaneously, both, long term fading and short term fading. Microdiversity SC receivers reduces Rayleigh fading effects on system performance and macrodiversity SC receiver mitigate Gamma shadowing effects on system performance. Closed form expressions for level crossing rate of microdiversity SC receivers output signals envelopes are calculated. This expression is used for evaluation of level crossing rate of macrodiversity SC receiver output signal envelope. Numerical expressions are illustrated to show the influence of Gamma shadowing severity on level crossing rate

Nanostructuring Graphene by Dense Electronic Excitation

The ability to manufacture tailored graphene nanostructures is a key factor to fully exploit its enormous technological potential. We have investigated nanostructures created in graphene by swift heavy ion induced folding. For our experiments, single layers of graphene exfoliated on various substrates and freestanding graphene have been irradiated and analyzed by atomic force and high resolution transmission electron microscopy as well as Raman spectroscopy. We show that the dense electronic excitation in the wake of the traversing ion yields characteristic nanostructures each of which may be fabricated by choosing the proper irradiation conditions. These nanostructures include unique morphologies such as closed bilayer edges with a given chirality or nanopores within supported as well as freestanding graphene. The length and orientation of the nanopore, and thus of the associated closed bilayer edge, may be simply controlled by the direction of the incoming ion beam. In freestanding graphene, swift heavy ion irradiation induces extremely small openings, offering the possibility to perforate graphene membranes in a controlled way.Comment: 16 pages, 5 figures, submitted to Nanotechnolog

Properties of latent interface-trap buildup in irradiated metal-oxide-semiconductor transistors determined by switched bias isothermal annealing experiments

Isothermal annealing experiments with switched gate bias have been performed to determine the properties of the latent interface-trap buildup during postirradiation annealing of metal-oxide-semiconductor transistors. It has been found that a bias-independent process occurs until the start of the latent interface-trap buildup. During the buildup itself, oxide-trap charge is not permanently neutralized, but is temporarily compensated. (C) 2000 American Institute of Physics. (DOI: 10.1063/1.1336159

Historia natural del águila <i>Geranoaetus melanoleucus</i>: una revisión

Realizamos una revisión de la literatura y condensamos la informacion de diferentes autores acerca de la historia natural del águila Geranoaetus melanoleucus. Complementamos esta información con nuestras propias observaciones de campo entre localidades a lo largo de Chile. Ellas provienen de la Reserva Nacional Las Chinchillas (300 km al norte de Santiago), de San Carlos de Apoquindo (20 km al este de Santiago) y del Parque Nacional Torres del Paine (350 km al norte de Punta Arenas). Tratamos detalladamente los siguientes tópicos: distribución y taxonomía, color del plumaje e identificación, morfometría y peso, historia de vida y reproducción, uso del hábitat, dieta, ritmos de actividad, tipos de vuelo y conductas de caza, agresión, vocalizaciones, abundancia, mortalidad y otros hábitos.Con este trabajo se actualiza el estado del conocimiento de la biología del águila y se hace accesible la información que se ha documentado en revistas de circulación local y documentos de dificil acceso a la comunidad científica interesada.Natural history of the Grey Eagle-buzzard, Geranoaetus melanolucus: a review. We reviewed and summarized the literature concerning the natural history of the Grey Eagle-buzzard Geranoaetus melanoleucus. We suplement this information with our own field records from three sites along Chile. They are the Chinchilla National Reserve (300 km north of Santiago), San Carlos de Apoquindo (20km east of Santiago), and Torres del Paine National Park (350 km north of Punta Arenas).We covered in detail the following topics: distribution and taxonomy, color and field identification, morphometry and weigth, life history and reproduction, habitat use, diet, activity, flight modes and hunting behavior, aggression, vocalizations, abundance, mortality, and other topics. With this review we update the current knowledge of the biology of the Grey Eagly-buzzard, and render more accessible the information documented in journals and books of local circulation to the interested scientific community

Hamiltonian structure for dispersive and dissipative dynamical systems

We develop a Hamiltonian theory of a time dispersive and dissipative inhomogeneous medium, as described by a linear response equation respecting causality and power dissipation. The proposed Hamiltonian couples the given system to auxiliary fields, in the universal form of a so-called canonical heat bath. After integrating out the heat bath the original dissipative evolution is exactly reproduced. Furthermore, we show that the dynamics associated to a minimal Hamiltonian are essentially unique, up to a natural class of isomorphisms. Using this formalism, we obtain closed form expressions for the energy density, energy flux, momentum density, and stress tensor involving the auxiliary fields, from which we derive an approximate, ``Brillouin-type,'' formula for the time averaged energy density and stress tensor associated to an almost mono-chromatic wave.Comment: 68 pages, 1 figure; introduction revised, typos correcte

Exactly solvable model of quantum diffusion

We study the transport property of diffusion in a finite translationally invariant quantum subsystem described by a tight-binding Hamiltonian with a single energy band and interacting with its environment by a coupling in terms of correlation functions which are delta-correlated in space and time. For weak coupling, the time evolution of the subsystem density matrix is ruled by a quantum master equation of Lindblad type. Thanks to the invariance under spatial translations, we can apply the Bloch theorem to the subsystem density matrix and exactly diagonalize the time evolution superoperator to obtain the complete spectrum of its eigenvalues, which fully describe the relaxation to equilibrium. Above a critical coupling which is inversely proportional to the size of the subsystem, the spectrum at given wavenumber contains an isolated eigenvalue describing diffusion. The other eigenvalues rule the decay of the populations and quantum coherences with decay rates which are proportional to the intensity of the environmental noise. On the other hand, an analytical expression is obtained for the dispersion relation of diffusion. The diffusion coefficient is proportional to the square of the width of the energy band and inversely proportional to the intensity of the environmental noise because diffusion results from the perturbation of quantum tunneling by the environmental fluctuations in this model. Diffusion disappears below the critical coupling.Comment: Submitted to J. Stat. Phy