455 research outputs found
Opportunities for farming in alpine countries – pathways to truly grassland-based beef and milk production in Austria and Switzerland
Farming in the alpine countries of Austria and Switzerland fulfils important economic, socio-cultural and ecological functions for society. However, even though both Austria and Switzerland have increasingly focused their agricultural policy towards ecology, in both countries negative environmental impacts of agriculture still have to be reduced massively
A mean‐field modeling study of the interaction between hydrogen and a palladium (110) single crystal
A new interpretation of the temperature programmed desorption (TPD) spectra of hydrogen on a Pd(110) single crystal surface is presented. The transient mean‐field model developed accounts for both adsorption on the surface and diffusion of hydrogen into the lattice of the crystal. A new approach for modeling TPD spectra is developed, in which both the isothermal exposure as well as the temperature ramp of the TPD experiment are modeled in a consistent way. We demonstrate that for systems with substantial diffusion of the adsorbate into the substrate’s lattice it is not sufficient to report exposure values. For such systems, exposure time has a far more pronounced effect than the exposure pressure has on the TPD spectra, because diffusion is a strongly time‐dependent process. The modeling and experimental results for the H2/Pd(110) system are in good agreement and suggest the existence of a distinct subsurface state, in addition to the surface and bulk states of hydrogen. Low frequency factors derived from the model for the processes connecting the subsurface with the surface and bulk state emphasize the restricted nature of the corresponding transition states. © 1996 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70193/2/JCPSA6-105-18-8398-1.pd
The Effect of Crystallization on the Pulsations of White Dwarf Stars
We consider the pulsational properties of white dwarf star models with
temperatures appropriate for the ZZ Ceti instability strip and with masses
large enough that they should be substantially crystallized. Our work is
motivated by the existence of a potentially crystallized DAV, BPM 37093, and
the expectation that digital surveys in progress will yield many more such
massive pulsators.
A crystallized core makes possible a new class of oscillations, the torsional
modes, although we expect these modes to couple at most weakly to any motions
in the fluid and therefore to remain unobservable. The p-modes should be
affected at the level of a few percent in period, but are unlikely to be
present with observable amplitudes in crystallizing white dwarfs any more than
they are in the other ZZ Ceti's. Most relevant to the observed light variations
in white dwarfs are the g-modes. We find that the kinetic energy of these modes
is effectively excluded from the crystallized cores of our models. As
increasing crystallization pushes these modes farther out from the center, the
mean period spacing between radial overtones increases substantially with the
crystallized mass fraction. In addition, the degree and structure of mode
trapping is affected. The fact that some periods are strongly affected by
changes in the crystallized mass fraction while others are not suggests that we
may be able to disentangle the effects of crystallization from those due to
different surface layer masses.Comment: 18 pages, 5 figures, accepted on 1999 July 2 for publication in the
Astrophysical Journa
Validación a largo plazo de datos de nivel 3 de tierra de SMOS con medidas de ELBARA-II en la Valencia Anchor Station
Revista oficial de la Asociación Española de Teledetección[EN] The Soil Moisture and Ocean Salinity (SMOS) mission was launched on 2nd November 2009 with the objective of providing global estimations of soil moisture and sea salinity. The main activity of the Valencia Anchor Station (VAS) is currently to assist in a long-term validation of SMOS land products. This study focus on a level 3 SMOS data validation with in situ measurements carried out in the period 2010-2012 over the VAS. ELBARA-II radiometer is placed in the VAS area, observing a vineyard field considered as representative of a major proportion of an area of 50×50 km, enough to cover a SMOS footprint. Brightness temperatures (TB) acquired by ELBARA-II have been compared to those observed by SMOS at the same dates and time. They were also used for the L-MEB model inversion to retrieve soil moisture (SM), which later on have been compared to those provided by SMOS as level 3 data. A good correlation between both TB datasets was found, improving year by year, mainly due to the decrease of precipitations in the analyzed period and the mitigation of radio frequency interferences at L-band. The larger homogeneity of the radiometer footprint as compared to SMOS explains the higher variability of its TB. Periods of more intense precipitation (spring and autumn) also presented higher SM, which corroborates the consistency of SM retrieved from ELBARA-II’s observations. However, the results show that SMOS level 3 data underestimate SM as compared to ELBARA-II’s, probably due to the influence of the small soil fraction which is not cultivated in vineyards. SMOS estimations in descending orbit (6 pm) had better quality (higher correlation, lower RMSE and bias) than the ones in ascending orbit (6 am, when there is a higher soil moisture).
Guardar / Salir Siguiente >[ES] La misión de SMOS (Soil Moisture and Ocean Salinity) se lanzó el 2 de Noviembre de 2009 con el objetivo de proporcionar datos de humedad del suelo y salinidad del mar. La principal actividad de la conocida como Valencia Anchor Station(VAS) es asistir en la validación a largo plazo de productos de suelo de SMOS. El presente estudio se centra en una validación de datos de nivel 3 de SMOS en la VAS con medidas in situ tomadas en el periodo 2010-2012. El radiómetro ELBARA-II está situado dentro de los confines de la VAS, observando un campo de viñedos que se con-sidera representativo de una gran proporción de un área de 50×50 km, suficiente para cubrir un footprint de SMOS. Las temperaturas de brillo (TB) adquiridas por ELBARA-II se compararon con las observadas por SMOS en las mismas fechas y horas. También se utilizó la inversión del modelo L-MEB con el fin de obtener humedades de suelo (SM) que, posteriormente, se compararon con datos de nivel 3 de SMOS. Se ha encontrado una buena correlación entre ambas series de TB, con mejoras año tras año, achacable fundamentalmente a la disminución de precipitaciones en el perio-do objeto de estudio y a la mitigación de las interferencias por radiofrecuencia en banda L. La mayor homogeneidad del footprintdel radiómetro ELBARA-II frente al de SMOS explica la mayor variabilidad de sus TB. Los periodos de preci-pitación más intensa (primavera y otoño) también son de mayor SM, lo que corrobora la consistencia de los resultados de SM simulados a través de las observaciones del radiómetro. Sin embargo, se debe resaltar una subestimación por parte de SMOS de los valores de SM respecto a los obtenidos por ELBARA-II, presumiblemente debido a la influencia que la pequeña fracción de suelo no destinado al cultivo de la vid tiene sobre SMOS. Las estimaciones por parte de SMOS en órbita descendente (6 p.m.) resultaron de mayor calidad (mayor correlación y menores RMSE y bias) que en órbita ascendente (6 a.m., momento de mayor humedad de suelo).This work is carried out within the framework of the project MIDAS-7/UVEG Productos y Aplicaciones Avanzados de SMOS y Futuras Misiones (Parte UVEG) from the Spanish Research Programme on Space, Spanish Ministry
for Economy and Competitiveness.Fernandez-Moran, R.; Wigneron, JP.; López-Baeza, E.; Miernecki, M.; Salgado-Hernanz, P.; Coll, M.; Kerr, YH.... (2015). Towards a long-term dataset of ELBARA-II measurements assisting SMOS level-3 land product and algorithm validation at the Valencia Anchor Station. Revista de Teledetección. (43):55-62. doi:10.4995/raet.2015.2297.SWORD55624
CO hydrogenation over alumina-supported sulfide cluster catalysts
Bimetallic Mo-Fe and Mo-Co sulfide clusters were anchored on Al 2 O 3 and used for CO hydrogenation. In addition to methane, significant amounts of dimethyl ether were produced. The reaction orders obtained from power rate laws for methanation indicated that the surfaces of the catalytic ensembles were not completely saturated by CO, in contrast to the observations for most conventional CO hydrogenation catalysts. A kinetic analysis and parameter estimation was performed to identify the rate-determining step for methanation. A catalytic cycle was postulated that could account not only for the formation of methane and higher hydrocarbons, but also for dimethyl ether as a primary product.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37405/1/690350112_ftp.pd
Illumination in symbiotic binary stars: Non-LTE photoionization models. II. Wind case
We describe a non-LTE photoionization code to calculate the wind structure
and emergent spectrum of a red giant wind illuminated by the hot component of a
symbiotic binary system. We consider spherically symmetric winds with several
different velocity and temperature laws and derive predicted line fluxes as a
function of the red giant mass loss rate, \mdot. Our models generally match
observations of the symbiotic stars EG And and AG Peg for \mdot about 10^{-8}
\msunyr to 10^{-7} \msunyr. The optically thick cross- section of the red giant
wind as viewed from the hot component is a crucial parameter in these models.
Winds with cross-sections of 2--3 red giant radii reproduce the observed
fluxes, because the wind density is then high, about 10^9 cm^{-3}. Our models
favor winds with acceleration regions that either lie far from the red giant
photosphere or extend for 2--3 red giant radii.Comment: 51 pages, LaTeX including three tables, requires 15 Encapsulated
Postscript figures, to appear in Ap
Alumina-supported triosmium clusters and ensembles: Characterization by high-resolution transmission electron microscopy
Structurally defined supported osmium clusters [HOs3(CO)10---O---Al3(CO)12] with the -OH groups of [gamma]-Al2O3. The supported clusters were heated to 200 [deg]C in argon and then reduced in hydrogen at 400 [deg]C, being characterized at different stages of the treatment by high-resolution transmission electron microscopy. After the sample had been heated to 200 [deg]C, scattering centers about 6 A in diameter were evident in the micrographs, their size being consistent with the expected geometry of three-atom ensembles of Os(II) complexes formed by cluster breakup. The ensembles were remarkably stable, and even prolonged exposure of the same area to the 100 keV electron beam caused neither disintegration nor agglomeration. After reduction of the osmium in hydrogen at 400 [deg]C, aggregates of similar size were observed. In contrast to the ensembles of Os(II) complexes, the aggregates seemed to disintegrate slowly under the impact of the electron beam. The difference in stability of the ensembles and the reduced osmium aggregates is attributed to the difference between the strong ionic bonds in the former sample and the weaker interaction between the reduced metal and the Al2O3 surface.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25063/1/0000494.pd
The hydrogen and helium lines of the symbiotic binary Z And during its brightening at the end of 2002
High resolution observations in the region of the lines Halpha, He II 4686
and Hgamma of the spectrum of the symbiotic binary Z And were performed during
its small-amplitude brightening at the end of 2002. The profiles of the
hydrogen lines were double-peaked. These profiles give a reason to suppose that
the lines can be emitted mainly by an optically thin accretion disc. The Halpha
line is strongly contaminated by the emission of the envelope, therefore for
consideration of accretion disc properties we use the Hgamma line. The Halpha
line had broad wings which are supposed to be determined mostly from radiation
damping but high velocity stellar wind from the compact object in the system
can also contribute to their appearance. The Hgamma line had a broad emission
component which is assumed to be emitted mainly from the inner part of the
accretion disc. The line He II 4686 had a broad emission component too, but it
is supposed to appear in a region of a high velocity stellar wind. The outer
radius of the accretion disc can be calculated from the shift between the
peaks. Assuming, that the orbit inclination can ranges from 47 to
76, we estimate the outer radius as 20 - 50 R_sun. The behaviour of the
observed lines can be considered in the framework of the model proposed for
interpretation of the line spectrum during the major 2000 - 2002 brightening of
this binary.Comment: 19 pages, 5 figures. Accepted for publication in Astronomy Report
Estimating soil hydraulic properties using L-band radiometer and ground-penetrating radar
peer reviewedIn this study, we experimentally analyze the feasibility of estimating the soil hydraulic properties from L-band radiometer and ground-penetrating radar (GPR) data. L-band radiometer and ultrawideband off-ground GPR measurements were performed above a sand box in hydrostatic equilibrium with a water table located at different depths. The results of the inversions showed that the radar and radiometer signals contain sufficient information to estimate the soil water retention curve and its related hydraulic parameters with a relatively good accuracy compared to time-domain reflectometry estimates. However, an accurate estimation of the hydraulic parameters was only obtained by considering the saturated water content parameter as known during the inversion. © 2012 IEEE
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Final Version Zurich, 27th July 2010
Adaptation to climate change requires an integrated risk management approach, including risk
assessment, prevention and insurance. Insurance solutions can potentially provide a significant
contribution in expanding and strengthening adaptation response to climate change risks.
Numerous proposals and submissions under the United Nations Framework Convention on
Climate Change (UNFCCC) make reference to risk transfer and insurance solutions as a com-
plementary element of a systematic adaptation approach, but no consensus has been achieved
regarding their role and eventual implementation under UNFCCC.
This paper intends to raise awareness on existing work and the current challenges related to
climate relevant insurance, in developing countries and to contribute to a further discussion of
the insurance topic under UNFCCC.
Past experiences and discussions can provide a framework for larger policies on the role of
insurance in the emerging climate financing architecture. Further pilot implementation, research,
and systematic learning is required. Many of the elements such as data collection, research, ca-
pacity building and exploration of public private partnerships are valuable for achieving broader
adaptation objectives. It is therefore encouraged that the Parties further explore and define the
scope of insurance solutions as part of climate change adaptation
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