6,442 research outputs found
A pure-carbon ring transistor: The role of topology and structure
We report results on the rectification properties of a carbon nanotube (CNT)
ring transistor, contacted by CNT leads, whose novel features have been
recently communicated by Watanabe et al. [Appl. Phys. Lett. 78, 2928 (2001)].
This paper contains results which are validated by the experimental
observations. Moreover, we report on additional features of the transmission of
this ring device which are associated with the possibility of breaking the lead
inversion symmetry. The linear conductance displays a "chessboard"-like
behavior alternated with anomalous zero-lines which should be directly
observable in experiments. We are also able to discriminate in our results
structural properties (quasi-onedimensional confinement) from pure topological
effects (ring configuration), thus helping to gain physical intuition on the
rich ring phenomenology.Comment: 3 pages, 4 figure
Generating random networks with given degree-degree correlations and degree-dependent clustering
Random networks are widely used to model complex networks and research their
properties. In order to get a good approximation of complex networks
encountered in various disciplines of science, the ability to tune various
statistical properties of random networks is very important. In this manuscript
we present an algorithm which is able to construct arbitrarily degree-degree
correlated networks with adjustable degree-dependent clustering. We verify the
algorithm by using empirical networks as input and describe additionally a
simple way to fix a degree-dependent clustering function if degree-degree
correlations are given.Comment: 4 pages, 3 figure
The double of the doubles of Klein surfaces
A Klein surface is a surface with a dianalytic structure. A double of a Klein
surface is a Klein surface such that there is a degree two morphism (of
Klein surfaces) . There are many doubles of a given Klein
surface and among them the so-called natural doubles which are: the complex
double, the Schottky double and the orienting double. We prove that if is a
non-orientable Klein surface with non-empty boundary, the three natural
doubles, although distinct Klein surfaces, share a common double: "the double
of doubles" denoted by . We describe how to use the double of doubles in
the study of both moduli spaces and automorphisms of Klein surfaces.
Furthermore, we show that the morphism from to is not given by the
action of an isometry group on classical surfaces.Comment: 14 pages; more details in the proof of theorem
Fermion masses in a model for spontaneous parity breaking
In this paper we discuss a left-right symmetric model for elementary
particles and their connection with the mass spectrum of elementary fermions.
The model is based on the group . New
mirror fermions and a minimal set of Higgs particles that breaks the symmetry
down to are proposed. The model can accommodate a consistent
pattern for charged and neutral fermion masses as well as neutrino
oscillations. An important consequence of the model is that the connection
between the left and right sectors can be done by the neutral vector gauge
bosons Z and a new heavy Z'.Comment: 7 pages, 3 figures. Accepted in Eur. Phys. J.
Constraints on a scale-dependent bias from galaxy clustering
We forecast the future constraints on scale-dependent parametrizations of
galaxy bias and their impact on the estimate of cosmological parameters from
the power spectrum of galaxies measured in a spectroscopic redshift survey. For
the latter we assume a wide survey at relatively large redshifts, similar to
the planned Euclid survey, as baseline for future experiments. To assess the
impact of the bias we perform a Fisher matrix analysis and we adopt two
different parametrizations of scale-dependent bias. The fiducial models for
galaxy bias are calibrated using a mock catalogs of H emitting galaxies
mimicking the expected properties of the objects that will be targeted by the
Euclid survey.
In our analysis we have obtained two main results. First of all, allowing for
a scale-dependent bias does not significantly increase the errors on the other
cosmological parameters apart from the rms amplitude of density fluctuations,
, and the growth index , whose uncertainties increase by a
factor up to two, depending on the bias model adopted. Second, we find that the
accuracy in the linear bias parameter can be estimated to within 1-2\%
at various redshifts regardless of the fiducial model. The non-linear bias
parameters have significantly large errors that depend on the model adopted.
Despite of this, in the more realistic scenarios departures from the simple
linear bias prescription can be detected with a significance at
each redshift explored.
Finally, we use the Fisher Matrix formalism to assess the impact of assuming
an incorrect bias model and found that the systematic errors induced on the
cosmological parameters are similar or even larger than the statistical ones.Comment: new section added; conclusions unchanged; accepted for publication in
PR
The Construction of the Concept Internet through Metaphors
The expressions by which we refer to the Internet reveal how we conceptualize
it. Rather than “a network of networks of computers”, as it is usually defined, we actually
perceive and experience the Internet as a PLACE. This paper will particularly analyse THE
INTERNET IS A CITY as one of the most productive metaphors that shape the concept INTERNET
in English, whereas THE INTERNET IS A SEA seems to be the most common metaphor for
Spanish speakers. Finally, some possible reasons and consequences for this variation will be
advanced.Las expresiones con las que nos referimos a Internet y a sus posibles usos revelan
cómo lo conceptualizamos. Más que «una red de redes de ordenadores», como normalmente
se la define, percibimos y experimentamos Internet como un LUGAR. Este trabajo analiza
concretamente la metáfora INTERNET ES UNA CIUDAD como una de las más productivas para
formar el concepto INTERNET en inglés, mientras que INTERNET ES UN MAR parece ser la
metáfora más habitual para los hablantes de español. Finalmente, se consideran algunas de
las posibles razones y consecuencias de esta variación
Seismic vulnerability assessment of clustered historical centers: fragility curves based on local collapse mechanisms analyses
open5noProtection and preservation of minor historical centres against earthquakes effects are
not trivial tasks, particularly in the cases, quite common, of complex aggregate buildings. The paper
aims at evaluating the seismic vulnerability of historical clustered buildings on a urban scale, through the
analysis of local collapse mechanisms, carried out with a parametric approach. This procedure is applied
to four historical centres of L’Aquila province struck by the 2009 earthquake. The identification of the
significant parameters is related to the definition of representative typologies within the city centres. Each
typology is characterized by recurring features, mainly recognizable with a survey performed outside the
buildings. After the identification of the relevant aspects, local mechanisms of collapse analyses are carried
out, by varying the parameters between defined range of values, in order to take into account possible
uncertainties in the data collection. A set of fragility curves for each identified typology is defined
and the obtained results are compared to the damage data gathered in the post-earthquake phase for the
buildings. This approach allows for possible extensions to buildings that may be included in the typology
categories here defined.openTaffarel, S.; Caliman, M.; Valluzzi, M.R; da Porto, F.; Modena, C.Taffarel, Sabrina; Caliman, M.; Valluzzi, MARIA ROSA; DA PORTO, Francesca; Modena, Claudi
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