Sensing with magnetic dipolar resonances in semiconductor nanospheres

In this work we propose two novel sensing principles of detection that exploit the magnetic dipolar Mie resonance in high-refractiveindex dielectric nanospheres. In particular, we theoretically investigate the spectral evolution of the extinction and scattering cross sections of these nanospheres as a function of the refractive index of the external medium (next). Unlike resonances in plasmonic nanospheres, the spectral position of magnetic resonances in high-refractive-index nanospheres barely shifts as next changes. Nevertheless, there is a drastic reduction in the extinction cross section of the nanospheres when next increases, especially in the magnetic dipolar spectral region, which is accompanied with remarkable variations in the radiation patterns. Thanks to these changes, we propose two new sensing parameters, which are based on the detection of: i) the intensity variations in the transmitted or backscattered radiation by the dielectric nanospheres at the magnetic dipole resonant frequency, and ii) the changes in the radiation pattern at the frequency that satisfies Kerker's condition of near-zero forward radiation. To optimize the sensitivity, we consider several semiconductor materials and particles sizes. © 2013 Optical Society of America.B.G.-C. acknowledges support from the JAE-Doc program of the Spanish Council of Research (CSIC). This research has been funded by Ministerio de Ciencia e Innovación, through grants: Consolider NanoLight (CSD2007-00046), FIS2009-13430-C02, as well as by the Comunidad de Madrid (Microseres-CM, S2009/TIC-1476).Peer Reviewe

Modeling high-energy light curves of the PSR B1259-63/LS 2883 binary based on 3-D SPH simulations

Temporal changes of X-ray to very-high-energy gamma-ray emissions from the pulsar-Be star binary PSR B1259-63/LS 2883 are studied based on 3-D SPH simulations of pulsar wind interaction with Be-disk and wind. We focus on the periastron passage of the binary and calculate the variation of the synchrotron and inverse-Compton emissions using the simulated shock geometry and pressure distribution of the pulsar wind. The characteristic double-peaked X-ray light curve from observations is reproduced by our simulation under a dense Be disk condition (base density ~10^{-9} g cm^{-3}). We interpret the pre- and post-periastron peaks as being due to a significant increase in the conversion efficiency from pulsar spin down power to the shock-accelerated particle energy at orbital phases when the pulsar crosses the disk before periastron passage, and when the pulsar wind creates a cavity in the disk gas after periastron passage, respectively. On the contrary, in the model TeV light curve, which also shows a double peak feature, the first peak appears around the periastron phase. The possible effects of cooling processes on the TeV light curve are briefly discussed.Comment: 32 pages, 6 figues. Accepted for publication in Ap

Computational Indistinguishability between Quantum States and Its Cryptographic Application

We introduce a computational problem of distinguishing between two specific quantum states as a new cryptographic problem to design a quantum cryptographic scheme that is "secure" against any polynomial-time quantum adversary. Our problem, QSCDff, is to distinguish between two types of random coset states with a hidden permutation over the symmetric group of finite degree. This naturally generalizes the commonly-used distinction problem between two probability distributions in computational cryptography. As our major contribution, we show that QSCDff has three properties of cryptographic interest: (i) QSCDff has a trapdoor; (ii) the average-case hardness of QSCDff coincides with its worst-case hardness; and (iii) QSCDff is computationally at least as hard as the graph automorphism problem in the worst case. These cryptographic properties enable us to construct a quantum public-key cryptosystem, which is likely to withstand any chosen plaintext attack of a polynomial-time quantum adversary. We further discuss a generalization of QSCDff, called QSCDcyc, and introduce a multi-bit encryption scheme that relies on similar cryptographic properties of QSCDcyc.Comment: 24 pages, 2 figures. We improved presentation, and added more detail proofs and follow-up of recent wor

Socioeconomic Inequalities in Disability-free Life Expectancy in Older People from England and the United States: A Cross-national Population-Based Study

BACKGROUND: We examined socioeconomic inequalities in disability-free life expectancy in older men and women from England and the United States and explored whether people in England can expect to live longer and healthier lives than those in the United States. METHODS: We used harmonized data from the Gateway to Global Aging Data on 14,803 individuals aged 50+ from the U.S. Health and Retirement Study (HRS) and 10,754 from the English Longitudinal Study of Ageing (ELSA). Disability was measured in terms of impaired activities and instrumental activities of daily living. We used discrete-time multistate life table models to estimate total life expectancy and life expectancy free of disability. RESULTS: Socioeconomic inequalities in disability-free life expectancy were of a similar magnitude (in absolute terms) in England and the United States. The socioeconomic disadvantage in disability-free life expectancy was largest for wealth, in both countries: people in the poorest group could expect to live seven to nine fewer years without disability than those in the richest group at the age of 50. CONCLUSIONS: Inequalities in healthy life expectancy exist in both countries and are of similar magnitude. In both countries, efforts in reducing health inequalities should target people from disadvantaged socioeconomic groups

The Importance of Neighborhood Social Cohesion and Social Capital for the Well Being of Older Adults in the Community

We aimed to investigate whether social capital (obtaining support through indirect ties such as from neighbors) and social cohesion (interdependencies among neighbors) within neighborhoods positively affect the well being of older adults. Design and Methods: This crosssectional study included 945 of 1,440 (66% response rate) independently living older adults (aged !70 years) in Rotterdam. We fitted a hierarchical random effects model to account for the hierarchical structure of the study design: 945 older adults (Level 1) nested in 72 neighborhoods (Level 2). Results: Univariate analyses showed that being born in the Netherlands, house ownership, education, income, social capital of individuals, neighborhood security, neighborhood services, neighborhood social capital, and neighborhood social cohesion were significantly related to the well being of older adults. Multilevel analyses showed that social capital of individuals, neighborhood services, neighborhood social capital, and neighborhood social cohesion predicted the well being of older adults. Single and poor older adults reported lower well being than did better off and married older adults. However, the effects of marital status and income were mediated by neighborhood services, social capital, and social cohesion. Neighborhood services, social capital, and social cohesion may act as buffer against the adverse effects of being single and poor on the well being of older adults. Implications: The results of this study support the importance of social capital of individuals, as well as social capital within the neighborhood and social cohesion within the neighborhood for well being of older adults. The well being of older adults may also be enhanced through the improvement of quality of neighborhood services

Depression and Risk of Sudden Cardiac Death and Coronary Heart Disease in Women Results From the Nurses' Health Study

ObjectivesWe assessed the association between depression and sudden cardiac death (SCD) and cardiac events among individuals without baseline coronary heart disease (CHD).BackgroundDepression is a risk factor for cardiac events and mortality among those with CHD, possibly from arrhythmia.MethodsWe studied depressive symptoms and a proxy variable for clinical depression consisting of severe symptoms and/or antidepressant medication use and their relationship to cardiac events in the Nurses' Health Study. Questionnaires in 1992, 1996, and 2000 assessed symptoms with the Mental Health Index (MHI-5), and antidepressant use was assessed in 1996 and 2000. Primary end points included SCD, fatal CHD, and nonfatal myocardial infarction.ResultsAmong 63,469 women without prior CHD/stroke in 1992, 7.9% had MHI-5 scores <53, previously found to predict clinical depression. Depressive symptoms were associated with CHD events, and the relationship was strongest for fatal CHD, where the association remained significant even after controlling for CHD risk factors (hazard ratio [HR]: 1.49; 95% confidence interval [CI]: 1.11 to 2.00 for MHI-5 score <53). In models from 1996 onward, our proxy variable for clinical depression was most associated with SCD in multivariable models (HR: 2.33, 95% CI: 1.47 to 3.70), and this risk was primarily due to a specific relationship between antidepressant use and SCD (HR: 3.34, 95% CI: 2.03 to 5.50).ConclusionsIn this cohort of women without baseline CHD, depressive symptoms were associated with fatal CHD, and a measure of clinical depression including antidepressant use was specifically associated with SCD. Although antidepressant use might be a marker of worse depression, its specific association with SCD merits further study

Detection of diffuse TeV gamma-ray emission from the nearby starburst galaxy NGC 253

We report the TeV gamma-ray observations of the nearby normal spiral galaxy NGC 253. At a distance of $\sim$2.5 Mpc, NGC 253 is one of the nearest starburst galaxies. This relative closeness, coupled with the high star formation rate in the galaxy, make it a good candidate TeV gamma-ray source. Observations were carried out in 2000 and 2001 with the CANGAROO-II 10 m imaging atmospheric Cerenkov telescope. TeV gamma-ray emission is detected at the $\sim 11\sigma$ level with a flux of $(7.8 \pm 2.5)\times 10^{-12} {\rm cm}^{-2} {\rm sec}^{-1}$ at energies $>$0.5 TeV. The data indicate that the emission region is broader than the point spread function of our telescope.Comment: 4 pages, double colomn, 3 figures, aa.cl