4,115 research outputs found
Singlet-triplet transition in a few-electron lateral InGaAs-InAlAs quantum dot
The magnetic-field evolution of Coulomb blockade peaks in lateral
InGaAs/InAlAs quantum dots in the few-electron regime is reported. Quantum dots
are defined by gates evaporated onto a 60 nm-thick hydrogen silsesquioxane
insulating film. A gyromagnetic factor of 4.4 is measured via zero-bias spin
spectroscopy and a transition from singlet to triplet spin configuration is
found at an in-plane magnetic field B = 0.7 T. This observation opens the way
to the manipulation of singlet and triplet states at moderate fields and its
relevance for quantum information applications will be discussed.Comment: 4 pages, 3 figure
Electrostatic tailoring of magnetic interference in quantum point contact ballistic Josephson junctions
The magneto-electrostatic tailoring of the supercurrent in quantum point
contact ballistic Josephson junctions is demonstrated. An etched InAs-based
heterostructure is laterally contacted to superconducting niobium leads and the
existence of two etched side gates permits, in combination with the application
of a perpendicular magnetic field, to modify continuously the magnetic
interference pattern by depleting the weak link. For wider junctions the
supercurrent presents a Fraunhofer-like interference pattern with periodicity
h/2e whereas by shrinking electrostatically the weak link, the periodicity
evolves continuously to a monotonic decay. These devices represent novel
tunable structures that might lead to the study of the elusive Majorana
fermions.Comment: 4.5 pages, 4 color figure
Magneto-transport in high g-factor, low-density two-dimensional electron systems confined in In_0.75Ga_0.25As/In_0.75Al_0.25As quantum wells
We report magneto-transport measurements on high-mobility two-dimensional
electron systems (2DESs) confined in In_0.75Ga_0.25As/In_0.75Al_0.25As single
quantum wells. Several quantum Hall states are observed in a wide range of
temperatures and electron densities, the latter controlled by a gate voltage
down to values of 1.10^11 cm^-2. A tilted-field configuration is used to induce
Landau level crossings and magnetic transitions between quantum Hall states
with different spin polarizations. A large filling factor dependent effective
electronic g-factor is determined by the coincidence method and cyclotron
resonance measurements. From these measurements the change in
exchange-correlation energy at the magnetic transition is deduced. These
results demonstrate the impact of many-body effects in tilted-field
magneto-transport of high-mobility 2DESs confined in
In_0.75Ga_0.25As/In_0.75Al_0.25As quantum wells. The large tunability of
electron density and effective g-factor, in addition, make this material system
a promising candidate for the observation of a large variety of spin-related
phenomena.Comment: 7 pages, 5 figure
DEVELOPMENT AND VALIDATION OF A SYSTEM FOR POLING FORCE MEASUREMENT IN CROSS-COUNTRY SKIING AND NORDIC WALKING
The purpose of this study was to describe and validate a force transducer system specifically designed to measure the force exerted through the poles in cross-country skiing and Nordic walking. It is constituted by a custom built load cell and by a mounting system that allow to minimise cross talk effects. The system is applicable to standard carbon racing shafts to ensure the standard stiffness of the pole. The reliability of the system has been tested performing different static and dynamic tests. The comparison with the reference load cell has shown a good measurement linearity in the range of typical values for poling propulsion and a sensitivity only to the force axially applied to the shaft. The test performed on a 2D platform and with a motion capture system for the measurement of pole inclination, demonstrated the possibility to obtain a reliable measure of the vertical, longitudinal and lateral components of the force exerted by the subject. The accuracy, the portability of the system and their applicability to different shafts allow evaluation of poling action in both laboratory and field conditions, providing important information in cross-country skiing and Nordic walking biomechanical research
Multi-wavelength and black hole mass properties of Low Luminosity Active Nuclei
We investigate the relation between the X-ray nuclear emission, optical
emission line, radio luminosity and black hole mass for a sample of nearby
Seyfert galaxies. Strong linear correlations between the 2-10 keV and [OIII],
radio luminosities have been found, showing the same slopes found in quasars
and luminous Seyfert galaxies, thus implying independence from the level of
nuclear activity displayed by the sources. Moreover, despite the wide range of
Eddington ratios (L/L(Edd)) tested here (six orders of magnitude, from 0.1 down
to 10^(-7), no correlation is found between the X-ray, optical emission lines,
radio luminosities and the black hole mass. These results suggest that low
luminosity Seyfert galaxies are a scaled down version of luminous AGN and
probably are powered by the same physical processes.Comment: 6 pages, 3 figures, contributed talk presented at the Workshop "The
multicoloured landscape of compact objects and their explosive origin",
Cefalu' (Sicily), 11-24 June 2006, to be published by AI
Non Markovian Quantum Repeated Interactions and Measurements
A non-Markovian model of quantum repeated interactions between a small
quantum system and an infinite chain of quantum systems is presented. By
adapting and applying usual pro jection operator techniques in this context,
discrete versions of the integro-differential and time-convolutioness Master
equations for the reduced system are derived. Next, an intuitive and rigorous
description of the indirect quantum measurement principle is developed and a
discrete non Markovian stochastic Master equation for the open system is
obtained. Finally, the question of unravelling in a particular model of
non-Markovian quantum interactions is discussed.Comment: 22 page
Association between Resistin Levels and All-Cause and Cardiovascular Mortality: A New Study and a Systematic Review and Meta-Analysis.
CONTEXT: Studies concerning the association between circulating resistin and mortality risk have reported, so far, conflicting results.
OBJECTIVE: To investigate the association between resistin and both all-cause and cardiovascular (CV) mortality risk by 1) analyzing data from the Gargano Heart Study (GHS) prospective design (n=359 patients; 81 and 58 all-cause and CV deaths, respectively); 2) performing meta-analyses of all published studies addressing the above mentioned associations.
DATA SOURCE AND STUDY SELECTION: MEDLINE and Web of Science search of studies reporting hazard ratios (HR) of circulating resistin for all-cause or CV mortality.
DATA EXTRACTION: Performed independently by two investigators, using a standardized data extraction sheet.
DATA SYNTHESIS: In GHS, adjusted HRs per one standard deviation (SD) increment in resistin concentration were 1.28 (95% CI: 1.07-1.54) and 1.32 (95% CI: 1.06-1.64) for all-cause and CV mortality, respectively. The meta-analyses included 7 studies (n=4016; 961 events) for all-cause mortality and 6 studies (n=4,187: 412 events) for CV mortality. Pooled HRs per one SD increment in resistin levels were 1.21 (95% CI: 1.03-1.42, Q-test p for heterogeneity<0.001) and 1.05 (95% CI: 1.01-1.10, Q-test p for heterogeneity=0.199) for all-cause and CV mortality, respectively. At meta-regression analyses, study mean age explained 9.9% of all-cause mortality studies heterogeneity. After adjusting for age, HR for all-cause mortality was 1.24 (95% CI: 1.06-1.45).
CONCLUSIONS: Our results provide evidence for an association between circulating resistin and mortality risk among high-risk patients as are those with diabetes and coronary artery disease
Anti-crossings of spin-split Landau levels in an InAs two-dimensional electron gas with spin-orbit coupling
We report tilted-field transport measurements in the quantum-Hall regime in
an InAs/In_0.75Ga_0.25As/In_0.75Al_0.25As quantum well. We observe
anti-crossings of spin-split Landau levels, which suggest a mixing of spin
states at Landau level coincidence. We propose that the level repulsion is due
to the presence of spin-orbit and of band-non-parabolicity terms which are
relevant in narrow-gap systems. Furthermore, electron-electron interaction is
significant in our structure, as demonstrated by the large values of the
interaction-induced enhancement of the electronic g-factor.Comment: 4 pages, 3 figure
Ophthalmic manifestations of cat scratch disease
Cat scratch disease (CSD) is a worldwide distributed zoonosis caused by Bartonella henselae and other Bartonella spp. The reservoirs of Bartonella are domestic animals, especially cats, and the transmission to humans is thought to occur from a cat scratch or even through the cat flea Ctenocephalides felix. With more and more pet owners, the physicians should keep in mind signs and symptoms of CSD. A widespread infection may occur in 5-14% of cases, and ocular involvement, called ocular bartonellosis, is a quite common consequence of disseminated CSD. Although the most typical manifestations of ocular Bartonellosis are Parinaud's oculoglandular syndrome, neuroretinitis and retinochoroiditis, many other ophthalmic conditions have been reported. The diagnosis of CSD is often based on history of contact with a cat and high serum titers of immunoglobulin G antibodies against B. henselae. Polymerase chain reaction could be helpful for CSD diagnosis when serology is negative but clinical findings are suggestive for the disease. Multimodal imaging, including fundus autofluorescence, fluorescein and indocyanine green angiography, optical coherence tomography (OCT) and OCT angiography, can be used for diagnosis and monitoring of ocular Bartonellosis. Since CSD is more often a self-limited infection in immunocompetent individuals, no antibiotic treatment is usually needed. However, when a therapy is prescribed, doxycycline is the most used antibiotic. The aim of this article is to review the current literature relating to epidemiology, systemic and ocular manifestations, diagnosis, treatment and prognosis of bartonellosis, in order to give the ophthalmologists a useful tool for daily practice
Acid gas removal from natural gas by water washing
Projections in the future energy scenario outline an important role played by fossil fuels to meet the increasing
global energy demand. A “golden age” has been recently outlined for natural gas, in particular, as the fastest
growing and the cleanest of all fossil fuels. Although natural gas is mostly considered to be a “clean” fuel with
respect to the emission of pollutants from its combustion, the raw natural gas found in reservoir deposits is not
free of contaminants. Among the others, hydrogen sulphide and carbon dioxide are two undesired
compounds, which are responsible for the sour or acidic nature of natural gas and must be removed for
operational and safety reasons. Acid gas treating is typically performed in facilities built at surface locations,
mainly by means of chemical absorption into aqueous amine solutions. However, subsurface technologies
may allow to possibly separate the gas undesired compounds directly downhole. The high pressure
encountered in this environment makes the use of water as liquid absorbent worth considering. This work
investigates the possibility of acid gas removal from natural gas by downhole water washing and presents a
preliminary evaluation of the performances of the process, which is assumed to be carried out in the gas
production casing that can be represented as a bubble column. A previously proposed correlation for the gas
holdup in this type of contacting device operated counter-currently has been used to determine the volumetric
mass transfer coefficient for design purposes, considering different raw gas flow rates and inlet acid gas
concentrations. By solving a simplified model of a bubble column and by using water flow rates compatible
with reinjection into the reservoir, it has been found that it is possible to reduce the H2S content from the inlet
concentration to the commonly accepted value to meet pipeline specifications and, depending on the inlet CO2
concentration, to perform a bulk removal of it
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