3,963 research outputs found
Una aproximación empírica a través de las relaciones Ciencia-Tecnología-Sociedad (CTS) en estudiantes de secundaria y universitarios valencianos
The study reveals the Science-Technology-Society (STS) outlooks of high school students and university students. The VOSTS inventory (Aikenhead et al., 1989) was used to reflect The STS beliefs, positions and literacy. The outcomes of the study point to the need of introducing new concepts and attitudes, emphasizing epistemology, information and cognition
Quadratic cavity soliton optical frequency combs
We theoretically investigate the formation of frequency combs in a dispersive second-harmonic generation cavity system, and predict the existence of quadratic cavity solitons in the absence of a temporal walk-off
Role of dipolar interactions in a system of Ni nanoparticles studied by magnetic susceptibility measurements
The role of dipolar interactions among Ni nanoparticles (NP) embedded in an
amorphous SiO2/C matrix with different concentrations has been studied
performing ac magnetic susceptibility Chi_ac measurements. For very diluted
samples, with Ni concentrations < 4 wt % Ni or very weak dipolar interactions,
the data are well described by the Neel-Arrhenius law. Increasing Ni
concentration to values up to 12.8 wt % Ni results in changes in the
Neel-Arrhenius behavior, the dipolar interactions become important, and need to
be considered to describe the magnetic response of the NPs system. We have
found no evidence of a spin-glasslike behavior in our Ni NP systems even when
dipolar interactions are clearly present.Comment: 7 pages, 5 figures, 3 table
Oxone-promoted wet air oxidation of landfill leachates
Landfill leachates of the city of Badajoz (in the southwest of Spain) have been treated by wet air oxidation at high temperature (180-270 °C) and pressure (40-70 atm). Typical operating variables such as temperature and oxygen partial pressure have been investigated with no effect of any being found and moderate to low chemical oxygen demand conversions (20-30% depending on initial COD concentration). Initial pH shows a positive influence when acidic conditions are used. Addition of hydrogen peroxide (0.01 M) as a hydroxyl radical promoter is able to provide an additional 15% increase in the final COD removal achieved. If a sulfate radical promoter is used (i.e., Oxone) the process is significantly improved, with COD conversions in the range 60-80%, also depending on the initial COD of the leachates. A first attempt to comprehend the chemistry of this oxidizing system suggests an instantaneous decomposition of Oxone that initiates the radical chain also involving hydroxyl and organic radicals
Estudio geológico del sector de Puerto-López (Granada, zona subbética)
La geología del sector de Puerto-López, situado al NW de Granada, ofrece varios aspectos de interés. Hemos podido establecer la sucesión estratigráfica, con términos comprendidos entre el Lías y el Senonense, con dataciones muchas veces precisas gracias a las faunas de Ammonites. La estructura es relativamente violenta y son de destacar los pliegues vergentes al S y las fallas inversas del mismo sentido. Por la naturaleza de la serie y por su posición en el Subbético medio, se ha llegado a la correlación de la serie establecida con otras series subbéticas, de la transversal de Granada
Estudio geológico del sector de Puerto-López (Granada, zona subbética)
La geología del sector de Puerto-López, situado al NW de Granada, ofrece varios aspectos de interés. Hemos podido establecer la sucesión estratigráfica, con términos comprendidos entre el Lías y el Senonense, con dataciones muchas veces precisas gracias a las faunas de Ammonites. La estructura es relativamente violenta y son de destacar los pliegues vergentes al S y las fallas inversas del mismo sentido. Por la naturaleza de la serie y por su posición en el Subbético medio, se ha llegado a la correlación de la serie establecida con otras series subbéticas, de la transversal de Granada
Parametric localized patterns and breathers in dispersive quadratic cavities
We study the formation of localized patterns arising in doubly resonant
dispersive optical parametric oscillators. They form through the locking of
fronts connecting a continuous-wave and a Turing pattern state. This type of
localized pattern can be seen as a slug of the pattern embedded in a
homogeneous surrounding. They are organized in terms of a homoclinic snaking
bifurcation structure, which is preserved under the modification of the control
parameter of the system. We show that, in the presence of phase mismatch,
localized patterns can undergo oscillatory instabilities which make them
breathe in a complex manner
From weak to strong coupling of localized surface plasmons to guided modes in a luminescent slab
We investigate a periodic array of aluminum nanoantennas embedded in a
light-emitting slab waveguide. By varying the waveguide thickness we
demonstrate the transition from weak to strong coupling between localized
surface plasmons in the nanoantennas and refractive index guided modes in the
waveguide. We experimentally observe a non-trivial relationship between
extinction and emission dispersion diagrams across the weak to strong coupling
transition. These results have implications for a broad class of photonic
structures where sources are embedded within coupled resonators. For
nanoantenna arrays, strong vs. weak coupling leads to drastic modifications of
radiation patterns without modifying the nanoantennas themselves, thereby
representing an unprecedented design strategy for nanoscale light sources
Stable classical structures in dissipative quantum chaotic systems
We study the stability of classical structures in chaotic systems when a
dissipative quantum evolution takes place. We consider a paradigmatic model,
the quantum baker map in contact with a heat bath at finite temperature. We
analyze the behavior of the purity, fidelity and Husimi distributions
corresponding to initial states localized on short periodic orbits (scar
functions) and map eigenstates. Scar functions, that have a fundamental role in
the semiclassical description of chaotic systems, emerge as very robust against
environmental perturbations. This is confirmed by the study of other states
localized on classical structures. Also, purity and fidelity show a
complementary behavior as decoherence measures.Comment: 4 pages, 3 figure
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