1,854 research outputs found
Correlates of Poverty and Participation in Food Assistance Programs among Hispanic Elders in Massachusetts
Hispanics are a rapidly growing population in Massachusetts, but little is known about the health, nutrition, and economic situation of the elder segment of these groups. In this report, we examine factors associated with poverty and the use of food assistance programs, using data from an NIA-funded project on Hispanic elders in Massachusetts. Poverty is shown to be a major problem with differences across Hispanic subgroups. Puerto Rican and Dominican elders have lower incomes, on average, than other Hispanics—mainly Cubans, and Central and South Americans—or than non-Hispanic whites living in the same neighborhoods. Older age, lower education, and living alone are associated with poverty within this population. Limited income sources and recent immigration are also important factors. Hispanic elders are more likely to receive SSI benefits, but are much less likely to have pension income. Financial insecurity in old age among Hispanics is associated with more chronic ailment and mobility limitations. Puerto Rican and Dominican elders have the highest poverty and disability rates and report the most food insecurity. However, with the exception of the Food Stamp program, participation in food programs tends to be very low for these Hispanic elders. Given the prevalence of problems demonstrated by these groups, more attention to program outreach and adaptation for Hispanic elders is needed.
Robust Trapped-Ion Quantum Logic Gates by Continuous Dynamical Decoupling
We introduce a novel scheme that combines phonon-mediated quantum logic gates
in trapped ions with the benefits of continuous dynamical decoupling. We
demonstrate theoretically that a strong driving of the qubit decouples it from
external magnetic-field noise, enhancing the fidelity of two-qubit quantum
gates. Moreover, the scheme does not require ground-state cooling, and is
inherently robust to undesired ac-Stark shifts. The underlying mechanism can be
extended to a variety of other systems where a strong driving protects the
quantum coherence of the qubits without compromising the two-qubit couplings.Comment: Slightly longer than the published versio
Nonlinear unmixing of hyperspectral images: Models and algorithms
When considering the problem of unmixing hyperspectral images, most of the literature in the geoscience and image processing areas relies on the widely used linear mixing model (LMM). However, the LMM may be not valid, and other nonlinear models need to be considered, for instance, when there are multiscattering effects or intimate interactions. Consequently, over the last few years, several significant contributions have been proposed to overcome the limitations inherent in the LMM. In this article, we present an overview of recent advances in nonlinear unmixing modeling
The circumstellar environment of HD50138 revealed by VLTI/AMBER at high angular resolution
HD50138 is a Herbig B[e] star with a circumstellar disc detected at IR and mm
wavelength. Its brightness makes it a good candidate for NIR interferometry
observations. We aim to resolve, spatially and spectrally, the continuum and
hydrogen emission lines in the 2.12-2.47 micron region, to shed light on the
immediate circumstellar environment of the star. VLTI/AMBER K-band observations
provide spectra, visibilities, differential phases, and closure phases along
three long baselines for the continuum, and HI emission in Br and five
high-n Pfund lines. By computing the pure-line visibilities, we derive the
angular size of the different line-emitting regions. A simple LTE model was
created to constrain the physical conditions of HI emitting region. The
continuum region cannot be reproduced by a geometrical 2D elongated Gaussian
fitting model. We estimate the size of the region to be 1 au. We find the
Br and Pfund lines come from a more compact region of size 0.4 au. The
Br line exhibits an S-shaped differential phase, indicative of
rotation. The continuum and Br line closure phase show offsets of
-255 and 2010, respectively. This is evidence of an
asymmetry in their origin, but with opposing directions. We find that we cannot
converge on constraints for the HI physical parameters without a more detailed
model. Our analysis reveals that HD50138 hosts a complex circumstellar
environment. Its continuum emission cannot be reproduced by a simple disc
brightness distribution. Similarly, several components must be evoked to
reproduce the interferometric observables within the Br, line.
Combining the spectroscopic and interferometric data of the Br and
Pfund lines favours an origin in a wind region with a large opening angle.
Finally, our results point to an evolved source.Comment: accepted for publication in A&
Matrix Assisted Formation of Ferrihydrite Nanoparticles in a Siloxane/Poly(Oxyethylene) Nanohybrid
Matrix-assisted formation of ferrihydrite, an iron oxide hydroxide analogue
of the protein ferritin-core, in a sol-gel derived organic-inorganic hybrid is
reported. The hybrid network (named di-ureasil) is composed of
poly(oxyethylene) chains of different average polymer molecular weights grafted
to siloxane domains by means of urea cross-linkages and accommodates
ferrihydrite nanoparticles. Magnetic measurements, Fourier transform infrared
and nuclear magnetic resonance spectroscopy reveal that the controlled
modification of the polymer molecular weight allows the fine-tuning of the
ability of the hybrid matrix to assist and promote iron coordination at the
organic-inorganic interface and subsequent nucleation and growth of the
ferrihydrite nanoparticles whose core size (2-4 nm) is tuned by the amount of
iron incorporated. The polymer chain length, its arrangement and crystallinity,
are key factors on the anchoring and formation of the ferrihydrite particles.Comment: 7 pages, 6 figures. To be published in J. Mater. Che
Raman microprobe characterization of electrodeposited S-rich CuIn(S,Se)2 for photovoltaic applications: Microstructural analysis
This article reports a detailed Raman scattering and microstructural characterization of S-rich CuIn(S,Se)2 absorbers produced by electrodeposition of nanocrystalline CuInSe2 precursors and subsequent reactive annealing under sulfurizing conditions. Surface and in-depth resolved Raman microprobe measurements have been correlated with the analysis of the layers by optical and scanning electron microscopy, x-ray diffraction, and in-depth Auger electron spectroscopy. This has allowed corroboration of the high crystalline quality of the sulfurized layers. The sulfurizing conditions used also lead to the formation of a relatively thick MoS2 intermediate layer between the absorber and the Mo back contact. The analysis of the absorbers has also allowed identification of the presence of In-rich secondary phases, which are likely related to the coexistence in the electrodeposited precursors of ordered vacancy compound domains with the main chalcopyrite phase, in spite of the Cu-rich conditions used in the growth. This points out the higher complexity of the electrodeposition and sulfurization processes in relation to those based in vacuum deposition techniques
An Optical-Lattice-Based Quantum Simulator For Relativistic Field Theories and Topological Insulators
We present a proposal for a versatile cold-atom-based quantum simulator of
relativistic fermionic theories and topological insulators in arbitrary
dimensions. The setup consists of a spin-independent optical lattice that traps
a collection of hyperfine states of the same alkaline atom, to which the
different degrees of freedom of the field theory to be simulated are then
mapped. We show that the combination of bi-chromatic optical lattices with
Raman transitions can allow the engineering of a spin-dependent tunneling of
the atoms between neighboring lattice sites. These assisted-hopping processes
can be employed for the quantum simulation of various interesting models,
ranging from non-interacting relativistic fermionic theories to topological
insulators. We present a toolbox for the realization of different types of
relativistic lattice fermions, which can then be exploited to synthesize the
majority of phases in the periodic table of topological insulators.Comment: 24 pages, 6 figure
Exploiting line metric reconstruction from non-central circular panoramas
In certain non-central imaging systems, straight lines are projected via a non-planar surface encapsulating the 4 degrees of freedom of the 3D line. Consequently the geometry of the 3D line can be recovered from a minimum of four image points. However, with classical non-central catadioptric systems there is not enough effective baseline for a practical implementation of the method. In this paper we propose a multi-camera system configuration resembling the circular panoramic model which results in a particular non-central projection allowing the stitching of a non-central panorama. From a single panorama we obtain well-conditioned 3D reconstruction of lines, which are specially interesting in texture-less scenarios. No previous information about the direction or arrangement of the lines in the scene is assumed. The proposed method is evaluated on both synthetic and real images
Interaction-dependent photon-assisted tunneling in optical lattices: a quantum simulator of strongly-correlated electrons and dynamical gauge fields
We introduce a scheme that combines photon-assisted tunneling by a moving optical lattice with strong Hubbard interactions, and allows for the quantum simulation of paradigmatic quantum many-body models. We show that, in a certain regime, this quantum simulator yields an effective Hubbard Hamiltonian with tunable bond-charge interactions, a model studied in the context of strongly-correlated electrons. In a different regime, we show how to exploit a correlated destruction of tunneling to explore Nagaoka ferromagnetism at finite Hubbard repulsion. By changing the photon-assisted tunneling parameters, we can also obtain a t-J model with independently controllable tunneling t, super-exchange interaction J, and even a Heisenberg-Ising anisotropy. Hence, the full phase diagram of this paradigmatic model becomes accessible to cold-atom experiments, departing from the region t _ J allowed by standard single-band Hubbard Hamiltonians in the strong-repulsion limit. We finally show that, by generalizing the photon-assisted tunneling scheme, the quantum simulator yields models of dynamical Gauge fields, where atoms of a given electronic state dress the tunneling of the atoms with a different internal state, leading to Peierls phases that mimic a dynamical magnetic field
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