602 research outputs found
Resonant tunneling through protected quantum dots at phosphorene edges
We theoretically investigate phosphorene zigzag nanorribons as a platform for
constriction engineering. In the presence of a constriction at the upper edge,
quantum confinement of edge protected states reveals resonant tunnelling
Breit-Wigner transmission peaks, if the upper edge is uncoupled to the lower
edge. Coupling between edges in thin constrictions gives rise to Fano-like and
anti-resonances in the transmission spectrum of the system.Comment: 8 pages,7 figure
Effects of group membership on the transmission of negative historical events
Los estudios muestran que la fuente de un rumor, o el que implica al endogrupo o exogrupo son aspectos fundamentales a tener en cuenta en cómo las personas se enfrentan a la transmisión de informa-ción. Los tres trabajos que se presentan aunando los resultados de estudios lleva-dos a cabo sobre las emociones colecti-vas, los rumores y las variables que inci-den en su transmisión, y los mecanismos de defensa de las identidades sociales, analizarán la manera en la que los miem-bros de un grupo se enfrentan con hechos negativos para este mismo endogrupo
A simulational and theoretical study of the spherical electrical double layer for a size-asymmetric electrolyte: the case of big coions
Monte Carlo simulations of a spherical macroion, surrounded by a
size-asymmetric electrolyte in the primitive model, were performed. We
considered 1:1 and 2:2 salts with a size ratio of 2 (i.e., with coions twice
the size of counterions), for several surface charge densities of the
macrosphere. The radial distribution functions, electrostatic potential at the
Helmholtz surfaces, and integrated charge are reported. We compare these
simulational data with original results obtained from the Ornstein-Zernike
integral equation, supplemented by the hypernetted chain/hypernetted chain
(HNC/HNC) and hypernetted chain/mean spherical approximation (HNC/MSA)
closures, and with the corresponding calculations using the modified
Gouy-Chapman and unequal-radius modified Gouy-Chapman theories. The HNC/HNC and
HNC/MSA integral equations formalisms show good concordance with Monte Carlo
"experiments", whereas the notable limitations of point-ion approaches are
evidenced. Most importantly, the simulations confirm our previous theoretical
predictions of the non-dominance of the counterions in the size-asymmetric
spherical electrical double layer [J. Chem. Phys. 123, 034703 (2005)], the
appearance of anomalous curvatures at the outer Helmholtz plane and the
enhancement of charge reversal and screening at high colloidal surface charge
densities due to the ionic size asymmetry.Comment: 11 pages, 7 figure
A search for Galactic runaway stars using Gaia Data Release 1 and Hipparcos proper motions
CONTEXT.The first Gaia Data Release (DR1) significantly improved the
previously available proper motions for the majority of the Tycho-2 stars.
AIMS. We want to detect runaway stars using Gaia DR1 proper motions and compare
our results with previous searches. METHODS. Runaway O stars and BA supergiants
are detected using a 2-D proper-motion method. The sample is selected using
Simbad, spectra from our GOSSS project, literature spectral types, and
photometry processed using CHORIZOS. RESULTS. We detect 76 runaway stars, 17
(possibly 19) of them with no prior identification as such, with an estimated
detection rate of approximately one half of the real runaway fraction. An age
effect appears to be present, with objects of spectral subtype B1 and later
having travelled for longer distances than runaways of earlier subtypes. We
also tentatively propose that the fraction of runaways is lower among BA
supergiants that among O stars but further studies using future Gaia data
releases are needed to confirm this. The frequency of fast rotators is high
among runaway O stars, which indicates that a significant fraction of them (and
possibly a majority) is produced in supernova explosions.Comment: Accepted for publication in A&
Electronic localization at mesoscopic length scales: different definitions of localization and contact effects in a heuristic DNA model
In this work we investigate the electronic transport along model DNA
molecules using an effective tight-binding approach that includes the backbone
on site energies. The localization length and participation number are examined
as a function of system size, energy dependence, and the contact coupling
between the leads and the DNA molecule. On one hand, the transition from an
diffusive regime to a localized regime for short systems is identified,
suggesting the necessity of a further length scale revealing the system borders
sensibility. On the other hand, we show that the lenght localization and
participation number, do not depended of system size and contact coupling in
the thermodynamic limit. Finally we discuss possible length dependent origins
for the large discrepancies among experimental results for the electronic
transport in DNA sample
Hábitos alimentares do aruanã (Osteoglossum bicirrhosum Vandelli, 1829) (Pisces: Osteoglossidae) no alto rio Putumayo, área do Parque Nacional de Paya, Putumayo, Colombia
Hábitos alimentarios de la arawana (Osteoglossum bicirrhosum Vandelli, 1829) (Pisces: Osteoglossidae) en el alto río Putumayo, área del Parque Nacional Natural La Paya, Putumayo, ColombiaHábitos alimentares do aruanã (Osteoglossum bicirrhosum Vandelli, 1829) (Pisces: Osteoglossidae) no alto rio Putumayo, área do Parque Nacional de Paya, Putumayo, Colombia
Multivariate Modelling of Pedestrian Fatality Risk Through on the Spot Accident Investigation
Pedestrians are the most vulnerable users of public roads and represent one of the largest groups of road casualties; their death rate around the world due to vehicle-pedestrian collisions is high and tending to rise. In Spain, as in other countries of the European Union, steps have been taken to reduce the number and consequences of such accidents, with encouraging results in recent years. A key to countering this concern is the accident research activity that has obtained remarkable achievements in different fields, especially when multidisciplinary approaches are taken. This paper describes the development of a multivariate model that is able to detect the most influential parameters on the consequences of vehicle-pedestrian collision and to quantify their impact on pedestrian fatality risk. First, an accident database containing detailed information and parameters of vehicle-pedestrian collisions in Madrid has been developed. The accidents were investigated on the spot by INSIA accident investigation teams and analyzed using advanced reconstruction techniques. The model was then developed with two components: (1) a classification tree that characterizes and selects the explanatory variables, identifying their interactions, and (2) a binary logistic regression to quantify the influence of each variable and interaction resulting from the classification tree. The whole model represents an important tool for identifying, quantifying and predicting the potential impact of measures aimed at reducing injuries in vehicle-pedestrian collisions
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