12,318 research outputs found
Manipulation of single-photon states encoded in transverse spatial modes: possible and impossible tasks
Controlled generation and manipulation of photon states encoded in their
spatial degrees of freedom is a crucial ingredient in many quantum information
tasks exploiting higher-than-two dimensional encoding. Here, we prove the
impossibility to arbitrarily modify -level state superpositions (quits)
for , encoded in the transverse modes of light, with optical components
associated to the group of symplectic transforms (Gaussian operations).
Surprisingly, we also provide an explicit construction of how non-Gaussian
operations acting on mode subspaces do enable to overcome the limit . In
addition, this set of operations realizes the full SU(3) algebra.Comment: Published in PR
Share Opportunity Sets and Cooperative Games
In many share problems there is a priori given a natural set of possible divisions to solve the sharing problem.Cooperative games related to such share sets are introduced, which may be helpful in solving share problems.Relations between properties of share sets and properties of games are investigated.The average lexicographic value for share sets and for cooperative games is studied.cooperative games;bankruptcy games;average lexicographic value;opportunity sets
Intrinsic switching field distribution of arrays of Ni80Fe20 nanowires probed by magnetic force microscopy
The progress of magnetization reversal of weakly packed ferromagnetic
Ni80Fe20 nanowire arrays of different diameters (40, 50, 70 and 100 nm)
electrodeposited in polycarbonate membranes was studied by magnetic force
microscopy (MFM). For such a low packing density of nanomagnets, the dipolar
interactions between neighbouring wires can be neglected. The intrinsic
switching field distribution has been extracted from in situ MFM images and its
width was found to be considerably smaller than for densely packed nanowire
arrays.Comment: 4 pages, 5 figures. To appear in Journal of Superconductivity and
Novel Magnetis
Magnetic force microscopy investigation of arrays of nickel nanowires and nanotubes
The magnetic properties of arrays of nanowires (NWs) and nanotubes (NTs), 150
nm in diameter, electrodeposited inside nanoporous polycarbonate membranes are
investigated. The comparison of the nanoscopic magnetic force microscopy (MFM)
imaging and the macroscopic behavior as measured by alternating gradient force
magnetometry (AGFM) is made. It is shown that MFM is a complementary technique
that provides an understanding of the magnetization reversal characteristics at
the microscopic scale of individual nanostructures. The local hysteresis loops
have been extracted by MFM measurements. The influence of the shape of such
elongated nanostructures on the dipolar coupling and consequently on the
squareness of the hysteresis curves is demonstrated. It is shown that the
nanowires exhibit stronger magnetic interactions than nanotubes. The
non-uniformity of the magnetization states is also revealed by combining the
MFM and AGFM measurements.Comment: 7 pages, 5 figure
Thermomechanical and morphological properties of poly(ethylene terephthalate)/anhydrous calcium terephthalate nanocomposites
Calcium terephthalate anhydrous salts (CATAS), synthetized by reaction of terephthalic acid with metal (Ca) oxide were incorporated at dierent weight contents (0-30 wt. %) in recycled Poly(ethylene terephthalate) (rPET) by melt processing. Their structure, morphology, thermal and mechanical properties (tensile and flexural behavior) were investigated. Results of tensile strength of the dierent formulations showed that when the CATAS content increased from 0.1 to 0.4 wt. %, tangible changes were observed (variation of tensile strength from 65.5 to 69.4 MPa, increasing value for E from 2887 up to 3131 MPa, respectively for neat rPET and rPET_0.4CATAS). A threshold weight amount (0.4 wt. %) of CATAS was also found, by formation at low loading, of a rigid amorphous fraction at the rPET/CATAS interface, due to the aromatic interactions (Ï-Ï conjugation) between the matrix and the filler. Above the threshold, a restriction of rPET/CATAS molecular chains mobility was detected, due to the formation of hybrid mechanical percolation networks. Additionally, enhanced thermal stability of CATAS filled rPET was registered at high content (Tmax shift from 426 to 441 offiC, respectively, for rPET and rPET_30CATAS), essentially due to chemical compatibility between terephthalate salts and polymer molecules, rich in stable aromatic rings. The singularity of a cold crystallization event, identified at the same loading level, confirmed the presence of an equilibrium state between nucleation and blocking eect of amorphous phase, basically related to the characteristic common terephthalate structure of synthetized Ca-Metal Organic Framework and the rPET matrix
Development and Testing of Pt/Al2O3 Catalysts for Hydrogen Peroxide Decomposition
Supported Pt/Al2O3 and Pt/SiC catalysts for hydrogen peroxide (HP) decomposition have been prepared by means of two innovative implantation techniques on spheres and granules of several alumina-based carriers (lanthanum-doped alumina, bimodal delta âalumina and theta âalumina, silicon carbide and alphaâalumina) with BET surface areas between 4 and 200 m2/g. In order to evaluate the chemical activity and thermal shock resistance of the supporting pellets, two focused sets of experiments have been carried out in a specifically-designed test bench. Scanning electron microscopy (SEM) measurements of the platinum load on the supporting surface have been used to assess the effectiveness of the deposition and monitor the degradation induced by hydrogen peroxide decomposition. Two of the Pt/αâAl2O3 catalysts showed excellent activity, high thermo-mechanical strength, and negligible loss of platinum after repeated cycles of hydrogen peroxide decomposition. In addition, h..
Mediterranean diet adherence and synergy with acute myocardial infarction and its determinants. a multicenter case-control study in Italy.
Cardiovascular diseases are the leading causes of mortality and morbidity in Western countries. The possible synergistic effect of poor adherence to a Mediterranean diet (MD) and other risk factors for acute myocardial infarction (AMI) such as hypertension, cholesterol, ever smoker, BMI> 25, diabetes, has not been deeply studied.
Design Case-control study. Methods Patients with first AMI and controls from four tertiary referral Italian centers were screened for enrolment. Dietary information was collected through a questionnaire and a MD adherence score was calculated. Physical activity and smoking habits were also registered. The Synergy Index was calculated according to Rothman. Results 127 cases and 173 controls were enrolled. The analysis was conducted using a dichotomous variable for the MD score with values 7 representing good adherence. Multivariate analysis showed the following variables associated to AMI: ever smoker (OR = 2.08), diabetes (OR = 1.42), hypertension (OR = 2.08), hypercholesterolemia (OR = 2.47), BMI> 25 (OR = 1.99), while a protective effect emerged both in subjects scoring > 7 on the MD score(OR = 0.55) and in subjects
resident of Southern Italy (OR = 0.38). A synergistic effect does exist between poor adherence to the MD and the following risk factors: hypertension, hypercholesterolemia,
BMI >25, diabetes and being a resident in central and northern Italy.
Conclusion
Synergy between heart disease risk factors and MD underlines the need to enlarge the list of known modifiable cardiovascular risk factors to include and promote adherence to Mediterranean dietary habits
On the Coherent State Path Integral for Linear Systems
We present a computation of the coherent state path integral for a generic
linear system using ``functional methods'' (as opposed to discrete time
approaches). The Gaussian phase space path integral is formally given by a
determinant built from a first-order differential operator with coherent state
boundary conditions. We show how this determinant can be expressed in terms of
the symplectic transformation generated by the (in general, time-dependent)
quadratic Hamiltonian for the system. We briefly discuss the conditions under
which the coherent state path integral for a linear system actually exists. A
necessary -- but not sufficient -- condition for existence of the path integral
is that the symplectic transformation generated by the Hamiltonian is
(unitarily) implementable on the Fock space for the system.Comment: 15 pages, plain Te
Chemical abundances and radial velocities in the extremely metal-poor galaxy DDO 68
We present chemical abundances and radial velocities of six HII regions in
the extremely metal-poor star-forming dwarf galaxy DDO 68. They are derived
from deep spectra in the wavelength range 3500 - 10,000 {\AA}, acquired with
the Multi Object Double Spectrograph (MODS) at the Large Binocular Telescope
(LBT). In the three regions where the [O III]4363 {\AA} line was
detected, we inferred the abundance of He, N, O, Ne, Ar, and S through the
"direct" method. We also derived the oxygen abundances of all the six regions
adopting indirect method calibrations. We confirm that DDO 68 is an extremely
metal-poor galaxy, and a strong outlier in the luminosity - metallicity
relation defined by star-forming galaxies. With the direct-method we find
indeed an oxygen abundance of 12+log(O/H)=7.140.07 in the northernmost
region of the galaxy and, although with large uncertainties, an even lower
12+log(O/H)=6.960.09 in the "tail". This is, at face value, the most
metal-poor direct abundance detection of any galaxy known. We derive a radial
oxygen gradient of -0.060.03 dex/kpc (or -0.30 dex ) with the
direct method, and a steeper gradient of -0.120.03 dex/kpc (or -0.59 dex
) from the indirect method. For the -element to oxygen
ratios we obtain values in agreement with those found in other metal-poor
star-forming dwarfs. For nitrogen, instead, we infer much higher values,
leading to log(N/O), at variance with the suggested existence of a
tight plateau at in extremely metal poor dwarfs. The derived helium mass
fraction ranges from Y=0.2400.005 to Y=0.250.02, compatible with
standard big bang nucleosynthesis. Finally, we measured HII region radial
velocities in the range 479522 km/s from the tail to the head of the
"comet", consistent with the rotation derived in the HI.Comment: Accepted for publication in MNRA
Electrical plasmon detection in graphene waveguides
We present a simple device architecture that allows all-electrical detection
of plasmons in a graphene waveguide. The key principle of our electrical
plasmon detection scheme is the non-linear nature of the hydrodynamic equations
of motion that describe transport in graphene at room temperature and in a wide
range of carrier densities. These non-linearities yield a dc voltage in
response to the oscillating field of a propagating plasmon. For illustrative
purposes, we calculate the dc voltage arising from the propagation of the
lowest-energy modes in a fully analytical fashion. Our device architecture for
all-electrical plasmon detection paves the way for the integration of graphene
plasmonic waveguides in electronic circuits.Comment: 9 pages, 3 figure
- âŠ