Two-Ray Modeling of Recombination Effects in the Presence of a Phase Conjugation Array

This article describes by means of a simple model how signal recombination effects behave under the influence of phase conjugating retrodirective array (RDA) technology. A two-ray ground reflection model is used to predict the operational advantages of RDA technology in multipath rich environments. The simulation results show that advantageous signal recombination occurs due to automatic self-phasing. As the number of elements in the RDA increases, the fading effect normally observed due to out of phase multipath signal is mitigated to the extent that the system approaches that of one operating in a free space environment. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1987–1989, 2013

Linear Optics Simulation of Quantum Non-Markovian Dynamics

The simulation of open quantum dynamics has recently allowed the direct investigation of the features of system-environment interaction and of their consequences on the evolution of a quantum system. Such interaction threatens the quantum properties of the system, spoiling them and causing the phenomenon of decoherence. Sometimes however a coherent exchange of information takes place between system and environment, memory effects arise and the dynamics of the system becomes non-Markovian. Here we report the experimental realisation of a non-Markovian process where system and environment are coupled through a simulated transverse Ising model. By engineering the evolution in a photonic quantum simulator, we demonstrate the role played by system-environment correlations in the emergence of memory effects.

Ordering the cytochrome c-initiated caspase cascade:hierarchical activation of caspases-2, -3, -6, -7, -8, and -10 in a caspase-9-dependent manner

Exit of cytochrome c from mitochondria into the cytosol has been implicated as an important step in apoptosis. In the cytosol, cytochrome c binds to the CED-4 homologue, Apaf-1, thereby triggering Apaf-1-mediated activation of caspase-9. Caspase-9 is thought to propagate the death signal by triggering other caspase activation events, the details of which remain obscure. Here, we report that six additional caspases (caspases-2, -3, -6, -7, -8, and -10) are processed in cell-free extracts in response to cytochrome c, and that three others (caspases-1, -4, and -5) failed to be activated under the same conditions. In vitro association assays confirmed that caspase-9 selectively bound to Apaf-1, whereas caspases-1, -2, -3, -6, -7, -8, and -10 did not. Depletion of caspase-9 from cell extracts abrogated cytochrome c-inducible activation of caspases-2, -3, -6, -7, -8, and -10, suggesting that caspase-9 is required for all of these downstream caspase activation events. Immunodepletion of caspases-3, -6, and -7 from cell extracts enabled us to order the sequence of caspase activation events downstream of caspase-9 and reveal the presence of a branched caspase cascade. Caspase-3 is required for the activation of four other caspases (-2, -6, -8, and -10) in this pathway and also participates in a feedback amplification loop involving caspase-9.

Multi-Dimensional Deprivation in Ireland Among 9-Year-Olds in Ireland:An Analysis of the Growing Up in Ireland Survey’

In this paper we make use of the 9-year old wave of the Growing Up in Ireland study to analyse multidimensional deprivation in Ireland. The Alkire and Foster adjusted head count ratio approach (AHCR; 2007, 2011a, 2011b) applied here constitutes a significant improvement on union and intersection approaches and allows for the decomposition of multidimensional poverty in terms of dimensions and sub-groups. The approach involves a censoring of data such that deprivations count only for those above the specified multidimensional threshold leading to a stronger set of interrelationships between deprivation dimensions. Our analysis shows that the composition of the adjusted head ratio is influenced by a range of socio-economic factors. For less-favoured socio-economic groups dimensions relating to material deprivation are disproportionately represented while for the more advantaged groups, those relating to behavioral and emotional issues and social interaction play a greater role. Notwithstanding such variation in composition, our analysis showed that the AHCR varied systematically across categories of household type, and the social class, education and age group of the primary care giver. Furthermore, these variables combined in a cumulative manner. The most systematic variation was in relation to the head count of those above the multidimensional threshold rather than intensity, conditional on being above that cut-off point. Without seeking to arbitrate on the relative value of composite indices versus disaggregated profiles, our analysis demonstrates that there is much to be gained from adopting an approach with clearly understood axiomatic properties. Doing so allows one to evaluate the consequences of the measurement strategy employed for the understanding of levels of multidimensional deprivation, the nature of such deprivation profiles and socio-economic risk patterns. Ultimately it permits an informed assessment of the strengths and weaknesses of the particular choices made.

Nonlinear optics from an ab initio approach by means of the dynamical Berry phase: Application to second- and third-harmonic generation in semiconductors

We present an ab initio real-time-based computational approach to study nonlinear optical properties in condensed matter systems that is especially suitable for crystalline solids and periodic nanostructures. The equations of motion and the coupling of the electrons with the external electric field are derived from the Berry-phase formulation of the dynamical polarization [Souza et al., Phys. Rev. B 69, 085106 (2004)]. Many-body effects are introduced by adding single-particle operators to the independent-particle Hamiltonian. We add a Hartree operator to account for crystal local effects and a scissor operator to correct the independent particle band structure for quasiparticle effects. We also discuss the possibility of accurately treating excitonic effects by adding a screened Hartree-Fock self-energy operator. The approach is validated by calculating the second-harmonic generation of SiC and AlAs bulk semiconductors: an excellent agreement is obtained with existing ab initio calculations from response theory in frequency domain [Luppi et al., Phys. Rev. B 82, 235201 (2010)]. We finally show applications to the second-harmonic generation of CdTe and the third-harmonic generation of Si. 

The controlled fabrication and geometry tunable optics of gold nanotube arrays

Arrays of vertically aligned gold nanotubes are fabricated over several square centimetres which display a geometry tunable plasmonic extinction peak at visible wavelengths and at normal incidence. The fabrication method gives control over nanotube dimensions with inner core diameters of 15–30 nm, wall thicknesses of 5–15 nm and nanotube lengths of up to 300 nm. It is possible to tune the position of the extinction peak through the wavelength range 600–900 nm by varying the inner core diameter and wall thickness. The experimental data are in agreement with numerical modelling of the optical properties which further reveal highly localized and enhanced electric fields around the nanotubes. The tunable nature of the optical response exhibited by such structures could be important for various label-free sensing applications based on both refractive index sensing and surface-enhanced Raman scattering.

Physical Activity, Gender, Weight Status, and Wellbeing in 9- to 11-Year-Old Children: A Cross-Sectional Survey

Background: The aim of this study was to examine the relationship between physical activity and wellbeing in children, and to further explore the extent to which this may vary by gender and weight status. Method: A representative sample of 1424 9- to 11-year-olds completed a self-report measure of physical activity, the Child Health and Illness Profile, KIDSCREEN, and a self-esteem scale. Body Mass Index (BMI) measurements were also obtained. Results: 24% of children achieved the recommended level of 60 minutes of moderate-tovigorous intensity physical activity (MVPA) per day, with more boys than girls achieving this level. Children achieving the recommended level of MVPA scored significantly higher on measures of the Child Health and Illness Profile (F(5, 1354) = 5.03; P < .001), KIDSCREEN (F(3, 1298) = 4.68; P = .003), and self-esteem (F(1,1271) = 18.73; P = .003) than less active children although the effect sizes were small (ηp2 ≈ .01). Substantial gender differences in wellbeing were found reflecting gender specific behaviors and socialization. Weight status had negligible influence on wellbeing. Conclusions: Children who meet the recommended guidelines of MVPA were more likely to have better wellbeing. When attempting to raise children’s physical activity levels consideration should be given to the specific relationships between wellbeing and physical activity.

INTERPLAY OF CAF2 SUBSTRATE ROUGHENING AND FILM DEPOSITION RATE ON RADIATIVE SCATTERING OF SURFACE-PLASMON POLARITONS FROM AG FILMS

The radiative decay of surface plasmon polaritons has been investigated in an attempt to characterize the surface roughness of Ag films prepared under different conditions. The polaritons were excited by the method of attenuated total reflection of light. The films were deposited on the face of a 60-degrees BK-7 glass prism at a rate that was deliberately fixed in two different ranges (centred on 0.1 and 10 nm s-1) and in some cases a CaF2 underlayer was used to roughen the film surfaces. The intensity of the scattered light emitted from the opposite face of the films was measured as a function of direction for each using the same sensitivity scale and was correlated with the preparation of the film. It was found that on nominally smooth substrates fast-deposited thinner films give out more light and are deduced to have greater short wavelength (300-600 nm) roughness amplitude. There is also evidence for long wavelenth (7 mum) periodic roughness due to the prism substrate itself. On CaF2 roughened surfaces the light output from the films is further increased and the peak intensity is backward directed with respect to the exciting laser beam direction. Here roughness on a lateral scale of 350 nm is responsible. Also, elastic scattering of surface plasmon polaritons at grain boundaries reduces the light output from fast deposited, small grain, films on CaF2 roughened surfaces. Overall, a consistent picture of roughness induced radiative polariton decay emerges for all cases studied.