1,589 research outputs found
Effect of dephasing on the current statistics of mesoscopic devices
We investigate the effects of dephasing on the current statistics of
mesoscopic conductors with a recently developed statistical model, focusing in
particular on mesoscopic cavities and Aharonov-Bohm rings. For such devices, we
analyze the influence of an arbitrary degree of decoherence on the cumulants of
the current. We recover known results for the limiting cases of fully coherent
and totally incoherent transport and are able to obtain detailed information on
the intermediate regime of partial coherence for a varying number of open
channels. We show that dephasing affects the average current, shot noise, and
higher order cumulants in a quantitatively and qualitatively similar way, and
that consequently shot noise or higher order cumulants of the current do not
provide information on decoherence additional or complementary to what can be
already obtained from the average current.Comment: 4 pages, 4 figure
Mitochondrial DNA lineages of Italian Giara and Sarcidano horses
Giara and Sarcidano are 2 of the 15 extant native Italian horse breeds with limited dispersal capability that originated from a larger number of individuals. The 2 breeds live in two distinct isolated locations on the island of Sardinia. To determine the genetic structure and evolutionary history of these 2 Sardinian breeds, the first hypervariable segment of the mitochondrial DNA (mtDNA) was sequenced and analyzed in 40 Giara and Sarcidano horses and compared with publicly available mtDNA data from 43 Old World breeds. Four different analyses, including genetic distance, analysis of molecular variance, haplotype sharing, and clustering methods, were used to study the genetic relationships between the Sardinian and other horse breeds. The analyses yielded similar results, and the FST values indicated that a high percentage of the total genetic variation was explained by between-breed differences. Consistent with their distinct phenotypes and geographic isolation, the two Sardinian breeds were shown to consist of 2 distinct gene pools that had no gene flow between them. Giara horses were clearly separated from the other breeds examined and showed traces of ancient separation from horses of other breeds that share the same mitochondrial lineage. On the other hand, the data from the Sarcidano horses fit well with variation among breeds from the Iberian Peninsula and North-West Europe: genetic relationships among Sarcidano and the other breeds are consistent with the documented history of this breed
Assessment of psychological predictors of weight loss: How and what for?
Obesity is a multifactorial disease and the prominent factors playing a role in its pathogenesis are biological, environmental and psychological. There is a growing interest in understanding psychological functioning of obese subjects and the influence of psychological factors on treatment outcome. The aim of the present narrative review is to critically analyze the current literature, in order to point out the most common psychological constructs studied in obesity and to give an overview of the main existing tools investigating psychological features which have been considered significant for the prediction of success in weight loss and maintenance programs in obese patients. In this framework, the most common psychological constructs studied are: self-motivation, self-efficacy, locus of control, health related quality of life, self-esteem, self-control, concerns about body image, outcome expectations, and personality traits. These features have been explored through a wide variety of psychometric instruments. However, as an overall, studies evaluating the association between psychological features and treatment outcome failed to give consistent results. A possible explanation may consist on the fact that many tools widely used to explore psychological features were not specifically designed for obese patients and none of them was comprehensive of all possible psychological features involved. The identification of well-defined sub-groups of patients and the validation of more reliable and comprehensive tools, specifically designed for obese subjects, should be forecasted in order to reach a better knowledge of psychological functioning of obese individuals and to improve the outcome of weight loss programs
Catching VY Sculptoris in a low state
Context. In the context of a large campaign to determine the system
parameters of high mass transfer cataclysmic variables, we found VY Scl in a
low state in 2008. Aims. Making use of this low state, we study the stellar
components of the binary with little influence of the normally dominating
accretion disc. Methods. Time-resolved spectroscopy and photometry of VY Scl
taken during the low state are presented. We analysed the light-curve and
radial velocity curve and use time-resolved spectroscopy to calculate Doppler
maps of the dominant emission lines. Results. The spectra show narrow emission
lines of Halpha, Hbeta, HeI, NaID, and FeII, as well as faint TiO absorption
bands that trace the motion of the irradiated secondary star, and Halpha and
HeI emission line wings that trace the motion of the white dwarf. From these
radial velocities, we find an orbital period of 3.84 h, and put constraints on
binary parameters such as the mass ratio M2/M1 of 0.43 and the inclination of
15 deg. With a secondary's mass between 0.3 and 0.35 Msol, we derive the mass
for the white dwarf as M1 = 0.6-0.1 Msol.Comment: 8 pages, 9 figures, accepted for publication in A&
Formation of quantum dots in the potential fluctuations of InGaAs heterostructures probed by scanning gate microscopy
The disordered potential landscape in an InGaAs/InAlAs two-dimensional
electron gas patterned into narrow wires is investigated by means of scanning
gate microscopy. It is found that scanning a negatively charged tip above
particular sites of the wires produces conductance oscillations that are
periodic in the tip voltage. These oscillations take the shape of concentric
circles whose number and diameter increase for more negative tip voltages until
full depletion occurs in the probed region. These observations cannot be
explained by charging events in material traps, but are consistent with Coulomb
blockade in quantum dots forming when the potential fluctuations are raised
locally at the Fermi level by the gating action of the tip. This interpretation
is supported by simple electrostatic simulations in the case of a disorder
potential induced by ionized dopants. This work represents a local
investigation of the mechanisms responsible for the disorder-induced
metal-to-insulator transition observed in macroscopic two-dimensional electron
systems at low enough density
Scanning Gate Spectroscopy of transport across a Quantum Hall Nano-Island
We explore transport across an ultra-small Quantum Hall Island (QHI) formed
by closed quan- tum Hall edge states and connected to propagating edge channels
through tunnel barriers. Scanning gate microscopy and scanning gate
spectroscopy are used to first localize and then study a single QHI near a
quantum point contact. The presence of Coulomb diamonds in the spectroscopy
con- firms that Coulomb blockade governs transport across the QHI. Varying the
microscope tip bias as well as current bias across the device, we uncover the
QHI discrete energy spectrum arising from electronic confinement and we extract
estimates of the gradient of the confining potential and of the edge state
velocity.Comment: 13 pages, 3 figure
Scanning-gate microscopy of semiconductor nanostructures: an overview
This paper presents an overview of scanning-gate microscopy applied to the
imaging of electron transport through buried semiconductor nanostructures.
After a brief description of the technique and of its possible artifacts, we
give a summary of some of its most instructive achievements found in the
literature and we present an updated review of our own research. It focuses on
the imaging of GaInAs-based quantum rings both in the low magnetic field
Aharonov-Bohm regime and in the high-field quantum Hall regime. In all of the
given examples, we emphasize how a local-probe approach is able to shed new, or
complementary, light on transport phenomena which are usually studied by means
of macroscopic conductance measurements.Comment: Invited talk by SH at 39th "Jaszowiec" International School and
Conference on the Physics of Semiconductors, Krynica-Zdroj, Poland, June 201
Increasing the agricultural sustainability of closed agrivoltaic systems with the integration of vertical farming: A case study on baby-leaf lettuce
The photovoltaic (PV) greenhouses are closed agrivoltaic (CA) systems that allow the production of energy and food on the same land, but may result in a yield reduction when the shading of the PV panels is excessive. Adopting innovative cropping systems can increase the yield of the CA area, generating a more productive and sustainable agrosystem. In this case study we quantified the increase of land productivity derived from the integration of an experimental vertical farm (VF) for baby leaf lettuce inside a pre-existing commercial CA. The mixed system increased the yield by 13 times compared to the CA and the average LER was 1.31, but only 12 % of the energy consumption was covered by the CA energy. To achieve the energy self-sufficiency and avoid the related CO2 emissions, the VF area should not exceed 7–18 % of the CA area, depending on the PV energy yield and the daily light integral (DLI) of the LED lighting, meaning a land consumption from 5 to 14 times higher than the VF area. The support of the PV energy was essential for the profitability of the VFCA. Design features and solutions were proposed to increase the agronomic and economic sustainability of the VFCA. The VFs can be considered a possible answer for the reconversion of the actual underutilized CAs with high PV cover ratios into productive and efficient cropping systems, but a trade-off between energy production and land consumption should be identified to ensure an acceptable environmental sustainability of the mixed system
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