6,241 research outputs found
Electronic structure and dimerization of a single monatomic gold wire
The electronic structure of a single monatomic gold wire is presented for the
first time. It has been obtained with state-of-the-art ab-initio full-potential
density-functional (DFT) LMTO (linearized muffin-tin orbital) calculations
taking into account relativistic effects. For stretched structures in the
experimentally accessible range the conduction band is exactly half-filled,
whereas the band structures are more complex for the optimized structure. By
studying the total energy as a function of unit-cell length and of a possible
bond-length alternation we find that the system can lower its total energy by
letting the bond lengths alternate leading to a structure containing separated
dimers with bond lengths of about 2.5 \AA, largely independent of the
stretching. However, first for fairly large unit cells (above roughly 7 \AA),
is the total-energy gain upon this dimerization comparable with the energy
costs upon stretching. We propose that this together with band-structure
effects is the reason for the larger interatomic distances observed in recent
experiments. We find also that although spin-orbit couplings lead to
significant effects on the band structure, the overall conclusions are not
altered, and that finite Au_2, Au_4, and Au_6 chains possess electronic
properties very similar to those of the infinite chain.Comment: (14 pages, 5 figures; Elsevier Preprint style elsart.sty
Nuevos datos sobre la sedimentación terciaria en La Mancha (Ciudad Real)
Los datos obtenidos de la investigación geofísica y perforación de sondeos en la parte occidental de La Mancha han permitido determinar la estructura del sustrato del Neógeno: un conjunto de fosas controladas por fallas, que se generaron en periodos de tectónica distensiva. Se han separado tres unidades litoestratigráficas: Unidad detrítica de la base, Unidad lutítica roja intermedia y Unidad carbonatada superior
Fission program at n_TOF
Since its start in 2001 the n_TOF collaboration developed a measurement
program on fission, in view of advanced fuels in new generation reactors.
A special effort was made on measurement of cross sections of actinides, exploiting
the peculiarity of the n_TOF neutron beam which spans a huge energy
domain, from the thermal region up to GeV. Moreover fission fragment angular
distributions have also been measured. An overview of the cross section
results achieved with different detectors is presented, including a discussion of
the 237Np case where discrepancies showed up between different detector systems.
The results on the anisotropy of the fission fragments and its implication
on the mechanism of neutron absorption, and in applications, are also shown
Nuevos datos sobre la sedimentación terciaria en La Mancha (Ciudad Real)
Los datos obtenidos de la investigación geofísica y perforación de sondeos en la parte occidental de La Mancha han permitido determinar la estructura del sustrato del Neógeno: un conjunto de fosas controladas por fallas, que se generaron en periodos de tectónica distensiva. Se han separado tres unidades litoestratigráficas: Unidad detrítica de la base, Unidad lutítica roja intermedia y Unidad carbonatada superior
Molecular gas at supernova local environments unveiled by EDGE
CO observations allow estimations of the gas content of molecular clouds,
which trace the reservoir of cold gas fuelling star formation, as well as to
determine extinction via H column density, N(H). Here, we studied
millimetric and optical properties at 26 supernovae (SNe) locations of
different types in a sample of 23 nearby galaxies by combining molecular
CO (J = 1 0) resolved maps from the EDGE survey and
optical Integral Field Spectroscopy from the CALIFA survey. We found an even
clearer separation between type II and type Ibc SNe in terms of molecular gas
than what we found in the optical using H emission as a proxy for
current SF rate, which reinforces the fact that SNe Ibc are more associated
with SF-environments. While A at SN locations is similar for SNe II and SNe
Ibc, and higher compared to SNe Ia, N(H) is significantly higher for SNe
Ibc than for SNe II and SNe Ia. When compared to alternative extinction
estimations directly from SN photometry and spectroscopy, we find that our SNe
Ibc have also redder color excess but showed standard Na I D absorption
pseudo-equivalent widths (1 \AA). In some cases we find no extinction
when estimated from the environment, but high amounts of extinction when
measured from SN observations, which suggests that circumstellar material or
dust sublimation may be playing a role. This work serves as a benchmark for
future studies combining last generation millimeter and optical IFS instruments
to reveal the local environmental properties of extragalactic SNe.Comment: MNRAS accepted, 17 pages, 8 Figures, 4 Table
Contenido de aminoácidos libres en frutos de chirimoyo durante la maduración
El chirimoyo es un fruto tropical que crece en algunos países de América y en una
serie de selectivas áreas del sur de España, siendo una fuente rica de aminoácidos libres.
Los efectos de las temperaturas después de la postrecolección de este fruto han sido
estudiadas. La firmeza del fruto se ha determinado con un medidor de textura y los
aminoácidos libres se determinaron por cromatografía en columna de intercambio iónico,
utilizando un autoanalizador de aminoácidos. El chirimoyo se caracterizó por un alto
contenido en prolina y citrulina. El ácido glutámico y la glutamina estaban también
presentes pero en pequeñas cantidades. La citrulina y la prolina se incrementaron durante
la maduración; el aumento dependió de la temperatura de almacenamiento
Experimental evidences of a large extrinsic spin Hall effect in AuW alloy
We report an experimental study of a gold-tungsten alloy (7% at. W
concentration in Au host) displaying remarkable properties for spintronics
applications using both magneto-transport in lateral spin valve devices and
spin-pumping with inverse spin Hall effect experiments. A very large spin Hall
angle of about 10% is consistently found using both techniques with the
reliable spin diffusion length of 2 nm estimated by the spin sink experiments
in the lateral spin valves. With its chemical stability, high resistivity and
small induced damping, this AuW alloy may find applications in the nearest
future
Note: "Lock-in accelerometry" to follow sink dynamics in shaken granular matter
Understanding the penetration dynamics of intruders in granular beds is
relevant not only for fundamental Physics, but also for geophysical processes
and construction on sediments or granular soils in areas potentially affected
by earthquakes. While the penetration of intruders in two dimensional (2D)
laboratory granular beds can be followed using video recording, it is useless
in three dimensional (3D) beds of non-transparent materials such as common
sand. Here we propose a method to quantify the sink dynamics of an intruder
into laterally shaken granular beds based on the temporal correlations between
the signals from a reference accelerometer fixed to the shaken granular bed,
and a probe accelerometer deployed inside the intruder. Due to its analogy with
the working principle of a lock in amplifier, we call this technique Lock in
accelerometry (LIA). During Earthquakes, some soils can lose their ability to
sustain shear and deform, causing subsidence and sometimes substantial building
damage due to deformation or tumblin
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