1,092 research outputs found
Generational Transition of Subsistence Fishing Practices in the Pacific Community of Venado Island, Costa Rica
The goal of this ethnographic study is to document the way that tourism has affected the subsistence fishing activities on the island of Venado, Costa Rica. A key question is how tourism has forced the residents of this fishing community to make choices between a traditional economy and the need to survive in an expanding global market of ecological tourism. The method of research is ethnographic. The goal is to portray cultural issues through the life of the islanders. I hope that this research will create a better understanding of the cultural impact of global change on the people of Venado Island, as well as a wider appreciation of their rights and perspectives in this rapidly changing region of the Americas
Collapse of the ESR fine structure throughout the coherent temperature of the Gd-doped Kondo Semiconductor
Experiments on the Electron Spin Resonance (ESR) in the filled
skutterudite (), at temperatures
where the host resistivity manifests a smooth insulator-metal crossover,
provides evidence of the underlying Kondo physics associated with this system.
At low temperatures (below ), behaves
as a Kondo-insulator with a relatively large hybridization gap, and the
ESR spectra displays a fine structure with lorentzian line shape,
typical of insulating media. The electronic gap is attributed to the large
hybridization present in the coherent regime of a Kondo lattice, when Ce
4f-electrons cooperate with band properties at half-filling. Mean-field
calculations suggest that the electron-phonon interaction is fundamental at
explaining the strong 4f-electron hybridization in this filled skutterudite.
The resulting electronic structure is strongly temperature dependent, and at
about the system undergoes an insulator-to-metal
transition induced by the withdrawal of 4f-electrons from the Fermi volume, the
system becoming metallic and non-magnetic. The ESR fine structure
coalesces into a single dysonian resonance, as in metals. Still, our
simulations suggest that exchange-narrowing via the usual Korringa mechanism,
alone, is not capable of describing the thermal behavior of the ESR spectra in
the entire temperature region ( - K). We propose that temperature
activated fluctuating-valence of the Ce ions is the missing ingredient that,
added to the usual exchange-narrowing mechanism, fully describes this unique
temperature dependence of the ESR fine structure observed in
.Comment: 19 pages, 6 figure
Analytical study of an exclusive genetic switch
The nonequilibrium stationary state of an exclusive genetic switch is
considered. The model comprises two competing species and a single binding site
which, when bound to by a protein of one species, causes the other species to
be repressed. The model may be thought of as a minimal model of the power
struggle between two competing parties. Exact solutions are given for the
limits of vanishing binding/unbinding rates and infinite binding/unbinding
rates. A mean field theory is introduced which is exact in the limit of
vanishing binding/unbinding rates. The mean field theory and numerical
simulations reveal that generically bistability occurs and the system is in a
symmetry broken state. An exact perturbative solution which in principle allows
the nonequilibrium stationary state to be computed is also developed and
computed to first and second order.Comment: 28 pages, 6 figure
Low frequency sound propagation in activated carbon
Activated carbon can adsorb and desorb gas molecules onto and off its surface. Research has examined
whether this sorption affects low frequency sound waves, with pressures typical of audible
sound, interacting with granular activated carbon. Impedance tube measurements were undertaken
examining the resonant frequencies of Helmholtz resonators with different backing materials. It
was found that the addition of activated carbon increased the compliance of the backing volume.
The effect was observed up to the highest frequency measured (500 Hz), but was most significant at
lower frequencies (at higher frequencies another phenomenon can explain the behavior). An apparatus
was constructed to measure the effective porosity of the activated carbon as well as the number
of moles adsorbed at sound pressures between 104 and 118 dB and low frequencies between 20
and 55 Hz. Whilst the results were consistent with adsorption affecting sound propagation, other
phenomena cannot be ruled out. Measurements of sorption isotherms showed that additional energy
losses can be caused by water vapor condensing onto and then evaporating from the surface of the
material. However, the excess absorption measured for low frequency sound waves is primarily
caused by decreases in surface reactance rather than changes in surface resistance
El Derecho de acceso al documento administrativo, perfiles sustanciales y procedimentales respecto al acceso a la administracion del estado.
105 p.La relevancia de esta investigación se sustenta en dar un marco jurÃdicodoctrinal al derecho de acceso al documento público, para lo cuál es primordial hacer un análisis desde la perspectiva del Derecho realizando un rastreo del
panorama legislativo actual, cuya novedad está dada por la existencia de un nuevo proyecto de ley que busca dar respuesta a una materia que ha sido tratada con especial dedicación por otras legislaciones del mundo occidental, especialmente la de los paÃses europeos, utilizando para estos efectos aspectos de la normativa de la Comunidad Europea
Inducible Degradation of the Human SMC5/6 Complex Reveals an Essential Role Only during Interphase
Translocação e redistribuição de enxofre em plantas de milho e de soja.
O objetivo deste trabalho foi estudar a translocação e a redistribuição de S pelo transporte acrópeto e basÃpeto em plantas de milho e de soja. Plantas das duas espécies foram cultivadas em solução nutritiva contendo 35 S em casa de vegetação. O 35S aplicado em uma única raiz foi prontamente absorvido e translocado para a parte aérea, assim como para as demais raÃzes cultivadas na ausência de enxofre. O radioisótopo aplicado em uma única folha foi transportado tanto na direção acrópeta quanto na basÃpeta. Entretanto, o milho e a soja mostraram comportaments diferentes na absorção e na distribuição do enxofre. O milho, apesar de ter apresentado maior absorção radicular, reteve grande parte desse elemento na raiz, enquanto a soja absorveu consideravelmente menos, porém apresentou maior eficiência de translocação. Nas plantas de soja, as folhas superiores, principalmente as mais novas, mostraram ser os principais drenos fisiológicos do enxofre
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