1,101 research outputs found
Continuity and differentiability of regression M functionals
This paper deals with the Fisher-consistency, weak continuity and
differentiability of estimating functionals corresponding to a class of both
linear and nonlinear regression high breakdown M estimates, which includes S
and MM estimates. A restricted type of differentiability, called weak
differentiability, is defined, which suffices to prove the asymptotic normality
of estimates based on the functionals. This approach allows to prove the
consistency, asymptotic normality and qualitative robustness of M estimates
under more general conditions than those required in standard approaches. In
particular, we prove that regression MM-estimates are asymptotically normal
when the observations are -mixing.Comment: Published in at http://dx.doi.org/10.3150/11-BEJ368 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
Backlund transformations and Hamiltonian flows
In this work we show that, under certain conditions, parametric Backlund
transformations (BTs) for a finite dimensional integrable system can be
interpreted as solutions to the equations of motion defined by an associated
non-autonomous Hamiltonian. The two systems share the same constants of motion.
This observation lead to the identification of the Hamiltonian interpolating
the iteration of the discrete map defined by the transformations, that indeed
will be a linear combination of the integrals appearing in the spectral curve
of the Lax matrix. An application to the Toda periodic lattice is given.Comment: 19 pages, 2 figures. to appear in J. Phys.
Control of photon transport properties in nanocomposite nanowires
Active nanowires and nanofibers can be realized by the electric-field induced
stretching of polymer solutions with sufficient molecular entanglements. The
resulting nanomaterials are attracting an increasing attention in view of their
application in a wide variety of fields, including optoelectronics, photonics,
energy harvesting, nanoelectronics, and microelectromechanical systems.
Realizing nanocomposite nanofibers is especially interesting in this respect.
In particular, methods suitable for embedding inorganic nanocrystals in
electrified jets and then in active fiber systems allow for controlling
light-scattering and refractive index properties in the realized fibrous
materials. We here report on the design, realization, and morphological and
spectroscopic characterization of new species of active, composite nanowires
and nanofibers for nanophotonics. We focus on the properties of
light-confinement and photon transport along the nanowire longitudinal axis,
and on how these depend on nanoparticle incorporation. Optical losses
mechanisms and their influence on device design and performances are also
presented and discussed.Comment: 7 pages, 3 figures, 29 references. Invited contribution. Copyright
(2016) Society of Photo Optical Instrumentation Engineers. One print or
electronic copy may be made for personal use only. Systematic reproduction
and distribution, duplication of any material in this paper for a fee or for
commercial purposes, or modification of the content of the paper are
prohibite
Polychlorinated biphenyls, organochlorine pesticides, and polycyclic aromatic hydrocarbons in wild, farmed, and frozen marine seafood marketed in Campania, Italy.
Polychlorinated biphenyls (PCBs), organochlorine pesticides, and polycyclic aromatic hydrocarbons (PAHs) were detected in fresh-catch, farmed, and frozen marine fish marketed in Campania, Italy. Additionally, polychlorobiphenyl congeners were found: six were non-dioxin-like (NDL-PCB) (IUPAC no. 28, 52, 101, 138, 153, and 180), and one was dioxin-like (DL-PCB) (IUPAC no. 118). In all, 93% of fresh-catch, 100% of aquaculture, and 74% of the frozen specimens contained PCBs at concentrations varying from 0.12 to 35.11 ng/g, wet weight; NDL-PCBs ranged between 0.12 and 32.44 ng/g. Penta-, hexa-, and heptachlorobiphenyls were predominant. Regarding organochlorine pesticides, hexachlorobenzene was detected in 35% of fresh catch, 36% of farmed, and 46% of the frozen fish specimens, in a range between < 0.01 and 3.29 ng/g. Contents of the dichlorodiphenyltrichloroethane isomer amounted to 0.12 to 11.00 ng/g. Finally, PAHs were detected in 100% of the specimens. Benzo[a]pyrene was detected in 66% of the aquaculture, 35% of the fresh catch, and 24% of the frozen species, at concentrations varying from 0.03 to 9.18 ng/g. On the basis of annual fish consumption, an average daily intake of NDL-PCBs of 6.02 ng/kg of body weight was estimated. Calculated daily hexachlorobenzene and total dichlorodiphenyltrichloroethane intakes were, respectively, 0.11 and 0.90 ng/kg of body weight per day. The contribution of fish to the daily consumption of the noncarcinogenic PAHs can be considered low; for benzo[a]pyrene, the estimated daily intake is considerably lower than the doses considered carcinogenic for experimental animals by the European Union Scientific Committee on Food
Tracing Galaxy Formation with Stellar Halos I: Methods
If the favored hierarchical cosmological model is correct, then the Milky Way
system should have accreted ~100-200 luminous satellite galaxies in the past
\~12 Gyr. We model this process using a hybrid semi-analytic plus N-body
approach which distinguishes explicitly between the evolution of light and dark
matter in accreted satellites. This distinction is essential to our ability to
produce a realistic stellar halo, with mass and density profile much like that
of our own Galaxy, and a surviving satellite population that matches the
observed number counts and structural parameter distributions of the satellite
galaxies of the Milky Way. Our model stellar halos have density profiles which
typically drop off with radius faster than those of the dark matter. They are
assembled from the inside out, with the majority of mass (~80%) coming from the
\~15 most massive accretion events. The satellites that contribute to the
stellar halo have median accretion times of ~9 Gyr in the past, while surviving
satellite systems have median accretion times of ~5 Gyr in the past. This
implies that stars associated with the inner halo should be quite different
chemically from stars in surviving satellites and also from stars in the outer
halo or those liberated in recent disruption events. We briefly discuss the
expected spatial structure and phase space structure for halos formed in this
manner. Searches for this type of structure offer a direct test of whether
cosmology is indeed hierarchical on small scales.Comment: 22 pages, 16 figures, submitted to Ap
Baryon resonances and polarization transfer in hyperon photoproduction
A partial wave analysis is presented of data on photoproduction of hyperons
including single and double polarization observables. The large spin transfer
probability reported by the CLAS collaboration can be successfully described
with an isobar partial wave analysis.Comment: 12 pages, 9 figure
Individual and Multi Vortex Pinning in Systems with Periodic Pinning Arrays
We examine multi and individual vortex pinning in thin superconductors with
periodic pinning arrays. For multi-vortex pinning we observe peaks in the
critical current of equal magnitude at every matching field, while for
individual vortex pinning we observe a sharp drop in the critical current after
the first matching field in agreement with experiments. We examine the scaling
of the critical current at commensurate and incommensurate fields for varied
pinning strength and show that the depinning force at incommensurate fields
decreases faster than at the commensurate fields.Comment: 4 figuure
Occurrence of polychlorobiphenyls in buffalo mozzarella cheese from Campania (Italy)
Buffalo milk and mozzarella cheese produced in the Caserta and Salerno areas in Campania region have been investigated on the presence and the levels of polychlorobiphenyls (PCBs). Seven congeners, six non dioxin-like (NDL-PCBs nos. 28, 52, 101, 138, 153 and 180) and one dioxin-like (DL-PCB n. 118), were detected. PCBs were found at detectable levels in the 83% of the buffalo milk and in the 100% of the mozzarella cheese samples from Caserta; in those from Salerno the prevalence of contamination was 77% for milk and 73% for mozzarellas, respectively. The NDL-PCB content of mozzarellas collected in Caserta was significantly higher than that found in those from Salerno. The more diffuse congeners were PCB 28, 138 and 153 both in milk and in mozzarella cheese; PCB 118 contributed to the total PCB content for the 7% in milk and 2-3% in mozzarella cheese. On the basis of the Italian annual average consumption the contribution of mozzarella to the daily dietary intake of NDL-PCB can vary between 0.41 and 21.33 ng kg-1 bw, median value of 3.66 ng kg-1 bw. The levels of contamination in milk and dairies analyzed are similar or quite lower than those found in other European countries
Dynamic centrifuge testing to assess liquefaction potential
A set of centrifuge tests has been carried out at ISMGEO (Italy) laboratory on models of a liquefiable soil. A natural sand from the Emilia-Romagna region in Italy was used in the tests, in order to reproduce typical ground conditions where liquefaction occurred during the seismic sequence of 2012. The models were instrumented with miniaturised accelerometers and with pore pressure and displacement transducers. Spectrum-compatible acceleration time histories were applied at the base of the model. In this way triggering of the liquefaction was detected and post-liquefaction settlements were evaluated. The paper describes with the tests carried out on free-field models. Further tests are currently ongoing to assess the seismic response of simple model structures lying on liquefiable ground. The testing programme, funded within the H2020 research project LIQUEFACT, is aimed at an experimental verification of ground improvement techniques used to mitigate the liquefaction susceptibility of fully saturated loose sands
Imaging the essential role of spin-fluctuations in high-Tc superconductivity
We have used scanning tunneling spectroscopy to investigate short-length
electronic correlations in three-layer Bi2Sr2Ca2Cu3O(10+d) (Bi-2223). We show
that the superconducting gap and the energy Omega_dip, defined as the
difference between the dip minimum and the gap, are both modulated in space
following the lattice superstructure, and are locally anti-correlated. Based on
fits of our data to a microscopic strong-coupling model we show that Omega_dip
is an accurate measure of the collective mode energy in Bi-2223. We conclude
that the collective mode responsible for the dip is a local excitation with a
doping dependent energy, and is most likely the (pi,pi) spin resonance.Comment: 4 pages, 4 figure
- …