417 research outputs found
Noise thermometry applied to thermoelectric measurements in InAs nanowires
We apply noise thermometry to characterize charge and thermoelectric
transport in single InAs nanowires (NWs) at a bath temperature of 4.2 K. Shot
noise measurements identify elastic diffusive transport in our NWs with
negligible electron-phonon interaction. This enables us to set up a measurement
of the diffusion thermopower. Unlike in previous approaches, we make use of a
primary electronic noise thermometry to calibrate a thermal bias across the NW.
In particular, this enables us to apply a contact heating scheme, which is much
more efficient in creating the thermal bias as compared to conventional
substrate heating. The measured thermoelectric Seebeck coefficient exhibits
strong mesoscopic fluctuations in dependence on the back-gate voltage that is
used to tune the NW carrier density. We analyze the transport and
thermoelectric data in terms of approximate Mott's thermopower relation and to
evaluate a gate-voltage to Fermi energy conversion factor
Local noise in a diffusive conductor
The control and measurement of local non-equilibrium configurations is of
utmost importance in applications on energy harvesting, thermoelectrics and
heat management in nano-electronics. This challenging task can be achieved with
the help of various local probes, prominent examples including superconducting
or quantum dot based tunnel junctions, classical and quantum resistors, and
Raman thermography. Beyond time-averaged properties, valuable information can
also be gained from spontaneous fluctuations of current (noise). From these
perspective, however, a fundamental constraint is set by current conservation,
which makes noise a characteristic of the whole conductor, rather than some
part of it. Here we demonstrate how to remove this obstacle and pick up a local
noise temperature of a current biased diffusive conductor with the help of a
miniature noise probe. This approach is virtually noninvasive and extends
primary local measurements towards strongly non-equilibrium regimes.Comment: minor revision, accepted in Scientific Report
Topological Phenomena in the Real Periodic Sine-Gordon Theory
The set of real finite-gap Sine-Gordon solutions corresponding to a fixed
spectral curve consists of several connected components. A simple explicit
description of these components obtained by the authors recently is used to
study the consequences of this property. In particular this description allows
to calculate the topological charge of solutions (the averaging of the
-derivative of the potential) and to show that the averaging of other
standard conservation laws is the same for all components.Comment: LaTeX, 18 pages, 3 figure
Isoperiodic deformations of the acoustic operator and periodic solutions of the Harry Dym equation
We consider the problem of describing the possible spectra of an acoustic
operator with a periodic finite-gap density. We construct flows on the moduli
space of algebraic Riemann surfaces that preserve the periods of the
corresponding operator. By a suitable extension of the phase space, these
equations can be written with quadratic irrationalities.Comment: 15 page
On Soliton-type Solutions of Equations Associated with N-component Systems
The algebraic geometric approach to -component systems of nonlinear
integrable PDE's is used to obtain and analyze explicit solutions of the
coupled KdV and Dym equations. Detailed analysis of soliton fission, kink to
anti-kink transitions and multi-peaked soliton solutions is carried out.
Transformations are used to connect these solutions to several other equations
that model physical phenomena in fluid dynamics and nonlinear optics.Comment: 43 pages, 16 figure
Wannier functions for quasi-periodic finite-gap potentials
In this paper we consider Wannier functions of quasi-periodic g-gap () potentials and investigate their main properties. In particular, we discuss
the problem of averaging underlying the definition of Wannier functions for
both periodic and quasi-periodic potentials and express Bloch functions and
quasi-momenta in terms of hyperelliptic functions. Using this approach
we derive a power series expansion of the Wannier function for quasi-periodic
potentials valid at and an asymptotic expansion valid at large
distance. These functions are important for a number of applied problems
LE ATTIVITA’ INFORMATIVE DELL’INGV IN EMERGENZA SISMICA: MOTIVAZIONI E IPOTESI DI SVILUPPO FUTURO
Negli ultimi anni, in particolare a partire dalla sequenza sismica aquilana del 2009, il tema dell’informazione e della comunicazione collegata ad una situazione di emergenza sismica è diventato oggetto di dibattito pubblico, di discussione all’interno della comunità scientifica, di studio in ambienti disciplinari molto diversi (sociologia della comunicazione, psicologia dell’emergenza, ambito giuridico, ecc.) e di riflessione più generale all’interno del Sistema di protezione civile.
In questa nostro lavoro si intende discutere del tema più generale dell’informazione che il Sistema di protezione civile (e la comunità scientifica che ne è una componente essenziale) produce in situazioni di emergenza o post-emergenza.
Indubbia è l’importanza di una buona comunicazione, attentamente testata, in momenti di crisi. Essa infatti può aiutare a migliorare la risposta all’emergenza, ridurre i costi del disastro, migliorare la trasparenza del processo decisionale e aumentare il potenziale di accettazione delle conseguenze (Del Lungo, 2012; Wendling et al., 2013).
Lo scopo del presente lavoro è quello di sintetizzare ragioni, forme e contenuti delle attività informative che, in modo sempre più organico, sono state realizzate in numerose occasioni, a partire principalmente dal 2009, ipotizzando uno schema di protocollo operativo per la gestione di tali attività .
Va ricordato che le esperienze qui descritte sono state realizzate in modo coordinato con il Dipartimento della Protezione Civile e che questa attività è formalmente parte del programma di lavoro annuale all’interno della convenzione decennale DPC-INGV
Integrable equations in nonlinear geometrical optics
Geometrical optics limit of the Maxwell equations for nonlinear media with
the Cole-Cole dependence of dielectric function and magnetic permeability on
the frequency is considered. It is shown that for media with slow variation
along one axis such a limit gives rise to the dispersionless Veselov-Novikov
equation for the refractive index. It is demonstrated that the Veselov-Novikov
hierarchy is amenable to the quasiclassical DBAR-dressing method. Under more
specific requirements for the media, one gets the dispersionless
Kadomtsev-Petviashvili equation. Geometrical optics interpretation of some
solutions of the above equations is discussed.Comment: 33 pages, 7 figure
Biliary Diseases from the Microbiome Perspective: How Microorganisms Could Change the Approach to Benign and Malignant Diseases
Recent evidence regarding microbiota is modifying the cornerstones on pathogenesis and the approaches to several gastrointestinal diseases, including biliary diseases. The burden of biliary diseases, indeed, is progressively increasing, considering that gallstone disease affects up to 20% of the European population. At the same time, neoplasms of the biliary system have an increasing incidence and poor prognosis. Framing the specific state of biliary eubiosis or dysbiosis is made difficult by the use of heterogeneous techniques and the sometimes unwarranted invasive sampling in healthy subjects. The influence of the microbial balance on the health status of the biliary tract could also account for some of the complications surrounding the post-liver-transplant phase. The aim of this extensive narrative review is to summarize the current evidence on this topic, to highlight gaps in the available evidence in order to guide further clinical research in these settings, and, eventually, to provide new tools to treat biliary lithiasis, biliopancreatic cancers, and even cholestatic disease
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