3,359 research outputs found
Exciton Gas Compression and Metallic Condensation in a Single Semiconductor Quantum Wire
We study the metal-insulator transition in individual self-assembled quantum
wires and report optical evidences of metallic liquid condensation at low
temperatures. Firstly, we observe that the temperature and power dependence of
the single nanowire photoluminescence follow the evolution expected for an
electron-hole liquid in one dimension. Secondly, we find novel spectral
features that suggest that in this situation the expanding liquid condensate
compresses the exciton gas in real space. Finally, we estimate the critical
density and critical temperature of the phase transition diagram at
cm and K, respectively.Comment: 4 pages, 5 figure
Temporal characterization of the requests to Wikipedia
This paper presents an empirical study about the temporal patterns
characterizing the requests submitted by users to Wikipedia.
The study is based on the analysis of the log lines registered by the
Wikimedia Foundation Squid servers after having sent the appropriate
content in response to users' requests. The
analysis has been conducted regarding the ten most visited editions of
Wikipedia and has involved more than 14,000 million log lines
corresponding to the traffic of the entire year 2009. The conducted methodology
has mainly consisted in the parsing and filtering
of users' requests according to the study directives. As a result, relevant information
fields have been finally stored in a database for persistence and further
characterization. In this way, we, first, assessed, whether the traffic to Wikipedia could serve
as a reliable estimator of the overall traffic to all the Wikimedia Foundation
projects. Our subsequent analysis of the temporal evolutions corresponding to
the different types of requests to Wikipedia revealed interesting differences
and similarities among them that can be related to the users' attention to the Encyclopedia.
In addition, we have performed separated characterizations of each Wikipedia edition
to compare their respective evolutions over time
A quantitative examination of the impact of featured articles in Wikipedia
This paper presents a quantitative examination of the impact of the presentation of featured articles as quality content in the main page of several Wikipedia editions. Moreover, the paper also presents the analysis performed to determine the number of visits received by the articles promoted to the featured status. We have analyzed the visits not only in the month when articles awarded the promotion or were included in the main page, but also in the previous and following ones. The main aim for this is to assess the attention attracted by the featured content and the different dynamics exhibited by each community of users in respect to the promotion process. The main results of this paper are twofold: it shows how to extract relevant information related to the use of Wikipedia, which is an emerging research topic, and it analyzes whether the featured articles mechanism achieve to attract more attention
Tensorial analisis of the superposed deformation in the easthern border of the Madrid basin
An analysis of Neogene brittle deformation using fault populatÃon analysis methods has been carried out between the SW border of the Iberian Range and Altomira Range. Two main paleostress fields have been established: 1) N70E - N120E compression (Altomira paleostress field) ofLate Oligocene - Early Miocene age that induced the formation of the SW border of Iberian Range and Altomira - Pareja thrust belts with reverse and strike-slip faults.
2) N140-N160E compression (Guadarrama paleostress field) of Middle Aragonian - early Pleistocene age that reactivated previous faults with strikeslip movement along the Iberian Range. A superposition of two regional stress fields (Iberian and Guadarrama) is proposed to explain E-W compression that formed Altomira Range. Stress tensorial additions have been realized to check this hypothesis
Strain quantification related to the Berzosa/fault (Spanish Central System)
[Resumen] En relación con la zona de cizalla dúctil de Berzosa Honrubia que actúa durante la segunda fase de deformación HercÃnica, se han calculado los elipsoides de deformación finita asociados a la misma. Para el cálculo se usan los métodos de Ramsay (1967), Dunnet (1969), y Fry (1979). Los resultados muestran una variación en el tipo de elipsoide a lo largo de la traza de la zona de cizalla. En los extremos tienen valores K>t, y en la parte central de Kl en la región donde son paralelos.[Abstract] In the ductil shear zone of Berzosa Honrubia, active during the Hercynic second phase, finite strain ellipsoids have been calculated. Methods of Ramsay, Dunnet, and Fry have been used for this calculation. The results show a variation in the strain elipsoid shape through the shear zone trace. The central part h(!s strain ellipsoids with K1. Interpretation of those values is based on the variation in the orientation of the fault cartographic trace and tectonic transport direction. Ellipsoids with K1 are located where the trace and tectonic transport direction are parallel
Charge control in laterally coupled double quantum dots
We investigate the electronic and optical properties of InAs double quantum
dots grown on GaAs (001) and laterally aligned along the [110] crystal
direction. The emission spectrum has been investigated as a function of a
lateral electric field applied along the quantum dot pair mutual axis. The
number of confined electrons can be controlled with the external bias leading
to sharp energy shifts which we use to identify the emission from neutral and
charged exciton complexes. Quantum tunnelling of these electrons is proposed to
explain the reversed ordering of the trion emission lines as compared to that
of excitons in our system.Comment: 4 pages, 4 figures submitted to PRB Rapid Com
KMOS LENsing Survey (KLENS) : morpho-kinematic analysis of star-forming galaxies at
We present results from the KMOS lensing survey-KLENS which is exploiting
gravitational lensing to study the kinematics of 24 star forming galaxies at
with a median mass of and median
star formation rate (SFR) of . We find that 25% of
these low-mass/low-SFR galaxies are rotation dominated, while the majority of
our sample shows no velocity gradient. When combining our data with other
surveys, we find that the fraction of rotation dominated galaxies increases
with the stellar mass, and decreases for galaxies with a positive offset from
the main sequence. We also investigate the evolution of the intrinsic velocity
dispersion, , as a function of the redshift, , and stellar mass,
, assuming galaxies in quasi-equilibrium (Toomre Q parameter equal
to 1). From the relation, we find that the redshift evolution of
the velocity dispersion is mostly expected for massive galaxies (). We derive a relation, using
the Tully-Fisher relation, which highlights that a different evolution of the
velocity dispersion is expected depending on the stellar mass, with lower
velocity dispersions for lower masses, and an increase for higher masses,
stronger at higher redshift. The observed velocity dispersions from this work
and from comparison samples spanning appear to follow this relation,
except at higher redshift (), where we observe higher velocity dispersions
for low masses () and lower velocity
dispersions for high masses () than
expected. This discrepancy could, for instance, suggest that galaxies at
high- do not satisfy the stability criterion, or that the adopted
parametrisation of the specific star formation rate and molecular properties
fail at high redshift.Comment: Accepted for publication in A&A, 21 pages, 10 figure
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