Time delay between photoemission from the 2p and 2s subshells of neon

The R-matrix incorporating time (RMT) method is a method developed recently for solving the time-dependent Schrödinger equation for multielectron atomic systems exposed to intense short-pulse laser light. We have employed the RMT method to investigate the time delay in the photoemission of an electron liberated from a 2p orbital in a neon atom with respect to one released from a 2s orbital following absorption of an attosecond xuv pulse. Time delays due to xuv pulses in the range 76-105 eV are presented. For an xuv pulse at the experimentally relevant energy of 105.2 eV, we calculate the time delay to be 10.2±1.3 attoseconds (as), somewhat larger than estimated by other theoretical calculations, but still a factor of 2 smaller than experiment. We repeated the calculation for a photon energy of 89.8 eV with a larger basis set capable of modeling correlated-electron dynamics within the neon atom and the residual Ne ion. A time delay of 14.5±1.5 as was observed, compared to a 16.7±1.5 as result using a single-configuration representation of the residual Ne⁺ ion. 

Segregation Preferences of Urban and Rural 16-year-olds in Northern Ireland

Sectarian violence in the Northern Ireland is often perceived to be mostly confined to cities. The aim of this paper is to explore statistically what factors contribute to segregation preferences among young people living in rural and urban areas, using the 2005–2009 Young Life and Times (YLT) survey – an annual attitudes survey of 16-year-olds. The findings show that religious and national identities are the strongest predictors of segregation preferences among 16-year-olds, regardless of where they live and what background they have. Those living in rural areas of Northern Ireland are more supportive of residential, workplace and educational segregation than those living in more urban areas. This research highlights the need for government policy to take rurality into account. Nevertheless, some variables significantly determine segregation preferences regardless of where respondents live, such as attendance of segregated schools, being female, or strength of national and religious identity. Consequently, policy initiatives should continue to address the effect of segregation, especially in relation to education, and future research exploring social class and gender is recommended. In conclusion, the perception of the violent ‘urban spaces’ and the ‘peaceful countryside’ has to be challenged.

A Trip from a Tube to a Chip Applied Micro and Nanotechnology in Biotechnology, Veterinary and Life Sciences

More than 200 known diseases are transmitted via foods or food products. In the United States, food-borne diseases are responsible for 76 million cases of illness, 32,500 cases of hospitalisation and 5000 cases of death yearly. The ongoing increase in worldwide trade in livestock, food, and food products in combination with increase in human mobility (business- and leisure travel, emigration etc.) will increase the risk of emergence and spreading of such pathogens. There is therefore an urgent need for development of rapid, efficient and reliable methods for detection and identification of such pathogens.

Microchipfabrication has had a major impact on electronics and is expected to have an equally pronounced effect on life sciences. By combining micro-fluidics with micromechanics, micro-optics, and microelectronics, systems can be realized to perform complete chemical or biochemical analyses. These socalled ’Lab-on-a-Chip’ will completely change the face of laboratories in the future where smaller, fully automated devices will be able to perform assays faster, more accurately, and at a lower cost than equipment of today. A general introduction of food safety and applied micro-nanotechnology in life sciences will be given. In addition, examples of DNA micro arrays, micro fabricated integrated PCR chips and total integrated lab-on-achip systems from different National and EU research projects being carried out at the Laboratory of Applied Micro- Nanotechnology (LAMINATE) group at the National Veterinary Institute (DTU-Vet) Technical University of Denmark and the BioLabchip group at the Department of Micro and Nanotechnology (DTU-Nanotech), Technical University of Denmark (DTU), Ikerlan-IK4 (Spain) and other 16 partners from different European countries will be presented.

Performance of Nonlocal Optics When Applied to Plasmonic Nanostructures

Semiclassical nonlocal optics based on the hydrodynamic description of conduction electrons might be an adequate tool to study complex phenomena in the emerging field of nanoplasmonics. With the aim of confirming this idea, we obtain the local and nonlocal optical absorption spectra in a model nanoplasmonic device in which there are spatial gaps between the components at nanometric and subnanometric scales. After a comparison against time-dependent density functional calculations, we conclude that hydrodynamic nonlocal optics provides absorption spectra exhibiting qualitative agreement but not quantitative accuracy. This lack of accuracy, which is manifest even in the limit where induced electric currents are not established between the constituents of the device, is mainly due to the poor description of induced electron densities.

You have free access to this content 5.8 GHz full duplex amplitude shift keying retrodirective interrogator array

This article describes a practical demonstration of a complete full-duplex “amplitude shift keying (ASK)” retrodirective radio frequency identification (RFID) transceiver array.The interrogator incorporates a “retrodirective array (RDA)” with a dual-conversion phase conjugating architecture in order to achieve better performance than is possible with conventional RFID solutions. Here mixers phase conjugate the incoming signal and a carrier recovery circuit recovers incoming angle of arrival phase information of an encoded amplitude shift keyed signal. The resulting interrogator provides a receiver sensitivity level of -109 dBm. A four element square patch RDA gives a 3 dB automatic beam steering angle of acceptance of ±45°. When compared to an RFID system operating by conventional (non-retrodirective) means retrodirective action leads to improved range extension of up to 16 times at ±45°. Operator pointing accuracy requirements are also reduced due to automatic retrodirective self-pointing. These features significantly enhance deployment opportunities requiring long range low equivalent isotropic radiation power (EIRP) and/or RFID tagging of moving platforms. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:160–164, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27258

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.

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.

Individual differences provide psychophysical evidence for separate on- and off-pathways deriving from short-wave cones

Distinct neural populations carry signals from short-wave (S) cones. We used individual differences to test whether two types of pathways, those that receive excitatory input (S+) and those that receive inhibitory input (S-), contribute independently to psychophysical performance. We also conducted a genome-wide association study (GWAS) to look for genetic correlates of the individual differences. Our psychophysical test was based on the Cambridge Color Test, but detection thresholds were measured separately for S-cone spatial increments and decrements. Our participants were 1060 healthy adults aged 16-40. Test-retest reliabilities for thresholds were good (ρ=0.64 for S-cone increments, 0.67 for decrements and 0.73 for the average of the two). "Regression scores," isolating variability unique to incremental or decremental sensitivity, were also reliable (ρ=0.53 for increments and ρ=0.51 for decrements). The correlation between incremental and decremental thresholds was ρ=0.65. No genetic markers reached genome-wide significance (p-7). We identified 18 "suggestive" loci (p-5). The significant test-retest reliabilities show stable individual differences in S-cone sensitivity in a normal adult population. Though a portion of the variance in sensitivity is shared between incremental and decremental sensitivity, over 26% of the variance is stable across individuals, but unique to increments or decrements, suggesting distinct neural substrates. Some of the variability in sensitivity is likely to be genetic. We note that four of the suggestive associations found in the GWAS are with genes that are involved in glucose metabolism or have been associated with diabetes.

Classical and quantum aspects of multimode parametric interactions

Parametric interactions in nonlinear crystals represent a powerful tool in the optical manipulation of information, both in the classical and the quantum regime. Here, we analyze in detail classical and quantum aspects of three-and five-mode parametric interactions in chi(2) nonlinear crystals. The equations of motion are explicitly derived and then solved within the parametric approximation. We describe several applications, including holography, all-optical gates, generation of entanglement, and telecloning. Experimental results on the photon distributions and correlations of the generated beams are also reported and discussed.